849293c4f4187fd9da77554edd98e11785d9298d
[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/slab.h>
14 #include <linux/compiler.h>
15 #include <linux/fs.h>
16 #include <linux/uaccess.h>
17 #include <linux/aio.h>
18 #include <linux/capability.h>
19 #include <linux/kernel_stat.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               (vmtruncate)
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  *  ->task->proc_lock
106  *    ->dcache_lock             (proc_pid_lookup)
107  */
108
109 /*
110  * Remove a page from the page cache and free it. Caller has to make
111  * sure the page is locked and that nobody else uses it - or that usage
112  * is safe.  The caller must hold the mapping's tree_lock.
113  */
114 void __remove_from_page_cache(struct page *page)
115 {
116         struct address_space *mapping = page->mapping;
117
118         radix_tree_delete(&mapping->page_tree, page->index);
119         page->mapping = NULL;
120         mapping->nrpages--;
121         __dec_zone_page_state(page, NR_FILE_PAGES);
122         BUG_ON(page_mapped(page));
123
124         /*
125          * Some filesystems seem to re-dirty the page even after
126          * the VM has canceled the dirty bit (eg ext3 journaling).
127          *
128          * Fix it up by doing a final dirty accounting check after
129          * having removed the page entirely.
130          */
131         if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
132                 dec_zone_page_state(page, NR_FILE_DIRTY);
133                 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
134         }
135 }
136
137 void remove_from_page_cache(struct page *page)
138 {
139         struct address_space *mapping = page->mapping;
140
141         BUG_ON(!PageLocked(page));
142
143         spin_lock_irq(&mapping->tree_lock);
144         __remove_from_page_cache(page);
145         spin_unlock_irq(&mapping->tree_lock);
146         mem_cgroup_uncharge_cache_page(page);
147 }
148
149 static int sync_page(void *word)
150 {
151         struct address_space *mapping;
152         struct page *page;
153
154         page = container_of((unsigned long *)word, struct page, flags);
155
156         /*
157          * page_mapping() is being called without PG_locked held.
158          * Some knowledge of the state and use of the page is used to
159          * reduce the requirements down to a memory barrier.
160          * The danger here is of a stale page_mapping() return value
161          * indicating a struct address_space different from the one it's
162          * associated with when it is associated with one.
163          * After smp_mb(), it's either the correct page_mapping() for
164          * the page, or an old page_mapping() and the page's own
165          * page_mapping() has gone NULL.
166          * The ->sync_page() address_space operation must tolerate
167          * page_mapping() going NULL. By an amazing coincidence,
168          * this comes about because none of the users of the page
169          * in the ->sync_page() methods make essential use of the
170          * page_mapping(), merely passing the page down to the backing
171          * device's unplug functions when it's non-NULL, which in turn
172          * ignore it for all cases but swap, where only page_private(page) is
173          * of interest. When page_mapping() does go NULL, the entire
174          * call stack gracefully ignores the page and returns.
175          * -- wli
176          */
177         smp_mb();
178         mapping = page_mapping(page);
179         if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
180                 mapping->a_ops->sync_page(page);
181         io_schedule();
182         return 0;
183 }
184
185 static int sync_page_killable(void *word)
186 {
187         sync_page(word);
188         return fatal_signal_pending(current) ? -EINTR : 0;
189 }
190
191 /**
192  * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
193  * @mapping:    address space structure to write
194  * @start:      offset in bytes where the range starts
195  * @end:        offset in bytes where the range ends (inclusive)
196  * @sync_mode:  enable synchronous operation
197  *
198  * Start writeback against all of a mapping's dirty pages that lie
199  * within the byte offsets <start, end> inclusive.
200  *
201  * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
202  * opposed to a regular memory cleansing writeback.  The difference between
203  * these two operations is that if a dirty page/buffer is encountered, it must
204  * be waited upon, and not just skipped over.
205  */
206 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
207                                 loff_t end, int sync_mode)
208 {
209         int ret;
210         struct writeback_control wbc = {
211                 .sync_mode = sync_mode,
212                 .nr_to_write = LONG_MAX,
213                 .range_start = start,
214                 .range_end = end,
215         };
216
217         if (!mapping_cap_writeback_dirty(mapping))
218                 return 0;
219
220         ret = do_writepages(mapping, &wbc);
221         return ret;
222 }
223
224 static inline int __filemap_fdatawrite(struct address_space *mapping,
225         int sync_mode)
226 {
227         return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
228 }
229
230 int filemap_fdatawrite(struct address_space *mapping)
231 {
232         return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
233 }
234 EXPORT_SYMBOL(filemap_fdatawrite);
235
236 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
237                                 loff_t end)
238 {
239         return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
240 }
241 EXPORT_SYMBOL(filemap_fdatawrite_range);
242
243 /**
244  * filemap_flush - mostly a non-blocking flush
245  * @mapping:    target address_space
246  *
247  * This is a mostly non-blocking flush.  Not suitable for data-integrity
248  * purposes - I/O may not be started against all dirty pages.
249  */
250 int filemap_flush(struct address_space *mapping)
251 {
252         return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
253 }
254 EXPORT_SYMBOL(filemap_flush);
255
256 /**
257  * wait_on_page_writeback_range - wait for writeback to complete
258  * @mapping:    target address_space
259  * @start:      beginning page index
260  * @end:        ending page index
261  *
262  * Wait for writeback to complete against pages indexed by start->end
263  * inclusive
264  */
265 int wait_on_page_writeback_range(struct address_space *mapping,
266                                 pgoff_t start, pgoff_t end)
267 {
268         struct pagevec pvec;
269         int nr_pages;
270         int ret = 0;
271         pgoff_t index;
272
273         if (end < start)
274                 return 0;
275
276         pagevec_init(&pvec, 0);
277         index = start;
278         while ((index <= end) &&
279                         (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
280                         PAGECACHE_TAG_WRITEBACK,
281                         min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
282                 unsigned i;
283
284                 for (i = 0; i < nr_pages; i++) {
285                         struct page *page = pvec.pages[i];
286
287                         /* until radix tree lookup accepts end_index */
288                         if (page->index > end)
289                                 continue;
290
291                         wait_on_page_writeback(page);
292                         if (PageError(page))
293                                 ret = -EIO;
294                 }
295                 pagevec_release(&pvec);
296                 cond_resched();
297         }
298
299         /* Check for outstanding write errors */
300         if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
301                 ret = -ENOSPC;
302         if (test_and_clear_bit(AS_EIO, &mapping->flags))
303                 ret = -EIO;
304
305         return ret;
306 }
307
308 /**
309  * filemap_fdatawait_range - wait for all under-writeback pages to complete in a given range
310  * @mapping: address space structure to wait for
311  * @start:      offset in bytes where the range starts
312  * @end:        offset in bytes where the range ends (inclusive)
313  *
314  * Walk the list of under-writeback pages of the given address space
315  * in the given range and wait for all of them.
316  *
317  * This is just a simple wrapper so that callers don't have to convert offsets
318  * to page indexes themselves
319  */
320 int filemap_fdatawait_range(struct address_space *mapping, loff_t start,
321                             loff_t end)
322 {
323         return wait_on_page_writeback_range(mapping, start >> PAGE_CACHE_SHIFT,
324                                             end >> PAGE_CACHE_SHIFT);
325 }
326 EXPORT_SYMBOL(filemap_fdatawait_range);
327
328 /**
329  * sync_page_range - write and wait on all pages in the passed range
330  * @inode:      target inode
331  * @mapping:    target address_space
332  * @pos:        beginning offset in pages to write
333  * @count:      number of bytes to write
334  *
335  * Write and wait upon all the pages in the passed range.  This is a "data
336  * integrity" operation.  It waits upon in-flight writeout before starting and
337  * waiting upon new writeout.  If there was an IO error, return it.
338  *
339  * We need to re-take i_mutex during the generic_osync_inode list walk because
340  * it is otherwise livelockable.
341  */
342 int sync_page_range(struct inode *inode, struct address_space *mapping,
343                         loff_t pos, loff_t count)
344 {
345         pgoff_t start = pos >> PAGE_CACHE_SHIFT;
346         pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
347         int ret;
348
349         if (!mapping_cap_writeback_dirty(mapping) || !count)
350                 return 0;
351         ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
352         if (ret == 0) {
353                 mutex_lock(&inode->i_mutex);
354                 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
355                 mutex_unlock(&inode->i_mutex);
356         }
357         if (ret == 0)
358                 ret = wait_on_page_writeback_range(mapping, start, end);
359         return ret;
360 }
361 EXPORT_SYMBOL(sync_page_range);
362
363 /**
364  * sync_page_range_nolock - write & wait on all pages in the passed range without locking
365  * @inode:      target inode
366  * @mapping:    target address_space
367  * @pos:        beginning offset in pages to write
368  * @count:      number of bytes to write
369  *
370  * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea
371  * as it forces O_SYNC writers to different parts of the same file
372  * to be serialised right until io completion.
373  */
374 int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
375                            loff_t pos, loff_t count)
376 {
377         pgoff_t start = pos >> PAGE_CACHE_SHIFT;
378         pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
379         int ret;
380
381         if (!mapping_cap_writeback_dirty(mapping) || !count)
382                 return 0;
383         ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
384         if (ret == 0)
385                 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
386         if (ret == 0)
387                 ret = wait_on_page_writeback_range(mapping, start, end);
388         return ret;
389 }
390 EXPORT_SYMBOL(sync_page_range_nolock);
391
392 /**
393  * filemap_fdatawait - wait for all under-writeback pages to complete
394  * @mapping: address space structure to wait for
395  *
396  * Walk the list of under-writeback pages of the given address space
397  * and wait for all of them.
398  */
399 int filemap_fdatawait(struct address_space *mapping)
400 {
401         loff_t i_size = i_size_read(mapping->host);
402
403         if (i_size == 0)
404                 return 0;
405
406         return wait_on_page_writeback_range(mapping, 0,
407                                 (i_size - 1) >> PAGE_CACHE_SHIFT);
408 }
409 EXPORT_SYMBOL(filemap_fdatawait);
410
411 int filemap_write_and_wait(struct address_space *mapping)
412 {
413         int err = 0;
414
415         if (mapping->nrpages) {
416                 err = filemap_fdatawrite(mapping);
417                 /*
418                  * Even if the above returned error, the pages may be
419                  * written partially (e.g. -ENOSPC), so we wait for it.
420                  * But the -EIO is special case, it may indicate the worst
421                  * thing (e.g. bug) happened, so we avoid waiting for it.
422                  */
423                 if (err != -EIO) {
424                         int err2 = filemap_fdatawait(mapping);
425                         if (!err)
426                                 err = err2;
427                 }
428         }
429         return err;
430 }
431 EXPORT_SYMBOL(filemap_write_and_wait);
432
433 /**
434  * filemap_write_and_wait_range - write out & wait on a file range
435  * @mapping:    the address_space for the pages
436  * @lstart:     offset in bytes where the range starts
437  * @lend:       offset in bytes where the range ends (inclusive)
438  *
439  * Write out and wait upon file offsets lstart->lend, inclusive.
440  *
441  * Note that `lend' is inclusive (describes the last byte to be written) so
442  * that this function can be used to write to the very end-of-file (end = -1).
443  */
444 int filemap_write_and_wait_range(struct address_space *mapping,
445                                  loff_t lstart, loff_t lend)
446 {
447         int err = 0;
448
449         if (mapping->nrpages) {
450                 err = __filemap_fdatawrite_range(mapping, lstart, lend,
451                                                  WB_SYNC_ALL);
452                 /* See comment of filemap_write_and_wait() */
453                 if (err != -EIO) {
454                         int err2 = wait_on_page_writeback_range(mapping,
455                                                 lstart >> PAGE_CACHE_SHIFT,
456                                                 lend >> PAGE_CACHE_SHIFT);
457                         if (!err)
458                                 err = err2;
459                 }
460         }
461         return err;
462 }
463 EXPORT_SYMBOL(filemap_write_and_wait_range);
464
465 /**
466  * add_to_page_cache_locked - add a locked page to the pagecache
467  * @page:       page to add
468  * @mapping:    the page's address_space
469  * @offset:     page index
470  * @gfp_mask:   page allocation mode
471  *
472  * This function is used to add a page to the pagecache. It must be locked.
473  * This function does not add the page to the LRU.  The caller must do that.
474  */
475 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
476                 pgoff_t offset, gfp_t gfp_mask)
477 {
478         int error;
479
480         VM_BUG_ON(!PageLocked(page));
481
482         error = mem_cgroup_cache_charge(page, current->mm,
483                                         gfp_mask & GFP_RECLAIM_MASK);
484         if (error)
485                 goto out;
486
487         error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
488         if (error == 0) {
489                 page_cache_get(page);
490                 page->mapping = mapping;
491                 page->index = offset;
492
493                 spin_lock_irq(&mapping->tree_lock);
494                 error = radix_tree_insert(&mapping->page_tree, offset, page);
495                 if (likely(!error)) {
496                         mapping->nrpages++;
497                         __inc_zone_page_state(page, NR_FILE_PAGES);
498                         spin_unlock_irq(&mapping->tree_lock);
499                 } else {
500                         page->mapping = NULL;
501                         spin_unlock_irq(&mapping->tree_lock);
502                         mem_cgroup_uncharge_cache_page(page);
503                         page_cache_release(page);
504                 }
505                 radix_tree_preload_end();
506         } else
507                 mem_cgroup_uncharge_cache_page(page);
508 out:
509         return error;
510 }
511 EXPORT_SYMBOL(add_to_page_cache_locked);
512
513 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
514                                 pgoff_t offset, gfp_t gfp_mask)
515 {
516         int ret;
517
518         /*
519          * Splice_read and readahead add shmem/tmpfs pages into the page cache
520          * before shmem_readpage has a chance to mark them as SwapBacked: they
521          * need to go on the active_anon lru below, and mem_cgroup_cache_charge
522          * (called in add_to_page_cache) needs to know where they're going too.
523          */
524         if (mapping_cap_swap_backed(mapping))
525                 SetPageSwapBacked(page);
526
527         ret = add_to_page_cache(page, mapping, offset, gfp_mask);
528         if (ret == 0) {
529                 if (page_is_file_cache(page))
530                         lru_cache_add_file(page);
531                 else
532                         lru_cache_add_active_anon(page);
533         }
534         return ret;
535 }
536 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
537
538 #ifdef CONFIG_NUMA
539 struct page *__page_cache_alloc(gfp_t gfp)
540 {
541         if (cpuset_do_page_mem_spread()) {
542                 int n = cpuset_mem_spread_node();
543                 return alloc_pages_exact_node(n, gfp, 0);
544         }
545         return alloc_pages(gfp, 0);
546 }
547 EXPORT_SYMBOL(__page_cache_alloc);
548 #endif
549
550 static int __sleep_on_page_lock(void *word)
551 {
552         io_schedule();
553         return 0;
554 }
555
556 /*
557  * In order to wait for pages to become available there must be
558  * waitqueues associated with pages. By using a hash table of
559  * waitqueues where the bucket discipline is to maintain all
560  * waiters on the same queue and wake all when any of the pages
561  * become available, and for the woken contexts to check to be
562  * sure the appropriate page became available, this saves space
563  * at a cost of "thundering herd" phenomena during rare hash
564  * collisions.
565  */
566 static wait_queue_head_t *page_waitqueue(struct page *page)
567 {
568         const struct zone *zone = page_zone(page);
569
570         return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
571 }
572
573 static inline void wake_up_page(struct page *page, int bit)
574 {
575         __wake_up_bit(page_waitqueue(page), &page->flags, bit);
576 }
577
578 void wait_on_page_bit(struct page *page, int bit_nr)
579 {
580         DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
581
582         if (test_bit(bit_nr, &page->flags))
583                 __wait_on_bit(page_waitqueue(page), &wait, sync_page,
584                                                         TASK_UNINTERRUPTIBLE);
585 }
586 EXPORT_SYMBOL(wait_on_page_bit);
587
588 /**
589  * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
590  * @page: Page defining the wait queue of interest
591  * @waiter: Waiter to add to the queue
592  *
593  * Add an arbitrary @waiter to the wait queue for the nominated @page.
594  */
595 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
596 {
597         wait_queue_head_t *q = page_waitqueue(page);
598         unsigned long flags;
599
600         spin_lock_irqsave(&q->lock, flags);
601         __add_wait_queue(q, waiter);
602         spin_unlock_irqrestore(&q->lock, flags);
603 }
604 EXPORT_SYMBOL_GPL(add_page_wait_queue);
605
606 /**
607  * unlock_page - unlock a locked page
608  * @page: the page
609  *
610  * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
611  * Also wakes sleepers in wait_on_page_writeback() because the wakeup
612  * mechananism between PageLocked pages and PageWriteback pages is shared.
613  * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
614  *
615  * The mb is necessary to enforce ordering between the clear_bit and the read
616  * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
617  */
618 void unlock_page(struct page *page)
619 {
620         VM_BUG_ON(!PageLocked(page));
621         clear_bit_unlock(PG_locked, &page->flags);
622         smp_mb__after_clear_bit();
623         wake_up_page(page, PG_locked);
624 }
625 EXPORT_SYMBOL(unlock_page);
626
627 /**
628  * end_page_writeback - end writeback against a page
629  * @page: the page
630  */
631 void end_page_writeback(struct page *page)
632 {
633         if (TestClearPageReclaim(page))
634                 rotate_reclaimable_page(page);
635
636         if (!test_clear_page_writeback(page))
637                 BUG();
638
639         smp_mb__after_clear_bit();
640         wake_up_page(page, PG_writeback);
641 }
642 EXPORT_SYMBOL(end_page_writeback);
643
644 /**
645  * __lock_page - get a lock on the page, assuming we need to sleep to get it
646  * @page: the page to lock
647  *
648  * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
649  * random driver's requestfn sets TASK_RUNNING, we could busywait.  However
650  * chances are that on the second loop, the block layer's plug list is empty,
651  * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
652  */
653 void __lock_page(struct page *page)
654 {
655         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
656
657         __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
658                                                         TASK_UNINTERRUPTIBLE);
659 }
660 EXPORT_SYMBOL(__lock_page);
661
662 int __lock_page_killable(struct page *page)
663 {
664         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
665
666         return __wait_on_bit_lock(page_waitqueue(page), &wait,
667                                         sync_page_killable, TASK_KILLABLE);
668 }
669 EXPORT_SYMBOL_GPL(__lock_page_killable);
670
671 /**
672  * __lock_page_nosync - get a lock on the page, without calling sync_page()
673  * @page: the page to lock
674  *
675  * Variant of lock_page that does not require the caller to hold a reference
676  * on the page's mapping.
677  */
678 void __lock_page_nosync(struct page *page)
679 {
680         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
681         __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
682                                                         TASK_UNINTERRUPTIBLE);
683 }
684
685 /**
686  * find_get_page - find and get a page reference
687  * @mapping: the address_space to search
688  * @offset: the page index
689  *
690  * Is there a pagecache struct page at the given (mapping, offset) tuple?
691  * If yes, increment its refcount and return it; if no, return NULL.
692  */
693 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
694 {
695         void **pagep;
696         struct page *page;
697
698         rcu_read_lock();
699 repeat:
700         page = NULL;
701         pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
702         if (pagep) {
703                 page = radix_tree_deref_slot(pagep);
704                 if (unlikely(!page || page == RADIX_TREE_RETRY))
705                         goto repeat;
706
707                 if (!page_cache_get_speculative(page))
708                         goto repeat;
709
710                 /*
711                  * Has the page moved?
712                  * This is part of the lockless pagecache protocol. See
713                  * include/linux/pagemap.h for details.
714                  */
715                 if (unlikely(page != *pagep)) {
716                         page_cache_release(page);
717                         goto repeat;
718                 }
719         }
720         rcu_read_unlock();
721
722         return page;
723 }
724 EXPORT_SYMBOL(find_get_page);
725
726 /**
727  * find_lock_page - locate, pin and lock a pagecache page
728  * @mapping: the address_space to search
729  * @offset: the page index
730  *
731  * Locates the desired pagecache page, locks it, increments its reference
732  * count and returns its address.
733  *
734  * Returns zero if the page was not present. find_lock_page() may sleep.
735  */
736 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
737 {
738         struct page *page;
739
740 repeat:
741         page = find_get_page(mapping, offset);
742         if (page) {
743                 lock_page(page);
744                 /* Has the page been truncated? */
745                 if (unlikely(page->mapping != mapping)) {
746                         unlock_page(page);
747                         page_cache_release(page);
748                         goto repeat;
749                 }
750                 VM_BUG_ON(page->index != offset);
751         }
752         return page;
753 }
754 EXPORT_SYMBOL(find_lock_page);
755
756 /**
757  * find_or_create_page - locate or add a pagecache page
758  * @mapping: the page's address_space
759  * @index: the page's index into the mapping
760  * @gfp_mask: page allocation mode
761  *
762  * Locates a page in the pagecache.  If the page is not present, a new page
763  * is allocated using @gfp_mask and is added to the pagecache and to the VM's
764  * LRU list.  The returned page is locked and has its reference count
765  * incremented.
766  *
767  * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
768  * allocation!
769  *
770  * find_or_create_page() returns the desired page's address, or zero on
771  * memory exhaustion.
772  */
773 struct page *find_or_create_page(struct address_space *mapping,
774                 pgoff_t index, gfp_t gfp_mask)
775 {
776         struct page *page;
777         int err;
778 repeat:
779         page = find_lock_page(mapping, index);
780         if (!page) {
781                 page = __page_cache_alloc(gfp_mask);
782                 if (!page)
783                         return NULL;
784                 /*
785                  * We want a regular kernel memory (not highmem or DMA etc)
786                  * allocation for the radix tree nodes, but we need to honour
787                  * the context-specific requirements the caller has asked for.
788                  * GFP_RECLAIM_MASK collects those requirements.
789                  */
790                 err = add_to_page_cache_lru(page, mapping, index,
791                         (gfp_mask & GFP_RECLAIM_MASK));
792                 if (unlikely(err)) {
793                         page_cache_release(page);
794                         page = NULL;
795                         if (err == -EEXIST)
796                                 goto repeat;
797                 }
798         }
799         return page;
800 }
801 EXPORT_SYMBOL(find_or_create_page);
802
803 /**
804  * find_get_pages - gang pagecache lookup
805  * @mapping:    The address_space to search
806  * @start:      The starting page index
807  * @nr_pages:   The maximum number of pages
808  * @pages:      Where the resulting pages are placed
809  *
810  * find_get_pages() will search for and return a group of up to
811  * @nr_pages pages in the mapping.  The pages are placed at @pages.
812  * find_get_pages() takes a reference against the returned pages.
813  *
814  * The search returns a group of mapping-contiguous pages with ascending
815  * indexes.  There may be holes in the indices due to not-present pages.
816  *
817  * find_get_pages() returns the number of pages which were found.
818  */
819 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
820                             unsigned int nr_pages, struct page **pages)
821 {
822         unsigned int i;
823         unsigned int ret;
824         unsigned int nr_found;
825
826         rcu_read_lock();
827 restart:
828         nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
829                                 (void ***)pages, start, nr_pages);
830         ret = 0;
831         for (i = 0; i < nr_found; i++) {
832                 struct page *page;
833 repeat:
834                 page = radix_tree_deref_slot((void **)pages[i]);
835                 if (unlikely(!page))
836                         continue;
837                 /*
838                  * this can only trigger if nr_found == 1, making livelock
839                  * a non issue.
840                  */
841                 if (unlikely(page == RADIX_TREE_RETRY))
842                         goto restart;
843
844                 if (!page_cache_get_speculative(page))
845                         goto repeat;
846
847                 /* Has the page moved? */
848                 if (unlikely(page != *((void **)pages[i]))) {
849                         page_cache_release(page);
850                         goto repeat;
851                 }
852
853                 pages[ret] = page;
854                 ret++;
855         }
856         rcu_read_unlock();
857         return ret;
858 }
859
860 /**
861  * find_get_pages_contig - gang contiguous pagecache lookup
862  * @mapping:    The address_space to search
863  * @index:      The starting page index
864  * @nr_pages:   The maximum number of pages
865  * @pages:      Where the resulting pages are placed
866  *
867  * find_get_pages_contig() works exactly like find_get_pages(), except
868  * that the returned number of pages are guaranteed to be contiguous.
869  *
870  * find_get_pages_contig() returns the number of pages which were found.
871  */
872 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
873                                unsigned int nr_pages, struct page **pages)
874 {
875         unsigned int i;
876         unsigned int ret;
877         unsigned int nr_found;
878
879         rcu_read_lock();
880 restart:
881         nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
882                                 (void ***)pages, index, nr_pages);
883         ret = 0;
884         for (i = 0; i < nr_found; i++) {
885                 struct page *page;
886 repeat:
887                 page = radix_tree_deref_slot((void **)pages[i]);
888                 if (unlikely(!page))
889                         continue;
890                 /*
891                  * this can only trigger if nr_found == 1, making livelock
892                  * a non issue.
893                  */
894                 if (unlikely(page == RADIX_TREE_RETRY))
895                         goto restart;
896
897                 if (page->mapping == NULL || page->index != index)
898                         break;
899
900                 if (!page_cache_get_speculative(page))
901                         goto repeat;
902
903                 /* Has the page moved? */
904                 if (unlikely(page != *((void **)pages[i]))) {
905                         page_cache_release(page);
906                         goto repeat;
907                 }
908
909                 pages[ret] = page;
910                 ret++;
911                 index++;
912         }
913         rcu_read_unlock();
914         return ret;
915 }
916 EXPORT_SYMBOL(find_get_pages_contig);
917
918 /**
919  * find_get_pages_tag - find and return pages that match @tag
920  * @mapping:    the address_space to search
921  * @index:      the starting page index
922  * @tag:        the tag index
923  * @nr_pages:   the maximum number of pages
924  * @pages:      where the resulting pages are placed
925  *
926  * Like find_get_pages, except we only return pages which are tagged with
927  * @tag.   We update @index to index the next page for the traversal.
928  */
929 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
930                         int tag, unsigned int nr_pages, struct page **pages)
931 {
932         unsigned int i;
933         unsigned int ret;
934         unsigned int nr_found;
935
936         rcu_read_lock();
937 restart:
938         nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
939                                 (void ***)pages, *index, nr_pages, tag);
940         ret = 0;
941         for (i = 0; i < nr_found; i++) {
942                 struct page *page;
943 repeat:
944                 page = radix_tree_deref_slot((void **)pages[i]);
945                 if (unlikely(!page))
946                         continue;
947                 /*
948                  * this can only trigger if nr_found == 1, making livelock
949                  * a non issue.
950                  */
951                 if (unlikely(page == RADIX_TREE_RETRY))
952                         goto restart;
953
954                 if (!page_cache_get_speculative(page))
955                         goto repeat;
956
957                 /* Has the page moved? */
958                 if (unlikely(page != *((void **)pages[i]))) {
959                         page_cache_release(page);
960                         goto repeat;
961                 }
962
963                 pages[ret] = page;
964                 ret++;
965         }
966         rcu_read_unlock();
967
968         if (ret)
969                 *index = pages[ret - 1]->index + 1;
970
971         return ret;
972 }
973 EXPORT_SYMBOL(find_get_pages_tag);
974
975 /**
976  * grab_cache_page_nowait - returns locked page at given index in given cache
977  * @mapping: target address_space
978  * @index: the page index
979  *
980  * Same as grab_cache_page(), but do not wait if the page is unavailable.
981  * This is intended for speculative data generators, where the data can
982  * be regenerated if the page couldn't be grabbed.  This routine should
983  * be safe to call while holding the lock for another page.
984  *
985  * Clear __GFP_FS when allocating the page to avoid recursion into the fs
986  * and deadlock against the caller's locked page.
987  */
988 struct page *
989 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
990 {
991         struct page *page = find_get_page(mapping, index);
992
993         if (page) {
994                 if (trylock_page(page))
995                         return page;
996                 page_cache_release(page);
997                 return NULL;
998         }
999         page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1000         if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1001                 page_cache_release(page);
1002                 page = NULL;
1003         }
1004         return page;
1005 }
1006 EXPORT_SYMBOL(grab_cache_page_nowait);
1007
1008 /*
1009  * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1010  * a _large_ part of the i/o request. Imagine the worst scenario:
1011  *
1012  *      ---R__________________________________________B__________
1013  *         ^ reading here                             ^ bad block(assume 4k)
1014  *
1015  * read(R) => miss => readahead(R...B) => media error => frustrating retries
1016  * => failing the whole request => read(R) => read(R+1) =>
1017  * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1018  * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1019  * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1020  *
1021  * It is going insane. Fix it by quickly scaling down the readahead size.
1022  */
1023 static void shrink_readahead_size_eio(struct file *filp,
1024                                         struct file_ra_state *ra)
1025 {
1026         ra->ra_pages /= 4;
1027 }
1028
1029 /**
1030  * do_generic_file_read - generic file read routine
1031  * @filp:       the file to read
1032  * @ppos:       current file position
1033  * @desc:       read_descriptor
1034  * @actor:      read method
1035  *
1036  * This is a generic file read routine, and uses the
1037  * mapping->a_ops->readpage() function for the actual low-level stuff.
1038  *
1039  * This is really ugly. But the goto's actually try to clarify some
1040  * of the logic when it comes to error handling etc.
1041  */
1042 static void do_generic_file_read(struct file *filp, loff_t *ppos,
1043                 read_descriptor_t *desc, read_actor_t actor)
1044 {
1045         struct address_space *mapping = filp->f_mapping;
1046         struct inode *inode = mapping->host;
1047         struct file_ra_state *ra = &filp->f_ra;
1048         pgoff_t index;
1049         pgoff_t last_index;
1050         pgoff_t prev_index;
1051         unsigned long offset;      /* offset into pagecache page */
1052         unsigned int prev_offset;
1053         int error;
1054
1055         index = *ppos >> PAGE_CACHE_SHIFT;
1056         prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1057         prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1058         last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1059         offset = *ppos & ~PAGE_CACHE_MASK;
1060
1061         for (;;) {
1062                 struct page *page;
1063                 pgoff_t end_index;
1064                 loff_t isize;
1065                 unsigned long nr, ret;
1066
1067                 cond_resched();
1068 find_page:
1069                 page = find_get_page(mapping, index);
1070                 if (!page) {
1071                         page_cache_sync_readahead(mapping,
1072                                         ra, filp,
1073                                         index, last_index - index);
1074                         page = find_get_page(mapping, index);
1075                         if (unlikely(page == NULL))
1076                                 goto no_cached_page;
1077                 }
1078                 if (PageReadahead(page)) {
1079                         page_cache_async_readahead(mapping,
1080                                         ra, filp, page,
1081                                         index, last_index - index);
1082                 }
1083                 if (!PageUptodate(page)) {
1084                         if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1085                                         !mapping->a_ops->is_partially_uptodate)
1086                                 goto page_not_up_to_date;
1087                         if (!trylock_page(page))
1088                                 goto page_not_up_to_date;
1089                         if (!mapping->a_ops->is_partially_uptodate(page,
1090                                                                 desc, offset))
1091                                 goto page_not_up_to_date_locked;
1092                         unlock_page(page);
1093                 }
1094 page_ok:
1095                 /*
1096                  * i_size must be checked after we know the page is Uptodate.
1097                  *
1098                  * Checking i_size after the check allows us to calculate
1099                  * the correct value for "nr", which means the zero-filled
1100                  * part of the page is not copied back to userspace (unless
1101                  * another truncate extends the file - this is desired though).
1102                  */
1103
1104                 isize = i_size_read(inode);
1105                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1106                 if (unlikely(!isize || index > end_index)) {
1107                         page_cache_release(page);
1108                         goto out;
1109                 }
1110
1111                 /* nr is the maximum number of bytes to copy from this page */
1112                 nr = PAGE_CACHE_SIZE;
1113                 if (index == end_index) {
1114                         nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1115                         if (nr <= offset) {
1116                                 page_cache_release(page);
1117                                 goto out;
1118                         }
1119                 }
1120                 nr = nr - offset;
1121
1122                 /* If users can be writing to this page using arbitrary
1123                  * virtual addresses, take care about potential aliasing
1124                  * before reading the page on the kernel side.
1125                  */
1126                 if (mapping_writably_mapped(mapping))
1127                         flush_dcache_page(page);
1128
1129                 /*
1130                  * When a sequential read accesses a page several times,
1131                  * only mark it as accessed the first time.
1132                  */
1133                 if (prev_index != index || offset != prev_offset)
1134                         mark_page_accessed(page);
1135                 prev_index = index;
1136
1137                 /*
1138                  * Ok, we have the page, and it's up-to-date, so
1139                  * now we can copy it to user space...
1140                  *
1141                  * The actor routine returns how many bytes were actually used..
1142                  * NOTE! This may not be the same as how much of a user buffer
1143                  * we filled up (we may be padding etc), so we can only update
1144                  * "pos" here (the actor routine has to update the user buffer
1145                  * pointers and the remaining count).
1146                  */
1147                 ret = actor(desc, page, offset, nr);
1148                 offset += ret;
1149                 index += offset >> PAGE_CACHE_SHIFT;
1150                 offset &= ~PAGE_CACHE_MASK;
1151                 prev_offset = offset;
1152
1153                 page_cache_release(page);
1154                 if (ret == nr && desc->count)
1155                         continue;
1156                 goto out;
1157
1158 page_not_up_to_date:
1159                 /* Get exclusive access to the page ... */
1160                 error = lock_page_killable(page);
1161                 if (unlikely(error))
1162                         goto readpage_error;
1163
1164 page_not_up_to_date_locked:
1165                 /* Did it get truncated before we got the lock? */
1166                 if (!page->mapping) {
1167                         unlock_page(page);
1168                         page_cache_release(page);
1169                         continue;
1170                 }
1171
1172                 /* Did somebody else fill it already? */
1173                 if (PageUptodate(page)) {
1174                         unlock_page(page);
1175                         goto page_ok;
1176                 }
1177
1178 readpage:
1179                 /* Start the actual read. The read will unlock the page. */
1180                 error = mapping->a_ops->readpage(filp, page);
1181
1182                 if (unlikely(error)) {
1183                         if (error == AOP_TRUNCATED_PAGE) {
1184                                 page_cache_release(page);
1185                                 goto find_page;
1186                         }
1187                         goto readpage_error;
1188                 }
1189
1190                 if (!PageUptodate(page)) {
1191                         error = lock_page_killable(page);
1192                         if (unlikely(error))
1193                                 goto readpage_error;
1194                         if (!PageUptodate(page)) {
1195                                 if (page->mapping == NULL) {
1196                                         /*
1197                                          * invalidate_inode_pages got it
1198                                          */
1199                                         unlock_page(page);
1200                                         page_cache_release(page);
1201                                         goto find_page;
1202                                 }
1203                                 unlock_page(page);
1204                                 shrink_readahead_size_eio(filp, ra);
1205                                 error = -EIO;
1206                                 goto readpage_error;
1207                         }
1208                         unlock_page(page);
1209                 }
1210
1211                 goto page_ok;
1212
1213 readpage_error:
1214                 /* UHHUH! A synchronous read error occurred. Report it */
1215                 desc->error = error;
1216                 page_cache_release(page);
1217                 goto out;
1218
1219 no_cached_page:
1220                 /*
1221                  * Ok, it wasn't cached, so we need to create a new
1222                  * page..
1223                  */
1224                 page = page_cache_alloc_cold(mapping);
1225                 if (!page) {
1226                         desc->error = -ENOMEM;
1227                         goto out;
1228                 }
1229                 error = add_to_page_cache_lru(page, mapping,
1230                                                 index, GFP_KERNEL);
1231                 if (error) {
1232                         page_cache_release(page);
1233                         if (error == -EEXIST)
1234                                 goto find_page;
1235                         desc->error = error;
1236                         goto out;
1237                 }
1238                 goto readpage;
1239         }
1240
1241 out:
1242         ra->prev_pos = prev_index;
1243         ra->prev_pos <<= PAGE_CACHE_SHIFT;
1244         ra->prev_pos |= prev_offset;
1245
1246         *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1247         file_accessed(filp);
1248 }
1249
1250 int file_read_actor(read_descriptor_t *desc, struct page *page,
1251                         unsigned long offset, unsigned long size)
1252 {
1253         char *kaddr;
1254         unsigned long left, count = desc->count;
1255
1256         if (size > count)
1257                 size = count;
1258
1259         /*
1260          * Faults on the destination of a read are common, so do it before
1261          * taking the kmap.
1262          */
1263         if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1264                 kaddr = kmap_atomic(page, KM_USER0);
1265                 left = __copy_to_user_inatomic(desc->arg.buf,
1266                                                 kaddr + offset, size);
1267                 kunmap_atomic(kaddr, KM_USER0);
1268                 if (left == 0)
1269                         goto success;
1270         }
1271
1272         /* Do it the slow way */
1273         kaddr = kmap(page);
1274         left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1275         kunmap(page);
1276
1277         if (left) {
1278                 size -= left;
1279                 desc->error = -EFAULT;
1280         }
1281 success:
1282         desc->count = count - size;
1283         desc->written += size;
1284         desc->arg.buf += size;
1285         return size;
1286 }
1287
1288 /*
1289  * Performs necessary checks before doing a write
1290  * @iov:        io vector request
1291  * @nr_segs:    number of segments in the iovec
1292  * @count:      number of bytes to write
1293  * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1294  *
1295  * Adjust number of segments and amount of bytes to write (nr_segs should be
1296  * properly initialized first). Returns appropriate error code that caller
1297  * should return or zero in case that write should be allowed.
1298  */
1299 int generic_segment_checks(const struct iovec *iov,
1300                         unsigned long *nr_segs, size_t *count, int access_flags)
1301 {
1302         unsigned long   seg;
1303         size_t cnt = 0;
1304         for (seg = 0; seg < *nr_segs; seg++) {
1305                 const struct iovec *iv = &iov[seg];
1306
1307                 /*
1308                  * If any segment has a negative length, or the cumulative
1309                  * length ever wraps negative then return -EINVAL.
1310                  */
1311                 cnt += iv->iov_len;
1312                 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1313                         return -EINVAL;
1314                 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1315                         continue;
1316                 if (seg == 0)
1317                         return -EFAULT;
1318                 *nr_segs = seg;
1319                 cnt -= iv->iov_len;     /* This segment is no good */
1320                 break;
1321         }
1322         *count = cnt;
1323         return 0;
1324 }
1325 EXPORT_SYMBOL(generic_segment_checks);
1326
1327 /**
1328  * generic_file_aio_read - generic filesystem read routine
1329  * @iocb:       kernel I/O control block
1330  * @iov:        io vector request
1331  * @nr_segs:    number of segments in the iovec
1332  * @pos:        current file position
1333  *
1334  * This is the "read()" routine for all filesystems
1335  * that can use the page cache directly.
1336  */
1337 ssize_t
1338 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1339                 unsigned long nr_segs, loff_t pos)
1340 {
1341         struct file *filp = iocb->ki_filp;
1342         ssize_t retval;
1343         unsigned long seg;
1344         size_t count;
1345         loff_t *ppos = &iocb->ki_pos;
1346
1347         count = 0;
1348         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1349         if (retval)
1350                 return retval;
1351
1352         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1353         if (filp->f_flags & O_DIRECT) {
1354                 loff_t size;
1355                 struct address_space *mapping;
1356                 struct inode *inode;
1357
1358                 mapping = filp->f_mapping;
1359                 inode = mapping->host;
1360                 if (!count)
1361                         goto out; /* skip atime */
1362                 size = i_size_read(inode);
1363                 if (pos < size) {
1364                         retval = filemap_write_and_wait_range(mapping, pos,
1365                                         pos + iov_length(iov, nr_segs) - 1);
1366                         if (!retval) {
1367                                 retval = mapping->a_ops->direct_IO(READ, iocb,
1368                                                         iov, pos, nr_segs);
1369                         }
1370                         if (retval > 0)
1371                                 *ppos = pos + retval;
1372                         if (retval) {
1373                                 file_accessed(filp);
1374                                 goto out;
1375                         }
1376                 }
1377         }
1378
1379         for (seg = 0; seg < nr_segs; seg++) {
1380                 read_descriptor_t desc;
1381
1382                 desc.written = 0;
1383                 desc.arg.buf = iov[seg].iov_base;
1384                 desc.count = iov[seg].iov_len;
1385                 if (desc.count == 0)
1386                         continue;
1387                 desc.error = 0;
1388                 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1389                 retval += desc.written;
1390                 if (desc.error) {
1391                         retval = retval ?: desc.error;
1392                         break;
1393                 }
1394                 if (desc.count > 0)
1395                         break;
1396         }
1397 out:
1398         return retval;
1399 }
1400 EXPORT_SYMBOL(generic_file_aio_read);
1401
1402 static ssize_t
1403 do_readahead(struct address_space *mapping, struct file *filp,
1404              pgoff_t index, unsigned long nr)
1405 {
1406         if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1407                 return -EINVAL;
1408
1409         force_page_cache_readahead(mapping, filp, index, nr);
1410         return 0;
1411 }
1412
1413 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1414 {
1415         ssize_t ret;
1416         struct file *file;
1417
1418         ret = -EBADF;
1419         file = fget(fd);
1420         if (file) {
1421                 if (file->f_mode & FMODE_READ) {
1422                         struct address_space *mapping = file->f_mapping;
1423                         pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1424                         pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1425                         unsigned long len = end - start + 1;
1426                         ret = do_readahead(mapping, file, start, len);
1427                 }
1428                 fput(file);
1429         }
1430         return ret;
1431 }
1432 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1433 asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1434 {
1435         return SYSC_readahead((int) fd, offset, (size_t) count);
1436 }
1437 SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1438 #endif
1439
1440 #ifdef CONFIG_MMU
1441 /**
1442  * page_cache_read - adds requested page to the page cache if not already there
1443  * @file:       file to read
1444  * @offset:     page index
1445  *
1446  * This adds the requested page to the page cache if it isn't already there,
1447  * and schedules an I/O to read in its contents from disk.
1448  */
1449 static int page_cache_read(struct file *file, pgoff_t offset)
1450 {
1451         struct address_space *mapping = file->f_mapping;
1452         struct page *page; 
1453         int ret;
1454
1455         do {
1456                 page = page_cache_alloc_cold(mapping);
1457                 if (!page)
1458                         return -ENOMEM;
1459
1460                 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1461                 if (ret == 0)
1462                         ret = mapping->a_ops->readpage(file, page);
1463                 else if (ret == -EEXIST)
1464                         ret = 0; /* losing race to add is OK */
1465
1466                 page_cache_release(page);
1467
1468         } while (ret == AOP_TRUNCATED_PAGE);
1469                 
1470         return ret;
1471 }
1472
1473 #define MMAP_LOTSAMISS  (100)
1474
1475 /*
1476  * Synchronous readahead happens when we don't even find
1477  * a page in the page cache at all.
1478  */
1479 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1480                                    struct file_ra_state *ra,
1481                                    struct file *file,
1482                                    pgoff_t offset)
1483 {
1484         unsigned long ra_pages;
1485         struct address_space *mapping = file->f_mapping;
1486
1487         /* If we don't want any read-ahead, don't bother */
1488         if (VM_RandomReadHint(vma))
1489                 return;
1490
1491         if (VM_SequentialReadHint(vma) ||
1492                         offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
1493                 page_cache_sync_readahead(mapping, ra, file, offset,
1494                                           ra->ra_pages);
1495                 return;
1496         }
1497
1498         if (ra->mmap_miss < INT_MAX)
1499                 ra->mmap_miss++;
1500
1501         /*
1502          * Do we miss much more than hit in this file? If so,
1503          * stop bothering with read-ahead. It will only hurt.
1504          */
1505         if (ra->mmap_miss > MMAP_LOTSAMISS)
1506                 return;
1507
1508         /*
1509          * mmap read-around
1510          */
1511         ra_pages = max_sane_readahead(ra->ra_pages);
1512         if (ra_pages) {
1513                 ra->start = max_t(long, 0, offset - ra_pages/2);
1514                 ra->size = ra_pages;
1515                 ra->async_size = 0;
1516                 ra_submit(ra, mapping, file);
1517         }
1518 }
1519
1520 /*
1521  * Asynchronous readahead happens when we find the page and PG_readahead,
1522  * so we want to possibly extend the readahead further..
1523  */
1524 static void do_async_mmap_readahead(struct vm_area_struct *vma,
1525                                     struct file_ra_state *ra,
1526                                     struct file *file,
1527                                     struct page *page,
1528                                     pgoff_t offset)
1529 {
1530         struct address_space *mapping = file->f_mapping;
1531
1532         /* If we don't want any read-ahead, don't bother */
1533         if (VM_RandomReadHint(vma))
1534                 return;
1535         if (ra->mmap_miss > 0)
1536                 ra->mmap_miss--;
1537         if (PageReadahead(page))
1538                 page_cache_async_readahead(mapping, ra, file,
1539                                            page, offset, ra->ra_pages);
1540 }
1541
1542 /**
1543  * filemap_fault - read in file data for page fault handling
1544  * @vma:        vma in which the fault was taken
1545  * @vmf:        struct vm_fault containing details of the fault
1546  *
1547  * filemap_fault() is invoked via the vma operations vector for a
1548  * mapped memory region to read in file data during a page fault.
1549  *
1550  * The goto's are kind of ugly, but this streamlines the normal case of having
1551  * it in the page cache, and handles the special cases reasonably without
1552  * having a lot of duplicated code.
1553  */
1554 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1555 {
1556         int error;
1557         struct file *file = vma->vm_file;
1558         struct address_space *mapping = file->f_mapping;
1559         struct file_ra_state *ra = &file->f_ra;
1560         struct inode *inode = mapping->host;
1561         pgoff_t offset = vmf->pgoff;
1562         struct page *page;
1563         pgoff_t size;
1564         int ret = 0;
1565
1566         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1567         if (offset >= size)
1568                 return VM_FAULT_SIGBUS;
1569
1570         /*
1571          * Do we have something in the page cache already?
1572          */
1573         page = find_get_page(mapping, offset);
1574         if (likely(page)) {
1575                 /*
1576                  * We found the page, so try async readahead before
1577                  * waiting for the lock.
1578                  */
1579                 do_async_mmap_readahead(vma, ra, file, page, offset);
1580                 lock_page(page);
1581
1582                 /* Did it get truncated? */
1583                 if (unlikely(page->mapping != mapping)) {
1584                         unlock_page(page);
1585                         put_page(page);
1586                         goto no_cached_page;
1587                 }
1588         } else {
1589                 /* No page in the page cache at all */
1590                 do_sync_mmap_readahead(vma, ra, file, offset);
1591                 count_vm_event(PGMAJFAULT);
1592                 ret = VM_FAULT_MAJOR;
1593 retry_find:
1594                 page = find_lock_page(mapping, offset);
1595                 if (!page)
1596                         goto no_cached_page;
1597         }
1598
1599         /*
1600          * We have a locked page in the page cache, now we need to check
1601          * that it's up-to-date. If not, it is going to be due to an error.
1602          */
1603         if (unlikely(!PageUptodate(page)))
1604                 goto page_not_uptodate;
1605
1606         /*
1607          * Found the page and have a reference on it.
1608          * We must recheck i_size under page lock.
1609          */
1610         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1611         if (unlikely(offset >= size)) {
1612                 unlock_page(page);
1613                 page_cache_release(page);
1614                 return VM_FAULT_SIGBUS;
1615         }
1616
1617         ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT;
1618         vmf->page = page;
1619         return ret | VM_FAULT_LOCKED;
1620
1621 no_cached_page:
1622         /*
1623          * We're only likely to ever get here if MADV_RANDOM is in
1624          * effect.
1625          */
1626         error = page_cache_read(file, offset);
1627
1628         /*
1629          * The page we want has now been added to the page cache.
1630          * In the unlikely event that someone removed it in the
1631          * meantime, we'll just come back here and read it again.
1632          */
1633         if (error >= 0)
1634                 goto retry_find;
1635
1636         /*
1637          * An error return from page_cache_read can result if the
1638          * system is low on memory, or a problem occurs while trying
1639          * to schedule I/O.
1640          */
1641         if (error == -ENOMEM)
1642                 return VM_FAULT_OOM;
1643         return VM_FAULT_SIGBUS;
1644
1645 page_not_uptodate:
1646         /*
1647          * Umm, take care of errors if the page isn't up-to-date.
1648          * Try to re-read it _once_. We do this synchronously,
1649          * because there really aren't any performance issues here
1650          * and we need to check for errors.
1651          */
1652         ClearPageError(page);
1653         error = mapping->a_ops->readpage(file, page);
1654         if (!error) {
1655                 wait_on_page_locked(page);
1656                 if (!PageUptodate(page))
1657                         error = -EIO;
1658         }
1659         page_cache_release(page);
1660
1661         if (!error || error == AOP_TRUNCATED_PAGE)
1662                 goto retry_find;
1663
1664         /* Things didn't work out. Return zero to tell the mm layer so. */
1665         shrink_readahead_size_eio(file, ra);
1666         return VM_FAULT_SIGBUS;
1667 }
1668 EXPORT_SYMBOL(filemap_fault);
1669
1670 struct vm_operations_struct generic_file_vm_ops = {
1671         .fault          = filemap_fault,
1672 };
1673
1674 /* This is used for a general mmap of a disk file */
1675
1676 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1677 {
1678         struct address_space *mapping = file->f_mapping;
1679
1680         if (!mapping->a_ops->readpage)
1681                 return -ENOEXEC;
1682         file_accessed(file);
1683         vma->vm_ops = &generic_file_vm_ops;
1684         vma->vm_flags |= VM_CAN_NONLINEAR;
1685         return 0;
1686 }
1687
1688 /*
1689  * This is for filesystems which do not implement ->writepage.
1690  */
1691 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1692 {
1693         if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1694                 return -EINVAL;
1695         return generic_file_mmap(file, vma);
1696 }
1697 #else
1698 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1699 {
1700         return -ENOSYS;
1701 }
1702 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1703 {
1704         return -ENOSYS;
1705 }
1706 #endif /* CONFIG_MMU */
1707
1708 EXPORT_SYMBOL(generic_file_mmap);
1709 EXPORT_SYMBOL(generic_file_readonly_mmap);
1710
1711 static struct page *__read_cache_page(struct address_space *mapping,
1712                                 pgoff_t index,
1713                                 int (*filler)(void *,struct page*),
1714                                 void *data)
1715 {
1716         struct page *page;
1717         int err;
1718 repeat:
1719         page = find_get_page(mapping, index);
1720         if (!page) {
1721                 page = page_cache_alloc_cold(mapping);
1722                 if (!page)
1723                         return ERR_PTR(-ENOMEM);
1724                 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1725                 if (unlikely(err)) {
1726                         page_cache_release(page);
1727                         if (err == -EEXIST)
1728                                 goto repeat;
1729                         /* Presumably ENOMEM for radix tree node */
1730                         return ERR_PTR(err);
1731                 }
1732                 err = filler(data, page);
1733                 if (err < 0) {
1734                         page_cache_release(page);
1735                         page = ERR_PTR(err);
1736                 }
1737         }
1738         return page;
1739 }
1740
1741 /**
1742  * read_cache_page_async - read into page cache, fill it if needed
1743  * @mapping:    the page's address_space
1744  * @index:      the page index
1745  * @filler:     function to perform the read
1746  * @data:       destination for read data
1747  *
1748  * Same as read_cache_page, but don't wait for page to become unlocked
1749  * after submitting it to the filler.
1750  *
1751  * Read into the page cache. If a page already exists, and PageUptodate() is
1752  * not set, try to fill the page but don't wait for it to become unlocked.
1753  *
1754  * If the page does not get brought uptodate, return -EIO.
1755  */
1756 struct page *read_cache_page_async(struct address_space *mapping,
1757                                 pgoff_t index,
1758                                 int (*filler)(void *,struct page*),
1759                                 void *data)
1760 {
1761         struct page *page;
1762         int err;
1763
1764 retry:
1765         page = __read_cache_page(mapping, index, filler, data);
1766         if (IS_ERR(page))
1767                 return page;
1768         if (PageUptodate(page))
1769                 goto out;
1770
1771         lock_page(page);
1772         if (!page->mapping) {
1773                 unlock_page(page);
1774                 page_cache_release(page);
1775                 goto retry;
1776         }
1777         if (PageUptodate(page)) {
1778                 unlock_page(page);
1779                 goto out;
1780         }
1781         err = filler(data, page);
1782         if (err < 0) {
1783                 page_cache_release(page);
1784                 return ERR_PTR(err);
1785         }
1786 out:
1787         mark_page_accessed(page);
1788         return page;
1789 }
1790 EXPORT_SYMBOL(read_cache_page_async);
1791
1792 /**
1793  * read_cache_page - read into page cache, fill it if needed
1794  * @mapping:    the page's address_space
1795  * @index:      the page index
1796  * @filler:     function to perform the read
1797  * @data:       destination for read data
1798  *
1799  * Read into the page cache. If a page already exists, and PageUptodate() is
1800  * not set, try to fill the page then wait for it to become unlocked.
1801  *
1802  * If the page does not get brought uptodate, return -EIO.
1803  */
1804 struct page *read_cache_page(struct address_space *mapping,
1805                                 pgoff_t index,
1806                                 int (*filler)(void *,struct page*),
1807                                 void *data)
1808 {
1809         struct page *page;
1810
1811         page = read_cache_page_async(mapping, index, filler, data);
1812         if (IS_ERR(page))
1813                 goto out;
1814         wait_on_page_locked(page);
1815         if (!PageUptodate(page)) {
1816                 page_cache_release(page);
1817                 page = ERR_PTR(-EIO);
1818         }
1819  out:
1820         return page;
1821 }
1822 EXPORT_SYMBOL(read_cache_page);
1823
1824 /*
1825  * The logic we want is
1826  *
1827  *      if suid or (sgid and xgrp)
1828  *              remove privs
1829  */
1830 int should_remove_suid(struct dentry *dentry)
1831 {
1832         mode_t mode = dentry->d_inode->i_mode;
1833         int kill = 0;
1834
1835         /* suid always must be killed */
1836         if (unlikely(mode & S_ISUID))
1837                 kill = ATTR_KILL_SUID;
1838
1839         /*
1840          * sgid without any exec bits is just a mandatory locking mark; leave
1841          * it alone.  If some exec bits are set, it's a real sgid; kill it.
1842          */
1843         if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1844                 kill |= ATTR_KILL_SGID;
1845
1846         if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1847                 return kill;
1848
1849         return 0;
1850 }
1851 EXPORT_SYMBOL(should_remove_suid);
1852
1853 static int __remove_suid(struct dentry *dentry, int kill)
1854 {
1855         struct iattr newattrs;
1856
1857         newattrs.ia_valid = ATTR_FORCE | kill;
1858         return notify_change(dentry, &newattrs);
1859 }
1860
1861 int file_remove_suid(struct file *file)
1862 {
1863         struct dentry *dentry = file->f_path.dentry;
1864         int killsuid = should_remove_suid(dentry);
1865         int killpriv = security_inode_need_killpriv(dentry);
1866         int error = 0;
1867
1868         if (killpriv < 0)
1869                 return killpriv;
1870         if (killpriv)
1871                 error = security_inode_killpriv(dentry);
1872         if (!error && killsuid)
1873                 error = __remove_suid(dentry, killsuid);
1874
1875         return error;
1876 }
1877 EXPORT_SYMBOL(file_remove_suid);
1878
1879 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1880                         const struct iovec *iov, size_t base, size_t bytes)
1881 {
1882         size_t copied = 0, left = 0;
1883
1884         while (bytes) {
1885                 char __user *buf = iov->iov_base + base;
1886                 int copy = min(bytes, iov->iov_len - base);
1887
1888                 base = 0;
1889                 left = __copy_from_user_inatomic(vaddr, buf, copy);
1890                 copied += copy;
1891                 bytes -= copy;
1892                 vaddr += copy;
1893                 iov++;
1894
1895                 if (unlikely(left))
1896                         break;
1897         }
1898         return copied - left;
1899 }
1900
1901 /*
1902  * Copy as much as we can into the page and return the number of bytes which
1903  * were sucessfully copied.  If a fault is encountered then return the number of
1904  * bytes which were copied.
1905  */
1906 size_t iov_iter_copy_from_user_atomic(struct page *page,
1907                 struct iov_iter *i, unsigned long offset, size_t bytes)
1908 {
1909         char *kaddr;
1910         size_t copied;
1911
1912         BUG_ON(!in_atomic());
1913         kaddr = kmap_atomic(page, KM_USER0);
1914         if (likely(i->nr_segs == 1)) {
1915                 int left;
1916                 char __user *buf = i->iov->iov_base + i->iov_offset;
1917                 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
1918                 copied = bytes - left;
1919         } else {
1920                 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1921                                                 i->iov, i->iov_offset, bytes);
1922         }
1923         kunmap_atomic(kaddr, KM_USER0);
1924
1925         return copied;
1926 }
1927 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1928
1929 /*
1930  * This has the same sideeffects and return value as
1931  * iov_iter_copy_from_user_atomic().
1932  * The difference is that it attempts to resolve faults.
1933  * Page must not be locked.
1934  */
1935 size_t iov_iter_copy_from_user(struct page *page,
1936                 struct iov_iter *i, unsigned long offset, size_t bytes)
1937 {
1938         char *kaddr;
1939         size_t copied;
1940
1941         kaddr = kmap(page);
1942         if (likely(i->nr_segs == 1)) {
1943                 int left;
1944                 char __user *buf = i->iov->iov_base + i->iov_offset;
1945                 left = __copy_from_user(kaddr + offset, buf, bytes);
1946                 copied = bytes - left;
1947         } else {
1948                 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1949                                                 i->iov, i->iov_offset, bytes);
1950         }
1951         kunmap(page);
1952         return copied;
1953 }
1954 EXPORT_SYMBOL(iov_iter_copy_from_user);
1955
1956 void iov_iter_advance(struct iov_iter *i, size_t bytes)
1957 {
1958         BUG_ON(i->count < bytes);
1959
1960         if (likely(i->nr_segs == 1)) {
1961                 i->iov_offset += bytes;
1962                 i->count -= bytes;
1963         } else {
1964                 const struct iovec *iov = i->iov;
1965                 size_t base = i->iov_offset;
1966
1967                 /*
1968                  * The !iov->iov_len check ensures we skip over unlikely
1969                  * zero-length segments (without overruning the iovec).
1970                  */
1971                 while (bytes || unlikely(i->count && !iov->iov_len)) {
1972                         int copy;
1973
1974                         copy = min(bytes, iov->iov_len - base);
1975                         BUG_ON(!i->count || i->count < copy);
1976                         i->count -= copy;
1977                         bytes -= copy;
1978                         base += copy;
1979                         if (iov->iov_len == base) {
1980                                 iov++;
1981                                 base = 0;
1982                         }
1983                 }
1984                 i->iov = iov;
1985                 i->iov_offset = base;
1986         }
1987 }
1988 EXPORT_SYMBOL(iov_iter_advance);
1989
1990 /*
1991  * Fault in the first iovec of the given iov_iter, to a maximum length
1992  * of bytes. Returns 0 on success, or non-zero if the memory could not be
1993  * accessed (ie. because it is an invalid address).
1994  *
1995  * writev-intensive code may want this to prefault several iovecs -- that
1996  * would be possible (callers must not rely on the fact that _only_ the
1997  * first iovec will be faulted with the current implementation).
1998  */
1999 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2000 {
2001         char __user *buf = i->iov->iov_base + i->iov_offset;
2002         bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2003         return fault_in_pages_readable(buf, bytes);
2004 }
2005 EXPORT_SYMBOL(iov_iter_fault_in_readable);
2006
2007 /*
2008  * Return the count of just the current iov_iter segment.
2009  */
2010 size_t iov_iter_single_seg_count(struct iov_iter *i)
2011 {
2012         const struct iovec *iov = i->iov;
2013         if (i->nr_segs == 1)
2014                 return i->count;
2015         else
2016                 return min(i->count, iov->iov_len - i->iov_offset);
2017 }
2018 EXPORT_SYMBOL(iov_iter_single_seg_count);
2019
2020 /*
2021  * Performs necessary checks before doing a write
2022  *
2023  * Can adjust writing position or amount of bytes to write.
2024  * Returns appropriate error code that caller should return or
2025  * zero in case that write should be allowed.
2026  */
2027 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2028 {
2029         struct inode *inode = file->f_mapping->host;
2030         unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2031
2032         if (unlikely(*pos < 0))
2033                 return -EINVAL;
2034
2035         if (!isblk) {
2036                 /* FIXME: this is for backwards compatibility with 2.4 */
2037                 if (file->f_flags & O_APPEND)
2038                         *pos = i_size_read(inode);
2039
2040                 if (limit != RLIM_INFINITY) {
2041                         if (*pos >= limit) {
2042                                 send_sig(SIGXFSZ, current, 0);
2043                                 return -EFBIG;
2044                         }
2045                         if (*count > limit - (typeof(limit))*pos) {
2046                                 *count = limit - (typeof(limit))*pos;
2047                         }
2048                 }
2049         }
2050
2051         /*
2052          * LFS rule
2053          */
2054         if (unlikely(*pos + *count > MAX_NON_LFS &&
2055                                 !(file->f_flags & O_LARGEFILE))) {
2056                 if (*pos >= MAX_NON_LFS) {
2057                         return -EFBIG;
2058                 }
2059                 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2060                         *count = MAX_NON_LFS - (unsigned long)*pos;
2061                 }
2062         }
2063
2064         /*
2065          * Are we about to exceed the fs block limit ?
2066          *
2067          * If we have written data it becomes a short write.  If we have
2068          * exceeded without writing data we send a signal and return EFBIG.
2069          * Linus frestrict idea will clean these up nicely..
2070          */
2071         if (likely(!isblk)) {
2072                 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2073                         if (*count || *pos > inode->i_sb->s_maxbytes) {
2074                                 return -EFBIG;
2075                         }
2076                         /* zero-length writes at ->s_maxbytes are OK */
2077                 }
2078
2079                 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2080                         *count = inode->i_sb->s_maxbytes - *pos;
2081         } else {
2082 #ifdef CONFIG_BLOCK
2083                 loff_t isize;
2084                 if (bdev_read_only(I_BDEV(inode)))
2085                         return -EPERM;
2086                 isize = i_size_read(inode);
2087                 if (*pos >= isize) {
2088                         if (*count || *pos > isize)
2089                                 return -ENOSPC;
2090                 }
2091
2092                 if (*pos + *count > isize)
2093                         *count = isize - *pos;
2094 #else
2095                 return -EPERM;
2096 #endif
2097         }
2098         return 0;
2099 }
2100 EXPORT_SYMBOL(generic_write_checks);
2101
2102 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2103                                 loff_t pos, unsigned len, unsigned flags,
2104                                 struct page **pagep, void **fsdata)
2105 {
2106         const struct address_space_operations *aops = mapping->a_ops;
2107
2108         return aops->write_begin(file, mapping, pos, len, flags,
2109                                                         pagep, fsdata);
2110 }
2111 EXPORT_SYMBOL(pagecache_write_begin);
2112
2113 int pagecache_write_end(struct file *file, struct address_space *mapping,
2114                                 loff_t pos, unsigned len, unsigned copied,
2115                                 struct page *page, void *fsdata)
2116 {
2117         const struct address_space_operations *aops = mapping->a_ops;
2118
2119         mark_page_accessed(page);
2120         return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2121 }
2122 EXPORT_SYMBOL(pagecache_write_end);
2123
2124 ssize_t
2125 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2126                 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2127                 size_t count, size_t ocount)
2128 {
2129         struct file     *file = iocb->ki_filp;
2130         struct address_space *mapping = file->f_mapping;
2131         struct inode    *inode = mapping->host;
2132         ssize_t         written;
2133         size_t          write_len;
2134         pgoff_t         end;
2135
2136         if (count != ocount)
2137                 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2138
2139         write_len = iov_length(iov, *nr_segs);
2140         end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2141
2142         written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2143         if (written)
2144                 goto out;
2145
2146         /*
2147          * After a write we want buffered reads to be sure to go to disk to get
2148          * the new data.  We invalidate clean cached page from the region we're
2149          * about to write.  We do this *before* the write so that we can return
2150          * without clobbering -EIOCBQUEUED from ->direct_IO().
2151          */
2152         if (mapping->nrpages) {
2153                 written = invalidate_inode_pages2_range(mapping,
2154                                         pos >> PAGE_CACHE_SHIFT, end);
2155                 /*
2156                  * If a page can not be invalidated, return 0 to fall back
2157                  * to buffered write.
2158                  */
2159                 if (written) {
2160                         if (written == -EBUSY)
2161                                 return 0;
2162                         goto out;
2163                 }
2164         }
2165
2166         written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2167
2168         /*
2169          * Finally, try again to invalidate clean pages which might have been
2170          * cached by non-direct readahead, or faulted in by get_user_pages()
2171          * if the source of the write was an mmap'ed region of the file
2172          * we're writing.  Either one is a pretty crazy thing to do,
2173          * so we don't support it 100%.  If this invalidation
2174          * fails, tough, the write still worked...
2175          */
2176         if (mapping->nrpages) {
2177                 invalidate_inode_pages2_range(mapping,
2178                                               pos >> PAGE_CACHE_SHIFT, end);
2179         }
2180
2181         if (written > 0) {
2182                 loff_t end = pos + written;
2183                 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2184                         i_size_write(inode,  end);
2185                         mark_inode_dirty(inode);
2186                 }
2187                 *ppos = end;
2188         }
2189 out:
2190         return written;
2191 }
2192 EXPORT_SYMBOL(generic_file_direct_write);
2193
2194 /*
2195  * Find or create a page at the given pagecache position. Return the locked
2196  * page. This function is specifically for buffered writes.
2197  */
2198 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2199                                         pgoff_t index, unsigned flags)
2200 {
2201         int status;
2202         struct page *page;
2203         gfp_t gfp_notmask = 0;
2204         if (flags & AOP_FLAG_NOFS)
2205                 gfp_notmask = __GFP_FS;
2206 repeat:
2207         page = find_lock_page(mapping, index);
2208         if (likely(page))
2209                 return page;
2210
2211         page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2212         if (!page)
2213                 return NULL;
2214         status = add_to_page_cache_lru(page, mapping, index,
2215                                                 GFP_KERNEL & ~gfp_notmask);
2216         if (unlikely(status)) {
2217                 page_cache_release(page);
2218                 if (status == -EEXIST)
2219                         goto repeat;
2220                 return NULL;
2221         }
2222         return page;
2223 }
2224 EXPORT_SYMBOL(grab_cache_page_write_begin);
2225
2226 static ssize_t generic_perform_write(struct file *file,
2227                                 struct iov_iter *i, loff_t pos)
2228 {
2229         struct address_space *mapping = file->f_mapping;
2230         const struct address_space_operations *a_ops = mapping->a_ops;
2231         long status = 0;
2232         ssize_t written = 0;
2233         unsigned int flags = 0;
2234
2235         /*
2236          * Copies from kernel address space cannot fail (NFSD is a big user).
2237          */
2238         if (segment_eq(get_fs(), KERNEL_DS))
2239                 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2240
2241         do {
2242                 struct page *page;
2243                 pgoff_t index;          /* Pagecache index for current page */
2244                 unsigned long offset;   /* Offset into pagecache page */
2245                 unsigned long bytes;    /* Bytes to write to page */
2246                 size_t copied;          /* Bytes copied from user */
2247                 void *fsdata;
2248
2249                 offset = (pos & (PAGE_CACHE_SIZE - 1));
2250                 index = pos >> PAGE_CACHE_SHIFT;
2251                 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2252                                                 iov_iter_count(i));
2253
2254 again:
2255
2256                 /*
2257                  * Bring in the user page that we will copy from _first_.
2258                  * Otherwise there's a nasty deadlock on copying from the
2259                  * same page as we're writing to, without it being marked
2260                  * up-to-date.
2261                  *
2262                  * Not only is this an optimisation, but it is also required
2263                  * to check that the address is actually valid, when atomic
2264                  * usercopies are used, below.
2265                  */
2266                 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2267                         status = -EFAULT;
2268                         break;
2269                 }
2270
2271                 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2272                                                 &page, &fsdata);
2273                 if (unlikely(status))
2274                         break;
2275
2276                 pagefault_disable();
2277                 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2278                 pagefault_enable();
2279                 flush_dcache_page(page);
2280
2281                 mark_page_accessed(page);
2282                 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2283                                                 page, fsdata);
2284                 if (unlikely(status < 0))
2285                         break;
2286                 copied = status;
2287
2288                 cond_resched();
2289
2290                 iov_iter_advance(i, copied);
2291                 if (unlikely(copied == 0)) {
2292                         /*
2293                          * If we were unable to copy any data at all, we must
2294                          * fall back to a single segment length write.
2295                          *
2296                          * If we didn't fallback here, we could livelock
2297                          * because not all segments in the iov can be copied at
2298                          * once without a pagefault.
2299                          */
2300                         bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2301                                                 iov_iter_single_seg_count(i));
2302                         goto again;
2303                 }
2304                 pos += copied;
2305                 written += copied;
2306
2307                 balance_dirty_pages_ratelimited(mapping);
2308
2309         } while (iov_iter_count(i));
2310
2311         return written ? written : status;
2312 }
2313
2314 ssize_t
2315 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2316                 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2317                 size_t count, ssize_t written)
2318 {
2319         struct file *file = iocb->ki_filp;
2320         struct address_space *mapping = file->f_mapping;
2321         ssize_t status;
2322         struct iov_iter i;
2323
2324         iov_iter_init(&i, iov, nr_segs, count, written);
2325         status = generic_perform_write(file, &i, pos);
2326
2327         if (likely(status >= 0)) {
2328                 written += status;
2329                 *ppos = pos + status;
2330         }
2331         
2332         /*
2333          * If we get here for O_DIRECT writes then we must have fallen through
2334          * to buffered writes (block instantiation inside i_size).  So we sync
2335          * the file data here, to try to honour O_DIRECT expectations.
2336          */
2337         if (unlikely(file->f_flags & O_DIRECT) && written)
2338                 status = filemap_write_and_wait_range(mapping,
2339                                         pos, pos + written - 1);
2340
2341         return written ? written : status;
2342 }
2343 EXPORT_SYMBOL(generic_file_buffered_write);
2344
2345 /**
2346  * __generic_file_aio_write - write data to a file
2347  * @iocb:       IO state structure (file, offset, etc.)
2348  * @iov:        vector with data to write
2349  * @nr_segs:    number of segments in the vector
2350  * @ppos:       position where to write
2351  *
2352  * This function does all the work needed for actually writing data to a
2353  * file. It does all basic checks, removes SUID from the file, updates
2354  * modification times and calls proper subroutines depending on whether we
2355  * do direct IO or a standard buffered write.
2356  *
2357  * It expects i_mutex to be grabbed unless we work on a block device or similar
2358  * object which does not need locking at all.
2359  *
2360  * This function does *not* take care of syncing data in case of O_SYNC write.
2361  * A caller has to handle it. This is mainly due to the fact that we want to
2362  * avoid syncing under i_mutex.
2363  */
2364 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2365                                  unsigned long nr_segs, loff_t *ppos)
2366 {
2367         struct file *file = iocb->ki_filp;
2368         struct address_space * mapping = file->f_mapping;
2369         size_t ocount;          /* original count */
2370         size_t count;           /* after file limit checks */
2371         struct inode    *inode = mapping->host;
2372         loff_t          pos;
2373         ssize_t         written;
2374         ssize_t         err;
2375
2376         ocount = 0;
2377         err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2378         if (err)
2379                 return err;
2380
2381         count = ocount;
2382         pos = *ppos;
2383
2384         vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2385
2386         /* We can write back this queue in page reclaim */
2387         current->backing_dev_info = mapping->backing_dev_info;
2388         written = 0;
2389
2390         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2391         if (err)
2392                 goto out;
2393
2394         if (count == 0)
2395                 goto out;
2396
2397         err = file_remove_suid(file);
2398         if (err)
2399                 goto out;
2400
2401         file_update_time(file);
2402
2403         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2404         if (unlikely(file->f_flags & O_DIRECT)) {
2405                 loff_t endbyte;
2406                 ssize_t written_buffered;
2407
2408                 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2409                                                         ppos, count, ocount);
2410                 if (written < 0 || written == count)
2411                         goto out;
2412                 /*
2413                  * direct-io write to a hole: fall through to buffered I/O
2414                  * for completing the rest of the request.
2415                  */
2416                 pos += written;
2417                 count -= written;
2418                 written_buffered = generic_file_buffered_write(iocb, iov,
2419                                                 nr_segs, pos, ppos, count,
2420                                                 written);
2421                 /*
2422                  * If generic_file_buffered_write() retuned a synchronous error
2423                  * then we want to return the number of bytes which were
2424                  * direct-written, or the error code if that was zero.  Note
2425                  * that this differs from normal direct-io semantics, which
2426                  * will return -EFOO even if some bytes were written.
2427                  */
2428                 if (written_buffered < 0) {
2429                         err = written_buffered;
2430                         goto out;
2431                 }
2432
2433                 /*
2434                  * We need to ensure that the page cache pages are written to
2435                  * disk and invalidated to preserve the expected O_DIRECT
2436                  * semantics.
2437                  */
2438                 endbyte = pos + written_buffered - written - 1;
2439                 err = do_sync_mapping_range(file->f_mapping, pos, endbyte,
2440                                             SYNC_FILE_RANGE_WAIT_BEFORE|
2441                                             SYNC_FILE_RANGE_WRITE|
2442                                             SYNC_FILE_RANGE_WAIT_AFTER);
2443                 if (err == 0) {
2444                         written = written_buffered;
2445                         invalidate_mapping_pages(mapping,
2446                                                  pos >> PAGE_CACHE_SHIFT,
2447                                                  endbyte >> PAGE_CACHE_SHIFT);
2448                 } else {
2449                         /*
2450                          * We don't know how much we wrote, so just return
2451                          * the number of bytes which were direct-written
2452                          */
2453                 }
2454         } else {
2455                 written = generic_file_buffered_write(iocb, iov, nr_segs,
2456                                 pos, ppos, count, written);
2457         }
2458 out:
2459         current->backing_dev_info = NULL;
2460         return written ? written : err;
2461 }
2462 EXPORT_SYMBOL(__generic_file_aio_write);
2463
2464 /**
2465  * generic_file_aio_write - write data to a file
2466  * @iocb:       IO state structure
2467  * @iov:        vector with data to write
2468  * @nr_segs:    number of segments in the vector
2469  * @pos:        position in file where to write
2470  *
2471  * This is a wrapper around __generic_file_aio_write() to be used by most
2472  * filesystems. It takes care of syncing the file in case of O_SYNC file
2473  * and acquires i_mutex as needed.
2474  */
2475 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2476                 unsigned long nr_segs, loff_t pos)
2477 {
2478         struct file *file = iocb->ki_filp;
2479         struct inode *inode = file->f_mapping->host;
2480         ssize_t ret;
2481
2482         BUG_ON(iocb->ki_pos != pos);
2483
2484         mutex_lock(&inode->i_mutex);
2485         ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2486         mutex_unlock(&inode->i_mutex);
2487
2488         if (ret > 0 || ret == -EIOCBQUEUED) {
2489                 ssize_t err;
2490
2491                 err = generic_write_sync(file, pos, ret);
2492                 if (err < 0 && ret > 0)
2493                         ret = err;
2494         }
2495         return ret;
2496 }
2497 EXPORT_SYMBOL(generic_file_aio_write);
2498
2499 /**
2500  * try_to_release_page() - release old fs-specific metadata on a page
2501  *
2502  * @page: the page which the kernel is trying to free
2503  * @gfp_mask: memory allocation flags (and I/O mode)
2504  *
2505  * The address_space is to try to release any data against the page
2506  * (presumably at page->private).  If the release was successful, return `1'.
2507  * Otherwise return zero.
2508  *
2509  * This may also be called if PG_fscache is set on a page, indicating that the
2510  * page is known to the local caching routines.
2511  *
2512  * The @gfp_mask argument specifies whether I/O may be performed to release
2513  * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2514  *
2515  */
2516 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2517 {
2518         struct address_space * const mapping = page->mapping;
2519
2520         BUG_ON(!PageLocked(page));
2521         if (PageWriteback(page))
2522                 return 0;
2523
2524         if (mapping && mapping->a_ops->releasepage)
2525                 return mapping->a_ops->releasepage(page, gfp_mask);
2526         return try_to_free_buffers(page);
2527 }
2528
2529 EXPORT_SYMBOL(try_to_release_page);