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1 | /* |
2 | * linux/mm/filemap.c |
3 | * |
4 | * Copyright (C) 1994-1999 Linus Torvalds |
5 | */ |
6 | |
7 | /* |
8 | * This file handles the generic file mmap semantics used by |
9 | * most "normal" filesystems (but you don't /have/ to use this: |
10 | * the NFS filesystem used to do this differently, for example) |
11 | */ |
12 | #include <linux/module.h> |
13 | #include <linux/slab.h> |
14 | #include <linux/compiler.h> |
15 | #include <linux/fs.h> |
16 | #include <linux/uaccess.h> |
17 | #include <linux/aio.h> |
18 | #include <linux/capability.h> |
19 | #include <linux/kernel_stat.h> |
20 | #include <linux/mm.h> |
21 | #include <linux/swap.h> |
22 | #include <linux/mman.h> |
23 | #include <linux/pagemap.h> |
24 | #include <linux/file.h> |
25 | #include <linux/uio.h> |
26 | #include <linux/hash.h> |
27 | #include <linux/writeback.h> |
28 | #include <linux/backing-dev.h> |
29 | #include <linux/pagevec.h> |
30 | #include <linux/blkdev.h> |
31 | #include <linux/security.h> |
32 | #include <linux/syscalls.h> |
33 | #include <linux/cpuset.h> |
34 | #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ |
35 | #include <linux/memcontrol.h> |
36 | #include <linux/mm_inline.h> /* for page_is_file_cache() */ |
37 | #include "internal.h" |
38 | |
39 | /* |
40 | * FIXME: remove all knowledge of the buffer layer from the core VM |
41 | */ |
42 | #include <linux/buffer_head.h> /* for try_to_free_buffers */ |
43 | |
44 | #include <asm/mman.h> |
45 | |
46 | /* |
47 | * Shared mappings implemented 30.11.1994. It's not fully working yet, |
48 | * though. |
49 | * |
50 | * Shared mappings now work. 15.8.1995 Bruno. |
51 | * |
52 | * finished 'unifying' the page and buffer cache and SMP-threaded the |
53 | * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> |
54 | * |
55 | * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> |
56 | */ |
57 | |
58 | /* |
59 | * Lock ordering: |
60 | * |
61 | * ->i_mmap_lock (truncate_pagecache) |
62 | * ->private_lock (__free_pte->__set_page_dirty_buffers) |
63 | * ->swap_lock (exclusive_swap_page, others) |
64 | * ->mapping->tree_lock |
65 | * |
66 | * ->i_mutex |
67 | * ->i_mmap_lock (truncate->unmap_mapping_range) |
68 | * |
69 | * ->mmap_sem |
70 | * ->i_mmap_lock |
71 | * ->page_table_lock or pte_lock (various, mainly in memory.c) |
72 | * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock) |
73 | * |
74 | * ->mmap_sem |
75 | * ->lock_page (access_process_vm) |
76 | * |
77 | * ->i_mutex (generic_file_buffered_write) |
78 | * ->mmap_sem (fault_in_pages_readable->do_page_fault) |
79 | * |
80 | * ->i_mutex |
81 | * ->i_alloc_sem (various) |
82 | * |
83 | * ->inode_lock |
84 | * ->sb_lock (fs/fs-writeback.c) |
85 | * ->mapping->tree_lock (__sync_single_inode) |
86 | * |
87 | * ->i_mmap_lock |
88 | * ->anon_vma.lock (vma_adjust) |
89 | * |
90 | * ->anon_vma.lock |
91 | * ->page_table_lock or pte_lock (anon_vma_prepare and various) |
92 | * |
93 | * ->page_table_lock or pte_lock |
94 | * ->swap_lock (try_to_unmap_one) |
95 | * ->private_lock (try_to_unmap_one) |
96 | * ->tree_lock (try_to_unmap_one) |
97 | * ->zone.lru_lock (follow_page->mark_page_accessed) |
98 | * ->zone.lru_lock (check_pte_range->isolate_lru_page) |
99 | * ->private_lock (page_remove_rmap->set_page_dirty) |
100 | * ->tree_lock (page_remove_rmap->set_page_dirty) |
101 | * ->inode_lock (page_remove_rmap->set_page_dirty) |
102 | * ->inode_lock (zap_pte_range->set_page_dirty) |
103 | * ->private_lock (zap_pte_range->__set_page_dirty_buffers) |
104 | * |
105 | * ->task->proc_lock |
106 | * ->dcache_lock (proc_pid_lookup) |
107 | * |
108 | * (code doesn't rely on that order, so you could switch it around) |
109 | * ->tasklist_lock (memory_failure, collect_procs_ao) |
110 | * ->i_mmap_lock |
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 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 | if (PageSwapBacked(page)) |
127 | __dec_zone_page_state(page, NR_SHMEM); |
128 | BUG_ON(page_mapped(page)); |
129 | |
130 | /* |
131 | * Some filesystems seem to re-dirty the page even after |
132 | * the VM has canceled the dirty bit (eg ext3 journaling). |
133 | * |
134 | * Fix it up by doing a final dirty accounting check after |
135 | * having removed the page entirely. |
136 | */ |
137 | if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { |
138 | dec_zone_page_state(page, NR_FILE_DIRTY); |
139 | dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
140 | } |
141 | } |
142 | |
143 | void remove_from_page_cache(struct page *page) |
144 | { |
145 | struct address_space *mapping = page->mapping; |
146 | |
147 | BUG_ON(!PageLocked(page)); |
148 | |
149 | spin_lock_irq(&mapping->tree_lock); |
150 | __remove_from_page_cache(page); |
151 | spin_unlock_irq(&mapping->tree_lock); |
152 | mem_cgroup_uncharge_cache_page(page); |
153 | } |
154 | |
155 | static int sync_page(void *word) |
156 | { |
157 | struct address_space *mapping; |
158 | struct page *page; |
159 | |
160 | page = container_of((unsigned long *)word, struct page, flags); |
161 | |
162 | /* |
163 | * page_mapping() is being called without PG_locked held. |
164 | * Some knowledge of the state and use of the page is used to |
165 | * reduce the requirements down to a memory barrier. |
166 | * The danger here is of a stale page_mapping() return value |
167 | * indicating a struct address_space different from the one it's |
168 | * associated with when it is associated with one. |
169 | * After smp_mb(), it's either the correct page_mapping() for |
170 | * the page, or an old page_mapping() and the page's own |
171 | * page_mapping() has gone NULL. |
172 | * The ->sync_page() address_space operation must tolerate |
173 | * page_mapping() going NULL. By an amazing coincidence, |
174 | * this comes about because none of the users of the page |
175 | * in the ->sync_page() methods make essential use of the |
176 | * page_mapping(), merely passing the page down to the backing |
177 | * device's unplug functions when it's non-NULL, which in turn |
178 | * ignore it for all cases but swap, where only page_private(page) is |
179 | * of interest. When page_mapping() does go NULL, the entire |
180 | * call stack gracefully ignores the page and returns. |
181 | * -- wli |
182 | */ |
183 | smp_mb(); |
184 | mapping = page_mapping(page); |
185 | if (mapping && mapping->a_ops && mapping->a_ops->sync_page) |
186 | mapping->a_ops->sync_page(page); |
187 | io_schedule(); |
188 | return 0; |
189 | } |
190 | |
191 | static int sync_page_killable(void *word) |
192 | { |
193 | sync_page(word); |
194 | return fatal_signal_pending(current) ? -EINTR : 0; |
195 | } |
196 | |
197 | /** |
198 | * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range |
199 | * @mapping: address space structure to write |
200 | * @start: offset in bytes where the range starts |
201 | * @end: offset in bytes where the range ends (inclusive) |
202 | * @sync_mode: enable synchronous operation |
203 | * |
204 | * Start writeback against all of a mapping's dirty pages that lie |
205 | * within the byte offsets <start, end> inclusive. |
206 | * |
207 | * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as |
208 | * opposed to a regular memory cleansing writeback. The difference between |
209 | * these two operations is that if a dirty page/buffer is encountered, it must |
210 | * be waited upon, and not just skipped over. |
211 | */ |
212 | int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
213 | loff_t end, int sync_mode) |
214 | { |
215 | int ret; |
216 | struct writeback_control wbc = { |
217 | .sync_mode = sync_mode, |
218 | .nr_to_write = LONG_MAX, |
219 | .range_start = start, |
220 | .range_end = end, |
221 | }; |
222 | |
223 | if (!mapping_cap_writeback_dirty(mapping)) |
224 | return 0; |
225 | |
226 | ret = do_writepages(mapping, &wbc); |
227 | return ret; |
228 | } |
229 | |
230 | static inline int __filemap_fdatawrite(struct address_space *mapping, |
231 | int sync_mode) |
232 | { |
233 | return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); |
234 | } |
235 | |
236 | int filemap_fdatawrite(struct address_space *mapping) |
237 | { |
238 | return __filemap_fdatawrite(mapping, WB_SYNC_ALL); |
239 | } |
240 | EXPORT_SYMBOL(filemap_fdatawrite); |
241 | |
242 | int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
243 | loff_t end) |
244 | { |
245 | return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); |
246 | } |
247 | EXPORT_SYMBOL(filemap_fdatawrite_range); |
248 | |
249 | /** |
250 | * filemap_flush - mostly a non-blocking flush |
251 | * @mapping: target address_space |
252 | * |
253 | * This is a mostly non-blocking flush. Not suitable for data-integrity |
254 | * purposes - I/O may not be started against all dirty pages. |
255 | */ |
256 | int filemap_flush(struct address_space *mapping) |
257 | { |
258 | return __filemap_fdatawrite(mapping, WB_SYNC_NONE); |
259 | } |
260 | EXPORT_SYMBOL(filemap_flush); |
261 | |
262 | /** |
263 | * wait_on_page_writeback_range - wait for writeback to complete |
264 | * @mapping: target address_space |
265 | * @start: beginning page index |
266 | * @end: ending page index |
267 | * |
268 | * Wait for writeback to complete against pages indexed by start->end |
269 | * inclusive |
270 | */ |
271 | int wait_on_page_writeback_range(struct address_space *mapping, |
272 | pgoff_t start, pgoff_t end) |
273 | { |
274 | struct pagevec pvec; |
275 | int nr_pages; |
276 | int ret = 0; |
277 | pgoff_t index; |
278 | |
279 | if (end < start) |
280 | return 0; |
281 | |
282 | pagevec_init(&pvec, 0); |
283 | index = start; |
284 | while ((index <= end) && |
285 | (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, |
286 | PAGECACHE_TAG_WRITEBACK, |
287 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { |
288 | unsigned i; |
289 | |
290 | for (i = 0; i < nr_pages; i++) { |
291 | struct page *page = pvec.pages[i]; |
292 | |
293 | /* until radix tree lookup accepts end_index */ |
294 | if (page->index > end) |
295 | continue; |
296 | |
297 | wait_on_page_writeback(page); |
298 | if (PageError(page)) |
299 | ret = -EIO; |
300 | } |
301 | pagevec_release(&pvec); |
302 | cond_resched(); |
303 | } |
304 | |
305 | /* Check for outstanding write errors */ |
306 | if (test_and_clear_bit(AS_ENOSPC, &mapping->flags)) |
307 | ret = -ENOSPC; |
308 | if (test_and_clear_bit(AS_EIO, &mapping->flags)) |
309 | ret = -EIO; |
310 | |
311 | return ret; |
312 | } |
313 | |
314 | /** |
315 | * filemap_fdatawait_range - wait for all under-writeback pages to complete in a given range |
316 | * @mapping: address space structure to wait for |
317 | * @start: offset in bytes where the range starts |
318 | * @end: offset in bytes where the range ends (inclusive) |
319 | * |
320 | * Walk the list of under-writeback pages of the given address space |
321 | * in the given range and wait for all of them. |
322 | * |
323 | * This is just a simple wrapper so that callers don't have to convert offsets |
324 | * to page indexes themselves |
325 | */ |
326 | int filemap_fdatawait_range(struct address_space *mapping, loff_t start, |
327 | loff_t end) |
328 | { |
329 | return wait_on_page_writeback_range(mapping, start >> PAGE_CACHE_SHIFT, |
330 | end >> PAGE_CACHE_SHIFT); |
331 | } |
332 | EXPORT_SYMBOL(filemap_fdatawait_range); |
333 | |
334 | /** |
335 | * filemap_fdatawait - wait for all under-writeback pages to complete |
336 | * @mapping: address space structure to wait for |
337 | * |
338 | * Walk the list of under-writeback pages of the given address space |
339 | * and wait for all of them. |
340 | */ |
341 | int filemap_fdatawait(struct address_space *mapping) |
342 | { |
343 | loff_t i_size = i_size_read(mapping->host); |
344 | |
345 | if (i_size == 0) |
346 | return 0; |
347 | |
348 | return wait_on_page_writeback_range(mapping, 0, |
349 | (i_size - 1) >> PAGE_CACHE_SHIFT); |
350 | } |
351 | EXPORT_SYMBOL(filemap_fdatawait); |
352 | |
353 | int filemap_write_and_wait(struct address_space *mapping) |
354 | { |
355 | int err = 0; |
356 | |
357 | if (mapping->nrpages) { |
358 | err = filemap_fdatawrite(mapping); |
359 | /* |
360 | * Even if the above returned error, the pages may be |
361 | * written partially (e.g. -ENOSPC), so we wait for it. |
362 | * But the -EIO is special case, it may indicate the worst |
363 | * thing (e.g. bug) happened, so we avoid waiting for it. |
364 | */ |
365 | if (err != -EIO) { |
366 | int err2 = filemap_fdatawait(mapping); |
367 | if (!err) |
368 | err = err2; |
369 | } |
370 | } |
371 | return err; |
372 | } |
373 | EXPORT_SYMBOL(filemap_write_and_wait); |
374 | |
375 | /** |
376 | * filemap_write_and_wait_range - write out & wait on a file range |
377 | * @mapping: the address_space for the pages |
378 | * @lstart: offset in bytes where the range starts |
379 | * @lend: offset in bytes where the range ends (inclusive) |
380 | * |
381 | * Write out and wait upon file offsets lstart->lend, inclusive. |
382 | * |
383 | * Note that `lend' is inclusive (describes the last byte to be written) so |
384 | * that this function can be used to write to the very end-of-file (end = -1). |
385 | */ |
386 | int filemap_write_and_wait_range(struct address_space *mapping, |
387 | loff_t lstart, loff_t lend) |
388 | { |
389 | int err = 0; |
390 | |
391 | if (mapping->nrpages) { |
392 | err = __filemap_fdatawrite_range(mapping, lstart, lend, |
393 | WB_SYNC_ALL); |
394 | /* See comment of filemap_write_and_wait() */ |
395 | if (err != -EIO) { |
396 | int err2 = wait_on_page_writeback_range(mapping, |
397 | lstart >> PAGE_CACHE_SHIFT, |
398 | lend >> PAGE_CACHE_SHIFT); |
399 | if (!err) |
400 | err = err2; |
401 | } |
402 | } |
403 | return err; |
404 | } |
405 | EXPORT_SYMBOL(filemap_write_and_wait_range); |
406 | |
407 | /** |
408 | * add_to_page_cache_locked - add a locked page to the pagecache |
409 | * @page: page to add |
410 | * @mapping: the page's address_space |
411 | * @offset: page index |
412 | * @gfp_mask: page allocation mode |
413 | * |
414 | * This function is used to add a page to the pagecache. It must be locked. |
415 | * This function does not add the page to the LRU. The caller must do that. |
416 | */ |
417 | int add_to_page_cache_locked(struct page *page, struct address_space *mapping, |
418 | pgoff_t offset, gfp_t gfp_mask) |
419 | { |
420 | int error; |
421 | |
422 | VM_BUG_ON(!PageLocked(page)); |
423 | |
424 | error = mem_cgroup_cache_charge(page, current->mm, |
425 | gfp_mask & GFP_RECLAIM_MASK); |
426 | if (error) |
427 | goto out; |
428 | |
429 | error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); |
430 | if (error == 0) { |
431 | page_cache_get(page); |
432 | page->mapping = mapping; |
433 | page->index = offset; |
434 | |
435 | spin_lock_irq(&mapping->tree_lock); |
436 | error = radix_tree_insert(&mapping->page_tree, offset, page); |
437 | if (likely(!error)) { |
438 | mapping->nrpages++; |
439 | __inc_zone_page_state(page, NR_FILE_PAGES); |
440 | if (PageSwapBacked(page)) |
441 | __inc_zone_page_state(page, NR_SHMEM); |
442 | spin_unlock_irq(&mapping->tree_lock); |
443 | } else { |
444 | page->mapping = NULL; |
445 | spin_unlock_irq(&mapping->tree_lock); |
446 | mem_cgroup_uncharge_cache_page(page); |
447 | page_cache_release(page); |
448 | } |
449 | radix_tree_preload_end(); |
450 | } else |
451 | mem_cgroup_uncharge_cache_page(page); |
452 | out: |
453 | return error; |
454 | } |
455 | EXPORT_SYMBOL(add_to_page_cache_locked); |
456 | |
457 | int add_to_page_cache_lru(struct page *page, struct address_space *mapping, |
458 | pgoff_t offset, gfp_t gfp_mask) |
459 | { |
460 | int ret; |
461 | |
462 | /* |
463 | * Splice_read and readahead add shmem/tmpfs pages into the page cache |
464 | * before shmem_readpage has a chance to mark them as SwapBacked: they |
465 | * need to go on the active_anon lru below, and mem_cgroup_cache_charge |
466 | * (called in add_to_page_cache) needs to know where they're going too. |
467 | */ |
468 | if (mapping_cap_swap_backed(mapping)) |
469 | SetPageSwapBacked(page); |
470 | |
471 | ret = add_to_page_cache(page, mapping, offset, gfp_mask); |
472 | if (ret == 0) { |
473 | if (page_is_file_cache(page)) |
474 | lru_cache_add_file(page); |
475 | else |
476 | lru_cache_add_active_anon(page); |
477 | } |
478 | return ret; |
479 | } |
480 | EXPORT_SYMBOL_GPL(add_to_page_cache_lru); |
481 | |
482 | #ifdef CONFIG_NUMA |
483 | struct page *__page_cache_alloc(gfp_t gfp) |
484 | { |
485 | if (cpuset_do_page_mem_spread()) { |
486 | int n = cpuset_mem_spread_node(); |
487 | return alloc_pages_exact_node(n, gfp, 0); |
488 | } |
489 | return alloc_pages(gfp, 0); |
490 | } |
491 | EXPORT_SYMBOL(__page_cache_alloc); |
492 | #endif |
493 | |
494 | static int __sleep_on_page_lock(void *word) |
495 | { |
496 | io_schedule(); |
497 | return 0; |
498 | } |
499 | |
500 | /* |
501 | * In order to wait for pages to become available there must be |
502 | * waitqueues associated with pages. By using a hash table of |
503 | * waitqueues where the bucket discipline is to maintain all |
504 | * waiters on the same queue and wake all when any of the pages |
505 | * become available, and for the woken contexts to check to be |
506 | * sure the appropriate page became available, this saves space |
507 | * at a cost of "thundering herd" phenomena during rare hash |
508 | * collisions. |
509 | */ |
510 | static wait_queue_head_t *page_waitqueue(struct page *page) |
511 | { |
512 | const struct zone *zone = page_zone(page); |
513 | |
514 | return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; |
515 | } |
516 | |
517 | static inline void wake_up_page(struct page *page, int bit) |
518 | { |
519 | __wake_up_bit(page_waitqueue(page), &page->flags, bit); |
520 | } |
521 | |
522 | void wait_on_page_bit(struct page *page, int bit_nr) |
523 | { |
524 | DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); |
525 | |
526 | if (test_bit(bit_nr, &page->flags)) |
527 | __wait_on_bit(page_waitqueue(page), &wait, sync_page, |
528 | TASK_UNINTERRUPTIBLE); |
529 | } |
530 | EXPORT_SYMBOL(wait_on_page_bit); |
531 | |
532 | /** |
533 | * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue |
534 | * @page: Page defining the wait queue of interest |
535 | * @waiter: Waiter to add to the queue |
536 | * |
537 | * Add an arbitrary @waiter to the wait queue for the nominated @page. |
538 | */ |
539 | void add_page_wait_queue(struct page *page, wait_queue_t *waiter) |
540 | { |
541 | wait_queue_head_t *q = page_waitqueue(page); |
542 | unsigned long flags; |
543 | |
544 | spin_lock_irqsave(&q->lock, flags); |
545 | __add_wait_queue(q, waiter); |
546 | spin_unlock_irqrestore(&q->lock, flags); |
547 | } |
548 | EXPORT_SYMBOL_GPL(add_page_wait_queue); |
549 | |
550 | /** |
551 | * unlock_page - unlock a locked page |
552 | * @page: the page |
553 | * |
554 | * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). |
555 | * Also wakes sleepers in wait_on_page_writeback() because the wakeup |
556 | * mechananism between PageLocked pages and PageWriteback pages is shared. |
557 | * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. |
558 | * |
559 | * The mb is necessary to enforce ordering between the clear_bit and the read |
560 | * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()). |
561 | */ |
562 | void unlock_page(struct page *page) |
563 | { |
564 | VM_BUG_ON(!PageLocked(page)); |
565 | clear_bit_unlock(PG_locked, &page->flags); |
566 | smp_mb__after_clear_bit(); |
567 | wake_up_page(page, PG_locked); |
568 | } |
569 | EXPORT_SYMBOL(unlock_page); |
570 | |
571 | /** |
572 | * end_page_writeback - end writeback against a page |
573 | * @page: the page |
574 | */ |
575 | void end_page_writeback(struct page *page) |
576 | { |
577 | if (TestClearPageReclaim(page)) |
578 | rotate_reclaimable_page(page); |
579 | |
580 | if (!test_clear_page_writeback(page)) |
581 | BUG(); |
582 | |
583 | smp_mb__after_clear_bit(); |
584 | wake_up_page(page, PG_writeback); |
585 | } |
586 | EXPORT_SYMBOL(end_page_writeback); |
587 | |
588 | /** |
589 | * __lock_page - get a lock on the page, assuming we need to sleep to get it |
590 | * @page: the page to lock |
591 | * |
592 | * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some |
593 | * random driver's requestfn sets TASK_RUNNING, we could busywait. However |
594 | * chances are that on the second loop, the block layer's plug list is empty, |
595 | * so sync_page() will then return in state TASK_UNINTERRUPTIBLE. |
596 | */ |
597 | void __lock_page(struct page *page) |
598 | { |
599 | DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); |
600 | |
601 | __wait_on_bit_lock(page_waitqueue(page), &wait, sync_page, |
602 | TASK_UNINTERRUPTIBLE); |
603 | } |
604 | EXPORT_SYMBOL(__lock_page); |
605 | |
606 | int __lock_page_killable(struct page *page) |
607 | { |
608 | DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); |
609 | |
610 | return __wait_on_bit_lock(page_waitqueue(page), &wait, |
611 | sync_page_killable, TASK_KILLABLE); |
612 | } |
613 | EXPORT_SYMBOL_GPL(__lock_page_killable); |
614 | |
615 | /** |
616 | * __lock_page_nosync - get a lock on the page, without calling sync_page() |
617 | * @page: the page to lock |
618 | * |
619 | * Variant of lock_page that does not require the caller to hold a reference |
620 | * on the page's mapping. |
621 | */ |
622 | void __lock_page_nosync(struct page *page) |
623 | { |
624 | DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); |
625 | __wait_on_bit_lock(page_waitqueue(page), &wait, __sleep_on_page_lock, |
626 | TASK_UNINTERRUPTIBLE); |
627 | } |
628 | |
629 | /** |
630 | * find_get_page - find and get a page reference |
631 | * @mapping: the address_space to search |
632 | * @offset: the page index |
633 | * |
634 | * Is there a pagecache struct page at the given (mapping, offset) tuple? |
635 | * If yes, increment its refcount and return it; if no, return NULL. |
636 | */ |
637 | struct page *find_get_page(struct address_space *mapping, pgoff_t offset) |
638 | { |
639 | void **pagep; |
640 | struct page *page; |
641 | |
642 | rcu_read_lock(); |
643 | repeat: |
644 | page = NULL; |
645 | pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); |
646 | if (pagep) { |
647 | page = radix_tree_deref_slot(pagep); |
648 | if (unlikely(!page || page == RADIX_TREE_RETRY)) |
649 | goto repeat; |
650 | |
651 | if (!page_cache_get_speculative(page)) |
652 | goto repeat; |
653 | |
654 | /* |
655 | * Has the page moved? |
656 | * This is part of the lockless pagecache protocol. See |
657 | * include/linux/pagemap.h for details. |
658 | */ |
659 | if (unlikely(page != *pagep)) { |
660 | page_cache_release(page); |
661 | goto repeat; |
662 | } |
663 | } |
664 | rcu_read_unlock(); |
665 | |
666 | return page; |
667 | } |
668 | EXPORT_SYMBOL(find_get_page); |
669 | |
670 | /** |
671 | * find_lock_page - locate, pin and lock a pagecache page |
672 | * @mapping: the address_space to search |
673 | * @offset: the page index |
674 | * |
675 | * Locates the desired pagecache page, locks it, increments its reference |
676 | * count and returns its address. |
677 | * |
678 | * Returns zero if the page was not present. find_lock_page() may sleep. |
679 | */ |
680 | struct page *find_lock_page(struct address_space *mapping, pgoff_t offset) |
681 | { |
682 | struct page *page; |
683 | |
684 | repeat: |
685 | page = find_get_page(mapping, offset); |
686 | if (page) { |
687 | lock_page(page); |
688 | /* Has the page been truncated? */ |
689 | if (unlikely(page->mapping != mapping)) { |
690 | unlock_page(page); |
691 | page_cache_release(page); |
692 | goto repeat; |
693 | } |
694 | VM_BUG_ON(page->index != offset); |
695 | } |
696 | return page; |
697 | } |
698 | EXPORT_SYMBOL(find_lock_page); |
699 | |
700 | /** |
701 | * find_or_create_page - locate or add a pagecache page |
702 | * @mapping: the page's address_space |
703 | * @index: the page's index into the mapping |
704 | * @gfp_mask: page allocation mode |
705 | * |
706 | * Locates a page in the pagecache. If the page is not present, a new page |
707 | * is allocated using @gfp_mask and is added to the pagecache and to the VM's |
708 | * LRU list. The returned page is locked and has its reference count |
709 | * incremented. |
710 | * |
711 | * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic |
712 | * allocation! |
713 | * |
714 | * find_or_create_page() returns the desired page's address, or zero on |
715 | * memory exhaustion. |
716 | */ |
717 | struct page *find_or_create_page(struct address_space *mapping, |
718 | pgoff_t index, gfp_t gfp_mask) |
719 | { |
720 | struct page *page; |
721 | int err; |
722 | repeat: |
723 | page = find_lock_page(mapping, index); |
724 | if (!page) { |
725 | page = __page_cache_alloc(gfp_mask); |
726 | if (!page) |
727 | return NULL; |
728 | /* |
729 | * We want a regular kernel memory (not highmem or DMA etc) |
730 | * allocation for the radix tree nodes, but we need to honour |
731 | * the context-specific requirements the caller has asked for. |
732 | * GFP_RECLAIM_MASK collects those requirements. |
733 | */ |
734 | err = add_to_page_cache_lru(page, mapping, index, |
735 | (gfp_mask & GFP_RECLAIM_MASK)); |
736 | if (unlikely(err)) { |
737 | page_cache_release(page); |
738 | page = NULL; |
739 | if (err == -EEXIST) |
740 | goto repeat; |
741 | } |
742 | } |
743 | return page; |
744 | } |
745 | EXPORT_SYMBOL(find_or_create_page); |
746 | |
747 | /** |
748 | * find_get_pages - gang pagecache lookup |
749 | * @mapping: The address_space to search |
750 | * @start: The starting page index |
751 | * @nr_pages: The maximum number of pages |
752 | * @pages: Where the resulting pages are placed |
753 | * |
754 | * find_get_pages() will search for and return a group of up to |
755 | * @nr_pages pages in the mapping. The pages are placed at @pages. |
756 | * find_get_pages() takes a reference against the returned pages. |
757 | * |
758 | * The search returns a group of mapping-contiguous pages with ascending |
759 | * indexes. There may be holes in the indices due to not-present pages. |
760 | * |
761 | * find_get_pages() returns the number of pages which were found. |
762 | */ |
763 | unsigned find_get_pages(struct address_space *mapping, pgoff_t start, |
764 | unsigned int nr_pages, struct page **pages) |
765 | { |
766 | unsigned int i; |
767 | unsigned int ret; |
768 | unsigned int nr_found; |
769 | |
770 | rcu_read_lock(); |
771 | restart: |
772 | nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, |
773 | (void ***)pages, start, nr_pages); |
774 | ret = 0; |
775 | for (i = 0; i < nr_found; i++) { |
776 | struct page *page; |
777 | repeat: |
778 | page = radix_tree_deref_slot((void **)pages[i]); |
779 | if (unlikely(!page)) |
780 | continue; |
781 | /* |
782 | * this can only trigger if nr_found == 1, making livelock |
783 | * a non issue. |
784 | */ |
785 | if (unlikely(page == RADIX_TREE_RETRY)) |
786 | goto restart; |
787 | |
788 | if (!page_cache_get_speculative(page)) |
789 | goto repeat; |
790 | |
791 | /* Has the page moved? */ |
792 | if (unlikely(page != *((void **)pages[i]))) { |
793 | page_cache_release(page); |
794 | goto repeat; |
795 | } |
796 | |
797 | pages[ret] = page; |
798 | ret++; |
799 | } |
800 | rcu_read_unlock(); |
801 | return ret; |
802 | } |
803 | |
804 | /** |
805 | * find_get_pages_contig - gang contiguous pagecache lookup |
806 | * @mapping: The address_space to search |
807 | * @index: The starting page index |
808 | * @nr_pages: The maximum number of pages |
809 | * @pages: Where the resulting pages are placed |
810 | * |
811 | * find_get_pages_contig() works exactly like find_get_pages(), except |
812 | * that the returned number of pages are guaranteed to be contiguous. |
813 | * |
814 | * find_get_pages_contig() returns the number of pages which were found. |
815 | */ |
816 | unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, |
817 | unsigned int nr_pages, struct page **pages) |
818 | { |
819 | unsigned int i; |
820 | unsigned int ret; |
821 | unsigned int nr_found; |
822 | |
823 | rcu_read_lock(); |
824 | restart: |
825 | nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, |
826 | (void ***)pages, index, nr_pages); |
827 | ret = 0; |
828 | for (i = 0; i < nr_found; i++) { |
829 | struct page *page; |
830 | repeat: |
831 | page = radix_tree_deref_slot((void **)pages[i]); |
832 | if (unlikely(!page)) |
833 | continue; |
834 | /* |
835 | * this can only trigger if nr_found == 1, making livelock |
836 | * a non issue. |
837 | */ |
838 | if (unlikely(page == RADIX_TREE_RETRY)) |
839 | goto restart; |
840 | |
841 | if (page->mapping == NULL || page->index != index) |
842 | break; |
843 | |
844 | if (!page_cache_get_speculative(page)) |
845 | goto repeat; |
846 | |
847 | /* Has the page moved? */ |
848 | if (unlikely(page != *((void **)pages[i]))) { |
849 | page_cache_release(page); |
850 | goto repeat; |
851 | } |
852 | |
853 | pages[ret] = page; |
854 | ret++; |
855 | index++; |
856 | } |
857 | rcu_read_unlock(); |
858 | return ret; |
859 | } |
860 | EXPORT_SYMBOL(find_get_pages_contig); |
861 | |
862 | /** |
863 | * find_get_pages_tag - find and return pages that match @tag |
864 | * @mapping: the address_space to search |
865 | * @index: the starting page index |
866 | * @tag: the tag index |
867 | * @nr_pages: the maximum number of pages |
868 | * @pages: where the resulting pages are placed |
869 | * |
870 | * Like find_get_pages, except we only return pages which are tagged with |
871 | * @tag. We update @index to index the next page for the traversal. |
872 | */ |
873 | unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, |
874 | int tag, unsigned int nr_pages, struct page **pages) |
875 | { |
876 | unsigned int i; |
877 | unsigned int ret; |
878 | unsigned int nr_found; |
879 | |
880 | rcu_read_lock(); |
881 | restart: |
882 | nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree, |
883 | (void ***)pages, *index, nr_pages, tag); |
884 | ret = 0; |
885 | for (i = 0; i < nr_found; i++) { |
886 | struct page *page; |
887 | repeat: |
888 | page = radix_tree_deref_slot((void **)pages[i]); |
889 | if (unlikely(!page)) |
890 | continue; |
891 | /* |
892 | * this can only trigger if nr_found == 1, making livelock |
893 | * a non issue. |
894 | */ |
895 | if (unlikely(page == RADIX_TREE_RETRY)) |
896 | goto restart; |
897 | |
898 | if (!page_cache_get_speculative(page)) |
899 | goto repeat; |
900 | |
901 | /* Has the page moved? */ |
902 | if (unlikely(page != *((void **)pages[i]))) { |
903 | page_cache_release(page); |
904 | goto repeat; |
905 | } |
906 | |
907 | pages[ret] = page; |
908 | ret++; |
909 | } |
910 | rcu_read_unlock(); |
911 | |
912 | if (ret) |
913 | *index = pages[ret - 1]->index + 1; |
914 | |
915 | return ret; |
916 | } |
917 | EXPORT_SYMBOL(find_get_pages_tag); |
918 | |
919 | /** |
920 | * grab_cache_page_nowait - returns locked page at given index in given cache |
921 | * @mapping: target address_space |
922 | * @index: the page index |
923 | * |
924 | * Same as grab_cache_page(), but do not wait if the page is unavailable. |
925 | * This is intended for speculative data generators, where the data can |
926 | * be regenerated if the page couldn't be grabbed. This routine should |
927 | * be safe to call while holding the lock for another page. |
928 | * |
929 | * Clear __GFP_FS when allocating the page to avoid recursion into the fs |
930 | * and deadlock against the caller's locked page. |
931 | */ |
932 | struct page * |
933 | grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) |
934 | { |
935 | struct page *page = find_get_page(mapping, index); |
936 | |
937 | if (page) { |
938 | if (trylock_page(page)) |
939 | return page; |
940 | page_cache_release(page); |
941 | return NULL; |
942 | } |
943 | page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); |
944 | if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) { |
945 | page_cache_release(page); |
946 | page = NULL; |
947 | } |
948 | return page; |
949 | } |
950 | EXPORT_SYMBOL(grab_cache_page_nowait); |
951 | |
952 | /* |
953 | * CD/DVDs are error prone. When a medium error occurs, the driver may fail |
954 | * a _large_ part of the i/o request. Imagine the worst scenario: |
955 | * |
956 | * ---R__________________________________________B__________ |
957 | * ^ reading here ^ bad block(assume 4k) |
958 | * |
959 | * read(R) => miss => readahead(R...B) => media error => frustrating retries |
960 | * => failing the whole request => read(R) => read(R+1) => |
961 | * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => |
962 | * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => |
963 | * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... |
964 | * |
965 | * It is going insane. Fix it by quickly scaling down the readahead size. |
966 | */ |
967 | static void shrink_readahead_size_eio(struct file *filp, |
968 | struct file_ra_state *ra) |
969 | { |
970 | ra->ra_pages /= 4; |
971 | } |
972 | |
973 | /** |
974 | * do_generic_file_read - generic file read routine |
975 | * @filp: the file to read |
976 | * @ppos: current file position |
977 | * @desc: read_descriptor |
978 | * @actor: read method |
979 | * |
980 | * This is a generic file read routine, and uses the |
981 | * mapping->a_ops->readpage() function for the actual low-level stuff. |
982 | * |
983 | * This is really ugly. But the goto's actually try to clarify some |
984 | * of the logic when it comes to error handling etc. |
985 | */ |
986 | static void do_generic_file_read(struct file *filp, loff_t *ppos, |
987 | read_descriptor_t *desc, read_actor_t actor) |
988 | { |
989 | struct address_space *mapping = filp->f_mapping; |
990 | struct inode *inode = mapping->host; |
991 | struct file_ra_state *ra = &filp->f_ra; |
992 | pgoff_t index; |
993 | pgoff_t last_index; |
994 | pgoff_t prev_index; |
995 | unsigned long offset; /* offset into pagecache page */ |
996 | unsigned int prev_offset; |
997 | int error; |
998 | |
999 | index = *ppos >> PAGE_CACHE_SHIFT; |
1000 | prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; |
1001 | prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); |
1002 | last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; |
1003 | offset = *ppos & ~PAGE_CACHE_MASK; |
1004 | |
1005 | for (;;) { |
1006 | struct page *page; |
1007 | pgoff_t end_index; |
1008 | loff_t isize; |
1009 | unsigned long nr, ret; |
1010 | |
1011 | cond_resched(); |
1012 | find_page: |
1013 | page = find_get_page(mapping, index); |
1014 | if (!page) { |
1015 | page_cache_sync_readahead(mapping, |
1016 | ra, filp, |
1017 | index, last_index - index); |
1018 | page = find_get_page(mapping, index); |
1019 | if (unlikely(page == NULL)) |
1020 | goto no_cached_page; |
1021 | } |
1022 | if (PageReadahead(page)) { |
1023 | page_cache_async_readahead(mapping, |
1024 | ra, filp, page, |
1025 | index, last_index - index); |
1026 | } |
1027 | if (!PageUptodate(page)) { |
1028 | if (inode->i_blkbits == PAGE_CACHE_SHIFT || |
1029 | !mapping->a_ops->is_partially_uptodate) |
1030 | goto page_not_up_to_date; |
1031 | if (!trylock_page(page)) |
1032 | goto page_not_up_to_date; |
1033 | if (!mapping->a_ops->is_partially_uptodate(page, |
1034 | desc, offset)) |
1035 | goto page_not_up_to_date_locked; |
1036 | unlock_page(page); |
1037 | } |
1038 | page_ok: |
1039 | /* |
1040 | * i_size must be checked after we know the page is Uptodate. |
1041 | * |
1042 | * Checking i_size after the check allows us to calculate |
1043 | * the correct value for "nr", which means the zero-filled |
1044 | * part of the page is not copied back to userspace (unless |
1045 | * another truncate extends the file - this is desired though). |
1046 | */ |
1047 | |
1048 | isize = i_size_read(inode); |
1049 | end_index = (isize - 1) >> PAGE_CACHE_SHIFT; |
1050 | if (unlikely(!isize || index > end_index)) { |
1051 | page_cache_release(page); |
1052 | goto out; |
1053 | } |
1054 | |
1055 | /* nr is the maximum number of bytes to copy from this page */ |
1056 | nr = PAGE_CACHE_SIZE; |
1057 | if (index == end_index) { |
1058 | nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; |
1059 | if (nr <= offset) { |
1060 | page_cache_release(page); |
1061 | goto out; |
1062 | } |
1063 | } |
1064 | nr = nr - offset; |
1065 | |
1066 | /* If users can be writing to this page using arbitrary |
1067 | * virtual addresses, take care about potential aliasing |
1068 | * before reading the page on the kernel side. |
1069 | */ |
1070 | if (mapping_writably_mapped(mapping)) |
1071 | flush_dcache_page(page); |
1072 | |
1073 | /* |
1074 | * When a sequential read accesses a page several times, |
1075 | * only mark it as accessed the first time. |
1076 | */ |
1077 | if (prev_index != index || offset != prev_offset) |
1078 | mark_page_accessed(page); |
1079 | prev_index = index; |
1080 | |
1081 | /* |
1082 | * Ok, we have the page, and it's up-to-date, so |
1083 | * now we can copy it to user space... |
1084 | * |
1085 | * The actor routine returns how many bytes were actually used.. |
1086 | * NOTE! This may not be the same as how much of a user buffer |
1087 | * we filled up (we may be padding etc), so we can only update |
1088 | * "pos" here (the actor routine has to update the user buffer |
1089 | * pointers and the remaining count). |
1090 | */ |
1091 | ret = actor(desc, page, offset, nr); |
1092 | offset += ret; |
1093 | index += offset >> PAGE_CACHE_SHIFT; |
1094 | offset &= ~PAGE_CACHE_MASK; |
1095 | prev_offset = offset; |
1096 | |
1097 | page_cache_release(page); |
1098 | if (ret == nr && desc->count) |
1099 | continue; |
1100 | goto out; |
1101 | |
1102 | page_not_up_to_date: |
1103 | /* Get exclusive access to the page ... */ |
1104 | error = lock_page_killable(page); |
1105 | if (unlikely(error)) |
1106 | goto readpage_error; |
1107 | |
1108 | page_not_up_to_date_locked: |
1109 | /* Did it get truncated before we got the lock? */ |
1110 | if (!page->mapping) { |
1111 | unlock_page(page); |
1112 | page_cache_release(page); |
1113 | continue; |
1114 | } |
1115 | |
1116 | /* Did somebody else fill it already? */ |
1117 | if (PageUptodate(page)) { |
1118 | unlock_page(page); |
1119 | goto page_ok; |
1120 | } |
1121 | |
1122 | readpage: |
1123 | /* Start the actual read. The read will unlock the page. */ |
1124 | error = mapping->a_ops->readpage(filp, page); |
1125 | |
1126 | if (unlikely(error)) { |
1127 | if (error == AOP_TRUNCATED_PAGE) { |
1128 | page_cache_release(page); |
1129 | goto find_page; |
1130 | } |
1131 | goto readpage_error; |
1132 | } |
1133 | |
1134 | if (!PageUptodate(page)) { |
1135 | error = lock_page_killable(page); |
1136 | if (unlikely(error)) |
1137 | goto readpage_error; |
1138 | if (!PageUptodate(page)) { |
1139 | if (page->mapping == NULL) { |
1140 | /* |
1141 | * invalidate_inode_pages got it |
1142 | */ |
1143 | unlock_page(page); |
1144 | page_cache_release(page); |
1145 | goto find_page; |
1146 | } |
1147 | unlock_page(page); |
1148 | shrink_readahead_size_eio(filp, ra); |
1149 | error = -EIO; |
1150 | goto readpage_error; |
1151 | } |
1152 | unlock_page(page); |
1153 | } |
1154 | |
1155 | goto page_ok; |
1156 | |
1157 | readpage_error: |
1158 | /* UHHUH! A synchronous read error occurred. Report it */ |
1159 | desc->error = error; |
1160 | page_cache_release(page); |
1161 | goto out; |
1162 | |
1163 | no_cached_page: |
1164 | /* |
1165 | * Ok, it wasn't cached, so we need to create a new |
1166 | * page.. |
1167 | */ |
1168 | page = page_cache_alloc_cold(mapping); |
1169 | if (!page) { |
1170 | desc->error = -ENOMEM; |
1171 | goto out; |
1172 | } |
1173 | error = add_to_page_cache_lru(page, mapping, |
1174 | index, GFP_KERNEL); |
1175 | if (error) { |
1176 | page_cache_release(page); |
1177 | if (error == -EEXIST) |
1178 | goto find_page; |
1179 | desc->error = error; |
1180 | goto out; |
1181 | } |
1182 | goto readpage; |
1183 | } |
1184 | |
1185 | out: |
1186 | ra->prev_pos = prev_index; |
1187 | ra->prev_pos <<= PAGE_CACHE_SHIFT; |
1188 | ra->prev_pos |= prev_offset; |
1189 | |
1190 | *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; |
1191 | file_accessed(filp); |
1192 | } |
1193 | |
1194 | int file_read_actor(read_descriptor_t *desc, struct page *page, |
1195 | unsigned long offset, unsigned long size) |
1196 | { |
1197 | char *kaddr; |
1198 | unsigned long left, count = desc->count; |
1199 | |
1200 | if (size > count) |
1201 | size = count; |
1202 | |
1203 | /* |
1204 | * Faults on the destination of a read are common, so do it before |
1205 | * taking the kmap. |
1206 | */ |
1207 | if (!fault_in_pages_writeable(desc->arg.buf, size)) { |
1208 | kaddr = kmap_atomic(page, KM_USER0); |
1209 | left = __copy_to_user_inatomic(desc->arg.buf, |
1210 | kaddr + offset, size); |
1211 | kunmap_atomic(kaddr, KM_USER0); |
1212 | if (left == 0) |
1213 | goto success; |
1214 | } |
1215 | |
1216 | /* Do it the slow way */ |
1217 | kaddr = kmap(page); |
1218 | left = __copy_to_user(desc->arg.buf, kaddr + offset, size); |
1219 | kunmap(page); |
1220 | |
1221 | if (left) { |
1222 | size -= left; |
1223 | desc->error = -EFAULT; |
1224 | } |
1225 | success: |
1226 | desc->count = count - size; |
1227 | desc->written += size; |
1228 | desc->arg.buf += size; |
1229 | return size; |
1230 | } |
1231 | |
1232 | /* |
1233 | * Performs necessary checks before doing a write |
1234 | * @iov: io vector request |
1235 | * @nr_segs: number of segments in the iovec |
1236 | * @count: number of bytes to write |
1237 | * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE |
1238 | * |
1239 | * Adjust number of segments and amount of bytes to write (nr_segs should be |
1240 | * properly initialized first). Returns appropriate error code that caller |
1241 | * should return or zero in case that write should be allowed. |
1242 | */ |
1243 | int generic_segment_checks(const struct iovec *iov, |
1244 | unsigned long *nr_segs, size_t *count, int access_flags) |
1245 | { |
1246 | unsigned long seg; |
1247 | size_t cnt = 0; |
1248 | for (seg = 0; seg < *nr_segs; seg++) { |
1249 | const struct iovec *iv = &iov[seg]; |
1250 | |
1251 | /* |
1252 | * If any segment has a negative length, or the cumulative |
1253 | * length ever wraps negative then return -EINVAL. |
1254 | */ |
1255 | cnt += iv->iov_len; |
1256 | if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) |
1257 | return -EINVAL; |
1258 | if (access_ok(access_flags, iv->iov_base, iv->iov_len)) |
1259 | continue; |
1260 | if (seg == 0) |
1261 | return -EFAULT; |
1262 | *nr_segs = seg; |
1263 | cnt -= iv->iov_len; /* This segment is no good */ |
1264 | break; |
1265 | } |
1266 | *count = cnt; |
1267 | return 0; |
1268 | } |
1269 | EXPORT_SYMBOL(generic_segment_checks); |
1270 | |
1271 | /** |
1272 | * generic_file_aio_read - generic filesystem read routine |
1273 | * @iocb: kernel I/O control block |
1274 | * @iov: io vector request |
1275 | * @nr_segs: number of segments in the iovec |
1276 | * @pos: current file position |
1277 | * |
1278 | * This is the "read()" routine for all filesystems |
1279 | * that can use the page cache directly. |
1280 | */ |
1281 | ssize_t |
1282 | generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, |
1283 | unsigned long nr_segs, loff_t pos) |
1284 | { |
1285 | struct file *filp = iocb->ki_filp; |
1286 | ssize_t retval; |
1287 | unsigned long seg; |
1288 | size_t count; |
1289 | loff_t *ppos = &iocb->ki_pos; |
1290 | |
1291 | count = 0; |
1292 | retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); |
1293 | if (retval) |
1294 | return retval; |
1295 | |
1296 | /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ |
1297 | if (filp->f_flags & O_DIRECT) { |
1298 | loff_t size; |
1299 | struct address_space *mapping; |
1300 | struct inode *inode; |
1301 | |
1302 | mapping = filp->f_mapping; |
1303 | inode = mapping->host; |
1304 | if (!count) |
1305 | goto out; /* skip atime */ |
1306 | size = i_size_read(inode); |
1307 | if (pos < size) { |
1308 | retval = filemap_write_and_wait_range(mapping, pos, |
1309 | pos + iov_length(iov, nr_segs) - 1); |
1310 | if (!retval) { |
1311 | retval = mapping->a_ops->direct_IO(READ, iocb, |
1312 | iov, pos, nr_segs); |
1313 | } |
1314 | if (retval > 0) |
1315 | *ppos = pos + retval; |
1316 | if (retval) { |
1317 | file_accessed(filp); |
1318 | goto out; |
1319 | } |
1320 | } |
1321 | } |
1322 | |
1323 | for (seg = 0; seg < nr_segs; seg++) { |
1324 | read_descriptor_t desc; |
1325 | |
1326 | desc.written = 0; |
1327 | desc.arg.buf = iov[seg].iov_base; |
1328 | desc.count = iov[seg].iov_len; |
1329 | if (desc.count == 0) |
1330 | continue; |
1331 | desc.error = 0; |
1332 | do_generic_file_read(filp, ppos, &desc, file_read_actor); |
1333 | retval += desc.written; |
1334 | if (desc.error) { |
1335 | retval = retval ?: desc.error; |
1336 | break; |
1337 | } |
1338 | if (desc.count > 0) |
1339 | break; |
1340 | } |
1341 | out: |
1342 | return retval; |
1343 | } |
1344 | EXPORT_SYMBOL(generic_file_aio_read); |
1345 | |
1346 | static ssize_t |
1347 | do_readahead(struct address_space *mapping, struct file *filp, |
1348 | pgoff_t index, unsigned long nr) |
1349 | { |
1350 | if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) |
1351 | return -EINVAL; |
1352 | |
1353 | force_page_cache_readahead(mapping, filp, index, nr); |
1354 | return 0; |
1355 | } |
1356 | |
1357 | SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count) |
1358 | { |
1359 | ssize_t ret; |
1360 | struct file *file; |
1361 | |
1362 | ret = -EBADF; |
1363 | file = fget(fd); |
1364 | if (file) { |
1365 | if (file->f_mode & FMODE_READ) { |
1366 | struct address_space *mapping = file->f_mapping; |
1367 | pgoff_t start = offset >> PAGE_CACHE_SHIFT; |
1368 | pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; |
1369 | unsigned long len = end - start + 1; |
1370 | ret = do_readahead(mapping, file, start, len); |
1371 | } |
1372 | fput(file); |
1373 | } |
1374 | return ret; |
1375 | } |
1376 | #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS |
1377 | asmlinkage long SyS_readahead(long fd, loff_t offset, long count) |
1378 | { |
1379 | return SYSC_readahead((int) fd, offset, (size_t) count); |
1380 | } |
1381 | SYSCALL_ALIAS(sys_readahead, SyS_readahead); |
1382 | #endif |
1383 | |
1384 | #ifdef CONFIG_MMU |
1385 | /** |
1386 | * page_cache_read - adds requested page to the page cache if not already there |
1387 | * @file: file to read |
1388 | * @offset: page index |
1389 | * |
1390 | * This adds the requested page to the page cache if it isn't already there, |
1391 | * and schedules an I/O to read in its contents from disk. |
1392 | */ |
1393 | static int page_cache_read(struct file *file, pgoff_t offset) |
1394 | { |
1395 | struct address_space *mapping = file->f_mapping; |
1396 | struct page *page; |
1397 | int ret; |
1398 | |
1399 | do { |
1400 | page = page_cache_alloc_cold(mapping); |
1401 | if (!page) |
1402 | return -ENOMEM; |
1403 | |
1404 | ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); |
1405 | if (ret == 0) |
1406 | ret = mapping->a_ops->readpage(file, page); |
1407 | else if (ret == -EEXIST) |
1408 | ret = 0; /* losing race to add is OK */ |
1409 | |
1410 | page_cache_release(page); |
1411 | |
1412 | } while (ret == AOP_TRUNCATED_PAGE); |
1413 | |
1414 | return ret; |
1415 | } |
1416 | |
1417 | #define MMAP_LOTSAMISS (100) |
1418 | |
1419 | /* |
1420 | * Synchronous readahead happens when we don't even find |
1421 | * a page in the page cache at all. |
1422 | */ |
1423 | static void do_sync_mmap_readahead(struct vm_area_struct *vma, |
1424 | struct file_ra_state *ra, |
1425 | struct file *file, |
1426 | pgoff_t offset) |
1427 | { |
1428 | unsigned long ra_pages; |
1429 | struct address_space *mapping = file->f_mapping; |
1430 | |
1431 | /* If we don't want any read-ahead, don't bother */ |
1432 | if (VM_RandomReadHint(vma)) |
1433 | return; |
1434 | |
1435 | if (VM_SequentialReadHint(vma) || |
1436 | offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) { |
1437 | page_cache_sync_readahead(mapping, ra, file, offset, |
1438 | ra->ra_pages); |
1439 | return; |
1440 | } |
1441 | |
1442 | if (ra->mmap_miss < INT_MAX) |
1443 | ra->mmap_miss++; |
1444 | |
1445 | /* |
1446 | * Do we miss much more than hit in this file? If so, |
1447 | * stop bothering with read-ahead. It will only hurt. |
1448 | */ |
1449 | if (ra->mmap_miss > MMAP_LOTSAMISS) |
1450 | return; |
1451 | |
1452 | /* |
1453 | * mmap read-around |
1454 | */ |
1455 | ra_pages = max_sane_readahead(ra->ra_pages); |
1456 | if (ra_pages) { |
1457 | ra->start = max_t(long, 0, offset - ra_pages/2); |
1458 | ra->size = ra_pages; |
1459 | ra->async_size = 0; |
1460 | ra_submit(ra, mapping, file); |
1461 | } |
1462 | } |
1463 | |
1464 | /* |
1465 | * Asynchronous readahead happens when we find the page and PG_readahead, |
1466 | * so we want to possibly extend the readahead further.. |
1467 | */ |
1468 | static void do_async_mmap_readahead(struct vm_area_struct *vma, |
1469 | struct file_ra_state *ra, |
1470 | struct file *file, |
1471 | struct page *page, |
1472 | pgoff_t offset) |
1473 | { |
1474 | struct address_space *mapping = file->f_mapping; |
1475 | |
1476 | /* If we don't want any read-ahead, don't bother */ |
1477 | if (VM_RandomReadHint(vma)) |
1478 | return; |
1479 | if (ra->mmap_miss > 0) |
1480 | ra->mmap_miss--; |
1481 | if (PageReadahead(page)) |
1482 | page_cache_async_readahead(mapping, ra, file, |
1483 | page, offset, ra->ra_pages); |
1484 | } |
1485 | |
1486 | /** |
1487 | * filemap_fault - read in file data for page fault handling |
1488 | * @vma: vma in which the fault was taken |
1489 | * @vmf: struct vm_fault containing details of the fault |
1490 | * |
1491 | * filemap_fault() is invoked via the vma operations vector for a |
1492 | * mapped memory region to read in file data during a page fault. |
1493 | * |
1494 | * The goto's are kind of ugly, but this streamlines the normal case of having |
1495 | * it in the page cache, and handles the special cases reasonably without |
1496 | * having a lot of duplicated code. |
1497 | */ |
1498 | int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) |
1499 | { |
1500 | int error; |
1501 | struct file *file = vma->vm_file; |
1502 | struct address_space *mapping = file->f_mapping; |
1503 | struct file_ra_state *ra = &file->f_ra; |
1504 | struct inode *inode = mapping->host; |
1505 | pgoff_t offset = vmf->pgoff; |
1506 | struct page *page; |
1507 | pgoff_t size; |
1508 | int ret = 0; |
1509 | |
1510 | size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; |
1511 | if (offset >= size) |
1512 | return VM_FAULT_SIGBUS; |
1513 | |
1514 | /* |
1515 | * Do we have something in the page cache already? |
1516 | */ |
1517 | page = find_get_page(mapping, offset); |
1518 | if (likely(page)) { |
1519 | /* |
1520 | * We found the page, so try async readahead before |
1521 | * waiting for the lock. |
1522 | */ |
1523 | do_async_mmap_readahead(vma, ra, file, page, offset); |
1524 | lock_page(page); |
1525 | |
1526 | /* Did it get truncated? */ |
1527 | if (unlikely(page->mapping != mapping)) { |
1528 | unlock_page(page); |
1529 | put_page(page); |
1530 | goto no_cached_page; |
1531 | } |
1532 | } else { |
1533 | /* No page in the page cache at all */ |
1534 | do_sync_mmap_readahead(vma, ra, file, offset); |
1535 | count_vm_event(PGMAJFAULT); |
1536 | ret = VM_FAULT_MAJOR; |
1537 | retry_find: |
1538 | page = find_lock_page(mapping, offset); |
1539 | if (!page) |
1540 | goto no_cached_page; |
1541 | } |
1542 | |
1543 | /* |
1544 | * We have a locked page in the page cache, now we need to check |
1545 | * that it's up-to-date. If not, it is going to be due to an error. |
1546 | */ |
1547 | if (unlikely(!PageUptodate(page))) |
1548 | goto page_not_uptodate; |
1549 | |
1550 | /* |
1551 | * Found the page and have a reference on it. |
1552 | * We must recheck i_size under page lock. |
1553 | */ |
1554 | size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; |
1555 | if (unlikely(offset >= size)) { |
1556 | unlock_page(page); |
1557 | page_cache_release(page); |
1558 | return VM_FAULT_SIGBUS; |
1559 | } |
1560 | |
1561 | ra->prev_pos = (loff_t)offset << PAGE_CACHE_SHIFT; |
1562 | vmf->page = page; |
1563 | return ret | VM_FAULT_LOCKED; |
1564 | |
1565 | no_cached_page: |
1566 | /* |
1567 | * We're only likely to ever get here if MADV_RANDOM is in |
1568 | * effect. |
1569 | */ |
1570 | error = page_cache_read(file, offset); |
1571 | |
1572 | /* |
1573 | * The page we want has now been added to the page cache. |
1574 | * In the unlikely event that someone removed it in the |
1575 | * meantime, we'll just come back here and read it again. |
1576 | */ |
1577 | if (error >= 0) |
1578 | goto retry_find; |
1579 | |
1580 | /* |
1581 | * An error return from page_cache_read can result if the |
1582 | * system is low on memory, or a problem occurs while trying |
1583 | * to schedule I/O. |
1584 | */ |
1585 | if (error == -ENOMEM) |
1586 | return VM_FAULT_OOM; |
1587 | return VM_FAULT_SIGBUS; |
1588 | |
1589 | page_not_uptodate: |
1590 | /* |
1591 | * Umm, take care of errors if the page isn't up-to-date. |
1592 | * Try to re-read it _once_. We do this synchronously, |
1593 | * because there really aren't any performance issues here |
1594 | * and we need to check for errors. |
1595 | */ |
1596 | ClearPageError(page); |
1597 | error = mapping->a_ops->readpage(file, page); |
1598 | if (!error) { |
1599 | wait_on_page_locked(page); |
1600 | if (!PageUptodate(page)) |
1601 | error = -EIO; |
1602 | } |
1603 | page_cache_release(page); |
1604 | |
1605 | if (!error || error == AOP_TRUNCATED_PAGE) |
1606 | goto retry_find; |
1607 | |
1608 | /* Things didn't work out. Return zero to tell the mm layer so. */ |
1609 | shrink_readahead_size_eio(file, ra); |
1610 | return VM_FAULT_SIGBUS; |
1611 | } |
1612 | EXPORT_SYMBOL(filemap_fault); |
1613 | |
1614 | const struct vm_operations_struct generic_file_vm_ops = { |
1615 | .fault = filemap_fault, |
1616 | }; |
1617 | |
1618 | /* This is used for a general mmap of a disk file */ |
1619 | |
1620 | int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
1621 | { |
1622 | struct address_space *mapping = file->f_mapping; |
1623 | |
1624 | if (!mapping->a_ops->readpage) |
1625 | return -ENOEXEC; |
1626 | file_accessed(file); |
1627 | vma->vm_ops = &generic_file_vm_ops; |
1628 | vma->vm_flags |= VM_CAN_NONLINEAR; |
1629 | return 0; |
1630 | } |
1631 | |
1632 | /* |
1633 | * This is for filesystems which do not implement ->writepage. |
1634 | */ |
1635 | int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) |
1636 | { |
1637 | if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) |
1638 | return -EINVAL; |
1639 | return generic_file_mmap(file, vma); |
1640 | } |
1641 | #else |
1642 | int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
1643 | { |
1644 | return -ENOSYS; |
1645 | } |
1646 | int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) |
1647 | { |
1648 | return -ENOSYS; |
1649 | } |
1650 | #endif /* CONFIG_MMU */ |
1651 | |
1652 | EXPORT_SYMBOL(generic_file_mmap); |
1653 | EXPORT_SYMBOL(generic_file_readonly_mmap); |
1654 | |
1655 | static struct page *__read_cache_page(struct address_space *mapping, |
1656 | pgoff_t index, |
1657 | int (*filler)(void *,struct page*), |
1658 | void *data, |
1659 | gfp_t gfp) |
1660 | { |
1661 | struct page *page; |
1662 | int err; |
1663 | repeat: |
1664 | page = find_get_page(mapping, index); |
1665 | if (!page) { |
1666 | page = __page_cache_alloc(gfp | __GFP_COLD); |
1667 | if (!page) |
1668 | return ERR_PTR(-ENOMEM); |
1669 | err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); |
1670 | if (unlikely(err)) { |
1671 | page_cache_release(page); |
1672 | if (err == -EEXIST) |
1673 | goto repeat; |
1674 | /* Presumably ENOMEM for radix tree node */ |
1675 | return ERR_PTR(err); |
1676 | } |
1677 | err = filler(data, page); |
1678 | if (err < 0) { |
1679 | page_cache_release(page); |
1680 | page = ERR_PTR(err); |
1681 | } |
1682 | } |
1683 | return page; |
1684 | } |
1685 | |
1686 | static struct page *do_read_cache_page(struct address_space *mapping, |
1687 | pgoff_t index, |
1688 | int (*filler)(void *,struct page*), |
1689 | void *data, |
1690 | gfp_t gfp) |
1691 | |
1692 | { |
1693 | struct page *page; |
1694 | int err; |
1695 | |
1696 | retry: |
1697 | page = __read_cache_page(mapping, index, filler, data, gfp); |
1698 | if (IS_ERR(page)) |
1699 | return page; |
1700 | if (PageUptodate(page)) |
1701 | goto out; |
1702 | |
1703 | lock_page(page); |
1704 | if (!page->mapping) { |
1705 | unlock_page(page); |
1706 | page_cache_release(page); |
1707 | goto retry; |
1708 | } |
1709 | if (PageUptodate(page)) { |
1710 | unlock_page(page); |
1711 | goto out; |
1712 | } |
1713 | err = filler(data, page); |
1714 | if (err < 0) { |
1715 | page_cache_release(page); |
1716 | return ERR_PTR(err); |
1717 | } |
1718 | out: |
1719 | mark_page_accessed(page); |
1720 | return page; |
1721 | } |
1722 | |
1723 | /** |
1724 | * read_cache_page_async - read into page cache, fill it if needed |
1725 | * @mapping: the page's address_space |
1726 | * @index: the page index |
1727 | * @filler: function to perform the read |
1728 | * @data: destination for read data |
1729 | * |
1730 | * Same as read_cache_page, but don't wait for page to become unlocked |
1731 | * after submitting it to the filler. |
1732 | * |
1733 | * Read into the page cache. If a page already exists, and PageUptodate() is |
1734 | * not set, try to fill the page but don't wait for it to become unlocked. |
1735 | * |
1736 | * If the page does not get brought uptodate, return -EIO. |
1737 | */ |
1738 | struct page *read_cache_page_async(struct address_space *mapping, |
1739 | pgoff_t index, |
1740 | int (*filler)(void *,struct page*), |
1741 | void *data) |
1742 | { |
1743 | return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping)); |
1744 | } |
1745 | EXPORT_SYMBOL(read_cache_page_async); |
1746 | |
1747 | static struct page *wait_on_page_read(struct page *page) |
1748 | { |
1749 | if (!IS_ERR(page)) { |
1750 | wait_on_page_locked(page); |
1751 | if (!PageUptodate(page)) { |
1752 | page_cache_release(page); |
1753 | page = ERR_PTR(-EIO); |
1754 | } |
1755 | } |
1756 | return page; |
1757 | } |
1758 | |
1759 | /** |
1760 | * read_cache_page_gfp - read into page cache, using specified page allocation flags. |
1761 | * @mapping: the page's address_space |
1762 | * @index: the page index |
1763 | * @gfp: the page allocator flags to use if allocating |
1764 | * |
1765 | * This is the same as "read_mapping_page(mapping, index, NULL)", but with |
1766 | * any new page allocations done using the specified allocation flags. Note |
1767 | * that the Radix tree operations will still use GFP_KERNEL, so you can't |
1768 | * expect to do this atomically or anything like that - but you can pass in |
1769 | * other page requirements. |
1770 | * |
1771 | * If the page does not get brought uptodate, return -EIO. |
1772 | */ |
1773 | struct page *read_cache_page_gfp(struct address_space *mapping, |
1774 | pgoff_t index, |
1775 | gfp_t gfp) |
1776 | { |
1777 | filler_t *filler = (filler_t *)mapping->a_ops->readpage; |
1778 | |
1779 | return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp)); |
1780 | } |
1781 | EXPORT_SYMBOL(read_cache_page_gfp); |
1782 | |
1783 | /** |
1784 | * read_cache_page - read into page cache, fill it if needed |
1785 | * @mapping: the page's address_space |
1786 | * @index: the page index |
1787 | * @filler: function to perform the read |
1788 | * @data: destination for read data |
1789 | * |
1790 | * Read into the page cache. If a page already exists, and PageUptodate() is |
1791 | * not set, try to fill the page then wait for it to become unlocked. |
1792 | * |
1793 | * If the page does not get brought uptodate, return -EIO. |
1794 | */ |
1795 | struct page *read_cache_page(struct address_space *mapping, |
1796 | pgoff_t index, |
1797 | int (*filler)(void *,struct page*), |
1798 | void *data) |
1799 | { |
1800 | return wait_on_page_read(read_cache_page_async(mapping, index, filler, data)); |
1801 | } |
1802 | EXPORT_SYMBOL(read_cache_page); |
1803 | |
1804 | /* |
1805 | * The logic we want is |
1806 | * |
1807 | * if suid or (sgid and xgrp) |
1808 | * remove privs |
1809 | */ |
1810 | int should_remove_suid(struct dentry *dentry) |
1811 | { |
1812 | mode_t mode = dentry->d_inode->i_mode; |
1813 | int kill = 0; |
1814 | |
1815 | /* suid always must be killed */ |
1816 | if (unlikely(mode & S_ISUID)) |
1817 | kill = ATTR_KILL_SUID; |
1818 | |
1819 | /* |
1820 | * sgid without any exec bits is just a mandatory locking mark; leave |
1821 | * it alone. If some exec bits are set, it's a real sgid; kill it. |
1822 | */ |
1823 | if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) |
1824 | kill |= ATTR_KILL_SGID; |
1825 | |
1826 | if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode))) |
1827 | return kill; |
1828 | |
1829 | return 0; |
1830 | } |
1831 | EXPORT_SYMBOL(should_remove_suid); |
1832 | |
1833 | static int __remove_suid(struct dentry *dentry, int kill) |
1834 | { |
1835 | struct iattr newattrs; |
1836 | |
1837 | newattrs.ia_valid = ATTR_FORCE | kill; |
1838 | return notify_change(dentry, &newattrs); |
1839 | } |
1840 | |
1841 | int file_remove_suid(struct file *file) |
1842 | { |
1843 | struct dentry *dentry = file->f_path.dentry; |
1844 | int killsuid = should_remove_suid(dentry); |
1845 | int killpriv = security_inode_need_killpriv(dentry); |
1846 | int error = 0; |
1847 | |
1848 | if (killpriv < 0) |
1849 | return killpriv; |
1850 | if (killpriv) |
1851 | error = security_inode_killpriv(dentry); |
1852 | if (!error && killsuid) |
1853 | error = __remove_suid(dentry, killsuid); |
1854 | |
1855 | return error; |
1856 | } |
1857 | EXPORT_SYMBOL(file_remove_suid); |
1858 | |
1859 | static size_t __iovec_copy_from_user_inatomic(char *vaddr, |
1860 | const struct iovec *iov, size_t base, size_t bytes) |
1861 | { |
1862 | size_t copied = 0, left = 0; |
1863 | |
1864 | while (bytes) { |
1865 | char __user *buf = iov->iov_base + base; |
1866 | int copy = min(bytes, iov->iov_len - base); |
1867 | |
1868 | base = 0; |
1869 | left = __copy_from_user_inatomic(vaddr, buf, copy); |
1870 | copied += copy; |
1871 | bytes -= copy; |
1872 | vaddr += copy; |
1873 | iov++; |
1874 | |
1875 | if (unlikely(left)) |
1876 | break; |
1877 | } |
1878 | return copied - left; |
1879 | } |
1880 | |
1881 | /* |
1882 | * Copy as much as we can into the page and return the number of bytes which |
1883 | * were sucessfully copied. If a fault is encountered then return the number of |
1884 | * bytes which were copied. |
1885 | */ |
1886 | size_t iov_iter_copy_from_user_atomic(struct page *page, |
1887 | struct iov_iter *i, unsigned long offset, size_t bytes) |
1888 | { |
1889 | char *kaddr; |
1890 | size_t copied; |
1891 | |
1892 | BUG_ON(!in_atomic()); |
1893 | kaddr = kmap_atomic(page, KM_USER0); |
1894 | if (likely(i->nr_segs == 1)) { |
1895 | int left; |
1896 | char __user *buf = i->iov->iov_base + i->iov_offset; |
1897 | left = __copy_from_user_inatomic(kaddr + offset, buf, bytes); |
1898 | copied = bytes - left; |
1899 | } else { |
1900 | copied = __iovec_copy_from_user_inatomic(kaddr + offset, |
1901 | i->iov, i->iov_offset, bytes); |
1902 | } |
1903 | kunmap_atomic(kaddr, KM_USER0); |
1904 | |
1905 | return copied; |
1906 | } |
1907 | EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); |
1908 | |
1909 | /* |
1910 | * This has the same sideeffects and return value as |
1911 | * iov_iter_copy_from_user_atomic(). |
1912 | * The difference is that it attempts to resolve faults. |
1913 | * Page must not be locked. |
1914 | */ |
1915 | size_t iov_iter_copy_from_user(struct page *page, |
1916 | struct iov_iter *i, unsigned long offset, size_t bytes) |
1917 | { |
1918 | char *kaddr; |
1919 | size_t copied; |
1920 | |
1921 | kaddr = kmap(page); |
1922 | if (likely(i->nr_segs == 1)) { |
1923 | int left; |
1924 | char __user *buf = i->iov->iov_base + i->iov_offset; |
1925 | left = __copy_from_user(kaddr + offset, buf, bytes); |
1926 | copied = bytes - left; |
1927 | } else { |
1928 | copied = __iovec_copy_from_user_inatomic(kaddr + offset, |
1929 | i->iov, i->iov_offset, bytes); |
1930 | } |
1931 | kunmap(page); |
1932 | return copied; |
1933 | } |
1934 | EXPORT_SYMBOL(iov_iter_copy_from_user); |
1935 | |
1936 | void iov_iter_advance(struct iov_iter *i, size_t bytes) |
1937 | { |
1938 | BUG_ON(i->count < bytes); |
1939 | |
1940 | if (likely(i->nr_segs == 1)) { |
1941 | i->iov_offset += bytes; |
1942 | i->count -= bytes; |
1943 | } else { |
1944 | const struct iovec *iov = i->iov; |
1945 | size_t base = i->iov_offset; |
1946 | |
1947 | /* |
1948 | * The !iov->iov_len check ensures we skip over unlikely |
1949 | * zero-length segments (without overruning the iovec). |
1950 | */ |
1951 | while (bytes || unlikely(i->count && !iov->iov_len)) { |
1952 | int copy; |
1953 | |
1954 | copy = min(bytes, iov->iov_len - base); |
1955 | BUG_ON(!i->count || i->count < copy); |
1956 | i->count -= copy; |
1957 | bytes -= copy; |
1958 | base += copy; |
1959 | if (iov->iov_len == base) { |
1960 | iov++; |
1961 | base = 0; |
1962 | } |
1963 | } |
1964 | i->iov = iov; |
1965 | i->iov_offset = base; |
1966 | } |
1967 | } |
1968 | EXPORT_SYMBOL(iov_iter_advance); |
1969 | |
1970 | /* |
1971 | * Fault in the first iovec of the given iov_iter, to a maximum length |
1972 | * of bytes. Returns 0 on success, or non-zero if the memory could not be |
1973 | * accessed (ie. because it is an invalid address). |
1974 | * |
1975 | * writev-intensive code may want this to prefault several iovecs -- that |
1976 | * would be possible (callers must not rely on the fact that _only_ the |
1977 | * first iovec will be faulted with the current implementation). |
1978 | */ |
1979 | int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) |
1980 | { |
1981 | char __user *buf = i->iov->iov_base + i->iov_offset; |
1982 | bytes = min(bytes, i->iov->iov_len - i->iov_offset); |
1983 | return fault_in_pages_readable(buf, bytes); |
1984 | } |
1985 | EXPORT_SYMBOL(iov_iter_fault_in_readable); |
1986 | |
1987 | /* |
1988 | * Return the count of just the current iov_iter segment. |
1989 | */ |
1990 | size_t iov_iter_single_seg_count(struct iov_iter *i) |
1991 | { |
1992 | const struct iovec *iov = i->iov; |
1993 | if (i->nr_segs == 1) |
1994 | return i->count; |
1995 | else |
1996 | return min(i->count, iov->iov_len - i->iov_offset); |
1997 | } |
1998 | EXPORT_SYMBOL(iov_iter_single_seg_count); |
1999 | |
2000 | /* |
2001 | * Performs necessary checks before doing a write |
2002 | * |
2003 | * Can adjust writing position or amount of bytes to write. |
2004 | * Returns appropriate error code that caller should return or |
2005 | * zero in case that write should be allowed. |
2006 | */ |
2007 | inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) |
2008 | { |
2009 | struct inode *inode = file->f_mapping->host; |
2010 | unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; |
2011 | |
2012 | if (unlikely(*pos < 0)) |
2013 | return -EINVAL; |
2014 | |
2015 | if (!isblk) { |
2016 | /* FIXME: this is for backwards compatibility with 2.4 */ |
2017 | if (file->f_flags & O_APPEND) |
2018 | *pos = i_size_read(inode); |
2019 | |
2020 | if (limit != RLIM_INFINITY) { |
2021 | if (*pos >= limit) { |
2022 | send_sig(SIGXFSZ, current, 0); |
2023 | return -EFBIG; |
2024 | } |
2025 | if (*count > limit - (typeof(limit))*pos) { |
2026 | *count = limit - (typeof(limit))*pos; |
2027 | } |
2028 | } |
2029 | } |
2030 | |
2031 | /* |
2032 | * LFS rule |
2033 | */ |
2034 | if (unlikely(*pos + *count > MAX_NON_LFS && |
2035 | !(file->f_flags & O_LARGEFILE))) { |
2036 | if (*pos >= MAX_NON_LFS) { |
2037 | return -EFBIG; |
2038 | } |
2039 | if (*count > MAX_NON_LFS - (unsigned long)*pos) { |
2040 | *count = MAX_NON_LFS - (unsigned long)*pos; |
2041 | } |
2042 | } |
2043 | |
2044 | /* |
2045 | * Are we about to exceed the fs block limit ? |
2046 | * |
2047 | * If we have written data it becomes a short write. If we have |
2048 | * exceeded without writing data we send a signal and return EFBIG. |
2049 | * Linus frestrict idea will clean these up nicely.. |
2050 | */ |
2051 | if (likely(!isblk)) { |
2052 | if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { |
2053 | if (*count || *pos > inode->i_sb->s_maxbytes) { |
2054 | return -EFBIG; |
2055 | } |
2056 | /* zero-length writes at ->s_maxbytes are OK */ |
2057 | } |
2058 | |
2059 | if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) |
2060 | *count = inode->i_sb->s_maxbytes - *pos; |
2061 | } else { |
2062 | #ifdef CONFIG_BLOCK |
2063 | loff_t isize; |
2064 | if (bdev_read_only(I_BDEV(inode))) |
2065 | return -EPERM; |
2066 | isize = i_size_read(inode); |
2067 | if (*pos >= isize) { |
2068 | if (*count || *pos > isize) |
2069 | return -ENOSPC; |
2070 | } |
2071 | |
2072 | if (*pos + *count > isize) |
2073 | *count = isize - *pos; |
2074 | #else |
2075 | return -EPERM; |
2076 | #endif |
2077 | } |
2078 | return 0; |
2079 | } |
2080 | EXPORT_SYMBOL(generic_write_checks); |
2081 | |
2082 | int pagecache_write_begin(struct file *file, struct address_space *mapping, |
2083 | loff_t pos, unsigned len, unsigned flags, |
2084 | struct page **pagep, void **fsdata) |
2085 | { |
2086 | const struct address_space_operations *aops = mapping->a_ops; |
2087 | |
2088 | return aops->write_begin(file, mapping, pos, len, flags, |
2089 | pagep, fsdata); |
2090 | } |
2091 | EXPORT_SYMBOL(pagecache_write_begin); |
2092 | |
2093 | int pagecache_write_end(struct file *file, struct address_space *mapping, |
2094 | loff_t pos, unsigned len, unsigned copied, |
2095 | struct page *page, void *fsdata) |
2096 | { |
2097 | const struct address_space_operations *aops = mapping->a_ops; |
2098 | |
2099 | mark_page_accessed(page); |
2100 | return aops->write_end(file, mapping, pos, len, copied, page, fsdata); |
2101 | } |
2102 | EXPORT_SYMBOL(pagecache_write_end); |
2103 | |
2104 | ssize_t |
2105 | generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, |
2106 | unsigned long *nr_segs, loff_t pos, loff_t *ppos, |
2107 | size_t count, size_t ocount) |
2108 | { |
2109 | struct file *file = iocb->ki_filp; |
2110 | struct address_space *mapping = file->f_mapping; |
2111 | struct inode *inode = mapping->host; |
2112 | ssize_t written; |
2113 | size_t write_len; |
2114 | pgoff_t end; |
2115 | |
2116 | if (count != ocount) |
2117 | *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); |
2118 | |
2119 | write_len = iov_length(iov, *nr_segs); |
2120 | end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT; |
2121 | |
2122 | written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); |
2123 | if (written) |
2124 | goto out; |
2125 | |
2126 | /* |
2127 | * After a write we want buffered reads to be sure to go to disk to get |
2128 | * the new data. We invalidate clean cached page from the region we're |
2129 | * about to write. We do this *before* the write so that we can return |
2130 | * without clobbering -EIOCBQUEUED from ->direct_IO(). |
2131 | */ |
2132 | if (mapping->nrpages) { |
2133 | written = invalidate_inode_pages2_range(mapping, |
2134 | pos >> PAGE_CACHE_SHIFT, end); |
2135 | /* |
2136 | * If a page can not be invalidated, return 0 to fall back |
2137 | * to buffered write. |
2138 | */ |
2139 | if (written) { |
2140 | if (written == -EBUSY) |
2141 | return 0; |
2142 | goto out; |
2143 | } |
2144 | } |
2145 | |
2146 | written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); |
2147 | |
2148 | /* |
2149 | * Finally, try again to invalidate clean pages which might have been |
2150 | * cached by non-direct readahead, or faulted in by get_user_pages() |
2151 | * if the source of the write was an mmap'ed region of the file |
2152 | * we're writing. Either one is a pretty crazy thing to do, |
2153 | * so we don't support it 100%. If this invalidation |
2154 | * fails, tough, the write still worked... |
2155 | */ |
2156 | if (mapping->nrpages) { |
2157 | invalidate_inode_pages2_range(mapping, |
2158 | pos >> PAGE_CACHE_SHIFT, end); |
2159 | } |
2160 | |
2161 | if (written > 0) { |
2162 | loff_t end = pos + written; |
2163 | if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { |
2164 | i_size_write(inode, end); |
2165 | mark_inode_dirty(inode); |
2166 | } |
2167 | *ppos = end; |
2168 | } |
2169 | out: |
2170 | return written; |
2171 | } |
2172 | EXPORT_SYMBOL(generic_file_direct_write); |
2173 | |
2174 | /* |
2175 | * Find or create a page at the given pagecache position. Return the locked |
2176 | * page. This function is specifically for buffered writes. |
2177 | */ |
2178 | struct page *grab_cache_page_write_begin(struct address_space *mapping, |
2179 | pgoff_t index, unsigned flags) |
2180 | { |
2181 | int status; |
2182 | struct page *page; |
2183 | gfp_t gfp_notmask = 0; |
2184 | if (flags & AOP_FLAG_NOFS) |
2185 | gfp_notmask = __GFP_FS; |
2186 | repeat: |
2187 | page = find_lock_page(mapping, index); |
2188 | if (likely(page)) |
2189 | return page; |
2190 | |
2191 | page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask); |
2192 | if (!page) |
2193 | return NULL; |
2194 | status = add_to_page_cache_lru(page, mapping, index, |
2195 | GFP_KERNEL & ~gfp_notmask); |
2196 | if (unlikely(status)) { |
2197 | page_cache_release(page); |
2198 | if (status == -EEXIST) |
2199 | goto repeat; |
2200 | return NULL; |
2201 | } |
2202 | return page; |
2203 | } |
2204 | EXPORT_SYMBOL(grab_cache_page_write_begin); |
2205 | |
2206 | static ssize_t generic_perform_write(struct file *file, |
2207 | struct iov_iter *i, loff_t pos) |
2208 | { |
2209 | struct address_space *mapping = file->f_mapping; |
2210 | const struct address_space_operations *a_ops = mapping->a_ops; |
2211 | long status = 0; |
2212 | ssize_t written = 0; |
2213 | unsigned int flags = 0; |
2214 | |
2215 | /* |
2216 | * Copies from kernel address space cannot fail (NFSD is a big user). |
2217 | */ |
2218 | if (segment_eq(get_fs(), KERNEL_DS)) |
2219 | flags |= AOP_FLAG_UNINTERRUPTIBLE; |
2220 | |
2221 | do { |
2222 | struct page *page; |
2223 | pgoff_t index; /* Pagecache index for current page */ |
2224 | unsigned long offset; /* Offset into pagecache page */ |
2225 | unsigned long bytes; /* Bytes to write to page */ |
2226 | size_t copied; /* Bytes copied from user */ |
2227 | void *fsdata; |
2228 | |
2229 | offset = (pos & (PAGE_CACHE_SIZE - 1)); |
2230 | index = pos >> PAGE_CACHE_SHIFT; |
2231 | bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, |
2232 | iov_iter_count(i)); |
2233 | |
2234 | again: |
2235 | |
2236 | /* |
2237 | * Bring in the user page that we will copy from _first_. |
2238 | * Otherwise there's a nasty deadlock on copying from the |
2239 | * same page as we're writing to, without it being marked |
2240 | * up-to-date. |
2241 | * |
2242 | * Not only is this an optimisation, but it is also required |
2243 | * to check that the address is actually valid, when atomic |
2244 | * usercopies are used, below. |
2245 | */ |
2246 | if (unlikely(iov_iter_fault_in_readable(i, bytes))) { |
2247 | status = -EFAULT; |
2248 | break; |
2249 | } |
2250 | |
2251 | status = a_ops->write_begin(file, mapping, pos, bytes, flags, |
2252 | &page, &fsdata); |
2253 | if (unlikely(status)) |
2254 | break; |
2255 | |
2256 | if (mapping_writably_mapped(mapping)) |
2257 | flush_dcache_page(page); |
2258 | |
2259 | pagefault_disable(); |
2260 | copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); |
2261 | pagefault_enable(); |
2262 | flush_dcache_page(page); |
2263 | |
2264 | mark_page_accessed(page); |
2265 | status = a_ops->write_end(file, mapping, pos, bytes, copied, |
2266 | page, fsdata); |
2267 | if (unlikely(status < 0)) |
2268 | break; |
2269 | copied = status; |
2270 | |
2271 | cond_resched(); |
2272 | |
2273 | iov_iter_advance(i, copied); |
2274 | if (unlikely(copied == 0)) { |
2275 | /* |
2276 | * If we were unable to copy any data at all, we must |
2277 | * fall back to a single segment length write. |
2278 | * |
2279 | * If we didn't fallback here, we could livelock |
2280 | * because not all segments in the iov can be copied at |
2281 | * once without a pagefault. |
2282 | */ |
2283 | bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, |
2284 | iov_iter_single_seg_count(i)); |
2285 | goto again; |
2286 | } |
2287 | pos += copied; |
2288 | written += copied; |
2289 | |
2290 | balance_dirty_pages_ratelimited(mapping); |
2291 | |
2292 | } while (iov_iter_count(i)); |
2293 | |
2294 | return written ? written : status; |
2295 | } |
2296 | |
2297 | ssize_t |
2298 | generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, |
2299 | unsigned long nr_segs, loff_t pos, loff_t *ppos, |
2300 | size_t count, ssize_t written) |
2301 | { |
2302 | struct file *file = iocb->ki_filp; |
2303 | struct address_space *mapping = file->f_mapping; |
2304 | ssize_t status; |
2305 | struct iov_iter i; |
2306 | |
2307 | iov_iter_init(&i, iov, nr_segs, count, written); |
2308 | status = generic_perform_write(file, &i, pos); |
2309 | |
2310 | if (likely(status >= 0)) { |
2311 | written += status; |
2312 | *ppos = pos + status; |
2313 | } |
2314 | |
2315 | /* |
2316 | * If we get here for O_DIRECT writes then we must have fallen through |
2317 | * to buffered writes (block instantiation inside i_size). So we sync |
2318 | * the file data here, to try to honour O_DIRECT expectations. |
2319 | */ |
2320 | if (unlikely(file->f_flags & O_DIRECT) && written) |
2321 | status = filemap_write_and_wait_range(mapping, |
2322 | pos, pos + written - 1); |
2323 | |
2324 | return written ? written : status; |
2325 | } |
2326 | EXPORT_SYMBOL(generic_file_buffered_write); |
2327 | |
2328 | /** |
2329 | * __generic_file_aio_write - write data to a file |
2330 | * @iocb: IO state structure (file, offset, etc.) |
2331 | * @iov: vector with data to write |
2332 | * @nr_segs: number of segments in the vector |
2333 | * @ppos: position where to write |
2334 | * |
2335 | * This function does all the work needed for actually writing data to a |
2336 | * file. It does all basic checks, removes SUID from the file, updates |
2337 | * modification times and calls proper subroutines depending on whether we |
2338 | * do direct IO or a standard buffered write. |
2339 | * |
2340 | * It expects i_mutex to be grabbed unless we work on a block device or similar |
2341 | * object which does not need locking at all. |
2342 | * |
2343 | * This function does *not* take care of syncing data in case of O_SYNC write. |
2344 | * A caller has to handle it. This is mainly due to the fact that we want to |
2345 | * avoid syncing under i_mutex. |
2346 | */ |
2347 | ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, |
2348 | unsigned long nr_segs, loff_t *ppos) |
2349 | { |
2350 | struct file *file = iocb->ki_filp; |
2351 | struct address_space * mapping = file->f_mapping; |
2352 | size_t ocount; /* original count */ |
2353 | size_t count; /* after file limit checks */ |
2354 | struct inode *inode = mapping->host; |
2355 | loff_t pos; |
2356 | ssize_t written; |
2357 | ssize_t err; |
2358 | |
2359 | ocount = 0; |
2360 | err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); |
2361 | if (err) |
2362 | return err; |
2363 | |
2364 | count = ocount; |
2365 | pos = *ppos; |
2366 | |
2367 | vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); |
2368 | |
2369 | /* We can write back this queue in page reclaim */ |
2370 | current->backing_dev_info = mapping->backing_dev_info; |
2371 | written = 0; |
2372 | |
2373 | err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); |
2374 | if (err) |
2375 | goto out; |
2376 | |
2377 | if (count == 0) |
2378 | goto out; |
2379 | |
2380 | err = file_remove_suid(file); |
2381 | if (err) |
2382 | goto out; |
2383 | |
2384 | file_update_time(file); |
2385 | |
2386 | /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ |
2387 | if (unlikely(file->f_flags & O_DIRECT)) { |
2388 | loff_t endbyte; |
2389 | ssize_t written_buffered; |
2390 | |
2391 | written = generic_file_direct_write(iocb, iov, &nr_segs, pos, |
2392 | ppos, count, ocount); |
2393 | if (written < 0 || written == count) |
2394 | goto out; |
2395 | /* |
2396 | * direct-io write to a hole: fall through to buffered I/O |
2397 | * for completing the rest of the request. |
2398 | */ |
2399 | pos += written; |
2400 | count -= written; |
2401 | written_buffered = generic_file_buffered_write(iocb, iov, |
2402 | nr_segs, pos, ppos, count, |
2403 | written); |
2404 | /* |
2405 | * If generic_file_buffered_write() retuned a synchronous error |
2406 | * then we want to return the number of bytes which were |
2407 | * direct-written, or the error code if that was zero. Note |
2408 | * that this differs from normal direct-io semantics, which |
2409 | * will return -EFOO even if some bytes were written. |
2410 | */ |
2411 | if (written_buffered < 0) { |
2412 | err = written_buffered; |
2413 | goto out; |
2414 | } |
2415 | |
2416 | /* |
2417 | * We need to ensure that the page cache pages are written to |
2418 | * disk and invalidated to preserve the expected O_DIRECT |
2419 | * semantics. |
2420 | */ |
2421 | endbyte = pos + written_buffered - written - 1; |
2422 | err = do_sync_mapping_range(file->f_mapping, pos, endbyte, |
2423 | SYNC_FILE_RANGE_WAIT_BEFORE| |
2424 | SYNC_FILE_RANGE_WRITE| |
2425 | SYNC_FILE_RANGE_WAIT_AFTER); |
2426 | if (err == 0) { |
2427 | written = written_buffered; |
2428 | invalidate_mapping_pages(mapping, |
2429 | pos >> PAGE_CACHE_SHIFT, |
2430 | endbyte >> PAGE_CACHE_SHIFT); |
2431 | } else { |
2432 | /* |
2433 | * We don't know how much we wrote, so just return |
2434 | * the number of bytes which were direct-written |
2435 | */ |
2436 | } |
2437 | } else { |
2438 | written = generic_file_buffered_write(iocb, iov, nr_segs, |
2439 | pos, ppos, count, written); |
2440 | } |
2441 | out: |
2442 | current->backing_dev_info = NULL; |
2443 | return written ? written : err; |
2444 | } |
2445 | EXPORT_SYMBOL(__generic_file_aio_write); |
2446 | |
2447 | /** |
2448 | * generic_file_aio_write - write data to a file |
2449 | * @iocb: IO state structure |
2450 | * @iov: vector with data to write |
2451 | * @nr_segs: number of segments in the vector |
2452 | * @pos: position in file where to write |
2453 | * |
2454 | * This is a wrapper around __generic_file_aio_write() to be used by most |
2455 | * filesystems. It takes care of syncing the file in case of O_SYNC file |
2456 | * and acquires i_mutex as needed. |
2457 | */ |
2458 | ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, |
2459 | unsigned long nr_segs, loff_t pos) |
2460 | { |
2461 | struct file *file = iocb->ki_filp; |
2462 | struct inode *inode = file->f_mapping->host; |
2463 | ssize_t ret; |
2464 | |
2465 | BUG_ON(iocb->ki_pos != pos); |
2466 | |
2467 | mutex_lock(&inode->i_mutex); |
2468 | ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); |
2469 | mutex_unlock(&inode->i_mutex); |
2470 | |
2471 | if (ret > 0 || ret == -EIOCBQUEUED) { |
2472 | ssize_t err; |
2473 | |
2474 | err = generic_write_sync(file, pos, ret); |
2475 | if (err < 0 && ret > 0) |
2476 | ret = err; |
2477 | } |
2478 | return ret; |
2479 | } |
2480 | EXPORT_SYMBOL(generic_file_aio_write); |
2481 | |
2482 | /** |
2483 | * try_to_release_page() - release old fs-specific metadata on a page |
2484 | * |
2485 | * @page: the page which the kernel is trying to free |
2486 | * @gfp_mask: memory allocation flags (and I/O mode) |
2487 | * |
2488 | * The address_space is to try to release any data against the page |
2489 | * (presumably at page->private). If the release was successful, return `1'. |
2490 | * Otherwise return zero. |
2491 | * |
2492 | * This may also be called if PG_fscache is set on a page, indicating that the |
2493 | * page is known to the local caching routines. |
2494 | * |
2495 | * The @gfp_mask argument specifies whether I/O may be performed to release |
2496 | * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS). |
2497 | * |
2498 | */ |
2499 | int try_to_release_page(struct page *page, gfp_t gfp_mask) |
2500 | { |
2501 | struct address_space * const mapping = page->mapping; |
2502 | |
2503 | BUG_ON(!PageLocked(page)); |
2504 | if (PageWriteback(page)) |
2505 | return 0; |
2506 | |
2507 | if (mapping && mapping->a_ops->releasepage) |
2508 | return mapping->a_ops->releasepage(page, gfp_mask); |
2509 | return try_to_free_buffers(page); |
2510 | } |
2511 | |
2512 | EXPORT_SYMBOL(try_to_release_page); |
2513 |
Branches:
ben-wpan
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javiroman/ks7010
jz-2.6.34
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9