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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/filemap.c
4 *
5 * Copyright (C) 1994-1999 Linus Torvalds
6 */
7
8/*
9 * This file handles the generic file mmap semantics used by
10 * most "normal" filesystems (but you don't /have/ to use this:
11 * the NFS filesystem used to do this differently, for example)
12 */
13#include <linux/export.h>
14#include <linux/compiler.h>
15#include <linux/dax.h>
16#include <linux/fs.h>
17#include <linux/sched/signal.h>
18#include <linux/uaccess.h>
19#include <linux/capability.h>
20#include <linux/kernel_stat.h>
21#include <linux/gfp.h>
22#include <linux/mm.h>
23#include <linux/swap.h>
24#include <linux/mman.h>
25#include <linux/pagemap.h>
26#include <linux/file.h>
27#include <linux/uio.h>
28#include <linux/error-injection.h>
29#include <linux/hash.h>
30#include <linux/writeback.h>
31#include <linux/backing-dev.h>
32#include <linux/pagevec.h>
33#include <linux/blkdev.h>
34#include <linux/security.h>
35#include <linux/cpuset.h>
36#include <linux/hugetlb.h>
37#include <linux/memcontrol.h>
38#include <linux/cleancache.h>
39#include <linux/shmem_fs.h>
40#include <linux/rmap.h>
41#include <linux/delayacct.h>
42#include <linux/psi.h>
43#include <linux/ramfs.h>
44#include "internal.h"
45
46#define CREATE_TRACE_POINTS
47#include <trace/events/filemap.h>
48
49/*
50 * FIXME: remove all knowledge of the buffer layer from the core VM
51 */
52#include <linux/buffer_head.h> /* for try_to_free_buffers */
53
54#include <asm/mman.h>
55
56/*
57 * Shared mappings implemented 30.11.1994. It's not fully working yet,
58 * though.
59 *
60 * Shared mappings now work. 15.8.1995 Bruno.
61 *
62 * finished 'unifying' the page and buffer cache and SMP-threaded the
63 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
64 *
65 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
66 */
67
68/*
69 * Lock ordering:
70 *
71 * ->i_mmap_rwsem (truncate_pagecache)
72 * ->private_lock (__free_pte->__set_page_dirty_buffers)
73 * ->swap_lock (exclusive_swap_page, others)
74 * ->i_pages lock
75 *
76 * ->i_mutex
77 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
78 *
79 * ->mmap_sem
80 * ->i_mmap_rwsem
81 * ->page_table_lock or pte_lock (various, mainly in memory.c)
82 * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
83 *
84 * ->mmap_sem
85 * ->lock_page (access_process_vm)
86 *
87 * ->i_mutex (generic_perform_write)
88 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
89 *
90 * bdi->wb.list_lock
91 * sb_lock (fs/fs-writeback.c)
92 * ->i_pages lock (__sync_single_inode)
93 *
94 * ->i_mmap_rwsem
95 * ->anon_vma.lock (vma_adjust)
96 *
97 * ->anon_vma.lock
98 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
99 *
100 * ->page_table_lock or pte_lock
101 * ->swap_lock (try_to_unmap_one)
102 * ->private_lock (try_to_unmap_one)
103 * ->i_pages lock (try_to_unmap_one)
104 * ->pgdat->lru_lock (follow_page->mark_page_accessed)
105 * ->pgdat->lru_lock (check_pte_range->isolate_lru_page)
106 * ->private_lock (page_remove_rmap->set_page_dirty)
107 * ->i_pages lock (page_remove_rmap->set_page_dirty)
108 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
109 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
110 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
111 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
112 * ->inode->i_lock (zap_pte_range->set_page_dirty)
113 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
114 *
115 * ->i_mmap_rwsem
116 * ->tasklist_lock (memory_failure, collect_procs_ao)
117 */
118
119static void page_cache_delete(struct address_space *mapping,
120 struct page *page, void *shadow)
121{
122 XA_STATE(xas, &mapping->i_pages, page->index);
123 unsigned int nr = 1;
124
125 mapping_set_update(&xas, mapping);
126
127 /* hugetlb pages are represented by a single entry in the xarray */
128 if (!PageHuge(page)) {
129 xas_set_order(&xas, page->index, compound_order(page));
130 nr = compound_nr(page);
131 }
132
133 VM_BUG_ON_PAGE(!PageLocked(page), page);
134 VM_BUG_ON_PAGE(PageTail(page), page);
135 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
136
137 xas_store(&xas, shadow);
138 xas_init_marks(&xas);
139
140 page->mapping = NULL;
141 /* Leave page->index set: truncation lookup relies upon it */
142
143 if (shadow) {
144 mapping->nrexceptional += nr;
145 /*
146 * Make sure the nrexceptional update is committed before
147 * the nrpages update so that final truncate racing
148 * with reclaim does not see both counters 0 at the
149 * same time and miss a shadow entry.
150 */
151 smp_wmb();
152 }
153 mapping->nrpages -= nr;
154}
155
156static void unaccount_page_cache_page(struct address_space *mapping,
157 struct page *page)
158{
159 int nr;
160
161 /*
162 * if we're uptodate, flush out into the cleancache, otherwise
163 * invalidate any existing cleancache entries. We can't leave
164 * stale data around in the cleancache once our page is gone
165 */
166 if (PageUptodate(page) && PageMappedToDisk(page))
167 cleancache_put_page(page);
168 else
169 cleancache_invalidate_page(mapping, page);
170
171 VM_BUG_ON_PAGE(PageTail(page), page);
172 VM_BUG_ON_PAGE(page_mapped(page), page);
173 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
174 int mapcount;
175
176 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
177 current->comm, page_to_pfn(page));
178 dump_page(page, "still mapped when deleted");
179 dump_stack();
180 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
181
182 mapcount = page_mapcount(page);
183 if (mapping_exiting(mapping) &&
184 page_count(page) >= mapcount + 2) {
185 /*
186 * All vmas have already been torn down, so it's
187 * a good bet that actually the page is unmapped,
188 * and we'd prefer not to leak it: if we're wrong,
189 * some other bad page check should catch it later.
190 */
191 page_mapcount_reset(page);
192 page_ref_sub(page, mapcount);
193 }
194 }
195
196 /* hugetlb pages do not participate in page cache accounting. */
197 if (PageHuge(page))
198 return;
199
200 nr = hpage_nr_pages(page);
201
202 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
203 if (PageSwapBacked(page)) {
204 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
205 if (PageTransHuge(page))
206 __dec_node_page_state(page, NR_SHMEM_THPS);
207 } else if (PageTransHuge(page)) {
208 __dec_node_page_state(page, NR_FILE_THPS);
209 filemap_nr_thps_dec(mapping);
210 }
211
212 /*
213 * At this point page must be either written or cleaned by
214 * truncate. Dirty page here signals a bug and loss of
215 * unwritten data.
216 *
217 * This fixes dirty accounting after removing the page entirely
218 * but leaves PageDirty set: it has no effect for truncated
219 * page and anyway will be cleared before returning page into
220 * buddy allocator.
221 */
222 if (WARN_ON_ONCE(PageDirty(page)))
223 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
224}
225
226/*
227 * Delete a page from the page cache and free it. Caller has to make
228 * sure the page is locked and that nobody else uses it - or that usage
229 * is safe. The caller must hold the i_pages lock.
230 */
231void __delete_from_page_cache(struct page *page, void *shadow)
232{
233 struct address_space *mapping = page->mapping;
234
235 trace_mm_filemap_delete_from_page_cache(page);
236
237 unaccount_page_cache_page(mapping, page);
238 page_cache_delete(mapping, page, shadow);
239}
240
241static void page_cache_free_page(struct address_space *mapping,
242 struct page *page)
243{
244 void (*freepage)(struct page *);
245
246 freepage = mapping->a_ops->freepage;
247 if (freepage)
248 freepage(page);
249
250 if (PageTransHuge(page) && !PageHuge(page)) {
251 page_ref_sub(page, HPAGE_PMD_NR);
252 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
253 } else {
254 put_page(page);
255 }
256}
257
258/**
259 * delete_from_page_cache - delete page from page cache
260 * @page: the page which the kernel is trying to remove from page cache
261 *
262 * This must be called only on pages that have been verified to be in the page
263 * cache and locked. It will never put the page into the free list, the caller
264 * has a reference on the page.
265 */
266void delete_from_page_cache(struct page *page)
267{
268 struct address_space *mapping = page_mapping(page);
269 unsigned long flags;
270
271 BUG_ON(!PageLocked(page));
272 xa_lock_irqsave(&mapping->i_pages, flags);
273 __delete_from_page_cache(page, NULL);
274 xa_unlock_irqrestore(&mapping->i_pages, flags);
275
276 page_cache_free_page(mapping, page);
277}
278EXPORT_SYMBOL(delete_from_page_cache);
279
280/*
281 * page_cache_delete_batch - delete several pages from page cache
282 * @mapping: the mapping to which pages belong
283 * @pvec: pagevec with pages to delete
284 *
285 * The function walks over mapping->i_pages and removes pages passed in @pvec
286 * from the mapping. The function expects @pvec to be sorted by page index
287 * and is optimised for it to be dense.
288 * It tolerates holes in @pvec (mapping entries at those indices are not
289 * modified). The function expects only THP head pages to be present in the
290 * @pvec.
291 *
292 * The function expects the i_pages lock to be held.
293 */
294static void page_cache_delete_batch(struct address_space *mapping,
295 struct pagevec *pvec)
296{
297 XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index);
298 int total_pages = 0;
299 int i = 0;
300 struct page *page;
301
302 mapping_set_update(&xas, mapping);
303 xas_for_each(&xas, page, ULONG_MAX) {
304 if (i >= pagevec_count(pvec))
305 break;
306
307 /* A swap/dax/shadow entry got inserted? Skip it. */
308 if (xa_is_value(page))
309 continue;
310 /*
311 * A page got inserted in our range? Skip it. We have our
312 * pages locked so they are protected from being removed.
313 * If we see a page whose index is higher than ours, it
314 * means our page has been removed, which shouldn't be
315 * possible because we're holding the PageLock.
316 */
317 if (page != pvec->pages[i]) {
318 VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index,
319 page);
320 continue;
321 }
322
323 WARN_ON_ONCE(!PageLocked(page));
324
325 if (page->index == xas.xa_index)
326 page->mapping = NULL;
327 /* Leave page->index set: truncation lookup relies on it */
328
329 /*
330 * Move to the next page in the vector if this is a regular
331 * page or the index is of the last sub-page of this compound
332 * page.
333 */
334 if (page->index + compound_nr(page) - 1 == xas.xa_index)
335 i++;
336 xas_store(&xas, NULL);
337 total_pages++;
338 }
339 mapping->nrpages -= total_pages;
340}
341
342void delete_from_page_cache_batch(struct address_space *mapping,
343 struct pagevec *pvec)
344{
345 int i;
346 unsigned long flags;
347
348 if (!pagevec_count(pvec))
349 return;
350
351 xa_lock_irqsave(&mapping->i_pages, flags);
352 for (i = 0; i < pagevec_count(pvec); i++) {
353 trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);
354
355 unaccount_page_cache_page(mapping, pvec->pages[i]);
356 }
357 page_cache_delete_batch(mapping, pvec);
358 xa_unlock_irqrestore(&mapping->i_pages, flags);
359
360 for (i = 0; i < pagevec_count(pvec); i++)
361 page_cache_free_page(mapping, pvec->pages[i]);
362}
363
364int filemap_check_errors(struct address_space *mapping)
365{
366 int ret = 0;
367 /* Check for outstanding write errors */
368 if (test_bit(AS_ENOSPC, &mapping->flags) &&
369 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
370 ret = -ENOSPC;
371 if (test_bit(AS_EIO, &mapping->flags) &&
372 test_and_clear_bit(AS_EIO, &mapping->flags))
373 ret = -EIO;
374 return ret;
375}
376EXPORT_SYMBOL(filemap_check_errors);
377
378static int filemap_check_and_keep_errors(struct address_space *mapping)
379{
380 /* Check for outstanding write errors */
381 if (test_bit(AS_EIO, &mapping->flags))
382 return -EIO;
383 if (test_bit(AS_ENOSPC, &mapping->flags))
384 return -ENOSPC;
385 return 0;
386}
387
388/**
389 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
390 * @mapping: address space structure to write
391 * @start: offset in bytes where the range starts
392 * @end: offset in bytes where the range ends (inclusive)
393 * @sync_mode: enable synchronous operation
394 *
395 * Start writeback against all of a mapping's dirty pages that lie
396 * within the byte offsets <start, end> inclusive.
397 *
398 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
399 * opposed to a regular memory cleansing writeback. The difference between
400 * these two operations is that if a dirty page/buffer is encountered, it must
401 * be waited upon, and not just skipped over.
402 *
403 * Return: %0 on success, negative error code otherwise.
404 */
405int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
406 loff_t end, int sync_mode)
407{
408 int ret;
409 struct writeback_control wbc = {
410 .sync_mode = sync_mode,
411 .nr_to_write = LONG_MAX,
412 .range_start = start,
413 .range_end = end,
414 };
415
416 if (!mapping_cap_writeback_dirty(mapping) ||
417 !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
418 return 0;
419
420 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
421 ret = do_writepages(mapping, &wbc);
422 wbc_detach_inode(&wbc);
423 return ret;
424}
425
426static inline int __filemap_fdatawrite(struct address_space *mapping,
427 int sync_mode)
428{
429 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
430}
431
432int filemap_fdatawrite(struct address_space *mapping)
433{
434 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
435}
436EXPORT_SYMBOL(filemap_fdatawrite);
437
438int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
439 loff_t end)
440{
441 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
442}
443EXPORT_SYMBOL(filemap_fdatawrite_range);
444
445/**
446 * filemap_flush - mostly a non-blocking flush
447 * @mapping: target address_space
448 *
449 * This is a mostly non-blocking flush. Not suitable for data-integrity
450 * purposes - I/O may not be started against all dirty pages.
451 *
452 * Return: %0 on success, negative error code otherwise.
453 */
454int filemap_flush(struct address_space *mapping)
455{
456 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
457}
458EXPORT_SYMBOL(filemap_flush);
459
460/**
461 * filemap_range_has_page - check if a page exists in range.
462 * @mapping: address space within which to check
463 * @start_byte: offset in bytes where the range starts
464 * @end_byte: offset in bytes where the range ends (inclusive)
465 *
466 * Find at least one page in the range supplied, usually used to check if
467 * direct writing in this range will trigger a writeback.
468 *
469 * Return: %true if at least one page exists in the specified range,
470 * %false otherwise.
471 */
472bool filemap_range_has_page(struct address_space *mapping,
473 loff_t start_byte, loff_t end_byte)
474{
475 struct page *page;
476 XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
477 pgoff_t max = end_byte >> PAGE_SHIFT;
478
479 if (end_byte < start_byte)
480 return false;
481
482 rcu_read_lock();
483 for (;;) {
484 page = xas_find(&xas, max);
485 if (xas_retry(&xas, page))
486 continue;
487 /* Shadow entries don't count */
488 if (xa_is_value(page))
489 continue;
490 /*
491 * We don't need to try to pin this page; we're about to
492 * release the RCU lock anyway. It is enough to know that
493 * there was a page here recently.
494 */
495 break;
496 }
497 rcu_read_unlock();
498
499 return page != NULL;
500}
501EXPORT_SYMBOL(filemap_range_has_page);
502
503static void __filemap_fdatawait_range(struct address_space *mapping,
504 loff_t start_byte, loff_t end_byte)
505{
506 pgoff_t index = start_byte >> PAGE_SHIFT;
507 pgoff_t end = end_byte >> PAGE_SHIFT;
508 struct pagevec pvec;
509 int nr_pages;
510
511 if (end_byte < start_byte)
512 return;
513
514 pagevec_init(&pvec);
515 while (index <= end) {
516 unsigned i;
517
518 nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
519 end, PAGECACHE_TAG_WRITEBACK);
520 if (!nr_pages)
521 break;
522
523 for (i = 0; i < nr_pages; i++) {
524 struct page *page = pvec.pages[i];
525
526 wait_on_page_writeback(page);
527 ClearPageError(page);
528 }
529 pagevec_release(&pvec);
530 cond_resched();
531 }
532}
533
534/**
535 * filemap_fdatawait_range - wait for writeback to complete
536 * @mapping: address space structure to wait for
537 * @start_byte: offset in bytes where the range starts
538 * @end_byte: offset in bytes where the range ends (inclusive)
539 *
540 * Walk the list of under-writeback pages of the given address space
541 * in the given range and wait for all of them. Check error status of
542 * the address space and return it.
543 *
544 * Since the error status of the address space is cleared by this function,
545 * callers are responsible for checking the return value and handling and/or
546 * reporting the error.
547 *
548 * Return: error status of the address space.
549 */
550int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
551 loff_t end_byte)
552{
553 __filemap_fdatawait_range(mapping, start_byte, end_byte);
554 return filemap_check_errors(mapping);
555}
556EXPORT_SYMBOL(filemap_fdatawait_range);
557
558/**
559 * filemap_fdatawait_range_keep_errors - wait for writeback to complete
560 * @mapping: address space structure to wait for
561 * @start_byte: offset in bytes where the range starts
562 * @end_byte: offset in bytes where the range ends (inclusive)
563 *
564 * Walk the list of under-writeback pages of the given address space in the
565 * given range and wait for all of them. Unlike filemap_fdatawait_range(),
566 * this function does not clear error status of the address space.
567 *
568 * Use this function if callers don't handle errors themselves. Expected
569 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
570 * fsfreeze(8)
571 */
572int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
573 loff_t start_byte, loff_t end_byte)
574{
575 __filemap_fdatawait_range(mapping, start_byte, end_byte);
576 return filemap_check_and_keep_errors(mapping);
577}
578EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
579
580/**
581 * file_fdatawait_range - wait for writeback to complete
582 * @file: file pointing to address space structure to wait for
583 * @start_byte: offset in bytes where the range starts
584 * @end_byte: offset in bytes where the range ends (inclusive)
585 *
586 * Walk the list of under-writeback pages of the address space that file
587 * refers to, in the given range and wait for all of them. Check error
588 * status of the address space vs. the file->f_wb_err cursor and return it.
589 *
590 * Since the error status of the file is advanced by this function,
591 * callers are responsible for checking the return value and handling and/or
592 * reporting the error.
593 *
594 * Return: error status of the address space vs. the file->f_wb_err cursor.
595 */
596int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
597{
598 struct address_space *mapping = file->f_mapping;
599
600 __filemap_fdatawait_range(mapping, start_byte, end_byte);
601 return file_check_and_advance_wb_err(file);
602}
603EXPORT_SYMBOL(file_fdatawait_range);
604
605/**
606 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
607 * @mapping: address space structure to wait for
608 *
609 * Walk the list of under-writeback pages of the given address space
610 * and wait for all of them. Unlike filemap_fdatawait(), this function
611 * does not clear error status of the address space.
612 *
613 * Use this function if callers don't handle errors themselves. Expected
614 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
615 * fsfreeze(8)
616 *
617 * Return: error status of the address space.
618 */
619int filemap_fdatawait_keep_errors(struct address_space *mapping)
620{
621 __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
622 return filemap_check_and_keep_errors(mapping);
623}
624EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
625
626/* Returns true if writeback might be needed or already in progress. */
627static bool mapping_needs_writeback(struct address_space *mapping)
628{
629 if (dax_mapping(mapping))
630 return mapping->nrexceptional;
631
632 return mapping->nrpages;
633}
634
635int filemap_write_and_wait(struct address_space *mapping)
636{
637 int err = 0;
638
639 if (mapping_needs_writeback(mapping)) {
640 err = filemap_fdatawrite(mapping);
641 /*
642 * Even if the above returned error, the pages may be
643 * written partially (e.g. -ENOSPC), so we wait for it.
644 * But the -EIO is special case, it may indicate the worst
645 * thing (e.g. bug) happened, so we avoid waiting for it.
646 */
647 if (err != -EIO) {
648 int err2 = filemap_fdatawait(mapping);
649 if (!err)
650 err = err2;
651 } else {
652 /* Clear any previously stored errors */
653 filemap_check_errors(mapping);
654 }
655 } else {
656 err = filemap_check_errors(mapping);
657 }
658 return err;
659}
660EXPORT_SYMBOL(filemap_write_and_wait);
661
662/**
663 * filemap_write_and_wait_range - write out & wait on a file range
664 * @mapping: the address_space for the pages
665 * @lstart: offset in bytes where the range starts
666 * @lend: offset in bytes where the range ends (inclusive)
667 *
668 * Write out and wait upon file offsets lstart->lend, inclusive.
669 *
670 * Note that @lend is inclusive (describes the last byte to be written) so
671 * that this function can be used to write to the very end-of-file (end = -1).
672 *
673 * Return: error status of the address space.
674 */
675int filemap_write_and_wait_range(struct address_space *mapping,
676 loff_t lstart, loff_t lend)
677{
678 int err = 0;
679
680 if (mapping_needs_writeback(mapping)) {
681 err = __filemap_fdatawrite_range(mapping, lstart, lend,
682 WB_SYNC_ALL);
683 /* See comment of filemap_write_and_wait() */
684 if (err != -EIO) {
685 int err2 = filemap_fdatawait_range(mapping,
686 lstart, lend);
687 if (!err)
688 err = err2;
689 } else {
690 /* Clear any previously stored errors */
691 filemap_check_errors(mapping);
692 }
693 } else {
694 err = filemap_check_errors(mapping);
695 }
696 return err;
697}
698EXPORT_SYMBOL(filemap_write_and_wait_range);
699
700void __filemap_set_wb_err(struct address_space *mapping, int err)
701{
702 errseq_t eseq = errseq_set(&mapping->wb_err, err);
703
704 trace_filemap_set_wb_err(mapping, eseq);
705}
706EXPORT_SYMBOL(__filemap_set_wb_err);
707
708/**
709 * file_check_and_advance_wb_err - report wb error (if any) that was previously
710 * and advance wb_err to current one
711 * @file: struct file on which the error is being reported
712 *
713 * When userland calls fsync (or something like nfsd does the equivalent), we
714 * want to report any writeback errors that occurred since the last fsync (or
715 * since the file was opened if there haven't been any).
716 *
717 * Grab the wb_err from the mapping. If it matches what we have in the file,
718 * then just quickly return 0. The file is all caught up.
719 *
720 * If it doesn't match, then take the mapping value, set the "seen" flag in
721 * it and try to swap it into place. If it works, or another task beat us
722 * to it with the new value, then update the f_wb_err and return the error
723 * portion. The error at this point must be reported via proper channels
724 * (a'la fsync, or NFS COMMIT operation, etc.).
725 *
726 * While we handle mapping->wb_err with atomic operations, the f_wb_err
727 * value is protected by the f_lock since we must ensure that it reflects
728 * the latest value swapped in for this file descriptor.
729 *
730 * Return: %0 on success, negative error code otherwise.
731 */
732int file_check_and_advance_wb_err(struct file *file)
733{
734 int err = 0;
735 errseq_t old = READ_ONCE(file->f_wb_err);
736 struct address_space *mapping = file->f_mapping;
737
738 /* Locklessly handle the common case where nothing has changed */
739 if (errseq_check(&mapping->wb_err, old)) {
740 /* Something changed, must use slow path */
741 spin_lock(&file->f_lock);
742 old = file->f_wb_err;
743 err = errseq_check_and_advance(&mapping->wb_err,
744 &file->f_wb_err);
745 trace_file_check_and_advance_wb_err(file, old);
746 spin_unlock(&file->f_lock);
747 }
748
749 /*
750 * We're mostly using this function as a drop in replacement for
751 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
752 * that the legacy code would have had on these flags.
753 */
754 clear_bit(AS_EIO, &mapping->flags);
755 clear_bit(AS_ENOSPC, &mapping->flags);
756 return err;
757}
758EXPORT_SYMBOL(file_check_and_advance_wb_err);
759
760/**
761 * file_write_and_wait_range - write out & wait on a file range
762 * @file: file pointing to address_space with pages
763 * @lstart: offset in bytes where the range starts
764 * @lend: offset in bytes where the range ends (inclusive)
765 *
766 * Write out and wait upon file offsets lstart->lend, inclusive.
767 *
768 * Note that @lend is inclusive (describes the last byte to be written) so
769 * that this function can be used to write to the very end-of-file (end = -1).
770 *
771 * After writing out and waiting on the data, we check and advance the
772 * f_wb_err cursor to the latest value, and return any errors detected there.
773 *
774 * Return: %0 on success, negative error code otherwise.
775 */
776int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
777{
778 int err = 0, err2;
779 struct address_space *mapping = file->f_mapping;
780
781 if (mapping_needs_writeback(mapping)) {
782 err = __filemap_fdatawrite_range(mapping, lstart, lend,
783 WB_SYNC_ALL);
784 /* See comment of filemap_write_and_wait() */
785 if (err != -EIO)
786 __filemap_fdatawait_range(mapping, lstart, lend);
787 }
788 err2 = file_check_and_advance_wb_err(file);
789 if (!err)
790 err = err2;
791 return err;
792}
793EXPORT_SYMBOL(file_write_and_wait_range);
794
795/**
796 * replace_page_cache_page - replace a pagecache page with a new one
797 * @old: page to be replaced
798 * @new: page to replace with
799 * @gfp_mask: allocation mode
800 *
801 * This function replaces a page in the pagecache with a new one. On
802 * success it acquires the pagecache reference for the new page and
803 * drops it for the old page. Both the old and new pages must be
804 * locked. This function does not add the new page to the LRU, the
805 * caller must do that.
806 *
807 * The remove + add is atomic. This function cannot fail.
808 *
809 * Return: %0
810 */
811int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
812{
813 struct address_space *mapping = old->mapping;
814 void (*freepage)(struct page *) = mapping->a_ops->freepage;
815 pgoff_t offset = old->index;
816 XA_STATE(xas, &mapping->i_pages, offset);
817 unsigned long flags;
818
819 VM_BUG_ON_PAGE(!PageLocked(old), old);
820 VM_BUG_ON_PAGE(!PageLocked(new), new);
821 VM_BUG_ON_PAGE(new->mapping, new);
822
823 get_page(new);
824 new->mapping = mapping;
825 new->index = offset;
826
827 xas_lock_irqsave(&xas, flags);
828 xas_store(&xas, new);
829
830 old->mapping = NULL;
831 /* hugetlb pages do not participate in page cache accounting. */
832 if (!PageHuge(old))
833 __dec_node_page_state(new, NR_FILE_PAGES);
834 if (!PageHuge(new))
835 __inc_node_page_state(new, NR_FILE_PAGES);
836 if (PageSwapBacked(old))
837 __dec_node_page_state(new, NR_SHMEM);
838 if (PageSwapBacked(new))
839 __inc_node_page_state(new, NR_SHMEM);
840 xas_unlock_irqrestore(&xas, flags);
841 mem_cgroup_migrate(old, new);
842 if (freepage)
843 freepage(old);
844 put_page(old);
845
846 return 0;
847}
848EXPORT_SYMBOL_GPL(replace_page_cache_page);
849
850static int __add_to_page_cache_locked(struct page *page,
851 struct address_space *mapping,
852 pgoff_t offset, gfp_t gfp_mask,
853 void **shadowp)
854{
855 XA_STATE(xas, &mapping->i_pages, offset);
856 int huge = PageHuge(page);
857 struct mem_cgroup *memcg;
858 int error;
859 void *old;
860
861 VM_BUG_ON_PAGE(!PageLocked(page), page);
862 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
863 mapping_set_update(&xas, mapping);
864
865 if (!huge) {
866 error = mem_cgroup_try_charge(page, current->mm,
867 gfp_mask, &memcg, false);
868 if (error)
869 return error;
870 }
871
872 get_page(page);
873 page->mapping = mapping;
874 page->index = offset;
875
876 do {
877 xas_lock_irq(&xas);
878 old = xas_load(&xas);
879 if (old && !xa_is_value(old))
880 xas_set_err(&xas, -EEXIST);
881 xas_store(&xas, page);
882 if (xas_error(&xas))
883 goto unlock;
884
885 if (xa_is_value(old)) {
886 mapping->nrexceptional--;
887 if (shadowp)
888 *shadowp = old;
889 }
890 mapping->nrpages++;
891
892 /* hugetlb pages do not participate in page cache accounting */
893 if (!huge)
894 __inc_node_page_state(page, NR_FILE_PAGES);
895unlock:
896 xas_unlock_irq(&xas);
897 } while (xas_nomem(&xas, gfp_mask & GFP_RECLAIM_MASK));
898
899 if (xas_error(&xas))
900 goto error;
901
902 if (!huge)
903 mem_cgroup_commit_charge(page, memcg, false, false);
904 trace_mm_filemap_add_to_page_cache(page);
905 return 0;
906error:
907 page->mapping = NULL;
908 /* Leave page->index set: truncation relies upon it */
909 if (!huge)
910 mem_cgroup_cancel_charge(page, memcg, false);
911 put_page(page);
912 return xas_error(&xas);
913}
914ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO);
915
916/**
917 * add_to_page_cache_locked - add a locked page to the pagecache
918 * @page: page to add
919 * @mapping: the page's address_space
920 * @offset: page index
921 * @gfp_mask: page allocation mode
922 *
923 * This function is used to add a page to the pagecache. It must be locked.
924 * This function does not add the page to the LRU. The caller must do that.
925 *
926 * Return: %0 on success, negative error code otherwise.
927 */
928int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
929 pgoff_t offset, gfp_t gfp_mask)
930{
931 return __add_to_page_cache_locked(page, mapping, offset,
932 gfp_mask, NULL);
933}
934EXPORT_SYMBOL(add_to_page_cache_locked);
935
936int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
937 pgoff_t offset, gfp_t gfp_mask)
938{
939 void *shadow = NULL;
940 int ret;
941
942 __SetPageLocked(page);
943 ret = __add_to_page_cache_locked(page, mapping, offset,
944 gfp_mask, &shadow);
945 if (unlikely(ret))
946 __ClearPageLocked(page);
947 else {
948 /*
949 * The page might have been evicted from cache only
950 * recently, in which case it should be activated like
951 * any other repeatedly accessed page.
952 * The exception is pages getting rewritten; evicting other
953 * data from the working set, only to cache data that will
954 * get overwritten with something else, is a waste of memory.
955 */
956 WARN_ON_ONCE(PageActive(page));
957 if (!(gfp_mask & __GFP_WRITE) && shadow)
958 workingset_refault(page, shadow);
959 lru_cache_add(page);
960 }
961 return ret;
962}
963EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
964
965#ifdef CONFIG_NUMA
966struct page *__page_cache_alloc(gfp_t gfp)
967{
968 int n;
969 struct page *page;
970
971 if (cpuset_do_page_mem_spread()) {
972 unsigned int cpuset_mems_cookie;
973 do {
974 cpuset_mems_cookie = read_mems_allowed_begin();
975 n = cpuset_mem_spread_node();
976 page = __alloc_pages_node(n, gfp, 0);
977 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
978
979 return page;
980 }
981 return alloc_pages(gfp, 0);
982}
983EXPORT_SYMBOL(__page_cache_alloc);
984#endif
985
986/*
987 * In order to wait for pages to become available there must be
988 * waitqueues associated with pages. By using a hash table of
989 * waitqueues where the bucket discipline is to maintain all
990 * waiters on the same queue and wake all when any of the pages
991 * become available, and for the woken contexts to check to be
992 * sure the appropriate page became available, this saves space
993 * at a cost of "thundering herd" phenomena during rare hash
994 * collisions.
995 */
996#define PAGE_WAIT_TABLE_BITS 8
997#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
998static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
999
1000static wait_queue_head_t *page_waitqueue(struct page *page)
1001{
1002 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
1003}
1004
1005void __init pagecache_init(void)
1006{
1007 int i;
1008
1009 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
1010 init_waitqueue_head(&page_wait_table[i]);
1011
1012 page_writeback_init();
1013}
1014
1015/* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
1016struct wait_page_key {
1017 struct page *page;
1018 int bit_nr;
1019 int page_match;
1020};
1021
1022struct wait_page_queue {
1023 struct page *page;
1024 int bit_nr;
1025 wait_queue_entry_t wait;
1026};
1027
1028static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
1029{
1030 struct wait_page_key *key = arg;
1031 struct wait_page_queue *wait_page
1032 = container_of(wait, struct wait_page_queue, wait);
1033
1034 if (wait_page->page != key->page)
1035 return 0;
1036 key->page_match = 1;
1037
1038 if (wait_page->bit_nr != key->bit_nr)
1039 return 0;
1040
1041 /*
1042 * Stop walking if it's locked.
1043 * Is this safe if put_and_wait_on_page_locked() is in use?
1044 * Yes: the waker must hold a reference to this page, and if PG_locked
1045 * has now already been set by another task, that task must also hold
1046 * a reference to the *same usage* of this page; so there is no need
1047 * to walk on to wake even the put_and_wait_on_page_locked() callers.
1048 */
1049 if (test_bit(key->bit_nr, &key->page->flags))
1050 return -1;
1051
1052 return autoremove_wake_function(wait, mode, sync, key);
1053}
1054
1055static void wake_up_page_bit(struct page *page, int bit_nr)
1056{
1057 wait_queue_head_t *q = page_waitqueue(page);
1058 struct wait_page_key key;
1059 unsigned long flags;
1060 wait_queue_entry_t bookmark;
1061
1062 key.page = page;
1063 key.bit_nr = bit_nr;
1064 key.page_match = 0;
1065
1066 bookmark.flags = 0;
1067 bookmark.private = NULL;
1068 bookmark.func = NULL;
1069 INIT_LIST_HEAD(&bookmark.entry);
1070
1071 spin_lock_irqsave(&q->lock, flags);
1072 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1073
1074 while (bookmark.flags & WQ_FLAG_BOOKMARK) {
1075 /*
1076 * Take a breather from holding the lock,
1077 * allow pages that finish wake up asynchronously
1078 * to acquire the lock and remove themselves
1079 * from wait queue
1080 */
1081 spin_unlock_irqrestore(&q->lock, flags);
1082 cpu_relax();
1083 spin_lock_irqsave(&q->lock, flags);
1084 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1085 }
1086
1087 /*
1088 * It is possible for other pages to have collided on the waitqueue
1089 * hash, so in that case check for a page match. That prevents a long-
1090 * term waiter
1091 *
1092 * It is still possible to miss a case here, when we woke page waiters
1093 * and removed them from the waitqueue, but there are still other
1094 * page waiters.
1095 */
1096 if (!waitqueue_active(q) || !key.page_match) {
1097 ClearPageWaiters(page);
1098 /*
1099 * It's possible to miss clearing Waiters here, when we woke
1100 * our page waiters, but the hashed waitqueue has waiters for
1101 * other pages on it.
1102 *
1103 * That's okay, it's a rare case. The next waker will clear it.
1104 */
1105 }
1106 spin_unlock_irqrestore(&q->lock, flags);
1107}
1108
1109static void wake_up_page(struct page *page, int bit)
1110{
1111 if (!PageWaiters(page))
1112 return;
1113 wake_up_page_bit(page, bit);
1114}
1115
1116/*
1117 * A choice of three behaviors for wait_on_page_bit_common():
1118 */
1119enum behavior {
1120 EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
1121 * __lock_page() waiting on then setting PG_locked.
1122 */
1123 SHARED, /* Hold ref to page and check the bit when woken, like
1124 * wait_on_page_writeback() waiting on PG_writeback.
1125 */
1126 DROP, /* Drop ref to page before wait, no check when woken,
1127 * like put_and_wait_on_page_locked() on PG_locked.
1128 */
1129};
1130
1131static inline int wait_on_page_bit_common(wait_queue_head_t *q,
1132 struct page *page, int bit_nr, int state, enum behavior behavior)
1133{
1134 struct wait_page_queue wait_page;
1135 wait_queue_entry_t *wait = &wait_page.wait;
1136 bool bit_is_set;
1137 bool thrashing = false;
1138 bool delayacct = false;
1139 unsigned long pflags;
1140 int ret = 0;
1141
1142 if (bit_nr == PG_locked &&
1143 !PageUptodate(page) && PageWorkingset(page)) {
1144 if (!PageSwapBacked(page)) {
1145 delayacct_thrashing_start();
1146 delayacct = true;
1147 }
1148 psi_memstall_enter(&pflags);
1149 thrashing = true;
1150 }
1151
1152 init_wait(wait);
1153 wait->flags = behavior == EXCLUSIVE ? WQ_FLAG_EXCLUSIVE : 0;
1154 wait->func = wake_page_function;
1155 wait_page.page = page;
1156 wait_page.bit_nr = bit_nr;
1157
1158 for (;;) {
1159 spin_lock_irq(&q->lock);
1160
1161 if (likely(list_empty(&wait->entry))) {
1162 __add_wait_queue_entry_tail(q, wait);
1163 SetPageWaiters(page);
1164 }
1165
1166 set_current_state(state);
1167
1168 spin_unlock_irq(&q->lock);
1169
1170 bit_is_set = test_bit(bit_nr, &page->flags);
1171 if (behavior == DROP)
1172 put_page(page);
1173
1174 if (likely(bit_is_set))
1175 io_schedule();
1176
1177 if (behavior == EXCLUSIVE) {
1178 if (!test_and_set_bit_lock(bit_nr, &page->flags))
1179 break;
1180 } else if (behavior == SHARED) {
1181 if (!test_bit(bit_nr, &page->flags))
1182 break;
1183 }
1184
1185 if (signal_pending_state(state, current)) {
1186 ret = -EINTR;
1187 break;
1188 }
1189
1190 if (behavior == DROP) {
1191 /*
1192 * We can no longer safely access page->flags:
1193 * even if CONFIG_MEMORY_HOTREMOVE is not enabled,
1194 * there is a risk of waiting forever on a page reused
1195 * for something that keeps it locked indefinitely.
1196 * But best check for -EINTR above before breaking.
1197 */
1198 break;
1199 }
1200 }
1201
1202 finish_wait(q, wait);
1203
1204 if (thrashing) {
1205 if (delayacct)
1206 delayacct_thrashing_end();
1207 psi_memstall_leave(&pflags);
1208 }
1209
1210 /*
1211 * A signal could leave PageWaiters set. Clearing it here if
1212 * !waitqueue_active would be possible (by open-coding finish_wait),
1213 * but still fail to catch it in the case of wait hash collision. We
1214 * already can fail to clear wait hash collision cases, so don't
1215 * bother with signals either.
1216 */
1217
1218 return ret;
1219}
1220
1221void wait_on_page_bit(struct page *page, int bit_nr)
1222{
1223 wait_queue_head_t *q = page_waitqueue(page);
1224 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
1225}
1226EXPORT_SYMBOL(wait_on_page_bit);
1227
1228int wait_on_page_bit_killable(struct page *page, int bit_nr)
1229{
1230 wait_queue_head_t *q = page_waitqueue(page);
1231 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, SHARED);
1232}
1233EXPORT_SYMBOL(wait_on_page_bit_killable);
1234
1235/**
1236 * put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked
1237 * @page: The page to wait for.
1238 *
1239 * The caller should hold a reference on @page. They expect the page to
1240 * become unlocked relatively soon, but do not wish to hold up migration
1241 * (for example) by holding the reference while waiting for the page to
1242 * come unlocked. After this function returns, the caller should not
1243 * dereference @page.
1244 */
1245void put_and_wait_on_page_locked(struct page *page)
1246{
1247 wait_queue_head_t *q;
1248
1249 page = compound_head(page);
1250 q = page_waitqueue(page);
1251 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, DROP);
1252}
1253
1254/**
1255 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1256 * @page: Page defining the wait queue of interest
1257 * @waiter: Waiter to add to the queue
1258 *
1259 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1260 */
1261void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
1262{
1263 wait_queue_head_t *q = page_waitqueue(page);
1264 unsigned long flags;
1265
1266 spin_lock_irqsave(&q->lock, flags);
1267 __add_wait_queue_entry_tail(q, waiter);
1268 SetPageWaiters(page);
1269 spin_unlock_irqrestore(&q->lock, flags);
1270}
1271EXPORT_SYMBOL_GPL(add_page_wait_queue);
1272
1273#ifndef clear_bit_unlock_is_negative_byte
1274
1275/*
1276 * PG_waiters is the high bit in the same byte as PG_lock.
1277 *
1278 * On x86 (and on many other architectures), we can clear PG_lock and
1279 * test the sign bit at the same time. But if the architecture does
1280 * not support that special operation, we just do this all by hand
1281 * instead.
1282 *
1283 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1284 * being cleared, but a memory barrier should be unneccssary since it is
1285 * in the same byte as PG_locked.
1286 */
1287static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
1288{
1289 clear_bit_unlock(nr, mem);
1290 /* smp_mb__after_atomic(); */
1291 return test_bit(PG_waiters, mem);
1292}
1293
1294#endif
1295
1296/**
1297 * unlock_page - unlock a locked page
1298 * @page: the page
1299 *
1300 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
1301 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1302 * mechanism between PageLocked pages and PageWriteback pages is shared.
1303 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1304 *
1305 * Note that this depends on PG_waiters being the sign bit in the byte
1306 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1307 * clear the PG_locked bit and test PG_waiters at the same time fairly
1308 * portably (architectures that do LL/SC can test any bit, while x86 can
1309 * test the sign bit).
1310 */
1311void unlock_page(struct page *page)
1312{
1313 BUILD_BUG_ON(PG_waiters != 7);
1314 page = compound_head(page);
1315 VM_BUG_ON_PAGE(!PageLocked(page), page);
1316 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
1317 wake_up_page_bit(page, PG_locked);
1318}
1319EXPORT_SYMBOL(unlock_page);
1320
1321/**
1322 * end_page_writeback - end writeback against a page
1323 * @page: the page
1324 */
1325void end_page_writeback(struct page *page)
1326{
1327 /*
1328 * TestClearPageReclaim could be used here but it is an atomic
1329 * operation and overkill in this particular case. Failing to
1330 * shuffle a page marked for immediate reclaim is too mild to
1331 * justify taking an atomic operation penalty at the end of
1332 * ever page writeback.
1333 */
1334 if (PageReclaim(page)) {
1335 ClearPageReclaim(page);
1336 rotate_reclaimable_page(page);
1337 }
1338
1339 if (!test_clear_page_writeback(page))
1340 BUG();
1341
1342 smp_mb__after_atomic();
1343 wake_up_page(page, PG_writeback);
1344}
1345EXPORT_SYMBOL(end_page_writeback);
1346
1347/*
1348 * After completing I/O on a page, call this routine to update the page
1349 * flags appropriately
1350 */
1351void page_endio(struct page *page, bool is_write, int err)
1352{
1353 if (!is_write) {
1354 if (!err) {
1355 SetPageUptodate(page);
1356 } else {
1357 ClearPageUptodate(page);
1358 SetPageError(page);
1359 }
1360 unlock_page(page);
1361 } else {
1362 if (err) {
1363 struct address_space *mapping;
1364
1365 SetPageError(page);
1366 mapping = page_mapping(page);
1367 if (mapping)
1368 mapping_set_error(mapping, err);
1369 }
1370 end_page_writeback(page);
1371 }
1372}
1373EXPORT_SYMBOL_GPL(page_endio);
1374
1375/**
1376 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1377 * @__page: the page to lock
1378 */
1379void __lock_page(struct page *__page)
1380{
1381 struct page *page = compound_head(__page);
1382 wait_queue_head_t *q = page_waitqueue(page);
1383 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE,
1384 EXCLUSIVE);
1385}
1386EXPORT_SYMBOL(__lock_page);
1387
1388int __lock_page_killable(struct page *__page)
1389{
1390 struct page *page = compound_head(__page);
1391 wait_queue_head_t *q = page_waitqueue(page);
1392 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE,
1393 EXCLUSIVE);
1394}
1395EXPORT_SYMBOL_GPL(__lock_page_killable);
1396
1397/*
1398 * Return values:
1399 * 1 - page is locked; mmap_sem is still held.
1400 * 0 - page is not locked.
1401 * mmap_sem has been released (up_read()), unless flags had both
1402 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1403 * which case mmap_sem is still held.
1404 *
1405 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1406 * with the page locked and the mmap_sem unperturbed.
1407 */
1408int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1409 unsigned int flags)
1410{
1411 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1412 /*
1413 * CAUTION! In this case, mmap_sem is not released
1414 * even though return 0.
1415 */
1416 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1417 return 0;
1418
1419 up_read(&mm->mmap_sem);
1420 if (flags & FAULT_FLAG_KILLABLE)
1421 wait_on_page_locked_killable(page);
1422 else
1423 wait_on_page_locked(page);
1424 return 0;
1425 } else {
1426 if (flags & FAULT_FLAG_KILLABLE) {
1427 int ret;
1428
1429 ret = __lock_page_killable(page);
1430 if (ret) {
1431 up_read(&mm->mmap_sem);
1432 return 0;
1433 }
1434 } else
1435 __lock_page(page);
1436 return 1;
1437 }
1438}
1439
1440/**
1441 * page_cache_next_miss() - Find the next gap in the page cache.
1442 * @mapping: Mapping.
1443 * @index: Index.
1444 * @max_scan: Maximum range to search.
1445 *
1446 * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
1447 * gap with the lowest index.
1448 *
1449 * This function may be called under the rcu_read_lock. However, this will
1450 * not atomically search a snapshot of the cache at a single point in time.
1451 * For example, if a gap is created at index 5, then subsequently a gap is
1452 * created at index 10, page_cache_next_miss covering both indices may
1453 * return 10 if called under the rcu_read_lock.
1454 *
1455 * Return: The index of the gap if found, otherwise an index outside the
1456 * range specified (in which case 'return - index >= max_scan' will be true).
1457 * In the rare case of index wrap-around, 0 will be returned.
1458 */
1459pgoff_t page_cache_next_miss(struct address_space *mapping,
1460 pgoff_t index, unsigned long max_scan)
1461{
1462 XA_STATE(xas, &mapping->i_pages, index);
1463
1464 while (max_scan--) {
1465 void *entry = xas_next(&xas);
1466 if (!entry || xa_is_value(entry))
1467 break;
1468 if (xas.xa_index == 0)
1469 break;
1470 }
1471
1472 return xas.xa_index;
1473}
1474EXPORT_SYMBOL(page_cache_next_miss);
1475
1476/**
1477 * page_cache_prev_miss() - Find the previous gap in the page cache.
1478 * @mapping: Mapping.
1479 * @index: Index.
1480 * @max_scan: Maximum range to search.
1481 *
1482 * Search the range [max(index - max_scan + 1, 0), index] for the
1483 * gap with the highest index.
1484 *
1485 * This function may be called under the rcu_read_lock. However, this will
1486 * not atomically search a snapshot of the cache at a single point in time.
1487 * For example, if a gap is created at index 10, then subsequently a gap is
1488 * created at index 5, page_cache_prev_miss() covering both indices may
1489 * return 5 if called under the rcu_read_lock.
1490 *
1491 * Return: The index of the gap if found, otherwise an index outside the
1492 * range specified (in which case 'index - return >= max_scan' will be true).
1493 * In the rare case of wrap-around, ULONG_MAX will be returned.
1494 */
1495pgoff_t page_cache_prev_miss(struct address_space *mapping,
1496 pgoff_t index, unsigned long max_scan)
1497{
1498 XA_STATE(xas, &mapping->i_pages, index);
1499
1500 while (max_scan--) {
1501 void *entry = xas_prev(&xas);
1502 if (!entry || xa_is_value(entry))
1503 break;
1504 if (xas.xa_index == ULONG_MAX)
1505 break;
1506 }
1507
1508 return xas.xa_index;
1509}
1510EXPORT_SYMBOL(page_cache_prev_miss);
1511
1512/**
1513 * find_get_entry - find and get a page cache entry
1514 * @mapping: the address_space to search
1515 * @offset: the page cache index
1516 *
1517 * Looks up the page cache slot at @mapping & @offset. If there is a
1518 * page cache page, it is returned with an increased refcount.
1519 *
1520 * If the slot holds a shadow entry of a previously evicted page, or a
1521 * swap entry from shmem/tmpfs, it is returned.
1522 *
1523 * Return: the found page or shadow entry, %NULL if nothing is found.
1524 */
1525struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1526{
1527 XA_STATE(xas, &mapping->i_pages, offset);
1528 struct page *page;
1529
1530 rcu_read_lock();
1531repeat:
1532 xas_reset(&xas);
1533 page = xas_load(&xas);
1534 if (xas_retry(&xas, page))
1535 goto repeat;
1536 /*
1537 * A shadow entry of a recently evicted page, or a swap entry from
1538 * shmem/tmpfs. Return it without attempting to raise page count.
1539 */
1540 if (!page || xa_is_value(page))
1541 goto out;
1542
1543 if (!page_cache_get_speculative(page))
1544 goto repeat;
1545
1546 /*
1547 * Has the page moved or been split?
1548 * This is part of the lockless pagecache protocol. See
1549 * include/linux/pagemap.h for details.
1550 */
1551 if (unlikely(page != xas_reload(&xas))) {
1552 put_page(page);
1553 goto repeat;
1554 }
1555 page = find_subpage(page, offset);
1556out:
1557 rcu_read_unlock();
1558
1559 return page;
1560}
1561EXPORT_SYMBOL(find_get_entry);
1562
1563/**
1564 * find_lock_entry - locate, pin and lock a page cache entry
1565 * @mapping: the address_space to search
1566 * @offset: the page cache index
1567 *
1568 * Looks up the page cache slot at @mapping & @offset. If there is a
1569 * page cache page, it is returned locked and with an increased
1570 * refcount.
1571 *
1572 * If the slot holds a shadow entry of a previously evicted page, or a
1573 * swap entry from shmem/tmpfs, it is returned.
1574 *
1575 * find_lock_entry() may sleep.
1576 *
1577 * Return: the found page or shadow entry, %NULL if nothing is found.
1578 */
1579struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1580{
1581 struct page *page;
1582
1583repeat:
1584 page = find_get_entry(mapping, offset);
1585 if (page && !xa_is_value(page)) {
1586 lock_page(page);
1587 /* Has the page been truncated? */
1588 if (unlikely(page_mapping(page) != mapping)) {
1589 unlock_page(page);
1590 put_page(page);
1591 goto repeat;
1592 }
1593 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
1594 }
1595 return page;
1596}
1597EXPORT_SYMBOL(find_lock_entry);
1598
1599/**
1600 * pagecache_get_page - find and get a page reference
1601 * @mapping: the address_space to search
1602 * @offset: the page index
1603 * @fgp_flags: PCG flags
1604 * @gfp_mask: gfp mask to use for the page cache data page allocation
1605 *
1606 * Looks up the page cache slot at @mapping & @offset.
1607 *
1608 * PCG flags modify how the page is returned.
1609 *
1610 * @fgp_flags can be:
1611 *
1612 * - FGP_ACCESSED: the page will be marked accessed
1613 * - FGP_LOCK: Page is return locked
1614 * - FGP_CREAT: If page is not present then a new page is allocated using
1615 * @gfp_mask and added to the page cache and the VM's LRU
1616 * list. The page is returned locked and with an increased
1617 * refcount.
1618 * - FGP_FOR_MMAP: Similar to FGP_CREAT, only we want to allow the caller to do
1619 * its own locking dance if the page is already in cache, or unlock the page
1620 * before returning if we had to add the page to pagecache.
1621 *
1622 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1623 * if the GFP flags specified for FGP_CREAT are atomic.
1624 *
1625 * If there is a page cache page, it is returned with an increased refcount.
1626 *
1627 * Return: the found page or %NULL otherwise.
1628 */
1629struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1630 int fgp_flags, gfp_t gfp_mask)
1631{
1632 struct page *page;
1633
1634repeat:
1635 page = find_get_entry(mapping, offset);
1636 if (xa_is_value(page))
1637 page = NULL;
1638 if (!page)
1639 goto no_page;
1640
1641 if (fgp_flags & FGP_LOCK) {
1642 if (fgp_flags & FGP_NOWAIT) {
1643 if (!trylock_page(page)) {
1644 put_page(page);
1645 return NULL;
1646 }
1647 } else {
1648 lock_page(page);
1649 }
1650
1651 /* Has the page been truncated? */
1652 if (unlikely(compound_head(page)->mapping != mapping)) {
1653 unlock_page(page);
1654 put_page(page);
1655 goto repeat;
1656 }
1657 VM_BUG_ON_PAGE(page->index != offset, page);
1658 }
1659
1660 if (fgp_flags & FGP_ACCESSED)
1661 mark_page_accessed(page);
1662
1663no_page:
1664 if (!page && (fgp_flags & FGP_CREAT)) {
1665 int err;
1666 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1667 gfp_mask |= __GFP_WRITE;
1668 if (fgp_flags & FGP_NOFS)
1669 gfp_mask &= ~__GFP_FS;
1670
1671 page = __page_cache_alloc(gfp_mask);
1672 if (!page)
1673 return NULL;
1674
1675 if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
1676 fgp_flags |= FGP_LOCK;
1677
1678 /* Init accessed so avoid atomic mark_page_accessed later */
1679 if (fgp_flags & FGP_ACCESSED)
1680 __SetPageReferenced(page);
1681
1682 err = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
1683 if (unlikely(err)) {
1684 put_page(page);
1685 page = NULL;
1686 if (err == -EEXIST)
1687 goto repeat;
1688 }
1689
1690 /*
1691 * add_to_page_cache_lru locks the page, and for mmap we expect
1692 * an unlocked page.
1693 */
1694 if (page && (fgp_flags & FGP_FOR_MMAP))
1695 unlock_page(page);
1696 }
1697
1698 return page;
1699}
1700EXPORT_SYMBOL(pagecache_get_page);
1701
1702/**
1703 * find_get_entries - gang pagecache lookup
1704 * @mapping: The address_space to search
1705 * @start: The starting page cache index
1706 * @nr_entries: The maximum number of entries
1707 * @entries: Where the resulting entries are placed
1708 * @indices: The cache indices corresponding to the entries in @entries
1709 *
1710 * find_get_entries() will search for and return a group of up to
1711 * @nr_entries entries in the mapping. The entries are placed at
1712 * @entries. find_get_entries() takes a reference against any actual
1713 * pages it returns.
1714 *
1715 * The search returns a group of mapping-contiguous page cache entries
1716 * with ascending indexes. There may be holes in the indices due to
1717 * not-present pages.
1718 *
1719 * Any shadow entries of evicted pages, or swap entries from
1720 * shmem/tmpfs, are included in the returned array.
1721 *
1722 * Return: the number of pages and shadow entries which were found.
1723 */
1724unsigned find_get_entries(struct address_space *mapping,
1725 pgoff_t start, unsigned int nr_entries,
1726 struct page **entries, pgoff_t *indices)
1727{
1728 XA_STATE(xas, &mapping->i_pages, start);
1729 struct page *page;
1730 unsigned int ret = 0;
1731
1732 if (!nr_entries)
1733 return 0;
1734
1735 rcu_read_lock();
1736 xas_for_each(&xas, page, ULONG_MAX) {
1737 if (xas_retry(&xas, page))
1738 continue;
1739 /*
1740 * A shadow entry of a recently evicted page, a swap
1741 * entry from shmem/tmpfs or a DAX entry. Return it
1742 * without attempting to raise page count.
1743 */
1744 if (xa_is_value(page))
1745 goto export;
1746
1747 if (!page_cache_get_speculative(page))
1748 goto retry;
1749
1750 /* Has the page moved or been split? */
1751 if (unlikely(page != xas_reload(&xas)))
1752 goto put_page;
1753 page = find_subpage(page, xas.xa_index);
1754
1755export:
1756 indices[ret] = xas.xa_index;
1757 entries[ret] = page;
1758 if (++ret == nr_entries)
1759 break;
1760 continue;
1761put_page:
1762 put_page(page);
1763retry:
1764 xas_reset(&xas);
1765 }
1766 rcu_read_unlock();
1767 return ret;
1768}
1769
1770/**
1771 * find_get_pages_range - gang pagecache lookup
1772 * @mapping: The address_space to search
1773 * @start: The starting page index
1774 * @end: The final page index (inclusive)
1775 * @nr_pages: The maximum number of pages
1776 * @pages: Where the resulting pages are placed
1777 *
1778 * find_get_pages_range() will search for and return a group of up to @nr_pages
1779 * pages in the mapping starting at index @start and up to index @end
1780 * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
1781 * a reference against the returned pages.
1782 *
1783 * The search returns a group of mapping-contiguous pages with ascending
1784 * indexes. There may be holes in the indices due to not-present pages.
1785 * We also update @start to index the next page for the traversal.
1786 *
1787 * Return: the number of pages which were found. If this number is
1788 * smaller than @nr_pages, the end of specified range has been
1789 * reached.
1790 */
1791unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
1792 pgoff_t end, unsigned int nr_pages,
1793 struct page **pages)
1794{
1795 XA_STATE(xas, &mapping->i_pages, *start);
1796 struct page *page;
1797 unsigned ret = 0;
1798
1799 if (unlikely(!nr_pages))
1800 return 0;
1801
1802 rcu_read_lock();
1803 xas_for_each(&xas, page, end) {
1804 if (xas_retry(&xas, page))
1805 continue;
1806 /* Skip over shadow, swap and DAX entries */
1807 if (xa_is_value(page))
1808 continue;
1809
1810 if (!page_cache_get_speculative(page))
1811 goto retry;
1812
1813 /* Has the page moved or been split? */
1814 if (unlikely(page != xas_reload(&xas)))
1815 goto put_page;
1816
1817 pages[ret] = find_subpage(page, xas.xa_index);
1818 if (++ret == nr_pages) {
1819 *start = xas.xa_index + 1;
1820 goto out;
1821 }
1822 continue;
1823put_page:
1824 put_page(page);
1825retry:
1826 xas_reset(&xas);
1827 }
1828
1829 /*
1830 * We come here when there is no page beyond @end. We take care to not
1831 * overflow the index @start as it confuses some of the callers. This
1832 * breaks the iteration when there is a page at index -1 but that is
1833 * already broken anyway.
1834 */
1835 if (end == (pgoff_t)-1)
1836 *start = (pgoff_t)-1;
1837 else
1838 *start = end + 1;
1839out:
1840 rcu_read_unlock();
1841
1842 return ret;
1843}
1844
1845/**
1846 * find_get_pages_contig - gang contiguous pagecache lookup
1847 * @mapping: The address_space to search
1848 * @index: The starting page index
1849 * @nr_pages: The maximum number of pages
1850 * @pages: Where the resulting pages are placed
1851 *
1852 * find_get_pages_contig() works exactly like find_get_pages(), except
1853 * that the returned number of pages are guaranteed to be contiguous.
1854 *
1855 * Return: the number of pages which were found.
1856 */
1857unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1858 unsigned int nr_pages, struct page **pages)
1859{
1860 XA_STATE(xas, &mapping->i_pages, index);
1861 struct page *page;
1862 unsigned int ret = 0;
1863
1864 if (unlikely(!nr_pages))
1865 return 0;
1866
1867 rcu_read_lock();
1868 for (page = xas_load(&xas); page; page = xas_next(&xas)) {
1869 if (xas_retry(&xas, page))
1870 continue;
1871 /*
1872 * If the entry has been swapped out, we can stop looking.
1873 * No current caller is looking for DAX entries.
1874 */
1875 if (xa_is_value(page))
1876 break;
1877
1878 if (!page_cache_get_speculative(page))
1879 goto retry;
1880
1881 /* Has the page moved or been split? */
1882 if (unlikely(page != xas_reload(&xas)))
1883 goto put_page;
1884
1885 pages[ret] = find_subpage(page, xas.xa_index);
1886 if (++ret == nr_pages)
1887 break;
1888 continue;
1889put_page:
1890 put_page(page);
1891retry:
1892 xas_reset(&xas);
1893 }
1894 rcu_read_unlock();
1895 return ret;
1896}
1897EXPORT_SYMBOL(find_get_pages_contig);
1898
1899/**
1900 * find_get_pages_range_tag - find and return pages in given range matching @tag
1901 * @mapping: the address_space to search
1902 * @index: the starting page index
1903 * @end: The final page index (inclusive)
1904 * @tag: the tag index
1905 * @nr_pages: the maximum number of pages
1906 * @pages: where the resulting pages are placed
1907 *
1908 * Like find_get_pages, except we only return pages which are tagged with
1909 * @tag. We update @index to index the next page for the traversal.
1910 *
1911 * Return: the number of pages which were found.
1912 */
1913unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
1914 pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
1915 struct page **pages)
1916{
1917 XA_STATE(xas, &mapping->i_pages, *index);
1918 struct page *page;
1919 unsigned ret = 0;
1920
1921 if (unlikely(!nr_pages))
1922 return 0;
1923
1924 rcu_read_lock();
1925 xas_for_each_marked(&xas, page, end, tag) {
1926 if (xas_retry(&xas, page))
1927 continue;
1928 /*
1929 * Shadow entries should never be tagged, but this iteration
1930 * is lockless so there is a window for page reclaim to evict
1931 * a page we saw tagged. Skip over it.
1932 */
1933 if (xa_is_value(page))
1934 continue;
1935
1936 if (!page_cache_get_speculative(page))
1937 goto retry;
1938
1939 /* Has the page moved or been split? */
1940 if (unlikely(page != xas_reload(&xas)))
1941 goto put_page;
1942
1943 pages[ret] = find_subpage(page, xas.xa_index);
1944 if (++ret == nr_pages) {
1945 *index = xas.xa_index + 1;
1946 goto out;
1947 }
1948 continue;
1949put_page:
1950 put_page(page);
1951retry:
1952 xas_reset(&xas);
1953 }
1954
1955 /*
1956 * We come here when we got to @end. We take care to not overflow the
1957 * index @index as it confuses some of the callers. This breaks the
1958 * iteration when there is a page at index -1 but that is already
1959 * broken anyway.
1960 */
1961 if (end == (pgoff_t)-1)
1962 *index = (pgoff_t)-1;
1963 else
1964 *index = end + 1;
1965out:
1966 rcu_read_unlock();
1967
1968 return ret;
1969}
1970EXPORT_SYMBOL(find_get_pages_range_tag);
1971
1972/*
1973 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1974 * a _large_ part of the i/o request. Imagine the worst scenario:
1975 *
1976 * ---R__________________________________________B__________
1977 * ^ reading here ^ bad block(assume 4k)
1978 *
1979 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1980 * => failing the whole request => read(R) => read(R+1) =>
1981 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1982 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1983 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1984 *
1985 * It is going insane. Fix it by quickly scaling down the readahead size.
1986 */
1987static void shrink_readahead_size_eio(struct file *filp,
1988 struct file_ra_state *ra)
1989{
1990 ra->ra_pages /= 4;
1991}
1992
1993/**
1994 * generic_file_buffered_read - generic file read routine
1995 * @iocb: the iocb to read
1996 * @iter: data destination
1997 * @written: already copied
1998 *
1999 * This is a generic file read routine, and uses the
2000 * mapping->a_ops->readpage() function for the actual low-level stuff.
2001 *
2002 * This is really ugly. But the goto's actually try to clarify some
2003 * of the logic when it comes to error handling etc.
2004 *
2005 * Return:
2006 * * total number of bytes copied, including those the were already @written
2007 * * negative error code if nothing was copied
2008 */
2009static ssize_t generic_file_buffered_read(struct kiocb *iocb,
2010 struct iov_iter *iter, ssize_t written)
2011{
2012 struct file *filp = iocb->ki_filp;
2013 struct address_space *mapping = filp->f_mapping;
2014 struct inode *inode = mapping->host;
2015 struct file_ra_state *ra = &filp->f_ra;
2016 loff_t *ppos = &iocb->ki_pos;
2017 pgoff_t index;
2018 pgoff_t last_index;
2019 pgoff_t prev_index;
2020 unsigned long offset; /* offset into pagecache page */
2021 unsigned int prev_offset;
2022 int error = 0;
2023
2024 if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
2025 return 0;
2026 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
2027
2028 index = *ppos >> PAGE_SHIFT;
2029 prev_index = ra->prev_pos >> PAGE_SHIFT;
2030 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
2031 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
2032 offset = *ppos & ~PAGE_MASK;
2033
2034 for (;;) {
2035 struct page *page;
2036 pgoff_t end_index;
2037 loff_t isize;
2038 unsigned long nr, ret;
2039
2040 cond_resched();
2041find_page:
2042 if (fatal_signal_pending(current)) {
2043 error = -EINTR;
2044 goto out;
2045 }
2046
2047 page = find_get_page(mapping, index);
2048 if (!page) {
2049 if (iocb->ki_flags & IOCB_NOWAIT)
2050 goto would_block;
2051 page_cache_sync_readahead(mapping,
2052 ra, filp,
2053 index, last_index - index);
2054 page = find_get_page(mapping, index);
2055 if (unlikely(page == NULL))
2056 goto no_cached_page;
2057 }
2058 if (PageReadahead(page)) {
2059 page_cache_async_readahead(mapping,
2060 ra, filp, page,
2061 index, last_index - index);
2062 }
2063 if (!PageUptodate(page)) {
2064 if (iocb->ki_flags & IOCB_NOWAIT) {
2065 put_page(page);
2066 goto would_block;
2067 }
2068
2069 /*
2070 * See comment in do_read_cache_page on why
2071 * wait_on_page_locked is used to avoid unnecessarily
2072 * serialisations and why it's safe.
2073 */
2074 error = wait_on_page_locked_killable(page);
2075 if (unlikely(error))
2076 goto readpage_error;
2077 if (PageUptodate(page))
2078 goto page_ok;
2079
2080 if (inode->i_blkbits == PAGE_SHIFT ||
2081 !mapping->a_ops->is_partially_uptodate)
2082 goto page_not_up_to_date;
2083 /* pipes can't handle partially uptodate pages */
2084 if (unlikely(iov_iter_is_pipe(iter)))
2085 goto page_not_up_to_date;
2086 if (!trylock_page(page))
2087 goto page_not_up_to_date;
2088 /* Did it get truncated before we got the lock? */
2089 if (!page->mapping)
2090 goto page_not_up_to_date_locked;
2091 if (!mapping->a_ops->is_partially_uptodate(page,
2092 offset, iter->count))
2093 goto page_not_up_to_date_locked;
2094 unlock_page(page);
2095 }
2096page_ok:
2097 /*
2098 * i_size must be checked after we know the page is Uptodate.
2099 *
2100 * Checking i_size after the check allows us to calculate
2101 * the correct value for "nr", which means the zero-filled
2102 * part of the page is not copied back to userspace (unless
2103 * another truncate extends the file - this is desired though).
2104 */
2105
2106 isize = i_size_read(inode);
2107 end_index = (isize - 1) >> PAGE_SHIFT;
2108 if (unlikely(!isize || index > end_index)) {
2109 put_page(page);
2110 goto out;
2111 }
2112
2113 /* nr is the maximum number of bytes to copy from this page */
2114 nr = PAGE_SIZE;
2115 if (index == end_index) {
2116 nr = ((isize - 1) & ~PAGE_MASK) + 1;
2117 if (nr <= offset) {
2118 put_page(page);
2119 goto out;
2120 }
2121 }
2122 nr = nr - offset;
2123
2124 /* If users can be writing to this page using arbitrary
2125 * virtual addresses, take care about potential aliasing
2126 * before reading the page on the kernel side.
2127 */
2128 if (mapping_writably_mapped(mapping))
2129 flush_dcache_page(page);
2130
2131 /*
2132 * When a sequential read accesses a page several times,
2133 * only mark it as accessed the first time.
2134 */
2135 if (prev_index != index || offset != prev_offset)
2136 mark_page_accessed(page);
2137 prev_index = index;
2138
2139 /*
2140 * Ok, we have the page, and it's up-to-date, so
2141 * now we can copy it to user space...
2142 */
2143
2144 ret = copy_page_to_iter(page, offset, nr, iter);
2145 offset += ret;
2146 index += offset >> PAGE_SHIFT;
2147 offset &= ~PAGE_MASK;
2148 prev_offset = offset;
2149
2150 put_page(page);
2151 written += ret;
2152 if (!iov_iter_count(iter))
2153 goto out;
2154 if (ret < nr) {
2155 error = -EFAULT;
2156 goto out;
2157 }
2158 continue;
2159
2160page_not_up_to_date:
2161 /* Get exclusive access to the page ... */
2162 error = lock_page_killable(page);
2163 if (unlikely(error))
2164 goto readpage_error;
2165
2166page_not_up_to_date_locked:
2167 /* Did it get truncated before we got the lock? */
2168 if (!page->mapping) {
2169 unlock_page(page);
2170 put_page(page);
2171 continue;
2172 }
2173
2174 /* Did somebody else fill it already? */
2175 if (PageUptodate(page)) {
2176 unlock_page(page);
2177 goto page_ok;
2178 }
2179
2180readpage:
2181 /*
2182 * A previous I/O error may have been due to temporary
2183 * failures, eg. multipath errors.
2184 * PG_error will be set again if readpage fails.
2185 */
2186 ClearPageError(page);
2187 /* Start the actual read. The read will unlock the page. */
2188 error = mapping->a_ops->readpage(filp, page);
2189
2190 if (unlikely(error)) {
2191 if (error == AOP_TRUNCATED_PAGE) {
2192 put_page(page);
2193 error = 0;
2194 goto find_page;
2195 }
2196 goto readpage_error;
2197 }
2198
2199 if (!PageUptodate(page)) {
2200 error = lock_page_killable(page);
2201 if (unlikely(error))
2202 goto readpage_error;
2203 if (!PageUptodate(page)) {
2204 if (page->mapping == NULL) {
2205 /*
2206 * invalidate_mapping_pages got it
2207 */
2208 unlock_page(page);
2209 put_page(page);
2210 goto find_page;
2211 }
2212 unlock_page(page);
2213 shrink_readahead_size_eio(filp, ra);
2214 error = -EIO;
2215 goto readpage_error;
2216 }
2217 unlock_page(page);
2218 }
2219
2220 goto page_ok;
2221
2222readpage_error:
2223 /* UHHUH! A synchronous read error occurred. Report it */
2224 put_page(page);
2225 goto out;
2226
2227no_cached_page:
2228 /*
2229 * Ok, it wasn't cached, so we need to create a new
2230 * page..
2231 */
2232 page = page_cache_alloc(mapping);
2233 if (!page) {
2234 error = -ENOMEM;
2235 goto out;
2236 }
2237 error = add_to_page_cache_lru(page, mapping, index,
2238 mapping_gfp_constraint(mapping, GFP_KERNEL));
2239 if (error) {
2240 put_page(page);
2241 if (error == -EEXIST) {
2242 error = 0;
2243 goto find_page;
2244 }
2245 goto out;
2246 }
2247 goto readpage;
2248 }
2249
2250would_block:
2251 error = -EAGAIN;
2252out:
2253 ra->prev_pos = prev_index;
2254 ra->prev_pos <<= PAGE_SHIFT;
2255 ra->prev_pos |= prev_offset;
2256
2257 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
2258 file_accessed(filp);
2259 return written ? written : error;
2260}
2261
2262/**
2263 * generic_file_read_iter - generic filesystem read routine
2264 * @iocb: kernel I/O control block
2265 * @iter: destination for the data read
2266 *
2267 * This is the "read_iter()" routine for all filesystems
2268 * that can use the page cache directly.
2269 * Return:
2270 * * number of bytes copied, even for partial reads
2271 * * negative error code if nothing was read
2272 */
2273ssize_t
2274generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2275{
2276 size_t count = iov_iter_count(iter);
2277 ssize_t retval = 0;
2278
2279 if (!count)
2280 goto out; /* skip atime */
2281
2282 if (iocb->ki_flags & IOCB_DIRECT) {
2283 struct file *file = iocb->ki_filp;
2284 struct address_space *mapping = file->f_mapping;
2285 struct inode *inode = mapping->host;
2286 loff_t size;
2287
2288 size = i_size_read(inode);
2289 if (iocb->ki_flags & IOCB_NOWAIT) {
2290 if (filemap_range_has_page(mapping, iocb->ki_pos,
2291 iocb->ki_pos + count - 1))
2292 return -EAGAIN;
2293 } else {
2294 retval = filemap_write_and_wait_range(mapping,
2295 iocb->ki_pos,
2296 iocb->ki_pos + count - 1);
2297 if (retval < 0)
2298 goto out;
2299 }
2300
2301 file_accessed(file);
2302
2303 retval = mapping->a_ops->direct_IO(iocb, iter);
2304 if (retval >= 0) {
2305 iocb->ki_pos += retval;
2306 count -= retval;
2307 }
2308 iov_iter_revert(iter, count - iov_iter_count(iter));
2309
2310 /*
2311 * Btrfs can have a short DIO read if we encounter
2312 * compressed extents, so if there was an error, or if
2313 * we've already read everything we wanted to, or if
2314 * there was a short read because we hit EOF, go ahead
2315 * and return. Otherwise fallthrough to buffered io for
2316 * the rest of the read. Buffered reads will not work for
2317 * DAX files, so don't bother trying.
2318 */
2319 if (retval < 0 || !count || iocb->ki_pos >= size ||
2320 IS_DAX(inode))
2321 goto out;
2322 }
2323
2324 retval = generic_file_buffered_read(iocb, iter, retval);
2325out:
2326 return retval;
2327}
2328EXPORT_SYMBOL(generic_file_read_iter);
2329
2330#ifdef CONFIG_MMU
2331#define MMAP_LOTSAMISS (100)
2332static struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
2333 struct file *fpin)
2334{
2335 int flags = vmf->flags;
2336
2337 if (fpin)
2338 return fpin;
2339
2340 /*
2341 * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or
2342 * anything, so we only pin the file and drop the mmap_sem if only
2343 * FAULT_FLAG_ALLOW_RETRY is set.
2344 */
2345 if ((flags & (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT)) ==
2346 FAULT_FLAG_ALLOW_RETRY) {
2347 fpin = get_file(vmf->vma->vm_file);
2348 up_read(&vmf->vma->vm_mm->mmap_sem);
2349 }
2350 return fpin;
2351}
2352
2353/*
2354 * lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_sem
2355 * @vmf - the vm_fault for this fault.
2356 * @page - the page to lock.
2357 * @fpin - the pointer to the file we may pin (or is already pinned).
2358 *
2359 * This works similar to lock_page_or_retry in that it can drop the mmap_sem.
2360 * It differs in that it actually returns the page locked if it returns 1 and 0
2361 * if it couldn't lock the page. If we did have to drop the mmap_sem then fpin
2362 * will point to the pinned file and needs to be fput()'ed at a later point.
2363 */
2364static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
2365 struct file **fpin)
2366{
2367 if (trylock_page(page))
2368 return 1;
2369
2370 /*
2371 * NOTE! This will make us return with VM_FAULT_RETRY, but with
2372 * the mmap_sem still held. That's how FAULT_FLAG_RETRY_NOWAIT
2373 * is supposed to work. We have way too many special cases..
2374 */
2375 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
2376 return 0;
2377
2378 *fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
2379 if (vmf->flags & FAULT_FLAG_KILLABLE) {
2380 if (__lock_page_killable(page)) {
2381 /*
2382 * We didn't have the right flags to drop the mmap_sem,
2383 * but all fault_handlers only check for fatal signals
2384 * if we return VM_FAULT_RETRY, so we need to drop the
2385 * mmap_sem here and return 0 if we don't have a fpin.
2386 */
2387 if (*fpin == NULL)
2388 up_read(&vmf->vma->vm_mm->mmap_sem);
2389 return 0;
2390 }
2391 } else
2392 __lock_page(page);
2393 return 1;
2394}
2395
2396
2397/*
2398 * Synchronous readahead happens when we don't even find a page in the page
2399 * cache at all. We don't want to perform IO under the mmap sem, so if we have
2400 * to drop the mmap sem we return the file that was pinned in order for us to do
2401 * that. If we didn't pin a file then we return NULL. The file that is
2402 * returned needs to be fput()'ed when we're done with it.
2403 */
2404static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
2405{
2406 struct file *file = vmf->vma->vm_file;
2407 struct file_ra_state *ra = &file->f_ra;
2408 struct address_space *mapping = file->f_mapping;
2409 struct file *fpin = NULL;
2410 pgoff_t offset = vmf->pgoff;
2411
2412 /* If we don't want any read-ahead, don't bother */
2413 if (vmf->vma->vm_flags & VM_RAND_READ)
2414 return fpin;
2415 if (!ra->ra_pages)
2416 return fpin;
2417
2418 if (vmf->vma->vm_flags & VM_SEQ_READ) {
2419 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2420 page_cache_sync_readahead(mapping, ra, file, offset,
2421 ra->ra_pages);
2422 return fpin;
2423 }
2424
2425 /* Avoid banging the cache line if not needed */
2426 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
2427 ra->mmap_miss++;
2428
2429 /*
2430 * Do we miss much more than hit in this file? If so,
2431 * stop bothering with read-ahead. It will only hurt.
2432 */
2433 if (ra->mmap_miss > MMAP_LOTSAMISS)
2434 return fpin;
2435
2436 /*
2437 * mmap read-around
2438 */
2439 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2440 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
2441 ra->size = ra->ra_pages;
2442 ra->async_size = ra->ra_pages / 4;
2443 ra_submit(ra, mapping, file);
2444 return fpin;
2445}
2446
2447/*
2448 * Asynchronous readahead happens when we find the page and PG_readahead,
2449 * so we want to possibly extend the readahead further. We return the file that
2450 * was pinned if we have to drop the mmap_sem in order to do IO.
2451 */
2452static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
2453 struct page *page)
2454{
2455 struct file *file = vmf->vma->vm_file;
2456 struct file_ra_state *ra = &file->f_ra;
2457 struct address_space *mapping = file->f_mapping;
2458 struct file *fpin = NULL;
2459 pgoff_t offset = vmf->pgoff;
2460
2461 /* If we don't want any read-ahead, don't bother */
2462 if (vmf->vma->vm_flags & VM_RAND_READ)
2463 return fpin;
2464 if (ra->mmap_miss > 0)
2465 ra->mmap_miss--;
2466 if (PageReadahead(page)) {
2467 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2468 page_cache_async_readahead(mapping, ra, file,
2469 page, offset, ra->ra_pages);
2470 }
2471 return fpin;
2472}
2473
2474/**
2475 * filemap_fault - read in file data for page fault handling
2476 * @vmf: struct vm_fault containing details of the fault
2477 *
2478 * filemap_fault() is invoked via the vma operations vector for a
2479 * mapped memory region to read in file data during a page fault.
2480 *
2481 * The goto's are kind of ugly, but this streamlines the normal case of having
2482 * it in the page cache, and handles the special cases reasonably without
2483 * having a lot of duplicated code.
2484 *
2485 * vma->vm_mm->mmap_sem must be held on entry.
2486 *
2487 * If our return value has VM_FAULT_RETRY set, it's because the mmap_sem
2488 * may be dropped before doing I/O or by lock_page_maybe_drop_mmap().
2489 *
2490 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2491 * has not been released.
2492 *
2493 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2494 *
2495 * Return: bitwise-OR of %VM_FAULT_ codes.
2496 */
2497vm_fault_t filemap_fault(struct vm_fault *vmf)
2498{
2499 int error;
2500 struct file *file = vmf->vma->vm_file;
2501 struct file *fpin = NULL;
2502 struct address_space *mapping = file->f_mapping;
2503 struct file_ra_state *ra = &file->f_ra;
2504 struct inode *inode = mapping->host;
2505 pgoff_t offset = vmf->pgoff;
2506 pgoff_t max_off;
2507 struct page *page;
2508 vm_fault_t ret = 0;
2509
2510 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2511 if (unlikely(offset >= max_off))
2512 return VM_FAULT_SIGBUS;
2513
2514 /*
2515 * Do we have something in the page cache already?
2516 */
2517 page = find_get_page(mapping, offset);
2518 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2519 /*
2520 * We found the page, so try async readahead before
2521 * waiting for the lock.
2522 */
2523 fpin = do_async_mmap_readahead(vmf, page);
2524 } else if (!page) {
2525 /* No page in the page cache at all */
2526 count_vm_event(PGMAJFAULT);
2527 count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
2528 ret = VM_FAULT_MAJOR;
2529 fpin = do_sync_mmap_readahead(vmf);
2530retry_find:
2531 page = pagecache_get_page(mapping, offset,
2532 FGP_CREAT|FGP_FOR_MMAP,
2533 vmf->gfp_mask);
2534 if (!page) {
2535 if (fpin)
2536 goto out_retry;
2537 return vmf_error(-ENOMEM);
2538 }
2539 }
2540
2541 if (!lock_page_maybe_drop_mmap(vmf, page, &fpin))
2542 goto out_retry;
2543
2544 /* Did it get truncated? */
2545 if (unlikely(compound_head(page)->mapping != mapping)) {
2546 unlock_page(page);
2547 put_page(page);
2548 goto retry_find;
2549 }
2550 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
2551
2552 /*
2553 * We have a locked page in the page cache, now we need to check
2554 * that it's up-to-date. If not, it is going to be due to an error.
2555 */
2556 if (unlikely(!PageUptodate(page)))
2557 goto page_not_uptodate;
2558
2559 /*
2560 * We've made it this far and we had to drop our mmap_sem, now is the
2561 * time to return to the upper layer and have it re-find the vma and
2562 * redo the fault.
2563 */
2564 if (fpin) {
2565 unlock_page(page);
2566 goto out_retry;
2567 }
2568
2569 /*
2570 * Found the page and have a reference on it.
2571 * We must recheck i_size under page lock.
2572 */
2573 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2574 if (unlikely(offset >= max_off)) {
2575 unlock_page(page);
2576 put_page(page);
2577 return VM_FAULT_SIGBUS;
2578 }
2579
2580 vmf->page = page;
2581 return ret | VM_FAULT_LOCKED;
2582
2583page_not_uptodate:
2584 /*
2585 * Umm, take care of errors if the page isn't up-to-date.
2586 * Try to re-read it _once_. We do this synchronously,
2587 * because there really aren't any performance issues here
2588 * and we need to check for errors.
2589 */
2590 ClearPageError(page);
2591 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2592 error = mapping->a_ops->readpage(file, page);
2593 if (!error) {
2594 wait_on_page_locked(page);
2595 if (!PageUptodate(page))
2596 error = -EIO;
2597 }
2598 if (fpin)
2599 goto out_retry;
2600 put_page(page);
2601
2602 if (!error || error == AOP_TRUNCATED_PAGE)
2603 goto retry_find;
2604
2605 /* Things didn't work out. Return zero to tell the mm layer so. */
2606 shrink_readahead_size_eio(file, ra);
2607 return VM_FAULT_SIGBUS;
2608
2609out_retry:
2610 /*
2611 * We dropped the mmap_sem, we need to return to the fault handler to
2612 * re-find the vma and come back and find our hopefully still populated
2613 * page.
2614 */
2615 if (page)
2616 put_page(page);
2617 if (fpin)
2618 fput(fpin);
2619 return ret | VM_FAULT_RETRY;
2620}
2621EXPORT_SYMBOL(filemap_fault);
2622
2623void filemap_map_pages(struct vm_fault *vmf,
2624 pgoff_t start_pgoff, pgoff_t end_pgoff)
2625{
2626 struct file *file = vmf->vma->vm_file;
2627 struct address_space *mapping = file->f_mapping;
2628 pgoff_t last_pgoff = start_pgoff;
2629 unsigned long max_idx;
2630 XA_STATE(xas, &mapping->i_pages, start_pgoff);
2631 struct page *page;
2632
2633 rcu_read_lock();
2634 xas_for_each(&xas, page, end_pgoff) {
2635 if (xas_retry(&xas, page))
2636 continue;
2637 if (xa_is_value(page))
2638 goto next;
2639
2640 /*
2641 * Check for a locked page first, as a speculative
2642 * reference may adversely influence page migration.
2643 */
2644 if (PageLocked(page))
2645 goto next;
2646 if (!page_cache_get_speculative(page))
2647 goto next;
2648
2649 /* Has the page moved or been split? */
2650 if (unlikely(page != xas_reload(&xas)))
2651 goto skip;
2652 page = find_subpage(page, xas.xa_index);
2653
2654 if (!PageUptodate(page) ||
2655 PageReadahead(page) ||
2656 PageHWPoison(page))
2657 goto skip;
2658 if (!trylock_page(page))
2659 goto skip;
2660
2661 if (page->mapping != mapping || !PageUptodate(page))
2662 goto unlock;
2663
2664 max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2665 if (page->index >= max_idx)
2666 goto unlock;
2667
2668 if (file->f_ra.mmap_miss > 0)
2669 file->f_ra.mmap_miss--;
2670
2671 vmf->address += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
2672 if (vmf->pte)
2673 vmf->pte += xas.xa_index - last_pgoff;
2674 last_pgoff = xas.xa_index;
2675 if (alloc_set_pte(vmf, NULL, page))
2676 goto unlock;
2677 unlock_page(page);
2678 goto next;
2679unlock:
2680 unlock_page(page);
2681skip:
2682 put_page(page);
2683next:
2684 /* Huge page is mapped? No need to proceed. */
2685 if (pmd_trans_huge(*vmf->pmd))
2686 break;
2687 }
2688 rcu_read_unlock();
2689}
2690EXPORT_SYMBOL(filemap_map_pages);
2691
2692vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
2693{
2694 struct page *page = vmf->page;
2695 struct inode *inode = file_inode(vmf->vma->vm_file);
2696 vm_fault_t ret = VM_FAULT_LOCKED;
2697
2698 sb_start_pagefault(inode->i_sb);
2699 file_update_time(vmf->vma->vm_file);
2700 lock_page(page);
2701 if (page->mapping != inode->i_mapping) {
2702 unlock_page(page);
2703 ret = VM_FAULT_NOPAGE;
2704 goto out;
2705 }
2706 /*
2707 * We mark the page dirty already here so that when freeze is in
2708 * progress, we are guaranteed that writeback during freezing will
2709 * see the dirty page and writeprotect it again.
2710 */
2711 set_page_dirty(page);
2712 wait_for_stable_page(page);
2713out:
2714 sb_end_pagefault(inode->i_sb);
2715 return ret;
2716}
2717
2718const struct vm_operations_struct generic_file_vm_ops = {
2719 .fault = filemap_fault,
2720 .map_pages = filemap_map_pages,
2721 .page_mkwrite = filemap_page_mkwrite,
2722};
2723
2724/* This is used for a general mmap of a disk file */
2725
2726int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2727{
2728 struct address_space *mapping = file->f_mapping;
2729
2730 if (!mapping->a_ops->readpage)
2731 return -ENOEXEC;
2732 file_accessed(file);
2733 vma->vm_ops = &generic_file_vm_ops;
2734 return 0;
2735}
2736
2737/*
2738 * This is for filesystems which do not implement ->writepage.
2739 */
2740int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2741{
2742 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2743 return -EINVAL;
2744 return generic_file_mmap(file, vma);
2745}
2746#else
2747vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
2748{
2749 return VM_FAULT_SIGBUS;
2750}
2751int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2752{
2753 return -ENOSYS;
2754}
2755int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2756{
2757 return -ENOSYS;
2758}
2759#endif /* CONFIG_MMU */
2760
2761EXPORT_SYMBOL(filemap_page_mkwrite);
2762EXPORT_SYMBOL(generic_file_mmap);
2763EXPORT_SYMBOL(generic_file_readonly_mmap);
2764
2765static struct page *wait_on_page_read(struct page *page)
2766{
2767 if (!IS_ERR(page)) {
2768 wait_on_page_locked(page);
2769 if (!PageUptodate(page)) {
2770 put_page(page);
2771 page = ERR_PTR(-EIO);
2772 }
2773 }
2774 return page;
2775}
2776
2777static struct page *do_read_cache_page(struct address_space *mapping,
2778 pgoff_t index,
2779 int (*filler)(void *, struct page *),
2780 void *data,
2781 gfp_t gfp)
2782{
2783 struct page *page;
2784 int err;
2785repeat:
2786 page = find_get_page(mapping, index);
2787 if (!page) {
2788 page = __page_cache_alloc(gfp);
2789 if (!page)
2790 return ERR_PTR(-ENOMEM);
2791 err = add_to_page_cache_lru(page, mapping, index, gfp);
2792 if (unlikely(err)) {
2793 put_page(page);
2794 if (err == -EEXIST)
2795 goto repeat;
2796 /* Presumably ENOMEM for xarray node */
2797 return ERR_PTR(err);
2798 }
2799
2800filler:
2801 if (filler)
2802 err = filler(data, page);
2803 else
2804 err = mapping->a_ops->readpage(data, page);
2805
2806 if (err < 0) {
2807 put_page(page);
2808 return ERR_PTR(err);
2809 }
2810
2811 page = wait_on_page_read(page);
2812 if (IS_ERR(page))
2813 return page;
2814 goto out;
2815 }
2816 if (PageUptodate(page))
2817 goto out;
2818
2819 /*
2820 * Page is not up to date and may be locked due one of the following
2821 * case a: Page is being filled and the page lock is held
2822 * case b: Read/write error clearing the page uptodate status
2823 * case c: Truncation in progress (page locked)
2824 * case d: Reclaim in progress
2825 *
2826 * Case a, the page will be up to date when the page is unlocked.
2827 * There is no need to serialise on the page lock here as the page
2828 * is pinned so the lock gives no additional protection. Even if the
2829 * the page is truncated, the data is still valid if PageUptodate as
2830 * it's a race vs truncate race.
2831 * Case b, the page will not be up to date
2832 * Case c, the page may be truncated but in itself, the data may still
2833 * be valid after IO completes as it's a read vs truncate race. The
2834 * operation must restart if the page is not uptodate on unlock but
2835 * otherwise serialising on page lock to stabilise the mapping gives
2836 * no additional guarantees to the caller as the page lock is
2837 * released before return.
2838 * Case d, similar to truncation. If reclaim holds the page lock, it
2839 * will be a race with remove_mapping that determines if the mapping
2840 * is valid on unlock but otherwise the data is valid and there is
2841 * no need to serialise with page lock.
2842 *
2843 * As the page lock gives no additional guarantee, we optimistically
2844 * wait on the page to be unlocked and check if it's up to date and
2845 * use the page if it is. Otherwise, the page lock is required to
2846 * distinguish between the different cases. The motivation is that we
2847 * avoid spurious serialisations and wakeups when multiple processes
2848 * wait on the same page for IO to complete.
2849 */
2850 wait_on_page_locked(page);
2851 if (PageUptodate(page))
2852 goto out;
2853
2854 /* Distinguish between all the cases under the safety of the lock */
2855 lock_page(page);
2856
2857 /* Case c or d, restart the operation */
2858 if (!page->mapping) {
2859 unlock_page(page);
2860 put_page(page);
2861 goto repeat;
2862 }
2863
2864 /* Someone else locked and filled the page in a very small window */
2865 if (PageUptodate(page)) {
2866 unlock_page(page);
2867 goto out;
2868 }
2869 goto filler;
2870
2871out:
2872 mark_page_accessed(page);
2873 return page;
2874}
2875
2876/**
2877 * read_cache_page - read into page cache, fill it if needed
2878 * @mapping: the page's address_space
2879 * @index: the page index
2880 * @filler: function to perform the read
2881 * @data: first arg to filler(data, page) function, often left as NULL
2882 *
2883 * Read into the page cache. If a page already exists, and PageUptodate() is
2884 * not set, try to fill the page and wait for it to become unlocked.
2885 *
2886 * If the page does not get brought uptodate, return -EIO.
2887 *
2888 * Return: up to date page on success, ERR_PTR() on failure.
2889 */
2890struct page *read_cache_page(struct address_space *mapping,
2891 pgoff_t index,
2892 int (*filler)(void *, struct page *),
2893 void *data)
2894{
2895 return do_read_cache_page(mapping, index, filler, data,
2896 mapping_gfp_mask(mapping));
2897}
2898EXPORT_SYMBOL(read_cache_page);
2899
2900/**
2901 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2902 * @mapping: the page's address_space
2903 * @index: the page index
2904 * @gfp: the page allocator flags to use if allocating
2905 *
2906 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2907 * any new page allocations done using the specified allocation flags.
2908 *
2909 * If the page does not get brought uptodate, return -EIO.
2910 *
2911 * Return: up to date page on success, ERR_PTR() on failure.
2912 */
2913struct page *read_cache_page_gfp(struct address_space *mapping,
2914 pgoff_t index,
2915 gfp_t gfp)
2916{
2917 return do_read_cache_page(mapping, index, NULL, NULL, gfp);
2918}
2919EXPORT_SYMBOL(read_cache_page_gfp);
2920
2921/*
2922 * Don't operate on ranges the page cache doesn't support, and don't exceed the
2923 * LFS limits. If pos is under the limit it becomes a short access. If it
2924 * exceeds the limit we return -EFBIG.
2925 */
2926static int generic_write_check_limits(struct file *file, loff_t pos,
2927 loff_t *count)
2928{
2929 struct inode *inode = file->f_mapping->host;
2930 loff_t max_size = inode->i_sb->s_maxbytes;
2931 loff_t limit = rlimit(RLIMIT_FSIZE);
2932
2933 if (limit != RLIM_INFINITY) {
2934 if (pos >= limit) {
2935 send_sig(SIGXFSZ, current, 0);
2936 return -EFBIG;
2937 }
2938 *count = min(*count, limit - pos);
2939 }
2940
2941 if (!(file->f_flags & O_LARGEFILE))
2942 max_size = MAX_NON_LFS;
2943
2944 if (unlikely(pos >= max_size))
2945 return -EFBIG;
2946
2947 *count = min(*count, max_size - pos);
2948
2949 return 0;
2950}
2951
2952/*
2953 * Performs necessary checks before doing a write
2954 *
2955 * Can adjust writing position or amount of bytes to write.
2956 * Returns appropriate error code that caller should return or
2957 * zero in case that write should be allowed.
2958 */
2959inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2960{
2961 struct file *file = iocb->ki_filp;
2962 struct inode *inode = file->f_mapping->host;
2963 loff_t count;
2964 int ret;
2965
2966 if (IS_SWAPFILE(inode))
2967 return -ETXTBSY;
2968
2969 if (!iov_iter_count(from))
2970 return 0;
2971
2972 /* FIXME: this is for backwards compatibility with 2.4 */
2973 if (iocb->ki_flags & IOCB_APPEND)
2974 iocb->ki_pos = i_size_read(inode);
2975
2976 if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
2977 return -EINVAL;
2978
2979 count = iov_iter_count(from);
2980 ret = generic_write_check_limits(file, iocb->ki_pos, &count);
2981 if (ret)
2982 return ret;
2983
2984 iov_iter_truncate(from, count);
2985 return iov_iter_count(from);
2986}
2987EXPORT_SYMBOL(generic_write_checks);
2988
2989/*
2990 * Performs necessary checks before doing a clone.
2991 *
2992 * Can adjust amount of bytes to clone via @req_count argument.
2993 * Returns appropriate error code that caller should return or
2994 * zero in case the clone should be allowed.
2995 */
2996int generic_remap_checks(struct file *file_in, loff_t pos_in,
2997 struct file *file_out, loff_t pos_out,
2998 loff_t *req_count, unsigned int remap_flags)
2999{
3000 struct inode *inode_in = file_in->f_mapping->host;
3001 struct inode *inode_out = file_out->f_mapping->host;
3002 uint64_t count = *req_count;
3003 uint64_t bcount;
3004 loff_t size_in, size_out;
3005 loff_t bs = inode_out->i_sb->s_blocksize;
3006 int ret;
3007
3008 /* The start of both ranges must be aligned to an fs block. */
3009 if (!IS_ALIGNED(pos_in, bs) || !IS_ALIGNED(pos_out, bs))
3010 return -EINVAL;
3011
3012 /* Ensure offsets don't wrap. */
3013 if (pos_in + count < pos_in || pos_out + count < pos_out)
3014 return -EINVAL;
3015
3016 size_in = i_size_read(inode_in);
3017 size_out = i_size_read(inode_out);
3018
3019 /* Dedupe requires both ranges to be within EOF. */
3020 if ((remap_flags & REMAP_FILE_DEDUP) &&
3021 (pos_in >= size_in || pos_in + count > size_in ||
3022 pos_out >= size_out || pos_out + count > size_out))
3023 return -EINVAL;
3024
3025 /* Ensure the infile range is within the infile. */
3026 if (pos_in >= size_in)
3027 return -EINVAL;
3028 count = min(count, size_in - (uint64_t)pos_in);
3029
3030 ret = generic_write_check_limits(file_out, pos_out, &count);
3031 if (ret)
3032 return ret;
3033
3034 /*
3035 * If the user wanted us to link to the infile's EOF, round up to the
3036 * next block boundary for this check.
3037 *
3038 * Otherwise, make sure the count is also block-aligned, having
3039 * already confirmed the starting offsets' block alignment.
3040 */
3041 if (pos_in + count == size_in) {
3042 bcount = ALIGN(size_in, bs) - pos_in;
3043 } else {
3044 if (!IS_ALIGNED(count, bs))
3045 count = ALIGN_DOWN(count, bs);
3046 bcount = count;
3047 }
3048
3049 /* Don't allow overlapped cloning within the same file. */
3050 if (inode_in == inode_out &&
3051 pos_out + bcount > pos_in &&
3052 pos_out < pos_in + bcount)
3053 return -EINVAL;
3054
3055 /*
3056 * We shortened the request but the caller can't deal with that, so
3057 * bounce the request back to userspace.
3058 */
3059 if (*req_count != count && !(remap_flags & REMAP_FILE_CAN_SHORTEN))
3060 return -EINVAL;
3061
3062 *req_count = count;
3063 return 0;
3064}
3065
3066
3067/*
3068 * Performs common checks before doing a file copy/clone
3069 * from @file_in to @file_out.
3070 */
3071int generic_file_rw_checks(struct file *file_in, struct file *file_out)
3072{
3073 struct inode *inode_in = file_inode(file_in);
3074 struct inode *inode_out = file_inode(file_out);
3075
3076 /* Don't copy dirs, pipes, sockets... */
3077 if (S_ISDIR(inode_in->i_mode) || S_ISDIR(inode_out->i_mode))
3078 return -EISDIR;
3079 if (!S_ISREG(inode_in->i_mode) || !S_ISREG(inode_out->i_mode))
3080 return -EINVAL;
3081
3082 if (!(file_in->f_mode & FMODE_READ) ||
3083 !(file_out->f_mode & FMODE_WRITE) ||
3084 (file_out->f_flags & O_APPEND))
3085 return -EBADF;
3086
3087 return 0;
3088}
3089
3090/*
3091 * Performs necessary checks before doing a file copy
3092 *
3093 * Can adjust amount of bytes to copy via @req_count argument.
3094 * Returns appropriate error code that caller should return or
3095 * zero in case the copy should be allowed.
3096 */
3097int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
3098 struct file *file_out, loff_t pos_out,
3099 size_t *req_count, unsigned int flags)
3100{
3101 struct inode *inode_in = file_inode(file_in);
3102 struct inode *inode_out = file_inode(file_out);
3103 uint64_t count = *req_count;
3104 loff_t size_in;
3105 int ret;
3106
3107 ret = generic_file_rw_checks(file_in, file_out);
3108 if (ret)
3109 return ret;
3110
3111 /* Don't touch certain kinds of inodes */
3112 if (IS_IMMUTABLE(inode_out))
3113 return -EPERM;
3114
3115 if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
3116 return -ETXTBSY;
3117
3118 /* Ensure offsets don't wrap. */
3119 if (pos_in + count < pos_in || pos_out + count < pos_out)
3120 return -EOVERFLOW;
3121
3122 /* Shorten the copy to EOF */
3123 size_in = i_size_read(inode_in);
3124 if (pos_in >= size_in)
3125 count = 0;
3126 else
3127 count = min(count, size_in - (uint64_t)pos_in);
3128
3129 ret = generic_write_check_limits(file_out, pos_out, &count);
3130 if (ret)
3131 return ret;
3132
3133 /* Don't allow overlapped copying within the same file. */
3134 if (inode_in == inode_out &&
3135 pos_out + count > pos_in &&
3136 pos_out < pos_in + count)
3137 return -EINVAL;
3138
3139 *req_count = count;
3140 return 0;
3141}
3142
3143int pagecache_write_begin(struct file *file, struct address_space *mapping,
3144 loff_t pos, unsigned len, unsigned flags,
3145 struct page **pagep, void **fsdata)
3146{
3147 const struct address_space_operations *aops = mapping->a_ops;
3148
3149 return aops->write_begin(file, mapping, pos, len, flags,
3150 pagep, fsdata);
3151}
3152EXPORT_SYMBOL(pagecache_write_begin);
3153
3154int pagecache_write_end(struct file *file, struct address_space *mapping,
3155 loff_t pos, unsigned len, unsigned copied,
3156 struct page *page, void *fsdata)
3157{
3158 const struct address_space_operations *aops = mapping->a_ops;
3159
3160 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
3161}
3162EXPORT_SYMBOL(pagecache_write_end);
3163
3164ssize_t
3165generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
3166{
3167 struct file *file = iocb->ki_filp;
3168 struct address_space *mapping = file->f_mapping;
3169 struct inode *inode = mapping->host;
3170 loff_t pos = iocb->ki_pos;
3171 ssize_t written;
3172 size_t write_len;
3173 pgoff_t end;
3174
3175 write_len = iov_iter_count(from);
3176 end = (pos + write_len - 1) >> PAGE_SHIFT;
3177
3178 if (iocb->ki_flags & IOCB_NOWAIT) {
3179 /* If there are pages to writeback, return */
3180 if (filemap_range_has_page(inode->i_mapping, pos,
3181 pos + write_len - 1))
3182 return -EAGAIN;
3183 } else {
3184 written = filemap_write_and_wait_range(mapping, pos,
3185 pos + write_len - 1);
3186 if (written)
3187 goto out;
3188 }
3189
3190 /*
3191 * After a write we want buffered reads to be sure to go to disk to get
3192 * the new data. We invalidate clean cached page from the region we're
3193 * about to write. We do this *before* the write so that we can return
3194 * without clobbering -EIOCBQUEUED from ->direct_IO().
3195 */
3196 written = invalidate_inode_pages2_range(mapping,
3197 pos >> PAGE_SHIFT, end);
3198 /*
3199 * If a page can not be invalidated, return 0 to fall back
3200 * to buffered write.
3201 */
3202 if (written) {
3203 if (written == -EBUSY)
3204 return 0;
3205 goto out;
3206 }
3207
3208 written = mapping->a_ops->direct_IO(iocb, from);
3209
3210 /*
3211 * Finally, try again to invalidate clean pages which might have been
3212 * cached by non-direct readahead, or faulted in by get_user_pages()
3213 * if the source of the write was an mmap'ed region of the file
3214 * we're writing. Either one is a pretty crazy thing to do,
3215 * so we don't support it 100%. If this invalidation
3216 * fails, tough, the write still worked...
3217 *
3218 * Most of the time we do not need this since dio_complete() will do
3219 * the invalidation for us. However there are some file systems that
3220 * do not end up with dio_complete() being called, so let's not break
3221 * them by removing it completely
3222 */
3223 if (mapping->nrpages)
3224 invalidate_inode_pages2_range(mapping,
3225 pos >> PAGE_SHIFT, end);
3226
3227 if (written > 0) {
3228 pos += written;
3229 write_len -= written;
3230 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
3231 i_size_write(inode, pos);
3232 mark_inode_dirty(inode);
3233 }
3234 iocb->ki_pos = pos;
3235 }
3236 iov_iter_revert(from, write_len - iov_iter_count(from));
3237out:
3238 return written;
3239}
3240EXPORT_SYMBOL(generic_file_direct_write);
3241
3242/*
3243 * Find or create a page at the given pagecache position. Return the locked
3244 * page. This function is specifically for buffered writes.
3245 */
3246struct page *grab_cache_page_write_begin(struct address_space *mapping,
3247 pgoff_t index, unsigned flags)
3248{
3249 struct page *page;
3250 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
3251
3252 if (flags & AOP_FLAG_NOFS)
3253 fgp_flags |= FGP_NOFS;
3254
3255 page = pagecache_get_page(mapping, index, fgp_flags,
3256 mapping_gfp_mask(mapping));
3257 if (page)
3258 wait_for_stable_page(page);
3259
3260 return page;
3261}
3262EXPORT_SYMBOL(grab_cache_page_write_begin);
3263
3264ssize_t generic_perform_write(struct file *file,
3265 struct iov_iter *i, loff_t pos)
3266{
3267 struct address_space *mapping = file->f_mapping;
3268 const struct address_space_operations *a_ops = mapping->a_ops;
3269 long status = 0;
3270 ssize_t written = 0;
3271 unsigned int flags = 0;
3272
3273 do {
3274 struct page *page;
3275 unsigned long offset; /* Offset into pagecache page */
3276 unsigned long bytes; /* Bytes to write to page */
3277 size_t copied; /* Bytes copied from user */
3278 void *fsdata;
3279
3280 offset = (pos & (PAGE_SIZE - 1));
3281 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3282 iov_iter_count(i));
3283
3284again:
3285 /*
3286 * Bring in the user page that we will copy from _first_.
3287 * Otherwise there's a nasty deadlock on copying from the
3288 * same page as we're writing to, without it being marked
3289 * up-to-date.
3290 *
3291 * Not only is this an optimisation, but it is also required
3292 * to check that the address is actually valid, when atomic
3293 * usercopies are used, below.
3294 */
3295 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
3296 status = -EFAULT;
3297 break;
3298 }
3299
3300 if (fatal_signal_pending(current)) {
3301 status = -EINTR;
3302 break;
3303 }
3304
3305 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
3306 &page, &fsdata);
3307 if (unlikely(status < 0))
3308 break;
3309
3310 if (mapping_writably_mapped(mapping))
3311 flush_dcache_page(page);
3312
3313 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
3314 flush_dcache_page(page);
3315
3316 status = a_ops->write_end(file, mapping, pos, bytes, copied,
3317 page, fsdata);
3318 if (unlikely(status < 0))
3319 break;
3320 copied = status;
3321
3322 cond_resched();
3323
3324 iov_iter_advance(i, copied);
3325 if (unlikely(copied == 0)) {
3326 /*
3327 * If we were unable to copy any data at all, we must
3328 * fall back to a single segment length write.
3329 *
3330 * If we didn't fallback here, we could livelock
3331 * because not all segments in the iov can be copied at
3332 * once without a pagefault.
3333 */
3334 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3335 iov_iter_single_seg_count(i));
3336 goto again;
3337 }
3338 pos += copied;
3339 written += copied;
3340
3341 balance_dirty_pages_ratelimited(mapping);
3342 } while (iov_iter_count(i));
3343
3344 return written ? written : status;
3345}
3346EXPORT_SYMBOL(generic_perform_write);
3347
3348/**
3349 * __generic_file_write_iter - write data to a file
3350 * @iocb: IO state structure (file, offset, etc.)
3351 * @from: iov_iter with data to write
3352 *
3353 * This function does all the work needed for actually writing data to a
3354 * file. It does all basic checks, removes SUID from the file, updates
3355 * modification times and calls proper subroutines depending on whether we
3356 * do direct IO or a standard buffered write.
3357 *
3358 * It expects i_mutex to be grabbed unless we work on a block device or similar
3359 * object which does not need locking at all.
3360 *
3361 * This function does *not* take care of syncing data in case of O_SYNC write.
3362 * A caller has to handle it. This is mainly due to the fact that we want to
3363 * avoid syncing under i_mutex.
3364 *
3365 * Return:
3366 * * number of bytes written, even for truncated writes
3367 * * negative error code if no data has been written at all
3368 */
3369ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3370{
3371 struct file *file = iocb->ki_filp;
3372 struct address_space * mapping = file->f_mapping;
3373 struct inode *inode = mapping->host;
3374 ssize_t written = 0;
3375 ssize_t err;
3376 ssize_t status;
3377
3378 /* We can write back this queue in page reclaim */
3379 current->backing_dev_info = inode_to_bdi(inode);
3380 err = file_remove_privs(file);
3381 if (err)
3382 goto out;
3383
3384 err = file_update_time(file);
3385 if (err)
3386 goto out;
3387
3388 if (iocb->ki_flags & IOCB_DIRECT) {
3389 loff_t pos, endbyte;
3390
3391 written = generic_file_direct_write(iocb, from);
3392 /*
3393 * If the write stopped short of completing, fall back to
3394 * buffered writes. Some filesystems do this for writes to
3395 * holes, for example. For DAX files, a buffered write will
3396 * not succeed (even if it did, DAX does not handle dirty
3397 * page-cache pages correctly).
3398 */
3399 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
3400 goto out;
3401
3402 status = generic_perform_write(file, from, pos = iocb->ki_pos);
3403 /*
3404 * If generic_perform_write() returned a synchronous error
3405 * then we want to return the number of bytes which were
3406 * direct-written, or the error code if that was zero. Note
3407 * that this differs from normal direct-io semantics, which
3408 * will return -EFOO even if some bytes were written.
3409 */
3410 if (unlikely(status < 0)) {
3411 err = status;
3412 goto out;
3413 }
3414 /*
3415 * We need to ensure that the page cache pages are written to
3416 * disk and invalidated to preserve the expected O_DIRECT
3417 * semantics.
3418 */
3419 endbyte = pos + status - 1;
3420 err = filemap_write_and_wait_range(mapping, pos, endbyte);
3421 if (err == 0) {
3422 iocb->ki_pos = endbyte + 1;
3423 written += status;
3424 invalidate_mapping_pages(mapping,
3425 pos >> PAGE_SHIFT,
3426 endbyte >> PAGE_SHIFT);
3427 } else {
3428 /*
3429 * We don't know how much we wrote, so just return
3430 * the number of bytes which were direct-written
3431 */
3432 }
3433 } else {
3434 written = generic_perform_write(file, from, iocb->ki_pos);
3435 if (likely(written > 0))
3436 iocb->ki_pos += written;
3437 }
3438out:
3439 current->backing_dev_info = NULL;
3440 return written ? written : err;
3441}
3442EXPORT_SYMBOL(__generic_file_write_iter);
3443
3444/**
3445 * generic_file_write_iter - write data to a file
3446 * @iocb: IO state structure
3447 * @from: iov_iter with data to write
3448 *
3449 * This is a wrapper around __generic_file_write_iter() to be used by most
3450 * filesystems. It takes care of syncing the file in case of O_SYNC file
3451 * and acquires i_mutex as needed.
3452 * Return:
3453 * * negative error code if no data has been written at all of
3454 * vfs_fsync_range() failed for a synchronous write
3455 * * number of bytes written, even for truncated writes
3456 */
3457ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3458{
3459 struct file *file = iocb->ki_filp;
3460 struct inode *inode = file->f_mapping->host;
3461 ssize_t ret;
3462
3463 inode_lock(inode);
3464 ret = generic_write_checks(iocb, from);
3465 if (ret > 0)
3466 ret = __generic_file_write_iter(iocb, from);
3467 inode_unlock(inode);
3468
3469 if (ret > 0)
3470 ret = generic_write_sync(iocb, ret);
3471 return ret;
3472}
3473EXPORT_SYMBOL(generic_file_write_iter);
3474
3475/**
3476 * try_to_release_page() - release old fs-specific metadata on a page
3477 *
3478 * @page: the page which the kernel is trying to free
3479 * @gfp_mask: memory allocation flags (and I/O mode)
3480 *
3481 * The address_space is to try to release any data against the page
3482 * (presumably at page->private).
3483 *
3484 * This may also be called if PG_fscache is set on a page, indicating that the
3485 * page is known to the local caching routines.
3486 *
3487 * The @gfp_mask argument specifies whether I/O may be performed to release
3488 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3489 *
3490 * Return: %1 if the release was successful, otherwise return zero.
3491 */
3492int try_to_release_page(struct page *page, gfp_t gfp_mask)
3493{
3494 struct address_space * const mapping = page->mapping;
3495
3496 BUG_ON(!PageLocked(page));
3497 if (PageWriteback(page))
3498 return 0;
3499
3500 if (mapping && mapping->a_ops->releasepage)
3501 return mapping->a_ops->releasepage(page, gfp_mask);
3502 return try_to_free_buffers(page);
3503}
3504
3505EXPORT_SYMBOL(try_to_release_page);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/mm/filemap.c
4 *
5 * Copyright (C) 1994-1999 Linus Torvalds
6 */
7
8/*
9 * This file handles the generic file mmap semantics used by
10 * most "normal" filesystems (but you don't /have/ to use this:
11 * the NFS filesystem used to do this differently, for example)
12 */
13#include <linux/export.h>
14#include <linux/compiler.h>
15#include <linux/dax.h>
16#include <linux/fs.h>
17#include <linux/sched/signal.h>
18#include <linux/uaccess.h>
19#include <linux/capability.h>
20#include <linux/kernel_stat.h>
21#include <linux/gfp.h>
22#include <linux/mm.h>
23#include <linux/swap.h>
24#include <linux/swapops.h>
25#include <linux/syscalls.h>
26#include <linux/mman.h>
27#include <linux/pagemap.h>
28#include <linux/file.h>
29#include <linux/uio.h>
30#include <linux/error-injection.h>
31#include <linux/hash.h>
32#include <linux/writeback.h>
33#include <linux/backing-dev.h>
34#include <linux/pagevec.h>
35#include <linux/security.h>
36#include <linux/cpuset.h>
37#include <linux/hugetlb.h>
38#include <linux/memcontrol.h>
39#include <linux/shmem_fs.h>
40#include <linux/rmap.h>
41#include <linux/delayacct.h>
42#include <linux/psi.h>
43#include <linux/ramfs.h>
44#include <linux/page_idle.h>
45#include <linux/migrate.h>
46#include <linux/pipe_fs_i.h>
47#include <linux/splice.h>
48#include <linux/rcupdate_wait.h>
49#include <asm/pgalloc.h>
50#include <asm/tlbflush.h>
51#include "internal.h"
52
53#define CREATE_TRACE_POINTS
54#include <trace/events/filemap.h>
55
56/*
57 * FIXME: remove all knowledge of the buffer layer from the core VM
58 */
59#include <linux/buffer_head.h> /* for try_to_free_buffers */
60
61#include <asm/mman.h>
62
63#include "swap.h"
64
65/*
66 * Shared mappings implemented 30.11.1994. It's not fully working yet,
67 * though.
68 *
69 * Shared mappings now work. 15.8.1995 Bruno.
70 *
71 * finished 'unifying' the page and buffer cache and SMP-threaded the
72 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
73 *
74 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
75 */
76
77/*
78 * Lock ordering:
79 *
80 * ->i_mmap_rwsem (truncate_pagecache)
81 * ->private_lock (__free_pte->block_dirty_folio)
82 * ->swap_lock (exclusive_swap_page, others)
83 * ->i_pages lock
84 *
85 * ->i_rwsem
86 * ->invalidate_lock (acquired by fs in truncate path)
87 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
88 *
89 * ->mmap_lock
90 * ->i_mmap_rwsem
91 * ->page_table_lock or pte_lock (various, mainly in memory.c)
92 * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
93 *
94 * ->mmap_lock
95 * ->invalidate_lock (filemap_fault)
96 * ->lock_page (filemap_fault, access_process_vm)
97 *
98 * ->i_rwsem (generic_perform_write)
99 * ->mmap_lock (fault_in_readable->do_page_fault)
100 *
101 * bdi->wb.list_lock
102 * sb_lock (fs/fs-writeback.c)
103 * ->i_pages lock (__sync_single_inode)
104 *
105 * ->i_mmap_rwsem
106 * ->anon_vma.lock (vma_merge)
107 *
108 * ->anon_vma.lock
109 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
110 *
111 * ->page_table_lock or pte_lock
112 * ->swap_lock (try_to_unmap_one)
113 * ->private_lock (try_to_unmap_one)
114 * ->i_pages lock (try_to_unmap_one)
115 * ->lruvec->lru_lock (follow_page->mark_page_accessed)
116 * ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
117 * ->private_lock (folio_remove_rmap_pte->set_page_dirty)
118 * ->i_pages lock (folio_remove_rmap_pte->set_page_dirty)
119 * bdi.wb->list_lock (folio_remove_rmap_pte->set_page_dirty)
120 * ->inode->i_lock (folio_remove_rmap_pte->set_page_dirty)
121 * ->memcg->move_lock (folio_remove_rmap_pte->folio_memcg_lock)
122 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
123 * ->inode->i_lock (zap_pte_range->set_page_dirty)
124 * ->private_lock (zap_pte_range->block_dirty_folio)
125 */
126
127static void page_cache_delete(struct address_space *mapping,
128 struct folio *folio, void *shadow)
129{
130 XA_STATE(xas, &mapping->i_pages, folio->index);
131 long nr = 1;
132
133 mapping_set_update(&xas, mapping);
134
135 xas_set_order(&xas, folio->index, folio_order(folio));
136 nr = folio_nr_pages(folio);
137
138 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
139
140 xas_store(&xas, shadow);
141 xas_init_marks(&xas);
142
143 folio->mapping = NULL;
144 /* Leave page->index set: truncation lookup relies upon it */
145 mapping->nrpages -= nr;
146}
147
148static void filemap_unaccount_folio(struct address_space *mapping,
149 struct folio *folio)
150{
151 long nr;
152
153 VM_BUG_ON_FOLIO(folio_mapped(folio), folio);
154 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) {
155 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
156 current->comm, folio_pfn(folio));
157 dump_page(&folio->page, "still mapped when deleted");
158 dump_stack();
159 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
160
161 if (mapping_exiting(mapping) && !folio_test_large(folio)) {
162 int mapcount = page_mapcount(&folio->page);
163
164 if (folio_ref_count(folio) >= mapcount + 2) {
165 /*
166 * All vmas have already been torn down, so it's
167 * a good bet that actually the page is unmapped
168 * and we'd rather not leak it: if we're wrong,
169 * another bad page check should catch it later.
170 */
171 page_mapcount_reset(&folio->page);
172 folio_ref_sub(folio, mapcount);
173 }
174 }
175 }
176
177 /* hugetlb folios do not participate in page cache accounting. */
178 if (folio_test_hugetlb(folio))
179 return;
180
181 nr = folio_nr_pages(folio);
182
183 __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
184 if (folio_test_swapbacked(folio)) {
185 __lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);
186 if (folio_test_pmd_mappable(folio))
187 __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr);
188 } else if (folio_test_pmd_mappable(folio)) {
189 __lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);
190 filemap_nr_thps_dec(mapping);
191 }
192
193 /*
194 * At this point folio must be either written or cleaned by
195 * truncate. Dirty folio here signals a bug and loss of
196 * unwritten data - on ordinary filesystems.
197 *
198 * But it's harmless on in-memory filesystems like tmpfs; and can
199 * occur when a driver which did get_user_pages() sets page dirty
200 * before putting it, while the inode is being finally evicted.
201 *
202 * Below fixes dirty accounting after removing the folio entirely
203 * but leaves the dirty flag set: it has no effect for truncated
204 * folio and anyway will be cleared before returning folio to
205 * buddy allocator.
206 */
207 if (WARN_ON_ONCE(folio_test_dirty(folio) &&
208 mapping_can_writeback(mapping)))
209 folio_account_cleaned(folio, inode_to_wb(mapping->host));
210}
211
212/*
213 * Delete a page from the page cache and free it. Caller has to make
214 * sure the page is locked and that nobody else uses it - or that usage
215 * is safe. The caller must hold the i_pages lock.
216 */
217void __filemap_remove_folio(struct folio *folio, void *shadow)
218{
219 struct address_space *mapping = folio->mapping;
220
221 trace_mm_filemap_delete_from_page_cache(folio);
222 filemap_unaccount_folio(mapping, folio);
223 page_cache_delete(mapping, folio, shadow);
224}
225
226void filemap_free_folio(struct address_space *mapping, struct folio *folio)
227{
228 void (*free_folio)(struct folio *);
229 int refs = 1;
230
231 free_folio = mapping->a_ops->free_folio;
232 if (free_folio)
233 free_folio(folio);
234
235 if (folio_test_large(folio))
236 refs = folio_nr_pages(folio);
237 folio_put_refs(folio, refs);
238}
239
240/**
241 * filemap_remove_folio - Remove folio from page cache.
242 * @folio: The folio.
243 *
244 * This must be called only on folios that are locked and have been
245 * verified to be in the page cache. It will never put the folio into
246 * the free list because the caller has a reference on the page.
247 */
248void filemap_remove_folio(struct folio *folio)
249{
250 struct address_space *mapping = folio->mapping;
251
252 BUG_ON(!folio_test_locked(folio));
253 spin_lock(&mapping->host->i_lock);
254 xa_lock_irq(&mapping->i_pages);
255 __filemap_remove_folio(folio, NULL);
256 xa_unlock_irq(&mapping->i_pages);
257 if (mapping_shrinkable(mapping))
258 inode_add_lru(mapping->host);
259 spin_unlock(&mapping->host->i_lock);
260
261 filemap_free_folio(mapping, folio);
262}
263
264/*
265 * page_cache_delete_batch - delete several folios from page cache
266 * @mapping: the mapping to which folios belong
267 * @fbatch: batch of folios to delete
268 *
269 * The function walks over mapping->i_pages and removes folios passed in
270 * @fbatch from the mapping. The function expects @fbatch to be sorted
271 * by page index and is optimised for it to be dense.
272 * It tolerates holes in @fbatch (mapping entries at those indices are not
273 * modified).
274 *
275 * The function expects the i_pages lock to be held.
276 */
277static void page_cache_delete_batch(struct address_space *mapping,
278 struct folio_batch *fbatch)
279{
280 XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index);
281 long total_pages = 0;
282 int i = 0;
283 struct folio *folio;
284
285 mapping_set_update(&xas, mapping);
286 xas_for_each(&xas, folio, ULONG_MAX) {
287 if (i >= folio_batch_count(fbatch))
288 break;
289
290 /* A swap/dax/shadow entry got inserted? Skip it. */
291 if (xa_is_value(folio))
292 continue;
293 /*
294 * A page got inserted in our range? Skip it. We have our
295 * pages locked so they are protected from being removed.
296 * If we see a page whose index is higher than ours, it
297 * means our page has been removed, which shouldn't be
298 * possible because we're holding the PageLock.
299 */
300 if (folio != fbatch->folios[i]) {
301 VM_BUG_ON_FOLIO(folio->index >
302 fbatch->folios[i]->index, folio);
303 continue;
304 }
305
306 WARN_ON_ONCE(!folio_test_locked(folio));
307
308 folio->mapping = NULL;
309 /* Leave folio->index set: truncation lookup relies on it */
310
311 i++;
312 xas_store(&xas, NULL);
313 total_pages += folio_nr_pages(folio);
314 }
315 mapping->nrpages -= total_pages;
316}
317
318void delete_from_page_cache_batch(struct address_space *mapping,
319 struct folio_batch *fbatch)
320{
321 int i;
322
323 if (!folio_batch_count(fbatch))
324 return;
325
326 spin_lock(&mapping->host->i_lock);
327 xa_lock_irq(&mapping->i_pages);
328 for (i = 0; i < folio_batch_count(fbatch); i++) {
329 struct folio *folio = fbatch->folios[i];
330
331 trace_mm_filemap_delete_from_page_cache(folio);
332 filemap_unaccount_folio(mapping, folio);
333 }
334 page_cache_delete_batch(mapping, fbatch);
335 xa_unlock_irq(&mapping->i_pages);
336 if (mapping_shrinkable(mapping))
337 inode_add_lru(mapping->host);
338 spin_unlock(&mapping->host->i_lock);
339
340 for (i = 0; i < folio_batch_count(fbatch); i++)
341 filemap_free_folio(mapping, fbatch->folios[i]);
342}
343
344int filemap_check_errors(struct address_space *mapping)
345{
346 int ret = 0;
347 /* Check for outstanding write errors */
348 if (test_bit(AS_ENOSPC, &mapping->flags) &&
349 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
350 ret = -ENOSPC;
351 if (test_bit(AS_EIO, &mapping->flags) &&
352 test_and_clear_bit(AS_EIO, &mapping->flags))
353 ret = -EIO;
354 return ret;
355}
356EXPORT_SYMBOL(filemap_check_errors);
357
358static int filemap_check_and_keep_errors(struct address_space *mapping)
359{
360 /* Check for outstanding write errors */
361 if (test_bit(AS_EIO, &mapping->flags))
362 return -EIO;
363 if (test_bit(AS_ENOSPC, &mapping->flags))
364 return -ENOSPC;
365 return 0;
366}
367
368/**
369 * filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range
370 * @mapping: address space structure to write
371 * @wbc: the writeback_control controlling the writeout
372 *
373 * Call writepages on the mapping using the provided wbc to control the
374 * writeout.
375 *
376 * Return: %0 on success, negative error code otherwise.
377 */
378int filemap_fdatawrite_wbc(struct address_space *mapping,
379 struct writeback_control *wbc)
380{
381 int ret;
382
383 if (!mapping_can_writeback(mapping) ||
384 !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
385 return 0;
386
387 wbc_attach_fdatawrite_inode(wbc, mapping->host);
388 ret = do_writepages(mapping, wbc);
389 wbc_detach_inode(wbc);
390 return ret;
391}
392EXPORT_SYMBOL(filemap_fdatawrite_wbc);
393
394/**
395 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
396 * @mapping: address space structure to write
397 * @start: offset in bytes where the range starts
398 * @end: offset in bytes where the range ends (inclusive)
399 * @sync_mode: enable synchronous operation
400 *
401 * Start writeback against all of a mapping's dirty pages that lie
402 * within the byte offsets <start, end> inclusive.
403 *
404 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
405 * opposed to a regular memory cleansing writeback. The difference between
406 * these two operations is that if a dirty page/buffer is encountered, it must
407 * be waited upon, and not just skipped over.
408 *
409 * Return: %0 on success, negative error code otherwise.
410 */
411int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
412 loff_t end, int sync_mode)
413{
414 struct writeback_control wbc = {
415 .sync_mode = sync_mode,
416 .nr_to_write = LONG_MAX,
417 .range_start = start,
418 .range_end = end,
419 };
420
421 return filemap_fdatawrite_wbc(mapping, &wbc);
422}
423
424static inline int __filemap_fdatawrite(struct address_space *mapping,
425 int sync_mode)
426{
427 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
428}
429
430int filemap_fdatawrite(struct address_space *mapping)
431{
432 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
433}
434EXPORT_SYMBOL(filemap_fdatawrite);
435
436int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
437 loff_t end)
438{
439 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
440}
441EXPORT_SYMBOL(filemap_fdatawrite_range);
442
443/**
444 * filemap_flush - mostly a non-blocking flush
445 * @mapping: target address_space
446 *
447 * This is a mostly non-blocking flush. Not suitable for data-integrity
448 * purposes - I/O may not be started against all dirty pages.
449 *
450 * Return: %0 on success, negative error code otherwise.
451 */
452int filemap_flush(struct address_space *mapping)
453{
454 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
455}
456EXPORT_SYMBOL(filemap_flush);
457
458/**
459 * filemap_range_has_page - check if a page exists in range.
460 * @mapping: address space within which to check
461 * @start_byte: offset in bytes where the range starts
462 * @end_byte: offset in bytes where the range ends (inclusive)
463 *
464 * Find at least one page in the range supplied, usually used to check if
465 * direct writing in this range will trigger a writeback.
466 *
467 * Return: %true if at least one page exists in the specified range,
468 * %false otherwise.
469 */
470bool filemap_range_has_page(struct address_space *mapping,
471 loff_t start_byte, loff_t end_byte)
472{
473 struct folio *folio;
474 XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
475 pgoff_t max = end_byte >> PAGE_SHIFT;
476
477 if (end_byte < start_byte)
478 return false;
479
480 rcu_read_lock();
481 for (;;) {
482 folio = xas_find(&xas, max);
483 if (xas_retry(&xas, folio))
484 continue;
485 /* Shadow entries don't count */
486 if (xa_is_value(folio))
487 continue;
488 /*
489 * We don't need to try to pin this page; we're about to
490 * release the RCU lock anyway. It is enough to know that
491 * there was a page here recently.
492 */
493 break;
494 }
495 rcu_read_unlock();
496
497 return folio != NULL;
498}
499EXPORT_SYMBOL(filemap_range_has_page);
500
501static void __filemap_fdatawait_range(struct address_space *mapping,
502 loff_t start_byte, loff_t end_byte)
503{
504 pgoff_t index = start_byte >> PAGE_SHIFT;
505 pgoff_t end = end_byte >> PAGE_SHIFT;
506 struct folio_batch fbatch;
507 unsigned nr_folios;
508
509 folio_batch_init(&fbatch);
510
511 while (index <= end) {
512 unsigned i;
513
514 nr_folios = filemap_get_folios_tag(mapping, &index, end,
515 PAGECACHE_TAG_WRITEBACK, &fbatch);
516
517 if (!nr_folios)
518 break;
519
520 for (i = 0; i < nr_folios; i++) {
521 struct folio *folio = fbatch.folios[i];
522
523 folio_wait_writeback(folio);
524 folio_clear_error(folio);
525 }
526 folio_batch_release(&fbatch);
527 cond_resched();
528 }
529}
530
531/**
532 * filemap_fdatawait_range - wait for writeback to complete
533 * @mapping: address space structure to wait for
534 * @start_byte: offset in bytes where the range starts
535 * @end_byte: offset in bytes where the range ends (inclusive)
536 *
537 * Walk the list of under-writeback pages of the given address space
538 * in the given range and wait for all of them. Check error status of
539 * the address space and return it.
540 *
541 * Since the error status of the address space is cleared by this function,
542 * callers are responsible for checking the return value and handling and/or
543 * reporting the error.
544 *
545 * Return: error status of the address space.
546 */
547int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
548 loff_t end_byte)
549{
550 __filemap_fdatawait_range(mapping, start_byte, end_byte);
551 return filemap_check_errors(mapping);
552}
553EXPORT_SYMBOL(filemap_fdatawait_range);
554
555/**
556 * filemap_fdatawait_range_keep_errors - wait for writeback to complete
557 * @mapping: address space structure to wait for
558 * @start_byte: offset in bytes where the range starts
559 * @end_byte: offset in bytes where the range ends (inclusive)
560 *
561 * Walk the list of under-writeback pages of the given address space in the
562 * given range and wait for all of them. Unlike filemap_fdatawait_range(),
563 * this function does not clear error status of the address space.
564 *
565 * Use this function if callers don't handle errors themselves. Expected
566 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
567 * fsfreeze(8)
568 */
569int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
570 loff_t start_byte, loff_t end_byte)
571{
572 __filemap_fdatawait_range(mapping, start_byte, end_byte);
573 return filemap_check_and_keep_errors(mapping);
574}
575EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
576
577/**
578 * file_fdatawait_range - wait for writeback to complete
579 * @file: file pointing to address space structure to wait for
580 * @start_byte: offset in bytes where the range starts
581 * @end_byte: offset in bytes where the range ends (inclusive)
582 *
583 * Walk the list of under-writeback pages of the address space that file
584 * refers to, in the given range and wait for all of them. Check error
585 * status of the address space vs. the file->f_wb_err cursor and return it.
586 *
587 * Since the error status of the file is advanced by this function,
588 * callers are responsible for checking the return value and handling and/or
589 * reporting the error.
590 *
591 * Return: error status of the address space vs. the file->f_wb_err cursor.
592 */
593int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
594{
595 struct address_space *mapping = file->f_mapping;
596
597 __filemap_fdatawait_range(mapping, start_byte, end_byte);
598 return file_check_and_advance_wb_err(file);
599}
600EXPORT_SYMBOL(file_fdatawait_range);
601
602/**
603 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
604 * @mapping: address space structure to wait for
605 *
606 * Walk the list of under-writeback pages of the given address space
607 * and wait for all of them. Unlike filemap_fdatawait(), this function
608 * does not clear error status of the address space.
609 *
610 * Use this function if callers don't handle errors themselves. Expected
611 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
612 * fsfreeze(8)
613 *
614 * Return: error status of the address space.
615 */
616int filemap_fdatawait_keep_errors(struct address_space *mapping)
617{
618 __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
619 return filemap_check_and_keep_errors(mapping);
620}
621EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
622
623/* Returns true if writeback might be needed or already in progress. */
624static bool mapping_needs_writeback(struct address_space *mapping)
625{
626 return mapping->nrpages;
627}
628
629bool filemap_range_has_writeback(struct address_space *mapping,
630 loff_t start_byte, loff_t end_byte)
631{
632 XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
633 pgoff_t max = end_byte >> PAGE_SHIFT;
634 struct folio *folio;
635
636 if (end_byte < start_byte)
637 return false;
638
639 rcu_read_lock();
640 xas_for_each(&xas, folio, max) {
641 if (xas_retry(&xas, folio))
642 continue;
643 if (xa_is_value(folio))
644 continue;
645 if (folio_test_dirty(folio) || folio_test_locked(folio) ||
646 folio_test_writeback(folio))
647 break;
648 }
649 rcu_read_unlock();
650 return folio != NULL;
651}
652EXPORT_SYMBOL_GPL(filemap_range_has_writeback);
653
654/**
655 * filemap_write_and_wait_range - write out & wait on a file range
656 * @mapping: the address_space for the pages
657 * @lstart: offset in bytes where the range starts
658 * @lend: offset in bytes where the range ends (inclusive)
659 *
660 * Write out and wait upon file offsets lstart->lend, inclusive.
661 *
662 * Note that @lend is inclusive (describes the last byte to be written) so
663 * that this function can be used to write to the very end-of-file (end = -1).
664 *
665 * Return: error status of the address space.
666 */
667int filemap_write_and_wait_range(struct address_space *mapping,
668 loff_t lstart, loff_t lend)
669{
670 int err = 0, err2;
671
672 if (lend < lstart)
673 return 0;
674
675 if (mapping_needs_writeback(mapping)) {
676 err = __filemap_fdatawrite_range(mapping, lstart, lend,
677 WB_SYNC_ALL);
678 /*
679 * Even if the above returned error, the pages may be
680 * written partially (e.g. -ENOSPC), so we wait for it.
681 * But the -EIO is special case, it may indicate the worst
682 * thing (e.g. bug) happened, so we avoid waiting for it.
683 */
684 if (err != -EIO)
685 __filemap_fdatawait_range(mapping, lstart, lend);
686 }
687 err2 = filemap_check_errors(mapping);
688 if (!err)
689 err = err2;
690 return err;
691}
692EXPORT_SYMBOL(filemap_write_and_wait_range);
693
694void __filemap_set_wb_err(struct address_space *mapping, int err)
695{
696 errseq_t eseq = errseq_set(&mapping->wb_err, err);
697
698 trace_filemap_set_wb_err(mapping, eseq);
699}
700EXPORT_SYMBOL(__filemap_set_wb_err);
701
702/**
703 * file_check_and_advance_wb_err - report wb error (if any) that was previously
704 * and advance wb_err to current one
705 * @file: struct file on which the error is being reported
706 *
707 * When userland calls fsync (or something like nfsd does the equivalent), we
708 * want to report any writeback errors that occurred since the last fsync (or
709 * since the file was opened if there haven't been any).
710 *
711 * Grab the wb_err from the mapping. If it matches what we have in the file,
712 * then just quickly return 0. The file is all caught up.
713 *
714 * If it doesn't match, then take the mapping value, set the "seen" flag in
715 * it and try to swap it into place. If it works, or another task beat us
716 * to it with the new value, then update the f_wb_err and return the error
717 * portion. The error at this point must be reported via proper channels
718 * (a'la fsync, or NFS COMMIT operation, etc.).
719 *
720 * While we handle mapping->wb_err with atomic operations, the f_wb_err
721 * value is protected by the f_lock since we must ensure that it reflects
722 * the latest value swapped in for this file descriptor.
723 *
724 * Return: %0 on success, negative error code otherwise.
725 */
726int file_check_and_advance_wb_err(struct file *file)
727{
728 int err = 0;
729 errseq_t old = READ_ONCE(file->f_wb_err);
730 struct address_space *mapping = file->f_mapping;
731
732 /* Locklessly handle the common case where nothing has changed */
733 if (errseq_check(&mapping->wb_err, old)) {
734 /* Something changed, must use slow path */
735 spin_lock(&file->f_lock);
736 old = file->f_wb_err;
737 err = errseq_check_and_advance(&mapping->wb_err,
738 &file->f_wb_err);
739 trace_file_check_and_advance_wb_err(file, old);
740 spin_unlock(&file->f_lock);
741 }
742
743 /*
744 * We're mostly using this function as a drop in replacement for
745 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
746 * that the legacy code would have had on these flags.
747 */
748 clear_bit(AS_EIO, &mapping->flags);
749 clear_bit(AS_ENOSPC, &mapping->flags);
750 return err;
751}
752EXPORT_SYMBOL(file_check_and_advance_wb_err);
753
754/**
755 * file_write_and_wait_range - write out & wait on a file range
756 * @file: file pointing to address_space with pages
757 * @lstart: offset in bytes where the range starts
758 * @lend: offset in bytes where the range ends (inclusive)
759 *
760 * Write out and wait upon file offsets lstart->lend, inclusive.
761 *
762 * Note that @lend is inclusive (describes the last byte to be written) so
763 * that this function can be used to write to the very end-of-file (end = -1).
764 *
765 * After writing out and waiting on the data, we check and advance the
766 * f_wb_err cursor to the latest value, and return any errors detected there.
767 *
768 * Return: %0 on success, negative error code otherwise.
769 */
770int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
771{
772 int err = 0, err2;
773 struct address_space *mapping = file->f_mapping;
774
775 if (lend < lstart)
776 return 0;
777
778 if (mapping_needs_writeback(mapping)) {
779 err = __filemap_fdatawrite_range(mapping, lstart, lend,
780 WB_SYNC_ALL);
781 /* See comment of filemap_write_and_wait() */
782 if (err != -EIO)
783 __filemap_fdatawait_range(mapping, lstart, lend);
784 }
785 err2 = file_check_and_advance_wb_err(file);
786 if (!err)
787 err = err2;
788 return err;
789}
790EXPORT_SYMBOL(file_write_and_wait_range);
791
792/**
793 * replace_page_cache_folio - replace a pagecache folio with a new one
794 * @old: folio to be replaced
795 * @new: folio to replace with
796 *
797 * This function replaces a folio in the pagecache with a new one. On
798 * success it acquires the pagecache reference for the new folio and
799 * drops it for the old folio. Both the old and new folios must be
800 * locked. This function does not add the new folio to the LRU, the
801 * caller must do that.
802 *
803 * The remove + add is atomic. This function cannot fail.
804 */
805void replace_page_cache_folio(struct folio *old, struct folio *new)
806{
807 struct address_space *mapping = old->mapping;
808 void (*free_folio)(struct folio *) = mapping->a_ops->free_folio;
809 pgoff_t offset = old->index;
810 XA_STATE(xas, &mapping->i_pages, offset);
811
812 VM_BUG_ON_FOLIO(!folio_test_locked(old), old);
813 VM_BUG_ON_FOLIO(!folio_test_locked(new), new);
814 VM_BUG_ON_FOLIO(new->mapping, new);
815
816 folio_get(new);
817 new->mapping = mapping;
818 new->index = offset;
819
820 mem_cgroup_replace_folio(old, new);
821
822 xas_lock_irq(&xas);
823 xas_store(&xas, new);
824
825 old->mapping = NULL;
826 /* hugetlb pages do not participate in page cache accounting. */
827 if (!folio_test_hugetlb(old))
828 __lruvec_stat_sub_folio(old, NR_FILE_PAGES);
829 if (!folio_test_hugetlb(new))
830 __lruvec_stat_add_folio(new, NR_FILE_PAGES);
831 if (folio_test_swapbacked(old))
832 __lruvec_stat_sub_folio(old, NR_SHMEM);
833 if (folio_test_swapbacked(new))
834 __lruvec_stat_add_folio(new, NR_SHMEM);
835 xas_unlock_irq(&xas);
836 if (free_folio)
837 free_folio(old);
838 folio_put(old);
839}
840EXPORT_SYMBOL_GPL(replace_page_cache_folio);
841
842noinline int __filemap_add_folio(struct address_space *mapping,
843 struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp)
844{
845 XA_STATE(xas, &mapping->i_pages, index);
846 int huge = folio_test_hugetlb(folio);
847 bool charged = false;
848 long nr = 1;
849
850 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
851 VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
852 mapping_set_update(&xas, mapping);
853
854 if (!huge) {
855 int error = mem_cgroup_charge(folio, NULL, gfp);
856 if (error)
857 return error;
858 charged = true;
859 }
860
861 VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
862 xas_set_order(&xas, index, folio_order(folio));
863 nr = folio_nr_pages(folio);
864
865 gfp &= GFP_RECLAIM_MASK;
866 folio_ref_add(folio, nr);
867 folio->mapping = mapping;
868 folio->index = xas.xa_index;
869
870 do {
871 unsigned int order = xa_get_order(xas.xa, xas.xa_index);
872 void *entry, *old = NULL;
873
874 if (order > folio_order(folio))
875 xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
876 order, gfp);
877 xas_lock_irq(&xas);
878 xas_for_each_conflict(&xas, entry) {
879 old = entry;
880 if (!xa_is_value(entry)) {
881 xas_set_err(&xas, -EEXIST);
882 goto unlock;
883 }
884 }
885
886 if (old) {
887 if (shadowp)
888 *shadowp = old;
889 /* entry may have been split before we acquired lock */
890 order = xa_get_order(xas.xa, xas.xa_index);
891 if (order > folio_order(folio)) {
892 /* How to handle large swap entries? */
893 BUG_ON(shmem_mapping(mapping));
894 xas_split(&xas, old, order);
895 xas_reset(&xas);
896 }
897 }
898
899 xas_store(&xas, folio);
900 if (xas_error(&xas))
901 goto unlock;
902
903 mapping->nrpages += nr;
904
905 /* hugetlb pages do not participate in page cache accounting */
906 if (!huge) {
907 __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
908 if (folio_test_pmd_mappable(folio))
909 __lruvec_stat_mod_folio(folio,
910 NR_FILE_THPS, nr);
911 }
912unlock:
913 xas_unlock_irq(&xas);
914 } while (xas_nomem(&xas, gfp));
915
916 if (xas_error(&xas))
917 goto error;
918
919 trace_mm_filemap_add_to_page_cache(folio);
920 return 0;
921error:
922 if (charged)
923 mem_cgroup_uncharge(folio);
924 folio->mapping = NULL;
925 /* Leave page->index set: truncation relies upon it */
926 folio_put_refs(folio, nr);
927 return xas_error(&xas);
928}
929ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO);
930
931int filemap_add_folio(struct address_space *mapping, struct folio *folio,
932 pgoff_t index, gfp_t gfp)
933{
934 void *shadow = NULL;
935 int ret;
936
937 __folio_set_locked(folio);
938 ret = __filemap_add_folio(mapping, folio, index, gfp, &shadow);
939 if (unlikely(ret))
940 __folio_clear_locked(folio);
941 else {
942 /*
943 * The folio might have been evicted from cache only
944 * recently, in which case it should be activated like
945 * any other repeatedly accessed folio.
946 * The exception is folios getting rewritten; evicting other
947 * data from the working set, only to cache data that will
948 * get overwritten with something else, is a waste of memory.
949 */
950 WARN_ON_ONCE(folio_test_active(folio));
951 if (!(gfp & __GFP_WRITE) && shadow)
952 workingset_refault(folio, shadow);
953 folio_add_lru(folio);
954 }
955 return ret;
956}
957EXPORT_SYMBOL_GPL(filemap_add_folio);
958
959#ifdef CONFIG_NUMA
960struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order)
961{
962 int n;
963 struct folio *folio;
964
965 if (cpuset_do_page_mem_spread()) {
966 unsigned int cpuset_mems_cookie;
967 do {
968 cpuset_mems_cookie = read_mems_allowed_begin();
969 n = cpuset_mem_spread_node();
970 folio = __folio_alloc_node(gfp, order, n);
971 } while (!folio && read_mems_allowed_retry(cpuset_mems_cookie));
972
973 return folio;
974 }
975 return folio_alloc(gfp, order);
976}
977EXPORT_SYMBOL(filemap_alloc_folio);
978#endif
979
980/*
981 * filemap_invalidate_lock_two - lock invalidate_lock for two mappings
982 *
983 * Lock exclusively invalidate_lock of any passed mapping that is not NULL.
984 *
985 * @mapping1: the first mapping to lock
986 * @mapping2: the second mapping to lock
987 */
988void filemap_invalidate_lock_two(struct address_space *mapping1,
989 struct address_space *mapping2)
990{
991 if (mapping1 > mapping2)
992 swap(mapping1, mapping2);
993 if (mapping1)
994 down_write(&mapping1->invalidate_lock);
995 if (mapping2 && mapping1 != mapping2)
996 down_write_nested(&mapping2->invalidate_lock, 1);
997}
998EXPORT_SYMBOL(filemap_invalidate_lock_two);
999
1000/*
1001 * filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
1002 *
1003 * Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
1004 *
1005 * @mapping1: the first mapping to unlock
1006 * @mapping2: the second mapping to unlock
1007 */
1008void filemap_invalidate_unlock_two(struct address_space *mapping1,
1009 struct address_space *mapping2)
1010{
1011 if (mapping1)
1012 up_write(&mapping1->invalidate_lock);
1013 if (mapping2 && mapping1 != mapping2)
1014 up_write(&mapping2->invalidate_lock);
1015}
1016EXPORT_SYMBOL(filemap_invalidate_unlock_two);
1017
1018/*
1019 * In order to wait for pages to become available there must be
1020 * waitqueues associated with pages. By using a hash table of
1021 * waitqueues where the bucket discipline is to maintain all
1022 * waiters on the same queue and wake all when any of the pages
1023 * become available, and for the woken contexts to check to be
1024 * sure the appropriate page became available, this saves space
1025 * at a cost of "thundering herd" phenomena during rare hash
1026 * collisions.
1027 */
1028#define PAGE_WAIT_TABLE_BITS 8
1029#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
1030static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
1031
1032static wait_queue_head_t *folio_waitqueue(struct folio *folio)
1033{
1034 return &folio_wait_table[hash_ptr(folio, PAGE_WAIT_TABLE_BITS)];
1035}
1036
1037void __init pagecache_init(void)
1038{
1039 int i;
1040
1041 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
1042 init_waitqueue_head(&folio_wait_table[i]);
1043
1044 page_writeback_init();
1045}
1046
1047/*
1048 * The page wait code treats the "wait->flags" somewhat unusually, because
1049 * we have multiple different kinds of waits, not just the usual "exclusive"
1050 * one.
1051 *
1052 * We have:
1053 *
1054 * (a) no special bits set:
1055 *
1056 * We're just waiting for the bit to be released, and when a waker
1057 * calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
1058 * and remove it from the wait queue.
1059 *
1060 * Simple and straightforward.
1061 *
1062 * (b) WQ_FLAG_EXCLUSIVE:
1063 *
1064 * The waiter is waiting to get the lock, and only one waiter should
1065 * be woken up to avoid any thundering herd behavior. We'll set the
1066 * WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
1067 *
1068 * This is the traditional exclusive wait.
1069 *
1070 * (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
1071 *
1072 * The waiter is waiting to get the bit, and additionally wants the
1073 * lock to be transferred to it for fair lock behavior. If the lock
1074 * cannot be taken, we stop walking the wait queue without waking
1075 * the waiter.
1076 *
1077 * This is the "fair lock handoff" case, and in addition to setting
1078 * WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
1079 * that it now has the lock.
1080 */
1081static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
1082{
1083 unsigned int flags;
1084 struct wait_page_key *key = arg;
1085 struct wait_page_queue *wait_page
1086 = container_of(wait, struct wait_page_queue, wait);
1087
1088 if (!wake_page_match(wait_page, key))
1089 return 0;
1090
1091 /*
1092 * If it's a lock handoff wait, we get the bit for it, and
1093 * stop walking (and do not wake it up) if we can't.
1094 */
1095 flags = wait->flags;
1096 if (flags & WQ_FLAG_EXCLUSIVE) {
1097 if (test_bit(key->bit_nr, &key->folio->flags))
1098 return -1;
1099 if (flags & WQ_FLAG_CUSTOM) {
1100 if (test_and_set_bit(key->bit_nr, &key->folio->flags))
1101 return -1;
1102 flags |= WQ_FLAG_DONE;
1103 }
1104 }
1105
1106 /*
1107 * We are holding the wait-queue lock, but the waiter that
1108 * is waiting for this will be checking the flags without
1109 * any locking.
1110 *
1111 * So update the flags atomically, and wake up the waiter
1112 * afterwards to avoid any races. This store-release pairs
1113 * with the load-acquire in folio_wait_bit_common().
1114 */
1115 smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
1116 wake_up_state(wait->private, mode);
1117
1118 /*
1119 * Ok, we have successfully done what we're waiting for,
1120 * and we can unconditionally remove the wait entry.
1121 *
1122 * Note that this pairs with the "finish_wait()" in the
1123 * waiter, and has to be the absolute last thing we do.
1124 * After this list_del_init(&wait->entry) the wait entry
1125 * might be de-allocated and the process might even have
1126 * exited.
1127 */
1128 list_del_init_careful(&wait->entry);
1129 return (flags & WQ_FLAG_EXCLUSIVE) != 0;
1130}
1131
1132static void folio_wake_bit(struct folio *folio, int bit_nr)
1133{
1134 wait_queue_head_t *q = folio_waitqueue(folio);
1135 struct wait_page_key key;
1136 unsigned long flags;
1137
1138 key.folio = folio;
1139 key.bit_nr = bit_nr;
1140 key.page_match = 0;
1141
1142 spin_lock_irqsave(&q->lock, flags);
1143 __wake_up_locked_key(q, TASK_NORMAL, &key);
1144
1145 /*
1146 * It's possible to miss clearing waiters here, when we woke our page
1147 * waiters, but the hashed waitqueue has waiters for other pages on it.
1148 * That's okay, it's a rare case. The next waker will clear it.
1149 *
1150 * Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE,
1151 * other), the flag may be cleared in the course of freeing the page;
1152 * but that is not required for correctness.
1153 */
1154 if (!waitqueue_active(q) || !key.page_match)
1155 folio_clear_waiters(folio);
1156
1157 spin_unlock_irqrestore(&q->lock, flags);
1158}
1159
1160/*
1161 * A choice of three behaviors for folio_wait_bit_common():
1162 */
1163enum behavior {
1164 EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
1165 * __folio_lock() waiting on then setting PG_locked.
1166 */
1167 SHARED, /* Hold ref to page and check the bit when woken, like
1168 * folio_wait_writeback() waiting on PG_writeback.
1169 */
1170 DROP, /* Drop ref to page before wait, no check when woken,
1171 * like folio_put_wait_locked() on PG_locked.
1172 */
1173};
1174
1175/*
1176 * Attempt to check (or get) the folio flag, and mark us done
1177 * if successful.
1178 */
1179static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
1180 struct wait_queue_entry *wait)
1181{
1182 if (wait->flags & WQ_FLAG_EXCLUSIVE) {
1183 if (test_and_set_bit(bit_nr, &folio->flags))
1184 return false;
1185 } else if (test_bit(bit_nr, &folio->flags))
1186 return false;
1187
1188 wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
1189 return true;
1190}
1191
1192/* How many times do we accept lock stealing from under a waiter? */
1193int sysctl_page_lock_unfairness = 5;
1194
1195static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
1196 int state, enum behavior behavior)
1197{
1198 wait_queue_head_t *q = folio_waitqueue(folio);
1199 int unfairness = sysctl_page_lock_unfairness;
1200 struct wait_page_queue wait_page;
1201 wait_queue_entry_t *wait = &wait_page.wait;
1202 bool thrashing = false;
1203 unsigned long pflags;
1204 bool in_thrashing;
1205
1206 if (bit_nr == PG_locked &&
1207 !folio_test_uptodate(folio) && folio_test_workingset(folio)) {
1208 delayacct_thrashing_start(&in_thrashing);
1209 psi_memstall_enter(&pflags);
1210 thrashing = true;
1211 }
1212
1213 init_wait(wait);
1214 wait->func = wake_page_function;
1215 wait_page.folio = folio;
1216 wait_page.bit_nr = bit_nr;
1217
1218repeat:
1219 wait->flags = 0;
1220 if (behavior == EXCLUSIVE) {
1221 wait->flags = WQ_FLAG_EXCLUSIVE;
1222 if (--unfairness < 0)
1223 wait->flags |= WQ_FLAG_CUSTOM;
1224 }
1225
1226 /*
1227 * Do one last check whether we can get the
1228 * page bit synchronously.
1229 *
1230 * Do the folio_set_waiters() marking before that
1231 * to let any waker we _just_ missed know they
1232 * need to wake us up (otherwise they'll never
1233 * even go to the slow case that looks at the
1234 * page queue), and add ourselves to the wait
1235 * queue if we need to sleep.
1236 *
1237 * This part needs to be done under the queue
1238 * lock to avoid races.
1239 */
1240 spin_lock_irq(&q->lock);
1241 folio_set_waiters(folio);
1242 if (!folio_trylock_flag(folio, bit_nr, wait))
1243 __add_wait_queue_entry_tail(q, wait);
1244 spin_unlock_irq(&q->lock);
1245
1246 /*
1247 * From now on, all the logic will be based on
1248 * the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to
1249 * see whether the page bit testing has already
1250 * been done by the wake function.
1251 *
1252 * We can drop our reference to the folio.
1253 */
1254 if (behavior == DROP)
1255 folio_put(folio);
1256
1257 /*
1258 * Note that until the "finish_wait()", or until
1259 * we see the WQ_FLAG_WOKEN flag, we need to
1260 * be very careful with the 'wait->flags', because
1261 * we may race with a waker that sets them.
1262 */
1263 for (;;) {
1264 unsigned int flags;
1265
1266 set_current_state(state);
1267
1268 /* Loop until we've been woken or interrupted */
1269 flags = smp_load_acquire(&wait->flags);
1270 if (!(flags & WQ_FLAG_WOKEN)) {
1271 if (signal_pending_state(state, current))
1272 break;
1273
1274 io_schedule();
1275 continue;
1276 }
1277
1278 /* If we were non-exclusive, we're done */
1279 if (behavior != EXCLUSIVE)
1280 break;
1281
1282 /* If the waker got the lock for us, we're done */
1283 if (flags & WQ_FLAG_DONE)
1284 break;
1285
1286 /*
1287 * Otherwise, if we're getting the lock, we need to
1288 * try to get it ourselves.
1289 *
1290 * And if that fails, we'll have to retry this all.
1291 */
1292 if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0))))
1293 goto repeat;
1294
1295 wait->flags |= WQ_FLAG_DONE;
1296 break;
1297 }
1298
1299 /*
1300 * If a signal happened, this 'finish_wait()' may remove the last
1301 * waiter from the wait-queues, but the folio waiters bit will remain
1302 * set. That's ok. The next wakeup will take care of it, and trying
1303 * to do it here would be difficult and prone to races.
1304 */
1305 finish_wait(q, wait);
1306
1307 if (thrashing) {
1308 delayacct_thrashing_end(&in_thrashing);
1309 psi_memstall_leave(&pflags);
1310 }
1311
1312 /*
1313 * NOTE! The wait->flags weren't stable until we've done the
1314 * 'finish_wait()', and we could have exited the loop above due
1315 * to a signal, and had a wakeup event happen after the signal
1316 * test but before the 'finish_wait()'.
1317 *
1318 * So only after the finish_wait() can we reliably determine
1319 * if we got woken up or not, so we can now figure out the final
1320 * return value based on that state without races.
1321 *
1322 * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
1323 * waiter, but an exclusive one requires WQ_FLAG_DONE.
1324 */
1325 if (behavior == EXCLUSIVE)
1326 return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;
1327
1328 return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
1329}
1330
1331#ifdef CONFIG_MIGRATION
1332/**
1333 * migration_entry_wait_on_locked - Wait for a migration entry to be removed
1334 * @entry: migration swap entry.
1335 * @ptl: already locked ptl. This function will drop the lock.
1336 *
1337 * Wait for a migration entry referencing the given page to be removed. This is
1338 * equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except
1339 * this can be called without taking a reference on the page. Instead this
1340 * should be called while holding the ptl for the migration entry referencing
1341 * the page.
1342 *
1343 * Returns after unlocking the ptl.
1344 *
1345 * This follows the same logic as folio_wait_bit_common() so see the comments
1346 * there.
1347 */
1348void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl)
1349 __releases(ptl)
1350{
1351 struct wait_page_queue wait_page;
1352 wait_queue_entry_t *wait = &wait_page.wait;
1353 bool thrashing = false;
1354 unsigned long pflags;
1355 bool in_thrashing;
1356 wait_queue_head_t *q;
1357 struct folio *folio = page_folio(pfn_swap_entry_to_page(entry));
1358
1359 q = folio_waitqueue(folio);
1360 if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
1361 delayacct_thrashing_start(&in_thrashing);
1362 psi_memstall_enter(&pflags);
1363 thrashing = true;
1364 }
1365
1366 init_wait(wait);
1367 wait->func = wake_page_function;
1368 wait_page.folio = folio;
1369 wait_page.bit_nr = PG_locked;
1370 wait->flags = 0;
1371
1372 spin_lock_irq(&q->lock);
1373 folio_set_waiters(folio);
1374 if (!folio_trylock_flag(folio, PG_locked, wait))
1375 __add_wait_queue_entry_tail(q, wait);
1376 spin_unlock_irq(&q->lock);
1377
1378 /*
1379 * If a migration entry exists for the page the migration path must hold
1380 * a valid reference to the page, and it must take the ptl to remove the
1381 * migration entry. So the page is valid until the ptl is dropped.
1382 */
1383 spin_unlock(ptl);
1384
1385 for (;;) {
1386 unsigned int flags;
1387
1388 set_current_state(TASK_UNINTERRUPTIBLE);
1389
1390 /* Loop until we've been woken or interrupted */
1391 flags = smp_load_acquire(&wait->flags);
1392 if (!(flags & WQ_FLAG_WOKEN)) {
1393 if (signal_pending_state(TASK_UNINTERRUPTIBLE, current))
1394 break;
1395
1396 io_schedule();
1397 continue;
1398 }
1399 break;
1400 }
1401
1402 finish_wait(q, wait);
1403
1404 if (thrashing) {
1405 delayacct_thrashing_end(&in_thrashing);
1406 psi_memstall_leave(&pflags);
1407 }
1408}
1409#endif
1410
1411void folio_wait_bit(struct folio *folio, int bit_nr)
1412{
1413 folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
1414}
1415EXPORT_SYMBOL(folio_wait_bit);
1416
1417int folio_wait_bit_killable(struct folio *folio, int bit_nr)
1418{
1419 return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, SHARED);
1420}
1421EXPORT_SYMBOL(folio_wait_bit_killable);
1422
1423/**
1424 * folio_put_wait_locked - Drop a reference and wait for it to be unlocked
1425 * @folio: The folio to wait for.
1426 * @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
1427 *
1428 * The caller should hold a reference on @folio. They expect the page to
1429 * become unlocked relatively soon, but do not wish to hold up migration
1430 * (for example) by holding the reference while waiting for the folio to
1431 * come unlocked. After this function returns, the caller should not
1432 * dereference @folio.
1433 *
1434 * Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal.
1435 */
1436static int folio_put_wait_locked(struct folio *folio, int state)
1437{
1438 return folio_wait_bit_common(folio, PG_locked, state, DROP);
1439}
1440
1441/**
1442 * folio_add_wait_queue - Add an arbitrary waiter to a folio's wait queue
1443 * @folio: Folio defining the wait queue of interest
1444 * @waiter: Waiter to add to the queue
1445 *
1446 * Add an arbitrary @waiter to the wait queue for the nominated @folio.
1447 */
1448void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter)
1449{
1450 wait_queue_head_t *q = folio_waitqueue(folio);
1451 unsigned long flags;
1452
1453 spin_lock_irqsave(&q->lock, flags);
1454 __add_wait_queue_entry_tail(q, waiter);
1455 folio_set_waiters(folio);
1456 spin_unlock_irqrestore(&q->lock, flags);
1457}
1458EXPORT_SYMBOL_GPL(folio_add_wait_queue);
1459
1460/**
1461 * folio_unlock - Unlock a locked folio.
1462 * @folio: The folio.
1463 *
1464 * Unlocks the folio and wakes up any thread sleeping on the page lock.
1465 *
1466 * Context: May be called from interrupt or process context. May not be
1467 * called from NMI context.
1468 */
1469void folio_unlock(struct folio *folio)
1470{
1471 /* Bit 7 allows x86 to check the byte's sign bit */
1472 BUILD_BUG_ON(PG_waiters != 7);
1473 BUILD_BUG_ON(PG_locked > 7);
1474 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1475 if (folio_xor_flags_has_waiters(folio, 1 << PG_locked))
1476 folio_wake_bit(folio, PG_locked);
1477}
1478EXPORT_SYMBOL(folio_unlock);
1479
1480/**
1481 * folio_end_read - End read on a folio.
1482 * @folio: The folio.
1483 * @success: True if all reads completed successfully.
1484 *
1485 * When all reads against a folio have completed, filesystems should
1486 * call this function to let the pagecache know that no more reads
1487 * are outstanding. This will unlock the folio and wake up any thread
1488 * sleeping on the lock. The folio will also be marked uptodate if all
1489 * reads succeeded.
1490 *
1491 * Context: May be called from interrupt or process context. May not be
1492 * called from NMI context.
1493 */
1494void folio_end_read(struct folio *folio, bool success)
1495{
1496 unsigned long mask = 1 << PG_locked;
1497
1498 /* Must be in bottom byte for x86 to work */
1499 BUILD_BUG_ON(PG_uptodate > 7);
1500 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1501 VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);
1502
1503 if (likely(success))
1504 mask |= 1 << PG_uptodate;
1505 if (folio_xor_flags_has_waiters(folio, mask))
1506 folio_wake_bit(folio, PG_locked);
1507}
1508EXPORT_SYMBOL(folio_end_read);
1509
1510/**
1511 * folio_end_private_2 - Clear PG_private_2 and wake any waiters.
1512 * @folio: The folio.
1513 *
1514 * Clear the PG_private_2 bit on a folio and wake up any sleepers waiting for
1515 * it. The folio reference held for PG_private_2 being set is released.
1516 *
1517 * This is, for example, used when a netfs folio is being written to a local
1518 * disk cache, thereby allowing writes to the cache for the same folio to be
1519 * serialised.
1520 */
1521void folio_end_private_2(struct folio *folio)
1522{
1523 VM_BUG_ON_FOLIO(!folio_test_private_2(folio), folio);
1524 clear_bit_unlock(PG_private_2, folio_flags(folio, 0));
1525 folio_wake_bit(folio, PG_private_2);
1526 folio_put(folio);
1527}
1528EXPORT_SYMBOL(folio_end_private_2);
1529
1530/**
1531 * folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio.
1532 * @folio: The folio to wait on.
1533 *
1534 * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio.
1535 */
1536void folio_wait_private_2(struct folio *folio)
1537{
1538 while (folio_test_private_2(folio))
1539 folio_wait_bit(folio, PG_private_2);
1540}
1541EXPORT_SYMBOL(folio_wait_private_2);
1542
1543/**
1544 * folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio.
1545 * @folio: The folio to wait on.
1546 *
1547 * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a
1548 * fatal signal is received by the calling task.
1549 *
1550 * Return:
1551 * - 0 if successful.
1552 * - -EINTR if a fatal signal was encountered.
1553 */
1554int folio_wait_private_2_killable(struct folio *folio)
1555{
1556 int ret = 0;
1557
1558 while (folio_test_private_2(folio)) {
1559 ret = folio_wait_bit_killable(folio, PG_private_2);
1560 if (ret < 0)
1561 break;
1562 }
1563
1564 return ret;
1565}
1566EXPORT_SYMBOL(folio_wait_private_2_killable);
1567
1568/**
1569 * folio_end_writeback - End writeback against a folio.
1570 * @folio: The folio.
1571 *
1572 * The folio must actually be under writeback.
1573 *
1574 * Context: May be called from process or interrupt context.
1575 */
1576void folio_end_writeback(struct folio *folio)
1577{
1578 VM_BUG_ON_FOLIO(!folio_test_writeback(folio), folio);
1579
1580 /*
1581 * folio_test_clear_reclaim() could be used here but it is an
1582 * atomic operation and overkill in this particular case. Failing
1583 * to shuffle a folio marked for immediate reclaim is too mild
1584 * a gain to justify taking an atomic operation penalty at the
1585 * end of every folio writeback.
1586 */
1587 if (folio_test_reclaim(folio)) {
1588 folio_clear_reclaim(folio);
1589 folio_rotate_reclaimable(folio);
1590 }
1591
1592 /*
1593 * Writeback does not hold a folio reference of its own, relying
1594 * on truncation to wait for the clearing of PG_writeback.
1595 * But here we must make sure that the folio is not freed and
1596 * reused before the folio_wake_bit().
1597 */
1598 folio_get(folio);
1599 if (__folio_end_writeback(folio))
1600 folio_wake_bit(folio, PG_writeback);
1601 acct_reclaim_writeback(folio);
1602 folio_put(folio);
1603}
1604EXPORT_SYMBOL(folio_end_writeback);
1605
1606/**
1607 * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.
1608 * @folio: The folio to lock
1609 */
1610void __folio_lock(struct folio *folio)
1611{
1612 folio_wait_bit_common(folio, PG_locked, TASK_UNINTERRUPTIBLE,
1613 EXCLUSIVE);
1614}
1615EXPORT_SYMBOL(__folio_lock);
1616
1617int __folio_lock_killable(struct folio *folio)
1618{
1619 return folio_wait_bit_common(folio, PG_locked, TASK_KILLABLE,
1620 EXCLUSIVE);
1621}
1622EXPORT_SYMBOL_GPL(__folio_lock_killable);
1623
1624static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
1625{
1626 struct wait_queue_head *q = folio_waitqueue(folio);
1627 int ret;
1628
1629 wait->folio = folio;
1630 wait->bit_nr = PG_locked;
1631
1632 spin_lock_irq(&q->lock);
1633 __add_wait_queue_entry_tail(q, &wait->wait);
1634 folio_set_waiters(folio);
1635 ret = !folio_trylock(folio);
1636 /*
1637 * If we were successful now, we know we're still on the
1638 * waitqueue as we're still under the lock. This means it's
1639 * safe to remove and return success, we know the callback
1640 * isn't going to trigger.
1641 */
1642 if (!ret)
1643 __remove_wait_queue(q, &wait->wait);
1644 else
1645 ret = -EIOCBQUEUED;
1646 spin_unlock_irq(&q->lock);
1647 return ret;
1648}
1649
1650/*
1651 * Return values:
1652 * 0 - folio is locked.
1653 * non-zero - folio is not locked.
1654 * mmap_lock or per-VMA lock has been released (mmap_read_unlock() or
1655 * vma_end_read()), unless flags had both FAULT_FLAG_ALLOW_RETRY and
1656 * FAULT_FLAG_RETRY_NOWAIT set, in which case the lock is still held.
1657 *
1658 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 0
1659 * with the folio locked and the mmap_lock/per-VMA lock is left unperturbed.
1660 */
1661vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf)
1662{
1663 unsigned int flags = vmf->flags;
1664
1665 if (fault_flag_allow_retry_first(flags)) {
1666 /*
1667 * CAUTION! In this case, mmap_lock/per-VMA lock is not
1668 * released even though returning VM_FAULT_RETRY.
1669 */
1670 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1671 return VM_FAULT_RETRY;
1672
1673 release_fault_lock(vmf);
1674 if (flags & FAULT_FLAG_KILLABLE)
1675 folio_wait_locked_killable(folio);
1676 else
1677 folio_wait_locked(folio);
1678 return VM_FAULT_RETRY;
1679 }
1680 if (flags & FAULT_FLAG_KILLABLE) {
1681 bool ret;
1682
1683 ret = __folio_lock_killable(folio);
1684 if (ret) {
1685 release_fault_lock(vmf);
1686 return VM_FAULT_RETRY;
1687 }
1688 } else {
1689 __folio_lock(folio);
1690 }
1691
1692 return 0;
1693}
1694
1695/**
1696 * page_cache_next_miss() - Find the next gap in the page cache.
1697 * @mapping: Mapping.
1698 * @index: Index.
1699 * @max_scan: Maximum range to search.
1700 *
1701 * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
1702 * gap with the lowest index.
1703 *
1704 * This function may be called under the rcu_read_lock. However, this will
1705 * not atomically search a snapshot of the cache at a single point in time.
1706 * For example, if a gap is created at index 5, then subsequently a gap is
1707 * created at index 10, page_cache_next_miss covering both indices may
1708 * return 10 if called under the rcu_read_lock.
1709 *
1710 * Return: The index of the gap if found, otherwise an index outside the
1711 * range specified (in which case 'return - index >= max_scan' will be true).
1712 * In the rare case of index wrap-around, 0 will be returned.
1713 */
1714pgoff_t page_cache_next_miss(struct address_space *mapping,
1715 pgoff_t index, unsigned long max_scan)
1716{
1717 XA_STATE(xas, &mapping->i_pages, index);
1718
1719 while (max_scan--) {
1720 void *entry = xas_next(&xas);
1721 if (!entry || xa_is_value(entry))
1722 break;
1723 if (xas.xa_index == 0)
1724 break;
1725 }
1726
1727 return xas.xa_index;
1728}
1729EXPORT_SYMBOL(page_cache_next_miss);
1730
1731/**
1732 * page_cache_prev_miss() - Find the previous gap in the page cache.
1733 * @mapping: Mapping.
1734 * @index: Index.
1735 * @max_scan: Maximum range to search.
1736 *
1737 * Search the range [max(index - max_scan + 1, 0), index] for the
1738 * gap with the highest index.
1739 *
1740 * This function may be called under the rcu_read_lock. However, this will
1741 * not atomically search a snapshot of the cache at a single point in time.
1742 * For example, if a gap is created at index 10, then subsequently a gap is
1743 * created at index 5, page_cache_prev_miss() covering both indices may
1744 * return 5 if called under the rcu_read_lock.
1745 *
1746 * Return: The index of the gap if found, otherwise an index outside the
1747 * range specified (in which case 'index - return >= max_scan' will be true).
1748 * In the rare case of wrap-around, ULONG_MAX will be returned.
1749 */
1750pgoff_t page_cache_prev_miss(struct address_space *mapping,
1751 pgoff_t index, unsigned long max_scan)
1752{
1753 XA_STATE(xas, &mapping->i_pages, index);
1754
1755 while (max_scan--) {
1756 void *entry = xas_prev(&xas);
1757 if (!entry || xa_is_value(entry))
1758 break;
1759 if (xas.xa_index == ULONG_MAX)
1760 break;
1761 }
1762
1763 return xas.xa_index;
1764}
1765EXPORT_SYMBOL(page_cache_prev_miss);
1766
1767/*
1768 * Lockless page cache protocol:
1769 * On the lookup side:
1770 * 1. Load the folio from i_pages
1771 * 2. Increment the refcount if it's not zero
1772 * 3. If the folio is not found by xas_reload(), put the refcount and retry
1773 *
1774 * On the removal side:
1775 * A. Freeze the page (by zeroing the refcount if nobody else has a reference)
1776 * B. Remove the page from i_pages
1777 * C. Return the page to the page allocator
1778 *
1779 * This means that any page may have its reference count temporarily
1780 * increased by a speculative page cache (or fast GUP) lookup as it can
1781 * be allocated by another user before the RCU grace period expires.
1782 * Because the refcount temporarily acquired here may end up being the
1783 * last refcount on the page, any page allocation must be freeable by
1784 * folio_put().
1785 */
1786
1787/*
1788 * filemap_get_entry - Get a page cache entry.
1789 * @mapping: the address_space to search
1790 * @index: The page cache index.
1791 *
1792 * Looks up the page cache entry at @mapping & @index. If it is a folio,
1793 * it is returned with an increased refcount. If it is a shadow entry
1794 * of a previously evicted folio, or a swap entry from shmem/tmpfs,
1795 * it is returned without further action.
1796 *
1797 * Return: The folio, swap or shadow entry, %NULL if nothing is found.
1798 */
1799void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
1800{
1801 XA_STATE(xas, &mapping->i_pages, index);
1802 struct folio *folio;
1803
1804 rcu_read_lock();
1805repeat:
1806 xas_reset(&xas);
1807 folio = xas_load(&xas);
1808 if (xas_retry(&xas, folio))
1809 goto repeat;
1810 /*
1811 * A shadow entry of a recently evicted page, or a swap entry from
1812 * shmem/tmpfs. Return it without attempting to raise page count.
1813 */
1814 if (!folio || xa_is_value(folio))
1815 goto out;
1816
1817 if (!folio_try_get_rcu(folio))
1818 goto repeat;
1819
1820 if (unlikely(folio != xas_reload(&xas))) {
1821 folio_put(folio);
1822 goto repeat;
1823 }
1824out:
1825 rcu_read_unlock();
1826
1827 return folio;
1828}
1829
1830/**
1831 * __filemap_get_folio - Find and get a reference to a folio.
1832 * @mapping: The address_space to search.
1833 * @index: The page index.
1834 * @fgp_flags: %FGP flags modify how the folio is returned.
1835 * @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
1836 *
1837 * Looks up the page cache entry at @mapping & @index.
1838 *
1839 * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
1840 * if the %GFP flags specified for %FGP_CREAT are atomic.
1841 *
1842 * If this function returns a folio, it is returned with an increased refcount.
1843 *
1844 * Return: The found folio or an ERR_PTR() otherwise.
1845 */
1846struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
1847 fgf_t fgp_flags, gfp_t gfp)
1848{
1849 struct folio *folio;
1850
1851repeat:
1852 folio = filemap_get_entry(mapping, index);
1853 if (xa_is_value(folio))
1854 folio = NULL;
1855 if (!folio)
1856 goto no_page;
1857
1858 if (fgp_flags & FGP_LOCK) {
1859 if (fgp_flags & FGP_NOWAIT) {
1860 if (!folio_trylock(folio)) {
1861 folio_put(folio);
1862 return ERR_PTR(-EAGAIN);
1863 }
1864 } else {
1865 folio_lock(folio);
1866 }
1867
1868 /* Has the page been truncated? */
1869 if (unlikely(folio->mapping != mapping)) {
1870 folio_unlock(folio);
1871 folio_put(folio);
1872 goto repeat;
1873 }
1874 VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
1875 }
1876
1877 if (fgp_flags & FGP_ACCESSED)
1878 folio_mark_accessed(folio);
1879 else if (fgp_flags & FGP_WRITE) {
1880 /* Clear idle flag for buffer write */
1881 if (folio_test_idle(folio))
1882 folio_clear_idle(folio);
1883 }
1884
1885 if (fgp_flags & FGP_STABLE)
1886 folio_wait_stable(folio);
1887no_page:
1888 if (!folio && (fgp_flags & FGP_CREAT)) {
1889 unsigned order = FGF_GET_ORDER(fgp_flags);
1890 int err;
1891
1892 if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
1893 gfp |= __GFP_WRITE;
1894 if (fgp_flags & FGP_NOFS)
1895 gfp &= ~__GFP_FS;
1896 if (fgp_flags & FGP_NOWAIT) {
1897 gfp &= ~GFP_KERNEL;
1898 gfp |= GFP_NOWAIT | __GFP_NOWARN;
1899 }
1900 if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
1901 fgp_flags |= FGP_LOCK;
1902
1903 if (!mapping_large_folio_support(mapping))
1904 order = 0;
1905 if (order > MAX_PAGECACHE_ORDER)
1906 order = MAX_PAGECACHE_ORDER;
1907 /* If we're not aligned, allocate a smaller folio */
1908 if (index & ((1UL << order) - 1))
1909 order = __ffs(index);
1910
1911 do {
1912 gfp_t alloc_gfp = gfp;
1913
1914 err = -ENOMEM;
1915 if (order == 1)
1916 order = 0;
1917 if (order > 0)
1918 alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN;
1919 folio = filemap_alloc_folio(alloc_gfp, order);
1920 if (!folio)
1921 continue;
1922
1923 /* Init accessed so avoid atomic mark_page_accessed later */
1924 if (fgp_flags & FGP_ACCESSED)
1925 __folio_set_referenced(folio);
1926
1927 err = filemap_add_folio(mapping, folio, index, gfp);
1928 if (!err)
1929 break;
1930 folio_put(folio);
1931 folio = NULL;
1932 } while (order-- > 0);
1933
1934 if (err == -EEXIST)
1935 goto repeat;
1936 if (err)
1937 return ERR_PTR(err);
1938 /*
1939 * filemap_add_folio locks the page, and for mmap
1940 * we expect an unlocked page.
1941 */
1942 if (folio && (fgp_flags & FGP_FOR_MMAP))
1943 folio_unlock(folio);
1944 }
1945
1946 if (!folio)
1947 return ERR_PTR(-ENOENT);
1948 return folio;
1949}
1950EXPORT_SYMBOL(__filemap_get_folio);
1951
1952static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
1953 xa_mark_t mark)
1954{
1955 struct folio *folio;
1956
1957retry:
1958 if (mark == XA_PRESENT)
1959 folio = xas_find(xas, max);
1960 else
1961 folio = xas_find_marked(xas, max, mark);
1962
1963 if (xas_retry(xas, folio))
1964 goto retry;
1965 /*
1966 * A shadow entry of a recently evicted page, a swap
1967 * entry from shmem/tmpfs or a DAX entry. Return it
1968 * without attempting to raise page count.
1969 */
1970 if (!folio || xa_is_value(folio))
1971 return folio;
1972
1973 if (!folio_try_get_rcu(folio))
1974 goto reset;
1975
1976 if (unlikely(folio != xas_reload(xas))) {
1977 folio_put(folio);
1978 goto reset;
1979 }
1980
1981 return folio;
1982reset:
1983 xas_reset(xas);
1984 goto retry;
1985}
1986
1987/**
1988 * find_get_entries - gang pagecache lookup
1989 * @mapping: The address_space to search
1990 * @start: The starting page cache index
1991 * @end: The final page index (inclusive).
1992 * @fbatch: Where the resulting entries are placed.
1993 * @indices: The cache indices corresponding to the entries in @entries
1994 *
1995 * find_get_entries() will search for and return a batch of entries in
1996 * the mapping. The entries are placed in @fbatch. find_get_entries()
1997 * takes a reference on any actual folios it returns.
1998 *
1999 * The entries have ascending indexes. The indices may not be consecutive
2000 * due to not-present entries or large folios.
2001 *
2002 * Any shadow entries of evicted folios, or swap entries from
2003 * shmem/tmpfs, are included in the returned array.
2004 *
2005 * Return: The number of entries which were found.
2006 */
2007unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
2008 pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
2009{
2010 XA_STATE(xas, &mapping->i_pages, *start);
2011 struct folio *folio;
2012
2013 rcu_read_lock();
2014 while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
2015 indices[fbatch->nr] = xas.xa_index;
2016 if (!folio_batch_add(fbatch, folio))
2017 break;
2018 }
2019 rcu_read_unlock();
2020
2021 if (folio_batch_count(fbatch)) {
2022 unsigned long nr = 1;
2023 int idx = folio_batch_count(fbatch) - 1;
2024
2025 folio = fbatch->folios[idx];
2026 if (!xa_is_value(folio))
2027 nr = folio_nr_pages(folio);
2028 *start = indices[idx] + nr;
2029 }
2030 return folio_batch_count(fbatch);
2031}
2032
2033/**
2034 * find_lock_entries - Find a batch of pagecache entries.
2035 * @mapping: The address_space to search.
2036 * @start: The starting page cache index.
2037 * @end: The final page index (inclusive).
2038 * @fbatch: Where the resulting entries are placed.
2039 * @indices: The cache indices of the entries in @fbatch.
2040 *
2041 * find_lock_entries() will return a batch of entries from @mapping.
2042 * Swap, shadow and DAX entries are included. Folios are returned
2043 * locked and with an incremented refcount. Folios which are locked
2044 * by somebody else or under writeback are skipped. Folios which are
2045 * partially outside the range are not returned.
2046 *
2047 * The entries have ascending indexes. The indices may not be consecutive
2048 * due to not-present entries, large folios, folios which could not be
2049 * locked or folios under writeback.
2050 *
2051 * Return: The number of entries which were found.
2052 */
2053unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
2054 pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
2055{
2056 XA_STATE(xas, &mapping->i_pages, *start);
2057 struct folio *folio;
2058
2059 rcu_read_lock();
2060 while ((folio = find_get_entry(&xas, end, XA_PRESENT))) {
2061 if (!xa_is_value(folio)) {
2062 if (folio->index < *start)
2063 goto put;
2064 if (folio_next_index(folio) - 1 > end)
2065 goto put;
2066 if (!folio_trylock(folio))
2067 goto put;
2068 if (folio->mapping != mapping ||
2069 folio_test_writeback(folio))
2070 goto unlock;
2071 VM_BUG_ON_FOLIO(!folio_contains(folio, xas.xa_index),
2072 folio);
2073 }
2074 indices[fbatch->nr] = xas.xa_index;
2075 if (!folio_batch_add(fbatch, folio))
2076 break;
2077 continue;
2078unlock:
2079 folio_unlock(folio);
2080put:
2081 folio_put(folio);
2082 }
2083 rcu_read_unlock();
2084
2085 if (folio_batch_count(fbatch)) {
2086 unsigned long nr = 1;
2087 int idx = folio_batch_count(fbatch) - 1;
2088
2089 folio = fbatch->folios[idx];
2090 if (!xa_is_value(folio))
2091 nr = folio_nr_pages(folio);
2092 *start = indices[idx] + nr;
2093 }
2094 return folio_batch_count(fbatch);
2095}
2096
2097/**
2098 * filemap_get_folios - Get a batch of folios
2099 * @mapping: The address_space to search
2100 * @start: The starting page index
2101 * @end: The final page index (inclusive)
2102 * @fbatch: The batch to fill.
2103 *
2104 * Search for and return a batch of folios in the mapping starting at
2105 * index @start and up to index @end (inclusive). The folios are returned
2106 * in @fbatch with an elevated reference count.
2107 *
2108 * Return: The number of folios which were found.
2109 * We also update @start to index the next folio for the traversal.
2110 */
2111unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
2112 pgoff_t end, struct folio_batch *fbatch)
2113{
2114 return filemap_get_folios_tag(mapping, start, end, XA_PRESENT, fbatch);
2115}
2116EXPORT_SYMBOL(filemap_get_folios);
2117
2118/**
2119 * filemap_get_folios_contig - Get a batch of contiguous folios
2120 * @mapping: The address_space to search
2121 * @start: The starting page index
2122 * @end: The final page index (inclusive)
2123 * @fbatch: The batch to fill
2124 *
2125 * filemap_get_folios_contig() works exactly like filemap_get_folios(),
2126 * except the returned folios are guaranteed to be contiguous. This may
2127 * not return all contiguous folios if the batch gets filled up.
2128 *
2129 * Return: The number of folios found.
2130 * Also update @start to be positioned for traversal of the next folio.
2131 */
2132
2133unsigned filemap_get_folios_contig(struct address_space *mapping,
2134 pgoff_t *start, pgoff_t end, struct folio_batch *fbatch)
2135{
2136 XA_STATE(xas, &mapping->i_pages, *start);
2137 unsigned long nr;
2138 struct folio *folio;
2139
2140 rcu_read_lock();
2141
2142 for (folio = xas_load(&xas); folio && xas.xa_index <= end;
2143 folio = xas_next(&xas)) {
2144 if (xas_retry(&xas, folio))
2145 continue;
2146 /*
2147 * If the entry has been swapped out, we can stop looking.
2148 * No current caller is looking for DAX entries.
2149 */
2150 if (xa_is_value(folio))
2151 goto update_start;
2152
2153 if (!folio_try_get_rcu(folio))
2154 goto retry;
2155
2156 if (unlikely(folio != xas_reload(&xas)))
2157 goto put_folio;
2158
2159 if (!folio_batch_add(fbatch, folio)) {
2160 nr = folio_nr_pages(folio);
2161 *start = folio->index + nr;
2162 goto out;
2163 }
2164 continue;
2165put_folio:
2166 folio_put(folio);
2167
2168retry:
2169 xas_reset(&xas);
2170 }
2171
2172update_start:
2173 nr = folio_batch_count(fbatch);
2174
2175 if (nr) {
2176 folio = fbatch->folios[nr - 1];
2177 *start = folio_next_index(folio);
2178 }
2179out:
2180 rcu_read_unlock();
2181 return folio_batch_count(fbatch);
2182}
2183EXPORT_SYMBOL(filemap_get_folios_contig);
2184
2185/**
2186 * filemap_get_folios_tag - Get a batch of folios matching @tag
2187 * @mapping: The address_space to search
2188 * @start: The starting page index
2189 * @end: The final page index (inclusive)
2190 * @tag: The tag index
2191 * @fbatch: The batch to fill
2192 *
2193 * The first folio may start before @start; if it does, it will contain
2194 * @start. The final folio may extend beyond @end; if it does, it will
2195 * contain @end. The folios have ascending indices. There may be gaps
2196 * between the folios if there are indices which have no folio in the
2197 * page cache. If folios are added to or removed from the page cache
2198 * while this is running, they may or may not be found by this call.
2199 * Only returns folios that are tagged with @tag.
2200 *
2201 * Return: The number of folios found.
2202 * Also update @start to index the next folio for traversal.
2203 */
2204unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start,
2205 pgoff_t end, xa_mark_t tag, struct folio_batch *fbatch)
2206{
2207 XA_STATE(xas, &mapping->i_pages, *start);
2208 struct folio *folio;
2209
2210 rcu_read_lock();
2211 while ((folio = find_get_entry(&xas, end, tag)) != NULL) {
2212 /*
2213 * Shadow entries should never be tagged, but this iteration
2214 * is lockless so there is a window for page reclaim to evict
2215 * a page we saw tagged. Skip over it.
2216 */
2217 if (xa_is_value(folio))
2218 continue;
2219 if (!folio_batch_add(fbatch, folio)) {
2220 unsigned long nr = folio_nr_pages(folio);
2221 *start = folio->index + nr;
2222 goto out;
2223 }
2224 }
2225 /*
2226 * We come here when there is no page beyond @end. We take care to not
2227 * overflow the index @start as it confuses some of the callers. This
2228 * breaks the iteration when there is a page at index -1 but that is
2229 * already broke anyway.
2230 */
2231 if (end == (pgoff_t)-1)
2232 *start = (pgoff_t)-1;
2233 else
2234 *start = end + 1;
2235out:
2236 rcu_read_unlock();
2237
2238 return folio_batch_count(fbatch);
2239}
2240EXPORT_SYMBOL(filemap_get_folios_tag);
2241
2242/*
2243 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
2244 * a _large_ part of the i/o request. Imagine the worst scenario:
2245 *
2246 * ---R__________________________________________B__________
2247 * ^ reading here ^ bad block(assume 4k)
2248 *
2249 * read(R) => miss => readahead(R...B) => media error => frustrating retries
2250 * => failing the whole request => read(R) => read(R+1) =>
2251 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
2252 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
2253 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
2254 *
2255 * It is going insane. Fix it by quickly scaling down the readahead size.
2256 */
2257static void shrink_readahead_size_eio(struct file_ra_state *ra)
2258{
2259 ra->ra_pages /= 4;
2260}
2261
2262/*
2263 * filemap_get_read_batch - Get a batch of folios for read
2264 *
2265 * Get a batch of folios which represent a contiguous range of bytes in
2266 * the file. No exceptional entries will be returned. If @index is in
2267 * the middle of a folio, the entire folio will be returned. The last
2268 * folio in the batch may have the readahead flag set or the uptodate flag
2269 * clear so that the caller can take the appropriate action.
2270 */
2271static void filemap_get_read_batch(struct address_space *mapping,
2272 pgoff_t index, pgoff_t max, struct folio_batch *fbatch)
2273{
2274 XA_STATE(xas, &mapping->i_pages, index);
2275 struct folio *folio;
2276
2277 rcu_read_lock();
2278 for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
2279 if (xas_retry(&xas, folio))
2280 continue;
2281 if (xas.xa_index > max || xa_is_value(folio))
2282 break;
2283 if (xa_is_sibling(folio))
2284 break;
2285 if (!folio_try_get_rcu(folio))
2286 goto retry;
2287
2288 if (unlikely(folio != xas_reload(&xas)))
2289 goto put_folio;
2290
2291 if (!folio_batch_add(fbatch, folio))
2292 break;
2293 if (!folio_test_uptodate(folio))
2294 break;
2295 if (folio_test_readahead(folio))
2296 break;
2297 xas_advance(&xas, folio_next_index(folio) - 1);
2298 continue;
2299put_folio:
2300 folio_put(folio);
2301retry:
2302 xas_reset(&xas);
2303 }
2304 rcu_read_unlock();
2305}
2306
2307static int filemap_read_folio(struct file *file, filler_t filler,
2308 struct folio *folio)
2309{
2310 bool workingset = folio_test_workingset(folio);
2311 unsigned long pflags;
2312 int error;
2313
2314 /*
2315 * A previous I/O error may have been due to temporary failures,
2316 * eg. multipath errors. PG_error will be set again if read_folio
2317 * fails.
2318 */
2319 folio_clear_error(folio);
2320
2321 /* Start the actual read. The read will unlock the page. */
2322 if (unlikely(workingset))
2323 psi_memstall_enter(&pflags);
2324 error = filler(file, folio);
2325 if (unlikely(workingset))
2326 psi_memstall_leave(&pflags);
2327 if (error)
2328 return error;
2329
2330 error = folio_wait_locked_killable(folio);
2331 if (error)
2332 return error;
2333 if (folio_test_uptodate(folio))
2334 return 0;
2335 if (file)
2336 shrink_readahead_size_eio(&file->f_ra);
2337 return -EIO;
2338}
2339
2340static bool filemap_range_uptodate(struct address_space *mapping,
2341 loff_t pos, size_t count, struct folio *folio,
2342 bool need_uptodate)
2343{
2344 if (folio_test_uptodate(folio))
2345 return true;
2346 /* pipes can't handle partially uptodate pages */
2347 if (need_uptodate)
2348 return false;
2349 if (!mapping->a_ops->is_partially_uptodate)
2350 return false;
2351 if (mapping->host->i_blkbits >= folio_shift(folio))
2352 return false;
2353
2354 if (folio_pos(folio) > pos) {
2355 count -= folio_pos(folio) - pos;
2356 pos = 0;
2357 } else {
2358 pos -= folio_pos(folio);
2359 }
2360
2361 return mapping->a_ops->is_partially_uptodate(folio, pos, count);
2362}
2363
2364static int filemap_update_page(struct kiocb *iocb,
2365 struct address_space *mapping, size_t count,
2366 struct folio *folio, bool need_uptodate)
2367{
2368 int error;
2369
2370 if (iocb->ki_flags & IOCB_NOWAIT) {
2371 if (!filemap_invalidate_trylock_shared(mapping))
2372 return -EAGAIN;
2373 } else {
2374 filemap_invalidate_lock_shared(mapping);
2375 }
2376
2377 if (!folio_trylock(folio)) {
2378 error = -EAGAIN;
2379 if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
2380 goto unlock_mapping;
2381 if (!(iocb->ki_flags & IOCB_WAITQ)) {
2382 filemap_invalidate_unlock_shared(mapping);
2383 /*
2384 * This is where we usually end up waiting for a
2385 * previously submitted readahead to finish.
2386 */
2387 folio_put_wait_locked(folio, TASK_KILLABLE);
2388 return AOP_TRUNCATED_PAGE;
2389 }
2390 error = __folio_lock_async(folio, iocb->ki_waitq);
2391 if (error)
2392 goto unlock_mapping;
2393 }
2394
2395 error = AOP_TRUNCATED_PAGE;
2396 if (!folio->mapping)
2397 goto unlock;
2398
2399 error = 0;
2400 if (filemap_range_uptodate(mapping, iocb->ki_pos, count, folio,
2401 need_uptodate))
2402 goto unlock;
2403
2404 error = -EAGAIN;
2405 if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
2406 goto unlock;
2407
2408 error = filemap_read_folio(iocb->ki_filp, mapping->a_ops->read_folio,
2409 folio);
2410 goto unlock_mapping;
2411unlock:
2412 folio_unlock(folio);
2413unlock_mapping:
2414 filemap_invalidate_unlock_shared(mapping);
2415 if (error == AOP_TRUNCATED_PAGE)
2416 folio_put(folio);
2417 return error;
2418}
2419
2420static int filemap_create_folio(struct file *file,
2421 struct address_space *mapping, pgoff_t index,
2422 struct folio_batch *fbatch)
2423{
2424 struct folio *folio;
2425 int error;
2426
2427 folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
2428 if (!folio)
2429 return -ENOMEM;
2430
2431 /*
2432 * Protect against truncate / hole punch. Grabbing invalidate_lock
2433 * here assures we cannot instantiate and bring uptodate new
2434 * pagecache folios after evicting page cache during truncate
2435 * and before actually freeing blocks. Note that we could
2436 * release invalidate_lock after inserting the folio into
2437 * the page cache as the locked folio would then be enough to
2438 * synchronize with hole punching. But there are code paths
2439 * such as filemap_update_page() filling in partially uptodate
2440 * pages or ->readahead() that need to hold invalidate_lock
2441 * while mapping blocks for IO so let's hold the lock here as
2442 * well to keep locking rules simple.
2443 */
2444 filemap_invalidate_lock_shared(mapping);
2445 error = filemap_add_folio(mapping, folio, index,
2446 mapping_gfp_constraint(mapping, GFP_KERNEL));
2447 if (error == -EEXIST)
2448 error = AOP_TRUNCATED_PAGE;
2449 if (error)
2450 goto error;
2451
2452 error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
2453 if (error)
2454 goto error;
2455
2456 filemap_invalidate_unlock_shared(mapping);
2457 folio_batch_add(fbatch, folio);
2458 return 0;
2459error:
2460 filemap_invalidate_unlock_shared(mapping);
2461 folio_put(folio);
2462 return error;
2463}
2464
2465static int filemap_readahead(struct kiocb *iocb, struct file *file,
2466 struct address_space *mapping, struct folio *folio,
2467 pgoff_t last_index)
2468{
2469 DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, folio->index);
2470
2471 if (iocb->ki_flags & IOCB_NOIO)
2472 return -EAGAIN;
2473 page_cache_async_ra(&ractl, folio, last_index - folio->index);
2474 return 0;
2475}
2476
2477static int filemap_get_pages(struct kiocb *iocb, size_t count,
2478 struct folio_batch *fbatch, bool need_uptodate)
2479{
2480 struct file *filp = iocb->ki_filp;
2481 struct address_space *mapping = filp->f_mapping;
2482 struct file_ra_state *ra = &filp->f_ra;
2483 pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
2484 pgoff_t last_index;
2485 struct folio *folio;
2486 int err = 0;
2487
2488 /* "last_index" is the index of the page beyond the end of the read */
2489 last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE);
2490retry:
2491 if (fatal_signal_pending(current))
2492 return -EINTR;
2493
2494 filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
2495 if (!folio_batch_count(fbatch)) {
2496 if (iocb->ki_flags & IOCB_NOIO)
2497 return -EAGAIN;
2498 page_cache_sync_readahead(mapping, ra, filp, index,
2499 last_index - index);
2500 filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
2501 }
2502 if (!folio_batch_count(fbatch)) {
2503 if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
2504 return -EAGAIN;
2505 err = filemap_create_folio(filp, mapping,
2506 iocb->ki_pos >> PAGE_SHIFT, fbatch);
2507 if (err == AOP_TRUNCATED_PAGE)
2508 goto retry;
2509 return err;
2510 }
2511
2512 folio = fbatch->folios[folio_batch_count(fbatch) - 1];
2513 if (folio_test_readahead(folio)) {
2514 err = filemap_readahead(iocb, filp, mapping, folio, last_index);
2515 if (err)
2516 goto err;
2517 }
2518 if (!folio_test_uptodate(folio)) {
2519 if ((iocb->ki_flags & IOCB_WAITQ) &&
2520 folio_batch_count(fbatch) > 1)
2521 iocb->ki_flags |= IOCB_NOWAIT;
2522 err = filemap_update_page(iocb, mapping, count, folio,
2523 need_uptodate);
2524 if (err)
2525 goto err;
2526 }
2527
2528 return 0;
2529err:
2530 if (err < 0)
2531 folio_put(folio);
2532 if (likely(--fbatch->nr))
2533 return 0;
2534 if (err == AOP_TRUNCATED_PAGE)
2535 goto retry;
2536 return err;
2537}
2538
2539static inline bool pos_same_folio(loff_t pos1, loff_t pos2, struct folio *folio)
2540{
2541 unsigned int shift = folio_shift(folio);
2542
2543 return (pos1 >> shift == pos2 >> shift);
2544}
2545
2546/**
2547 * filemap_read - Read data from the page cache.
2548 * @iocb: The iocb to read.
2549 * @iter: Destination for the data.
2550 * @already_read: Number of bytes already read by the caller.
2551 *
2552 * Copies data from the page cache. If the data is not currently present,
2553 * uses the readahead and read_folio address_space operations to fetch it.
2554 *
2555 * Return: Total number of bytes copied, including those already read by
2556 * the caller. If an error happens before any bytes are copied, returns
2557 * a negative error number.
2558 */
2559ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
2560 ssize_t already_read)
2561{
2562 struct file *filp = iocb->ki_filp;
2563 struct file_ra_state *ra = &filp->f_ra;
2564 struct address_space *mapping = filp->f_mapping;
2565 struct inode *inode = mapping->host;
2566 struct folio_batch fbatch;
2567 int i, error = 0;
2568 bool writably_mapped;
2569 loff_t isize, end_offset;
2570 loff_t last_pos = ra->prev_pos;
2571
2572 if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
2573 return 0;
2574 if (unlikely(!iov_iter_count(iter)))
2575 return 0;
2576
2577 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
2578 folio_batch_init(&fbatch);
2579
2580 do {
2581 cond_resched();
2582
2583 /*
2584 * If we've already successfully copied some data, then we
2585 * can no longer safely return -EIOCBQUEUED. Hence mark
2586 * an async read NOWAIT at that point.
2587 */
2588 if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
2589 iocb->ki_flags |= IOCB_NOWAIT;
2590
2591 if (unlikely(iocb->ki_pos >= i_size_read(inode)))
2592 break;
2593
2594 error = filemap_get_pages(iocb, iter->count, &fbatch, false);
2595 if (error < 0)
2596 break;
2597
2598 /*
2599 * i_size must be checked after we know the pages are Uptodate.
2600 *
2601 * Checking i_size after the check allows us to calculate
2602 * the correct value for "nr", which means the zero-filled
2603 * part of the page is not copied back to userspace (unless
2604 * another truncate extends the file - this is desired though).
2605 */
2606 isize = i_size_read(inode);
2607 if (unlikely(iocb->ki_pos >= isize))
2608 goto put_folios;
2609 end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
2610
2611 /*
2612 * Pairs with a barrier in
2613 * block_write_end()->mark_buffer_dirty() or other page
2614 * dirtying routines like iomap_write_end() to ensure
2615 * changes to page contents are visible before we see
2616 * increased inode size.
2617 */
2618 smp_rmb();
2619
2620 /*
2621 * Once we start copying data, we don't want to be touching any
2622 * cachelines that might be contended:
2623 */
2624 writably_mapped = mapping_writably_mapped(mapping);
2625
2626 /*
2627 * When a read accesses the same folio several times, only
2628 * mark it as accessed the first time.
2629 */
2630 if (!pos_same_folio(iocb->ki_pos, last_pos - 1,
2631 fbatch.folios[0]))
2632 folio_mark_accessed(fbatch.folios[0]);
2633
2634 for (i = 0; i < folio_batch_count(&fbatch); i++) {
2635 struct folio *folio = fbatch.folios[i];
2636 size_t fsize = folio_size(folio);
2637 size_t offset = iocb->ki_pos & (fsize - 1);
2638 size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
2639 fsize - offset);
2640 size_t copied;
2641
2642 if (end_offset < folio_pos(folio))
2643 break;
2644 if (i > 0)
2645 folio_mark_accessed(folio);
2646 /*
2647 * If users can be writing to this folio using arbitrary
2648 * virtual addresses, take care of potential aliasing
2649 * before reading the folio on the kernel side.
2650 */
2651 if (writably_mapped)
2652 flush_dcache_folio(folio);
2653
2654 copied = copy_folio_to_iter(folio, offset, bytes, iter);
2655
2656 already_read += copied;
2657 iocb->ki_pos += copied;
2658 last_pos = iocb->ki_pos;
2659
2660 if (copied < bytes) {
2661 error = -EFAULT;
2662 break;
2663 }
2664 }
2665put_folios:
2666 for (i = 0; i < folio_batch_count(&fbatch); i++)
2667 folio_put(fbatch.folios[i]);
2668 folio_batch_init(&fbatch);
2669 } while (iov_iter_count(iter) && iocb->ki_pos < isize && !error);
2670
2671 file_accessed(filp);
2672 ra->prev_pos = last_pos;
2673 return already_read ? already_read : error;
2674}
2675EXPORT_SYMBOL_GPL(filemap_read);
2676
2677int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
2678{
2679 struct address_space *mapping = iocb->ki_filp->f_mapping;
2680 loff_t pos = iocb->ki_pos;
2681 loff_t end = pos + count - 1;
2682
2683 if (iocb->ki_flags & IOCB_NOWAIT) {
2684 if (filemap_range_needs_writeback(mapping, pos, end))
2685 return -EAGAIN;
2686 return 0;
2687 }
2688
2689 return filemap_write_and_wait_range(mapping, pos, end);
2690}
2691EXPORT_SYMBOL_GPL(kiocb_write_and_wait);
2692
2693int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
2694{
2695 struct address_space *mapping = iocb->ki_filp->f_mapping;
2696 loff_t pos = iocb->ki_pos;
2697 loff_t end = pos + count - 1;
2698 int ret;
2699
2700 if (iocb->ki_flags & IOCB_NOWAIT) {
2701 /* we could block if there are any pages in the range */
2702 if (filemap_range_has_page(mapping, pos, end))
2703 return -EAGAIN;
2704 } else {
2705 ret = filemap_write_and_wait_range(mapping, pos, end);
2706 if (ret)
2707 return ret;
2708 }
2709
2710 /*
2711 * After a write we want buffered reads to be sure to go to disk to get
2712 * the new data. We invalidate clean cached page from the region we're
2713 * about to write. We do this *before* the write so that we can return
2714 * without clobbering -EIOCBQUEUED from ->direct_IO().
2715 */
2716 return invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
2717 end >> PAGE_SHIFT);
2718}
2719EXPORT_SYMBOL_GPL(kiocb_invalidate_pages);
2720
2721/**
2722 * generic_file_read_iter - generic filesystem read routine
2723 * @iocb: kernel I/O control block
2724 * @iter: destination for the data read
2725 *
2726 * This is the "read_iter()" routine for all filesystems
2727 * that can use the page cache directly.
2728 *
2729 * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
2730 * be returned when no data can be read without waiting for I/O requests
2731 * to complete; it doesn't prevent readahead.
2732 *
2733 * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
2734 * requests shall be made for the read or for readahead. When no data
2735 * can be read, -EAGAIN shall be returned. When readahead would be
2736 * triggered, a partial, possibly empty read shall be returned.
2737 *
2738 * Return:
2739 * * number of bytes copied, even for partial reads
2740 * * negative error code (or 0 if IOCB_NOIO) if nothing was read
2741 */
2742ssize_t
2743generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2744{
2745 size_t count = iov_iter_count(iter);
2746 ssize_t retval = 0;
2747
2748 if (!count)
2749 return 0; /* skip atime */
2750
2751 if (iocb->ki_flags & IOCB_DIRECT) {
2752 struct file *file = iocb->ki_filp;
2753 struct address_space *mapping = file->f_mapping;
2754 struct inode *inode = mapping->host;
2755
2756 retval = kiocb_write_and_wait(iocb, count);
2757 if (retval < 0)
2758 return retval;
2759 file_accessed(file);
2760
2761 retval = mapping->a_ops->direct_IO(iocb, iter);
2762 if (retval >= 0) {
2763 iocb->ki_pos += retval;
2764 count -= retval;
2765 }
2766 if (retval != -EIOCBQUEUED)
2767 iov_iter_revert(iter, count - iov_iter_count(iter));
2768
2769 /*
2770 * Btrfs can have a short DIO read if we encounter
2771 * compressed extents, so if there was an error, or if
2772 * we've already read everything we wanted to, or if
2773 * there was a short read because we hit EOF, go ahead
2774 * and return. Otherwise fallthrough to buffered io for
2775 * the rest of the read. Buffered reads will not work for
2776 * DAX files, so don't bother trying.
2777 */
2778 if (retval < 0 || !count || IS_DAX(inode))
2779 return retval;
2780 if (iocb->ki_pos >= i_size_read(inode))
2781 return retval;
2782 }
2783
2784 return filemap_read(iocb, iter, retval);
2785}
2786EXPORT_SYMBOL(generic_file_read_iter);
2787
2788/*
2789 * Splice subpages from a folio into a pipe.
2790 */
2791size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
2792 struct folio *folio, loff_t fpos, size_t size)
2793{
2794 struct page *page;
2795 size_t spliced = 0, offset = offset_in_folio(folio, fpos);
2796
2797 page = folio_page(folio, offset / PAGE_SIZE);
2798 size = min(size, folio_size(folio) - offset);
2799 offset %= PAGE_SIZE;
2800
2801 while (spliced < size &&
2802 !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
2803 struct pipe_buffer *buf = pipe_head_buf(pipe);
2804 size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);
2805
2806 *buf = (struct pipe_buffer) {
2807 .ops = &page_cache_pipe_buf_ops,
2808 .page = page,
2809 .offset = offset,
2810 .len = part,
2811 };
2812 folio_get(folio);
2813 pipe->head++;
2814 page++;
2815 spliced += part;
2816 offset = 0;
2817 }
2818
2819 return spliced;
2820}
2821
2822/**
2823 * filemap_splice_read - Splice data from a file's pagecache into a pipe
2824 * @in: The file to read from
2825 * @ppos: Pointer to the file position to read from
2826 * @pipe: The pipe to splice into
2827 * @len: The amount to splice
2828 * @flags: The SPLICE_F_* flags
2829 *
2830 * This function gets folios from a file's pagecache and splices them into the
2831 * pipe. Readahead will be called as necessary to fill more folios. This may
2832 * be used for blockdevs also.
2833 *
2834 * Return: On success, the number of bytes read will be returned and *@ppos
2835 * will be updated if appropriate; 0 will be returned if there is no more data
2836 * to be read; -EAGAIN will be returned if the pipe had no space, and some
2837 * other negative error code will be returned on error. A short read may occur
2838 * if the pipe has insufficient space, we reach the end of the data or we hit a
2839 * hole.
2840 */
2841ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
2842 struct pipe_inode_info *pipe,
2843 size_t len, unsigned int flags)
2844{
2845 struct folio_batch fbatch;
2846 struct kiocb iocb;
2847 size_t total_spliced = 0, used, npages;
2848 loff_t isize, end_offset;
2849 bool writably_mapped;
2850 int i, error = 0;
2851
2852 if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
2853 return 0;
2854
2855 init_sync_kiocb(&iocb, in);
2856 iocb.ki_pos = *ppos;
2857
2858 /* Work out how much data we can actually add into the pipe */
2859 used = pipe_occupancy(pipe->head, pipe->tail);
2860 npages = max_t(ssize_t, pipe->max_usage - used, 0);
2861 len = min_t(size_t, len, npages * PAGE_SIZE);
2862
2863 folio_batch_init(&fbatch);
2864
2865 do {
2866 cond_resched();
2867
2868 if (*ppos >= i_size_read(in->f_mapping->host))
2869 break;
2870
2871 iocb.ki_pos = *ppos;
2872 error = filemap_get_pages(&iocb, len, &fbatch, true);
2873 if (error < 0)
2874 break;
2875
2876 /*
2877 * i_size must be checked after we know the pages are Uptodate.
2878 *
2879 * Checking i_size after the check allows us to calculate
2880 * the correct value for "nr", which means the zero-filled
2881 * part of the page is not copied back to userspace (unless
2882 * another truncate extends the file - this is desired though).
2883 */
2884 isize = i_size_read(in->f_mapping->host);
2885 if (unlikely(*ppos >= isize))
2886 break;
2887 end_offset = min_t(loff_t, isize, *ppos + len);
2888
2889 /*
2890 * Once we start copying data, we don't want to be touching any
2891 * cachelines that might be contended:
2892 */
2893 writably_mapped = mapping_writably_mapped(in->f_mapping);
2894
2895 for (i = 0; i < folio_batch_count(&fbatch); i++) {
2896 struct folio *folio = fbatch.folios[i];
2897 size_t n;
2898
2899 if (folio_pos(folio) >= end_offset)
2900 goto out;
2901 folio_mark_accessed(folio);
2902
2903 /*
2904 * If users can be writing to this folio using arbitrary
2905 * virtual addresses, take care of potential aliasing
2906 * before reading the folio on the kernel side.
2907 */
2908 if (writably_mapped)
2909 flush_dcache_folio(folio);
2910
2911 n = min_t(loff_t, len, isize - *ppos);
2912 n = splice_folio_into_pipe(pipe, folio, *ppos, n);
2913 if (!n)
2914 goto out;
2915 len -= n;
2916 total_spliced += n;
2917 *ppos += n;
2918 in->f_ra.prev_pos = *ppos;
2919 if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
2920 goto out;
2921 }
2922
2923 folio_batch_release(&fbatch);
2924 } while (len);
2925
2926out:
2927 folio_batch_release(&fbatch);
2928 file_accessed(in);
2929
2930 return total_spliced ? total_spliced : error;
2931}
2932EXPORT_SYMBOL(filemap_splice_read);
2933
2934static inline loff_t folio_seek_hole_data(struct xa_state *xas,
2935 struct address_space *mapping, struct folio *folio,
2936 loff_t start, loff_t end, bool seek_data)
2937{
2938 const struct address_space_operations *ops = mapping->a_ops;
2939 size_t offset, bsz = i_blocksize(mapping->host);
2940
2941 if (xa_is_value(folio) || folio_test_uptodate(folio))
2942 return seek_data ? start : end;
2943 if (!ops->is_partially_uptodate)
2944 return seek_data ? end : start;
2945
2946 xas_pause(xas);
2947 rcu_read_unlock();
2948 folio_lock(folio);
2949 if (unlikely(folio->mapping != mapping))
2950 goto unlock;
2951
2952 offset = offset_in_folio(folio, start) & ~(bsz - 1);
2953
2954 do {
2955 if (ops->is_partially_uptodate(folio, offset, bsz) ==
2956 seek_data)
2957 break;
2958 start = (start + bsz) & ~(bsz - 1);
2959 offset += bsz;
2960 } while (offset < folio_size(folio));
2961unlock:
2962 folio_unlock(folio);
2963 rcu_read_lock();
2964 return start;
2965}
2966
2967static inline size_t seek_folio_size(struct xa_state *xas, struct folio *folio)
2968{
2969 if (xa_is_value(folio))
2970 return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index);
2971 return folio_size(folio);
2972}
2973
2974/**
2975 * mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache.
2976 * @mapping: Address space to search.
2977 * @start: First byte to consider.
2978 * @end: Limit of search (exclusive).
2979 * @whence: Either SEEK_HOLE or SEEK_DATA.
2980 *
2981 * If the page cache knows which blocks contain holes and which blocks
2982 * contain data, your filesystem can use this function to implement
2983 * SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are
2984 * entirely memory-based such as tmpfs, and filesystems which support
2985 * unwritten extents.
2986 *
2987 * Return: The requested offset on success, or -ENXIO if @whence specifies
2988 * SEEK_DATA and there is no data after @start. There is an implicit hole
2989 * after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start
2990 * and @end contain data.
2991 */
2992loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
2993 loff_t end, int whence)
2994{
2995 XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
2996 pgoff_t max = (end - 1) >> PAGE_SHIFT;
2997 bool seek_data = (whence == SEEK_DATA);
2998 struct folio *folio;
2999
3000 if (end <= start)
3001 return -ENXIO;
3002
3003 rcu_read_lock();
3004 while ((folio = find_get_entry(&xas, max, XA_PRESENT))) {
3005 loff_t pos = (u64)xas.xa_index << PAGE_SHIFT;
3006 size_t seek_size;
3007
3008 if (start < pos) {
3009 if (!seek_data)
3010 goto unlock;
3011 start = pos;
3012 }
3013
3014 seek_size = seek_folio_size(&xas, folio);
3015 pos = round_up((u64)pos + 1, seek_size);
3016 start = folio_seek_hole_data(&xas, mapping, folio, start, pos,
3017 seek_data);
3018 if (start < pos)
3019 goto unlock;
3020 if (start >= end)
3021 break;
3022 if (seek_size > PAGE_SIZE)
3023 xas_set(&xas, pos >> PAGE_SHIFT);
3024 if (!xa_is_value(folio))
3025 folio_put(folio);
3026 }
3027 if (seek_data)
3028 start = -ENXIO;
3029unlock:
3030 rcu_read_unlock();
3031 if (folio && !xa_is_value(folio))
3032 folio_put(folio);
3033 if (start > end)
3034 return end;
3035 return start;
3036}
3037
3038#ifdef CONFIG_MMU
3039#define MMAP_LOTSAMISS (100)
3040/*
3041 * lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
3042 * @vmf - the vm_fault for this fault.
3043 * @folio - the folio to lock.
3044 * @fpin - the pointer to the file we may pin (or is already pinned).
3045 *
3046 * This works similar to lock_folio_or_retry in that it can drop the
3047 * mmap_lock. It differs in that it actually returns the folio locked
3048 * if it returns 1 and 0 if it couldn't lock the folio. If we did have
3049 * to drop the mmap_lock then fpin will point to the pinned file and
3050 * needs to be fput()'ed at a later point.
3051 */
3052static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
3053 struct file **fpin)
3054{
3055 if (folio_trylock(folio))
3056 return 1;
3057
3058 /*
3059 * NOTE! This will make us return with VM_FAULT_RETRY, but with
3060 * the fault lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
3061 * is supposed to work. We have way too many special cases..
3062 */
3063 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
3064 return 0;
3065
3066 *fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
3067 if (vmf->flags & FAULT_FLAG_KILLABLE) {
3068 if (__folio_lock_killable(folio)) {
3069 /*
3070 * We didn't have the right flags to drop the
3071 * fault lock, but all fault_handlers only check
3072 * for fatal signals if we return VM_FAULT_RETRY,
3073 * so we need to drop the fault lock here and
3074 * return 0 if we don't have a fpin.
3075 */
3076 if (*fpin == NULL)
3077 release_fault_lock(vmf);
3078 return 0;
3079 }
3080 } else
3081 __folio_lock(folio);
3082
3083 return 1;
3084}
3085
3086/*
3087 * Synchronous readahead happens when we don't even find a page in the page
3088 * cache at all. We don't want to perform IO under the mmap sem, so if we have
3089 * to drop the mmap sem we return the file that was pinned in order for us to do
3090 * that. If we didn't pin a file then we return NULL. The file that is
3091 * returned needs to be fput()'ed when we're done with it.
3092 */
3093static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
3094{
3095 struct file *file = vmf->vma->vm_file;
3096 struct file_ra_state *ra = &file->f_ra;
3097 struct address_space *mapping = file->f_mapping;
3098 DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
3099 struct file *fpin = NULL;
3100 unsigned long vm_flags = vmf->vma->vm_flags;
3101 unsigned int mmap_miss;
3102
3103#ifdef CONFIG_TRANSPARENT_HUGEPAGE
3104 /* Use the readahead code, even if readahead is disabled */
3105 if (vm_flags & VM_HUGEPAGE) {
3106 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3107 ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1);
3108 ra->size = HPAGE_PMD_NR;
3109 /*
3110 * Fetch two PMD folios, so we get the chance to actually
3111 * readahead, unless we've been told not to.
3112 */
3113 if (!(vm_flags & VM_RAND_READ))
3114 ra->size *= 2;
3115 ra->async_size = HPAGE_PMD_NR;
3116 page_cache_ra_order(&ractl, ra, HPAGE_PMD_ORDER);
3117 return fpin;
3118 }
3119#endif
3120
3121 /* If we don't want any read-ahead, don't bother */
3122 if (vm_flags & VM_RAND_READ)
3123 return fpin;
3124 if (!ra->ra_pages)
3125 return fpin;
3126
3127 if (vm_flags & VM_SEQ_READ) {
3128 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3129 page_cache_sync_ra(&ractl, ra->ra_pages);
3130 return fpin;
3131 }
3132
3133 /* Avoid banging the cache line if not needed */
3134 mmap_miss = READ_ONCE(ra->mmap_miss);
3135 if (mmap_miss < MMAP_LOTSAMISS * 10)
3136 WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
3137
3138 /*
3139 * Do we miss much more than hit in this file? If so,
3140 * stop bothering with read-ahead. It will only hurt.
3141 */
3142 if (mmap_miss > MMAP_LOTSAMISS)
3143 return fpin;
3144
3145 /*
3146 * mmap read-around
3147 */
3148 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3149 ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
3150 ra->size = ra->ra_pages;
3151 ra->async_size = ra->ra_pages / 4;
3152 ractl._index = ra->start;
3153 page_cache_ra_order(&ractl, ra, 0);
3154 return fpin;
3155}
3156
3157/*
3158 * Asynchronous readahead happens when we find the page and PG_readahead,
3159 * so we want to possibly extend the readahead further. We return the file that
3160 * was pinned if we have to drop the mmap_lock in order to do IO.
3161 */
3162static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
3163 struct folio *folio)
3164{
3165 struct file *file = vmf->vma->vm_file;
3166 struct file_ra_state *ra = &file->f_ra;
3167 DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff);
3168 struct file *fpin = NULL;
3169 unsigned int mmap_miss;
3170
3171 /* If we don't want any read-ahead, don't bother */
3172 if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
3173 return fpin;
3174
3175 mmap_miss = READ_ONCE(ra->mmap_miss);
3176 if (mmap_miss)
3177 WRITE_ONCE(ra->mmap_miss, --mmap_miss);
3178
3179 if (folio_test_readahead(folio)) {
3180 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3181 page_cache_async_ra(&ractl, folio, ra->ra_pages);
3182 }
3183 return fpin;
3184}
3185
3186/**
3187 * filemap_fault - read in file data for page fault handling
3188 * @vmf: struct vm_fault containing details of the fault
3189 *
3190 * filemap_fault() is invoked via the vma operations vector for a
3191 * mapped memory region to read in file data during a page fault.
3192 *
3193 * The goto's are kind of ugly, but this streamlines the normal case of having
3194 * it in the page cache, and handles the special cases reasonably without
3195 * having a lot of duplicated code.
3196 *
3197 * vma->vm_mm->mmap_lock must be held on entry.
3198 *
3199 * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
3200 * may be dropped before doing I/O or by lock_folio_maybe_drop_mmap().
3201 *
3202 * If our return value does not have VM_FAULT_RETRY set, the mmap_lock
3203 * has not been released.
3204 *
3205 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
3206 *
3207 * Return: bitwise-OR of %VM_FAULT_ codes.
3208 */
3209vm_fault_t filemap_fault(struct vm_fault *vmf)
3210{
3211 int error;
3212 struct file *file = vmf->vma->vm_file;
3213 struct file *fpin = NULL;
3214 struct address_space *mapping = file->f_mapping;
3215 struct inode *inode = mapping->host;
3216 pgoff_t max_idx, index = vmf->pgoff;
3217 struct folio *folio;
3218 vm_fault_t ret = 0;
3219 bool mapping_locked = false;
3220
3221 max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
3222 if (unlikely(index >= max_idx))
3223 return VM_FAULT_SIGBUS;
3224
3225 /*
3226 * Do we have something in the page cache already?
3227 */
3228 folio = filemap_get_folio(mapping, index);
3229 if (likely(!IS_ERR(folio))) {
3230 /*
3231 * We found the page, so try async readahead before waiting for
3232 * the lock.
3233 */
3234 if (!(vmf->flags & FAULT_FLAG_TRIED))
3235 fpin = do_async_mmap_readahead(vmf, folio);
3236 if (unlikely(!folio_test_uptodate(folio))) {
3237 filemap_invalidate_lock_shared(mapping);
3238 mapping_locked = true;
3239 }
3240 } else {
3241 /* No page in the page cache at all */
3242 count_vm_event(PGMAJFAULT);
3243 count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
3244 ret = VM_FAULT_MAJOR;
3245 fpin = do_sync_mmap_readahead(vmf);
3246retry_find:
3247 /*
3248 * See comment in filemap_create_folio() why we need
3249 * invalidate_lock
3250 */
3251 if (!mapping_locked) {
3252 filemap_invalidate_lock_shared(mapping);
3253 mapping_locked = true;
3254 }
3255 folio = __filemap_get_folio(mapping, index,
3256 FGP_CREAT|FGP_FOR_MMAP,
3257 vmf->gfp_mask);
3258 if (IS_ERR(folio)) {
3259 if (fpin)
3260 goto out_retry;
3261 filemap_invalidate_unlock_shared(mapping);
3262 return VM_FAULT_OOM;
3263 }
3264 }
3265
3266 if (!lock_folio_maybe_drop_mmap(vmf, folio, &fpin))
3267 goto out_retry;
3268
3269 /* Did it get truncated? */
3270 if (unlikely(folio->mapping != mapping)) {
3271 folio_unlock(folio);
3272 folio_put(folio);
3273 goto retry_find;
3274 }
3275 VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
3276
3277 /*
3278 * We have a locked folio in the page cache, now we need to check
3279 * that it's up-to-date. If not, it is going to be due to an error,
3280 * or because readahead was otherwise unable to retrieve it.
3281 */
3282 if (unlikely(!folio_test_uptodate(folio))) {
3283 /*
3284 * If the invalidate lock is not held, the folio was in cache
3285 * and uptodate and now it is not. Strange but possible since we
3286 * didn't hold the page lock all the time. Let's drop
3287 * everything, get the invalidate lock and try again.
3288 */
3289 if (!mapping_locked) {
3290 folio_unlock(folio);
3291 folio_put(folio);
3292 goto retry_find;
3293 }
3294
3295 /*
3296 * OK, the folio is really not uptodate. This can be because the
3297 * VMA has the VM_RAND_READ flag set, or because an error
3298 * arose. Let's read it in directly.
3299 */
3300 goto page_not_uptodate;
3301 }
3302
3303 /*
3304 * We've made it this far and we had to drop our mmap_lock, now is the
3305 * time to return to the upper layer and have it re-find the vma and
3306 * redo the fault.
3307 */
3308 if (fpin) {
3309 folio_unlock(folio);
3310 goto out_retry;
3311 }
3312 if (mapping_locked)
3313 filemap_invalidate_unlock_shared(mapping);
3314
3315 /*
3316 * Found the page and have a reference on it.
3317 * We must recheck i_size under page lock.
3318 */
3319 max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
3320 if (unlikely(index >= max_idx)) {
3321 folio_unlock(folio);
3322 folio_put(folio);
3323 return VM_FAULT_SIGBUS;
3324 }
3325
3326 vmf->page = folio_file_page(folio, index);
3327 return ret | VM_FAULT_LOCKED;
3328
3329page_not_uptodate:
3330 /*
3331 * Umm, take care of errors if the page isn't up-to-date.
3332 * Try to re-read it _once_. We do this synchronously,
3333 * because there really aren't any performance issues here
3334 * and we need to check for errors.
3335 */
3336 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3337 error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
3338 if (fpin)
3339 goto out_retry;
3340 folio_put(folio);
3341
3342 if (!error || error == AOP_TRUNCATED_PAGE)
3343 goto retry_find;
3344 filemap_invalidate_unlock_shared(mapping);
3345
3346 return VM_FAULT_SIGBUS;
3347
3348out_retry:
3349 /*
3350 * We dropped the mmap_lock, we need to return to the fault handler to
3351 * re-find the vma and come back and find our hopefully still populated
3352 * page.
3353 */
3354 if (!IS_ERR(folio))
3355 folio_put(folio);
3356 if (mapping_locked)
3357 filemap_invalidate_unlock_shared(mapping);
3358 if (fpin)
3359 fput(fpin);
3360 return ret | VM_FAULT_RETRY;
3361}
3362EXPORT_SYMBOL(filemap_fault);
3363
3364static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
3365 pgoff_t start)
3366{
3367 struct mm_struct *mm = vmf->vma->vm_mm;
3368
3369 /* Huge page is mapped? No need to proceed. */
3370 if (pmd_trans_huge(*vmf->pmd)) {
3371 folio_unlock(folio);
3372 folio_put(folio);
3373 return true;
3374 }
3375
3376 if (pmd_none(*vmf->pmd) && folio_test_pmd_mappable(folio)) {
3377 struct page *page = folio_file_page(folio, start);
3378 vm_fault_t ret = do_set_pmd(vmf, page);
3379 if (!ret) {
3380 /* The page is mapped successfully, reference consumed. */
3381 folio_unlock(folio);
3382 return true;
3383 }
3384 }
3385
3386 if (pmd_none(*vmf->pmd) && vmf->prealloc_pte)
3387 pmd_install(mm, vmf->pmd, &vmf->prealloc_pte);
3388
3389 return false;
3390}
3391
3392static struct folio *next_uptodate_folio(struct xa_state *xas,
3393 struct address_space *mapping, pgoff_t end_pgoff)
3394{
3395 struct folio *folio = xas_next_entry(xas, end_pgoff);
3396 unsigned long max_idx;
3397
3398 do {
3399 if (!folio)
3400 return NULL;
3401 if (xas_retry(xas, folio))
3402 continue;
3403 if (xa_is_value(folio))
3404 continue;
3405 if (folio_test_locked(folio))
3406 continue;
3407 if (!folio_try_get_rcu(folio))
3408 continue;
3409 /* Has the page moved or been split? */
3410 if (unlikely(folio != xas_reload(xas)))
3411 goto skip;
3412 if (!folio_test_uptodate(folio) || folio_test_readahead(folio))
3413 goto skip;
3414 if (!folio_trylock(folio))
3415 goto skip;
3416 if (folio->mapping != mapping)
3417 goto unlock;
3418 if (!folio_test_uptodate(folio))
3419 goto unlock;
3420 max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
3421 if (xas->xa_index >= max_idx)
3422 goto unlock;
3423 return folio;
3424unlock:
3425 folio_unlock(folio);
3426skip:
3427 folio_put(folio);
3428 } while ((folio = xas_next_entry(xas, end_pgoff)) != NULL);
3429
3430 return NULL;
3431}
3432
3433/*
3434 * Map page range [start_page, start_page + nr_pages) of folio.
3435 * start_page is gotten from start by folio_page(folio, start)
3436 */
3437static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
3438 struct folio *folio, unsigned long start,
3439 unsigned long addr, unsigned int nr_pages,
3440 unsigned int *mmap_miss)
3441{
3442 vm_fault_t ret = 0;
3443 struct page *page = folio_page(folio, start);
3444 unsigned int count = 0;
3445 pte_t *old_ptep = vmf->pte;
3446
3447 do {
3448 if (PageHWPoison(page + count))
3449 goto skip;
3450
3451 (*mmap_miss)++;
3452
3453 /*
3454 * NOTE: If there're PTE markers, we'll leave them to be
3455 * handled in the specific fault path, and it'll prohibit the
3456 * fault-around logic.
3457 */
3458 if (!pte_none(ptep_get(&vmf->pte[count])))
3459 goto skip;
3460
3461 count++;
3462 continue;
3463skip:
3464 if (count) {
3465 set_pte_range(vmf, folio, page, count, addr);
3466 folio_ref_add(folio, count);
3467 if (in_range(vmf->address, addr, count * PAGE_SIZE))
3468 ret = VM_FAULT_NOPAGE;
3469 }
3470
3471 count++;
3472 page += count;
3473 vmf->pte += count;
3474 addr += count * PAGE_SIZE;
3475 count = 0;
3476 } while (--nr_pages > 0);
3477
3478 if (count) {
3479 set_pte_range(vmf, folio, page, count, addr);
3480 folio_ref_add(folio, count);
3481 if (in_range(vmf->address, addr, count * PAGE_SIZE))
3482 ret = VM_FAULT_NOPAGE;
3483 }
3484
3485 vmf->pte = old_ptep;
3486
3487 return ret;
3488}
3489
3490static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf,
3491 struct folio *folio, unsigned long addr,
3492 unsigned int *mmap_miss)
3493{
3494 vm_fault_t ret = 0;
3495 struct page *page = &folio->page;
3496
3497 if (PageHWPoison(page))
3498 return ret;
3499
3500 (*mmap_miss)++;
3501
3502 /*
3503 * NOTE: If there're PTE markers, we'll leave them to be
3504 * handled in the specific fault path, and it'll prohibit
3505 * the fault-around logic.
3506 */
3507 if (!pte_none(ptep_get(vmf->pte)))
3508 return ret;
3509
3510 if (vmf->address == addr)
3511 ret = VM_FAULT_NOPAGE;
3512
3513 set_pte_range(vmf, folio, page, 1, addr);
3514 folio_ref_inc(folio);
3515
3516 return ret;
3517}
3518
3519vm_fault_t filemap_map_pages(struct vm_fault *vmf,
3520 pgoff_t start_pgoff, pgoff_t end_pgoff)
3521{
3522 struct vm_area_struct *vma = vmf->vma;
3523 struct file *file = vma->vm_file;
3524 struct address_space *mapping = file->f_mapping;
3525 pgoff_t last_pgoff = start_pgoff;
3526 unsigned long addr;
3527 XA_STATE(xas, &mapping->i_pages, start_pgoff);
3528 struct folio *folio;
3529 vm_fault_t ret = 0;
3530 unsigned int nr_pages = 0, mmap_miss = 0, mmap_miss_saved;
3531
3532 rcu_read_lock();
3533 folio = next_uptodate_folio(&xas, mapping, end_pgoff);
3534 if (!folio)
3535 goto out;
3536
3537 if (filemap_map_pmd(vmf, folio, start_pgoff)) {
3538 ret = VM_FAULT_NOPAGE;
3539 goto out;
3540 }
3541
3542 addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
3543 vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
3544 if (!vmf->pte) {
3545 folio_unlock(folio);
3546 folio_put(folio);
3547 goto out;
3548 }
3549 do {
3550 unsigned long end;
3551
3552 addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
3553 vmf->pte += xas.xa_index - last_pgoff;
3554 last_pgoff = xas.xa_index;
3555 end = folio_next_index(folio) - 1;
3556 nr_pages = min(end, end_pgoff) - xas.xa_index + 1;
3557
3558 if (!folio_test_large(folio))
3559 ret |= filemap_map_order0_folio(vmf,
3560 folio, addr, &mmap_miss);
3561 else
3562 ret |= filemap_map_folio_range(vmf, folio,
3563 xas.xa_index - folio->index, addr,
3564 nr_pages, &mmap_miss);
3565
3566 folio_unlock(folio);
3567 folio_put(folio);
3568 } while ((folio = next_uptodate_folio(&xas, mapping, end_pgoff)) != NULL);
3569 pte_unmap_unlock(vmf->pte, vmf->ptl);
3570out:
3571 rcu_read_unlock();
3572
3573 mmap_miss_saved = READ_ONCE(file->f_ra.mmap_miss);
3574 if (mmap_miss >= mmap_miss_saved)
3575 WRITE_ONCE(file->f_ra.mmap_miss, 0);
3576 else
3577 WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss_saved - mmap_miss);
3578
3579 return ret;
3580}
3581EXPORT_SYMBOL(filemap_map_pages);
3582
3583vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3584{
3585 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
3586 struct folio *folio = page_folio(vmf->page);
3587 vm_fault_t ret = VM_FAULT_LOCKED;
3588
3589 sb_start_pagefault(mapping->host->i_sb);
3590 file_update_time(vmf->vma->vm_file);
3591 folio_lock(folio);
3592 if (folio->mapping != mapping) {
3593 folio_unlock(folio);
3594 ret = VM_FAULT_NOPAGE;
3595 goto out;
3596 }
3597 /*
3598 * We mark the folio dirty already here so that when freeze is in
3599 * progress, we are guaranteed that writeback during freezing will
3600 * see the dirty folio and writeprotect it again.
3601 */
3602 folio_mark_dirty(folio);
3603 folio_wait_stable(folio);
3604out:
3605 sb_end_pagefault(mapping->host->i_sb);
3606 return ret;
3607}
3608
3609const struct vm_operations_struct generic_file_vm_ops = {
3610 .fault = filemap_fault,
3611 .map_pages = filemap_map_pages,
3612 .page_mkwrite = filemap_page_mkwrite,
3613};
3614
3615/* This is used for a general mmap of a disk file */
3616
3617int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
3618{
3619 struct address_space *mapping = file->f_mapping;
3620
3621 if (!mapping->a_ops->read_folio)
3622 return -ENOEXEC;
3623 file_accessed(file);
3624 vma->vm_ops = &generic_file_vm_ops;
3625 return 0;
3626}
3627
3628/*
3629 * This is for filesystems which do not implement ->writepage.
3630 */
3631int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3632{
3633 if (vma_is_shared_maywrite(vma))
3634 return -EINVAL;
3635 return generic_file_mmap(file, vma);
3636}
3637#else
3638vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3639{
3640 return VM_FAULT_SIGBUS;
3641}
3642int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
3643{
3644 return -ENOSYS;
3645}
3646int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3647{
3648 return -ENOSYS;
3649}
3650#endif /* CONFIG_MMU */
3651
3652EXPORT_SYMBOL(filemap_page_mkwrite);
3653EXPORT_SYMBOL(generic_file_mmap);
3654EXPORT_SYMBOL(generic_file_readonly_mmap);
3655
3656static struct folio *do_read_cache_folio(struct address_space *mapping,
3657 pgoff_t index, filler_t filler, struct file *file, gfp_t gfp)
3658{
3659 struct folio *folio;
3660 int err;
3661
3662 if (!filler)
3663 filler = mapping->a_ops->read_folio;
3664repeat:
3665 folio = filemap_get_folio(mapping, index);
3666 if (IS_ERR(folio)) {
3667 folio = filemap_alloc_folio(gfp, 0);
3668 if (!folio)
3669 return ERR_PTR(-ENOMEM);
3670 err = filemap_add_folio(mapping, folio, index, gfp);
3671 if (unlikely(err)) {
3672 folio_put(folio);
3673 if (err == -EEXIST)
3674 goto repeat;
3675 /* Presumably ENOMEM for xarray node */
3676 return ERR_PTR(err);
3677 }
3678
3679 goto filler;
3680 }
3681 if (folio_test_uptodate(folio))
3682 goto out;
3683
3684 if (!folio_trylock(folio)) {
3685 folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE);
3686 goto repeat;
3687 }
3688
3689 /* Folio was truncated from mapping */
3690 if (!folio->mapping) {
3691 folio_unlock(folio);
3692 folio_put(folio);
3693 goto repeat;
3694 }
3695
3696 /* Someone else locked and filled the page in a very small window */
3697 if (folio_test_uptodate(folio)) {
3698 folio_unlock(folio);
3699 goto out;
3700 }
3701
3702filler:
3703 err = filemap_read_folio(file, filler, folio);
3704 if (err) {
3705 folio_put(folio);
3706 if (err == AOP_TRUNCATED_PAGE)
3707 goto repeat;
3708 return ERR_PTR(err);
3709 }
3710
3711out:
3712 folio_mark_accessed(folio);
3713 return folio;
3714}
3715
3716/**
3717 * read_cache_folio - Read into page cache, fill it if needed.
3718 * @mapping: The address_space to read from.
3719 * @index: The index to read.
3720 * @filler: Function to perform the read, or NULL to use aops->read_folio().
3721 * @file: Passed to filler function, may be NULL if not required.
3722 *
3723 * Read one page into the page cache. If it succeeds, the folio returned
3724 * will contain @index, but it may not be the first page of the folio.
3725 *
3726 * If the filler function returns an error, it will be returned to the
3727 * caller.
3728 *
3729 * Context: May sleep. Expects mapping->invalidate_lock to be held.
3730 * Return: An uptodate folio on success, ERR_PTR() on failure.
3731 */
3732struct folio *read_cache_folio(struct address_space *mapping, pgoff_t index,
3733 filler_t filler, struct file *file)
3734{
3735 return do_read_cache_folio(mapping, index, filler, file,
3736 mapping_gfp_mask(mapping));
3737}
3738EXPORT_SYMBOL(read_cache_folio);
3739
3740/**
3741 * mapping_read_folio_gfp - Read into page cache, using specified allocation flags.
3742 * @mapping: The address_space for the folio.
3743 * @index: The index that the allocated folio will contain.
3744 * @gfp: The page allocator flags to use if allocating.
3745 *
3746 * This is the same as "read_cache_folio(mapping, index, NULL, NULL)", but with
3747 * any new memory allocations done using the specified allocation flags.
3748 *
3749 * The most likely error from this function is EIO, but ENOMEM is
3750 * possible and so is EINTR. If ->read_folio returns another error,
3751 * that will be returned to the caller.
3752 *
3753 * The function expects mapping->invalidate_lock to be already held.
3754 *
3755 * Return: Uptodate folio on success, ERR_PTR() on failure.
3756 */
3757struct folio *mapping_read_folio_gfp(struct address_space *mapping,
3758 pgoff_t index, gfp_t gfp)
3759{
3760 return do_read_cache_folio(mapping, index, NULL, NULL, gfp);
3761}
3762EXPORT_SYMBOL(mapping_read_folio_gfp);
3763
3764static struct page *do_read_cache_page(struct address_space *mapping,
3765 pgoff_t index, filler_t *filler, struct file *file, gfp_t gfp)
3766{
3767 struct folio *folio;
3768
3769 folio = do_read_cache_folio(mapping, index, filler, file, gfp);
3770 if (IS_ERR(folio))
3771 return &folio->page;
3772 return folio_file_page(folio, index);
3773}
3774
3775struct page *read_cache_page(struct address_space *mapping,
3776 pgoff_t index, filler_t *filler, struct file *file)
3777{
3778 return do_read_cache_page(mapping, index, filler, file,
3779 mapping_gfp_mask(mapping));
3780}
3781EXPORT_SYMBOL(read_cache_page);
3782
3783/**
3784 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
3785 * @mapping: the page's address_space
3786 * @index: the page index
3787 * @gfp: the page allocator flags to use if allocating
3788 *
3789 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
3790 * any new page allocations done using the specified allocation flags.
3791 *
3792 * If the page does not get brought uptodate, return -EIO.
3793 *
3794 * The function expects mapping->invalidate_lock to be already held.
3795 *
3796 * Return: up to date page on success, ERR_PTR() on failure.
3797 */
3798struct page *read_cache_page_gfp(struct address_space *mapping,
3799 pgoff_t index,
3800 gfp_t gfp)
3801{
3802 return do_read_cache_page(mapping, index, NULL, NULL, gfp);
3803}
3804EXPORT_SYMBOL(read_cache_page_gfp);
3805
3806/*
3807 * Warn about a page cache invalidation failure during a direct I/O write.
3808 */
3809static void dio_warn_stale_pagecache(struct file *filp)
3810{
3811 static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
3812 char pathname[128];
3813 char *path;
3814
3815 errseq_set(&filp->f_mapping->wb_err, -EIO);
3816 if (__ratelimit(&_rs)) {
3817 path = file_path(filp, pathname, sizeof(pathname));
3818 if (IS_ERR(path))
3819 path = "(unknown)";
3820 pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
3821 pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
3822 current->comm);
3823 }
3824}
3825
3826void kiocb_invalidate_post_direct_write(struct kiocb *iocb, size_t count)
3827{
3828 struct address_space *mapping = iocb->ki_filp->f_mapping;
3829
3830 if (mapping->nrpages &&
3831 invalidate_inode_pages2_range(mapping,
3832 iocb->ki_pos >> PAGE_SHIFT,
3833 (iocb->ki_pos + count - 1) >> PAGE_SHIFT))
3834 dio_warn_stale_pagecache(iocb->ki_filp);
3835}
3836
3837ssize_t
3838generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
3839{
3840 struct address_space *mapping = iocb->ki_filp->f_mapping;
3841 size_t write_len = iov_iter_count(from);
3842 ssize_t written;
3843
3844 /*
3845 * If a page can not be invalidated, return 0 to fall back
3846 * to buffered write.
3847 */
3848 written = kiocb_invalidate_pages(iocb, write_len);
3849 if (written) {
3850 if (written == -EBUSY)
3851 return 0;
3852 return written;
3853 }
3854
3855 written = mapping->a_ops->direct_IO(iocb, from);
3856
3857 /*
3858 * Finally, try again to invalidate clean pages which might have been
3859 * cached by non-direct readahead, or faulted in by get_user_pages()
3860 * if the source of the write was an mmap'ed region of the file
3861 * we're writing. Either one is a pretty crazy thing to do,
3862 * so we don't support it 100%. If this invalidation
3863 * fails, tough, the write still worked...
3864 *
3865 * Most of the time we do not need this since dio_complete() will do
3866 * the invalidation for us. However there are some file systems that
3867 * do not end up with dio_complete() being called, so let's not break
3868 * them by removing it completely.
3869 *
3870 * Noticeable example is a blkdev_direct_IO().
3871 *
3872 * Skip invalidation for async writes or if mapping has no pages.
3873 */
3874 if (written > 0) {
3875 struct inode *inode = mapping->host;
3876 loff_t pos = iocb->ki_pos;
3877
3878 kiocb_invalidate_post_direct_write(iocb, written);
3879 pos += written;
3880 write_len -= written;
3881 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
3882 i_size_write(inode, pos);
3883 mark_inode_dirty(inode);
3884 }
3885 iocb->ki_pos = pos;
3886 }
3887 if (written != -EIOCBQUEUED)
3888 iov_iter_revert(from, write_len - iov_iter_count(from));
3889 return written;
3890}
3891EXPORT_SYMBOL(generic_file_direct_write);
3892
3893ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
3894{
3895 struct file *file = iocb->ki_filp;
3896 loff_t pos = iocb->ki_pos;
3897 struct address_space *mapping = file->f_mapping;
3898 const struct address_space_operations *a_ops = mapping->a_ops;
3899 long status = 0;
3900 ssize_t written = 0;
3901
3902 do {
3903 struct page *page;
3904 unsigned long offset; /* Offset into pagecache page */
3905 unsigned long bytes; /* Bytes to write to page */
3906 size_t copied; /* Bytes copied from user */
3907 void *fsdata = NULL;
3908
3909 offset = (pos & (PAGE_SIZE - 1));
3910 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3911 iov_iter_count(i));
3912
3913again:
3914 /*
3915 * Bring in the user page that we will copy from _first_.
3916 * Otherwise there's a nasty deadlock on copying from the
3917 * same page as we're writing to, without it being marked
3918 * up-to-date.
3919 */
3920 if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
3921 status = -EFAULT;
3922 break;
3923 }
3924
3925 if (fatal_signal_pending(current)) {
3926 status = -EINTR;
3927 break;
3928 }
3929
3930 status = a_ops->write_begin(file, mapping, pos, bytes,
3931 &page, &fsdata);
3932 if (unlikely(status < 0))
3933 break;
3934
3935 if (mapping_writably_mapped(mapping))
3936 flush_dcache_page(page);
3937
3938 copied = copy_page_from_iter_atomic(page, offset, bytes, i);
3939 flush_dcache_page(page);
3940
3941 status = a_ops->write_end(file, mapping, pos, bytes, copied,
3942 page, fsdata);
3943 if (unlikely(status != copied)) {
3944 iov_iter_revert(i, copied - max(status, 0L));
3945 if (unlikely(status < 0))
3946 break;
3947 }
3948 cond_resched();
3949
3950 if (unlikely(status == 0)) {
3951 /*
3952 * A short copy made ->write_end() reject the
3953 * thing entirely. Might be memory poisoning
3954 * halfway through, might be a race with munmap,
3955 * might be severe memory pressure.
3956 */
3957 if (copied)
3958 bytes = copied;
3959 goto again;
3960 }
3961 pos += status;
3962 written += status;
3963
3964 balance_dirty_pages_ratelimited(mapping);
3965 } while (iov_iter_count(i));
3966
3967 if (!written)
3968 return status;
3969 iocb->ki_pos += written;
3970 return written;
3971}
3972EXPORT_SYMBOL(generic_perform_write);
3973
3974/**
3975 * __generic_file_write_iter - write data to a file
3976 * @iocb: IO state structure (file, offset, etc.)
3977 * @from: iov_iter with data to write
3978 *
3979 * This function does all the work needed for actually writing data to a
3980 * file. It does all basic checks, removes SUID from the file, updates
3981 * modification times and calls proper subroutines depending on whether we
3982 * do direct IO or a standard buffered write.
3983 *
3984 * It expects i_rwsem to be grabbed unless we work on a block device or similar
3985 * object which does not need locking at all.
3986 *
3987 * This function does *not* take care of syncing data in case of O_SYNC write.
3988 * A caller has to handle it. This is mainly due to the fact that we want to
3989 * avoid syncing under i_rwsem.
3990 *
3991 * Return:
3992 * * number of bytes written, even for truncated writes
3993 * * negative error code if no data has been written at all
3994 */
3995ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3996{
3997 struct file *file = iocb->ki_filp;
3998 struct address_space *mapping = file->f_mapping;
3999 struct inode *inode = mapping->host;
4000 ssize_t ret;
4001
4002 ret = file_remove_privs(file);
4003 if (ret)
4004 return ret;
4005
4006 ret = file_update_time(file);
4007 if (ret)
4008 return ret;
4009
4010 if (iocb->ki_flags & IOCB_DIRECT) {
4011 ret = generic_file_direct_write(iocb, from);
4012 /*
4013 * If the write stopped short of completing, fall back to
4014 * buffered writes. Some filesystems do this for writes to
4015 * holes, for example. For DAX files, a buffered write will
4016 * not succeed (even if it did, DAX does not handle dirty
4017 * page-cache pages correctly).
4018 */
4019 if (ret < 0 || !iov_iter_count(from) || IS_DAX(inode))
4020 return ret;
4021 return direct_write_fallback(iocb, from, ret,
4022 generic_perform_write(iocb, from));
4023 }
4024
4025 return generic_perform_write(iocb, from);
4026}
4027EXPORT_SYMBOL(__generic_file_write_iter);
4028
4029/**
4030 * generic_file_write_iter - write data to a file
4031 * @iocb: IO state structure
4032 * @from: iov_iter with data to write
4033 *
4034 * This is a wrapper around __generic_file_write_iter() to be used by most
4035 * filesystems. It takes care of syncing the file in case of O_SYNC file
4036 * and acquires i_rwsem as needed.
4037 * Return:
4038 * * negative error code if no data has been written at all of
4039 * vfs_fsync_range() failed for a synchronous write
4040 * * number of bytes written, even for truncated writes
4041 */
4042ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
4043{
4044 struct file *file = iocb->ki_filp;
4045 struct inode *inode = file->f_mapping->host;
4046 ssize_t ret;
4047
4048 inode_lock(inode);
4049 ret = generic_write_checks(iocb, from);
4050 if (ret > 0)
4051 ret = __generic_file_write_iter(iocb, from);
4052 inode_unlock(inode);
4053
4054 if (ret > 0)
4055 ret = generic_write_sync(iocb, ret);
4056 return ret;
4057}
4058EXPORT_SYMBOL(generic_file_write_iter);
4059
4060/**
4061 * filemap_release_folio() - Release fs-specific metadata on a folio.
4062 * @folio: The folio which the kernel is trying to free.
4063 * @gfp: Memory allocation flags (and I/O mode).
4064 *
4065 * The address_space is trying to release any data attached to a folio
4066 * (presumably at folio->private).
4067 *
4068 * This will also be called if the private_2 flag is set on a page,
4069 * indicating that the folio has other metadata associated with it.
4070 *
4071 * The @gfp argument specifies whether I/O may be performed to release
4072 * this page (__GFP_IO), and whether the call may block
4073 * (__GFP_RECLAIM & __GFP_FS).
4074 *
4075 * Return: %true if the release was successful, otherwise %false.
4076 */
4077bool filemap_release_folio(struct folio *folio, gfp_t gfp)
4078{
4079 struct address_space * const mapping = folio->mapping;
4080
4081 BUG_ON(!folio_test_locked(folio));
4082 if (!folio_needs_release(folio))
4083 return true;
4084 if (folio_test_writeback(folio))
4085 return false;
4086
4087 if (mapping && mapping->a_ops->release_folio)
4088 return mapping->a_ops->release_folio(folio, gfp);
4089 return try_to_free_buffers(folio);
4090}
4091EXPORT_SYMBOL(filemap_release_folio);
4092
4093#ifdef CONFIG_CACHESTAT_SYSCALL
4094/**
4095 * filemap_cachestat() - compute the page cache statistics of a mapping
4096 * @mapping: The mapping to compute the statistics for.
4097 * @first_index: The starting page cache index.
4098 * @last_index: The final page index (inclusive).
4099 * @cs: the cachestat struct to write the result to.
4100 *
4101 * This will query the page cache statistics of a mapping in the
4102 * page range of [first_index, last_index] (inclusive). The statistics
4103 * queried include: number of dirty pages, number of pages marked for
4104 * writeback, and the number of (recently) evicted pages.
4105 */
4106static void filemap_cachestat(struct address_space *mapping,
4107 pgoff_t first_index, pgoff_t last_index, struct cachestat *cs)
4108{
4109 XA_STATE(xas, &mapping->i_pages, first_index);
4110 struct folio *folio;
4111
4112 rcu_read_lock();
4113 xas_for_each(&xas, folio, last_index) {
4114 int order;
4115 unsigned long nr_pages;
4116 pgoff_t folio_first_index, folio_last_index;
4117
4118 /*
4119 * Don't deref the folio. It is not pinned, and might
4120 * get freed (and reused) underneath us.
4121 *
4122 * We *could* pin it, but that would be expensive for
4123 * what should be a fast and lightweight syscall.
4124 *
4125 * Instead, derive all information of interest from
4126 * the rcu-protected xarray.
4127 */
4128
4129 if (xas_retry(&xas, folio))
4130 continue;
4131
4132 order = xa_get_order(xas.xa, xas.xa_index);
4133 nr_pages = 1 << order;
4134 folio_first_index = round_down(xas.xa_index, 1 << order);
4135 folio_last_index = folio_first_index + nr_pages - 1;
4136
4137 /* Folios might straddle the range boundaries, only count covered pages */
4138 if (folio_first_index < first_index)
4139 nr_pages -= first_index - folio_first_index;
4140
4141 if (folio_last_index > last_index)
4142 nr_pages -= folio_last_index - last_index;
4143
4144 if (xa_is_value(folio)) {
4145 /* page is evicted */
4146 void *shadow = (void *)folio;
4147 bool workingset; /* not used */
4148
4149 cs->nr_evicted += nr_pages;
4150
4151#ifdef CONFIG_SWAP /* implies CONFIG_MMU */
4152 if (shmem_mapping(mapping)) {
4153 /* shmem file - in swap cache */
4154 swp_entry_t swp = radix_to_swp_entry(folio);
4155
4156 shadow = get_shadow_from_swap_cache(swp);
4157 }
4158#endif
4159 if (workingset_test_recent(shadow, true, &workingset))
4160 cs->nr_recently_evicted += nr_pages;
4161
4162 goto resched;
4163 }
4164
4165 /* page is in cache */
4166 cs->nr_cache += nr_pages;
4167
4168 if (xas_get_mark(&xas, PAGECACHE_TAG_DIRTY))
4169 cs->nr_dirty += nr_pages;
4170
4171 if (xas_get_mark(&xas, PAGECACHE_TAG_WRITEBACK))
4172 cs->nr_writeback += nr_pages;
4173
4174resched:
4175 if (need_resched()) {
4176 xas_pause(&xas);
4177 cond_resched_rcu();
4178 }
4179 }
4180 rcu_read_unlock();
4181}
4182
4183/*
4184 * The cachestat(2) system call.
4185 *
4186 * cachestat() returns the page cache statistics of a file in the
4187 * bytes range specified by `off` and `len`: number of cached pages,
4188 * number of dirty pages, number of pages marked for writeback,
4189 * number of evicted pages, and number of recently evicted pages.
4190 *
4191 * An evicted page is a page that is previously in the page cache
4192 * but has been evicted since. A page is recently evicted if its last
4193 * eviction was recent enough that its reentry to the cache would
4194 * indicate that it is actively being used by the system, and that
4195 * there is memory pressure on the system.
4196 *
4197 * `off` and `len` must be non-negative integers. If `len` > 0,
4198 * the queried range is [`off`, `off` + `len`]. If `len` == 0,
4199 * we will query in the range from `off` to the end of the file.
4200 *
4201 * The `flags` argument is unused for now, but is included for future
4202 * extensibility. User should pass 0 (i.e no flag specified).
4203 *
4204 * Currently, hugetlbfs is not supported.
4205 *
4206 * Because the status of a page can change after cachestat() checks it
4207 * but before it returns to the application, the returned values may
4208 * contain stale information.
4209 *
4210 * return values:
4211 * zero - success
4212 * -EFAULT - cstat or cstat_range points to an illegal address
4213 * -EINVAL - invalid flags
4214 * -EBADF - invalid file descriptor
4215 * -EOPNOTSUPP - file descriptor is of a hugetlbfs file
4216 */
4217SYSCALL_DEFINE4(cachestat, unsigned int, fd,
4218 struct cachestat_range __user *, cstat_range,
4219 struct cachestat __user *, cstat, unsigned int, flags)
4220{
4221 struct fd f = fdget(fd);
4222 struct address_space *mapping;
4223 struct cachestat_range csr;
4224 struct cachestat cs;
4225 pgoff_t first_index, last_index;
4226
4227 if (!f.file)
4228 return -EBADF;
4229
4230 if (copy_from_user(&csr, cstat_range,
4231 sizeof(struct cachestat_range))) {
4232 fdput(f);
4233 return -EFAULT;
4234 }
4235
4236 /* hugetlbfs is not supported */
4237 if (is_file_hugepages(f.file)) {
4238 fdput(f);
4239 return -EOPNOTSUPP;
4240 }
4241
4242 if (flags != 0) {
4243 fdput(f);
4244 return -EINVAL;
4245 }
4246
4247 first_index = csr.off >> PAGE_SHIFT;
4248 last_index =
4249 csr.len == 0 ? ULONG_MAX : (csr.off + csr.len - 1) >> PAGE_SHIFT;
4250 memset(&cs, 0, sizeof(struct cachestat));
4251 mapping = f.file->f_mapping;
4252 filemap_cachestat(mapping, first_index, last_index, &cs);
4253 fdput(f);
4254
4255 if (copy_to_user(cstat, &cs, sizeof(struct cachestat)))
4256 return -EFAULT;
4257
4258 return 0;
4259}
4260#endif /* CONFIG_CACHESTAT_SYSCALL */