4 * Copyright (C) 1994-1999 Linus Torvalds
8 * This file handles the generic file mmap semantics used by
9 * most "normal" filesystems (but you don't /have/ to use this:
10 * the NFS filesystem used to do this differently, for example)
12 #include <linux/module.h>
13 #include <linux/compiler.h>
15 #include <linux/uaccess.h>
16 #include <linux/aio.h>
17 #include <linux/capability.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/gfp.h>
21 #include <linux/swap.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/file.h>
25 #include <linux/uio.h>
26 #include <linux/hash.h>
27 #include <linux/writeback.h>
28 #include <linux/backing-dev.h>
29 #include <linux/pagevec.h>
30 #include <linux/blkdev.h>
31 #include <linux/security.h>
32 #include <linux/syscalls.h>
33 #include <linux/cpuset.h>
34 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
35 #include <linux/memcontrol.h>
36 #include <linux/mm_inline.h> /* for page_is_file_cache() */
40 * FIXME: remove all knowledge of the buffer layer from the core VM
42 #include <linux/buffer_head.h> /* for try_to_free_buffers */
47 * Shared mappings implemented 30.11.1994. It's not fully working yet,
50 * Shared mappings now work. 15.8.1995 Bruno.
52 * finished 'unifying' the page and buffer cache and SMP-threaded the
53 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
55 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
61 * ->i_mmap_lock (truncate_pagecache)
62 * ->private_lock (__free_pte->__set_page_dirty_buffers)
63 * ->swap_lock (exclusive_swap_page, others)
64 * ->mapping->tree_lock
67 * ->i_mmap_lock (truncate->unmap_mapping_range)
71 * ->page_table_lock or pte_lock (various, mainly in memory.c)
72 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
75 * ->lock_page (access_process_vm)
77 * ->i_mutex (generic_file_buffered_write)
78 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
81 * ->i_alloc_sem (various)
84 * ->sb_lock (fs/fs-writeback.c)
85 * ->mapping->tree_lock (__sync_single_inode)
88 * ->anon_vma.lock (vma_adjust)
91 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
93 * ->page_table_lock or pte_lock
94 * ->swap_lock (try_to_unmap_one)
95 * ->private_lock (try_to_unmap_one)
96 * ->tree_lock (try_to_unmap_one)
97 * ->zone.lru_lock (follow_page->mark_page_accessed)
98 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
99 * ->private_lock (page_remove_rmap->set_page_dirty)
100 * ->tree_lock (page_remove_rmap->set_page_dirty)
101 * ->inode_lock (page_remove_rmap->set_page_dirty)
102 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
103 * ->inode_lock (zap_pte_range->set_page_dirty)
104 * ->inode->i_lock (zap_pte_range->set_page_dirty)
105 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
107 * (code doesn't rely on that order, so you could switch it around)
108 * ->tasklist_lock (memory_failure, collect_procs_ao)
113 * Delete a page from the page cache and free it. Caller has to make
114 * sure the page is locked and that nobody else uses it - or that usage
115 * is safe. The caller must hold the mapping's tree_lock.
117 void __delete_from_page_cache(struct page *page)
119 struct address_space *mapping = page->mapping;
121 radix_tree_delete(&mapping->page_tree, page->index);
122 page->mapping = NULL;
124 __dec_zone_page_state(page, NR_FILE_PAGES);
125 if (PageSwapBacked(page))
126 __dec_zone_page_state(page, NR_SHMEM);
127 BUG_ON(page_mapped(page));
130 * Some filesystems seem to re-dirty the page even after
131 * the VM has canceled the dirty bit (eg ext3 journaling).
133 * Fix it up by doing a final dirty accounting check after
134 * having removed the page entirely.
136 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
137 dec_zone_page_state(page, NR_FILE_DIRTY);
138 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
143 * delete_from_page_cache - delete page from page cache
144 * @page: the page which the kernel is trying to remove from page cache
146 * This must be called only on pages that have been verified to be in the page
147 * cache and locked. It will never put the page into the free list, the caller
148 * has a reference on the page.
150 void delete_from_page_cache(struct page *page)
152 struct address_space *mapping = page->mapping;
153 void (*freepage)(struct page *);
155 BUG_ON(!PageLocked(page));
157 freepage = mapping->a_ops->freepage;
158 spin_lock_irq(&mapping->tree_lock);
159 __delete_from_page_cache(page);
160 spin_unlock_irq(&mapping->tree_lock);
161 mem_cgroup_uncharge_cache_page(page);
165 page_cache_release(page);
167 EXPORT_SYMBOL(delete_from_page_cache);
169 static int sync_page(void *word)
171 struct address_space *mapping;
174 page = container_of((unsigned long *)word, struct page, flags);
177 * page_mapping() is being called without PG_locked held.
178 * Some knowledge of the state and use of the page is used to
179 * reduce the requirements down to a memory barrier.
180 * The danger here is of a stale page_mapping() return value
181 * indicating a struct address_space different from the one it's
182 * associated with when it is associated with one.
183 * After smp_mb(), it's either the correct page_mapping() for
184 * the page, or an old page_mapping() and the page's own
185 * page_mapping() has gone NULL.
186 * The ->sync_page() address_space operation must tolerate
187 * page_mapping() going NULL. By an amazing coincidence,
188 * this comes about because none of the users of the page
189 * in the ->sync_page() methods make essential use of the
190 * page_mapping(), merely passing the page down to the backing
191 * device's unplug functions when it's non-NULL, which in turn
192 * ignore it for all cases but swap, where only page_private(page) is
193 * of interest. When page_mapping() does go NULL, the entire
194 * call stack gracefully ignores the page and returns.
198 mapping = page_mapping(page);
199 if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
200 mapping->a_ops->sync_page(page);
205 static int sync_page_killable(void *word)
208 return fatal_signal_pending(current) ? -EINTR : 0;
212 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
213 * @mapping: address space structure to write
214 * @start: offset in bytes where the range starts
215 * @end: offset in bytes where the range ends (inclusive)
216 * @sync_mode: enable synchronous operation
218 * Start writeback against all of a mapping's dirty pages that lie
219 * within the byte offsets <start, end> inclusive.
221 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
222 * opposed to a regular memory cleansing writeback. The difference between
223 * these two operations is that if a dirty page/buffer is encountered, it must
224 * be waited upon, and not just skipped over.
226 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
227 loff_t end, int sync_mode)
230 struct writeback_control wbc = {
231 .sync_mode = sync_mode,
232 .nr_to_write = LONG_MAX,
233 .range_start = start,
237 if (!mapping_cap_writeback_dirty(mapping))
240 ret = do_writepages(mapping, &wbc);
244 static inline int __filemap_fdatawrite(struct address_space *mapping,
247 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
250 int filemap_fdatawrite(struct address_space *mapping)
252 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
254 EXPORT_SYMBOL(filemap_fdatawrite);
256 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
259 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
261 EXPORT_SYMBOL(filemap_fdatawrite_range);
264 * filemap_flush - mostly a non-blocking flush
265 * @mapping: target address_space
267 * This is a mostly non-blocking flush. Not suitable for data-integrity
268 * purposes - I/O may not be started against all dirty pages.
270 int filemap_flush(struct address_space *mapping)
272 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
274 EXPORT_SYMBOL(filemap_flush);
277 * filemap_fdatawait_range - wait for writeback to complete
278 * @mapping: address space structure to wait for
279 * @start_byte: offset in bytes where the range starts
280 * @end_byte: offset in bytes where the range ends (inclusive)
282 * Walk the list of under-writeback pages of the given address space
283 * in the given range and wait for all of them.
285 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
288 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
289 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
294 if (end_byte < start_byte)
297 pagevec_init(&pvec, 0);
298 while ((index <= end) &&
299 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
300 PAGECACHE_TAG_WRITEBACK,
301 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
304 for (i = 0; i < nr_pages; i++) {
305 struct page *page = pvec.pages[i];
307 /* until radix tree lookup accepts end_index */
308 if (page->index > end)
311 wait_on_page_writeback(page);
312 if (TestClearPageError(page))
315 pagevec_release(&pvec);
319 /* Check for outstanding write errors */
320 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
322 if (test_and_clear_bit(AS_EIO, &mapping->flags))
327 EXPORT_SYMBOL(filemap_fdatawait_range);
330 * filemap_fdatawait - wait for all under-writeback pages to complete
331 * @mapping: address space structure to wait for
333 * Walk the list of under-writeback pages of the given address space
334 * and wait for all of them.
336 int filemap_fdatawait(struct address_space *mapping)
338 loff_t i_size = i_size_read(mapping->host);
343 return filemap_fdatawait_range(mapping, 0, i_size - 1);
345 EXPORT_SYMBOL(filemap_fdatawait);
347 int filemap_write_and_wait(struct address_space *mapping)
351 if (mapping->nrpages) {
352 err = filemap_fdatawrite(mapping);
354 * Even if the above returned error, the pages may be
355 * written partially (e.g. -ENOSPC), so we wait for it.
356 * But the -EIO is special case, it may indicate the worst
357 * thing (e.g. bug) happened, so we avoid waiting for it.
360 int err2 = filemap_fdatawait(mapping);
367 EXPORT_SYMBOL(filemap_write_and_wait);
370 * filemap_write_and_wait_range - write out & wait on a file range
371 * @mapping: the address_space for the pages
372 * @lstart: offset in bytes where the range starts
373 * @lend: offset in bytes where the range ends (inclusive)
375 * Write out and wait upon file offsets lstart->lend, inclusive.
377 * Note that `lend' is inclusive (describes the last byte to be written) so
378 * that this function can be used to write to the very end-of-file (end = -1).
380 int filemap_write_and_wait_range(struct address_space *mapping,
381 loff_t lstart, loff_t lend)
385 if (mapping->nrpages) {
386 err = __filemap_fdatawrite_range(mapping, lstart, lend,
388 /* See comment of filemap_write_and_wait() */
390 int err2 = filemap_fdatawait_range(mapping,
398 EXPORT_SYMBOL(filemap_write_and_wait_range);
401 * replace_page_cache_page - replace a pagecache page with a new one
402 * @old: page to be replaced
403 * @new: page to replace with
404 * @gfp_mask: allocation mode
406 * This function replaces a page in the pagecache with a new one. On
407 * success it acquires the pagecache reference for the new page and
408 * drops it for the old page. Both the old and new pages must be
409 * locked. This function does not add the new page to the LRU, the
410 * caller must do that.
412 * The remove + add is atomic. The only way this function can fail is
413 * memory allocation failure.
415 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
418 struct mem_cgroup *memcg = NULL;
420 VM_BUG_ON(!PageLocked(old));
421 VM_BUG_ON(!PageLocked(new));
422 VM_BUG_ON(new->mapping);
425 * This is not page migration, but prepare_migration and
426 * end_migration does enough work for charge replacement.
428 * In the longer term we probably want a specialized function
429 * for moving the charge from old to new in a more efficient
432 error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
436 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
438 struct address_space *mapping = old->mapping;
439 void (*freepage)(struct page *);
441 pgoff_t offset = old->index;
442 freepage = mapping->a_ops->freepage;
445 new->mapping = mapping;
448 spin_lock_irq(&mapping->tree_lock);
449 __delete_from_page_cache(old);
450 error = radix_tree_insert(&mapping->page_tree, offset, new);
453 __inc_zone_page_state(new, NR_FILE_PAGES);
454 if (PageSwapBacked(new))
455 __inc_zone_page_state(new, NR_SHMEM);
456 spin_unlock_irq(&mapping->tree_lock);
457 radix_tree_preload_end();
460 page_cache_release(old);
461 mem_cgroup_end_migration(memcg, old, new, true);
463 mem_cgroup_end_migration(memcg, old, new, false);
468 EXPORT_SYMBOL_GPL(replace_page_cache_page);
471 * add_to_page_cache_locked - add a locked page to the pagecache
473 * @mapping: the page's address_space
474 * @offset: page index
475 * @gfp_mask: page allocation mode
477 * This function is used to add a page to the pagecache. It must be locked.
478 * This function does not add the page to the LRU. The caller must do that.
480 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
481 pgoff_t offset, gfp_t gfp_mask)
485 VM_BUG_ON(!PageLocked(page));
487 error = mem_cgroup_cache_charge(page, current->mm,
488 gfp_mask & GFP_RECLAIM_MASK);
492 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
494 page_cache_get(page);
495 page->mapping = mapping;
496 page->index = offset;
498 spin_lock_irq(&mapping->tree_lock);
499 error = radix_tree_insert(&mapping->page_tree, offset, page);
500 if (likely(!error)) {
502 __inc_zone_page_state(page, NR_FILE_PAGES);
503 if (PageSwapBacked(page))
504 __inc_zone_page_state(page, NR_SHMEM);
505 spin_unlock_irq(&mapping->tree_lock);
507 page->mapping = NULL;
508 spin_unlock_irq(&mapping->tree_lock);
509 mem_cgroup_uncharge_cache_page(page);
510 page_cache_release(page);
512 radix_tree_preload_end();
514 mem_cgroup_uncharge_cache_page(page);
518 EXPORT_SYMBOL(add_to_page_cache_locked);
520 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
521 pgoff_t offset, gfp_t gfp_mask)
526 * Splice_read and readahead add shmem/tmpfs pages into the page cache
527 * before shmem_readpage has a chance to mark them as SwapBacked: they
528 * need to go on the anon lru below, and mem_cgroup_cache_charge
529 * (called in add_to_page_cache) needs to know where they're going too.
531 if (mapping_cap_swap_backed(mapping))
532 SetPageSwapBacked(page);
534 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
536 if (page_is_file_cache(page))
537 lru_cache_add_file(page);
539 lru_cache_add_anon(page);
543 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
546 struct page *__page_cache_alloc(gfp_t gfp)
551 if (cpuset_do_page_mem_spread()) {
553 n = cpuset_mem_spread_node();
554 page = alloc_pages_exact_node(n, gfp, 0);
558 return alloc_pages(gfp, 0);
560 EXPORT_SYMBOL(__page_cache_alloc);
563 static int __sleep_on_page_lock(void *word)
570 * In order to wait for pages to become available there must be
571 * waitqueues associated with pages. By using a hash table of
572 * waitqueues where the bucket discipline is to maintain all
573 * waiters on the same queue and wake all when any of the pages
574 * become available, and for the woken contexts to check to be
575 * sure the appropriate page became available, this saves space
576 * at a cost of "thundering herd" phenomena during rare hash
579 static wait_queue_head_t *page_waitqueue(struct page *page)
581 const struct zone *zone = page_zone(page);
583 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
586 static inline void wake_up_page(struct page *page, int bit)
588 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
591 void wait_on_page_bit(struct page *page, int bit_nr)
593 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
595 if (test_bit(bit_nr, &page->flags))
596 __wait_on_bit(page_waitqueue(page), &wait, sync_page,
597 TASK_UNINTERRUPTIBLE);
599 EXPORT_SYMBOL(wait_on_page_bit);
602 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
603 * @page: Page defining the wait queue of interest
604 * @waiter: Waiter to add to the queue
606 * Add an arbitrary @waiter to the wait queue for the nominated @page.
608 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
610 wait_queue_head_t *q = page_waitqueue(page);
613 spin_lock_irqsave(&q->lock, flags);
614 __add_wait_queue(q, waiter);
615 spin_unlock_irqrestore(&q->lock, flags);
617 EXPORT_SYMBOL_GPL(add_page_wait_queue);
620 * unlock_page - unlock a locked page
623 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
624 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
625 * mechananism between PageLocked pages and PageWriteback pages is shared.
626 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
628 * The mb is necessary to enforce ordering between the clear_bit and the read
629 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
631 void unlock_page(struct page *page)
633 VM_BUG_ON(!PageLocked(page));
634 clear_bit_unlock(PG_locked, &page->flags);
635 smp_mb__after_clear_bit();
636 wake_up_page(page, PG_locked);
638 EXPORT_SYMBOL(unlock_page);
641 * end_page_writeback - end writeback against a page
644 void end_page_writeback(struct page *page)
646 if (TestClearPageReclaim(page))
647 rotate_reclaimable_page(page);
649 if (!test_clear_page_writeback(page))
652 smp_mb__after_clear_bit();
653 wake_up_page(page, PG_writeback);
655 EXPORT_SYMBOL(end_page_writeback);
658 * __lock_page - get a lock on the page, assuming we need to sleep to get it
659 * @page: the page to lock
661 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some
662 * random driver's requestfn sets TASK_RUNNING, we could busywait. However
663 * chances are that on the second loop, the block layer's plug list is empty,
664 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
666 void __lock_page(struct page *page)
668 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
670 __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
671 TASK_UNINTERRUPTIBLE);
673 EXPORT_SYMBOL(__lock_page);
675 int __lock_page_killable(struct page *page)
677 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
679 return __wait_on_bit_lock(page_waitqueue(page), &wait,
680 sync_page_killable, TASK_KILLABLE);
682 EXPORT_SYMBOL_GPL(__lock_page_killable);
685 * __lock_page_nosync - get a lock on the page, without calling sync_page()
686 * @page: the page to lock
688 * Variant of lock_page that does not require the caller to hold a reference
689 * on the page's mapping.
691 void __lock_page_nosync(struct page *page)
693 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
694 __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
695 TASK_UNINTERRUPTIBLE);
698 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
701 if (!(flags & FAULT_FLAG_ALLOW_RETRY)) {
705 if (!(flags & FAULT_FLAG_RETRY_NOWAIT)) {
706 up_read(&mm->mmap_sem);
707 wait_on_page_locked(page);
714 * find_get_page - find and get a page reference
715 * @mapping: the address_space to search
716 * @offset: the page index
718 * Is there a pagecache struct page at the given (mapping, offset) tuple?
719 * If yes, increment its refcount and return it; if no, return NULL.
721 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
729 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
731 page = radix_tree_deref_slot(pagep);
734 if (radix_tree_deref_retry(page))
737 if (!page_cache_get_speculative(page))
741 * Has the page moved?
742 * This is part of the lockless pagecache protocol. See
743 * include/linux/pagemap.h for details.
745 if (unlikely(page != *pagep)) {
746 page_cache_release(page);
755 EXPORT_SYMBOL(find_get_page);
758 * find_lock_page - locate, pin and lock a pagecache page
759 * @mapping: the address_space to search
760 * @offset: the page index
762 * Locates the desired pagecache page, locks it, increments its reference
763 * count and returns its address.
765 * Returns zero if the page was not present. find_lock_page() may sleep.
767 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
772 page = find_get_page(mapping, offset);
775 /* Has the page been truncated? */
776 if (unlikely(page->mapping != mapping)) {
778 page_cache_release(page);
781 VM_BUG_ON(page->index != offset);
785 EXPORT_SYMBOL(find_lock_page);
788 * find_or_create_page - locate or add a pagecache page
789 * @mapping: the page's address_space
790 * @index: the page's index into the mapping
791 * @gfp_mask: page allocation mode
793 * Locates a page in the pagecache. If the page is not present, a new page
794 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
795 * LRU list. The returned page is locked and has its reference count
798 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
801 * find_or_create_page() returns the desired page's address, or zero on
804 struct page *find_or_create_page(struct address_space *mapping,
805 pgoff_t index, gfp_t gfp_mask)
810 page = find_lock_page(mapping, index);
812 page = __page_cache_alloc(gfp_mask);
816 * We want a regular kernel memory (not highmem or DMA etc)
817 * allocation for the radix tree nodes, but we need to honour
818 * the context-specific requirements the caller has asked for.
819 * GFP_RECLAIM_MASK collects those requirements.
821 err = add_to_page_cache_lru(page, mapping, index,
822 (gfp_mask & GFP_RECLAIM_MASK));
824 page_cache_release(page);
832 EXPORT_SYMBOL(find_or_create_page);
835 * find_get_pages - gang pagecache lookup
836 * @mapping: The address_space to search
837 * @start: The starting page index
838 * @nr_pages: The maximum number of pages
839 * @pages: Where the resulting pages are placed
841 * find_get_pages() will search for and return a group of up to
842 * @nr_pages pages in the mapping. The pages are placed at @pages.
843 * find_get_pages() takes a reference against the returned pages.
845 * The search returns a group of mapping-contiguous pages with ascending
846 * indexes. There may be holes in the indices due to not-present pages.
848 * find_get_pages() returns the number of pages which were found.
850 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
851 unsigned int nr_pages, struct page **pages)
855 unsigned int nr_found;
859 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
860 (void ***)pages, start, nr_pages);
862 for (i = 0; i < nr_found; i++) {
865 page = radix_tree_deref_slot((void **)pages[i]);
870 * This can only trigger when the entry at index 0 moves out
871 * of or back to the root: none yet gotten, safe to restart.
873 if (radix_tree_deref_retry(page)) {
878 if (!page_cache_get_speculative(page))
881 /* Has the page moved? */
882 if (unlikely(page != *((void **)pages[i]))) {
883 page_cache_release(page);
892 * If all entries were removed before we could secure them,
893 * try again, because callers stop trying once 0 is returned.
895 if (unlikely(!ret && nr_found))
902 * find_get_pages_contig - gang contiguous pagecache lookup
903 * @mapping: The address_space to search
904 * @index: The starting page index
905 * @nr_pages: The maximum number of pages
906 * @pages: Where the resulting pages are placed
908 * find_get_pages_contig() works exactly like find_get_pages(), except
909 * that the returned number of pages are guaranteed to be contiguous.
911 * find_get_pages_contig() returns the number of pages which were found.
913 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
914 unsigned int nr_pages, struct page **pages)
918 unsigned int nr_found;
922 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
923 (void ***)pages, index, nr_pages);
925 for (i = 0; i < nr_found; i++) {
928 page = radix_tree_deref_slot((void **)pages[i]);
933 * This can only trigger when the entry at index 0 moves out
934 * of or back to the root: none yet gotten, safe to restart.
936 if (radix_tree_deref_retry(page))
939 if (!page_cache_get_speculative(page))
942 /* Has the page moved? */
943 if (unlikely(page != *((void **)pages[i]))) {
944 page_cache_release(page);
949 * must check mapping and index after taking the ref.
950 * otherwise we can get both false positives and false
951 * negatives, which is just confusing to the caller.
953 if (page->mapping == NULL || page->index != index) {
954 page_cache_release(page);
965 EXPORT_SYMBOL(find_get_pages_contig);
968 * find_get_pages_tag - find and return pages that match @tag
969 * @mapping: the address_space to search
970 * @index: the starting page index
971 * @tag: the tag index
972 * @nr_pages: the maximum number of pages
973 * @pages: where the resulting pages are placed
975 * Like find_get_pages, except we only return pages which are tagged with
976 * @tag. We update @index to index the next page for the traversal.
978 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
979 int tag, unsigned int nr_pages, struct page **pages)
983 unsigned int nr_found;
987 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
988 (void ***)pages, *index, nr_pages, tag);
990 for (i = 0; i < nr_found; i++) {
993 page = radix_tree_deref_slot((void **)pages[i]);
998 * This can only trigger when the entry at index 0 moves out
999 * of or back to the root: none yet gotten, safe to restart.
1001 if (radix_tree_deref_retry(page))
1004 if (!page_cache_get_speculative(page))
1007 /* Has the page moved? */
1008 if (unlikely(page != *((void **)pages[i]))) {
1009 page_cache_release(page);
1018 * If all entries were removed before we could secure them,
1019 * try again, because callers stop trying once 0 is returned.
1021 if (unlikely(!ret && nr_found))
1026 *index = pages[ret - 1]->index + 1;
1030 EXPORT_SYMBOL(find_get_pages_tag);
1033 * grab_cache_page_nowait - returns locked page at given index in given cache
1034 * @mapping: target address_space
1035 * @index: the page index
1037 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1038 * This is intended for speculative data generators, where the data can
1039 * be regenerated if the page couldn't be grabbed. This routine should
1040 * be safe to call while holding the lock for another page.
1042 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1043 * and deadlock against the caller's locked page.
1046 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1048 struct page *page = find_get_page(mapping, index);
1051 if (trylock_page(page))
1053 page_cache_release(page);
1056 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1057 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1058 page_cache_release(page);
1063 EXPORT_SYMBOL(grab_cache_page_nowait);
1066 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1067 * a _large_ part of the i/o request. Imagine the worst scenario:
1069 * ---R__________________________________________B__________
1070 * ^ reading here ^ bad block(assume 4k)
1072 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1073 * => failing the whole request => read(R) => read(R+1) =>
1074 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1075 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1076 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1078 * It is going insane. Fix it by quickly scaling down the readahead size.
1080 static void shrink_readahead_size_eio(struct file *filp,
1081 struct file_ra_state *ra)
1087 * do_generic_file_read - generic file read routine
1088 * @filp: the file to read
1089 * @ppos: current file position
1090 * @desc: read_descriptor
1091 * @actor: read method
1093 * This is a generic file read routine, and uses the
1094 * mapping->a_ops->readpage() function for the actual low-level stuff.
1096 * This is really ugly. But the goto's actually try to clarify some
1097 * of the logic when it comes to error handling etc.
1099 static void do_generic_file_read(struct file *filp, loff_t *ppos,
1100 read_descriptor_t *desc, read_actor_t actor)
1102 struct address_space *mapping = filp->f_mapping;
1103 struct inode *inode = mapping->host;
1104 struct file_ra_state *ra = &filp->f_ra;
1108 unsigned long offset; /* offset into pagecache page */
1109 unsigned int prev_offset;
1112 index = *ppos >> PAGE_CACHE_SHIFT;
1113 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1114 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1115 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1116 offset = *ppos & ~PAGE_CACHE_MASK;
1122 unsigned long nr, ret;
1126 page = find_get_page(mapping, index);
1128 page_cache_sync_readahead(mapping,
1130 index, last_index - index);
1131 page = find_get_page(mapping, index);
1132 if (unlikely(page == NULL))
1133 goto no_cached_page;
1135 if (PageReadahead(page)) {
1136 page_cache_async_readahead(mapping,
1138 index, last_index - index);
1140 if (!PageUptodate(page)) {
1141 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1142 !mapping->a_ops->is_partially_uptodate)
1143 goto page_not_up_to_date;
1144 if (!trylock_page(page))
1145 goto page_not_up_to_date;
1146 /* Did it get truncated before we got the lock? */
1148 goto page_not_up_to_date_locked;
1149 if (!mapping->a_ops->is_partially_uptodate(page,
1151 goto page_not_up_to_date_locked;
1156 * i_size must be checked after we know the page is Uptodate.
1158 * Checking i_size after the check allows us to calculate
1159 * the correct value for "nr", which means the zero-filled
1160 * part of the page is not copied back to userspace (unless
1161 * another truncate extends the file - this is desired though).
1164 isize = i_size_read(inode);
1165 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1166 if (unlikely(!isize || index > end_index)) {
1167 page_cache_release(page);
1171 /* nr is the maximum number of bytes to copy from this page */
1172 nr = PAGE_CACHE_SIZE;
1173 if (index == end_index) {
1174 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1176 page_cache_release(page);
1182 /* If users can be writing to this page using arbitrary
1183 * virtual addresses, take care about potential aliasing
1184 * before reading the page on the kernel side.
1186 if (mapping_writably_mapped(mapping))
1187 flush_dcache_page(page);
1190 * When a sequential read accesses a page several times,
1191 * only mark it as accessed the first time.
1193 if (prev_index != index || offset != prev_offset)
1194 mark_page_accessed(page);
1198 * Ok, we have the page, and it's up-to-date, so
1199 * now we can copy it to user space...
1201 * The actor routine returns how many bytes were actually used..
1202 * NOTE! This may not be the same as how much of a user buffer
1203 * we filled up (we may be padding etc), so we can only update
1204 * "pos" here (the actor routine has to update the user buffer
1205 * pointers and the remaining count).
1207 ret = actor(desc, page, offset, nr);
1209 index += offset >> PAGE_CACHE_SHIFT;
1210 offset &= ~PAGE_CACHE_MASK;
1211 prev_offset = offset;
1213 page_cache_release(page);
1214 if (ret == nr && desc->count)
1218 page_not_up_to_date:
1219 /* Get exclusive access to the page ... */
1220 error = lock_page_killable(page);
1221 if (unlikely(error))
1222 goto readpage_error;
1224 page_not_up_to_date_locked:
1225 /* Did it get truncated before we got the lock? */
1226 if (!page->mapping) {
1228 page_cache_release(page);
1232 /* Did somebody else fill it already? */
1233 if (PageUptodate(page)) {
1240 * A previous I/O error may have been due to temporary
1241 * failures, eg. multipath errors.
1242 * PG_error will be set again if readpage fails.
1244 ClearPageError(page);
1245 /* Start the actual read. The read will unlock the page. */
1246 error = mapping->a_ops->readpage(filp, page);
1248 if (unlikely(error)) {
1249 if (error == AOP_TRUNCATED_PAGE) {
1250 page_cache_release(page);
1253 goto readpage_error;
1256 if (!PageUptodate(page)) {
1257 error = lock_page_killable(page);
1258 if (unlikely(error))
1259 goto readpage_error;
1260 if (!PageUptodate(page)) {
1261 if (page->mapping == NULL) {
1263 * invalidate_mapping_pages got it
1266 page_cache_release(page);
1270 shrink_readahead_size_eio(filp, ra);
1272 goto readpage_error;
1280 /* UHHUH! A synchronous read error occurred. Report it */
1281 desc->error = error;
1282 page_cache_release(page);
1287 * Ok, it wasn't cached, so we need to create a new
1290 page = page_cache_alloc_cold(mapping);
1292 desc->error = -ENOMEM;
1295 error = add_to_page_cache_lru(page, mapping,
1298 page_cache_release(page);
1299 if (error == -EEXIST)
1301 desc->error = error;
1308 ra->prev_pos = prev_index;
1309 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1310 ra->prev_pos |= prev_offset;
1312 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1313 file_accessed(filp);
1316 int file_read_actor(read_descriptor_t *desc, struct page *page,
1317 unsigned long offset, unsigned long size)
1320 unsigned long left, count = desc->count;
1326 * Faults on the destination of a read are common, so do it before
1329 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1330 kaddr = kmap_atomic(page, KM_USER0);
1331 left = __copy_to_user_inatomic(desc->arg.buf,
1332 kaddr + offset, size);
1333 kunmap_atomic(kaddr, KM_USER0);
1338 /* Do it the slow way */
1340 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1345 desc->error = -EFAULT;
1348 desc->count = count - size;
1349 desc->written += size;
1350 desc->arg.buf += size;
1355 * Performs necessary checks before doing a write
1356 * @iov: io vector request
1357 * @nr_segs: number of segments in the iovec
1358 * @count: number of bytes to write
1359 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1361 * Adjust number of segments and amount of bytes to write (nr_segs should be
1362 * properly initialized first). Returns appropriate error code that caller
1363 * should return or zero in case that write should be allowed.
1365 int generic_segment_checks(const struct iovec *iov,
1366 unsigned long *nr_segs, size_t *count, int access_flags)
1370 for (seg = 0; seg < *nr_segs; seg++) {
1371 const struct iovec *iv = &iov[seg];
1374 * If any segment has a negative length, or the cumulative
1375 * length ever wraps negative then return -EINVAL.
1378 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1380 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1385 cnt -= iv->iov_len; /* This segment is no good */
1391 EXPORT_SYMBOL(generic_segment_checks);
1394 * generic_file_aio_read - generic filesystem read routine
1395 * @iocb: kernel I/O control block
1396 * @iov: io vector request
1397 * @nr_segs: number of segments in the iovec
1398 * @pos: current file position
1400 * This is the "read()" routine for all filesystems
1401 * that can use the page cache directly.
1404 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1405 unsigned long nr_segs, loff_t pos)
1407 struct file *filp = iocb->ki_filp;
1409 unsigned long seg = 0;
1411 loff_t *ppos = &iocb->ki_pos;
1414 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1418 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1419 if (filp->f_flags & O_DIRECT) {
1421 struct address_space *mapping;
1422 struct inode *inode;
1424 mapping = filp->f_mapping;
1425 inode = mapping->host;
1427 goto out; /* skip atime */
1428 size = i_size_read(inode);
1430 retval = filemap_write_and_wait_range(mapping, pos,
1431 pos + iov_length(iov, nr_segs) - 1);
1433 retval = mapping->a_ops->direct_IO(READ, iocb,
1437 *ppos = pos + retval;
1442 * Btrfs can have a short DIO read if we encounter
1443 * compressed extents, so if there was an error, or if
1444 * we've already read everything we wanted to, or if
1445 * there was a short read because we hit EOF, go ahead
1446 * and return. Otherwise fallthrough to buffered io for
1447 * the rest of the read.
1449 if (retval < 0 || !count || *ppos >= size) {
1450 file_accessed(filp);
1457 for (seg = 0; seg < nr_segs; seg++) {
1458 read_descriptor_t desc;
1462 * If we did a short DIO read we need to skip the section of the
1463 * iov that we've already read data into.
1466 if (count > iov[seg].iov_len) {
1467 count -= iov[seg].iov_len;
1475 desc.arg.buf = iov[seg].iov_base + offset;
1476 desc.count = iov[seg].iov_len - offset;
1477 if (desc.count == 0)
1480 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1481 retval += desc.written;
1483 retval = retval ?: desc.error;
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))
1583 if (VM_SequentialReadHint(vma) ||
1584 offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
1585 page_cache_sync_readahead(mapping, ra, file, offset,
1590 if (ra->mmap_miss < INT_MAX)
1594 * Do we miss much more than hit in this file? If so,
1595 * stop bothering with read-ahead. It will only hurt.
1597 if (ra->mmap_miss > MMAP_LOTSAMISS)
1603 ra_pages = max_sane_readahead(ra->ra_pages);
1605 ra->start = max_t(long, 0, offset - ra_pages/2);
1606 ra->size = ra_pages;
1608 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 ret = VM_FAULT_MAJOR;
1678 page = find_get_page(mapping, offset);
1680 goto no_cached_page;
1683 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1684 page_cache_release(page);
1685 return ret | VM_FAULT_RETRY;
1688 /* Did it get truncated? */
1689 if (unlikely(page->mapping != mapping)) {
1694 VM_BUG_ON(page->index != offset);
1697 * We have a locked page in the page cache, now we need to check
1698 * that it's up-to-date. If not, it is going to be due to an error.
1700 if (unlikely(!PageUptodate(page)))
1701 goto page_not_uptodate;
1704 * Found the page and have a reference on it.
1705 * We must recheck i_size under page lock.
1707 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1708 if (unlikely(offset >= size)) {
1710 page_cache_release(page);
1711 return VM_FAULT_SIGBUS;
1714 ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
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: destination for read data
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: destination for read data
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 int killsuid = should_remove_suid(dentry);
1998 int killpriv = security_inode_need_killpriv(dentry);
2004 error = security_inode_killpriv(dentry);
2005 if (!error && killsuid)
2006 error = __remove_suid(dentry, killsuid);
2010 EXPORT_SYMBOL(file_remove_suid);
2012 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
2013 const struct iovec *iov, size_t base, size_t bytes)
2015 size_t copied = 0, left = 0;
2018 char __user *buf = iov->iov_base + base;
2019 int copy = min(bytes, iov->iov_len - base);
2022 left = __copy_from_user_inatomic(vaddr, buf, copy);
2031 return copied - left;
2035 * Copy as much as we can into the page and return the number of bytes which
2036 * were successfully copied. If a fault is encountered then return the number of
2037 * bytes which were copied.
2039 size_t iov_iter_copy_from_user_atomic(struct page *page,
2040 struct iov_iter *i, unsigned long offset, size_t bytes)
2045 BUG_ON(!in_atomic());
2046 kaddr = kmap_atomic(page, KM_USER0);
2047 if (likely(i->nr_segs == 1)) {
2049 char __user *buf = i->iov->iov_base + i->iov_offset;
2050 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
2051 copied = bytes - left;
2053 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2054 i->iov, i->iov_offset, bytes);
2056 kunmap_atomic(kaddr, KM_USER0);
2060 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
2063 * This has the same sideeffects and return value as
2064 * iov_iter_copy_from_user_atomic().
2065 * The difference is that it attempts to resolve faults.
2066 * Page must not be locked.
2068 size_t iov_iter_copy_from_user(struct page *page,
2069 struct iov_iter *i, unsigned long offset, size_t bytes)
2075 if (likely(i->nr_segs == 1)) {
2077 char __user *buf = i->iov->iov_base + i->iov_offset;
2078 left = __copy_from_user(kaddr + offset, buf, bytes);
2079 copied = bytes - left;
2081 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2082 i->iov, i->iov_offset, bytes);
2087 EXPORT_SYMBOL(iov_iter_copy_from_user);
2089 void iov_iter_advance(struct iov_iter *i, size_t bytes)
2091 BUG_ON(i->count < bytes);
2093 if (likely(i->nr_segs == 1)) {
2094 i->iov_offset += bytes;
2097 const struct iovec *iov = i->iov;
2098 size_t base = i->iov_offset;
2101 * The !iov->iov_len check ensures we skip over unlikely
2102 * zero-length segments (without overruning the iovec).
2104 while (bytes || unlikely(i->count && !iov->iov_len)) {
2107 copy = min(bytes, iov->iov_len - base);
2108 BUG_ON(!i->count || i->count < copy);
2112 if (iov->iov_len == base) {
2118 i->iov_offset = base;
2121 EXPORT_SYMBOL(iov_iter_advance);
2124 * Fault in the first iovec of the given iov_iter, to a maximum length
2125 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2126 * accessed (ie. because it is an invalid address).
2128 * writev-intensive code may want this to prefault several iovecs -- that
2129 * would be possible (callers must not rely on the fact that _only_ the
2130 * first iovec will be faulted with the current implementation).
2132 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2134 char __user *buf = i->iov->iov_base + i->iov_offset;
2135 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2136 return fault_in_pages_readable(buf, bytes);
2138 EXPORT_SYMBOL(iov_iter_fault_in_readable);
2141 * Return the count of just the current iov_iter segment.
2143 size_t iov_iter_single_seg_count(struct iov_iter *i)
2145 const struct iovec *iov = i->iov;
2146 if (i->nr_segs == 1)
2149 return min(i->count, iov->iov_len - i->iov_offset);
2151 EXPORT_SYMBOL(iov_iter_single_seg_count);
2154 * Performs necessary checks before doing a write
2156 * Can adjust writing position or amount of bytes to write.
2157 * Returns appropriate error code that caller should return or
2158 * zero in case that write should be allowed.
2160 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2162 struct inode *inode = file->f_mapping->host;
2163 unsigned long limit = rlimit(RLIMIT_FSIZE);
2165 if (unlikely(*pos < 0))
2169 /* FIXME: this is for backwards compatibility with 2.4 */
2170 if (file->f_flags & O_APPEND)
2171 *pos = i_size_read(inode);
2173 if (limit != RLIM_INFINITY) {
2174 if (*pos >= limit) {
2175 send_sig(SIGXFSZ, current, 0);
2178 if (*count > limit - (typeof(limit))*pos) {
2179 *count = limit - (typeof(limit))*pos;
2187 if (unlikely(*pos + *count > MAX_NON_LFS &&
2188 !(file->f_flags & O_LARGEFILE))) {
2189 if (*pos >= MAX_NON_LFS) {
2192 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2193 *count = MAX_NON_LFS - (unsigned long)*pos;
2198 * Are we about to exceed the fs block limit ?
2200 * If we have written data it becomes a short write. If we have
2201 * exceeded without writing data we send a signal and return EFBIG.
2202 * Linus frestrict idea will clean these up nicely..
2204 if (likely(!isblk)) {
2205 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2206 if (*count || *pos > inode->i_sb->s_maxbytes) {
2209 /* zero-length writes at ->s_maxbytes are OK */
2212 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2213 *count = inode->i_sb->s_maxbytes - *pos;
2217 if (bdev_read_only(I_BDEV(inode)))
2219 isize = i_size_read(inode);
2220 if (*pos >= isize) {
2221 if (*count || *pos > isize)
2225 if (*pos + *count > isize)
2226 *count = isize - *pos;
2233 EXPORT_SYMBOL(generic_write_checks);
2235 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2236 loff_t pos, unsigned len, unsigned flags,
2237 struct page **pagep, void **fsdata)
2239 const struct address_space_operations *aops = mapping->a_ops;
2241 return aops->write_begin(file, mapping, pos, len, flags,
2244 EXPORT_SYMBOL(pagecache_write_begin);
2246 int pagecache_write_end(struct file *file, struct address_space *mapping,
2247 loff_t pos, unsigned len, unsigned copied,
2248 struct page *page, void *fsdata)
2250 const struct address_space_operations *aops = mapping->a_ops;
2252 mark_page_accessed(page);
2253 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2255 EXPORT_SYMBOL(pagecache_write_end);
2258 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2259 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2260 size_t count, size_t ocount)
2262 struct file *file = iocb->ki_filp;
2263 struct address_space *mapping = file->f_mapping;
2264 struct inode *inode = mapping->host;
2269 if (count != ocount)
2270 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2272 write_len = iov_length(iov, *nr_segs);
2273 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2275 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2280 * After a write we want buffered reads to be sure to go to disk to get
2281 * the new data. We invalidate clean cached page from the region we're
2282 * about to write. We do this *before* the write so that we can return
2283 * without clobbering -EIOCBQUEUED from ->direct_IO().
2285 if (mapping->nrpages) {
2286 written = invalidate_inode_pages2_range(mapping,
2287 pos >> PAGE_CACHE_SHIFT, end);
2289 * If a page can not be invalidated, return 0 to fall back
2290 * to buffered write.
2293 if (written == -EBUSY)
2299 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2302 * Finally, try again to invalidate clean pages which might have been
2303 * cached by non-direct readahead, or faulted in by get_user_pages()
2304 * if the source of the write was an mmap'ed region of the file
2305 * we're writing. Either one is a pretty crazy thing to do,
2306 * so we don't support it 100%. If this invalidation
2307 * fails, tough, the write still worked...
2309 if (mapping->nrpages) {
2310 invalidate_inode_pages2_range(mapping,
2311 pos >> PAGE_CACHE_SHIFT, end);
2316 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2317 i_size_write(inode, pos);
2318 mark_inode_dirty(inode);
2325 EXPORT_SYMBOL(generic_file_direct_write);
2328 * Find or create a page at the given pagecache position. Return the locked
2329 * page. This function is specifically for buffered writes.
2331 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2332 pgoff_t index, unsigned flags)
2336 gfp_t gfp_notmask = 0;
2337 if (flags & AOP_FLAG_NOFS)
2338 gfp_notmask = __GFP_FS;
2340 page = find_lock_page(mapping, index);
2344 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2347 status = add_to_page_cache_lru(page, mapping, index,
2348 GFP_KERNEL & ~gfp_notmask);
2349 if (unlikely(status)) {
2350 page_cache_release(page);
2351 if (status == -EEXIST)
2357 EXPORT_SYMBOL(grab_cache_page_write_begin);
2359 static ssize_t generic_perform_write(struct file *file,
2360 struct iov_iter *i, loff_t pos)
2362 struct address_space *mapping = file->f_mapping;
2363 const struct address_space_operations *a_ops = mapping->a_ops;
2365 ssize_t written = 0;
2366 unsigned int flags = 0;
2369 * Copies from kernel address space cannot fail (NFSD is a big user).
2371 if (segment_eq(get_fs(), KERNEL_DS))
2372 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2376 unsigned long offset; /* Offset into pagecache page */
2377 unsigned long bytes; /* Bytes to write to page */
2378 size_t copied; /* Bytes copied from user */
2381 offset = (pos & (PAGE_CACHE_SIZE - 1));
2382 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2388 * Bring in the user page that we will copy from _first_.
2389 * Otherwise there's a nasty deadlock on copying from the
2390 * same page as we're writing to, without it being marked
2393 * Not only is this an optimisation, but it is also required
2394 * to check that the address is actually valid, when atomic
2395 * usercopies are used, below.
2397 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2402 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2404 if (unlikely(status))
2407 if (mapping_writably_mapped(mapping))
2408 flush_dcache_page(page);
2410 pagefault_disable();
2411 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2413 flush_dcache_page(page);
2415 mark_page_accessed(page);
2416 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2418 if (unlikely(status < 0))
2424 iov_iter_advance(i, copied);
2425 if (unlikely(copied == 0)) {
2427 * If we were unable to copy any data at all, we must
2428 * fall back to a single segment length write.
2430 * If we didn't fallback here, we could livelock
2431 * because not all segments in the iov can be copied at
2432 * once without a pagefault.
2434 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2435 iov_iter_single_seg_count(i));
2441 balance_dirty_pages_ratelimited(mapping);
2443 } while (iov_iter_count(i));
2445 return written ? written : status;
2449 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2450 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2451 size_t count, ssize_t written)
2453 struct file *file = iocb->ki_filp;
2457 iov_iter_init(&i, iov, nr_segs, count, written);
2458 status = generic_perform_write(file, &i, pos);
2460 if (likely(status >= 0)) {
2462 *ppos = pos + status;
2465 return written ? written : status;
2467 EXPORT_SYMBOL(generic_file_buffered_write);
2470 * __generic_file_aio_write - write data to a file
2471 * @iocb: IO state structure (file, offset, etc.)
2472 * @iov: vector with data to write
2473 * @nr_segs: number of segments in the vector
2474 * @ppos: position where to write
2476 * This function does all the work needed for actually writing data to a
2477 * file. It does all basic checks, removes SUID from the file, updates
2478 * modification times and calls proper subroutines depending on whether we
2479 * do direct IO or a standard buffered write.
2481 * It expects i_mutex to be grabbed unless we work on a block device or similar
2482 * object which does not need locking at all.
2484 * This function does *not* take care of syncing data in case of O_SYNC write.
2485 * A caller has to handle it. This is mainly due to the fact that we want to
2486 * avoid syncing under i_mutex.
2488 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2489 unsigned long nr_segs, loff_t *ppos)
2491 struct file *file = iocb->ki_filp;
2492 struct address_space * mapping = file->f_mapping;
2493 size_t ocount; /* original count */
2494 size_t count; /* after file limit checks */
2495 struct inode *inode = mapping->host;
2501 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2508 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2510 /* We can write back this queue in page reclaim */
2511 current->backing_dev_info = mapping->backing_dev_info;
2514 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2521 err = file_remove_suid(file);
2525 file_update_time(file);
2527 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2528 if (unlikely(file->f_flags & O_DIRECT)) {
2530 ssize_t written_buffered;
2532 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2533 ppos, count, ocount);
2534 if (written < 0 || written == count)
2537 * direct-io write to a hole: fall through to buffered I/O
2538 * for completing the rest of the request.
2542 written_buffered = generic_file_buffered_write(iocb, iov,
2543 nr_segs, pos, ppos, count,
2546 * If generic_file_buffered_write() retuned a synchronous error
2547 * then we want to return the number of bytes which were
2548 * direct-written, or the error code if that was zero. Note
2549 * that this differs from normal direct-io semantics, which
2550 * will return -EFOO even if some bytes were written.
2552 if (written_buffered < 0) {
2553 err = written_buffered;
2558 * We need to ensure that the page cache pages are written to
2559 * disk and invalidated to preserve the expected O_DIRECT
2562 endbyte = pos + written_buffered - written - 1;
2563 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2565 written = written_buffered;
2566 invalidate_mapping_pages(mapping,
2567 pos >> PAGE_CACHE_SHIFT,
2568 endbyte >> PAGE_CACHE_SHIFT);
2571 * We don't know how much we wrote, so just return
2572 * the number of bytes which were direct-written
2576 written = generic_file_buffered_write(iocb, iov, nr_segs,
2577 pos, ppos, count, written);
2580 current->backing_dev_info = NULL;
2581 return written ? written : err;
2583 EXPORT_SYMBOL(__generic_file_aio_write);
2586 * generic_file_aio_write - write data to a file
2587 * @iocb: IO state structure
2588 * @iov: vector with data to write
2589 * @nr_segs: number of segments in the vector
2590 * @pos: position in file where to write
2592 * This is a wrapper around __generic_file_aio_write() to be used by most
2593 * filesystems. It takes care of syncing the file in case of O_SYNC file
2594 * and acquires i_mutex as needed.
2596 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2597 unsigned long nr_segs, loff_t pos)
2599 struct file *file = iocb->ki_filp;
2600 struct inode *inode = file->f_mapping->host;
2603 BUG_ON(iocb->ki_pos != pos);
2605 mutex_lock(&inode->i_mutex);
2606 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2607 mutex_unlock(&inode->i_mutex);
2609 if (ret > 0 || ret == -EIOCBQUEUED) {
2612 err = generic_write_sync(file, pos, ret);
2613 if (err < 0 && ret > 0)
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);