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/hugetlb.h> |
35 | #include <linux/memcontrol.h> |
36 | #include <linux/cleancache.h> |
37 | #include <linux/shmem_fs.h> |
38 | #include <linux/rmap.h> |
39 | #include <linux/delayacct.h> |
40 | #include <linux/psi.h> |
41 | #include "internal.h" |
42 | |
43 | #define CREATE_TRACE_POINTS |
44 | #include <trace/events/filemap.h> |
45 | |
46 | /* |
47 | * FIXME: remove all knowledge of the buffer layer from the core VM |
48 | */ |
49 | #include <linux/buffer_head.h> /* for try_to_free_buffers */ |
50 | |
51 | #include <asm/mman.h> |
52 | |
53 | /* |
54 | * Shared mappings implemented 30.11.1994. It's not fully working yet, |
55 | * though. |
56 | * |
57 | * Shared mappings now work. 15.8.1995 Bruno. |
58 | * |
59 | * finished 'unifying' the page and buffer cache and SMP-threaded the |
60 | * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com> |
61 | * |
62 | * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de> |
63 | */ |
64 | |
65 | /* |
66 | * Lock ordering: |
67 | * |
68 | * ->i_mmap_rwsem (truncate_pagecache) |
69 | * ->private_lock (__free_pte->__set_page_dirty_buffers) |
70 | * ->swap_lock (exclusive_swap_page, others) |
71 | * ->i_pages lock |
72 | * |
73 | * ->i_mutex |
74 | * ->i_mmap_rwsem (truncate->unmap_mapping_range) |
75 | * |
76 | * ->mmap_sem |
77 | * ->i_mmap_rwsem |
78 | * ->page_table_lock or pte_lock (various, mainly in memory.c) |
79 | * ->i_pages lock (arch-dependent flush_dcache_mmap_lock) |
80 | * |
81 | * ->mmap_sem |
82 | * ->lock_page (access_process_vm) |
83 | * |
84 | * ->i_mutex (generic_perform_write) |
85 | * ->mmap_sem (fault_in_pages_readable->do_page_fault) |
86 | * |
87 | * bdi->wb.list_lock |
88 | * sb_lock (fs/fs-writeback.c) |
89 | * ->i_pages lock (__sync_single_inode) |
90 | * |
91 | * ->i_mmap_rwsem |
92 | * ->anon_vma.lock (vma_adjust) |
93 | * |
94 | * ->anon_vma.lock |
95 | * ->page_table_lock or pte_lock (anon_vma_prepare and various) |
96 | * |
97 | * ->page_table_lock or pte_lock |
98 | * ->swap_lock (try_to_unmap_one) |
99 | * ->private_lock (try_to_unmap_one) |
100 | * ->i_pages lock (try_to_unmap_one) |
101 | * ->pgdat->lru_lock (follow_page->mark_page_accessed) |
102 | * ->pgdat->lru_lock (check_pte_range->isolate_lru_page) |
103 | * ->private_lock (page_remove_rmap->set_page_dirty) |
104 | * ->i_pages lock (page_remove_rmap->set_page_dirty) |
105 | * bdi.wb->list_lock (page_remove_rmap->set_page_dirty) |
106 | * ->inode->i_lock (page_remove_rmap->set_page_dirty) |
107 | * ->memcg->move_lock (page_remove_rmap->lock_page_memcg) |
108 | * bdi.wb->list_lock (zap_pte_range->set_page_dirty) |
109 | * ->inode->i_lock (zap_pte_range->set_page_dirty) |
110 | * ->private_lock (zap_pte_range->__set_page_dirty_buffers) |
111 | * |
112 | * ->i_mmap_rwsem |
113 | * ->tasklist_lock (memory_failure, collect_procs_ao) |
114 | */ |
115 | |
116 | static void page_cache_delete(struct address_space *mapping, |
117 | struct page *page, void *shadow) |
118 | { |
119 | XA_STATE(xas, &mapping->i_pages, page->index); |
120 | unsigned int nr = 1; |
121 | |
122 | mapping_set_update(&xas, mapping); |
123 | |
124 | /* hugetlb pages are represented by a single entry in the xarray */ |
125 | if (!PageHuge(page)) { |
126 | xas_set_order(&xas, page->index, compound_order(page)); |
127 | nr = 1U << compound_order(page); |
128 | } |
129 | |
130 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
131 | VM_BUG_ON_PAGE(PageTail(page), page); |
132 | VM_BUG_ON_PAGE(nr != 1 && shadow, page); |
133 | |
134 | xas_store(&xas, shadow); |
135 | xas_init_marks(&xas); |
136 | |
137 | page->mapping = NULL; |
138 | /* Leave page->index set: truncation lookup relies upon it */ |
139 | |
140 | if (shadow) { |
141 | mapping->nrexceptional += nr; |
142 | /* |
143 | * Make sure the nrexceptional update is committed before |
144 | * the nrpages update so that final truncate racing |
145 | * with reclaim does not see both counters 0 at the |
146 | * same time and miss a shadow entry. |
147 | */ |
148 | smp_wmb(); |
149 | } |
150 | mapping->nrpages -= nr; |
151 | } |
152 | |
153 | static void unaccount_page_cache_page(struct address_space *mapping, |
154 | struct page *page) |
155 | { |
156 | int nr; |
157 | |
158 | /* |
159 | * if we're uptodate, flush out into the cleancache, otherwise |
160 | * invalidate any existing cleancache entries. We can't leave |
161 | * stale data around in the cleancache once our page is gone |
162 | */ |
163 | if (PageUptodate(page) && PageMappedToDisk(page)) |
164 | cleancache_put_page(page); |
165 | else |
166 | cleancache_invalidate_page(mapping, page); |
167 | |
168 | VM_BUG_ON_PAGE(PageTail(page), page); |
169 | VM_BUG_ON_PAGE(page_mapped(page), page); |
170 | if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) { |
171 | int mapcount; |
172 | |
173 | pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n" , |
174 | current->comm, page_to_pfn(page)); |
175 | dump_page(page, "still mapped when deleted" ); |
176 | dump_stack(); |
177 | add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); |
178 | |
179 | mapcount = page_mapcount(page); |
180 | if (mapping_exiting(mapping) && |
181 | page_count(page) >= mapcount + 2) { |
182 | /* |
183 | * All vmas have already been torn down, so it's |
184 | * a good bet that actually the page is unmapped, |
185 | * and we'd prefer not to leak it: if we're wrong, |
186 | * some other bad page check should catch it later. |
187 | */ |
188 | page_mapcount_reset(page); |
189 | page_ref_sub(page, mapcount); |
190 | } |
191 | } |
192 | |
193 | /* hugetlb pages do not participate in page cache accounting. */ |
194 | if (PageHuge(page)) |
195 | return; |
196 | |
197 | nr = hpage_nr_pages(page); |
198 | |
199 | __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr); |
200 | if (PageSwapBacked(page)) { |
201 | __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr); |
202 | if (PageTransHuge(page)) |
203 | __dec_node_page_state(page, NR_SHMEM_THPS); |
204 | } else { |
205 | VM_BUG_ON_PAGE(PageTransHuge(page), page); |
206 | } |
207 | |
208 | /* |
209 | * At this point page must be either written or cleaned by |
210 | * truncate. Dirty page here signals a bug and loss of |
211 | * unwritten data. |
212 | * |
213 | * This fixes dirty accounting after removing the page entirely |
214 | * but leaves PageDirty set: it has no effect for truncated |
215 | * page and anyway will be cleared before returning page into |
216 | * buddy allocator. |
217 | */ |
218 | if (WARN_ON_ONCE(PageDirty(page))) |
219 | account_page_cleaned(page, mapping, inode_to_wb(mapping->host)); |
220 | } |
221 | |
222 | /* |
223 | * Delete a page from the page cache and free it. Caller has to make |
224 | * sure the page is locked and that nobody else uses it - or that usage |
225 | * is safe. The caller must hold the i_pages lock. |
226 | */ |
227 | void __delete_from_page_cache(struct page *page, void *shadow) |
228 | { |
229 | struct address_space *mapping = page->mapping; |
230 | |
231 | trace_mm_filemap_delete_from_page_cache(page); |
232 | |
233 | unaccount_page_cache_page(mapping, page); |
234 | page_cache_delete(mapping, page, shadow); |
235 | } |
236 | |
237 | static void page_cache_free_page(struct address_space *mapping, |
238 | struct page *page) |
239 | { |
240 | void (*freepage)(struct page *); |
241 | |
242 | freepage = mapping->a_ops->freepage; |
243 | if (freepage) |
244 | freepage(page); |
245 | |
246 | if (PageTransHuge(page) && !PageHuge(page)) { |
247 | page_ref_sub(page, HPAGE_PMD_NR); |
248 | VM_BUG_ON_PAGE(page_count(page) <= 0, page); |
249 | } else { |
250 | put_page(page); |
251 | } |
252 | } |
253 | |
254 | /** |
255 | * delete_from_page_cache - delete page from page cache |
256 | * @page: the page which the kernel is trying to remove from page cache |
257 | * |
258 | * This must be called only on pages that have been verified to be in the page |
259 | * cache and locked. It will never put the page into the free list, the caller |
260 | * has a reference on the page. |
261 | */ |
262 | void delete_from_page_cache(struct page *page) |
263 | { |
264 | struct address_space *mapping = page_mapping(page); |
265 | unsigned long flags; |
266 | |
267 | BUG_ON(!PageLocked(page)); |
268 | xa_lock_irqsave(&mapping->i_pages, flags); |
269 | __delete_from_page_cache(page, NULL); |
270 | xa_unlock_irqrestore(&mapping->i_pages, flags); |
271 | |
272 | page_cache_free_page(mapping, page); |
273 | } |
274 | EXPORT_SYMBOL(delete_from_page_cache); |
275 | |
276 | /* |
277 | * page_cache_delete_batch - delete several pages from page cache |
278 | * @mapping: the mapping to which pages belong |
279 | * @pvec: pagevec with pages to delete |
280 | * |
281 | * The function walks over mapping->i_pages and removes pages passed in @pvec |
282 | * from the mapping. The function expects @pvec to be sorted by page index. |
283 | * It tolerates holes in @pvec (mapping entries at those indices are not |
284 | * modified). The function expects only THP head pages to be present in the |
285 | * @pvec and takes care to delete all corresponding tail pages from the |
286 | * mapping as well. |
287 | * |
288 | * The function expects the i_pages lock to be held. |
289 | */ |
290 | static void page_cache_delete_batch(struct address_space *mapping, |
291 | struct pagevec *pvec) |
292 | { |
293 | XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index); |
294 | int total_pages = 0; |
295 | int i = 0, tail_pages = 0; |
296 | struct page *page; |
297 | |
298 | mapping_set_update(&xas, mapping); |
299 | xas_for_each(&xas, page, ULONG_MAX) { |
300 | if (i >= pagevec_count(pvec) && !tail_pages) |
301 | break; |
302 | if (xa_is_value(page)) |
303 | continue; |
304 | if (!tail_pages) { |
305 | /* |
306 | * Some page got inserted in our range? Skip it. We |
307 | * have our pages locked so they are protected from |
308 | * being removed. |
309 | */ |
310 | if (page != pvec->pages[i]) { |
311 | VM_BUG_ON_PAGE(page->index > |
312 | pvec->pages[i]->index, page); |
313 | continue; |
314 | } |
315 | WARN_ON_ONCE(!PageLocked(page)); |
316 | if (PageTransHuge(page) && !PageHuge(page)) |
317 | tail_pages = HPAGE_PMD_NR - 1; |
318 | page->mapping = NULL; |
319 | /* |
320 | * Leave page->index set: truncation lookup relies |
321 | * upon it |
322 | */ |
323 | i++; |
324 | } else { |
325 | VM_BUG_ON_PAGE(page->index + HPAGE_PMD_NR - tail_pages |
326 | != pvec->pages[i]->index, page); |
327 | tail_pages--; |
328 | } |
329 | xas_store(&xas, NULL); |
330 | total_pages++; |
331 | } |
332 | mapping->nrpages -= total_pages; |
333 | } |
334 | |
335 | void delete_from_page_cache_batch(struct address_space *mapping, |
336 | struct pagevec *pvec) |
337 | { |
338 | int i; |
339 | unsigned long flags; |
340 | |
341 | if (!pagevec_count(pvec)) |
342 | return; |
343 | |
344 | xa_lock_irqsave(&mapping->i_pages, flags); |
345 | for (i = 0; i < pagevec_count(pvec); i++) { |
346 | trace_mm_filemap_delete_from_page_cache(pvec->pages[i]); |
347 | |
348 | unaccount_page_cache_page(mapping, pvec->pages[i]); |
349 | } |
350 | page_cache_delete_batch(mapping, pvec); |
351 | xa_unlock_irqrestore(&mapping->i_pages, flags); |
352 | |
353 | for (i = 0; i < pagevec_count(pvec); i++) |
354 | page_cache_free_page(mapping, pvec->pages[i]); |
355 | } |
356 | |
357 | int filemap_check_errors(struct address_space *mapping) |
358 | { |
359 | int ret = 0; |
360 | /* Check for outstanding write errors */ |
361 | if (test_bit(AS_ENOSPC, &mapping->flags) && |
362 | test_and_clear_bit(AS_ENOSPC, &mapping->flags)) |
363 | ret = -ENOSPC; |
364 | if (test_bit(AS_EIO, &mapping->flags) && |
365 | test_and_clear_bit(AS_EIO, &mapping->flags)) |
366 | ret = -EIO; |
367 | return ret; |
368 | } |
369 | EXPORT_SYMBOL(filemap_check_errors); |
370 | |
371 | static int filemap_check_and_keep_errors(struct address_space *mapping) |
372 | { |
373 | /* Check for outstanding write errors */ |
374 | if (test_bit(AS_EIO, &mapping->flags)) |
375 | return -EIO; |
376 | if (test_bit(AS_ENOSPC, &mapping->flags)) |
377 | return -ENOSPC; |
378 | return 0; |
379 | } |
380 | |
381 | /** |
382 | * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range |
383 | * @mapping: address space structure to write |
384 | * @start: offset in bytes where the range starts |
385 | * @end: offset in bytes where the range ends (inclusive) |
386 | * @sync_mode: enable synchronous operation |
387 | * |
388 | * Start writeback against all of a mapping's dirty pages that lie |
389 | * within the byte offsets <start, end> inclusive. |
390 | * |
391 | * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as |
392 | * opposed to a regular memory cleansing writeback. The difference between |
393 | * these two operations is that if a dirty page/buffer is encountered, it must |
394 | * be waited upon, and not just skipped over. |
395 | * |
396 | * Return: %0 on success, negative error code otherwise. |
397 | */ |
398 | int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
399 | loff_t end, int sync_mode) |
400 | { |
401 | int ret; |
402 | struct writeback_control wbc = { |
403 | .sync_mode = sync_mode, |
404 | .nr_to_write = LONG_MAX, |
405 | .range_start = start, |
406 | .range_end = end, |
407 | }; |
408 | |
409 | if (!mapping_cap_writeback_dirty(mapping)) |
410 | return 0; |
411 | |
412 | wbc_attach_fdatawrite_inode(&wbc, mapping->host); |
413 | ret = do_writepages(mapping, &wbc); |
414 | wbc_detach_inode(&wbc); |
415 | return ret; |
416 | } |
417 | |
418 | static inline int __filemap_fdatawrite(struct address_space *mapping, |
419 | int sync_mode) |
420 | { |
421 | return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode); |
422 | } |
423 | |
424 | int filemap_fdatawrite(struct address_space *mapping) |
425 | { |
426 | return __filemap_fdatawrite(mapping, WB_SYNC_ALL); |
427 | } |
428 | EXPORT_SYMBOL(filemap_fdatawrite); |
429 | |
430 | int filemap_fdatawrite_range(struct address_space *mapping, loff_t start, |
431 | loff_t end) |
432 | { |
433 | return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL); |
434 | } |
435 | EXPORT_SYMBOL(filemap_fdatawrite_range); |
436 | |
437 | /** |
438 | * filemap_flush - mostly a non-blocking flush |
439 | * @mapping: target address_space |
440 | * |
441 | * This is a mostly non-blocking flush. Not suitable for data-integrity |
442 | * purposes - I/O may not be started against all dirty pages. |
443 | * |
444 | * Return: %0 on success, negative error code otherwise. |
445 | */ |
446 | int filemap_flush(struct address_space *mapping) |
447 | { |
448 | return __filemap_fdatawrite(mapping, WB_SYNC_NONE); |
449 | } |
450 | EXPORT_SYMBOL(filemap_flush); |
451 | |
452 | /** |
453 | * filemap_range_has_page - check if a page exists in range. |
454 | * @mapping: address space within which to check |
455 | * @start_byte: offset in bytes where the range starts |
456 | * @end_byte: offset in bytes where the range ends (inclusive) |
457 | * |
458 | * Find at least one page in the range supplied, usually used to check if |
459 | * direct writing in this range will trigger a writeback. |
460 | * |
461 | * Return: %true if at least one page exists in the specified range, |
462 | * %false otherwise. |
463 | */ |
464 | bool filemap_range_has_page(struct address_space *mapping, |
465 | loff_t start_byte, loff_t end_byte) |
466 | { |
467 | struct page *page; |
468 | XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT); |
469 | pgoff_t max = end_byte >> PAGE_SHIFT; |
470 | |
471 | if (end_byte < start_byte) |
472 | return false; |
473 | |
474 | rcu_read_lock(); |
475 | for (;;) { |
476 | page = xas_find(&xas, max); |
477 | if (xas_retry(&xas, page)) |
478 | continue; |
479 | /* Shadow entries don't count */ |
480 | if (xa_is_value(page)) |
481 | continue; |
482 | /* |
483 | * We don't need to try to pin this page; we're about to |
484 | * release the RCU lock anyway. It is enough to know that |
485 | * there was a page here recently. |
486 | */ |
487 | break; |
488 | } |
489 | rcu_read_unlock(); |
490 | |
491 | return page != NULL; |
492 | } |
493 | EXPORT_SYMBOL(filemap_range_has_page); |
494 | |
495 | static void __filemap_fdatawait_range(struct address_space *mapping, |
496 | loff_t start_byte, loff_t end_byte) |
497 | { |
498 | pgoff_t index = start_byte >> PAGE_SHIFT; |
499 | pgoff_t end = end_byte >> PAGE_SHIFT; |
500 | struct pagevec pvec; |
501 | int nr_pages; |
502 | |
503 | if (end_byte < start_byte) |
504 | return; |
505 | |
506 | pagevec_init(&pvec); |
507 | while (index <= end) { |
508 | unsigned i; |
509 | |
510 | nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, |
511 | end, PAGECACHE_TAG_WRITEBACK); |
512 | if (!nr_pages) |
513 | break; |
514 | |
515 | for (i = 0; i < nr_pages; i++) { |
516 | struct page *page = pvec.pages[i]; |
517 | |
518 | wait_on_page_writeback(page); |
519 | ClearPageError(page); |
520 | } |
521 | pagevec_release(&pvec); |
522 | cond_resched(); |
523 | } |
524 | } |
525 | |
526 | /** |
527 | * filemap_fdatawait_range - wait for writeback to complete |
528 | * @mapping: address space structure to wait for |
529 | * @start_byte: offset in bytes where the range starts |
530 | * @end_byte: offset in bytes where the range ends (inclusive) |
531 | * |
532 | * Walk the list of under-writeback pages of the given address space |
533 | * in the given range and wait for all of them. Check error status of |
534 | * the address space and return it. |
535 | * |
536 | * Since the error status of the address space is cleared by this function, |
537 | * callers are responsible for checking the return value and handling and/or |
538 | * reporting the error. |
539 | * |
540 | * Return: error status of the address space. |
541 | */ |
542 | int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, |
543 | loff_t end_byte) |
544 | { |
545 | __filemap_fdatawait_range(mapping, start_byte, end_byte); |
546 | return filemap_check_errors(mapping); |
547 | } |
548 | EXPORT_SYMBOL(filemap_fdatawait_range); |
549 | |
550 | /** |
551 | * file_fdatawait_range - wait for writeback to complete |
552 | * @file: file pointing to address space structure to wait for |
553 | * @start_byte: offset in bytes where the range starts |
554 | * @end_byte: offset in bytes where the range ends (inclusive) |
555 | * |
556 | * Walk the list of under-writeback pages of the address space that file |
557 | * refers to, in the given range and wait for all of them. Check error |
558 | * status of the address space vs. the file->f_wb_err cursor and return it. |
559 | * |
560 | * Since the error status of the file is advanced by this function, |
561 | * callers are responsible for checking the return value and handling and/or |
562 | * reporting the error. |
563 | * |
564 | * Return: error status of the address space vs. the file->f_wb_err cursor. |
565 | */ |
566 | int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte) |
567 | { |
568 | struct address_space *mapping = file->f_mapping; |
569 | |
570 | __filemap_fdatawait_range(mapping, start_byte, end_byte); |
571 | return file_check_and_advance_wb_err(file); |
572 | } |
573 | EXPORT_SYMBOL(file_fdatawait_range); |
574 | |
575 | /** |
576 | * filemap_fdatawait_keep_errors - wait for writeback without clearing errors |
577 | * @mapping: address space structure to wait for |
578 | * |
579 | * Walk the list of under-writeback pages of the given address space |
580 | * and wait for all of them. Unlike filemap_fdatawait(), this function |
581 | * does not clear error status of the address space. |
582 | * |
583 | * Use this function if callers don't handle errors themselves. Expected |
584 | * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2), |
585 | * fsfreeze(8) |
586 | * |
587 | * Return: error status of the address space. |
588 | */ |
589 | int filemap_fdatawait_keep_errors(struct address_space *mapping) |
590 | { |
591 | __filemap_fdatawait_range(mapping, 0, LLONG_MAX); |
592 | return filemap_check_and_keep_errors(mapping); |
593 | } |
594 | EXPORT_SYMBOL(filemap_fdatawait_keep_errors); |
595 | |
596 | static bool mapping_needs_writeback(struct address_space *mapping) |
597 | { |
598 | return (!dax_mapping(mapping) && mapping->nrpages) || |
599 | (dax_mapping(mapping) && mapping->nrexceptional); |
600 | } |
601 | |
602 | int filemap_write_and_wait(struct address_space *mapping) |
603 | { |
604 | int err = 0; |
605 | |
606 | if (mapping_needs_writeback(mapping)) { |
607 | err = filemap_fdatawrite(mapping); |
608 | /* |
609 | * Even if the above returned error, the pages may be |
610 | * written partially (e.g. -ENOSPC), so we wait for it. |
611 | * But the -EIO is special case, it may indicate the worst |
612 | * thing (e.g. bug) happened, so we avoid waiting for it. |
613 | */ |
614 | if (err != -EIO) { |
615 | int err2 = filemap_fdatawait(mapping); |
616 | if (!err) |
617 | err = err2; |
618 | } else { |
619 | /* Clear any previously stored errors */ |
620 | filemap_check_errors(mapping); |
621 | } |
622 | } else { |
623 | err = filemap_check_errors(mapping); |
624 | } |
625 | return err; |
626 | } |
627 | EXPORT_SYMBOL(filemap_write_and_wait); |
628 | |
629 | /** |
630 | * filemap_write_and_wait_range - write out & wait on a file range |
631 | * @mapping: the address_space for the pages |
632 | * @lstart: offset in bytes where the range starts |
633 | * @lend: offset in bytes where the range ends (inclusive) |
634 | * |
635 | * Write out and wait upon file offsets lstart->lend, inclusive. |
636 | * |
637 | * Note that @lend is inclusive (describes the last byte to be written) so |
638 | * that this function can be used to write to the very end-of-file (end = -1). |
639 | * |
640 | * Return: error status of the address space. |
641 | */ |
642 | int filemap_write_and_wait_range(struct address_space *mapping, |
643 | loff_t lstart, loff_t lend) |
644 | { |
645 | int err = 0; |
646 | |
647 | if (mapping_needs_writeback(mapping)) { |
648 | err = __filemap_fdatawrite_range(mapping, lstart, lend, |
649 | WB_SYNC_ALL); |
650 | /* See comment of filemap_write_and_wait() */ |
651 | if (err != -EIO) { |
652 | int err2 = filemap_fdatawait_range(mapping, |
653 | lstart, lend); |
654 | if (!err) |
655 | err = err2; |
656 | } else { |
657 | /* Clear any previously stored errors */ |
658 | filemap_check_errors(mapping); |
659 | } |
660 | } else { |
661 | err = filemap_check_errors(mapping); |
662 | } |
663 | return err; |
664 | } |
665 | EXPORT_SYMBOL(filemap_write_and_wait_range); |
666 | |
667 | void __filemap_set_wb_err(struct address_space *mapping, int err) |
668 | { |
669 | errseq_t eseq = errseq_set(&mapping->wb_err, err); |
670 | |
671 | trace_filemap_set_wb_err(mapping, eseq); |
672 | } |
673 | EXPORT_SYMBOL(__filemap_set_wb_err); |
674 | |
675 | /** |
676 | * file_check_and_advance_wb_err - report wb error (if any) that was previously |
677 | * and advance wb_err to current one |
678 | * @file: struct file on which the error is being reported |
679 | * |
680 | * When userland calls fsync (or something like nfsd does the equivalent), we |
681 | * want to report any writeback errors that occurred since the last fsync (or |
682 | * since the file was opened if there haven't been any). |
683 | * |
684 | * Grab the wb_err from the mapping. If it matches what we have in the file, |
685 | * then just quickly return 0. The file is all caught up. |
686 | * |
687 | * If it doesn't match, then take the mapping value, set the "seen" flag in |
688 | * it and try to swap it into place. If it works, or another task beat us |
689 | * to it with the new value, then update the f_wb_err and return the error |
690 | * portion. The error at this point must be reported via proper channels |
691 | * (a'la fsync, or NFS COMMIT operation, etc.). |
692 | * |
693 | * While we handle mapping->wb_err with atomic operations, the f_wb_err |
694 | * value is protected by the f_lock since we must ensure that it reflects |
695 | * the latest value swapped in for this file descriptor. |
696 | * |
697 | * Return: %0 on success, negative error code otherwise. |
698 | */ |
699 | int file_check_and_advance_wb_err(struct file *file) |
700 | { |
701 | int err = 0; |
702 | errseq_t old = READ_ONCE(file->f_wb_err); |
703 | struct address_space *mapping = file->f_mapping; |
704 | |
705 | /* Locklessly handle the common case where nothing has changed */ |
706 | if (errseq_check(&mapping->wb_err, old)) { |
707 | /* Something changed, must use slow path */ |
708 | spin_lock(&file->f_lock); |
709 | old = file->f_wb_err; |
710 | err = errseq_check_and_advance(&mapping->wb_err, |
711 | &file->f_wb_err); |
712 | trace_file_check_and_advance_wb_err(file, old); |
713 | spin_unlock(&file->f_lock); |
714 | } |
715 | |
716 | /* |
717 | * We're mostly using this function as a drop in replacement for |
718 | * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect |
719 | * that the legacy code would have had on these flags. |
720 | */ |
721 | clear_bit(AS_EIO, &mapping->flags); |
722 | clear_bit(AS_ENOSPC, &mapping->flags); |
723 | return err; |
724 | } |
725 | EXPORT_SYMBOL(file_check_and_advance_wb_err); |
726 | |
727 | /** |
728 | * file_write_and_wait_range - write out & wait on a file range |
729 | * @file: file pointing to address_space with pages |
730 | * @lstart: offset in bytes where the range starts |
731 | * @lend: offset in bytes where the range ends (inclusive) |
732 | * |
733 | * Write out and wait upon file offsets lstart->lend, inclusive. |
734 | * |
735 | * Note that @lend is inclusive (describes the last byte to be written) so |
736 | * that this function can be used to write to the very end-of-file (end = -1). |
737 | * |
738 | * After writing out and waiting on the data, we check and advance the |
739 | * f_wb_err cursor to the latest value, and return any errors detected there. |
740 | * |
741 | * Return: %0 on success, negative error code otherwise. |
742 | */ |
743 | int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend) |
744 | { |
745 | int err = 0, err2; |
746 | struct address_space *mapping = file->f_mapping; |
747 | |
748 | if (mapping_needs_writeback(mapping)) { |
749 | err = __filemap_fdatawrite_range(mapping, lstart, lend, |
750 | WB_SYNC_ALL); |
751 | /* See comment of filemap_write_and_wait() */ |
752 | if (err != -EIO) |
753 | __filemap_fdatawait_range(mapping, lstart, lend); |
754 | } |
755 | err2 = file_check_and_advance_wb_err(file); |
756 | if (!err) |
757 | err = err2; |
758 | return err; |
759 | } |
760 | EXPORT_SYMBOL(file_write_and_wait_range); |
761 | |
762 | /** |
763 | * replace_page_cache_page - replace a pagecache page with a new one |
764 | * @old: page to be replaced |
765 | * @new: page to replace with |
766 | * @gfp_mask: allocation mode |
767 | * |
768 | * This function replaces a page in the pagecache with a new one. On |
769 | * success it acquires the pagecache reference for the new page and |
770 | * drops it for the old page. Both the old and new pages must be |
771 | * locked. This function does not add the new page to the LRU, the |
772 | * caller must do that. |
773 | * |
774 | * The remove + add is atomic. This function cannot fail. |
775 | * |
776 | * Return: %0 |
777 | */ |
778 | int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) |
779 | { |
780 | struct address_space *mapping = old->mapping; |
781 | void (*freepage)(struct page *) = mapping->a_ops->freepage; |
782 | pgoff_t offset = old->index; |
783 | XA_STATE(xas, &mapping->i_pages, offset); |
784 | unsigned long flags; |
785 | |
786 | VM_BUG_ON_PAGE(!PageLocked(old), old); |
787 | VM_BUG_ON_PAGE(!PageLocked(new), new); |
788 | VM_BUG_ON_PAGE(new->mapping, new); |
789 | |
790 | get_page(new); |
791 | new->mapping = mapping; |
792 | new->index = offset; |
793 | |
794 | xas_lock_irqsave(&xas, flags); |
795 | xas_store(&xas, new); |
796 | |
797 | old->mapping = NULL; |
798 | /* hugetlb pages do not participate in page cache accounting. */ |
799 | if (!PageHuge(old)) |
800 | __dec_node_page_state(new, NR_FILE_PAGES); |
801 | if (!PageHuge(new)) |
802 | __inc_node_page_state(new, NR_FILE_PAGES); |
803 | if (PageSwapBacked(old)) |
804 | __dec_node_page_state(new, NR_SHMEM); |
805 | if (PageSwapBacked(new)) |
806 | __inc_node_page_state(new, NR_SHMEM); |
807 | xas_unlock_irqrestore(&xas, flags); |
808 | mem_cgroup_migrate(old, new); |
809 | if (freepage) |
810 | freepage(old); |
811 | put_page(old); |
812 | |
813 | return 0; |
814 | } |
815 | EXPORT_SYMBOL_GPL(replace_page_cache_page); |
816 | |
817 | static int __add_to_page_cache_locked(struct page *page, |
818 | struct address_space *mapping, |
819 | pgoff_t offset, gfp_t gfp_mask, |
820 | void **shadowp) |
821 | { |
822 | XA_STATE(xas, &mapping->i_pages, offset); |
823 | int huge = PageHuge(page); |
824 | struct mem_cgroup *memcg; |
825 | int error; |
826 | void *old; |
827 | |
828 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
829 | VM_BUG_ON_PAGE(PageSwapBacked(page), page); |
830 | mapping_set_update(&xas, mapping); |
831 | |
832 | if (!huge) { |
833 | error = mem_cgroup_try_charge(page, current->mm, |
834 | gfp_mask, &memcg, false); |
835 | if (error) |
836 | return error; |
837 | } |
838 | |
839 | get_page(page); |
840 | page->mapping = mapping; |
841 | page->index = offset; |
842 | |
843 | do { |
844 | xas_lock_irq(&xas); |
845 | old = xas_load(&xas); |
846 | if (old && !xa_is_value(old)) |
847 | xas_set_err(&xas, -EEXIST); |
848 | xas_store(&xas, page); |
849 | if (xas_error(&xas)) |
850 | goto unlock; |
851 | |
852 | if (xa_is_value(old)) { |
853 | mapping->nrexceptional--; |
854 | if (shadowp) |
855 | *shadowp = old; |
856 | } |
857 | mapping->nrpages++; |
858 | |
859 | /* hugetlb pages do not participate in page cache accounting */ |
860 | if (!huge) |
861 | __inc_node_page_state(page, NR_FILE_PAGES); |
862 | unlock: |
863 | xas_unlock_irq(&xas); |
864 | } while (xas_nomem(&xas, gfp_mask & GFP_RECLAIM_MASK)); |
865 | |
866 | if (xas_error(&xas)) |
867 | goto error; |
868 | |
869 | if (!huge) |
870 | mem_cgroup_commit_charge(page, memcg, false, false); |
871 | trace_mm_filemap_add_to_page_cache(page); |
872 | return 0; |
873 | error: |
874 | page->mapping = NULL; |
875 | /* Leave page->index set: truncation relies upon it */ |
876 | if (!huge) |
877 | mem_cgroup_cancel_charge(page, memcg, false); |
878 | put_page(page); |
879 | return xas_error(&xas); |
880 | } |
881 | |
882 | /** |
883 | * add_to_page_cache_locked - add a locked page to the pagecache |
884 | * @page: page to add |
885 | * @mapping: the page's address_space |
886 | * @offset: page index |
887 | * @gfp_mask: page allocation mode |
888 | * |
889 | * This function is used to add a page to the pagecache. It must be locked. |
890 | * This function does not add the page to the LRU. The caller must do that. |
891 | * |
892 | * Return: %0 on success, negative error code otherwise. |
893 | */ |
894 | int add_to_page_cache_locked(struct page *page, struct address_space *mapping, |
895 | pgoff_t offset, gfp_t gfp_mask) |
896 | { |
897 | return __add_to_page_cache_locked(page, mapping, offset, |
898 | gfp_mask, NULL); |
899 | } |
900 | EXPORT_SYMBOL(add_to_page_cache_locked); |
901 | |
902 | int add_to_page_cache_lru(struct page *page, struct address_space *mapping, |
903 | pgoff_t offset, gfp_t gfp_mask) |
904 | { |
905 | void *shadow = NULL; |
906 | int ret; |
907 | |
908 | __SetPageLocked(page); |
909 | ret = __add_to_page_cache_locked(page, mapping, offset, |
910 | gfp_mask, &shadow); |
911 | if (unlikely(ret)) |
912 | __ClearPageLocked(page); |
913 | else { |
914 | /* |
915 | * The page might have been evicted from cache only |
916 | * recently, in which case it should be activated like |
917 | * any other repeatedly accessed page. |
918 | * The exception is pages getting rewritten; evicting other |
919 | * data from the working set, only to cache data that will |
920 | * get overwritten with something else, is a waste of memory. |
921 | */ |
922 | WARN_ON_ONCE(PageActive(page)); |
923 | if (!(gfp_mask & __GFP_WRITE) && shadow) |
924 | workingset_refault(page, shadow); |
925 | lru_cache_add(page); |
926 | } |
927 | return ret; |
928 | } |
929 | EXPORT_SYMBOL_GPL(add_to_page_cache_lru); |
930 | |
931 | #ifdef CONFIG_NUMA |
932 | struct page *__page_cache_alloc(gfp_t gfp) |
933 | { |
934 | int n; |
935 | struct page *page; |
936 | |
937 | if (cpuset_do_page_mem_spread()) { |
938 | unsigned int cpuset_mems_cookie; |
939 | do { |
940 | cpuset_mems_cookie = read_mems_allowed_begin(); |
941 | n = cpuset_mem_spread_node(); |
942 | page = __alloc_pages_node(n, gfp, 0); |
943 | } while (!page && read_mems_allowed_retry(cpuset_mems_cookie)); |
944 | |
945 | return page; |
946 | } |
947 | return alloc_pages(gfp, 0); |
948 | } |
949 | EXPORT_SYMBOL(__page_cache_alloc); |
950 | #endif |
951 | |
952 | /* |
953 | * In order to wait for pages to become available there must be |
954 | * waitqueues associated with pages. By using a hash table of |
955 | * waitqueues where the bucket discipline is to maintain all |
956 | * waiters on the same queue and wake all when any of the pages |
957 | * become available, and for the woken contexts to check to be |
958 | * sure the appropriate page became available, this saves space |
959 | * at a cost of "thundering herd" phenomena during rare hash |
960 | * collisions. |
961 | */ |
962 | #define PAGE_WAIT_TABLE_BITS 8 |
963 | #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS) |
964 | static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned; |
965 | |
966 | static wait_queue_head_t *page_waitqueue(struct page *page) |
967 | { |
968 | return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)]; |
969 | } |
970 | |
971 | void __init pagecache_init(void) |
972 | { |
973 | int i; |
974 | |
975 | for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++) |
976 | init_waitqueue_head(&page_wait_table[i]); |
977 | |
978 | page_writeback_init(); |
979 | } |
980 | |
981 | /* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */ |
982 | struct wait_page_key { |
983 | struct page *page; |
984 | int bit_nr; |
985 | int page_match; |
986 | }; |
987 | |
988 | struct wait_page_queue { |
989 | struct page *page; |
990 | int bit_nr; |
991 | wait_queue_entry_t wait; |
992 | }; |
993 | |
994 | static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg) |
995 | { |
996 | struct wait_page_key *key = arg; |
997 | struct wait_page_queue *wait_page |
998 | = container_of(wait, struct wait_page_queue, wait); |
999 | |
1000 | if (wait_page->page != key->page) |
1001 | return 0; |
1002 | key->page_match = 1; |
1003 | |
1004 | if (wait_page->bit_nr != key->bit_nr) |
1005 | return 0; |
1006 | |
1007 | /* |
1008 | * Stop walking if it's locked. |
1009 | * Is this safe if put_and_wait_on_page_locked() is in use? |
1010 | * Yes: the waker must hold a reference to this page, and if PG_locked |
1011 | * has now already been set by another task, that task must also hold |
1012 | * a reference to the *same usage* of this page; so there is no need |
1013 | * to walk on to wake even the put_and_wait_on_page_locked() callers. |
1014 | */ |
1015 | if (test_bit(key->bit_nr, &key->page->flags)) |
1016 | return -1; |
1017 | |
1018 | return autoremove_wake_function(wait, mode, sync, key); |
1019 | } |
1020 | |
1021 | static void wake_up_page_bit(struct page *page, int bit_nr) |
1022 | { |
1023 | wait_queue_head_t *q = page_waitqueue(page); |
1024 | struct wait_page_key key; |
1025 | unsigned long flags; |
1026 | wait_queue_entry_t bookmark; |
1027 | |
1028 | key.page = page; |
1029 | key.bit_nr = bit_nr; |
1030 | key.page_match = 0; |
1031 | |
1032 | bookmark.flags = 0; |
1033 | bookmark.private = NULL; |
1034 | bookmark.func = NULL; |
1035 | INIT_LIST_HEAD(&bookmark.entry); |
1036 | |
1037 | spin_lock_irqsave(&q->lock, flags); |
1038 | __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
1039 | |
1040 | while (bookmark.flags & WQ_FLAG_BOOKMARK) { |
1041 | /* |
1042 | * Take a breather from holding the lock, |
1043 | * allow pages that finish wake up asynchronously |
1044 | * to acquire the lock and remove themselves |
1045 | * from wait queue |
1046 | */ |
1047 | spin_unlock_irqrestore(&q->lock, flags); |
1048 | cpu_relax(); |
1049 | spin_lock_irqsave(&q->lock, flags); |
1050 | __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); |
1051 | } |
1052 | |
1053 | /* |
1054 | * It is possible for other pages to have collided on the waitqueue |
1055 | * hash, so in that case check for a page match. That prevents a long- |
1056 | * term waiter |
1057 | * |
1058 | * It is still possible to miss a case here, when we woke page waiters |
1059 | * and removed them from the waitqueue, but there are still other |
1060 | * page waiters. |
1061 | */ |
1062 | if (!waitqueue_active(q) || !key.page_match) { |
1063 | ClearPageWaiters(page); |
1064 | /* |
1065 | * It's possible to miss clearing Waiters here, when we woke |
1066 | * our page waiters, but the hashed waitqueue has waiters for |
1067 | * other pages on it. |
1068 | * |
1069 | * That's okay, it's a rare case. The next waker will clear it. |
1070 | */ |
1071 | } |
1072 | spin_unlock_irqrestore(&q->lock, flags); |
1073 | } |
1074 | |
1075 | static void wake_up_page(struct page *page, int bit) |
1076 | { |
1077 | if (!PageWaiters(page)) |
1078 | return; |
1079 | wake_up_page_bit(page, bit); |
1080 | } |
1081 | |
1082 | /* |
1083 | * A choice of three behaviors for wait_on_page_bit_common(): |
1084 | */ |
1085 | enum behavior { |
1086 | EXCLUSIVE, /* Hold ref to page and take the bit when woken, like |
1087 | * __lock_page() waiting on then setting PG_locked. |
1088 | */ |
1089 | SHARED, /* Hold ref to page and check the bit when woken, like |
1090 | * wait_on_page_writeback() waiting on PG_writeback. |
1091 | */ |
1092 | DROP, /* Drop ref to page before wait, no check when woken, |
1093 | * like put_and_wait_on_page_locked() on PG_locked. |
1094 | */ |
1095 | }; |
1096 | |
1097 | static inline int wait_on_page_bit_common(wait_queue_head_t *q, |
1098 | struct page *page, int bit_nr, int state, enum behavior behavior) |
1099 | { |
1100 | struct wait_page_queue wait_page; |
1101 | wait_queue_entry_t *wait = &wait_page.wait; |
1102 | bool bit_is_set; |
1103 | bool thrashing = false; |
1104 | bool delayacct = false; |
1105 | unsigned long pflags; |
1106 | int ret = 0; |
1107 | |
1108 | if (bit_nr == PG_locked && |
1109 | !PageUptodate(page) && PageWorkingset(page)) { |
1110 | if (!PageSwapBacked(page)) { |
1111 | delayacct_thrashing_start(); |
1112 | delayacct = true; |
1113 | } |
1114 | psi_memstall_enter(&pflags); |
1115 | thrashing = true; |
1116 | } |
1117 | |
1118 | init_wait(wait); |
1119 | wait->flags = behavior == EXCLUSIVE ? WQ_FLAG_EXCLUSIVE : 0; |
1120 | wait->func = wake_page_function; |
1121 | wait_page.page = page; |
1122 | wait_page.bit_nr = bit_nr; |
1123 | |
1124 | for (;;) { |
1125 | spin_lock_irq(&q->lock); |
1126 | |
1127 | if (likely(list_empty(&wait->entry))) { |
1128 | __add_wait_queue_entry_tail(q, wait); |
1129 | SetPageWaiters(page); |
1130 | } |
1131 | |
1132 | set_current_state(state); |
1133 | |
1134 | spin_unlock_irq(&q->lock); |
1135 | |
1136 | bit_is_set = test_bit(bit_nr, &page->flags); |
1137 | if (behavior == DROP) |
1138 | put_page(page); |
1139 | |
1140 | if (likely(bit_is_set)) |
1141 | io_schedule(); |
1142 | |
1143 | if (behavior == EXCLUSIVE) { |
1144 | if (!test_and_set_bit_lock(bit_nr, &page->flags)) |
1145 | break; |
1146 | } else if (behavior == SHARED) { |
1147 | if (!test_bit(bit_nr, &page->flags)) |
1148 | break; |
1149 | } |
1150 | |
1151 | if (signal_pending_state(state, current)) { |
1152 | ret = -EINTR; |
1153 | break; |
1154 | } |
1155 | |
1156 | if (behavior == DROP) { |
1157 | /* |
1158 | * We can no longer safely access page->flags: |
1159 | * even if CONFIG_MEMORY_HOTREMOVE is not enabled, |
1160 | * there is a risk of waiting forever on a page reused |
1161 | * for something that keeps it locked indefinitely. |
1162 | * But best check for -EINTR above before breaking. |
1163 | */ |
1164 | break; |
1165 | } |
1166 | } |
1167 | |
1168 | finish_wait(q, wait); |
1169 | |
1170 | if (thrashing) { |
1171 | if (delayacct) |
1172 | delayacct_thrashing_end(); |
1173 | psi_memstall_leave(&pflags); |
1174 | } |
1175 | |
1176 | /* |
1177 | * A signal could leave PageWaiters set. Clearing it here if |
1178 | * !waitqueue_active would be possible (by open-coding finish_wait), |
1179 | * but still fail to catch it in the case of wait hash collision. We |
1180 | * already can fail to clear wait hash collision cases, so don't |
1181 | * bother with signals either. |
1182 | */ |
1183 | |
1184 | return ret; |
1185 | } |
1186 | |
1187 | void wait_on_page_bit(struct page *page, int bit_nr) |
1188 | { |
1189 | wait_queue_head_t *q = page_waitqueue(page); |
1190 | wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, SHARED); |
1191 | } |
1192 | EXPORT_SYMBOL(wait_on_page_bit); |
1193 | |
1194 | int wait_on_page_bit_killable(struct page *page, int bit_nr) |
1195 | { |
1196 | wait_queue_head_t *q = page_waitqueue(page); |
1197 | return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, SHARED); |
1198 | } |
1199 | EXPORT_SYMBOL(wait_on_page_bit_killable); |
1200 | |
1201 | /** |
1202 | * put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked |
1203 | * @page: The page to wait for. |
1204 | * |
1205 | * The caller should hold a reference on @page. They expect the page to |
1206 | * become unlocked relatively soon, but do not wish to hold up migration |
1207 | * (for example) by holding the reference while waiting for the page to |
1208 | * come unlocked. After this function returns, the caller should not |
1209 | * dereference @page. |
1210 | */ |
1211 | void put_and_wait_on_page_locked(struct page *page) |
1212 | { |
1213 | wait_queue_head_t *q; |
1214 | |
1215 | page = compound_head(page); |
1216 | q = page_waitqueue(page); |
1217 | wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, DROP); |
1218 | } |
1219 | |
1220 | /** |
1221 | * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue |
1222 | * @page: Page defining the wait queue of interest |
1223 | * @waiter: Waiter to add to the queue |
1224 | * |
1225 | * Add an arbitrary @waiter to the wait queue for the nominated @page. |
1226 | */ |
1227 | void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter) |
1228 | { |
1229 | wait_queue_head_t *q = page_waitqueue(page); |
1230 | unsigned long flags; |
1231 | |
1232 | spin_lock_irqsave(&q->lock, flags); |
1233 | __add_wait_queue_entry_tail(q, waiter); |
1234 | SetPageWaiters(page); |
1235 | spin_unlock_irqrestore(&q->lock, flags); |
1236 | } |
1237 | EXPORT_SYMBOL_GPL(add_page_wait_queue); |
1238 | |
1239 | #ifndef clear_bit_unlock_is_negative_byte |
1240 | |
1241 | /* |
1242 | * PG_waiters is the high bit in the same byte as PG_lock. |
1243 | * |
1244 | * On x86 (and on many other architectures), we can clear PG_lock and |
1245 | * test the sign bit at the same time. But if the architecture does |
1246 | * not support that special operation, we just do this all by hand |
1247 | * instead. |
1248 | * |
1249 | * The read of PG_waiters has to be after (or concurrently with) PG_locked |
1250 | * being cleared, but a memory barrier should be unneccssary since it is |
1251 | * in the same byte as PG_locked. |
1252 | */ |
1253 | static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem) |
1254 | { |
1255 | clear_bit_unlock(nr, mem); |
1256 | /* smp_mb__after_atomic(); */ |
1257 | return test_bit(PG_waiters, mem); |
1258 | } |
1259 | |
1260 | #endif |
1261 | |
1262 | /** |
1263 | * unlock_page - unlock a locked page |
1264 | * @page: the page |
1265 | * |
1266 | * Unlocks the page and wakes up sleepers in ___wait_on_page_locked(). |
1267 | * Also wakes sleepers in wait_on_page_writeback() because the wakeup |
1268 | * mechanism between PageLocked pages and PageWriteback pages is shared. |
1269 | * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep. |
1270 | * |
1271 | * Note that this depends on PG_waiters being the sign bit in the byte |
1272 | * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to |
1273 | * clear the PG_locked bit and test PG_waiters at the same time fairly |
1274 | * portably (architectures that do LL/SC can test any bit, while x86 can |
1275 | * test the sign bit). |
1276 | */ |
1277 | void unlock_page(struct page *page) |
1278 | { |
1279 | BUILD_BUG_ON(PG_waiters != 7); |
1280 | page = compound_head(page); |
1281 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
1282 | if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags)) |
1283 | wake_up_page_bit(page, PG_locked); |
1284 | } |
1285 | EXPORT_SYMBOL(unlock_page); |
1286 | |
1287 | /** |
1288 | * end_page_writeback - end writeback against a page |
1289 | * @page: the page |
1290 | */ |
1291 | void end_page_writeback(struct page *page) |
1292 | { |
1293 | /* |
1294 | * TestClearPageReclaim could be used here but it is an atomic |
1295 | * operation and overkill in this particular case. Failing to |
1296 | * shuffle a page marked for immediate reclaim is too mild to |
1297 | * justify taking an atomic operation penalty at the end of |
1298 | * ever page writeback. |
1299 | */ |
1300 | if (PageReclaim(page)) { |
1301 | ClearPageReclaim(page); |
1302 | rotate_reclaimable_page(page); |
1303 | } |
1304 | |
1305 | if (!test_clear_page_writeback(page)) |
1306 | BUG(); |
1307 | |
1308 | smp_mb__after_atomic(); |
1309 | wake_up_page(page, PG_writeback); |
1310 | } |
1311 | EXPORT_SYMBOL(end_page_writeback); |
1312 | |
1313 | /* |
1314 | * After completing I/O on a page, call this routine to update the page |
1315 | * flags appropriately |
1316 | */ |
1317 | void page_endio(struct page *page, bool is_write, int err) |
1318 | { |
1319 | if (!is_write) { |
1320 | if (!err) { |
1321 | SetPageUptodate(page); |
1322 | } else { |
1323 | ClearPageUptodate(page); |
1324 | SetPageError(page); |
1325 | } |
1326 | unlock_page(page); |
1327 | } else { |
1328 | if (err) { |
1329 | struct address_space *mapping; |
1330 | |
1331 | SetPageError(page); |
1332 | mapping = page_mapping(page); |
1333 | if (mapping) |
1334 | mapping_set_error(mapping, err); |
1335 | } |
1336 | end_page_writeback(page); |
1337 | } |
1338 | } |
1339 | EXPORT_SYMBOL_GPL(page_endio); |
1340 | |
1341 | /** |
1342 | * __lock_page - get a lock on the page, assuming we need to sleep to get it |
1343 | * @__page: the page to lock |
1344 | */ |
1345 | void __lock_page(struct page *__page) |
1346 | { |
1347 | struct page *page = compound_head(__page); |
1348 | wait_queue_head_t *q = page_waitqueue(page); |
1349 | wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, |
1350 | EXCLUSIVE); |
1351 | } |
1352 | EXPORT_SYMBOL(__lock_page); |
1353 | |
1354 | int __lock_page_killable(struct page *__page) |
1355 | { |
1356 | struct page *page = compound_head(__page); |
1357 | wait_queue_head_t *q = page_waitqueue(page); |
1358 | return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, |
1359 | EXCLUSIVE); |
1360 | } |
1361 | EXPORT_SYMBOL_GPL(__lock_page_killable); |
1362 | |
1363 | /* |
1364 | * Return values: |
1365 | * 1 - page is locked; mmap_sem is still held. |
1366 | * 0 - page is not locked. |
1367 | * mmap_sem has been released (up_read()), unless flags had both |
1368 | * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in |
1369 | * which case mmap_sem is still held. |
1370 | * |
1371 | * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1 |
1372 | * with the page locked and the mmap_sem unperturbed. |
1373 | */ |
1374 | int __lock_page_or_retry(struct page *page, struct mm_struct *mm, |
1375 | unsigned int flags) |
1376 | { |
1377 | if (flags & FAULT_FLAG_ALLOW_RETRY) { |
1378 | /* |
1379 | * CAUTION! In this case, mmap_sem is not released |
1380 | * even though return 0. |
1381 | */ |
1382 | if (flags & FAULT_FLAG_RETRY_NOWAIT) |
1383 | return 0; |
1384 | |
1385 | up_read(&mm->mmap_sem); |
1386 | if (flags & FAULT_FLAG_KILLABLE) |
1387 | wait_on_page_locked_killable(page); |
1388 | else |
1389 | wait_on_page_locked(page); |
1390 | return 0; |
1391 | } else { |
1392 | if (flags & FAULT_FLAG_KILLABLE) { |
1393 | int ret; |
1394 | |
1395 | ret = __lock_page_killable(page); |
1396 | if (ret) { |
1397 | up_read(&mm->mmap_sem); |
1398 | return 0; |
1399 | } |
1400 | } else |
1401 | __lock_page(page); |
1402 | return 1; |
1403 | } |
1404 | } |
1405 | |
1406 | /** |
1407 | * page_cache_next_miss() - Find the next gap in the page cache. |
1408 | * @mapping: Mapping. |
1409 | * @index: Index. |
1410 | * @max_scan: Maximum range to search. |
1411 | * |
1412 | * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the |
1413 | * gap with the lowest index. |
1414 | * |
1415 | * This function may be called under the rcu_read_lock. However, this will |
1416 | * not atomically search a snapshot of the cache at a single point in time. |
1417 | * For example, if a gap is created at index 5, then subsequently a gap is |
1418 | * created at index 10, page_cache_next_miss covering both indices may |
1419 | * return 10 if called under the rcu_read_lock. |
1420 | * |
1421 | * Return: The index of the gap if found, otherwise an index outside the |
1422 | * range specified (in which case 'return - index >= max_scan' will be true). |
1423 | * In the rare case of index wrap-around, 0 will be returned. |
1424 | */ |
1425 | pgoff_t page_cache_next_miss(struct address_space *mapping, |
1426 | pgoff_t index, unsigned long max_scan) |
1427 | { |
1428 | XA_STATE(xas, &mapping->i_pages, index); |
1429 | |
1430 | while (max_scan--) { |
1431 | void *entry = xas_next(&xas); |
1432 | if (!entry || xa_is_value(entry)) |
1433 | break; |
1434 | if (xas.xa_index == 0) |
1435 | break; |
1436 | } |
1437 | |
1438 | return xas.xa_index; |
1439 | } |
1440 | EXPORT_SYMBOL(page_cache_next_miss); |
1441 | |
1442 | /** |
1443 | * page_cache_prev_miss() - Find the next gap in the page cache. |
1444 | * @mapping: Mapping. |
1445 | * @index: Index. |
1446 | * @max_scan: Maximum range to search. |
1447 | * |
1448 | * Search the range [max(index - max_scan + 1, 0), index] for the |
1449 | * gap with the highest index. |
1450 | * |
1451 | * This function may be called under the rcu_read_lock. However, this will |
1452 | * not atomically search a snapshot of the cache at a single point in time. |
1453 | * For example, if a gap is created at index 10, then subsequently a gap is |
1454 | * created at index 5, page_cache_prev_miss() covering both indices may |
1455 | * return 5 if called under the rcu_read_lock. |
1456 | * |
1457 | * Return: The index of the gap if found, otherwise an index outside the |
1458 | * range specified (in which case 'index - return >= max_scan' will be true). |
1459 | * In the rare case of wrap-around, ULONG_MAX will be returned. |
1460 | */ |
1461 | pgoff_t page_cache_prev_miss(struct address_space *mapping, |
1462 | pgoff_t index, unsigned long max_scan) |
1463 | { |
1464 | XA_STATE(xas, &mapping->i_pages, index); |
1465 | |
1466 | while (max_scan--) { |
1467 | void *entry = xas_prev(&xas); |
1468 | if (!entry || xa_is_value(entry)) |
1469 | break; |
1470 | if (xas.xa_index == ULONG_MAX) |
1471 | break; |
1472 | } |
1473 | |
1474 | return xas.xa_index; |
1475 | } |
1476 | EXPORT_SYMBOL(page_cache_prev_miss); |
1477 | |
1478 | /** |
1479 | * find_get_entry - find and get a page cache entry |
1480 | * @mapping: the address_space to search |
1481 | * @offset: the page cache index |
1482 | * |
1483 | * Looks up the page cache slot at @mapping & @offset. If there is a |
1484 | * page cache page, it is returned with an increased refcount. |
1485 | * |
1486 | * If the slot holds a shadow entry of a previously evicted page, or a |
1487 | * swap entry from shmem/tmpfs, it is returned. |
1488 | * |
1489 | * Return: the found page or shadow entry, %NULL if nothing is found. |
1490 | */ |
1491 | struct page *find_get_entry(struct address_space *mapping, pgoff_t offset) |
1492 | { |
1493 | XA_STATE(xas, &mapping->i_pages, offset); |
1494 | struct page *head, *page; |
1495 | |
1496 | rcu_read_lock(); |
1497 | repeat: |
1498 | xas_reset(&xas); |
1499 | page = xas_load(&xas); |
1500 | if (xas_retry(&xas, page)) |
1501 | goto repeat; |
1502 | /* |
1503 | * A shadow entry of a recently evicted page, or a swap entry from |
1504 | * shmem/tmpfs. Return it without attempting to raise page count. |
1505 | */ |
1506 | if (!page || xa_is_value(page)) |
1507 | goto out; |
1508 | |
1509 | head = compound_head(page); |
1510 | if (!page_cache_get_speculative(head)) |
1511 | goto repeat; |
1512 | |
1513 | /* The page was split under us? */ |
1514 | if (compound_head(page) != head) { |
1515 | put_page(head); |
1516 | goto repeat; |
1517 | } |
1518 | |
1519 | /* |
1520 | * Has the page moved? |
1521 | * This is part of the lockless pagecache protocol. See |
1522 | * include/linux/pagemap.h for details. |
1523 | */ |
1524 | if (unlikely(page != xas_reload(&xas))) { |
1525 | put_page(head); |
1526 | goto repeat; |
1527 | } |
1528 | out: |
1529 | rcu_read_unlock(); |
1530 | |
1531 | return page; |
1532 | } |
1533 | EXPORT_SYMBOL(find_get_entry); |
1534 | |
1535 | /** |
1536 | * find_lock_entry - locate, pin and lock a page cache entry |
1537 | * @mapping: the address_space to search |
1538 | * @offset: the page cache index |
1539 | * |
1540 | * Looks up the page cache slot at @mapping & @offset. If there is a |
1541 | * page cache page, it is returned locked and with an increased |
1542 | * refcount. |
1543 | * |
1544 | * If the slot holds a shadow entry of a previously evicted page, or a |
1545 | * swap entry from shmem/tmpfs, it is returned. |
1546 | * |
1547 | * find_lock_entry() may sleep. |
1548 | * |
1549 | * Return: the found page or shadow entry, %NULL if nothing is found. |
1550 | */ |
1551 | struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset) |
1552 | { |
1553 | struct page *page; |
1554 | |
1555 | repeat: |
1556 | page = find_get_entry(mapping, offset); |
1557 | if (page && !xa_is_value(page)) { |
1558 | lock_page(page); |
1559 | /* Has the page been truncated? */ |
1560 | if (unlikely(page_mapping(page) != mapping)) { |
1561 | unlock_page(page); |
1562 | put_page(page); |
1563 | goto repeat; |
1564 | } |
1565 | VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page); |
1566 | } |
1567 | return page; |
1568 | } |
1569 | EXPORT_SYMBOL(find_lock_entry); |
1570 | |
1571 | /** |
1572 | * pagecache_get_page - find and get a page reference |
1573 | * @mapping: the address_space to search |
1574 | * @offset: the page index |
1575 | * @fgp_flags: PCG flags |
1576 | * @gfp_mask: gfp mask to use for the page cache data page allocation |
1577 | * |
1578 | * Looks up the page cache slot at @mapping & @offset. |
1579 | * |
1580 | * PCG flags modify how the page is returned. |
1581 | * |
1582 | * @fgp_flags can be: |
1583 | * |
1584 | * - FGP_ACCESSED: the page will be marked accessed |
1585 | * - FGP_LOCK: Page is return locked |
1586 | * - FGP_CREAT: If page is not present then a new page is allocated using |
1587 | * @gfp_mask and added to the page cache and the VM's LRU |
1588 | * list. The page is returned locked and with an increased |
1589 | * refcount. |
1590 | * - FGP_FOR_MMAP: Similar to FGP_CREAT, only we want to allow the caller to do |
1591 | * its own locking dance if the page is already in cache, or unlock the page |
1592 | * before returning if we had to add the page to pagecache. |
1593 | * |
1594 | * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even |
1595 | * if the GFP flags specified for FGP_CREAT are atomic. |
1596 | * |
1597 | * If there is a page cache page, it is returned with an increased refcount. |
1598 | * |
1599 | * Return: the found page or %NULL otherwise. |
1600 | */ |
1601 | struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, |
1602 | int fgp_flags, gfp_t gfp_mask) |
1603 | { |
1604 | struct page *page; |
1605 | |
1606 | repeat: |
1607 | page = find_get_entry(mapping, offset); |
1608 | if (xa_is_value(page)) |
1609 | page = NULL; |
1610 | if (!page) |
1611 | goto no_page; |
1612 | |
1613 | if (fgp_flags & FGP_LOCK) { |
1614 | if (fgp_flags & FGP_NOWAIT) { |
1615 | if (!trylock_page(page)) { |
1616 | put_page(page); |
1617 | return NULL; |
1618 | } |
1619 | } else { |
1620 | lock_page(page); |
1621 | } |
1622 | |
1623 | /* Has the page been truncated? */ |
1624 | if (unlikely(page->mapping != mapping)) { |
1625 | unlock_page(page); |
1626 | put_page(page); |
1627 | goto repeat; |
1628 | } |
1629 | VM_BUG_ON_PAGE(page->index != offset, page); |
1630 | } |
1631 | |
1632 | if (fgp_flags & FGP_ACCESSED) |
1633 | mark_page_accessed(page); |
1634 | |
1635 | no_page: |
1636 | if (!page && (fgp_flags & FGP_CREAT)) { |
1637 | int err; |
1638 | if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping)) |
1639 | gfp_mask |= __GFP_WRITE; |
1640 | if (fgp_flags & FGP_NOFS) |
1641 | gfp_mask &= ~__GFP_FS; |
1642 | |
1643 | page = __page_cache_alloc(gfp_mask); |
1644 | if (!page) |
1645 | return NULL; |
1646 | |
1647 | if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP)))) |
1648 | fgp_flags |= FGP_LOCK; |
1649 | |
1650 | /* Init accessed so avoid atomic mark_page_accessed later */ |
1651 | if (fgp_flags & FGP_ACCESSED) |
1652 | __SetPageReferenced(page); |
1653 | |
1654 | err = add_to_page_cache_lru(page, mapping, offset, gfp_mask); |
1655 | if (unlikely(err)) { |
1656 | put_page(page); |
1657 | page = NULL; |
1658 | if (err == -EEXIST) |
1659 | goto repeat; |
1660 | } |
1661 | |
1662 | /* |
1663 | * add_to_page_cache_lru locks the page, and for mmap we expect |
1664 | * an unlocked page. |
1665 | */ |
1666 | if (page && (fgp_flags & FGP_FOR_MMAP)) |
1667 | unlock_page(page); |
1668 | } |
1669 | |
1670 | return page; |
1671 | } |
1672 | EXPORT_SYMBOL(pagecache_get_page); |
1673 | |
1674 | /** |
1675 | * find_get_entries - gang pagecache lookup |
1676 | * @mapping: The address_space to search |
1677 | * @start: The starting page cache index |
1678 | * @nr_entries: The maximum number of entries |
1679 | * @entries: Where the resulting entries are placed |
1680 | * @indices: The cache indices corresponding to the entries in @entries |
1681 | * |
1682 | * find_get_entries() will search for and return a group of up to |
1683 | * @nr_entries entries in the mapping. The entries are placed at |
1684 | * @entries. find_get_entries() takes a reference against any actual |
1685 | * pages it returns. |
1686 | * |
1687 | * The search returns a group of mapping-contiguous page cache entries |
1688 | * with ascending indexes. There may be holes in the indices due to |
1689 | * not-present pages. |
1690 | * |
1691 | * Any shadow entries of evicted pages, or swap entries from |
1692 | * shmem/tmpfs, are included in the returned array. |
1693 | * |
1694 | * Return: the number of pages and shadow entries which were found. |
1695 | */ |
1696 | unsigned find_get_entries(struct address_space *mapping, |
1697 | pgoff_t start, unsigned int nr_entries, |
1698 | struct page **entries, pgoff_t *indices) |
1699 | { |
1700 | XA_STATE(xas, &mapping->i_pages, start); |
1701 | struct page *page; |
1702 | unsigned int ret = 0; |
1703 | |
1704 | if (!nr_entries) |
1705 | return 0; |
1706 | |
1707 | rcu_read_lock(); |
1708 | xas_for_each(&xas, page, ULONG_MAX) { |
1709 | struct page *head; |
1710 | if (xas_retry(&xas, page)) |
1711 | continue; |
1712 | /* |
1713 | * A shadow entry of a recently evicted page, a swap |
1714 | * entry from shmem/tmpfs or a DAX entry. Return it |
1715 | * without attempting to raise page count. |
1716 | */ |
1717 | if (xa_is_value(page)) |
1718 | goto export; |
1719 | |
1720 | head = compound_head(page); |
1721 | if (!page_cache_get_speculative(head)) |
1722 | goto retry; |
1723 | |
1724 | /* The page was split under us? */ |
1725 | if (compound_head(page) != head) |
1726 | goto put_page; |
1727 | |
1728 | /* Has the page moved? */ |
1729 | if (unlikely(page != xas_reload(&xas))) |
1730 | goto put_page; |
1731 | |
1732 | export: |
1733 | indices[ret] = xas.xa_index; |
1734 | entries[ret] = page; |
1735 | if (++ret == nr_entries) |
1736 | break; |
1737 | continue; |
1738 | put_page: |
1739 | put_page(head); |
1740 | retry: |
1741 | xas_reset(&xas); |
1742 | } |
1743 | rcu_read_unlock(); |
1744 | return ret; |
1745 | } |
1746 | |
1747 | /** |
1748 | * find_get_pages_range - gang pagecache lookup |
1749 | * @mapping: The address_space to search |
1750 | * @start: The starting page index |
1751 | * @end: The final page index (inclusive) |
1752 | * @nr_pages: The maximum number of pages |
1753 | * @pages: Where the resulting pages are placed |
1754 | * |
1755 | * find_get_pages_range() will search for and return a group of up to @nr_pages |
1756 | * pages in the mapping starting at index @start and up to index @end |
1757 | * (inclusive). The pages are placed at @pages. find_get_pages_range() takes |
1758 | * a reference against the returned pages. |
1759 | * |
1760 | * The search returns a group of mapping-contiguous pages with ascending |
1761 | * indexes. There may be holes in the indices due to not-present pages. |
1762 | * We also update @start to index the next page for the traversal. |
1763 | * |
1764 | * Return: the number of pages which were found. If this number is |
1765 | * smaller than @nr_pages, the end of specified range has been |
1766 | * reached. |
1767 | */ |
1768 | unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start, |
1769 | pgoff_t end, unsigned int nr_pages, |
1770 | struct page **pages) |
1771 | { |
1772 | XA_STATE(xas, &mapping->i_pages, *start); |
1773 | struct page *page; |
1774 | unsigned ret = 0; |
1775 | |
1776 | if (unlikely(!nr_pages)) |
1777 | return 0; |
1778 | |
1779 | rcu_read_lock(); |
1780 | xas_for_each(&xas, page, end) { |
1781 | struct page *head; |
1782 | if (xas_retry(&xas, page)) |
1783 | continue; |
1784 | /* Skip over shadow, swap and DAX entries */ |
1785 | if (xa_is_value(page)) |
1786 | continue; |
1787 | |
1788 | head = compound_head(page); |
1789 | if (!page_cache_get_speculative(head)) |
1790 | goto retry; |
1791 | |
1792 | /* The page was split under us? */ |
1793 | if (compound_head(page) != head) |
1794 | goto put_page; |
1795 | |
1796 | /* Has the page moved? */ |
1797 | if (unlikely(page != xas_reload(&xas))) |
1798 | goto put_page; |
1799 | |
1800 | pages[ret] = page; |
1801 | if (++ret == nr_pages) { |
1802 | *start = xas.xa_index + 1; |
1803 | goto out; |
1804 | } |
1805 | continue; |
1806 | put_page: |
1807 | put_page(head); |
1808 | retry: |
1809 | xas_reset(&xas); |
1810 | } |
1811 | |
1812 | /* |
1813 | * We come here when there is no page beyond @end. We take care to not |
1814 | * overflow the index @start as it confuses some of the callers. This |
1815 | * breaks the iteration when there is a page at index -1 but that is |
1816 | * already broken anyway. |
1817 | */ |
1818 | if (end == (pgoff_t)-1) |
1819 | *start = (pgoff_t)-1; |
1820 | else |
1821 | *start = end + 1; |
1822 | out: |
1823 | rcu_read_unlock(); |
1824 | |
1825 | return ret; |
1826 | } |
1827 | |
1828 | /** |
1829 | * find_get_pages_contig - gang contiguous pagecache lookup |
1830 | * @mapping: The address_space to search |
1831 | * @index: The starting page index |
1832 | * @nr_pages: The maximum number of pages |
1833 | * @pages: Where the resulting pages are placed |
1834 | * |
1835 | * find_get_pages_contig() works exactly like find_get_pages(), except |
1836 | * that the returned number of pages are guaranteed to be contiguous. |
1837 | * |
1838 | * Return: the number of pages which were found. |
1839 | */ |
1840 | unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, |
1841 | unsigned int nr_pages, struct page **pages) |
1842 | { |
1843 | XA_STATE(xas, &mapping->i_pages, index); |
1844 | struct page *page; |
1845 | unsigned int ret = 0; |
1846 | |
1847 | if (unlikely(!nr_pages)) |
1848 | return 0; |
1849 | |
1850 | rcu_read_lock(); |
1851 | for (page = xas_load(&xas); page; page = xas_next(&xas)) { |
1852 | struct page *head; |
1853 | if (xas_retry(&xas, page)) |
1854 | continue; |
1855 | /* |
1856 | * If the entry has been swapped out, we can stop looking. |
1857 | * No current caller is looking for DAX entries. |
1858 | */ |
1859 | if (xa_is_value(page)) |
1860 | break; |
1861 | |
1862 | head = compound_head(page); |
1863 | if (!page_cache_get_speculative(head)) |
1864 | goto retry; |
1865 | |
1866 | /* The page was split under us? */ |
1867 | if (compound_head(page) != head) |
1868 | goto put_page; |
1869 | |
1870 | /* Has the page moved? */ |
1871 | if (unlikely(page != xas_reload(&xas))) |
1872 | goto put_page; |
1873 | |
1874 | pages[ret] = page; |
1875 | if (++ret == nr_pages) |
1876 | break; |
1877 | continue; |
1878 | put_page: |
1879 | put_page(head); |
1880 | retry: |
1881 | xas_reset(&xas); |
1882 | } |
1883 | rcu_read_unlock(); |
1884 | return ret; |
1885 | } |
1886 | EXPORT_SYMBOL(find_get_pages_contig); |
1887 | |
1888 | /** |
1889 | * find_get_pages_range_tag - find and return pages in given range matching @tag |
1890 | * @mapping: the address_space to search |
1891 | * @index: the starting page index |
1892 | * @end: The final page index (inclusive) |
1893 | * @tag: the tag index |
1894 | * @nr_pages: the maximum number of pages |
1895 | * @pages: where the resulting pages are placed |
1896 | * |
1897 | * Like find_get_pages, except we only return pages which are tagged with |
1898 | * @tag. We update @index to index the next page for the traversal. |
1899 | * |
1900 | * Return: the number of pages which were found. |
1901 | */ |
1902 | unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, |
1903 | pgoff_t end, xa_mark_t tag, unsigned int nr_pages, |
1904 | struct page **pages) |
1905 | { |
1906 | XA_STATE(xas, &mapping->i_pages, *index); |
1907 | struct page *page; |
1908 | unsigned ret = 0; |
1909 | |
1910 | if (unlikely(!nr_pages)) |
1911 | return 0; |
1912 | |
1913 | rcu_read_lock(); |
1914 | xas_for_each_marked(&xas, page, end, tag) { |
1915 | struct page *head; |
1916 | if (xas_retry(&xas, page)) |
1917 | continue; |
1918 | /* |
1919 | * Shadow entries should never be tagged, but this iteration |
1920 | * is lockless so there is a window for page reclaim to evict |
1921 | * a page we saw tagged. Skip over it. |
1922 | */ |
1923 | if (xa_is_value(page)) |
1924 | continue; |
1925 | |
1926 | head = compound_head(page); |
1927 | if (!page_cache_get_speculative(head)) |
1928 | goto retry; |
1929 | |
1930 | /* The page was split under us? */ |
1931 | if (compound_head(page) != head) |
1932 | goto put_page; |
1933 | |
1934 | /* Has the page moved? */ |
1935 | if (unlikely(page != xas_reload(&xas))) |
1936 | goto put_page; |
1937 | |
1938 | pages[ret] = page; |
1939 | if (++ret == nr_pages) { |
1940 | *index = xas.xa_index + 1; |
1941 | goto out; |
1942 | } |
1943 | continue; |
1944 | put_page: |
1945 | put_page(head); |
1946 | retry: |
1947 | xas_reset(&xas); |
1948 | } |
1949 | |
1950 | /* |
1951 | * We come here when we got to @end. We take care to not overflow the |
1952 | * index @index as it confuses some of the callers. This breaks the |
1953 | * iteration when there is a page at index -1 but that is already |
1954 | * broken anyway. |
1955 | */ |
1956 | if (end == (pgoff_t)-1) |
1957 | *index = (pgoff_t)-1; |
1958 | else |
1959 | *index = end + 1; |
1960 | out: |
1961 | rcu_read_unlock(); |
1962 | |
1963 | return ret; |
1964 | } |
1965 | EXPORT_SYMBOL(find_get_pages_range_tag); |
1966 | |
1967 | /** |
1968 | * find_get_entries_tag - find and return entries that match @tag |
1969 | * @mapping: the address_space to search |
1970 | * @start: the starting page cache index |
1971 | * @tag: the tag index |
1972 | * @nr_entries: the maximum number of entries |
1973 | * @entries: where the resulting entries are placed |
1974 | * @indices: the cache indices corresponding to the entries in @entries |
1975 | * |
1976 | * Like find_get_entries, except we only return entries which are tagged with |
1977 | * @tag. |
1978 | * |
1979 | * Return: the number of entries which were found. |
1980 | */ |
1981 | unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, |
1982 | xa_mark_t tag, unsigned int nr_entries, |
1983 | struct page **entries, pgoff_t *indices) |
1984 | { |
1985 | XA_STATE(xas, &mapping->i_pages, start); |
1986 | struct page *page; |
1987 | unsigned int ret = 0; |
1988 | |
1989 | if (!nr_entries) |
1990 | return 0; |
1991 | |
1992 | rcu_read_lock(); |
1993 | xas_for_each_marked(&xas, page, ULONG_MAX, tag) { |
1994 | struct page *head; |
1995 | if (xas_retry(&xas, page)) |
1996 | continue; |
1997 | /* |
1998 | * A shadow entry of a recently evicted page, a swap |
1999 | * entry from shmem/tmpfs or a DAX entry. Return it |
2000 | * without attempting to raise page count. |
2001 | */ |
2002 | if (xa_is_value(page)) |
2003 | goto export; |
2004 | |
2005 | head = compound_head(page); |
2006 | if (!page_cache_get_speculative(head)) |
2007 | goto retry; |
2008 | |
2009 | /* The page was split under us? */ |
2010 | if (compound_head(page) != head) |
2011 | goto put_page; |
2012 | |
2013 | /* Has the page moved? */ |
2014 | if (unlikely(page != xas_reload(&xas))) |
2015 | goto put_page; |
2016 | |
2017 | export: |
2018 | indices[ret] = xas.xa_index; |
2019 | entries[ret] = page; |
2020 | if (++ret == nr_entries) |
2021 | break; |
2022 | continue; |
2023 | put_page: |
2024 | put_page(head); |
2025 | retry: |
2026 | xas_reset(&xas); |
2027 | } |
2028 | rcu_read_unlock(); |
2029 | return ret; |
2030 | } |
2031 | EXPORT_SYMBOL(find_get_entries_tag); |
2032 | |
2033 | /* |
2034 | * CD/DVDs are error prone. When a medium error occurs, the driver may fail |
2035 | * a _large_ part of the i/o request. Imagine the worst scenario: |
2036 | * |
2037 | * ---R__________________________________________B__________ |
2038 | * ^ reading here ^ bad block(assume 4k) |
2039 | * |
2040 | * read(R) => miss => readahead(R...B) => media error => frustrating retries |
2041 | * => failing the whole request => read(R) => read(R+1) => |
2042 | * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) => |
2043 | * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) => |
2044 | * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ...... |
2045 | * |
2046 | * It is going insane. Fix it by quickly scaling down the readahead size. |
2047 | */ |
2048 | static void shrink_readahead_size_eio(struct file *filp, |
2049 | struct file_ra_state *ra) |
2050 | { |
2051 | ra->ra_pages /= 4; |
2052 | } |
2053 | |
2054 | /** |
2055 | * generic_file_buffered_read - generic file read routine |
2056 | * @iocb: the iocb to read |
2057 | * @iter: data destination |
2058 | * @written: already copied |
2059 | * |
2060 | * This is a generic file read routine, and uses the |
2061 | * mapping->a_ops->readpage() function for the actual low-level stuff. |
2062 | * |
2063 | * This is really ugly. But the goto's actually try to clarify some |
2064 | * of the logic when it comes to error handling etc. |
2065 | * |
2066 | * Return: |
2067 | * * total number of bytes copied, including those the were already @written |
2068 | * * negative error code if nothing was copied |
2069 | */ |
2070 | static ssize_t generic_file_buffered_read(struct kiocb *iocb, |
2071 | struct iov_iter *iter, ssize_t written) |
2072 | { |
2073 | struct file *filp = iocb->ki_filp; |
2074 | struct address_space *mapping = filp->f_mapping; |
2075 | struct inode *inode = mapping->host; |
2076 | struct file_ra_state *ra = &filp->f_ra; |
2077 | loff_t *ppos = &iocb->ki_pos; |
2078 | pgoff_t index; |
2079 | pgoff_t last_index; |
2080 | pgoff_t prev_index; |
2081 | unsigned long offset; /* offset into pagecache page */ |
2082 | unsigned int prev_offset; |
2083 | int error = 0; |
2084 | |
2085 | if (unlikely(*ppos >= inode->i_sb->s_maxbytes)) |
2086 | return 0; |
2087 | iov_iter_truncate(iter, inode->i_sb->s_maxbytes); |
2088 | |
2089 | index = *ppos >> PAGE_SHIFT; |
2090 | prev_index = ra->prev_pos >> PAGE_SHIFT; |
2091 | prev_offset = ra->prev_pos & (PAGE_SIZE-1); |
2092 | last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT; |
2093 | offset = *ppos & ~PAGE_MASK; |
2094 | |
2095 | for (;;) { |
2096 | struct page *page; |
2097 | pgoff_t end_index; |
2098 | loff_t isize; |
2099 | unsigned long nr, ret; |
2100 | |
2101 | cond_resched(); |
2102 | find_page: |
2103 | if (fatal_signal_pending(current)) { |
2104 | error = -EINTR; |
2105 | goto out; |
2106 | } |
2107 | |
2108 | page = find_get_page(mapping, index); |
2109 | if (!page) { |
2110 | if (iocb->ki_flags & IOCB_NOWAIT) |
2111 | goto would_block; |
2112 | page_cache_sync_readahead(mapping, |
2113 | ra, filp, |
2114 | index, last_index - index); |
2115 | page = find_get_page(mapping, index); |
2116 | if (unlikely(page == NULL)) |
2117 | goto no_cached_page; |
2118 | } |
2119 | if (PageReadahead(page)) { |
2120 | page_cache_async_readahead(mapping, |
2121 | ra, filp, page, |
2122 | index, last_index - index); |
2123 | } |
2124 | if (!PageUptodate(page)) { |
2125 | if (iocb->ki_flags & IOCB_NOWAIT) { |
2126 | put_page(page); |
2127 | goto would_block; |
2128 | } |
2129 | |
2130 | /* |
2131 | * See comment in do_read_cache_page on why |
2132 | * wait_on_page_locked is used to avoid unnecessarily |
2133 | * serialisations and why it's safe. |
2134 | */ |
2135 | error = wait_on_page_locked_killable(page); |
2136 | if (unlikely(error)) |
2137 | goto readpage_error; |
2138 | if (PageUptodate(page)) |
2139 | goto page_ok; |
2140 | |
2141 | if (inode->i_blkbits == PAGE_SHIFT || |
2142 | !mapping->a_ops->is_partially_uptodate) |
2143 | goto page_not_up_to_date; |
2144 | /* pipes can't handle partially uptodate pages */ |
2145 | if (unlikely(iov_iter_is_pipe(iter))) |
2146 | goto page_not_up_to_date; |
2147 | if (!trylock_page(page)) |
2148 | goto page_not_up_to_date; |
2149 | /* Did it get truncated before we got the lock? */ |
2150 | if (!page->mapping) |
2151 | goto page_not_up_to_date_locked; |
2152 | if (!mapping->a_ops->is_partially_uptodate(page, |
2153 | offset, iter->count)) |
2154 | goto page_not_up_to_date_locked; |
2155 | unlock_page(page); |
2156 | } |
2157 | page_ok: |
2158 | /* |
2159 | * i_size must be checked after we know the page is Uptodate. |
2160 | * |
2161 | * Checking i_size after the check allows us to calculate |
2162 | * the correct value for "nr", which means the zero-filled |
2163 | * part of the page is not copied back to userspace (unless |
2164 | * another truncate extends the file - this is desired though). |
2165 | */ |
2166 | |
2167 | isize = i_size_read(inode); |
2168 | end_index = (isize - 1) >> PAGE_SHIFT; |
2169 | if (unlikely(!isize || index > end_index)) { |
2170 | put_page(page); |
2171 | goto out; |
2172 | } |
2173 | |
2174 | /* nr is the maximum number of bytes to copy from this page */ |
2175 | nr = PAGE_SIZE; |
2176 | if (index == end_index) { |
2177 | nr = ((isize - 1) & ~PAGE_MASK) + 1; |
2178 | if (nr <= offset) { |
2179 | put_page(page); |
2180 | goto out; |
2181 | } |
2182 | } |
2183 | nr = nr - offset; |
2184 | |
2185 | /* If users can be writing to this page using arbitrary |
2186 | * virtual addresses, take care about potential aliasing |
2187 | * before reading the page on the kernel side. |
2188 | */ |
2189 | if (mapping_writably_mapped(mapping)) |
2190 | flush_dcache_page(page); |
2191 | |
2192 | /* |
2193 | * When a sequential read accesses a page several times, |
2194 | * only mark it as accessed the first time. |
2195 | */ |
2196 | if (prev_index != index || offset != prev_offset) |
2197 | mark_page_accessed(page); |
2198 | prev_index = index; |
2199 | |
2200 | /* |
2201 | * Ok, we have the page, and it's up-to-date, so |
2202 | * now we can copy it to user space... |
2203 | */ |
2204 | |
2205 | ret = copy_page_to_iter(page, offset, nr, iter); |
2206 | offset += ret; |
2207 | index += offset >> PAGE_SHIFT; |
2208 | offset &= ~PAGE_MASK; |
2209 | prev_offset = offset; |
2210 | |
2211 | put_page(page); |
2212 | written += ret; |
2213 | if (!iov_iter_count(iter)) |
2214 | goto out; |
2215 | if (ret < nr) { |
2216 | error = -EFAULT; |
2217 | goto out; |
2218 | } |
2219 | continue; |
2220 | |
2221 | page_not_up_to_date: |
2222 | /* Get exclusive access to the page ... */ |
2223 | error = lock_page_killable(page); |
2224 | if (unlikely(error)) |
2225 | goto readpage_error; |
2226 | |
2227 | page_not_up_to_date_locked: |
2228 | /* Did it get truncated before we got the lock? */ |
2229 | if (!page->mapping) { |
2230 | unlock_page(page); |
2231 | put_page(page); |
2232 | continue; |
2233 | } |
2234 | |
2235 | /* Did somebody else fill it already? */ |
2236 | if (PageUptodate(page)) { |
2237 | unlock_page(page); |
2238 | goto page_ok; |
2239 | } |
2240 | |
2241 | readpage: |
2242 | /* |
2243 | * A previous I/O error may have been due to temporary |
2244 | * failures, eg. multipath errors. |
2245 | * PG_error will be set again if readpage fails. |
2246 | */ |
2247 | ClearPageError(page); |
2248 | /* Start the actual read. The read will unlock the page. */ |
2249 | error = mapping->a_ops->readpage(filp, page); |
2250 | |
2251 | if (unlikely(error)) { |
2252 | if (error == AOP_TRUNCATED_PAGE) { |
2253 | put_page(page); |
2254 | error = 0; |
2255 | goto find_page; |
2256 | } |
2257 | goto readpage_error; |
2258 | } |
2259 | |
2260 | if (!PageUptodate(page)) { |
2261 | error = lock_page_killable(page); |
2262 | if (unlikely(error)) |
2263 | goto readpage_error; |
2264 | if (!PageUptodate(page)) { |
2265 | if (page->mapping == NULL) { |
2266 | /* |
2267 | * invalidate_mapping_pages got it |
2268 | */ |
2269 | unlock_page(page); |
2270 | put_page(page); |
2271 | goto find_page; |
2272 | } |
2273 | unlock_page(page); |
2274 | shrink_readahead_size_eio(filp, ra); |
2275 | error = -EIO; |
2276 | goto readpage_error; |
2277 | } |
2278 | unlock_page(page); |
2279 | } |
2280 | |
2281 | goto page_ok; |
2282 | |
2283 | readpage_error: |
2284 | /* UHHUH! A synchronous read error occurred. Report it */ |
2285 | put_page(page); |
2286 | goto out; |
2287 | |
2288 | no_cached_page: |
2289 | /* |
2290 | * Ok, it wasn't cached, so we need to create a new |
2291 | * page.. |
2292 | */ |
2293 | page = page_cache_alloc(mapping); |
2294 | if (!page) { |
2295 | error = -ENOMEM; |
2296 | goto out; |
2297 | } |
2298 | error = add_to_page_cache_lru(page, mapping, index, |
2299 | mapping_gfp_constraint(mapping, GFP_KERNEL)); |
2300 | if (error) { |
2301 | put_page(page); |
2302 | if (error == -EEXIST) { |
2303 | error = 0; |
2304 | goto find_page; |
2305 | } |
2306 | goto out; |
2307 | } |
2308 | goto readpage; |
2309 | } |
2310 | |
2311 | would_block: |
2312 | error = -EAGAIN; |
2313 | out: |
2314 | ra->prev_pos = prev_index; |
2315 | ra->prev_pos <<= PAGE_SHIFT; |
2316 | ra->prev_pos |= prev_offset; |
2317 | |
2318 | *ppos = ((loff_t)index << PAGE_SHIFT) + offset; |
2319 | file_accessed(filp); |
2320 | return written ? written : error; |
2321 | } |
2322 | |
2323 | /** |
2324 | * generic_file_read_iter - generic filesystem read routine |
2325 | * @iocb: kernel I/O control block |
2326 | * @iter: destination for the data read |
2327 | * |
2328 | * This is the "read_iter()" routine for all filesystems |
2329 | * that can use the page cache directly. |
2330 | * Return: |
2331 | * * number of bytes copied, even for partial reads |
2332 | * * negative error code if nothing was read |
2333 | */ |
2334 | ssize_t |
2335 | generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) |
2336 | { |
2337 | size_t count = iov_iter_count(iter); |
2338 | ssize_t retval = 0; |
2339 | |
2340 | if (!count) |
2341 | goto out; /* skip atime */ |
2342 | |
2343 | if (iocb->ki_flags & IOCB_DIRECT) { |
2344 | struct file *file = iocb->ki_filp; |
2345 | struct address_space *mapping = file->f_mapping; |
2346 | struct inode *inode = mapping->host; |
2347 | loff_t size; |
2348 | |
2349 | size = i_size_read(inode); |
2350 | if (iocb->ki_flags & IOCB_NOWAIT) { |
2351 | if (filemap_range_has_page(mapping, iocb->ki_pos, |
2352 | iocb->ki_pos + count - 1)) |
2353 | return -EAGAIN; |
2354 | } else { |
2355 | retval = filemap_write_and_wait_range(mapping, |
2356 | iocb->ki_pos, |
2357 | iocb->ki_pos + count - 1); |
2358 | if (retval < 0) |
2359 | goto out; |
2360 | } |
2361 | |
2362 | file_accessed(file); |
2363 | |
2364 | retval = mapping->a_ops->direct_IO(iocb, iter); |
2365 | if (retval >= 0) { |
2366 | iocb->ki_pos += retval; |
2367 | count -= retval; |
2368 | } |
2369 | iov_iter_revert(iter, count - iov_iter_count(iter)); |
2370 | |
2371 | /* |
2372 | * Btrfs can have a short DIO read if we encounter |
2373 | * compressed extents, so if there was an error, or if |
2374 | * we've already read everything we wanted to, or if |
2375 | * there was a short read because we hit EOF, go ahead |
2376 | * and return. Otherwise fallthrough to buffered io for |
2377 | * the rest of the read. Buffered reads will not work for |
2378 | * DAX files, so don't bother trying. |
2379 | */ |
2380 | if (retval < 0 || !count || iocb->ki_pos >= size || |
2381 | IS_DAX(inode)) |
2382 | goto out; |
2383 | } |
2384 | |
2385 | retval = generic_file_buffered_read(iocb, iter, retval); |
2386 | out: |
2387 | return retval; |
2388 | } |
2389 | EXPORT_SYMBOL(generic_file_read_iter); |
2390 | |
2391 | #ifdef CONFIG_MMU |
2392 | #define MMAP_LOTSAMISS (100) |
2393 | static struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, |
2394 | struct file *fpin) |
2395 | { |
2396 | int flags = vmf->flags; |
2397 | |
2398 | if (fpin) |
2399 | return fpin; |
2400 | |
2401 | /* |
2402 | * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or |
2403 | * anything, so we only pin the file and drop the mmap_sem if only |
2404 | * FAULT_FLAG_ALLOW_RETRY is set. |
2405 | */ |
2406 | if ((flags & (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT)) == |
2407 | FAULT_FLAG_ALLOW_RETRY) { |
2408 | fpin = get_file(vmf->vma->vm_file); |
2409 | up_read(&vmf->vma->vm_mm->mmap_sem); |
2410 | } |
2411 | return fpin; |
2412 | } |
2413 | |
2414 | /* |
2415 | * lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_sem |
2416 | * @vmf - the vm_fault for this fault. |
2417 | * @page - the page to lock. |
2418 | * @fpin - the pointer to the file we may pin (or is already pinned). |
2419 | * |
2420 | * This works similar to lock_page_or_retry in that it can drop the mmap_sem. |
2421 | * It differs in that it actually returns the page locked if it returns 1 and 0 |
2422 | * if it couldn't lock the page. If we did have to drop the mmap_sem then fpin |
2423 | * will point to the pinned file and needs to be fput()'ed at a later point. |
2424 | */ |
2425 | static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page, |
2426 | struct file **fpin) |
2427 | { |
2428 | if (trylock_page(page)) |
2429 | return 1; |
2430 | |
2431 | /* |
2432 | * NOTE! This will make us return with VM_FAULT_RETRY, but with |
2433 | * the mmap_sem still held. That's how FAULT_FLAG_RETRY_NOWAIT |
2434 | * is supposed to work. We have way too many special cases.. |
2435 | */ |
2436 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
2437 | return 0; |
2438 | |
2439 | *fpin = maybe_unlock_mmap_for_io(vmf, *fpin); |
2440 | if (vmf->flags & FAULT_FLAG_KILLABLE) { |
2441 | if (__lock_page_killable(page)) { |
2442 | /* |
2443 | * We didn't have the right flags to drop the mmap_sem, |
2444 | * but all fault_handlers only check for fatal signals |
2445 | * if we return VM_FAULT_RETRY, so we need to drop the |
2446 | * mmap_sem here and return 0 if we don't have a fpin. |
2447 | */ |
2448 | if (*fpin == NULL) |
2449 | up_read(&vmf->vma->vm_mm->mmap_sem); |
2450 | return 0; |
2451 | } |
2452 | } else |
2453 | __lock_page(page); |
2454 | return 1; |
2455 | } |
2456 | |
2457 | |
2458 | /* |
2459 | * Synchronous readahead happens when we don't even find a page in the page |
2460 | * cache at all. We don't want to perform IO under the mmap sem, so if we have |
2461 | * to drop the mmap sem we return the file that was pinned in order for us to do |
2462 | * that. If we didn't pin a file then we return NULL. The file that is |
2463 | * returned needs to be fput()'ed when we're done with it. |
2464 | */ |
2465 | static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) |
2466 | { |
2467 | struct file *file = vmf->vma->vm_file; |
2468 | struct file_ra_state *ra = &file->f_ra; |
2469 | struct address_space *mapping = file->f_mapping; |
2470 | struct file *fpin = NULL; |
2471 | pgoff_t offset = vmf->pgoff; |
2472 | |
2473 | /* If we don't want any read-ahead, don't bother */ |
2474 | if (vmf->vma->vm_flags & VM_RAND_READ) |
2475 | return fpin; |
2476 | if (!ra->ra_pages) |
2477 | return fpin; |
2478 | |
2479 | if (vmf->vma->vm_flags & VM_SEQ_READ) { |
2480 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
2481 | page_cache_sync_readahead(mapping, ra, file, offset, |
2482 | ra->ra_pages); |
2483 | return fpin; |
2484 | } |
2485 | |
2486 | /* Avoid banging the cache line if not needed */ |
2487 | if (ra->mmap_miss < MMAP_LOTSAMISS * 10) |
2488 | ra->mmap_miss++; |
2489 | |
2490 | /* |
2491 | * Do we miss much more than hit in this file? If so, |
2492 | * stop bothering with read-ahead. It will only hurt. |
2493 | */ |
2494 | if (ra->mmap_miss > MMAP_LOTSAMISS) |
2495 | return fpin; |
2496 | |
2497 | /* |
2498 | * mmap read-around |
2499 | */ |
2500 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
2501 | ra->start = max_t(long, 0, offset - ra->ra_pages / 2); |
2502 | ra->size = ra->ra_pages; |
2503 | ra->async_size = ra->ra_pages / 4; |
2504 | ra_submit(ra, mapping, file); |
2505 | return fpin; |
2506 | } |
2507 | |
2508 | /* |
2509 | * Asynchronous readahead happens when we find the page and PG_readahead, |
2510 | * so we want to possibly extend the readahead further. We return the file that |
2511 | * was pinned if we have to drop the mmap_sem in order to do IO. |
2512 | */ |
2513 | static struct file *do_async_mmap_readahead(struct vm_fault *vmf, |
2514 | struct page *page) |
2515 | { |
2516 | struct file *file = vmf->vma->vm_file; |
2517 | struct file_ra_state *ra = &file->f_ra; |
2518 | struct address_space *mapping = file->f_mapping; |
2519 | struct file *fpin = NULL; |
2520 | pgoff_t offset = vmf->pgoff; |
2521 | |
2522 | /* If we don't want any read-ahead, don't bother */ |
2523 | if (vmf->vma->vm_flags & VM_RAND_READ) |
2524 | return fpin; |
2525 | if (ra->mmap_miss > 0) |
2526 | ra->mmap_miss--; |
2527 | if (PageReadahead(page)) { |
2528 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
2529 | page_cache_async_readahead(mapping, ra, file, |
2530 | page, offset, ra->ra_pages); |
2531 | } |
2532 | return fpin; |
2533 | } |
2534 | |
2535 | /** |
2536 | * filemap_fault - read in file data for page fault handling |
2537 | * @vmf: struct vm_fault containing details of the fault |
2538 | * |
2539 | * filemap_fault() is invoked via the vma operations vector for a |
2540 | * mapped memory region to read in file data during a page fault. |
2541 | * |
2542 | * The goto's are kind of ugly, but this streamlines the normal case of having |
2543 | * it in the page cache, and handles the special cases reasonably without |
2544 | * having a lot of duplicated code. |
2545 | * |
2546 | * vma->vm_mm->mmap_sem must be held on entry. |
2547 | * |
2548 | * If our return value has VM_FAULT_RETRY set, it's because |
2549 | * lock_page_or_retry() returned 0. |
2550 | * The mmap_sem has usually been released in this case. |
2551 | * See __lock_page_or_retry() for the exception. |
2552 | * |
2553 | * If our return value does not have VM_FAULT_RETRY set, the mmap_sem |
2554 | * has not been released. |
2555 | * |
2556 | * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set. |
2557 | * |
2558 | * Return: bitwise-OR of %VM_FAULT_ codes. |
2559 | */ |
2560 | vm_fault_t filemap_fault(struct vm_fault *vmf) |
2561 | { |
2562 | int error; |
2563 | struct file *file = vmf->vma->vm_file; |
2564 | struct file *fpin = NULL; |
2565 | struct address_space *mapping = file->f_mapping; |
2566 | struct file_ra_state *ra = &file->f_ra; |
2567 | struct inode *inode = mapping->host; |
2568 | pgoff_t offset = vmf->pgoff; |
2569 | pgoff_t max_off; |
2570 | struct page *page; |
2571 | vm_fault_t ret = 0; |
2572 | |
2573 | max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
2574 | if (unlikely(offset >= max_off)) |
2575 | return VM_FAULT_SIGBUS; |
2576 | |
2577 | /* |
2578 | * Do we have something in the page cache already? |
2579 | */ |
2580 | page = find_get_page(mapping, offset); |
2581 | if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { |
2582 | /* |
2583 | * We found the page, so try async readahead before |
2584 | * waiting for the lock. |
2585 | */ |
2586 | fpin = do_async_mmap_readahead(vmf, page); |
2587 | } else if (!page) { |
2588 | /* No page in the page cache at all */ |
2589 | count_vm_event(PGMAJFAULT); |
2590 | count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); |
2591 | ret = VM_FAULT_MAJOR; |
2592 | fpin = do_sync_mmap_readahead(vmf); |
2593 | retry_find: |
2594 | page = pagecache_get_page(mapping, offset, |
2595 | FGP_CREAT|FGP_FOR_MMAP, |
2596 | vmf->gfp_mask); |
2597 | if (!page) { |
2598 | if (fpin) |
2599 | goto out_retry; |
2600 | return vmf_error(-ENOMEM); |
2601 | } |
2602 | } |
2603 | |
2604 | if (!lock_page_maybe_drop_mmap(vmf, page, &fpin)) |
2605 | goto out_retry; |
2606 | |
2607 | /* Did it get truncated? */ |
2608 | if (unlikely(page->mapping != mapping)) { |
2609 | unlock_page(page); |
2610 | put_page(page); |
2611 | goto retry_find; |
2612 | } |
2613 | VM_BUG_ON_PAGE(page->index != offset, page); |
2614 | |
2615 | /* |
2616 | * We have a locked page in the page cache, now we need to check |
2617 | * that it's up-to-date. If not, it is going to be due to an error. |
2618 | */ |
2619 | if (unlikely(!PageUptodate(page))) |
2620 | goto page_not_uptodate; |
2621 | |
2622 | /* |
2623 | * We've made it this far and we had to drop our mmap_sem, now is the |
2624 | * time to return to the upper layer and have it re-find the vma and |
2625 | * redo the fault. |
2626 | */ |
2627 | if (fpin) { |
2628 | unlock_page(page); |
2629 | goto out_retry; |
2630 | } |
2631 | |
2632 | /* |
2633 | * Found the page and have a reference on it. |
2634 | * We must recheck i_size under page lock. |
2635 | */ |
2636 | max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); |
2637 | if (unlikely(offset >= max_off)) { |
2638 | unlock_page(page); |
2639 | put_page(page); |
2640 | return VM_FAULT_SIGBUS; |
2641 | } |
2642 | |
2643 | vmf->page = page; |
2644 | return ret | VM_FAULT_LOCKED; |
2645 | |
2646 | page_not_uptodate: |
2647 | /* |
2648 | * Umm, take care of errors if the page isn't up-to-date. |
2649 | * Try to re-read it _once_. We do this synchronously, |
2650 | * because there really aren't any performance issues here |
2651 | * and we need to check for errors. |
2652 | */ |
2653 | ClearPageError(page); |
2654 | fpin = maybe_unlock_mmap_for_io(vmf, fpin); |
2655 | error = mapping->a_ops->readpage(file, page); |
2656 | if (!error) { |
2657 | wait_on_page_locked(page); |
2658 | if (!PageUptodate(page)) |
2659 | error = -EIO; |
2660 | } |
2661 | if (fpin) |
2662 | goto out_retry; |
2663 | put_page(page); |
2664 | |
2665 | if (!error || error == AOP_TRUNCATED_PAGE) |
2666 | goto retry_find; |
2667 | |
2668 | /* Things didn't work out. Return zero to tell the mm layer so. */ |
2669 | shrink_readahead_size_eio(file, ra); |
2670 | return VM_FAULT_SIGBUS; |
2671 | |
2672 | out_retry: |
2673 | /* |
2674 | * We dropped the mmap_sem, we need to return to the fault handler to |
2675 | * re-find the vma and come back and find our hopefully still populated |
2676 | * page. |
2677 | */ |
2678 | if (page) |
2679 | put_page(page); |
2680 | if (fpin) |
2681 | fput(fpin); |
2682 | return ret | VM_FAULT_RETRY; |
2683 | } |
2684 | EXPORT_SYMBOL(filemap_fault); |
2685 | |
2686 | void filemap_map_pages(struct vm_fault *vmf, |
2687 | pgoff_t start_pgoff, pgoff_t end_pgoff) |
2688 | { |
2689 | struct file *file = vmf->vma->vm_file; |
2690 | struct address_space *mapping = file->f_mapping; |
2691 | pgoff_t last_pgoff = start_pgoff; |
2692 | unsigned long max_idx; |
2693 | XA_STATE(xas, &mapping->i_pages, start_pgoff); |
2694 | struct page *head, *page; |
2695 | |
2696 | rcu_read_lock(); |
2697 | xas_for_each(&xas, page, end_pgoff) { |
2698 | if (xas_retry(&xas, page)) |
2699 | continue; |
2700 | if (xa_is_value(page)) |
2701 | goto next; |
2702 | |
2703 | head = compound_head(page); |
2704 | |
2705 | /* |
2706 | * Check for a locked page first, as a speculative |
2707 | * reference may adversely influence page migration. |
2708 | */ |
2709 | if (PageLocked(head)) |
2710 | goto next; |
2711 | if (!page_cache_get_speculative(head)) |
2712 | goto next; |
2713 | |
2714 | /* The page was split under us? */ |
2715 | if (compound_head(page) != head) |
2716 | goto skip; |
2717 | |
2718 | /* Has the page moved? */ |
2719 | if (unlikely(page != xas_reload(&xas))) |
2720 | goto skip; |
2721 | |
2722 | if (!PageUptodate(page) || |
2723 | PageReadahead(page) || |
2724 | PageHWPoison(page)) |
2725 | goto skip; |
2726 | if (!trylock_page(page)) |
2727 | goto skip; |
2728 | |
2729 | if (page->mapping != mapping || !PageUptodate(page)) |
2730 | goto unlock; |
2731 | |
2732 | max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); |
2733 | if (page->index >= max_idx) |
2734 | goto unlock; |
2735 | |
2736 | if (file->f_ra.mmap_miss > 0) |
2737 | file->f_ra.mmap_miss--; |
2738 | |
2739 | vmf->address += (xas.xa_index - last_pgoff) << PAGE_SHIFT; |
2740 | if (vmf->pte) |
2741 | vmf->pte += xas.xa_index - last_pgoff; |
2742 | last_pgoff = xas.xa_index; |
2743 | if (alloc_set_pte(vmf, NULL, page)) |
2744 | goto unlock; |
2745 | unlock_page(page); |
2746 | goto next; |
2747 | unlock: |
2748 | unlock_page(page); |
2749 | skip: |
2750 | put_page(page); |
2751 | next: |
2752 | /* Huge page is mapped? No need to proceed. */ |
2753 | if (pmd_trans_huge(*vmf->pmd)) |
2754 | break; |
2755 | } |
2756 | rcu_read_unlock(); |
2757 | } |
2758 | EXPORT_SYMBOL(filemap_map_pages); |
2759 | |
2760 | vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf) |
2761 | { |
2762 | struct page *page = vmf->page; |
2763 | struct inode *inode = file_inode(vmf->vma->vm_file); |
2764 | vm_fault_t ret = VM_FAULT_LOCKED; |
2765 | |
2766 | sb_start_pagefault(inode->i_sb); |
2767 | file_update_time(vmf->vma->vm_file); |
2768 | lock_page(page); |
2769 | if (page->mapping != inode->i_mapping) { |
2770 | unlock_page(page); |
2771 | ret = VM_FAULT_NOPAGE; |
2772 | goto out; |
2773 | } |
2774 | /* |
2775 | * We mark the page dirty already here so that when freeze is in |
2776 | * progress, we are guaranteed that writeback during freezing will |
2777 | * see the dirty page and writeprotect it again. |
2778 | */ |
2779 | set_page_dirty(page); |
2780 | wait_for_stable_page(page); |
2781 | out: |
2782 | sb_end_pagefault(inode->i_sb); |
2783 | return ret; |
2784 | } |
2785 | |
2786 | const struct vm_operations_struct generic_file_vm_ops = { |
2787 | .fault = filemap_fault, |
2788 | .map_pages = filemap_map_pages, |
2789 | .page_mkwrite = filemap_page_mkwrite, |
2790 | }; |
2791 | |
2792 | /* This is used for a general mmap of a disk file */ |
2793 | |
2794 | int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
2795 | { |
2796 | struct address_space *mapping = file->f_mapping; |
2797 | |
2798 | if (!mapping->a_ops->readpage) |
2799 | return -ENOEXEC; |
2800 | file_accessed(file); |
2801 | vma->vm_ops = &generic_file_vm_ops; |
2802 | return 0; |
2803 | } |
2804 | |
2805 | /* |
2806 | * This is for filesystems which do not implement ->writepage. |
2807 | */ |
2808 | int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) |
2809 | { |
2810 | if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) |
2811 | return -EINVAL; |
2812 | return generic_file_mmap(file, vma); |
2813 | } |
2814 | #else |
2815 | vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf) |
2816 | { |
2817 | return VM_FAULT_SIGBUS; |
2818 | } |
2819 | int generic_file_mmap(struct file * file, struct vm_area_struct * vma) |
2820 | { |
2821 | return -ENOSYS; |
2822 | } |
2823 | int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma) |
2824 | { |
2825 | return -ENOSYS; |
2826 | } |
2827 | #endif /* CONFIG_MMU */ |
2828 | |
2829 | EXPORT_SYMBOL(filemap_page_mkwrite); |
2830 | EXPORT_SYMBOL(generic_file_mmap); |
2831 | EXPORT_SYMBOL(generic_file_readonly_mmap); |
2832 | |
2833 | static struct page *wait_on_page_read(struct page *page) |
2834 | { |
2835 | if (!IS_ERR(page)) { |
2836 | wait_on_page_locked(page); |
2837 | if (!PageUptodate(page)) { |
2838 | put_page(page); |
2839 | page = ERR_PTR(-EIO); |
2840 | } |
2841 | } |
2842 | return page; |
2843 | } |
2844 | |
2845 | static struct page *do_read_cache_page(struct address_space *mapping, |
2846 | pgoff_t index, |
2847 | int (*filler)(void *, struct page *), |
2848 | void *data, |
2849 | gfp_t gfp) |
2850 | { |
2851 | struct page *page; |
2852 | int err; |
2853 | repeat: |
2854 | page = find_get_page(mapping, index); |
2855 | if (!page) { |
2856 | page = __page_cache_alloc(gfp); |
2857 | if (!page) |
2858 | return ERR_PTR(-ENOMEM); |
2859 | err = add_to_page_cache_lru(page, mapping, index, gfp); |
2860 | if (unlikely(err)) { |
2861 | put_page(page); |
2862 | if (err == -EEXIST) |
2863 | goto repeat; |
2864 | /* Presumably ENOMEM for xarray node */ |
2865 | return ERR_PTR(err); |
2866 | } |
2867 | |
2868 | filler: |
2869 | err = filler(data, page); |
2870 | if (err < 0) { |
2871 | put_page(page); |
2872 | return ERR_PTR(err); |
2873 | } |
2874 | |
2875 | page = wait_on_page_read(page); |
2876 | if (IS_ERR(page)) |
2877 | return page; |
2878 | goto out; |
2879 | } |
2880 | if (PageUptodate(page)) |
2881 | goto out; |
2882 | |
2883 | /* |
2884 | * Page is not up to date and may be locked due one of the following |
2885 | * case a: Page is being filled and the page lock is held |
2886 | * case b: Read/write error clearing the page uptodate status |
2887 | * case c: Truncation in progress (page locked) |
2888 | * case d: Reclaim in progress |
2889 | * |
2890 | * Case a, the page will be up to date when the page is unlocked. |
2891 | * There is no need to serialise on the page lock here as the page |
2892 | * is pinned so the lock gives no additional protection. Even if the |
2893 | * the page is truncated, the data is still valid if PageUptodate as |
2894 | * it's a race vs truncate race. |
2895 | * Case b, the page will not be up to date |
2896 | * Case c, the page may be truncated but in itself, the data may still |
2897 | * be valid after IO completes as it's a read vs truncate race. The |
2898 | * operation must restart if the page is not uptodate on unlock but |
2899 | * otherwise serialising on page lock to stabilise the mapping gives |
2900 | * no additional guarantees to the caller as the page lock is |
2901 | * released before return. |
2902 | * Case d, similar to truncation. If reclaim holds the page lock, it |
2903 | * will be a race with remove_mapping that determines if the mapping |
2904 | * is valid on unlock but otherwise the data is valid and there is |
2905 | * no need to serialise with page lock. |
2906 | * |
2907 | * As the page lock gives no additional guarantee, we optimistically |
2908 | * wait on the page to be unlocked and check if it's up to date and |
2909 | * use the page if it is. Otherwise, the page lock is required to |
2910 | * distinguish between the different cases. The motivation is that we |
2911 | * avoid spurious serialisations and wakeups when multiple processes |
2912 | * wait on the same page for IO to complete. |
2913 | */ |
2914 | wait_on_page_locked(page); |
2915 | if (PageUptodate(page)) |
2916 | goto out; |
2917 | |
2918 | /* Distinguish between all the cases under the safety of the lock */ |
2919 | lock_page(page); |
2920 | |
2921 | /* Case c or d, restart the operation */ |
2922 | if (!page->mapping) { |
2923 | unlock_page(page); |
2924 | put_page(page); |
2925 | goto repeat; |
2926 | } |
2927 | |
2928 | /* Someone else locked and filled the page in a very small window */ |
2929 | if (PageUptodate(page)) { |
2930 | unlock_page(page); |
2931 | goto out; |
2932 | } |
2933 | goto filler; |
2934 | |
2935 | out: |
2936 | mark_page_accessed(page); |
2937 | return page; |
2938 | } |
2939 | |
2940 | /** |
2941 | * read_cache_page - read into page cache, fill it if needed |
2942 | * @mapping: the page's address_space |
2943 | * @index: the page index |
2944 | * @filler: function to perform the read |
2945 | * @data: first arg to filler(data, page) function, often left as NULL |
2946 | * |
2947 | * Read into the page cache. If a page already exists, and PageUptodate() is |
2948 | * not set, try to fill the page and wait for it to become unlocked. |
2949 | * |
2950 | * If the page does not get brought uptodate, return -EIO. |
2951 | * |
2952 | * Return: up to date page on success, ERR_PTR() on failure. |
2953 | */ |
2954 | struct page *read_cache_page(struct address_space *mapping, |
2955 | pgoff_t index, |
2956 | int (*filler)(void *, struct page *), |
2957 | void *data) |
2958 | { |
2959 | return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping)); |
2960 | } |
2961 | EXPORT_SYMBOL(read_cache_page); |
2962 | |
2963 | /** |
2964 | * read_cache_page_gfp - read into page cache, using specified page allocation flags. |
2965 | * @mapping: the page's address_space |
2966 | * @index: the page index |
2967 | * @gfp: the page allocator flags to use if allocating |
2968 | * |
2969 | * This is the same as "read_mapping_page(mapping, index, NULL)", but with |
2970 | * any new page allocations done using the specified allocation flags. |
2971 | * |
2972 | * If the page does not get brought uptodate, return -EIO. |
2973 | * |
2974 | * Return: up to date page on success, ERR_PTR() on failure. |
2975 | */ |
2976 | struct page *read_cache_page_gfp(struct address_space *mapping, |
2977 | pgoff_t index, |
2978 | gfp_t gfp) |
2979 | { |
2980 | filler_t *filler = (filler_t *)mapping->a_ops->readpage; |
2981 | |
2982 | return do_read_cache_page(mapping, index, filler, NULL, gfp); |
2983 | } |
2984 | EXPORT_SYMBOL(read_cache_page_gfp); |
2985 | |
2986 | /* |
2987 | * Don't operate on ranges the page cache doesn't support, and don't exceed the |
2988 | * LFS limits. If pos is under the limit it becomes a short access. If it |
2989 | * exceeds the limit we return -EFBIG. |
2990 | */ |
2991 | static int generic_access_check_limits(struct file *file, loff_t pos, |
2992 | loff_t *count) |
2993 | { |
2994 | struct inode *inode = file->f_mapping->host; |
2995 | loff_t max_size = inode->i_sb->s_maxbytes; |
2996 | |
2997 | if (!(file->f_flags & O_LARGEFILE)) |
2998 | max_size = MAX_NON_LFS; |
2999 | |
3000 | if (unlikely(pos >= max_size)) |
3001 | return -EFBIG; |
3002 | *count = min(*count, max_size - pos); |
3003 | return 0; |
3004 | } |
3005 | |
3006 | static int generic_write_check_limits(struct file *file, loff_t pos, |
3007 | loff_t *count) |
3008 | { |
3009 | loff_t limit = rlimit(RLIMIT_FSIZE); |
3010 | |
3011 | if (limit != RLIM_INFINITY) { |
3012 | if (pos >= limit) { |
3013 | send_sig(SIGXFSZ, current, 0); |
3014 | return -EFBIG; |
3015 | } |
3016 | *count = min(*count, limit - pos); |
3017 | } |
3018 | |
3019 | return generic_access_check_limits(file, pos, count); |
3020 | } |
3021 | |
3022 | /* |
3023 | * Performs necessary checks before doing a write |
3024 | * |
3025 | * Can adjust writing position or amount of bytes to write. |
3026 | * Returns appropriate error code that caller should return or |
3027 | * zero in case that write should be allowed. |
3028 | */ |
3029 | inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) |
3030 | { |
3031 | struct file *file = iocb->ki_filp; |
3032 | struct inode *inode = file->f_mapping->host; |
3033 | loff_t count; |
3034 | int ret; |
3035 | |
3036 | if (!iov_iter_count(from)) |
3037 | return 0; |
3038 | |
3039 | /* FIXME: this is for backwards compatibility with 2.4 */ |
3040 | if (iocb->ki_flags & IOCB_APPEND) |
3041 | iocb->ki_pos = i_size_read(inode); |
3042 | |
3043 | if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT)) |
3044 | return -EINVAL; |
3045 | |
3046 | count = iov_iter_count(from); |
3047 | ret = generic_write_check_limits(file, iocb->ki_pos, &count); |
3048 | if (ret) |
3049 | return ret; |
3050 | |
3051 | iov_iter_truncate(from, count); |
3052 | return iov_iter_count(from); |
3053 | } |
3054 | EXPORT_SYMBOL(generic_write_checks); |
3055 | |
3056 | /* |
3057 | * Performs necessary checks before doing a clone. |
3058 | * |
3059 | * Can adjust amount of bytes to clone. |
3060 | * Returns appropriate error code that caller should return or |
3061 | * zero in case the clone should be allowed. |
3062 | */ |
3063 | int generic_remap_checks(struct file *file_in, loff_t pos_in, |
3064 | struct file *file_out, loff_t pos_out, |
3065 | loff_t *req_count, unsigned int remap_flags) |
3066 | { |
3067 | struct inode *inode_in = file_in->f_mapping->host; |
3068 | struct inode *inode_out = file_out->f_mapping->host; |
3069 | uint64_t count = *req_count; |
3070 | uint64_t bcount; |
3071 | loff_t size_in, size_out; |
3072 | loff_t bs = inode_out->i_sb->s_blocksize; |
3073 | int ret; |
3074 | |
3075 | /* The start of both ranges must be aligned to an fs block. */ |
3076 | if (!IS_ALIGNED(pos_in, bs) || !IS_ALIGNED(pos_out, bs)) |
3077 | return -EINVAL; |
3078 | |
3079 | /* Ensure offsets don't wrap. */ |
3080 | if (pos_in + count < pos_in || pos_out + count < pos_out) |
3081 | return -EINVAL; |
3082 | |
3083 | size_in = i_size_read(inode_in); |
3084 | size_out = i_size_read(inode_out); |
3085 | |
3086 | /* Dedupe requires both ranges to be within EOF. */ |
3087 | if ((remap_flags & REMAP_FILE_DEDUP) && |
3088 | (pos_in >= size_in || pos_in + count > size_in || |
3089 | pos_out >= size_out || pos_out + count > size_out)) |
3090 | return -EINVAL; |
3091 | |
3092 | /* Ensure the infile range is within the infile. */ |
3093 | if (pos_in >= size_in) |
3094 | return -EINVAL; |
3095 | count = min(count, size_in - (uint64_t)pos_in); |
3096 | |
3097 | ret = generic_access_check_limits(file_in, pos_in, &count); |
3098 | if (ret) |
3099 | return ret; |
3100 | |
3101 | ret = generic_write_check_limits(file_out, pos_out, &count); |
3102 | if (ret) |
3103 | return ret; |
3104 | |
3105 | /* |
3106 | * If the user wanted us to link to the infile's EOF, round up to the |
3107 | * next block boundary for this check. |
3108 | * |
3109 | * Otherwise, make sure the count is also block-aligned, having |
3110 | * already confirmed the starting offsets' block alignment. |
3111 | */ |
3112 | if (pos_in + count == size_in) { |
3113 | bcount = ALIGN(size_in, bs) - pos_in; |
3114 | } else { |
3115 | if (!IS_ALIGNED(count, bs)) |
3116 | count = ALIGN_DOWN(count, bs); |
3117 | bcount = count; |
3118 | } |
3119 | |
3120 | /* Don't allow overlapped cloning within the same file. */ |
3121 | if (inode_in == inode_out && |
3122 | pos_out + bcount > pos_in && |
3123 | pos_out < pos_in + bcount) |
3124 | return -EINVAL; |
3125 | |
3126 | /* |
3127 | * We shortened the request but the caller can't deal with that, so |
3128 | * bounce the request back to userspace. |
3129 | */ |
3130 | if (*req_count != count && !(remap_flags & REMAP_FILE_CAN_SHORTEN)) |
3131 | return -EINVAL; |
3132 | |
3133 | *req_count = count; |
3134 | return 0; |
3135 | } |
3136 | |
3137 | int pagecache_write_begin(struct file *file, struct address_space *mapping, |
3138 | loff_t pos, unsigned len, unsigned flags, |
3139 | struct page **pagep, void **fsdata) |
3140 | { |
3141 | const struct address_space_operations *aops = mapping->a_ops; |
3142 | |
3143 | return aops->write_begin(file, mapping, pos, len, flags, |
3144 | pagep, fsdata); |
3145 | } |
3146 | EXPORT_SYMBOL(pagecache_write_begin); |
3147 | |
3148 | int pagecache_write_end(struct file *file, struct address_space *mapping, |
3149 | loff_t pos, unsigned len, unsigned copied, |
3150 | struct page *page, void *fsdata) |
3151 | { |
3152 | const struct address_space_operations *aops = mapping->a_ops; |
3153 | |
3154 | return aops->write_end(file, mapping, pos, len, copied, page, fsdata); |
3155 | } |
3156 | EXPORT_SYMBOL(pagecache_write_end); |
3157 | |
3158 | ssize_t |
3159 | generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) |
3160 | { |
3161 | struct file *file = iocb->ki_filp; |
3162 | struct address_space *mapping = file->f_mapping; |
3163 | struct inode *inode = mapping->host; |
3164 | loff_t pos = iocb->ki_pos; |
3165 | ssize_t written; |
3166 | size_t write_len; |
3167 | pgoff_t end; |
3168 | |
3169 | write_len = iov_iter_count(from); |
3170 | end = (pos + write_len - 1) >> PAGE_SHIFT; |
3171 | |
3172 | if (iocb->ki_flags & IOCB_NOWAIT) { |
3173 | /* If there are pages to writeback, return */ |
3174 | if (filemap_range_has_page(inode->i_mapping, pos, |
3175 | pos + write_len - 1)) |
3176 | return -EAGAIN; |
3177 | } else { |
3178 | written = filemap_write_and_wait_range(mapping, pos, |
3179 | pos + write_len - 1); |
3180 | if (written) |
3181 | goto out; |
3182 | } |
3183 | |
3184 | /* |
3185 | * After a write we want buffered reads to be sure to go to disk to get |
3186 | * the new data. We invalidate clean cached page from the region we're |
3187 | * about to write. We do this *before* the write so that we can return |
3188 | * without clobbering -EIOCBQUEUED from ->direct_IO(). |
3189 | */ |
3190 | written = invalidate_inode_pages2_range(mapping, |
3191 | pos >> PAGE_SHIFT, end); |
3192 | /* |
3193 | * If a page can not be invalidated, return 0 to fall back |
3194 | * to buffered write. |
3195 | */ |
3196 | if (written) { |
3197 | if (written == -EBUSY) |
3198 | return 0; |
3199 | goto out; |
3200 | } |
3201 | |
3202 | written = mapping->a_ops->direct_IO(iocb, from); |
3203 | |
3204 | /* |
3205 | * Finally, try again to invalidate clean pages which might have been |
3206 | * cached by non-direct readahead, or faulted in by get_user_pages() |
3207 | * if the source of the write was an mmap'ed region of the file |
3208 | * we're writing. Either one is a pretty crazy thing to do, |
3209 | * so we don't support it 100%. If this invalidation |
3210 | * fails, tough, the write still worked... |
3211 | * |
3212 | * Most of the time we do not need this since dio_complete() will do |
3213 | * the invalidation for us. However there are some file systems that |
3214 | * do not end up with dio_complete() being called, so let's not break |
3215 | * them by removing it completely |
3216 | */ |
3217 | if (mapping->nrpages) |
3218 | invalidate_inode_pages2_range(mapping, |
3219 | pos >> PAGE_SHIFT, end); |
3220 | |
3221 | if (written > 0) { |
3222 | pos += written; |
3223 | write_len -= written; |
3224 | if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) { |
3225 | i_size_write(inode, pos); |
3226 | mark_inode_dirty(inode); |
3227 | } |
3228 | iocb->ki_pos = pos; |
3229 | } |
3230 | iov_iter_revert(from, write_len - iov_iter_count(from)); |
3231 | out: |
3232 | return written; |
3233 | } |
3234 | EXPORT_SYMBOL(generic_file_direct_write); |
3235 | |
3236 | /* |
3237 | * Find or create a page at the given pagecache position. Return the locked |
3238 | * page. This function is specifically for buffered writes. |
3239 | */ |
3240 | struct page *grab_cache_page_write_begin(struct address_space *mapping, |
3241 | pgoff_t index, unsigned flags) |
3242 | { |
3243 | struct page *page; |
3244 | int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT; |
3245 | |
3246 | if (flags & AOP_FLAG_NOFS) |
3247 | fgp_flags |= FGP_NOFS; |
3248 | |
3249 | page = pagecache_get_page(mapping, index, fgp_flags, |
3250 | mapping_gfp_mask(mapping)); |
3251 | if (page) |
3252 | wait_for_stable_page(page); |
3253 | |
3254 | return page; |
3255 | } |
3256 | EXPORT_SYMBOL(grab_cache_page_write_begin); |
3257 | |
3258 | ssize_t generic_perform_write(struct file *file, |
3259 | struct iov_iter *i, loff_t pos) |
3260 | { |
3261 | struct address_space *mapping = file->f_mapping; |
3262 | const struct address_space_operations *a_ops = mapping->a_ops; |
3263 | long status = 0; |
3264 | ssize_t written = 0; |
3265 | unsigned int flags = 0; |
3266 | |
3267 | do { |
3268 | struct page *page; |
3269 | unsigned long offset; /* Offset into pagecache page */ |
3270 | unsigned long bytes; /* Bytes to write to page */ |
3271 | size_t copied; /* Bytes copied from user */ |
3272 | void *fsdata; |
3273 | |
3274 | offset = (pos & (PAGE_SIZE - 1)); |
3275 | bytes = min_t(unsigned long, PAGE_SIZE - offset, |
3276 | iov_iter_count(i)); |
3277 | |
3278 | again: |
3279 | /* |
3280 | * Bring in the user page that we will copy from _first_. |
3281 | * Otherwise there's a nasty deadlock on copying from the |
3282 | * same page as we're writing to, without it being marked |
3283 | * up-to-date. |
3284 | * |
3285 | * Not only is this an optimisation, but it is also required |
3286 | * to check that the address is actually valid, when atomic |
3287 | * usercopies are used, below. |
3288 | */ |
3289 | if (unlikely(iov_iter_fault_in_readable(i, bytes))) { |
3290 | status = -EFAULT; |
3291 | break; |
3292 | } |
3293 | |
3294 | if (fatal_signal_pending(current)) { |
3295 | status = -EINTR; |
3296 | break; |
3297 | } |
3298 | |
3299 | status = a_ops->write_begin(file, mapping, pos, bytes, flags, |
3300 | &page, &fsdata); |
3301 | if (unlikely(status < 0)) |
3302 | break; |
3303 | |
3304 | if (mapping_writably_mapped(mapping)) |
3305 | flush_dcache_page(page); |
3306 | |
3307 | copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); |
3308 | flush_dcache_page(page); |
3309 | |
3310 | status = a_ops->write_end(file, mapping, pos, bytes, copied, |
3311 | page, fsdata); |
3312 | if (unlikely(status < 0)) |
3313 | break; |
3314 | copied = status; |
3315 | |
3316 | cond_resched(); |
3317 | |
3318 | iov_iter_advance(i, copied); |
3319 | if (unlikely(copied == 0)) { |
3320 | /* |
3321 | * If we were unable to copy any data at all, we must |
3322 | * fall back to a single segment length write. |
3323 | * |
3324 | * If we didn't fallback here, we could livelock |
3325 | * because not all segments in the iov can be copied at |
3326 | * once without a pagefault. |
3327 | */ |
3328 | bytes = min_t(unsigned long, PAGE_SIZE - offset, |
3329 | iov_iter_single_seg_count(i)); |
3330 | goto again; |
3331 | } |
3332 | pos += copied; |
3333 | written += copied; |
3334 | |
3335 | balance_dirty_pages_ratelimited(mapping); |
3336 | } while (iov_iter_count(i)); |
3337 | |
3338 | return written ? written : status; |
3339 | } |
3340 | EXPORT_SYMBOL(generic_perform_write); |
3341 | |
3342 | /** |
3343 | * __generic_file_write_iter - write data to a file |
3344 | * @iocb: IO state structure (file, offset, etc.) |
3345 | * @from: iov_iter with data to write |
3346 | * |
3347 | * This function does all the work needed for actually writing data to a |
3348 | * file. It does all basic checks, removes SUID from the file, updates |
3349 | * modification times and calls proper subroutines depending on whether we |
3350 | * do direct IO or a standard buffered write. |
3351 | * |
3352 | * It expects i_mutex to be grabbed unless we work on a block device or similar |
3353 | * object which does not need locking at all. |
3354 | * |
3355 | * This function does *not* take care of syncing data in case of O_SYNC write. |
3356 | * A caller has to handle it. This is mainly due to the fact that we want to |
3357 | * avoid syncing under i_mutex. |
3358 | * |
3359 | * Return: |
3360 | * * number of bytes written, even for truncated writes |
3361 | * * negative error code if no data has been written at all |
3362 | */ |
3363 | ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) |
3364 | { |
3365 | struct file *file = iocb->ki_filp; |
3366 | struct address_space * mapping = file->f_mapping; |
3367 | struct inode *inode = mapping->host; |
3368 | ssize_t written = 0; |
3369 | ssize_t err; |
3370 | ssize_t status; |
3371 | |
3372 | /* We can write back this queue in page reclaim */ |
3373 | current->backing_dev_info = inode_to_bdi(inode); |
3374 | err = file_remove_privs(file); |
3375 | if (err) |
3376 | goto out; |
3377 | |
3378 | err = file_update_time(file); |
3379 | if (err) |
3380 | goto out; |
3381 | |
3382 | if (iocb->ki_flags & IOCB_DIRECT) { |
3383 | loff_t pos, endbyte; |
3384 | |
3385 | written = generic_file_direct_write(iocb, from); |
3386 | /* |
3387 | * If the write stopped short of completing, fall back to |
3388 | * buffered writes. Some filesystems do this for writes to |
3389 | * holes, for example. For DAX files, a buffered write will |
3390 | * not succeed (even if it did, DAX does not handle dirty |
3391 | * page-cache pages correctly). |
3392 | */ |
3393 | if (written < 0 || !iov_iter_count(from) || IS_DAX(inode)) |
3394 | goto out; |
3395 | |
3396 | status = generic_perform_write(file, from, pos = iocb->ki_pos); |
3397 | /* |
3398 | * If generic_perform_write() returned a synchronous error |
3399 | * then we want to return the number of bytes which were |
3400 | * direct-written, or the error code if that was zero. Note |
3401 | * that this differs from normal direct-io semantics, which |
3402 | * will return -EFOO even if some bytes were written. |
3403 | */ |
3404 | if (unlikely(status < 0)) { |
3405 | err = status; |
3406 | goto out; |
3407 | } |
3408 | /* |
3409 | * We need to ensure that the page cache pages are written to |
3410 | * disk and invalidated to preserve the expected O_DIRECT |
3411 | * semantics. |
3412 | */ |
3413 | endbyte = pos + status - 1; |
3414 | err = filemap_write_and_wait_range(mapping, pos, endbyte); |
3415 | if (err == 0) { |
3416 | iocb->ki_pos = endbyte + 1; |
3417 | written += status; |
3418 | invalidate_mapping_pages(mapping, |
3419 | pos >> PAGE_SHIFT, |
3420 | endbyte >> PAGE_SHIFT); |
3421 | } else { |
3422 | /* |
3423 | * We don't know how much we wrote, so just return |
3424 | * the number of bytes which were direct-written |
3425 | */ |
3426 | } |
3427 | } else { |
3428 | written = generic_perform_write(file, from, iocb->ki_pos); |
3429 | if (likely(written > 0)) |
3430 | iocb->ki_pos += written; |
3431 | } |
3432 | out: |
3433 | current->backing_dev_info = NULL; |
3434 | return written ? written : err; |
3435 | } |
3436 | EXPORT_SYMBOL(__generic_file_write_iter); |
3437 | |
3438 | /** |
3439 | * generic_file_write_iter - write data to a file |
3440 | * @iocb: IO state structure |
3441 | * @from: iov_iter with data to write |
3442 | * |
3443 | * This is a wrapper around __generic_file_write_iter() to be used by most |
3444 | * filesystems. It takes care of syncing the file in case of O_SYNC file |
3445 | * and acquires i_mutex as needed. |
3446 | * Return: |
3447 | * * negative error code if no data has been written at all of |
3448 | * vfs_fsync_range() failed for a synchronous write |
3449 | * * number of bytes written, even for truncated writes |
3450 | */ |
3451 | ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from) |
3452 | { |
3453 | struct file *file = iocb->ki_filp; |
3454 | struct inode *inode = file->f_mapping->host; |
3455 | ssize_t ret; |
3456 | |
3457 | inode_lock(inode); |
3458 | ret = generic_write_checks(iocb, from); |
3459 | if (ret > 0) |
3460 | ret = __generic_file_write_iter(iocb, from); |
3461 | inode_unlock(inode); |
3462 | |
3463 | if (ret > 0) |
3464 | ret = generic_write_sync(iocb, ret); |
3465 | return ret; |
3466 | } |
3467 | EXPORT_SYMBOL(generic_file_write_iter); |
3468 | |
3469 | /** |
3470 | * try_to_release_page() - release old fs-specific metadata on a page |
3471 | * |
3472 | * @page: the page which the kernel is trying to free |
3473 | * @gfp_mask: memory allocation flags (and I/O mode) |
3474 | * |
3475 | * The address_space is to try to release any data against the page |
3476 | * (presumably at page->private). |
3477 | * |
3478 | * This may also be called if PG_fscache is set on a page, indicating that the |
3479 | * page is known to the local caching routines. |
3480 | * |
3481 | * The @gfp_mask argument specifies whether I/O may be performed to release |
3482 | * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS). |
3483 | * |
3484 | * Return: %1 if the release was successful, otherwise return zero. |
3485 | */ |
3486 | int try_to_release_page(struct page *page, gfp_t gfp_mask) |
3487 | { |
3488 | struct address_space * const mapping = page->mapping; |
3489 | |
3490 | BUG_ON(!PageLocked(page)); |
3491 | if (PageWriteback(page)) |
3492 | return 0; |
3493 | |
3494 | if (mapping && mapping->a_ops->releasepage) |
3495 | return mapping->a_ops->releasepage(page, gfp_mask); |
3496 | return try_to_free_buffers(page); |
3497 | } |
3498 | |
3499 | EXPORT_SYMBOL(try_to_release_page); |
3500 | |