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
56static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
57static 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
62inline void touch_buffer(struct buffer_head *bh)
63{
64 trace_block_touch_buffer(bh);
65 folio_mark_accessed(bh->b_folio);
66}
67EXPORT_SYMBOL(touch_buffer);
68
69void __lock_buffer(struct buffer_head *bh)
70{
71 wait_on_bit_lock_io(word: &bh->b_state, bit: BH_Lock, TASK_UNINTERRUPTIBLE);
72}
73EXPORT_SYMBOL(__lock_buffer);
74
75void unlock_buffer(struct buffer_head *bh)
76{
77 clear_bit_unlock(nr: BH_Lock, addr: &bh->b_state);
78 smp_mb__after_atomic();
79 wake_up_bit(word: &bh->b_state, bit: BH_Lock);
80}
81EXPORT_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 */
88void 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 */
121void __wait_on_buffer(struct buffer_head * bh)
122{
123 wait_on_bit_io(word: &bh->b_state, bit: BH_Lock, TASK_UNINTERRUPTIBLE);
124}
125EXPORT_SYMBOL(__wait_on_buffer);
126
127static 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 */
143static 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 */
158void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
159{
160 put_bh(bh);
161 __end_buffer_read_notouch(bh, uptodate);
162}
163EXPORT_SYMBOL(end_buffer_read_sync);
164
165void 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, msg: ", 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}
177EXPORT_SYMBOL(end_buffer_write_sync);
178
179static struct buffer_head *
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(mapping: bd_mapping, index, FGP_ACCESSED, gfp: 0);
194 if (IS_ERR(ptr: 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(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(rs: &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 }
246out_unlock:
247 if (atomic)
248 spin_unlock(lock: &bd_mapping->i_private_lock);
249 else
250 folio_unlock(folio);
251 folio_put(folio);
252out:
253 return ret;
254}
255
256static 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, msg: ", 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(bh: tmp))
286 folio_uptodate = 0;
287 if (buffer_async_read(bh: 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(lock: &first->b_uptodate_lock, flags);
294
295 folio_end_read(folio, success: folio_uptodate);
296 return;
297
298still_busy:
299 spin_unlock_irqrestore(lock: &first->b_uptodate_lock, flags);
300}
301
302struct postprocess_bh_ctx {
303 struct work_struct work;
304 struct buffer_head *bh;
305};
306
307static 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(folio: bh->b_folio, len: bh->b_size, offset: bh_offset(bh));
315 end_buffer_async_read(bh, uptodate: valid);
316 kfree(objp: ctx);
317}
318
319static 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
329static 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(folio: bh->b_folio, len: bh->b_size,
337 offs: 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(work: &ctx->work);
346 return;
347 }
348 end_buffer_async_read(bh, uptodate: err == 0);
349 kfree(objp: 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 */
356static 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(work: &ctx->work);
372 } else {
373 INIT_WORK(&ctx->work, verify_bh);
374 fsverity_enqueue_verify_work(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 */
387static 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, msg: ", 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(bh: tmp)) {
413 BUG_ON(!buffer_locked(tmp));
414 goto still_busy;
415 }
416 tmp = tmp->b_this_page;
417 }
418 spin_unlock_irqrestore(lock: &first->b_uptodate_lock, flags);
419 folio_end_writeback(folio);
420 return;
421
422still_busy:
423 spin_unlock_irqrestore(lock: &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 */
447static 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
453static 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
460void mark_buffer_async_write(struct buffer_head *bh)
461{
462 mark_buffer_async_write_endio(bh, handler: end_buffer_async_write);
463}
464EXPORT_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 */
519static void __remove_assoc_queue(struct buffer_head *bh)
520{
521 list_del_init(entry: &bh->b_assoc_buffers);
522 WARN_ON(!bh->b_assoc_map);
523 bh->b_assoc_map = NULL;
524}
525
526int inode_has_buffers(struct inode *inode)
527{
528 return !list_empty(head: &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 */
541static 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);
548repeat:
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 */
577int 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(head: &mapping->i_private_list))
582 return 0;
583
584 return fsync_buffers_list(lock: &buffer_mapping->i_private_lock,
585 list: &mapping->i_private_list);
586}
587EXPORT_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 */
602int 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, wait: 1);
620 if (ret == 0)
621 ret = err;
622
623out:
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}
630EXPORT_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 */
646int 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(bdev: inode->i_sb->s_bdev);
655 return ret;
656}
657EXPORT_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 */
665void 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, block: bblock + 1, size: blocksize);
671 if (bh) {
672 if (buffer_dirty(bh))
673 write_dirty_buffer(bh, op_flags: 0);
674 put_bh(bh);
675 }
676}
677
678void 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(lock: &buffer_mapping->i_private_lock);
691 list_move_tail(list: &bh->b_assoc_buffers,
692 head: &mapping->i_private_list);
693 bh->b_assoc_map = mapping;
694 spin_unlock(lock: &buffer_mapping->i_private_lock);
695 }
696}
697EXPORT_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 */
731bool block_dirty_folio(struct address_space *mapping, struct folio *folio)
732{
733 struct buffer_head *head;
734 bool newly_dirty;
735
736 spin_lock(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(lock: &mapping->i_private_lock);
752
753 if (newly_dirty)
754 __folio_mark_dirty(folio, mapping, warn: 1);
755
756 if (newly_dirty)
757 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
758
759 return newly_dirty;
760}
761EXPORT_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 */
782static 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(head: 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(new: &bh->b_assoc_buffers, head: &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(head: &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(new: &bh->b_assoc_buffers,
841 head: &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 */
868void 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(lock: &buffer_mapping->i_private_lock);
876 while (!list_empty(head: list))
877 __remove_assoc_queue(BH_ENTRY(list->next));
878 spin_unlock(lock: &buffer_mapping->i_private_lock);
879 }
880}
881EXPORT_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 */
889int 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(lock: &buffer_mapping->i_private_lock);
899 while (!list_empty(head: 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(lock: &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 */
921struct 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_flags: 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 }
948out:
949 set_active_memcg(old_memcg);
950 return head;
951/*
952 * In case anything failed, we just free everything we got.
953 */
954no_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}
965EXPORT_SYMBOL_GPL(folio_alloc_buffers);
966
967struct 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}
973EXPORT_SYMBOL_GPL(alloc_page_buffers);
974
975static 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, data: head);
987}
988
989static 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 */
1004static 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(dividend: folio_pos(folio), divisor: 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 */
1042static 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(ptr: 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(lock: &mapping->i_private_lock);
1085 link_dev_buffers(folio, head: bh);
1086 end_block = folio_init_buffers(folio, bdev, size);
1087 spin_unlock(lock: &mapping->i_private_lock);
1088unlock:
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 */
1099static 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, index: pos / PAGE_SIZE, size, gfp);
1117}
1118
1119static struct buffer_head *
1120__getblk_slow(struct block_device *bdev, sector_t block,
1121 unsigned size, gfp_t gfp)
1122{
1123 bool blocking = gfpflags_allow_blocking(gfp_flags: gfp);
1124
1125 if (WARN_ON_ONCE(!IS_ALIGNED(size, bdev_logical_block_size(bdev)))) {
1126 printk(KERN_ERR "getblk(): block size %d not aligned to logical block size %d\n",
1127 size, bdev_logical_block_size(bdev));
1128 return NULL;
1129 }
1130
1131 for (;;) {
1132 struct buffer_head *bh;
1133
1134 if (!grow_buffers(bdev, block, size, gfp))
1135 return NULL;
1136
1137 if (blocking)
1138 bh = __find_get_block_nonatomic(bdev, block, size);
1139 else
1140 bh = __find_get_block(bdev, block, size);
1141 if (bh)
1142 return bh;
1143 }
1144}
1145
1146/*
1147 * The relationship between dirty buffers and dirty pages:
1148 *
1149 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1150 * the page is tagged dirty in the page cache.
1151 *
1152 * At all times, the dirtiness of the buffers represents the dirtiness of
1153 * subsections of the page. If the page has buffers, the page dirty bit is
1154 * merely a hint about the true dirty state.
1155 *
1156 * When a page is set dirty in its entirety, all its buffers are marked dirty
1157 * (if the page has buffers).
1158 *
1159 * When a buffer is marked dirty, its page is dirtied, but the page's other
1160 * buffers are not.
1161 *
1162 * Also. When blockdev buffers are explicitly read with bread(), they
1163 * individually become uptodate. But their backing page remains not
1164 * uptodate - even if all of its buffers are uptodate. A subsequent
1165 * block_read_full_folio() against that folio will discover all the uptodate
1166 * buffers, will set the folio uptodate and will perform no I/O.
1167 */
1168
1169/**
1170 * mark_buffer_dirty - mark a buffer_head as needing writeout
1171 * @bh: the buffer_head to mark dirty
1172 *
1173 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1174 * its backing page dirty, then tag the page as dirty in the page cache
1175 * and then attach the address_space's inode to its superblock's dirty
1176 * inode list.
1177 *
1178 * mark_buffer_dirty() is atomic. It takes bh->b_folio->mapping->i_private_lock,
1179 * i_pages lock and mapping->host->i_lock.
1180 */
1181void mark_buffer_dirty(struct buffer_head *bh)
1182{
1183 WARN_ON_ONCE(!buffer_uptodate(bh));
1184
1185 trace_block_dirty_buffer(bh);
1186
1187 /*
1188 * Very *carefully* optimize the it-is-already-dirty case.
1189 *
1190 * Don't let the final "is it dirty" escape to before we
1191 * perhaps modified the buffer.
1192 */
1193 if (buffer_dirty(bh)) {
1194 smp_mb();
1195 if (buffer_dirty(bh))
1196 return;
1197 }
1198
1199 if (!test_set_buffer_dirty(bh)) {
1200 struct folio *folio = bh->b_folio;
1201 struct address_space *mapping = NULL;
1202
1203 if (!folio_test_set_dirty(folio)) {
1204 mapping = folio->mapping;
1205 if (mapping)
1206 __folio_mark_dirty(folio, mapping, warn: 0);
1207 }
1208 if (mapping)
1209 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1210 }
1211}
1212EXPORT_SYMBOL(mark_buffer_dirty);
1213
1214void mark_buffer_write_io_error(struct buffer_head *bh)
1215{
1216 set_buffer_write_io_error(bh);
1217 /* FIXME: do we need to set this in both places? */
1218 if (bh->b_folio && bh->b_folio->mapping)
1219 mapping_set_error(mapping: bh->b_folio->mapping, error: -EIO);
1220 if (bh->b_assoc_map)
1221 mapping_set_error(mapping: bh->b_assoc_map, error: -EIO);
1222}
1223EXPORT_SYMBOL(mark_buffer_write_io_error);
1224
1225/**
1226 * __brelse - Release a buffer.
1227 * @bh: The buffer to release.
1228 *
1229 * This variant of brelse() can be called if @bh is guaranteed to not be NULL.
1230 */
1231void __brelse(struct buffer_head *bh)
1232{
1233 if (atomic_read(v: &bh->b_count)) {
1234 put_bh(bh);
1235 return;
1236 }
1237 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1238}
1239EXPORT_SYMBOL(__brelse);
1240
1241/**
1242 * __bforget - Discard any dirty data in a buffer.
1243 * @bh: The buffer to forget.
1244 *
1245 * This variant of bforget() can be called if @bh is guaranteed to not
1246 * be NULL.
1247 */
1248void __bforget(struct buffer_head *bh)
1249{
1250 clear_buffer_dirty(bh);
1251 if (bh->b_assoc_map) {
1252 struct address_space *buffer_mapping = bh->b_folio->mapping;
1253
1254 spin_lock(lock: &buffer_mapping->i_private_lock);
1255 list_del_init(entry: &bh->b_assoc_buffers);
1256 bh->b_assoc_map = NULL;
1257 spin_unlock(lock: &buffer_mapping->i_private_lock);
1258 }
1259 __brelse(bh);
1260}
1261EXPORT_SYMBOL(__bforget);
1262
1263static struct buffer_head *__bread_slow(struct buffer_head *bh)
1264{
1265 lock_buffer(bh);
1266 if (buffer_uptodate(bh)) {
1267 unlock_buffer(bh);
1268 return bh;
1269 } else {
1270 get_bh(bh);
1271 bh->b_end_io = end_buffer_read_sync;
1272 submit_bh(REQ_OP_READ, bh);
1273 wait_on_buffer(bh);
1274 if (buffer_uptodate(bh))
1275 return bh;
1276 }
1277 brelse(bh);
1278 return NULL;
1279}
1280
1281/*
1282 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1283 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1284 * refcount elevated by one when they're in an LRU. A buffer can only appear
1285 * once in a particular CPU's LRU. A single buffer can be present in multiple
1286 * CPU's LRUs at the same time.
1287 *
1288 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1289 * sb_find_get_block().
1290 *
1291 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1292 * a local interrupt disable for that.
1293 */
1294
1295#define BH_LRU_SIZE 16
1296
1297struct bh_lru {
1298 struct buffer_head *bhs[BH_LRU_SIZE];
1299};
1300
1301static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1302
1303#ifdef CONFIG_SMP
1304#define bh_lru_lock() local_irq_disable()
1305#define bh_lru_unlock() local_irq_enable()
1306#else
1307#define bh_lru_lock() preempt_disable()
1308#define bh_lru_unlock() preempt_enable()
1309#endif
1310
1311static inline void check_irqs_on(void)
1312{
1313#ifdef irqs_disabled
1314 BUG_ON(irqs_disabled());
1315#endif
1316}
1317
1318/*
1319 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1320 * inserted at the front, and the buffer_head at the back if any is evicted.
1321 * Or, if already in the LRU it is moved to the front.
1322 */
1323static void bh_lru_install(struct buffer_head *bh)
1324{
1325 struct buffer_head *evictee = bh;
1326 struct bh_lru *b;
1327 int i;
1328
1329 check_irqs_on();
1330 bh_lru_lock();
1331
1332 /*
1333 * the refcount of buffer_head in bh_lru prevents dropping the
1334 * attached page(i.e., try_to_free_buffers) so it could cause
1335 * failing page migration.
1336 * Skip putting upcoming bh into bh_lru until migration is done.
1337 */
1338 if (lru_cache_disabled() || cpu_is_isolated(smp_processor_id())) {
1339 bh_lru_unlock();
1340 return;
1341 }
1342
1343 b = this_cpu_ptr(&bh_lrus);
1344 for (i = 0; i < BH_LRU_SIZE; i++) {
1345 swap(evictee, b->bhs[i]);
1346 if (evictee == bh) {
1347 bh_lru_unlock();
1348 return;
1349 }
1350 }
1351
1352 get_bh(bh);
1353 bh_lru_unlock();
1354 brelse(bh: evictee);
1355}
1356
1357/*
1358 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1359 */
1360static struct buffer_head *
1361lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1362{
1363 struct buffer_head *ret = NULL;
1364 unsigned int i;
1365
1366 check_irqs_on();
1367 bh_lru_lock();
1368 if (cpu_is_isolated(smp_processor_id())) {
1369 bh_lru_unlock();
1370 return NULL;
1371 }
1372 for (i = 0; i < BH_LRU_SIZE; i++) {
1373 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1374
1375 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1376 bh->b_size == size) {
1377 if (i) {
1378 while (i) {
1379 __this_cpu_write(bh_lrus.bhs[i],
1380 __this_cpu_read(bh_lrus.bhs[i - 1]));
1381 i--;
1382 }
1383 __this_cpu_write(bh_lrus.bhs[0], bh);
1384 }
1385 get_bh(bh);
1386 ret = bh;
1387 break;
1388 }
1389 }
1390 bh_lru_unlock();
1391 return ret;
1392}
1393
1394/*
1395 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1396 * it in the LRU and mark it as accessed. If it is not present then return
1397 * NULL. Atomic context callers may also return NULL if the buffer is being
1398 * migrated; similarly the page is not marked accessed either.
1399 */
1400static struct buffer_head *
1401find_get_block_common(struct block_device *bdev, sector_t block,
1402 unsigned size, bool atomic)
1403{
1404 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1405
1406 if (bh == NULL) {
1407 /* __find_get_block_slow will mark the page accessed */
1408 bh = __find_get_block_slow(bdev, block, atomic);
1409 if (bh)
1410 bh_lru_install(bh);
1411 } else
1412 touch_buffer(bh);
1413
1414 return bh;
1415}
1416
1417struct buffer_head *
1418__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1419{
1420 return find_get_block_common(bdev, block, size, atomic: true);
1421}
1422EXPORT_SYMBOL(__find_get_block);
1423
1424/* same as __find_get_block() but allows sleeping contexts */
1425struct buffer_head *
1426__find_get_block_nonatomic(struct block_device *bdev, sector_t block,
1427 unsigned size)
1428{
1429 return find_get_block_common(bdev, block, size, atomic: false);
1430}
1431EXPORT_SYMBOL(__find_get_block_nonatomic);
1432
1433/**
1434 * bdev_getblk - Get a buffer_head in a block device's buffer cache.
1435 * @bdev: The block device.
1436 * @block: The block number.
1437 * @size: The size of buffer_heads for this @bdev.
1438 * @gfp: The memory allocation flags to use.
1439 *
1440 * The returned buffer head has its reference count incremented, but is
1441 * not locked. The caller should call brelse() when it has finished
1442 * with the buffer. The buffer may not be uptodate. If needed, the
1443 * caller can bring it uptodate either by reading it or overwriting it.
1444 *
1445 * Return: The buffer head, or NULL if memory could not be allocated.
1446 */
1447struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block,
1448 unsigned size, gfp_t gfp)
1449{
1450 struct buffer_head *bh;
1451
1452 if (gfpflags_allow_blocking(gfp_flags: gfp))
1453 bh = __find_get_block_nonatomic(bdev, block, size);
1454 else
1455 bh = __find_get_block(bdev, block, size);
1456
1457 might_alloc(gfp_mask: gfp);
1458 if (bh)
1459 return bh;
1460
1461 return __getblk_slow(bdev, block, size, gfp);
1462}
1463EXPORT_SYMBOL(bdev_getblk);
1464
1465/*
1466 * Do async read-ahead on a buffer..
1467 */
1468void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1469{
1470 struct buffer_head *bh = bdev_getblk(bdev, block, size,
1471 GFP_NOWAIT | __GFP_MOVABLE);
1472
1473 if (likely(bh)) {
1474 bh_readahead(bh, REQ_RAHEAD);
1475 brelse(bh);
1476 }
1477}
1478EXPORT_SYMBOL(__breadahead);
1479
1480/**
1481 * __bread_gfp() - Read a block.
1482 * @bdev: The block device to read from.
1483 * @block: Block number in units of block size.
1484 * @size: The block size of this device in bytes.
1485 * @gfp: Not page allocation flags; see below.
1486 *
1487 * You are not expected to call this function. You should use one of
1488 * sb_bread(), sb_bread_unmovable() or __bread().
1489 *
1490 * Read a specified block, and return the buffer head that refers to it.
1491 * If @gfp is 0, the memory will be allocated using the block device's
1492 * default GFP flags. If @gfp is __GFP_MOVABLE, the memory may be
1493 * allocated from a movable area. Do not pass in a complete set of
1494 * GFP flags.
1495 *
1496 * The returned buffer head has its refcount increased. The caller should
1497 * call brelse() when it has finished with the buffer.
1498 *
1499 * Context: May sleep waiting for I/O.
1500 * Return: NULL if the block was unreadable.
1501 */
1502struct buffer_head *__bread_gfp(struct block_device *bdev, sector_t block,
1503 unsigned size, gfp_t gfp)
1504{
1505 struct buffer_head *bh;
1506
1507 gfp |= mapping_gfp_constraint(mapping: bdev->bd_mapping, gfp_mask: ~__GFP_FS);
1508
1509 /*
1510 * Prefer looping in the allocator rather than here, at least that
1511 * code knows what it's doing.
1512 */
1513 gfp |= __GFP_NOFAIL;
1514
1515 bh = bdev_getblk(bdev, block, size, gfp);
1516
1517 if (likely(bh) && !buffer_uptodate(bh))
1518 bh = __bread_slow(bh);
1519 return bh;
1520}
1521EXPORT_SYMBOL(__bread_gfp);
1522
1523static void __invalidate_bh_lrus(struct bh_lru *b)
1524{
1525 int i;
1526
1527 for (i = 0; i < BH_LRU_SIZE; i++) {
1528 brelse(bh: b->bhs[i]);
1529 b->bhs[i] = NULL;
1530 }
1531}
1532/*
1533 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1534 * This doesn't race because it runs in each cpu either in irq
1535 * or with preempt disabled.
1536 */
1537static void invalidate_bh_lru(void *arg)
1538{
1539 struct bh_lru *b = &get_cpu_var(bh_lrus);
1540
1541 __invalidate_bh_lrus(b);
1542 put_cpu_var(bh_lrus);
1543}
1544
1545bool has_bh_in_lru(int cpu, void *dummy)
1546{
1547 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1548 int i;
1549
1550 for (i = 0; i < BH_LRU_SIZE; i++) {
1551 if (b->bhs[i])
1552 return true;
1553 }
1554
1555 return false;
1556}
1557
1558void invalidate_bh_lrus(void)
1559{
1560 on_each_cpu_cond(cond_func: has_bh_in_lru, func: invalidate_bh_lru, NULL, wait: 1);
1561}
1562EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1563
1564/*
1565 * It's called from workqueue context so we need a bh_lru_lock to close
1566 * the race with preemption/irq.
1567 */
1568void invalidate_bh_lrus_cpu(void)
1569{
1570 struct bh_lru *b;
1571
1572 bh_lru_lock();
1573 b = this_cpu_ptr(&bh_lrus);
1574 __invalidate_bh_lrus(b);
1575 bh_lru_unlock();
1576}
1577
1578void folio_set_bh(struct buffer_head *bh, struct folio *folio,
1579 unsigned long offset)
1580{
1581 bh->b_folio = folio;
1582 BUG_ON(offset >= folio_size(folio));
1583 if (folio_test_highmem(folio))
1584 /*
1585 * This catches illegal uses and preserves the offset:
1586 */
1587 bh->b_data = (char *)(0 + offset);
1588 else
1589 bh->b_data = folio_address(folio) + offset;
1590}
1591EXPORT_SYMBOL(folio_set_bh);
1592
1593/*
1594 * Called when truncating a buffer on a page completely.
1595 */
1596
1597/* Bits that are cleared during an invalidate */
1598#define BUFFER_FLAGS_DISCARD \
1599 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1600 1 << BH_Delay | 1 << BH_Unwritten)
1601
1602static void discard_buffer(struct buffer_head * bh)
1603{
1604 unsigned long b_state;
1605
1606 lock_buffer(bh);
1607 clear_buffer_dirty(bh);
1608 bh->b_bdev = NULL;
1609 b_state = READ_ONCE(bh->b_state);
1610 do {
1611 } while (!try_cmpxchg_relaxed(&bh->b_state, &b_state,
1612 b_state & ~BUFFER_FLAGS_DISCARD));
1613 unlock_buffer(bh);
1614}
1615
1616/**
1617 * block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1618 * @folio: The folio which is affected.
1619 * @offset: start of the range to invalidate
1620 * @length: length of the range to invalidate
1621 *
1622 * block_invalidate_folio() is called when all or part of the folio has been
1623 * invalidated by a truncate operation.
1624 *
1625 * block_invalidate_folio() does not have to release all buffers, but it must
1626 * ensure that no dirty buffer is left outside @offset and that no I/O
1627 * is underway against any of the blocks which are outside the truncation
1628 * point. Because the caller is about to free (and possibly reuse) those
1629 * blocks on-disk.
1630 */
1631void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
1632{
1633 struct buffer_head *head, *bh, *next;
1634 size_t curr_off = 0;
1635 size_t stop = length + offset;
1636
1637 BUG_ON(!folio_test_locked(folio));
1638
1639 /*
1640 * Check for overflow
1641 */
1642 BUG_ON(stop > folio_size(folio) || stop < length);
1643
1644 head = folio_buffers(folio);
1645 if (!head)
1646 return;
1647
1648 bh = head;
1649 do {
1650 size_t next_off = curr_off + bh->b_size;
1651 next = bh->b_this_page;
1652
1653 /*
1654 * Are we still fully in range ?
1655 */
1656 if (next_off > stop)
1657 goto out;
1658
1659 /*
1660 * is this block fully invalidated?
1661 */
1662 if (offset <= curr_off)
1663 discard_buffer(bh);
1664 curr_off = next_off;
1665 bh = next;
1666 } while (bh != head);
1667
1668 /*
1669 * We release buffers only if the entire folio is being invalidated.
1670 * The get_block cached value has been unconditionally invalidated,
1671 * so real IO is not possible anymore.
1672 */
1673 if (length == folio_size(folio))
1674 filemap_release_folio(folio, gfp: 0);
1675out:
1676 folio_clear_mappedtodisk(folio);
1677}
1678EXPORT_SYMBOL(block_invalidate_folio);
1679
1680/*
1681 * We attach and possibly dirty the buffers atomically wrt
1682 * block_dirty_folio() via i_private_lock. try_to_free_buffers
1683 * is already excluded via the folio lock.
1684 */
1685struct buffer_head *create_empty_buffers(struct folio *folio,
1686 unsigned long blocksize, unsigned long b_state)
1687{
1688 struct buffer_head *bh, *head, *tail;
1689 gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT | __GFP_NOFAIL;
1690
1691 head = folio_alloc_buffers(folio, blocksize, gfp);
1692 bh = head;
1693 do {
1694 bh->b_state |= b_state;
1695 tail = bh;
1696 bh = bh->b_this_page;
1697 } while (bh);
1698 tail->b_this_page = head;
1699
1700 spin_lock(lock: &folio->mapping->i_private_lock);
1701 if (folio_test_uptodate(folio) || folio_test_dirty(folio)) {
1702 bh = head;
1703 do {
1704 if (folio_test_dirty(folio))
1705 set_buffer_dirty(bh);
1706 if (folio_test_uptodate(folio))
1707 set_buffer_uptodate(bh);
1708 bh = bh->b_this_page;
1709 } while (bh != head);
1710 }
1711 folio_attach_private(folio, data: head);
1712 spin_unlock(lock: &folio->mapping->i_private_lock);
1713
1714 return head;
1715}
1716EXPORT_SYMBOL(create_empty_buffers);
1717
1718/**
1719 * clean_bdev_aliases: clean a range of buffers in block device
1720 * @bdev: Block device to clean buffers in
1721 * @block: Start of a range of blocks to clean
1722 * @len: Number of blocks to clean
1723 *
1724 * We are taking a range of blocks for data and we don't want writeback of any
1725 * buffer-cache aliases starting from return from this function and until the
1726 * moment when something will explicitly mark the buffer dirty (hopefully that
1727 * will not happen until we will free that block ;-) We don't even need to mark
1728 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1729 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1730 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1731 * would confuse anyone who might pick it with bread() afterwards...
1732 *
1733 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1734 * writeout I/O going on against recently-freed buffers. We don't wait on that
1735 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1736 * need to. That happens here.
1737 */
1738void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1739{
1740 struct address_space *bd_mapping = bdev->bd_mapping;
1741 const int blkbits = bd_mapping->host->i_blkbits;
1742 struct folio_batch fbatch;
1743 pgoff_t index = ((loff_t)block << blkbits) / PAGE_SIZE;
1744 pgoff_t end;
1745 int i, count;
1746 struct buffer_head *bh;
1747 struct buffer_head *head;
1748
1749 end = ((loff_t)(block + len - 1) << blkbits) / PAGE_SIZE;
1750 folio_batch_init(fbatch: &fbatch);
1751 while (filemap_get_folios(mapping: bd_mapping, start: &index, end, fbatch: &fbatch)) {
1752 count = folio_batch_count(fbatch: &fbatch);
1753 for (i = 0; i < count; i++) {
1754 struct folio *folio = fbatch.folios[i];
1755
1756 if (!folio_buffers(folio))
1757 continue;
1758 /*
1759 * We use folio lock instead of bd_mapping->i_private_lock
1760 * to pin buffers here since we can afford to sleep and
1761 * it scales better than a global spinlock lock.
1762 */
1763 folio_lock(folio);
1764 /* Recheck when the folio is locked which pins bhs */
1765 head = folio_buffers(folio);
1766 if (!head)
1767 goto unlock_page;
1768 bh = head;
1769 do {
1770 if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1771 goto next;
1772 if (bh->b_blocknr >= block + len)
1773 break;
1774 clear_buffer_dirty(bh);
1775 wait_on_buffer(bh);
1776 clear_buffer_req(bh);
1777next:
1778 bh = bh->b_this_page;
1779 } while (bh != head);
1780unlock_page:
1781 folio_unlock(folio);
1782 }
1783 folio_batch_release(fbatch: &fbatch);
1784 cond_resched();
1785 /* End of range already reached? */
1786 if (index > end || !index)
1787 break;
1788 }
1789}
1790EXPORT_SYMBOL(clean_bdev_aliases);
1791
1792static struct buffer_head *folio_create_buffers(struct folio *folio,
1793 struct inode *inode,
1794 unsigned int b_state)
1795{
1796 struct buffer_head *bh;
1797
1798 BUG_ON(!folio_test_locked(folio));
1799
1800 bh = folio_buffers(folio);
1801 if (!bh)
1802 bh = create_empty_buffers(folio,
1803 1 << READ_ONCE(inode->i_blkbits), b_state);
1804 return bh;
1805}
1806
1807/*
1808 * NOTE! All mapped/uptodate combinations are valid:
1809 *
1810 * Mapped Uptodate Meaning
1811 *
1812 * No No "unknown" - must do get_block()
1813 * No Yes "hole" - zero-filled
1814 * Yes No "allocated" - allocated on disk, not read in
1815 * Yes Yes "valid" - allocated and up-to-date in memory.
1816 *
1817 * "Dirty" is valid only with the last case (mapped+uptodate).
1818 */
1819
1820/*
1821 * While block_write_full_folio is writing back the dirty buffers under
1822 * the page lock, whoever dirtied the buffers may decide to clean them
1823 * again at any time. We handle that by only looking at the buffer
1824 * state inside lock_buffer().
1825 *
1826 * If block_write_full_folio() is called for regular writeback
1827 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1828 * locked buffer. This only can happen if someone has written the buffer
1829 * directly, with submit_bh(). At the address_space level PageWriteback
1830 * prevents this contention from occurring.
1831 *
1832 * If block_write_full_folio() is called with wbc->sync_mode ==
1833 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1834 * causes the writes to be flagged as synchronous writes.
1835 */
1836int __block_write_full_folio(struct inode *inode, struct folio *folio,
1837 get_block_t *get_block, struct writeback_control *wbc)
1838{
1839 int err;
1840 sector_t block;
1841 sector_t last_block;
1842 struct buffer_head *bh, *head;
1843 size_t blocksize;
1844 int nr_underway = 0;
1845 blk_opf_t write_flags = wbc_to_write_flags(wbc);
1846
1847 head = folio_create_buffers(folio, inode,
1848 b_state: (1 << BH_Dirty) | (1 << BH_Uptodate));
1849
1850 /*
1851 * Be very careful. We have no exclusion from block_dirty_folio
1852 * here, and the (potentially unmapped) buffers may become dirty at
1853 * any time. If a buffer becomes dirty here after we've inspected it
1854 * then we just miss that fact, and the folio stays dirty.
1855 *
1856 * Buffers outside i_size may be dirtied by block_dirty_folio;
1857 * handle that here by just cleaning them.
1858 */
1859
1860 bh = head;
1861 blocksize = bh->b_size;
1862
1863 block = div_u64(dividend: folio_pos(folio), divisor: blocksize);
1864 last_block = div_u64(dividend: i_size_read(inode) - 1, divisor: blocksize);
1865
1866 /*
1867 * Get all the dirty buffers mapped to disk addresses and
1868 * handle any aliases from the underlying blockdev's mapping.
1869 */
1870 do {
1871 if (block > last_block) {
1872 /*
1873 * mapped buffers outside i_size will occur, because
1874 * this folio can be outside i_size when there is a
1875 * truncate in progress.
1876 */
1877 /*
1878 * The buffer was zeroed by block_write_full_folio()
1879 */
1880 clear_buffer_dirty(bh);
1881 set_buffer_uptodate(bh);
1882 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1883 buffer_dirty(bh)) {
1884 WARN_ON(bh->b_size != blocksize);
1885 err = get_block(inode, block, bh, 1);
1886 if (err)
1887 goto recover;
1888 clear_buffer_delay(bh);
1889 if (buffer_new(bh)) {
1890 /* blockdev mappings never come here */
1891 clear_buffer_new(bh);
1892 clean_bdev_bh_alias(bh);
1893 }
1894 }
1895 bh = bh->b_this_page;
1896 block++;
1897 } while (bh != head);
1898
1899 do {
1900 if (!buffer_mapped(bh))
1901 continue;
1902 /*
1903 * If it's a fully non-blocking write attempt and we cannot
1904 * lock the buffer then redirty the folio. Note that this can
1905 * potentially cause a busy-wait loop from writeback threads
1906 * and kswapd activity, but those code paths have their own
1907 * higher-level throttling.
1908 */
1909 if (wbc->sync_mode != WB_SYNC_NONE) {
1910 lock_buffer(bh);
1911 } else if (!trylock_buffer(bh)) {
1912 folio_redirty_for_writepage(wbc, folio);
1913 continue;
1914 }
1915 if (test_clear_buffer_dirty(bh)) {
1916 mark_buffer_async_write_endio(bh,
1917 handler: end_buffer_async_write);
1918 } else {
1919 unlock_buffer(bh);
1920 }
1921 } while ((bh = bh->b_this_page) != head);
1922
1923 /*
1924 * The folio and its buffers are protected by the writeback flag,
1925 * so we can drop the bh refcounts early.
1926 */
1927 BUG_ON(folio_test_writeback(folio));
1928 folio_start_writeback(folio);
1929
1930 do {
1931 struct buffer_head *next = bh->b_this_page;
1932 if (buffer_async_write(bh)) {
1933 submit_bh_wbc(opf: REQ_OP_WRITE | write_flags, bh,
1934 hint: inode->i_write_hint, wbc);
1935 nr_underway++;
1936 }
1937 bh = next;
1938 } while (bh != head);
1939 folio_unlock(folio);
1940
1941 err = 0;
1942done:
1943 if (nr_underway == 0) {
1944 /*
1945 * The folio was marked dirty, but the buffers were
1946 * clean. Someone wrote them back by hand with
1947 * write_dirty_buffer/submit_bh. A rare case.
1948 */
1949 folio_end_writeback(folio);
1950
1951 /*
1952 * The folio and buffer_heads can be released at any time from
1953 * here on.
1954 */
1955 }
1956 return err;
1957
1958recover:
1959 /*
1960 * ENOSPC, or some other error. We may already have added some
1961 * blocks to the file, so we need to write these out to avoid
1962 * exposing stale data.
1963 * The folio is currently locked and not marked for writeback
1964 */
1965 bh = head;
1966 /* Recovery: lock and submit the mapped buffers */
1967 do {
1968 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1969 !buffer_delay(bh)) {
1970 lock_buffer(bh);
1971 mark_buffer_async_write_endio(bh,
1972 handler: end_buffer_async_write);
1973 } else {
1974 /*
1975 * The buffer may have been set dirty during
1976 * attachment to a dirty folio.
1977 */
1978 clear_buffer_dirty(bh);
1979 }
1980 } while ((bh = bh->b_this_page) != head);
1981 BUG_ON(folio_test_writeback(folio));
1982 mapping_set_error(mapping: folio->mapping, error: err);
1983 folio_start_writeback(folio);
1984 do {
1985 struct buffer_head *next = bh->b_this_page;
1986 if (buffer_async_write(bh)) {
1987 clear_buffer_dirty(bh);
1988 submit_bh_wbc(opf: REQ_OP_WRITE | write_flags, bh,
1989 hint: inode->i_write_hint, wbc);
1990 nr_underway++;
1991 }
1992 bh = next;
1993 } while (bh != head);
1994 folio_unlock(folio);
1995 goto done;
1996}
1997EXPORT_SYMBOL(__block_write_full_folio);
1998
1999/*
2000 * If a folio has any new buffers, zero them out here, and mark them uptodate
2001 * and dirty so they'll be written out (in order to prevent uninitialised
2002 * block data from leaking). And clear the new bit.
2003 */
2004void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to)
2005{
2006 size_t block_start, block_end;
2007 struct buffer_head *head, *bh;
2008
2009 BUG_ON(!folio_test_locked(folio));
2010 head = folio_buffers(folio);
2011 if (!head)
2012 return;
2013
2014 bh = head;
2015 block_start = 0;
2016 do {
2017 block_end = block_start + bh->b_size;
2018
2019 if (buffer_new(bh)) {
2020 if (block_end > from && block_start < to) {
2021 if (!folio_test_uptodate(folio)) {
2022 size_t start, xend;
2023
2024 start = max(from, block_start);
2025 xend = min(to, block_end);
2026
2027 folio_zero_segment(folio, start, xend);
2028 set_buffer_uptodate(bh);
2029 }
2030
2031 clear_buffer_new(bh);
2032 mark_buffer_dirty(bh);
2033 }
2034 }
2035
2036 block_start = block_end;
2037 bh = bh->b_this_page;
2038 } while (bh != head);
2039}
2040EXPORT_SYMBOL(folio_zero_new_buffers);
2041
2042static int
2043iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
2044 const struct iomap *iomap)
2045{
2046 loff_t offset = (loff_t)block << inode->i_blkbits;
2047
2048 bh->b_bdev = iomap->bdev;
2049
2050 /*
2051 * Block points to offset in file we need to map, iomap contains
2052 * the offset at which the map starts. If the map ends before the
2053 * current block, then do not map the buffer and let the caller
2054 * handle it.
2055 */
2056 if (offset >= iomap->offset + iomap->length)
2057 return -EIO;
2058
2059 switch (iomap->type) {
2060 case IOMAP_HOLE:
2061 /*
2062 * If the buffer is not up to date or beyond the current EOF,
2063 * we need to mark it as new to ensure sub-block zeroing is
2064 * executed if necessary.
2065 */
2066 if (!buffer_uptodate(bh) ||
2067 (offset >= i_size_read(inode)))
2068 set_buffer_new(bh);
2069 return 0;
2070 case IOMAP_DELALLOC:
2071 if (!buffer_uptodate(bh) ||
2072 (offset >= i_size_read(inode)))
2073 set_buffer_new(bh);
2074 set_buffer_uptodate(bh);
2075 set_buffer_mapped(bh);
2076 set_buffer_delay(bh);
2077 return 0;
2078 case IOMAP_UNWRITTEN:
2079 /*
2080 * For unwritten regions, we always need to ensure that regions
2081 * in the block we are not writing to are zeroed. Mark the
2082 * buffer as new to ensure this.
2083 */
2084 set_buffer_new(bh);
2085 set_buffer_unwritten(bh);
2086 fallthrough;
2087 case IOMAP_MAPPED:
2088 if ((iomap->flags & IOMAP_F_NEW) ||
2089 offset >= i_size_read(inode)) {
2090 /*
2091 * This can happen if truncating the block device races
2092 * with the check in the caller as i_size updates on
2093 * block devices aren't synchronized by i_rwsem for
2094 * block devices.
2095 */
2096 if (S_ISBLK(inode->i_mode))
2097 return -EIO;
2098 set_buffer_new(bh);
2099 }
2100 bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
2101 inode->i_blkbits;
2102 set_buffer_mapped(bh);
2103 return 0;
2104 default:
2105 WARN_ON_ONCE(1);
2106 return -EIO;
2107 }
2108}
2109
2110int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
2111 get_block_t *get_block, const struct iomap *iomap)
2112{
2113 size_t from = offset_in_folio(folio, pos);
2114 size_t to = from + len;
2115 struct inode *inode = folio->mapping->host;
2116 size_t block_start, block_end;
2117 sector_t block;
2118 int err = 0;
2119 size_t blocksize;
2120 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
2121
2122 BUG_ON(!folio_test_locked(folio));
2123 BUG_ON(to > folio_size(folio));
2124 BUG_ON(from > to);
2125
2126 head = folio_create_buffers(folio, inode, b_state: 0);
2127 blocksize = head->b_size;
2128 block = div_u64(dividend: folio_pos(folio), divisor: blocksize);
2129
2130 for (bh = head, block_start = 0; bh != head || !block_start;
2131 block++, block_start=block_end, bh = bh->b_this_page) {
2132 block_end = block_start + blocksize;
2133 if (block_end <= from || block_start >= to) {
2134 if (folio_test_uptodate(folio)) {
2135 if (!buffer_uptodate(bh))
2136 set_buffer_uptodate(bh);
2137 }
2138 continue;
2139 }
2140 if (buffer_new(bh))
2141 clear_buffer_new(bh);
2142 if (!buffer_mapped(bh)) {
2143 WARN_ON(bh->b_size != blocksize);
2144 if (get_block)
2145 err = get_block(inode, block, bh, 1);
2146 else
2147 err = iomap_to_bh(inode, block, bh, iomap);
2148 if (err)
2149 break;
2150
2151 if (buffer_new(bh)) {
2152 clean_bdev_bh_alias(bh);
2153 if (folio_test_uptodate(folio)) {
2154 clear_buffer_new(bh);
2155 set_buffer_uptodate(bh);
2156 mark_buffer_dirty(bh);
2157 continue;
2158 }
2159 if (block_end > to || block_start < from)
2160 folio_zero_segments(folio,
2161 start1: to, xend1: block_end,
2162 start2: block_start, xend2: from);
2163 continue;
2164 }
2165 }
2166 if (folio_test_uptodate(folio)) {
2167 if (!buffer_uptodate(bh))
2168 set_buffer_uptodate(bh);
2169 continue;
2170 }
2171 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2172 !buffer_unwritten(bh) &&
2173 (block_start < from || block_end > to)) {
2174 bh_read_nowait(bh, op_flags: 0);
2175 *wait_bh++=bh;
2176 }
2177 }
2178 /*
2179 * If we issued read requests - let them complete.
2180 */
2181 while(wait_bh > wait) {
2182 wait_on_buffer(bh: *--wait_bh);
2183 if (!buffer_uptodate(bh: *wait_bh))
2184 err = -EIO;
2185 }
2186 if (unlikely(err))
2187 folio_zero_new_buffers(folio, from, to);
2188 return err;
2189}
2190
2191int __block_write_begin(struct folio *folio, loff_t pos, unsigned len,
2192 get_block_t *get_block)
2193{
2194 return __block_write_begin_int(folio, pos, len, get_block, NULL);
2195}
2196EXPORT_SYMBOL(__block_write_begin);
2197
2198void block_commit_write(struct folio *folio, size_t from, size_t to)
2199{
2200 size_t block_start, block_end;
2201 bool partial = false;
2202 unsigned blocksize;
2203 struct buffer_head *bh, *head;
2204
2205 bh = head = folio_buffers(folio);
2206 if (!bh)
2207 return;
2208 blocksize = bh->b_size;
2209
2210 block_start = 0;
2211 do {
2212 block_end = block_start + blocksize;
2213 if (block_end <= from || block_start >= to) {
2214 if (!buffer_uptodate(bh))
2215 partial = true;
2216 } else {
2217 set_buffer_uptodate(bh);
2218 mark_buffer_dirty(bh);
2219 }
2220 if (buffer_new(bh))
2221 clear_buffer_new(bh);
2222
2223 block_start = block_end;
2224 bh = bh->b_this_page;
2225 } while (bh != head);
2226
2227 /*
2228 * If this is a partial write which happened to make all buffers
2229 * uptodate then we can optimize away a bogus read_folio() for
2230 * the next read(). Here we 'discover' whether the folio went
2231 * uptodate as a result of this (potentially partial) write.
2232 */
2233 if (!partial)
2234 folio_mark_uptodate(folio);
2235}
2236EXPORT_SYMBOL(block_commit_write);
2237
2238/*
2239 * block_write_begin takes care of the basic task of block allocation and
2240 * bringing partial write blocks uptodate first.
2241 *
2242 * The filesystem needs to handle block truncation upon failure.
2243 */
2244int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2245 struct folio **foliop, get_block_t *get_block)
2246{
2247 pgoff_t index = pos >> PAGE_SHIFT;
2248 struct folio *folio;
2249 int status;
2250
2251 folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
2252 gfp: mapping_gfp_mask(mapping));
2253 if (IS_ERR(ptr: folio))
2254 return PTR_ERR(ptr: folio);
2255
2256 status = __block_write_begin_int(folio, pos, len, get_block, NULL);
2257 if (unlikely(status)) {
2258 folio_unlock(folio);
2259 folio_put(folio);
2260 folio = NULL;
2261 }
2262
2263 *foliop = folio;
2264 return status;
2265}
2266EXPORT_SYMBOL(block_write_begin);
2267
2268int block_write_end(loff_t pos, unsigned len, unsigned copied,
2269 struct folio *folio)
2270{
2271 size_t start = pos - folio_pos(folio);
2272
2273 if (unlikely(copied < len)) {
2274 /*
2275 * The buffers that were written will now be uptodate, so
2276 * we don't have to worry about a read_folio reading them
2277 * and overwriting a partial write. However if we have
2278 * encountered a short write and only partially written
2279 * into a buffer, it will not be marked uptodate, so a
2280 * read_folio might come in and destroy our partial write.
2281 *
2282 * Do the simplest thing, and just treat any short write to a
2283 * non uptodate folio as a zero-length write, and force the
2284 * caller to redo the whole thing.
2285 */
2286 if (!folio_test_uptodate(folio))
2287 copied = 0;
2288
2289 folio_zero_new_buffers(folio, start+copied, start+len);
2290 }
2291 flush_dcache_folio(folio);
2292
2293 /* This could be a short (even 0-length) commit */
2294 block_commit_write(folio, start, start + copied);
2295
2296 return copied;
2297}
2298EXPORT_SYMBOL(block_write_end);
2299
2300int generic_write_end(const struct kiocb *iocb, struct address_space *mapping,
2301 loff_t pos, unsigned len, unsigned copied,
2302 struct folio *folio, void *fsdata)
2303{
2304 struct inode *inode = mapping->host;
2305 loff_t old_size = inode->i_size;
2306 bool i_size_changed = false;
2307
2308 copied = block_write_end(pos, len, copied, folio);
2309
2310 /*
2311 * No need to use i_size_read() here, the i_size cannot change under us
2312 * because we hold i_rwsem.
2313 *
2314 * But it's important to update i_size while still holding folio lock:
2315 * page writeout could otherwise come in and zero beyond i_size.
2316 */
2317 if (pos + copied > inode->i_size) {
2318 i_size_write(inode, i_size: pos + copied);
2319 i_size_changed = true;
2320 }
2321
2322 folio_unlock(folio);
2323 folio_put(folio);
2324
2325 if (old_size < pos)
2326 pagecache_isize_extended(inode, from: old_size, to: pos);
2327 /*
2328 * Don't mark the inode dirty under page lock. First, it unnecessarily
2329 * makes the holding time of page lock longer. Second, it forces lock
2330 * ordering of page lock and transaction start for journaling
2331 * filesystems.
2332 */
2333 if (i_size_changed)
2334 mark_inode_dirty(inode);
2335 return copied;
2336}
2337EXPORT_SYMBOL(generic_write_end);
2338
2339/*
2340 * block_is_partially_uptodate checks whether buffers within a folio are
2341 * uptodate or not.
2342 *
2343 * Returns true if all buffers which correspond to the specified part
2344 * of the folio are uptodate.
2345 */
2346bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
2347{
2348 unsigned block_start, block_end, blocksize;
2349 unsigned to;
2350 struct buffer_head *bh, *head;
2351 bool ret = true;
2352
2353 head = folio_buffers(folio);
2354 if (!head)
2355 return false;
2356 blocksize = head->b_size;
2357 to = min_t(unsigned, folio_size(folio) - from, count);
2358 to = from + to;
2359 if (from < blocksize && to > folio_size(folio) - blocksize)
2360 return false;
2361
2362 bh = head;
2363 block_start = 0;
2364 do {
2365 block_end = block_start + blocksize;
2366 if (block_end > from && block_start < to) {
2367 if (!buffer_uptodate(bh)) {
2368 ret = false;
2369 break;
2370 }
2371 if (block_end >= to)
2372 break;
2373 }
2374 block_start = block_end;
2375 bh = bh->b_this_page;
2376 } while (bh != head);
2377
2378 return ret;
2379}
2380EXPORT_SYMBOL(block_is_partially_uptodate);
2381
2382/*
2383 * Generic "read_folio" function for block devices that have the normal
2384 * get_block functionality. This is most of the block device filesystems.
2385 * Reads the folio asynchronously --- the unlock_buffer() and
2386 * set/clear_buffer_uptodate() functions propagate buffer state into the
2387 * folio once IO has completed.
2388 */
2389int block_read_full_folio(struct folio *folio, get_block_t *get_block)
2390{
2391 struct inode *inode = folio->mapping->host;
2392 sector_t iblock, lblock;
2393 struct buffer_head *bh, *head, *prev = NULL;
2394 size_t blocksize;
2395 int fully_mapped = 1;
2396 bool page_error = false;
2397 loff_t limit = i_size_read(inode);
2398
2399 /* This is needed for ext4. */
2400 if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
2401 limit = inode->i_sb->s_maxbytes;
2402
2403 head = folio_create_buffers(folio, inode, b_state: 0);
2404 blocksize = head->b_size;
2405
2406 iblock = div_u64(dividend: folio_pos(folio), divisor: blocksize);
2407 lblock = div_u64(dividend: limit + blocksize - 1, divisor: blocksize);
2408 bh = head;
2409
2410 do {
2411 if (buffer_uptodate(bh))
2412 continue;
2413
2414 if (!buffer_mapped(bh)) {
2415 int err = 0;
2416
2417 fully_mapped = 0;
2418 if (iblock < lblock) {
2419 WARN_ON(bh->b_size != blocksize);
2420 err = get_block(inode, iblock, bh, 0);
2421 if (err)
2422 page_error = true;
2423 }
2424 if (!buffer_mapped(bh)) {
2425 folio_zero_range(folio, start: bh_offset(bh),
2426 length: blocksize);
2427 if (!err)
2428 set_buffer_uptodate(bh);
2429 continue;
2430 }
2431 /*
2432 * get_block() might have updated the buffer
2433 * synchronously
2434 */
2435 if (buffer_uptodate(bh))
2436 continue;
2437 }
2438
2439 lock_buffer(bh);
2440 if (buffer_uptodate(bh)) {
2441 unlock_buffer(bh);
2442 continue;
2443 }
2444
2445 mark_buffer_async_read(bh);
2446 if (prev)
2447 submit_bh(REQ_OP_READ, prev);
2448 prev = bh;
2449 } while (iblock++, (bh = bh->b_this_page) != head);
2450
2451 if (fully_mapped)
2452 folio_set_mappedtodisk(folio);
2453
2454 /*
2455 * All buffers are uptodate or get_block() returned an error
2456 * when trying to map them - we must finish the read because
2457 * end_buffer_async_read() will never be called on any buffer
2458 * in this folio.
2459 */
2460 if (prev)
2461 submit_bh(REQ_OP_READ, prev);
2462 else
2463 folio_end_read(folio, success: !page_error);
2464
2465 return 0;
2466}
2467EXPORT_SYMBOL(block_read_full_folio);
2468
2469/* utility function for filesystems that need to do work on expanding
2470 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2471 * deal with the hole.
2472 */
2473int generic_cont_expand_simple(struct inode *inode, loff_t size)
2474{
2475 struct address_space *mapping = inode->i_mapping;
2476 const struct address_space_operations *aops = mapping->a_ops;
2477 struct folio *folio;
2478 void *fsdata = NULL;
2479 int err;
2480
2481 err = inode_newsize_ok(inode, offset: size);
2482 if (err)
2483 goto out;
2484
2485 err = aops->write_begin(NULL, mapping, size, 0, &folio, &fsdata);
2486 if (err)
2487 goto out;
2488
2489 err = aops->write_end(NULL, mapping, size, 0, 0, folio, fsdata);
2490 BUG_ON(err > 0);
2491
2492out:
2493 return err;
2494}
2495EXPORT_SYMBOL(generic_cont_expand_simple);
2496
2497static int cont_expand_zero(const struct kiocb *iocb,
2498 struct address_space *mapping,
2499 loff_t pos, loff_t *bytes)
2500{
2501 struct inode *inode = mapping->host;
2502 const struct address_space_operations *aops = mapping->a_ops;
2503 unsigned int blocksize = i_blocksize(node: inode);
2504 struct folio *folio;
2505 void *fsdata = NULL;
2506 pgoff_t index, curidx;
2507 loff_t curpos;
2508 unsigned zerofrom, offset, len;
2509 int err = 0;
2510
2511 index = pos >> PAGE_SHIFT;
2512 offset = pos & ~PAGE_MASK;
2513
2514 while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2515 zerofrom = curpos & ~PAGE_MASK;
2516 if (zerofrom & (blocksize-1)) {
2517 *bytes |= (blocksize-1);
2518 (*bytes)++;
2519 }
2520 len = PAGE_SIZE - zerofrom;
2521
2522 err = aops->write_begin(iocb, mapping, curpos, len,
2523 &folio, &fsdata);
2524 if (err)
2525 goto out;
2526 folio_zero_range(folio, offset_in_folio(folio, curpos), length: len);
2527 err = aops->write_end(iocb, mapping, curpos, len, len,
2528 folio, fsdata);
2529 if (err < 0)
2530 goto out;
2531 BUG_ON(err != len);
2532 err = 0;
2533
2534 balance_dirty_pages_ratelimited(mapping);
2535
2536 if (fatal_signal_pending(current)) {
2537 err = -EINTR;
2538 goto out;
2539 }
2540 }
2541
2542 /* page covers the boundary, find the boundary offset */
2543 if (index == curidx) {
2544 zerofrom = curpos & ~PAGE_MASK;
2545 /* if we will expand the thing last block will be filled */
2546 if (offset <= zerofrom) {
2547 goto out;
2548 }
2549 if (zerofrom & (blocksize-1)) {
2550 *bytes |= (blocksize-1);
2551 (*bytes)++;
2552 }
2553 len = offset - zerofrom;
2554
2555 err = aops->write_begin(iocb, mapping, curpos, len,
2556 &folio, &fsdata);
2557 if (err)
2558 goto out;
2559 folio_zero_range(folio, offset_in_folio(folio, curpos), length: len);
2560 err = aops->write_end(iocb, mapping, curpos, len, len,
2561 folio, fsdata);
2562 if (err < 0)
2563 goto out;
2564 BUG_ON(err != len);
2565 err = 0;
2566 }
2567out:
2568 return err;
2569}
2570
2571/*
2572 * For moronic filesystems that do not allow holes in file.
2573 * We may have to extend the file.
2574 */
2575int cont_write_begin(const struct kiocb *iocb, struct address_space *mapping,
2576 loff_t pos, unsigned len, struct folio **foliop,
2577 void **fsdata, get_block_t *get_block, loff_t *bytes)
2578{
2579 struct inode *inode = mapping->host;
2580 unsigned int blocksize = i_blocksize(node: inode);
2581 unsigned int zerofrom;
2582 int err;
2583
2584 err = cont_expand_zero(iocb, mapping, pos, bytes);
2585 if (err)
2586 return err;
2587
2588 zerofrom = *bytes & ~PAGE_MASK;
2589 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2590 *bytes |= (blocksize-1);
2591 (*bytes)++;
2592 }
2593
2594 return block_write_begin(mapping, pos, len, foliop, get_block);
2595}
2596EXPORT_SYMBOL(cont_write_begin);
2597
2598/*
2599 * block_page_mkwrite() is not allowed to change the file size as it gets
2600 * called from a page fault handler when a page is first dirtied. Hence we must
2601 * be careful to check for EOF conditions here. We set the page up correctly
2602 * for a written page which means we get ENOSPC checking when writing into
2603 * holes and correct delalloc and unwritten extent mapping on filesystems that
2604 * support these features.
2605 *
2606 * We are not allowed to take the i_rwsem here so we have to play games to
2607 * protect against truncate races as the page could now be beyond EOF. Because
2608 * truncate writes the inode size before removing pages, once we have the
2609 * page lock we can determine safely if the page is beyond EOF. If it is not
2610 * beyond EOF, then the page is guaranteed safe against truncation until we
2611 * unlock the page.
2612 *
2613 * Direct callers of this function should protect against filesystem freezing
2614 * using sb_start_pagefault() - sb_end_pagefault() functions.
2615 */
2616int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2617 get_block_t get_block)
2618{
2619 struct folio *folio = page_folio(vmf->page);
2620 struct inode *inode = file_inode(f: vma->vm_file);
2621 unsigned long end;
2622 loff_t size;
2623 int ret;
2624
2625 folio_lock(folio);
2626 size = i_size_read(inode);
2627 if ((folio->mapping != inode->i_mapping) ||
2628 (folio_pos(folio) >= size)) {
2629 /* We overload EFAULT to mean page got truncated */
2630 ret = -EFAULT;
2631 goto out_unlock;
2632 }
2633
2634 end = folio_size(folio);
2635 /* folio is wholly or partially inside EOF */
2636 if (folio_pos(folio) + end > size)
2637 end = size - folio_pos(folio);
2638
2639 ret = __block_write_begin_int(folio, pos: 0, len: end, get_block, NULL);
2640 if (unlikely(ret))
2641 goto out_unlock;
2642
2643 block_commit_write(folio, 0, end);
2644
2645 folio_mark_dirty(folio);
2646 folio_wait_stable(folio);
2647 return 0;
2648out_unlock:
2649 folio_unlock(folio);
2650 return ret;
2651}
2652EXPORT_SYMBOL(block_page_mkwrite);
2653
2654int block_truncate_page(struct address_space *mapping,
2655 loff_t from, get_block_t *get_block)
2656{
2657 pgoff_t index = from >> PAGE_SHIFT;
2658 unsigned blocksize;
2659 sector_t iblock;
2660 size_t offset, length, pos;
2661 struct inode *inode = mapping->host;
2662 struct folio *folio;
2663 struct buffer_head *bh;
2664 int err = 0;
2665
2666 blocksize = i_blocksize(node: inode);
2667 length = from & (blocksize - 1);
2668
2669 /* Block boundary? Nothing to do */
2670 if (!length)
2671 return 0;
2672
2673 length = blocksize - length;
2674 iblock = ((loff_t)index * PAGE_SIZE) >> inode->i_blkbits;
2675
2676 folio = filemap_grab_folio(mapping, index);
2677 if (IS_ERR(ptr: folio))
2678 return PTR_ERR(ptr: folio);
2679
2680 bh = folio_buffers(folio);
2681 if (!bh)
2682 bh = create_empty_buffers(folio, blocksize, 0);
2683
2684 /* Find the buffer that contains "offset" */
2685 offset = offset_in_folio(folio, from);
2686 pos = blocksize;
2687 while (offset >= pos) {
2688 bh = bh->b_this_page;
2689 iblock++;
2690 pos += blocksize;
2691 }
2692
2693 if (!buffer_mapped(bh)) {
2694 WARN_ON(bh->b_size != blocksize);
2695 err = get_block(inode, iblock, bh, 0);
2696 if (err)
2697 goto unlock;
2698 /* unmapped? It's a hole - nothing to do */
2699 if (!buffer_mapped(bh))
2700 goto unlock;
2701 }
2702
2703 /* Ok, it's mapped. Make sure it's up-to-date */
2704 if (folio_test_uptodate(folio))
2705 set_buffer_uptodate(bh);
2706
2707 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2708 err = bh_read(bh, op_flags: 0);
2709 /* Uhhuh. Read error. Complain and punt. */
2710 if (err < 0)
2711 goto unlock;
2712 }
2713
2714 folio_zero_range(folio, start: offset, length);
2715 mark_buffer_dirty(bh);
2716
2717unlock:
2718 folio_unlock(folio);
2719 folio_put(folio);
2720
2721 return err;
2722}
2723EXPORT_SYMBOL(block_truncate_page);
2724
2725/*
2726 * The generic write folio function for buffer-backed address_spaces
2727 */
2728int block_write_full_folio(struct folio *folio, struct writeback_control *wbc,
2729 void *get_block)
2730{
2731 struct inode * const inode = folio->mapping->host;
2732 loff_t i_size = i_size_read(inode);
2733
2734 /* Is the folio fully inside i_size? */
2735 if (folio_pos(folio) + folio_size(folio) <= i_size)
2736 return __block_write_full_folio(inode, folio, get_block, wbc);
2737
2738 /* Is the folio fully outside i_size? (truncate in progress) */
2739 if (folio_pos(folio) >= i_size) {
2740 folio_unlock(folio);
2741 return 0; /* don't care */
2742 }
2743
2744 /*
2745 * The folio straddles i_size. It must be zeroed out on each and every
2746 * writeback invocation because it may be mmapped. "A file is mapped
2747 * in multiples of the page size. For a file that is not a multiple of
2748 * the page size, the remaining memory is zeroed when mapped, and
2749 * writes to that region are not written out to the file."
2750 */
2751 folio_zero_segment(folio, offset_in_folio(folio, i_size),
2752 xend: folio_size(folio));
2753 return __block_write_full_folio(inode, folio, get_block, wbc);
2754}
2755
2756sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2757 get_block_t *get_block)
2758{
2759 struct inode *inode = mapping->host;
2760 struct buffer_head tmp = {
2761 .b_size = i_blocksize(node: inode),
2762 };
2763
2764 get_block(inode, block, &tmp, 0);
2765 return tmp.b_blocknr;
2766}
2767EXPORT_SYMBOL(generic_block_bmap);
2768
2769static void end_bio_bh_io_sync(struct bio *bio)
2770{
2771 struct buffer_head *bh = bio->bi_private;
2772
2773 if (unlikely(bio_flagged(bio, BIO_QUIET)))
2774 set_bit(nr: BH_Quiet, addr: &bh->b_state);
2775
2776 bh->b_end_io(bh, !bio->bi_status);
2777 bio_put(bio);
2778}
2779
2780static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
2781 enum rw_hint write_hint,
2782 struct writeback_control *wbc)
2783{
2784 const enum req_op op = opf & REQ_OP_MASK;
2785 struct bio *bio;
2786
2787 BUG_ON(!buffer_locked(bh));
2788 BUG_ON(!buffer_mapped(bh));
2789 BUG_ON(!bh->b_end_io);
2790 BUG_ON(buffer_delay(bh));
2791 BUG_ON(buffer_unwritten(bh));
2792
2793 /*
2794 * Only clear out a write error when rewriting
2795 */
2796 if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
2797 clear_buffer_write_io_error(bh);
2798
2799 if (buffer_meta(bh))
2800 opf |= REQ_META;
2801 if (buffer_prio(bh))
2802 opf |= REQ_PRIO;
2803
2804 bio = bio_alloc(bdev: bh->b_bdev, nr_vecs: 1, opf, GFP_NOIO);
2805
2806 fscrypt_set_bio_crypt_ctx_bh(bio, first_bh: bh, GFP_NOIO);
2807
2808 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2809 bio->bi_write_hint = write_hint;
2810
2811 bio_add_folio_nofail(bio, folio: bh->b_folio, len: bh->b_size, off: bh_offset(bh));
2812
2813 bio->bi_end_io = end_bio_bh_io_sync;
2814 bio->bi_private = bh;
2815
2816 /* Take care of bh's that straddle the end of the device */
2817 guard_bio_eod(bio);
2818
2819 if (wbc) {
2820 wbc_init_bio(wbc, bio);
2821 wbc_account_cgroup_owner(wbc, folio: bh->b_folio, bytes: bh->b_size);
2822 }
2823
2824 submit_bio(bio);
2825}
2826
2827void submit_bh(blk_opf_t opf, struct buffer_head *bh)
2828{
2829 submit_bh_wbc(opf, bh, write_hint: WRITE_LIFE_NOT_SET, NULL);
2830}
2831EXPORT_SYMBOL(submit_bh);
2832
2833void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2834{
2835 lock_buffer(bh);
2836 if (!test_clear_buffer_dirty(bh)) {
2837 unlock_buffer(bh);
2838 return;
2839 }
2840 bh->b_end_io = end_buffer_write_sync;
2841 get_bh(bh);
2842 submit_bh(REQ_OP_WRITE | op_flags, bh);
2843}
2844EXPORT_SYMBOL(write_dirty_buffer);
2845
2846/*
2847 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2848 * and then start new I/O and then wait upon it. The caller must have a ref on
2849 * the buffer_head.
2850 */
2851int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2852{
2853 WARN_ON(atomic_read(&bh->b_count) < 1);
2854 lock_buffer(bh);
2855 if (test_clear_buffer_dirty(bh)) {
2856 /*
2857 * The bh should be mapped, but it might not be if the
2858 * device was hot-removed. Not much we can do but fail the I/O.
2859 */
2860 if (!buffer_mapped(bh)) {
2861 unlock_buffer(bh);
2862 return -EIO;
2863 }
2864
2865 get_bh(bh);
2866 bh->b_end_io = end_buffer_write_sync;
2867 submit_bh(REQ_OP_WRITE | op_flags, bh);
2868 wait_on_buffer(bh);
2869 if (!buffer_uptodate(bh))
2870 return -EIO;
2871 } else {
2872 unlock_buffer(bh);
2873 }
2874 return 0;
2875}
2876EXPORT_SYMBOL(__sync_dirty_buffer);
2877
2878int sync_dirty_buffer(struct buffer_head *bh)
2879{
2880 return __sync_dirty_buffer(bh, REQ_SYNC);
2881}
2882EXPORT_SYMBOL(sync_dirty_buffer);
2883
2884static inline int buffer_busy(struct buffer_head *bh)
2885{
2886 return atomic_read(v: &bh->b_count) |
2887 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2888}
2889
2890static bool
2891drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
2892{
2893 struct buffer_head *head = folio_buffers(folio);
2894 struct buffer_head *bh;
2895
2896 bh = head;
2897 do {
2898 if (buffer_busy(bh))
2899 goto failed;
2900 bh = bh->b_this_page;
2901 } while (bh != head);
2902
2903 do {
2904 struct buffer_head *next = bh->b_this_page;
2905
2906 if (bh->b_assoc_map)
2907 __remove_assoc_queue(bh);
2908 bh = next;
2909 } while (bh != head);
2910 *buffers_to_free = head;
2911 folio_detach_private(folio);
2912 return true;
2913failed:
2914 return false;
2915}
2916
2917/**
2918 * try_to_free_buffers - Release buffers attached to this folio.
2919 * @folio: The folio.
2920 *
2921 * If any buffers are in use (dirty, under writeback, elevated refcount),
2922 * no buffers will be freed.
2923 *
2924 * If the folio is dirty but all the buffers are clean then we need to
2925 * be sure to mark the folio clean as well. This is because the folio
2926 * may be against a block device, and a later reattachment of buffers
2927 * to a dirty folio will set *all* buffers dirty. Which would corrupt
2928 * filesystem data on the same device.
2929 *
2930 * The same applies to regular filesystem folios: if all the buffers are
2931 * clean then we set the folio clean and proceed. To do that, we require
2932 * total exclusion from block_dirty_folio(). That is obtained with
2933 * i_private_lock.
2934 *
2935 * Exclusion against try_to_free_buffers may be obtained by either
2936 * locking the folio or by holding its mapping's i_private_lock.
2937 *
2938 * Context: Process context. @folio must be locked. Will not sleep.
2939 * Return: true if all buffers attached to this folio were freed.
2940 */
2941bool try_to_free_buffers(struct folio *folio)
2942{
2943 struct address_space * const mapping = folio->mapping;
2944 struct buffer_head *buffers_to_free = NULL;
2945 bool ret = 0;
2946
2947 BUG_ON(!folio_test_locked(folio));
2948 if (folio_test_writeback(folio))
2949 return false;
2950
2951 if (mapping == NULL) { /* can this still happen? */
2952 ret = drop_buffers(folio, buffers_to_free: &buffers_to_free);
2953 goto out;
2954 }
2955
2956 spin_lock(lock: &mapping->i_private_lock);
2957 ret = drop_buffers(folio, buffers_to_free: &buffers_to_free);
2958
2959 /*
2960 * If the filesystem writes its buffers by hand (eg ext3)
2961 * then we can have clean buffers against a dirty folio. We
2962 * clean the folio here; otherwise the VM will never notice
2963 * that the filesystem did any IO at all.
2964 *
2965 * Also, during truncate, discard_buffer will have marked all
2966 * the folio's buffers clean. We discover that here and clean
2967 * the folio also.
2968 *
2969 * i_private_lock must be held over this entire operation in order
2970 * to synchronise against block_dirty_folio and prevent the
2971 * dirty bit from being lost.
2972 */
2973 if (ret)
2974 folio_cancel_dirty(folio);
2975 spin_unlock(lock: &mapping->i_private_lock);
2976out:
2977 if (buffers_to_free) {
2978 struct buffer_head *bh = buffers_to_free;
2979
2980 do {
2981 struct buffer_head *next = bh->b_this_page;
2982 free_buffer_head(bh);
2983 bh = next;
2984 } while (bh != buffers_to_free);
2985 }
2986 return ret;
2987}
2988EXPORT_SYMBOL(try_to_free_buffers);
2989
2990/*
2991 * Buffer-head allocation
2992 */
2993static struct kmem_cache *bh_cachep __ro_after_init;
2994
2995/*
2996 * Once the number of bh's in the machine exceeds this level, we start
2997 * stripping them in writeback.
2998 */
2999static unsigned long max_buffer_heads __ro_after_init;
3000
3001int buffer_heads_over_limit;
3002
3003struct bh_accounting {
3004 int nr; /* Number of live bh's */
3005 int ratelimit; /* Limit cacheline bouncing */
3006};
3007
3008static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3009
3010static void recalc_bh_state(void)
3011{
3012 int i;
3013 int tot = 0;
3014
3015 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3016 return;
3017 __this_cpu_write(bh_accounting.ratelimit, 0);
3018 for_each_online_cpu(i)
3019 tot += per_cpu(bh_accounting, i).nr;
3020 buffer_heads_over_limit = (tot > max_buffer_heads);
3021}
3022
3023struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3024{
3025 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3026 if (ret) {
3027 INIT_LIST_HEAD(list: &ret->b_assoc_buffers);
3028 spin_lock_init(&ret->b_uptodate_lock);
3029 preempt_disable();
3030 __this_cpu_inc(bh_accounting.nr);
3031 recalc_bh_state();
3032 preempt_enable();
3033 }
3034 return ret;
3035}
3036EXPORT_SYMBOL(alloc_buffer_head);
3037
3038void free_buffer_head(struct buffer_head *bh)
3039{
3040 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3041 kmem_cache_free(s: bh_cachep, objp: bh);
3042 preempt_disable();
3043 __this_cpu_dec(bh_accounting.nr);
3044 recalc_bh_state();
3045 preempt_enable();
3046}
3047EXPORT_SYMBOL(free_buffer_head);
3048
3049static int buffer_exit_cpu_dead(unsigned int cpu)
3050{
3051 int i;
3052 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3053
3054 for (i = 0; i < BH_LRU_SIZE; i++) {
3055 brelse(bh: b->bhs[i]);
3056 b->bhs[i] = NULL;
3057 }
3058 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3059 per_cpu(bh_accounting, cpu).nr = 0;
3060 return 0;
3061}
3062
3063/**
3064 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3065 * @bh: struct buffer_head
3066 *
3067 * Return true if the buffer is up-to-date and false,
3068 * with the buffer locked, if not.
3069 */
3070int bh_uptodate_or_lock(struct buffer_head *bh)
3071{
3072 if (!buffer_uptodate(bh)) {
3073 lock_buffer(bh);
3074 if (!buffer_uptodate(bh))
3075 return 0;
3076 unlock_buffer(bh);
3077 }
3078 return 1;
3079}
3080EXPORT_SYMBOL(bh_uptodate_or_lock);
3081
3082/**
3083 * __bh_read - Submit read for a locked buffer
3084 * @bh: struct buffer_head
3085 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3086 * @wait: wait until reading finish
3087 *
3088 * Returns zero on success or don't wait, and -EIO on error.
3089 */
3090int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
3091{
3092 int ret = 0;
3093
3094 BUG_ON(!buffer_locked(bh));
3095
3096 get_bh(bh);
3097 bh->b_end_io = end_buffer_read_sync;
3098 submit_bh(REQ_OP_READ | op_flags, bh);
3099 if (wait) {
3100 wait_on_buffer(bh);
3101 if (!buffer_uptodate(bh))
3102 ret = -EIO;
3103 }
3104 return ret;
3105}
3106EXPORT_SYMBOL(__bh_read);
3107
3108/**
3109 * __bh_read_batch - Submit read for a batch of unlocked buffers
3110 * @nr: entry number of the buffer batch
3111 * @bhs: a batch of struct buffer_head
3112 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3113 * @force_lock: force to get a lock on the buffer if set, otherwise drops any
3114 * buffer that cannot lock.
3115 *
3116 * Returns zero on success or don't wait, and -EIO on error.
3117 */
3118void __bh_read_batch(int nr, struct buffer_head *bhs[],
3119 blk_opf_t op_flags, bool force_lock)
3120{
3121 int i;
3122
3123 for (i = 0; i < nr; i++) {
3124 struct buffer_head *bh = bhs[i];
3125
3126 if (buffer_uptodate(bh))
3127 continue;
3128
3129 if (force_lock)
3130 lock_buffer(bh);
3131 else
3132 if (!trylock_buffer(bh))
3133 continue;
3134
3135 if (buffer_uptodate(bh)) {
3136 unlock_buffer(bh);
3137 continue;
3138 }
3139
3140 bh->b_end_io = end_buffer_read_sync;
3141 get_bh(bh);
3142 submit_bh(REQ_OP_READ | op_flags, bh);
3143 }
3144}
3145EXPORT_SYMBOL(__bh_read_batch);
3146
3147void __init buffer_init(void)
3148{
3149 unsigned long nrpages;
3150 int ret;
3151
3152 bh_cachep = KMEM_CACHE(buffer_head,
3153 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC);
3154 /*
3155 * Limit the bh occupancy to 10% of ZONE_NORMAL
3156 */
3157 nrpages = (nr_free_buffer_pages() * 10) / 100;
3158 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3159 ret = cpuhp_setup_state_nocalls(state: CPUHP_FS_BUFF_DEAD, name: "fs/buffer:dead",
3160 NULL, teardown: buffer_exit_cpu_dead);
3161 WARN_ON(ret < 0);
3162}
3163