Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : /*
3 : * linux/mm/filemap.c
4 : *
5 : * Copyright (C) 1994-1999 Linus Torvalds
6 : */
7 :
8 : /*
9 : * This file handles the generic file mmap semantics used by
10 : * most "normal" filesystems (but you don't /have/ to use this:
11 : * the NFS filesystem used to do this differently, for example)
12 : */
13 : #include <linux/export.h>
14 : #include <linux/compiler.h>
15 : #include <linux/dax.h>
16 : #include <linux/fs.h>
17 : #include <linux/sched/signal.h>
18 : #include <linux/uaccess.h>
19 : #include <linux/capability.h>
20 : #include <linux/kernel_stat.h>
21 : #include <linux/gfp.h>
22 : #include <linux/mm.h>
23 : #include <linux/swap.h>
24 : #include <linux/swapops.h>
25 : #include <linux/syscalls.h>
26 : #include <linux/mman.h>
27 : #include <linux/pagemap.h>
28 : #include <linux/file.h>
29 : #include <linux/uio.h>
30 : #include <linux/error-injection.h>
31 : #include <linux/hash.h>
32 : #include <linux/writeback.h>
33 : #include <linux/backing-dev.h>
34 : #include <linux/pagevec.h>
35 : #include <linux/security.h>
36 : #include <linux/cpuset.h>
37 : #include <linux/hugetlb.h>
38 : #include <linux/memcontrol.h>
39 : #include <linux/shmem_fs.h>
40 : #include <linux/rmap.h>
41 : #include <linux/delayacct.h>
42 : #include <linux/psi.h>
43 : #include <linux/ramfs.h>
44 : #include <linux/page_idle.h>
45 : #include <linux/migrate.h>
46 : #include <linux/pipe_fs_i.h>
47 : #include <linux/splice.h>
48 : #include <asm/pgalloc.h>
49 : #include <asm/tlbflush.h>
50 : #include "internal.h"
51 :
52 : #define CREATE_TRACE_POINTS
53 : #include <trace/events/filemap.h>
54 :
55 : /*
56 : * FIXME: remove all knowledge of the buffer layer from the core VM
57 : */
58 : #include <linux/buffer_head.h> /* for try_to_free_buffers */
59 :
60 : #include <asm/mman.h>
61 :
62 : #include "swap.h"
63 :
64 : /*
65 : * Shared mappings implemented 30.11.1994. It's not fully working yet,
66 : * though.
67 : *
68 : * Shared mappings now work. 15.8.1995 Bruno.
69 : *
70 : * finished 'unifying' the page and buffer cache and SMP-threaded the
71 : * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
72 : *
73 : * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
74 : */
75 :
76 : /*
77 : * Lock ordering:
78 : *
79 : * ->i_mmap_rwsem (truncate_pagecache)
80 : * ->private_lock (__free_pte->block_dirty_folio)
81 : * ->swap_lock (exclusive_swap_page, others)
82 : * ->i_pages lock
83 : *
84 : * ->i_rwsem
85 : * ->invalidate_lock (acquired by fs in truncate path)
86 : * ->i_mmap_rwsem (truncate->unmap_mapping_range)
87 : *
88 : * ->mmap_lock
89 : * ->i_mmap_rwsem
90 : * ->page_table_lock or pte_lock (various, mainly in memory.c)
91 : * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
92 : *
93 : * ->mmap_lock
94 : * ->invalidate_lock (filemap_fault)
95 : * ->lock_page (filemap_fault, access_process_vm)
96 : *
97 : * ->i_rwsem (generic_perform_write)
98 : * ->mmap_lock (fault_in_readable->do_page_fault)
99 : *
100 : * bdi->wb.list_lock
101 : * sb_lock (fs/fs-writeback.c)
102 : * ->i_pages lock (__sync_single_inode)
103 : *
104 : * ->i_mmap_rwsem
105 : * ->anon_vma.lock (vma_merge)
106 : *
107 : * ->anon_vma.lock
108 : * ->page_table_lock or pte_lock (anon_vma_prepare and various)
109 : *
110 : * ->page_table_lock or pte_lock
111 : * ->swap_lock (try_to_unmap_one)
112 : * ->private_lock (try_to_unmap_one)
113 : * ->i_pages lock (try_to_unmap_one)
114 : * ->lruvec->lru_lock (follow_page->mark_page_accessed)
115 : * ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
116 : * ->private_lock (page_remove_rmap->set_page_dirty)
117 : * ->i_pages lock (page_remove_rmap->set_page_dirty)
118 : * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
119 : * ->inode->i_lock (page_remove_rmap->set_page_dirty)
120 : * ->memcg->move_lock (page_remove_rmap->folio_memcg_lock)
121 : * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
122 : * ->inode->i_lock (zap_pte_range->set_page_dirty)
123 : * ->private_lock (zap_pte_range->block_dirty_folio)
124 : *
125 : * ->i_mmap_rwsem
126 : * ->tasklist_lock (memory_failure, collect_procs_ao)
127 : */
128 :
129 0 : static void page_cache_delete(struct address_space *mapping,
130 : struct folio *folio, void *shadow)
131 : {
132 0 : XA_STATE(xas, &mapping->i_pages, folio->index);
133 0 : long nr = 1;
134 :
135 0 : mapping_set_update(&xas, mapping);
136 :
137 : /* hugetlb pages are represented by a single entry in the xarray */
138 0 : if (!folio_test_hugetlb(folio)) {
139 0 : xas_set_order(&xas, folio->index, folio_order(folio));
140 0 : nr = folio_nr_pages(folio);
141 : }
142 :
143 : VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
144 :
145 0 : xas_store(&xas, shadow);
146 0 : xas_init_marks(&xas);
147 :
148 0 : folio->mapping = NULL;
149 : /* Leave page->index set: truncation lookup relies upon it */
150 0 : mapping->nrpages -= nr;
151 0 : }
152 :
153 0 : static void filemap_unaccount_folio(struct address_space *mapping,
154 : struct folio *folio)
155 : {
156 : long nr;
157 :
158 : VM_BUG_ON_FOLIO(folio_mapped(folio), folio);
159 0 : if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) {
160 0 : pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
161 : current->comm, folio_pfn(folio));
162 0 : dump_page(&folio->page, "still mapped when deleted");
163 0 : dump_stack();
164 0 : add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
165 :
166 0 : if (mapping_exiting(mapping) && !folio_test_large(folio)) {
167 0 : int mapcount = page_mapcount(&folio->page);
168 :
169 0 : if (folio_ref_count(folio) >= mapcount + 2) {
170 : /*
171 : * All vmas have already been torn down, so it's
172 : * a good bet that actually the page is unmapped
173 : * and we'd rather not leak it: if we're wrong,
174 : * another bad page check should catch it later.
175 : */
176 0 : page_mapcount_reset(&folio->page);
177 : folio_ref_sub(folio, mapcount);
178 : }
179 : }
180 : }
181 :
182 : /* hugetlb folios do not participate in page cache accounting. */
183 0 : if (folio_test_hugetlb(folio))
184 : return;
185 :
186 0 : nr = folio_nr_pages(folio);
187 :
188 0 : __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
189 0 : if (folio_test_swapbacked(folio)) {
190 0 : __lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);
191 0 : if (folio_test_pmd_mappable(folio))
192 : __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr);
193 : } else if (folio_test_pmd_mappable(folio)) {
194 : __lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);
195 : filemap_nr_thps_dec(mapping);
196 : }
197 :
198 : /*
199 : * At this point folio must be either written or cleaned by
200 : * truncate. Dirty folio here signals a bug and loss of
201 : * unwritten data - on ordinary filesystems.
202 : *
203 : * But it's harmless on in-memory filesystems like tmpfs; and can
204 : * occur when a driver which did get_user_pages() sets page dirty
205 : * before putting it, while the inode is being finally evicted.
206 : *
207 : * Below fixes dirty accounting after removing the folio entirely
208 : * but leaves the dirty flag set: it has no effect for truncated
209 : * folio and anyway will be cleared before returning folio to
210 : * buddy allocator.
211 : */
212 0 : if (WARN_ON_ONCE(folio_test_dirty(folio) &&
213 : mapping_can_writeback(mapping)))
214 0 : folio_account_cleaned(folio, inode_to_wb(mapping->host));
215 : }
216 :
217 : /*
218 : * Delete a page from the page cache and free it. Caller has to make
219 : * sure the page is locked and that nobody else uses it - or that usage
220 : * is safe. The caller must hold the i_pages lock.
221 : */
222 0 : void __filemap_remove_folio(struct folio *folio, void *shadow)
223 : {
224 0 : struct address_space *mapping = folio->mapping;
225 :
226 0 : trace_mm_filemap_delete_from_page_cache(folio);
227 0 : filemap_unaccount_folio(mapping, folio);
228 0 : page_cache_delete(mapping, folio, shadow);
229 0 : }
230 :
231 0 : void filemap_free_folio(struct address_space *mapping, struct folio *folio)
232 : {
233 : void (*free_folio)(struct folio *);
234 0 : int refs = 1;
235 :
236 0 : free_folio = mapping->a_ops->free_folio;
237 0 : if (free_folio)
238 0 : free_folio(folio);
239 :
240 0 : if (folio_test_large(folio) && !folio_test_hugetlb(folio))
241 0 : refs = folio_nr_pages(folio);
242 0 : folio_put_refs(folio, refs);
243 0 : }
244 :
245 : /**
246 : * filemap_remove_folio - Remove folio from page cache.
247 : * @folio: The folio.
248 : *
249 : * This must be called only on folios that are locked and have been
250 : * verified to be in the page cache. It will never put the folio into
251 : * the free list because the caller has a reference on the page.
252 : */
253 0 : void filemap_remove_folio(struct folio *folio)
254 : {
255 0 : struct address_space *mapping = folio->mapping;
256 :
257 0 : BUG_ON(!folio_test_locked(folio));
258 0 : spin_lock(&mapping->host->i_lock);
259 0 : xa_lock_irq(&mapping->i_pages);
260 0 : __filemap_remove_folio(folio, NULL);
261 0 : xa_unlock_irq(&mapping->i_pages);
262 0 : if (mapping_shrinkable(mapping))
263 0 : inode_add_lru(mapping->host);
264 0 : spin_unlock(&mapping->host->i_lock);
265 :
266 0 : filemap_free_folio(mapping, folio);
267 0 : }
268 :
269 : /*
270 : * page_cache_delete_batch - delete several folios from page cache
271 : * @mapping: the mapping to which folios belong
272 : * @fbatch: batch of folios to delete
273 : *
274 : * The function walks over mapping->i_pages and removes folios passed in
275 : * @fbatch from the mapping. The function expects @fbatch to be sorted
276 : * by page index and is optimised for it to be dense.
277 : * It tolerates holes in @fbatch (mapping entries at those indices are not
278 : * modified).
279 : *
280 : * The function expects the i_pages lock to be held.
281 : */
282 0 : static void page_cache_delete_batch(struct address_space *mapping,
283 : struct folio_batch *fbatch)
284 : {
285 0 : XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index);
286 0 : long total_pages = 0;
287 0 : int i = 0;
288 : struct folio *folio;
289 :
290 0 : mapping_set_update(&xas, mapping);
291 0 : xas_for_each(&xas, folio, ULONG_MAX) {
292 0 : if (i >= folio_batch_count(fbatch))
293 : break;
294 :
295 : /* A swap/dax/shadow entry got inserted? Skip it. */
296 0 : if (xa_is_value(folio))
297 0 : continue;
298 : /*
299 : * A page got inserted in our range? Skip it. We have our
300 : * pages locked so they are protected from being removed.
301 : * If we see a page whose index is higher than ours, it
302 : * means our page has been removed, which shouldn't be
303 : * possible because we're holding the PageLock.
304 : */
305 0 : if (folio != fbatch->folios[i]) {
306 : VM_BUG_ON_FOLIO(folio->index >
307 : fbatch->folios[i]->index, folio);
308 0 : continue;
309 : }
310 :
311 0 : WARN_ON_ONCE(!folio_test_locked(folio));
312 :
313 0 : folio->mapping = NULL;
314 : /* Leave folio->index set: truncation lookup relies on it */
315 :
316 0 : i++;
317 0 : xas_store(&xas, NULL);
318 0 : total_pages += folio_nr_pages(folio);
319 : }
320 0 : mapping->nrpages -= total_pages;
321 0 : }
322 :
323 0 : void delete_from_page_cache_batch(struct address_space *mapping,
324 : struct folio_batch *fbatch)
325 : {
326 : int i;
327 :
328 0 : if (!folio_batch_count(fbatch))
329 : return;
330 :
331 0 : spin_lock(&mapping->host->i_lock);
332 0 : xa_lock_irq(&mapping->i_pages);
333 0 : for (i = 0; i < folio_batch_count(fbatch); i++) {
334 0 : struct folio *folio = fbatch->folios[i];
335 :
336 0 : trace_mm_filemap_delete_from_page_cache(folio);
337 0 : filemap_unaccount_folio(mapping, folio);
338 : }
339 0 : page_cache_delete_batch(mapping, fbatch);
340 0 : xa_unlock_irq(&mapping->i_pages);
341 0 : if (mapping_shrinkable(mapping))
342 0 : inode_add_lru(mapping->host);
343 0 : spin_unlock(&mapping->host->i_lock);
344 :
345 0 : for (i = 0; i < folio_batch_count(fbatch); i++)
346 0 : filemap_free_folio(mapping, fbatch->folios[i]);
347 : }
348 :
349 0 : int filemap_check_errors(struct address_space *mapping)
350 : {
351 0 : int ret = 0;
352 : /* Check for outstanding write errors */
353 0 : if (test_bit(AS_ENOSPC, &mapping->flags) &&
354 0 : test_and_clear_bit(AS_ENOSPC, &mapping->flags))
355 0 : ret = -ENOSPC;
356 0 : if (test_bit(AS_EIO, &mapping->flags) &&
357 0 : test_and_clear_bit(AS_EIO, &mapping->flags))
358 0 : ret = -EIO;
359 0 : return ret;
360 : }
361 : EXPORT_SYMBOL(filemap_check_errors);
362 :
363 0 : static int filemap_check_and_keep_errors(struct address_space *mapping)
364 : {
365 : /* Check for outstanding write errors */
366 0 : if (test_bit(AS_EIO, &mapping->flags))
367 : return -EIO;
368 0 : if (test_bit(AS_ENOSPC, &mapping->flags))
369 : return -ENOSPC;
370 0 : return 0;
371 : }
372 :
373 : /**
374 : * filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range
375 : * @mapping: address space structure to write
376 : * @wbc: the writeback_control controlling the writeout
377 : *
378 : * Call writepages on the mapping using the provided wbc to control the
379 : * writeout.
380 : *
381 : * Return: %0 on success, negative error code otherwise.
382 : */
383 0 : int filemap_fdatawrite_wbc(struct address_space *mapping,
384 : struct writeback_control *wbc)
385 : {
386 : int ret;
387 :
388 0 : if (!mapping_can_writeback(mapping) ||
389 0 : !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
390 : return 0;
391 :
392 0 : wbc_attach_fdatawrite_inode(wbc, mapping->host);
393 0 : ret = do_writepages(mapping, wbc);
394 0 : wbc_detach_inode(wbc);
395 0 : return ret;
396 : }
397 : EXPORT_SYMBOL(filemap_fdatawrite_wbc);
398 :
399 : /**
400 : * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
401 : * @mapping: address space structure to write
402 : * @start: offset in bytes where the range starts
403 : * @end: offset in bytes where the range ends (inclusive)
404 : * @sync_mode: enable synchronous operation
405 : *
406 : * Start writeback against all of a mapping's dirty pages that lie
407 : * within the byte offsets <start, end> inclusive.
408 : *
409 : * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
410 : * opposed to a regular memory cleansing writeback. The difference between
411 : * these two operations is that if a dirty page/buffer is encountered, it must
412 : * be waited upon, and not just skipped over.
413 : *
414 : * Return: %0 on success, negative error code otherwise.
415 : */
416 0 : int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
417 : loff_t end, int sync_mode)
418 : {
419 0 : struct writeback_control wbc = {
420 : .sync_mode = sync_mode,
421 : .nr_to_write = LONG_MAX,
422 : .range_start = start,
423 : .range_end = end,
424 : };
425 :
426 0 : return filemap_fdatawrite_wbc(mapping, &wbc);
427 : }
428 :
429 : static inline int __filemap_fdatawrite(struct address_space *mapping,
430 : int sync_mode)
431 : {
432 0 : return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
433 : }
434 :
435 0 : int filemap_fdatawrite(struct address_space *mapping)
436 : {
437 0 : return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
438 : }
439 : EXPORT_SYMBOL(filemap_fdatawrite);
440 :
441 0 : int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
442 : loff_t end)
443 : {
444 0 : return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
445 : }
446 : EXPORT_SYMBOL(filemap_fdatawrite_range);
447 :
448 : /**
449 : * filemap_flush - mostly a non-blocking flush
450 : * @mapping: target address_space
451 : *
452 : * This is a mostly non-blocking flush. Not suitable for data-integrity
453 : * purposes - I/O may not be started against all dirty pages.
454 : *
455 : * Return: %0 on success, negative error code otherwise.
456 : */
457 0 : int filemap_flush(struct address_space *mapping)
458 : {
459 0 : return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
460 : }
461 : EXPORT_SYMBOL(filemap_flush);
462 :
463 : /**
464 : * filemap_range_has_page - check if a page exists in range.
465 : * @mapping: address space within which to check
466 : * @start_byte: offset in bytes where the range starts
467 : * @end_byte: offset in bytes where the range ends (inclusive)
468 : *
469 : * Find at least one page in the range supplied, usually used to check if
470 : * direct writing in this range will trigger a writeback.
471 : *
472 : * Return: %true if at least one page exists in the specified range,
473 : * %false otherwise.
474 : */
475 0 : bool filemap_range_has_page(struct address_space *mapping,
476 : loff_t start_byte, loff_t end_byte)
477 : {
478 : struct folio *folio;
479 0 : XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
480 0 : pgoff_t max = end_byte >> PAGE_SHIFT;
481 :
482 0 : if (end_byte < start_byte)
483 : return false;
484 :
485 : rcu_read_lock();
486 : for (;;) {
487 0 : folio = xas_find(&xas, max);
488 0 : if (xas_retry(&xas, folio))
489 0 : continue;
490 : /* Shadow entries don't count */
491 0 : if (xa_is_value(folio))
492 0 : continue;
493 : /*
494 : * We don't need to try to pin this page; we're about to
495 : * release the RCU lock anyway. It is enough to know that
496 : * there was a page here recently.
497 : */
498 : break;
499 : }
500 : rcu_read_unlock();
501 :
502 0 : return folio != NULL;
503 : }
504 : EXPORT_SYMBOL(filemap_range_has_page);
505 :
506 0 : static void __filemap_fdatawait_range(struct address_space *mapping,
507 : loff_t start_byte, loff_t end_byte)
508 : {
509 0 : pgoff_t index = start_byte >> PAGE_SHIFT;
510 0 : pgoff_t end = end_byte >> PAGE_SHIFT;
511 : struct folio_batch fbatch;
512 : unsigned nr_folios;
513 :
514 0 : folio_batch_init(&fbatch);
515 :
516 0 : while (index <= end) {
517 : unsigned i;
518 :
519 0 : nr_folios = filemap_get_folios_tag(mapping, &index, end,
520 : PAGECACHE_TAG_WRITEBACK, &fbatch);
521 :
522 0 : if (!nr_folios)
523 : break;
524 :
525 0 : for (i = 0; i < nr_folios; i++) {
526 0 : struct folio *folio = fbatch.folios[i];
527 :
528 0 : folio_wait_writeback(folio);
529 0 : folio_clear_error(folio);
530 : }
531 0 : folio_batch_release(&fbatch);
532 0 : cond_resched();
533 : }
534 0 : }
535 :
536 : /**
537 : * filemap_fdatawait_range - wait for writeback to complete
538 : * @mapping: address space structure to wait for
539 : * @start_byte: offset in bytes where the range starts
540 : * @end_byte: offset in bytes where the range ends (inclusive)
541 : *
542 : * Walk the list of under-writeback pages of the given address space
543 : * in the given range and wait for all of them. Check error status of
544 : * the address space and return it.
545 : *
546 : * Since the error status of the address space is cleared by this function,
547 : * callers are responsible for checking the return value and handling and/or
548 : * reporting the error.
549 : *
550 : * Return: error status of the address space.
551 : */
552 0 : int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
553 : loff_t end_byte)
554 : {
555 0 : __filemap_fdatawait_range(mapping, start_byte, end_byte);
556 0 : return filemap_check_errors(mapping);
557 : }
558 : EXPORT_SYMBOL(filemap_fdatawait_range);
559 :
560 : /**
561 : * filemap_fdatawait_range_keep_errors - wait for writeback to complete
562 : * @mapping: address space structure to wait for
563 : * @start_byte: offset in bytes where the range starts
564 : * @end_byte: offset in bytes where the range ends (inclusive)
565 : *
566 : * Walk the list of under-writeback pages of the given address space in the
567 : * given range and wait for all of them. Unlike filemap_fdatawait_range(),
568 : * this function does not clear error status of the address space.
569 : *
570 : * Use this function if callers don't handle errors themselves. Expected
571 : * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
572 : * fsfreeze(8)
573 : */
574 0 : int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
575 : loff_t start_byte, loff_t end_byte)
576 : {
577 0 : __filemap_fdatawait_range(mapping, start_byte, end_byte);
578 0 : return filemap_check_and_keep_errors(mapping);
579 : }
580 : EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
581 :
582 : /**
583 : * file_fdatawait_range - wait for writeback to complete
584 : * @file: file pointing to address space structure to wait for
585 : * @start_byte: offset in bytes where the range starts
586 : * @end_byte: offset in bytes where the range ends (inclusive)
587 : *
588 : * Walk the list of under-writeback pages of the address space that file
589 : * refers to, in the given range and wait for all of them. Check error
590 : * status of the address space vs. the file->f_wb_err cursor and return it.
591 : *
592 : * Since the error status of the file is advanced by this function,
593 : * callers are responsible for checking the return value and handling and/or
594 : * reporting the error.
595 : *
596 : * Return: error status of the address space vs. the file->f_wb_err cursor.
597 : */
598 0 : int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
599 : {
600 0 : struct address_space *mapping = file->f_mapping;
601 :
602 0 : __filemap_fdatawait_range(mapping, start_byte, end_byte);
603 0 : return file_check_and_advance_wb_err(file);
604 : }
605 : EXPORT_SYMBOL(file_fdatawait_range);
606 :
607 : /**
608 : * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
609 : * @mapping: address space structure to wait for
610 : *
611 : * Walk the list of under-writeback pages of the given address space
612 : * and wait for all of them. Unlike filemap_fdatawait(), this function
613 : * does not clear error status of the address space.
614 : *
615 : * Use this function if callers don't handle errors themselves. Expected
616 : * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
617 : * fsfreeze(8)
618 : *
619 : * Return: error status of the address space.
620 : */
621 0 : int filemap_fdatawait_keep_errors(struct address_space *mapping)
622 : {
623 0 : __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
624 0 : return filemap_check_and_keep_errors(mapping);
625 : }
626 : EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
627 :
628 : /* Returns true if writeback might be needed or already in progress. */
629 : static bool mapping_needs_writeback(struct address_space *mapping)
630 : {
631 : return mapping->nrpages;
632 : }
633 :
634 0 : bool filemap_range_has_writeback(struct address_space *mapping,
635 : loff_t start_byte, loff_t end_byte)
636 : {
637 0 : XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
638 0 : pgoff_t max = end_byte >> PAGE_SHIFT;
639 : struct folio *folio;
640 :
641 0 : if (end_byte < start_byte)
642 : return false;
643 :
644 : rcu_read_lock();
645 0 : xas_for_each(&xas, folio, max) {
646 0 : if (xas_retry(&xas, folio))
647 0 : continue;
648 0 : if (xa_is_value(folio))
649 0 : continue;
650 0 : if (folio_test_dirty(folio) || folio_test_locked(folio) ||
651 0 : folio_test_writeback(folio))
652 : break;
653 : }
654 : rcu_read_unlock();
655 0 : return folio != NULL;
656 : }
657 : EXPORT_SYMBOL_GPL(filemap_range_has_writeback);
658 :
659 : /**
660 : * filemap_write_and_wait_range - write out & wait on a file range
661 : * @mapping: the address_space for the pages
662 : * @lstart: offset in bytes where the range starts
663 : * @lend: offset in bytes where the range ends (inclusive)
664 : *
665 : * Write out and wait upon file offsets lstart->lend, inclusive.
666 : *
667 : * Note that @lend is inclusive (describes the last byte to be written) so
668 : * that this function can be used to write to the very end-of-file (end = -1).
669 : *
670 : * Return: error status of the address space.
671 : */
672 0 : int filemap_write_and_wait_range(struct address_space *mapping,
673 : loff_t lstart, loff_t lend)
674 : {
675 0 : int err = 0, err2;
676 :
677 0 : if (lend < lstart)
678 : return 0;
679 :
680 0 : if (mapping_needs_writeback(mapping)) {
681 0 : err = __filemap_fdatawrite_range(mapping, lstart, lend,
682 : WB_SYNC_ALL);
683 : /*
684 : * Even if the above returned error, the pages may be
685 : * written partially (e.g. -ENOSPC), so we wait for it.
686 : * But the -EIO is special case, it may indicate the worst
687 : * thing (e.g. bug) happened, so we avoid waiting for it.
688 : */
689 0 : if (err != -EIO)
690 0 : __filemap_fdatawait_range(mapping, lstart, lend);
691 : }
692 0 : err2 = filemap_check_errors(mapping);
693 0 : if (!err)
694 0 : err = err2;
695 : return err;
696 : }
697 : EXPORT_SYMBOL(filemap_write_and_wait_range);
698 :
699 0 : void __filemap_set_wb_err(struct address_space *mapping, int err)
700 : {
701 0 : errseq_t eseq = errseq_set(&mapping->wb_err, err);
702 :
703 0 : trace_filemap_set_wb_err(mapping, eseq);
704 0 : }
705 : EXPORT_SYMBOL(__filemap_set_wb_err);
706 :
707 : /**
708 : * file_check_and_advance_wb_err - report wb error (if any) that was previously
709 : * and advance wb_err to current one
710 : * @file: struct file on which the error is being reported
711 : *
712 : * When userland calls fsync (or something like nfsd does the equivalent), we
713 : * want to report any writeback errors that occurred since the last fsync (or
714 : * since the file was opened if there haven't been any).
715 : *
716 : * Grab the wb_err from the mapping. If it matches what we have in the file,
717 : * then just quickly return 0. The file is all caught up.
718 : *
719 : * If it doesn't match, then take the mapping value, set the "seen" flag in
720 : * it and try to swap it into place. If it works, or another task beat us
721 : * to it with the new value, then update the f_wb_err and return the error
722 : * portion. The error at this point must be reported via proper channels
723 : * (a'la fsync, or NFS COMMIT operation, etc.).
724 : *
725 : * While we handle mapping->wb_err with atomic operations, the f_wb_err
726 : * value is protected by the f_lock since we must ensure that it reflects
727 : * the latest value swapped in for this file descriptor.
728 : *
729 : * Return: %0 on success, negative error code otherwise.
730 : */
731 0 : int file_check_and_advance_wb_err(struct file *file)
732 : {
733 0 : int err = 0;
734 0 : errseq_t old = READ_ONCE(file->f_wb_err);
735 0 : struct address_space *mapping = file->f_mapping;
736 :
737 : /* Locklessly handle the common case where nothing has changed */
738 0 : if (errseq_check(&mapping->wb_err, old)) {
739 : /* Something changed, must use slow path */
740 0 : spin_lock(&file->f_lock);
741 0 : old = file->f_wb_err;
742 0 : err = errseq_check_and_advance(&mapping->wb_err,
743 : &file->f_wb_err);
744 0 : trace_file_check_and_advance_wb_err(file, old);
745 0 : spin_unlock(&file->f_lock);
746 : }
747 :
748 : /*
749 : * We're mostly using this function as a drop in replacement for
750 : * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
751 : * that the legacy code would have had on these flags.
752 : */
753 0 : clear_bit(AS_EIO, &mapping->flags);
754 0 : clear_bit(AS_ENOSPC, &mapping->flags);
755 0 : return err;
756 : }
757 : EXPORT_SYMBOL(file_check_and_advance_wb_err);
758 :
759 : /**
760 : * file_write_and_wait_range - write out & wait on a file range
761 : * @file: file pointing to address_space with pages
762 : * @lstart: offset in bytes where the range starts
763 : * @lend: offset in bytes where the range ends (inclusive)
764 : *
765 : * Write out and wait upon file offsets lstart->lend, inclusive.
766 : *
767 : * Note that @lend is inclusive (describes the last byte to be written) so
768 : * that this function can be used to write to the very end-of-file (end = -1).
769 : *
770 : * After writing out and waiting on the data, we check and advance the
771 : * f_wb_err cursor to the latest value, and return any errors detected there.
772 : *
773 : * Return: %0 on success, negative error code otherwise.
774 : */
775 0 : int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
776 : {
777 0 : int err = 0, err2;
778 0 : struct address_space *mapping = file->f_mapping;
779 :
780 0 : if (lend < lstart)
781 : return 0;
782 :
783 0 : if (mapping_needs_writeback(mapping)) {
784 0 : err = __filemap_fdatawrite_range(mapping, lstart, lend,
785 : WB_SYNC_ALL);
786 : /* See comment of filemap_write_and_wait() */
787 0 : if (err != -EIO)
788 0 : __filemap_fdatawait_range(mapping, lstart, lend);
789 : }
790 0 : err2 = file_check_and_advance_wb_err(file);
791 0 : if (!err)
792 0 : err = err2;
793 : return err;
794 : }
795 : EXPORT_SYMBOL(file_write_and_wait_range);
796 :
797 : /**
798 : * replace_page_cache_folio - replace a pagecache folio with a new one
799 : * @old: folio to be replaced
800 : * @new: folio to replace with
801 : *
802 : * This function replaces a folio in the pagecache with a new one. On
803 : * success it acquires the pagecache reference for the new folio and
804 : * drops it for the old folio. Both the old and new folios must be
805 : * locked. This function does not add the new folio to the LRU, the
806 : * caller must do that.
807 : *
808 : * The remove + add is atomic. This function cannot fail.
809 : */
810 0 : void replace_page_cache_folio(struct folio *old, struct folio *new)
811 : {
812 0 : struct address_space *mapping = old->mapping;
813 0 : void (*free_folio)(struct folio *) = mapping->a_ops->free_folio;
814 0 : pgoff_t offset = old->index;
815 0 : XA_STATE(xas, &mapping->i_pages, offset);
816 :
817 : VM_BUG_ON_FOLIO(!folio_test_locked(old), old);
818 : VM_BUG_ON_FOLIO(!folio_test_locked(new), new);
819 : VM_BUG_ON_FOLIO(new->mapping, new);
820 :
821 0 : folio_get(new);
822 0 : new->mapping = mapping;
823 0 : new->index = offset;
824 :
825 0 : mem_cgroup_migrate(old, new);
826 :
827 0 : xas_lock_irq(&xas);
828 0 : xas_store(&xas, new);
829 :
830 0 : old->mapping = NULL;
831 : /* hugetlb pages do not participate in page cache accounting. */
832 0 : if (!folio_test_hugetlb(old))
833 : __lruvec_stat_sub_folio(old, NR_FILE_PAGES);
834 0 : if (!folio_test_hugetlb(new))
835 : __lruvec_stat_add_folio(new, NR_FILE_PAGES);
836 0 : if (folio_test_swapbacked(old))
837 : __lruvec_stat_sub_folio(old, NR_SHMEM);
838 0 : if (folio_test_swapbacked(new))
839 : __lruvec_stat_add_folio(new, NR_SHMEM);
840 0 : xas_unlock_irq(&xas);
841 0 : if (free_folio)
842 0 : free_folio(old);
843 0 : folio_put(old);
844 0 : }
845 : EXPORT_SYMBOL_GPL(replace_page_cache_folio);
846 :
847 0 : noinline int __filemap_add_folio(struct address_space *mapping,
848 : struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp)
849 : {
850 0 : XA_STATE(xas, &mapping->i_pages, index);
851 0 : int huge = folio_test_hugetlb(folio);
852 0 : bool charged = false;
853 0 : long nr = 1;
854 :
855 : VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
856 : VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
857 0 : mapping_set_update(&xas, mapping);
858 :
859 : if (!huge) {
860 0 : int error = mem_cgroup_charge(folio, NULL, gfp);
861 : VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
862 : if (error)
863 : return error;
864 0 : charged = true;
865 0 : xas_set_order(&xas, index, folio_order(folio));
866 0 : nr = folio_nr_pages(folio);
867 : }
868 :
869 0 : gfp &= GFP_RECLAIM_MASK;
870 0 : folio_ref_add(folio, nr);
871 0 : folio->mapping = mapping;
872 0 : folio->index = xas.xa_index;
873 :
874 : do {
875 0 : unsigned int order = xa_get_order(xas.xa, xas.xa_index);
876 0 : void *entry, *old = NULL;
877 :
878 0 : if (order > folio_order(folio))
879 : xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
880 : order, gfp);
881 0 : xas_lock_irq(&xas);
882 0 : xas_for_each_conflict(&xas, entry) {
883 0 : old = entry;
884 0 : if (!xa_is_value(entry)) {
885 0 : xas_set_err(&xas, -EEXIST);
886 : goto unlock;
887 : }
888 : }
889 :
890 0 : if (old) {
891 0 : if (shadowp)
892 0 : *shadowp = old;
893 : /* entry may have been split before we acquired lock */
894 0 : order = xa_get_order(xas.xa, xas.xa_index);
895 : if (order > folio_order(folio)) {
896 : /* How to handle large swap entries? */
897 : BUG_ON(shmem_mapping(mapping));
898 : xas_split(&xas, old, order);
899 : xas_reset(&xas);
900 : }
901 : }
902 :
903 0 : xas_store(&xas, folio);
904 0 : if (xas_error(&xas))
905 : goto unlock;
906 :
907 0 : mapping->nrpages += nr;
908 :
909 : /* hugetlb pages do not participate in page cache accounting */
910 : if (!huge) {
911 0 : __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
912 0 : if (folio_test_pmd_mappable(folio))
913 : __lruvec_stat_mod_folio(folio,
914 : NR_FILE_THPS, nr);
915 : }
916 : unlock:
917 0 : xas_unlock_irq(&xas);
918 0 : } while (xas_nomem(&xas, gfp));
919 :
920 0 : if (xas_error(&xas))
921 : goto error;
922 :
923 : trace_mm_filemap_add_to_page_cache(folio);
924 : return 0;
925 : error:
926 : if (charged)
927 : mem_cgroup_uncharge(folio);
928 0 : folio->mapping = NULL;
929 : /* Leave page->index set: truncation relies upon it */
930 0 : folio_put_refs(folio, nr);
931 0 : return xas_error(&xas);
932 : }
933 : ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO);
934 :
935 0 : int filemap_add_folio(struct address_space *mapping, struct folio *folio,
936 : pgoff_t index, gfp_t gfp)
937 : {
938 0 : void *shadow = NULL;
939 : int ret;
940 :
941 0 : __folio_set_locked(folio);
942 0 : ret = __filemap_add_folio(mapping, folio, index, gfp, &shadow);
943 0 : if (unlikely(ret))
944 : __folio_clear_locked(folio);
945 : else {
946 : /*
947 : * The folio might have been evicted from cache only
948 : * recently, in which case it should be activated like
949 : * any other repeatedly accessed folio.
950 : * The exception is folios getting rewritten; evicting other
951 : * data from the working set, only to cache data that will
952 : * get overwritten with something else, is a waste of memory.
953 : */
954 0 : WARN_ON_ONCE(folio_test_active(folio));
955 0 : if (!(gfp & __GFP_WRITE) && shadow)
956 0 : workingset_refault(folio, shadow);
957 0 : folio_add_lru(folio);
958 : }
959 0 : return ret;
960 : }
961 : EXPORT_SYMBOL_GPL(filemap_add_folio);
962 :
963 : #ifdef CONFIG_NUMA
964 : struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order)
965 : {
966 : int n;
967 : struct folio *folio;
968 :
969 : if (cpuset_do_page_mem_spread()) {
970 : unsigned int cpuset_mems_cookie;
971 : do {
972 : cpuset_mems_cookie = read_mems_allowed_begin();
973 : n = cpuset_mem_spread_node();
974 : folio = __folio_alloc_node(gfp, order, n);
975 : } while (!folio && read_mems_allowed_retry(cpuset_mems_cookie));
976 :
977 : return folio;
978 : }
979 : return folio_alloc(gfp, order);
980 : }
981 : EXPORT_SYMBOL(filemap_alloc_folio);
982 : #endif
983 :
984 : /*
985 : * filemap_invalidate_lock_two - lock invalidate_lock for two mappings
986 : *
987 : * Lock exclusively invalidate_lock of any passed mapping that is not NULL.
988 : *
989 : * @mapping1: the first mapping to lock
990 : * @mapping2: the second mapping to lock
991 : */
992 0 : void filemap_invalidate_lock_two(struct address_space *mapping1,
993 : struct address_space *mapping2)
994 : {
995 0 : if (mapping1 > mapping2)
996 0 : swap(mapping1, mapping2);
997 0 : if (mapping1)
998 0 : down_write(&mapping1->invalidate_lock);
999 0 : if (mapping2 && mapping1 != mapping2)
1000 0 : down_write_nested(&mapping2->invalidate_lock, 1);
1001 0 : }
1002 : EXPORT_SYMBOL(filemap_invalidate_lock_two);
1003 :
1004 : /*
1005 : * filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
1006 : *
1007 : * Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
1008 : *
1009 : * @mapping1: the first mapping to unlock
1010 : * @mapping2: the second mapping to unlock
1011 : */
1012 0 : void filemap_invalidate_unlock_two(struct address_space *mapping1,
1013 : struct address_space *mapping2)
1014 : {
1015 0 : if (mapping1)
1016 0 : up_write(&mapping1->invalidate_lock);
1017 0 : if (mapping2 && mapping1 != mapping2)
1018 0 : up_write(&mapping2->invalidate_lock);
1019 0 : }
1020 : EXPORT_SYMBOL(filemap_invalidate_unlock_two);
1021 :
1022 : /*
1023 : * In order to wait for pages to become available there must be
1024 : * waitqueues associated with pages. By using a hash table of
1025 : * waitqueues where the bucket discipline is to maintain all
1026 : * waiters on the same queue and wake all when any of the pages
1027 : * become available, and for the woken contexts to check to be
1028 : * sure the appropriate page became available, this saves space
1029 : * at a cost of "thundering herd" phenomena during rare hash
1030 : * collisions.
1031 : */
1032 : #define PAGE_WAIT_TABLE_BITS 8
1033 : #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
1034 : static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
1035 :
1036 : static wait_queue_head_t *folio_waitqueue(struct folio *folio)
1037 : {
1038 0 : return &folio_wait_table[hash_ptr(folio, PAGE_WAIT_TABLE_BITS)];
1039 : }
1040 :
1041 1 : void __init pagecache_init(void)
1042 : {
1043 : int i;
1044 :
1045 257 : for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
1046 256 : init_waitqueue_head(&folio_wait_table[i]);
1047 :
1048 1 : page_writeback_init();
1049 1 : }
1050 :
1051 : /*
1052 : * The page wait code treats the "wait->flags" somewhat unusually, because
1053 : * we have multiple different kinds of waits, not just the usual "exclusive"
1054 : * one.
1055 : *
1056 : * We have:
1057 : *
1058 : * (a) no special bits set:
1059 : *
1060 : * We're just waiting for the bit to be released, and when a waker
1061 : * calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
1062 : * and remove it from the wait queue.
1063 : *
1064 : * Simple and straightforward.
1065 : *
1066 : * (b) WQ_FLAG_EXCLUSIVE:
1067 : *
1068 : * The waiter is waiting to get the lock, and only one waiter should
1069 : * be woken up to avoid any thundering herd behavior. We'll set the
1070 : * WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
1071 : *
1072 : * This is the traditional exclusive wait.
1073 : *
1074 : * (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
1075 : *
1076 : * The waiter is waiting to get the bit, and additionally wants the
1077 : * lock to be transferred to it for fair lock behavior. If the lock
1078 : * cannot be taken, we stop walking the wait queue without waking
1079 : * the waiter.
1080 : *
1081 : * This is the "fair lock handoff" case, and in addition to setting
1082 : * WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
1083 : * that it now has the lock.
1084 : */
1085 0 : static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
1086 : {
1087 : unsigned int flags;
1088 0 : struct wait_page_key *key = arg;
1089 0 : struct wait_page_queue *wait_page
1090 0 : = container_of(wait, struct wait_page_queue, wait);
1091 :
1092 0 : if (!wake_page_match(wait_page, key))
1093 : return 0;
1094 :
1095 : /*
1096 : * If it's a lock handoff wait, we get the bit for it, and
1097 : * stop walking (and do not wake it up) if we can't.
1098 : */
1099 0 : flags = wait->flags;
1100 0 : if (flags & WQ_FLAG_EXCLUSIVE) {
1101 0 : if (test_bit(key->bit_nr, &key->folio->flags))
1102 : return -1;
1103 0 : if (flags & WQ_FLAG_CUSTOM) {
1104 0 : if (test_and_set_bit(key->bit_nr, &key->folio->flags))
1105 : return -1;
1106 0 : flags |= WQ_FLAG_DONE;
1107 : }
1108 : }
1109 :
1110 : /*
1111 : * We are holding the wait-queue lock, but the waiter that
1112 : * is waiting for this will be checking the flags without
1113 : * any locking.
1114 : *
1115 : * So update the flags atomically, and wake up the waiter
1116 : * afterwards to avoid any races. This store-release pairs
1117 : * with the load-acquire in folio_wait_bit_common().
1118 : */
1119 0 : smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
1120 0 : wake_up_state(wait->private, mode);
1121 :
1122 : /*
1123 : * Ok, we have successfully done what we're waiting for,
1124 : * and we can unconditionally remove the wait entry.
1125 : *
1126 : * Note that this pairs with the "finish_wait()" in the
1127 : * waiter, and has to be the absolute last thing we do.
1128 : * After this list_del_init(&wait->entry) the wait entry
1129 : * might be de-allocated and the process might even have
1130 : * exited.
1131 : */
1132 0 : list_del_init_careful(&wait->entry);
1133 0 : return (flags & WQ_FLAG_EXCLUSIVE) != 0;
1134 : }
1135 :
1136 0 : static void folio_wake_bit(struct folio *folio, int bit_nr)
1137 : {
1138 0 : wait_queue_head_t *q = folio_waitqueue(folio);
1139 : struct wait_page_key key;
1140 : unsigned long flags;
1141 : wait_queue_entry_t bookmark;
1142 :
1143 0 : key.folio = folio;
1144 0 : key.bit_nr = bit_nr;
1145 0 : key.page_match = 0;
1146 :
1147 0 : bookmark.flags = 0;
1148 0 : bookmark.private = NULL;
1149 0 : bookmark.func = NULL;
1150 0 : INIT_LIST_HEAD(&bookmark.entry);
1151 :
1152 0 : spin_lock_irqsave(&q->lock, flags);
1153 0 : __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1154 :
1155 0 : while (bookmark.flags & WQ_FLAG_BOOKMARK) {
1156 : /*
1157 : * Take a breather from holding the lock,
1158 : * allow pages that finish wake up asynchronously
1159 : * to acquire the lock and remove themselves
1160 : * from wait queue
1161 : */
1162 0 : spin_unlock_irqrestore(&q->lock, flags);
1163 : cpu_relax();
1164 0 : spin_lock_irqsave(&q->lock, flags);
1165 0 : __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1166 : }
1167 :
1168 : /*
1169 : * It's possible to miss clearing waiters here, when we woke our page
1170 : * waiters, but the hashed waitqueue has waiters for other pages on it.
1171 : * That's okay, it's a rare case. The next waker will clear it.
1172 : *
1173 : * Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE,
1174 : * other), the flag may be cleared in the course of freeing the page;
1175 : * but that is not required for correctness.
1176 : */
1177 0 : if (!waitqueue_active(q) || !key.page_match)
1178 : folio_clear_waiters(folio);
1179 :
1180 0 : spin_unlock_irqrestore(&q->lock, flags);
1181 0 : }
1182 :
1183 : static void folio_wake(struct folio *folio, int bit)
1184 : {
1185 0 : if (!folio_test_waiters(folio))
1186 : return;
1187 0 : folio_wake_bit(folio, bit);
1188 : }
1189 :
1190 : /*
1191 : * A choice of three behaviors for folio_wait_bit_common():
1192 : */
1193 : enum behavior {
1194 : EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
1195 : * __folio_lock() waiting on then setting PG_locked.
1196 : */
1197 : SHARED, /* Hold ref to page and check the bit when woken, like
1198 : * folio_wait_writeback() waiting on PG_writeback.
1199 : */
1200 : DROP, /* Drop ref to page before wait, no check when woken,
1201 : * like folio_put_wait_locked() on PG_locked.
1202 : */
1203 : };
1204 :
1205 : /*
1206 : * Attempt to check (or get) the folio flag, and mark us done
1207 : * if successful.
1208 : */
1209 0 : static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
1210 : struct wait_queue_entry *wait)
1211 : {
1212 0 : if (wait->flags & WQ_FLAG_EXCLUSIVE) {
1213 0 : if (test_and_set_bit(bit_nr, &folio->flags))
1214 : return false;
1215 0 : } else if (test_bit(bit_nr, &folio->flags))
1216 : return false;
1217 :
1218 0 : wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
1219 : return true;
1220 : }
1221 :
1222 : /* How many times do we accept lock stealing from under a waiter? */
1223 : int sysctl_page_lock_unfairness = 5;
1224 :
1225 0 : static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
1226 : int state, enum behavior behavior)
1227 : {
1228 0 : wait_queue_head_t *q = folio_waitqueue(folio);
1229 0 : int unfairness = sysctl_page_lock_unfairness;
1230 : struct wait_page_queue wait_page;
1231 0 : wait_queue_entry_t *wait = &wait_page.wait;
1232 0 : bool thrashing = false;
1233 : unsigned long pflags;
1234 : bool in_thrashing;
1235 :
1236 0 : if (bit_nr == PG_locked &&
1237 0 : !folio_test_uptodate(folio) && folio_test_workingset(folio)) {
1238 : delayacct_thrashing_start(&in_thrashing);
1239 : psi_memstall_enter(&pflags);
1240 : thrashing = true;
1241 : }
1242 :
1243 0 : init_wait(wait);
1244 0 : wait->func = wake_page_function;
1245 0 : wait_page.folio = folio;
1246 0 : wait_page.bit_nr = bit_nr;
1247 :
1248 : repeat:
1249 0 : wait->flags = 0;
1250 0 : if (behavior == EXCLUSIVE) {
1251 0 : wait->flags = WQ_FLAG_EXCLUSIVE;
1252 0 : if (--unfairness < 0)
1253 0 : wait->flags |= WQ_FLAG_CUSTOM;
1254 : }
1255 :
1256 : /*
1257 : * Do one last check whether we can get the
1258 : * page bit synchronously.
1259 : *
1260 : * Do the folio_set_waiters() marking before that
1261 : * to let any waker we _just_ missed know they
1262 : * need to wake us up (otherwise they'll never
1263 : * even go to the slow case that looks at the
1264 : * page queue), and add ourselves to the wait
1265 : * queue if we need to sleep.
1266 : *
1267 : * This part needs to be done under the queue
1268 : * lock to avoid races.
1269 : */
1270 0 : spin_lock_irq(&q->lock);
1271 0 : folio_set_waiters(folio);
1272 0 : if (!folio_trylock_flag(folio, bit_nr, wait))
1273 : __add_wait_queue_entry_tail(q, wait);
1274 0 : spin_unlock_irq(&q->lock);
1275 :
1276 : /*
1277 : * From now on, all the logic will be based on
1278 : * the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to
1279 : * see whether the page bit testing has already
1280 : * been done by the wake function.
1281 : *
1282 : * We can drop our reference to the folio.
1283 : */
1284 0 : if (behavior == DROP)
1285 : folio_put(folio);
1286 :
1287 : /*
1288 : * Note that until the "finish_wait()", or until
1289 : * we see the WQ_FLAG_WOKEN flag, we need to
1290 : * be very careful with the 'wait->flags', because
1291 : * we may race with a waker that sets them.
1292 : */
1293 0 : for (;;) {
1294 : unsigned int flags;
1295 :
1296 0 : set_current_state(state);
1297 :
1298 : /* Loop until we've been woken or interrupted */
1299 0 : flags = smp_load_acquire(&wait->flags);
1300 0 : if (!(flags & WQ_FLAG_WOKEN)) {
1301 0 : if (signal_pending_state(state, current))
1302 : break;
1303 :
1304 0 : io_schedule();
1305 0 : continue;
1306 : }
1307 :
1308 : /* If we were non-exclusive, we're done */
1309 0 : if (behavior != EXCLUSIVE)
1310 : break;
1311 :
1312 : /* If the waker got the lock for us, we're done */
1313 0 : if (flags & WQ_FLAG_DONE)
1314 : break;
1315 :
1316 : /*
1317 : * Otherwise, if we're getting the lock, we need to
1318 : * try to get it ourselves.
1319 : *
1320 : * And if that fails, we'll have to retry this all.
1321 : */
1322 0 : if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0))))
1323 : goto repeat;
1324 :
1325 0 : wait->flags |= WQ_FLAG_DONE;
1326 0 : break;
1327 : }
1328 :
1329 : /*
1330 : * If a signal happened, this 'finish_wait()' may remove the last
1331 : * waiter from the wait-queues, but the folio waiters bit will remain
1332 : * set. That's ok. The next wakeup will take care of it, and trying
1333 : * to do it here would be difficult and prone to races.
1334 : */
1335 0 : finish_wait(q, wait);
1336 :
1337 : if (thrashing) {
1338 : delayacct_thrashing_end(&in_thrashing);
1339 : psi_memstall_leave(&pflags);
1340 : }
1341 :
1342 : /*
1343 : * NOTE! The wait->flags weren't stable until we've done the
1344 : * 'finish_wait()', and we could have exited the loop above due
1345 : * to a signal, and had a wakeup event happen after the signal
1346 : * test but before the 'finish_wait()'.
1347 : *
1348 : * So only after the finish_wait() can we reliably determine
1349 : * if we got woken up or not, so we can now figure out the final
1350 : * return value based on that state without races.
1351 : *
1352 : * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
1353 : * waiter, but an exclusive one requires WQ_FLAG_DONE.
1354 : */
1355 0 : if (behavior == EXCLUSIVE)
1356 0 : return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;
1357 :
1358 0 : return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
1359 : }
1360 :
1361 : #ifdef CONFIG_MIGRATION
1362 : /**
1363 : * migration_entry_wait_on_locked - Wait for a migration entry to be removed
1364 : * @entry: migration swap entry.
1365 : * @ptl: already locked ptl. This function will drop the lock.
1366 : *
1367 : * Wait for a migration entry referencing the given page to be removed. This is
1368 : * equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except
1369 : * this can be called without taking a reference on the page. Instead this
1370 : * should be called while holding the ptl for the migration entry referencing
1371 : * the page.
1372 : *
1373 : * Returns after unlocking the ptl.
1374 : *
1375 : * This follows the same logic as folio_wait_bit_common() so see the comments
1376 : * there.
1377 : */
1378 0 : void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl)
1379 : __releases(ptl)
1380 : {
1381 : struct wait_page_queue wait_page;
1382 0 : wait_queue_entry_t *wait = &wait_page.wait;
1383 0 : bool thrashing = false;
1384 : unsigned long pflags;
1385 : bool in_thrashing;
1386 : wait_queue_head_t *q;
1387 0 : struct folio *folio = page_folio(pfn_swap_entry_to_page(entry));
1388 :
1389 0 : q = folio_waitqueue(folio);
1390 0 : if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
1391 : delayacct_thrashing_start(&in_thrashing);
1392 : psi_memstall_enter(&pflags);
1393 : thrashing = true;
1394 : }
1395 :
1396 0 : init_wait(wait);
1397 0 : wait->func = wake_page_function;
1398 0 : wait_page.folio = folio;
1399 0 : wait_page.bit_nr = PG_locked;
1400 : wait->flags = 0;
1401 :
1402 0 : spin_lock_irq(&q->lock);
1403 0 : folio_set_waiters(folio);
1404 0 : if (!folio_trylock_flag(folio, PG_locked, wait))
1405 : __add_wait_queue_entry_tail(q, wait);
1406 0 : spin_unlock_irq(&q->lock);
1407 :
1408 : /*
1409 : * If a migration entry exists for the page the migration path must hold
1410 : * a valid reference to the page, and it must take the ptl to remove the
1411 : * migration entry. So the page is valid until the ptl is dropped.
1412 : */
1413 : spin_unlock(ptl);
1414 :
1415 0 : for (;;) {
1416 : unsigned int flags;
1417 :
1418 0 : set_current_state(TASK_UNINTERRUPTIBLE);
1419 :
1420 : /* Loop until we've been woken or interrupted */
1421 0 : flags = smp_load_acquire(&wait->flags);
1422 0 : if (!(flags & WQ_FLAG_WOKEN)) {
1423 0 : if (signal_pending_state(TASK_UNINTERRUPTIBLE, current))
1424 : break;
1425 :
1426 0 : io_schedule();
1427 0 : continue;
1428 : }
1429 : break;
1430 : }
1431 :
1432 0 : finish_wait(q, wait);
1433 :
1434 : if (thrashing) {
1435 : delayacct_thrashing_end(&in_thrashing);
1436 : psi_memstall_leave(&pflags);
1437 : }
1438 0 : }
1439 : #endif
1440 :
1441 0 : void folio_wait_bit(struct folio *folio, int bit_nr)
1442 : {
1443 0 : folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
1444 0 : }
1445 : EXPORT_SYMBOL(folio_wait_bit);
1446 :
1447 0 : int folio_wait_bit_killable(struct folio *folio, int bit_nr)
1448 : {
1449 0 : return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, SHARED);
1450 : }
1451 : EXPORT_SYMBOL(folio_wait_bit_killable);
1452 :
1453 : /**
1454 : * folio_put_wait_locked - Drop a reference and wait for it to be unlocked
1455 : * @folio: The folio to wait for.
1456 : * @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
1457 : *
1458 : * The caller should hold a reference on @folio. They expect the page to
1459 : * become unlocked relatively soon, but do not wish to hold up migration
1460 : * (for example) by holding the reference while waiting for the folio to
1461 : * come unlocked. After this function returns, the caller should not
1462 : * dereference @folio.
1463 : *
1464 : * Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal.
1465 : */
1466 : static int folio_put_wait_locked(struct folio *folio, int state)
1467 : {
1468 0 : return folio_wait_bit_common(folio, PG_locked, state, DROP);
1469 : }
1470 :
1471 : /**
1472 : * folio_add_wait_queue - Add an arbitrary waiter to a folio's wait queue
1473 : * @folio: Folio defining the wait queue of interest
1474 : * @waiter: Waiter to add to the queue
1475 : *
1476 : * Add an arbitrary @waiter to the wait queue for the nominated @folio.
1477 : */
1478 0 : void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter)
1479 : {
1480 0 : wait_queue_head_t *q = folio_waitqueue(folio);
1481 : unsigned long flags;
1482 :
1483 0 : spin_lock_irqsave(&q->lock, flags);
1484 0 : __add_wait_queue_entry_tail(q, waiter);
1485 0 : folio_set_waiters(folio);
1486 0 : spin_unlock_irqrestore(&q->lock, flags);
1487 0 : }
1488 : EXPORT_SYMBOL_GPL(folio_add_wait_queue);
1489 :
1490 : #ifndef clear_bit_unlock_is_negative_byte
1491 :
1492 : /*
1493 : * PG_waiters is the high bit in the same byte as PG_lock.
1494 : *
1495 : * On x86 (and on many other architectures), we can clear PG_lock and
1496 : * test the sign bit at the same time. But if the architecture does
1497 : * not support that special operation, we just do this all by hand
1498 : * instead.
1499 : *
1500 : * The read of PG_waiters has to be after (or concurrently with) PG_locked
1501 : * being cleared, but a memory barrier should be unnecessary since it is
1502 : * in the same byte as PG_locked.
1503 : */
1504 : static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
1505 : {
1506 : clear_bit_unlock(nr, mem);
1507 : /* smp_mb__after_atomic(); */
1508 : return test_bit(PG_waiters, mem);
1509 : }
1510 :
1511 : #endif
1512 :
1513 : /**
1514 : * folio_unlock - Unlock a locked folio.
1515 : * @folio: The folio.
1516 : *
1517 : * Unlocks the folio and wakes up any thread sleeping on the page lock.
1518 : *
1519 : * Context: May be called from interrupt or process context. May not be
1520 : * called from NMI context.
1521 : */
1522 0 : void folio_unlock(struct folio *folio)
1523 : {
1524 : /* Bit 7 allows x86 to check the byte's sign bit */
1525 : BUILD_BUG_ON(PG_waiters != 7);
1526 : BUILD_BUG_ON(PG_locked > 7);
1527 : VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1528 0 : if (clear_bit_unlock_is_negative_byte(PG_locked, folio_flags(folio, 0)))
1529 0 : folio_wake_bit(folio, PG_locked);
1530 0 : }
1531 : EXPORT_SYMBOL(folio_unlock);
1532 :
1533 : /**
1534 : * folio_end_private_2 - Clear PG_private_2 and wake any waiters.
1535 : * @folio: The folio.
1536 : *
1537 : * Clear the PG_private_2 bit on a folio and wake up any sleepers waiting for
1538 : * it. The folio reference held for PG_private_2 being set is released.
1539 : *
1540 : * This is, for example, used when a netfs folio is being written to a local
1541 : * disk cache, thereby allowing writes to the cache for the same folio to be
1542 : * serialised.
1543 : */
1544 0 : void folio_end_private_2(struct folio *folio)
1545 : {
1546 : VM_BUG_ON_FOLIO(!folio_test_private_2(folio), folio);
1547 0 : clear_bit_unlock(PG_private_2, folio_flags(folio, 0));
1548 0 : folio_wake_bit(folio, PG_private_2);
1549 0 : folio_put(folio);
1550 0 : }
1551 : EXPORT_SYMBOL(folio_end_private_2);
1552 :
1553 : /**
1554 : * folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio.
1555 : * @folio: The folio to wait on.
1556 : *
1557 : * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio.
1558 : */
1559 0 : void folio_wait_private_2(struct folio *folio)
1560 : {
1561 0 : while (folio_test_private_2(folio))
1562 : folio_wait_bit(folio, PG_private_2);
1563 0 : }
1564 : EXPORT_SYMBOL(folio_wait_private_2);
1565 :
1566 : /**
1567 : * folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio.
1568 : * @folio: The folio to wait on.
1569 : *
1570 : * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a
1571 : * fatal signal is received by the calling task.
1572 : *
1573 : * Return:
1574 : * - 0 if successful.
1575 : * - -EINTR if a fatal signal was encountered.
1576 : */
1577 0 : int folio_wait_private_2_killable(struct folio *folio)
1578 : {
1579 0 : int ret = 0;
1580 :
1581 0 : while (folio_test_private_2(folio)) {
1582 0 : ret = folio_wait_bit_killable(folio, PG_private_2);
1583 0 : if (ret < 0)
1584 : break;
1585 : }
1586 :
1587 0 : return ret;
1588 : }
1589 : EXPORT_SYMBOL(folio_wait_private_2_killable);
1590 :
1591 : /**
1592 : * folio_end_writeback - End writeback against a folio.
1593 : * @folio: The folio.
1594 : */
1595 0 : void folio_end_writeback(struct folio *folio)
1596 : {
1597 : /*
1598 : * folio_test_clear_reclaim() could be used here but it is an
1599 : * atomic operation and overkill in this particular case. Failing
1600 : * to shuffle a folio marked for immediate reclaim is too mild
1601 : * a gain to justify taking an atomic operation penalty at the
1602 : * end of every folio writeback.
1603 : */
1604 0 : if (folio_test_reclaim(folio)) {
1605 0 : folio_clear_reclaim(folio);
1606 0 : folio_rotate_reclaimable(folio);
1607 : }
1608 :
1609 : /*
1610 : * Writeback does not hold a folio reference of its own, relying
1611 : * on truncation to wait for the clearing of PG_writeback.
1612 : * But here we must make sure that the folio is not freed and
1613 : * reused before the folio_wake().
1614 : */
1615 0 : folio_get(folio);
1616 0 : if (!__folio_end_writeback(folio))
1617 0 : BUG();
1618 :
1619 0 : smp_mb__after_atomic();
1620 0 : folio_wake(folio, PG_writeback);
1621 0 : acct_reclaim_writeback(folio);
1622 0 : folio_put(folio);
1623 0 : }
1624 : EXPORT_SYMBOL(folio_end_writeback);
1625 :
1626 : /**
1627 : * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.
1628 : * @folio: The folio to lock
1629 : */
1630 0 : void __folio_lock(struct folio *folio)
1631 : {
1632 0 : folio_wait_bit_common(folio, PG_locked, TASK_UNINTERRUPTIBLE,
1633 : EXCLUSIVE);
1634 0 : }
1635 : EXPORT_SYMBOL(__folio_lock);
1636 :
1637 0 : int __folio_lock_killable(struct folio *folio)
1638 : {
1639 0 : return folio_wait_bit_common(folio, PG_locked, TASK_KILLABLE,
1640 : EXCLUSIVE);
1641 : }
1642 : EXPORT_SYMBOL_GPL(__folio_lock_killable);
1643 :
1644 0 : static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
1645 : {
1646 0 : struct wait_queue_head *q = folio_waitqueue(folio);
1647 0 : int ret = 0;
1648 :
1649 0 : wait->folio = folio;
1650 0 : wait->bit_nr = PG_locked;
1651 :
1652 0 : spin_lock_irq(&q->lock);
1653 0 : __add_wait_queue_entry_tail(q, &wait->wait);
1654 0 : folio_set_waiters(folio);
1655 0 : ret = !folio_trylock(folio);
1656 : /*
1657 : * If we were successful now, we know we're still on the
1658 : * waitqueue as we're still under the lock. This means it's
1659 : * safe to remove and return success, we know the callback
1660 : * isn't going to trigger.
1661 : */
1662 0 : if (!ret)
1663 0 : __remove_wait_queue(q, &wait->wait);
1664 : else
1665 : ret = -EIOCBQUEUED;
1666 0 : spin_unlock_irq(&q->lock);
1667 0 : return ret;
1668 : }
1669 :
1670 : /*
1671 : * Return values:
1672 : * true - folio is locked; mmap_lock is still held.
1673 : * false - folio is not locked.
1674 : * mmap_lock has been released (mmap_read_unlock(), unless flags had both
1675 : * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1676 : * which case mmap_lock is still held.
1677 : *
1678 : * If neither ALLOW_RETRY nor KILLABLE are set, will always return true
1679 : * with the folio locked and the mmap_lock unperturbed.
1680 : */
1681 0 : bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm,
1682 : unsigned int flags)
1683 : {
1684 0 : if (fault_flag_allow_retry_first(flags)) {
1685 : /*
1686 : * CAUTION! In this case, mmap_lock is not released
1687 : * even though return 0.
1688 : */
1689 0 : if (flags & FAULT_FLAG_RETRY_NOWAIT)
1690 : return false;
1691 :
1692 0 : mmap_read_unlock(mm);
1693 0 : if (flags & FAULT_FLAG_KILLABLE)
1694 0 : folio_wait_locked_killable(folio);
1695 : else
1696 : folio_wait_locked(folio);
1697 : return false;
1698 : }
1699 0 : if (flags & FAULT_FLAG_KILLABLE) {
1700 : bool ret;
1701 :
1702 0 : ret = __folio_lock_killable(folio);
1703 0 : if (ret) {
1704 0 : mmap_read_unlock(mm);
1705 0 : return false;
1706 : }
1707 : } else {
1708 : __folio_lock(folio);
1709 : }
1710 :
1711 : return true;
1712 : }
1713 :
1714 : /**
1715 : * page_cache_next_miss() - Find the next gap in the page cache.
1716 : * @mapping: Mapping.
1717 : * @index: Index.
1718 : * @max_scan: Maximum range to search.
1719 : *
1720 : * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
1721 : * gap with the lowest index.
1722 : *
1723 : * This function may be called under the rcu_read_lock. However, this will
1724 : * not atomically search a snapshot of the cache at a single point in time.
1725 : * For example, if a gap is created at index 5, then subsequently a gap is
1726 : * created at index 10, page_cache_next_miss covering both indices may
1727 : * return 10 if called under the rcu_read_lock.
1728 : *
1729 : * Return: The index of the gap if found, otherwise an index outside the
1730 : * range specified (in which case 'return - index >= max_scan' will be true).
1731 : * In the rare case of index wrap-around, 0 will be returned.
1732 : */
1733 0 : pgoff_t page_cache_next_miss(struct address_space *mapping,
1734 : pgoff_t index, unsigned long max_scan)
1735 : {
1736 0 : XA_STATE(xas, &mapping->i_pages, index);
1737 :
1738 0 : while (max_scan--) {
1739 0 : void *entry = xas_next(&xas);
1740 0 : if (!entry || xa_is_value(entry))
1741 : break;
1742 0 : if (xas.xa_index == 0)
1743 : break;
1744 : }
1745 :
1746 0 : return xas.xa_index;
1747 : }
1748 : EXPORT_SYMBOL(page_cache_next_miss);
1749 :
1750 : /**
1751 : * page_cache_prev_miss() - Find the previous gap in the page cache.
1752 : * @mapping: Mapping.
1753 : * @index: Index.
1754 : * @max_scan: Maximum range to search.
1755 : *
1756 : * Search the range [max(index - max_scan + 1, 0), index] for the
1757 : * gap with the highest index.
1758 : *
1759 : * This function may be called under the rcu_read_lock. However, this will
1760 : * not atomically search a snapshot of the cache at a single point in time.
1761 : * For example, if a gap is created at index 10, then subsequently a gap is
1762 : * created at index 5, page_cache_prev_miss() covering both indices may
1763 : * return 5 if called under the rcu_read_lock.
1764 : *
1765 : * Return: The index of the gap if found, otherwise an index outside the
1766 : * range specified (in which case 'index - return >= max_scan' will be true).
1767 : * In the rare case of wrap-around, ULONG_MAX will be returned.
1768 : */
1769 0 : pgoff_t page_cache_prev_miss(struct address_space *mapping,
1770 : pgoff_t index, unsigned long max_scan)
1771 : {
1772 0 : XA_STATE(xas, &mapping->i_pages, index);
1773 :
1774 0 : while (max_scan--) {
1775 0 : void *entry = xas_prev(&xas);
1776 0 : if (!entry || xa_is_value(entry))
1777 : break;
1778 0 : if (xas.xa_index == ULONG_MAX)
1779 : break;
1780 : }
1781 :
1782 0 : return xas.xa_index;
1783 : }
1784 : EXPORT_SYMBOL(page_cache_prev_miss);
1785 :
1786 : /*
1787 : * Lockless page cache protocol:
1788 : * On the lookup side:
1789 : * 1. Load the folio from i_pages
1790 : * 2. Increment the refcount if it's not zero
1791 : * 3. If the folio is not found by xas_reload(), put the refcount and retry
1792 : *
1793 : * On the removal side:
1794 : * A. Freeze the page (by zeroing the refcount if nobody else has a reference)
1795 : * B. Remove the page from i_pages
1796 : * C. Return the page to the page allocator
1797 : *
1798 : * This means that any page may have its reference count temporarily
1799 : * increased by a speculative page cache (or fast GUP) lookup as it can
1800 : * be allocated by another user before the RCU grace period expires.
1801 : * Because the refcount temporarily acquired here may end up being the
1802 : * last refcount on the page, any page allocation must be freeable by
1803 : * folio_put().
1804 : */
1805 :
1806 : /*
1807 : * filemap_get_entry - Get a page cache entry.
1808 : * @mapping: the address_space to search
1809 : * @index: The page cache index.
1810 : *
1811 : * Looks up the page cache entry at @mapping & @index. If it is a folio,
1812 : * it is returned with an increased refcount. If it is a shadow entry
1813 : * of a previously evicted folio, or a swap entry from shmem/tmpfs,
1814 : * it is returned without further action.
1815 : *
1816 : * Return: The folio, swap or shadow entry, %NULL if nothing is found.
1817 : */
1818 0 : void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
1819 : {
1820 0 : XA_STATE(xas, &mapping->i_pages, index);
1821 : struct folio *folio;
1822 :
1823 : rcu_read_lock();
1824 : repeat:
1825 0 : xas_reset(&xas);
1826 0 : folio = xas_load(&xas);
1827 0 : if (xas_retry(&xas, folio))
1828 : goto repeat;
1829 : /*
1830 : * A shadow entry of a recently evicted page, or a swap entry from
1831 : * shmem/tmpfs. Return it without attempting to raise page count.
1832 : */
1833 0 : if (!folio || xa_is_value(folio))
1834 : goto out;
1835 :
1836 0 : if (!folio_try_get_rcu(folio))
1837 : goto repeat;
1838 :
1839 0 : if (unlikely(folio != xas_reload(&xas))) {
1840 : folio_put(folio);
1841 : goto repeat;
1842 : }
1843 : out:
1844 : rcu_read_unlock();
1845 :
1846 0 : return folio;
1847 : }
1848 :
1849 : /**
1850 : * __filemap_get_folio - Find and get a reference to a folio.
1851 : * @mapping: The address_space to search.
1852 : * @index: The page index.
1853 : * @fgp_flags: %FGP flags modify how the folio is returned.
1854 : * @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
1855 : *
1856 : * Looks up the page cache entry at @mapping & @index.
1857 : *
1858 : * @fgp_flags can be zero or more of these flags:
1859 : *
1860 : * * %FGP_ACCESSED - The folio will be marked accessed.
1861 : * * %FGP_LOCK - The folio is returned locked.
1862 : * * %FGP_CREAT - If no page is present then a new page is allocated using
1863 : * @gfp and added to the page cache and the VM's LRU list.
1864 : * The page is returned locked and with an increased refcount.
1865 : * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
1866 : * page is already in cache. If the page was allocated, unlock it before
1867 : * returning so the caller can do the same dance.
1868 : * * %FGP_WRITE - The page will be written to by the caller.
1869 : * * %FGP_NOFS - __GFP_FS will get cleared in gfp.
1870 : * * %FGP_NOWAIT - Don't get blocked by page lock.
1871 : * * %FGP_STABLE - Wait for the folio to be stable (finished writeback)
1872 : *
1873 : * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
1874 : * if the %GFP flags specified for %FGP_CREAT are atomic.
1875 : *
1876 : * If there is a page cache page, it is returned with an increased refcount.
1877 : *
1878 : * Return: The found folio or an ERR_PTR() otherwise.
1879 : */
1880 0 : struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
1881 : int fgp_flags, gfp_t gfp)
1882 : {
1883 : struct folio *folio;
1884 :
1885 : repeat:
1886 0 : folio = filemap_get_entry(mapping, index);
1887 0 : if (xa_is_value(folio))
1888 0 : folio = NULL;
1889 0 : if (!folio)
1890 : goto no_page;
1891 :
1892 0 : if (fgp_flags & FGP_LOCK) {
1893 0 : if (fgp_flags & FGP_NOWAIT) {
1894 0 : if (!folio_trylock(folio)) {
1895 : folio_put(folio);
1896 : return ERR_PTR(-EAGAIN);
1897 : }
1898 : } else {
1899 0 : folio_lock(folio);
1900 : }
1901 :
1902 : /* Has the page been truncated? */
1903 0 : if (unlikely(folio->mapping != mapping)) {
1904 0 : folio_unlock(folio);
1905 : folio_put(folio);
1906 : goto repeat;
1907 : }
1908 : VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
1909 : }
1910 :
1911 0 : if (fgp_flags & FGP_ACCESSED)
1912 0 : folio_mark_accessed(folio);
1913 : else if (fgp_flags & FGP_WRITE) {
1914 : /* Clear idle flag for buffer write */
1915 : if (folio_test_idle(folio))
1916 : folio_clear_idle(folio);
1917 : }
1918 :
1919 0 : if (fgp_flags & FGP_STABLE)
1920 0 : folio_wait_stable(folio);
1921 : no_page:
1922 0 : if (!folio && (fgp_flags & FGP_CREAT)) {
1923 : int err;
1924 0 : if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
1925 0 : gfp |= __GFP_WRITE;
1926 0 : if (fgp_flags & FGP_NOFS)
1927 0 : gfp &= ~__GFP_FS;
1928 0 : if (fgp_flags & FGP_NOWAIT) {
1929 0 : gfp &= ~GFP_KERNEL;
1930 0 : gfp |= GFP_NOWAIT | __GFP_NOWARN;
1931 : }
1932 :
1933 0 : folio = filemap_alloc_folio(gfp, 0);
1934 0 : if (!folio)
1935 : return ERR_PTR(-ENOMEM);
1936 :
1937 0 : if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
1938 0 : fgp_flags |= FGP_LOCK;
1939 :
1940 : /* Init accessed so avoid atomic mark_page_accessed later */
1941 0 : if (fgp_flags & FGP_ACCESSED)
1942 : __folio_set_referenced(folio);
1943 :
1944 0 : err = filemap_add_folio(mapping, folio, index, gfp);
1945 0 : if (unlikely(err)) {
1946 0 : folio_put(folio);
1947 0 : folio = NULL;
1948 0 : if (err == -EEXIST)
1949 : goto repeat;
1950 : }
1951 :
1952 : /*
1953 : * filemap_add_folio locks the page, and for mmap
1954 : * we expect an unlocked page.
1955 : */
1956 0 : if (folio && (fgp_flags & FGP_FOR_MMAP))
1957 : folio_unlock(folio);
1958 : }
1959 :
1960 0 : if (!folio)
1961 : return ERR_PTR(-ENOENT);
1962 0 : return folio;
1963 : }
1964 : EXPORT_SYMBOL(__filemap_get_folio);
1965 :
1966 0 : static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
1967 : xa_mark_t mark)
1968 : {
1969 : struct folio *folio;
1970 :
1971 : retry:
1972 0 : if (mark == XA_PRESENT)
1973 0 : folio = xas_find(xas, max);
1974 : else
1975 0 : folio = xas_find_marked(xas, max, mark);
1976 :
1977 0 : if (xas_retry(xas, folio))
1978 : goto retry;
1979 : /*
1980 : * A shadow entry of a recently evicted page, a swap
1981 : * entry from shmem/tmpfs or a DAX entry. Return it
1982 : * without attempting to raise page count.
1983 : */
1984 0 : if (!folio || xa_is_value(folio))
1985 : return folio;
1986 :
1987 0 : if (!folio_try_get_rcu(folio))
1988 : goto reset;
1989 :
1990 0 : if (unlikely(folio != xas_reload(xas))) {
1991 : folio_put(folio);
1992 : goto reset;
1993 : }
1994 :
1995 : return folio;
1996 : reset:
1997 0 : xas_reset(xas);
1998 : goto retry;
1999 : }
2000 :
2001 : /**
2002 : * find_get_entries - gang pagecache lookup
2003 : * @mapping: The address_space to search
2004 : * @start: The starting page cache index
2005 : * @end: The final page index (inclusive).
2006 : * @fbatch: Where the resulting entries are placed.
2007 : * @indices: The cache indices corresponding to the entries in @entries
2008 : *
2009 : * find_get_entries() will search for and return a batch of entries in
2010 : * the mapping. The entries are placed in @fbatch. find_get_entries()
2011 : * takes a reference on any actual folios it returns.
2012 : *
2013 : * The entries have ascending indexes. The indices may not be consecutive
2014 : * due to not-present entries or large folios.
2015 : *
2016 : * Any shadow entries of evicted folios, or swap entries from
2017 : * shmem/tmpfs, are included in the returned array.
2018 : *
2019 : * Return: The number of entries which were found.
2020 : */
2021 0 : unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
2022 : pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
2023 : {
2024 0 : XA_STATE(xas, &mapping->i_pages, *start);
2025 : struct folio *folio;
2026 :
2027 : rcu_read_lock();
2028 0 : while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
2029 0 : indices[fbatch->nr] = xas.xa_index;
2030 0 : if (!folio_batch_add(fbatch, folio))
2031 : break;
2032 : }
2033 : rcu_read_unlock();
2034 :
2035 0 : if (folio_batch_count(fbatch)) {
2036 0 : unsigned long nr = 1;
2037 0 : int idx = folio_batch_count(fbatch) - 1;
2038 :
2039 0 : folio = fbatch->folios[idx];
2040 0 : if (!xa_is_value(folio) && !folio_test_hugetlb(folio))
2041 0 : nr = folio_nr_pages(folio);
2042 0 : *start = indices[idx] + nr;
2043 : }
2044 0 : return folio_batch_count(fbatch);
2045 : }
2046 :
2047 : /**
2048 : * find_lock_entries - Find a batch of pagecache entries.
2049 : * @mapping: The address_space to search.
2050 : * @start: The starting page cache index.
2051 : * @end: The final page index (inclusive).
2052 : * @fbatch: Where the resulting entries are placed.
2053 : * @indices: The cache indices of the entries in @fbatch.
2054 : *
2055 : * find_lock_entries() will return a batch of entries from @mapping.
2056 : * Swap, shadow and DAX entries are included. Folios are returned
2057 : * locked and with an incremented refcount. Folios which are locked
2058 : * by somebody else or under writeback are skipped. Folios which are
2059 : * partially outside the range are not returned.
2060 : *
2061 : * The entries have ascending indexes. The indices may not be consecutive
2062 : * due to not-present entries, large folios, folios which could not be
2063 : * locked or folios under writeback.
2064 : *
2065 : * Return: The number of entries which were found.
2066 : */
2067 0 : unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
2068 : pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
2069 : {
2070 0 : XA_STATE(xas, &mapping->i_pages, *start);
2071 : struct folio *folio;
2072 :
2073 : rcu_read_lock();
2074 0 : while ((folio = find_get_entry(&xas, end, XA_PRESENT))) {
2075 0 : if (!xa_is_value(folio)) {
2076 0 : if (folio->index < *start)
2077 : goto put;
2078 0 : if (folio->index + folio_nr_pages(folio) - 1 > end)
2079 : goto put;
2080 0 : if (!folio_trylock(folio))
2081 : goto put;
2082 0 : if (folio->mapping != mapping ||
2083 0 : folio_test_writeback(folio))
2084 : goto unlock;
2085 : VM_BUG_ON_FOLIO(!folio_contains(folio, xas.xa_index),
2086 : folio);
2087 : }
2088 0 : indices[fbatch->nr] = xas.xa_index;
2089 0 : if (!folio_batch_add(fbatch, folio))
2090 : break;
2091 0 : continue;
2092 : unlock:
2093 : folio_unlock(folio);
2094 : put:
2095 : folio_put(folio);
2096 : }
2097 : rcu_read_unlock();
2098 :
2099 0 : if (folio_batch_count(fbatch)) {
2100 0 : unsigned long nr = 1;
2101 0 : int idx = folio_batch_count(fbatch) - 1;
2102 :
2103 0 : folio = fbatch->folios[idx];
2104 0 : if (!xa_is_value(folio) && !folio_test_hugetlb(folio))
2105 0 : nr = folio_nr_pages(folio);
2106 0 : *start = indices[idx] + nr;
2107 : }
2108 0 : return folio_batch_count(fbatch);
2109 : }
2110 :
2111 : /**
2112 : * filemap_get_folios - Get a batch of folios
2113 : * @mapping: The address_space to search
2114 : * @start: The starting page index
2115 : * @end: The final page index (inclusive)
2116 : * @fbatch: The batch to fill.
2117 : *
2118 : * Search for and return a batch of folios in the mapping starting at
2119 : * index @start and up to index @end (inclusive). The folios are returned
2120 : * in @fbatch with an elevated reference count.
2121 : *
2122 : * The first folio may start before @start; if it does, it will contain
2123 : * @start. The final folio may extend beyond @end; if it does, it will
2124 : * contain @end. The folios have ascending indices. There may be gaps
2125 : * between the folios if there are indices which have no folio in the
2126 : * page cache. If folios are added to or removed from the page cache
2127 : * while this is running, they may or may not be found by this call.
2128 : *
2129 : * Return: The number of folios which were found.
2130 : * We also update @start to index the next folio for the traversal.
2131 : */
2132 0 : unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
2133 : pgoff_t end, struct folio_batch *fbatch)
2134 : {
2135 0 : XA_STATE(xas, &mapping->i_pages, *start);
2136 : struct folio *folio;
2137 :
2138 : rcu_read_lock();
2139 0 : while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
2140 : /* Skip over shadow, swap and DAX entries */
2141 0 : if (xa_is_value(folio))
2142 0 : continue;
2143 0 : if (!folio_batch_add(fbatch, folio)) {
2144 0 : unsigned long nr = folio_nr_pages(folio);
2145 :
2146 0 : if (folio_test_hugetlb(folio))
2147 : nr = 1;
2148 0 : *start = folio->index + nr;
2149 0 : goto out;
2150 : }
2151 : }
2152 :
2153 : /*
2154 : * We come here when there is no page beyond @end. We take care to not
2155 : * overflow the index @start as it confuses some of the callers. This
2156 : * breaks the iteration when there is a page at index -1 but that is
2157 : * already broken anyway.
2158 : */
2159 0 : if (end == (pgoff_t)-1)
2160 0 : *start = (pgoff_t)-1;
2161 : else
2162 0 : *start = end + 1;
2163 : out:
2164 : rcu_read_unlock();
2165 :
2166 0 : return folio_batch_count(fbatch);
2167 : }
2168 : EXPORT_SYMBOL(filemap_get_folios);
2169 :
2170 : static inline
2171 : bool folio_more_pages(struct folio *folio, pgoff_t index, pgoff_t max)
2172 : {
2173 0 : if (!folio_test_large(folio) || folio_test_hugetlb(folio))
2174 : return false;
2175 0 : if (index >= max)
2176 : return false;
2177 0 : return index < folio->index + folio_nr_pages(folio) - 1;
2178 : }
2179 :
2180 : /**
2181 : * filemap_get_folios_contig - Get a batch of contiguous folios
2182 : * @mapping: The address_space to search
2183 : * @start: The starting page index
2184 : * @end: The final page index (inclusive)
2185 : * @fbatch: The batch to fill
2186 : *
2187 : * filemap_get_folios_contig() works exactly like filemap_get_folios(),
2188 : * except the returned folios are guaranteed to be contiguous. This may
2189 : * not return all contiguous folios if the batch gets filled up.
2190 : *
2191 : * Return: The number of folios found.
2192 : * Also update @start to be positioned for traversal of the next folio.
2193 : */
2194 :
2195 0 : unsigned filemap_get_folios_contig(struct address_space *mapping,
2196 : pgoff_t *start, pgoff_t end, struct folio_batch *fbatch)
2197 : {
2198 0 : XA_STATE(xas, &mapping->i_pages, *start);
2199 : unsigned long nr;
2200 : struct folio *folio;
2201 :
2202 : rcu_read_lock();
2203 :
2204 0 : for (folio = xas_load(&xas); folio && xas.xa_index <= end;
2205 0 : folio = xas_next(&xas)) {
2206 0 : if (xas_retry(&xas, folio))
2207 0 : continue;
2208 : /*
2209 : * If the entry has been swapped out, we can stop looking.
2210 : * No current caller is looking for DAX entries.
2211 : */
2212 0 : if (xa_is_value(folio))
2213 : goto update_start;
2214 :
2215 0 : if (!folio_try_get_rcu(folio))
2216 : goto retry;
2217 :
2218 0 : if (unlikely(folio != xas_reload(&xas)))
2219 : goto put_folio;
2220 :
2221 0 : if (!folio_batch_add(fbatch, folio)) {
2222 0 : nr = folio_nr_pages(folio);
2223 :
2224 0 : if (folio_test_hugetlb(folio))
2225 : nr = 1;
2226 0 : *start = folio->index + nr;
2227 0 : goto out;
2228 : }
2229 0 : continue;
2230 : put_folio:
2231 : folio_put(folio);
2232 :
2233 : retry:
2234 0 : xas_reset(&xas);
2235 : }
2236 :
2237 : update_start:
2238 0 : nr = folio_batch_count(fbatch);
2239 :
2240 0 : if (nr) {
2241 0 : folio = fbatch->folios[nr - 1];
2242 0 : if (folio_test_hugetlb(folio))
2243 : *start = folio->index + 1;
2244 : else
2245 0 : *start = folio->index + folio_nr_pages(folio);
2246 : }
2247 : out:
2248 : rcu_read_unlock();
2249 0 : return folio_batch_count(fbatch);
2250 : }
2251 : EXPORT_SYMBOL(filemap_get_folios_contig);
2252 :
2253 : /**
2254 : * filemap_get_folios_tag - Get a batch of folios matching @tag
2255 : * @mapping: The address_space to search
2256 : * @start: The starting page index
2257 : * @end: The final page index (inclusive)
2258 : * @tag: The tag index
2259 : * @fbatch: The batch to fill
2260 : *
2261 : * Same as filemap_get_folios(), but only returning folios tagged with @tag.
2262 : *
2263 : * Return: The number of folios found.
2264 : * Also update @start to index the next folio for traversal.
2265 : */
2266 0 : unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start,
2267 : pgoff_t end, xa_mark_t tag, struct folio_batch *fbatch)
2268 : {
2269 0 : XA_STATE(xas, &mapping->i_pages, *start);
2270 : struct folio *folio;
2271 :
2272 : rcu_read_lock();
2273 0 : while ((folio = find_get_entry(&xas, end, tag)) != NULL) {
2274 : /*
2275 : * Shadow entries should never be tagged, but this iteration
2276 : * is lockless so there is a window for page reclaim to evict
2277 : * a page we saw tagged. Skip over it.
2278 : */
2279 0 : if (xa_is_value(folio))
2280 0 : continue;
2281 0 : if (!folio_batch_add(fbatch, folio)) {
2282 0 : unsigned long nr = folio_nr_pages(folio);
2283 :
2284 0 : if (folio_test_hugetlb(folio))
2285 : nr = 1;
2286 0 : *start = folio->index + nr;
2287 0 : goto out;
2288 : }
2289 : }
2290 : /*
2291 : * We come here when there is no page beyond @end. We take care to not
2292 : * overflow the index @start as it confuses some of the callers. This
2293 : * breaks the iteration when there is a page at index -1 but that is
2294 : * already broke anyway.
2295 : */
2296 0 : if (end == (pgoff_t)-1)
2297 0 : *start = (pgoff_t)-1;
2298 : else
2299 0 : *start = end + 1;
2300 : out:
2301 : rcu_read_unlock();
2302 :
2303 0 : return folio_batch_count(fbatch);
2304 : }
2305 : EXPORT_SYMBOL(filemap_get_folios_tag);
2306 :
2307 : /*
2308 : * CD/DVDs are error prone. When a medium error occurs, the driver may fail
2309 : * a _large_ part of the i/o request. Imagine the worst scenario:
2310 : *
2311 : * ---R__________________________________________B__________
2312 : * ^ reading here ^ bad block(assume 4k)
2313 : *
2314 : * read(R) => miss => readahead(R...B) => media error => frustrating retries
2315 : * => failing the whole request => read(R) => read(R+1) =>
2316 : * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
2317 : * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
2318 : * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
2319 : *
2320 : * It is going insane. Fix it by quickly scaling down the readahead size.
2321 : */
2322 : static void shrink_readahead_size_eio(struct file_ra_state *ra)
2323 : {
2324 0 : ra->ra_pages /= 4;
2325 : }
2326 :
2327 : /*
2328 : * filemap_get_read_batch - Get a batch of folios for read
2329 : *
2330 : * Get a batch of folios which represent a contiguous range of bytes in
2331 : * the file. No exceptional entries will be returned. If @index is in
2332 : * the middle of a folio, the entire folio will be returned. The last
2333 : * folio in the batch may have the readahead flag set or the uptodate flag
2334 : * clear so that the caller can take the appropriate action.
2335 : */
2336 0 : static void filemap_get_read_batch(struct address_space *mapping,
2337 : pgoff_t index, pgoff_t max, struct folio_batch *fbatch)
2338 : {
2339 0 : XA_STATE(xas, &mapping->i_pages, index);
2340 : struct folio *folio;
2341 :
2342 : rcu_read_lock();
2343 0 : for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
2344 0 : if (xas_retry(&xas, folio))
2345 0 : continue;
2346 0 : if (xas.xa_index > max || xa_is_value(folio))
2347 : break;
2348 0 : if (xa_is_sibling(folio))
2349 : break;
2350 0 : if (!folio_try_get_rcu(folio))
2351 : goto retry;
2352 :
2353 0 : if (unlikely(folio != xas_reload(&xas)))
2354 : goto put_folio;
2355 :
2356 0 : if (!folio_batch_add(fbatch, folio))
2357 : break;
2358 0 : if (!folio_test_uptodate(folio))
2359 : break;
2360 0 : if (folio_test_readahead(folio))
2361 : break;
2362 0 : xas_advance(&xas, folio->index + folio_nr_pages(folio) - 1);
2363 0 : continue;
2364 : put_folio:
2365 : folio_put(folio);
2366 : retry:
2367 0 : xas_reset(&xas);
2368 : }
2369 : rcu_read_unlock();
2370 0 : }
2371 :
2372 0 : static int filemap_read_folio(struct file *file, filler_t filler,
2373 : struct folio *folio)
2374 : {
2375 0 : bool workingset = folio_test_workingset(folio);
2376 : unsigned long pflags;
2377 : int error;
2378 :
2379 : /*
2380 : * A previous I/O error may have been due to temporary failures,
2381 : * eg. multipath errors. PG_error will be set again if read_folio
2382 : * fails.
2383 : */
2384 0 : folio_clear_error(folio);
2385 :
2386 : /* Start the actual read. The read will unlock the page. */
2387 : if (unlikely(workingset))
2388 : psi_memstall_enter(&pflags);
2389 0 : error = filler(file, folio);
2390 : if (unlikely(workingset))
2391 : psi_memstall_leave(&pflags);
2392 0 : if (error)
2393 : return error;
2394 :
2395 0 : error = folio_wait_locked_killable(folio);
2396 0 : if (error)
2397 : return error;
2398 0 : if (folio_test_uptodate(folio))
2399 : return 0;
2400 0 : if (file)
2401 0 : shrink_readahead_size_eio(&file->f_ra);
2402 : return -EIO;
2403 : }
2404 :
2405 0 : static bool filemap_range_uptodate(struct address_space *mapping,
2406 : loff_t pos, size_t count, struct folio *folio,
2407 : bool need_uptodate)
2408 : {
2409 0 : if (folio_test_uptodate(folio))
2410 : return true;
2411 : /* pipes can't handle partially uptodate pages */
2412 0 : if (need_uptodate)
2413 : return false;
2414 0 : if (!mapping->a_ops->is_partially_uptodate)
2415 : return false;
2416 0 : if (mapping->host->i_blkbits >= folio_shift(folio))
2417 : return false;
2418 :
2419 0 : if (folio_pos(folio) > pos) {
2420 0 : count -= folio_pos(folio) - pos;
2421 0 : pos = 0;
2422 : } else {
2423 0 : pos -= folio_pos(folio);
2424 : }
2425 :
2426 0 : return mapping->a_ops->is_partially_uptodate(folio, pos, count);
2427 : }
2428 :
2429 0 : static int filemap_update_page(struct kiocb *iocb,
2430 : struct address_space *mapping, size_t count,
2431 : struct folio *folio, bool need_uptodate)
2432 : {
2433 : int error;
2434 :
2435 0 : if (iocb->ki_flags & IOCB_NOWAIT) {
2436 0 : if (!filemap_invalidate_trylock_shared(mapping))
2437 : return -EAGAIN;
2438 : } else {
2439 : filemap_invalidate_lock_shared(mapping);
2440 : }
2441 :
2442 0 : if (!folio_trylock(folio)) {
2443 0 : error = -EAGAIN;
2444 0 : if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
2445 : goto unlock_mapping;
2446 0 : if (!(iocb->ki_flags & IOCB_WAITQ)) {
2447 0 : filemap_invalidate_unlock_shared(mapping);
2448 : /*
2449 : * This is where we usually end up waiting for a
2450 : * previously submitted readahead to finish.
2451 : */
2452 0 : folio_put_wait_locked(folio, TASK_KILLABLE);
2453 0 : return AOP_TRUNCATED_PAGE;
2454 : }
2455 0 : error = __folio_lock_async(folio, iocb->ki_waitq);
2456 0 : if (error)
2457 : goto unlock_mapping;
2458 : }
2459 :
2460 0 : error = AOP_TRUNCATED_PAGE;
2461 0 : if (!folio->mapping)
2462 : goto unlock;
2463 :
2464 0 : error = 0;
2465 0 : if (filemap_range_uptodate(mapping, iocb->ki_pos, count, folio,
2466 : need_uptodate))
2467 : goto unlock;
2468 :
2469 0 : error = -EAGAIN;
2470 0 : if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
2471 : goto unlock;
2472 :
2473 0 : error = filemap_read_folio(iocb->ki_filp, mapping->a_ops->read_folio,
2474 : folio);
2475 0 : goto unlock_mapping;
2476 : unlock:
2477 : folio_unlock(folio);
2478 : unlock_mapping:
2479 0 : filemap_invalidate_unlock_shared(mapping);
2480 0 : if (error == AOP_TRUNCATED_PAGE)
2481 : folio_put(folio);
2482 : return error;
2483 : }
2484 :
2485 0 : static int filemap_create_folio(struct file *file,
2486 : struct address_space *mapping, pgoff_t index,
2487 : struct folio_batch *fbatch)
2488 : {
2489 : struct folio *folio;
2490 : int error;
2491 :
2492 0 : folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
2493 0 : if (!folio)
2494 : return -ENOMEM;
2495 :
2496 : /*
2497 : * Protect against truncate / hole punch. Grabbing invalidate_lock
2498 : * here assures we cannot instantiate and bring uptodate new
2499 : * pagecache folios after evicting page cache during truncate
2500 : * and before actually freeing blocks. Note that we could
2501 : * release invalidate_lock after inserting the folio into
2502 : * the page cache as the locked folio would then be enough to
2503 : * synchronize with hole punching. But there are code paths
2504 : * such as filemap_update_page() filling in partially uptodate
2505 : * pages or ->readahead() that need to hold invalidate_lock
2506 : * while mapping blocks for IO so let's hold the lock here as
2507 : * well to keep locking rules simple.
2508 : */
2509 0 : filemap_invalidate_lock_shared(mapping);
2510 0 : error = filemap_add_folio(mapping, folio, index,
2511 : mapping_gfp_constraint(mapping, GFP_KERNEL));
2512 0 : if (error == -EEXIST)
2513 0 : error = AOP_TRUNCATED_PAGE;
2514 0 : if (error)
2515 : goto error;
2516 :
2517 0 : error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
2518 0 : if (error)
2519 : goto error;
2520 :
2521 0 : filemap_invalidate_unlock_shared(mapping);
2522 0 : folio_batch_add(fbatch, folio);
2523 0 : return 0;
2524 : error:
2525 0 : filemap_invalidate_unlock_shared(mapping);
2526 : folio_put(folio);
2527 : return error;
2528 : }
2529 :
2530 0 : static int filemap_readahead(struct kiocb *iocb, struct file *file,
2531 : struct address_space *mapping, struct folio *folio,
2532 : pgoff_t last_index)
2533 : {
2534 0 : DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, folio->index);
2535 :
2536 0 : if (iocb->ki_flags & IOCB_NOIO)
2537 : return -EAGAIN;
2538 0 : page_cache_async_ra(&ractl, folio, last_index - folio->index);
2539 : return 0;
2540 : }
2541 :
2542 0 : static int filemap_get_pages(struct kiocb *iocb, size_t count,
2543 : struct folio_batch *fbatch, bool need_uptodate)
2544 : {
2545 0 : struct file *filp = iocb->ki_filp;
2546 0 : struct address_space *mapping = filp->f_mapping;
2547 0 : struct file_ra_state *ra = &filp->f_ra;
2548 0 : pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
2549 : pgoff_t last_index;
2550 : struct folio *folio;
2551 0 : int err = 0;
2552 :
2553 : /* "last_index" is the index of the page beyond the end of the read */
2554 0 : last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE);
2555 : retry:
2556 0 : if (fatal_signal_pending(current))
2557 : return -EINTR;
2558 :
2559 0 : filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
2560 0 : if (!folio_batch_count(fbatch)) {
2561 0 : if (iocb->ki_flags & IOCB_NOIO)
2562 : return -EAGAIN;
2563 0 : page_cache_sync_readahead(mapping, ra, filp, index,
2564 : last_index - index);
2565 0 : filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
2566 : }
2567 0 : if (!folio_batch_count(fbatch)) {
2568 0 : if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
2569 : return -EAGAIN;
2570 0 : err = filemap_create_folio(filp, mapping,
2571 0 : iocb->ki_pos >> PAGE_SHIFT, fbatch);
2572 0 : if (err == AOP_TRUNCATED_PAGE)
2573 : goto retry;
2574 : return err;
2575 : }
2576 :
2577 0 : folio = fbatch->folios[folio_batch_count(fbatch) - 1];
2578 0 : if (folio_test_readahead(folio)) {
2579 0 : err = filemap_readahead(iocb, filp, mapping, folio, last_index);
2580 0 : if (err)
2581 : goto err;
2582 : }
2583 0 : if (!folio_test_uptodate(folio)) {
2584 0 : if ((iocb->ki_flags & IOCB_WAITQ) &&
2585 0 : folio_batch_count(fbatch) > 1)
2586 0 : iocb->ki_flags |= IOCB_NOWAIT;
2587 0 : err = filemap_update_page(iocb, mapping, count, folio,
2588 : need_uptodate);
2589 0 : if (err)
2590 : goto err;
2591 : }
2592 :
2593 : return 0;
2594 : err:
2595 0 : if (err < 0)
2596 : folio_put(folio);
2597 0 : if (likely(--fbatch->nr))
2598 : return 0;
2599 0 : if (err == AOP_TRUNCATED_PAGE)
2600 : goto retry;
2601 : return err;
2602 : }
2603 :
2604 : static inline bool pos_same_folio(loff_t pos1, loff_t pos2, struct folio *folio)
2605 : {
2606 0 : unsigned int shift = folio_shift(folio);
2607 :
2608 0 : return (pos1 >> shift == pos2 >> shift);
2609 : }
2610 :
2611 : /**
2612 : * filemap_read - Read data from the page cache.
2613 : * @iocb: The iocb to read.
2614 : * @iter: Destination for the data.
2615 : * @already_read: Number of bytes already read by the caller.
2616 : *
2617 : * Copies data from the page cache. If the data is not currently present,
2618 : * uses the readahead and read_folio address_space operations to fetch it.
2619 : *
2620 : * Return: Total number of bytes copied, including those already read by
2621 : * the caller. If an error happens before any bytes are copied, returns
2622 : * a negative error number.
2623 : */
2624 0 : ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
2625 : ssize_t already_read)
2626 : {
2627 0 : struct file *filp = iocb->ki_filp;
2628 0 : struct file_ra_state *ra = &filp->f_ra;
2629 0 : struct address_space *mapping = filp->f_mapping;
2630 0 : struct inode *inode = mapping->host;
2631 : struct folio_batch fbatch;
2632 0 : int i, error = 0;
2633 : bool writably_mapped;
2634 : loff_t isize, end_offset;
2635 :
2636 0 : if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
2637 : return 0;
2638 0 : if (unlikely(!iov_iter_count(iter)))
2639 : return 0;
2640 :
2641 0 : iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
2642 0 : folio_batch_init(&fbatch);
2643 :
2644 : do {
2645 0 : cond_resched();
2646 :
2647 : /*
2648 : * If we've already successfully copied some data, then we
2649 : * can no longer safely return -EIOCBQUEUED. Hence mark
2650 : * an async read NOWAIT at that point.
2651 : */
2652 0 : if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
2653 0 : iocb->ki_flags |= IOCB_NOWAIT;
2654 :
2655 0 : if (unlikely(iocb->ki_pos >= i_size_read(inode)))
2656 : break;
2657 :
2658 0 : error = filemap_get_pages(iocb, iter->count, &fbatch, false);
2659 0 : if (error < 0)
2660 : break;
2661 :
2662 : /*
2663 : * i_size must be checked after we know the pages are Uptodate.
2664 : *
2665 : * Checking i_size after the check allows us to calculate
2666 : * the correct value for "nr", which means the zero-filled
2667 : * part of the page is not copied back to userspace (unless
2668 : * another truncate extends the file - this is desired though).
2669 : */
2670 0 : isize = i_size_read(inode);
2671 0 : if (unlikely(iocb->ki_pos >= isize))
2672 : goto put_folios;
2673 0 : end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
2674 :
2675 : /*
2676 : * Once we start copying data, we don't want to be touching any
2677 : * cachelines that might be contended:
2678 : */
2679 0 : writably_mapped = mapping_writably_mapped(mapping);
2680 :
2681 : /*
2682 : * When a read accesses the same folio several times, only
2683 : * mark it as accessed the first time.
2684 : */
2685 0 : if (!pos_same_folio(iocb->ki_pos, ra->prev_pos - 1,
2686 : fbatch.folios[0]))
2687 0 : folio_mark_accessed(fbatch.folios[0]);
2688 :
2689 0 : for (i = 0; i < folio_batch_count(&fbatch); i++) {
2690 0 : struct folio *folio = fbatch.folios[i];
2691 0 : size_t fsize = folio_size(folio);
2692 0 : size_t offset = iocb->ki_pos & (fsize - 1);
2693 0 : size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
2694 : fsize - offset);
2695 : size_t copied;
2696 :
2697 0 : if (end_offset < folio_pos(folio))
2698 : break;
2699 0 : if (i > 0)
2700 0 : folio_mark_accessed(folio);
2701 : /*
2702 : * If users can be writing to this folio using arbitrary
2703 : * virtual addresses, take care of potential aliasing
2704 : * before reading the folio on the kernel side.
2705 : */
2706 : if (writably_mapped)
2707 : flush_dcache_folio(folio);
2708 :
2709 0 : copied = copy_folio_to_iter(folio, offset, bytes, iter);
2710 :
2711 0 : already_read += copied;
2712 0 : iocb->ki_pos += copied;
2713 0 : ra->prev_pos = iocb->ki_pos;
2714 :
2715 0 : if (copied < bytes) {
2716 : error = -EFAULT;
2717 : break;
2718 : }
2719 : }
2720 : put_folios:
2721 0 : for (i = 0; i < folio_batch_count(&fbatch); i++)
2722 0 : folio_put(fbatch.folios[i]);
2723 0 : folio_batch_init(&fbatch);
2724 0 : } while (iov_iter_count(iter) && iocb->ki_pos < isize && !error);
2725 :
2726 0 : file_accessed(filp);
2727 :
2728 0 : return already_read ? already_read : error;
2729 : }
2730 : EXPORT_SYMBOL_GPL(filemap_read);
2731 :
2732 0 : int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
2733 : {
2734 0 : struct address_space *mapping = iocb->ki_filp->f_mapping;
2735 0 : loff_t pos = iocb->ki_pos;
2736 0 : loff_t end = pos + count - 1;
2737 :
2738 0 : if (iocb->ki_flags & IOCB_NOWAIT) {
2739 0 : if (filemap_range_needs_writeback(mapping, pos, end))
2740 : return -EAGAIN;
2741 0 : return 0;
2742 : }
2743 :
2744 0 : return filemap_write_and_wait_range(mapping, pos, end);
2745 : }
2746 :
2747 0 : int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
2748 : {
2749 0 : struct address_space *mapping = iocb->ki_filp->f_mapping;
2750 0 : loff_t pos = iocb->ki_pos;
2751 0 : loff_t end = pos + count - 1;
2752 : int ret;
2753 :
2754 0 : if (iocb->ki_flags & IOCB_NOWAIT) {
2755 : /* we could block if there are any pages in the range */
2756 0 : if (filemap_range_has_page(mapping, pos, end))
2757 : return -EAGAIN;
2758 : } else {
2759 0 : ret = filemap_write_and_wait_range(mapping, pos, end);
2760 0 : if (ret)
2761 : return ret;
2762 : }
2763 :
2764 : /*
2765 : * After a write we want buffered reads to be sure to go to disk to get
2766 : * the new data. We invalidate clean cached page from the region we're
2767 : * about to write. We do this *before* the write so that we can return
2768 : * without clobbering -EIOCBQUEUED from ->direct_IO().
2769 : */
2770 0 : return invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
2771 0 : end >> PAGE_SHIFT);
2772 : }
2773 :
2774 : /**
2775 : * generic_file_read_iter - generic filesystem read routine
2776 : * @iocb: kernel I/O control block
2777 : * @iter: destination for the data read
2778 : *
2779 : * This is the "read_iter()" routine for all filesystems
2780 : * that can use the page cache directly.
2781 : *
2782 : * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
2783 : * be returned when no data can be read without waiting for I/O requests
2784 : * to complete; it doesn't prevent readahead.
2785 : *
2786 : * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
2787 : * requests shall be made for the read or for readahead. When no data
2788 : * can be read, -EAGAIN shall be returned. When readahead would be
2789 : * triggered, a partial, possibly empty read shall be returned.
2790 : *
2791 : * Return:
2792 : * * number of bytes copied, even for partial reads
2793 : * * negative error code (or 0 if IOCB_NOIO) if nothing was read
2794 : */
2795 : ssize_t
2796 0 : generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2797 : {
2798 0 : size_t count = iov_iter_count(iter);
2799 0 : ssize_t retval = 0;
2800 :
2801 0 : if (!count)
2802 : return 0; /* skip atime */
2803 :
2804 0 : if (iocb->ki_flags & IOCB_DIRECT) {
2805 0 : struct file *file = iocb->ki_filp;
2806 0 : struct address_space *mapping = file->f_mapping;
2807 0 : struct inode *inode = mapping->host;
2808 :
2809 0 : retval = kiocb_write_and_wait(iocb, count);
2810 0 : if (retval < 0)
2811 : return retval;
2812 0 : file_accessed(file);
2813 :
2814 0 : retval = mapping->a_ops->direct_IO(iocb, iter);
2815 0 : if (retval >= 0) {
2816 0 : iocb->ki_pos += retval;
2817 0 : count -= retval;
2818 : }
2819 0 : if (retval != -EIOCBQUEUED)
2820 0 : iov_iter_revert(iter, count - iov_iter_count(iter));
2821 :
2822 : /*
2823 : * Btrfs can have a short DIO read if we encounter
2824 : * compressed extents, so if there was an error, or if
2825 : * we've already read everything we wanted to, or if
2826 : * there was a short read because we hit EOF, go ahead
2827 : * and return. Otherwise fallthrough to buffered io for
2828 : * the rest of the read. Buffered reads will not work for
2829 : * DAX files, so don't bother trying.
2830 : */
2831 0 : if (retval < 0 || !count || IS_DAX(inode))
2832 : return retval;
2833 0 : if (iocb->ki_pos >= i_size_read(inode))
2834 : return retval;
2835 : }
2836 :
2837 0 : return filemap_read(iocb, iter, retval);
2838 : }
2839 : EXPORT_SYMBOL(generic_file_read_iter);
2840 :
2841 : /*
2842 : * Splice subpages from a folio into a pipe.
2843 : */
2844 0 : size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
2845 : struct folio *folio, loff_t fpos, size_t size)
2846 : {
2847 : struct page *page;
2848 0 : size_t spliced = 0, offset = offset_in_folio(folio, fpos);
2849 :
2850 0 : page = folio_page(folio, offset / PAGE_SIZE);
2851 0 : size = min(size, folio_size(folio) - offset);
2852 0 : offset %= PAGE_SIZE;
2853 :
2854 0 : while (spliced < size &&
2855 0 : !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
2856 0 : struct pipe_buffer *buf = pipe_head_buf(pipe);
2857 0 : size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);
2858 :
2859 0 : *buf = (struct pipe_buffer) {
2860 : .ops = &page_cache_pipe_buf_ops,
2861 : .page = page,
2862 : .offset = offset,
2863 : .len = part,
2864 : };
2865 0 : folio_get(folio);
2866 0 : pipe->head++;
2867 0 : page++;
2868 0 : spliced += part;
2869 0 : offset = 0;
2870 : }
2871 :
2872 0 : return spliced;
2873 : }
2874 :
2875 : /**
2876 : * filemap_splice_read - Splice data from a file's pagecache into a pipe
2877 : * @in: The file to read from
2878 : * @ppos: Pointer to the file position to read from
2879 : * @pipe: The pipe to splice into
2880 : * @len: The amount to splice
2881 : * @flags: The SPLICE_F_* flags
2882 : *
2883 : * This function gets folios from a file's pagecache and splices them into the
2884 : * pipe. Readahead will be called as necessary to fill more folios. This may
2885 : * be used for blockdevs also.
2886 : *
2887 : * Return: On success, the number of bytes read will be returned and *@ppos
2888 : * will be updated if appropriate; 0 will be returned if there is no more data
2889 : * to be read; -EAGAIN will be returned if the pipe had no space, and some
2890 : * other negative error code will be returned on error. A short read may occur
2891 : * if the pipe has insufficient space, we reach the end of the data or we hit a
2892 : * hole.
2893 : */
2894 0 : ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
2895 : struct pipe_inode_info *pipe,
2896 : size_t len, unsigned int flags)
2897 : {
2898 : struct folio_batch fbatch;
2899 : struct kiocb iocb;
2900 0 : size_t total_spliced = 0, used, npages;
2901 : loff_t isize, end_offset;
2902 : bool writably_mapped;
2903 0 : int i, error = 0;
2904 :
2905 0 : if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
2906 : return 0;
2907 :
2908 0 : init_sync_kiocb(&iocb, in);
2909 0 : iocb.ki_pos = *ppos;
2910 :
2911 : /* Work out how much data we can actually add into the pipe */
2912 0 : used = pipe_occupancy(pipe->head, pipe->tail);
2913 0 : npages = max_t(ssize_t, pipe->max_usage - used, 0);
2914 0 : len = min_t(size_t, len, npages * PAGE_SIZE);
2915 :
2916 0 : folio_batch_init(&fbatch);
2917 :
2918 : do {
2919 0 : cond_resched();
2920 :
2921 0 : if (*ppos >= i_size_read(in->f_mapping->host))
2922 : break;
2923 :
2924 0 : iocb.ki_pos = *ppos;
2925 0 : error = filemap_get_pages(&iocb, len, &fbatch, true);
2926 0 : if (error < 0)
2927 : break;
2928 :
2929 : /*
2930 : * i_size must be checked after we know the pages are Uptodate.
2931 : *
2932 : * Checking i_size after the check allows us to calculate
2933 : * the correct value for "nr", which means the zero-filled
2934 : * part of the page is not copied back to userspace (unless
2935 : * another truncate extends the file - this is desired though).
2936 : */
2937 0 : isize = i_size_read(in->f_mapping->host);
2938 0 : if (unlikely(*ppos >= isize))
2939 : break;
2940 0 : end_offset = min_t(loff_t, isize, *ppos + len);
2941 :
2942 : /*
2943 : * Once we start copying data, we don't want to be touching any
2944 : * cachelines that might be contended:
2945 : */
2946 0 : writably_mapped = mapping_writably_mapped(in->f_mapping);
2947 :
2948 0 : for (i = 0; i < folio_batch_count(&fbatch); i++) {
2949 0 : struct folio *folio = fbatch.folios[i];
2950 : size_t n;
2951 :
2952 0 : if (folio_pos(folio) >= end_offset)
2953 : goto out;
2954 0 : folio_mark_accessed(folio);
2955 :
2956 : /*
2957 : * If users can be writing to this folio using arbitrary
2958 : * virtual addresses, take care of potential aliasing
2959 : * before reading the folio on the kernel side.
2960 : */
2961 : if (writably_mapped)
2962 : flush_dcache_folio(folio);
2963 :
2964 0 : n = min_t(loff_t, len, isize - *ppos);
2965 0 : n = splice_folio_into_pipe(pipe, folio, *ppos, n);
2966 0 : if (!n)
2967 : goto out;
2968 0 : len -= n;
2969 0 : total_spliced += n;
2970 0 : *ppos += n;
2971 0 : in->f_ra.prev_pos = *ppos;
2972 0 : if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
2973 : goto out;
2974 : }
2975 :
2976 0 : folio_batch_release(&fbatch);
2977 0 : } while (len);
2978 :
2979 : out:
2980 0 : folio_batch_release(&fbatch);
2981 0 : file_accessed(in);
2982 :
2983 0 : return total_spliced ? total_spliced : error;
2984 : }
2985 : EXPORT_SYMBOL(filemap_splice_read);
2986 :
2987 0 : static inline loff_t folio_seek_hole_data(struct xa_state *xas,
2988 : struct address_space *mapping, struct folio *folio,
2989 : loff_t start, loff_t end, bool seek_data)
2990 : {
2991 0 : const struct address_space_operations *ops = mapping->a_ops;
2992 0 : size_t offset, bsz = i_blocksize(mapping->host);
2993 :
2994 0 : if (xa_is_value(folio) || folio_test_uptodate(folio))
2995 0 : return seek_data ? start : end;
2996 0 : if (!ops->is_partially_uptodate)
2997 0 : return seek_data ? end : start;
2998 :
2999 0 : xas_pause(xas);
3000 : rcu_read_unlock();
3001 0 : folio_lock(folio);
3002 0 : if (unlikely(folio->mapping != mapping))
3003 : goto unlock;
3004 :
3005 0 : offset = offset_in_folio(folio, start) & ~(bsz - 1);
3006 :
3007 : do {
3008 0 : if (ops->is_partially_uptodate(folio, offset, bsz) ==
3009 : seek_data)
3010 : break;
3011 0 : start = (start + bsz) & ~(bsz - 1);
3012 0 : offset += bsz;
3013 0 : } while (offset < folio_size(folio));
3014 : unlock:
3015 0 : folio_unlock(folio);
3016 : rcu_read_lock();
3017 0 : return start;
3018 : }
3019 :
3020 : static inline size_t seek_folio_size(struct xa_state *xas, struct folio *folio)
3021 : {
3022 0 : if (xa_is_value(folio))
3023 : return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index);
3024 0 : return folio_size(folio);
3025 : }
3026 :
3027 : /**
3028 : * mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache.
3029 : * @mapping: Address space to search.
3030 : * @start: First byte to consider.
3031 : * @end: Limit of search (exclusive).
3032 : * @whence: Either SEEK_HOLE or SEEK_DATA.
3033 : *
3034 : * If the page cache knows which blocks contain holes and which blocks
3035 : * contain data, your filesystem can use this function to implement
3036 : * SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are
3037 : * entirely memory-based such as tmpfs, and filesystems which support
3038 : * unwritten extents.
3039 : *
3040 : * Return: The requested offset on success, or -ENXIO if @whence specifies
3041 : * SEEK_DATA and there is no data after @start. There is an implicit hole
3042 : * after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start
3043 : * and @end contain data.
3044 : */
3045 0 : loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
3046 : loff_t end, int whence)
3047 : {
3048 0 : XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
3049 0 : pgoff_t max = (end - 1) >> PAGE_SHIFT;
3050 0 : bool seek_data = (whence == SEEK_DATA);
3051 : struct folio *folio;
3052 :
3053 0 : if (end <= start)
3054 : return -ENXIO;
3055 :
3056 : rcu_read_lock();
3057 0 : while ((folio = find_get_entry(&xas, max, XA_PRESENT))) {
3058 0 : loff_t pos = (u64)xas.xa_index << PAGE_SHIFT;
3059 : size_t seek_size;
3060 :
3061 0 : if (start < pos) {
3062 0 : if (!seek_data)
3063 : goto unlock;
3064 : start = pos;
3065 : }
3066 :
3067 0 : seek_size = seek_folio_size(&xas, folio);
3068 0 : pos = round_up((u64)pos + 1, seek_size);
3069 0 : start = folio_seek_hole_data(&xas, mapping, folio, start, pos,
3070 : seek_data);
3071 0 : if (start < pos)
3072 : goto unlock;
3073 0 : if (start >= end)
3074 : break;
3075 0 : if (seek_size > PAGE_SIZE)
3076 0 : xas_set(&xas, pos >> PAGE_SHIFT);
3077 0 : if (!xa_is_value(folio))
3078 : folio_put(folio);
3079 : }
3080 0 : if (seek_data)
3081 0 : start = -ENXIO;
3082 : unlock:
3083 : rcu_read_unlock();
3084 0 : if (folio && !xa_is_value(folio))
3085 : folio_put(folio);
3086 0 : if (start > end)
3087 : return end;
3088 0 : return start;
3089 : }
3090 :
3091 : #ifdef CONFIG_MMU
3092 : #define MMAP_LOTSAMISS (100)
3093 : /*
3094 : * lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
3095 : * @vmf - the vm_fault for this fault.
3096 : * @folio - the folio to lock.
3097 : * @fpin - the pointer to the file we may pin (or is already pinned).
3098 : *
3099 : * This works similar to lock_folio_or_retry in that it can drop the
3100 : * mmap_lock. It differs in that it actually returns the folio locked
3101 : * if it returns 1 and 0 if it couldn't lock the folio. If we did have
3102 : * to drop the mmap_lock then fpin will point to the pinned file and
3103 : * needs to be fput()'ed at a later point.
3104 : */
3105 0 : static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
3106 : struct file **fpin)
3107 : {
3108 0 : if (folio_trylock(folio))
3109 : return 1;
3110 :
3111 : /*
3112 : * NOTE! This will make us return with VM_FAULT_RETRY, but with
3113 : * the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
3114 : * is supposed to work. We have way too many special cases..
3115 : */
3116 0 : if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
3117 : return 0;
3118 :
3119 0 : *fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
3120 0 : if (vmf->flags & FAULT_FLAG_KILLABLE) {
3121 0 : if (__folio_lock_killable(folio)) {
3122 : /*
3123 : * We didn't have the right flags to drop the mmap_lock,
3124 : * but all fault_handlers only check for fatal signals
3125 : * if we return VM_FAULT_RETRY, so we need to drop the
3126 : * mmap_lock here and return 0 if we don't have a fpin.
3127 : */
3128 0 : if (*fpin == NULL)
3129 0 : mmap_read_unlock(vmf->vma->vm_mm);
3130 : return 0;
3131 : }
3132 : } else
3133 : __folio_lock(folio);
3134 :
3135 : return 1;
3136 : }
3137 :
3138 : /*
3139 : * Synchronous readahead happens when we don't even find a page in the page
3140 : * cache at all. We don't want to perform IO under the mmap sem, so if we have
3141 : * to drop the mmap sem we return the file that was pinned in order for us to do
3142 : * that. If we didn't pin a file then we return NULL. The file that is
3143 : * returned needs to be fput()'ed when we're done with it.
3144 : */
3145 0 : static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
3146 : {
3147 0 : struct file *file = vmf->vma->vm_file;
3148 0 : struct file_ra_state *ra = &file->f_ra;
3149 0 : struct address_space *mapping = file->f_mapping;
3150 0 : DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
3151 0 : struct file *fpin = NULL;
3152 0 : unsigned long vm_flags = vmf->vma->vm_flags;
3153 : unsigned int mmap_miss;
3154 :
3155 : #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3156 : /* Use the readahead code, even if readahead is disabled */
3157 : if (vm_flags & VM_HUGEPAGE) {
3158 : fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3159 : ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1);
3160 : ra->size = HPAGE_PMD_NR;
3161 : /*
3162 : * Fetch two PMD folios, so we get the chance to actually
3163 : * readahead, unless we've been told not to.
3164 : */
3165 : if (!(vm_flags & VM_RAND_READ))
3166 : ra->size *= 2;
3167 : ra->async_size = HPAGE_PMD_NR;
3168 : page_cache_ra_order(&ractl, ra, HPAGE_PMD_ORDER);
3169 : return fpin;
3170 : }
3171 : #endif
3172 :
3173 : /* If we don't want any read-ahead, don't bother */
3174 0 : if (vm_flags & VM_RAND_READ)
3175 : return fpin;
3176 0 : if (!ra->ra_pages)
3177 : return fpin;
3178 :
3179 0 : if (vm_flags & VM_SEQ_READ) {
3180 0 : fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3181 0 : page_cache_sync_ra(&ractl, ra->ra_pages);
3182 0 : return fpin;
3183 : }
3184 :
3185 : /* Avoid banging the cache line if not needed */
3186 0 : mmap_miss = READ_ONCE(ra->mmap_miss);
3187 0 : if (mmap_miss < MMAP_LOTSAMISS * 10)
3188 0 : WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
3189 :
3190 : /*
3191 : * Do we miss much more than hit in this file? If so,
3192 : * stop bothering with read-ahead. It will only hurt.
3193 : */
3194 0 : if (mmap_miss > MMAP_LOTSAMISS)
3195 : return fpin;
3196 :
3197 : /*
3198 : * mmap read-around
3199 : */
3200 0 : fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3201 0 : ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
3202 0 : ra->size = ra->ra_pages;
3203 0 : ra->async_size = ra->ra_pages / 4;
3204 0 : ractl._index = ra->start;
3205 0 : page_cache_ra_order(&ractl, ra, 0);
3206 0 : return fpin;
3207 : }
3208 :
3209 : /*
3210 : * Asynchronous readahead happens when we find the page and PG_readahead,
3211 : * so we want to possibly extend the readahead further. We return the file that
3212 : * was pinned if we have to drop the mmap_lock in order to do IO.
3213 : */
3214 0 : static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
3215 : struct folio *folio)
3216 : {
3217 0 : struct file *file = vmf->vma->vm_file;
3218 0 : struct file_ra_state *ra = &file->f_ra;
3219 0 : DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff);
3220 0 : struct file *fpin = NULL;
3221 : unsigned int mmap_miss;
3222 :
3223 : /* If we don't want any read-ahead, don't bother */
3224 0 : if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
3225 : return fpin;
3226 :
3227 0 : mmap_miss = READ_ONCE(ra->mmap_miss);
3228 0 : if (mmap_miss)
3229 0 : WRITE_ONCE(ra->mmap_miss, --mmap_miss);
3230 :
3231 0 : if (folio_test_readahead(folio)) {
3232 0 : fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3233 0 : page_cache_async_ra(&ractl, folio, ra->ra_pages);
3234 : }
3235 : return fpin;
3236 : }
3237 :
3238 : /**
3239 : * filemap_fault - read in file data for page fault handling
3240 : * @vmf: struct vm_fault containing details of the fault
3241 : *
3242 : * filemap_fault() is invoked via the vma operations vector for a
3243 : * mapped memory region to read in file data during a page fault.
3244 : *
3245 : * The goto's are kind of ugly, but this streamlines the normal case of having
3246 : * it in the page cache, and handles the special cases reasonably without
3247 : * having a lot of duplicated code.
3248 : *
3249 : * vma->vm_mm->mmap_lock must be held on entry.
3250 : *
3251 : * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
3252 : * may be dropped before doing I/O or by lock_folio_maybe_drop_mmap().
3253 : *
3254 : * If our return value does not have VM_FAULT_RETRY set, the mmap_lock
3255 : * has not been released.
3256 : *
3257 : * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
3258 : *
3259 : * Return: bitwise-OR of %VM_FAULT_ codes.
3260 : */
3261 0 : vm_fault_t filemap_fault(struct vm_fault *vmf)
3262 : {
3263 : int error;
3264 0 : struct file *file = vmf->vma->vm_file;
3265 0 : struct file *fpin = NULL;
3266 0 : struct address_space *mapping = file->f_mapping;
3267 0 : struct inode *inode = mapping->host;
3268 0 : pgoff_t max_idx, index = vmf->pgoff;
3269 : struct folio *folio;
3270 0 : vm_fault_t ret = 0;
3271 0 : bool mapping_locked = false;
3272 :
3273 0 : max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
3274 0 : if (unlikely(index >= max_idx))
3275 : return VM_FAULT_SIGBUS;
3276 :
3277 : /*
3278 : * Do we have something in the page cache already?
3279 : */
3280 0 : folio = filemap_get_folio(mapping, index);
3281 0 : if (likely(!IS_ERR(folio))) {
3282 : /*
3283 : * We found the page, so try async readahead before waiting for
3284 : * the lock.
3285 : */
3286 0 : if (!(vmf->flags & FAULT_FLAG_TRIED))
3287 0 : fpin = do_async_mmap_readahead(vmf, folio);
3288 0 : if (unlikely(!folio_test_uptodate(folio))) {
3289 0 : filemap_invalidate_lock_shared(mapping);
3290 0 : mapping_locked = true;
3291 : }
3292 : } else {
3293 : /* No page in the page cache at all */
3294 0 : count_vm_event(PGMAJFAULT);
3295 0 : count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
3296 0 : ret = VM_FAULT_MAJOR;
3297 0 : fpin = do_sync_mmap_readahead(vmf);
3298 : retry_find:
3299 : /*
3300 : * See comment in filemap_create_folio() why we need
3301 : * invalidate_lock
3302 : */
3303 0 : if (!mapping_locked) {
3304 0 : filemap_invalidate_lock_shared(mapping);
3305 0 : mapping_locked = true;
3306 : }
3307 0 : folio = __filemap_get_folio(mapping, index,
3308 : FGP_CREAT|FGP_FOR_MMAP,
3309 : vmf->gfp_mask);
3310 0 : if (IS_ERR(folio)) {
3311 0 : if (fpin)
3312 : goto out_retry;
3313 0 : filemap_invalidate_unlock_shared(mapping);
3314 0 : return VM_FAULT_OOM;
3315 : }
3316 : }
3317 :
3318 0 : if (!lock_folio_maybe_drop_mmap(vmf, folio, &fpin))
3319 : goto out_retry;
3320 :
3321 : /* Did it get truncated? */
3322 0 : if (unlikely(folio->mapping != mapping)) {
3323 0 : folio_unlock(folio);
3324 : folio_put(folio);
3325 : goto retry_find;
3326 : }
3327 : VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
3328 :
3329 : /*
3330 : * We have a locked page in the page cache, now we need to check
3331 : * that it's up-to-date. If not, it is going to be due to an error.
3332 : */
3333 0 : if (unlikely(!folio_test_uptodate(folio))) {
3334 : /*
3335 : * The page was in cache and uptodate and now it is not.
3336 : * Strange but possible since we didn't hold the page lock all
3337 : * the time. Let's drop everything get the invalidate lock and
3338 : * try again.
3339 : */
3340 0 : if (!mapping_locked) {
3341 0 : folio_unlock(folio);
3342 : folio_put(folio);
3343 : goto retry_find;
3344 : }
3345 : goto page_not_uptodate;
3346 : }
3347 :
3348 : /*
3349 : * We've made it this far and we had to drop our mmap_lock, now is the
3350 : * time to return to the upper layer and have it re-find the vma and
3351 : * redo the fault.
3352 : */
3353 0 : if (fpin) {
3354 : folio_unlock(folio);
3355 : goto out_retry;
3356 : }
3357 0 : if (mapping_locked)
3358 : filemap_invalidate_unlock_shared(mapping);
3359 :
3360 : /*
3361 : * Found the page and have a reference on it.
3362 : * We must recheck i_size under page lock.
3363 : */
3364 0 : max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
3365 0 : if (unlikely(index >= max_idx)) {
3366 0 : folio_unlock(folio);
3367 : folio_put(folio);
3368 : return VM_FAULT_SIGBUS;
3369 : }
3370 :
3371 0 : vmf->page = folio_file_page(folio, index);
3372 0 : return ret | VM_FAULT_LOCKED;
3373 :
3374 : page_not_uptodate:
3375 : /*
3376 : * Umm, take care of errors if the page isn't up-to-date.
3377 : * Try to re-read it _once_. We do this synchronously,
3378 : * because there really aren't any performance issues here
3379 : * and we need to check for errors.
3380 : */
3381 0 : fpin = maybe_unlock_mmap_for_io(vmf, fpin);
3382 0 : error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
3383 0 : if (fpin)
3384 : goto out_retry;
3385 0 : folio_put(folio);
3386 :
3387 0 : if (!error || error == AOP_TRUNCATED_PAGE)
3388 : goto retry_find;
3389 0 : filemap_invalidate_unlock_shared(mapping);
3390 :
3391 0 : return VM_FAULT_SIGBUS;
3392 :
3393 : out_retry:
3394 : /*
3395 : * We dropped the mmap_lock, we need to return to the fault handler to
3396 : * re-find the vma and come back and find our hopefully still populated
3397 : * page.
3398 : */
3399 0 : if (!IS_ERR(folio))
3400 : folio_put(folio);
3401 0 : if (mapping_locked)
3402 : filemap_invalidate_unlock_shared(mapping);
3403 0 : if (fpin)
3404 0 : fput(fpin);
3405 0 : return ret | VM_FAULT_RETRY;
3406 : }
3407 : EXPORT_SYMBOL(filemap_fault);
3408 :
3409 : static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
3410 : pgoff_t start)
3411 : {
3412 0 : struct mm_struct *mm = vmf->vma->vm_mm;
3413 :
3414 : /* Huge page is mapped? No need to proceed. */
3415 0 : if (pmd_trans_huge(*vmf->pmd)) {
3416 : folio_unlock(folio);
3417 : folio_put(folio);
3418 : return true;
3419 : }
3420 :
3421 0 : if (pmd_none(*vmf->pmd) && folio_test_pmd_mappable(folio)) {
3422 : struct page *page = folio_file_page(folio, start);
3423 : vm_fault_t ret = do_set_pmd(vmf, page);
3424 : if (!ret) {
3425 : /* The page is mapped successfully, reference consumed. */
3426 : folio_unlock(folio);
3427 : return true;
3428 : }
3429 : }
3430 :
3431 0 : if (pmd_none(*vmf->pmd))
3432 0 : pmd_install(mm, vmf->pmd, &vmf->prealloc_pte);
3433 :
3434 : return false;
3435 : }
3436 :
3437 0 : static struct folio *next_uptodate_page(struct folio *folio,
3438 : struct address_space *mapping,
3439 : struct xa_state *xas, pgoff_t end_pgoff)
3440 : {
3441 : unsigned long max_idx;
3442 :
3443 : do {
3444 0 : if (!folio)
3445 : return NULL;
3446 0 : if (xas_retry(xas, folio))
3447 0 : continue;
3448 0 : if (xa_is_value(folio))
3449 0 : continue;
3450 0 : if (folio_test_locked(folio))
3451 0 : continue;
3452 0 : if (!folio_try_get_rcu(folio))
3453 : continue;
3454 : /* Has the page moved or been split? */
3455 0 : if (unlikely(folio != xas_reload(xas)))
3456 : goto skip;
3457 0 : if (!folio_test_uptodate(folio) || folio_test_readahead(folio))
3458 : goto skip;
3459 0 : if (!folio_trylock(folio))
3460 : goto skip;
3461 0 : if (folio->mapping != mapping)
3462 : goto unlock;
3463 0 : if (!folio_test_uptodate(folio))
3464 : goto unlock;
3465 0 : max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
3466 0 : if (xas->xa_index >= max_idx)
3467 : goto unlock;
3468 : return folio;
3469 : unlock:
3470 : folio_unlock(folio);
3471 : skip:
3472 : folio_put(folio);
3473 0 : } while ((folio = xas_next_entry(xas, end_pgoff)) != NULL);
3474 :
3475 : return NULL;
3476 : }
3477 :
3478 0 : static inline struct folio *first_map_page(struct address_space *mapping,
3479 : struct xa_state *xas,
3480 : pgoff_t end_pgoff)
3481 : {
3482 0 : return next_uptodate_page(xas_find(xas, end_pgoff),
3483 : mapping, xas, end_pgoff);
3484 : }
3485 :
3486 0 : static inline struct folio *next_map_page(struct address_space *mapping,
3487 : struct xa_state *xas,
3488 : pgoff_t end_pgoff)
3489 : {
3490 0 : return next_uptodate_page(xas_next_entry(xas, end_pgoff),
3491 : mapping, xas, end_pgoff);
3492 : }
3493 :
3494 0 : vm_fault_t filemap_map_pages(struct vm_fault *vmf,
3495 : pgoff_t start_pgoff, pgoff_t end_pgoff)
3496 : {
3497 0 : struct vm_area_struct *vma = vmf->vma;
3498 0 : struct file *file = vma->vm_file;
3499 0 : struct address_space *mapping = file->f_mapping;
3500 0 : pgoff_t last_pgoff = start_pgoff;
3501 : unsigned long addr;
3502 0 : XA_STATE(xas, &mapping->i_pages, start_pgoff);
3503 : struct folio *folio;
3504 : struct page *page;
3505 0 : unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
3506 0 : vm_fault_t ret = 0;
3507 :
3508 : rcu_read_lock();
3509 0 : folio = first_map_page(mapping, &xas, end_pgoff);
3510 0 : if (!folio)
3511 : goto out;
3512 :
3513 0 : if (filemap_map_pmd(vmf, folio, start_pgoff)) {
3514 : ret = VM_FAULT_NOPAGE;
3515 : goto out;
3516 : }
3517 :
3518 0 : addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
3519 0 : vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
3520 0 : if (!vmf->pte) {
3521 0 : folio_unlock(folio);
3522 : folio_put(folio);
3523 : goto out;
3524 : }
3525 : do {
3526 : again:
3527 0 : page = folio_file_page(folio, xas.xa_index);
3528 : if (PageHWPoison(page))
3529 : goto unlock;
3530 :
3531 0 : if (mmap_miss > 0)
3532 0 : mmap_miss--;
3533 :
3534 0 : addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
3535 0 : vmf->pte += xas.xa_index - last_pgoff;
3536 0 : last_pgoff = xas.xa_index;
3537 :
3538 : /*
3539 : * NOTE: If there're PTE markers, we'll leave them to be
3540 : * handled in the specific fault path, and it'll prohibit the
3541 : * fault-around logic.
3542 : */
3543 0 : if (!pte_none(ptep_get(vmf->pte)))
3544 : goto unlock;
3545 :
3546 : /* We're about to handle the fault */
3547 0 : if (vmf->address == addr)
3548 0 : ret = VM_FAULT_NOPAGE;
3549 :
3550 0 : do_set_pte(vmf, page, addr);
3551 : /* no need to invalidate: a not-present page won't be cached */
3552 : update_mmu_cache(vma, addr, vmf->pte);
3553 0 : if (folio_more_pages(folio, xas.xa_index, end_pgoff)) {
3554 0 : xas.xa_index++;
3555 : folio_ref_inc(folio);
3556 : goto again;
3557 : }
3558 0 : folio_unlock(folio);
3559 0 : continue;
3560 : unlock:
3561 0 : if (folio_more_pages(folio, xas.xa_index, end_pgoff)) {
3562 0 : xas.xa_index++;
3563 0 : goto again;
3564 : }
3565 0 : folio_unlock(folio);
3566 : folio_put(folio);
3567 0 : } while ((folio = next_map_page(mapping, &xas, end_pgoff)) != NULL);
3568 0 : pte_unmap_unlock(vmf->pte, vmf->ptl);
3569 : out:
3570 : rcu_read_unlock();
3571 0 : WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);
3572 0 : return ret;
3573 : }
3574 : EXPORT_SYMBOL(filemap_map_pages);
3575 :
3576 0 : vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3577 : {
3578 0 : struct address_space *mapping = vmf->vma->vm_file->f_mapping;
3579 0 : struct folio *folio = page_folio(vmf->page);
3580 0 : vm_fault_t ret = VM_FAULT_LOCKED;
3581 :
3582 0 : sb_start_pagefault(mapping->host->i_sb);
3583 0 : file_update_time(vmf->vma->vm_file);
3584 0 : folio_lock(folio);
3585 0 : if (folio->mapping != mapping) {
3586 : folio_unlock(folio);
3587 : ret = VM_FAULT_NOPAGE;
3588 : goto out;
3589 : }
3590 : /*
3591 : * We mark the folio dirty already here so that when freeze is in
3592 : * progress, we are guaranteed that writeback during freezing will
3593 : * see the dirty folio and writeprotect it again.
3594 : */
3595 0 : folio_mark_dirty(folio);
3596 0 : folio_wait_stable(folio);
3597 : out:
3598 0 : sb_end_pagefault(mapping->host->i_sb);
3599 0 : return ret;
3600 : }
3601 :
3602 : const struct vm_operations_struct generic_file_vm_ops = {
3603 : .fault = filemap_fault,
3604 : .map_pages = filemap_map_pages,
3605 : .page_mkwrite = filemap_page_mkwrite,
3606 : };
3607 :
3608 : /* This is used for a general mmap of a disk file */
3609 :
3610 0 : int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
3611 : {
3612 0 : struct address_space *mapping = file->f_mapping;
3613 :
3614 0 : if (!mapping->a_ops->read_folio)
3615 : return -ENOEXEC;
3616 0 : file_accessed(file);
3617 0 : vma->vm_ops = &generic_file_vm_ops;
3618 0 : return 0;
3619 : }
3620 :
3621 : /*
3622 : * This is for filesystems which do not implement ->writepage.
3623 : */
3624 0 : int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3625 : {
3626 0 : if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
3627 : return -EINVAL;
3628 : return generic_file_mmap(file, vma);
3629 : }
3630 : #else
3631 : vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
3632 : {
3633 : return VM_FAULT_SIGBUS;
3634 : }
3635 : int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
3636 : {
3637 : return -ENOSYS;
3638 : }
3639 : int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
3640 : {
3641 : return -ENOSYS;
3642 : }
3643 : #endif /* CONFIG_MMU */
3644 :
3645 : EXPORT_SYMBOL(filemap_page_mkwrite);
3646 : EXPORT_SYMBOL(generic_file_mmap);
3647 : EXPORT_SYMBOL(generic_file_readonly_mmap);
3648 :
3649 0 : static struct folio *do_read_cache_folio(struct address_space *mapping,
3650 : pgoff_t index, filler_t filler, struct file *file, gfp_t gfp)
3651 : {
3652 : struct folio *folio;
3653 : int err;
3654 :
3655 0 : if (!filler)
3656 0 : filler = mapping->a_ops->read_folio;
3657 : repeat:
3658 0 : folio = filemap_get_folio(mapping, index);
3659 0 : if (IS_ERR(folio)) {
3660 0 : folio = filemap_alloc_folio(gfp, 0);
3661 0 : if (!folio)
3662 : return ERR_PTR(-ENOMEM);
3663 0 : err = filemap_add_folio(mapping, folio, index, gfp);
3664 0 : if (unlikely(err)) {
3665 0 : folio_put(folio);
3666 0 : if (err == -EEXIST)
3667 : goto repeat;
3668 : /* Presumably ENOMEM for xarray node */
3669 0 : return ERR_PTR(err);
3670 : }
3671 :
3672 : goto filler;
3673 : }
3674 0 : if (folio_test_uptodate(folio))
3675 : goto out;
3676 :
3677 0 : if (!folio_trylock(folio)) {
3678 : folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE);
3679 : goto repeat;
3680 : }
3681 :
3682 : /* Folio was truncated from mapping */
3683 0 : if (!folio->mapping) {
3684 0 : folio_unlock(folio);
3685 : folio_put(folio);
3686 : goto repeat;
3687 : }
3688 :
3689 : /* Someone else locked and filled the page in a very small window */
3690 0 : if (folio_test_uptodate(folio)) {
3691 : folio_unlock(folio);
3692 : goto out;
3693 : }
3694 :
3695 : filler:
3696 0 : err = filemap_read_folio(file, filler, folio);
3697 0 : if (err) {
3698 0 : folio_put(folio);
3699 0 : if (err == AOP_TRUNCATED_PAGE)
3700 : goto repeat;
3701 0 : return ERR_PTR(err);
3702 : }
3703 :
3704 : out:
3705 0 : folio_mark_accessed(folio);
3706 0 : return folio;
3707 : }
3708 :
3709 : /**
3710 : * read_cache_folio - Read into page cache, fill it if needed.
3711 : * @mapping: The address_space to read from.
3712 : * @index: The index to read.
3713 : * @filler: Function to perform the read, or NULL to use aops->read_folio().
3714 : * @file: Passed to filler function, may be NULL if not required.
3715 : *
3716 : * Read one page into the page cache. If it succeeds, the folio returned
3717 : * will contain @index, but it may not be the first page of the folio.
3718 : *
3719 : * If the filler function returns an error, it will be returned to the
3720 : * caller.
3721 : *
3722 : * Context: May sleep. Expects mapping->invalidate_lock to be held.
3723 : * Return: An uptodate folio on success, ERR_PTR() on failure.
3724 : */
3725 0 : struct folio *read_cache_folio(struct address_space *mapping, pgoff_t index,
3726 : filler_t filler, struct file *file)
3727 : {
3728 0 : return do_read_cache_folio(mapping, index, filler, file,
3729 : mapping_gfp_mask(mapping));
3730 : }
3731 : EXPORT_SYMBOL(read_cache_folio);
3732 :
3733 : /**
3734 : * mapping_read_folio_gfp - Read into page cache, using specified allocation flags.
3735 : * @mapping: The address_space for the folio.
3736 : * @index: The index that the allocated folio will contain.
3737 : * @gfp: The page allocator flags to use if allocating.
3738 : *
3739 : * This is the same as "read_cache_folio(mapping, index, NULL, NULL)", but with
3740 : * any new memory allocations done using the specified allocation flags.
3741 : *
3742 : * The most likely error from this function is EIO, but ENOMEM is
3743 : * possible and so is EINTR. If ->read_folio returns another error,
3744 : * that will be returned to the caller.
3745 : *
3746 : * The function expects mapping->invalidate_lock to be already held.
3747 : *
3748 : * Return: Uptodate folio on success, ERR_PTR() on failure.
3749 : */
3750 0 : struct folio *mapping_read_folio_gfp(struct address_space *mapping,
3751 : pgoff_t index, gfp_t gfp)
3752 : {
3753 0 : return do_read_cache_folio(mapping, index, NULL, NULL, gfp);
3754 : }
3755 : EXPORT_SYMBOL(mapping_read_folio_gfp);
3756 :
3757 0 : static struct page *do_read_cache_page(struct address_space *mapping,
3758 : pgoff_t index, filler_t *filler, struct file *file, gfp_t gfp)
3759 : {
3760 : struct folio *folio;
3761 :
3762 0 : folio = do_read_cache_folio(mapping, index, filler, file, gfp);
3763 0 : if (IS_ERR(folio))
3764 0 : return &folio->page;
3765 0 : return folio_file_page(folio, index);
3766 : }
3767 :
3768 0 : struct page *read_cache_page(struct address_space *mapping,
3769 : pgoff_t index, filler_t *filler, struct file *file)
3770 : {
3771 0 : return do_read_cache_page(mapping, index, filler, file,
3772 : mapping_gfp_mask(mapping));
3773 : }
3774 : EXPORT_SYMBOL(read_cache_page);
3775 :
3776 : /**
3777 : * read_cache_page_gfp - read into page cache, using specified page allocation flags.
3778 : * @mapping: the page's address_space
3779 : * @index: the page index
3780 : * @gfp: the page allocator flags to use if allocating
3781 : *
3782 : * This is the same as "read_mapping_page(mapping, index, NULL)", but with
3783 : * any new page allocations done using the specified allocation flags.
3784 : *
3785 : * If the page does not get brought uptodate, return -EIO.
3786 : *
3787 : * The function expects mapping->invalidate_lock to be already held.
3788 : *
3789 : * Return: up to date page on success, ERR_PTR() on failure.
3790 : */
3791 0 : struct page *read_cache_page_gfp(struct address_space *mapping,
3792 : pgoff_t index,
3793 : gfp_t gfp)
3794 : {
3795 0 : return do_read_cache_page(mapping, index, NULL, NULL, gfp);
3796 : }
3797 : EXPORT_SYMBOL(read_cache_page_gfp);
3798 :
3799 : /*
3800 : * Warn about a page cache invalidation failure during a direct I/O write.
3801 : */
3802 0 : static void dio_warn_stale_pagecache(struct file *filp)
3803 : {
3804 : static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
3805 : char pathname[128];
3806 : char *path;
3807 :
3808 0 : errseq_set(&filp->f_mapping->wb_err, -EIO);
3809 0 : if (__ratelimit(&_rs)) {
3810 0 : path = file_path(filp, pathname, sizeof(pathname));
3811 0 : if (IS_ERR(path))
3812 0 : path = "(unknown)";
3813 0 : pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
3814 0 : pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
3815 : current->comm);
3816 : }
3817 0 : }
3818 :
3819 0 : void kiocb_invalidate_post_direct_write(struct kiocb *iocb, size_t count)
3820 : {
3821 0 : struct address_space *mapping = iocb->ki_filp->f_mapping;
3822 :
3823 0 : if (mapping->nrpages &&
3824 0 : invalidate_inode_pages2_range(mapping,
3825 0 : iocb->ki_pos >> PAGE_SHIFT,
3826 0 : (iocb->ki_pos + count - 1) >> PAGE_SHIFT))
3827 0 : dio_warn_stale_pagecache(iocb->ki_filp);
3828 0 : }
3829 :
3830 : ssize_t
3831 0 : generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
3832 : {
3833 0 : struct address_space *mapping = iocb->ki_filp->f_mapping;
3834 0 : size_t write_len = iov_iter_count(from);
3835 : ssize_t written;
3836 :
3837 : /*
3838 : * If a page can not be invalidated, return 0 to fall back
3839 : * to buffered write.
3840 : */
3841 0 : written = kiocb_invalidate_pages(iocb, write_len);
3842 0 : if (written) {
3843 0 : if (written == -EBUSY)
3844 : return 0;
3845 0 : return written;
3846 : }
3847 :
3848 0 : written = mapping->a_ops->direct_IO(iocb, from);
3849 :
3850 : /*
3851 : * Finally, try again to invalidate clean pages which might have been
3852 : * cached by non-direct readahead, or faulted in by get_user_pages()
3853 : * if the source of the write was an mmap'ed region of the file
3854 : * we're writing. Either one is a pretty crazy thing to do,
3855 : * so we don't support it 100%. If this invalidation
3856 : * fails, tough, the write still worked...
3857 : *
3858 : * Most of the time we do not need this since dio_complete() will do
3859 : * the invalidation for us. However there are some file systems that
3860 : * do not end up with dio_complete() being called, so let's not break
3861 : * them by removing it completely.
3862 : *
3863 : * Noticeable example is a blkdev_direct_IO().
3864 : *
3865 : * Skip invalidation for async writes or if mapping has no pages.
3866 : */
3867 0 : if (written > 0) {
3868 0 : struct inode *inode = mapping->host;
3869 0 : loff_t pos = iocb->ki_pos;
3870 :
3871 0 : kiocb_invalidate_post_direct_write(iocb, written);
3872 0 : pos += written;
3873 0 : write_len -= written;
3874 0 : if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
3875 0 : i_size_write(inode, pos);
3876 : mark_inode_dirty(inode);
3877 : }
3878 0 : iocb->ki_pos = pos;
3879 : }
3880 0 : if (written != -EIOCBQUEUED)
3881 0 : iov_iter_revert(from, write_len - iov_iter_count(from));
3882 : return written;
3883 : }
3884 : EXPORT_SYMBOL(generic_file_direct_write);
3885 :
3886 0 : ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
3887 : {
3888 0 : struct file *file = iocb->ki_filp;
3889 0 : loff_t pos = iocb->ki_pos;
3890 0 : struct address_space *mapping = file->f_mapping;
3891 0 : const struct address_space_operations *a_ops = mapping->a_ops;
3892 0 : long status = 0;
3893 0 : ssize_t written = 0;
3894 :
3895 : do {
3896 : struct page *page;
3897 : unsigned long offset; /* Offset into pagecache page */
3898 : unsigned long bytes; /* Bytes to write to page */
3899 : size_t copied; /* Bytes copied from user */
3900 0 : void *fsdata = NULL;
3901 :
3902 0 : offset = (pos & (PAGE_SIZE - 1));
3903 0 : bytes = min_t(unsigned long, PAGE_SIZE - offset,
3904 : iov_iter_count(i));
3905 :
3906 : again:
3907 : /*
3908 : * Bring in the user page that we will copy from _first_.
3909 : * Otherwise there's a nasty deadlock on copying from the
3910 : * same page as we're writing to, without it being marked
3911 : * up-to-date.
3912 : */
3913 0 : if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
3914 : status = -EFAULT;
3915 0 : break;
3916 : }
3917 :
3918 0 : if (fatal_signal_pending(current)) {
3919 : status = -EINTR;
3920 : break;
3921 : }
3922 :
3923 0 : status = a_ops->write_begin(file, mapping, pos, bytes,
3924 : &page, &fsdata);
3925 0 : if (unlikely(status < 0))
3926 : break;
3927 :
3928 0 : if (mapping_writably_mapped(mapping))
3929 : flush_dcache_page(page);
3930 :
3931 0 : copied = copy_page_from_iter_atomic(page, offset, bytes, i);
3932 0 : flush_dcache_page(page);
3933 :
3934 0 : status = a_ops->write_end(file, mapping, pos, bytes, copied,
3935 : page, fsdata);
3936 0 : if (unlikely(status != copied)) {
3937 0 : iov_iter_revert(i, copied - max(status, 0L));
3938 0 : if (unlikely(status < 0))
3939 : break;
3940 : }
3941 0 : cond_resched();
3942 :
3943 0 : if (unlikely(status == 0)) {
3944 : /*
3945 : * A short copy made ->write_end() reject the
3946 : * thing entirely. Might be memory poisoning
3947 : * halfway through, might be a race with munmap,
3948 : * might be severe memory pressure.
3949 : */
3950 0 : if (copied)
3951 0 : bytes = copied;
3952 : goto again;
3953 : }
3954 0 : pos += status;
3955 0 : written += status;
3956 :
3957 0 : balance_dirty_pages_ratelimited(mapping);
3958 0 : } while (iov_iter_count(i));
3959 :
3960 0 : if (!written)
3961 : return status;
3962 0 : iocb->ki_pos += written;
3963 0 : return written;
3964 : }
3965 : EXPORT_SYMBOL(generic_perform_write);
3966 :
3967 : /**
3968 : * __generic_file_write_iter - write data to a file
3969 : * @iocb: IO state structure (file, offset, etc.)
3970 : * @from: iov_iter with data to write
3971 : *
3972 : * This function does all the work needed for actually writing data to a
3973 : * file. It does all basic checks, removes SUID from the file, updates
3974 : * modification times and calls proper subroutines depending on whether we
3975 : * do direct IO or a standard buffered write.
3976 : *
3977 : * It expects i_rwsem to be grabbed unless we work on a block device or similar
3978 : * object which does not need locking at all.
3979 : *
3980 : * This function does *not* take care of syncing data in case of O_SYNC write.
3981 : * A caller has to handle it. This is mainly due to the fact that we want to
3982 : * avoid syncing under i_rwsem.
3983 : *
3984 : * Return:
3985 : * * number of bytes written, even for truncated writes
3986 : * * negative error code if no data has been written at all
3987 : */
3988 0 : ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3989 : {
3990 0 : struct file *file = iocb->ki_filp;
3991 0 : struct address_space *mapping = file->f_mapping;
3992 0 : struct inode *inode = mapping->host;
3993 : ssize_t ret;
3994 :
3995 0 : ret = file_remove_privs(file);
3996 0 : if (ret)
3997 : return ret;
3998 :
3999 0 : ret = file_update_time(file);
4000 0 : if (ret)
4001 : return ret;
4002 :
4003 0 : if (iocb->ki_flags & IOCB_DIRECT) {
4004 0 : ret = generic_file_direct_write(iocb, from);
4005 : /*
4006 : * If the write stopped short of completing, fall back to
4007 : * buffered writes. Some filesystems do this for writes to
4008 : * holes, for example. For DAX files, a buffered write will
4009 : * not succeed (even if it did, DAX does not handle dirty
4010 : * page-cache pages correctly).
4011 : */
4012 0 : if (ret < 0 || !iov_iter_count(from) || IS_DAX(inode))
4013 : return ret;
4014 0 : return direct_write_fallback(iocb, from, ret,
4015 : generic_perform_write(iocb, from));
4016 : }
4017 :
4018 0 : return generic_perform_write(iocb, from);
4019 : }
4020 : EXPORT_SYMBOL(__generic_file_write_iter);
4021 :
4022 : /**
4023 : * generic_file_write_iter - write data to a file
4024 : * @iocb: IO state structure
4025 : * @from: iov_iter with data to write
4026 : *
4027 : * This is a wrapper around __generic_file_write_iter() to be used by most
4028 : * filesystems. It takes care of syncing the file in case of O_SYNC file
4029 : * and acquires i_rwsem as needed.
4030 : * Return:
4031 : * * negative error code if no data has been written at all of
4032 : * vfs_fsync_range() failed for a synchronous write
4033 : * * number of bytes written, even for truncated writes
4034 : */
4035 0 : ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
4036 : {
4037 0 : struct file *file = iocb->ki_filp;
4038 0 : struct inode *inode = file->f_mapping->host;
4039 : ssize_t ret;
4040 :
4041 0 : inode_lock(inode);
4042 0 : ret = generic_write_checks(iocb, from);
4043 0 : if (ret > 0)
4044 0 : ret = __generic_file_write_iter(iocb, from);
4045 0 : inode_unlock(inode);
4046 :
4047 0 : if (ret > 0)
4048 0 : ret = generic_write_sync(iocb, ret);
4049 0 : return ret;
4050 : }
4051 : EXPORT_SYMBOL(generic_file_write_iter);
4052 :
4053 : /**
4054 : * filemap_release_folio() - Release fs-specific metadata on a folio.
4055 : * @folio: The folio which the kernel is trying to free.
4056 : * @gfp: Memory allocation flags (and I/O mode).
4057 : *
4058 : * The address_space is trying to release any data attached to a folio
4059 : * (presumably at folio->private).
4060 : *
4061 : * This will also be called if the private_2 flag is set on a page,
4062 : * indicating that the folio has other metadata associated with it.
4063 : *
4064 : * The @gfp argument specifies whether I/O may be performed to release
4065 : * this page (__GFP_IO), and whether the call may block
4066 : * (__GFP_RECLAIM & __GFP_FS).
4067 : *
4068 : * Return: %true if the release was successful, otherwise %false.
4069 : */
4070 0 : bool filemap_release_folio(struct folio *folio, gfp_t gfp)
4071 : {
4072 0 : struct address_space * const mapping = folio->mapping;
4073 :
4074 0 : BUG_ON(!folio_test_locked(folio));
4075 0 : if (folio_test_writeback(folio))
4076 : return false;
4077 :
4078 0 : if (mapping && mapping->a_ops->release_folio)
4079 0 : return mapping->a_ops->release_folio(folio, gfp);
4080 0 : return try_to_free_buffers(folio);
4081 : }
4082 : EXPORT_SYMBOL(filemap_release_folio);
4083 :
4084 : #ifdef CONFIG_CACHESTAT_SYSCALL
4085 : /**
4086 : * filemap_cachestat() - compute the page cache statistics of a mapping
4087 : * @mapping: The mapping to compute the statistics for.
4088 : * @first_index: The starting page cache index.
4089 : * @last_index: The final page index (inclusive).
4090 : * @cs: the cachestat struct to write the result to.
4091 : *
4092 : * This will query the page cache statistics of a mapping in the
4093 : * page range of [first_index, last_index] (inclusive). The statistics
4094 : * queried include: number of dirty pages, number of pages marked for
4095 : * writeback, and the number of (recently) evicted pages.
4096 : */
4097 0 : static void filemap_cachestat(struct address_space *mapping,
4098 : pgoff_t first_index, pgoff_t last_index, struct cachestat *cs)
4099 : {
4100 0 : XA_STATE(xas, &mapping->i_pages, first_index);
4101 : struct folio *folio;
4102 :
4103 : rcu_read_lock();
4104 0 : xas_for_each(&xas, folio, last_index) {
4105 : unsigned long nr_pages;
4106 : pgoff_t folio_first_index, folio_last_index;
4107 :
4108 0 : if (xas_retry(&xas, folio))
4109 0 : continue;
4110 :
4111 0 : if (xa_is_value(folio)) {
4112 : /* page is evicted */
4113 0 : void *shadow = (void *)folio;
4114 : bool workingset; /* not used */
4115 0 : int order = xa_get_order(xas.xa, xas.xa_index);
4116 :
4117 0 : nr_pages = 1 << order;
4118 0 : folio_first_index = round_down(xas.xa_index, 1 << order);
4119 0 : folio_last_index = folio_first_index + nr_pages - 1;
4120 :
4121 : /* Folios might straddle the range boundaries, only count covered pages */
4122 0 : if (folio_first_index < first_index)
4123 0 : nr_pages -= first_index - folio_first_index;
4124 :
4125 0 : if (folio_last_index > last_index)
4126 0 : nr_pages -= folio_last_index - last_index;
4127 :
4128 0 : cs->nr_evicted += nr_pages;
4129 :
4130 : #ifdef CONFIG_SWAP /* implies CONFIG_MMU */
4131 0 : if (shmem_mapping(mapping)) {
4132 : /* shmem file - in swap cache */
4133 0 : swp_entry_t swp = radix_to_swp_entry(folio);
4134 :
4135 0 : shadow = get_shadow_from_swap_cache(swp);
4136 : }
4137 : #endif
4138 0 : if (workingset_test_recent(shadow, true, &workingset))
4139 0 : cs->nr_recently_evicted += nr_pages;
4140 :
4141 : goto resched;
4142 : }
4143 :
4144 0 : nr_pages = folio_nr_pages(folio);
4145 0 : folio_first_index = folio_pgoff(folio);
4146 0 : folio_last_index = folio_first_index + nr_pages - 1;
4147 :
4148 : /* Folios might straddle the range boundaries, only count covered pages */
4149 0 : if (folio_first_index < first_index)
4150 0 : nr_pages -= first_index - folio_first_index;
4151 :
4152 0 : if (folio_last_index > last_index)
4153 0 : nr_pages -= folio_last_index - last_index;
4154 :
4155 : /* page is in cache */
4156 0 : cs->nr_cache += nr_pages;
4157 :
4158 0 : if (folio_test_dirty(folio))
4159 0 : cs->nr_dirty += nr_pages;
4160 :
4161 0 : if (folio_test_writeback(folio))
4162 0 : cs->nr_writeback += nr_pages;
4163 :
4164 : resched:
4165 0 : if (need_resched()) {
4166 0 : xas_pause(&xas);
4167 : cond_resched_rcu();
4168 : }
4169 : }
4170 : rcu_read_unlock();
4171 0 : }
4172 :
4173 : /*
4174 : * The cachestat(2) system call.
4175 : *
4176 : * cachestat() returns the page cache statistics of a file in the
4177 : * bytes range specified by `off` and `len`: number of cached pages,
4178 : * number of dirty pages, number of pages marked for writeback,
4179 : * number of evicted pages, and number of recently evicted pages.
4180 : *
4181 : * An evicted page is a page that is previously in the page cache
4182 : * but has been evicted since. A page is recently evicted if its last
4183 : * eviction was recent enough that its reentry to the cache would
4184 : * indicate that it is actively being used by the system, and that
4185 : * there is memory pressure on the system.
4186 : *
4187 : * `off` and `len` must be non-negative integers. If `len` > 0,
4188 : * the queried range is [`off`, `off` + `len`]. If `len` == 0,
4189 : * we will query in the range from `off` to the end of the file.
4190 : *
4191 : * The `flags` argument is unused for now, but is included for future
4192 : * extensibility. User should pass 0 (i.e no flag specified).
4193 : *
4194 : * Currently, hugetlbfs is not supported.
4195 : *
4196 : * Because the status of a page can change after cachestat() checks it
4197 : * but before it returns to the application, the returned values may
4198 : * contain stale information.
4199 : *
4200 : * return values:
4201 : * zero - success
4202 : * -EFAULT - cstat or cstat_range points to an illegal address
4203 : * -EINVAL - invalid flags
4204 : * -EBADF - invalid file descriptor
4205 : * -EOPNOTSUPP - file descriptor is of a hugetlbfs file
4206 : */
4207 0 : SYSCALL_DEFINE4(cachestat, unsigned int, fd,
4208 : struct cachestat_range __user *, cstat_range,
4209 : struct cachestat __user *, cstat, unsigned int, flags)
4210 : {
4211 0 : struct fd f = fdget(fd);
4212 : struct address_space *mapping;
4213 : struct cachestat_range csr;
4214 : struct cachestat cs;
4215 : pgoff_t first_index, last_index;
4216 :
4217 0 : if (!f.file)
4218 : return -EBADF;
4219 :
4220 0 : if (copy_from_user(&csr, cstat_range,
4221 : sizeof(struct cachestat_range))) {
4222 0 : fdput(f);
4223 : return -EFAULT;
4224 : }
4225 :
4226 : /* hugetlbfs is not supported */
4227 : if (is_file_hugepages(f.file)) {
4228 : fdput(f);
4229 : return -EOPNOTSUPP;
4230 : }
4231 :
4232 0 : if (flags != 0) {
4233 0 : fdput(f);
4234 : return -EINVAL;
4235 : }
4236 :
4237 0 : first_index = csr.off >> PAGE_SHIFT;
4238 0 : last_index =
4239 0 : csr.len == 0 ? ULONG_MAX : (csr.off + csr.len - 1) >> PAGE_SHIFT;
4240 0 : memset(&cs, 0, sizeof(struct cachestat));
4241 0 : mapping = f.file->f_mapping;
4242 0 : filemap_cachestat(mapping, first_index, last_index, &cs);
4243 0 : fdput(f);
4244 :
4245 0 : if (copy_to_user(cstat, &cs, sizeof(struct cachestat)))
4246 : return -EFAULT;
4247 :
4248 0 : return 0;
4249 : }
4250 : #endif /* CONFIG_CACHESTAT_SYSCALL */
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