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 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
100 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
101 * bdi.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;
131 /* Leave page->index set: truncation lookup relies upon it */
133 __dec_zone_page_state(page, NR_FILE_PAGES);
134 if (PageSwapBacked(page))
135 __dec_zone_page_state(page, NR_SHMEM);
136 BUG_ON(page_mapped(page));
139 * Some filesystems seem to re-dirty the page even after
140 * the VM has canceled the dirty bit (eg ext3 journaling).
142 * Fix it up by doing a final dirty accounting check after
143 * having removed the page entirely.
145 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
146 dec_zone_page_state(page, NR_FILE_DIRTY);
147 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
152 * delete_from_page_cache - delete page from page cache
153 * @page: the page which the kernel is trying to remove from page cache
155 * This must be called only on pages that have been verified to be in the page
156 * cache and locked. It will never put the page into the free list, the caller
157 * has a reference on the page.
159 void delete_from_page_cache(struct page *page)
161 struct address_space *mapping = page->mapping;
162 void (*freepage)(struct page *);
164 BUG_ON(!PageLocked(page));
166 freepage = mapping->a_ops->freepage;
167 spin_lock_irq(&mapping->tree_lock);
168 __delete_from_page_cache(page);
169 spin_unlock_irq(&mapping->tree_lock);
170 mem_cgroup_uncharge_cache_page(page);
174 page_cache_release(page);
176 EXPORT_SYMBOL(delete_from_page_cache);
178 static int sleep_on_page(void *word)
184 static int sleep_on_page_killable(void *word)
187 return fatal_signal_pending(current) ? -EINTR : 0;
191 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
192 * @mapping: address space structure to write
193 * @start: offset in bytes where the range starts
194 * @end: offset in bytes where the range ends (inclusive)
195 * @sync_mode: enable synchronous operation
197 * Start writeback against all of a mapping's dirty pages that lie
198 * within the byte offsets <start, end> inclusive.
200 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
201 * opposed to a regular memory cleansing writeback. The difference between
202 * these two operations is that if a dirty page/buffer is encountered, it must
203 * be waited upon, and not just skipped over.
205 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
206 loff_t end, int sync_mode)
209 struct writeback_control wbc = {
210 .sync_mode = sync_mode,
211 .nr_to_write = LONG_MAX,
212 .range_start = start,
216 if (!mapping_cap_writeback_dirty(mapping))
219 ret = do_writepages(mapping, &wbc);
223 static inline int __filemap_fdatawrite(struct address_space *mapping,
226 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
229 int filemap_fdatawrite(struct address_space *mapping)
231 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
233 EXPORT_SYMBOL(filemap_fdatawrite);
235 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
238 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
240 EXPORT_SYMBOL(filemap_fdatawrite_range);
243 * filemap_flush - mostly a non-blocking flush
244 * @mapping: target address_space
246 * This is a mostly non-blocking flush. Not suitable for data-integrity
247 * purposes - I/O may not be started against all dirty pages.
249 int filemap_flush(struct address_space *mapping)
251 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
253 EXPORT_SYMBOL(filemap_flush);
256 * filemap_fdatawait_range - wait for writeback to complete
257 * @mapping: address space structure to wait for
258 * @start_byte: offset in bytes where the range starts
259 * @end_byte: offset in bytes where the range ends (inclusive)
261 * Walk the list of under-writeback pages of the given address space
262 * in the given range and wait for all of them.
264 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
267 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
268 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
273 if (end_byte < start_byte)
276 pagevec_init(&pvec, 0);
277 while ((index <= end) &&
278 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
279 PAGECACHE_TAG_WRITEBACK,
280 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
283 for (i = 0; i < nr_pages; i++) {
284 struct page *page = pvec.pages[i];
286 /* until radix tree lookup accepts end_index */
287 if (page->index > end)
290 wait_on_page_writeback(page);
291 if (TestClearPageError(page))
294 pagevec_release(&pvec);
298 /* Check for outstanding write errors */
299 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
301 if (test_and_clear_bit(AS_EIO, &mapping->flags))
306 EXPORT_SYMBOL(filemap_fdatawait_range);
309 * filemap_fdatawait - wait for all under-writeback pages to complete
310 * @mapping: address space structure to wait for
312 * Walk the list of under-writeback pages of the given address space
313 * and wait for all of them.
315 int filemap_fdatawait(struct address_space *mapping)
317 loff_t i_size = i_size_read(mapping->host);
322 return filemap_fdatawait_range(mapping, 0, i_size - 1);
324 EXPORT_SYMBOL(filemap_fdatawait);
326 int filemap_write_and_wait(struct address_space *mapping)
330 if (mapping->nrpages) {
331 err = filemap_fdatawrite(mapping);
333 * Even if the above returned error, the pages may be
334 * written partially (e.g. -ENOSPC), so we wait for it.
335 * But the -EIO is special case, it may indicate the worst
336 * thing (e.g. bug) happened, so we avoid waiting for it.
339 int err2 = filemap_fdatawait(mapping);
346 EXPORT_SYMBOL(filemap_write_and_wait);
349 * filemap_write_and_wait_range - write out & wait on a file range
350 * @mapping: the address_space for the pages
351 * @lstart: offset in bytes where the range starts
352 * @lend: offset in bytes where the range ends (inclusive)
354 * Write out and wait upon file offsets lstart->lend, inclusive.
356 * Note that `lend' is inclusive (describes the last byte to be written) so
357 * that this function can be used to write to the very end-of-file (end = -1).
359 int filemap_write_and_wait_range(struct address_space *mapping,
360 loff_t lstart, loff_t lend)
364 if (mapping->nrpages) {
365 err = __filemap_fdatawrite_range(mapping, lstart, lend,
367 /* See comment of filemap_write_and_wait() */
369 int err2 = filemap_fdatawait_range(mapping,
377 EXPORT_SYMBOL(filemap_write_and_wait_range);
380 * replace_page_cache_page - replace a pagecache page with a new one
381 * @old: page to be replaced
382 * @new: page to replace with
383 * @gfp_mask: allocation mode
385 * This function replaces a page in the pagecache with a new one. On
386 * success it acquires the pagecache reference for the new page and
387 * drops it for the old page. Both the old and new pages must be
388 * locked. This function does not add the new page to the LRU, the
389 * caller must do that.
391 * The remove + add is atomic. The only way this function can fail is
392 * memory allocation failure.
394 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
397 struct mem_cgroup *memcg = NULL;
399 VM_BUG_ON(!PageLocked(old));
400 VM_BUG_ON(!PageLocked(new));
401 VM_BUG_ON(new->mapping);
404 * This is not page migration, but prepare_migration and
405 * end_migration does enough work for charge replacement.
407 * In the longer term we probably want a specialized function
408 * for moving the charge from old to new in a more efficient
411 error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
415 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
417 struct address_space *mapping = old->mapping;
418 void (*freepage)(struct page *);
420 pgoff_t offset = old->index;
421 freepage = mapping->a_ops->freepage;
424 new->mapping = mapping;
427 spin_lock_irq(&mapping->tree_lock);
428 __delete_from_page_cache(old);
429 error = radix_tree_insert(&mapping->page_tree, offset, new);
432 __inc_zone_page_state(new, NR_FILE_PAGES);
433 if (PageSwapBacked(new))
434 __inc_zone_page_state(new, NR_SHMEM);
435 spin_unlock_irq(&mapping->tree_lock);
436 radix_tree_preload_end();
439 page_cache_release(old);
440 mem_cgroup_end_migration(memcg, old, new, true);
442 mem_cgroup_end_migration(memcg, old, new, false);
447 EXPORT_SYMBOL_GPL(replace_page_cache_page);
450 * add_to_page_cache_locked - add a locked page to the pagecache
452 * @mapping: the page's address_space
453 * @offset: page index
454 * @gfp_mask: page allocation mode
456 * This function is used to add a page to the pagecache. It must be locked.
457 * This function does not add the page to the LRU. The caller must do that.
459 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
460 pgoff_t offset, gfp_t gfp_mask)
464 VM_BUG_ON(!PageLocked(page));
466 error = mem_cgroup_cache_charge(page, current->mm,
467 gfp_mask & GFP_RECLAIM_MASK);
471 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
473 page_cache_get(page);
474 page->mapping = mapping;
475 page->index = offset;
477 spin_lock_irq(&mapping->tree_lock);
478 error = radix_tree_insert(&mapping->page_tree, offset, page);
479 if (likely(!error)) {
481 __inc_zone_page_state(page, NR_FILE_PAGES);
482 if (PageSwapBacked(page))
483 __inc_zone_page_state(page, NR_SHMEM);
484 spin_unlock_irq(&mapping->tree_lock);
486 page->mapping = NULL;
487 /* Leave page->index set: truncation relies upon it */
488 spin_unlock_irq(&mapping->tree_lock);
489 mem_cgroup_uncharge_cache_page(page);
490 page_cache_release(page);
492 radix_tree_preload_end();
494 mem_cgroup_uncharge_cache_page(page);
498 EXPORT_SYMBOL(add_to_page_cache_locked);
500 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
501 pgoff_t offset, gfp_t gfp_mask)
506 * Splice_read and readahead add shmem/tmpfs pages into the page cache
507 * before shmem_readpage has a chance to mark them as SwapBacked: they
508 * need to go on the anon lru below, and mem_cgroup_cache_charge
509 * (called in add_to_page_cache) needs to know where they're going too.
511 if (mapping_cap_swap_backed(mapping))
512 SetPageSwapBacked(page);
514 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
516 if (page_is_file_cache(page))
517 lru_cache_add_file(page);
519 lru_cache_add_anon(page);
523 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
526 struct page *__page_cache_alloc(gfp_t gfp)
531 if (cpuset_do_page_mem_spread()) {
533 n = cpuset_mem_spread_node();
534 page = alloc_pages_exact_node(n, gfp, 0);
538 return alloc_pages(gfp, 0);
540 EXPORT_SYMBOL(__page_cache_alloc);
544 * In order to wait for pages to become available there must be
545 * waitqueues associated with pages. By using a hash table of
546 * waitqueues where the bucket discipline is to maintain all
547 * waiters on the same queue and wake all when any of the pages
548 * become available, and for the woken contexts to check to be
549 * sure the appropriate page became available, this saves space
550 * at a cost of "thundering herd" phenomena during rare hash
553 static wait_queue_head_t *page_waitqueue(struct page *page)
555 const struct zone *zone = page_zone(page);
557 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
560 static inline void wake_up_page(struct page *page, int bit)
562 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
565 void wait_on_page_bit(struct page *page, int bit_nr)
567 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
569 if (test_bit(bit_nr, &page->flags))
570 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
571 TASK_UNINTERRUPTIBLE);
573 EXPORT_SYMBOL(wait_on_page_bit);
575 int wait_on_page_bit_killable(struct page *page, int bit_nr)
577 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
579 if (!test_bit(bit_nr, &page->flags))
582 return __wait_on_bit(page_waitqueue(page), &wait,
583 sleep_on_page_killable, TASK_KILLABLE);
587 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
588 * @page: Page defining the wait queue of interest
589 * @waiter: Waiter to add to the queue
591 * Add an arbitrary @waiter to the wait queue for the nominated @page.
593 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
595 wait_queue_head_t *q = page_waitqueue(page);
598 spin_lock_irqsave(&q->lock, flags);
599 __add_wait_queue(q, waiter);
600 spin_unlock_irqrestore(&q->lock, flags);
602 EXPORT_SYMBOL_GPL(add_page_wait_queue);
605 * unlock_page - unlock a locked page
608 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
609 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
610 * mechananism between PageLocked pages and PageWriteback pages is shared.
611 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
613 * The mb is necessary to enforce ordering between the clear_bit and the read
614 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
616 void unlock_page(struct page *page)
618 VM_BUG_ON(!PageLocked(page));
619 clear_bit_unlock(PG_locked, &page->flags);
620 smp_mb__after_clear_bit();
621 wake_up_page(page, PG_locked);
623 EXPORT_SYMBOL(unlock_page);
626 * end_page_writeback - end writeback against a page
629 void end_page_writeback(struct page *page)
631 if (TestClearPageReclaim(page))
632 rotate_reclaimable_page(page);
634 if (!test_clear_page_writeback(page))
637 smp_mb__after_clear_bit();
638 wake_up_page(page, PG_writeback);
640 EXPORT_SYMBOL(end_page_writeback);
643 * __lock_page - get a lock on the page, assuming we need to sleep to get it
644 * @page: the page to lock
646 void __lock_page(struct page *page)
648 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
650 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
651 TASK_UNINTERRUPTIBLE);
653 EXPORT_SYMBOL(__lock_page);
655 int __lock_page_killable(struct page *page)
657 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
659 return __wait_on_bit_lock(page_waitqueue(page), &wait,
660 sleep_on_page_killable, TASK_KILLABLE);
662 EXPORT_SYMBOL_GPL(__lock_page_killable);
664 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
667 if (flags & FAULT_FLAG_ALLOW_RETRY) {
669 * CAUTION! In this case, mmap_sem is not released
670 * even though return 0.
672 if (flags & FAULT_FLAG_RETRY_NOWAIT)
675 up_read(&mm->mmap_sem);
676 if (flags & FAULT_FLAG_KILLABLE)
677 wait_on_page_locked_killable(page);
679 wait_on_page_locked(page);
682 if (flags & FAULT_FLAG_KILLABLE) {
685 ret = __lock_page_killable(page);
687 up_read(&mm->mmap_sem);
697 * find_get_page - find and get a page reference
698 * @mapping: the address_space to search
699 * @offset: the page index
701 * Is there a pagecache struct page at the given (mapping, offset) tuple?
702 * If yes, increment its refcount and return it; if no, return NULL.
704 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
712 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
714 page = radix_tree_deref_slot(pagep);
717 if (radix_tree_exception(page)) {
718 if (radix_tree_exceptional_entry(page))
720 /* radix_tree_deref_retry(page) */
723 if (!page_cache_get_speculative(page))
727 * Has the page moved?
728 * This is part of the lockless pagecache protocol. See
729 * include/linux/pagemap.h for details.
731 if (unlikely(page != *pagep)) {
732 page_cache_release(page);
741 EXPORT_SYMBOL(find_get_page);
744 * find_lock_page - locate, pin and lock a pagecache page
745 * @mapping: the address_space to search
746 * @offset: the page index
748 * Locates the desired pagecache page, locks it, increments its reference
749 * count and returns its address.
751 * Returns zero if the page was not present. find_lock_page() may sleep.
753 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
758 page = find_get_page(mapping, offset);
759 if (page && !radix_tree_exception(page)) {
761 /* Has the page been truncated? */
762 if (unlikely(page->mapping != mapping)) {
764 page_cache_release(page);
767 VM_BUG_ON(page->index != offset);
771 EXPORT_SYMBOL(find_lock_page);
774 * find_or_create_page - locate or add a pagecache page
775 * @mapping: the page's address_space
776 * @index: the page's index into the mapping
777 * @gfp_mask: page allocation mode
779 * Locates a page in the pagecache. If the page is not present, a new page
780 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
781 * LRU list. The returned page is locked and has its reference count
784 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
787 * find_or_create_page() returns the desired page's address, or zero on
790 struct page *find_or_create_page(struct address_space *mapping,
791 pgoff_t index, gfp_t gfp_mask)
796 page = find_lock_page(mapping, index);
798 page = __page_cache_alloc(gfp_mask);
802 * We want a regular kernel memory (not highmem or DMA etc)
803 * allocation for the radix tree nodes, but we need to honour
804 * the context-specific requirements the caller has asked for.
805 * GFP_RECLAIM_MASK collects those requirements.
807 err = add_to_page_cache_lru(page, mapping, index,
808 (gfp_mask & GFP_RECLAIM_MASK));
810 page_cache_release(page);
818 EXPORT_SYMBOL(find_or_create_page);
821 * find_get_pages - gang pagecache lookup
822 * @mapping: The address_space to search
823 * @start: The starting page index
824 * @nr_pages: The maximum number of pages
825 * @pages: Where the resulting pages are placed
827 * find_get_pages() will search for and return a group of up to
828 * @nr_pages pages in the mapping. The pages are placed at @pages.
829 * find_get_pages() takes a reference against the returned pages.
831 * The search returns a group of mapping-contiguous pages with ascending
832 * indexes. There may be holes in the indices due to not-present pages.
834 * find_get_pages() returns the number of pages which were found.
836 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
837 unsigned int nr_pages, struct page **pages)
841 unsigned int nr_found;
845 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
846 (void ***)pages, NULL, start, nr_pages);
848 for (i = 0; i < nr_found; i++) {
851 page = radix_tree_deref_slot((void **)pages[i]);
855 if (radix_tree_exception(page)) {
856 if (radix_tree_exceptional_entry(page))
859 * radix_tree_deref_retry(page):
860 * can only trigger when entry at index 0 moves out of
861 * or back to root: none yet gotten, safe to restart.
867 if (!page_cache_get_speculative(page))
870 /* Has the page moved? */
871 if (unlikely(page != *((void **)pages[i]))) {
872 page_cache_release(page);
881 * If all entries were removed before we could secure them,
882 * try again, because callers stop trying once 0 is returned.
884 if (unlikely(!ret && nr_found))
891 * find_get_pages_contig - gang contiguous pagecache lookup
892 * @mapping: The address_space to search
893 * @index: The starting page index
894 * @nr_pages: The maximum number of pages
895 * @pages: Where the resulting pages are placed
897 * find_get_pages_contig() works exactly like find_get_pages(), except
898 * that the returned number of pages are guaranteed to be contiguous.
900 * find_get_pages_contig() returns the number of pages which were found.
902 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
903 unsigned int nr_pages, struct page **pages)
907 unsigned int nr_found;
911 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
912 (void ***)pages, NULL, index, nr_pages);
914 for (i = 0; i < nr_found; i++) {
917 page = radix_tree_deref_slot((void **)pages[i]);
921 if (radix_tree_exception(page)) {
922 if (radix_tree_exceptional_entry(page))
925 * radix_tree_deref_retry(page):
926 * can only trigger when entry at index 0 moves out of
927 * or back to root: none yet gotten, safe to restart.
932 if (!page_cache_get_speculative(page))
935 /* Has the page moved? */
936 if (unlikely(page != *((void **)pages[i]))) {
937 page_cache_release(page);
942 * must check mapping and index after taking the ref.
943 * otherwise we can get both false positives and false
944 * negatives, which is just confusing to the caller.
946 if (page->mapping == NULL || page->index != index) {
947 page_cache_release(page);
958 EXPORT_SYMBOL(find_get_pages_contig);
961 * find_get_pages_tag - find and return pages that match @tag
962 * @mapping: the address_space to search
963 * @index: the starting page index
964 * @tag: the tag index
965 * @nr_pages: the maximum number of pages
966 * @pages: where the resulting pages are placed
968 * Like find_get_pages, except we only return pages which are tagged with
969 * @tag. We update @index to index the next page for the traversal.
971 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
972 int tag, unsigned int nr_pages, struct page **pages)
976 unsigned int nr_found;
980 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
981 (void ***)pages, *index, nr_pages, tag);
983 for (i = 0; i < nr_found; i++) {
986 page = radix_tree_deref_slot((void **)pages[i]);
990 if (radix_tree_exception(page)) {
991 BUG_ON(radix_tree_exceptional_entry(page));
993 * radix_tree_deref_retry(page):
994 * can only trigger when entry at index 0 moves out of
995 * or back to root: none yet gotten, safe to restart.
1000 if (!page_cache_get_speculative(page))
1003 /* Has the page moved? */
1004 if (unlikely(page != *((void **)pages[i]))) {
1005 page_cache_release(page);
1014 * If all entries were removed before we could secure them,
1015 * try again, because callers stop trying once 0 is returned.
1017 if (unlikely(!ret && nr_found))
1022 *index = pages[ret - 1]->index + 1;
1026 EXPORT_SYMBOL(find_get_pages_tag);
1029 * grab_cache_page_nowait - returns locked page at given index in given cache
1030 * @mapping: target address_space
1031 * @index: the page index
1033 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1034 * This is intended for speculative data generators, where the data can
1035 * be regenerated if the page couldn't be grabbed. This routine should
1036 * be safe to call while holding the lock for another page.
1038 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1039 * and deadlock against the caller's locked page.
1042 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1044 struct page *page = find_get_page(mapping, index);
1047 if (trylock_page(page))
1049 page_cache_release(page);
1052 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1053 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1054 page_cache_release(page);
1059 EXPORT_SYMBOL(grab_cache_page_nowait);
1062 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1063 * a _large_ part of the i/o request. Imagine the worst scenario:
1065 * ---R__________________________________________B__________
1066 * ^ reading here ^ bad block(assume 4k)
1068 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1069 * => failing the whole request => read(R) => read(R+1) =>
1070 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1071 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1072 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1074 * It is going insane. Fix it by quickly scaling down the readahead size.
1076 static void shrink_readahead_size_eio(struct file *filp,
1077 struct file_ra_state *ra)
1083 * do_generic_file_read - generic file read routine
1084 * @filp: the file to read
1085 * @ppos: current file position
1086 * @desc: read_descriptor
1087 * @actor: read method
1089 * This is a generic file read routine, and uses the
1090 * mapping->a_ops->readpage() function for the actual low-level stuff.
1092 * This is really ugly. But the goto's actually try to clarify some
1093 * of the logic when it comes to error handling etc.
1095 static void do_generic_file_read(struct file *filp, loff_t *ppos,
1096 read_descriptor_t *desc, read_actor_t actor)
1098 struct address_space *mapping = filp->f_mapping;
1099 struct inode *inode = mapping->host;
1100 struct file_ra_state *ra = &filp->f_ra;
1104 unsigned long offset; /* offset into pagecache page */
1105 unsigned int prev_offset;
1108 index = *ppos >> PAGE_CACHE_SHIFT;
1109 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1110 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1111 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1112 offset = *ppos & ~PAGE_CACHE_MASK;
1118 unsigned long nr, ret;
1122 page = find_get_page(mapping, index);
1124 page_cache_sync_readahead(mapping,
1126 index, last_index - index);
1127 page = find_get_page(mapping, index);
1128 if (unlikely(page == NULL))
1129 goto no_cached_page;
1131 if (PageReadahead(page)) {
1132 page_cache_async_readahead(mapping,
1134 index, last_index - index);
1136 if (!PageUptodate(page)) {
1137 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1138 !mapping->a_ops->is_partially_uptodate)
1139 goto page_not_up_to_date;
1140 if (!trylock_page(page))
1141 goto page_not_up_to_date;
1142 /* Did it get truncated before we got the lock? */
1144 goto page_not_up_to_date_locked;
1145 if (!mapping->a_ops->is_partially_uptodate(page,
1147 goto page_not_up_to_date_locked;
1152 * i_size must be checked after we know the page is Uptodate.
1154 * Checking i_size after the check allows us to calculate
1155 * the correct value for "nr", which means the zero-filled
1156 * part of the page is not copied back to userspace (unless
1157 * another truncate extends the file - this is desired though).
1160 isize = i_size_read(inode);
1161 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1162 if (unlikely(!isize || index > end_index)) {
1163 page_cache_release(page);
1167 /* nr is the maximum number of bytes to copy from this page */
1168 nr = PAGE_CACHE_SIZE;
1169 if (index == end_index) {
1170 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1172 page_cache_release(page);
1178 /* If users can be writing to this page using arbitrary
1179 * virtual addresses, take care about potential aliasing
1180 * before reading the page on the kernel side.
1182 if (mapping_writably_mapped(mapping))
1183 flush_dcache_page(page);
1186 * When a sequential read accesses a page several times,
1187 * only mark it as accessed the first time.
1189 if (prev_index != index || offset != prev_offset)
1190 mark_page_accessed(page);
1194 * Ok, we have the page, and it's up-to-date, so
1195 * now we can copy it to user space...
1197 * The actor routine returns how many bytes were actually used..
1198 * NOTE! This may not be the same as how much of a user buffer
1199 * we filled up (we may be padding etc), so we can only update
1200 * "pos" here (the actor routine has to update the user buffer
1201 * pointers and the remaining count).
1203 ret = actor(desc, page, offset, nr);
1205 index += offset >> PAGE_CACHE_SHIFT;
1206 offset &= ~PAGE_CACHE_MASK;
1207 prev_offset = offset;
1209 page_cache_release(page);
1210 if (ret == nr && desc->count)
1214 page_not_up_to_date:
1215 /* Get exclusive access to the page ... */
1216 error = lock_page_killable(page);
1217 if (unlikely(error))
1218 goto readpage_error;
1220 page_not_up_to_date_locked:
1221 /* Did it get truncated before we got the lock? */
1222 if (!page->mapping) {
1224 page_cache_release(page);
1228 /* Did somebody else fill it already? */
1229 if (PageUptodate(page)) {
1236 * A previous I/O error may have been due to temporary
1237 * failures, eg. multipath errors.
1238 * PG_error will be set again if readpage fails.
1240 ClearPageError(page);
1241 /* Start the actual read. The read will unlock the page. */
1242 error = mapping->a_ops->readpage(filp, page);
1244 if (unlikely(error)) {
1245 if (error == AOP_TRUNCATED_PAGE) {
1246 page_cache_release(page);
1249 goto readpage_error;
1252 if (!PageUptodate(page)) {
1253 error = lock_page_killable(page);
1254 if (unlikely(error))
1255 goto readpage_error;
1256 if (!PageUptodate(page)) {
1257 if (page->mapping == NULL) {
1259 * invalidate_mapping_pages got it
1262 page_cache_release(page);
1266 shrink_readahead_size_eio(filp, ra);
1268 goto readpage_error;
1276 /* UHHUH! A synchronous read error occurred. Report it */
1277 desc->error = error;
1278 page_cache_release(page);
1283 * Ok, it wasn't cached, so we need to create a new
1286 page = page_cache_alloc_cold(mapping);
1288 desc->error = -ENOMEM;
1291 error = add_to_page_cache_lru(page, mapping,
1294 page_cache_release(page);
1295 if (error == -EEXIST)
1297 desc->error = error;
1304 ra->prev_pos = prev_index;
1305 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1306 ra->prev_pos |= prev_offset;
1308 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1309 file_accessed(filp);
1312 int file_read_actor(read_descriptor_t *desc, struct page *page,
1313 unsigned long offset, unsigned long size)
1316 unsigned long left, count = desc->count;
1322 * Faults on the destination of a read are common, so do it before
1325 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1326 kaddr = kmap_atomic(page, KM_USER0);
1327 left = __copy_to_user_inatomic(desc->arg.buf,
1328 kaddr + offset, size);
1329 kunmap_atomic(kaddr, KM_USER0);
1334 /* Do it the slow way */
1336 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1341 desc->error = -EFAULT;
1344 desc->count = count - size;
1345 desc->written += size;
1346 desc->arg.buf += size;
1351 * Performs necessary checks before doing a write
1352 * @iov: io vector request
1353 * @nr_segs: number of segments in the iovec
1354 * @count: number of bytes to write
1355 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1357 * Adjust number of segments and amount of bytes to write (nr_segs should be
1358 * properly initialized first). Returns appropriate error code that caller
1359 * should return or zero in case that write should be allowed.
1361 int generic_segment_checks(const struct iovec *iov,
1362 unsigned long *nr_segs, size_t *count, int access_flags)
1366 for (seg = 0; seg < *nr_segs; seg++) {
1367 const struct iovec *iv = &iov[seg];
1370 * If any segment has a negative length, or the cumulative
1371 * length ever wraps negative then return -EINVAL.
1374 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1376 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1381 cnt -= iv->iov_len; /* This segment is no good */
1387 EXPORT_SYMBOL(generic_segment_checks);
1390 * generic_file_aio_read - generic filesystem read routine
1391 * @iocb: kernel I/O control block
1392 * @iov: io vector request
1393 * @nr_segs: number of segments in the iovec
1394 * @pos: current file position
1396 * This is the "read()" routine for all filesystems
1397 * that can use the page cache directly.
1400 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1401 unsigned long nr_segs, loff_t pos)
1403 struct file *filp = iocb->ki_filp;
1405 unsigned long seg = 0;
1407 loff_t *ppos = &iocb->ki_pos;
1408 struct blk_plug plug;
1411 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1415 blk_start_plug(&plug);
1417 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1418 if (filp->f_flags & O_DIRECT) {
1420 struct address_space *mapping;
1421 struct inode *inode;
1423 mapping = filp->f_mapping;
1424 inode = mapping->host;
1426 goto out; /* skip atime */
1427 size = i_size_read(inode);
1429 retval = filemap_write_and_wait_range(mapping, pos,
1430 pos + iov_length(iov, nr_segs) - 1);
1432 retval = mapping->a_ops->direct_IO(READ, iocb,
1436 *ppos = pos + retval;
1441 * Btrfs can have a short DIO read if we encounter
1442 * compressed extents, so if there was an error, or if
1443 * we've already read everything we wanted to, or if
1444 * there was a short read because we hit EOF, go ahead
1445 * and return. Otherwise fallthrough to buffered io for
1446 * the rest of the read.
1448 if (retval < 0 || !count || *ppos >= size) {
1449 file_accessed(filp);
1456 for (seg = 0; seg < nr_segs; seg++) {
1457 read_descriptor_t desc;
1461 * If we did a short DIO read we need to skip the section of the
1462 * iov that we've already read data into.
1465 if (count > iov[seg].iov_len) {
1466 count -= iov[seg].iov_len;
1474 desc.arg.buf = iov[seg].iov_base + offset;
1475 desc.count = iov[seg].iov_len - offset;
1476 if (desc.count == 0)
1479 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1480 retval += desc.written;
1482 retval = retval ?: desc.error;
1489 blk_finish_plug(&plug);
1492 EXPORT_SYMBOL(generic_file_aio_read);
1495 do_readahead(struct address_space *mapping, struct file *filp,
1496 pgoff_t index, unsigned long nr)
1498 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1501 force_page_cache_readahead(mapping, filp, index, nr);
1505 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1513 if (file->f_mode & FMODE_READ) {
1514 struct address_space *mapping = file->f_mapping;
1515 pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1516 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1517 unsigned long len = end - start + 1;
1518 ret = do_readahead(mapping, file, start, len);
1524 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1525 asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1527 return SYSC_readahead((int) fd, offset, (size_t) count);
1529 SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1534 * page_cache_read - adds requested page to the page cache if not already there
1535 * @file: file to read
1536 * @offset: page index
1538 * This adds the requested page to the page cache if it isn't already there,
1539 * and schedules an I/O to read in its contents from disk.
1541 static int page_cache_read(struct file *file, pgoff_t offset)
1543 struct address_space *mapping = file->f_mapping;
1548 page = page_cache_alloc_cold(mapping);
1552 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1554 ret = mapping->a_ops->readpage(file, page);
1555 else if (ret == -EEXIST)
1556 ret = 0; /* losing race to add is OK */
1558 page_cache_release(page);
1560 } while (ret == AOP_TRUNCATED_PAGE);
1565 #define MMAP_LOTSAMISS (100)
1568 * Synchronous readahead happens when we don't even find
1569 * a page in the page cache at all.
1571 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1572 struct file_ra_state *ra,
1576 unsigned long ra_pages;
1577 struct address_space *mapping = file->f_mapping;
1579 /* If we don't want any read-ahead, don't bother */
1580 if (VM_RandomReadHint(vma))
1585 if (VM_SequentialReadHint(vma)) {
1586 page_cache_sync_readahead(mapping, ra, file, offset,
1591 /* Avoid banging the cache line if not needed */
1592 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1596 * Do we miss much more than hit in this file? If so,
1597 * stop bothering with read-ahead. It will only hurt.
1599 if (ra->mmap_miss > MMAP_LOTSAMISS)
1605 ra_pages = max_sane_readahead(ra->ra_pages);
1606 ra->start = max_t(long, 0, offset - ra_pages / 2);
1607 ra->size = ra_pages;
1608 ra->async_size = ra_pages / 4;
1609 ra_submit(ra, mapping, file);
1613 * Asynchronous readahead happens when we find the page and PG_readahead,
1614 * so we want to possibly extend the readahead further..
1616 static void do_async_mmap_readahead(struct vm_area_struct *vma,
1617 struct file_ra_state *ra,
1622 struct address_space *mapping = file->f_mapping;
1624 /* If we don't want any read-ahead, don't bother */
1625 if (VM_RandomReadHint(vma))
1627 if (ra->mmap_miss > 0)
1629 if (PageReadahead(page))
1630 page_cache_async_readahead(mapping, ra, file,
1631 page, offset, ra->ra_pages);
1635 * filemap_fault - read in file data for page fault handling
1636 * @vma: vma in which the fault was taken
1637 * @vmf: struct vm_fault containing details of the fault
1639 * filemap_fault() is invoked via the vma operations vector for a
1640 * mapped memory region to read in file data during a page fault.
1642 * The goto's are kind of ugly, but this streamlines the normal case of having
1643 * it in the page cache, and handles the special cases reasonably without
1644 * having a lot of duplicated code.
1646 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1649 struct file *file = vma->vm_file;
1650 struct address_space *mapping = file->f_mapping;
1651 struct file_ra_state *ra = &file->f_ra;
1652 struct inode *inode = mapping->host;
1653 pgoff_t offset = vmf->pgoff;
1658 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1660 return VM_FAULT_SIGBUS;
1663 * Do we have something in the page cache already?
1665 page = find_get_page(mapping, offset);
1668 * We found the page, so try async readahead before
1669 * waiting for the lock.
1671 do_async_mmap_readahead(vma, ra, file, page, offset);
1673 /* No page in the page cache at all */
1674 do_sync_mmap_readahead(vma, ra, file, offset);
1675 count_vm_event(PGMAJFAULT);
1676 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1677 ret = VM_FAULT_MAJOR;
1679 page = find_get_page(mapping, offset);
1681 goto no_cached_page;
1684 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1685 page_cache_release(page);
1686 return ret | VM_FAULT_RETRY;
1689 /* Did it get truncated? */
1690 if (unlikely(page->mapping != mapping)) {
1695 VM_BUG_ON(page->index != offset);
1698 * We have a locked page in the page cache, now we need to check
1699 * that it's up-to-date. If not, it is going to be due to an error.
1701 if (unlikely(!PageUptodate(page)))
1702 goto page_not_uptodate;
1705 * Found the page and have a reference on it.
1706 * We must recheck i_size under page lock.
1708 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1709 if (unlikely(offset >= size)) {
1711 page_cache_release(page);
1712 return VM_FAULT_SIGBUS;
1716 return ret | VM_FAULT_LOCKED;
1720 * We're only likely to ever get here if MADV_RANDOM is in
1723 error = page_cache_read(file, offset);
1726 * The page we want has now been added to the page cache.
1727 * In the unlikely event that someone removed it in the
1728 * meantime, we'll just come back here and read it again.
1734 * An error return from page_cache_read can result if the
1735 * system is low on memory, or a problem occurs while trying
1738 if (error == -ENOMEM)
1739 return VM_FAULT_OOM;
1740 return VM_FAULT_SIGBUS;
1744 * Umm, take care of errors if the page isn't up-to-date.
1745 * Try to re-read it _once_. We do this synchronously,
1746 * because there really aren't any performance issues here
1747 * and we need to check for errors.
1749 ClearPageError(page);
1750 error = mapping->a_ops->readpage(file, page);
1752 wait_on_page_locked(page);
1753 if (!PageUptodate(page))
1756 page_cache_release(page);
1758 if (!error || error == AOP_TRUNCATED_PAGE)
1761 /* Things didn't work out. Return zero to tell the mm layer so. */
1762 shrink_readahead_size_eio(file, ra);
1763 return VM_FAULT_SIGBUS;
1765 EXPORT_SYMBOL(filemap_fault);
1767 const struct vm_operations_struct generic_file_vm_ops = {
1768 .fault = filemap_fault,
1771 /* This is used for a general mmap of a disk file */
1773 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1775 struct address_space *mapping = file->f_mapping;
1777 if (!mapping->a_ops->readpage)
1779 file_accessed(file);
1780 vma->vm_ops = &generic_file_vm_ops;
1781 vma->vm_flags |= VM_CAN_NONLINEAR;
1786 * This is for filesystems which do not implement ->writepage.
1788 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1790 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1792 return generic_file_mmap(file, vma);
1795 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1799 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1803 #endif /* CONFIG_MMU */
1805 EXPORT_SYMBOL(generic_file_mmap);
1806 EXPORT_SYMBOL(generic_file_readonly_mmap);
1808 static struct page *__read_cache_page(struct address_space *mapping,
1810 int (*filler)(void *, struct page *),
1817 page = find_get_page(mapping, index);
1819 page = __page_cache_alloc(gfp | __GFP_COLD);
1821 return ERR_PTR(-ENOMEM);
1822 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1823 if (unlikely(err)) {
1824 page_cache_release(page);
1827 /* Presumably ENOMEM for radix tree node */
1828 return ERR_PTR(err);
1830 err = filler(data, page);
1832 page_cache_release(page);
1833 page = ERR_PTR(err);
1839 static struct page *do_read_cache_page(struct address_space *mapping,
1841 int (*filler)(void *, struct page *),
1850 page = __read_cache_page(mapping, index, filler, data, gfp);
1853 if (PageUptodate(page))
1857 if (!page->mapping) {
1859 page_cache_release(page);
1862 if (PageUptodate(page)) {
1866 err = filler(data, page);
1868 page_cache_release(page);
1869 return ERR_PTR(err);
1872 mark_page_accessed(page);
1877 * read_cache_page_async - read into page cache, fill it if needed
1878 * @mapping: the page's address_space
1879 * @index: the page index
1880 * @filler: function to perform the read
1881 * @data: first arg to filler(data, page) function, often left as NULL
1883 * Same as read_cache_page, but don't wait for page to become unlocked
1884 * after submitting it to the filler.
1886 * Read into the page cache. If a page already exists, and PageUptodate() is
1887 * not set, try to fill the page but don't wait for it to become unlocked.
1889 * If the page does not get brought uptodate, return -EIO.
1891 struct page *read_cache_page_async(struct address_space *mapping,
1893 int (*filler)(void *, struct page *),
1896 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1898 EXPORT_SYMBOL(read_cache_page_async);
1900 static struct page *wait_on_page_read(struct page *page)
1902 if (!IS_ERR(page)) {
1903 wait_on_page_locked(page);
1904 if (!PageUptodate(page)) {
1905 page_cache_release(page);
1906 page = ERR_PTR(-EIO);
1913 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1914 * @mapping: the page's address_space
1915 * @index: the page index
1916 * @gfp: the page allocator flags to use if allocating
1918 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1919 * any new page allocations done using the specified allocation flags. Note
1920 * that the Radix tree operations will still use GFP_KERNEL, so you can't
1921 * expect to do this atomically or anything like that - but you can pass in
1922 * other page requirements.
1924 * If the page does not get brought uptodate, return -EIO.
1926 struct page *read_cache_page_gfp(struct address_space *mapping,
1930 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1932 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1934 EXPORT_SYMBOL(read_cache_page_gfp);
1937 * read_cache_page - read into page cache, fill it if needed
1938 * @mapping: the page's address_space
1939 * @index: the page index
1940 * @filler: function to perform the read
1941 * @data: first arg to filler(data, page) function, often left as NULL
1943 * Read into the page cache. If a page already exists, and PageUptodate() is
1944 * not set, try to fill the page then wait for it to become unlocked.
1946 * If the page does not get brought uptodate, return -EIO.
1948 struct page *read_cache_page(struct address_space *mapping,
1950 int (*filler)(void *, struct page *),
1953 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1955 EXPORT_SYMBOL(read_cache_page);
1958 * The logic we want is
1960 * if suid or (sgid and xgrp)
1963 int should_remove_suid(struct dentry *dentry)
1965 mode_t mode = dentry->d_inode->i_mode;
1968 /* suid always must be killed */
1969 if (unlikely(mode & S_ISUID))
1970 kill = ATTR_KILL_SUID;
1973 * sgid without any exec bits is just a mandatory locking mark; leave
1974 * it alone. If some exec bits are set, it's a real sgid; kill it.
1976 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1977 kill |= ATTR_KILL_SGID;
1979 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1984 EXPORT_SYMBOL(should_remove_suid);
1986 static int __remove_suid(struct dentry *dentry, int kill)
1988 struct iattr newattrs;
1990 newattrs.ia_valid = ATTR_FORCE | kill;
1991 return notify_change(dentry, &newattrs);
1994 int file_remove_suid(struct file *file)
1996 struct dentry *dentry = file->f_path.dentry;
1997 struct inode *inode = dentry->d_inode;
2002 /* Fast path for nothing security related */
2003 if (IS_NOSEC(inode))
2006 killsuid = should_remove_suid(dentry);
2007 killpriv = security_inode_need_killpriv(dentry);
2012 error = security_inode_killpriv(dentry);
2013 if (!error && killsuid)
2014 error = __remove_suid(dentry, killsuid);
2015 if (!error && (inode->i_sb->s_flags & MS_NOSEC))
2016 inode->i_flags |= S_NOSEC;
2020 EXPORT_SYMBOL(file_remove_suid);
2022 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
2023 const struct iovec *iov, size_t base, size_t bytes)
2025 size_t copied = 0, left = 0;
2028 char __user *buf = iov->iov_base + base;
2029 int copy = min(bytes, iov->iov_len - base);
2032 left = __copy_from_user_inatomic(vaddr, buf, copy);
2041 return copied - left;
2045 * Copy as much as we can into the page and return the number of bytes which
2046 * were successfully copied. If a fault is encountered then return the number of
2047 * bytes which were copied.
2049 size_t iov_iter_copy_from_user_atomic(struct page *page,
2050 struct iov_iter *i, unsigned long offset, size_t bytes)
2055 BUG_ON(!in_atomic());
2056 kaddr = kmap_atomic(page, KM_USER0);
2057 if (likely(i->nr_segs == 1)) {
2059 char __user *buf = i->iov->iov_base + i->iov_offset;
2060 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
2061 copied = bytes - left;
2063 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2064 i->iov, i->iov_offset, bytes);
2066 kunmap_atomic(kaddr, KM_USER0);
2070 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
2073 * This has the same sideeffects and return value as
2074 * iov_iter_copy_from_user_atomic().
2075 * The difference is that it attempts to resolve faults.
2076 * Page must not be locked.
2078 size_t iov_iter_copy_from_user(struct page *page,
2079 struct iov_iter *i, unsigned long offset, size_t bytes)
2085 if (likely(i->nr_segs == 1)) {
2087 char __user *buf = i->iov->iov_base + i->iov_offset;
2088 left = __copy_from_user(kaddr + offset, buf, bytes);
2089 copied = bytes - left;
2091 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2092 i->iov, i->iov_offset, bytes);
2097 EXPORT_SYMBOL(iov_iter_copy_from_user);
2099 void iov_iter_advance(struct iov_iter *i, size_t bytes)
2101 BUG_ON(i->count < bytes);
2103 if (likely(i->nr_segs == 1)) {
2104 i->iov_offset += bytes;
2107 const struct iovec *iov = i->iov;
2108 size_t base = i->iov_offset;
2111 * The !iov->iov_len check ensures we skip over unlikely
2112 * zero-length segments (without overruning the iovec).
2114 while (bytes || unlikely(i->count && !iov->iov_len)) {
2117 copy = min(bytes, iov->iov_len - base);
2118 BUG_ON(!i->count || i->count < copy);
2122 if (iov->iov_len == base) {
2128 i->iov_offset = base;
2131 EXPORT_SYMBOL(iov_iter_advance);
2134 * Fault in the first iovec of the given iov_iter, to a maximum length
2135 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2136 * accessed (ie. because it is an invalid address).
2138 * writev-intensive code may want this to prefault several iovecs -- that
2139 * would be possible (callers must not rely on the fact that _only_ the
2140 * first iovec will be faulted with the current implementation).
2142 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2144 char __user *buf = i->iov->iov_base + i->iov_offset;
2145 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2146 return fault_in_pages_readable(buf, bytes);
2148 EXPORT_SYMBOL(iov_iter_fault_in_readable);
2151 * Return the count of just the current iov_iter segment.
2153 size_t iov_iter_single_seg_count(struct iov_iter *i)
2155 const struct iovec *iov = i->iov;
2156 if (i->nr_segs == 1)
2159 return min(i->count, iov->iov_len - i->iov_offset);
2161 EXPORT_SYMBOL(iov_iter_single_seg_count);
2164 * Performs necessary checks before doing a write
2166 * Can adjust writing position or amount of bytes to write.
2167 * Returns appropriate error code that caller should return or
2168 * zero in case that write should be allowed.
2170 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2172 struct inode *inode = file->f_mapping->host;
2173 unsigned long limit = rlimit(RLIMIT_FSIZE);
2175 if (unlikely(*pos < 0))
2179 /* FIXME: this is for backwards compatibility with 2.4 */
2180 if (file->f_flags & O_APPEND)
2181 *pos = i_size_read(inode);
2183 if (limit != RLIM_INFINITY) {
2184 if (*pos >= limit) {
2185 send_sig(SIGXFSZ, current, 0);
2188 if (*count > limit - (typeof(limit))*pos) {
2189 *count = limit - (typeof(limit))*pos;
2197 if (unlikely(*pos + *count > MAX_NON_LFS &&
2198 !(file->f_flags & O_LARGEFILE))) {
2199 if (*pos >= MAX_NON_LFS) {
2202 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2203 *count = MAX_NON_LFS - (unsigned long)*pos;
2208 * Are we about to exceed the fs block limit ?
2210 * If we have written data it becomes a short write. If we have
2211 * exceeded without writing data we send a signal and return EFBIG.
2212 * Linus frestrict idea will clean these up nicely..
2214 if (likely(!isblk)) {
2215 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2216 if (*count || *pos > inode->i_sb->s_maxbytes) {
2219 /* zero-length writes at ->s_maxbytes are OK */
2222 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2223 *count = inode->i_sb->s_maxbytes - *pos;
2227 if (bdev_read_only(I_BDEV(inode)))
2229 isize = i_size_read(inode);
2230 if (*pos >= isize) {
2231 if (*count || *pos > isize)
2235 if (*pos + *count > isize)
2236 *count = isize - *pos;
2243 EXPORT_SYMBOL(generic_write_checks);
2245 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2246 loff_t pos, unsigned len, unsigned flags,
2247 struct page **pagep, void **fsdata)
2249 const struct address_space_operations *aops = mapping->a_ops;
2251 return aops->write_begin(file, mapping, pos, len, flags,
2254 EXPORT_SYMBOL(pagecache_write_begin);
2256 int pagecache_write_end(struct file *file, struct address_space *mapping,
2257 loff_t pos, unsigned len, unsigned copied,
2258 struct page *page, void *fsdata)
2260 const struct address_space_operations *aops = mapping->a_ops;
2262 mark_page_accessed(page);
2263 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2265 EXPORT_SYMBOL(pagecache_write_end);
2268 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2269 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2270 size_t count, size_t ocount)
2272 struct file *file = iocb->ki_filp;
2273 struct address_space *mapping = file->f_mapping;
2274 struct inode *inode = mapping->host;
2279 if (count != ocount)
2280 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2282 write_len = iov_length(iov, *nr_segs);
2283 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2285 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2290 * After a write we want buffered reads to be sure to go to disk to get
2291 * the new data. We invalidate clean cached page from the region we're
2292 * about to write. We do this *before* the write so that we can return
2293 * without clobbering -EIOCBQUEUED from ->direct_IO().
2295 if (mapping->nrpages) {
2296 written = invalidate_inode_pages2_range(mapping,
2297 pos >> PAGE_CACHE_SHIFT, end);
2299 * If a page can not be invalidated, return 0 to fall back
2300 * to buffered write.
2303 if (written == -EBUSY)
2309 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2312 * Finally, try again to invalidate clean pages which might have been
2313 * cached by non-direct readahead, or faulted in by get_user_pages()
2314 * if the source of the write was an mmap'ed region of the file
2315 * we're writing. Either one is a pretty crazy thing to do,
2316 * so we don't support it 100%. If this invalidation
2317 * fails, tough, the write still worked...
2319 if (mapping->nrpages) {
2320 invalidate_inode_pages2_range(mapping,
2321 pos >> PAGE_CACHE_SHIFT, end);
2326 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2327 i_size_write(inode, pos);
2328 mark_inode_dirty(inode);
2335 EXPORT_SYMBOL(generic_file_direct_write);
2338 * Find or create a page at the given pagecache position. Return the locked
2339 * page. This function is specifically for buffered writes.
2341 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2342 pgoff_t index, unsigned flags)
2346 gfp_t gfp_notmask = 0;
2347 if (flags & AOP_FLAG_NOFS)
2348 gfp_notmask = __GFP_FS;
2350 page = find_lock_page(mapping, index);
2354 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2357 status = add_to_page_cache_lru(page, mapping, index,
2358 GFP_KERNEL & ~gfp_notmask);
2359 if (unlikely(status)) {
2360 page_cache_release(page);
2361 if (status == -EEXIST)
2366 wait_on_page_writeback(page);
2369 EXPORT_SYMBOL(grab_cache_page_write_begin);
2371 static ssize_t generic_perform_write(struct file *file,
2372 struct iov_iter *i, loff_t pos)
2374 struct address_space *mapping = file->f_mapping;
2375 const struct address_space_operations *a_ops = mapping->a_ops;
2377 ssize_t written = 0;
2378 unsigned int flags = 0;
2381 * Copies from kernel address space cannot fail (NFSD is a big user).
2383 if (segment_eq(get_fs(), KERNEL_DS))
2384 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2388 unsigned long offset; /* Offset into pagecache page */
2389 unsigned long bytes; /* Bytes to write to page */
2390 size_t copied; /* Bytes copied from user */
2393 offset = (pos & (PAGE_CACHE_SIZE - 1));
2394 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2400 * Bring in the user page that we will copy from _first_.
2401 * Otherwise there's a nasty deadlock on copying from the
2402 * same page as we're writing to, without it being marked
2405 * Not only is this an optimisation, but it is also required
2406 * to check that the address is actually valid, when atomic
2407 * usercopies are used, below.
2409 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2414 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2416 if (unlikely(status))
2419 if (mapping_writably_mapped(mapping))
2420 flush_dcache_page(page);
2422 pagefault_disable();
2423 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2425 flush_dcache_page(page);
2427 mark_page_accessed(page);
2428 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2430 if (unlikely(status < 0))
2436 iov_iter_advance(i, copied);
2437 if (unlikely(copied == 0)) {
2439 * If we were unable to copy any data at all, we must
2440 * fall back to a single segment length write.
2442 * If we didn't fallback here, we could livelock
2443 * because not all segments in the iov can be copied at
2444 * once without a pagefault.
2446 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2447 iov_iter_single_seg_count(i));
2453 balance_dirty_pages_ratelimited(mapping);
2455 } while (iov_iter_count(i));
2457 return written ? written : status;
2461 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2462 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2463 size_t count, ssize_t written)
2465 struct file *file = iocb->ki_filp;
2469 iov_iter_init(&i, iov, nr_segs, count, written);
2470 status = generic_perform_write(file, &i, pos);
2472 if (likely(status >= 0)) {
2474 *ppos = pos + status;
2477 return written ? written : status;
2479 EXPORT_SYMBOL(generic_file_buffered_write);
2482 * __generic_file_aio_write - write data to a file
2483 * @iocb: IO state structure (file, offset, etc.)
2484 * @iov: vector with data to write
2485 * @nr_segs: number of segments in the vector
2486 * @ppos: position where to write
2488 * This function does all the work needed for actually writing data to a
2489 * file. It does all basic checks, removes SUID from the file, updates
2490 * modification times and calls proper subroutines depending on whether we
2491 * do direct IO or a standard buffered write.
2493 * It expects i_mutex to be grabbed unless we work on a block device or similar
2494 * object which does not need locking at all.
2496 * This function does *not* take care of syncing data in case of O_SYNC write.
2497 * A caller has to handle it. This is mainly due to the fact that we want to
2498 * avoid syncing under i_mutex.
2500 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2501 unsigned long nr_segs, loff_t *ppos)
2503 struct file *file = iocb->ki_filp;
2504 struct address_space * mapping = file->f_mapping;
2505 size_t ocount; /* original count */
2506 size_t count; /* after file limit checks */
2507 struct inode *inode = mapping->host;
2513 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2520 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2522 /* We can write back this queue in page reclaim */
2523 current->backing_dev_info = mapping->backing_dev_info;
2526 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2533 err = file_remove_suid(file);
2537 file_update_time(file);
2539 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2540 if (unlikely(file->f_flags & O_DIRECT)) {
2542 ssize_t written_buffered;
2544 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2545 ppos, count, ocount);
2546 if (written < 0 || written == count)
2549 * direct-io write to a hole: fall through to buffered I/O
2550 * for completing the rest of the request.
2554 written_buffered = generic_file_buffered_write(iocb, iov,
2555 nr_segs, pos, ppos, count,
2558 * If generic_file_buffered_write() retuned a synchronous error
2559 * then we want to return the number of bytes which were
2560 * direct-written, or the error code if that was zero. Note
2561 * that this differs from normal direct-io semantics, which
2562 * will return -EFOO even if some bytes were written.
2564 if (written_buffered < 0) {
2565 err = written_buffered;
2570 * We need to ensure that the page cache pages are written to
2571 * disk and invalidated to preserve the expected O_DIRECT
2574 endbyte = pos + written_buffered - written - 1;
2575 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2577 written = written_buffered;
2578 invalidate_mapping_pages(mapping,
2579 pos >> PAGE_CACHE_SHIFT,
2580 endbyte >> PAGE_CACHE_SHIFT);
2583 * We don't know how much we wrote, so just return
2584 * the number of bytes which were direct-written
2588 written = generic_file_buffered_write(iocb, iov, nr_segs,
2589 pos, ppos, count, written);
2592 current->backing_dev_info = NULL;
2593 return written ? written : err;
2595 EXPORT_SYMBOL(__generic_file_aio_write);
2598 * generic_file_aio_write - write data to a file
2599 * @iocb: IO state structure
2600 * @iov: vector with data to write
2601 * @nr_segs: number of segments in the vector
2602 * @pos: position in file where to write
2604 * This is a wrapper around __generic_file_aio_write() to be used by most
2605 * filesystems. It takes care of syncing the file in case of O_SYNC file
2606 * and acquires i_mutex as needed.
2608 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2609 unsigned long nr_segs, loff_t pos)
2611 struct file *file = iocb->ki_filp;
2612 struct inode *inode = file->f_mapping->host;
2613 struct blk_plug plug;
2616 BUG_ON(iocb->ki_pos != pos);
2618 mutex_lock(&inode->i_mutex);
2619 blk_start_plug(&plug);
2620 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2621 mutex_unlock(&inode->i_mutex);
2623 if (ret > 0 || ret == -EIOCBQUEUED) {
2626 err = generic_write_sync(file, pos, ret);
2627 if (err < 0 && ret > 0)
2630 blk_finish_plug(&plug);
2633 EXPORT_SYMBOL(generic_file_aio_write);
2636 * try_to_release_page() - release old fs-specific metadata on a page
2638 * @page: the page which the kernel is trying to free
2639 * @gfp_mask: memory allocation flags (and I/O mode)
2641 * The address_space is to try to release any data against the page
2642 * (presumably at page->private). If the release was successful, return `1'.
2643 * Otherwise return zero.
2645 * This may also be called if PG_fscache is set on a page, indicating that the
2646 * page is known to the local caching routines.
2648 * The @gfp_mask argument specifies whether I/O may be performed to release
2649 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2652 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2654 struct address_space * const mapping = page->mapping;
2656 BUG_ON(!PageLocked(page));
2657 if (PageWriteback(page))
2660 if (mapping && mapping->a_ops->releasepage)
2661 return mapping->a_ops->releasepage(page, gfp_mask);
2662 return try_to_free_buffers(page);
2665 EXPORT_SYMBOL(try_to_release_page);