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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/sched/signal.h>
17#include <linux/uaccess.h>
18#include <linux/capability.h>
19#include <linux/kernel_stat.h>
20#include <linux/gfp.h>
21#include <linux/mm.h>
22#include <linux/swap.h>
23#include <linux/mman.h>
24#include <linux/pagemap.h>
25#include <linux/file.h>
26#include <linux/uio.h>
27#include <linux/hash.h>
28#include <linux/writeback.h>
29#include <linux/backing-dev.h>
30#include <linux/pagevec.h>
31#include <linux/blkdev.h>
32#include <linux/security.h>
33#include <linux/cpuset.h>
34#include <linux/hugetlb.h>
35#include <linux/memcontrol.h>
36#include <linux/cleancache.h>
37#include <linux/shmem_fs.h>
38#include <linux/rmap.h>
39#include "internal.h"
40
41#define CREATE_TRACE_POINTS
42#include <trace/events/filemap.h>
43
44/*
45 * FIXME: remove all knowledge of the buffer layer from the core VM
46 */
47#include <linux/buffer_head.h> /* for try_to_free_buffers */
48
49#include <asm/mman.h>
50
51/*
52 * Shared mappings implemented 30.11.1994. It's not fully working yet,
53 * though.
54 *
55 * Shared mappings now work. 15.8.1995 Bruno.
56 *
57 * finished 'unifying' the page and buffer cache and SMP-threaded the
58 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
59 *
60 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
61 */
62
63/*
64 * Lock ordering:
65 *
66 * ->i_mmap_rwsem (truncate_pagecache)
67 * ->private_lock (__free_pte->__set_page_dirty_buffers)
68 * ->swap_lock (exclusive_swap_page, others)
69 * ->i_pages lock
70 *
71 * ->i_mutex
72 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
73 *
74 * ->mmap_sem
75 * ->i_mmap_rwsem
76 * ->page_table_lock or pte_lock (various, mainly in memory.c)
77 * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
78 *
79 * ->mmap_sem
80 * ->lock_page (access_process_vm)
81 *
82 * ->i_mutex (generic_perform_write)
83 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
84 *
85 * bdi->wb.list_lock
86 * sb_lock (fs/fs-writeback.c)
87 * ->i_pages lock (__sync_single_inode)
88 *
89 * ->i_mmap_rwsem
90 * ->anon_vma.lock (vma_adjust)
91 *
92 * ->anon_vma.lock
93 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
94 *
95 * ->page_table_lock or pte_lock
96 * ->swap_lock (try_to_unmap_one)
97 * ->private_lock (try_to_unmap_one)
98 * ->i_pages lock (try_to_unmap_one)
99 * ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
100 * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
101 * ->private_lock (page_remove_rmap->set_page_dirty)
102 * ->i_pages lock (page_remove_rmap->set_page_dirty)
103 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
104 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
105 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
106 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
107 * ->inode->i_lock (zap_pte_range->set_page_dirty)
108 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
109 *
110 * ->i_mmap_rwsem
111 * ->tasklist_lock (memory_failure, collect_procs_ao)
112 */
113
114static int page_cache_tree_insert(struct address_space *mapping,
115 struct page *page, void **shadowp)
116{
117 struct radix_tree_node *node;
118 void **slot;
119 int error;
120
121 error = __radix_tree_create(&mapping->i_pages, page->index, 0,
122 &node, &slot);
123 if (error)
124 return error;
125 if (*slot) {
126 void *p;
127
128 p = radix_tree_deref_slot_protected(slot,
129 &mapping->i_pages.xa_lock);
130 if (!radix_tree_exceptional_entry(p))
131 return -EEXIST;
132
133 mapping->nrexceptional--;
134 if (shadowp)
135 *shadowp = p;
136 }
137 __radix_tree_replace(&mapping->i_pages, node, slot, page,
138 workingset_lookup_update(mapping));
139 mapping->nrpages++;
140 return 0;
141}
142
143static void page_cache_tree_delete(struct address_space *mapping,
144 struct page *page, void *shadow)
145{
146 int i, nr;
147
148 /* hugetlb pages are represented by one entry in the radix tree */
149 nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
150
151 VM_BUG_ON_PAGE(!PageLocked(page), page);
152 VM_BUG_ON_PAGE(PageTail(page), page);
153 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
154
155 for (i = 0; i < nr; i++) {
156 struct radix_tree_node *node;
157 void **slot;
158
159 __radix_tree_lookup(&mapping->i_pages, page->index + i,
160 &node, &slot);
161
162 VM_BUG_ON_PAGE(!node && nr != 1, page);
163
164 radix_tree_clear_tags(&mapping->i_pages, node, slot);
165 __radix_tree_replace(&mapping->i_pages, node, slot, shadow,
166 workingset_lookup_update(mapping));
167 }
168
169 page->mapping = NULL;
170 /* Leave page->index set: truncation lookup relies upon it */
171
172 if (shadow) {
173 mapping->nrexceptional += nr;
174 /*
175 * Make sure the nrexceptional update is committed before
176 * the nrpages update so that final truncate racing
177 * with reclaim does not see both counters 0 at the
178 * same time and miss a shadow entry.
179 */
180 smp_wmb();
181 }
182 mapping->nrpages -= nr;
183}
184
185static void unaccount_page_cache_page(struct address_space *mapping,
186 struct page *page)
187{
188 int nr;
189
190 /*
191 * if we're uptodate, flush out into the cleancache, otherwise
192 * invalidate any existing cleancache entries. We can't leave
193 * stale data around in the cleancache once our page is gone
194 */
195 if (PageUptodate(page) && PageMappedToDisk(page))
196 cleancache_put_page(page);
197 else
198 cleancache_invalidate_page(mapping, page);
199
200 VM_BUG_ON_PAGE(PageTail(page), page);
201 VM_BUG_ON_PAGE(page_mapped(page), page);
202 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
203 int mapcount;
204
205 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
206 current->comm, page_to_pfn(page));
207 dump_page(page, "still mapped when deleted");
208 dump_stack();
209 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
210
211 mapcount = page_mapcount(page);
212 if (mapping_exiting(mapping) &&
213 page_count(page) >= mapcount + 2) {
214 /*
215 * All vmas have already been torn down, so it's
216 * a good bet that actually the page is unmapped,
217 * and we'd prefer not to leak it: if we're wrong,
218 * some other bad page check should catch it later.
219 */
220 page_mapcount_reset(page);
221 page_ref_sub(page, mapcount);
222 }
223 }
224
225 /* hugetlb pages do not participate in page cache accounting. */
226 if (PageHuge(page))
227 return;
228
229 nr = hpage_nr_pages(page);
230
231 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
232 if (PageSwapBacked(page)) {
233 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
234 if (PageTransHuge(page))
235 __dec_node_page_state(page, NR_SHMEM_THPS);
236 } else {
237 VM_BUG_ON_PAGE(PageTransHuge(page), page);
238 }
239
240 /*
241 * At this point page must be either written or cleaned by
242 * truncate. Dirty page here signals a bug and loss of
243 * unwritten data.
244 *
245 * This fixes dirty accounting after removing the page entirely
246 * but leaves PageDirty set: it has no effect for truncated
247 * page and anyway will be cleared before returning page into
248 * buddy allocator.
249 */
250 if (WARN_ON_ONCE(PageDirty(page)))
251 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
252}
253
254/*
255 * Delete a page from the page cache and free it. Caller has to make
256 * sure the page is locked and that nobody else uses it - or that usage
257 * is safe. The caller must hold the i_pages lock.
258 */
259void __delete_from_page_cache(struct page *page, void *shadow)
260{
261 struct address_space *mapping = page->mapping;
262
263 trace_mm_filemap_delete_from_page_cache(page);
264
265 unaccount_page_cache_page(mapping, page);
266 page_cache_tree_delete(mapping, page, shadow);
267}
268
269static void page_cache_free_page(struct address_space *mapping,
270 struct page *page)
271{
272 void (*freepage)(struct page *);
273
274 freepage = mapping->a_ops->freepage;
275 if (freepage)
276 freepage(page);
277
278 if (PageTransHuge(page) && !PageHuge(page)) {
279 page_ref_sub(page, HPAGE_PMD_NR);
280 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
281 } else {
282 put_page(page);
283 }
284}
285
286/**
287 * delete_from_page_cache - delete page from page cache
288 * @page: the page which the kernel is trying to remove from page cache
289 *
290 * This must be called only on pages that have been verified to be in the page
291 * cache and locked. It will never put the page into the free list, the caller
292 * has a reference on the page.
293 */
294void delete_from_page_cache(struct page *page)
295{
296 struct address_space *mapping = page_mapping(page);
297 unsigned long flags;
298
299 BUG_ON(!PageLocked(page));
300 xa_lock_irqsave(&mapping->i_pages, flags);
301 __delete_from_page_cache(page, NULL);
302 xa_unlock_irqrestore(&mapping->i_pages, flags);
303
304 page_cache_free_page(mapping, page);
305}
306EXPORT_SYMBOL(delete_from_page_cache);
307
308/*
309 * page_cache_tree_delete_batch - delete several pages from page cache
310 * @mapping: the mapping to which pages belong
311 * @pvec: pagevec with pages to delete
312 *
313 * The function walks over mapping->i_pages and removes pages passed in @pvec
314 * from the mapping. The function expects @pvec to be sorted by page index.
315 * It tolerates holes in @pvec (mapping entries at those indices are not
316 * modified). The function expects only THP head pages to be present in the
317 * @pvec and takes care to delete all corresponding tail pages from the
318 * mapping as well.
319 *
320 * The function expects the i_pages lock to be held.
321 */
322static void
323page_cache_tree_delete_batch(struct address_space *mapping,
324 struct pagevec *pvec)
325{
326 struct radix_tree_iter iter;
327 void **slot;
328 int total_pages = 0;
329 int i = 0, tail_pages = 0;
330 struct page *page;
331 pgoff_t start;
332
333 start = pvec->pages[0]->index;
334 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
335 if (i >= pagevec_count(pvec) && !tail_pages)
336 break;
337 page = radix_tree_deref_slot_protected(slot,
338 &mapping->i_pages.xa_lock);
339 if (radix_tree_exceptional_entry(page))
340 continue;
341 if (!tail_pages) {
342 /*
343 * Some page got inserted in our range? Skip it. We
344 * have our pages locked so they are protected from
345 * being removed.
346 */
347 if (page != pvec->pages[i])
348 continue;
349 WARN_ON_ONCE(!PageLocked(page));
350 if (PageTransHuge(page) && !PageHuge(page))
351 tail_pages = HPAGE_PMD_NR - 1;
352 page->mapping = NULL;
353 /*
354 * Leave page->index set: truncation lookup relies
355 * upon it
356 */
357 i++;
358 } else {
359 tail_pages--;
360 }
361 radix_tree_clear_tags(&mapping->i_pages, iter.node, slot);
362 __radix_tree_replace(&mapping->i_pages, iter.node, slot, NULL,
363 workingset_lookup_update(mapping));
364 total_pages++;
365 }
366 mapping->nrpages -= total_pages;
367}
368
369void delete_from_page_cache_batch(struct address_space *mapping,
370 struct pagevec *pvec)
371{
372 int i;
373 unsigned long flags;
374
375 if (!pagevec_count(pvec))
376 return;
377
378 xa_lock_irqsave(&mapping->i_pages, flags);
379 for (i = 0; i < pagevec_count(pvec); i++) {
380 trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);
381
382 unaccount_page_cache_page(mapping, pvec->pages[i]);
383 }
384 page_cache_tree_delete_batch(mapping, pvec);
385 xa_unlock_irqrestore(&mapping->i_pages, flags);
386
387 for (i = 0; i < pagevec_count(pvec); i++)
388 page_cache_free_page(mapping, pvec->pages[i]);
389}
390
391int filemap_check_errors(struct address_space *mapping)
392{
393 int ret = 0;
394 /* Check for outstanding write errors */
395 if (test_bit(AS_ENOSPC, &mapping->flags) &&
396 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
397 ret = -ENOSPC;
398 if (test_bit(AS_EIO, &mapping->flags) &&
399 test_and_clear_bit(AS_EIO, &mapping->flags))
400 ret = -EIO;
401 return ret;
402}
403EXPORT_SYMBOL(filemap_check_errors);
404
405static int filemap_check_and_keep_errors(struct address_space *mapping)
406{
407 /* Check for outstanding write errors */
408 if (test_bit(AS_EIO, &mapping->flags))
409 return -EIO;
410 if (test_bit(AS_ENOSPC, &mapping->flags))
411 return -ENOSPC;
412 return 0;
413}
414
415/**
416 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
417 * @mapping: address space structure to write
418 * @start: offset in bytes where the range starts
419 * @end: offset in bytes where the range ends (inclusive)
420 * @sync_mode: enable synchronous operation
421 *
422 * Start writeback against all of a mapping's dirty pages that lie
423 * within the byte offsets <start, end> inclusive.
424 *
425 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
426 * opposed to a regular memory cleansing writeback. The difference between
427 * these two operations is that if a dirty page/buffer is encountered, it must
428 * be waited upon, and not just skipped over.
429 */
430int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
431 loff_t end, int sync_mode)
432{
433 int ret;
434 struct writeback_control wbc = {
435 .sync_mode = sync_mode,
436 .nr_to_write = LONG_MAX,
437 .range_start = start,
438 .range_end = end,
439 };
440
441 if (!mapping_cap_writeback_dirty(mapping))
442 return 0;
443
444 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
445 ret = do_writepages(mapping, &wbc);
446 wbc_detach_inode(&wbc);
447 return ret;
448}
449
450static inline int __filemap_fdatawrite(struct address_space *mapping,
451 int sync_mode)
452{
453 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
454}
455
456int filemap_fdatawrite(struct address_space *mapping)
457{
458 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
459}
460EXPORT_SYMBOL(filemap_fdatawrite);
461
462int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
463 loff_t end)
464{
465 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
466}
467EXPORT_SYMBOL(filemap_fdatawrite_range);
468
469/**
470 * filemap_flush - mostly a non-blocking flush
471 * @mapping: target address_space
472 *
473 * This is a mostly non-blocking flush. Not suitable for data-integrity
474 * purposes - I/O may not be started against all dirty pages.
475 */
476int filemap_flush(struct address_space *mapping)
477{
478 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
479}
480EXPORT_SYMBOL(filemap_flush);
481
482/**
483 * filemap_range_has_page - check if a page exists in range.
484 * @mapping: address space within which to check
485 * @start_byte: offset in bytes where the range starts
486 * @end_byte: offset in bytes where the range ends (inclusive)
487 *
488 * Find at least one page in the range supplied, usually used to check if
489 * direct writing in this range will trigger a writeback.
490 */
491bool filemap_range_has_page(struct address_space *mapping,
492 loff_t start_byte, loff_t end_byte)
493{
494 pgoff_t index = start_byte >> PAGE_SHIFT;
495 pgoff_t end = end_byte >> PAGE_SHIFT;
496 struct page *page;
497
498 if (end_byte < start_byte)
499 return false;
500
501 if (mapping->nrpages == 0)
502 return false;
503
504 if (!find_get_pages_range(mapping, &index, end, 1, &page))
505 return false;
506 put_page(page);
507 return true;
508}
509EXPORT_SYMBOL(filemap_range_has_page);
510
511static void __filemap_fdatawait_range(struct address_space *mapping,
512 loff_t start_byte, loff_t end_byte)
513{
514 pgoff_t index = start_byte >> PAGE_SHIFT;
515 pgoff_t end = end_byte >> PAGE_SHIFT;
516 struct pagevec pvec;
517 int nr_pages;
518
519 if (end_byte < start_byte)
520 return;
521
522 pagevec_init(&pvec);
523 while (index <= end) {
524 unsigned i;
525
526 nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
527 end, PAGECACHE_TAG_WRITEBACK);
528 if (!nr_pages)
529 break;
530
531 for (i = 0; i < nr_pages; i++) {
532 struct page *page = pvec.pages[i];
533
534 wait_on_page_writeback(page);
535 ClearPageError(page);
536 }
537 pagevec_release(&pvec);
538 cond_resched();
539 }
540}
541
542/**
543 * filemap_fdatawait_range - wait for writeback to complete
544 * @mapping: address space structure to wait for
545 * @start_byte: offset in bytes where the range starts
546 * @end_byte: offset in bytes where the range ends (inclusive)
547 *
548 * Walk the list of under-writeback pages of the given address space
549 * in the given range and wait for all of them. Check error status of
550 * the address space and return it.
551 *
552 * Since the error status of the address space is cleared by this function,
553 * callers are responsible for checking the return value and handling and/or
554 * reporting the error.
555 */
556int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
557 loff_t end_byte)
558{
559 __filemap_fdatawait_range(mapping, start_byte, end_byte);
560 return filemap_check_errors(mapping);
561}
562EXPORT_SYMBOL(filemap_fdatawait_range);
563
564/**
565 * file_fdatawait_range - wait for writeback to complete
566 * @file: file pointing to address space structure to wait for
567 * @start_byte: offset in bytes where the range starts
568 * @end_byte: offset in bytes where the range ends (inclusive)
569 *
570 * Walk the list of under-writeback pages of the address space that file
571 * refers to, in the given range and wait for all of them. Check error
572 * status of the address space vs. the file->f_wb_err cursor and return it.
573 *
574 * Since the error status of the file is advanced by this function,
575 * callers are responsible for checking the return value and handling and/or
576 * reporting the error.
577 */
578int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
579{
580 struct address_space *mapping = file->f_mapping;
581
582 __filemap_fdatawait_range(mapping, start_byte, end_byte);
583 return file_check_and_advance_wb_err(file);
584}
585EXPORT_SYMBOL(file_fdatawait_range);
586
587/**
588 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
589 * @mapping: address space structure to wait for
590 *
591 * Walk the list of under-writeback pages of the given address space
592 * and wait for all of them. Unlike filemap_fdatawait(), this function
593 * does not clear error status of the address space.
594 *
595 * Use this function if callers don't handle errors themselves. Expected
596 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
597 * fsfreeze(8)
598 */
599int filemap_fdatawait_keep_errors(struct address_space *mapping)
600{
601 __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
602 return filemap_check_and_keep_errors(mapping);
603}
604EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
605
606static bool mapping_needs_writeback(struct address_space *mapping)
607{
608 return (!dax_mapping(mapping) && mapping->nrpages) ||
609 (dax_mapping(mapping) && mapping->nrexceptional);
610}
611
612int filemap_write_and_wait(struct address_space *mapping)
613{
614 int err = 0;
615
616 if (mapping_needs_writeback(mapping)) {
617 err = filemap_fdatawrite(mapping);
618 /*
619 * Even if the above returned error, the pages may be
620 * written partially (e.g. -ENOSPC), so we wait for it.
621 * But the -EIO is special case, it may indicate the worst
622 * thing (e.g. bug) happened, so we avoid waiting for it.
623 */
624 if (err != -EIO) {
625 int err2 = filemap_fdatawait(mapping);
626 if (!err)
627 err = err2;
628 } else {
629 /* Clear any previously stored errors */
630 filemap_check_errors(mapping);
631 }
632 } else {
633 err = filemap_check_errors(mapping);
634 }
635 return err;
636}
637EXPORT_SYMBOL(filemap_write_and_wait);
638
639/**
640 * filemap_write_and_wait_range - write out & wait on a file range
641 * @mapping: the address_space for the pages
642 * @lstart: offset in bytes where the range starts
643 * @lend: offset in bytes where the range ends (inclusive)
644 *
645 * Write out and wait upon file offsets lstart->lend, inclusive.
646 *
647 * Note that @lend is inclusive (describes the last byte to be written) so
648 * that this function can be used to write to the very end-of-file (end = -1).
649 */
650int filemap_write_and_wait_range(struct address_space *mapping,
651 loff_t lstart, loff_t lend)
652{
653 int err = 0;
654
655 if (mapping_needs_writeback(mapping)) {
656 err = __filemap_fdatawrite_range(mapping, lstart, lend,
657 WB_SYNC_ALL);
658 /* See comment of filemap_write_and_wait() */
659 if (err != -EIO) {
660 int err2 = filemap_fdatawait_range(mapping,
661 lstart, lend);
662 if (!err)
663 err = err2;
664 } else {
665 /* Clear any previously stored errors */
666 filemap_check_errors(mapping);
667 }
668 } else {
669 err = filemap_check_errors(mapping);
670 }
671 return err;
672}
673EXPORT_SYMBOL(filemap_write_and_wait_range);
674
675void __filemap_set_wb_err(struct address_space *mapping, int err)
676{
677 errseq_t eseq = errseq_set(&mapping->wb_err, err);
678
679 trace_filemap_set_wb_err(mapping, eseq);
680}
681EXPORT_SYMBOL(__filemap_set_wb_err);
682
683/**
684 * file_check_and_advance_wb_err - report wb error (if any) that was previously
685 * and advance wb_err to current one
686 * @file: struct file on which the error is being reported
687 *
688 * When userland calls fsync (or something like nfsd does the equivalent), we
689 * want to report any writeback errors that occurred since the last fsync (or
690 * since the file was opened if there haven't been any).
691 *
692 * Grab the wb_err from the mapping. If it matches what we have in the file,
693 * then just quickly return 0. The file is all caught up.
694 *
695 * If it doesn't match, then take the mapping value, set the "seen" flag in
696 * it and try to swap it into place. If it works, or another task beat us
697 * to it with the new value, then update the f_wb_err and return the error
698 * portion. The error at this point must be reported via proper channels
699 * (a'la fsync, or NFS COMMIT operation, etc.).
700 *
701 * While we handle mapping->wb_err with atomic operations, the f_wb_err
702 * value is protected by the f_lock since we must ensure that it reflects
703 * the latest value swapped in for this file descriptor.
704 */
705int file_check_and_advance_wb_err(struct file *file)
706{
707 int err = 0;
708 errseq_t old = READ_ONCE(file->f_wb_err);
709 struct address_space *mapping = file->f_mapping;
710
711 /* Locklessly handle the common case where nothing has changed */
712 if (errseq_check(&mapping->wb_err, old)) {
713 /* Something changed, must use slow path */
714 spin_lock(&file->f_lock);
715 old = file->f_wb_err;
716 err = errseq_check_and_advance(&mapping->wb_err,
717 &file->f_wb_err);
718 trace_file_check_and_advance_wb_err(file, old);
719 spin_unlock(&file->f_lock);
720 }
721
722 /*
723 * We're mostly using this function as a drop in replacement for
724 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
725 * that the legacy code would have had on these flags.
726 */
727 clear_bit(AS_EIO, &mapping->flags);
728 clear_bit(AS_ENOSPC, &mapping->flags);
729 return err;
730}
731EXPORT_SYMBOL(file_check_and_advance_wb_err);
732
733/**
734 * file_write_and_wait_range - write out & wait on a file range
735 * @file: file pointing to address_space with pages
736 * @lstart: offset in bytes where the range starts
737 * @lend: offset in bytes where the range ends (inclusive)
738 *
739 * Write out and wait upon file offsets lstart->lend, inclusive.
740 *
741 * Note that @lend is inclusive (describes the last byte to be written) so
742 * that this function can be used to write to the very end-of-file (end = -1).
743 *
744 * After writing out and waiting on the data, we check and advance the
745 * f_wb_err cursor to the latest value, and return any errors detected there.
746 */
747int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
748{
749 int err = 0, err2;
750 struct address_space *mapping = file->f_mapping;
751
752 if (mapping_needs_writeback(mapping)) {
753 err = __filemap_fdatawrite_range(mapping, lstart, lend,
754 WB_SYNC_ALL);
755 /* See comment of filemap_write_and_wait() */
756 if (err != -EIO)
757 __filemap_fdatawait_range(mapping, lstart, lend);
758 }
759 err2 = file_check_and_advance_wb_err(file);
760 if (!err)
761 err = err2;
762 return err;
763}
764EXPORT_SYMBOL(file_write_and_wait_range);
765
766/**
767 * replace_page_cache_page - replace a pagecache page with a new one
768 * @old: page to be replaced
769 * @new: page to replace with
770 * @gfp_mask: allocation mode
771 *
772 * This function replaces a page in the pagecache with a new one. On
773 * success it acquires the pagecache reference for the new page and
774 * drops it for the old page. Both the old and new pages must be
775 * locked. This function does not add the new page to the LRU, the
776 * caller must do that.
777 *
778 * The remove + add is atomic. The only way this function can fail is
779 * memory allocation failure.
780 */
781int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
782{
783 int error;
784
785 VM_BUG_ON_PAGE(!PageLocked(old), old);
786 VM_BUG_ON_PAGE(!PageLocked(new), new);
787 VM_BUG_ON_PAGE(new->mapping, new);
788
789 error = radix_tree_preload(gfp_mask & GFP_RECLAIM_MASK);
790 if (!error) {
791 struct address_space *mapping = old->mapping;
792 void (*freepage)(struct page *);
793 unsigned long flags;
794
795 pgoff_t offset = old->index;
796 freepage = mapping->a_ops->freepage;
797
798 get_page(new);
799 new->mapping = mapping;
800 new->index = offset;
801
802 xa_lock_irqsave(&mapping->i_pages, flags);
803 __delete_from_page_cache(old, NULL);
804 error = page_cache_tree_insert(mapping, new, NULL);
805 BUG_ON(error);
806
807 /*
808 * hugetlb pages do not participate in page cache accounting.
809 */
810 if (!PageHuge(new))
811 __inc_node_page_state(new, NR_FILE_PAGES);
812 if (PageSwapBacked(new))
813 __inc_node_page_state(new, NR_SHMEM);
814 xa_unlock_irqrestore(&mapping->i_pages, flags);
815 mem_cgroup_migrate(old, new);
816 radix_tree_preload_end();
817 if (freepage)
818 freepage(old);
819 put_page(old);
820 }
821
822 return error;
823}
824EXPORT_SYMBOL_GPL(replace_page_cache_page);
825
826static int __add_to_page_cache_locked(struct page *page,
827 struct address_space *mapping,
828 pgoff_t offset, gfp_t gfp_mask,
829 void **shadowp)
830{
831 int huge = PageHuge(page);
832 struct mem_cgroup *memcg;
833 int error;
834
835 VM_BUG_ON_PAGE(!PageLocked(page), page);
836 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
837
838 if (!huge) {
839 error = mem_cgroup_try_charge(page, current->mm,
840 gfp_mask, &memcg, false);
841 if (error)
842 return error;
843 }
844
845 error = radix_tree_maybe_preload(gfp_mask & GFP_RECLAIM_MASK);
846 if (error) {
847 if (!huge)
848 mem_cgroup_cancel_charge(page, memcg, false);
849 return error;
850 }
851
852 get_page(page);
853 page->mapping = mapping;
854 page->index = offset;
855
856 xa_lock_irq(&mapping->i_pages);
857 error = page_cache_tree_insert(mapping, page, shadowp);
858 radix_tree_preload_end();
859 if (unlikely(error))
860 goto err_insert;
861
862 /* hugetlb pages do not participate in page cache accounting. */
863 if (!huge)
864 __inc_node_page_state(page, NR_FILE_PAGES);
865 xa_unlock_irq(&mapping->i_pages);
866 if (!huge)
867 mem_cgroup_commit_charge(page, memcg, false, false);
868 trace_mm_filemap_add_to_page_cache(page);
869 return 0;
870err_insert:
871 page->mapping = NULL;
872 /* Leave page->index set: truncation relies upon it */
873 xa_unlock_irq(&mapping->i_pages);
874 if (!huge)
875 mem_cgroup_cancel_charge(page, memcg, false);
876 put_page(page);
877 return error;
878}
879
880/**
881 * add_to_page_cache_locked - add a locked page to the pagecache
882 * @page: page to add
883 * @mapping: the page's address_space
884 * @offset: page index
885 * @gfp_mask: page allocation mode
886 *
887 * This function is used to add a page to the pagecache. It must be locked.
888 * This function does not add the page to the LRU. The caller must do that.
889 */
890int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
891 pgoff_t offset, gfp_t gfp_mask)
892{
893 return __add_to_page_cache_locked(page, mapping, offset,
894 gfp_mask, NULL);
895}
896EXPORT_SYMBOL(add_to_page_cache_locked);
897
898int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
899 pgoff_t offset, gfp_t gfp_mask)
900{
901 void *shadow = NULL;
902 int ret;
903
904 __SetPageLocked(page);
905 ret = __add_to_page_cache_locked(page, mapping, offset,
906 gfp_mask, &shadow);
907 if (unlikely(ret))
908 __ClearPageLocked(page);
909 else {
910 /*
911 * The page might have been evicted from cache only
912 * recently, in which case it should be activated like
913 * any other repeatedly accessed page.
914 * The exception is pages getting rewritten; evicting other
915 * data from the working set, only to cache data that will
916 * get overwritten with something else, is a waste of memory.
917 */
918 if (!(gfp_mask & __GFP_WRITE) &&
919 shadow && workingset_refault(shadow)) {
920 SetPageActive(page);
921 workingset_activation(page);
922 } else
923 ClearPageActive(page);
924 lru_cache_add(page);
925 }
926 return ret;
927}
928EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
929
930#ifdef CONFIG_NUMA
931struct page *__page_cache_alloc(gfp_t gfp)
932{
933 int n;
934 struct page *page;
935
936 if (cpuset_do_page_mem_spread()) {
937 unsigned int cpuset_mems_cookie;
938 do {
939 cpuset_mems_cookie = read_mems_allowed_begin();
940 n = cpuset_mem_spread_node();
941 page = __alloc_pages_node(n, gfp, 0);
942 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
943
944 return page;
945 }
946 return alloc_pages(gfp, 0);
947}
948EXPORT_SYMBOL(__page_cache_alloc);
949#endif
950
951/*
952 * In order to wait for pages to become available there must be
953 * waitqueues associated with pages. By using a hash table of
954 * waitqueues where the bucket discipline is to maintain all
955 * waiters on the same queue and wake all when any of the pages
956 * become available, and for the woken contexts to check to be
957 * sure the appropriate page became available, this saves space
958 * at a cost of "thundering herd" phenomena during rare hash
959 * collisions.
960 */
961#define PAGE_WAIT_TABLE_BITS 8
962#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
963static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
964
965static wait_queue_head_t *page_waitqueue(struct page *page)
966{
967 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
968}
969
970void __init pagecache_init(void)
971{
972 int i;
973
974 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
975 init_waitqueue_head(&page_wait_table[i]);
976
977 page_writeback_init();
978}
979
980/* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
981struct wait_page_key {
982 struct page *page;
983 int bit_nr;
984 int page_match;
985};
986
987struct wait_page_queue {
988 struct page *page;
989 int bit_nr;
990 wait_queue_entry_t wait;
991};
992
993static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
994{
995 struct wait_page_key *key = arg;
996 struct wait_page_queue *wait_page
997 = container_of(wait, struct wait_page_queue, wait);
998
999 if (wait_page->page != key->page)
1000 return 0;
1001 key->page_match = 1;
1002
1003 if (wait_page->bit_nr != key->bit_nr)
1004 return 0;
1005
1006 /* Stop walking if it's locked */
1007 if (test_bit(key->bit_nr, &key->page->flags))
1008 return -1;
1009
1010 return autoremove_wake_function(wait, mode, sync, key);
1011}
1012
1013static void wake_up_page_bit(struct page *page, int bit_nr)
1014{
1015 wait_queue_head_t *q = page_waitqueue(page);
1016 struct wait_page_key key;
1017 unsigned long flags;
1018 wait_queue_entry_t bookmark;
1019
1020 key.page = page;
1021 key.bit_nr = bit_nr;
1022 key.page_match = 0;
1023
1024 bookmark.flags = 0;
1025 bookmark.private = NULL;
1026 bookmark.func = NULL;
1027 INIT_LIST_HEAD(&bookmark.entry);
1028
1029 spin_lock_irqsave(&q->lock, flags);
1030 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1031
1032 while (bookmark.flags & WQ_FLAG_BOOKMARK) {
1033 /*
1034 * Take a breather from holding the lock,
1035 * allow pages that finish wake up asynchronously
1036 * to acquire the lock and remove themselves
1037 * from wait queue
1038 */
1039 spin_unlock_irqrestore(&q->lock, flags);
1040 cpu_relax();
1041 spin_lock_irqsave(&q->lock, flags);
1042 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1043 }
1044
1045 /*
1046 * It is possible for other pages to have collided on the waitqueue
1047 * hash, so in that case check for a page match. That prevents a long-
1048 * term waiter
1049 *
1050 * It is still possible to miss a case here, when we woke page waiters
1051 * and removed them from the waitqueue, but there are still other
1052 * page waiters.
1053 */
1054 if (!waitqueue_active(q) || !key.page_match) {
1055 ClearPageWaiters(page);
1056 /*
1057 * It's possible to miss clearing Waiters here, when we woke
1058 * our page waiters, but the hashed waitqueue has waiters for
1059 * other pages on it.
1060 *
1061 * That's okay, it's a rare case. The next waker will clear it.
1062 */
1063 }
1064 spin_unlock_irqrestore(&q->lock, flags);
1065}
1066
1067static void wake_up_page(struct page *page, int bit)
1068{
1069 if (!PageWaiters(page))
1070 return;
1071 wake_up_page_bit(page, bit);
1072}
1073
1074static inline int wait_on_page_bit_common(wait_queue_head_t *q,
1075 struct page *page, int bit_nr, int state, bool lock)
1076{
1077 struct wait_page_queue wait_page;
1078 wait_queue_entry_t *wait = &wait_page.wait;
1079 int ret = 0;
1080
1081 init_wait(wait);
1082 wait->flags = lock ? WQ_FLAG_EXCLUSIVE : 0;
1083 wait->func = wake_page_function;
1084 wait_page.page = page;
1085 wait_page.bit_nr = bit_nr;
1086
1087 for (;;) {
1088 spin_lock_irq(&q->lock);
1089
1090 if (likely(list_empty(&wait->entry))) {
1091 __add_wait_queue_entry_tail(q, wait);
1092 SetPageWaiters(page);
1093 }
1094
1095 set_current_state(state);
1096
1097 spin_unlock_irq(&q->lock);
1098
1099 if (likely(test_bit(bit_nr, &page->flags))) {
1100 io_schedule();
1101 }
1102
1103 if (lock) {
1104 if (!test_and_set_bit_lock(bit_nr, &page->flags))
1105 break;
1106 } else {
1107 if (!test_bit(bit_nr, &page->flags))
1108 break;
1109 }
1110
1111 if (unlikely(signal_pending_state(state, current))) {
1112 ret = -EINTR;
1113 break;
1114 }
1115 }
1116
1117 finish_wait(q, wait);
1118
1119 /*
1120 * A signal could leave PageWaiters set. Clearing it here if
1121 * !waitqueue_active would be possible (by open-coding finish_wait),
1122 * but still fail to catch it in the case of wait hash collision. We
1123 * already can fail to clear wait hash collision cases, so don't
1124 * bother with signals either.
1125 */
1126
1127 return ret;
1128}
1129
1130void wait_on_page_bit(struct page *page, int bit_nr)
1131{
1132 wait_queue_head_t *q = page_waitqueue(page);
1133 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
1134}
1135EXPORT_SYMBOL(wait_on_page_bit);
1136
1137int wait_on_page_bit_killable(struct page *page, int bit_nr)
1138{
1139 wait_queue_head_t *q = page_waitqueue(page);
1140 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
1141}
1142EXPORT_SYMBOL(wait_on_page_bit_killable);
1143
1144/**
1145 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1146 * @page: Page defining the wait queue of interest
1147 * @waiter: Waiter to add to the queue
1148 *
1149 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1150 */
1151void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
1152{
1153 wait_queue_head_t *q = page_waitqueue(page);
1154 unsigned long flags;
1155
1156 spin_lock_irqsave(&q->lock, flags);
1157 __add_wait_queue_entry_tail(q, waiter);
1158 SetPageWaiters(page);
1159 spin_unlock_irqrestore(&q->lock, flags);
1160}
1161EXPORT_SYMBOL_GPL(add_page_wait_queue);
1162
1163#ifndef clear_bit_unlock_is_negative_byte
1164
1165/*
1166 * PG_waiters is the high bit in the same byte as PG_lock.
1167 *
1168 * On x86 (and on many other architectures), we can clear PG_lock and
1169 * test the sign bit at the same time. But if the architecture does
1170 * not support that special operation, we just do this all by hand
1171 * instead.
1172 *
1173 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1174 * being cleared, but a memory barrier should be unneccssary since it is
1175 * in the same byte as PG_locked.
1176 */
1177static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
1178{
1179 clear_bit_unlock(nr, mem);
1180 /* smp_mb__after_atomic(); */
1181 return test_bit(PG_waiters, mem);
1182}
1183
1184#endif
1185
1186/**
1187 * unlock_page - unlock a locked page
1188 * @page: the page
1189 *
1190 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
1191 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1192 * mechanism between PageLocked pages and PageWriteback pages is shared.
1193 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1194 *
1195 * Note that this depends on PG_waiters being the sign bit in the byte
1196 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1197 * clear the PG_locked bit and test PG_waiters at the same time fairly
1198 * portably (architectures that do LL/SC can test any bit, while x86 can
1199 * test the sign bit).
1200 */
1201void unlock_page(struct page *page)
1202{
1203 BUILD_BUG_ON(PG_waiters != 7);
1204 page = compound_head(page);
1205 VM_BUG_ON_PAGE(!PageLocked(page), page);
1206 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
1207 wake_up_page_bit(page, PG_locked);
1208}
1209EXPORT_SYMBOL(unlock_page);
1210
1211/**
1212 * end_page_writeback - end writeback against a page
1213 * @page: the page
1214 */
1215void end_page_writeback(struct page *page)
1216{
1217 /*
1218 * TestClearPageReclaim could be used here but it is an atomic
1219 * operation and overkill in this particular case. Failing to
1220 * shuffle a page marked for immediate reclaim is too mild to
1221 * justify taking an atomic operation penalty at the end of
1222 * ever page writeback.
1223 */
1224 if (PageReclaim(page)) {
1225 ClearPageReclaim(page);
1226 rotate_reclaimable_page(page);
1227 }
1228
1229 if (!test_clear_page_writeback(page))
1230 BUG();
1231
1232 smp_mb__after_atomic();
1233 wake_up_page(page, PG_writeback);
1234}
1235EXPORT_SYMBOL(end_page_writeback);
1236
1237/*
1238 * After completing I/O on a page, call this routine to update the page
1239 * flags appropriately
1240 */
1241void page_endio(struct page *page, bool is_write, int err)
1242{
1243 if (!is_write) {
1244 if (!err) {
1245 SetPageUptodate(page);
1246 } else {
1247 ClearPageUptodate(page);
1248 SetPageError(page);
1249 }
1250 unlock_page(page);
1251 } else {
1252 if (err) {
1253 struct address_space *mapping;
1254
1255 SetPageError(page);
1256 mapping = page_mapping(page);
1257 if (mapping)
1258 mapping_set_error(mapping, err);
1259 }
1260 end_page_writeback(page);
1261 }
1262}
1263EXPORT_SYMBOL_GPL(page_endio);
1264
1265/**
1266 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1267 * @__page: the page to lock
1268 */
1269void __lock_page(struct page *__page)
1270{
1271 struct page *page = compound_head(__page);
1272 wait_queue_head_t *q = page_waitqueue(page);
1273 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
1274}
1275EXPORT_SYMBOL(__lock_page);
1276
1277int __lock_page_killable(struct page *__page)
1278{
1279 struct page *page = compound_head(__page);
1280 wait_queue_head_t *q = page_waitqueue(page);
1281 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
1282}
1283EXPORT_SYMBOL_GPL(__lock_page_killable);
1284
1285/*
1286 * Return values:
1287 * 1 - page is locked; mmap_sem is still held.
1288 * 0 - page is not locked.
1289 * mmap_sem has been released (up_read()), unless flags had both
1290 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1291 * which case mmap_sem is still held.
1292 *
1293 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1294 * with the page locked and the mmap_sem unperturbed.
1295 */
1296int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1297 unsigned int flags)
1298{
1299 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1300 /*
1301 * CAUTION! In this case, mmap_sem is not released
1302 * even though return 0.
1303 */
1304 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1305 return 0;
1306
1307 up_read(&mm->mmap_sem);
1308 if (flags & FAULT_FLAG_KILLABLE)
1309 wait_on_page_locked_killable(page);
1310 else
1311 wait_on_page_locked(page);
1312 return 0;
1313 } else {
1314 if (flags & FAULT_FLAG_KILLABLE) {
1315 int ret;
1316
1317 ret = __lock_page_killable(page);
1318 if (ret) {
1319 up_read(&mm->mmap_sem);
1320 return 0;
1321 }
1322 } else
1323 __lock_page(page);
1324 return 1;
1325 }
1326}
1327
1328/**
1329 * page_cache_next_hole - find the next hole (not-present entry)
1330 * @mapping: mapping
1331 * @index: index
1332 * @max_scan: maximum range to search
1333 *
1334 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1335 * lowest indexed hole.
1336 *
1337 * Returns: the index of the hole if found, otherwise returns an index
1338 * outside of the set specified (in which case 'return - index >=
1339 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1340 * be returned.
1341 *
1342 * page_cache_next_hole may be called under rcu_read_lock. However,
1343 * like radix_tree_gang_lookup, this will not atomically search a
1344 * snapshot of the tree at a single point in time. For example, if a
1345 * hole is created at index 5, then subsequently a hole is created at
1346 * index 10, page_cache_next_hole covering both indexes may return 10
1347 * if called under rcu_read_lock.
1348 */
1349pgoff_t page_cache_next_hole(struct address_space *mapping,
1350 pgoff_t index, unsigned long max_scan)
1351{
1352 unsigned long i;
1353
1354 for (i = 0; i < max_scan; i++) {
1355 struct page *page;
1356
1357 page = radix_tree_lookup(&mapping->i_pages, index);
1358 if (!page || radix_tree_exceptional_entry(page))
1359 break;
1360 index++;
1361 if (index == 0)
1362 break;
1363 }
1364
1365 return index;
1366}
1367EXPORT_SYMBOL(page_cache_next_hole);
1368
1369/**
1370 * page_cache_prev_hole - find the prev hole (not-present entry)
1371 * @mapping: mapping
1372 * @index: index
1373 * @max_scan: maximum range to search
1374 *
1375 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1376 * the first hole.
1377 *
1378 * Returns: the index of the hole if found, otherwise returns an index
1379 * outside of the set specified (in which case 'index - return >=
1380 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1381 * will be returned.
1382 *
1383 * page_cache_prev_hole may be called under rcu_read_lock. However,
1384 * like radix_tree_gang_lookup, this will not atomically search a
1385 * snapshot of the tree at a single point in time. For example, if a
1386 * hole is created at index 10, then subsequently a hole is created at
1387 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1388 * called under rcu_read_lock.
1389 */
1390pgoff_t page_cache_prev_hole(struct address_space *mapping,
1391 pgoff_t index, unsigned long max_scan)
1392{
1393 unsigned long i;
1394
1395 for (i = 0; i < max_scan; i++) {
1396 struct page *page;
1397
1398 page = radix_tree_lookup(&mapping->i_pages, index);
1399 if (!page || radix_tree_exceptional_entry(page))
1400 break;
1401 index--;
1402 if (index == ULONG_MAX)
1403 break;
1404 }
1405
1406 return index;
1407}
1408EXPORT_SYMBOL(page_cache_prev_hole);
1409
1410/**
1411 * find_get_entry - find and get a page cache entry
1412 * @mapping: the address_space to search
1413 * @offset: the page cache index
1414 *
1415 * Looks up the page cache slot at @mapping & @offset. If there is a
1416 * page cache page, it is returned with an increased refcount.
1417 *
1418 * If the slot holds a shadow entry of a previously evicted page, or a
1419 * swap entry from shmem/tmpfs, it is returned.
1420 *
1421 * Otherwise, %NULL is returned.
1422 */
1423struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1424{
1425 void **pagep;
1426 struct page *head, *page;
1427
1428 rcu_read_lock();
1429repeat:
1430 page = NULL;
1431 pagep = radix_tree_lookup_slot(&mapping->i_pages, offset);
1432 if (pagep) {
1433 page = radix_tree_deref_slot(pagep);
1434 if (unlikely(!page))
1435 goto out;
1436 if (radix_tree_exception(page)) {
1437 if (radix_tree_deref_retry(page))
1438 goto repeat;
1439 /*
1440 * A shadow entry of a recently evicted page,
1441 * or a swap entry from shmem/tmpfs. Return
1442 * it without attempting to raise page count.
1443 */
1444 goto out;
1445 }
1446
1447 head = compound_head(page);
1448 if (!page_cache_get_speculative(head))
1449 goto repeat;
1450
1451 /* The page was split under us? */
1452 if (compound_head(page) != head) {
1453 put_page(head);
1454 goto repeat;
1455 }
1456
1457 /*
1458 * Has the page moved?
1459 * This is part of the lockless pagecache protocol. See
1460 * include/linux/pagemap.h for details.
1461 */
1462 if (unlikely(page != *pagep)) {
1463 put_page(head);
1464 goto repeat;
1465 }
1466 }
1467out:
1468 rcu_read_unlock();
1469
1470 return page;
1471}
1472EXPORT_SYMBOL(find_get_entry);
1473
1474/**
1475 * find_lock_entry - locate, pin and lock a page cache entry
1476 * @mapping: the address_space to search
1477 * @offset: the page cache index
1478 *
1479 * Looks up the page cache slot at @mapping & @offset. If there is a
1480 * page cache page, it is returned locked and with an increased
1481 * refcount.
1482 *
1483 * If the slot holds a shadow entry of a previously evicted page, or a
1484 * swap entry from shmem/tmpfs, it is returned.
1485 *
1486 * Otherwise, %NULL is returned.
1487 *
1488 * find_lock_entry() may sleep.
1489 */
1490struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1491{
1492 struct page *page;
1493
1494repeat:
1495 page = find_get_entry(mapping, offset);
1496 if (page && !radix_tree_exception(page)) {
1497 lock_page(page);
1498 /* Has the page been truncated? */
1499 if (unlikely(page_mapping(page) != mapping)) {
1500 unlock_page(page);
1501 put_page(page);
1502 goto repeat;
1503 }
1504 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
1505 }
1506 return page;
1507}
1508EXPORT_SYMBOL(find_lock_entry);
1509
1510/**
1511 * pagecache_get_page - find and get a page reference
1512 * @mapping: the address_space to search
1513 * @offset: the page index
1514 * @fgp_flags: PCG flags
1515 * @gfp_mask: gfp mask to use for the page cache data page allocation
1516 *
1517 * Looks up the page cache slot at @mapping & @offset.
1518 *
1519 * PCG flags modify how the page is returned.
1520 *
1521 * @fgp_flags can be:
1522 *
1523 * - FGP_ACCESSED: the page will be marked accessed
1524 * - FGP_LOCK: Page is return locked
1525 * - FGP_CREAT: If page is not present then a new page is allocated using
1526 * @gfp_mask and added to the page cache and the VM's LRU
1527 * list. The page is returned locked and with an increased
1528 * refcount. Otherwise, NULL is returned.
1529 *
1530 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1531 * if the GFP flags specified for FGP_CREAT are atomic.
1532 *
1533 * If there is a page cache page, it is returned with an increased refcount.
1534 */
1535struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1536 int fgp_flags, gfp_t gfp_mask)
1537{
1538 struct page *page;
1539
1540repeat:
1541 page = find_get_entry(mapping, offset);
1542 if (radix_tree_exceptional_entry(page))
1543 page = NULL;
1544 if (!page)
1545 goto no_page;
1546
1547 if (fgp_flags & FGP_LOCK) {
1548 if (fgp_flags & FGP_NOWAIT) {
1549 if (!trylock_page(page)) {
1550 put_page(page);
1551 return NULL;
1552 }
1553 } else {
1554 lock_page(page);
1555 }
1556
1557 /* Has the page been truncated? */
1558 if (unlikely(page->mapping != mapping)) {
1559 unlock_page(page);
1560 put_page(page);
1561 goto repeat;
1562 }
1563 VM_BUG_ON_PAGE(page->index != offset, page);
1564 }
1565
1566 if (page && (fgp_flags & FGP_ACCESSED))
1567 mark_page_accessed(page);
1568
1569no_page:
1570 if (!page && (fgp_flags & FGP_CREAT)) {
1571 int err;
1572 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1573 gfp_mask |= __GFP_WRITE;
1574 if (fgp_flags & FGP_NOFS)
1575 gfp_mask &= ~__GFP_FS;
1576
1577 page = __page_cache_alloc(gfp_mask);
1578 if (!page)
1579 return NULL;
1580
1581 if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
1582 fgp_flags |= FGP_LOCK;
1583
1584 /* Init accessed so avoid atomic mark_page_accessed later */
1585 if (fgp_flags & FGP_ACCESSED)
1586 __SetPageReferenced(page);
1587
1588 err = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
1589 if (unlikely(err)) {
1590 put_page(page);
1591 page = NULL;
1592 if (err == -EEXIST)
1593 goto repeat;
1594 }
1595 }
1596
1597 return page;
1598}
1599EXPORT_SYMBOL(pagecache_get_page);
1600
1601/**
1602 * find_get_entries - gang pagecache lookup
1603 * @mapping: The address_space to search
1604 * @start: The starting page cache index
1605 * @nr_entries: The maximum number of entries
1606 * @entries: Where the resulting entries are placed
1607 * @indices: The cache indices corresponding to the entries in @entries
1608 *
1609 * find_get_entries() will search for and return a group of up to
1610 * @nr_entries entries in the mapping. The entries are placed at
1611 * @entries. find_get_entries() takes a reference against any actual
1612 * pages it returns.
1613 *
1614 * The search returns a group of mapping-contiguous page cache entries
1615 * with ascending indexes. There may be holes in the indices due to
1616 * not-present pages.
1617 *
1618 * Any shadow entries of evicted pages, or swap entries from
1619 * shmem/tmpfs, are included in the returned array.
1620 *
1621 * find_get_entries() returns the number of pages and shadow entries
1622 * which were found.
1623 */
1624unsigned find_get_entries(struct address_space *mapping,
1625 pgoff_t start, unsigned int nr_entries,
1626 struct page **entries, pgoff_t *indices)
1627{
1628 void **slot;
1629 unsigned int ret = 0;
1630 struct radix_tree_iter iter;
1631
1632 if (!nr_entries)
1633 return 0;
1634
1635 rcu_read_lock();
1636 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
1637 struct page *head, *page;
1638repeat:
1639 page = radix_tree_deref_slot(slot);
1640 if (unlikely(!page))
1641 continue;
1642 if (radix_tree_exception(page)) {
1643 if (radix_tree_deref_retry(page)) {
1644 slot = radix_tree_iter_retry(&iter);
1645 continue;
1646 }
1647 /*
1648 * A shadow entry of a recently evicted page, a swap
1649 * entry from shmem/tmpfs or a DAX entry. Return it
1650 * without attempting to raise page count.
1651 */
1652 goto export;
1653 }
1654
1655 head = compound_head(page);
1656 if (!page_cache_get_speculative(head))
1657 goto repeat;
1658
1659 /* The page was split under us? */
1660 if (compound_head(page) != head) {
1661 put_page(head);
1662 goto repeat;
1663 }
1664
1665 /* Has the page moved? */
1666 if (unlikely(page != *slot)) {
1667 put_page(head);
1668 goto repeat;
1669 }
1670export:
1671 indices[ret] = iter.index;
1672 entries[ret] = page;
1673 if (++ret == nr_entries)
1674 break;
1675 }
1676 rcu_read_unlock();
1677 return ret;
1678}
1679
1680/**
1681 * find_get_pages_range - gang pagecache lookup
1682 * @mapping: The address_space to search
1683 * @start: The starting page index
1684 * @end: The final page index (inclusive)
1685 * @nr_pages: The maximum number of pages
1686 * @pages: Where the resulting pages are placed
1687 *
1688 * find_get_pages_range() will search for and return a group of up to @nr_pages
1689 * pages in the mapping starting at index @start and up to index @end
1690 * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
1691 * a reference against the returned pages.
1692 *
1693 * The search returns a group of mapping-contiguous pages with ascending
1694 * indexes. There may be holes in the indices due to not-present pages.
1695 * We also update @start to index the next page for the traversal.
1696 *
1697 * find_get_pages_range() returns the number of pages which were found. If this
1698 * number is smaller than @nr_pages, the end of specified range has been
1699 * reached.
1700 */
1701unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
1702 pgoff_t end, unsigned int nr_pages,
1703 struct page **pages)
1704{
1705 struct radix_tree_iter iter;
1706 void **slot;
1707 unsigned ret = 0;
1708
1709 if (unlikely(!nr_pages))
1710 return 0;
1711
1712 rcu_read_lock();
1713 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, *start) {
1714 struct page *head, *page;
1715
1716 if (iter.index > end)
1717 break;
1718repeat:
1719 page = radix_tree_deref_slot(slot);
1720 if (unlikely(!page))
1721 continue;
1722
1723 if (radix_tree_exception(page)) {
1724 if (radix_tree_deref_retry(page)) {
1725 slot = radix_tree_iter_retry(&iter);
1726 continue;
1727 }
1728 /*
1729 * A shadow entry of a recently evicted page,
1730 * or a swap entry from shmem/tmpfs. Skip
1731 * over it.
1732 */
1733 continue;
1734 }
1735
1736 head = compound_head(page);
1737 if (!page_cache_get_speculative(head))
1738 goto repeat;
1739
1740 /* The page was split under us? */
1741 if (compound_head(page) != head) {
1742 put_page(head);
1743 goto repeat;
1744 }
1745
1746 /* Has the page moved? */
1747 if (unlikely(page != *slot)) {
1748 put_page(head);
1749 goto repeat;
1750 }
1751
1752 pages[ret] = page;
1753 if (++ret == nr_pages) {
1754 *start = pages[ret - 1]->index + 1;
1755 goto out;
1756 }
1757 }
1758
1759 /*
1760 * We come here when there is no page beyond @end. We take care to not
1761 * overflow the index @start as it confuses some of the callers. This
1762 * breaks the iteration when there is page at index -1 but that is
1763 * already broken anyway.
1764 */
1765 if (end == (pgoff_t)-1)
1766 *start = (pgoff_t)-1;
1767 else
1768 *start = end + 1;
1769out:
1770 rcu_read_unlock();
1771
1772 return ret;
1773}
1774
1775/**
1776 * find_get_pages_contig - gang contiguous pagecache lookup
1777 * @mapping: The address_space to search
1778 * @index: The starting page index
1779 * @nr_pages: The maximum number of pages
1780 * @pages: Where the resulting pages are placed
1781 *
1782 * find_get_pages_contig() works exactly like find_get_pages(), except
1783 * that the returned number of pages are guaranteed to be contiguous.
1784 *
1785 * find_get_pages_contig() returns the number of pages which were found.
1786 */
1787unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1788 unsigned int nr_pages, struct page **pages)
1789{
1790 struct radix_tree_iter iter;
1791 void **slot;
1792 unsigned int ret = 0;
1793
1794 if (unlikely(!nr_pages))
1795 return 0;
1796
1797 rcu_read_lock();
1798 radix_tree_for_each_contig(slot, &mapping->i_pages, &iter, index) {
1799 struct page *head, *page;
1800repeat:
1801 page = radix_tree_deref_slot(slot);
1802 /* The hole, there no reason to continue */
1803 if (unlikely(!page))
1804 break;
1805
1806 if (radix_tree_exception(page)) {
1807 if (radix_tree_deref_retry(page)) {
1808 slot = radix_tree_iter_retry(&iter);
1809 continue;
1810 }
1811 /*
1812 * A shadow entry of a recently evicted page,
1813 * or a swap entry from shmem/tmpfs. Stop
1814 * looking for contiguous pages.
1815 */
1816 break;
1817 }
1818
1819 head = compound_head(page);
1820 if (!page_cache_get_speculative(head))
1821 goto repeat;
1822
1823 /* The page was split under us? */
1824 if (compound_head(page) != head) {
1825 put_page(head);
1826 goto repeat;
1827 }
1828
1829 /* Has the page moved? */
1830 if (unlikely(page != *slot)) {
1831 put_page(head);
1832 goto repeat;
1833 }
1834
1835 /*
1836 * must check mapping and index after taking the ref.
1837 * otherwise we can get both false positives and false
1838 * negatives, which is just confusing to the caller.
1839 */
1840 if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
1841 put_page(page);
1842 break;
1843 }
1844
1845 pages[ret] = page;
1846 if (++ret == nr_pages)
1847 break;
1848 }
1849 rcu_read_unlock();
1850 return ret;
1851}
1852EXPORT_SYMBOL(find_get_pages_contig);
1853
1854/**
1855 * find_get_pages_range_tag - find and return pages in given range matching @tag
1856 * @mapping: the address_space to search
1857 * @index: the starting page index
1858 * @end: The final page index (inclusive)
1859 * @tag: the tag index
1860 * @nr_pages: the maximum number of pages
1861 * @pages: where the resulting pages are placed
1862 *
1863 * Like find_get_pages, except we only return pages which are tagged with
1864 * @tag. We update @index to index the next page for the traversal.
1865 */
1866unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
1867 pgoff_t end, int tag, unsigned int nr_pages,
1868 struct page **pages)
1869{
1870 struct radix_tree_iter iter;
1871 void **slot;
1872 unsigned ret = 0;
1873
1874 if (unlikely(!nr_pages))
1875 return 0;
1876
1877 rcu_read_lock();
1878 radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, *index, tag) {
1879 struct page *head, *page;
1880
1881 if (iter.index > end)
1882 break;
1883repeat:
1884 page = radix_tree_deref_slot(slot);
1885 if (unlikely(!page))
1886 continue;
1887
1888 if (radix_tree_exception(page)) {
1889 if (radix_tree_deref_retry(page)) {
1890 slot = radix_tree_iter_retry(&iter);
1891 continue;
1892 }
1893 /*
1894 * A shadow entry of a recently evicted page.
1895 *
1896 * Those entries should never be tagged, but
1897 * this tree walk is lockless and the tags are
1898 * looked up in bulk, one radix tree node at a
1899 * time, so there is a sizable window for page
1900 * reclaim to evict a page we saw tagged.
1901 *
1902 * Skip over it.
1903 */
1904 continue;
1905 }
1906
1907 head = compound_head(page);
1908 if (!page_cache_get_speculative(head))
1909 goto repeat;
1910
1911 /* The page was split under us? */
1912 if (compound_head(page) != head) {
1913 put_page(head);
1914 goto repeat;
1915 }
1916
1917 /* Has the page moved? */
1918 if (unlikely(page != *slot)) {
1919 put_page(head);
1920 goto repeat;
1921 }
1922
1923 pages[ret] = page;
1924 if (++ret == nr_pages) {
1925 *index = pages[ret - 1]->index + 1;
1926 goto out;
1927 }
1928 }
1929
1930 /*
1931 * We come here when we got at @end. We take care to not overflow the
1932 * index @index as it confuses some of the callers. This breaks the
1933 * iteration when there is page at index -1 but that is already broken
1934 * anyway.
1935 */
1936 if (end == (pgoff_t)-1)
1937 *index = (pgoff_t)-1;
1938 else
1939 *index = end + 1;
1940out:
1941 rcu_read_unlock();
1942
1943 return ret;
1944}
1945EXPORT_SYMBOL(find_get_pages_range_tag);
1946
1947/**
1948 * find_get_entries_tag - find and return entries that match @tag
1949 * @mapping: the address_space to search
1950 * @start: the starting page cache index
1951 * @tag: the tag index
1952 * @nr_entries: the maximum number of entries
1953 * @entries: where the resulting entries are placed
1954 * @indices: the cache indices corresponding to the entries in @entries
1955 *
1956 * Like find_get_entries, except we only return entries which are tagged with
1957 * @tag.
1958 */
1959unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
1960 int tag, unsigned int nr_entries,
1961 struct page **entries, pgoff_t *indices)
1962{
1963 void **slot;
1964 unsigned int ret = 0;
1965 struct radix_tree_iter iter;
1966
1967 if (!nr_entries)
1968 return 0;
1969
1970 rcu_read_lock();
1971 radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, start, tag) {
1972 struct page *head, *page;
1973repeat:
1974 page = radix_tree_deref_slot(slot);
1975 if (unlikely(!page))
1976 continue;
1977 if (radix_tree_exception(page)) {
1978 if (radix_tree_deref_retry(page)) {
1979 slot = radix_tree_iter_retry(&iter);
1980 continue;
1981 }
1982
1983 /*
1984 * A shadow entry of a recently evicted page, a swap
1985 * entry from shmem/tmpfs or a DAX entry. Return it
1986 * without attempting to raise page count.
1987 */
1988 goto export;
1989 }
1990
1991 head = compound_head(page);
1992 if (!page_cache_get_speculative(head))
1993 goto repeat;
1994
1995 /* The page was split under us? */
1996 if (compound_head(page) != head) {
1997 put_page(head);
1998 goto repeat;
1999 }
2000
2001 /* Has the page moved? */
2002 if (unlikely(page != *slot)) {
2003 put_page(head);
2004 goto repeat;
2005 }
2006export:
2007 indices[ret] = iter.index;
2008 entries[ret] = page;
2009 if (++ret == nr_entries)
2010 break;
2011 }
2012 rcu_read_unlock();
2013 return ret;
2014}
2015EXPORT_SYMBOL(find_get_entries_tag);
2016
2017/*
2018 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
2019 * a _large_ part of the i/o request. Imagine the worst scenario:
2020 *
2021 * ---R__________________________________________B__________
2022 * ^ reading here ^ bad block(assume 4k)
2023 *
2024 * read(R) => miss => readahead(R...B) => media error => frustrating retries
2025 * => failing the whole request => read(R) => read(R+1) =>
2026 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
2027 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
2028 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
2029 *
2030 * It is going insane. Fix it by quickly scaling down the readahead size.
2031 */
2032static void shrink_readahead_size_eio(struct file *filp,
2033 struct file_ra_state *ra)
2034{
2035 ra->ra_pages /= 4;
2036}
2037
2038/**
2039 * generic_file_buffered_read - generic file read routine
2040 * @iocb: the iocb to read
2041 * @iter: data destination
2042 * @written: already copied
2043 *
2044 * This is a generic file read routine, and uses the
2045 * mapping->a_ops->readpage() function for the actual low-level stuff.
2046 *
2047 * This is really ugly. But the goto's actually try to clarify some
2048 * of the logic when it comes to error handling etc.
2049 */
2050static ssize_t generic_file_buffered_read(struct kiocb *iocb,
2051 struct iov_iter *iter, ssize_t written)
2052{
2053 struct file *filp = iocb->ki_filp;
2054 struct address_space *mapping = filp->f_mapping;
2055 struct inode *inode = mapping->host;
2056 struct file_ra_state *ra = &filp->f_ra;
2057 loff_t *ppos = &iocb->ki_pos;
2058 pgoff_t index;
2059 pgoff_t last_index;
2060 pgoff_t prev_index;
2061 unsigned long offset; /* offset into pagecache page */
2062 unsigned int prev_offset;
2063 int error = 0;
2064
2065 if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
2066 return 0;
2067 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
2068
2069 index = *ppos >> PAGE_SHIFT;
2070 prev_index = ra->prev_pos >> PAGE_SHIFT;
2071 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
2072 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
2073 offset = *ppos & ~PAGE_MASK;
2074
2075 for (;;) {
2076 struct page *page;
2077 pgoff_t end_index;
2078 loff_t isize;
2079 unsigned long nr, ret;
2080
2081 cond_resched();
2082find_page:
2083 if (fatal_signal_pending(current)) {
2084 error = -EINTR;
2085 goto out;
2086 }
2087
2088 page = find_get_page(mapping, index);
2089 if (!page) {
2090 if (iocb->ki_flags & IOCB_NOWAIT)
2091 goto would_block;
2092 page_cache_sync_readahead(mapping,
2093 ra, filp,
2094 index, last_index - index);
2095 page = find_get_page(mapping, index);
2096 if (unlikely(page == NULL))
2097 goto no_cached_page;
2098 }
2099 if (PageReadahead(page)) {
2100 page_cache_async_readahead(mapping,
2101 ra, filp, page,
2102 index, last_index - index);
2103 }
2104 if (!PageUptodate(page)) {
2105 if (iocb->ki_flags & IOCB_NOWAIT) {
2106 put_page(page);
2107 goto would_block;
2108 }
2109
2110 /*
2111 * See comment in do_read_cache_page on why
2112 * wait_on_page_locked is used to avoid unnecessarily
2113 * serialisations and why it's safe.
2114 */
2115 error = wait_on_page_locked_killable(page);
2116 if (unlikely(error))
2117 goto readpage_error;
2118 if (PageUptodate(page))
2119 goto page_ok;
2120
2121 if (inode->i_blkbits == PAGE_SHIFT ||
2122 !mapping->a_ops->is_partially_uptodate)
2123 goto page_not_up_to_date;
2124 /* pipes can't handle partially uptodate pages */
2125 if (unlikely(iter->type & ITER_PIPE))
2126 goto page_not_up_to_date;
2127 if (!trylock_page(page))
2128 goto page_not_up_to_date;
2129 /* Did it get truncated before we got the lock? */
2130 if (!page->mapping)
2131 goto page_not_up_to_date_locked;
2132 if (!mapping->a_ops->is_partially_uptodate(page,
2133 offset, iter->count))
2134 goto page_not_up_to_date_locked;
2135 unlock_page(page);
2136 }
2137page_ok:
2138 /*
2139 * i_size must be checked after we know the page is Uptodate.
2140 *
2141 * Checking i_size after the check allows us to calculate
2142 * the correct value for "nr", which means the zero-filled
2143 * part of the page is not copied back to userspace (unless
2144 * another truncate extends the file - this is desired though).
2145 */
2146
2147 isize = i_size_read(inode);
2148 end_index = (isize - 1) >> PAGE_SHIFT;
2149 if (unlikely(!isize || index > end_index)) {
2150 put_page(page);
2151 goto out;
2152 }
2153
2154 /* nr is the maximum number of bytes to copy from this page */
2155 nr = PAGE_SIZE;
2156 if (index == end_index) {
2157 nr = ((isize - 1) & ~PAGE_MASK) + 1;
2158 if (nr <= offset) {
2159 put_page(page);
2160 goto out;
2161 }
2162 }
2163 nr = nr - offset;
2164
2165 /* If users can be writing to this page using arbitrary
2166 * virtual addresses, take care about potential aliasing
2167 * before reading the page on the kernel side.
2168 */
2169 if (mapping_writably_mapped(mapping))
2170 flush_dcache_page(page);
2171
2172 /*
2173 * When a sequential read accesses a page several times,
2174 * only mark it as accessed the first time.
2175 */
2176 if (prev_index != index || offset != prev_offset)
2177 mark_page_accessed(page);
2178 prev_index = index;
2179
2180 /*
2181 * Ok, we have the page, and it's up-to-date, so
2182 * now we can copy it to user space...
2183 */
2184
2185 ret = copy_page_to_iter(page, offset, nr, iter);
2186 offset += ret;
2187 index += offset >> PAGE_SHIFT;
2188 offset &= ~PAGE_MASK;
2189 prev_offset = offset;
2190
2191 put_page(page);
2192 written += ret;
2193 if (!iov_iter_count(iter))
2194 goto out;
2195 if (ret < nr) {
2196 error = -EFAULT;
2197 goto out;
2198 }
2199 continue;
2200
2201page_not_up_to_date:
2202 /* Get exclusive access to the page ... */
2203 error = lock_page_killable(page);
2204 if (unlikely(error))
2205 goto readpage_error;
2206
2207page_not_up_to_date_locked:
2208 /* Did it get truncated before we got the lock? */
2209 if (!page->mapping) {
2210 unlock_page(page);
2211 put_page(page);
2212 continue;
2213 }
2214
2215 /* Did somebody else fill it already? */
2216 if (PageUptodate(page)) {
2217 unlock_page(page);
2218 goto page_ok;
2219 }
2220
2221readpage:
2222 /*
2223 * A previous I/O error may have been due to temporary
2224 * failures, eg. multipath errors.
2225 * PG_error will be set again if readpage fails.
2226 */
2227 ClearPageError(page);
2228 /* Start the actual read. The read will unlock the page. */
2229 error = mapping->a_ops->readpage(filp, page);
2230
2231 if (unlikely(error)) {
2232 if (error == AOP_TRUNCATED_PAGE) {
2233 put_page(page);
2234 error = 0;
2235 goto find_page;
2236 }
2237 goto readpage_error;
2238 }
2239
2240 if (!PageUptodate(page)) {
2241 error = lock_page_killable(page);
2242 if (unlikely(error))
2243 goto readpage_error;
2244 if (!PageUptodate(page)) {
2245 if (page->mapping == NULL) {
2246 /*
2247 * invalidate_mapping_pages got it
2248 */
2249 unlock_page(page);
2250 put_page(page);
2251 goto find_page;
2252 }
2253 unlock_page(page);
2254 shrink_readahead_size_eio(filp, ra);
2255 error = -EIO;
2256 goto readpage_error;
2257 }
2258 unlock_page(page);
2259 }
2260
2261 goto page_ok;
2262
2263readpage_error:
2264 /* UHHUH! A synchronous read error occurred. Report it */
2265 put_page(page);
2266 goto out;
2267
2268no_cached_page:
2269 /*
2270 * Ok, it wasn't cached, so we need to create a new
2271 * page..
2272 */
2273 page = page_cache_alloc(mapping);
2274 if (!page) {
2275 error = -ENOMEM;
2276 goto out;
2277 }
2278 error = add_to_page_cache_lru(page, mapping, index,
2279 mapping_gfp_constraint(mapping, GFP_KERNEL));
2280 if (error) {
2281 put_page(page);
2282 if (error == -EEXIST) {
2283 error = 0;
2284 goto find_page;
2285 }
2286 goto out;
2287 }
2288 goto readpage;
2289 }
2290
2291would_block:
2292 error = -EAGAIN;
2293out:
2294 ra->prev_pos = prev_index;
2295 ra->prev_pos <<= PAGE_SHIFT;
2296 ra->prev_pos |= prev_offset;
2297
2298 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
2299 file_accessed(filp);
2300 return written ? written : error;
2301}
2302
2303/**
2304 * generic_file_read_iter - generic filesystem read routine
2305 * @iocb: kernel I/O control block
2306 * @iter: destination for the data read
2307 *
2308 * This is the "read_iter()" routine for all filesystems
2309 * that can use the page cache directly.
2310 */
2311ssize_t
2312generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2313{
2314 size_t count = iov_iter_count(iter);
2315 ssize_t retval = 0;
2316
2317 if (!count)
2318 goto out; /* skip atime */
2319
2320 if (iocb->ki_flags & IOCB_DIRECT) {
2321 struct file *file = iocb->ki_filp;
2322 struct address_space *mapping = file->f_mapping;
2323 struct inode *inode = mapping->host;
2324 loff_t size;
2325
2326 size = i_size_read(inode);
2327 if (iocb->ki_flags & IOCB_NOWAIT) {
2328 if (filemap_range_has_page(mapping, iocb->ki_pos,
2329 iocb->ki_pos + count - 1))
2330 return -EAGAIN;
2331 } else {
2332 retval = filemap_write_and_wait_range(mapping,
2333 iocb->ki_pos,
2334 iocb->ki_pos + count - 1);
2335 if (retval < 0)
2336 goto out;
2337 }
2338
2339 file_accessed(file);
2340
2341 retval = mapping->a_ops->direct_IO(iocb, iter);
2342 if (retval >= 0) {
2343 iocb->ki_pos += retval;
2344 count -= retval;
2345 }
2346 iov_iter_revert(iter, count - iov_iter_count(iter));
2347
2348 /*
2349 * Btrfs can have a short DIO read if we encounter
2350 * compressed extents, so if there was an error, or if
2351 * we've already read everything we wanted to, or if
2352 * there was a short read because we hit EOF, go ahead
2353 * and return. Otherwise fallthrough to buffered io for
2354 * the rest of the read. Buffered reads will not work for
2355 * DAX files, so don't bother trying.
2356 */
2357 if (retval < 0 || !count || iocb->ki_pos >= size ||
2358 IS_DAX(inode))
2359 goto out;
2360 }
2361
2362 retval = generic_file_buffered_read(iocb, iter, retval);
2363out:
2364 return retval;
2365}
2366EXPORT_SYMBOL(generic_file_read_iter);
2367
2368#ifdef CONFIG_MMU
2369/**
2370 * page_cache_read - adds requested page to the page cache if not already there
2371 * @file: file to read
2372 * @offset: page index
2373 * @gfp_mask: memory allocation flags
2374 *
2375 * This adds the requested page to the page cache if it isn't already there,
2376 * and schedules an I/O to read in its contents from disk.
2377 */
2378static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
2379{
2380 struct address_space *mapping = file->f_mapping;
2381 struct page *page;
2382 int ret;
2383
2384 do {
2385 page = __page_cache_alloc(gfp_mask);
2386 if (!page)
2387 return -ENOMEM;
2388
2389 ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
2390 if (ret == 0)
2391 ret = mapping->a_ops->readpage(file, page);
2392 else if (ret == -EEXIST)
2393 ret = 0; /* losing race to add is OK */
2394
2395 put_page(page);
2396
2397 } while (ret == AOP_TRUNCATED_PAGE);
2398
2399 return ret;
2400}
2401
2402#define MMAP_LOTSAMISS (100)
2403
2404/*
2405 * Synchronous readahead happens when we don't even find
2406 * a page in the page cache at all.
2407 */
2408static void do_sync_mmap_readahead(struct vm_area_struct *vma,
2409 struct file_ra_state *ra,
2410 struct file *file,
2411 pgoff_t offset)
2412{
2413 struct address_space *mapping = file->f_mapping;
2414
2415 /* If we don't want any read-ahead, don't bother */
2416 if (vma->vm_flags & VM_RAND_READ)
2417 return;
2418 if (!ra->ra_pages)
2419 return;
2420
2421 if (vma->vm_flags & VM_SEQ_READ) {
2422 page_cache_sync_readahead(mapping, ra, file, offset,
2423 ra->ra_pages);
2424 return;
2425 }
2426
2427 /* Avoid banging the cache line if not needed */
2428 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
2429 ra->mmap_miss++;
2430
2431 /*
2432 * Do we miss much more than hit in this file? If so,
2433 * stop bothering with read-ahead. It will only hurt.
2434 */
2435 if (ra->mmap_miss > MMAP_LOTSAMISS)
2436 return;
2437
2438 /*
2439 * mmap read-around
2440 */
2441 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
2442 ra->size = ra->ra_pages;
2443 ra->async_size = ra->ra_pages / 4;
2444 ra_submit(ra, mapping, file);
2445}
2446
2447/*
2448 * Asynchronous readahead happens when we find the page and PG_readahead,
2449 * so we want to possibly extend the readahead further..
2450 */
2451static void do_async_mmap_readahead(struct vm_area_struct *vma,
2452 struct file_ra_state *ra,
2453 struct file *file,
2454 struct page *page,
2455 pgoff_t offset)
2456{
2457 struct address_space *mapping = file->f_mapping;
2458
2459 /* If we don't want any read-ahead, don't bother */
2460 if (vma->vm_flags & VM_RAND_READ)
2461 return;
2462 if (ra->mmap_miss > 0)
2463 ra->mmap_miss--;
2464 if (PageReadahead(page))
2465 page_cache_async_readahead(mapping, ra, file,
2466 page, offset, ra->ra_pages);
2467}
2468
2469/**
2470 * filemap_fault - read in file data for page fault handling
2471 * @vmf: struct vm_fault containing details of the fault
2472 *
2473 * filemap_fault() is invoked via the vma operations vector for a
2474 * mapped memory region to read in file data during a page fault.
2475 *
2476 * The goto's are kind of ugly, but this streamlines the normal case of having
2477 * it in the page cache, and handles the special cases reasonably without
2478 * having a lot of duplicated code.
2479 *
2480 * vma->vm_mm->mmap_sem must be held on entry.
2481 *
2482 * If our return value has VM_FAULT_RETRY set, it's because
2483 * lock_page_or_retry() returned 0.
2484 * The mmap_sem has usually been released in this case.
2485 * See __lock_page_or_retry() for the exception.
2486 *
2487 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2488 * has not been released.
2489 *
2490 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2491 */
2492int filemap_fault(struct vm_fault *vmf)
2493{
2494 int error;
2495 struct file *file = vmf->vma->vm_file;
2496 struct address_space *mapping = file->f_mapping;
2497 struct file_ra_state *ra = &file->f_ra;
2498 struct inode *inode = mapping->host;
2499 pgoff_t offset = vmf->pgoff;
2500 pgoff_t max_off;
2501 struct page *page;
2502 int ret = 0;
2503
2504 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2505 if (unlikely(offset >= max_off))
2506 return VM_FAULT_SIGBUS;
2507
2508 /*
2509 * Do we have something in the page cache already?
2510 */
2511 page = find_get_page(mapping, offset);
2512 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2513 /*
2514 * We found the page, so try async readahead before
2515 * waiting for the lock.
2516 */
2517 do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
2518 } else if (!page) {
2519 /* No page in the page cache at all */
2520 do_sync_mmap_readahead(vmf->vma, ra, file, offset);
2521 count_vm_event(PGMAJFAULT);
2522 count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
2523 ret = VM_FAULT_MAJOR;
2524retry_find:
2525 page = find_get_page(mapping, offset);
2526 if (!page)
2527 goto no_cached_page;
2528 }
2529
2530 if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) {
2531 put_page(page);
2532 return ret | VM_FAULT_RETRY;
2533 }
2534
2535 /* Did it get truncated? */
2536 if (unlikely(page->mapping != mapping)) {
2537 unlock_page(page);
2538 put_page(page);
2539 goto retry_find;
2540 }
2541 VM_BUG_ON_PAGE(page->index != offset, page);
2542
2543 /*
2544 * We have a locked page in the page cache, now we need to check
2545 * that it's up-to-date. If not, it is going to be due to an error.
2546 */
2547 if (unlikely(!PageUptodate(page)))
2548 goto page_not_uptodate;
2549
2550 /*
2551 * Found the page and have a reference on it.
2552 * We must recheck i_size under page lock.
2553 */
2554 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2555 if (unlikely(offset >= max_off)) {
2556 unlock_page(page);
2557 put_page(page);
2558 return VM_FAULT_SIGBUS;
2559 }
2560
2561 vmf->page = page;
2562 return ret | VM_FAULT_LOCKED;
2563
2564no_cached_page:
2565 /*
2566 * We're only likely to ever get here if MADV_RANDOM is in
2567 * effect.
2568 */
2569 error = page_cache_read(file, offset, vmf->gfp_mask);
2570
2571 /*
2572 * The page we want has now been added to the page cache.
2573 * In the unlikely event that someone removed it in the
2574 * meantime, we'll just come back here and read it again.
2575 */
2576 if (error >= 0)
2577 goto retry_find;
2578
2579 /*
2580 * An error return from page_cache_read can result if the
2581 * system is low on memory, or a problem occurs while trying
2582 * to schedule I/O.
2583 */
2584 if (error == -ENOMEM)
2585 return VM_FAULT_OOM;
2586 return VM_FAULT_SIGBUS;
2587
2588page_not_uptodate:
2589 /*
2590 * Umm, take care of errors if the page isn't up-to-date.
2591 * Try to re-read it _once_. We do this synchronously,
2592 * because there really aren't any performance issues here
2593 * and we need to check for errors.
2594 */
2595 ClearPageError(page);
2596 error = mapping->a_ops->readpage(file, page);
2597 if (!error) {
2598 wait_on_page_locked(page);
2599 if (!PageUptodate(page))
2600 error = -EIO;
2601 }
2602 put_page(page);
2603
2604 if (!error || error == AOP_TRUNCATED_PAGE)
2605 goto retry_find;
2606
2607 /* Things didn't work out. Return zero to tell the mm layer so. */
2608 shrink_readahead_size_eio(file, ra);
2609 return VM_FAULT_SIGBUS;
2610}
2611EXPORT_SYMBOL(filemap_fault);
2612
2613void filemap_map_pages(struct vm_fault *vmf,
2614 pgoff_t start_pgoff, pgoff_t end_pgoff)
2615{
2616 struct radix_tree_iter iter;
2617 void **slot;
2618 struct file *file = vmf->vma->vm_file;
2619 struct address_space *mapping = file->f_mapping;
2620 pgoff_t last_pgoff = start_pgoff;
2621 unsigned long max_idx;
2622 struct page *head, *page;
2623
2624 rcu_read_lock();
2625 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start_pgoff) {
2626 if (iter.index > end_pgoff)
2627 break;
2628repeat:
2629 page = radix_tree_deref_slot(slot);
2630 if (unlikely(!page))
2631 goto next;
2632 if (radix_tree_exception(page)) {
2633 if (radix_tree_deref_retry(page)) {
2634 slot = radix_tree_iter_retry(&iter);
2635 continue;
2636 }
2637 goto next;
2638 }
2639
2640 head = compound_head(page);
2641 if (!page_cache_get_speculative(head))
2642 goto repeat;
2643
2644 /* The page was split under us? */
2645 if (compound_head(page) != head) {
2646 put_page(head);
2647 goto repeat;
2648 }
2649
2650 /* Has the page moved? */
2651 if (unlikely(page != *slot)) {
2652 put_page(head);
2653 goto repeat;
2654 }
2655
2656 if (!PageUptodate(page) ||
2657 PageReadahead(page) ||
2658 PageHWPoison(page))
2659 goto skip;
2660 if (!trylock_page(page))
2661 goto skip;
2662
2663 if (page->mapping != mapping || !PageUptodate(page))
2664 goto unlock;
2665
2666 max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2667 if (page->index >= max_idx)
2668 goto unlock;
2669
2670 if (file->f_ra.mmap_miss > 0)
2671 file->f_ra.mmap_miss--;
2672
2673 vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
2674 if (vmf->pte)
2675 vmf->pte += iter.index - last_pgoff;
2676 last_pgoff = iter.index;
2677 if (alloc_set_pte(vmf, NULL, page))
2678 goto unlock;
2679 unlock_page(page);
2680 goto next;
2681unlock:
2682 unlock_page(page);
2683skip:
2684 put_page(page);
2685next:
2686 /* Huge page is mapped? No need to proceed. */
2687 if (pmd_trans_huge(*vmf->pmd))
2688 break;
2689 if (iter.index == end_pgoff)
2690 break;
2691 }
2692 rcu_read_unlock();
2693}
2694EXPORT_SYMBOL(filemap_map_pages);
2695
2696int filemap_page_mkwrite(struct vm_fault *vmf)
2697{
2698 struct page *page = vmf->page;
2699 struct inode *inode = file_inode(vmf->vma->vm_file);
2700 int ret = VM_FAULT_LOCKED;
2701
2702 sb_start_pagefault(inode->i_sb);
2703 file_update_time(vmf->vma->vm_file);
2704 lock_page(page);
2705 if (page->mapping != inode->i_mapping) {
2706 unlock_page(page);
2707 ret = VM_FAULT_NOPAGE;
2708 goto out;
2709 }
2710 /*
2711 * We mark the page dirty already here so that when freeze is in
2712 * progress, we are guaranteed that writeback during freezing will
2713 * see the dirty page and writeprotect it again.
2714 */
2715 set_page_dirty(page);
2716 wait_for_stable_page(page);
2717out:
2718 sb_end_pagefault(inode->i_sb);
2719 return ret;
2720}
2721
2722const struct vm_operations_struct generic_file_vm_ops = {
2723 .fault = filemap_fault,
2724 .map_pages = filemap_map_pages,
2725 .page_mkwrite = filemap_page_mkwrite,
2726};
2727
2728/* This is used for a general mmap of a disk file */
2729
2730int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2731{
2732 struct address_space *mapping = file->f_mapping;
2733
2734 if (!mapping->a_ops->readpage)
2735 return -ENOEXEC;
2736 file_accessed(file);
2737 vma->vm_ops = &generic_file_vm_ops;
2738 return 0;
2739}
2740
2741/*
2742 * This is for filesystems which do not implement ->writepage.
2743 */
2744int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2745{
2746 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2747 return -EINVAL;
2748 return generic_file_mmap(file, vma);
2749}
2750#else
2751int filemap_page_mkwrite(struct vm_fault *vmf)
2752{
2753 return -ENOSYS;
2754}
2755int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2756{
2757 return -ENOSYS;
2758}
2759int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2760{
2761 return -ENOSYS;
2762}
2763#endif /* CONFIG_MMU */
2764
2765EXPORT_SYMBOL(filemap_page_mkwrite);
2766EXPORT_SYMBOL(generic_file_mmap);
2767EXPORT_SYMBOL(generic_file_readonly_mmap);
2768
2769static struct page *wait_on_page_read(struct page *page)
2770{
2771 if (!IS_ERR(page)) {
2772 wait_on_page_locked(page);
2773 if (!PageUptodate(page)) {
2774 put_page(page);
2775 page = ERR_PTR(-EIO);
2776 }
2777 }
2778 return page;
2779}
2780
2781static struct page *do_read_cache_page(struct address_space *mapping,
2782 pgoff_t index,
2783 int (*filler)(void *, struct page *),
2784 void *data,
2785 gfp_t gfp)
2786{
2787 struct page *page;
2788 int err;
2789repeat:
2790 page = find_get_page(mapping, index);
2791 if (!page) {
2792 page = __page_cache_alloc(gfp);
2793 if (!page)
2794 return ERR_PTR(-ENOMEM);
2795 err = add_to_page_cache_lru(page, mapping, index, gfp);
2796 if (unlikely(err)) {
2797 put_page(page);
2798 if (err == -EEXIST)
2799 goto repeat;
2800 /* Presumably ENOMEM for radix tree node */
2801 return ERR_PTR(err);
2802 }
2803
2804filler:
2805 err = filler(data, page);
2806 if (err < 0) {
2807 put_page(page);
2808 return ERR_PTR(err);
2809 }
2810
2811 page = wait_on_page_read(page);
2812 if (IS_ERR(page))
2813 return page;
2814 goto out;
2815 }
2816 if (PageUptodate(page))
2817 goto out;
2818
2819 /*
2820 * Page is not up to date and may be locked due one of the following
2821 * case a: Page is being filled and the page lock is held
2822 * case b: Read/write error clearing the page uptodate status
2823 * case c: Truncation in progress (page locked)
2824 * case d: Reclaim in progress
2825 *
2826 * Case a, the page will be up to date when the page is unlocked.
2827 * There is no need to serialise on the page lock here as the page
2828 * is pinned so the lock gives no additional protection. Even if the
2829 * the page is truncated, the data is still valid if PageUptodate as
2830 * it's a race vs truncate race.
2831 * Case b, the page will not be up to date
2832 * Case c, the page may be truncated but in itself, the data may still
2833 * be valid after IO completes as it's a read vs truncate race. The
2834 * operation must restart if the page is not uptodate on unlock but
2835 * otherwise serialising on page lock to stabilise the mapping gives
2836 * no additional guarantees to the caller as the page lock is
2837 * released before return.
2838 * Case d, similar to truncation. If reclaim holds the page lock, it
2839 * will be a race with remove_mapping that determines if the mapping
2840 * is valid on unlock but otherwise the data is valid and there is
2841 * no need to serialise with page lock.
2842 *
2843 * As the page lock gives no additional guarantee, we optimistically
2844 * wait on the page to be unlocked and check if it's up to date and
2845 * use the page if it is. Otherwise, the page lock is required to
2846 * distinguish between the different cases. The motivation is that we
2847 * avoid spurious serialisations and wakeups when multiple processes
2848 * wait on the same page for IO to complete.
2849 */
2850 wait_on_page_locked(page);
2851 if (PageUptodate(page))
2852 goto out;
2853
2854 /* Distinguish between all the cases under the safety of the lock */
2855 lock_page(page);
2856
2857 /* Case c or d, restart the operation */
2858 if (!page->mapping) {
2859 unlock_page(page);
2860 put_page(page);
2861 goto repeat;
2862 }
2863
2864 /* Someone else locked and filled the page in a very small window */
2865 if (PageUptodate(page)) {
2866 unlock_page(page);
2867 goto out;
2868 }
2869 goto filler;
2870
2871out:
2872 mark_page_accessed(page);
2873 return page;
2874}
2875
2876/**
2877 * read_cache_page - read into page cache, fill it if needed
2878 * @mapping: the page's address_space
2879 * @index: the page index
2880 * @filler: function to perform the read
2881 * @data: first arg to filler(data, page) function, often left as NULL
2882 *
2883 * Read into the page cache. If a page already exists, and PageUptodate() is
2884 * not set, try to fill the page and wait for it to become unlocked.
2885 *
2886 * If the page does not get brought uptodate, return -EIO.
2887 */
2888struct page *read_cache_page(struct address_space *mapping,
2889 pgoff_t index,
2890 int (*filler)(void *, struct page *),
2891 void *data)
2892{
2893 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2894}
2895EXPORT_SYMBOL(read_cache_page);
2896
2897/**
2898 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2899 * @mapping: the page's address_space
2900 * @index: the page index
2901 * @gfp: the page allocator flags to use if allocating
2902 *
2903 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2904 * any new page allocations done using the specified allocation flags.
2905 *
2906 * If the page does not get brought uptodate, return -EIO.
2907 */
2908struct page *read_cache_page_gfp(struct address_space *mapping,
2909 pgoff_t index,
2910 gfp_t gfp)
2911{
2912 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2913
2914 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2915}
2916EXPORT_SYMBOL(read_cache_page_gfp);
2917
2918/*
2919 * Performs necessary checks before doing a write
2920 *
2921 * Can adjust writing position or amount of bytes to write.
2922 * Returns appropriate error code that caller should return or
2923 * zero in case that write should be allowed.
2924 */
2925inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2926{
2927 struct file *file = iocb->ki_filp;
2928 struct inode *inode = file->f_mapping->host;
2929 unsigned long limit = rlimit(RLIMIT_FSIZE);
2930 loff_t pos;
2931
2932 if (!iov_iter_count(from))
2933 return 0;
2934
2935 /* FIXME: this is for backwards compatibility with 2.4 */
2936 if (iocb->ki_flags & IOCB_APPEND)
2937 iocb->ki_pos = i_size_read(inode);
2938
2939 pos = iocb->ki_pos;
2940
2941 if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
2942 return -EINVAL;
2943
2944 if (limit != RLIM_INFINITY) {
2945 if (iocb->ki_pos >= limit) {
2946 send_sig(SIGXFSZ, current, 0);
2947 return -EFBIG;
2948 }
2949 iov_iter_truncate(from, limit - (unsigned long)pos);
2950 }
2951
2952 /*
2953 * LFS rule
2954 */
2955 if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
2956 !(file->f_flags & O_LARGEFILE))) {
2957 if (pos >= MAX_NON_LFS)
2958 return -EFBIG;
2959 iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
2960 }
2961
2962 /*
2963 * Are we about to exceed the fs block limit ?
2964 *
2965 * If we have written data it becomes a short write. If we have
2966 * exceeded without writing data we send a signal and return EFBIG.
2967 * Linus frestrict idea will clean these up nicely..
2968 */
2969 if (unlikely(pos >= inode->i_sb->s_maxbytes))
2970 return -EFBIG;
2971
2972 iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
2973 return iov_iter_count(from);
2974}
2975EXPORT_SYMBOL(generic_write_checks);
2976
2977int pagecache_write_begin(struct file *file, struct address_space *mapping,
2978 loff_t pos, unsigned len, unsigned flags,
2979 struct page **pagep, void **fsdata)
2980{
2981 const struct address_space_operations *aops = mapping->a_ops;
2982
2983 return aops->write_begin(file, mapping, pos, len, flags,
2984 pagep, fsdata);
2985}
2986EXPORT_SYMBOL(pagecache_write_begin);
2987
2988int pagecache_write_end(struct file *file, struct address_space *mapping,
2989 loff_t pos, unsigned len, unsigned copied,
2990 struct page *page, void *fsdata)
2991{
2992 const struct address_space_operations *aops = mapping->a_ops;
2993
2994 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2995}
2996EXPORT_SYMBOL(pagecache_write_end);
2997
2998ssize_t
2999generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
3000{
3001 struct file *file = iocb->ki_filp;
3002 struct address_space *mapping = file->f_mapping;
3003 struct inode *inode = mapping->host;
3004 loff_t pos = iocb->ki_pos;
3005 ssize_t written;
3006 size_t write_len;
3007 pgoff_t end;
3008
3009 write_len = iov_iter_count(from);
3010 end = (pos + write_len - 1) >> PAGE_SHIFT;
3011
3012 if (iocb->ki_flags & IOCB_NOWAIT) {
3013 /* If there are pages to writeback, return */
3014 if (filemap_range_has_page(inode->i_mapping, pos,
3015 pos + iov_iter_count(from)))
3016 return -EAGAIN;
3017 } else {
3018 written = filemap_write_and_wait_range(mapping, pos,
3019 pos + write_len - 1);
3020 if (written)
3021 goto out;
3022 }
3023
3024 /*
3025 * After a write we want buffered reads to be sure to go to disk to get
3026 * the new data. We invalidate clean cached page from the region we're
3027 * about to write. We do this *before* the write so that we can return
3028 * without clobbering -EIOCBQUEUED from ->direct_IO().
3029 */
3030 written = invalidate_inode_pages2_range(mapping,
3031 pos >> PAGE_SHIFT, end);
3032 /*
3033 * If a page can not be invalidated, return 0 to fall back
3034 * to buffered write.
3035 */
3036 if (written) {
3037 if (written == -EBUSY)
3038 return 0;
3039 goto out;
3040 }
3041
3042 written = mapping->a_ops->direct_IO(iocb, from);
3043
3044 /*
3045 * Finally, try again to invalidate clean pages which might have been
3046 * cached by non-direct readahead, or faulted in by get_user_pages()
3047 * if the source of the write was an mmap'ed region of the file
3048 * we're writing. Either one is a pretty crazy thing to do,
3049 * so we don't support it 100%. If this invalidation
3050 * fails, tough, the write still worked...
3051 *
3052 * Most of the time we do not need this since dio_complete() will do
3053 * the invalidation for us. However there are some file systems that
3054 * do not end up with dio_complete() being called, so let's not break
3055 * them by removing it completely
3056 */
3057 if (mapping->nrpages)
3058 invalidate_inode_pages2_range(mapping,
3059 pos >> PAGE_SHIFT, end);
3060
3061 if (written > 0) {
3062 pos += written;
3063 write_len -= written;
3064 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
3065 i_size_write(inode, pos);
3066 mark_inode_dirty(inode);
3067 }
3068 iocb->ki_pos = pos;
3069 }
3070 iov_iter_revert(from, write_len - iov_iter_count(from));
3071out:
3072 return written;
3073}
3074EXPORT_SYMBOL(generic_file_direct_write);
3075
3076/*
3077 * Find or create a page at the given pagecache position. Return the locked
3078 * page. This function is specifically for buffered writes.
3079 */
3080struct page *grab_cache_page_write_begin(struct address_space *mapping,
3081 pgoff_t index, unsigned flags)
3082{
3083 struct page *page;
3084 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
3085
3086 if (flags & AOP_FLAG_NOFS)
3087 fgp_flags |= FGP_NOFS;
3088
3089 page = pagecache_get_page(mapping, index, fgp_flags,
3090 mapping_gfp_mask(mapping));
3091 if (page)
3092 wait_for_stable_page(page);
3093
3094 return page;
3095}
3096EXPORT_SYMBOL(grab_cache_page_write_begin);
3097
3098ssize_t generic_perform_write(struct file *file,
3099 struct iov_iter *i, loff_t pos)
3100{
3101 struct address_space *mapping = file->f_mapping;
3102 const struct address_space_operations *a_ops = mapping->a_ops;
3103 long status = 0;
3104 ssize_t written = 0;
3105 unsigned int flags = 0;
3106
3107 do {
3108 struct page *page;
3109 unsigned long offset; /* Offset into pagecache page */
3110 unsigned long bytes; /* Bytes to write to page */
3111 size_t copied; /* Bytes copied from user */
3112 void *fsdata;
3113
3114 offset = (pos & (PAGE_SIZE - 1));
3115 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3116 iov_iter_count(i));
3117
3118again:
3119 /*
3120 * Bring in the user page that we will copy from _first_.
3121 * Otherwise there's a nasty deadlock on copying from the
3122 * same page as we're writing to, without it being marked
3123 * up-to-date.
3124 *
3125 * Not only is this an optimisation, but it is also required
3126 * to check that the address is actually valid, when atomic
3127 * usercopies are used, below.
3128 */
3129 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
3130 status = -EFAULT;
3131 break;
3132 }
3133
3134 if (fatal_signal_pending(current)) {
3135 status = -EINTR;
3136 break;
3137 }
3138
3139 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
3140 &page, &fsdata);
3141 if (unlikely(status < 0))
3142 break;
3143
3144 if (mapping_writably_mapped(mapping))
3145 flush_dcache_page(page);
3146
3147 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
3148 flush_dcache_page(page);
3149
3150 status = a_ops->write_end(file, mapping, pos, bytes, copied,
3151 page, fsdata);
3152 if (unlikely(status < 0))
3153 break;
3154 copied = status;
3155
3156 cond_resched();
3157
3158 iov_iter_advance(i, copied);
3159 if (unlikely(copied == 0)) {
3160 /*
3161 * If we were unable to copy any data at all, we must
3162 * fall back to a single segment length write.
3163 *
3164 * If we didn't fallback here, we could livelock
3165 * because not all segments in the iov can be copied at
3166 * once without a pagefault.
3167 */
3168 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3169 iov_iter_single_seg_count(i));
3170 goto again;
3171 }
3172 pos += copied;
3173 written += copied;
3174
3175 balance_dirty_pages_ratelimited(mapping);
3176 } while (iov_iter_count(i));
3177
3178 return written ? written : status;
3179}
3180EXPORT_SYMBOL(generic_perform_write);
3181
3182/**
3183 * __generic_file_write_iter - write data to a file
3184 * @iocb: IO state structure (file, offset, etc.)
3185 * @from: iov_iter with data to write
3186 *
3187 * This function does all the work needed for actually writing data to a
3188 * file. It does all basic checks, removes SUID from the file, updates
3189 * modification times and calls proper subroutines depending on whether we
3190 * do direct IO or a standard buffered write.
3191 *
3192 * It expects i_mutex to be grabbed unless we work on a block device or similar
3193 * object which does not need locking at all.
3194 *
3195 * This function does *not* take care of syncing data in case of O_SYNC write.
3196 * A caller has to handle it. This is mainly due to the fact that we want to
3197 * avoid syncing under i_mutex.
3198 */
3199ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3200{
3201 struct file *file = iocb->ki_filp;
3202 struct address_space * mapping = file->f_mapping;
3203 struct inode *inode = mapping->host;
3204 ssize_t written = 0;
3205 ssize_t err;
3206 ssize_t status;
3207
3208 /* We can write back this queue in page reclaim */
3209 current->backing_dev_info = inode_to_bdi(inode);
3210 err = file_remove_privs(file);
3211 if (err)
3212 goto out;
3213
3214 err = file_update_time(file);
3215 if (err)
3216 goto out;
3217
3218 if (iocb->ki_flags & IOCB_DIRECT) {
3219 loff_t pos, endbyte;
3220
3221 written = generic_file_direct_write(iocb, from);
3222 /*
3223 * If the write stopped short of completing, fall back to
3224 * buffered writes. Some filesystems do this for writes to
3225 * holes, for example. For DAX files, a buffered write will
3226 * not succeed (even if it did, DAX does not handle dirty
3227 * page-cache pages correctly).
3228 */
3229 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
3230 goto out;
3231
3232 status = generic_perform_write(file, from, pos = iocb->ki_pos);
3233 /*
3234 * If generic_perform_write() returned a synchronous error
3235 * then we want to return the number of bytes which were
3236 * direct-written, or the error code if that was zero. Note
3237 * that this differs from normal direct-io semantics, which
3238 * will return -EFOO even if some bytes were written.
3239 */
3240 if (unlikely(status < 0)) {
3241 err = status;
3242 goto out;
3243 }
3244 /*
3245 * We need to ensure that the page cache pages are written to
3246 * disk and invalidated to preserve the expected O_DIRECT
3247 * semantics.
3248 */
3249 endbyte = pos + status - 1;
3250 err = filemap_write_and_wait_range(mapping, pos, endbyte);
3251 if (err == 0) {
3252 iocb->ki_pos = endbyte + 1;
3253 written += status;
3254 invalidate_mapping_pages(mapping,
3255 pos >> PAGE_SHIFT,
3256 endbyte >> PAGE_SHIFT);
3257 } else {
3258 /*
3259 * We don't know how much we wrote, so just return
3260 * the number of bytes which were direct-written
3261 */
3262 }
3263 } else {
3264 written = generic_perform_write(file, from, iocb->ki_pos);
3265 if (likely(written > 0))
3266 iocb->ki_pos += written;
3267 }
3268out:
3269 current->backing_dev_info = NULL;
3270 return written ? written : err;
3271}
3272EXPORT_SYMBOL(__generic_file_write_iter);
3273
3274/**
3275 * generic_file_write_iter - write data to a file
3276 * @iocb: IO state structure
3277 * @from: iov_iter with data to write
3278 *
3279 * This is a wrapper around __generic_file_write_iter() to be used by most
3280 * filesystems. It takes care of syncing the file in case of O_SYNC file
3281 * and acquires i_mutex as needed.
3282 */
3283ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3284{
3285 struct file *file = iocb->ki_filp;
3286 struct inode *inode = file->f_mapping->host;
3287 ssize_t ret;
3288
3289 inode_lock(inode);
3290 ret = generic_write_checks(iocb, from);
3291 if (ret > 0)
3292 ret = __generic_file_write_iter(iocb, from);
3293 inode_unlock(inode);
3294
3295 if (ret > 0)
3296 ret = generic_write_sync(iocb, ret);
3297 return ret;
3298}
3299EXPORT_SYMBOL(generic_file_write_iter);
3300
3301/**
3302 * try_to_release_page() - release old fs-specific metadata on a page
3303 *
3304 * @page: the page which the kernel is trying to free
3305 * @gfp_mask: memory allocation flags (and I/O mode)
3306 *
3307 * The address_space is to try to release any data against the page
3308 * (presumably at page->private). If the release was successful, return '1'.
3309 * Otherwise return zero.
3310 *
3311 * This may also be called if PG_fscache is set on a page, indicating that the
3312 * page is known to the local caching routines.
3313 *
3314 * The @gfp_mask argument specifies whether I/O may be performed to release
3315 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3316 *
3317 */
3318int try_to_release_page(struct page *page, gfp_t gfp_mask)
3319{
3320 struct address_space * const mapping = page->mapping;
3321
3322 BUG_ON(!PageLocked(page));
3323 if (PageWriteback(page))
3324 return 0;
3325
3326 if (mapping && mapping->a_ops->releasepage)
3327 return mapping->a_ops->releasepage(page, gfp_mask);
3328 return try_to_free_buffers(page);
3329}
3330
3331EXPORT_SYMBOL(try_to_release_page);