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/module.h>
13 #include <linux/compiler.h>
15 #include <linux/uaccess.h>
16 #include <linux/aio.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/syscalls.h>
33 #include <linux/cpuset.h>
34 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
35 #include <linux/memcontrol.h>
36 #include <linux/mm_inline.h> /* for page_is_file_cache() */
40 * FIXME: remove all knowledge of the buffer layer from the core VM
42 #include <linux/buffer_head.h> /* for try_to_free_buffers */
47 * Shared mappings implemented 30.11.1994. It's not fully working yet,
50 * Shared mappings now work. 15.8.1995 Bruno.
52 * finished 'unifying' the page and buffer cache and SMP-threaded the
53 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
55 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
61 * ->i_mmap_lock (truncate_pagecache)
62 * ->private_lock (__free_pte->__set_page_dirty_buffers)
63 * ->swap_lock (exclusive_swap_page, others)
64 * ->mapping->tree_lock
67 * ->i_mmap_lock (truncate->unmap_mapping_range)
71 * ->page_table_lock or pte_lock (various, mainly in memory.c)
72 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
75 * ->lock_page (access_process_vm)
77 * ->i_mutex (generic_file_buffered_write)
78 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
81 * ->i_alloc_sem (various)
84 * sb_lock (fs/fs-writeback.c)
85 * ->mapping->tree_lock (__sync_single_inode)
88 * ->anon_vma.lock (vma_adjust)
91 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
93 * ->page_table_lock or pte_lock
94 * ->swap_lock (try_to_unmap_one)
95 * ->private_lock (try_to_unmap_one)
96 * ->tree_lock (try_to_unmap_one)
97 * ->zone.lru_lock (follow_page->mark_page_accessed)
98 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
99 * ->private_lock (page_remove_rmap->set_page_dirty)
100 * ->tree_lock (page_remove_rmap->set_page_dirty)
101 * inode_wb_list_lock (page_remove_rmap->set_page_dirty)
102 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
103 * inode_wb_list_lock (zap_pte_range->set_page_dirty)
104 * ->inode->i_lock (zap_pte_range->set_page_dirty)
105 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
107 * (code doesn't rely on that order, so you could switch it around)
108 * ->tasklist_lock (memory_failure, collect_procs_ao)
113 * Delete a page from the page cache and free it. Caller has to make
114 * sure the page is locked and that nobody else uses it - or that usage
115 * is safe. The caller must hold the mapping's tree_lock.
117 void __delete_from_page_cache(struct page *page)
119 struct address_space *mapping = page->mapping;
121 radix_tree_delete(&mapping->page_tree, page->index);
122 page->mapping = NULL;
124 __dec_zone_page_state(page, NR_FILE_PAGES);
125 if (PageSwapBacked(page))
126 __dec_zone_page_state(page, NR_SHMEM);
127 BUG_ON(page_mapped(page));
130 * Some filesystems seem to re-dirty the page even after
131 * the VM has canceled the dirty bit (eg ext3 journaling).
133 * Fix it up by doing a final dirty accounting check after
134 * having removed the page entirely.
136 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
137 dec_zone_page_state(page, NR_FILE_DIRTY);
138 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
143 * delete_from_page_cache - delete page from page cache
144 * @page: the page which the kernel is trying to remove from page cache
146 * This must be called only on pages that have been verified to be in the page
147 * cache and locked. It will never put the page into the free list, the caller
148 * has a reference on the page.
150 void delete_from_page_cache(struct page *page)
152 struct address_space *mapping = page->mapping;
153 void (*freepage)(struct page *);
155 BUG_ON(!PageLocked(page));
157 freepage = mapping->a_ops->freepage;
158 spin_lock_irq(&mapping->tree_lock);
159 __delete_from_page_cache(page);
160 spin_unlock_irq(&mapping->tree_lock);
161 mem_cgroup_uncharge_cache_page(page);
165 page_cache_release(page);
167 EXPORT_SYMBOL(delete_from_page_cache);
169 static int sleep_on_page(void *word)
175 static int sleep_on_page_killable(void *word)
178 return fatal_signal_pending(current) ? -EINTR : 0;
182 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
183 * @mapping: address space structure to write
184 * @start: offset in bytes where the range starts
185 * @end: offset in bytes where the range ends (inclusive)
186 * @sync_mode: enable synchronous operation
188 * Start writeback against all of a mapping's dirty pages that lie
189 * within the byte offsets <start, end> inclusive.
191 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
192 * opposed to a regular memory cleansing writeback. The difference between
193 * these two operations is that if a dirty page/buffer is encountered, it must
194 * be waited upon, and not just skipped over.
196 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
197 loff_t end, int sync_mode)
200 struct writeback_control wbc = {
201 .sync_mode = sync_mode,
202 .nr_to_write = LONG_MAX,
203 .range_start = start,
207 if (!mapping_cap_writeback_dirty(mapping))
210 ret = do_writepages(mapping, &wbc);
214 static inline int __filemap_fdatawrite(struct address_space *mapping,
217 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
220 int filemap_fdatawrite(struct address_space *mapping)
222 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
224 EXPORT_SYMBOL(filemap_fdatawrite);
226 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
229 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
231 EXPORT_SYMBOL(filemap_fdatawrite_range);
234 * filemap_flush - mostly a non-blocking flush
235 * @mapping: target address_space
237 * This is a mostly non-blocking flush. Not suitable for data-integrity
238 * purposes - I/O may not be started against all dirty pages.
240 int filemap_flush(struct address_space *mapping)
242 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
244 EXPORT_SYMBOL(filemap_flush);
247 * filemap_fdatawait_range - wait for writeback to complete
248 * @mapping: address space structure to wait for
249 * @start_byte: offset in bytes where the range starts
250 * @end_byte: offset in bytes where the range ends (inclusive)
252 * Walk the list of under-writeback pages of the given address space
253 * in the given range and wait for all of them.
255 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
258 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
259 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
264 if (end_byte < start_byte)
267 pagevec_init(&pvec, 0);
268 while ((index <= end) &&
269 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
270 PAGECACHE_TAG_WRITEBACK,
271 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
274 for (i = 0; i < nr_pages; i++) {
275 struct page *page = pvec.pages[i];
277 /* until radix tree lookup accepts end_index */
278 if (page->index > end)
281 wait_on_page_writeback(page);
282 if (TestClearPageError(page))
285 pagevec_release(&pvec);
289 /* Check for outstanding write errors */
290 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
292 if (test_and_clear_bit(AS_EIO, &mapping->flags))
297 EXPORT_SYMBOL(filemap_fdatawait_range);
300 * filemap_fdatawait - wait for all under-writeback pages to complete
301 * @mapping: address space structure to wait for
303 * Walk the list of under-writeback pages of the given address space
304 * and wait for all of them.
306 int filemap_fdatawait(struct address_space *mapping)
308 loff_t i_size = i_size_read(mapping->host);
313 return filemap_fdatawait_range(mapping, 0, i_size - 1);
315 EXPORT_SYMBOL(filemap_fdatawait);
317 int filemap_write_and_wait(struct address_space *mapping)
321 if (mapping->nrpages) {
322 err = filemap_fdatawrite(mapping);
324 * Even if the above returned error, the pages may be
325 * written partially (e.g. -ENOSPC), so we wait for it.
326 * But the -EIO is special case, it may indicate the worst
327 * thing (e.g. bug) happened, so we avoid waiting for it.
330 int err2 = filemap_fdatawait(mapping);
337 EXPORT_SYMBOL(filemap_write_and_wait);
340 * filemap_write_and_wait_range - write out & wait on a file range
341 * @mapping: the address_space for the pages
342 * @lstart: offset in bytes where the range starts
343 * @lend: offset in bytes where the range ends (inclusive)
345 * Write out and wait upon file offsets lstart->lend, inclusive.
347 * Note that `lend' is inclusive (describes the last byte to be written) so
348 * that this function can be used to write to the very end-of-file (end = -1).
350 int filemap_write_and_wait_range(struct address_space *mapping,
351 loff_t lstart, loff_t lend)
355 if (mapping->nrpages) {
356 err = __filemap_fdatawrite_range(mapping, lstart, lend,
358 /* See comment of filemap_write_and_wait() */
360 int err2 = filemap_fdatawait_range(mapping,
368 EXPORT_SYMBOL(filemap_write_and_wait_range);
371 * replace_page_cache_page - replace a pagecache page with a new one
372 * @old: page to be replaced
373 * @new: page to replace with
374 * @gfp_mask: allocation mode
376 * This function replaces a page in the pagecache with a new one. On
377 * success it acquires the pagecache reference for the new page and
378 * drops it for the old page. Both the old and new pages must be
379 * locked. This function does not add the new page to the LRU, the
380 * caller must do that.
382 * The remove + add is atomic. The only way this function can fail is
383 * memory allocation failure.
385 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
388 struct mem_cgroup *memcg = NULL;
390 VM_BUG_ON(!PageLocked(old));
391 VM_BUG_ON(!PageLocked(new));
392 VM_BUG_ON(new->mapping);
395 * This is not page migration, but prepare_migration and
396 * end_migration does enough work for charge replacement.
398 * In the longer term we probably want a specialized function
399 * for moving the charge from old to new in a more efficient
402 error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
406 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
408 struct address_space *mapping = old->mapping;
409 void (*freepage)(struct page *);
411 pgoff_t offset = old->index;
412 freepage = mapping->a_ops->freepage;
415 new->mapping = mapping;
418 spin_lock_irq(&mapping->tree_lock);
419 __delete_from_page_cache(old);
420 error = radix_tree_insert(&mapping->page_tree, offset, new);
423 __inc_zone_page_state(new, NR_FILE_PAGES);
424 if (PageSwapBacked(new))
425 __inc_zone_page_state(new, NR_SHMEM);
426 spin_unlock_irq(&mapping->tree_lock);
427 radix_tree_preload_end();
430 page_cache_release(old);
431 mem_cgroup_end_migration(memcg, old, new, true);
433 mem_cgroup_end_migration(memcg, old, new, false);
438 EXPORT_SYMBOL_GPL(replace_page_cache_page);
441 * add_to_page_cache_locked - add a locked page to the pagecache
443 * @mapping: the page's address_space
444 * @offset: page index
445 * @gfp_mask: page allocation mode
447 * This function is used to add a page to the pagecache. It must be locked.
448 * This function does not add the page to the LRU. The caller must do that.
450 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
451 pgoff_t offset, gfp_t gfp_mask)
455 VM_BUG_ON(!PageLocked(page));
457 error = mem_cgroup_cache_charge(page, current->mm,
458 gfp_mask & GFP_RECLAIM_MASK);
462 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
464 page_cache_get(page);
465 page->mapping = mapping;
466 page->index = offset;
468 spin_lock_irq(&mapping->tree_lock);
469 error = radix_tree_insert(&mapping->page_tree, offset, page);
470 if (likely(!error)) {
472 __inc_zone_page_state(page, NR_FILE_PAGES);
473 if (PageSwapBacked(page))
474 __inc_zone_page_state(page, NR_SHMEM);
475 spin_unlock_irq(&mapping->tree_lock);
477 page->mapping = NULL;
478 spin_unlock_irq(&mapping->tree_lock);
479 mem_cgroup_uncharge_cache_page(page);
480 page_cache_release(page);
482 radix_tree_preload_end();
484 mem_cgroup_uncharge_cache_page(page);
488 EXPORT_SYMBOL(add_to_page_cache_locked);
490 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
491 pgoff_t offset, gfp_t gfp_mask)
496 * Splice_read and readahead add shmem/tmpfs pages into the page cache
497 * before shmem_readpage has a chance to mark them as SwapBacked: they
498 * need to go on the anon lru below, and mem_cgroup_cache_charge
499 * (called in add_to_page_cache) needs to know where they're going too.
501 if (mapping_cap_swap_backed(mapping))
502 SetPageSwapBacked(page);
504 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
506 if (page_is_file_cache(page))
507 lru_cache_add_file(page);
509 lru_cache_add_anon(page);
513 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
516 struct page *__page_cache_alloc(gfp_t gfp)
521 if (cpuset_do_page_mem_spread()) {
523 n = cpuset_mem_spread_node();
524 page = alloc_pages_exact_node(n, gfp, 0);
528 return alloc_pages(gfp, 0);
530 EXPORT_SYMBOL(__page_cache_alloc);
534 * In order to wait for pages to become available there must be
535 * waitqueues associated with pages. By using a hash table of
536 * waitqueues where the bucket discipline is to maintain all
537 * waiters on the same queue and wake all when any of the pages
538 * become available, and for the woken contexts to check to be
539 * sure the appropriate page became available, this saves space
540 * at a cost of "thundering herd" phenomena during rare hash
543 static wait_queue_head_t *page_waitqueue(struct page *page)
545 const struct zone *zone = page_zone(page);
547 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
550 static inline void wake_up_page(struct page *page, int bit)
552 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
555 void wait_on_page_bit(struct page *page, int bit_nr)
557 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
559 if (test_bit(bit_nr, &page->flags))
560 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
561 TASK_UNINTERRUPTIBLE);
563 EXPORT_SYMBOL(wait_on_page_bit);
566 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
567 * @page: Page defining the wait queue of interest
568 * @waiter: Waiter to add to the queue
570 * Add an arbitrary @waiter to the wait queue for the nominated @page.
572 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
574 wait_queue_head_t *q = page_waitqueue(page);
577 spin_lock_irqsave(&q->lock, flags);
578 __add_wait_queue(q, waiter);
579 spin_unlock_irqrestore(&q->lock, flags);
581 EXPORT_SYMBOL_GPL(add_page_wait_queue);
584 * unlock_page - unlock a locked page
587 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
588 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
589 * mechananism between PageLocked pages and PageWriteback pages is shared.
590 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
592 * The mb is necessary to enforce ordering between the clear_bit and the read
593 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
595 void unlock_page(struct page *page)
597 VM_BUG_ON(!PageLocked(page));
598 clear_bit_unlock(PG_locked, &page->flags);
599 smp_mb__after_clear_bit();
600 wake_up_page(page, PG_locked);
602 EXPORT_SYMBOL(unlock_page);
605 * end_page_writeback - end writeback against a page
608 void end_page_writeback(struct page *page)
610 if (TestClearPageReclaim(page))
611 rotate_reclaimable_page(page);
613 if (!test_clear_page_writeback(page))
616 smp_mb__after_clear_bit();
617 wake_up_page(page, PG_writeback);
619 EXPORT_SYMBOL(end_page_writeback);
622 * __lock_page - get a lock on the page, assuming we need to sleep to get it
623 * @page: the page to lock
625 void __lock_page(struct page *page)
627 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
629 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
630 TASK_UNINTERRUPTIBLE);
632 EXPORT_SYMBOL(__lock_page);
634 int __lock_page_killable(struct page *page)
636 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
638 return __wait_on_bit_lock(page_waitqueue(page), &wait,
639 sleep_on_page_killable, TASK_KILLABLE);
641 EXPORT_SYMBOL_GPL(__lock_page_killable);
643 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
646 if (!(flags & FAULT_FLAG_ALLOW_RETRY)) {
650 if (!(flags & FAULT_FLAG_RETRY_NOWAIT)) {
651 up_read(&mm->mmap_sem);
652 wait_on_page_locked(page);
659 * find_get_page - find and get a page reference
660 * @mapping: the address_space to search
661 * @offset: the page index
663 * Is there a pagecache struct page at the given (mapping, offset) tuple?
664 * If yes, increment its refcount and return it; if no, return NULL.
666 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
674 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
676 page = radix_tree_deref_slot(pagep);
679 if (radix_tree_deref_retry(page))
682 if (!page_cache_get_speculative(page))
686 * Has the page moved?
687 * This is part of the lockless pagecache protocol. See
688 * include/linux/pagemap.h for details.
690 if (unlikely(page != *pagep)) {
691 page_cache_release(page);
700 EXPORT_SYMBOL(find_get_page);
703 * find_lock_page - locate, pin and lock a pagecache page
704 * @mapping: the address_space to search
705 * @offset: the page index
707 * Locates the desired pagecache page, locks it, increments its reference
708 * count and returns its address.
710 * Returns zero if the page was not present. find_lock_page() may sleep.
712 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
717 page = find_get_page(mapping, offset);
720 /* Has the page been truncated? */
721 if (unlikely(page->mapping != mapping)) {
723 page_cache_release(page);
726 VM_BUG_ON(page->index != offset);
730 EXPORT_SYMBOL(find_lock_page);
733 * find_or_create_page - locate or add a pagecache page
734 * @mapping: the page's address_space
735 * @index: the page's index into the mapping
736 * @gfp_mask: page allocation mode
738 * Locates a page in the pagecache. If the page is not present, a new page
739 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
740 * LRU list. The returned page is locked and has its reference count
743 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
746 * find_or_create_page() returns the desired page's address, or zero on
749 struct page *find_or_create_page(struct address_space *mapping,
750 pgoff_t index, gfp_t gfp_mask)
755 page = find_lock_page(mapping, index);
757 page = __page_cache_alloc(gfp_mask);
761 * We want a regular kernel memory (not highmem or DMA etc)
762 * allocation for the radix tree nodes, but we need to honour
763 * the context-specific requirements the caller has asked for.
764 * GFP_RECLAIM_MASK collects those requirements.
766 err = add_to_page_cache_lru(page, mapping, index,
767 (gfp_mask & GFP_RECLAIM_MASK));
769 page_cache_release(page);
777 EXPORT_SYMBOL(find_or_create_page);
780 * find_get_pages - gang pagecache lookup
781 * @mapping: The address_space to search
782 * @start: The starting page index
783 * @nr_pages: The maximum number of pages
784 * @pages: Where the resulting pages are placed
786 * find_get_pages() will search for and return a group of up to
787 * @nr_pages pages in the mapping. The pages are placed at @pages.
788 * find_get_pages() takes a reference against the returned pages.
790 * The search returns a group of mapping-contiguous pages with ascending
791 * indexes. There may be holes in the indices due to not-present pages.
793 * find_get_pages() returns the number of pages which were found.
795 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
796 unsigned int nr_pages, struct page **pages)
800 unsigned int nr_found;
804 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
805 (void ***)pages, start, nr_pages);
807 for (i = 0; i < nr_found; i++) {
810 page = radix_tree_deref_slot((void **)pages[i]);
815 * This can only trigger when the entry at index 0 moves out
816 * of or back to the root: none yet gotten, safe to restart.
818 if (radix_tree_deref_retry(page)) {
823 if (!page_cache_get_speculative(page))
826 /* Has the page moved? */
827 if (unlikely(page != *((void **)pages[i]))) {
828 page_cache_release(page);
837 * If all entries were removed before we could secure them,
838 * try again, because callers stop trying once 0 is returned.
840 if (unlikely(!ret && nr_found))
847 * find_get_pages_contig - gang contiguous pagecache lookup
848 * @mapping: The address_space to search
849 * @index: The starting page index
850 * @nr_pages: The maximum number of pages
851 * @pages: Where the resulting pages are placed
853 * find_get_pages_contig() works exactly like find_get_pages(), except
854 * that the returned number of pages are guaranteed to be contiguous.
856 * find_get_pages_contig() returns the number of pages which were found.
858 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
859 unsigned int nr_pages, struct page **pages)
863 unsigned int nr_found;
867 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
868 (void ***)pages, index, nr_pages);
870 for (i = 0; i < nr_found; i++) {
873 page = radix_tree_deref_slot((void **)pages[i]);
878 * This can only trigger when the entry at index 0 moves out
879 * of or back to the root: none yet gotten, safe to restart.
881 if (radix_tree_deref_retry(page))
884 if (!page_cache_get_speculative(page))
887 /* Has the page moved? */
888 if (unlikely(page != *((void **)pages[i]))) {
889 page_cache_release(page);
894 * must check mapping and index after taking the ref.
895 * otherwise we can get both false positives and false
896 * negatives, which is just confusing to the caller.
898 if (page->mapping == NULL || page->index != index) {
899 page_cache_release(page);
910 EXPORT_SYMBOL(find_get_pages_contig);
913 * find_get_pages_tag - find and return pages that match @tag
914 * @mapping: the address_space to search
915 * @index: the starting page index
916 * @tag: the tag index
917 * @nr_pages: the maximum number of pages
918 * @pages: where the resulting pages are placed
920 * Like find_get_pages, except we only return pages which are tagged with
921 * @tag. We update @index to index the next page for the traversal.
923 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
924 int tag, unsigned int nr_pages, struct page **pages)
928 unsigned int nr_found;
932 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
933 (void ***)pages, *index, nr_pages, tag);
935 for (i = 0; i < nr_found; i++) {
938 page = radix_tree_deref_slot((void **)pages[i]);
943 * This can only trigger when the entry at index 0 moves out
944 * of or back to the root: none yet gotten, safe to restart.
946 if (radix_tree_deref_retry(page))
949 if (!page_cache_get_speculative(page))
952 /* Has the page moved? */
953 if (unlikely(page != *((void **)pages[i]))) {
954 page_cache_release(page);
963 * If all entries were removed before we could secure them,
964 * try again, because callers stop trying once 0 is returned.
966 if (unlikely(!ret && nr_found))
971 *index = pages[ret - 1]->index + 1;
975 EXPORT_SYMBOL(find_get_pages_tag);
978 * grab_cache_page_nowait - returns locked page at given index in given cache
979 * @mapping: target address_space
980 * @index: the page index
982 * Same as grab_cache_page(), but do not wait if the page is unavailable.
983 * This is intended for speculative data generators, where the data can
984 * be regenerated if the page couldn't be grabbed. This routine should
985 * be safe to call while holding the lock for another page.
987 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
988 * and deadlock against the caller's locked page.
991 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
993 struct page *page = find_get_page(mapping, index);
996 if (trylock_page(page))
998 page_cache_release(page);
1001 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1002 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1003 page_cache_release(page);
1008 EXPORT_SYMBOL(grab_cache_page_nowait);
1011 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1012 * a _large_ part of the i/o request. Imagine the worst scenario:
1014 * ---R__________________________________________B__________
1015 * ^ reading here ^ bad block(assume 4k)
1017 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1018 * => failing the whole request => read(R) => read(R+1) =>
1019 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1020 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1021 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1023 * It is going insane. Fix it by quickly scaling down the readahead size.
1025 static void shrink_readahead_size_eio(struct file *filp,
1026 struct file_ra_state *ra)
1032 * do_generic_file_read - generic file read routine
1033 * @filp: the file to read
1034 * @ppos: current file position
1035 * @desc: read_descriptor
1036 * @actor: read method
1038 * This is a generic file read routine, and uses the
1039 * mapping->a_ops->readpage() function for the actual low-level stuff.
1041 * This is really ugly. But the goto's actually try to clarify some
1042 * of the logic when it comes to error handling etc.
1044 static void do_generic_file_read(struct file *filp, loff_t *ppos,
1045 read_descriptor_t *desc, read_actor_t actor)
1047 struct address_space *mapping = filp->f_mapping;
1048 struct inode *inode = mapping->host;
1049 struct file_ra_state *ra = &filp->f_ra;
1053 unsigned long offset; /* offset into pagecache page */
1054 unsigned int prev_offset;
1057 index = *ppos >> PAGE_CACHE_SHIFT;
1058 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1059 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1060 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1061 offset = *ppos & ~PAGE_CACHE_MASK;
1067 unsigned long nr, ret;
1071 page = find_get_page(mapping, index);
1073 page_cache_sync_readahead(mapping,
1075 index, last_index - index);
1076 page = find_get_page(mapping, index);
1077 if (unlikely(page == NULL))
1078 goto no_cached_page;
1080 if (PageReadahead(page)) {
1081 page_cache_async_readahead(mapping,
1083 index, last_index - index);
1085 if (!PageUptodate(page)) {
1086 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1087 !mapping->a_ops->is_partially_uptodate)
1088 goto page_not_up_to_date;
1089 if (!trylock_page(page))
1090 goto page_not_up_to_date;
1091 /* Did it get truncated before we got the lock? */
1093 goto page_not_up_to_date_locked;
1094 if (!mapping->a_ops->is_partially_uptodate(page,
1096 goto page_not_up_to_date_locked;
1101 * i_size must be checked after we know the page is Uptodate.
1103 * Checking i_size after the check allows us to calculate
1104 * the correct value for "nr", which means the zero-filled
1105 * part of the page is not copied back to userspace (unless
1106 * another truncate extends the file - this is desired though).
1109 isize = i_size_read(inode);
1110 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1111 if (unlikely(!isize || index > end_index)) {
1112 page_cache_release(page);
1116 /* nr is the maximum number of bytes to copy from this page */
1117 nr = PAGE_CACHE_SIZE;
1118 if (index == end_index) {
1119 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1121 page_cache_release(page);
1127 /* If users can be writing to this page using arbitrary
1128 * virtual addresses, take care about potential aliasing
1129 * before reading the page on the kernel side.
1131 if (mapping_writably_mapped(mapping))
1132 flush_dcache_page(page);
1135 * When a sequential read accesses a page several times,
1136 * only mark it as accessed the first time.
1138 if (prev_index != index || offset != prev_offset)
1139 mark_page_accessed(page);
1143 * Ok, we have the page, and it's up-to-date, so
1144 * now we can copy it to user space...
1146 * The actor routine returns how many bytes were actually used..
1147 * NOTE! This may not be the same as how much of a user buffer
1148 * we filled up (we may be padding etc), so we can only update
1149 * "pos" here (the actor routine has to update the user buffer
1150 * pointers and the remaining count).
1152 ret = actor(desc, page, offset, nr);
1154 index += offset >> PAGE_CACHE_SHIFT;
1155 offset &= ~PAGE_CACHE_MASK;
1156 prev_offset = offset;
1158 page_cache_release(page);
1159 if (ret == nr && desc->count)
1163 page_not_up_to_date:
1164 /* Get exclusive access to the page ... */
1165 error = lock_page_killable(page);
1166 if (unlikely(error))
1167 goto readpage_error;
1169 page_not_up_to_date_locked:
1170 /* Did it get truncated before we got the lock? */
1171 if (!page->mapping) {
1173 page_cache_release(page);
1177 /* Did somebody else fill it already? */
1178 if (PageUptodate(page)) {
1185 * A previous I/O error may have been due to temporary
1186 * failures, eg. multipath errors.
1187 * PG_error will be set again if readpage fails.
1189 ClearPageError(page);
1190 /* Start the actual read. The read will unlock the page. */
1191 error = mapping->a_ops->readpage(filp, page);
1193 if (unlikely(error)) {
1194 if (error == AOP_TRUNCATED_PAGE) {
1195 page_cache_release(page);
1198 goto readpage_error;
1201 if (!PageUptodate(page)) {
1202 error = lock_page_killable(page);
1203 if (unlikely(error))
1204 goto readpage_error;
1205 if (!PageUptodate(page)) {
1206 if (page->mapping == NULL) {
1208 * invalidate_mapping_pages got it
1211 page_cache_release(page);
1215 shrink_readahead_size_eio(filp, ra);
1217 goto readpage_error;
1225 /* UHHUH! A synchronous read error occurred. Report it */
1226 desc->error = error;
1227 page_cache_release(page);
1232 * Ok, it wasn't cached, so we need to create a new
1235 page = page_cache_alloc_cold(mapping);
1237 desc->error = -ENOMEM;
1240 error = add_to_page_cache_lru(page, mapping,
1243 page_cache_release(page);
1244 if (error == -EEXIST)
1246 desc->error = error;
1253 ra->prev_pos = prev_index;
1254 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1255 ra->prev_pos |= prev_offset;
1257 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1258 file_accessed(filp);
1261 int file_read_actor(read_descriptor_t *desc, struct page *page,
1262 unsigned long offset, unsigned long size)
1265 unsigned long left, count = desc->count;
1271 * Faults on the destination of a read are common, so do it before
1274 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1275 kaddr = kmap_atomic(page, KM_USER0);
1276 left = __copy_to_user_inatomic(desc->arg.buf,
1277 kaddr + offset, size);
1278 kunmap_atomic(kaddr, KM_USER0);
1283 /* Do it the slow way */
1285 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1290 desc->error = -EFAULT;
1293 desc->count = count - size;
1294 desc->written += size;
1295 desc->arg.buf += size;
1300 * Performs necessary checks before doing a write
1301 * @iov: io vector request
1302 * @nr_segs: number of segments in the iovec
1303 * @count: number of bytes to write
1304 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1306 * Adjust number of segments and amount of bytes to write (nr_segs should be
1307 * properly initialized first). Returns appropriate error code that caller
1308 * should return or zero in case that write should be allowed.
1310 int generic_segment_checks(const struct iovec *iov,
1311 unsigned long *nr_segs, size_t *count, int access_flags)
1315 for (seg = 0; seg < *nr_segs; seg++) {
1316 const struct iovec *iv = &iov[seg];
1319 * If any segment has a negative length, or the cumulative
1320 * length ever wraps negative then return -EINVAL.
1323 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1325 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1330 cnt -= iv->iov_len; /* This segment is no good */
1336 EXPORT_SYMBOL(generic_segment_checks);
1339 * generic_file_aio_read - generic filesystem read routine
1340 * @iocb: kernel I/O control block
1341 * @iov: io vector request
1342 * @nr_segs: number of segments in the iovec
1343 * @pos: current file position
1345 * This is the "read()" routine for all filesystems
1346 * that can use the page cache directly.
1349 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1350 unsigned long nr_segs, loff_t pos)
1352 struct file *filp = iocb->ki_filp;
1354 unsigned long seg = 0;
1356 loff_t *ppos = &iocb->ki_pos;
1357 struct blk_plug plug;
1360 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1364 blk_start_plug(&plug);
1366 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1367 if (filp->f_flags & O_DIRECT) {
1369 struct address_space *mapping;
1370 struct inode *inode;
1372 mapping = filp->f_mapping;
1373 inode = mapping->host;
1375 goto out; /* skip atime */
1376 size = i_size_read(inode);
1378 retval = filemap_write_and_wait_range(mapping, pos,
1379 pos + iov_length(iov, nr_segs) - 1);
1381 retval = mapping->a_ops->direct_IO(READ, iocb,
1385 *ppos = pos + retval;
1390 * Btrfs can have a short DIO read if we encounter
1391 * compressed extents, so if there was an error, or if
1392 * we've already read everything we wanted to, or if
1393 * there was a short read because we hit EOF, go ahead
1394 * and return. Otherwise fallthrough to buffered io for
1395 * the rest of the read.
1397 if (retval < 0 || !count || *ppos >= size) {
1398 file_accessed(filp);
1405 for (seg = 0; seg < nr_segs; seg++) {
1406 read_descriptor_t desc;
1410 * If we did a short DIO read we need to skip the section of the
1411 * iov that we've already read data into.
1414 if (count > iov[seg].iov_len) {
1415 count -= iov[seg].iov_len;
1423 desc.arg.buf = iov[seg].iov_base + offset;
1424 desc.count = iov[seg].iov_len - offset;
1425 if (desc.count == 0)
1428 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1429 retval += desc.written;
1431 retval = retval ?: desc.error;
1438 blk_finish_plug(&plug);
1441 EXPORT_SYMBOL(generic_file_aio_read);
1444 do_readahead(struct address_space *mapping, struct file *filp,
1445 pgoff_t index, unsigned long nr)
1447 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1450 force_page_cache_readahead(mapping, filp, index, nr);
1454 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1462 if (file->f_mode & FMODE_READ) {
1463 struct address_space *mapping = file->f_mapping;
1464 pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1465 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1466 unsigned long len = end - start + 1;
1467 ret = do_readahead(mapping, file, start, len);
1473 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1474 asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1476 return SYSC_readahead((int) fd, offset, (size_t) count);
1478 SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1483 * page_cache_read - adds requested page to the page cache if not already there
1484 * @file: file to read
1485 * @offset: page index
1487 * This adds the requested page to the page cache if it isn't already there,
1488 * and schedules an I/O to read in its contents from disk.
1490 static int page_cache_read(struct file *file, pgoff_t offset)
1492 struct address_space *mapping = file->f_mapping;
1497 page = page_cache_alloc_cold(mapping);
1501 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1503 ret = mapping->a_ops->readpage(file, page);
1504 else if (ret == -EEXIST)
1505 ret = 0; /* losing race to add is OK */
1507 page_cache_release(page);
1509 } while (ret == AOP_TRUNCATED_PAGE);
1514 #define MMAP_LOTSAMISS (100)
1517 * Synchronous readahead happens when we don't even find
1518 * a page in the page cache at all.
1520 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1521 struct file_ra_state *ra,
1525 unsigned long ra_pages;
1526 struct address_space *mapping = file->f_mapping;
1528 /* If we don't want any read-ahead, don't bother */
1529 if (VM_RandomReadHint(vma))
1532 if (VM_SequentialReadHint(vma) ||
1533 offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
1534 page_cache_sync_readahead(mapping, ra, file, offset,
1539 if (ra->mmap_miss < INT_MAX)
1543 * Do we miss much more than hit in this file? If so,
1544 * stop bothering with read-ahead. It will only hurt.
1546 if (ra->mmap_miss > MMAP_LOTSAMISS)
1552 ra_pages = max_sane_readahead(ra->ra_pages);
1554 ra->start = max_t(long, 0, offset - ra_pages/2);
1555 ra->size = ra_pages;
1557 ra_submit(ra, mapping, file);
1562 * Asynchronous readahead happens when we find the page and PG_readahead,
1563 * so we want to possibly extend the readahead further..
1565 static void do_async_mmap_readahead(struct vm_area_struct *vma,
1566 struct file_ra_state *ra,
1571 struct address_space *mapping = file->f_mapping;
1573 /* If we don't want any read-ahead, don't bother */
1574 if (VM_RandomReadHint(vma))
1576 if (ra->mmap_miss > 0)
1578 if (PageReadahead(page))
1579 page_cache_async_readahead(mapping, ra, file,
1580 page, offset, ra->ra_pages);
1584 * filemap_fault - read in file data for page fault handling
1585 * @vma: vma in which the fault was taken
1586 * @vmf: struct vm_fault containing details of the fault
1588 * filemap_fault() is invoked via the vma operations vector for a
1589 * mapped memory region to read in file data during a page fault.
1591 * The goto's are kind of ugly, but this streamlines the normal case of having
1592 * it in the page cache, and handles the special cases reasonably without
1593 * having a lot of duplicated code.
1595 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1598 struct file *file = vma->vm_file;
1599 struct address_space *mapping = file->f_mapping;
1600 struct file_ra_state *ra = &file->f_ra;
1601 struct inode *inode = mapping->host;
1602 pgoff_t offset = vmf->pgoff;
1607 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1609 return VM_FAULT_SIGBUS;
1612 * Do we have something in the page cache already?
1614 page = find_get_page(mapping, offset);
1617 * We found the page, so try async readahead before
1618 * waiting for the lock.
1620 do_async_mmap_readahead(vma, ra, file, page, offset);
1622 /* No page in the page cache at all */
1623 do_sync_mmap_readahead(vma, ra, file, offset);
1624 count_vm_event(PGMAJFAULT);
1625 ret = VM_FAULT_MAJOR;
1627 page = find_get_page(mapping, offset);
1629 goto no_cached_page;
1632 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1633 page_cache_release(page);
1634 return ret | VM_FAULT_RETRY;
1637 /* Did it get truncated? */
1638 if (unlikely(page->mapping != mapping)) {
1643 VM_BUG_ON(page->index != offset);
1646 * We have a locked page in the page cache, now we need to check
1647 * that it's up-to-date. If not, it is going to be due to an error.
1649 if (unlikely(!PageUptodate(page)))
1650 goto page_not_uptodate;
1653 * Found the page and have a reference on it.
1654 * We must recheck i_size under page lock.
1656 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1657 if (unlikely(offset >= size)) {
1659 page_cache_release(page);
1660 return VM_FAULT_SIGBUS;
1663 ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
1665 return ret | VM_FAULT_LOCKED;
1669 * We're only likely to ever get here if MADV_RANDOM is in
1672 error = page_cache_read(file, offset);
1675 * The page we want has now been added to the page cache.
1676 * In the unlikely event that someone removed it in the
1677 * meantime, we'll just come back here and read it again.
1683 * An error return from page_cache_read can result if the
1684 * system is low on memory, or a problem occurs while trying
1687 if (error == -ENOMEM)
1688 return VM_FAULT_OOM;
1689 return VM_FAULT_SIGBUS;
1693 * Umm, take care of errors if the page isn't up-to-date.
1694 * Try to re-read it _once_. We do this synchronously,
1695 * because there really aren't any performance issues here
1696 * and we need to check for errors.
1698 ClearPageError(page);
1699 error = mapping->a_ops->readpage(file, page);
1701 wait_on_page_locked(page);
1702 if (!PageUptodate(page))
1705 page_cache_release(page);
1707 if (!error || error == AOP_TRUNCATED_PAGE)
1710 /* Things didn't work out. Return zero to tell the mm layer so. */
1711 shrink_readahead_size_eio(file, ra);
1712 return VM_FAULT_SIGBUS;
1714 EXPORT_SYMBOL(filemap_fault);
1716 const struct vm_operations_struct generic_file_vm_ops = {
1717 .fault = filemap_fault,
1720 /* This is used for a general mmap of a disk file */
1722 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1724 struct address_space *mapping = file->f_mapping;
1726 if (!mapping->a_ops->readpage)
1728 file_accessed(file);
1729 vma->vm_ops = &generic_file_vm_ops;
1730 vma->vm_flags |= VM_CAN_NONLINEAR;
1735 * This is for filesystems which do not implement ->writepage.
1737 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1739 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1741 return generic_file_mmap(file, vma);
1744 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1748 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1752 #endif /* CONFIG_MMU */
1754 EXPORT_SYMBOL(generic_file_mmap);
1755 EXPORT_SYMBOL(generic_file_readonly_mmap);
1757 static struct page *__read_cache_page(struct address_space *mapping,
1759 int (*filler)(void *,struct page*),
1766 page = find_get_page(mapping, index);
1768 page = __page_cache_alloc(gfp | __GFP_COLD);
1770 return ERR_PTR(-ENOMEM);
1771 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1772 if (unlikely(err)) {
1773 page_cache_release(page);
1776 /* Presumably ENOMEM for radix tree node */
1777 return ERR_PTR(err);
1779 err = filler(data, page);
1781 page_cache_release(page);
1782 page = ERR_PTR(err);
1788 static struct page *do_read_cache_page(struct address_space *mapping,
1790 int (*filler)(void *,struct page*),
1799 page = __read_cache_page(mapping, index, filler, data, gfp);
1802 if (PageUptodate(page))
1806 if (!page->mapping) {
1808 page_cache_release(page);
1811 if (PageUptodate(page)) {
1815 err = filler(data, page);
1817 page_cache_release(page);
1818 return ERR_PTR(err);
1821 mark_page_accessed(page);
1826 * read_cache_page_async - read into page cache, fill it if needed
1827 * @mapping: the page's address_space
1828 * @index: the page index
1829 * @filler: function to perform the read
1830 * @data: destination for read data
1832 * Same as read_cache_page, but don't wait for page to become unlocked
1833 * after submitting it to the filler.
1835 * Read into the page cache. If a page already exists, and PageUptodate() is
1836 * not set, try to fill the page but don't wait for it to become unlocked.
1838 * If the page does not get brought uptodate, return -EIO.
1840 struct page *read_cache_page_async(struct address_space *mapping,
1842 int (*filler)(void *,struct page*),
1845 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1847 EXPORT_SYMBOL(read_cache_page_async);
1849 static struct page *wait_on_page_read(struct page *page)
1851 if (!IS_ERR(page)) {
1852 wait_on_page_locked(page);
1853 if (!PageUptodate(page)) {
1854 page_cache_release(page);
1855 page = ERR_PTR(-EIO);
1862 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1863 * @mapping: the page's address_space
1864 * @index: the page index
1865 * @gfp: the page allocator flags to use if allocating
1867 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1868 * any new page allocations done using the specified allocation flags. Note
1869 * that the Radix tree operations will still use GFP_KERNEL, so you can't
1870 * expect to do this atomically or anything like that - but you can pass in
1871 * other page requirements.
1873 * If the page does not get brought uptodate, return -EIO.
1875 struct page *read_cache_page_gfp(struct address_space *mapping,
1879 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1881 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1883 EXPORT_SYMBOL(read_cache_page_gfp);
1886 * read_cache_page - read into page cache, fill it if needed
1887 * @mapping: the page's address_space
1888 * @index: the page index
1889 * @filler: function to perform the read
1890 * @data: destination for read data
1892 * Read into the page cache. If a page already exists, and PageUptodate() is
1893 * not set, try to fill the page then wait for it to become unlocked.
1895 * If the page does not get brought uptodate, return -EIO.
1897 struct page *read_cache_page(struct address_space *mapping,
1899 int (*filler)(void *,struct page*),
1902 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1904 EXPORT_SYMBOL(read_cache_page);
1907 * The logic we want is
1909 * if suid or (sgid and xgrp)
1912 int should_remove_suid(struct dentry *dentry)
1914 mode_t mode = dentry->d_inode->i_mode;
1917 /* suid always must be killed */
1918 if (unlikely(mode & S_ISUID))
1919 kill = ATTR_KILL_SUID;
1922 * sgid without any exec bits is just a mandatory locking mark; leave
1923 * it alone. If some exec bits are set, it's a real sgid; kill it.
1925 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1926 kill |= ATTR_KILL_SGID;
1928 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1933 EXPORT_SYMBOL(should_remove_suid);
1935 static int __remove_suid(struct dentry *dentry, int kill)
1937 struct iattr newattrs;
1939 newattrs.ia_valid = ATTR_FORCE | kill;
1940 return notify_change(dentry, &newattrs);
1943 int file_remove_suid(struct file *file)
1945 struct dentry *dentry = file->f_path.dentry;
1946 int killsuid = should_remove_suid(dentry);
1947 int killpriv = security_inode_need_killpriv(dentry);
1953 error = security_inode_killpriv(dentry);
1954 if (!error && killsuid)
1955 error = __remove_suid(dentry, killsuid);
1959 EXPORT_SYMBOL(file_remove_suid);
1961 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1962 const struct iovec *iov, size_t base, size_t bytes)
1964 size_t copied = 0, left = 0;
1967 char __user *buf = iov->iov_base + base;
1968 int copy = min(bytes, iov->iov_len - base);
1971 left = __copy_from_user_inatomic(vaddr, buf, copy);
1980 return copied - left;
1984 * Copy as much as we can into the page and return the number of bytes which
1985 * were successfully copied. If a fault is encountered then return the number of
1986 * bytes which were copied.
1988 size_t iov_iter_copy_from_user_atomic(struct page *page,
1989 struct iov_iter *i, unsigned long offset, size_t bytes)
1994 BUG_ON(!in_atomic());
1995 kaddr = kmap_atomic(page, KM_USER0);
1996 if (likely(i->nr_segs == 1)) {
1998 char __user *buf = i->iov->iov_base + i->iov_offset;
1999 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
2000 copied = bytes - left;
2002 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2003 i->iov, i->iov_offset, bytes);
2005 kunmap_atomic(kaddr, KM_USER0);
2009 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
2012 * This has the same sideeffects and return value as
2013 * iov_iter_copy_from_user_atomic().
2014 * The difference is that it attempts to resolve faults.
2015 * Page must not be locked.
2017 size_t iov_iter_copy_from_user(struct page *page,
2018 struct iov_iter *i, unsigned long offset, size_t bytes)
2024 if (likely(i->nr_segs == 1)) {
2026 char __user *buf = i->iov->iov_base + i->iov_offset;
2027 left = __copy_from_user(kaddr + offset, buf, bytes);
2028 copied = bytes - left;
2030 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2031 i->iov, i->iov_offset, bytes);
2036 EXPORT_SYMBOL(iov_iter_copy_from_user);
2038 void iov_iter_advance(struct iov_iter *i, size_t bytes)
2040 BUG_ON(i->count < bytes);
2042 if (likely(i->nr_segs == 1)) {
2043 i->iov_offset += bytes;
2046 const struct iovec *iov = i->iov;
2047 size_t base = i->iov_offset;
2050 * The !iov->iov_len check ensures we skip over unlikely
2051 * zero-length segments (without overruning the iovec).
2053 while (bytes || unlikely(i->count && !iov->iov_len)) {
2056 copy = min(bytes, iov->iov_len - base);
2057 BUG_ON(!i->count || i->count < copy);
2061 if (iov->iov_len == base) {
2067 i->iov_offset = base;
2070 EXPORT_SYMBOL(iov_iter_advance);
2073 * Fault in the first iovec of the given iov_iter, to a maximum length
2074 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2075 * accessed (ie. because it is an invalid address).
2077 * writev-intensive code may want this to prefault several iovecs -- that
2078 * would be possible (callers must not rely on the fact that _only_ the
2079 * first iovec will be faulted with the current implementation).
2081 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2083 char __user *buf = i->iov->iov_base + i->iov_offset;
2084 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2085 return fault_in_pages_readable(buf, bytes);
2087 EXPORT_SYMBOL(iov_iter_fault_in_readable);
2090 * Return the count of just the current iov_iter segment.
2092 size_t iov_iter_single_seg_count(struct iov_iter *i)
2094 const struct iovec *iov = i->iov;
2095 if (i->nr_segs == 1)
2098 return min(i->count, iov->iov_len - i->iov_offset);
2100 EXPORT_SYMBOL(iov_iter_single_seg_count);
2103 * Performs necessary checks before doing a write
2105 * Can adjust writing position or amount of bytes to write.
2106 * Returns appropriate error code that caller should return or
2107 * zero in case that write should be allowed.
2109 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2111 struct inode *inode = file->f_mapping->host;
2112 unsigned long limit = rlimit(RLIMIT_FSIZE);
2114 if (unlikely(*pos < 0))
2118 /* FIXME: this is for backwards compatibility with 2.4 */
2119 if (file->f_flags & O_APPEND)
2120 *pos = i_size_read(inode);
2122 if (limit != RLIM_INFINITY) {
2123 if (*pos >= limit) {
2124 send_sig(SIGXFSZ, current, 0);
2127 if (*count > limit - (typeof(limit))*pos) {
2128 *count = limit - (typeof(limit))*pos;
2136 if (unlikely(*pos + *count > MAX_NON_LFS &&
2137 !(file->f_flags & O_LARGEFILE))) {
2138 if (*pos >= MAX_NON_LFS) {
2141 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2142 *count = MAX_NON_LFS - (unsigned long)*pos;
2147 * Are we about to exceed the fs block limit ?
2149 * If we have written data it becomes a short write. If we have
2150 * exceeded without writing data we send a signal and return EFBIG.
2151 * Linus frestrict idea will clean these up nicely..
2153 if (likely(!isblk)) {
2154 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2155 if (*count || *pos > inode->i_sb->s_maxbytes) {
2158 /* zero-length writes at ->s_maxbytes are OK */
2161 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2162 *count = inode->i_sb->s_maxbytes - *pos;
2166 if (bdev_read_only(I_BDEV(inode)))
2168 isize = i_size_read(inode);
2169 if (*pos >= isize) {
2170 if (*count || *pos > isize)
2174 if (*pos + *count > isize)
2175 *count = isize - *pos;
2182 EXPORT_SYMBOL(generic_write_checks);
2184 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2185 loff_t pos, unsigned len, unsigned flags,
2186 struct page **pagep, void **fsdata)
2188 const struct address_space_operations *aops = mapping->a_ops;
2190 return aops->write_begin(file, mapping, pos, len, flags,
2193 EXPORT_SYMBOL(pagecache_write_begin);
2195 int pagecache_write_end(struct file *file, struct address_space *mapping,
2196 loff_t pos, unsigned len, unsigned copied,
2197 struct page *page, void *fsdata)
2199 const struct address_space_operations *aops = mapping->a_ops;
2201 mark_page_accessed(page);
2202 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2204 EXPORT_SYMBOL(pagecache_write_end);
2207 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2208 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2209 size_t count, size_t ocount)
2211 struct file *file = iocb->ki_filp;
2212 struct address_space *mapping = file->f_mapping;
2213 struct inode *inode = mapping->host;
2218 if (count != ocount)
2219 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2221 write_len = iov_length(iov, *nr_segs);
2222 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2224 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2229 * After a write we want buffered reads to be sure to go to disk to get
2230 * the new data. We invalidate clean cached page from the region we're
2231 * about to write. We do this *before* the write so that we can return
2232 * without clobbering -EIOCBQUEUED from ->direct_IO().
2234 if (mapping->nrpages) {
2235 written = invalidate_inode_pages2_range(mapping,
2236 pos >> PAGE_CACHE_SHIFT, end);
2238 * If a page can not be invalidated, return 0 to fall back
2239 * to buffered write.
2242 if (written == -EBUSY)
2248 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2251 * Finally, try again to invalidate clean pages which might have been
2252 * cached by non-direct readahead, or faulted in by get_user_pages()
2253 * if the source of the write was an mmap'ed region of the file
2254 * we're writing. Either one is a pretty crazy thing to do,
2255 * so we don't support it 100%. If this invalidation
2256 * fails, tough, the write still worked...
2258 if (mapping->nrpages) {
2259 invalidate_inode_pages2_range(mapping,
2260 pos >> PAGE_CACHE_SHIFT, end);
2265 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2266 i_size_write(inode, pos);
2267 mark_inode_dirty(inode);
2274 EXPORT_SYMBOL(generic_file_direct_write);
2277 * Find or create a page at the given pagecache position. Return the locked
2278 * page. This function is specifically for buffered writes.
2280 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2281 pgoff_t index, unsigned flags)
2285 gfp_t gfp_notmask = 0;
2286 if (flags & AOP_FLAG_NOFS)
2287 gfp_notmask = __GFP_FS;
2289 page = find_lock_page(mapping, index);
2293 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2296 status = add_to_page_cache_lru(page, mapping, index,
2297 GFP_KERNEL & ~gfp_notmask);
2298 if (unlikely(status)) {
2299 page_cache_release(page);
2300 if (status == -EEXIST)
2306 EXPORT_SYMBOL(grab_cache_page_write_begin);
2308 static ssize_t generic_perform_write(struct file *file,
2309 struct iov_iter *i, loff_t pos)
2311 struct address_space *mapping = file->f_mapping;
2312 const struct address_space_operations *a_ops = mapping->a_ops;
2314 ssize_t written = 0;
2315 unsigned int flags = 0;
2318 * Copies from kernel address space cannot fail (NFSD is a big user).
2320 if (segment_eq(get_fs(), KERNEL_DS))
2321 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2325 unsigned long offset; /* Offset into pagecache page */
2326 unsigned long bytes; /* Bytes to write to page */
2327 size_t copied; /* Bytes copied from user */
2330 offset = (pos & (PAGE_CACHE_SIZE - 1));
2331 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2337 * Bring in the user page that we will copy from _first_.
2338 * Otherwise there's a nasty deadlock on copying from the
2339 * same page as we're writing to, without it being marked
2342 * Not only is this an optimisation, but it is also required
2343 * to check that the address is actually valid, when atomic
2344 * usercopies are used, below.
2346 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2351 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2353 if (unlikely(status))
2356 if (mapping_writably_mapped(mapping))
2357 flush_dcache_page(page);
2359 pagefault_disable();
2360 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2362 flush_dcache_page(page);
2364 mark_page_accessed(page);
2365 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2367 if (unlikely(status < 0))
2373 iov_iter_advance(i, copied);
2374 if (unlikely(copied == 0)) {
2376 * If we were unable to copy any data at all, we must
2377 * fall back to a single segment length write.
2379 * If we didn't fallback here, we could livelock
2380 * because not all segments in the iov can be copied at
2381 * once without a pagefault.
2383 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2384 iov_iter_single_seg_count(i));
2390 balance_dirty_pages_ratelimited(mapping);
2392 } while (iov_iter_count(i));
2394 return written ? written : status;
2398 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2399 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2400 size_t count, ssize_t written)
2402 struct file *file = iocb->ki_filp;
2406 iov_iter_init(&i, iov, nr_segs, count, written);
2407 status = generic_perform_write(file, &i, pos);
2409 if (likely(status >= 0)) {
2411 *ppos = pos + status;
2414 return written ? written : status;
2416 EXPORT_SYMBOL(generic_file_buffered_write);
2419 * __generic_file_aio_write - write data to a file
2420 * @iocb: IO state structure (file, offset, etc.)
2421 * @iov: vector with data to write
2422 * @nr_segs: number of segments in the vector
2423 * @ppos: position where to write
2425 * This function does all the work needed for actually writing data to a
2426 * file. It does all basic checks, removes SUID from the file, updates
2427 * modification times and calls proper subroutines depending on whether we
2428 * do direct IO or a standard buffered write.
2430 * It expects i_mutex to be grabbed unless we work on a block device or similar
2431 * object which does not need locking at all.
2433 * This function does *not* take care of syncing data in case of O_SYNC write.
2434 * A caller has to handle it. This is mainly due to the fact that we want to
2435 * avoid syncing under i_mutex.
2437 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2438 unsigned long nr_segs, loff_t *ppos)
2440 struct file *file = iocb->ki_filp;
2441 struct address_space * mapping = file->f_mapping;
2442 size_t ocount; /* original count */
2443 size_t count; /* after file limit checks */
2444 struct inode *inode = mapping->host;
2450 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2457 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2459 /* We can write back this queue in page reclaim */
2460 current->backing_dev_info = mapping->backing_dev_info;
2463 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2470 err = file_remove_suid(file);
2474 file_update_time(file);
2476 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2477 if (unlikely(file->f_flags & O_DIRECT)) {
2479 ssize_t written_buffered;
2481 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2482 ppos, count, ocount);
2483 if (written < 0 || written == count)
2486 * direct-io write to a hole: fall through to buffered I/O
2487 * for completing the rest of the request.
2491 written_buffered = generic_file_buffered_write(iocb, iov,
2492 nr_segs, pos, ppos, count,
2495 * If generic_file_buffered_write() retuned a synchronous error
2496 * then we want to return the number of bytes which were
2497 * direct-written, or the error code if that was zero. Note
2498 * that this differs from normal direct-io semantics, which
2499 * will return -EFOO even if some bytes were written.
2501 if (written_buffered < 0) {
2502 err = written_buffered;
2507 * We need to ensure that the page cache pages are written to
2508 * disk and invalidated to preserve the expected O_DIRECT
2511 endbyte = pos + written_buffered - written - 1;
2512 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2514 written = written_buffered;
2515 invalidate_mapping_pages(mapping,
2516 pos >> PAGE_CACHE_SHIFT,
2517 endbyte >> PAGE_CACHE_SHIFT);
2520 * We don't know how much we wrote, so just return
2521 * the number of bytes which were direct-written
2525 written = generic_file_buffered_write(iocb, iov, nr_segs,
2526 pos, ppos, count, written);
2529 current->backing_dev_info = NULL;
2530 return written ? written : err;
2532 EXPORT_SYMBOL(__generic_file_aio_write);
2535 * generic_file_aio_write - write data to a file
2536 * @iocb: IO state structure
2537 * @iov: vector with data to write
2538 * @nr_segs: number of segments in the vector
2539 * @pos: position in file where to write
2541 * This is a wrapper around __generic_file_aio_write() to be used by most
2542 * filesystems. It takes care of syncing the file in case of O_SYNC file
2543 * and acquires i_mutex as needed.
2545 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2546 unsigned long nr_segs, loff_t pos)
2548 struct file *file = iocb->ki_filp;
2549 struct inode *inode = file->f_mapping->host;
2550 struct blk_plug plug;
2553 BUG_ON(iocb->ki_pos != pos);
2555 mutex_lock(&inode->i_mutex);
2556 blk_start_plug(&plug);
2557 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2558 mutex_unlock(&inode->i_mutex);
2560 if (ret > 0 || ret == -EIOCBQUEUED) {
2563 err = generic_write_sync(file, pos, ret);
2564 if (err < 0 && ret > 0)
2567 blk_finish_plug(&plug);
2570 EXPORT_SYMBOL(generic_file_aio_write);
2573 * try_to_release_page() - release old fs-specific metadata on a page
2575 * @page: the page which the kernel is trying to free
2576 * @gfp_mask: memory allocation flags (and I/O mode)
2578 * The address_space is to try to release any data against the page
2579 * (presumably at page->private). If the release was successful, return `1'.
2580 * Otherwise return zero.
2582 * This may also be called if PG_fscache is set on a page, indicating that the
2583 * page is known to the local caching routines.
2585 * The @gfp_mask argument specifies whether I/O may be performed to release
2586 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2589 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2591 struct address_space * const mapping = page->mapping;
2593 BUG_ON(!PageLocked(page));
2594 if (PageWriteback(page))
2597 if (mapping && mapping->a_ops->releasepage)
2598 return mapping->a_ops->releasepage(page, gfp_mask);
2599 return try_to_free_buffers(page);
2602 EXPORT_SYMBOL(try_to_release_page);