Merge branch 'juju' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux13...
[linux-2.6] / 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/pagevec.h>
29 #include <linux/blkdev.h>
30 #include <linux/security.h>
31 #include <linux/syscalls.h>
32 #include <linux/cpuset.h>
33 #include "filemap.h"
34 #include "internal.h"
35
36 /*
37  * FIXME: remove all knowledge of the buffer layer from the core VM
38  */
39 #include <linux/buffer_head.h> /* for generic_osync_inode */
40
41 #include <asm/mman.h>
42
43 static ssize_t
44 generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
45         loff_t offset, unsigned long nr_segs);
46
47 /*
48  * Shared mappings implemented 30.11.1994. It's not fully working yet,
49  * though.
50  *
51  * Shared mappings now work. 15.8.1995  Bruno.
52  *
53  * finished 'unifying' the page and buffer cache and SMP-threaded the
54  * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
55  *
56  * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
57  */
58
59 /*
60  * Lock ordering:
61  *
62  *  ->i_mmap_lock               (vmtruncate)
63  *    ->private_lock            (__free_pte->__set_page_dirty_buffers)
64  *      ->swap_lock             (exclusive_swap_page, others)
65  *        ->mapping->tree_lock
66  *
67  *  ->i_mutex
68  *    ->i_mmap_lock             (truncate->unmap_mapping_range)
69  *
70  *  ->mmap_sem
71  *    ->i_mmap_lock
72  *      ->page_table_lock or pte_lock   (various, mainly in memory.c)
73  *        ->mapping->tree_lock  (arch-dependent flush_dcache_mmap_lock)
74  *
75  *  ->mmap_sem
76  *    ->lock_page               (access_process_vm)
77  *
78  *  ->i_mutex                   (generic_file_buffered_write)
79  *    ->mmap_sem                (fault_in_pages_readable->do_page_fault)
80  *
81  *  ->i_mutex
82  *    ->i_alloc_sem             (various)
83  *
84  *  ->inode_lock
85  *    ->sb_lock                 (fs/fs-writeback.c)
86  *    ->mapping->tree_lock      (__sync_single_inode)
87  *
88  *  ->i_mmap_lock
89  *    ->anon_vma.lock           (vma_adjust)
90  *
91  *  ->anon_vma.lock
92  *    ->page_table_lock or pte_lock     (anon_vma_prepare and various)
93  *
94  *  ->page_table_lock or pte_lock
95  *    ->swap_lock               (try_to_unmap_one)
96  *    ->private_lock            (try_to_unmap_one)
97  *    ->tree_lock               (try_to_unmap_one)
98  *    ->zone.lru_lock           (follow_page->mark_page_accessed)
99  *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
100  *    ->private_lock            (page_remove_rmap->set_page_dirty)
101  *    ->tree_lock               (page_remove_rmap->set_page_dirty)
102  *    ->inode_lock              (page_remove_rmap->set_page_dirty)
103  *    ->inode_lock              (zap_pte_range->set_page_dirty)
104  *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
105  *
106  *  ->task->proc_lock
107  *    ->dcache_lock             (proc_pid_lookup)
108  */
109
110 /*
111  * Remove a page from the page cache and free it. Caller has to make
112  * sure the page is locked and that nobody else uses it - or that usage
113  * is safe.  The caller must hold a write_lock on the mapping's tree_lock.
114  */
115 void __remove_from_page_cache(struct page *page)
116 {
117         struct address_space *mapping = page->mapping;
118
119         radix_tree_delete(&mapping->page_tree, page->index);
120         page->mapping = NULL;
121         mapping->nrpages--;
122         __dec_zone_page_state(page, NR_FILE_PAGES);
123 }
124
125 void remove_from_page_cache(struct page *page)
126 {
127         struct address_space *mapping = page->mapping;
128
129         BUG_ON(!PageLocked(page));
130
131         write_lock_irq(&mapping->tree_lock);
132         __remove_from_page_cache(page);
133         write_unlock_irq(&mapping->tree_lock);
134 }
135
136 static int sync_page(void *word)
137 {
138         struct address_space *mapping;
139         struct page *page;
140
141         page = container_of((unsigned long *)word, struct page, flags);
142
143         /*
144          * page_mapping() is being called without PG_locked held.
145          * Some knowledge of the state and use of the page is used to
146          * reduce the requirements down to a memory barrier.
147          * The danger here is of a stale page_mapping() return value
148          * indicating a struct address_space different from the one it's
149          * associated with when it is associated with one.
150          * After smp_mb(), it's either the correct page_mapping() for
151          * the page, or an old page_mapping() and the page's own
152          * page_mapping() has gone NULL.
153          * The ->sync_page() address_space operation must tolerate
154          * page_mapping() going NULL. By an amazing coincidence,
155          * this comes about because none of the users of the page
156          * in the ->sync_page() methods make essential use of the
157          * page_mapping(), merely passing the page down to the backing
158          * device's unplug functions when it's non-NULL, which in turn
159          * ignore it for all cases but swap, where only page_private(page) is
160          * of interest. When page_mapping() does go NULL, the entire
161          * call stack gracefully ignores the page and returns.
162          * -- wli
163          */
164         smp_mb();
165         mapping = page_mapping(page);
166         if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
167                 mapping->a_ops->sync_page(page);
168         io_schedule();
169         return 0;
170 }
171
172 /**
173  * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
174  * @mapping:    address space structure to write
175  * @start:      offset in bytes where the range starts
176  * @end:        offset in bytes where the range ends (inclusive)
177  * @sync_mode:  enable synchronous operation
178  *
179  * Start writeback against all of a mapping's dirty pages that lie
180  * within the byte offsets <start, end> inclusive.
181  *
182  * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
183  * opposed to a regular memory cleansing writeback.  The difference between
184  * these two operations is that if a dirty page/buffer is encountered, it must
185  * be waited upon, and not just skipped over.
186  */
187 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
188                                 loff_t end, int sync_mode)
189 {
190         int ret;
191         struct writeback_control wbc = {
192                 .sync_mode = sync_mode,
193                 .nr_to_write = mapping->nrpages * 2,
194                 .range_start = start,
195                 .range_end = end,
196         };
197
198         if (!mapping_cap_writeback_dirty(mapping))
199                 return 0;
200
201         ret = do_writepages(mapping, &wbc);
202         return ret;
203 }
204
205 static inline int __filemap_fdatawrite(struct address_space *mapping,
206         int sync_mode)
207 {
208         return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
209 }
210
211 int filemap_fdatawrite(struct address_space *mapping)
212 {
213         return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
214 }
215 EXPORT_SYMBOL(filemap_fdatawrite);
216
217 static int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
218                                 loff_t end)
219 {
220         return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
221 }
222
223 /**
224  * filemap_flush - mostly a non-blocking flush
225  * @mapping:    target address_space
226  *
227  * This is a mostly non-blocking flush.  Not suitable for data-integrity
228  * purposes - I/O may not be started against all dirty pages.
229  */
230 int filemap_flush(struct address_space *mapping)
231 {
232         return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
233 }
234 EXPORT_SYMBOL(filemap_flush);
235
236 /**
237  * wait_on_page_writeback_range - wait for writeback to complete
238  * @mapping:    target address_space
239  * @start:      beginning page index
240  * @end:        ending page index
241  *
242  * Wait for writeback to complete against pages indexed by start->end
243  * inclusive
244  */
245 int wait_on_page_writeback_range(struct address_space *mapping,
246                                 pgoff_t start, pgoff_t end)
247 {
248         struct pagevec pvec;
249         int nr_pages;
250         int ret = 0;
251         pgoff_t index;
252
253         if (end < start)
254                 return 0;
255
256         pagevec_init(&pvec, 0);
257         index = start;
258         while ((index <= end) &&
259                         (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
260                         PAGECACHE_TAG_WRITEBACK,
261                         min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
262                 unsigned i;
263
264                 for (i = 0; i < nr_pages; i++) {
265                         struct page *page = pvec.pages[i];
266
267                         /* until radix tree lookup accepts end_index */
268                         if (page->index > end)
269                                 continue;
270
271                         wait_on_page_writeback(page);
272                         if (PageError(page))
273                                 ret = -EIO;
274                 }
275                 pagevec_release(&pvec);
276                 cond_resched();
277         }
278
279         /* Check for outstanding write errors */
280         if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
281                 ret = -ENOSPC;
282         if (test_and_clear_bit(AS_EIO, &mapping->flags))
283                 ret = -EIO;
284
285         return ret;
286 }
287
288 /**
289  * sync_page_range - write and wait on all pages in the passed range
290  * @inode:      target inode
291  * @mapping:    target address_space
292  * @pos:        beginning offset in pages to write
293  * @count:      number of bytes to write
294  *
295  * Write and wait upon all the pages in the passed range.  This is a "data
296  * integrity" operation.  It waits upon in-flight writeout before starting and
297  * waiting upon new writeout.  If there was an IO error, return it.
298  *
299  * We need to re-take i_mutex during the generic_osync_inode list walk because
300  * it is otherwise livelockable.
301  */
302 int sync_page_range(struct inode *inode, struct address_space *mapping,
303                         loff_t pos, loff_t count)
304 {
305         pgoff_t start = pos >> PAGE_CACHE_SHIFT;
306         pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
307         int ret;
308
309         if (!mapping_cap_writeback_dirty(mapping) || !count)
310                 return 0;
311         ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
312         if (ret == 0) {
313                 mutex_lock(&inode->i_mutex);
314                 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
315                 mutex_unlock(&inode->i_mutex);
316         }
317         if (ret == 0)
318                 ret = wait_on_page_writeback_range(mapping, start, end);
319         return ret;
320 }
321 EXPORT_SYMBOL(sync_page_range);
322
323 /**
324  * sync_page_range_nolock
325  * @inode:      target inode
326  * @mapping:    target address_space
327  * @pos:        beginning offset in pages to write
328  * @count:      number of bytes to write
329  *
330  * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea
331  * as it forces O_SYNC writers to different parts of the same file
332  * to be serialised right until io completion.
333  */
334 int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
335                            loff_t pos, loff_t count)
336 {
337         pgoff_t start = pos >> PAGE_CACHE_SHIFT;
338         pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
339         int ret;
340
341         if (!mapping_cap_writeback_dirty(mapping) || !count)
342                 return 0;
343         ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
344         if (ret == 0)
345                 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
346         if (ret == 0)
347                 ret = wait_on_page_writeback_range(mapping, start, end);
348         return ret;
349 }
350 EXPORT_SYMBOL(sync_page_range_nolock);
351
352 /**
353  * filemap_fdatawait - wait for all under-writeback pages to complete
354  * @mapping: address space structure to wait for
355  *
356  * Walk the list of under-writeback pages of the given address space
357  * and wait for all of them.
358  */
359 int filemap_fdatawait(struct address_space *mapping)
360 {
361         loff_t i_size = i_size_read(mapping->host);
362
363         if (i_size == 0)
364                 return 0;
365
366         return wait_on_page_writeback_range(mapping, 0,
367                                 (i_size - 1) >> PAGE_CACHE_SHIFT);
368 }
369 EXPORT_SYMBOL(filemap_fdatawait);
370
371 int filemap_write_and_wait(struct address_space *mapping)
372 {
373         int err = 0;
374
375         if (mapping->nrpages) {
376                 err = filemap_fdatawrite(mapping);
377                 /*
378                  * Even if the above returned error, the pages may be
379                  * written partially (e.g. -ENOSPC), so we wait for it.
380                  * But the -EIO is special case, it may indicate the worst
381                  * thing (e.g. bug) happened, so we avoid waiting for it.
382                  */
383                 if (err != -EIO) {
384                         int err2 = filemap_fdatawait(mapping);
385                         if (!err)
386                                 err = err2;
387                 }
388         }
389         return err;
390 }
391 EXPORT_SYMBOL(filemap_write_and_wait);
392
393 /**
394  * filemap_write_and_wait_range - write out & wait on a file range
395  * @mapping:    the address_space for the pages
396  * @lstart:     offset in bytes where the range starts
397  * @lend:       offset in bytes where the range ends (inclusive)
398  *
399  * Write out and wait upon file offsets lstart->lend, inclusive.
400  *
401  * Note that `lend' is inclusive (describes the last byte to be written) so
402  * that this function can be used to write to the very end-of-file (end = -1).
403  */
404 int filemap_write_and_wait_range(struct address_space *mapping,
405                                  loff_t lstart, loff_t lend)
406 {
407         int err = 0;
408
409         if (mapping->nrpages) {
410                 err = __filemap_fdatawrite_range(mapping, lstart, lend,
411                                                  WB_SYNC_ALL);
412                 /* See comment of filemap_write_and_wait() */
413                 if (err != -EIO) {
414                         int err2 = wait_on_page_writeback_range(mapping,
415                                                 lstart >> PAGE_CACHE_SHIFT,
416                                                 lend >> PAGE_CACHE_SHIFT);
417                         if (!err)
418                                 err = err2;
419                 }
420         }
421         return err;
422 }
423
424 /**
425  * add_to_page_cache - add newly allocated pagecache pages
426  * @page:       page to add
427  * @mapping:    the page's address_space
428  * @offset:     page index
429  * @gfp_mask:   page allocation mode
430  *
431  * This function is used to add newly allocated pagecache pages;
432  * the page is new, so we can just run SetPageLocked() against it.
433  * The other page state flags were set by rmqueue().
434  *
435  * This function does not add the page to the LRU.  The caller must do that.
436  */
437 int add_to_page_cache(struct page *page, struct address_space *mapping,
438                 pgoff_t offset, gfp_t gfp_mask)
439 {
440         int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
441
442         if (error == 0) {
443                 write_lock_irq(&mapping->tree_lock);
444                 error = radix_tree_insert(&mapping->page_tree, offset, page);
445                 if (!error) {
446                         page_cache_get(page);
447                         SetPageLocked(page);
448                         page->mapping = mapping;
449                         page->index = offset;
450                         mapping->nrpages++;
451                         __inc_zone_page_state(page, NR_FILE_PAGES);
452                 }
453                 write_unlock_irq(&mapping->tree_lock);
454                 radix_tree_preload_end();
455         }
456         return error;
457 }
458 EXPORT_SYMBOL(add_to_page_cache);
459
460 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
461                                 pgoff_t offset, gfp_t gfp_mask)
462 {
463         int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
464         if (ret == 0)
465                 lru_cache_add(page);
466         return ret;
467 }
468
469 #ifdef CONFIG_NUMA
470 struct page *__page_cache_alloc(gfp_t gfp)
471 {
472         if (cpuset_do_page_mem_spread()) {
473                 int n = cpuset_mem_spread_node();
474                 return alloc_pages_node(n, gfp, 0);
475         }
476         return alloc_pages(gfp, 0);
477 }
478 EXPORT_SYMBOL(__page_cache_alloc);
479 #endif
480
481 static int __sleep_on_page_lock(void *word)
482 {
483         io_schedule();
484         return 0;
485 }
486
487 /*
488  * In order to wait for pages to become available there must be
489  * waitqueues associated with pages. By using a hash table of
490  * waitqueues where the bucket discipline is to maintain all
491  * waiters on the same queue and wake all when any of the pages
492  * become available, and for the woken contexts to check to be
493  * sure the appropriate page became available, this saves space
494  * at a cost of "thundering herd" phenomena during rare hash
495  * collisions.
496  */
497 static wait_queue_head_t *page_waitqueue(struct page *page)
498 {
499         const struct zone *zone = page_zone(page);
500
501         return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
502 }
503
504 static inline void wake_up_page(struct page *page, int bit)
505 {
506         __wake_up_bit(page_waitqueue(page), &page->flags, bit);
507 }
508
509 void fastcall wait_on_page_bit(struct page *page, int bit_nr)
510 {
511         DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
512
513         if (test_bit(bit_nr, &page->flags))
514                 __wait_on_bit(page_waitqueue(page), &wait, sync_page,
515                                                         TASK_UNINTERRUPTIBLE);
516 }
517 EXPORT_SYMBOL(wait_on_page_bit);
518
519 /**
520  * unlock_page - unlock a locked page
521  * @page: the page
522  *
523  * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
524  * Also wakes sleepers in wait_on_page_writeback() because the wakeup
525  * mechananism between PageLocked pages and PageWriteback pages is shared.
526  * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
527  *
528  * The first mb is necessary to safely close the critical section opened by the
529  * TestSetPageLocked(), the second mb is necessary to enforce ordering between
530  * the clear_bit and the read of the waitqueue (to avoid SMP races with a
531  * parallel wait_on_page_locked()).
532  */
533 void fastcall unlock_page(struct page *page)
534 {
535         smp_mb__before_clear_bit();
536         if (!TestClearPageLocked(page))
537                 BUG();
538         smp_mb__after_clear_bit(); 
539         wake_up_page(page, PG_locked);
540 }
541 EXPORT_SYMBOL(unlock_page);
542
543 /**
544  * end_page_writeback - end writeback against a page
545  * @page: the page
546  */
547 void end_page_writeback(struct page *page)
548 {
549         if (!TestClearPageReclaim(page) || rotate_reclaimable_page(page)) {
550                 if (!test_clear_page_writeback(page))
551                         BUG();
552         }
553         smp_mb__after_clear_bit();
554         wake_up_page(page, PG_writeback);
555 }
556 EXPORT_SYMBOL(end_page_writeback);
557
558 /**
559  * __lock_page - get a lock on the page, assuming we need to sleep to get it
560  * @page: the page to lock
561  *
562  * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
563  * random driver's requestfn sets TASK_RUNNING, we could busywait.  However
564  * chances are that on the second loop, the block layer's plug list is empty,
565  * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
566  */
567 void fastcall __lock_page(struct page *page)
568 {
569         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
570
571         __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
572                                                         TASK_UNINTERRUPTIBLE);
573 }
574 EXPORT_SYMBOL(__lock_page);
575
576 /*
577  * Variant of lock_page that does not require the caller to hold a reference
578  * on the page's mapping.
579  */
580 void fastcall __lock_page_nosync(struct page *page)
581 {
582         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
583         __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
584                                                         TASK_UNINTERRUPTIBLE);
585 }
586
587 /**
588  * find_get_page - find and get a page reference
589  * @mapping: the address_space to search
590  * @offset: the page index
591  *
592  * Is there a pagecache struct page at the given (mapping, offset) tuple?
593  * If yes, increment its refcount and return it; if no, return NULL.
594  */
595 struct page * find_get_page(struct address_space *mapping, unsigned long offset)
596 {
597         struct page *page;
598
599         read_lock_irq(&mapping->tree_lock);
600         page = radix_tree_lookup(&mapping->page_tree, offset);
601         if (page)
602                 page_cache_get(page);
603         read_unlock_irq(&mapping->tree_lock);
604         return page;
605 }
606 EXPORT_SYMBOL(find_get_page);
607
608 /**
609  * find_lock_page - locate, pin and lock a pagecache page
610  * @mapping: the address_space to search
611  * @offset: the page index
612  *
613  * Locates the desired pagecache page, locks it, increments its reference
614  * count and returns its address.
615  *
616  * Returns zero if the page was not present. find_lock_page() may sleep.
617  */
618 struct page *find_lock_page(struct address_space *mapping,
619                                 unsigned long offset)
620 {
621         struct page *page;
622
623         read_lock_irq(&mapping->tree_lock);
624 repeat:
625         page = radix_tree_lookup(&mapping->page_tree, offset);
626         if (page) {
627                 page_cache_get(page);
628                 if (TestSetPageLocked(page)) {
629                         read_unlock_irq(&mapping->tree_lock);
630                         __lock_page(page);
631                         read_lock_irq(&mapping->tree_lock);
632
633                         /* Has the page been truncated while we slept? */
634                         if (unlikely(page->mapping != mapping ||
635                                      page->index != offset)) {
636                                 unlock_page(page);
637                                 page_cache_release(page);
638                                 goto repeat;
639                         }
640                 }
641         }
642         read_unlock_irq(&mapping->tree_lock);
643         return page;
644 }
645 EXPORT_SYMBOL(find_lock_page);
646
647 /**
648  * find_or_create_page - locate or add a pagecache page
649  * @mapping: the page's address_space
650  * @index: the page's index into the mapping
651  * @gfp_mask: page allocation mode
652  *
653  * Locates a page in the pagecache.  If the page is not present, a new page
654  * is allocated using @gfp_mask and is added to the pagecache and to the VM's
655  * LRU list.  The returned page is locked and has its reference count
656  * incremented.
657  *
658  * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
659  * allocation!
660  *
661  * find_or_create_page() returns the desired page's address, or zero on
662  * memory exhaustion.
663  */
664 struct page *find_or_create_page(struct address_space *mapping,
665                 unsigned long index, gfp_t gfp_mask)
666 {
667         struct page *page, *cached_page = NULL;
668         int err;
669 repeat:
670         page = find_lock_page(mapping, index);
671         if (!page) {
672                 if (!cached_page) {
673                         cached_page = alloc_page(gfp_mask);
674                         if (!cached_page)
675                                 return NULL;
676                 }
677                 err = add_to_page_cache_lru(cached_page, mapping,
678                                         index, gfp_mask);
679                 if (!err) {
680                         page = cached_page;
681                         cached_page = NULL;
682                 } else if (err == -EEXIST)
683                         goto repeat;
684         }
685         if (cached_page)
686                 page_cache_release(cached_page);
687         return page;
688 }
689 EXPORT_SYMBOL(find_or_create_page);
690
691 /**
692  * find_get_pages - gang pagecache lookup
693  * @mapping:    The address_space to search
694  * @start:      The starting page index
695  * @nr_pages:   The maximum number of pages
696  * @pages:      Where the resulting pages are placed
697  *
698  * find_get_pages() will search for and return a group of up to
699  * @nr_pages pages in the mapping.  The pages are placed at @pages.
700  * find_get_pages() takes a reference against the returned pages.
701  *
702  * The search returns a group of mapping-contiguous pages with ascending
703  * indexes.  There may be holes in the indices due to not-present pages.
704  *
705  * find_get_pages() returns the number of pages which were found.
706  */
707 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
708                             unsigned int nr_pages, struct page **pages)
709 {
710         unsigned int i;
711         unsigned int ret;
712
713         read_lock_irq(&mapping->tree_lock);
714         ret = radix_tree_gang_lookup(&mapping->page_tree,
715                                 (void **)pages, start, nr_pages);
716         for (i = 0; i < ret; i++)
717                 page_cache_get(pages[i]);
718         read_unlock_irq(&mapping->tree_lock);
719         return ret;
720 }
721
722 /**
723  * find_get_pages_contig - gang contiguous pagecache lookup
724  * @mapping:    The address_space to search
725  * @index:      The starting page index
726  * @nr_pages:   The maximum number of pages
727  * @pages:      Where the resulting pages are placed
728  *
729  * find_get_pages_contig() works exactly like find_get_pages(), except
730  * that the returned number of pages are guaranteed to be contiguous.
731  *
732  * find_get_pages_contig() returns the number of pages which were found.
733  */
734 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
735                                unsigned int nr_pages, struct page **pages)
736 {
737         unsigned int i;
738         unsigned int ret;
739
740         read_lock_irq(&mapping->tree_lock);
741         ret = radix_tree_gang_lookup(&mapping->page_tree,
742                                 (void **)pages, index, nr_pages);
743         for (i = 0; i < ret; i++) {
744                 if (pages[i]->mapping == NULL || pages[i]->index != index)
745                         break;
746
747                 page_cache_get(pages[i]);
748                 index++;
749         }
750         read_unlock_irq(&mapping->tree_lock);
751         return i;
752 }
753 EXPORT_SYMBOL(find_get_pages_contig);
754
755 /**
756  * find_get_pages_tag - find and return pages that match @tag
757  * @mapping:    the address_space to search
758  * @index:      the starting page index
759  * @tag:        the tag index
760  * @nr_pages:   the maximum number of pages
761  * @pages:      where the resulting pages are placed
762  *
763  * Like find_get_pages, except we only return pages which are tagged with
764  * @tag.   We update @index to index the next page for the traversal.
765  */
766 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
767                         int tag, unsigned int nr_pages, struct page **pages)
768 {
769         unsigned int i;
770         unsigned int ret;
771
772         read_lock_irq(&mapping->tree_lock);
773         ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
774                                 (void **)pages, *index, nr_pages, tag);
775         for (i = 0; i < ret; i++)
776                 page_cache_get(pages[i]);
777         if (ret)
778                 *index = pages[ret - 1]->index + 1;
779         read_unlock_irq(&mapping->tree_lock);
780         return ret;
781 }
782 EXPORT_SYMBOL(find_get_pages_tag);
783
784 /**
785  * grab_cache_page_nowait - returns locked page at given index in given cache
786  * @mapping: target address_space
787  * @index: the page index
788  *
789  * Same as grab_cache_page(), but do not wait if the page is unavailable.
790  * This is intended for speculative data generators, where the data can
791  * be regenerated if the page couldn't be grabbed.  This routine should
792  * be safe to call while holding the lock for another page.
793  *
794  * Clear __GFP_FS when allocating the page to avoid recursion into the fs
795  * and deadlock against the caller's locked page.
796  */
797 struct page *
798 grab_cache_page_nowait(struct address_space *mapping, unsigned long index)
799 {
800         struct page *page = find_get_page(mapping, index);
801
802         if (page) {
803                 if (!TestSetPageLocked(page))
804                         return page;
805                 page_cache_release(page);
806                 return NULL;
807         }
808         page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
809         if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) {
810                 page_cache_release(page);
811                 page = NULL;
812         }
813         return page;
814 }
815 EXPORT_SYMBOL(grab_cache_page_nowait);
816
817 /*
818  * CD/DVDs are error prone. When a medium error occurs, the driver may fail
819  * a _large_ part of the i/o request. Imagine the worst scenario:
820  *
821  *      ---R__________________________________________B__________
822  *         ^ reading here                             ^ bad block(assume 4k)
823  *
824  * read(R) => miss => readahead(R...B) => media error => frustrating retries
825  * => failing the whole request => read(R) => read(R+1) =>
826  * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
827  * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
828  * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
829  *
830  * It is going insane. Fix it by quickly scaling down the readahead size.
831  */
832 static void shrink_readahead_size_eio(struct file *filp,
833                                         struct file_ra_state *ra)
834 {
835         if (!ra->ra_pages)
836                 return;
837
838         ra->ra_pages /= 4;
839 }
840
841 /**
842  * do_generic_mapping_read - generic file read routine
843  * @mapping:    address_space to be read
844  * @_ra:        file's readahead state
845  * @filp:       the file to read
846  * @ppos:       current file position
847  * @desc:       read_descriptor
848  * @actor:      read method
849  *
850  * This is a generic file read routine, and uses the
851  * mapping->a_ops->readpage() function for the actual low-level stuff.
852  *
853  * This is really ugly. But the goto's actually try to clarify some
854  * of the logic when it comes to error handling etc.
855  *
856  * Note the struct file* is only passed for the use of readpage.
857  * It may be NULL.
858  */
859 void do_generic_mapping_read(struct address_space *mapping,
860                              struct file_ra_state *_ra,
861                              struct file *filp,
862                              loff_t *ppos,
863                              read_descriptor_t *desc,
864                              read_actor_t actor)
865 {
866         struct inode *inode = mapping->host;
867         unsigned long index;
868         unsigned long end_index;
869         unsigned long offset;
870         unsigned long last_index;
871         unsigned long next_index;
872         unsigned long prev_index;
873         unsigned int prev_offset;
874         loff_t isize;
875         struct page *cached_page;
876         int error;
877         struct file_ra_state ra = *_ra;
878
879         cached_page = NULL;
880         index = *ppos >> PAGE_CACHE_SHIFT;
881         next_index = index;
882         prev_index = ra.prev_index;
883         prev_offset = ra.prev_offset;
884         last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
885         offset = *ppos & ~PAGE_CACHE_MASK;
886
887         isize = i_size_read(inode);
888         if (!isize)
889                 goto out;
890
891         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
892         for (;;) {
893                 struct page *page;
894                 unsigned long nr, ret;
895
896                 /* nr is the maximum number of bytes to copy from this page */
897                 nr = PAGE_CACHE_SIZE;
898                 if (index >= end_index) {
899                         if (index > end_index)
900                                 goto out;
901                         nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
902                         if (nr <= offset) {
903                                 goto out;
904                         }
905                 }
906                 nr = nr - offset;
907
908                 cond_resched();
909                 if (index == next_index)
910                         next_index = page_cache_readahead(mapping, &ra, filp,
911                                         index, last_index - index);
912
913 find_page:
914                 page = find_get_page(mapping, index);
915                 if (unlikely(page == NULL)) {
916                         handle_ra_miss(mapping, &ra, index);
917                         goto no_cached_page;
918                 }
919                 if (!PageUptodate(page))
920                         goto page_not_up_to_date;
921 page_ok:
922
923                 /* If users can be writing to this page using arbitrary
924                  * virtual addresses, take care about potential aliasing
925                  * before reading the page on the kernel side.
926                  */
927                 if (mapping_writably_mapped(mapping))
928                         flush_dcache_page(page);
929
930                 /*
931                  * When a sequential read accesses a page several times,
932                  * only mark it as accessed the first time.
933                  */
934                 if (prev_index != index || offset != prev_offset)
935                         mark_page_accessed(page);
936                 prev_index = index;
937
938                 /*
939                  * Ok, we have the page, and it's up-to-date, so
940                  * now we can copy it to user space...
941                  *
942                  * The actor routine returns how many bytes were actually used..
943                  * NOTE! This may not be the same as how much of a user buffer
944                  * we filled up (we may be padding etc), so we can only update
945                  * "pos" here (the actor routine has to update the user buffer
946                  * pointers and the remaining count).
947                  */
948                 ret = actor(desc, page, offset, nr);
949                 offset += ret;
950                 index += offset >> PAGE_CACHE_SHIFT;
951                 offset &= ~PAGE_CACHE_MASK;
952                 prev_offset = offset;
953                 ra.prev_offset = offset;
954
955                 page_cache_release(page);
956                 if (ret == nr && desc->count)
957                         continue;
958                 goto out;
959
960 page_not_up_to_date:
961                 /* Get exclusive access to the page ... */
962                 lock_page(page);
963
964                 /* Did it get truncated before we got the lock? */
965                 if (!page->mapping) {
966                         unlock_page(page);
967                         page_cache_release(page);
968                         continue;
969                 }
970
971                 /* Did somebody else fill it already? */
972                 if (PageUptodate(page)) {
973                         unlock_page(page);
974                         goto page_ok;
975                 }
976
977 readpage:
978                 /* Start the actual read. The read will unlock the page. */
979                 error = mapping->a_ops->readpage(filp, page);
980
981                 if (unlikely(error)) {
982                         if (error == AOP_TRUNCATED_PAGE) {
983                                 page_cache_release(page);
984                                 goto find_page;
985                         }
986                         goto readpage_error;
987                 }
988
989                 if (!PageUptodate(page)) {
990                         lock_page(page);
991                         if (!PageUptodate(page)) {
992                                 if (page->mapping == NULL) {
993                                         /*
994                                          * invalidate_inode_pages got it
995                                          */
996                                         unlock_page(page);
997                                         page_cache_release(page);
998                                         goto find_page;
999                                 }
1000                                 unlock_page(page);
1001                                 error = -EIO;
1002                                 shrink_readahead_size_eio(filp, &ra);
1003                                 goto readpage_error;
1004                         }
1005                         unlock_page(page);
1006                 }
1007
1008                 /*
1009                  * i_size must be checked after we have done ->readpage.
1010                  *
1011                  * Checking i_size after the readpage allows us to calculate
1012                  * the correct value for "nr", which means the zero-filled
1013                  * part of the page is not copied back to userspace (unless
1014                  * another truncate extends the file - this is desired though).
1015                  */
1016                 isize = i_size_read(inode);
1017                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1018                 if (unlikely(!isize || index > end_index)) {
1019                         page_cache_release(page);
1020                         goto out;
1021                 }
1022
1023                 /* nr is the maximum number of bytes to copy from this page */
1024                 nr = PAGE_CACHE_SIZE;
1025                 if (index == end_index) {
1026                         nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1027                         if (nr <= offset) {
1028                                 page_cache_release(page);
1029                                 goto out;
1030                         }
1031                 }
1032                 nr = nr - offset;
1033                 goto page_ok;
1034
1035 readpage_error:
1036                 /* UHHUH! A synchronous read error occurred. Report it */
1037                 desc->error = error;
1038                 page_cache_release(page);
1039                 goto out;
1040
1041 no_cached_page:
1042                 /*
1043                  * Ok, it wasn't cached, so we need to create a new
1044                  * page..
1045                  */
1046                 if (!cached_page) {
1047                         cached_page = page_cache_alloc_cold(mapping);
1048                         if (!cached_page) {
1049                                 desc->error = -ENOMEM;
1050                                 goto out;
1051                         }
1052                 }
1053                 error = add_to_page_cache_lru(cached_page, mapping,
1054                                                 index, GFP_KERNEL);
1055                 if (error) {
1056                         if (error == -EEXIST)
1057                                 goto find_page;
1058                         desc->error = error;
1059                         goto out;
1060                 }
1061                 page = cached_page;
1062                 cached_page = NULL;
1063                 goto readpage;
1064         }
1065
1066 out:
1067         *_ra = ra;
1068
1069         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1070         if (cached_page)
1071                 page_cache_release(cached_page);
1072         if (filp)
1073                 file_accessed(filp);
1074 }
1075 EXPORT_SYMBOL(do_generic_mapping_read);
1076
1077 int file_read_actor(read_descriptor_t *desc, struct page *page,
1078                         unsigned long offset, unsigned long size)
1079 {
1080         char *kaddr;
1081         unsigned long left, count = desc->count;
1082
1083         if (size > count)
1084                 size = count;
1085
1086         /*
1087          * Faults on the destination of a read are common, so do it before
1088          * taking the kmap.
1089          */
1090         if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1091                 kaddr = kmap_atomic(page, KM_USER0);
1092                 left = __copy_to_user_inatomic(desc->arg.buf,
1093                                                 kaddr + offset, size);
1094                 kunmap_atomic(kaddr, KM_USER0);
1095                 if (left == 0)
1096                         goto success;
1097         }
1098
1099         /* Do it the slow way */
1100         kaddr = kmap(page);
1101         left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1102         kunmap(page);
1103
1104         if (left) {
1105                 size -= left;
1106                 desc->error = -EFAULT;
1107         }
1108 success:
1109         desc->count = count - size;
1110         desc->written += size;
1111         desc->arg.buf += size;
1112         return size;
1113 }
1114
1115 /*
1116  * Performs necessary checks before doing a write
1117  * @iov:        io vector request
1118  * @nr_segs:    number of segments in the iovec
1119  * @count:      number of bytes to write
1120  * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1121  *
1122  * Adjust number of segments and amount of bytes to write (nr_segs should be
1123  * properly initialized first). Returns appropriate error code that caller
1124  * should return or zero in case that write should be allowed.
1125  */
1126 int generic_segment_checks(const struct iovec *iov,
1127                         unsigned long *nr_segs, size_t *count, int access_flags)
1128 {
1129         unsigned long   seg;
1130         size_t cnt = 0;
1131         for (seg = 0; seg < *nr_segs; seg++) {
1132                 const struct iovec *iv = &iov[seg];
1133
1134                 /*
1135                  * If any segment has a negative length, or the cumulative
1136                  * length ever wraps negative then return -EINVAL.
1137                  */
1138                 cnt += iv->iov_len;
1139                 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1140                         return -EINVAL;
1141                 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1142                         continue;
1143                 if (seg == 0)
1144                         return -EFAULT;
1145                 *nr_segs = seg;
1146                 cnt -= iv->iov_len;     /* This segment is no good */
1147                 break;
1148         }
1149         *count = cnt;
1150         return 0;
1151 }
1152 EXPORT_SYMBOL(generic_segment_checks);
1153
1154 /**
1155  * generic_file_aio_read - generic filesystem read routine
1156  * @iocb:       kernel I/O control block
1157  * @iov:        io vector request
1158  * @nr_segs:    number of segments in the iovec
1159  * @pos:        current file position
1160  *
1161  * This is the "read()" routine for all filesystems
1162  * that can use the page cache directly.
1163  */
1164 ssize_t
1165 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1166                 unsigned long nr_segs, loff_t pos)
1167 {
1168         struct file *filp = iocb->ki_filp;
1169         ssize_t retval;
1170         unsigned long seg;
1171         size_t count;
1172         loff_t *ppos = &iocb->ki_pos;
1173
1174         count = 0;
1175         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1176         if (retval)
1177                 return retval;
1178
1179         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1180         if (filp->f_flags & O_DIRECT) {
1181                 loff_t size;
1182                 struct address_space *mapping;
1183                 struct inode *inode;
1184
1185                 mapping = filp->f_mapping;
1186                 inode = mapping->host;
1187                 retval = 0;
1188                 if (!count)
1189                         goto out; /* skip atime */
1190                 size = i_size_read(inode);
1191                 if (pos < size) {
1192                         retval = generic_file_direct_IO(READ, iocb,
1193                                                 iov, pos, nr_segs);
1194                         if (retval > 0)
1195                                 *ppos = pos + retval;
1196                 }
1197                 if (likely(retval != 0)) {
1198                         file_accessed(filp);
1199                         goto out;
1200                 }
1201         }
1202
1203         retval = 0;
1204         if (count) {
1205                 for (seg = 0; seg < nr_segs; seg++) {
1206                         read_descriptor_t desc;
1207
1208                         desc.written = 0;
1209                         desc.arg.buf = iov[seg].iov_base;
1210                         desc.count = iov[seg].iov_len;
1211                         if (desc.count == 0)
1212                                 continue;
1213                         desc.error = 0;
1214                         do_generic_file_read(filp,ppos,&desc,file_read_actor);
1215                         retval += desc.written;
1216                         if (desc.error) {
1217                                 retval = retval ?: desc.error;
1218                                 break;
1219                         }
1220                 }
1221         }
1222 out:
1223         return retval;
1224 }
1225 EXPORT_SYMBOL(generic_file_aio_read);
1226
1227 int file_send_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size)
1228 {
1229         ssize_t written;
1230         unsigned long count = desc->count;
1231         struct file *file = desc->arg.data;
1232
1233         if (size > count)
1234                 size = count;
1235
1236         written = file->f_op->sendpage(file, page, offset,
1237                                        size, &file->f_pos, size<count);
1238         if (written < 0) {
1239                 desc->error = written;
1240                 written = 0;
1241         }
1242         desc->count = count - written;
1243         desc->written += written;
1244         return written;
1245 }
1246
1247 ssize_t generic_file_sendfile(struct file *in_file, loff_t *ppos,
1248                          size_t count, read_actor_t actor, void *target)
1249 {
1250         read_descriptor_t desc;
1251
1252         if (!count)
1253                 return 0;
1254
1255         desc.written = 0;
1256         desc.count = count;
1257         desc.arg.data = target;
1258         desc.error = 0;
1259
1260         do_generic_file_read(in_file, ppos, &desc, actor);
1261         if (desc.written)
1262                 return desc.written;
1263         return desc.error;
1264 }
1265 EXPORT_SYMBOL(generic_file_sendfile);
1266
1267 static ssize_t
1268 do_readahead(struct address_space *mapping, struct file *filp,
1269              unsigned long index, unsigned long nr)
1270 {
1271         if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1272                 return -EINVAL;
1273
1274         force_page_cache_readahead(mapping, filp, index,
1275                                         max_sane_readahead(nr));
1276         return 0;
1277 }
1278
1279 asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
1280 {
1281         ssize_t ret;
1282         struct file *file;
1283
1284         ret = -EBADF;
1285         file = fget(fd);
1286         if (file) {
1287                 if (file->f_mode & FMODE_READ) {
1288                         struct address_space *mapping = file->f_mapping;
1289                         unsigned long start = offset >> PAGE_CACHE_SHIFT;
1290                         unsigned long end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1291                         unsigned long len = end - start + 1;
1292                         ret = do_readahead(mapping, file, start, len);
1293                 }
1294                 fput(file);
1295         }
1296         return ret;
1297 }
1298
1299 #ifdef CONFIG_MMU
1300 static int FASTCALL(page_cache_read(struct file * file, unsigned long offset));
1301 /**
1302  * page_cache_read - adds requested page to the page cache if not already there
1303  * @file:       file to read
1304  * @offset:     page index
1305  *
1306  * This adds the requested page to the page cache if it isn't already there,
1307  * and schedules an I/O to read in its contents from disk.
1308  */
1309 static int fastcall page_cache_read(struct file * file, unsigned long offset)
1310 {
1311         struct address_space *mapping = file->f_mapping;
1312         struct page *page; 
1313         int ret;
1314
1315         do {
1316                 page = page_cache_alloc_cold(mapping);
1317                 if (!page)
1318                         return -ENOMEM;
1319
1320                 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1321                 if (ret == 0)
1322                         ret = mapping->a_ops->readpage(file, page);
1323                 else if (ret == -EEXIST)
1324                         ret = 0; /* losing race to add is OK */
1325
1326                 page_cache_release(page);
1327
1328         } while (ret == AOP_TRUNCATED_PAGE);
1329                 
1330         return ret;
1331 }
1332
1333 #define MMAP_LOTSAMISS  (100)
1334
1335 /**
1336  * filemap_nopage - read in file data for page fault handling
1337  * @area:       the applicable vm_area
1338  * @address:    target address to read in
1339  * @type:       returned with VM_FAULT_{MINOR,MAJOR} if not %NULL
1340  *
1341  * filemap_nopage() is invoked via the vma operations vector for a
1342  * mapped memory region to read in file data during a page fault.
1343  *
1344  * The goto's are kind of ugly, but this streamlines the normal case of having
1345  * it in the page cache, and handles the special cases reasonably without
1346  * having a lot of duplicated code.
1347  */
1348 struct page *filemap_nopage(struct vm_area_struct *area,
1349                                 unsigned long address, int *type)
1350 {
1351         int error;
1352         struct file *file = area->vm_file;
1353         struct address_space *mapping = file->f_mapping;
1354         struct file_ra_state *ra = &file->f_ra;
1355         struct inode *inode = mapping->host;
1356         struct page *page;
1357         unsigned long size, pgoff;
1358         int did_readaround = 0, majmin = VM_FAULT_MINOR;
1359
1360         pgoff = ((address-area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;
1361
1362 retry_all:
1363         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1364         if (pgoff >= size)
1365                 goto outside_data_content;
1366
1367         /* If we don't want any read-ahead, don't bother */
1368         if (VM_RandomReadHint(area))
1369                 goto no_cached_page;
1370
1371         /*
1372          * The readahead code wants to be told about each and every page
1373          * so it can build and shrink its windows appropriately
1374          *
1375          * For sequential accesses, we use the generic readahead logic.
1376          */
1377         if (VM_SequentialReadHint(area))
1378                 page_cache_readahead(mapping, ra, file, pgoff, 1);
1379
1380         /*
1381          * Do we have something in the page cache already?
1382          */
1383 retry_find:
1384         page = find_get_page(mapping, pgoff);
1385         if (!page) {
1386                 unsigned long ra_pages;
1387
1388                 if (VM_SequentialReadHint(area)) {
1389                         handle_ra_miss(mapping, ra, pgoff);
1390                         goto no_cached_page;
1391                 }
1392                 ra->mmap_miss++;
1393
1394                 /*
1395                  * Do we miss much more than hit in this file? If so,
1396                  * stop bothering with read-ahead. It will only hurt.
1397                  */
1398                 if (ra->mmap_miss > ra->mmap_hit + MMAP_LOTSAMISS)
1399                         goto no_cached_page;
1400
1401                 /*
1402                  * To keep the pgmajfault counter straight, we need to
1403                  * check did_readaround, as this is an inner loop.
1404                  */
1405                 if (!did_readaround) {
1406                         majmin = VM_FAULT_MAJOR;
1407                         count_vm_event(PGMAJFAULT);
1408                 }
1409                 did_readaround = 1;
1410                 ra_pages = max_sane_readahead(file->f_ra.ra_pages);
1411                 if (ra_pages) {
1412                         pgoff_t start = 0;
1413
1414                         if (pgoff > ra_pages / 2)
1415                                 start = pgoff - ra_pages / 2;
1416                         do_page_cache_readahead(mapping, file, start, ra_pages);
1417                 }
1418                 page = find_get_page(mapping, pgoff);
1419                 if (!page)
1420                         goto no_cached_page;
1421         }
1422
1423         if (!did_readaround)
1424                 ra->mmap_hit++;
1425
1426         /*
1427          * Ok, found a page in the page cache, now we need to check
1428          * that it's up-to-date.
1429          */
1430         if (!PageUptodate(page))
1431                 goto page_not_uptodate;
1432
1433 success:
1434         /*
1435          * Found the page and have a reference on it.
1436          */
1437         mark_page_accessed(page);
1438         if (type)
1439                 *type = majmin;
1440         return page;
1441
1442 outside_data_content:
1443         /*
1444          * An external ptracer can access pages that normally aren't
1445          * accessible..
1446          */
1447         if (area->vm_mm == current->mm)
1448                 return NOPAGE_SIGBUS;
1449         /* Fall through to the non-read-ahead case */
1450 no_cached_page:
1451         /*
1452          * We're only likely to ever get here if MADV_RANDOM is in
1453          * effect.
1454          */
1455         error = page_cache_read(file, pgoff);
1456
1457         /*
1458          * The page we want has now been added to the page cache.
1459          * In the unlikely event that someone removed it in the
1460          * meantime, we'll just come back here and read it again.
1461          */
1462         if (error >= 0)
1463                 goto retry_find;
1464
1465         /*
1466          * An error return from page_cache_read can result if the
1467          * system is low on memory, or a problem occurs while trying
1468          * to schedule I/O.
1469          */
1470         if (error == -ENOMEM)
1471                 return NOPAGE_OOM;
1472         return NOPAGE_SIGBUS;
1473
1474 page_not_uptodate:
1475         if (!did_readaround) {
1476                 majmin = VM_FAULT_MAJOR;
1477                 count_vm_event(PGMAJFAULT);
1478         }
1479
1480         /*
1481          * Umm, take care of errors if the page isn't up-to-date.
1482          * Try to re-read it _once_. We do this synchronously,
1483          * because there really aren't any performance issues here
1484          * and we need to check for errors.
1485          */
1486         lock_page(page);
1487
1488         /* Somebody truncated the page on us? */
1489         if (!page->mapping) {
1490                 unlock_page(page);
1491                 page_cache_release(page);
1492                 goto retry_all;
1493         }
1494
1495         /* Somebody else successfully read it in? */
1496         if (PageUptodate(page)) {
1497                 unlock_page(page);
1498                 goto success;
1499         }
1500         ClearPageError(page);
1501         error = mapping->a_ops->readpage(file, page);
1502         if (!error) {
1503                 wait_on_page_locked(page);
1504                 if (PageUptodate(page))
1505                         goto success;
1506         } else if (error == AOP_TRUNCATED_PAGE) {
1507                 page_cache_release(page);
1508                 goto retry_find;
1509         }
1510
1511         /*
1512          * Things didn't work out. Return zero to tell the
1513          * mm layer so, possibly freeing the page cache page first.
1514          */
1515         shrink_readahead_size_eio(file, ra);
1516         page_cache_release(page);
1517         return NOPAGE_SIGBUS;
1518 }
1519 EXPORT_SYMBOL(filemap_nopage);
1520
1521 static struct page * filemap_getpage(struct file *file, unsigned long pgoff,
1522                                         int nonblock)
1523 {
1524         struct address_space *mapping = file->f_mapping;
1525         struct page *page;
1526         int error;
1527
1528         /*
1529          * Do we have something in the page cache already?
1530          */
1531 retry_find:
1532         page = find_get_page(mapping, pgoff);
1533         if (!page) {
1534                 if (nonblock)
1535                         return NULL;
1536                 goto no_cached_page;
1537         }
1538
1539         /*
1540          * Ok, found a page in the page cache, now we need to check
1541          * that it's up-to-date.
1542          */
1543         if (!PageUptodate(page)) {
1544                 if (nonblock) {
1545                         page_cache_release(page);
1546                         return NULL;
1547                 }
1548                 goto page_not_uptodate;
1549         }
1550
1551 success:
1552         /*
1553          * Found the page and have a reference on it.
1554          */
1555         mark_page_accessed(page);
1556         return page;
1557
1558 no_cached_page:
1559         error = page_cache_read(file, pgoff);
1560
1561         /*
1562          * The page we want has now been added to the page cache.
1563          * In the unlikely event that someone removed it in the
1564          * meantime, we'll just come back here and read it again.
1565          */
1566         if (error >= 0)
1567                 goto retry_find;
1568
1569         /*
1570          * An error return from page_cache_read can result if the
1571          * system is low on memory, or a problem occurs while trying
1572          * to schedule I/O.
1573          */
1574         return NULL;
1575
1576 page_not_uptodate:
1577         lock_page(page);
1578
1579         /* Did it get truncated while we waited for it? */
1580         if (!page->mapping) {
1581                 unlock_page(page);
1582                 goto err;
1583         }
1584
1585         /* Did somebody else get it up-to-date? */
1586         if (PageUptodate(page)) {
1587                 unlock_page(page);
1588                 goto success;
1589         }
1590
1591         error = mapping->a_ops->readpage(file, page);
1592         if (!error) {
1593                 wait_on_page_locked(page);
1594                 if (PageUptodate(page))
1595                         goto success;
1596         } else if (error == AOP_TRUNCATED_PAGE) {
1597                 page_cache_release(page);
1598                 goto retry_find;
1599         }
1600
1601         /*
1602          * Umm, take care of errors if the page isn't up-to-date.
1603          * Try to re-read it _once_. We do this synchronously,
1604          * because there really aren't any performance issues here
1605          * and we need to check for errors.
1606          */
1607         lock_page(page);
1608
1609         /* Somebody truncated the page on us? */
1610         if (!page->mapping) {
1611                 unlock_page(page);
1612                 goto err;
1613         }
1614         /* Somebody else successfully read it in? */
1615         if (PageUptodate(page)) {
1616                 unlock_page(page);
1617                 goto success;
1618         }
1619
1620         ClearPageError(page);
1621         error = mapping->a_ops->readpage(file, page);
1622         if (!error) {
1623                 wait_on_page_locked(page);
1624                 if (PageUptodate(page))
1625                         goto success;
1626         } else if (error == AOP_TRUNCATED_PAGE) {
1627                 page_cache_release(page);
1628                 goto retry_find;
1629         }
1630
1631         /*
1632          * Things didn't work out. Return zero to tell the
1633          * mm layer so, possibly freeing the page cache page first.
1634          */
1635 err:
1636         page_cache_release(page);
1637
1638         return NULL;
1639 }
1640
1641 int filemap_populate(struct vm_area_struct *vma, unsigned long addr,
1642                 unsigned long len, pgprot_t prot, unsigned long pgoff,
1643                 int nonblock)
1644 {
1645         struct file *file = vma->vm_file;
1646         struct address_space *mapping = file->f_mapping;
1647         struct inode *inode = mapping->host;
1648         unsigned long size;
1649         struct mm_struct *mm = vma->vm_mm;
1650         struct page *page;
1651         int err;
1652
1653         if (!nonblock)
1654                 force_page_cache_readahead(mapping, vma->vm_file,
1655                                         pgoff, len >> PAGE_CACHE_SHIFT);
1656
1657 repeat:
1658         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1659         if (pgoff + (len >> PAGE_CACHE_SHIFT) > size)
1660                 return -EINVAL;
1661
1662         page = filemap_getpage(file, pgoff, nonblock);
1663
1664         /* XXX: This is wrong, a filesystem I/O error may have happened. Fix that as
1665          * done in shmem_populate calling shmem_getpage */
1666         if (!page && !nonblock)
1667                 return -ENOMEM;
1668
1669         if (page) {
1670                 err = install_page(mm, vma, addr, page, prot);
1671                 if (err) {
1672                         page_cache_release(page);
1673                         return err;
1674                 }
1675         } else if (vma->vm_flags & VM_NONLINEAR) {
1676                 /* No page was found just because we can't read it in now (being
1677                  * here implies nonblock != 0), but the page may exist, so set
1678                  * the PTE to fault it in later. */
1679                 err = install_file_pte(mm, vma, addr, pgoff, prot);
1680                 if (err)
1681                         return err;
1682         }
1683
1684         len -= PAGE_SIZE;
1685         addr += PAGE_SIZE;
1686         pgoff++;
1687         if (len)
1688                 goto repeat;
1689
1690         return 0;
1691 }
1692 EXPORT_SYMBOL(filemap_populate);
1693
1694 struct vm_operations_struct generic_file_vm_ops = {
1695         .nopage         = filemap_nopage,
1696         .populate       = filemap_populate,
1697 };
1698
1699 /* This is used for a general mmap of a disk file */
1700
1701 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1702 {
1703         struct address_space *mapping = file->f_mapping;
1704
1705         if (!mapping->a_ops->readpage)
1706                 return -ENOEXEC;
1707         file_accessed(file);
1708         vma->vm_ops = &generic_file_vm_ops;
1709         return 0;
1710 }
1711
1712 /*
1713  * This is for filesystems which do not implement ->writepage.
1714  */
1715 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1716 {
1717         if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1718                 return -EINVAL;
1719         return generic_file_mmap(file, vma);
1720 }
1721 #else
1722 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1723 {
1724         return -ENOSYS;
1725 }
1726 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1727 {
1728         return -ENOSYS;
1729 }
1730 #endif /* CONFIG_MMU */
1731
1732 EXPORT_SYMBOL(generic_file_mmap);
1733 EXPORT_SYMBOL(generic_file_readonly_mmap);
1734
1735 static struct page *__read_cache_page(struct address_space *mapping,
1736                                 unsigned long index,
1737                                 int (*filler)(void *,struct page*),
1738                                 void *data)
1739 {
1740         struct page *page, *cached_page = NULL;
1741         int err;
1742 repeat:
1743         page = find_get_page(mapping, index);
1744         if (!page) {
1745                 if (!cached_page) {
1746                         cached_page = page_cache_alloc_cold(mapping);
1747                         if (!cached_page)
1748                                 return ERR_PTR(-ENOMEM);
1749                 }
1750                 err = add_to_page_cache_lru(cached_page, mapping,
1751                                         index, GFP_KERNEL);
1752                 if (err == -EEXIST)
1753                         goto repeat;
1754                 if (err < 0) {
1755                         /* Presumably ENOMEM for radix tree node */
1756                         page_cache_release(cached_page);
1757                         return ERR_PTR(err);
1758                 }
1759                 page = cached_page;
1760                 cached_page = NULL;
1761                 err = filler(data, page);
1762                 if (err < 0) {
1763                         page_cache_release(page);
1764                         page = ERR_PTR(err);
1765                 }
1766         }
1767         if (cached_page)
1768                 page_cache_release(cached_page);
1769         return page;
1770 }
1771
1772 /*
1773  * Same as read_cache_page, but don't wait for page to become unlocked
1774  * after submitting it to the filler.
1775  */
1776 struct page *read_cache_page_async(struct address_space *mapping,
1777                                 unsigned long index,
1778                                 int (*filler)(void *,struct page*),
1779                                 void *data)
1780 {
1781         struct page *page;
1782         int err;
1783
1784 retry:
1785         page = __read_cache_page(mapping, index, filler, data);
1786         if (IS_ERR(page))
1787                 return page;
1788         mark_page_accessed(page);
1789         if (PageUptodate(page))
1790                 goto out;
1791
1792         lock_page(page);
1793         if (!page->mapping) {
1794                 unlock_page(page);
1795                 page_cache_release(page);
1796                 goto retry;
1797         }
1798         if (PageUptodate(page)) {
1799                 unlock_page(page);
1800                 goto out;
1801         }
1802         err = filler(data, page);
1803         if (err < 0) {
1804                 page_cache_release(page);
1805                 return ERR_PTR(err);
1806         }
1807 out:
1808         mark_page_accessed(page);
1809         return page;
1810 }
1811 EXPORT_SYMBOL(read_cache_page_async);
1812
1813 /**
1814  * read_cache_page - read into page cache, fill it if needed
1815  * @mapping:    the page's address_space
1816  * @index:      the page index
1817  * @filler:     function to perform the read
1818  * @data:       destination for read data
1819  *
1820  * Read into the page cache. If a page already exists, and PageUptodate() is
1821  * not set, try to fill the page then wait for it to become unlocked.
1822  *
1823  * If the page does not get brought uptodate, return -EIO.
1824  */
1825 struct page *read_cache_page(struct address_space *mapping,
1826                                 unsigned long index,
1827                                 int (*filler)(void *,struct page*),
1828                                 void *data)
1829 {
1830         struct page *page;
1831
1832         page = read_cache_page_async(mapping, index, filler, data);
1833         if (IS_ERR(page))
1834                 goto out;
1835         wait_on_page_locked(page);
1836         if (!PageUptodate(page)) {
1837                 page_cache_release(page);
1838                 page = ERR_PTR(-EIO);
1839         }
1840  out:
1841         return page;
1842 }
1843 EXPORT_SYMBOL(read_cache_page);
1844
1845 /*
1846  * If the page was newly created, increment its refcount and add it to the
1847  * caller's lru-buffering pagevec.  This function is specifically for
1848  * generic_file_write().
1849  */
1850 static inline struct page *
1851 __grab_cache_page(struct address_space *mapping, unsigned long index,
1852                         struct page **cached_page, struct pagevec *lru_pvec)
1853 {
1854         int err;
1855         struct page *page;
1856 repeat:
1857         page = find_lock_page(mapping, index);
1858         if (!page) {
1859                 if (!*cached_page) {
1860                         *cached_page = page_cache_alloc(mapping);
1861                         if (!*cached_page)
1862                                 return NULL;
1863                 }
1864                 err = add_to_page_cache(*cached_page, mapping,
1865                                         index, GFP_KERNEL);
1866                 if (err == -EEXIST)
1867                         goto repeat;
1868                 if (err == 0) {
1869                         page = *cached_page;
1870                         page_cache_get(page);
1871                         if (!pagevec_add(lru_pvec, page))
1872                                 __pagevec_lru_add(lru_pvec);
1873                         *cached_page = NULL;
1874                 }
1875         }
1876         return page;
1877 }
1878
1879 /*
1880  * The logic we want is
1881  *
1882  *      if suid or (sgid and xgrp)
1883  *              remove privs
1884  */
1885 int should_remove_suid(struct dentry *dentry)
1886 {
1887         mode_t mode = dentry->d_inode->i_mode;
1888         int kill = 0;
1889
1890         /* suid always must be killed */
1891         if (unlikely(mode & S_ISUID))
1892                 kill = ATTR_KILL_SUID;
1893
1894         /*
1895          * sgid without any exec bits is just a mandatory locking mark; leave
1896          * it alone.  If some exec bits are set, it's a real sgid; kill it.
1897          */
1898         if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1899                 kill |= ATTR_KILL_SGID;
1900
1901         if (unlikely(kill && !capable(CAP_FSETID)))
1902                 return kill;
1903
1904         return 0;
1905 }
1906 EXPORT_SYMBOL(should_remove_suid);
1907
1908 int __remove_suid(struct dentry *dentry, int kill)
1909 {
1910         struct iattr newattrs;
1911
1912         newattrs.ia_valid = ATTR_FORCE | kill;
1913         return notify_change(dentry, &newattrs);
1914 }
1915
1916 int remove_suid(struct dentry *dentry)
1917 {
1918         int kill = should_remove_suid(dentry);
1919
1920         if (unlikely(kill))
1921                 return __remove_suid(dentry, kill);
1922
1923         return 0;
1924 }
1925 EXPORT_SYMBOL(remove_suid);
1926
1927 size_t
1928 __filemap_copy_from_user_iovec_inatomic(char *vaddr,
1929                         const struct iovec *iov, size_t base, size_t bytes)
1930 {
1931         size_t copied = 0, left = 0;
1932
1933         while (bytes) {
1934                 char __user *buf = iov->iov_base + base;
1935                 int copy = min(bytes, iov->iov_len - base);
1936
1937                 base = 0;
1938                 left = __copy_from_user_inatomic_nocache(vaddr, buf, copy);
1939                 copied += copy;
1940                 bytes -= copy;
1941                 vaddr += copy;
1942                 iov++;
1943
1944                 if (unlikely(left))
1945                         break;
1946         }
1947         return copied - left;
1948 }
1949
1950 /*
1951  * Performs necessary checks before doing a write
1952  *
1953  * Can adjust writing position or amount of bytes to write.
1954  * Returns appropriate error code that caller should return or
1955  * zero in case that write should be allowed.
1956  */
1957 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
1958 {
1959         struct inode *inode = file->f_mapping->host;
1960         unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
1961
1962         if (unlikely(*pos < 0))
1963                 return -EINVAL;
1964
1965         if (!isblk) {
1966                 /* FIXME: this is for backwards compatibility with 2.4 */
1967                 if (file->f_flags & O_APPEND)
1968                         *pos = i_size_read(inode);
1969
1970                 if (limit != RLIM_INFINITY) {
1971                         if (*pos >= limit) {
1972                                 send_sig(SIGXFSZ, current, 0);
1973                                 return -EFBIG;
1974                         }
1975                         if (*count > limit - (typeof(limit))*pos) {
1976                                 *count = limit - (typeof(limit))*pos;
1977                         }
1978                 }
1979         }
1980
1981         /*
1982          * LFS rule
1983          */
1984         if (unlikely(*pos + *count > MAX_NON_LFS &&
1985                                 !(file->f_flags & O_LARGEFILE))) {
1986                 if (*pos >= MAX_NON_LFS) {
1987                         send_sig(SIGXFSZ, current, 0);
1988                         return -EFBIG;
1989                 }
1990                 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
1991                         *count = MAX_NON_LFS - (unsigned long)*pos;
1992                 }
1993         }
1994
1995         /*
1996          * Are we about to exceed the fs block limit ?
1997          *
1998          * If we have written data it becomes a short write.  If we have
1999          * exceeded without writing data we send a signal and return EFBIG.
2000          * Linus frestrict idea will clean these up nicely..
2001          */
2002         if (likely(!isblk)) {
2003                 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2004                         if (*count || *pos > inode->i_sb->s_maxbytes) {
2005                                 send_sig(SIGXFSZ, current, 0);
2006                                 return -EFBIG;
2007                         }
2008                         /* zero-length writes at ->s_maxbytes are OK */
2009                 }
2010
2011                 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2012                         *count = inode->i_sb->s_maxbytes - *pos;
2013         } else {
2014 #ifdef CONFIG_BLOCK
2015                 loff_t isize;
2016                 if (bdev_read_only(I_BDEV(inode)))
2017                         return -EPERM;
2018                 isize = i_size_read(inode);
2019                 if (*pos >= isize) {
2020                         if (*count || *pos > isize)
2021                                 return -ENOSPC;
2022                 }
2023
2024                 if (*pos + *count > isize)
2025                         *count = isize - *pos;
2026 #else
2027                 return -EPERM;
2028 #endif
2029         }
2030         return 0;
2031 }
2032 EXPORT_SYMBOL(generic_write_checks);
2033
2034 ssize_t
2035 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2036                 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2037                 size_t count, size_t ocount)
2038 {
2039         struct file     *file = iocb->ki_filp;
2040         struct address_space *mapping = file->f_mapping;
2041         struct inode    *inode = mapping->host;
2042         ssize_t         written;
2043
2044         if (count != ocount)
2045                 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2046
2047         written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2048         if (written > 0) {
2049                 loff_t end = pos + written;
2050                 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2051                         i_size_write(inode,  end);
2052                         mark_inode_dirty(inode);
2053                 }
2054                 *ppos = end;
2055         }
2056
2057         /*
2058          * Sync the fs metadata but not the minor inode changes and
2059          * of course not the data as we did direct DMA for the IO.
2060          * i_mutex is held, which protects generic_osync_inode() from
2061          * livelocking.  AIO O_DIRECT ops attempt to sync metadata here.
2062          */
2063         if ((written >= 0 || written == -EIOCBQUEUED) &&
2064             ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2065                 int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
2066                 if (err < 0)
2067                         written = err;
2068         }
2069         return written;
2070 }
2071 EXPORT_SYMBOL(generic_file_direct_write);
2072
2073 ssize_t
2074 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2075                 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2076                 size_t count, ssize_t written)
2077 {
2078         struct file *file = iocb->ki_filp;
2079         struct address_space * mapping = file->f_mapping;
2080         const struct address_space_operations *a_ops = mapping->a_ops;
2081         struct inode    *inode = mapping->host;
2082         long            status = 0;
2083         struct page     *page;
2084         struct page     *cached_page = NULL;
2085         size_t          bytes;
2086         struct pagevec  lru_pvec;
2087         const struct iovec *cur_iov = iov; /* current iovec */
2088         size_t          iov_base = 0;      /* offset in the current iovec */
2089         char __user     *buf;
2090
2091         pagevec_init(&lru_pvec, 0);
2092
2093         /*
2094          * handle partial DIO write.  Adjust cur_iov if needed.
2095          */
2096         if (likely(nr_segs == 1))
2097                 buf = iov->iov_base + written;
2098         else {
2099                 filemap_set_next_iovec(&cur_iov, &iov_base, written);
2100                 buf = cur_iov->iov_base + iov_base;
2101         }
2102
2103         do {
2104                 unsigned long index;
2105                 unsigned long offset;
2106                 size_t copied;
2107
2108                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
2109                 index = pos >> PAGE_CACHE_SHIFT;
2110                 bytes = PAGE_CACHE_SIZE - offset;
2111
2112                 /* Limit the size of the copy to the caller's write size */
2113                 bytes = min(bytes, count);
2114
2115                 /* We only need to worry about prefaulting when writes are from
2116                  * user-space.  NFSd uses vfs_writev with several non-aligned
2117                  * segments in the vector, and limiting to one segment a time is
2118                  * a noticeable performance for re-write
2119                  */
2120                 if (!segment_eq(get_fs(), KERNEL_DS)) {
2121                         /*
2122                          * Limit the size of the copy to that of the current
2123                          * segment, because fault_in_pages_readable() doesn't
2124                          * know how to walk segments.
2125                          */
2126                         bytes = min(bytes, cur_iov->iov_len - iov_base);
2127
2128                         /*
2129                          * Bring in the user page that we will copy from
2130                          * _first_.  Otherwise there's a nasty deadlock on
2131                          * copying from the same page as we're writing to,
2132                          * without it being marked up-to-date.
2133                          */
2134                         fault_in_pages_readable(buf, bytes);
2135                 }
2136                 page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
2137                 if (!page) {
2138                         status = -ENOMEM;
2139                         break;
2140                 }
2141
2142                 if (unlikely(bytes == 0)) {
2143                         status = 0;
2144                         copied = 0;
2145                         goto zero_length_segment;
2146                 }
2147
2148                 status = a_ops->prepare_write(file, page, offset, offset+bytes);
2149                 if (unlikely(status)) {
2150                         loff_t isize = i_size_read(inode);
2151
2152                         if (status != AOP_TRUNCATED_PAGE)
2153                                 unlock_page(page);
2154                         page_cache_release(page);
2155                         if (status == AOP_TRUNCATED_PAGE)
2156                                 continue;
2157                         /*
2158                          * prepare_write() may have instantiated a few blocks
2159                          * outside i_size.  Trim these off again.
2160                          */
2161                         if (pos + bytes > isize)
2162                                 vmtruncate(inode, isize);
2163                         break;
2164                 }
2165                 if (likely(nr_segs == 1))
2166                         copied = filemap_copy_from_user(page, offset,
2167                                                         buf, bytes);
2168                 else
2169                         copied = filemap_copy_from_user_iovec(page, offset,
2170                                                 cur_iov, iov_base, bytes);
2171                 flush_dcache_page(page);
2172                 status = a_ops->commit_write(file, page, offset, offset+bytes);
2173                 if (status == AOP_TRUNCATED_PAGE) {
2174                         page_cache_release(page);
2175                         continue;
2176                 }
2177 zero_length_segment:
2178                 if (likely(copied >= 0)) {
2179                         if (!status)
2180                                 status = copied;
2181
2182                         if (status >= 0) {
2183                                 written += status;
2184                                 count -= status;
2185                                 pos += status;
2186                                 buf += status;
2187                                 if (unlikely(nr_segs > 1)) {
2188                                         filemap_set_next_iovec(&cur_iov,
2189                                                         &iov_base, status);
2190                                         if (count)
2191                                                 buf = cur_iov->iov_base +
2192                                                         iov_base;
2193                                 } else {
2194                                         iov_base += status;
2195                                 }
2196                         }
2197                 }
2198                 if (unlikely(copied != bytes))
2199                         if (status >= 0)
2200                                 status = -EFAULT;
2201                 unlock_page(page);
2202                 mark_page_accessed(page);
2203                 page_cache_release(page);
2204                 if (status < 0)
2205                         break;
2206                 balance_dirty_pages_ratelimited(mapping);
2207                 cond_resched();
2208         } while (count);
2209         *ppos = pos;
2210
2211         if (cached_page)
2212                 page_cache_release(cached_page);
2213
2214         /*
2215          * For now, when the user asks for O_SYNC, we'll actually give O_DSYNC
2216          */
2217         if (likely(status >= 0)) {
2218                 if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2219                         if (!a_ops->writepage || !is_sync_kiocb(iocb))
2220                                 status = generic_osync_inode(inode, mapping,
2221                                                 OSYNC_METADATA|OSYNC_DATA);
2222                 }
2223         }
2224         
2225         /*
2226          * If we get here for O_DIRECT writes then we must have fallen through
2227          * to buffered writes (block instantiation inside i_size).  So we sync
2228          * the file data here, to try to honour O_DIRECT expectations.
2229          */
2230         if (unlikely(file->f_flags & O_DIRECT) && written)
2231                 status = filemap_write_and_wait(mapping);
2232
2233         pagevec_lru_add(&lru_pvec);
2234         return written ? written : status;
2235 }
2236 EXPORT_SYMBOL(generic_file_buffered_write);
2237
2238 static ssize_t
2239 __generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
2240                                 unsigned long nr_segs, loff_t *ppos)
2241 {
2242         struct file *file = iocb->ki_filp;
2243         struct address_space * mapping = file->f_mapping;
2244         size_t ocount;          /* original count */
2245         size_t count;           /* after file limit checks */
2246         struct inode    *inode = mapping->host;
2247         loff_t          pos;
2248         ssize_t         written;
2249         ssize_t         err;
2250
2251         ocount = 0;
2252         err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2253         if (err)
2254                 return err;
2255
2256         count = ocount;
2257         pos = *ppos;
2258
2259         vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2260
2261         /* We can write back this queue in page reclaim */
2262         current->backing_dev_info = mapping->backing_dev_info;
2263         written = 0;
2264
2265         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2266         if (err)
2267                 goto out;
2268
2269         if (count == 0)
2270                 goto out;
2271
2272         err = remove_suid(file->f_path.dentry);
2273         if (err)
2274                 goto out;
2275
2276         file_update_time(file);
2277
2278         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2279         if (unlikely(file->f_flags & O_DIRECT)) {
2280                 loff_t endbyte;
2281                 ssize_t written_buffered;
2282
2283                 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2284                                                         ppos, count, ocount);
2285                 if (written < 0 || written == count)
2286                         goto out;
2287                 /*
2288                  * direct-io write to a hole: fall through to buffered I/O
2289                  * for completing the rest of the request.
2290                  */
2291                 pos += written;
2292                 count -= written;
2293                 written_buffered = generic_file_buffered_write(iocb, iov,
2294                                                 nr_segs, pos, ppos, count,
2295                                                 written);
2296                 /*
2297                  * If generic_file_buffered_write() retuned a synchronous error
2298                  * then we want to return the number of bytes which were
2299                  * direct-written, or the error code if that was zero.  Note
2300                  * that this differs from normal direct-io semantics, which
2301                  * will return -EFOO even if some bytes were written.
2302                  */
2303                 if (written_buffered < 0) {
2304                         err = written_buffered;
2305                         goto out;
2306                 }
2307
2308                 /*
2309                  * We need to ensure that the page cache pages are written to
2310                  * disk and invalidated to preserve the expected O_DIRECT
2311                  * semantics.
2312                  */
2313                 endbyte = pos + written_buffered - written - 1;
2314                 err = do_sync_mapping_range(file->f_mapping, pos, endbyte,
2315                                             SYNC_FILE_RANGE_WAIT_BEFORE|
2316                                             SYNC_FILE_RANGE_WRITE|
2317                                             SYNC_FILE_RANGE_WAIT_AFTER);
2318                 if (err == 0) {
2319                         written = written_buffered;
2320                         invalidate_mapping_pages(mapping,
2321                                                  pos >> PAGE_CACHE_SHIFT,
2322                                                  endbyte >> PAGE_CACHE_SHIFT);
2323                 } else {
2324                         /*
2325                          * We don't know how much we wrote, so just return
2326                          * the number of bytes which were direct-written
2327                          */
2328                 }
2329         } else {
2330                 written = generic_file_buffered_write(iocb, iov, nr_segs,
2331                                 pos, ppos, count, written);
2332         }
2333 out:
2334         current->backing_dev_info = NULL;
2335         return written ? written : err;
2336 }
2337
2338 ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
2339                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
2340 {
2341         struct file *file = iocb->ki_filp;
2342         struct address_space *mapping = file->f_mapping;
2343         struct inode *inode = mapping->host;
2344         ssize_t ret;
2345
2346         BUG_ON(iocb->ki_pos != pos);
2347
2348         ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2349                         &iocb->ki_pos);
2350
2351         if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2352                 ssize_t err;
2353
2354                 err = sync_page_range_nolock(inode, mapping, pos, ret);
2355                 if (err < 0)
2356                         ret = err;
2357         }
2358         return ret;
2359 }
2360 EXPORT_SYMBOL(generic_file_aio_write_nolock);
2361
2362 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2363                 unsigned long nr_segs, loff_t pos)
2364 {
2365         struct file *file = iocb->ki_filp;
2366         struct address_space *mapping = file->f_mapping;
2367         struct inode *inode = mapping->host;
2368         ssize_t ret;
2369
2370         BUG_ON(iocb->ki_pos != pos);
2371
2372         mutex_lock(&inode->i_mutex);
2373         ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2374                         &iocb->ki_pos);
2375         mutex_unlock(&inode->i_mutex);
2376
2377         if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2378                 ssize_t err;
2379
2380                 err = sync_page_range(inode, mapping, pos, ret);
2381                 if (err < 0)
2382                         ret = err;
2383         }
2384         return ret;
2385 }
2386 EXPORT_SYMBOL(generic_file_aio_write);
2387
2388 /*
2389  * Called under i_mutex for writes to S_ISREG files.   Returns -EIO if something
2390  * went wrong during pagecache shootdown.
2391  */
2392 static ssize_t
2393 generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
2394         loff_t offset, unsigned long nr_segs)
2395 {
2396         struct file *file = iocb->ki_filp;
2397         struct address_space *mapping = file->f_mapping;
2398         ssize_t retval;
2399         size_t write_len;
2400         pgoff_t end = 0; /* silence gcc */
2401
2402         /*
2403          * If it's a write, unmap all mmappings of the file up-front.  This
2404          * will cause any pte dirty bits to be propagated into the pageframes
2405          * for the subsequent filemap_write_and_wait().
2406          */
2407         if (rw == WRITE) {
2408                 write_len = iov_length(iov, nr_segs);
2409                 end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT;
2410                 if (mapping_mapped(mapping))
2411                         unmap_mapping_range(mapping, offset, write_len, 0);
2412         }
2413
2414         retval = filemap_write_and_wait(mapping);
2415         if (retval)
2416                 goto out;
2417
2418         /*
2419          * After a write we want buffered reads to be sure to go to disk to get
2420          * the new data.  We invalidate clean cached page from the region we're
2421          * about to write.  We do this *before* the write so that we can return
2422          * -EIO without clobbering -EIOCBQUEUED from ->direct_IO().
2423          */
2424         if (rw == WRITE && mapping->nrpages) {
2425                 retval = invalidate_inode_pages2_range(mapping,
2426                                         offset >> PAGE_CACHE_SHIFT, end);
2427                 if (retval)
2428                         goto out;
2429         }
2430
2431         retval = mapping->a_ops->direct_IO(rw, iocb, iov, offset, nr_segs);
2432         if (retval)
2433                 goto out;
2434
2435         /*
2436          * Finally, try again to invalidate clean pages which might have been
2437          * faulted in by get_user_pages() if the source of the write was an
2438          * mmap()ed region of the file we're writing.  That's a pretty crazy
2439          * thing to do, so we don't support it 100%.  If this invalidation
2440          * fails and we have -EIOCBQUEUED we ignore the failure.
2441          */
2442         if (rw == WRITE && mapping->nrpages) {
2443                 int err = invalidate_inode_pages2_range(mapping,
2444                                               offset >> PAGE_CACHE_SHIFT, end);
2445                 if (err && retval >= 0)
2446                         retval = err;
2447         }
2448 out:
2449         return retval;
2450 }
2451
2452 /**
2453  * try_to_release_page() - release old fs-specific metadata on a page
2454  *
2455  * @page: the page which the kernel is trying to free
2456  * @gfp_mask: memory allocation flags (and I/O mode)
2457  *
2458  * The address_space is to try to release any data against the page
2459  * (presumably at page->private).  If the release was successful, return `1'.
2460  * Otherwise return zero.
2461  *
2462  * The @gfp_mask argument specifies whether I/O may be performed to release
2463  * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
2464  *
2465  * NOTE: @gfp_mask may go away, and this function may become non-blocking.
2466  */
2467 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2468 {
2469         struct address_space * const mapping = page->mapping;
2470
2471         BUG_ON(!PageLocked(page));
2472         if (PageWriteback(page))
2473                 return 0;
2474
2475         if (mapping && mapping->a_ops->releasepage)
2476                 return mapping->a_ops->releasepage(page, gfp_mask);
2477         return try_to_free_buffers(page);
2478 }
2479
2480 EXPORT_SYMBOL(try_to_release_page);