OMAP3: PM: Add voltage levels to prm_setup_vc (previously prm_setup_time)
[linux-ginger.git] / mm / filemap.c
blobef169f37156da22cc3f07d5dd9092dea00315b7f
1 /*
2 * linux/mm/filemap.c
4 * Copyright (C) 1994-1999 Linus Torvalds
5 */
7 /*
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/slab.h>
14 #include <linux/compiler.h>
15 #include <linux/fs.h>
16 #include <linux/uaccess.h>
17 #include <linux/aio.h>
18 #include <linux/capability.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/mm.h>
21 #include <linux/swap.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/file.h>
25 #include <linux/uio.h>
26 #include <linux/hash.h>
27 #include <linux/writeback.h>
28 #include <linux/backing-dev.h>
29 #include <linux/pagevec.h>
30 #include <linux/blkdev.h>
31 #include <linux/security.h>
32 #include <linux/syscalls.h>
33 #include <linux/cpuset.h>
34 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
35 #include <linux/memcontrol.h>
36 #include <linux/mm_inline.h> /* for page_is_file_cache() */
37 #include "internal.h"
40 * FIXME: remove all knowledge of the buffer layer from the core VM
42 #include <linux/buffer_head.h> /* for try_to_free_buffers */
44 #include <asm/mman.h>
47 * Shared mappings implemented 30.11.1994. It's not fully working yet,
48 * though.
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>
59 * Lock ordering:
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
66 * ->i_mutex
67 * ->i_mmap_lock (truncate->unmap_mapping_range)
69 * ->mmap_sem
70 * ->i_mmap_lock
71 * ->page_table_lock or pte_lock (various, mainly in memory.c)
72 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
74 * ->mmap_sem
75 * ->lock_page (access_process_vm)
77 * ->i_mutex (generic_file_buffered_write)
78 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
80 * ->i_mutex
81 * ->i_alloc_sem (various)
83 * ->inode_lock
84 * ->sb_lock (fs/fs-writeback.c)
85 * ->mapping->tree_lock (__sync_single_inode)
87 * ->i_mmap_lock
88 * ->anon_vma.lock (vma_adjust)
90 * ->anon_vma.lock
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)
105 * ->task->proc_lock
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)
110 * ->i_mmap_lock
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;
124 mapping->nrpages--;
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;
158 struct page *page;
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.
181 * -- wli
183 smp_mb();
184 mapping = page_mapping(page);
185 if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
186 mapping->a_ops->sync_page(page);
187 io_schedule();
188 return 0;
191 static int sync_page_killable(void *word)
193 sync_page(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)
215 int ret;
216 struct writeback_control wbc = {
217 .sync_mode = sync_mode,
218 .nr_to_write = LONG_MAX,
219 .range_start = start,
220 .range_end = end,
223 if (!mapping_cap_writeback_dirty(mapping))
224 return 0;
226 ret = do_writepages(mapping, &wbc);
227 return ret;
230 static inline int __filemap_fdatawrite(struct address_space *mapping,
231 int sync_mode)
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,
243 loff_t end)
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 * wait_on_page_writeback_range - wait for writeback to complete
264 * @mapping: target address_space
265 * @start: beginning page index
266 * @end: ending page index
268 * Wait for writeback to complete against pages indexed by start->end
269 * inclusive
271 int wait_on_page_writeback_range(struct address_space *mapping,
272 pgoff_t start, pgoff_t end)
274 struct pagevec pvec;
275 int nr_pages;
276 int ret = 0;
277 pgoff_t index;
279 if (end < start)
280 return 0;
282 pagevec_init(&pvec, 0);
283 index = start;
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) {
288 unsigned i;
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)
295 continue;
297 wait_on_page_writeback(page);
298 if (PageError(page))
299 ret = -EIO;
301 pagevec_release(&pvec);
302 cond_resched();
305 /* Check for outstanding write errors */
306 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
307 ret = -ENOSPC;
308 if (test_and_clear_bit(AS_EIO, &mapping->flags))
309 ret = -EIO;
311 return ret;
315 * filemap_fdatawait_range - wait for all under-writeback pages to complete in a given range
316 * @mapping: address space structure to wait for
317 * @start: offset in bytes where the range starts
318 * @end: offset in bytes where the range ends (inclusive)
320 * Walk the list of under-writeback pages of the given address space
321 * in the given range and wait for all of them.
323 * This is just a simple wrapper so that callers don't have to convert offsets
324 * to page indexes themselves
326 int filemap_fdatawait_range(struct address_space *mapping, loff_t start,
327 loff_t end)
329 return wait_on_page_writeback_range(mapping, start >> PAGE_CACHE_SHIFT,
330 end >> PAGE_CACHE_SHIFT);
332 EXPORT_SYMBOL(filemap_fdatawait_range);
335 * filemap_fdatawait - wait for all under-writeback pages to complete
336 * @mapping: address space structure to wait for
338 * Walk the list of under-writeback pages of the given address space
339 * and wait for all of them.
341 int filemap_fdatawait(struct address_space *mapping)
343 loff_t i_size = i_size_read(mapping->host);
345 if (i_size == 0)
346 return 0;
348 return wait_on_page_writeback_range(mapping, 0,
349 (i_size - 1) >> PAGE_CACHE_SHIFT);
351 EXPORT_SYMBOL(filemap_fdatawait);
353 int filemap_write_and_wait(struct address_space *mapping)
355 int err = 0;
357 if (mapping->nrpages) {
358 err = filemap_fdatawrite(mapping);
360 * Even if the above returned error, the pages may be
361 * written partially (e.g. -ENOSPC), so we wait for it.
362 * But the -EIO is special case, it may indicate the worst
363 * thing (e.g. bug) happened, so we avoid waiting for it.
365 if (err != -EIO) {
366 int err2 = filemap_fdatawait(mapping);
367 if (!err)
368 err = err2;
371 return err;
373 EXPORT_SYMBOL(filemap_write_and_wait);
376 * filemap_write_and_wait_range - write out & wait on a file range
377 * @mapping: the address_space for the pages
378 * @lstart: offset in bytes where the range starts
379 * @lend: offset in bytes where the range ends (inclusive)
381 * Write out and wait upon file offsets lstart->lend, inclusive.
383 * Note that `lend' is inclusive (describes the last byte to be written) so
384 * that this function can be used to write to the very end-of-file (end = -1).
386 int filemap_write_and_wait_range(struct address_space *mapping,
387 loff_t lstart, loff_t lend)
389 int err = 0;
391 if (mapping->nrpages) {
392 err = __filemap_fdatawrite_range(mapping, lstart, lend,
393 WB_SYNC_ALL);
394 /* See comment of filemap_write_and_wait() */
395 if (err != -EIO) {
396 int err2 = wait_on_page_writeback_range(mapping,
397 lstart >> PAGE_CACHE_SHIFT,
398 lend >> PAGE_CACHE_SHIFT);
399 if (!err)
400 err = err2;
403 return err;
405 EXPORT_SYMBOL(filemap_write_and_wait_range);
408 * add_to_page_cache_locked - add a locked page to the pagecache
409 * @page: page to add
410 * @mapping: the page's address_space
411 * @offset: page index
412 * @gfp_mask: page allocation mode
414 * This function is used to add a page to the pagecache. It must be locked.
415 * This function does not add the page to the LRU. The caller must do that.
417 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
418 pgoff_t offset, gfp_t gfp_mask)
420 int error;
422 VM_BUG_ON(!PageLocked(page));
424 error = mem_cgroup_cache_charge(page, current->mm,
425 gfp_mask & GFP_RECLAIM_MASK);
426 if (error)
427 goto out;
429 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
430 if (error == 0) {
431 page_cache_get(page);
432 page->mapping = mapping;
433 page->index = offset;
435 spin_lock_irq(&mapping->tree_lock);
436 error = radix_tree_insert(&mapping->page_tree, offset, page);
437 if (likely(!error)) {
438 mapping->nrpages++;
439 __inc_zone_page_state(page, NR_FILE_PAGES);
440 if (PageSwapBacked(page))
441 __inc_zone_page_state(page, NR_SHMEM);
442 spin_unlock_irq(&mapping->tree_lock);
443 } else {
444 page->mapping = NULL;
445 spin_unlock_irq(&mapping->tree_lock);
446 mem_cgroup_uncharge_cache_page(page);
447 page_cache_release(page);
449 radix_tree_preload_end();
450 } else
451 mem_cgroup_uncharge_cache_page(page);
452 out:
453 return error;
455 EXPORT_SYMBOL(add_to_page_cache_locked);
457 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
458 pgoff_t offset, gfp_t gfp_mask)
460 int ret;
463 * Splice_read and readahead add shmem/tmpfs pages into the page cache
464 * before shmem_readpage has a chance to mark them as SwapBacked: they
465 * need to go on the active_anon lru below, and mem_cgroup_cache_charge
466 * (called in add_to_page_cache) needs to know where they're going too.
468 if (mapping_cap_swap_backed(mapping))
469 SetPageSwapBacked(page);
471 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
472 if (ret == 0) {
473 if (page_is_file_cache(page))
474 lru_cache_add_file(page);
475 else
476 lru_cache_add_active_anon(page);
478 return ret;
480 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
482 #ifdef CONFIG_NUMA
483 struct page *__page_cache_alloc(gfp_t gfp)
485 if (cpuset_do_page_mem_spread()) {
486 int n = cpuset_mem_spread_node();
487 return alloc_pages_exact_node(n, gfp, 0);
489 return alloc_pages(gfp, 0);
491 EXPORT_SYMBOL(__page_cache_alloc);
492 #endif
494 static int __sleep_on_page_lock(void *word)
496 io_schedule();
497 return 0;
501 * In order to wait for pages to become available there must be
502 * waitqueues associated with pages. By using a hash table of
503 * waitqueues where the bucket discipline is to maintain all
504 * waiters on the same queue and wake all when any of the pages
505 * become available, and for the woken contexts to check to be
506 * sure the appropriate page became available, this saves space
507 * at a cost of "thundering herd" phenomena during rare hash
508 * collisions.
510 static wait_queue_head_t *page_waitqueue(struct page *page)
512 const struct zone *zone = page_zone(page);
514 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
517 static inline void wake_up_page(struct page *page, int bit)
519 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
522 void wait_on_page_bit(struct page *page, int bit_nr)
524 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
526 if (test_bit(bit_nr, &page->flags))
527 __wait_on_bit(page_waitqueue(page), &wait, sync_page,
528 TASK_UNINTERRUPTIBLE);
530 EXPORT_SYMBOL(wait_on_page_bit);
533 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
534 * @page: Page defining the wait queue of interest
535 * @waiter: Waiter to add to the queue
537 * Add an arbitrary @waiter to the wait queue for the nominated @page.
539 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
541 wait_queue_head_t *q = page_waitqueue(page);
542 unsigned long flags;
544 spin_lock_irqsave(&q->lock, flags);
545 __add_wait_queue(q, waiter);
546 spin_unlock_irqrestore(&q->lock, flags);
548 EXPORT_SYMBOL_GPL(add_page_wait_queue);
551 * unlock_page - unlock a locked page
552 * @page: the page
554 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
555 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
556 * mechananism between PageLocked pages and PageWriteback pages is shared.
557 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
559 * The mb is necessary to enforce ordering between the clear_bit and the read
560 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
562 void unlock_page(struct page *page)
564 VM_BUG_ON(!PageLocked(page));
565 clear_bit_unlock(PG_locked, &page->flags);
566 smp_mb__after_clear_bit();
567 wake_up_page(page, PG_locked);
569 EXPORT_SYMBOL(unlock_page);
572 * end_page_writeback - end writeback against a page
573 * @page: the page
575 void end_page_writeback(struct page *page)
577 if (TestClearPageReclaim(page))
578 rotate_reclaimable_page(page);
580 if (!test_clear_page_writeback(page))
581 BUG();
583 smp_mb__after_clear_bit();
584 wake_up_page(page, PG_writeback);
586 EXPORT_SYMBOL(end_page_writeback);
589 * __lock_page - get a lock on the page, assuming we need to sleep to get it
590 * @page: the page to lock
592 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some
593 * random driver's requestfn sets TASK_RUNNING, we could busywait. However
594 * chances are that on the second loop, the block layer's plug list is empty,
595 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
597 void __lock_page(struct page *page)
599 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
601 __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
602 TASK_UNINTERRUPTIBLE);
604 EXPORT_SYMBOL(__lock_page);
606 int __lock_page_killable(struct page *page)
608 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
610 return __wait_on_bit_lock(page_waitqueue(page), &wait,
611 sync_page_killable, TASK_KILLABLE);
613 EXPORT_SYMBOL_GPL(__lock_page_killable);
616 * __lock_page_nosync - get a lock on the page, without calling sync_page()
617 * @page: the page to lock
619 * Variant of lock_page that does not require the caller to hold a reference
620 * on the page's mapping.
622 void __lock_page_nosync(struct page *page)
624 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
625 __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
626 TASK_UNINTERRUPTIBLE);
630 * find_get_page - find and get a page reference
631 * @mapping: the address_space to search
632 * @offset: the page index
634 * Is there a pagecache struct page at the given (mapping, offset) tuple?
635 * If yes, increment its refcount and return it; if no, return NULL.
637 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
639 void **pagep;
640 struct page *page;
642 rcu_read_lock();
643 repeat:
644 page = NULL;
645 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
646 if (pagep) {
647 page = radix_tree_deref_slot(pagep);
648 if (unlikely(!page || page == RADIX_TREE_RETRY))
649 goto repeat;
651 if (!page_cache_get_speculative(page))
652 goto repeat;
655 * Has the page moved?
656 * This is part of the lockless pagecache protocol. See
657 * include/linux/pagemap.h for details.
659 if (unlikely(page != *pagep)) {
660 page_cache_release(page);
661 goto repeat;
664 rcu_read_unlock();
666 return page;
668 EXPORT_SYMBOL(find_get_page);
671 * find_lock_page - locate, pin and lock a pagecache page
672 * @mapping: the address_space to search
673 * @offset: the page index
675 * Locates the desired pagecache page, locks it, increments its reference
676 * count and returns its address.
678 * Returns zero if the page was not present. find_lock_page() may sleep.
680 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
682 struct page *page;
684 repeat:
685 page = find_get_page(mapping, offset);
686 if (page) {
687 lock_page(page);
688 /* Has the page been truncated? */
689 if (unlikely(page->mapping != mapping)) {
690 unlock_page(page);
691 page_cache_release(page);
692 goto repeat;
694 VM_BUG_ON(page->index != offset);
696 return page;
698 EXPORT_SYMBOL(find_lock_page);
701 * find_or_create_page - locate or add a pagecache page
702 * @mapping: the page's address_space
703 * @index: the page's index into the mapping
704 * @gfp_mask: page allocation mode
706 * Locates a page in the pagecache. If the page is not present, a new page
707 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
708 * LRU list. The returned page is locked and has its reference count
709 * incremented.
711 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
712 * allocation!
714 * find_or_create_page() returns the desired page's address, or zero on
715 * memory exhaustion.
717 struct page *find_or_create_page(struct address_space *mapping,
718 pgoff_t index, gfp_t gfp_mask)
720 struct page *page;
721 int err;
722 repeat:
723 page = find_lock_page(mapping, index);
724 if (!page) {
725 page = __page_cache_alloc(gfp_mask);
726 if (!page)
727 return NULL;
729 * We want a regular kernel memory (not highmem or DMA etc)
730 * allocation for the radix tree nodes, but we need to honour
731 * the context-specific requirements the caller has asked for.
732 * GFP_RECLAIM_MASK collects those requirements.
734 err = add_to_page_cache_lru(page, mapping, index,
735 (gfp_mask & GFP_RECLAIM_MASK));
736 if (unlikely(err)) {
737 page_cache_release(page);
738 page = NULL;
739 if (err == -EEXIST)
740 goto repeat;
743 return page;
745 EXPORT_SYMBOL(find_or_create_page);
748 * find_get_pages - gang pagecache lookup
749 * @mapping: The address_space to search
750 * @start: The starting page index
751 * @nr_pages: The maximum number of pages
752 * @pages: Where the resulting pages are placed
754 * find_get_pages() will search for and return a group of up to
755 * @nr_pages pages in the mapping. The pages are placed at @pages.
756 * find_get_pages() takes a reference against the returned pages.
758 * The search returns a group of mapping-contiguous pages with ascending
759 * indexes. There may be holes in the indices due to not-present pages.
761 * find_get_pages() returns the number of pages which were found.
763 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
764 unsigned int nr_pages, struct page **pages)
766 unsigned int i;
767 unsigned int ret;
768 unsigned int nr_found;
770 rcu_read_lock();
771 restart:
772 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
773 (void ***)pages, start, nr_pages);
774 ret = 0;
775 for (i = 0; i < nr_found; i++) {
776 struct page *page;
777 repeat:
778 page = radix_tree_deref_slot((void **)pages[i]);
779 if (unlikely(!page))
780 continue;
782 * this can only trigger if nr_found == 1, making livelock
783 * a non issue.
785 if (unlikely(page == RADIX_TREE_RETRY))
786 goto restart;
788 if (!page_cache_get_speculative(page))
789 goto repeat;
791 /* Has the page moved? */
792 if (unlikely(page != *((void **)pages[i]))) {
793 page_cache_release(page);
794 goto repeat;
797 pages[ret] = page;
798 ret++;
800 rcu_read_unlock();
801 return ret;
805 * find_get_pages_contig - gang contiguous pagecache lookup
806 * @mapping: The address_space to search
807 * @index: The starting page index
808 * @nr_pages: The maximum number of pages
809 * @pages: Where the resulting pages are placed
811 * find_get_pages_contig() works exactly like find_get_pages(), except
812 * that the returned number of pages are guaranteed to be contiguous.
814 * find_get_pages_contig() returns the number of pages which were found.
816 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
817 unsigned int nr_pages, struct page **pages)
819 unsigned int i;
820 unsigned int ret;
821 unsigned int nr_found;
823 rcu_read_lock();
824 restart:
825 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
826 (void ***)pages, index, nr_pages);
827 ret = 0;
828 for (i = 0; i < nr_found; i++) {
829 struct page *page;
830 repeat:
831 page = radix_tree_deref_slot((void **)pages[i]);
832 if (unlikely(!page))
833 continue;
835 * this can only trigger if nr_found == 1, making livelock
836 * a non issue.
838 if (unlikely(page == RADIX_TREE_RETRY))
839 goto restart;
841 if (page->mapping == NULL || page->index != index)
842 break;
844 if (!page_cache_get_speculative(page))
845 goto repeat;
847 /* Has the page moved? */
848 if (unlikely(page != *((void **)pages[i]))) {
849 page_cache_release(page);
850 goto repeat;
853 pages[ret] = page;
854 ret++;
855 index++;
857 rcu_read_unlock();
858 return ret;
860 EXPORT_SYMBOL(find_get_pages_contig);
863 * find_get_pages_tag - find and return pages that match @tag
864 * @mapping: the address_space to search
865 * @index: the starting page index
866 * @tag: the tag index
867 * @nr_pages: the maximum number of pages
868 * @pages: where the resulting pages are placed
870 * Like find_get_pages, except we only return pages which are tagged with
871 * @tag. We update @index to index the next page for the traversal.
873 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
874 int tag, unsigned int nr_pages, struct page **pages)
876 unsigned int i;
877 unsigned int ret;
878 unsigned int nr_found;
880 rcu_read_lock();
881 restart:
882 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
883 (void ***)pages, *index, nr_pages, tag);
884 ret = 0;
885 for (i = 0; i < nr_found; i++) {
886 struct page *page;
887 repeat:
888 page = radix_tree_deref_slot((void **)pages[i]);
889 if (unlikely(!page))
890 continue;
892 * this can only trigger if nr_found == 1, making livelock
893 * a non issue.
895 if (unlikely(page == RADIX_TREE_RETRY))
896 goto restart;
898 if (!page_cache_get_speculative(page))
899 goto repeat;
901 /* Has the page moved? */
902 if (unlikely(page != *((void **)pages[i]))) {
903 page_cache_release(page);
904 goto repeat;
907 pages[ret] = page;
908 ret++;
910 rcu_read_unlock();
912 if (ret)
913 *index = pages[ret - 1]->index + 1;
915 return ret;
917 EXPORT_SYMBOL(find_get_pages_tag);
920 * grab_cache_page_nowait - returns locked page at given index in given cache
921 * @mapping: target address_space
922 * @index: the page index
924 * Same as grab_cache_page(), but do not wait if the page is unavailable.
925 * This is intended for speculative data generators, where the data can
926 * be regenerated if the page couldn't be grabbed. This routine should
927 * be safe to call while holding the lock for another page.
929 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
930 * and deadlock against the caller's locked page.
932 struct page *
933 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
935 struct page *page = find_get_page(mapping, index);
937 if (page) {
938 if (trylock_page(page))
939 return page;
940 page_cache_release(page);
941 return NULL;
943 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
944 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
945 page_cache_release(page);
946 page = NULL;
948 return page;
950 EXPORT_SYMBOL(grab_cache_page_nowait);
953 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
954 * a _large_ part of the i/o request. Imagine the worst scenario:
956 * ---R__________________________________________B__________
957 * ^ reading here ^ bad block(assume 4k)
959 * read(R) => miss => readahead(R...B) => media error => frustrating retries
960 * => failing the whole request => read(R) => read(R+1) =>
961 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
962 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
963 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
965 * It is going insane. Fix it by quickly scaling down the readahead size.
967 static void shrink_readahead_size_eio(struct file *filp,
968 struct file_ra_state *ra)
970 ra->ra_pages /= 4;
974 * do_generic_file_read - generic file read routine
975 * @filp: the file to read
976 * @ppos: current file position
977 * @desc: read_descriptor
978 * @actor: read method
980 * This is a generic file read routine, and uses the
981 * mapping->a_ops->readpage() function for the actual low-level stuff.
983 * This is really ugly. But the goto's actually try to clarify some
984 * of the logic when it comes to error handling etc.
986 static void do_generic_file_read(struct file *filp, loff_t *ppos,
987 read_descriptor_t *desc, read_actor_t actor)
989 struct address_space *mapping = filp->f_mapping;
990 struct inode *inode = mapping->host;
991 struct file_ra_state *ra = &filp->f_ra;
992 pgoff_t index;
993 pgoff_t last_index;
994 pgoff_t prev_index;
995 unsigned long offset; /* offset into pagecache page */
996 unsigned int prev_offset;
997 int error;
999 index = *ppos >> PAGE_CACHE_SHIFT;
1000 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1001 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1002 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1003 offset = *ppos & ~PAGE_CACHE_MASK;
1005 for (;;) {
1006 struct page *page;
1007 pgoff_t end_index;
1008 loff_t isize;
1009 unsigned long nr, ret;
1011 cond_resched();
1012 find_page:
1013 page = find_get_page(mapping, index);
1014 if (!page) {
1015 page_cache_sync_readahead(mapping,
1016 ra, filp,
1017 index, last_index - index);
1018 page = find_get_page(mapping, index);
1019 if (unlikely(page == NULL))
1020 goto no_cached_page;
1022 if (PageReadahead(page)) {
1023 page_cache_async_readahead(mapping,
1024 ra, filp, page,
1025 index, last_index - index);
1027 if (!PageUptodate(page)) {
1028 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1029 !mapping->a_ops->is_partially_uptodate)
1030 goto page_not_up_to_date;
1031 if (!trylock_page(page))
1032 goto page_not_up_to_date;
1033 if (!mapping->a_ops->is_partially_uptodate(page,
1034 desc, offset))
1035 goto page_not_up_to_date_locked;
1036 unlock_page(page);
1038 page_ok:
1040 * i_size must be checked after we know the page is Uptodate.
1042 * Checking i_size after the check allows us to calculate
1043 * the correct value for "nr", which means the zero-filled
1044 * part of the page is not copied back to userspace (unless
1045 * another truncate extends the file - this is desired though).
1048 isize = i_size_read(inode);
1049 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1050 if (unlikely(!isize || index > end_index)) {
1051 page_cache_release(page);
1052 goto out;
1055 /* nr is the maximum number of bytes to copy from this page */
1056 nr = PAGE_CACHE_SIZE;
1057 if (index == end_index) {
1058 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1059 if (nr <= offset) {
1060 page_cache_release(page);
1061 goto out;
1064 nr = nr - offset;
1066 /* If users can be writing to this page using arbitrary
1067 * virtual addresses, take care about potential aliasing
1068 * before reading the page on the kernel side.
1070 if (mapping_writably_mapped(mapping))
1071 flush_dcache_page(page);
1074 * When a sequential read accesses a page several times,
1075 * only mark it as accessed the first time.
1077 if (prev_index != index || offset != prev_offset)
1078 mark_page_accessed(page);
1079 prev_index = index;
1082 * Ok, we have the page, and it's up-to-date, so
1083 * now we can copy it to user space...
1085 * The actor routine returns how many bytes were actually used..
1086 * NOTE! This may not be the same as how much of a user buffer
1087 * we filled up (we may be padding etc), so we can only update
1088 * "pos" here (the actor routine has to update the user buffer
1089 * pointers and the remaining count).
1091 ret = actor(desc, page, offset, nr);
1092 offset += ret;
1093 index += offset >> PAGE_CACHE_SHIFT;
1094 offset &= ~PAGE_CACHE_MASK;
1095 prev_offset = offset;
1097 page_cache_release(page);
1098 if (ret == nr && desc->count)
1099 continue;
1100 goto out;
1102 page_not_up_to_date:
1103 /* Get exclusive access to the page ... */
1104 error = lock_page_killable(page);
1105 if (unlikely(error))
1106 goto readpage_error;
1108 page_not_up_to_date_locked:
1109 /* Did it get truncated before we got the lock? */
1110 if (!page->mapping) {
1111 unlock_page(page);
1112 page_cache_release(page);
1113 continue;
1116 /* Did somebody else fill it already? */
1117 if (PageUptodate(page)) {
1118 unlock_page(page);
1119 goto page_ok;
1122 readpage:
1123 /* Start the actual read. The read will unlock the page. */
1124 error = mapping->a_ops->readpage(filp, page);
1126 if (unlikely(error)) {
1127 if (error == AOP_TRUNCATED_PAGE) {
1128 page_cache_release(page);
1129 goto find_page;
1131 goto readpage_error;
1134 if (!PageUptodate(page)) {
1135 error = lock_page_killable(page);
1136 if (unlikely(error))
1137 goto readpage_error;
1138 if (!PageUptodate(page)) {
1139 if (page->mapping == NULL) {
1141 * invalidate_inode_pages got it
1143 unlock_page(page);
1144 page_cache_release(page);
1145 goto find_page;
1147 unlock_page(page);
1148 shrink_readahead_size_eio(filp, ra);
1149 error = -EIO;
1150 goto readpage_error;
1152 unlock_page(page);
1155 goto page_ok;
1157 readpage_error:
1158 /* UHHUH! A synchronous read error occurred. Report it */
1159 desc->error = error;
1160 page_cache_release(page);
1161 goto out;
1163 no_cached_page:
1165 * Ok, it wasn't cached, so we need to create a new
1166 * page..
1168 page = page_cache_alloc_cold(mapping);
1169 if (!page) {
1170 desc->error = -ENOMEM;
1171 goto out;
1173 error = add_to_page_cache_lru(page, mapping,
1174 index, GFP_KERNEL);
1175 if (error) {
1176 page_cache_release(page);
1177 if (error == -EEXIST)
1178 goto find_page;
1179 desc->error = error;
1180 goto out;
1182 goto readpage;
1185 out:
1186 ra->prev_pos = prev_index;
1187 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1188 ra->prev_pos |= prev_offset;
1190 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1191 file_accessed(filp);
1194 int file_read_actor(read_descriptor_t *desc, struct page *page,
1195 unsigned long offset, unsigned long size)
1197 char *kaddr;
1198 unsigned long left, count = desc->count;
1200 if (size > count)
1201 size = count;
1204 * Faults on the destination of a read are common, so do it before
1205 * taking the kmap.
1207 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1208 kaddr = kmap_atomic(page, KM_USER0);
1209 left = __copy_to_user_inatomic(desc->arg.buf,
1210 kaddr + offset, size);
1211 kunmap_atomic(kaddr, KM_USER0);
1212 if (left == 0)
1213 goto success;
1216 /* Do it the slow way */
1217 kaddr = kmap(page);
1218 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1219 kunmap(page);
1221 if (left) {
1222 size -= left;
1223 desc->error = -EFAULT;
1225 success:
1226 desc->count = count - size;
1227 desc->written += size;
1228 desc->arg.buf += size;
1229 return size;
1233 * Performs necessary checks before doing a write
1234 * @iov: io vector request
1235 * @nr_segs: number of segments in the iovec
1236 * @count: number of bytes to write
1237 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1239 * Adjust number of segments and amount of bytes to write (nr_segs should be
1240 * properly initialized first). Returns appropriate error code that caller
1241 * should return or zero in case that write should be allowed.
1243 int generic_segment_checks(const struct iovec *iov,
1244 unsigned long *nr_segs, size_t *count, int access_flags)
1246 unsigned long seg;
1247 size_t cnt = 0;
1248 for (seg = 0; seg < *nr_segs; seg++) {
1249 const struct iovec *iv = &iov[seg];
1252 * If any segment has a negative length, or the cumulative
1253 * length ever wraps negative then return -EINVAL.
1255 cnt += iv->iov_len;
1256 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1257 return -EINVAL;
1258 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1259 continue;
1260 if (seg == 0)
1261 return -EFAULT;
1262 *nr_segs = seg;
1263 cnt -= iv->iov_len; /* This segment is no good */
1264 break;
1266 *count = cnt;
1267 return 0;
1269 EXPORT_SYMBOL(generic_segment_checks);
1272 * generic_file_aio_read - generic filesystem read routine
1273 * @iocb: kernel I/O control block
1274 * @iov: io vector request
1275 * @nr_segs: number of segments in the iovec
1276 * @pos: current file position
1278 * This is the "read()" routine for all filesystems
1279 * that can use the page cache directly.
1281 ssize_t
1282 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1283 unsigned long nr_segs, loff_t pos)
1285 struct file *filp = iocb->ki_filp;
1286 ssize_t retval;
1287 unsigned long seg;
1288 size_t count;
1289 loff_t *ppos = &iocb->ki_pos;
1291 count = 0;
1292 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1293 if (retval)
1294 return retval;
1296 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1297 if (filp->f_flags & O_DIRECT) {
1298 loff_t size;
1299 struct address_space *mapping;
1300 struct inode *inode;
1302 mapping = filp->f_mapping;
1303 inode = mapping->host;
1304 if (!count)
1305 goto out; /* skip atime */
1306 size = i_size_read(inode);
1307 if (pos < size) {
1308 retval = filemap_write_and_wait_range(mapping, pos,
1309 pos + iov_length(iov, nr_segs) - 1);
1310 if (!retval) {
1311 retval = mapping->a_ops->direct_IO(READ, iocb,
1312 iov, pos, nr_segs);
1314 if (retval > 0)
1315 *ppos = pos + retval;
1316 if (retval) {
1317 file_accessed(filp);
1318 goto out;
1323 for (seg = 0; seg < nr_segs; seg++) {
1324 read_descriptor_t desc;
1326 desc.written = 0;
1327 desc.arg.buf = iov[seg].iov_base;
1328 desc.count = iov[seg].iov_len;
1329 if (desc.count == 0)
1330 continue;
1331 desc.error = 0;
1332 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1333 retval += desc.written;
1334 if (desc.error) {
1335 retval = retval ?: desc.error;
1336 break;
1338 if (desc.count > 0)
1339 break;
1341 out:
1342 return retval;
1344 EXPORT_SYMBOL(generic_file_aio_read);
1346 static ssize_t
1347 do_readahead(struct address_space *mapping, struct file *filp,
1348 pgoff_t index, unsigned long nr)
1350 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1351 return -EINVAL;
1353 force_page_cache_readahead(mapping, filp, index, nr);
1354 return 0;
1357 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1359 ssize_t ret;
1360 struct file *file;
1362 ret = -EBADF;
1363 file = fget(fd);
1364 if (file) {
1365 if (file->f_mode & FMODE_READ) {
1366 struct address_space *mapping = file->f_mapping;
1367 pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1368 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1369 unsigned long len = end - start + 1;
1370 ret = do_readahead(mapping, file, start, len);
1372 fput(file);
1374 return ret;
1376 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1377 asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1379 return SYSC_readahead((int) fd, offset, (size_t) count);
1381 SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1382 #endif
1384 #ifdef CONFIG_MMU
1386 * page_cache_read - adds requested page to the page cache if not already there
1387 * @file: file to read
1388 * @offset: page index
1390 * This adds the requested page to the page cache if it isn't already there,
1391 * and schedules an I/O to read in its contents from disk.
1393 static int page_cache_read(struct file *file, pgoff_t offset)
1395 struct address_space *mapping = file->f_mapping;
1396 struct page *page;
1397 int ret;
1399 do {
1400 page = page_cache_alloc_cold(mapping);
1401 if (!page)
1402 return -ENOMEM;
1404 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1405 if (ret == 0)
1406 ret = mapping->a_ops->readpage(file, page);
1407 else if (ret == -EEXIST)
1408 ret = 0; /* losing race to add is OK */
1410 page_cache_release(page);
1412 } while (ret == AOP_TRUNCATED_PAGE);
1414 return ret;
1417 #define MMAP_LOTSAMISS (100)
1420 * Synchronous readahead happens when we don't even find
1421 * a page in the page cache at all.
1423 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1424 struct file_ra_state *ra,
1425 struct file *file,
1426 pgoff_t offset)
1428 unsigned long ra_pages;
1429 struct address_space *mapping = file->f_mapping;
1431 /* If we don't want any read-ahead, don't bother */
1432 if (VM_RandomReadHint(vma))
1433 return;
1435 if (VM_SequentialReadHint(vma) ||
1436 offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
1437 page_cache_sync_readahead(mapping, ra, file, offset,
1438 ra->ra_pages);
1439 return;
1442 if (ra->mmap_miss < INT_MAX)
1443 ra->mmap_miss++;
1446 * Do we miss much more than hit in this file? If so,
1447 * stop bothering with read-ahead. It will only hurt.
1449 if (ra->mmap_miss > MMAP_LOTSAMISS)
1450 return;
1453 * mmap read-around
1455 ra_pages = max_sane_readahead(ra->ra_pages);
1456 if (ra_pages) {
1457 ra->start = max_t(long, 0, offset - ra_pages/2);
1458 ra->size = ra_pages;
1459 ra->async_size = 0;
1460 ra_submit(ra, mapping, file);
1465 * Asynchronous readahead happens when we find the page and PG_readahead,
1466 * so we want to possibly extend the readahead further..
1468 static void do_async_mmap_readahead(struct vm_area_struct *vma,
1469 struct file_ra_state *ra,
1470 struct file *file,
1471 struct page *page,
1472 pgoff_t offset)
1474 struct address_space *mapping = file->f_mapping;
1476 /* If we don't want any read-ahead, don't bother */
1477 if (VM_RandomReadHint(vma))
1478 return;
1479 if (ra->mmap_miss > 0)
1480 ra->mmap_miss--;
1481 if (PageReadahead(page))
1482 page_cache_async_readahead(mapping, ra, file,
1483 page, offset, ra->ra_pages);
1487 * filemap_fault - read in file data for page fault handling
1488 * @vma: vma in which the fault was taken
1489 * @vmf: struct vm_fault containing details of the fault
1491 * filemap_fault() is invoked via the vma operations vector for a
1492 * mapped memory region to read in file data during a page fault.
1494 * The goto's are kind of ugly, but this streamlines the normal case of having
1495 * it in the page cache, and handles the special cases reasonably without
1496 * having a lot of duplicated code.
1498 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1500 int error;
1501 struct file *file = vma->vm_file;
1502 struct address_space *mapping = file->f_mapping;
1503 struct file_ra_state *ra = &file->f_ra;
1504 struct inode *inode = mapping->host;
1505 pgoff_t offset = vmf->pgoff;
1506 struct page *page;
1507 pgoff_t size;
1508 int ret = 0;
1510 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1511 if (offset >= size)
1512 return VM_FAULT_SIGBUS;
1515 * Do we have something in the page cache already?
1517 page = find_get_page(mapping, offset);
1518 if (likely(page)) {
1520 * We found the page, so try async readahead before
1521 * waiting for the lock.
1523 do_async_mmap_readahead(vma, ra, file, page, offset);
1524 lock_page(page);
1526 /* Did it get truncated? */
1527 if (unlikely(page->mapping != mapping)) {
1528 unlock_page(page);
1529 put_page(page);
1530 goto no_cached_page;
1532 } else {
1533 /* No page in the page cache at all */
1534 do_sync_mmap_readahead(vma, ra, file, offset);
1535 count_vm_event(PGMAJFAULT);
1536 ret = VM_FAULT_MAJOR;
1537 retry_find:
1538 page = find_lock_page(mapping, offset);
1539 if (!page)
1540 goto no_cached_page;
1544 * We have a locked page in the page cache, now we need to check
1545 * that it's up-to-date. If not, it is going to be due to an error.
1547 if (unlikely(!PageUptodate(page)))
1548 goto page_not_uptodate;
1551 * Found the page and have a reference on it.
1552 * We must recheck i_size under page lock.
1554 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1555 if (unlikely(offset >= size)) {
1556 unlock_page(page);
1557 page_cache_release(page);
1558 return VM_FAULT_SIGBUS;
1561 ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
1562 vmf->page = page;
1563 return ret | VM_FAULT_LOCKED;
1565 no_cached_page:
1567 * We're only likely to ever get here if MADV_RANDOM is in
1568 * effect.
1570 error = page_cache_read(file, offset);
1573 * The page we want has now been added to the page cache.
1574 * In the unlikely event that someone removed it in the
1575 * meantime, we'll just come back here and read it again.
1577 if (error >= 0)
1578 goto retry_find;
1581 * An error return from page_cache_read can result if the
1582 * system is low on memory, or a problem occurs while trying
1583 * to schedule I/O.
1585 if (error == -ENOMEM)
1586 return VM_FAULT_OOM;
1587 return VM_FAULT_SIGBUS;
1589 page_not_uptodate:
1591 * Umm, take care of errors if the page isn't up-to-date.
1592 * Try to re-read it _once_. We do this synchronously,
1593 * because there really aren't any performance issues here
1594 * and we need to check for errors.
1596 ClearPageError(page);
1597 error = mapping->a_ops->readpage(file, page);
1598 if (!error) {
1599 wait_on_page_locked(page);
1600 if (!PageUptodate(page))
1601 error = -EIO;
1603 page_cache_release(page);
1605 if (!error || error == AOP_TRUNCATED_PAGE)
1606 goto retry_find;
1608 /* Things didn't work out. Return zero to tell the mm layer so. */
1609 shrink_readahead_size_eio(file, ra);
1610 return VM_FAULT_SIGBUS;
1612 EXPORT_SYMBOL(filemap_fault);
1614 const struct vm_operations_struct generic_file_vm_ops = {
1615 .fault = filemap_fault,
1618 /* This is used for a general mmap of a disk file */
1620 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1622 struct address_space *mapping = file->f_mapping;
1624 if (!mapping->a_ops->readpage)
1625 return -ENOEXEC;
1626 file_accessed(file);
1627 vma->vm_ops = &generic_file_vm_ops;
1628 vma->vm_flags |= VM_CAN_NONLINEAR;
1629 return 0;
1633 * This is for filesystems which do not implement ->writepage.
1635 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1637 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1638 return -EINVAL;
1639 return generic_file_mmap(file, vma);
1641 #else
1642 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1644 return -ENOSYS;
1646 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1648 return -ENOSYS;
1650 #endif /* CONFIG_MMU */
1652 EXPORT_SYMBOL(generic_file_mmap);
1653 EXPORT_SYMBOL(generic_file_readonly_mmap);
1655 static struct page *__read_cache_page(struct address_space *mapping,
1656 pgoff_t index,
1657 int (*filler)(void *,struct page*),
1658 void *data)
1660 struct page *page;
1661 int err;
1662 repeat:
1663 page = find_get_page(mapping, index);
1664 if (!page) {
1665 page = page_cache_alloc_cold(mapping);
1666 if (!page)
1667 return ERR_PTR(-ENOMEM);
1668 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1669 if (unlikely(err)) {
1670 page_cache_release(page);
1671 if (err == -EEXIST)
1672 goto repeat;
1673 /* Presumably ENOMEM for radix tree node */
1674 return ERR_PTR(err);
1676 err = filler(data, page);
1677 if (err < 0) {
1678 page_cache_release(page);
1679 page = ERR_PTR(err);
1682 return page;
1686 * read_cache_page_async - read into page cache, fill it if needed
1687 * @mapping: the page's address_space
1688 * @index: the page index
1689 * @filler: function to perform the read
1690 * @data: destination for read data
1692 * Same as read_cache_page, but don't wait for page to become unlocked
1693 * after submitting it to the filler.
1695 * Read into the page cache. If a page already exists, and PageUptodate() is
1696 * not set, try to fill the page but don't wait for it to become unlocked.
1698 * If the page does not get brought uptodate, return -EIO.
1700 struct page *read_cache_page_async(struct address_space *mapping,
1701 pgoff_t index,
1702 int (*filler)(void *,struct page*),
1703 void *data)
1705 struct page *page;
1706 int err;
1708 retry:
1709 page = __read_cache_page(mapping, index, filler, data);
1710 if (IS_ERR(page))
1711 return page;
1712 if (PageUptodate(page))
1713 goto out;
1715 lock_page(page);
1716 if (!page->mapping) {
1717 unlock_page(page);
1718 page_cache_release(page);
1719 goto retry;
1721 if (PageUptodate(page)) {
1722 unlock_page(page);
1723 goto out;
1725 err = filler(data, page);
1726 if (err < 0) {
1727 page_cache_release(page);
1728 return ERR_PTR(err);
1730 out:
1731 mark_page_accessed(page);
1732 return page;
1734 EXPORT_SYMBOL(read_cache_page_async);
1737 * read_cache_page - read into page cache, fill it if needed
1738 * @mapping: the page's address_space
1739 * @index: the page index
1740 * @filler: function to perform the read
1741 * @data: destination for read data
1743 * Read into the page cache. If a page already exists, and PageUptodate() is
1744 * not set, try to fill the page then wait for it to become unlocked.
1746 * If the page does not get brought uptodate, return -EIO.
1748 struct page *read_cache_page(struct address_space *mapping,
1749 pgoff_t index,
1750 int (*filler)(void *,struct page*),
1751 void *data)
1753 struct page *page;
1755 page = read_cache_page_async(mapping, index, filler, data);
1756 if (IS_ERR(page))
1757 goto out;
1758 wait_on_page_locked(page);
1759 if (!PageUptodate(page)) {
1760 page_cache_release(page);
1761 page = ERR_PTR(-EIO);
1763 out:
1764 return page;
1766 EXPORT_SYMBOL(read_cache_page);
1769 * The logic we want is
1771 * if suid or (sgid and xgrp)
1772 * remove privs
1774 int should_remove_suid(struct dentry *dentry)
1776 mode_t mode = dentry->d_inode->i_mode;
1777 int kill = 0;
1779 /* suid always must be killed */
1780 if (unlikely(mode & S_ISUID))
1781 kill = ATTR_KILL_SUID;
1784 * sgid without any exec bits is just a mandatory locking mark; leave
1785 * it alone. If some exec bits are set, it's a real sgid; kill it.
1787 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1788 kill |= ATTR_KILL_SGID;
1790 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1791 return kill;
1793 return 0;
1795 EXPORT_SYMBOL(should_remove_suid);
1797 static int __remove_suid(struct dentry *dentry, int kill)
1799 struct iattr newattrs;
1801 newattrs.ia_valid = ATTR_FORCE | kill;
1802 return notify_change(dentry, &newattrs);
1805 int file_remove_suid(struct file *file)
1807 struct dentry *dentry = file->f_path.dentry;
1808 int killsuid = should_remove_suid(dentry);
1809 int killpriv = security_inode_need_killpriv(dentry);
1810 int error = 0;
1812 if (killpriv < 0)
1813 return killpriv;
1814 if (killpriv)
1815 error = security_inode_killpriv(dentry);
1816 if (!error && killsuid)
1817 error = __remove_suid(dentry, killsuid);
1819 return error;
1821 EXPORT_SYMBOL(file_remove_suid);
1823 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1824 const struct iovec *iov, size_t base, size_t bytes)
1826 size_t copied = 0, left = 0;
1828 while (bytes) {
1829 char __user *buf = iov->iov_base + base;
1830 int copy = min(bytes, iov->iov_len - base);
1832 base = 0;
1833 left = __copy_from_user_inatomic(vaddr, buf, copy);
1834 copied += copy;
1835 bytes -= copy;
1836 vaddr += copy;
1837 iov++;
1839 if (unlikely(left))
1840 break;
1842 return copied - left;
1846 * Copy as much as we can into the page and return the number of bytes which
1847 * were sucessfully copied. If a fault is encountered then return the number of
1848 * bytes which were copied.
1850 size_t iov_iter_copy_from_user_atomic(struct page *page,
1851 struct iov_iter *i, unsigned long offset, size_t bytes)
1853 char *kaddr;
1854 size_t copied;
1856 BUG_ON(!in_atomic());
1857 kaddr = kmap_atomic(page, KM_USER0);
1858 if (likely(i->nr_segs == 1)) {
1859 int left;
1860 char __user *buf = i->iov->iov_base + i->iov_offset;
1861 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
1862 copied = bytes - left;
1863 } else {
1864 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1865 i->iov, i->iov_offset, bytes);
1867 kunmap_atomic(kaddr, KM_USER0);
1869 return copied;
1871 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1874 * This has the same sideeffects and return value as
1875 * iov_iter_copy_from_user_atomic().
1876 * The difference is that it attempts to resolve faults.
1877 * Page must not be locked.
1879 size_t iov_iter_copy_from_user(struct page *page,
1880 struct iov_iter *i, unsigned long offset, size_t bytes)
1882 char *kaddr;
1883 size_t copied;
1885 kaddr = kmap(page);
1886 if (likely(i->nr_segs == 1)) {
1887 int left;
1888 char __user *buf = i->iov->iov_base + i->iov_offset;
1889 left = __copy_from_user(kaddr + offset, buf, bytes);
1890 copied = bytes - left;
1891 } else {
1892 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1893 i->iov, i->iov_offset, bytes);
1895 kunmap(page);
1896 return copied;
1898 EXPORT_SYMBOL(iov_iter_copy_from_user);
1900 void iov_iter_advance(struct iov_iter *i, size_t bytes)
1902 BUG_ON(i->count < bytes);
1904 if (likely(i->nr_segs == 1)) {
1905 i->iov_offset += bytes;
1906 i->count -= bytes;
1907 } else {
1908 const struct iovec *iov = i->iov;
1909 size_t base = i->iov_offset;
1912 * The !iov->iov_len check ensures we skip over unlikely
1913 * zero-length segments (without overruning the iovec).
1915 while (bytes || unlikely(i->count && !iov->iov_len)) {
1916 int copy;
1918 copy = min(bytes, iov->iov_len - base);
1919 BUG_ON(!i->count || i->count < copy);
1920 i->count -= copy;
1921 bytes -= copy;
1922 base += copy;
1923 if (iov->iov_len == base) {
1924 iov++;
1925 base = 0;
1928 i->iov = iov;
1929 i->iov_offset = base;
1932 EXPORT_SYMBOL(iov_iter_advance);
1935 * Fault in the first iovec of the given iov_iter, to a maximum length
1936 * of bytes. Returns 0 on success, or non-zero if the memory could not be
1937 * accessed (ie. because it is an invalid address).
1939 * writev-intensive code may want this to prefault several iovecs -- that
1940 * would be possible (callers must not rely on the fact that _only_ the
1941 * first iovec will be faulted with the current implementation).
1943 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
1945 char __user *buf = i->iov->iov_base + i->iov_offset;
1946 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
1947 return fault_in_pages_readable(buf, bytes);
1949 EXPORT_SYMBOL(iov_iter_fault_in_readable);
1952 * Return the count of just the current iov_iter segment.
1954 size_t iov_iter_single_seg_count(struct iov_iter *i)
1956 const struct iovec *iov = i->iov;
1957 if (i->nr_segs == 1)
1958 return i->count;
1959 else
1960 return min(i->count, iov->iov_len - i->iov_offset);
1962 EXPORT_SYMBOL(iov_iter_single_seg_count);
1965 * Performs necessary checks before doing a write
1967 * Can adjust writing position or amount of bytes to write.
1968 * Returns appropriate error code that caller should return or
1969 * zero in case that write should be allowed.
1971 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
1973 struct inode *inode = file->f_mapping->host;
1974 unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
1976 if (unlikely(*pos < 0))
1977 return -EINVAL;
1979 if (!isblk) {
1980 /* FIXME: this is for backwards compatibility with 2.4 */
1981 if (file->f_flags & O_APPEND)
1982 *pos = i_size_read(inode);
1984 if (limit != RLIM_INFINITY) {
1985 if (*pos >= limit) {
1986 send_sig(SIGXFSZ, current, 0);
1987 return -EFBIG;
1989 if (*count > limit - (typeof(limit))*pos) {
1990 *count = limit - (typeof(limit))*pos;
1996 * LFS rule
1998 if (unlikely(*pos + *count > MAX_NON_LFS &&
1999 !(file->f_flags & O_LARGEFILE))) {
2000 if (*pos >= MAX_NON_LFS) {
2001 return -EFBIG;
2003 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2004 *count = MAX_NON_LFS - (unsigned long)*pos;
2009 * Are we about to exceed the fs block limit ?
2011 * If we have written data it becomes a short write. If we have
2012 * exceeded without writing data we send a signal and return EFBIG.
2013 * Linus frestrict idea will clean these up nicely..
2015 if (likely(!isblk)) {
2016 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2017 if (*count || *pos > inode->i_sb->s_maxbytes) {
2018 return -EFBIG;
2020 /* zero-length writes at ->s_maxbytes are OK */
2023 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2024 *count = inode->i_sb->s_maxbytes - *pos;
2025 } else {
2026 #ifdef CONFIG_BLOCK
2027 loff_t isize;
2028 if (bdev_read_only(I_BDEV(inode)))
2029 return -EPERM;
2030 isize = i_size_read(inode);
2031 if (*pos >= isize) {
2032 if (*count || *pos > isize)
2033 return -ENOSPC;
2036 if (*pos + *count > isize)
2037 *count = isize - *pos;
2038 #else
2039 return -EPERM;
2040 #endif
2042 return 0;
2044 EXPORT_SYMBOL(generic_write_checks);
2046 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2047 loff_t pos, unsigned len, unsigned flags,
2048 struct page **pagep, void **fsdata)
2050 const struct address_space_operations *aops = mapping->a_ops;
2052 return aops->write_begin(file, mapping, pos, len, flags,
2053 pagep, fsdata);
2055 EXPORT_SYMBOL(pagecache_write_begin);
2057 int pagecache_write_end(struct file *file, struct address_space *mapping,
2058 loff_t pos, unsigned len, unsigned copied,
2059 struct page *page, void *fsdata)
2061 const struct address_space_operations *aops = mapping->a_ops;
2063 mark_page_accessed(page);
2064 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2066 EXPORT_SYMBOL(pagecache_write_end);
2068 ssize_t
2069 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2070 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2071 size_t count, size_t ocount)
2073 struct file *file = iocb->ki_filp;
2074 struct address_space *mapping = file->f_mapping;
2075 struct inode *inode = mapping->host;
2076 ssize_t written;
2077 size_t write_len;
2078 pgoff_t end;
2080 if (count != ocount)
2081 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2083 write_len = iov_length(iov, *nr_segs);
2084 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2086 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2087 if (written)
2088 goto out;
2091 * After a write we want buffered reads to be sure to go to disk to get
2092 * the new data. We invalidate clean cached page from the region we're
2093 * about to write. We do this *before* the write so that we can return
2094 * without clobbering -EIOCBQUEUED from ->direct_IO().
2096 if (mapping->nrpages) {
2097 written = invalidate_inode_pages2_range(mapping,
2098 pos >> PAGE_CACHE_SHIFT, end);
2100 * If a page can not be invalidated, return 0 to fall back
2101 * to buffered write.
2103 if (written) {
2104 if (written == -EBUSY)
2105 return 0;
2106 goto out;
2110 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2113 * Finally, try again to invalidate clean pages which might have been
2114 * cached by non-direct readahead, or faulted in by get_user_pages()
2115 * if the source of the write was an mmap'ed region of the file
2116 * we're writing. Either one is a pretty crazy thing to do,
2117 * so we don't support it 100%. If this invalidation
2118 * fails, tough, the write still worked...
2120 if (mapping->nrpages) {
2121 invalidate_inode_pages2_range(mapping,
2122 pos >> PAGE_CACHE_SHIFT, end);
2125 if (written > 0) {
2126 loff_t end = pos + written;
2127 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2128 i_size_write(inode, end);
2129 mark_inode_dirty(inode);
2131 *ppos = end;
2133 out:
2134 return written;
2136 EXPORT_SYMBOL(generic_file_direct_write);
2139 * Find or create a page at the given pagecache position. Return the locked
2140 * page. This function is specifically for buffered writes.
2142 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2143 pgoff_t index, unsigned flags)
2145 int status;
2146 struct page *page;
2147 gfp_t gfp_notmask = 0;
2148 if (flags & AOP_FLAG_NOFS)
2149 gfp_notmask = __GFP_FS;
2150 repeat:
2151 page = find_lock_page(mapping, index);
2152 if (likely(page))
2153 return page;
2155 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2156 if (!page)
2157 return NULL;
2158 status = add_to_page_cache_lru(page, mapping, index,
2159 GFP_KERNEL & ~gfp_notmask);
2160 if (unlikely(status)) {
2161 page_cache_release(page);
2162 if (status == -EEXIST)
2163 goto repeat;
2164 return NULL;
2166 return page;
2168 EXPORT_SYMBOL(grab_cache_page_write_begin);
2170 static ssize_t generic_perform_write(struct file *file,
2171 struct iov_iter *i, loff_t pos)
2173 struct address_space *mapping = file->f_mapping;
2174 const struct address_space_operations *a_ops = mapping->a_ops;
2175 long status = 0;
2176 ssize_t written = 0;
2177 unsigned int flags = 0;
2180 * Copies from kernel address space cannot fail (NFSD is a big user).
2182 if (segment_eq(get_fs(), KERNEL_DS))
2183 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2185 do {
2186 struct page *page;
2187 pgoff_t index; /* Pagecache index for current page */
2188 unsigned long offset; /* Offset into pagecache page */
2189 unsigned long bytes; /* Bytes to write to page */
2190 size_t copied; /* Bytes copied from user */
2191 void *fsdata;
2193 offset = (pos & (PAGE_CACHE_SIZE - 1));
2194 index = pos >> PAGE_CACHE_SHIFT;
2195 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2196 iov_iter_count(i));
2198 again:
2201 * Bring in the user page that we will copy from _first_.
2202 * Otherwise there's a nasty deadlock on copying from the
2203 * same page as we're writing to, without it being marked
2204 * up-to-date.
2206 * Not only is this an optimisation, but it is also required
2207 * to check that the address is actually valid, when atomic
2208 * usercopies are used, below.
2210 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2211 status = -EFAULT;
2212 break;
2215 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2216 &page, &fsdata);
2217 if (unlikely(status))
2218 break;
2220 pagefault_disable();
2221 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2222 pagefault_enable();
2223 flush_dcache_page(page);
2225 mark_page_accessed(page);
2226 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2227 page, fsdata);
2228 if (unlikely(status < 0))
2229 break;
2230 copied = status;
2232 cond_resched();
2234 iov_iter_advance(i, copied);
2235 if (unlikely(copied == 0)) {
2237 * If we were unable to copy any data at all, we must
2238 * fall back to a single segment length write.
2240 * If we didn't fallback here, we could livelock
2241 * because not all segments in the iov can be copied at
2242 * once without a pagefault.
2244 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2245 iov_iter_single_seg_count(i));
2246 goto again;
2248 pos += copied;
2249 written += copied;
2251 balance_dirty_pages_ratelimited(mapping);
2253 } while (iov_iter_count(i));
2255 return written ? written : status;
2258 ssize_t
2259 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2260 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2261 size_t count, ssize_t written)
2263 struct file *file = iocb->ki_filp;
2264 struct address_space *mapping = file->f_mapping;
2265 ssize_t status;
2266 struct iov_iter i;
2268 iov_iter_init(&i, iov, nr_segs, count, written);
2269 status = generic_perform_write(file, &i, pos);
2271 if (likely(status >= 0)) {
2272 written += status;
2273 *ppos = pos + status;
2277 * If we get here for O_DIRECT writes then we must have fallen through
2278 * to buffered writes (block instantiation inside i_size). So we sync
2279 * the file data here, to try to honour O_DIRECT expectations.
2281 if (unlikely(file->f_flags & O_DIRECT) && written)
2282 status = filemap_write_and_wait_range(mapping,
2283 pos, pos + written - 1);
2285 return written ? written : status;
2287 EXPORT_SYMBOL(generic_file_buffered_write);
2290 * __generic_file_aio_write - write data to a file
2291 * @iocb: IO state structure (file, offset, etc.)
2292 * @iov: vector with data to write
2293 * @nr_segs: number of segments in the vector
2294 * @ppos: position where to write
2296 * This function does all the work needed for actually writing data to a
2297 * file. It does all basic checks, removes SUID from the file, updates
2298 * modification times and calls proper subroutines depending on whether we
2299 * do direct IO or a standard buffered write.
2301 * It expects i_mutex to be grabbed unless we work on a block device or similar
2302 * object which does not need locking at all.
2304 * This function does *not* take care of syncing data in case of O_SYNC write.
2305 * A caller has to handle it. This is mainly due to the fact that we want to
2306 * avoid syncing under i_mutex.
2308 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2309 unsigned long nr_segs, loff_t *ppos)
2311 struct file *file = iocb->ki_filp;
2312 struct address_space * mapping = file->f_mapping;
2313 size_t ocount; /* original count */
2314 size_t count; /* after file limit checks */
2315 struct inode *inode = mapping->host;
2316 loff_t pos;
2317 ssize_t written;
2318 ssize_t err;
2320 ocount = 0;
2321 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2322 if (err)
2323 return err;
2325 count = ocount;
2326 pos = *ppos;
2328 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2330 /* We can write back this queue in page reclaim */
2331 current->backing_dev_info = mapping->backing_dev_info;
2332 written = 0;
2334 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2335 if (err)
2336 goto out;
2338 if (count == 0)
2339 goto out;
2341 err = file_remove_suid(file);
2342 if (err)
2343 goto out;
2345 file_update_time(file);
2347 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2348 if (unlikely(file->f_flags & O_DIRECT)) {
2349 loff_t endbyte;
2350 ssize_t written_buffered;
2352 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2353 ppos, count, ocount);
2354 if (written < 0 || written == count)
2355 goto out;
2357 * direct-io write to a hole: fall through to buffered I/O
2358 * for completing the rest of the request.
2360 pos += written;
2361 count -= written;
2362 written_buffered = generic_file_buffered_write(iocb, iov,
2363 nr_segs, pos, ppos, count,
2364 written);
2366 * If generic_file_buffered_write() retuned a synchronous error
2367 * then we want to return the number of bytes which were
2368 * direct-written, or the error code if that was zero. Note
2369 * that this differs from normal direct-io semantics, which
2370 * will return -EFOO even if some bytes were written.
2372 if (written_buffered < 0) {
2373 err = written_buffered;
2374 goto out;
2378 * We need to ensure that the page cache pages are written to
2379 * disk and invalidated to preserve the expected O_DIRECT
2380 * semantics.
2382 endbyte = pos + written_buffered - written - 1;
2383 err = do_sync_mapping_range(file->f_mapping, pos, endbyte,
2384 SYNC_FILE_RANGE_WAIT_BEFORE|
2385 SYNC_FILE_RANGE_WRITE|
2386 SYNC_FILE_RANGE_WAIT_AFTER);
2387 if (err == 0) {
2388 written = written_buffered;
2389 invalidate_mapping_pages(mapping,
2390 pos >> PAGE_CACHE_SHIFT,
2391 endbyte >> PAGE_CACHE_SHIFT);
2392 } else {
2394 * We don't know how much we wrote, so just return
2395 * the number of bytes which were direct-written
2398 } else {
2399 written = generic_file_buffered_write(iocb, iov, nr_segs,
2400 pos, ppos, count, written);
2402 out:
2403 current->backing_dev_info = NULL;
2404 return written ? written : err;
2406 EXPORT_SYMBOL(__generic_file_aio_write);
2409 * generic_file_aio_write - write data to a file
2410 * @iocb: IO state structure
2411 * @iov: vector with data to write
2412 * @nr_segs: number of segments in the vector
2413 * @pos: position in file where to write
2415 * This is a wrapper around __generic_file_aio_write() to be used by most
2416 * filesystems. It takes care of syncing the file in case of O_SYNC file
2417 * and acquires i_mutex as needed.
2419 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2420 unsigned long nr_segs, loff_t pos)
2422 struct file *file = iocb->ki_filp;
2423 struct inode *inode = file->f_mapping->host;
2424 ssize_t ret;
2426 BUG_ON(iocb->ki_pos != pos);
2428 mutex_lock(&inode->i_mutex);
2429 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2430 mutex_unlock(&inode->i_mutex);
2432 if (ret > 0 || ret == -EIOCBQUEUED) {
2433 ssize_t err;
2435 err = generic_write_sync(file, pos, ret);
2436 if (err < 0 && ret > 0)
2437 ret = err;
2439 return ret;
2441 EXPORT_SYMBOL(generic_file_aio_write);
2444 * try_to_release_page() - release old fs-specific metadata on a page
2446 * @page: the page which the kernel is trying to free
2447 * @gfp_mask: memory allocation flags (and I/O mode)
2449 * The address_space is to try to release any data against the page
2450 * (presumably at page->private). If the release was successful, return `1'.
2451 * Otherwise return zero.
2453 * This may also be called if PG_fscache is set on a page, indicating that the
2454 * page is known to the local caching routines.
2456 * The @gfp_mask argument specifies whether I/O may be performed to release
2457 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2460 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2462 struct address_space * const mapping = page->mapping;
2464 BUG_ON(!PageLocked(page));
2465 if (PageWriteback(page))
2466 return 0;
2468 if (mapping && mapping->a_ops->releasepage)
2469 return mapping->a_ops->releasepage(page, gfp_mask);
2470 return try_to_free_buffers(page);
2473 EXPORT_SYMBOL(try_to_release_page);