net: fix potential neighbour race in dst_ifdown()
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / mm / filemap.c
blob645a080ba4dfb3be15ba5ab03983f42715f637f9
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/compiler.h>
14 #include <linux/fs.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>
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/cleancache.h>
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_mutex (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_mutex (truncate->unmap_mapping_range)
69 * ->mmap_sem
70 * ->i_mmap_mutex
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 * bdi->wb.list_lock
81 * sb_lock (fs/fs-writeback.c)
82 * ->mapping->tree_lock (__sync_single_inode)
84 * ->i_mmap_mutex
85 * ->anon_vma.lock (vma_adjust)
87 * ->anon_vma.lock
88 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
90 * ->page_table_lock or pte_lock
91 * ->swap_lock (try_to_unmap_one)
92 * ->private_lock (try_to_unmap_one)
93 * ->tree_lock (try_to_unmap_one)
94 * ->zone.lru_lock (follow_page->mark_page_accessed)
95 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
96 * ->private_lock (page_remove_rmap->set_page_dirty)
97 * ->tree_lock (page_remove_rmap->set_page_dirty)
98 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
99 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
100 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
101 * ->inode->i_lock (zap_pte_range->set_page_dirty)
102 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
104 * (code doesn't rely on that order, so you could switch it around)
105 * ->tasklist_lock (memory_failure, collect_procs_ao)
106 * ->i_mmap_mutex
110 * Delete a page from the page cache and free it. Caller has to make
111 * sure the page is locked and that nobody else uses it - or that usage
112 * is safe. The caller must hold the mapping's tree_lock.
114 void __delete_from_page_cache(struct page *page)
116 struct address_space *mapping = page->mapping;
119 * if we're uptodate, flush out into the cleancache, otherwise
120 * invalidate any existing cleancache entries. We can't leave
121 * stale data around in the cleancache once our page is gone
123 if (PageUptodate(page) && PageMappedToDisk(page))
124 cleancache_put_page(page);
125 else
126 cleancache_flush_page(mapping, page);
128 radix_tree_delete(&mapping->page_tree, page->index);
129 page->mapping = NULL;
130 /* Leave page->index set: truncation lookup relies upon it */
131 mapping->nrpages--;
132 __dec_zone_page_state(page, NR_FILE_PAGES);
133 if (PageSwapBacked(page))
134 __dec_zone_page_state(page, NR_SHMEM);
135 BUG_ON(page_mapped(page));
138 * Some filesystems seem to re-dirty the page even after
139 * the VM has canceled the dirty bit (eg ext3 journaling).
141 * Fix it up by doing a final dirty accounting check after
142 * having removed the page entirely.
144 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
145 dec_zone_page_state(page, NR_FILE_DIRTY);
146 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
151 * delete_from_page_cache - delete page from page cache
152 * @page: the page which the kernel is trying to remove from page cache
154 * This must be called only on pages that have been verified to be in the page
155 * cache and locked. It will never put the page into the free list, the caller
156 * has a reference on the page.
158 void delete_from_page_cache(struct page *page)
160 struct address_space *mapping = page->mapping;
161 void (*freepage)(struct page *);
163 BUG_ON(!PageLocked(page));
165 freepage = mapping->a_ops->freepage;
166 spin_lock_irq(&mapping->tree_lock);
167 __delete_from_page_cache(page);
168 spin_unlock_irq(&mapping->tree_lock);
169 mem_cgroup_uncharge_cache_page(page);
171 if (freepage)
172 freepage(page);
173 page_cache_release(page);
175 EXPORT_SYMBOL(delete_from_page_cache);
177 static int sleep_on_page(void *word)
179 io_schedule();
180 return 0;
183 static int sleep_on_page_killable(void *word)
185 sleep_on_page(word);
186 return fatal_signal_pending(current) ? -EINTR : 0;
190 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
191 * @mapping: address space structure to write
192 * @start: offset in bytes where the range starts
193 * @end: offset in bytes where the range ends (inclusive)
194 * @sync_mode: enable synchronous operation
196 * Start writeback against all of a mapping's dirty pages that lie
197 * within the byte offsets <start, end> inclusive.
199 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
200 * opposed to a regular memory cleansing writeback. The difference between
201 * these two operations is that if a dirty page/buffer is encountered, it must
202 * be waited upon, and not just skipped over.
204 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
205 loff_t end, int sync_mode)
207 int ret;
208 struct writeback_control wbc = {
209 .sync_mode = sync_mode,
210 .nr_to_write = LONG_MAX,
211 .range_start = start,
212 .range_end = end,
215 if (!mapping_cap_writeback_dirty(mapping))
216 return 0;
218 ret = do_writepages(mapping, &wbc);
219 return ret;
222 static inline int __filemap_fdatawrite(struct address_space *mapping,
223 int sync_mode)
225 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
228 int filemap_fdatawrite(struct address_space *mapping)
230 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
232 EXPORT_SYMBOL(filemap_fdatawrite);
234 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
235 loff_t end)
237 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
239 EXPORT_SYMBOL(filemap_fdatawrite_range);
242 * filemap_flush - mostly a non-blocking flush
243 * @mapping: target address_space
245 * This is a mostly non-blocking flush. Not suitable for data-integrity
246 * purposes - I/O may not be started against all dirty pages.
248 int filemap_flush(struct address_space *mapping)
250 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
252 EXPORT_SYMBOL(filemap_flush);
255 * filemap_fdatawait_range - wait for writeback to complete
256 * @mapping: address space structure to wait for
257 * @start_byte: offset in bytes where the range starts
258 * @end_byte: offset in bytes where the range ends (inclusive)
260 * Walk the list of under-writeback pages of the given address space
261 * in the given range and wait for all of them.
263 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
264 loff_t end_byte)
266 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
267 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
268 struct pagevec pvec;
269 int nr_pages;
270 int ret = 0;
272 if (end_byte < start_byte)
273 return 0;
275 pagevec_init(&pvec, 0);
276 while ((index <= end) &&
277 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
278 PAGECACHE_TAG_WRITEBACK,
279 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
280 unsigned i;
282 for (i = 0; i < nr_pages; i++) {
283 struct page *page = pvec.pages[i];
285 /* until radix tree lookup accepts end_index */
286 if (page->index > end)
287 continue;
289 wait_on_page_writeback(page);
290 if (TestClearPageError(page))
291 ret = -EIO;
293 pagevec_release(&pvec);
294 cond_resched();
297 /* Check for outstanding write errors */
298 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
299 ret = -ENOSPC;
300 if (test_and_clear_bit(AS_EIO, &mapping->flags))
301 ret = -EIO;
303 return ret;
305 EXPORT_SYMBOL(filemap_fdatawait_range);
308 * filemap_fdatawait - wait for all under-writeback pages to complete
309 * @mapping: address space structure to wait for
311 * Walk the list of under-writeback pages of the given address space
312 * and wait for all of them.
314 int filemap_fdatawait(struct address_space *mapping)
316 loff_t i_size = i_size_read(mapping->host);
318 if (i_size == 0)
319 return 0;
321 return filemap_fdatawait_range(mapping, 0, i_size - 1);
323 EXPORT_SYMBOL(filemap_fdatawait);
325 int filemap_write_and_wait(struct address_space *mapping)
327 int err = 0;
329 if (mapping->nrpages) {
330 err = filemap_fdatawrite(mapping);
332 * Even if the above returned error, the pages may be
333 * written partially (e.g. -ENOSPC), so we wait for it.
334 * But the -EIO is special case, it may indicate the worst
335 * thing (e.g. bug) happened, so we avoid waiting for it.
337 if (err != -EIO) {
338 int err2 = filemap_fdatawait(mapping);
339 if (!err)
340 err = err2;
343 return err;
345 EXPORT_SYMBOL(filemap_write_and_wait);
348 * filemap_write_and_wait_range - write out & wait on a file range
349 * @mapping: the address_space for the pages
350 * @lstart: offset in bytes where the range starts
351 * @lend: offset in bytes where the range ends (inclusive)
353 * Write out and wait upon file offsets lstart->lend, inclusive.
355 * Note that `lend' is inclusive (describes the last byte to be written) so
356 * that this function can be used to write to the very end-of-file (end = -1).
358 int filemap_write_and_wait_range(struct address_space *mapping,
359 loff_t lstart, loff_t lend)
361 int err = 0;
363 if (mapping->nrpages) {
364 err = __filemap_fdatawrite_range(mapping, lstart, lend,
365 WB_SYNC_ALL);
366 /* See comment of filemap_write_and_wait() */
367 if (err != -EIO) {
368 int err2 = filemap_fdatawait_range(mapping,
369 lstart, lend);
370 if (!err)
371 err = err2;
374 return err;
376 EXPORT_SYMBOL(filemap_write_and_wait_range);
379 * replace_page_cache_page - replace a pagecache page with a new one
380 * @old: page to be replaced
381 * @new: page to replace with
382 * @gfp_mask: allocation mode
384 * This function replaces a page in the pagecache with a new one. On
385 * success it acquires the pagecache reference for the new page and
386 * drops it for the old page. Both the old and new pages must be
387 * locked. This function does not add the new page to the LRU, the
388 * caller must do that.
390 * The remove + add is atomic. The only way this function can fail is
391 * memory allocation failure.
393 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
395 int error;
396 struct mem_cgroup *memcg = NULL;
398 VM_BUG_ON(!PageLocked(old));
399 VM_BUG_ON(!PageLocked(new));
400 VM_BUG_ON(new->mapping);
403 * This is not page migration, but prepare_migration and
404 * end_migration does enough work for charge replacement.
406 * In the longer term we probably want a specialized function
407 * for moving the charge from old to new in a more efficient
408 * manner.
410 error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
411 if (error)
412 return error;
414 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
415 if (!error) {
416 struct address_space *mapping = old->mapping;
417 void (*freepage)(struct page *);
419 pgoff_t offset = old->index;
420 freepage = mapping->a_ops->freepage;
422 page_cache_get(new);
423 new->mapping = mapping;
424 new->index = offset;
426 spin_lock_irq(&mapping->tree_lock);
427 __delete_from_page_cache(old);
428 error = radix_tree_insert(&mapping->page_tree, offset, new);
429 BUG_ON(error);
430 mapping->nrpages++;
431 __inc_zone_page_state(new, NR_FILE_PAGES);
432 if (PageSwapBacked(new))
433 __inc_zone_page_state(new, NR_SHMEM);
434 spin_unlock_irq(&mapping->tree_lock);
435 radix_tree_preload_end();
436 if (freepage)
437 freepage(old);
438 page_cache_release(old);
439 mem_cgroup_end_migration(memcg, old, new, true);
440 } else {
441 mem_cgroup_end_migration(memcg, old, new, false);
444 return error;
446 EXPORT_SYMBOL_GPL(replace_page_cache_page);
449 * add_to_page_cache_locked - add a locked page to the pagecache
450 * @page: page to add
451 * @mapping: the page's address_space
452 * @offset: page index
453 * @gfp_mask: page allocation mode
455 * This function is used to add a page to the pagecache. It must be locked.
456 * This function does not add the page to the LRU. The caller must do that.
458 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
459 pgoff_t offset, gfp_t gfp_mask)
461 int error;
463 VM_BUG_ON(!PageLocked(page));
464 VM_BUG_ON(PageSwapBacked(page));
466 error = mem_cgroup_cache_charge(page, current->mm,
467 gfp_mask & GFP_RECLAIM_MASK);
468 if (error)
469 goto out;
471 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
472 if (error == 0) {
473 page_cache_get(page);
474 page->mapping = mapping;
475 page->index = offset;
477 spin_lock_irq(&mapping->tree_lock);
478 error = radix_tree_insert(&mapping->page_tree, offset, page);
479 if (likely(!error)) {
480 mapping->nrpages++;
481 __inc_zone_page_state(page, NR_FILE_PAGES);
482 spin_unlock_irq(&mapping->tree_lock);
483 } else {
484 page->mapping = NULL;
485 /* Leave page->index set: truncation relies upon it */
486 spin_unlock_irq(&mapping->tree_lock);
487 mem_cgroup_uncharge_cache_page(page);
488 page_cache_release(page);
490 radix_tree_preload_end();
491 } else
492 mem_cgroup_uncharge_cache_page(page);
493 out:
494 return error;
496 EXPORT_SYMBOL(add_to_page_cache_locked);
498 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
499 pgoff_t offset, gfp_t gfp_mask)
501 int ret;
503 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
504 if (ret == 0)
505 lru_cache_add_file(page);
506 return ret;
508 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
510 #ifdef CONFIG_NUMA
511 struct page *__page_cache_alloc(gfp_t gfp)
513 int n;
514 struct page *page;
516 if (cpuset_do_page_mem_spread()) {
517 get_mems_allowed();
518 n = cpuset_mem_spread_node();
519 page = alloc_pages_exact_node(n, gfp, 0);
520 put_mems_allowed();
521 return page;
523 return alloc_pages(gfp, 0);
525 EXPORT_SYMBOL(__page_cache_alloc);
526 #endif
529 * In order to wait for pages to become available there must be
530 * waitqueues associated with pages. By using a hash table of
531 * waitqueues where the bucket discipline is to maintain all
532 * waiters on the same queue and wake all when any of the pages
533 * become available, and for the woken contexts to check to be
534 * sure the appropriate page became available, this saves space
535 * at a cost of "thundering herd" phenomena during rare hash
536 * collisions.
538 static wait_queue_head_t *page_waitqueue(struct page *page)
540 const struct zone *zone = page_zone(page);
542 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
545 static inline void wake_up_page(struct page *page, int bit)
547 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
550 void wait_on_page_bit(struct page *page, int bit_nr)
552 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
554 if (test_bit(bit_nr, &page->flags))
555 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
556 TASK_UNINTERRUPTIBLE);
558 EXPORT_SYMBOL(wait_on_page_bit);
560 int wait_on_page_bit_killable(struct page *page, int bit_nr)
562 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
564 if (!test_bit(bit_nr, &page->flags))
565 return 0;
567 return __wait_on_bit(page_waitqueue(page), &wait,
568 sleep_on_page_killable, TASK_KILLABLE);
572 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
573 * @page: Page defining the wait queue of interest
574 * @waiter: Waiter to add to the queue
576 * Add an arbitrary @waiter to the wait queue for the nominated @page.
578 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
580 wait_queue_head_t *q = page_waitqueue(page);
581 unsigned long flags;
583 spin_lock_irqsave(&q->lock, flags);
584 __add_wait_queue(q, waiter);
585 spin_unlock_irqrestore(&q->lock, flags);
587 EXPORT_SYMBOL_GPL(add_page_wait_queue);
590 * unlock_page - unlock a locked page
591 * @page: the page
593 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
594 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
595 * mechananism between PageLocked pages and PageWriteback pages is shared.
596 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
598 * The mb is necessary to enforce ordering between the clear_bit and the read
599 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
601 void unlock_page(struct page *page)
603 VM_BUG_ON(!PageLocked(page));
604 clear_bit_unlock(PG_locked, &page->flags);
605 smp_mb__after_clear_bit();
606 wake_up_page(page, PG_locked);
608 EXPORT_SYMBOL(unlock_page);
611 * end_page_writeback - end writeback against a page
612 * @page: the page
614 void end_page_writeback(struct page *page)
616 if (TestClearPageReclaim(page))
617 rotate_reclaimable_page(page);
619 if (!test_clear_page_writeback(page))
620 BUG();
622 smp_mb__after_clear_bit();
623 wake_up_page(page, PG_writeback);
625 EXPORT_SYMBOL(end_page_writeback);
628 * __lock_page - get a lock on the page, assuming we need to sleep to get it
629 * @page: the page to lock
631 void __lock_page(struct page *page)
633 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
635 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
636 TASK_UNINTERRUPTIBLE);
638 EXPORT_SYMBOL(__lock_page);
640 int __lock_page_killable(struct page *page)
642 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
644 return __wait_on_bit_lock(page_waitqueue(page), &wait,
645 sleep_on_page_killable, TASK_KILLABLE);
647 EXPORT_SYMBOL_GPL(__lock_page_killable);
649 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
650 unsigned int flags)
652 if (flags & FAULT_FLAG_ALLOW_RETRY) {
654 * CAUTION! In this case, mmap_sem is not released
655 * even though return 0.
657 if (flags & FAULT_FLAG_RETRY_NOWAIT)
658 return 0;
660 up_read(&mm->mmap_sem);
661 if (flags & FAULT_FLAG_KILLABLE)
662 wait_on_page_locked_killable(page);
663 else
664 wait_on_page_locked(page);
665 return 0;
666 } else {
667 if (flags & FAULT_FLAG_KILLABLE) {
668 int ret;
670 ret = __lock_page_killable(page);
671 if (ret) {
672 up_read(&mm->mmap_sem);
673 return 0;
675 } else
676 __lock_page(page);
677 return 1;
682 * find_get_page - find and get a page reference
683 * @mapping: the address_space to search
684 * @offset: the page index
686 * Is there a pagecache struct page at the given (mapping, offset) tuple?
687 * If yes, increment its refcount and return it; if no, return NULL.
689 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
691 void **pagep;
692 struct page *page;
694 rcu_read_lock();
695 repeat:
696 page = NULL;
697 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
698 if (pagep) {
699 page = radix_tree_deref_slot(pagep);
700 if (unlikely(!page))
701 goto out;
702 if (radix_tree_exception(page)) {
703 if (radix_tree_deref_retry(page))
704 goto repeat;
706 * Otherwise, shmem/tmpfs must be storing a swap entry
707 * here as an exceptional entry: so return it without
708 * attempting to raise page count.
710 goto out;
712 if (!page_cache_get_speculative(page))
713 goto repeat;
716 * Has the page moved?
717 * This is part of the lockless pagecache protocol. See
718 * include/linux/pagemap.h for details.
720 if (unlikely(page != *pagep)) {
721 page_cache_release(page);
722 goto repeat;
725 out:
726 rcu_read_unlock();
728 return page;
730 EXPORT_SYMBOL(find_get_page);
733 * find_lock_page - locate, pin and lock a pagecache page
734 * @mapping: the address_space to search
735 * @offset: the page index
737 * Locates the desired pagecache page, locks it, increments its reference
738 * count and returns its address.
740 * Returns zero if the page was not present. find_lock_page() may sleep.
742 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
744 struct page *page;
746 repeat:
747 page = find_get_page(mapping, offset);
748 if (page && !radix_tree_exception(page)) {
749 lock_page(page);
750 /* Has the page been truncated? */
751 if (unlikely(page->mapping != mapping)) {
752 unlock_page(page);
753 page_cache_release(page);
754 goto repeat;
756 VM_BUG_ON(page->index != offset);
758 return page;
760 EXPORT_SYMBOL(find_lock_page);
763 * find_or_create_page - locate or add a pagecache page
764 * @mapping: the page's address_space
765 * @index: the page's index into the mapping
766 * @gfp_mask: page allocation mode
768 * Locates a page in the pagecache. If the page is not present, a new page
769 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
770 * LRU list. The returned page is locked and has its reference count
771 * incremented.
773 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
774 * allocation!
776 * find_or_create_page() returns the desired page's address, or zero on
777 * memory exhaustion.
779 struct page *find_or_create_page(struct address_space *mapping,
780 pgoff_t index, gfp_t gfp_mask)
782 struct page *page;
783 int err;
784 repeat:
785 page = find_lock_page(mapping, index);
786 if (!page) {
787 page = __page_cache_alloc(gfp_mask);
788 if (!page)
789 return NULL;
791 * We want a regular kernel memory (not highmem or DMA etc)
792 * allocation for the radix tree nodes, but we need to honour
793 * the context-specific requirements the caller has asked for.
794 * GFP_RECLAIM_MASK collects those requirements.
796 err = add_to_page_cache_lru(page, mapping, index,
797 (gfp_mask & GFP_RECLAIM_MASK));
798 if (unlikely(err)) {
799 page_cache_release(page);
800 page = NULL;
801 if (err == -EEXIST)
802 goto repeat;
805 return page;
807 EXPORT_SYMBOL(find_or_create_page);
810 * find_get_pages - gang pagecache lookup
811 * @mapping: The address_space to search
812 * @start: The starting page index
813 * @nr_pages: The maximum number of pages
814 * @pages: Where the resulting pages are placed
816 * find_get_pages() will search for and return a group of up to
817 * @nr_pages pages in the mapping. The pages are placed at @pages.
818 * find_get_pages() takes a reference against the returned pages.
820 * The search returns a group of mapping-contiguous pages with ascending
821 * indexes. There may be holes in the indices due to not-present pages.
823 * find_get_pages() returns the number of pages which were found.
825 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
826 unsigned int nr_pages, struct page **pages)
828 unsigned int i;
829 unsigned int ret;
830 unsigned int nr_found;
832 rcu_read_lock();
833 restart:
834 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
835 (void ***)pages, NULL, start, nr_pages);
836 ret = 0;
837 for (i = 0; i < nr_found; i++) {
838 struct page *page;
839 repeat:
840 page = radix_tree_deref_slot((void **)pages[i]);
841 if (unlikely(!page))
842 continue;
844 if (radix_tree_exception(page)) {
845 if (radix_tree_deref_retry(page)) {
847 * Transient condition which can only trigger
848 * when entry at index 0 moves out of or back
849 * to root: none yet gotten, safe to restart.
851 WARN_ON(start | i);
852 goto restart;
855 * Otherwise, shmem/tmpfs must be storing a swap entry
856 * here as an exceptional entry: so skip over it -
857 * we only reach this from invalidate_mapping_pages().
859 continue;
862 if (!page_cache_get_speculative(page))
863 goto repeat;
865 /* Has the page moved? */
866 if (unlikely(page != *((void **)pages[i]))) {
867 page_cache_release(page);
868 goto repeat;
871 pages[ret] = page;
872 ret++;
876 * If all entries were removed before we could secure them,
877 * try again, because callers stop trying once 0 is returned.
879 if (unlikely(!ret && nr_found))
880 goto restart;
881 rcu_read_unlock();
882 return ret;
886 * find_get_pages_contig - gang contiguous pagecache lookup
887 * @mapping: The address_space to search
888 * @index: The starting page index
889 * @nr_pages: The maximum number of pages
890 * @pages: Where the resulting pages are placed
892 * find_get_pages_contig() works exactly like find_get_pages(), except
893 * that the returned number of pages are guaranteed to be contiguous.
895 * find_get_pages_contig() returns the number of pages which were found.
897 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
898 unsigned int nr_pages, struct page **pages)
900 unsigned int i;
901 unsigned int ret;
902 unsigned int nr_found;
904 rcu_read_lock();
905 restart:
906 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
907 (void ***)pages, NULL, index, nr_pages);
908 ret = 0;
909 for (i = 0; i < nr_found; i++) {
910 struct page *page;
911 repeat:
912 page = radix_tree_deref_slot((void **)pages[i]);
913 if (unlikely(!page))
914 continue;
916 if (radix_tree_exception(page)) {
917 if (radix_tree_deref_retry(page)) {
919 * Transient condition which can only trigger
920 * when entry at index 0 moves out of or back
921 * to root: none yet gotten, safe to restart.
923 goto restart;
926 * Otherwise, shmem/tmpfs must be storing a swap entry
927 * here as an exceptional entry: so stop looking for
928 * contiguous pages.
930 break;
933 if (!page_cache_get_speculative(page))
934 goto repeat;
936 /* Has the page moved? */
937 if (unlikely(page != *((void **)pages[i]))) {
938 page_cache_release(page);
939 goto repeat;
943 * must check mapping and index after taking the ref.
944 * otherwise we can get both false positives and false
945 * negatives, which is just confusing to the caller.
947 if (page->mapping == NULL || page->index != index) {
948 page_cache_release(page);
949 break;
952 pages[ret] = page;
953 ret++;
954 index++;
956 rcu_read_unlock();
957 return ret;
959 EXPORT_SYMBOL(find_get_pages_contig);
962 * find_get_pages_tag - find and return pages that match @tag
963 * @mapping: the address_space to search
964 * @index: the starting page index
965 * @tag: the tag index
966 * @nr_pages: the maximum number of pages
967 * @pages: where the resulting pages are placed
969 * Like find_get_pages, except we only return pages which are tagged with
970 * @tag. We update @index to index the next page for the traversal.
972 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
973 int tag, unsigned int nr_pages, struct page **pages)
975 unsigned int i;
976 unsigned int ret;
977 unsigned int nr_found;
979 rcu_read_lock();
980 restart:
981 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
982 (void ***)pages, *index, nr_pages, tag);
983 ret = 0;
984 for (i = 0; i < nr_found; i++) {
985 struct page *page;
986 repeat:
987 page = radix_tree_deref_slot((void **)pages[i]);
988 if (unlikely(!page))
989 continue;
991 if (radix_tree_exception(page)) {
992 if (radix_tree_deref_retry(page)) {
994 * Transient condition which can only trigger
995 * when entry at index 0 moves out of or back
996 * to root: none yet gotten, safe to restart.
998 goto restart;
1001 * This function is never used on a shmem/tmpfs
1002 * mapping, so a swap entry won't be found here.
1004 BUG();
1007 if (!page_cache_get_speculative(page))
1008 goto repeat;
1010 /* Has the page moved? */
1011 if (unlikely(page != *((void **)pages[i]))) {
1012 page_cache_release(page);
1013 goto repeat;
1016 pages[ret] = page;
1017 ret++;
1021 * If all entries were removed before we could secure them,
1022 * try again, because callers stop trying once 0 is returned.
1024 if (unlikely(!ret && nr_found))
1025 goto restart;
1026 rcu_read_unlock();
1028 if (ret)
1029 *index = pages[ret - 1]->index + 1;
1031 return ret;
1033 EXPORT_SYMBOL(find_get_pages_tag);
1036 * grab_cache_page_nowait - returns locked page at given index in given cache
1037 * @mapping: target address_space
1038 * @index: the page index
1040 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1041 * This is intended for speculative data generators, where the data can
1042 * be regenerated if the page couldn't be grabbed. This routine should
1043 * be safe to call while holding the lock for another page.
1045 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1046 * and deadlock against the caller's locked page.
1048 struct page *
1049 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1051 struct page *page = find_get_page(mapping, index);
1053 if (page) {
1054 if (trylock_page(page))
1055 return page;
1056 page_cache_release(page);
1057 return NULL;
1059 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1060 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1061 page_cache_release(page);
1062 page = NULL;
1064 return page;
1066 EXPORT_SYMBOL(grab_cache_page_nowait);
1069 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1070 * a _large_ part of the i/o request. Imagine the worst scenario:
1072 * ---R__________________________________________B__________
1073 * ^ reading here ^ bad block(assume 4k)
1075 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1076 * => failing the whole request => read(R) => read(R+1) =>
1077 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1078 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1079 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1081 * It is going insane. Fix it by quickly scaling down the readahead size.
1083 static void shrink_readahead_size_eio(struct file *filp,
1084 struct file_ra_state *ra)
1086 ra->ra_pages /= 4;
1090 * do_generic_file_read - generic file read routine
1091 * @filp: the file to read
1092 * @ppos: current file position
1093 * @desc: read_descriptor
1094 * @actor: read method
1096 * This is a generic file read routine, and uses the
1097 * mapping->a_ops->readpage() function for the actual low-level stuff.
1099 * This is really ugly. But the goto's actually try to clarify some
1100 * of the logic when it comes to error handling etc.
1102 static void do_generic_file_read(struct file *filp, loff_t *ppos,
1103 read_descriptor_t *desc, read_actor_t actor)
1105 struct address_space *mapping = filp->f_mapping;
1106 struct inode *inode = mapping->host;
1107 struct file_ra_state *ra = &filp->f_ra;
1108 pgoff_t index;
1109 pgoff_t last_index;
1110 pgoff_t prev_index;
1111 unsigned long offset; /* offset into pagecache page */
1112 unsigned int prev_offset;
1113 int error;
1115 index = *ppos >> PAGE_CACHE_SHIFT;
1116 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1117 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1118 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1119 offset = *ppos & ~PAGE_CACHE_MASK;
1121 for (;;) {
1122 struct page *page;
1123 pgoff_t end_index;
1124 loff_t isize;
1125 unsigned long nr, ret;
1127 cond_resched();
1128 find_page:
1129 page = find_get_page(mapping, index);
1130 if (!page) {
1131 page_cache_sync_readahead(mapping,
1132 ra, filp,
1133 index, last_index - index);
1134 page = find_get_page(mapping, index);
1135 if (unlikely(page == NULL))
1136 goto no_cached_page;
1138 if (PageReadahead(page)) {
1139 page_cache_async_readahead(mapping,
1140 ra, filp, page,
1141 index, last_index - index);
1143 if (!PageUptodate(page)) {
1144 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1145 !mapping->a_ops->is_partially_uptodate)
1146 goto page_not_up_to_date;
1147 if (!trylock_page(page))
1148 goto page_not_up_to_date;
1149 /* Did it get truncated before we got the lock? */
1150 if (!page->mapping)
1151 goto page_not_up_to_date_locked;
1152 if (!mapping->a_ops->is_partially_uptodate(page,
1153 desc, offset))
1154 goto page_not_up_to_date_locked;
1155 unlock_page(page);
1157 page_ok:
1159 * i_size must be checked after we know the page is Uptodate.
1161 * Checking i_size after the check allows us to calculate
1162 * the correct value for "nr", which means the zero-filled
1163 * part of the page is not copied back to userspace (unless
1164 * another truncate extends the file - this is desired though).
1167 isize = i_size_read(inode);
1168 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1169 if (unlikely(!isize || index > end_index)) {
1170 page_cache_release(page);
1171 goto out;
1174 /* nr is the maximum number of bytes to copy from this page */
1175 nr = PAGE_CACHE_SIZE;
1176 if (index == end_index) {
1177 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1178 if (nr <= offset) {
1179 page_cache_release(page);
1180 goto out;
1183 nr = nr - offset;
1185 /* If users can be writing to this page using arbitrary
1186 * virtual addresses, take care about potential aliasing
1187 * before reading the page on the kernel side.
1189 if (mapping_writably_mapped(mapping))
1190 flush_dcache_page(page);
1193 * When a sequential read accesses a page several times,
1194 * only mark it as accessed the first time.
1196 if (prev_index != index || offset != prev_offset)
1197 mark_page_accessed(page);
1198 prev_index = index;
1201 * Ok, we have the page, and it's up-to-date, so
1202 * now we can copy it to user space...
1204 * The actor routine returns how many bytes were actually used..
1205 * NOTE! This may not be the same as how much of a user buffer
1206 * we filled up (we may be padding etc), so we can only update
1207 * "pos" here (the actor routine has to update the user buffer
1208 * pointers and the remaining count).
1210 ret = actor(desc, page, offset, nr);
1211 offset += ret;
1212 index += offset >> PAGE_CACHE_SHIFT;
1213 offset &= ~PAGE_CACHE_MASK;
1214 prev_offset = offset;
1216 page_cache_release(page);
1217 if (ret == nr && desc->count)
1218 continue;
1219 goto out;
1221 page_not_up_to_date:
1222 /* Get exclusive access to the page ... */
1223 error = lock_page_killable(page);
1224 if (unlikely(error))
1225 goto readpage_error;
1227 page_not_up_to_date_locked:
1228 /* Did it get truncated before we got the lock? */
1229 if (!page->mapping) {
1230 unlock_page(page);
1231 page_cache_release(page);
1232 continue;
1235 /* Did somebody else fill it already? */
1236 if (PageUptodate(page)) {
1237 unlock_page(page);
1238 goto page_ok;
1241 readpage:
1243 * A previous I/O error may have been due to temporary
1244 * failures, eg. multipath errors.
1245 * PG_error will be set again if readpage fails.
1247 ClearPageError(page);
1248 /* Start the actual read. The read will unlock the page. */
1249 error = mapping->a_ops->readpage(filp, page);
1251 if (unlikely(error)) {
1252 if (error == AOP_TRUNCATED_PAGE) {
1253 page_cache_release(page);
1254 goto find_page;
1256 goto readpage_error;
1259 if (!PageUptodate(page)) {
1260 error = lock_page_killable(page);
1261 if (unlikely(error))
1262 goto readpage_error;
1263 if (!PageUptodate(page)) {
1264 if (page->mapping == NULL) {
1266 * invalidate_mapping_pages got it
1268 unlock_page(page);
1269 page_cache_release(page);
1270 goto find_page;
1272 unlock_page(page);
1273 shrink_readahead_size_eio(filp, ra);
1274 error = -EIO;
1275 goto readpage_error;
1277 unlock_page(page);
1280 goto page_ok;
1282 readpage_error:
1283 /* UHHUH! A synchronous read error occurred. Report it */
1284 desc->error = error;
1285 page_cache_release(page);
1286 goto out;
1288 no_cached_page:
1290 * Ok, it wasn't cached, so we need to create a new
1291 * page..
1293 page = page_cache_alloc_cold(mapping);
1294 if (!page) {
1295 desc->error = -ENOMEM;
1296 goto out;
1298 error = add_to_page_cache_lru(page, mapping,
1299 index, GFP_KERNEL);
1300 if (error) {
1301 page_cache_release(page);
1302 if (error == -EEXIST)
1303 goto find_page;
1304 desc->error = error;
1305 goto out;
1307 goto readpage;
1310 out:
1311 ra->prev_pos = prev_index;
1312 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1313 ra->prev_pos |= prev_offset;
1315 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1316 file_accessed(filp);
1319 int file_read_actor(read_descriptor_t *desc, struct page *page,
1320 unsigned long offset, unsigned long size)
1322 char *kaddr;
1323 unsigned long left, count = desc->count;
1325 if (size > count)
1326 size = count;
1329 * Faults on the destination of a read are common, so do it before
1330 * taking the kmap.
1332 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1333 kaddr = kmap_atomic(page, KM_USER0);
1334 left = __copy_to_user_inatomic(desc->arg.buf,
1335 kaddr + offset, size);
1336 kunmap_atomic(kaddr, KM_USER0);
1337 if (left == 0)
1338 goto success;
1341 /* Do it the slow way */
1342 kaddr = kmap(page);
1343 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1344 kunmap(page);
1346 if (left) {
1347 size -= left;
1348 desc->error = -EFAULT;
1350 success:
1351 desc->count = count - size;
1352 desc->written += size;
1353 desc->arg.buf += size;
1354 return size;
1358 * Performs necessary checks before doing a write
1359 * @iov: io vector request
1360 * @nr_segs: number of segments in the iovec
1361 * @count: number of bytes to write
1362 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1364 * Adjust number of segments and amount of bytes to write (nr_segs should be
1365 * properly initialized first). Returns appropriate error code that caller
1366 * should return or zero in case that write should be allowed.
1368 int generic_segment_checks(const struct iovec *iov,
1369 unsigned long *nr_segs, size_t *count, int access_flags)
1371 unsigned long seg;
1372 size_t cnt = 0;
1373 for (seg = 0; seg < *nr_segs; seg++) {
1374 const struct iovec *iv = &iov[seg];
1377 * If any segment has a negative length, or the cumulative
1378 * length ever wraps negative then return -EINVAL.
1380 cnt += iv->iov_len;
1381 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1382 return -EINVAL;
1383 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1384 continue;
1385 if (seg == 0)
1386 return -EFAULT;
1387 *nr_segs = seg;
1388 cnt -= iv->iov_len; /* This segment is no good */
1389 break;
1391 *count = cnt;
1392 return 0;
1394 EXPORT_SYMBOL(generic_segment_checks);
1397 * generic_file_aio_read - generic filesystem read routine
1398 * @iocb: kernel I/O control block
1399 * @iov: io vector request
1400 * @nr_segs: number of segments in the iovec
1401 * @pos: current file position
1403 * This is the "read()" routine for all filesystems
1404 * that can use the page cache directly.
1406 ssize_t
1407 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1408 unsigned long nr_segs, loff_t pos)
1410 struct file *filp = iocb->ki_filp;
1411 ssize_t retval;
1412 unsigned long seg = 0;
1413 size_t count;
1414 loff_t *ppos = &iocb->ki_pos;
1415 struct blk_plug plug;
1417 count = 0;
1418 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1419 if (retval)
1420 return retval;
1422 blk_start_plug(&plug);
1424 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1425 if (filp->f_flags & O_DIRECT) {
1426 loff_t size;
1427 struct address_space *mapping;
1428 struct inode *inode;
1430 mapping = filp->f_mapping;
1431 inode = mapping->host;
1432 if (!count)
1433 goto out; /* skip atime */
1434 size = i_size_read(inode);
1435 if (pos < size) {
1436 retval = filemap_write_and_wait_range(mapping, pos,
1437 pos + iov_length(iov, nr_segs) - 1);
1438 if (!retval) {
1439 retval = mapping->a_ops->direct_IO(READ, iocb,
1440 iov, pos, nr_segs);
1442 if (retval > 0) {
1443 *ppos = pos + retval;
1444 count -= retval;
1448 * Btrfs can have a short DIO read if we encounter
1449 * compressed extents, so if there was an error, or if
1450 * we've already read everything we wanted to, or if
1451 * there was a short read because we hit EOF, go ahead
1452 * and return. Otherwise fallthrough to buffered io for
1453 * the rest of the read.
1455 if (retval < 0 || !count || *ppos >= size) {
1456 file_accessed(filp);
1457 goto out;
1462 count = retval;
1463 for (seg = 0; seg < nr_segs; seg++) {
1464 read_descriptor_t desc;
1465 loff_t offset = 0;
1468 * If we did a short DIO read we need to skip the section of the
1469 * iov that we've already read data into.
1471 if (count) {
1472 if (count > iov[seg].iov_len) {
1473 count -= iov[seg].iov_len;
1474 continue;
1476 offset = count;
1477 count = 0;
1480 desc.written = 0;
1481 desc.arg.buf = iov[seg].iov_base + offset;
1482 desc.count = iov[seg].iov_len - offset;
1483 if (desc.count == 0)
1484 continue;
1485 desc.error = 0;
1486 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1487 retval += desc.written;
1488 if (desc.error) {
1489 retval = retval ?: desc.error;
1490 break;
1492 if (desc.count > 0)
1493 break;
1495 out:
1496 blk_finish_plug(&plug);
1497 return retval;
1499 EXPORT_SYMBOL(generic_file_aio_read);
1501 static ssize_t
1502 do_readahead(struct address_space *mapping, struct file *filp,
1503 pgoff_t index, unsigned long nr)
1505 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1506 return -EINVAL;
1508 force_page_cache_readahead(mapping, filp, index, nr);
1509 return 0;
1512 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1514 ssize_t ret;
1515 struct file *file;
1517 ret = -EBADF;
1518 file = fget(fd);
1519 if (file) {
1520 if (file->f_mode & FMODE_READ) {
1521 struct address_space *mapping = file->f_mapping;
1522 pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1523 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1524 unsigned long len = end - start + 1;
1525 ret = do_readahead(mapping, file, start, len);
1527 fput(file);
1529 return ret;
1531 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1532 asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1534 return SYSC_readahead((int) fd, offset, (size_t) count);
1536 SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1537 #endif
1539 #ifdef CONFIG_MMU
1541 * page_cache_read - adds requested page to the page cache if not already there
1542 * @file: file to read
1543 * @offset: page index
1545 * This adds the requested page to the page cache if it isn't already there,
1546 * and schedules an I/O to read in its contents from disk.
1548 static int page_cache_read(struct file *file, pgoff_t offset)
1550 struct address_space *mapping = file->f_mapping;
1551 struct page *page;
1552 int ret;
1554 do {
1555 page = page_cache_alloc_cold(mapping);
1556 if (!page)
1557 return -ENOMEM;
1559 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1560 if (ret == 0)
1561 ret = mapping->a_ops->readpage(file, page);
1562 else if (ret == -EEXIST)
1563 ret = 0; /* losing race to add is OK */
1565 page_cache_release(page);
1567 } while (ret == AOP_TRUNCATED_PAGE);
1569 return ret;
1572 #define MMAP_LOTSAMISS (100)
1575 * Synchronous readahead happens when we don't even find
1576 * a page in the page cache at all.
1578 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1579 struct file_ra_state *ra,
1580 struct file *file,
1581 pgoff_t offset)
1583 unsigned long ra_pages;
1584 struct address_space *mapping = file->f_mapping;
1586 /* If we don't want any read-ahead, don't bother */
1587 if (VM_RandomReadHint(vma))
1588 return;
1589 if (!ra->ra_pages)
1590 return;
1592 if (VM_SequentialReadHint(vma)) {
1593 page_cache_sync_readahead(mapping, ra, file, offset,
1594 ra->ra_pages);
1595 return;
1598 /* Avoid banging the cache line if not needed */
1599 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1600 ra->mmap_miss++;
1603 * Do we miss much more than hit in this file? If so,
1604 * stop bothering with read-ahead. It will only hurt.
1606 if (ra->mmap_miss > MMAP_LOTSAMISS)
1607 return;
1610 * mmap read-around
1612 ra_pages = max_sane_readahead(ra->ra_pages);
1613 ra->start = max_t(long, 0, offset - ra_pages / 2);
1614 ra->size = ra_pages;
1615 ra->async_size = ra_pages / 4;
1616 ra_submit(ra, mapping, file);
1620 * Asynchronous readahead happens when we find the page and PG_readahead,
1621 * so we want to possibly extend the readahead further..
1623 static void do_async_mmap_readahead(struct vm_area_struct *vma,
1624 struct file_ra_state *ra,
1625 struct file *file,
1626 struct page *page,
1627 pgoff_t offset)
1629 struct address_space *mapping = file->f_mapping;
1631 /* If we don't want any read-ahead, don't bother */
1632 if (VM_RandomReadHint(vma))
1633 return;
1634 if (ra->mmap_miss > 0)
1635 ra->mmap_miss--;
1636 if (PageReadahead(page))
1637 page_cache_async_readahead(mapping, ra, file,
1638 page, offset, ra->ra_pages);
1642 * filemap_fault - read in file data for page fault handling
1643 * @vma: vma in which the fault was taken
1644 * @vmf: struct vm_fault containing details of the fault
1646 * filemap_fault() is invoked via the vma operations vector for a
1647 * mapped memory region to read in file data during a page fault.
1649 * The goto's are kind of ugly, but this streamlines the normal case of having
1650 * it in the page cache, and handles the special cases reasonably without
1651 * having a lot of duplicated code.
1653 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1655 int error;
1656 struct file *file = vma->vm_file;
1657 struct address_space *mapping = file->f_mapping;
1658 struct file_ra_state *ra = &file->f_ra;
1659 struct inode *inode = mapping->host;
1660 pgoff_t offset = vmf->pgoff;
1661 struct page *page;
1662 pgoff_t size;
1663 int ret = 0;
1665 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1666 if (offset >= size)
1667 return VM_FAULT_SIGBUS;
1670 * Do we have something in the page cache already?
1672 page = find_get_page(mapping, offset);
1673 if (likely(page)) {
1675 * We found the page, so try async readahead before
1676 * waiting for the lock.
1678 do_async_mmap_readahead(vma, ra, file, page, offset);
1679 } else {
1680 /* No page in the page cache at all */
1681 do_sync_mmap_readahead(vma, ra, file, offset);
1682 count_vm_event(PGMAJFAULT);
1683 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1684 ret = VM_FAULT_MAJOR;
1685 retry_find:
1686 page = find_get_page(mapping, offset);
1687 if (!page)
1688 goto no_cached_page;
1691 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1692 page_cache_release(page);
1693 return ret | VM_FAULT_RETRY;
1696 /* Did it get truncated? */
1697 if (unlikely(page->mapping != mapping)) {
1698 unlock_page(page);
1699 put_page(page);
1700 goto retry_find;
1702 VM_BUG_ON(page->index != offset);
1705 * We have a locked page in the page cache, now we need to check
1706 * that it's up-to-date. If not, it is going to be due to an error.
1708 if (unlikely(!PageUptodate(page)))
1709 goto page_not_uptodate;
1712 * Found the page and have a reference on it.
1713 * We must recheck i_size under page lock.
1715 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1716 if (unlikely(offset >= size)) {
1717 unlock_page(page);
1718 page_cache_release(page);
1719 return VM_FAULT_SIGBUS;
1722 vmf->page = page;
1723 return ret | VM_FAULT_LOCKED;
1725 no_cached_page:
1727 * We're only likely to ever get here if MADV_RANDOM is in
1728 * effect.
1730 error = page_cache_read(file, offset);
1733 * The page we want has now been added to the page cache.
1734 * In the unlikely event that someone removed it in the
1735 * meantime, we'll just come back here and read it again.
1737 if (error >= 0)
1738 goto retry_find;
1741 * An error return from page_cache_read can result if the
1742 * system is low on memory, or a problem occurs while trying
1743 * to schedule I/O.
1745 if (error == -ENOMEM)
1746 return VM_FAULT_OOM;
1747 return VM_FAULT_SIGBUS;
1749 page_not_uptodate:
1751 * Umm, take care of errors if the page isn't up-to-date.
1752 * Try to re-read it _once_. We do this synchronously,
1753 * because there really aren't any performance issues here
1754 * and we need to check for errors.
1756 ClearPageError(page);
1757 error = mapping->a_ops->readpage(file, page);
1758 if (!error) {
1759 wait_on_page_locked(page);
1760 if (!PageUptodate(page))
1761 error = -EIO;
1763 page_cache_release(page);
1765 if (!error || error == AOP_TRUNCATED_PAGE)
1766 goto retry_find;
1768 /* Things didn't work out. Return zero to tell the mm layer so. */
1769 shrink_readahead_size_eio(file, ra);
1770 return VM_FAULT_SIGBUS;
1772 EXPORT_SYMBOL(filemap_fault);
1774 const struct vm_operations_struct generic_file_vm_ops = {
1775 .fault = filemap_fault,
1778 /* This is used for a general mmap of a disk file */
1780 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1782 struct address_space *mapping = file->f_mapping;
1784 if (!mapping->a_ops->readpage)
1785 return -ENOEXEC;
1786 file_accessed(file);
1787 vma->vm_ops = &generic_file_vm_ops;
1788 vma->vm_flags |= VM_CAN_NONLINEAR;
1789 return 0;
1793 * This is for filesystems which do not implement ->writepage.
1795 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1797 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1798 return -EINVAL;
1799 return generic_file_mmap(file, vma);
1801 #else
1802 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1804 return -ENOSYS;
1806 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1808 return -ENOSYS;
1810 #endif /* CONFIG_MMU */
1812 EXPORT_SYMBOL(generic_file_mmap);
1813 EXPORT_SYMBOL(generic_file_readonly_mmap);
1815 static struct page *__read_cache_page(struct address_space *mapping,
1816 pgoff_t index,
1817 int (*filler)(void *, struct page *),
1818 void *data,
1819 gfp_t gfp)
1821 struct page *page;
1822 int err;
1823 repeat:
1824 page = find_get_page(mapping, index);
1825 if (!page) {
1826 page = __page_cache_alloc(gfp | __GFP_COLD);
1827 if (!page)
1828 return ERR_PTR(-ENOMEM);
1829 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1830 if (unlikely(err)) {
1831 page_cache_release(page);
1832 if (err == -EEXIST)
1833 goto repeat;
1834 /* Presumably ENOMEM for radix tree node */
1835 return ERR_PTR(err);
1837 err = filler(data, page);
1838 if (err < 0) {
1839 page_cache_release(page);
1840 page = ERR_PTR(err);
1843 return page;
1846 static struct page *do_read_cache_page(struct address_space *mapping,
1847 pgoff_t index,
1848 int (*filler)(void *, struct page *),
1849 void *data,
1850 gfp_t gfp)
1853 struct page *page;
1854 int err;
1856 retry:
1857 page = __read_cache_page(mapping, index, filler, data, gfp);
1858 if (IS_ERR(page))
1859 return page;
1860 if (PageUptodate(page))
1861 goto out;
1863 lock_page(page);
1864 if (!page->mapping) {
1865 unlock_page(page);
1866 page_cache_release(page);
1867 goto retry;
1869 if (PageUptodate(page)) {
1870 unlock_page(page);
1871 goto out;
1873 err = filler(data, page);
1874 if (err < 0) {
1875 page_cache_release(page);
1876 return ERR_PTR(err);
1878 out:
1879 mark_page_accessed(page);
1880 return page;
1884 * read_cache_page_async - read into page cache, fill it if needed
1885 * @mapping: the page's address_space
1886 * @index: the page index
1887 * @filler: function to perform the read
1888 * @data: first arg to filler(data, page) function, often left as NULL
1890 * Same as read_cache_page, but don't wait for page to become unlocked
1891 * after submitting it to the filler.
1893 * Read into the page cache. If a page already exists, and PageUptodate() is
1894 * not set, try to fill the page but don't wait for it to become unlocked.
1896 * If the page does not get brought uptodate, return -EIO.
1898 struct page *read_cache_page_async(struct address_space *mapping,
1899 pgoff_t index,
1900 int (*filler)(void *, struct page *),
1901 void *data)
1903 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1905 EXPORT_SYMBOL(read_cache_page_async);
1907 static struct page *wait_on_page_read(struct page *page)
1909 if (!IS_ERR(page)) {
1910 wait_on_page_locked(page);
1911 if (!PageUptodate(page)) {
1912 page_cache_release(page);
1913 page = ERR_PTR(-EIO);
1916 return page;
1920 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1921 * @mapping: the page's address_space
1922 * @index: the page index
1923 * @gfp: the page allocator flags to use if allocating
1925 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1926 * any new page allocations done using the specified allocation flags. Note
1927 * that the Radix tree operations will still use GFP_KERNEL, so you can't
1928 * expect to do this atomically or anything like that - but you can pass in
1929 * other page requirements.
1931 * If the page does not get brought uptodate, return -EIO.
1933 struct page *read_cache_page_gfp(struct address_space *mapping,
1934 pgoff_t index,
1935 gfp_t gfp)
1937 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1939 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1941 EXPORT_SYMBOL(read_cache_page_gfp);
1944 * read_cache_page - read into page cache, fill it if needed
1945 * @mapping: the page's address_space
1946 * @index: the page index
1947 * @filler: function to perform the read
1948 * @data: first arg to filler(data, page) function, often left as NULL
1950 * Read into the page cache. If a page already exists, and PageUptodate() is
1951 * not set, try to fill the page then wait for it to become unlocked.
1953 * If the page does not get brought uptodate, return -EIO.
1955 struct page *read_cache_page(struct address_space *mapping,
1956 pgoff_t index,
1957 int (*filler)(void *, struct page *),
1958 void *data)
1960 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1962 EXPORT_SYMBOL(read_cache_page);
1965 * The logic we want is
1967 * if suid or (sgid and xgrp)
1968 * remove privs
1970 int should_remove_suid(struct dentry *dentry)
1972 mode_t mode = dentry->d_inode->i_mode;
1973 int kill = 0;
1975 /* suid always must be killed */
1976 if (unlikely(mode & S_ISUID))
1977 kill = ATTR_KILL_SUID;
1980 * sgid without any exec bits is just a mandatory locking mark; leave
1981 * it alone. If some exec bits are set, it's a real sgid; kill it.
1983 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1984 kill |= ATTR_KILL_SGID;
1986 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1987 return kill;
1989 return 0;
1991 EXPORT_SYMBOL(should_remove_suid);
1993 static int __remove_suid(struct dentry *dentry, int kill)
1995 struct iattr newattrs;
1997 newattrs.ia_valid = ATTR_FORCE | kill;
1998 return notify_change(dentry, &newattrs);
2001 int file_remove_suid(struct file *file)
2003 struct dentry *dentry = file->f_path.dentry;
2004 struct inode *inode = dentry->d_inode;
2005 int killsuid;
2006 int killpriv;
2007 int error = 0;
2009 /* Fast path for nothing security related */
2010 if (IS_NOSEC(inode))
2011 return 0;
2013 killsuid = should_remove_suid(dentry);
2014 killpriv = security_inode_need_killpriv(dentry);
2016 if (killpriv < 0)
2017 return killpriv;
2018 if (killpriv)
2019 error = security_inode_killpriv(dentry);
2020 if (!error && killsuid)
2021 error = __remove_suid(dentry, killsuid);
2022 if (!error && (inode->i_sb->s_flags & MS_NOSEC))
2023 inode->i_flags |= S_NOSEC;
2025 return error;
2027 EXPORT_SYMBOL(file_remove_suid);
2029 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
2030 const struct iovec *iov, size_t base, size_t bytes)
2032 size_t copied = 0, left = 0;
2034 while (bytes) {
2035 char __user *buf = iov->iov_base + base;
2036 int copy = min(bytes, iov->iov_len - base);
2038 base = 0;
2039 left = __copy_from_user_inatomic(vaddr, buf, copy);
2040 copied += copy;
2041 bytes -= copy;
2042 vaddr += copy;
2043 iov++;
2045 if (unlikely(left))
2046 break;
2048 return copied - left;
2052 * Copy as much as we can into the page and return the number of bytes which
2053 * were successfully copied. If a fault is encountered then return the number of
2054 * bytes which were copied.
2056 size_t iov_iter_copy_from_user_atomic(struct page *page,
2057 struct iov_iter *i, unsigned long offset, size_t bytes)
2059 char *kaddr;
2060 size_t copied;
2062 BUG_ON(!in_atomic());
2063 kaddr = kmap_atomic(page, KM_USER0);
2064 if (likely(i->nr_segs == 1)) {
2065 int left;
2066 char __user *buf = i->iov->iov_base + i->iov_offset;
2067 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
2068 copied = bytes - left;
2069 } else {
2070 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2071 i->iov, i->iov_offset, bytes);
2073 kunmap_atomic(kaddr, KM_USER0);
2075 return copied;
2077 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
2080 * This has the same sideeffects and return value as
2081 * iov_iter_copy_from_user_atomic().
2082 * The difference is that it attempts to resolve faults.
2083 * Page must not be locked.
2085 size_t iov_iter_copy_from_user(struct page *page,
2086 struct iov_iter *i, unsigned long offset, size_t bytes)
2088 char *kaddr;
2089 size_t copied;
2091 kaddr = kmap(page);
2092 if (likely(i->nr_segs == 1)) {
2093 int left;
2094 char __user *buf = i->iov->iov_base + i->iov_offset;
2095 left = __copy_from_user(kaddr + offset, buf, bytes);
2096 copied = bytes - left;
2097 } else {
2098 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2099 i->iov, i->iov_offset, bytes);
2101 kunmap(page);
2102 return copied;
2104 EXPORT_SYMBOL(iov_iter_copy_from_user);
2106 void iov_iter_advance(struct iov_iter *i, size_t bytes)
2108 BUG_ON(i->count < bytes);
2110 if (likely(i->nr_segs == 1)) {
2111 i->iov_offset += bytes;
2112 i->count -= bytes;
2113 } else {
2114 const struct iovec *iov = i->iov;
2115 size_t base = i->iov_offset;
2118 * The !iov->iov_len check ensures we skip over unlikely
2119 * zero-length segments (without overruning the iovec).
2121 while (bytes || unlikely(i->count && !iov->iov_len)) {
2122 int copy;
2124 copy = min(bytes, iov->iov_len - base);
2125 BUG_ON(!i->count || i->count < copy);
2126 i->count -= copy;
2127 bytes -= copy;
2128 base += copy;
2129 if (iov->iov_len == base) {
2130 iov++;
2131 base = 0;
2134 i->iov = iov;
2135 i->iov_offset = base;
2138 EXPORT_SYMBOL(iov_iter_advance);
2141 * Fault in the first iovec of the given iov_iter, to a maximum length
2142 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2143 * accessed (ie. because it is an invalid address).
2145 * writev-intensive code may want this to prefault several iovecs -- that
2146 * would be possible (callers must not rely on the fact that _only_ the
2147 * first iovec will be faulted with the current implementation).
2149 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2151 char __user *buf = i->iov->iov_base + i->iov_offset;
2152 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2153 return fault_in_pages_readable(buf, bytes);
2155 EXPORT_SYMBOL(iov_iter_fault_in_readable);
2158 * Return the count of just the current iov_iter segment.
2160 size_t iov_iter_single_seg_count(struct iov_iter *i)
2162 const struct iovec *iov = i->iov;
2163 if (i->nr_segs == 1)
2164 return i->count;
2165 else
2166 return min(i->count, iov->iov_len - i->iov_offset);
2168 EXPORT_SYMBOL(iov_iter_single_seg_count);
2171 * Performs necessary checks before doing a write
2173 * Can adjust writing position or amount of bytes to write.
2174 * Returns appropriate error code that caller should return or
2175 * zero in case that write should be allowed.
2177 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2179 struct inode *inode = file->f_mapping->host;
2180 unsigned long limit = rlimit(RLIMIT_FSIZE);
2182 if (unlikely(*pos < 0))
2183 return -EINVAL;
2185 if (!isblk) {
2186 /* FIXME: this is for backwards compatibility with 2.4 */
2187 if (file->f_flags & O_APPEND)
2188 *pos = i_size_read(inode);
2190 if (limit != RLIM_INFINITY) {
2191 if (*pos >= limit) {
2192 send_sig(SIGXFSZ, current, 0);
2193 return -EFBIG;
2195 if (*count > limit - (typeof(limit))*pos) {
2196 *count = limit - (typeof(limit))*pos;
2202 * LFS rule
2204 if (unlikely(*pos + *count > MAX_NON_LFS &&
2205 !(file->f_flags & O_LARGEFILE))) {
2206 if (*pos >= MAX_NON_LFS) {
2207 return -EFBIG;
2209 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2210 *count = MAX_NON_LFS - (unsigned long)*pos;
2215 * Are we about to exceed the fs block limit ?
2217 * If we have written data it becomes a short write. If we have
2218 * exceeded without writing data we send a signal and return EFBIG.
2219 * Linus frestrict idea will clean these up nicely..
2221 if (likely(!isblk)) {
2222 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2223 if (*count || *pos > inode->i_sb->s_maxbytes) {
2224 return -EFBIG;
2226 /* zero-length writes at ->s_maxbytes are OK */
2229 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2230 *count = inode->i_sb->s_maxbytes - *pos;
2231 } else {
2232 #ifdef CONFIG_BLOCK
2233 loff_t isize;
2234 if (bdev_read_only(I_BDEV(inode)))
2235 return -EPERM;
2236 isize = i_size_read(inode);
2237 if (*pos >= isize) {
2238 if (*count || *pos > isize)
2239 return -ENOSPC;
2242 if (*pos + *count > isize)
2243 *count = isize - *pos;
2244 #else
2245 return -EPERM;
2246 #endif
2248 return 0;
2250 EXPORT_SYMBOL(generic_write_checks);
2252 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2253 loff_t pos, unsigned len, unsigned flags,
2254 struct page **pagep, void **fsdata)
2256 const struct address_space_operations *aops = mapping->a_ops;
2258 return aops->write_begin(file, mapping, pos, len, flags,
2259 pagep, fsdata);
2261 EXPORT_SYMBOL(pagecache_write_begin);
2263 int pagecache_write_end(struct file *file, struct address_space *mapping,
2264 loff_t pos, unsigned len, unsigned copied,
2265 struct page *page, void *fsdata)
2267 const struct address_space_operations *aops = mapping->a_ops;
2269 mark_page_accessed(page);
2270 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2272 EXPORT_SYMBOL(pagecache_write_end);
2274 ssize_t
2275 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2276 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2277 size_t count, size_t ocount)
2279 struct file *file = iocb->ki_filp;
2280 struct address_space *mapping = file->f_mapping;
2281 struct inode *inode = mapping->host;
2282 ssize_t written;
2283 size_t write_len;
2284 pgoff_t end;
2286 if (count != ocount)
2287 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2289 write_len = iov_length(iov, *nr_segs);
2290 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2292 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2293 if (written)
2294 goto out;
2297 * After a write we want buffered reads to be sure to go to disk to get
2298 * the new data. We invalidate clean cached page from the region we're
2299 * about to write. We do this *before* the write so that we can return
2300 * without clobbering -EIOCBQUEUED from ->direct_IO().
2302 if (mapping->nrpages) {
2303 written = invalidate_inode_pages2_range(mapping,
2304 pos >> PAGE_CACHE_SHIFT, end);
2306 * If a page can not be invalidated, return 0 to fall back
2307 * to buffered write.
2309 if (written) {
2310 if (written == -EBUSY)
2311 return 0;
2312 goto out;
2316 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2319 * Finally, try again to invalidate clean pages which might have been
2320 * cached by non-direct readahead, or faulted in by get_user_pages()
2321 * if the source of the write was an mmap'ed region of the file
2322 * we're writing. Either one is a pretty crazy thing to do,
2323 * so we don't support it 100%. If this invalidation
2324 * fails, tough, the write still worked...
2326 if (mapping->nrpages) {
2327 invalidate_inode_pages2_range(mapping,
2328 pos >> PAGE_CACHE_SHIFT, end);
2331 if (written > 0) {
2332 pos += written;
2333 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2334 i_size_write(inode, pos);
2335 mark_inode_dirty(inode);
2337 *ppos = pos;
2339 out:
2340 return written;
2342 EXPORT_SYMBOL(generic_file_direct_write);
2345 * Find or create a page at the given pagecache position. Return the locked
2346 * page. This function is specifically for buffered writes.
2348 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2349 pgoff_t index, unsigned flags)
2351 int status;
2352 struct page *page;
2353 gfp_t gfp_notmask = 0;
2354 if (flags & AOP_FLAG_NOFS)
2355 gfp_notmask = __GFP_FS;
2356 repeat:
2357 page = find_lock_page(mapping, index);
2358 if (page)
2359 goto found;
2361 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2362 if (!page)
2363 return NULL;
2364 status = add_to_page_cache_lru(page, mapping, index,
2365 GFP_KERNEL & ~gfp_notmask);
2366 if (unlikely(status)) {
2367 page_cache_release(page);
2368 if (status == -EEXIST)
2369 goto repeat;
2370 return NULL;
2372 found:
2373 wait_on_page_writeback(page);
2374 return page;
2376 EXPORT_SYMBOL(grab_cache_page_write_begin);
2378 static ssize_t generic_perform_write(struct file *file,
2379 struct iov_iter *i, loff_t pos)
2381 struct address_space *mapping = file->f_mapping;
2382 const struct address_space_operations *a_ops = mapping->a_ops;
2383 long status = 0;
2384 ssize_t written = 0;
2385 unsigned int flags = 0;
2388 * Copies from kernel address space cannot fail (NFSD is a big user).
2390 if (segment_eq(get_fs(), KERNEL_DS))
2391 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2393 do {
2394 struct page *page;
2395 unsigned long offset; /* Offset into pagecache page */
2396 unsigned long bytes; /* Bytes to write to page */
2397 size_t copied; /* Bytes copied from user */
2398 void *fsdata;
2400 offset = (pos & (PAGE_CACHE_SIZE - 1));
2401 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2402 iov_iter_count(i));
2404 again:
2407 * Bring in the user page that we will copy from _first_.
2408 * Otherwise there's a nasty deadlock on copying from the
2409 * same page as we're writing to, without it being marked
2410 * up-to-date.
2412 * Not only is this an optimisation, but it is also required
2413 * to check that the address is actually valid, when atomic
2414 * usercopies are used, below.
2416 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2417 status = -EFAULT;
2418 break;
2421 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2422 &page, &fsdata);
2423 if (unlikely(status))
2424 break;
2426 if (mapping_writably_mapped(mapping))
2427 flush_dcache_page(page);
2429 pagefault_disable();
2430 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2431 pagefault_enable();
2432 flush_dcache_page(page);
2434 mark_page_accessed(page);
2435 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2436 page, fsdata);
2437 if (unlikely(status < 0))
2438 break;
2439 copied = status;
2441 cond_resched();
2443 iov_iter_advance(i, copied);
2444 if (unlikely(copied == 0)) {
2446 * If we were unable to copy any data at all, we must
2447 * fall back to a single segment length write.
2449 * If we didn't fallback here, we could livelock
2450 * because not all segments in the iov can be copied at
2451 * once without a pagefault.
2453 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2454 iov_iter_single_seg_count(i));
2455 goto again;
2457 pos += copied;
2458 written += copied;
2460 balance_dirty_pages_ratelimited(mapping);
2462 } while (iov_iter_count(i));
2464 return written ? written : status;
2467 ssize_t
2468 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2469 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2470 size_t count, ssize_t written)
2472 struct file *file = iocb->ki_filp;
2473 ssize_t status;
2474 struct iov_iter i;
2476 iov_iter_init(&i, iov, nr_segs, count, written);
2477 status = generic_perform_write(file, &i, pos);
2479 if (likely(status >= 0)) {
2480 written += status;
2481 *ppos = pos + status;
2484 return written ? written : status;
2486 EXPORT_SYMBOL(generic_file_buffered_write);
2489 * __generic_file_aio_write - write data to a file
2490 * @iocb: IO state structure (file, offset, etc.)
2491 * @iov: vector with data to write
2492 * @nr_segs: number of segments in the vector
2493 * @ppos: position where to write
2495 * This function does all the work needed for actually writing data to a
2496 * file. It does all basic checks, removes SUID from the file, updates
2497 * modification times and calls proper subroutines depending on whether we
2498 * do direct IO or a standard buffered write.
2500 * It expects i_mutex to be grabbed unless we work on a block device or similar
2501 * object which does not need locking at all.
2503 * This function does *not* take care of syncing data in case of O_SYNC write.
2504 * A caller has to handle it. This is mainly due to the fact that we want to
2505 * avoid syncing under i_mutex.
2507 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2508 unsigned long nr_segs, loff_t *ppos)
2510 struct file *file = iocb->ki_filp;
2511 struct address_space * mapping = file->f_mapping;
2512 size_t ocount; /* original count */
2513 size_t count; /* after file limit checks */
2514 struct inode *inode = mapping->host;
2515 loff_t pos;
2516 ssize_t written;
2517 ssize_t err;
2519 ocount = 0;
2520 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2521 if (err)
2522 return err;
2524 count = ocount;
2525 pos = *ppos;
2527 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2529 /* We can write back this queue in page reclaim */
2530 current->backing_dev_info = mapping->backing_dev_info;
2531 written = 0;
2533 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2534 if (err)
2535 goto out;
2537 if (count == 0)
2538 goto out;
2540 err = file_remove_suid(file);
2541 if (err)
2542 goto out;
2544 file_update_time(file);
2546 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2547 if (unlikely(file->f_flags & O_DIRECT)) {
2548 loff_t endbyte;
2549 ssize_t written_buffered;
2551 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2552 ppos, count, ocount);
2553 if (written < 0 || written == count)
2554 goto out;
2556 * direct-io write to a hole: fall through to buffered I/O
2557 * for completing the rest of the request.
2559 pos += written;
2560 count -= written;
2561 written_buffered = generic_file_buffered_write(iocb, iov,
2562 nr_segs, pos, ppos, count,
2563 written);
2565 * If generic_file_buffered_write() retuned a synchronous error
2566 * then we want to return the number of bytes which were
2567 * direct-written, or the error code if that was zero. Note
2568 * that this differs from normal direct-io semantics, which
2569 * will return -EFOO even if some bytes were written.
2571 if (written_buffered < 0) {
2572 err = written_buffered;
2573 goto out;
2577 * We need to ensure that the page cache pages are written to
2578 * disk and invalidated to preserve the expected O_DIRECT
2579 * semantics.
2581 endbyte = pos + written_buffered - written - 1;
2582 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2583 if (err == 0) {
2584 written = written_buffered;
2585 invalidate_mapping_pages(mapping,
2586 pos >> PAGE_CACHE_SHIFT,
2587 endbyte >> PAGE_CACHE_SHIFT);
2588 } else {
2590 * We don't know how much we wrote, so just return
2591 * the number of bytes which were direct-written
2594 } else {
2595 written = generic_file_buffered_write(iocb, iov, nr_segs,
2596 pos, ppos, count, written);
2598 out:
2599 current->backing_dev_info = NULL;
2600 return written ? written : err;
2602 EXPORT_SYMBOL(__generic_file_aio_write);
2605 * generic_file_aio_write - write data to a file
2606 * @iocb: IO state structure
2607 * @iov: vector with data to write
2608 * @nr_segs: number of segments in the vector
2609 * @pos: position in file where to write
2611 * This is a wrapper around __generic_file_aio_write() to be used by most
2612 * filesystems. It takes care of syncing the file in case of O_SYNC file
2613 * and acquires i_mutex as needed.
2615 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2616 unsigned long nr_segs, loff_t pos)
2618 struct file *file = iocb->ki_filp;
2619 struct inode *inode = file->f_mapping->host;
2620 struct blk_plug plug;
2621 ssize_t ret;
2623 BUG_ON(iocb->ki_pos != pos);
2625 mutex_lock(&inode->i_mutex);
2626 blk_start_plug(&plug);
2627 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2628 mutex_unlock(&inode->i_mutex);
2630 if (ret > 0 || ret == -EIOCBQUEUED) {
2631 ssize_t err;
2633 err = generic_write_sync(file, pos, ret);
2634 if (err < 0 && ret > 0)
2635 ret = err;
2637 blk_finish_plug(&plug);
2638 return ret;
2640 EXPORT_SYMBOL(generic_file_aio_write);
2643 * try_to_release_page() - release old fs-specific metadata on a page
2645 * @page: the page which the kernel is trying to free
2646 * @gfp_mask: memory allocation flags (and I/O mode)
2648 * The address_space is to try to release any data against the page
2649 * (presumably at page->private). If the release was successful, return `1'.
2650 * Otherwise return zero.
2652 * This may also be called if PG_fscache is set on a page, indicating that the
2653 * page is known to the local caching routines.
2655 * The @gfp_mask argument specifies whether I/O may be performed to release
2656 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2659 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2661 struct address_space * const mapping = page->mapping;
2663 BUG_ON(!PageLocked(page));
2664 if (PageWriteback(page))
2665 return 0;
2667 if (mapping && mapping->a_ops->releasepage)
2668 return mapping->a_ops->releasepage(page, gfp_mask);
2669 return try_to_free_buffers(page);
2672 EXPORT_SYMBOL(try_to_release_page);