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