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