1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1994-1999 Linus Torvalds
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)
13 #include <linux/export.h>
14 #include <linux/compiler.h>
15 #include <linux/dax.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>
23 #include <linux/swap.h>
24 #include <linux/mman.h>
25 #include <linux/pagemap.h>
26 #include <linux/file.h>
27 #include <linux/uio.h>
28 #include <linux/error-injection.h>
29 #include <linux/hash.h>
30 #include <linux/writeback.h>
31 #include <linux/backing-dev.h>
32 #include <linux/pagevec.h>
33 #include <linux/blkdev.h>
34 #include <linux/security.h>
35 #include <linux/cpuset.h>
36 #include <linux/hugetlb.h>
37 #include <linux/memcontrol.h>
38 #include <linux/cleancache.h>
39 #include <linux/shmem_fs.h>
40 #include <linux/rmap.h>
41 #include <linux/delayacct.h>
42 #include <linux/psi.h>
43 #include <linux/ramfs.h>
44 #include <linux/page_idle.h>
45 #include <asm/pgalloc.h>
46 #include <asm/tlbflush.h>
49 #define CREATE_TRACE_POINTS
50 #include <trace/events/filemap.h>
53 * FIXME: remove all knowledge of the buffer layer from the core VM
55 #include <linux/buffer_head.h> /* for try_to_free_buffers */
60 * Shared mappings implemented 30.11.1994. It's not fully working yet,
63 * Shared mappings now work. 15.8.1995 Bruno.
65 * finished 'unifying' the page and buffer cache and SMP-threaded the
66 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
68 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
74 * ->i_mmap_rwsem (truncate_pagecache)
75 * ->private_lock (__free_pte->__set_page_dirty_buffers)
76 * ->swap_lock (exclusive_swap_page, others)
80 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
84 * ->page_table_lock or pte_lock (various, mainly in memory.c)
85 * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
88 * ->lock_page (access_process_vm)
90 * ->i_mutex (generic_perform_write)
91 * ->mmap_lock (fault_in_pages_readable->do_page_fault)
94 * sb_lock (fs/fs-writeback.c)
95 * ->i_pages lock (__sync_single_inode)
98 * ->anon_vma.lock (vma_adjust)
101 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
103 * ->page_table_lock or pte_lock
104 * ->swap_lock (try_to_unmap_one)
105 * ->private_lock (try_to_unmap_one)
106 * ->i_pages lock (try_to_unmap_one)
107 * ->lruvec->lru_lock (follow_page->mark_page_accessed)
108 * ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
109 * ->private_lock (page_remove_rmap->set_page_dirty)
110 * ->i_pages lock (page_remove_rmap->set_page_dirty)
111 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
112 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
113 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
114 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
115 * ->inode->i_lock (zap_pte_range->set_page_dirty)
116 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
119 * ->tasklist_lock (memory_failure, collect_procs_ao)
122 static void page_cache_delete(struct address_space *mapping,
123 struct page *page, void *shadow)
125 XA_STATE(xas, &mapping->i_pages, page->index);
128 mapping_set_update(&xas, mapping);
130 /* hugetlb pages are represented by a single entry in the xarray */
131 if (!PageHuge(page)) {
132 xas_set_order(&xas, page->index, compound_order(page));
133 nr = compound_nr(page);
136 VM_BUG_ON_PAGE(!PageLocked(page), page);
137 VM_BUG_ON_PAGE(PageTail(page), page);
138 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
140 xas_store(&xas, shadow);
141 xas_init_marks(&xas);
143 page->mapping = NULL;
144 /* Leave page->index set: truncation lookup relies upon it */
147 mapping->nrexceptional += nr;
149 * Make sure the nrexceptional update is committed before
150 * the nrpages update so that final truncate racing
151 * with reclaim does not see both counters 0 at the
152 * same time and miss a shadow entry.
156 mapping->nrpages -= nr;
159 static void unaccount_page_cache_page(struct address_space *mapping,
165 * if we're uptodate, flush out into the cleancache, otherwise
166 * invalidate any existing cleancache entries. We can't leave
167 * stale data around in the cleancache once our page is gone
169 if (PageUptodate(page) && PageMappedToDisk(page))
170 cleancache_put_page(page);
172 cleancache_invalidate_page(mapping, page);
174 VM_BUG_ON_PAGE(PageTail(page), page);
175 VM_BUG_ON_PAGE(page_mapped(page), page);
176 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
179 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
180 current->comm, page_to_pfn(page));
181 dump_page(page, "still mapped when deleted");
183 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
185 mapcount = page_mapcount(page);
186 if (mapping_exiting(mapping) &&
187 page_count(page) >= mapcount + 2) {
189 * All vmas have already been torn down, so it's
190 * a good bet that actually the page is unmapped,
191 * and we'd prefer not to leak it: if we're wrong,
192 * some other bad page check should catch it later.
194 page_mapcount_reset(page);
195 page_ref_sub(page, mapcount);
199 /* hugetlb pages do not participate in page cache accounting. */
203 nr = thp_nr_pages(page);
205 __mod_lruvec_page_state(page, NR_FILE_PAGES, -nr);
206 if (PageSwapBacked(page)) {
207 __mod_lruvec_page_state(page, NR_SHMEM, -nr);
208 if (PageTransHuge(page))
209 __mod_lruvec_page_state(page, NR_SHMEM_THPS, -nr);
210 } else if (PageTransHuge(page)) {
211 __mod_lruvec_page_state(page, NR_FILE_THPS, -nr);
212 filemap_nr_thps_dec(mapping);
216 * At this point page must be either written or cleaned by
217 * truncate. Dirty page here signals a bug and loss of
220 * This fixes dirty accounting after removing the page entirely
221 * but leaves PageDirty set: it has no effect for truncated
222 * page and anyway will be cleared before returning page into
225 if (WARN_ON_ONCE(PageDirty(page)))
226 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
230 * Delete a page from the page cache and free it. Caller has to make
231 * sure the page is locked and that nobody else uses it - or that usage
232 * is safe. The caller must hold the i_pages lock.
234 void __delete_from_page_cache(struct page *page, void *shadow)
236 struct address_space *mapping = page->mapping;
238 trace_mm_filemap_delete_from_page_cache(page);
240 unaccount_page_cache_page(mapping, page);
241 page_cache_delete(mapping, page, shadow);
244 static void page_cache_free_page(struct address_space *mapping,
247 void (*freepage)(struct page *);
249 freepage = mapping->a_ops->freepage;
253 if (PageTransHuge(page) && !PageHuge(page)) {
254 page_ref_sub(page, thp_nr_pages(page));
255 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
262 * delete_from_page_cache - delete page from page cache
263 * @page: the page which the kernel is trying to remove from page cache
265 * This must be called only on pages that have been verified to be in the page
266 * cache and locked. It will never put the page into the free list, the caller
267 * has a reference on the page.
269 void delete_from_page_cache(struct page *page)
271 struct address_space *mapping = page_mapping(page);
274 BUG_ON(!PageLocked(page));
275 xa_lock_irqsave(&mapping->i_pages, flags);
276 __delete_from_page_cache(page, NULL);
277 xa_unlock_irqrestore(&mapping->i_pages, flags);
279 page_cache_free_page(mapping, page);
281 EXPORT_SYMBOL(delete_from_page_cache);
284 * page_cache_delete_batch - delete several pages from page cache
285 * @mapping: the mapping to which pages belong
286 * @pvec: pagevec with pages to delete
288 * The function walks over mapping->i_pages and removes pages passed in @pvec
289 * from the mapping. The function expects @pvec to be sorted by page index
290 * and is optimised for it to be dense.
291 * It tolerates holes in @pvec (mapping entries at those indices are not
292 * modified). The function expects only THP head pages to be present in the
295 * The function expects the i_pages lock to be held.
297 static void page_cache_delete_batch(struct address_space *mapping,
298 struct pagevec *pvec)
300 XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index);
305 mapping_set_update(&xas, mapping);
306 xas_for_each(&xas, page, ULONG_MAX) {
307 if (i >= pagevec_count(pvec))
310 /* A swap/dax/shadow entry got inserted? Skip it. */
311 if (xa_is_value(page))
314 * A page got inserted in our range? Skip it. We have our
315 * pages locked so they are protected from being removed.
316 * If we see a page whose index is higher than ours, it
317 * means our page has been removed, which shouldn't be
318 * possible because we're holding the PageLock.
320 if (page != pvec->pages[i]) {
321 VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index,
326 WARN_ON_ONCE(!PageLocked(page));
328 if (page->index == xas.xa_index)
329 page->mapping = NULL;
330 /* Leave page->index set: truncation lookup relies on it */
333 * Move to the next page in the vector if this is a regular
334 * page or the index is of the last sub-page of this compound
337 if (page->index + compound_nr(page) - 1 == xas.xa_index)
339 xas_store(&xas, NULL);
342 mapping->nrpages -= total_pages;
345 void delete_from_page_cache_batch(struct address_space *mapping,
346 struct pagevec *pvec)
351 if (!pagevec_count(pvec))
354 xa_lock_irqsave(&mapping->i_pages, flags);
355 for (i = 0; i < pagevec_count(pvec); i++) {
356 trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);
358 unaccount_page_cache_page(mapping, pvec->pages[i]);
360 page_cache_delete_batch(mapping, pvec);
361 xa_unlock_irqrestore(&mapping->i_pages, flags);
363 for (i = 0; i < pagevec_count(pvec); i++)
364 page_cache_free_page(mapping, pvec->pages[i]);
367 int filemap_check_errors(struct address_space *mapping)
370 /* Check for outstanding write errors */
371 if (test_bit(AS_ENOSPC, &mapping->flags) &&
372 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
374 if (test_bit(AS_EIO, &mapping->flags) &&
375 test_and_clear_bit(AS_EIO, &mapping->flags))
379 EXPORT_SYMBOL(filemap_check_errors);
381 static int filemap_check_and_keep_errors(struct address_space *mapping)
383 /* Check for outstanding write errors */
384 if (test_bit(AS_EIO, &mapping->flags))
386 if (test_bit(AS_ENOSPC, &mapping->flags))
392 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
393 * @mapping: address space structure to write
394 * @start: offset in bytes where the range starts
395 * @end: offset in bytes where the range ends (inclusive)
396 * @sync_mode: enable synchronous operation
398 * Start writeback against all of a mapping's dirty pages that lie
399 * within the byte offsets <start, end> inclusive.
401 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
402 * opposed to a regular memory cleansing writeback. The difference between
403 * these two operations is that if a dirty page/buffer is encountered, it must
404 * be waited upon, and not just skipped over.
406 * Return: %0 on success, negative error code otherwise.
408 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
409 loff_t end, int sync_mode)
412 struct writeback_control wbc = {
413 .sync_mode = sync_mode,
414 .nr_to_write = LONG_MAX,
415 .range_start = start,
419 if (!mapping_can_writeback(mapping) ||
420 !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
423 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
424 ret = do_writepages(mapping, &wbc);
425 wbc_detach_inode(&wbc);
429 static inline int __filemap_fdatawrite(struct address_space *mapping,
432 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
435 int filemap_fdatawrite(struct address_space *mapping)
437 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
439 EXPORT_SYMBOL(filemap_fdatawrite);
441 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
444 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
446 EXPORT_SYMBOL(filemap_fdatawrite_range);
449 * filemap_flush - mostly a non-blocking flush
450 * @mapping: target address_space
452 * This is a mostly non-blocking flush. Not suitable for data-integrity
453 * purposes - I/O may not be started against all dirty pages.
455 * Return: %0 on success, negative error code otherwise.
457 int filemap_flush(struct address_space *mapping)
459 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
461 EXPORT_SYMBOL(filemap_flush);
464 * filemap_range_has_page - check if a page exists in range.
465 * @mapping: address space within which to check
466 * @start_byte: offset in bytes where the range starts
467 * @end_byte: offset in bytes where the range ends (inclusive)
469 * Find at least one page in the range supplied, usually used to check if
470 * direct writing in this range will trigger a writeback.
472 * Return: %true if at least one page exists in the specified range,
475 bool filemap_range_has_page(struct address_space *mapping,
476 loff_t start_byte, loff_t end_byte)
479 XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
480 pgoff_t max = end_byte >> PAGE_SHIFT;
482 if (end_byte < start_byte)
487 page = xas_find(&xas, max);
488 if (xas_retry(&xas, page))
490 /* Shadow entries don't count */
491 if (xa_is_value(page))
494 * We don't need to try to pin this page; we're about to
495 * release the RCU lock anyway. It is enough to know that
496 * there was a page here recently.
504 EXPORT_SYMBOL(filemap_range_has_page);
506 static void __filemap_fdatawait_range(struct address_space *mapping,
507 loff_t start_byte, loff_t end_byte)
509 pgoff_t index = start_byte >> PAGE_SHIFT;
510 pgoff_t end = end_byte >> PAGE_SHIFT;
514 if (end_byte < start_byte)
518 while (index <= end) {
521 nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
522 end, PAGECACHE_TAG_WRITEBACK);
526 for (i = 0; i < nr_pages; i++) {
527 struct page *page = pvec.pages[i];
529 wait_on_page_writeback(page);
530 ClearPageError(page);
532 pagevec_release(&pvec);
538 * filemap_fdatawait_range - wait for writeback to complete
539 * @mapping: address space structure to wait for
540 * @start_byte: offset in bytes where the range starts
541 * @end_byte: offset in bytes where the range ends (inclusive)
543 * Walk the list of under-writeback pages of the given address space
544 * in the given range and wait for all of them. Check error status of
545 * the address space and return it.
547 * Since the error status of the address space is cleared by this function,
548 * callers are responsible for checking the return value and handling and/or
549 * reporting the error.
551 * Return: error status of the address space.
553 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
556 __filemap_fdatawait_range(mapping, start_byte, end_byte);
557 return filemap_check_errors(mapping);
559 EXPORT_SYMBOL(filemap_fdatawait_range);
562 * filemap_fdatawait_range_keep_errors - wait for writeback to complete
563 * @mapping: address space structure to wait for
564 * @start_byte: offset in bytes where the range starts
565 * @end_byte: offset in bytes where the range ends (inclusive)
567 * Walk the list of under-writeback pages of the given address space in the
568 * given range and wait for all of them. Unlike filemap_fdatawait_range(),
569 * this function does not clear error status of the address space.
571 * Use this function if callers don't handle errors themselves. Expected
572 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
575 int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
576 loff_t start_byte, loff_t end_byte)
578 __filemap_fdatawait_range(mapping, start_byte, end_byte);
579 return filemap_check_and_keep_errors(mapping);
581 EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
584 * file_fdatawait_range - wait for writeback to complete
585 * @file: file pointing to address space structure to wait for
586 * @start_byte: offset in bytes where the range starts
587 * @end_byte: offset in bytes where the range ends (inclusive)
589 * Walk the list of under-writeback pages of the address space that file
590 * refers to, in the given range and wait for all of them. Check error
591 * status of the address space vs. the file->f_wb_err cursor and return it.
593 * Since the error status of the file is advanced by this function,
594 * callers are responsible for checking the return value and handling and/or
595 * reporting the error.
597 * Return: error status of the address space vs. the file->f_wb_err cursor.
599 int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
601 struct address_space *mapping = file->f_mapping;
603 __filemap_fdatawait_range(mapping, start_byte, end_byte);
604 return file_check_and_advance_wb_err(file);
606 EXPORT_SYMBOL(file_fdatawait_range);
609 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
610 * @mapping: address space structure to wait for
612 * Walk the list of under-writeback pages of the given address space
613 * and wait for all of them. Unlike filemap_fdatawait(), this function
614 * does not clear error status of the address space.
616 * Use this function if callers don't handle errors themselves. Expected
617 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
620 * Return: error status of the address space.
622 int filemap_fdatawait_keep_errors(struct address_space *mapping)
624 __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
625 return filemap_check_and_keep_errors(mapping);
627 EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
629 /* Returns true if writeback might be needed or already in progress. */
630 static bool mapping_needs_writeback(struct address_space *mapping)
632 if (dax_mapping(mapping))
633 return mapping->nrexceptional;
635 return mapping->nrpages;
639 * filemap_write_and_wait_range - write out & wait on a file range
640 * @mapping: the address_space for the pages
641 * @lstart: offset in bytes where the range starts
642 * @lend: offset in bytes where the range ends (inclusive)
644 * Write out and wait upon file offsets lstart->lend, inclusive.
646 * Note that @lend is inclusive (describes the last byte to be written) so
647 * that this function can be used to write to the very end-of-file (end = -1).
649 * Return: error status of the address space.
651 int filemap_write_and_wait_range(struct address_space *mapping,
652 loff_t lstart, loff_t lend)
656 if (mapping_needs_writeback(mapping)) {
657 err = __filemap_fdatawrite_range(mapping, lstart, lend,
660 * Even if the above returned error, the pages may be
661 * written partially (e.g. -ENOSPC), so we wait for it.
662 * But the -EIO is special case, it may indicate the worst
663 * thing (e.g. bug) happened, so we avoid waiting for it.
666 int err2 = filemap_fdatawait_range(mapping,
671 /* Clear any previously stored errors */
672 filemap_check_errors(mapping);
675 err = filemap_check_errors(mapping);
679 EXPORT_SYMBOL(filemap_write_and_wait_range);
681 void __filemap_set_wb_err(struct address_space *mapping, int err)
683 errseq_t eseq = errseq_set(&mapping->wb_err, err);
685 trace_filemap_set_wb_err(mapping, eseq);
687 EXPORT_SYMBOL(__filemap_set_wb_err);
690 * file_check_and_advance_wb_err - report wb error (if any) that was previously
691 * and advance wb_err to current one
692 * @file: struct file on which the error is being reported
694 * When userland calls fsync (or something like nfsd does the equivalent), we
695 * want to report any writeback errors that occurred since the last fsync (or
696 * since the file was opened if there haven't been any).
698 * Grab the wb_err from the mapping. If it matches what we have in the file,
699 * then just quickly return 0. The file is all caught up.
701 * If it doesn't match, then take the mapping value, set the "seen" flag in
702 * it and try to swap it into place. If it works, or another task beat us
703 * to it with the new value, then update the f_wb_err and return the error
704 * portion. The error at this point must be reported via proper channels
705 * (a'la fsync, or NFS COMMIT operation, etc.).
707 * While we handle mapping->wb_err with atomic operations, the f_wb_err
708 * value is protected by the f_lock since we must ensure that it reflects
709 * the latest value swapped in for this file descriptor.
711 * Return: %0 on success, negative error code otherwise.
713 int file_check_and_advance_wb_err(struct file *file)
716 errseq_t old = READ_ONCE(file->f_wb_err);
717 struct address_space *mapping = file->f_mapping;
719 /* Locklessly handle the common case where nothing has changed */
720 if (errseq_check(&mapping->wb_err, old)) {
721 /* Something changed, must use slow path */
722 spin_lock(&file->f_lock);
723 old = file->f_wb_err;
724 err = errseq_check_and_advance(&mapping->wb_err,
726 trace_file_check_and_advance_wb_err(file, old);
727 spin_unlock(&file->f_lock);
731 * We're mostly using this function as a drop in replacement for
732 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
733 * that the legacy code would have had on these flags.
735 clear_bit(AS_EIO, &mapping->flags);
736 clear_bit(AS_ENOSPC, &mapping->flags);
739 EXPORT_SYMBOL(file_check_and_advance_wb_err);
742 * file_write_and_wait_range - write out & wait on a file range
743 * @file: file pointing to address_space with pages
744 * @lstart: offset in bytes where the range starts
745 * @lend: offset in bytes where the range ends (inclusive)
747 * Write out and wait upon file offsets lstart->lend, inclusive.
749 * Note that @lend is inclusive (describes the last byte to be written) so
750 * that this function can be used to write to the very end-of-file (end = -1).
752 * After writing out and waiting on the data, we check and advance the
753 * f_wb_err cursor to the latest value, and return any errors detected there.
755 * Return: %0 on success, negative error code otherwise.
757 int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
760 struct address_space *mapping = file->f_mapping;
762 if (mapping_needs_writeback(mapping)) {
763 err = __filemap_fdatawrite_range(mapping, lstart, lend,
765 /* See comment of filemap_write_and_wait() */
767 __filemap_fdatawait_range(mapping, lstart, lend);
769 err2 = file_check_and_advance_wb_err(file);
774 EXPORT_SYMBOL(file_write_and_wait_range);
777 * replace_page_cache_page - replace a pagecache page with a new one
778 * @old: page to be replaced
779 * @new: page to replace with
781 * This function replaces a page in the pagecache with a new one. On
782 * success it acquires the pagecache reference for the new page and
783 * drops it for the old page. Both the old and new pages must be
784 * locked. This function does not add the new page to the LRU, the
785 * caller must do that.
787 * The remove + add is atomic. This function cannot fail.
789 void replace_page_cache_page(struct page *old, struct page *new)
791 struct address_space *mapping = old->mapping;
792 void (*freepage)(struct page *) = mapping->a_ops->freepage;
793 pgoff_t offset = old->index;
794 XA_STATE(xas, &mapping->i_pages, offset);
797 VM_BUG_ON_PAGE(!PageLocked(old), old);
798 VM_BUG_ON_PAGE(!PageLocked(new), new);
799 VM_BUG_ON_PAGE(new->mapping, new);
802 new->mapping = mapping;
805 mem_cgroup_migrate(old, new);
807 xas_lock_irqsave(&xas, flags);
808 xas_store(&xas, new);
811 /* hugetlb pages do not participate in page cache accounting. */
813 __dec_lruvec_page_state(old, NR_FILE_PAGES);
815 __inc_lruvec_page_state(new, NR_FILE_PAGES);
816 if (PageSwapBacked(old))
817 __dec_lruvec_page_state(old, NR_SHMEM);
818 if (PageSwapBacked(new))
819 __inc_lruvec_page_state(new, NR_SHMEM);
820 xas_unlock_irqrestore(&xas, flags);
825 EXPORT_SYMBOL_GPL(replace_page_cache_page);
827 noinline int __add_to_page_cache_locked(struct page *page,
828 struct address_space *mapping,
829 pgoff_t offset, gfp_t gfp,
832 XA_STATE(xas, &mapping->i_pages, offset);
833 int huge = PageHuge(page);
835 bool charged = false;
837 VM_BUG_ON_PAGE(!PageLocked(page), page);
838 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
839 mapping_set_update(&xas, mapping);
842 page->mapping = mapping;
843 page->index = offset;
846 error = mem_cgroup_charge(page, current->mm, gfp);
852 gfp &= GFP_RECLAIM_MASK;
855 unsigned int order = xa_get_order(xas.xa, xas.xa_index);
856 void *entry, *old = NULL;
858 if (order > thp_order(page))
859 xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
862 xas_for_each_conflict(&xas, entry) {
864 if (!xa_is_value(entry)) {
865 xas_set_err(&xas, -EEXIST);
873 /* entry may have been split before we acquired lock */
874 order = xa_get_order(xas.xa, xas.xa_index);
875 if (order > thp_order(page)) {
876 xas_split(&xas, old, order);
881 xas_store(&xas, page);
886 mapping->nrexceptional--;
889 /* hugetlb pages do not participate in page cache accounting */
891 __inc_lruvec_page_state(page, NR_FILE_PAGES);
893 xas_unlock_irq(&xas);
894 } while (xas_nomem(&xas, gfp));
896 if (xas_error(&xas)) {
897 error = xas_error(&xas);
899 mem_cgroup_uncharge(page);
903 trace_mm_filemap_add_to_page_cache(page);
906 page->mapping = NULL;
907 /* Leave page->index set: truncation relies upon it */
911 ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO);
914 * add_to_page_cache_locked - add a locked page to the pagecache
916 * @mapping: the page's address_space
917 * @offset: page index
918 * @gfp_mask: page allocation mode
920 * This function is used to add a page to the pagecache. It must be locked.
921 * This function does not add the page to the LRU. The caller must do that.
923 * Return: %0 on success, negative error code otherwise.
925 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
926 pgoff_t offset, gfp_t gfp_mask)
928 return __add_to_page_cache_locked(page, mapping, offset,
931 EXPORT_SYMBOL(add_to_page_cache_locked);
933 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
934 pgoff_t offset, gfp_t gfp_mask)
939 __SetPageLocked(page);
940 ret = __add_to_page_cache_locked(page, mapping, offset,
943 __ClearPageLocked(page);
946 * The page might have been evicted from cache only
947 * recently, in which case it should be activated like
948 * any other repeatedly accessed page.
949 * The exception is pages getting rewritten; evicting other
950 * data from the working set, only to cache data that will
951 * get overwritten with something else, is a waste of memory.
953 WARN_ON_ONCE(PageActive(page));
954 if (!(gfp_mask & __GFP_WRITE) && shadow)
955 workingset_refault(page, shadow);
960 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
963 struct page *__page_cache_alloc(gfp_t gfp)
968 if (cpuset_do_page_mem_spread()) {
969 unsigned int cpuset_mems_cookie;
971 cpuset_mems_cookie = read_mems_allowed_begin();
972 n = cpuset_mem_spread_node();
973 page = __alloc_pages_node(n, gfp, 0);
974 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
978 return alloc_pages(gfp, 0);
980 EXPORT_SYMBOL(__page_cache_alloc);
984 * In order to wait for pages to become available there must be
985 * waitqueues associated with pages. By using a hash table of
986 * waitqueues where the bucket discipline is to maintain all
987 * waiters on the same queue and wake all when any of the pages
988 * become available, and for the woken contexts to check to be
989 * sure the appropriate page became available, this saves space
990 * at a cost of "thundering herd" phenomena during rare hash
993 #define PAGE_WAIT_TABLE_BITS 8
994 #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
995 static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
997 static wait_queue_head_t *page_waitqueue(struct page *page)
999 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
1002 void __init pagecache_init(void)
1006 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
1007 init_waitqueue_head(&page_wait_table[i]);
1009 page_writeback_init();
1013 * The page wait code treats the "wait->flags" somewhat unusually, because
1014 * we have multiple different kinds of waits, not just the usual "exclusive"
1019 * (a) no special bits set:
1021 * We're just waiting for the bit to be released, and when a waker
1022 * calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
1023 * and remove it from the wait queue.
1025 * Simple and straightforward.
1027 * (b) WQ_FLAG_EXCLUSIVE:
1029 * The waiter is waiting to get the lock, and only one waiter should
1030 * be woken up to avoid any thundering herd behavior. We'll set the
1031 * WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
1033 * This is the traditional exclusive wait.
1035 * (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
1037 * The waiter is waiting to get the bit, and additionally wants the
1038 * lock to be transferred to it for fair lock behavior. If the lock
1039 * cannot be taken, we stop walking the wait queue without waking
1042 * This is the "fair lock handoff" case, and in addition to setting
1043 * WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
1044 * that it now has the lock.
1046 static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
1049 struct wait_page_key *key = arg;
1050 struct wait_page_queue *wait_page
1051 = container_of(wait, struct wait_page_queue, wait);
1053 if (!wake_page_match(wait_page, key))
1057 * If it's a lock handoff wait, we get the bit for it, and
1058 * stop walking (and do not wake it up) if we can't.
1060 flags = wait->flags;
1061 if (flags & WQ_FLAG_EXCLUSIVE) {
1062 if (test_bit(key->bit_nr, &key->page->flags))
1064 if (flags & WQ_FLAG_CUSTOM) {
1065 if (test_and_set_bit(key->bit_nr, &key->page->flags))
1067 flags |= WQ_FLAG_DONE;
1072 * We are holding the wait-queue lock, but the waiter that
1073 * is waiting for this will be checking the flags without
1076 * So update the flags atomically, and wake up the waiter
1077 * afterwards to avoid any races. This store-release pairs
1078 * with the load-acquire in wait_on_page_bit_common().
1080 smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
1081 wake_up_state(wait->private, mode);
1084 * Ok, we have successfully done what we're waiting for,
1085 * and we can unconditionally remove the wait entry.
1087 * Note that this pairs with the "finish_wait()" in the
1088 * waiter, and has to be the absolute last thing we do.
1089 * After this list_del_init(&wait->entry) the wait entry
1090 * might be de-allocated and the process might even have
1093 list_del_init_careful(&wait->entry);
1094 return (flags & WQ_FLAG_EXCLUSIVE) != 0;
1097 static void wake_up_page_bit(struct page *page, int bit_nr)
1099 wait_queue_head_t *q = page_waitqueue(page);
1100 struct wait_page_key key;
1101 unsigned long flags;
1102 wait_queue_entry_t bookmark;
1105 key.bit_nr = bit_nr;
1109 bookmark.private = NULL;
1110 bookmark.func = NULL;
1111 INIT_LIST_HEAD(&bookmark.entry);
1113 spin_lock_irqsave(&q->lock, flags);
1114 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1116 while (bookmark.flags & WQ_FLAG_BOOKMARK) {
1118 * Take a breather from holding the lock,
1119 * allow pages that finish wake up asynchronously
1120 * to acquire the lock and remove themselves
1123 spin_unlock_irqrestore(&q->lock, flags);
1125 spin_lock_irqsave(&q->lock, flags);
1126 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1130 * It is possible for other pages to have collided on the waitqueue
1131 * hash, so in that case check for a page match. That prevents a long-
1134 * It is still possible to miss a case here, when we woke page waiters
1135 * and removed them from the waitqueue, but there are still other
1138 if (!waitqueue_active(q) || !key.page_match) {
1139 ClearPageWaiters(page);
1141 * It's possible to miss clearing Waiters here, when we woke
1142 * our page waiters, but the hashed waitqueue has waiters for
1143 * other pages on it.
1145 * That's okay, it's a rare case. The next waker will clear it.
1148 spin_unlock_irqrestore(&q->lock, flags);
1151 static void wake_up_page(struct page *page, int bit)
1153 if (!PageWaiters(page))
1155 wake_up_page_bit(page, bit);
1159 * A choice of three behaviors for wait_on_page_bit_common():
1162 EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
1163 * __lock_page() waiting on then setting PG_locked.
1165 SHARED, /* Hold ref to page and check the bit when woken, like
1166 * wait_on_page_writeback() waiting on PG_writeback.
1168 DROP, /* Drop ref to page before wait, no check when woken,
1169 * like put_and_wait_on_page_locked() on PG_locked.
1174 * Attempt to check (or get) the page bit, and mark us done
1177 static inline bool trylock_page_bit_common(struct page *page, int bit_nr,
1178 struct wait_queue_entry *wait)
1180 if (wait->flags & WQ_FLAG_EXCLUSIVE) {
1181 if (test_and_set_bit(bit_nr, &page->flags))
1183 } else if (test_bit(bit_nr, &page->flags))
1186 wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
1190 /* How many times do we accept lock stealing from under a waiter? */
1191 int sysctl_page_lock_unfairness = 5;
1193 static inline int wait_on_page_bit_common(wait_queue_head_t *q,
1194 struct page *page, int bit_nr, int state, enum behavior behavior)
1196 int unfairness = sysctl_page_lock_unfairness;
1197 struct wait_page_queue wait_page;
1198 wait_queue_entry_t *wait = &wait_page.wait;
1199 bool thrashing = false;
1200 bool delayacct = false;
1201 unsigned long pflags;
1203 if (bit_nr == PG_locked &&
1204 !PageUptodate(page) && PageWorkingset(page)) {
1205 if (!PageSwapBacked(page)) {
1206 delayacct_thrashing_start();
1209 psi_memstall_enter(&pflags);
1214 wait->func = wake_page_function;
1215 wait_page.page = page;
1216 wait_page.bit_nr = bit_nr;
1220 if (behavior == EXCLUSIVE) {
1221 wait->flags = WQ_FLAG_EXCLUSIVE;
1222 if (--unfairness < 0)
1223 wait->flags |= WQ_FLAG_CUSTOM;
1227 * Do one last check whether we can get the
1228 * page bit synchronously.
1230 * Do the SetPageWaiters() 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.
1237 * This part needs to be done under the queue
1238 * lock to avoid races.
1240 spin_lock_irq(&q->lock);
1241 SetPageWaiters(page);
1242 if (!trylock_page_bit_common(page, bit_nr, wait))
1243 __add_wait_queue_entry_tail(q, wait);
1244 spin_unlock_irq(&q->lock);
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.
1252 * We can drop our reference to the page.
1254 if (behavior == DROP)
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.
1266 set_current_state(state);
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))
1278 /* If we were non-exclusive, we're done */
1279 if (behavior != EXCLUSIVE)
1282 /* If the waker got the lock for us, we're done */
1283 if (flags & WQ_FLAG_DONE)
1287 * Otherwise, if we're getting the lock, we need to
1288 * try to get it ourselves.
1290 * And if that fails, we'll have to retry this all.
1292 if (unlikely(test_and_set_bit(bit_nr, &page->flags)))
1295 wait->flags |= WQ_FLAG_DONE;
1300 * If a signal happened, this 'finish_wait()' may remove the last
1301 * waiter from the wait-queues, but the PageWaiters 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.
1305 finish_wait(q, wait);
1309 delayacct_thrashing_end();
1310 psi_memstall_leave(&pflags);
1314 * NOTE! The wait->flags weren't stable until we've done the
1315 * 'finish_wait()', and we could have exited the loop above due
1316 * to a signal, and had a wakeup event happen after the signal
1317 * test but before the 'finish_wait()'.
1319 * So only after the finish_wait() can we reliably determine
1320 * if we got woken up or not, so we can now figure out the final
1321 * return value based on that state without races.
1323 * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
1324 * waiter, but an exclusive one requires WQ_FLAG_DONE.
1326 if (behavior == EXCLUSIVE)
1327 return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;
1329 return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
1332 void wait_on_page_bit(struct page *page, int bit_nr)
1334 wait_queue_head_t *q = page_waitqueue(page);
1335 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
1337 EXPORT_SYMBOL(wait_on_page_bit);
1339 int wait_on_page_bit_killable(struct page *page, int bit_nr)
1341 wait_queue_head_t *q = page_waitqueue(page);
1342 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, SHARED);
1344 EXPORT_SYMBOL(wait_on_page_bit_killable);
1347 * put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked
1348 * @page: The page to wait for.
1349 * @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
1351 * The caller should hold a reference on @page. They expect the page to
1352 * become unlocked relatively soon, but do not wish to hold up migration
1353 * (for example) by holding the reference while waiting for the page to
1354 * come unlocked. After this function returns, the caller should not
1355 * dereference @page.
1357 * Return: 0 if the page was unlocked or -EINTR if interrupted by a signal.
1359 int put_and_wait_on_page_locked(struct page *page, int state)
1361 wait_queue_head_t *q;
1363 page = compound_head(page);
1364 q = page_waitqueue(page);
1365 return wait_on_page_bit_common(q, page, PG_locked, state, DROP);
1369 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1370 * @page: Page defining the wait queue of interest
1371 * @waiter: Waiter to add to the queue
1373 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1375 void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
1377 wait_queue_head_t *q = page_waitqueue(page);
1378 unsigned long flags;
1380 spin_lock_irqsave(&q->lock, flags);
1381 __add_wait_queue_entry_tail(q, waiter);
1382 SetPageWaiters(page);
1383 spin_unlock_irqrestore(&q->lock, flags);
1385 EXPORT_SYMBOL_GPL(add_page_wait_queue);
1387 #ifndef clear_bit_unlock_is_negative_byte
1390 * PG_waiters is the high bit in the same byte as PG_lock.
1392 * On x86 (and on many other architectures), we can clear PG_lock and
1393 * test the sign bit at the same time. But if the architecture does
1394 * not support that special operation, we just do this all by hand
1397 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1398 * being cleared, but a memory barrier should be unnecessary since it is
1399 * in the same byte as PG_locked.
1401 static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
1403 clear_bit_unlock(nr, mem);
1404 /* smp_mb__after_atomic(); */
1405 return test_bit(PG_waiters, mem);
1411 * unlock_page - unlock a locked page
1414 * Unlocks the page and wakes up sleepers in wait_on_page_locked().
1415 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1416 * mechanism between PageLocked pages and PageWriteback pages is shared.
1417 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1419 * Note that this depends on PG_waiters being the sign bit in the byte
1420 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1421 * clear the PG_locked bit and test PG_waiters at the same time fairly
1422 * portably (architectures that do LL/SC can test any bit, while x86 can
1423 * test the sign bit).
1425 void unlock_page(struct page *page)
1427 BUILD_BUG_ON(PG_waiters != 7);
1428 page = compound_head(page);
1429 VM_BUG_ON_PAGE(!PageLocked(page), page);
1430 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
1431 wake_up_page_bit(page, PG_locked);
1433 EXPORT_SYMBOL(unlock_page);
1436 * end_page_writeback - end writeback against a page
1439 void end_page_writeback(struct page *page)
1442 * TestClearPageReclaim could be used here but it is an atomic
1443 * operation and overkill in this particular case. Failing to
1444 * shuffle a page marked for immediate reclaim is too mild to
1445 * justify taking an atomic operation penalty at the end of
1446 * ever page writeback.
1448 if (PageReclaim(page)) {
1449 ClearPageReclaim(page);
1450 rotate_reclaimable_page(page);
1454 * Writeback does not hold a page reference of its own, relying
1455 * on truncation to wait for the clearing of PG_writeback.
1456 * But here we must make sure that the page is not freed and
1457 * reused before the wake_up_page().
1460 if (!test_clear_page_writeback(page))
1463 smp_mb__after_atomic();
1464 wake_up_page(page, PG_writeback);
1467 EXPORT_SYMBOL(end_page_writeback);
1470 * After completing I/O on a page, call this routine to update the page
1471 * flags appropriately
1473 void page_endio(struct page *page, bool is_write, int err)
1477 SetPageUptodate(page);
1479 ClearPageUptodate(page);
1485 struct address_space *mapping;
1488 mapping = page_mapping(page);
1490 mapping_set_error(mapping, err);
1492 end_page_writeback(page);
1495 EXPORT_SYMBOL_GPL(page_endio);
1498 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1499 * @__page: the page to lock
1501 void __lock_page(struct page *__page)
1503 struct page *page = compound_head(__page);
1504 wait_queue_head_t *q = page_waitqueue(page);
1505 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE,
1508 EXPORT_SYMBOL(__lock_page);
1510 int __lock_page_killable(struct page *__page)
1512 struct page *page = compound_head(__page);
1513 wait_queue_head_t *q = page_waitqueue(page);
1514 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE,
1517 EXPORT_SYMBOL_GPL(__lock_page_killable);
1519 int __lock_page_async(struct page *page, struct wait_page_queue *wait)
1521 struct wait_queue_head *q = page_waitqueue(page);
1525 wait->bit_nr = PG_locked;
1527 spin_lock_irq(&q->lock);
1528 __add_wait_queue_entry_tail(q, &wait->wait);
1529 SetPageWaiters(page);
1530 ret = !trylock_page(page);
1532 * If we were successful now, we know we're still on the
1533 * waitqueue as we're still under the lock. This means it's
1534 * safe to remove and return success, we know the callback
1535 * isn't going to trigger.
1538 __remove_wait_queue(q, &wait->wait);
1541 spin_unlock_irq(&q->lock);
1547 * 1 - page is locked; mmap_lock is still held.
1548 * 0 - page is not locked.
1549 * mmap_lock has been released (mmap_read_unlock(), unless flags had both
1550 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1551 * which case mmap_lock is still held.
1553 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1554 * with the page locked and the mmap_lock unperturbed.
1556 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1559 if (fault_flag_allow_retry_first(flags)) {
1561 * CAUTION! In this case, mmap_lock is not released
1562 * even though return 0.
1564 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1567 mmap_read_unlock(mm);
1568 if (flags & FAULT_FLAG_KILLABLE)
1569 wait_on_page_locked_killable(page);
1571 wait_on_page_locked(page);
1574 if (flags & FAULT_FLAG_KILLABLE) {
1577 ret = __lock_page_killable(page);
1579 mmap_read_unlock(mm);
1590 * page_cache_next_miss() - Find the next gap in the page cache.
1591 * @mapping: Mapping.
1593 * @max_scan: Maximum range to search.
1595 * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
1596 * gap with the lowest index.
1598 * This function may be called under the rcu_read_lock. However, this will
1599 * not atomically search a snapshot of the cache at a single point in time.
1600 * For example, if a gap is created at index 5, then subsequently a gap is
1601 * created at index 10, page_cache_next_miss covering both indices may
1602 * return 10 if called under the rcu_read_lock.
1604 * Return: The index of the gap if found, otherwise an index outside the
1605 * range specified (in which case 'return - index >= max_scan' will be true).
1606 * In the rare case of index wrap-around, 0 will be returned.
1608 pgoff_t page_cache_next_miss(struct address_space *mapping,
1609 pgoff_t index, unsigned long max_scan)
1611 XA_STATE(xas, &mapping->i_pages, index);
1613 while (max_scan--) {
1614 void *entry = xas_next(&xas);
1615 if (!entry || xa_is_value(entry))
1617 if (xas.xa_index == 0)
1621 return xas.xa_index;
1623 EXPORT_SYMBOL(page_cache_next_miss);
1626 * page_cache_prev_miss() - Find the previous gap in the page cache.
1627 * @mapping: Mapping.
1629 * @max_scan: Maximum range to search.
1631 * Search the range [max(index - max_scan + 1, 0), index] for the
1632 * gap with the highest index.
1634 * This function may be called under the rcu_read_lock. However, this will
1635 * not atomically search a snapshot of the cache at a single point in time.
1636 * For example, if a gap is created at index 10, then subsequently a gap is
1637 * created at index 5, page_cache_prev_miss() covering both indices may
1638 * return 5 if called under the rcu_read_lock.
1640 * Return: The index of the gap if found, otherwise an index outside the
1641 * range specified (in which case 'index - return >= max_scan' will be true).
1642 * In the rare case of wrap-around, ULONG_MAX will be returned.
1644 pgoff_t page_cache_prev_miss(struct address_space *mapping,
1645 pgoff_t index, unsigned long max_scan)
1647 XA_STATE(xas, &mapping->i_pages, index);
1649 while (max_scan--) {
1650 void *entry = xas_prev(&xas);
1651 if (!entry || xa_is_value(entry))
1653 if (xas.xa_index == ULONG_MAX)
1657 return xas.xa_index;
1659 EXPORT_SYMBOL(page_cache_prev_miss);
1662 * find_get_entry - find and get a page cache entry
1663 * @mapping: the address_space to search
1664 * @index: The page cache index.
1666 * Looks up the page cache slot at @mapping & @offset. If there is a
1667 * page cache page, the head page is returned with an increased refcount.
1669 * If the slot holds a shadow entry of a previously evicted page, or a
1670 * swap entry from shmem/tmpfs, it is returned.
1672 * Return: The head page or shadow entry, %NULL if nothing is found.
1674 struct page *find_get_entry(struct address_space *mapping, pgoff_t index)
1676 XA_STATE(xas, &mapping->i_pages, index);
1682 page = xas_load(&xas);
1683 if (xas_retry(&xas, page))
1686 * A shadow entry of a recently evicted page, or a swap entry from
1687 * shmem/tmpfs. Return it without attempting to raise page count.
1689 if (!page || xa_is_value(page))
1692 if (!page_cache_get_speculative(page))
1696 * Has the page moved or been split?
1697 * This is part of the lockless pagecache protocol. See
1698 * include/linux/pagemap.h for details.
1700 if (unlikely(page != xas_reload(&xas))) {
1711 * find_lock_entry - Locate and lock a page cache entry.
1712 * @mapping: The address_space to search.
1713 * @index: The page cache index.
1715 * Looks up the page at @mapping & @index. If there is a page in the
1716 * cache, the head page is returned locked and with an increased refcount.
1718 * If the slot holds a shadow entry of a previously evicted page, or a
1719 * swap entry from shmem/tmpfs, it is returned.
1721 * Context: May sleep.
1722 * Return: The head page or shadow entry, %NULL if nothing is found.
1724 struct page *find_lock_entry(struct address_space *mapping, pgoff_t index)
1729 page = find_get_entry(mapping, index);
1730 if (page && !xa_is_value(page)) {
1732 /* Has the page been truncated? */
1733 if (unlikely(page->mapping != mapping)) {
1738 VM_BUG_ON_PAGE(!thp_contains(page, index), page);
1744 * pagecache_get_page - Find and get a reference to a page.
1745 * @mapping: The address_space to search.
1746 * @index: The page index.
1747 * @fgp_flags: %FGP flags modify how the page is returned.
1748 * @gfp_mask: Memory allocation flags to use if %FGP_CREAT is specified.
1750 * Looks up the page cache entry at @mapping & @index.
1752 * @fgp_flags can be zero or more of these flags:
1754 * * %FGP_ACCESSED - The page will be marked accessed.
1755 * * %FGP_LOCK - The page is returned locked.
1756 * * %FGP_HEAD - If the page is present and a THP, return the head page
1757 * rather than the exact page specified by the index.
1758 * * %FGP_CREAT - If no page is present then a new page is allocated using
1759 * @gfp_mask and added to the page cache and the VM's LRU list.
1760 * The page is returned locked and with an increased refcount.
1761 * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
1762 * page is already in cache. If the page was allocated, unlock it before
1763 * returning so the caller can do the same dance.
1764 * * %FGP_WRITE - The page will be written
1765 * * %FGP_NOFS - __GFP_FS will get cleared in gfp mask
1766 * * %FGP_NOWAIT - Don't get blocked by page lock
1768 * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
1769 * if the %GFP flags specified for %FGP_CREAT are atomic.
1771 * If there is a page cache page, it is returned with an increased refcount.
1773 * Return: The found page or %NULL otherwise.
1775 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
1776 int fgp_flags, gfp_t gfp_mask)
1781 page = find_get_entry(mapping, index);
1782 if (xa_is_value(page))
1787 if (fgp_flags & FGP_LOCK) {
1788 if (fgp_flags & FGP_NOWAIT) {
1789 if (!trylock_page(page)) {
1797 /* Has the page been truncated? */
1798 if (unlikely(page->mapping != mapping)) {
1803 VM_BUG_ON_PAGE(!thp_contains(page, index), page);
1806 if (fgp_flags & FGP_ACCESSED)
1807 mark_page_accessed(page);
1808 else if (fgp_flags & FGP_WRITE) {
1809 /* Clear idle flag for buffer write */
1810 if (page_is_idle(page))
1811 clear_page_idle(page);
1813 if (!(fgp_flags & FGP_HEAD))
1814 page = find_subpage(page, index);
1817 if (!page && (fgp_flags & FGP_CREAT)) {
1819 if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
1820 gfp_mask |= __GFP_WRITE;
1821 if (fgp_flags & FGP_NOFS)
1822 gfp_mask &= ~__GFP_FS;
1824 page = __page_cache_alloc(gfp_mask);
1828 if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
1829 fgp_flags |= FGP_LOCK;
1831 /* Init accessed so avoid atomic mark_page_accessed later */
1832 if (fgp_flags & FGP_ACCESSED)
1833 __SetPageReferenced(page);
1835 err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
1836 if (unlikely(err)) {
1844 * add_to_page_cache_lru locks the page, and for mmap we expect
1847 if (page && (fgp_flags & FGP_FOR_MMAP))
1853 EXPORT_SYMBOL(pagecache_get_page);
1856 * find_get_entries - gang pagecache lookup
1857 * @mapping: The address_space to search
1858 * @start: The starting page cache index
1859 * @nr_entries: The maximum number of entries
1860 * @entries: Where the resulting entries are placed
1861 * @indices: The cache indices corresponding to the entries in @entries
1863 * find_get_entries() will search for and return a group of up to
1864 * @nr_entries entries in the mapping. The entries are placed at
1865 * @entries. find_get_entries() takes a reference against any actual
1868 * The search returns a group of mapping-contiguous page cache entries
1869 * with ascending indexes. There may be holes in the indices due to
1870 * not-present pages.
1872 * Any shadow entries of evicted pages, or swap entries from
1873 * shmem/tmpfs, are included in the returned array.
1875 * If it finds a Transparent Huge Page, head or tail, find_get_entries()
1876 * stops at that page: the caller is likely to have a better way to handle
1877 * the compound page as a whole, and then skip its extent, than repeatedly
1878 * calling find_get_entries() to return all its tails.
1880 * Return: the number of pages and shadow entries which were found.
1882 unsigned find_get_entries(struct address_space *mapping,
1883 pgoff_t start, unsigned int nr_entries,
1884 struct page **entries, pgoff_t *indices)
1886 XA_STATE(xas, &mapping->i_pages, start);
1888 unsigned int ret = 0;
1894 xas_for_each(&xas, page, ULONG_MAX) {
1895 if (xas_retry(&xas, page))
1898 * A shadow entry of a recently evicted page, a swap
1899 * entry from shmem/tmpfs or a DAX entry. Return it
1900 * without attempting to raise page count.
1902 if (xa_is_value(page))
1905 if (!page_cache_get_speculative(page))
1908 /* Has the page moved or been split? */
1909 if (unlikely(page != xas_reload(&xas)))
1913 * Terminate early on finding a THP, to allow the caller to
1914 * handle it all at once; but continue if this is hugetlbfs.
1916 if (PageTransHuge(page) && !PageHuge(page)) {
1917 page = find_subpage(page, xas.xa_index);
1918 nr_entries = ret + 1;
1921 indices[ret] = xas.xa_index;
1922 entries[ret] = page;
1923 if (++ret == nr_entries)
1936 * find_get_pages_range - gang pagecache lookup
1937 * @mapping: The address_space to search
1938 * @start: The starting page index
1939 * @end: The final page index (inclusive)
1940 * @nr_pages: The maximum number of pages
1941 * @pages: Where the resulting pages are placed
1943 * find_get_pages_range() will search for and return a group of up to @nr_pages
1944 * pages in the mapping starting at index @start and up to index @end
1945 * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
1946 * a reference against the returned pages.
1948 * The search returns a group of mapping-contiguous pages with ascending
1949 * indexes. There may be holes in the indices due to not-present pages.
1950 * We also update @start to index the next page for the traversal.
1952 * Return: the number of pages which were found. If this number is
1953 * smaller than @nr_pages, the end of specified range has been
1956 unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
1957 pgoff_t end, unsigned int nr_pages,
1958 struct page **pages)
1960 XA_STATE(xas, &mapping->i_pages, *start);
1964 if (unlikely(!nr_pages))
1968 xas_for_each(&xas, page, end) {
1969 if (xas_retry(&xas, page))
1971 /* Skip over shadow, swap and DAX entries */
1972 if (xa_is_value(page))
1975 if (!page_cache_get_speculative(page))
1978 /* Has the page moved or been split? */
1979 if (unlikely(page != xas_reload(&xas)))
1982 pages[ret] = find_subpage(page, xas.xa_index);
1983 if (++ret == nr_pages) {
1984 *start = xas.xa_index + 1;
1995 * We come here when there is no page beyond @end. We take care to not
1996 * overflow the index @start as it confuses some of the callers. This
1997 * breaks the iteration when there is a page at index -1 but that is
1998 * already broken anyway.
2000 if (end == (pgoff_t)-1)
2001 *start = (pgoff_t)-1;
2011 * find_get_pages_contig - gang contiguous pagecache lookup
2012 * @mapping: The address_space to search
2013 * @index: The starting page index
2014 * @nr_pages: The maximum number of pages
2015 * @pages: Where the resulting pages are placed
2017 * find_get_pages_contig() works exactly like find_get_pages(), except
2018 * that the returned number of pages are guaranteed to be contiguous.
2020 * Return: the number of pages which were found.
2022 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
2023 unsigned int nr_pages, struct page **pages)
2025 XA_STATE(xas, &mapping->i_pages, index);
2027 unsigned int ret = 0;
2029 if (unlikely(!nr_pages))
2033 for (page = xas_load(&xas); page; page = xas_next(&xas)) {
2034 if (xas_retry(&xas, page))
2037 * If the entry has been swapped out, we can stop looking.
2038 * No current caller is looking for DAX entries.
2040 if (xa_is_value(page))
2043 if (!page_cache_get_speculative(page))
2046 /* Has the page moved or been split? */
2047 if (unlikely(page != xas_reload(&xas)))
2050 pages[ret] = find_subpage(page, xas.xa_index);
2051 if (++ret == nr_pages)
2062 EXPORT_SYMBOL(find_get_pages_contig);
2065 * find_get_pages_range_tag - find and return pages in given range matching @tag
2066 * @mapping: the address_space to search
2067 * @index: the starting page index
2068 * @end: The final page index (inclusive)
2069 * @tag: the tag index
2070 * @nr_pages: the maximum number of pages
2071 * @pages: where the resulting pages are placed
2073 * Like find_get_pages, except we only return pages which are tagged with
2074 * @tag. We update @index to index the next page for the traversal.
2076 * Return: the number of pages which were found.
2078 unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
2079 pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
2080 struct page **pages)
2082 XA_STATE(xas, &mapping->i_pages, *index);
2086 if (unlikely(!nr_pages))
2090 xas_for_each_marked(&xas, page, end, tag) {
2091 if (xas_retry(&xas, page))
2094 * Shadow entries should never be tagged, but this iteration
2095 * is lockless so there is a window for page reclaim to evict
2096 * a page we saw tagged. Skip over it.
2098 if (xa_is_value(page))
2101 if (!page_cache_get_speculative(page))
2104 /* Has the page moved or been split? */
2105 if (unlikely(page != xas_reload(&xas)))
2108 pages[ret] = find_subpage(page, xas.xa_index);
2109 if (++ret == nr_pages) {
2110 *index = xas.xa_index + 1;
2121 * We come here when we got to @end. We take care to not overflow the
2122 * index @index as it confuses some of the callers. This breaks the
2123 * iteration when there is a page at index -1 but that is already
2126 if (end == (pgoff_t)-1)
2127 *index = (pgoff_t)-1;
2135 EXPORT_SYMBOL(find_get_pages_range_tag);
2138 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
2139 * a _large_ part of the i/o request. Imagine the worst scenario:
2141 * ---R__________________________________________B__________
2142 * ^ reading here ^ bad block(assume 4k)
2144 * read(R) => miss => readahead(R...B) => media error => frustrating retries
2145 * => failing the whole request => read(R) => read(R+1) =>
2146 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
2147 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
2148 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
2150 * It is going insane. Fix it by quickly scaling down the readahead size.
2152 static void shrink_readahead_size_eio(struct file_ra_state *ra)
2158 * filemap_get_read_batch - Get a batch of pages for read
2160 * Get a batch of pages which represent a contiguous range of bytes
2161 * in the file. No tail pages will be returned. If @index is in the
2162 * middle of a THP, the entire THP will be returned. The last page in
2163 * the batch may have Readahead set or be not Uptodate so that the
2164 * caller can take the appropriate action.
2166 static void filemap_get_read_batch(struct address_space *mapping,
2167 pgoff_t index, pgoff_t max, struct pagevec *pvec)
2169 XA_STATE(xas, &mapping->i_pages, index);
2173 for (head = xas_load(&xas); head; head = xas_next(&xas)) {
2174 if (xas_retry(&xas, head))
2176 if (xas.xa_index > max || xa_is_value(head))
2178 if (!page_cache_get_speculative(head))
2181 /* Has the page moved or been split? */
2182 if (unlikely(head != xas_reload(&xas)))
2185 if (!pagevec_add(pvec, head))
2187 if (!PageUptodate(head))
2189 if (PageReadahead(head))
2191 xas.xa_index = head->index + thp_nr_pages(head) - 1;
2192 xas.xa_offset = (xas.xa_index >> xas.xa_shift) & XA_CHUNK_MASK;
2202 static int filemap_read_page(struct file *file, struct address_space *mapping,
2208 * A previous I/O error may have been due to temporary failures,
2209 * eg. multipath errors. PG_error will be set again if readpage
2212 ClearPageError(page);
2213 /* Start the actual read. The read will unlock the page. */
2214 error = mapping->a_ops->readpage(file, page);
2218 error = wait_on_page_locked_killable(page);
2221 if (PageUptodate(page))
2223 if (!page->mapping) /* page truncated */
2224 return AOP_TRUNCATED_PAGE;
2225 shrink_readahead_size_eio(&file->f_ra);
2229 static bool filemap_range_uptodate(struct address_space *mapping,
2230 loff_t pos, struct iov_iter *iter, struct page *page)
2234 if (PageUptodate(page))
2236 /* pipes can't handle partially uptodate pages */
2237 if (iov_iter_is_pipe(iter))
2239 if (!mapping->a_ops->is_partially_uptodate)
2241 if (mapping->host->i_blkbits >= (PAGE_SHIFT + thp_order(page)))
2244 count = iter->count;
2245 if (page_offset(page) > pos) {
2246 count -= page_offset(page) - pos;
2249 pos -= page_offset(page);
2252 return mapping->a_ops->is_partially_uptodate(page, pos, count);
2255 static int filemap_update_page(struct kiocb *iocb,
2256 struct address_space *mapping, struct iov_iter *iter,
2261 if (!trylock_page(page)) {
2262 if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
2264 if (!(iocb->ki_flags & IOCB_WAITQ)) {
2265 put_and_wait_on_page_locked(page, TASK_KILLABLE);
2266 return AOP_TRUNCATED_PAGE;
2268 error = __lock_page_async(page, iocb->ki_waitq);
2277 if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, page))
2281 if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
2284 error = filemap_read_page(iocb->ki_filp, mapping, page);
2285 if (error == AOP_TRUNCATED_PAGE)
2291 return AOP_TRUNCATED_PAGE;
2297 static int filemap_create_page(struct file *file,
2298 struct address_space *mapping, pgoff_t index,
2299 struct pagevec *pvec)
2304 page = page_cache_alloc(mapping);
2308 error = add_to_page_cache_lru(page, mapping, index,
2309 mapping_gfp_constraint(mapping, GFP_KERNEL));
2310 if (error == -EEXIST)
2311 error = AOP_TRUNCATED_PAGE;
2315 error = filemap_read_page(file, mapping, page);
2319 pagevec_add(pvec, page);
2326 static int filemap_readahead(struct kiocb *iocb, struct file *file,
2327 struct address_space *mapping, struct page *page,
2330 if (iocb->ki_flags & IOCB_NOIO)
2332 page_cache_async_readahead(mapping, &file->f_ra, file, page,
2333 page->index, last_index - page->index);
2337 static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter,
2338 struct pagevec *pvec)
2340 struct file *filp = iocb->ki_filp;
2341 struct address_space *mapping = filp->f_mapping;
2342 struct file_ra_state *ra = &filp->f_ra;
2343 pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
2348 last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE);
2350 if (fatal_signal_pending(current))
2353 filemap_get_read_batch(mapping, index, last_index, pvec);
2354 if (!pagevec_count(pvec)) {
2355 if (iocb->ki_flags & IOCB_NOIO)
2357 page_cache_sync_readahead(mapping, ra, filp, index,
2358 last_index - index);
2359 filemap_get_read_batch(mapping, index, last_index, pvec);
2361 if (!pagevec_count(pvec)) {
2362 if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
2364 err = filemap_create_page(filp, mapping,
2365 iocb->ki_pos >> PAGE_SHIFT, pvec);
2366 if (err == AOP_TRUNCATED_PAGE)
2371 page = pvec->pages[pagevec_count(pvec) - 1];
2372 if (PageReadahead(page)) {
2373 err = filemap_readahead(iocb, filp, mapping, page, last_index);
2377 if (!PageUptodate(page)) {
2378 if ((iocb->ki_flags & IOCB_WAITQ) && pagevec_count(pvec) > 1)
2379 iocb->ki_flags |= IOCB_NOWAIT;
2380 err = filemap_update_page(iocb, mapping, iter, page);
2389 if (likely(--pvec->nr))
2391 if (err == AOP_TRUNCATED_PAGE)
2397 * filemap_read - Read data from the page cache.
2398 * @iocb: The iocb to read.
2399 * @iter: Destination for the data.
2400 * @already_read: Number of bytes already read by the caller.
2402 * Copies data from the page cache. If the data is not currently present,
2403 * uses the readahead and readpage address_space operations to fetch it.
2405 * Return: Total number of bytes copied, including those already read by
2406 * the caller. If an error happens before any bytes are copied, returns
2407 * a negative error number.
2409 ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
2410 ssize_t already_read)
2412 struct file *filp = iocb->ki_filp;
2413 struct file_ra_state *ra = &filp->f_ra;
2414 struct address_space *mapping = filp->f_mapping;
2415 struct inode *inode = mapping->host;
2416 struct pagevec pvec;
2418 bool writably_mapped;
2419 loff_t isize, end_offset;
2421 if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
2423 if (unlikely(!iov_iter_count(iter)))
2426 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
2427 pagevec_init(&pvec);
2433 * If we've already successfully copied some data, then we
2434 * can no longer safely return -EIOCBQUEUED. Hence mark
2435 * an async read NOWAIT at that point.
2437 if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
2438 iocb->ki_flags |= IOCB_NOWAIT;
2440 error = filemap_get_pages(iocb, iter, &pvec);
2445 * i_size must be checked after we know the pages are Uptodate.
2447 * Checking i_size after the check allows us to calculate
2448 * the correct value for "nr", which means the zero-filled
2449 * part of the page is not copied back to userspace (unless
2450 * another truncate extends the file - this is desired though).
2452 isize = i_size_read(inode);
2453 if (unlikely(iocb->ki_pos >= isize))
2455 end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
2458 * Once we start copying data, we don't want to be touching any
2459 * cachelines that might be contended:
2461 writably_mapped = mapping_writably_mapped(mapping);
2464 * When a sequential read accesses a page several times, only
2465 * mark it as accessed the first time.
2467 if (iocb->ki_pos >> PAGE_SHIFT !=
2468 ra->prev_pos >> PAGE_SHIFT)
2469 mark_page_accessed(pvec.pages[0]);
2471 for (i = 0; i < pagevec_count(&pvec); i++) {
2472 struct page *page = pvec.pages[i];
2473 size_t page_size = thp_size(page);
2474 size_t offset = iocb->ki_pos & (page_size - 1);
2475 size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
2476 page_size - offset);
2479 if (end_offset < page_offset(page))
2482 mark_page_accessed(page);
2484 * If users can be writing to this page using arbitrary
2485 * virtual addresses, take care about potential aliasing
2486 * before reading the page on the kernel side.
2488 if (writably_mapped) {
2491 for (j = 0; j < thp_nr_pages(page); j++)
2492 flush_dcache_page(page + j);
2495 copied = copy_page_to_iter(page, offset, bytes, iter);
2497 already_read += copied;
2498 iocb->ki_pos += copied;
2499 ra->prev_pos = iocb->ki_pos;
2501 if (copied < bytes) {
2507 for (i = 0; i < pagevec_count(&pvec); i++)
2508 put_page(pvec.pages[i]);
2509 pagevec_reinit(&pvec);
2510 } while (iov_iter_count(iter) && iocb->ki_pos < isize && !error);
2512 file_accessed(filp);
2514 return already_read ? already_read : error;
2516 EXPORT_SYMBOL_GPL(filemap_read);
2519 * generic_file_read_iter - generic filesystem read routine
2520 * @iocb: kernel I/O control block
2521 * @iter: destination for the data read
2523 * This is the "read_iter()" routine for all filesystems
2524 * that can use the page cache directly.
2526 * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
2527 * be returned when no data can be read without waiting for I/O requests
2528 * to complete; it doesn't prevent readahead.
2530 * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
2531 * requests shall be made for the read or for readahead. When no data
2532 * can be read, -EAGAIN shall be returned. When readahead would be
2533 * triggered, a partial, possibly empty read shall be returned.
2536 * * number of bytes copied, even for partial reads
2537 * * negative error code (or 0 if IOCB_NOIO) if nothing was read
2540 generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2542 size_t count = iov_iter_count(iter);
2546 return 0; /* skip atime */
2548 if (iocb->ki_flags & IOCB_DIRECT) {
2549 struct file *file = iocb->ki_filp;
2550 struct address_space *mapping = file->f_mapping;
2551 struct inode *inode = mapping->host;
2554 size = i_size_read(inode);
2555 if (iocb->ki_flags & IOCB_NOWAIT) {
2556 if (filemap_range_has_page(mapping, iocb->ki_pos,
2557 iocb->ki_pos + count - 1))
2560 retval = filemap_write_and_wait_range(mapping,
2562 iocb->ki_pos + count - 1);
2567 file_accessed(file);
2569 retval = mapping->a_ops->direct_IO(iocb, iter);
2571 iocb->ki_pos += retval;
2574 if (retval != -EIOCBQUEUED)
2575 iov_iter_revert(iter, count - iov_iter_count(iter));
2578 * Btrfs can have a short DIO read if we encounter
2579 * compressed extents, so if there was an error, or if
2580 * we've already read everything we wanted to, or if
2581 * there was a short read because we hit EOF, go ahead
2582 * and return. Otherwise fallthrough to buffered io for
2583 * the rest of the read. Buffered reads will not work for
2584 * DAX files, so don't bother trying.
2586 if (retval < 0 || !count || iocb->ki_pos >= size ||
2591 return filemap_read(iocb, iter, retval);
2593 EXPORT_SYMBOL(generic_file_read_iter);
2596 #define MMAP_LOTSAMISS (100)
2598 * lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
2599 * @vmf - the vm_fault for this fault.
2600 * @page - the page to lock.
2601 * @fpin - the pointer to the file we may pin (or is already pinned).
2603 * This works similar to lock_page_or_retry in that it can drop the mmap_lock.
2604 * It differs in that it actually returns the page locked if it returns 1 and 0
2605 * if it couldn't lock the page. If we did have to drop the mmap_lock then fpin
2606 * will point to the pinned file and needs to be fput()'ed at a later point.
2608 static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
2611 if (trylock_page(page))
2615 * NOTE! This will make us return with VM_FAULT_RETRY, but with
2616 * the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
2617 * is supposed to work. We have way too many special cases..
2619 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
2622 *fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
2623 if (vmf->flags & FAULT_FLAG_KILLABLE) {
2624 if (__lock_page_killable(page)) {
2626 * We didn't have the right flags to drop the mmap_lock,
2627 * but all fault_handlers only check for fatal signals
2628 * if we return VM_FAULT_RETRY, so we need to drop the
2629 * mmap_lock here and return 0 if we don't have a fpin.
2632 mmap_read_unlock(vmf->vma->vm_mm);
2642 * Synchronous readahead happens when we don't even find a page in the page
2643 * cache at all. We don't want to perform IO under the mmap sem, so if we have
2644 * to drop the mmap sem we return the file that was pinned in order for us to do
2645 * that. If we didn't pin a file then we return NULL. The file that is
2646 * returned needs to be fput()'ed when we're done with it.
2648 static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
2650 struct file *file = vmf->vma->vm_file;
2651 struct file_ra_state *ra = &file->f_ra;
2652 struct address_space *mapping = file->f_mapping;
2653 DEFINE_READAHEAD(ractl, file, mapping, vmf->pgoff);
2654 struct file *fpin = NULL;
2655 unsigned int mmap_miss;
2657 /* If we don't want any read-ahead, don't bother */
2658 if (vmf->vma->vm_flags & VM_RAND_READ)
2663 if (vmf->vma->vm_flags & VM_SEQ_READ) {
2664 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2665 page_cache_sync_ra(&ractl, ra, ra->ra_pages);
2669 /* Avoid banging the cache line if not needed */
2670 mmap_miss = READ_ONCE(ra->mmap_miss);
2671 if (mmap_miss < MMAP_LOTSAMISS * 10)
2672 WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
2675 * Do we miss much more than hit in this file? If so,
2676 * stop bothering with read-ahead. It will only hurt.
2678 if (mmap_miss > MMAP_LOTSAMISS)
2684 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2685 ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
2686 ra->size = ra->ra_pages;
2687 ra->async_size = ra->ra_pages / 4;
2688 ractl._index = ra->start;
2689 do_page_cache_ra(&ractl, ra->size, ra->async_size);
2694 * Asynchronous readahead happens when we find the page and PG_readahead,
2695 * so we want to possibly extend the readahead further. We return the file that
2696 * was pinned if we have to drop the mmap_lock in order to do IO.
2698 static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
2701 struct file *file = vmf->vma->vm_file;
2702 struct file_ra_state *ra = &file->f_ra;
2703 struct address_space *mapping = file->f_mapping;
2704 struct file *fpin = NULL;
2705 unsigned int mmap_miss;
2706 pgoff_t offset = vmf->pgoff;
2708 /* If we don't want any read-ahead, don't bother */
2709 if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
2711 mmap_miss = READ_ONCE(ra->mmap_miss);
2713 WRITE_ONCE(ra->mmap_miss, --mmap_miss);
2714 if (PageReadahead(page)) {
2715 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2716 page_cache_async_readahead(mapping, ra, file,
2717 page, offset, ra->ra_pages);
2723 * filemap_fault - read in file data for page fault handling
2724 * @vmf: struct vm_fault containing details of the fault
2726 * filemap_fault() is invoked via the vma operations vector for a
2727 * mapped memory region to read in file data during a page fault.
2729 * The goto's are kind of ugly, but this streamlines the normal case of having
2730 * it in the page cache, and handles the special cases reasonably without
2731 * having a lot of duplicated code.
2733 * vma->vm_mm->mmap_lock must be held on entry.
2735 * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
2736 * may be dropped before doing I/O or by lock_page_maybe_drop_mmap().
2738 * If our return value does not have VM_FAULT_RETRY set, the mmap_lock
2739 * has not been released.
2741 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2743 * Return: bitwise-OR of %VM_FAULT_ codes.
2745 vm_fault_t filemap_fault(struct vm_fault *vmf)
2748 struct file *file = vmf->vma->vm_file;
2749 struct file *fpin = NULL;
2750 struct address_space *mapping = file->f_mapping;
2751 struct file_ra_state *ra = &file->f_ra;
2752 struct inode *inode = mapping->host;
2753 pgoff_t offset = vmf->pgoff;
2758 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2759 if (unlikely(offset >= max_off))
2760 return VM_FAULT_SIGBUS;
2763 * Do we have something in the page cache already?
2765 page = find_get_page(mapping, offset);
2766 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2768 * We found the page, so try async readahead before
2769 * waiting for the lock.
2771 fpin = do_async_mmap_readahead(vmf, page);
2773 /* No page in the page cache at all */
2774 count_vm_event(PGMAJFAULT);
2775 count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
2776 ret = VM_FAULT_MAJOR;
2777 fpin = do_sync_mmap_readahead(vmf);
2779 page = pagecache_get_page(mapping, offset,
2780 FGP_CREAT|FGP_FOR_MMAP,
2785 return VM_FAULT_OOM;
2789 if (!lock_page_maybe_drop_mmap(vmf, page, &fpin))
2792 /* Did it get truncated? */
2793 if (unlikely(compound_head(page)->mapping != mapping)) {
2798 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
2801 * We have a locked page in the page cache, now we need to check
2802 * that it's up-to-date. If not, it is going to be due to an error.
2804 if (unlikely(!PageUptodate(page)))
2805 goto page_not_uptodate;
2808 * We've made it this far and we had to drop our mmap_lock, now is the
2809 * time to return to the upper layer and have it re-find the vma and
2818 * Found the page and have a reference on it.
2819 * We must recheck i_size under page lock.
2821 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2822 if (unlikely(offset >= max_off)) {
2825 return VM_FAULT_SIGBUS;
2829 return ret | VM_FAULT_LOCKED;
2833 * Umm, take care of errors if the page isn't up-to-date.
2834 * Try to re-read it _once_. We do this synchronously,
2835 * because there really aren't any performance issues here
2836 * and we need to check for errors.
2838 ClearPageError(page);
2839 fpin = maybe_unlock_mmap_for_io(vmf, fpin);
2840 error = mapping->a_ops->readpage(file, page);
2842 wait_on_page_locked(page);
2843 if (!PageUptodate(page))
2850 if (!error || error == AOP_TRUNCATED_PAGE)
2853 shrink_readahead_size_eio(ra);
2854 return VM_FAULT_SIGBUS;
2858 * We dropped the mmap_lock, we need to return to the fault handler to
2859 * re-find the vma and come back and find our hopefully still populated
2866 return ret | VM_FAULT_RETRY;
2868 EXPORT_SYMBOL(filemap_fault);
2870 static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page)
2872 struct mm_struct *mm = vmf->vma->vm_mm;
2874 /* Huge page is mapped? No need to proceed. */
2875 if (pmd_trans_huge(*vmf->pmd)) {
2881 if (pmd_none(*vmf->pmd) && PageTransHuge(page)) {
2882 vm_fault_t ret = do_set_pmd(vmf, page);
2884 /* The page is mapped successfully, reference consumed. */
2890 if (pmd_none(*vmf->pmd)) {
2891 vmf->ptl = pmd_lock(mm, vmf->pmd);
2892 if (likely(pmd_none(*vmf->pmd))) {
2894 pmd_populate(mm, vmf->pmd, vmf->prealloc_pte);
2895 vmf->prealloc_pte = NULL;
2897 spin_unlock(vmf->ptl);
2900 /* See comment in handle_pte_fault() */
2901 if (pmd_devmap_trans_unstable(vmf->pmd)) {
2910 static struct page *next_uptodate_page(struct page *page,
2911 struct address_space *mapping,
2912 struct xa_state *xas, pgoff_t end_pgoff)
2914 unsigned long max_idx;
2919 if (xas_retry(xas, page))
2921 if (xa_is_value(page))
2923 if (PageLocked(page))
2925 if (!page_cache_get_speculative(page))
2927 /* Has the page moved or been split? */
2928 if (unlikely(page != xas_reload(xas)))
2930 if (!PageUptodate(page) || PageReadahead(page))
2932 if (PageHWPoison(page))
2934 if (!trylock_page(page))
2936 if (page->mapping != mapping)
2938 if (!PageUptodate(page))
2940 max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2941 if (xas->xa_index >= max_idx)
2948 } while ((page = xas_next_entry(xas, end_pgoff)) != NULL);
2953 static inline struct page *first_map_page(struct address_space *mapping,
2954 struct xa_state *xas,
2957 return next_uptodate_page(xas_find(xas, end_pgoff),
2958 mapping, xas, end_pgoff);
2961 static inline struct page *next_map_page(struct address_space *mapping,
2962 struct xa_state *xas,
2965 return next_uptodate_page(xas_next_entry(xas, end_pgoff),
2966 mapping, xas, end_pgoff);
2969 vm_fault_t filemap_map_pages(struct vm_fault *vmf,
2970 pgoff_t start_pgoff, pgoff_t end_pgoff)
2972 struct vm_area_struct *vma = vmf->vma;
2973 struct file *file = vma->vm_file;
2974 struct address_space *mapping = file->f_mapping;
2975 pgoff_t last_pgoff = start_pgoff;
2977 XA_STATE(xas, &mapping->i_pages, start_pgoff);
2978 struct page *head, *page;
2979 unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
2983 head = first_map_page(mapping, &xas, end_pgoff);
2987 if (filemap_map_pmd(vmf, head)) {
2988 ret = VM_FAULT_NOPAGE;
2992 addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
2993 vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
2995 page = find_subpage(head, xas.xa_index);
2996 if (PageHWPoison(page))
3002 addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
3003 vmf->pte += xas.xa_index - last_pgoff;
3004 last_pgoff = xas.xa_index;
3006 if (!pte_none(*vmf->pte))
3009 /* We're about to handle the fault */
3010 if (vmf->address == addr)
3011 ret = VM_FAULT_NOPAGE;
3013 do_set_pte(vmf, page, addr);
3014 /* no need to invalidate: a not-present page won't be cached */
3015 update_mmu_cache(vma, addr, vmf->pte);
3021 } while ((head = next_map_page(mapping, &xas, end_pgoff)) != NULL);
3022 pte_unmap_unlock(vmf->pte, vmf->ptl);
3025 WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);
3028 EXPORT_SYMBOL(filemap_map_pages);
3030 vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3032 struct address_space *mapping = vmf->vma->vm_file->f_mapping;
3033 struct page *page = vmf->page;
3034 vm_fault_t ret = VM_FAULT_LOCKED;
3036 sb_start_pagefault(mapping->host->i_sb);
3037 file_update_time(vmf->vma->vm_file);
3039 if (page->mapping != mapping) {
3041 ret = VM_FAULT_NOPAGE;
3045 * We mark the page dirty already here so that when freeze is in
3046 * progress, we are guaranteed that writeback during freezing will
3047 * see the dirty page and writeprotect it again.
3049 set_page_dirty(page);
3050 wait_for_stable_page(page);
3052 sb_end_pagefault(mapping->host->i_sb);
3056 const struct vm_operations_struct generic_file_vm_ops = {
3057 .fault = filemap_fault,
3058 .map_pages = filemap_map_pages,
3059 .page_mkwrite = filemap_page_mkwrite,
3062 /* This is used for a general mmap of a disk file */
3064 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
3066 struct address_space *mapping = file->f_mapping;
3068 if (!mapping->a_ops->readpage)
3070 file_accessed(file);
3071 vma->vm_ops = &generic_file_vm_ops;
3076 * This is for filesystems which do not implement ->writepage.
3078 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3080 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
3082 return generic_file_mmap(file, vma);
3085 vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3087 return VM_FAULT_SIGBUS;
3089 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
3093 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
3097 #endif /* CONFIG_MMU */
3099 EXPORT_SYMBOL(filemap_page_mkwrite);
3100 EXPORT_SYMBOL(generic_file_mmap);
3101 EXPORT_SYMBOL(generic_file_readonly_mmap);
3103 static struct page *wait_on_page_read(struct page *page)
3105 if (!IS_ERR(page)) {
3106 wait_on_page_locked(page);
3107 if (!PageUptodate(page)) {
3109 page = ERR_PTR(-EIO);
3115 static struct page *do_read_cache_page(struct address_space *mapping,
3117 int (*filler)(void *, struct page *),
3124 page = find_get_page(mapping, index);
3126 page = __page_cache_alloc(gfp);
3128 return ERR_PTR(-ENOMEM);
3129 err = add_to_page_cache_lru(page, mapping, index, gfp);
3130 if (unlikely(err)) {
3134 /* Presumably ENOMEM for xarray node */
3135 return ERR_PTR(err);
3140 err = filler(data, page);
3142 err = mapping->a_ops->readpage(data, page);
3146 return ERR_PTR(err);
3149 page = wait_on_page_read(page);
3154 if (PageUptodate(page))
3158 * Page is not up to date and may be locked due to one of the following
3159 * case a: Page is being filled and the page lock is held
3160 * case b: Read/write error clearing the page uptodate status
3161 * case c: Truncation in progress (page locked)
3162 * case d: Reclaim in progress
3164 * Case a, the page will be up to date when the page is unlocked.
3165 * There is no need to serialise on the page lock here as the page
3166 * is pinned so the lock gives no additional protection. Even if the
3167 * page is truncated, the data is still valid if PageUptodate as
3168 * it's a race vs truncate race.
3169 * Case b, the page will not be up to date
3170 * Case c, the page may be truncated but in itself, the data may still
3171 * be valid after IO completes as it's a read vs truncate race. The
3172 * operation must restart if the page is not uptodate on unlock but
3173 * otherwise serialising on page lock to stabilise the mapping gives
3174 * no additional guarantees to the caller as the page lock is
3175 * released before return.
3176 * Case d, similar to truncation. If reclaim holds the page lock, it
3177 * will be a race with remove_mapping that determines if the mapping
3178 * is valid on unlock but otherwise the data is valid and there is
3179 * no need to serialise with page lock.
3181 * As the page lock gives no additional guarantee, we optimistically
3182 * wait on the page to be unlocked and check if it's up to date and
3183 * use the page if it is. Otherwise, the page lock is required to
3184 * distinguish between the different cases. The motivation is that we
3185 * avoid spurious serialisations and wakeups when multiple processes
3186 * wait on the same page for IO to complete.
3188 wait_on_page_locked(page);
3189 if (PageUptodate(page))
3192 /* Distinguish between all the cases under the safety of the lock */
3195 /* Case c or d, restart the operation */
3196 if (!page->mapping) {
3202 /* Someone else locked and filled the page in a very small window */
3203 if (PageUptodate(page)) {
3209 * A previous I/O error may have been due to temporary
3211 * Clear page error before actual read, PG_error will be
3212 * set again if read page fails.
3214 ClearPageError(page);
3218 mark_page_accessed(page);
3223 * read_cache_page - read into page cache, fill it if needed
3224 * @mapping: the page's address_space
3225 * @index: the page index
3226 * @filler: function to perform the read
3227 * @data: first arg to filler(data, page) function, often left as NULL
3229 * Read into the page cache. If a page already exists, and PageUptodate() is
3230 * not set, try to fill the page and wait for it to become unlocked.
3232 * If the page does not get brought uptodate, return -EIO.
3234 * Return: up to date page on success, ERR_PTR() on failure.
3236 struct page *read_cache_page(struct address_space *mapping,
3238 int (*filler)(void *, struct page *),
3241 return do_read_cache_page(mapping, index, filler, data,
3242 mapping_gfp_mask(mapping));
3244 EXPORT_SYMBOL(read_cache_page);
3247 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
3248 * @mapping: the page's address_space
3249 * @index: the page index
3250 * @gfp: the page allocator flags to use if allocating
3252 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
3253 * any new page allocations done using the specified allocation flags.
3255 * If the page does not get brought uptodate, return -EIO.
3257 * Return: up to date page on success, ERR_PTR() on failure.
3259 struct page *read_cache_page_gfp(struct address_space *mapping,
3263 return do_read_cache_page(mapping, index, NULL, NULL, gfp);
3265 EXPORT_SYMBOL(read_cache_page_gfp);
3267 int pagecache_write_begin(struct file *file, struct address_space *mapping,
3268 loff_t pos, unsigned len, unsigned flags,
3269 struct page **pagep, void **fsdata)
3271 const struct address_space_operations *aops = mapping->a_ops;
3273 return aops->write_begin(file, mapping, pos, len, flags,
3276 EXPORT_SYMBOL(pagecache_write_begin);
3278 int pagecache_write_end(struct file *file, struct address_space *mapping,
3279 loff_t pos, unsigned len, unsigned copied,
3280 struct page *page, void *fsdata)
3282 const struct address_space_operations *aops = mapping->a_ops;
3284 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
3286 EXPORT_SYMBOL(pagecache_write_end);
3289 * Warn about a page cache invalidation failure during a direct I/O write.
3291 void dio_warn_stale_pagecache(struct file *filp)
3293 static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
3297 errseq_set(&filp->f_mapping->wb_err, -EIO);
3298 if (__ratelimit(&_rs)) {
3299 path = file_path(filp, pathname, sizeof(pathname));
3302 pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
3303 pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
3309 generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
3311 struct file *file = iocb->ki_filp;
3312 struct address_space *mapping = file->f_mapping;
3313 struct inode *inode = mapping->host;
3314 loff_t pos = iocb->ki_pos;
3319 write_len = iov_iter_count(from);
3320 end = (pos + write_len - 1) >> PAGE_SHIFT;
3322 if (iocb->ki_flags & IOCB_NOWAIT) {
3323 /* If there are pages to writeback, return */
3324 if (filemap_range_has_page(file->f_mapping, pos,
3325 pos + write_len - 1))
3328 written = filemap_write_and_wait_range(mapping, pos,
3329 pos + write_len - 1);
3335 * After a write we want buffered reads to be sure to go to disk to get
3336 * the new data. We invalidate clean cached page from the region we're
3337 * about to write. We do this *before* the write so that we can return
3338 * without clobbering -EIOCBQUEUED from ->direct_IO().
3340 written = invalidate_inode_pages2_range(mapping,
3341 pos >> PAGE_SHIFT, end);
3343 * If a page can not be invalidated, return 0 to fall back
3344 * to buffered write.
3347 if (written == -EBUSY)
3352 written = mapping->a_ops->direct_IO(iocb, from);
3355 * Finally, try again to invalidate clean pages which might have been
3356 * cached by non-direct readahead, or faulted in by get_user_pages()
3357 * if the source of the write was an mmap'ed region of the file
3358 * we're writing. Either one is a pretty crazy thing to do,
3359 * so we don't support it 100%. If this invalidation
3360 * fails, tough, the write still worked...
3362 * Most of the time we do not need this since dio_complete() will do
3363 * the invalidation for us. However there are some file systems that
3364 * do not end up with dio_complete() being called, so let's not break
3365 * them by removing it completely.
3367 * Noticeable example is a blkdev_direct_IO().
3369 * Skip invalidation for async writes or if mapping has no pages.
3371 if (written > 0 && mapping->nrpages &&
3372 invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end))
3373 dio_warn_stale_pagecache(file);
3377 write_len -= written;
3378 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
3379 i_size_write(inode, pos);
3380 mark_inode_dirty(inode);
3384 if (written != -EIOCBQUEUED)
3385 iov_iter_revert(from, write_len - iov_iter_count(from));
3389 EXPORT_SYMBOL(generic_file_direct_write);
3392 * Find or create a page at the given pagecache position. Return the locked
3393 * page. This function is specifically for buffered writes.
3395 struct page *grab_cache_page_write_begin(struct address_space *mapping,
3396 pgoff_t index, unsigned flags)
3399 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
3401 if (flags & AOP_FLAG_NOFS)
3402 fgp_flags |= FGP_NOFS;
3404 page = pagecache_get_page(mapping, index, fgp_flags,
3405 mapping_gfp_mask(mapping));
3407 wait_for_stable_page(page);
3411 EXPORT_SYMBOL(grab_cache_page_write_begin);
3413 ssize_t generic_perform_write(struct file *file,
3414 struct iov_iter *i, loff_t pos)
3416 struct address_space *mapping = file->f_mapping;
3417 const struct address_space_operations *a_ops = mapping->a_ops;
3419 ssize_t written = 0;
3420 unsigned int flags = 0;
3424 unsigned long offset; /* Offset into pagecache page */
3425 unsigned long bytes; /* Bytes to write to page */
3426 size_t copied; /* Bytes copied from user */
3429 offset = (pos & (PAGE_SIZE - 1));
3430 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3435 * Bring in the user page that we will copy from _first_.
3436 * Otherwise there's a nasty deadlock on copying from the
3437 * same page as we're writing to, without it being marked
3440 * Not only is this an optimisation, but it is also required
3441 * to check that the address is actually valid, when atomic
3442 * usercopies are used, below.
3444 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
3449 if (fatal_signal_pending(current)) {
3454 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
3456 if (unlikely(status < 0))
3459 if (mapping_writably_mapped(mapping))
3460 flush_dcache_page(page);
3462 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
3463 flush_dcache_page(page);
3465 status = a_ops->write_end(file, mapping, pos, bytes, copied,
3467 if (unlikely(status < 0))
3473 iov_iter_advance(i, copied);
3474 if (unlikely(copied == 0)) {
3476 * If we were unable to copy any data at all, we must
3477 * fall back to a single segment length write.
3479 * If we didn't fallback here, we could livelock
3480 * because not all segments in the iov can be copied at
3481 * once without a pagefault.
3483 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3484 iov_iter_single_seg_count(i));
3490 balance_dirty_pages_ratelimited(mapping);
3491 } while (iov_iter_count(i));
3493 return written ? written : status;
3495 EXPORT_SYMBOL(generic_perform_write);
3498 * __generic_file_write_iter - write data to a file
3499 * @iocb: IO state structure (file, offset, etc.)
3500 * @from: iov_iter with data to write
3502 * This function does all the work needed for actually writing data to a
3503 * file. It does all basic checks, removes SUID from the file, updates
3504 * modification times and calls proper subroutines depending on whether we
3505 * do direct IO or a standard buffered write.
3507 * It expects i_mutex to be grabbed unless we work on a block device or similar
3508 * object which does not need locking at all.
3510 * This function does *not* take care of syncing data in case of O_SYNC write.
3511 * A caller has to handle it. This is mainly due to the fact that we want to
3512 * avoid syncing under i_mutex.
3515 * * number of bytes written, even for truncated writes
3516 * * negative error code if no data has been written at all
3518 ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3520 struct file *file = iocb->ki_filp;
3521 struct address_space * mapping = file->f_mapping;
3522 struct inode *inode = mapping->host;
3523 ssize_t written = 0;
3527 /* We can write back this queue in page reclaim */
3528 current->backing_dev_info = inode_to_bdi(inode);
3529 err = file_remove_privs(file);
3533 err = file_update_time(file);
3537 if (iocb->ki_flags & IOCB_DIRECT) {
3538 loff_t pos, endbyte;
3540 written = generic_file_direct_write(iocb, from);
3542 * If the write stopped short of completing, fall back to
3543 * buffered writes. Some filesystems do this for writes to
3544 * holes, for example. For DAX files, a buffered write will
3545 * not succeed (even if it did, DAX does not handle dirty
3546 * page-cache pages correctly).
3548 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
3551 status = generic_perform_write(file, from, pos = iocb->ki_pos);
3553 * If generic_perform_write() returned a synchronous error
3554 * then we want to return the number of bytes which were
3555 * direct-written, or the error code if that was zero. Note
3556 * that this differs from normal direct-io semantics, which
3557 * will return -EFOO even if some bytes were written.
3559 if (unlikely(status < 0)) {
3564 * We need to ensure that the page cache pages are written to
3565 * disk and invalidated to preserve the expected O_DIRECT
3568 endbyte = pos + status - 1;
3569 err = filemap_write_and_wait_range(mapping, pos, endbyte);
3571 iocb->ki_pos = endbyte + 1;
3573 invalidate_mapping_pages(mapping,
3575 endbyte >> PAGE_SHIFT);
3578 * We don't know how much we wrote, so just return
3579 * the number of bytes which were direct-written
3583 written = generic_perform_write(file, from, iocb->ki_pos);
3584 if (likely(written > 0))
3585 iocb->ki_pos += written;
3588 current->backing_dev_info = NULL;
3589 return written ? written : err;
3591 EXPORT_SYMBOL(__generic_file_write_iter);
3594 * generic_file_write_iter - write data to a file
3595 * @iocb: IO state structure
3596 * @from: iov_iter with data to write
3598 * This is a wrapper around __generic_file_write_iter() to be used by most
3599 * filesystems. It takes care of syncing the file in case of O_SYNC file
3600 * and acquires i_mutex as needed.
3602 * * negative error code if no data has been written at all of
3603 * vfs_fsync_range() failed for a synchronous write
3604 * * number of bytes written, even for truncated writes
3606 ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3608 struct file *file = iocb->ki_filp;
3609 struct inode *inode = file->f_mapping->host;
3613 ret = generic_write_checks(iocb, from);
3615 ret = __generic_file_write_iter(iocb, from);
3616 inode_unlock(inode);
3619 ret = generic_write_sync(iocb, ret);
3622 EXPORT_SYMBOL(generic_file_write_iter);
3625 * try_to_release_page() - release old fs-specific metadata on a page
3627 * @page: the page which the kernel is trying to free
3628 * @gfp_mask: memory allocation flags (and I/O mode)
3630 * The address_space is to try to release any data against the page
3631 * (presumably at page->private).
3633 * This may also be called if PG_fscache is set on a page, indicating that the
3634 * page is known to the local caching routines.
3636 * The @gfp_mask argument specifies whether I/O may be performed to release
3637 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3639 * Return: %1 if the release was successful, otherwise return zero.
3641 int try_to_release_page(struct page *page, gfp_t gfp_mask)
3643 struct address_space * const mapping = page->mapping;
3645 BUG_ON(!PageLocked(page));
3646 if (PageWriteback(page))
3649 if (mapping && mapping->a_ops->releasepage)
3650 return mapping->a_ops->releasepage(page, gfp_mask);
3651 return try_to_free_buffers(page);
3654 EXPORT_SYMBOL(try_to_release_page);