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() */
37 #include <linux/cleancache.h>
41 * FIXME: remove all knowledge of the buffer layer from the core VM
43 #include <linux/buffer_head.h> /* for try_to_free_buffers */
48 * Shared mappings implemented 30.11.1994. It's not fully working yet,
51 * Shared mappings now work. 15.8.1995 Bruno.
53 * finished 'unifying' the page and buffer cache and SMP-threaded the
54 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
56 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
62 * ->i_mmap_mutex (truncate_pagecache)
63 * ->private_lock (__free_pte->__set_page_dirty_buffers)
64 * ->swap_lock (exclusive_swap_page, others)
65 * ->mapping->tree_lock
68 * ->i_mmap_mutex (truncate->unmap_mapping_range)
72 * ->page_table_lock or pte_lock (various, mainly in memory.c)
73 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
76 * ->lock_page (access_process_vm)
78 * ->i_mutex (generic_file_buffered_write)
79 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
82 * sb_lock (fs/fs-writeback.c)
83 * ->mapping->tree_lock (__sync_single_inode)
86 * ->anon_vma.lock (vma_adjust)
89 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
91 * ->page_table_lock or pte_lock
92 * ->swap_lock (try_to_unmap_one)
93 * ->private_lock (try_to_unmap_one)
94 * ->tree_lock (try_to_unmap_one)
95 * ->zone.lru_lock (follow_page->mark_page_accessed)
96 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
97 * ->private_lock (page_remove_rmap->set_page_dirty)
98 * ->tree_lock (page_remove_rmap->set_page_dirty)
99 * inode_wb_list_lock (page_remove_rmap->set_page_dirty)
100 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
101 * inode_wb_list_lock (zap_pte_range->set_page_dirty)
102 * ->inode->i_lock (zap_pte_range->set_page_dirty)
103 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
105 * (code doesn't rely on that order, so you could switch it around)
106 * ->tasklist_lock (memory_failure, collect_procs_ao)
111 * Delete a page from the page cache and free it. Caller has to make
112 * sure the page is locked and that nobody else uses it - or that usage
113 * is safe. The caller must hold the mapping's tree_lock.
115 void __delete_from_page_cache(struct page *page)
117 struct address_space *mapping = page->mapping;
120 * if we're uptodate, flush out into the cleancache, otherwise
121 * invalidate any existing cleancache entries. We can't leave
122 * stale data around in the cleancache once our page is gone
124 if (PageUptodate(page) && PageMappedToDisk(page))
125 cleancache_put_page(page);
127 cleancache_flush_page(mapping, page);
129 radix_tree_delete(&mapping->page_tree, page->index);
130 page->mapping = NULL;
132 __dec_zone_page_state(page, NR_FILE_PAGES);
133 if (PageSwapBacked(page))
134 __dec_zone_page_state(page, NR_SHMEM);
135 BUG_ON(page_mapped(page));
138 * Some filesystems seem to re-dirty the page even after
139 * the VM has canceled the dirty bit (eg ext3 journaling).
141 * Fix it up by doing a final dirty accounting check after
142 * having removed the page entirely.
144 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
145 dec_zone_page_state(page, NR_FILE_DIRTY);
146 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
151 * delete_from_page_cache - delete page from page cache
152 * @page: the page which the kernel is trying to remove from page cache
154 * This must be called only on pages that have been verified to be in the page
155 * cache and locked. It will never put the page into the free list, the caller
156 * has a reference on the page.
158 void delete_from_page_cache(struct page *page)
160 struct address_space *mapping = page->mapping;
161 void (*freepage)(struct page *);
163 BUG_ON(!PageLocked(page));
165 freepage = mapping->a_ops->freepage;
166 spin_lock_irq(&mapping->tree_lock);
167 __delete_from_page_cache(page);
168 spin_unlock_irq(&mapping->tree_lock);
169 mem_cgroup_uncharge_cache_page(page);
173 page_cache_release(page);
175 EXPORT_SYMBOL(delete_from_page_cache);
177 static int sleep_on_page(void *word)
183 static int sleep_on_page_killable(void *word)
186 return fatal_signal_pending(current) ? -EINTR : 0;
190 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
191 * @mapping: address space structure to write
192 * @start: offset in bytes where the range starts
193 * @end: offset in bytes where the range ends (inclusive)
194 * @sync_mode: enable synchronous operation
196 * Start writeback against all of a mapping's dirty pages that lie
197 * within the byte offsets <start, end> inclusive.
199 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
200 * opposed to a regular memory cleansing writeback. The difference between
201 * these two operations is that if a dirty page/buffer is encountered, it must
202 * be waited upon, and not just skipped over.
204 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
205 loff_t end, int sync_mode)
208 struct writeback_control wbc = {
209 .sync_mode = sync_mode,
210 .nr_to_write = LONG_MAX,
211 .range_start = start,
215 if (!mapping_cap_writeback_dirty(mapping))
218 ret = do_writepages(mapping, &wbc);
222 static inline int __filemap_fdatawrite(struct address_space *mapping,
225 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
228 int filemap_fdatawrite(struct address_space *mapping)
230 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
232 EXPORT_SYMBOL(filemap_fdatawrite);
234 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
237 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
239 EXPORT_SYMBOL(filemap_fdatawrite_range);
242 * filemap_flush - mostly a non-blocking flush
243 * @mapping: target address_space
245 * This is a mostly non-blocking flush. Not suitable for data-integrity
246 * purposes - I/O may not be started against all dirty pages.
248 int filemap_flush(struct address_space *mapping)
250 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
252 EXPORT_SYMBOL(filemap_flush);
255 * filemap_fdatawait_range - wait for writeback to complete
256 * @mapping: address space structure to wait for
257 * @start_byte: offset in bytes where the range starts
258 * @end_byte: offset in bytes where the range ends (inclusive)
260 * Walk the list of under-writeback pages of the given address space
261 * in the given range and wait for all of them.
263 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
266 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
267 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
272 if (end_byte < start_byte)
275 pagevec_init(&pvec, 0);
276 while ((index <= end) &&
277 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
278 PAGECACHE_TAG_WRITEBACK,
279 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
282 for (i = 0; i < nr_pages; i++) {
283 struct page *page = pvec.pages[i];
285 /* until radix tree lookup accepts end_index */
286 if (page->index > end)
289 wait_on_page_writeback(page);
290 if (TestClearPageError(page))
293 pagevec_release(&pvec);
297 /* Check for outstanding write errors */
298 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
300 if (test_and_clear_bit(AS_EIO, &mapping->flags))
305 EXPORT_SYMBOL(filemap_fdatawait_range);
308 * filemap_fdatawait - wait for all under-writeback pages to complete
309 * @mapping: address space structure to wait for
311 * Walk the list of under-writeback pages of the given address space
312 * and wait for all of them.
314 int filemap_fdatawait(struct address_space *mapping)
316 loff_t i_size = i_size_read(mapping->host);
321 return filemap_fdatawait_range(mapping, 0, i_size - 1);
323 EXPORT_SYMBOL(filemap_fdatawait);
325 int filemap_write_and_wait(struct address_space *mapping)
329 if (mapping->nrpages) {
330 err = filemap_fdatawrite(mapping);
332 * Even if the above returned error, the pages may be
333 * written partially (e.g. -ENOSPC), so we wait for it.
334 * But the -EIO is special case, it may indicate the worst
335 * thing (e.g. bug) happened, so we avoid waiting for it.
338 int err2 = filemap_fdatawait(mapping);
345 EXPORT_SYMBOL(filemap_write_and_wait);
348 * filemap_write_and_wait_range - write out & wait on a file range
349 * @mapping: the address_space for the pages
350 * @lstart: offset in bytes where the range starts
351 * @lend: offset in bytes where the range ends (inclusive)
353 * Write out and wait upon file offsets lstart->lend, inclusive.
355 * Note that `lend' is inclusive (describes the last byte to be written) so
356 * that this function can be used to write to the very end-of-file (end = -1).
358 int filemap_write_and_wait_range(struct address_space *mapping,
359 loff_t lstart, loff_t lend)
363 if (mapping->nrpages) {
364 err = __filemap_fdatawrite_range(mapping, lstart, lend,
366 /* See comment of filemap_write_and_wait() */
368 int err2 = filemap_fdatawait_range(mapping,
376 EXPORT_SYMBOL(filemap_write_and_wait_range);
379 * replace_page_cache_page - replace a pagecache page with a new one
380 * @old: page to be replaced
381 * @new: page to replace with
382 * @gfp_mask: allocation mode
384 * This function replaces a page in the pagecache with a new one. On
385 * success it acquires the pagecache reference for the new page and
386 * drops it for the old page. Both the old and new pages must be
387 * locked. This function does not add the new page to the LRU, the
388 * caller must do that.
390 * The remove + add is atomic. The only way this function can fail is
391 * memory allocation failure.
393 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
396 struct mem_cgroup *memcg = NULL;
398 VM_BUG_ON(!PageLocked(old));
399 VM_BUG_ON(!PageLocked(new));
400 VM_BUG_ON(new->mapping);
403 * This is not page migration, but prepare_migration and
404 * end_migration does enough work for charge replacement.
406 * In the longer term we probably want a specialized function
407 * for moving the charge from old to new in a more efficient
410 error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
414 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
416 struct address_space *mapping = old->mapping;
417 void (*freepage)(struct page *);
419 pgoff_t offset = old->index;
420 freepage = mapping->a_ops->freepage;
423 new->mapping = mapping;
426 spin_lock_irq(&mapping->tree_lock);
427 __delete_from_page_cache(old);
428 error = radix_tree_insert(&mapping->page_tree, offset, new);
431 __inc_zone_page_state(new, NR_FILE_PAGES);
432 if (PageSwapBacked(new))
433 __inc_zone_page_state(new, NR_SHMEM);
434 spin_unlock_irq(&mapping->tree_lock);
435 radix_tree_preload_end();
438 page_cache_release(old);
439 mem_cgroup_end_migration(memcg, old, new, true);
441 mem_cgroup_end_migration(memcg, old, new, false);
446 EXPORT_SYMBOL_GPL(replace_page_cache_page);
449 * add_to_page_cache_locked - add a locked page to the pagecache
451 * @mapping: the page's address_space
452 * @offset: page index
453 * @gfp_mask: page allocation mode
455 * This function is used to add a page to the pagecache. It must be locked.
456 * This function does not add the page to the LRU. The caller must do that.
458 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
459 pgoff_t offset, gfp_t gfp_mask)
463 VM_BUG_ON(!PageLocked(page));
465 error = mem_cgroup_cache_charge(page, current->mm,
466 gfp_mask & GFP_RECLAIM_MASK);
470 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
472 page_cache_get(page);
473 page->mapping = mapping;
474 page->index = offset;
476 spin_lock_irq(&mapping->tree_lock);
477 error = radix_tree_insert(&mapping->page_tree, offset, page);
478 if (likely(!error)) {
480 __inc_zone_page_state(page, NR_FILE_PAGES);
481 if (PageSwapBacked(page))
482 __inc_zone_page_state(page, NR_SHMEM);
483 spin_unlock_irq(&mapping->tree_lock);
485 page->mapping = NULL;
486 spin_unlock_irq(&mapping->tree_lock);
487 mem_cgroup_uncharge_cache_page(page);
488 page_cache_release(page);
490 radix_tree_preload_end();
492 mem_cgroup_uncharge_cache_page(page);
496 EXPORT_SYMBOL(add_to_page_cache_locked);
498 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
499 pgoff_t offset, gfp_t gfp_mask)
504 * Splice_read and readahead add shmem/tmpfs pages into the page cache
505 * before shmem_readpage has a chance to mark them as SwapBacked: they
506 * need to go on the anon lru below, and mem_cgroup_cache_charge
507 * (called in add_to_page_cache) needs to know where they're going too.
509 if (mapping_cap_swap_backed(mapping))
510 SetPageSwapBacked(page);
512 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
514 if (page_is_file_cache(page))
515 lru_cache_add_file(page);
517 lru_cache_add_anon(page);
521 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
524 struct page *__page_cache_alloc(gfp_t gfp)
529 if (cpuset_do_page_mem_spread()) {
531 n = cpuset_mem_spread_node();
532 page = alloc_pages_exact_node(n, gfp, 0);
536 return alloc_pages(gfp, 0);
538 EXPORT_SYMBOL(__page_cache_alloc);
542 * In order to wait for pages to become available there must be
543 * waitqueues associated with pages. By using a hash table of
544 * waitqueues where the bucket discipline is to maintain all
545 * waiters on the same queue and wake all when any of the pages
546 * become available, and for the woken contexts to check to be
547 * sure the appropriate page became available, this saves space
548 * at a cost of "thundering herd" phenomena during rare hash
551 static wait_queue_head_t *page_waitqueue(struct page *page)
553 const struct zone *zone = page_zone(page);
555 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
558 static inline void wake_up_page(struct page *page, int bit)
560 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
563 void wait_on_page_bit(struct page *page, int bit_nr)
565 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
567 if (test_bit(bit_nr, &page->flags))
568 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
569 TASK_UNINTERRUPTIBLE);
571 EXPORT_SYMBOL(wait_on_page_bit);
573 int wait_on_page_bit_killable(struct page *page, int bit_nr)
575 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
577 if (!test_bit(bit_nr, &page->flags))
580 return __wait_on_bit(page_waitqueue(page), &wait,
581 sleep_on_page_killable, TASK_KILLABLE);
585 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
586 * @page: Page defining the wait queue of interest
587 * @waiter: Waiter to add to the queue
589 * Add an arbitrary @waiter to the wait queue for the nominated @page.
591 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
593 wait_queue_head_t *q = page_waitqueue(page);
596 spin_lock_irqsave(&q->lock, flags);
597 __add_wait_queue(q, waiter);
598 spin_unlock_irqrestore(&q->lock, flags);
600 EXPORT_SYMBOL_GPL(add_page_wait_queue);
603 * unlock_page - unlock a locked page
606 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
607 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
608 * mechananism between PageLocked pages and PageWriteback pages is shared.
609 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
611 * The mb is necessary to enforce ordering between the clear_bit and the read
612 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
614 void unlock_page(struct page *page)
616 VM_BUG_ON(!PageLocked(page));
617 clear_bit_unlock(PG_locked, &page->flags);
618 smp_mb__after_clear_bit();
619 wake_up_page(page, PG_locked);
621 EXPORT_SYMBOL(unlock_page);
624 * end_page_writeback - end writeback against a page
627 void end_page_writeback(struct page *page)
629 if (TestClearPageReclaim(page))
630 rotate_reclaimable_page(page);
632 if (!test_clear_page_writeback(page))
635 smp_mb__after_clear_bit();
636 wake_up_page(page, PG_writeback);
638 EXPORT_SYMBOL(end_page_writeback);
641 * __lock_page - get a lock on the page, assuming we need to sleep to get it
642 * @page: the page to lock
644 void __lock_page(struct page *page)
646 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
648 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
649 TASK_UNINTERRUPTIBLE);
651 EXPORT_SYMBOL(__lock_page);
653 int __lock_page_killable(struct page *page)
655 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
657 return __wait_on_bit_lock(page_waitqueue(page), &wait,
658 sleep_on_page_killable, TASK_KILLABLE);
660 EXPORT_SYMBOL_GPL(__lock_page_killable);
662 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
665 if (flags & FAULT_FLAG_ALLOW_RETRY) {
667 * CAUTION! In this case, mmap_sem is not released
668 * even though return 0.
670 if (flags & FAULT_FLAG_RETRY_NOWAIT)
673 up_read(&mm->mmap_sem);
674 if (flags & FAULT_FLAG_KILLABLE)
675 wait_on_page_locked_killable(page);
677 wait_on_page_locked(page);
680 if (flags & FAULT_FLAG_KILLABLE) {
683 ret = __lock_page_killable(page);
685 up_read(&mm->mmap_sem);
695 * find_get_page - find and get a page reference
696 * @mapping: the address_space to search
697 * @offset: the page index
699 * Is there a pagecache struct page at the given (mapping, offset) tuple?
700 * If yes, increment its refcount and return it; if no, return NULL.
702 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
710 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
712 page = radix_tree_deref_slot(pagep);
715 if (radix_tree_deref_retry(page))
718 if (!page_cache_get_speculative(page))
722 * Has the page moved?
723 * This is part of the lockless pagecache protocol. See
724 * include/linux/pagemap.h for details.
726 if (unlikely(page != *pagep)) {
727 page_cache_release(page);
736 EXPORT_SYMBOL(find_get_page);
739 * find_lock_page - locate, pin and lock a pagecache page
740 * @mapping: the address_space to search
741 * @offset: the page index
743 * Locates the desired pagecache page, locks it, increments its reference
744 * count and returns its address.
746 * Returns zero if the page was not present. find_lock_page() may sleep.
748 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
753 page = find_get_page(mapping, offset);
756 /* Has the page been truncated? */
757 if (unlikely(page->mapping != mapping)) {
759 page_cache_release(page);
762 VM_BUG_ON(page->index != offset);
766 EXPORT_SYMBOL(find_lock_page);
769 * find_or_create_page - locate or add a pagecache page
770 * @mapping: the page's address_space
771 * @index: the page's index into the mapping
772 * @gfp_mask: page allocation mode
774 * Locates a page in the pagecache. If the page is not present, a new page
775 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
776 * LRU list. The returned page is locked and has its reference count
779 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
782 * find_or_create_page() returns the desired page's address, or zero on
785 struct page *find_or_create_page(struct address_space *mapping,
786 pgoff_t index, gfp_t gfp_mask)
791 page = find_lock_page(mapping, index);
793 page = __page_cache_alloc(gfp_mask);
797 * We want a regular kernel memory (not highmem or DMA etc)
798 * allocation for the radix tree nodes, but we need to honour
799 * the context-specific requirements the caller has asked for.
800 * GFP_RECLAIM_MASK collects those requirements.
802 err = add_to_page_cache_lru(page, mapping, index,
803 (gfp_mask & GFP_RECLAIM_MASK));
805 page_cache_release(page);
813 EXPORT_SYMBOL(find_or_create_page);
816 * find_get_pages - gang pagecache lookup
817 * @mapping: The address_space to search
818 * @start: The starting page index
819 * @nr_pages: The maximum number of pages
820 * @pages: Where the resulting pages are placed
822 * find_get_pages() will search for and return a group of up to
823 * @nr_pages pages in the mapping. The pages are placed at @pages.
824 * find_get_pages() takes a reference against the returned pages.
826 * The search returns a group of mapping-contiguous pages with ascending
827 * indexes. There may be holes in the indices due to not-present pages.
829 * find_get_pages() returns the number of pages which were found.
831 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
832 unsigned int nr_pages, struct page **pages)
836 unsigned int nr_found;
840 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
841 (void ***)pages, start, nr_pages);
843 for (i = 0; i < nr_found; i++) {
846 page = radix_tree_deref_slot((void **)pages[i]);
851 * This can only trigger when the entry at index 0 moves out
852 * of or back to the root: none yet gotten, safe to restart.
854 if (radix_tree_deref_retry(page)) {
859 if (!page_cache_get_speculative(page))
862 /* Has the page moved? */
863 if (unlikely(page != *((void **)pages[i]))) {
864 page_cache_release(page);
873 * If all entries were removed before we could secure them,
874 * try again, because callers stop trying once 0 is returned.
876 if (unlikely(!ret && nr_found))
883 * find_get_pages_contig - gang contiguous pagecache lookup
884 * @mapping: The address_space to search
885 * @index: The starting page index
886 * @nr_pages: The maximum number of pages
887 * @pages: Where the resulting pages are placed
889 * find_get_pages_contig() works exactly like find_get_pages(), except
890 * that the returned number of pages are guaranteed to be contiguous.
892 * find_get_pages_contig() returns the number of pages which were found.
894 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
895 unsigned int nr_pages, struct page **pages)
899 unsigned int nr_found;
903 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
904 (void ***)pages, index, nr_pages);
906 for (i = 0; i < nr_found; i++) {
909 page = radix_tree_deref_slot((void **)pages[i]);
914 * This can only trigger when the entry at index 0 moves out
915 * of or back to the root: none yet gotten, safe to restart.
917 if (radix_tree_deref_retry(page))
920 if (!page_cache_get_speculative(page))
923 /* Has the page moved? */
924 if (unlikely(page != *((void **)pages[i]))) {
925 page_cache_release(page);
930 * must check mapping and index after taking the ref.
931 * otherwise we can get both false positives and false
932 * negatives, which is just confusing to the caller.
934 if (page->mapping == NULL || page->index != index) {
935 page_cache_release(page);
946 EXPORT_SYMBOL(find_get_pages_contig);
949 * find_get_pages_tag - find and return pages that match @tag
950 * @mapping: the address_space to search
951 * @index: the starting page index
952 * @tag: the tag index
953 * @nr_pages: the maximum number of pages
954 * @pages: where the resulting pages are placed
956 * Like find_get_pages, except we only return pages which are tagged with
957 * @tag. We update @index to index the next page for the traversal.
959 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
960 int tag, unsigned int nr_pages, struct page **pages)
964 unsigned int nr_found;
968 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
969 (void ***)pages, *index, nr_pages, tag);
971 for (i = 0; i < nr_found; i++) {
974 page = radix_tree_deref_slot((void **)pages[i]);
979 * This can only trigger when the entry at index 0 moves out
980 * of or back to the root: none yet gotten, safe to restart.
982 if (radix_tree_deref_retry(page))
985 if (!page_cache_get_speculative(page))
988 /* Has the page moved? */
989 if (unlikely(page != *((void **)pages[i]))) {
990 page_cache_release(page);
999 * If all entries were removed before we could secure them,
1000 * try again, because callers stop trying once 0 is returned.
1002 if (unlikely(!ret && nr_found))
1007 *index = pages[ret - 1]->index + 1;
1011 EXPORT_SYMBOL(find_get_pages_tag);
1014 * grab_cache_page_nowait - returns locked page at given index in given cache
1015 * @mapping: target address_space
1016 * @index: the page index
1018 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1019 * This is intended for speculative data generators, where the data can
1020 * be regenerated if the page couldn't be grabbed. This routine should
1021 * be safe to call while holding the lock for another page.
1023 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1024 * and deadlock against the caller's locked page.
1027 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1029 struct page *page = find_get_page(mapping, index);
1032 if (trylock_page(page))
1034 page_cache_release(page);
1037 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1038 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1039 page_cache_release(page);
1044 EXPORT_SYMBOL(grab_cache_page_nowait);
1047 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1048 * a _large_ part of the i/o request. Imagine the worst scenario:
1050 * ---R__________________________________________B__________
1051 * ^ reading here ^ bad block(assume 4k)
1053 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1054 * => failing the whole request => read(R) => read(R+1) =>
1055 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1056 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1057 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1059 * It is going insane. Fix it by quickly scaling down the readahead size.
1061 static void shrink_readahead_size_eio(struct file *filp,
1062 struct file_ra_state *ra)
1068 * do_generic_file_read - generic file read routine
1069 * @filp: the file to read
1070 * @ppos: current file position
1071 * @desc: read_descriptor
1072 * @actor: read method
1074 * This is a generic file read routine, and uses the
1075 * mapping->a_ops->readpage() function for the actual low-level stuff.
1077 * This is really ugly. But the goto's actually try to clarify some
1078 * of the logic when it comes to error handling etc.
1080 static void do_generic_file_read(struct file *filp, loff_t *ppos,
1081 read_descriptor_t *desc, read_actor_t actor)
1083 struct address_space *mapping = filp->f_mapping;
1084 struct inode *inode = mapping->host;
1085 struct file_ra_state *ra = &filp->f_ra;
1089 unsigned long offset; /* offset into pagecache page */
1090 unsigned int prev_offset;
1093 index = *ppos >> PAGE_CACHE_SHIFT;
1094 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1095 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1096 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1097 offset = *ppos & ~PAGE_CACHE_MASK;
1103 unsigned long nr, ret;
1107 page = find_get_page(mapping, index);
1109 page_cache_sync_readahead(mapping,
1111 index, last_index - index);
1112 page = find_get_page(mapping, index);
1113 if (unlikely(page == NULL))
1114 goto no_cached_page;
1116 if (PageReadahead(page)) {
1117 page_cache_async_readahead(mapping,
1119 index, last_index - index);
1121 if (!PageUptodate(page)) {
1122 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1123 !mapping->a_ops->is_partially_uptodate)
1124 goto page_not_up_to_date;
1125 if (!trylock_page(page))
1126 goto page_not_up_to_date;
1127 /* Did it get truncated before we got the lock? */
1129 goto page_not_up_to_date_locked;
1130 if (!mapping->a_ops->is_partially_uptodate(page,
1132 goto page_not_up_to_date_locked;
1137 * i_size must be checked after we know the page is Uptodate.
1139 * Checking i_size after the check allows us to calculate
1140 * the correct value for "nr", which means the zero-filled
1141 * part of the page is not copied back to userspace (unless
1142 * another truncate extends the file - this is desired though).
1145 isize = i_size_read(inode);
1146 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1147 if (unlikely(!isize || index > end_index)) {
1148 page_cache_release(page);
1152 /* nr is the maximum number of bytes to copy from this page */
1153 nr = PAGE_CACHE_SIZE;
1154 if (index == end_index) {
1155 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1157 page_cache_release(page);
1163 /* If users can be writing to this page using arbitrary
1164 * virtual addresses, take care about potential aliasing
1165 * before reading the page on the kernel side.
1167 if (mapping_writably_mapped(mapping))
1168 flush_dcache_page(page);
1171 * When a sequential read accesses a page several times,
1172 * only mark it as accessed the first time.
1174 if (prev_index != index || offset != prev_offset)
1175 mark_page_accessed(page);
1179 * Ok, we have the page, and it's up-to-date, so
1180 * now we can copy it to user space...
1182 * The actor routine returns how many bytes were actually used..
1183 * NOTE! This may not be the same as how much of a user buffer
1184 * we filled up (we may be padding etc), so we can only update
1185 * "pos" here (the actor routine has to update the user buffer
1186 * pointers and the remaining count).
1188 ret = actor(desc, page, offset, nr);
1190 index += offset >> PAGE_CACHE_SHIFT;
1191 offset &= ~PAGE_CACHE_MASK;
1192 prev_offset = offset;
1194 page_cache_release(page);
1195 if (ret == nr && desc->count)
1199 page_not_up_to_date:
1200 /* Get exclusive access to the page ... */
1201 error = lock_page_killable(page);
1202 if (unlikely(error))
1203 goto readpage_error;
1205 page_not_up_to_date_locked:
1206 /* Did it get truncated before we got the lock? */
1207 if (!page->mapping) {
1209 page_cache_release(page);
1213 /* Did somebody else fill it already? */
1214 if (PageUptodate(page)) {
1221 * A previous I/O error may have been due to temporary
1222 * failures, eg. multipath errors.
1223 * PG_error will be set again if readpage fails.
1225 ClearPageError(page);
1226 /* Start the actual read. The read will unlock the page. */
1227 error = mapping->a_ops->readpage(filp, page);
1229 if (unlikely(error)) {
1230 if (error == AOP_TRUNCATED_PAGE) {
1231 page_cache_release(page);
1234 goto readpage_error;
1237 if (!PageUptodate(page)) {
1238 error = lock_page_killable(page);
1239 if (unlikely(error))
1240 goto readpage_error;
1241 if (!PageUptodate(page)) {
1242 if (page->mapping == NULL) {
1244 * invalidate_mapping_pages got it
1247 page_cache_release(page);
1251 shrink_readahead_size_eio(filp, ra);
1253 goto readpage_error;
1261 /* UHHUH! A synchronous read error occurred. Report it */
1262 desc->error = error;
1263 page_cache_release(page);
1268 * Ok, it wasn't cached, so we need to create a new
1271 page = page_cache_alloc_cold(mapping);
1273 desc->error = -ENOMEM;
1276 error = add_to_page_cache_lru(page, mapping,
1279 page_cache_release(page);
1280 if (error == -EEXIST)
1282 desc->error = error;
1289 ra->prev_pos = prev_index;
1290 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1291 ra->prev_pos |= prev_offset;
1293 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1294 file_accessed(filp);
1297 int file_read_actor(read_descriptor_t *desc, struct page *page,
1298 unsigned long offset, unsigned long size)
1301 unsigned long left, count = desc->count;
1307 * Faults on the destination of a read are common, so do it before
1310 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1311 kaddr = kmap_atomic(page, KM_USER0);
1312 left = __copy_to_user_inatomic(desc->arg.buf,
1313 kaddr + offset, size);
1314 kunmap_atomic(kaddr, KM_USER0);
1319 /* Do it the slow way */
1321 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1326 desc->error = -EFAULT;
1329 desc->count = count - size;
1330 desc->written += size;
1331 desc->arg.buf += size;
1336 * Performs necessary checks before doing a write
1337 * @iov: io vector request
1338 * @nr_segs: number of segments in the iovec
1339 * @count: number of bytes to write
1340 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1342 * Adjust number of segments and amount of bytes to write (nr_segs should be
1343 * properly initialized first). Returns appropriate error code that caller
1344 * should return or zero in case that write should be allowed.
1346 int generic_segment_checks(const struct iovec *iov,
1347 unsigned long *nr_segs, size_t *count, int access_flags)
1351 for (seg = 0; seg < *nr_segs; seg++) {
1352 const struct iovec *iv = &iov[seg];
1355 * If any segment has a negative length, or the cumulative
1356 * length ever wraps negative then return -EINVAL.
1359 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1361 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1366 cnt -= iv->iov_len; /* This segment is no good */
1372 EXPORT_SYMBOL(generic_segment_checks);
1375 * generic_file_aio_read - generic filesystem read routine
1376 * @iocb: kernel I/O control block
1377 * @iov: io vector request
1378 * @nr_segs: number of segments in the iovec
1379 * @pos: current file position
1381 * This is the "read()" routine for all filesystems
1382 * that can use the page cache directly.
1385 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1386 unsigned long nr_segs, loff_t pos)
1388 struct file *filp = iocb->ki_filp;
1390 unsigned long seg = 0;
1392 loff_t *ppos = &iocb->ki_pos;
1393 struct blk_plug plug;
1396 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1400 blk_start_plug(&plug);
1402 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1403 if (filp->f_flags & O_DIRECT) {
1405 struct address_space *mapping;
1406 struct inode *inode;
1408 mapping = filp->f_mapping;
1409 inode = mapping->host;
1411 goto out; /* skip atime */
1412 size = i_size_read(inode);
1414 retval = filemap_write_and_wait_range(mapping, pos,
1415 pos + iov_length(iov, nr_segs) - 1);
1417 retval = mapping->a_ops->direct_IO(READ, iocb,
1421 *ppos = pos + retval;
1426 * Btrfs can have a short DIO read if we encounter
1427 * compressed extents, so if there was an error, or if
1428 * we've already read everything we wanted to, or if
1429 * there was a short read because we hit EOF, go ahead
1430 * and return. Otherwise fallthrough to buffered io for
1431 * the rest of the read.
1433 if (retval < 0 || !count || *ppos >= size) {
1434 file_accessed(filp);
1441 for (seg = 0; seg < nr_segs; seg++) {
1442 read_descriptor_t desc;
1446 * If we did a short DIO read we need to skip the section of the
1447 * iov that we've already read data into.
1450 if (count > iov[seg].iov_len) {
1451 count -= iov[seg].iov_len;
1459 desc.arg.buf = iov[seg].iov_base + offset;
1460 desc.count = iov[seg].iov_len - offset;
1461 if (desc.count == 0)
1464 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1465 retval += desc.written;
1467 retval = retval ?: desc.error;
1474 blk_finish_plug(&plug);
1477 EXPORT_SYMBOL(generic_file_aio_read);
1480 do_readahead(struct address_space *mapping, struct file *filp,
1481 pgoff_t index, unsigned long nr)
1483 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1486 force_page_cache_readahead(mapping, filp, index, nr);
1490 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1498 if (file->f_mode & FMODE_READ) {
1499 struct address_space *mapping = file->f_mapping;
1500 pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1501 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1502 unsigned long len = end - start + 1;
1503 ret = do_readahead(mapping, file, start, len);
1509 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1510 asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1512 return SYSC_readahead((int) fd, offset, (size_t) count);
1514 SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1519 * page_cache_read - adds requested page to the page cache if not already there
1520 * @file: file to read
1521 * @offset: page index
1523 * This adds the requested page to the page cache if it isn't already there,
1524 * and schedules an I/O to read in its contents from disk.
1526 static int page_cache_read(struct file *file, pgoff_t offset)
1528 struct address_space *mapping = file->f_mapping;
1533 page = page_cache_alloc_cold(mapping);
1537 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1539 ret = mapping->a_ops->readpage(file, page);
1540 else if (ret == -EEXIST)
1541 ret = 0; /* losing race to add is OK */
1543 page_cache_release(page);
1545 } while (ret == AOP_TRUNCATED_PAGE);
1550 #define MMAP_LOTSAMISS (100)
1553 * Synchronous readahead happens when we don't even find
1554 * a page in the page cache at all.
1556 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1557 struct file_ra_state *ra,
1561 unsigned long ra_pages;
1562 struct address_space *mapping = file->f_mapping;
1564 /* If we don't want any read-ahead, don't bother */
1565 if (VM_RandomReadHint(vma))
1570 if (VM_SequentialReadHint(vma)) {
1571 page_cache_sync_readahead(mapping, ra, file, offset,
1576 /* Avoid banging the cache line if not needed */
1577 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1581 * Do we miss much more than hit in this file? If so,
1582 * stop bothering with read-ahead. It will only hurt.
1584 if (ra->mmap_miss > MMAP_LOTSAMISS)
1590 ra_pages = max_sane_readahead(ra->ra_pages);
1591 ra->start = max_t(long, 0, offset - ra_pages / 2);
1592 ra->size = ra_pages;
1593 ra->async_size = ra_pages / 4;
1594 ra_submit(ra, mapping, file);
1598 * Asynchronous readahead happens when we find the page and PG_readahead,
1599 * so we want to possibly extend the readahead further..
1601 static void do_async_mmap_readahead(struct vm_area_struct *vma,
1602 struct file_ra_state *ra,
1607 struct address_space *mapping = file->f_mapping;
1609 /* If we don't want any read-ahead, don't bother */
1610 if (VM_RandomReadHint(vma))
1612 if (ra->mmap_miss > 0)
1614 if (PageReadahead(page))
1615 page_cache_async_readahead(mapping, ra, file,
1616 page, offset, ra->ra_pages);
1620 * filemap_fault - read in file data for page fault handling
1621 * @vma: vma in which the fault was taken
1622 * @vmf: struct vm_fault containing details of the fault
1624 * filemap_fault() is invoked via the vma operations vector for a
1625 * mapped memory region to read in file data during a page fault.
1627 * The goto's are kind of ugly, but this streamlines the normal case of having
1628 * it in the page cache, and handles the special cases reasonably without
1629 * having a lot of duplicated code.
1631 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1634 struct file *file = vma->vm_file;
1635 struct address_space *mapping = file->f_mapping;
1636 struct file_ra_state *ra = &file->f_ra;
1637 struct inode *inode = mapping->host;
1638 pgoff_t offset = vmf->pgoff;
1643 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1645 return VM_FAULT_SIGBUS;
1648 * Do we have something in the page cache already?
1650 page = find_get_page(mapping, offset);
1653 * We found the page, so try async readahead before
1654 * waiting for the lock.
1656 do_async_mmap_readahead(vma, ra, file, page, offset);
1658 /* No page in the page cache at all */
1659 do_sync_mmap_readahead(vma, ra, file, offset);
1660 count_vm_event(PGMAJFAULT);
1661 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1662 ret = VM_FAULT_MAJOR;
1664 page = find_get_page(mapping, offset);
1666 goto no_cached_page;
1669 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1670 page_cache_release(page);
1671 return ret | VM_FAULT_RETRY;
1674 /* Did it get truncated? */
1675 if (unlikely(page->mapping != mapping)) {
1680 VM_BUG_ON(page->index != offset);
1683 * We have a locked page in the page cache, now we need to check
1684 * that it's up-to-date. If not, it is going to be due to an error.
1686 if (unlikely(!PageUptodate(page)))
1687 goto page_not_uptodate;
1690 * Found the page and have a reference on it.
1691 * We must recheck i_size under page lock.
1693 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1694 if (unlikely(offset >= size)) {
1696 page_cache_release(page);
1697 return VM_FAULT_SIGBUS;
1701 return ret | VM_FAULT_LOCKED;
1705 * We're only likely to ever get here if MADV_RANDOM is in
1708 error = page_cache_read(file, offset);
1711 * The page we want has now been added to the page cache.
1712 * In the unlikely event that someone removed it in the
1713 * meantime, we'll just come back here and read it again.
1719 * An error return from page_cache_read can result if the
1720 * system is low on memory, or a problem occurs while trying
1723 if (error == -ENOMEM)
1724 return VM_FAULT_OOM;
1725 return VM_FAULT_SIGBUS;
1729 * Umm, take care of errors if the page isn't up-to-date.
1730 * Try to re-read it _once_. We do this synchronously,
1731 * because there really aren't any performance issues here
1732 * and we need to check for errors.
1734 ClearPageError(page);
1735 error = mapping->a_ops->readpage(file, page);
1737 wait_on_page_locked(page);
1738 if (!PageUptodate(page))
1741 page_cache_release(page);
1743 if (!error || error == AOP_TRUNCATED_PAGE)
1746 /* Things didn't work out. Return zero to tell the mm layer so. */
1747 shrink_readahead_size_eio(file, ra);
1748 return VM_FAULT_SIGBUS;
1750 EXPORT_SYMBOL(filemap_fault);
1752 const struct vm_operations_struct generic_file_vm_ops = {
1753 .fault = filemap_fault,
1756 /* This is used for a general mmap of a disk file */
1758 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1760 struct address_space *mapping = file->f_mapping;
1762 if (!mapping->a_ops->readpage)
1764 file_accessed(file);
1765 vma->vm_ops = &generic_file_vm_ops;
1766 vma->vm_flags |= VM_CAN_NONLINEAR;
1771 * This is for filesystems which do not implement ->writepage.
1773 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1775 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1777 return generic_file_mmap(file, vma);
1780 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1784 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1788 #endif /* CONFIG_MMU */
1790 EXPORT_SYMBOL(generic_file_mmap);
1791 EXPORT_SYMBOL(generic_file_readonly_mmap);
1793 static struct page *__read_cache_page(struct address_space *mapping,
1795 int (*filler)(void *, struct page *),
1802 page = find_get_page(mapping, index);
1804 page = __page_cache_alloc(gfp | __GFP_COLD);
1806 return ERR_PTR(-ENOMEM);
1807 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1808 if (unlikely(err)) {
1809 page_cache_release(page);
1812 /* Presumably ENOMEM for radix tree node */
1813 return ERR_PTR(err);
1815 err = filler(data, page);
1817 page_cache_release(page);
1818 page = ERR_PTR(err);
1824 static struct page *do_read_cache_page(struct address_space *mapping,
1826 int (*filler)(void *, struct page *),
1835 page = __read_cache_page(mapping, index, filler, data, gfp);
1838 if (PageUptodate(page))
1842 if (!page->mapping) {
1844 page_cache_release(page);
1847 if (PageUptodate(page)) {
1851 err = filler(data, page);
1853 page_cache_release(page);
1854 return ERR_PTR(err);
1857 mark_page_accessed(page);
1862 * read_cache_page_async - read into page cache, fill it if needed
1863 * @mapping: the page's address_space
1864 * @index: the page index
1865 * @filler: function to perform the read
1866 * @data: first arg to filler(data, page) function, often left as NULL
1868 * Same as read_cache_page, but don't wait for page to become unlocked
1869 * after submitting it to the filler.
1871 * Read into the page cache. If a page already exists, and PageUptodate() is
1872 * not set, try to fill the page but don't wait for it to become unlocked.
1874 * If the page does not get brought uptodate, return -EIO.
1876 struct page *read_cache_page_async(struct address_space *mapping,
1878 int (*filler)(void *, struct page *),
1881 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1883 EXPORT_SYMBOL(read_cache_page_async);
1885 static struct page *wait_on_page_read(struct page *page)
1887 if (!IS_ERR(page)) {
1888 wait_on_page_locked(page);
1889 if (!PageUptodate(page)) {
1890 page_cache_release(page);
1891 page = ERR_PTR(-EIO);
1898 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1899 * @mapping: the page's address_space
1900 * @index: the page index
1901 * @gfp: the page allocator flags to use if allocating
1903 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1904 * any new page allocations done using the specified allocation flags. Note
1905 * that the Radix tree operations will still use GFP_KERNEL, so you can't
1906 * expect to do this atomically or anything like that - but you can pass in
1907 * other page requirements.
1909 * If the page does not get brought uptodate, return -EIO.
1911 struct page *read_cache_page_gfp(struct address_space *mapping,
1915 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1917 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1919 EXPORT_SYMBOL(read_cache_page_gfp);
1922 * read_cache_page - read into page cache, fill it if needed
1923 * @mapping: the page's address_space
1924 * @index: the page index
1925 * @filler: function to perform the read
1926 * @data: first arg to filler(data, page) function, often left as NULL
1928 * Read into the page cache. If a page already exists, and PageUptodate() is
1929 * not set, try to fill the page then wait for it to become unlocked.
1931 * If the page does not get brought uptodate, return -EIO.
1933 struct page *read_cache_page(struct address_space *mapping,
1935 int (*filler)(void *, struct page *),
1938 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1940 EXPORT_SYMBOL(read_cache_page);
1943 * The logic we want is
1945 * if suid or (sgid and xgrp)
1948 int should_remove_suid(struct dentry *dentry)
1950 mode_t mode = dentry->d_inode->i_mode;
1953 /* suid always must be killed */
1954 if (unlikely(mode & S_ISUID))
1955 kill = ATTR_KILL_SUID;
1958 * sgid without any exec bits is just a mandatory locking mark; leave
1959 * it alone. If some exec bits are set, it's a real sgid; kill it.
1961 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1962 kill |= ATTR_KILL_SGID;
1964 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1969 EXPORT_SYMBOL(should_remove_suid);
1971 static int __remove_suid(struct dentry *dentry, int kill)
1973 struct iattr newattrs;
1975 newattrs.ia_valid = ATTR_FORCE | kill;
1976 return notify_change(dentry, &newattrs);
1979 int file_remove_suid(struct file *file)
1981 struct dentry *dentry = file->f_path.dentry;
1982 struct inode *inode = dentry->d_inode;
1987 /* Fast path for nothing security related */
1988 if (IS_NOSEC(inode))
1991 killsuid = should_remove_suid(dentry);
1992 killpriv = security_inode_need_killpriv(dentry);
1997 error = security_inode_killpriv(dentry);
1998 if (!error && killsuid)
1999 error = __remove_suid(dentry, killsuid);
2000 if (!error && (inode->i_sb->s_flags & MS_NOSEC))
2001 inode->i_flags |= S_NOSEC;
2005 EXPORT_SYMBOL(file_remove_suid);
2007 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
2008 const struct iovec *iov, size_t base, size_t bytes)
2010 size_t copied = 0, left = 0;
2013 char __user *buf = iov->iov_base + base;
2014 int copy = min(bytes, iov->iov_len - base);
2017 left = __copy_from_user_inatomic(vaddr, buf, copy);
2026 return copied - left;
2030 * Copy as much as we can into the page and return the number of bytes which
2031 * were successfully copied. If a fault is encountered then return the number of
2032 * bytes which were copied.
2034 size_t iov_iter_copy_from_user_atomic(struct page *page,
2035 struct iov_iter *i, unsigned long offset, size_t bytes)
2040 BUG_ON(!in_atomic());
2041 kaddr = kmap_atomic(page, KM_USER0);
2042 if (likely(i->nr_segs == 1)) {
2044 char __user *buf = i->iov->iov_base + i->iov_offset;
2045 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
2046 copied = bytes - left;
2048 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2049 i->iov, i->iov_offset, bytes);
2051 kunmap_atomic(kaddr, KM_USER0);
2055 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
2058 * This has the same sideeffects and return value as
2059 * iov_iter_copy_from_user_atomic().
2060 * The difference is that it attempts to resolve faults.
2061 * Page must not be locked.
2063 size_t iov_iter_copy_from_user(struct page *page,
2064 struct iov_iter *i, unsigned long offset, size_t bytes)
2070 if (likely(i->nr_segs == 1)) {
2072 char __user *buf = i->iov->iov_base + i->iov_offset;
2073 left = __copy_from_user(kaddr + offset, buf, bytes);
2074 copied = bytes - left;
2076 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2077 i->iov, i->iov_offset, bytes);
2082 EXPORT_SYMBOL(iov_iter_copy_from_user);
2084 void iov_iter_advance(struct iov_iter *i, size_t bytes)
2086 BUG_ON(i->count < bytes);
2088 if (likely(i->nr_segs == 1)) {
2089 i->iov_offset += bytes;
2092 const struct iovec *iov = i->iov;
2093 size_t base = i->iov_offset;
2096 * The !iov->iov_len check ensures we skip over unlikely
2097 * zero-length segments (without overruning the iovec).
2099 while (bytes || unlikely(i->count && !iov->iov_len)) {
2102 copy = min(bytes, iov->iov_len - base);
2103 BUG_ON(!i->count || i->count < copy);
2107 if (iov->iov_len == base) {
2113 i->iov_offset = base;
2116 EXPORT_SYMBOL(iov_iter_advance);
2119 * Fault in the first iovec of the given iov_iter, to a maximum length
2120 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2121 * accessed (ie. because it is an invalid address).
2123 * writev-intensive code may want this to prefault several iovecs -- that
2124 * would be possible (callers must not rely on the fact that _only_ the
2125 * first iovec will be faulted with the current implementation).
2127 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2129 char __user *buf = i->iov->iov_base + i->iov_offset;
2130 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2131 return fault_in_pages_readable(buf, bytes);
2133 EXPORT_SYMBOL(iov_iter_fault_in_readable);
2136 * Return the count of just the current iov_iter segment.
2138 size_t iov_iter_single_seg_count(struct iov_iter *i)
2140 const struct iovec *iov = i->iov;
2141 if (i->nr_segs == 1)
2144 return min(i->count, iov->iov_len - i->iov_offset);
2146 EXPORT_SYMBOL(iov_iter_single_seg_count);
2149 * Performs necessary checks before doing a write
2151 * Can adjust writing position or amount of bytes to write.
2152 * Returns appropriate error code that caller should return or
2153 * zero in case that write should be allowed.
2155 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2157 struct inode *inode = file->f_mapping->host;
2158 unsigned long limit = rlimit(RLIMIT_FSIZE);
2160 if (unlikely(*pos < 0))
2164 /* FIXME: this is for backwards compatibility with 2.4 */
2165 if (file->f_flags & O_APPEND)
2166 *pos = i_size_read(inode);
2168 if (limit != RLIM_INFINITY) {
2169 if (*pos >= limit) {
2170 send_sig(SIGXFSZ, current, 0);
2173 if (*count > limit - (typeof(limit))*pos) {
2174 *count = limit - (typeof(limit))*pos;
2182 if (unlikely(*pos + *count > MAX_NON_LFS &&
2183 !(file->f_flags & O_LARGEFILE))) {
2184 if (*pos >= MAX_NON_LFS) {
2187 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2188 *count = MAX_NON_LFS - (unsigned long)*pos;
2193 * Are we about to exceed the fs block limit ?
2195 * If we have written data it becomes a short write. If we have
2196 * exceeded without writing data we send a signal and return EFBIG.
2197 * Linus frestrict idea will clean these up nicely..
2199 if (likely(!isblk)) {
2200 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2201 if (*count || *pos > inode->i_sb->s_maxbytes) {
2204 /* zero-length writes at ->s_maxbytes are OK */
2207 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2208 *count = inode->i_sb->s_maxbytes - *pos;
2212 if (bdev_read_only(I_BDEV(inode)))
2214 isize = i_size_read(inode);
2215 if (*pos >= isize) {
2216 if (*count || *pos > isize)
2220 if (*pos + *count > isize)
2221 *count = isize - *pos;
2228 EXPORT_SYMBOL(generic_write_checks);
2230 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2231 loff_t pos, unsigned len, unsigned flags,
2232 struct page **pagep, void **fsdata)
2234 const struct address_space_operations *aops = mapping->a_ops;
2236 return aops->write_begin(file, mapping, pos, len, flags,
2239 EXPORT_SYMBOL(pagecache_write_begin);
2241 int pagecache_write_end(struct file *file, struct address_space *mapping,
2242 loff_t pos, unsigned len, unsigned copied,
2243 struct page *page, void *fsdata)
2245 const struct address_space_operations *aops = mapping->a_ops;
2247 mark_page_accessed(page);
2248 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2250 EXPORT_SYMBOL(pagecache_write_end);
2253 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2254 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2255 size_t count, size_t ocount)
2257 struct file *file = iocb->ki_filp;
2258 struct address_space *mapping = file->f_mapping;
2259 struct inode *inode = mapping->host;
2264 if (count != ocount)
2265 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2267 write_len = iov_length(iov, *nr_segs);
2268 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2270 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2275 * After a write we want buffered reads to be sure to go to disk to get
2276 * the new data. We invalidate clean cached page from the region we're
2277 * about to write. We do this *before* the write so that we can return
2278 * without clobbering -EIOCBQUEUED from ->direct_IO().
2280 if (mapping->nrpages) {
2281 written = invalidate_inode_pages2_range(mapping,
2282 pos >> PAGE_CACHE_SHIFT, end);
2284 * If a page can not be invalidated, return 0 to fall back
2285 * to buffered write.
2288 if (written == -EBUSY)
2294 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2297 * Finally, try again to invalidate clean pages which might have been
2298 * cached by non-direct readahead, or faulted in by get_user_pages()
2299 * if the source of the write was an mmap'ed region of the file
2300 * we're writing. Either one is a pretty crazy thing to do,
2301 * so we don't support it 100%. If this invalidation
2302 * fails, tough, the write still worked...
2304 if (mapping->nrpages) {
2305 invalidate_inode_pages2_range(mapping,
2306 pos >> PAGE_CACHE_SHIFT, end);
2311 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2312 i_size_write(inode, pos);
2313 mark_inode_dirty(inode);
2320 EXPORT_SYMBOL(generic_file_direct_write);
2323 * Find or create a page at the given pagecache position. Return the locked
2324 * page. This function is specifically for buffered writes.
2326 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2327 pgoff_t index, unsigned flags)
2331 gfp_t gfp_notmask = 0;
2332 if (flags & AOP_FLAG_NOFS)
2333 gfp_notmask = __GFP_FS;
2335 page = find_lock_page(mapping, index);
2339 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2342 status = add_to_page_cache_lru(page, mapping, index,
2343 GFP_KERNEL & ~gfp_notmask);
2344 if (unlikely(status)) {
2345 page_cache_release(page);
2346 if (status == -EEXIST)
2351 wait_on_page_writeback(page);
2354 EXPORT_SYMBOL(grab_cache_page_write_begin);
2356 static ssize_t generic_perform_write(struct file *file,
2357 struct iov_iter *i, loff_t pos)
2359 struct address_space *mapping = file->f_mapping;
2360 const struct address_space_operations *a_ops = mapping->a_ops;
2362 ssize_t written = 0;
2363 unsigned int flags = 0;
2366 * Copies from kernel address space cannot fail (NFSD is a big user).
2368 if (segment_eq(get_fs(), KERNEL_DS))
2369 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2373 unsigned long offset; /* Offset into pagecache page */
2374 unsigned long bytes; /* Bytes to write to page */
2375 size_t copied; /* Bytes copied from user */
2378 offset = (pos & (PAGE_CACHE_SIZE - 1));
2379 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2385 * Bring in the user page that we will copy from _first_.
2386 * Otherwise there's a nasty deadlock on copying from the
2387 * same page as we're writing to, without it being marked
2390 * Not only is this an optimisation, but it is also required
2391 * to check that the address is actually valid, when atomic
2392 * usercopies are used, below.
2394 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2399 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2401 if (unlikely(status))
2404 if (mapping_writably_mapped(mapping))
2405 flush_dcache_page(page);
2407 pagefault_disable();
2408 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2410 flush_dcache_page(page);
2412 mark_page_accessed(page);
2413 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2415 if (unlikely(status < 0))
2421 iov_iter_advance(i, copied);
2422 if (unlikely(copied == 0)) {
2424 * If we were unable to copy any data at all, we must
2425 * fall back to a single segment length write.
2427 * If we didn't fallback here, we could livelock
2428 * because not all segments in the iov can be copied at
2429 * once without a pagefault.
2431 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2432 iov_iter_single_seg_count(i));
2438 balance_dirty_pages_ratelimited(mapping);
2440 } while (iov_iter_count(i));
2442 return written ? written : status;
2446 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2447 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2448 size_t count, ssize_t written)
2450 struct file *file = iocb->ki_filp;
2454 iov_iter_init(&i, iov, nr_segs, count, written);
2455 status = generic_perform_write(file, &i, pos);
2457 if (likely(status >= 0)) {
2459 *ppos = pos + status;
2462 return written ? written : status;
2464 EXPORT_SYMBOL(generic_file_buffered_write);
2467 * __generic_file_aio_write - write data to a file
2468 * @iocb: IO state structure (file, offset, etc.)
2469 * @iov: vector with data to write
2470 * @nr_segs: number of segments in the vector
2471 * @ppos: position where to write
2473 * This function does all the work needed for actually writing data to a
2474 * file. It does all basic checks, removes SUID from the file, updates
2475 * modification times and calls proper subroutines depending on whether we
2476 * do direct IO or a standard buffered write.
2478 * It expects i_mutex to be grabbed unless we work on a block device or similar
2479 * object which does not need locking at all.
2481 * This function does *not* take care of syncing data in case of O_SYNC write.
2482 * A caller has to handle it. This is mainly due to the fact that we want to
2483 * avoid syncing under i_mutex.
2485 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2486 unsigned long nr_segs, loff_t *ppos)
2488 struct file *file = iocb->ki_filp;
2489 struct address_space * mapping = file->f_mapping;
2490 size_t ocount; /* original count */
2491 size_t count; /* after file limit checks */
2492 struct inode *inode = mapping->host;
2498 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2505 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2507 /* We can write back this queue in page reclaim */
2508 current->backing_dev_info = mapping->backing_dev_info;
2511 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2518 err = file_remove_suid(file);
2522 file_update_time(file);
2524 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2525 if (unlikely(file->f_flags & O_DIRECT)) {
2527 ssize_t written_buffered;
2529 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2530 ppos, count, ocount);
2531 if (written < 0 || written == count)
2534 * direct-io write to a hole: fall through to buffered I/O
2535 * for completing the rest of the request.
2539 written_buffered = generic_file_buffered_write(iocb, iov,
2540 nr_segs, pos, ppos, count,
2543 * If generic_file_buffered_write() retuned a synchronous error
2544 * then we want to return the number of bytes which were
2545 * direct-written, or the error code if that was zero. Note
2546 * that this differs from normal direct-io semantics, which
2547 * will return -EFOO even if some bytes were written.
2549 if (written_buffered < 0) {
2550 err = written_buffered;
2555 * We need to ensure that the page cache pages are written to
2556 * disk and invalidated to preserve the expected O_DIRECT
2559 endbyte = pos + written_buffered - written - 1;
2560 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2562 written = written_buffered;
2563 invalidate_mapping_pages(mapping,
2564 pos >> PAGE_CACHE_SHIFT,
2565 endbyte >> PAGE_CACHE_SHIFT);
2568 * We don't know how much we wrote, so just return
2569 * the number of bytes which were direct-written
2573 written = generic_file_buffered_write(iocb, iov, nr_segs,
2574 pos, ppos, count, written);
2577 current->backing_dev_info = NULL;
2578 return written ? written : err;
2580 EXPORT_SYMBOL(__generic_file_aio_write);
2583 * generic_file_aio_write - write data to a file
2584 * @iocb: IO state structure
2585 * @iov: vector with data to write
2586 * @nr_segs: number of segments in the vector
2587 * @pos: position in file where to write
2589 * This is a wrapper around __generic_file_aio_write() to be used by most
2590 * filesystems. It takes care of syncing the file in case of O_SYNC file
2591 * and acquires i_mutex as needed.
2593 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2594 unsigned long nr_segs, loff_t pos)
2596 struct file *file = iocb->ki_filp;
2597 struct inode *inode = file->f_mapping->host;
2598 struct blk_plug plug;
2601 BUG_ON(iocb->ki_pos != pos);
2603 mutex_lock(&inode->i_mutex);
2604 blk_start_plug(&plug);
2605 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2606 mutex_unlock(&inode->i_mutex);
2608 if (ret > 0 || ret == -EIOCBQUEUED) {
2611 err = generic_write_sync(file, pos, ret);
2612 if (err < 0 && ret > 0)
2615 blk_finish_plug(&plug);
2618 EXPORT_SYMBOL(generic_file_aio_write);
2621 * try_to_release_page() - release old fs-specific metadata on a page
2623 * @page: the page which the kernel is trying to free
2624 * @gfp_mask: memory allocation flags (and I/O mode)
2626 * The address_space is to try to release any data against the page
2627 * (presumably at page->private). If the release was successful, return `1'.
2628 * Otherwise return zero.
2630 * This may also be called if PG_fscache is set on a page, indicating that the
2631 * page is known to the local caching routines.
2633 * The @gfp_mask argument specifies whether I/O may be performed to release
2634 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2637 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2639 struct address_space * const mapping = page->mapping;
2641 BUG_ON(!PageLocked(page));
2642 if (PageWriteback(page))
2645 if (mapping && mapping->a_ops->releasepage)
2646 return mapping->a_ops->releasepage(page, gfp_mask);
2647 return try_to_free_buffers(page);
2650 EXPORT_SYMBOL(try_to_release_page);