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_lock (zap_pte_range->set_page_dirty)
103 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
106 * ->dcache_lock (proc_pid_lookup)
108 * (code doesn't rely on that order, so you could switch it around)
109 * ->tasklist_lock (memory_failure, collect_procs_ao)
114 * Remove a page from the page cache and free it. Caller has to make
115 * sure the page is locked and that nobody else uses it - or that usage
116 * is safe. The caller must hold the mapping's tree_lock.
118 void __remove_from_page_cache(struct page
*page
)
120 struct address_space
*mapping
= page
->mapping
;
122 radix_tree_delete(&mapping
->page_tree
, page
->index
);
123 page
->mapping
= NULL
;
125 __dec_zone_page_state(page
, NR_FILE_PAGES
);
126 if (PageSwapBacked(page
))
127 __dec_zone_page_state(page
, NR_SHMEM
);
128 BUG_ON(page_mapped(page
));
131 * Some filesystems seem to re-dirty the page even after
132 * the VM has canceled the dirty bit (eg ext3 journaling).
134 * Fix it up by doing a final dirty accounting check after
135 * having removed the page entirely.
137 if (PageDirty(page
) && mapping_cap_account_dirty(mapping
)) {
138 dec_zone_page_state(page
, NR_FILE_DIRTY
);
139 dec_bdi_stat(mapping
->backing_dev_info
, BDI_RECLAIMABLE
);
143 void remove_from_page_cache(struct page
*page
)
145 struct address_space
*mapping
= page
->mapping
;
147 BUG_ON(!PageLocked(page
));
149 spin_lock_irq(&mapping
->tree_lock
);
150 __remove_from_page_cache(page
);
151 spin_unlock_irq(&mapping
->tree_lock
);
152 mem_cgroup_uncharge_cache_page(page
);
155 static int sync_page(void *word
)
157 struct address_space
*mapping
;
160 page
= container_of((unsigned long *)word
, struct page
, flags
);
163 * page_mapping() is being called without PG_locked held.
164 * Some knowledge of the state and use of the page is used to
165 * reduce the requirements down to a memory barrier.
166 * The danger here is of a stale page_mapping() return value
167 * indicating a struct address_space different from the one it's
168 * associated with when it is associated with one.
169 * After smp_mb(), it's either the correct page_mapping() for
170 * the page, or an old page_mapping() and the page's own
171 * page_mapping() has gone NULL.
172 * The ->sync_page() address_space operation must tolerate
173 * page_mapping() going NULL. By an amazing coincidence,
174 * this comes about because none of the users of the page
175 * in the ->sync_page() methods make essential use of the
176 * page_mapping(), merely passing the page down to the backing
177 * device's unplug functions when it's non-NULL, which in turn
178 * ignore it for all cases but swap, where only page_private(page) is
179 * of interest. When page_mapping() does go NULL, the entire
180 * call stack gracefully ignores the page and returns.
184 mapping
= page_mapping(page
);
185 if (mapping
&& mapping
->a_ops
&& mapping
->a_ops
->sync_page
)
186 mapping
->a_ops
->sync_page(page
);
191 static int sync_page_killable(void *word
)
194 return fatal_signal_pending(current
) ? -EINTR
: 0;
198 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
199 * @mapping: address space structure to write
200 * @start: offset in bytes where the range starts
201 * @end: offset in bytes where the range ends (inclusive)
202 * @sync_mode: enable synchronous operation
204 * Start writeback against all of a mapping's dirty pages that lie
205 * within the byte offsets <start, end> inclusive.
207 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
208 * opposed to a regular memory cleansing writeback. The difference between
209 * these two operations is that if a dirty page/buffer is encountered, it must
210 * be waited upon, and not just skipped over.
212 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
213 loff_t end
, int sync_mode
)
216 struct writeback_control wbc
= {
217 .sync_mode
= sync_mode
,
218 .nr_to_write
= LONG_MAX
,
219 .range_start
= start
,
223 if (!mapping_cap_writeback_dirty(mapping
))
226 ret
= do_writepages(mapping
, &wbc
);
230 static inline int __filemap_fdatawrite(struct address_space
*mapping
,
233 return __filemap_fdatawrite_range(mapping
, 0, LLONG_MAX
, sync_mode
);
236 int filemap_fdatawrite(struct address_space
*mapping
)
238 return __filemap_fdatawrite(mapping
, WB_SYNC_ALL
);
240 EXPORT_SYMBOL(filemap_fdatawrite
);
242 int filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
245 return __filemap_fdatawrite_range(mapping
, start
, end
, WB_SYNC_ALL
);
247 EXPORT_SYMBOL(filemap_fdatawrite_range
);
250 * filemap_flush - mostly a non-blocking flush
251 * @mapping: target address_space
253 * This is a mostly non-blocking flush. Not suitable for data-integrity
254 * purposes - I/O may not be started against all dirty pages.
256 int filemap_flush(struct address_space
*mapping
)
258 return __filemap_fdatawrite(mapping
, WB_SYNC_NONE
);
260 EXPORT_SYMBOL(filemap_flush
);
263 * filemap_fdatawait_range - wait for writeback to complete
264 * @mapping: address space structure to wait for
265 * @start_byte: offset in bytes where the range starts
266 * @end_byte: offset in bytes where the range ends (inclusive)
268 * Walk the list of under-writeback pages of the given address space
269 * in the given range and wait for all of them.
271 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
274 pgoff_t index
= start_byte
>> PAGE_CACHE_SHIFT
;
275 pgoff_t end
= end_byte
>> PAGE_CACHE_SHIFT
;
280 if (end_byte
< start_byte
)
283 pagevec_init(&pvec
, 0);
284 while ((index
<= end
) &&
285 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
286 PAGECACHE_TAG_WRITEBACK
,
287 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
290 for (i
= 0; i
< nr_pages
; i
++) {
291 struct page
*page
= pvec
.pages
[i
];
293 /* until radix tree lookup accepts end_index */
294 if (page
->index
> end
)
297 wait_on_page_writeback(page
);
301 pagevec_release(&pvec
);
305 /* Check for outstanding write errors */
306 if (test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
308 if (test_and_clear_bit(AS_EIO
, &mapping
->flags
))
313 EXPORT_SYMBOL(filemap_fdatawait_range
);
316 * filemap_fdatawait - wait for all under-writeback pages to complete
317 * @mapping: address space structure to wait for
319 * Walk the list of under-writeback pages of the given address space
320 * and wait for all of them.
322 int filemap_fdatawait(struct address_space
*mapping
)
324 loff_t i_size
= i_size_read(mapping
->host
);
329 return filemap_fdatawait_range(mapping
, 0, i_size
- 1);
331 EXPORT_SYMBOL(filemap_fdatawait
);
333 int filemap_write_and_wait(struct address_space
*mapping
)
337 if (mapping
->nrpages
) {
338 err
= filemap_fdatawrite(mapping
);
340 * Even if the above returned error, the pages may be
341 * written partially (e.g. -ENOSPC), so we wait for it.
342 * But the -EIO is special case, it may indicate the worst
343 * thing (e.g. bug) happened, so we avoid waiting for it.
346 int err2
= filemap_fdatawait(mapping
);
353 EXPORT_SYMBOL(filemap_write_and_wait
);
356 * filemap_write_and_wait_range - write out & wait on a file range
357 * @mapping: the address_space for the pages
358 * @lstart: offset in bytes where the range starts
359 * @lend: offset in bytes where the range ends (inclusive)
361 * Write out and wait upon file offsets lstart->lend, inclusive.
363 * Note that `lend' is inclusive (describes the last byte to be written) so
364 * that this function can be used to write to the very end-of-file (end = -1).
366 int filemap_write_and_wait_range(struct address_space
*mapping
,
367 loff_t lstart
, loff_t lend
)
371 if (mapping
->nrpages
) {
372 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
374 /* See comment of filemap_write_and_wait() */
376 int err2
= filemap_fdatawait_range(mapping
,
384 EXPORT_SYMBOL(filemap_write_and_wait_range
);
387 * add_to_page_cache_locked - add a locked page to the pagecache
389 * @mapping: the page's address_space
390 * @offset: page index
391 * @gfp_mask: page allocation mode
393 * This function is used to add a page to the pagecache. It must be locked.
394 * This function does not add the page to the LRU. The caller must do that.
396 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
397 pgoff_t offset
, gfp_t gfp_mask
)
401 VM_BUG_ON(!PageLocked(page
));
403 error
= mem_cgroup_cache_charge(page
, current
->mm
,
404 gfp_mask
& GFP_RECLAIM_MASK
);
408 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
410 page_cache_get(page
);
411 page
->mapping
= mapping
;
412 page
->index
= offset
;
414 spin_lock_irq(&mapping
->tree_lock
);
415 error
= radix_tree_insert(&mapping
->page_tree
, offset
, page
);
416 if (likely(!error
)) {
418 __inc_zone_page_state(page
, NR_FILE_PAGES
);
419 if (PageSwapBacked(page
))
420 __inc_zone_page_state(page
, NR_SHMEM
);
421 spin_unlock_irq(&mapping
->tree_lock
);
423 page
->mapping
= NULL
;
424 spin_unlock_irq(&mapping
->tree_lock
);
425 mem_cgroup_uncharge_cache_page(page
);
426 page_cache_release(page
);
428 radix_tree_preload_end();
430 mem_cgroup_uncharge_cache_page(page
);
434 EXPORT_SYMBOL(add_to_page_cache_locked
);
436 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
437 pgoff_t offset
, gfp_t gfp_mask
)
442 * Splice_read and readahead add shmem/tmpfs pages into the page cache
443 * before shmem_readpage has a chance to mark them as SwapBacked: they
444 * need to go on the active_anon lru below, and mem_cgroup_cache_charge
445 * (called in add_to_page_cache) needs to know where they're going too.
447 if (mapping_cap_swap_backed(mapping
))
448 SetPageSwapBacked(page
);
450 ret
= add_to_page_cache(page
, mapping
, offset
, gfp_mask
);
452 if (page_is_file_cache(page
))
453 lru_cache_add_file(page
);
455 lru_cache_add_active_anon(page
);
459 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
462 struct page
*__page_cache_alloc(gfp_t gfp
)
464 if (cpuset_do_page_mem_spread()) {
465 int n
= cpuset_mem_spread_node();
466 return alloc_pages_exact_node(n
, gfp
, 0);
468 return alloc_pages(gfp
, 0);
470 EXPORT_SYMBOL(__page_cache_alloc
);
473 static int __sleep_on_page_lock(void *word
)
480 * In order to wait for pages to become available there must be
481 * waitqueues associated with pages. By using a hash table of
482 * waitqueues where the bucket discipline is to maintain all
483 * waiters on the same queue and wake all when any of the pages
484 * become available, and for the woken contexts to check to be
485 * sure the appropriate page became available, this saves space
486 * at a cost of "thundering herd" phenomena during rare hash
489 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
491 const struct zone
*zone
= page_zone(page
);
493 return &zone
->wait_table
[hash_ptr(page
, zone
->wait_table_bits
)];
496 static inline void wake_up_page(struct page
*page
, int bit
)
498 __wake_up_bit(page_waitqueue(page
), &page
->flags
, bit
);
501 void wait_on_page_bit(struct page
*page
, int bit_nr
)
503 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
505 if (test_bit(bit_nr
, &page
->flags
))
506 __wait_on_bit(page_waitqueue(page
), &wait
, sync_page
,
507 TASK_UNINTERRUPTIBLE
);
509 EXPORT_SYMBOL(wait_on_page_bit
);
512 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
513 * @page: Page defining the wait queue of interest
514 * @waiter: Waiter to add to the queue
516 * Add an arbitrary @waiter to the wait queue for the nominated @page.
518 void add_page_wait_queue(struct page
*page
, wait_queue_t
*waiter
)
520 wait_queue_head_t
*q
= page_waitqueue(page
);
523 spin_lock_irqsave(&q
->lock
, flags
);
524 __add_wait_queue(q
, waiter
);
525 spin_unlock_irqrestore(&q
->lock
, flags
);
527 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
530 * unlock_page - unlock a locked page
533 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
534 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
535 * mechananism between PageLocked pages and PageWriteback pages is shared.
536 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
538 * The mb is necessary to enforce ordering between the clear_bit and the read
539 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
541 void unlock_page(struct page
*page
)
543 VM_BUG_ON(!PageLocked(page
));
544 clear_bit_unlock(PG_locked
, &page
->flags
);
545 smp_mb__after_clear_bit();
546 wake_up_page(page
, PG_locked
);
548 EXPORT_SYMBOL(unlock_page
);
551 * end_page_writeback - end writeback against a page
554 void end_page_writeback(struct page
*page
)
556 if (TestClearPageReclaim(page
))
557 rotate_reclaimable_page(page
);
559 if (!test_clear_page_writeback(page
))
562 smp_mb__after_clear_bit();
563 wake_up_page(page
, PG_writeback
);
565 EXPORT_SYMBOL(end_page_writeback
);
568 * __lock_page - get a lock on the page, assuming we need to sleep to get it
569 * @page: the page to lock
571 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some
572 * random driver's requestfn sets TASK_RUNNING, we could busywait. However
573 * chances are that on the second loop, the block layer's plug list is empty,
574 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
576 void __lock_page(struct page
*page
)
578 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
580 __wait_on_bit_lock(page_waitqueue(page
), &wait
, sync_page
,
581 TASK_UNINTERRUPTIBLE
);
583 EXPORT_SYMBOL(__lock_page
);
585 int __lock_page_killable(struct page
*page
)
587 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
589 return __wait_on_bit_lock(page_waitqueue(page
), &wait
,
590 sync_page_killable
, TASK_KILLABLE
);
592 EXPORT_SYMBOL_GPL(__lock_page_killable
);
595 * __lock_page_nosync - get a lock on the page, without calling sync_page()
596 * @page: the page to lock
598 * Variant of lock_page that does not require the caller to hold a reference
599 * on the page's mapping.
601 void __lock_page_nosync(struct page
*page
)
603 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
604 __wait_on_bit_lock(page_waitqueue(page
), &wait
, __sleep_on_page_lock
,
605 TASK_UNINTERRUPTIBLE
);
609 * find_get_page - find and get a page reference
610 * @mapping: the address_space to search
611 * @offset: the page index
613 * Is there a pagecache struct page at the given (mapping, offset) tuple?
614 * If yes, increment its refcount and return it; if no, return NULL.
616 struct page
*find_get_page(struct address_space
*mapping
, pgoff_t offset
)
624 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
626 page
= radix_tree_deref_slot(pagep
);
627 if (unlikely(!page
|| page
== RADIX_TREE_RETRY
))
630 if (!page_cache_get_speculative(page
))
634 * Has the page moved?
635 * This is part of the lockless pagecache protocol. See
636 * include/linux/pagemap.h for details.
638 if (unlikely(page
!= *pagep
)) {
639 page_cache_release(page
);
647 EXPORT_SYMBOL(find_get_page
);
650 * find_lock_page - locate, pin and lock a pagecache page
651 * @mapping: the address_space to search
652 * @offset: the page index
654 * Locates the desired pagecache page, locks it, increments its reference
655 * count and returns its address.
657 * Returns zero if the page was not present. find_lock_page() may sleep.
659 struct page
*find_lock_page(struct address_space
*mapping
, pgoff_t offset
)
664 page
= find_get_page(mapping
, offset
);
667 /* Has the page been truncated? */
668 if (unlikely(page
->mapping
!= mapping
)) {
670 page_cache_release(page
);
673 VM_BUG_ON(page
->index
!= offset
);
677 EXPORT_SYMBOL(find_lock_page
);
680 * find_or_create_page - locate or add a pagecache page
681 * @mapping: the page's address_space
682 * @index: the page's index into the mapping
683 * @gfp_mask: page allocation mode
685 * Locates a page in the pagecache. If the page is not present, a new page
686 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
687 * LRU list. The returned page is locked and has its reference count
690 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
693 * find_or_create_page() returns the desired page's address, or zero on
696 struct page
*find_or_create_page(struct address_space
*mapping
,
697 pgoff_t index
, gfp_t gfp_mask
)
702 page
= find_lock_page(mapping
, index
);
704 page
= __page_cache_alloc(gfp_mask
);
708 * We want a regular kernel memory (not highmem or DMA etc)
709 * allocation for the radix tree nodes, but we need to honour
710 * the context-specific requirements the caller has asked for.
711 * GFP_RECLAIM_MASK collects those requirements.
713 err
= add_to_page_cache_lru(page
, mapping
, index
,
714 (gfp_mask
& GFP_RECLAIM_MASK
));
716 page_cache_release(page
);
724 EXPORT_SYMBOL(find_or_create_page
);
727 * find_get_pages - gang pagecache lookup
728 * @mapping: The address_space to search
729 * @start: The starting page index
730 * @nr_pages: The maximum number of pages
731 * @pages: Where the resulting pages are placed
733 * find_get_pages() will search for and return a group of up to
734 * @nr_pages pages in the mapping. The pages are placed at @pages.
735 * find_get_pages() takes a reference against the returned pages.
737 * The search returns a group of mapping-contiguous pages with ascending
738 * indexes. There may be holes in the indices due to not-present pages.
740 * find_get_pages() returns the number of pages which were found.
742 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
743 unsigned int nr_pages
, struct page
**pages
)
747 unsigned int nr_found
;
751 nr_found
= radix_tree_gang_lookup_slot(&mapping
->page_tree
,
752 (void ***)pages
, start
, nr_pages
);
754 for (i
= 0; i
< nr_found
; i
++) {
757 page
= radix_tree_deref_slot((void **)pages
[i
]);
761 * this can only trigger if nr_found == 1, making livelock
764 if (unlikely(page
== RADIX_TREE_RETRY
))
767 if (!page_cache_get_speculative(page
))
770 /* Has the page moved? */
771 if (unlikely(page
!= *((void **)pages
[i
]))) {
772 page_cache_release(page
);
784 * find_get_pages_contig - gang contiguous pagecache lookup
785 * @mapping: The address_space to search
786 * @index: The starting page index
787 * @nr_pages: The maximum number of pages
788 * @pages: Where the resulting pages are placed
790 * find_get_pages_contig() works exactly like find_get_pages(), except
791 * that the returned number of pages are guaranteed to be contiguous.
793 * find_get_pages_contig() returns the number of pages which were found.
795 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
796 unsigned int nr_pages
, struct page
**pages
)
800 unsigned int nr_found
;
804 nr_found
= radix_tree_gang_lookup_slot(&mapping
->page_tree
,
805 (void ***)pages
, index
, nr_pages
);
807 for (i
= 0; i
< nr_found
; i
++) {
810 page
= radix_tree_deref_slot((void **)pages
[i
]);
814 * this can only trigger if nr_found == 1, making livelock
817 if (unlikely(page
== RADIX_TREE_RETRY
))
820 if (page
->mapping
== NULL
|| page
->index
!= index
)
823 if (!page_cache_get_speculative(page
))
826 /* Has the page moved? */
827 if (unlikely(page
!= *((void **)pages
[i
]))) {
828 page_cache_release(page
);
839 EXPORT_SYMBOL(find_get_pages_contig
);
842 * find_get_pages_tag - find and return pages that match @tag
843 * @mapping: the address_space to search
844 * @index: the starting page index
845 * @tag: the tag index
846 * @nr_pages: the maximum number of pages
847 * @pages: where the resulting pages are placed
849 * Like find_get_pages, except we only return pages which are tagged with
850 * @tag. We update @index to index the next page for the traversal.
852 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
853 int tag
, unsigned int nr_pages
, struct page
**pages
)
857 unsigned int nr_found
;
861 nr_found
= radix_tree_gang_lookup_tag_slot(&mapping
->page_tree
,
862 (void ***)pages
, *index
, nr_pages
, tag
);
864 for (i
= 0; i
< nr_found
; i
++) {
867 page
= radix_tree_deref_slot((void **)pages
[i
]);
871 * this can only trigger if nr_found == 1, making livelock
874 if (unlikely(page
== RADIX_TREE_RETRY
))
877 if (!page_cache_get_speculative(page
))
880 /* Has the page moved? */
881 if (unlikely(page
!= *((void **)pages
[i
]))) {
882 page_cache_release(page
);
892 *index
= pages
[ret
- 1]->index
+ 1;
896 EXPORT_SYMBOL(find_get_pages_tag
);
899 * grab_cache_page_nowait - returns locked page at given index in given cache
900 * @mapping: target address_space
901 * @index: the page index
903 * Same as grab_cache_page(), but do not wait if the page is unavailable.
904 * This is intended for speculative data generators, where the data can
905 * be regenerated if the page couldn't be grabbed. This routine should
906 * be safe to call while holding the lock for another page.
908 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
909 * and deadlock against the caller's locked page.
912 grab_cache_page_nowait(struct address_space
*mapping
, pgoff_t index
)
914 struct page
*page
= find_get_page(mapping
, index
);
917 if (trylock_page(page
))
919 page_cache_release(page
);
922 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) & ~__GFP_FS
);
923 if (page
&& add_to_page_cache_lru(page
, mapping
, index
, GFP_NOFS
)) {
924 page_cache_release(page
);
929 EXPORT_SYMBOL(grab_cache_page_nowait
);
932 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
933 * a _large_ part of the i/o request. Imagine the worst scenario:
935 * ---R__________________________________________B__________
936 * ^ reading here ^ bad block(assume 4k)
938 * read(R) => miss => readahead(R...B) => media error => frustrating retries
939 * => failing the whole request => read(R) => read(R+1) =>
940 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
941 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
942 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
944 * It is going insane. Fix it by quickly scaling down the readahead size.
946 static void shrink_readahead_size_eio(struct file
*filp
,
947 struct file_ra_state
*ra
)
953 * do_generic_file_read - generic file read routine
954 * @filp: the file to read
955 * @ppos: current file position
956 * @desc: read_descriptor
957 * @actor: read method
959 * This is a generic file read routine, and uses the
960 * mapping->a_ops->readpage() function for the actual low-level stuff.
962 * This is really ugly. But the goto's actually try to clarify some
963 * of the logic when it comes to error handling etc.
965 static void do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
966 read_descriptor_t
*desc
, read_actor_t actor
)
968 struct address_space
*mapping
= filp
->f_mapping
;
969 struct inode
*inode
= mapping
->host
;
970 struct file_ra_state
*ra
= &filp
->f_ra
;
974 unsigned long offset
; /* offset into pagecache page */
975 unsigned int prev_offset
;
978 index
= *ppos
>> PAGE_CACHE_SHIFT
;
979 prev_index
= ra
->prev_pos
>> PAGE_CACHE_SHIFT
;
980 prev_offset
= ra
->prev_pos
& (PAGE_CACHE_SIZE
-1);
981 last_index
= (*ppos
+ desc
->count
+ PAGE_CACHE_SIZE
-1) >> PAGE_CACHE_SHIFT
;
982 offset
= *ppos
& ~PAGE_CACHE_MASK
;
988 unsigned long nr
, ret
;
992 page
= find_get_page(mapping
, index
);
994 page_cache_sync_readahead(mapping
,
996 index
, last_index
- index
);
997 page
= find_get_page(mapping
, index
);
998 if (unlikely(page
== NULL
))
1001 if (PageReadahead(page
)) {
1002 page_cache_async_readahead(mapping
,
1004 index
, last_index
- index
);
1006 if (!PageUptodate(page
)) {
1007 if (inode
->i_blkbits
== PAGE_CACHE_SHIFT
||
1008 !mapping
->a_ops
->is_partially_uptodate
)
1009 goto page_not_up_to_date
;
1010 if (!trylock_page(page
))
1011 goto page_not_up_to_date
;
1012 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1014 goto page_not_up_to_date_locked
;
1019 * i_size must be checked after we know the page is Uptodate.
1021 * Checking i_size after the check allows us to calculate
1022 * the correct value for "nr", which means the zero-filled
1023 * part of the page is not copied back to userspace (unless
1024 * another truncate extends the file - this is desired though).
1027 isize
= i_size_read(inode
);
1028 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
1029 if (unlikely(!isize
|| index
> end_index
)) {
1030 page_cache_release(page
);
1034 /* nr is the maximum number of bytes to copy from this page */
1035 nr
= PAGE_CACHE_SIZE
;
1036 if (index
== end_index
) {
1037 nr
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
1039 page_cache_release(page
);
1045 /* If users can be writing to this page using arbitrary
1046 * virtual addresses, take care about potential aliasing
1047 * before reading the page on the kernel side.
1049 if (mapping_writably_mapped(mapping
))
1050 flush_dcache_page(page
);
1053 * When a sequential read accesses a page several times,
1054 * only mark it as accessed the first time.
1056 if (prev_index
!= index
|| offset
!= prev_offset
)
1057 mark_page_accessed(page
);
1061 * Ok, we have the page, and it's up-to-date, so
1062 * now we can copy it to user space...
1064 * The actor routine returns how many bytes were actually used..
1065 * NOTE! This may not be the same as how much of a user buffer
1066 * we filled up (we may be padding etc), so we can only update
1067 * "pos" here (the actor routine has to update the user buffer
1068 * pointers and the remaining count).
1070 ret
= actor(desc
, page
, offset
, nr
);
1072 index
+= offset
>> PAGE_CACHE_SHIFT
;
1073 offset
&= ~PAGE_CACHE_MASK
;
1074 prev_offset
= offset
;
1076 page_cache_release(page
);
1077 if (ret
== nr
&& desc
->count
)
1081 page_not_up_to_date
:
1082 /* Get exclusive access to the page ... */
1083 error
= lock_page_killable(page
);
1084 if (unlikely(error
))
1085 goto readpage_error
;
1087 page_not_up_to_date_locked
:
1088 /* Did it get truncated before we got the lock? */
1089 if (!page
->mapping
) {
1091 page_cache_release(page
);
1095 /* Did somebody else fill it already? */
1096 if (PageUptodate(page
)) {
1102 /* Start the actual read. The read will unlock the page. */
1103 error
= mapping
->a_ops
->readpage(filp
, page
);
1105 if (unlikely(error
)) {
1106 if (error
== AOP_TRUNCATED_PAGE
) {
1107 page_cache_release(page
);
1110 goto readpage_error
;
1113 if (!PageUptodate(page
)) {
1114 error
= lock_page_killable(page
);
1115 if (unlikely(error
))
1116 goto readpage_error
;
1117 if (!PageUptodate(page
)) {
1118 if (page
->mapping
== NULL
) {
1120 * invalidate_mapping_pages got it
1123 page_cache_release(page
);
1127 shrink_readahead_size_eio(filp
, ra
);
1129 goto readpage_error
;
1137 /* UHHUH! A synchronous read error occurred. Report it */
1138 desc
->error
= error
;
1139 page_cache_release(page
);
1144 * Ok, it wasn't cached, so we need to create a new
1147 page
= page_cache_alloc_cold(mapping
);
1149 desc
->error
= -ENOMEM
;
1152 error
= add_to_page_cache_lru(page
, mapping
,
1155 page_cache_release(page
);
1156 if (error
== -EEXIST
)
1158 desc
->error
= error
;
1165 ra
->prev_pos
= prev_index
;
1166 ra
->prev_pos
<<= PAGE_CACHE_SHIFT
;
1167 ra
->prev_pos
|= prev_offset
;
1169 *ppos
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
) + offset
;
1170 file_accessed(filp
);
1173 int file_read_actor(read_descriptor_t
*desc
, struct page
*page
,
1174 unsigned long offset
, unsigned long size
)
1177 unsigned long left
, count
= desc
->count
;
1183 * Faults on the destination of a read are common, so do it before
1186 if (!fault_in_pages_writeable(desc
->arg
.buf
, size
)) {
1187 kaddr
= kmap_atomic(page
, KM_USER0
);
1188 left
= __copy_to_user_inatomic(desc
->arg
.buf
,
1189 kaddr
+ offset
, size
);
1190 kunmap_atomic(kaddr
, KM_USER0
);
1195 /* Do it the slow way */
1197 left
= __copy_to_user(desc
->arg
.buf
, kaddr
+ offset
, size
);
1202 desc
->error
= -EFAULT
;
1205 desc
->count
= count
- size
;
1206 desc
->written
+= size
;
1207 desc
->arg
.buf
+= size
;
1212 * Performs necessary checks before doing a write
1213 * @iov: io vector request
1214 * @nr_segs: number of segments in the iovec
1215 * @count: number of bytes to write
1216 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1218 * Adjust number of segments and amount of bytes to write (nr_segs should be
1219 * properly initialized first). Returns appropriate error code that caller
1220 * should return or zero in case that write should be allowed.
1222 int generic_segment_checks(const struct iovec
*iov
,
1223 unsigned long *nr_segs
, size_t *count
, int access_flags
)
1227 for (seg
= 0; seg
< *nr_segs
; seg
++) {
1228 const struct iovec
*iv
= &iov
[seg
];
1231 * If any segment has a negative length, or the cumulative
1232 * length ever wraps negative then return -EINVAL.
1235 if (unlikely((ssize_t
)(cnt
|iv
->iov_len
) < 0))
1237 if (access_ok(access_flags
, iv
->iov_base
, iv
->iov_len
))
1242 cnt
-= iv
->iov_len
; /* This segment is no good */
1248 EXPORT_SYMBOL(generic_segment_checks
);
1251 * generic_file_aio_read - generic filesystem read routine
1252 * @iocb: kernel I/O control block
1253 * @iov: io vector request
1254 * @nr_segs: number of segments in the iovec
1255 * @pos: current file position
1257 * This is the "read()" routine for all filesystems
1258 * that can use the page cache directly.
1261 generic_file_aio_read(struct kiocb
*iocb
, const struct iovec
*iov
,
1262 unsigned long nr_segs
, loff_t pos
)
1264 struct file
*filp
= iocb
->ki_filp
;
1266 unsigned long seg
= 0;
1268 loff_t
*ppos
= &iocb
->ki_pos
;
1271 retval
= generic_segment_checks(iov
, &nr_segs
, &count
, VERIFY_WRITE
);
1275 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1276 if (filp
->f_flags
& O_DIRECT
) {
1278 struct address_space
*mapping
;
1279 struct inode
*inode
;
1281 mapping
= filp
->f_mapping
;
1282 inode
= mapping
->host
;
1284 goto out
; /* skip atime */
1285 size
= i_size_read(inode
);
1287 retval
= filemap_write_and_wait_range(mapping
, pos
,
1288 pos
+ iov_length(iov
, nr_segs
) - 1);
1290 retval
= mapping
->a_ops
->direct_IO(READ
, iocb
,
1294 *ppos
= pos
+ retval
;
1299 * Btrfs can have a short DIO read if we encounter
1300 * compressed extents, so if there was an error, or if
1301 * we've already read everything we wanted to, or if
1302 * there was a short read because we hit EOF, go ahead
1303 * and return. Otherwise fallthrough to buffered io for
1304 * the rest of the read.
1306 if (retval
< 0 || !count
|| *ppos
>= size
) {
1307 file_accessed(filp
);
1314 for (seg
= 0; seg
< nr_segs
; seg
++) {
1315 read_descriptor_t desc
;
1319 * If we did a short DIO read we need to skip the section of the
1320 * iov that we've already read data into.
1323 if (count
> iov
[seg
].iov_len
) {
1324 count
-= iov
[seg
].iov_len
;
1332 desc
.arg
.buf
= iov
[seg
].iov_base
+ offset
;
1333 desc
.count
= iov
[seg
].iov_len
- offset
;
1334 if (desc
.count
== 0)
1337 do_generic_file_read(filp
, ppos
, &desc
, file_read_actor
);
1338 retval
+= desc
.written
;
1340 retval
= retval
?: desc
.error
;
1349 EXPORT_SYMBOL(generic_file_aio_read
);
1352 do_readahead(struct address_space
*mapping
, struct file
*filp
,
1353 pgoff_t index
, unsigned long nr
)
1355 if (!mapping
|| !mapping
->a_ops
|| !mapping
->a_ops
->readpage
)
1358 force_page_cache_readahead(mapping
, filp
, index
, nr
);
1362 SYSCALL_DEFINE(readahead
)(int fd
, loff_t offset
, size_t count
)
1370 if (file
->f_mode
& FMODE_READ
) {
1371 struct address_space
*mapping
= file
->f_mapping
;
1372 pgoff_t start
= offset
>> PAGE_CACHE_SHIFT
;
1373 pgoff_t end
= (offset
+ count
- 1) >> PAGE_CACHE_SHIFT
;
1374 unsigned long len
= end
- start
+ 1;
1375 ret
= do_readahead(mapping
, file
, start
, len
);
1381 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1382 asmlinkage
long SyS_readahead(long fd
, loff_t offset
, long count
)
1384 return SYSC_readahead((int) fd
, offset
, (size_t) count
);
1386 SYSCALL_ALIAS(sys_readahead
, SyS_readahead
);
1391 * page_cache_read - adds requested page to the page cache if not already there
1392 * @file: file to read
1393 * @offset: page index
1395 * This adds the requested page to the page cache if it isn't already there,
1396 * and schedules an I/O to read in its contents from disk.
1398 static int page_cache_read(struct file
*file
, pgoff_t offset
)
1400 struct address_space
*mapping
= file
->f_mapping
;
1405 page
= page_cache_alloc_cold(mapping
);
1409 ret
= add_to_page_cache_lru(page
, mapping
, offset
, GFP_KERNEL
);
1411 ret
= mapping
->a_ops
->readpage(file
, page
);
1412 else if (ret
== -EEXIST
)
1413 ret
= 0; /* losing race to add is OK */
1415 page_cache_release(page
);
1417 } while (ret
== AOP_TRUNCATED_PAGE
);
1422 #define MMAP_LOTSAMISS (100)
1425 * Synchronous readahead happens when we don't even find
1426 * a page in the page cache at all.
1428 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
1429 struct file_ra_state
*ra
,
1433 unsigned long ra_pages
;
1434 struct address_space
*mapping
= file
->f_mapping
;
1436 /* If we don't want any read-ahead, don't bother */
1437 if (VM_RandomReadHint(vma
))
1440 if (VM_SequentialReadHint(vma
) ||
1441 offset
- 1 == (ra
->prev_pos
>> PAGE_CACHE_SHIFT
)) {
1442 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
1447 if (ra
->mmap_miss
< INT_MAX
)
1451 * Do we miss much more than hit in this file? If so,
1452 * stop bothering with read-ahead. It will only hurt.
1454 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
1460 ra_pages
= max_sane_readahead(ra
->ra_pages
);
1462 ra
->start
= max_t(long, 0, offset
- ra_pages
/2);
1463 ra
->size
= ra_pages
;
1465 ra_submit(ra
, mapping
, file
);
1470 * Asynchronous readahead happens when we find the page and PG_readahead,
1471 * so we want to possibly extend the readahead further..
1473 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
1474 struct file_ra_state
*ra
,
1479 struct address_space
*mapping
= file
->f_mapping
;
1481 /* If we don't want any read-ahead, don't bother */
1482 if (VM_RandomReadHint(vma
))
1484 if (ra
->mmap_miss
> 0)
1486 if (PageReadahead(page
))
1487 page_cache_async_readahead(mapping
, ra
, file
,
1488 page
, offset
, ra
->ra_pages
);
1492 * filemap_fault - read in file data for page fault handling
1493 * @vma: vma in which the fault was taken
1494 * @vmf: struct vm_fault containing details of the fault
1496 * filemap_fault() is invoked via the vma operations vector for a
1497 * mapped memory region to read in file data during a page fault.
1499 * The goto's are kind of ugly, but this streamlines the normal case of having
1500 * it in the page cache, and handles the special cases reasonably without
1501 * having a lot of duplicated code.
1503 int filemap_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1506 struct file
*file
= vma
->vm_file
;
1507 struct address_space
*mapping
= file
->f_mapping
;
1508 struct file_ra_state
*ra
= &file
->f_ra
;
1509 struct inode
*inode
= mapping
->host
;
1510 pgoff_t offset
= vmf
->pgoff
;
1515 size
= (i_size_read(inode
) + PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
1517 return VM_FAULT_SIGBUS
;
1520 * Do we have something in the page cache already?
1522 page
= find_get_page(mapping
, offset
);
1525 * We found the page, so try async readahead before
1526 * waiting for the lock.
1528 do_async_mmap_readahead(vma
, ra
, file
, page
, offset
);
1531 /* Did it get truncated? */
1532 if (unlikely(page
->mapping
!= mapping
)) {
1535 goto no_cached_page
;
1538 /* No page in the page cache at all */
1539 do_sync_mmap_readahead(vma
, ra
, file
, offset
);
1540 count_vm_event(PGMAJFAULT
);
1541 ret
= VM_FAULT_MAJOR
;
1543 page
= find_lock_page(mapping
, offset
);
1545 goto no_cached_page
;
1549 * We have a locked page in the page cache, now we need to check
1550 * that it's up-to-date. If not, it is going to be due to an error.
1552 if (unlikely(!PageUptodate(page
)))
1553 goto page_not_uptodate
;
1556 * Found the page and have a reference on it.
1557 * We must recheck i_size under page lock.
1559 size
= (i_size_read(inode
) + PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
1560 if (unlikely(offset
>= size
)) {
1562 page_cache_release(page
);
1563 return VM_FAULT_SIGBUS
;
1566 ra
->prev_pos
= (loff_t
)offset
<< PAGE_CACHE_SHIFT
;
1568 return ret
| VM_FAULT_LOCKED
;
1572 * We're only likely to ever get here if MADV_RANDOM is in
1575 error
= page_cache_read(file
, offset
);
1578 * The page we want has now been added to the page cache.
1579 * In the unlikely event that someone removed it in the
1580 * meantime, we'll just come back here and read it again.
1586 * An error return from page_cache_read can result if the
1587 * system is low on memory, or a problem occurs while trying
1590 if (error
== -ENOMEM
)
1591 return VM_FAULT_OOM
;
1592 return VM_FAULT_SIGBUS
;
1596 * Umm, take care of errors if the page isn't up-to-date.
1597 * Try to re-read it _once_. We do this synchronously,
1598 * because there really aren't any performance issues here
1599 * and we need to check for errors.
1601 ClearPageError(page
);
1602 error
= mapping
->a_ops
->readpage(file
, page
);
1604 wait_on_page_locked(page
);
1605 if (!PageUptodate(page
))
1608 page_cache_release(page
);
1610 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
1613 /* Things didn't work out. Return zero to tell the mm layer so. */
1614 shrink_readahead_size_eio(file
, ra
);
1615 return VM_FAULT_SIGBUS
;
1617 EXPORT_SYMBOL(filemap_fault
);
1619 const struct vm_operations_struct generic_file_vm_ops
= {
1620 .fault
= filemap_fault
,
1623 /* This is used for a general mmap of a disk file */
1625 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1627 struct address_space
*mapping
= file
->f_mapping
;
1629 if (!mapping
->a_ops
->readpage
)
1631 file_accessed(file
);
1632 vma
->vm_ops
= &generic_file_vm_ops
;
1633 vma
->vm_flags
|= VM_CAN_NONLINEAR
;
1638 * This is for filesystems which do not implement ->writepage.
1640 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
1642 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
1644 return generic_file_mmap(file
, vma
);
1647 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1651 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1655 #endif /* CONFIG_MMU */
1657 EXPORT_SYMBOL(generic_file_mmap
);
1658 EXPORT_SYMBOL(generic_file_readonly_mmap
);
1660 static struct page
*__read_cache_page(struct address_space
*mapping
,
1662 int (*filler
)(void *,struct page
*),
1669 page
= find_get_page(mapping
, index
);
1671 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
1673 return ERR_PTR(-ENOMEM
);
1674 err
= add_to_page_cache_lru(page
, mapping
, index
, GFP_KERNEL
);
1675 if (unlikely(err
)) {
1676 page_cache_release(page
);
1679 /* Presumably ENOMEM for radix tree node */
1680 return ERR_PTR(err
);
1682 err
= filler(data
, page
);
1684 page_cache_release(page
);
1685 page
= ERR_PTR(err
);
1691 static struct page
*do_read_cache_page(struct address_space
*mapping
,
1693 int (*filler
)(void *,struct page
*),
1702 page
= __read_cache_page(mapping
, index
, filler
, data
, gfp
);
1705 if (PageUptodate(page
))
1709 if (!page
->mapping
) {
1711 page_cache_release(page
);
1714 if (PageUptodate(page
)) {
1718 err
= filler(data
, page
);
1720 page_cache_release(page
);
1721 return ERR_PTR(err
);
1724 mark_page_accessed(page
);
1729 * read_cache_page_async - read into page cache, fill it if needed
1730 * @mapping: the page's address_space
1731 * @index: the page index
1732 * @filler: function to perform the read
1733 * @data: destination for read data
1735 * Same as read_cache_page, but don't wait for page to become unlocked
1736 * after submitting it to the filler.
1738 * Read into the page cache. If a page already exists, and PageUptodate() is
1739 * not set, try to fill the page but don't wait for it to become unlocked.
1741 * If the page does not get brought uptodate, return -EIO.
1743 struct page
*read_cache_page_async(struct address_space
*mapping
,
1745 int (*filler
)(void *,struct page
*),
1748 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
1750 EXPORT_SYMBOL(read_cache_page_async
);
1752 static struct page
*wait_on_page_read(struct page
*page
)
1754 if (!IS_ERR(page
)) {
1755 wait_on_page_locked(page
);
1756 if (!PageUptodate(page
)) {
1757 page_cache_release(page
);
1758 page
= ERR_PTR(-EIO
);
1765 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1766 * @mapping: the page's address_space
1767 * @index: the page index
1768 * @gfp: the page allocator flags to use if allocating
1770 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1771 * any new page allocations done using the specified allocation flags. Note
1772 * that the Radix tree operations will still use GFP_KERNEL, so you can't
1773 * expect to do this atomically or anything like that - but you can pass in
1774 * other page requirements.
1776 * If the page does not get brought uptodate, return -EIO.
1778 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
1782 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
1784 return wait_on_page_read(do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
));
1786 EXPORT_SYMBOL(read_cache_page_gfp
);
1789 * read_cache_page - read into page cache, fill it if needed
1790 * @mapping: the page's address_space
1791 * @index: the page index
1792 * @filler: function to perform the read
1793 * @data: destination for read data
1795 * Read into the page cache. If a page already exists, and PageUptodate() is
1796 * not set, try to fill the page then wait for it to become unlocked.
1798 * If the page does not get brought uptodate, return -EIO.
1800 struct page
*read_cache_page(struct address_space
*mapping
,
1802 int (*filler
)(void *,struct page
*),
1805 return wait_on_page_read(read_cache_page_async(mapping
, index
, filler
, data
));
1807 EXPORT_SYMBOL(read_cache_page
);
1810 * The logic we want is
1812 * if suid or (sgid and xgrp)
1815 int should_remove_suid(struct dentry
*dentry
)
1817 mode_t mode
= dentry
->d_inode
->i_mode
;
1820 /* suid always must be killed */
1821 if (unlikely(mode
& S_ISUID
))
1822 kill
= ATTR_KILL_SUID
;
1825 * sgid without any exec bits is just a mandatory locking mark; leave
1826 * it alone. If some exec bits are set, it's a real sgid; kill it.
1828 if (unlikely((mode
& S_ISGID
) && (mode
& S_IXGRP
)))
1829 kill
|= ATTR_KILL_SGID
;
1831 if (unlikely(kill
&& !capable(CAP_FSETID
) && S_ISREG(mode
)))
1836 EXPORT_SYMBOL(should_remove_suid
);
1838 static int __remove_suid(struct dentry
*dentry
, int kill
)
1840 struct iattr newattrs
;
1842 newattrs
.ia_valid
= ATTR_FORCE
| kill
;
1843 return notify_change(dentry
, &newattrs
);
1846 int file_remove_suid(struct file
*file
)
1848 struct dentry
*dentry
= file
->f_path
.dentry
;
1849 int killsuid
= should_remove_suid(dentry
);
1850 int killpriv
= security_inode_need_killpriv(dentry
);
1856 error
= security_inode_killpriv(dentry
);
1857 if (!error
&& killsuid
)
1858 error
= __remove_suid(dentry
, killsuid
);
1862 EXPORT_SYMBOL(file_remove_suid
);
1864 static size_t __iovec_copy_from_user_inatomic(char *vaddr
,
1865 const struct iovec
*iov
, size_t base
, size_t bytes
)
1867 size_t copied
= 0, left
= 0;
1870 char __user
*buf
= iov
->iov_base
+ base
;
1871 int copy
= min(bytes
, iov
->iov_len
- base
);
1874 left
= __copy_from_user_inatomic(vaddr
, buf
, copy
);
1883 return copied
- left
;
1887 * Copy as much as we can into the page and return the number of bytes which
1888 * were successfully copied. If a fault is encountered then return the number of
1889 * bytes which were copied.
1891 size_t iov_iter_copy_from_user_atomic(struct page
*page
,
1892 struct iov_iter
*i
, unsigned long offset
, size_t bytes
)
1897 BUG_ON(!in_atomic());
1898 kaddr
= kmap_atomic(page
, KM_USER0
);
1899 if (likely(i
->nr_segs
== 1)) {
1901 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1902 left
= __copy_from_user_inatomic(kaddr
+ offset
, buf
, bytes
);
1903 copied
= bytes
- left
;
1905 copied
= __iovec_copy_from_user_inatomic(kaddr
+ offset
,
1906 i
->iov
, i
->iov_offset
, bytes
);
1908 kunmap_atomic(kaddr
, KM_USER0
);
1912 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic
);
1915 * This has the same sideeffects and return value as
1916 * iov_iter_copy_from_user_atomic().
1917 * The difference is that it attempts to resolve faults.
1918 * Page must not be locked.
1920 size_t iov_iter_copy_from_user(struct page
*page
,
1921 struct iov_iter
*i
, unsigned long offset
, size_t bytes
)
1927 if (likely(i
->nr_segs
== 1)) {
1929 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1930 left
= __copy_from_user(kaddr
+ offset
, buf
, bytes
);
1931 copied
= bytes
- left
;
1933 copied
= __iovec_copy_from_user_inatomic(kaddr
+ offset
,
1934 i
->iov
, i
->iov_offset
, bytes
);
1939 EXPORT_SYMBOL(iov_iter_copy_from_user
);
1941 void iov_iter_advance(struct iov_iter
*i
, size_t bytes
)
1943 BUG_ON(i
->count
< bytes
);
1945 if (likely(i
->nr_segs
== 1)) {
1946 i
->iov_offset
+= bytes
;
1949 const struct iovec
*iov
= i
->iov
;
1950 size_t base
= i
->iov_offset
;
1953 * The !iov->iov_len check ensures we skip over unlikely
1954 * zero-length segments (without overruning the iovec).
1956 while (bytes
|| unlikely(i
->count
&& !iov
->iov_len
)) {
1959 copy
= min(bytes
, iov
->iov_len
- base
);
1960 BUG_ON(!i
->count
|| i
->count
< copy
);
1964 if (iov
->iov_len
== base
) {
1970 i
->iov_offset
= base
;
1973 EXPORT_SYMBOL(iov_iter_advance
);
1976 * Fault in the first iovec of the given iov_iter, to a maximum length
1977 * of bytes. Returns 0 on success, or non-zero if the memory could not be
1978 * accessed (ie. because it is an invalid address).
1980 * writev-intensive code may want this to prefault several iovecs -- that
1981 * would be possible (callers must not rely on the fact that _only_ the
1982 * first iovec will be faulted with the current implementation).
1984 int iov_iter_fault_in_readable(struct iov_iter
*i
, size_t bytes
)
1986 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1987 bytes
= min(bytes
, i
->iov
->iov_len
- i
->iov_offset
);
1988 return fault_in_pages_readable(buf
, bytes
);
1990 EXPORT_SYMBOL(iov_iter_fault_in_readable
);
1993 * Return the count of just the current iov_iter segment.
1995 size_t iov_iter_single_seg_count(struct iov_iter
*i
)
1997 const struct iovec
*iov
= i
->iov
;
1998 if (i
->nr_segs
== 1)
2001 return min(i
->count
, iov
->iov_len
- i
->iov_offset
);
2003 EXPORT_SYMBOL(iov_iter_single_seg_count
);
2006 * Performs necessary checks before doing a write
2008 * Can adjust writing position or amount of bytes to write.
2009 * Returns appropriate error code that caller should return or
2010 * zero in case that write should be allowed.
2012 inline int generic_write_checks(struct file
*file
, loff_t
*pos
, size_t *count
, int isblk
)
2014 struct inode
*inode
= file
->f_mapping
->host
;
2015 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2017 if (unlikely(*pos
< 0))
2021 /* FIXME: this is for backwards compatibility with 2.4 */
2022 if (file
->f_flags
& O_APPEND
)
2023 *pos
= i_size_read(inode
);
2025 if (limit
!= RLIM_INFINITY
) {
2026 if (*pos
>= limit
) {
2027 send_sig(SIGXFSZ
, current
, 0);
2030 if (*count
> limit
- (typeof(limit
))*pos
) {
2031 *count
= limit
- (typeof(limit
))*pos
;
2039 if (unlikely(*pos
+ *count
> MAX_NON_LFS
&&
2040 !(file
->f_flags
& O_LARGEFILE
))) {
2041 if (*pos
>= MAX_NON_LFS
) {
2044 if (*count
> MAX_NON_LFS
- (unsigned long)*pos
) {
2045 *count
= MAX_NON_LFS
- (unsigned long)*pos
;
2050 * Are we about to exceed the fs block limit ?
2052 * If we have written data it becomes a short write. If we have
2053 * exceeded without writing data we send a signal and return EFBIG.
2054 * Linus frestrict idea will clean these up nicely..
2056 if (likely(!isblk
)) {
2057 if (unlikely(*pos
>= inode
->i_sb
->s_maxbytes
)) {
2058 if (*count
|| *pos
> inode
->i_sb
->s_maxbytes
) {
2061 /* zero-length writes at ->s_maxbytes are OK */
2064 if (unlikely(*pos
+ *count
> inode
->i_sb
->s_maxbytes
))
2065 *count
= inode
->i_sb
->s_maxbytes
- *pos
;
2069 if (bdev_read_only(I_BDEV(inode
)))
2071 isize
= i_size_read(inode
);
2072 if (*pos
>= isize
) {
2073 if (*count
|| *pos
> isize
)
2077 if (*pos
+ *count
> isize
)
2078 *count
= isize
- *pos
;
2085 EXPORT_SYMBOL(generic_write_checks
);
2087 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2088 loff_t pos
, unsigned len
, unsigned flags
,
2089 struct page
**pagep
, void **fsdata
)
2091 const struct address_space_operations
*aops
= mapping
->a_ops
;
2093 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2096 EXPORT_SYMBOL(pagecache_write_begin
);
2098 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2099 loff_t pos
, unsigned len
, unsigned copied
,
2100 struct page
*page
, void *fsdata
)
2102 const struct address_space_operations
*aops
= mapping
->a_ops
;
2104 mark_page_accessed(page
);
2105 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2107 EXPORT_SYMBOL(pagecache_write_end
);
2110 generic_file_direct_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2111 unsigned long *nr_segs
, loff_t pos
, loff_t
*ppos
,
2112 size_t count
, size_t ocount
)
2114 struct file
*file
= iocb
->ki_filp
;
2115 struct address_space
*mapping
= file
->f_mapping
;
2116 struct inode
*inode
= mapping
->host
;
2121 if (count
!= ocount
)
2122 *nr_segs
= iov_shorten((struct iovec
*)iov
, *nr_segs
, count
);
2124 write_len
= iov_length(iov
, *nr_segs
);
2125 end
= (pos
+ write_len
- 1) >> PAGE_CACHE_SHIFT
;
2127 written
= filemap_write_and_wait_range(mapping
, pos
, pos
+ write_len
- 1);
2132 * After a write we want buffered reads to be sure to go to disk to get
2133 * the new data. We invalidate clean cached page from the region we're
2134 * about to write. We do this *before* the write so that we can return
2135 * without clobbering -EIOCBQUEUED from ->direct_IO().
2137 if (mapping
->nrpages
) {
2138 written
= invalidate_inode_pages2_range(mapping
,
2139 pos
>> PAGE_CACHE_SHIFT
, end
);
2141 * If a page can not be invalidated, return 0 to fall back
2142 * to buffered write.
2145 if (written
== -EBUSY
)
2151 written
= mapping
->a_ops
->direct_IO(WRITE
, iocb
, iov
, pos
, *nr_segs
);
2154 * Finally, try again to invalidate clean pages which might have been
2155 * cached by non-direct readahead, or faulted in by get_user_pages()
2156 * if the source of the write was an mmap'ed region of the file
2157 * we're writing. Either one is a pretty crazy thing to do,
2158 * so we don't support it 100%. If this invalidation
2159 * fails, tough, the write still worked...
2161 if (mapping
->nrpages
) {
2162 invalidate_inode_pages2_range(mapping
,
2163 pos
>> PAGE_CACHE_SHIFT
, end
);
2167 loff_t end
= pos
+ written
;
2168 if (end
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2169 i_size_write(inode
, end
);
2170 mark_inode_dirty(inode
);
2177 EXPORT_SYMBOL(generic_file_direct_write
);
2180 * Find or create a page at the given pagecache position. Return the locked
2181 * page. This function is specifically for buffered writes.
2183 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2184 pgoff_t index
, unsigned flags
)
2188 gfp_t gfp_notmask
= 0;
2189 if (flags
& AOP_FLAG_NOFS
)
2190 gfp_notmask
= __GFP_FS
;
2192 page
= find_lock_page(mapping
, index
);
2196 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) & ~gfp_notmask
);
2199 status
= add_to_page_cache_lru(page
, mapping
, index
,
2200 GFP_KERNEL
& ~gfp_notmask
);
2201 if (unlikely(status
)) {
2202 page_cache_release(page
);
2203 if (status
== -EEXIST
)
2209 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2211 static ssize_t
generic_perform_write(struct file
*file
,
2212 struct iov_iter
*i
, loff_t pos
)
2214 struct address_space
*mapping
= file
->f_mapping
;
2215 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2217 ssize_t written
= 0;
2218 unsigned int flags
= 0;
2221 * Copies from kernel address space cannot fail (NFSD is a big user).
2223 if (segment_eq(get_fs(), KERNEL_DS
))
2224 flags
|= AOP_FLAG_UNINTERRUPTIBLE
;
2228 pgoff_t index
; /* Pagecache index for current page */
2229 unsigned long offset
; /* Offset into pagecache page */
2230 unsigned long bytes
; /* Bytes to write to page */
2231 size_t copied
; /* Bytes copied from user */
2234 offset
= (pos
& (PAGE_CACHE_SIZE
- 1));
2235 index
= pos
>> PAGE_CACHE_SHIFT
;
2236 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2242 * Bring in the user page that we will copy from _first_.
2243 * Otherwise there's a nasty deadlock on copying from the
2244 * same page as we're writing to, without it being marked
2247 * Not only is this an optimisation, but it is also required
2248 * to check that the address is actually valid, when atomic
2249 * usercopies are used, below.
2251 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2256 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2258 if (unlikely(status
))
2261 if (mapping_writably_mapped(mapping
))
2262 flush_dcache_page(page
);
2264 pagefault_disable();
2265 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2267 flush_dcache_page(page
);
2269 mark_page_accessed(page
);
2270 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2272 if (unlikely(status
< 0))
2278 iov_iter_advance(i
, copied
);
2279 if (unlikely(copied
== 0)) {
2281 * If we were unable to copy any data at all, we must
2282 * fall back to a single segment length write.
2284 * If we didn't fallback here, we could livelock
2285 * because not all segments in the iov can be copied at
2286 * once without a pagefault.
2288 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2289 iov_iter_single_seg_count(i
));
2295 balance_dirty_pages_ratelimited(mapping
);
2297 } while (iov_iter_count(i
));
2299 return written
? written
: status
;
2303 generic_file_buffered_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2304 unsigned long nr_segs
, loff_t pos
, loff_t
*ppos
,
2305 size_t count
, ssize_t written
)
2307 struct file
*file
= iocb
->ki_filp
;
2311 iov_iter_init(&i
, iov
, nr_segs
, count
, written
);
2312 status
= generic_perform_write(file
, &i
, pos
);
2314 if (likely(status
>= 0)) {
2316 *ppos
= pos
+ status
;
2319 return written
? written
: status
;
2321 EXPORT_SYMBOL(generic_file_buffered_write
);
2324 * __generic_file_aio_write - write data to a file
2325 * @iocb: IO state structure (file, offset, etc.)
2326 * @iov: vector with data to write
2327 * @nr_segs: number of segments in the vector
2328 * @ppos: position where to write
2330 * This function does all the work needed for actually writing data to a
2331 * file. It does all basic checks, removes SUID from the file, updates
2332 * modification times and calls proper subroutines depending on whether we
2333 * do direct IO or a standard buffered write.
2335 * It expects i_mutex to be grabbed unless we work on a block device or similar
2336 * object which does not need locking at all.
2338 * This function does *not* take care of syncing data in case of O_SYNC write.
2339 * A caller has to handle it. This is mainly due to the fact that we want to
2340 * avoid syncing under i_mutex.
2342 ssize_t
__generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2343 unsigned long nr_segs
, loff_t
*ppos
)
2345 struct file
*file
= iocb
->ki_filp
;
2346 struct address_space
* mapping
= file
->f_mapping
;
2347 size_t ocount
; /* original count */
2348 size_t count
; /* after file limit checks */
2349 struct inode
*inode
= mapping
->host
;
2355 err
= generic_segment_checks(iov
, &nr_segs
, &ocount
, VERIFY_READ
);
2362 vfs_check_frozen(inode
->i_sb
, SB_FREEZE_WRITE
);
2364 /* We can write back this queue in page reclaim */
2365 current
->backing_dev_info
= mapping
->backing_dev_info
;
2368 err
= generic_write_checks(file
, &pos
, &count
, S_ISBLK(inode
->i_mode
));
2375 err
= file_remove_suid(file
);
2379 file_update_time(file
);
2381 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2382 if (unlikely(file
->f_flags
& O_DIRECT
)) {
2384 ssize_t written_buffered
;
2386 written
= generic_file_direct_write(iocb
, iov
, &nr_segs
, pos
,
2387 ppos
, count
, ocount
);
2388 if (written
< 0 || written
== count
)
2391 * direct-io write to a hole: fall through to buffered I/O
2392 * for completing the rest of the request.
2396 written_buffered
= generic_file_buffered_write(iocb
, iov
,
2397 nr_segs
, pos
, ppos
, count
,
2400 * If generic_file_buffered_write() retuned a synchronous error
2401 * then we want to return the number of bytes which were
2402 * direct-written, or the error code if that was zero. Note
2403 * that this differs from normal direct-io semantics, which
2404 * will return -EFOO even if some bytes were written.
2406 if (written_buffered
< 0) {
2407 err
= written_buffered
;
2412 * We need to ensure that the page cache pages are written to
2413 * disk and invalidated to preserve the expected O_DIRECT
2416 endbyte
= pos
+ written_buffered
- written
- 1;
2417 err
= filemap_write_and_wait_range(file
->f_mapping
, pos
, endbyte
);
2419 written
= written_buffered
;
2420 invalidate_mapping_pages(mapping
,
2421 pos
>> PAGE_CACHE_SHIFT
,
2422 endbyte
>> PAGE_CACHE_SHIFT
);
2425 * We don't know how much we wrote, so just return
2426 * the number of bytes which were direct-written
2430 written
= generic_file_buffered_write(iocb
, iov
, nr_segs
,
2431 pos
, ppos
, count
, written
);
2434 current
->backing_dev_info
= NULL
;
2435 return written
? written
: err
;
2437 EXPORT_SYMBOL(__generic_file_aio_write
);
2440 * generic_file_aio_write - write data to a file
2441 * @iocb: IO state structure
2442 * @iov: vector with data to write
2443 * @nr_segs: number of segments in the vector
2444 * @pos: position in file where to write
2446 * This is a wrapper around __generic_file_aio_write() to be used by most
2447 * filesystems. It takes care of syncing the file in case of O_SYNC file
2448 * and acquires i_mutex as needed.
2450 ssize_t
generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2451 unsigned long nr_segs
, loff_t pos
)
2453 struct file
*file
= iocb
->ki_filp
;
2454 struct inode
*inode
= file
->f_mapping
->host
;
2457 BUG_ON(iocb
->ki_pos
!= pos
);
2459 mutex_lock(&inode
->i_mutex
);
2460 ret
= __generic_file_aio_write(iocb
, iov
, nr_segs
, &iocb
->ki_pos
);
2461 mutex_unlock(&inode
->i_mutex
);
2463 if (ret
> 0 || ret
== -EIOCBQUEUED
) {
2466 err
= generic_write_sync(file
, pos
, ret
);
2467 if (err
< 0 && ret
> 0)
2472 EXPORT_SYMBOL(generic_file_aio_write
);
2475 * try_to_release_page() - release old fs-specific metadata on a page
2477 * @page: the page which the kernel is trying to free
2478 * @gfp_mask: memory allocation flags (and I/O mode)
2480 * The address_space is to try to release any data against the page
2481 * (presumably at page->private). If the release was successful, return `1'.
2482 * Otherwise return zero.
2484 * This may also be called if PG_fscache is set on a page, indicating that the
2485 * page is known to the local caching routines.
2487 * The @gfp_mask argument specifies whether I/O may be performed to release
2488 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2491 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
2493 struct address_space
* const mapping
= page
->mapping
;
2495 BUG_ON(!PageLocked(page
));
2496 if (PageWriteback(page
))
2499 if (mapping
&& mapping
->a_ops
->releasepage
)
2500 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
2501 return try_to_free_buffers(page
);
2504 EXPORT_SYMBOL(try_to_release_page
);