4 * Copyright (C) 1994-1999 Linus Torvalds
8 * This file handles the generic file mmap semantics used by
9 * most "normal" filesystems (but you don't /have/ to use this:
10 * the NFS filesystem used to do this differently, for example)
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/compiler.h>
16 #include <linux/uaccess.h>
17 #include <linux/aio.h>
18 #include <linux/capability.h>
19 #include <linux/kernel_stat.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>
39 * FIXME: remove all knowledge of the buffer layer from the core VM
41 #include <linux/buffer_head.h> /* for generic_osync_inode */
46 generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
47 loff_t offset, unsigned long nr_segs);
50 * Shared mappings implemented 30.11.1994. It's not fully working yet,
53 * Shared mappings now work. 15.8.1995 Bruno.
55 * finished 'unifying' the page and buffer cache and SMP-threaded the
56 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
58 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
64 * ->i_mmap_lock (vmtruncate)
65 * ->private_lock (__free_pte->__set_page_dirty_buffers)
66 * ->swap_lock (exclusive_swap_page, others)
67 * ->mapping->tree_lock
70 * ->i_mmap_lock (truncate->unmap_mapping_range)
74 * ->page_table_lock or pte_lock (various, mainly in memory.c)
75 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
78 * ->lock_page (access_process_vm)
80 * ->i_mutex (generic_file_buffered_write)
81 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
84 * ->i_alloc_sem (various)
87 * ->sb_lock (fs/fs-writeback.c)
88 * ->mapping->tree_lock (__sync_single_inode)
91 * ->anon_vma.lock (vma_adjust)
94 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
96 * ->page_table_lock or pte_lock
97 * ->swap_lock (try_to_unmap_one)
98 * ->private_lock (try_to_unmap_one)
99 * ->tree_lock (try_to_unmap_one)
100 * ->zone.lru_lock (follow_page->mark_page_accessed)
101 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
102 * ->private_lock (page_remove_rmap->set_page_dirty)
103 * ->tree_lock (page_remove_rmap->set_page_dirty)
104 * ->inode_lock (page_remove_rmap->set_page_dirty)
105 * ->inode_lock (zap_pte_range->set_page_dirty)
106 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
109 * ->dcache_lock (proc_pid_lookup)
113 * Remove a page from the page cache and free it. Caller has to make
114 * sure the page is locked and that nobody else uses it - or that usage
115 * is safe. The caller must hold a write_lock on the mapping's tree_lock.
117 void __remove_from_page_cache(struct page *page)
119 struct address_space *mapping = page->mapping;
121 mem_cgroup_uncharge_page(page);
122 radix_tree_delete(&mapping->page_tree, page->index);
123 page->mapping = NULL;
125 __dec_zone_page_state(page, NR_FILE_PAGES);
126 BUG_ON(page_mapped(page));
129 * Some filesystems seem to re-dirty the page even after
130 * the VM has canceled the dirty bit (eg ext3 journaling).
132 * Fix it up by doing a final dirty accounting check after
133 * having removed the page entirely.
135 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
136 dec_zone_page_state(page, NR_FILE_DIRTY);
137 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
141 void remove_from_page_cache(struct page *page)
143 struct address_space *mapping = page->mapping;
145 BUG_ON(!PageLocked(page));
147 write_lock_irq(&mapping->tree_lock);
148 __remove_from_page_cache(page);
149 write_unlock_irq(&mapping->tree_lock);
152 static int sync_page(void *word)
154 struct address_space *mapping;
157 page = container_of((unsigned long *)word, struct page, flags);
160 * page_mapping() is being called without PG_locked held.
161 * Some knowledge of the state and use of the page is used to
162 * reduce the requirements down to a memory barrier.
163 * The danger here is of a stale page_mapping() return value
164 * indicating a struct address_space different from the one it's
165 * associated with when it is associated with one.
166 * After smp_mb(), it's either the correct page_mapping() for
167 * the page, or an old page_mapping() and the page's own
168 * page_mapping() has gone NULL.
169 * The ->sync_page() address_space operation must tolerate
170 * page_mapping() going NULL. By an amazing coincidence,
171 * this comes about because none of the users of the page
172 * in the ->sync_page() methods make essential use of the
173 * page_mapping(), merely passing the page down to the backing
174 * device's unplug functions when it's non-NULL, which in turn
175 * ignore it for all cases but swap, where only page_private(page) is
176 * of interest. When page_mapping() does go NULL, the entire
177 * call stack gracefully ignores the page and returns.
181 mapping = page_mapping(page);
182 if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
183 mapping->a_ops->sync_page(page);
188 static int sync_page_killable(void *word)
191 return fatal_signal_pending(current) ? -EINTR : 0;
195 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
196 * @mapping: address space structure to write
197 * @start: offset in bytes where the range starts
198 * @end: offset in bytes where the range ends (inclusive)
199 * @sync_mode: enable synchronous operation
201 * Start writeback against all of a mapping's dirty pages that lie
202 * within the byte offsets <start, end> inclusive.
204 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
205 * opposed to a regular memory cleansing writeback. The difference between
206 * these two operations is that if a dirty page/buffer is encountered, it must
207 * be waited upon, and not just skipped over.
209 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
210 loff_t end, int sync_mode)
213 struct writeback_control wbc = {
214 .sync_mode = sync_mode,
215 .nr_to_write = mapping->nrpages * 2,
216 .range_start = start,
220 if (!mapping_cap_writeback_dirty(mapping))
223 ret = do_writepages(mapping, &wbc);
227 static inline int __filemap_fdatawrite(struct address_space *mapping,
230 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
233 int filemap_fdatawrite(struct address_space *mapping)
235 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
237 EXPORT_SYMBOL(filemap_fdatawrite);
239 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
242 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
244 EXPORT_SYMBOL(filemap_fdatawrite_range);
247 * filemap_flush - mostly a non-blocking flush
248 * @mapping: target address_space
250 * This is a mostly non-blocking flush. Not suitable for data-integrity
251 * purposes - I/O may not be started against all dirty pages.
253 int filemap_flush(struct address_space *mapping)
255 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
257 EXPORT_SYMBOL(filemap_flush);
260 * wait_on_page_writeback_range - wait for writeback to complete
261 * @mapping: target address_space
262 * @start: beginning page index
263 * @end: ending page index
265 * Wait for writeback to complete against pages indexed by start->end
268 int wait_on_page_writeback_range(struct address_space *mapping,
269 pgoff_t start, pgoff_t end)
279 pagevec_init(&pvec, 0);
281 while ((index <= end) &&
282 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
283 PAGECACHE_TAG_WRITEBACK,
284 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
287 for (i = 0; i < nr_pages; i++) {
288 struct page *page = pvec.pages[i];
290 /* until radix tree lookup accepts end_index */
291 if (page->index > end)
294 wait_on_page_writeback(page);
298 pagevec_release(&pvec);
302 /* Check for outstanding write errors */
303 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
305 if (test_and_clear_bit(AS_EIO, &mapping->flags))
312 * sync_page_range - write and wait on all pages in the passed range
313 * @inode: target inode
314 * @mapping: target address_space
315 * @pos: beginning offset in pages to write
316 * @count: number of bytes to write
318 * Write and wait upon all the pages in the passed range. This is a "data
319 * integrity" operation. It waits upon in-flight writeout before starting and
320 * waiting upon new writeout. If there was an IO error, return it.
322 * We need to re-take i_mutex during the generic_osync_inode list walk because
323 * it is otherwise livelockable.
325 int sync_page_range(struct inode *inode, struct address_space *mapping,
326 loff_t pos, loff_t count)
328 pgoff_t start = pos >> PAGE_CACHE_SHIFT;
329 pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
332 if (!mapping_cap_writeback_dirty(mapping) || !count)
334 ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
336 mutex_lock(&inode->i_mutex);
337 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
338 mutex_unlock(&inode->i_mutex);
341 ret = wait_on_page_writeback_range(mapping, start, end);
344 EXPORT_SYMBOL(sync_page_range);
347 * sync_page_range_nolock - write & wait on all pages in the passed range without locking
348 * @inode: target inode
349 * @mapping: target address_space
350 * @pos: beginning offset in pages to write
351 * @count: number of bytes to write
353 * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea
354 * as it forces O_SYNC writers to different parts of the same file
355 * to be serialised right until io completion.
357 int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
358 loff_t pos, loff_t count)
360 pgoff_t start = pos >> PAGE_CACHE_SHIFT;
361 pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
364 if (!mapping_cap_writeback_dirty(mapping) || !count)
366 ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
368 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
370 ret = wait_on_page_writeback_range(mapping, start, end);
373 EXPORT_SYMBOL(sync_page_range_nolock);
376 * filemap_fdatawait - wait for all under-writeback pages to complete
377 * @mapping: address space structure to wait for
379 * Walk the list of under-writeback pages of the given address space
380 * and wait for all of them.
382 int filemap_fdatawait(struct address_space *mapping)
384 loff_t i_size = i_size_read(mapping->host);
389 return wait_on_page_writeback_range(mapping, 0,
390 (i_size - 1) >> PAGE_CACHE_SHIFT);
392 EXPORT_SYMBOL(filemap_fdatawait);
394 int filemap_write_and_wait(struct address_space *mapping)
398 if (mapping->nrpages) {
399 err = filemap_fdatawrite(mapping);
401 * Even if the above returned error, the pages may be
402 * written partially (e.g. -ENOSPC), so we wait for it.
403 * But the -EIO is special case, it may indicate the worst
404 * thing (e.g. bug) happened, so we avoid waiting for it.
407 int err2 = filemap_fdatawait(mapping);
414 EXPORT_SYMBOL(filemap_write_and_wait);
417 * filemap_write_and_wait_range - write out & wait on a file range
418 * @mapping: the address_space for the pages
419 * @lstart: offset in bytes where the range starts
420 * @lend: offset in bytes where the range ends (inclusive)
422 * Write out and wait upon file offsets lstart->lend, inclusive.
424 * Note that `lend' is inclusive (describes the last byte to be written) so
425 * that this function can be used to write to the very end-of-file (end = -1).
427 int filemap_write_and_wait_range(struct address_space *mapping,
428 loff_t lstart, loff_t lend)
432 if (mapping->nrpages) {
433 err = __filemap_fdatawrite_range(mapping, lstart, lend,
435 /* See comment of filemap_write_and_wait() */
437 int err2 = wait_on_page_writeback_range(mapping,
438 lstart >> PAGE_CACHE_SHIFT,
439 lend >> PAGE_CACHE_SHIFT);
448 * add_to_page_cache - add newly allocated pagecache pages
450 * @mapping: the page's address_space
451 * @offset: page index
452 * @gfp_mask: page allocation mode
454 * This function is used to add newly allocated pagecache pages;
455 * the page is new, so we can just run SetPageLocked() against it.
456 * The other page state flags were set by rmqueue().
458 * This function does not add the page to the LRU. The caller must do that.
460 int add_to_page_cache(struct page *page, struct address_space *mapping,
461 pgoff_t offset, gfp_t gfp_mask)
463 int error = mem_cgroup_cache_charge(page, current->mm,
464 gfp_mask & ~__GFP_HIGHMEM);
468 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
470 write_lock_irq(&mapping->tree_lock);
471 error = radix_tree_insert(&mapping->page_tree, offset, page);
473 page_cache_get(page);
475 page->mapping = mapping;
476 page->index = offset;
478 __inc_zone_page_state(page, NR_FILE_PAGES);
480 mem_cgroup_uncharge_page(page);
482 write_unlock_irq(&mapping->tree_lock);
483 radix_tree_preload_end();
485 mem_cgroup_uncharge_page(page);
489 EXPORT_SYMBOL(add_to_page_cache);
491 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
492 pgoff_t offset, gfp_t gfp_mask)
494 int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
501 struct page *__page_cache_alloc(gfp_t gfp)
503 if (cpuset_do_page_mem_spread()) {
504 int n = cpuset_mem_spread_node();
505 return alloc_pages_node(n, gfp, 0);
507 return alloc_pages(gfp, 0);
509 EXPORT_SYMBOL(__page_cache_alloc);
512 static int __sleep_on_page_lock(void *word)
519 * In order to wait for pages to become available there must be
520 * waitqueues associated with pages. By using a hash table of
521 * waitqueues where the bucket discipline is to maintain all
522 * waiters on the same queue and wake all when any of the pages
523 * become available, and for the woken contexts to check to be
524 * sure the appropriate page became available, this saves space
525 * at a cost of "thundering herd" phenomena during rare hash
528 static wait_queue_head_t *page_waitqueue(struct page *page)
530 const struct zone *zone = page_zone(page);
532 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
535 static inline void wake_up_page(struct page *page, int bit)
537 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
540 void wait_on_page_bit(struct page *page, int bit_nr)
542 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
544 if (test_bit(bit_nr, &page->flags))
545 __wait_on_bit(page_waitqueue(page), &wait, sync_page,
546 TASK_UNINTERRUPTIBLE);
548 EXPORT_SYMBOL(wait_on_page_bit);
551 * unlock_page - unlock a locked 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 first mb is necessary to safely close the critical section opened by the
560 * TestSetPageLocked(), the second mb is necessary to enforce ordering between
561 * the clear_bit and the read of the waitqueue (to avoid SMP races with a
562 * parallel wait_on_page_locked()).
564 void unlock_page(struct page *page)
566 smp_mb__before_clear_bit();
567 if (!TestClearPageLocked(page))
569 smp_mb__after_clear_bit();
570 wake_up_page(page, PG_locked);
572 EXPORT_SYMBOL(unlock_page);
575 * end_page_writeback - end writeback against a page
578 void end_page_writeback(struct page *page)
580 if (TestClearPageReclaim(page))
581 rotate_reclaimable_page(page);
583 if (!test_clear_page_writeback(page))
586 smp_mb__after_clear_bit();
587 wake_up_page(page, PG_writeback);
589 EXPORT_SYMBOL(end_page_writeback);
592 * __lock_page - get a lock on the page, assuming we need to sleep to get it
593 * @page: the page to lock
595 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some
596 * random driver's requestfn sets TASK_RUNNING, we could busywait. However
597 * chances are that on the second loop, the block layer's plug list is empty,
598 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
600 void __lock_page(struct page *page)
602 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
604 __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
605 TASK_UNINTERRUPTIBLE);
607 EXPORT_SYMBOL(__lock_page);
609 int __lock_page_killable(struct page *page)
611 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
613 return __wait_on_bit_lock(page_waitqueue(page), &wait,
614 sync_page_killable, TASK_KILLABLE);
618 * __lock_page_nosync - get a lock on the page, without calling sync_page()
619 * @page: the page to lock
621 * Variant of lock_page that does not require the caller to hold a reference
622 * on the page's mapping.
624 void __lock_page_nosync(struct page *page)
626 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
627 __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
628 TASK_UNINTERRUPTIBLE);
632 * find_get_page - find and get a page reference
633 * @mapping: the address_space to search
634 * @offset: the page index
636 * Is there a pagecache struct page at the given (mapping, offset) tuple?
637 * If yes, increment its refcount and return it; if no, return NULL.
639 struct page * find_get_page(struct address_space *mapping, pgoff_t offset)
643 read_lock_irq(&mapping->tree_lock);
644 page = radix_tree_lookup(&mapping->page_tree, offset);
646 page_cache_get(page);
647 read_unlock_irq(&mapping->tree_lock);
650 EXPORT_SYMBOL(find_get_page);
653 * find_lock_page - locate, pin and lock a pagecache page
654 * @mapping: the address_space to search
655 * @offset: the page index
657 * Locates the desired pagecache page, locks it, increments its reference
658 * count and returns its address.
660 * Returns zero if the page was not present. find_lock_page() may sleep.
662 struct page *find_lock_page(struct address_space *mapping,
668 read_lock_irq(&mapping->tree_lock);
669 page = radix_tree_lookup(&mapping->page_tree, offset);
671 page_cache_get(page);
672 if (TestSetPageLocked(page)) {
673 read_unlock_irq(&mapping->tree_lock);
676 /* Has the page been truncated while we slept? */
677 if (unlikely(page->mapping != mapping)) {
679 page_cache_release(page);
682 VM_BUG_ON(page->index != offset);
686 read_unlock_irq(&mapping->tree_lock);
690 EXPORT_SYMBOL(find_lock_page);
693 * find_or_create_page - locate or add a pagecache page
694 * @mapping: the page's address_space
695 * @index: the page's index into the mapping
696 * @gfp_mask: page allocation mode
698 * Locates a page in the pagecache. If the page is not present, a new page
699 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
700 * LRU list. The returned page is locked and has its reference count
703 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
706 * find_or_create_page() returns the desired page's address, or zero on
709 struct page *find_or_create_page(struct address_space *mapping,
710 pgoff_t index, gfp_t gfp_mask)
715 page = find_lock_page(mapping, index);
717 page = __page_cache_alloc(gfp_mask);
720 err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
722 page_cache_release(page);
730 EXPORT_SYMBOL(find_or_create_page);
733 * find_get_pages - gang pagecache lookup
734 * @mapping: The address_space to search
735 * @start: The starting page index
736 * @nr_pages: The maximum number of pages
737 * @pages: Where the resulting pages are placed
739 * find_get_pages() will search for and return a group of up to
740 * @nr_pages pages in the mapping. The pages are placed at @pages.
741 * find_get_pages() takes a reference against the returned pages.
743 * The search returns a group of mapping-contiguous pages with ascending
744 * indexes. There may be holes in the indices due to not-present pages.
746 * find_get_pages() returns the number of pages which were found.
748 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
749 unsigned int nr_pages, struct page **pages)
754 read_lock_irq(&mapping->tree_lock);
755 ret = radix_tree_gang_lookup(&mapping->page_tree,
756 (void **)pages, start, nr_pages);
757 for (i = 0; i < ret; i++)
758 page_cache_get(pages[i]);
759 read_unlock_irq(&mapping->tree_lock);
764 * find_get_pages_contig - gang contiguous pagecache lookup
765 * @mapping: The address_space to search
766 * @index: The starting page index
767 * @nr_pages: The maximum number of pages
768 * @pages: Where the resulting pages are placed
770 * find_get_pages_contig() works exactly like find_get_pages(), except
771 * that the returned number of pages are guaranteed to be contiguous.
773 * find_get_pages_contig() returns the number of pages which were found.
775 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
776 unsigned int nr_pages, struct page **pages)
781 read_lock_irq(&mapping->tree_lock);
782 ret = radix_tree_gang_lookup(&mapping->page_tree,
783 (void **)pages, index, nr_pages);
784 for (i = 0; i < ret; i++) {
785 if (pages[i]->mapping == NULL || pages[i]->index != index)
788 page_cache_get(pages[i]);
791 read_unlock_irq(&mapping->tree_lock);
794 EXPORT_SYMBOL(find_get_pages_contig);
797 * find_get_pages_tag - find and return pages that match @tag
798 * @mapping: the address_space to search
799 * @index: the starting page index
800 * @tag: the tag index
801 * @nr_pages: the maximum number of pages
802 * @pages: where the resulting pages are placed
804 * Like find_get_pages, except we only return pages which are tagged with
805 * @tag. We update @index to index the next page for the traversal.
807 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
808 int tag, unsigned int nr_pages, struct page **pages)
813 read_lock_irq(&mapping->tree_lock);
814 ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
815 (void **)pages, *index, nr_pages, tag);
816 for (i = 0; i < ret; i++)
817 page_cache_get(pages[i]);
819 *index = pages[ret - 1]->index + 1;
820 read_unlock_irq(&mapping->tree_lock);
823 EXPORT_SYMBOL(find_get_pages_tag);
826 * grab_cache_page_nowait - returns locked page at given index in given cache
827 * @mapping: target address_space
828 * @index: the page index
830 * Same as grab_cache_page(), but do not wait if the page is unavailable.
831 * This is intended for speculative data generators, where the data can
832 * be regenerated if the page couldn't be grabbed. This routine should
833 * be safe to call while holding the lock for another page.
835 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
836 * and deadlock against the caller's locked page.
839 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
841 struct page *page = find_get_page(mapping, index);
844 if (!TestSetPageLocked(page))
846 page_cache_release(page);
849 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
850 if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) {
851 page_cache_release(page);
856 EXPORT_SYMBOL(grab_cache_page_nowait);
859 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
860 * a _large_ part of the i/o request. Imagine the worst scenario:
862 * ---R__________________________________________B__________
863 * ^ reading here ^ bad block(assume 4k)
865 * read(R) => miss => readahead(R...B) => media error => frustrating retries
866 * => failing the whole request => read(R) => read(R+1) =>
867 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
868 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
869 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
871 * It is going insane. Fix it by quickly scaling down the readahead size.
873 static void shrink_readahead_size_eio(struct file *filp,
874 struct file_ra_state *ra)
883 * do_generic_file_read - generic file read routine
884 * @filp: the file to read
885 * @ppos: current file position
886 * @desc: read_descriptor
887 * @actor: read method
889 * This is a generic file read routine, and uses the
890 * mapping->a_ops->readpage() function for the actual low-level stuff.
892 * This is really ugly. But the goto's actually try to clarify some
893 * of the logic when it comes to error handling etc.
895 static void do_generic_file_read(struct file *filp, loff_t *ppos,
896 read_descriptor_t *desc, read_actor_t actor)
898 struct address_space *mapping = filp->f_mapping;
899 struct inode *inode = mapping->host;
900 struct file_ra_state *ra = &filp->f_ra;
904 unsigned long offset; /* offset into pagecache page */
905 unsigned int prev_offset;
908 index = *ppos >> PAGE_CACHE_SHIFT;
909 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
910 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
911 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
912 offset = *ppos & ~PAGE_CACHE_MASK;
918 unsigned long nr, ret;
922 page = find_get_page(mapping, index);
924 page_cache_sync_readahead(mapping,
926 index, last_index - index);
927 page = find_get_page(mapping, index);
928 if (unlikely(page == NULL))
931 if (PageReadahead(page)) {
932 page_cache_async_readahead(mapping,
934 index, last_index - index);
936 if (!PageUptodate(page))
937 goto page_not_up_to_date;
940 * i_size must be checked after we know the page is Uptodate.
942 * Checking i_size after the check allows us to calculate
943 * the correct value for "nr", which means the zero-filled
944 * part of the page is not copied back to userspace (unless
945 * another truncate extends the file - this is desired though).
948 isize = i_size_read(inode);
949 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
950 if (unlikely(!isize || index > end_index)) {
951 page_cache_release(page);
955 /* nr is the maximum number of bytes to copy from this page */
956 nr = PAGE_CACHE_SIZE;
957 if (index == end_index) {
958 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
960 page_cache_release(page);
966 /* If users can be writing to this page using arbitrary
967 * virtual addresses, take care about potential aliasing
968 * before reading the page on the kernel side.
970 if (mapping_writably_mapped(mapping))
971 flush_dcache_page(page);
974 * When a sequential read accesses a page several times,
975 * only mark it as accessed the first time.
977 if (prev_index != index || offset != prev_offset)
978 mark_page_accessed(page);
982 * Ok, we have the page, and it's up-to-date, so
983 * now we can copy it to user space...
985 * The actor routine returns how many bytes were actually used..
986 * NOTE! This may not be the same as how much of a user buffer
987 * we filled up (we may be padding etc), so we can only update
988 * "pos" here (the actor routine has to update the user buffer
989 * pointers and the remaining count).
991 ret = actor(desc, page, offset, nr);
993 index += offset >> PAGE_CACHE_SHIFT;
994 offset &= ~PAGE_CACHE_MASK;
995 prev_offset = offset;
997 page_cache_release(page);
998 if (ret == nr && desc->count)
1002 page_not_up_to_date:
1003 /* Get exclusive access to the page ... */
1004 if (lock_page_killable(page))
1007 /* Did it get truncated before we got the lock? */
1008 if (!page->mapping) {
1010 page_cache_release(page);
1014 /* Did somebody else fill it already? */
1015 if (PageUptodate(page)) {
1021 /* Start the actual read. The read will unlock the page. */
1022 error = mapping->a_ops->readpage(filp, page);
1024 if (unlikely(error)) {
1025 if (error == AOP_TRUNCATED_PAGE) {
1026 page_cache_release(page);
1029 goto readpage_error;
1032 if (!PageUptodate(page)) {
1033 if (lock_page_killable(page))
1035 if (!PageUptodate(page)) {
1036 if (page->mapping == NULL) {
1038 * invalidate_inode_pages got it
1041 page_cache_release(page);
1045 shrink_readahead_size_eio(filp, ra);
1056 /* UHHUH! A synchronous read error occurred. Report it */
1057 desc->error = error;
1058 page_cache_release(page);
1063 * Ok, it wasn't cached, so we need to create a new
1066 page = page_cache_alloc_cold(mapping);
1068 desc->error = -ENOMEM;
1071 error = add_to_page_cache_lru(page, mapping,
1074 page_cache_release(page);
1075 if (error == -EEXIST)
1077 desc->error = error;
1084 ra->prev_pos = prev_index;
1085 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1086 ra->prev_pos |= prev_offset;
1088 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1090 file_accessed(filp);
1093 int file_read_actor(read_descriptor_t *desc, struct page *page,
1094 unsigned long offset, unsigned long size)
1097 unsigned long left, count = desc->count;
1103 * Faults on the destination of a read are common, so do it before
1106 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1107 kaddr = kmap_atomic(page, KM_USER0);
1108 left = __copy_to_user_inatomic(desc->arg.buf,
1109 kaddr + offset, size);
1110 kunmap_atomic(kaddr, KM_USER0);
1115 /* Do it the slow way */
1117 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1122 desc->error = -EFAULT;
1125 desc->count = count - size;
1126 desc->written += size;
1127 desc->arg.buf += size;
1132 * Performs necessary checks before doing a write
1133 * @iov: io vector request
1134 * @nr_segs: number of segments in the iovec
1135 * @count: number of bytes to write
1136 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1138 * Adjust number of segments and amount of bytes to write (nr_segs should be
1139 * properly initialized first). Returns appropriate error code that caller
1140 * should return or zero in case that write should be allowed.
1142 int generic_segment_checks(const struct iovec *iov,
1143 unsigned long *nr_segs, size_t *count, int access_flags)
1147 for (seg = 0; seg < *nr_segs; seg++) {
1148 const struct iovec *iv = &iov[seg];
1151 * If any segment has a negative length, or the cumulative
1152 * length ever wraps negative then return -EINVAL.
1155 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1157 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1162 cnt -= iv->iov_len; /* This segment is no good */
1168 EXPORT_SYMBOL(generic_segment_checks);
1171 * generic_file_aio_read - generic filesystem read routine
1172 * @iocb: kernel I/O control block
1173 * @iov: io vector request
1174 * @nr_segs: number of segments in the iovec
1175 * @pos: current file position
1177 * This is the "read()" routine for all filesystems
1178 * that can use the page cache directly.
1181 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1182 unsigned long nr_segs, loff_t pos)
1184 struct file *filp = iocb->ki_filp;
1188 loff_t *ppos = &iocb->ki_pos;
1191 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1195 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1196 if (filp->f_flags & O_DIRECT) {
1198 struct address_space *mapping;
1199 struct inode *inode;
1201 mapping = filp->f_mapping;
1202 inode = mapping->host;
1205 goto out; /* skip atime */
1206 size = i_size_read(inode);
1208 retval = generic_file_direct_IO(READ, iocb,
1211 *ppos = pos + retval;
1213 if (likely(retval != 0)) {
1214 file_accessed(filp);
1221 for (seg = 0; seg < nr_segs; seg++) {
1222 read_descriptor_t desc;
1225 desc.arg.buf = iov[seg].iov_base;
1226 desc.count = iov[seg].iov_len;
1227 if (desc.count == 0)
1230 do_generic_file_read(filp,ppos,&desc,file_read_actor);
1231 retval += desc.written;
1233 retval = retval ?: desc.error;
1243 EXPORT_SYMBOL(generic_file_aio_read);
1246 do_readahead(struct address_space *mapping, struct file *filp,
1247 pgoff_t index, unsigned long nr)
1249 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1252 force_page_cache_readahead(mapping, filp, index,
1253 max_sane_readahead(nr));
1257 asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
1265 if (file->f_mode & FMODE_READ) {
1266 struct address_space *mapping = file->f_mapping;
1267 pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1268 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1269 unsigned long len = end - start + 1;
1270 ret = do_readahead(mapping, file, start, len);
1279 * page_cache_read - adds requested page to the page cache if not already there
1280 * @file: file to read
1281 * @offset: page index
1283 * This adds the requested page to the page cache if it isn't already there,
1284 * and schedules an I/O to read in its contents from disk.
1286 static int page_cache_read(struct file *file, pgoff_t offset)
1288 struct address_space *mapping = file->f_mapping;
1293 page = page_cache_alloc_cold(mapping);
1297 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1299 ret = mapping->a_ops->readpage(file, page);
1300 else if (ret == -EEXIST)
1301 ret = 0; /* losing race to add is OK */
1303 page_cache_release(page);
1305 } while (ret == AOP_TRUNCATED_PAGE);
1310 #define MMAP_LOTSAMISS (100)
1313 * filemap_fault - read in file data for page fault handling
1314 * @vma: vma in which the fault was taken
1315 * @vmf: struct vm_fault containing details of the fault
1317 * filemap_fault() is invoked via the vma operations vector for a
1318 * mapped memory region to read in file data during a page fault.
1320 * The goto's are kind of ugly, but this streamlines the normal case of having
1321 * it in the page cache, and handles the special cases reasonably without
1322 * having a lot of duplicated code.
1324 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1327 struct file *file = vma->vm_file;
1328 struct address_space *mapping = file->f_mapping;
1329 struct file_ra_state *ra = &file->f_ra;
1330 struct inode *inode = mapping->host;
1333 int did_readaround = 0;
1336 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1337 if (vmf->pgoff >= size)
1338 return VM_FAULT_SIGBUS;
1340 /* If we don't want any read-ahead, don't bother */
1341 if (VM_RandomReadHint(vma))
1342 goto no_cached_page;
1345 * Do we have something in the page cache already?
1348 page = find_lock_page(mapping, vmf->pgoff);
1350 * For sequential accesses, we use the generic readahead logic.
1352 if (VM_SequentialReadHint(vma)) {
1354 page_cache_sync_readahead(mapping, ra, file,
1356 page = find_lock_page(mapping, vmf->pgoff);
1358 goto no_cached_page;
1360 if (PageReadahead(page)) {
1361 page_cache_async_readahead(mapping, ra, file, page,
1367 unsigned long ra_pages;
1372 * Do we miss much more than hit in this file? If so,
1373 * stop bothering with read-ahead. It will only hurt.
1375 if (ra->mmap_miss > MMAP_LOTSAMISS)
1376 goto no_cached_page;
1379 * To keep the pgmajfault counter straight, we need to
1380 * check did_readaround, as this is an inner loop.
1382 if (!did_readaround) {
1383 ret = VM_FAULT_MAJOR;
1384 count_vm_event(PGMAJFAULT);
1387 ra_pages = max_sane_readahead(file->f_ra.ra_pages);
1391 if (vmf->pgoff > ra_pages / 2)
1392 start = vmf->pgoff - ra_pages / 2;
1393 do_page_cache_readahead(mapping, file, start, ra_pages);
1395 page = find_lock_page(mapping, vmf->pgoff);
1397 goto no_cached_page;
1400 if (!did_readaround)
1404 * We have a locked page in the page cache, now we need to check
1405 * that it's up-to-date. If not, it is going to be due to an error.
1407 if (unlikely(!PageUptodate(page)))
1408 goto page_not_uptodate;
1410 /* Must recheck i_size under page lock */
1411 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1412 if (unlikely(vmf->pgoff >= size)) {
1414 page_cache_release(page);
1415 return VM_FAULT_SIGBUS;
1419 * Found the page and have a reference on it.
1421 mark_page_accessed(page);
1422 ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT;
1424 return ret | VM_FAULT_LOCKED;
1428 * We're only likely to ever get here if MADV_RANDOM is in
1431 error = page_cache_read(file, vmf->pgoff);
1434 * The page we want has now been added to the page cache.
1435 * In the unlikely event that someone removed it in the
1436 * meantime, we'll just come back here and read it again.
1442 * An error return from page_cache_read can result if the
1443 * system is low on memory, or a problem occurs while trying
1446 if (error == -ENOMEM)
1447 return VM_FAULT_OOM;
1448 return VM_FAULT_SIGBUS;
1452 if (!did_readaround) {
1453 ret = VM_FAULT_MAJOR;
1454 count_vm_event(PGMAJFAULT);
1458 * Umm, take care of errors if the page isn't up-to-date.
1459 * Try to re-read it _once_. We do this synchronously,
1460 * because there really aren't any performance issues here
1461 * and we need to check for errors.
1463 ClearPageError(page);
1464 error = mapping->a_ops->readpage(file, page);
1466 wait_on_page_locked(page);
1467 if (!PageUptodate(page))
1470 page_cache_release(page);
1472 if (!error || error == AOP_TRUNCATED_PAGE)
1475 /* Things didn't work out. Return zero to tell the mm layer so. */
1476 shrink_readahead_size_eio(file, ra);
1477 return VM_FAULT_SIGBUS;
1479 EXPORT_SYMBOL(filemap_fault);
1481 struct vm_operations_struct generic_file_vm_ops = {
1482 .fault = filemap_fault,
1485 /* This is used for a general mmap of a disk file */
1487 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1489 struct address_space *mapping = file->f_mapping;
1491 if (!mapping->a_ops->readpage)
1493 file_accessed(file);
1494 vma->vm_ops = &generic_file_vm_ops;
1495 vma->vm_flags |= VM_CAN_NONLINEAR;
1500 * This is for filesystems which do not implement ->writepage.
1502 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1504 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1506 return generic_file_mmap(file, vma);
1509 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1513 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1517 #endif /* CONFIG_MMU */
1519 EXPORT_SYMBOL(generic_file_mmap);
1520 EXPORT_SYMBOL(generic_file_readonly_mmap);
1522 static struct page *__read_cache_page(struct address_space *mapping,
1524 int (*filler)(void *,struct page*),
1530 page = find_get_page(mapping, index);
1532 page = page_cache_alloc_cold(mapping);
1534 return ERR_PTR(-ENOMEM);
1535 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1536 if (unlikely(err)) {
1537 page_cache_release(page);
1540 /* Presumably ENOMEM for radix tree node */
1541 return ERR_PTR(err);
1543 err = filler(data, page);
1545 page_cache_release(page);
1546 page = ERR_PTR(err);
1553 * read_cache_page_async - read into page cache, fill it if needed
1554 * @mapping: the page's address_space
1555 * @index: the page index
1556 * @filler: function to perform the read
1557 * @data: destination for read data
1559 * Same as read_cache_page, but don't wait for page to become unlocked
1560 * after submitting it to the filler.
1562 * Read into the page cache. If a page already exists, and PageUptodate() is
1563 * not set, try to fill the page but don't wait for it to become unlocked.
1565 * If the page does not get brought uptodate, return -EIO.
1567 struct page *read_cache_page_async(struct address_space *mapping,
1569 int (*filler)(void *,struct page*),
1576 page = __read_cache_page(mapping, index, filler, data);
1579 if (PageUptodate(page))
1583 if (!page->mapping) {
1585 page_cache_release(page);
1588 if (PageUptodate(page)) {
1592 err = filler(data, page);
1594 page_cache_release(page);
1595 return ERR_PTR(err);
1598 mark_page_accessed(page);
1601 EXPORT_SYMBOL(read_cache_page_async);
1604 * read_cache_page - read into page cache, fill it if needed
1605 * @mapping: the page's address_space
1606 * @index: the page index
1607 * @filler: function to perform the read
1608 * @data: destination for read data
1610 * Read into the page cache. If a page already exists, and PageUptodate() is
1611 * not set, try to fill the page then wait for it to become unlocked.
1613 * If the page does not get brought uptodate, return -EIO.
1615 struct page *read_cache_page(struct address_space *mapping,
1617 int (*filler)(void *,struct page*),
1622 page = read_cache_page_async(mapping, index, filler, data);
1625 wait_on_page_locked(page);
1626 if (!PageUptodate(page)) {
1627 page_cache_release(page);
1628 page = ERR_PTR(-EIO);
1633 EXPORT_SYMBOL(read_cache_page);
1636 * The logic we want is
1638 * if suid or (sgid and xgrp)
1641 int should_remove_suid(struct dentry *dentry)
1643 mode_t mode = dentry->d_inode->i_mode;
1646 /* suid always must be killed */
1647 if (unlikely(mode & S_ISUID))
1648 kill = ATTR_KILL_SUID;
1651 * sgid without any exec bits is just a mandatory locking mark; leave
1652 * it alone. If some exec bits are set, it's a real sgid; kill it.
1654 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1655 kill |= ATTR_KILL_SGID;
1657 if (unlikely(kill && !capable(CAP_FSETID)))
1662 EXPORT_SYMBOL(should_remove_suid);
1664 static int __remove_suid(struct dentry *dentry, int kill)
1666 struct iattr newattrs;
1668 newattrs.ia_valid = ATTR_FORCE | kill;
1669 return notify_change(dentry, &newattrs);
1672 int remove_suid(struct dentry *dentry)
1674 int killsuid = should_remove_suid(dentry);
1675 int killpriv = security_inode_need_killpriv(dentry);
1681 error = security_inode_killpriv(dentry);
1682 if (!error && killsuid)
1683 error = __remove_suid(dentry, killsuid);
1687 EXPORT_SYMBOL(remove_suid);
1689 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1690 const struct iovec *iov, size_t base, size_t bytes)
1692 size_t copied = 0, left = 0;
1695 char __user *buf = iov->iov_base + base;
1696 int copy = min(bytes, iov->iov_len - base);
1699 left = __copy_from_user_inatomic_nocache(vaddr, buf, copy);
1708 return copied - left;
1712 * Copy as much as we can into the page and return the number of bytes which
1713 * were sucessfully copied. If a fault is encountered then return the number of
1714 * bytes which were copied.
1716 size_t iov_iter_copy_from_user_atomic(struct page *page,
1717 struct iov_iter *i, unsigned long offset, size_t bytes)
1722 BUG_ON(!in_atomic());
1723 kaddr = kmap_atomic(page, KM_USER0);
1724 if (likely(i->nr_segs == 1)) {
1726 char __user *buf = i->iov->iov_base + i->iov_offset;
1727 left = __copy_from_user_inatomic_nocache(kaddr + offset,
1729 copied = bytes - left;
1731 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1732 i->iov, i->iov_offset, bytes);
1734 kunmap_atomic(kaddr, KM_USER0);
1738 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1741 * This has the same sideeffects and return value as
1742 * iov_iter_copy_from_user_atomic().
1743 * The difference is that it attempts to resolve faults.
1744 * Page must not be locked.
1746 size_t iov_iter_copy_from_user(struct page *page,
1747 struct iov_iter *i, unsigned long offset, size_t bytes)
1753 if (likely(i->nr_segs == 1)) {
1755 char __user *buf = i->iov->iov_base + i->iov_offset;
1756 left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
1757 copied = bytes - left;
1759 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1760 i->iov, i->iov_offset, bytes);
1765 EXPORT_SYMBOL(iov_iter_copy_from_user);
1767 void iov_iter_advance(struct iov_iter *i, size_t bytes)
1769 BUG_ON(i->count < bytes);
1771 if (likely(i->nr_segs == 1)) {
1772 i->iov_offset += bytes;
1775 const struct iovec *iov = i->iov;
1776 size_t base = i->iov_offset;
1779 * The !iov->iov_len check ensures we skip over unlikely
1780 * zero-length segments (without overruning the iovec).
1782 while (bytes || unlikely(!iov->iov_len && i->count)) {
1785 copy = min(bytes, iov->iov_len - base);
1786 BUG_ON(!i->count || i->count < copy);
1790 if (iov->iov_len == base) {
1796 i->iov_offset = base;
1799 EXPORT_SYMBOL(iov_iter_advance);
1802 * Fault in the first iovec of the given iov_iter, to a maximum length
1803 * of bytes. Returns 0 on success, or non-zero if the memory could not be
1804 * accessed (ie. because it is an invalid address).
1806 * writev-intensive code may want this to prefault several iovecs -- that
1807 * would be possible (callers must not rely on the fact that _only_ the
1808 * first iovec will be faulted with the current implementation).
1810 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
1812 char __user *buf = i->iov->iov_base + i->iov_offset;
1813 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
1814 return fault_in_pages_readable(buf, bytes);
1816 EXPORT_SYMBOL(iov_iter_fault_in_readable);
1819 * Return the count of just the current iov_iter segment.
1821 size_t iov_iter_single_seg_count(struct iov_iter *i)
1823 const struct iovec *iov = i->iov;
1824 if (i->nr_segs == 1)
1827 return min(i->count, iov->iov_len - i->iov_offset);
1829 EXPORT_SYMBOL(iov_iter_single_seg_count);
1832 * Performs necessary checks before doing a write
1834 * Can adjust writing position or amount of bytes to write.
1835 * Returns appropriate error code that caller should return or
1836 * zero in case that write should be allowed.
1838 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
1840 struct inode *inode = file->f_mapping->host;
1841 unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
1843 if (unlikely(*pos < 0))
1847 /* FIXME: this is for backwards compatibility with 2.4 */
1848 if (file->f_flags & O_APPEND)
1849 *pos = i_size_read(inode);
1851 if (limit != RLIM_INFINITY) {
1852 if (*pos >= limit) {
1853 send_sig(SIGXFSZ, current, 0);
1856 if (*count > limit - (typeof(limit))*pos) {
1857 *count = limit - (typeof(limit))*pos;
1865 if (unlikely(*pos + *count > MAX_NON_LFS &&
1866 !(file->f_flags & O_LARGEFILE))) {
1867 if (*pos >= MAX_NON_LFS) {
1870 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
1871 *count = MAX_NON_LFS - (unsigned long)*pos;
1876 * Are we about to exceed the fs block limit ?
1878 * If we have written data it becomes a short write. If we have
1879 * exceeded without writing data we send a signal and return EFBIG.
1880 * Linus frestrict idea will clean these up nicely..
1882 if (likely(!isblk)) {
1883 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
1884 if (*count || *pos > inode->i_sb->s_maxbytes) {
1887 /* zero-length writes at ->s_maxbytes are OK */
1890 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
1891 *count = inode->i_sb->s_maxbytes - *pos;
1895 if (bdev_read_only(I_BDEV(inode)))
1897 isize = i_size_read(inode);
1898 if (*pos >= isize) {
1899 if (*count || *pos > isize)
1903 if (*pos + *count > isize)
1904 *count = isize - *pos;
1911 EXPORT_SYMBOL(generic_write_checks);
1913 int pagecache_write_begin(struct file *file, struct address_space *mapping,
1914 loff_t pos, unsigned len, unsigned flags,
1915 struct page **pagep, void **fsdata)
1917 const struct address_space_operations *aops = mapping->a_ops;
1919 if (aops->write_begin) {
1920 return aops->write_begin(file, mapping, pos, len, flags,
1924 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1925 unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
1926 struct inode *inode = mapping->host;
1929 page = __grab_cache_page(mapping, index);
1934 if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) {
1936 * There is no way to resolve a short write situation
1937 * for a !Uptodate page (except by double copying in
1938 * the caller done by generic_perform_write_2copy).
1940 * Instead, we have to bring it uptodate here.
1942 ret = aops->readpage(file, page);
1943 page_cache_release(page);
1945 if (ret == AOP_TRUNCATED_PAGE)
1952 ret = aops->prepare_write(file, page, offset, offset+len);
1955 page_cache_release(page);
1956 if (pos + len > inode->i_size)
1957 vmtruncate(inode, inode->i_size);
1962 EXPORT_SYMBOL(pagecache_write_begin);
1964 int pagecache_write_end(struct file *file, struct address_space *mapping,
1965 loff_t pos, unsigned len, unsigned copied,
1966 struct page *page, void *fsdata)
1968 const struct address_space_operations *aops = mapping->a_ops;
1971 if (aops->write_end) {
1972 mark_page_accessed(page);
1973 ret = aops->write_end(file, mapping, pos, len, copied,
1976 unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
1977 struct inode *inode = mapping->host;
1979 flush_dcache_page(page);
1980 ret = aops->commit_write(file, page, offset, offset+len);
1982 mark_page_accessed(page);
1983 page_cache_release(page);
1986 if (pos + len > inode->i_size)
1987 vmtruncate(inode, inode->i_size);
1989 ret = min_t(size_t, copied, ret);
1996 EXPORT_SYMBOL(pagecache_write_end);
1999 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2000 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2001 size_t count, size_t ocount)
2003 struct file *file = iocb->ki_filp;
2004 struct address_space *mapping = file->f_mapping;
2005 struct inode *inode = mapping->host;
2008 if (count != ocount)
2009 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2011 written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2013 loff_t end = pos + written;
2014 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2015 i_size_write(inode, end);
2016 mark_inode_dirty(inode);
2022 * Sync the fs metadata but not the minor inode changes and
2023 * of course not the data as we did direct DMA for the IO.
2024 * i_mutex is held, which protects generic_osync_inode() from
2025 * livelocking. AIO O_DIRECT ops attempt to sync metadata here.
2027 if ((written >= 0 || written == -EIOCBQUEUED) &&
2028 ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2029 int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
2035 EXPORT_SYMBOL(generic_file_direct_write);
2038 * Find or create a page at the given pagecache position. Return the locked
2039 * page. This function is specifically for buffered writes.
2041 struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index)
2046 page = find_lock_page(mapping, index);
2050 page = page_cache_alloc(mapping);
2053 status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
2054 if (unlikely(status)) {
2055 page_cache_release(page);
2056 if (status == -EEXIST)
2062 EXPORT_SYMBOL(__grab_cache_page);
2064 static ssize_t generic_perform_write_2copy(struct file *file,
2065 struct iov_iter *i, loff_t pos)
2067 struct address_space *mapping = file->f_mapping;
2068 const struct address_space_operations *a_ops = mapping->a_ops;
2069 struct inode *inode = mapping->host;
2071 ssize_t written = 0;
2074 struct page *src_page;
2076 pgoff_t index; /* Pagecache index for current page */
2077 unsigned long offset; /* Offset into pagecache page */
2078 unsigned long bytes; /* Bytes to write to page */
2079 size_t copied; /* Bytes copied from user */
2081 offset = (pos & (PAGE_CACHE_SIZE - 1));
2082 index = pos >> PAGE_CACHE_SHIFT;
2083 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2087 * a non-NULL src_page indicates that we're doing the
2088 * copy via get_user_pages and kmap.
2093 * Bring in the user page that we will copy from _first_.
2094 * Otherwise there's a nasty deadlock on copying from the
2095 * same page as we're writing to, without it being marked
2098 * Not only is this an optimisation, but it is also required
2099 * to check that the address is actually valid, when atomic
2100 * usercopies are used, below.
2102 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2107 page = __grab_cache_page(mapping, index);
2114 * non-uptodate pages cannot cope with short copies, and we
2115 * cannot take a pagefault with the destination page locked.
2116 * So pin the source page to copy it.
2118 if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) {
2121 src_page = alloc_page(GFP_KERNEL);
2123 page_cache_release(page);
2129 * Cannot get_user_pages with a page locked for the
2130 * same reason as we can't take a page fault with a
2131 * page locked (as explained below).
2133 copied = iov_iter_copy_from_user(src_page, i,
2135 if (unlikely(copied == 0)) {
2137 page_cache_release(page);
2138 page_cache_release(src_page);
2145 * Can't handle the page going uptodate here, because
2146 * that means we would use non-atomic usercopies, which
2147 * zero out the tail of the page, which can cause
2148 * zeroes to become transiently visible. We could just
2149 * use a non-zeroing copy, but the APIs aren't too
2152 if (unlikely(!page->mapping || PageUptodate(page))) {
2154 page_cache_release(page);
2155 page_cache_release(src_page);
2160 status = a_ops->prepare_write(file, page, offset, offset+bytes);
2161 if (unlikely(status))
2162 goto fs_write_aop_error;
2166 * Must not enter the pagefault handler here, because
2167 * we hold the page lock, so we might recursively
2168 * deadlock on the same lock, or get an ABBA deadlock
2169 * against a different lock, or against the mmap_sem
2170 * (which nests outside the page lock). So increment
2171 * preempt count, and use _atomic usercopies.
2173 * The page is uptodate so we are OK to encounter a
2174 * short copy: if unmodified parts of the page are
2175 * marked dirty and written out to disk, it doesn't
2178 pagefault_disable();
2179 copied = iov_iter_copy_from_user_atomic(page, i,
2184 src = kmap_atomic(src_page, KM_USER0);
2185 dst = kmap_atomic(page, KM_USER1);
2186 memcpy(dst + offset, src + offset, bytes);
2187 kunmap_atomic(dst, KM_USER1);
2188 kunmap_atomic(src, KM_USER0);
2191 flush_dcache_page(page);
2193 status = a_ops->commit_write(file, page, offset, offset+bytes);
2194 if (unlikely(status < 0))
2195 goto fs_write_aop_error;
2196 if (unlikely(status > 0)) /* filesystem did partial write */
2197 copied = min_t(size_t, copied, status);
2200 mark_page_accessed(page);
2201 page_cache_release(page);
2203 page_cache_release(src_page);
2205 iov_iter_advance(i, copied);
2209 balance_dirty_pages_ratelimited(mapping);
2215 page_cache_release(page);
2217 page_cache_release(src_page);
2220 * prepare_write() may have instantiated a few blocks
2221 * outside i_size. Trim these off again. Don't need
2222 * i_size_read because we hold i_mutex.
2224 if (pos + bytes > inode->i_size)
2225 vmtruncate(inode, inode->i_size);
2227 } while (iov_iter_count(i));
2229 return written ? written : status;
2232 static ssize_t generic_perform_write(struct file *file,
2233 struct iov_iter *i, loff_t pos)
2235 struct address_space *mapping = file->f_mapping;
2236 const struct address_space_operations *a_ops = mapping->a_ops;
2238 ssize_t written = 0;
2239 unsigned int flags = 0;
2242 * Copies from kernel address space cannot fail (NFSD is a big user).
2244 if (segment_eq(get_fs(), KERNEL_DS))
2245 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2249 pgoff_t index; /* Pagecache index for current page */
2250 unsigned long offset; /* Offset into pagecache page */
2251 unsigned long bytes; /* Bytes to write to page */
2252 size_t copied; /* Bytes copied from user */
2255 offset = (pos & (PAGE_CACHE_SIZE - 1));
2256 index = pos >> PAGE_CACHE_SHIFT;
2257 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2263 * Bring in the user page that we will copy from _first_.
2264 * Otherwise there's a nasty deadlock on copying from the
2265 * same page as we're writing to, without it being marked
2268 * Not only is this an optimisation, but it is also required
2269 * to check that the address is actually valid, when atomic
2270 * usercopies are used, below.
2272 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2277 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2279 if (unlikely(status))
2282 pagefault_disable();
2283 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2285 flush_dcache_page(page);
2287 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2289 if (unlikely(status < 0))
2295 iov_iter_advance(i, copied);
2296 if (unlikely(copied == 0)) {
2298 * If we were unable to copy any data at all, we must
2299 * fall back to a single segment length write.
2301 * If we didn't fallback here, we could livelock
2302 * because not all segments in the iov can be copied at
2303 * once without a pagefault.
2305 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2306 iov_iter_single_seg_count(i));
2312 balance_dirty_pages_ratelimited(mapping);
2314 } while (iov_iter_count(i));
2316 return written ? written : status;
2320 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2321 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2322 size_t count, ssize_t written)
2324 struct file *file = iocb->ki_filp;
2325 struct address_space *mapping = file->f_mapping;
2326 const struct address_space_operations *a_ops = mapping->a_ops;
2327 struct inode *inode = mapping->host;
2331 iov_iter_init(&i, iov, nr_segs, count, written);
2332 if (a_ops->write_begin)
2333 status = generic_perform_write(file, &i, pos);
2335 status = generic_perform_write_2copy(file, &i, pos);
2337 if (likely(status >= 0)) {
2339 *ppos = pos + status;
2342 * For now, when the user asks for O_SYNC, we'll actually give
2345 if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2346 if (!a_ops->writepage || !is_sync_kiocb(iocb))
2347 status = generic_osync_inode(inode, mapping,
2348 OSYNC_METADATA|OSYNC_DATA);
2353 * If we get here for O_DIRECT writes then we must have fallen through
2354 * to buffered writes (block instantiation inside i_size). So we sync
2355 * the file data here, to try to honour O_DIRECT expectations.
2357 if (unlikely(file->f_flags & O_DIRECT) && written)
2358 status = filemap_write_and_wait(mapping);
2360 return written ? written : status;
2362 EXPORT_SYMBOL(generic_file_buffered_write);
2365 __generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
2366 unsigned long nr_segs, loff_t *ppos)
2368 struct file *file = iocb->ki_filp;
2369 struct address_space * mapping = file->f_mapping;
2370 size_t ocount; /* original count */
2371 size_t count; /* after file limit checks */
2372 struct inode *inode = mapping->host;
2378 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2385 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2387 /* We can write back this queue in page reclaim */
2388 current->backing_dev_info = mapping->backing_dev_info;
2391 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2398 err = remove_suid(file->f_path.dentry);
2402 file_update_time(file);
2404 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2405 if (unlikely(file->f_flags & O_DIRECT)) {
2407 ssize_t written_buffered;
2409 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2410 ppos, count, ocount);
2411 if (written < 0 || written == count)
2414 * direct-io write to a hole: fall through to buffered I/O
2415 * for completing the rest of the request.
2419 written_buffered = generic_file_buffered_write(iocb, iov,
2420 nr_segs, pos, ppos, count,
2423 * If generic_file_buffered_write() retuned a synchronous error
2424 * then we want to return the number of bytes which were
2425 * direct-written, or the error code if that was zero. Note
2426 * that this differs from normal direct-io semantics, which
2427 * will return -EFOO even if some bytes were written.
2429 if (written_buffered < 0) {
2430 err = written_buffered;
2435 * We need to ensure that the page cache pages are written to
2436 * disk and invalidated to preserve the expected O_DIRECT
2439 endbyte = pos + written_buffered - written - 1;
2440 err = do_sync_mapping_range(file->f_mapping, pos, endbyte,
2441 SYNC_FILE_RANGE_WAIT_BEFORE|
2442 SYNC_FILE_RANGE_WRITE|
2443 SYNC_FILE_RANGE_WAIT_AFTER);
2445 written = written_buffered;
2446 invalidate_mapping_pages(mapping,
2447 pos >> PAGE_CACHE_SHIFT,
2448 endbyte >> PAGE_CACHE_SHIFT);
2451 * We don't know how much we wrote, so just return
2452 * the number of bytes which were direct-written
2456 written = generic_file_buffered_write(iocb, iov, nr_segs,
2457 pos, ppos, count, written);
2460 current->backing_dev_info = NULL;
2461 return written ? written : err;
2464 ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
2465 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
2467 struct file *file = iocb->ki_filp;
2468 struct address_space *mapping = file->f_mapping;
2469 struct inode *inode = mapping->host;
2472 BUG_ON(iocb->ki_pos != pos);
2474 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2477 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2480 err = sync_page_range_nolock(inode, mapping, pos, ret);
2486 EXPORT_SYMBOL(generic_file_aio_write_nolock);
2488 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2489 unsigned long nr_segs, loff_t pos)
2491 struct file *file = iocb->ki_filp;
2492 struct address_space *mapping = file->f_mapping;
2493 struct inode *inode = mapping->host;
2496 BUG_ON(iocb->ki_pos != pos);
2498 mutex_lock(&inode->i_mutex);
2499 ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2501 mutex_unlock(&inode->i_mutex);
2503 if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2506 err = sync_page_range(inode, mapping, pos, ret);
2512 EXPORT_SYMBOL(generic_file_aio_write);
2515 * Called under i_mutex for writes to S_ISREG files. Returns -EIO if something
2516 * went wrong during pagecache shootdown.
2519 generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
2520 loff_t offset, unsigned long nr_segs)
2522 struct file *file = iocb->ki_filp;
2523 struct address_space *mapping = file->f_mapping;
2526 pgoff_t end = 0; /* silence gcc */
2529 * If it's a write, unmap all mmappings of the file up-front. This
2530 * will cause any pte dirty bits to be propagated into the pageframes
2531 * for the subsequent filemap_write_and_wait().
2534 write_len = iov_length(iov, nr_segs);
2535 end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT;
2536 if (mapping_mapped(mapping))
2537 unmap_mapping_range(mapping, offset, write_len, 0);
2540 retval = filemap_write_and_wait(mapping);
2545 * After a write we want buffered reads to be sure to go to disk to get
2546 * the new data. We invalidate clean cached page from the region we're
2547 * about to write. We do this *before* the write so that we can return
2548 * -EIO without clobbering -EIOCBQUEUED from ->direct_IO().
2550 if (rw == WRITE && mapping->nrpages) {
2551 retval = invalidate_inode_pages2_range(mapping,
2552 offset >> PAGE_CACHE_SHIFT, end);
2557 retval = mapping->a_ops->direct_IO(rw, iocb, iov, offset, nr_segs);
2560 * Finally, try again to invalidate clean pages which might have been
2561 * cached by non-direct readahead, or faulted in by get_user_pages()
2562 * if the source of the write was an mmap'ed region of the file
2563 * we're writing. Either one is a pretty crazy thing to do,
2564 * so we don't support it 100%. If this invalidation
2565 * fails, tough, the write still worked...
2567 if (rw == WRITE && mapping->nrpages) {
2568 invalidate_inode_pages2_range(mapping, offset >> PAGE_CACHE_SHIFT, end);
2575 * try_to_release_page() - release old fs-specific metadata on a page
2577 * @page: the page which the kernel is trying to free
2578 * @gfp_mask: memory allocation flags (and I/O mode)
2580 * The address_space is to try to release any data against the page
2581 * (presumably at page->private). If the release was successful, return `1'.
2582 * Otherwise return zero.
2584 * The @gfp_mask argument specifies whether I/O may be performed to release
2585 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
2587 * NOTE: @gfp_mask may go away, and this function may become non-blocking.
2589 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2591 struct address_space * const mapping = page->mapping;
2593 BUG_ON(!PageLocked(page));
2594 if (PageWriteback(page))
2597 if (mapping && mapping->a_ops->releasepage)
2598 return mapping->a_ops->releasepage(page, gfp_mask);
2599 return try_to_free_buffers(page);
2602 EXPORT_SYMBOL(try_to_release_page);