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
);
154 EXPORT_SYMBOL(remove_from_page_cache
);
156 static int sync_page(void *word
)
158 struct address_space
*mapping
;
161 page
= container_of((unsigned long *)word
, struct page
, flags
);
164 * page_mapping() is being called without PG_locked held.
165 * Some knowledge of the state and use of the page is used to
166 * reduce the requirements down to a memory barrier.
167 * The danger here is of a stale page_mapping() return value
168 * indicating a struct address_space different from the one it's
169 * associated with when it is associated with one.
170 * After smp_mb(), it's either the correct page_mapping() for
171 * the page, or an old page_mapping() and the page's own
172 * page_mapping() has gone NULL.
173 * The ->sync_page() address_space operation must tolerate
174 * page_mapping() going NULL. By an amazing coincidence,
175 * this comes about because none of the users of the page
176 * in the ->sync_page() methods make essential use of the
177 * page_mapping(), merely passing the page down to the backing
178 * device's unplug functions when it's non-NULL, which in turn
179 * ignore it for all cases but swap, where only page_private(page) is
180 * of interest. When page_mapping() does go NULL, the entire
181 * call stack gracefully ignores the page and returns.
185 mapping
= page_mapping(page
);
186 if (mapping
&& mapping
->a_ops
&& mapping
->a_ops
->sync_page
)
187 mapping
->a_ops
->sync_page(page
);
192 static int sync_page_killable(void *word
)
195 return fatal_signal_pending(current
) ? -EINTR
: 0;
199 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
200 * @mapping: address space structure to write
201 * @start: offset in bytes where the range starts
202 * @end: offset in bytes where the range ends (inclusive)
203 * @sync_mode: enable synchronous operation
205 * Start writeback against all of a mapping's dirty pages that lie
206 * within the byte offsets <start, end> inclusive.
208 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
209 * opposed to a regular memory cleansing writeback. The difference between
210 * these two operations is that if a dirty page/buffer is encountered, it must
211 * be waited upon, and not just skipped over.
213 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
214 loff_t end
, int sync_mode
)
217 struct writeback_control wbc
= {
218 .sync_mode
= sync_mode
,
219 .nr_to_write
= LONG_MAX
,
220 .range_start
= start
,
224 if (!mapping_cap_writeback_dirty(mapping
))
227 ret
= do_writepages(mapping
, &wbc
);
231 static inline int __filemap_fdatawrite(struct address_space
*mapping
,
234 return __filemap_fdatawrite_range(mapping
, 0, LLONG_MAX
, sync_mode
);
237 int filemap_fdatawrite(struct address_space
*mapping
)
239 return __filemap_fdatawrite(mapping
, WB_SYNC_ALL
);
241 EXPORT_SYMBOL(filemap_fdatawrite
);
243 int filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
246 return __filemap_fdatawrite_range(mapping
, start
, end
, WB_SYNC_ALL
);
248 EXPORT_SYMBOL(filemap_fdatawrite_range
);
251 * filemap_flush - mostly a non-blocking flush
252 * @mapping: target address_space
254 * This is a mostly non-blocking flush. Not suitable for data-integrity
255 * purposes - I/O may not be started against all dirty pages.
257 int filemap_flush(struct address_space
*mapping
)
259 return __filemap_fdatawrite(mapping
, WB_SYNC_NONE
);
261 EXPORT_SYMBOL(filemap_flush
);
264 * filemap_fdatawait_range - wait for writeback to complete
265 * @mapping: address space structure to wait for
266 * @start_byte: offset in bytes where the range starts
267 * @end_byte: offset in bytes where the range ends (inclusive)
269 * Walk the list of under-writeback pages of the given address space
270 * in the given range and wait for all of them.
272 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
275 pgoff_t index
= start_byte
>> PAGE_CACHE_SHIFT
;
276 pgoff_t end
= end_byte
>> PAGE_CACHE_SHIFT
;
281 if (end_byte
< start_byte
)
284 pagevec_init(&pvec
, 0);
285 while ((index
<= end
) &&
286 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
287 PAGECACHE_TAG_WRITEBACK
,
288 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
291 for (i
= 0; i
< nr_pages
; i
++) {
292 struct page
*page
= pvec
.pages
[i
];
294 /* until radix tree lookup accepts end_index */
295 if (page
->index
> end
)
298 wait_on_page_writeback(page
);
302 pagevec_release(&pvec
);
306 /* Check for outstanding write errors */
307 if (test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
309 if (test_and_clear_bit(AS_EIO
, &mapping
->flags
))
314 EXPORT_SYMBOL(filemap_fdatawait_range
);
317 * filemap_fdatawait - wait for all under-writeback pages to complete
318 * @mapping: address space structure to wait for
320 * Walk the list of under-writeback pages of the given address space
321 * and wait for all of them.
323 int filemap_fdatawait(struct address_space
*mapping
)
325 loff_t i_size
= i_size_read(mapping
->host
);
330 return filemap_fdatawait_range(mapping
, 0, i_size
- 1);
332 EXPORT_SYMBOL(filemap_fdatawait
);
334 int filemap_write_and_wait(struct address_space
*mapping
)
338 if (mapping
->nrpages
) {
339 err
= filemap_fdatawrite(mapping
);
341 * Even if the above returned error, the pages may be
342 * written partially (e.g. -ENOSPC), so we wait for it.
343 * But the -EIO is special case, it may indicate the worst
344 * thing (e.g. bug) happened, so we avoid waiting for it.
347 int err2
= filemap_fdatawait(mapping
);
354 EXPORT_SYMBOL(filemap_write_and_wait
);
357 * filemap_write_and_wait_range - write out & wait on a file range
358 * @mapping: the address_space for the pages
359 * @lstart: offset in bytes where the range starts
360 * @lend: offset in bytes where the range ends (inclusive)
362 * Write out and wait upon file offsets lstart->lend, inclusive.
364 * Note that `lend' is inclusive (describes the last byte to be written) so
365 * that this function can be used to write to the very end-of-file (end = -1).
367 int filemap_write_and_wait_range(struct address_space
*mapping
,
368 loff_t lstart
, loff_t lend
)
372 if (mapping
->nrpages
) {
373 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
375 /* See comment of filemap_write_and_wait() */
377 int err2
= filemap_fdatawait_range(mapping
,
385 EXPORT_SYMBOL(filemap_write_and_wait_range
);
388 * add_to_page_cache_locked - add a locked page to the pagecache
390 * @mapping: the page's address_space
391 * @offset: page index
392 * @gfp_mask: page allocation mode
394 * This function is used to add a page to the pagecache. It must be locked.
395 * This function does not add the page to the LRU. The caller must do that.
397 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
398 pgoff_t offset
, gfp_t gfp_mask
)
402 VM_BUG_ON(!PageLocked(page
));
404 error
= mem_cgroup_cache_charge(page
, current
->mm
,
405 gfp_mask
& GFP_RECLAIM_MASK
);
409 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
411 page_cache_get(page
);
412 page
->mapping
= mapping
;
413 page
->index
= offset
;
415 spin_lock_irq(&mapping
->tree_lock
);
416 error
= radix_tree_insert(&mapping
->page_tree
, offset
, page
);
417 if (likely(!error
)) {
419 __inc_zone_page_state(page
, NR_FILE_PAGES
);
420 if (PageSwapBacked(page
))
421 __inc_zone_page_state(page
, NR_SHMEM
);
422 spin_unlock_irq(&mapping
->tree_lock
);
424 page
->mapping
= NULL
;
425 spin_unlock_irq(&mapping
->tree_lock
);
426 mem_cgroup_uncharge_cache_page(page
);
427 page_cache_release(page
);
429 radix_tree_preload_end();
431 mem_cgroup_uncharge_cache_page(page
);
435 EXPORT_SYMBOL(add_to_page_cache_locked
);
437 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
438 pgoff_t offset
, gfp_t gfp_mask
)
443 * Splice_read and readahead add shmem/tmpfs pages into the page cache
444 * before shmem_readpage has a chance to mark them as SwapBacked: they
445 * need to go on the active_anon lru below, and mem_cgroup_cache_charge
446 * (called in add_to_page_cache) needs to know where they're going too.
448 if (mapping_cap_swap_backed(mapping
))
449 SetPageSwapBacked(page
);
451 ret
= add_to_page_cache(page
, mapping
, offset
, gfp_mask
);
453 if (page_is_file_cache(page
))
454 lru_cache_add_file(page
);
456 lru_cache_add_active_anon(page
);
460 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
463 struct page
*__page_cache_alloc(gfp_t gfp
)
465 if (cpuset_do_page_mem_spread()) {
466 int n
= cpuset_mem_spread_node();
467 return alloc_pages_exact_node(n
, gfp
, 0);
469 return alloc_pages(gfp
, 0);
471 EXPORT_SYMBOL(__page_cache_alloc
);
474 static int __sleep_on_page_lock(void *word
)
481 * In order to wait for pages to become available there must be
482 * waitqueues associated with pages. By using a hash table of
483 * waitqueues where the bucket discipline is to maintain all
484 * waiters on the same queue and wake all when any of the pages
485 * become available, and for the woken contexts to check to be
486 * sure the appropriate page became available, this saves space
487 * at a cost of "thundering herd" phenomena during rare hash
490 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
492 const struct zone
*zone
= page_zone(page
);
494 return &zone
->wait_table
[hash_ptr(page
, zone
->wait_table_bits
)];
497 static inline void wake_up_page(struct page
*page
, int bit
)
499 __wake_up_bit(page_waitqueue(page
), &page
->flags
, bit
);
502 void wait_on_page_bit(struct page
*page
, int bit_nr
)
504 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
506 if (test_bit(bit_nr
, &page
->flags
))
507 __wait_on_bit(page_waitqueue(page
), &wait
, sync_page
,
508 TASK_UNINTERRUPTIBLE
);
510 EXPORT_SYMBOL(wait_on_page_bit
);
513 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
514 * @page: Page defining the wait queue of interest
515 * @waiter: Waiter to add to the queue
517 * Add an arbitrary @waiter to the wait queue for the nominated @page.
519 void add_page_wait_queue(struct page
*page
, wait_queue_t
*waiter
)
521 wait_queue_head_t
*q
= page_waitqueue(page
);
524 spin_lock_irqsave(&q
->lock
, flags
);
525 __add_wait_queue(q
, waiter
);
526 spin_unlock_irqrestore(&q
->lock
, flags
);
528 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
531 * unlock_page - unlock a locked page
534 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
535 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
536 * mechananism between PageLocked pages and PageWriteback pages is shared.
537 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
539 * The mb is necessary to enforce ordering between the clear_bit and the read
540 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
542 void unlock_page(struct page
*page
)
544 VM_BUG_ON(!PageLocked(page
));
545 clear_bit_unlock(PG_locked
, &page
->flags
);
546 smp_mb__after_clear_bit();
547 wake_up_page(page
, PG_locked
);
549 EXPORT_SYMBOL(unlock_page
);
552 * end_page_writeback - end writeback against a page
555 void end_page_writeback(struct page
*page
)
557 if (TestClearPageReclaim(page
))
558 rotate_reclaimable_page(page
);
560 if (!test_clear_page_writeback(page
))
563 smp_mb__after_clear_bit();
564 wake_up_page(page
, PG_writeback
);
566 EXPORT_SYMBOL(end_page_writeback
);
569 * __lock_page - get a lock on the page, assuming we need to sleep to get it
570 * @page: the page to lock
572 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some
573 * random driver's requestfn sets TASK_RUNNING, we could busywait. However
574 * chances are that on the second loop, the block layer's plug list is empty,
575 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
577 void __lock_page(struct page
*page
)
579 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
581 __wait_on_bit_lock(page_waitqueue(page
), &wait
, sync_page
,
582 TASK_UNINTERRUPTIBLE
);
584 EXPORT_SYMBOL(__lock_page
);
586 int __lock_page_killable(struct page
*page
)
588 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
590 return __wait_on_bit_lock(page_waitqueue(page
), &wait
,
591 sync_page_killable
, TASK_KILLABLE
);
593 EXPORT_SYMBOL_GPL(__lock_page_killable
);
596 * __lock_page_nosync - get a lock on the page, without calling sync_page()
597 * @page: the page to lock
599 * Variant of lock_page that does not require the caller to hold a reference
600 * on the page's mapping.
602 void __lock_page_nosync(struct page
*page
)
604 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
605 __wait_on_bit_lock(page_waitqueue(page
), &wait
, __sleep_on_page_lock
,
606 TASK_UNINTERRUPTIBLE
);
610 * find_get_page - find and get a page reference
611 * @mapping: the address_space to search
612 * @offset: the page index
614 * Is there a pagecache struct page at the given (mapping, offset) tuple?
615 * If yes, increment its refcount and return it; if no, return NULL.
617 struct page
*find_get_page(struct address_space
*mapping
, pgoff_t offset
)
625 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
627 page
= radix_tree_deref_slot(pagep
);
628 if (unlikely(!page
|| page
== RADIX_TREE_RETRY
))
631 if (!page_cache_get_speculative(page
))
635 * Has the page moved?
636 * This is part of the lockless pagecache protocol. See
637 * include/linux/pagemap.h for details.
639 if (unlikely(page
!= *pagep
)) {
640 page_cache_release(page
);
648 EXPORT_SYMBOL(find_get_page
);
651 * find_lock_page - locate, pin and lock a pagecache page
652 * @mapping: the address_space to search
653 * @offset: the page index
655 * Locates the desired pagecache page, locks it, increments its reference
656 * count and returns its address.
658 * Returns zero if the page was not present. find_lock_page() may sleep.
660 struct page
*find_lock_page(struct address_space
*mapping
, pgoff_t offset
)
665 page
= find_get_page(mapping
, offset
);
668 /* Has the page been truncated? */
669 if (unlikely(page
->mapping
!= mapping
)) {
671 page_cache_release(page
);
674 VM_BUG_ON(page
->index
!= offset
);
678 EXPORT_SYMBOL(find_lock_page
);
681 * find_or_create_page - locate or add a pagecache page
682 * @mapping: the page's address_space
683 * @index: the page's index into the mapping
684 * @gfp_mask: page allocation mode
686 * Locates a page in the pagecache. If the page is not present, a new page
687 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
688 * LRU list. The returned page is locked and has its reference count
691 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
694 * find_or_create_page() returns the desired page's address, or zero on
697 struct page
*find_or_create_page(struct address_space
*mapping
,
698 pgoff_t index
, gfp_t gfp_mask
)
703 page
= find_lock_page(mapping
, index
);
705 page
= __page_cache_alloc(gfp_mask
);
709 * We want a regular kernel memory (not highmem or DMA etc)
710 * allocation for the radix tree nodes, but we need to honour
711 * the context-specific requirements the caller has asked for.
712 * GFP_RECLAIM_MASK collects those requirements.
714 err
= add_to_page_cache_lru(page
, mapping
, index
,
715 (gfp_mask
& GFP_RECLAIM_MASK
));
717 page_cache_release(page
);
725 EXPORT_SYMBOL(find_or_create_page
);
728 * find_get_pages - gang pagecache lookup
729 * @mapping: The address_space to search
730 * @start: The starting page index
731 * @nr_pages: The maximum number of pages
732 * @pages: Where the resulting pages are placed
734 * find_get_pages() will search for and return a group of up to
735 * @nr_pages pages in the mapping. The pages are placed at @pages.
736 * find_get_pages() takes a reference against the returned pages.
738 * The search returns a group of mapping-contiguous pages with ascending
739 * indexes. There may be holes in the indices due to not-present pages.
741 * find_get_pages() returns the number of pages which were found.
743 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
744 unsigned int nr_pages
, struct page
**pages
)
748 unsigned int nr_found
;
752 nr_found
= radix_tree_gang_lookup_slot(&mapping
->page_tree
,
753 (void ***)pages
, start
, nr_pages
);
755 for (i
= 0; i
< nr_found
; i
++) {
758 page
= radix_tree_deref_slot((void **)pages
[i
]);
762 * this can only trigger if nr_found == 1, making livelock
765 if (unlikely(page
== RADIX_TREE_RETRY
))
768 if (!page_cache_get_speculative(page
))
771 /* Has the page moved? */
772 if (unlikely(page
!= *((void **)pages
[i
]))) {
773 page_cache_release(page
);
785 * find_get_pages_contig - gang contiguous pagecache lookup
786 * @mapping: The address_space to search
787 * @index: The starting page index
788 * @nr_pages: The maximum number of pages
789 * @pages: Where the resulting pages are placed
791 * find_get_pages_contig() works exactly like find_get_pages(), except
792 * that the returned number of pages are guaranteed to be contiguous.
794 * find_get_pages_contig() returns the number of pages which were found.
796 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
797 unsigned int nr_pages
, struct page
**pages
)
801 unsigned int nr_found
;
805 nr_found
= radix_tree_gang_lookup_slot(&mapping
->page_tree
,
806 (void ***)pages
, index
, nr_pages
);
808 for (i
= 0; i
< nr_found
; i
++) {
811 page
= radix_tree_deref_slot((void **)pages
[i
]);
815 * this can only trigger if nr_found == 1, making livelock
818 if (unlikely(page
== RADIX_TREE_RETRY
))
821 if (page
->mapping
== NULL
|| page
->index
!= index
)
824 if (!page_cache_get_speculative(page
))
827 /* Has the page moved? */
828 if (unlikely(page
!= *((void **)pages
[i
]))) {
829 page_cache_release(page
);
840 EXPORT_SYMBOL(find_get_pages_contig
);
843 * find_get_pages_tag - find and return pages that match @tag
844 * @mapping: the address_space to search
845 * @index: the starting page index
846 * @tag: the tag index
847 * @nr_pages: the maximum number of pages
848 * @pages: where the resulting pages are placed
850 * Like find_get_pages, except we only return pages which are tagged with
851 * @tag. We update @index to index the next page for the traversal.
853 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
854 int tag
, unsigned int nr_pages
, struct page
**pages
)
858 unsigned int nr_found
;
862 nr_found
= radix_tree_gang_lookup_tag_slot(&mapping
->page_tree
,
863 (void ***)pages
, *index
, nr_pages
, tag
);
865 for (i
= 0; i
< nr_found
; i
++) {
868 page
= radix_tree_deref_slot((void **)pages
[i
]);
872 * this can only trigger if nr_found == 1, making livelock
875 if (unlikely(page
== RADIX_TREE_RETRY
))
878 if (!page_cache_get_speculative(page
))
881 /* Has the page moved? */
882 if (unlikely(page
!= *((void **)pages
[i
]))) {
883 page_cache_release(page
);
893 *index
= pages
[ret
- 1]->index
+ 1;
897 EXPORT_SYMBOL(find_get_pages_tag
);
900 * grab_cache_page_nowait - returns locked page at given index in given cache
901 * @mapping: target address_space
902 * @index: the page index
904 * Same as grab_cache_page(), but do not wait if the page is unavailable.
905 * This is intended for speculative data generators, where the data can
906 * be regenerated if the page couldn't be grabbed. This routine should
907 * be safe to call while holding the lock for another page.
909 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
910 * and deadlock against the caller's locked page.
913 grab_cache_page_nowait(struct address_space
*mapping
, pgoff_t index
)
915 struct page
*page
= find_get_page(mapping
, index
);
918 if (trylock_page(page
))
920 page_cache_release(page
);
923 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) & ~__GFP_FS
);
924 if (page
&& add_to_page_cache_lru(page
, mapping
, index
, GFP_NOFS
)) {
925 page_cache_release(page
);
930 EXPORT_SYMBOL(grab_cache_page_nowait
);
933 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
934 * a _large_ part of the i/o request. Imagine the worst scenario:
936 * ---R__________________________________________B__________
937 * ^ reading here ^ bad block(assume 4k)
939 * read(R) => miss => readahead(R...B) => media error => frustrating retries
940 * => failing the whole request => read(R) => read(R+1) =>
941 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
942 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
943 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
945 * It is going insane. Fix it by quickly scaling down the readahead size.
947 static void shrink_readahead_size_eio(struct file
*filp
,
948 struct file_ra_state
*ra
)
954 * do_generic_file_read - generic file read routine
955 * @filp: the file to read
956 * @ppos: current file position
957 * @desc: read_descriptor
958 * @actor: read method
960 * This is a generic file read routine, and uses the
961 * mapping->a_ops->readpage() function for the actual low-level stuff.
963 * This is really ugly. But the goto's actually try to clarify some
964 * of the logic when it comes to error handling etc.
966 static void do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
967 read_descriptor_t
*desc
, read_actor_t actor
)
969 struct address_space
*mapping
= filp
->f_mapping
;
970 struct inode
*inode
= mapping
->host
;
971 struct file_ra_state
*ra
= &filp
->f_ra
;
975 unsigned long offset
; /* offset into pagecache page */
976 unsigned int prev_offset
;
979 index
= *ppos
>> PAGE_CACHE_SHIFT
;
980 prev_index
= ra
->prev_pos
>> PAGE_CACHE_SHIFT
;
981 prev_offset
= ra
->prev_pos
& (PAGE_CACHE_SIZE
-1);
982 last_index
= (*ppos
+ desc
->count
+ PAGE_CACHE_SIZE
-1) >> PAGE_CACHE_SHIFT
;
983 offset
= *ppos
& ~PAGE_CACHE_MASK
;
989 unsigned long nr
, ret
;
993 page
= find_get_page(mapping
, index
);
995 page_cache_sync_readahead(mapping
,
997 index
, last_index
- index
);
998 page
= find_get_page(mapping
, index
);
999 if (unlikely(page
== NULL
))
1000 goto no_cached_page
;
1002 if (PageReadahead(page
)) {
1003 page_cache_async_readahead(mapping
,
1005 index
, last_index
- index
);
1007 if (!PageUptodate(page
)) {
1008 if (inode
->i_blkbits
== PAGE_CACHE_SHIFT
||
1009 !mapping
->a_ops
->is_partially_uptodate
)
1010 goto page_not_up_to_date
;
1011 if (!trylock_page(page
))
1012 goto page_not_up_to_date
;
1013 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1015 goto page_not_up_to_date_locked
;
1020 * i_size must be checked after we know the page is Uptodate.
1022 * Checking i_size after the check allows us to calculate
1023 * the correct value for "nr", which means the zero-filled
1024 * part of the page is not copied back to userspace (unless
1025 * another truncate extends the file - this is desired though).
1028 isize
= i_size_read(inode
);
1029 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
1030 if (unlikely(!isize
|| index
> end_index
)) {
1031 page_cache_release(page
);
1035 /* nr is the maximum number of bytes to copy from this page */
1036 nr
= PAGE_CACHE_SIZE
;
1037 if (index
== end_index
) {
1038 nr
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
1040 page_cache_release(page
);
1046 /* If users can be writing to this page using arbitrary
1047 * virtual addresses, take care about potential aliasing
1048 * before reading the page on the kernel side.
1050 if (mapping_writably_mapped(mapping
))
1051 flush_dcache_page(page
);
1054 * When a sequential read accesses a page several times,
1055 * only mark it as accessed the first time.
1057 if (prev_index
!= index
|| offset
!= prev_offset
)
1058 mark_page_accessed(page
);
1062 * Ok, we have the page, and it's up-to-date, so
1063 * now we can copy it to user space...
1065 * The actor routine returns how many bytes were actually used..
1066 * NOTE! This may not be the same as how much of a user buffer
1067 * we filled up (we may be padding etc), so we can only update
1068 * "pos" here (the actor routine has to update the user buffer
1069 * pointers and the remaining count).
1071 ret
= actor(desc
, page
, offset
, nr
);
1073 index
+= offset
>> PAGE_CACHE_SHIFT
;
1074 offset
&= ~PAGE_CACHE_MASK
;
1075 prev_offset
= offset
;
1077 page_cache_release(page
);
1078 if (ret
== nr
&& desc
->count
)
1082 page_not_up_to_date
:
1083 /* Get exclusive access to the page ... */
1084 error
= lock_page_killable(page
);
1085 if (unlikely(error
))
1086 goto readpage_error
;
1088 page_not_up_to_date_locked
:
1089 /* Did it get truncated before we got the lock? */
1090 if (!page
->mapping
) {
1092 page_cache_release(page
);
1096 /* Did somebody else fill it already? */
1097 if (PageUptodate(page
)) {
1103 /* Start the actual read. The read will unlock the page. */
1104 error
= mapping
->a_ops
->readpage(filp
, page
);
1106 if (unlikely(error
)) {
1107 if (error
== AOP_TRUNCATED_PAGE
) {
1108 page_cache_release(page
);
1111 goto readpage_error
;
1114 if (!PageUptodate(page
)) {
1115 error
= lock_page_killable(page
);
1116 if (unlikely(error
))
1117 goto readpage_error
;
1118 if (!PageUptodate(page
)) {
1119 if (page
->mapping
== NULL
) {
1121 * invalidate_mapping_pages got it
1124 page_cache_release(page
);
1128 shrink_readahead_size_eio(filp
, ra
);
1130 goto readpage_error
;
1138 /* UHHUH! A synchronous read error occurred. Report it */
1139 desc
->error
= error
;
1140 page_cache_release(page
);
1145 * Ok, it wasn't cached, so we need to create a new
1148 page
= page_cache_alloc_cold(mapping
);
1150 desc
->error
= -ENOMEM
;
1153 error
= add_to_page_cache_lru(page
, mapping
,
1156 page_cache_release(page
);
1157 if (error
== -EEXIST
)
1159 desc
->error
= error
;
1166 ra
->prev_pos
= prev_index
;
1167 ra
->prev_pos
<<= PAGE_CACHE_SHIFT
;
1168 ra
->prev_pos
|= prev_offset
;
1170 *ppos
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
) + offset
;
1171 file_accessed(filp
);
1174 int file_read_actor(read_descriptor_t
*desc
, struct page
*page
,
1175 unsigned long offset
, unsigned long size
)
1178 unsigned long left
, count
= desc
->count
;
1184 * Faults on the destination of a read are common, so do it before
1187 if (!fault_in_pages_writeable(desc
->arg
.buf
, size
)) {
1188 kaddr
= kmap_atomic(page
, KM_USER0
);
1189 left
= __copy_to_user_inatomic(desc
->arg
.buf
,
1190 kaddr
+ offset
, size
);
1191 kunmap_atomic(kaddr
, KM_USER0
);
1196 /* Do it the slow way */
1198 left
= __copy_to_user(desc
->arg
.buf
, kaddr
+ offset
, size
);
1203 desc
->error
= -EFAULT
;
1206 desc
->count
= count
- size
;
1207 desc
->written
+= size
;
1208 desc
->arg
.buf
+= size
;
1213 * Performs necessary checks before doing a write
1214 * @iov: io vector request
1215 * @nr_segs: number of segments in the iovec
1216 * @count: number of bytes to write
1217 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1219 * Adjust number of segments and amount of bytes to write (nr_segs should be
1220 * properly initialized first). Returns appropriate error code that caller
1221 * should return or zero in case that write should be allowed.
1223 int generic_segment_checks(const struct iovec
*iov
,
1224 unsigned long *nr_segs
, size_t *count
, int access_flags
)
1228 for (seg
= 0; seg
< *nr_segs
; seg
++) {
1229 const struct iovec
*iv
= &iov
[seg
];
1232 * If any segment has a negative length, or the cumulative
1233 * length ever wraps negative then return -EINVAL.
1236 if (unlikely((ssize_t
)(cnt
|iv
->iov_len
) < 0))
1238 if (access_ok(access_flags
, iv
->iov_base
, iv
->iov_len
))
1243 cnt
-= iv
->iov_len
; /* This segment is no good */
1249 EXPORT_SYMBOL(generic_segment_checks
);
1252 * generic_file_aio_read - generic filesystem read routine
1253 * @iocb: kernel I/O control block
1254 * @iov: io vector request
1255 * @nr_segs: number of segments in the iovec
1256 * @pos: current file position
1258 * This is the "read()" routine for all filesystems
1259 * that can use the page cache directly.
1262 generic_file_aio_read(struct kiocb
*iocb
, const struct iovec
*iov
,
1263 unsigned long nr_segs
, loff_t pos
)
1265 struct file
*filp
= iocb
->ki_filp
;
1269 loff_t
*ppos
= &iocb
->ki_pos
;
1272 retval
= generic_segment_checks(iov
, &nr_segs
, &count
, VERIFY_WRITE
);
1276 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1277 if (filp
->f_flags
& O_DIRECT
) {
1279 struct address_space
*mapping
;
1280 struct inode
*inode
;
1282 mapping
= filp
->f_mapping
;
1283 inode
= mapping
->host
;
1285 goto out
; /* skip atime */
1286 size
= i_size_read(inode
);
1288 retval
= filemap_write_and_wait_range(mapping
, pos
,
1289 pos
+ iov_length(iov
, nr_segs
) - 1);
1291 retval
= mapping
->a_ops
->direct_IO(READ
, iocb
,
1295 *ppos
= pos
+ retval
;
1297 file_accessed(filp
);
1303 for (seg
= 0; seg
< nr_segs
; seg
++) {
1304 read_descriptor_t desc
;
1307 desc
.arg
.buf
= iov
[seg
].iov_base
;
1308 desc
.count
= iov
[seg
].iov_len
;
1309 if (desc
.count
== 0)
1312 do_generic_file_read(filp
, ppos
, &desc
, file_read_actor
);
1313 retval
+= desc
.written
;
1315 retval
= retval
?: desc
.error
;
1324 EXPORT_SYMBOL(generic_file_aio_read
);
1327 do_readahead(struct address_space
*mapping
, struct file
*filp
,
1328 pgoff_t index
, unsigned long nr
)
1330 if (!mapping
|| !mapping
->a_ops
|| !mapping
->a_ops
->readpage
)
1333 force_page_cache_readahead(mapping
, filp
, index
, nr
);
1337 SYSCALL_DEFINE(readahead
)(int fd
, loff_t offset
, size_t count
)
1345 if (file
->f_mode
& FMODE_READ
) {
1346 struct address_space
*mapping
= file
->f_mapping
;
1347 pgoff_t start
= offset
>> PAGE_CACHE_SHIFT
;
1348 pgoff_t end
= (offset
+ count
- 1) >> PAGE_CACHE_SHIFT
;
1349 unsigned long len
= end
- start
+ 1;
1350 ret
= do_readahead(mapping
, file
, start
, len
);
1356 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1357 asmlinkage
long SyS_readahead(long fd
, loff_t offset
, long count
)
1359 return SYSC_readahead((int) fd
, offset
, (size_t) count
);
1361 SYSCALL_ALIAS(sys_readahead
, SyS_readahead
);
1366 * page_cache_read - adds requested page to the page cache if not already there
1367 * @file: file to read
1368 * @offset: page index
1370 * This adds the requested page to the page cache if it isn't already there,
1371 * and schedules an I/O to read in its contents from disk.
1373 static int page_cache_read(struct file
*file
, pgoff_t offset
)
1375 struct address_space
*mapping
= file
->f_mapping
;
1380 page
= page_cache_alloc_cold(mapping
);
1384 ret
= add_to_page_cache_lru(page
, mapping
, offset
, GFP_KERNEL
);
1386 ret
= mapping
->a_ops
->readpage(file
, page
);
1387 else if (ret
== -EEXIST
)
1388 ret
= 0; /* losing race to add is OK */
1390 page_cache_release(page
);
1392 } while (ret
== AOP_TRUNCATED_PAGE
);
1397 #define MMAP_LOTSAMISS (100)
1400 * Synchronous readahead happens when we don't even find
1401 * a page in the page cache at all.
1403 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
1404 struct file_ra_state
*ra
,
1408 unsigned long ra_pages
;
1409 struct address_space
*mapping
= file
->f_mapping
;
1411 /* If we don't want any read-ahead, don't bother */
1412 if (VM_RandomReadHint(vma
))
1415 if (VM_SequentialReadHint(vma
) ||
1416 offset
- 1 == (ra
->prev_pos
>> PAGE_CACHE_SHIFT
)) {
1417 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
1422 if (ra
->mmap_miss
< INT_MAX
)
1426 * Do we miss much more than hit in this file? If so,
1427 * stop bothering with read-ahead. It will only hurt.
1429 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
1435 ra_pages
= max_sane_readahead(ra
->ra_pages
);
1437 ra
->start
= max_t(long, 0, offset
- ra_pages
/2);
1438 ra
->size
= ra_pages
;
1440 ra_submit(ra
, mapping
, file
);
1445 * Asynchronous readahead happens when we find the page and PG_readahead,
1446 * so we want to possibly extend the readahead further..
1448 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
1449 struct file_ra_state
*ra
,
1454 struct address_space
*mapping
= file
->f_mapping
;
1456 /* If we don't want any read-ahead, don't bother */
1457 if (VM_RandomReadHint(vma
))
1459 if (ra
->mmap_miss
> 0)
1461 if (PageReadahead(page
))
1462 page_cache_async_readahead(mapping
, ra
, file
,
1463 page
, offset
, ra
->ra_pages
);
1467 * filemap_fault - read in file data for page fault handling
1468 * @vma: vma in which the fault was taken
1469 * @vmf: struct vm_fault containing details of the fault
1471 * filemap_fault() is invoked via the vma operations vector for a
1472 * mapped memory region to read in file data during a page fault.
1474 * The goto's are kind of ugly, but this streamlines the normal case of having
1475 * it in the page cache, and handles the special cases reasonably without
1476 * having a lot of duplicated code.
1478 int filemap_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1481 struct file
*file
= vma
->vm_file
;
1482 struct address_space
*mapping
= file
->f_mapping
;
1483 struct file_ra_state
*ra
= &file
->f_ra
;
1484 struct inode
*inode
= mapping
->host
;
1485 pgoff_t offset
= vmf
->pgoff
;
1490 size
= (i_size_read(inode
) + PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
1492 return VM_FAULT_SIGBUS
;
1495 * Do we have something in the page cache already?
1497 page
= find_get_page(mapping
, offset
);
1500 * We found the page, so try async readahead before
1501 * waiting for the lock.
1503 do_async_mmap_readahead(vma
, ra
, file
, page
, offset
);
1506 /* Did it get truncated? */
1507 if (unlikely(page
->mapping
!= mapping
)) {
1510 goto no_cached_page
;
1513 /* No page in the page cache at all */
1514 do_sync_mmap_readahead(vma
, ra
, file
, offset
);
1515 count_vm_event(PGMAJFAULT
);
1516 ret
= VM_FAULT_MAJOR
;
1518 page
= find_lock_page(mapping
, offset
);
1520 goto no_cached_page
;
1524 * We have a locked page in the page cache, now we need to check
1525 * that it's up-to-date. If not, it is going to be due to an error.
1527 if (unlikely(!PageUptodate(page
)))
1528 goto page_not_uptodate
;
1531 * Found the page and have a reference on it.
1532 * We must recheck i_size under page lock.
1534 size
= (i_size_read(inode
) + PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
1535 if (unlikely(offset
>= size
)) {
1537 page_cache_release(page
);
1538 return VM_FAULT_SIGBUS
;
1541 ra
->prev_pos
= (loff_t
)offset
<< PAGE_CACHE_SHIFT
;
1543 return ret
| VM_FAULT_LOCKED
;
1547 * We're only likely to ever get here if MADV_RANDOM is in
1550 error
= page_cache_read(file
, offset
);
1553 * The page we want has now been added to the page cache.
1554 * In the unlikely event that someone removed it in the
1555 * meantime, we'll just come back here and read it again.
1561 * An error return from page_cache_read can result if the
1562 * system is low on memory, or a problem occurs while trying
1565 if (error
== -ENOMEM
)
1566 return VM_FAULT_OOM
;
1567 return VM_FAULT_SIGBUS
;
1571 * Umm, take care of errors if the page isn't up-to-date.
1572 * Try to re-read it _once_. We do this synchronously,
1573 * because there really aren't any performance issues here
1574 * and we need to check for errors.
1576 ClearPageError(page
);
1577 error
= mapping
->a_ops
->readpage(file
, page
);
1579 wait_on_page_locked(page
);
1580 if (!PageUptodate(page
))
1583 page_cache_release(page
);
1585 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
1588 /* Things didn't work out. Return zero to tell the mm layer so. */
1589 shrink_readahead_size_eio(file
, ra
);
1590 return VM_FAULT_SIGBUS
;
1592 EXPORT_SYMBOL(filemap_fault
);
1594 const struct vm_operations_struct generic_file_vm_ops
= {
1595 .fault
= filemap_fault
,
1598 /* This is used for a general mmap of a disk file */
1600 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1602 struct address_space
*mapping
= file
->f_mapping
;
1604 if (!mapping
->a_ops
->readpage
)
1606 file_accessed(file
);
1607 vma
->vm_ops
= &generic_file_vm_ops
;
1608 vma
->vm_flags
|= VM_CAN_NONLINEAR
;
1613 * This is for filesystems which do not implement ->writepage.
1615 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
1617 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
1619 return generic_file_mmap(file
, vma
);
1622 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1626 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1630 #endif /* CONFIG_MMU */
1632 EXPORT_SYMBOL(generic_file_mmap
);
1633 EXPORT_SYMBOL(generic_file_readonly_mmap
);
1635 static struct page
*__read_cache_page(struct address_space
*mapping
,
1637 int (*filler
)(void *,struct page
*),
1644 page
= find_get_page(mapping
, index
);
1646 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
1648 return ERR_PTR(-ENOMEM
);
1649 err
= add_to_page_cache_lru(page
, mapping
, index
, GFP_KERNEL
);
1650 if (unlikely(err
)) {
1651 page_cache_release(page
);
1654 /* Presumably ENOMEM for radix tree node */
1655 return ERR_PTR(err
);
1657 err
= filler(data
, page
);
1659 page_cache_release(page
);
1660 page
= ERR_PTR(err
);
1666 static struct page
*do_read_cache_page(struct address_space
*mapping
,
1668 int (*filler
)(void *,struct page
*),
1677 page
= __read_cache_page(mapping
, index
, filler
, data
, gfp
);
1680 if (PageUptodate(page
))
1684 if (!page
->mapping
) {
1686 page_cache_release(page
);
1689 if (PageUptodate(page
)) {
1693 err
= filler(data
, page
);
1695 page_cache_release(page
);
1696 return ERR_PTR(err
);
1699 mark_page_accessed(page
);
1704 * read_cache_page_async - read into page cache, fill it if needed
1705 * @mapping: the page's address_space
1706 * @index: the page index
1707 * @filler: function to perform the read
1708 * @data: destination for read data
1710 * Same as read_cache_page, but don't wait for page to become unlocked
1711 * after submitting it to the filler.
1713 * Read into the page cache. If a page already exists, and PageUptodate() is
1714 * not set, try to fill the page but don't wait for it to become unlocked.
1716 * If the page does not get brought uptodate, return -EIO.
1718 struct page
*read_cache_page_async(struct address_space
*mapping
,
1720 int (*filler
)(void *,struct page
*),
1723 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
1725 EXPORT_SYMBOL(read_cache_page_async
);
1727 static struct page
*wait_on_page_read(struct page
*page
)
1729 if (!IS_ERR(page
)) {
1730 wait_on_page_locked(page
);
1731 if (!PageUptodate(page
)) {
1732 page_cache_release(page
);
1733 page
= ERR_PTR(-EIO
);
1740 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1741 * @mapping: the page's address_space
1742 * @index: the page index
1743 * @gfp: the page allocator flags to use if allocating
1745 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1746 * any new page allocations done using the specified allocation flags. Note
1747 * that the Radix tree operations will still use GFP_KERNEL, so you can't
1748 * expect to do this atomically or anything like that - but you can pass in
1749 * other page requirements.
1751 * If the page does not get brought uptodate, return -EIO.
1753 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
1757 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
1759 return wait_on_page_read(do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
));
1761 EXPORT_SYMBOL(read_cache_page_gfp
);
1764 * read_cache_page - read into page cache, fill it if needed
1765 * @mapping: the page's address_space
1766 * @index: the page index
1767 * @filler: function to perform the read
1768 * @data: destination for read data
1770 * Read into the page cache. If a page already exists, and PageUptodate() is
1771 * not set, try to fill the page then wait for it to become unlocked.
1773 * If the page does not get brought uptodate, return -EIO.
1775 struct page
*read_cache_page(struct address_space
*mapping
,
1777 int (*filler
)(void *,struct page
*),
1780 return wait_on_page_read(read_cache_page_async(mapping
, index
, filler
, data
));
1782 EXPORT_SYMBOL(read_cache_page
);
1785 * The logic we want is
1787 * if suid or (sgid and xgrp)
1790 int should_remove_suid(struct dentry
*dentry
)
1792 mode_t mode
= dentry
->d_inode
->i_mode
;
1795 /* suid always must be killed */
1796 if (unlikely(mode
& S_ISUID
))
1797 kill
= ATTR_KILL_SUID
;
1800 * sgid without any exec bits is just a mandatory locking mark; leave
1801 * it alone. If some exec bits are set, it's a real sgid; kill it.
1803 if (unlikely((mode
& S_ISGID
) && (mode
& S_IXGRP
)))
1804 kill
|= ATTR_KILL_SGID
;
1806 if (unlikely(kill
&& !capable(CAP_FSETID
) && S_ISREG(mode
)))
1811 EXPORT_SYMBOL(should_remove_suid
);
1813 static int __remove_suid(struct dentry
*dentry
, int kill
)
1815 struct iattr newattrs
;
1817 newattrs
.ia_valid
= ATTR_FORCE
| kill
;
1818 return notify_change(dentry
, &newattrs
);
1821 int file_remove_suid(struct file
*file
)
1823 struct dentry
*dentry
= file
->f_path
.dentry
;
1824 int killsuid
= should_remove_suid(dentry
);
1825 int killpriv
= security_inode_need_killpriv(dentry
);
1831 error
= security_inode_killpriv(dentry
);
1832 if (!error
&& killsuid
)
1833 error
= __remove_suid(dentry
, killsuid
);
1837 EXPORT_SYMBOL(file_remove_suid
);
1839 static size_t __iovec_copy_from_user_inatomic(char *vaddr
,
1840 const struct iovec
*iov
, size_t base
, size_t bytes
)
1842 size_t copied
= 0, left
= 0;
1845 char __user
*buf
= iov
->iov_base
+ base
;
1846 int copy
= min(bytes
, iov
->iov_len
- base
);
1849 left
= __copy_from_user_inatomic(vaddr
, buf
, copy
);
1858 return copied
- left
;
1862 * Copy as much as we can into the page and return the number of bytes which
1863 * were successfully copied. If a fault is encountered then return the number of
1864 * bytes which were copied.
1866 size_t iov_iter_copy_from_user_atomic(struct page
*page
,
1867 struct iov_iter
*i
, unsigned long offset
, size_t bytes
)
1872 BUG_ON(!in_atomic());
1873 kaddr
= kmap_atomic(page
, KM_USER0
);
1874 if (likely(i
->nr_segs
== 1)) {
1876 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1877 left
= __copy_from_user_inatomic(kaddr
+ offset
, buf
, bytes
);
1878 copied
= bytes
- left
;
1880 copied
= __iovec_copy_from_user_inatomic(kaddr
+ offset
,
1881 i
->iov
, i
->iov_offset
, bytes
);
1883 kunmap_atomic(kaddr
, KM_USER0
);
1887 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic
);
1890 * This has the same sideeffects and return value as
1891 * iov_iter_copy_from_user_atomic().
1892 * The difference is that it attempts to resolve faults.
1893 * Page must not be locked.
1895 size_t iov_iter_copy_from_user(struct page
*page
,
1896 struct iov_iter
*i
, unsigned long offset
, size_t bytes
)
1902 if (likely(i
->nr_segs
== 1)) {
1904 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1905 left
= __copy_from_user(kaddr
+ offset
, buf
, bytes
);
1906 copied
= bytes
- left
;
1908 copied
= __iovec_copy_from_user_inatomic(kaddr
+ offset
,
1909 i
->iov
, i
->iov_offset
, bytes
);
1914 EXPORT_SYMBOL(iov_iter_copy_from_user
);
1916 void iov_iter_advance(struct iov_iter
*i
, size_t bytes
)
1918 BUG_ON(i
->count
< bytes
);
1920 if (likely(i
->nr_segs
== 1)) {
1921 i
->iov_offset
+= bytes
;
1924 const struct iovec
*iov
= i
->iov
;
1925 size_t base
= i
->iov_offset
;
1928 * The !iov->iov_len check ensures we skip over unlikely
1929 * zero-length segments (without overruning the iovec).
1931 while (bytes
|| unlikely(i
->count
&& !iov
->iov_len
)) {
1934 copy
= min(bytes
, iov
->iov_len
- base
);
1935 BUG_ON(!i
->count
|| i
->count
< copy
);
1939 if (iov
->iov_len
== base
) {
1945 i
->iov_offset
= base
;
1948 EXPORT_SYMBOL(iov_iter_advance
);
1951 * Fault in the first iovec of the given iov_iter, to a maximum length
1952 * of bytes. Returns 0 on success, or non-zero if the memory could not be
1953 * accessed (ie. because it is an invalid address).
1955 * writev-intensive code may want this to prefault several iovecs -- that
1956 * would be possible (callers must not rely on the fact that _only_ the
1957 * first iovec will be faulted with the current implementation).
1959 int iov_iter_fault_in_readable(struct iov_iter
*i
, size_t bytes
)
1961 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1962 bytes
= min(bytes
, i
->iov
->iov_len
- i
->iov_offset
);
1963 return fault_in_pages_readable(buf
, bytes
);
1965 EXPORT_SYMBOL(iov_iter_fault_in_readable
);
1968 * Return the count of just the current iov_iter segment.
1970 size_t iov_iter_single_seg_count(struct iov_iter
*i
)
1972 const struct iovec
*iov
= i
->iov
;
1973 if (i
->nr_segs
== 1)
1976 return min(i
->count
, iov
->iov_len
- i
->iov_offset
);
1978 EXPORT_SYMBOL(iov_iter_single_seg_count
);
1981 * Performs necessary checks before doing a write
1983 * Can adjust writing position or amount of bytes to write.
1984 * Returns appropriate error code that caller should return or
1985 * zero in case that write should be allowed.
1987 inline int generic_write_checks(struct file
*file
, loff_t
*pos
, size_t *count
, int isblk
)
1989 struct inode
*inode
= file
->f_mapping
->host
;
1990 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
1992 if (unlikely(*pos
< 0))
1996 /* FIXME: this is for backwards compatibility with 2.4 */
1997 if (file
->f_flags
& O_APPEND
)
1998 *pos
= i_size_read(inode
);
2000 if (limit
!= RLIM_INFINITY
) {
2001 if (*pos
>= limit
) {
2002 send_sig(SIGXFSZ
, current
, 0);
2005 if (*count
> limit
- (typeof(limit
))*pos
) {
2006 *count
= limit
- (typeof(limit
))*pos
;
2014 if (unlikely(*pos
+ *count
> MAX_NON_LFS
&&
2015 !(file
->f_flags
& O_LARGEFILE
))) {
2016 if (*pos
>= MAX_NON_LFS
) {
2019 if (*count
> MAX_NON_LFS
- (unsigned long)*pos
) {
2020 *count
= MAX_NON_LFS
- (unsigned long)*pos
;
2025 * Are we about to exceed the fs block limit ?
2027 * If we have written data it becomes a short write. If we have
2028 * exceeded without writing data we send a signal and return EFBIG.
2029 * Linus frestrict idea will clean these up nicely..
2031 if (likely(!isblk
)) {
2032 if (unlikely(*pos
>= inode
->i_sb
->s_maxbytes
)) {
2033 if (*count
|| *pos
> inode
->i_sb
->s_maxbytes
) {
2036 /* zero-length writes at ->s_maxbytes are OK */
2039 if (unlikely(*pos
+ *count
> inode
->i_sb
->s_maxbytes
))
2040 *count
= inode
->i_sb
->s_maxbytes
- *pos
;
2044 if (bdev_read_only(I_BDEV(inode
)))
2046 isize
= i_size_read(inode
);
2047 if (*pos
>= isize
) {
2048 if (*count
|| *pos
> isize
)
2052 if (*pos
+ *count
> isize
)
2053 *count
= isize
- *pos
;
2060 EXPORT_SYMBOL(generic_write_checks
);
2062 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2063 loff_t pos
, unsigned len
, unsigned flags
,
2064 struct page
**pagep
, void **fsdata
)
2066 const struct address_space_operations
*aops
= mapping
->a_ops
;
2068 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2071 EXPORT_SYMBOL(pagecache_write_begin
);
2073 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2074 loff_t pos
, unsigned len
, unsigned copied
,
2075 struct page
*page
, void *fsdata
)
2077 const struct address_space_operations
*aops
= mapping
->a_ops
;
2079 mark_page_accessed(page
);
2080 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2082 EXPORT_SYMBOL(pagecache_write_end
);
2085 generic_file_direct_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2086 unsigned long *nr_segs
, loff_t pos
, loff_t
*ppos
,
2087 size_t count
, size_t ocount
)
2089 struct file
*file
= iocb
->ki_filp
;
2090 struct address_space
*mapping
= file
->f_mapping
;
2091 struct inode
*inode
= mapping
->host
;
2096 if (count
!= ocount
)
2097 *nr_segs
= iov_shorten((struct iovec
*)iov
, *nr_segs
, count
);
2099 write_len
= iov_length(iov
, *nr_segs
);
2100 end
= (pos
+ write_len
- 1) >> PAGE_CACHE_SHIFT
;
2102 written
= filemap_write_and_wait_range(mapping
, pos
, pos
+ write_len
- 1);
2107 * After a write we want buffered reads to be sure to go to disk to get
2108 * the new data. We invalidate clean cached page from the region we're
2109 * about to write. We do this *before* the write so that we can return
2110 * without clobbering -EIOCBQUEUED from ->direct_IO().
2112 if (mapping
->nrpages
) {
2113 written
= invalidate_inode_pages2_range(mapping
,
2114 pos
>> PAGE_CACHE_SHIFT
, end
);
2116 * If a page can not be invalidated, return 0 to fall back
2117 * to buffered write.
2120 if (written
== -EBUSY
)
2126 written
= mapping
->a_ops
->direct_IO(WRITE
, iocb
, iov
, pos
, *nr_segs
);
2129 * Finally, try again to invalidate clean pages which might have been
2130 * cached by non-direct readahead, or faulted in by get_user_pages()
2131 * if the source of the write was an mmap'ed region of the file
2132 * we're writing. Either one is a pretty crazy thing to do,
2133 * so we don't support it 100%. If this invalidation
2134 * fails, tough, the write still worked...
2136 if (mapping
->nrpages
) {
2137 invalidate_inode_pages2_range(mapping
,
2138 pos
>> PAGE_CACHE_SHIFT
, end
);
2142 loff_t end
= pos
+ written
;
2143 if (end
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2144 i_size_write(inode
, end
);
2145 mark_inode_dirty(inode
);
2152 EXPORT_SYMBOL(generic_file_direct_write
);
2155 * Find or create a page at the given pagecache position. Return the locked
2156 * page. This function is specifically for buffered writes.
2158 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2159 pgoff_t index
, unsigned flags
)
2163 gfp_t gfp_notmask
= 0;
2164 if (flags
& AOP_FLAG_NOFS
)
2165 gfp_notmask
= __GFP_FS
;
2167 page
= find_lock_page(mapping
, index
);
2171 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) & ~gfp_notmask
);
2174 status
= add_to_page_cache_lru(page
, mapping
, index
,
2175 GFP_KERNEL
& ~gfp_notmask
);
2176 if (unlikely(status
)) {
2177 page_cache_release(page
);
2178 if (status
== -EEXIST
)
2184 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2186 static ssize_t
generic_perform_write(struct file
*file
,
2187 struct iov_iter
*i
, loff_t pos
)
2189 struct address_space
*mapping
= file
->f_mapping
;
2190 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2192 ssize_t written
= 0;
2193 unsigned int flags
= 0;
2196 * Copies from kernel address space cannot fail (NFSD is a big user).
2198 if (segment_eq(get_fs(), KERNEL_DS
))
2199 flags
|= AOP_FLAG_UNINTERRUPTIBLE
;
2203 pgoff_t index
; /* Pagecache index for current page */
2204 unsigned long offset
; /* Offset into pagecache page */
2205 unsigned long bytes
; /* Bytes to write to page */
2206 size_t copied
; /* Bytes copied from user */
2209 offset
= (pos
& (PAGE_CACHE_SIZE
- 1));
2210 index
= pos
>> PAGE_CACHE_SHIFT
;
2211 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2217 * Bring in the user page that we will copy from _first_.
2218 * Otherwise there's a nasty deadlock on copying from the
2219 * same page as we're writing to, without it being marked
2222 * Not only is this an optimisation, but it is also required
2223 * to check that the address is actually valid, when atomic
2224 * usercopies are used, below.
2226 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2231 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2233 if (unlikely(status
))
2236 if (mapping_writably_mapped(mapping
))
2237 flush_dcache_page(page
);
2239 pagefault_disable();
2240 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2242 flush_dcache_page(page
);
2244 mark_page_accessed(page
);
2245 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2247 if (unlikely(status
< 0))
2253 iov_iter_advance(i
, copied
);
2254 if (unlikely(copied
== 0)) {
2256 * If we were unable to copy any data at all, we must
2257 * fall back to a single segment length write.
2259 * If we didn't fallback here, we could livelock
2260 * because not all segments in the iov can be copied at
2261 * once without a pagefault.
2263 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2264 iov_iter_single_seg_count(i
));
2270 balance_dirty_pages_ratelimited(mapping
);
2272 } while (iov_iter_count(i
));
2274 return written
? written
: status
;
2278 generic_file_buffered_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2279 unsigned long nr_segs
, loff_t pos
, loff_t
*ppos
,
2280 size_t count
, ssize_t written
)
2282 struct file
*file
= iocb
->ki_filp
;
2286 iov_iter_init(&i
, iov
, nr_segs
, count
, written
);
2287 status
= generic_perform_write(file
, &i
, pos
);
2289 if (likely(status
>= 0)) {
2291 *ppos
= pos
+ status
;
2294 return written
? written
: status
;
2296 EXPORT_SYMBOL(generic_file_buffered_write
);
2299 * __generic_file_aio_write - write data to a file
2300 * @iocb: IO state structure (file, offset, etc.)
2301 * @iov: vector with data to write
2302 * @nr_segs: number of segments in the vector
2303 * @ppos: position where to write
2305 * This function does all the work needed for actually writing data to a
2306 * file. It does all basic checks, removes SUID from the file, updates
2307 * modification times and calls proper subroutines depending on whether we
2308 * do direct IO or a standard buffered write.
2310 * It expects i_mutex to be grabbed unless we work on a block device or similar
2311 * object which does not need locking at all.
2313 * This function does *not* take care of syncing data in case of O_SYNC write.
2314 * A caller has to handle it. This is mainly due to the fact that we want to
2315 * avoid syncing under i_mutex.
2317 ssize_t
__generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2318 unsigned long nr_segs
, loff_t
*ppos
)
2320 struct file
*file
= iocb
->ki_filp
;
2321 struct address_space
* mapping
= file
->f_mapping
;
2322 size_t ocount
; /* original count */
2323 size_t count
; /* after file limit checks */
2324 struct inode
*inode
= mapping
->host
;
2330 err
= generic_segment_checks(iov
, &nr_segs
, &ocount
, VERIFY_READ
);
2337 vfs_check_frozen(inode
->i_sb
, SB_FREEZE_WRITE
);
2339 /* We can write back this queue in page reclaim */
2340 current
->backing_dev_info
= mapping
->backing_dev_info
;
2343 err
= generic_write_checks(file
, &pos
, &count
, S_ISBLK(inode
->i_mode
));
2350 err
= file_remove_suid(file
);
2354 file_update_time(file
);
2356 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2357 if (unlikely(file
->f_flags
& O_DIRECT
)) {
2359 ssize_t written_buffered
;
2361 written
= generic_file_direct_write(iocb
, iov
, &nr_segs
, pos
,
2362 ppos
, count
, ocount
);
2363 if (written
< 0 || written
== count
)
2366 * direct-io write to a hole: fall through to buffered I/O
2367 * for completing the rest of the request.
2371 written_buffered
= generic_file_buffered_write(iocb
, iov
,
2372 nr_segs
, pos
, ppos
, count
,
2375 * If generic_file_buffered_write() retuned a synchronous error
2376 * then we want to return the number of bytes which were
2377 * direct-written, or the error code if that was zero. Note
2378 * that this differs from normal direct-io semantics, which
2379 * will return -EFOO even if some bytes were written.
2381 if (written_buffered
< 0) {
2382 err
= written_buffered
;
2387 * We need to ensure that the page cache pages are written to
2388 * disk and invalidated to preserve the expected O_DIRECT
2391 endbyte
= pos
+ written_buffered
- written
- 1;
2392 err
= filemap_write_and_wait_range(file
->f_mapping
, pos
, endbyte
);
2394 written
= written_buffered
;
2395 invalidate_mapping_pages(mapping
,
2396 pos
>> PAGE_CACHE_SHIFT
,
2397 endbyte
>> PAGE_CACHE_SHIFT
);
2400 * We don't know how much we wrote, so just return
2401 * the number of bytes which were direct-written
2405 written
= generic_file_buffered_write(iocb
, iov
, nr_segs
,
2406 pos
, ppos
, count
, written
);
2409 current
->backing_dev_info
= NULL
;
2410 return written
? written
: err
;
2412 EXPORT_SYMBOL(__generic_file_aio_write
);
2415 * generic_file_aio_write - write data to a file
2416 * @iocb: IO state structure
2417 * @iov: vector with data to write
2418 * @nr_segs: number of segments in the vector
2419 * @pos: position in file where to write
2421 * This is a wrapper around __generic_file_aio_write() to be used by most
2422 * filesystems. It takes care of syncing the file in case of O_SYNC file
2423 * and acquires i_mutex as needed.
2425 ssize_t
generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2426 unsigned long nr_segs
, loff_t pos
)
2428 struct file
*file
= iocb
->ki_filp
;
2429 struct inode
*inode
= file
->f_mapping
->host
;
2432 BUG_ON(iocb
->ki_pos
!= pos
);
2434 mutex_lock(&inode
->i_mutex
);
2435 ret
= __generic_file_aio_write(iocb
, iov
, nr_segs
, &iocb
->ki_pos
);
2436 mutex_unlock(&inode
->i_mutex
);
2438 if (ret
> 0 || ret
== -EIOCBQUEUED
) {
2441 err
= generic_write_sync(file
, pos
, ret
);
2442 if (err
< 0 && ret
> 0)
2447 EXPORT_SYMBOL(generic_file_aio_write
);
2450 * try_to_release_page() - release old fs-specific metadata on a page
2452 * @page: the page which the kernel is trying to free
2453 * @gfp_mask: memory allocation flags (and I/O mode)
2455 * The address_space is to try to release any data against the page
2456 * (presumably at page->private). If the release was successful, return `1'.
2457 * Otherwise return zero.
2459 * This may also be called if PG_fscache is set on a page, indicating that the
2460 * page is known to the local caching routines.
2462 * The @gfp_mask argument specifies whether I/O may be performed to release
2463 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2466 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
2468 struct address_space
* const mapping
= page
->mapping
;
2470 BUG_ON(!PageLocked(page
));
2471 if (PageWriteback(page
))
2474 if (mapping
&& mapping
->a_ops
->releasepage
)
2475 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
2476 return try_to_free_buffers(page
);
2479 EXPORT_SYMBOL(try_to_release_page
);