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1/*
2 * linux/mm/filemap.c
3 *
4 * Copyright (C) 1994-1999 Linus Torvalds
5 */
6
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)
11 */
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"
38
39/*
40 * FIXME: remove all knowledge of the buffer layer from the core VM
41 */
42#include <linux/buffer_head.h> /* for try_to_free_buffers */
43
44#include <asm/mman.h>
45
46/*
47 * Shared mappings implemented 30.11.1994. It's not fully working yet,
48 * though.
49 *
50 * Shared mappings now work. 15.8.1995 Bruno.
51 *
52 * finished 'unifying' the page and buffer cache and SMP-threaded the
53 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
54 *
55 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
56 */
57
58/*
59 * Lock ordering:
60 *
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
65 *
66 * ->i_mutex
67 * ->i_mmap_mutex (truncate->unmap_mapping_range)
68 *
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)
73 *
74 * ->mmap_sem
75 * ->lock_page (access_process_vm)
76 *
77 * ->i_mutex (generic_file_buffered_write)
78 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
79 *
80 * bdi->wb.list_lock
81 * sb_lock (fs/fs-writeback.c)
82 * ->mapping->tree_lock (__sync_single_inode)
83 *
84 * ->i_mmap_mutex
85 * ->anon_vma.lock (vma_adjust)
86 *
87 * ->anon_vma.lock
88 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
89 *
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)
103 *
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
107 */
108
109/*
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.
113 */
114void __delete_from_page_cache(struct page *page)
115{
116 struct address_space *mapping = page->mapping;
117
118 /*
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
122 */
123 if (PageUptodate(page) && PageMappedToDisk(page))
124 cleancache_put_page(page);
125 else
126 cleancache_flush_page(mapping, page);
127
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));
136
137 /*
138 * Some filesystems seem to re-dirty the page even after
139 * the VM has canceled the dirty bit (eg ext3 journaling).
140 *
141 * Fix it up by doing a final dirty accounting check after
142 * having removed the page entirely.
143 */
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);
147 }
148}
149
150/**
151 * delete_from_page_cache - delete page from page cache
152 * @page: the page which the kernel is trying to remove from page cache
153 *
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.
157 */
158void delete_from_page_cache(struct page *page)
159{
160 struct address_space *mapping = page->mapping;
161 void (*freepage)(struct page *);
162
163 BUG_ON(!PageLocked(page));
164
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);
170
171 if (freepage)
172 freepage(page);
173 page_cache_release(page);
174}
175EXPORT_SYMBOL(delete_from_page_cache);
176
177static int sleep_on_page(void *word)
178{
179 io_schedule();
180 return 0;
181}
182
183static int sleep_on_page_killable(void *word)
184{
185 sleep_on_page(word);
186 return fatal_signal_pending(current) ? -EINTR : 0;
187}
188
189/**
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
195 *
196 * Start writeback against all of a mapping's dirty pages that lie
197 * within the byte offsets <start, end> inclusive.
198 *
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.
203 */
204int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
205 loff_t end, int sync_mode)
206{
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,
213 };
214
215 if (!mapping_cap_writeback_dirty(mapping))
216 return 0;
217
218 ret = do_writepages(mapping, &wbc);
219 return ret;
220}
221
222static inline int __filemap_fdatawrite(struct address_space *mapping,
223 int sync_mode)
224{
225 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
226}
227
228int filemap_fdatawrite(struct address_space *mapping)
229{
230 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
231}
232EXPORT_SYMBOL(filemap_fdatawrite);
233
234int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
235 loff_t end)
236{
237 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
238}
239EXPORT_SYMBOL(filemap_fdatawrite_range);
240
241/**
242 * filemap_flush - mostly a non-blocking flush
243 * @mapping: target address_space
244 *
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.
247 */
248int filemap_flush(struct address_space *mapping)
249{
250 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
251}
252EXPORT_SYMBOL(filemap_flush);
253
254/**
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)
259 *
260 * Walk the list of under-writeback pages of the given address space
261 * in the given range and wait for all of them.
262 */
263int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
264 loff_t end_byte)
265{
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;
271
272 if (end_byte < start_byte)
273 return 0;
274
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;
281
282 for (i = 0; i < nr_pages; i++) {
283 struct page *page = pvec.pages[i];
284
285 /* until radix tree lookup accepts end_index */
286 if (page->index > end)
287 continue;
288
289 wait_on_page_writeback(page);
290 if (TestClearPageError(page))
291 ret = -EIO;
292 }
293 pagevec_release(&pvec);
294 cond_resched();
295 }
296
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;
302
303 return ret;
304}
305EXPORT_SYMBOL(filemap_fdatawait_range);
306
307/**
308 * filemap_fdatawait - wait for all under-writeback pages to complete
309 * @mapping: address space structure to wait for
310 *
311 * Walk the list of under-writeback pages of the given address space
312 * and wait for all of them.
313 */
314int filemap_fdatawait(struct address_space *mapping)
315{
316 loff_t i_size = i_size_read(mapping->host);
317
318 if (i_size == 0)
319 return 0;
320
321 return filemap_fdatawait_range(mapping, 0, i_size - 1);
322}
323EXPORT_SYMBOL(filemap_fdatawait);
324
325int filemap_write_and_wait(struct address_space *mapping)
326{
327 int err = 0;
328
329 if (mapping->nrpages) {
330 err = filemap_fdatawrite(mapping);
331 /*
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.
336 */
337 if (err != -EIO) {
338 int err2 = filemap_fdatawait(mapping);
339 if (!err)
340 err = err2;
341 }
342 }
343 return err;
344}
345EXPORT_SYMBOL(filemap_write_and_wait);
346
347/**
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)
352 *
353 * Write out and wait upon file offsets lstart->lend, inclusive.
354 *
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).
357 */
358int filemap_write_and_wait_range(struct address_space *mapping,
359 loff_t lstart, loff_t lend)
360{
361 int err = 0;
362
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;
372 }
373 }
374 return err;
375}
376EXPORT_SYMBOL(filemap_write_and_wait_range);
377
378/**
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
383 *
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.
389 *
390 * The remove + add is atomic. The only way this function can fail is
391 * memory allocation failure.
392 */
393int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
394{
395 int error;
396 struct mem_cgroup *memcg = NULL;
397
398 VM_BUG_ON(!PageLocked(old));
399 VM_BUG_ON(!PageLocked(new));
400 VM_BUG_ON(new->mapping);
401
402 /*
403 * This is not page migration, but prepare_migration and
404 * end_migration does enough work for charge replacement.
405 *
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.
409 */
410 error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
411 if (error)
412 return error;
413
414 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
415 if (!error) {
416 struct address_space *mapping = old->mapping;
417 void (*freepage)(struct page *);
418
419 pgoff_t offset = old->index;
420 freepage = mapping->a_ops->freepage;
421
422 page_cache_get(new);
423 new->mapping = mapping;
424 new->index = offset;
425
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);
442 }
443
444 return error;
445}
446EXPORT_SYMBOL_GPL(replace_page_cache_page);
447
448/**
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
454 *
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.
457 */
458int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
459 pgoff_t offset, gfp_t gfp_mask)
460{
461 int error;
462
463 VM_BUG_ON(!PageLocked(page));
464 VM_BUG_ON(PageSwapBacked(page));
465
466 error = mem_cgroup_cache_charge(page, current->mm,
467 gfp_mask & GFP_RECLAIM_MASK);
468 if (error)
469 goto out;
470
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;
476
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);
489 }
490 radix_tree_preload_end();
491 } else
492 mem_cgroup_uncharge_cache_page(page);
493out:
494 return error;
495}
496EXPORT_SYMBOL(add_to_page_cache_locked);
497
498int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
499 pgoff_t offset, gfp_t gfp_mask)
500{
501 int ret;
502
503 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
504 if (ret == 0)
505 lru_cache_add_file(page);
506 return ret;
507}
508EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
509
510#ifdef CONFIG_NUMA
511struct page *__page_cache_alloc(gfp_t gfp)
512{
513 int n;
514 struct page *page;
515
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;
522 }
523 return alloc_pages(gfp, 0);
524}
525EXPORT_SYMBOL(__page_cache_alloc);
526#endif
527
528/*
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.
537 */
538static wait_queue_head_t *page_waitqueue(struct page *page)
539{
540 const struct zone *zone = page_zone(page);
541
542 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
543}
544
545static inline void wake_up_page(struct page *page, int bit)
546{
547 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
548}
549
550void wait_on_page_bit(struct page *page, int bit_nr)
551{
552 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
553
554 if (test_bit(bit_nr, &page->flags))
555 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
556 TASK_UNINTERRUPTIBLE);
557}
558EXPORT_SYMBOL(wait_on_page_bit);
559
560int wait_on_page_bit_killable(struct page *page, int bit_nr)
561{
562 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
563
564 if (!test_bit(bit_nr, &page->flags))
565 return 0;
566
567 return __wait_on_bit(page_waitqueue(page), &wait,
568 sleep_on_page_killable, TASK_KILLABLE);
569}
570
571/**
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
575 *
576 * Add an arbitrary @waiter to the wait queue for the nominated @page.
577 */
578void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
579{
580 wait_queue_head_t *q = page_waitqueue(page);
581 unsigned long flags;
582
583 spin_lock_irqsave(&q->lock, flags);
584 __add_wait_queue(q, waiter);
585 spin_unlock_irqrestore(&q->lock, flags);
586}
587EXPORT_SYMBOL_GPL(add_page_wait_queue);
588
589/**
590 * unlock_page - unlock a locked page
591 * @page: the page
592 *
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.
597 *
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()).
600 */
601void unlock_page(struct page *page)
602{
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);
607}
608EXPORT_SYMBOL(unlock_page);
609
610/**
611 * end_page_writeback - end writeback against a page
612 * @page: the page
613 */
614void end_page_writeback(struct page *page)
615{
616 if (TestClearPageReclaim(page))
617 rotate_reclaimable_page(page);
618
619 if (!test_clear_page_writeback(page))
620 BUG();
621
622 smp_mb__after_clear_bit();
623 wake_up_page(page, PG_writeback);
624}
625EXPORT_SYMBOL(end_page_writeback);
626
627/**
628 * __lock_page - get a lock on the page, assuming we need to sleep to get it
629 * @page: the page to lock
630 */
631void __lock_page(struct page *page)
632{
633 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
634
635 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
636 TASK_UNINTERRUPTIBLE);
637}
638EXPORT_SYMBOL(__lock_page);
639
640int __lock_page_killable(struct page *page)
641{
642 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
643
644 return __wait_on_bit_lock(page_waitqueue(page), &wait,
645 sleep_on_page_killable, TASK_KILLABLE);
646}
647EXPORT_SYMBOL_GPL(__lock_page_killable);
648
649int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
650 unsigned int flags)
651{
652 if (flags & FAULT_FLAG_ALLOW_RETRY) {
653 /*
654 * CAUTION! In this case, mmap_sem is not released
655 * even though return 0.
656 */
657 if (flags & FAULT_FLAG_RETRY_NOWAIT)
658 return 0;
659
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;
669
670 ret = __lock_page_killable(page);
671 if (ret) {
672 up_read(&mm->mmap_sem);
673 return 0;
674 }
675 } else
676 __lock_page(page);
677 return 1;
678 }
679}
680
681/**
682 * find_get_page - find and get a page reference
683 * @mapping: the address_space to search
684 * @offset: the page index
685 *
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.
688 */
689struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
690{
691 void **pagep;
692 struct page *page;
693
694 rcu_read_lock();
695repeat:
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;
705 /*
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.
709 */
710 goto out;
711 }
712 if (!page_cache_get_speculative(page))
713 goto repeat;
714
715 /*
716 * Has the page moved?
717 * This is part of the lockless pagecache protocol. See
718 * include/linux/pagemap.h for details.
719 */
720 if (unlikely(page != *pagep)) {
721 page_cache_release(page);
722 goto repeat;
723 }
724 }
725out:
726 rcu_read_unlock();
727
728 return page;
729}
730EXPORT_SYMBOL(find_get_page);
731
732/**
733 * find_lock_page - locate, pin and lock a pagecache page
734 * @mapping: the address_space to search
735 * @offset: the page index
736 *
737 * Locates the desired pagecache page, locks it, increments its reference
738 * count and returns its address.
739 *
740 * Returns zero if the page was not present. find_lock_page() may sleep.
741 */
742struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
743{
744 struct page *page;
745
746repeat:
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;
755 }
756 VM_BUG_ON(page->index != offset);
757 }
758 return page;
759}
760EXPORT_SYMBOL(find_lock_page);
761
762/**
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
767 *
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.
772 *
773 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
774 * allocation!
775 *
776 * find_or_create_page() returns the desired page's address, or zero on
777 * memory exhaustion.
778 */
779struct page *find_or_create_page(struct address_space *mapping,
780 pgoff_t index, gfp_t gfp_mask)
781{
782 struct page *page;
783 int err;
784repeat:
785 page = find_lock_page(mapping, index);
786 if (!page) {
787 page = __page_cache_alloc(gfp_mask);
788 if (!page)
789 return NULL;
790 /*
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.
795 */
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;
803 }
804 }
805 return page;
806}
807EXPORT_SYMBOL(find_or_create_page);
808
809/**
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
815 *
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.
819 *
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.
822 *
823 * find_get_pages() returns the number of pages which were found.
824 */
825unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
826 unsigned int nr_pages, struct page **pages)
827{
828 unsigned int i;
829 unsigned int ret;
830 unsigned int nr_found, nr_skip;
831
832 rcu_read_lock();
833restart:
834 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
835 (void ***)pages, NULL, start, nr_pages);
836 ret = 0;
837 nr_skip = 0;
838 for (i = 0; i < nr_found; i++) {
839 struct page *page;
840repeat:
841 page = radix_tree_deref_slot((void **)pages[i]);
842 if (unlikely(!page))
843 continue;
844
845 if (radix_tree_exception(page)) {
846 if (radix_tree_deref_retry(page)) {
847 /*
848 * Transient condition which can only trigger
849 * when entry at index 0 moves out of or back
850 * to root: none yet gotten, safe to restart.
851 */
852 WARN_ON(start | i);
853 goto restart;
854 }
855 /*
856 * Otherwise, shmem/tmpfs must be storing a swap entry
857 * here as an exceptional entry: so skip over it -
858 * we only reach this from invalidate_mapping_pages().
859 */
860 nr_skip++;
861 continue;
862 }
863
864 if (!page_cache_get_speculative(page))
865 goto repeat;
866
867 /* Has the page moved? */
868 if (unlikely(page != *((void **)pages[i]))) {
869 page_cache_release(page);
870 goto repeat;
871 }
872
873 pages[ret] = page;
874 ret++;
875 }
876
877 /*
878 * If all entries were removed before we could secure them,
879 * try again, because callers stop trying once 0 is returned.
880 */
881 if (unlikely(!ret && nr_found > nr_skip))
882 goto restart;
883 rcu_read_unlock();
884 return ret;
885}
886
887/**
888 * find_get_pages_contig - gang contiguous pagecache lookup
889 * @mapping: The address_space to search
890 * @index: The starting page index
891 * @nr_pages: The maximum number of pages
892 * @pages: Where the resulting pages are placed
893 *
894 * find_get_pages_contig() works exactly like find_get_pages(), except
895 * that the returned number of pages are guaranteed to be contiguous.
896 *
897 * find_get_pages_contig() returns the number of pages which were found.
898 */
899unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
900 unsigned int nr_pages, struct page **pages)
901{
902 unsigned int i;
903 unsigned int ret;
904 unsigned int nr_found;
905
906 rcu_read_lock();
907restart:
908 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
909 (void ***)pages, NULL, index, nr_pages);
910 ret = 0;
911 for (i = 0; i < nr_found; i++) {
912 struct page *page;
913repeat:
914 page = radix_tree_deref_slot((void **)pages[i]);
915 if (unlikely(!page))
916 continue;
917
918 if (radix_tree_exception(page)) {
919 if (radix_tree_deref_retry(page)) {
920 /*
921 * Transient condition which can only trigger
922 * when entry at index 0 moves out of or back
923 * to root: none yet gotten, safe to restart.
924 */
925 goto restart;
926 }
927 /*
928 * Otherwise, shmem/tmpfs must be storing a swap entry
929 * here as an exceptional entry: so stop looking for
930 * contiguous pages.
931 */
932 break;
933 }
934
935 if (!page_cache_get_speculative(page))
936 goto repeat;
937
938 /* Has the page moved? */
939 if (unlikely(page != *((void **)pages[i]))) {
940 page_cache_release(page);
941 goto repeat;
942 }
943
944 /*
945 * must check mapping and index after taking the ref.
946 * otherwise we can get both false positives and false
947 * negatives, which is just confusing to the caller.
948 */
949 if (page->mapping == NULL || page->index != index) {
950 page_cache_release(page);
951 break;
952 }
953
954 pages[ret] = page;
955 ret++;
956 index++;
957 }
958 rcu_read_unlock();
959 return ret;
960}
961EXPORT_SYMBOL(find_get_pages_contig);
962
963/**
964 * find_get_pages_tag - find and return pages that match @tag
965 * @mapping: the address_space to search
966 * @index: the starting page index
967 * @tag: the tag index
968 * @nr_pages: the maximum number of pages
969 * @pages: where the resulting pages are placed
970 *
971 * Like find_get_pages, except we only return pages which are tagged with
972 * @tag. We update @index to index the next page for the traversal.
973 */
974unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
975 int tag, unsigned int nr_pages, struct page **pages)
976{
977 unsigned int i;
978 unsigned int ret;
979 unsigned int nr_found;
980
981 rcu_read_lock();
982restart:
983 nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
984 (void ***)pages, *index, nr_pages, tag);
985 ret = 0;
986 for (i = 0; i < nr_found; i++) {
987 struct page *page;
988repeat:
989 page = radix_tree_deref_slot((void **)pages[i]);
990 if (unlikely(!page))
991 continue;
992
993 if (radix_tree_exception(page)) {
994 if (radix_tree_deref_retry(page)) {
995 /*
996 * Transient condition which can only trigger
997 * when entry at index 0 moves out of or back
998 * to root: none yet gotten, safe to restart.
999 */
1000 goto restart;
1001 }
1002 /*
1003 * This function is never used on a shmem/tmpfs
1004 * mapping, so a swap entry won't be found here.
1005 */
1006 BUG();
1007 }
1008
1009 if (!page_cache_get_speculative(page))
1010 goto repeat;
1011
1012 /* Has the page moved? */
1013 if (unlikely(page != *((void **)pages[i]))) {
1014 page_cache_release(page);
1015 goto repeat;
1016 }
1017
1018 pages[ret] = page;
1019 ret++;
1020 }
1021
1022 /*
1023 * If all entries were removed before we could secure them,
1024 * try again, because callers stop trying once 0 is returned.
1025 */
1026 if (unlikely(!ret && nr_found))
1027 goto restart;
1028 rcu_read_unlock();
1029
1030 if (ret)
1031 *index = pages[ret - 1]->index + 1;
1032
1033 return ret;
1034}
1035EXPORT_SYMBOL(find_get_pages_tag);
1036
1037/**
1038 * grab_cache_page_nowait - returns locked page at given index in given cache
1039 * @mapping: target address_space
1040 * @index: the page index
1041 *
1042 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1043 * This is intended for speculative data generators, where the data can
1044 * be regenerated if the page couldn't be grabbed. This routine should
1045 * be safe to call while holding the lock for another page.
1046 *
1047 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1048 * and deadlock against the caller's locked page.
1049 */
1050struct page *
1051grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1052{
1053 struct page *page = find_get_page(mapping, index);
1054
1055 if (page) {
1056 if (trylock_page(page))
1057 return page;
1058 page_cache_release(page);
1059 return NULL;
1060 }
1061 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1062 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1063 page_cache_release(page);
1064 page = NULL;
1065 }
1066 return page;
1067}
1068EXPORT_SYMBOL(grab_cache_page_nowait);
1069
1070/*
1071 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1072 * a _large_ part of the i/o request. Imagine the worst scenario:
1073 *
1074 * ---R__________________________________________B__________
1075 * ^ reading here ^ bad block(assume 4k)
1076 *
1077 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1078 * => failing the whole request => read(R) => read(R+1) =>
1079 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1080 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1081 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1082 *
1083 * It is going insane. Fix it by quickly scaling down the readahead size.
1084 */
1085static void shrink_readahead_size_eio(struct file *filp,
1086 struct file_ra_state *ra)
1087{
1088 ra->ra_pages /= 4;
1089}
1090
1091/**
1092 * do_generic_file_read - generic file read routine
1093 * @filp: the file to read
1094 * @ppos: current file position
1095 * @desc: read_descriptor
1096 * @actor: read method
1097 *
1098 * This is a generic file read routine, and uses the
1099 * mapping->a_ops->readpage() function for the actual low-level stuff.
1100 *
1101 * This is really ugly. But the goto's actually try to clarify some
1102 * of the logic when it comes to error handling etc.
1103 */
1104static void do_generic_file_read(struct file *filp, loff_t *ppos,
1105 read_descriptor_t *desc, read_actor_t actor)
1106{
1107 struct address_space *mapping = filp->f_mapping;
1108 struct inode *inode = mapping->host;
1109 struct file_ra_state *ra = &filp->f_ra;
1110 pgoff_t index;
1111 pgoff_t last_index;
1112 pgoff_t prev_index;
1113 unsigned long offset; /* offset into pagecache page */
1114 unsigned int prev_offset;
1115 int error;
1116
1117 index = *ppos >> PAGE_CACHE_SHIFT;
1118 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1119 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1120 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1121 offset = *ppos & ~PAGE_CACHE_MASK;
1122
1123 for (;;) {
1124 struct page *page;
1125 pgoff_t end_index;
1126 loff_t isize;
1127 unsigned long nr, ret;
1128
1129 cond_resched();
1130find_page:
1131 page = find_get_page(mapping, index);
1132 if (!page) {
1133 page_cache_sync_readahead(mapping,
1134 ra, filp,
1135 index, last_index - index);
1136 page = find_get_page(mapping, index);
1137 if (unlikely(page == NULL))
1138 goto no_cached_page;
1139 }
1140 if (PageReadahead(page)) {
1141 page_cache_async_readahead(mapping,
1142 ra, filp, page,
1143 index, last_index - index);
1144 }
1145 if (!PageUptodate(page)) {
1146 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1147 !mapping->a_ops->is_partially_uptodate)
1148 goto page_not_up_to_date;
1149 if (!trylock_page(page))
1150 goto page_not_up_to_date;
1151 /* Did it get truncated before we got the lock? */
1152 if (!page->mapping)
1153 goto page_not_up_to_date_locked;
1154 if (!mapping->a_ops->is_partially_uptodate(page,
1155 desc, offset))
1156 goto page_not_up_to_date_locked;
1157 unlock_page(page);
1158 }
1159page_ok:
1160 /*
1161 * i_size must be checked after we know the page is Uptodate.
1162 *
1163 * Checking i_size after the check allows us to calculate
1164 * the correct value for "nr", which means the zero-filled
1165 * part of the page is not copied back to userspace (unless
1166 * another truncate extends the file - this is desired though).
1167 */
1168
1169 isize = i_size_read(inode);
1170 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1171 if (unlikely(!isize || index > end_index)) {
1172 page_cache_release(page);
1173 goto out;
1174 }
1175
1176 /* nr is the maximum number of bytes to copy from this page */
1177 nr = PAGE_CACHE_SIZE;
1178 if (index == end_index) {
1179 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1180 if (nr <= offset) {
1181 page_cache_release(page);
1182 goto out;
1183 }
1184 }
1185 nr = nr - offset;
1186
1187 /* If users can be writing to this page using arbitrary
1188 * virtual addresses, take care about potential aliasing
1189 * before reading the page on the kernel side.
1190 */
1191 if (mapping_writably_mapped(mapping))
1192 flush_dcache_page(page);
1193
1194 /*
1195 * When a sequential read accesses a page several times,
1196 * only mark it as accessed the first time.
1197 */
1198 if (prev_index != index || offset != prev_offset)
1199 mark_page_accessed(page);
1200 prev_index = index;
1201
1202 /*
1203 * Ok, we have the page, and it's up-to-date, so
1204 * now we can copy it to user space...
1205 *
1206 * The actor routine returns how many bytes were actually used..
1207 * NOTE! This may not be the same as how much of a user buffer
1208 * we filled up (we may be padding etc), so we can only update
1209 * "pos" here (the actor routine has to update the user buffer
1210 * pointers and the remaining count).
1211 */
1212 ret = actor(desc, page, offset, nr);
1213 offset += ret;
1214 index += offset >> PAGE_CACHE_SHIFT;
1215 offset &= ~PAGE_CACHE_MASK;
1216 prev_offset = offset;
1217
1218 page_cache_release(page);
1219 if (ret == nr && desc->count)
1220 continue;
1221 goto out;
1222
1223page_not_up_to_date:
1224 /* Get exclusive access to the page ... */
1225 error = lock_page_killable(page);
1226 if (unlikely(error))
1227 goto readpage_error;
1228
1229page_not_up_to_date_locked:
1230 /* Did it get truncated before we got the lock? */
1231 if (!page->mapping) {
1232 unlock_page(page);
1233 page_cache_release(page);
1234 continue;
1235 }
1236
1237 /* Did somebody else fill it already? */
1238 if (PageUptodate(page)) {
1239 unlock_page(page);
1240 goto page_ok;
1241 }
1242
1243readpage:
1244 /*
1245 * A previous I/O error may have been due to temporary
1246 * failures, eg. multipath errors.
1247 * PG_error will be set again if readpage fails.
1248 */
1249 ClearPageError(page);
1250 /* Start the actual read. The read will unlock the page. */
1251 error = mapping->a_ops->readpage(filp, page);
1252
1253 if (unlikely(error)) {
1254 if (error == AOP_TRUNCATED_PAGE) {
1255 page_cache_release(page);
1256 goto find_page;
1257 }
1258 goto readpage_error;
1259 }
1260
1261 if (!PageUptodate(page)) {
1262 error = lock_page_killable(page);
1263 if (unlikely(error))
1264 goto readpage_error;
1265 if (!PageUptodate(page)) {
1266 if (page->mapping == NULL) {
1267 /*
1268 * invalidate_mapping_pages got it
1269 */
1270 unlock_page(page);
1271 page_cache_release(page);
1272 goto find_page;
1273 }
1274 unlock_page(page);
1275 shrink_readahead_size_eio(filp, ra);
1276 error = -EIO;
1277 goto readpage_error;
1278 }
1279 unlock_page(page);
1280 }
1281
1282 goto page_ok;
1283
1284readpage_error:
1285 /* UHHUH! A synchronous read error occurred. Report it */
1286 desc->error = error;
1287 page_cache_release(page);
1288 goto out;
1289
1290no_cached_page:
1291 /*
1292 * Ok, it wasn't cached, so we need to create a new
1293 * page..
1294 */
1295 page = page_cache_alloc_cold(mapping);
1296 if (!page) {
1297 desc->error = -ENOMEM;
1298 goto out;
1299 }
1300 error = add_to_page_cache_lru(page, mapping,
1301 index, GFP_KERNEL);
1302 if (error) {
1303 page_cache_release(page);
1304 if (error == -EEXIST)
1305 goto find_page;
1306 desc->error = error;
1307 goto out;
1308 }
1309 goto readpage;
1310 }
1311
1312out:
1313 ra->prev_pos = prev_index;
1314 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1315 ra->prev_pos |= prev_offset;
1316
1317 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1318 file_accessed(filp);
1319}
1320
1321int file_read_actor(read_descriptor_t *desc, struct page *page,
1322 unsigned long offset, unsigned long size)
1323{
1324 char *kaddr;
1325 unsigned long left, count = desc->count;
1326
1327 if (size > count)
1328 size = count;
1329
1330 /*
1331 * Faults on the destination of a read are common, so do it before
1332 * taking the kmap.
1333 */
1334 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1335 kaddr = kmap_atomic(page, KM_USER0);
1336 left = __copy_to_user_inatomic(desc->arg.buf,
1337 kaddr + offset, size);
1338 kunmap_atomic(kaddr, KM_USER0);
1339 if (left == 0)
1340 goto success;
1341 }
1342
1343 /* Do it the slow way */
1344 kaddr = kmap(page);
1345 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1346 kunmap(page);
1347
1348 if (left) {
1349 size -= left;
1350 desc->error = -EFAULT;
1351 }
1352success:
1353 desc->count = count - size;
1354 desc->written += size;
1355 desc->arg.buf += size;
1356 return size;
1357}
1358
1359/*
1360 * Performs necessary checks before doing a write
1361 * @iov: io vector request
1362 * @nr_segs: number of segments in the iovec
1363 * @count: number of bytes to write
1364 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1365 *
1366 * Adjust number of segments and amount of bytes to write (nr_segs should be
1367 * properly initialized first). Returns appropriate error code that caller
1368 * should return or zero in case that write should be allowed.
1369 */
1370int generic_segment_checks(const struct iovec *iov,
1371 unsigned long *nr_segs, size_t *count, int access_flags)
1372{
1373 unsigned long seg;
1374 size_t cnt = 0;
1375 for (seg = 0; seg < *nr_segs; seg++) {
1376 const struct iovec *iv = &iov[seg];
1377
1378 /*
1379 * If any segment has a negative length, or the cumulative
1380 * length ever wraps negative then return -EINVAL.
1381 */
1382 cnt += iv->iov_len;
1383 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1384 return -EINVAL;
1385 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1386 continue;
1387 if (seg == 0)
1388 return -EFAULT;
1389 *nr_segs = seg;
1390 cnt -= iv->iov_len; /* This segment is no good */
1391 break;
1392 }
1393 *count = cnt;
1394 return 0;
1395}
1396EXPORT_SYMBOL(generic_segment_checks);
1397
1398/**
1399 * generic_file_aio_read - generic filesystem read routine
1400 * @iocb: kernel I/O control block
1401 * @iov: io vector request
1402 * @nr_segs: number of segments in the iovec
1403 * @pos: current file position
1404 *
1405 * This is the "read()" routine for all filesystems
1406 * that can use the page cache directly.
1407 */
1408ssize_t
1409generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1410 unsigned long nr_segs, loff_t pos)
1411{
1412 struct file *filp = iocb->ki_filp;
1413 ssize_t retval;
1414 unsigned long seg = 0;
1415 size_t count;
1416 loff_t *ppos = &iocb->ki_pos;
1417 struct blk_plug plug;
1418
1419 count = 0;
1420 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1421 if (retval)
1422 return retval;
1423
1424 blk_start_plug(&plug);
1425
1426 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1427 if (filp->f_flags & O_DIRECT) {
1428 loff_t size;
1429 struct address_space *mapping;
1430 struct inode *inode;
1431
1432 mapping = filp->f_mapping;
1433 inode = mapping->host;
1434 if (!count)
1435 goto out; /* skip atime */
1436 size = i_size_read(inode);
1437 if (pos < size) {
1438 retval = filemap_write_and_wait_range(mapping, pos,
1439 pos + iov_length(iov, nr_segs) - 1);
1440 if (!retval) {
1441 retval = mapping->a_ops->direct_IO(READ, iocb,
1442 iov, pos, nr_segs);
1443 }
1444 if (retval > 0) {
1445 *ppos = pos + retval;
1446 count -= retval;
1447 }
1448
1449 /*
1450 * Btrfs can have a short DIO read if we encounter
1451 * compressed extents, so if there was an error, or if
1452 * we've already read everything we wanted to, or if
1453 * there was a short read because we hit EOF, go ahead
1454 * and return. Otherwise fallthrough to buffered io for
1455 * the rest of the read.
1456 */
1457 if (retval < 0 || !count || *ppos >= size) {
1458 file_accessed(filp);
1459 goto out;
1460 }
1461 }
1462 }
1463
1464 count = retval;
1465 for (seg = 0; seg < nr_segs; seg++) {
1466 read_descriptor_t desc;
1467 loff_t offset = 0;
1468
1469 /*
1470 * If we did a short DIO read we need to skip the section of the
1471 * iov that we've already read data into.
1472 */
1473 if (count) {
1474 if (count > iov[seg].iov_len) {
1475 count -= iov[seg].iov_len;
1476 continue;
1477 }
1478 offset = count;
1479 count = 0;
1480 }
1481
1482 desc.written = 0;
1483 desc.arg.buf = iov[seg].iov_base + offset;
1484 desc.count = iov[seg].iov_len - offset;
1485 if (desc.count == 0)
1486 continue;
1487 desc.error = 0;
1488 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1489 retval += desc.written;
1490 if (desc.error) {
1491 retval = retval ?: desc.error;
1492 break;
1493 }
1494 if (desc.count > 0)
1495 break;
1496 }
1497out:
1498 blk_finish_plug(&plug);
1499 return retval;
1500}
1501EXPORT_SYMBOL(generic_file_aio_read);
1502
1503static ssize_t
1504do_readahead(struct address_space *mapping, struct file *filp,
1505 pgoff_t index, unsigned long nr)
1506{
1507 if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1508 return -EINVAL;
1509
1510 force_page_cache_readahead(mapping, filp, index, nr);
1511 return 0;
1512}
1513
1514SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1515{
1516 ssize_t ret;
1517 struct file *file;
1518
1519 ret = -EBADF;
1520 file = fget(fd);
1521 if (file) {
1522 if (file->f_mode & FMODE_READ) {
1523 struct address_space *mapping = file->f_mapping;
1524 pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1525 pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1526 unsigned long len = end - start + 1;
1527 ret = do_readahead(mapping, file, start, len);
1528 }
1529 fput(file);
1530 }
1531 return ret;
1532}
1533#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1534asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1535{
1536 return SYSC_readahead((int) fd, offset, (size_t) count);
1537}
1538SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1539#endif
1540
1541#ifdef CONFIG_MMU
1542/**
1543 * page_cache_read - adds requested page to the page cache if not already there
1544 * @file: file to read
1545 * @offset: page index
1546 *
1547 * This adds the requested page to the page cache if it isn't already there,
1548 * and schedules an I/O to read in its contents from disk.
1549 */
1550static int page_cache_read(struct file *file, pgoff_t offset)
1551{
1552 struct address_space *mapping = file->f_mapping;
1553 struct page *page;
1554 int ret;
1555
1556 do {
1557 page = page_cache_alloc_cold(mapping);
1558 if (!page)
1559 return -ENOMEM;
1560
1561 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1562 if (ret == 0)
1563 ret = mapping->a_ops->readpage(file, page);
1564 else if (ret == -EEXIST)
1565 ret = 0; /* losing race to add is OK */
1566
1567 page_cache_release(page);
1568
1569 } while (ret == AOP_TRUNCATED_PAGE);
1570
1571 return ret;
1572}
1573
1574#define MMAP_LOTSAMISS (100)
1575
1576/*
1577 * Synchronous readahead happens when we don't even find
1578 * a page in the page cache at all.
1579 */
1580static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1581 struct file_ra_state *ra,
1582 struct file *file,
1583 pgoff_t offset)
1584{
1585 unsigned long ra_pages;
1586 struct address_space *mapping = file->f_mapping;
1587
1588 /* If we don't want any read-ahead, don't bother */
1589 if (VM_RandomReadHint(vma))
1590 return;
1591 if (!ra->ra_pages)
1592 return;
1593
1594 if (VM_SequentialReadHint(vma)) {
1595 page_cache_sync_readahead(mapping, ra, file, offset,
1596 ra->ra_pages);
1597 return;
1598 }
1599
1600 /* Avoid banging the cache line if not needed */
1601 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1602 ra->mmap_miss++;
1603
1604 /*
1605 * Do we miss much more than hit in this file? If so,
1606 * stop bothering with read-ahead. It will only hurt.
1607 */
1608 if (ra->mmap_miss > MMAP_LOTSAMISS)
1609 return;
1610
1611 /*
1612 * mmap read-around
1613 */
1614 ra_pages = max_sane_readahead(ra->ra_pages);
1615 ra->start = max_t(long, 0, offset - ra_pages / 2);
1616 ra->size = ra_pages;
1617 ra->async_size = ra_pages / 4;
1618 ra_submit(ra, mapping, file);
1619}
1620
1621/*
1622 * Asynchronous readahead happens when we find the page and PG_readahead,
1623 * so we want to possibly extend the readahead further..
1624 */
1625static void do_async_mmap_readahead(struct vm_area_struct *vma,
1626 struct file_ra_state *ra,
1627 struct file *file,
1628 struct page *page,
1629 pgoff_t offset)
1630{
1631 struct address_space *mapping = file->f_mapping;
1632
1633 /* If we don't want any read-ahead, don't bother */
1634 if (VM_RandomReadHint(vma))
1635 return;
1636 if (ra->mmap_miss > 0)
1637 ra->mmap_miss--;
1638 if (PageReadahead(page))
1639 page_cache_async_readahead(mapping, ra, file,
1640 page, offset, ra->ra_pages);
1641}
1642
1643/**
1644 * filemap_fault - read in file data for page fault handling
1645 * @vma: vma in which the fault was taken
1646 * @vmf: struct vm_fault containing details of the fault
1647 *
1648 * filemap_fault() is invoked via the vma operations vector for a
1649 * mapped memory region to read in file data during a page fault.
1650 *
1651 * The goto's are kind of ugly, but this streamlines the normal case of having
1652 * it in the page cache, and handles the special cases reasonably without
1653 * having a lot of duplicated code.
1654 */
1655int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1656{
1657 int error;
1658 struct file *file = vma->vm_file;
1659 struct address_space *mapping = file->f_mapping;
1660 struct file_ra_state *ra = &file->f_ra;
1661 struct inode *inode = mapping->host;
1662 pgoff_t offset = vmf->pgoff;
1663 struct page *page;
1664 pgoff_t size;
1665 int ret = 0;
1666
1667 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1668 if (offset >= size)
1669 return VM_FAULT_SIGBUS;
1670
1671 /*
1672 * Do we have something in the page cache already?
1673 */
1674 page = find_get_page(mapping, offset);
1675 if (likely(page)) {
1676 /*
1677 * We found the page, so try async readahead before
1678 * waiting for the lock.
1679 */
1680 do_async_mmap_readahead(vma, ra, file, page, offset);
1681 } else {
1682 /* No page in the page cache at all */
1683 do_sync_mmap_readahead(vma, ra, file, offset);
1684 count_vm_event(PGMAJFAULT);
1685 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1686 ret = VM_FAULT_MAJOR;
1687retry_find:
1688 page = find_get_page(mapping, offset);
1689 if (!page)
1690 goto no_cached_page;
1691 }
1692
1693 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1694 page_cache_release(page);
1695 return ret | VM_FAULT_RETRY;
1696 }
1697
1698 /* Did it get truncated? */
1699 if (unlikely(page->mapping != mapping)) {
1700 unlock_page(page);
1701 put_page(page);
1702 goto retry_find;
1703 }
1704 VM_BUG_ON(page->index != offset);
1705
1706 /*
1707 * We have a locked page in the page cache, now we need to check
1708 * that it's up-to-date. If not, it is going to be due to an error.
1709 */
1710 if (unlikely(!PageUptodate(page)))
1711 goto page_not_uptodate;
1712
1713 /*
1714 * Found the page and have a reference on it.
1715 * We must recheck i_size under page lock.
1716 */
1717 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1718 if (unlikely(offset >= size)) {
1719 unlock_page(page);
1720 page_cache_release(page);
1721 return VM_FAULT_SIGBUS;
1722 }
1723
1724 vmf->page = page;
1725 return ret | VM_FAULT_LOCKED;
1726
1727no_cached_page:
1728 /*
1729 * We're only likely to ever get here if MADV_RANDOM is in
1730 * effect.
1731 */
1732 error = page_cache_read(file, offset);
1733
1734 /*
1735 * The page we want has now been added to the page cache.
1736 * In the unlikely event that someone removed it in the
1737 * meantime, we'll just come back here and read it again.
1738 */
1739 if (error >= 0)
1740 goto retry_find;
1741
1742 /*
1743 * An error return from page_cache_read can result if the
1744 * system is low on memory, or a problem occurs while trying
1745 * to schedule I/O.
1746 */
1747 if (error == -ENOMEM)
1748 return VM_FAULT_OOM;
1749 return VM_FAULT_SIGBUS;
1750
1751page_not_uptodate:
1752 /*
1753 * Umm, take care of errors if the page isn't up-to-date.
1754 * Try to re-read it _once_. We do this synchronously,
1755 * because there really aren't any performance issues here
1756 * and we need to check for errors.
1757 */
1758 ClearPageError(page);
1759 error = mapping->a_ops->readpage(file, page);
1760 if (!error) {
1761 wait_on_page_locked(page);
1762 if (!PageUptodate(page))
1763 error = -EIO;
1764 }
1765 page_cache_release(page);
1766
1767 if (!error || error == AOP_TRUNCATED_PAGE)
1768 goto retry_find;
1769
1770 /* Things didn't work out. Return zero to tell the mm layer so. */
1771 shrink_readahead_size_eio(file, ra);
1772 return VM_FAULT_SIGBUS;
1773}
1774EXPORT_SYMBOL(filemap_fault);
1775
1776const struct vm_operations_struct generic_file_vm_ops = {
1777 .fault = filemap_fault,
1778};
1779
1780/* This is used for a general mmap of a disk file */
1781
1782int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1783{
1784 struct address_space *mapping = file->f_mapping;
1785
1786 if (!mapping->a_ops->readpage)
1787 return -ENOEXEC;
1788 file_accessed(file);
1789 vma->vm_ops = &generic_file_vm_ops;
1790 vma->vm_flags |= VM_CAN_NONLINEAR;
1791 return 0;
1792}
1793
1794/*
1795 * This is for filesystems which do not implement ->writepage.
1796 */
1797int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1798{
1799 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1800 return -EINVAL;
1801 return generic_file_mmap(file, vma);
1802}
1803#else
1804int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1805{
1806 return -ENOSYS;
1807}
1808int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1809{
1810 return -ENOSYS;
1811}
1812#endif /* CONFIG_MMU */
1813
1814EXPORT_SYMBOL(generic_file_mmap);
1815EXPORT_SYMBOL(generic_file_readonly_mmap);
1816
1817static struct page *__read_cache_page(struct address_space *mapping,
1818 pgoff_t index,
1819 int (*filler)(void *, struct page *),
1820 void *data,
1821 gfp_t gfp)
1822{
1823 struct page *page;
1824 int err;
1825repeat:
1826 page = find_get_page(mapping, index);
1827 if (!page) {
1828 page = __page_cache_alloc(gfp | __GFP_COLD);
1829 if (!page)
1830 return ERR_PTR(-ENOMEM);
1831 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1832 if (unlikely(err)) {
1833 page_cache_release(page);
1834 if (err == -EEXIST)
1835 goto repeat;
1836 /* Presumably ENOMEM for radix tree node */
1837 return ERR_PTR(err);
1838 }
1839 err = filler(data, page);
1840 if (err < 0) {
1841 page_cache_release(page);
1842 page = ERR_PTR(err);
1843 }
1844 }
1845 return page;
1846}
1847
1848static struct page *do_read_cache_page(struct address_space *mapping,
1849 pgoff_t index,
1850 int (*filler)(void *, struct page *),
1851 void *data,
1852 gfp_t gfp)
1853
1854{
1855 struct page *page;
1856 int err;
1857
1858retry:
1859 page = __read_cache_page(mapping, index, filler, data, gfp);
1860 if (IS_ERR(page))
1861 return page;
1862 if (PageUptodate(page))
1863 goto out;
1864
1865 lock_page(page);
1866 if (!page->mapping) {
1867 unlock_page(page);
1868 page_cache_release(page);
1869 goto retry;
1870 }
1871 if (PageUptodate(page)) {
1872 unlock_page(page);
1873 goto out;
1874 }
1875 err = filler(data, page);
1876 if (err < 0) {
1877 page_cache_release(page);
1878 return ERR_PTR(err);
1879 }
1880out:
1881 mark_page_accessed(page);
1882 return page;
1883}
1884
1885/**
1886 * read_cache_page_async - read into page cache, fill it if needed
1887 * @mapping: the page's address_space
1888 * @index: the page index
1889 * @filler: function to perform the read
1890 * @data: first arg to filler(data, page) function, often left as NULL
1891 *
1892 * Same as read_cache_page, but don't wait for page to become unlocked
1893 * after submitting it to the filler.
1894 *
1895 * Read into the page cache. If a page already exists, and PageUptodate() is
1896 * not set, try to fill the page but don't wait for it to become unlocked.
1897 *
1898 * If the page does not get brought uptodate, return -EIO.
1899 */
1900struct page *read_cache_page_async(struct address_space *mapping,
1901 pgoff_t index,
1902 int (*filler)(void *, struct page *),
1903 void *data)
1904{
1905 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1906}
1907EXPORT_SYMBOL(read_cache_page_async);
1908
1909static struct page *wait_on_page_read(struct page *page)
1910{
1911 if (!IS_ERR(page)) {
1912 wait_on_page_locked(page);
1913 if (!PageUptodate(page)) {
1914 page_cache_release(page);
1915 page = ERR_PTR(-EIO);
1916 }
1917 }
1918 return page;
1919}
1920
1921/**
1922 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1923 * @mapping: the page's address_space
1924 * @index: the page index
1925 * @gfp: the page allocator flags to use if allocating
1926 *
1927 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1928 * any new page allocations done using the specified allocation flags. Note
1929 * that the Radix tree operations will still use GFP_KERNEL, so you can't
1930 * expect to do this atomically or anything like that - but you can pass in
1931 * other page requirements.
1932 *
1933 * If the page does not get brought uptodate, return -EIO.
1934 */
1935struct page *read_cache_page_gfp(struct address_space *mapping,
1936 pgoff_t index,
1937 gfp_t gfp)
1938{
1939 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1940
1941 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1942}
1943EXPORT_SYMBOL(read_cache_page_gfp);
1944
1945/**
1946 * read_cache_page - read into page cache, fill it if needed
1947 * @mapping: the page's address_space
1948 * @index: the page index
1949 * @filler: function to perform the read
1950 * @data: first arg to filler(data, page) function, often left as NULL
1951 *
1952 * Read into the page cache. If a page already exists, and PageUptodate() is
1953 * not set, try to fill the page then wait for it to become unlocked.
1954 *
1955 * If the page does not get brought uptodate, return -EIO.
1956 */
1957struct page *read_cache_page(struct address_space *mapping,
1958 pgoff_t index,
1959 int (*filler)(void *, struct page *),
1960 void *data)
1961{
1962 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1963}
1964EXPORT_SYMBOL(read_cache_page);
1965
1966/*
1967 * The logic we want is
1968 *
1969 * if suid or (sgid and xgrp)
1970 * remove privs
1971 */
1972int should_remove_suid(struct dentry *dentry)
1973{
1974 mode_t mode = dentry->d_inode->i_mode;
1975 int kill = 0;
1976
1977 /* suid always must be killed */
1978 if (unlikely(mode & S_ISUID))
1979 kill = ATTR_KILL_SUID;
1980
1981 /*
1982 * sgid without any exec bits is just a mandatory locking mark; leave
1983 * it alone. If some exec bits are set, it's a real sgid; kill it.
1984 */
1985 if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1986 kill |= ATTR_KILL_SGID;
1987
1988 if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1989 return kill;
1990
1991 return 0;
1992}
1993EXPORT_SYMBOL(should_remove_suid);
1994
1995static int __remove_suid(struct dentry *dentry, int kill)
1996{
1997 struct iattr newattrs;
1998
1999 newattrs.ia_valid = ATTR_FORCE | kill;
2000 return notify_change(dentry, &newattrs);
2001}
2002
2003int file_remove_suid(struct file *file)
2004{
2005 struct dentry *dentry = file->f_path.dentry;
2006 struct inode *inode = dentry->d_inode;
2007 int killsuid;
2008 int killpriv;
2009 int error = 0;
2010
2011 /* Fast path for nothing security related */
2012 if (IS_NOSEC(inode))
2013 return 0;
2014
2015 killsuid = should_remove_suid(dentry);
2016 killpriv = security_inode_need_killpriv(dentry);
2017
2018 if (killpriv < 0)
2019 return killpriv;
2020 if (killpriv)
2021 error = security_inode_killpriv(dentry);
2022 if (!error && killsuid)
2023 error = __remove_suid(dentry, killsuid);
2024 if (!error && (inode->i_sb->s_flags & MS_NOSEC))
2025 inode->i_flags |= S_NOSEC;
2026
2027 return error;
2028}
2029EXPORT_SYMBOL(file_remove_suid);
2030
2031static size_t __iovec_copy_from_user_inatomic(char *vaddr,
2032 const struct iovec *iov, size_t base, size_t bytes)
2033{
2034 size_t copied = 0, left = 0;
2035
2036 while (bytes) {
2037 char __user *buf = iov->iov_base + base;
2038 int copy = min(bytes, iov->iov_len - base);
2039
2040 base = 0;
2041 left = __copy_from_user_inatomic(vaddr, buf, copy);
2042 copied += copy;
2043 bytes -= copy;
2044 vaddr += copy;
2045 iov++;
2046
2047 if (unlikely(left))
2048 break;
2049 }
2050 return copied - left;
2051}
2052
2053/*
2054 * Copy as much as we can into the page and return the number of bytes which
2055 * were successfully copied. If a fault is encountered then return the number of
2056 * bytes which were copied.
2057 */
2058size_t iov_iter_copy_from_user_atomic(struct page *page,
2059 struct iov_iter *i, unsigned long offset, size_t bytes)
2060{
2061 char *kaddr;
2062 size_t copied;
2063
2064 BUG_ON(!in_atomic());
2065 kaddr = kmap_atomic(page, KM_USER0);
2066 if (likely(i->nr_segs == 1)) {
2067 int left;
2068 char __user *buf = i->iov->iov_base + i->iov_offset;
2069 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
2070 copied = bytes - left;
2071 } else {
2072 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2073 i->iov, i->iov_offset, bytes);
2074 }
2075 kunmap_atomic(kaddr, KM_USER0);
2076
2077 return copied;
2078}
2079EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
2080
2081/*
2082 * This has the same sideeffects and return value as
2083 * iov_iter_copy_from_user_atomic().
2084 * The difference is that it attempts to resolve faults.
2085 * Page must not be locked.
2086 */
2087size_t iov_iter_copy_from_user(struct page *page,
2088 struct iov_iter *i, unsigned long offset, size_t bytes)
2089{
2090 char *kaddr;
2091 size_t copied;
2092
2093 kaddr = kmap(page);
2094 if (likely(i->nr_segs == 1)) {
2095 int left;
2096 char __user *buf = i->iov->iov_base + i->iov_offset;
2097 left = __copy_from_user(kaddr + offset, buf, bytes);
2098 copied = bytes - left;
2099 } else {
2100 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2101 i->iov, i->iov_offset, bytes);
2102 }
2103 kunmap(page);
2104 return copied;
2105}
2106EXPORT_SYMBOL(iov_iter_copy_from_user);
2107
2108void iov_iter_advance(struct iov_iter *i, size_t bytes)
2109{
2110 BUG_ON(i->count < bytes);
2111
2112 if (likely(i->nr_segs == 1)) {
2113 i->iov_offset += bytes;
2114 i->count -= bytes;
2115 } else {
2116 const struct iovec *iov = i->iov;
2117 size_t base = i->iov_offset;
2118
2119 /*
2120 * The !iov->iov_len check ensures we skip over unlikely
2121 * zero-length segments (without overruning the iovec).
2122 */
2123 while (bytes || unlikely(i->count && !iov->iov_len)) {
2124 int copy;
2125
2126 copy = min(bytes, iov->iov_len - base);
2127 BUG_ON(!i->count || i->count < copy);
2128 i->count -= copy;
2129 bytes -= copy;
2130 base += copy;
2131 if (iov->iov_len == base) {
2132 iov++;
2133 base = 0;
2134 }
2135 }
2136 i->iov = iov;
2137 i->iov_offset = base;
2138 }
2139}
2140EXPORT_SYMBOL(iov_iter_advance);
2141
2142/*
2143 * Fault in the first iovec of the given iov_iter, to a maximum length
2144 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2145 * accessed (ie. because it is an invalid address).
2146 *
2147 * writev-intensive code may want this to prefault several iovecs -- that
2148 * would be possible (callers must not rely on the fact that _only_ the
2149 * first iovec will be faulted with the current implementation).
2150 */
2151int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2152{
2153 char __user *buf = i->iov->iov_base + i->iov_offset;
2154 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2155 return fault_in_pages_readable(buf, bytes);
2156}
2157EXPORT_SYMBOL(iov_iter_fault_in_readable);
2158
2159/*
2160 * Return the count of just the current iov_iter segment.
2161 */
2162size_t iov_iter_single_seg_count(struct iov_iter *i)
2163{
2164 const struct iovec *iov = i->iov;
2165 if (i->nr_segs == 1)
2166 return i->count;
2167 else
2168 return min(i->count, iov->iov_len - i->iov_offset);
2169}
2170EXPORT_SYMBOL(iov_iter_single_seg_count);
2171
2172/*
2173 * Performs necessary checks before doing a write
2174 *
2175 * Can adjust writing position or amount of bytes to write.
2176 * Returns appropriate error code that caller should return or
2177 * zero in case that write should be allowed.
2178 */
2179inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2180{
2181 struct inode *inode = file->f_mapping->host;
2182 unsigned long limit = rlimit(RLIMIT_FSIZE);
2183
2184 if (unlikely(*pos < 0))
2185 return -EINVAL;
2186
2187 if (!isblk) {
2188 /* FIXME: this is for backwards compatibility with 2.4 */
2189 if (file->f_flags & O_APPEND)
2190 *pos = i_size_read(inode);
2191
2192 if (limit != RLIM_INFINITY) {
2193 if (*pos >= limit) {
2194 send_sig(SIGXFSZ, current, 0);
2195 return -EFBIG;
2196 }
2197 if (*count > limit - (typeof(limit))*pos) {
2198 *count = limit - (typeof(limit))*pos;
2199 }
2200 }
2201 }
2202
2203 /*
2204 * LFS rule
2205 */
2206 if (unlikely(*pos + *count > MAX_NON_LFS &&
2207 !(file->f_flags & O_LARGEFILE))) {
2208 if (*pos >= MAX_NON_LFS) {
2209 return -EFBIG;
2210 }
2211 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2212 *count = MAX_NON_LFS - (unsigned long)*pos;
2213 }
2214 }
2215
2216 /*
2217 * Are we about to exceed the fs block limit ?
2218 *
2219 * If we have written data it becomes a short write. If we have
2220 * exceeded without writing data we send a signal and return EFBIG.
2221 * Linus frestrict idea will clean these up nicely..
2222 */
2223 if (likely(!isblk)) {
2224 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2225 if (*count || *pos > inode->i_sb->s_maxbytes) {
2226 return -EFBIG;
2227 }
2228 /* zero-length writes at ->s_maxbytes are OK */
2229 }
2230
2231 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2232 *count = inode->i_sb->s_maxbytes - *pos;
2233 } else {
2234#ifdef CONFIG_BLOCK
2235 loff_t isize;
2236 if (bdev_read_only(I_BDEV(inode)))
2237 return -EPERM;
2238 isize = i_size_read(inode);
2239 if (*pos >= isize) {
2240 if (*count || *pos > isize)
2241 return -ENOSPC;
2242 }
2243
2244 if (*pos + *count > isize)
2245 *count = isize - *pos;
2246#else
2247 return -EPERM;
2248#endif
2249 }
2250 return 0;
2251}
2252EXPORT_SYMBOL(generic_write_checks);
2253
2254int pagecache_write_begin(struct file *file, struct address_space *mapping,
2255 loff_t pos, unsigned len, unsigned flags,
2256 struct page **pagep, void **fsdata)
2257{
2258 const struct address_space_operations *aops = mapping->a_ops;
2259
2260 return aops->write_begin(file, mapping, pos, len, flags,
2261 pagep, fsdata);
2262}
2263EXPORT_SYMBOL(pagecache_write_begin);
2264
2265int pagecache_write_end(struct file *file, struct address_space *mapping,
2266 loff_t pos, unsigned len, unsigned copied,
2267 struct page *page, void *fsdata)
2268{
2269 const struct address_space_operations *aops = mapping->a_ops;
2270
2271 mark_page_accessed(page);
2272 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2273}
2274EXPORT_SYMBOL(pagecache_write_end);
2275
2276ssize_t
2277generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2278 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2279 size_t count, size_t ocount)
2280{
2281 struct file *file = iocb->ki_filp;
2282 struct address_space *mapping = file->f_mapping;
2283 struct inode *inode = mapping->host;
2284 ssize_t written;
2285 size_t write_len;
2286 pgoff_t end;
2287
2288 if (count != ocount)
2289 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2290
2291 write_len = iov_length(iov, *nr_segs);
2292 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2293
2294 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2295 if (written)
2296 goto out;
2297
2298 /*
2299 * After a write we want buffered reads to be sure to go to disk to get
2300 * the new data. We invalidate clean cached page from the region we're
2301 * about to write. We do this *before* the write so that we can return
2302 * without clobbering -EIOCBQUEUED from ->direct_IO().
2303 */
2304 if (mapping->nrpages) {
2305 written = invalidate_inode_pages2_range(mapping,
2306 pos >> PAGE_CACHE_SHIFT, end);
2307 /*
2308 * If a page can not be invalidated, return 0 to fall back
2309 * to buffered write.
2310 */
2311 if (written) {
2312 if (written == -EBUSY)
2313 return 0;
2314 goto out;
2315 }
2316 }
2317
2318 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2319
2320 /*
2321 * Finally, try again to invalidate clean pages which might have been
2322 * cached by non-direct readahead, or faulted in by get_user_pages()
2323 * if the source of the write was an mmap'ed region of the file
2324 * we're writing. Either one is a pretty crazy thing to do,
2325 * so we don't support it 100%. If this invalidation
2326 * fails, tough, the write still worked...
2327 */
2328 if (mapping->nrpages) {
2329 invalidate_inode_pages2_range(mapping,
2330 pos >> PAGE_CACHE_SHIFT, end);
2331 }
2332
2333 if (written > 0) {
2334 pos += written;
2335 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2336 i_size_write(inode, pos);
2337 mark_inode_dirty(inode);
2338 }
2339 *ppos = pos;
2340 }
2341out:
2342 return written;
2343}
2344EXPORT_SYMBOL(generic_file_direct_write);
2345
2346/*
2347 * Find or create a page at the given pagecache position. Return the locked
2348 * page. This function is specifically for buffered writes.
2349 */
2350struct page *grab_cache_page_write_begin(struct address_space *mapping,
2351 pgoff_t index, unsigned flags)
2352{
2353 int status;
2354 struct page *page;
2355 gfp_t gfp_notmask = 0;
2356 if (flags & AOP_FLAG_NOFS)
2357 gfp_notmask = __GFP_FS;
2358repeat:
2359 page = find_lock_page(mapping, index);
2360 if (page)
2361 goto found;
2362
2363 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2364 if (!page)
2365 return NULL;
2366 status = add_to_page_cache_lru(page, mapping, index,
2367 GFP_KERNEL & ~gfp_notmask);
2368 if (unlikely(status)) {
2369 page_cache_release(page);
2370 if (status == -EEXIST)
2371 goto repeat;
2372 return NULL;
2373 }
2374found:
2375 wait_on_page_writeback(page);
2376 return page;
2377}
2378EXPORT_SYMBOL(grab_cache_page_write_begin);
2379
2380static ssize_t generic_perform_write(struct file *file,
2381 struct iov_iter *i, loff_t pos)
2382{
2383 struct address_space *mapping = file->f_mapping;
2384 const struct address_space_operations *a_ops = mapping->a_ops;
2385 long status = 0;
2386 ssize_t written = 0;
2387 unsigned int flags = 0;
2388
2389 /*
2390 * Copies from kernel address space cannot fail (NFSD is a big user).
2391 */
2392 if (segment_eq(get_fs(), KERNEL_DS))
2393 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2394
2395 do {
2396 struct page *page;
2397 unsigned long offset; /* Offset into pagecache page */
2398 unsigned long bytes; /* Bytes to write to page */
2399 size_t copied; /* Bytes copied from user */
2400 void *fsdata;
2401
2402 offset = (pos & (PAGE_CACHE_SIZE - 1));
2403 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2404 iov_iter_count(i));
2405
2406again:
2407
2408 /*
2409 * Bring in the user page that we will copy from _first_.
2410 * Otherwise there's a nasty deadlock on copying from the
2411 * same page as we're writing to, without it being marked
2412 * up-to-date.
2413 *
2414 * Not only is this an optimisation, but it is also required
2415 * to check that the address is actually valid, when atomic
2416 * usercopies are used, below.
2417 */
2418 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2419 status = -EFAULT;
2420 break;
2421 }
2422
2423 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2424 &page, &fsdata);
2425 if (unlikely(status))
2426 break;
2427
2428 if (mapping_writably_mapped(mapping))
2429 flush_dcache_page(page);
2430
2431 pagefault_disable();
2432 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2433 pagefault_enable();
2434 flush_dcache_page(page);
2435
2436 mark_page_accessed(page);
2437 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2438 page, fsdata);
2439 if (unlikely(status < 0))
2440 break;
2441 copied = status;
2442
2443 cond_resched();
2444
2445 iov_iter_advance(i, copied);
2446 if (unlikely(copied == 0)) {
2447 /*
2448 * If we were unable to copy any data at all, we must
2449 * fall back to a single segment length write.
2450 *
2451 * If we didn't fallback here, we could livelock
2452 * because not all segments in the iov can be copied at
2453 * once without a pagefault.
2454 */
2455 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2456 iov_iter_single_seg_count(i));
2457 goto again;
2458 }
2459 pos += copied;
2460 written += copied;
2461
2462 balance_dirty_pages_ratelimited(mapping);
2463
2464 } while (iov_iter_count(i));
2465
2466 return written ? written : status;
2467}
2468
2469ssize_t
2470generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2471 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2472 size_t count, ssize_t written)
2473{
2474 struct file *file = iocb->ki_filp;
2475 ssize_t status;
2476 struct iov_iter i;
2477
2478 iov_iter_init(&i, iov, nr_segs, count, written);
2479 status = generic_perform_write(file, &i, pos);
2480
2481 if (likely(status >= 0)) {
2482 written += status;
2483 *ppos = pos + status;
2484 }
2485
2486 return written ? written : status;
2487}
2488EXPORT_SYMBOL(generic_file_buffered_write);
2489
2490/**
2491 * __generic_file_aio_write - write data to a file
2492 * @iocb: IO state structure (file, offset, etc.)
2493 * @iov: vector with data to write
2494 * @nr_segs: number of segments in the vector
2495 * @ppos: position where to write
2496 *
2497 * This function does all the work needed for actually writing data to a
2498 * file. It does all basic checks, removes SUID from the file, updates
2499 * modification times and calls proper subroutines depending on whether we
2500 * do direct IO or a standard buffered write.
2501 *
2502 * It expects i_mutex to be grabbed unless we work on a block device or similar
2503 * object which does not need locking at all.
2504 *
2505 * This function does *not* take care of syncing data in case of O_SYNC write.
2506 * A caller has to handle it. This is mainly due to the fact that we want to
2507 * avoid syncing under i_mutex.
2508 */
2509ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2510 unsigned long nr_segs, loff_t *ppos)
2511{
2512 struct file *file = iocb->ki_filp;
2513 struct address_space * mapping = file->f_mapping;
2514 size_t ocount; /* original count */
2515 size_t count; /* after file limit checks */
2516 struct inode *inode = mapping->host;
2517 loff_t pos;
2518 ssize_t written;
2519 ssize_t err;
2520
2521 ocount = 0;
2522 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2523 if (err)
2524 return err;
2525
2526 count = ocount;
2527 pos = *ppos;
2528
2529 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2530
2531 /* We can write back this queue in page reclaim */
2532 current->backing_dev_info = mapping->backing_dev_info;
2533 written = 0;
2534
2535 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2536 if (err)
2537 goto out;
2538
2539 if (count == 0)
2540 goto out;
2541
2542 err = file_remove_suid(file);
2543 if (err)
2544 goto out;
2545
2546 file_update_time(file);
2547
2548 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2549 if (unlikely(file->f_flags & O_DIRECT)) {
2550 loff_t endbyte;
2551 ssize_t written_buffered;
2552
2553 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2554 ppos, count, ocount);
2555 if (written < 0 || written == count)
2556 goto out;
2557 /*
2558 * direct-io write to a hole: fall through to buffered I/O
2559 * for completing the rest of the request.
2560 */
2561 pos += written;
2562 count -= written;
2563 written_buffered = generic_file_buffered_write(iocb, iov,
2564 nr_segs, pos, ppos, count,
2565 written);
2566 /*
2567 * If generic_file_buffered_write() retuned a synchronous error
2568 * then we want to return the number of bytes which were
2569 * direct-written, or the error code if that was zero. Note
2570 * that this differs from normal direct-io semantics, which
2571 * will return -EFOO even if some bytes were written.
2572 */
2573 if (written_buffered < 0) {
2574 err = written_buffered;
2575 goto out;
2576 }
2577
2578 /*
2579 * We need to ensure that the page cache pages are written to
2580 * disk and invalidated to preserve the expected O_DIRECT
2581 * semantics.
2582 */
2583 endbyte = pos + written_buffered - written - 1;
2584 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2585 if (err == 0) {
2586 written = written_buffered;
2587 invalidate_mapping_pages(mapping,
2588 pos >> PAGE_CACHE_SHIFT,
2589 endbyte >> PAGE_CACHE_SHIFT);
2590 } else {
2591 /*
2592 * We don't know how much we wrote, so just return
2593 * the number of bytes which were direct-written
2594 */
2595 }
2596 } else {
2597 written = generic_file_buffered_write(iocb, iov, nr_segs,
2598 pos, ppos, count, written);
2599 }
2600out:
2601 current->backing_dev_info = NULL;
2602 return written ? written : err;
2603}
2604EXPORT_SYMBOL(__generic_file_aio_write);
2605
2606/**
2607 * generic_file_aio_write - write data to a file
2608 * @iocb: IO state structure
2609 * @iov: vector with data to write
2610 * @nr_segs: number of segments in the vector
2611 * @pos: position in file where to write
2612 *
2613 * This is a wrapper around __generic_file_aio_write() to be used by most
2614 * filesystems. It takes care of syncing the file in case of O_SYNC file
2615 * and acquires i_mutex as needed.
2616 */
2617ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2618 unsigned long nr_segs, loff_t pos)
2619{
2620 struct file *file = iocb->ki_filp;
2621 struct inode *inode = file->f_mapping->host;
2622 struct blk_plug plug;
2623 ssize_t ret;
2624
2625 BUG_ON(iocb->ki_pos != pos);
2626
2627 mutex_lock(&inode->i_mutex);
2628 blk_start_plug(&plug);
2629 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2630 mutex_unlock(&inode->i_mutex);
2631
2632 if (ret > 0 || ret == -EIOCBQUEUED) {
2633 ssize_t err;
2634
2635 err = generic_write_sync(file, pos, ret);
2636 if (err < 0 && ret > 0)
2637 ret = err;
2638 }
2639 blk_finish_plug(&plug);
2640 return ret;
2641}
2642EXPORT_SYMBOL(generic_file_aio_write);
2643
2644/**
2645 * try_to_release_page() - release old fs-specific metadata on a page
2646 *
2647 * @page: the page which the kernel is trying to free
2648 * @gfp_mask: memory allocation flags (and I/O mode)
2649 *
2650 * The address_space is to try to release any data against the page
2651 * (presumably at page->private). If the release was successful, return `1'.
2652 * Otherwise return zero.
2653 *
2654 * This may also be called if PG_fscache is set on a page, indicating that the
2655 * page is known to the local caching routines.
2656 *
2657 * The @gfp_mask argument specifies whether I/O may be performed to release
2658 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2659 *
2660 */
2661int try_to_release_page(struct page *page, gfp_t gfp_mask)
2662{
2663 struct address_space * const mapping = page->mapping;
2664
2665 BUG_ON(!PageLocked(page));
2666 if (PageWriteback(page))
2667 return 0;
2668
2669 if (mapping && mapping->a_ops->releasepage)
2670 return mapping->a_ops->releasepage(page, gfp_mask);
2671 return try_to_free_buffers(page);
2672}
2673
2674EXPORT_SYMBOL(try_to_release_page);
1/*
2 * linux/mm/filemap.c
3 *
4 * Copyright (C) 1994-1999 Linus Torvalds
5 */
6
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)
11 */
12#include <linux/export.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/cpuset.h>
33#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
34#include <linux/memcontrol.h>
35#include <linux/cleancache.h>
36#include "internal.h"
37
38/*
39 * FIXME: remove all knowledge of the buffer layer from the core VM
40 */
41#include <linux/buffer_head.h> /* for try_to_free_buffers */
42
43#include <asm/mman.h>
44
45/*
46 * Shared mappings implemented 30.11.1994. It's not fully working yet,
47 * though.
48 *
49 * Shared mappings now work. 15.8.1995 Bruno.
50 *
51 * finished 'unifying' the page and buffer cache and SMP-threaded the
52 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
53 *
54 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
55 */
56
57/*
58 * Lock ordering:
59 *
60 * ->i_mmap_mutex (truncate_pagecache)
61 * ->private_lock (__free_pte->__set_page_dirty_buffers)
62 * ->swap_lock (exclusive_swap_page, others)
63 * ->mapping->tree_lock
64 *
65 * ->i_mutex
66 * ->i_mmap_mutex (truncate->unmap_mapping_range)
67 *
68 * ->mmap_sem
69 * ->i_mmap_mutex
70 * ->page_table_lock or pte_lock (various, mainly in memory.c)
71 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
72 *
73 * ->mmap_sem
74 * ->lock_page (access_process_vm)
75 *
76 * ->i_mutex (generic_file_buffered_write)
77 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
78 *
79 * bdi->wb.list_lock
80 * sb_lock (fs/fs-writeback.c)
81 * ->mapping->tree_lock (__sync_single_inode)
82 *
83 * ->i_mmap_mutex
84 * ->anon_vma.lock (vma_adjust)
85 *
86 * ->anon_vma.lock
87 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
88 *
89 * ->page_table_lock or pte_lock
90 * ->swap_lock (try_to_unmap_one)
91 * ->private_lock (try_to_unmap_one)
92 * ->tree_lock (try_to_unmap_one)
93 * ->zone.lru_lock (follow_page->mark_page_accessed)
94 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
95 * ->private_lock (page_remove_rmap->set_page_dirty)
96 * ->tree_lock (page_remove_rmap->set_page_dirty)
97 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
98 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
99 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
100 * ->inode->i_lock (zap_pte_range->set_page_dirty)
101 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
102 *
103 * ->i_mmap_mutex
104 * ->tasklist_lock (memory_failure, collect_procs_ao)
105 */
106
107/*
108 * Delete a page from the page cache and free it. Caller has to make
109 * sure the page is locked and that nobody else uses it - or that usage
110 * is safe. The caller must hold the mapping's tree_lock.
111 */
112void __delete_from_page_cache(struct page *page)
113{
114 struct address_space *mapping = page->mapping;
115
116 /*
117 * if we're uptodate, flush out into the cleancache, otherwise
118 * invalidate any existing cleancache entries. We can't leave
119 * stale data around in the cleancache once our page is gone
120 */
121 if (PageUptodate(page) && PageMappedToDisk(page))
122 cleancache_put_page(page);
123 else
124 cleancache_invalidate_page(mapping, page);
125
126 radix_tree_delete(&mapping->page_tree, page->index);
127 page->mapping = NULL;
128 /* Leave page->index set: truncation lookup relies upon it */
129 mapping->nrpages--;
130 __dec_zone_page_state(page, NR_FILE_PAGES);
131 if (PageSwapBacked(page))
132 __dec_zone_page_state(page, NR_SHMEM);
133 BUG_ON(page_mapped(page));
134
135 /*
136 * Some filesystems seem to re-dirty the page even after
137 * the VM has canceled the dirty bit (eg ext3 journaling).
138 *
139 * Fix it up by doing a final dirty accounting check after
140 * having removed the page entirely.
141 */
142 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
143 dec_zone_page_state(page, NR_FILE_DIRTY);
144 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
145 }
146}
147
148/**
149 * delete_from_page_cache - delete page from page cache
150 * @page: the page which the kernel is trying to remove from page cache
151 *
152 * This must be called only on pages that have been verified to be in the page
153 * cache and locked. It will never put the page into the free list, the caller
154 * has a reference on the page.
155 */
156void delete_from_page_cache(struct page *page)
157{
158 struct address_space *mapping = page->mapping;
159 void (*freepage)(struct page *);
160
161 BUG_ON(!PageLocked(page));
162
163 freepage = mapping->a_ops->freepage;
164 spin_lock_irq(&mapping->tree_lock);
165 __delete_from_page_cache(page);
166 spin_unlock_irq(&mapping->tree_lock);
167 mem_cgroup_uncharge_cache_page(page);
168
169 if (freepage)
170 freepage(page);
171 page_cache_release(page);
172}
173EXPORT_SYMBOL(delete_from_page_cache);
174
175static int sleep_on_page(void *word)
176{
177 io_schedule();
178 return 0;
179}
180
181static int sleep_on_page_killable(void *word)
182{
183 sleep_on_page(word);
184 return fatal_signal_pending(current) ? -EINTR : 0;
185}
186
187/**
188 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
189 * @mapping: address space structure to write
190 * @start: offset in bytes where the range starts
191 * @end: offset in bytes where the range ends (inclusive)
192 * @sync_mode: enable synchronous operation
193 *
194 * Start writeback against all of a mapping's dirty pages that lie
195 * within the byte offsets <start, end> inclusive.
196 *
197 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
198 * opposed to a regular memory cleansing writeback. The difference between
199 * these two operations is that if a dirty page/buffer is encountered, it must
200 * be waited upon, and not just skipped over.
201 */
202int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
203 loff_t end, int sync_mode)
204{
205 int ret;
206 struct writeback_control wbc = {
207 .sync_mode = sync_mode,
208 .nr_to_write = LONG_MAX,
209 .range_start = start,
210 .range_end = end,
211 };
212
213 if (!mapping_cap_writeback_dirty(mapping))
214 return 0;
215
216 ret = do_writepages(mapping, &wbc);
217 return ret;
218}
219
220static inline int __filemap_fdatawrite(struct address_space *mapping,
221 int sync_mode)
222{
223 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
224}
225
226int filemap_fdatawrite(struct address_space *mapping)
227{
228 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
229}
230EXPORT_SYMBOL(filemap_fdatawrite);
231
232int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
233 loff_t end)
234{
235 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
236}
237EXPORT_SYMBOL(filemap_fdatawrite_range);
238
239/**
240 * filemap_flush - mostly a non-blocking flush
241 * @mapping: target address_space
242 *
243 * This is a mostly non-blocking flush. Not suitable for data-integrity
244 * purposes - I/O may not be started against all dirty pages.
245 */
246int filemap_flush(struct address_space *mapping)
247{
248 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
249}
250EXPORT_SYMBOL(filemap_flush);
251
252/**
253 * filemap_fdatawait_range - wait for writeback to complete
254 * @mapping: address space structure to wait for
255 * @start_byte: offset in bytes where the range starts
256 * @end_byte: offset in bytes where the range ends (inclusive)
257 *
258 * Walk the list of under-writeback pages of the given address space
259 * in the given range and wait for all of them.
260 */
261int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
262 loff_t end_byte)
263{
264 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
265 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
266 struct pagevec pvec;
267 int nr_pages;
268 int ret = 0;
269
270 if (end_byte < start_byte)
271 return 0;
272
273 pagevec_init(&pvec, 0);
274 while ((index <= end) &&
275 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
276 PAGECACHE_TAG_WRITEBACK,
277 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
278 unsigned i;
279
280 for (i = 0; i < nr_pages; i++) {
281 struct page *page = pvec.pages[i];
282
283 /* until radix tree lookup accepts end_index */
284 if (page->index > end)
285 continue;
286
287 wait_on_page_writeback(page);
288 if (TestClearPageError(page))
289 ret = -EIO;
290 }
291 pagevec_release(&pvec);
292 cond_resched();
293 }
294
295 /* Check for outstanding write errors */
296 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
297 ret = -ENOSPC;
298 if (test_and_clear_bit(AS_EIO, &mapping->flags))
299 ret = -EIO;
300
301 return ret;
302}
303EXPORT_SYMBOL(filemap_fdatawait_range);
304
305/**
306 * filemap_fdatawait - wait for all under-writeback pages to complete
307 * @mapping: address space structure to wait for
308 *
309 * Walk the list of under-writeback pages of the given address space
310 * and wait for all of them.
311 */
312int filemap_fdatawait(struct address_space *mapping)
313{
314 loff_t i_size = i_size_read(mapping->host);
315
316 if (i_size == 0)
317 return 0;
318
319 return filemap_fdatawait_range(mapping, 0, i_size - 1);
320}
321EXPORT_SYMBOL(filemap_fdatawait);
322
323int filemap_write_and_wait(struct address_space *mapping)
324{
325 int err = 0;
326
327 if (mapping->nrpages) {
328 err = filemap_fdatawrite(mapping);
329 /*
330 * Even if the above returned error, the pages may be
331 * written partially (e.g. -ENOSPC), so we wait for it.
332 * But the -EIO is special case, it may indicate the worst
333 * thing (e.g. bug) happened, so we avoid waiting for it.
334 */
335 if (err != -EIO) {
336 int err2 = filemap_fdatawait(mapping);
337 if (!err)
338 err = err2;
339 }
340 }
341 return err;
342}
343EXPORT_SYMBOL(filemap_write_and_wait);
344
345/**
346 * filemap_write_and_wait_range - write out & wait on a file range
347 * @mapping: the address_space for the pages
348 * @lstart: offset in bytes where the range starts
349 * @lend: offset in bytes where the range ends (inclusive)
350 *
351 * Write out and wait upon file offsets lstart->lend, inclusive.
352 *
353 * Note that `lend' is inclusive (describes the last byte to be written) so
354 * that this function can be used to write to the very end-of-file (end = -1).
355 */
356int filemap_write_and_wait_range(struct address_space *mapping,
357 loff_t lstart, loff_t lend)
358{
359 int err = 0;
360
361 if (mapping->nrpages) {
362 err = __filemap_fdatawrite_range(mapping, lstart, lend,
363 WB_SYNC_ALL);
364 /* See comment of filemap_write_and_wait() */
365 if (err != -EIO) {
366 int err2 = filemap_fdatawait_range(mapping,
367 lstart, lend);
368 if (!err)
369 err = err2;
370 }
371 }
372 return err;
373}
374EXPORT_SYMBOL(filemap_write_and_wait_range);
375
376/**
377 * replace_page_cache_page - replace a pagecache page with a new one
378 * @old: page to be replaced
379 * @new: page to replace with
380 * @gfp_mask: allocation mode
381 *
382 * This function replaces a page in the pagecache with a new one. On
383 * success it acquires the pagecache reference for the new page and
384 * drops it for the old page. Both the old and new pages must be
385 * locked. This function does not add the new page to the LRU, the
386 * caller must do that.
387 *
388 * The remove + add is atomic. The only way this function can fail is
389 * memory allocation failure.
390 */
391int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
392{
393 int error;
394
395 VM_BUG_ON(!PageLocked(old));
396 VM_BUG_ON(!PageLocked(new));
397 VM_BUG_ON(new->mapping);
398
399 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
400 if (!error) {
401 struct address_space *mapping = old->mapping;
402 void (*freepage)(struct page *);
403
404 pgoff_t offset = old->index;
405 freepage = mapping->a_ops->freepage;
406
407 page_cache_get(new);
408 new->mapping = mapping;
409 new->index = offset;
410
411 spin_lock_irq(&mapping->tree_lock);
412 __delete_from_page_cache(old);
413 error = radix_tree_insert(&mapping->page_tree, offset, new);
414 BUG_ON(error);
415 mapping->nrpages++;
416 __inc_zone_page_state(new, NR_FILE_PAGES);
417 if (PageSwapBacked(new))
418 __inc_zone_page_state(new, NR_SHMEM);
419 spin_unlock_irq(&mapping->tree_lock);
420 /* mem_cgroup codes must not be called under tree_lock */
421 mem_cgroup_replace_page_cache(old, new);
422 radix_tree_preload_end();
423 if (freepage)
424 freepage(old);
425 page_cache_release(old);
426 }
427
428 return error;
429}
430EXPORT_SYMBOL_GPL(replace_page_cache_page);
431
432/**
433 * add_to_page_cache_locked - add a locked page to the pagecache
434 * @page: page to add
435 * @mapping: the page's address_space
436 * @offset: page index
437 * @gfp_mask: page allocation mode
438 *
439 * This function is used to add a page to the pagecache. It must be locked.
440 * This function does not add the page to the LRU. The caller must do that.
441 */
442int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
443 pgoff_t offset, gfp_t gfp_mask)
444{
445 int error;
446
447 VM_BUG_ON(!PageLocked(page));
448 VM_BUG_ON(PageSwapBacked(page));
449
450 error = mem_cgroup_cache_charge(page, current->mm,
451 gfp_mask & GFP_RECLAIM_MASK);
452 if (error)
453 goto out;
454
455 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
456 if (error == 0) {
457 page_cache_get(page);
458 page->mapping = mapping;
459 page->index = offset;
460
461 spin_lock_irq(&mapping->tree_lock);
462 error = radix_tree_insert(&mapping->page_tree, offset, page);
463 if (likely(!error)) {
464 mapping->nrpages++;
465 __inc_zone_page_state(page, NR_FILE_PAGES);
466 spin_unlock_irq(&mapping->tree_lock);
467 } else {
468 page->mapping = NULL;
469 /* Leave page->index set: truncation relies upon it */
470 spin_unlock_irq(&mapping->tree_lock);
471 mem_cgroup_uncharge_cache_page(page);
472 page_cache_release(page);
473 }
474 radix_tree_preload_end();
475 } else
476 mem_cgroup_uncharge_cache_page(page);
477out:
478 return error;
479}
480EXPORT_SYMBOL(add_to_page_cache_locked);
481
482int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
483 pgoff_t offset, gfp_t gfp_mask)
484{
485 int ret;
486
487 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
488 if (ret == 0)
489 lru_cache_add_file(page);
490 return ret;
491}
492EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
493
494#ifdef CONFIG_NUMA
495struct page *__page_cache_alloc(gfp_t gfp)
496{
497 int n;
498 struct page *page;
499
500 if (cpuset_do_page_mem_spread()) {
501 unsigned int cpuset_mems_cookie;
502 do {
503 cpuset_mems_cookie = get_mems_allowed();
504 n = cpuset_mem_spread_node();
505 page = alloc_pages_exact_node(n, gfp, 0);
506 } while (!put_mems_allowed(cpuset_mems_cookie) && !page);
507
508 return page;
509 }
510 return alloc_pages(gfp, 0);
511}
512EXPORT_SYMBOL(__page_cache_alloc);
513#endif
514
515/*
516 * In order to wait for pages to become available there must be
517 * waitqueues associated with pages. By using a hash table of
518 * waitqueues where the bucket discipline is to maintain all
519 * waiters on the same queue and wake all when any of the pages
520 * become available, and for the woken contexts to check to be
521 * sure the appropriate page became available, this saves space
522 * at a cost of "thundering herd" phenomena during rare hash
523 * collisions.
524 */
525static wait_queue_head_t *page_waitqueue(struct page *page)
526{
527 const struct zone *zone = page_zone(page);
528
529 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
530}
531
532static inline void wake_up_page(struct page *page, int bit)
533{
534 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
535}
536
537void wait_on_page_bit(struct page *page, int bit_nr)
538{
539 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
540
541 if (test_bit(bit_nr, &page->flags))
542 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
543 TASK_UNINTERRUPTIBLE);
544}
545EXPORT_SYMBOL(wait_on_page_bit);
546
547int wait_on_page_bit_killable(struct page *page, int bit_nr)
548{
549 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
550
551 if (!test_bit(bit_nr, &page->flags))
552 return 0;
553
554 return __wait_on_bit(page_waitqueue(page), &wait,
555 sleep_on_page_killable, TASK_KILLABLE);
556}
557
558/**
559 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
560 * @page: Page defining the wait queue of interest
561 * @waiter: Waiter to add to the queue
562 *
563 * Add an arbitrary @waiter to the wait queue for the nominated @page.
564 */
565void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
566{
567 wait_queue_head_t *q = page_waitqueue(page);
568 unsigned long flags;
569
570 spin_lock_irqsave(&q->lock, flags);
571 __add_wait_queue(q, waiter);
572 spin_unlock_irqrestore(&q->lock, flags);
573}
574EXPORT_SYMBOL_GPL(add_page_wait_queue);
575
576/**
577 * unlock_page - unlock a locked page
578 * @page: the page
579 *
580 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
581 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
582 * mechananism between PageLocked pages and PageWriteback pages is shared.
583 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
584 *
585 * The mb is necessary to enforce ordering between the clear_bit and the read
586 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
587 */
588void unlock_page(struct page *page)
589{
590 VM_BUG_ON(!PageLocked(page));
591 clear_bit_unlock(PG_locked, &page->flags);
592 smp_mb__after_clear_bit();
593 wake_up_page(page, PG_locked);
594}
595EXPORT_SYMBOL(unlock_page);
596
597/**
598 * end_page_writeback - end writeback against a page
599 * @page: the page
600 */
601void end_page_writeback(struct page *page)
602{
603 if (TestClearPageReclaim(page))
604 rotate_reclaimable_page(page);
605
606 if (!test_clear_page_writeback(page))
607 BUG();
608
609 smp_mb__after_clear_bit();
610 wake_up_page(page, PG_writeback);
611}
612EXPORT_SYMBOL(end_page_writeback);
613
614/**
615 * __lock_page - get a lock on the page, assuming we need to sleep to get it
616 * @page: the page to lock
617 */
618void __lock_page(struct page *page)
619{
620 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
621
622 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
623 TASK_UNINTERRUPTIBLE);
624}
625EXPORT_SYMBOL(__lock_page);
626
627int __lock_page_killable(struct page *page)
628{
629 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
630
631 return __wait_on_bit_lock(page_waitqueue(page), &wait,
632 sleep_on_page_killable, TASK_KILLABLE);
633}
634EXPORT_SYMBOL_GPL(__lock_page_killable);
635
636int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
637 unsigned int flags)
638{
639 if (flags & FAULT_FLAG_ALLOW_RETRY) {
640 /*
641 * CAUTION! In this case, mmap_sem is not released
642 * even though return 0.
643 */
644 if (flags & FAULT_FLAG_RETRY_NOWAIT)
645 return 0;
646
647 up_read(&mm->mmap_sem);
648 if (flags & FAULT_FLAG_KILLABLE)
649 wait_on_page_locked_killable(page);
650 else
651 wait_on_page_locked(page);
652 return 0;
653 } else {
654 if (flags & FAULT_FLAG_KILLABLE) {
655 int ret;
656
657 ret = __lock_page_killable(page);
658 if (ret) {
659 up_read(&mm->mmap_sem);
660 return 0;
661 }
662 } else
663 __lock_page(page);
664 return 1;
665 }
666}
667
668/**
669 * find_get_page - find and get a page reference
670 * @mapping: the address_space to search
671 * @offset: the page index
672 *
673 * Is there a pagecache struct page at the given (mapping, offset) tuple?
674 * If yes, increment its refcount and return it; if no, return NULL.
675 */
676struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
677{
678 void **pagep;
679 struct page *page;
680
681 rcu_read_lock();
682repeat:
683 page = NULL;
684 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
685 if (pagep) {
686 page = radix_tree_deref_slot(pagep);
687 if (unlikely(!page))
688 goto out;
689 if (radix_tree_exception(page)) {
690 if (radix_tree_deref_retry(page))
691 goto repeat;
692 /*
693 * Otherwise, shmem/tmpfs must be storing a swap entry
694 * here as an exceptional entry: so return it without
695 * attempting to raise page count.
696 */
697 goto out;
698 }
699 if (!page_cache_get_speculative(page))
700 goto repeat;
701
702 /*
703 * Has the page moved?
704 * This is part of the lockless pagecache protocol. See
705 * include/linux/pagemap.h for details.
706 */
707 if (unlikely(page != *pagep)) {
708 page_cache_release(page);
709 goto repeat;
710 }
711 }
712out:
713 rcu_read_unlock();
714
715 return page;
716}
717EXPORT_SYMBOL(find_get_page);
718
719/**
720 * find_lock_page - locate, pin and lock a pagecache page
721 * @mapping: the address_space to search
722 * @offset: the page index
723 *
724 * Locates the desired pagecache page, locks it, increments its reference
725 * count and returns its address.
726 *
727 * Returns zero if the page was not present. find_lock_page() may sleep.
728 */
729struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
730{
731 struct page *page;
732
733repeat:
734 page = find_get_page(mapping, offset);
735 if (page && !radix_tree_exception(page)) {
736 lock_page(page);
737 /* Has the page been truncated? */
738 if (unlikely(page->mapping != mapping)) {
739 unlock_page(page);
740 page_cache_release(page);
741 goto repeat;
742 }
743 VM_BUG_ON(page->index != offset);
744 }
745 return page;
746}
747EXPORT_SYMBOL(find_lock_page);
748
749/**
750 * find_or_create_page - locate or add a pagecache page
751 * @mapping: the page's address_space
752 * @index: the page's index into the mapping
753 * @gfp_mask: page allocation mode
754 *
755 * Locates a page in the pagecache. If the page is not present, a new page
756 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
757 * LRU list. The returned page is locked and has its reference count
758 * incremented.
759 *
760 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
761 * allocation!
762 *
763 * find_or_create_page() returns the desired page's address, or zero on
764 * memory exhaustion.
765 */
766struct page *find_or_create_page(struct address_space *mapping,
767 pgoff_t index, gfp_t gfp_mask)
768{
769 struct page *page;
770 int err;
771repeat:
772 page = find_lock_page(mapping, index);
773 if (!page) {
774 page = __page_cache_alloc(gfp_mask);
775 if (!page)
776 return NULL;
777 /*
778 * We want a regular kernel memory (not highmem or DMA etc)
779 * allocation for the radix tree nodes, but we need to honour
780 * the context-specific requirements the caller has asked for.
781 * GFP_RECLAIM_MASK collects those requirements.
782 */
783 err = add_to_page_cache_lru(page, mapping, index,
784 (gfp_mask & GFP_RECLAIM_MASK));
785 if (unlikely(err)) {
786 page_cache_release(page);
787 page = NULL;
788 if (err == -EEXIST)
789 goto repeat;
790 }
791 }
792 return page;
793}
794EXPORT_SYMBOL(find_or_create_page);
795
796/**
797 * find_get_pages - gang pagecache lookup
798 * @mapping: The address_space to search
799 * @start: The starting page index
800 * @nr_pages: The maximum number of pages
801 * @pages: Where the resulting pages are placed
802 *
803 * find_get_pages() will search for and return a group of up to
804 * @nr_pages pages in the mapping. The pages are placed at @pages.
805 * find_get_pages() takes a reference against the returned pages.
806 *
807 * The search returns a group of mapping-contiguous pages with ascending
808 * indexes. There may be holes in the indices due to not-present pages.
809 *
810 * find_get_pages() returns the number of pages which were found.
811 */
812unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
813 unsigned int nr_pages, struct page **pages)
814{
815 struct radix_tree_iter iter;
816 void **slot;
817 unsigned ret = 0;
818
819 if (unlikely(!nr_pages))
820 return 0;
821
822 rcu_read_lock();
823restart:
824 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
825 struct page *page;
826repeat:
827 page = radix_tree_deref_slot(slot);
828 if (unlikely(!page))
829 continue;
830
831 if (radix_tree_exception(page)) {
832 if (radix_tree_deref_retry(page)) {
833 /*
834 * Transient condition which can only trigger
835 * when entry at index 0 moves out of or back
836 * to root: none yet gotten, safe to restart.
837 */
838 WARN_ON(iter.index);
839 goto restart;
840 }
841 /*
842 * Otherwise, shmem/tmpfs must be storing a swap entry
843 * here as an exceptional entry: so skip over it -
844 * we only reach this from invalidate_mapping_pages().
845 */
846 continue;
847 }
848
849 if (!page_cache_get_speculative(page))
850 goto repeat;
851
852 /* Has the page moved? */
853 if (unlikely(page != *slot)) {
854 page_cache_release(page);
855 goto repeat;
856 }
857
858 pages[ret] = page;
859 if (++ret == nr_pages)
860 break;
861 }
862
863 rcu_read_unlock();
864 return ret;
865}
866
867/**
868 * find_get_pages_contig - gang contiguous pagecache lookup
869 * @mapping: The address_space to search
870 * @index: The starting page index
871 * @nr_pages: The maximum number of pages
872 * @pages: Where the resulting pages are placed
873 *
874 * find_get_pages_contig() works exactly like find_get_pages(), except
875 * that the returned number of pages are guaranteed to be contiguous.
876 *
877 * find_get_pages_contig() returns the number of pages which were found.
878 */
879unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
880 unsigned int nr_pages, struct page **pages)
881{
882 struct radix_tree_iter iter;
883 void **slot;
884 unsigned int ret = 0;
885
886 if (unlikely(!nr_pages))
887 return 0;
888
889 rcu_read_lock();
890restart:
891 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
892 struct page *page;
893repeat:
894 page = radix_tree_deref_slot(slot);
895 /* The hole, there no reason to continue */
896 if (unlikely(!page))
897 break;
898
899 if (radix_tree_exception(page)) {
900 if (radix_tree_deref_retry(page)) {
901 /*
902 * Transient condition which can only trigger
903 * when entry at index 0 moves out of or back
904 * to root: none yet gotten, safe to restart.
905 */
906 goto restart;
907 }
908 /*
909 * Otherwise, shmem/tmpfs must be storing a swap entry
910 * here as an exceptional entry: so stop looking for
911 * contiguous pages.
912 */
913 break;
914 }
915
916 if (!page_cache_get_speculative(page))
917 goto repeat;
918
919 /* Has the page moved? */
920 if (unlikely(page != *slot)) {
921 page_cache_release(page);
922 goto repeat;
923 }
924
925 /*
926 * must check mapping and index after taking the ref.
927 * otherwise we can get both false positives and false
928 * negatives, which is just confusing to the caller.
929 */
930 if (page->mapping == NULL || page->index != iter.index) {
931 page_cache_release(page);
932 break;
933 }
934
935 pages[ret] = page;
936 if (++ret == nr_pages)
937 break;
938 }
939 rcu_read_unlock();
940 return ret;
941}
942EXPORT_SYMBOL(find_get_pages_contig);
943
944/**
945 * find_get_pages_tag - find and return pages that match @tag
946 * @mapping: the address_space to search
947 * @index: the starting page index
948 * @tag: the tag index
949 * @nr_pages: the maximum number of pages
950 * @pages: where the resulting pages are placed
951 *
952 * Like find_get_pages, except we only return pages which are tagged with
953 * @tag. We update @index to index the next page for the traversal.
954 */
955unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
956 int tag, unsigned int nr_pages, struct page **pages)
957{
958 struct radix_tree_iter iter;
959 void **slot;
960 unsigned ret = 0;
961
962 if (unlikely(!nr_pages))
963 return 0;
964
965 rcu_read_lock();
966restart:
967 radix_tree_for_each_tagged(slot, &mapping->page_tree,
968 &iter, *index, tag) {
969 struct page *page;
970repeat:
971 page = radix_tree_deref_slot(slot);
972 if (unlikely(!page))
973 continue;
974
975 if (radix_tree_exception(page)) {
976 if (radix_tree_deref_retry(page)) {
977 /*
978 * Transient condition which can only trigger
979 * when entry at index 0 moves out of or back
980 * to root: none yet gotten, safe to restart.
981 */
982 goto restart;
983 }
984 /*
985 * This function is never used on a shmem/tmpfs
986 * mapping, so a swap entry won't be found here.
987 */
988 BUG();
989 }
990
991 if (!page_cache_get_speculative(page))
992 goto repeat;
993
994 /* Has the page moved? */
995 if (unlikely(page != *slot)) {
996 page_cache_release(page);
997 goto repeat;
998 }
999
1000 pages[ret] = page;
1001 if (++ret == nr_pages)
1002 break;
1003 }
1004
1005 rcu_read_unlock();
1006
1007 if (ret)
1008 *index = pages[ret - 1]->index + 1;
1009
1010 return ret;
1011}
1012EXPORT_SYMBOL(find_get_pages_tag);
1013
1014/**
1015 * grab_cache_page_nowait - returns locked page at given index in given cache
1016 * @mapping: target address_space
1017 * @index: the page index
1018 *
1019 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1020 * This is intended for speculative data generators, where the data can
1021 * be regenerated if the page couldn't be grabbed. This routine should
1022 * be safe to call while holding the lock for another page.
1023 *
1024 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1025 * and deadlock against the caller's locked page.
1026 */
1027struct page *
1028grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1029{
1030 struct page *page = find_get_page(mapping, index);
1031
1032 if (page) {
1033 if (trylock_page(page))
1034 return page;
1035 page_cache_release(page);
1036 return NULL;
1037 }
1038 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1039 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1040 page_cache_release(page);
1041 page = NULL;
1042 }
1043 return page;
1044}
1045EXPORT_SYMBOL(grab_cache_page_nowait);
1046
1047/*
1048 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1049 * a _large_ part of the i/o request. Imagine the worst scenario:
1050 *
1051 * ---R__________________________________________B__________
1052 * ^ reading here ^ bad block(assume 4k)
1053 *
1054 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1055 * => failing the whole request => read(R) => read(R+1) =>
1056 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1057 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1058 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1059 *
1060 * It is going insane. Fix it by quickly scaling down the readahead size.
1061 */
1062static void shrink_readahead_size_eio(struct file *filp,
1063 struct file_ra_state *ra)
1064{
1065 ra->ra_pages /= 4;
1066}
1067
1068/**
1069 * do_generic_file_read - generic file read routine
1070 * @filp: the file to read
1071 * @ppos: current file position
1072 * @desc: read_descriptor
1073 * @actor: read method
1074 *
1075 * This is a generic file read routine, and uses the
1076 * mapping->a_ops->readpage() function for the actual low-level stuff.
1077 *
1078 * This is really ugly. But the goto's actually try to clarify some
1079 * of the logic when it comes to error handling etc.
1080 */
1081static void do_generic_file_read(struct file *filp, loff_t *ppos,
1082 read_descriptor_t *desc, read_actor_t actor)
1083{
1084 struct address_space *mapping = filp->f_mapping;
1085 struct inode *inode = mapping->host;
1086 struct file_ra_state *ra = &filp->f_ra;
1087 pgoff_t index;
1088 pgoff_t last_index;
1089 pgoff_t prev_index;
1090 unsigned long offset; /* offset into pagecache page */
1091 unsigned int prev_offset;
1092 int error;
1093
1094 index = *ppos >> PAGE_CACHE_SHIFT;
1095 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1096 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1097 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1098 offset = *ppos & ~PAGE_CACHE_MASK;
1099
1100 for (;;) {
1101 struct page *page;
1102 pgoff_t end_index;
1103 loff_t isize;
1104 unsigned long nr, ret;
1105
1106 cond_resched();
1107find_page:
1108 page = find_get_page(mapping, index);
1109 if (!page) {
1110 page_cache_sync_readahead(mapping,
1111 ra, filp,
1112 index, last_index - index);
1113 page = find_get_page(mapping, index);
1114 if (unlikely(page == NULL))
1115 goto no_cached_page;
1116 }
1117 if (PageReadahead(page)) {
1118 page_cache_async_readahead(mapping,
1119 ra, filp, page,
1120 index, last_index - index);
1121 }
1122 if (!PageUptodate(page)) {
1123 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1124 !mapping->a_ops->is_partially_uptodate)
1125 goto page_not_up_to_date;
1126 if (!trylock_page(page))
1127 goto page_not_up_to_date;
1128 /* Did it get truncated before we got the lock? */
1129 if (!page->mapping)
1130 goto page_not_up_to_date_locked;
1131 if (!mapping->a_ops->is_partially_uptodate(page,
1132 desc, offset))
1133 goto page_not_up_to_date_locked;
1134 unlock_page(page);
1135 }
1136page_ok:
1137 /*
1138 * i_size must be checked after we know the page is Uptodate.
1139 *
1140 * Checking i_size after the check allows us to calculate
1141 * the correct value for "nr", which means the zero-filled
1142 * part of the page is not copied back to userspace (unless
1143 * another truncate extends the file - this is desired though).
1144 */
1145
1146 isize = i_size_read(inode);
1147 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1148 if (unlikely(!isize || index > end_index)) {
1149 page_cache_release(page);
1150 goto out;
1151 }
1152
1153 /* nr is the maximum number of bytes to copy from this page */
1154 nr = PAGE_CACHE_SIZE;
1155 if (index == end_index) {
1156 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1157 if (nr <= offset) {
1158 page_cache_release(page);
1159 goto out;
1160 }
1161 }
1162 nr = nr - offset;
1163
1164 /* If users can be writing to this page using arbitrary
1165 * virtual addresses, take care about potential aliasing
1166 * before reading the page on the kernel side.
1167 */
1168 if (mapping_writably_mapped(mapping))
1169 flush_dcache_page(page);
1170
1171 /*
1172 * When a sequential read accesses a page several times,
1173 * only mark it as accessed the first time.
1174 */
1175 if (prev_index != index || offset != prev_offset)
1176 mark_page_accessed(page);
1177 prev_index = index;
1178
1179 /*
1180 * Ok, we have the page, and it's up-to-date, so
1181 * now we can copy it to user space...
1182 *
1183 * The actor routine returns how many bytes were actually used..
1184 * NOTE! This may not be the same as how much of a user buffer
1185 * we filled up (we may be padding etc), so we can only update
1186 * "pos" here (the actor routine has to update the user buffer
1187 * pointers and the remaining count).
1188 */
1189 ret = actor(desc, page, offset, nr);
1190 offset += ret;
1191 index += offset >> PAGE_CACHE_SHIFT;
1192 offset &= ~PAGE_CACHE_MASK;
1193 prev_offset = offset;
1194
1195 page_cache_release(page);
1196 if (ret == nr && desc->count)
1197 continue;
1198 goto out;
1199
1200page_not_up_to_date:
1201 /* Get exclusive access to the page ... */
1202 error = lock_page_killable(page);
1203 if (unlikely(error))
1204 goto readpage_error;
1205
1206page_not_up_to_date_locked:
1207 /* Did it get truncated before we got the lock? */
1208 if (!page->mapping) {
1209 unlock_page(page);
1210 page_cache_release(page);
1211 continue;
1212 }
1213
1214 /* Did somebody else fill it already? */
1215 if (PageUptodate(page)) {
1216 unlock_page(page);
1217 goto page_ok;
1218 }
1219
1220readpage:
1221 /*
1222 * A previous I/O error may have been due to temporary
1223 * failures, eg. multipath errors.
1224 * PG_error will be set again if readpage fails.
1225 */
1226 ClearPageError(page);
1227 /* Start the actual read. The read will unlock the page. */
1228 error = mapping->a_ops->readpage(filp, page);
1229
1230 if (unlikely(error)) {
1231 if (error == AOP_TRUNCATED_PAGE) {
1232 page_cache_release(page);
1233 goto find_page;
1234 }
1235 goto readpage_error;
1236 }
1237
1238 if (!PageUptodate(page)) {
1239 error = lock_page_killable(page);
1240 if (unlikely(error))
1241 goto readpage_error;
1242 if (!PageUptodate(page)) {
1243 if (page->mapping == NULL) {
1244 /*
1245 * invalidate_mapping_pages got it
1246 */
1247 unlock_page(page);
1248 page_cache_release(page);
1249 goto find_page;
1250 }
1251 unlock_page(page);
1252 shrink_readahead_size_eio(filp, ra);
1253 error = -EIO;
1254 goto readpage_error;
1255 }
1256 unlock_page(page);
1257 }
1258
1259 goto page_ok;
1260
1261readpage_error:
1262 /* UHHUH! A synchronous read error occurred. Report it */
1263 desc->error = error;
1264 page_cache_release(page);
1265 goto out;
1266
1267no_cached_page:
1268 /*
1269 * Ok, it wasn't cached, so we need to create a new
1270 * page..
1271 */
1272 page = page_cache_alloc_cold(mapping);
1273 if (!page) {
1274 desc->error = -ENOMEM;
1275 goto out;
1276 }
1277 error = add_to_page_cache_lru(page, mapping,
1278 index, GFP_KERNEL);
1279 if (error) {
1280 page_cache_release(page);
1281 if (error == -EEXIST)
1282 goto find_page;
1283 desc->error = error;
1284 goto out;
1285 }
1286 goto readpage;
1287 }
1288
1289out:
1290 ra->prev_pos = prev_index;
1291 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1292 ra->prev_pos |= prev_offset;
1293
1294 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1295 file_accessed(filp);
1296}
1297
1298int file_read_actor(read_descriptor_t *desc, struct page *page,
1299 unsigned long offset, unsigned long size)
1300{
1301 char *kaddr;
1302 unsigned long left, count = desc->count;
1303
1304 if (size > count)
1305 size = count;
1306
1307 /*
1308 * Faults on the destination of a read are common, so do it before
1309 * taking the kmap.
1310 */
1311 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1312 kaddr = kmap_atomic(page);
1313 left = __copy_to_user_inatomic(desc->arg.buf,
1314 kaddr + offset, size);
1315 kunmap_atomic(kaddr);
1316 if (left == 0)
1317 goto success;
1318 }
1319
1320 /* Do it the slow way */
1321 kaddr = kmap(page);
1322 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1323 kunmap(page);
1324
1325 if (left) {
1326 size -= left;
1327 desc->error = -EFAULT;
1328 }
1329success:
1330 desc->count = count - size;
1331 desc->written += size;
1332 desc->arg.buf += size;
1333 return size;
1334}
1335
1336/*
1337 * Performs necessary checks before doing a write
1338 * @iov: io vector request
1339 * @nr_segs: number of segments in the iovec
1340 * @count: number of bytes to write
1341 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1342 *
1343 * Adjust number of segments and amount of bytes to write (nr_segs should be
1344 * properly initialized first). Returns appropriate error code that caller
1345 * should return or zero in case that write should be allowed.
1346 */
1347int generic_segment_checks(const struct iovec *iov,
1348 unsigned long *nr_segs, size_t *count, int access_flags)
1349{
1350 unsigned long seg;
1351 size_t cnt = 0;
1352 for (seg = 0; seg < *nr_segs; seg++) {
1353 const struct iovec *iv = &iov[seg];
1354
1355 /*
1356 * If any segment has a negative length, or the cumulative
1357 * length ever wraps negative then return -EINVAL.
1358 */
1359 cnt += iv->iov_len;
1360 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1361 return -EINVAL;
1362 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1363 continue;
1364 if (seg == 0)
1365 return -EFAULT;
1366 *nr_segs = seg;
1367 cnt -= iv->iov_len; /* This segment is no good */
1368 break;
1369 }
1370 *count = cnt;
1371 return 0;
1372}
1373EXPORT_SYMBOL(generic_segment_checks);
1374
1375/**
1376 * generic_file_aio_read - generic filesystem read routine
1377 * @iocb: kernel I/O control block
1378 * @iov: io vector request
1379 * @nr_segs: number of segments in the iovec
1380 * @pos: current file position
1381 *
1382 * This is the "read()" routine for all filesystems
1383 * that can use the page cache directly.
1384 */
1385ssize_t
1386generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1387 unsigned long nr_segs, loff_t pos)
1388{
1389 struct file *filp = iocb->ki_filp;
1390 ssize_t retval;
1391 unsigned long seg = 0;
1392 size_t count;
1393 loff_t *ppos = &iocb->ki_pos;
1394
1395 count = 0;
1396 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1397 if (retval)
1398 return retval;
1399
1400 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1401 if (filp->f_flags & O_DIRECT) {
1402 loff_t size;
1403 struct address_space *mapping;
1404 struct inode *inode;
1405
1406 mapping = filp->f_mapping;
1407 inode = mapping->host;
1408 if (!count)
1409 goto out; /* skip atime */
1410 size = i_size_read(inode);
1411 if (pos < size) {
1412 retval = filemap_write_and_wait_range(mapping, pos,
1413 pos + iov_length(iov, nr_segs) - 1);
1414 if (!retval) {
1415 struct blk_plug plug;
1416
1417 blk_start_plug(&plug);
1418 retval = mapping->a_ops->direct_IO(READ, iocb,
1419 iov, pos, nr_segs);
1420 blk_finish_plug(&plug);
1421 }
1422 if (retval > 0) {
1423 *ppos = pos + retval;
1424 count -= retval;
1425 }
1426
1427 /*
1428 * Btrfs can have a short DIO read if we encounter
1429 * compressed extents, so if there was an error, or if
1430 * we've already read everything we wanted to, or if
1431 * there was a short read because we hit EOF, go ahead
1432 * and return. Otherwise fallthrough to buffered io for
1433 * the rest of the read.
1434 */
1435 if (retval < 0 || !count || *ppos >= size) {
1436 file_accessed(filp);
1437 goto out;
1438 }
1439 }
1440 }
1441
1442 count = retval;
1443 for (seg = 0; seg < nr_segs; seg++) {
1444 read_descriptor_t desc;
1445 loff_t offset = 0;
1446
1447 /*
1448 * If we did a short DIO read we need to skip the section of the
1449 * iov that we've already read data into.
1450 */
1451 if (count) {
1452 if (count > iov[seg].iov_len) {
1453 count -= iov[seg].iov_len;
1454 continue;
1455 }
1456 offset = count;
1457 count = 0;
1458 }
1459
1460 desc.written = 0;
1461 desc.arg.buf = iov[seg].iov_base + offset;
1462 desc.count = iov[seg].iov_len - offset;
1463 if (desc.count == 0)
1464 continue;
1465 desc.error = 0;
1466 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1467 retval += desc.written;
1468 if (desc.error) {
1469 retval = retval ?: desc.error;
1470 break;
1471 }
1472 if (desc.count > 0)
1473 break;
1474 }
1475out:
1476 return retval;
1477}
1478EXPORT_SYMBOL(generic_file_aio_read);
1479
1480#ifdef CONFIG_MMU
1481/**
1482 * page_cache_read - adds requested page to the page cache if not already there
1483 * @file: file to read
1484 * @offset: page index
1485 *
1486 * This adds the requested page to the page cache if it isn't already there,
1487 * and schedules an I/O to read in its contents from disk.
1488 */
1489static int page_cache_read(struct file *file, pgoff_t offset)
1490{
1491 struct address_space *mapping = file->f_mapping;
1492 struct page *page;
1493 int ret;
1494
1495 do {
1496 page = page_cache_alloc_cold(mapping);
1497 if (!page)
1498 return -ENOMEM;
1499
1500 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1501 if (ret == 0)
1502 ret = mapping->a_ops->readpage(file, page);
1503 else if (ret == -EEXIST)
1504 ret = 0; /* losing race to add is OK */
1505
1506 page_cache_release(page);
1507
1508 } while (ret == AOP_TRUNCATED_PAGE);
1509
1510 return ret;
1511}
1512
1513#define MMAP_LOTSAMISS (100)
1514
1515/*
1516 * Synchronous readahead happens when we don't even find
1517 * a page in the page cache at all.
1518 */
1519static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1520 struct file_ra_state *ra,
1521 struct file *file,
1522 pgoff_t offset)
1523{
1524 unsigned long ra_pages;
1525 struct address_space *mapping = file->f_mapping;
1526
1527 /* If we don't want any read-ahead, don't bother */
1528 if (VM_RandomReadHint(vma))
1529 return;
1530 if (!ra->ra_pages)
1531 return;
1532
1533 if (VM_SequentialReadHint(vma)) {
1534 page_cache_sync_readahead(mapping, ra, file, offset,
1535 ra->ra_pages);
1536 return;
1537 }
1538
1539 /* Avoid banging the cache line if not needed */
1540 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1541 ra->mmap_miss++;
1542
1543 /*
1544 * Do we miss much more than hit in this file? If so,
1545 * stop bothering with read-ahead. It will only hurt.
1546 */
1547 if (ra->mmap_miss > MMAP_LOTSAMISS)
1548 return;
1549
1550 /*
1551 * mmap read-around
1552 */
1553 ra_pages = max_sane_readahead(ra->ra_pages);
1554 ra->start = max_t(long, 0, offset - ra_pages / 2);
1555 ra->size = ra_pages;
1556 ra->async_size = ra_pages / 4;
1557 ra_submit(ra, mapping, file);
1558}
1559
1560/*
1561 * Asynchronous readahead happens when we find the page and PG_readahead,
1562 * so we want to possibly extend the readahead further..
1563 */
1564static void do_async_mmap_readahead(struct vm_area_struct *vma,
1565 struct file_ra_state *ra,
1566 struct file *file,
1567 struct page *page,
1568 pgoff_t offset)
1569{
1570 struct address_space *mapping = file->f_mapping;
1571
1572 /* If we don't want any read-ahead, don't bother */
1573 if (VM_RandomReadHint(vma))
1574 return;
1575 if (ra->mmap_miss > 0)
1576 ra->mmap_miss--;
1577 if (PageReadahead(page))
1578 page_cache_async_readahead(mapping, ra, file,
1579 page, offset, ra->ra_pages);
1580}
1581
1582/**
1583 * filemap_fault - read in file data for page fault handling
1584 * @vma: vma in which the fault was taken
1585 * @vmf: struct vm_fault containing details of the fault
1586 *
1587 * filemap_fault() is invoked via the vma operations vector for a
1588 * mapped memory region to read in file data during a page fault.
1589 *
1590 * The goto's are kind of ugly, but this streamlines the normal case of having
1591 * it in the page cache, and handles the special cases reasonably without
1592 * having a lot of duplicated code.
1593 */
1594int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1595{
1596 int error;
1597 struct file *file = vma->vm_file;
1598 struct address_space *mapping = file->f_mapping;
1599 struct file_ra_state *ra = &file->f_ra;
1600 struct inode *inode = mapping->host;
1601 pgoff_t offset = vmf->pgoff;
1602 struct page *page;
1603 pgoff_t size;
1604 int ret = 0;
1605
1606 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1607 if (offset >= size)
1608 return VM_FAULT_SIGBUS;
1609
1610 /*
1611 * Do we have something in the page cache already?
1612 */
1613 page = find_get_page(mapping, offset);
1614 if (likely(page)) {
1615 /*
1616 * We found the page, so try async readahead before
1617 * waiting for the lock.
1618 */
1619 do_async_mmap_readahead(vma, ra, file, page, offset);
1620 } else {
1621 /* No page in the page cache at all */
1622 do_sync_mmap_readahead(vma, ra, file, offset);
1623 count_vm_event(PGMAJFAULT);
1624 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1625 ret = VM_FAULT_MAJOR;
1626retry_find:
1627 page = find_get_page(mapping, offset);
1628 if (!page)
1629 goto no_cached_page;
1630 }
1631
1632 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1633 page_cache_release(page);
1634 return ret | VM_FAULT_RETRY;
1635 }
1636
1637 /* Did it get truncated? */
1638 if (unlikely(page->mapping != mapping)) {
1639 unlock_page(page);
1640 put_page(page);
1641 goto retry_find;
1642 }
1643 VM_BUG_ON(page->index != offset);
1644
1645 /*
1646 * We have a locked page in the page cache, now we need to check
1647 * that it's up-to-date. If not, it is going to be due to an error.
1648 */
1649 if (unlikely(!PageUptodate(page)))
1650 goto page_not_uptodate;
1651
1652 /*
1653 * Found the page and have a reference on it.
1654 * We must recheck i_size under page lock.
1655 */
1656 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1657 if (unlikely(offset >= size)) {
1658 unlock_page(page);
1659 page_cache_release(page);
1660 return VM_FAULT_SIGBUS;
1661 }
1662
1663 vmf->page = page;
1664 return ret | VM_FAULT_LOCKED;
1665
1666no_cached_page:
1667 /*
1668 * We're only likely to ever get here if MADV_RANDOM is in
1669 * effect.
1670 */
1671 error = page_cache_read(file, offset);
1672
1673 /*
1674 * The page we want has now been added to the page cache.
1675 * In the unlikely event that someone removed it in the
1676 * meantime, we'll just come back here and read it again.
1677 */
1678 if (error >= 0)
1679 goto retry_find;
1680
1681 /*
1682 * An error return from page_cache_read can result if the
1683 * system is low on memory, or a problem occurs while trying
1684 * to schedule I/O.
1685 */
1686 if (error == -ENOMEM)
1687 return VM_FAULT_OOM;
1688 return VM_FAULT_SIGBUS;
1689
1690page_not_uptodate:
1691 /*
1692 * Umm, take care of errors if the page isn't up-to-date.
1693 * Try to re-read it _once_. We do this synchronously,
1694 * because there really aren't any performance issues here
1695 * and we need to check for errors.
1696 */
1697 ClearPageError(page);
1698 error = mapping->a_ops->readpage(file, page);
1699 if (!error) {
1700 wait_on_page_locked(page);
1701 if (!PageUptodate(page))
1702 error = -EIO;
1703 }
1704 page_cache_release(page);
1705
1706 if (!error || error == AOP_TRUNCATED_PAGE)
1707 goto retry_find;
1708
1709 /* Things didn't work out. Return zero to tell the mm layer so. */
1710 shrink_readahead_size_eio(file, ra);
1711 return VM_FAULT_SIGBUS;
1712}
1713EXPORT_SYMBOL(filemap_fault);
1714
1715const struct vm_operations_struct generic_file_vm_ops = {
1716 .fault = filemap_fault,
1717};
1718
1719/* This is used for a general mmap of a disk file */
1720
1721int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1722{
1723 struct address_space *mapping = file->f_mapping;
1724
1725 if (!mapping->a_ops->readpage)
1726 return -ENOEXEC;
1727 file_accessed(file);
1728 vma->vm_ops = &generic_file_vm_ops;
1729 vma->vm_flags |= VM_CAN_NONLINEAR;
1730 return 0;
1731}
1732
1733/*
1734 * This is for filesystems which do not implement ->writepage.
1735 */
1736int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1737{
1738 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1739 return -EINVAL;
1740 return generic_file_mmap(file, vma);
1741}
1742#else
1743int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1744{
1745 return -ENOSYS;
1746}
1747int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1748{
1749 return -ENOSYS;
1750}
1751#endif /* CONFIG_MMU */
1752
1753EXPORT_SYMBOL(generic_file_mmap);
1754EXPORT_SYMBOL(generic_file_readonly_mmap);
1755
1756static struct page *__read_cache_page(struct address_space *mapping,
1757 pgoff_t index,
1758 int (*filler)(void *, struct page *),
1759 void *data,
1760 gfp_t gfp)
1761{
1762 struct page *page;
1763 int err;
1764repeat:
1765 page = find_get_page(mapping, index);
1766 if (!page) {
1767 page = __page_cache_alloc(gfp | __GFP_COLD);
1768 if (!page)
1769 return ERR_PTR(-ENOMEM);
1770 err = add_to_page_cache_lru(page, mapping, index, gfp);
1771 if (unlikely(err)) {
1772 page_cache_release(page);
1773 if (err == -EEXIST)
1774 goto repeat;
1775 /* Presumably ENOMEM for radix tree node */
1776 return ERR_PTR(err);
1777 }
1778 err = filler(data, page);
1779 if (err < 0) {
1780 page_cache_release(page);
1781 page = ERR_PTR(err);
1782 }
1783 }
1784 return page;
1785}
1786
1787static struct page *do_read_cache_page(struct address_space *mapping,
1788 pgoff_t index,
1789 int (*filler)(void *, struct page *),
1790 void *data,
1791 gfp_t gfp)
1792
1793{
1794 struct page *page;
1795 int err;
1796
1797retry:
1798 page = __read_cache_page(mapping, index, filler, data, gfp);
1799 if (IS_ERR(page))
1800 return page;
1801 if (PageUptodate(page))
1802 goto out;
1803
1804 lock_page(page);
1805 if (!page->mapping) {
1806 unlock_page(page);
1807 page_cache_release(page);
1808 goto retry;
1809 }
1810 if (PageUptodate(page)) {
1811 unlock_page(page);
1812 goto out;
1813 }
1814 err = filler(data, page);
1815 if (err < 0) {
1816 page_cache_release(page);
1817 return ERR_PTR(err);
1818 }
1819out:
1820 mark_page_accessed(page);
1821 return page;
1822}
1823
1824/**
1825 * read_cache_page_async - read into page cache, fill it if needed
1826 * @mapping: the page's address_space
1827 * @index: the page index
1828 * @filler: function to perform the read
1829 * @data: first arg to filler(data, page) function, often left as NULL
1830 *
1831 * Same as read_cache_page, but don't wait for page to become unlocked
1832 * after submitting it to the filler.
1833 *
1834 * Read into the page cache. If a page already exists, and PageUptodate() is
1835 * not set, try to fill the page but don't wait for it to become unlocked.
1836 *
1837 * If the page does not get brought uptodate, return -EIO.
1838 */
1839struct page *read_cache_page_async(struct address_space *mapping,
1840 pgoff_t index,
1841 int (*filler)(void *, struct page *),
1842 void *data)
1843{
1844 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1845}
1846EXPORT_SYMBOL(read_cache_page_async);
1847
1848static struct page *wait_on_page_read(struct page *page)
1849{
1850 if (!IS_ERR(page)) {
1851 wait_on_page_locked(page);
1852 if (!PageUptodate(page)) {
1853 page_cache_release(page);
1854 page = ERR_PTR(-EIO);
1855 }
1856 }
1857 return page;
1858}
1859
1860/**
1861 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1862 * @mapping: the page's address_space
1863 * @index: the page index
1864 * @gfp: the page allocator flags to use if allocating
1865 *
1866 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1867 * any new page allocations done using the specified allocation flags.
1868 *
1869 * If the page does not get brought uptodate, return -EIO.
1870 */
1871struct page *read_cache_page_gfp(struct address_space *mapping,
1872 pgoff_t index,
1873 gfp_t gfp)
1874{
1875 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1876
1877 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1878}
1879EXPORT_SYMBOL(read_cache_page_gfp);
1880
1881/**
1882 * read_cache_page - read into page cache, fill it if needed
1883 * @mapping: the page's address_space
1884 * @index: the page index
1885 * @filler: function to perform the read
1886 * @data: first arg to filler(data, page) function, often left as NULL
1887 *
1888 * Read into the page cache. If a page already exists, and PageUptodate() is
1889 * not set, try to fill the page then wait for it to become unlocked.
1890 *
1891 * If the page does not get brought uptodate, return -EIO.
1892 */
1893struct page *read_cache_page(struct address_space *mapping,
1894 pgoff_t index,
1895 int (*filler)(void *, struct page *),
1896 void *data)
1897{
1898 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1899}
1900EXPORT_SYMBOL(read_cache_page);
1901
1902static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1903 const struct iovec *iov, size_t base, size_t bytes)
1904{
1905 size_t copied = 0, left = 0;
1906
1907 while (bytes) {
1908 char __user *buf = iov->iov_base + base;
1909 int copy = min(bytes, iov->iov_len - base);
1910
1911 base = 0;
1912 left = __copy_from_user_inatomic(vaddr, buf, copy);
1913 copied += copy;
1914 bytes -= copy;
1915 vaddr += copy;
1916 iov++;
1917
1918 if (unlikely(left))
1919 break;
1920 }
1921 return copied - left;
1922}
1923
1924/*
1925 * Copy as much as we can into the page and return the number of bytes which
1926 * were successfully copied. If a fault is encountered then return the number of
1927 * bytes which were copied.
1928 */
1929size_t iov_iter_copy_from_user_atomic(struct page *page,
1930 struct iov_iter *i, unsigned long offset, size_t bytes)
1931{
1932 char *kaddr;
1933 size_t copied;
1934
1935 BUG_ON(!in_atomic());
1936 kaddr = kmap_atomic(page);
1937 if (likely(i->nr_segs == 1)) {
1938 int left;
1939 char __user *buf = i->iov->iov_base + i->iov_offset;
1940 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
1941 copied = bytes - left;
1942 } else {
1943 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1944 i->iov, i->iov_offset, bytes);
1945 }
1946 kunmap_atomic(kaddr);
1947
1948 return copied;
1949}
1950EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1951
1952/*
1953 * This has the same sideeffects and return value as
1954 * iov_iter_copy_from_user_atomic().
1955 * The difference is that it attempts to resolve faults.
1956 * Page must not be locked.
1957 */
1958size_t iov_iter_copy_from_user(struct page *page,
1959 struct iov_iter *i, unsigned long offset, size_t bytes)
1960{
1961 char *kaddr;
1962 size_t copied;
1963
1964 kaddr = kmap(page);
1965 if (likely(i->nr_segs == 1)) {
1966 int left;
1967 char __user *buf = i->iov->iov_base + i->iov_offset;
1968 left = __copy_from_user(kaddr + offset, buf, bytes);
1969 copied = bytes - left;
1970 } else {
1971 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1972 i->iov, i->iov_offset, bytes);
1973 }
1974 kunmap(page);
1975 return copied;
1976}
1977EXPORT_SYMBOL(iov_iter_copy_from_user);
1978
1979void iov_iter_advance(struct iov_iter *i, size_t bytes)
1980{
1981 BUG_ON(i->count < bytes);
1982
1983 if (likely(i->nr_segs == 1)) {
1984 i->iov_offset += bytes;
1985 i->count -= bytes;
1986 } else {
1987 const struct iovec *iov = i->iov;
1988 size_t base = i->iov_offset;
1989 unsigned long nr_segs = i->nr_segs;
1990
1991 /*
1992 * The !iov->iov_len check ensures we skip over unlikely
1993 * zero-length segments (without overruning the iovec).
1994 */
1995 while (bytes || unlikely(i->count && !iov->iov_len)) {
1996 int copy;
1997
1998 copy = min(bytes, iov->iov_len - base);
1999 BUG_ON(!i->count || i->count < copy);
2000 i->count -= copy;
2001 bytes -= copy;
2002 base += copy;
2003 if (iov->iov_len == base) {
2004 iov++;
2005 nr_segs--;
2006 base = 0;
2007 }
2008 }
2009 i->iov = iov;
2010 i->iov_offset = base;
2011 i->nr_segs = nr_segs;
2012 }
2013}
2014EXPORT_SYMBOL(iov_iter_advance);
2015
2016/*
2017 * Fault in the first iovec of the given iov_iter, to a maximum length
2018 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2019 * accessed (ie. because it is an invalid address).
2020 *
2021 * writev-intensive code may want this to prefault several iovecs -- that
2022 * would be possible (callers must not rely on the fact that _only_ the
2023 * first iovec will be faulted with the current implementation).
2024 */
2025int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2026{
2027 char __user *buf = i->iov->iov_base + i->iov_offset;
2028 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2029 return fault_in_pages_readable(buf, bytes);
2030}
2031EXPORT_SYMBOL(iov_iter_fault_in_readable);
2032
2033/*
2034 * Return the count of just the current iov_iter segment.
2035 */
2036size_t iov_iter_single_seg_count(struct iov_iter *i)
2037{
2038 const struct iovec *iov = i->iov;
2039 if (i->nr_segs == 1)
2040 return i->count;
2041 else
2042 return min(i->count, iov->iov_len - i->iov_offset);
2043}
2044EXPORT_SYMBOL(iov_iter_single_seg_count);
2045
2046/*
2047 * Performs necessary checks before doing a write
2048 *
2049 * Can adjust writing position or amount of bytes to write.
2050 * Returns appropriate error code that caller should return or
2051 * zero in case that write should be allowed.
2052 */
2053inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2054{
2055 struct inode *inode = file->f_mapping->host;
2056 unsigned long limit = rlimit(RLIMIT_FSIZE);
2057
2058 if (unlikely(*pos < 0))
2059 return -EINVAL;
2060
2061 if (!isblk) {
2062 /* FIXME: this is for backwards compatibility with 2.4 */
2063 if (file->f_flags & O_APPEND)
2064 *pos = i_size_read(inode);
2065
2066 if (limit != RLIM_INFINITY) {
2067 if (*pos >= limit) {
2068 send_sig(SIGXFSZ, current, 0);
2069 return -EFBIG;
2070 }
2071 if (*count > limit - (typeof(limit))*pos) {
2072 *count = limit - (typeof(limit))*pos;
2073 }
2074 }
2075 }
2076
2077 /*
2078 * LFS rule
2079 */
2080 if (unlikely(*pos + *count > MAX_NON_LFS &&
2081 !(file->f_flags & O_LARGEFILE))) {
2082 if (*pos >= MAX_NON_LFS) {
2083 return -EFBIG;
2084 }
2085 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2086 *count = MAX_NON_LFS - (unsigned long)*pos;
2087 }
2088 }
2089
2090 /*
2091 * Are we about to exceed the fs block limit ?
2092 *
2093 * If we have written data it becomes a short write. If we have
2094 * exceeded without writing data we send a signal and return EFBIG.
2095 * Linus frestrict idea will clean these up nicely..
2096 */
2097 if (likely(!isblk)) {
2098 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2099 if (*count || *pos > inode->i_sb->s_maxbytes) {
2100 return -EFBIG;
2101 }
2102 /* zero-length writes at ->s_maxbytes are OK */
2103 }
2104
2105 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2106 *count = inode->i_sb->s_maxbytes - *pos;
2107 } else {
2108#ifdef CONFIG_BLOCK
2109 loff_t isize;
2110 if (bdev_read_only(I_BDEV(inode)))
2111 return -EPERM;
2112 isize = i_size_read(inode);
2113 if (*pos >= isize) {
2114 if (*count || *pos > isize)
2115 return -ENOSPC;
2116 }
2117
2118 if (*pos + *count > isize)
2119 *count = isize - *pos;
2120#else
2121 return -EPERM;
2122#endif
2123 }
2124 return 0;
2125}
2126EXPORT_SYMBOL(generic_write_checks);
2127
2128int pagecache_write_begin(struct file *file, struct address_space *mapping,
2129 loff_t pos, unsigned len, unsigned flags,
2130 struct page **pagep, void **fsdata)
2131{
2132 const struct address_space_operations *aops = mapping->a_ops;
2133
2134 return aops->write_begin(file, mapping, pos, len, flags,
2135 pagep, fsdata);
2136}
2137EXPORT_SYMBOL(pagecache_write_begin);
2138
2139int pagecache_write_end(struct file *file, struct address_space *mapping,
2140 loff_t pos, unsigned len, unsigned copied,
2141 struct page *page, void *fsdata)
2142{
2143 const struct address_space_operations *aops = mapping->a_ops;
2144
2145 mark_page_accessed(page);
2146 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2147}
2148EXPORT_SYMBOL(pagecache_write_end);
2149
2150ssize_t
2151generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2152 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2153 size_t count, size_t ocount)
2154{
2155 struct file *file = iocb->ki_filp;
2156 struct address_space *mapping = file->f_mapping;
2157 struct inode *inode = mapping->host;
2158 ssize_t written;
2159 size_t write_len;
2160 pgoff_t end;
2161
2162 if (count != ocount)
2163 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2164
2165 write_len = iov_length(iov, *nr_segs);
2166 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2167
2168 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2169 if (written)
2170 goto out;
2171
2172 /*
2173 * After a write we want buffered reads to be sure to go to disk to get
2174 * the new data. We invalidate clean cached page from the region we're
2175 * about to write. We do this *before* the write so that we can return
2176 * without clobbering -EIOCBQUEUED from ->direct_IO().
2177 */
2178 if (mapping->nrpages) {
2179 written = invalidate_inode_pages2_range(mapping,
2180 pos >> PAGE_CACHE_SHIFT, end);
2181 /*
2182 * If a page can not be invalidated, return 0 to fall back
2183 * to buffered write.
2184 */
2185 if (written) {
2186 if (written == -EBUSY)
2187 return 0;
2188 goto out;
2189 }
2190 }
2191
2192 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2193
2194 /*
2195 * Finally, try again to invalidate clean pages which might have been
2196 * cached by non-direct readahead, or faulted in by get_user_pages()
2197 * if the source of the write was an mmap'ed region of the file
2198 * we're writing. Either one is a pretty crazy thing to do,
2199 * so we don't support it 100%. If this invalidation
2200 * fails, tough, the write still worked...
2201 */
2202 if (mapping->nrpages) {
2203 invalidate_inode_pages2_range(mapping,
2204 pos >> PAGE_CACHE_SHIFT, end);
2205 }
2206
2207 if (written > 0) {
2208 pos += written;
2209 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2210 i_size_write(inode, pos);
2211 mark_inode_dirty(inode);
2212 }
2213 *ppos = pos;
2214 }
2215out:
2216 return written;
2217}
2218EXPORT_SYMBOL(generic_file_direct_write);
2219
2220/*
2221 * Find or create a page at the given pagecache position. Return the locked
2222 * page. This function is specifically for buffered writes.
2223 */
2224struct page *grab_cache_page_write_begin(struct address_space *mapping,
2225 pgoff_t index, unsigned flags)
2226{
2227 int status;
2228 gfp_t gfp_mask;
2229 struct page *page;
2230 gfp_t gfp_notmask = 0;
2231
2232 gfp_mask = mapping_gfp_mask(mapping);
2233 if (mapping_cap_account_dirty(mapping))
2234 gfp_mask |= __GFP_WRITE;
2235 if (flags & AOP_FLAG_NOFS)
2236 gfp_notmask = __GFP_FS;
2237repeat:
2238 page = find_lock_page(mapping, index);
2239 if (page)
2240 goto found;
2241
2242 page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
2243 if (!page)
2244 return NULL;
2245 status = add_to_page_cache_lru(page, mapping, index,
2246 GFP_KERNEL & ~gfp_notmask);
2247 if (unlikely(status)) {
2248 page_cache_release(page);
2249 if (status == -EEXIST)
2250 goto repeat;
2251 return NULL;
2252 }
2253found:
2254 wait_on_page_writeback(page);
2255 return page;
2256}
2257EXPORT_SYMBOL(grab_cache_page_write_begin);
2258
2259static ssize_t generic_perform_write(struct file *file,
2260 struct iov_iter *i, loff_t pos)
2261{
2262 struct address_space *mapping = file->f_mapping;
2263 const struct address_space_operations *a_ops = mapping->a_ops;
2264 long status = 0;
2265 ssize_t written = 0;
2266 unsigned int flags = 0;
2267
2268 /*
2269 * Copies from kernel address space cannot fail (NFSD is a big user).
2270 */
2271 if (segment_eq(get_fs(), KERNEL_DS))
2272 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2273
2274 do {
2275 struct page *page;
2276 unsigned long offset; /* Offset into pagecache page */
2277 unsigned long bytes; /* Bytes to write to page */
2278 size_t copied; /* Bytes copied from user */
2279 void *fsdata;
2280
2281 offset = (pos & (PAGE_CACHE_SIZE - 1));
2282 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2283 iov_iter_count(i));
2284
2285again:
2286 /*
2287 * Bring in the user page that we will copy from _first_.
2288 * Otherwise there's a nasty deadlock on copying from the
2289 * same page as we're writing to, without it being marked
2290 * up-to-date.
2291 *
2292 * Not only is this an optimisation, but it is also required
2293 * to check that the address is actually valid, when atomic
2294 * usercopies are used, below.
2295 */
2296 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2297 status = -EFAULT;
2298 break;
2299 }
2300
2301 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2302 &page, &fsdata);
2303 if (unlikely(status))
2304 break;
2305
2306 if (mapping_writably_mapped(mapping))
2307 flush_dcache_page(page);
2308
2309 pagefault_disable();
2310 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2311 pagefault_enable();
2312 flush_dcache_page(page);
2313
2314 mark_page_accessed(page);
2315 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2316 page, fsdata);
2317 if (unlikely(status < 0))
2318 break;
2319 copied = status;
2320
2321 cond_resched();
2322
2323 iov_iter_advance(i, copied);
2324 if (unlikely(copied == 0)) {
2325 /*
2326 * If we were unable to copy any data at all, we must
2327 * fall back to a single segment length write.
2328 *
2329 * If we didn't fallback here, we could livelock
2330 * because not all segments in the iov can be copied at
2331 * once without a pagefault.
2332 */
2333 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2334 iov_iter_single_seg_count(i));
2335 goto again;
2336 }
2337 pos += copied;
2338 written += copied;
2339
2340 balance_dirty_pages_ratelimited(mapping);
2341 if (fatal_signal_pending(current)) {
2342 status = -EINTR;
2343 break;
2344 }
2345 } while (iov_iter_count(i));
2346
2347 return written ? written : status;
2348}
2349
2350ssize_t
2351generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2352 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2353 size_t count, ssize_t written)
2354{
2355 struct file *file = iocb->ki_filp;
2356 ssize_t status;
2357 struct iov_iter i;
2358
2359 iov_iter_init(&i, iov, nr_segs, count, written);
2360 status = generic_perform_write(file, &i, pos);
2361
2362 if (likely(status >= 0)) {
2363 written += status;
2364 *ppos = pos + status;
2365 }
2366
2367 return written ? written : status;
2368}
2369EXPORT_SYMBOL(generic_file_buffered_write);
2370
2371/**
2372 * __generic_file_aio_write - write data to a file
2373 * @iocb: IO state structure (file, offset, etc.)
2374 * @iov: vector with data to write
2375 * @nr_segs: number of segments in the vector
2376 * @ppos: position where to write
2377 *
2378 * This function does all the work needed for actually writing data to a
2379 * file. It does all basic checks, removes SUID from the file, updates
2380 * modification times and calls proper subroutines depending on whether we
2381 * do direct IO or a standard buffered write.
2382 *
2383 * It expects i_mutex to be grabbed unless we work on a block device or similar
2384 * object which does not need locking at all.
2385 *
2386 * This function does *not* take care of syncing data in case of O_SYNC write.
2387 * A caller has to handle it. This is mainly due to the fact that we want to
2388 * avoid syncing under i_mutex.
2389 */
2390ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2391 unsigned long nr_segs, loff_t *ppos)
2392{
2393 struct file *file = iocb->ki_filp;
2394 struct address_space * mapping = file->f_mapping;
2395 size_t ocount; /* original count */
2396 size_t count; /* after file limit checks */
2397 struct inode *inode = mapping->host;
2398 loff_t pos;
2399 ssize_t written;
2400 ssize_t err;
2401
2402 ocount = 0;
2403 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2404 if (err)
2405 return err;
2406
2407 count = ocount;
2408 pos = *ppos;
2409
2410 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2411
2412 /* We can write back this queue in page reclaim */
2413 current->backing_dev_info = mapping->backing_dev_info;
2414 written = 0;
2415
2416 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2417 if (err)
2418 goto out;
2419
2420 if (count == 0)
2421 goto out;
2422
2423 err = file_remove_suid(file);
2424 if (err)
2425 goto out;
2426
2427 err = file_update_time(file);
2428 if (err)
2429 goto out;
2430
2431 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2432 if (unlikely(file->f_flags & O_DIRECT)) {
2433 loff_t endbyte;
2434 ssize_t written_buffered;
2435
2436 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2437 ppos, count, ocount);
2438 if (written < 0 || written == count)
2439 goto out;
2440 /*
2441 * direct-io write to a hole: fall through to buffered I/O
2442 * for completing the rest of the request.
2443 */
2444 pos += written;
2445 count -= written;
2446 written_buffered = generic_file_buffered_write(iocb, iov,
2447 nr_segs, pos, ppos, count,
2448 written);
2449 /*
2450 * If generic_file_buffered_write() retuned a synchronous error
2451 * then we want to return the number of bytes which were
2452 * direct-written, or the error code if that was zero. Note
2453 * that this differs from normal direct-io semantics, which
2454 * will return -EFOO even if some bytes were written.
2455 */
2456 if (written_buffered < 0) {
2457 err = written_buffered;
2458 goto out;
2459 }
2460
2461 /*
2462 * We need to ensure that the page cache pages are written to
2463 * disk and invalidated to preserve the expected O_DIRECT
2464 * semantics.
2465 */
2466 endbyte = pos + written_buffered - written - 1;
2467 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2468 if (err == 0) {
2469 written = written_buffered;
2470 invalidate_mapping_pages(mapping,
2471 pos >> PAGE_CACHE_SHIFT,
2472 endbyte >> PAGE_CACHE_SHIFT);
2473 } else {
2474 /*
2475 * We don't know how much we wrote, so just return
2476 * the number of bytes which were direct-written
2477 */
2478 }
2479 } else {
2480 written = generic_file_buffered_write(iocb, iov, nr_segs,
2481 pos, ppos, count, written);
2482 }
2483out:
2484 current->backing_dev_info = NULL;
2485 return written ? written : err;
2486}
2487EXPORT_SYMBOL(__generic_file_aio_write);
2488
2489/**
2490 * generic_file_aio_write - write data to a file
2491 * @iocb: IO state structure
2492 * @iov: vector with data to write
2493 * @nr_segs: number of segments in the vector
2494 * @pos: position in file where to write
2495 *
2496 * This is a wrapper around __generic_file_aio_write() to be used by most
2497 * filesystems. It takes care of syncing the file in case of O_SYNC file
2498 * and acquires i_mutex as needed.
2499 */
2500ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2501 unsigned long nr_segs, loff_t pos)
2502{
2503 struct file *file = iocb->ki_filp;
2504 struct inode *inode = file->f_mapping->host;
2505 struct blk_plug plug;
2506 ssize_t ret;
2507
2508 BUG_ON(iocb->ki_pos != pos);
2509
2510 mutex_lock(&inode->i_mutex);
2511 blk_start_plug(&plug);
2512 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2513 mutex_unlock(&inode->i_mutex);
2514
2515 if (ret > 0 || ret == -EIOCBQUEUED) {
2516 ssize_t err;
2517
2518 err = generic_write_sync(file, pos, ret);
2519 if (err < 0 && ret > 0)
2520 ret = err;
2521 }
2522 blk_finish_plug(&plug);
2523 return ret;
2524}
2525EXPORT_SYMBOL(generic_file_aio_write);
2526
2527/**
2528 * try_to_release_page() - release old fs-specific metadata on a page
2529 *
2530 * @page: the page which the kernel is trying to free
2531 * @gfp_mask: memory allocation flags (and I/O mode)
2532 *
2533 * The address_space is to try to release any data against the page
2534 * (presumably at page->private). If the release was successful, return `1'.
2535 * Otherwise return zero.
2536 *
2537 * This may also be called if PG_fscache is set on a page, indicating that the
2538 * page is known to the local caching routines.
2539 *
2540 * The @gfp_mask argument specifies whether I/O may be performed to release
2541 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2542 *
2543 */
2544int try_to_release_page(struct page *page, gfp_t gfp_mask)
2545{
2546 struct address_space * const mapping = page->mapping;
2547
2548 BUG_ON(!PageLocked(page));
2549 if (PageWriteback(page))
2550 return 0;
2551
2552 if (mapping && mapping->a_ops->releasepage)
2553 return mapping->a_ops->releasepage(page, gfp_mask);
2554 return try_to_free_buffers(page);
2555}
2556
2557EXPORT_SYMBOL(try_to_release_page);