]>
Commit | Line | Data |
---|---|---|
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/export.h> | |
13 | #include <linux/compiler.h> | |
14 | #include <linux/dax.h> | |
15 | #include <linux/fs.h> | |
16 | #include <linux/sched/signal.h> | |
17 | #include <linux/uaccess.h> | |
18 | #include <linux/capability.h> | |
19 | #include <linux/kernel_stat.h> | |
20 | #include <linux/gfp.h> | |
21 | #include <linux/mm.h> | |
22 | #include <linux/swap.h> | |
23 | #include <linux/mman.h> | |
24 | #include <linux/pagemap.h> | |
25 | #include <linux/file.h> | |
26 | #include <linux/uio.h> | |
27 | #include <linux/hash.h> | |
28 | #include <linux/writeback.h> | |
29 | #include <linux/backing-dev.h> | |
30 | #include <linux/pagevec.h> | |
31 | #include <linux/blkdev.h> | |
32 | #include <linux/security.h> | |
33 | #include <linux/cpuset.h> | |
34 | #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */ | |
35 | #include <linux/hugetlb.h> | |
36 | #include <linux/memcontrol.h> | |
37 | #include <linux/cleancache.h> | |
38 | #include <linux/rmap.h> | |
39 | #include "internal.h" | |
40 | ||
41 | #define CREATE_TRACE_POINTS | |
42 | #include <trace/events/filemap.h> | |
43 | ||
44 | /* | |
45 | * FIXME: remove all knowledge of the buffer layer from the core VM | |
46 | */ | |
47 | #include <linux/buffer_head.h> /* for try_to_free_buffers */ | |
48 | ||
49 | #include <asm/mman.h> | |
50 | ||
51 | /* | |
52 | * Shared mappings implemented 30.11.1994. It's not fully working yet, | |
53 | * though. | |
54 | * | |
55 | * Shared mappings now work. 15.8.1995 Bruno. | |
56 | * | |
57 | * finished 'unifying' the page and buffer cache and SMP-threaded the | |
58 | * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> | |
59 | * | |
60 | * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> | |
61 | */ | |
62 | ||
63 | /* | |
64 | * Lock ordering: | |
65 | * | |
66 | * ->i_mmap_rwsem (truncate_pagecache) | |
67 | * ->private_lock (__free_pte->__set_page_dirty_buffers) | |
68 | * ->swap_lock (exclusive_swap_page, others) | |
69 | * ->mapping->tree_lock | |
70 | * | |
71 | * ->i_mutex | |
72 | * ->i_mmap_rwsem (truncate->unmap_mapping_range) | |
73 | * | |
74 | * ->mmap_sem | |
75 | * ->i_mmap_rwsem | |
76 | * ->page_table_lock or pte_lock (various, mainly in memory.c) | |
77 | * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock) | |
78 | * | |
79 | * ->mmap_sem | |
80 | * ->lock_page (access_process_vm) | |
81 | * | |
82 | * ->i_mutex (generic_perform_write) | |
83 | * ->mmap_sem (fault_in_pages_readable->do_page_fault) | |
84 | * | |
85 | * bdi->wb.list_lock | |
86 | * sb_lock (fs/fs-writeback.c) | |
87 | * ->mapping->tree_lock (__sync_single_inode) | |
88 | * | |
89 | * ->i_mmap_rwsem | |
90 | * ->anon_vma.lock (vma_adjust) | |
91 | * | |
92 | * ->anon_vma.lock | |
93 | * ->page_table_lock or pte_lock (anon_vma_prepare and various) | |
94 | * | |
95 | * ->page_table_lock or pte_lock | |
96 | * ->swap_lock (try_to_unmap_one) | |
97 | * ->private_lock (try_to_unmap_one) | |
98 | * ->tree_lock (try_to_unmap_one) | |
99 | * ->zone_lru_lock(zone) (follow_page->mark_page_accessed) | |
100 | * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page) | |
101 | * ->private_lock (page_remove_rmap->set_page_dirty) | |
102 | * ->tree_lock (page_remove_rmap->set_page_dirty) | |
103 | * bdi.wb->list_lock (page_remove_rmap->set_page_dirty) | |
104 | * ->inode->i_lock (page_remove_rmap->set_page_dirty) | |
105 | * ->memcg->move_lock (page_remove_rmap->lock_page_memcg) | |
106 | * bdi.wb->list_lock (zap_pte_range->set_page_dirty) | |
107 | * ->inode->i_lock (zap_pte_range->set_page_dirty) | |
108 | * ->private_lock (zap_pte_range->__set_page_dirty_buffers) | |
109 | * | |
110 | * ->i_mmap_rwsem | |
111 | * ->tasklist_lock (memory_failure, collect_procs_ao) | |
112 | */ | |
113 | ||
114 | static int page_cache_tree_insert(struct address_space *mapping, | |
115 | struct page *page, void **shadowp) | |
116 | { | |
117 | struct radix_tree_node *node; | |
118 | void **slot; | |
119 | int error; | |
120 | ||
121 | error = __radix_tree_create(&mapping->page_tree, page->index, 0, | |
122 | &node, &slot); | |
123 | if (error) | |
124 | return error; | |
125 | if (*slot) { | |
126 | void *p; | |
127 | ||
128 | p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock); | |
129 | if (!radix_tree_exceptional_entry(p)) | |
130 | return -EEXIST; | |
131 | ||
132 | mapping->nrexceptional--; | |
133 | if (!dax_mapping(mapping)) { | |
134 | if (shadowp) | |
135 | *shadowp = p; | |
136 | } else { | |
137 | /* DAX can replace empty locked entry with a hole */ | |
138 | WARN_ON_ONCE(p != | |
139 | dax_radix_locked_entry(0, RADIX_DAX_EMPTY)); | |
140 | /* Wakeup waiters for exceptional entry lock */ | |
141 | dax_wake_mapping_entry_waiter(mapping, page->index, p, | |
142 | true); | |
143 | } | |
144 | } | |
145 | __radix_tree_replace(&mapping->page_tree, node, slot, page, | |
146 | workingset_update_node, mapping); | |
147 | mapping->nrpages++; | |
148 | return 0; | |
149 | } | |
150 | ||
151 | static void page_cache_tree_delete(struct address_space *mapping, | |
152 | struct page *page, void *shadow) | |
153 | { | |
154 | int i, nr; | |
155 | ||
156 | /* hugetlb pages are represented by one entry in the radix tree */ | |
157 | nr = PageHuge(page) ? 1 : hpage_nr_pages(page); | |
158 | ||
159 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
160 | VM_BUG_ON_PAGE(PageTail(page), page); | |
161 | VM_BUG_ON_PAGE(nr != 1 && shadow, page); | |
162 | ||
163 | for (i = 0; i < nr; i++) { | |
164 | struct radix_tree_node *node; | |
165 | void **slot; | |
166 | ||
167 | __radix_tree_lookup(&mapping->page_tree, page->index + i, | |
168 | &node, &slot); | |
169 | ||
170 | VM_BUG_ON_PAGE(!node && nr != 1, page); | |
171 | ||
172 | radix_tree_clear_tags(&mapping->page_tree, node, slot); | |
173 | __radix_tree_replace(&mapping->page_tree, node, slot, shadow, | |
174 | workingset_update_node, mapping); | |
175 | } | |
176 | ||
177 | if (shadow) { | |
178 | mapping->nrexceptional += nr; | |
179 | /* | |
180 | * Make sure the nrexceptional update is committed before | |
181 | * the nrpages update so that final truncate racing | |
182 | * with reclaim does not see both counters 0 at the | |
183 | * same time and miss a shadow entry. | |
184 | */ | |
185 | smp_wmb(); | |
186 | } | |
187 | mapping->nrpages -= nr; | |
188 | } | |
189 | ||
190 | /* | |
191 | * Delete a page from the page cache and free it. Caller has to make | |
192 | * sure the page is locked and that nobody else uses it - or that usage | |
193 | * is safe. The caller must hold the mapping's tree_lock. | |
194 | */ | |
195 | void __delete_from_page_cache(struct page *page, void *shadow) | |
196 | { | |
197 | struct address_space *mapping = page->mapping; | |
198 | int nr = hpage_nr_pages(page); | |
199 | ||
200 | trace_mm_filemap_delete_from_page_cache(page); | |
201 | /* | |
202 | * if we're uptodate, flush out into the cleancache, otherwise | |
203 | * invalidate any existing cleancache entries. We can't leave | |
204 | * stale data around in the cleancache once our page is gone | |
205 | */ | |
206 | if (PageUptodate(page) && PageMappedToDisk(page)) | |
207 | cleancache_put_page(page); | |
208 | else | |
209 | cleancache_invalidate_page(mapping, page); | |
210 | ||
211 | VM_BUG_ON_PAGE(PageTail(page), page); | |
212 | VM_BUG_ON_PAGE(page_mapped(page), page); | |
213 | if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) { | |
214 | int mapcount; | |
215 | ||
216 | pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n", | |
217 | current->comm, page_to_pfn(page)); | |
218 | dump_page(page, "still mapped when deleted"); | |
219 | dump_stack(); | |
220 | add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); | |
221 | ||
222 | mapcount = page_mapcount(page); | |
223 | if (mapping_exiting(mapping) && | |
224 | page_count(page) >= mapcount + 2) { | |
225 | /* | |
226 | * All vmas have already been torn down, so it's | |
227 | * a good bet that actually the page is unmapped, | |
228 | * and we'd prefer not to leak it: if we're wrong, | |
229 | * some other bad page check should catch it later. | |
230 | */ | |
231 | page_mapcount_reset(page); | |
232 | page_ref_sub(page, mapcount); | |
233 | } | |
234 | } | |
235 | ||
236 | page_cache_tree_delete(mapping, page, shadow); | |
237 | ||
238 | page->mapping = NULL; | |
239 | /* Leave page->index set: truncation lookup relies upon it */ | |
240 | ||
241 | /* hugetlb pages do not participate in page cache accounting. */ | |
242 | if (!PageHuge(page)) | |
243 | __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr); | |
244 | if (PageSwapBacked(page)) { | |
245 | __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr); | |
246 | if (PageTransHuge(page)) | |
247 | __dec_node_page_state(page, NR_SHMEM_THPS); | |
248 | } else { | |
249 | VM_BUG_ON_PAGE(PageTransHuge(page) && !PageHuge(page), page); | |
250 | } | |
251 | ||
252 | /* | |
253 | * At this point page must be either written or cleaned by truncate. | |
254 | * Dirty page here signals a bug and loss of unwritten data. | |
255 | * | |
256 | * This fixes dirty accounting after removing the page entirely but | |
257 | * leaves PageDirty set: it has no effect for truncated page and | |
258 | * anyway will be cleared before returning page into buddy allocator. | |
259 | */ | |
260 | if (WARN_ON_ONCE(PageDirty(page))) | |
261 | account_page_cleaned(page, mapping, inode_to_wb(mapping->host)); | |
262 | } | |
263 | ||
264 | /** | |
265 | * delete_from_page_cache - delete page from page cache | |
266 | * @page: the page which the kernel is trying to remove from page cache | |
267 | * | |
268 | * This must be called only on pages that have been verified to be in the page | |
269 | * cache and locked. It will never put the page into the free list, the caller | |
270 | * has a reference on the page. | |
271 | */ | |
272 | void delete_from_page_cache(struct page *page) | |
273 | { | |
274 | struct address_space *mapping = page_mapping(page); | |
275 | unsigned long flags; | |
276 | void (*freepage)(struct page *); | |
277 | ||
278 | BUG_ON(!PageLocked(page)); | |
279 | ||
280 | freepage = mapping->a_ops->freepage; | |
281 | ||
282 | spin_lock_irqsave(&mapping->tree_lock, flags); | |
283 | __delete_from_page_cache(page, NULL); | |
284 | spin_unlock_irqrestore(&mapping->tree_lock, flags); | |
285 | ||
286 | if (freepage) | |
287 | freepage(page); | |
288 | ||
289 | if (PageTransHuge(page) && !PageHuge(page)) { | |
290 | page_ref_sub(page, HPAGE_PMD_NR); | |
291 | VM_BUG_ON_PAGE(page_count(page) <= 0, page); | |
292 | } else { | |
293 | put_page(page); | |
294 | } | |
295 | } | |
296 | EXPORT_SYMBOL(delete_from_page_cache); | |
297 | ||
298 | int filemap_check_errors(struct address_space *mapping) | |
299 | { | |
300 | int ret = 0; | |
301 | /* Check for outstanding write errors */ | |
302 | if (test_bit(AS_ENOSPC, &mapping->flags) && | |
303 | test_and_clear_bit(AS_ENOSPC, &mapping->flags)) | |
304 | ret = -ENOSPC; | |
305 | if (test_bit(AS_EIO, &mapping->flags) && | |
306 | test_and_clear_bit(AS_EIO, &mapping->flags)) | |
307 | ret = -EIO; | |
308 | return ret; | |
309 | } | |
310 | EXPORT_SYMBOL(filemap_check_errors); | |
311 | ||
312 | /** | |
313 | * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range | |
314 | * @mapping: address space structure to write | |
315 | * @start: offset in bytes where the range starts | |
316 | * @end: offset in bytes where the range ends (inclusive) | |
317 | * @sync_mode: enable synchronous operation | |
318 | * | |
319 | * Start writeback against all of a mapping's dirty pages that lie | |
320 | * within the byte offsets <start, end> inclusive. | |
321 | * | |
322 | * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as | |
323 | * opposed to a regular memory cleansing writeback. The difference between | |
324 | * these two operations is that if a dirty page/buffer is encountered, it must | |
325 | * be waited upon, and not just skipped over. | |
326 | */ | |
327 | int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, | |
328 | loff_t end, int sync_mode) | |
329 | { | |
330 | int ret; | |
331 | struct writeback_control wbc = { | |
332 | .sync_mode = sync_mode, | |
333 | .nr_to_write = LONG_MAX, | |
334 | .range_start = start, | |
335 | .range_end = end, | |
336 | }; | |
337 | ||
338 | if (!mapping_cap_writeback_dirty(mapping)) | |
339 | return 0; | |
340 | ||
341 | wbc_attach_fdatawrite_inode(&wbc, mapping->host); | |
342 | ret = do_writepages(mapping, &wbc); | |
343 | wbc_detach_inode(&wbc); | |
344 | return ret; | |
345 | } | |
346 | ||
347 | static inline int __filemap_fdatawrite(struct address_space *mapping, | |
348 | int sync_mode) | |
349 | { | |
350 | return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); | |
351 | } | |
352 | ||
353 | int filemap_fdatawrite(struct address_space *mapping) | |
354 | { | |
355 | return __filemap_fdatawrite(mapping, WB_SYNC_ALL); | |
356 | } | |
357 | EXPORT_SYMBOL(filemap_fdatawrite); | |
358 | ||
359 | int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, | |
360 | loff_t end) | |
361 | { | |
362 | return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); | |
363 | } | |
364 | EXPORT_SYMBOL(filemap_fdatawrite_range); | |
365 | ||
366 | /** | |
367 | * filemap_flush - mostly a non-blocking flush | |
368 | * @mapping: target address_space | |
369 | * | |
370 | * This is a mostly non-blocking flush. Not suitable for data-integrity | |
371 | * purposes - I/O may not be started against all dirty pages. | |
372 | */ | |
373 | int filemap_flush(struct address_space *mapping) | |
374 | { | |
375 | return __filemap_fdatawrite(mapping, WB_SYNC_NONE); | |
376 | } | |
377 | EXPORT_SYMBOL(filemap_flush); | |
378 | ||
379 | static int __filemap_fdatawait_range(struct address_space *mapping, | |
380 | loff_t start_byte, loff_t end_byte) | |
381 | { | |
382 | pgoff_t index = start_byte >> PAGE_SHIFT; | |
383 | pgoff_t end = end_byte >> PAGE_SHIFT; | |
384 | struct pagevec pvec; | |
385 | int nr_pages; | |
386 | int ret = 0; | |
387 | ||
388 | if (end_byte < start_byte) | |
389 | goto out; | |
390 | ||
391 | pagevec_init(&pvec, 0); | |
392 | while ((index <= end) && | |
393 | (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, | |
394 | PAGECACHE_TAG_WRITEBACK, | |
395 | min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) { | |
396 | unsigned i; | |
397 | ||
398 | for (i = 0; i < nr_pages; i++) { | |
399 | struct page *page = pvec.pages[i]; | |
400 | ||
401 | /* until radix tree lookup accepts end_index */ | |
402 | if (page->index > end) | |
403 | continue; | |
404 | ||
405 | wait_on_page_writeback(page); | |
406 | if (TestClearPageError(page)) | |
407 | ret = -EIO; | |
408 | } | |
409 | pagevec_release(&pvec); | |
410 | cond_resched(); | |
411 | } | |
412 | out: | |
413 | return ret; | |
414 | } | |
415 | ||
416 | /** | |
417 | * filemap_fdatawait_range - wait for writeback to complete | |
418 | * @mapping: address space structure to wait for | |
419 | * @start_byte: offset in bytes where the range starts | |
420 | * @end_byte: offset in bytes where the range ends (inclusive) | |
421 | * | |
422 | * Walk the list of under-writeback pages of the given address space | |
423 | * in the given range and wait for all of them. Check error status of | |
424 | * the address space and return it. | |
425 | * | |
426 | * Since the error status of the address space is cleared by this function, | |
427 | * callers are responsible for checking the return value and handling and/or | |
428 | * reporting the error. | |
429 | */ | |
430 | int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, | |
431 | loff_t end_byte) | |
432 | { | |
433 | int ret, ret2; | |
434 | ||
435 | ret = __filemap_fdatawait_range(mapping, start_byte, end_byte); | |
436 | ret2 = filemap_check_errors(mapping); | |
437 | if (!ret) | |
438 | ret = ret2; | |
439 | ||
440 | return ret; | |
441 | } | |
442 | EXPORT_SYMBOL(filemap_fdatawait_range); | |
443 | ||
444 | /** | |
445 | * filemap_fdatawait_keep_errors - wait for writeback without clearing errors | |
446 | * @mapping: address space structure to wait for | |
447 | * | |
448 | * Walk the list of under-writeback pages of the given address space | |
449 | * and wait for all of them. Unlike filemap_fdatawait(), this function | |
450 | * does not clear error status of the address space. | |
451 | * | |
452 | * Use this function if callers don't handle errors themselves. Expected | |
453 | * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), | |
454 | * fsfreeze(8) | |
455 | */ | |
456 | void filemap_fdatawait_keep_errors(struct address_space *mapping) | |
457 | { | |
458 | loff_t i_size = i_size_read(mapping->host); | |
459 | ||
460 | if (i_size == 0) | |
461 | return; | |
462 | ||
463 | __filemap_fdatawait_range(mapping, 0, i_size - 1); | |
464 | } | |
465 | ||
466 | /** | |
467 | * filemap_fdatawait - wait for all under-writeback pages to complete | |
468 | * @mapping: address space structure to wait for | |
469 | * | |
470 | * Walk the list of under-writeback pages of the given address space | |
471 | * and wait for all of them. Check error status of the address space | |
472 | * and return it. | |
473 | * | |
474 | * Since the error status of the address space is cleared by this function, | |
475 | * callers are responsible for checking the return value and handling and/or | |
476 | * reporting the error. | |
477 | */ | |
478 | int filemap_fdatawait(struct address_space *mapping) | |
479 | { | |
480 | loff_t i_size = i_size_read(mapping->host); | |
481 | ||
482 | if (i_size == 0) | |
483 | return 0; | |
484 | ||
485 | return filemap_fdatawait_range(mapping, 0, i_size - 1); | |
486 | } | |
487 | EXPORT_SYMBOL(filemap_fdatawait); | |
488 | ||
489 | int filemap_write_and_wait(struct address_space *mapping) | |
490 | { | |
491 | int err = 0; | |
492 | ||
493 | if ((!dax_mapping(mapping) && mapping->nrpages) || | |
494 | (dax_mapping(mapping) && mapping->nrexceptional)) { | |
495 | err = filemap_fdatawrite(mapping); | |
496 | /* | |
497 | * Even if the above returned error, the pages may be | |
498 | * written partially (e.g. -ENOSPC), so we wait for it. | |
499 | * But the -EIO is special case, it may indicate the worst | |
500 | * thing (e.g. bug) happened, so we avoid waiting for it. | |
501 | */ | |
502 | if (err != -EIO) { | |
503 | int err2 = filemap_fdatawait(mapping); | |
504 | if (!err) | |
505 | err = err2; | |
506 | } | |
507 | } else { | |
508 | err = filemap_check_errors(mapping); | |
509 | } | |
510 | return err; | |
511 | } | |
512 | EXPORT_SYMBOL(filemap_write_and_wait); | |
513 | ||
514 | /** | |
515 | * filemap_write_and_wait_range - write out & wait on a file range | |
516 | * @mapping: the address_space for the pages | |
517 | * @lstart: offset in bytes where the range starts | |
518 | * @lend: offset in bytes where the range ends (inclusive) | |
519 | * | |
520 | * Write out and wait upon file offsets lstart->lend, inclusive. | |
521 | * | |
522 | * Note that @lend is inclusive (describes the last byte to be written) so | |
523 | * that this function can be used to write to the very end-of-file (end = -1). | |
524 | */ | |
525 | int filemap_write_and_wait_range(struct address_space *mapping, | |
526 | loff_t lstart, loff_t lend) | |
527 | { | |
528 | int err = 0; | |
529 | ||
530 | if ((!dax_mapping(mapping) && mapping->nrpages) || | |
531 | (dax_mapping(mapping) && mapping->nrexceptional)) { | |
532 | err = __filemap_fdatawrite_range(mapping, lstart, lend, | |
533 | WB_SYNC_ALL); | |
534 | /* See comment of filemap_write_and_wait() */ | |
535 | if (err != -EIO) { | |
536 | int err2 = filemap_fdatawait_range(mapping, | |
537 | lstart, lend); | |
538 | if (!err) | |
539 | err = err2; | |
540 | } | |
541 | } else { | |
542 | err = filemap_check_errors(mapping); | |
543 | } | |
544 | return err; | |
545 | } | |
546 | EXPORT_SYMBOL(filemap_write_and_wait_range); | |
547 | ||
548 | /** | |
549 | * replace_page_cache_page - replace a pagecache page with a new one | |
550 | * @old: page to be replaced | |
551 | * @new: page to replace with | |
552 | * @gfp_mask: allocation mode | |
553 | * | |
554 | * This function replaces a page in the pagecache with a new one. On | |
555 | * success it acquires the pagecache reference for the new page and | |
556 | * drops it for the old page. Both the old and new pages must be | |
557 | * locked. This function does not add the new page to the LRU, the | |
558 | * caller must do that. | |
559 | * | |
560 | * The remove + add is atomic. The only way this function can fail is | |
561 | * memory allocation failure. | |
562 | */ | |
563 | int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) | |
564 | { | |
565 | int error; | |
566 | ||
567 | VM_BUG_ON_PAGE(!PageLocked(old), old); | |
568 | VM_BUG_ON_PAGE(!PageLocked(new), new); | |
569 | VM_BUG_ON_PAGE(new->mapping, new); | |
570 | ||
571 | error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); | |
572 | if (!error) { | |
573 | struct address_space *mapping = old->mapping; | |
574 | void (*freepage)(struct page *); | |
575 | unsigned long flags; | |
576 | ||
577 | pgoff_t offset = old->index; | |
578 | freepage = mapping->a_ops->freepage; | |
579 | ||
580 | get_page(new); | |
581 | new->mapping = mapping; | |
582 | new->index = offset; | |
583 | ||
584 | spin_lock_irqsave(&mapping->tree_lock, flags); | |
585 | __delete_from_page_cache(old, NULL); | |
586 | error = page_cache_tree_insert(mapping, new, NULL); | |
587 | BUG_ON(error); | |
588 | ||
589 | /* | |
590 | * hugetlb pages do not participate in page cache accounting. | |
591 | */ | |
592 | if (!PageHuge(new)) | |
593 | __inc_node_page_state(new, NR_FILE_PAGES); | |
594 | if (PageSwapBacked(new)) | |
595 | __inc_node_page_state(new, NR_SHMEM); | |
596 | spin_unlock_irqrestore(&mapping->tree_lock, flags); | |
597 | mem_cgroup_migrate(old, new); | |
598 | radix_tree_preload_end(); | |
599 | if (freepage) | |
600 | freepage(old); | |
601 | put_page(old); | |
602 | } | |
603 | ||
604 | return error; | |
605 | } | |
606 | EXPORT_SYMBOL_GPL(replace_page_cache_page); | |
607 | ||
608 | static int __add_to_page_cache_locked(struct page *page, | |
609 | struct address_space *mapping, | |
610 | pgoff_t offset, gfp_t gfp_mask, | |
611 | void **shadowp) | |
612 | { | |
613 | int huge = PageHuge(page); | |
614 | struct mem_cgroup *memcg; | |
615 | int error; | |
616 | ||
617 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
618 | VM_BUG_ON_PAGE(PageSwapBacked(page), page); | |
619 | ||
620 | if (!huge) { | |
621 | error = mem_cgroup_try_charge(page, current->mm, | |
622 | gfp_mask, &memcg, false); | |
623 | if (error) | |
624 | return error; | |
625 | } | |
626 | ||
627 | error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM); | |
628 | if (error) { | |
629 | if (!huge) | |
630 | mem_cgroup_cancel_charge(page, memcg, false); | |
631 | return error; | |
632 | } | |
633 | ||
634 | get_page(page); | |
635 | page->mapping = mapping; | |
636 | page->index = offset; | |
637 | ||
638 | spin_lock_irq(&mapping->tree_lock); | |
639 | error = page_cache_tree_insert(mapping, page, shadowp); | |
640 | radix_tree_preload_end(); | |
641 | if (unlikely(error)) | |
642 | goto err_insert; | |
643 | ||
644 | /* hugetlb pages do not participate in page cache accounting. */ | |
645 | if (!huge) | |
646 | __inc_node_page_state(page, NR_FILE_PAGES); | |
647 | spin_unlock_irq(&mapping->tree_lock); | |
648 | if (!huge) | |
649 | mem_cgroup_commit_charge(page, memcg, false, false); | |
650 | trace_mm_filemap_add_to_page_cache(page); | |
651 | return 0; | |
652 | err_insert: | |
653 | page->mapping = NULL; | |
654 | /* Leave page->index set: truncation relies upon it */ | |
655 | spin_unlock_irq(&mapping->tree_lock); | |
656 | if (!huge) | |
657 | mem_cgroup_cancel_charge(page, memcg, false); | |
658 | put_page(page); | |
659 | return error; | |
660 | } | |
661 | ||
662 | /** | |
663 | * add_to_page_cache_locked - add a locked page to the pagecache | |
664 | * @page: page to add | |
665 | * @mapping: the page's address_space | |
666 | * @offset: page index | |
667 | * @gfp_mask: page allocation mode | |
668 | * | |
669 | * This function is used to add a page to the pagecache. It must be locked. | |
670 | * This function does not add the page to the LRU. The caller must do that. | |
671 | */ | |
672 | int add_to_page_cache_locked(struct page *page, struct address_space *mapping, | |
673 | pgoff_t offset, gfp_t gfp_mask) | |
674 | { | |
675 | return __add_to_page_cache_locked(page, mapping, offset, | |
676 | gfp_mask, NULL); | |
677 | } | |
678 | EXPORT_SYMBOL(add_to_page_cache_locked); | |
679 | ||
680 | int add_to_page_cache_lru(struct page *page, struct address_space *mapping, | |
681 | pgoff_t offset, gfp_t gfp_mask) | |
682 | { | |
683 | void *shadow = NULL; | |
684 | int ret; | |
685 | ||
686 | __SetPageLocked(page); | |
687 | ret = __add_to_page_cache_locked(page, mapping, offset, | |
688 | gfp_mask, &shadow); | |
689 | if (unlikely(ret)) | |
690 | __ClearPageLocked(page); | |
691 | else { | |
692 | /* | |
693 | * The page might have been evicted from cache only | |
694 | * recently, in which case it should be activated like | |
695 | * any other repeatedly accessed page. | |
696 | * The exception is pages getting rewritten; evicting other | |
697 | * data from the working set, only to cache data that will | |
698 | * get overwritten with something else, is a waste of memory. | |
699 | */ | |
700 | if (!(gfp_mask & __GFP_WRITE) && | |
701 | shadow && workingset_refault(shadow)) { | |
702 | SetPageActive(page); | |
703 | workingset_activation(page); | |
704 | } else | |
705 | ClearPageActive(page); | |
706 | lru_cache_add(page); | |
707 | } | |
708 | return ret; | |
709 | } | |
710 | EXPORT_SYMBOL_GPL(add_to_page_cache_lru); | |
711 | ||
712 | #ifdef CONFIG_NUMA | |
713 | struct page *__page_cache_alloc(gfp_t gfp) | |
714 | { | |
715 | int n; | |
716 | struct page *page; | |
717 | ||
718 | if (cpuset_do_page_mem_spread()) { | |
719 | unsigned int cpuset_mems_cookie; | |
720 | do { | |
721 | cpuset_mems_cookie = read_mems_allowed_begin(); | |
722 | n = cpuset_mem_spread_node(); | |
723 | page = __alloc_pages_node(n, gfp, 0); | |
724 | } while (!page && read_mems_allowed_retry(cpuset_mems_cookie)); | |
725 | ||
726 | return page; | |
727 | } | |
728 | return alloc_pages(gfp, 0); | |
729 | } | |
730 | EXPORT_SYMBOL(__page_cache_alloc); | |
731 | #endif | |
732 | ||
733 | /* | |
734 | * In order to wait for pages to become available there must be | |
735 | * waitqueues associated with pages. By using a hash table of | |
736 | * waitqueues where the bucket discipline is to maintain all | |
737 | * waiters on the same queue and wake all when any of the pages | |
738 | * become available, and for the woken contexts to check to be | |
739 | * sure the appropriate page became available, this saves space | |
740 | * at a cost of "thundering herd" phenomena during rare hash | |
741 | * collisions. | |
742 | */ | |
743 | #define PAGE_WAIT_TABLE_BITS 8 | |
744 | #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS) | |
745 | static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned; | |
746 | ||
747 | static wait_queue_head_t *page_waitqueue(struct page *page) | |
748 | { | |
749 | return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)]; | |
750 | } | |
751 | ||
752 | void __init pagecache_init(void) | |
753 | { | |
754 | int i; | |
755 | ||
756 | for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++) | |
757 | init_waitqueue_head(&page_wait_table[i]); | |
758 | ||
759 | page_writeback_init(); | |
760 | } | |
761 | ||
762 | struct wait_page_key { | |
763 | struct page *page; | |
764 | int bit_nr; | |
765 | int page_match; | |
766 | }; | |
767 | ||
768 | struct wait_page_queue { | |
769 | struct page *page; | |
770 | int bit_nr; | |
771 | wait_queue_t wait; | |
772 | }; | |
773 | ||
774 | static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void *arg) | |
775 | { | |
776 | struct wait_page_key *key = arg; | |
777 | struct wait_page_queue *wait_page | |
778 | = container_of(wait, struct wait_page_queue, wait); | |
779 | ||
780 | if (wait_page->page != key->page) | |
781 | return 0; | |
782 | key->page_match = 1; | |
783 | ||
784 | if (wait_page->bit_nr != key->bit_nr) | |
785 | return 0; | |
786 | if (test_bit(key->bit_nr, &key->page->flags)) | |
787 | return 0; | |
788 | ||
789 | return autoremove_wake_function(wait, mode, sync, key); | |
790 | } | |
791 | ||
792 | static void wake_up_page_bit(struct page *page, int bit_nr) | |
793 | { | |
794 | wait_queue_head_t *q = page_waitqueue(page); | |
795 | struct wait_page_key key; | |
796 | unsigned long flags; | |
797 | ||
798 | key.page = page; | |
799 | key.bit_nr = bit_nr; | |
800 | key.page_match = 0; | |
801 | ||
802 | spin_lock_irqsave(&q->lock, flags); | |
803 | __wake_up_locked_key(q, TASK_NORMAL, &key); | |
804 | /* | |
805 | * It is possible for other pages to have collided on the waitqueue | |
806 | * hash, so in that case check for a page match. That prevents a long- | |
807 | * term waiter | |
808 | * | |
809 | * It is still possible to miss a case here, when we woke page waiters | |
810 | * and removed them from the waitqueue, but there are still other | |
811 | * page waiters. | |
812 | */ | |
813 | if (!waitqueue_active(q) || !key.page_match) { | |
814 | ClearPageWaiters(page); | |
815 | /* | |
816 | * It's possible to miss clearing Waiters here, when we woke | |
817 | * our page waiters, but the hashed waitqueue has waiters for | |
818 | * other pages on it. | |
819 | * | |
820 | * That's okay, it's a rare case. The next waker will clear it. | |
821 | */ | |
822 | } | |
823 | spin_unlock_irqrestore(&q->lock, flags); | |
824 | } | |
825 | ||
826 | static void wake_up_page(struct page *page, int bit) | |
827 | { | |
828 | if (!PageWaiters(page)) | |
829 | return; | |
830 | wake_up_page_bit(page, bit); | |
831 | } | |
832 | ||
833 | static inline int wait_on_page_bit_common(wait_queue_head_t *q, | |
834 | struct page *page, int bit_nr, int state, bool lock) | |
835 | { | |
836 | struct wait_page_queue wait_page; | |
837 | wait_queue_t *wait = &wait_page.wait; | |
838 | int ret = 0; | |
839 | ||
840 | init_wait(wait); | |
841 | wait->func = wake_page_function; | |
842 | wait_page.page = page; | |
843 | wait_page.bit_nr = bit_nr; | |
844 | ||
845 | for (;;) { | |
846 | spin_lock_irq(&q->lock); | |
847 | ||
848 | if (likely(list_empty(&wait->task_list))) { | |
849 | if (lock) | |
850 | __add_wait_queue_tail_exclusive(q, wait); | |
851 | else | |
852 | __add_wait_queue(q, wait); | |
853 | SetPageWaiters(page); | |
854 | } | |
855 | ||
856 | set_current_state(state); | |
857 | ||
858 | spin_unlock_irq(&q->lock); | |
859 | ||
860 | if (likely(test_bit(bit_nr, &page->flags))) { | |
861 | io_schedule(); | |
862 | if (unlikely(signal_pending_state(state, current))) { | |
863 | ret = -EINTR; | |
864 | break; | |
865 | } | |
866 | } | |
867 | ||
868 | if (lock) { | |
869 | if (!test_and_set_bit_lock(bit_nr, &page->flags)) | |
870 | break; | |
871 | } else { | |
872 | if (!test_bit(bit_nr, &page->flags)) | |
873 | break; | |
874 | } | |
875 | } | |
876 | ||
877 | finish_wait(q, wait); | |
878 | ||
879 | /* | |
880 | * A signal could leave PageWaiters set. Clearing it here if | |
881 | * !waitqueue_active would be possible (by open-coding finish_wait), | |
882 | * but still fail to catch it in the case of wait hash collision. We | |
883 | * already can fail to clear wait hash collision cases, so don't | |
884 | * bother with signals either. | |
885 | */ | |
886 | ||
887 | return ret; | |
888 | } | |
889 | ||
890 | void wait_on_page_bit(struct page *page, int bit_nr) | |
891 | { | |
892 | wait_queue_head_t *q = page_waitqueue(page); | |
893 | wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false); | |
894 | } | |
895 | EXPORT_SYMBOL(wait_on_page_bit); | |
896 | ||
897 | int wait_on_page_bit_killable(struct page *page, int bit_nr) | |
898 | { | |
899 | wait_queue_head_t *q = page_waitqueue(page); | |
900 | return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false); | |
901 | } | |
902 | ||
903 | /** | |
904 | * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue | |
905 | * @page: Page defining the wait queue of interest | |
906 | * @waiter: Waiter to add to the queue | |
907 | * | |
908 | * Add an arbitrary @waiter to the wait queue for the nominated @page. | |
909 | */ | |
910 | void add_page_wait_queue(struct page *page, wait_queue_t *waiter) | |
911 | { | |
912 | wait_queue_head_t *q = page_waitqueue(page); | |
913 | unsigned long flags; | |
914 | ||
915 | spin_lock_irqsave(&q->lock, flags); | |
916 | __add_wait_queue(q, waiter); | |
917 | SetPageWaiters(page); | |
918 | spin_unlock_irqrestore(&q->lock, flags); | |
919 | } | |
920 | EXPORT_SYMBOL_GPL(add_page_wait_queue); | |
921 | ||
922 | #ifndef clear_bit_unlock_is_negative_byte | |
923 | ||
924 | /* | |
925 | * PG_waiters is the high bit in the same byte as PG_lock. | |
926 | * | |
927 | * On x86 (and on many other architectures), we can clear PG_lock and | |
928 | * test the sign bit at the same time. But if the architecture does | |
929 | * not support that special operation, we just do this all by hand | |
930 | * instead. | |
931 | * | |
932 | * The read of PG_waiters has to be after (or concurrently with) PG_locked | |
933 | * being cleared, but a memory barrier should be unneccssary since it is | |
934 | * in the same byte as PG_locked. | |
935 | */ | |
936 | static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem) | |
937 | { | |
938 | clear_bit_unlock(nr, mem); | |
939 | /* smp_mb__after_atomic(); */ | |
940 | return test_bit(PG_waiters, mem); | |
941 | } | |
942 | ||
943 | #endif | |
944 | ||
945 | /** | |
946 | * unlock_page - unlock a locked page | |
947 | * @page: the page | |
948 | * | |
949 | * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). | |
950 | * Also wakes sleepers in wait_on_page_writeback() because the wakeup | |
951 | * mechanism between PageLocked pages and PageWriteback pages is shared. | |
952 | * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. | |
953 | * | |
954 | * Note that this depends on PG_waiters being the sign bit in the byte | |
955 | * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to | |
956 | * clear the PG_locked bit and test PG_waiters at the same time fairly | |
957 | * portably (architectures that do LL/SC can test any bit, while x86 can | |
958 | * test the sign bit). | |
959 | */ | |
960 | void unlock_page(struct page *page) | |
961 | { | |
962 | BUILD_BUG_ON(PG_waiters != 7); | |
963 | page = compound_head(page); | |
964 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
965 | if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags)) | |
966 | wake_up_page_bit(page, PG_locked); | |
967 | } | |
968 | EXPORT_SYMBOL(unlock_page); | |
969 | ||
970 | /** | |
971 | * end_page_writeback - end writeback against a page | |
972 | * @page: the page | |
973 | */ | |
974 | void end_page_writeback(struct page *page) | |
975 | { | |
976 | /* | |
977 | * TestClearPageReclaim could be used here but it is an atomic | |
978 | * operation and overkill in this particular case. Failing to | |
979 | * shuffle a page marked for immediate reclaim is too mild to | |
980 | * justify taking an atomic operation penalty at the end of | |
981 | * ever page writeback. | |
982 | */ | |
983 | if (PageReclaim(page)) { | |
984 | ClearPageReclaim(page); | |
985 | rotate_reclaimable_page(page); | |
986 | } | |
987 | ||
988 | if (!test_clear_page_writeback(page)) | |
989 | BUG(); | |
990 | ||
991 | smp_mb__after_atomic(); | |
992 | wake_up_page(page, PG_writeback); | |
993 | } | |
994 | EXPORT_SYMBOL(end_page_writeback); | |
995 | ||
996 | /* | |
997 | * After completing I/O on a page, call this routine to update the page | |
998 | * flags appropriately | |
999 | */ | |
1000 | void page_endio(struct page *page, bool is_write, int err) | |
1001 | { | |
1002 | if (!is_write) { | |
1003 | if (!err) { | |
1004 | SetPageUptodate(page); | |
1005 | } else { | |
1006 | ClearPageUptodate(page); | |
1007 | SetPageError(page); | |
1008 | } | |
1009 | unlock_page(page); | |
1010 | } else { | |
1011 | if (err) { | |
1012 | struct address_space *mapping; | |
1013 | ||
1014 | SetPageError(page); | |
1015 | mapping = page_mapping(page); | |
1016 | if (mapping) | |
1017 | mapping_set_error(mapping, err); | |
1018 | } | |
1019 | end_page_writeback(page); | |
1020 | } | |
1021 | } | |
1022 | EXPORT_SYMBOL_GPL(page_endio); | |
1023 | ||
1024 | /** | |
1025 | * __lock_page - get a lock on the page, assuming we need to sleep to get it | |
1026 | * @__page: the page to lock | |
1027 | */ | |
1028 | void __lock_page(struct page *__page) | |
1029 | { | |
1030 | struct page *page = compound_head(__page); | |
1031 | wait_queue_head_t *q = page_waitqueue(page); | |
1032 | wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true); | |
1033 | } | |
1034 | EXPORT_SYMBOL(__lock_page); | |
1035 | ||
1036 | int __lock_page_killable(struct page *__page) | |
1037 | { | |
1038 | struct page *page = compound_head(__page); | |
1039 | wait_queue_head_t *q = page_waitqueue(page); | |
1040 | return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true); | |
1041 | } | |
1042 | EXPORT_SYMBOL_GPL(__lock_page_killable); | |
1043 | ||
1044 | /* | |
1045 | * Return values: | |
1046 | * 1 - page is locked; mmap_sem is still held. | |
1047 | * 0 - page is not locked. | |
1048 | * mmap_sem has been released (up_read()), unless flags had both | |
1049 | * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in | |
1050 | * which case mmap_sem is still held. | |
1051 | * | |
1052 | * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1 | |
1053 | * with the page locked and the mmap_sem unperturbed. | |
1054 | */ | |
1055 | int __lock_page_or_retry(struct page *page, struct mm_struct *mm, | |
1056 | unsigned int flags) | |
1057 | { | |
1058 | if (flags & FAULT_FLAG_ALLOW_RETRY) { | |
1059 | /* | |
1060 | * CAUTION! In this case, mmap_sem is not released | |
1061 | * even though return 0. | |
1062 | */ | |
1063 | if (flags & FAULT_FLAG_RETRY_NOWAIT) | |
1064 | return 0; | |
1065 | ||
1066 | up_read(&mm->mmap_sem); | |
1067 | if (flags & FAULT_FLAG_KILLABLE) | |
1068 | wait_on_page_locked_killable(page); | |
1069 | else | |
1070 | wait_on_page_locked(page); | |
1071 | return 0; | |
1072 | } else { | |
1073 | if (flags & FAULT_FLAG_KILLABLE) { | |
1074 | int ret; | |
1075 | ||
1076 | ret = __lock_page_killable(page); | |
1077 | if (ret) { | |
1078 | up_read(&mm->mmap_sem); | |
1079 | return 0; | |
1080 | } | |
1081 | } else | |
1082 | __lock_page(page); | |
1083 | return 1; | |
1084 | } | |
1085 | } | |
1086 | ||
1087 | /** | |
1088 | * page_cache_next_hole - find the next hole (not-present entry) | |
1089 | * @mapping: mapping | |
1090 | * @index: index | |
1091 | * @max_scan: maximum range to search | |
1092 | * | |
1093 | * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the | |
1094 | * lowest indexed hole. | |
1095 | * | |
1096 | * Returns: the index of the hole if found, otherwise returns an index | |
1097 | * outside of the set specified (in which case 'return - index >= | |
1098 | * max_scan' will be true). In rare cases of index wrap-around, 0 will | |
1099 | * be returned. | |
1100 | * | |
1101 | * page_cache_next_hole may be called under rcu_read_lock. However, | |
1102 | * like radix_tree_gang_lookup, this will not atomically search a | |
1103 | * snapshot of the tree at a single point in time. For example, if a | |
1104 | * hole is created at index 5, then subsequently a hole is created at | |
1105 | * index 10, page_cache_next_hole covering both indexes may return 10 | |
1106 | * if called under rcu_read_lock. | |
1107 | */ | |
1108 | pgoff_t page_cache_next_hole(struct address_space *mapping, | |
1109 | pgoff_t index, unsigned long max_scan) | |
1110 | { | |
1111 | unsigned long i; | |
1112 | ||
1113 | for (i = 0; i < max_scan; i++) { | |
1114 | struct page *page; | |
1115 | ||
1116 | page = radix_tree_lookup(&mapping->page_tree, index); | |
1117 | if (!page || radix_tree_exceptional_entry(page)) | |
1118 | break; | |
1119 | index++; | |
1120 | if (index == 0) | |
1121 | break; | |
1122 | } | |
1123 | ||
1124 | return index; | |
1125 | } | |
1126 | EXPORT_SYMBOL(page_cache_next_hole); | |
1127 | ||
1128 | /** | |
1129 | * page_cache_prev_hole - find the prev hole (not-present entry) | |
1130 | * @mapping: mapping | |
1131 | * @index: index | |
1132 | * @max_scan: maximum range to search | |
1133 | * | |
1134 | * Search backwards in the range [max(index-max_scan+1, 0), index] for | |
1135 | * the first hole. | |
1136 | * | |
1137 | * Returns: the index of the hole if found, otherwise returns an index | |
1138 | * outside of the set specified (in which case 'index - return >= | |
1139 | * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX | |
1140 | * will be returned. | |
1141 | * | |
1142 | * page_cache_prev_hole may be called under rcu_read_lock. However, | |
1143 | * like radix_tree_gang_lookup, this will not atomically search a | |
1144 | * snapshot of the tree at a single point in time. For example, if a | |
1145 | * hole is created at index 10, then subsequently a hole is created at | |
1146 | * index 5, page_cache_prev_hole covering both indexes may return 5 if | |
1147 | * called under rcu_read_lock. | |
1148 | */ | |
1149 | pgoff_t page_cache_prev_hole(struct address_space *mapping, | |
1150 | pgoff_t index, unsigned long max_scan) | |
1151 | { | |
1152 | unsigned long i; | |
1153 | ||
1154 | for (i = 0; i < max_scan; i++) { | |
1155 | struct page *page; | |
1156 | ||
1157 | page = radix_tree_lookup(&mapping->page_tree, index); | |
1158 | if (!page || radix_tree_exceptional_entry(page)) | |
1159 | break; | |
1160 | index--; | |
1161 | if (index == ULONG_MAX) | |
1162 | break; | |
1163 | } | |
1164 | ||
1165 | return index; | |
1166 | } | |
1167 | EXPORT_SYMBOL(page_cache_prev_hole); | |
1168 | ||
1169 | /** | |
1170 | * find_get_entry - find and get a page cache entry | |
1171 | * @mapping: the address_space to search | |
1172 | * @offset: the page cache index | |
1173 | * | |
1174 | * Looks up the page cache slot at @mapping & @offset. If there is a | |
1175 | * page cache page, it is returned with an increased refcount. | |
1176 | * | |
1177 | * If the slot holds a shadow entry of a previously evicted page, or a | |
1178 | * swap entry from shmem/tmpfs, it is returned. | |
1179 | * | |
1180 | * Otherwise, %NULL is returned. | |
1181 | */ | |
1182 | struct page *find_get_entry(struct address_space *mapping, pgoff_t offset) | |
1183 | { | |
1184 | void **pagep; | |
1185 | struct page *head, *page; | |
1186 | ||
1187 | rcu_read_lock(); | |
1188 | repeat: | |
1189 | page = NULL; | |
1190 | pagep = radix_tree_lookup_slot(&mapping->page_tree, offset); | |
1191 | if (pagep) { | |
1192 | page = radix_tree_deref_slot(pagep); | |
1193 | if (unlikely(!page)) | |
1194 | goto out; | |
1195 | if (radix_tree_exception(page)) { | |
1196 | if (radix_tree_deref_retry(page)) | |
1197 | goto repeat; | |
1198 | /* | |
1199 | * A shadow entry of a recently evicted page, | |
1200 | * or a swap entry from shmem/tmpfs. Return | |
1201 | * it without attempting to raise page count. | |
1202 | */ | |
1203 | goto out; | |
1204 | } | |
1205 | ||
1206 | head = compound_head(page); | |
1207 | if (!page_cache_get_speculative(head)) | |
1208 | goto repeat; | |
1209 | ||
1210 | /* The page was split under us? */ | |
1211 | if (compound_head(page) != head) { | |
1212 | put_page(head); | |
1213 | goto repeat; | |
1214 | } | |
1215 | ||
1216 | /* | |
1217 | * Has the page moved? | |
1218 | * This is part of the lockless pagecache protocol. See | |
1219 | * include/linux/pagemap.h for details. | |
1220 | */ | |
1221 | if (unlikely(page != *pagep)) { | |
1222 | put_page(head); | |
1223 | goto repeat; | |
1224 | } | |
1225 | } | |
1226 | out: | |
1227 | rcu_read_unlock(); | |
1228 | ||
1229 | return page; | |
1230 | } | |
1231 | EXPORT_SYMBOL(find_get_entry); | |
1232 | ||
1233 | /** | |
1234 | * find_lock_entry - locate, pin and lock a page cache entry | |
1235 | * @mapping: the address_space to search | |
1236 | * @offset: the page cache index | |
1237 | * | |
1238 | * Looks up the page cache slot at @mapping & @offset. If there is a | |
1239 | * page cache page, it is returned locked and with an increased | |
1240 | * refcount. | |
1241 | * | |
1242 | * If the slot holds a shadow entry of a previously evicted page, or a | |
1243 | * swap entry from shmem/tmpfs, it is returned. | |
1244 | * | |
1245 | * Otherwise, %NULL is returned. | |
1246 | * | |
1247 | * find_lock_entry() may sleep. | |
1248 | */ | |
1249 | struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset) | |
1250 | { | |
1251 | struct page *page; | |
1252 | ||
1253 | repeat: | |
1254 | page = find_get_entry(mapping, offset); | |
1255 | if (page && !radix_tree_exception(page)) { | |
1256 | lock_page(page); | |
1257 | /* Has the page been truncated? */ | |
1258 | if (unlikely(page_mapping(page) != mapping)) { | |
1259 | unlock_page(page); | |
1260 | put_page(page); | |
1261 | goto repeat; | |
1262 | } | |
1263 | VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page); | |
1264 | } | |
1265 | return page; | |
1266 | } | |
1267 | EXPORT_SYMBOL(find_lock_entry); | |
1268 | ||
1269 | /** | |
1270 | * pagecache_get_page - find and get a page reference | |
1271 | * @mapping: the address_space to search | |
1272 | * @offset: the page index | |
1273 | * @fgp_flags: PCG flags | |
1274 | * @gfp_mask: gfp mask to use for the page cache data page allocation | |
1275 | * | |
1276 | * Looks up the page cache slot at @mapping & @offset. | |
1277 | * | |
1278 | * PCG flags modify how the page is returned. | |
1279 | * | |
1280 | * @fgp_flags can be: | |
1281 | * | |
1282 | * - FGP_ACCESSED: the page will be marked accessed | |
1283 | * - FGP_LOCK: Page is return locked | |
1284 | * - FGP_CREAT: If page is not present then a new page is allocated using | |
1285 | * @gfp_mask and added to the page cache and the VM's LRU | |
1286 | * list. The page is returned locked and with an increased | |
1287 | * refcount. Otherwise, NULL is returned. | |
1288 | * | |
1289 | * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even | |
1290 | * if the GFP flags specified for FGP_CREAT are atomic. | |
1291 | * | |
1292 | * If there is a page cache page, it is returned with an increased refcount. | |
1293 | */ | |
1294 | struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, | |
1295 | int fgp_flags, gfp_t gfp_mask) | |
1296 | { | |
1297 | struct page *page; | |
1298 | ||
1299 | repeat: | |
1300 | page = find_get_entry(mapping, offset); | |
1301 | if (radix_tree_exceptional_entry(page)) | |
1302 | page = NULL; | |
1303 | if (!page) | |
1304 | goto no_page; | |
1305 | ||
1306 | if (fgp_flags & FGP_LOCK) { | |
1307 | if (fgp_flags & FGP_NOWAIT) { | |
1308 | if (!trylock_page(page)) { | |
1309 | put_page(page); | |
1310 | return NULL; | |
1311 | } | |
1312 | } else { | |
1313 | lock_page(page); | |
1314 | } | |
1315 | ||
1316 | /* Has the page been truncated? */ | |
1317 | if (unlikely(page->mapping != mapping)) { | |
1318 | unlock_page(page); | |
1319 | put_page(page); | |
1320 | goto repeat; | |
1321 | } | |
1322 | VM_BUG_ON_PAGE(page->index != offset, page); | |
1323 | } | |
1324 | ||
1325 | if (page && (fgp_flags & FGP_ACCESSED)) | |
1326 | mark_page_accessed(page); | |
1327 | ||
1328 | no_page: | |
1329 | if (!page && (fgp_flags & FGP_CREAT)) { | |
1330 | int err; | |
1331 | if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping)) | |
1332 | gfp_mask |= __GFP_WRITE; | |
1333 | if (fgp_flags & FGP_NOFS) | |
1334 | gfp_mask &= ~__GFP_FS; | |
1335 | ||
1336 | page = __page_cache_alloc(gfp_mask); | |
1337 | if (!page) | |
1338 | return NULL; | |
1339 | ||
1340 | if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK))) | |
1341 | fgp_flags |= FGP_LOCK; | |
1342 | ||
1343 | /* Init accessed so avoid atomic mark_page_accessed later */ | |
1344 | if (fgp_flags & FGP_ACCESSED) | |
1345 | __SetPageReferenced(page); | |
1346 | ||
1347 | err = add_to_page_cache_lru(page, mapping, offset, | |
1348 | gfp_mask & GFP_RECLAIM_MASK); | |
1349 | if (unlikely(err)) { | |
1350 | put_page(page); | |
1351 | page = NULL; | |
1352 | if (err == -EEXIST) | |
1353 | goto repeat; | |
1354 | } | |
1355 | } | |
1356 | ||
1357 | return page; | |
1358 | } | |
1359 | EXPORT_SYMBOL(pagecache_get_page); | |
1360 | ||
1361 | /** | |
1362 | * find_get_entries - gang pagecache lookup | |
1363 | * @mapping: The address_space to search | |
1364 | * @start: The starting page cache index | |
1365 | * @nr_entries: The maximum number of entries | |
1366 | * @entries: Where the resulting entries are placed | |
1367 | * @indices: The cache indices corresponding to the entries in @entries | |
1368 | * | |
1369 | * find_get_entries() will search for and return a group of up to | |
1370 | * @nr_entries entries in the mapping. The entries are placed at | |
1371 | * @entries. find_get_entries() takes a reference against any actual | |
1372 | * pages it returns. | |
1373 | * | |
1374 | * The search returns a group of mapping-contiguous page cache entries | |
1375 | * with ascending indexes. There may be holes in the indices due to | |
1376 | * not-present pages. | |
1377 | * | |
1378 | * Any shadow entries of evicted pages, or swap entries from | |
1379 | * shmem/tmpfs, are included in the returned array. | |
1380 | * | |
1381 | * find_get_entries() returns the number of pages and shadow entries | |
1382 | * which were found. | |
1383 | */ | |
1384 | unsigned find_get_entries(struct address_space *mapping, | |
1385 | pgoff_t start, unsigned int nr_entries, | |
1386 | struct page **entries, pgoff_t *indices) | |
1387 | { | |
1388 | void **slot; | |
1389 | unsigned int ret = 0; | |
1390 | struct radix_tree_iter iter; | |
1391 | ||
1392 | if (!nr_entries) | |
1393 | return 0; | |
1394 | ||
1395 | rcu_read_lock(); | |
1396 | radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { | |
1397 | struct page *head, *page; | |
1398 | repeat: | |
1399 | page = radix_tree_deref_slot(slot); | |
1400 | if (unlikely(!page)) | |
1401 | continue; | |
1402 | if (radix_tree_exception(page)) { | |
1403 | if (radix_tree_deref_retry(page)) { | |
1404 | slot = radix_tree_iter_retry(&iter); | |
1405 | continue; | |
1406 | } | |
1407 | /* | |
1408 | * A shadow entry of a recently evicted page, a swap | |
1409 | * entry from shmem/tmpfs or a DAX entry. Return it | |
1410 | * without attempting to raise page count. | |
1411 | */ | |
1412 | goto export; | |
1413 | } | |
1414 | ||
1415 | head = compound_head(page); | |
1416 | if (!page_cache_get_speculative(head)) | |
1417 | goto repeat; | |
1418 | ||
1419 | /* The page was split under us? */ | |
1420 | if (compound_head(page) != head) { | |
1421 | put_page(head); | |
1422 | goto repeat; | |
1423 | } | |
1424 | ||
1425 | /* Has the page moved? */ | |
1426 | if (unlikely(page != *slot)) { | |
1427 | put_page(head); | |
1428 | goto repeat; | |
1429 | } | |
1430 | export: | |
1431 | indices[ret] = iter.index; | |
1432 | entries[ret] = page; | |
1433 | if (++ret == nr_entries) | |
1434 | break; | |
1435 | } | |
1436 | rcu_read_unlock(); | |
1437 | return ret; | |
1438 | } | |
1439 | ||
1440 | /** | |
1441 | * find_get_pages - gang pagecache lookup | |
1442 | * @mapping: The address_space to search | |
1443 | * @start: The starting page index | |
1444 | * @nr_pages: The maximum number of pages | |
1445 | * @pages: Where the resulting pages are placed | |
1446 | * | |
1447 | * find_get_pages() will search for and return a group of up to | |
1448 | * @nr_pages pages in the mapping. The pages are placed at @pages. | |
1449 | * find_get_pages() takes a reference against the returned pages. | |
1450 | * | |
1451 | * The search returns a group of mapping-contiguous pages with ascending | |
1452 | * indexes. There may be holes in the indices due to not-present pages. | |
1453 | * | |
1454 | * find_get_pages() returns the number of pages which were found. | |
1455 | */ | |
1456 | unsigned find_get_pages(struct address_space *mapping, pgoff_t start, | |
1457 | unsigned int nr_pages, struct page **pages) | |
1458 | { | |
1459 | struct radix_tree_iter iter; | |
1460 | void **slot; | |
1461 | unsigned ret = 0; | |
1462 | ||
1463 | if (unlikely(!nr_pages)) | |
1464 | return 0; | |
1465 | ||
1466 | rcu_read_lock(); | |
1467 | radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { | |
1468 | struct page *head, *page; | |
1469 | repeat: | |
1470 | page = radix_tree_deref_slot(slot); | |
1471 | if (unlikely(!page)) | |
1472 | continue; | |
1473 | ||
1474 | if (radix_tree_exception(page)) { | |
1475 | if (radix_tree_deref_retry(page)) { | |
1476 | slot = radix_tree_iter_retry(&iter); | |
1477 | continue; | |
1478 | } | |
1479 | /* | |
1480 | * A shadow entry of a recently evicted page, | |
1481 | * or a swap entry from shmem/tmpfs. Skip | |
1482 | * over it. | |
1483 | */ | |
1484 | continue; | |
1485 | } | |
1486 | ||
1487 | head = compound_head(page); | |
1488 | if (!page_cache_get_speculative(head)) | |
1489 | goto repeat; | |
1490 | ||
1491 | /* The page was split under us? */ | |
1492 | if (compound_head(page) != head) { | |
1493 | put_page(head); | |
1494 | goto repeat; | |
1495 | } | |
1496 | ||
1497 | /* Has the page moved? */ | |
1498 | if (unlikely(page != *slot)) { | |
1499 | put_page(head); | |
1500 | goto repeat; | |
1501 | } | |
1502 | ||
1503 | pages[ret] = page; | |
1504 | if (++ret == nr_pages) | |
1505 | break; | |
1506 | } | |
1507 | ||
1508 | rcu_read_unlock(); | |
1509 | return ret; | |
1510 | } | |
1511 | ||
1512 | /** | |
1513 | * find_get_pages_contig - gang contiguous pagecache lookup | |
1514 | * @mapping: The address_space to search | |
1515 | * @index: The starting page index | |
1516 | * @nr_pages: The maximum number of pages | |
1517 | * @pages: Where the resulting pages are placed | |
1518 | * | |
1519 | * find_get_pages_contig() works exactly like find_get_pages(), except | |
1520 | * that the returned number of pages are guaranteed to be contiguous. | |
1521 | * | |
1522 | * find_get_pages_contig() returns the number of pages which were found. | |
1523 | */ | |
1524 | unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, | |
1525 | unsigned int nr_pages, struct page **pages) | |
1526 | { | |
1527 | struct radix_tree_iter iter; | |
1528 | void **slot; | |
1529 | unsigned int ret = 0; | |
1530 | ||
1531 | if (unlikely(!nr_pages)) | |
1532 | return 0; | |
1533 | ||
1534 | rcu_read_lock(); | |
1535 | radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) { | |
1536 | struct page *head, *page; | |
1537 | repeat: | |
1538 | page = radix_tree_deref_slot(slot); | |
1539 | /* The hole, there no reason to continue */ | |
1540 | if (unlikely(!page)) | |
1541 | break; | |
1542 | ||
1543 | if (radix_tree_exception(page)) { | |
1544 | if (radix_tree_deref_retry(page)) { | |
1545 | slot = radix_tree_iter_retry(&iter); | |
1546 | continue; | |
1547 | } | |
1548 | /* | |
1549 | * A shadow entry of a recently evicted page, | |
1550 | * or a swap entry from shmem/tmpfs. Stop | |
1551 | * looking for contiguous pages. | |
1552 | */ | |
1553 | break; | |
1554 | } | |
1555 | ||
1556 | head = compound_head(page); | |
1557 | if (!page_cache_get_speculative(head)) | |
1558 | goto repeat; | |
1559 | ||
1560 | /* The page was split under us? */ | |
1561 | if (compound_head(page) != head) { | |
1562 | put_page(head); | |
1563 | goto repeat; | |
1564 | } | |
1565 | ||
1566 | /* Has the page moved? */ | |
1567 | if (unlikely(page != *slot)) { | |
1568 | put_page(head); | |
1569 | goto repeat; | |
1570 | } | |
1571 | ||
1572 | /* | |
1573 | * must check mapping and index after taking the ref. | |
1574 | * otherwise we can get both false positives and false | |
1575 | * negatives, which is just confusing to the caller. | |
1576 | */ | |
1577 | if (page->mapping == NULL || page_to_pgoff(page) != iter.index) { | |
1578 | put_page(page); | |
1579 | break; | |
1580 | } | |
1581 | ||
1582 | pages[ret] = page; | |
1583 | if (++ret == nr_pages) | |
1584 | break; | |
1585 | } | |
1586 | rcu_read_unlock(); | |
1587 | return ret; | |
1588 | } | |
1589 | EXPORT_SYMBOL(find_get_pages_contig); | |
1590 | ||
1591 | /** | |
1592 | * find_get_pages_tag - find and return pages that match @tag | |
1593 | * @mapping: the address_space to search | |
1594 | * @index: the starting page index | |
1595 | * @tag: the tag index | |
1596 | * @nr_pages: the maximum number of pages | |
1597 | * @pages: where the resulting pages are placed | |
1598 | * | |
1599 | * Like find_get_pages, except we only return pages which are tagged with | |
1600 | * @tag. We update @index to index the next page for the traversal. | |
1601 | */ | |
1602 | unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, | |
1603 | int tag, unsigned int nr_pages, struct page **pages) | |
1604 | { | |
1605 | struct radix_tree_iter iter; | |
1606 | void **slot; | |
1607 | unsigned ret = 0; | |
1608 | ||
1609 | if (unlikely(!nr_pages)) | |
1610 | return 0; | |
1611 | ||
1612 | rcu_read_lock(); | |
1613 | radix_tree_for_each_tagged(slot, &mapping->page_tree, | |
1614 | &iter, *index, tag) { | |
1615 | struct page *head, *page; | |
1616 | repeat: | |
1617 | page = radix_tree_deref_slot(slot); | |
1618 | if (unlikely(!page)) | |
1619 | continue; | |
1620 | ||
1621 | if (radix_tree_exception(page)) { | |
1622 | if (radix_tree_deref_retry(page)) { | |
1623 | slot = radix_tree_iter_retry(&iter); | |
1624 | continue; | |
1625 | } | |
1626 | /* | |
1627 | * A shadow entry of a recently evicted page. | |
1628 | * | |
1629 | * Those entries should never be tagged, but | |
1630 | * this tree walk is lockless and the tags are | |
1631 | * looked up in bulk, one radix tree node at a | |
1632 | * time, so there is a sizable window for page | |
1633 | * reclaim to evict a page we saw tagged. | |
1634 | * | |
1635 | * Skip over it. | |
1636 | */ | |
1637 | continue; | |
1638 | } | |
1639 | ||
1640 | head = compound_head(page); | |
1641 | if (!page_cache_get_speculative(head)) | |
1642 | goto repeat; | |
1643 | ||
1644 | /* The page was split under us? */ | |
1645 | if (compound_head(page) != head) { | |
1646 | put_page(head); | |
1647 | goto repeat; | |
1648 | } | |
1649 | ||
1650 | /* Has the page moved? */ | |
1651 | if (unlikely(page != *slot)) { | |
1652 | put_page(head); | |
1653 | goto repeat; | |
1654 | } | |
1655 | ||
1656 | pages[ret] = page; | |
1657 | if (++ret == nr_pages) | |
1658 | break; | |
1659 | } | |
1660 | ||
1661 | rcu_read_unlock(); | |
1662 | ||
1663 | if (ret) | |
1664 | *index = pages[ret - 1]->index + 1; | |
1665 | ||
1666 | return ret; | |
1667 | } | |
1668 | EXPORT_SYMBOL(find_get_pages_tag); | |
1669 | ||
1670 | /** | |
1671 | * find_get_entries_tag - find and return entries that match @tag | |
1672 | * @mapping: the address_space to search | |
1673 | * @start: the starting page cache index | |
1674 | * @tag: the tag index | |
1675 | * @nr_entries: the maximum number of entries | |
1676 | * @entries: where the resulting entries are placed | |
1677 | * @indices: the cache indices corresponding to the entries in @entries | |
1678 | * | |
1679 | * Like find_get_entries, except we only return entries which are tagged with | |
1680 | * @tag. | |
1681 | */ | |
1682 | unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, | |
1683 | int tag, unsigned int nr_entries, | |
1684 | struct page **entries, pgoff_t *indices) | |
1685 | { | |
1686 | void **slot; | |
1687 | unsigned int ret = 0; | |
1688 | struct radix_tree_iter iter; | |
1689 | ||
1690 | if (!nr_entries) | |
1691 | return 0; | |
1692 | ||
1693 | rcu_read_lock(); | |
1694 | radix_tree_for_each_tagged(slot, &mapping->page_tree, | |
1695 | &iter, start, tag) { | |
1696 | struct page *head, *page; | |
1697 | repeat: | |
1698 | page = radix_tree_deref_slot(slot); | |
1699 | if (unlikely(!page)) | |
1700 | continue; | |
1701 | if (radix_tree_exception(page)) { | |
1702 | if (radix_tree_deref_retry(page)) { | |
1703 | slot = radix_tree_iter_retry(&iter); | |
1704 | continue; | |
1705 | } | |
1706 | ||
1707 | /* | |
1708 | * A shadow entry of a recently evicted page, a swap | |
1709 | * entry from shmem/tmpfs or a DAX entry. Return it | |
1710 | * without attempting to raise page count. | |
1711 | */ | |
1712 | goto export; | |
1713 | } | |
1714 | ||
1715 | head = compound_head(page); | |
1716 | if (!page_cache_get_speculative(head)) | |
1717 | goto repeat; | |
1718 | ||
1719 | /* The page was split under us? */ | |
1720 | if (compound_head(page) != head) { | |
1721 | put_page(head); | |
1722 | goto repeat; | |
1723 | } | |
1724 | ||
1725 | /* Has the page moved? */ | |
1726 | if (unlikely(page != *slot)) { | |
1727 | put_page(head); | |
1728 | goto repeat; | |
1729 | } | |
1730 | export: | |
1731 | indices[ret] = iter.index; | |
1732 | entries[ret] = page; | |
1733 | if (++ret == nr_entries) | |
1734 | break; | |
1735 | } | |
1736 | rcu_read_unlock(); | |
1737 | return ret; | |
1738 | } | |
1739 | EXPORT_SYMBOL(find_get_entries_tag); | |
1740 | ||
1741 | /* | |
1742 | * CD/DVDs are error prone. When a medium error occurs, the driver may fail | |
1743 | * a _large_ part of the i/o request. Imagine the worst scenario: | |
1744 | * | |
1745 | * ---R__________________________________________B__________ | |
1746 | * ^ reading here ^ bad block(assume 4k) | |
1747 | * | |
1748 | * read(R) => miss => readahead(R...B) => media error => frustrating retries | |
1749 | * => failing the whole request => read(R) => read(R+1) => | |
1750 | * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => | |
1751 | * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => | |
1752 | * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... | |
1753 | * | |
1754 | * It is going insane. Fix it by quickly scaling down the readahead size. | |
1755 | */ | |
1756 | static void shrink_readahead_size_eio(struct file *filp, | |
1757 | struct file_ra_state *ra) | |
1758 | { | |
1759 | ra->ra_pages /= 4; | |
1760 | } | |
1761 | ||
1762 | /** | |
1763 | * do_generic_file_read - generic file read routine | |
1764 | * @filp: the file to read | |
1765 | * @ppos: current file position | |
1766 | * @iter: data destination | |
1767 | * @written: already copied | |
1768 | * | |
1769 | * This is a generic file read routine, and uses the | |
1770 | * mapping->a_ops->readpage() function for the actual low-level stuff. | |
1771 | * | |
1772 | * This is really ugly. But the goto's actually try to clarify some | |
1773 | * of the logic when it comes to error handling etc. | |
1774 | */ | |
1775 | static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos, | |
1776 | struct iov_iter *iter, ssize_t written) | |
1777 | { | |
1778 | struct address_space *mapping = filp->f_mapping; | |
1779 | struct inode *inode = mapping->host; | |
1780 | struct file_ra_state *ra = &filp->f_ra; | |
1781 | pgoff_t index; | |
1782 | pgoff_t last_index; | |
1783 | pgoff_t prev_index; | |
1784 | unsigned long offset; /* offset into pagecache page */ | |
1785 | unsigned int prev_offset; | |
1786 | int error = 0; | |
1787 | ||
1788 | if (unlikely(*ppos >= inode->i_sb->s_maxbytes)) | |
1789 | return 0; | |
1790 | iov_iter_truncate(iter, inode->i_sb->s_maxbytes); | |
1791 | ||
1792 | index = *ppos >> PAGE_SHIFT; | |
1793 | prev_index = ra->prev_pos >> PAGE_SHIFT; | |
1794 | prev_offset = ra->prev_pos & (PAGE_SIZE-1); | |
1795 | last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT; | |
1796 | offset = *ppos & ~PAGE_MASK; | |
1797 | ||
1798 | for (;;) { | |
1799 | struct page *page; | |
1800 | pgoff_t end_index; | |
1801 | loff_t isize; | |
1802 | unsigned long nr, ret; | |
1803 | ||
1804 | cond_resched(); | |
1805 | find_page: | |
1806 | if (fatal_signal_pending(current)) { | |
1807 | error = -EINTR; | |
1808 | goto out; | |
1809 | } | |
1810 | ||
1811 | page = find_get_page(mapping, index); | |
1812 | if (!page) { | |
1813 | page_cache_sync_readahead(mapping, | |
1814 | ra, filp, | |
1815 | index, last_index - index); | |
1816 | page = find_get_page(mapping, index); | |
1817 | if (unlikely(page == NULL)) | |
1818 | goto no_cached_page; | |
1819 | } | |
1820 | if (PageReadahead(page)) { | |
1821 | page_cache_async_readahead(mapping, | |
1822 | ra, filp, page, | |
1823 | index, last_index - index); | |
1824 | } | |
1825 | if (!PageUptodate(page)) { | |
1826 | /* | |
1827 | * See comment in do_read_cache_page on why | |
1828 | * wait_on_page_locked is used to avoid unnecessarily | |
1829 | * serialisations and why it's safe. | |
1830 | */ | |
1831 | error = wait_on_page_locked_killable(page); | |
1832 | if (unlikely(error)) | |
1833 | goto readpage_error; | |
1834 | if (PageUptodate(page)) | |
1835 | goto page_ok; | |
1836 | ||
1837 | if (inode->i_blkbits == PAGE_SHIFT || | |
1838 | !mapping->a_ops->is_partially_uptodate) | |
1839 | goto page_not_up_to_date; | |
1840 | /* pipes can't handle partially uptodate pages */ | |
1841 | if (unlikely(iter->type & ITER_PIPE)) | |
1842 | goto page_not_up_to_date; | |
1843 | if (!trylock_page(page)) | |
1844 | goto page_not_up_to_date; | |
1845 | /* Did it get truncated before we got the lock? */ | |
1846 | if (!page->mapping) | |
1847 | goto page_not_up_to_date_locked; | |
1848 | if (!mapping->a_ops->is_partially_uptodate(page, | |
1849 | offset, iter->count)) | |
1850 | goto page_not_up_to_date_locked; | |
1851 | unlock_page(page); | |
1852 | } | |
1853 | page_ok: | |
1854 | /* | |
1855 | * i_size must be checked after we know the page is Uptodate. | |
1856 | * | |
1857 | * Checking i_size after the check allows us to calculate | |
1858 | * the correct value for "nr", which means the zero-filled | |
1859 | * part of the page is not copied back to userspace (unless | |
1860 | * another truncate extends the file - this is desired though). | |
1861 | */ | |
1862 | ||
1863 | isize = i_size_read(inode); | |
1864 | end_index = (isize - 1) >> PAGE_SHIFT; | |
1865 | if (unlikely(!isize || index > end_index)) { | |
1866 | put_page(page); | |
1867 | goto out; | |
1868 | } | |
1869 | ||
1870 | /* nr is the maximum number of bytes to copy from this page */ | |
1871 | nr = PAGE_SIZE; | |
1872 | if (index == end_index) { | |
1873 | nr = ((isize - 1) & ~PAGE_MASK) + 1; | |
1874 | if (nr <= offset) { | |
1875 | put_page(page); | |
1876 | goto out; | |
1877 | } | |
1878 | } | |
1879 | nr = nr - offset; | |
1880 | ||
1881 | /* If users can be writing to this page using arbitrary | |
1882 | * virtual addresses, take care about potential aliasing | |
1883 | * before reading the page on the kernel side. | |
1884 | */ | |
1885 | if (mapping_writably_mapped(mapping)) | |
1886 | flush_dcache_page(page); | |
1887 | ||
1888 | /* | |
1889 | * When a sequential read accesses a page several times, | |
1890 | * only mark it as accessed the first time. | |
1891 | */ | |
1892 | if (prev_index != index || offset != prev_offset) | |
1893 | mark_page_accessed(page); | |
1894 | prev_index = index; | |
1895 | ||
1896 | /* | |
1897 | * Ok, we have the page, and it's up-to-date, so | |
1898 | * now we can copy it to user space... | |
1899 | */ | |
1900 | ||
1901 | ret = copy_page_to_iter(page, offset, nr, iter); | |
1902 | offset += ret; | |
1903 | index += offset >> PAGE_SHIFT; | |
1904 | offset &= ~PAGE_MASK; | |
1905 | prev_offset = offset; | |
1906 | ||
1907 | put_page(page); | |
1908 | written += ret; | |
1909 | if (!iov_iter_count(iter)) | |
1910 | goto out; | |
1911 | if (ret < nr) { | |
1912 | error = -EFAULT; | |
1913 | goto out; | |
1914 | } | |
1915 | continue; | |
1916 | ||
1917 | page_not_up_to_date: | |
1918 | /* Get exclusive access to the page ... */ | |
1919 | error = lock_page_killable(page); | |
1920 | if (unlikely(error)) | |
1921 | goto readpage_error; | |
1922 | ||
1923 | page_not_up_to_date_locked: | |
1924 | /* Did it get truncated before we got the lock? */ | |
1925 | if (!page->mapping) { | |
1926 | unlock_page(page); | |
1927 | put_page(page); | |
1928 | continue; | |
1929 | } | |
1930 | ||
1931 | /* Did somebody else fill it already? */ | |
1932 | if (PageUptodate(page)) { | |
1933 | unlock_page(page); | |
1934 | goto page_ok; | |
1935 | } | |
1936 | ||
1937 | readpage: | |
1938 | /* | |
1939 | * A previous I/O error may have been due to temporary | |
1940 | * failures, eg. multipath errors. | |
1941 | * PG_error will be set again if readpage fails. | |
1942 | */ | |
1943 | ClearPageError(page); | |
1944 | /* Start the actual read. The read will unlock the page. */ | |
1945 | error = mapping->a_ops->readpage(filp, page); | |
1946 | ||
1947 | if (unlikely(error)) { | |
1948 | if (error == AOP_TRUNCATED_PAGE) { | |
1949 | put_page(page); | |
1950 | error = 0; | |
1951 | goto find_page; | |
1952 | } | |
1953 | goto readpage_error; | |
1954 | } | |
1955 | ||
1956 | if (!PageUptodate(page)) { | |
1957 | error = lock_page_killable(page); | |
1958 | if (unlikely(error)) | |
1959 | goto readpage_error; | |
1960 | if (!PageUptodate(page)) { | |
1961 | if (page->mapping == NULL) { | |
1962 | /* | |
1963 | * invalidate_mapping_pages got it | |
1964 | */ | |
1965 | unlock_page(page); | |
1966 | put_page(page); | |
1967 | goto find_page; | |
1968 | } | |
1969 | unlock_page(page); | |
1970 | shrink_readahead_size_eio(filp, ra); | |
1971 | error = -EIO; | |
1972 | goto readpage_error; | |
1973 | } | |
1974 | unlock_page(page); | |
1975 | } | |
1976 | ||
1977 | goto page_ok; | |
1978 | ||
1979 | readpage_error: | |
1980 | /* UHHUH! A synchronous read error occurred. Report it */ | |
1981 | put_page(page); | |
1982 | goto out; | |
1983 | ||
1984 | no_cached_page: | |
1985 | /* | |
1986 | * Ok, it wasn't cached, so we need to create a new | |
1987 | * page.. | |
1988 | */ | |
1989 | page = page_cache_alloc_cold(mapping); | |
1990 | if (!page) { | |
1991 | error = -ENOMEM; | |
1992 | goto out; | |
1993 | } | |
1994 | error = add_to_page_cache_lru(page, mapping, index, | |
1995 | mapping_gfp_constraint(mapping, GFP_KERNEL)); | |
1996 | if (error) { | |
1997 | put_page(page); | |
1998 | if (error == -EEXIST) { | |
1999 | error = 0; | |
2000 | goto find_page; | |
2001 | } | |
2002 | goto out; | |
2003 | } | |
2004 | goto readpage; | |
2005 | } | |
2006 | ||
2007 | out: | |
2008 | ra->prev_pos = prev_index; | |
2009 | ra->prev_pos <<= PAGE_SHIFT; | |
2010 | ra->prev_pos |= prev_offset; | |
2011 | ||
2012 | *ppos = ((loff_t)index << PAGE_SHIFT) + offset; | |
2013 | file_accessed(filp); | |
2014 | return written ? written : error; | |
2015 | } | |
2016 | ||
2017 | /** | |
2018 | * generic_file_read_iter - generic filesystem read routine | |
2019 | * @iocb: kernel I/O control block | |
2020 | * @iter: destination for the data read | |
2021 | * | |
2022 | * This is the "read_iter()" routine for all filesystems | |
2023 | * that can use the page cache directly. | |
2024 | */ | |
2025 | ssize_t | |
2026 | generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) | |
2027 | { | |
2028 | struct file *file = iocb->ki_filp; | |
2029 | ssize_t retval = 0; | |
2030 | size_t count = iov_iter_count(iter); | |
2031 | ||
2032 | if (!count) | |
2033 | goto out; /* skip atime */ | |
2034 | ||
2035 | if (iocb->ki_flags & IOCB_DIRECT) { | |
2036 | struct address_space *mapping = file->f_mapping; | |
2037 | struct inode *inode = mapping->host; | |
2038 | loff_t size; | |
2039 | ||
2040 | size = i_size_read(inode); | |
2041 | retval = filemap_write_and_wait_range(mapping, iocb->ki_pos, | |
2042 | iocb->ki_pos + count - 1); | |
2043 | if (retval < 0) | |
2044 | goto out; | |
2045 | ||
2046 | file_accessed(file); | |
2047 | ||
2048 | retval = mapping->a_ops->direct_IO(iocb, iter); | |
2049 | if (retval >= 0) { | |
2050 | iocb->ki_pos += retval; | |
2051 | count -= retval; | |
2052 | } | |
2053 | iov_iter_revert(iter, count - iov_iter_count(iter)); | |
2054 | ||
2055 | /* | |
2056 | * Btrfs can have a short DIO read if we encounter | |
2057 | * compressed extents, so if there was an error, or if | |
2058 | * we've already read everything we wanted to, or if | |
2059 | * there was a short read because we hit EOF, go ahead | |
2060 | * and return. Otherwise fallthrough to buffered io for | |
2061 | * the rest of the read. Buffered reads will not work for | |
2062 | * DAX files, so don't bother trying. | |
2063 | */ | |
2064 | if (retval < 0 || !count || iocb->ki_pos >= size || | |
2065 | IS_DAX(inode)) | |
2066 | goto out; | |
2067 | } | |
2068 | ||
2069 | retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval); | |
2070 | out: | |
2071 | return retval; | |
2072 | } | |
2073 | EXPORT_SYMBOL(generic_file_read_iter); | |
2074 | ||
2075 | #ifdef CONFIG_MMU | |
2076 | /** | |
2077 | * page_cache_read - adds requested page to the page cache if not already there | |
2078 | * @file: file to read | |
2079 | * @offset: page index | |
2080 | * @gfp_mask: memory allocation flags | |
2081 | * | |
2082 | * This adds the requested page to the page cache if it isn't already there, | |
2083 | * and schedules an I/O to read in its contents from disk. | |
2084 | */ | |
2085 | static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask) | |
2086 | { | |
2087 | struct address_space *mapping = file->f_mapping; | |
2088 | struct page *page; | |
2089 | int ret; | |
2090 | ||
2091 | do { | |
2092 | page = __page_cache_alloc(gfp_mask|__GFP_COLD); | |
2093 | if (!page) | |
2094 | return -ENOMEM; | |
2095 | ||
2096 | ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL); | |
2097 | if (ret == 0) | |
2098 | ret = mapping->a_ops->readpage(file, page); | |
2099 | else if (ret == -EEXIST) | |
2100 | ret = 0; /* losing race to add is OK */ | |
2101 | ||
2102 | put_page(page); | |
2103 | ||
2104 | } while (ret == AOP_TRUNCATED_PAGE); | |
2105 | ||
2106 | return ret; | |
2107 | } | |
2108 | ||
2109 | #define MMAP_LOTSAMISS (100) | |
2110 | ||
2111 | /* | |
2112 | * Synchronous readahead happens when we don't even find | |
2113 | * a page in the page cache at all. | |
2114 | */ | |
2115 | static void do_sync_mmap_readahead(struct vm_area_struct *vma, | |
2116 | struct file_ra_state *ra, | |
2117 | struct file *file, | |
2118 | pgoff_t offset) | |
2119 | { | |
2120 | struct address_space *mapping = file->f_mapping; | |
2121 | ||
2122 | /* If we don't want any read-ahead, don't bother */ | |
2123 | if (vma->vm_flags & VM_RAND_READ) | |
2124 | return; | |
2125 | if (!ra->ra_pages) | |
2126 | return; | |
2127 | ||
2128 | if (vma->vm_flags & VM_SEQ_READ) { | |
2129 | page_cache_sync_readahead(mapping, ra, file, offset, | |
2130 | ra->ra_pages); | |
2131 | return; | |
2132 | } | |
2133 | ||
2134 | /* Avoid banging the cache line if not needed */ | |
2135 | if (ra->mmap_miss < MMAP_LOTSAMISS * 10) | |
2136 | ra->mmap_miss++; | |
2137 | ||
2138 | /* | |
2139 | * Do we miss much more than hit in this file? If so, | |
2140 | * stop bothering with read-ahead. It will only hurt. | |
2141 | */ | |
2142 | if (ra->mmap_miss > MMAP_LOTSAMISS) | |
2143 | return; | |
2144 | ||
2145 | /* | |
2146 | * mmap read-around | |
2147 | */ | |
2148 | ra->start = max_t(long, 0, offset - ra->ra_pages / 2); | |
2149 | ra->size = ra->ra_pages; | |
2150 | ra->async_size = ra->ra_pages / 4; | |
2151 | ra_submit(ra, mapping, file); | |
2152 | } | |
2153 | ||
2154 | /* | |
2155 | * Asynchronous readahead happens when we find the page and PG_readahead, | |
2156 | * so we want to possibly extend the readahead further.. | |
2157 | */ | |
2158 | static void do_async_mmap_readahead(struct vm_area_struct *vma, | |
2159 | struct file_ra_state *ra, | |
2160 | struct file *file, | |
2161 | struct page *page, | |
2162 | pgoff_t offset) | |
2163 | { | |
2164 | struct address_space *mapping = file->f_mapping; | |
2165 | ||
2166 | /* If we don't want any read-ahead, don't bother */ | |
2167 | if (vma->vm_flags & VM_RAND_READ) | |
2168 | return; | |
2169 | if (ra->mmap_miss > 0) | |
2170 | ra->mmap_miss--; | |
2171 | if (PageReadahead(page)) | |
2172 | page_cache_async_readahead(mapping, ra, file, | |
2173 | page, offset, ra->ra_pages); | |
2174 | } | |
2175 | ||
2176 | /** | |
2177 | * filemap_fault - read in file data for page fault handling | |
2178 | * @vmf: struct vm_fault containing details of the fault | |
2179 | * | |
2180 | * filemap_fault() is invoked via the vma operations vector for a | |
2181 | * mapped memory region to read in file data during a page fault. | |
2182 | * | |
2183 | * The goto's are kind of ugly, but this streamlines the normal case of having | |
2184 | * it in the page cache, and handles the special cases reasonably without | |
2185 | * having a lot of duplicated code. | |
2186 | * | |
2187 | * vma->vm_mm->mmap_sem must be held on entry. | |
2188 | * | |
2189 | * If our return value has VM_FAULT_RETRY set, it's because | |
2190 | * lock_page_or_retry() returned 0. | |
2191 | * The mmap_sem has usually been released in this case. | |
2192 | * See __lock_page_or_retry() for the exception. | |
2193 | * | |
2194 | * If our return value does not have VM_FAULT_RETRY set, the mmap_sem | |
2195 | * has not been released. | |
2196 | * | |
2197 | * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set. | |
2198 | */ | |
2199 | int filemap_fault(struct vm_fault *vmf) | |
2200 | { | |
2201 | int error; | |
2202 | struct file *file = vmf->vma->vm_file; | |
2203 | struct address_space *mapping = file->f_mapping; | |
2204 | struct file_ra_state *ra = &file->f_ra; | |
2205 | struct inode *inode = mapping->host; | |
2206 | pgoff_t offset = vmf->pgoff; | |
2207 | pgoff_t max_off; | |
2208 | struct page *page; | |
2209 | int ret = 0; | |
2210 | ||
2211 | max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); | |
2212 | if (unlikely(offset >= max_off)) | |
2213 | return VM_FAULT_SIGBUS; | |
2214 | ||
2215 | /* | |
2216 | * Do we have something in the page cache already? | |
2217 | */ | |
2218 | page = find_get_page(mapping, offset); | |
2219 | if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { | |
2220 | /* | |
2221 | * We found the page, so try async readahead before | |
2222 | * waiting for the lock. | |
2223 | */ | |
2224 | do_async_mmap_readahead(vmf->vma, ra, file, page, offset); | |
2225 | } else if (!page) { | |
2226 | /* No page in the page cache at all */ | |
2227 | do_sync_mmap_readahead(vmf->vma, ra, file, offset); | |
2228 | count_vm_event(PGMAJFAULT); | |
2229 | mem_cgroup_count_vm_event(vmf->vma->vm_mm, PGMAJFAULT); | |
2230 | ret = VM_FAULT_MAJOR; | |
2231 | retry_find: | |
2232 | page = find_get_page(mapping, offset); | |
2233 | if (!page) | |
2234 | goto no_cached_page; | |
2235 | } | |
2236 | ||
2237 | if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) { | |
2238 | put_page(page); | |
2239 | return ret | VM_FAULT_RETRY; | |
2240 | } | |
2241 | ||
2242 | /* Did it get truncated? */ | |
2243 | if (unlikely(page->mapping != mapping)) { | |
2244 | unlock_page(page); | |
2245 | put_page(page); | |
2246 | goto retry_find; | |
2247 | } | |
2248 | VM_BUG_ON_PAGE(page->index != offset, page); | |
2249 | ||
2250 | /* | |
2251 | * We have a locked page in the page cache, now we need to check | |
2252 | * that it's up-to-date. If not, it is going to be due to an error. | |
2253 | */ | |
2254 | if (unlikely(!PageUptodate(page))) | |
2255 | goto page_not_uptodate; | |
2256 | ||
2257 | /* | |
2258 | * Found the page and have a reference on it. | |
2259 | * We must recheck i_size under page lock. | |
2260 | */ | |
2261 | max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); | |
2262 | if (unlikely(offset >= max_off)) { | |
2263 | unlock_page(page); | |
2264 | put_page(page); | |
2265 | return VM_FAULT_SIGBUS; | |
2266 | } | |
2267 | ||
2268 | vmf->page = page; | |
2269 | return ret | VM_FAULT_LOCKED; | |
2270 | ||
2271 | no_cached_page: | |
2272 | /* | |
2273 | * We're only likely to ever get here if MADV_RANDOM is in | |
2274 | * effect. | |
2275 | */ | |
2276 | error = page_cache_read(file, offset, vmf->gfp_mask); | |
2277 | ||
2278 | /* | |
2279 | * The page we want has now been added to the page cache. | |
2280 | * In the unlikely event that someone removed it in the | |
2281 | * meantime, we'll just come back here and read it again. | |
2282 | */ | |
2283 | if (error >= 0) | |
2284 | goto retry_find; | |
2285 | ||
2286 | /* | |
2287 | * An error return from page_cache_read can result if the | |
2288 | * system is low on memory, or a problem occurs while trying | |
2289 | * to schedule I/O. | |
2290 | */ | |
2291 | if (error == -ENOMEM) | |
2292 | return VM_FAULT_OOM; | |
2293 | return VM_FAULT_SIGBUS; | |
2294 | ||
2295 | page_not_uptodate: | |
2296 | /* | |
2297 | * Umm, take care of errors if the page isn't up-to-date. | |
2298 | * Try to re-read it _once_. We do this synchronously, | |
2299 | * because there really aren't any performance issues here | |
2300 | * and we need to check for errors. | |
2301 | */ | |
2302 | ClearPageError(page); | |
2303 | error = mapping->a_ops->readpage(file, page); | |
2304 | if (!error) { | |
2305 | wait_on_page_locked(page); | |
2306 | if (!PageUptodate(page)) | |
2307 | error = -EIO; | |
2308 | } | |
2309 | put_page(page); | |
2310 | ||
2311 | if (!error || error == AOP_TRUNCATED_PAGE) | |
2312 | goto retry_find; | |
2313 | ||
2314 | /* Things didn't work out. Return zero to tell the mm layer so. */ | |
2315 | shrink_readahead_size_eio(file, ra); | |
2316 | return VM_FAULT_SIGBUS; | |
2317 | } | |
2318 | EXPORT_SYMBOL(filemap_fault); | |
2319 | ||
2320 | void filemap_map_pages(struct vm_fault *vmf, | |
2321 | pgoff_t start_pgoff, pgoff_t end_pgoff) | |
2322 | { | |
2323 | struct radix_tree_iter iter; | |
2324 | void **slot; | |
2325 | struct file *file = vmf->vma->vm_file; | |
2326 | struct address_space *mapping = file->f_mapping; | |
2327 | pgoff_t last_pgoff = start_pgoff; | |
2328 | unsigned long max_idx; | |
2329 | struct page *head, *page; | |
2330 | ||
2331 | rcu_read_lock(); | |
2332 | radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, | |
2333 | start_pgoff) { | |
2334 | if (iter.index > end_pgoff) | |
2335 | break; | |
2336 | repeat: | |
2337 | page = radix_tree_deref_slot(slot); | |
2338 | if (unlikely(!page)) | |
2339 | goto next; | |
2340 | if (radix_tree_exception(page)) { | |
2341 | if (radix_tree_deref_retry(page)) { | |
2342 | slot = radix_tree_iter_retry(&iter); | |
2343 | continue; | |
2344 | } | |
2345 | goto next; | |
2346 | } | |
2347 | ||
2348 | head = compound_head(page); | |
2349 | if (!page_cache_get_speculative(head)) | |
2350 | goto repeat; | |
2351 | ||
2352 | /* The page was split under us? */ | |
2353 | if (compound_head(page) != head) { | |
2354 | put_page(head); | |
2355 | goto repeat; | |
2356 | } | |
2357 | ||
2358 | /* Has the page moved? */ | |
2359 | if (unlikely(page != *slot)) { | |
2360 | put_page(head); | |
2361 | goto repeat; | |
2362 | } | |
2363 | ||
2364 | if (!PageUptodate(page) || | |
2365 | PageReadahead(page) || | |
2366 | PageHWPoison(page)) | |
2367 | goto skip; | |
2368 | if (!trylock_page(page)) | |
2369 | goto skip; | |
2370 | ||
2371 | if (page->mapping != mapping || !PageUptodate(page)) | |
2372 | goto unlock; | |
2373 | ||
2374 | max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); | |
2375 | if (page->index >= max_idx) | |
2376 | goto unlock; | |
2377 | ||
2378 | if (file->f_ra.mmap_miss > 0) | |
2379 | file->f_ra.mmap_miss--; | |
2380 | ||
2381 | vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT; | |
2382 | if (vmf->pte) | |
2383 | vmf->pte += iter.index - last_pgoff; | |
2384 | last_pgoff = iter.index; | |
2385 | if (alloc_set_pte(vmf, NULL, page)) | |
2386 | goto unlock; | |
2387 | unlock_page(page); | |
2388 | goto next; | |
2389 | unlock: | |
2390 | unlock_page(page); | |
2391 | skip: | |
2392 | put_page(page); | |
2393 | next: | |
2394 | /* Huge page is mapped? No need to proceed. */ | |
2395 | if (pmd_trans_huge(*vmf->pmd)) | |
2396 | break; | |
2397 | if (iter.index == end_pgoff) | |
2398 | break; | |
2399 | } | |
2400 | rcu_read_unlock(); | |
2401 | } | |
2402 | EXPORT_SYMBOL(filemap_map_pages); | |
2403 | ||
2404 | int filemap_page_mkwrite(struct vm_fault *vmf) | |
2405 | { | |
2406 | struct page *page = vmf->page; | |
2407 | struct inode *inode = file_inode(vmf->vma->vm_file); | |
2408 | int ret = VM_FAULT_LOCKED; | |
2409 | ||
2410 | sb_start_pagefault(inode->i_sb); | |
2411 | file_update_time(vmf->vma->vm_file); | |
2412 | lock_page(page); | |
2413 | if (page->mapping != inode->i_mapping) { | |
2414 | unlock_page(page); | |
2415 | ret = VM_FAULT_NOPAGE; | |
2416 | goto out; | |
2417 | } | |
2418 | /* | |
2419 | * We mark the page dirty already here so that when freeze is in | |
2420 | * progress, we are guaranteed that writeback during freezing will | |
2421 | * see the dirty page and writeprotect it again. | |
2422 | */ | |
2423 | set_page_dirty(page); | |
2424 | wait_for_stable_page(page); | |
2425 | out: | |
2426 | sb_end_pagefault(inode->i_sb); | |
2427 | return ret; | |
2428 | } | |
2429 | EXPORT_SYMBOL(filemap_page_mkwrite); | |
2430 | ||
2431 | const struct vm_operations_struct generic_file_vm_ops = { | |
2432 | .fault = filemap_fault, | |
2433 | .map_pages = filemap_map_pages, | |
2434 | .page_mkwrite = filemap_page_mkwrite, | |
2435 | }; | |
2436 | ||
2437 | /* This is used for a general mmap of a disk file */ | |
2438 | ||
2439 | int generic_file_mmap(struct file * file, struct vm_area_struct * vma) | |
2440 | { | |
2441 | struct address_space *mapping = file->f_mapping; | |
2442 | ||
2443 | if (!mapping->a_ops->readpage) | |
2444 | return -ENOEXEC; | |
2445 | file_accessed(file); | |
2446 | vma->vm_ops = &generic_file_vm_ops; | |
2447 | return 0; | |
2448 | } | |
2449 | ||
2450 | /* | |
2451 | * This is for filesystems which do not implement ->writepage. | |
2452 | */ | |
2453 | int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) | |
2454 | { | |
2455 | if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) | |
2456 | return -EINVAL; | |
2457 | return generic_file_mmap(file, vma); | |
2458 | } | |
2459 | #else | |
2460 | int generic_file_mmap(struct file * file, struct vm_area_struct * vma) | |
2461 | { | |
2462 | return -ENOSYS; | |
2463 | } | |
2464 | int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) | |
2465 | { | |
2466 | return -ENOSYS; | |
2467 | } | |
2468 | #endif /* CONFIG_MMU */ | |
2469 | ||
2470 | EXPORT_SYMBOL(generic_file_mmap); | |
2471 | EXPORT_SYMBOL(generic_file_readonly_mmap); | |
2472 | ||
2473 | static struct page *wait_on_page_read(struct page *page) | |
2474 | { | |
2475 | if (!IS_ERR(page)) { | |
2476 | wait_on_page_locked(page); | |
2477 | if (!PageUptodate(page)) { | |
2478 | put_page(page); | |
2479 | page = ERR_PTR(-EIO); | |
2480 | } | |
2481 | } | |
2482 | return page; | |
2483 | } | |
2484 | ||
2485 | static struct page *do_read_cache_page(struct address_space *mapping, | |
2486 | pgoff_t index, | |
2487 | int (*filler)(void *, struct page *), | |
2488 | void *data, | |
2489 | gfp_t gfp) | |
2490 | { | |
2491 | struct page *page; | |
2492 | int err; | |
2493 | repeat: | |
2494 | page = find_get_page(mapping, index); | |
2495 | if (!page) { | |
2496 | page = __page_cache_alloc(gfp | __GFP_COLD); | |
2497 | if (!page) | |
2498 | return ERR_PTR(-ENOMEM); | |
2499 | err = add_to_page_cache_lru(page, mapping, index, gfp); | |
2500 | if (unlikely(err)) { | |
2501 | put_page(page); | |
2502 | if (err == -EEXIST) | |
2503 | goto repeat; | |
2504 | /* Presumably ENOMEM for radix tree node */ | |
2505 | return ERR_PTR(err); | |
2506 | } | |
2507 | ||
2508 | filler: | |
2509 | err = filler(data, page); | |
2510 | if (err < 0) { | |
2511 | put_page(page); | |
2512 | return ERR_PTR(err); | |
2513 | } | |
2514 | ||
2515 | page = wait_on_page_read(page); | |
2516 | if (IS_ERR(page)) | |
2517 | return page; | |
2518 | goto out; | |
2519 | } | |
2520 | if (PageUptodate(page)) | |
2521 | goto out; | |
2522 | ||
2523 | /* | |
2524 | * Page is not up to date and may be locked due one of the following | |
2525 | * case a: Page is being filled and the page lock is held | |
2526 | * case b: Read/write error clearing the page uptodate status | |
2527 | * case c: Truncation in progress (page locked) | |
2528 | * case d: Reclaim in progress | |
2529 | * | |
2530 | * Case a, the page will be up to date when the page is unlocked. | |
2531 | * There is no need to serialise on the page lock here as the page | |
2532 | * is pinned so the lock gives no additional protection. Even if the | |
2533 | * the page is truncated, the data is still valid if PageUptodate as | |
2534 | * it's a race vs truncate race. | |
2535 | * Case b, the page will not be up to date | |
2536 | * Case c, the page may be truncated but in itself, the data may still | |
2537 | * be valid after IO completes as it's a read vs truncate race. The | |
2538 | * operation must restart if the page is not uptodate on unlock but | |
2539 | * otherwise serialising on page lock to stabilise the mapping gives | |
2540 | * no additional guarantees to the caller as the page lock is | |
2541 | * released before return. | |
2542 | * Case d, similar to truncation. If reclaim holds the page lock, it | |
2543 | * will be a race with remove_mapping that determines if the mapping | |
2544 | * is valid on unlock but otherwise the data is valid and there is | |
2545 | * no need to serialise with page lock. | |
2546 | * | |
2547 | * As the page lock gives no additional guarantee, we optimistically | |
2548 | * wait on the page to be unlocked and check if it's up to date and | |
2549 | * use the page if it is. Otherwise, the page lock is required to | |
2550 | * distinguish between the different cases. The motivation is that we | |
2551 | * avoid spurious serialisations and wakeups when multiple processes | |
2552 | * wait on the same page for IO to complete. | |
2553 | */ | |
2554 | wait_on_page_locked(page); | |
2555 | if (PageUptodate(page)) | |
2556 | goto out; | |
2557 | ||
2558 | /* Distinguish between all the cases under the safety of the lock */ | |
2559 | lock_page(page); | |
2560 | ||
2561 | /* Case c or d, restart the operation */ | |
2562 | if (!page->mapping) { | |
2563 | unlock_page(page); | |
2564 | put_page(page); | |
2565 | goto repeat; | |
2566 | } | |
2567 | ||
2568 | /* Someone else locked and filled the page in a very small window */ | |
2569 | if (PageUptodate(page)) { | |
2570 | unlock_page(page); | |
2571 | goto out; | |
2572 | } | |
2573 | goto filler; | |
2574 | ||
2575 | out: | |
2576 | mark_page_accessed(page); | |
2577 | return page; | |
2578 | } | |
2579 | ||
2580 | /** | |
2581 | * read_cache_page - read into page cache, fill it if needed | |
2582 | * @mapping: the page's address_space | |
2583 | * @index: the page index | |
2584 | * @filler: function to perform the read | |
2585 | * @data: first arg to filler(data, page) function, often left as NULL | |
2586 | * | |
2587 | * Read into the page cache. If a page already exists, and PageUptodate() is | |
2588 | * not set, try to fill the page and wait for it to become unlocked. | |
2589 | * | |
2590 | * If the page does not get brought uptodate, return -EIO. | |
2591 | */ | |
2592 | struct page *read_cache_page(struct address_space *mapping, | |
2593 | pgoff_t index, | |
2594 | int (*filler)(void *, struct page *), | |
2595 | void *data) | |
2596 | { | |
2597 | return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping)); | |
2598 | } | |
2599 | EXPORT_SYMBOL(read_cache_page); | |
2600 | ||
2601 | /** | |
2602 | * read_cache_page_gfp - read into page cache, using specified page allocation flags. | |
2603 | * @mapping: the page's address_space | |
2604 | * @index: the page index | |
2605 | * @gfp: the page allocator flags to use if allocating | |
2606 | * | |
2607 | * This is the same as "read_mapping_page(mapping, index, NULL)", but with | |
2608 | * any new page allocations done using the specified allocation flags. | |
2609 | * | |
2610 | * If the page does not get brought uptodate, return -EIO. | |
2611 | */ | |
2612 | struct page *read_cache_page_gfp(struct address_space *mapping, | |
2613 | pgoff_t index, | |
2614 | gfp_t gfp) | |
2615 | { | |
2616 | filler_t *filler = (filler_t *)mapping->a_ops->readpage; | |
2617 | ||
2618 | return do_read_cache_page(mapping, index, filler, NULL, gfp); | |
2619 | } | |
2620 | EXPORT_SYMBOL(read_cache_page_gfp); | |
2621 | ||
2622 | /* | |
2623 | * Performs necessary checks before doing a write | |
2624 | * | |
2625 | * Can adjust writing position or amount of bytes to write. | |
2626 | * Returns appropriate error code that caller should return or | |
2627 | * zero in case that write should be allowed. | |
2628 | */ | |
2629 | inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) | |
2630 | { | |
2631 | struct file *file = iocb->ki_filp; | |
2632 | struct inode *inode = file->f_mapping->host; | |
2633 | unsigned long limit = rlimit(RLIMIT_FSIZE); | |
2634 | loff_t pos; | |
2635 | ||
2636 | if (!iov_iter_count(from)) | |
2637 | return 0; | |
2638 | ||
2639 | /* FIXME: this is for backwards compatibility with 2.4 */ | |
2640 | if (iocb->ki_flags & IOCB_APPEND) | |
2641 | iocb->ki_pos = i_size_read(inode); | |
2642 | ||
2643 | pos = iocb->ki_pos; | |
2644 | ||
2645 | if (limit != RLIM_INFINITY) { | |
2646 | if (iocb->ki_pos >= limit) { | |
2647 | send_sig(SIGXFSZ, current, 0); | |
2648 | return -EFBIG; | |
2649 | } | |
2650 | iov_iter_truncate(from, limit - (unsigned long)pos); | |
2651 | } | |
2652 | ||
2653 | /* | |
2654 | * LFS rule | |
2655 | */ | |
2656 | if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS && | |
2657 | !(file->f_flags & O_LARGEFILE))) { | |
2658 | if (pos >= MAX_NON_LFS) | |
2659 | return -EFBIG; | |
2660 | iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos); | |
2661 | } | |
2662 | ||
2663 | /* | |
2664 | * Are we about to exceed the fs block limit ? | |
2665 | * | |
2666 | * If we have written data it becomes a short write. If we have | |
2667 | * exceeded without writing data we send a signal and return EFBIG. | |
2668 | * Linus frestrict idea will clean these up nicely.. | |
2669 | */ | |
2670 | if (unlikely(pos >= inode->i_sb->s_maxbytes)) | |
2671 | return -EFBIG; | |
2672 | ||
2673 | iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos); | |
2674 | return iov_iter_count(from); | |
2675 | } | |
2676 | EXPORT_SYMBOL(generic_write_checks); | |
2677 | ||
2678 | int pagecache_write_begin(struct file *file, struct address_space *mapping, | |
2679 | loff_t pos, unsigned len, unsigned flags, | |
2680 | struct page **pagep, void **fsdata) | |
2681 | { | |
2682 | const struct address_space_operations *aops = mapping->a_ops; | |
2683 | ||
2684 | return aops->write_begin(file, mapping, pos, len, flags, | |
2685 | pagep, fsdata); | |
2686 | } | |
2687 | EXPORT_SYMBOL(pagecache_write_begin); | |
2688 | ||
2689 | int pagecache_write_end(struct file *file, struct address_space *mapping, | |
2690 | loff_t pos, unsigned len, unsigned copied, | |
2691 | struct page *page, void *fsdata) | |
2692 | { | |
2693 | const struct address_space_operations *aops = mapping->a_ops; | |
2694 | ||
2695 | return aops->write_end(file, mapping, pos, len, copied, page, fsdata); | |
2696 | } | |
2697 | EXPORT_SYMBOL(pagecache_write_end); | |
2698 | ||
2699 | ssize_t | |
2700 | generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) | |
2701 | { | |
2702 | struct file *file = iocb->ki_filp; | |
2703 | struct address_space *mapping = file->f_mapping; | |
2704 | struct inode *inode = mapping->host; | |
2705 | loff_t pos = iocb->ki_pos; | |
2706 | ssize_t written; | |
2707 | size_t write_len; | |
2708 | pgoff_t end; | |
2709 | ||
2710 | write_len = iov_iter_count(from); | |
2711 | end = (pos + write_len - 1) >> PAGE_SHIFT; | |
2712 | ||
2713 | written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); | |
2714 | if (written) | |
2715 | goto out; | |
2716 | ||
2717 | /* | |
2718 | * After a write we want buffered reads to be sure to go to disk to get | |
2719 | * the new data. We invalidate clean cached page from the region we're | |
2720 | * about to write. We do this *before* the write so that we can return | |
2721 | * without clobbering -EIOCBQUEUED from ->direct_IO(). | |
2722 | */ | |
2723 | written = invalidate_inode_pages2_range(mapping, | |
2724 | pos >> PAGE_SHIFT, end); | |
2725 | /* | |
2726 | * If a page can not be invalidated, return 0 to fall back | |
2727 | * to buffered write. | |
2728 | */ | |
2729 | if (written) { | |
2730 | if (written == -EBUSY) | |
2731 | return 0; | |
2732 | goto out; | |
2733 | } | |
2734 | ||
2735 | written = mapping->a_ops->direct_IO(iocb, from); | |
2736 | ||
2737 | /* | |
2738 | * Finally, try again to invalidate clean pages which might have been | |
2739 | * cached by non-direct readahead, or faulted in by get_user_pages() | |
2740 | * if the source of the write was an mmap'ed region of the file | |
2741 | * we're writing. Either one is a pretty crazy thing to do, | |
2742 | * so we don't support it 100%. If this invalidation | |
2743 | * fails, tough, the write still worked... | |
2744 | */ | |
2745 | invalidate_inode_pages2_range(mapping, | |
2746 | pos >> PAGE_SHIFT, end); | |
2747 | ||
2748 | if (written > 0) { | |
2749 | pos += written; | |
2750 | write_len -= written; | |
2751 | if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { | |
2752 | i_size_write(inode, pos); | |
2753 | mark_inode_dirty(inode); | |
2754 | } | |
2755 | iocb->ki_pos = pos; | |
2756 | } | |
2757 | iov_iter_revert(from, write_len - iov_iter_count(from)); | |
2758 | out: | |
2759 | return written; | |
2760 | } | |
2761 | EXPORT_SYMBOL(generic_file_direct_write); | |
2762 | ||
2763 | /* | |
2764 | * Find or create a page at the given pagecache position. Return the locked | |
2765 | * page. This function is specifically for buffered writes. | |
2766 | */ | |
2767 | struct page *grab_cache_page_write_begin(struct address_space *mapping, | |
2768 | pgoff_t index, unsigned flags) | |
2769 | { | |
2770 | struct page *page; | |
2771 | int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT; | |
2772 | ||
2773 | if (flags & AOP_FLAG_NOFS) | |
2774 | fgp_flags |= FGP_NOFS; | |
2775 | ||
2776 | page = pagecache_get_page(mapping, index, fgp_flags, | |
2777 | mapping_gfp_mask(mapping)); | |
2778 | if (page) | |
2779 | wait_for_stable_page(page); | |
2780 | ||
2781 | return page; | |
2782 | } | |
2783 | EXPORT_SYMBOL(grab_cache_page_write_begin); | |
2784 | ||
2785 | ssize_t generic_perform_write(struct file *file, | |
2786 | struct iov_iter *i, loff_t pos) | |
2787 | { | |
2788 | struct address_space *mapping = file->f_mapping; | |
2789 | const struct address_space_operations *a_ops = mapping->a_ops; | |
2790 | long status = 0; | |
2791 | ssize_t written = 0; | |
2792 | unsigned int flags = 0; | |
2793 | ||
2794 | do { | |
2795 | struct page *page; | |
2796 | unsigned long offset; /* Offset into pagecache page */ | |
2797 | unsigned long bytes; /* Bytes to write to page */ | |
2798 | size_t copied; /* Bytes copied from user */ | |
2799 | void *fsdata; | |
2800 | ||
2801 | offset = (pos & (PAGE_SIZE - 1)); | |
2802 | bytes = min_t(unsigned long, PAGE_SIZE - offset, | |
2803 | iov_iter_count(i)); | |
2804 | ||
2805 | again: | |
2806 | /* | |
2807 | * Bring in the user page that we will copy from _first_. | |
2808 | * Otherwise there's a nasty deadlock on copying from the | |
2809 | * same page as we're writing to, without it being marked | |
2810 | * up-to-date. | |
2811 | * | |
2812 | * Not only is this an optimisation, but it is also required | |
2813 | * to check that the address is actually valid, when atomic | |
2814 | * usercopies are used, below. | |
2815 | */ | |
2816 | if (unlikely(iov_iter_fault_in_readable(i, bytes))) { | |
2817 | status = -EFAULT; | |
2818 | break; | |
2819 | } | |
2820 | ||
2821 | if (fatal_signal_pending(current)) { | |
2822 | status = -EINTR; | |
2823 | break; | |
2824 | } | |
2825 | ||
2826 | status = a_ops->write_begin(file, mapping, pos, bytes, flags, | |
2827 | &page, &fsdata); | |
2828 | if (unlikely(status < 0)) | |
2829 | break; | |
2830 | ||
2831 | if (mapping_writably_mapped(mapping)) | |
2832 | flush_dcache_page(page); | |
2833 | ||
2834 | copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); | |
2835 | flush_dcache_page(page); | |
2836 | ||
2837 | status = a_ops->write_end(file, mapping, pos, bytes, copied, | |
2838 | page, fsdata); | |
2839 | if (unlikely(status < 0)) | |
2840 | break; | |
2841 | copied = status; | |
2842 | ||
2843 | cond_resched(); | |
2844 | ||
2845 | iov_iter_advance(i, copied); | |
2846 | if (unlikely(copied == 0)) { | |
2847 | /* | |
2848 | * If we were unable to copy any data at all, we must | |
2849 | * fall back to a single segment length write. | |
2850 | * | |
2851 | * If we didn't fallback here, we could livelock | |
2852 | * because not all segments in the iov can be copied at | |
2853 | * once without a pagefault. | |
2854 | */ | |
2855 | bytes = min_t(unsigned long, PAGE_SIZE - offset, | |
2856 | iov_iter_single_seg_count(i)); | |
2857 | goto again; | |
2858 | } | |
2859 | pos += copied; | |
2860 | written += copied; | |
2861 | ||
2862 | balance_dirty_pages_ratelimited(mapping); | |
2863 | } while (iov_iter_count(i)); | |
2864 | ||
2865 | return written ? written : status; | |
2866 | } | |
2867 | EXPORT_SYMBOL(generic_perform_write); | |
2868 | ||
2869 | /** | |
2870 | * __generic_file_write_iter - write data to a file | |
2871 | * @iocb: IO state structure (file, offset, etc.) | |
2872 | * @from: iov_iter with data to write | |
2873 | * | |
2874 | * This function does all the work needed for actually writing data to a | |
2875 | * file. It does all basic checks, removes SUID from the file, updates | |
2876 | * modification times and calls proper subroutines depending on whether we | |
2877 | * do direct IO or a standard buffered write. | |
2878 | * | |
2879 | * It expects i_mutex to be grabbed unless we work on a block device or similar | |
2880 | * object which does not need locking at all. | |
2881 | * | |
2882 | * This function does *not* take care of syncing data in case of O_SYNC write. | |
2883 | * A caller has to handle it. This is mainly due to the fact that we want to | |
2884 | * avoid syncing under i_mutex. | |
2885 | */ | |
2886 | ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) | |
2887 | { | |
2888 | struct file *file = iocb->ki_filp; | |
2889 | struct address_space * mapping = file->f_mapping; | |
2890 | struct inode *inode = mapping->host; | |
2891 | ssize_t written = 0; | |
2892 | ssize_t err; | |
2893 | ssize_t status; | |
2894 | ||
2895 | /* We can write back this queue in page reclaim */ | |
2896 | current->backing_dev_info = inode_to_bdi(inode); | |
2897 | err = file_remove_privs(file); | |
2898 | if (err) | |
2899 | goto out; | |
2900 | ||
2901 | err = file_update_time(file); | |
2902 | if (err) | |
2903 | goto out; | |
2904 | ||
2905 | if (iocb->ki_flags & IOCB_DIRECT) { | |
2906 | loff_t pos, endbyte; | |
2907 | ||
2908 | written = generic_file_direct_write(iocb, from); | |
2909 | /* | |
2910 | * If the write stopped short of completing, fall back to | |
2911 | * buffered writes. Some filesystems do this for writes to | |
2912 | * holes, for example. For DAX files, a buffered write will | |
2913 | * not succeed (even if it did, DAX does not handle dirty | |
2914 | * page-cache pages correctly). | |
2915 | */ | |
2916 | if (written < 0 || !iov_iter_count(from) || IS_DAX(inode)) | |
2917 | goto out; | |
2918 | ||
2919 | status = generic_perform_write(file, from, pos = iocb->ki_pos); | |
2920 | /* | |
2921 | * If generic_perform_write() returned a synchronous error | |
2922 | * then we want to return the number of bytes which were | |
2923 | * direct-written, or the error code if that was zero. Note | |
2924 | * that this differs from normal direct-io semantics, which | |
2925 | * will return -EFOO even if some bytes were written. | |
2926 | */ | |
2927 | if (unlikely(status < 0)) { | |
2928 | err = status; | |
2929 | goto out; | |
2930 | } | |
2931 | /* | |
2932 | * We need to ensure that the page cache pages are written to | |
2933 | * disk and invalidated to preserve the expected O_DIRECT | |
2934 | * semantics. | |
2935 | */ | |
2936 | endbyte = pos + status - 1; | |
2937 | err = filemap_write_and_wait_range(mapping, pos, endbyte); | |
2938 | if (err == 0) { | |
2939 | iocb->ki_pos = endbyte + 1; | |
2940 | written += status; | |
2941 | invalidate_mapping_pages(mapping, | |
2942 | pos >> PAGE_SHIFT, | |
2943 | endbyte >> PAGE_SHIFT); | |
2944 | } else { | |
2945 | /* | |
2946 | * We don't know how much we wrote, so just return | |
2947 | * the number of bytes which were direct-written | |
2948 | */ | |
2949 | } | |
2950 | } else { | |
2951 | written = generic_perform_write(file, from, iocb->ki_pos); | |
2952 | if (likely(written > 0)) | |
2953 | iocb->ki_pos += written; | |
2954 | } | |
2955 | out: | |
2956 | current->backing_dev_info = NULL; | |
2957 | return written ? written : err; | |
2958 | } | |
2959 | EXPORT_SYMBOL(__generic_file_write_iter); | |
2960 | ||
2961 | /** | |
2962 | * generic_file_write_iter - write data to a file | |
2963 | * @iocb: IO state structure | |
2964 | * @from: iov_iter with data to write | |
2965 | * | |
2966 | * This is a wrapper around __generic_file_write_iter() to be used by most | |
2967 | * filesystems. It takes care of syncing the file in case of O_SYNC file | |
2968 | * and acquires i_mutex as needed. | |
2969 | */ | |
2970 | ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) | |
2971 | { | |
2972 | struct file *file = iocb->ki_filp; | |
2973 | struct inode *inode = file->f_mapping->host; | |
2974 | ssize_t ret; | |
2975 | ||
2976 | inode_lock(inode); | |
2977 | ret = generic_write_checks(iocb, from); | |
2978 | if (ret > 0) | |
2979 | ret = __generic_file_write_iter(iocb, from); | |
2980 | inode_unlock(inode); | |
2981 | ||
2982 | if (ret > 0) | |
2983 | ret = generic_write_sync(iocb, ret); | |
2984 | return ret; | |
2985 | } | |
2986 | EXPORT_SYMBOL(generic_file_write_iter); | |
2987 | ||
2988 | /** | |
2989 | * try_to_release_page() - release old fs-specific metadata on a page | |
2990 | * | |
2991 | * @page: the page which the kernel is trying to free | |
2992 | * @gfp_mask: memory allocation flags (and I/O mode) | |
2993 | * | |
2994 | * The address_space is to try to release any data against the page | |
2995 | * (presumably at page->private). If the release was successful, return '1'. | |
2996 | * Otherwise return zero. | |
2997 | * | |
2998 | * This may also be called if PG_fscache is set on a page, indicating that the | |
2999 | * page is known to the local caching routines. | |
3000 | * | |
3001 | * The @gfp_mask argument specifies whether I/O may be performed to release | |
3002 | * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS). | |
3003 | * | |
3004 | */ | |
3005 | int try_to_release_page(struct page *page, gfp_t gfp_mask) | |
3006 | { | |
3007 | struct address_space * const mapping = page->mapping; | |
3008 | ||
3009 | BUG_ON(!PageLocked(page)); | |
3010 | if (PageWriteback(page)) | |
3011 | return 0; | |
3012 | ||
3013 | if (mapping && mapping->a_ops->releasepage) | |
3014 | return mapping->a_ops->releasepage(page, gfp_mask); | |
3015 | return try_to_free_buffers(page); | |
3016 | } | |
3017 | ||
3018 | EXPORT_SYMBOL(try_to_release_page); |