4 * Copyright (C) 1994-1999 Linus Torvalds
8 * This file handles the generic file mmap semantics used by
9 * most "normal" filesystems (but you don't /have/ to use this:
10 * the NFS filesystem used to do this differently, for example)
12 #include <linux/export.h>
13 #include <linux/compiler.h>
14 #include <linux/dax.h>
16 #include <linux/sched/signal.h>
17 #include <linux/uaccess.h>
18 #include <linux/capability.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/gfp.h>
22 #include <linux/swap.h>
23 #include <linux/mman.h>
24 #include <linux/pagemap.h>
25 #include <linux/file.h>
26 #include <linux/uio.h>
27 #include <linux/hash.h>
28 #include <linux/writeback.h>
29 #include <linux/backing-dev.h>
30 #include <linux/pagevec.h>
31 #include <linux/blkdev.h>
32 #include <linux/security.h>
33 #include <linux/cpuset.h>
34 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
35 #include <linux/hugetlb.h>
36 #include <linux/memcontrol.h>
37 #include <linux/cleancache.h>
38 #include <linux/rmap.h>
41 #define CREATE_TRACE_POINTS
42 #include <trace/events/filemap.h>
45 * FIXME: remove all knowledge of the buffer layer from the core VM
47 #include <linux/buffer_head.h> /* for try_to_free_buffers */
52 * Shared mappings implemented 30.11.1994. It's not fully working yet,
55 * Shared mappings now work. 15.8.1995 Bruno.
57 * finished 'unifying' the page and buffer cache and SMP-threaded the
58 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
60 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
66 * ->i_mmap_rwsem (truncate_pagecache)
67 * ->private_lock (__free_pte->__set_page_dirty_buffers)
68 * ->swap_lock (exclusive_swap_page, others)
69 * ->mapping->tree_lock
72 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
76 * ->page_table_lock or pte_lock (various, mainly in memory.c)
77 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
80 * ->lock_page (access_process_vm)
82 * ->i_mutex (generic_perform_write)
83 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
86 * sb_lock (fs/fs-writeback.c)
87 * ->mapping->tree_lock (__sync_single_inode)
90 * ->anon_vma.lock (vma_adjust)
93 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
95 * ->page_table_lock or pte_lock
96 * ->swap_lock (try_to_unmap_one)
97 * ->private_lock (try_to_unmap_one)
98 * ->tree_lock (try_to_unmap_one)
99 * ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
100 * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
101 * ->private_lock (page_remove_rmap->set_page_dirty)
102 * ->tree_lock (page_remove_rmap->set_page_dirty)
103 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
104 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
105 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
106 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
107 * ->inode->i_lock (zap_pte_range->set_page_dirty)
108 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
111 * ->tasklist_lock (memory_failure, collect_procs_ao)
114 static int page_cache_tree_insert(struct address_space *mapping,
115 struct page *page, void **shadowp)
117 struct radix_tree_node *node;
121 error = __radix_tree_create(&mapping->page_tree, page->index, 0,
128 p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
129 if (!radix_tree_exceptional_entry(p))
132 mapping->nrexceptional--;
136 __radix_tree_replace(&mapping->page_tree, node, slot, page,
137 workingset_update_node, mapping);
142 static void page_cache_tree_delete(struct address_space *mapping,
143 struct page *page, void *shadow)
147 /* hugetlb pages are represented by one entry in the radix tree */
148 nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
150 VM_BUG_ON_PAGE(!PageLocked(page), page);
151 VM_BUG_ON_PAGE(PageTail(page), page);
152 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
154 for (i = 0; i < nr; i++) {
155 struct radix_tree_node *node;
158 __radix_tree_lookup(&mapping->page_tree, page->index + i,
161 VM_BUG_ON_PAGE(!node && nr != 1, page);
163 radix_tree_clear_tags(&mapping->page_tree, node, slot);
164 __radix_tree_replace(&mapping->page_tree, node, slot, shadow,
165 workingset_update_node, mapping);
169 mapping->nrexceptional += nr;
171 * Make sure the nrexceptional update is committed before
172 * the nrpages update so that final truncate racing
173 * with reclaim does not see both counters 0 at the
174 * same time and miss a shadow entry.
178 mapping->nrpages -= nr;
182 * Delete a page from the page cache and free it. Caller has to make
183 * sure the page is locked and that nobody else uses it - or that usage
184 * is safe. The caller must hold the mapping's tree_lock.
186 void __delete_from_page_cache(struct page *page, void *shadow)
188 struct address_space *mapping = page->mapping;
189 int nr = hpage_nr_pages(page);
191 trace_mm_filemap_delete_from_page_cache(page);
193 * if we're uptodate, flush out into the cleancache, otherwise
194 * invalidate any existing cleancache entries. We can't leave
195 * stale data around in the cleancache once our page is gone
197 if (PageUptodate(page) && PageMappedToDisk(page))
198 cleancache_put_page(page);
200 cleancache_invalidate_page(mapping, page);
202 VM_BUG_ON_PAGE(PageTail(page), page);
203 VM_BUG_ON_PAGE(page_mapped(page), page);
204 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
207 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
208 current->comm, page_to_pfn(page));
209 dump_page(page, "still mapped when deleted");
211 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
213 mapcount = page_mapcount(page);
214 if (mapping_exiting(mapping) &&
215 page_count(page) >= mapcount + 2) {
217 * All vmas have already been torn down, so it's
218 * a good bet that actually the page is unmapped,
219 * and we'd prefer not to leak it: if we're wrong,
220 * some other bad page check should catch it later.
222 page_mapcount_reset(page);
223 page_ref_sub(page, mapcount);
227 page_cache_tree_delete(mapping, page, shadow);
229 page->mapping = NULL;
230 /* Leave page->index set: truncation lookup relies upon it */
232 /* hugetlb pages do not participate in page cache accounting. */
236 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
237 if (PageSwapBacked(page)) {
238 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
239 if (PageTransHuge(page))
240 __dec_node_page_state(page, NR_SHMEM_THPS);
242 VM_BUG_ON_PAGE(PageTransHuge(page), page);
246 * At this point page must be either written or cleaned by truncate.
247 * Dirty page here signals a bug and loss of unwritten data.
249 * This fixes dirty accounting after removing the page entirely but
250 * leaves PageDirty set: it has no effect for truncated page and
251 * anyway will be cleared before returning page into buddy allocator.
253 if (WARN_ON_ONCE(PageDirty(page)))
254 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
258 * delete_from_page_cache - delete page from page cache
259 * @page: the page which the kernel is trying to remove from page cache
261 * This must be called only on pages that have been verified to be in the page
262 * cache and locked. It will never put the page into the free list, the caller
263 * has a reference on the page.
265 void delete_from_page_cache(struct page *page)
267 struct address_space *mapping = page_mapping(page);
269 void (*freepage)(struct page *);
271 BUG_ON(!PageLocked(page));
273 freepage = mapping->a_ops->freepage;
275 spin_lock_irqsave(&mapping->tree_lock, flags);
276 __delete_from_page_cache(page, NULL);
277 spin_unlock_irqrestore(&mapping->tree_lock, flags);
282 if (PageTransHuge(page) && !PageHuge(page)) {
283 page_ref_sub(page, HPAGE_PMD_NR);
284 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
289 EXPORT_SYMBOL(delete_from_page_cache);
291 int filemap_check_errors(struct address_space *mapping)
294 /* Check for outstanding write errors */
295 if (test_bit(AS_ENOSPC, &mapping->flags) &&
296 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
298 if (test_bit(AS_EIO, &mapping->flags) &&
299 test_and_clear_bit(AS_EIO, &mapping->flags))
303 EXPORT_SYMBOL(filemap_check_errors);
305 static int filemap_check_and_keep_errors(struct address_space *mapping)
307 /* Check for outstanding write errors */
308 if (test_bit(AS_EIO, &mapping->flags))
310 if (test_bit(AS_ENOSPC, &mapping->flags))
316 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
317 * @mapping: address space structure to write
318 * @start: offset in bytes where the range starts
319 * @end: offset in bytes where the range ends (inclusive)
320 * @sync_mode: enable synchronous operation
322 * Start writeback against all of a mapping's dirty pages that lie
323 * within the byte offsets <start, end> inclusive.
325 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
326 * opposed to a regular memory cleansing writeback. The difference between
327 * these two operations is that if a dirty page/buffer is encountered, it must
328 * be waited upon, and not just skipped over.
330 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
331 loff_t end, int sync_mode)
334 struct writeback_control wbc = {
335 .sync_mode = sync_mode,
336 .nr_to_write = LONG_MAX,
337 .range_start = start,
341 if (!mapping_cap_writeback_dirty(mapping))
344 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
345 ret = do_writepages(mapping, &wbc);
346 wbc_detach_inode(&wbc);
350 static inline int __filemap_fdatawrite(struct address_space *mapping,
353 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
356 int filemap_fdatawrite(struct address_space *mapping)
358 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
360 EXPORT_SYMBOL(filemap_fdatawrite);
362 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
365 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
367 EXPORT_SYMBOL(filemap_fdatawrite_range);
370 * filemap_flush - mostly a non-blocking flush
371 * @mapping: target address_space
373 * This is a mostly non-blocking flush. Not suitable for data-integrity
374 * purposes - I/O may not be started against all dirty pages.
376 int filemap_flush(struct address_space *mapping)
378 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
380 EXPORT_SYMBOL(filemap_flush);
383 * filemap_range_has_page - check if a page exists in range.
384 * @mapping: address space within which to check
385 * @start_byte: offset in bytes where the range starts
386 * @end_byte: offset in bytes where the range ends (inclusive)
388 * Find at least one page in the range supplied, usually used to check if
389 * direct writing in this range will trigger a writeback.
391 bool filemap_range_has_page(struct address_space *mapping,
392 loff_t start_byte, loff_t end_byte)
394 pgoff_t index = start_byte >> PAGE_SHIFT;
395 pgoff_t end = end_byte >> PAGE_SHIFT;
398 if (end_byte < start_byte)
401 if (mapping->nrpages == 0)
404 if (!find_get_pages_range(mapping, &index, end, 1, &page))
409 EXPORT_SYMBOL(filemap_range_has_page);
411 static void __filemap_fdatawait_range(struct address_space *mapping,
412 loff_t start_byte, loff_t end_byte)
414 pgoff_t index = start_byte >> PAGE_SHIFT;
415 pgoff_t end = end_byte >> PAGE_SHIFT;
419 if (end_byte < start_byte)
422 pagevec_init(&pvec, 0);
423 while (index <= end) {
426 nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
427 end, PAGECACHE_TAG_WRITEBACK, PAGEVEC_SIZE);
431 for (i = 0; i < nr_pages; i++) {
432 struct page *page = pvec.pages[i];
434 wait_on_page_writeback(page);
435 ClearPageError(page);
437 pagevec_release(&pvec);
443 * filemap_fdatawait_range - wait for writeback to complete
444 * @mapping: address space structure to wait for
445 * @start_byte: offset in bytes where the range starts
446 * @end_byte: offset in bytes where the range ends (inclusive)
448 * Walk the list of under-writeback pages of the given address space
449 * in the given range and wait for all of them. Check error status of
450 * the address space and return it.
452 * Since the error status of the address space is cleared by this function,
453 * callers are responsible for checking the return value and handling and/or
454 * reporting the error.
456 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
459 __filemap_fdatawait_range(mapping, start_byte, end_byte);
460 return filemap_check_errors(mapping);
462 EXPORT_SYMBOL(filemap_fdatawait_range);
465 * file_fdatawait_range - wait for writeback to complete
466 * @file: file pointing to address space structure to wait for
467 * @start_byte: offset in bytes where the range starts
468 * @end_byte: offset in bytes where the range ends (inclusive)
470 * Walk the list of under-writeback pages of the address space that file
471 * refers to, in the given range and wait for all of them. Check error
472 * status of the address space vs. the file->f_wb_err cursor and return it.
474 * Since the error status of the file is advanced by this function,
475 * callers are responsible for checking the return value and handling and/or
476 * reporting the error.
478 int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
480 struct address_space *mapping = file->f_mapping;
482 __filemap_fdatawait_range(mapping, start_byte, end_byte);
483 return file_check_and_advance_wb_err(file);
485 EXPORT_SYMBOL(file_fdatawait_range);
488 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
489 * @mapping: address space structure to wait for
491 * Walk the list of under-writeback pages of the given address space
492 * and wait for all of them. Unlike filemap_fdatawait(), this function
493 * does not clear error status of the address space.
495 * Use this function if callers don't handle errors themselves. Expected
496 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
499 int filemap_fdatawait_keep_errors(struct address_space *mapping)
501 __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
502 return filemap_check_and_keep_errors(mapping);
504 EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
506 static bool mapping_needs_writeback(struct address_space *mapping)
508 return (!dax_mapping(mapping) && mapping->nrpages) ||
509 (dax_mapping(mapping) && mapping->nrexceptional);
512 int filemap_write_and_wait(struct address_space *mapping)
516 if (mapping_needs_writeback(mapping)) {
517 err = filemap_fdatawrite(mapping);
519 * Even if the above returned error, the pages may be
520 * written partially (e.g. -ENOSPC), so we wait for it.
521 * But the -EIO is special case, it may indicate the worst
522 * thing (e.g. bug) happened, so we avoid waiting for it.
525 int err2 = filemap_fdatawait(mapping);
529 /* Clear any previously stored errors */
530 filemap_check_errors(mapping);
533 err = filemap_check_errors(mapping);
537 EXPORT_SYMBOL(filemap_write_and_wait);
540 * filemap_write_and_wait_range - write out & wait on a file range
541 * @mapping: the address_space for the pages
542 * @lstart: offset in bytes where the range starts
543 * @lend: offset in bytes where the range ends (inclusive)
545 * Write out and wait upon file offsets lstart->lend, inclusive.
547 * Note that @lend is inclusive (describes the last byte to be written) so
548 * that this function can be used to write to the very end-of-file (end = -1).
550 int filemap_write_and_wait_range(struct address_space *mapping,
551 loff_t lstart, loff_t lend)
555 if (mapping_needs_writeback(mapping)) {
556 err = __filemap_fdatawrite_range(mapping, lstart, lend,
558 /* See comment of filemap_write_and_wait() */
560 int err2 = filemap_fdatawait_range(mapping,
565 /* Clear any previously stored errors */
566 filemap_check_errors(mapping);
569 err = filemap_check_errors(mapping);
573 EXPORT_SYMBOL(filemap_write_and_wait_range);
575 void __filemap_set_wb_err(struct address_space *mapping, int err)
577 errseq_t eseq = errseq_set(&mapping->wb_err, err);
579 trace_filemap_set_wb_err(mapping, eseq);
581 EXPORT_SYMBOL(__filemap_set_wb_err);
584 * file_check_and_advance_wb_err - report wb error (if any) that was previously
585 * and advance wb_err to current one
586 * @file: struct file on which the error is being reported
588 * When userland calls fsync (or something like nfsd does the equivalent), we
589 * want to report any writeback errors that occurred since the last fsync (or
590 * since the file was opened if there haven't been any).
592 * Grab the wb_err from the mapping. If it matches what we have in the file,
593 * then just quickly return 0. The file is all caught up.
595 * If it doesn't match, then take the mapping value, set the "seen" flag in
596 * it and try to swap it into place. If it works, or another task beat us
597 * to it with the new value, then update the f_wb_err and return the error
598 * portion. The error at this point must be reported via proper channels
599 * (a'la fsync, or NFS COMMIT operation, etc.).
601 * While we handle mapping->wb_err with atomic operations, the f_wb_err
602 * value is protected by the f_lock since we must ensure that it reflects
603 * the latest value swapped in for this file descriptor.
605 int file_check_and_advance_wb_err(struct file *file)
608 errseq_t old = READ_ONCE(file->f_wb_err);
609 struct address_space *mapping = file->f_mapping;
611 /* Locklessly handle the common case where nothing has changed */
612 if (errseq_check(&mapping->wb_err, old)) {
613 /* Something changed, must use slow path */
614 spin_lock(&file->f_lock);
615 old = file->f_wb_err;
616 err = errseq_check_and_advance(&mapping->wb_err,
618 trace_file_check_and_advance_wb_err(file, old);
619 spin_unlock(&file->f_lock);
623 * We're mostly using this function as a drop in replacement for
624 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
625 * that the legacy code would have had on these flags.
627 clear_bit(AS_EIO, &mapping->flags);
628 clear_bit(AS_ENOSPC, &mapping->flags);
631 EXPORT_SYMBOL(file_check_and_advance_wb_err);
634 * file_write_and_wait_range - write out & wait on a file range
635 * @file: file pointing to address_space with pages
636 * @lstart: offset in bytes where the range starts
637 * @lend: offset in bytes where the range ends (inclusive)
639 * Write out and wait upon file offsets lstart->lend, inclusive.
641 * Note that @lend is inclusive (describes the last byte to be written) so
642 * that this function can be used to write to the very end-of-file (end = -1).
644 * After writing out and waiting on the data, we check and advance the
645 * f_wb_err cursor to the latest value, and return any errors detected there.
647 int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
650 struct address_space *mapping = file->f_mapping;
652 if (mapping_needs_writeback(mapping)) {
653 err = __filemap_fdatawrite_range(mapping, lstart, lend,
655 /* See comment of filemap_write_and_wait() */
657 __filemap_fdatawait_range(mapping, lstart, lend);
659 err2 = file_check_and_advance_wb_err(file);
664 EXPORT_SYMBOL(file_write_and_wait_range);
667 * replace_page_cache_page - replace a pagecache page with a new one
668 * @old: page to be replaced
669 * @new: page to replace with
670 * @gfp_mask: allocation mode
672 * This function replaces a page in the pagecache with a new one. On
673 * success it acquires the pagecache reference for the new page and
674 * drops it for the old page. Both the old and new pages must be
675 * locked. This function does not add the new page to the LRU, the
676 * caller must do that.
678 * The remove + add is atomic. The only way this function can fail is
679 * memory allocation failure.
681 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
685 VM_BUG_ON_PAGE(!PageLocked(old), old);
686 VM_BUG_ON_PAGE(!PageLocked(new), new);
687 VM_BUG_ON_PAGE(new->mapping, new);
689 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
691 struct address_space *mapping = old->mapping;
692 void (*freepage)(struct page *);
695 pgoff_t offset = old->index;
696 freepage = mapping->a_ops->freepage;
699 new->mapping = mapping;
702 spin_lock_irqsave(&mapping->tree_lock, flags);
703 __delete_from_page_cache(old, NULL);
704 error = page_cache_tree_insert(mapping, new, NULL);
708 * hugetlb pages do not participate in page cache accounting.
711 __inc_node_page_state(new, NR_FILE_PAGES);
712 if (PageSwapBacked(new))
713 __inc_node_page_state(new, NR_SHMEM);
714 spin_unlock_irqrestore(&mapping->tree_lock, flags);
715 mem_cgroup_migrate(old, new);
716 radix_tree_preload_end();
724 EXPORT_SYMBOL_GPL(replace_page_cache_page);
726 static int __add_to_page_cache_locked(struct page *page,
727 struct address_space *mapping,
728 pgoff_t offset, gfp_t gfp_mask,
731 int huge = PageHuge(page);
732 struct mem_cgroup *memcg;
735 VM_BUG_ON_PAGE(!PageLocked(page), page);
736 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
739 error = mem_cgroup_try_charge(page, current->mm,
740 gfp_mask, &memcg, false);
745 error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
748 mem_cgroup_cancel_charge(page, memcg, false);
753 page->mapping = mapping;
754 page->index = offset;
756 spin_lock_irq(&mapping->tree_lock);
757 error = page_cache_tree_insert(mapping, page, shadowp);
758 radix_tree_preload_end();
762 /* hugetlb pages do not participate in page cache accounting. */
764 __inc_node_page_state(page, NR_FILE_PAGES);
765 spin_unlock_irq(&mapping->tree_lock);
767 mem_cgroup_commit_charge(page, memcg, false, false);
768 trace_mm_filemap_add_to_page_cache(page);
771 page->mapping = NULL;
772 /* Leave page->index set: truncation relies upon it */
773 spin_unlock_irq(&mapping->tree_lock);
775 mem_cgroup_cancel_charge(page, memcg, false);
781 * add_to_page_cache_locked - add a locked page to the pagecache
783 * @mapping: the page's address_space
784 * @offset: page index
785 * @gfp_mask: page allocation mode
787 * This function is used to add a page to the pagecache. It must be locked.
788 * This function does not add the page to the LRU. The caller must do that.
790 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
791 pgoff_t offset, gfp_t gfp_mask)
793 return __add_to_page_cache_locked(page, mapping, offset,
796 EXPORT_SYMBOL(add_to_page_cache_locked);
798 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
799 pgoff_t offset, gfp_t gfp_mask)
804 __SetPageLocked(page);
805 ret = __add_to_page_cache_locked(page, mapping, offset,
808 __ClearPageLocked(page);
811 * The page might have been evicted from cache only
812 * recently, in which case it should be activated like
813 * any other repeatedly accessed page.
814 * The exception is pages getting rewritten; evicting other
815 * data from the working set, only to cache data that will
816 * get overwritten with something else, is a waste of memory.
818 if (!(gfp_mask & __GFP_WRITE) &&
819 shadow && workingset_refault(shadow)) {
821 workingset_activation(page);
823 ClearPageActive(page);
828 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
831 struct page *__page_cache_alloc(gfp_t gfp)
836 if (cpuset_do_page_mem_spread()) {
837 unsigned int cpuset_mems_cookie;
839 cpuset_mems_cookie = read_mems_allowed_begin();
840 n = cpuset_mem_spread_node();
841 page = __alloc_pages_node(n, gfp, 0);
842 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
846 return alloc_pages(gfp, 0);
848 EXPORT_SYMBOL(__page_cache_alloc);
852 * In order to wait for pages to become available there must be
853 * waitqueues associated with pages. By using a hash table of
854 * waitqueues where the bucket discipline is to maintain all
855 * waiters on the same queue and wake all when any of the pages
856 * become available, and for the woken contexts to check to be
857 * sure the appropriate page became available, this saves space
858 * at a cost of "thundering herd" phenomena during rare hash
861 #define PAGE_WAIT_TABLE_BITS 8
862 #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
863 static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
865 static wait_queue_head_t *page_waitqueue(struct page *page)
867 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
870 void __init pagecache_init(void)
874 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
875 init_waitqueue_head(&page_wait_table[i]);
877 page_writeback_init();
880 /* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
881 struct wait_page_key {
887 struct wait_page_queue {
890 wait_queue_entry_t wait;
893 static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
895 struct wait_page_key *key = arg;
896 struct wait_page_queue *wait_page
897 = container_of(wait, struct wait_page_queue, wait);
899 if (wait_page->page != key->page)
903 if (wait_page->bit_nr != key->bit_nr)
906 /* Stop walking if it's locked */
907 if (test_bit(key->bit_nr, &key->page->flags))
910 return autoremove_wake_function(wait, mode, sync, key);
913 static void wake_up_page_bit(struct page *page, int bit_nr)
915 wait_queue_head_t *q = page_waitqueue(page);
916 struct wait_page_key key;
918 wait_queue_entry_t bookmark;
925 bookmark.private = NULL;
926 bookmark.func = NULL;
927 INIT_LIST_HEAD(&bookmark.entry);
929 spin_lock_irqsave(&q->lock, flags);
930 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
932 while (bookmark.flags & WQ_FLAG_BOOKMARK) {
934 * Take a breather from holding the lock,
935 * allow pages that finish wake up asynchronously
936 * to acquire the lock and remove themselves
939 spin_unlock_irqrestore(&q->lock, flags);
941 spin_lock_irqsave(&q->lock, flags);
942 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
946 * It is possible for other pages to have collided on the waitqueue
947 * hash, so in that case check for a page match. That prevents a long-
950 * It is still possible to miss a case here, when we woke page waiters
951 * and removed them from the waitqueue, but there are still other
954 if (!waitqueue_active(q) || !key.page_match) {
955 ClearPageWaiters(page);
957 * It's possible to miss clearing Waiters here, when we woke
958 * our page waiters, but the hashed waitqueue has waiters for
961 * That's okay, it's a rare case. The next waker will clear it.
964 spin_unlock_irqrestore(&q->lock, flags);
967 static void wake_up_page(struct page *page, int bit)
969 if (!PageWaiters(page))
971 wake_up_page_bit(page, bit);
974 static inline int wait_on_page_bit_common(wait_queue_head_t *q,
975 struct page *page, int bit_nr, int state, bool lock)
977 struct wait_page_queue wait_page;
978 wait_queue_entry_t *wait = &wait_page.wait;
982 wait->flags = lock ? WQ_FLAG_EXCLUSIVE : 0;
983 wait->func = wake_page_function;
984 wait_page.page = page;
985 wait_page.bit_nr = bit_nr;
988 spin_lock_irq(&q->lock);
990 if (likely(list_empty(&wait->entry))) {
991 __add_wait_queue_entry_tail(q, wait);
992 SetPageWaiters(page);
995 set_current_state(state);
997 spin_unlock_irq(&q->lock);
999 if (likely(test_bit(bit_nr, &page->flags))) {
1004 if (!test_and_set_bit_lock(bit_nr, &page->flags))
1007 if (!test_bit(bit_nr, &page->flags))
1011 if (unlikely(signal_pending_state(state, current))) {
1017 finish_wait(q, wait);
1020 * A signal could leave PageWaiters set. Clearing it here if
1021 * !waitqueue_active would be possible (by open-coding finish_wait),
1022 * but still fail to catch it in the case of wait hash collision. We
1023 * already can fail to clear wait hash collision cases, so don't
1024 * bother with signals either.
1030 void wait_on_page_bit(struct page *page, int bit_nr)
1032 wait_queue_head_t *q = page_waitqueue(page);
1033 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
1035 EXPORT_SYMBOL(wait_on_page_bit);
1037 int wait_on_page_bit_killable(struct page *page, int bit_nr)
1039 wait_queue_head_t *q = page_waitqueue(page);
1040 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
1044 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1045 * @page: Page defining the wait queue of interest
1046 * @waiter: Waiter to add to the queue
1048 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1050 void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
1052 wait_queue_head_t *q = page_waitqueue(page);
1053 unsigned long flags;
1055 spin_lock_irqsave(&q->lock, flags);
1056 __add_wait_queue_entry_tail(q, waiter);
1057 SetPageWaiters(page);
1058 spin_unlock_irqrestore(&q->lock, flags);
1060 EXPORT_SYMBOL_GPL(add_page_wait_queue);
1062 #ifndef clear_bit_unlock_is_negative_byte
1065 * PG_waiters is the high bit in the same byte as PG_lock.
1067 * On x86 (and on many other architectures), we can clear PG_lock and
1068 * test the sign bit at the same time. But if the architecture does
1069 * not support that special operation, we just do this all by hand
1072 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1073 * being cleared, but a memory barrier should be unneccssary since it is
1074 * in the same byte as PG_locked.
1076 static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
1078 clear_bit_unlock(nr, mem);
1079 /* smp_mb__after_atomic(); */
1080 return test_bit(PG_waiters, mem);
1086 * unlock_page - unlock a locked page
1089 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
1090 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1091 * mechanism between PageLocked pages and PageWriteback pages is shared.
1092 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1094 * Note that this depends on PG_waiters being the sign bit in the byte
1095 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1096 * clear the PG_locked bit and test PG_waiters at the same time fairly
1097 * portably (architectures that do LL/SC can test any bit, while x86 can
1098 * test the sign bit).
1100 void unlock_page(struct page *page)
1102 BUILD_BUG_ON(PG_waiters != 7);
1103 page = compound_head(page);
1104 VM_BUG_ON_PAGE(!PageLocked(page), page);
1105 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
1106 wake_up_page_bit(page, PG_locked);
1108 EXPORT_SYMBOL(unlock_page);
1111 * end_page_writeback - end writeback against a page
1114 void end_page_writeback(struct page *page)
1117 * TestClearPageReclaim could be used here but it is an atomic
1118 * operation and overkill in this particular case. Failing to
1119 * shuffle a page marked for immediate reclaim is too mild to
1120 * justify taking an atomic operation penalty at the end of
1121 * ever page writeback.
1123 if (PageReclaim(page)) {
1124 ClearPageReclaim(page);
1125 rotate_reclaimable_page(page);
1128 if (!test_clear_page_writeback(page))
1131 smp_mb__after_atomic();
1132 wake_up_page(page, PG_writeback);
1134 EXPORT_SYMBOL(end_page_writeback);
1137 * After completing I/O on a page, call this routine to update the page
1138 * flags appropriately
1140 void page_endio(struct page *page, bool is_write, int err)
1144 SetPageUptodate(page);
1146 ClearPageUptodate(page);
1152 struct address_space *mapping;
1155 mapping = page_mapping(page);
1157 mapping_set_error(mapping, err);
1159 end_page_writeback(page);
1162 EXPORT_SYMBOL_GPL(page_endio);
1165 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1166 * @__page: the page to lock
1168 void __lock_page(struct page *__page)
1170 struct page *page = compound_head(__page);
1171 wait_queue_head_t *q = page_waitqueue(page);
1172 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
1174 EXPORT_SYMBOL(__lock_page);
1176 int __lock_page_killable(struct page *__page)
1178 struct page *page = compound_head(__page);
1179 wait_queue_head_t *q = page_waitqueue(page);
1180 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
1182 EXPORT_SYMBOL_GPL(__lock_page_killable);
1186 * 1 - page is locked; mmap_sem is still held.
1187 * 0 - page is not locked.
1188 * mmap_sem has been released (up_read()), unless flags had both
1189 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1190 * which case mmap_sem is still held.
1192 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1193 * with the page locked and the mmap_sem unperturbed.
1195 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1198 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1200 * CAUTION! In this case, mmap_sem is not released
1201 * even though return 0.
1203 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1206 up_read(&mm->mmap_sem);
1207 if (flags & FAULT_FLAG_KILLABLE)
1208 wait_on_page_locked_killable(page);
1210 wait_on_page_locked(page);
1213 if (flags & FAULT_FLAG_KILLABLE) {
1216 ret = __lock_page_killable(page);
1218 up_read(&mm->mmap_sem);
1228 * page_cache_next_hole - find the next hole (not-present entry)
1231 * @max_scan: maximum range to search
1233 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1234 * lowest indexed hole.
1236 * Returns: the index of the hole if found, otherwise returns an index
1237 * outside of the set specified (in which case 'return - index >=
1238 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1241 * page_cache_next_hole may be called under rcu_read_lock. However,
1242 * like radix_tree_gang_lookup, this will not atomically search a
1243 * snapshot of the tree at a single point in time. For example, if a
1244 * hole is created at index 5, then subsequently a hole is created at
1245 * index 10, page_cache_next_hole covering both indexes may return 10
1246 * if called under rcu_read_lock.
1248 pgoff_t page_cache_next_hole(struct address_space *mapping,
1249 pgoff_t index, unsigned long max_scan)
1253 for (i = 0; i < max_scan; i++) {
1256 page = radix_tree_lookup(&mapping->page_tree, index);
1257 if (!page || radix_tree_exceptional_entry(page))
1266 EXPORT_SYMBOL(page_cache_next_hole);
1269 * page_cache_prev_hole - find the prev hole (not-present entry)
1272 * @max_scan: maximum range to search
1274 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1277 * Returns: the index of the hole if found, otherwise returns an index
1278 * outside of the set specified (in which case 'index - return >=
1279 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1282 * page_cache_prev_hole may be called under rcu_read_lock. However,
1283 * like radix_tree_gang_lookup, this will not atomically search a
1284 * snapshot of the tree at a single point in time. For example, if a
1285 * hole is created at index 10, then subsequently a hole is created at
1286 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1287 * called under rcu_read_lock.
1289 pgoff_t page_cache_prev_hole(struct address_space *mapping,
1290 pgoff_t index, unsigned long max_scan)
1294 for (i = 0; i < max_scan; i++) {
1297 page = radix_tree_lookup(&mapping->page_tree, index);
1298 if (!page || radix_tree_exceptional_entry(page))
1301 if (index == ULONG_MAX)
1307 EXPORT_SYMBOL(page_cache_prev_hole);
1310 * find_get_entry - find and get a page cache entry
1311 * @mapping: the address_space to search
1312 * @offset: the page cache index
1314 * Looks up the page cache slot at @mapping & @offset. If there is a
1315 * page cache page, it is returned with an increased refcount.
1317 * If the slot holds a shadow entry of a previously evicted page, or a
1318 * swap entry from shmem/tmpfs, it is returned.
1320 * Otherwise, %NULL is returned.
1322 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1325 struct page *head, *page;
1330 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
1332 page = radix_tree_deref_slot(pagep);
1333 if (unlikely(!page))
1335 if (radix_tree_exception(page)) {
1336 if (radix_tree_deref_retry(page))
1339 * A shadow entry of a recently evicted page,
1340 * or a swap entry from shmem/tmpfs. Return
1341 * it without attempting to raise page count.
1346 head = compound_head(page);
1347 if (!page_cache_get_speculative(head))
1350 /* The page was split under us? */
1351 if (compound_head(page) != head) {
1357 * Has the page moved?
1358 * This is part of the lockless pagecache protocol. See
1359 * include/linux/pagemap.h for details.
1361 if (unlikely(page != *pagep)) {
1371 EXPORT_SYMBOL(find_get_entry);
1374 * find_lock_entry - locate, pin and lock a page cache entry
1375 * @mapping: the address_space to search
1376 * @offset: the page cache index
1378 * Looks up the page cache slot at @mapping & @offset. If there is a
1379 * page cache page, it is returned locked and with an increased
1382 * If the slot holds a shadow entry of a previously evicted page, or a
1383 * swap entry from shmem/tmpfs, it is returned.
1385 * Otherwise, %NULL is returned.
1387 * find_lock_entry() may sleep.
1389 struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1394 page = find_get_entry(mapping, offset);
1395 if (page && !radix_tree_exception(page)) {
1397 /* Has the page been truncated? */
1398 if (unlikely(page_mapping(page) != mapping)) {
1403 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
1407 EXPORT_SYMBOL(find_lock_entry);
1410 * pagecache_get_page - find and get a page reference
1411 * @mapping: the address_space to search
1412 * @offset: the page index
1413 * @fgp_flags: PCG flags
1414 * @gfp_mask: gfp mask to use for the page cache data page allocation
1416 * Looks up the page cache slot at @mapping & @offset.
1418 * PCG flags modify how the page is returned.
1420 * @fgp_flags can be:
1422 * - FGP_ACCESSED: the page will be marked accessed
1423 * - FGP_LOCK: Page is return locked
1424 * - FGP_CREAT: If page is not present then a new page is allocated using
1425 * @gfp_mask and added to the page cache and the VM's LRU
1426 * list. The page is returned locked and with an increased
1427 * refcount. Otherwise, NULL is returned.
1429 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1430 * if the GFP flags specified for FGP_CREAT are atomic.
1432 * If there is a page cache page, it is returned with an increased refcount.
1434 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1435 int fgp_flags, gfp_t gfp_mask)
1440 page = find_get_entry(mapping, offset);
1441 if (radix_tree_exceptional_entry(page))
1446 if (fgp_flags & FGP_LOCK) {
1447 if (fgp_flags & FGP_NOWAIT) {
1448 if (!trylock_page(page)) {
1456 /* Has the page been truncated? */
1457 if (unlikely(page->mapping != mapping)) {
1462 VM_BUG_ON_PAGE(page->index != offset, page);
1465 if (page && (fgp_flags & FGP_ACCESSED))
1466 mark_page_accessed(page);
1469 if (!page && (fgp_flags & FGP_CREAT)) {
1471 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1472 gfp_mask |= __GFP_WRITE;
1473 if (fgp_flags & FGP_NOFS)
1474 gfp_mask &= ~__GFP_FS;
1476 page = __page_cache_alloc(gfp_mask);
1480 if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
1481 fgp_flags |= FGP_LOCK;
1483 /* Init accessed so avoid atomic mark_page_accessed later */
1484 if (fgp_flags & FGP_ACCESSED)
1485 __SetPageReferenced(page);
1487 err = add_to_page_cache_lru(page, mapping, offset,
1488 gfp_mask & GFP_RECLAIM_MASK);
1489 if (unlikely(err)) {
1499 EXPORT_SYMBOL(pagecache_get_page);
1502 * find_get_entries - gang pagecache lookup
1503 * @mapping: The address_space to search
1504 * @start: The starting page cache index
1505 * @nr_entries: The maximum number of entries
1506 * @entries: Where the resulting entries are placed
1507 * @indices: The cache indices corresponding to the entries in @entries
1509 * find_get_entries() will search for and return a group of up to
1510 * @nr_entries entries in the mapping. The entries are placed at
1511 * @entries. find_get_entries() takes a reference against any actual
1514 * The search returns a group of mapping-contiguous page cache entries
1515 * with ascending indexes. There may be holes in the indices due to
1516 * not-present pages.
1518 * Any shadow entries of evicted pages, or swap entries from
1519 * shmem/tmpfs, are included in the returned array.
1521 * find_get_entries() returns the number of pages and shadow entries
1524 unsigned find_get_entries(struct address_space *mapping,
1525 pgoff_t start, unsigned int nr_entries,
1526 struct page **entries, pgoff_t *indices)
1529 unsigned int ret = 0;
1530 struct radix_tree_iter iter;
1536 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1537 struct page *head, *page;
1539 page = radix_tree_deref_slot(slot);
1540 if (unlikely(!page))
1542 if (radix_tree_exception(page)) {
1543 if (radix_tree_deref_retry(page)) {
1544 slot = radix_tree_iter_retry(&iter);
1548 * A shadow entry of a recently evicted page, a swap
1549 * entry from shmem/tmpfs or a DAX entry. Return it
1550 * without attempting to raise page count.
1555 head = compound_head(page);
1556 if (!page_cache_get_speculative(head))
1559 /* The page was split under us? */
1560 if (compound_head(page) != head) {
1565 /* Has the page moved? */
1566 if (unlikely(page != *slot)) {
1571 indices[ret] = iter.index;
1572 entries[ret] = page;
1573 if (++ret == nr_entries)
1581 * find_get_pages_range - gang pagecache lookup
1582 * @mapping: The address_space to search
1583 * @start: The starting page index
1584 * @end: The final page index (inclusive)
1585 * @nr_pages: The maximum number of pages
1586 * @pages: Where the resulting pages are placed
1588 * find_get_pages_range() will search for and return a group of up to @nr_pages
1589 * pages in the mapping starting at index @start and up to index @end
1590 * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
1591 * a reference against the returned pages.
1593 * The search returns a group of mapping-contiguous pages with ascending
1594 * indexes. There may be holes in the indices due to not-present pages.
1595 * We also update @start to index the next page for the traversal.
1597 * find_get_pages_range() returns the number of pages which were found. If this
1598 * number is smaller than @nr_pages, the end of specified range has been
1601 unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
1602 pgoff_t end, unsigned int nr_pages,
1603 struct page **pages)
1605 struct radix_tree_iter iter;
1609 if (unlikely(!nr_pages))
1613 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, *start) {
1614 struct page *head, *page;
1616 if (iter.index > end)
1619 page = radix_tree_deref_slot(slot);
1620 if (unlikely(!page))
1623 if (radix_tree_exception(page)) {
1624 if (radix_tree_deref_retry(page)) {
1625 slot = radix_tree_iter_retry(&iter);
1629 * A shadow entry of a recently evicted page,
1630 * or a swap entry from shmem/tmpfs. Skip
1636 head = compound_head(page);
1637 if (!page_cache_get_speculative(head))
1640 /* The page was split under us? */
1641 if (compound_head(page) != head) {
1646 /* Has the page moved? */
1647 if (unlikely(page != *slot)) {
1653 if (++ret == nr_pages) {
1654 *start = pages[ret - 1]->index + 1;
1660 * We come here when there is no page beyond @end. We take care to not
1661 * overflow the index @start as it confuses some of the callers. This
1662 * breaks the iteration when there is page at index -1 but that is
1663 * already broken anyway.
1665 if (end == (pgoff_t)-1)
1666 *start = (pgoff_t)-1;
1676 * find_get_pages_contig - gang contiguous pagecache lookup
1677 * @mapping: The address_space to search
1678 * @index: The starting page index
1679 * @nr_pages: The maximum number of pages
1680 * @pages: Where the resulting pages are placed
1682 * find_get_pages_contig() works exactly like find_get_pages(), except
1683 * that the returned number of pages are guaranteed to be contiguous.
1685 * find_get_pages_contig() returns the number of pages which were found.
1687 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1688 unsigned int nr_pages, struct page **pages)
1690 struct radix_tree_iter iter;
1692 unsigned int ret = 0;
1694 if (unlikely(!nr_pages))
1698 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
1699 struct page *head, *page;
1701 page = radix_tree_deref_slot(slot);
1702 /* The hole, there no reason to continue */
1703 if (unlikely(!page))
1706 if (radix_tree_exception(page)) {
1707 if (radix_tree_deref_retry(page)) {
1708 slot = radix_tree_iter_retry(&iter);
1712 * A shadow entry of a recently evicted page,
1713 * or a swap entry from shmem/tmpfs. Stop
1714 * looking for contiguous pages.
1719 head = compound_head(page);
1720 if (!page_cache_get_speculative(head))
1723 /* The page was split under us? */
1724 if (compound_head(page) != head) {
1729 /* Has the page moved? */
1730 if (unlikely(page != *slot)) {
1736 * must check mapping and index after taking the ref.
1737 * otherwise we can get both false positives and false
1738 * negatives, which is just confusing to the caller.
1740 if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
1746 if (++ret == nr_pages)
1752 EXPORT_SYMBOL(find_get_pages_contig);
1755 * find_get_pages_range_tag - find and return pages in given range matching @tag
1756 * @mapping: the address_space to search
1757 * @index: the starting page index
1758 * @end: The final page index (inclusive)
1759 * @tag: the tag index
1760 * @nr_pages: the maximum number of pages
1761 * @pages: where the resulting pages are placed
1763 * Like find_get_pages, except we only return pages which are tagged with
1764 * @tag. We update @index to index the next page for the traversal.
1766 unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
1767 pgoff_t end, int tag, unsigned int nr_pages,
1768 struct page **pages)
1770 struct radix_tree_iter iter;
1774 if (unlikely(!nr_pages))
1778 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1779 &iter, *index, tag) {
1780 struct page *head, *page;
1782 if (iter.index > end)
1785 page = radix_tree_deref_slot(slot);
1786 if (unlikely(!page))
1789 if (radix_tree_exception(page)) {
1790 if (radix_tree_deref_retry(page)) {
1791 slot = radix_tree_iter_retry(&iter);
1795 * A shadow entry of a recently evicted page.
1797 * Those entries should never be tagged, but
1798 * this tree walk is lockless and the tags are
1799 * looked up in bulk, one radix tree node at a
1800 * time, so there is a sizable window for page
1801 * reclaim to evict a page we saw tagged.
1808 head = compound_head(page);
1809 if (!page_cache_get_speculative(head))
1812 /* The page was split under us? */
1813 if (compound_head(page) != head) {
1818 /* Has the page moved? */
1819 if (unlikely(page != *slot)) {
1825 if (++ret == nr_pages) {
1826 *index = pages[ret - 1]->index + 1;
1832 * We come here when we got at @end. We take care to not overflow the
1833 * index @index as it confuses some of the callers. This breaks the
1834 * iteration when there is page at index -1 but that is already broken
1837 if (end == (pgoff_t)-1)
1838 *index = (pgoff_t)-1;
1846 EXPORT_SYMBOL(find_get_pages_range_tag);
1849 * find_get_entries_tag - find and return entries that match @tag
1850 * @mapping: the address_space to search
1851 * @start: the starting page cache index
1852 * @tag: the tag index
1853 * @nr_entries: the maximum number of entries
1854 * @entries: where the resulting entries are placed
1855 * @indices: the cache indices corresponding to the entries in @entries
1857 * Like find_get_entries, except we only return entries which are tagged with
1860 unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
1861 int tag, unsigned int nr_entries,
1862 struct page **entries, pgoff_t *indices)
1865 unsigned int ret = 0;
1866 struct radix_tree_iter iter;
1872 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1873 &iter, start, tag) {
1874 struct page *head, *page;
1876 page = radix_tree_deref_slot(slot);
1877 if (unlikely(!page))
1879 if (radix_tree_exception(page)) {
1880 if (radix_tree_deref_retry(page)) {
1881 slot = radix_tree_iter_retry(&iter);
1886 * A shadow entry of a recently evicted page, a swap
1887 * entry from shmem/tmpfs or a DAX entry. Return it
1888 * without attempting to raise page count.
1893 head = compound_head(page);
1894 if (!page_cache_get_speculative(head))
1897 /* The page was split under us? */
1898 if (compound_head(page) != head) {
1903 /* Has the page moved? */
1904 if (unlikely(page != *slot)) {
1909 indices[ret] = iter.index;
1910 entries[ret] = page;
1911 if (++ret == nr_entries)
1917 EXPORT_SYMBOL(find_get_entries_tag);
1920 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1921 * a _large_ part of the i/o request. Imagine the worst scenario:
1923 * ---R__________________________________________B__________
1924 * ^ reading here ^ bad block(assume 4k)
1926 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1927 * => failing the whole request => read(R) => read(R+1) =>
1928 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1929 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1930 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1932 * It is going insane. Fix it by quickly scaling down the readahead size.
1934 static void shrink_readahead_size_eio(struct file *filp,
1935 struct file_ra_state *ra)
1941 * generic_file_buffered_read - generic file read routine
1942 * @iocb: the iocb to read
1943 * @iter: data destination
1944 * @written: already copied
1946 * This is a generic file read routine, and uses the
1947 * mapping->a_ops->readpage() function for the actual low-level stuff.
1949 * This is really ugly. But the goto's actually try to clarify some
1950 * of the logic when it comes to error handling etc.
1952 static ssize_t generic_file_buffered_read(struct kiocb *iocb,
1953 struct iov_iter *iter, ssize_t written)
1955 struct file *filp = iocb->ki_filp;
1956 struct address_space *mapping = filp->f_mapping;
1957 struct inode *inode = mapping->host;
1958 struct file_ra_state *ra = &filp->f_ra;
1959 loff_t *ppos = &iocb->ki_pos;
1963 unsigned long offset; /* offset into pagecache page */
1964 unsigned int prev_offset;
1967 if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
1969 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
1971 index = *ppos >> PAGE_SHIFT;
1972 prev_index = ra->prev_pos >> PAGE_SHIFT;
1973 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
1974 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
1975 offset = *ppos & ~PAGE_MASK;
1981 unsigned long nr, ret;
1985 if (fatal_signal_pending(current)) {
1990 page = find_get_page(mapping, index);
1992 if (iocb->ki_flags & IOCB_NOWAIT)
1994 page_cache_sync_readahead(mapping,
1996 index, last_index - index);
1997 page = find_get_page(mapping, index);
1998 if (unlikely(page == NULL))
1999 goto no_cached_page;
2001 if (PageReadahead(page)) {
2002 page_cache_async_readahead(mapping,
2004 index, last_index - index);
2006 if (!PageUptodate(page)) {
2007 if (iocb->ki_flags & IOCB_NOWAIT) {
2013 * See comment in do_read_cache_page on why
2014 * wait_on_page_locked is used to avoid unnecessarily
2015 * serialisations and why it's safe.
2017 error = wait_on_page_locked_killable(page);
2018 if (unlikely(error))
2019 goto readpage_error;
2020 if (PageUptodate(page))
2023 if (inode->i_blkbits == PAGE_SHIFT ||
2024 !mapping->a_ops->is_partially_uptodate)
2025 goto page_not_up_to_date;
2026 /* pipes can't handle partially uptodate pages */
2027 if (unlikely(iter->type & ITER_PIPE))
2028 goto page_not_up_to_date;
2029 if (!trylock_page(page))
2030 goto page_not_up_to_date;
2031 /* Did it get truncated before we got the lock? */
2033 goto page_not_up_to_date_locked;
2034 if (!mapping->a_ops->is_partially_uptodate(page,
2035 offset, iter->count))
2036 goto page_not_up_to_date_locked;
2041 * i_size must be checked after we know the page is Uptodate.
2043 * Checking i_size after the check allows us to calculate
2044 * the correct value for "nr", which means the zero-filled
2045 * part of the page is not copied back to userspace (unless
2046 * another truncate extends the file - this is desired though).
2049 isize = i_size_read(inode);
2050 end_index = (isize - 1) >> PAGE_SHIFT;
2051 if (unlikely(!isize || index > end_index)) {
2056 /* nr is the maximum number of bytes to copy from this page */
2058 if (index == end_index) {
2059 nr = ((isize - 1) & ~PAGE_MASK) + 1;
2067 /* If users can be writing to this page using arbitrary
2068 * virtual addresses, take care about potential aliasing
2069 * before reading the page on the kernel side.
2071 if (mapping_writably_mapped(mapping))
2072 flush_dcache_page(page);
2075 * When a sequential read accesses a page several times,
2076 * only mark it as accessed the first time.
2078 if (prev_index != index || offset != prev_offset)
2079 mark_page_accessed(page);
2083 * Ok, we have the page, and it's up-to-date, so
2084 * now we can copy it to user space...
2087 ret = copy_page_to_iter(page, offset, nr, iter);
2089 index += offset >> PAGE_SHIFT;
2090 offset &= ~PAGE_MASK;
2091 prev_offset = offset;
2095 if (!iov_iter_count(iter))
2103 page_not_up_to_date:
2104 /* Get exclusive access to the page ... */
2105 error = lock_page_killable(page);
2106 if (unlikely(error))
2107 goto readpage_error;
2109 page_not_up_to_date_locked:
2110 /* Did it get truncated before we got the lock? */
2111 if (!page->mapping) {
2117 /* Did somebody else fill it already? */
2118 if (PageUptodate(page)) {
2125 * A previous I/O error may have been due to temporary
2126 * failures, eg. multipath errors.
2127 * PG_error will be set again if readpage fails.
2129 ClearPageError(page);
2130 /* Start the actual read. The read will unlock the page. */
2131 error = mapping->a_ops->readpage(filp, page);
2133 if (unlikely(error)) {
2134 if (error == AOP_TRUNCATED_PAGE) {
2139 goto readpage_error;
2142 if (!PageUptodate(page)) {
2143 error = lock_page_killable(page);
2144 if (unlikely(error))
2145 goto readpage_error;
2146 if (!PageUptodate(page)) {
2147 if (page->mapping == NULL) {
2149 * invalidate_mapping_pages got it
2156 shrink_readahead_size_eio(filp, ra);
2158 goto readpage_error;
2166 /* UHHUH! A synchronous read error occurred. Report it */
2172 * Ok, it wasn't cached, so we need to create a new
2175 page = page_cache_alloc_cold(mapping);
2180 error = add_to_page_cache_lru(page, mapping, index,
2181 mapping_gfp_constraint(mapping, GFP_KERNEL));
2184 if (error == -EEXIST) {
2196 ra->prev_pos = prev_index;
2197 ra->prev_pos <<= PAGE_SHIFT;
2198 ra->prev_pos |= prev_offset;
2200 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
2201 file_accessed(filp);
2202 return written ? written : error;
2206 * generic_file_read_iter - generic filesystem read routine
2207 * @iocb: kernel I/O control block
2208 * @iter: destination for the data read
2210 * This is the "read_iter()" routine for all filesystems
2211 * that can use the page cache directly.
2214 generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2216 size_t count = iov_iter_count(iter);
2220 goto out; /* skip atime */
2222 if (iocb->ki_flags & IOCB_DIRECT) {
2223 struct file *file = iocb->ki_filp;
2224 struct address_space *mapping = file->f_mapping;
2225 struct inode *inode = mapping->host;
2228 size = i_size_read(inode);
2229 if (iocb->ki_flags & IOCB_NOWAIT) {
2230 if (filemap_range_has_page(mapping, iocb->ki_pos,
2231 iocb->ki_pos + count - 1))
2234 retval = filemap_write_and_wait_range(mapping,
2236 iocb->ki_pos + count - 1);
2241 file_accessed(file);
2243 retval = mapping->a_ops->direct_IO(iocb, iter);
2245 iocb->ki_pos += retval;
2248 iov_iter_revert(iter, count - iov_iter_count(iter));
2251 * Btrfs can have a short DIO read if we encounter
2252 * compressed extents, so if there was an error, or if
2253 * we've already read everything we wanted to, or if
2254 * there was a short read because we hit EOF, go ahead
2255 * and return. Otherwise fallthrough to buffered io for
2256 * the rest of the read. Buffered reads will not work for
2257 * DAX files, so don't bother trying.
2259 if (retval < 0 || !count || iocb->ki_pos >= size ||
2264 retval = generic_file_buffered_read(iocb, iter, retval);
2268 EXPORT_SYMBOL(generic_file_read_iter);
2272 * page_cache_read - adds requested page to the page cache if not already there
2273 * @file: file to read
2274 * @offset: page index
2275 * @gfp_mask: memory allocation flags
2277 * This adds the requested page to the page cache if it isn't already there,
2278 * and schedules an I/O to read in its contents from disk.
2280 static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
2282 struct address_space *mapping = file->f_mapping;
2287 page = __page_cache_alloc(gfp_mask|__GFP_COLD);
2291 ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
2293 ret = mapping->a_ops->readpage(file, page);
2294 else if (ret == -EEXIST)
2295 ret = 0; /* losing race to add is OK */
2299 } while (ret == AOP_TRUNCATED_PAGE);
2304 #define MMAP_LOTSAMISS (100)
2307 * Synchronous readahead happens when we don't even find
2308 * a page in the page cache at all.
2310 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
2311 struct file_ra_state *ra,
2315 struct address_space *mapping = file->f_mapping;
2317 /* If we don't want any read-ahead, don't bother */
2318 if (vma->vm_flags & VM_RAND_READ)
2323 if (vma->vm_flags & VM_SEQ_READ) {
2324 page_cache_sync_readahead(mapping, ra, file, offset,
2329 /* Avoid banging the cache line if not needed */
2330 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
2334 * Do we miss much more than hit in this file? If so,
2335 * stop bothering with read-ahead. It will only hurt.
2337 if (ra->mmap_miss > MMAP_LOTSAMISS)
2343 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
2344 ra->size = ra->ra_pages;
2345 ra->async_size = ra->ra_pages / 4;
2346 ra_submit(ra, mapping, file);
2350 * Asynchronous readahead happens when we find the page and PG_readahead,
2351 * so we want to possibly extend the readahead further..
2353 static void do_async_mmap_readahead(struct vm_area_struct *vma,
2354 struct file_ra_state *ra,
2359 struct address_space *mapping = file->f_mapping;
2361 /* If we don't want any read-ahead, don't bother */
2362 if (vma->vm_flags & VM_RAND_READ)
2364 if (ra->mmap_miss > 0)
2366 if (PageReadahead(page))
2367 page_cache_async_readahead(mapping, ra, file,
2368 page, offset, ra->ra_pages);
2372 * filemap_fault - read in file data for page fault handling
2373 * @vmf: struct vm_fault containing details of the fault
2375 * filemap_fault() is invoked via the vma operations vector for a
2376 * mapped memory region to read in file data during a page fault.
2378 * The goto's are kind of ugly, but this streamlines the normal case of having
2379 * it in the page cache, and handles the special cases reasonably without
2380 * having a lot of duplicated code.
2382 * vma->vm_mm->mmap_sem must be held on entry.
2384 * If our return value has VM_FAULT_RETRY set, it's because
2385 * lock_page_or_retry() returned 0.
2386 * The mmap_sem has usually been released in this case.
2387 * See __lock_page_or_retry() for the exception.
2389 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2390 * has not been released.
2392 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2394 int filemap_fault(struct vm_fault *vmf)
2397 struct file *file = vmf->vma->vm_file;
2398 struct address_space *mapping = file->f_mapping;
2399 struct file_ra_state *ra = &file->f_ra;
2400 struct inode *inode = mapping->host;
2401 pgoff_t offset = vmf->pgoff;
2406 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2407 if (unlikely(offset >= max_off))
2408 return VM_FAULT_SIGBUS;
2411 * Do we have something in the page cache already?
2413 page = find_get_page(mapping, offset);
2414 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2416 * We found the page, so try async readahead before
2417 * waiting for the lock.
2419 do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
2421 /* No page in the page cache at all */
2422 do_sync_mmap_readahead(vmf->vma, ra, file, offset);
2423 count_vm_event(PGMAJFAULT);
2424 count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
2425 ret = VM_FAULT_MAJOR;
2427 page = find_get_page(mapping, offset);
2429 goto no_cached_page;
2432 if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) {
2434 return ret | VM_FAULT_RETRY;
2437 /* Did it get truncated? */
2438 if (unlikely(page->mapping != mapping)) {
2443 VM_BUG_ON_PAGE(page->index != offset, page);
2446 * We have a locked page in the page cache, now we need to check
2447 * that it's up-to-date. If not, it is going to be due to an error.
2449 if (unlikely(!PageUptodate(page)))
2450 goto page_not_uptodate;
2453 * Found the page and have a reference on it.
2454 * We must recheck i_size under page lock.
2456 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2457 if (unlikely(offset >= max_off)) {
2460 return VM_FAULT_SIGBUS;
2464 return ret | VM_FAULT_LOCKED;
2468 * We're only likely to ever get here if MADV_RANDOM is in
2471 error = page_cache_read(file, offset, vmf->gfp_mask);
2474 * The page we want has now been added to the page cache.
2475 * In the unlikely event that someone removed it in the
2476 * meantime, we'll just come back here and read it again.
2482 * An error return from page_cache_read can result if the
2483 * system is low on memory, or a problem occurs while trying
2486 if (error == -ENOMEM)
2487 return VM_FAULT_OOM;
2488 return VM_FAULT_SIGBUS;
2492 * Umm, take care of errors if the page isn't up-to-date.
2493 * Try to re-read it _once_. We do this synchronously,
2494 * because there really aren't any performance issues here
2495 * and we need to check for errors.
2497 ClearPageError(page);
2498 error = mapping->a_ops->readpage(file, page);
2500 wait_on_page_locked(page);
2501 if (!PageUptodate(page))
2506 if (!error || error == AOP_TRUNCATED_PAGE)
2509 /* Things didn't work out. Return zero to tell the mm layer so. */
2510 shrink_readahead_size_eio(file, ra);
2511 return VM_FAULT_SIGBUS;
2513 EXPORT_SYMBOL(filemap_fault);
2515 void filemap_map_pages(struct vm_fault *vmf,
2516 pgoff_t start_pgoff, pgoff_t end_pgoff)
2518 struct radix_tree_iter iter;
2520 struct file *file = vmf->vma->vm_file;
2521 struct address_space *mapping = file->f_mapping;
2522 pgoff_t last_pgoff = start_pgoff;
2523 unsigned long max_idx;
2524 struct page *head, *page;
2527 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
2529 if (iter.index > end_pgoff)
2532 page = radix_tree_deref_slot(slot);
2533 if (unlikely(!page))
2535 if (radix_tree_exception(page)) {
2536 if (radix_tree_deref_retry(page)) {
2537 slot = radix_tree_iter_retry(&iter);
2543 head = compound_head(page);
2544 if (!page_cache_get_speculative(head))
2547 /* The page was split under us? */
2548 if (compound_head(page) != head) {
2553 /* Has the page moved? */
2554 if (unlikely(page != *slot)) {
2559 if (!PageUptodate(page) ||
2560 PageReadahead(page) ||
2563 if (!trylock_page(page))
2566 if (page->mapping != mapping || !PageUptodate(page))
2569 max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2570 if (page->index >= max_idx)
2573 if (file->f_ra.mmap_miss > 0)
2574 file->f_ra.mmap_miss--;
2576 vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
2578 vmf->pte += iter.index - last_pgoff;
2579 last_pgoff = iter.index;
2580 if (alloc_set_pte(vmf, NULL, page))
2589 /* Huge page is mapped? No need to proceed. */
2590 if (pmd_trans_huge(*vmf->pmd))
2592 if (iter.index == end_pgoff)
2597 EXPORT_SYMBOL(filemap_map_pages);
2599 int filemap_page_mkwrite(struct vm_fault *vmf)
2601 struct page *page = vmf->page;
2602 struct inode *inode = file_inode(vmf->vma->vm_file);
2603 int ret = VM_FAULT_LOCKED;
2605 sb_start_pagefault(inode->i_sb);
2606 file_update_time(vmf->vma->vm_file);
2608 if (page->mapping != inode->i_mapping) {
2610 ret = VM_FAULT_NOPAGE;
2614 * We mark the page dirty already here so that when freeze is in
2615 * progress, we are guaranteed that writeback during freezing will
2616 * see the dirty page and writeprotect it again.
2618 set_page_dirty(page);
2619 wait_for_stable_page(page);
2621 sb_end_pagefault(inode->i_sb);
2624 EXPORT_SYMBOL(filemap_page_mkwrite);
2626 const struct vm_operations_struct generic_file_vm_ops = {
2627 .fault = filemap_fault,
2628 .map_pages = filemap_map_pages,
2629 .page_mkwrite = filemap_page_mkwrite,
2632 /* This is used for a general mmap of a disk file */
2634 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2636 struct address_space *mapping = file->f_mapping;
2638 if (!mapping->a_ops->readpage)
2640 file_accessed(file);
2641 vma->vm_ops = &generic_file_vm_ops;
2646 * This is for filesystems which do not implement ->writepage.
2648 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2650 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2652 return generic_file_mmap(file, vma);
2655 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2659 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2663 #endif /* CONFIG_MMU */
2665 EXPORT_SYMBOL(generic_file_mmap);
2666 EXPORT_SYMBOL(generic_file_readonly_mmap);
2668 static struct page *wait_on_page_read(struct page *page)
2670 if (!IS_ERR(page)) {
2671 wait_on_page_locked(page);
2672 if (!PageUptodate(page)) {
2674 page = ERR_PTR(-EIO);
2680 static struct page *do_read_cache_page(struct address_space *mapping,
2682 int (*filler)(void *, struct page *),
2689 page = find_get_page(mapping, index);
2691 page = __page_cache_alloc(gfp | __GFP_COLD);
2693 return ERR_PTR(-ENOMEM);
2694 err = add_to_page_cache_lru(page, mapping, index, gfp);
2695 if (unlikely(err)) {
2699 /* Presumably ENOMEM for radix tree node */
2700 return ERR_PTR(err);
2704 err = filler(data, page);
2707 return ERR_PTR(err);
2710 page = wait_on_page_read(page);
2715 if (PageUptodate(page))
2719 * Page is not up to date and may be locked due one of the following
2720 * case a: Page is being filled and the page lock is held
2721 * case b: Read/write error clearing the page uptodate status
2722 * case c: Truncation in progress (page locked)
2723 * case d: Reclaim in progress
2725 * Case a, the page will be up to date when the page is unlocked.
2726 * There is no need to serialise on the page lock here as the page
2727 * is pinned so the lock gives no additional protection. Even if the
2728 * the page is truncated, the data is still valid if PageUptodate as
2729 * it's a race vs truncate race.
2730 * Case b, the page will not be up to date
2731 * Case c, the page may be truncated but in itself, the data may still
2732 * be valid after IO completes as it's a read vs truncate race. The
2733 * operation must restart if the page is not uptodate on unlock but
2734 * otherwise serialising on page lock to stabilise the mapping gives
2735 * no additional guarantees to the caller as the page lock is
2736 * released before return.
2737 * Case d, similar to truncation. If reclaim holds the page lock, it
2738 * will be a race with remove_mapping that determines if the mapping
2739 * is valid on unlock but otherwise the data is valid and there is
2740 * no need to serialise with page lock.
2742 * As the page lock gives no additional guarantee, we optimistically
2743 * wait on the page to be unlocked and check if it's up to date and
2744 * use the page if it is. Otherwise, the page lock is required to
2745 * distinguish between the different cases. The motivation is that we
2746 * avoid spurious serialisations and wakeups when multiple processes
2747 * wait on the same page for IO to complete.
2749 wait_on_page_locked(page);
2750 if (PageUptodate(page))
2753 /* Distinguish between all the cases under the safety of the lock */
2756 /* Case c or d, restart the operation */
2757 if (!page->mapping) {
2763 /* Someone else locked and filled the page in a very small window */
2764 if (PageUptodate(page)) {
2771 mark_page_accessed(page);
2776 * read_cache_page - read into page cache, fill it if needed
2777 * @mapping: the page's address_space
2778 * @index: the page index
2779 * @filler: function to perform the read
2780 * @data: first arg to filler(data, page) function, often left as NULL
2782 * Read into the page cache. If a page already exists, and PageUptodate() is
2783 * not set, try to fill the page and wait for it to become unlocked.
2785 * If the page does not get brought uptodate, return -EIO.
2787 struct page *read_cache_page(struct address_space *mapping,
2789 int (*filler)(void *, struct page *),
2792 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2794 EXPORT_SYMBOL(read_cache_page);
2797 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2798 * @mapping: the page's address_space
2799 * @index: the page index
2800 * @gfp: the page allocator flags to use if allocating
2802 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2803 * any new page allocations done using the specified allocation flags.
2805 * If the page does not get brought uptodate, return -EIO.
2807 struct page *read_cache_page_gfp(struct address_space *mapping,
2811 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2813 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2815 EXPORT_SYMBOL(read_cache_page_gfp);
2818 * Performs necessary checks before doing a write
2820 * Can adjust writing position or amount of bytes to write.
2821 * Returns appropriate error code that caller should return or
2822 * zero in case that write should be allowed.
2824 inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2826 struct file *file = iocb->ki_filp;
2827 struct inode *inode = file->f_mapping->host;
2828 unsigned long limit = rlimit(RLIMIT_FSIZE);
2831 if (!iov_iter_count(from))
2834 /* FIXME: this is for backwards compatibility with 2.4 */
2835 if (iocb->ki_flags & IOCB_APPEND)
2836 iocb->ki_pos = i_size_read(inode);
2840 if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
2843 if (limit != RLIM_INFINITY) {
2844 if (iocb->ki_pos >= limit) {
2845 send_sig(SIGXFSZ, current, 0);
2848 iov_iter_truncate(from, limit - (unsigned long)pos);
2854 if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
2855 !(file->f_flags & O_LARGEFILE))) {
2856 if (pos >= MAX_NON_LFS)
2858 iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
2862 * Are we about to exceed the fs block limit ?
2864 * If we have written data it becomes a short write. If we have
2865 * exceeded without writing data we send a signal and return EFBIG.
2866 * Linus frestrict idea will clean these up nicely..
2868 if (unlikely(pos >= inode->i_sb->s_maxbytes))
2871 iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
2872 return iov_iter_count(from);
2874 EXPORT_SYMBOL(generic_write_checks);
2876 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2877 loff_t pos, unsigned len, unsigned flags,
2878 struct page **pagep, void **fsdata)
2880 const struct address_space_operations *aops = mapping->a_ops;
2882 return aops->write_begin(file, mapping, pos, len, flags,
2885 EXPORT_SYMBOL(pagecache_write_begin);
2887 int pagecache_write_end(struct file *file, struct address_space *mapping,
2888 loff_t pos, unsigned len, unsigned copied,
2889 struct page *page, void *fsdata)
2891 const struct address_space_operations *aops = mapping->a_ops;
2893 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2895 EXPORT_SYMBOL(pagecache_write_end);
2898 generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
2900 struct file *file = iocb->ki_filp;
2901 struct address_space *mapping = file->f_mapping;
2902 struct inode *inode = mapping->host;
2903 loff_t pos = iocb->ki_pos;
2908 write_len = iov_iter_count(from);
2909 end = (pos + write_len - 1) >> PAGE_SHIFT;
2911 if (iocb->ki_flags & IOCB_NOWAIT) {
2912 /* If there are pages to writeback, return */
2913 if (filemap_range_has_page(inode->i_mapping, pos,
2914 pos + iov_iter_count(from)))
2917 written = filemap_write_and_wait_range(mapping, pos,
2918 pos + write_len - 1);
2924 * After a write we want buffered reads to be sure to go to disk to get
2925 * the new data. We invalidate clean cached page from the region we're
2926 * about to write. We do this *before* the write so that we can return
2927 * without clobbering -EIOCBQUEUED from ->direct_IO().
2929 written = invalidate_inode_pages2_range(mapping,
2930 pos >> PAGE_SHIFT, end);
2932 * If a page can not be invalidated, return 0 to fall back
2933 * to buffered write.
2936 if (written == -EBUSY)
2941 written = mapping->a_ops->direct_IO(iocb, from);
2944 * Finally, try again to invalidate clean pages which might have been
2945 * cached by non-direct readahead, or faulted in by get_user_pages()
2946 * if the source of the write was an mmap'ed region of the file
2947 * we're writing. Either one is a pretty crazy thing to do,
2948 * so we don't support it 100%. If this invalidation
2949 * fails, tough, the write still worked...
2951 * Most of the time we do not need this since dio_complete() will do
2952 * the invalidation for us. However there are some file systems that
2953 * do not end up with dio_complete() being called, so let's not break
2954 * them by removing it completely
2956 if (mapping->nrpages)
2957 invalidate_inode_pages2_range(mapping,
2958 pos >> PAGE_SHIFT, end);
2962 write_len -= written;
2963 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2964 i_size_write(inode, pos);
2965 mark_inode_dirty(inode);
2969 iov_iter_revert(from, write_len - iov_iter_count(from));
2973 EXPORT_SYMBOL(generic_file_direct_write);
2976 * Find or create a page at the given pagecache position. Return the locked
2977 * page. This function is specifically for buffered writes.
2979 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2980 pgoff_t index, unsigned flags)
2983 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
2985 if (flags & AOP_FLAG_NOFS)
2986 fgp_flags |= FGP_NOFS;
2988 page = pagecache_get_page(mapping, index, fgp_flags,
2989 mapping_gfp_mask(mapping));
2991 wait_for_stable_page(page);
2995 EXPORT_SYMBOL(grab_cache_page_write_begin);
2997 ssize_t generic_perform_write(struct file *file,
2998 struct iov_iter *i, loff_t pos)
3000 struct address_space *mapping = file->f_mapping;
3001 const struct address_space_operations *a_ops = mapping->a_ops;
3003 ssize_t written = 0;
3004 unsigned int flags = 0;
3008 unsigned long offset; /* Offset into pagecache page */
3009 unsigned long bytes; /* Bytes to write to page */
3010 size_t copied; /* Bytes copied from user */
3013 offset = (pos & (PAGE_SIZE - 1));
3014 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3019 * Bring in the user page that we will copy from _first_.
3020 * Otherwise there's a nasty deadlock on copying from the
3021 * same page as we're writing to, without it being marked
3024 * Not only is this an optimisation, but it is also required
3025 * to check that the address is actually valid, when atomic
3026 * usercopies are used, below.
3028 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
3033 if (fatal_signal_pending(current)) {
3038 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
3040 if (unlikely(status < 0))
3043 if (mapping_writably_mapped(mapping))
3044 flush_dcache_page(page);
3046 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
3047 flush_dcache_page(page);
3049 status = a_ops->write_end(file, mapping, pos, bytes, copied,
3051 if (unlikely(status < 0))
3057 iov_iter_advance(i, copied);
3058 if (unlikely(copied == 0)) {
3060 * If we were unable to copy any data at all, we must
3061 * fall back to a single segment length write.
3063 * If we didn't fallback here, we could livelock
3064 * because not all segments in the iov can be copied at
3065 * once without a pagefault.
3067 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3068 iov_iter_single_seg_count(i));
3074 balance_dirty_pages_ratelimited(mapping);
3075 } while (iov_iter_count(i));
3077 return written ? written : status;
3079 EXPORT_SYMBOL(generic_perform_write);
3082 * __generic_file_write_iter - write data to a file
3083 * @iocb: IO state structure (file, offset, etc.)
3084 * @from: iov_iter with data to write
3086 * This function does all the work needed for actually writing data to a
3087 * file. It does all basic checks, removes SUID from the file, updates
3088 * modification times and calls proper subroutines depending on whether we
3089 * do direct IO or a standard buffered write.
3091 * It expects i_mutex to be grabbed unless we work on a block device or similar
3092 * object which does not need locking at all.
3094 * This function does *not* take care of syncing data in case of O_SYNC write.
3095 * A caller has to handle it. This is mainly due to the fact that we want to
3096 * avoid syncing under i_mutex.
3098 ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3100 struct file *file = iocb->ki_filp;
3101 struct address_space * mapping = file->f_mapping;
3102 struct inode *inode = mapping->host;
3103 ssize_t written = 0;
3107 /* We can write back this queue in page reclaim */
3108 current->backing_dev_info = inode_to_bdi(inode);
3109 err = file_remove_privs(file);
3113 err = file_update_time(file);
3117 if (iocb->ki_flags & IOCB_DIRECT) {
3118 loff_t pos, endbyte;
3120 written = generic_file_direct_write(iocb, from);
3122 * If the write stopped short of completing, fall back to
3123 * buffered writes. Some filesystems do this for writes to
3124 * holes, for example. For DAX files, a buffered write will
3125 * not succeed (even if it did, DAX does not handle dirty
3126 * page-cache pages correctly).
3128 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
3131 status = generic_perform_write(file, from, pos = iocb->ki_pos);
3133 * If generic_perform_write() returned a synchronous error
3134 * then we want to return the number of bytes which were
3135 * direct-written, or the error code if that was zero. Note
3136 * that this differs from normal direct-io semantics, which
3137 * will return -EFOO even if some bytes were written.
3139 if (unlikely(status < 0)) {
3144 * We need to ensure that the page cache pages are written to
3145 * disk and invalidated to preserve the expected O_DIRECT
3148 endbyte = pos + status - 1;
3149 err = filemap_write_and_wait_range(mapping, pos, endbyte);
3151 iocb->ki_pos = endbyte + 1;
3153 invalidate_mapping_pages(mapping,
3155 endbyte >> PAGE_SHIFT);
3158 * We don't know how much we wrote, so just return
3159 * the number of bytes which were direct-written
3163 written = generic_perform_write(file, from, iocb->ki_pos);
3164 if (likely(written > 0))
3165 iocb->ki_pos += written;
3168 current->backing_dev_info = NULL;
3169 return written ? written : err;
3171 EXPORT_SYMBOL(__generic_file_write_iter);
3174 * generic_file_write_iter - write data to a file
3175 * @iocb: IO state structure
3176 * @from: iov_iter with data to write
3178 * This is a wrapper around __generic_file_write_iter() to be used by most
3179 * filesystems. It takes care of syncing the file in case of O_SYNC file
3180 * and acquires i_mutex as needed.
3182 ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3184 struct file *file = iocb->ki_filp;
3185 struct inode *inode = file->f_mapping->host;
3189 ret = generic_write_checks(iocb, from);
3191 ret = __generic_file_write_iter(iocb, from);
3192 inode_unlock(inode);
3195 ret = generic_write_sync(iocb, ret);
3198 EXPORT_SYMBOL(generic_file_write_iter);
3201 * try_to_release_page() - release old fs-specific metadata on a page
3203 * @page: the page which the kernel is trying to free
3204 * @gfp_mask: memory allocation flags (and I/O mode)
3206 * The address_space is to try to release any data against the page
3207 * (presumably at page->private). If the release was successful, return '1'.
3208 * Otherwise return zero.
3210 * This may also be called if PG_fscache is set on a page, indicating that the
3211 * page is known to the local caching routines.
3213 * The @gfp_mask argument specifies whether I/O may be performed to release
3214 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3217 int try_to_release_page(struct page *page, gfp_t gfp_mask)
3219 struct address_space * const mapping = page->mapping;
3221 BUG_ON(!PageLocked(page));
3222 if (PageWriteback(page))
3225 if (mapping && mapping->a_ops->releasepage)
3226 return mapping->a_ops->releasepage(page, gfp_mask);
3227 return try_to_free_buffers(page);
3230 EXPORT_SYMBOL(try_to_release_page);