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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/dax.h>
15#include <linux/fs.h>
16#include <linux/uaccess.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/hugetlb.h>
35#include <linux/memcontrol.h>
36#include <linux/cleancache.h>
37#include <linux/rmap.h>
38#include "internal.h"
39
40#define CREATE_TRACE_POINTS
41#include <trace/events/filemap.h>
42
43/*
44 * FIXME: remove all knowledge of the buffer layer from the core VM
45 */
46#include <linux/buffer_head.h> /* for try_to_free_buffers */
47
48#include <asm/mman.h>
49
50/*
51 * Shared mappings implemented 30.11.1994. It's not fully working yet,
52 * though.
53 *
54 * Shared mappings now work. 15.8.1995 Bruno.
55 *
56 * finished 'unifying' the page and buffer cache and SMP-threaded the
57 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
58 *
59 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
60 */
61
62/*
63 * Lock ordering:
64 *
65 * ->i_mmap_rwsem (truncate_pagecache)
66 * ->private_lock (__free_pte->__set_page_dirty_buffers)
67 * ->swap_lock (exclusive_swap_page, others)
68 * ->mapping->tree_lock
69 *
70 * ->i_mutex
71 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
72 *
73 * ->mmap_sem
74 * ->i_mmap_rwsem
75 * ->page_table_lock or pte_lock (various, mainly in memory.c)
76 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
77 *
78 * ->mmap_sem
79 * ->lock_page (access_process_vm)
80 *
81 * ->i_mutex (generic_perform_write)
82 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
83 *
84 * bdi->wb.list_lock
85 * sb_lock (fs/fs-writeback.c)
86 * ->mapping->tree_lock (__sync_single_inode)
87 *
88 * ->i_mmap_rwsem
89 * ->anon_vma.lock (vma_adjust)
90 *
91 * ->anon_vma.lock
92 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
93 *
94 * ->page_table_lock or pte_lock
95 * ->swap_lock (try_to_unmap_one)
96 * ->private_lock (try_to_unmap_one)
97 * ->tree_lock (try_to_unmap_one)
98 * ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
99 * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
100 * ->private_lock (page_remove_rmap->set_page_dirty)
101 * ->tree_lock (page_remove_rmap->set_page_dirty)
102 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
103 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
104 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
105 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
106 * ->inode->i_lock (zap_pte_range->set_page_dirty)
107 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
108 *
109 * ->i_mmap_rwsem
110 * ->tasklist_lock (memory_failure, collect_procs_ao)
111 */
112
113static int page_cache_tree_insert(struct address_space *mapping,
114 struct page *page, void **shadowp)
115{
116 struct radix_tree_node *node;
117 void **slot;
118 int error;
119
120 error = __radix_tree_create(&mapping->page_tree, page->index, 0,
121 &node, &slot);
122 if (error)
123 return error;
124 if (*slot) {
125 void *p;
126
127 p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
128 if (!radix_tree_exceptional_entry(p))
129 return -EEXIST;
130
131 mapping->nrexceptional--;
132 if (!dax_mapping(mapping)) {
133 if (shadowp)
134 *shadowp = p;
135 } else {
136 /* DAX can replace empty locked entry with a hole */
137 WARN_ON_ONCE(p !=
138 dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
139 /* Wakeup waiters for exceptional entry lock */
140 dax_wake_mapping_entry_waiter(mapping, page->index, p,
141 true);
142 }
143 }
144 __radix_tree_replace(&mapping->page_tree, node, slot, page,
145 workingset_update_node, mapping);
146 mapping->nrpages++;
147 return 0;
148}
149
150static void page_cache_tree_delete(struct address_space *mapping,
151 struct page *page, void *shadow)
152{
153 int i, nr;
154
155 /* hugetlb pages are represented by one entry in the radix tree */
156 nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
157
158 VM_BUG_ON_PAGE(!PageLocked(page), page);
159 VM_BUG_ON_PAGE(PageTail(page), page);
160 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
161
162 for (i = 0; i < nr; i++) {
163 struct radix_tree_node *node;
164 void **slot;
165
166 __radix_tree_lookup(&mapping->page_tree, page->index + i,
167 &node, &slot);
168
169 VM_BUG_ON_PAGE(!node && nr != 1, page);
170
171 radix_tree_clear_tags(&mapping->page_tree, node, slot);
172 __radix_tree_replace(&mapping->page_tree, node, slot, shadow,
173 workingset_update_node, mapping);
174 }
175
176 if (shadow) {
177 mapping->nrexceptional += nr;
178 /*
179 * Make sure the nrexceptional update is committed before
180 * the nrpages update so that final truncate racing
181 * with reclaim does not see both counters 0 at the
182 * same time and miss a shadow entry.
183 */
184 smp_wmb();
185 }
186 mapping->nrpages -= nr;
187}
188
189/*
190 * Delete a page from the page cache and free it. Caller has to make
191 * sure the page is locked and that nobody else uses it - or that usage
192 * is safe. The caller must hold the mapping's tree_lock.
193 */
194void __delete_from_page_cache(struct page *page, void *shadow)
195{
196 struct address_space *mapping = page->mapping;
197 int nr = hpage_nr_pages(page);
198
199 trace_mm_filemap_delete_from_page_cache(page);
200 /*
201 * if we're uptodate, flush out into the cleancache, otherwise
202 * invalidate any existing cleancache entries. We can't leave
203 * stale data around in the cleancache once our page is gone
204 */
205 if (PageUptodate(page) && PageMappedToDisk(page))
206 cleancache_put_page(page);
207 else
208 cleancache_invalidate_page(mapping, page);
209
210 VM_BUG_ON_PAGE(PageTail(page), page);
211 VM_BUG_ON_PAGE(page_mapped(page), page);
212 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
213 int mapcount;
214
215 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
216 current->comm, page_to_pfn(page));
217 dump_page(page, "still mapped when deleted");
218 dump_stack();
219 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
220
221 mapcount = page_mapcount(page);
222 if (mapping_exiting(mapping) &&
223 page_count(page) >= mapcount + 2) {
224 /*
225 * All vmas have already been torn down, so it's
226 * a good bet that actually the page is unmapped,
227 * and we'd prefer not to leak it: if we're wrong,
228 * some other bad page check should catch it later.
229 */
230 page_mapcount_reset(page);
231 page_ref_sub(page, mapcount);
232 }
233 }
234
235 page_cache_tree_delete(mapping, page, shadow);
236
237 page->mapping = NULL;
238 /* Leave page->index set: truncation lookup relies upon it */
239
240 /* hugetlb pages do not participate in page cache accounting. */
241 if (!PageHuge(page))
242 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
243 if (PageSwapBacked(page)) {
244 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
245 if (PageTransHuge(page))
246 __dec_node_page_state(page, NR_SHMEM_THPS);
247 } else {
248 VM_BUG_ON_PAGE(PageTransHuge(page) && !PageHuge(page), page);
249 }
250
251 /*
252 * At this point page must be either written or cleaned by truncate.
253 * Dirty page here signals a bug and loss of unwritten data.
254 *
255 * This fixes dirty accounting after removing the page entirely but
256 * leaves PageDirty set: it has no effect for truncated page and
257 * anyway will be cleared before returning page into buddy allocator.
258 */
259 if (WARN_ON_ONCE(PageDirty(page)))
260 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
261}
262
263/**
264 * delete_from_page_cache - delete page from page cache
265 * @page: the page which the kernel is trying to remove from page cache
266 *
267 * This must be called only on pages that have been verified to be in the page
268 * cache and locked. It will never put the page into the free list, the caller
269 * has a reference on the page.
270 */
271void delete_from_page_cache(struct page *page)
272{
273 struct address_space *mapping = page_mapping(page);
274 unsigned long flags;
275 void (*freepage)(struct page *);
276
277 BUG_ON(!PageLocked(page));
278
279 freepage = mapping->a_ops->freepage;
280
281 spin_lock_irqsave(&mapping->tree_lock, flags);
282 __delete_from_page_cache(page, NULL);
283 spin_unlock_irqrestore(&mapping->tree_lock, flags);
284
285 if (freepage)
286 freepage(page);
287
288 if (PageTransHuge(page) && !PageHuge(page)) {
289 page_ref_sub(page, HPAGE_PMD_NR);
290 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
291 } else {
292 put_page(page);
293 }
294}
295EXPORT_SYMBOL(delete_from_page_cache);
296
297int filemap_check_errors(struct address_space *mapping)
298{
299 int ret = 0;
300 /* Check for outstanding write errors */
301 if (test_bit(AS_ENOSPC, &mapping->flags) &&
302 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
303 ret = -ENOSPC;
304 if (test_bit(AS_EIO, &mapping->flags) &&
305 test_and_clear_bit(AS_EIO, &mapping->flags))
306 ret = -EIO;
307 return ret;
308}
309EXPORT_SYMBOL(filemap_check_errors);
310
311/**
312 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
313 * @mapping: address space structure to write
314 * @start: offset in bytes where the range starts
315 * @end: offset in bytes where the range ends (inclusive)
316 * @sync_mode: enable synchronous operation
317 *
318 * Start writeback against all of a mapping's dirty pages that lie
319 * within the byte offsets <start, end> inclusive.
320 *
321 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
322 * opposed to a regular memory cleansing writeback. The difference between
323 * these two operations is that if a dirty page/buffer is encountered, it must
324 * be waited upon, and not just skipped over.
325 */
326int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
327 loff_t end, int sync_mode)
328{
329 int ret;
330 struct writeback_control wbc = {
331 .sync_mode = sync_mode,
332 .nr_to_write = LONG_MAX,
333 .range_start = start,
334 .range_end = end,
335 };
336
337 if (!mapping_cap_writeback_dirty(mapping))
338 return 0;
339
340 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
341 ret = do_writepages(mapping, &wbc);
342 wbc_detach_inode(&wbc);
343 return ret;
344}
345
346static inline int __filemap_fdatawrite(struct address_space *mapping,
347 int sync_mode)
348{
349 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
350}
351
352int filemap_fdatawrite(struct address_space *mapping)
353{
354 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
355}
356EXPORT_SYMBOL(filemap_fdatawrite);
357
358int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
359 loff_t end)
360{
361 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
362}
363EXPORT_SYMBOL(filemap_fdatawrite_range);
364
365/**
366 * filemap_flush - mostly a non-blocking flush
367 * @mapping: target address_space
368 *
369 * This is a mostly non-blocking flush. Not suitable for data-integrity
370 * purposes - I/O may not be started against all dirty pages.
371 */
372int filemap_flush(struct address_space *mapping)
373{
374 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
375}
376EXPORT_SYMBOL(filemap_flush);
377
378static int __filemap_fdatawait_range(struct address_space *mapping,
379 loff_t start_byte, loff_t end_byte)
380{
381 pgoff_t index = start_byte >> PAGE_SHIFT;
382 pgoff_t end = end_byte >> PAGE_SHIFT;
383 struct pagevec pvec;
384 int nr_pages;
385 int ret = 0;
386
387 if (end_byte < start_byte)
388 goto out;
389
390 pagevec_init(&pvec, 0);
391 while ((index <= end) &&
392 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
393 PAGECACHE_TAG_WRITEBACK,
394 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
395 unsigned i;
396
397 for (i = 0; i < nr_pages; i++) {
398 struct page *page = pvec.pages[i];
399
400 /* until radix tree lookup accepts end_index */
401 if (page->index > end)
402 continue;
403
404 wait_on_page_writeback(page);
405 if (TestClearPageError(page))
406 ret = -EIO;
407 }
408 pagevec_release(&pvec);
409 cond_resched();
410 }
411out:
412 return ret;
413}
414
415/**
416 * filemap_fdatawait_range - wait for writeback to complete
417 * @mapping: address space structure to wait for
418 * @start_byte: offset in bytes where the range starts
419 * @end_byte: offset in bytes where the range ends (inclusive)
420 *
421 * Walk the list of under-writeback pages of the given address space
422 * in the given range and wait for all of them. Check error status of
423 * the address space and return it.
424 *
425 * Since the error status of the address space is cleared by this function,
426 * callers are responsible for checking the return value and handling and/or
427 * reporting the error.
428 */
429int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
430 loff_t end_byte)
431{
432 int ret, ret2;
433
434 ret = __filemap_fdatawait_range(mapping, start_byte, end_byte);
435 ret2 = filemap_check_errors(mapping);
436 if (!ret)
437 ret = ret2;
438
439 return ret;
440}
441EXPORT_SYMBOL(filemap_fdatawait_range);
442
443/**
444 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
445 * @mapping: address space structure to wait for
446 *
447 * Walk the list of under-writeback pages of the given address space
448 * and wait for all of them. Unlike filemap_fdatawait(), this function
449 * does not clear error status of the address space.
450 *
451 * Use this function if callers don't handle errors themselves. Expected
452 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
453 * fsfreeze(8)
454 */
455void filemap_fdatawait_keep_errors(struct address_space *mapping)
456{
457 loff_t i_size = i_size_read(mapping->host);
458
459 if (i_size == 0)
460 return;
461
462 __filemap_fdatawait_range(mapping, 0, i_size - 1);
463}
464
465/**
466 * filemap_fdatawait - wait for all under-writeback pages to complete
467 * @mapping: address space structure to wait for
468 *
469 * Walk the list of under-writeback pages of the given address space
470 * and wait for all of them. Check error status of the address space
471 * and return it.
472 *
473 * Since the error status of the address space is cleared by this function,
474 * callers are responsible for checking the return value and handling and/or
475 * reporting the error.
476 */
477int filemap_fdatawait(struct address_space *mapping)
478{
479 loff_t i_size = i_size_read(mapping->host);
480
481 if (i_size == 0)
482 return 0;
483
484 return filemap_fdatawait_range(mapping, 0, i_size - 1);
485}
486EXPORT_SYMBOL(filemap_fdatawait);
487
488int filemap_write_and_wait(struct address_space *mapping)
489{
490 int err = 0;
491
492 if ((!dax_mapping(mapping) && mapping->nrpages) ||
493 (dax_mapping(mapping) && mapping->nrexceptional)) {
494 err = filemap_fdatawrite(mapping);
495 /*
496 * Even if the above returned error, the pages may be
497 * written partially (e.g. -ENOSPC), so we wait for it.
498 * But the -EIO is special case, it may indicate the worst
499 * thing (e.g. bug) happened, so we avoid waiting for it.
500 */
501 if (err != -EIO) {
502 int err2 = filemap_fdatawait(mapping);
503 if (!err)
504 err = err2;
505 }
506 } else {
507 err = filemap_check_errors(mapping);
508 }
509 return err;
510}
511EXPORT_SYMBOL(filemap_write_and_wait);
512
513/**
514 * filemap_write_and_wait_range - write out & wait on a file range
515 * @mapping: the address_space for the pages
516 * @lstart: offset in bytes where the range starts
517 * @lend: offset in bytes where the range ends (inclusive)
518 *
519 * Write out and wait upon file offsets lstart->lend, inclusive.
520 *
521 * Note that `lend' is inclusive (describes the last byte to be written) so
522 * that this function can be used to write to the very end-of-file (end = -1).
523 */
524int filemap_write_and_wait_range(struct address_space *mapping,
525 loff_t lstart, loff_t lend)
526{
527 int err = 0;
528
529 if ((!dax_mapping(mapping) && mapping->nrpages) ||
530 (dax_mapping(mapping) && mapping->nrexceptional)) {
531 err = __filemap_fdatawrite_range(mapping, lstart, lend,
532 WB_SYNC_ALL);
533 /* See comment of filemap_write_and_wait() */
534 if (err != -EIO) {
535 int err2 = filemap_fdatawait_range(mapping,
536 lstart, lend);
537 if (!err)
538 err = err2;
539 }
540 } else {
541 err = filemap_check_errors(mapping);
542 }
543 return err;
544}
545EXPORT_SYMBOL(filemap_write_and_wait_range);
546
547/**
548 * replace_page_cache_page - replace a pagecache page with a new one
549 * @old: page to be replaced
550 * @new: page to replace with
551 * @gfp_mask: allocation mode
552 *
553 * This function replaces a page in the pagecache with a new one. On
554 * success it acquires the pagecache reference for the new page and
555 * drops it for the old page. Both the old and new pages must be
556 * locked. This function does not add the new page to the LRU, the
557 * caller must do that.
558 *
559 * The remove + add is atomic. The only way this function can fail is
560 * memory allocation failure.
561 */
562int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
563{
564 int error;
565
566 VM_BUG_ON_PAGE(!PageLocked(old), old);
567 VM_BUG_ON_PAGE(!PageLocked(new), new);
568 VM_BUG_ON_PAGE(new->mapping, new);
569
570 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
571 if (!error) {
572 struct address_space *mapping = old->mapping;
573 void (*freepage)(struct page *);
574 unsigned long flags;
575
576 pgoff_t offset = old->index;
577 freepage = mapping->a_ops->freepage;
578
579 get_page(new);
580 new->mapping = mapping;
581 new->index = offset;
582
583 spin_lock_irqsave(&mapping->tree_lock, flags);
584 __delete_from_page_cache(old, NULL);
585 error = page_cache_tree_insert(mapping, new, NULL);
586 BUG_ON(error);
587
588 /*
589 * hugetlb pages do not participate in page cache accounting.
590 */
591 if (!PageHuge(new))
592 __inc_node_page_state(new, NR_FILE_PAGES);
593 if (PageSwapBacked(new))
594 __inc_node_page_state(new, NR_SHMEM);
595 spin_unlock_irqrestore(&mapping->tree_lock, flags);
596 mem_cgroup_migrate(old, new);
597 radix_tree_preload_end();
598 if (freepage)
599 freepage(old);
600 put_page(old);
601 }
602
603 return error;
604}
605EXPORT_SYMBOL_GPL(replace_page_cache_page);
606
607static int __add_to_page_cache_locked(struct page *page,
608 struct address_space *mapping,
609 pgoff_t offset, gfp_t gfp_mask,
610 void **shadowp)
611{
612 int huge = PageHuge(page);
613 struct mem_cgroup *memcg;
614 int error;
615
616 VM_BUG_ON_PAGE(!PageLocked(page), page);
617 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
618
619 if (!huge) {
620 error = mem_cgroup_try_charge(page, current->mm,
621 gfp_mask, &memcg, false);
622 if (error)
623 return error;
624 }
625
626 error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
627 if (error) {
628 if (!huge)
629 mem_cgroup_cancel_charge(page, memcg, false);
630 return error;
631 }
632
633 get_page(page);
634 page->mapping = mapping;
635 page->index = offset;
636
637 spin_lock_irq(&mapping->tree_lock);
638 error = page_cache_tree_insert(mapping, page, shadowp);
639 radix_tree_preload_end();
640 if (unlikely(error))
641 goto err_insert;
642
643 /* hugetlb pages do not participate in page cache accounting. */
644 if (!huge)
645 __inc_node_page_state(page, NR_FILE_PAGES);
646 spin_unlock_irq(&mapping->tree_lock);
647 if (!huge)
648 mem_cgroup_commit_charge(page, memcg, false, false);
649 trace_mm_filemap_add_to_page_cache(page);
650 return 0;
651err_insert:
652 page->mapping = NULL;
653 /* Leave page->index set: truncation relies upon it */
654 spin_unlock_irq(&mapping->tree_lock);
655 if (!huge)
656 mem_cgroup_cancel_charge(page, memcg, false);
657 put_page(page);
658 return error;
659}
660
661/**
662 * add_to_page_cache_locked - add a locked page to the pagecache
663 * @page: page to add
664 * @mapping: the page's address_space
665 * @offset: page index
666 * @gfp_mask: page allocation mode
667 *
668 * This function is used to add a page to the pagecache. It must be locked.
669 * This function does not add the page to the LRU. The caller must do that.
670 */
671int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
672 pgoff_t offset, gfp_t gfp_mask)
673{
674 return __add_to_page_cache_locked(page, mapping, offset,
675 gfp_mask, NULL);
676}
677EXPORT_SYMBOL(add_to_page_cache_locked);
678
679int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
680 pgoff_t offset, gfp_t gfp_mask)
681{
682 void *shadow = NULL;
683 int ret;
684
685 __SetPageLocked(page);
686 ret = __add_to_page_cache_locked(page, mapping, offset,
687 gfp_mask, &shadow);
688 if (unlikely(ret))
689 __ClearPageLocked(page);
690 else {
691 /*
692 * The page might have been evicted from cache only
693 * recently, in which case it should be activated like
694 * any other repeatedly accessed page.
695 * The exception is pages getting rewritten; evicting other
696 * data from the working set, only to cache data that will
697 * get overwritten with something else, is a waste of memory.
698 */
699 if (!(gfp_mask & __GFP_WRITE) &&
700 shadow && workingset_refault(shadow)) {
701 SetPageActive(page);
702 workingset_activation(page);
703 } else
704 ClearPageActive(page);
705 lru_cache_add(page);
706 }
707 return ret;
708}
709EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
710
711#ifdef CONFIG_NUMA
712struct page *__page_cache_alloc(gfp_t gfp)
713{
714 int n;
715 struct page *page;
716
717 if (cpuset_do_page_mem_spread()) {
718 unsigned int cpuset_mems_cookie;
719 do {
720 cpuset_mems_cookie = read_mems_allowed_begin();
721 n = cpuset_mem_spread_node();
722 page = __alloc_pages_node(n, gfp, 0);
723 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
724
725 return page;
726 }
727 return alloc_pages(gfp, 0);
728}
729EXPORT_SYMBOL(__page_cache_alloc);
730#endif
731
732/*
733 * In order to wait for pages to become available there must be
734 * waitqueues associated with pages. By using a hash table of
735 * waitqueues where the bucket discipline is to maintain all
736 * waiters on the same queue and wake all when any of the pages
737 * become available, and for the woken contexts to check to be
738 * sure the appropriate page became available, this saves space
739 * at a cost of "thundering herd" phenomena during rare hash
740 * collisions.
741 */
742#define PAGE_WAIT_TABLE_BITS 8
743#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
744static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
745
746static wait_queue_head_t *page_waitqueue(struct page *page)
747{
748 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
749}
750
751void __init pagecache_init(void)
752{
753 int i;
754
755 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
756 init_waitqueue_head(&page_wait_table[i]);
757
758 page_writeback_init();
759}
760
761struct wait_page_key {
762 struct page *page;
763 int bit_nr;
764 int page_match;
765};
766
767struct wait_page_queue {
768 struct page *page;
769 int bit_nr;
770 wait_queue_t wait;
771};
772
773static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
774{
775 struct wait_page_key *key = arg;
776 struct wait_page_queue *wait_page
777 = container_of(wait, struct wait_page_queue, wait);
778
779 if (wait_page->page != key->page)
780 return 0;
781 key->page_match = 1;
782
783 if (wait_page->bit_nr != key->bit_nr)
784 return 0;
785 if (test_bit(key->bit_nr, &key->page->flags))
786 return 0;
787
788 return autoremove_wake_function(wait, mode, sync, key);
789}
790
791void wake_up_page_bit(struct page *page, int bit_nr)
792{
793 wait_queue_head_t *q = page_waitqueue(page);
794 struct wait_page_key key;
795 unsigned long flags;
796
797 key.page = page;
798 key.bit_nr = bit_nr;
799 key.page_match = 0;
800
801 spin_lock_irqsave(&q->lock, flags);
802 __wake_up_locked_key(q, TASK_NORMAL, &key);
803 /*
804 * It is possible for other pages to have collided on the waitqueue
805 * hash, so in that case check for a page match. That prevents a long-
806 * term waiter
807 *
808 * It is still possible to miss a case here, when we woke page waiters
809 * and removed them from the waitqueue, but there are still other
810 * page waiters.
811 */
812 if (!waitqueue_active(q) || !key.page_match) {
813 ClearPageWaiters(page);
814 /*
815 * It's possible to miss clearing Waiters here, when we woke
816 * our page waiters, but the hashed waitqueue has waiters for
817 * other pages on it.
818 *
819 * That's okay, it's a rare case. The next waker will clear it.
820 */
821 }
822 spin_unlock_irqrestore(&q->lock, flags);
823}
824EXPORT_SYMBOL(wake_up_page_bit);
825
826static inline int wait_on_page_bit_common(wait_queue_head_t *q,
827 struct page *page, int bit_nr, int state, bool lock)
828{
829 struct wait_page_queue wait_page;
830 wait_queue_t *wait = &wait_page.wait;
831 int ret = 0;
832
833 init_wait(wait);
834 wait->func = wake_page_function;
835 wait_page.page = page;
836 wait_page.bit_nr = bit_nr;
837
838 for (;;) {
839 spin_lock_irq(&q->lock);
840
841 if (likely(list_empty(&wait->task_list))) {
842 if (lock)
843 __add_wait_queue_tail_exclusive(q, wait);
844 else
845 __add_wait_queue(q, wait);
846 SetPageWaiters(page);
847 }
848
849 set_current_state(state);
850
851 spin_unlock_irq(&q->lock);
852
853 if (likely(test_bit(bit_nr, &page->flags))) {
854 io_schedule();
855 if (unlikely(signal_pending_state(state, current))) {
856 ret = -EINTR;
857 break;
858 }
859 }
860
861 if (lock) {
862 if (!test_and_set_bit_lock(bit_nr, &page->flags))
863 break;
864 } else {
865 if (!test_bit(bit_nr, &page->flags))
866 break;
867 }
868 }
869
870 finish_wait(q, wait);
871
872 /*
873 * A signal could leave PageWaiters set. Clearing it here if
874 * !waitqueue_active would be possible (by open-coding finish_wait),
875 * but still fail to catch it in the case of wait hash collision. We
876 * already can fail to clear wait hash collision cases, so don't
877 * bother with signals either.
878 */
879
880 return ret;
881}
882
883void wait_on_page_bit(struct page *page, int bit_nr)
884{
885 wait_queue_head_t *q = page_waitqueue(page);
886 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
887}
888EXPORT_SYMBOL(wait_on_page_bit);
889
890int wait_on_page_bit_killable(struct page *page, int bit_nr)
891{
892 wait_queue_head_t *q = page_waitqueue(page);
893 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
894}
895
896/**
897 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
898 * @page: Page defining the wait queue of interest
899 * @waiter: Waiter to add to the queue
900 *
901 * Add an arbitrary @waiter to the wait queue for the nominated @page.
902 */
903void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
904{
905 wait_queue_head_t *q = page_waitqueue(page);
906 unsigned long flags;
907
908 spin_lock_irqsave(&q->lock, flags);
909 __add_wait_queue(q, waiter);
910 SetPageWaiters(page);
911 spin_unlock_irqrestore(&q->lock, flags);
912}
913EXPORT_SYMBOL_GPL(add_page_wait_queue);
914
915#ifndef clear_bit_unlock_is_negative_byte
916
917/*
918 * PG_waiters is the high bit in the same byte as PG_lock.
919 *
920 * On x86 (and on many other architectures), we can clear PG_lock and
921 * test the sign bit at the same time. But if the architecture does
922 * not support that special operation, we just do this all by hand
923 * instead.
924 *
925 * The read of PG_waiters has to be after (or concurrently with) PG_locked
926 * being cleared, but a memory barrier should be unneccssary since it is
927 * in the same byte as PG_locked.
928 */
929static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
930{
931 clear_bit_unlock(nr, mem);
932 /* smp_mb__after_atomic(); */
933 return test_bit(PG_waiters, mem);
934}
935
936#endif
937
938/**
939 * unlock_page - unlock a locked page
940 * @page: the page
941 *
942 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
943 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
944 * mechanism between PageLocked pages and PageWriteback pages is shared.
945 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
946 *
947 * Note that this depends on PG_waiters being the sign bit in the byte
948 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
949 * clear the PG_locked bit and test PG_waiters at the same time fairly
950 * portably (architectures that do LL/SC can test any bit, while x86 can
951 * test the sign bit).
952 */
953void unlock_page(struct page *page)
954{
955 BUILD_BUG_ON(PG_waiters != 7);
956 page = compound_head(page);
957 VM_BUG_ON_PAGE(!PageLocked(page), page);
958 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
959 wake_up_page_bit(page, PG_locked);
960}
961EXPORT_SYMBOL(unlock_page);
962
963/**
964 * end_page_writeback - end writeback against a page
965 * @page: the page
966 */
967void end_page_writeback(struct page *page)
968{
969 /*
970 * TestClearPageReclaim could be used here but it is an atomic
971 * operation and overkill in this particular case. Failing to
972 * shuffle a page marked for immediate reclaim is too mild to
973 * justify taking an atomic operation penalty at the end of
974 * ever page writeback.
975 */
976 if (PageReclaim(page)) {
977 ClearPageReclaim(page);
978 rotate_reclaimable_page(page);
979 }
980
981 if (!test_clear_page_writeback(page))
982 BUG();
983
984 smp_mb__after_atomic();
985 wake_up_page(page, PG_writeback);
986}
987EXPORT_SYMBOL(end_page_writeback);
988
989/*
990 * After completing I/O on a page, call this routine to update the page
991 * flags appropriately
992 */
993void page_endio(struct page *page, bool is_write, int err)
994{
995 if (!is_write) {
996 if (!err) {
997 SetPageUptodate(page);
998 } else {
999 ClearPageUptodate(page);
1000 SetPageError(page);
1001 }
1002 unlock_page(page);
1003 } else {
1004 if (err) {
1005 struct address_space *mapping;
1006
1007 SetPageError(page);
1008 mapping = page_mapping(page);
1009 if (mapping)
1010 mapping_set_error(mapping, err);
1011 }
1012 end_page_writeback(page);
1013 }
1014}
1015EXPORT_SYMBOL_GPL(page_endio);
1016
1017/**
1018 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1019 * @page: the page to lock
1020 */
1021void __lock_page(struct page *__page)
1022{
1023 struct page *page = compound_head(__page);
1024 wait_queue_head_t *q = page_waitqueue(page);
1025 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
1026}
1027EXPORT_SYMBOL(__lock_page);
1028
1029int __lock_page_killable(struct page *__page)
1030{
1031 struct page *page = compound_head(__page);
1032 wait_queue_head_t *q = page_waitqueue(page);
1033 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
1034}
1035EXPORT_SYMBOL_GPL(__lock_page_killable);
1036
1037/*
1038 * Return values:
1039 * 1 - page is locked; mmap_sem is still held.
1040 * 0 - page is not locked.
1041 * mmap_sem has been released (up_read()), unless flags had both
1042 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1043 * which case mmap_sem is still held.
1044 *
1045 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1046 * with the page locked and the mmap_sem unperturbed.
1047 */
1048int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1049 unsigned int flags)
1050{
1051 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1052 /*
1053 * CAUTION! In this case, mmap_sem is not released
1054 * even though return 0.
1055 */
1056 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1057 return 0;
1058
1059 up_read(&mm->mmap_sem);
1060 if (flags & FAULT_FLAG_KILLABLE)
1061 wait_on_page_locked_killable(page);
1062 else
1063 wait_on_page_locked(page);
1064 return 0;
1065 } else {
1066 if (flags & FAULT_FLAG_KILLABLE) {
1067 int ret;
1068
1069 ret = __lock_page_killable(page);
1070 if (ret) {
1071 up_read(&mm->mmap_sem);
1072 return 0;
1073 }
1074 } else
1075 __lock_page(page);
1076 return 1;
1077 }
1078}
1079
1080/**
1081 * page_cache_next_hole - find the next hole (not-present entry)
1082 * @mapping: mapping
1083 * @index: index
1084 * @max_scan: maximum range to search
1085 *
1086 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1087 * lowest indexed hole.
1088 *
1089 * Returns: the index of the hole if found, otherwise returns an index
1090 * outside of the set specified (in which case 'return - index >=
1091 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1092 * be returned.
1093 *
1094 * page_cache_next_hole may be called under rcu_read_lock. However,
1095 * like radix_tree_gang_lookup, this will not atomically search a
1096 * snapshot of the tree at a single point in time. For example, if a
1097 * hole is created at index 5, then subsequently a hole is created at
1098 * index 10, page_cache_next_hole covering both indexes may return 10
1099 * if called under rcu_read_lock.
1100 */
1101pgoff_t page_cache_next_hole(struct address_space *mapping,
1102 pgoff_t index, unsigned long max_scan)
1103{
1104 unsigned long i;
1105
1106 for (i = 0; i < max_scan; i++) {
1107 struct page *page;
1108
1109 page = radix_tree_lookup(&mapping->page_tree, index);
1110 if (!page || radix_tree_exceptional_entry(page))
1111 break;
1112 index++;
1113 if (index == 0)
1114 break;
1115 }
1116
1117 return index;
1118}
1119EXPORT_SYMBOL(page_cache_next_hole);
1120
1121/**
1122 * page_cache_prev_hole - find the prev hole (not-present entry)
1123 * @mapping: mapping
1124 * @index: index
1125 * @max_scan: maximum range to search
1126 *
1127 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1128 * the first hole.
1129 *
1130 * Returns: the index of the hole if found, otherwise returns an index
1131 * outside of the set specified (in which case 'index - return >=
1132 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1133 * will be returned.
1134 *
1135 * page_cache_prev_hole may be called under rcu_read_lock. However,
1136 * like radix_tree_gang_lookup, this will not atomically search a
1137 * snapshot of the tree at a single point in time. For example, if a
1138 * hole is created at index 10, then subsequently a hole is created at
1139 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1140 * called under rcu_read_lock.
1141 */
1142pgoff_t page_cache_prev_hole(struct address_space *mapping,
1143 pgoff_t index, unsigned long max_scan)
1144{
1145 unsigned long i;
1146
1147 for (i = 0; i < max_scan; i++) {
1148 struct page *page;
1149
1150 page = radix_tree_lookup(&mapping->page_tree, index);
1151 if (!page || radix_tree_exceptional_entry(page))
1152 break;
1153 index--;
1154 if (index == ULONG_MAX)
1155 break;
1156 }
1157
1158 return index;
1159}
1160EXPORT_SYMBOL(page_cache_prev_hole);
1161
1162/**
1163 * find_get_entry - find and get a page cache entry
1164 * @mapping: the address_space to search
1165 * @offset: the page cache index
1166 *
1167 * Looks up the page cache slot at @mapping & @offset. If there is a
1168 * page cache page, it is returned with an increased refcount.
1169 *
1170 * If the slot holds a shadow entry of a previously evicted page, or a
1171 * swap entry from shmem/tmpfs, it is returned.
1172 *
1173 * Otherwise, %NULL is returned.
1174 */
1175struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1176{
1177 void **pagep;
1178 struct page *head, *page;
1179
1180 rcu_read_lock();
1181repeat:
1182 page = NULL;
1183 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
1184 if (pagep) {
1185 page = radix_tree_deref_slot(pagep);
1186 if (unlikely(!page))
1187 goto out;
1188 if (radix_tree_exception(page)) {
1189 if (radix_tree_deref_retry(page))
1190 goto repeat;
1191 /*
1192 * A shadow entry of a recently evicted page,
1193 * or a swap entry from shmem/tmpfs. Return
1194 * it without attempting to raise page count.
1195 */
1196 goto out;
1197 }
1198
1199 head = compound_head(page);
1200 if (!page_cache_get_speculative(head))
1201 goto repeat;
1202
1203 /* The page was split under us? */
1204 if (compound_head(page) != head) {
1205 put_page(head);
1206 goto repeat;
1207 }
1208
1209 /*
1210 * Has the page moved?
1211 * This is part of the lockless pagecache protocol. See
1212 * include/linux/pagemap.h for details.
1213 */
1214 if (unlikely(page != *pagep)) {
1215 put_page(head);
1216 goto repeat;
1217 }
1218 }
1219out:
1220 rcu_read_unlock();
1221
1222 return page;
1223}
1224EXPORT_SYMBOL(find_get_entry);
1225
1226/**
1227 * find_lock_entry - locate, pin and lock a page cache entry
1228 * @mapping: the address_space to search
1229 * @offset: the page cache index
1230 *
1231 * Looks up the page cache slot at @mapping & @offset. If there is a
1232 * page cache page, it is returned locked and with an increased
1233 * refcount.
1234 *
1235 * If the slot holds a shadow entry of a previously evicted page, or a
1236 * swap entry from shmem/tmpfs, it is returned.
1237 *
1238 * Otherwise, %NULL is returned.
1239 *
1240 * find_lock_entry() may sleep.
1241 */
1242struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1243{
1244 struct page *page;
1245
1246repeat:
1247 page = find_get_entry(mapping, offset);
1248 if (page && !radix_tree_exception(page)) {
1249 lock_page(page);
1250 /* Has the page been truncated? */
1251 if (unlikely(page_mapping(page) != mapping)) {
1252 unlock_page(page);
1253 put_page(page);
1254 goto repeat;
1255 }
1256 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
1257 }
1258 return page;
1259}
1260EXPORT_SYMBOL(find_lock_entry);
1261
1262/**
1263 * pagecache_get_page - find and get a page reference
1264 * @mapping: the address_space to search
1265 * @offset: the page index
1266 * @fgp_flags: PCG flags
1267 * @gfp_mask: gfp mask to use for the page cache data page allocation
1268 *
1269 * Looks up the page cache slot at @mapping & @offset.
1270 *
1271 * PCG flags modify how the page is returned.
1272 *
1273 * FGP_ACCESSED: the page will be marked accessed
1274 * FGP_LOCK: Page is return locked
1275 * FGP_CREAT: If page is not present then a new page is allocated using
1276 * @gfp_mask and added to the page cache and the VM's LRU
1277 * list. The page is returned locked and with an increased
1278 * refcount. Otherwise, %NULL is returned.
1279 *
1280 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1281 * if the GFP flags specified for FGP_CREAT are atomic.
1282 *
1283 * If there is a page cache page, it is returned with an increased refcount.
1284 */
1285struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1286 int fgp_flags, gfp_t gfp_mask)
1287{
1288 struct page *page;
1289
1290repeat:
1291 page = find_get_entry(mapping, offset);
1292 if (radix_tree_exceptional_entry(page))
1293 page = NULL;
1294 if (!page)
1295 goto no_page;
1296
1297 if (fgp_flags & FGP_LOCK) {
1298 if (fgp_flags & FGP_NOWAIT) {
1299 if (!trylock_page(page)) {
1300 put_page(page);
1301 return NULL;
1302 }
1303 } else {
1304 lock_page(page);
1305 }
1306
1307 /* Has the page been truncated? */
1308 if (unlikely(page->mapping != mapping)) {
1309 unlock_page(page);
1310 put_page(page);
1311 goto repeat;
1312 }
1313 VM_BUG_ON_PAGE(page->index != offset, page);
1314 }
1315
1316 if (page && (fgp_flags & FGP_ACCESSED))
1317 mark_page_accessed(page);
1318
1319no_page:
1320 if (!page && (fgp_flags & FGP_CREAT)) {
1321 int err;
1322 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1323 gfp_mask |= __GFP_WRITE;
1324 if (fgp_flags & FGP_NOFS)
1325 gfp_mask &= ~__GFP_FS;
1326
1327 page = __page_cache_alloc(gfp_mask);
1328 if (!page)
1329 return NULL;
1330
1331 if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
1332 fgp_flags |= FGP_LOCK;
1333
1334 /* Init accessed so avoid atomic mark_page_accessed later */
1335 if (fgp_flags & FGP_ACCESSED)
1336 __SetPageReferenced(page);
1337
1338 err = add_to_page_cache_lru(page, mapping, offset,
1339 gfp_mask & GFP_RECLAIM_MASK);
1340 if (unlikely(err)) {
1341 put_page(page);
1342 page = NULL;
1343 if (err == -EEXIST)
1344 goto repeat;
1345 }
1346 }
1347
1348 return page;
1349}
1350EXPORT_SYMBOL(pagecache_get_page);
1351
1352/**
1353 * find_get_entries - gang pagecache lookup
1354 * @mapping: The address_space to search
1355 * @start: The starting page cache index
1356 * @nr_entries: The maximum number of entries
1357 * @entries: Where the resulting entries are placed
1358 * @indices: The cache indices corresponding to the entries in @entries
1359 *
1360 * find_get_entries() will search for and return a group of up to
1361 * @nr_entries entries in the mapping. The entries are placed at
1362 * @entries. find_get_entries() takes a reference against any actual
1363 * pages it returns.
1364 *
1365 * The search returns a group of mapping-contiguous page cache entries
1366 * with ascending indexes. There may be holes in the indices due to
1367 * not-present pages.
1368 *
1369 * Any shadow entries of evicted pages, or swap entries from
1370 * shmem/tmpfs, are included in the returned array.
1371 *
1372 * find_get_entries() returns the number of pages and shadow entries
1373 * which were found.
1374 */
1375unsigned find_get_entries(struct address_space *mapping,
1376 pgoff_t start, unsigned int nr_entries,
1377 struct page **entries, pgoff_t *indices)
1378{
1379 void **slot;
1380 unsigned int ret = 0;
1381 struct radix_tree_iter iter;
1382
1383 if (!nr_entries)
1384 return 0;
1385
1386 rcu_read_lock();
1387 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1388 struct page *head, *page;
1389repeat:
1390 page = radix_tree_deref_slot(slot);
1391 if (unlikely(!page))
1392 continue;
1393 if (radix_tree_exception(page)) {
1394 if (radix_tree_deref_retry(page)) {
1395 slot = radix_tree_iter_retry(&iter);
1396 continue;
1397 }
1398 /*
1399 * A shadow entry of a recently evicted page, a swap
1400 * entry from shmem/tmpfs or a DAX entry. Return it
1401 * without attempting to raise page count.
1402 */
1403 goto export;
1404 }
1405
1406 head = compound_head(page);
1407 if (!page_cache_get_speculative(head))
1408 goto repeat;
1409
1410 /* The page was split under us? */
1411 if (compound_head(page) != head) {
1412 put_page(head);
1413 goto repeat;
1414 }
1415
1416 /* Has the page moved? */
1417 if (unlikely(page != *slot)) {
1418 put_page(head);
1419 goto repeat;
1420 }
1421export:
1422 indices[ret] = iter.index;
1423 entries[ret] = page;
1424 if (++ret == nr_entries)
1425 break;
1426 }
1427 rcu_read_unlock();
1428 return ret;
1429}
1430
1431/**
1432 * find_get_pages - gang pagecache lookup
1433 * @mapping: The address_space to search
1434 * @start: The starting page index
1435 * @nr_pages: The maximum number of pages
1436 * @pages: Where the resulting pages are placed
1437 *
1438 * find_get_pages() will search for and return a group of up to
1439 * @nr_pages pages in the mapping. The pages are placed at @pages.
1440 * find_get_pages() takes a reference against the returned pages.
1441 *
1442 * The search returns a group of mapping-contiguous pages with ascending
1443 * indexes. There may be holes in the indices due to not-present pages.
1444 *
1445 * find_get_pages() returns the number of pages which were found.
1446 */
1447unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
1448 unsigned int nr_pages, struct page **pages)
1449{
1450 struct radix_tree_iter iter;
1451 void **slot;
1452 unsigned ret = 0;
1453
1454 if (unlikely(!nr_pages))
1455 return 0;
1456
1457 rcu_read_lock();
1458 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1459 struct page *head, *page;
1460repeat:
1461 page = radix_tree_deref_slot(slot);
1462 if (unlikely(!page))
1463 continue;
1464
1465 if (radix_tree_exception(page)) {
1466 if (radix_tree_deref_retry(page)) {
1467 slot = radix_tree_iter_retry(&iter);
1468 continue;
1469 }
1470 /*
1471 * A shadow entry of a recently evicted page,
1472 * or a swap entry from shmem/tmpfs. Skip
1473 * over it.
1474 */
1475 continue;
1476 }
1477
1478 head = compound_head(page);
1479 if (!page_cache_get_speculative(head))
1480 goto repeat;
1481
1482 /* The page was split under us? */
1483 if (compound_head(page) != head) {
1484 put_page(head);
1485 goto repeat;
1486 }
1487
1488 /* Has the page moved? */
1489 if (unlikely(page != *slot)) {
1490 put_page(head);
1491 goto repeat;
1492 }
1493
1494 pages[ret] = page;
1495 if (++ret == nr_pages)
1496 break;
1497 }
1498
1499 rcu_read_unlock();
1500 return ret;
1501}
1502
1503/**
1504 * find_get_pages_contig - gang contiguous pagecache lookup
1505 * @mapping: The address_space to search
1506 * @index: The starting page index
1507 * @nr_pages: The maximum number of pages
1508 * @pages: Where the resulting pages are placed
1509 *
1510 * find_get_pages_contig() works exactly like find_get_pages(), except
1511 * that the returned number of pages are guaranteed to be contiguous.
1512 *
1513 * find_get_pages_contig() returns the number of pages which were found.
1514 */
1515unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1516 unsigned int nr_pages, struct page **pages)
1517{
1518 struct radix_tree_iter iter;
1519 void **slot;
1520 unsigned int ret = 0;
1521
1522 if (unlikely(!nr_pages))
1523 return 0;
1524
1525 rcu_read_lock();
1526 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
1527 struct page *head, *page;
1528repeat:
1529 page = radix_tree_deref_slot(slot);
1530 /* The hole, there no reason to continue */
1531 if (unlikely(!page))
1532 break;
1533
1534 if (radix_tree_exception(page)) {
1535 if (radix_tree_deref_retry(page)) {
1536 slot = radix_tree_iter_retry(&iter);
1537 continue;
1538 }
1539 /*
1540 * A shadow entry of a recently evicted page,
1541 * or a swap entry from shmem/tmpfs. Stop
1542 * looking for contiguous pages.
1543 */
1544 break;
1545 }
1546
1547 head = compound_head(page);
1548 if (!page_cache_get_speculative(head))
1549 goto repeat;
1550
1551 /* The page was split under us? */
1552 if (compound_head(page) != head) {
1553 put_page(head);
1554 goto repeat;
1555 }
1556
1557 /* Has the page moved? */
1558 if (unlikely(page != *slot)) {
1559 put_page(head);
1560 goto repeat;
1561 }
1562
1563 /*
1564 * must check mapping and index after taking the ref.
1565 * otherwise we can get both false positives and false
1566 * negatives, which is just confusing to the caller.
1567 */
1568 if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
1569 put_page(page);
1570 break;
1571 }
1572
1573 pages[ret] = page;
1574 if (++ret == nr_pages)
1575 break;
1576 }
1577 rcu_read_unlock();
1578 return ret;
1579}
1580EXPORT_SYMBOL(find_get_pages_contig);
1581
1582/**
1583 * find_get_pages_tag - find and return pages that match @tag
1584 * @mapping: the address_space to search
1585 * @index: the starting page index
1586 * @tag: the tag index
1587 * @nr_pages: the maximum number of pages
1588 * @pages: where the resulting pages are placed
1589 *
1590 * Like find_get_pages, except we only return pages which are tagged with
1591 * @tag. We update @index to index the next page for the traversal.
1592 */
1593unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
1594 int tag, unsigned int nr_pages, struct page **pages)
1595{
1596 struct radix_tree_iter iter;
1597 void **slot;
1598 unsigned ret = 0;
1599
1600 if (unlikely(!nr_pages))
1601 return 0;
1602
1603 rcu_read_lock();
1604 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1605 &iter, *index, tag) {
1606 struct page *head, *page;
1607repeat:
1608 page = radix_tree_deref_slot(slot);
1609 if (unlikely(!page))
1610 continue;
1611
1612 if (radix_tree_exception(page)) {
1613 if (radix_tree_deref_retry(page)) {
1614 slot = radix_tree_iter_retry(&iter);
1615 continue;
1616 }
1617 /*
1618 * A shadow entry of a recently evicted page.
1619 *
1620 * Those entries should never be tagged, but
1621 * this tree walk is lockless and the tags are
1622 * looked up in bulk, one radix tree node at a
1623 * time, so there is a sizable window for page
1624 * reclaim to evict a page we saw tagged.
1625 *
1626 * Skip over it.
1627 */
1628 continue;
1629 }
1630
1631 head = compound_head(page);
1632 if (!page_cache_get_speculative(head))
1633 goto repeat;
1634
1635 /* The page was split under us? */
1636 if (compound_head(page) != head) {
1637 put_page(head);
1638 goto repeat;
1639 }
1640
1641 /* Has the page moved? */
1642 if (unlikely(page != *slot)) {
1643 put_page(head);
1644 goto repeat;
1645 }
1646
1647 pages[ret] = page;
1648 if (++ret == nr_pages)
1649 break;
1650 }
1651
1652 rcu_read_unlock();
1653
1654 if (ret)
1655 *index = pages[ret - 1]->index + 1;
1656
1657 return ret;
1658}
1659EXPORT_SYMBOL(find_get_pages_tag);
1660
1661/**
1662 * find_get_entries_tag - find and return entries that match @tag
1663 * @mapping: the address_space to search
1664 * @start: the starting page cache index
1665 * @tag: the tag index
1666 * @nr_entries: the maximum number of entries
1667 * @entries: where the resulting entries are placed
1668 * @indices: the cache indices corresponding to the entries in @entries
1669 *
1670 * Like find_get_entries, except we only return entries which are tagged with
1671 * @tag.
1672 */
1673unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
1674 int tag, unsigned int nr_entries,
1675 struct page **entries, pgoff_t *indices)
1676{
1677 void **slot;
1678 unsigned int ret = 0;
1679 struct radix_tree_iter iter;
1680
1681 if (!nr_entries)
1682 return 0;
1683
1684 rcu_read_lock();
1685 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1686 &iter, start, tag) {
1687 struct page *head, *page;
1688repeat:
1689 page = radix_tree_deref_slot(slot);
1690 if (unlikely(!page))
1691 continue;
1692 if (radix_tree_exception(page)) {
1693 if (radix_tree_deref_retry(page)) {
1694 slot = radix_tree_iter_retry(&iter);
1695 continue;
1696 }
1697
1698 /*
1699 * A shadow entry of a recently evicted page, a swap
1700 * entry from shmem/tmpfs or a DAX entry. Return it
1701 * without attempting to raise page count.
1702 */
1703 goto export;
1704 }
1705
1706 head = compound_head(page);
1707 if (!page_cache_get_speculative(head))
1708 goto repeat;
1709
1710 /* The page was split under us? */
1711 if (compound_head(page) != head) {
1712 put_page(head);
1713 goto repeat;
1714 }
1715
1716 /* Has the page moved? */
1717 if (unlikely(page != *slot)) {
1718 put_page(head);
1719 goto repeat;
1720 }
1721export:
1722 indices[ret] = iter.index;
1723 entries[ret] = page;
1724 if (++ret == nr_entries)
1725 break;
1726 }
1727 rcu_read_unlock();
1728 return ret;
1729}
1730EXPORT_SYMBOL(find_get_entries_tag);
1731
1732/*
1733 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1734 * a _large_ part of the i/o request. Imagine the worst scenario:
1735 *
1736 * ---R__________________________________________B__________
1737 * ^ reading here ^ bad block(assume 4k)
1738 *
1739 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1740 * => failing the whole request => read(R) => read(R+1) =>
1741 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1742 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1743 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1744 *
1745 * It is going insane. Fix it by quickly scaling down the readahead size.
1746 */
1747static void shrink_readahead_size_eio(struct file *filp,
1748 struct file_ra_state *ra)
1749{
1750 ra->ra_pages /= 4;
1751}
1752
1753/**
1754 * do_generic_file_read - generic file read routine
1755 * @filp: the file to read
1756 * @ppos: current file position
1757 * @iter: data destination
1758 * @written: already copied
1759 *
1760 * This is a generic file read routine, and uses the
1761 * mapping->a_ops->readpage() function for the actual low-level stuff.
1762 *
1763 * This is really ugly. But the goto's actually try to clarify some
1764 * of the logic when it comes to error handling etc.
1765 */
1766static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
1767 struct iov_iter *iter, ssize_t written)
1768{
1769 struct address_space *mapping = filp->f_mapping;
1770 struct inode *inode = mapping->host;
1771 struct file_ra_state *ra = &filp->f_ra;
1772 pgoff_t index;
1773 pgoff_t last_index;
1774 pgoff_t prev_index;
1775 unsigned long offset; /* offset into pagecache page */
1776 unsigned int prev_offset;
1777 int error = 0;
1778
1779 if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
1780 return 0;
1781 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
1782
1783 index = *ppos >> PAGE_SHIFT;
1784 prev_index = ra->prev_pos >> PAGE_SHIFT;
1785 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
1786 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
1787 offset = *ppos & ~PAGE_MASK;
1788
1789 for (;;) {
1790 struct page *page;
1791 pgoff_t end_index;
1792 loff_t isize;
1793 unsigned long nr, ret;
1794
1795 cond_resched();
1796find_page:
1797 if (fatal_signal_pending(current)) {
1798 error = -EINTR;
1799 goto out;
1800 }
1801
1802 page = find_get_page(mapping, index);
1803 if (!page) {
1804 page_cache_sync_readahead(mapping,
1805 ra, filp,
1806 index, last_index - index);
1807 page = find_get_page(mapping, index);
1808 if (unlikely(page == NULL))
1809 goto no_cached_page;
1810 }
1811 if (PageReadahead(page)) {
1812 page_cache_async_readahead(mapping,
1813 ra, filp, page,
1814 index, last_index - index);
1815 }
1816 if (!PageUptodate(page)) {
1817 /*
1818 * See comment in do_read_cache_page on why
1819 * wait_on_page_locked is used to avoid unnecessarily
1820 * serialisations and why it's safe.
1821 */
1822 error = wait_on_page_locked_killable(page);
1823 if (unlikely(error))
1824 goto readpage_error;
1825 if (PageUptodate(page))
1826 goto page_ok;
1827
1828 if (inode->i_blkbits == PAGE_SHIFT ||
1829 !mapping->a_ops->is_partially_uptodate)
1830 goto page_not_up_to_date;
1831 /* pipes can't handle partially uptodate pages */
1832 if (unlikely(iter->type & ITER_PIPE))
1833 goto page_not_up_to_date;
1834 if (!trylock_page(page))
1835 goto page_not_up_to_date;
1836 /* Did it get truncated before we got the lock? */
1837 if (!page->mapping)
1838 goto page_not_up_to_date_locked;
1839 if (!mapping->a_ops->is_partially_uptodate(page,
1840 offset, iter->count))
1841 goto page_not_up_to_date_locked;
1842 unlock_page(page);
1843 }
1844page_ok:
1845 /*
1846 * i_size must be checked after we know the page is Uptodate.
1847 *
1848 * Checking i_size after the check allows us to calculate
1849 * the correct value for "nr", which means the zero-filled
1850 * part of the page is not copied back to userspace (unless
1851 * another truncate extends the file - this is desired though).
1852 */
1853
1854 isize = i_size_read(inode);
1855 end_index = (isize - 1) >> PAGE_SHIFT;
1856 if (unlikely(!isize || index > end_index)) {
1857 put_page(page);
1858 goto out;
1859 }
1860
1861 /* nr is the maximum number of bytes to copy from this page */
1862 nr = PAGE_SIZE;
1863 if (index == end_index) {
1864 nr = ((isize - 1) & ~PAGE_MASK) + 1;
1865 if (nr <= offset) {
1866 put_page(page);
1867 goto out;
1868 }
1869 }
1870 nr = nr - offset;
1871
1872 /* If users can be writing to this page using arbitrary
1873 * virtual addresses, take care about potential aliasing
1874 * before reading the page on the kernel side.
1875 */
1876 if (mapping_writably_mapped(mapping))
1877 flush_dcache_page(page);
1878
1879 /*
1880 * When a sequential read accesses a page several times,
1881 * only mark it as accessed the first time.
1882 */
1883 if (prev_index != index || offset != prev_offset)
1884 mark_page_accessed(page);
1885 prev_index = index;
1886
1887 /*
1888 * Ok, we have the page, and it's up-to-date, so
1889 * now we can copy it to user space...
1890 */
1891
1892 ret = copy_page_to_iter(page, offset, nr, iter);
1893 offset += ret;
1894 index += offset >> PAGE_SHIFT;
1895 offset &= ~PAGE_MASK;
1896 prev_offset = offset;
1897
1898 put_page(page);
1899 written += ret;
1900 if (!iov_iter_count(iter))
1901 goto out;
1902 if (ret < nr) {
1903 error = -EFAULT;
1904 goto out;
1905 }
1906 continue;
1907
1908page_not_up_to_date:
1909 /* Get exclusive access to the page ... */
1910 error = lock_page_killable(page);
1911 if (unlikely(error))
1912 goto readpage_error;
1913
1914page_not_up_to_date_locked:
1915 /* Did it get truncated before we got the lock? */
1916 if (!page->mapping) {
1917 unlock_page(page);
1918 put_page(page);
1919 continue;
1920 }
1921
1922 /* Did somebody else fill it already? */
1923 if (PageUptodate(page)) {
1924 unlock_page(page);
1925 goto page_ok;
1926 }
1927
1928readpage:
1929 /*
1930 * A previous I/O error may have been due to temporary
1931 * failures, eg. multipath errors.
1932 * PG_error will be set again if readpage fails.
1933 */
1934 ClearPageError(page);
1935 /* Start the actual read. The read will unlock the page. */
1936 error = mapping->a_ops->readpage(filp, page);
1937
1938 if (unlikely(error)) {
1939 if (error == AOP_TRUNCATED_PAGE) {
1940 put_page(page);
1941 error = 0;
1942 goto find_page;
1943 }
1944 goto readpage_error;
1945 }
1946
1947 if (!PageUptodate(page)) {
1948 error = lock_page_killable(page);
1949 if (unlikely(error))
1950 goto readpage_error;
1951 if (!PageUptodate(page)) {
1952 if (page->mapping == NULL) {
1953 /*
1954 * invalidate_mapping_pages got it
1955 */
1956 unlock_page(page);
1957 put_page(page);
1958 goto find_page;
1959 }
1960 unlock_page(page);
1961 shrink_readahead_size_eio(filp, ra);
1962 error = -EIO;
1963 goto readpage_error;
1964 }
1965 unlock_page(page);
1966 }
1967
1968 goto page_ok;
1969
1970readpage_error:
1971 /* UHHUH! A synchronous read error occurred. Report it */
1972 put_page(page);
1973 goto out;
1974
1975no_cached_page:
1976 /*
1977 * Ok, it wasn't cached, so we need to create a new
1978 * page..
1979 */
1980 page = page_cache_alloc_cold(mapping);
1981 if (!page) {
1982 error = -ENOMEM;
1983 goto out;
1984 }
1985 error = add_to_page_cache_lru(page, mapping, index,
1986 mapping_gfp_constraint(mapping, GFP_KERNEL));
1987 if (error) {
1988 put_page(page);
1989 if (error == -EEXIST) {
1990 error = 0;
1991 goto find_page;
1992 }
1993 goto out;
1994 }
1995 goto readpage;
1996 }
1997
1998out:
1999 ra->prev_pos = prev_index;
2000 ra->prev_pos <<= PAGE_SHIFT;
2001 ra->prev_pos |= prev_offset;
2002
2003 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
2004 file_accessed(filp);
2005 return written ? written : error;
2006}
2007
2008/**
2009 * generic_file_read_iter - generic filesystem read routine
2010 * @iocb: kernel I/O control block
2011 * @iter: destination for the data read
2012 *
2013 * This is the "read_iter()" routine for all filesystems
2014 * that can use the page cache directly.
2015 */
2016ssize_t
2017generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2018{
2019 struct file *file = iocb->ki_filp;
2020 ssize_t retval = 0;
2021 size_t count = iov_iter_count(iter);
2022
2023 if (!count)
2024 goto out; /* skip atime */
2025
2026 if (iocb->ki_flags & IOCB_DIRECT) {
2027 struct address_space *mapping = file->f_mapping;
2028 struct inode *inode = mapping->host;
2029 struct iov_iter data = *iter;
2030 loff_t size;
2031
2032 size = i_size_read(inode);
2033 retval = filemap_write_and_wait_range(mapping, iocb->ki_pos,
2034 iocb->ki_pos + count - 1);
2035 if (retval < 0)
2036 goto out;
2037
2038 file_accessed(file);
2039
2040 retval = mapping->a_ops->direct_IO(iocb, &data);
2041 if (retval >= 0) {
2042 iocb->ki_pos += retval;
2043 iov_iter_advance(iter, retval);
2044 }
2045
2046 /*
2047 * Btrfs can have a short DIO read if we encounter
2048 * compressed extents, so if there was an error, or if
2049 * we've already read everything we wanted to, or if
2050 * there was a short read because we hit EOF, go ahead
2051 * and return. Otherwise fallthrough to buffered io for
2052 * the rest of the read. Buffered reads will not work for
2053 * DAX files, so don't bother trying.
2054 */
2055 if (retval < 0 || !iov_iter_count(iter) || iocb->ki_pos >= size ||
2056 IS_DAX(inode))
2057 goto out;
2058 }
2059
2060 retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval);
2061out:
2062 return retval;
2063}
2064EXPORT_SYMBOL(generic_file_read_iter);
2065
2066#ifdef CONFIG_MMU
2067/**
2068 * page_cache_read - adds requested page to the page cache if not already there
2069 * @file: file to read
2070 * @offset: page index
2071 * @gfp_mask: memory allocation flags
2072 *
2073 * This adds the requested page to the page cache if it isn't already there,
2074 * and schedules an I/O to read in its contents from disk.
2075 */
2076static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
2077{
2078 struct address_space *mapping = file->f_mapping;
2079 struct page *page;
2080 int ret;
2081
2082 do {
2083 page = __page_cache_alloc(gfp_mask|__GFP_COLD);
2084 if (!page)
2085 return -ENOMEM;
2086
2087 ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
2088 if (ret == 0)
2089 ret = mapping->a_ops->readpage(file, page);
2090 else if (ret == -EEXIST)
2091 ret = 0; /* losing race to add is OK */
2092
2093 put_page(page);
2094
2095 } while (ret == AOP_TRUNCATED_PAGE);
2096
2097 return ret;
2098}
2099
2100#define MMAP_LOTSAMISS (100)
2101
2102/*
2103 * Synchronous readahead happens when we don't even find
2104 * a page in the page cache at all.
2105 */
2106static void do_sync_mmap_readahead(struct vm_area_struct *vma,
2107 struct file_ra_state *ra,
2108 struct file *file,
2109 pgoff_t offset)
2110{
2111 struct address_space *mapping = file->f_mapping;
2112
2113 /* If we don't want any read-ahead, don't bother */
2114 if (vma->vm_flags & VM_RAND_READ)
2115 return;
2116 if (!ra->ra_pages)
2117 return;
2118
2119 if (vma->vm_flags & VM_SEQ_READ) {
2120 page_cache_sync_readahead(mapping, ra, file, offset,
2121 ra->ra_pages);
2122 return;
2123 }
2124
2125 /* Avoid banging the cache line if not needed */
2126 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
2127 ra->mmap_miss++;
2128
2129 /*
2130 * Do we miss much more than hit in this file? If so,
2131 * stop bothering with read-ahead. It will only hurt.
2132 */
2133 if (ra->mmap_miss > MMAP_LOTSAMISS)
2134 return;
2135
2136 /*
2137 * mmap read-around
2138 */
2139 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
2140 ra->size = ra->ra_pages;
2141 ra->async_size = ra->ra_pages / 4;
2142 ra_submit(ra, mapping, file);
2143}
2144
2145/*
2146 * Asynchronous readahead happens when we find the page and PG_readahead,
2147 * so we want to possibly extend the readahead further..
2148 */
2149static void do_async_mmap_readahead(struct vm_area_struct *vma,
2150 struct file_ra_state *ra,
2151 struct file *file,
2152 struct page *page,
2153 pgoff_t offset)
2154{
2155 struct address_space *mapping = file->f_mapping;
2156
2157 /* If we don't want any read-ahead, don't bother */
2158 if (vma->vm_flags & VM_RAND_READ)
2159 return;
2160 if (ra->mmap_miss > 0)
2161 ra->mmap_miss--;
2162 if (PageReadahead(page))
2163 page_cache_async_readahead(mapping, ra, file,
2164 page, offset, ra->ra_pages);
2165}
2166
2167/**
2168 * filemap_fault - read in file data for page fault handling
2169 * @vma: vma in which the fault was taken
2170 * @vmf: struct vm_fault containing details of the fault
2171 *
2172 * filemap_fault() is invoked via the vma operations vector for a
2173 * mapped memory region to read in file data during a page fault.
2174 *
2175 * The goto's are kind of ugly, but this streamlines the normal case of having
2176 * it in the page cache, and handles the special cases reasonably without
2177 * having a lot of duplicated code.
2178 *
2179 * vma->vm_mm->mmap_sem must be held on entry.
2180 *
2181 * If our return value has VM_FAULT_RETRY set, it's because
2182 * lock_page_or_retry() returned 0.
2183 * The mmap_sem has usually been released in this case.
2184 * See __lock_page_or_retry() for the exception.
2185 *
2186 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2187 * has not been released.
2188 *
2189 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2190 */
2191int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
2192{
2193 int error;
2194 struct file *file = vma->vm_file;
2195 struct address_space *mapping = file->f_mapping;
2196 struct file_ra_state *ra = &file->f_ra;
2197 struct inode *inode = mapping->host;
2198 pgoff_t offset = vmf->pgoff;
2199 struct page *page;
2200 loff_t size;
2201 int ret = 0;
2202
2203 size = round_up(i_size_read(inode), PAGE_SIZE);
2204 if (offset >= size >> PAGE_SHIFT)
2205 return VM_FAULT_SIGBUS;
2206
2207 /*
2208 * Do we have something in the page cache already?
2209 */
2210 page = find_get_page(mapping, offset);
2211 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2212 /*
2213 * We found the page, so try async readahead before
2214 * waiting for the lock.
2215 */
2216 do_async_mmap_readahead(vma, ra, file, page, offset);
2217 } else if (!page) {
2218 /* No page in the page cache at all */
2219 do_sync_mmap_readahead(vma, ra, file, offset);
2220 count_vm_event(PGMAJFAULT);
2221 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
2222 ret = VM_FAULT_MAJOR;
2223retry_find:
2224 page = find_get_page(mapping, offset);
2225 if (!page)
2226 goto no_cached_page;
2227 }
2228
2229 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
2230 put_page(page);
2231 return ret | VM_FAULT_RETRY;
2232 }
2233
2234 /* Did it get truncated? */
2235 if (unlikely(page->mapping != mapping)) {
2236 unlock_page(page);
2237 put_page(page);
2238 goto retry_find;
2239 }
2240 VM_BUG_ON_PAGE(page->index != offset, page);
2241
2242 /*
2243 * We have a locked page in the page cache, now we need to check
2244 * that it's up-to-date. If not, it is going to be due to an error.
2245 */
2246 if (unlikely(!PageUptodate(page)))
2247 goto page_not_uptodate;
2248
2249 /*
2250 * Found the page and have a reference on it.
2251 * We must recheck i_size under page lock.
2252 */
2253 size = round_up(i_size_read(inode), PAGE_SIZE);
2254 if (unlikely(offset >= size >> PAGE_SHIFT)) {
2255 unlock_page(page);
2256 put_page(page);
2257 return VM_FAULT_SIGBUS;
2258 }
2259
2260 vmf->page = page;
2261 return ret | VM_FAULT_LOCKED;
2262
2263no_cached_page:
2264 /*
2265 * We're only likely to ever get here if MADV_RANDOM is in
2266 * effect.
2267 */
2268 error = page_cache_read(file, offset, vmf->gfp_mask);
2269
2270 /*
2271 * The page we want has now been added to the page cache.
2272 * In the unlikely event that someone removed it in the
2273 * meantime, we'll just come back here and read it again.
2274 */
2275 if (error >= 0)
2276 goto retry_find;
2277
2278 /*
2279 * An error return from page_cache_read can result if the
2280 * system is low on memory, or a problem occurs while trying
2281 * to schedule I/O.
2282 */
2283 if (error == -ENOMEM)
2284 return VM_FAULT_OOM;
2285 return VM_FAULT_SIGBUS;
2286
2287page_not_uptodate:
2288 /*
2289 * Umm, take care of errors if the page isn't up-to-date.
2290 * Try to re-read it _once_. We do this synchronously,
2291 * because there really aren't any performance issues here
2292 * and we need to check for errors.
2293 */
2294 ClearPageError(page);
2295 error = mapping->a_ops->readpage(file, page);
2296 if (!error) {
2297 wait_on_page_locked(page);
2298 if (!PageUptodate(page))
2299 error = -EIO;
2300 }
2301 put_page(page);
2302
2303 if (!error || error == AOP_TRUNCATED_PAGE)
2304 goto retry_find;
2305
2306 /* Things didn't work out. Return zero to tell the mm layer so. */
2307 shrink_readahead_size_eio(file, ra);
2308 return VM_FAULT_SIGBUS;
2309}
2310EXPORT_SYMBOL(filemap_fault);
2311
2312void filemap_map_pages(struct vm_fault *vmf,
2313 pgoff_t start_pgoff, pgoff_t end_pgoff)
2314{
2315 struct radix_tree_iter iter;
2316 void **slot;
2317 struct file *file = vmf->vma->vm_file;
2318 struct address_space *mapping = file->f_mapping;
2319 pgoff_t last_pgoff = start_pgoff;
2320 loff_t size;
2321 struct page *head, *page;
2322
2323 rcu_read_lock();
2324 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
2325 start_pgoff) {
2326 if (iter.index > end_pgoff)
2327 break;
2328repeat:
2329 page = radix_tree_deref_slot(slot);
2330 if (unlikely(!page))
2331 goto next;
2332 if (radix_tree_exception(page)) {
2333 if (radix_tree_deref_retry(page)) {
2334 slot = radix_tree_iter_retry(&iter);
2335 continue;
2336 }
2337 goto next;
2338 }
2339
2340 head = compound_head(page);
2341 if (!page_cache_get_speculative(head))
2342 goto repeat;
2343
2344 /* The page was split under us? */
2345 if (compound_head(page) != head) {
2346 put_page(head);
2347 goto repeat;
2348 }
2349
2350 /* Has the page moved? */
2351 if (unlikely(page != *slot)) {
2352 put_page(head);
2353 goto repeat;
2354 }
2355
2356 if (!PageUptodate(page) ||
2357 PageReadahead(page) ||
2358 PageHWPoison(page))
2359 goto skip;
2360 if (!trylock_page(page))
2361 goto skip;
2362
2363 if (page->mapping != mapping || !PageUptodate(page))
2364 goto unlock;
2365
2366 size = round_up(i_size_read(mapping->host), PAGE_SIZE);
2367 if (page->index >= size >> PAGE_SHIFT)
2368 goto unlock;
2369
2370 if (file->f_ra.mmap_miss > 0)
2371 file->f_ra.mmap_miss--;
2372
2373 vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
2374 if (vmf->pte)
2375 vmf->pte += iter.index - last_pgoff;
2376 last_pgoff = iter.index;
2377 if (alloc_set_pte(vmf, NULL, page))
2378 goto unlock;
2379 unlock_page(page);
2380 goto next;
2381unlock:
2382 unlock_page(page);
2383skip:
2384 put_page(page);
2385next:
2386 /* Huge page is mapped? No need to proceed. */
2387 if (pmd_trans_huge(*vmf->pmd))
2388 break;
2389 if (iter.index == end_pgoff)
2390 break;
2391 }
2392 rcu_read_unlock();
2393}
2394EXPORT_SYMBOL(filemap_map_pages);
2395
2396int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
2397{
2398 struct page *page = vmf->page;
2399 struct inode *inode = file_inode(vma->vm_file);
2400 int ret = VM_FAULT_LOCKED;
2401
2402 sb_start_pagefault(inode->i_sb);
2403 file_update_time(vma->vm_file);
2404 lock_page(page);
2405 if (page->mapping != inode->i_mapping) {
2406 unlock_page(page);
2407 ret = VM_FAULT_NOPAGE;
2408 goto out;
2409 }
2410 /*
2411 * We mark the page dirty already here so that when freeze is in
2412 * progress, we are guaranteed that writeback during freezing will
2413 * see the dirty page and writeprotect it again.
2414 */
2415 set_page_dirty(page);
2416 wait_for_stable_page(page);
2417out:
2418 sb_end_pagefault(inode->i_sb);
2419 return ret;
2420}
2421EXPORT_SYMBOL(filemap_page_mkwrite);
2422
2423const struct vm_operations_struct generic_file_vm_ops = {
2424 .fault = filemap_fault,
2425 .map_pages = filemap_map_pages,
2426 .page_mkwrite = filemap_page_mkwrite,
2427};
2428
2429/* This is used for a general mmap of a disk file */
2430
2431int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2432{
2433 struct address_space *mapping = file->f_mapping;
2434
2435 if (!mapping->a_ops->readpage)
2436 return -ENOEXEC;
2437 file_accessed(file);
2438 vma->vm_ops = &generic_file_vm_ops;
2439 return 0;
2440}
2441
2442/*
2443 * This is for filesystems which do not implement ->writepage.
2444 */
2445int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2446{
2447 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2448 return -EINVAL;
2449 return generic_file_mmap(file, vma);
2450}
2451#else
2452int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2453{
2454 return -ENOSYS;
2455}
2456int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2457{
2458 return -ENOSYS;
2459}
2460#endif /* CONFIG_MMU */
2461
2462EXPORT_SYMBOL(generic_file_mmap);
2463EXPORT_SYMBOL(generic_file_readonly_mmap);
2464
2465static struct page *wait_on_page_read(struct page *page)
2466{
2467 if (!IS_ERR(page)) {
2468 wait_on_page_locked(page);
2469 if (!PageUptodate(page)) {
2470 put_page(page);
2471 page = ERR_PTR(-EIO);
2472 }
2473 }
2474 return page;
2475}
2476
2477static struct page *do_read_cache_page(struct address_space *mapping,
2478 pgoff_t index,
2479 int (*filler)(void *, struct page *),
2480 void *data,
2481 gfp_t gfp)
2482{
2483 struct page *page;
2484 int err;
2485repeat:
2486 page = find_get_page(mapping, index);
2487 if (!page) {
2488 page = __page_cache_alloc(gfp | __GFP_COLD);
2489 if (!page)
2490 return ERR_PTR(-ENOMEM);
2491 err = add_to_page_cache_lru(page, mapping, index, gfp);
2492 if (unlikely(err)) {
2493 put_page(page);
2494 if (err == -EEXIST)
2495 goto repeat;
2496 /* Presumably ENOMEM for radix tree node */
2497 return ERR_PTR(err);
2498 }
2499
2500filler:
2501 err = filler(data, page);
2502 if (err < 0) {
2503 put_page(page);
2504 return ERR_PTR(err);
2505 }
2506
2507 page = wait_on_page_read(page);
2508 if (IS_ERR(page))
2509 return page;
2510 goto out;
2511 }
2512 if (PageUptodate(page))
2513 goto out;
2514
2515 /*
2516 * Page is not up to date and may be locked due one of the following
2517 * case a: Page is being filled and the page lock is held
2518 * case b: Read/write error clearing the page uptodate status
2519 * case c: Truncation in progress (page locked)
2520 * case d: Reclaim in progress
2521 *
2522 * Case a, the page will be up to date when the page is unlocked.
2523 * There is no need to serialise on the page lock here as the page
2524 * is pinned so the lock gives no additional protection. Even if the
2525 * the page is truncated, the data is still valid if PageUptodate as
2526 * it's a race vs truncate race.
2527 * Case b, the page will not be up to date
2528 * Case c, the page may be truncated but in itself, the data may still
2529 * be valid after IO completes as it's a read vs truncate race. The
2530 * operation must restart if the page is not uptodate on unlock but
2531 * otherwise serialising on page lock to stabilise the mapping gives
2532 * no additional guarantees to the caller as the page lock is
2533 * released before return.
2534 * Case d, similar to truncation. If reclaim holds the page lock, it
2535 * will be a race with remove_mapping that determines if the mapping
2536 * is valid on unlock but otherwise the data is valid and there is
2537 * no need to serialise with page lock.
2538 *
2539 * As the page lock gives no additional guarantee, we optimistically
2540 * wait on the page to be unlocked and check if it's up to date and
2541 * use the page if it is. Otherwise, the page lock is required to
2542 * distinguish between the different cases. The motivation is that we
2543 * avoid spurious serialisations and wakeups when multiple processes
2544 * wait on the same page for IO to complete.
2545 */
2546 wait_on_page_locked(page);
2547 if (PageUptodate(page))
2548 goto out;
2549
2550 /* Distinguish between all the cases under the safety of the lock */
2551 lock_page(page);
2552
2553 /* Case c or d, restart the operation */
2554 if (!page->mapping) {
2555 unlock_page(page);
2556 put_page(page);
2557 goto repeat;
2558 }
2559
2560 /* Someone else locked and filled the page in a very small window */
2561 if (PageUptodate(page)) {
2562 unlock_page(page);
2563 goto out;
2564 }
2565 goto filler;
2566
2567out:
2568 mark_page_accessed(page);
2569 return page;
2570}
2571
2572/**
2573 * read_cache_page - read into page cache, fill it if needed
2574 * @mapping: the page's address_space
2575 * @index: the page index
2576 * @filler: function to perform the read
2577 * @data: first arg to filler(data, page) function, often left as NULL
2578 *
2579 * Read into the page cache. If a page already exists, and PageUptodate() is
2580 * not set, try to fill the page and wait for it to become unlocked.
2581 *
2582 * If the page does not get brought uptodate, return -EIO.
2583 */
2584struct page *read_cache_page(struct address_space *mapping,
2585 pgoff_t index,
2586 int (*filler)(void *, struct page *),
2587 void *data)
2588{
2589 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2590}
2591EXPORT_SYMBOL(read_cache_page);
2592
2593/**
2594 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2595 * @mapping: the page's address_space
2596 * @index: the page index
2597 * @gfp: the page allocator flags to use if allocating
2598 *
2599 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2600 * any new page allocations done using the specified allocation flags.
2601 *
2602 * If the page does not get brought uptodate, return -EIO.
2603 */
2604struct page *read_cache_page_gfp(struct address_space *mapping,
2605 pgoff_t index,
2606 gfp_t gfp)
2607{
2608 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2609
2610 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2611}
2612EXPORT_SYMBOL(read_cache_page_gfp);
2613
2614/*
2615 * Performs necessary checks before doing a write
2616 *
2617 * Can adjust writing position or amount of bytes to write.
2618 * Returns appropriate error code that caller should return or
2619 * zero in case that write should be allowed.
2620 */
2621inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2622{
2623 struct file *file = iocb->ki_filp;
2624 struct inode *inode = file->f_mapping->host;
2625 unsigned long limit = rlimit(RLIMIT_FSIZE);
2626 loff_t pos;
2627
2628 if (!iov_iter_count(from))
2629 return 0;
2630
2631 /* FIXME: this is for backwards compatibility with 2.4 */
2632 if (iocb->ki_flags & IOCB_APPEND)
2633 iocb->ki_pos = i_size_read(inode);
2634
2635 pos = iocb->ki_pos;
2636
2637 if (limit != RLIM_INFINITY) {
2638 if (iocb->ki_pos >= limit) {
2639 send_sig(SIGXFSZ, current, 0);
2640 return -EFBIG;
2641 }
2642 iov_iter_truncate(from, limit - (unsigned long)pos);
2643 }
2644
2645 /*
2646 * LFS rule
2647 */
2648 if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
2649 !(file->f_flags & O_LARGEFILE))) {
2650 if (pos >= MAX_NON_LFS)
2651 return -EFBIG;
2652 iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
2653 }
2654
2655 /*
2656 * Are we about to exceed the fs block limit ?
2657 *
2658 * If we have written data it becomes a short write. If we have
2659 * exceeded without writing data we send a signal and return EFBIG.
2660 * Linus frestrict idea will clean these up nicely..
2661 */
2662 if (unlikely(pos >= inode->i_sb->s_maxbytes))
2663 return -EFBIG;
2664
2665 iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
2666 return iov_iter_count(from);
2667}
2668EXPORT_SYMBOL(generic_write_checks);
2669
2670int pagecache_write_begin(struct file *file, struct address_space *mapping,
2671 loff_t pos, unsigned len, unsigned flags,
2672 struct page **pagep, void **fsdata)
2673{
2674 const struct address_space_operations *aops = mapping->a_ops;
2675
2676 return aops->write_begin(file, mapping, pos, len, flags,
2677 pagep, fsdata);
2678}
2679EXPORT_SYMBOL(pagecache_write_begin);
2680
2681int pagecache_write_end(struct file *file, struct address_space *mapping,
2682 loff_t pos, unsigned len, unsigned copied,
2683 struct page *page, void *fsdata)
2684{
2685 const struct address_space_operations *aops = mapping->a_ops;
2686
2687 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2688}
2689EXPORT_SYMBOL(pagecache_write_end);
2690
2691ssize_t
2692generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
2693{
2694 struct file *file = iocb->ki_filp;
2695 struct address_space *mapping = file->f_mapping;
2696 struct inode *inode = mapping->host;
2697 loff_t pos = iocb->ki_pos;
2698 ssize_t written;
2699 size_t write_len;
2700 pgoff_t end;
2701 struct iov_iter data;
2702
2703 write_len = iov_iter_count(from);
2704 end = (pos + write_len - 1) >> PAGE_SHIFT;
2705
2706 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2707 if (written)
2708 goto out;
2709
2710 /*
2711 * After a write we want buffered reads to be sure to go to disk to get
2712 * the new data. We invalidate clean cached page from the region we're
2713 * about to write. We do this *before* the write so that we can return
2714 * without clobbering -EIOCBQUEUED from ->direct_IO().
2715 */
2716 if (mapping->nrpages) {
2717 written = invalidate_inode_pages2_range(mapping,
2718 pos >> PAGE_SHIFT, end);
2719 /*
2720 * If a page can not be invalidated, return 0 to fall back
2721 * to buffered write.
2722 */
2723 if (written) {
2724 if (written == -EBUSY)
2725 return 0;
2726 goto out;
2727 }
2728 }
2729
2730 data = *from;
2731 written = mapping->a_ops->direct_IO(iocb, &data);
2732
2733 /*
2734 * Finally, try again to invalidate clean pages which might have been
2735 * cached by non-direct readahead, or faulted in by get_user_pages()
2736 * if the source of the write was an mmap'ed region of the file
2737 * we're writing. Either one is a pretty crazy thing to do,
2738 * so we don't support it 100%. If this invalidation
2739 * fails, tough, the write still worked...
2740 */
2741 if (mapping->nrpages) {
2742 invalidate_inode_pages2_range(mapping,
2743 pos >> PAGE_SHIFT, end);
2744 }
2745
2746 if (written > 0) {
2747 pos += written;
2748 iov_iter_advance(from, written);
2749 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2750 i_size_write(inode, pos);
2751 mark_inode_dirty(inode);
2752 }
2753 iocb->ki_pos = pos;
2754 }
2755out:
2756 return written;
2757}
2758EXPORT_SYMBOL(generic_file_direct_write);
2759
2760/*
2761 * Find or create a page at the given pagecache position. Return the locked
2762 * page. This function is specifically for buffered writes.
2763 */
2764struct page *grab_cache_page_write_begin(struct address_space *mapping,
2765 pgoff_t index, unsigned flags)
2766{
2767 struct page *page;
2768 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
2769
2770 if (flags & AOP_FLAG_NOFS)
2771 fgp_flags |= FGP_NOFS;
2772
2773 page = pagecache_get_page(mapping, index, fgp_flags,
2774 mapping_gfp_mask(mapping));
2775 if (page)
2776 wait_for_stable_page(page);
2777
2778 return page;
2779}
2780EXPORT_SYMBOL(grab_cache_page_write_begin);
2781
2782ssize_t generic_perform_write(struct file *file,
2783 struct iov_iter *i, loff_t pos)
2784{
2785 struct address_space *mapping = file->f_mapping;
2786 const struct address_space_operations *a_ops = mapping->a_ops;
2787 long status = 0;
2788 ssize_t written = 0;
2789 unsigned int flags = 0;
2790
2791 /*
2792 * Copies from kernel address space cannot fail (NFSD is a big user).
2793 */
2794 if (!iter_is_iovec(i))
2795 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2796
2797 do {
2798 struct page *page;
2799 unsigned long offset; /* Offset into pagecache page */
2800 unsigned long bytes; /* Bytes to write to page */
2801 size_t copied; /* Bytes copied from user */
2802 void *fsdata;
2803
2804 offset = (pos & (PAGE_SIZE - 1));
2805 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2806 iov_iter_count(i));
2807
2808again:
2809 /*
2810 * Bring in the user page that we will copy from _first_.
2811 * Otherwise there's a nasty deadlock on copying from the
2812 * same page as we're writing to, without it being marked
2813 * up-to-date.
2814 *
2815 * Not only is this an optimisation, but it is also required
2816 * to check that the address is actually valid, when atomic
2817 * usercopies are used, below.
2818 */
2819 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2820 status = -EFAULT;
2821 break;
2822 }
2823
2824 if (fatal_signal_pending(current)) {
2825 status = -EINTR;
2826 break;
2827 }
2828
2829 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2830 &page, &fsdata);
2831 if (unlikely(status < 0))
2832 break;
2833
2834 if (mapping_writably_mapped(mapping))
2835 flush_dcache_page(page);
2836
2837 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2838 flush_dcache_page(page);
2839
2840 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2841 page, fsdata);
2842 if (unlikely(status < 0))
2843 break;
2844 copied = status;
2845
2846 cond_resched();
2847
2848 iov_iter_advance(i, copied);
2849 if (unlikely(copied == 0)) {
2850 /*
2851 * If we were unable to copy any data at all, we must
2852 * fall back to a single segment length write.
2853 *
2854 * If we didn't fallback here, we could livelock
2855 * because not all segments in the iov can be copied at
2856 * once without a pagefault.
2857 */
2858 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2859 iov_iter_single_seg_count(i));
2860 goto again;
2861 }
2862 pos += copied;
2863 written += copied;
2864
2865 balance_dirty_pages_ratelimited(mapping);
2866 } while (iov_iter_count(i));
2867
2868 return written ? written : status;
2869}
2870EXPORT_SYMBOL(generic_perform_write);
2871
2872/**
2873 * __generic_file_write_iter - write data to a file
2874 * @iocb: IO state structure (file, offset, etc.)
2875 * @from: iov_iter with data to write
2876 *
2877 * This function does all the work needed for actually writing data to a
2878 * file. It does all basic checks, removes SUID from the file, updates
2879 * modification times and calls proper subroutines depending on whether we
2880 * do direct IO or a standard buffered write.
2881 *
2882 * It expects i_mutex to be grabbed unless we work on a block device or similar
2883 * object which does not need locking at all.
2884 *
2885 * This function does *not* take care of syncing data in case of O_SYNC write.
2886 * A caller has to handle it. This is mainly due to the fact that we want to
2887 * avoid syncing under i_mutex.
2888 */
2889ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2890{
2891 struct file *file = iocb->ki_filp;
2892 struct address_space * mapping = file->f_mapping;
2893 struct inode *inode = mapping->host;
2894 ssize_t written = 0;
2895 ssize_t err;
2896 ssize_t status;
2897
2898 /* We can write back this queue in page reclaim */
2899 current->backing_dev_info = inode_to_bdi(inode);
2900 err = file_remove_privs(file);
2901 if (err)
2902 goto out;
2903
2904 err = file_update_time(file);
2905 if (err)
2906 goto out;
2907
2908 if (iocb->ki_flags & IOCB_DIRECT) {
2909 loff_t pos, endbyte;
2910
2911 written = generic_file_direct_write(iocb, from);
2912 /*
2913 * If the write stopped short of completing, fall back to
2914 * buffered writes. Some filesystems do this for writes to
2915 * holes, for example. For DAX files, a buffered write will
2916 * not succeed (even if it did, DAX does not handle dirty
2917 * page-cache pages correctly).
2918 */
2919 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
2920 goto out;
2921
2922 status = generic_perform_write(file, from, pos = iocb->ki_pos);
2923 /*
2924 * If generic_perform_write() returned a synchronous error
2925 * then we want to return the number of bytes which were
2926 * direct-written, or the error code if that was zero. Note
2927 * that this differs from normal direct-io semantics, which
2928 * will return -EFOO even if some bytes were written.
2929 */
2930 if (unlikely(status < 0)) {
2931 err = status;
2932 goto out;
2933 }
2934 /*
2935 * We need to ensure that the page cache pages are written to
2936 * disk and invalidated to preserve the expected O_DIRECT
2937 * semantics.
2938 */
2939 endbyte = pos + status - 1;
2940 err = filemap_write_and_wait_range(mapping, pos, endbyte);
2941 if (err == 0) {
2942 iocb->ki_pos = endbyte + 1;
2943 written += status;
2944 invalidate_mapping_pages(mapping,
2945 pos >> PAGE_SHIFT,
2946 endbyte >> PAGE_SHIFT);
2947 } else {
2948 /*
2949 * We don't know how much we wrote, so just return
2950 * the number of bytes which were direct-written
2951 */
2952 }
2953 } else {
2954 written = generic_perform_write(file, from, iocb->ki_pos);
2955 if (likely(written > 0))
2956 iocb->ki_pos += written;
2957 }
2958out:
2959 current->backing_dev_info = NULL;
2960 return written ? written : err;
2961}
2962EXPORT_SYMBOL(__generic_file_write_iter);
2963
2964/**
2965 * generic_file_write_iter - write data to a file
2966 * @iocb: IO state structure
2967 * @from: iov_iter with data to write
2968 *
2969 * This is a wrapper around __generic_file_write_iter() to be used by most
2970 * filesystems. It takes care of syncing the file in case of O_SYNC file
2971 * and acquires i_mutex as needed.
2972 */
2973ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2974{
2975 struct file *file = iocb->ki_filp;
2976 struct inode *inode = file->f_mapping->host;
2977 ssize_t ret;
2978
2979 inode_lock(inode);
2980 ret = generic_write_checks(iocb, from);
2981 if (ret > 0)
2982 ret = __generic_file_write_iter(iocb, from);
2983 inode_unlock(inode);
2984
2985 if (ret > 0)
2986 ret = generic_write_sync(iocb, ret);
2987 return ret;
2988}
2989EXPORT_SYMBOL(generic_file_write_iter);
2990
2991/**
2992 * try_to_release_page() - release old fs-specific metadata on a page
2993 *
2994 * @page: the page which the kernel is trying to free
2995 * @gfp_mask: memory allocation flags (and I/O mode)
2996 *
2997 * The address_space is to try to release any data against the page
2998 * (presumably at page->private). If the release was successful, return `1'.
2999 * Otherwise return zero.
3000 *
3001 * This may also be called if PG_fscache is set on a page, indicating that the
3002 * page is known to the local caching routines.
3003 *
3004 * The @gfp_mask argument specifies whether I/O may be performed to release
3005 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3006 *
3007 */
3008int try_to_release_page(struct page *page, gfp_t gfp_mask)
3009{
3010 struct address_space * const mapping = page->mapping;
3011
3012 BUG_ON(!PageLocked(page));
3013 if (PageWriteback(page))
3014 return 0;
3015
3016 if (mapping && mapping->a_ops->releasepage)
3017 return mapping->a_ops->releasepage(page, gfp_mask);
3018 return try_to_free_buffers(page);
3019}
3020
3021EXPORT_SYMBOL(try_to_release_page);