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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 <linux/cleancache.h> |
38 | #include "internal.h" |
39 | |
40 | /* |
41 | * FIXME: remove all knowledge of the buffer layer from the core VM |
42 | */ |
43 | #include <linux/buffer_head.h> /* for try_to_free_buffers */ |
44 | |
45 | #include <asm/mman.h> |
46 | |
47 | /* |
48 | * Shared mappings implemented 30.11.1994. It's not fully working yet, |
49 | * though. |
50 | * |
51 | * Shared mappings now work. 15.8.1995 Bruno. |
52 | * |
53 | * finished 'unifying' the page and buffer cache and SMP-threaded the |
54 | * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> |
55 | * |
56 | * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> |
57 | */ |
58 | |
59 | /* |
60 | * Lock ordering: |
61 | * |
62 | * ->i_mmap_mutex (truncate_pagecache) |
63 | * ->private_lock (__free_pte->__set_page_dirty_buffers) |
64 | * ->swap_lock (exclusive_swap_page, others) |
65 | * ->mapping->tree_lock |
66 | * |
67 | * ->i_mutex |
68 | * ->i_mmap_mutex (truncate->unmap_mapping_range) |
69 | * |
70 | * ->mmap_sem |
71 | * ->i_mmap_mutex |
72 | * ->page_table_lock or pte_lock (various, mainly in memory.c) |
73 | * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock) |
74 | * |
75 | * ->mmap_sem |
76 | * ->lock_page (access_process_vm) |
77 | * |
78 | * ->i_mutex (generic_file_buffered_write) |
79 | * ->mmap_sem (fault_in_pages_readable->do_page_fault) |
80 | * |
81 | * ->i_mutex |
82 | * ->i_alloc_sem (various) |
83 | * |
84 | * inode_wb_list_lock |
85 | * sb_lock (fs/fs-writeback.c) |
86 | * ->mapping->tree_lock (__sync_single_inode) |
87 | * |
88 | * ->i_mmap_mutex |
89 | * ->anon_vma.lock (vma_adjust) |
90 | * |
91 | * ->anon_vma.lock |
92 | * ->page_table_lock or pte_lock (anon_vma_prepare and various) |
93 | * |
94 | * ->page_table_lock or pte_lock |
95 | * ->swap_lock (try_to_unmap_one) |
96 | * ->private_lock (try_to_unmap_one) |
97 | * ->tree_lock (try_to_unmap_one) |
98 | * ->zone.lru_lock (follow_page->mark_page_accessed) |
99 | * ->zone.lru_lock (check_pte_range->isolate_lru_page) |
100 | * ->private_lock (page_remove_rmap->set_page_dirty) |
101 | * ->tree_lock (page_remove_rmap->set_page_dirty) |
102 | * inode_wb_list_lock (page_remove_rmap->set_page_dirty) |
103 | * ->inode->i_lock (page_remove_rmap->set_page_dirty) |
104 | * inode_wb_list_lock (zap_pte_range->set_page_dirty) |
105 | * ->inode->i_lock (zap_pte_range->set_page_dirty) |
106 | * ->private_lock (zap_pte_range->__set_page_dirty_buffers) |
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_mutex |
111 | */ |
112 | |
113 | /* |
114 | * Delete 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 __delete_from_page_cache(struct page *page) |
119 | { |
120 | struct address_space *mapping = page->mapping; |
121 | |
122 | /* |
123 | * if we're uptodate, flush out into the cleancache, otherwise |
124 | * invalidate any existing cleancache entries. We can't leave |
125 | * stale data around in the cleancache once our page is gone |
126 | */ |
127 | if (PageUptodate(page) && PageMappedToDisk(page)) |
128 | cleancache_put_page(page); |
129 | else |
130 | cleancache_flush_page(mapping, page); |
131 | |
132 | radix_tree_delete(&mapping->page_tree, page->index); |
133 | page->mapping = NULL; |
134 | mapping->nrpages--; |
135 | __dec_zone_page_state(page, NR_FILE_PAGES); |
136 | if (PageSwapBacked(page)) |
137 | __dec_zone_page_state(page, NR_SHMEM); |
138 | BUG_ON(page_mapped(page)); |
139 | |
140 | /* |
141 | * Some filesystems seem to re-dirty the page even after |
142 | * the VM has canceled the dirty bit (eg ext3 journaling). |
143 | * |
144 | * Fix it up by doing a final dirty accounting check after |
145 | * having removed the page entirely. |
146 | */ |
147 | if (PageDirty(page) && mapping_cap_account_dirty(mapping)) { |
148 | dec_zone_page_state(page, NR_FILE_DIRTY); |
149 | dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); |
150 | } |
151 | } |
152 | |
153 | /** |
154 | * delete_from_page_cache - delete page from page cache |
155 | * @page: the page which the kernel is trying to remove from page cache |
156 | * |
157 | * This must be called only on pages that have been verified to be in the page |
158 | * cache and locked. It will never put the page into the free list, the caller |
159 | * has a reference on the page. |
160 | */ |
161 | void delete_from_page_cache(struct page *page) |
162 | { |
163 | struct address_space *mapping = page->mapping; |
164 | void (*freepage)(struct page *); |
165 | |
166 | BUG_ON(!PageLocked(page)); |
167 | |
168 | freepage = mapping->a_ops->freepage; |
169 | spin_lock_irq(&mapping->tree_lock); |
170 | __delete_from_page_cache(page); |
171 | spin_unlock_irq(&mapping->tree_lock); |
172 | mem_cgroup_uncharge_cache_page(page); |
173 | |
174 | if (freepage) |
175 | freepage(page); |
176 | page_cache_release(page); |
177 | } |
178 | EXPORT_SYMBOL(delete_from_page_cache); |
179 | |
180 | static int sleep_on_page(void *word) |
181 | { |
182 | io_schedule(); |
183 | return 0; |
184 | } |
185 | |
186 | static int sleep_on_page_killable(void *word) |
187 | { |
188 | sleep_on_page(word); |
189 | return fatal_signal_pending(current) ? -EINTR : 0; |
190 | } |
191 | |
192 | /** |
193 | * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range |
194 | * @mapping: address space structure to write |
195 | * @start: offset in bytes where the range starts |
196 | * @end: offset in bytes where the range ends (inclusive) |
197 | * @sync_mode: enable synchronous operation |
198 | * |
199 | * Start writeback against all of a mapping's dirty pages that lie |
200 | * within the byte offsets <start, end> inclusive. |
201 | * |
202 | * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as |
203 | * opposed to a regular memory cleansing writeback. The difference between |
204 | * these two operations is that if a dirty page/buffer is encountered, it must |
205 | * be waited upon, and not just skipped over. |
206 | */ |
207 | int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
208 | loff_t end, int sync_mode) |
209 | { |
210 | int ret; |
211 | struct writeback_control wbc = { |
212 | .sync_mode = sync_mode, |
213 | .nr_to_write = LONG_MAX, |
214 | .range_start = start, |
215 | .range_end = end, |
216 | }; |
217 | |
218 | if (!mapping_cap_writeback_dirty(mapping)) |
219 | return 0; |
220 | |
221 | ret = do_writepages(mapping, &wbc); |
222 | return ret; |
223 | } |
224 | |
225 | static inline int __filemap_fdatawrite(struct address_space *mapping, |
226 | int sync_mode) |
227 | { |
228 | return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); |
229 | } |
230 | |
231 | int filemap_fdatawrite(struct address_space *mapping) |
232 | { |
233 | return __filemap_fdatawrite(mapping, WB_SYNC_ALL); |
234 | } |
235 | EXPORT_SYMBOL(filemap_fdatawrite); |
236 | |
237 | int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
238 | loff_t end) |
239 | { |
240 | return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); |
241 | } |
242 | EXPORT_SYMBOL(filemap_fdatawrite_range); |
243 | |
244 | /** |
245 | * filemap_flush - mostly a non-blocking flush |
246 | * @mapping: target address_space |
247 | * |
248 | * This is a mostly non-blocking flush. Not suitable for data-integrity |
249 | * purposes - I/O may not be started against all dirty pages. |
250 | */ |
251 | int filemap_flush(struct address_space *mapping) |
252 | { |
253 | return __filemap_fdatawrite(mapping, WB_SYNC_NONE); |
254 | } |
255 | EXPORT_SYMBOL(filemap_flush); |
256 | |
257 | /** |
258 | * filemap_fdatawait_range - wait for writeback to complete |
259 | * @mapping: address space structure to wait for |
260 | * @start_byte: offset in bytes where the range starts |
261 | * @end_byte: offset in bytes where the range ends (inclusive) |
262 | * |
263 | * Walk the list of under-writeback pages of the given address space |
264 | * in the given range and wait for all of them. |
265 | */ |
266 | int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, |
267 | loff_t end_byte) |
268 | { |
269 | pgoff_t index = start_byte >> PAGE_CACHE_SHIFT; |
270 | pgoff_t end = end_byte >> PAGE_CACHE_SHIFT; |
271 | struct pagevec pvec; |
272 | int nr_pages; |
273 | int ret = 0; |
274 | |
275 | if (end_byte < start_byte) |
276 | return 0; |
277 | |
278 | pagevec_init(&pvec, 0); |
279 | while ((index <= end) && |
280 | (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, |
281 | PAGECACHE_TAG_WRITEBACK, |
282 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { |
283 | unsigned i; |
284 | |
285 | for (i = 0; i < nr_pages; i++) { |
286 | struct page *page = pvec.pages[i]; |
287 | |
288 | /* until radix tree lookup accepts end_index */ |
289 | if (page->index > end) |
290 | continue; |
291 | |
292 | wait_on_page_writeback(page); |
293 | if (TestClearPageError(page)) |
294 | ret = -EIO; |
295 | } |
296 | pagevec_release(&pvec); |
297 | cond_resched(); |
298 | } |
299 | |
300 | /* Check for outstanding write errors */ |
301 | if (test_and_clear_bit(AS_ENOSPC, &mapping->flags)) |
302 | ret = -ENOSPC; |
303 | if (test_and_clear_bit(AS_EIO, &mapping->flags)) |
304 | ret = -EIO; |
305 | |
306 | return ret; |
307 | } |
308 | EXPORT_SYMBOL(filemap_fdatawait_range); |
309 | |
310 | /** |
311 | * filemap_fdatawait - wait for all under-writeback pages to complete |
312 | * @mapping: address space structure to wait for |
313 | * |
314 | * Walk the list of under-writeback pages of the given address space |
315 | * and wait for all of them. |
316 | */ |
317 | int filemap_fdatawait(struct address_space *mapping) |
318 | { |
319 | loff_t i_size = i_size_read(mapping->host); |
320 | |
321 | if (i_size == 0) |
322 | return 0; |
323 | |
324 | return filemap_fdatawait_range(mapping, 0, i_size - 1); |
325 | } |
326 | EXPORT_SYMBOL(filemap_fdatawait); |
327 | |
328 | int filemap_write_and_wait(struct address_space *mapping) |
329 | { |
330 | int err = 0; |
331 | |
332 | if (mapping->nrpages) { |
333 | err = filemap_fdatawrite(mapping); |
334 | /* |
335 | * Even if the above returned error, the pages may be |
336 | * written partially (e.g. -ENOSPC), so we wait for it. |
337 | * But the -EIO is special case, it may indicate the worst |
338 | * thing (e.g. bug) happened, so we avoid waiting for it. |
339 | */ |
340 | if (err != -EIO) { |
341 | int err2 = filemap_fdatawait(mapping); |
342 | if (!err) |
343 | err = err2; |
344 | } |
345 | } |
346 | return err; |
347 | } |
348 | EXPORT_SYMBOL(filemap_write_and_wait); |
349 | |
350 | /** |
351 | * filemap_write_and_wait_range - write out & wait on a file range |
352 | * @mapping: the address_space for the pages |
353 | * @lstart: offset in bytes where the range starts |
354 | * @lend: offset in bytes where the range ends (inclusive) |
355 | * |
356 | * Write out and wait upon file offsets lstart->lend, inclusive. |
357 | * |
358 | * Note that `lend' is inclusive (describes the last byte to be written) so |
359 | * that this function can be used to write to the very end-of-file (end = -1). |
360 | */ |
361 | int filemap_write_and_wait_range(struct address_space *mapping, |
362 | loff_t lstart, loff_t lend) |
363 | { |
364 | int err = 0; |
365 | |
366 | if (mapping->nrpages) { |
367 | err = __filemap_fdatawrite_range(mapping, lstart, lend, |
368 | WB_SYNC_ALL); |
369 | /* See comment of filemap_write_and_wait() */ |
370 | if (err != -EIO) { |
371 | int err2 = filemap_fdatawait_range(mapping, |
372 | lstart, lend); |
373 | if (!err) |
374 | err = err2; |
375 | } |
376 | } |
377 | return err; |
378 | } |
379 | EXPORT_SYMBOL(filemap_write_and_wait_range); |
380 | |
381 | /** |
382 | * replace_page_cache_page - replace a pagecache page with a new one |
383 | * @old: page to be replaced |
384 | * @new: page to replace with |
385 | * @gfp_mask: allocation mode |
386 | * |
387 | * This function replaces a page in the pagecache with a new one. On |
388 | * success it acquires the pagecache reference for the new page and |
389 | * drops it for the old page. Both the old and new pages must be |
390 | * locked. This function does not add the new page to the LRU, the |
391 | * caller must do that. |
392 | * |
393 | * The remove + add is atomic. The only way this function can fail is |
394 | * memory allocation failure. |
395 | */ |
396 | int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) |
397 | { |
398 | int error; |
399 | struct mem_cgroup *memcg = NULL; |
400 | |
401 | VM_BUG_ON(!PageLocked(old)); |
402 | VM_BUG_ON(!PageLocked(new)); |
403 | VM_BUG_ON(new->mapping); |
404 | |
405 | /* |
406 | * This is not page migration, but prepare_migration and |
407 | * end_migration does enough work for charge replacement. |
408 | * |
409 | * In the longer term we probably want a specialized function |
410 | * for moving the charge from old to new in a more efficient |
411 | * manner. |
412 | */ |
413 | error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask); |
414 | if (error) |
415 | return error; |
416 | |
417 | error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); |
418 | if (!error) { |
419 | struct address_space *mapping = old->mapping; |
420 | void (*freepage)(struct page *); |
421 | |
422 | pgoff_t offset = old->index; |
423 | freepage = mapping->a_ops->freepage; |
424 | |
425 | page_cache_get(new); |
426 | new->mapping = mapping; |
427 | new->index = offset; |
428 | |
429 | spin_lock_irq(&mapping->tree_lock); |
430 | __delete_from_page_cache(old); |
431 | error = radix_tree_insert(&mapping->page_tree, offset, new); |
432 | BUG_ON(error); |
433 | mapping->nrpages++; |
434 | __inc_zone_page_state(new, NR_FILE_PAGES); |
435 | if (PageSwapBacked(new)) |
436 | __inc_zone_page_state(new, NR_SHMEM); |
437 | spin_unlock_irq(&mapping->tree_lock); |
438 | radix_tree_preload_end(); |
439 | if (freepage) |
440 | freepage(old); |
441 | page_cache_release(old); |
442 | mem_cgroup_end_migration(memcg, old, new, true); |
443 | } else { |
444 | mem_cgroup_end_migration(memcg, old, new, false); |
445 | } |
446 | |
447 | return error; |
448 | } |
449 | EXPORT_SYMBOL_GPL(replace_page_cache_page); |
450 | |
451 | /** |
452 | * add_to_page_cache_locked - add a locked page to the pagecache |
453 | * @page: page to add |
454 | * @mapping: the page's address_space |
455 | * @offset: page index |
456 | * @gfp_mask: page allocation mode |
457 | * |
458 | * This function is used to add a page to the pagecache. It must be locked. |
459 | * This function does not add the page to the LRU. The caller must do that. |
460 | */ |
461 | int add_to_page_cache_locked(struct page *page, struct address_space *mapping, |
462 | pgoff_t offset, gfp_t gfp_mask) |
463 | { |
464 | int error; |
465 | |
466 | VM_BUG_ON(!PageLocked(page)); |
467 | |
468 | error = mem_cgroup_cache_charge(page, current->mm, |
469 | gfp_mask & GFP_RECLAIM_MASK); |
470 | if (error) |
471 | goto out; |
472 | |
473 | error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); |
474 | if (error == 0) { |
475 | page_cache_get(page); |
476 | page->mapping = mapping; |
477 | page->index = offset; |
478 | |
479 | spin_lock_irq(&mapping->tree_lock); |
480 | error = radix_tree_insert(&mapping->page_tree, offset, page); |
481 | if (likely(!error)) { |
482 | mapping->nrpages++; |
483 | __inc_zone_page_state(page, NR_FILE_PAGES); |
484 | if (PageSwapBacked(page)) |
485 | __inc_zone_page_state(page, NR_SHMEM); |
486 | spin_unlock_irq(&mapping->tree_lock); |
487 | } else { |
488 | page->mapping = NULL; |
489 | spin_unlock_irq(&mapping->tree_lock); |
490 | mem_cgroup_uncharge_cache_page(page); |
491 | page_cache_release(page); |
492 | } |
493 | radix_tree_preload_end(); |
494 | } else |
495 | mem_cgroup_uncharge_cache_page(page); |
496 | out: |
497 | return error; |
498 | } |
499 | EXPORT_SYMBOL(add_to_page_cache_locked); |
500 | |
501 | int add_to_page_cache_lru(struct page *page, struct address_space *mapping, |
502 | pgoff_t offset, gfp_t gfp_mask) |
503 | { |
504 | int ret; |
505 | |
506 | /* |
507 | * Splice_read and readahead add shmem/tmpfs pages into the page cache |
508 | * before shmem_readpage has a chance to mark them as SwapBacked: they |
509 | * need to go on the anon lru below, and mem_cgroup_cache_charge |
510 | * (called in add_to_page_cache) needs to know where they're going too. |
511 | */ |
512 | if (mapping_cap_swap_backed(mapping)) |
513 | SetPageSwapBacked(page); |
514 | |
515 | ret = add_to_page_cache(page, mapping, offset, gfp_mask); |
516 | if (ret == 0) { |
517 | if (page_is_file_cache(page)) |
518 | lru_cache_add_file(page); |
519 | else |
520 | lru_cache_add_anon(page); |
521 | } |
522 | return ret; |
523 | } |
524 | EXPORT_SYMBOL_GPL(add_to_page_cache_lru); |
525 | |
526 | #ifdef CONFIG_NUMA |
527 | struct page *__page_cache_alloc(gfp_t gfp) |
528 | { |
529 | int n; |
530 | struct page *page; |
531 | |
532 | if (cpuset_do_page_mem_spread()) { |
533 | get_mems_allowed(); |
534 | n = cpuset_mem_spread_node(); |
535 | page = alloc_pages_exact_node(n, gfp, 0); |
536 | put_mems_allowed(); |
537 | return page; |
538 | } |
539 | return alloc_pages(gfp, 0); |
540 | } |
541 | EXPORT_SYMBOL(__page_cache_alloc); |
542 | #endif |
543 | |
544 | /* |
545 | * In order to wait for pages to become available there must be |
546 | * waitqueues associated with pages. By using a hash table of |
547 | * waitqueues where the bucket discipline is to maintain all |
548 | * waiters on the same queue and wake all when any of the pages |
549 | * become available, and for the woken contexts to check to be |
550 | * sure the appropriate page became available, this saves space |
551 | * at a cost of "thundering herd" phenomena during rare hash |
552 | * collisions. |
553 | */ |
554 | static wait_queue_head_t *page_waitqueue(struct page *page) |
555 | { |
556 | const struct zone *zone = page_zone(page); |
557 | |
558 | return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)]; |
559 | } |
560 | |
561 | static inline void wake_up_page(struct page *page, int bit) |
562 | { |
563 | __wake_up_bit(page_waitqueue(page), &page->flags, bit); |
564 | } |
565 | |
566 | void wait_on_page_bit(struct page *page, int bit_nr) |
567 | { |
568 | DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); |
569 | |
570 | if (test_bit(bit_nr, &page->flags)) |
571 | __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page, |
572 | TASK_UNINTERRUPTIBLE); |
573 | } |
574 | EXPORT_SYMBOL(wait_on_page_bit); |
575 | |
576 | int wait_on_page_bit_killable(struct page *page, int bit_nr) |
577 | { |
578 | DEFINE_WAIT_BIT(wait, &page->flags, bit_nr); |
579 | |
580 | if (!test_bit(bit_nr, &page->flags)) |
581 | return 0; |
582 | |
583 | return __wait_on_bit(page_waitqueue(page), &wait, |
584 | sleep_on_page_killable, TASK_KILLABLE); |
585 | } |
586 | |
587 | /** |
588 | * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue |
589 | * @page: Page defining the wait queue of interest |
590 | * @waiter: Waiter to add to the queue |
591 | * |
592 | * Add an arbitrary @waiter to the wait queue for the nominated @page. |
593 | */ |
594 | void add_page_wait_queue(struct page *page, wait_queue_t *waiter) |
595 | { |
596 | wait_queue_head_t *q = page_waitqueue(page); |
597 | unsigned long flags; |
598 | |
599 | spin_lock_irqsave(&q->lock, flags); |
600 | __add_wait_queue(q, waiter); |
601 | spin_unlock_irqrestore(&q->lock, flags); |
602 | } |
603 | EXPORT_SYMBOL_GPL(add_page_wait_queue); |
604 | |
605 | /** |
606 | * unlock_page - unlock a locked page |
607 | * @page: the page |
608 | * |
609 | * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). |
610 | * Also wakes sleepers in wait_on_page_writeback() because the wakeup |
611 | * mechananism between PageLocked pages and PageWriteback pages is shared. |
612 | * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. |
613 | * |
614 | * The mb is necessary to enforce ordering between the clear_bit and the read |
615 | * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()). |
616 | */ |
617 | void unlock_page(struct page *page) |
618 | { |
619 | VM_BUG_ON(!PageLocked(page)); |
620 | clear_bit_unlock(PG_locked, &page->flags); |
621 | smp_mb__after_clear_bit(); |
622 | wake_up_page(page, PG_locked); |
623 | } |
624 | EXPORT_SYMBOL(unlock_page); |
625 | |
626 | /** |
627 | * end_page_writeback - end writeback against a page |
628 | * @page: the page |
629 | */ |
630 | void end_page_writeback(struct page *page) |
631 | { |
632 | if (TestClearPageReclaim(page)) |
633 | rotate_reclaimable_page(page); |
634 | |
635 | if (!test_clear_page_writeback(page)) |
636 | BUG(); |
637 | |
638 | smp_mb__after_clear_bit(); |
639 | wake_up_page(page, PG_writeback); |
640 | } |
641 | EXPORT_SYMBOL(end_page_writeback); |
642 | |
643 | /** |
644 | * __lock_page - get a lock on the page, assuming we need to sleep to get it |
645 | * @page: the page to lock |
646 | */ |
647 | void __lock_page(struct page *page) |
648 | { |
649 | DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); |
650 | |
651 | __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page, |
652 | TASK_UNINTERRUPTIBLE); |
653 | } |
654 | EXPORT_SYMBOL(__lock_page); |
655 | |
656 | int __lock_page_killable(struct page *page) |
657 | { |
658 | DEFINE_WAIT_BIT(wait, &page->flags, PG_locked); |
659 | |
660 | return __wait_on_bit_lock(page_waitqueue(page), &wait, |
661 | sleep_on_page_killable, TASK_KILLABLE); |
662 | } |
663 | EXPORT_SYMBOL_GPL(__lock_page_killable); |
664 | |
665 | int __lock_page_or_retry(struct page *page, struct mm_struct *mm, |
666 | unsigned int flags) |
667 | { |
668 | if (flags & FAULT_FLAG_ALLOW_RETRY) { |
669 | /* |
670 | * CAUTION! In this case, mmap_sem is not released |
671 | * even though return 0. |
672 | */ |
673 | if (flags & FAULT_FLAG_RETRY_NOWAIT) |
674 | return 0; |
675 | |
676 | up_read(&mm->mmap_sem); |
677 | if (flags & FAULT_FLAG_KILLABLE) |
678 | wait_on_page_locked_killable(page); |
679 | else |
680 | wait_on_page_locked(page); |
681 | return 0; |
682 | } else { |
683 | if (flags & FAULT_FLAG_KILLABLE) { |
684 | int ret; |
685 | |
686 | ret = __lock_page_killable(page); |
687 | if (ret) { |
688 | up_read(&mm->mmap_sem); |
689 | return 0; |
690 | } |
691 | } else |
692 | __lock_page(page); |
693 | return 1; |
694 | } |
695 | } |
696 | |
697 | /** |
698 | * find_get_page - find and get a page reference |
699 | * @mapping: the address_space to search |
700 | * @offset: the page index |
701 | * |
702 | * Is there a pagecache struct page at the given (mapping, offset) tuple? |
703 | * If yes, increment its refcount and return it; if no, return NULL. |
704 | */ |
705 | struct page *find_get_page(struct address_space *mapping, pgoff_t offset) |
706 | { |
707 | void **pagep; |
708 | struct page *page; |
709 | |
710 | rcu_read_lock(); |
711 | repeat: |
712 | page = NULL; |
713 | pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); |
714 | if (pagep) { |
715 | page = radix_tree_deref_slot(pagep); |
716 | if (unlikely(!page)) |
717 | goto out; |
718 | if (radix_tree_deref_retry(page)) |
719 | goto repeat; |
720 | |
721 | if (!page_cache_get_speculative(page)) |
722 | goto repeat; |
723 | |
724 | /* |
725 | * Has the page moved? |
726 | * This is part of the lockless pagecache protocol. See |
727 | * include/linux/pagemap.h for details. |
728 | */ |
729 | if (unlikely(page != *pagep)) { |
730 | page_cache_release(page); |
731 | goto repeat; |
732 | } |
733 | } |
734 | out: |
735 | rcu_read_unlock(); |
736 | |
737 | return page; |
738 | } |
739 | EXPORT_SYMBOL(find_get_page); |
740 | |
741 | /** |
742 | * find_lock_page - locate, pin and lock a pagecache page |
743 | * @mapping: the address_space to search |
744 | * @offset: the page index |
745 | * |
746 | * Locates the desired pagecache page, locks it, increments its reference |
747 | * count and returns its address. |
748 | * |
749 | * Returns zero if the page was not present. find_lock_page() may sleep. |
750 | */ |
751 | struct page *find_lock_page(struct address_space *mapping, pgoff_t offset) |
752 | { |
753 | struct page *page; |
754 | |
755 | repeat: |
756 | page = find_get_page(mapping, offset); |
757 | if (page) { |
758 | lock_page(page); |
759 | /* Has the page been truncated? */ |
760 | if (unlikely(page->mapping != mapping)) { |
761 | unlock_page(page); |
762 | page_cache_release(page); |
763 | goto repeat; |
764 | } |
765 | VM_BUG_ON(page->index != offset); |
766 | } |
767 | return page; |
768 | } |
769 | EXPORT_SYMBOL(find_lock_page); |
770 | |
771 | /** |
772 | * find_or_create_page - locate or add a pagecache page |
773 | * @mapping: the page's address_space |
774 | * @index: the page's index into the mapping |
775 | * @gfp_mask: page allocation mode |
776 | * |
777 | * Locates a page in the pagecache. If the page is not present, a new page |
778 | * is allocated using @gfp_mask and is added to the pagecache and to the VM's |
779 | * LRU list. The returned page is locked and has its reference count |
780 | * incremented. |
781 | * |
782 | * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic |
783 | * allocation! |
784 | * |
785 | * find_or_create_page() returns the desired page's address, or zero on |
786 | * memory exhaustion. |
787 | */ |
788 | struct page *find_or_create_page(struct address_space *mapping, |
789 | pgoff_t index, gfp_t gfp_mask) |
790 | { |
791 | struct page *page; |
792 | int err; |
793 | repeat: |
794 | page = find_lock_page(mapping, index); |
795 | if (!page) { |
796 | page = __page_cache_alloc(gfp_mask); |
797 | if (!page) |
798 | return NULL; |
799 | /* |
800 | * We want a regular kernel memory (not highmem or DMA etc) |
801 | * allocation for the radix tree nodes, but we need to honour |
802 | * the context-specific requirements the caller has asked for. |
803 | * GFP_RECLAIM_MASK collects those requirements. |
804 | */ |
805 | err = add_to_page_cache_lru(page, mapping, index, |
806 | (gfp_mask & GFP_RECLAIM_MASK)); |
807 | if (unlikely(err)) { |
808 | page_cache_release(page); |
809 | page = NULL; |
810 | if (err == -EEXIST) |
811 | goto repeat; |
812 | } |
813 | } |
814 | return page; |
815 | } |
816 | EXPORT_SYMBOL(find_or_create_page); |
817 | |
818 | /** |
819 | * find_get_pages - gang pagecache lookup |
820 | * @mapping: The address_space to search |
821 | * @start: The starting page index |
822 | * @nr_pages: The maximum number of pages |
823 | * @pages: Where the resulting pages are placed |
824 | * |
825 | * find_get_pages() will search for and return a group of up to |
826 | * @nr_pages pages in the mapping. The pages are placed at @pages. |
827 | * find_get_pages() takes a reference against the returned pages. |
828 | * |
829 | * The search returns a group of mapping-contiguous pages with ascending |
830 | * indexes. There may be holes in the indices due to not-present pages. |
831 | * |
832 | * find_get_pages() returns the number of pages which were found. |
833 | */ |
834 | unsigned find_get_pages(struct address_space *mapping, pgoff_t start, |
835 | unsigned int nr_pages, struct page **pages) |
836 | { |
837 | unsigned int i; |
838 | unsigned int ret; |
839 | unsigned int nr_found; |
840 | |
841 | rcu_read_lock(); |
842 | restart: |
843 | nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, |
844 | (void ***)pages, start, nr_pages); |
845 | ret = 0; |
846 | for (i = 0; i < nr_found; i++) { |
847 | struct page *page; |
848 | repeat: |
849 | page = radix_tree_deref_slot((void **)pages[i]); |
850 | if (unlikely(!page)) |
851 | continue; |
852 | |
853 | /* |
854 | * This can only trigger when the entry at index 0 moves out |
855 | * of or back to the root: none yet gotten, safe to restart. |
856 | */ |
857 | if (radix_tree_deref_retry(page)) { |
858 | WARN_ON(start | i); |
859 | goto restart; |
860 | } |
861 | |
862 | if (!page_cache_get_speculative(page)) |
863 | goto repeat; |
864 | |
865 | /* Has the page moved? */ |
866 | if (unlikely(page != *((void **)pages[i]))) { |
867 | page_cache_release(page); |
868 | goto repeat; |
869 | } |
870 | |
871 | pages[ret] = page; |
872 | ret++; |
873 | } |
874 | |
875 | /* |
876 | * If all entries were removed before we could secure them, |
877 | * try again, because callers stop trying once 0 is returned. |
878 | */ |
879 | if (unlikely(!ret && nr_found)) |
880 | goto restart; |
881 | rcu_read_unlock(); |
882 | return ret; |
883 | } |
884 | |
885 | /** |
886 | * find_get_pages_contig - gang contiguous pagecache lookup |
887 | * @mapping: The address_space to search |
888 | * @index: The starting page index |
889 | * @nr_pages: The maximum number of pages |
890 | * @pages: Where the resulting pages are placed |
891 | * |
892 | * find_get_pages_contig() works exactly like find_get_pages(), except |
893 | * that the returned number of pages are guaranteed to be contiguous. |
894 | * |
895 | * find_get_pages_contig() returns the number of pages which were found. |
896 | */ |
897 | unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, |
898 | unsigned int nr_pages, struct page **pages) |
899 | { |
900 | unsigned int i; |
901 | unsigned int ret; |
902 | unsigned int nr_found; |
903 | |
904 | rcu_read_lock(); |
905 | restart: |
906 | nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, |
907 | (void ***)pages, index, nr_pages); |
908 | ret = 0; |
909 | for (i = 0; i < nr_found; i++) { |
910 | struct page *page; |
911 | repeat: |
912 | page = radix_tree_deref_slot((void **)pages[i]); |
913 | if (unlikely(!page)) |
914 | continue; |
915 | |
916 | /* |
917 | * This can only trigger when the entry at index 0 moves out |
918 | * of or back to the root: none yet gotten, safe to restart. |
919 | */ |
920 | if (radix_tree_deref_retry(page)) |
921 | goto restart; |
922 | |
923 | if (!page_cache_get_speculative(page)) |
924 | goto repeat; |
925 | |
926 | /* Has the page moved? */ |
927 | if (unlikely(page != *((void **)pages[i]))) { |
928 | page_cache_release(page); |
929 | goto repeat; |
930 | } |
931 | |
932 | /* |
933 | * must check mapping and index after taking the ref. |
934 | * otherwise we can get both false positives and false |
935 | * negatives, which is just confusing to the caller. |
936 | */ |
937 | if (page->mapping == NULL || page->index != index) { |
938 | page_cache_release(page); |
939 | break; |
940 | } |
941 | |
942 | pages[ret] = page; |
943 | ret++; |
944 | index++; |
945 | } |
946 | rcu_read_unlock(); |
947 | return ret; |
948 | } |
949 | EXPORT_SYMBOL(find_get_pages_contig); |
950 | |
951 | /** |
952 | * find_get_pages_tag - find and return pages that match @tag |
953 | * @mapping: the address_space to search |
954 | * @index: the starting page index |
955 | * @tag: the tag index |
956 | * @nr_pages: the maximum number of pages |
957 | * @pages: where the resulting pages are placed |
958 | * |
959 | * Like find_get_pages, except we only return pages which are tagged with |
960 | * @tag. We update @index to index the next page for the traversal. |
961 | */ |
962 | unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, |
963 | int tag, unsigned int nr_pages, struct page **pages) |
964 | { |
965 | unsigned int i; |
966 | unsigned int ret; |
967 | unsigned int nr_found; |
968 | |
969 | rcu_read_lock(); |
970 | restart: |
971 | nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree, |
972 | (void ***)pages, *index, nr_pages, tag); |
973 | ret = 0; |
974 | for (i = 0; i < nr_found; i++) { |
975 | struct page *page; |
976 | repeat: |
977 | page = radix_tree_deref_slot((void **)pages[i]); |
978 | if (unlikely(!page)) |
979 | continue; |
980 | |
981 | /* |
982 | * This can only trigger when the entry at index 0 moves out |
983 | * of or back to the root: none yet gotten, safe to restart. |
984 | */ |
985 | if (radix_tree_deref_retry(page)) |
986 | goto restart; |
987 | |
988 | if (!page_cache_get_speculative(page)) |
989 | goto repeat; |
990 | |
991 | /* Has the page moved? */ |
992 | if (unlikely(page != *((void **)pages[i]))) { |
993 | page_cache_release(page); |
994 | goto repeat; |
995 | } |
996 | |
997 | pages[ret] = page; |
998 | ret++; |
999 | } |
1000 | |
1001 | /* |
1002 | * If all entries were removed before we could secure them, |
1003 | * try again, because callers stop trying once 0 is returned. |
1004 | */ |
1005 | if (unlikely(!ret && nr_found)) |
1006 | goto restart; |
1007 | rcu_read_unlock(); |
1008 | |
1009 | if (ret) |
1010 | *index = pages[ret - 1]->index + 1; |
1011 | |
1012 | return ret; |
1013 | } |
1014 | EXPORT_SYMBOL(find_get_pages_tag); |
1015 | |
1016 | /** |
1017 | * grab_cache_page_nowait - returns locked page at given index in given cache |
1018 | * @mapping: target address_space |
1019 | * @index: the page index |
1020 | * |
1021 | * Same as grab_cache_page(), but do not wait if the page is unavailable. |
1022 | * This is intended for speculative data generators, where the data can |
1023 | * be regenerated if the page couldn't be grabbed. This routine should |
1024 | * be safe to call while holding the lock for another page. |
1025 | * |
1026 | * Clear __GFP_FS when allocating the page to avoid recursion into the fs |
1027 | * and deadlock against the caller's locked page. |
1028 | */ |
1029 | struct page * |
1030 | grab_cache_page_nowait(struct address_space *mapping, pgoff_t index) |
1031 | { |
1032 | struct page *page = find_get_page(mapping, index); |
1033 | |
1034 | if (page) { |
1035 | if (trylock_page(page)) |
1036 | return page; |
1037 | page_cache_release(page); |
1038 | return NULL; |
1039 | } |
1040 | page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); |
1041 | if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) { |
1042 | page_cache_release(page); |
1043 | page = NULL; |
1044 | } |
1045 | return page; |
1046 | } |
1047 | EXPORT_SYMBOL(grab_cache_page_nowait); |
1048 | |
1049 | /* |
1050 | * CD/DVDs are error prone. When a medium error occurs, the driver may fail |
1051 | * a _large_ part of the i/o request. Imagine the worst scenario: |
1052 | * |
1053 | * ---R__________________________________________B__________ |
1054 | * ^ reading here ^ bad block(assume 4k) |
1055 | * |
1056 | * read(R) => miss => readahead(R...B) => media error => frustrating retries |
1057 | * => failing the whole request => read(R) => read(R+1) => |
1058 | * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => |
1059 | * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => |
1060 | * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... |
1061 | * |
1062 | * It is going insane. Fix it by quickly scaling down the readahead size. |
1063 | */ |
1064 | static void shrink_readahead_size_eio(struct file *filp, |
1065 | struct file_ra_state *ra) |
1066 | { |
1067 | ra->ra_pages /= 4; |
1068 | } |
1069 | |
1070 | /** |
1071 | * do_generic_file_read - generic file read routine |
1072 | * @filp: the file to read |
1073 | * @ppos: current file position |
1074 | * @desc: read_descriptor |
1075 | * @actor: read method |
1076 | * |
1077 | * This is a generic file read routine, and uses the |
1078 | * mapping->a_ops->readpage() function for the actual low-level stuff. |
1079 | * |
1080 | * This is really ugly. But the goto's actually try to clarify some |
1081 | * of the logic when it comes to error handling etc. |
1082 | */ |
1083 | static void do_generic_file_read(struct file *filp, loff_t *ppos, |
1084 | read_descriptor_t *desc, read_actor_t actor) |
1085 | { |
1086 | struct address_space *mapping = filp->f_mapping; |
1087 | struct inode *inode = mapping->host; |
1088 | struct file_ra_state *ra = &filp->f_ra; |
1089 | pgoff_t index; |
1090 | pgoff_t last_index; |
1091 | pgoff_t prev_index; |
1092 | unsigned long offset; /* offset into pagecache page */ |
1093 | unsigned int prev_offset; |
1094 | int error; |
1095 | |
1096 | index = *ppos >> PAGE_CACHE_SHIFT; |
1097 | prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT; |
1098 | prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1); |
1099 | last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; |
1100 | offset = *ppos & ~PAGE_CACHE_MASK; |
1101 | |
1102 | for (;;) { |
1103 | struct page *page; |
1104 | pgoff_t end_index; |
1105 | loff_t isize; |
1106 | unsigned long nr, ret; |
1107 | |
1108 | cond_resched(); |
1109 | find_page: |
1110 | page = find_get_page(mapping, index); |
1111 | if (!page) { |
1112 | page_cache_sync_readahead(mapping, |
1113 | ra, filp, |
1114 | index, last_index - index); |
1115 | page = find_get_page(mapping, index); |
1116 | if (unlikely(page == NULL)) |
1117 | goto no_cached_page; |
1118 | } |
1119 | if (PageReadahead(page)) { |
1120 | page_cache_async_readahead(mapping, |
1121 | ra, filp, page, |
1122 | index, last_index - index); |
1123 | } |
1124 | if (!PageUptodate(page)) { |
1125 | if (inode->i_blkbits == PAGE_CACHE_SHIFT || |
1126 | !mapping->a_ops->is_partially_uptodate) |
1127 | goto page_not_up_to_date; |
1128 | if (!trylock_page(page)) |
1129 | goto page_not_up_to_date; |
1130 | /* Did it get truncated before we got the lock? */ |
1131 | if (!page->mapping) |
1132 | goto page_not_up_to_date_locked; |
1133 | if (!mapping->a_ops->is_partially_uptodate(page, |
1134 | desc, offset)) |
1135 | goto page_not_up_to_date_locked; |
1136 | unlock_page(page); |
1137 | } |
1138 | page_ok: |
1139 | /* |
1140 | * i_size must be checked after we know the page is Uptodate. |
1141 | * |
1142 | * Checking i_size after the check allows us to calculate |
1143 | * the correct value for "nr", which means the zero-filled |
1144 | * part of the page is not copied back to userspace (unless |
1145 | * another truncate extends the file - this is desired though). |
1146 | */ |
1147 | |
1148 | isize = i_size_read(inode); |
1149 | end_index = (isize - 1) >> PAGE_CACHE_SHIFT; |
1150 | if (unlikely(!isize || index > end_index)) { |
1151 | page_cache_release(page); |
1152 | goto out; |
1153 | } |
1154 | |
1155 | /* nr is the maximum number of bytes to copy from this page */ |
1156 | nr = PAGE_CACHE_SIZE; |
1157 | if (index == end_index) { |
1158 | nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; |
1159 | if (nr <= offset) { |
1160 | page_cache_release(page); |
1161 | goto out; |
1162 | } |
1163 | } |
1164 | nr = nr - offset; |
1165 | |
1166 | /* If users can be writing to this page using arbitrary |
1167 | * virtual addresses, take care about potential aliasing |
1168 | * before reading the page on the kernel side. |
1169 | */ |
1170 | if (mapping_writably_mapped(mapping)) |
1171 | flush_dcache_page(page); |
1172 | |
1173 | /* |
1174 | * When a sequential read accesses a page several times, |
1175 | * only mark it as accessed the first time. |
1176 | */ |
1177 | if (prev_index != index || offset != prev_offset) |
1178 | mark_page_accessed(page); |
1179 | prev_index = index; |
1180 | |
1181 | /* |
1182 | * Ok, we have the page, and it's up-to-date, so |
1183 | * now we can copy it to user space... |
1184 | * |
1185 | * The actor routine returns how many bytes were actually used.. |
1186 | * NOTE! This may not be the same as how much of a user buffer |
1187 | * we filled up (we may be padding etc), so we can only update |
1188 | * "pos" here (the actor routine has to update the user buffer |
1189 | * pointers and the remaining count). |
1190 | */ |
1191 | ret = actor(desc, page, offset, nr); |
1192 | offset += ret; |
1193 | index += offset >> PAGE_CACHE_SHIFT; |
1194 | offset &= ~PAGE_CACHE_MASK; |
1195 | prev_offset = offset; |
1196 | |
1197 | page_cache_release(page); |
1198 | if (ret == nr && desc->count) |
1199 | continue; |
1200 | goto out; |
1201 | |
1202 | page_not_up_to_date: |
1203 | /* Get exclusive access to the page ... */ |
1204 | error = lock_page_killable(page); |
1205 | if (unlikely(error)) |
1206 | goto readpage_error; |
1207 | |
1208 | page_not_up_to_date_locked: |
1209 | /* Did it get truncated before we got the lock? */ |
1210 | if (!page->mapping) { |
1211 | unlock_page(page); |
1212 | page_cache_release(page); |
1213 | continue; |
1214 | } |
1215 | |
1216 | /* Did somebody else fill it already? */ |
1217 | if (PageUptodate(page)) { |
1218 | unlock_page(page); |
1219 | goto page_ok; |
1220 | } |
1221 | |
1222 | readpage: |
1223 | /* |
1224 | * A previous I/O error may have been due to temporary |
1225 | * failures, eg. multipath errors. |
1226 | * PG_error will be set again if readpage fails. |
1227 | */ |
1228 | ClearPageError(page); |
1229 | /* Start the actual read. The read will unlock the page. */ |
1230 | error = mapping->a_ops->readpage(filp, page); |
1231 | |
1232 | if (unlikely(error)) { |
1233 | if (error == AOP_TRUNCATED_PAGE) { |
1234 | page_cache_release(page); |
1235 | goto find_page; |
1236 | } |
1237 | goto readpage_error; |
1238 | } |
1239 | |
1240 | if (!PageUptodate(page)) { |
1241 | error = lock_page_killable(page); |
1242 | if (unlikely(error)) |
1243 | goto readpage_error; |
1244 | if (!PageUptodate(page)) { |
1245 | if (page->mapping == NULL) { |
1246 | /* |
1247 | * invalidate_mapping_pages got it |
1248 | */ |
1249 | unlock_page(page); |
1250 | page_cache_release(page); |
1251 | goto find_page; |
1252 | } |
1253 | unlock_page(page); |
1254 | shrink_readahead_size_eio(filp, ra); |
1255 | error = -EIO; |
1256 | goto readpage_error; |
1257 | } |
1258 | unlock_page(page); |
1259 | } |
1260 | |
1261 | goto page_ok; |
1262 | |
1263 | readpage_error: |
1264 | /* UHHUH! A synchronous read error occurred. Report it */ |
1265 | desc->error = error; |
1266 | page_cache_release(page); |
1267 | goto out; |
1268 | |
1269 | no_cached_page: |
1270 | /* |
1271 | * Ok, it wasn't cached, so we need to create a new |
1272 | * page.. |
1273 | */ |
1274 | page = page_cache_alloc_cold(mapping); |
1275 | if (!page) { |
1276 | desc->error = -ENOMEM; |
1277 | goto out; |
1278 | } |
1279 | error = add_to_page_cache_lru(page, mapping, |
1280 | index, GFP_KERNEL); |
1281 | if (error) { |
1282 | page_cache_release(page); |
1283 | if (error == -EEXIST) |
1284 | goto find_page; |
1285 | desc->error = error; |
1286 | goto out; |
1287 | } |
1288 | goto readpage; |
1289 | } |
1290 | |
1291 | out: |
1292 | ra->prev_pos = prev_index; |
1293 | ra->prev_pos <<= PAGE_CACHE_SHIFT; |
1294 | ra->prev_pos |= prev_offset; |
1295 | |
1296 | *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset; |
1297 | file_accessed(filp); |
1298 | } |
1299 | |
1300 | int file_read_actor(read_descriptor_t *desc, struct page *page, |
1301 | unsigned long offset, unsigned long size) |
1302 | { |
1303 | char *kaddr; |
1304 | unsigned long left, count = desc->count; |
1305 | |
1306 | if (size > count) |
1307 | size = count; |
1308 | |
1309 | /* |
1310 | * Faults on the destination of a read are common, so do it before |
1311 | * taking the kmap. |
1312 | */ |
1313 | if (!fault_in_pages_writeable(desc->arg.buf, size)) { |
1314 | kaddr = kmap_atomic(page, KM_USER0); |
1315 | left = __copy_to_user_inatomic(desc->arg.buf, |
1316 | kaddr + offset, size); |
1317 | kunmap_atomic(kaddr, KM_USER0); |
1318 | if (left == 0) |
1319 | goto success; |
1320 | } |
1321 | |
1322 | /* Do it the slow way */ |
1323 | kaddr = kmap(page); |
1324 | left = __copy_to_user(desc->arg.buf, kaddr + offset, size); |
1325 | kunmap(page); |
1326 | |
1327 | if (left) { |
1328 | size -= left; |
1329 | desc->error = -EFAULT; |
1330 | } |
1331 | success: |
1332 | desc->count = count - size; |
1333 | desc->written += size; |
1334 | desc->arg.buf += size; |
1335 | return size; |
1336 | } |
1337 | |
1338 | /* |
1339 | * Performs necessary checks before doing a write |
1340 | * @iov: io vector request |
1341 | * @nr_segs: number of segments in the iovec |
1342 | * @count: number of bytes to write |
1343 | * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE |
1344 | * |
1345 | * Adjust number of segments and amount of bytes to write (nr_segs should be |
1346 | * properly initialized first). Returns appropriate error code that caller |
1347 | * should return or zero in case that write should be allowed. |
1348 | */ |
1349 | int generic_segment_checks(const struct iovec *iov, |
1350 | unsigned long *nr_segs, size_t *count, int access_flags) |
1351 | { |
1352 | unsigned long seg; |
1353 | size_t cnt = 0; |
1354 | for (seg = 0; seg < *nr_segs; seg++) { |
1355 | const struct iovec *iv = &iov[seg]; |
1356 | |
1357 | /* |
1358 | * If any segment has a negative length, or the cumulative |
1359 | * length ever wraps negative then return -EINVAL. |
1360 | */ |
1361 | cnt += iv->iov_len; |
1362 | if (unlikely((ssize_t)(cnt|iv->iov_len) < 0)) |
1363 | return -EINVAL; |
1364 | if (access_ok(access_flags, iv->iov_base, iv->iov_len)) |
1365 | continue; |
1366 | if (seg == 0) |
1367 | return -EFAULT; |
1368 | *nr_segs = seg; |
1369 | cnt -= iv->iov_len; /* This segment is no good */ |
1370 | break; |
1371 | } |
1372 | *count = cnt; |
1373 | return 0; |
1374 | } |
1375 | EXPORT_SYMBOL(generic_segment_checks); |
1376 | |
1377 | /** |
1378 | * generic_file_aio_read - generic filesystem read routine |
1379 | * @iocb: kernel I/O control block |
1380 | * @iov: io vector request |
1381 | * @nr_segs: number of segments in the iovec |
1382 | * @pos: current file position |
1383 | * |
1384 | * This is the "read()" routine for all filesystems |
1385 | * that can use the page cache directly. |
1386 | */ |
1387 | ssize_t |
1388 | generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, |
1389 | unsigned long nr_segs, loff_t pos) |
1390 | { |
1391 | struct file *filp = iocb->ki_filp; |
1392 | ssize_t retval; |
1393 | unsigned long seg = 0; |
1394 | size_t count; |
1395 | loff_t *ppos = &iocb->ki_pos; |
1396 | struct blk_plug plug; |
1397 | |
1398 | count = 0; |
1399 | retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); |
1400 | if (retval) |
1401 | return retval; |
1402 | |
1403 | blk_start_plug(&plug); |
1404 | |
1405 | /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ |
1406 | if (filp->f_flags & O_DIRECT) { |
1407 | loff_t size; |
1408 | struct address_space *mapping; |
1409 | struct inode *inode; |
1410 | |
1411 | mapping = filp->f_mapping; |
1412 | inode = mapping->host; |
1413 | if (!count) |
1414 | goto out; /* skip atime */ |
1415 | size = i_size_read(inode); |
1416 | if (pos < size) { |
1417 | retval = filemap_write_and_wait_range(mapping, pos, |
1418 | pos + iov_length(iov, nr_segs) - 1); |
1419 | if (!retval) { |
1420 | retval = mapping->a_ops->direct_IO(READ, iocb, |
1421 | iov, pos, nr_segs); |
1422 | } |
1423 | if (retval > 0) { |
1424 | *ppos = pos + retval; |
1425 | count -= retval; |
1426 | } |
1427 | |
1428 | /* |
1429 | * Btrfs can have a short DIO read if we encounter |
1430 | * compressed extents, so if there was an error, or if |
1431 | * we've already read everything we wanted to, or if |
1432 | * there was a short read because we hit EOF, go ahead |
1433 | * and return. Otherwise fallthrough to buffered io for |
1434 | * the rest of the read. |
1435 | */ |
1436 | if (retval < 0 || !count || *ppos >= size) { |
1437 | file_accessed(filp); |
1438 | goto out; |
1439 | } |
1440 | } |
1441 | } |
1442 | |
1443 | count = retval; |
1444 | for (seg = 0; seg < nr_segs; seg++) { |
1445 | read_descriptor_t desc; |
1446 | loff_t offset = 0; |
1447 | |
1448 | /* |
1449 | * If we did a short DIO read we need to skip the section of the |
1450 | * iov that we've already read data into. |
1451 | */ |
1452 | if (count) { |
1453 | if (count > iov[seg].iov_len) { |
1454 | count -= iov[seg].iov_len; |
1455 | continue; |
1456 | } |
1457 | offset = count; |
1458 | count = 0; |
1459 | } |
1460 | |
1461 | desc.written = 0; |
1462 | desc.arg.buf = iov[seg].iov_base + offset; |
1463 | desc.count = iov[seg].iov_len - offset; |
1464 | if (desc.count == 0) |
1465 | continue; |
1466 | desc.error = 0; |
1467 | do_generic_file_read(filp, ppos, &desc, file_read_actor); |
1468 | retval += desc.written; |
1469 | if (desc.error) { |
1470 | retval = retval ?: desc.error; |
1471 | break; |
1472 | } |
1473 | if (desc.count > 0) |
1474 | break; |
1475 | } |
1476 | out: |
1477 | blk_finish_plug(&plug); |
1478 | return retval; |
1479 | } |
1480 | EXPORT_SYMBOL(generic_file_aio_read); |
1481 | |
1482 | static ssize_t |
1483 | do_readahead(struct address_space *mapping, struct file *filp, |
1484 | pgoff_t index, unsigned long nr) |
1485 | { |
1486 | if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage) |
1487 | return -EINVAL; |
1488 | |
1489 | force_page_cache_readahead(mapping, filp, index, nr); |
1490 | return 0; |
1491 | } |
1492 | |
1493 | SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count) |
1494 | { |
1495 | ssize_t ret; |
1496 | struct file *file; |
1497 | |
1498 | ret = -EBADF; |
1499 | file = fget(fd); |
1500 | if (file) { |
1501 | if (file->f_mode & FMODE_READ) { |
1502 | struct address_space *mapping = file->f_mapping; |
1503 | pgoff_t start = offset >> PAGE_CACHE_SHIFT; |
1504 | pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT; |
1505 | unsigned long len = end - start + 1; |
1506 | ret = do_readahead(mapping, file, start, len); |
1507 | } |
1508 | fput(file); |
1509 | } |
1510 | return ret; |
1511 | } |
1512 | #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS |
1513 | asmlinkage long SyS_readahead(long fd, loff_t offset, long count) |
1514 | { |
1515 | return SYSC_readahead((int) fd, offset, (size_t) count); |
1516 | } |
1517 | SYSCALL_ALIAS(sys_readahead, SyS_readahead); |
1518 | #endif |
1519 | |
1520 | #ifdef CONFIG_MMU |
1521 | /** |
1522 | * page_cache_read - adds requested page to the page cache if not already there |
1523 | * @file: file to read |
1524 | * @offset: page index |
1525 | * |
1526 | * This adds the requested page to the page cache if it isn't already there, |
1527 | * and schedules an I/O to read in its contents from disk. |
1528 | */ |
1529 | static int page_cache_read(struct file *file, pgoff_t offset) |
1530 | { |
1531 | struct address_space *mapping = file->f_mapping; |
1532 | struct page *page; |
1533 | int ret; |
1534 | |
1535 | do { |
1536 | page = page_cache_alloc_cold(mapping); |
1537 | if (!page) |
1538 | return -ENOMEM; |
1539 | |
1540 | ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL); |
1541 | if (ret == 0) |
1542 | ret = mapping->a_ops->readpage(file, page); |
1543 | else if (ret == -EEXIST) |
1544 | ret = 0; /* losing race to add is OK */ |
1545 | |
1546 | page_cache_release(page); |
1547 | |
1548 | } while (ret == AOP_TRUNCATED_PAGE); |
1549 | |
1550 | return ret; |
1551 | } |
1552 | |
1553 | #define MMAP_LOTSAMISS (100) |
1554 | |
1555 | /* |
1556 | * Synchronous readahead happens when we don't even find |
1557 | * a page in the page cache at all. |
1558 | */ |
1559 | static void do_sync_mmap_readahead(struct vm_area_struct *vma, |
1560 | struct file_ra_state *ra, |
1561 | struct file *file, |
1562 | pgoff_t offset) |
1563 | { |
1564 | unsigned long ra_pages; |
1565 | struct address_space *mapping = file->f_mapping; |
1566 | |
1567 | /* If we don't want any read-ahead, don't bother */ |
1568 | if (VM_RandomReadHint(vma)) |
1569 | return; |
1570 | if (!ra->ra_pages) |
1571 | return; |
1572 | |
1573 | if (VM_SequentialReadHint(vma)) { |
1574 | page_cache_sync_readahead(mapping, ra, file, offset, |
1575 | ra->ra_pages); |
1576 | return; |
1577 | } |
1578 | |
1579 | /* Avoid banging the cache line if not needed */ |
1580 | if (ra->mmap_miss < MMAP_LOTSAMISS * 10) |
1581 | ra->mmap_miss++; |
1582 | |
1583 | /* |
1584 | * Do we miss much more than hit in this file? If so, |
1585 | * stop bothering with read-ahead. It will only hurt. |
1586 | */ |
1587 | if (ra->mmap_miss > MMAP_LOTSAMISS) |
1588 | return; |
1589 | |
1590 | /* |
1591 | * mmap read-around |
1592 | */ |
1593 | ra_pages = max_sane_readahead(ra->ra_pages); |
1594 | ra->start = max_t(long, 0, offset - ra_pages / 2); |
1595 | ra->size = ra_pages; |
1596 | ra->async_size = ra_pages / 4; |
1597 | ra_submit(ra, mapping, file); |
1598 | } |
1599 | |
1600 | /* |
1601 | * Asynchronous readahead happens when we find the page and PG_readahead, |
1602 | * so we want to possibly extend the readahead further.. |
1603 | */ |
1604 | static void do_async_mmap_readahead(struct vm_area_struct *vma, |
1605 | struct file_ra_state *ra, |
1606 | struct file *file, |
1607 | struct page *page, |
1608 | pgoff_t offset) |
1609 | { |
1610 | struct address_space *mapping = file->f_mapping; |
1611 | |
1612 | /* If we don't want any read-ahead, don't bother */ |
1613 | if (VM_RandomReadHint(vma)) |
1614 | return; |
1615 | if (ra->mmap_miss > 0) |
1616 | ra->mmap_miss--; |
1617 | if (PageReadahead(page)) |
1618 | page_cache_async_readahead(mapping, ra, file, |
1619 | page, offset, ra->ra_pages); |
1620 | } |
1621 | |
1622 | /** |
1623 | * filemap_fault - read in file data for page fault handling |
1624 | * @vma: vma in which the fault was taken |
1625 | * @vmf: struct vm_fault containing details of the fault |
1626 | * |
1627 | * filemap_fault() is invoked via the vma operations vector for a |
1628 | * mapped memory region to read in file data during a page fault. |
1629 | * |
1630 | * The goto's are kind of ugly, but this streamlines the normal case of having |
1631 | * it in the page cache, and handles the special cases reasonably without |
1632 | * having a lot of duplicated code. |
1633 | */ |
1634 | int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) |
1635 | { |
1636 | int error; |
1637 | struct file *file = vma->vm_file; |
1638 | struct address_space *mapping = file->f_mapping; |
1639 | struct file_ra_state *ra = &file->f_ra; |
1640 | struct inode *inode = mapping->host; |
1641 | pgoff_t offset = vmf->pgoff; |
1642 | struct page *page; |
1643 | pgoff_t size; |
1644 | int ret = 0; |
1645 | |
1646 | size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; |
1647 | if (offset >= size) |
1648 | return VM_FAULT_SIGBUS; |
1649 | |
1650 | /* |
1651 | * Do we have something in the page cache already? |
1652 | */ |
1653 | page = find_get_page(mapping, offset); |
1654 | if (likely(page)) { |
1655 | /* |
1656 | * We found the page, so try async readahead before |
1657 | * waiting for the lock. |
1658 | */ |
1659 | do_async_mmap_readahead(vma, ra, file, page, offset); |
1660 | } else { |
1661 | /* No page in the page cache at all */ |
1662 | do_sync_mmap_readahead(vma, ra, file, offset); |
1663 | count_vm_event(PGMAJFAULT); |
1664 | mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); |
1665 | ret = VM_FAULT_MAJOR; |
1666 | retry_find: |
1667 | page = find_get_page(mapping, offset); |
1668 | if (!page) |
1669 | goto no_cached_page; |
1670 | } |
1671 | |
1672 | if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) { |
1673 | page_cache_release(page); |
1674 | return ret | VM_FAULT_RETRY; |
1675 | } |
1676 | |
1677 | /* Did it get truncated? */ |
1678 | if (unlikely(page->mapping != mapping)) { |
1679 | unlock_page(page); |
1680 | put_page(page); |
1681 | goto retry_find; |
1682 | } |
1683 | VM_BUG_ON(page->index != offset); |
1684 | |
1685 | /* |
1686 | * We have a locked page in the page cache, now we need to check |
1687 | * that it's up-to-date. If not, it is going to be due to an error. |
1688 | */ |
1689 | if (unlikely(!PageUptodate(page))) |
1690 | goto page_not_uptodate; |
1691 | |
1692 | /* |
1693 | * Found the page and have a reference on it. |
1694 | * We must recheck i_size under page lock. |
1695 | */ |
1696 | size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; |
1697 | if (unlikely(offset >= size)) { |
1698 | unlock_page(page); |
1699 | page_cache_release(page); |
1700 | return VM_FAULT_SIGBUS; |
1701 | } |
1702 | |
1703 | vmf->page = page; |
1704 | return ret | VM_FAULT_LOCKED; |
1705 | |
1706 | no_cached_page: |
1707 | /* |
1708 | * We're only likely to ever get here if MADV_RANDOM is in |
1709 | * effect. |
1710 | */ |
1711 | error = page_cache_read(file, offset); |
1712 | |
1713 | /* |
1714 | * The page we want has now been added to the page cache. |
1715 | * In the unlikely event that someone removed it in the |
1716 | * meantime, we'll just come back here and read it again. |
1717 | */ |
1718 | if (error >= 0) |
1719 | goto retry_find; |
1720 | |
1721 | /* |
1722 | * An error return from page_cache_read can result if the |
1723 | * system is low on memory, or a problem occurs while trying |
1724 | * to schedule I/O. |
1725 | */ |
1726 | if (error == -ENOMEM) |
1727 | return VM_FAULT_OOM; |
1728 | return VM_FAULT_SIGBUS; |
1729 | |
1730 | page_not_uptodate: |
1731 | /* |
1732 | * Umm, take care of errors if the page isn't up-to-date. |
1733 | * Try to re-read it _once_. We do this synchronously, |
1734 | * because there really aren't any performance issues here |
1735 | * and we need to check for errors. |
1736 | */ |
1737 | ClearPageError(page); |
1738 | error = mapping->a_ops->readpage(file, page); |
1739 | if (!error) { |
1740 | wait_on_page_locked(page); |
1741 | if (!PageUptodate(page)) |
1742 | error = -EIO; |
1743 | } |
1744 | page_cache_release(page); |
1745 | |
1746 | if (!error || error == AOP_TRUNCATED_PAGE) |
1747 | goto retry_find; |
1748 | |
1749 | /* Things didn't work out. Return zero to tell the mm layer so. */ |
1750 | shrink_readahead_size_eio(file, ra); |
1751 | return VM_FAULT_SIGBUS; |
1752 | } |
1753 | EXPORT_SYMBOL(filemap_fault); |
1754 | |
1755 | const struct vm_operations_struct generic_file_vm_ops = { |
1756 | .fault = filemap_fault, |
1757 | }; |
1758 | |
1759 | /* This is used for a general mmap of a disk file */ |
1760 | |
1761 | int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
1762 | { |
1763 | struct address_space *mapping = file->f_mapping; |
1764 | |
1765 | if (!mapping->a_ops->readpage) |
1766 | return -ENOEXEC; |
1767 | file_accessed(file); |
1768 | vma->vm_ops = &generic_file_vm_ops; |
1769 | vma->vm_flags |= VM_CAN_NONLINEAR; |
1770 | return 0; |
1771 | } |
1772 | |
1773 | /* |
1774 | * This is for filesystems which do not implement ->writepage. |
1775 | */ |
1776 | int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) |
1777 | { |
1778 | if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) |
1779 | return -EINVAL; |
1780 | return generic_file_mmap(file, vma); |
1781 | } |
1782 | #else |
1783 | int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
1784 | { |
1785 | return -ENOSYS; |
1786 | } |
1787 | int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) |
1788 | { |
1789 | return -ENOSYS; |
1790 | } |
1791 | #endif /* CONFIG_MMU */ |
1792 | |
1793 | EXPORT_SYMBOL(generic_file_mmap); |
1794 | EXPORT_SYMBOL(generic_file_readonly_mmap); |
1795 | |
1796 | static struct page *__read_cache_page(struct address_space *mapping, |
1797 | pgoff_t index, |
1798 | int (*filler)(void *,struct page*), |
1799 | void *data, |
1800 | gfp_t gfp) |
1801 | { |
1802 | struct page *page; |
1803 | int err; |
1804 | repeat: |
1805 | page = find_get_page(mapping, index); |
1806 | if (!page) { |
1807 | page = __page_cache_alloc(gfp | __GFP_COLD); |
1808 | if (!page) |
1809 | return ERR_PTR(-ENOMEM); |
1810 | err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL); |
1811 | if (unlikely(err)) { |
1812 | page_cache_release(page); |
1813 | if (err == -EEXIST) |
1814 | goto repeat; |
1815 | /* Presumably ENOMEM for radix tree node */ |
1816 | return ERR_PTR(err); |
1817 | } |
1818 | err = filler(data, page); |
1819 | if (err < 0) { |
1820 | page_cache_release(page); |
1821 | page = ERR_PTR(err); |
1822 | } |
1823 | } |
1824 | return page; |
1825 | } |
1826 | |
1827 | static struct page *do_read_cache_page(struct address_space *mapping, |
1828 | pgoff_t index, |
1829 | int (*filler)(void *,struct page*), |
1830 | void *data, |
1831 | gfp_t gfp) |
1832 | |
1833 | { |
1834 | struct page *page; |
1835 | int err; |
1836 | |
1837 | retry: |
1838 | page = __read_cache_page(mapping, index, filler, data, gfp); |
1839 | if (IS_ERR(page)) |
1840 | return page; |
1841 | if (PageUptodate(page)) |
1842 | goto out; |
1843 | |
1844 | lock_page(page); |
1845 | if (!page->mapping) { |
1846 | unlock_page(page); |
1847 | page_cache_release(page); |
1848 | goto retry; |
1849 | } |
1850 | if (PageUptodate(page)) { |
1851 | unlock_page(page); |
1852 | goto out; |
1853 | } |
1854 | err = filler(data, page); |
1855 | if (err < 0) { |
1856 | page_cache_release(page); |
1857 | return ERR_PTR(err); |
1858 | } |
1859 | out: |
1860 | mark_page_accessed(page); |
1861 | return page; |
1862 | } |
1863 | |
1864 | /** |
1865 | * read_cache_page_async - read into page cache, fill it if needed |
1866 | * @mapping: the page's address_space |
1867 | * @index: the page index |
1868 | * @filler: function to perform the read |
1869 | * @data: destination for read data |
1870 | * |
1871 | * Same as read_cache_page, but don't wait for page to become unlocked |
1872 | * after submitting it to the filler. |
1873 | * |
1874 | * Read into the page cache. If a page already exists, and PageUptodate() is |
1875 | * not set, try to fill the page but don't wait for it to become unlocked. |
1876 | * |
1877 | * If the page does not get brought uptodate, return -EIO. |
1878 | */ |
1879 | struct page *read_cache_page_async(struct address_space *mapping, |
1880 | pgoff_t index, |
1881 | int (*filler)(void *,struct page*), |
1882 | void *data) |
1883 | { |
1884 | return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping)); |
1885 | } |
1886 | EXPORT_SYMBOL(read_cache_page_async); |
1887 | |
1888 | static struct page *wait_on_page_read(struct page *page) |
1889 | { |
1890 | if (!IS_ERR(page)) { |
1891 | wait_on_page_locked(page); |
1892 | if (!PageUptodate(page)) { |
1893 | page_cache_release(page); |
1894 | page = ERR_PTR(-EIO); |
1895 | } |
1896 | } |
1897 | return page; |
1898 | } |
1899 | |
1900 | /** |
1901 | * read_cache_page_gfp - read into page cache, using specified page allocation flags. |
1902 | * @mapping: the page's address_space |
1903 | * @index: the page index |
1904 | * @gfp: the page allocator flags to use if allocating |
1905 | * |
1906 | * This is the same as "read_mapping_page(mapping, index, NULL)", but with |
1907 | * any new page allocations done using the specified allocation flags. Note |
1908 | * that the Radix tree operations will still use GFP_KERNEL, so you can't |
1909 | * expect to do this atomically or anything like that - but you can pass in |
1910 | * other page requirements. |
1911 | * |
1912 | * If the page does not get brought uptodate, return -EIO. |
1913 | */ |
1914 | struct page *read_cache_page_gfp(struct address_space *mapping, |
1915 | pgoff_t index, |
1916 | gfp_t gfp) |
1917 | { |
1918 | filler_t *filler = (filler_t *)mapping->a_ops->readpage; |
1919 | |
1920 | return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp)); |
1921 | } |
1922 | EXPORT_SYMBOL(read_cache_page_gfp); |
1923 | |
1924 | /** |
1925 | * read_cache_page - read into page cache, fill it if needed |
1926 | * @mapping: the page's address_space |
1927 | * @index: the page index |
1928 | * @filler: function to perform the read |
1929 | * @data: destination for read data |
1930 | * |
1931 | * Read into the page cache. If a page already exists, and PageUptodate() is |
1932 | * not set, try to fill the page then wait for it to become unlocked. |
1933 | * |
1934 | * If the page does not get brought uptodate, return -EIO. |
1935 | */ |
1936 | struct page *read_cache_page(struct address_space *mapping, |
1937 | pgoff_t index, |
1938 | int (*filler)(void *,struct page*), |
1939 | void *data) |
1940 | { |
1941 | return wait_on_page_read(read_cache_page_async(mapping, index, filler, data)); |
1942 | } |
1943 | EXPORT_SYMBOL(read_cache_page); |
1944 | |
1945 | /* |
1946 | * The logic we want is |
1947 | * |
1948 | * if suid or (sgid and xgrp) |
1949 | * remove privs |
1950 | */ |
1951 | int should_remove_suid(struct dentry *dentry) |
1952 | { |
1953 | mode_t mode = dentry->d_inode->i_mode; |
1954 | int kill = 0; |
1955 | |
1956 | /* suid always must be killed */ |
1957 | if (unlikely(mode & S_ISUID)) |
1958 | kill = ATTR_KILL_SUID; |
1959 | |
1960 | /* |
1961 | * sgid without any exec bits is just a mandatory locking mark; leave |
1962 | * it alone. If some exec bits are set, it's a real sgid; kill it. |
1963 | */ |
1964 | if (unlikely((mode & S_ISGID) && (mode & S_IXGRP))) |
1965 | kill |= ATTR_KILL_SGID; |
1966 | |
1967 | if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode))) |
1968 | return kill; |
1969 | |
1970 | return 0; |
1971 | } |
1972 | EXPORT_SYMBOL(should_remove_suid); |
1973 | |
1974 | static int __remove_suid(struct dentry *dentry, int kill) |
1975 | { |
1976 | struct iattr newattrs; |
1977 | |
1978 | newattrs.ia_valid = ATTR_FORCE | kill; |
1979 | return notify_change(dentry, &newattrs); |
1980 | } |
1981 | |
1982 | int file_remove_suid(struct file *file) |
1983 | { |
1984 | struct dentry *dentry = file->f_path.dentry; |
1985 | struct inode *inode = dentry->d_inode; |
1986 | int killsuid; |
1987 | int killpriv; |
1988 | int error = 0; |
1989 | |
1990 | /* Fast path for nothing security related */ |
1991 | if (IS_NOSEC(inode)) |
1992 | return 0; |
1993 | |
1994 | killsuid = should_remove_suid(dentry); |
1995 | killpriv = security_inode_need_killpriv(dentry); |
1996 | |
1997 | if (killpriv < 0) |
1998 | return killpriv; |
1999 | if (killpriv) |
2000 | error = security_inode_killpriv(dentry); |
2001 | if (!error && killsuid) |
2002 | error = __remove_suid(dentry, killsuid); |
2003 | if (!error && (inode->i_sb->s_flags & MS_NOSEC)) |
2004 | inode->i_flags |= S_NOSEC; |
2005 | |
2006 | return error; |
2007 | } |
2008 | EXPORT_SYMBOL(file_remove_suid); |
2009 | |
2010 | static size_t __iovec_copy_from_user_inatomic(char *vaddr, |
2011 | const struct iovec *iov, size_t base, size_t bytes) |
2012 | { |
2013 | size_t copied = 0, left = 0; |
2014 | |
2015 | while (bytes) { |
2016 | char __user *buf = iov->iov_base + base; |
2017 | int copy = min(bytes, iov->iov_len - base); |
2018 | |
2019 | base = 0; |
2020 | left = __copy_from_user_inatomic(vaddr, buf, copy); |
2021 | copied += copy; |
2022 | bytes -= copy; |
2023 | vaddr += copy; |
2024 | iov++; |
2025 | |
2026 | if (unlikely(left)) |
2027 | break; |
2028 | } |
2029 | return copied - left; |
2030 | } |
2031 | |
2032 | /* |
2033 | * Copy as much as we can into the page and return the number of bytes which |
2034 | * were successfully copied. If a fault is encountered then return the number of |
2035 | * bytes which were copied. |
2036 | */ |
2037 | size_t iov_iter_copy_from_user_atomic(struct page *page, |
2038 | struct iov_iter *i, unsigned long offset, size_t bytes) |
2039 | { |
2040 | char *kaddr; |
2041 | size_t copied; |
2042 | |
2043 | BUG_ON(!in_atomic()); |
2044 | kaddr = kmap_atomic(page, KM_USER0); |
2045 | if (likely(i->nr_segs == 1)) { |
2046 | int left; |
2047 | char __user *buf = i->iov->iov_base + i->iov_offset; |
2048 | left = __copy_from_user_inatomic(kaddr + offset, buf, bytes); |
2049 | copied = bytes - left; |
2050 | } else { |
2051 | copied = __iovec_copy_from_user_inatomic(kaddr + offset, |
2052 | i->iov, i->iov_offset, bytes); |
2053 | } |
2054 | kunmap_atomic(kaddr, KM_USER0); |
2055 | |
2056 | return copied; |
2057 | } |
2058 | EXPORT_SYMBOL(iov_iter_copy_from_user_atomic); |
2059 | |
2060 | /* |
2061 | * This has the same sideeffects and return value as |
2062 | * iov_iter_copy_from_user_atomic(). |
2063 | * The difference is that it attempts to resolve faults. |
2064 | * Page must not be locked. |
2065 | */ |
2066 | size_t iov_iter_copy_from_user(struct page *page, |
2067 | struct iov_iter *i, unsigned long offset, size_t bytes) |
2068 | { |
2069 | char *kaddr; |
2070 | size_t copied; |
2071 | |
2072 | kaddr = kmap(page); |
2073 | if (likely(i->nr_segs == 1)) { |
2074 | int left; |
2075 | char __user *buf = i->iov->iov_base + i->iov_offset; |
2076 | left = __copy_from_user(kaddr + offset, buf, bytes); |
2077 | copied = bytes - left; |
2078 | } else { |
2079 | copied = __iovec_copy_from_user_inatomic(kaddr + offset, |
2080 | i->iov, i->iov_offset, bytes); |
2081 | } |
2082 | kunmap(page); |
2083 | return copied; |
2084 | } |
2085 | EXPORT_SYMBOL(iov_iter_copy_from_user); |
2086 | |
2087 | void iov_iter_advance(struct iov_iter *i, size_t bytes) |
2088 | { |
2089 | BUG_ON(i->count < bytes); |
2090 | |
2091 | if (likely(i->nr_segs == 1)) { |
2092 | i->iov_offset += bytes; |
2093 | i->count -= bytes; |
2094 | } else { |
2095 | const struct iovec *iov = i->iov; |
2096 | size_t base = i->iov_offset; |
2097 | |
2098 | /* |
2099 | * The !iov->iov_len check ensures we skip over unlikely |
2100 | * zero-length segments (without overruning the iovec). |
2101 | */ |
2102 | while (bytes || unlikely(i->count && !iov->iov_len)) { |
2103 | int copy; |
2104 | |
2105 | copy = min(bytes, iov->iov_len - base); |
2106 | BUG_ON(!i->count || i->count < copy); |
2107 | i->count -= copy; |
2108 | bytes -= copy; |
2109 | base += copy; |
2110 | if (iov->iov_len == base) { |
2111 | iov++; |
2112 | base = 0; |
2113 | } |
2114 | } |
2115 | i->iov = iov; |
2116 | i->iov_offset = base; |
2117 | } |
2118 | } |
2119 | EXPORT_SYMBOL(iov_iter_advance); |
2120 | |
2121 | /* |
2122 | * Fault in the first iovec of the given iov_iter, to a maximum length |
2123 | * of bytes. Returns 0 on success, or non-zero if the memory could not be |
2124 | * accessed (ie. because it is an invalid address). |
2125 | * |
2126 | * writev-intensive code may want this to prefault several iovecs -- that |
2127 | * would be possible (callers must not rely on the fact that _only_ the |
2128 | * first iovec will be faulted with the current implementation). |
2129 | */ |
2130 | int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes) |
2131 | { |
2132 | char __user *buf = i->iov->iov_base + i->iov_offset; |
2133 | bytes = min(bytes, i->iov->iov_len - i->iov_offset); |
2134 | return fault_in_pages_readable(buf, bytes); |
2135 | } |
2136 | EXPORT_SYMBOL(iov_iter_fault_in_readable); |
2137 | |
2138 | /* |
2139 | * Return the count of just the current iov_iter segment. |
2140 | */ |
2141 | size_t iov_iter_single_seg_count(struct iov_iter *i) |
2142 | { |
2143 | const struct iovec *iov = i->iov; |
2144 | if (i->nr_segs == 1) |
2145 | return i->count; |
2146 | else |
2147 | return min(i->count, iov->iov_len - i->iov_offset); |
2148 | } |
2149 | EXPORT_SYMBOL(iov_iter_single_seg_count); |
2150 | |
2151 | /* |
2152 | * Performs necessary checks before doing a write |
2153 | * |
2154 | * Can adjust writing position or amount of bytes to write. |
2155 | * Returns appropriate error code that caller should return or |
2156 | * zero in case that write should be allowed. |
2157 | */ |
2158 | inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk) |
2159 | { |
2160 | struct inode *inode = file->f_mapping->host; |
2161 | unsigned long limit = rlimit(RLIMIT_FSIZE); |
2162 | |
2163 | if (unlikely(*pos < 0)) |
2164 | return -EINVAL; |
2165 | |
2166 | if (!isblk) { |
2167 | /* FIXME: this is for backwards compatibility with 2.4 */ |
2168 | if (file->f_flags & O_APPEND) |
2169 | *pos = i_size_read(inode); |
2170 | |
2171 | if (limit != RLIM_INFINITY) { |
2172 | if (*pos >= limit) { |
2173 | send_sig(SIGXFSZ, current, 0); |
2174 | return -EFBIG; |
2175 | } |
2176 | if (*count > limit - (typeof(limit))*pos) { |
2177 | *count = limit - (typeof(limit))*pos; |
2178 | } |
2179 | } |
2180 | } |
2181 | |
2182 | /* |
2183 | * LFS rule |
2184 | */ |
2185 | if (unlikely(*pos + *count > MAX_NON_LFS && |
2186 | !(file->f_flags & O_LARGEFILE))) { |
2187 | if (*pos >= MAX_NON_LFS) { |
2188 | return -EFBIG; |
2189 | } |
2190 | if (*count > MAX_NON_LFS - (unsigned long)*pos) { |
2191 | *count = MAX_NON_LFS - (unsigned long)*pos; |
2192 | } |
2193 | } |
2194 | |
2195 | /* |
2196 | * Are we about to exceed the fs block limit ? |
2197 | * |
2198 | * If we have written data it becomes a short write. If we have |
2199 | * exceeded without writing data we send a signal and return EFBIG. |
2200 | * Linus frestrict idea will clean these up nicely.. |
2201 | */ |
2202 | if (likely(!isblk)) { |
2203 | if (unlikely(*pos >= inode->i_sb->s_maxbytes)) { |
2204 | if (*count || *pos > inode->i_sb->s_maxbytes) { |
2205 | return -EFBIG; |
2206 | } |
2207 | /* zero-length writes at ->s_maxbytes are OK */ |
2208 | } |
2209 | |
2210 | if (unlikely(*pos + *count > inode->i_sb->s_maxbytes)) |
2211 | *count = inode->i_sb->s_maxbytes - *pos; |
2212 | } else { |
2213 | #ifdef CONFIG_BLOCK |
2214 | loff_t isize; |
2215 | if (bdev_read_only(I_BDEV(inode))) |
2216 | return -EPERM; |
2217 | isize = i_size_read(inode); |
2218 | if (*pos >= isize) { |
2219 | if (*count || *pos > isize) |
2220 | return -ENOSPC; |
2221 | } |
2222 | |
2223 | if (*pos + *count > isize) |
2224 | *count = isize - *pos; |
2225 | #else |
2226 | return -EPERM; |
2227 | #endif |
2228 | } |
2229 | return 0; |
2230 | } |
2231 | EXPORT_SYMBOL(generic_write_checks); |
2232 | |
2233 | int pagecache_write_begin(struct file *file, struct address_space *mapping, |
2234 | loff_t pos, unsigned len, unsigned flags, |
2235 | struct page **pagep, void **fsdata) |
2236 | { |
2237 | const struct address_space_operations *aops = mapping->a_ops; |
2238 | |
2239 | return aops->write_begin(file, mapping, pos, len, flags, |
2240 | pagep, fsdata); |
2241 | } |
2242 | EXPORT_SYMBOL(pagecache_write_begin); |
2243 | |
2244 | int pagecache_write_end(struct file *file, struct address_space *mapping, |
2245 | loff_t pos, unsigned len, unsigned copied, |
2246 | struct page *page, void *fsdata) |
2247 | { |
2248 | const struct address_space_operations *aops = mapping->a_ops; |
2249 | |
2250 | mark_page_accessed(page); |
2251 | return aops->write_end(file, mapping, pos, len, copied, page, fsdata); |
2252 | } |
2253 | EXPORT_SYMBOL(pagecache_write_end); |
2254 | |
2255 | ssize_t |
2256 | generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, |
2257 | unsigned long *nr_segs, loff_t pos, loff_t *ppos, |
2258 | size_t count, size_t ocount) |
2259 | { |
2260 | struct file *file = iocb->ki_filp; |
2261 | struct address_space *mapping = file->f_mapping; |
2262 | struct inode *inode = mapping->host; |
2263 | ssize_t written; |
2264 | size_t write_len; |
2265 | pgoff_t end; |
2266 | |
2267 | if (count != ocount) |
2268 | *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count); |
2269 | |
2270 | write_len = iov_length(iov, *nr_segs); |
2271 | end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT; |
2272 | |
2273 | written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); |
2274 | if (written) |
2275 | goto out; |
2276 | |
2277 | /* |
2278 | * After a write we want buffered reads to be sure to go to disk to get |
2279 | * the new data. We invalidate clean cached page from the region we're |
2280 | * about to write. We do this *before* the write so that we can return |
2281 | * without clobbering -EIOCBQUEUED from ->direct_IO(). |
2282 | */ |
2283 | if (mapping->nrpages) { |
2284 | written = invalidate_inode_pages2_range(mapping, |
2285 | pos >> PAGE_CACHE_SHIFT, end); |
2286 | /* |
2287 | * If a page can not be invalidated, return 0 to fall back |
2288 | * to buffered write. |
2289 | */ |
2290 | if (written) { |
2291 | if (written == -EBUSY) |
2292 | return 0; |
2293 | goto out; |
2294 | } |
2295 | } |
2296 | |
2297 | written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); |
2298 | |
2299 | /* |
2300 | * Finally, try again to invalidate clean pages which might have been |
2301 | * cached by non-direct readahead, or faulted in by get_user_pages() |
2302 | * if the source of the write was an mmap'ed region of the file |
2303 | * we're writing. Either one is a pretty crazy thing to do, |
2304 | * so we don't support it 100%. If this invalidation |
2305 | * fails, tough, the write still worked... |
2306 | */ |
2307 | if (mapping->nrpages) { |
2308 | invalidate_inode_pages2_range(mapping, |
2309 | pos >> PAGE_CACHE_SHIFT, end); |
2310 | } |
2311 | |
2312 | if (written > 0) { |
2313 | pos += written; |
2314 | if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { |
2315 | i_size_write(inode, pos); |
2316 | mark_inode_dirty(inode); |
2317 | } |
2318 | *ppos = pos; |
2319 | } |
2320 | out: |
2321 | return written; |
2322 | } |
2323 | EXPORT_SYMBOL(generic_file_direct_write); |
2324 | |
2325 | /* |
2326 | * Find or create a page at the given pagecache position. Return the locked |
2327 | * page. This function is specifically for buffered writes. |
2328 | */ |
2329 | struct page *grab_cache_page_write_begin(struct address_space *mapping, |
2330 | pgoff_t index, unsigned flags) |
2331 | { |
2332 | int status; |
2333 | struct page *page; |
2334 | gfp_t gfp_notmask = 0; |
2335 | if (flags & AOP_FLAG_NOFS) |
2336 | gfp_notmask = __GFP_FS; |
2337 | repeat: |
2338 | page = find_lock_page(mapping, index); |
2339 | if (page) |
2340 | goto found; |
2341 | |
2342 | page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask); |
2343 | if (!page) |
2344 | return NULL; |
2345 | status = add_to_page_cache_lru(page, mapping, index, |
2346 | GFP_KERNEL & ~gfp_notmask); |
2347 | if (unlikely(status)) { |
2348 | page_cache_release(page); |
2349 | if (status == -EEXIST) |
2350 | goto repeat; |
2351 | return NULL; |
2352 | } |
2353 | found: |
2354 | wait_on_page_writeback(page); |
2355 | return page; |
2356 | } |
2357 | EXPORT_SYMBOL(grab_cache_page_write_begin); |
2358 | |
2359 | static ssize_t generic_perform_write(struct file *file, |
2360 | struct iov_iter *i, loff_t pos) |
2361 | { |
2362 | struct address_space *mapping = file->f_mapping; |
2363 | const struct address_space_operations *a_ops = mapping->a_ops; |
2364 | long status = 0; |
2365 | ssize_t written = 0; |
2366 | unsigned int flags = 0; |
2367 | |
2368 | /* |
2369 | * Copies from kernel address space cannot fail (NFSD is a big user). |
2370 | */ |
2371 | if (segment_eq(get_fs(), KERNEL_DS)) |
2372 | flags |= AOP_FLAG_UNINTERRUPTIBLE; |
2373 | |
2374 | do { |
2375 | struct page *page; |
2376 | unsigned long offset; /* Offset into pagecache page */ |
2377 | unsigned long bytes; /* Bytes to write to page */ |
2378 | size_t copied; /* Bytes copied from user */ |
2379 | void *fsdata; |
2380 | |
2381 | offset = (pos & (PAGE_CACHE_SIZE - 1)); |
2382 | bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, |
2383 | iov_iter_count(i)); |
2384 | |
2385 | again: |
2386 | |
2387 | /* |
2388 | * Bring in the user page that we will copy from _first_. |
2389 | * Otherwise there's a nasty deadlock on copying from the |
2390 | * same page as we're writing to, without it being marked |
2391 | * up-to-date. |
2392 | * |
2393 | * Not only is this an optimisation, but it is also required |
2394 | * to check that the address is actually valid, when atomic |
2395 | * usercopies are used, below. |
2396 | */ |
2397 | if (unlikely(iov_iter_fault_in_readable(i, bytes))) { |
2398 | status = -EFAULT; |
2399 | break; |
2400 | } |
2401 | |
2402 | status = a_ops->write_begin(file, mapping, pos, bytes, flags, |
2403 | &page, &fsdata); |
2404 | if (unlikely(status)) |
2405 | break; |
2406 | |
2407 | if (mapping_writably_mapped(mapping)) |
2408 | flush_dcache_page(page); |
2409 | |
2410 | pagefault_disable(); |
2411 | copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); |
2412 | pagefault_enable(); |
2413 | flush_dcache_page(page); |
2414 | |
2415 | mark_page_accessed(page); |
2416 | status = a_ops->write_end(file, mapping, pos, bytes, copied, |
2417 | page, fsdata); |
2418 | if (unlikely(status < 0)) |
2419 | break; |
2420 | copied = status; |
2421 | |
2422 | cond_resched(); |
2423 | |
2424 | iov_iter_advance(i, copied); |
2425 | if (unlikely(copied == 0)) { |
2426 | /* |
2427 | * If we were unable to copy any data at all, we must |
2428 | * fall back to a single segment length write. |
2429 | * |
2430 | * If we didn't fallback here, we could livelock |
2431 | * because not all segments in the iov can be copied at |
2432 | * once without a pagefault. |
2433 | */ |
2434 | bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, |
2435 | iov_iter_single_seg_count(i)); |
2436 | goto again; |
2437 | } |
2438 | pos += copied; |
2439 | written += copied; |
2440 | |
2441 | balance_dirty_pages_ratelimited(mapping); |
2442 | |
2443 | } while (iov_iter_count(i)); |
2444 | |
2445 | return written ? written : status; |
2446 | } |
2447 | |
2448 | ssize_t |
2449 | generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov, |
2450 | unsigned long nr_segs, loff_t pos, loff_t *ppos, |
2451 | size_t count, ssize_t written) |
2452 | { |
2453 | struct file *file = iocb->ki_filp; |
2454 | ssize_t status; |
2455 | struct iov_iter i; |
2456 | |
2457 | iov_iter_init(&i, iov, nr_segs, count, written); |
2458 | status = generic_perform_write(file, &i, pos); |
2459 | |
2460 | if (likely(status >= 0)) { |
2461 | written += status; |
2462 | *ppos = pos + status; |
2463 | } |
2464 | |
2465 | return written ? written : status; |
2466 | } |
2467 | EXPORT_SYMBOL(generic_file_buffered_write); |
2468 | |
2469 | /** |
2470 | * __generic_file_aio_write - write data to a file |
2471 | * @iocb: IO state structure (file, offset, etc.) |
2472 | * @iov: vector with data to write |
2473 | * @nr_segs: number of segments in the vector |
2474 | * @ppos: position where to write |
2475 | * |
2476 | * This function does all the work needed for actually writing data to a |
2477 | * file. It does all basic checks, removes SUID from the file, updates |
2478 | * modification times and calls proper subroutines depending on whether we |
2479 | * do direct IO or a standard buffered write. |
2480 | * |
2481 | * It expects i_mutex to be grabbed unless we work on a block device or similar |
2482 | * object which does not need locking at all. |
2483 | * |
2484 | * This function does *not* take care of syncing data in case of O_SYNC write. |
2485 | * A caller has to handle it. This is mainly due to the fact that we want to |
2486 | * avoid syncing under i_mutex. |
2487 | */ |
2488 | ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, |
2489 | unsigned long nr_segs, loff_t *ppos) |
2490 | { |
2491 | struct file *file = iocb->ki_filp; |
2492 | struct address_space * mapping = file->f_mapping; |
2493 | size_t ocount; /* original count */ |
2494 | size_t count; /* after file limit checks */ |
2495 | struct inode *inode = mapping->host; |
2496 | loff_t pos; |
2497 | ssize_t written; |
2498 | ssize_t err; |
2499 | |
2500 | ocount = 0; |
2501 | err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ); |
2502 | if (err) |
2503 | return err; |
2504 | |
2505 | count = ocount; |
2506 | pos = *ppos; |
2507 | |
2508 | vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE); |
2509 | |
2510 | /* We can write back this queue in page reclaim */ |
2511 | current->backing_dev_info = mapping->backing_dev_info; |
2512 | written = 0; |
2513 | |
2514 | err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode)); |
2515 | if (err) |
2516 | goto out; |
2517 | |
2518 | if (count == 0) |
2519 | goto out; |
2520 | |
2521 | err = file_remove_suid(file); |
2522 | if (err) |
2523 | goto out; |
2524 | |
2525 | file_update_time(file); |
2526 | |
2527 | /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */ |
2528 | if (unlikely(file->f_flags & O_DIRECT)) { |
2529 | loff_t endbyte; |
2530 | ssize_t written_buffered; |
2531 | |
2532 | written = generic_file_direct_write(iocb, iov, &nr_segs, pos, |
2533 | ppos, count, ocount); |
2534 | if (written < 0 || written == count) |
2535 | goto out; |
2536 | /* |
2537 | * direct-io write to a hole: fall through to buffered I/O |
2538 | * for completing the rest of the request. |
2539 | */ |
2540 | pos += written; |
2541 | count -= written; |
2542 | written_buffered = generic_file_buffered_write(iocb, iov, |
2543 | nr_segs, pos, ppos, count, |
2544 | written); |
2545 | /* |
2546 | * If generic_file_buffered_write() retuned a synchronous error |
2547 | * then we want to return the number of bytes which were |
2548 | * direct-written, or the error code if that was zero. Note |
2549 | * that this differs from normal direct-io semantics, which |
2550 | * will return -EFOO even if some bytes were written. |
2551 | */ |
2552 | if (written_buffered < 0) { |
2553 | err = written_buffered; |
2554 | goto out; |
2555 | } |
2556 | |
2557 | /* |
2558 | * We need to ensure that the page cache pages are written to |
2559 | * disk and invalidated to preserve the expected O_DIRECT |
2560 | * semantics. |
2561 | */ |
2562 | endbyte = pos + written_buffered - written - 1; |
2563 | err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte); |
2564 | if (err == 0) { |
2565 | written = written_buffered; |
2566 | invalidate_mapping_pages(mapping, |
2567 | pos >> PAGE_CACHE_SHIFT, |
2568 | endbyte >> PAGE_CACHE_SHIFT); |
2569 | } else { |
2570 | /* |
2571 | * We don't know how much we wrote, so just return |
2572 | * the number of bytes which were direct-written |
2573 | */ |
2574 | } |
2575 | } else { |
2576 | written = generic_file_buffered_write(iocb, iov, nr_segs, |
2577 | pos, ppos, count, written); |
2578 | } |
2579 | out: |
2580 | current->backing_dev_info = NULL; |
2581 | return written ? written : err; |
2582 | } |
2583 | EXPORT_SYMBOL(__generic_file_aio_write); |
2584 | |
2585 | /** |
2586 | * generic_file_aio_write - write data to a file |
2587 | * @iocb: IO state structure |
2588 | * @iov: vector with data to write |
2589 | * @nr_segs: number of segments in the vector |
2590 | * @pos: position in file where to write |
2591 | * |
2592 | * This is a wrapper around __generic_file_aio_write() to be used by most |
2593 | * filesystems. It takes care of syncing the file in case of O_SYNC file |
2594 | * and acquires i_mutex as needed. |
2595 | */ |
2596 | ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, |
2597 | unsigned long nr_segs, loff_t pos) |
2598 | { |
2599 | struct file *file = iocb->ki_filp; |
2600 | struct inode *inode = file->f_mapping->host; |
2601 | struct blk_plug plug; |
2602 | ssize_t ret; |
2603 | |
2604 | BUG_ON(iocb->ki_pos != pos); |
2605 | |
2606 | mutex_lock(&inode->i_mutex); |
2607 | blk_start_plug(&plug); |
2608 | ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); |
2609 | mutex_unlock(&inode->i_mutex); |
2610 | |
2611 | if (ret > 0 || ret == -EIOCBQUEUED) { |
2612 | ssize_t err; |
2613 | |
2614 | err = generic_write_sync(file, pos, ret); |
2615 | if (err < 0 && ret > 0) |
2616 | ret = err; |
2617 | } |
2618 | blk_finish_plug(&plug); |
2619 | return ret; |
2620 | } |
2621 | EXPORT_SYMBOL(generic_file_aio_write); |
2622 | |
2623 | /** |
2624 | * try_to_release_page() - release old fs-specific metadata on a page |
2625 | * |
2626 | * @page: the page which the kernel is trying to free |
2627 | * @gfp_mask: memory allocation flags (and I/O mode) |
2628 | * |
2629 | * The address_space is to try to release any data against the page |
2630 | * (presumably at page->private). If the release was successful, return `1'. |
2631 | * Otherwise return zero. |
2632 | * |
2633 | * This may also be called if PG_fscache is set on a page, indicating that the |
2634 | * page is known to the local caching routines. |
2635 | * |
2636 | * The @gfp_mask argument specifies whether I/O may be performed to release |
2637 | * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS). |
2638 | * |
2639 | */ |
2640 | int try_to_release_page(struct page *page, gfp_t gfp_mask) |
2641 | { |
2642 | struct address_space * const mapping = page->mapping; |
2643 | |
2644 | BUG_ON(!PageLocked(page)); |
2645 | if (PageWriteback(page)) |
2646 | return 0; |
2647 | |
2648 | if (mapping && mapping->a_ops->releasepage) |
2649 | return mapping->a_ops->releasepage(page, gfp_mask); |
2650 | return try_to_free_buffers(page); |
2651 | } |
2652 | |
2653 | EXPORT_SYMBOL(try_to_release_page); |
2654 |
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