fs: make generic file read/write functions plug
[linux-2.6.git] / mm / filemap.c
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/mm_inline.h> /* for page_is_file_cache() */
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_lock               (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_lock             (truncate->unmap_mapping_range)
68  *
69  *  ->mmap_sem
70  *    ->i_mmap_lock
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  *  ->i_mutex
81  *    ->i_alloc_sem             (various)
82  *
83  *  ->inode_lock
84  *    ->sb_lock                 (fs/fs-writeback.c)
85  *    ->mapping->tree_lock      (__sync_single_inode)
86  *
87  *  ->i_mmap_lock
88  *    ->anon_vma.lock           (vma_adjust)
89  *
90  *  ->anon_vma.lock
91  *    ->page_table_lock or pte_lock     (anon_vma_prepare and various)
92  *
93  *  ->page_table_lock or pte_lock
94  *    ->swap_lock               (try_to_unmap_one)
95  *    ->private_lock            (try_to_unmap_one)
96  *    ->tree_lock               (try_to_unmap_one)
97  *    ->zone.lru_lock           (follow_page->mark_page_accessed)
98  *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
99  *    ->private_lock            (page_remove_rmap->set_page_dirty)
100  *    ->tree_lock               (page_remove_rmap->set_page_dirty)
101  *    ->inode_lock              (page_remove_rmap->set_page_dirty)
102  *    ->inode_lock              (zap_pte_range->set_page_dirty)
103  *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
104  *
105  *  (code doesn't rely on that order, so you could switch it around)
106  *  ->tasklist_lock             (memory_failure, collect_procs_ao)
107  *    ->i_mmap_lock
108  */
109
110 /*
111  * Remove a page from the page cache and free it. Caller has to make
112  * sure the page is locked and that nobody else uses it - or that usage
113  * is safe.  The caller must hold the mapping's tree_lock.
114  */
115 void __remove_from_page_cache(struct page *page)
116 {
117         struct address_space *mapping = page->mapping;
118
119         radix_tree_delete(&mapping->page_tree, page->index);
120         page->mapping = NULL;
121         mapping->nrpages--;
122         __dec_zone_page_state(page, NR_FILE_PAGES);
123         if (PageSwapBacked(page))
124                 __dec_zone_page_state(page, NR_SHMEM);
125         BUG_ON(page_mapped(page));
126
127         /*
128          * Some filesystems seem to re-dirty the page even after
129          * the VM has canceled the dirty bit (eg ext3 journaling).
130          *
131          * Fix it up by doing a final dirty accounting check after
132          * having removed the page entirely.
133          */
134         if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
135                 dec_zone_page_state(page, NR_FILE_DIRTY);
136                 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
137         }
138 }
139
140 void remove_from_page_cache(struct page *page)
141 {
142         struct address_space *mapping = page->mapping;
143         void (*freepage)(struct page *);
144
145         BUG_ON(!PageLocked(page));
146
147         freepage = mapping->a_ops->freepage;
148         spin_lock_irq(&mapping->tree_lock);
149         __remove_from_page_cache(page);
150         spin_unlock_irq(&mapping->tree_lock);
151         mem_cgroup_uncharge_cache_page(page);
152
153         if (freepage)
154                 freepage(page);
155 }
156 EXPORT_SYMBOL(remove_from_page_cache);
157
158 static int sleep_on_page(void *word)
159 {
160         io_schedule();
161         return 0;
162 }
163
164 static int sleep_on_page_killable(void *word)
165 {
166         sleep_on_page(word);
167         return fatal_signal_pending(current) ? -EINTR : 0;
168 }
169
170 /**
171  * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
172  * @mapping:    address space structure to write
173  * @start:      offset in bytes where the range starts
174  * @end:        offset in bytes where the range ends (inclusive)
175  * @sync_mode:  enable synchronous operation
176  *
177  * Start writeback against all of a mapping's dirty pages that lie
178  * within the byte offsets <start, end> inclusive.
179  *
180  * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
181  * opposed to a regular memory cleansing writeback.  The difference between
182  * these two operations is that if a dirty page/buffer is encountered, it must
183  * be waited upon, and not just skipped over.
184  */
185 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
186                                 loff_t end, int sync_mode)
187 {
188         int ret;
189         struct writeback_control wbc = {
190                 .sync_mode = sync_mode,
191                 .nr_to_write = LONG_MAX,
192                 .range_start = start,
193                 .range_end = end,
194         };
195
196         if (!mapping_cap_writeback_dirty(mapping))
197                 return 0;
198
199         ret = do_writepages(mapping, &wbc);
200         return ret;
201 }
202
203 static inline int __filemap_fdatawrite(struct address_space *mapping,
204         int sync_mode)
205 {
206         return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
207 }
208
209 int filemap_fdatawrite(struct address_space *mapping)
210 {
211         return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
212 }
213 EXPORT_SYMBOL(filemap_fdatawrite);
214
215 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
216                                 loff_t end)
217 {
218         return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
219 }
220 EXPORT_SYMBOL(filemap_fdatawrite_range);
221
222 /**
223  * filemap_flush - mostly a non-blocking flush
224  * @mapping:    target address_space
225  *
226  * This is a mostly non-blocking flush.  Not suitable for data-integrity
227  * purposes - I/O may not be started against all dirty pages.
228  */
229 int filemap_flush(struct address_space *mapping)
230 {
231         return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
232 }
233 EXPORT_SYMBOL(filemap_flush);
234
235 /**
236  * filemap_fdatawait_range - wait for writeback to complete
237  * @mapping:            address space structure to wait for
238  * @start_byte:         offset in bytes where the range starts
239  * @end_byte:           offset in bytes where the range ends (inclusive)
240  *
241  * Walk the list of under-writeback pages of the given address space
242  * in the given range and wait for all of them.
243  */
244 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
245                             loff_t end_byte)
246 {
247         pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
248         pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
249         struct pagevec pvec;
250         int nr_pages;
251         int ret = 0;
252
253         if (end_byte < start_byte)
254                 return 0;
255
256         pagevec_init(&pvec, 0);
257         while ((index <= end) &&
258                         (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
259                         PAGECACHE_TAG_WRITEBACK,
260                         min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
261                 unsigned i;
262
263                 for (i = 0; i < nr_pages; i++) {
264                         struct page *page = pvec.pages[i];
265
266                         /* until radix tree lookup accepts end_index */
267                         if (page->index > end)
268                                 continue;
269
270                         wait_on_page_writeback(page);
271                         if (TestClearPageError(page))
272                                 ret = -EIO;
273                 }
274                 pagevec_release(&pvec);
275                 cond_resched();
276         }
277
278         /* Check for outstanding write errors */
279         if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
280                 ret = -ENOSPC;
281         if (test_and_clear_bit(AS_EIO, &mapping->flags))
282                 ret = -EIO;
283
284         return ret;
285 }
286 EXPORT_SYMBOL(filemap_fdatawait_range);
287
288 /**
289  * filemap_fdatawait - wait for all under-writeback pages to complete
290  * @mapping: address space structure to wait for
291  *
292  * Walk the list of under-writeback pages of the given address space
293  * and wait for all of them.
294  */
295 int filemap_fdatawait(struct address_space *mapping)
296 {
297         loff_t i_size = i_size_read(mapping->host);
298
299         if (i_size == 0)
300                 return 0;
301
302         return filemap_fdatawait_range(mapping, 0, i_size - 1);
303 }
304 EXPORT_SYMBOL(filemap_fdatawait);
305
306 int filemap_write_and_wait(struct address_space *mapping)
307 {
308         int err = 0;
309
310         if (mapping->nrpages) {
311                 err = filemap_fdatawrite(mapping);
312                 /*
313                  * Even if the above returned error, the pages may be
314                  * written partially (e.g. -ENOSPC), so we wait for it.
315                  * But the -EIO is special case, it may indicate the worst
316                  * thing (e.g. bug) happened, so we avoid waiting for it.
317                  */
318                 if (err != -EIO) {
319                         int err2 = filemap_fdatawait(mapping);
320                         if (!err)
321                                 err = err2;
322                 }
323         }
324         return err;
325 }
326 EXPORT_SYMBOL(filemap_write_and_wait);
327
328 /**
329  * filemap_write_and_wait_range - write out & wait on a file range
330  * @mapping:    the address_space for the pages
331  * @lstart:     offset in bytes where the range starts
332  * @lend:       offset in bytes where the range ends (inclusive)
333  *
334  * Write out and wait upon file offsets lstart->lend, inclusive.
335  *
336  * Note that `lend' is inclusive (describes the last byte to be written) so
337  * that this function can be used to write to the very end-of-file (end = -1).
338  */
339 int filemap_write_and_wait_range(struct address_space *mapping,
340                                  loff_t lstart, loff_t lend)
341 {
342         int err = 0;
343
344         if (mapping->nrpages) {
345                 err = __filemap_fdatawrite_range(mapping, lstart, lend,
346                                                  WB_SYNC_ALL);
347                 /* See comment of filemap_write_and_wait() */
348                 if (err != -EIO) {
349                         int err2 = filemap_fdatawait_range(mapping,
350                                                 lstart, lend);
351                         if (!err)
352                                 err = err2;
353                 }
354         }
355         return err;
356 }
357 EXPORT_SYMBOL(filemap_write_and_wait_range);
358
359 /**
360  * add_to_page_cache_locked - add a locked page to the pagecache
361  * @page:       page to add
362  * @mapping:    the page's address_space
363  * @offset:     page index
364  * @gfp_mask:   page allocation mode
365  *
366  * This function is used to add a page to the pagecache. It must be locked.
367  * This function does not add the page to the LRU.  The caller must do that.
368  */
369 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
370                 pgoff_t offset, gfp_t gfp_mask)
371 {
372         int error;
373
374         VM_BUG_ON(!PageLocked(page));
375
376         error = mem_cgroup_cache_charge(page, current->mm,
377                                         gfp_mask & GFP_RECLAIM_MASK);
378         if (error)
379                 goto out;
380
381         error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
382         if (error == 0) {
383                 page_cache_get(page);
384                 page->mapping = mapping;
385                 page->index = offset;
386
387                 spin_lock_irq(&mapping->tree_lock);
388                 error = radix_tree_insert(&mapping->page_tree, offset, page);
389                 if (likely(!error)) {
390                         mapping->nrpages++;
391                         __inc_zone_page_state(page, NR_FILE_PAGES);
392                         if (PageSwapBacked(page))
393                                 __inc_zone_page_state(page, NR_SHMEM);
394                         spin_unlock_irq(&mapping->tree_lock);
395                 } else {
396                         page->mapping = NULL;
397                         spin_unlock_irq(&mapping->tree_lock);
398                         mem_cgroup_uncharge_cache_page(page);
399                         page_cache_release(page);
400                 }
401                 radix_tree_preload_end();
402         } else
403                 mem_cgroup_uncharge_cache_page(page);
404 out:
405         return error;
406 }
407 EXPORT_SYMBOL(add_to_page_cache_locked);
408
409 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
410                                 pgoff_t offset, gfp_t gfp_mask)
411 {
412         int ret;
413
414         /*
415          * Splice_read and readahead add shmem/tmpfs pages into the page cache
416          * before shmem_readpage has a chance to mark them as SwapBacked: they
417          * need to go on the anon lru below, and mem_cgroup_cache_charge
418          * (called in add_to_page_cache) needs to know where they're going too.
419          */
420         if (mapping_cap_swap_backed(mapping))
421                 SetPageSwapBacked(page);
422
423         ret = add_to_page_cache(page, mapping, offset, gfp_mask);
424         if (ret == 0) {
425                 if (page_is_file_cache(page))
426                         lru_cache_add_file(page);
427                 else
428                         lru_cache_add_anon(page);
429         }
430         return ret;
431 }
432 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
433
434 #ifdef CONFIG_NUMA
435 struct page *__page_cache_alloc(gfp_t gfp)
436 {
437         int n;
438         struct page *page;
439
440         if (cpuset_do_page_mem_spread()) {
441                 get_mems_allowed();
442                 n = cpuset_mem_spread_node();
443                 page = alloc_pages_exact_node(n, gfp, 0);
444                 put_mems_allowed();
445                 return page;
446         }
447         return alloc_pages(gfp, 0);
448 }
449 EXPORT_SYMBOL(__page_cache_alloc);
450 #endif
451
452 /*
453  * In order to wait for pages to become available there must be
454  * waitqueues associated with pages. By using a hash table of
455  * waitqueues where the bucket discipline is to maintain all
456  * waiters on the same queue and wake all when any of the pages
457  * become available, and for the woken contexts to check to be
458  * sure the appropriate page became available, this saves space
459  * at a cost of "thundering herd" phenomena during rare hash
460  * collisions.
461  */
462 static wait_queue_head_t *page_waitqueue(struct page *page)
463 {
464         const struct zone *zone = page_zone(page);
465
466         return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
467 }
468
469 static inline void wake_up_page(struct page *page, int bit)
470 {
471         __wake_up_bit(page_waitqueue(page), &page->flags, bit);
472 }
473
474 void wait_on_page_bit(struct page *page, int bit_nr)
475 {
476         DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
477
478         if (test_bit(bit_nr, &page->flags))
479                 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
480                                                         TASK_UNINTERRUPTIBLE);
481 }
482 EXPORT_SYMBOL(wait_on_page_bit);
483
484 /**
485  * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
486  * @page: Page defining the wait queue of interest
487  * @waiter: Waiter to add to the queue
488  *
489  * Add an arbitrary @waiter to the wait queue for the nominated @page.
490  */
491 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
492 {
493         wait_queue_head_t *q = page_waitqueue(page);
494         unsigned long flags;
495
496         spin_lock_irqsave(&q->lock, flags);
497         __add_wait_queue(q, waiter);
498         spin_unlock_irqrestore(&q->lock, flags);
499 }
500 EXPORT_SYMBOL_GPL(add_page_wait_queue);
501
502 /**
503  * unlock_page - unlock a locked page
504  * @page: the page
505  *
506  * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
507  * Also wakes sleepers in wait_on_page_writeback() because the wakeup
508  * mechananism between PageLocked pages and PageWriteback pages is shared.
509  * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
510  *
511  * The mb is necessary to enforce ordering between the clear_bit and the read
512  * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
513  */
514 void unlock_page(struct page *page)
515 {
516         VM_BUG_ON(!PageLocked(page));
517         clear_bit_unlock(PG_locked, &page->flags);
518         smp_mb__after_clear_bit();
519         wake_up_page(page, PG_locked);
520 }
521 EXPORT_SYMBOL(unlock_page);
522
523 /**
524  * end_page_writeback - end writeback against a page
525  * @page: the page
526  */
527 void end_page_writeback(struct page *page)
528 {
529         if (TestClearPageReclaim(page))
530                 rotate_reclaimable_page(page);
531
532         if (!test_clear_page_writeback(page))
533                 BUG();
534
535         smp_mb__after_clear_bit();
536         wake_up_page(page, PG_writeback);
537 }
538 EXPORT_SYMBOL(end_page_writeback);
539
540 /**
541  * __lock_page - get a lock on the page, assuming we need to sleep to get it
542  * @page: the page to lock
543  */
544 void __lock_page(struct page *page)
545 {
546         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
547
548         __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
549                                                         TASK_UNINTERRUPTIBLE);
550 }
551 EXPORT_SYMBOL(__lock_page);
552
553 int __lock_page_killable(struct page *page)
554 {
555         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
556
557         return __wait_on_bit_lock(page_waitqueue(page), &wait,
558                                         sleep_on_page_killable, TASK_KILLABLE);
559 }
560 EXPORT_SYMBOL_GPL(__lock_page_killable);
561
562 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
563                          unsigned int flags)
564 {
565         if (!(flags & FAULT_FLAG_ALLOW_RETRY)) {
566                 __lock_page(page);
567                 return 1;
568         } else {
569                 up_read(&mm->mmap_sem);
570                 wait_on_page_locked(page);
571                 return 0;
572         }
573 }
574
575 /**
576  * find_get_page - find and get a page reference
577  * @mapping: the address_space to search
578  * @offset: the page index
579  *
580  * Is there a pagecache struct page at the given (mapping, offset) tuple?
581  * If yes, increment its refcount and return it; if no, return NULL.
582  */
583 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
584 {
585         void **pagep;
586         struct page *page;
587
588         rcu_read_lock();
589 repeat:
590         page = NULL;
591         pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
592         if (pagep) {
593                 page = radix_tree_deref_slot(pagep);
594                 if (unlikely(!page))
595                         goto out;
596                 if (radix_tree_deref_retry(page))
597                         goto repeat;
598
599                 if (!page_cache_get_speculative(page))
600                         goto repeat;
601
602                 /*
603                  * Has the page moved?
604                  * This is part of the lockless pagecache protocol. See
605                  * include/linux/pagemap.h for details.
606                  */
607                 if (unlikely(page != *pagep)) {
608                         page_cache_release(page);
609                         goto repeat;
610                 }
611         }
612 out:
613         rcu_read_unlock();
614
615         return page;
616 }
617 EXPORT_SYMBOL(find_get_page);
618
619 /**
620  * find_lock_page - locate, pin and lock a pagecache page
621  * @mapping: the address_space to search
622  * @offset: the page index
623  *
624  * Locates the desired pagecache page, locks it, increments its reference
625  * count and returns its address.
626  *
627  * Returns zero if the page was not present. find_lock_page() may sleep.
628  */
629 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
630 {
631         struct page *page;
632
633 repeat:
634         page = find_get_page(mapping, offset);
635         if (page) {
636                 lock_page(page);
637                 /* Has the page been truncated? */
638                 if (unlikely(page->mapping != mapping)) {
639                         unlock_page(page);
640                         page_cache_release(page);
641                         goto repeat;
642                 }
643                 VM_BUG_ON(page->index != offset);
644         }
645         return page;
646 }
647 EXPORT_SYMBOL(find_lock_page);
648
649 /**
650  * find_or_create_page - locate or add a pagecache page
651  * @mapping: the page's address_space
652  * @index: the page's index into the mapping
653  * @gfp_mask: page allocation mode
654  *
655  * Locates a page in the pagecache.  If the page is not present, a new page
656  * is allocated using @gfp_mask and is added to the pagecache and to the VM's
657  * LRU list.  The returned page is locked and has its reference count
658  * incremented.
659  *
660  * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
661  * allocation!
662  *
663  * find_or_create_page() returns the desired page's address, or zero on
664  * memory exhaustion.
665  */
666 struct page *find_or_create_page(struct address_space *mapping,
667                 pgoff_t index, gfp_t gfp_mask)
668 {
669         struct page *page;
670         int err;
671 repeat:
672         page = find_lock_page(mapping, index);
673         if (!page) {
674                 page = __page_cache_alloc(gfp_mask);
675                 if (!page)
676                         return NULL;
677                 /*
678                  * We want a regular kernel memory (not highmem or DMA etc)
679                  * allocation for the radix tree nodes, but we need to honour
680                  * the context-specific requirements the caller has asked for.
681                  * GFP_RECLAIM_MASK collects those requirements.
682                  */
683                 err = add_to_page_cache_lru(page, mapping, index,
684                         (gfp_mask & GFP_RECLAIM_MASK));
685                 if (unlikely(err)) {
686                         page_cache_release(page);
687                         page = NULL;
688                         if (err == -EEXIST)
689                                 goto repeat;
690                 }
691         }
692         return page;
693 }
694 EXPORT_SYMBOL(find_or_create_page);
695
696 /**
697  * find_get_pages - gang pagecache lookup
698  * @mapping:    The address_space to search
699  * @start:      The starting page index
700  * @nr_pages:   The maximum number of pages
701  * @pages:      Where the resulting pages are placed
702  *
703  * find_get_pages() will search for and return a group of up to
704  * @nr_pages pages in the mapping.  The pages are placed at @pages.
705  * find_get_pages() takes a reference against the returned pages.
706  *
707  * The search returns a group of mapping-contiguous pages with ascending
708  * indexes.  There may be holes in the indices due to not-present pages.
709  *
710  * find_get_pages() returns the number of pages which were found.
711  */
712 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
713                             unsigned int nr_pages, struct page **pages)
714 {
715         unsigned int i;
716         unsigned int ret;
717         unsigned int nr_found;
718
719         rcu_read_lock();
720 restart:
721         nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
722                                 (void ***)pages, start, nr_pages);
723         ret = 0;
724         for (i = 0; i < nr_found; i++) {
725                 struct page *page;
726 repeat:
727                 page = radix_tree_deref_slot((void **)pages[i]);
728                 if (unlikely(!page))
729                         continue;
730                 if (radix_tree_deref_retry(page)) {
731                         if (ret)
732                                 start = pages[ret-1]->index;
733                         goto restart;
734                 }
735
736                 if (!page_cache_get_speculative(page))
737                         goto repeat;
738
739                 /* Has the page moved? */
740                 if (unlikely(page != *((void **)pages[i]))) {
741                         page_cache_release(page);
742                         goto repeat;
743                 }
744
745                 pages[ret] = page;
746                 ret++;
747         }
748         rcu_read_unlock();
749         return ret;
750 }
751
752 /**
753  * find_get_pages_contig - gang contiguous pagecache lookup
754  * @mapping:    The address_space to search
755  * @index:      The starting page index
756  * @nr_pages:   The maximum number of pages
757  * @pages:      Where the resulting pages are placed
758  *
759  * find_get_pages_contig() works exactly like find_get_pages(), except
760  * that the returned number of pages are guaranteed to be contiguous.
761  *
762  * find_get_pages_contig() returns the number of pages which were found.
763  */
764 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
765                                unsigned int nr_pages, struct page **pages)
766 {
767         unsigned int i;
768         unsigned int ret;
769         unsigned int nr_found;
770
771         rcu_read_lock();
772 restart:
773         nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
774                                 (void ***)pages, index, nr_pages);
775         ret = 0;
776         for (i = 0; i < nr_found; i++) {
777                 struct page *page;
778 repeat:
779                 page = radix_tree_deref_slot((void **)pages[i]);
780                 if (unlikely(!page))
781                         continue;
782                 if (radix_tree_deref_retry(page))
783                         goto restart;
784
785                 if (!page_cache_get_speculative(page))
786                         goto repeat;
787
788                 /* Has the page moved? */
789                 if (unlikely(page != *((void **)pages[i]))) {
790                         page_cache_release(page);
791                         goto repeat;
792                 }
793
794                 /*
795                  * must check mapping and index after taking the ref.
796                  * otherwise we can get both false positives and false
797                  * negatives, which is just confusing to the caller.
798                  */
799                 if (page->mapping == NULL || page->index != index) {
800                         page_cache_release(page);
801                         break;
802                 }
803
804                 pages[ret] = page;
805                 ret++;
806                 index++;
807         }
808         rcu_read_unlock();
809         return ret;
810 }
811 EXPORT_SYMBOL(find_get_pages_contig);
812
813 /**
814  * find_get_pages_tag - find and return pages that match @tag
815  * @mapping:    the address_space to search
816  * @index:      the starting page index
817  * @tag:        the tag index
818  * @nr_pages:   the maximum number of pages
819  * @pages:      where the resulting pages are placed
820  *
821  * Like find_get_pages, except we only return pages which are tagged with
822  * @tag.   We update @index to index the next page for the traversal.
823  */
824 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
825                         int tag, unsigned int nr_pages, struct page **pages)
826 {
827         unsigned int i;
828         unsigned int ret;
829         unsigned int nr_found;
830
831         rcu_read_lock();
832 restart:
833         nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
834                                 (void ***)pages, *index, nr_pages, tag);
835         ret = 0;
836         for (i = 0; i < nr_found; i++) {
837                 struct page *page;
838 repeat:
839                 page = radix_tree_deref_slot((void **)pages[i]);
840                 if (unlikely(!page))
841                         continue;
842                 if (radix_tree_deref_retry(page))
843                         goto restart;
844
845                 if (!page_cache_get_speculative(page))
846                         goto repeat;
847
848                 /* Has the page moved? */
849                 if (unlikely(page != *((void **)pages[i]))) {
850                         page_cache_release(page);
851                         goto repeat;
852                 }
853
854                 pages[ret] = page;
855                 ret++;
856         }
857         rcu_read_unlock();
858
859         if (ret)
860                 *index = pages[ret - 1]->index + 1;
861
862         return ret;
863 }
864 EXPORT_SYMBOL(find_get_pages_tag);
865
866 /**
867  * grab_cache_page_nowait - returns locked page at given index in given cache
868  * @mapping: target address_space
869  * @index: the page index
870  *
871  * Same as grab_cache_page(), but do not wait if the page is unavailable.
872  * This is intended for speculative data generators, where the data can
873  * be regenerated if the page couldn't be grabbed.  This routine should
874  * be safe to call while holding the lock for another page.
875  *
876  * Clear __GFP_FS when allocating the page to avoid recursion into the fs
877  * and deadlock against the caller's locked page.
878  */
879 struct page *
880 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
881 {
882         struct page *page = find_get_page(mapping, index);
883
884         if (page) {
885                 if (trylock_page(page))
886                         return page;
887                 page_cache_release(page);
888                 return NULL;
889         }
890         page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
891         if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
892                 page_cache_release(page);
893                 page = NULL;
894         }
895         return page;
896 }
897 EXPORT_SYMBOL(grab_cache_page_nowait);
898
899 /*
900  * CD/DVDs are error prone. When a medium error occurs, the driver may fail
901  * a _large_ part of the i/o request. Imagine the worst scenario:
902  *
903  *      ---R__________________________________________B__________
904  *         ^ reading here                             ^ bad block(assume 4k)
905  *
906  * read(R) => miss => readahead(R...B) => media error => frustrating retries
907  * => failing the whole request => read(R) => read(R+1) =>
908  * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
909  * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
910  * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
911  *
912  * It is going insane. Fix it by quickly scaling down the readahead size.
913  */
914 static void shrink_readahead_size_eio(struct file *filp,
915                                         struct file_ra_state *ra)
916 {
917         ra->ra_pages /= 4;
918 }
919
920 /**
921  * do_generic_file_read - generic file read routine
922  * @filp:       the file to read
923  * @ppos:       current file position
924  * @desc:       read_descriptor
925  * @actor:      read method
926  *
927  * This is a generic file read routine, and uses the
928  * mapping->a_ops->readpage() function for the actual low-level stuff.
929  *
930  * This is really ugly. But the goto's actually try to clarify some
931  * of the logic when it comes to error handling etc.
932  */
933 static void do_generic_file_read(struct file *filp, loff_t *ppos,
934                 read_descriptor_t *desc, read_actor_t actor)
935 {
936         struct address_space *mapping = filp->f_mapping;
937         struct inode *inode = mapping->host;
938         struct file_ra_state *ra = &filp->f_ra;
939         pgoff_t index;
940         pgoff_t last_index;
941         pgoff_t prev_index;
942         unsigned long offset;      /* offset into pagecache page */
943         unsigned int prev_offset;
944         int error;
945
946         index = *ppos >> PAGE_CACHE_SHIFT;
947         prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
948         prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
949         last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
950         offset = *ppos & ~PAGE_CACHE_MASK;
951
952         for (;;) {
953                 struct page *page;
954                 pgoff_t end_index;
955                 loff_t isize;
956                 unsigned long nr, ret;
957
958                 cond_resched();
959 find_page:
960                 page = find_get_page(mapping, index);
961                 if (!page) {
962                         page_cache_sync_readahead(mapping,
963                                         ra, filp,
964                                         index, last_index - index);
965                         page = find_get_page(mapping, index);
966                         if (unlikely(page == NULL))
967                                 goto no_cached_page;
968                 }
969                 if (PageReadahead(page)) {
970                         page_cache_async_readahead(mapping,
971                                         ra, filp, page,
972                                         index, last_index - index);
973                 }
974                 if (!PageUptodate(page)) {
975                         if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
976                                         !mapping->a_ops->is_partially_uptodate)
977                                 goto page_not_up_to_date;
978                         if (!trylock_page(page))
979                                 goto page_not_up_to_date;
980                         /* Did it get truncated before we got the lock? */
981                         if (!page->mapping)
982                                 goto page_not_up_to_date_locked;
983                         if (!mapping->a_ops->is_partially_uptodate(page,
984                                                                 desc, offset))
985                                 goto page_not_up_to_date_locked;
986                         unlock_page(page);
987                 }
988 page_ok:
989                 /*
990                  * i_size must be checked after we know the page is Uptodate.
991                  *
992                  * Checking i_size after the check allows us to calculate
993                  * the correct value for "nr", which means the zero-filled
994                  * part of the page is not copied back to userspace (unless
995                  * another truncate extends the file - this is desired though).
996                  */
997
998                 isize = i_size_read(inode);
999                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1000                 if (unlikely(!isize || index > end_index)) {
1001                         page_cache_release(page);
1002                         goto out;
1003                 }
1004
1005                 /* nr is the maximum number of bytes to copy from this page */
1006                 nr = PAGE_CACHE_SIZE;
1007                 if (index == end_index) {
1008                         nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1009                         if (nr <= offset) {
1010                                 page_cache_release(page);
1011                                 goto out;
1012                         }
1013                 }
1014                 nr = nr - offset;
1015
1016                 /* If users can be writing to this page using arbitrary
1017                  * virtual addresses, take care about potential aliasing
1018                  * before reading the page on the kernel side.
1019                  */
1020                 if (mapping_writably_mapped(mapping))
1021                         flush_dcache_page(page);
1022
1023                 /*
1024                  * When a sequential read accesses a page several times,
1025                  * only mark it as accessed the first time.
1026                  */
1027                 if (prev_index != index || offset != prev_offset)
1028                         mark_page_accessed(page);
1029                 prev_index = index;
1030
1031                 /*
1032                  * Ok, we have the page, and it's up-to-date, so
1033                  * now we can copy it to user space...
1034                  *
1035                  * The actor routine returns how many bytes were actually used..
1036                  * NOTE! This may not be the same as how much of a user buffer
1037                  * we filled up (we may be padding etc), so we can only update
1038                  * "pos" here (the actor routine has to update the user buffer
1039                  * pointers and the remaining count).
1040                  */
1041                 ret = actor(desc, page, offset, nr);
1042                 offset += ret;
1043                 index += offset >> PAGE_CACHE_SHIFT;
1044                 offset &= ~PAGE_CACHE_MASK;
1045                 prev_offset = offset;
1046
1047                 page_cache_release(page);
1048                 if (ret == nr && desc->count)
1049                         continue;
1050                 goto out;
1051
1052 page_not_up_to_date:
1053                 /* Get exclusive access to the page ... */
1054                 error = lock_page_killable(page);
1055                 if (unlikely(error))
1056                         goto readpage_error;
1057
1058 page_not_up_to_date_locked:
1059                 /* Did it get truncated before we got the lock? */
1060                 if (!page->mapping) {
1061                         unlock_page(page);
1062                         page_cache_release(page);
1063                         continue;
1064                 }
1065
1066                 /* Did somebody else fill it already? */
1067                 if (PageUptodate(page)) {
1068                         unlock_page(page);
1069                         goto page_ok;
1070                 }
1071
1072 readpage:
1073                 /*
1074                  * A previous I/O error may have been due to temporary
1075                  * failures, eg. multipath errors.
1076                  * PG_error will be set again if readpage fails.
1077                  */
1078                 ClearPageError(page);
1079                 /* Start the actual read. The read will unlock the page. */
1080                 error = mapping->a_ops->readpage(filp, page);
1081
1082                 if (unlikely(error)) {
1083                         if (error == AOP_TRUNCATED_PAGE) {
1084                                 page_cache_release(page);
1085                                 goto find_page;
1086                         }
1087                         goto readpage_error;
1088                 }
1089
1090                 if (!PageUptodate(page)) {
1091                         error = lock_page_killable(page);
1092                         if (unlikely(error))
1093                                 goto readpage_error;
1094                         if (!PageUptodate(page)) {
1095                                 if (page->mapping == NULL) {
1096                                         /*
1097                                          * invalidate_mapping_pages got it
1098                                          */
1099                                         unlock_page(page);
1100                                         page_cache_release(page);
1101                                         goto find_page;
1102                                 }
1103                                 unlock_page(page);
1104                                 shrink_readahead_size_eio(filp, ra);
1105                                 error = -EIO;
1106                                 goto readpage_error;
1107                         }
1108                         unlock_page(page);
1109                 }
1110
1111                 goto page_ok;
1112
1113 readpage_error:
1114                 /* UHHUH! A synchronous read error occurred. Report it */
1115                 desc->error = error;
1116                 page_cache_release(page);
1117                 goto out;
1118
1119 no_cached_page:
1120                 /*
1121                  * Ok, it wasn't cached, so we need to create a new
1122                  * page..
1123                  */
1124                 page = page_cache_alloc_cold(mapping);
1125                 if (!page) {
1126                         desc->error = -ENOMEM;
1127                         goto out;
1128                 }
1129                 error = add_to_page_cache_lru(page, mapping,
1130                                                 index, GFP_KERNEL);
1131                 if (error) {
1132                         page_cache_release(page);
1133                         if (error == -EEXIST)
1134                                 goto find_page;
1135                         desc->error = error;
1136                         goto out;
1137                 }
1138                 goto readpage;
1139         }
1140
1141 out:
1142         ra->prev_pos = prev_index;
1143         ra->prev_pos <<= PAGE_CACHE_SHIFT;
1144         ra->prev_pos |= prev_offset;
1145
1146         *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1147         file_accessed(filp);
1148 }
1149
1150 int file_read_actor(read_descriptor_t *desc, struct page *page,
1151                         unsigned long offset, unsigned long size)
1152 {
1153         char *kaddr;
1154         unsigned long left, count = desc->count;
1155
1156         if (size > count)
1157                 size = count;
1158
1159         /*
1160          * Faults on the destination of a read are common, so do it before
1161          * taking the kmap.
1162          */
1163         if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1164                 kaddr = kmap_atomic(page, KM_USER0);
1165                 left = __copy_to_user_inatomic(desc->arg.buf,
1166                                                 kaddr + offset, size);
1167                 kunmap_atomic(kaddr, KM_USER0);
1168                 if (left == 0)
1169                         goto success;
1170         }
1171
1172         /* Do it the slow way */
1173         kaddr = kmap(page);
1174         left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1175         kunmap(page);
1176
1177         if (left) {
1178                 size -= left;
1179                 desc->error = -EFAULT;
1180         }
1181 success:
1182         desc->count = count - size;
1183         desc->written += size;
1184         desc->arg.buf += size;
1185         return size;
1186 }
1187
1188 /*
1189  * Performs necessary checks before doing a write
1190  * @iov:        io vector request
1191  * @nr_segs:    number of segments in the iovec
1192  * @count:      number of bytes to write
1193  * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1194  *
1195  * Adjust number of segments and amount of bytes to write (nr_segs should be
1196  * properly initialized first). Returns appropriate error code that caller
1197  * should return or zero in case that write should be allowed.
1198  */
1199 int generic_segment_checks(const struct iovec *iov,
1200                         unsigned long *nr_segs, size_t *count, int access_flags)
1201 {
1202         unsigned long   seg;
1203         size_t cnt = 0;
1204         for (seg = 0; seg < *nr_segs; seg++) {
1205                 const struct iovec *iv = &iov[seg];
1206
1207                 /*
1208                  * If any segment has a negative length, or the cumulative
1209                  * length ever wraps negative then return -EINVAL.
1210                  */
1211                 cnt += iv->iov_len;
1212                 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1213                         return -EINVAL;
1214                 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1215                         continue;
1216                 if (seg == 0)
1217                         return -EFAULT;
1218                 *nr_segs = seg;
1219                 cnt -= iv->iov_len;     /* This segment is no good */
1220                 break;
1221         }
1222         *count = cnt;
1223         return 0;
1224 }
1225 EXPORT_SYMBOL(generic_segment_checks);
1226
1227 /**
1228  * generic_file_aio_read - generic filesystem read routine
1229  * @iocb:       kernel I/O control block
1230  * @iov:        io vector request
1231  * @nr_segs:    number of segments in the iovec
1232  * @pos:        current file position
1233  *
1234  * This is the "read()" routine for all filesystems
1235  * that can use the page cache directly.
1236  */
1237 ssize_t
1238 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1239                 unsigned long nr_segs, loff_t pos)
1240 {
1241         struct file *filp = iocb->ki_filp;
1242         ssize_t retval;
1243         unsigned long seg = 0;
1244         size_t count;
1245         loff_t *ppos = &iocb->ki_pos;
1246         struct blk_plug plug;
1247
1248         count = 0;
1249         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1250         if (retval)
1251                 return retval;
1252
1253         blk_start_plug(&plug);
1254
1255         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1256         if (filp->f_flags & O_DIRECT) {
1257                 loff_t size;
1258                 struct address_space *mapping;
1259                 struct inode *inode;
1260
1261                 mapping = filp->f_mapping;
1262                 inode = mapping->host;
1263                 if (!count)
1264                         goto out; /* skip atime */
1265                 size = i_size_read(inode);
1266                 if (pos < size) {
1267                         retval = filemap_write_and_wait_range(mapping, pos,
1268                                         pos + iov_length(iov, nr_segs) - 1);
1269                         if (!retval) {
1270                                 retval = mapping->a_ops->direct_IO(READ, iocb,
1271                                                         iov, pos, nr_segs);
1272                         }
1273                         if (retval > 0) {
1274                                 *ppos = pos + retval;
1275                                 count -= retval;
1276                         }
1277
1278                         /*
1279                          * Btrfs can have a short DIO read if we encounter
1280                          * compressed extents, so if there was an error, or if
1281                          * we've already read everything we wanted to, or if
1282                          * there was a short read because we hit EOF, go ahead
1283                          * and return.  Otherwise fallthrough to buffered io for
1284                          * the rest of the read.
1285                          */
1286                         if (retval < 0 || !count || *ppos >= size) {
1287                                 file_accessed(filp);
1288                                 goto out;
1289                         }
1290                 }
1291         }
1292
1293         count = retval;
1294         for (seg = 0; seg < nr_segs; seg++) {
1295                 read_descriptor_t desc;
1296                 loff_t offset = 0;
1297
1298                 /*
1299                  * If we did a short DIO read we need to skip the section of the
1300                  * iov that we've already read data into.
1301                  */
1302                 if (count) {
1303                         if (count > iov[seg].iov_len) {
1304                                 count -= iov[seg].iov_len;
1305                                 continue;
1306                         }
1307                         offset = count;
1308                         count = 0;
1309                 }
1310
1311                 desc.written = 0;
1312                 desc.arg.buf = iov[seg].iov_base + offset;
1313                 desc.count = iov[seg].iov_len - offset;
1314                 if (desc.count == 0)
1315                         continue;
1316                 desc.error = 0;
1317                 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1318                 retval += desc.written;
1319                 if (desc.error) {
1320                         retval = retval ?: desc.error;
1321                         break;
1322                 }
1323                 if (desc.count > 0)
1324                         break;
1325         }
1326 out:
1327         blk_finish_plug(&plug);
1328         return retval;
1329 }
1330 EXPORT_SYMBOL(generic_file_aio_read);
1331
1332 static ssize_t
1333 do_readahead(struct address_space *mapping, struct file *filp,
1334              pgoff_t index, unsigned long nr)
1335 {
1336         if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1337                 return -EINVAL;
1338
1339         force_page_cache_readahead(mapping, filp, index, nr);
1340         return 0;
1341 }
1342
1343 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1344 {
1345         ssize_t ret;
1346         struct file *file;
1347
1348         ret = -EBADF;
1349         file = fget(fd);
1350         if (file) {
1351                 if (file->f_mode & FMODE_READ) {
1352                         struct address_space *mapping = file->f_mapping;
1353                         pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1354                         pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1355                         unsigned long len = end - start + 1;
1356                         ret = do_readahead(mapping, file, start, len);
1357                 }
1358                 fput(file);
1359         }
1360         return ret;
1361 }
1362 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1363 asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1364 {
1365         return SYSC_readahead((int) fd, offset, (size_t) count);
1366 }
1367 SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1368 #endif
1369
1370 #ifdef CONFIG_MMU
1371 /**
1372  * page_cache_read - adds requested page to the page cache if not already there
1373  * @file:       file to read
1374  * @offset:     page index
1375  *
1376  * This adds the requested page to the page cache if it isn't already there,
1377  * and schedules an I/O to read in its contents from disk.
1378  */
1379 static int page_cache_read(struct file *file, pgoff_t offset)
1380 {
1381         struct address_space *mapping = file->f_mapping;
1382         struct page *page; 
1383         int ret;
1384
1385         do {
1386                 page = page_cache_alloc_cold(mapping);
1387                 if (!page)
1388                         return -ENOMEM;
1389
1390                 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1391                 if (ret == 0)
1392                         ret = mapping->a_ops->readpage(file, page);
1393                 else if (ret == -EEXIST)
1394                         ret = 0; /* losing race to add is OK */
1395
1396                 page_cache_release(page);
1397
1398         } while (ret == AOP_TRUNCATED_PAGE);
1399                 
1400         return ret;
1401 }
1402
1403 #define MMAP_LOTSAMISS  (100)
1404
1405 /*
1406  * Synchronous readahead happens when we don't even find
1407  * a page in the page cache at all.
1408  */
1409 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1410                                    struct file_ra_state *ra,
1411                                    struct file *file,
1412                                    pgoff_t offset)
1413 {
1414         unsigned long ra_pages;
1415         struct address_space *mapping = file->f_mapping;
1416
1417         /* If we don't want any read-ahead, don't bother */
1418         if (VM_RandomReadHint(vma))
1419                 return;
1420
1421         if (VM_SequentialReadHint(vma) ||
1422                         offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
1423                 page_cache_sync_readahead(mapping, ra, file, offset,
1424                                           ra->ra_pages);
1425                 return;
1426         }
1427
1428         if (ra->mmap_miss < INT_MAX)
1429                 ra->mmap_miss++;
1430
1431         /*
1432          * Do we miss much more than hit in this file? If so,
1433          * stop bothering with read-ahead. It will only hurt.
1434          */
1435         if (ra->mmap_miss > MMAP_LOTSAMISS)
1436                 return;
1437
1438         /*
1439          * mmap read-around
1440          */
1441         ra_pages = max_sane_readahead(ra->ra_pages);
1442         if (ra_pages) {
1443                 ra->start = max_t(long, 0, offset - ra_pages/2);
1444                 ra->size = ra_pages;
1445                 ra->async_size = 0;
1446                 ra_submit(ra, mapping, file);
1447         }
1448 }
1449
1450 /*
1451  * Asynchronous readahead happens when we find the page and PG_readahead,
1452  * so we want to possibly extend the readahead further..
1453  */
1454 static void do_async_mmap_readahead(struct vm_area_struct *vma,
1455                                     struct file_ra_state *ra,
1456                                     struct file *file,
1457                                     struct page *page,
1458                                     pgoff_t offset)
1459 {
1460         struct address_space *mapping = file->f_mapping;
1461
1462         /* If we don't want any read-ahead, don't bother */
1463         if (VM_RandomReadHint(vma))
1464                 return;
1465         if (ra->mmap_miss > 0)
1466                 ra->mmap_miss--;
1467         if (PageReadahead(page))
1468                 page_cache_async_readahead(mapping, ra, file,
1469                                            page, offset, ra->ra_pages);
1470 }
1471
1472 /**
1473  * filemap_fault - read in file data for page fault handling
1474  * @vma:        vma in which the fault was taken
1475  * @vmf:        struct vm_fault containing details of the fault
1476  *
1477  * filemap_fault() is invoked via the vma operations vector for a
1478  * mapped memory region to read in file data during a page fault.
1479  *
1480  * The goto's are kind of ugly, but this streamlines the normal case of having
1481  * it in the page cache, and handles the special cases reasonably without
1482  * having a lot of duplicated code.
1483  */
1484 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1485 {
1486         int error;
1487         struct file *file = vma->vm_file;
1488         struct address_space *mapping = file->f_mapping;
1489         struct file_ra_state *ra = &file->f_ra;
1490         struct inode *inode = mapping->host;
1491         pgoff_t offset = vmf->pgoff;
1492         struct page *page;
1493         pgoff_t size;
1494         int ret = 0;
1495
1496         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1497         if (offset >= size)
1498                 return VM_FAULT_SIGBUS;
1499
1500         /*
1501          * Do we have something in the page cache already?
1502          */
1503         page = find_get_page(mapping, offset);
1504         if (likely(page)) {
1505                 /*
1506                  * We found the page, so try async readahead before
1507                  * waiting for the lock.
1508                  */
1509                 do_async_mmap_readahead(vma, ra, file, page, offset);
1510         } else {
1511                 /* No page in the page cache at all */
1512                 do_sync_mmap_readahead(vma, ra, file, offset);
1513                 count_vm_event(PGMAJFAULT);
1514                 ret = VM_FAULT_MAJOR;
1515 retry_find:
1516                 page = find_get_page(mapping, offset);
1517                 if (!page)
1518                         goto no_cached_page;
1519         }
1520
1521         if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1522                 page_cache_release(page);
1523                 return ret | VM_FAULT_RETRY;
1524         }
1525
1526         /* Did it get truncated? */
1527         if (unlikely(page->mapping != mapping)) {
1528                 unlock_page(page);
1529                 put_page(page);
1530                 goto retry_find;
1531         }
1532         VM_BUG_ON(page->index != offset);
1533
1534         /*
1535          * We have a locked page in the page cache, now we need to check
1536          * that it's up-to-date. If not, it is going to be due to an error.
1537          */
1538         if (unlikely(!PageUptodate(page)))
1539                 goto page_not_uptodate;
1540
1541         /*
1542          * Found the page and have a reference on it.
1543          * We must recheck i_size under page lock.
1544          */
1545         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1546         if (unlikely(offset >= size)) {
1547                 unlock_page(page);
1548                 page_cache_release(page);
1549                 return VM_FAULT_SIGBUS;
1550         }
1551
1552         ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
1553         vmf->page = page;
1554         return ret | VM_FAULT_LOCKED;
1555
1556 no_cached_page:
1557         /*
1558          * We're only likely to ever get here if MADV_RANDOM is in
1559          * effect.
1560          */
1561         error = page_cache_read(file, offset);
1562
1563         /*
1564          * The page we want has now been added to the page cache.
1565          * In the unlikely event that someone removed it in the
1566          * meantime, we'll just come back here and read it again.
1567          */
1568         if (error >= 0)
1569                 goto retry_find;
1570
1571         /*
1572          * An error return from page_cache_read can result if the
1573          * system is low on memory, or a problem occurs while trying
1574          * to schedule I/O.
1575          */
1576         if (error == -ENOMEM)
1577                 return VM_FAULT_OOM;
1578         return VM_FAULT_SIGBUS;
1579
1580 page_not_uptodate:
1581         /*
1582          * Umm, take care of errors if the page isn't up-to-date.
1583          * Try to re-read it _once_. We do this synchronously,
1584          * because there really aren't any performance issues here
1585          * and we need to check for errors.
1586          */
1587         ClearPageError(page);
1588         error = mapping->a_ops->readpage(file, page);
1589         if (!error) {
1590                 wait_on_page_locked(page);
1591                 if (!PageUptodate(page))
1592                         error = -EIO;
1593         }
1594         page_cache_release(page);
1595
1596         if (!error || error == AOP_TRUNCATED_PAGE)
1597                 goto retry_find;
1598
1599         /* Things didn't work out. Return zero to tell the mm layer so. */
1600         shrink_readahead_size_eio(file, ra);
1601         return VM_FAULT_SIGBUS;
1602 }
1603 EXPORT_SYMBOL(filemap_fault);
1604
1605 const struct vm_operations_struct generic_file_vm_ops = {
1606         .fault          = filemap_fault,
1607 };
1608
1609 /* This is used for a general mmap of a disk file */
1610
1611 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1612 {
1613         struct address_space *mapping = file->f_mapping;
1614
1615         if (!mapping->a_ops->readpage)
1616                 return -ENOEXEC;
1617         file_accessed(file);
1618         vma->vm_ops = &generic_file_vm_ops;
1619         vma->vm_flags |= VM_CAN_NONLINEAR;
1620         return 0;
1621 }
1622
1623 /*
1624  * This is for filesystems which do not implement ->writepage.
1625  */
1626 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1627 {
1628         if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1629                 return -EINVAL;
1630         return generic_file_mmap(file, vma);
1631 }
1632 #else
1633 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1634 {
1635         return -ENOSYS;
1636 }
1637 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1638 {
1639         return -ENOSYS;
1640 }
1641 #endif /* CONFIG_MMU */
1642
1643 EXPORT_SYMBOL(generic_file_mmap);
1644 EXPORT_SYMBOL(generic_file_readonly_mmap);
1645
1646 static struct page *__read_cache_page(struct address_space *mapping,
1647                                 pgoff_t index,
1648                                 int (*filler)(void *,struct page*),
1649                                 void *data,
1650                                 gfp_t gfp)
1651 {
1652         struct page *page;
1653         int err;
1654 repeat:
1655         page = find_get_page(mapping, index);
1656         if (!page) {
1657                 page = __page_cache_alloc(gfp | __GFP_COLD);
1658                 if (!page)
1659                         return ERR_PTR(-ENOMEM);
1660                 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1661                 if (unlikely(err)) {
1662                         page_cache_release(page);
1663                         if (err == -EEXIST)
1664                                 goto repeat;
1665                         /* Presumably ENOMEM for radix tree node */
1666                         return ERR_PTR(err);
1667                 }
1668                 err = filler(data, page);
1669                 if (err < 0) {
1670                         page_cache_release(page);
1671                         page = ERR_PTR(err);
1672                 }
1673         }
1674         return page;
1675 }
1676
1677 static struct page *do_read_cache_page(struct address_space *mapping,
1678                                 pgoff_t index,
1679                                 int (*filler)(void *,struct page*),
1680                                 void *data,
1681                                 gfp_t gfp)
1682
1683 {
1684         struct page *page;
1685         int err;
1686
1687 retry:
1688         page = __read_cache_page(mapping, index, filler, data, gfp);
1689         if (IS_ERR(page))
1690                 return page;
1691         if (PageUptodate(page))
1692                 goto out;
1693
1694         lock_page(page);
1695         if (!page->mapping) {
1696                 unlock_page(page);
1697                 page_cache_release(page);
1698                 goto retry;
1699         }
1700         if (PageUptodate(page)) {
1701                 unlock_page(page);
1702                 goto out;
1703         }
1704         err = filler(data, page);
1705         if (err < 0) {
1706                 page_cache_release(page);
1707                 return ERR_PTR(err);
1708         }
1709 out:
1710         mark_page_accessed(page);
1711         return page;
1712 }
1713
1714 /**
1715  * read_cache_page_async - read into page cache, fill it if needed
1716  * @mapping:    the page's address_space
1717  * @index:      the page index
1718  * @filler:     function to perform the read
1719  * @data:       destination for read data
1720  *
1721  * Same as read_cache_page, but don't wait for page to become unlocked
1722  * after submitting it to the filler.
1723  *
1724  * Read into the page cache. If a page already exists, and PageUptodate() is
1725  * not set, try to fill the page but don't wait for it to become unlocked.
1726  *
1727  * If the page does not get brought uptodate, return -EIO.
1728  */
1729 struct page *read_cache_page_async(struct address_space *mapping,
1730                                 pgoff_t index,
1731                                 int (*filler)(void *,struct page*),
1732                                 void *data)
1733 {
1734         return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1735 }
1736 EXPORT_SYMBOL(read_cache_page_async);
1737
1738 static struct page *wait_on_page_read(struct page *page)
1739 {
1740         if (!IS_ERR(page)) {
1741                 wait_on_page_locked(page);
1742                 if (!PageUptodate(page)) {
1743                         page_cache_release(page);
1744                         page = ERR_PTR(-EIO);
1745                 }
1746         }
1747         return page;
1748 }
1749
1750 /**
1751  * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1752  * @mapping:    the page's address_space
1753  * @index:      the page index
1754  * @gfp:        the page allocator flags to use if allocating
1755  *
1756  * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1757  * any new page allocations done using the specified allocation flags. Note
1758  * that the Radix tree operations will still use GFP_KERNEL, so you can't
1759  * expect to do this atomically or anything like that - but you can pass in
1760  * other page requirements.
1761  *
1762  * If the page does not get brought uptodate, return -EIO.
1763  */
1764 struct page *read_cache_page_gfp(struct address_space *mapping,
1765                                 pgoff_t index,
1766                                 gfp_t gfp)
1767 {
1768         filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1769
1770         return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1771 }
1772 EXPORT_SYMBOL(read_cache_page_gfp);
1773
1774 /**
1775  * read_cache_page - read into page cache, fill it if needed
1776  * @mapping:    the page's address_space
1777  * @index:      the page index
1778  * @filler:     function to perform the read
1779  * @data:       destination for read data
1780  *
1781  * Read into the page cache. If a page already exists, and PageUptodate() is
1782  * not set, try to fill the page then wait for it to become unlocked.
1783  *
1784  * If the page does not get brought uptodate, return -EIO.
1785  */
1786 struct page *read_cache_page(struct address_space *mapping,
1787                                 pgoff_t index,
1788                                 int (*filler)(void *,struct page*),
1789                                 void *data)
1790 {
1791         return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1792 }
1793 EXPORT_SYMBOL(read_cache_page);
1794
1795 /*
1796  * The logic we want is
1797  *
1798  *      if suid or (sgid and xgrp)
1799  *              remove privs
1800  */
1801 int should_remove_suid(struct dentry *dentry)
1802 {
1803         mode_t mode = dentry->d_inode->i_mode;
1804         int kill = 0;
1805
1806         /* suid always must be killed */
1807         if (unlikely(mode & S_ISUID))
1808                 kill = ATTR_KILL_SUID;
1809
1810         /*
1811          * sgid without any exec bits is just a mandatory locking mark; leave
1812          * it alone.  If some exec bits are set, it's a real sgid; kill it.
1813          */
1814         if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1815                 kill |= ATTR_KILL_SGID;
1816
1817         if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1818                 return kill;
1819
1820         return 0;
1821 }
1822 EXPORT_SYMBOL(should_remove_suid);
1823
1824 static int __remove_suid(struct dentry *dentry, int kill)
1825 {
1826         struct iattr newattrs;
1827
1828         newattrs.ia_valid = ATTR_FORCE | kill;
1829         return notify_change(dentry, &newattrs);
1830 }
1831
1832 int file_remove_suid(struct file *file)
1833 {
1834         struct dentry *dentry = file->f_path.dentry;
1835         int killsuid = should_remove_suid(dentry);
1836         int killpriv = security_inode_need_killpriv(dentry);
1837         int error = 0;
1838
1839         if (killpriv < 0)
1840                 return killpriv;
1841         if (killpriv)
1842                 error = security_inode_killpriv(dentry);
1843         if (!error && killsuid)
1844                 error = __remove_suid(dentry, killsuid);
1845
1846         return error;
1847 }
1848 EXPORT_SYMBOL(file_remove_suid);
1849
1850 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1851                         const struct iovec *iov, size_t base, size_t bytes)
1852 {
1853         size_t copied = 0, left = 0;
1854
1855         while (bytes) {
1856                 char __user *buf = iov->iov_base + base;
1857                 int copy = min(bytes, iov->iov_len - base);
1858
1859                 base = 0;
1860                 left = __copy_from_user_inatomic(vaddr, buf, copy);
1861                 copied += copy;
1862                 bytes -= copy;
1863                 vaddr += copy;
1864                 iov++;
1865
1866                 if (unlikely(left))
1867                         break;
1868         }
1869         return copied - left;
1870 }
1871
1872 /*
1873  * Copy as much as we can into the page and return the number of bytes which
1874  * were successfully copied.  If a fault is encountered then return the number of
1875  * bytes which were copied.
1876  */
1877 size_t iov_iter_copy_from_user_atomic(struct page *page,
1878                 struct iov_iter *i, unsigned long offset, size_t bytes)
1879 {
1880         char *kaddr;
1881         size_t copied;
1882
1883         BUG_ON(!in_atomic());
1884         kaddr = kmap_atomic(page, KM_USER0);
1885         if (likely(i->nr_segs == 1)) {
1886                 int left;
1887                 char __user *buf = i->iov->iov_base + i->iov_offset;
1888                 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
1889                 copied = bytes - left;
1890         } else {
1891                 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1892                                                 i->iov, i->iov_offset, bytes);
1893         }
1894         kunmap_atomic(kaddr, KM_USER0);
1895
1896         return copied;
1897 }
1898 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1899
1900 /*
1901  * This has the same sideeffects and return value as
1902  * iov_iter_copy_from_user_atomic().
1903  * The difference is that it attempts to resolve faults.
1904  * Page must not be locked.
1905  */
1906 size_t iov_iter_copy_from_user(struct page *page,
1907                 struct iov_iter *i, unsigned long offset, size_t bytes)
1908 {
1909         char *kaddr;
1910         size_t copied;
1911
1912         kaddr = kmap(page);
1913         if (likely(i->nr_segs == 1)) {
1914                 int left;
1915                 char __user *buf = i->iov->iov_base + i->iov_offset;
1916                 left = __copy_from_user(kaddr + offset, buf, bytes);
1917                 copied = bytes - left;
1918         } else {
1919                 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1920                                                 i->iov, i->iov_offset, bytes);
1921         }
1922         kunmap(page);
1923         return copied;
1924 }
1925 EXPORT_SYMBOL(iov_iter_copy_from_user);
1926
1927 void iov_iter_advance(struct iov_iter *i, size_t bytes)
1928 {
1929         BUG_ON(i->count < bytes);
1930
1931         if (likely(i->nr_segs == 1)) {
1932                 i->iov_offset += bytes;
1933                 i->count -= bytes;
1934         } else {
1935                 const struct iovec *iov = i->iov;
1936                 size_t base = i->iov_offset;
1937
1938                 /*
1939                  * The !iov->iov_len check ensures we skip over unlikely
1940                  * zero-length segments (without overruning the iovec).
1941                  */
1942                 while (bytes || unlikely(i->count && !iov->iov_len)) {
1943                         int copy;
1944
1945                         copy = min(bytes, iov->iov_len - base);
1946                         BUG_ON(!i->count || i->count < copy);
1947                         i->count -= copy;
1948                         bytes -= copy;
1949                         base += copy;
1950                         if (iov->iov_len == base) {
1951                                 iov++;
1952                                 base = 0;
1953                         }
1954                 }
1955                 i->iov = iov;
1956                 i->iov_offset = base;
1957         }
1958 }
1959 EXPORT_SYMBOL(iov_iter_advance);
1960
1961 /*
1962  * Fault in the first iovec of the given iov_iter, to a maximum length
1963  * of bytes. Returns 0 on success, or non-zero if the memory could not be
1964  * accessed (ie. because it is an invalid address).
1965  *
1966  * writev-intensive code may want this to prefault several iovecs -- that
1967  * would be possible (callers must not rely on the fact that _only_ the
1968  * first iovec will be faulted with the current implementation).
1969  */
1970 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
1971 {
1972         char __user *buf = i->iov->iov_base + i->iov_offset;
1973         bytes = min(bytes, i->iov->iov_len - i->iov_offset);
1974         return fault_in_pages_readable(buf, bytes);
1975 }
1976 EXPORT_SYMBOL(iov_iter_fault_in_readable);
1977
1978 /*
1979  * Return the count of just the current iov_iter segment.
1980  */
1981 size_t iov_iter_single_seg_count(struct iov_iter *i)
1982 {
1983         const struct iovec *iov = i->iov;
1984         if (i->nr_segs == 1)
1985                 return i->count;
1986         else
1987                 return min(i->count, iov->iov_len - i->iov_offset);
1988 }
1989 EXPORT_SYMBOL(iov_iter_single_seg_count);
1990
1991 /*
1992  * Performs necessary checks before doing a write
1993  *
1994  * Can adjust writing position or amount of bytes to write.
1995  * Returns appropriate error code that caller should return or
1996  * zero in case that write should be allowed.
1997  */
1998 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
1999 {
2000         struct inode *inode = file->f_mapping->host;
2001         unsigned long limit = rlimit(RLIMIT_FSIZE);
2002
2003         if (unlikely(*pos < 0))
2004                 return -EINVAL;
2005
2006         if (!isblk) {
2007                 /* FIXME: this is for backwards compatibility with 2.4 */
2008                 if (file->f_flags & O_APPEND)
2009                         *pos = i_size_read(inode);
2010
2011                 if (limit != RLIM_INFINITY) {
2012                         if (*pos >= limit) {
2013                                 send_sig(SIGXFSZ, current, 0);
2014                                 return -EFBIG;
2015                         }
2016                         if (*count > limit - (typeof(limit))*pos) {
2017                                 *count = limit - (typeof(limit))*pos;
2018                         }
2019                 }
2020         }
2021
2022         /*
2023          * LFS rule
2024          */
2025         if (unlikely(*pos + *count > MAX_NON_LFS &&
2026                                 !(file->f_flags & O_LARGEFILE))) {
2027                 if (*pos >= MAX_NON_LFS) {
2028                         return -EFBIG;
2029                 }
2030                 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2031                         *count = MAX_NON_LFS - (unsigned long)*pos;
2032                 }
2033         }
2034
2035         /*
2036          * Are we about to exceed the fs block limit ?
2037          *
2038          * If we have written data it becomes a short write.  If we have
2039          * exceeded without writing data we send a signal and return EFBIG.
2040          * Linus frestrict idea will clean these up nicely..
2041          */
2042         if (likely(!isblk)) {
2043                 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2044                         if (*count || *pos > inode->i_sb->s_maxbytes) {
2045                                 return -EFBIG;
2046                         }
2047                         /* zero-length writes at ->s_maxbytes are OK */
2048                 }
2049
2050                 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2051                         *count = inode->i_sb->s_maxbytes - *pos;
2052         } else {
2053 #ifdef CONFIG_BLOCK
2054                 loff_t isize;
2055                 if (bdev_read_only(I_BDEV(inode)))
2056                         return -EPERM;
2057                 isize = i_size_read(inode);
2058                 if (*pos >= isize) {
2059                         if (*count || *pos > isize)
2060                                 return -ENOSPC;
2061                 }
2062
2063                 if (*pos + *count > isize)
2064                         *count = isize - *pos;
2065 #else
2066                 return -EPERM;
2067 #endif
2068         }
2069         return 0;
2070 }
2071 EXPORT_SYMBOL(generic_write_checks);
2072
2073 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2074                                 loff_t pos, unsigned len, unsigned flags,
2075                                 struct page **pagep, void **fsdata)
2076 {
2077         const struct address_space_operations *aops = mapping->a_ops;
2078
2079         return aops->write_begin(file, mapping, pos, len, flags,
2080                                                         pagep, fsdata);
2081 }
2082 EXPORT_SYMBOL(pagecache_write_begin);
2083
2084 int pagecache_write_end(struct file *file, struct address_space *mapping,
2085                                 loff_t pos, unsigned len, unsigned copied,
2086                                 struct page *page, void *fsdata)
2087 {
2088         const struct address_space_operations *aops = mapping->a_ops;
2089
2090         mark_page_accessed(page);
2091         return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2092 }
2093 EXPORT_SYMBOL(pagecache_write_end);
2094
2095 ssize_t
2096 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2097                 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2098                 size_t count, size_t ocount)
2099 {
2100         struct file     *file = iocb->ki_filp;
2101         struct address_space *mapping = file->f_mapping;
2102         struct inode    *inode = mapping->host;
2103         ssize_t         written;
2104         size_t          write_len;
2105         pgoff_t         end;
2106
2107         if (count != ocount)
2108                 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2109
2110         write_len = iov_length(iov, *nr_segs);
2111         end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2112
2113         written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2114         if (written)
2115                 goto out;
2116
2117         /*
2118          * After a write we want buffered reads to be sure to go to disk to get
2119          * the new data.  We invalidate clean cached page from the region we're
2120          * about to write.  We do this *before* the write so that we can return
2121          * without clobbering -EIOCBQUEUED from ->direct_IO().
2122          */
2123         if (mapping->nrpages) {
2124                 written = invalidate_inode_pages2_range(mapping,
2125                                         pos >> PAGE_CACHE_SHIFT, end);
2126                 /*
2127                  * If a page can not be invalidated, return 0 to fall back
2128                  * to buffered write.
2129                  */
2130                 if (written) {
2131                         if (written == -EBUSY)
2132                                 return 0;
2133                         goto out;
2134                 }
2135         }
2136
2137         written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2138
2139         /*
2140          * Finally, try again to invalidate clean pages which might have been
2141          * cached by non-direct readahead, or faulted in by get_user_pages()
2142          * if the source of the write was an mmap'ed region of the file
2143          * we're writing.  Either one is a pretty crazy thing to do,
2144          * so we don't support it 100%.  If this invalidation
2145          * fails, tough, the write still worked...
2146          */
2147         if (mapping->nrpages) {
2148                 invalidate_inode_pages2_range(mapping,
2149                                               pos >> PAGE_CACHE_SHIFT, end);
2150         }
2151
2152         if (written > 0) {
2153                 pos += written;
2154                 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2155                         i_size_write(inode, pos);
2156                         mark_inode_dirty(inode);
2157                 }
2158                 *ppos = pos;
2159         }
2160 out:
2161         return written;
2162 }
2163 EXPORT_SYMBOL(generic_file_direct_write);
2164
2165 /*
2166  * Find or create a page at the given pagecache position. Return the locked
2167  * page. This function is specifically for buffered writes.
2168  */
2169 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2170                                         pgoff_t index, unsigned flags)
2171 {
2172         int status;
2173         struct page *page;
2174         gfp_t gfp_notmask = 0;
2175         if (flags & AOP_FLAG_NOFS)
2176                 gfp_notmask = __GFP_FS;
2177 repeat:
2178         page = find_lock_page(mapping, index);
2179         if (page)
2180                 return page;
2181
2182         page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2183         if (!page)
2184                 return NULL;
2185         status = add_to_page_cache_lru(page, mapping, index,
2186                                                 GFP_KERNEL & ~gfp_notmask);
2187         if (unlikely(status)) {
2188                 page_cache_release(page);
2189                 if (status == -EEXIST)
2190                         goto repeat;
2191                 return NULL;
2192         }
2193         return page;
2194 }
2195 EXPORT_SYMBOL(grab_cache_page_write_begin);
2196
2197 static ssize_t generic_perform_write(struct file *file,
2198                                 struct iov_iter *i, loff_t pos)
2199 {
2200         struct address_space *mapping = file->f_mapping;
2201         const struct address_space_operations *a_ops = mapping->a_ops;
2202         long status = 0;
2203         ssize_t written = 0;
2204         unsigned int flags = 0;
2205
2206         /*
2207          * Copies from kernel address space cannot fail (NFSD is a big user).
2208          */
2209         if (segment_eq(get_fs(), KERNEL_DS))
2210                 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2211
2212         do {
2213                 struct page *page;
2214                 unsigned long offset;   /* Offset into pagecache page */
2215                 unsigned long bytes;    /* Bytes to write to page */
2216                 size_t copied;          /* Bytes copied from user */
2217                 void *fsdata;
2218
2219                 offset = (pos & (PAGE_CACHE_SIZE - 1));
2220                 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2221                                                 iov_iter_count(i));
2222
2223 again:
2224
2225                 /*
2226                  * Bring in the user page that we will copy from _first_.
2227                  * Otherwise there's a nasty deadlock on copying from the
2228                  * same page as we're writing to, without it being marked
2229                  * up-to-date.
2230                  *
2231                  * Not only is this an optimisation, but it is also required
2232                  * to check that the address is actually valid, when atomic
2233                  * usercopies are used, below.
2234                  */
2235                 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2236                         status = -EFAULT;
2237                         break;
2238                 }
2239
2240                 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2241                                                 &page, &fsdata);
2242                 if (unlikely(status))
2243                         break;
2244
2245                 if (mapping_writably_mapped(mapping))
2246                         flush_dcache_page(page);
2247
2248                 pagefault_disable();
2249                 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2250                 pagefault_enable();
2251                 flush_dcache_page(page);
2252
2253                 mark_page_accessed(page);
2254                 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2255                                                 page, fsdata);
2256                 if (unlikely(status < 0))
2257                         break;
2258                 copied = status;
2259
2260                 cond_resched();
2261
2262                 iov_iter_advance(i, copied);
2263                 if (unlikely(copied == 0)) {
2264                         /*
2265                          * If we were unable to copy any data at all, we must
2266                          * fall back to a single segment length write.
2267                          *
2268                          * If we didn't fallback here, we could livelock
2269                          * because not all segments in the iov can be copied at
2270                          * once without a pagefault.
2271                          */
2272                         bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2273                                                 iov_iter_single_seg_count(i));
2274                         goto again;
2275                 }
2276                 pos += copied;
2277                 written += copied;
2278
2279                 balance_dirty_pages_ratelimited(mapping);
2280
2281         } while (iov_iter_count(i));
2282
2283         return written ? written : status;
2284 }
2285
2286 ssize_t
2287 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2288                 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2289                 size_t count, ssize_t written)
2290 {
2291         struct file *file = iocb->ki_filp;
2292         ssize_t status;
2293         struct iov_iter i;
2294
2295         iov_iter_init(&i, iov, nr_segs, count, written);
2296         status = generic_perform_write(file, &i, pos);
2297
2298         if (likely(status >= 0)) {
2299                 written += status;
2300                 *ppos = pos + status;
2301         }
2302         
2303         return written ? written : status;
2304 }
2305 EXPORT_SYMBOL(generic_file_buffered_write);
2306
2307 /**
2308  * __generic_file_aio_write - write data to a file
2309  * @iocb:       IO state structure (file, offset, etc.)
2310  * @iov:        vector with data to write
2311  * @nr_segs:    number of segments in the vector
2312  * @ppos:       position where to write
2313  *
2314  * This function does all the work needed for actually writing data to a
2315  * file. It does all basic checks, removes SUID from the file, updates
2316  * modification times and calls proper subroutines depending on whether we
2317  * do direct IO or a standard buffered write.
2318  *
2319  * It expects i_mutex to be grabbed unless we work on a block device or similar
2320  * object which does not need locking at all.
2321  *
2322  * This function does *not* take care of syncing data in case of O_SYNC write.
2323  * A caller has to handle it. This is mainly due to the fact that we want to
2324  * avoid syncing under i_mutex.
2325  */
2326 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2327                                  unsigned long nr_segs, loff_t *ppos)
2328 {
2329         struct file *file = iocb->ki_filp;
2330         struct address_space * mapping = file->f_mapping;
2331         size_t ocount;          /* original count */
2332         size_t count;           /* after file limit checks */
2333         struct inode    *inode = mapping->host;
2334         loff_t          pos;
2335         ssize_t         written;
2336         ssize_t         err;
2337
2338         ocount = 0;
2339         err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2340         if (err)
2341                 return err;
2342
2343         count = ocount;
2344         pos = *ppos;
2345
2346         vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2347
2348         /* We can write back this queue in page reclaim */
2349         current->backing_dev_info = mapping->backing_dev_info;
2350         written = 0;
2351
2352         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2353         if (err)
2354                 goto out;
2355
2356         if (count == 0)
2357                 goto out;
2358
2359         err = file_remove_suid(file);
2360         if (err)
2361                 goto out;
2362
2363         file_update_time(file);
2364
2365         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2366         if (unlikely(file->f_flags & O_DIRECT)) {
2367                 loff_t endbyte;
2368                 ssize_t written_buffered;
2369
2370                 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2371                                                         ppos, count, ocount);
2372                 if (written < 0 || written == count)
2373                         goto out;
2374                 /*
2375                  * direct-io write to a hole: fall through to buffered I/O
2376                  * for completing the rest of the request.
2377                  */
2378                 pos += written;
2379                 count -= written;
2380                 written_buffered = generic_file_buffered_write(iocb, iov,
2381                                                 nr_segs, pos, ppos, count,
2382                                                 written);
2383                 /*
2384                  * If generic_file_buffered_write() retuned a synchronous error
2385                  * then we want to return the number of bytes which were
2386                  * direct-written, or the error code if that was zero.  Note
2387                  * that this differs from normal direct-io semantics, which
2388                  * will return -EFOO even if some bytes were written.
2389                  */
2390                 if (written_buffered < 0) {
2391                         err = written_buffered;
2392                         goto out;
2393                 }
2394
2395                 /*
2396                  * We need to ensure that the page cache pages are written to
2397                  * disk and invalidated to preserve the expected O_DIRECT
2398                  * semantics.
2399                  */
2400                 endbyte = pos + written_buffered - written - 1;
2401                 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2402                 if (err == 0) {
2403                         written = written_buffered;
2404                         invalidate_mapping_pages(mapping,
2405                                                  pos >> PAGE_CACHE_SHIFT,
2406                                                  endbyte >> PAGE_CACHE_SHIFT);
2407                 } else {
2408                         /*
2409                          * We don't know how much we wrote, so just return
2410                          * the number of bytes which were direct-written
2411                          */
2412                 }
2413         } else {
2414                 written = generic_file_buffered_write(iocb, iov, nr_segs,
2415                                 pos, ppos, count, written);
2416         }
2417 out:
2418         current->backing_dev_info = NULL;
2419         return written ? written : err;
2420 }
2421 EXPORT_SYMBOL(__generic_file_aio_write);
2422
2423 /**
2424  * generic_file_aio_write - write data to a file
2425  * @iocb:       IO state structure
2426  * @iov:        vector with data to write
2427  * @nr_segs:    number of segments in the vector
2428  * @pos:        position in file where to write
2429  *
2430  * This is a wrapper around __generic_file_aio_write() to be used by most
2431  * filesystems. It takes care of syncing the file in case of O_SYNC file
2432  * and acquires i_mutex as needed.
2433  */
2434 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2435                 unsigned long nr_segs, loff_t pos)
2436 {
2437         struct file *file = iocb->ki_filp;
2438         struct inode *inode = file->f_mapping->host;
2439         struct blk_plug plug;
2440         ssize_t ret;
2441
2442         BUG_ON(iocb->ki_pos != pos);
2443
2444         mutex_lock(&inode->i_mutex);
2445         blk_start_plug(&plug);
2446         ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2447         mutex_unlock(&inode->i_mutex);
2448
2449         if (ret > 0 || ret == -EIOCBQUEUED) {
2450                 ssize_t err;
2451
2452                 err = generic_write_sync(file, pos, ret);
2453                 if (err < 0 && ret > 0)
2454                         ret = err;
2455         }
2456         blk_finish_plug(&plug);
2457         return ret;
2458 }
2459 EXPORT_SYMBOL(generic_file_aio_write);
2460
2461 /**
2462  * try_to_release_page() - release old fs-specific metadata on a page
2463  *
2464  * @page: the page which the kernel is trying to free
2465  * @gfp_mask: memory allocation flags (and I/O mode)
2466  *
2467  * The address_space is to try to release any data against the page
2468  * (presumably at page->private).  If the release was successful, return `1'.
2469  * Otherwise return zero.
2470  *
2471  * This may also be called if PG_fscache is set on a page, indicating that the
2472  * page is known to the local caching routines.
2473  *
2474  * The @gfp_mask argument specifies whether I/O may be performed to release
2475  * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2476  *
2477  */
2478 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2479 {
2480         struct address_space * const mapping = page->mapping;
2481
2482         BUG_ON(!PageLocked(page));
2483         if (PageWriteback(page))
2484                 return 0;
2485
2486         if (mapping && mapping->a_ops->releasepage)
2487                 return mapping->a_ops->releasepage(page, gfp_mask);
2488         return try_to_free_buffers(page);
2489 }
2490
2491 EXPORT_SYMBOL(try_to_release_page);