1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/fs/buffer.c
4 *
5 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
6 */
7
8 /*
9 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
10 *
11 * Removed a lot of unnecessary code and simplified things now that
12 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
13 *
14 * Speed up hash, lru, and free list operations. Use gfp() for allocating
15 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
16 *
17 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
18 *
19 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
20 */
21
22 #include <linux/kernel.h>
23 #include <linux/sched/signal.h>
24 #include <linux/syscalls.h>
25 #include <linux/fs.h>
26 #include <linux/iomap.h>
27 #include <linux/mm.h>
28 #include <linux/percpu.h>
29 #include <linux/slab.h>
30 #include <linux/capability.h>
31 #include <linux/blkdev.h>
32 #include <linux/file.h>
33 #include <linux/quotaops.h>
34 #include <linux/highmem.h>
35 #include <linux/export.h>
36 #include <linux/backing-dev.h>
37 #include <linux/writeback.h>
38 #include <linux/hash.h>
39 #include <linux/suspend.h>
40 #include <linux/buffer_head.h>
41 #include <linux/task_io_accounting_ops.h>
42 #include <linux/bio.h>
43 #include <linux/cpu.h>
44 #include <linux/bitops.h>
45 #include <linux/mpage.h>
46 #include <linux/bit_spinlock.h>
47 #include <linux/pagevec.h>
48 #include <linux/sched/mm.h>
49 #include <trace/events/block.h>
50 #include <linux/fscrypt.h>
51 #include <linux/fsverity.h>
52 #include <linux/sched/isolation.h>
53
54 #include "internal.h"
55
56 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
57 static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
58 enum rw_hint hint, struct writeback_control *wbc);
59
60 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
61
touch_buffer(struct buffer_head * bh)62 inline void touch_buffer(struct buffer_head *bh)
63 {
64 trace_block_touch_buffer(bh);
65 folio_mark_accessed(bh->b_folio);
66 }
67 EXPORT_SYMBOL(touch_buffer);
68
__lock_buffer(struct buffer_head * bh)69 void __lock_buffer(struct buffer_head *bh)
70 {
71 wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
72 }
73 EXPORT_SYMBOL(__lock_buffer);
74
unlock_buffer(struct buffer_head * bh)75 void unlock_buffer(struct buffer_head *bh)
76 {
77 clear_bit_unlock(BH_Lock, &bh->b_state);
78 smp_mb__after_atomic();
79 wake_up_bit(&bh->b_state, BH_Lock);
80 }
81 EXPORT_SYMBOL(unlock_buffer);
82
83 /*
84 * Returns if the folio has dirty or writeback buffers. If all the buffers
85 * are unlocked and clean then the folio_test_dirty information is stale. If
86 * any of the buffers are locked, it is assumed they are locked for IO.
87 */
buffer_check_dirty_writeback(struct folio * folio,bool * dirty,bool * writeback)88 void buffer_check_dirty_writeback(struct folio *folio,
89 bool *dirty, bool *writeback)
90 {
91 struct buffer_head *head, *bh;
92 *dirty = false;
93 *writeback = false;
94
95 BUG_ON(!folio_test_locked(folio));
96
97 head = folio_buffers(folio);
98 if (!head)
99 return;
100
101 if (folio_test_writeback(folio))
102 *writeback = true;
103
104 bh = head;
105 do {
106 if (buffer_locked(bh))
107 *writeback = true;
108
109 if (buffer_dirty(bh))
110 *dirty = true;
111
112 bh = bh->b_this_page;
113 } while (bh != head);
114 }
115
116 /*
117 * Block until a buffer comes unlocked. This doesn't stop it
118 * from becoming locked again - you have to lock it yourself
119 * if you want to preserve its state.
120 */
__wait_on_buffer(struct buffer_head * bh)121 void __wait_on_buffer(struct buffer_head * bh)
122 {
123 wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
124 }
125 EXPORT_SYMBOL(__wait_on_buffer);
126
buffer_io_error(struct buffer_head * bh,char * msg)127 static void buffer_io_error(struct buffer_head *bh, char *msg)
128 {
129 if (!test_bit(BH_Quiet, &bh->b_state))
130 printk_ratelimited(KERN_ERR
131 "Buffer I/O error on dev %pg, logical block %llu%s\n",
132 bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
133 }
134
135 /*
136 * End-of-IO handler helper function which does not touch the bh after
137 * unlocking it.
138 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
139 * a race there is benign: unlock_buffer() only use the bh's address for
140 * hashing after unlocking the buffer, so it doesn't actually touch the bh
141 * itself.
142 */
__end_buffer_read_notouch(struct buffer_head * bh,int uptodate)143 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
144 {
145 if (uptodate) {
146 set_buffer_uptodate(bh);
147 } else {
148 /* This happens, due to failed read-ahead attempts. */
149 clear_buffer_uptodate(bh);
150 }
151 unlock_buffer(bh);
152 }
153
154 /*
155 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
156 * unlock the buffer.
157 */
end_buffer_read_sync(struct buffer_head * bh,int uptodate)158 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
159 {
160 __end_buffer_read_notouch(bh, uptodate);
161 put_bh(bh);
162 }
163 EXPORT_SYMBOL(end_buffer_read_sync);
164
end_buffer_write_sync(struct buffer_head * bh,int uptodate)165 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
166 {
167 if (uptodate) {
168 set_buffer_uptodate(bh);
169 } else {
170 buffer_io_error(bh, ", lost sync page write");
171 mark_buffer_write_io_error(bh);
172 clear_buffer_uptodate(bh);
173 }
174 unlock_buffer(bh);
175 put_bh(bh);
176 }
177 EXPORT_SYMBOL(end_buffer_write_sync);
178
179 static struct buffer_head *
__find_get_block_slow(struct block_device * bdev,sector_t block,bool atomic)180 __find_get_block_slow(struct block_device *bdev, sector_t block, bool atomic)
181 {
182 struct address_space *bd_mapping = bdev->bd_mapping;
183 const int blkbits = bd_mapping->host->i_blkbits;
184 struct buffer_head *ret = NULL;
185 pgoff_t index;
186 struct buffer_head *bh;
187 struct buffer_head *head;
188 struct folio *folio;
189 int all_mapped = 1;
190 static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
191
192 index = ((loff_t)block << blkbits) / PAGE_SIZE;
193 folio = __filemap_get_folio(bd_mapping, index, FGP_ACCESSED, 0);
194 if (IS_ERR(folio))
195 goto out;
196
197 /*
198 * Folio lock protects the buffers. Callers that cannot block
199 * will fallback to serializing vs try_to_free_buffers() via
200 * the i_private_lock.
201 */
202 if (atomic)
203 spin_lock(&bd_mapping->i_private_lock);
204 else
205 folio_lock(folio);
206
207 head = folio_buffers(folio);
208 if (!head)
209 goto out_unlock;
210 /*
211 * Upon a noref migration, the folio lock serializes here;
212 * otherwise bail.
213 */
214 if (test_bit_acquire(BH_Migrate, &head->b_state)) {
215 WARN_ON(!atomic);
216 goto out_unlock;
217 }
218
219 bh = head;
220 do {
221 if (!buffer_mapped(bh))
222 all_mapped = 0;
223 else if (bh->b_blocknr == block) {
224 ret = bh;
225 get_bh(bh);
226 goto out_unlock;
227 }
228 bh = bh->b_this_page;
229 } while (bh != head);
230
231 /* we might be here because some of the buffers on this page are
232 * not mapped. This is due to various races between
233 * file io on the block device and getblk. It gets dealt with
234 * elsewhere, don't buffer_error if we had some unmapped buffers
235 */
236 ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
237 if (all_mapped && __ratelimit(&last_warned)) {
238 printk("__find_get_block_slow() failed. block=%llu, "
239 "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
240 "device %pg blocksize: %d\n",
241 (unsigned long long)block,
242 (unsigned long long)bh->b_blocknr,
243 bh->b_state, bh->b_size, bdev,
244 1 << blkbits);
245 }
246 out_unlock:
247 if (atomic)
248 spin_unlock(&bd_mapping->i_private_lock);
249 else
250 folio_unlock(folio);
251 folio_put(folio);
252 out:
253 return ret;
254 }
255
end_buffer_async_read(struct buffer_head * bh,int uptodate)256 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
257 {
258 unsigned long flags;
259 struct buffer_head *first;
260 struct buffer_head *tmp;
261 struct folio *folio;
262 int folio_uptodate = 1;
263
264 BUG_ON(!buffer_async_read(bh));
265
266 folio = bh->b_folio;
267 if (uptodate) {
268 set_buffer_uptodate(bh);
269 } else {
270 clear_buffer_uptodate(bh);
271 buffer_io_error(bh, ", async page read");
272 }
273
274 /*
275 * Be _very_ careful from here on. Bad things can happen if
276 * two buffer heads end IO at almost the same time and both
277 * decide that the page is now completely done.
278 */
279 first = folio_buffers(folio);
280 spin_lock_irqsave(&first->b_uptodate_lock, flags);
281 clear_buffer_async_read(bh);
282 unlock_buffer(bh);
283 tmp = bh;
284 do {
285 if (!buffer_uptodate(tmp))
286 folio_uptodate = 0;
287 if (buffer_async_read(tmp)) {
288 BUG_ON(!buffer_locked(tmp));
289 goto still_busy;
290 }
291 tmp = tmp->b_this_page;
292 } while (tmp != bh);
293 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
294
295 folio_end_read(folio, folio_uptodate);
296 return;
297
298 still_busy:
299 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
300 }
301
302 struct postprocess_bh_ctx {
303 struct work_struct work;
304 struct buffer_head *bh;
305 };
306
verify_bh(struct work_struct * work)307 static void verify_bh(struct work_struct *work)
308 {
309 struct postprocess_bh_ctx *ctx =
310 container_of(work, struct postprocess_bh_ctx, work);
311 struct buffer_head *bh = ctx->bh;
312 bool valid;
313
314 valid = fsverity_verify_blocks(bh->b_folio, bh->b_size, bh_offset(bh));
315 end_buffer_async_read(bh, valid);
316 kfree(ctx);
317 }
318
need_fsverity(struct buffer_head * bh)319 static bool need_fsverity(struct buffer_head *bh)
320 {
321 struct folio *folio = bh->b_folio;
322 struct inode *inode = folio->mapping->host;
323
324 return fsverity_active(inode) &&
325 /* needed by ext4 */
326 folio->index < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
327 }
328
decrypt_bh(struct work_struct * work)329 static void decrypt_bh(struct work_struct *work)
330 {
331 struct postprocess_bh_ctx *ctx =
332 container_of(work, struct postprocess_bh_ctx, work);
333 struct buffer_head *bh = ctx->bh;
334 int err;
335
336 err = fscrypt_decrypt_pagecache_blocks(bh->b_folio, bh->b_size,
337 bh_offset(bh));
338 if (err == 0 && need_fsverity(bh)) {
339 /*
340 * We use different work queues for decryption and for verity
341 * because verity may require reading metadata pages that need
342 * decryption, and we shouldn't recurse to the same workqueue.
343 */
344 INIT_WORK(&ctx->work, verify_bh);
345 fsverity_enqueue_verify_work(&ctx->work);
346 return;
347 }
348 end_buffer_async_read(bh, err == 0);
349 kfree(ctx);
350 }
351
352 /*
353 * I/O completion handler for block_read_full_folio() - pages
354 * which come unlocked at the end of I/O.
355 */
end_buffer_async_read_io(struct buffer_head * bh,int uptodate)356 static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
357 {
358 struct inode *inode = bh->b_folio->mapping->host;
359 bool decrypt = fscrypt_inode_uses_fs_layer_crypto(inode);
360 bool verify = need_fsverity(bh);
361
362 /* Decrypt (with fscrypt) and/or verify (with fsverity) if needed. */
363 if (uptodate && (decrypt || verify)) {
364 struct postprocess_bh_ctx *ctx =
365 kmalloc(sizeof(*ctx), GFP_ATOMIC);
366
367 if (ctx) {
368 ctx->bh = bh;
369 if (decrypt) {
370 INIT_WORK(&ctx->work, decrypt_bh);
371 fscrypt_enqueue_decrypt_work(&ctx->work);
372 } else {
373 INIT_WORK(&ctx->work, verify_bh);
374 fsverity_enqueue_verify_work(&ctx->work);
375 }
376 return;
377 }
378 uptodate = 0;
379 }
380 end_buffer_async_read(bh, uptodate);
381 }
382
383 /*
384 * Completion handler for block_write_full_folio() - folios which are unlocked
385 * during I/O, and which have the writeback flag cleared upon I/O completion.
386 */
end_buffer_async_write(struct buffer_head * bh,int uptodate)387 static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
388 {
389 unsigned long flags;
390 struct buffer_head *first;
391 struct buffer_head *tmp;
392 struct folio *folio;
393
394 BUG_ON(!buffer_async_write(bh));
395
396 folio = bh->b_folio;
397 if (uptodate) {
398 set_buffer_uptodate(bh);
399 } else {
400 buffer_io_error(bh, ", lost async page write");
401 mark_buffer_write_io_error(bh);
402 clear_buffer_uptodate(bh);
403 }
404
405 first = folio_buffers(folio);
406 spin_lock_irqsave(&first->b_uptodate_lock, flags);
407
408 clear_buffer_async_write(bh);
409 unlock_buffer(bh);
410 tmp = bh->b_this_page;
411 while (tmp != bh) {
412 if (buffer_async_write(tmp)) {
413 BUG_ON(!buffer_locked(tmp));
414 goto still_busy;
415 }
416 tmp = tmp->b_this_page;
417 }
418 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
419 folio_end_writeback(folio);
420 return;
421
422 still_busy:
423 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
424 }
425
426 /*
427 * If a page's buffers are under async readin (end_buffer_async_read
428 * completion) then there is a possibility that another thread of
429 * control could lock one of the buffers after it has completed
430 * but while some of the other buffers have not completed. This
431 * locked buffer would confuse end_buffer_async_read() into not unlocking
432 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
433 * that this buffer is not under async I/O.
434 *
435 * The page comes unlocked when it has no locked buffer_async buffers
436 * left.
437 *
438 * PageLocked prevents anyone starting new async I/O reads any of
439 * the buffers.
440 *
441 * PageWriteback is used to prevent simultaneous writeout of the same
442 * page.
443 *
444 * PageLocked prevents anyone from starting writeback of a page which is
445 * under read I/O (PageWriteback is only ever set against a locked page).
446 */
mark_buffer_async_read(struct buffer_head * bh)447 static void mark_buffer_async_read(struct buffer_head *bh)
448 {
449 bh->b_end_io = end_buffer_async_read_io;
450 set_buffer_async_read(bh);
451 }
452
mark_buffer_async_write_endio(struct buffer_head * bh,bh_end_io_t * handler)453 static void mark_buffer_async_write_endio(struct buffer_head *bh,
454 bh_end_io_t *handler)
455 {
456 bh->b_end_io = handler;
457 set_buffer_async_write(bh);
458 }
459
mark_buffer_async_write(struct buffer_head * bh)460 void mark_buffer_async_write(struct buffer_head *bh)
461 {
462 mark_buffer_async_write_endio(bh, end_buffer_async_write);
463 }
464 EXPORT_SYMBOL(mark_buffer_async_write);
465
466
467 /*
468 * fs/buffer.c contains helper functions for buffer-backed address space's
469 * fsync functions. A common requirement for buffer-based filesystems is
470 * that certain data from the backing blockdev needs to be written out for
471 * a successful fsync(). For example, ext2 indirect blocks need to be
472 * written back and waited upon before fsync() returns.
473 *
474 * The functions mark_buffer_dirty_inode(), fsync_inode_buffers(),
475 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
476 * management of a list of dependent buffers at ->i_mapping->i_private_list.
477 *
478 * Locking is a little subtle: try_to_free_buffers() will remove buffers
479 * from their controlling inode's queue when they are being freed. But
480 * try_to_free_buffers() will be operating against the *blockdev* mapping
481 * at the time, not against the S_ISREG file which depends on those buffers.
482 * So the locking for i_private_list is via the i_private_lock in the address_space
483 * which backs the buffers. Which is different from the address_space
484 * against which the buffers are listed. So for a particular address_space,
485 * mapping->i_private_lock does *not* protect mapping->i_private_list! In fact,
486 * mapping->i_private_list will always be protected by the backing blockdev's
487 * ->i_private_lock.
488 *
489 * Which introduces a requirement: all buffers on an address_space's
490 * ->i_private_list must be from the same address_space: the blockdev's.
491 *
492 * address_spaces which do not place buffers at ->i_private_list via these
493 * utility functions are free to use i_private_lock and i_private_list for
494 * whatever they want. The only requirement is that list_empty(i_private_list)
495 * be true at clear_inode() time.
496 *
497 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
498 * filesystems should do that. invalidate_inode_buffers() should just go
499 * BUG_ON(!list_empty).
500 *
501 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
502 * take an address_space, not an inode. And it should be called
503 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
504 * queued up.
505 *
506 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
507 * list if it is already on a list. Because if the buffer is on a list,
508 * it *must* already be on the right one. If not, the filesystem is being
509 * silly. This will save a ton of locking. But first we have to ensure
510 * that buffers are taken *off* the old inode's list when they are freed
511 * (presumably in truncate). That requires careful auditing of all
512 * filesystems (do it inside bforget()). It could also be done by bringing
513 * b_inode back.
514 */
515
516 /*
517 * The buffer's backing address_space's i_private_lock must be held
518 */
__remove_assoc_queue(struct buffer_head * bh)519 static void __remove_assoc_queue(struct buffer_head *bh)
520 {
521 list_del_init(&bh->b_assoc_buffers);
522 WARN_ON(!bh->b_assoc_map);
523 bh->b_assoc_map = NULL;
524 }
525
inode_has_buffers(struct inode * inode)526 int inode_has_buffers(struct inode *inode)
527 {
528 return !list_empty(&inode->i_data.i_private_list);
529 }
530
531 /*
532 * osync is designed to support O_SYNC io. It waits synchronously for
533 * all already-submitted IO to complete, but does not queue any new
534 * writes to the disk.
535 *
536 * To do O_SYNC writes, just queue the buffer writes with write_dirty_buffer
537 * as you dirty the buffers, and then use osync_inode_buffers to wait for
538 * completion. Any other dirty buffers which are not yet queued for
539 * write will not be flushed to disk by the osync.
540 */
osync_buffers_list(spinlock_t * lock,struct list_head * list)541 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
542 {
543 struct buffer_head *bh;
544 struct list_head *p;
545 int err = 0;
546
547 spin_lock(lock);
548 repeat:
549 list_for_each_prev(p, list) {
550 bh = BH_ENTRY(p);
551 if (buffer_locked(bh)) {
552 get_bh(bh);
553 spin_unlock(lock);
554 wait_on_buffer(bh);
555 if (!buffer_uptodate(bh))
556 err = -EIO;
557 brelse(bh);
558 spin_lock(lock);
559 goto repeat;
560 }
561 }
562 spin_unlock(lock);
563 return err;
564 }
565
566 /**
567 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
568 * @mapping: the mapping which wants those buffers written
569 *
570 * Starts I/O against the buffers at mapping->i_private_list, and waits upon
571 * that I/O.
572 *
573 * Basically, this is a convenience function for fsync().
574 * @mapping is a file or directory which needs those buffers to be written for
575 * a successful fsync().
576 */
sync_mapping_buffers(struct address_space * mapping)577 int sync_mapping_buffers(struct address_space *mapping)
578 {
579 struct address_space *buffer_mapping = mapping->i_private_data;
580
581 if (buffer_mapping == NULL || list_empty(&mapping->i_private_list))
582 return 0;
583
584 return fsync_buffers_list(&buffer_mapping->i_private_lock,
585 &mapping->i_private_list);
586 }
587 EXPORT_SYMBOL(sync_mapping_buffers);
588
589 /**
590 * generic_buffers_fsync_noflush - generic buffer fsync implementation
591 * for simple filesystems with no inode lock
592 *
593 * @file: file to synchronize
594 * @start: start offset in bytes
595 * @end: end offset in bytes (inclusive)
596 * @datasync: only synchronize essential metadata if true
597 *
598 * This is a generic implementation of the fsync method for simple
599 * filesystems which track all non-inode metadata in the buffers list
600 * hanging off the address_space structure.
601 */
generic_buffers_fsync_noflush(struct file * file,loff_t start,loff_t end,bool datasync)602 int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end,
603 bool datasync)
604 {
605 struct inode *inode = file->f_mapping->host;
606 int err;
607 int ret;
608
609 err = file_write_and_wait_range(file, start, end);
610 if (err)
611 return err;
612
613 ret = sync_mapping_buffers(inode->i_mapping);
614 if (!(inode->i_state & I_DIRTY_ALL))
615 goto out;
616 if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
617 goto out;
618
619 err = sync_inode_metadata(inode, 1);
620 if (ret == 0)
621 ret = err;
622
623 out:
624 /* check and advance again to catch errors after syncing out buffers */
625 err = file_check_and_advance_wb_err(file);
626 if (ret == 0)
627 ret = err;
628 return ret;
629 }
630 EXPORT_SYMBOL(generic_buffers_fsync_noflush);
631
632 /**
633 * generic_buffers_fsync - generic buffer fsync implementation
634 * for simple filesystems with no inode lock
635 *
636 * @file: file to synchronize
637 * @start: start offset in bytes
638 * @end: end offset in bytes (inclusive)
639 * @datasync: only synchronize essential metadata if true
640 *
641 * This is a generic implementation of the fsync method for simple
642 * filesystems which track all non-inode metadata in the buffers list
643 * hanging off the address_space structure. This also makes sure that
644 * a device cache flush operation is called at the end.
645 */
generic_buffers_fsync(struct file * file,loff_t start,loff_t end,bool datasync)646 int generic_buffers_fsync(struct file *file, loff_t start, loff_t end,
647 bool datasync)
648 {
649 struct inode *inode = file->f_mapping->host;
650 int ret;
651
652 ret = generic_buffers_fsync_noflush(file, start, end, datasync);
653 if (!ret)
654 ret = blkdev_issue_flush(inode->i_sb->s_bdev);
655 return ret;
656 }
657 EXPORT_SYMBOL(generic_buffers_fsync);
658
659 /*
660 * Called when we've recently written block `bblock', and it is known that
661 * `bblock' was for a buffer_boundary() buffer. This means that the block at
662 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
663 * dirty, schedule it for IO. So that indirects merge nicely with their data.
664 */
write_boundary_block(struct block_device * bdev,sector_t bblock,unsigned blocksize)665 void write_boundary_block(struct block_device *bdev,
666 sector_t bblock, unsigned blocksize)
667 {
668 struct buffer_head *bh;
669
670 bh = __find_get_block_nonatomic(bdev, bblock + 1, blocksize);
671 if (bh) {
672 if (buffer_dirty(bh))
673 write_dirty_buffer(bh, 0);
674 put_bh(bh);
675 }
676 }
677
mark_buffer_dirty_inode(struct buffer_head * bh,struct inode * inode)678 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
679 {
680 struct address_space *mapping = inode->i_mapping;
681 struct address_space *buffer_mapping = bh->b_folio->mapping;
682
683 mark_buffer_dirty(bh);
684 if (!mapping->i_private_data) {
685 mapping->i_private_data = buffer_mapping;
686 } else {
687 BUG_ON(mapping->i_private_data != buffer_mapping);
688 }
689 if (!bh->b_assoc_map) {
690 spin_lock(&buffer_mapping->i_private_lock);
691 list_move_tail(&bh->b_assoc_buffers,
692 &mapping->i_private_list);
693 bh->b_assoc_map = mapping;
694 spin_unlock(&buffer_mapping->i_private_lock);
695 }
696 }
697 EXPORT_SYMBOL(mark_buffer_dirty_inode);
698
699 /**
700 * block_dirty_folio - Mark a folio as dirty.
701 * @mapping: The address space containing this folio.
702 * @folio: The folio to mark dirty.
703 *
704 * Filesystems which use buffer_heads can use this function as their
705 * ->dirty_folio implementation. Some filesystems need to do a little
706 * work before calling this function. Filesystems which do not use
707 * buffer_heads should call filemap_dirty_folio() instead.
708 *
709 * If the folio has buffers, the uptodate buffers are set dirty, to
710 * preserve dirty-state coherency between the folio and the buffers.
711 * Buffers added to a dirty folio are created dirty.
712 *
713 * The buffers are dirtied before the folio is dirtied. There's a small
714 * race window in which writeback may see the folio cleanness but not the
715 * buffer dirtiness. That's fine. If this code were to set the folio
716 * dirty before the buffers, writeback could clear the folio dirty flag,
717 * see a bunch of clean buffers and we'd end up with dirty buffers/clean
718 * folio on the dirty folio list.
719 *
720 * We use i_private_lock to lock against try_to_free_buffers() while
721 * using the folio's buffer list. This also prevents clean buffers
722 * being added to the folio after it was set dirty.
723 *
724 * Context: May only be called from process context. Does not sleep.
725 * Caller must ensure that @folio cannot be truncated during this call,
726 * typically by holding the folio lock or having a page in the folio
727 * mapped and holding the page table lock.
728 *
729 * Return: True if the folio was dirtied; false if it was already dirtied.
730 */
block_dirty_folio(struct address_space * mapping,struct folio * folio)731 bool block_dirty_folio(struct address_space *mapping, struct folio *folio)
732 {
733 struct buffer_head *head;
734 bool newly_dirty;
735
736 spin_lock(&mapping->i_private_lock);
737 head = folio_buffers(folio);
738 if (head) {
739 struct buffer_head *bh = head;
740
741 do {
742 set_buffer_dirty(bh);
743 bh = bh->b_this_page;
744 } while (bh != head);
745 }
746 /*
747 * Lock out page's memcg migration to keep PageDirty
748 * synchronized with per-memcg dirty page counters.
749 */
750 newly_dirty = !folio_test_set_dirty(folio);
751 spin_unlock(&mapping->i_private_lock);
752
753 if (newly_dirty)
754 __folio_mark_dirty(folio, mapping, 1);
755
756 if (newly_dirty)
757 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
758
759 return newly_dirty;
760 }
761 EXPORT_SYMBOL(block_dirty_folio);
762
763 /*
764 * Write out and wait upon a list of buffers.
765 *
766 * We have conflicting pressures: we want to make sure that all
767 * initially dirty buffers get waited on, but that any subsequently
768 * dirtied buffers don't. After all, we don't want fsync to last
769 * forever if somebody is actively writing to the file.
770 *
771 * Do this in two main stages: first we copy dirty buffers to a
772 * temporary inode list, queueing the writes as we go. Then we clean
773 * up, waiting for those writes to complete.
774 *
775 * During this second stage, any subsequent updates to the file may end
776 * up refiling the buffer on the original inode's dirty list again, so
777 * there is a chance we will end up with a buffer queued for write but
778 * not yet completed on that list. So, as a final cleanup we go through
779 * the osync code to catch these locked, dirty buffers without requeuing
780 * any newly dirty buffers for write.
781 */
fsync_buffers_list(spinlock_t * lock,struct list_head * list)782 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
783 {
784 struct buffer_head *bh;
785 struct address_space *mapping;
786 int err = 0, err2;
787 struct blk_plug plug;
788 LIST_HEAD(tmp);
789
790 blk_start_plug(&plug);
791
792 spin_lock(lock);
793 while (!list_empty(list)) {
794 bh = BH_ENTRY(list->next);
795 mapping = bh->b_assoc_map;
796 __remove_assoc_queue(bh);
797 /* Avoid race with mark_buffer_dirty_inode() which does
798 * a lockless check and we rely on seeing the dirty bit */
799 smp_mb();
800 if (buffer_dirty(bh) || buffer_locked(bh)) {
801 list_add(&bh->b_assoc_buffers, &tmp);
802 bh->b_assoc_map = mapping;
803 if (buffer_dirty(bh)) {
804 get_bh(bh);
805 spin_unlock(lock);
806 /*
807 * Ensure any pending I/O completes so that
808 * write_dirty_buffer() actually writes the
809 * current contents - it is a noop if I/O is
810 * still in flight on potentially older
811 * contents.
812 */
813 write_dirty_buffer(bh, REQ_SYNC);
814
815 /*
816 * Kick off IO for the previous mapping. Note
817 * that we will not run the very last mapping,
818 * wait_on_buffer() will do that for us
819 * through sync_buffer().
820 */
821 brelse(bh);
822 spin_lock(lock);
823 }
824 }
825 }
826
827 spin_unlock(lock);
828 blk_finish_plug(&plug);
829 spin_lock(lock);
830
831 while (!list_empty(&tmp)) {
832 bh = BH_ENTRY(tmp.prev);
833 get_bh(bh);
834 mapping = bh->b_assoc_map;
835 __remove_assoc_queue(bh);
836 /* Avoid race with mark_buffer_dirty_inode() which does
837 * a lockless check and we rely on seeing the dirty bit */
838 smp_mb();
839 if (buffer_dirty(bh)) {
840 list_add(&bh->b_assoc_buffers,
841 &mapping->i_private_list);
842 bh->b_assoc_map = mapping;
843 }
844 spin_unlock(lock);
845 wait_on_buffer(bh);
846 if (!buffer_uptodate(bh))
847 err = -EIO;
848 brelse(bh);
849 spin_lock(lock);
850 }
851
852 spin_unlock(lock);
853 err2 = osync_buffers_list(lock, list);
854 if (err)
855 return err;
856 else
857 return err2;
858 }
859
860 /*
861 * Invalidate any and all dirty buffers on a given inode. We are
862 * probably unmounting the fs, but that doesn't mean we have already
863 * done a sync(). Just drop the buffers from the inode list.
864 *
865 * NOTE: we take the inode's blockdev's mapping's i_private_lock. Which
866 * assumes that all the buffers are against the blockdev.
867 */
invalidate_inode_buffers(struct inode * inode)868 void invalidate_inode_buffers(struct inode *inode)
869 {
870 if (inode_has_buffers(inode)) {
871 struct address_space *mapping = &inode->i_data;
872 struct list_head *list = &mapping->i_private_list;
873 struct address_space *buffer_mapping = mapping->i_private_data;
874
875 spin_lock(&buffer_mapping->i_private_lock);
876 while (!list_empty(list))
877 __remove_assoc_queue(BH_ENTRY(list->next));
878 spin_unlock(&buffer_mapping->i_private_lock);
879 }
880 }
881 EXPORT_SYMBOL(invalidate_inode_buffers);
882
883 /*
884 * Remove any clean buffers from the inode's buffer list. This is called
885 * when we're trying to free the inode itself. Those buffers can pin it.
886 *
887 * Returns true if all buffers were removed.
888 */
remove_inode_buffers(struct inode * inode)889 int remove_inode_buffers(struct inode *inode)
890 {
891 int ret = 1;
892
893 if (inode_has_buffers(inode)) {
894 struct address_space *mapping = &inode->i_data;
895 struct list_head *list = &mapping->i_private_list;
896 struct address_space *buffer_mapping = mapping->i_private_data;
897
898 spin_lock(&buffer_mapping->i_private_lock);
899 while (!list_empty(list)) {
900 struct buffer_head *bh = BH_ENTRY(list->next);
901 if (buffer_dirty(bh)) {
902 ret = 0;
903 break;
904 }
905 __remove_assoc_queue(bh);
906 }
907 spin_unlock(&buffer_mapping->i_private_lock);
908 }
909 return ret;
910 }
911
912 /*
913 * Create the appropriate buffers when given a folio for data area and
914 * the size of each buffer.. Use the bh->b_this_page linked list to
915 * follow the buffers created. Return NULL if unable to create more
916 * buffers.
917 *
918 * The retry flag is used to differentiate async IO (paging, swapping)
919 * which may not fail from ordinary buffer allocations.
920 */
folio_alloc_buffers(struct folio * folio,unsigned long size,gfp_t gfp)921 struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size,
922 gfp_t gfp)
923 {
924 struct buffer_head *bh, *head;
925 long offset;
926 struct mem_cgroup *memcg, *old_memcg;
927
928 /* The folio lock pins the memcg */
929 memcg = folio_memcg(folio);
930 old_memcg = set_active_memcg(memcg);
931
932 head = NULL;
933 offset = folio_size(folio);
934 while ((offset -= size) >= 0) {
935 bh = alloc_buffer_head(gfp);
936 if (!bh)
937 goto no_grow;
938
939 bh->b_this_page = head;
940 bh->b_blocknr = -1;
941 head = bh;
942
943 bh->b_size = size;
944
945 /* Link the buffer to its folio */
946 folio_set_bh(bh, folio, offset);
947 }
948 out:
949 set_active_memcg(old_memcg);
950 return head;
951 /*
952 * In case anything failed, we just free everything we got.
953 */
954 no_grow:
955 if (head) {
956 do {
957 bh = head;
958 head = head->b_this_page;
959 free_buffer_head(bh);
960 } while (head);
961 }
962
963 goto out;
964 }
965 EXPORT_SYMBOL_GPL(folio_alloc_buffers);
966
alloc_page_buffers(struct page * page,unsigned long size)967 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size)
968 {
969 gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
970
971 return folio_alloc_buffers(page_folio(page), size, gfp);
972 }
973 EXPORT_SYMBOL_GPL(alloc_page_buffers);
974
link_dev_buffers(struct folio * folio,struct buffer_head * head)975 static inline void link_dev_buffers(struct folio *folio,
976 struct buffer_head *head)
977 {
978 struct buffer_head *bh, *tail;
979
980 bh = head;
981 do {
982 tail = bh;
983 bh = bh->b_this_page;
984 } while (bh);
985 tail->b_this_page = head;
986 folio_attach_private(folio, head);
987 }
988
blkdev_max_block(struct block_device * bdev,unsigned int size)989 static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
990 {
991 sector_t retval = ~((sector_t)0);
992 loff_t sz = bdev_nr_bytes(bdev);
993
994 if (sz) {
995 unsigned int sizebits = blksize_bits(size);
996 retval = (sz >> sizebits);
997 }
998 return retval;
999 }
1000
1001 /*
1002 * Initialise the state of a blockdev folio's buffers.
1003 */
folio_init_buffers(struct folio * folio,struct block_device * bdev,unsigned size)1004 static sector_t folio_init_buffers(struct folio *folio,
1005 struct block_device *bdev, unsigned size)
1006 {
1007 struct buffer_head *head = folio_buffers(folio);
1008 struct buffer_head *bh = head;
1009 bool uptodate = folio_test_uptodate(folio);
1010 sector_t block = div_u64(folio_pos(folio), size);
1011 sector_t end_block = blkdev_max_block(bdev, size);
1012
1013 do {
1014 if (!buffer_mapped(bh)) {
1015 bh->b_end_io = NULL;
1016 bh->b_private = NULL;
1017 bh->b_bdev = bdev;
1018 bh->b_blocknr = block;
1019 if (uptodate)
1020 set_buffer_uptodate(bh);
1021 if (block < end_block)
1022 set_buffer_mapped(bh);
1023 }
1024 block++;
1025 bh = bh->b_this_page;
1026 } while (bh != head);
1027
1028 /*
1029 * Caller needs to validate requested block against end of device.
1030 */
1031 return end_block;
1032 }
1033
1034 /*
1035 * Create the page-cache folio that contains the requested block.
1036 *
1037 * This is used purely for blockdev mappings.
1038 *
1039 * Returns false if we have a failure which cannot be cured by retrying
1040 * without sleeping. Returns true if we succeeded, or the caller should retry.
1041 */
grow_dev_folio(struct block_device * bdev,sector_t block,pgoff_t index,unsigned size,gfp_t gfp)1042 static bool grow_dev_folio(struct block_device *bdev, sector_t block,
1043 pgoff_t index, unsigned size, gfp_t gfp)
1044 {
1045 struct address_space *mapping = bdev->bd_mapping;
1046 struct folio *folio;
1047 struct buffer_head *bh;
1048 sector_t end_block = 0;
1049
1050 folio = __filemap_get_folio(mapping, index,
1051 FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
1052 if (IS_ERR(folio))
1053 return false;
1054
1055 bh = folio_buffers(folio);
1056 if (bh) {
1057 if (bh->b_size == size) {
1058 end_block = folio_init_buffers(folio, bdev, size);
1059 goto unlock;
1060 }
1061
1062 /*
1063 * Retrying may succeed; for example the folio may finish
1064 * writeback, or buffers may be cleaned. This should not
1065 * happen very often; maybe we have old buffers attached to
1066 * this blockdev's page cache and we're trying to change
1067 * the block size?
1068 */
1069 if (!try_to_free_buffers(folio)) {
1070 end_block = ~0ULL;
1071 goto unlock;
1072 }
1073 }
1074
1075 bh = folio_alloc_buffers(folio, size, gfp | __GFP_ACCOUNT);
1076 if (!bh)
1077 goto unlock;
1078
1079 /*
1080 * Link the folio to the buffers and initialise them. Take the
1081 * lock to be atomic wrt __find_get_block(), which does not
1082 * run under the folio lock.
1083 */
1084 spin_lock(&mapping->i_private_lock);
1085 link_dev_buffers(folio, bh);
1086 end_block = folio_init_buffers(folio, bdev, size);
1087 spin_unlock(&mapping->i_private_lock);
1088 unlock:
1089 folio_unlock(folio);
1090 folio_put(folio);
1091 return block < end_block;
1092 }
1093
1094 /*
1095 * Create buffers for the specified block device block's folio. If
1096 * that folio was dirty, the buffers are set dirty also. Returns false
1097 * if we've hit a permanent error.
1098 */
grow_buffers(struct block_device * bdev,sector_t block,unsigned size,gfp_t gfp)1099 static bool grow_buffers(struct block_device *bdev, sector_t block,
1100 unsigned size, gfp_t gfp)
1101 {
1102 loff_t pos;
1103
1104 /*
1105 * Check for a block which lies outside our maximum possible
1106 * pagecache index.
1107 */
1108 if (check_mul_overflow(block, (sector_t)size, &pos) || pos > MAX_LFS_FILESIZE) {
1109 printk(KERN_ERR "%s: requested out-of-range block %llu for device %pg\n",
1110 __func__, (unsigned long long)block,
1111 bdev);
1112 return false;
1113 }
1114
1115 /* Create a folio with the proper size buffers */
1116 return grow_dev_folio(bdev, block, pos / PAGE_SIZE, size, gfp);
1117 }
1118
1119 static struct buffer_head *
__getblk_slow(struct block_device * bdev,sector_t block,unsigned size,gfp_t gfp)1120 __getblk_slow(struct block_device *bdev, sector_t block,
1121 unsigned size, gfp_t gfp)
1122 {
1123 bool blocking = gfpflags_allow_blocking(gfp);
1124
1125 /* Size must be multiple of hard sectorsize */
1126 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1127 (size < 512 || size > PAGE_SIZE))) {
1128 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1129 size);
1130 printk(KERN_ERR "logical block size: %d\n",
1131 bdev_logical_block_size(bdev));
1132
1133 dump_stack();
1134 return NULL;
1135 }
1136
1137 for (;;) {
1138 struct buffer_head *bh;
1139
1140 if (!grow_buffers(bdev, block, size, gfp))
1141 return NULL;
1142
1143 if (blocking)
1144 bh = __find_get_block_nonatomic(bdev, block, size);
1145 else
1146 bh = __find_get_block(bdev, block, size);
1147 if (bh)
1148 return bh;
1149 }
1150 }
1151
1152 /*
1153 * The relationship between dirty buffers and dirty pages:
1154 *
1155 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1156 * the page is tagged dirty in the page cache.
1157 *
1158 * At all times, the dirtiness of the buffers represents the dirtiness of
1159 * subsections of the page. If the page has buffers, the page dirty bit is
1160 * merely a hint about the true dirty state.
1161 *
1162 * When a page is set dirty in its entirety, all its buffers are marked dirty
1163 * (if the page has buffers).
1164 *
1165 * When a buffer is marked dirty, its page is dirtied, but the page's other
1166 * buffers are not.
1167 *
1168 * Also. When blockdev buffers are explicitly read with bread(), they
1169 * individually become uptodate. But their backing page remains not
1170 * uptodate - even if all of its buffers are uptodate. A subsequent
1171 * block_read_full_folio() against that folio will discover all the uptodate
1172 * buffers, will set the folio uptodate and will perform no I/O.
1173 */
1174
1175 /**
1176 * mark_buffer_dirty - mark a buffer_head as needing writeout
1177 * @bh: the buffer_head to mark dirty
1178 *
1179 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1180 * its backing page dirty, then tag the page as dirty in the page cache
1181 * and then attach the address_space's inode to its superblock's dirty
1182 * inode list.
1183 *
1184 * mark_buffer_dirty() is atomic. It takes bh->b_folio->mapping->i_private_lock,
1185 * i_pages lock and mapping->host->i_lock.
1186 */
mark_buffer_dirty(struct buffer_head * bh)1187 void mark_buffer_dirty(struct buffer_head *bh)
1188 {
1189 WARN_ON_ONCE(!buffer_uptodate(bh));
1190
1191 trace_block_dirty_buffer(bh);
1192
1193 /*
1194 * Very *carefully* optimize the it-is-already-dirty case.
1195 *
1196 * Don't let the final "is it dirty" escape to before we
1197 * perhaps modified the buffer.
1198 */
1199 if (buffer_dirty(bh)) {
1200 smp_mb();
1201 if (buffer_dirty(bh))
1202 return;
1203 }
1204
1205 if (!test_set_buffer_dirty(bh)) {
1206 struct folio *folio = bh->b_folio;
1207 struct address_space *mapping = NULL;
1208
1209 if (!folio_test_set_dirty(folio)) {
1210 mapping = folio->mapping;
1211 if (mapping)
1212 __folio_mark_dirty(folio, mapping, 0);
1213 }
1214 if (mapping)
1215 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1216 }
1217 }
1218 EXPORT_SYMBOL(mark_buffer_dirty);
1219
mark_buffer_write_io_error(struct buffer_head * bh)1220 void mark_buffer_write_io_error(struct buffer_head *bh)
1221 {
1222 set_buffer_write_io_error(bh);
1223 /* FIXME: do we need to set this in both places? */
1224 if (bh->b_folio && bh->b_folio->mapping)
1225 mapping_set_error(bh->b_folio->mapping, -EIO);
1226 if (bh->b_assoc_map)
1227 mapping_set_error(bh->b_assoc_map, -EIO);
1228 }
1229 EXPORT_SYMBOL(mark_buffer_write_io_error);
1230
1231 /**
1232 * __brelse - Release a buffer.
1233 * @bh: The buffer to release.
1234 *
1235 * This variant of brelse() can be called if @bh is guaranteed to not be NULL.
1236 */
__brelse(struct buffer_head * bh)1237 void __brelse(struct buffer_head *bh)
1238 {
1239 if (atomic_read(&bh->b_count)) {
1240 put_bh(bh);
1241 return;
1242 }
1243 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1244 }
1245 EXPORT_SYMBOL(__brelse);
1246
1247 /**
1248 * __bforget - Discard any dirty data in a buffer.
1249 * @bh: The buffer to forget.
1250 *
1251 * This variant of bforget() can be called if @bh is guaranteed to not
1252 * be NULL.
1253 */
__bforget(struct buffer_head * bh)1254 void __bforget(struct buffer_head *bh)
1255 {
1256 clear_buffer_dirty(bh);
1257 if (bh->b_assoc_map) {
1258 struct address_space *buffer_mapping = bh->b_folio->mapping;
1259
1260 spin_lock(&buffer_mapping->i_private_lock);
1261 list_del_init(&bh->b_assoc_buffers);
1262 bh->b_assoc_map = NULL;
1263 spin_unlock(&buffer_mapping->i_private_lock);
1264 }
1265 __brelse(bh);
1266 }
1267 EXPORT_SYMBOL(__bforget);
1268
__bread_slow(struct buffer_head * bh)1269 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1270 {
1271 lock_buffer(bh);
1272 if (buffer_uptodate(bh)) {
1273 unlock_buffer(bh);
1274 return bh;
1275 } else {
1276 get_bh(bh);
1277 bh->b_end_io = end_buffer_read_sync;
1278 submit_bh(REQ_OP_READ, bh);
1279 wait_on_buffer(bh);
1280 if (buffer_uptodate(bh))
1281 return bh;
1282 }
1283 brelse(bh);
1284 return NULL;
1285 }
1286
1287 /*
1288 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1289 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1290 * refcount elevated by one when they're in an LRU. A buffer can only appear
1291 * once in a particular CPU's LRU. A single buffer can be present in multiple
1292 * CPU's LRUs at the same time.
1293 *
1294 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1295 * sb_find_get_block().
1296 *
1297 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1298 * a local interrupt disable for that.
1299 */
1300
1301 #define BH_LRU_SIZE 16
1302
1303 struct bh_lru {
1304 struct buffer_head *bhs[BH_LRU_SIZE];
1305 };
1306
1307 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1308
1309 #ifdef CONFIG_SMP
1310 #define bh_lru_lock() local_irq_disable()
1311 #define bh_lru_unlock() local_irq_enable()
1312 #else
1313 #define bh_lru_lock() preempt_disable()
1314 #define bh_lru_unlock() preempt_enable()
1315 #endif
1316
check_irqs_on(void)1317 static inline void check_irqs_on(void)
1318 {
1319 #ifdef irqs_disabled
1320 BUG_ON(irqs_disabled());
1321 #endif
1322 }
1323
1324 /*
1325 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1326 * inserted at the front, and the buffer_head at the back if any is evicted.
1327 * Or, if already in the LRU it is moved to the front.
1328 */
bh_lru_install(struct buffer_head * bh)1329 static void bh_lru_install(struct buffer_head *bh)
1330 {
1331 struct buffer_head *evictee = bh;
1332 struct bh_lru *b;
1333 int i;
1334
1335 check_irqs_on();
1336 bh_lru_lock();
1337
1338 /*
1339 * the refcount of buffer_head in bh_lru prevents dropping the
1340 * attached page(i.e., try_to_free_buffers) so it could cause
1341 * failing page migration.
1342 * Skip putting upcoming bh into bh_lru until migration is done.
1343 */
1344 if (lru_cache_disabled() || cpu_is_isolated(smp_processor_id())) {
1345 bh_lru_unlock();
1346 return;
1347 }
1348
1349 b = this_cpu_ptr(&bh_lrus);
1350 for (i = 0; i < BH_LRU_SIZE; i++) {
1351 swap(evictee, b->bhs[i]);
1352 if (evictee == bh) {
1353 bh_lru_unlock();
1354 return;
1355 }
1356 }
1357
1358 get_bh(bh);
1359 bh_lru_unlock();
1360 brelse(evictee);
1361 }
1362
1363 /*
1364 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1365 */
1366 static struct buffer_head *
lookup_bh_lru(struct block_device * bdev,sector_t block,unsigned size)1367 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1368 {
1369 struct buffer_head *ret = NULL;
1370 unsigned int i;
1371
1372 check_irqs_on();
1373 bh_lru_lock();
1374 if (cpu_is_isolated(smp_processor_id())) {
1375 bh_lru_unlock();
1376 return NULL;
1377 }
1378 for (i = 0; i < BH_LRU_SIZE; i++) {
1379 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1380
1381 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1382 bh->b_size == size) {
1383 if (i) {
1384 while (i) {
1385 __this_cpu_write(bh_lrus.bhs[i],
1386 __this_cpu_read(bh_lrus.bhs[i - 1]));
1387 i--;
1388 }
1389 __this_cpu_write(bh_lrus.bhs[0], bh);
1390 }
1391 get_bh(bh);
1392 ret = bh;
1393 break;
1394 }
1395 }
1396 bh_lru_unlock();
1397 return ret;
1398 }
1399
1400 /*
1401 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1402 * it in the LRU and mark it as accessed. If it is not present then return
1403 * NULL. Atomic context callers may also return NULL if the buffer is being
1404 * migrated; similarly the page is not marked accessed either.
1405 */
1406 static struct buffer_head *
find_get_block_common(struct block_device * bdev,sector_t block,unsigned size,bool atomic)1407 find_get_block_common(struct block_device *bdev, sector_t block,
1408 unsigned size, bool atomic)
1409 {
1410 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1411
1412 if (bh == NULL) {
1413 /* __find_get_block_slow will mark the page accessed */
1414 bh = __find_get_block_slow(bdev, block, atomic);
1415 if (bh)
1416 bh_lru_install(bh);
1417 } else
1418 touch_buffer(bh);
1419
1420 return bh;
1421 }
1422
1423 struct buffer_head *
__find_get_block(struct block_device * bdev,sector_t block,unsigned size)1424 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1425 {
1426 return find_get_block_common(bdev, block, size, true);
1427 }
1428 EXPORT_SYMBOL(__find_get_block);
1429
1430 /* same as __find_get_block() but allows sleeping contexts */
1431 struct buffer_head *
__find_get_block_nonatomic(struct block_device * bdev,sector_t block,unsigned size)1432 __find_get_block_nonatomic(struct block_device *bdev, sector_t block,
1433 unsigned size)
1434 {
1435 return find_get_block_common(bdev, block, size, false);
1436 }
1437 EXPORT_SYMBOL(__find_get_block_nonatomic);
1438
1439 /**
1440 * bdev_getblk - Get a buffer_head in a block device's buffer cache.
1441 * @bdev: The block device.
1442 * @block: The block number.
1443 * @size: The size of buffer_heads for this @bdev.
1444 * @gfp: The memory allocation flags to use.
1445 *
1446 * The returned buffer head has its reference count incremented, but is
1447 * not locked. The caller should call brelse() when it has finished
1448 * with the buffer. The buffer may not be uptodate. If needed, the
1449 * caller can bring it uptodate either by reading it or overwriting it.
1450 *
1451 * Return: The buffer head, or NULL if memory could not be allocated.
1452 */
bdev_getblk(struct block_device * bdev,sector_t block,unsigned size,gfp_t gfp)1453 struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block,
1454 unsigned size, gfp_t gfp)
1455 {
1456 struct buffer_head *bh;
1457
1458 if (gfpflags_allow_blocking(gfp))
1459 bh = __find_get_block_nonatomic(bdev, block, size);
1460 else
1461 bh = __find_get_block(bdev, block, size);
1462
1463 might_alloc(gfp);
1464 if (bh)
1465 return bh;
1466
1467 return __getblk_slow(bdev, block, size, gfp);
1468 }
1469 EXPORT_SYMBOL(bdev_getblk);
1470
1471 /*
1472 * Do async read-ahead on a buffer..
1473 */
__breadahead(struct block_device * bdev,sector_t block,unsigned size)1474 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1475 {
1476 struct buffer_head *bh = bdev_getblk(bdev, block, size,
1477 GFP_NOWAIT | __GFP_MOVABLE);
1478
1479 if (likely(bh)) {
1480 bh_readahead(bh, REQ_RAHEAD);
1481 brelse(bh);
1482 }
1483 }
1484 EXPORT_SYMBOL(__breadahead);
1485
1486 /**
1487 * __bread_gfp() - Read a block.
1488 * @bdev: The block device to read from.
1489 * @block: Block number in units of block size.
1490 * @size: The block size of this device in bytes.
1491 * @gfp: Not page allocation flags; see below.
1492 *
1493 * You are not expected to call this function. You should use one of
1494 * sb_bread(), sb_bread_unmovable() or __bread().
1495 *
1496 * Read a specified block, and return the buffer head that refers to it.
1497 * If @gfp is 0, the memory will be allocated using the block device's
1498 * default GFP flags. If @gfp is __GFP_MOVABLE, the memory may be
1499 * allocated from a movable area. Do not pass in a complete set of
1500 * GFP flags.
1501 *
1502 * The returned buffer head has its refcount increased. The caller should
1503 * call brelse() when it has finished with the buffer.
1504 *
1505 * Context: May sleep waiting for I/O.
1506 * Return: NULL if the block was unreadable.
1507 */
__bread_gfp(struct block_device * bdev,sector_t block,unsigned size,gfp_t gfp)1508 struct buffer_head *__bread_gfp(struct block_device *bdev, sector_t block,
1509 unsigned size, gfp_t gfp)
1510 {
1511 struct buffer_head *bh;
1512
1513 gfp |= mapping_gfp_constraint(bdev->bd_mapping, ~__GFP_FS);
1514
1515 /*
1516 * Prefer looping in the allocator rather than here, at least that
1517 * code knows what it's doing.
1518 */
1519 gfp |= __GFP_NOFAIL;
1520
1521 bh = bdev_getblk(bdev, block, size, gfp);
1522
1523 if (likely(bh) && !buffer_uptodate(bh))
1524 bh = __bread_slow(bh);
1525 return bh;
1526 }
1527 EXPORT_SYMBOL(__bread_gfp);
1528
__invalidate_bh_lrus(struct bh_lru * b)1529 static void __invalidate_bh_lrus(struct bh_lru *b)
1530 {
1531 int i;
1532
1533 for (i = 0; i < BH_LRU_SIZE; i++) {
1534 brelse(b->bhs[i]);
1535 b->bhs[i] = NULL;
1536 }
1537 }
1538 /*
1539 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1540 * This doesn't race because it runs in each cpu either in irq
1541 * or with preempt disabled.
1542 */
invalidate_bh_lru(void * arg)1543 static void invalidate_bh_lru(void *arg)
1544 {
1545 struct bh_lru *b = &get_cpu_var(bh_lrus);
1546
1547 __invalidate_bh_lrus(b);
1548 put_cpu_var(bh_lrus);
1549 }
1550
has_bh_in_lru(int cpu,void * dummy)1551 bool has_bh_in_lru(int cpu, void *dummy)
1552 {
1553 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1554 int i;
1555
1556 for (i = 0; i < BH_LRU_SIZE; i++) {
1557 if (b->bhs[i])
1558 return true;
1559 }
1560
1561 return false;
1562 }
1563
invalidate_bh_lrus(void)1564 void invalidate_bh_lrus(void)
1565 {
1566 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1);
1567 }
1568 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1569
1570 /*
1571 * It's called from workqueue context so we need a bh_lru_lock to close
1572 * the race with preemption/irq.
1573 */
invalidate_bh_lrus_cpu(void)1574 void invalidate_bh_lrus_cpu(void)
1575 {
1576 struct bh_lru *b;
1577
1578 bh_lru_lock();
1579 b = this_cpu_ptr(&bh_lrus);
1580 __invalidate_bh_lrus(b);
1581 bh_lru_unlock();
1582 }
1583
folio_set_bh(struct buffer_head * bh,struct folio * folio,unsigned long offset)1584 void folio_set_bh(struct buffer_head *bh, struct folio *folio,
1585 unsigned long offset)
1586 {
1587 bh->b_folio = folio;
1588 BUG_ON(offset >= folio_size(folio));
1589 if (folio_test_highmem(folio))
1590 /*
1591 * This catches illegal uses and preserves the offset:
1592 */
1593 bh->b_data = (char *)(0 + offset);
1594 else
1595 bh->b_data = folio_address(folio) + offset;
1596 }
1597 EXPORT_SYMBOL(folio_set_bh);
1598
1599 /*
1600 * Called when truncating a buffer on a page completely.
1601 */
1602
1603 /* Bits that are cleared during an invalidate */
1604 #define BUFFER_FLAGS_DISCARD \
1605 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1606 1 << BH_Delay | 1 << BH_Unwritten)
1607
discard_buffer(struct buffer_head * bh)1608 static void discard_buffer(struct buffer_head * bh)
1609 {
1610 unsigned long b_state;
1611
1612 lock_buffer(bh);
1613 clear_buffer_dirty(bh);
1614 bh->b_bdev = NULL;
1615 b_state = READ_ONCE(bh->b_state);
1616 do {
1617 } while (!try_cmpxchg_relaxed(&bh->b_state, &b_state,
1618 b_state & ~BUFFER_FLAGS_DISCARD));
1619 unlock_buffer(bh);
1620 }
1621
1622 /**
1623 * block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1624 * @folio: The folio which is affected.
1625 * @offset: start of the range to invalidate
1626 * @length: length of the range to invalidate
1627 *
1628 * block_invalidate_folio() is called when all or part of the folio has been
1629 * invalidated by a truncate operation.
1630 *
1631 * block_invalidate_folio() does not have to release all buffers, but it must
1632 * ensure that no dirty buffer is left outside @offset and that no I/O
1633 * is underway against any of the blocks which are outside the truncation
1634 * point. Because the caller is about to free (and possibly reuse) those
1635 * blocks on-disk.
1636 */
block_invalidate_folio(struct folio * folio,size_t offset,size_t length)1637 void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
1638 {
1639 struct buffer_head *head, *bh, *next;
1640 size_t curr_off = 0;
1641 size_t stop = length + offset;
1642
1643 BUG_ON(!folio_test_locked(folio));
1644
1645 /*
1646 * Check for overflow
1647 */
1648 BUG_ON(stop > folio_size(folio) || stop < length);
1649
1650 head = folio_buffers(folio);
1651 if (!head)
1652 return;
1653
1654 bh = head;
1655 do {
1656 size_t next_off = curr_off + bh->b_size;
1657 next = bh->b_this_page;
1658
1659 /*
1660 * Are we still fully in range ?
1661 */
1662 if (next_off > stop)
1663 goto out;
1664
1665 /*
1666 * is this block fully invalidated?
1667 */
1668 if (offset <= curr_off)
1669 discard_buffer(bh);
1670 curr_off = next_off;
1671 bh = next;
1672 } while (bh != head);
1673
1674 /*
1675 * We release buffers only if the entire folio is being invalidated.
1676 * The get_block cached value has been unconditionally invalidated,
1677 * so real IO is not possible anymore.
1678 */
1679 if (length == folio_size(folio))
1680 filemap_release_folio(folio, 0);
1681 out:
1682 folio_clear_mappedtodisk(folio);
1683 }
1684 EXPORT_SYMBOL(block_invalidate_folio);
1685
1686 /*
1687 * We attach and possibly dirty the buffers atomically wrt
1688 * block_dirty_folio() via i_private_lock. try_to_free_buffers
1689 * is already excluded via the folio lock.
1690 */
create_empty_buffers(struct folio * folio,unsigned long blocksize,unsigned long b_state)1691 struct buffer_head *create_empty_buffers(struct folio *folio,
1692 unsigned long blocksize, unsigned long b_state)
1693 {
1694 struct buffer_head *bh, *head, *tail;
1695 gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT | __GFP_NOFAIL;
1696
1697 head = folio_alloc_buffers(folio, blocksize, gfp);
1698 bh = head;
1699 do {
1700 bh->b_state |= b_state;
1701 tail = bh;
1702 bh = bh->b_this_page;
1703 } while (bh);
1704 tail->b_this_page = head;
1705
1706 spin_lock(&folio->mapping->i_private_lock);
1707 if (folio_test_uptodate(folio) || folio_test_dirty(folio)) {
1708 bh = head;
1709 do {
1710 if (folio_test_dirty(folio))
1711 set_buffer_dirty(bh);
1712 if (folio_test_uptodate(folio))
1713 set_buffer_uptodate(bh);
1714 bh = bh->b_this_page;
1715 } while (bh != head);
1716 }
1717 folio_attach_private(folio, head);
1718 spin_unlock(&folio->mapping->i_private_lock);
1719
1720 return head;
1721 }
1722 EXPORT_SYMBOL(create_empty_buffers);
1723
1724 /**
1725 * clean_bdev_aliases: clean a range of buffers in block device
1726 * @bdev: Block device to clean buffers in
1727 * @block: Start of a range of blocks to clean
1728 * @len: Number of blocks to clean
1729 *
1730 * We are taking a range of blocks for data and we don't want writeback of any
1731 * buffer-cache aliases starting from return from this function and until the
1732 * moment when something will explicitly mark the buffer dirty (hopefully that
1733 * will not happen until we will free that block ;-) We don't even need to mark
1734 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1735 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1736 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1737 * would confuse anyone who might pick it with bread() afterwards...
1738 *
1739 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1740 * writeout I/O going on against recently-freed buffers. We don't wait on that
1741 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1742 * need to. That happens here.
1743 */
clean_bdev_aliases(struct block_device * bdev,sector_t block,sector_t len)1744 void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1745 {
1746 struct address_space *bd_mapping = bdev->bd_mapping;
1747 const int blkbits = bd_mapping->host->i_blkbits;
1748 struct folio_batch fbatch;
1749 pgoff_t index = ((loff_t)block << blkbits) / PAGE_SIZE;
1750 pgoff_t end;
1751 int i, count;
1752 struct buffer_head *bh;
1753 struct buffer_head *head;
1754
1755 end = ((loff_t)(block + len - 1) << blkbits) / PAGE_SIZE;
1756 folio_batch_init(&fbatch);
1757 while (filemap_get_folios(bd_mapping, &index, end, &fbatch)) {
1758 count = folio_batch_count(&fbatch);
1759 for (i = 0; i < count; i++) {
1760 struct folio *folio = fbatch.folios[i];
1761
1762 if (!folio_buffers(folio))
1763 continue;
1764 /*
1765 * We use folio lock instead of bd_mapping->i_private_lock
1766 * to pin buffers here since we can afford to sleep and
1767 * it scales better than a global spinlock lock.
1768 */
1769 folio_lock(folio);
1770 /* Recheck when the folio is locked which pins bhs */
1771 head = folio_buffers(folio);
1772 if (!head)
1773 goto unlock_page;
1774 bh = head;
1775 do {
1776 if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1777 goto next;
1778 if (bh->b_blocknr >= block + len)
1779 break;
1780 clear_buffer_dirty(bh);
1781 wait_on_buffer(bh);
1782 clear_buffer_req(bh);
1783 next:
1784 bh = bh->b_this_page;
1785 } while (bh != head);
1786 unlock_page:
1787 folio_unlock(folio);
1788 }
1789 folio_batch_release(&fbatch);
1790 cond_resched();
1791 /* End of range already reached? */
1792 if (index > end || !index)
1793 break;
1794 }
1795 }
1796 EXPORT_SYMBOL(clean_bdev_aliases);
1797
folio_create_buffers(struct folio * folio,struct inode * inode,unsigned int b_state)1798 static struct buffer_head *folio_create_buffers(struct folio *folio,
1799 struct inode *inode,
1800 unsigned int b_state)
1801 {
1802 struct buffer_head *bh;
1803
1804 BUG_ON(!folio_test_locked(folio));
1805
1806 bh = folio_buffers(folio);
1807 if (!bh)
1808 bh = create_empty_buffers(folio,
1809 1 << READ_ONCE(inode->i_blkbits), b_state);
1810 return bh;
1811 }
1812
1813 /*
1814 * NOTE! All mapped/uptodate combinations are valid:
1815 *
1816 * Mapped Uptodate Meaning
1817 *
1818 * No No "unknown" - must do get_block()
1819 * No Yes "hole" - zero-filled
1820 * Yes No "allocated" - allocated on disk, not read in
1821 * Yes Yes "valid" - allocated and up-to-date in memory.
1822 *
1823 * "Dirty" is valid only with the last case (mapped+uptodate).
1824 */
1825
1826 /*
1827 * While block_write_full_folio is writing back the dirty buffers under
1828 * the page lock, whoever dirtied the buffers may decide to clean them
1829 * again at any time. We handle that by only looking at the buffer
1830 * state inside lock_buffer().
1831 *
1832 * If block_write_full_folio() is called for regular writeback
1833 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1834 * locked buffer. This only can happen if someone has written the buffer
1835 * directly, with submit_bh(). At the address_space level PageWriteback
1836 * prevents this contention from occurring.
1837 *
1838 * If block_write_full_folio() is called with wbc->sync_mode ==
1839 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1840 * causes the writes to be flagged as synchronous writes.
1841 */
__block_write_full_folio(struct inode * inode,struct folio * folio,get_block_t * get_block,struct writeback_control * wbc)1842 int __block_write_full_folio(struct inode *inode, struct folio *folio,
1843 get_block_t *get_block, struct writeback_control *wbc)
1844 {
1845 int err;
1846 sector_t block;
1847 sector_t last_block;
1848 struct buffer_head *bh, *head;
1849 size_t blocksize;
1850 int nr_underway = 0;
1851 blk_opf_t write_flags = wbc_to_write_flags(wbc);
1852
1853 head = folio_create_buffers(folio, inode,
1854 (1 << BH_Dirty) | (1 << BH_Uptodate));
1855
1856 /*
1857 * Be very careful. We have no exclusion from block_dirty_folio
1858 * here, and the (potentially unmapped) buffers may become dirty at
1859 * any time. If a buffer becomes dirty here after we've inspected it
1860 * then we just miss that fact, and the folio stays dirty.
1861 *
1862 * Buffers outside i_size may be dirtied by block_dirty_folio;
1863 * handle that here by just cleaning them.
1864 */
1865
1866 bh = head;
1867 blocksize = bh->b_size;
1868
1869 block = div_u64(folio_pos(folio), blocksize);
1870 last_block = div_u64(i_size_read(inode) - 1, blocksize);
1871
1872 /*
1873 * Get all the dirty buffers mapped to disk addresses and
1874 * handle any aliases from the underlying blockdev's mapping.
1875 */
1876 do {
1877 if (block > last_block) {
1878 /*
1879 * mapped buffers outside i_size will occur, because
1880 * this folio can be outside i_size when there is a
1881 * truncate in progress.
1882 */
1883 /*
1884 * The buffer was zeroed by block_write_full_folio()
1885 */
1886 clear_buffer_dirty(bh);
1887 set_buffer_uptodate(bh);
1888 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1889 buffer_dirty(bh)) {
1890 WARN_ON(bh->b_size != blocksize);
1891 err = get_block(inode, block, bh, 1);
1892 if (err)
1893 goto recover;
1894 clear_buffer_delay(bh);
1895 if (buffer_new(bh)) {
1896 /* blockdev mappings never come here */
1897 clear_buffer_new(bh);
1898 clean_bdev_bh_alias(bh);
1899 }
1900 }
1901 bh = bh->b_this_page;
1902 block++;
1903 } while (bh != head);
1904
1905 do {
1906 if (!buffer_mapped(bh))
1907 continue;
1908 /*
1909 * If it's a fully non-blocking write attempt and we cannot
1910 * lock the buffer then redirty the folio. Note that this can
1911 * potentially cause a busy-wait loop from writeback threads
1912 * and kswapd activity, but those code paths have their own
1913 * higher-level throttling.
1914 */
1915 if (wbc->sync_mode != WB_SYNC_NONE) {
1916 lock_buffer(bh);
1917 } else if (!trylock_buffer(bh)) {
1918 folio_redirty_for_writepage(wbc, folio);
1919 continue;
1920 }
1921 if (test_clear_buffer_dirty(bh)) {
1922 mark_buffer_async_write_endio(bh,
1923 end_buffer_async_write);
1924 } else {
1925 unlock_buffer(bh);
1926 }
1927 } while ((bh = bh->b_this_page) != head);
1928
1929 /*
1930 * The folio and its buffers are protected by the writeback flag,
1931 * so we can drop the bh refcounts early.
1932 */
1933 BUG_ON(folio_test_writeback(folio));
1934 folio_start_writeback(folio);
1935
1936 do {
1937 struct buffer_head *next = bh->b_this_page;
1938 if (buffer_async_write(bh)) {
1939 submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
1940 inode->i_write_hint, wbc);
1941 nr_underway++;
1942 }
1943 bh = next;
1944 } while (bh != head);
1945 folio_unlock(folio);
1946
1947 err = 0;
1948 done:
1949 if (nr_underway == 0) {
1950 /*
1951 * The folio was marked dirty, but the buffers were
1952 * clean. Someone wrote them back by hand with
1953 * write_dirty_buffer/submit_bh. A rare case.
1954 */
1955 folio_end_writeback(folio);
1956
1957 /*
1958 * The folio and buffer_heads can be released at any time from
1959 * here on.
1960 */
1961 }
1962 return err;
1963
1964 recover:
1965 /*
1966 * ENOSPC, or some other error. We may already have added some
1967 * blocks to the file, so we need to write these out to avoid
1968 * exposing stale data.
1969 * The folio is currently locked and not marked for writeback
1970 */
1971 bh = head;
1972 /* Recovery: lock and submit the mapped buffers */
1973 do {
1974 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1975 !buffer_delay(bh)) {
1976 lock_buffer(bh);
1977 mark_buffer_async_write_endio(bh,
1978 end_buffer_async_write);
1979 } else {
1980 /*
1981 * The buffer may have been set dirty during
1982 * attachment to a dirty folio.
1983 */
1984 clear_buffer_dirty(bh);
1985 }
1986 } while ((bh = bh->b_this_page) != head);
1987 BUG_ON(folio_test_writeback(folio));
1988 mapping_set_error(folio->mapping, err);
1989 folio_start_writeback(folio);
1990 do {
1991 struct buffer_head *next = bh->b_this_page;
1992 if (buffer_async_write(bh)) {
1993 clear_buffer_dirty(bh);
1994 submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
1995 inode->i_write_hint, wbc);
1996 nr_underway++;
1997 }
1998 bh = next;
1999 } while (bh != head);
2000 folio_unlock(folio);
2001 goto done;
2002 }
2003 EXPORT_SYMBOL(__block_write_full_folio);
2004
2005 /*
2006 * If a folio has any new buffers, zero them out here, and mark them uptodate
2007 * and dirty so they'll be written out (in order to prevent uninitialised
2008 * block data from leaking). And clear the new bit.
2009 */
folio_zero_new_buffers(struct folio * folio,size_t from,size_t to)2010 void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to)
2011 {
2012 size_t block_start, block_end;
2013 struct buffer_head *head, *bh;
2014
2015 BUG_ON(!folio_test_locked(folio));
2016 head = folio_buffers(folio);
2017 if (!head)
2018 return;
2019
2020 bh = head;
2021 block_start = 0;
2022 do {
2023 block_end = block_start + bh->b_size;
2024
2025 if (buffer_new(bh)) {
2026 if (block_end > from && block_start < to) {
2027 if (!folio_test_uptodate(folio)) {
2028 size_t start, xend;
2029
2030 start = max(from, block_start);
2031 xend = min(to, block_end);
2032
2033 folio_zero_segment(folio, start, xend);
2034 set_buffer_uptodate(bh);
2035 }
2036
2037 clear_buffer_new(bh);
2038 mark_buffer_dirty(bh);
2039 }
2040 }
2041
2042 block_start = block_end;
2043 bh = bh->b_this_page;
2044 } while (bh != head);
2045 }
2046 EXPORT_SYMBOL(folio_zero_new_buffers);
2047
2048 static int
iomap_to_bh(struct inode * inode,sector_t block,struct buffer_head * bh,const struct iomap * iomap)2049 iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
2050 const struct iomap *iomap)
2051 {
2052 loff_t offset = (loff_t)block << inode->i_blkbits;
2053
2054 bh->b_bdev = iomap->bdev;
2055
2056 /*
2057 * Block points to offset in file we need to map, iomap contains
2058 * the offset at which the map starts. If the map ends before the
2059 * current block, then do not map the buffer and let the caller
2060 * handle it.
2061 */
2062 if (offset >= iomap->offset + iomap->length)
2063 return -EIO;
2064
2065 switch (iomap->type) {
2066 case IOMAP_HOLE:
2067 /*
2068 * If the buffer is not up to date or beyond the current EOF,
2069 * we need to mark it as new to ensure sub-block zeroing is
2070 * executed if necessary.
2071 */
2072 if (!buffer_uptodate(bh) ||
2073 (offset >= i_size_read(inode)))
2074 set_buffer_new(bh);
2075 return 0;
2076 case IOMAP_DELALLOC:
2077 if (!buffer_uptodate(bh) ||
2078 (offset >= i_size_read(inode)))
2079 set_buffer_new(bh);
2080 set_buffer_uptodate(bh);
2081 set_buffer_mapped(bh);
2082 set_buffer_delay(bh);
2083 return 0;
2084 case IOMAP_UNWRITTEN:
2085 /*
2086 * For unwritten regions, we always need to ensure that regions
2087 * in the block we are not writing to are zeroed. Mark the
2088 * buffer as new to ensure this.
2089 */
2090 set_buffer_new(bh);
2091 set_buffer_unwritten(bh);
2092 fallthrough;
2093 case IOMAP_MAPPED:
2094 if ((iomap->flags & IOMAP_F_NEW) ||
2095 offset >= i_size_read(inode)) {
2096 /*
2097 * This can happen if truncating the block device races
2098 * with the check in the caller as i_size updates on
2099 * block devices aren't synchronized by i_rwsem for
2100 * block devices.
2101 */
2102 if (S_ISBLK(inode->i_mode))
2103 return -EIO;
2104 set_buffer_new(bh);
2105 }
2106 bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
2107 inode->i_blkbits;
2108 set_buffer_mapped(bh);
2109 return 0;
2110 default:
2111 WARN_ON_ONCE(1);
2112 return -EIO;
2113 }
2114 }
2115
__block_write_begin_int(struct folio * folio,loff_t pos,unsigned len,get_block_t * get_block,const struct iomap * iomap)2116 int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
2117 get_block_t *get_block, const struct iomap *iomap)
2118 {
2119 size_t from = offset_in_folio(folio, pos);
2120 size_t to = from + len;
2121 struct inode *inode = folio->mapping->host;
2122 size_t block_start, block_end;
2123 sector_t block;
2124 int err = 0;
2125 size_t blocksize;
2126 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
2127
2128 BUG_ON(!folio_test_locked(folio));
2129 BUG_ON(to > folio_size(folio));
2130 BUG_ON(from > to);
2131
2132 head = folio_create_buffers(folio, inode, 0);
2133 blocksize = head->b_size;
2134 block = div_u64(folio_pos(folio), blocksize);
2135
2136 for (bh = head, block_start = 0; bh != head || !block_start;
2137 block++, block_start=block_end, bh = bh->b_this_page) {
2138 block_end = block_start + blocksize;
2139 if (block_end <= from || block_start >= to) {
2140 if (folio_test_uptodate(folio)) {
2141 if (!buffer_uptodate(bh))
2142 set_buffer_uptodate(bh);
2143 }
2144 continue;
2145 }
2146 if (buffer_new(bh))
2147 clear_buffer_new(bh);
2148 if (!buffer_mapped(bh)) {
2149 WARN_ON(bh->b_size != blocksize);
2150 if (get_block)
2151 err = get_block(inode, block, bh, 1);
2152 else
2153 err = iomap_to_bh(inode, block, bh, iomap);
2154 if (err)
2155 break;
2156
2157 if (buffer_new(bh)) {
2158 clean_bdev_bh_alias(bh);
2159 if (folio_test_uptodate(folio)) {
2160 clear_buffer_new(bh);
2161 set_buffer_uptodate(bh);
2162 mark_buffer_dirty(bh);
2163 continue;
2164 }
2165 if (block_end > to || block_start < from)
2166 folio_zero_segments(folio,
2167 to, block_end,
2168 block_start, from);
2169 continue;
2170 }
2171 }
2172 if (folio_test_uptodate(folio)) {
2173 if (!buffer_uptodate(bh))
2174 set_buffer_uptodate(bh);
2175 continue;
2176 }
2177 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2178 !buffer_unwritten(bh) &&
2179 (block_start < from || block_end > to)) {
2180 bh_read_nowait(bh, 0);
2181 *wait_bh++=bh;
2182 }
2183 }
2184 /*
2185 * If we issued read requests - let them complete.
2186 */
2187 while(wait_bh > wait) {
2188 wait_on_buffer(*--wait_bh);
2189 if (!buffer_uptodate(*wait_bh))
2190 err = -EIO;
2191 }
2192 if (unlikely(err))
2193 folio_zero_new_buffers(folio, from, to);
2194 return err;
2195 }
2196
__block_write_begin(struct folio * folio,loff_t pos,unsigned len,get_block_t * get_block)2197 int __block_write_begin(struct folio *folio, loff_t pos, unsigned len,
2198 get_block_t *get_block)
2199 {
2200 return __block_write_begin_int(folio, pos, len, get_block, NULL);
2201 }
2202 EXPORT_SYMBOL(__block_write_begin);
2203
block_commit_write(struct folio * folio,size_t from,size_t to)2204 void block_commit_write(struct folio *folio, size_t from, size_t to)
2205 {
2206 size_t block_start, block_end;
2207 bool partial = false;
2208 unsigned blocksize;
2209 struct buffer_head *bh, *head;
2210
2211 bh = head = folio_buffers(folio);
2212 if (!bh)
2213 return;
2214 blocksize = bh->b_size;
2215
2216 block_start = 0;
2217 do {
2218 block_end = block_start + blocksize;
2219 if (block_end <= from || block_start >= to) {
2220 if (!buffer_uptodate(bh))
2221 partial = true;
2222 } else {
2223 set_buffer_uptodate(bh);
2224 mark_buffer_dirty(bh);
2225 }
2226 if (buffer_new(bh))
2227 clear_buffer_new(bh);
2228
2229 block_start = block_end;
2230 bh = bh->b_this_page;
2231 } while (bh != head);
2232
2233 /*
2234 * If this is a partial write which happened to make all buffers
2235 * uptodate then we can optimize away a bogus read_folio() for
2236 * the next read(). Here we 'discover' whether the folio went
2237 * uptodate as a result of this (potentially partial) write.
2238 */
2239 if (!partial)
2240 folio_mark_uptodate(folio);
2241 }
2242 EXPORT_SYMBOL(block_commit_write);
2243
2244 /*
2245 * block_write_begin takes care of the basic task of block allocation and
2246 * bringing partial write blocks uptodate first.
2247 *
2248 * The filesystem needs to handle block truncation upon failure.
2249 */
block_write_begin(struct address_space * mapping,loff_t pos,unsigned len,struct folio ** foliop,get_block_t * get_block)2250 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2251 struct folio **foliop, get_block_t *get_block)
2252 {
2253 pgoff_t index = pos >> PAGE_SHIFT;
2254 struct folio *folio;
2255 int status;
2256
2257 folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
2258 mapping_gfp_mask(mapping));
2259 if (IS_ERR(folio))
2260 return PTR_ERR(folio);
2261
2262 status = __block_write_begin_int(folio, pos, len, get_block, NULL);
2263 if (unlikely(status)) {
2264 folio_unlock(folio);
2265 folio_put(folio);
2266 folio = NULL;
2267 }
2268
2269 *foliop = folio;
2270 return status;
2271 }
2272 EXPORT_SYMBOL(block_write_begin);
2273
block_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct folio * folio,void * fsdata)2274 int block_write_end(struct file *file, struct address_space *mapping,
2275 loff_t pos, unsigned len, unsigned copied,
2276 struct folio *folio, void *fsdata)
2277 {
2278 size_t start = pos - folio_pos(folio);
2279
2280 if (unlikely(copied < len)) {
2281 /*
2282 * The buffers that were written will now be uptodate, so
2283 * we don't have to worry about a read_folio reading them
2284 * and overwriting a partial write. However if we have
2285 * encountered a short write and only partially written
2286 * into a buffer, it will not be marked uptodate, so a
2287 * read_folio might come in and destroy our partial write.
2288 *
2289 * Do the simplest thing, and just treat any short write to a
2290 * non uptodate folio as a zero-length write, and force the
2291 * caller to redo the whole thing.
2292 */
2293 if (!folio_test_uptodate(folio))
2294 copied = 0;
2295
2296 folio_zero_new_buffers(folio, start+copied, start+len);
2297 }
2298 flush_dcache_folio(folio);
2299
2300 /* This could be a short (even 0-length) commit */
2301 block_commit_write(folio, start, start + copied);
2302
2303 return copied;
2304 }
2305 EXPORT_SYMBOL(block_write_end);
2306
generic_write_end(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,unsigned copied,struct folio * folio,void * fsdata)2307 int generic_write_end(struct file *file, struct address_space *mapping,
2308 loff_t pos, unsigned len, unsigned copied,
2309 struct folio *folio, void *fsdata)
2310 {
2311 struct inode *inode = mapping->host;
2312 loff_t old_size = inode->i_size;
2313 bool i_size_changed = false;
2314
2315 copied = block_write_end(file, mapping, pos, len, copied, folio, fsdata);
2316
2317 /*
2318 * No need to use i_size_read() here, the i_size cannot change under us
2319 * because we hold i_rwsem.
2320 *
2321 * But it's important to update i_size while still holding folio lock:
2322 * page writeout could otherwise come in and zero beyond i_size.
2323 */
2324 if (pos + copied > inode->i_size) {
2325 i_size_write(inode, pos + copied);
2326 i_size_changed = true;
2327 }
2328
2329 folio_unlock(folio);
2330 folio_put(folio);
2331
2332 if (old_size < pos)
2333 pagecache_isize_extended(inode, old_size, pos);
2334 /*
2335 * Don't mark the inode dirty under page lock. First, it unnecessarily
2336 * makes the holding time of page lock longer. Second, it forces lock
2337 * ordering of page lock and transaction start for journaling
2338 * filesystems.
2339 */
2340 if (i_size_changed)
2341 mark_inode_dirty(inode);
2342 return copied;
2343 }
2344 EXPORT_SYMBOL(generic_write_end);
2345
2346 /*
2347 * block_is_partially_uptodate checks whether buffers within a folio are
2348 * uptodate or not.
2349 *
2350 * Returns true if all buffers which correspond to the specified part
2351 * of the folio are uptodate.
2352 */
block_is_partially_uptodate(struct folio * folio,size_t from,size_t count)2353 bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
2354 {
2355 unsigned block_start, block_end, blocksize;
2356 unsigned to;
2357 struct buffer_head *bh, *head;
2358 bool ret = true;
2359
2360 head = folio_buffers(folio);
2361 if (!head)
2362 return false;
2363 blocksize = head->b_size;
2364 to = min_t(unsigned, folio_size(folio) - from, count);
2365 to = from + to;
2366 if (from < blocksize && to > folio_size(folio) - blocksize)
2367 return false;
2368
2369 bh = head;
2370 block_start = 0;
2371 do {
2372 block_end = block_start + blocksize;
2373 if (block_end > from && block_start < to) {
2374 if (!buffer_uptodate(bh)) {
2375 ret = false;
2376 break;
2377 }
2378 if (block_end >= to)
2379 break;
2380 }
2381 block_start = block_end;
2382 bh = bh->b_this_page;
2383 } while (bh != head);
2384
2385 return ret;
2386 }
2387 EXPORT_SYMBOL(block_is_partially_uptodate);
2388
2389 /*
2390 * Generic "read_folio" function for block devices that have the normal
2391 * get_block functionality. This is most of the block device filesystems.
2392 * Reads the folio asynchronously --- the unlock_buffer() and
2393 * set/clear_buffer_uptodate() functions propagate buffer state into the
2394 * folio once IO has completed.
2395 */
block_read_full_folio(struct folio * folio,get_block_t * get_block)2396 int block_read_full_folio(struct folio *folio, get_block_t *get_block)
2397 {
2398 struct inode *inode = folio->mapping->host;
2399 sector_t iblock, lblock;
2400 struct buffer_head *bh, *head, *prev = NULL;
2401 size_t blocksize;
2402 int fully_mapped = 1;
2403 bool page_error = false;
2404 loff_t limit = i_size_read(inode);
2405
2406 /* This is needed for ext4. */
2407 if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
2408 limit = inode->i_sb->s_maxbytes;
2409
2410 head = folio_create_buffers(folio, inode, 0);
2411 blocksize = head->b_size;
2412
2413 iblock = div_u64(folio_pos(folio), blocksize);
2414 lblock = div_u64(limit + blocksize - 1, blocksize);
2415 bh = head;
2416
2417 do {
2418 if (buffer_uptodate(bh))
2419 continue;
2420
2421 if (!buffer_mapped(bh)) {
2422 int err = 0;
2423
2424 fully_mapped = 0;
2425 if (iblock < lblock) {
2426 WARN_ON(bh->b_size != blocksize);
2427 err = get_block(inode, iblock, bh, 0);
2428 if (err)
2429 page_error = true;
2430 }
2431 if (!buffer_mapped(bh)) {
2432 folio_zero_range(folio, bh_offset(bh),
2433 blocksize);
2434 if (!err)
2435 set_buffer_uptodate(bh);
2436 continue;
2437 }
2438 /*
2439 * get_block() might have updated the buffer
2440 * synchronously
2441 */
2442 if (buffer_uptodate(bh))
2443 continue;
2444 }
2445
2446 lock_buffer(bh);
2447 if (buffer_uptodate(bh)) {
2448 unlock_buffer(bh);
2449 continue;
2450 }
2451
2452 mark_buffer_async_read(bh);
2453 if (prev)
2454 submit_bh(REQ_OP_READ, prev);
2455 prev = bh;
2456 } while (iblock++, (bh = bh->b_this_page) != head);
2457
2458 if (fully_mapped)
2459 folio_set_mappedtodisk(folio);
2460
2461 /*
2462 * All buffers are uptodate or get_block() returned an error
2463 * when trying to map them - we must finish the read because
2464 * end_buffer_async_read() will never be called on any buffer
2465 * in this folio.
2466 */
2467 if (prev)
2468 submit_bh(REQ_OP_READ, prev);
2469 else
2470 folio_end_read(folio, !page_error);
2471
2472 return 0;
2473 }
2474 EXPORT_SYMBOL(block_read_full_folio);
2475
2476 /* utility function for filesystems that need to do work on expanding
2477 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2478 * deal with the hole.
2479 */
generic_cont_expand_simple(struct inode * inode,loff_t size)2480 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2481 {
2482 struct address_space *mapping = inode->i_mapping;
2483 const struct address_space_operations *aops = mapping->a_ops;
2484 struct folio *folio;
2485 void *fsdata = NULL;
2486 int err;
2487
2488 err = inode_newsize_ok(inode, size);
2489 if (err)
2490 goto out;
2491
2492 err = aops->write_begin(NULL, mapping, size, 0, &folio, &fsdata);
2493 if (err)
2494 goto out;
2495
2496 err = aops->write_end(NULL, mapping, size, 0, 0, folio, fsdata);
2497 BUG_ON(err > 0);
2498
2499 out:
2500 return err;
2501 }
2502 EXPORT_SYMBOL(generic_cont_expand_simple);
2503
cont_expand_zero(struct file * file,struct address_space * mapping,loff_t pos,loff_t * bytes)2504 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2505 loff_t pos, loff_t *bytes)
2506 {
2507 struct inode *inode = mapping->host;
2508 const struct address_space_operations *aops = mapping->a_ops;
2509 unsigned int blocksize = i_blocksize(inode);
2510 struct folio *folio;
2511 void *fsdata = NULL;
2512 pgoff_t index, curidx;
2513 loff_t curpos;
2514 unsigned zerofrom, offset, len;
2515 int err = 0;
2516
2517 index = pos >> PAGE_SHIFT;
2518 offset = pos & ~PAGE_MASK;
2519
2520 while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2521 zerofrom = curpos & ~PAGE_MASK;
2522 if (zerofrom & (blocksize-1)) {
2523 *bytes |= (blocksize-1);
2524 (*bytes)++;
2525 }
2526 len = PAGE_SIZE - zerofrom;
2527
2528 err = aops->write_begin(file, mapping, curpos, len,
2529 &folio, &fsdata);
2530 if (err)
2531 goto out;
2532 folio_zero_range(folio, offset_in_folio(folio, curpos), len);
2533 err = aops->write_end(file, mapping, curpos, len, len,
2534 folio, fsdata);
2535 if (err < 0)
2536 goto out;
2537 BUG_ON(err != len);
2538 err = 0;
2539
2540 balance_dirty_pages_ratelimited(mapping);
2541
2542 if (fatal_signal_pending(current)) {
2543 err = -EINTR;
2544 goto out;
2545 }
2546 }
2547
2548 /* page covers the boundary, find the boundary offset */
2549 if (index == curidx) {
2550 zerofrom = curpos & ~PAGE_MASK;
2551 /* if we will expand the thing last block will be filled */
2552 if (offset <= zerofrom) {
2553 goto out;
2554 }
2555 if (zerofrom & (blocksize-1)) {
2556 *bytes |= (blocksize-1);
2557 (*bytes)++;
2558 }
2559 len = offset - zerofrom;
2560
2561 err = aops->write_begin(file, mapping, curpos, len,
2562 &folio, &fsdata);
2563 if (err)
2564 goto out;
2565 folio_zero_range(folio, offset_in_folio(folio, curpos), len);
2566 err = aops->write_end(file, mapping, curpos, len, len,
2567 folio, fsdata);
2568 if (err < 0)
2569 goto out;
2570 BUG_ON(err != len);
2571 err = 0;
2572 }
2573 out:
2574 return err;
2575 }
2576
2577 /*
2578 * For moronic filesystems that do not allow holes in file.
2579 * We may have to extend the file.
2580 */
cont_write_begin(struct file * file,struct address_space * mapping,loff_t pos,unsigned len,struct folio ** foliop,void ** fsdata,get_block_t * get_block,loff_t * bytes)2581 int cont_write_begin(struct file *file, struct address_space *mapping,
2582 loff_t pos, unsigned len,
2583 struct folio **foliop, void **fsdata,
2584 get_block_t *get_block, loff_t *bytes)
2585 {
2586 struct inode *inode = mapping->host;
2587 unsigned int blocksize = i_blocksize(inode);
2588 unsigned int zerofrom;
2589 int err;
2590
2591 err = cont_expand_zero(file, mapping, pos, bytes);
2592 if (err)
2593 return err;
2594
2595 zerofrom = *bytes & ~PAGE_MASK;
2596 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2597 *bytes |= (blocksize-1);
2598 (*bytes)++;
2599 }
2600
2601 return block_write_begin(mapping, pos, len, foliop, get_block);
2602 }
2603 EXPORT_SYMBOL(cont_write_begin);
2604
2605 /*
2606 * block_page_mkwrite() is not allowed to change the file size as it gets
2607 * called from a page fault handler when a page is first dirtied. Hence we must
2608 * be careful to check for EOF conditions here. We set the page up correctly
2609 * for a written page which means we get ENOSPC checking when writing into
2610 * holes and correct delalloc and unwritten extent mapping on filesystems that
2611 * support these features.
2612 *
2613 * We are not allowed to take the i_mutex here so we have to play games to
2614 * protect against truncate races as the page could now be beyond EOF. Because
2615 * truncate writes the inode size before removing pages, once we have the
2616 * page lock we can determine safely if the page is beyond EOF. If it is not
2617 * beyond EOF, then the page is guaranteed safe against truncation until we
2618 * unlock the page.
2619 *
2620 * Direct callers of this function should protect against filesystem freezing
2621 * using sb_start_pagefault() - sb_end_pagefault() functions.
2622 */
block_page_mkwrite(struct vm_area_struct * vma,struct vm_fault * vmf,get_block_t get_block)2623 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2624 get_block_t get_block)
2625 {
2626 struct folio *folio = page_folio(vmf->page);
2627 struct inode *inode = file_inode(vma->vm_file);
2628 unsigned long end;
2629 loff_t size;
2630 int ret;
2631
2632 folio_lock(folio);
2633 size = i_size_read(inode);
2634 if ((folio->mapping != inode->i_mapping) ||
2635 (folio_pos(folio) >= size)) {
2636 /* We overload EFAULT to mean page got truncated */
2637 ret = -EFAULT;
2638 goto out_unlock;
2639 }
2640
2641 end = folio_size(folio);
2642 /* folio is wholly or partially inside EOF */
2643 if (folio_pos(folio) + end > size)
2644 end = size - folio_pos(folio);
2645
2646 ret = __block_write_begin_int(folio, 0, end, get_block, NULL);
2647 if (unlikely(ret))
2648 goto out_unlock;
2649
2650 block_commit_write(folio, 0, end);
2651
2652 folio_mark_dirty(folio);
2653 folio_wait_stable(folio);
2654 return 0;
2655 out_unlock:
2656 folio_unlock(folio);
2657 return ret;
2658 }
2659 EXPORT_SYMBOL(block_page_mkwrite);
2660
block_truncate_page(struct address_space * mapping,loff_t from,get_block_t * get_block)2661 int block_truncate_page(struct address_space *mapping,
2662 loff_t from, get_block_t *get_block)
2663 {
2664 pgoff_t index = from >> PAGE_SHIFT;
2665 unsigned blocksize;
2666 sector_t iblock;
2667 size_t offset, length, pos;
2668 struct inode *inode = mapping->host;
2669 struct folio *folio;
2670 struct buffer_head *bh;
2671 int err = 0;
2672
2673 blocksize = i_blocksize(inode);
2674 length = from & (blocksize - 1);
2675
2676 /* Block boundary? Nothing to do */
2677 if (!length)
2678 return 0;
2679
2680 length = blocksize - length;
2681 iblock = ((loff_t)index * PAGE_SIZE) >> inode->i_blkbits;
2682
2683 folio = filemap_grab_folio(mapping, index);
2684 if (IS_ERR(folio))
2685 return PTR_ERR(folio);
2686
2687 bh = folio_buffers(folio);
2688 if (!bh)
2689 bh = create_empty_buffers(folio, blocksize, 0);
2690
2691 /* Find the buffer that contains "offset" */
2692 offset = offset_in_folio(folio, from);
2693 pos = blocksize;
2694 while (offset >= pos) {
2695 bh = bh->b_this_page;
2696 iblock++;
2697 pos += blocksize;
2698 }
2699
2700 if (!buffer_mapped(bh)) {
2701 WARN_ON(bh->b_size != blocksize);
2702 err = get_block(inode, iblock, bh, 0);
2703 if (err)
2704 goto unlock;
2705 /* unmapped? It's a hole - nothing to do */
2706 if (!buffer_mapped(bh))
2707 goto unlock;
2708 }
2709
2710 /* Ok, it's mapped. Make sure it's up-to-date */
2711 if (folio_test_uptodate(folio))
2712 set_buffer_uptodate(bh);
2713
2714 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2715 err = bh_read(bh, 0);
2716 /* Uhhuh. Read error. Complain and punt. */
2717 if (err < 0)
2718 goto unlock;
2719 }
2720
2721 folio_zero_range(folio, offset, length);
2722 mark_buffer_dirty(bh);
2723
2724 unlock:
2725 folio_unlock(folio);
2726 folio_put(folio);
2727
2728 return err;
2729 }
2730 EXPORT_SYMBOL(block_truncate_page);
2731
2732 /*
2733 * The generic write folio function for buffer-backed address_spaces
2734 */
block_write_full_folio(struct folio * folio,struct writeback_control * wbc,void * get_block)2735 int block_write_full_folio(struct folio *folio, struct writeback_control *wbc,
2736 void *get_block)
2737 {
2738 struct inode * const inode = folio->mapping->host;
2739 loff_t i_size = i_size_read(inode);
2740
2741 /* Is the folio fully inside i_size? */
2742 if (folio_pos(folio) + folio_size(folio) <= i_size)
2743 return __block_write_full_folio(inode, folio, get_block, wbc);
2744
2745 /* Is the folio fully outside i_size? (truncate in progress) */
2746 if (folio_pos(folio) >= i_size) {
2747 folio_unlock(folio);
2748 return 0; /* don't care */
2749 }
2750
2751 /*
2752 * The folio straddles i_size. It must be zeroed out on each and every
2753 * writeback invocation because it may be mmapped. "A file is mapped
2754 * in multiples of the page size. For a file that is not a multiple of
2755 * the page size, the remaining memory is zeroed when mapped, and
2756 * writes to that region are not written out to the file."
2757 */
2758 folio_zero_segment(folio, offset_in_folio(folio, i_size),
2759 folio_size(folio));
2760 return __block_write_full_folio(inode, folio, get_block, wbc);
2761 }
2762
generic_block_bmap(struct address_space * mapping,sector_t block,get_block_t * get_block)2763 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2764 get_block_t *get_block)
2765 {
2766 struct inode *inode = mapping->host;
2767 struct buffer_head tmp = {
2768 .b_size = i_blocksize(inode),
2769 };
2770
2771 get_block(inode, block, &tmp, 0);
2772 return tmp.b_blocknr;
2773 }
2774 EXPORT_SYMBOL(generic_block_bmap);
2775
end_bio_bh_io_sync(struct bio * bio)2776 static void end_bio_bh_io_sync(struct bio *bio)
2777 {
2778 struct buffer_head *bh = bio->bi_private;
2779
2780 if (unlikely(bio_flagged(bio, BIO_QUIET)))
2781 set_bit(BH_Quiet, &bh->b_state);
2782
2783 bh->b_end_io(bh, !bio->bi_status);
2784 bio_put(bio);
2785 }
2786
submit_bh_wbc(blk_opf_t opf,struct buffer_head * bh,enum rw_hint write_hint,struct writeback_control * wbc)2787 static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
2788 enum rw_hint write_hint,
2789 struct writeback_control *wbc)
2790 {
2791 const enum req_op op = opf & REQ_OP_MASK;
2792 struct bio *bio;
2793
2794 BUG_ON(!buffer_locked(bh));
2795 BUG_ON(!buffer_mapped(bh));
2796 BUG_ON(!bh->b_end_io);
2797 BUG_ON(buffer_delay(bh));
2798 BUG_ON(buffer_unwritten(bh));
2799
2800 /*
2801 * Only clear out a write error when rewriting
2802 */
2803 if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
2804 clear_buffer_write_io_error(bh);
2805
2806 if (buffer_meta(bh))
2807 opf |= REQ_META;
2808 if (buffer_prio(bh))
2809 opf |= REQ_PRIO;
2810
2811 bio = bio_alloc(bh->b_bdev, 1, opf, GFP_NOIO);
2812
2813 fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
2814
2815 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2816 bio->bi_write_hint = write_hint;
2817
2818 bio_add_folio_nofail(bio, bh->b_folio, bh->b_size, bh_offset(bh));
2819
2820 bio->bi_end_io = end_bio_bh_io_sync;
2821 bio->bi_private = bh;
2822
2823 /* Take care of bh's that straddle the end of the device */
2824 guard_bio_eod(bio);
2825
2826 if (wbc) {
2827 wbc_init_bio(wbc, bio);
2828 wbc_account_cgroup_owner(wbc, bh->b_folio, bh->b_size);
2829 }
2830
2831 submit_bio(bio);
2832 }
2833
submit_bh(blk_opf_t opf,struct buffer_head * bh)2834 void submit_bh(blk_opf_t opf, struct buffer_head *bh)
2835 {
2836 submit_bh_wbc(opf, bh, WRITE_LIFE_NOT_SET, NULL);
2837 }
2838 EXPORT_SYMBOL(submit_bh);
2839
write_dirty_buffer(struct buffer_head * bh,blk_opf_t op_flags)2840 void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2841 {
2842 lock_buffer(bh);
2843 if (!test_clear_buffer_dirty(bh)) {
2844 unlock_buffer(bh);
2845 return;
2846 }
2847 bh->b_end_io = end_buffer_write_sync;
2848 get_bh(bh);
2849 submit_bh(REQ_OP_WRITE | op_flags, bh);
2850 }
2851 EXPORT_SYMBOL(write_dirty_buffer);
2852
2853 /*
2854 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2855 * and then start new I/O and then wait upon it. The caller must have a ref on
2856 * the buffer_head.
2857 */
__sync_dirty_buffer(struct buffer_head * bh,blk_opf_t op_flags)2858 int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2859 {
2860 WARN_ON(atomic_read(&bh->b_count) < 1);
2861 lock_buffer(bh);
2862 if (test_clear_buffer_dirty(bh)) {
2863 /*
2864 * The bh should be mapped, but it might not be if the
2865 * device was hot-removed. Not much we can do but fail the I/O.
2866 */
2867 if (!buffer_mapped(bh)) {
2868 unlock_buffer(bh);
2869 return -EIO;
2870 }
2871
2872 get_bh(bh);
2873 bh->b_end_io = end_buffer_write_sync;
2874 submit_bh(REQ_OP_WRITE | op_flags, bh);
2875 wait_on_buffer(bh);
2876 if (!buffer_uptodate(bh))
2877 return -EIO;
2878 } else {
2879 unlock_buffer(bh);
2880 }
2881 return 0;
2882 }
2883 EXPORT_SYMBOL(__sync_dirty_buffer);
2884
sync_dirty_buffer(struct buffer_head * bh)2885 int sync_dirty_buffer(struct buffer_head *bh)
2886 {
2887 return __sync_dirty_buffer(bh, REQ_SYNC);
2888 }
2889 EXPORT_SYMBOL(sync_dirty_buffer);
2890
buffer_busy(struct buffer_head * bh)2891 static inline int buffer_busy(struct buffer_head *bh)
2892 {
2893 return atomic_read(&bh->b_count) |
2894 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2895 }
2896
2897 static bool
drop_buffers(struct folio * folio,struct buffer_head ** buffers_to_free)2898 drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
2899 {
2900 struct buffer_head *head = folio_buffers(folio);
2901 struct buffer_head *bh;
2902
2903 bh = head;
2904 do {
2905 if (buffer_busy(bh))
2906 goto failed;
2907 bh = bh->b_this_page;
2908 } while (bh != head);
2909
2910 do {
2911 struct buffer_head *next = bh->b_this_page;
2912
2913 if (bh->b_assoc_map)
2914 __remove_assoc_queue(bh);
2915 bh = next;
2916 } while (bh != head);
2917 *buffers_to_free = head;
2918 folio_detach_private(folio);
2919 return true;
2920 failed:
2921 return false;
2922 }
2923
2924 /**
2925 * try_to_free_buffers - Release buffers attached to this folio.
2926 * @folio: The folio.
2927 *
2928 * If any buffers are in use (dirty, under writeback, elevated refcount),
2929 * no buffers will be freed.
2930 *
2931 * If the folio is dirty but all the buffers are clean then we need to
2932 * be sure to mark the folio clean as well. This is because the folio
2933 * may be against a block device, and a later reattachment of buffers
2934 * to a dirty folio will set *all* buffers dirty. Which would corrupt
2935 * filesystem data on the same device.
2936 *
2937 * The same applies to regular filesystem folios: if all the buffers are
2938 * clean then we set the folio clean and proceed. To do that, we require
2939 * total exclusion from block_dirty_folio(). That is obtained with
2940 * i_private_lock.
2941 *
2942 * Exclusion against try_to_free_buffers may be obtained by either
2943 * locking the folio or by holding its mapping's i_private_lock.
2944 *
2945 * Context: Process context. @folio must be locked. Will not sleep.
2946 * Return: true if all buffers attached to this folio were freed.
2947 */
try_to_free_buffers(struct folio * folio)2948 bool try_to_free_buffers(struct folio *folio)
2949 {
2950 struct address_space * const mapping = folio->mapping;
2951 struct buffer_head *buffers_to_free = NULL;
2952 bool ret = 0;
2953
2954 BUG_ON(!folio_test_locked(folio));
2955 if (folio_test_writeback(folio))
2956 return false;
2957
2958 if (mapping == NULL) { /* can this still happen? */
2959 ret = drop_buffers(folio, &buffers_to_free);
2960 goto out;
2961 }
2962
2963 spin_lock(&mapping->i_private_lock);
2964 ret = drop_buffers(folio, &buffers_to_free);
2965
2966 /*
2967 * If the filesystem writes its buffers by hand (eg ext3)
2968 * then we can have clean buffers against a dirty folio. We
2969 * clean the folio here; otherwise the VM will never notice
2970 * that the filesystem did any IO at all.
2971 *
2972 * Also, during truncate, discard_buffer will have marked all
2973 * the folio's buffers clean. We discover that here and clean
2974 * the folio also.
2975 *
2976 * i_private_lock must be held over this entire operation in order
2977 * to synchronise against block_dirty_folio and prevent the
2978 * dirty bit from being lost.
2979 */
2980 if (ret)
2981 folio_cancel_dirty(folio);
2982 spin_unlock(&mapping->i_private_lock);
2983 out:
2984 if (buffers_to_free) {
2985 struct buffer_head *bh = buffers_to_free;
2986
2987 do {
2988 struct buffer_head *next = bh->b_this_page;
2989 free_buffer_head(bh);
2990 bh = next;
2991 } while (bh != buffers_to_free);
2992 }
2993 return ret;
2994 }
2995 EXPORT_SYMBOL(try_to_free_buffers);
2996
2997 /*
2998 * Buffer-head allocation
2999 */
3000 static struct kmem_cache *bh_cachep __ro_after_init;
3001
3002 /*
3003 * Once the number of bh's in the machine exceeds this level, we start
3004 * stripping them in writeback.
3005 */
3006 static unsigned long max_buffer_heads __ro_after_init;
3007
3008 int buffer_heads_over_limit;
3009
3010 struct bh_accounting {
3011 int nr; /* Number of live bh's */
3012 int ratelimit; /* Limit cacheline bouncing */
3013 };
3014
3015 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3016
recalc_bh_state(void)3017 static void recalc_bh_state(void)
3018 {
3019 int i;
3020 int tot = 0;
3021
3022 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3023 return;
3024 __this_cpu_write(bh_accounting.ratelimit, 0);
3025 for_each_online_cpu(i)
3026 tot += per_cpu(bh_accounting, i).nr;
3027 buffer_heads_over_limit = (tot > max_buffer_heads);
3028 }
3029
alloc_buffer_head(gfp_t gfp_flags)3030 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3031 {
3032 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3033 if (ret) {
3034 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3035 spin_lock_init(&ret->b_uptodate_lock);
3036 preempt_disable();
3037 __this_cpu_inc(bh_accounting.nr);
3038 recalc_bh_state();
3039 preempt_enable();
3040 }
3041 return ret;
3042 }
3043 EXPORT_SYMBOL(alloc_buffer_head);
3044
free_buffer_head(struct buffer_head * bh)3045 void free_buffer_head(struct buffer_head *bh)
3046 {
3047 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3048 kmem_cache_free(bh_cachep, bh);
3049 preempt_disable();
3050 __this_cpu_dec(bh_accounting.nr);
3051 recalc_bh_state();
3052 preempt_enable();
3053 }
3054 EXPORT_SYMBOL(free_buffer_head);
3055
buffer_exit_cpu_dead(unsigned int cpu)3056 static int buffer_exit_cpu_dead(unsigned int cpu)
3057 {
3058 int i;
3059 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3060
3061 for (i = 0; i < BH_LRU_SIZE; i++) {
3062 brelse(b->bhs[i]);
3063 b->bhs[i] = NULL;
3064 }
3065 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3066 per_cpu(bh_accounting, cpu).nr = 0;
3067 return 0;
3068 }
3069
3070 /**
3071 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3072 * @bh: struct buffer_head
3073 *
3074 * Return true if the buffer is up-to-date and false,
3075 * with the buffer locked, if not.
3076 */
bh_uptodate_or_lock(struct buffer_head * bh)3077 int bh_uptodate_or_lock(struct buffer_head *bh)
3078 {
3079 if (!buffer_uptodate(bh)) {
3080 lock_buffer(bh);
3081 if (!buffer_uptodate(bh))
3082 return 0;
3083 unlock_buffer(bh);
3084 }
3085 return 1;
3086 }
3087 EXPORT_SYMBOL(bh_uptodate_or_lock);
3088
3089 /**
3090 * __bh_read - Submit read for a locked buffer
3091 * @bh: struct buffer_head
3092 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3093 * @wait: wait until reading finish
3094 *
3095 * Returns zero on success or don't wait, and -EIO on error.
3096 */
__bh_read(struct buffer_head * bh,blk_opf_t op_flags,bool wait)3097 int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
3098 {
3099 int ret = 0;
3100
3101 BUG_ON(!buffer_locked(bh));
3102
3103 get_bh(bh);
3104 bh->b_end_io = end_buffer_read_sync;
3105 submit_bh(REQ_OP_READ | op_flags, bh);
3106 if (wait) {
3107 wait_on_buffer(bh);
3108 if (!buffer_uptodate(bh))
3109 ret = -EIO;
3110 }
3111 return ret;
3112 }
3113 EXPORT_SYMBOL(__bh_read);
3114
3115 /**
3116 * __bh_read_batch - Submit read for a batch of unlocked buffers
3117 * @nr: entry number of the buffer batch
3118 * @bhs: a batch of struct buffer_head
3119 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3120 * @force_lock: force to get a lock on the buffer if set, otherwise drops any
3121 * buffer that cannot lock.
3122 *
3123 * Returns zero on success or don't wait, and -EIO on error.
3124 */
__bh_read_batch(int nr,struct buffer_head * bhs[],blk_opf_t op_flags,bool force_lock)3125 void __bh_read_batch(int nr, struct buffer_head *bhs[],
3126 blk_opf_t op_flags, bool force_lock)
3127 {
3128 int i;
3129
3130 for (i = 0; i < nr; i++) {
3131 struct buffer_head *bh = bhs[i];
3132
3133 if (buffer_uptodate(bh))
3134 continue;
3135
3136 if (force_lock)
3137 lock_buffer(bh);
3138 else
3139 if (!trylock_buffer(bh))
3140 continue;
3141
3142 if (buffer_uptodate(bh)) {
3143 unlock_buffer(bh);
3144 continue;
3145 }
3146
3147 bh->b_end_io = end_buffer_read_sync;
3148 get_bh(bh);
3149 submit_bh(REQ_OP_READ | op_flags, bh);
3150 }
3151 }
3152 EXPORT_SYMBOL(__bh_read_batch);
3153
buffer_init(void)3154 void __init buffer_init(void)
3155 {
3156 unsigned long nrpages;
3157 int ret;
3158
3159 bh_cachep = KMEM_CACHE(buffer_head,
3160 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC);
3161 /*
3162 * Limit the bh occupancy to 10% of ZONE_NORMAL
3163 */
3164 nrpages = (nr_free_buffer_pages() * 10) / 100;
3165 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3166 ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3167 NULL, buffer_exit_cpu_dead);
3168 WARN_ON(ret < 0);
3169 }
3170