mm: simplify filemap_nopage
[linux-2.6.git] / mm / filemap.c
1 /*
2  *      linux/mm/filemap.c
3  *
4  * Copyright (C) 1994-1999  Linus Torvalds
5  */
6
7 /*
8  * This file handles the generic file mmap semantics used by
9  * most "normal" filesystems (but you don't /have/ to use this:
10  * the NFS filesystem used to do this differently, for example)
11  */
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/compiler.h>
15 #include <linux/fs.h>
16 #include <linux/uaccess.h>
17 #include <linux/aio.h>
18 #include <linux/capability.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/mm.h>
21 #include <linux/swap.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/file.h>
25 #include <linux/uio.h>
26 #include <linux/hash.h>
27 #include <linux/writeback.h>
28 #include <linux/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
754 /**
755  * find_get_pages_tag - find and return pages that match @tag
756  * @mapping:    the address_space to search
757  * @index:      the starting page index
758  * @tag:        the tag index
759  * @nr_pages:   the maximum number of pages
760  * @pages:      where the resulting pages are placed
761  *
762  * Like find_get_pages, except we only return pages which are tagged with
763  * @tag.   We update @index to index the next page for the traversal.
764  */
765 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
766                         int tag, unsigned int nr_pages, struct page **pages)
767 {
768         unsigned int i;
769         unsigned int ret;
770
771         read_lock_irq(&mapping->tree_lock);
772         ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
773                                 (void **)pages, *index, nr_pages, tag);
774         for (i = 0; i < ret; i++)
775                 page_cache_get(pages[i]);
776         if (ret)
777                 *index = pages[ret - 1]->index + 1;
778         read_unlock_irq(&mapping->tree_lock);
779         return ret;
780 }
781
782 /**
783  * grab_cache_page_nowait - returns locked page at given index in given cache
784  * @mapping: target address_space
785  * @index: the page index
786  *
787  * Same as grab_cache_page(), but do not wait if the page is unavailable.
788  * This is intended for speculative data generators, where the data can
789  * be regenerated if the page couldn't be grabbed.  This routine should
790  * be safe to call while holding the lock for another page.
791  *
792  * Clear __GFP_FS when allocating the page to avoid recursion into the fs
793  * and deadlock against the caller's locked page.
794  */
795 struct page *
796 grab_cache_page_nowait(struct address_space *mapping, unsigned long index)
797 {
798         struct page *page = find_get_page(mapping, index);
799
800         if (page) {
801                 if (!TestSetPageLocked(page))
802                         return page;
803                 page_cache_release(page);
804                 return NULL;
805         }
806         page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
807         if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) {
808                 page_cache_release(page);
809                 page = NULL;
810         }
811         return page;
812 }
813 EXPORT_SYMBOL(grab_cache_page_nowait);
814
815 /*
816  * CD/DVDs are error prone. When a medium error occurs, the driver may fail
817  * a _large_ part of the i/o request. Imagine the worst scenario:
818  *
819  *      ---R__________________________________________B__________
820  *         ^ reading here                             ^ bad block(assume 4k)
821  *
822  * read(R) => miss => readahead(R...B) => media error => frustrating retries
823  * => failing the whole request => read(R) => read(R+1) =>
824  * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
825  * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
826  * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
827  *
828  * It is going insane. Fix it by quickly scaling down the readahead size.
829  */
830 static void shrink_readahead_size_eio(struct file *filp,
831                                         struct file_ra_state *ra)
832 {
833         if (!ra->ra_pages)
834                 return;
835
836         ra->ra_pages /= 4;
837 }
838
839 /**
840  * do_generic_mapping_read - generic file read routine
841  * @mapping:    address_space to be read
842  * @_ra:        file's readahead state
843  * @filp:       the file to read
844  * @ppos:       current file position
845  * @desc:       read_descriptor
846  * @actor:      read method
847  *
848  * This is a generic file read routine, and uses the
849  * mapping->a_ops->readpage() function for the actual low-level stuff.
850  *
851  * This is really ugly. But the goto's actually try to clarify some
852  * of the logic when it comes to error handling etc.
853  *
854  * Note the struct file* is only passed for the use of readpage.
855  * It may be NULL.
856  */
857 void do_generic_mapping_read(struct address_space *mapping,
858                              struct file_ra_state *_ra,
859                              struct file *filp,
860                              loff_t *ppos,
861                              read_descriptor_t *desc,
862                              read_actor_t actor)
863 {
864         struct inode *inode = mapping->host;
865         unsigned long index;
866         unsigned long end_index;
867         unsigned long offset;
868         unsigned long last_index;
869         unsigned long next_index;
870         unsigned long prev_index;
871         loff_t isize;
872         struct page *cached_page;
873         int error;
874         struct file_ra_state ra = *_ra;
875
876         cached_page = NULL;
877         index = *ppos >> PAGE_CACHE_SHIFT;
878         next_index = index;
879         prev_index = ra.prev_page;
880         last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
881         offset = *ppos & ~PAGE_CACHE_MASK;
882
883         isize = i_size_read(inode);
884         if (!isize)
885                 goto out;
886
887         end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
888         for (;;) {
889                 struct page *page;
890                 unsigned long nr, ret;
891
892                 /* nr is the maximum number of bytes to copy from this page */
893                 nr = PAGE_CACHE_SIZE;
894                 if (index >= end_index) {
895                         if (index > end_index)
896                                 goto out;
897                         nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
898                         if (nr <= offset) {
899                                 goto out;
900                         }
901                 }
902                 nr = nr - offset;
903
904                 cond_resched();
905                 if (index == next_index)
906                         next_index = page_cache_readahead(mapping, &ra, filp,
907                                         index, last_index - index);
908
909 find_page:
910                 page = find_get_page(mapping, index);
911                 if (unlikely(page == NULL)) {
912                         handle_ra_miss(mapping, &ra, index);
913                         goto no_cached_page;
914                 }
915                 if (!PageUptodate(page))
916                         goto page_not_up_to_date;
917 page_ok:
918
919                 /* If users can be writing to this page using arbitrary
920                  * virtual addresses, take care about potential aliasing
921                  * before reading the page on the kernel side.
922                  */
923                 if (mapping_writably_mapped(mapping))
924                         flush_dcache_page(page);
925
926                 /*
927                  * When (part of) the same page is read multiple times
928                  * in succession, only mark it as accessed the first time.
929                  */
930                 if (prev_index != index)
931                         mark_page_accessed(page);
932                 prev_index = index;
933
934                 /*
935                  * Ok, we have the page, and it's up-to-date, so
936                  * now we can copy it to user space...
937                  *
938                  * The actor routine returns how many bytes were actually used..
939                  * NOTE! This may not be the same as how much of a user buffer
940                  * we filled up (we may be padding etc), so we can only update
941                  * "pos" here (the actor routine has to update the user buffer
942                  * pointers and the remaining count).
943                  */
944                 ret = actor(desc, page, offset, nr);
945                 offset += ret;
946                 index += offset >> PAGE_CACHE_SHIFT;
947                 offset &= ~PAGE_CACHE_MASK;
948
949                 page_cache_release(page);
950                 if (ret == nr && desc->count)
951                         continue;
952                 goto out;
953
954 page_not_up_to_date:
955                 /* Get exclusive access to the page ... */
956                 lock_page(page);
957
958                 /* Did it get truncated before we got the lock? */
959                 if (!page->mapping) {
960                         unlock_page(page);
961                         page_cache_release(page);
962                         continue;
963                 }
964
965                 /* Did somebody else fill it already? */
966                 if (PageUptodate(page)) {
967                         unlock_page(page);
968                         goto page_ok;
969                 }
970
971 readpage:
972                 /* Start the actual read. The read will unlock the page. */
973                 error = mapping->a_ops->readpage(filp, page);
974
975                 if (unlikely(error)) {
976                         if (error == AOP_TRUNCATED_PAGE) {
977                                 page_cache_release(page);
978                                 goto find_page;
979                         }
980                         goto readpage_error;
981                 }
982
983                 if (!PageUptodate(page)) {
984                         lock_page(page);
985                         if (!PageUptodate(page)) {
986                                 if (page->mapping == NULL) {
987                                         /*
988                                          * invalidate_inode_pages got it
989                                          */
990                                         unlock_page(page);
991                                         page_cache_release(page);
992                                         goto find_page;
993                                 }
994                                 unlock_page(page);
995                                 error = -EIO;
996                                 shrink_readahead_size_eio(filp, &ra);
997                                 goto readpage_error;
998                         }
999                         unlock_page(page);
1000                 }
1001
1002                 /*
1003                  * i_size must be checked after we have done ->readpage.
1004                  *
1005                  * Checking i_size after the readpage allows us to calculate
1006                  * the correct value for "nr", which means the zero-filled
1007                  * part of the page is not copied back to userspace (unless
1008                  * another truncate extends the file - this is desired though).
1009                  */
1010                 isize = i_size_read(inode);
1011                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1012                 if (unlikely(!isize || index > end_index)) {
1013                         page_cache_release(page);
1014                         goto out;
1015                 }
1016
1017                 /* nr is the maximum number of bytes to copy from this page */
1018                 nr = PAGE_CACHE_SIZE;
1019                 if (index == end_index) {
1020                         nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1021                         if (nr <= offset) {
1022                                 page_cache_release(page);
1023                                 goto out;
1024                         }
1025                 }
1026                 nr = nr - offset;
1027                 goto page_ok;
1028
1029 readpage_error:
1030                 /* UHHUH! A synchronous read error occurred. Report it */
1031                 desc->error = error;
1032                 page_cache_release(page);
1033                 goto out;
1034
1035 no_cached_page:
1036                 /*
1037                  * Ok, it wasn't cached, so we need to create a new
1038                  * page..
1039                  */
1040                 if (!cached_page) {
1041                         cached_page = page_cache_alloc_cold(mapping);
1042                         if (!cached_page) {
1043                                 desc->error = -ENOMEM;
1044                                 goto out;
1045                         }
1046                 }
1047                 error = add_to_page_cache_lru(cached_page, mapping,
1048                                                 index, GFP_KERNEL);
1049                 if (error) {
1050                         if (error == -EEXIST)
1051                                 goto find_page;
1052                         desc->error = error;
1053                         goto out;
1054                 }
1055                 page = cached_page;
1056                 cached_page = NULL;
1057                 goto readpage;
1058         }
1059
1060 out:
1061         *_ra = ra;
1062
1063         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1064         if (cached_page)
1065                 page_cache_release(cached_page);
1066         if (filp)
1067                 file_accessed(filp);
1068 }
1069 EXPORT_SYMBOL(do_generic_mapping_read);
1070
1071 int file_read_actor(read_descriptor_t *desc, struct page *page,
1072                         unsigned long offset, unsigned long size)
1073 {
1074         char *kaddr;
1075         unsigned long left, count = desc->count;
1076
1077         if (size > count)
1078                 size = count;
1079
1080         /*
1081          * Faults on the destination of a read are common, so do it before
1082          * taking the kmap.
1083          */
1084         if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1085                 kaddr = kmap_atomic(page, KM_USER0);
1086                 left = __copy_to_user_inatomic(desc->arg.buf,
1087                                                 kaddr + offset, size);
1088                 kunmap_atomic(kaddr, KM_USER0);
1089                 if (left == 0)
1090                         goto success;
1091         }
1092
1093         /* Do it the slow way */
1094         kaddr = kmap(page);
1095         left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1096         kunmap(page);
1097
1098         if (left) {
1099                 size -= left;
1100                 desc->error = -EFAULT;
1101         }
1102 success:
1103         desc->count = count - size;
1104         desc->written += size;
1105         desc->arg.buf += size;
1106         return size;
1107 }
1108
1109 /**
1110  * generic_file_aio_read - generic filesystem read routine
1111  * @iocb:       kernel I/O control block
1112  * @iov:        io vector request
1113  * @nr_segs:    number of segments in the iovec
1114  * @pos:        current file position
1115  *
1116  * This is the "read()" routine for all filesystems
1117  * that can use the page cache directly.
1118  */
1119 ssize_t
1120 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1121                 unsigned long nr_segs, loff_t pos)
1122 {
1123         struct file *filp = iocb->ki_filp;
1124         ssize_t retval;
1125         unsigned long seg;
1126         size_t count;
1127         loff_t *ppos = &iocb->ki_pos;
1128
1129         count = 0;
1130         for (seg = 0; seg < nr_segs; seg++) {
1131                 const struct iovec *iv = &iov[seg];
1132
1133                 /*
1134                  * If any segment has a negative length, or the cumulative
1135                  * length ever wraps negative then return -EINVAL.
1136                  */
1137                 count += iv->iov_len;
1138                 if (unlikely((ssize_t)(count|iv->iov_len) < 0))
1139                         return -EINVAL;
1140                 if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
1141                         continue;
1142                 if (seg == 0)
1143                         return -EFAULT;
1144                 nr_segs = seg;
1145                 count -= iv->iov_len;   /* This segment is no good */
1146                 break;
1147         }
1148
1149         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1150         if (filp->f_flags & O_DIRECT) {
1151                 loff_t size;
1152                 struct address_space *mapping;
1153                 struct inode *inode;
1154
1155                 mapping = filp->f_mapping;
1156                 inode = mapping->host;
1157                 retval = 0;
1158                 if (!count)
1159                         goto out; /* skip atime */
1160                 size = i_size_read(inode);
1161                 if (pos < size) {
1162                         retval = generic_file_direct_IO(READ, iocb,
1163                                                 iov, pos, nr_segs);
1164                         if (retval > 0)
1165                                 *ppos = pos + retval;
1166                 }
1167                 if (likely(retval != 0)) {
1168                         file_accessed(filp);
1169                         goto out;
1170                 }
1171         }
1172
1173         retval = 0;
1174         if (count) {
1175                 for (seg = 0; seg < nr_segs; seg++) {
1176                         read_descriptor_t desc;
1177
1178                         desc.written = 0;
1179                         desc.arg.buf = iov[seg].iov_base;
1180                         desc.count = iov[seg].iov_len;
1181                         if (desc.count == 0)
1182                                 continue;
1183                         desc.error = 0;
1184                         do_generic_file_read(filp,ppos,&desc,file_read_actor);
1185                         retval += desc.written;
1186                         if (desc.error) {
1187                                 retval = retval ?: desc.error;
1188                                 break;
1189                         }
1190                 }
1191         }
1192 out:
1193         return retval;
1194 }
1195 EXPORT_SYMBOL(generic_file_aio_read);
1196
1197 int file_send_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size)
1198 {
1199         ssize_t written;
1200         unsigned long count = desc->count;
1201         struct file *file = desc->arg.data;
1202
1203         if (size > count)
1204                 size = count;
1205
1206         written = file->f_op->sendpage(file, page, offset,
1207                                        size, &file->f_pos, size<count);
1208         if (written < 0) {
1209                 desc->error = written;
1210                 written = 0;
1211         }
1212         desc->count = count - written;
1213         desc->written += written;
1214         return written;
1215 }
1216
1217 ssize_t generic_file_sendfile(struct file *in_file, loff_t *ppos,
1218                          size_t count, read_actor_t actor, void *target)
1219 {
1220         read_descriptor_t desc;
1221
1222         if (!count)
1223                 return 0;
1224
1225         desc.written = 0;
1226         desc.count = count;
1227         desc.arg.data = target;
1228         desc.error = 0;
1229
1230         do_generic_file_read(in_file, ppos, &desc, actor);
1231         if (desc.written)
1232                 return desc.written;
1233         return desc.error;
1234 }
1235 EXPORT_SYMBOL(generic_file_sendfile);
1236
1237 static ssize_t
1238 do_readahead(struct address_space *mapping, struct file *filp,
1239              unsigned long index, unsigned long nr)
1240 {
1241         if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1242                 return -EINVAL;
1243
1244         force_page_cache_readahead(mapping, filp, index,
1245                                         max_sane_readahead(nr));
1246         return 0;
1247 }
1248
1249 asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
1250 {
1251         ssize_t ret;
1252         struct file *file;
1253
1254         ret = -EBADF;
1255         file = fget(fd);
1256         if (file) {
1257                 if (file->f_mode & FMODE_READ) {
1258                         struct address_space *mapping = file->f_mapping;
1259                         unsigned long start = offset >> PAGE_CACHE_SHIFT;
1260                         unsigned long end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1261                         unsigned long len = end - start + 1;
1262                         ret = do_readahead(mapping, file, start, len);
1263                 }
1264                 fput(file);
1265         }
1266         return ret;
1267 }
1268
1269 #ifdef CONFIG_MMU
1270 static int FASTCALL(page_cache_read(struct file * file, unsigned long offset));
1271 /**
1272  * page_cache_read - adds requested page to the page cache if not already there
1273  * @file:       file to read
1274  * @offset:     page index
1275  *
1276  * This adds the requested page to the page cache if it isn't already there,
1277  * and schedules an I/O to read in its contents from disk.
1278  */
1279 static int fastcall page_cache_read(struct file * file, unsigned long offset)
1280 {
1281         struct address_space *mapping = file->f_mapping;
1282         struct page *page; 
1283         int ret;
1284
1285         do {
1286                 page = page_cache_alloc_cold(mapping);
1287                 if (!page)
1288                         return -ENOMEM;
1289
1290                 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1291                 if (ret == 0)
1292                         ret = mapping->a_ops->readpage(file, page);
1293                 else if (ret == -EEXIST)
1294                         ret = 0; /* losing race to add is OK */
1295
1296                 page_cache_release(page);
1297
1298         } while (ret == AOP_TRUNCATED_PAGE);
1299                 
1300         return ret;
1301 }
1302
1303 #define MMAP_LOTSAMISS  (100)
1304
1305 /**
1306  * filemap_nopage - read in file data for page fault handling
1307  * @area:       the applicable vm_area
1308  * @address:    target address to read in
1309  * @type:       returned with VM_FAULT_{MINOR,MAJOR} if not %NULL
1310  *
1311  * filemap_nopage() is invoked via the vma operations vector for a
1312  * mapped memory region to read in file data during a page fault.
1313  *
1314  * The goto's are kind of ugly, but this streamlines the normal case of having
1315  * it in the page cache, and handles the special cases reasonably without
1316  * having a lot of duplicated code.
1317  */
1318 struct page *filemap_nopage(struct vm_area_struct *area,
1319                                 unsigned long address, int *type)
1320 {
1321         int error;
1322         struct file *file = area->vm_file;
1323         struct address_space *mapping = file->f_mapping;
1324         struct file_ra_state *ra = &file->f_ra;
1325         struct inode *inode = mapping->host;
1326         struct page *page;
1327         unsigned long size, pgoff;
1328         int did_readaround = 0, majmin = VM_FAULT_MINOR;
1329
1330         pgoff = ((address-area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;
1331
1332 retry_all:
1333         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1334         if (pgoff >= size)
1335                 goto outside_data_content;
1336
1337         /* If we don't want any read-ahead, don't bother */
1338         if (VM_RandomReadHint(area))
1339                 goto no_cached_page;
1340
1341         /*
1342          * The readahead code wants to be told about each and every page
1343          * so it can build and shrink its windows appropriately
1344          *
1345          * For sequential accesses, we use the generic readahead logic.
1346          */
1347         if (VM_SequentialReadHint(area))
1348                 page_cache_readahead(mapping, ra, file, pgoff, 1);
1349
1350         /*
1351          * Do we have something in the page cache already?
1352          */
1353 retry_find:
1354         page = find_get_page(mapping, pgoff);
1355         if (!page) {
1356                 unsigned long ra_pages;
1357
1358                 if (VM_SequentialReadHint(area)) {
1359                         handle_ra_miss(mapping, ra, pgoff);
1360                         goto no_cached_page;
1361                 }
1362                 ra->mmap_miss++;
1363
1364                 /*
1365                  * Do we miss much more than hit in this file? If so,
1366                  * stop bothering with read-ahead. It will only hurt.
1367                  */
1368                 if (ra->mmap_miss > ra->mmap_hit + MMAP_LOTSAMISS)
1369                         goto no_cached_page;
1370
1371                 /*
1372                  * To keep the pgmajfault counter straight, we need to
1373                  * check did_readaround, as this is an inner loop.
1374                  */
1375                 if (!did_readaround) {
1376                         majmin = VM_FAULT_MAJOR;
1377                         count_vm_event(PGMAJFAULT);
1378                 }
1379                 did_readaround = 1;
1380                 ra_pages = max_sane_readahead(file->f_ra.ra_pages);
1381                 if (ra_pages) {
1382                         pgoff_t start = 0;
1383
1384                         if (pgoff > ra_pages / 2)
1385                                 start = pgoff - ra_pages / 2;
1386                         do_page_cache_readahead(mapping, file, start, ra_pages);
1387                 }
1388                 page = find_get_page(mapping, pgoff);
1389                 if (!page)
1390                         goto no_cached_page;
1391         }
1392
1393         if (!did_readaround)
1394                 ra->mmap_hit++;
1395
1396         /*
1397          * Ok, found a page in the page cache, now we need to check
1398          * that it's up-to-date.
1399          */
1400         if (!PageUptodate(page))
1401                 goto page_not_uptodate;
1402
1403 success:
1404         /*
1405          * Found the page and have a reference on it.
1406          */
1407         mark_page_accessed(page);
1408         if (type)
1409                 *type = majmin;
1410         return page;
1411
1412 outside_data_content:
1413         /*
1414          * An external ptracer can access pages that normally aren't
1415          * accessible..
1416          */
1417         if (area->vm_mm == current->mm)
1418                 return NOPAGE_SIGBUS;
1419         /* Fall through to the non-read-ahead case */
1420 no_cached_page:
1421         /*
1422          * We're only likely to ever get here if MADV_RANDOM is in
1423          * effect.
1424          */
1425         error = page_cache_read(file, pgoff);
1426
1427         /*
1428          * The page we want has now been added to the page cache.
1429          * In the unlikely event that someone removed it in the
1430          * meantime, we'll just come back here and read it again.
1431          */
1432         if (error >= 0)
1433                 goto retry_find;
1434
1435         /*
1436          * An error return from page_cache_read can result if the
1437          * system is low on memory, or a problem occurs while trying
1438          * to schedule I/O.
1439          */
1440         if (error == -ENOMEM)
1441                 return NOPAGE_OOM;
1442         return NOPAGE_SIGBUS;
1443
1444 page_not_uptodate:
1445         if (!did_readaround) {
1446                 majmin = VM_FAULT_MAJOR;
1447                 count_vm_event(PGMAJFAULT);
1448         }
1449
1450         /*
1451          * Umm, take care of errors if the page isn't up-to-date.
1452          * Try to re-read it _once_. We do this synchronously,
1453          * because there really aren't any performance issues here
1454          * and we need to check for errors.
1455          */
1456         lock_page(page);
1457
1458         /* Somebody truncated the page on us? */
1459         if (!page->mapping) {
1460                 unlock_page(page);
1461                 page_cache_release(page);
1462                 goto retry_all;
1463         }
1464
1465         /* Somebody else successfully read it in? */
1466         if (PageUptodate(page)) {
1467                 unlock_page(page);
1468                 goto success;
1469         }
1470         ClearPageError(page);
1471         error = mapping->a_ops->readpage(file, page);
1472         if (!error) {
1473                 wait_on_page_locked(page);
1474                 if (PageUptodate(page))
1475                         goto success;
1476         } else if (error == AOP_TRUNCATED_PAGE) {
1477                 page_cache_release(page);
1478                 goto retry_find;
1479         }
1480
1481         /*
1482          * Things didn't work out. Return zero to tell the
1483          * mm layer so, possibly freeing the page cache page first.
1484          */
1485         shrink_readahead_size_eio(file, ra);
1486         page_cache_release(page);
1487         return NOPAGE_SIGBUS;
1488 }
1489 EXPORT_SYMBOL(filemap_nopage);
1490
1491 static struct page * filemap_getpage(struct file *file, unsigned long pgoff,
1492                                         int nonblock)
1493 {
1494         struct address_space *mapping = file->f_mapping;
1495         struct page *page;
1496         int error;
1497
1498         /*
1499          * Do we have something in the page cache already?
1500          */
1501 retry_find:
1502         page = find_get_page(mapping, pgoff);
1503         if (!page) {
1504                 if (nonblock)
1505                         return NULL;
1506                 goto no_cached_page;
1507         }
1508
1509         /*
1510          * Ok, found a page in the page cache, now we need to check
1511          * that it's up-to-date.
1512          */
1513         if (!PageUptodate(page)) {
1514                 if (nonblock) {
1515                         page_cache_release(page);
1516                         return NULL;
1517                 }
1518                 goto page_not_uptodate;
1519         }
1520
1521 success:
1522         /*
1523          * Found the page and have a reference on it.
1524          */
1525         mark_page_accessed(page);
1526         return page;
1527
1528 no_cached_page:
1529         error = page_cache_read(file, pgoff);
1530
1531         /*
1532          * The page we want has now been added to the page cache.
1533          * In the unlikely event that someone removed it in the
1534          * meantime, we'll just come back here and read it again.
1535          */
1536         if (error >= 0)
1537                 goto retry_find;
1538
1539         /*
1540          * An error return from page_cache_read can result if the
1541          * system is low on memory, or a problem occurs while trying
1542          * to schedule I/O.
1543          */
1544         return NULL;
1545
1546 page_not_uptodate:
1547         lock_page(page);
1548
1549         /* Did it get truncated while we waited for it? */
1550         if (!page->mapping) {
1551                 unlock_page(page);
1552                 goto err;
1553         }
1554
1555         /* Did somebody else get it up-to-date? */
1556         if (PageUptodate(page)) {
1557                 unlock_page(page);
1558                 goto success;
1559         }
1560
1561         error = mapping->a_ops->readpage(file, page);
1562         if (!error) {
1563                 wait_on_page_locked(page);
1564                 if (PageUptodate(page))
1565                         goto success;
1566         } else if (error == AOP_TRUNCATED_PAGE) {
1567                 page_cache_release(page);
1568                 goto retry_find;
1569         }
1570
1571         /*
1572          * Umm, take care of errors if the page isn't up-to-date.
1573          * Try to re-read it _once_. We do this synchronously,
1574          * because there really aren't any performance issues here
1575          * and we need to check for errors.
1576          */
1577         lock_page(page);
1578
1579         /* Somebody truncated the page on us? */
1580         if (!page->mapping) {
1581                 unlock_page(page);
1582                 goto err;
1583         }
1584         /* Somebody else successfully read it in? */
1585         if (PageUptodate(page)) {
1586                 unlock_page(page);
1587                 goto success;
1588         }
1589
1590         ClearPageError(page);
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          * Things didn't work out. Return zero to tell the
1603          * mm layer so, possibly freeing the page cache page first.
1604          */
1605 err:
1606         page_cache_release(page);
1607
1608         return NULL;
1609 }
1610
1611 int filemap_populate(struct vm_area_struct *vma, unsigned long addr,
1612                 unsigned long len, pgprot_t prot, unsigned long pgoff,
1613                 int nonblock)
1614 {
1615         struct file *file = vma->vm_file;
1616         struct address_space *mapping = file->f_mapping;
1617         struct inode *inode = mapping->host;
1618         unsigned long size;
1619         struct mm_struct *mm = vma->vm_mm;
1620         struct page *page;
1621         int err;
1622
1623         if (!nonblock)
1624                 force_page_cache_readahead(mapping, vma->vm_file,
1625                                         pgoff, len >> PAGE_CACHE_SHIFT);
1626
1627 repeat:
1628         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1629         if (pgoff + (len >> PAGE_CACHE_SHIFT) > size)
1630                 return -EINVAL;
1631
1632         page = filemap_getpage(file, pgoff, nonblock);
1633
1634         /* XXX: This is wrong, a filesystem I/O error may have happened. Fix that as
1635          * done in shmem_populate calling shmem_getpage */
1636         if (!page && !nonblock)
1637                 return -ENOMEM;
1638
1639         if (page) {
1640                 err = install_page(mm, vma, addr, page, prot);
1641                 if (err) {
1642                         page_cache_release(page);
1643                         return err;
1644                 }
1645         } else if (vma->vm_flags & VM_NONLINEAR) {
1646                 /* No page was found just because we can't read it in now (being
1647                  * here implies nonblock != 0), but the page may exist, so set
1648                  * the PTE to fault it in later. */
1649                 err = install_file_pte(mm, vma, addr, pgoff, prot);
1650                 if (err)
1651                         return err;
1652         }
1653
1654         len -= PAGE_SIZE;
1655         addr += PAGE_SIZE;
1656         pgoff++;
1657         if (len)
1658                 goto repeat;
1659
1660         return 0;
1661 }
1662 EXPORT_SYMBOL(filemap_populate);
1663
1664 struct vm_operations_struct generic_file_vm_ops = {
1665         .nopage         = filemap_nopage,
1666         .populate       = filemap_populate,
1667 };
1668
1669 /* This is used for a general mmap of a disk file */
1670
1671 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1672 {
1673         struct address_space *mapping = file->f_mapping;
1674
1675         if (!mapping->a_ops->readpage)
1676                 return -ENOEXEC;
1677         file_accessed(file);
1678         vma->vm_ops = &generic_file_vm_ops;
1679         return 0;
1680 }
1681
1682 /*
1683  * This is for filesystems which do not implement ->writepage.
1684  */
1685 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1686 {
1687         if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1688                 return -EINVAL;
1689         return generic_file_mmap(file, vma);
1690 }
1691 #else
1692 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1693 {
1694         return -ENOSYS;
1695 }
1696 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1697 {
1698         return -ENOSYS;
1699 }
1700 #endif /* CONFIG_MMU */
1701
1702 EXPORT_SYMBOL(generic_file_mmap);
1703 EXPORT_SYMBOL(generic_file_readonly_mmap);
1704
1705 static struct page *__read_cache_page(struct address_space *mapping,
1706                                 unsigned long index,
1707                                 int (*filler)(void *,struct page*),
1708                                 void *data)
1709 {
1710         struct page *page, *cached_page = NULL;
1711         int err;
1712 repeat:
1713         page = find_get_page(mapping, index);
1714         if (!page) {
1715                 if (!cached_page) {
1716                         cached_page = page_cache_alloc_cold(mapping);
1717                         if (!cached_page)
1718                                 return ERR_PTR(-ENOMEM);
1719                 }
1720                 err = add_to_page_cache_lru(cached_page, mapping,
1721                                         index, GFP_KERNEL);
1722                 if (err == -EEXIST)
1723                         goto repeat;
1724                 if (err < 0) {
1725                         /* Presumably ENOMEM for radix tree node */
1726                         page_cache_release(cached_page);
1727                         return ERR_PTR(err);
1728                 }
1729                 page = cached_page;
1730                 cached_page = NULL;
1731                 err = filler(data, page);
1732                 if (err < 0) {
1733                         page_cache_release(page);
1734                         page = ERR_PTR(err);
1735                 }
1736         }
1737         if (cached_page)
1738                 page_cache_release(cached_page);
1739         return page;
1740 }
1741
1742 /*
1743  * Same as read_cache_page, but don't wait for page to become unlocked
1744  * after submitting it to the filler.
1745  */
1746 struct page *read_cache_page_async(struct address_space *mapping,
1747                                 unsigned long index,
1748                                 int (*filler)(void *,struct page*),
1749                                 void *data)
1750 {
1751         struct page *page;
1752         int err;
1753
1754 retry:
1755         page = __read_cache_page(mapping, index, filler, data);
1756         if (IS_ERR(page))
1757                 goto out;
1758         mark_page_accessed(page);
1759         if (PageUptodate(page))
1760                 goto out;
1761
1762         lock_page(page);
1763         if (!page->mapping) {
1764                 unlock_page(page);
1765                 page_cache_release(page);
1766                 goto retry;
1767         }
1768         if (PageUptodate(page)) {
1769                 unlock_page(page);
1770                 goto out;
1771         }
1772         err = filler(data, page);
1773         if (err < 0) {
1774                 page_cache_release(page);
1775                 page = ERR_PTR(err);
1776         }
1777  out:
1778         mark_page_accessed(page);
1779         return page;
1780 }
1781 EXPORT_SYMBOL(read_cache_page_async);
1782
1783 /**
1784  * read_cache_page - read into page cache, fill it if needed
1785  * @mapping:    the page's address_space
1786  * @index:      the page index
1787  * @filler:     function to perform the read
1788  * @data:       destination for read data
1789  *
1790  * Read into the page cache. If a page already exists, and PageUptodate() is
1791  * not set, try to fill the page then wait for it to become unlocked.
1792  *
1793  * If the page does not get brought uptodate, return -EIO.
1794  */
1795 struct page *read_cache_page(struct address_space *mapping,
1796                                 unsigned long index,
1797                                 int (*filler)(void *,struct page*),
1798                                 void *data)
1799 {
1800         struct page *page;
1801
1802         page = read_cache_page_async(mapping, index, filler, data);
1803         if (IS_ERR(page))
1804                 goto out;
1805         wait_on_page_locked(page);
1806         if (!PageUptodate(page)) {
1807                 page_cache_release(page);
1808                 page = ERR_PTR(-EIO);
1809         }
1810  out:
1811         return page;
1812 }
1813 EXPORT_SYMBOL(read_cache_page);
1814
1815 /*
1816  * If the page was newly created, increment its refcount and add it to the
1817  * caller's lru-buffering pagevec.  This function is specifically for
1818  * generic_file_write().
1819  */
1820 static inline struct page *
1821 __grab_cache_page(struct address_space *mapping, unsigned long index,
1822                         struct page **cached_page, struct pagevec *lru_pvec)
1823 {
1824         int err;
1825         struct page *page;
1826 repeat:
1827         page = find_lock_page(mapping, index);
1828         if (!page) {
1829                 if (!*cached_page) {
1830                         *cached_page = page_cache_alloc(mapping);
1831                         if (!*cached_page)
1832                                 return NULL;
1833                 }
1834                 err = add_to_page_cache(*cached_page, mapping,
1835                                         index, GFP_KERNEL);
1836                 if (err == -EEXIST)
1837                         goto repeat;
1838                 if (err == 0) {
1839                         page = *cached_page;
1840                         page_cache_get(page);
1841                         if (!pagevec_add(lru_pvec, page))
1842                                 __pagevec_lru_add(lru_pvec);
1843                         *cached_page = NULL;
1844                 }
1845         }
1846         return page;
1847 }
1848
1849 /*
1850  * The logic we want is
1851  *
1852  *      if suid or (sgid and xgrp)
1853  *              remove privs
1854  */
1855 int should_remove_suid(struct dentry *dentry)
1856 {
1857         mode_t mode = dentry->d_inode->i_mode;
1858         int kill = 0;
1859
1860         /* suid always must be killed */
1861         if (unlikely(mode & S_ISUID))
1862                 kill = ATTR_KILL_SUID;
1863
1864         /*
1865          * sgid without any exec bits is just a mandatory locking mark; leave
1866          * it alone.  If some exec bits are set, it's a real sgid; kill it.
1867          */
1868         if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1869                 kill |= ATTR_KILL_SGID;
1870
1871         if (unlikely(kill && !capable(CAP_FSETID)))
1872                 return kill;
1873
1874         return 0;
1875 }
1876 EXPORT_SYMBOL(should_remove_suid);
1877
1878 int __remove_suid(struct dentry *dentry, int kill)
1879 {
1880         struct iattr newattrs;
1881
1882         newattrs.ia_valid = ATTR_FORCE | kill;
1883         return notify_change(dentry, &newattrs);
1884 }
1885
1886 int remove_suid(struct dentry *dentry)
1887 {
1888         int kill = should_remove_suid(dentry);
1889
1890         if (unlikely(kill))
1891                 return __remove_suid(dentry, kill);
1892
1893         return 0;
1894 }
1895 EXPORT_SYMBOL(remove_suid);
1896
1897 size_t
1898 __filemap_copy_from_user_iovec_inatomic(char *vaddr,
1899                         const struct iovec *iov, size_t base, size_t bytes)
1900 {
1901         size_t copied = 0, left = 0;
1902
1903         while (bytes) {
1904                 char __user *buf = iov->iov_base + base;
1905                 int copy = min(bytes, iov->iov_len - base);
1906
1907                 base = 0;
1908                 left = __copy_from_user_inatomic_nocache(vaddr, buf, copy);
1909                 copied += copy;
1910                 bytes -= copy;
1911                 vaddr += copy;
1912                 iov++;
1913
1914                 if (unlikely(left))
1915                         break;
1916         }
1917         return copied - left;
1918 }
1919
1920 /*
1921  * Performs necessary checks before doing a write
1922  *
1923  * Can adjust writing position or amount of bytes to write.
1924  * Returns appropriate error code that caller should return or
1925  * zero in case that write should be allowed.
1926  */
1927 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
1928 {
1929         struct inode *inode = file->f_mapping->host;
1930         unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
1931
1932         if (unlikely(*pos < 0))
1933                 return -EINVAL;
1934
1935         if (!isblk) {
1936                 /* FIXME: this is for backwards compatibility with 2.4 */
1937                 if (file->f_flags & O_APPEND)
1938                         *pos = i_size_read(inode);
1939
1940                 if (limit != RLIM_INFINITY) {
1941                         if (*pos >= limit) {
1942                                 send_sig(SIGXFSZ, current, 0);
1943                                 return -EFBIG;
1944                         }
1945                         if (*count > limit - (typeof(limit))*pos) {
1946                                 *count = limit - (typeof(limit))*pos;
1947                         }
1948                 }
1949         }
1950
1951         /*
1952          * LFS rule
1953          */
1954         if (unlikely(*pos + *count > MAX_NON_LFS &&
1955                                 !(file->f_flags & O_LARGEFILE))) {
1956                 if (*pos >= MAX_NON_LFS) {
1957                         send_sig(SIGXFSZ, current, 0);
1958                         return -EFBIG;
1959                 }
1960                 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
1961                         *count = MAX_NON_LFS - (unsigned long)*pos;
1962                 }
1963         }
1964
1965         /*
1966          * Are we about to exceed the fs block limit ?
1967          *
1968          * If we have written data it becomes a short write.  If we have
1969          * exceeded without writing data we send a signal and return EFBIG.
1970          * Linus frestrict idea will clean these up nicely..
1971          */
1972         if (likely(!isblk)) {
1973                 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
1974                         if (*count || *pos > inode->i_sb->s_maxbytes) {
1975                                 send_sig(SIGXFSZ, current, 0);
1976                                 return -EFBIG;
1977                         }
1978                         /* zero-length writes at ->s_maxbytes are OK */
1979                 }
1980
1981                 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
1982                         *count = inode->i_sb->s_maxbytes - *pos;
1983         } else {
1984 #ifdef CONFIG_BLOCK
1985                 loff_t isize;
1986                 if (bdev_read_only(I_BDEV(inode)))
1987                         return -EPERM;
1988                 isize = i_size_read(inode);
1989                 if (*pos >= isize) {
1990                         if (*count || *pos > isize)
1991                                 return -ENOSPC;
1992                 }
1993
1994                 if (*pos + *count > isize)
1995                         *count = isize - *pos;
1996 #else
1997                 return -EPERM;
1998 #endif
1999         }
2000         return 0;
2001 }
2002 EXPORT_SYMBOL(generic_write_checks);
2003
2004 ssize_t
2005 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2006                 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2007                 size_t count, size_t ocount)
2008 {
2009         struct file     *file = iocb->ki_filp;
2010         struct address_space *mapping = file->f_mapping;
2011         struct inode    *inode = mapping->host;
2012         ssize_t         written;
2013
2014         if (count != ocount)
2015                 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2016
2017         written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2018         if (written > 0) {
2019                 loff_t end = pos + written;
2020                 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2021                         i_size_write(inode,  end);
2022                         mark_inode_dirty(inode);
2023                 }
2024                 *ppos = end;
2025         }
2026
2027         /*
2028          * Sync the fs metadata but not the minor inode changes and
2029          * of course not the data as we did direct DMA for the IO.
2030          * i_mutex is held, which protects generic_osync_inode() from
2031          * livelocking.  AIO O_DIRECT ops attempt to sync metadata here.
2032          */
2033         if ((written >= 0 || written == -EIOCBQUEUED) &&
2034             ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2035                 int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
2036                 if (err < 0)
2037                         written = err;
2038         }
2039         return written;
2040 }
2041 EXPORT_SYMBOL(generic_file_direct_write);
2042
2043 ssize_t
2044 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2045                 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2046                 size_t count, ssize_t written)
2047 {
2048         struct file *file = iocb->ki_filp;
2049         struct address_space * mapping = file->f_mapping;
2050         const struct address_space_operations *a_ops = mapping->a_ops;
2051         struct inode    *inode = mapping->host;
2052         long            status = 0;
2053         struct page     *page;
2054         struct page     *cached_page = NULL;
2055         size_t          bytes;
2056         struct pagevec  lru_pvec;
2057         const struct iovec *cur_iov = iov; /* current iovec */
2058         size_t          iov_base = 0;      /* offset in the current iovec */
2059         char __user     *buf;
2060
2061         pagevec_init(&lru_pvec, 0);
2062
2063         /*
2064          * handle partial DIO write.  Adjust cur_iov if needed.
2065          */
2066         if (likely(nr_segs == 1))
2067                 buf = iov->iov_base + written;
2068         else {
2069                 filemap_set_next_iovec(&cur_iov, &iov_base, written);
2070                 buf = cur_iov->iov_base + iov_base;
2071         }
2072
2073         do {
2074                 unsigned long index;
2075                 unsigned long offset;
2076                 size_t copied;
2077
2078                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
2079                 index = pos >> PAGE_CACHE_SHIFT;
2080                 bytes = PAGE_CACHE_SIZE - offset;
2081
2082                 /* Limit the size of the copy to the caller's write size */
2083                 bytes = min(bytes, count);
2084
2085                 /* We only need to worry about prefaulting when writes are from
2086                  * user-space.  NFSd uses vfs_writev with several non-aligned
2087                  * segments in the vector, and limiting to one segment a time is
2088                  * a noticeable performance for re-write
2089                  */
2090                 if (!segment_eq(get_fs(), KERNEL_DS)) {
2091                         /*
2092                          * Limit the size of the copy to that of the current
2093                          * segment, because fault_in_pages_readable() doesn't
2094                          * know how to walk segments.
2095                          */
2096                         bytes = min(bytes, cur_iov->iov_len - iov_base);
2097
2098                         /*
2099                          * Bring in the user page that we will copy from
2100                          * _first_.  Otherwise there's a nasty deadlock on
2101                          * copying from the same page as we're writing to,
2102                          * without it being marked up-to-date.
2103                          */
2104                         fault_in_pages_readable(buf, bytes);
2105                 }
2106                 page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
2107                 if (!page) {
2108                         status = -ENOMEM;
2109                         break;
2110                 }
2111
2112                 if (unlikely(bytes == 0)) {
2113                         status = 0;
2114                         copied = 0;
2115                         goto zero_length_segment;
2116                 }
2117
2118                 status = a_ops->prepare_write(file, page, offset, offset+bytes);
2119                 if (unlikely(status)) {
2120                         loff_t isize = i_size_read(inode);
2121
2122                         if (status != AOP_TRUNCATED_PAGE)
2123                                 unlock_page(page);
2124                         page_cache_release(page);
2125                         if (status == AOP_TRUNCATED_PAGE)
2126                                 continue;
2127                         /*
2128                          * prepare_write() may have instantiated a few blocks
2129                          * outside i_size.  Trim these off again.
2130                          */
2131                         if (pos + bytes > isize)
2132                                 vmtruncate(inode, isize);
2133                         break;
2134                 }
2135                 if (likely(nr_segs == 1))
2136                         copied = filemap_copy_from_user(page, offset,
2137                                                         buf, bytes);
2138                 else
2139                         copied = filemap_copy_from_user_iovec(page, offset,
2140                                                 cur_iov, iov_base, bytes);
2141                 flush_dcache_page(page);
2142                 status = a_ops->commit_write(file, page, offset, offset+bytes);
2143                 if (status == AOP_TRUNCATED_PAGE) {
2144                         page_cache_release(page);
2145                         continue;
2146                 }
2147 zero_length_segment:
2148                 if (likely(copied >= 0)) {
2149                         if (!status)
2150                                 status = copied;
2151
2152                         if (status >= 0) {
2153                                 written += status;
2154                                 count -= status;
2155                                 pos += status;
2156                                 buf += status;
2157                                 if (unlikely(nr_segs > 1)) {
2158                                         filemap_set_next_iovec(&cur_iov,
2159                                                         &iov_base, status);
2160                                         if (count)
2161                                                 buf = cur_iov->iov_base +
2162                                                         iov_base;
2163                                 } else {
2164                                         iov_base += status;
2165                                 }
2166                         }
2167                 }
2168                 if (unlikely(copied != bytes))
2169                         if (status >= 0)
2170                                 status = -EFAULT;
2171                 unlock_page(page);
2172                 mark_page_accessed(page);
2173                 page_cache_release(page);
2174                 if (status < 0)
2175                         break;
2176                 balance_dirty_pages_ratelimited(mapping);
2177                 cond_resched();
2178         } while (count);
2179         *ppos = pos;
2180
2181         if (cached_page)
2182                 page_cache_release(cached_page);
2183
2184         /*
2185          * For now, when the user asks for O_SYNC, we'll actually give O_DSYNC
2186          */
2187         if (likely(status >= 0)) {
2188                 if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2189                         if (!a_ops->writepage || !is_sync_kiocb(iocb))
2190                                 status = generic_osync_inode(inode, mapping,
2191                                                 OSYNC_METADATA|OSYNC_DATA);
2192                 }
2193         }
2194         
2195         /*
2196          * If we get here for O_DIRECT writes then we must have fallen through
2197          * to buffered writes (block instantiation inside i_size).  So we sync
2198          * the file data here, to try to honour O_DIRECT expectations.
2199          */
2200         if (unlikely(file->f_flags & O_DIRECT) && written)
2201                 status = filemap_write_and_wait(mapping);
2202
2203         pagevec_lru_add(&lru_pvec);
2204         return written ? written : status;
2205 }
2206 EXPORT_SYMBOL(generic_file_buffered_write);
2207
2208 static ssize_t
2209 __generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
2210                                 unsigned long nr_segs, loff_t *ppos)
2211 {
2212         struct file *file = iocb->ki_filp;
2213         struct address_space * mapping = file->f_mapping;
2214         size_t ocount;          /* original count */
2215         size_t count;           /* after file limit checks */
2216         struct inode    *inode = mapping->host;
2217         unsigned long   seg;
2218         loff_t          pos;
2219         ssize_t         written;
2220         ssize_t         err;
2221
2222         ocount = 0;
2223         for (seg = 0; seg < nr_segs; seg++) {
2224                 const struct iovec *iv = &iov[seg];
2225
2226                 /*
2227                  * If any segment has a negative length, or the cumulative
2228                  * length ever wraps negative then return -EINVAL.
2229                  */
2230                 ocount += iv->iov_len;
2231                 if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
2232                         return -EINVAL;
2233                 if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
2234                         continue;
2235                 if (seg == 0)
2236                         return -EFAULT;
2237                 nr_segs = seg;
2238                 ocount -= iv->iov_len;  /* This segment is no good */
2239                 break;
2240         }
2241
2242         count = ocount;
2243         pos = *ppos;
2244
2245         vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2246
2247         /* We can write back this queue in page reclaim */
2248         current->backing_dev_info = mapping->backing_dev_info;
2249         written = 0;
2250
2251         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2252         if (err)
2253                 goto out;
2254
2255         if (count == 0)
2256                 goto out;
2257
2258         err = remove_suid(file->f_path.dentry);
2259         if (err)
2260                 goto out;
2261
2262         file_update_time(file);
2263
2264         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2265         if (unlikely(file->f_flags & O_DIRECT)) {
2266                 loff_t endbyte;
2267                 ssize_t written_buffered;
2268
2269                 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2270                                                         ppos, count, ocount);
2271                 if (written < 0 || written == count)
2272                         goto out;
2273                 /*
2274                  * direct-io write to a hole: fall through to buffered I/O
2275                  * for completing the rest of the request.
2276                  */
2277                 pos += written;
2278                 count -= written;
2279                 written_buffered = generic_file_buffered_write(iocb, iov,
2280                                                 nr_segs, pos, ppos, count,
2281                                                 written);
2282                 /*
2283                  * If generic_file_buffered_write() retuned a synchronous error
2284                  * then we want to return the number of bytes which were
2285                  * direct-written, or the error code if that was zero.  Note
2286                  * that this differs from normal direct-io semantics, which
2287                  * will return -EFOO even if some bytes were written.
2288                  */
2289                 if (written_buffered < 0) {
2290                         err = written_buffered;
2291                         goto out;
2292                 }
2293
2294                 /*
2295                  * We need to ensure that the page cache pages are written to
2296                  * disk and invalidated to preserve the expected O_DIRECT
2297                  * semantics.
2298                  */
2299                 endbyte = pos + written_buffered - written - 1;
2300                 err = do_sync_file_range(file, pos, endbyte,
2301                                          SYNC_FILE_RANGE_WAIT_BEFORE|
2302                                          SYNC_FILE_RANGE_WRITE|
2303                                          SYNC_FILE_RANGE_WAIT_AFTER);
2304                 if (err == 0) {
2305                         written = written_buffered;
2306                         invalidate_mapping_pages(mapping,
2307                                                  pos >> PAGE_CACHE_SHIFT,
2308                                                  endbyte >> PAGE_CACHE_SHIFT);
2309                 } else {
2310                         /*
2311                          * We don't know how much we wrote, so just return
2312                          * the number of bytes which were direct-written
2313                          */
2314                 }
2315         } else {
2316                 written = generic_file_buffered_write(iocb, iov, nr_segs,
2317                                 pos, ppos, count, written);
2318         }
2319 out:
2320         current->backing_dev_info = NULL;
2321         return written ? written : err;
2322 }
2323
2324 ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
2325                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
2326 {
2327         struct file *file = iocb->ki_filp;
2328         struct address_space *mapping = file->f_mapping;
2329         struct inode *inode = mapping->host;
2330         ssize_t ret;
2331
2332         BUG_ON(iocb->ki_pos != pos);
2333
2334         ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2335                         &iocb->ki_pos);
2336
2337         if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2338                 ssize_t err;
2339
2340                 err = sync_page_range_nolock(inode, mapping, pos, ret);
2341                 if (err < 0)
2342                         ret = err;
2343         }
2344         return ret;
2345 }
2346 EXPORT_SYMBOL(generic_file_aio_write_nolock);
2347
2348 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2349                 unsigned long nr_segs, loff_t pos)
2350 {
2351         struct file *file = iocb->ki_filp;
2352         struct address_space *mapping = file->f_mapping;
2353         struct inode *inode = mapping->host;
2354         ssize_t ret;
2355
2356         BUG_ON(iocb->ki_pos != pos);
2357
2358         mutex_lock(&inode->i_mutex);
2359         ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2360                         &iocb->ki_pos);
2361         mutex_unlock(&inode->i_mutex);
2362
2363         if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2364                 ssize_t err;
2365
2366                 err = sync_page_range(inode, mapping, pos, ret);
2367                 if (err < 0)
2368                         ret = err;
2369         }
2370         return ret;
2371 }
2372 EXPORT_SYMBOL(generic_file_aio_write);
2373
2374 /*
2375  * Called under i_mutex for writes to S_ISREG files.   Returns -EIO if something
2376  * went wrong during pagecache shootdown.
2377  */
2378 static ssize_t
2379 generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
2380         loff_t offset, unsigned long nr_segs)
2381 {
2382         struct file *file = iocb->ki_filp;
2383         struct address_space *mapping = file->f_mapping;
2384         ssize_t retval;
2385         size_t write_len;
2386         pgoff_t end = 0; /* silence gcc */
2387
2388         /*
2389          * If it's a write, unmap all mmappings of the file up-front.  This
2390          * will cause any pte dirty bits to be propagated into the pageframes
2391          * for the subsequent filemap_write_and_wait().
2392          */
2393         if (rw == WRITE) {
2394                 write_len = iov_length(iov, nr_segs);
2395                 end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT;
2396                 if (mapping_mapped(mapping))
2397                         unmap_mapping_range(mapping, offset, write_len, 0);
2398         }
2399
2400         retval = filemap_write_and_wait(mapping);
2401         if (retval)
2402                 goto out;
2403
2404         /*
2405          * After a write we want buffered reads to be sure to go to disk to get
2406          * the new data.  We invalidate clean cached page from the region we're
2407          * about to write.  We do this *before* the write so that we can return
2408          * -EIO without clobbering -EIOCBQUEUED from ->direct_IO().
2409          */
2410         if (rw == WRITE && mapping->nrpages) {
2411                 retval = invalidate_inode_pages2_range(mapping,
2412                                         offset >> PAGE_CACHE_SHIFT, end);
2413                 if (retval)
2414                         goto out;
2415         }
2416
2417         retval = mapping->a_ops->direct_IO(rw, iocb, iov, offset, nr_segs);
2418         if (retval)
2419                 goto out;
2420
2421         /*
2422          * Finally, try again to invalidate clean pages which might have been
2423          * faulted in by get_user_pages() if the source of the write was an
2424          * mmap()ed region of the file we're writing.  That's a pretty crazy
2425          * thing to do, so we don't support it 100%.  If this invalidation
2426          * fails and we have -EIOCBQUEUED we ignore the failure.
2427          */
2428         if (rw == WRITE && mapping->nrpages) {
2429                 int err = invalidate_inode_pages2_range(mapping,
2430                                               offset >> PAGE_CACHE_SHIFT, end);
2431                 if (err && retval >= 0)
2432                         retval = err;
2433         }
2434 out:
2435         return retval;
2436 }
2437
2438 /**
2439  * try_to_release_page() - release old fs-specific metadata on a page
2440  *
2441  * @page: the page which the kernel is trying to free
2442  * @gfp_mask: memory allocation flags (and I/O mode)
2443  *
2444  * The address_space is to try to release any data against the page
2445  * (presumably at page->private).  If the release was successful, return `1'.
2446  * Otherwise return zero.
2447  *
2448  * The @gfp_mask argument specifies whether I/O may be performed to release
2449  * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
2450  *
2451  * NOTE: @gfp_mask may go away, and this function may become non-blocking.
2452  */
2453 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2454 {
2455         struct address_space * const mapping = page->mapping;
2456
2457         BUG_ON(!PageLocked(page));
2458         if (PageWriteback(page))
2459                 return 0;
2460
2461         if (mapping && mapping->a_ops->releasepage)
2462                 return mapping->a_ops->releasepage(page, gfp_mask);
2463         return try_to_free_buffers(page);
2464 }
2465
2466 EXPORT_SYMBOL(try_to_release_page);