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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/*
2 * linux/mm/filemap.c
3 *
4 * Copyright (C) 1994-1999 Linus Torvalds
5 */
6
7/*
8 * This file handles the generic file mmap semantics used by
9 * most "normal" filesystems (but you don't /have/ to use this:
10 * the NFS filesystem used to do this differently, for example)
11 */
12#include <linux/export.h>
13#include <linux/compiler.h>
14#include <linux/dax.h>
15#include <linux/fs.h>
16#include <linux/uaccess.h>
17#include <linux/capability.h>
18#include <linux/kernel_stat.h>
19#include <linux/gfp.h>
20#include <linux/mm.h>
21#include <linux/swap.h>
22#include <linux/mman.h>
23#include <linux/pagemap.h>
24#include <linux/file.h>
25#include <linux/uio.h>
26#include <linux/hash.h>
27#include <linux/writeback.h>
28#include <linux/backing-dev.h>
29#include <linux/pagevec.h>
30#include <linux/blkdev.h>
31#include <linux/security.h>
32#include <linux/cpuset.h>
33#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
34#include <linux/hugetlb.h>
35#include <linux/memcontrol.h>
36#include <linux/cleancache.h>
37#include <linux/rmap.h>
38#include "internal.h"
39
40#define CREATE_TRACE_POINTS
41#include <trace/events/filemap.h>
42
43/*
44 * FIXME: remove all knowledge of the buffer layer from the core VM
45 */
46#include <linux/buffer_head.h> /* for try_to_free_buffers */
47
48#include <asm/mman.h>
49
50/*
51 * Shared mappings implemented 30.11.1994. It's not fully working yet,
52 * though.
53 *
54 * Shared mappings now work. 15.8.1995 Bruno.
55 *
56 * finished 'unifying' the page and buffer cache and SMP-threaded the
57 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
58 *
59 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
60 */
61
62/*
63 * Lock ordering:
64 *
65 * ->i_mmap_rwsem (truncate_pagecache)
66 * ->private_lock (__free_pte->__set_page_dirty_buffers)
67 * ->swap_lock (exclusive_swap_page, others)
68 * ->mapping->tree_lock
69 *
70 * ->i_mutex
71 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
72 *
73 * ->mmap_sem
74 * ->i_mmap_rwsem
75 * ->page_table_lock or pte_lock (various, mainly in memory.c)
76 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
77 *
78 * ->mmap_sem
79 * ->lock_page (access_process_vm)
80 *
81 * ->i_mutex (generic_perform_write)
82 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
83 *
84 * bdi->wb.list_lock
85 * sb_lock (fs/fs-writeback.c)
86 * ->mapping->tree_lock (__sync_single_inode)
87 *
88 * ->i_mmap_rwsem
89 * ->anon_vma.lock (vma_adjust)
90 *
91 * ->anon_vma.lock
92 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
93 *
94 * ->page_table_lock or pte_lock
95 * ->swap_lock (try_to_unmap_one)
96 * ->private_lock (try_to_unmap_one)
97 * ->tree_lock (try_to_unmap_one)
98 * ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
99 * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
100 * ->private_lock (page_remove_rmap->set_page_dirty)
101 * ->tree_lock (page_remove_rmap->set_page_dirty)
102 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
103 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
104 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
105 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
106 * ->inode->i_lock (zap_pte_range->set_page_dirty)
107 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
108 *
109 * ->i_mmap_rwsem
110 * ->tasklist_lock (memory_failure, collect_procs_ao)
111 */
112
113static int page_cache_tree_insert(struct address_space *mapping,
114 struct page *page, void **shadowp)
115{
116 struct radix_tree_node *node;
117 void **slot;
118 int error;
119
120 error = __radix_tree_create(&mapping->page_tree, page->index, 0,
121 &node, &slot);
122 if (error)
123 return error;
124 if (*slot) {
125 void *p;
126
127 p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
128 if (!radix_tree_exceptional_entry(p))
129 return -EEXIST;
130
131 mapping->nrexceptional--;
132 if (!dax_mapping(mapping)) {
133 if (shadowp)
134 *shadowp = p;
135 } else {
136 /* DAX can replace empty locked entry with a hole */
137 WARN_ON_ONCE(p !=
138 dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
139 /* Wakeup waiters for exceptional entry lock */
140 dax_wake_mapping_entry_waiter(mapping, page->index, p,
141 true);
142 }
143 }
144 __radix_tree_replace(&mapping->page_tree, node, slot, page,
145 workingset_update_node, mapping);
146 mapping->nrpages++;
147 return 0;
148}
149
150static void page_cache_tree_delete(struct address_space *mapping,
151 struct page *page, void *shadow)
152{
153 int i, nr;
154
155 /* hugetlb pages are represented by one entry in the radix tree */
156 nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
157
158 VM_BUG_ON_PAGE(!PageLocked(page), page);
159 VM_BUG_ON_PAGE(PageTail(page), page);
160 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
161
162 for (i = 0; i < nr; i++) {
163 struct radix_tree_node *node;
164 void **slot;
165
166 __radix_tree_lookup(&mapping->page_tree, page->index + i,
167 &node, &slot);
168
169 VM_BUG_ON_PAGE(!node && nr != 1, page);
170
171 radix_tree_clear_tags(&mapping->page_tree, node, slot);
172 __radix_tree_replace(&mapping->page_tree, node, slot, shadow,
173 workingset_update_node, mapping);
174 }
175
176 if (shadow) {
177 mapping->nrexceptional += nr;
178 /*
179 * Make sure the nrexceptional update is committed before
180 * the nrpages update so that final truncate racing
181 * with reclaim does not see both counters 0 at the
182 * same time and miss a shadow entry.
183 */
184 smp_wmb();
185 }
186 mapping->nrpages -= nr;
187}
188
189/*
190 * Delete a page from the page cache and free it. Caller has to make
191 * sure the page is locked and that nobody else uses it - or that usage
192 * is safe. The caller must hold the mapping's tree_lock.
193 */
194void __delete_from_page_cache(struct page *page, void *shadow)
195{
196 struct address_space *mapping = page->mapping;
197 int nr = hpage_nr_pages(page);
198
199 trace_mm_filemap_delete_from_page_cache(page);
200 /*
201 * if we're uptodate, flush out into the cleancache, otherwise
202 * invalidate any existing cleancache entries. We can't leave
203 * stale data around in the cleancache once our page is gone
204 */
205 if (PageUptodate(page) && PageMappedToDisk(page))
206 cleancache_put_page(page);
207 else
208 cleancache_invalidate_page(mapping, page);
209
210 VM_BUG_ON_PAGE(PageTail(page), page);
211 VM_BUG_ON_PAGE(page_mapped(page), page);
212 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
213 int mapcount;
214
215 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
216 current->comm, page_to_pfn(page));
217 dump_page(page, "still mapped when deleted");
218 dump_stack();
219 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
220
221 mapcount = page_mapcount(page);
222 if (mapping_exiting(mapping) &&
223 page_count(page) >= mapcount + 2) {
224 /*
225 * All vmas have already been torn down, so it's
226 * a good bet that actually the page is unmapped,
227 * and we'd prefer not to leak it: if we're wrong,
228 * some other bad page check should catch it later.
229 */
230 page_mapcount_reset(page);
231 page_ref_sub(page, mapcount);
232 }
233 }
234
235 page_cache_tree_delete(mapping, page, shadow);
236
237 page->mapping = NULL;
238 /* Leave page->index set: truncation lookup relies upon it */
239
240 /* hugetlb pages do not participate in page cache accounting. */
241 if (!PageHuge(page))
242 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
243 if (PageSwapBacked(page)) {
244 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
245 if (PageTransHuge(page))
246 __dec_node_page_state(page, NR_SHMEM_THPS);
247 } else {
248 VM_BUG_ON_PAGE(PageTransHuge(page) && !PageHuge(page), page);
249 }
250
251 /*
252 * At this point page must be either written or cleaned by truncate.
253 * Dirty page here signals a bug and loss of unwritten data.
254 *
255 * This fixes dirty accounting after removing the page entirely but
256 * leaves PageDirty set: it has no effect for truncated page and
257 * anyway will be cleared before returning page into buddy allocator.
258 */
259 if (WARN_ON_ONCE(PageDirty(page)))
260 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
261}
262
263/**
264 * delete_from_page_cache - delete page from page cache
265 * @page: the page which the kernel is trying to remove from page cache
266 *
267 * This must be called only on pages that have been verified to be in the page
268 * cache and locked. It will never put the page into the free list, the caller
269 * has a reference on the page.
270 */
271void delete_from_page_cache(struct page *page)
272{
273 struct address_space *mapping = page_mapping(page);
274 unsigned long flags;
275 void (*freepage)(struct page *);
276
277 BUG_ON(!PageLocked(page));
278
279 freepage = mapping->a_ops->freepage;
280
281 spin_lock_irqsave(&mapping->tree_lock, flags);
282 __delete_from_page_cache(page, NULL);
283 spin_unlock_irqrestore(&mapping->tree_lock, flags);
284
285 if (freepage)
286 freepage(page);
287
288 if (PageTransHuge(page) && !PageHuge(page)) {
289 page_ref_sub(page, HPAGE_PMD_NR);
290 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
291 } else {
292 put_page(page);
293 }
294}
295EXPORT_SYMBOL(delete_from_page_cache);
296
297int filemap_check_errors(struct address_space *mapping)
298{
299 int ret = 0;
300 /* Check for outstanding write errors */
301 if (test_bit(AS_ENOSPC, &mapping->flags) &&
302 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
303 ret = -ENOSPC;
304 if (test_bit(AS_EIO, &mapping->flags) &&
305 test_and_clear_bit(AS_EIO, &mapping->flags))
306 ret = -EIO;
307 return ret;
308}
309EXPORT_SYMBOL(filemap_check_errors);
310
311/**
312 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
313 * @mapping: address space structure to write
314 * @start: offset in bytes where the range starts
315 * @end: offset in bytes where the range ends (inclusive)
316 * @sync_mode: enable synchronous operation
317 *
318 * Start writeback against all of a mapping's dirty pages that lie
319 * within the byte offsets <start, end> inclusive.
320 *
321 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
322 * opposed to a regular memory cleansing writeback. The difference between
323 * these two operations is that if a dirty page/buffer is encountered, it must
324 * be waited upon, and not just skipped over.
325 */
326int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
327 loff_t end, int sync_mode)
328{
329 int ret;
330 struct writeback_control wbc = {
331 .sync_mode = sync_mode,
332 .nr_to_write = LONG_MAX,
333 .range_start = start,
334 .range_end = end,
335 };
336
337 if (!mapping_cap_writeback_dirty(mapping))
338 return 0;
339
340 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
341 ret = do_writepages(mapping, &wbc);
342 wbc_detach_inode(&wbc);
343 return ret;
344}
345
346static inline int __filemap_fdatawrite(struct address_space *mapping,
347 int sync_mode)
348{
349 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
350}
351
352int filemap_fdatawrite(struct address_space *mapping)
353{
354 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
355}
356EXPORT_SYMBOL(filemap_fdatawrite);
357
358int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
359 loff_t end)
360{
361 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
362}
363EXPORT_SYMBOL(filemap_fdatawrite_range);
364
365/**
366 * filemap_flush - mostly a non-blocking flush
367 * @mapping: target address_space
368 *
369 * This is a mostly non-blocking flush. Not suitable for data-integrity
370 * purposes - I/O may not be started against all dirty pages.
371 */
372int filemap_flush(struct address_space *mapping)
373{
374 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
375}
376EXPORT_SYMBOL(filemap_flush);
377
378static int __filemap_fdatawait_range(struct address_space *mapping,
379 loff_t start_byte, loff_t end_byte)
380{
381 pgoff_t index = start_byte >> PAGE_SHIFT;
382 pgoff_t end = end_byte >> PAGE_SHIFT;
383 struct pagevec pvec;
384 int nr_pages;
385 int ret = 0;
386
387 if (end_byte < start_byte)
388 goto out;
389
390 pagevec_init(&pvec, 0);
391 while ((index <= end) &&
392 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
393 PAGECACHE_TAG_WRITEBACK,
394 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
395 unsigned i;
396
397 for (i = 0; i < nr_pages; i++) {
398 struct page *page = pvec.pages[i];
399
400 /* until radix tree lookup accepts end_index */
401 if (page->index > end)
402 continue;
403
404 wait_on_page_writeback(page);
405 if (TestClearPageError(page))
406 ret = -EIO;
407 }
408 pagevec_release(&pvec);
409 cond_resched();
410 }
411out:
412 return ret;
413}
414
415/**
416 * filemap_fdatawait_range - wait for writeback to complete
417 * @mapping: address space structure to wait for
418 * @start_byte: offset in bytes where the range starts
419 * @end_byte: offset in bytes where the range ends (inclusive)
420 *
421 * Walk the list of under-writeback pages of the given address space
422 * in the given range and wait for all of them. Check error status of
423 * the address space and return it.
424 *
425 * Since the error status of the address space is cleared by this function,
426 * callers are responsible for checking the return value and handling and/or
427 * reporting the error.
428 */
429int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
430 loff_t end_byte)
431{
432 int ret, ret2;
433
434 ret = __filemap_fdatawait_range(mapping, start_byte, end_byte);
435 ret2 = filemap_check_errors(mapping);
436 if (!ret)
437 ret = ret2;
438
439 return ret;
440}
441EXPORT_SYMBOL(filemap_fdatawait_range);
442
443/**
444 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
445 * @mapping: address space structure to wait for
446 *
447 * Walk the list of under-writeback pages of the given address space
448 * and wait for all of them. Unlike filemap_fdatawait(), this function
449 * does not clear error status of the address space.
450 *
451 * Use this function if callers don't handle errors themselves. Expected
452 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
453 * fsfreeze(8)
454 */
455void filemap_fdatawait_keep_errors(struct address_space *mapping)
456{
457 loff_t i_size = i_size_read(mapping->host);
458
459 if (i_size == 0)
460 return;
461
462 __filemap_fdatawait_range(mapping, 0, i_size - 1);
463}
464
465/**
466 * filemap_fdatawait - wait for all under-writeback pages to complete
467 * @mapping: address space structure to wait for
468 *
469 * Walk the list of under-writeback pages of the given address space
470 * and wait for all of them. Check error status of the address space
471 * and return it.
472 *
473 * Since the error status of the address space is cleared by this function,
474 * callers are responsible for checking the return value and handling and/or
475 * reporting the error.
476 */
477int filemap_fdatawait(struct address_space *mapping)
478{
479 loff_t i_size = i_size_read(mapping->host);
480
481 if (i_size == 0)
482 return 0;
483
484 return filemap_fdatawait_range(mapping, 0, i_size - 1);
485}
486EXPORT_SYMBOL(filemap_fdatawait);
487
488int filemap_write_and_wait(struct address_space *mapping)
489{
490 int err = 0;
491
492 if ((!dax_mapping(mapping) && mapping->nrpages) ||
493 (dax_mapping(mapping) && mapping->nrexceptional)) {
494 err = filemap_fdatawrite(mapping);
495 /*
496 * Even if the above returned error, the pages may be
497 * written partially (e.g. -ENOSPC), so we wait for it.
498 * But the -EIO is special case, it may indicate the worst
499 * thing (e.g. bug) happened, so we avoid waiting for it.
500 */
501 if (err != -EIO) {
502 int err2 = filemap_fdatawait(mapping);
503 if (!err)
504 err = err2;
505 }
506 } else {
507 err = filemap_check_errors(mapping);
508 }
509 return err;
510}
511EXPORT_SYMBOL(filemap_write_and_wait);
512
513/**
514 * filemap_write_and_wait_range - write out & wait on a file range
515 * @mapping: the address_space for the pages
516 * @lstart: offset in bytes where the range starts
517 * @lend: offset in bytes where the range ends (inclusive)
518 *
519 * Write out and wait upon file offsets lstart->lend, inclusive.
520 *
521 * Note that `lend' is inclusive (describes the last byte to be written) so
522 * that this function can be used to write to the very end-of-file (end = -1).
523 */
524int filemap_write_and_wait_range(struct address_space *mapping,
525 loff_t lstart, loff_t lend)
526{
527 int err = 0;
528
529 if ((!dax_mapping(mapping) && mapping->nrpages) ||
530 (dax_mapping(mapping) && mapping->nrexceptional)) {
531 err = __filemap_fdatawrite_range(mapping, lstart, lend,
532 WB_SYNC_ALL);
533 /* See comment of filemap_write_and_wait() */
534 if (err != -EIO) {
535 int err2 = filemap_fdatawait_range(mapping,
536 lstart, lend);
537 if (!err)
538 err = err2;
539 }
540 } else {
541 err = filemap_check_errors(mapping);
542 }
543 return err;
544}
545EXPORT_SYMBOL(filemap_write_and_wait_range);
546
547/**
548 * replace_page_cache_page - replace a pagecache page with a new one
549 * @old: page to be replaced
550 * @new: page to replace with
551 * @gfp_mask: allocation mode
552 *
553 * This function replaces a page in the pagecache with a new one. On
554 * success it acquires the pagecache reference for the new page and
555 * drops it for the old page. Both the old and new pages must be
556 * locked. This function does not add the new page to the LRU, the
557 * caller must do that.
558 *
559 * The remove + add is atomic. The only way this function can fail is
560 * memory allocation failure.
561 */
562int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
563{
564 int error;
565
566 VM_BUG_ON_PAGE(!PageLocked(old), old);
567 VM_BUG_ON_PAGE(!PageLocked(new), new);
568 VM_BUG_ON_PAGE(new->mapping, new);
569
570 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
571 if (!error) {
572 struct address_space *mapping = old->mapping;
573 void (*freepage)(struct page *);
574 unsigned long flags;
575
576 pgoff_t offset = old->index;
577 freepage = mapping->a_ops->freepage;
578
579 get_page(new);
580 new->mapping = mapping;
581 new->index = offset;
582
583 spin_lock_irqsave(&mapping->tree_lock, flags);
584 __delete_from_page_cache(old, NULL);
585 error = page_cache_tree_insert(mapping, new, NULL);
586 BUG_ON(error);
587
588 /*
589 * hugetlb pages do not participate in page cache accounting.
590 */
591 if (!PageHuge(new))
592 __inc_node_page_state(new, NR_FILE_PAGES);
593 if (PageSwapBacked(new))
594 __inc_node_page_state(new, NR_SHMEM);
595 spin_unlock_irqrestore(&mapping->tree_lock, flags);
596 mem_cgroup_migrate(old, new);
597 radix_tree_preload_end();
598 if (freepage)
599 freepage(old);
600 put_page(old);
601 }
602
603 return error;
604}
605EXPORT_SYMBOL_GPL(replace_page_cache_page);
606
607static int __add_to_page_cache_locked(struct page *page,
608 struct address_space *mapping,
609 pgoff_t offset, gfp_t gfp_mask,
610 void **shadowp)
611{
612 int huge = PageHuge(page);
613 struct mem_cgroup *memcg;
614 int error;
615
616 VM_BUG_ON_PAGE(!PageLocked(page), page);
617 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
618
619 if (!huge) {
620 error = mem_cgroup_try_charge(page, current->mm,
621 gfp_mask, &memcg, false);
622 if (error)
623 return error;
624 }
625
626 error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
627 if (error) {
628 if (!huge)
629 mem_cgroup_cancel_charge(page, memcg, false);
630 return error;
631 }
632
633 get_page(page);
634 page->mapping = mapping;
635 page->index = offset;
636
637 spin_lock_irq(&mapping->tree_lock);
638 error = page_cache_tree_insert(mapping, page, shadowp);
639 radix_tree_preload_end();
640 if (unlikely(error))
641 goto err_insert;
642
643 /* hugetlb pages do not participate in page cache accounting. */
644 if (!huge)
645 __inc_node_page_state(page, NR_FILE_PAGES);
646 spin_unlock_irq(&mapping->tree_lock);
647 if (!huge)
648 mem_cgroup_commit_charge(page, memcg, false, false);
649 trace_mm_filemap_add_to_page_cache(page);
650 return 0;
651err_insert:
652 page->mapping = NULL;
653 /* Leave page->index set: truncation relies upon it */
654 spin_unlock_irq(&mapping->tree_lock);
655 if (!huge)
656 mem_cgroup_cancel_charge(page, memcg, false);
657 put_page(page);
658 return error;
659}
660
661/**
662 * add_to_page_cache_locked - add a locked page to the pagecache
663 * @page: page to add
664 * @mapping: the page's address_space
665 * @offset: page index
666 * @gfp_mask: page allocation mode
667 *
668 * This function is used to add a page to the pagecache. It must be locked.
669 * This function does not add the page to the LRU. The caller must do that.
670 */
671int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
672 pgoff_t offset, gfp_t gfp_mask)
673{
674 return __add_to_page_cache_locked(page, mapping, offset,
675 gfp_mask, NULL);
676}
677EXPORT_SYMBOL(add_to_page_cache_locked);
678
679int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
680 pgoff_t offset, gfp_t gfp_mask)
681{
682 void *shadow = NULL;
683 int ret;
684
685 __SetPageLocked(page);
686 ret = __add_to_page_cache_locked(page, mapping, offset,
687 gfp_mask, &shadow);
688 if (unlikely(ret))
689 __ClearPageLocked(page);
690 else {
691 /*
692 * The page might have been evicted from cache only
693 * recently, in which case it should be activated like
694 * any other repeatedly accessed page.
695 * The exception is pages getting rewritten; evicting other
696 * data from the working set, only to cache data that will
697 * get overwritten with something else, is a waste of memory.
698 */
699 if (!(gfp_mask & __GFP_WRITE) &&
700 shadow && workingset_refault(shadow)) {
701 SetPageActive(page);
702 workingset_activation(page);
703 } else
704 ClearPageActive(page);
705 lru_cache_add(page);
706 }
707 return ret;
708}
709EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
710
711#ifdef CONFIG_NUMA
712struct page *__page_cache_alloc(gfp_t gfp)
713{
714 int n;
715 struct page *page;
716
717 if (cpuset_do_page_mem_spread()) {
718 unsigned int cpuset_mems_cookie;
719 do {
720 cpuset_mems_cookie = read_mems_allowed_begin();
721 n = cpuset_mem_spread_node();
722 page = __alloc_pages_node(n, gfp, 0);
723 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
724
725 return page;
726 }
727 return alloc_pages(gfp, 0);
728}
729EXPORT_SYMBOL(__page_cache_alloc);
730#endif
731
732/*
733 * In order to wait for pages to become available there must be
734 * waitqueues associated with pages. By using a hash table of
735 * waitqueues where the bucket discipline is to maintain all
736 * waiters on the same queue and wake all when any of the pages
737 * become available, and for the woken contexts to check to be
738 * sure the appropriate page became available, this saves space
739 * at a cost of "thundering herd" phenomena during rare hash
740 * collisions.
741 */
742#define PAGE_WAIT_TABLE_BITS 8
743#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
744static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
745
746static wait_queue_head_t *page_waitqueue(struct page *page)
747{
748 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
749}
750
751void __init pagecache_init(void)
752{
753 int i;
754
755 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
756 init_waitqueue_head(&page_wait_table[i]);
757
758 page_writeback_init();
759}
760
761struct wait_page_key {
762 struct page *page;
763 int bit_nr;
764 int page_match;
765};
766
767struct wait_page_queue {
768 struct page *page;
769 int bit_nr;
770 wait_queue_t wait;
771};
772
773static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
774{
775 struct wait_page_key *key = arg;
776 struct wait_page_queue *wait_page
777 = container_of(wait, struct wait_page_queue, wait);
778
779 if (wait_page->page != key->page)
780 return 0;
781 key->page_match = 1;
782
783 if (wait_page->bit_nr != key->bit_nr)
784 return 0;
785 if (test_bit(key->bit_nr, &key->page->flags))
786 return 0;
787
788 return autoremove_wake_function(wait, mode, sync, key);
789}
790
791void wake_up_page_bit(struct page *page, int bit_nr)
792{
793 wait_queue_head_t *q = page_waitqueue(page);
794 struct wait_page_key key;
795 unsigned long flags;
796
797 key.page = page;
798 key.bit_nr = bit_nr;
799 key.page_match = 0;
800
801 spin_lock_irqsave(&q->lock, flags);
802 __wake_up_locked_key(q, TASK_NORMAL, &key);
803 /*
804 * It is possible for other pages to have collided on the waitqueue
805 * hash, so in that case check for a page match. That prevents a long-
806 * term waiter
807 *
808 * It is still possible to miss a case here, when we woke page waiters
809 * and removed them from the waitqueue, but there are still other
810 * page waiters.
811 */
812 if (!waitqueue_active(q) || !key.page_match) {
813 ClearPageWaiters(page);
814 /*
815 * It's possible to miss clearing Waiters here, when we woke
816 * our page waiters, but the hashed waitqueue has waiters for
817 * other pages on it.
818 *
819 * That's okay, it's a rare case. The next waker will clear it.
820 */
821 }
822 spin_unlock_irqrestore(&q->lock, flags);
823}
824EXPORT_SYMBOL(wake_up_page_bit);
825
826static inline int wait_on_page_bit_common(wait_queue_head_t *q,
827 struct page *page, int bit_nr, int state, bool lock)
828{
829 struct wait_page_queue wait_page;
830 wait_queue_t *wait = &wait_page.wait;
831 int ret = 0;
832
833 init_wait(wait);
834 wait->func = wake_page_function;
835 wait_page.page = page;
836 wait_page.bit_nr = bit_nr;
837
838 for (;;) {
839 spin_lock_irq(&q->lock);
840
841 if (likely(list_empty(&wait->task_list))) {
842 if (lock)
843 __add_wait_queue_tail_exclusive(q, wait);
844 else
845 __add_wait_queue(q, wait);
846 SetPageWaiters(page);
847 }
848
849 set_current_state(state);
850
851 spin_unlock_irq(&q->lock);
852
853 if (likely(test_bit(bit_nr, &page->flags))) {
854 io_schedule();
855 if (unlikely(signal_pending_state(state, current))) {
856 ret = -EINTR;
857 break;
858 }
859 }
860
861 if (lock) {
862 if (!test_and_set_bit_lock(bit_nr, &page->flags))
863 break;
864 } else {
865 if (!test_bit(bit_nr, &page->flags))
866 break;
867 }
868 }
869
870 finish_wait(q, wait);
871
872 /*
873 * A signal could leave PageWaiters set. Clearing it here if
874 * !waitqueue_active would be possible (by open-coding finish_wait),
875 * but still fail to catch it in the case of wait hash collision. We
876 * already can fail to clear wait hash collision cases, so don't
877 * bother with signals either.
878 */
879
880 return ret;
881}
882
883void wait_on_page_bit(struct page *page, int bit_nr)
884{
885 wait_queue_head_t *q = page_waitqueue(page);
886 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
887}
888EXPORT_SYMBOL(wait_on_page_bit);
889
890int wait_on_page_bit_killable(struct page *page, int bit_nr)
891{
892 wait_queue_head_t *q = page_waitqueue(page);
893 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
894}
895
896/**
897 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
898 * @page: Page defining the wait queue of interest
899 * @waiter: Waiter to add to the queue
900 *
901 * Add an arbitrary @waiter to the wait queue for the nominated @page.
902 */
903void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
904{
905 wait_queue_head_t *q = page_waitqueue(page);
906 unsigned long flags;
907
908 spin_lock_irqsave(&q->lock, flags);
909 __add_wait_queue(q, waiter);
910 SetPageWaiters(page);
911 spin_unlock_irqrestore(&q->lock, flags);
912}
913EXPORT_SYMBOL_GPL(add_page_wait_queue);
914
915#ifndef clear_bit_unlock_is_negative_byte
916
917/*
918 * PG_waiters is the high bit in the same byte as PG_lock.
919 *
920 * On x86 (and on many other architectures), we can clear PG_lock and
921 * test the sign bit at the same time. But if the architecture does
922 * not support that special operation, we just do this all by hand
923 * instead.
924 *
925 * The read of PG_waiters has to be after (or concurrently with) PG_locked
926 * being cleared, but a memory barrier should be unneccssary since it is
927 * in the same byte as PG_locked.
928 */
929static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
930{
931 clear_bit_unlock(nr, mem);
932 /* smp_mb__after_atomic(); */
933 return test_bit(PG_waiters, mem);
934}
935
936#endif
937
938/**
939 * unlock_page - unlock a locked page
940 * @page: the page
941 *
942 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
943 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
944 * mechanism between PageLocked pages and PageWriteback pages is shared.
945 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
946 *
947 * Note that this depends on PG_waiters being the sign bit in the byte
948 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
949 * clear the PG_locked bit and test PG_waiters at the same time fairly
950 * portably (architectures that do LL/SC can test any bit, while x86 can
951 * test the sign bit).
952 */
953void unlock_page(struct page *page)
954{
955 BUILD_BUG_ON(PG_waiters != 7);
956 page = compound_head(page);
957 VM_BUG_ON_PAGE(!PageLocked(page), page);
958 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
959 wake_up_page_bit(page, PG_locked);
960}
961EXPORT_SYMBOL(unlock_page);
962
963/**
964 * end_page_writeback - end writeback against a page
965 * @page: the page
966 */
967void end_page_writeback(struct page *page)
968{
969 /*
970 * TestClearPageReclaim could be used here but it is an atomic
971 * operation and overkill in this particular case. Failing to
972 * shuffle a page marked for immediate reclaim is too mild to
973 * justify taking an atomic operation penalty at the end of
974 * ever page writeback.
975 */
976 if (PageReclaim(page)) {
977 ClearPageReclaim(page);
978 rotate_reclaimable_page(page);
979 }
980
981 if (!test_clear_page_writeback(page))
982 BUG();
983
984 smp_mb__after_atomic();
985 wake_up_page(page, PG_writeback);
986}
987EXPORT_SYMBOL(end_page_writeback);
988
989/*
990 * After completing I/O on a page, call this routine to update the page
991 * flags appropriately
992 */
993void page_endio(struct page *page, bool is_write, int err)
994{
995 if (!is_write) {
996 if (!err) {
997 SetPageUptodate(page);
998 } else {
999 ClearPageUptodate(page);
1000 SetPageError(page);
1001 }
1002 unlock_page(page);
1003 } else {
1004 if (err) {
1005 struct address_space *mapping;
1006
1007 SetPageError(page);
1008 mapping = page_mapping(page);
1009 if (mapping)
1010 mapping_set_error(mapping, err);
1011 }
1012 end_page_writeback(page);
1013 }
1014}
1015EXPORT_SYMBOL_GPL(page_endio);
1016
1017/**
1018 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1019 * @page: the page to lock
1020 */
1021void __lock_page(struct page *__page)
1022{
1023 struct page *page = compound_head(__page);
1024 wait_queue_head_t *q = page_waitqueue(page);
1025 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
1026}
1027EXPORT_SYMBOL(__lock_page);
1028
1029int __lock_page_killable(struct page *__page)
1030{
1031 struct page *page = compound_head(__page);
1032 wait_queue_head_t *q = page_waitqueue(page);
1033 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
1034}
1035EXPORT_SYMBOL_GPL(__lock_page_killable);
1036
1037/*
1038 * Return values:
1039 * 1 - page is locked; mmap_sem is still held.
1040 * 0 - page is not locked.
1041 * mmap_sem has been released (up_read()), unless flags had both
1042 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1043 * which case mmap_sem is still held.
1044 *
1045 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1046 * with the page locked and the mmap_sem unperturbed.
1047 */
1048int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1049 unsigned int flags)
1050{
1051 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1052 /*
1053 * CAUTION! In this case, mmap_sem is not released
1054 * even though return 0.
1055 */
1056 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1057 return 0;
1058
1059 up_read(&mm->mmap_sem);
1060 if (flags & FAULT_FLAG_KILLABLE)
1061 wait_on_page_locked_killable(page);
1062 else
1063 wait_on_page_locked(page);
1064 return 0;
1065 } else {
1066 if (flags & FAULT_FLAG_KILLABLE) {
1067 int ret;
1068
1069 ret = __lock_page_killable(page);
1070 if (ret) {
1071 up_read(&mm->mmap_sem);
1072 return 0;
1073 }
1074 } else
1075 __lock_page(page);
1076 return 1;
1077 }
1078}
1079
1080/**
1081 * page_cache_next_hole - find the next hole (not-present entry)
1082 * @mapping: mapping
1083 * @index: index
1084 * @max_scan: maximum range to search
1085 *
1086 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1087 * lowest indexed hole.
1088 *
1089 * Returns: the index of the hole if found, otherwise returns an index
1090 * outside of the set specified (in which case 'return - index >=
1091 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1092 * be returned.
1093 *
1094 * page_cache_next_hole may be called under rcu_read_lock. However,
1095 * like radix_tree_gang_lookup, this will not atomically search a
1096 * snapshot of the tree at a single point in time. For example, if a
1097 * hole is created at index 5, then subsequently a hole is created at
1098 * index 10, page_cache_next_hole covering both indexes may return 10
1099 * if called under rcu_read_lock.
1100 */
1101pgoff_t page_cache_next_hole(struct address_space *mapping,
1102 pgoff_t index, unsigned long max_scan)
1103{
1104 unsigned long i;
1105
1106 for (i = 0; i < max_scan; i++) {
1107 struct page *page;
1108
1109 page = radix_tree_lookup(&mapping->page_tree, index);
1110 if (!page || radix_tree_exceptional_entry(page))
1111 break;
1112 index++;
1113 if (index == 0)
1114 break;
1115 }
1116
1117 return index;
1118}
1119EXPORT_SYMBOL(page_cache_next_hole);
1120
1121/**
1122 * page_cache_prev_hole - find the prev hole (not-present entry)
1123 * @mapping: mapping
1124 * @index: index
1125 * @max_scan: maximum range to search
1126 *
1127 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1128 * the first hole.
1129 *
1130 * Returns: the index of the hole if found, otherwise returns an index
1131 * outside of the set specified (in which case 'index - return >=
1132 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1133 * will be returned.
1134 *
1135 * page_cache_prev_hole may be called under rcu_read_lock. However,
1136 * like radix_tree_gang_lookup, this will not atomically search a
1137 * snapshot of the tree at a single point in time. For example, if a
1138 * hole is created at index 10, then subsequently a hole is created at
1139 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1140 * called under rcu_read_lock.
1141 */
1142pgoff_t page_cache_prev_hole(struct address_space *mapping,
1143 pgoff_t index, unsigned long max_scan)
1144{
1145 unsigned long i;
1146
1147 for (i = 0; i < max_scan; i++) {
1148 struct page *page;
1149
1150 page = radix_tree_lookup(&mapping->page_tree, index);
1151 if (!page || radix_tree_exceptional_entry(page))
1152 break;
1153 index--;
1154 if (index == ULONG_MAX)
1155 break;
1156 }
1157
1158 return index;
1159}
1160EXPORT_SYMBOL(page_cache_prev_hole);
1161
1162/**
1163 * find_get_entry - find and get a page cache entry
1164 * @mapping: the address_space to search
1165 * @offset: the page cache index
1166 *
1167 * Looks up the page cache slot at @mapping & @offset. If there is a
1168 * page cache page, it is returned with an increased refcount.
1169 *
1170 * If the slot holds a shadow entry of a previously evicted page, or a
1171 * swap entry from shmem/tmpfs, it is returned.
1172 *
1173 * Otherwise, %NULL is returned.
1174 */
1175struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1176{
1177 void **pagep;
1178 struct page *head, *page;
1179
1180 rcu_read_lock();
1181repeat:
1182 page = NULL;
1183 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
1184 if (pagep) {
1185 page = radix_tree_deref_slot(pagep);
1186 if (unlikely(!page))
1187 goto out;
1188 if (radix_tree_exception(page)) {
1189 if (radix_tree_deref_retry(page))
1190 goto repeat;
1191 /*
1192 * A shadow entry of a recently evicted page,
1193 * or a swap entry from shmem/tmpfs. Return
1194 * it without attempting to raise page count.
1195 */
1196 goto out;
1197 }
1198
1199 head = compound_head(page);
1200 if (!page_cache_get_speculative(head))
1201 goto repeat;
1202
1203 /* The page was split under us? */
1204 if (compound_head(page) != head) {
1205 put_page(head);
1206 goto repeat;
1207 }
1208
1209 /*
1210 * Has the page moved?
1211 * This is part of the lockless pagecache protocol. See
1212 * include/linux/pagemap.h for details.
1213 */
1214 if (unlikely(page != *pagep)) {
1215 put_page(head);
1216 goto repeat;
1217 }
1218 }
1219out:
1220 rcu_read_unlock();
1221
1222 return page;
1223}
1224EXPORT_SYMBOL(find_get_entry);
1225
1226/**
1227 * find_lock_entry - locate, pin and lock a page cache entry
1228 * @mapping: the address_space to search
1229 * @offset: the page cache index
1230 *
1231 * Looks up the page cache slot at @mapping & @offset. If there is a
1232 * page cache page, it is returned locked and with an increased
1233 * refcount.
1234 *
1235 * If the slot holds a shadow entry of a previously evicted page, or a
1236 * swap entry from shmem/tmpfs, it is returned.
1237 *
1238 * Otherwise, %NULL is returned.
1239 *
1240 * find_lock_entry() may sleep.
1241 */
1242struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1243{
1244 struct page *page;
1245
1246repeat:
1247 page = find_get_entry(mapping, offset);
1248 if (page && !radix_tree_exception(page)) {
1249 lock_page(page);
1250 /* Has the page been truncated? */
1251 if (unlikely(page_mapping(page) != mapping)) {
1252 unlock_page(page);
1253 put_page(page);
1254 goto repeat;
1255 }
1256 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
1257 }
1258 return page;
1259}
1260EXPORT_SYMBOL(find_lock_entry);
1261
1262/**
1263 * pagecache_get_page - find and get a page reference
1264 * @mapping: the address_space to search
1265 * @offset: the page index
1266 * @fgp_flags: PCG flags
1267 * @gfp_mask: gfp mask to use for the page cache data page allocation
1268 *
1269 * Looks up the page cache slot at @mapping & @offset.
1270 *
1271 * PCG flags modify how the page is returned.
1272 *
1273 * FGP_ACCESSED: the page will be marked accessed
1274 * FGP_LOCK: Page is return locked
1275 * FGP_CREAT: If page is not present then a new page is allocated using
1276 * @gfp_mask and added to the page cache and the VM's LRU
1277 * list. The page is returned locked and with an increased
1278 * refcount. Otherwise, %NULL is returned.
1279 *
1280 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1281 * if the GFP flags specified for FGP_CREAT are atomic.
1282 *
1283 * If there is a page cache page, it is returned with an increased refcount.
1284 */
1285struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1286 int fgp_flags, gfp_t gfp_mask)
1287{
1288 struct page *page;
1289
1290repeat:
1291 page = find_get_entry(mapping, offset);
1292 if (radix_tree_exceptional_entry(page))
1293 page = NULL;
1294 if (!page)
1295 goto no_page;
1296
1297 if (fgp_flags & FGP_LOCK) {
1298 if (fgp_flags & FGP_NOWAIT) {
1299 if (!trylock_page(page)) {
1300 put_page(page);
1301 return NULL;
1302 }
1303 } else {
1304 lock_page(page);
1305 }
1306
1307 /* Has the page been truncated? */
1308 if (unlikely(page->mapping != mapping)) {
1309 unlock_page(page);
1310 put_page(page);
1311 goto repeat;
1312 }
1313 VM_BUG_ON_PAGE(page->index != offset, page);
1314 }
1315
1316 if (page && (fgp_flags & FGP_ACCESSED))
1317 mark_page_accessed(page);
1318
1319no_page:
1320 if (!page && (fgp_flags & FGP_CREAT)) {
1321 int err;
1322 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1323 gfp_mask |= __GFP_WRITE;
1324 if (fgp_flags & FGP_NOFS)
1325 gfp_mask &= ~__GFP_FS;
1326
1327 page = __page_cache_alloc(gfp_mask);
1328 if (!page)
1329 return NULL;
1330
1331 if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
1332 fgp_flags |= FGP_LOCK;
1333
1334 /* Init accessed so avoid atomic mark_page_accessed later */
1335 if (fgp_flags & FGP_ACCESSED)
1336 __SetPageReferenced(page);
1337
1338 err = add_to_page_cache_lru(page, mapping, offset,
1339 gfp_mask & GFP_RECLAIM_MASK);
1340 if (unlikely(err)) {
1341 put_page(page);
1342 page = NULL;
1343 if (err == -EEXIST)
1344 goto repeat;
1345 }
1346 }
1347
1348 return page;
1349}
1350EXPORT_SYMBOL(pagecache_get_page);
1351
1352/**
1353 * find_get_entries - gang pagecache lookup
1354 * @mapping: The address_space to search
1355 * @start: The starting page cache index
1356 * @nr_entries: The maximum number of entries
1357 * @entries: Where the resulting entries are placed
1358 * @indices: The cache indices corresponding to the entries in @entries
1359 *
1360 * find_get_entries() will search for and return a group of up to
1361 * @nr_entries entries in the mapping. The entries are placed at
1362 * @entries. find_get_entries() takes a reference against any actual
1363 * pages it returns.
1364 *
1365 * The search returns a group of mapping-contiguous page cache entries
1366 * with ascending indexes. There may be holes in the indices due to
1367 * not-present pages.
1368 *
1369 * Any shadow entries of evicted pages, or swap entries from
1370 * shmem/tmpfs, are included in the returned array.
1371 *
1372 * find_get_entries() returns the number of pages and shadow entries
1373 * which were found.
1374 */
1375unsigned find_get_entries(struct address_space *mapping,
1376 pgoff_t start, unsigned int nr_entries,
1377 struct page **entries, pgoff_t *indices)
1378{
1379 void **slot;
1380 unsigned int ret = 0;
1381 struct radix_tree_iter iter;
1382
1383 if (!nr_entries)
1384 return 0;
1385
1386 rcu_read_lock();
1387 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1388 struct page *head, *page;
1389repeat:
1390 page = radix_tree_deref_slot(slot);
1391 if (unlikely(!page))
1392 continue;
1393 if (radix_tree_exception(page)) {
1394 if (radix_tree_deref_retry(page)) {
1395 slot = radix_tree_iter_retry(&iter);
1396 continue;
1397 }
1398 /*
1399 * A shadow entry of a recently evicted page, a swap
1400 * entry from shmem/tmpfs or a DAX entry. Return it
1401 * without attempting to raise page count.
1402 */
1403 goto export;
1404 }
1405
1406 head = compound_head(page);
1407 if (!page_cache_get_speculative(head))
1408 goto repeat;
1409
1410 /* The page was split under us? */
1411 if (compound_head(page) != head) {
1412 put_page(head);
1413 goto repeat;
1414 }
1415
1416 /* Has the page moved? */
1417 if (unlikely(page != *slot)) {
1418 put_page(head);
1419 goto repeat;
1420 }
1421export:
1422 indices[ret] = iter.index;
1423 entries[ret] = page;
1424 if (++ret == nr_entries)
1425 break;
1426 }
1427 rcu_read_unlock();
1428 return ret;
1429}
1430
1431/**
1432 * find_get_pages - gang pagecache lookup
1433 * @mapping: The address_space to search
1434 * @start: The starting page index
1435 * @nr_pages: The maximum number of pages
1436 * @pages: Where the resulting pages are placed
1437 *
1438 * find_get_pages() will search for and return a group of up to
1439 * @nr_pages pages in the mapping. The pages are placed at @pages.
1440 * find_get_pages() takes a reference against the returned pages.
1441 *
1442 * The search returns a group of mapping-contiguous pages with ascending
1443 * indexes. There may be holes in the indices due to not-present pages.
1444 *
1445 * find_get_pages() returns the number of pages which were found.
1446 */
1447unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
1448 unsigned int nr_pages, struct page **pages)
1449{
1450 struct radix_tree_iter iter;
1451 void **slot;
1452 unsigned ret = 0;
1453
1454 if (unlikely(!nr_pages))
1455 return 0;
1456
1457 rcu_read_lock();
1458 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1459 struct page *head, *page;
1460repeat:
1461 page = radix_tree_deref_slot(slot);
1462 if (unlikely(!page))
1463 continue;
1464
1465 if (radix_tree_exception(page)) {
1466 if (radix_tree_deref_retry(page)) {
1467 slot = radix_tree_iter_retry(&iter);
1468 continue;
1469 }
1470 /*
1471 * A shadow entry of a recently evicted page,
1472 * or a swap entry from shmem/tmpfs. Skip
1473 * over it.
1474 */
1475 continue;
1476 }
1477
1478 head = compound_head(page);
1479 if (!page_cache_get_speculative(head))
1480 goto repeat;
1481
1482 /* The page was split under us? */
1483 if (compound_head(page) != head) {
1484 put_page(head);
1485 goto repeat;
1486 }
1487
1488 /* Has the page moved? */
1489 if (unlikely(page != *slot)) {
1490 put_page(head);
1491 goto repeat;
1492 }
1493
1494 pages[ret] = page;
1495 if (++ret == nr_pages)
1496 break;
1497 }
1498
1499 rcu_read_unlock();
1500 return ret;
1501}
1502
1503/**
1504 * find_get_pages_contig - gang contiguous pagecache lookup
1505 * @mapping: The address_space to search
1506 * @index: The starting page index
1507 * @nr_pages: The maximum number of pages
1508 * @pages: Where the resulting pages are placed
1509 *
1510 * find_get_pages_contig() works exactly like find_get_pages(), except
1511 * that the returned number of pages are guaranteed to be contiguous.
1512 *
1513 * find_get_pages_contig() returns the number of pages which were found.
1514 */
1515unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1516 unsigned int nr_pages, struct page **pages)
1517{
1518 struct radix_tree_iter iter;
1519 void **slot;
1520 unsigned int ret = 0;
1521
1522 if (unlikely(!nr_pages))
1523 return 0;
1524
1525 rcu_read_lock();
1526 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
1527 struct page *head, *page;
1528repeat:
1529 page = radix_tree_deref_slot(slot);
1530 /* The hole, there no reason to continue */
1531 if (unlikely(!page))
1532 break;
1533
1534 if (radix_tree_exception(page)) {
1535 if (radix_tree_deref_retry(page)) {
1536 slot = radix_tree_iter_retry(&iter);
1537 continue;
1538 }
1539 /*
1540 * A shadow entry of a recently evicted page,
1541 * or a swap entry from shmem/tmpfs. Stop
1542 * looking for contiguous pages.
1543 */
1544 break;
1545 }
1546
1547 head = compound_head(page);
1548 if (!page_cache_get_speculative(head))
1549 goto repeat;
1550
1551 /* The page was split under us? */
1552 if (compound_head(page) != head) {
1553 put_page(head);
1554 goto repeat;
1555 }
1556
1557 /* Has the page moved? */
1558 if (unlikely(page != *slot)) {
1559 put_page(head);
1560 goto repeat;
1561 }
1562
1563 /*
1564 * must check mapping and index after taking the ref.
1565 * otherwise we can get both false positives and false
1566 * negatives, which is just confusing to the caller.
1567 */
1568 if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
1569 put_page(page);
1570 break;
1571 }
1572
1573 pages[ret] = page;
1574 if (++ret == nr_pages)
1575 break;
1576 }
1577 rcu_read_unlock();
1578 return ret;
1579}
1580EXPORT_SYMBOL(find_get_pages_contig);
1581
1582/**
1583 * find_get_pages_tag - find and return pages that match @tag
1584 * @mapping: the address_space to search
1585 * @index: the starting page index
1586 * @tag: the tag index
1587 * @nr_pages: the maximum number of pages
1588 * @pages: where the resulting pages are placed
1589 *
1590 * Like find_get_pages, except we only return pages which are tagged with
1591 * @tag. We update @index to index the next page for the traversal.
1592 */
1593unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
1594 int tag, unsigned int nr_pages, struct page **pages)
1595{
1596 struct radix_tree_iter iter;
1597 void **slot;
1598 unsigned ret = 0;
1599
1600 if (unlikely(!nr_pages))
1601 return 0;
1602
1603 rcu_read_lock();
1604 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1605 &iter, *index, tag) {
1606 struct page *head, *page;
1607repeat:
1608 page = radix_tree_deref_slot(slot);
1609 if (unlikely(!page))
1610 continue;
1611
1612 if (radix_tree_exception(page)) {
1613 if (radix_tree_deref_retry(page)) {
1614 slot = radix_tree_iter_retry(&iter);
1615 continue;
1616 }
1617 /*
1618 * A shadow entry of a recently evicted page.
1619 *
1620 * Those entries should never be tagged, but
1621 * this tree walk is lockless and the tags are
1622 * looked up in bulk, one radix tree node at a
1623 * time, so there is a sizable window for page
1624 * reclaim to evict a page we saw tagged.
1625 *
1626 * Skip over it.
1627 */
1628 continue;
1629 }
1630
1631 head = compound_head(page);
1632 if (!page_cache_get_speculative(head))
1633 goto repeat;
1634
1635 /* The page was split under us? */
1636 if (compound_head(page) != head) {
1637 put_page(head);
1638 goto repeat;
1639 }
1640
1641 /* Has the page moved? */
1642 if (unlikely(page != *slot)) {
1643 put_page(head);
1644 goto repeat;
1645 }
1646
1647 pages[ret] = page;
1648 if (++ret == nr_pages)
1649 break;
1650 }
1651
1652 rcu_read_unlock();
1653
1654 if (ret)
1655 *index = pages[ret - 1]->index + 1;
1656
1657 return ret;
1658}
1659EXPORT_SYMBOL(find_get_pages_tag);
1660
1661/**
1662 * find_get_entries_tag - find and return entries that match @tag
1663 * @mapping: the address_space to search
1664 * @start: the starting page cache index
1665 * @tag: the tag index
1666 * @nr_entries: the maximum number of entries
1667 * @entries: where the resulting entries are placed
1668 * @indices: the cache indices corresponding to the entries in @entries
1669 *
1670 * Like find_get_entries, except we only return entries which are tagged with
1671 * @tag.
1672 */
1673unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
1674 int tag, unsigned int nr_entries,
1675 struct page **entries, pgoff_t *indices)
1676{
1677 void **slot;
1678 unsigned int ret = 0;
1679 struct radix_tree_iter iter;
1680
1681 if (!nr_entries)
1682 return 0;
1683
1684 rcu_read_lock();
1685 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1686 &iter, start, tag) {
1687 struct page *head, *page;
1688repeat:
1689 page = radix_tree_deref_slot(slot);
1690 if (unlikely(!page))
1691 continue;
1692 if (radix_tree_exception(page)) {
1693 if (radix_tree_deref_retry(page)) {
1694 slot = radix_tree_iter_retry(&iter);
1695 continue;
1696 }
1697
1698 /*
1699 * A shadow entry of a recently evicted page, a swap
1700 * entry from shmem/tmpfs or a DAX entry. Return it
1701 * without attempting to raise page count.
1702 */
1703 goto export;
1704 }
1705
1706 head = compound_head(page);
1707 if (!page_cache_get_speculative(head))
1708 goto repeat;
1709
1710 /* The page was split under us? */
1711 if (compound_head(page) != head) {
1712 put_page(head);
1713 goto repeat;
1714 }
1715
1716 /* Has the page moved? */
1717 if (unlikely(page != *slot)) {
1718 put_page(head);
1719 goto repeat;
1720 }
1721export:
1722 indices[ret] = iter.index;
1723 entries[ret] = page;
1724 if (++ret == nr_entries)
1725 break;
1726 }
1727 rcu_read_unlock();
1728 return ret;
1729}
1730EXPORT_SYMBOL(find_get_entries_tag);
1731
1732/*
1733 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1734 * a _large_ part of the i/o request. Imagine the worst scenario:
1735 *
1736 * ---R__________________________________________B__________
1737 * ^ reading here ^ bad block(assume 4k)
1738 *
1739 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1740 * => failing the whole request => read(R) => read(R+1) =>
1741 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1742 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1743 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1744 *
1745 * It is going insane. Fix it by quickly scaling down the readahead size.
1746 */
1747static void shrink_readahead_size_eio(struct file *filp,
1748 struct file_ra_state *ra)
1749{
1750 ra->ra_pages /= 4;
1751}
1752
1753/**
1754 * do_generic_file_read - generic file read routine
1755 * @filp: the file to read
1756 * @ppos: current file position
1757 * @iter: data destination
1758 * @written: already copied
1759 *
1760 * This is a generic file read routine, and uses the
1761 * mapping->a_ops->readpage() function for the actual low-level stuff.
1762 *
1763 * This is really ugly. But the goto's actually try to clarify some
1764 * of the logic when it comes to error handling etc.
1765 */
1766static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
1767 struct iov_iter *iter, ssize_t written)
1768{
1769 struct address_space *mapping = filp->f_mapping;
1770 struct inode *inode = mapping->host;
1771 struct file_ra_state *ra = &filp->f_ra;
1772 pgoff_t index;
1773 pgoff_t last_index;
1774 pgoff_t prev_index;
1775 unsigned long offset; /* offset into pagecache page */
1776 unsigned int prev_offset;
1777 int error = 0;
1778
1779 if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
1780 return 0;
1781 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
1782
1783 index = *ppos >> PAGE_SHIFT;
1784 prev_index = ra->prev_pos >> PAGE_SHIFT;
1785 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
1786 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
1787 offset = *ppos & ~PAGE_MASK;
1788
1789 for (;;) {
1790 struct page *page;
1791 pgoff_t end_index;
1792 loff_t isize;
1793 unsigned long nr, ret;
1794
1795 cond_resched();
1796find_page:
1797 if (fatal_signal_pending(current)) {
1798 error = -EINTR;
1799 goto out;
1800 }
1801
1802 page = find_get_page(mapping, index);
1803 if (!page) {
1804 page_cache_sync_readahead(mapping,
1805 ra, filp,
1806 index, last_index - index);
1807 page = find_get_page(mapping, index);
1808 if (unlikely(page == NULL))
1809 goto no_cached_page;
1810 }
1811 if (PageReadahead(page)) {
1812 page_cache_async_readahead(mapping,
1813 ra, filp, page,
1814 index, last_index - index);
1815 }
1816 if (!PageUptodate(page)) {
1817 /*
1818 * See comment in do_read_cache_page on why
1819 * wait_on_page_locked is used to avoid unnecessarily
1820 * serialisations and why it's safe.
1821 */
1822 error = wait_on_page_locked_killable(page);
1823 if (unlikely(error))
1824 goto readpage_error;
1825 if (PageUptodate(page))
1826 goto page_ok;
1827
1828 if (inode->i_blkbits == PAGE_SHIFT ||
1829 !mapping->a_ops->is_partially_uptodate)
1830 goto page_not_up_to_date;
1831 /* pipes can't handle partially uptodate pages */
1832 if (unlikely(iter->type & ITER_PIPE))
1833 goto page_not_up_to_date;
1834 if (!trylock_page(page))
1835 goto page_not_up_to_date;
1836 /* Did it get truncated before we got the lock? */
1837 if (!page->mapping)
1838 goto page_not_up_to_date_locked;
1839 if (!mapping->a_ops->is_partially_uptodate(page,
1840 offset, iter->count))
1841 goto page_not_up_to_date_locked;
1842 unlock_page(page);
1843 }
1844page_ok:
1845 /*
1846 * i_size must be checked after we know the page is Uptodate.
1847 *
1848 * Checking i_size after the check allows us to calculate
1849 * the correct value for "nr", which means the zero-filled
1850 * part of the page is not copied back to userspace (unless
1851 * another truncate extends the file - this is desired though).
1852 */
1853
1854 isize = i_size_read(inode);
1855 end_index = (isize - 1) >> PAGE_SHIFT;
1856 if (unlikely(!isize || index > end_index)) {
1857 put_page(page);
1858 goto out;
1859 }
1860
1861 /* nr is the maximum number of bytes to copy from this page */
1862 nr = PAGE_SIZE;
1863 if (index == end_index) {
1864 nr = ((isize - 1) & ~PAGE_MASK) + 1;
1865 if (nr <= offset) {
1866 put_page(page);
1867 goto out;
1868 }
1869 }
1870 nr = nr - offset;
1871
1872 /* If users can be writing to this page using arbitrary
1873 * virtual addresses, take care about potential aliasing
1874 * before reading the page on the kernel side.
1875 */
1876 if (mapping_writably_mapped(mapping))
1877 flush_dcache_page(page);
1878
1879 /*
1880 * When a sequential read accesses a page several times,
1881 * only mark it as accessed the first time.
1882 */
1883 if (prev_index != index || offset != prev_offset)
1884 mark_page_accessed(page);
1885 prev_index = index;
1886
1887 /*
1888 * Ok, we have the page, and it's up-to-date, so
1889 * now we can copy it to user space...
1890 */
1891
1892 ret = copy_page_to_iter(page, offset, nr, iter);
1893 offset += ret;
1894 index += offset >> PAGE_SHIFT;
1895 offset &= ~PAGE_MASK;
1896 prev_offset = offset;
1897
1898 put_page(page);
1899 written += ret;
1900 if (!iov_iter_count(iter))
1901 goto out;
1902 if (ret < nr) {
1903 error = -EFAULT;
1904 goto out;
1905 }
1906 continue;
1907
1908page_not_up_to_date:
1909 /* Get exclusive access to the page ... */
1910 error = lock_page_killable(page);
1911 if (unlikely(error))
1912 goto readpage_error;
1913
1914page_not_up_to_date_locked:
1915 /* Did it get truncated before we got the lock? */
1916 if (!page->mapping) {
1917 unlock_page(page);
1918 put_page(page);
1919 continue;
1920 }
1921
1922 /* Did somebody else fill it already? */
1923 if (PageUptodate(page)) {
1924 unlock_page(page);
1925 goto page_ok;
1926 }
1927
1928readpage:
1929 /*
1930 * A previous I/O error may have been due to temporary
1931 * failures, eg. multipath errors.
1932 * PG_error will be set again if readpage fails.
1933 */
1934 ClearPageError(page);
1935 /* Start the actual read. The read will unlock the page. */
1936 error = mapping->a_ops->readpage(filp, page);
1937
1938 if (unlikely(error)) {
1939 if (error == AOP_TRUNCATED_PAGE) {
1940 put_page(page);
1941 error = 0;
1942 goto find_page;
1943 }
1944 goto readpage_error;
1945 }
1946
1947 if (!PageUptodate(page)) {
1948 error = lock_page_killable(page);
1949 if (unlikely(error))
1950 goto readpage_error;
1951 if (!PageUptodate(page)) {
1952 if (page->mapping == NULL) {
1953 /*
1954 * invalidate_mapping_pages got it
1955 */
1956 unlock_page(page);
1957 put_page(page);
1958 goto find_page;
1959 }
1960 unlock_page(page);
1961 shrink_readahead_size_eio(filp, ra);
1962 error = -EIO;
1963 goto readpage_error;
1964 }
1965 unlock_page(page);
1966 }
1967
1968 goto page_ok;
1969
1970readpage_error:
1971 /* UHHUH! A synchronous read error occurred. Report it */
1972 put_page(page);
1973 goto out;
1974
1975no_cached_page:
1976 /*
1977 * Ok, it wasn't cached, so we need to create a new
1978 * page..
1979 */
1980 page = page_cache_alloc_cold(mapping);
1981 if (!page) {
1982 error = -ENOMEM;
1983 goto out;
1984 }
1985 error = add_to_page_cache_lru(page, mapping, index,
1986 mapping_gfp_constraint(mapping, GFP_KERNEL));
1987 if (error) {
1988 put_page(page);
1989 if (error == -EEXIST) {
1990 error = 0;
1991 goto find_page;
1992 }
1993 goto out;
1994 }
1995 goto readpage;
1996 }
1997
1998out:
1999 ra->prev_pos = prev_index;
2000 ra->prev_pos <<= PAGE_SHIFT;
2001 ra->prev_pos |= prev_offset;
2002
2003 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
2004 file_accessed(filp);
2005 return written ? written : error;
2006}
2007
2008/**
2009 * generic_file_read_iter - generic filesystem read routine
2010 * @iocb: kernel I/O control block
2011 * @iter: destination for the data read
2012 *
2013 * This is the "read_iter()" routine for all filesystems
2014 * that can use the page cache directly.
2015 */
2016ssize_t
2017generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2018{
2019 struct file *file = iocb->ki_filp;
2020 ssize_t retval = 0;
2021 size_t count = iov_iter_count(iter);
2022
2023 if (!count)
2024 goto out; /* skip atime */
2025
2026 if (iocb->ki_flags & IOCB_DIRECT) {
2027 struct address_space *mapping = file->f_mapping;
2028 struct inode *inode = mapping->host;
2029 struct iov_iter data = *iter;
2030 loff_t size;
2031
2032 size = i_size_read(inode);
2033 retval = filemap_write_and_wait_range(mapping, iocb->ki_pos,
2034 iocb->ki_pos + count - 1);
2035 if (retval < 0)
2036 goto out;
2037
2038 file_accessed(file);
2039
2040 retval = mapping->a_ops->direct_IO(iocb, &data);
2041 if (retval >= 0) {
2042 iocb->ki_pos += retval;
2043 iov_iter_advance(iter, retval);
2044 }
2045
2046 /*
2047 * Btrfs can have a short DIO read if we encounter
2048 * compressed extents, so if there was an error, or if
2049 * we've already read everything we wanted to, or if
2050 * there was a short read because we hit EOF, go ahead
2051 * and return. Otherwise fallthrough to buffered io for
2052 * the rest of the read. Buffered reads will not work for
2053 * DAX files, so don't bother trying.
2054 */
2055 if (retval < 0 || !iov_iter_count(iter) || iocb->ki_pos >= size ||
2056 IS_DAX(inode))
2057 goto out;
2058 }
2059
2060 retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval);
2061out:
2062 return retval;
2063}
2064EXPORT_SYMBOL(generic_file_read_iter);
2065
2066#ifdef CONFIG_MMU
2067/**
2068 * page_cache_read - adds requested page to the page cache if not already there
2069 * @file: file to read
2070 * @offset: page index
2071 * @gfp_mask: memory allocation flags
2072 *
2073 * This adds the requested page to the page cache if it isn't already there,
2074 * and schedules an I/O to read in its contents from disk.
2075 */
2076static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
2077{
2078 struct address_space *mapping = file->f_mapping;
2079 struct page *page;
2080 int ret;
2081
2082 do {
2083 page = __page_cache_alloc(gfp_mask|__GFP_COLD);
2084 if (!page)
2085 return -ENOMEM;
2086
2087 ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
2088 if (ret == 0)
2089 ret = mapping->a_ops->readpage(file, page);
2090 else if (ret == -EEXIST)
2091 ret = 0; /* losing race to add is OK */
2092
2093 put_page(page);
2094
2095 } while (ret == AOP_TRUNCATED_PAGE);
2096
2097 return ret;
2098}
2099
2100#define MMAP_LOTSAMISS (100)
2101
2102/*
2103 * Synchronous readahead happens when we don't even find
2104 * a page in the page cache at all.
2105 */
2106static void do_sync_mmap_readahead(struct vm_area_struct *vma,
2107 struct file_ra_state *ra,
2108 struct file *file,
2109 pgoff_t offset)
2110{
2111 struct address_space *mapping = file->f_mapping;
2112
2113 /* If we don't want any read-ahead, don't bother */
2114 if (vma->vm_flags & VM_RAND_READ)
2115 return;
2116 if (!ra->ra_pages)
2117 return;
2118
2119 if (vma->vm_flags & VM_SEQ_READ) {
2120 page_cache_sync_readahead(mapping, ra, file, offset,
2121 ra->ra_pages);
2122 return;
2123 }
2124
2125 /* Avoid banging the cache line if not needed */
2126 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
2127 ra->mmap_miss++;
2128
2129 /*
2130 * Do we miss much more than hit in this file? If so,
2131 * stop bothering with read-ahead. It will only hurt.
2132 */
2133 if (ra->mmap_miss > MMAP_LOTSAMISS)
2134 return;
2135
2136 /*
2137 * mmap read-around
2138 */
2139 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
2140 ra->size = ra->ra_pages;
2141 ra->async_size = ra->ra_pages / 4;
2142 ra_submit(ra, mapping, file);
2143}
2144
2145/*
2146 * Asynchronous readahead happens when we find the page and PG_readahead,
2147 * so we want to possibly extend the readahead further..
2148 */
2149static void do_async_mmap_readahead(struct vm_area_struct *vma,
2150 struct file_ra_state *ra,
2151 struct file *file,
2152 struct page *page,
2153 pgoff_t offset)
2154{
2155 struct address_space *mapping = file->f_mapping;
2156
2157 /* If we don't want any read-ahead, don't bother */
2158 if (vma->vm_flags & VM_RAND_READ)
2159 return;
2160 if (ra->mmap_miss > 0)
2161 ra->mmap_miss--;
2162 if (PageReadahead(page))
2163 page_cache_async_readahead(mapping, ra, file,
2164 page, offset, ra->ra_pages);
2165}
2166
2167/**
2168 * filemap_fault - read in file data for page fault handling
2169 * @vma: vma in which the fault was taken
2170 * @vmf: struct vm_fault containing details of the fault
2171 *
2172 * filemap_fault() is invoked via the vma operations vector for a
2173 * mapped memory region to read in file data during a page fault.
2174 *
2175 * The goto's are kind of ugly, but this streamlines the normal case of having
2176 * it in the page cache, and handles the special cases reasonably without
2177 * having a lot of duplicated code.
2178 *
2179 * vma->vm_mm->mmap_sem must be held on entry.
2180 *
2181 * If our return value has VM_FAULT_RETRY set, it's because
2182 * lock_page_or_retry() returned 0.
2183 * The mmap_sem has usually been released in this case.
2184 * See __lock_page_or_retry() for the exception.
2185 *
2186 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2187 * has not been released.
2188 *
2189 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2190 */
2191int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
2192{
2193 int error;
2194 struct file *file = vma->vm_file;
2195 struct address_space *mapping = file->f_mapping;
2196 struct file_ra_state *ra = &file->f_ra;
2197 struct inode *inode = mapping->host;
2198 pgoff_t offset = vmf->pgoff;
2199 struct page *page;
2200 loff_t size;
2201 int ret = 0;
2202
2203 size = round_up(i_size_read(inode), PAGE_SIZE);
2204 if (offset >= size >> PAGE_SHIFT)
2205 return VM_FAULT_SIGBUS;
2206
2207 /*
2208 * Do we have something in the page cache already?
2209 */
2210 page = find_get_page(mapping, offset);
2211 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2212 /*
2213 * We found the page, so try async readahead before
2214 * waiting for the lock.
2215 */
2216 do_async_mmap_readahead(vma, ra, file, page, offset);
2217 } else if (!page) {
2218 /* No page in the page cache at all */
2219 do_sync_mmap_readahead(vma, ra, file, offset);
2220 count_vm_event(PGMAJFAULT);
2221 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
2222 ret = VM_FAULT_MAJOR;
2223retry_find:
2224 page = find_get_page(mapping, offset);
2225 if (!page)
2226 goto no_cached_page;
2227 }
2228
2229 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
2230 put_page(page);
2231 return ret | VM_FAULT_RETRY;
2232 }
2233
2234 /* Did it get truncated? */
2235 if (unlikely(page->mapping != mapping)) {
2236 unlock_page(page);
2237 put_page(page);
2238 goto retry_find;
2239 }
2240 VM_BUG_ON_PAGE(page->index != offset, page);
2241
2242 /*
2243 * We have a locked page in the page cache, now we need to check
2244 * that it's up-to-date. If not, it is going to be due to an error.
2245 */
2246 if (unlikely(!PageUptodate(page)))
2247 goto page_not_uptodate;
2248
2249 /*
2250 * Found the page and have a reference on it.
2251 * We must recheck i_size under page lock.
2252 */
2253 size = round_up(i_size_read(inode), PAGE_SIZE);
2254 if (unlikely(offset >= size >> PAGE_SHIFT)) {
2255 unlock_page(page);
2256 put_page(page);
2257 return VM_FAULT_SIGBUS;
2258 }
2259
2260 vmf->page = page;
2261 return ret | VM_FAULT_LOCKED;
2262
2263no_cached_page:
2264 /*
2265 * We're only likely to ever get here if MADV_RANDOM is in
2266 * effect.
2267 */
2268 error = page_cache_read(file, offset, vmf->gfp_mask);
2269
2270 /*
2271 * The page we want has now been added to the page cache.
2272 * In the unlikely event that someone removed it in the
2273 * meantime, we'll just come back here and read it again.
2274 */
2275 if (error >= 0)
2276 goto retry_find;
2277
2278 /*
2279 * An error return from page_cache_read can result if the
2280 * system is low on memory, or a problem occurs while trying
2281 * to schedule I/O.
2282 */
2283 if (error == -ENOMEM)
2284 return VM_FAULT_OOM;
2285 return VM_FAULT_SIGBUS;
2286
2287page_not_uptodate:
2288 /*
2289 * Umm, take care of errors if the page isn't up-to-date.
2290 * Try to re-read it _once_. We do this synchronously,
2291 * because there really aren't any performance issues here
2292 * and we need to check for errors.
2293 */
2294 ClearPageError(page);
2295 error = mapping->a_ops->readpage(file, page);
2296 if (!error) {
2297 wait_on_page_locked(page);
2298 if (!PageUptodate(page))
2299 error = -EIO;
2300 }
2301 put_page(page);
2302
2303 if (!error || error == AOP_TRUNCATED_PAGE)
2304 goto retry_find;
2305
2306 /* Things didn't work out. Return zero to tell the mm layer so. */
2307 shrink_readahead_size_eio(file, ra);
2308 return VM_FAULT_SIGBUS;
2309}
2310EXPORT_SYMBOL(filemap_fault);
2311
2312void filemap_map_pages(struct vm_fault *vmf,
2313 pgoff_t start_pgoff, pgoff_t end_pgoff)
2314{
2315 struct radix_tree_iter iter;
2316 void **slot;
2317 struct file *file = vmf->vma->vm_file;
2318 struct address_space *mapping = file->f_mapping;
2319 pgoff_t last_pgoff = start_pgoff;
2320 loff_t size;
2321 struct page *head, *page;
2322
2323 rcu_read_lock();
2324 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
2325 start_pgoff) {
2326 if (iter.index > end_pgoff)
2327 break;
2328repeat:
2329 page = radix_tree_deref_slot(slot);
2330 if (unlikely(!page))
2331 goto next;
2332 if (radix_tree_exception(page)) {
2333 if (radix_tree_deref_retry(page)) {
2334 slot = radix_tree_iter_retry(&iter);
2335 continue;
2336 }
2337 goto next;
2338 }
2339
2340 head = compound_head(page);
2341 if (!page_cache_get_speculative(head))
2342 goto repeat;
2343
2344 /* The page was split under us? */
2345 if (compound_head(page) != head) {
2346 put_page(head);
2347 goto repeat;
2348 }
2349
2350 /* Has the page moved? */
2351 if (unlikely(page != *slot)) {
2352 put_page(head);
2353 goto repeat;
2354 }
2355
2356 if (!PageUptodate(page) ||
2357 PageReadahead(page) ||
2358 PageHWPoison(page))
2359 goto skip;
2360 if (!trylock_page(page))
2361 goto skip;
2362
2363 if (page->mapping != mapping || !PageUptodate(page))
2364 goto unlock;
2365
2366 size = round_up(i_size_read(mapping->host), PAGE_SIZE);
2367 if (page->index >= size >> PAGE_SHIFT)
2368 goto unlock;
2369
2370 if (file->f_ra.mmap_miss > 0)
2371 file->f_ra.mmap_miss--;
2372
2373 vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
2374 if (vmf->pte)
2375 vmf->pte += iter.index - last_pgoff;
2376 last_pgoff = iter.index;
2377 if (alloc_set_pte(vmf, NULL, page))
2378 goto unlock;
2379 unlock_page(page);
2380 goto next;
2381unlock:
2382 unlock_page(page);
2383skip:
2384 put_page(page);
2385next:
2386 /* Huge page is mapped? No need to proceed. */
2387 if (pmd_trans_huge(*vmf->pmd))
2388 break;
2389 if (iter.index == end_pgoff)
2390 break;
2391 }
2392 rcu_read_unlock();
2393}
2394EXPORT_SYMBOL(filemap_map_pages);
2395
2396int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
2397{
2398 struct page *page = vmf->page;
2399 struct inode *inode = file_inode(vma->vm_file);
2400 int ret = VM_FAULT_LOCKED;
2401
2402 sb_start_pagefault(inode->i_sb);
2403 file_update_time(vma->vm_file);
2404 lock_page(page);
2405 if (page->mapping != inode->i_mapping) {
2406 unlock_page(page);
2407 ret = VM_FAULT_NOPAGE;
2408 goto out;
2409 }
2410 /*
2411 * We mark the page dirty already here so that when freeze is in
2412 * progress, we are guaranteed that writeback during freezing will
2413 * see the dirty page and writeprotect it again.
2414 */
2415 set_page_dirty(page);
2416 wait_for_stable_page(page);
2417out:
2418 sb_end_pagefault(inode->i_sb);
2419 return ret;
2420}
2421EXPORT_SYMBOL(filemap_page_mkwrite);
2422
2423const struct vm_operations_struct generic_file_vm_ops = {
2424 .fault = filemap_fault,
2425 .map_pages = filemap_map_pages,
2426 .page_mkwrite = filemap_page_mkwrite,
2427};
2428
2429/* This is used for a general mmap of a disk file */
2430
2431int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2432{
2433 struct address_space *mapping = file->f_mapping;
2434
2435 if (!mapping->a_ops->readpage)
2436 return -ENOEXEC;
2437 file_accessed(file);
2438 vma->vm_ops = &generic_file_vm_ops;
2439 return 0;
2440}
2441
2442/*
2443 * This is for filesystems which do not implement ->writepage.
2444 */
2445int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2446{
2447 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2448 return -EINVAL;
2449 return generic_file_mmap(file, vma);
2450}
2451#else
2452int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2453{
2454 return -ENOSYS;
2455}
2456int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2457{
2458 return -ENOSYS;
2459}
2460#endif /* CONFIG_MMU */
2461
2462EXPORT_SYMBOL(generic_file_mmap);
2463EXPORT_SYMBOL(generic_file_readonly_mmap);
2464
2465static struct page *wait_on_page_read(struct page *page)
2466{
2467 if (!IS_ERR(page)) {
2468 wait_on_page_locked(page);
2469 if (!PageUptodate(page)) {
2470 put_page(page);
2471 page = ERR_PTR(-EIO);
2472 }
2473 }
2474 return page;
2475}
2476
2477static struct page *do_read_cache_page(struct address_space *mapping,
2478 pgoff_t index,
2479 int (*filler)(void *, struct page *),
2480 void *data,
2481 gfp_t gfp)
2482{
2483 struct page *page;
2484 int err;
2485repeat:
2486 page = find_get_page(mapping, index);
2487 if (!page) {
2488 page = __page_cache_alloc(gfp | __GFP_COLD);
2489 if (!page)
2490 return ERR_PTR(-ENOMEM);
2491 err = add_to_page_cache_lru(page, mapping, index, gfp);
2492 if (unlikely(err)) {
2493 put_page(page);
2494 if (err == -EEXIST)
2495 goto repeat;
2496 /* Presumably ENOMEM for radix tree node */
2497 return ERR_PTR(err);
2498 }
2499
2500filler:
2501 err = filler(data, page);
2502 if (err < 0) {
2503 put_page(page);
2504 return ERR_PTR(err);
2505 }
2506
2507 page = wait_on_page_read(page);
2508 if (IS_ERR(page))
2509 return page;
2510 goto out;
2511 }
2512 if (PageUptodate(page))
2513 goto out;
2514
2515 /*
2516 * Page is not up to date and may be locked due one of the following
2517 * case a: Page is being filled and the page lock is held
2518 * case b: Read/write error clearing the page uptodate status
2519 * case c: Truncation in progress (page locked)
2520 * case d: Reclaim in progress
2521 *
2522 * Case a, the page will be up to date when the page is unlocked.
2523 * There is no need to serialise on the page lock here as the page
2524 * is pinned so the lock gives no additional protection. Even if the
2525 * the page is truncated, the data is still valid if PageUptodate as
2526 * it's a race vs truncate race.
2527 * Case b, the page will not be up to date
2528 * Case c, the page may be truncated but in itself, the data may still
2529 * be valid after IO completes as it's a read vs truncate race. The
2530 * operation must restart if the page is not uptodate on unlock but
2531 * otherwise serialising on page lock to stabilise the mapping gives
2532 * no additional guarantees to the caller as the page lock is
2533 * released before return.
2534 * Case d, similar to truncation. If reclaim holds the page lock, it
2535 * will be a race with remove_mapping that determines if the mapping
2536 * is valid on unlock but otherwise the data is valid and there is
2537 * no need to serialise with page lock.
2538 *
2539 * As the page lock gives no additional guarantee, we optimistically
2540 * wait on the page to be unlocked and check if it's up to date and
2541 * use the page if it is. Otherwise, the page lock is required to
2542 * distinguish between the different cases. The motivation is that we
2543 * avoid spurious serialisations and wakeups when multiple processes
2544 * wait on the same page for IO to complete.
2545 */
2546 wait_on_page_locked(page);
2547 if (PageUptodate(page))
2548 goto out;
2549
2550 /* Distinguish between all the cases under the safety of the lock */
2551 lock_page(page);
2552
2553 /* Case c or d, restart the operation */
2554 if (!page->mapping) {
2555 unlock_page(page);
2556 put_page(page);
2557 goto repeat;
2558 }
2559
2560 /* Someone else locked and filled the page in a very small window */
2561 if (PageUptodate(page)) {
2562 unlock_page(page);
2563 goto out;
2564 }
2565 goto filler;
2566
2567out:
2568 mark_page_accessed(page);
2569 return page;
2570}
2571
2572/**
2573 * read_cache_page - read into page cache, fill it if needed
2574 * @mapping: the page's address_space
2575 * @index: the page index
2576 * @filler: function to perform the read
2577 * @data: first arg to filler(data, page) function, often left as NULL
2578 *
2579 * Read into the page cache. If a page already exists, and PageUptodate() is
2580 * not set, try to fill the page and wait for it to become unlocked.
2581 *
2582 * If the page does not get brought uptodate, return -EIO.
2583 */
2584struct page *read_cache_page(struct address_space *mapping,
2585 pgoff_t index,
2586 int (*filler)(void *, struct page *),
2587 void *data)
2588{
2589 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2590}
2591EXPORT_SYMBOL(read_cache_page);
2592
2593/**
2594 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2595 * @mapping: the page's address_space
2596 * @index: the page index
2597 * @gfp: the page allocator flags to use if allocating
2598 *
2599 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2600 * any new page allocations done using the specified allocation flags.
2601 *
2602 * If the page does not get brought uptodate, return -EIO.
2603 */
2604struct page *read_cache_page_gfp(struct address_space *mapping,
2605 pgoff_t index,
2606 gfp_t gfp)
2607{
2608 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2609
2610 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2611}
2612EXPORT_SYMBOL(read_cache_page_gfp);
2613
2614/*
2615 * Performs necessary checks before doing a write
2616 *
2617 * Can adjust writing position or amount of bytes to write.
2618 * Returns appropriate error code that caller should return or
2619 * zero in case that write should be allowed.
2620 */
2621inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2622{
2623 struct file *file = iocb->ki_filp;
2624 struct inode *inode = file->f_mapping->host;
2625 unsigned long limit = rlimit(RLIMIT_FSIZE);
2626 loff_t pos;
2627
2628 if (!iov_iter_count(from))
2629 return 0;
2630
2631 /* FIXME: this is for backwards compatibility with 2.4 */
2632 if (iocb->ki_flags & IOCB_APPEND)
2633 iocb->ki_pos = i_size_read(inode);
2634
2635 pos = iocb->ki_pos;
2636
2637 if (limit != RLIM_INFINITY) {
2638 if (iocb->ki_pos >= limit) {
2639 send_sig(SIGXFSZ, current, 0);
2640 return -EFBIG;
2641 }
2642 iov_iter_truncate(from, limit - (unsigned long)pos);
2643 }
2644
2645 /*
2646 * LFS rule
2647 */
2648 if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
2649 !(file->f_flags & O_LARGEFILE))) {
2650 if (pos >= MAX_NON_LFS)
2651 return -EFBIG;
2652 iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
2653 }
2654
2655 /*
2656 * Are we about to exceed the fs block limit ?
2657 *
2658 * If we have written data it becomes a short write. If we have
2659 * exceeded without writing data we send a signal and return EFBIG.
2660 * Linus frestrict idea will clean these up nicely..
2661 */
2662 if (unlikely(pos >= inode->i_sb->s_maxbytes))
2663 return -EFBIG;
2664
2665 iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
2666 return iov_iter_count(from);
2667}
2668EXPORT_SYMBOL(generic_write_checks);
2669
2670int pagecache_write_begin(struct file *file, struct address_space *mapping,
2671 loff_t pos, unsigned len, unsigned flags,
2672 struct page **pagep, void **fsdata)
2673{
2674 const struct address_space_operations *aops = mapping->a_ops;
2675
2676 return aops->write_begin(file, mapping, pos, len, flags,
2677 pagep, fsdata);
2678}
2679EXPORT_SYMBOL(pagecache_write_begin);
2680
2681int pagecache_write_end(struct file *file, struct address_space *mapping,
2682 loff_t pos, unsigned len, unsigned copied,
2683 struct page *page, void *fsdata)
2684{
2685 const struct address_space_operations *aops = mapping->a_ops;
2686
2687 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2688}
2689EXPORT_SYMBOL(pagecache_write_end);
2690
2691ssize_t
2692generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
2693{
2694 struct file *file = iocb->ki_filp;
2695 struct address_space *mapping = file->f_mapping;
2696 struct inode *inode = mapping->host;
2697 loff_t pos = iocb->ki_pos;
2698 ssize_t written;
2699 size_t write_len;
2700 pgoff_t end;
2701 struct iov_iter data;
2702
2703 write_len = iov_iter_count(from);
2704 end = (pos + write_len - 1) >> PAGE_SHIFT;
2705
2706 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2707 if (written)
2708 goto out;
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 if (mapping->nrpages) {
2717 written = invalidate_inode_pages2_range(mapping,
2718 pos >> PAGE_SHIFT, end);
2719 /*
2720 * If a page can not be invalidated, return 0 to fall back
2721 * to buffered write.
2722 */
2723 if (written) {
2724 if (written == -EBUSY)
2725 return 0;
2726 goto out;
2727 }
2728 }
2729
2730 data = *from;
2731 written = mapping->a_ops->direct_IO(iocb, &data);
2732
2733 /*
2734 * Finally, try again to invalidate clean pages which might have been
2735 * cached by non-direct readahead, or faulted in by get_user_pages()
2736 * if the source of the write was an mmap'ed region of the file
2737 * we're writing. Either one is a pretty crazy thing to do,
2738 * so we don't support it 100%. If this invalidation
2739 * fails, tough, the write still worked...
2740 */
2741 if (mapping->nrpages) {
2742 invalidate_inode_pages2_range(mapping,
2743 pos >> PAGE_SHIFT, end);
2744 }
2745
2746 if (written > 0) {
2747 pos += written;
2748 iov_iter_advance(from, written);
2749 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2750 i_size_write(inode, pos);
2751 mark_inode_dirty(inode);
2752 }
2753 iocb->ki_pos = pos;
2754 }
2755out:
2756 return written;
2757}
2758EXPORT_SYMBOL(generic_file_direct_write);
2759
2760/*
2761 * Find or create a page at the given pagecache position. Return the locked
2762 * page. This function is specifically for buffered writes.
2763 */
2764struct page *grab_cache_page_write_begin(struct address_space *mapping,
2765 pgoff_t index, unsigned flags)
2766{
2767 struct page *page;
2768 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
2769
2770 if (flags & AOP_FLAG_NOFS)
2771 fgp_flags |= FGP_NOFS;
2772
2773 page = pagecache_get_page(mapping, index, fgp_flags,
2774 mapping_gfp_mask(mapping));
2775 if (page)
2776 wait_for_stable_page(page);
2777
2778 return page;
2779}
2780EXPORT_SYMBOL(grab_cache_page_write_begin);
2781
2782ssize_t generic_perform_write(struct file *file,
2783 struct iov_iter *i, loff_t pos)
2784{
2785 struct address_space *mapping = file->f_mapping;
2786 const struct address_space_operations *a_ops = mapping->a_ops;
2787 long status = 0;
2788 ssize_t written = 0;
2789 unsigned int flags = 0;
2790
2791 /*
2792 * Copies from kernel address space cannot fail (NFSD is a big user).
2793 */
2794 if (!iter_is_iovec(i))
2795 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2796
2797 do {
2798 struct page *page;
2799 unsigned long offset; /* Offset into pagecache page */
2800 unsigned long bytes; /* Bytes to write to page */
2801 size_t copied; /* Bytes copied from user */
2802 void *fsdata;
2803
2804 offset = (pos & (PAGE_SIZE - 1));
2805 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2806 iov_iter_count(i));
2807
2808again:
2809 /*
2810 * Bring in the user page that we will copy from _first_.
2811 * Otherwise there's a nasty deadlock on copying from the
2812 * same page as we're writing to, without it being marked
2813 * up-to-date.
2814 *
2815 * Not only is this an optimisation, but it is also required
2816 * to check that the address is actually valid, when atomic
2817 * usercopies are used, below.
2818 */
2819 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2820 status = -EFAULT;
2821 break;
2822 }
2823
2824 if (fatal_signal_pending(current)) {
2825 status = -EINTR;
2826 break;
2827 }
2828
2829 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2830 &page, &fsdata);
2831 if (unlikely(status < 0))
2832 break;
2833
2834 if (mapping_writably_mapped(mapping))
2835 flush_dcache_page(page);
2836
2837 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2838 flush_dcache_page(page);
2839
2840 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2841 page, fsdata);
2842 if (unlikely(status < 0))
2843 break;
2844 copied = status;
2845
2846 cond_resched();
2847
2848 iov_iter_advance(i, copied);
2849 if (unlikely(copied == 0)) {
2850 /*
2851 * If we were unable to copy any data at all, we must
2852 * fall back to a single segment length write.
2853 *
2854 * If we didn't fallback here, we could livelock
2855 * because not all segments in the iov can be copied at
2856 * once without a pagefault.
2857 */
2858 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2859 iov_iter_single_seg_count(i));
2860 goto again;
2861 }
2862 pos += copied;
2863 written += copied;
2864
2865 balance_dirty_pages_ratelimited(mapping);
2866 } while (iov_iter_count(i));
2867
2868 return written ? written : status;
2869}
2870EXPORT_SYMBOL(generic_perform_write);
2871
2872/**
2873 * __generic_file_write_iter - write data to a file
2874 * @iocb: IO state structure (file, offset, etc.)
2875 * @from: iov_iter with data to write
2876 *
2877 * This function does all the work needed for actually writing data to a
2878 * file. It does all basic checks, removes SUID from the file, updates
2879 * modification times and calls proper subroutines depending on whether we
2880 * do direct IO or a standard buffered write.
2881 *
2882 * It expects i_mutex to be grabbed unless we work on a block device or similar
2883 * object which does not need locking at all.
2884 *
2885 * This function does *not* take care of syncing data in case of O_SYNC write.
2886 * A caller has to handle it. This is mainly due to the fact that we want to
2887 * avoid syncing under i_mutex.
2888 */
2889ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2890{
2891 struct file *file = iocb->ki_filp;
2892 struct address_space * mapping = file->f_mapping;
2893 struct inode *inode = mapping->host;
2894 ssize_t written = 0;
2895 ssize_t err;
2896 ssize_t status;
2897
2898 /* We can write back this queue in page reclaim */
2899 current->backing_dev_info = inode_to_bdi(inode);
2900 err = file_remove_privs(file);
2901 if (err)
2902 goto out;
2903
2904 err = file_update_time(file);
2905 if (err)
2906 goto out;
2907
2908 if (iocb->ki_flags & IOCB_DIRECT) {
2909 loff_t pos, endbyte;
2910
2911 written = generic_file_direct_write(iocb, from);
2912 /*
2913 * If the write stopped short of completing, fall back to
2914 * buffered writes. Some filesystems do this for writes to
2915 * holes, for example. For DAX files, a buffered write will
2916 * not succeed (even if it did, DAX does not handle dirty
2917 * page-cache pages correctly).
2918 */
2919 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
2920 goto out;
2921
2922 status = generic_perform_write(file, from, pos = iocb->ki_pos);
2923 /*
2924 * If generic_perform_write() returned a synchronous error
2925 * then we want to return the number of bytes which were
2926 * direct-written, or the error code if that was zero. Note
2927 * that this differs from normal direct-io semantics, which
2928 * will return -EFOO even if some bytes were written.
2929 */
2930 if (unlikely(status < 0)) {
2931 err = status;
2932 goto out;
2933 }
2934 /*
2935 * We need to ensure that the page cache pages are written to
2936 * disk and invalidated to preserve the expected O_DIRECT
2937 * semantics.
2938 */
2939 endbyte = pos + status - 1;
2940 err = filemap_write_and_wait_range(mapping, pos, endbyte);
2941 if (err == 0) {
2942 iocb->ki_pos = endbyte + 1;
2943 written += status;
2944 invalidate_mapping_pages(mapping,
2945 pos >> PAGE_SHIFT,
2946 endbyte >> PAGE_SHIFT);
2947 } else {
2948 /*
2949 * We don't know how much we wrote, so just return
2950 * the number of bytes which were direct-written
2951 */
2952 }
2953 } else {
2954 written = generic_perform_write(file, from, iocb->ki_pos);
2955 if (likely(written > 0))
2956 iocb->ki_pos += written;
2957 }
2958out:
2959 current->backing_dev_info = NULL;
2960 return written ? written : err;
2961}
2962EXPORT_SYMBOL(__generic_file_write_iter);
2963
2964/**
2965 * generic_file_write_iter - write data to a file
2966 * @iocb: IO state structure
2967 * @from: iov_iter with data to write
2968 *
2969 * This is a wrapper around __generic_file_write_iter() to be used by most
2970 * filesystems. It takes care of syncing the file in case of O_SYNC file
2971 * and acquires i_mutex as needed.
2972 */
2973ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2974{
2975 struct file *file = iocb->ki_filp;
2976 struct inode *inode = file->f_mapping->host;
2977 ssize_t ret;
2978
2979 inode_lock(inode);
2980 ret = generic_write_checks(iocb, from);
2981 if (ret > 0)
2982 ret = __generic_file_write_iter(iocb, from);
2983 inode_unlock(inode);
2984
2985 if (ret > 0)
2986 ret = generic_write_sync(iocb, ret);
2987 return ret;
2988}
2989EXPORT_SYMBOL(generic_file_write_iter);
2990
2991/**
2992 * try_to_release_page() - release old fs-specific metadata on a page
2993 *
2994 * @page: the page which the kernel is trying to free
2995 * @gfp_mask: memory allocation flags (and I/O mode)
2996 *
2997 * The address_space is to try to release any data against the page
2998 * (presumably at page->private). If the release was successful, return `1'.
2999 * Otherwise return zero.
3000 *
3001 * This may also be called if PG_fscache is set on a page, indicating that the
3002 * page is known to the local caching routines.
3003 *
3004 * The @gfp_mask argument specifies whether I/O may be performed to release
3005 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3006 *
3007 */
3008int try_to_release_page(struct page *page, gfp_t gfp_mask)
3009{
3010 struct address_space * const mapping = page->mapping;
3011
3012 BUG_ON(!PageLocked(page));
3013 if (PageWriteback(page))
3014 return 0;
3015
3016 if (mapping && mapping->a_ops->releasepage)
3017 return mapping->a_ops->releasepage(page, gfp_mask);
3018 return try_to_free_buffers(page);
3019}
3020
3021EXPORT_SYMBOL(try_to_release_page);