Remove broken ptrace() special-case code from file mapping
[linux-2.6.git] / mm / filemap.c
1 /*
2  *      linux/mm/filemap.c
3  *
4  * Copyright (C) 1994-1999  Linus Torvalds
5  */
6
7 /*
8  * This file handles the generic file mmap semantics used by
9  * most "normal" filesystems (but you don't /have/ to use this:
10  * the NFS filesystem used to do this differently, for example)
11  */
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/compiler.h>
15 #include <linux/fs.h>
16 #include <linux/uaccess.h>
17 #include <linux/aio.h>
18 #include <linux/capability.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/mm.h>
21 #include <linux/swap.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/file.h>
25 #include <linux/uio.h>
26 #include <linux/hash.h>
27 #include <linux/writeback.h>
28 #include <linux/backing-dev.h>
29 #include <linux/pagevec.h>
30 #include <linux/blkdev.h>
31 #include <linux/backing-dev.h>
32 #include <linux/security.h>
33 #include <linux/syscalls.h>
34 #include <linux/cpuset.h>
35 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
36 #include "internal.h"
37
38 /*
39  * FIXME: remove all knowledge of the buffer layer from the core VM
40  */
41 #include <linux/buffer_head.h> /* for generic_osync_inode */
42
43 #include <asm/mman.h>
44
45 static ssize_t
46 generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
47         loff_t offset, unsigned long nr_segs);
48
49 /*
50  * Shared mappings implemented 30.11.1994. It's not fully working yet,
51  * though.
52  *
53  * Shared mappings now work. 15.8.1995  Bruno.
54  *
55  * finished 'unifying' the page and buffer cache and SMP-threaded the
56  * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
57  *
58  * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
59  */
60
61 /*
62  * Lock ordering:
63  *
64  *  ->i_mmap_lock               (vmtruncate)
65  *    ->private_lock            (__free_pte->__set_page_dirty_buffers)
66  *      ->swap_lock             (exclusive_swap_page, others)
67  *        ->mapping->tree_lock
68  *          ->zone.lock
69  *
70  *  ->i_mutex
71  *    ->i_mmap_lock             (truncate->unmap_mapping_range)
72  *
73  *  ->mmap_sem
74  *    ->i_mmap_lock
75  *      ->page_table_lock or pte_lock   (various, mainly in memory.c)
76  *        ->mapping->tree_lock  (arch-dependent flush_dcache_mmap_lock)
77  *
78  *  ->mmap_sem
79  *    ->lock_page               (access_process_vm)
80  *
81  *  ->i_mutex                   (generic_file_buffered_write)
82  *    ->mmap_sem                (fault_in_pages_readable->do_page_fault)
83  *
84  *  ->i_mutex
85  *    ->i_alloc_sem             (various)
86  *
87  *  ->inode_lock
88  *    ->sb_lock                 (fs/fs-writeback.c)
89  *    ->mapping->tree_lock      (__sync_single_inode)
90  *
91  *  ->i_mmap_lock
92  *    ->anon_vma.lock           (vma_adjust)
93  *
94  *  ->anon_vma.lock
95  *    ->page_table_lock or pte_lock     (anon_vma_prepare and various)
96  *
97  *  ->page_table_lock or pte_lock
98  *    ->swap_lock               (try_to_unmap_one)
99  *    ->private_lock            (try_to_unmap_one)
100  *    ->tree_lock               (try_to_unmap_one)
101  *    ->zone.lru_lock           (follow_page->mark_page_accessed)
102  *    ->zone.lru_lock           (check_pte_range->isolate_lru_page)
103  *    ->private_lock            (page_remove_rmap->set_page_dirty)
104  *    ->tree_lock               (page_remove_rmap->set_page_dirty)
105  *    ->inode_lock              (page_remove_rmap->set_page_dirty)
106  *    ->inode_lock              (zap_pte_range->set_page_dirty)
107  *    ->private_lock            (zap_pte_range->__set_page_dirty_buffers)
108  *
109  *  ->task->proc_lock
110  *    ->dcache_lock             (proc_pid_lookup)
111  */
112
113 /*
114  * Remove a page from the page cache and free it. Caller has to make
115  * sure the page is locked and that nobody else uses it - or that usage
116  * is safe.  The caller must hold a write_lock on the mapping's tree_lock.
117  */
118 void __remove_from_page_cache(struct page *page)
119 {
120         struct address_space *mapping = page->mapping;
121
122         radix_tree_delete(&mapping->page_tree, page->index);
123         page->mapping = NULL;
124         mapping->nrpages--;
125         __dec_zone_page_state(page, NR_FILE_PAGES);
126         BUG_ON(page_mapped(page));
127 }
128
129 void remove_from_page_cache(struct page *page)
130 {
131         struct address_space *mapping = page->mapping;
132
133         BUG_ON(!PageLocked(page));
134
135         write_lock_irq(&mapping->tree_lock);
136         __remove_from_page_cache(page);
137         write_unlock_irq(&mapping->tree_lock);
138 }
139
140 static int sync_page(void *word)
141 {
142         struct address_space *mapping;
143         struct page *page;
144
145         page = container_of((unsigned long *)word, struct page, flags);
146
147         /*
148          * page_mapping() is being called without PG_locked held.
149          * Some knowledge of the state and use of the page is used to
150          * reduce the requirements down to a memory barrier.
151          * The danger here is of a stale page_mapping() return value
152          * indicating a struct address_space different from the one it's
153          * associated with when it is associated with one.
154          * After smp_mb(), it's either the correct page_mapping() for
155          * the page, or an old page_mapping() and the page's own
156          * page_mapping() has gone NULL.
157          * The ->sync_page() address_space operation must tolerate
158          * page_mapping() going NULL. By an amazing coincidence,
159          * this comes about because none of the users of the page
160          * in the ->sync_page() methods make essential use of the
161          * page_mapping(), merely passing the page down to the backing
162          * device's unplug functions when it's non-NULL, which in turn
163          * ignore it for all cases but swap, where only page_private(page) is
164          * of interest. When page_mapping() does go NULL, the entire
165          * call stack gracefully ignores the page and returns.
166          * -- wli
167          */
168         smp_mb();
169         mapping = page_mapping(page);
170         if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
171                 mapping->a_ops->sync_page(page);
172         io_schedule();
173         return 0;
174 }
175
176 /**
177  * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
178  * @mapping:    address space structure to write
179  * @start:      offset in bytes where the range starts
180  * @end:        offset in bytes where the range ends (inclusive)
181  * @sync_mode:  enable synchronous operation
182  *
183  * Start writeback against all of a mapping's dirty pages that lie
184  * within the byte offsets <start, end> inclusive.
185  *
186  * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
187  * opposed to a regular memory cleansing writeback.  The difference between
188  * these two operations is that if a dirty page/buffer is encountered, it must
189  * be waited upon, and not just skipped over.
190  */
191 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
192                                 loff_t end, int sync_mode)
193 {
194         int ret;
195         struct writeback_control wbc = {
196                 .sync_mode = sync_mode,
197                 .nr_to_write = mapping->nrpages * 2,
198                 .range_start = start,
199                 .range_end = end,
200         };
201
202         if (!mapping_cap_writeback_dirty(mapping))
203                 return 0;
204
205         ret = do_writepages(mapping, &wbc);
206         return ret;
207 }
208
209 static inline int __filemap_fdatawrite(struct address_space *mapping,
210         int sync_mode)
211 {
212         return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
213 }
214
215 int filemap_fdatawrite(struct address_space *mapping)
216 {
217         return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
218 }
219 EXPORT_SYMBOL(filemap_fdatawrite);
220
221 static int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
222                                 loff_t end)
223 {
224         return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
225 }
226
227 /**
228  * filemap_flush - mostly a non-blocking flush
229  * @mapping:    target address_space
230  *
231  * This is a mostly non-blocking flush.  Not suitable for data-integrity
232  * purposes - I/O may not be started against all dirty pages.
233  */
234 int filemap_flush(struct address_space *mapping)
235 {
236         return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
237 }
238 EXPORT_SYMBOL(filemap_flush);
239
240 /**
241  * wait_on_page_writeback_range - wait for writeback to complete
242  * @mapping:    target address_space
243  * @start:      beginning page index
244  * @end:        ending page index
245  *
246  * Wait for writeback to complete against pages indexed by start->end
247  * inclusive
248  */
249 int wait_on_page_writeback_range(struct address_space *mapping,
250                                 pgoff_t start, pgoff_t end)
251 {
252         struct pagevec pvec;
253         int nr_pages;
254         int ret = 0;
255         pgoff_t index;
256
257         if (end < start)
258                 return 0;
259
260         pagevec_init(&pvec, 0);
261         index = start;
262         while ((index <= end) &&
263                         (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
264                         PAGECACHE_TAG_WRITEBACK,
265                         min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
266                 unsigned i;
267
268                 for (i = 0; i < nr_pages; i++) {
269                         struct page *page = pvec.pages[i];
270
271                         /* until radix tree lookup accepts end_index */
272                         if (page->index > end)
273                                 continue;
274
275                         wait_on_page_writeback(page);
276                         if (PageError(page))
277                                 ret = -EIO;
278                 }
279                 pagevec_release(&pvec);
280                 cond_resched();
281         }
282
283         /* Check for outstanding write errors */
284         if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
285                 ret = -ENOSPC;
286         if (test_and_clear_bit(AS_EIO, &mapping->flags))
287                 ret = -EIO;
288
289         return ret;
290 }
291
292 /**
293  * sync_page_range - write and wait on all pages in the passed range
294  * @inode:      target inode
295  * @mapping:    target address_space
296  * @pos:        beginning offset in pages to write
297  * @count:      number of bytes to write
298  *
299  * Write and wait upon all the pages in the passed range.  This is a "data
300  * integrity" operation.  It waits upon in-flight writeout before starting and
301  * waiting upon new writeout.  If there was an IO error, return it.
302  *
303  * We need to re-take i_mutex during the generic_osync_inode list walk because
304  * it is otherwise livelockable.
305  */
306 int sync_page_range(struct inode *inode, struct address_space *mapping,
307                         loff_t pos, loff_t count)
308 {
309         pgoff_t start = pos >> PAGE_CACHE_SHIFT;
310         pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
311         int ret;
312
313         if (!mapping_cap_writeback_dirty(mapping) || !count)
314                 return 0;
315         ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
316         if (ret == 0) {
317                 mutex_lock(&inode->i_mutex);
318                 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
319                 mutex_unlock(&inode->i_mutex);
320         }
321         if (ret == 0)
322                 ret = wait_on_page_writeback_range(mapping, start, end);
323         return ret;
324 }
325 EXPORT_SYMBOL(sync_page_range);
326
327 /**
328  * sync_page_range_nolock
329  * @inode:      target inode
330  * @mapping:    target address_space
331  * @pos:        beginning offset in pages to write
332  * @count:      number of bytes to write
333  *
334  * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea
335  * as it forces O_SYNC writers to different parts of the same file
336  * to be serialised right until io completion.
337  */
338 int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
339                            loff_t pos, loff_t count)
340 {
341         pgoff_t start = pos >> PAGE_CACHE_SHIFT;
342         pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
343         int ret;
344
345         if (!mapping_cap_writeback_dirty(mapping) || !count)
346                 return 0;
347         ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
348         if (ret == 0)
349                 ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
350         if (ret == 0)
351                 ret = wait_on_page_writeback_range(mapping, start, end);
352         return ret;
353 }
354 EXPORT_SYMBOL(sync_page_range_nolock);
355
356 /**
357  * filemap_fdatawait - wait for all under-writeback pages to complete
358  * @mapping: address space structure to wait for
359  *
360  * Walk the list of under-writeback pages of the given address space
361  * and wait for all of them.
362  */
363 int filemap_fdatawait(struct address_space *mapping)
364 {
365         loff_t i_size = i_size_read(mapping->host);
366
367         if (i_size == 0)
368                 return 0;
369
370         return wait_on_page_writeback_range(mapping, 0,
371                                 (i_size - 1) >> PAGE_CACHE_SHIFT);
372 }
373 EXPORT_SYMBOL(filemap_fdatawait);
374
375 int filemap_write_and_wait(struct address_space *mapping)
376 {
377         int err = 0;
378
379         if (mapping->nrpages) {
380                 err = filemap_fdatawrite(mapping);
381                 /*
382                  * Even if the above returned error, the pages may be
383                  * written partially (e.g. -ENOSPC), so we wait for it.
384                  * But the -EIO is special case, it may indicate the worst
385                  * thing (e.g. bug) happened, so we avoid waiting for it.
386                  */
387                 if (err != -EIO) {
388                         int err2 = filemap_fdatawait(mapping);
389                         if (!err)
390                                 err = err2;
391                 }
392         }
393         return err;
394 }
395 EXPORT_SYMBOL(filemap_write_and_wait);
396
397 /**
398  * filemap_write_and_wait_range - write out & wait on a file range
399  * @mapping:    the address_space for the pages
400  * @lstart:     offset in bytes where the range starts
401  * @lend:       offset in bytes where the range ends (inclusive)
402  *
403  * Write out and wait upon file offsets lstart->lend, inclusive.
404  *
405  * Note that `lend' is inclusive (describes the last byte to be written) so
406  * that this function can be used to write to the very end-of-file (end = -1).
407  */
408 int filemap_write_and_wait_range(struct address_space *mapping,
409                                  loff_t lstart, loff_t lend)
410 {
411         int err = 0;
412
413         if (mapping->nrpages) {
414                 err = __filemap_fdatawrite_range(mapping, lstart, lend,
415                                                  WB_SYNC_ALL);
416                 /* See comment of filemap_write_and_wait() */
417                 if (err != -EIO) {
418                         int err2 = wait_on_page_writeback_range(mapping,
419                                                 lstart >> PAGE_CACHE_SHIFT,
420                                                 lend >> PAGE_CACHE_SHIFT);
421                         if (!err)
422                                 err = err2;
423                 }
424         }
425         return err;
426 }
427
428 /**
429  * add_to_page_cache - add newly allocated pagecache pages
430  * @page:       page to add
431  * @mapping:    the page's address_space
432  * @offset:     page index
433  * @gfp_mask:   page allocation mode
434  *
435  * This function is used to add newly allocated pagecache pages;
436  * the page is new, so we can just run SetPageLocked() against it.
437  * The other page state flags were set by rmqueue().
438  *
439  * This function does not add the page to the LRU.  The caller must do that.
440  */
441 int add_to_page_cache(struct page *page, struct address_space *mapping,
442                 pgoff_t offset, gfp_t gfp_mask)
443 {
444         int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
445
446         if (error == 0) {
447                 write_lock_irq(&mapping->tree_lock);
448                 error = radix_tree_insert(&mapping->page_tree, offset, page);
449                 if (!error) {
450                         page_cache_get(page);
451                         SetPageLocked(page);
452                         page->mapping = mapping;
453                         page->index = offset;
454                         mapping->nrpages++;
455                         __inc_zone_page_state(page, NR_FILE_PAGES);
456                 }
457                 write_unlock_irq(&mapping->tree_lock);
458                 radix_tree_preload_end();
459         }
460         return error;
461 }
462 EXPORT_SYMBOL(add_to_page_cache);
463
464 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
465                                 pgoff_t offset, gfp_t gfp_mask)
466 {
467         int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
468         if (ret == 0)
469                 lru_cache_add(page);
470         return ret;
471 }
472
473 #ifdef CONFIG_NUMA
474 struct page *__page_cache_alloc(gfp_t gfp)
475 {
476         if (cpuset_do_page_mem_spread()) {
477                 int n = cpuset_mem_spread_node();
478                 return alloc_pages_node(n, gfp, 0);
479         }
480         return alloc_pages(gfp, 0);
481 }
482 EXPORT_SYMBOL(__page_cache_alloc);
483 #endif
484
485 static int __sleep_on_page_lock(void *word)
486 {
487         io_schedule();
488         return 0;
489 }
490
491 /*
492  * In order to wait for pages to become available there must be
493  * waitqueues associated with pages. By using a hash table of
494  * waitqueues where the bucket discipline is to maintain all
495  * waiters on the same queue and wake all when any of the pages
496  * become available, and for the woken contexts to check to be
497  * sure the appropriate page became available, this saves space
498  * at a cost of "thundering herd" phenomena during rare hash
499  * collisions.
500  */
501 static wait_queue_head_t *page_waitqueue(struct page *page)
502 {
503         const struct zone *zone = page_zone(page);
504
505         return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
506 }
507
508 static inline void wake_up_page(struct page *page, int bit)
509 {
510         __wake_up_bit(page_waitqueue(page), &page->flags, bit);
511 }
512
513 void fastcall wait_on_page_bit(struct page *page, int bit_nr)
514 {
515         DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
516
517         if (test_bit(bit_nr, &page->flags))
518                 __wait_on_bit(page_waitqueue(page), &wait, sync_page,
519                                                         TASK_UNINTERRUPTIBLE);
520 }
521 EXPORT_SYMBOL(wait_on_page_bit);
522
523 /**
524  * unlock_page - unlock a locked page
525  * @page: the page
526  *
527  * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
528  * Also wakes sleepers in wait_on_page_writeback() because the wakeup
529  * mechananism between PageLocked pages and PageWriteback pages is shared.
530  * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
531  *
532  * The first mb is necessary to safely close the critical section opened by the
533  * TestSetPageLocked(), the second mb is necessary to enforce ordering between
534  * the clear_bit and the read of the waitqueue (to avoid SMP races with a
535  * parallel wait_on_page_locked()).
536  */
537 void fastcall unlock_page(struct page *page)
538 {
539         smp_mb__before_clear_bit();
540         if (!TestClearPageLocked(page))
541                 BUG();
542         smp_mb__after_clear_bit(); 
543         wake_up_page(page, PG_locked);
544 }
545 EXPORT_SYMBOL(unlock_page);
546
547 /**
548  * end_page_writeback - end writeback against a page
549  * @page: the page
550  */
551 void end_page_writeback(struct page *page)
552 {
553         if (!TestClearPageReclaim(page) || rotate_reclaimable_page(page)) {
554                 if (!test_clear_page_writeback(page))
555                         BUG();
556         }
557         smp_mb__after_clear_bit();
558         wake_up_page(page, PG_writeback);
559 }
560 EXPORT_SYMBOL(end_page_writeback);
561
562 /**
563  * __lock_page - get a lock on the page, assuming we need to sleep to get it
564  * @page: the page to lock
565  *
566  * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
567  * random driver's requestfn sets TASK_RUNNING, we could busywait.  However
568  * chances are that on the second loop, the block layer's plug list is empty,
569  * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
570  */
571 void fastcall __lock_page(struct page *page)
572 {
573         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
574
575         __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
576                                                         TASK_UNINTERRUPTIBLE);
577 }
578 EXPORT_SYMBOL(__lock_page);
579
580 /*
581  * Variant of lock_page that does not require the caller to hold a reference
582  * on the page's mapping.
583  */
584 void fastcall __lock_page_nosync(struct page *page)
585 {
586         DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
587         __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock,
588                                                         TASK_UNINTERRUPTIBLE);
589 }
590
591 /**
592  * find_get_page - find and get a page reference
593  * @mapping: the address_space to search
594  * @offset: the page index
595  *
596  * Is there a pagecache struct page at the given (mapping, offset) tuple?
597  * If yes, increment its refcount and return it; if no, return NULL.
598  */
599 struct page * find_get_page(struct address_space *mapping, pgoff_t offset)
600 {
601         struct page *page;
602
603         read_lock_irq(&mapping->tree_lock);
604         page = radix_tree_lookup(&mapping->page_tree, offset);
605         if (page)
606                 page_cache_get(page);
607         read_unlock_irq(&mapping->tree_lock);
608         return page;
609 }
610 EXPORT_SYMBOL(find_get_page);
611
612 /**
613  * find_lock_page - locate, pin and lock a pagecache page
614  * @mapping: the address_space to search
615  * @offset: the page index
616  *
617  * Locates the desired pagecache page, locks it, increments its reference
618  * count and returns its address.
619  *
620  * Returns zero if the page was not present. find_lock_page() may sleep.
621  */
622 struct page *find_lock_page(struct address_space *mapping,
623                                 pgoff_t offset)
624 {
625         struct page *page;
626
627 repeat:
628         read_lock_irq(&mapping->tree_lock);
629         page = radix_tree_lookup(&mapping->page_tree, offset);
630         if (page) {
631                 page_cache_get(page);
632                 if (TestSetPageLocked(page)) {
633                         read_unlock_irq(&mapping->tree_lock);
634                         __lock_page(page);
635
636                         /* Has the page been truncated while we slept? */
637                         if (unlikely(page->mapping != mapping)) {
638                                 unlock_page(page);
639                                 page_cache_release(page);
640                                 goto repeat;
641                         }
642                         VM_BUG_ON(page->index != offset);
643                         goto out;
644                 }
645         }
646         read_unlock_irq(&mapping->tree_lock);
647 out:
648         return page;
649 }
650 EXPORT_SYMBOL(find_lock_page);
651
652 /**
653  * find_or_create_page - locate or add a pagecache page
654  * @mapping: the page's address_space
655  * @index: the page's index into the mapping
656  * @gfp_mask: page allocation mode
657  *
658  * Locates a page in the pagecache.  If the page is not present, a new page
659  * is allocated using @gfp_mask and is added to the pagecache and to the VM's
660  * LRU list.  The returned page is locked and has its reference count
661  * incremented.
662  *
663  * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
664  * allocation!
665  *
666  * find_or_create_page() returns the desired page's address, or zero on
667  * memory exhaustion.
668  */
669 struct page *find_or_create_page(struct address_space *mapping,
670                 pgoff_t index, gfp_t gfp_mask)
671 {
672         struct page *page;
673         int err;
674 repeat:
675         page = find_lock_page(mapping, index);
676         if (!page) {
677                 page = __page_cache_alloc(gfp_mask);
678                 if (!page)
679                         return NULL;
680                 err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
681                 if (unlikely(err)) {
682                         page_cache_release(page);
683                         page = NULL;
684                         if (err == -EEXIST)
685                                 goto repeat;
686                 }
687         }
688         return page;
689 }
690 EXPORT_SYMBOL(find_or_create_page);
691
692 /**
693  * find_get_pages - gang pagecache lookup
694  * @mapping:    The address_space to search
695  * @start:      The starting page index
696  * @nr_pages:   The maximum number of pages
697  * @pages:      Where the resulting pages are placed
698  *
699  * find_get_pages() will search for and return a group of up to
700  * @nr_pages pages in the mapping.  The pages are placed at @pages.
701  * find_get_pages() takes a reference against the returned pages.
702  *
703  * The search returns a group of mapping-contiguous pages with ascending
704  * indexes.  There may be holes in the indices due to not-present pages.
705  *
706  * find_get_pages() returns the number of pages which were found.
707  */
708 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
709                             unsigned int nr_pages, struct page **pages)
710 {
711         unsigned int i;
712         unsigned int ret;
713
714         read_lock_irq(&mapping->tree_lock);
715         ret = radix_tree_gang_lookup(&mapping->page_tree,
716                                 (void **)pages, start, nr_pages);
717         for (i = 0; i < ret; i++)
718                 page_cache_get(pages[i]);
719         read_unlock_irq(&mapping->tree_lock);
720         return ret;
721 }
722
723 /**
724  * find_get_pages_contig - gang contiguous pagecache lookup
725  * @mapping:    The address_space to search
726  * @index:      The starting page index
727  * @nr_pages:   The maximum number of pages
728  * @pages:      Where the resulting pages are placed
729  *
730  * find_get_pages_contig() works exactly like find_get_pages(), except
731  * that the returned number of pages are guaranteed to be contiguous.
732  *
733  * find_get_pages_contig() returns the number of pages which were found.
734  */
735 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
736                                unsigned int nr_pages, struct page **pages)
737 {
738         unsigned int i;
739         unsigned int ret;
740
741         read_lock_irq(&mapping->tree_lock);
742         ret = radix_tree_gang_lookup(&mapping->page_tree,
743                                 (void **)pages, index, nr_pages);
744         for (i = 0; i < ret; i++) {
745                 if (pages[i]->mapping == NULL || pages[i]->index != index)
746                         break;
747
748                 page_cache_get(pages[i]);
749                 index++;
750         }
751         read_unlock_irq(&mapping->tree_lock);
752         return i;
753 }
754 EXPORT_SYMBOL(find_get_pages_contig);
755
756 /**
757  * find_get_pages_tag - find and return pages that match @tag
758  * @mapping:    the address_space to search
759  * @index:      the starting page index
760  * @tag:        the tag index
761  * @nr_pages:   the maximum number of pages
762  * @pages:      where the resulting pages are placed
763  *
764  * Like find_get_pages, except we only return pages which are tagged with
765  * @tag.   We update @index to index the next page for the traversal.
766  */
767 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
768                         int tag, unsigned int nr_pages, struct page **pages)
769 {
770         unsigned int i;
771         unsigned int ret;
772
773         read_lock_irq(&mapping->tree_lock);
774         ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
775                                 (void **)pages, *index, nr_pages, tag);
776         for (i = 0; i < ret; i++)
777                 page_cache_get(pages[i]);
778         if (ret)
779                 *index = pages[ret - 1]->index + 1;
780         read_unlock_irq(&mapping->tree_lock);
781         return ret;
782 }
783 EXPORT_SYMBOL(find_get_pages_tag);
784
785 /**
786  * grab_cache_page_nowait - returns locked page at given index in given cache
787  * @mapping: target address_space
788  * @index: the page index
789  *
790  * Same as grab_cache_page(), but do not wait if the page is unavailable.
791  * This is intended for speculative data generators, where the data can
792  * be regenerated if the page couldn't be grabbed.  This routine should
793  * be safe to call while holding the lock for another page.
794  *
795  * Clear __GFP_FS when allocating the page to avoid recursion into the fs
796  * and deadlock against the caller's locked page.
797  */
798 struct page *
799 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
800 {
801         struct page *page = find_get_page(mapping, index);
802
803         if (page) {
804                 if (!TestSetPageLocked(page))
805                         return page;
806                 page_cache_release(page);
807                 return NULL;
808         }
809         page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
810         if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) {
811                 page_cache_release(page);
812                 page = NULL;
813         }
814         return page;
815 }
816 EXPORT_SYMBOL(grab_cache_page_nowait);
817
818 /*
819  * CD/DVDs are error prone. When a medium error occurs, the driver may fail
820  * a _large_ part of the i/o request. Imagine the worst scenario:
821  *
822  *      ---R__________________________________________B__________
823  *         ^ reading here                             ^ bad block(assume 4k)
824  *
825  * read(R) => miss => readahead(R...B) => media error => frustrating retries
826  * => failing the whole request => read(R) => read(R+1) =>
827  * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
828  * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
829  * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
830  *
831  * It is going insane. Fix it by quickly scaling down the readahead size.
832  */
833 static void shrink_readahead_size_eio(struct file *filp,
834                                         struct file_ra_state *ra)
835 {
836         if (!ra->ra_pages)
837                 return;
838
839         ra->ra_pages /= 4;
840 }
841
842 /**
843  * do_generic_mapping_read - generic file read routine
844  * @mapping:    address_space to be read
845  * @ra:         file's readahead state
846  * @filp:       the file to read
847  * @ppos:       current file position
848  * @desc:       read_descriptor
849  * @actor:      read method
850  *
851  * This is a generic file read routine, and uses the
852  * mapping->a_ops->readpage() function for the actual low-level stuff.
853  *
854  * This is really ugly. But the goto's actually try to clarify some
855  * of the logic when it comes to error handling etc.
856  *
857  * Note the struct file* is only passed for the use of readpage.
858  * It may be NULL.
859  */
860 void do_generic_mapping_read(struct address_space *mapping,
861                              struct file_ra_state *ra,
862                              struct file *filp,
863                              loff_t *ppos,
864                              read_descriptor_t *desc,
865                              read_actor_t actor)
866 {
867         struct inode *inode = mapping->host;
868         pgoff_t index;
869         pgoff_t last_index;
870         pgoff_t prev_index;
871         unsigned long offset;      /* offset into pagecache page */
872         unsigned int prev_offset;
873         int error;
874
875         index = *ppos >> PAGE_CACHE_SHIFT;
876         prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
877         prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
878         last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
879         offset = *ppos & ~PAGE_CACHE_MASK;
880
881         for (;;) {
882                 struct page *page;
883                 pgoff_t end_index;
884                 loff_t isize;
885                 unsigned long nr, ret;
886
887                 cond_resched();
888 find_page:
889                 page = find_get_page(mapping, index);
890                 if (!page) {
891                         page_cache_sync_readahead(mapping,
892                                         ra, filp,
893                                         index, last_index - index);
894                         page = find_get_page(mapping, index);
895                         if (unlikely(page == NULL))
896                                 goto no_cached_page;
897                 }
898                 if (PageReadahead(page)) {
899                         page_cache_async_readahead(mapping,
900                                         ra, filp, page,
901                                         index, last_index - index);
902                 }
903                 if (!PageUptodate(page))
904                         goto page_not_up_to_date;
905 page_ok:
906                 /*
907                  * i_size must be checked after we know the page is Uptodate.
908                  *
909                  * Checking i_size after the check allows us to calculate
910                  * the correct value for "nr", which means the zero-filled
911                  * part of the page is not copied back to userspace (unless
912                  * another truncate extends the file - this is desired though).
913                  */
914
915                 isize = i_size_read(inode);
916                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
917                 if (unlikely(!isize || index > end_index)) {
918                         page_cache_release(page);
919                         goto out;
920                 }
921
922                 /* nr is the maximum number of bytes to copy from this page */
923                 nr = PAGE_CACHE_SIZE;
924                 if (index == end_index) {
925                         nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
926                         if (nr <= offset) {
927                                 page_cache_release(page);
928                                 goto out;
929                         }
930                 }
931                 nr = nr - offset;
932
933                 /* If users can be writing to this page using arbitrary
934                  * virtual addresses, take care about potential aliasing
935                  * before reading the page on the kernel side.
936                  */
937                 if (mapping_writably_mapped(mapping))
938                         flush_dcache_page(page);
939
940                 /*
941                  * When a sequential read accesses a page several times,
942                  * only mark it as accessed the first time.
943                  */
944                 if (prev_index != index || offset != prev_offset)
945                         mark_page_accessed(page);
946                 prev_index = index;
947
948                 /*
949                  * Ok, we have the page, and it's up-to-date, so
950                  * now we can copy it to user space...
951                  *
952                  * The actor routine returns how many bytes were actually used..
953                  * NOTE! This may not be the same as how much of a user buffer
954                  * we filled up (we may be padding etc), so we can only update
955                  * "pos" here (the actor routine has to update the user buffer
956                  * pointers and the remaining count).
957                  */
958                 ret = actor(desc, page, offset, nr);
959                 offset += ret;
960                 index += offset >> PAGE_CACHE_SHIFT;
961                 offset &= ~PAGE_CACHE_MASK;
962                 prev_offset = offset;
963
964                 page_cache_release(page);
965                 if (ret == nr && desc->count)
966                         continue;
967                 goto out;
968
969 page_not_up_to_date:
970                 /* Get exclusive access to the page ... */
971                 lock_page(page);
972
973                 /* Did it get truncated before we got the lock? */
974                 if (!page->mapping) {
975                         unlock_page(page);
976                         page_cache_release(page);
977                         continue;
978                 }
979
980                 /* Did somebody else fill it already? */
981                 if (PageUptodate(page)) {
982                         unlock_page(page);
983                         goto page_ok;
984                 }
985
986 readpage:
987                 /* Start the actual read. The read will unlock the page. */
988                 error = mapping->a_ops->readpage(filp, page);
989
990                 if (unlikely(error)) {
991                         if (error == AOP_TRUNCATED_PAGE) {
992                                 page_cache_release(page);
993                                 goto find_page;
994                         }
995                         goto readpage_error;
996                 }
997
998                 if (!PageUptodate(page)) {
999                         lock_page(page);
1000                         if (!PageUptodate(page)) {
1001                                 if (page->mapping == NULL) {
1002                                         /*
1003                                          * invalidate_inode_pages got it
1004                                          */
1005                                         unlock_page(page);
1006                                         page_cache_release(page);
1007                                         goto find_page;
1008                                 }
1009                                 unlock_page(page);
1010                                 error = -EIO;
1011                                 shrink_readahead_size_eio(filp, ra);
1012                                 goto readpage_error;
1013                         }
1014                         unlock_page(page);
1015                 }
1016
1017                 goto page_ok;
1018
1019 readpage_error:
1020                 /* UHHUH! A synchronous read error occurred. Report it */
1021                 desc->error = error;
1022                 page_cache_release(page);
1023                 goto out;
1024
1025 no_cached_page:
1026                 /*
1027                  * Ok, it wasn't cached, so we need to create a new
1028                  * page..
1029                  */
1030                 page = page_cache_alloc_cold(mapping);
1031                 if (!page) {
1032                         desc->error = -ENOMEM;
1033                         goto out;
1034                 }
1035                 error = add_to_page_cache_lru(page, mapping,
1036                                                 index, GFP_KERNEL);
1037                 if (error) {
1038                         page_cache_release(page);
1039                         if (error == -EEXIST)
1040                                 goto find_page;
1041                         desc->error = error;
1042                         goto out;
1043                 }
1044                 goto readpage;
1045         }
1046
1047 out:
1048         ra->prev_pos = prev_index;
1049         ra->prev_pos <<= PAGE_CACHE_SHIFT;
1050         ra->prev_pos |= prev_offset;
1051
1052         *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1053         if (filp)
1054                 file_accessed(filp);
1055 }
1056 EXPORT_SYMBOL(do_generic_mapping_read);
1057
1058 int file_read_actor(read_descriptor_t *desc, struct page *page,
1059                         unsigned long offset, unsigned long size)
1060 {
1061         char *kaddr;
1062         unsigned long left, count = desc->count;
1063
1064         if (size > count)
1065                 size = count;
1066
1067         /*
1068          * Faults on the destination of a read are common, so do it before
1069          * taking the kmap.
1070          */
1071         if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1072                 kaddr = kmap_atomic(page, KM_USER0);
1073                 left = __copy_to_user_inatomic(desc->arg.buf,
1074                                                 kaddr + offset, size);
1075                 kunmap_atomic(kaddr, KM_USER0);
1076                 if (left == 0)
1077                         goto success;
1078         }
1079
1080         /* Do it the slow way */
1081         kaddr = kmap(page);
1082         left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1083         kunmap(page);
1084
1085         if (left) {
1086                 size -= left;
1087                 desc->error = -EFAULT;
1088         }
1089 success:
1090         desc->count = count - size;
1091         desc->written += size;
1092         desc->arg.buf += size;
1093         return size;
1094 }
1095
1096 /*
1097  * Performs necessary checks before doing a write
1098  * @iov:        io vector request
1099  * @nr_segs:    number of segments in the iovec
1100  * @count:      number of bytes to write
1101  * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1102  *
1103  * Adjust number of segments and amount of bytes to write (nr_segs should be
1104  * properly initialized first). Returns appropriate error code that caller
1105  * should return or zero in case that write should be allowed.
1106  */
1107 int generic_segment_checks(const struct iovec *iov,
1108                         unsigned long *nr_segs, size_t *count, int access_flags)
1109 {
1110         unsigned long   seg;
1111         size_t cnt = 0;
1112         for (seg = 0; seg < *nr_segs; seg++) {
1113                 const struct iovec *iv = &iov[seg];
1114
1115                 /*
1116                  * If any segment has a negative length, or the cumulative
1117                  * length ever wraps negative then return -EINVAL.
1118                  */
1119                 cnt += iv->iov_len;
1120                 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1121                         return -EINVAL;
1122                 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1123                         continue;
1124                 if (seg == 0)
1125                         return -EFAULT;
1126                 *nr_segs = seg;
1127                 cnt -= iv->iov_len;     /* This segment is no good */
1128                 break;
1129         }
1130         *count = cnt;
1131         return 0;
1132 }
1133 EXPORT_SYMBOL(generic_segment_checks);
1134
1135 /**
1136  * generic_file_aio_read - generic filesystem read routine
1137  * @iocb:       kernel I/O control block
1138  * @iov:        io vector request
1139  * @nr_segs:    number of segments in the iovec
1140  * @pos:        current file position
1141  *
1142  * This is the "read()" routine for all filesystems
1143  * that can use the page cache directly.
1144  */
1145 ssize_t
1146 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1147                 unsigned long nr_segs, loff_t pos)
1148 {
1149         struct file *filp = iocb->ki_filp;
1150         ssize_t retval;
1151         unsigned long seg;
1152         size_t count;
1153         loff_t *ppos = &iocb->ki_pos;
1154
1155         count = 0;
1156         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1157         if (retval)
1158                 return retval;
1159
1160         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1161         if (filp->f_flags & O_DIRECT) {
1162                 loff_t size;
1163                 struct address_space *mapping;
1164                 struct inode *inode;
1165
1166                 mapping = filp->f_mapping;
1167                 inode = mapping->host;
1168                 retval = 0;
1169                 if (!count)
1170                         goto out; /* skip atime */
1171                 size = i_size_read(inode);
1172                 if (pos < size) {
1173                         retval = generic_file_direct_IO(READ, iocb,
1174                                                 iov, pos, nr_segs);
1175                         if (retval > 0)
1176                                 *ppos = pos + retval;
1177                 }
1178                 if (likely(retval != 0)) {
1179                         file_accessed(filp);
1180                         goto out;
1181                 }
1182         }
1183
1184         retval = 0;
1185         if (count) {
1186                 for (seg = 0; seg < nr_segs; seg++) {
1187                         read_descriptor_t desc;
1188
1189                         desc.written = 0;
1190                         desc.arg.buf = iov[seg].iov_base;
1191                         desc.count = iov[seg].iov_len;
1192                         if (desc.count == 0)
1193                                 continue;
1194                         desc.error = 0;
1195                         do_generic_file_read(filp,ppos,&desc,file_read_actor);
1196                         retval += desc.written;
1197                         if (desc.error) {
1198                                 retval = retval ?: desc.error;
1199                                 break;
1200                         }
1201                         if (desc.count > 0)
1202                                 break;
1203                 }
1204         }
1205 out:
1206         return retval;
1207 }
1208 EXPORT_SYMBOL(generic_file_aio_read);
1209
1210 static ssize_t
1211 do_readahead(struct address_space *mapping, struct file *filp,
1212              pgoff_t index, unsigned long nr)
1213 {
1214         if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1215                 return -EINVAL;
1216
1217         force_page_cache_readahead(mapping, filp, index,
1218                                         max_sane_readahead(nr));
1219         return 0;
1220 }
1221
1222 asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
1223 {
1224         ssize_t ret;
1225         struct file *file;
1226
1227         ret = -EBADF;
1228         file = fget(fd);
1229         if (file) {
1230                 if (file->f_mode & FMODE_READ) {
1231                         struct address_space *mapping = file->f_mapping;
1232                         pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1233                         pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1234                         unsigned long len = end - start + 1;
1235                         ret = do_readahead(mapping, file, start, len);
1236                 }
1237                 fput(file);
1238         }
1239         return ret;
1240 }
1241
1242 #ifdef CONFIG_MMU
1243 /**
1244  * page_cache_read - adds requested page to the page cache if not already there
1245  * @file:       file to read
1246  * @offset:     page index
1247  *
1248  * This adds the requested page to the page cache if it isn't already there,
1249  * and schedules an I/O to read in its contents from disk.
1250  */
1251 static int fastcall page_cache_read(struct file * file, pgoff_t offset)
1252 {
1253         struct address_space *mapping = file->f_mapping;
1254         struct page *page; 
1255         int ret;
1256
1257         do {
1258                 page = page_cache_alloc_cold(mapping);
1259                 if (!page)
1260                         return -ENOMEM;
1261
1262                 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1263                 if (ret == 0)
1264                         ret = mapping->a_ops->readpage(file, page);
1265                 else if (ret == -EEXIST)
1266                         ret = 0; /* losing race to add is OK */
1267
1268                 page_cache_release(page);
1269
1270         } while (ret == AOP_TRUNCATED_PAGE);
1271                 
1272         return ret;
1273 }
1274
1275 #define MMAP_LOTSAMISS  (100)
1276
1277 /**
1278  * filemap_fault - read in file data for page fault handling
1279  * @vma:        vma in which the fault was taken
1280  * @vmf:        struct vm_fault containing details of the fault
1281  *
1282  * filemap_fault() is invoked via the vma operations vector for a
1283  * mapped memory region to read in file data during a page fault.
1284  *
1285  * The goto's are kind of ugly, but this streamlines the normal case of having
1286  * it in the page cache, and handles the special cases reasonably without
1287  * having a lot of duplicated code.
1288  */
1289 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1290 {
1291         int error;
1292         struct file *file = vma->vm_file;
1293         struct address_space *mapping = file->f_mapping;
1294         struct file_ra_state *ra = &file->f_ra;
1295         struct inode *inode = mapping->host;
1296         struct page *page;
1297         unsigned long size;
1298         int did_readaround = 0;
1299         int ret = 0;
1300
1301         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1302         if (vmf->pgoff >= size)
1303                 return VM_FAULT_SIGBUS;
1304
1305         /* If we don't want any read-ahead, don't bother */
1306         if (VM_RandomReadHint(vma))
1307                 goto no_cached_page;
1308
1309         /*
1310          * Do we have something in the page cache already?
1311          */
1312 retry_find:
1313         page = find_lock_page(mapping, vmf->pgoff);
1314         /*
1315          * For sequential accesses, we use the generic readahead logic.
1316          */
1317         if (VM_SequentialReadHint(vma)) {
1318                 if (!page) {
1319                         page_cache_sync_readahead(mapping, ra, file,
1320                                                            vmf->pgoff, 1);
1321                         page = find_lock_page(mapping, vmf->pgoff);
1322                         if (!page)
1323                                 goto no_cached_page;
1324                 }
1325                 if (PageReadahead(page)) {
1326                         page_cache_async_readahead(mapping, ra, file, page,
1327                                                            vmf->pgoff, 1);
1328                 }
1329         }
1330
1331         if (!page) {
1332                 unsigned long ra_pages;
1333
1334                 ra->mmap_miss++;
1335
1336                 /*
1337                  * Do we miss much more than hit in this file? If so,
1338                  * stop bothering with read-ahead. It will only hurt.
1339                  */
1340                 if (ra->mmap_miss > MMAP_LOTSAMISS)
1341                         goto no_cached_page;
1342
1343                 /*
1344                  * To keep the pgmajfault counter straight, we need to
1345                  * check did_readaround, as this is an inner loop.
1346                  */
1347                 if (!did_readaround) {
1348                         ret = VM_FAULT_MAJOR;
1349                         count_vm_event(PGMAJFAULT);
1350                 }
1351                 did_readaround = 1;
1352                 ra_pages = max_sane_readahead(file->f_ra.ra_pages);
1353                 if (ra_pages) {
1354                         pgoff_t start = 0;
1355
1356                         if (vmf->pgoff > ra_pages / 2)
1357                                 start = vmf->pgoff - ra_pages / 2;
1358                         do_page_cache_readahead(mapping, file, start, ra_pages);
1359                 }
1360                 page = find_lock_page(mapping, vmf->pgoff);
1361                 if (!page)
1362                         goto no_cached_page;
1363         }
1364
1365         if (!did_readaround)
1366                 ra->mmap_miss--;
1367
1368         /*
1369          * We have a locked page in the page cache, now we need to check
1370          * that it's up-to-date. If not, it is going to be due to an error.
1371          */
1372         if (unlikely(!PageUptodate(page)))
1373                 goto page_not_uptodate;
1374
1375         /* Must recheck i_size under page lock */
1376         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1377         if (unlikely(vmf->pgoff >= size)) {
1378                 unlock_page(page);
1379                 page_cache_release(page);
1380                 return VM_FAULT_SIGBUS;
1381         }
1382
1383         /*
1384          * Found the page and have a reference on it.
1385          */
1386         mark_page_accessed(page);
1387         ra->prev_pos = (loff_t)page->index << PAGE_CACHE_SHIFT;
1388         vmf->page = page;
1389         return ret | VM_FAULT_LOCKED;
1390
1391 no_cached_page:
1392         /*
1393          * We're only likely to ever get here if MADV_RANDOM is in
1394          * effect.
1395          */
1396         error = page_cache_read(file, vmf->pgoff);
1397
1398         /*
1399          * The page we want has now been added to the page cache.
1400          * In the unlikely event that someone removed it in the
1401          * meantime, we'll just come back here and read it again.
1402          */
1403         if (error >= 0)
1404                 goto retry_find;
1405
1406         /*
1407          * An error return from page_cache_read can result if the
1408          * system is low on memory, or a problem occurs while trying
1409          * to schedule I/O.
1410          */
1411         if (error == -ENOMEM)
1412                 return VM_FAULT_OOM;
1413         return VM_FAULT_SIGBUS;
1414
1415 page_not_uptodate:
1416         /* IO error path */
1417         if (!did_readaround) {
1418                 ret = VM_FAULT_MAJOR;
1419                 count_vm_event(PGMAJFAULT);
1420         }
1421
1422         /*
1423          * Umm, take care of errors if the page isn't up-to-date.
1424          * Try to re-read it _once_. We do this synchronously,
1425          * because there really aren't any performance issues here
1426          * and we need to check for errors.
1427          */
1428         ClearPageError(page);
1429         error = mapping->a_ops->readpage(file, page);
1430         page_cache_release(page);
1431
1432         if (!error || error == AOP_TRUNCATED_PAGE)
1433                 goto retry_find;
1434
1435         /* Things didn't work out. Return zero to tell the mm layer so. */
1436         shrink_readahead_size_eio(file, ra);
1437         return VM_FAULT_SIGBUS;
1438 }
1439 EXPORT_SYMBOL(filemap_fault);
1440
1441 struct vm_operations_struct generic_file_vm_ops = {
1442         .fault          = filemap_fault,
1443 };
1444
1445 /* This is used for a general mmap of a disk file */
1446
1447 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1448 {
1449         struct address_space *mapping = file->f_mapping;
1450
1451         if (!mapping->a_ops->readpage)
1452                 return -ENOEXEC;
1453         file_accessed(file);
1454         vma->vm_ops = &generic_file_vm_ops;
1455         vma->vm_flags |= VM_CAN_NONLINEAR;
1456         return 0;
1457 }
1458
1459 /*
1460  * This is for filesystems which do not implement ->writepage.
1461  */
1462 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1463 {
1464         if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1465                 return -EINVAL;
1466         return generic_file_mmap(file, vma);
1467 }
1468 #else
1469 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1470 {
1471         return -ENOSYS;
1472 }
1473 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1474 {
1475         return -ENOSYS;
1476 }
1477 #endif /* CONFIG_MMU */
1478
1479 EXPORT_SYMBOL(generic_file_mmap);
1480 EXPORT_SYMBOL(generic_file_readonly_mmap);
1481
1482 static struct page *__read_cache_page(struct address_space *mapping,
1483                                 pgoff_t index,
1484                                 int (*filler)(void *,struct page*),
1485                                 void *data)
1486 {
1487         struct page *page;
1488         int err;
1489 repeat:
1490         page = find_get_page(mapping, index);
1491         if (!page) {
1492                 page = page_cache_alloc_cold(mapping);
1493                 if (!page)
1494                         return ERR_PTR(-ENOMEM);
1495                 err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1496                 if (unlikely(err)) {
1497                         page_cache_release(page);
1498                         if (err == -EEXIST)
1499                                 goto repeat;
1500                         /* Presumably ENOMEM for radix tree node */
1501                         return ERR_PTR(err);
1502                 }
1503                 err = filler(data, page);
1504                 if (err < 0) {
1505                         page_cache_release(page);
1506                         page = ERR_PTR(err);
1507                 }
1508         }
1509         return page;
1510 }
1511
1512 /*
1513  * Same as read_cache_page, but don't wait for page to become unlocked
1514  * after submitting it to the filler.
1515  */
1516 struct page *read_cache_page_async(struct address_space *mapping,
1517                                 pgoff_t index,
1518                                 int (*filler)(void *,struct page*),
1519                                 void *data)
1520 {
1521         struct page *page;
1522         int err;
1523
1524 retry:
1525         page = __read_cache_page(mapping, index, filler, data);
1526         if (IS_ERR(page))
1527                 return page;
1528         if (PageUptodate(page))
1529                 goto out;
1530
1531         lock_page(page);
1532         if (!page->mapping) {
1533                 unlock_page(page);
1534                 page_cache_release(page);
1535                 goto retry;
1536         }
1537         if (PageUptodate(page)) {
1538                 unlock_page(page);
1539                 goto out;
1540         }
1541         err = filler(data, page);
1542         if (err < 0) {
1543                 page_cache_release(page);
1544                 return ERR_PTR(err);
1545         }
1546 out:
1547         mark_page_accessed(page);
1548         return page;
1549 }
1550 EXPORT_SYMBOL(read_cache_page_async);
1551
1552 /**
1553  * read_cache_page - read into page cache, fill it if needed
1554  * @mapping:    the page's address_space
1555  * @index:      the page index
1556  * @filler:     function to perform the read
1557  * @data:       destination for read data
1558  *
1559  * Read into the page cache. If a page already exists, and PageUptodate() is
1560  * not set, try to fill the page then wait for it to become unlocked.
1561  *
1562  * If the page does not get brought uptodate, return -EIO.
1563  */
1564 struct page *read_cache_page(struct address_space *mapping,
1565                                 pgoff_t index,
1566                                 int (*filler)(void *,struct page*),
1567                                 void *data)
1568 {
1569         struct page *page;
1570
1571         page = read_cache_page_async(mapping, index, filler, data);
1572         if (IS_ERR(page))
1573                 goto out;
1574         wait_on_page_locked(page);
1575         if (!PageUptodate(page)) {
1576                 page_cache_release(page);
1577                 page = ERR_PTR(-EIO);
1578         }
1579  out:
1580         return page;
1581 }
1582 EXPORT_SYMBOL(read_cache_page);
1583
1584 /*
1585  * The logic we want is
1586  *
1587  *      if suid or (sgid and xgrp)
1588  *              remove privs
1589  */
1590 int should_remove_suid(struct dentry *dentry)
1591 {
1592         mode_t mode = dentry->d_inode->i_mode;
1593         int kill = 0;
1594
1595         /* suid always must be killed */
1596         if (unlikely(mode & S_ISUID))
1597                 kill = ATTR_KILL_SUID;
1598
1599         /*
1600          * sgid without any exec bits is just a mandatory locking mark; leave
1601          * it alone.  If some exec bits are set, it's a real sgid; kill it.
1602          */
1603         if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1604                 kill |= ATTR_KILL_SGID;
1605
1606         if (unlikely(kill && !capable(CAP_FSETID)))
1607                 return kill;
1608
1609         return 0;
1610 }
1611 EXPORT_SYMBOL(should_remove_suid);
1612
1613 int __remove_suid(struct dentry *dentry, int kill)
1614 {
1615         struct iattr newattrs;
1616
1617         newattrs.ia_valid = ATTR_FORCE | kill;
1618         return notify_change(dentry, &newattrs);
1619 }
1620
1621 int remove_suid(struct dentry *dentry)
1622 {
1623         int killsuid = should_remove_suid(dentry);
1624         int killpriv = security_inode_need_killpriv(dentry);
1625         int error = 0;
1626
1627         if (killpriv < 0)
1628                 return killpriv;
1629         if (killpriv)
1630                 error = security_inode_killpriv(dentry);
1631         if (!error && killsuid)
1632                 error = __remove_suid(dentry, killsuid);
1633
1634         return error;
1635 }
1636 EXPORT_SYMBOL(remove_suid);
1637
1638 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1639                         const struct iovec *iov, size_t base, size_t bytes)
1640 {
1641         size_t copied = 0, left = 0;
1642
1643         while (bytes) {
1644                 char __user *buf = iov->iov_base + base;
1645                 int copy = min(bytes, iov->iov_len - base);
1646
1647                 base = 0;
1648                 left = __copy_from_user_inatomic_nocache(vaddr, buf, copy);
1649                 copied += copy;
1650                 bytes -= copy;
1651                 vaddr += copy;
1652                 iov++;
1653
1654                 if (unlikely(left))
1655                         break;
1656         }
1657         return copied - left;
1658 }
1659
1660 /*
1661  * Copy as much as we can into the page and return the number of bytes which
1662  * were sucessfully copied.  If a fault is encountered then return the number of
1663  * bytes which were copied.
1664  */
1665 size_t iov_iter_copy_from_user_atomic(struct page *page,
1666                 struct iov_iter *i, unsigned long offset, size_t bytes)
1667 {
1668         char *kaddr;
1669         size_t copied;
1670
1671         BUG_ON(!in_atomic());
1672         kaddr = kmap_atomic(page, KM_USER0);
1673         if (likely(i->nr_segs == 1)) {
1674                 int left;
1675                 char __user *buf = i->iov->iov_base + i->iov_offset;
1676                 left = __copy_from_user_inatomic_nocache(kaddr + offset,
1677                                                         buf, bytes);
1678                 copied = bytes - left;
1679         } else {
1680                 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1681                                                 i->iov, i->iov_offset, bytes);
1682         }
1683         kunmap_atomic(kaddr, KM_USER0);
1684
1685         return copied;
1686 }
1687 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1688
1689 /*
1690  * This has the same sideeffects and return value as
1691  * iov_iter_copy_from_user_atomic().
1692  * The difference is that it attempts to resolve faults.
1693  * Page must not be locked.
1694  */
1695 size_t iov_iter_copy_from_user(struct page *page,
1696                 struct iov_iter *i, unsigned long offset, size_t bytes)
1697 {
1698         char *kaddr;
1699         size_t copied;
1700
1701         kaddr = kmap(page);
1702         if (likely(i->nr_segs == 1)) {
1703                 int left;
1704                 char __user *buf = i->iov->iov_base + i->iov_offset;
1705                 left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
1706                 copied = bytes - left;
1707         } else {
1708                 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1709                                                 i->iov, i->iov_offset, bytes);
1710         }
1711         kunmap(page);
1712         return copied;
1713 }
1714 EXPORT_SYMBOL(iov_iter_copy_from_user);
1715
1716 static void __iov_iter_advance_iov(struct iov_iter *i, size_t bytes)
1717 {
1718         if (likely(i->nr_segs == 1)) {
1719                 i->iov_offset += bytes;
1720         } else {
1721                 const struct iovec *iov = i->iov;
1722                 size_t base = i->iov_offset;
1723
1724                 while (bytes) {
1725                         int copy = min(bytes, iov->iov_len - base);
1726
1727                         bytes -= copy;
1728                         base += copy;
1729                         if (iov->iov_len == base) {
1730                                 iov++;
1731                                 base = 0;
1732                         }
1733                 }
1734                 i->iov = iov;
1735                 i->iov_offset = base;
1736         }
1737 }
1738
1739 void iov_iter_advance(struct iov_iter *i, size_t bytes)
1740 {
1741         BUG_ON(i->count < bytes);
1742
1743         __iov_iter_advance_iov(i, bytes);
1744         i->count -= bytes;
1745 }
1746 EXPORT_SYMBOL(iov_iter_advance);
1747
1748 /*
1749  * Fault in the first iovec of the given iov_iter, to a maximum length
1750  * of bytes. Returns 0 on success, or non-zero if the memory could not be
1751  * accessed (ie. because it is an invalid address).
1752  *
1753  * writev-intensive code may want this to prefault several iovecs -- that
1754  * would be possible (callers must not rely on the fact that _only_ the
1755  * first iovec will be faulted with the current implementation).
1756  */
1757 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
1758 {
1759         char __user *buf = i->iov->iov_base + i->iov_offset;
1760         bytes = min(bytes, i->iov->iov_len - i->iov_offset);
1761         return fault_in_pages_readable(buf, bytes);
1762 }
1763 EXPORT_SYMBOL(iov_iter_fault_in_readable);
1764
1765 /*
1766  * Return the count of just the current iov_iter segment.
1767  */
1768 size_t iov_iter_single_seg_count(struct iov_iter *i)
1769 {
1770         const struct iovec *iov = i->iov;
1771         if (i->nr_segs == 1)
1772                 return i->count;
1773         else
1774                 return min(i->count, iov->iov_len - i->iov_offset);
1775 }
1776 EXPORT_SYMBOL(iov_iter_single_seg_count);
1777
1778 /*
1779  * Performs necessary checks before doing a write
1780  *
1781  * Can adjust writing position or amount of bytes to write.
1782  * Returns appropriate error code that caller should return or
1783  * zero in case that write should be allowed.
1784  */
1785 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
1786 {
1787         struct inode *inode = file->f_mapping->host;
1788         unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
1789
1790         if (unlikely(*pos < 0))
1791                 return -EINVAL;
1792
1793         if (!isblk) {
1794                 /* FIXME: this is for backwards compatibility with 2.4 */
1795                 if (file->f_flags & O_APPEND)
1796                         *pos = i_size_read(inode);
1797
1798                 if (limit != RLIM_INFINITY) {
1799                         if (*pos >= limit) {
1800                                 send_sig(SIGXFSZ, current, 0);
1801                                 return -EFBIG;
1802                         }
1803                         if (*count > limit - (typeof(limit))*pos) {
1804                                 *count = limit - (typeof(limit))*pos;
1805                         }
1806                 }
1807         }
1808
1809         /*
1810          * LFS rule
1811          */
1812         if (unlikely(*pos + *count > MAX_NON_LFS &&
1813                                 !(file->f_flags & O_LARGEFILE))) {
1814                 if (*pos >= MAX_NON_LFS) {
1815                         return -EFBIG;
1816                 }
1817                 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
1818                         *count = MAX_NON_LFS - (unsigned long)*pos;
1819                 }
1820         }
1821
1822         /*
1823          * Are we about to exceed the fs block limit ?
1824          *
1825          * If we have written data it becomes a short write.  If we have
1826          * exceeded without writing data we send a signal and return EFBIG.
1827          * Linus frestrict idea will clean these up nicely..
1828          */
1829         if (likely(!isblk)) {
1830                 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
1831                         if (*count || *pos > inode->i_sb->s_maxbytes) {
1832                                 return -EFBIG;
1833                         }
1834                         /* zero-length writes at ->s_maxbytes are OK */
1835                 }
1836
1837                 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
1838                         *count = inode->i_sb->s_maxbytes - *pos;
1839         } else {
1840 #ifdef CONFIG_BLOCK
1841                 loff_t isize;
1842                 if (bdev_read_only(I_BDEV(inode)))
1843                         return -EPERM;
1844                 isize = i_size_read(inode);
1845                 if (*pos >= isize) {
1846                         if (*count || *pos > isize)
1847                                 return -ENOSPC;
1848                 }
1849
1850                 if (*pos + *count > isize)
1851                         *count = isize - *pos;
1852 #else
1853                 return -EPERM;
1854 #endif
1855         }
1856         return 0;
1857 }
1858 EXPORT_SYMBOL(generic_write_checks);
1859
1860 int pagecache_write_begin(struct file *file, struct address_space *mapping,
1861                                 loff_t pos, unsigned len, unsigned flags,
1862                                 struct page **pagep, void **fsdata)
1863 {
1864         const struct address_space_operations *aops = mapping->a_ops;
1865
1866         if (aops->write_begin) {
1867                 return aops->write_begin(file, mapping, pos, len, flags,
1868                                                         pagep, fsdata);
1869         } else {
1870                 int ret;
1871                 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1872                 unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
1873                 struct inode *inode = mapping->host;
1874                 struct page *page;
1875 again:
1876                 page = __grab_cache_page(mapping, index);
1877                 *pagep = page;
1878                 if (!page)
1879                         return -ENOMEM;
1880
1881                 if (flags & AOP_FLAG_UNINTERRUPTIBLE && !PageUptodate(page)) {
1882                         /*
1883                          * There is no way to resolve a short write situation
1884                          * for a !Uptodate page (except by double copying in
1885                          * the caller done by generic_perform_write_2copy).
1886                          *
1887                          * Instead, we have to bring it uptodate here.
1888                          */
1889                         ret = aops->readpage(file, page);
1890                         page_cache_release(page);
1891                         if (ret) {
1892                                 if (ret == AOP_TRUNCATED_PAGE)
1893                                         goto again;
1894                                 return ret;
1895                         }
1896                         goto again;
1897                 }
1898
1899                 ret = aops->prepare_write(file, page, offset, offset+len);
1900                 if (ret) {
1901                         unlock_page(page);
1902                         page_cache_release(page);
1903                         if (pos + len > inode->i_size)
1904                                 vmtruncate(inode, inode->i_size);
1905                 }
1906                 return ret;
1907         }
1908 }
1909 EXPORT_SYMBOL(pagecache_write_begin);
1910
1911 int pagecache_write_end(struct file *file, struct address_space *mapping,
1912                                 loff_t pos, unsigned len, unsigned copied,
1913                                 struct page *page, void *fsdata)
1914 {
1915         const struct address_space_operations *aops = mapping->a_ops;
1916         int ret;
1917
1918         if (aops->write_end) {
1919                 mark_page_accessed(page);
1920                 ret = aops->write_end(file, mapping, pos, len, copied,
1921                                                         page, fsdata);
1922         } else {
1923                 unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
1924                 struct inode *inode = mapping->host;
1925
1926                 flush_dcache_page(page);
1927                 ret = aops->commit_write(file, page, offset, offset+len);
1928                 unlock_page(page);
1929                 mark_page_accessed(page);
1930                 page_cache_release(page);
1931
1932                 if (ret < 0) {
1933                         if (pos + len > inode->i_size)
1934                                 vmtruncate(inode, inode->i_size);
1935                 } else if (ret > 0)
1936                         ret = min_t(size_t, copied, ret);
1937                 else
1938                         ret = copied;
1939         }
1940
1941         return ret;
1942 }
1943 EXPORT_SYMBOL(pagecache_write_end);
1944
1945 ssize_t
1946 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
1947                 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
1948                 size_t count, size_t ocount)
1949 {
1950         struct file     *file = iocb->ki_filp;
1951         struct address_space *mapping = file->f_mapping;
1952         struct inode    *inode = mapping->host;
1953         ssize_t         written;
1954
1955         if (count != ocount)
1956                 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
1957
1958         written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs);
1959         if (written > 0) {
1960                 loff_t end = pos + written;
1961                 if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
1962                         i_size_write(inode,  end);
1963                         mark_inode_dirty(inode);
1964                 }
1965                 *ppos = end;
1966         }
1967
1968         /*
1969          * Sync the fs metadata but not the minor inode changes and
1970          * of course not the data as we did direct DMA for the IO.
1971          * i_mutex is held, which protects generic_osync_inode() from
1972          * livelocking.  AIO O_DIRECT ops attempt to sync metadata here.
1973          */
1974         if ((written >= 0 || written == -EIOCBQUEUED) &&
1975             ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
1976                 int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
1977                 if (err < 0)
1978                         written = err;
1979         }
1980         return written;
1981 }
1982 EXPORT_SYMBOL(generic_file_direct_write);
1983
1984 /*
1985  * Find or create a page at the given pagecache position. Return the locked
1986  * page. This function is specifically for buffered writes.
1987  */
1988 struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index)
1989 {
1990         int status;
1991         struct page *page;
1992 repeat:
1993         page = find_lock_page(mapping, index);
1994         if (likely(page))
1995                 return page;
1996
1997         page = page_cache_alloc(mapping);
1998         if (!page)
1999                 return NULL;
2000         status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
2001         if (unlikely(status)) {
2002                 page_cache_release(page);
2003                 if (status == -EEXIST)
2004                         goto repeat;
2005                 return NULL;
2006         }
2007         return page;
2008 }
2009 EXPORT_SYMBOL(__grab_cache_page);
2010
2011 static ssize_t generic_perform_write_2copy(struct file *file,
2012                                 struct iov_iter *i, loff_t pos)
2013 {
2014         struct address_space *mapping = file->f_mapping;
2015         const struct address_space_operations *a_ops = mapping->a_ops;
2016         struct inode *inode = mapping->host;
2017         long status = 0;
2018         ssize_t written = 0;
2019
2020         do {
2021                 struct page *src_page;
2022                 struct page *page;
2023                 pgoff_t index;          /* Pagecache index for current page */
2024                 unsigned long offset;   /* Offset into pagecache page */
2025                 unsigned long bytes;    /* Bytes to write to page */
2026                 size_t copied;          /* Bytes copied from user */
2027
2028                 offset = (pos & (PAGE_CACHE_SIZE - 1));
2029                 index = pos >> PAGE_CACHE_SHIFT;
2030                 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2031                                                 iov_iter_count(i));
2032
2033                 /*
2034                  * a non-NULL src_page indicates that we're doing the
2035                  * copy via get_user_pages and kmap.
2036                  */
2037                 src_page = NULL;
2038
2039                 /*
2040                  * Bring in the user page that we will copy from _first_.
2041                  * Otherwise there's a nasty deadlock on copying from the
2042                  * same page as we're writing to, without it being marked
2043                  * up-to-date.
2044                  *
2045                  * Not only is this an optimisation, but it is also required
2046                  * to check that the address is actually valid, when atomic
2047                  * usercopies are used, below.
2048                  */
2049                 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2050                         status = -EFAULT;
2051                         break;
2052                 }
2053
2054                 page = __grab_cache_page(mapping, index);
2055                 if (!page) {
2056                         status = -ENOMEM;
2057                         break;
2058                 }
2059
2060                 /*
2061                  * non-uptodate pages cannot cope with short copies, and we
2062                  * cannot take a pagefault with the destination page locked.
2063                  * So pin the source page to copy it.
2064                  */
2065                 if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) {
2066                         unlock_page(page);
2067
2068                         src_page = alloc_page(GFP_KERNEL);
2069                         if (!src_page) {
2070                                 page_cache_release(page);
2071                                 status = -ENOMEM;
2072                                 break;
2073                         }
2074
2075                         /*
2076                          * Cannot get_user_pages with a page locked for the
2077                          * same reason as we can't take a page fault with a
2078                          * page locked (as explained below).
2079                          */
2080                         copied = iov_iter_copy_from_user(src_page, i,
2081                                                                 offset, bytes);
2082                         if (unlikely(copied == 0)) {
2083                                 status = -EFAULT;
2084                                 page_cache_release(page);
2085                                 page_cache_release(src_page);
2086                                 break;
2087                         }
2088                         bytes = copied;
2089
2090                         lock_page(page);
2091                         /*
2092                          * Can't handle the page going uptodate here, because
2093                          * that means we would use non-atomic usercopies, which
2094                          * zero out the tail of the page, which can cause
2095                          * zeroes to become transiently visible. We could just
2096                          * use a non-zeroing copy, but the APIs aren't too
2097                          * consistent.
2098                          */
2099                         if (unlikely(!page->mapping || PageUptodate(page))) {
2100                                 unlock_page(page);
2101                                 page_cache_release(page);
2102                                 page_cache_release(src_page);
2103                                 continue;
2104                         }
2105                 }
2106
2107                 status = a_ops->prepare_write(file, page, offset, offset+bytes);
2108                 if (unlikely(status))
2109                         goto fs_write_aop_error;
2110
2111                 if (!src_page) {
2112                         /*
2113                          * Must not enter the pagefault handler here, because
2114                          * we hold the page lock, so we might recursively
2115                          * deadlock on the same lock, or get an ABBA deadlock
2116                          * against a different lock, or against the mmap_sem
2117                          * (which nests outside the page lock).  So increment
2118                          * preempt count, and use _atomic usercopies.
2119                          *
2120                          * The page is uptodate so we are OK to encounter a
2121                          * short copy: if unmodified parts of the page are
2122                          * marked dirty and written out to disk, it doesn't
2123                          * really matter.
2124                          */
2125                         pagefault_disable();
2126                         copied = iov_iter_copy_from_user_atomic(page, i,
2127                                                                 offset, bytes);
2128                         pagefault_enable();
2129                 } else {
2130                         void *src, *dst;
2131                         src = kmap_atomic(src_page, KM_USER0);
2132                         dst = kmap_atomic(page, KM_USER1);
2133                         memcpy(dst + offset, src + offset, bytes);
2134                         kunmap_atomic(dst, KM_USER1);
2135                         kunmap_atomic(src, KM_USER0);
2136                         copied = bytes;
2137                 }
2138                 flush_dcache_page(page);
2139
2140                 status = a_ops->commit_write(file, page, offset, offset+bytes);
2141                 if (unlikely(status < 0))
2142                         goto fs_write_aop_error;
2143                 if (unlikely(status > 0)) /* filesystem did partial write */
2144                         copied = min_t(size_t, copied, status);
2145
2146                 unlock_page(page);
2147                 mark_page_accessed(page);
2148                 page_cache_release(page);
2149                 if (src_page)
2150                         page_cache_release(src_page);
2151
2152                 iov_iter_advance(i, copied);
2153                 pos += copied;
2154                 written += copied;
2155
2156                 balance_dirty_pages_ratelimited(mapping);
2157                 cond_resched();
2158                 continue;
2159
2160 fs_write_aop_error:
2161                 unlock_page(page);
2162                 page_cache_release(page);
2163                 if (src_page)
2164                         page_cache_release(src_page);
2165
2166                 /*
2167                  * prepare_write() may have instantiated a few blocks
2168                  * outside i_size.  Trim these off again. Don't need
2169                  * i_size_read because we hold i_mutex.
2170                  */
2171                 if (pos + bytes > inode->i_size)
2172                         vmtruncate(inode, inode->i_size);
2173                 break;
2174         } while (iov_iter_count(i));
2175
2176         return written ? written : status;
2177 }
2178
2179 static ssize_t generic_perform_write(struct file *file,
2180                                 struct iov_iter *i, loff_t pos)
2181 {
2182         struct address_space *mapping = file->f_mapping;
2183         const struct address_space_operations *a_ops = mapping->a_ops;
2184         long status = 0;
2185         ssize_t written = 0;
2186         unsigned int flags = 0;
2187
2188         /*
2189          * Copies from kernel address space cannot fail (NFSD is a big user).
2190          */
2191         if (segment_eq(get_fs(), KERNEL_DS))
2192                 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2193
2194         do {
2195                 struct page *page;
2196                 pgoff_t index;          /* Pagecache index for current page */
2197                 unsigned long offset;   /* Offset into pagecache page */
2198                 unsigned long bytes;    /* Bytes to write to page */
2199                 size_t copied;          /* Bytes copied from user */
2200                 void *fsdata;
2201
2202                 offset = (pos & (PAGE_CACHE_SIZE - 1));
2203                 index = pos >> PAGE_CACHE_SHIFT;
2204                 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2205                                                 iov_iter_count(i));
2206
2207 again:
2208
2209                 /*
2210                  * Bring in the user page that we will copy from _first_.
2211                  * Otherwise there's a nasty deadlock on copying from the
2212                  * same page as we're writing to, without it being marked
2213                  * up-to-date.
2214                  *
2215                  * Not only is this an optimisation, but it is also required
2216                  * to check that the address is actually valid, when atomic
2217                  * usercopies are used, below.
2218                  */
2219                 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2220                         status = -EFAULT;
2221                         break;
2222                 }
2223
2224                 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2225                                                 &page, &fsdata);
2226                 if (unlikely(status))
2227                         break;
2228
2229                 pagefault_disable();
2230                 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2231                 pagefault_enable();
2232                 flush_dcache_page(page);
2233
2234                 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2235                                                 page, fsdata);
2236                 if (unlikely(status < 0))
2237                         break;
2238                 copied = status;
2239
2240                 cond_resched();
2241
2242                 if (unlikely(copied == 0)) {
2243                         /*
2244                          * If we were unable to copy any data at all, we must
2245                          * fall back to a single segment length write.
2246                          *
2247                          * If we didn't fallback here, we could livelock
2248                          * because not all segments in the iov can be copied at
2249                          * once without a pagefault.
2250                          */
2251                         bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2252                                                 iov_iter_single_seg_count(i));
2253                         goto again;
2254                 }
2255                 iov_iter_advance(i, copied);
2256                 pos += copied;
2257                 written += copied;
2258
2259                 balance_dirty_pages_ratelimited(mapping);
2260
2261         } while (iov_iter_count(i));
2262
2263         return written ? written : status;
2264 }
2265
2266 ssize_t
2267 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2268                 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2269                 size_t count, ssize_t written)
2270 {
2271         struct file *file = iocb->ki_filp;
2272         struct address_space *mapping = file->f_mapping;
2273         const struct address_space_operations *a_ops = mapping->a_ops;
2274         struct inode *inode = mapping->host;
2275         ssize_t status;
2276         struct iov_iter i;
2277
2278         iov_iter_init(&i, iov, nr_segs, count, written);
2279         if (a_ops->write_begin)
2280                 status = generic_perform_write(file, &i, pos);
2281         else
2282                 status = generic_perform_write_2copy(file, &i, pos);
2283
2284         if (likely(status >= 0)) {
2285                 written += status;
2286                 *ppos = pos + status;
2287
2288                 /*
2289                  * For now, when the user asks for O_SYNC, we'll actually give
2290                  * O_DSYNC
2291                  */
2292                 if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2293                         if (!a_ops->writepage || !is_sync_kiocb(iocb))
2294                                 status = generic_osync_inode(inode, mapping,
2295                                                 OSYNC_METADATA|OSYNC_DATA);
2296                 }
2297         }
2298         
2299         /*
2300          * If we get here for O_DIRECT writes then we must have fallen through
2301          * to buffered writes (block instantiation inside i_size).  So we sync
2302          * the file data here, to try to honour O_DIRECT expectations.
2303          */
2304         if (unlikely(file->f_flags & O_DIRECT) && written)
2305                 status = filemap_write_and_wait(mapping);
2306
2307         return written ? written : status;
2308 }
2309 EXPORT_SYMBOL(generic_file_buffered_write);
2310
2311 static ssize_t
2312 __generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
2313                                 unsigned long nr_segs, loff_t *ppos)
2314 {
2315         struct file *file = iocb->ki_filp;
2316         struct address_space * mapping = file->f_mapping;
2317         size_t ocount;          /* original count */
2318         size_t count;           /* after file limit checks */
2319         struct inode    *inode = mapping->host;
2320         loff_t          pos;
2321         ssize_t         written;
2322         ssize_t         err;
2323
2324         ocount = 0;
2325         err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2326         if (err)
2327                 return err;
2328
2329         count = ocount;
2330         pos = *ppos;
2331
2332         vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2333
2334         /* We can write back this queue in page reclaim */
2335         current->backing_dev_info = mapping->backing_dev_info;
2336         written = 0;
2337
2338         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2339         if (err)
2340                 goto out;
2341
2342         if (count == 0)
2343                 goto out;
2344
2345         err = remove_suid(file->f_path.dentry);
2346         if (err)
2347                 goto out;
2348
2349         file_update_time(file);
2350
2351         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2352         if (unlikely(file->f_flags & O_DIRECT)) {
2353                 loff_t endbyte;
2354                 ssize_t written_buffered;
2355
2356                 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2357                                                         ppos, count, ocount);
2358                 if (written < 0 || written == count)
2359                         goto out;
2360                 /*
2361                  * direct-io write to a hole: fall through to buffered I/O
2362                  * for completing the rest of the request.
2363                  */
2364                 pos += written;
2365                 count -= written;
2366                 written_buffered = generic_file_buffered_write(iocb, iov,
2367                                                 nr_segs, pos, ppos, count,
2368                                                 written);
2369                 /*
2370                  * If generic_file_buffered_write() retuned a synchronous error
2371                  * then we want to return the number of bytes which were
2372                  * direct-written, or the error code if that was zero.  Note
2373                  * that this differs from normal direct-io semantics, which
2374                  * will return -EFOO even if some bytes were written.
2375                  */
2376                 if (written_buffered < 0) {
2377                         err = written_buffered;
2378                         goto out;
2379                 }
2380
2381                 /*
2382                  * We need to ensure that the page cache pages are written to
2383                  * disk and invalidated to preserve the expected O_DIRECT
2384                  * semantics.
2385                  */
2386                 endbyte = pos + written_buffered - written - 1;
2387                 err = do_sync_mapping_range(file->f_mapping, pos, endbyte,
2388                                             SYNC_FILE_RANGE_WAIT_BEFORE|
2389                                             SYNC_FILE_RANGE_WRITE|
2390                                             SYNC_FILE_RANGE_WAIT_AFTER);
2391                 if (err == 0) {
2392                         written = written_buffered;
2393                         invalidate_mapping_pages(mapping,
2394                                                  pos >> PAGE_CACHE_SHIFT,
2395                                                  endbyte >> PAGE_CACHE_SHIFT);
2396                 } else {
2397                         /*
2398                          * We don't know how much we wrote, so just return
2399                          * the number of bytes which were direct-written
2400                          */
2401                 }
2402         } else {
2403                 written = generic_file_buffered_write(iocb, iov, nr_segs,
2404                                 pos, ppos, count, written);
2405         }
2406 out:
2407         current->backing_dev_info = NULL;
2408         return written ? written : err;
2409 }
2410
2411 ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
2412                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
2413 {
2414         struct file *file = iocb->ki_filp;
2415         struct address_space *mapping = file->f_mapping;
2416         struct inode *inode = mapping->host;
2417         ssize_t ret;
2418
2419         BUG_ON(iocb->ki_pos != pos);
2420
2421         ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2422                         &iocb->ki_pos);
2423
2424         if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2425                 ssize_t err;
2426
2427                 err = sync_page_range_nolock(inode, mapping, pos, ret);
2428                 if (err < 0)
2429                         ret = err;
2430         }
2431         return ret;
2432 }
2433 EXPORT_SYMBOL(generic_file_aio_write_nolock);
2434
2435 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2436                 unsigned long nr_segs, loff_t pos)
2437 {
2438         struct file *file = iocb->ki_filp;
2439         struct address_space *mapping = file->f_mapping;
2440         struct inode *inode = mapping->host;
2441         ssize_t ret;
2442
2443         BUG_ON(iocb->ki_pos != pos);
2444
2445         mutex_lock(&inode->i_mutex);
2446         ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
2447                         &iocb->ki_pos);
2448         mutex_unlock(&inode->i_mutex);
2449
2450         if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2451                 ssize_t err;
2452
2453                 err = sync_page_range(inode, mapping, pos, ret);
2454                 if (err < 0)
2455                         ret = err;
2456         }
2457         return ret;
2458 }
2459 EXPORT_SYMBOL(generic_file_aio_write);
2460
2461 /*
2462  * Called under i_mutex for writes to S_ISREG files.   Returns -EIO if something
2463  * went wrong during pagecache shootdown.
2464  */
2465 static ssize_t
2466 generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
2467         loff_t offset, unsigned long nr_segs)
2468 {
2469         struct file *file = iocb->ki_filp;
2470         struct address_space *mapping = file->f_mapping;
2471         ssize_t retval;
2472         size_t write_len;
2473         pgoff_t end = 0; /* silence gcc */
2474
2475         /*
2476          * If it's a write, unmap all mmappings of the file up-front.  This
2477          * will cause any pte dirty bits to be propagated into the pageframes
2478          * for the subsequent filemap_write_and_wait().
2479          */
2480         if (rw == WRITE) {
2481                 write_len = iov_length(iov, nr_segs);
2482                 end = (offset + write_len - 1) >> PAGE_CACHE_SHIFT;
2483                 if (mapping_mapped(mapping))
2484                         unmap_mapping_range(mapping, offset, write_len, 0);
2485         }
2486
2487         retval = filemap_write_and_wait(mapping);
2488         if (retval)
2489                 goto out;
2490
2491         /*
2492          * After a write we want buffered reads to be sure to go to disk to get
2493          * the new data.  We invalidate clean cached page from the region we're
2494          * about to write.  We do this *before* the write so that we can return
2495          * -EIO without clobbering -EIOCBQUEUED from ->direct_IO().
2496          */
2497         if (rw == WRITE && mapping->nrpages) {
2498                 retval = invalidate_inode_pages2_range(mapping,
2499                                         offset >> PAGE_CACHE_SHIFT, end);
2500                 if (retval)
2501                         goto out;
2502         }
2503
2504         retval = mapping->a_ops->direct_IO(rw, iocb, iov, offset, nr_segs);
2505
2506         /*
2507          * Finally, try again to invalidate clean pages which might have been
2508          * cached by non-direct readahead, or faulted in by get_user_pages()
2509          * if the source of the write was an mmap'ed region of the file
2510          * we're writing.  Either one is a pretty crazy thing to do,
2511          * so we don't support it 100%.  If this invalidation
2512          * fails, tough, the write still worked...
2513          */
2514         if (rw == WRITE && mapping->nrpages) {
2515                 invalidate_inode_pages2_range(mapping, offset >> PAGE_CACHE_SHIFT, end);
2516         }
2517 out:
2518         return retval;
2519 }
2520
2521 /**
2522  * try_to_release_page() - release old fs-specific metadata on a page
2523  *
2524  * @page: the page which the kernel is trying to free
2525  * @gfp_mask: memory allocation flags (and I/O mode)
2526  *
2527  * The address_space is to try to release any data against the page
2528  * (presumably at page->private).  If the release was successful, return `1'.
2529  * Otherwise return zero.
2530  *
2531  * The @gfp_mask argument specifies whether I/O may be performed to release
2532  * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
2533  *
2534  * NOTE: @gfp_mask may go away, and this function may become non-blocking.
2535  */
2536 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2537 {
2538         struct address_space * const mapping = page->mapping;
2539
2540         BUG_ON(!PageLocked(page));
2541         if (PageWriteback(page))
2542                 return 0;
2543
2544         if (mapping && mapping->a_ops->releasepage)
2545                 return mapping->a_ops->releasepage(page, gfp_mask);
2546         return try_to_free_buffers(page);
2547 }
2548
2549 EXPORT_SYMBOL(try_to_release_page);