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