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/uaccess.h>
17 #include <linux/capability.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/gfp.h>
21 #include <linux/swap.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/file.h>
25 #include <linux/uio.h>
26 #include <linux/hash.h>
27 #include <linux/writeback.h>
28 #include <linux/backing-dev.h>
29 #include <linux/pagevec.h>
30 #include <linux/blkdev.h>
31 #include <linux/security.h>
32 #include <linux/cpuset.h>
33 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
34 #include <linux/hugetlb.h>
35 #include <linux/memcontrol.h>
36 #include <linux/cleancache.h>
37 #include <linux/rmap.h>
40 #define CREATE_TRACE_POINTS
41 #include <trace/events/filemap.h>
44 * FIXME: remove all knowledge of the buffer layer from the core VM
46 #include <linux/buffer_head.h> /* for try_to_free_buffers */
51 * Shared mappings implemented 30.11.1994. It's not fully working yet,
54 * Shared mappings now work. 15.8.1995 Bruno.
56 * finished 'unifying' the page and buffer cache and SMP-threaded the
57 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
59 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
65 * ->i_mmap_rwsem (truncate_pagecache)
66 * ->private_lock (__free_pte->__set_page_dirty_buffers)
67 * ->swap_lock (exclusive_swap_page, others)
68 * ->mapping->tree_lock
71 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
75 * ->page_table_lock or pte_lock (various, mainly in memory.c)
76 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
79 * ->lock_page (access_process_vm)
81 * ->i_mutex (generic_perform_write)
82 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
85 * sb_lock (fs/fs-writeback.c)
86 * ->mapping->tree_lock (__sync_single_inode)
89 * ->anon_vma.lock (vma_adjust)
92 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
94 * ->page_table_lock or pte_lock
95 * ->swap_lock (try_to_unmap_one)
96 * ->private_lock (try_to_unmap_one)
97 * ->tree_lock (try_to_unmap_one)
98 * ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
99 * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
100 * ->private_lock (page_remove_rmap->set_page_dirty)
101 * ->tree_lock (page_remove_rmap->set_page_dirty)
102 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
103 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
104 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
105 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
106 * ->inode->i_lock (zap_pte_range->set_page_dirty)
107 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
110 * ->tasklist_lock (memory_failure, collect_procs_ao)
113 static int page_cache_tree_insert(struct address_space *mapping,
114 struct page *page, void **shadowp)
116 struct radix_tree_node *node;
120 error = __radix_tree_create(&mapping->page_tree, page->index, 0,
127 p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
128 if (!radix_tree_exceptional_entry(p))
131 mapping->nrexceptional--;
132 if (!dax_mapping(mapping)) {
136 /* DAX can replace empty locked entry with a hole */
138 dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
139 /* Wakeup waiters for exceptional entry lock */
140 dax_wake_mapping_entry_waiter(mapping, page->index, p,
144 __radix_tree_replace(&mapping->page_tree, node, slot, page,
145 workingset_update_node, mapping);
150 static void page_cache_tree_delete(struct address_space *mapping,
151 struct page *page, void *shadow)
155 /* hugetlb pages are represented by one entry in the radix tree */
156 nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
158 VM_BUG_ON_PAGE(!PageLocked(page), page);
159 VM_BUG_ON_PAGE(PageTail(page), page);
160 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
162 for (i = 0; i < nr; i++) {
163 struct radix_tree_node *node;
166 __radix_tree_lookup(&mapping->page_tree, page->index + i,
169 VM_BUG_ON_PAGE(!node && nr != 1, page);
171 radix_tree_clear_tags(&mapping->page_tree, node, slot);
172 __radix_tree_replace(&mapping->page_tree, node, slot, shadow,
173 workingset_update_node, mapping);
177 mapping->nrexceptional += nr;
179 * Make sure the nrexceptional update is committed before
180 * the nrpages update so that final truncate racing
181 * with reclaim does not see both counters 0 at the
182 * same time and miss a shadow entry.
186 mapping->nrpages -= nr;
190 * Delete a page from the page cache and free it. Caller has to make
191 * sure the page is locked and that nobody else uses it - or that usage
192 * is safe. The caller must hold the mapping's tree_lock.
194 void __delete_from_page_cache(struct page *page, void *shadow)
196 struct address_space *mapping = page->mapping;
197 int nr = hpage_nr_pages(page);
199 trace_mm_filemap_delete_from_page_cache(page);
201 * if we're uptodate, flush out into the cleancache, otherwise
202 * invalidate any existing cleancache entries. We can't leave
203 * stale data around in the cleancache once our page is gone
205 if (PageUptodate(page) && PageMappedToDisk(page))
206 cleancache_put_page(page);
208 cleancache_invalidate_page(mapping, page);
210 VM_BUG_ON_PAGE(PageTail(page), page);
211 VM_BUG_ON_PAGE(page_mapped(page), page);
212 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
215 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
216 current->comm, page_to_pfn(page));
217 dump_page(page, "still mapped when deleted");
219 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
221 mapcount = page_mapcount(page);
222 if (mapping_exiting(mapping) &&
223 page_count(page) >= mapcount + 2) {
225 * All vmas have already been torn down, so it's
226 * a good bet that actually the page is unmapped,
227 * and we'd prefer not to leak it: if we're wrong,
228 * some other bad page check should catch it later.
230 page_mapcount_reset(page);
231 page_ref_sub(page, mapcount);
235 page_cache_tree_delete(mapping, page, shadow);
237 page->mapping = NULL;
238 /* Leave page->index set: truncation lookup relies upon it */
240 /* hugetlb pages do not participate in page cache accounting. */
242 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
243 if (PageSwapBacked(page)) {
244 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
245 if (PageTransHuge(page))
246 __dec_node_page_state(page, NR_SHMEM_THPS);
248 VM_BUG_ON_PAGE(PageTransHuge(page) && !PageHuge(page), page);
252 * At this point page must be either written or cleaned by truncate.
253 * Dirty page here signals a bug and loss of unwritten data.
255 * This fixes dirty accounting after removing the page entirely but
256 * leaves PageDirty set: it has no effect for truncated page and
257 * anyway will be cleared before returning page into buddy allocator.
259 if (WARN_ON_ONCE(PageDirty(page)))
260 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
264 * delete_from_page_cache - delete page from page cache
265 * @page: the page which the kernel is trying to remove from page cache
267 * This must be called only on pages that have been verified to be in the page
268 * cache and locked. It will never put the page into the free list, the caller
269 * has a reference on the page.
271 void delete_from_page_cache(struct page *page)
273 struct address_space *mapping = page_mapping(page);
275 void (*freepage)(struct page *);
277 BUG_ON(!PageLocked(page));
279 freepage = mapping->a_ops->freepage;
281 spin_lock_irqsave(&mapping->tree_lock, flags);
282 __delete_from_page_cache(page, NULL);
283 spin_unlock_irqrestore(&mapping->tree_lock, flags);
288 if (PageTransHuge(page) && !PageHuge(page)) {
289 page_ref_sub(page, HPAGE_PMD_NR);
290 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
295 EXPORT_SYMBOL(delete_from_page_cache);
297 int filemap_check_errors(struct address_space *mapping)
300 /* Check for outstanding write errors */
301 if (test_bit(AS_ENOSPC, &mapping->flags) &&
302 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
304 if (test_bit(AS_EIO, &mapping->flags) &&
305 test_and_clear_bit(AS_EIO, &mapping->flags))
309 EXPORT_SYMBOL(filemap_check_errors);
312 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
313 * @mapping: address space structure to write
314 * @start: offset in bytes where the range starts
315 * @end: offset in bytes where the range ends (inclusive)
316 * @sync_mode: enable synchronous operation
318 * Start writeback against all of a mapping's dirty pages that lie
319 * within the byte offsets <start, end> inclusive.
321 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
322 * opposed to a regular memory cleansing writeback. The difference between
323 * these two operations is that if a dirty page/buffer is encountered, it must
324 * be waited upon, and not just skipped over.
326 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
327 loff_t end, int sync_mode)
330 struct writeback_control wbc = {
331 .sync_mode = sync_mode,
332 .nr_to_write = LONG_MAX,
333 .range_start = start,
337 if (!mapping_cap_writeback_dirty(mapping))
340 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
341 ret = do_writepages(mapping, &wbc);
342 wbc_detach_inode(&wbc);
346 static inline int __filemap_fdatawrite(struct address_space *mapping,
349 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
352 int filemap_fdatawrite(struct address_space *mapping)
354 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
356 EXPORT_SYMBOL(filemap_fdatawrite);
358 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
361 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
363 EXPORT_SYMBOL(filemap_fdatawrite_range);
366 * filemap_flush - mostly a non-blocking flush
367 * @mapping: target address_space
369 * This is a mostly non-blocking flush. Not suitable for data-integrity
370 * purposes - I/O may not be started against all dirty pages.
372 int filemap_flush(struct address_space *mapping)
374 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
376 EXPORT_SYMBOL(filemap_flush);
378 static int __filemap_fdatawait_range(struct address_space *mapping,
379 loff_t start_byte, loff_t end_byte)
381 pgoff_t index = start_byte >> PAGE_SHIFT;
382 pgoff_t end = end_byte >> PAGE_SHIFT;
387 if (end_byte < start_byte)
390 pagevec_init(&pvec, 0);
391 while ((index <= end) &&
392 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
393 PAGECACHE_TAG_WRITEBACK,
394 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
397 for (i = 0; i < nr_pages; i++) {
398 struct page *page = pvec.pages[i];
400 /* until radix tree lookup accepts end_index */
401 if (page->index > end)
404 wait_on_page_writeback(page);
405 if (TestClearPageError(page))
408 pagevec_release(&pvec);
416 * filemap_fdatawait_range - wait for writeback to complete
417 * @mapping: address space structure to wait for
418 * @start_byte: offset in bytes where the range starts
419 * @end_byte: offset in bytes where the range ends (inclusive)
421 * Walk the list of under-writeback pages of the given address space
422 * in the given range and wait for all of them. Check error status of
423 * the address space and return it.
425 * Since the error status of the address space is cleared by this function,
426 * callers are responsible for checking the return value and handling and/or
427 * reporting the error.
429 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
434 ret = __filemap_fdatawait_range(mapping, start_byte, end_byte);
435 ret2 = filemap_check_errors(mapping);
441 EXPORT_SYMBOL(filemap_fdatawait_range);
444 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
445 * @mapping: address space structure to wait for
447 * Walk the list of under-writeback pages of the given address space
448 * and wait for all of them. Unlike filemap_fdatawait(), this function
449 * does not clear error status of the address space.
451 * Use this function if callers don't handle errors themselves. Expected
452 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
455 void filemap_fdatawait_keep_errors(struct address_space *mapping)
457 loff_t i_size = i_size_read(mapping->host);
462 __filemap_fdatawait_range(mapping, 0, i_size - 1);
466 * filemap_fdatawait - wait for all under-writeback pages to complete
467 * @mapping: address space structure to wait for
469 * Walk the list of under-writeback pages of the given address space
470 * and wait for all of them. Check error status of the address space
473 * Since the error status of the address space is cleared by this function,
474 * callers are responsible for checking the return value and handling and/or
475 * reporting the error.
477 int filemap_fdatawait(struct address_space *mapping)
479 loff_t i_size = i_size_read(mapping->host);
484 return filemap_fdatawait_range(mapping, 0, i_size - 1);
486 EXPORT_SYMBOL(filemap_fdatawait);
488 int filemap_write_and_wait(struct address_space *mapping)
492 if ((!dax_mapping(mapping) && mapping->nrpages) ||
493 (dax_mapping(mapping) && mapping->nrexceptional)) {
494 err = filemap_fdatawrite(mapping);
496 * Even if the above returned error, the pages may be
497 * written partially (e.g. -ENOSPC), so we wait for it.
498 * But the -EIO is special case, it may indicate the worst
499 * thing (e.g. bug) happened, so we avoid waiting for it.
502 int err2 = filemap_fdatawait(mapping);
507 err = filemap_check_errors(mapping);
511 EXPORT_SYMBOL(filemap_write_and_wait);
514 * filemap_write_and_wait_range - write out & wait on a file range
515 * @mapping: the address_space for the pages
516 * @lstart: offset in bytes where the range starts
517 * @lend: offset in bytes where the range ends (inclusive)
519 * Write out and wait upon file offsets lstart->lend, inclusive.
521 * Note that `lend' is inclusive (describes the last byte to be written) so
522 * that this function can be used to write to the very end-of-file (end = -1).
524 int filemap_write_and_wait_range(struct address_space *mapping,
525 loff_t lstart, loff_t lend)
529 if ((!dax_mapping(mapping) && mapping->nrpages) ||
530 (dax_mapping(mapping) && mapping->nrexceptional)) {
531 err = __filemap_fdatawrite_range(mapping, lstart, lend,
533 /* See comment of filemap_write_and_wait() */
535 int err2 = filemap_fdatawait_range(mapping,
541 err = filemap_check_errors(mapping);
545 EXPORT_SYMBOL(filemap_write_and_wait_range);
548 * replace_page_cache_page - replace a pagecache page with a new one
549 * @old: page to be replaced
550 * @new: page to replace with
551 * @gfp_mask: allocation mode
553 * This function replaces a page in the pagecache with a new one. On
554 * success it acquires the pagecache reference for the new page and
555 * drops it for the old page. Both the old and new pages must be
556 * locked. This function does not add the new page to the LRU, the
557 * caller must do that.
559 * The remove + add is atomic. The only way this function can fail is
560 * memory allocation failure.
562 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
566 VM_BUG_ON_PAGE(!PageLocked(old), old);
567 VM_BUG_ON_PAGE(!PageLocked(new), new);
568 VM_BUG_ON_PAGE(new->mapping, new);
570 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
572 struct address_space *mapping = old->mapping;
573 void (*freepage)(struct page *);
576 pgoff_t offset = old->index;
577 freepage = mapping->a_ops->freepage;
580 new->mapping = mapping;
583 spin_lock_irqsave(&mapping->tree_lock, flags);
584 __delete_from_page_cache(old, NULL);
585 error = page_cache_tree_insert(mapping, new, NULL);
589 * hugetlb pages do not participate in page cache accounting.
592 __inc_node_page_state(new, NR_FILE_PAGES);
593 if (PageSwapBacked(new))
594 __inc_node_page_state(new, NR_SHMEM);
595 spin_unlock_irqrestore(&mapping->tree_lock, flags);
596 mem_cgroup_migrate(old, new);
597 radix_tree_preload_end();
605 EXPORT_SYMBOL_GPL(replace_page_cache_page);
607 static int __add_to_page_cache_locked(struct page *page,
608 struct address_space *mapping,
609 pgoff_t offset, gfp_t gfp_mask,
612 int huge = PageHuge(page);
613 struct mem_cgroup *memcg;
616 VM_BUG_ON_PAGE(!PageLocked(page), page);
617 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
620 error = mem_cgroup_try_charge(page, current->mm,
621 gfp_mask, &memcg, false);
626 error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
629 mem_cgroup_cancel_charge(page, memcg, false);
634 page->mapping = mapping;
635 page->index = offset;
637 spin_lock_irq(&mapping->tree_lock);
638 error = page_cache_tree_insert(mapping, page, shadowp);
639 radix_tree_preload_end();
643 /* hugetlb pages do not participate in page cache accounting. */
645 __inc_node_page_state(page, NR_FILE_PAGES);
646 spin_unlock_irq(&mapping->tree_lock);
648 mem_cgroup_commit_charge(page, memcg, false, false);
649 trace_mm_filemap_add_to_page_cache(page);
652 page->mapping = NULL;
653 /* Leave page->index set: truncation relies upon it */
654 spin_unlock_irq(&mapping->tree_lock);
656 mem_cgroup_cancel_charge(page, memcg, false);
662 * add_to_page_cache_locked - add a locked page to the pagecache
664 * @mapping: the page's address_space
665 * @offset: page index
666 * @gfp_mask: page allocation mode
668 * This function is used to add a page to the pagecache. It must be locked.
669 * This function does not add the page to the LRU. The caller must do that.
671 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
672 pgoff_t offset, gfp_t gfp_mask)
674 return __add_to_page_cache_locked(page, mapping, offset,
677 EXPORT_SYMBOL(add_to_page_cache_locked);
679 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
680 pgoff_t offset, gfp_t gfp_mask)
685 __SetPageLocked(page);
686 ret = __add_to_page_cache_locked(page, mapping, offset,
689 __ClearPageLocked(page);
692 * The page might have been evicted from cache only
693 * recently, in which case it should be activated like
694 * any other repeatedly accessed page.
695 * The exception is pages getting rewritten; evicting other
696 * data from the working set, only to cache data that will
697 * get overwritten with something else, is a waste of memory.
699 if (!(gfp_mask & __GFP_WRITE) &&
700 shadow && workingset_refault(shadow)) {
702 workingset_activation(page);
704 ClearPageActive(page);
709 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
712 struct page *__page_cache_alloc(gfp_t gfp)
717 if (cpuset_do_page_mem_spread()) {
718 unsigned int cpuset_mems_cookie;
720 cpuset_mems_cookie = read_mems_allowed_begin();
721 n = cpuset_mem_spread_node();
722 page = __alloc_pages_node(n, gfp, 0);
723 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
727 return alloc_pages(gfp, 0);
729 EXPORT_SYMBOL(__page_cache_alloc);
733 * In order to wait for pages to become available there must be
734 * waitqueues associated with pages. By using a hash table of
735 * waitqueues where the bucket discipline is to maintain all
736 * waiters on the same queue and wake all when any of the pages
737 * become available, and for the woken contexts to check to be
738 * sure the appropriate page became available, this saves space
739 * at a cost of "thundering herd" phenomena during rare hash
742 #define PAGE_WAIT_TABLE_BITS 8
743 #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
744 static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
746 static wait_queue_head_t *page_waitqueue(struct page *page)
748 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
751 void __init pagecache_init(void)
755 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
756 init_waitqueue_head(&page_wait_table[i]);
758 page_writeback_init();
761 struct wait_page_key {
767 struct wait_page_queue {
773 static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
775 struct wait_page_key *key = arg;
776 struct wait_page_queue *wait_page
777 = container_of(wait, struct wait_page_queue, wait);
779 if (wait_page->page != key->page)
783 if (wait_page->bit_nr != key->bit_nr)
785 if (test_bit(key->bit_nr, &key->page->flags))
788 return autoremove_wake_function(wait, mode, sync, key);
791 static void wake_up_page_bit(struct page *page, int bit_nr)
793 wait_queue_head_t *q = page_waitqueue(page);
794 struct wait_page_key key;
801 spin_lock_irqsave(&q->lock, flags);
802 __wake_up_locked_key(q, TASK_NORMAL, &key);
804 * It is possible for other pages to have collided on the waitqueue
805 * hash, so in that case check for a page match. That prevents a long-
808 * It is still possible to miss a case here, when we woke page waiters
809 * and removed them from the waitqueue, but there are still other
812 if (!waitqueue_active(q) || !key.page_match) {
813 ClearPageWaiters(page);
815 * It's possible to miss clearing Waiters here, when we woke
816 * our page waiters, but the hashed waitqueue has waiters for
819 * That's okay, it's a rare case. The next waker will clear it.
822 spin_unlock_irqrestore(&q->lock, flags);
825 static void wake_up_page(struct page *page, int bit)
827 if (!PageWaiters(page))
829 wake_up_page_bit(page, bit);
832 static inline int wait_on_page_bit_common(wait_queue_head_t *q,
833 struct page *page, int bit_nr, int state, bool lock)
835 struct wait_page_queue wait_page;
836 wait_queue_t *wait = &wait_page.wait;
840 wait->func = wake_page_function;
841 wait_page.page = page;
842 wait_page.bit_nr = bit_nr;
845 spin_lock_irq(&q->lock);
847 if (likely(list_empty(&wait->task_list))) {
849 __add_wait_queue_tail_exclusive(q, wait);
851 __add_wait_queue(q, wait);
852 SetPageWaiters(page);
855 set_current_state(state);
857 spin_unlock_irq(&q->lock);
859 if (likely(test_bit(bit_nr, &page->flags))) {
861 if (unlikely(signal_pending_state(state, current))) {
868 if (!test_and_set_bit_lock(bit_nr, &page->flags))
871 if (!test_bit(bit_nr, &page->flags))
876 finish_wait(q, wait);
879 * A signal could leave PageWaiters set. Clearing it here if
880 * !waitqueue_active would be possible (by open-coding finish_wait),
881 * but still fail to catch it in the case of wait hash collision. We
882 * already can fail to clear wait hash collision cases, so don't
883 * bother with signals either.
889 void wait_on_page_bit(struct page *page, int bit_nr)
891 wait_queue_head_t *q = page_waitqueue(page);
892 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
894 EXPORT_SYMBOL(wait_on_page_bit);
896 int wait_on_page_bit_killable(struct page *page, int bit_nr)
898 wait_queue_head_t *q = page_waitqueue(page);
899 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
903 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
904 * @page: Page defining the wait queue of interest
905 * @waiter: Waiter to add to the queue
907 * Add an arbitrary @waiter to the wait queue for the nominated @page.
909 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
911 wait_queue_head_t *q = page_waitqueue(page);
914 spin_lock_irqsave(&q->lock, flags);
915 __add_wait_queue(q, waiter);
916 SetPageWaiters(page);
917 spin_unlock_irqrestore(&q->lock, flags);
919 EXPORT_SYMBOL_GPL(add_page_wait_queue);
921 #ifndef clear_bit_unlock_is_negative_byte
924 * PG_waiters is the high bit in the same byte as PG_lock.
926 * On x86 (and on many other architectures), we can clear PG_lock and
927 * test the sign bit at the same time. But if the architecture does
928 * not support that special operation, we just do this all by hand
931 * The read of PG_waiters has to be after (or concurrently with) PG_locked
932 * being cleared, but a memory barrier should be unneccssary since it is
933 * in the same byte as PG_locked.
935 static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
937 clear_bit_unlock(nr, mem);
938 /* smp_mb__after_atomic(); */
939 return test_bit(PG_waiters, mem);
945 * unlock_page - unlock a locked page
948 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
949 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
950 * mechanism between PageLocked pages and PageWriteback pages is shared.
951 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
953 * Note that this depends on PG_waiters being the sign bit in the byte
954 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
955 * clear the PG_locked bit and test PG_waiters at the same time fairly
956 * portably (architectures that do LL/SC can test any bit, while x86 can
957 * test the sign bit).
959 void unlock_page(struct page *page)
961 BUILD_BUG_ON(PG_waiters != 7);
962 page = compound_head(page);
963 VM_BUG_ON_PAGE(!PageLocked(page), page);
964 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
965 wake_up_page_bit(page, PG_locked);
967 EXPORT_SYMBOL(unlock_page);
970 * end_page_writeback - end writeback against a page
973 void end_page_writeback(struct page *page)
976 * TestClearPageReclaim could be used here but it is an atomic
977 * operation and overkill in this particular case. Failing to
978 * shuffle a page marked for immediate reclaim is too mild to
979 * justify taking an atomic operation penalty at the end of
980 * ever page writeback.
982 if (PageReclaim(page)) {
983 ClearPageReclaim(page);
984 rotate_reclaimable_page(page);
987 if (!test_clear_page_writeback(page))
990 smp_mb__after_atomic();
991 wake_up_page(page, PG_writeback);
993 EXPORT_SYMBOL(end_page_writeback);
996 * After completing I/O on a page, call this routine to update the page
997 * flags appropriately
999 void page_endio(struct page *page, bool is_write, int err)
1003 SetPageUptodate(page);
1005 ClearPageUptodate(page);
1013 mapping_set_error(page->mapping, err);
1015 end_page_writeback(page);
1018 EXPORT_SYMBOL_GPL(page_endio);
1021 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1022 * @__page: the page to lock
1024 void __lock_page(struct page *__page)
1026 struct page *page = compound_head(__page);
1027 wait_queue_head_t *q = page_waitqueue(page);
1028 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
1030 EXPORT_SYMBOL(__lock_page);
1032 int __lock_page_killable(struct page *__page)
1034 struct page *page = compound_head(__page);
1035 wait_queue_head_t *q = page_waitqueue(page);
1036 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
1038 EXPORT_SYMBOL_GPL(__lock_page_killable);
1042 * 1 - page is locked; mmap_sem is still held.
1043 * 0 - page is not locked.
1044 * mmap_sem has been released (up_read()), unless flags had both
1045 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1046 * which case mmap_sem is still held.
1048 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1049 * with the page locked and the mmap_sem unperturbed.
1051 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1054 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1056 * CAUTION! In this case, mmap_sem is not released
1057 * even though return 0.
1059 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1062 up_read(&mm->mmap_sem);
1063 if (flags & FAULT_FLAG_KILLABLE)
1064 wait_on_page_locked_killable(page);
1066 wait_on_page_locked(page);
1069 if (flags & FAULT_FLAG_KILLABLE) {
1072 ret = __lock_page_killable(page);
1074 up_read(&mm->mmap_sem);
1084 * page_cache_next_hole - find the next hole (not-present entry)
1087 * @max_scan: maximum range to search
1089 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1090 * lowest indexed hole.
1092 * Returns: the index of the hole if found, otherwise returns an index
1093 * outside of the set specified (in which case 'return - index >=
1094 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1097 * page_cache_next_hole may be called under rcu_read_lock. However,
1098 * like radix_tree_gang_lookup, this will not atomically search a
1099 * snapshot of the tree at a single point in time. For example, if a
1100 * hole is created at index 5, then subsequently a hole is created at
1101 * index 10, page_cache_next_hole covering both indexes may return 10
1102 * if called under rcu_read_lock.
1104 pgoff_t page_cache_next_hole(struct address_space *mapping,
1105 pgoff_t index, unsigned long max_scan)
1109 for (i = 0; i < max_scan; i++) {
1112 page = radix_tree_lookup(&mapping->page_tree, index);
1113 if (!page || radix_tree_exceptional_entry(page))
1122 EXPORT_SYMBOL(page_cache_next_hole);
1125 * page_cache_prev_hole - find the prev hole (not-present entry)
1128 * @max_scan: maximum range to search
1130 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1133 * Returns: the index of the hole if found, otherwise returns an index
1134 * outside of the set specified (in which case 'index - return >=
1135 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1138 * page_cache_prev_hole may be called under rcu_read_lock. However,
1139 * like radix_tree_gang_lookup, this will not atomically search a
1140 * snapshot of the tree at a single point in time. For example, if a
1141 * hole is created at index 10, then subsequently a hole is created at
1142 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1143 * called under rcu_read_lock.
1145 pgoff_t page_cache_prev_hole(struct address_space *mapping,
1146 pgoff_t index, unsigned long max_scan)
1150 for (i = 0; i < max_scan; i++) {
1153 page = radix_tree_lookup(&mapping->page_tree, index);
1154 if (!page || radix_tree_exceptional_entry(page))
1157 if (index == ULONG_MAX)
1163 EXPORT_SYMBOL(page_cache_prev_hole);
1166 * find_get_entry - find and get a page cache entry
1167 * @mapping: the address_space to search
1168 * @offset: the page cache index
1170 * Looks up the page cache slot at @mapping & @offset. If there is a
1171 * page cache page, it is returned with an increased refcount.
1173 * If the slot holds a shadow entry of a previously evicted page, or a
1174 * swap entry from shmem/tmpfs, it is returned.
1176 * Otherwise, %NULL is returned.
1178 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1181 struct page *head, *page;
1186 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
1188 page = radix_tree_deref_slot(pagep);
1189 if (unlikely(!page))
1191 if (radix_tree_exception(page)) {
1192 if (radix_tree_deref_retry(page))
1195 * A shadow entry of a recently evicted page,
1196 * or a swap entry from shmem/tmpfs. Return
1197 * it without attempting to raise page count.
1202 head = compound_head(page);
1203 if (!page_cache_get_speculative(head))
1206 /* The page was split under us? */
1207 if (compound_head(page) != head) {
1213 * Has the page moved?
1214 * This is part of the lockless pagecache protocol. See
1215 * include/linux/pagemap.h for details.
1217 if (unlikely(page != *pagep)) {
1227 EXPORT_SYMBOL(find_get_entry);
1230 * find_lock_entry - locate, pin and lock a page cache entry
1231 * @mapping: the address_space to search
1232 * @offset: the page cache index
1234 * Looks up the page cache slot at @mapping & @offset. If there is a
1235 * page cache page, it is returned locked and with an increased
1238 * If the slot holds a shadow entry of a previously evicted page, or a
1239 * swap entry from shmem/tmpfs, it is returned.
1241 * Otherwise, %NULL is returned.
1243 * find_lock_entry() may sleep.
1245 struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1250 page = find_get_entry(mapping, offset);
1251 if (page && !radix_tree_exception(page)) {
1253 /* Has the page been truncated? */
1254 if (unlikely(page_mapping(page) != mapping)) {
1259 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
1263 EXPORT_SYMBOL(find_lock_entry);
1266 * pagecache_get_page - find and get a page reference
1267 * @mapping: the address_space to search
1268 * @offset: the page index
1269 * @fgp_flags: PCG flags
1270 * @gfp_mask: gfp mask to use for the page cache data page allocation
1272 * Looks up the page cache slot at @mapping & @offset.
1274 * PCG flags modify how the page is returned.
1276 * FGP_ACCESSED: the page will be marked accessed
1277 * FGP_LOCK: Page is return locked
1278 * FGP_CREAT: If page is not present then a new page is allocated using
1279 * @gfp_mask and added to the page cache and the VM's LRU
1280 * list. The page is returned locked and with an increased
1281 * refcount. Otherwise, %NULL is returned.
1283 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1284 * if the GFP flags specified for FGP_CREAT are atomic.
1286 * If there is a page cache page, it is returned with an increased refcount.
1288 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1289 int fgp_flags, gfp_t gfp_mask)
1294 page = find_get_entry(mapping, offset);
1295 if (radix_tree_exceptional_entry(page))
1300 if (fgp_flags & FGP_LOCK) {
1301 if (fgp_flags & FGP_NOWAIT) {
1302 if (!trylock_page(page)) {
1310 /* Has the page been truncated? */
1311 if (unlikely(page->mapping != mapping)) {
1316 VM_BUG_ON_PAGE(page->index != offset, page);
1319 if (page && (fgp_flags & FGP_ACCESSED))
1320 mark_page_accessed(page);
1323 if (!page && (fgp_flags & FGP_CREAT)) {
1325 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1326 gfp_mask |= __GFP_WRITE;
1327 if (fgp_flags & FGP_NOFS)
1328 gfp_mask &= ~__GFP_FS;
1330 page = __page_cache_alloc(gfp_mask);
1334 if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
1335 fgp_flags |= FGP_LOCK;
1337 /* Init accessed so avoid atomic mark_page_accessed later */
1338 if (fgp_flags & FGP_ACCESSED)
1339 __SetPageReferenced(page);
1341 err = add_to_page_cache_lru(page, mapping, offset,
1342 gfp_mask & GFP_RECLAIM_MASK);
1343 if (unlikely(err)) {
1353 EXPORT_SYMBOL(pagecache_get_page);
1356 * find_get_entries - gang pagecache lookup
1357 * @mapping: The address_space to search
1358 * @start: The starting page cache index
1359 * @nr_entries: The maximum number of entries
1360 * @entries: Where the resulting entries are placed
1361 * @indices: The cache indices corresponding to the entries in @entries
1363 * find_get_entries() will search for and return a group of up to
1364 * @nr_entries entries in the mapping. The entries are placed at
1365 * @entries. find_get_entries() takes a reference against any actual
1368 * The search returns a group of mapping-contiguous page cache entries
1369 * with ascending indexes. There may be holes in the indices due to
1370 * not-present pages.
1372 * Any shadow entries of evicted pages, or swap entries from
1373 * shmem/tmpfs, are included in the returned array.
1375 * find_get_entries() returns the number of pages and shadow entries
1378 unsigned find_get_entries(struct address_space *mapping,
1379 pgoff_t start, unsigned int nr_entries,
1380 struct page **entries, pgoff_t *indices)
1383 unsigned int ret = 0;
1384 struct radix_tree_iter iter;
1390 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1391 struct page *head, *page;
1393 page = radix_tree_deref_slot(slot);
1394 if (unlikely(!page))
1396 if (radix_tree_exception(page)) {
1397 if (radix_tree_deref_retry(page)) {
1398 slot = radix_tree_iter_retry(&iter);
1402 * A shadow entry of a recently evicted page, a swap
1403 * entry from shmem/tmpfs or a DAX entry. Return it
1404 * without attempting to raise page count.
1409 head = compound_head(page);
1410 if (!page_cache_get_speculative(head))
1413 /* The page was split under us? */
1414 if (compound_head(page) != head) {
1419 /* Has the page moved? */
1420 if (unlikely(page != *slot)) {
1425 indices[ret] = iter.index;
1426 entries[ret] = page;
1427 if (++ret == nr_entries)
1435 * find_get_pages - gang pagecache lookup
1436 * @mapping: The address_space to search
1437 * @start: The starting page index
1438 * @nr_pages: The maximum number of pages
1439 * @pages: Where the resulting pages are placed
1441 * find_get_pages() will search for and return a group of up to
1442 * @nr_pages pages in the mapping. The pages are placed at @pages.
1443 * find_get_pages() takes a reference against the returned pages.
1445 * The search returns a group of mapping-contiguous pages with ascending
1446 * indexes. There may be holes in the indices due to not-present pages.
1448 * find_get_pages() returns the number of pages which were found.
1450 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
1451 unsigned int nr_pages, struct page **pages)
1453 struct radix_tree_iter iter;
1457 if (unlikely(!nr_pages))
1461 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1462 struct page *head, *page;
1464 page = radix_tree_deref_slot(slot);
1465 if (unlikely(!page))
1468 if (radix_tree_exception(page)) {
1469 if (radix_tree_deref_retry(page)) {
1470 slot = radix_tree_iter_retry(&iter);
1474 * A shadow entry of a recently evicted page,
1475 * or a swap entry from shmem/tmpfs. Skip
1481 head = compound_head(page);
1482 if (!page_cache_get_speculative(head))
1485 /* The page was split under us? */
1486 if (compound_head(page) != head) {
1491 /* Has the page moved? */
1492 if (unlikely(page != *slot)) {
1498 if (++ret == nr_pages)
1507 * find_get_pages_contig - gang contiguous pagecache lookup
1508 * @mapping: The address_space to search
1509 * @index: The starting page index
1510 * @nr_pages: The maximum number of pages
1511 * @pages: Where the resulting pages are placed
1513 * find_get_pages_contig() works exactly like find_get_pages(), except
1514 * that the returned number of pages are guaranteed to be contiguous.
1516 * find_get_pages_contig() returns the number of pages which were found.
1518 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1519 unsigned int nr_pages, struct page **pages)
1521 struct radix_tree_iter iter;
1523 unsigned int ret = 0;
1525 if (unlikely(!nr_pages))
1529 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
1530 struct page *head, *page;
1532 page = radix_tree_deref_slot(slot);
1533 /* The hole, there no reason to continue */
1534 if (unlikely(!page))
1537 if (radix_tree_exception(page)) {
1538 if (radix_tree_deref_retry(page)) {
1539 slot = radix_tree_iter_retry(&iter);
1543 * A shadow entry of a recently evicted page,
1544 * or a swap entry from shmem/tmpfs. Stop
1545 * looking for contiguous pages.
1550 head = compound_head(page);
1551 if (!page_cache_get_speculative(head))
1554 /* The page was split under us? */
1555 if (compound_head(page) != head) {
1560 /* Has the page moved? */
1561 if (unlikely(page != *slot)) {
1567 * must check mapping and index after taking the ref.
1568 * otherwise we can get both false positives and false
1569 * negatives, which is just confusing to the caller.
1571 if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
1577 if (++ret == nr_pages)
1583 EXPORT_SYMBOL(find_get_pages_contig);
1586 * find_get_pages_tag - find and return pages that match @tag
1587 * @mapping: the address_space to search
1588 * @index: the starting page index
1589 * @tag: the tag index
1590 * @nr_pages: the maximum number of pages
1591 * @pages: where the resulting pages are placed
1593 * Like find_get_pages, except we only return pages which are tagged with
1594 * @tag. We update @index to index the next page for the traversal.
1596 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
1597 int tag, unsigned int nr_pages, struct page **pages)
1599 struct radix_tree_iter iter;
1603 if (unlikely(!nr_pages))
1607 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1608 &iter, *index, tag) {
1609 struct page *head, *page;
1611 page = radix_tree_deref_slot(slot);
1612 if (unlikely(!page))
1615 if (radix_tree_exception(page)) {
1616 if (radix_tree_deref_retry(page)) {
1617 slot = radix_tree_iter_retry(&iter);
1621 * A shadow entry of a recently evicted page.
1623 * Those entries should never be tagged, but
1624 * this tree walk is lockless and the tags are
1625 * looked up in bulk, one radix tree node at a
1626 * time, so there is a sizable window for page
1627 * reclaim to evict a page we saw tagged.
1634 head = compound_head(page);
1635 if (!page_cache_get_speculative(head))
1638 /* The page was split under us? */
1639 if (compound_head(page) != head) {
1644 /* Has the page moved? */
1645 if (unlikely(page != *slot)) {
1651 if (++ret == nr_pages)
1658 *index = pages[ret - 1]->index + 1;
1662 EXPORT_SYMBOL(find_get_pages_tag);
1665 * find_get_entries_tag - find and return entries that match @tag
1666 * @mapping: the address_space to search
1667 * @start: the starting page cache index
1668 * @tag: the tag index
1669 * @nr_entries: the maximum number of entries
1670 * @entries: where the resulting entries are placed
1671 * @indices: the cache indices corresponding to the entries in @entries
1673 * Like find_get_entries, except we only return entries which are tagged with
1676 unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
1677 int tag, unsigned int nr_entries,
1678 struct page **entries, pgoff_t *indices)
1681 unsigned int ret = 0;
1682 struct radix_tree_iter iter;
1688 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1689 &iter, start, tag) {
1690 struct page *head, *page;
1692 page = radix_tree_deref_slot(slot);
1693 if (unlikely(!page))
1695 if (radix_tree_exception(page)) {
1696 if (radix_tree_deref_retry(page)) {
1697 slot = radix_tree_iter_retry(&iter);
1702 * A shadow entry of a recently evicted page, a swap
1703 * entry from shmem/tmpfs or a DAX entry. Return it
1704 * without attempting to raise page count.
1709 head = compound_head(page);
1710 if (!page_cache_get_speculative(head))
1713 /* The page was split under us? */
1714 if (compound_head(page) != head) {
1719 /* Has the page moved? */
1720 if (unlikely(page != *slot)) {
1725 indices[ret] = iter.index;
1726 entries[ret] = page;
1727 if (++ret == nr_entries)
1733 EXPORT_SYMBOL(find_get_entries_tag);
1736 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1737 * a _large_ part of the i/o request. Imagine the worst scenario:
1739 * ---R__________________________________________B__________
1740 * ^ reading here ^ bad block(assume 4k)
1742 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1743 * => failing the whole request => read(R) => read(R+1) =>
1744 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1745 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1746 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1748 * It is going insane. Fix it by quickly scaling down the readahead size.
1750 static void shrink_readahead_size_eio(struct file *filp,
1751 struct file_ra_state *ra)
1757 * do_generic_file_read - generic file read routine
1758 * @filp: the file to read
1759 * @ppos: current file position
1760 * @iter: data destination
1761 * @written: already copied
1763 * This is a generic file read routine, and uses the
1764 * mapping->a_ops->readpage() function for the actual low-level stuff.
1766 * This is really ugly. But the goto's actually try to clarify some
1767 * of the logic when it comes to error handling etc.
1769 static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
1770 struct iov_iter *iter, ssize_t written)
1772 struct address_space *mapping = filp->f_mapping;
1773 struct inode *inode = mapping->host;
1774 struct file_ra_state *ra = &filp->f_ra;
1778 unsigned long offset; /* offset into pagecache page */
1779 unsigned int prev_offset;
1782 if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
1784 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
1786 index = *ppos >> PAGE_SHIFT;
1787 prev_index = ra->prev_pos >> PAGE_SHIFT;
1788 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
1789 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
1790 offset = *ppos & ~PAGE_MASK;
1796 unsigned long nr, ret;
1800 if (fatal_signal_pending(current)) {
1805 page = find_get_page(mapping, index);
1807 page_cache_sync_readahead(mapping,
1809 index, last_index - index);
1810 page = find_get_page(mapping, index);
1811 if (unlikely(page == NULL))
1812 goto no_cached_page;
1814 if (PageReadahead(page)) {
1815 page_cache_async_readahead(mapping,
1817 index, last_index - index);
1819 if (!PageUptodate(page)) {
1821 * See comment in do_read_cache_page on why
1822 * wait_on_page_locked is used to avoid unnecessarily
1823 * serialisations and why it's safe.
1825 error = wait_on_page_locked_killable(page);
1826 if (unlikely(error))
1827 goto readpage_error;
1828 if (PageUptodate(page))
1831 if (inode->i_blkbits == PAGE_SHIFT ||
1832 !mapping->a_ops->is_partially_uptodate)
1833 goto page_not_up_to_date;
1834 /* pipes can't handle partially uptodate pages */
1835 if (unlikely(iter->type & ITER_PIPE))
1836 goto page_not_up_to_date;
1837 if (!trylock_page(page))
1838 goto page_not_up_to_date;
1839 /* Did it get truncated before we got the lock? */
1841 goto page_not_up_to_date_locked;
1842 if (!mapping->a_ops->is_partially_uptodate(page,
1843 offset, iter->count))
1844 goto page_not_up_to_date_locked;
1849 * i_size must be checked after we know the page is Uptodate.
1851 * Checking i_size after the check allows us to calculate
1852 * the correct value for "nr", which means the zero-filled
1853 * part of the page is not copied back to userspace (unless
1854 * another truncate extends the file - this is desired though).
1857 isize = i_size_read(inode);
1858 end_index = (isize - 1) >> PAGE_SHIFT;
1859 if (unlikely(!isize || index > end_index)) {
1864 /* nr is the maximum number of bytes to copy from this page */
1866 if (index == end_index) {
1867 nr = ((isize - 1) & ~PAGE_MASK) + 1;
1875 /* If users can be writing to this page using arbitrary
1876 * virtual addresses, take care about potential aliasing
1877 * before reading the page on the kernel side.
1879 if (mapping_writably_mapped(mapping))
1880 flush_dcache_page(page);
1883 * When a sequential read accesses a page several times,
1884 * only mark it as accessed the first time.
1886 if (prev_index != index || offset != prev_offset)
1887 mark_page_accessed(page);
1891 * Ok, we have the page, and it's up-to-date, so
1892 * now we can copy it to user space...
1895 ret = copy_page_to_iter(page, offset, nr, iter);
1897 index += offset >> PAGE_SHIFT;
1898 offset &= ~PAGE_MASK;
1899 prev_offset = offset;
1903 if (!iov_iter_count(iter))
1911 page_not_up_to_date:
1912 /* Get exclusive access to the page ... */
1913 error = lock_page_killable(page);
1914 if (unlikely(error))
1915 goto readpage_error;
1917 page_not_up_to_date_locked:
1918 /* Did it get truncated before we got the lock? */
1919 if (!page->mapping) {
1925 /* Did somebody else fill it already? */
1926 if (PageUptodate(page)) {
1933 * A previous I/O error may have been due to temporary
1934 * failures, eg. multipath errors.
1935 * PG_error will be set again if readpage fails.
1937 ClearPageError(page);
1938 /* Start the actual read. The read will unlock the page. */
1939 error = mapping->a_ops->readpage(filp, page);
1941 if (unlikely(error)) {
1942 if (error == AOP_TRUNCATED_PAGE) {
1947 goto readpage_error;
1950 if (!PageUptodate(page)) {
1951 error = lock_page_killable(page);
1952 if (unlikely(error))
1953 goto readpage_error;
1954 if (!PageUptodate(page)) {
1955 if (page->mapping == NULL) {
1957 * invalidate_mapping_pages got it
1964 shrink_readahead_size_eio(filp, ra);
1966 goto readpage_error;
1974 /* UHHUH! A synchronous read error occurred. Report it */
1980 * Ok, it wasn't cached, so we need to create a new
1983 page = page_cache_alloc_cold(mapping);
1988 error = add_to_page_cache_lru(page, mapping, index,
1989 mapping_gfp_constraint(mapping, GFP_KERNEL));
1992 if (error == -EEXIST) {
2002 ra->prev_pos = prev_index;
2003 ra->prev_pos <<= PAGE_SHIFT;
2004 ra->prev_pos |= prev_offset;
2006 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
2007 file_accessed(filp);
2008 return written ? written : error;
2012 * generic_file_read_iter - generic filesystem read routine
2013 * @iocb: kernel I/O control block
2014 * @iter: destination for the data read
2016 * This is the "read_iter()" routine for all filesystems
2017 * that can use the page cache directly.
2020 generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2022 struct file *file = iocb->ki_filp;
2024 size_t count = iov_iter_count(iter);
2027 goto out; /* skip atime */
2029 if (iocb->ki_flags & IOCB_DIRECT) {
2030 struct address_space *mapping = file->f_mapping;
2031 struct inode *inode = mapping->host;
2032 struct iov_iter data = *iter;
2035 size = i_size_read(inode);
2036 retval = filemap_write_and_wait_range(mapping, iocb->ki_pos,
2037 iocb->ki_pos + count - 1);
2041 file_accessed(file);
2043 retval = mapping->a_ops->direct_IO(iocb, &data);
2045 iocb->ki_pos += retval;
2046 iov_iter_advance(iter, retval);
2050 * Btrfs can have a short DIO read if we encounter
2051 * compressed extents, so if there was an error, or if
2052 * we've already read everything we wanted to, or if
2053 * there was a short read because we hit EOF, go ahead
2054 * and return. Otherwise fallthrough to buffered io for
2055 * the rest of the read. Buffered reads will not work for
2056 * DAX files, so don't bother trying.
2058 if (retval < 0 || !iov_iter_count(iter) || iocb->ki_pos >= size ||
2063 retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval);
2067 EXPORT_SYMBOL(generic_file_read_iter);
2071 * page_cache_read - adds requested page to the page cache if not already there
2072 * @file: file to read
2073 * @offset: page index
2074 * @gfp_mask: memory allocation flags
2076 * This adds the requested page to the page cache if it isn't already there,
2077 * and schedules an I/O to read in its contents from disk.
2079 static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
2081 struct address_space *mapping = file->f_mapping;
2086 page = __page_cache_alloc(gfp_mask|__GFP_COLD);
2090 ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
2092 ret = mapping->a_ops->readpage(file, page);
2093 else if (ret == -EEXIST)
2094 ret = 0; /* losing race to add is OK */
2098 } while (ret == AOP_TRUNCATED_PAGE);
2103 #define MMAP_LOTSAMISS (100)
2106 * Synchronous readahead happens when we don't even find
2107 * a page in the page cache at all.
2109 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
2110 struct file_ra_state *ra,
2114 struct address_space *mapping = file->f_mapping;
2116 /* If we don't want any read-ahead, don't bother */
2117 if (vma->vm_flags & VM_RAND_READ)
2122 if (vma->vm_flags & VM_SEQ_READ) {
2123 page_cache_sync_readahead(mapping, ra, file, offset,
2128 /* Avoid banging the cache line if not needed */
2129 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
2133 * Do we miss much more than hit in this file? If so,
2134 * stop bothering with read-ahead. It will only hurt.
2136 if (ra->mmap_miss > MMAP_LOTSAMISS)
2142 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
2143 ra->size = ra->ra_pages;
2144 ra->async_size = ra->ra_pages / 4;
2145 ra_submit(ra, mapping, file);
2149 * Asynchronous readahead happens when we find the page and PG_readahead,
2150 * so we want to possibly extend the readahead further..
2152 static void do_async_mmap_readahead(struct vm_area_struct *vma,
2153 struct file_ra_state *ra,
2158 struct address_space *mapping = file->f_mapping;
2160 /* If we don't want any read-ahead, don't bother */
2161 if (vma->vm_flags & VM_RAND_READ)
2163 if (ra->mmap_miss > 0)
2165 if (PageReadahead(page))
2166 page_cache_async_readahead(mapping, ra, file,
2167 page, offset, ra->ra_pages);
2171 * filemap_fault - read in file data for page fault handling
2172 * @vmf: struct vm_fault containing details of the fault
2174 * filemap_fault() is invoked via the vma operations vector for a
2175 * mapped memory region to read in file data during a page fault.
2177 * The goto's are kind of ugly, but this streamlines the normal case of having
2178 * it in the page cache, and handles the special cases reasonably without
2179 * having a lot of duplicated code.
2181 * vma->vm_mm->mmap_sem must be held on entry.
2183 * If our return value has VM_FAULT_RETRY set, it's because
2184 * lock_page_or_retry() returned 0.
2185 * The mmap_sem has usually been released in this case.
2186 * See __lock_page_or_retry() for the exception.
2188 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2189 * has not been released.
2191 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2193 int filemap_fault(struct vm_fault *vmf)
2196 struct file *file = vmf->vma->vm_file;
2197 struct address_space *mapping = file->f_mapping;
2198 struct file_ra_state *ra = &file->f_ra;
2199 struct inode *inode = mapping->host;
2200 pgoff_t offset = vmf->pgoff;
2205 size = round_up(i_size_read(inode), PAGE_SIZE);
2206 if (offset >= size >> PAGE_SHIFT)
2207 return VM_FAULT_SIGBUS;
2210 * Do we have something in the page cache already?
2212 page = find_get_page(mapping, offset);
2213 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2215 * We found the page, so try async readahead before
2216 * waiting for the lock.
2218 do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
2220 /* No page in the page cache at all */
2221 do_sync_mmap_readahead(vmf->vma, ra, file, offset);
2222 count_vm_event(PGMAJFAULT);
2223 mem_cgroup_count_vm_event(vmf->vma->vm_mm, PGMAJFAULT);
2224 ret = VM_FAULT_MAJOR;
2226 page = find_get_page(mapping, offset);
2228 goto no_cached_page;
2231 if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) {
2233 return ret | VM_FAULT_RETRY;
2236 /* Did it get truncated? */
2237 if (unlikely(page->mapping != mapping)) {
2242 VM_BUG_ON_PAGE(page->index != offset, page);
2245 * We have a locked page in the page cache, now we need to check
2246 * that it's up-to-date. If not, it is going to be due to an error.
2248 if (unlikely(!PageUptodate(page)))
2249 goto page_not_uptodate;
2252 * Found the page and have a reference on it.
2253 * We must recheck i_size under page lock.
2255 size = round_up(i_size_read(inode), PAGE_SIZE);
2256 if (unlikely(offset >= size >> PAGE_SHIFT)) {
2259 return VM_FAULT_SIGBUS;
2263 return ret | VM_FAULT_LOCKED;
2267 * We're only likely to ever get here if MADV_RANDOM is in
2270 error = page_cache_read(file, offset, vmf->gfp_mask);
2273 * The page we want has now been added to the page cache.
2274 * In the unlikely event that someone removed it in the
2275 * meantime, we'll just come back here and read it again.
2281 * An error return from page_cache_read can result if the
2282 * system is low on memory, or a problem occurs while trying
2285 if (error == -ENOMEM)
2286 return VM_FAULT_OOM;
2287 return VM_FAULT_SIGBUS;
2291 * Umm, take care of errors if the page isn't up-to-date.
2292 * Try to re-read it _once_. We do this synchronously,
2293 * because there really aren't any performance issues here
2294 * and we need to check for errors.
2296 ClearPageError(page);
2297 error = mapping->a_ops->readpage(file, page);
2299 wait_on_page_locked(page);
2300 if (!PageUptodate(page))
2305 if (!error || error == AOP_TRUNCATED_PAGE)
2308 /* Things didn't work out. Return zero to tell the mm layer so. */
2309 shrink_readahead_size_eio(file, ra);
2310 return VM_FAULT_SIGBUS;
2312 EXPORT_SYMBOL(filemap_fault);
2314 void filemap_map_pages(struct vm_fault *vmf,
2315 pgoff_t start_pgoff, pgoff_t end_pgoff)
2317 struct radix_tree_iter iter;
2319 struct file *file = vmf->vma->vm_file;
2320 struct address_space *mapping = file->f_mapping;
2321 pgoff_t last_pgoff = start_pgoff;
2323 struct page *head, *page;
2326 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
2328 if (iter.index > end_pgoff)
2331 page = radix_tree_deref_slot(slot);
2332 if (unlikely(!page))
2334 if (radix_tree_exception(page)) {
2335 if (radix_tree_deref_retry(page)) {
2336 slot = radix_tree_iter_retry(&iter);
2342 head = compound_head(page);
2343 if (!page_cache_get_speculative(head))
2346 /* The page was split under us? */
2347 if (compound_head(page) != head) {
2352 /* Has the page moved? */
2353 if (unlikely(page != *slot)) {
2358 if (!PageUptodate(page) ||
2359 PageReadahead(page) ||
2362 if (!trylock_page(page))
2365 if (page->mapping != mapping || !PageUptodate(page))
2368 size = round_up(i_size_read(mapping->host), PAGE_SIZE);
2369 if (page->index >= size >> PAGE_SHIFT)
2372 if (file->f_ra.mmap_miss > 0)
2373 file->f_ra.mmap_miss--;
2375 vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
2377 vmf->pte += iter.index - last_pgoff;
2378 last_pgoff = iter.index;
2379 if (alloc_set_pte(vmf, NULL, page))
2388 /* Huge page is mapped? No need to proceed. */
2389 if (pmd_trans_huge(*vmf->pmd))
2391 if (iter.index == end_pgoff)
2396 EXPORT_SYMBOL(filemap_map_pages);
2398 int filemap_page_mkwrite(struct vm_fault *vmf)
2400 struct page *page = vmf->page;
2401 struct inode *inode = file_inode(vmf->vma->vm_file);
2402 int ret = VM_FAULT_LOCKED;
2404 sb_start_pagefault(inode->i_sb);
2405 file_update_time(vmf->vma->vm_file);
2407 if (page->mapping != inode->i_mapping) {
2409 ret = VM_FAULT_NOPAGE;
2413 * We mark the page dirty already here so that when freeze is in
2414 * progress, we are guaranteed that writeback during freezing will
2415 * see the dirty page and writeprotect it again.
2417 set_page_dirty(page);
2418 wait_for_stable_page(page);
2420 sb_end_pagefault(inode->i_sb);
2423 EXPORT_SYMBOL(filemap_page_mkwrite);
2425 const struct vm_operations_struct generic_file_vm_ops = {
2426 .fault = filemap_fault,
2427 .map_pages = filemap_map_pages,
2428 .page_mkwrite = filemap_page_mkwrite,
2431 /* This is used for a general mmap of a disk file */
2433 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2435 struct address_space *mapping = file->f_mapping;
2437 if (!mapping->a_ops->readpage)
2439 file_accessed(file);
2440 vma->vm_ops = &generic_file_vm_ops;
2445 * This is for filesystems which do not implement ->writepage.
2447 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2449 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2451 return generic_file_mmap(file, vma);
2454 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2458 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2462 #endif /* CONFIG_MMU */
2464 EXPORT_SYMBOL(generic_file_mmap);
2465 EXPORT_SYMBOL(generic_file_readonly_mmap);
2467 static struct page *wait_on_page_read(struct page *page)
2469 if (!IS_ERR(page)) {
2470 wait_on_page_locked(page);
2471 if (!PageUptodate(page)) {
2473 page = ERR_PTR(-EIO);
2479 static struct page *do_read_cache_page(struct address_space *mapping,
2481 int (*filler)(void *, struct page *),
2488 page = find_get_page(mapping, index);
2490 page = __page_cache_alloc(gfp | __GFP_COLD);
2492 return ERR_PTR(-ENOMEM);
2493 err = add_to_page_cache_lru(page, mapping, index, gfp);
2494 if (unlikely(err)) {
2498 /* Presumably ENOMEM for radix tree node */
2499 return ERR_PTR(err);
2503 err = filler(data, page);
2506 return ERR_PTR(err);
2509 page = wait_on_page_read(page);
2514 if (PageUptodate(page))
2518 * Page is not up to date and may be locked due one of the following
2519 * case a: Page is being filled and the page lock is held
2520 * case b: Read/write error clearing the page uptodate status
2521 * case c: Truncation in progress (page locked)
2522 * case d: Reclaim in progress
2524 * Case a, the page will be up to date when the page is unlocked.
2525 * There is no need to serialise on the page lock here as the page
2526 * is pinned so the lock gives no additional protection. Even if the
2527 * the page is truncated, the data is still valid if PageUptodate as
2528 * it's a race vs truncate race.
2529 * Case b, the page will not be up to date
2530 * Case c, the page may be truncated but in itself, the data may still
2531 * be valid after IO completes as it's a read vs truncate race. The
2532 * operation must restart if the page is not uptodate on unlock but
2533 * otherwise serialising on page lock to stabilise the mapping gives
2534 * no additional guarantees to the caller as the page lock is
2535 * released before return.
2536 * Case d, similar to truncation. If reclaim holds the page lock, it
2537 * will be a race with remove_mapping that determines if the mapping
2538 * is valid on unlock but otherwise the data is valid and there is
2539 * no need to serialise with page lock.
2541 * As the page lock gives no additional guarantee, we optimistically
2542 * wait on the page to be unlocked and check if it's up to date and
2543 * use the page if it is. Otherwise, the page lock is required to
2544 * distinguish between the different cases. The motivation is that we
2545 * avoid spurious serialisations and wakeups when multiple processes
2546 * wait on the same page for IO to complete.
2548 wait_on_page_locked(page);
2549 if (PageUptodate(page))
2552 /* Distinguish between all the cases under the safety of the lock */
2555 /* Case c or d, restart the operation */
2556 if (!page->mapping) {
2562 /* Someone else locked and filled the page in a very small window */
2563 if (PageUptodate(page)) {
2570 mark_page_accessed(page);
2575 * read_cache_page - read into page cache, fill it if needed
2576 * @mapping: the page's address_space
2577 * @index: the page index
2578 * @filler: function to perform the read
2579 * @data: first arg to filler(data, page) function, often left as NULL
2581 * Read into the page cache. If a page already exists, and PageUptodate() is
2582 * not set, try to fill the page and wait for it to become unlocked.
2584 * If the page does not get brought uptodate, return -EIO.
2586 struct page *read_cache_page(struct address_space *mapping,
2588 int (*filler)(void *, struct page *),
2591 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2593 EXPORT_SYMBOL(read_cache_page);
2596 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2597 * @mapping: the page's address_space
2598 * @index: the page index
2599 * @gfp: the page allocator flags to use if allocating
2601 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2602 * any new page allocations done using the specified allocation flags.
2604 * If the page does not get brought uptodate, return -EIO.
2606 struct page *read_cache_page_gfp(struct address_space *mapping,
2610 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2612 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2614 EXPORT_SYMBOL(read_cache_page_gfp);
2617 * Performs necessary checks before doing a write
2619 * Can adjust writing position or amount of bytes to write.
2620 * Returns appropriate error code that caller should return or
2621 * zero in case that write should be allowed.
2623 inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2625 struct file *file = iocb->ki_filp;
2626 struct inode *inode = file->f_mapping->host;
2627 unsigned long limit = rlimit(RLIMIT_FSIZE);
2630 if (!iov_iter_count(from))
2633 /* FIXME: this is for backwards compatibility with 2.4 */
2634 if (iocb->ki_flags & IOCB_APPEND)
2635 iocb->ki_pos = i_size_read(inode);
2639 if (limit != RLIM_INFINITY) {
2640 if (iocb->ki_pos >= limit) {
2641 send_sig(SIGXFSZ, current, 0);
2644 iov_iter_truncate(from, limit - (unsigned long)pos);
2650 if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
2651 !(file->f_flags & O_LARGEFILE))) {
2652 if (pos >= MAX_NON_LFS)
2654 iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
2658 * Are we about to exceed the fs block limit ?
2660 * If we have written data it becomes a short write. If we have
2661 * exceeded without writing data we send a signal and return EFBIG.
2662 * Linus frestrict idea will clean these up nicely..
2664 if (unlikely(pos >= inode->i_sb->s_maxbytes))
2667 iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
2668 return iov_iter_count(from);
2670 EXPORT_SYMBOL(generic_write_checks);
2672 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2673 loff_t pos, unsigned len, unsigned flags,
2674 struct page **pagep, void **fsdata)
2676 const struct address_space_operations *aops = mapping->a_ops;
2678 return aops->write_begin(file, mapping, pos, len, flags,
2681 EXPORT_SYMBOL(pagecache_write_begin);
2683 int pagecache_write_end(struct file *file, struct address_space *mapping,
2684 loff_t pos, unsigned len, unsigned copied,
2685 struct page *page, void *fsdata)
2687 const struct address_space_operations *aops = mapping->a_ops;
2689 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2691 EXPORT_SYMBOL(pagecache_write_end);
2694 generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
2696 struct file *file = iocb->ki_filp;
2697 struct address_space *mapping = file->f_mapping;
2698 struct inode *inode = mapping->host;
2699 loff_t pos = iocb->ki_pos;
2703 struct iov_iter data;
2705 write_len = iov_iter_count(from);
2706 end = (pos + write_len - 1) >> PAGE_SHIFT;
2708 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2713 * After a write we want buffered reads to be sure to go to disk to get
2714 * the new data. We invalidate clean cached page from the region we're
2715 * about to write. We do this *before* the write so that we can return
2716 * without clobbering -EIOCBQUEUED from ->direct_IO().
2718 if (mapping->nrpages) {
2719 written = invalidate_inode_pages2_range(mapping,
2720 pos >> PAGE_SHIFT, end);
2722 * If a page can not be invalidated, return 0 to fall back
2723 * to buffered write.
2726 if (written == -EBUSY)
2733 written = mapping->a_ops->direct_IO(iocb, &data);
2736 * Finally, try again to invalidate clean pages which might have been
2737 * cached by non-direct readahead, or faulted in by get_user_pages()
2738 * if the source of the write was an mmap'ed region of the file
2739 * we're writing. Either one is a pretty crazy thing to do,
2740 * so we don't support it 100%. If this invalidation
2741 * fails, tough, the write still worked...
2743 if (mapping->nrpages) {
2744 invalidate_inode_pages2_range(mapping,
2745 pos >> PAGE_SHIFT, end);
2750 iov_iter_advance(from, written);
2751 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2752 i_size_write(inode, pos);
2753 mark_inode_dirty(inode);
2760 EXPORT_SYMBOL(generic_file_direct_write);
2763 * Find or create a page at the given pagecache position. Return the locked
2764 * page. This function is specifically for buffered writes.
2766 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2767 pgoff_t index, unsigned flags)
2770 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
2772 if (flags & AOP_FLAG_NOFS)
2773 fgp_flags |= FGP_NOFS;
2775 page = pagecache_get_page(mapping, index, fgp_flags,
2776 mapping_gfp_mask(mapping));
2778 wait_for_stable_page(page);
2782 EXPORT_SYMBOL(grab_cache_page_write_begin);
2784 ssize_t generic_perform_write(struct file *file,
2785 struct iov_iter *i, loff_t pos)
2787 struct address_space *mapping = file->f_mapping;
2788 const struct address_space_operations *a_ops = mapping->a_ops;
2790 ssize_t written = 0;
2791 unsigned int flags = 0;
2794 * Copies from kernel address space cannot fail (NFSD is a big user).
2796 if (!iter_is_iovec(i))
2797 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2801 unsigned long offset; /* Offset into pagecache page */
2802 unsigned long bytes; /* Bytes to write to page */
2803 size_t copied; /* Bytes copied from user */
2806 offset = (pos & (PAGE_SIZE - 1));
2807 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2812 * Bring in the user page that we will copy from _first_.
2813 * Otherwise there's a nasty deadlock on copying from the
2814 * same page as we're writing to, without it being marked
2817 * Not only is this an optimisation, but it is also required
2818 * to check that the address is actually valid, when atomic
2819 * usercopies are used, below.
2821 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2826 if (fatal_signal_pending(current)) {
2831 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2833 if (unlikely(status < 0))
2836 if (mapping_writably_mapped(mapping))
2837 flush_dcache_page(page);
2839 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2840 flush_dcache_page(page);
2842 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2844 if (unlikely(status < 0))
2850 iov_iter_advance(i, copied);
2851 if (unlikely(copied == 0)) {
2853 * If we were unable to copy any data at all, we must
2854 * fall back to a single segment length write.
2856 * If we didn't fallback here, we could livelock
2857 * because not all segments in the iov can be copied at
2858 * once without a pagefault.
2860 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2861 iov_iter_single_seg_count(i));
2867 balance_dirty_pages_ratelimited(mapping);
2868 } while (iov_iter_count(i));
2870 return written ? written : status;
2872 EXPORT_SYMBOL(generic_perform_write);
2875 * __generic_file_write_iter - write data to a file
2876 * @iocb: IO state structure (file, offset, etc.)
2877 * @from: iov_iter with data to write
2879 * This function does all the work needed for actually writing data to a
2880 * file. It does all basic checks, removes SUID from the file, updates
2881 * modification times and calls proper subroutines depending on whether we
2882 * do direct IO or a standard buffered write.
2884 * It expects i_mutex to be grabbed unless we work on a block device or similar
2885 * object which does not need locking at all.
2887 * This function does *not* take care of syncing data in case of O_SYNC write.
2888 * A caller has to handle it. This is mainly due to the fact that we want to
2889 * avoid syncing under i_mutex.
2891 ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2893 struct file *file = iocb->ki_filp;
2894 struct address_space * mapping = file->f_mapping;
2895 struct inode *inode = mapping->host;
2896 ssize_t written = 0;
2900 /* We can write back this queue in page reclaim */
2901 current->backing_dev_info = inode_to_bdi(inode);
2902 err = file_remove_privs(file);
2906 err = file_update_time(file);
2910 if (iocb->ki_flags & IOCB_DIRECT) {
2911 loff_t pos, endbyte;
2913 written = generic_file_direct_write(iocb, from);
2915 * If the write stopped short of completing, fall back to
2916 * buffered writes. Some filesystems do this for writes to
2917 * holes, for example. For DAX files, a buffered write will
2918 * not succeed (even if it did, DAX does not handle dirty
2919 * page-cache pages correctly).
2921 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
2924 status = generic_perform_write(file, from, pos = iocb->ki_pos);
2926 * If generic_perform_write() returned a synchronous error
2927 * then we want to return the number of bytes which were
2928 * direct-written, or the error code if that was zero. Note
2929 * that this differs from normal direct-io semantics, which
2930 * will return -EFOO even if some bytes were written.
2932 if (unlikely(status < 0)) {
2937 * We need to ensure that the page cache pages are written to
2938 * disk and invalidated to preserve the expected O_DIRECT
2941 endbyte = pos + status - 1;
2942 err = filemap_write_and_wait_range(mapping, pos, endbyte);
2944 iocb->ki_pos = endbyte + 1;
2946 invalidate_mapping_pages(mapping,
2948 endbyte >> PAGE_SHIFT);
2951 * We don't know how much we wrote, so just return
2952 * the number of bytes which were direct-written
2956 written = generic_perform_write(file, from, iocb->ki_pos);
2957 if (likely(written > 0))
2958 iocb->ki_pos += written;
2961 current->backing_dev_info = NULL;
2962 return written ? written : err;
2964 EXPORT_SYMBOL(__generic_file_write_iter);
2967 * generic_file_write_iter - write data to a file
2968 * @iocb: IO state structure
2969 * @from: iov_iter with data to write
2971 * This is a wrapper around __generic_file_write_iter() to be used by most
2972 * filesystems. It takes care of syncing the file in case of O_SYNC file
2973 * and acquires i_mutex as needed.
2975 ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2977 struct file *file = iocb->ki_filp;
2978 struct inode *inode = file->f_mapping->host;
2982 ret = generic_write_checks(iocb, from);
2984 ret = __generic_file_write_iter(iocb, from);
2985 inode_unlock(inode);
2988 ret = generic_write_sync(iocb, ret);
2991 EXPORT_SYMBOL(generic_file_write_iter);
2994 * try_to_release_page() - release old fs-specific metadata on a page
2996 * @page: the page which the kernel is trying to free
2997 * @gfp_mask: memory allocation flags (and I/O mode)
2999 * The address_space is to try to release any data against the page
3000 * (presumably at page->private). If the release was successful, return `1'.
3001 * Otherwise return zero.
3003 * This may also be called if PG_fscache is set on a page, indicating that the
3004 * page is known to the local caching routines.
3006 * The @gfp_mask argument specifies whether I/O may be performed to release
3007 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3010 int try_to_release_page(struct page *page, gfp_t gfp_mask)
3012 struct address_space * const mapping = page->mapping;
3014 BUG_ON(!PageLocked(page));
3015 if (PageWriteback(page))
3018 if (mapping && mapping->a_ops->releasepage)
3019 return mapping->a_ops->releasepage(page, gfp_mask);
3020 return try_to_free_buffers(page);
3023 EXPORT_SYMBOL(try_to_release_page);