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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(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
72}
73EXPORT_SYMBOL(__lock_buffer);
74
75void unlock_buffer(struct buffer_head *bh)
76{
77 clear_bit_unlock(BH_Lock, &bh->b_state);
78 smp_mb__after_atomic();
79 wake_up_bit(&bh->b_state, BH_Lock);
80}
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(&bh->b_state, 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 __end_buffer_read_notouch(bh, uptodate);
161 put_bh(bh);
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, ", 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
179/*
180 * Various filesystems appear to want __find_get_block to be non-blocking.
181 * But it's the page lock which protects the buffers. To get around this,
182 * we get exclusion from try_to_free_buffers with the blockdev mapping's
183 * i_private_lock.
184 *
185 * Hack idea: for the blockdev mapping, i_private_lock contention
186 * may be quite high. This code could TryLock the page, and if that
187 * succeeds, there is no need to take i_private_lock.
188 */
189static struct buffer_head *
190__find_get_block_slow(struct block_device *bdev, sector_t block)
191{
192 struct address_space *bd_mapping = bdev->bd_mapping;
193 const int blkbits = bd_mapping->host->i_blkbits;
194 struct buffer_head *ret = NULL;
195 pgoff_t index;
196 struct buffer_head *bh;
197 struct buffer_head *head;
198 struct folio *folio;
199 int all_mapped = 1;
200 static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
201
202 index = ((loff_t)block << blkbits) / PAGE_SIZE;
203 folio = __filemap_get_folio(bd_mapping, index, FGP_ACCESSED, 0);
204 if (IS_ERR(folio))
205 goto out;
206
207 spin_lock(&bd_mapping->i_private_lock);
208 head = folio_buffers(folio);
209 if (!head)
210 goto out_unlock;
211 bh = head;
212 do {
213 if (!buffer_mapped(bh))
214 all_mapped = 0;
215 else if (bh->b_blocknr == block) {
216 ret = bh;
217 get_bh(bh);
218 goto out_unlock;
219 }
220 bh = bh->b_this_page;
221 } while (bh != head);
222
223 /* we might be here because some of the buffers on this page are
224 * not mapped. This is due to various races between
225 * file io on the block device and getblk. It gets dealt with
226 * elsewhere, don't buffer_error if we had some unmapped buffers
227 */
228 ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
229 if (all_mapped && __ratelimit(&last_warned)) {
230 printk("__find_get_block_slow() failed. block=%llu, "
231 "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
232 "device %pg blocksize: %d\n",
233 (unsigned long long)block,
234 (unsigned long long)bh->b_blocknr,
235 bh->b_state, bh->b_size, bdev,
236 1 << blkbits);
237 }
238out_unlock:
239 spin_unlock(&bd_mapping->i_private_lock);
240 folio_put(folio);
241out:
242 return ret;
243}
244
245static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
246{
247 unsigned long flags;
248 struct buffer_head *first;
249 struct buffer_head *tmp;
250 struct folio *folio;
251 int folio_uptodate = 1;
252
253 BUG_ON(!buffer_async_read(bh));
254
255 folio = bh->b_folio;
256 if (uptodate) {
257 set_buffer_uptodate(bh);
258 } else {
259 clear_buffer_uptodate(bh);
260 buffer_io_error(bh, ", async page read");
261 }
262
263 /*
264 * Be _very_ careful from here on. Bad things can happen if
265 * two buffer heads end IO at almost the same time and both
266 * decide that the page is now completely done.
267 */
268 first = folio_buffers(folio);
269 spin_lock_irqsave(&first->b_uptodate_lock, flags);
270 clear_buffer_async_read(bh);
271 unlock_buffer(bh);
272 tmp = bh;
273 do {
274 if (!buffer_uptodate(tmp))
275 folio_uptodate = 0;
276 if (buffer_async_read(tmp)) {
277 BUG_ON(!buffer_locked(tmp));
278 goto still_busy;
279 }
280 tmp = tmp->b_this_page;
281 } while (tmp != bh);
282 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
283
284 folio_end_read(folio, folio_uptodate);
285 return;
286
287still_busy:
288 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
289 return;
290}
291
292struct postprocess_bh_ctx {
293 struct work_struct work;
294 struct buffer_head *bh;
295};
296
297static void verify_bh(struct work_struct *work)
298{
299 struct postprocess_bh_ctx *ctx =
300 container_of(work, struct postprocess_bh_ctx, work);
301 struct buffer_head *bh = ctx->bh;
302 bool valid;
303
304 valid = fsverity_verify_blocks(bh->b_folio, bh->b_size, bh_offset(bh));
305 end_buffer_async_read(bh, valid);
306 kfree(ctx);
307}
308
309static bool need_fsverity(struct buffer_head *bh)
310{
311 struct folio *folio = bh->b_folio;
312 struct inode *inode = folio->mapping->host;
313
314 return fsverity_active(inode) &&
315 /* needed by ext4 */
316 folio->index < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
317}
318
319static void decrypt_bh(struct work_struct *work)
320{
321 struct postprocess_bh_ctx *ctx =
322 container_of(work, struct postprocess_bh_ctx, work);
323 struct buffer_head *bh = ctx->bh;
324 int err;
325
326 err = fscrypt_decrypt_pagecache_blocks(bh->b_folio, bh->b_size,
327 bh_offset(bh));
328 if (err == 0 && need_fsverity(bh)) {
329 /*
330 * We use different work queues for decryption and for verity
331 * because verity may require reading metadata pages that need
332 * decryption, and we shouldn't recurse to the same workqueue.
333 */
334 INIT_WORK(&ctx->work, verify_bh);
335 fsverity_enqueue_verify_work(&ctx->work);
336 return;
337 }
338 end_buffer_async_read(bh, err == 0);
339 kfree(ctx);
340}
341
342/*
343 * I/O completion handler for block_read_full_folio() - pages
344 * which come unlocked at the end of I/O.
345 */
346static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
347{
348 struct inode *inode = bh->b_folio->mapping->host;
349 bool decrypt = fscrypt_inode_uses_fs_layer_crypto(inode);
350 bool verify = need_fsverity(bh);
351
352 /* Decrypt (with fscrypt) and/or verify (with fsverity) if needed. */
353 if (uptodate && (decrypt || verify)) {
354 struct postprocess_bh_ctx *ctx =
355 kmalloc(sizeof(*ctx), GFP_ATOMIC);
356
357 if (ctx) {
358 ctx->bh = bh;
359 if (decrypt) {
360 INIT_WORK(&ctx->work, decrypt_bh);
361 fscrypt_enqueue_decrypt_work(&ctx->work);
362 } else {
363 INIT_WORK(&ctx->work, verify_bh);
364 fsverity_enqueue_verify_work(&ctx->work);
365 }
366 return;
367 }
368 uptodate = 0;
369 }
370 end_buffer_async_read(bh, uptodate);
371}
372
373/*
374 * Completion handler for block_write_full_folio() - folios which are unlocked
375 * during I/O, and which have the writeback flag cleared upon I/O completion.
376 */
377static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
378{
379 unsigned long flags;
380 struct buffer_head *first;
381 struct buffer_head *tmp;
382 struct folio *folio;
383
384 BUG_ON(!buffer_async_write(bh));
385
386 folio = bh->b_folio;
387 if (uptodate) {
388 set_buffer_uptodate(bh);
389 } else {
390 buffer_io_error(bh, ", lost async page write");
391 mark_buffer_write_io_error(bh);
392 clear_buffer_uptodate(bh);
393 }
394
395 first = folio_buffers(folio);
396 spin_lock_irqsave(&first->b_uptodate_lock, flags);
397
398 clear_buffer_async_write(bh);
399 unlock_buffer(bh);
400 tmp = bh->b_this_page;
401 while (tmp != bh) {
402 if (buffer_async_write(tmp)) {
403 BUG_ON(!buffer_locked(tmp));
404 goto still_busy;
405 }
406 tmp = tmp->b_this_page;
407 }
408 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
409 folio_end_writeback(folio);
410 return;
411
412still_busy:
413 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
414 return;
415}
416
417/*
418 * If a page's buffers are under async readin (end_buffer_async_read
419 * completion) then there is a possibility that another thread of
420 * control could lock one of the buffers after it has completed
421 * but while some of the other buffers have not completed. This
422 * locked buffer would confuse end_buffer_async_read() into not unlocking
423 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
424 * that this buffer is not under async I/O.
425 *
426 * The page comes unlocked when it has no locked buffer_async buffers
427 * left.
428 *
429 * PageLocked prevents anyone starting new async I/O reads any of
430 * the buffers.
431 *
432 * PageWriteback is used to prevent simultaneous writeout of the same
433 * page.
434 *
435 * PageLocked prevents anyone from starting writeback of a page which is
436 * under read I/O (PageWriteback is only ever set against a locked page).
437 */
438static void mark_buffer_async_read(struct buffer_head *bh)
439{
440 bh->b_end_io = end_buffer_async_read_io;
441 set_buffer_async_read(bh);
442}
443
444static void mark_buffer_async_write_endio(struct buffer_head *bh,
445 bh_end_io_t *handler)
446{
447 bh->b_end_io = handler;
448 set_buffer_async_write(bh);
449}
450
451void mark_buffer_async_write(struct buffer_head *bh)
452{
453 mark_buffer_async_write_endio(bh, end_buffer_async_write);
454}
455EXPORT_SYMBOL(mark_buffer_async_write);
456
457
458/*
459 * fs/buffer.c contains helper functions for buffer-backed address space's
460 * fsync functions. A common requirement for buffer-based filesystems is
461 * that certain data from the backing blockdev needs to be written out for
462 * a successful fsync(). For example, ext2 indirect blocks need to be
463 * written back and waited upon before fsync() returns.
464 *
465 * The functions mark_buffer_dirty_inode(), fsync_inode_buffers(),
466 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
467 * management of a list of dependent buffers at ->i_mapping->i_private_list.
468 *
469 * Locking is a little subtle: try_to_free_buffers() will remove buffers
470 * from their controlling inode's queue when they are being freed. But
471 * try_to_free_buffers() will be operating against the *blockdev* mapping
472 * at the time, not against the S_ISREG file which depends on those buffers.
473 * So the locking for i_private_list is via the i_private_lock in the address_space
474 * which backs the buffers. Which is different from the address_space
475 * against which the buffers are listed. So for a particular address_space,
476 * mapping->i_private_lock does *not* protect mapping->i_private_list! In fact,
477 * mapping->i_private_list will always be protected by the backing blockdev's
478 * ->i_private_lock.
479 *
480 * Which introduces a requirement: all buffers on an address_space's
481 * ->i_private_list must be from the same address_space: the blockdev's.
482 *
483 * address_spaces which do not place buffers at ->i_private_list via these
484 * utility functions are free to use i_private_lock and i_private_list for
485 * whatever they want. The only requirement is that list_empty(i_private_list)
486 * be true at clear_inode() time.
487 *
488 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
489 * filesystems should do that. invalidate_inode_buffers() should just go
490 * BUG_ON(!list_empty).
491 *
492 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
493 * take an address_space, not an inode. And it should be called
494 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
495 * queued up.
496 *
497 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
498 * list if it is already on a list. Because if the buffer is on a list,
499 * it *must* already be on the right one. If not, the filesystem is being
500 * silly. This will save a ton of locking. But first we have to ensure
501 * that buffers are taken *off* the old inode's list when they are freed
502 * (presumably in truncate). That requires careful auditing of all
503 * filesystems (do it inside bforget()). It could also be done by bringing
504 * b_inode back.
505 */
506
507/*
508 * The buffer's backing address_space's i_private_lock must be held
509 */
510static void __remove_assoc_queue(struct buffer_head *bh)
511{
512 list_del_init(&bh->b_assoc_buffers);
513 WARN_ON(!bh->b_assoc_map);
514 bh->b_assoc_map = NULL;
515}
516
517int inode_has_buffers(struct inode *inode)
518{
519 return !list_empty(&inode->i_data.i_private_list);
520}
521
522/*
523 * osync is designed to support O_SYNC io. It waits synchronously for
524 * all already-submitted IO to complete, but does not queue any new
525 * writes to the disk.
526 *
527 * To do O_SYNC writes, just queue the buffer writes with write_dirty_buffer
528 * as you dirty the buffers, and then use osync_inode_buffers to wait for
529 * completion. Any other dirty buffers which are not yet queued for
530 * write will not be flushed to disk by the osync.
531 */
532static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
533{
534 struct buffer_head *bh;
535 struct list_head *p;
536 int err = 0;
537
538 spin_lock(lock);
539repeat:
540 list_for_each_prev(p, list) {
541 bh = BH_ENTRY(p);
542 if (buffer_locked(bh)) {
543 get_bh(bh);
544 spin_unlock(lock);
545 wait_on_buffer(bh);
546 if (!buffer_uptodate(bh))
547 err = -EIO;
548 brelse(bh);
549 spin_lock(lock);
550 goto repeat;
551 }
552 }
553 spin_unlock(lock);
554 return err;
555}
556
557/**
558 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
559 * @mapping: the mapping which wants those buffers written
560 *
561 * Starts I/O against the buffers at mapping->i_private_list, and waits upon
562 * that I/O.
563 *
564 * Basically, this is a convenience function for fsync().
565 * @mapping is a file or directory which needs those buffers to be written for
566 * a successful fsync().
567 */
568int sync_mapping_buffers(struct address_space *mapping)
569{
570 struct address_space *buffer_mapping = mapping->i_private_data;
571
572 if (buffer_mapping == NULL || list_empty(&mapping->i_private_list))
573 return 0;
574
575 return fsync_buffers_list(&buffer_mapping->i_private_lock,
576 &mapping->i_private_list);
577}
578EXPORT_SYMBOL(sync_mapping_buffers);
579
580/**
581 * generic_buffers_fsync_noflush - generic buffer fsync implementation
582 * for simple filesystems with no inode lock
583 *
584 * @file: file to synchronize
585 * @start: start offset in bytes
586 * @end: end offset in bytes (inclusive)
587 * @datasync: only synchronize essential metadata if true
588 *
589 * This is a generic implementation of the fsync method for simple
590 * filesystems which track all non-inode metadata in the buffers list
591 * hanging off the address_space structure.
592 */
593int generic_buffers_fsync_noflush(struct file *file, loff_t start, loff_t end,
594 bool datasync)
595{
596 struct inode *inode = file->f_mapping->host;
597 int err;
598 int ret;
599
600 err = file_write_and_wait_range(file, start, end);
601 if (err)
602 return err;
603
604 ret = sync_mapping_buffers(inode->i_mapping);
605 if (!(inode->i_state & I_DIRTY_ALL))
606 goto out;
607 if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
608 goto out;
609
610 err = sync_inode_metadata(inode, 1);
611 if (ret == 0)
612 ret = err;
613
614out:
615 /* check and advance again to catch errors after syncing out buffers */
616 err = file_check_and_advance_wb_err(file);
617 if (ret == 0)
618 ret = err;
619 return ret;
620}
621EXPORT_SYMBOL(generic_buffers_fsync_noflush);
622
623/**
624 * generic_buffers_fsync - generic buffer fsync implementation
625 * for simple filesystems with no inode lock
626 *
627 * @file: file to synchronize
628 * @start: start offset in bytes
629 * @end: end offset in bytes (inclusive)
630 * @datasync: only synchronize essential metadata if true
631 *
632 * This is a generic implementation of the fsync method for simple
633 * filesystems which track all non-inode metadata in the buffers list
634 * hanging off the address_space structure. This also makes sure that
635 * a device cache flush operation is called at the end.
636 */
637int generic_buffers_fsync(struct file *file, loff_t start, loff_t end,
638 bool datasync)
639{
640 struct inode *inode = file->f_mapping->host;
641 int ret;
642
643 ret = generic_buffers_fsync_noflush(file, start, end, datasync);
644 if (!ret)
645 ret = blkdev_issue_flush(inode->i_sb->s_bdev);
646 return ret;
647}
648EXPORT_SYMBOL(generic_buffers_fsync);
649
650/*
651 * Called when we've recently written block `bblock', and it is known that
652 * `bblock' was for a buffer_boundary() buffer. This means that the block at
653 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
654 * dirty, schedule it for IO. So that indirects merge nicely with their data.
655 */
656void write_boundary_block(struct block_device *bdev,
657 sector_t bblock, unsigned blocksize)
658{
659 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
660 if (bh) {
661 if (buffer_dirty(bh))
662 write_dirty_buffer(bh, 0);
663 put_bh(bh);
664 }
665}
666
667void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
668{
669 struct address_space *mapping = inode->i_mapping;
670 struct address_space *buffer_mapping = bh->b_folio->mapping;
671
672 mark_buffer_dirty(bh);
673 if (!mapping->i_private_data) {
674 mapping->i_private_data = buffer_mapping;
675 } else {
676 BUG_ON(mapping->i_private_data != buffer_mapping);
677 }
678 if (!bh->b_assoc_map) {
679 spin_lock(&buffer_mapping->i_private_lock);
680 list_move_tail(&bh->b_assoc_buffers,
681 &mapping->i_private_list);
682 bh->b_assoc_map = mapping;
683 spin_unlock(&buffer_mapping->i_private_lock);
684 }
685}
686EXPORT_SYMBOL(mark_buffer_dirty_inode);
687
688/**
689 * block_dirty_folio - Mark a folio as dirty.
690 * @mapping: The address space containing this folio.
691 * @folio: The folio to mark dirty.
692 *
693 * Filesystems which use buffer_heads can use this function as their
694 * ->dirty_folio implementation. Some filesystems need to do a little
695 * work before calling this function. Filesystems which do not use
696 * buffer_heads should call filemap_dirty_folio() instead.
697 *
698 * If the folio has buffers, the uptodate buffers are set dirty, to
699 * preserve dirty-state coherency between the folio and the buffers.
700 * Buffers added to a dirty folio are created dirty.
701 *
702 * The buffers are dirtied before the folio is dirtied. There's a small
703 * race window in which writeback may see the folio cleanness but not the
704 * buffer dirtiness. That's fine. If this code were to set the folio
705 * dirty before the buffers, writeback could clear the folio dirty flag,
706 * see a bunch of clean buffers and we'd end up with dirty buffers/clean
707 * folio on the dirty folio list.
708 *
709 * We use i_private_lock to lock against try_to_free_buffers() while
710 * using the folio's buffer list. This also prevents clean buffers
711 * being added to the folio after it was set dirty.
712 *
713 * Context: May only be called from process context. Does not sleep.
714 * Caller must ensure that @folio cannot be truncated during this call,
715 * typically by holding the folio lock or having a page in the folio
716 * mapped and holding the page table lock.
717 *
718 * Return: True if the folio was dirtied; false if it was already dirtied.
719 */
720bool block_dirty_folio(struct address_space *mapping, struct folio *folio)
721{
722 struct buffer_head *head;
723 bool newly_dirty;
724
725 spin_lock(&mapping->i_private_lock);
726 head = folio_buffers(folio);
727 if (head) {
728 struct buffer_head *bh = head;
729
730 do {
731 set_buffer_dirty(bh);
732 bh = bh->b_this_page;
733 } while (bh != head);
734 }
735 /*
736 * Lock out page's memcg migration to keep PageDirty
737 * synchronized with per-memcg dirty page counters.
738 */
739 newly_dirty = !folio_test_set_dirty(folio);
740 spin_unlock(&mapping->i_private_lock);
741
742 if (newly_dirty)
743 __folio_mark_dirty(folio, mapping, 1);
744
745 if (newly_dirty)
746 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
747
748 return newly_dirty;
749}
750EXPORT_SYMBOL(block_dirty_folio);
751
752/*
753 * Write out and wait upon a list of buffers.
754 *
755 * We have conflicting pressures: we want to make sure that all
756 * initially dirty buffers get waited on, but that any subsequently
757 * dirtied buffers don't. After all, we don't want fsync to last
758 * forever if somebody is actively writing to the file.
759 *
760 * Do this in two main stages: first we copy dirty buffers to a
761 * temporary inode list, queueing the writes as we go. Then we clean
762 * up, waiting for those writes to complete.
763 *
764 * During this second stage, any subsequent updates to the file may end
765 * up refiling the buffer on the original inode's dirty list again, so
766 * there is a chance we will end up with a buffer queued for write but
767 * not yet completed on that list. So, as a final cleanup we go through
768 * the osync code to catch these locked, dirty buffers without requeuing
769 * any newly dirty buffers for write.
770 */
771static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
772{
773 struct buffer_head *bh;
774 struct address_space *mapping;
775 int err = 0, err2;
776 struct blk_plug plug;
777 LIST_HEAD(tmp);
778
779 blk_start_plug(&plug);
780
781 spin_lock(lock);
782 while (!list_empty(list)) {
783 bh = BH_ENTRY(list->next);
784 mapping = bh->b_assoc_map;
785 __remove_assoc_queue(bh);
786 /* Avoid race with mark_buffer_dirty_inode() which does
787 * a lockless check and we rely on seeing the dirty bit */
788 smp_mb();
789 if (buffer_dirty(bh) || buffer_locked(bh)) {
790 list_add(&bh->b_assoc_buffers, &tmp);
791 bh->b_assoc_map = mapping;
792 if (buffer_dirty(bh)) {
793 get_bh(bh);
794 spin_unlock(lock);
795 /*
796 * Ensure any pending I/O completes so that
797 * write_dirty_buffer() actually writes the
798 * current contents - it is a noop if I/O is
799 * still in flight on potentially older
800 * contents.
801 */
802 write_dirty_buffer(bh, REQ_SYNC);
803
804 /*
805 * Kick off IO for the previous mapping. Note
806 * that we will not run the very last mapping,
807 * wait_on_buffer() will do that for us
808 * through sync_buffer().
809 */
810 brelse(bh);
811 spin_lock(lock);
812 }
813 }
814 }
815
816 spin_unlock(lock);
817 blk_finish_plug(&plug);
818 spin_lock(lock);
819
820 while (!list_empty(&tmp)) {
821 bh = BH_ENTRY(tmp.prev);
822 get_bh(bh);
823 mapping = bh->b_assoc_map;
824 __remove_assoc_queue(bh);
825 /* Avoid race with mark_buffer_dirty_inode() which does
826 * a lockless check and we rely on seeing the dirty bit */
827 smp_mb();
828 if (buffer_dirty(bh)) {
829 list_add(&bh->b_assoc_buffers,
830 &mapping->i_private_list);
831 bh->b_assoc_map = mapping;
832 }
833 spin_unlock(lock);
834 wait_on_buffer(bh);
835 if (!buffer_uptodate(bh))
836 err = -EIO;
837 brelse(bh);
838 spin_lock(lock);
839 }
840
841 spin_unlock(lock);
842 err2 = osync_buffers_list(lock, list);
843 if (err)
844 return err;
845 else
846 return err2;
847}
848
849/*
850 * Invalidate any and all dirty buffers on a given inode. We are
851 * probably unmounting the fs, but that doesn't mean we have already
852 * done a sync(). Just drop the buffers from the inode list.
853 *
854 * NOTE: we take the inode's blockdev's mapping's i_private_lock. Which
855 * assumes that all the buffers are against the blockdev.
856 */
857void invalidate_inode_buffers(struct inode *inode)
858{
859 if (inode_has_buffers(inode)) {
860 struct address_space *mapping = &inode->i_data;
861 struct list_head *list = &mapping->i_private_list;
862 struct address_space *buffer_mapping = mapping->i_private_data;
863
864 spin_lock(&buffer_mapping->i_private_lock);
865 while (!list_empty(list))
866 __remove_assoc_queue(BH_ENTRY(list->next));
867 spin_unlock(&buffer_mapping->i_private_lock);
868 }
869}
870EXPORT_SYMBOL(invalidate_inode_buffers);
871
872/*
873 * Remove any clean buffers from the inode's buffer list. This is called
874 * when we're trying to free the inode itself. Those buffers can pin it.
875 *
876 * Returns true if all buffers were removed.
877 */
878int remove_inode_buffers(struct inode *inode)
879{
880 int ret = 1;
881
882 if (inode_has_buffers(inode)) {
883 struct address_space *mapping = &inode->i_data;
884 struct list_head *list = &mapping->i_private_list;
885 struct address_space *buffer_mapping = mapping->i_private_data;
886
887 spin_lock(&buffer_mapping->i_private_lock);
888 while (!list_empty(list)) {
889 struct buffer_head *bh = BH_ENTRY(list->next);
890 if (buffer_dirty(bh)) {
891 ret = 0;
892 break;
893 }
894 __remove_assoc_queue(bh);
895 }
896 spin_unlock(&buffer_mapping->i_private_lock);
897 }
898 return ret;
899}
900
901/*
902 * Create the appropriate buffers when given a folio for data area and
903 * the size of each buffer.. Use the bh->b_this_page linked list to
904 * follow the buffers created. Return NULL if unable to create more
905 * buffers.
906 *
907 * The retry flag is used to differentiate async IO (paging, swapping)
908 * which may not fail from ordinary buffer allocations.
909 */
910struct buffer_head *folio_alloc_buffers(struct folio *folio, unsigned long size,
911 gfp_t gfp)
912{
913 struct buffer_head *bh, *head;
914 long offset;
915 struct mem_cgroup *memcg, *old_memcg;
916
917 /* The folio lock pins the memcg */
918 memcg = folio_memcg(folio);
919 old_memcg = set_active_memcg(memcg);
920
921 head = NULL;
922 offset = folio_size(folio);
923 while ((offset -= size) >= 0) {
924 bh = alloc_buffer_head(gfp);
925 if (!bh)
926 goto no_grow;
927
928 bh->b_this_page = head;
929 bh->b_blocknr = -1;
930 head = bh;
931
932 bh->b_size = size;
933
934 /* Link the buffer to its folio */
935 folio_set_bh(bh, folio, offset);
936 }
937out:
938 set_active_memcg(old_memcg);
939 return head;
940/*
941 * In case anything failed, we just free everything we got.
942 */
943no_grow:
944 if (head) {
945 do {
946 bh = head;
947 head = head->b_this_page;
948 free_buffer_head(bh);
949 } while (head);
950 }
951
952 goto out;
953}
954EXPORT_SYMBOL_GPL(folio_alloc_buffers);
955
956struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size)
957{
958 gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
959
960 return folio_alloc_buffers(page_folio(page), size, gfp);
961}
962EXPORT_SYMBOL_GPL(alloc_page_buffers);
963
964static inline void link_dev_buffers(struct folio *folio,
965 struct buffer_head *head)
966{
967 struct buffer_head *bh, *tail;
968
969 bh = head;
970 do {
971 tail = bh;
972 bh = bh->b_this_page;
973 } while (bh);
974 tail->b_this_page = head;
975 folio_attach_private(folio, head);
976}
977
978static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
979{
980 sector_t retval = ~((sector_t)0);
981 loff_t sz = bdev_nr_bytes(bdev);
982
983 if (sz) {
984 unsigned int sizebits = blksize_bits(size);
985 retval = (sz >> sizebits);
986 }
987 return retval;
988}
989
990/*
991 * Initialise the state of a blockdev folio's buffers.
992 */
993static sector_t folio_init_buffers(struct folio *folio,
994 struct block_device *bdev, unsigned size)
995{
996 struct buffer_head *head = folio_buffers(folio);
997 struct buffer_head *bh = head;
998 bool uptodate = folio_test_uptodate(folio);
999 sector_t block = div_u64(folio_pos(folio), size);
1000 sector_t end_block = blkdev_max_block(bdev, size);
1001
1002 do {
1003 if (!buffer_mapped(bh)) {
1004 bh->b_end_io = NULL;
1005 bh->b_private = NULL;
1006 bh->b_bdev = bdev;
1007 bh->b_blocknr = block;
1008 if (uptodate)
1009 set_buffer_uptodate(bh);
1010 if (block < end_block)
1011 set_buffer_mapped(bh);
1012 }
1013 block++;
1014 bh = bh->b_this_page;
1015 } while (bh != head);
1016
1017 /*
1018 * Caller needs to validate requested block against end of device.
1019 */
1020 return end_block;
1021}
1022
1023/*
1024 * Create the page-cache folio that contains the requested block.
1025 *
1026 * This is used purely for blockdev mappings.
1027 *
1028 * Returns false if we have a failure which cannot be cured by retrying
1029 * without sleeping. Returns true if we succeeded, or the caller should retry.
1030 */
1031static bool grow_dev_folio(struct block_device *bdev, sector_t block,
1032 pgoff_t index, unsigned size, gfp_t gfp)
1033{
1034 struct address_space *mapping = bdev->bd_mapping;
1035 struct folio *folio;
1036 struct buffer_head *bh;
1037 sector_t end_block = 0;
1038
1039 folio = __filemap_get_folio(mapping, index,
1040 FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp);
1041 if (IS_ERR(folio))
1042 return false;
1043
1044 bh = folio_buffers(folio);
1045 if (bh) {
1046 if (bh->b_size == size) {
1047 end_block = folio_init_buffers(folio, bdev, size);
1048 goto unlock;
1049 }
1050
1051 /*
1052 * Retrying may succeed; for example the folio may finish
1053 * writeback, or buffers may be cleaned. This should not
1054 * happen very often; maybe we have old buffers attached to
1055 * this blockdev's page cache and we're trying to change
1056 * the block size?
1057 */
1058 if (!try_to_free_buffers(folio)) {
1059 end_block = ~0ULL;
1060 goto unlock;
1061 }
1062 }
1063
1064 bh = folio_alloc_buffers(folio, size, gfp | __GFP_ACCOUNT);
1065 if (!bh)
1066 goto unlock;
1067
1068 /*
1069 * Link the folio to the buffers and initialise them. Take the
1070 * lock to be atomic wrt __find_get_block(), which does not
1071 * run under the folio lock.
1072 */
1073 spin_lock(&mapping->i_private_lock);
1074 link_dev_buffers(folio, bh);
1075 end_block = folio_init_buffers(folio, bdev, size);
1076 spin_unlock(&mapping->i_private_lock);
1077unlock:
1078 folio_unlock(folio);
1079 folio_put(folio);
1080 return block < end_block;
1081}
1082
1083/*
1084 * Create buffers for the specified block device block's folio. If
1085 * that folio was dirty, the buffers are set dirty also. Returns false
1086 * if we've hit a permanent error.
1087 */
1088static bool grow_buffers(struct block_device *bdev, sector_t block,
1089 unsigned size, gfp_t gfp)
1090{
1091 loff_t pos;
1092
1093 /*
1094 * Check for a block which lies outside our maximum possible
1095 * pagecache index.
1096 */
1097 if (check_mul_overflow(block, (sector_t)size, &pos) || pos > MAX_LFS_FILESIZE) {
1098 printk(KERN_ERR "%s: requested out-of-range block %llu for device %pg\n",
1099 __func__, (unsigned long long)block,
1100 bdev);
1101 return false;
1102 }
1103
1104 /* Create a folio with the proper size buffers */
1105 return grow_dev_folio(bdev, block, pos / PAGE_SIZE, size, gfp);
1106}
1107
1108static struct buffer_head *
1109__getblk_slow(struct block_device *bdev, sector_t block,
1110 unsigned size, gfp_t gfp)
1111{
1112 /* Size must be multiple of hard sectorsize */
1113 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1114 (size < 512 || size > PAGE_SIZE))) {
1115 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1116 size);
1117 printk(KERN_ERR "logical block size: %d\n",
1118 bdev_logical_block_size(bdev));
1119
1120 dump_stack();
1121 return NULL;
1122 }
1123
1124 for (;;) {
1125 struct buffer_head *bh;
1126
1127 bh = __find_get_block(bdev, block, size);
1128 if (bh)
1129 return bh;
1130
1131 if (!grow_buffers(bdev, block, size, gfp))
1132 return NULL;
1133 }
1134}
1135
1136/*
1137 * The relationship between dirty buffers and dirty pages:
1138 *
1139 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1140 * the page is tagged dirty in the page cache.
1141 *
1142 * At all times, the dirtiness of the buffers represents the dirtiness of
1143 * subsections of the page. If the page has buffers, the page dirty bit is
1144 * merely a hint about the true dirty state.
1145 *
1146 * When a page is set dirty in its entirety, all its buffers are marked dirty
1147 * (if the page has buffers).
1148 *
1149 * When a buffer is marked dirty, its page is dirtied, but the page's other
1150 * buffers are not.
1151 *
1152 * Also. When blockdev buffers are explicitly read with bread(), they
1153 * individually become uptodate. But their backing page remains not
1154 * uptodate - even if all of its buffers are uptodate. A subsequent
1155 * block_read_full_folio() against that folio will discover all the uptodate
1156 * buffers, will set the folio uptodate and will perform no I/O.
1157 */
1158
1159/**
1160 * mark_buffer_dirty - mark a buffer_head as needing writeout
1161 * @bh: the buffer_head to mark dirty
1162 *
1163 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1164 * its backing page dirty, then tag the page as dirty in the page cache
1165 * and then attach the address_space's inode to its superblock's dirty
1166 * inode list.
1167 *
1168 * mark_buffer_dirty() is atomic. It takes bh->b_folio->mapping->i_private_lock,
1169 * i_pages lock and mapping->host->i_lock.
1170 */
1171void mark_buffer_dirty(struct buffer_head *bh)
1172{
1173 WARN_ON_ONCE(!buffer_uptodate(bh));
1174
1175 trace_block_dirty_buffer(bh);
1176
1177 /*
1178 * Very *carefully* optimize the it-is-already-dirty case.
1179 *
1180 * Don't let the final "is it dirty" escape to before we
1181 * perhaps modified the buffer.
1182 */
1183 if (buffer_dirty(bh)) {
1184 smp_mb();
1185 if (buffer_dirty(bh))
1186 return;
1187 }
1188
1189 if (!test_set_buffer_dirty(bh)) {
1190 struct folio *folio = bh->b_folio;
1191 struct address_space *mapping = NULL;
1192
1193 if (!folio_test_set_dirty(folio)) {
1194 mapping = folio->mapping;
1195 if (mapping)
1196 __folio_mark_dirty(folio, mapping, 0);
1197 }
1198 if (mapping)
1199 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1200 }
1201}
1202EXPORT_SYMBOL(mark_buffer_dirty);
1203
1204void mark_buffer_write_io_error(struct buffer_head *bh)
1205{
1206 set_buffer_write_io_error(bh);
1207 /* FIXME: do we need to set this in both places? */
1208 if (bh->b_folio && bh->b_folio->mapping)
1209 mapping_set_error(bh->b_folio->mapping, -EIO);
1210 if (bh->b_assoc_map) {
1211 mapping_set_error(bh->b_assoc_map, -EIO);
1212 errseq_set(&bh->b_assoc_map->host->i_sb->s_wb_err, -EIO);
1213 }
1214}
1215EXPORT_SYMBOL(mark_buffer_write_io_error);
1216
1217/**
1218 * __brelse - Release a buffer.
1219 * @bh: The buffer to release.
1220 *
1221 * This variant of brelse() can be called if @bh is guaranteed to not be NULL.
1222 */
1223void __brelse(struct buffer_head *bh)
1224{
1225 if (atomic_read(&bh->b_count)) {
1226 put_bh(bh);
1227 return;
1228 }
1229 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1230}
1231EXPORT_SYMBOL(__brelse);
1232
1233/**
1234 * __bforget - Discard any dirty data in a buffer.
1235 * @bh: The buffer to forget.
1236 *
1237 * This variant of bforget() can be called if @bh is guaranteed to not
1238 * be NULL.
1239 */
1240void __bforget(struct buffer_head *bh)
1241{
1242 clear_buffer_dirty(bh);
1243 if (bh->b_assoc_map) {
1244 struct address_space *buffer_mapping = bh->b_folio->mapping;
1245
1246 spin_lock(&buffer_mapping->i_private_lock);
1247 list_del_init(&bh->b_assoc_buffers);
1248 bh->b_assoc_map = NULL;
1249 spin_unlock(&buffer_mapping->i_private_lock);
1250 }
1251 __brelse(bh);
1252}
1253EXPORT_SYMBOL(__bforget);
1254
1255static struct buffer_head *__bread_slow(struct buffer_head *bh)
1256{
1257 lock_buffer(bh);
1258 if (buffer_uptodate(bh)) {
1259 unlock_buffer(bh);
1260 return bh;
1261 } else {
1262 get_bh(bh);
1263 bh->b_end_io = end_buffer_read_sync;
1264 submit_bh(REQ_OP_READ, bh);
1265 wait_on_buffer(bh);
1266 if (buffer_uptodate(bh))
1267 return bh;
1268 }
1269 brelse(bh);
1270 return NULL;
1271}
1272
1273/*
1274 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1275 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1276 * refcount elevated by one when they're in an LRU. A buffer can only appear
1277 * once in a particular CPU's LRU. A single buffer can be present in multiple
1278 * CPU's LRUs at the same time.
1279 *
1280 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1281 * sb_find_get_block().
1282 *
1283 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1284 * a local interrupt disable for that.
1285 */
1286
1287#define BH_LRU_SIZE 16
1288
1289struct bh_lru {
1290 struct buffer_head *bhs[BH_LRU_SIZE];
1291};
1292
1293static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1294
1295#ifdef CONFIG_SMP
1296#define bh_lru_lock() local_irq_disable()
1297#define bh_lru_unlock() local_irq_enable()
1298#else
1299#define bh_lru_lock() preempt_disable()
1300#define bh_lru_unlock() preempt_enable()
1301#endif
1302
1303static inline void check_irqs_on(void)
1304{
1305#ifdef irqs_disabled
1306 BUG_ON(irqs_disabled());
1307#endif
1308}
1309
1310/*
1311 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1312 * inserted at the front, and the buffer_head at the back if any is evicted.
1313 * Or, if already in the LRU it is moved to the front.
1314 */
1315static void bh_lru_install(struct buffer_head *bh)
1316{
1317 struct buffer_head *evictee = bh;
1318 struct bh_lru *b;
1319 int i;
1320
1321 check_irqs_on();
1322 bh_lru_lock();
1323
1324 /*
1325 * the refcount of buffer_head in bh_lru prevents dropping the
1326 * attached page(i.e., try_to_free_buffers) so it could cause
1327 * failing page migration.
1328 * Skip putting upcoming bh into bh_lru until migration is done.
1329 */
1330 if (lru_cache_disabled() || cpu_is_isolated(smp_processor_id())) {
1331 bh_lru_unlock();
1332 return;
1333 }
1334
1335 b = this_cpu_ptr(&bh_lrus);
1336 for (i = 0; i < BH_LRU_SIZE; i++) {
1337 swap(evictee, b->bhs[i]);
1338 if (evictee == bh) {
1339 bh_lru_unlock();
1340 return;
1341 }
1342 }
1343
1344 get_bh(bh);
1345 bh_lru_unlock();
1346 brelse(evictee);
1347}
1348
1349/*
1350 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1351 */
1352static struct buffer_head *
1353lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1354{
1355 struct buffer_head *ret = NULL;
1356 unsigned int i;
1357
1358 check_irqs_on();
1359 bh_lru_lock();
1360 if (cpu_is_isolated(smp_processor_id())) {
1361 bh_lru_unlock();
1362 return NULL;
1363 }
1364 for (i = 0; i < BH_LRU_SIZE; i++) {
1365 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1366
1367 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1368 bh->b_size == size) {
1369 if (i) {
1370 while (i) {
1371 __this_cpu_write(bh_lrus.bhs[i],
1372 __this_cpu_read(bh_lrus.bhs[i - 1]));
1373 i--;
1374 }
1375 __this_cpu_write(bh_lrus.bhs[0], bh);
1376 }
1377 get_bh(bh);
1378 ret = bh;
1379 break;
1380 }
1381 }
1382 bh_lru_unlock();
1383 return ret;
1384}
1385
1386/*
1387 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1388 * it in the LRU and mark it as accessed. If it is not present then return
1389 * NULL
1390 */
1391struct buffer_head *
1392__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1393{
1394 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1395
1396 if (bh == NULL) {
1397 /* __find_get_block_slow will mark the page accessed */
1398 bh = __find_get_block_slow(bdev, block);
1399 if (bh)
1400 bh_lru_install(bh);
1401 } else
1402 touch_buffer(bh);
1403
1404 return bh;
1405}
1406EXPORT_SYMBOL(__find_get_block);
1407
1408/**
1409 * bdev_getblk - Get a buffer_head in a block device's buffer cache.
1410 * @bdev: The block device.
1411 * @block: The block number.
1412 * @size: The size of buffer_heads for this @bdev.
1413 * @gfp: The memory allocation flags to use.
1414 *
1415 * The returned buffer head has its reference count incremented, but is
1416 * not locked. The caller should call brelse() when it has finished
1417 * with the buffer. The buffer may not be uptodate. If needed, the
1418 * caller can bring it uptodate either by reading it or overwriting it.
1419 *
1420 * Return: The buffer head, or NULL if memory could not be allocated.
1421 */
1422struct buffer_head *bdev_getblk(struct block_device *bdev, sector_t block,
1423 unsigned size, gfp_t gfp)
1424{
1425 struct buffer_head *bh = __find_get_block(bdev, block, size);
1426
1427 might_alloc(gfp);
1428 if (bh)
1429 return bh;
1430
1431 return __getblk_slow(bdev, block, size, gfp);
1432}
1433EXPORT_SYMBOL(bdev_getblk);
1434
1435/*
1436 * Do async read-ahead on a buffer..
1437 */
1438void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1439{
1440 struct buffer_head *bh = bdev_getblk(bdev, block, size,
1441 GFP_NOWAIT | __GFP_MOVABLE);
1442
1443 if (likely(bh)) {
1444 bh_readahead(bh, REQ_RAHEAD);
1445 brelse(bh);
1446 }
1447}
1448EXPORT_SYMBOL(__breadahead);
1449
1450/**
1451 * __bread_gfp() - Read a block.
1452 * @bdev: The block device to read from.
1453 * @block: Block number in units of block size.
1454 * @size: The block size of this device in bytes.
1455 * @gfp: Not page allocation flags; see below.
1456 *
1457 * You are not expected to call this function. You should use one of
1458 * sb_bread(), sb_bread_unmovable() or __bread().
1459 *
1460 * Read a specified block, and return the buffer head that refers to it.
1461 * If @gfp is 0, the memory will be allocated using the block device's
1462 * default GFP flags. If @gfp is __GFP_MOVABLE, the memory may be
1463 * allocated from a movable area. Do not pass in a complete set of
1464 * GFP flags.
1465 *
1466 * The returned buffer head has its refcount increased. The caller should
1467 * call brelse() when it has finished with the buffer.
1468 *
1469 * Context: May sleep waiting for I/O.
1470 * Return: NULL if the block was unreadable.
1471 */
1472struct buffer_head *__bread_gfp(struct block_device *bdev, sector_t block,
1473 unsigned size, gfp_t gfp)
1474{
1475 struct buffer_head *bh;
1476
1477 gfp |= mapping_gfp_constraint(bdev->bd_mapping, ~__GFP_FS);
1478
1479 /*
1480 * Prefer looping in the allocator rather than here, at least that
1481 * code knows what it's doing.
1482 */
1483 gfp |= __GFP_NOFAIL;
1484
1485 bh = bdev_getblk(bdev, block, size, gfp);
1486
1487 if (likely(bh) && !buffer_uptodate(bh))
1488 bh = __bread_slow(bh);
1489 return bh;
1490}
1491EXPORT_SYMBOL(__bread_gfp);
1492
1493static void __invalidate_bh_lrus(struct bh_lru *b)
1494{
1495 int i;
1496
1497 for (i = 0; i < BH_LRU_SIZE; i++) {
1498 brelse(b->bhs[i]);
1499 b->bhs[i] = NULL;
1500 }
1501}
1502/*
1503 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1504 * This doesn't race because it runs in each cpu either in irq
1505 * or with preempt disabled.
1506 */
1507static void invalidate_bh_lru(void *arg)
1508{
1509 struct bh_lru *b = &get_cpu_var(bh_lrus);
1510
1511 __invalidate_bh_lrus(b);
1512 put_cpu_var(bh_lrus);
1513}
1514
1515bool has_bh_in_lru(int cpu, void *dummy)
1516{
1517 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1518 int i;
1519
1520 for (i = 0; i < BH_LRU_SIZE; i++) {
1521 if (b->bhs[i])
1522 return true;
1523 }
1524
1525 return false;
1526}
1527
1528void invalidate_bh_lrus(void)
1529{
1530 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1);
1531}
1532EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1533
1534/*
1535 * It's called from workqueue context so we need a bh_lru_lock to close
1536 * the race with preemption/irq.
1537 */
1538void invalidate_bh_lrus_cpu(void)
1539{
1540 struct bh_lru *b;
1541
1542 bh_lru_lock();
1543 b = this_cpu_ptr(&bh_lrus);
1544 __invalidate_bh_lrus(b);
1545 bh_lru_unlock();
1546}
1547
1548void folio_set_bh(struct buffer_head *bh, struct folio *folio,
1549 unsigned long offset)
1550{
1551 bh->b_folio = folio;
1552 BUG_ON(offset >= folio_size(folio));
1553 if (folio_test_highmem(folio))
1554 /*
1555 * This catches illegal uses and preserves the offset:
1556 */
1557 bh->b_data = (char *)(0 + offset);
1558 else
1559 bh->b_data = folio_address(folio) + offset;
1560}
1561EXPORT_SYMBOL(folio_set_bh);
1562
1563/*
1564 * Called when truncating a buffer on a page completely.
1565 */
1566
1567/* Bits that are cleared during an invalidate */
1568#define BUFFER_FLAGS_DISCARD \
1569 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1570 1 << BH_Delay | 1 << BH_Unwritten)
1571
1572static void discard_buffer(struct buffer_head * bh)
1573{
1574 unsigned long b_state;
1575
1576 lock_buffer(bh);
1577 clear_buffer_dirty(bh);
1578 bh->b_bdev = NULL;
1579 b_state = READ_ONCE(bh->b_state);
1580 do {
1581 } while (!try_cmpxchg(&bh->b_state, &b_state,
1582 b_state & ~BUFFER_FLAGS_DISCARD));
1583 unlock_buffer(bh);
1584}
1585
1586/**
1587 * block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1588 * @folio: The folio which is affected.
1589 * @offset: start of the range to invalidate
1590 * @length: length of the range to invalidate
1591 *
1592 * block_invalidate_folio() is called when all or part of the folio has been
1593 * invalidated by a truncate operation.
1594 *
1595 * block_invalidate_folio() does not have to release all buffers, but it must
1596 * ensure that no dirty buffer is left outside @offset and that no I/O
1597 * is underway against any of the blocks which are outside the truncation
1598 * point. Because the caller is about to free (and possibly reuse) those
1599 * blocks on-disk.
1600 */
1601void block_invalidate_folio(struct folio *folio, size_t offset, size_t length)
1602{
1603 struct buffer_head *head, *bh, *next;
1604 size_t curr_off = 0;
1605 size_t stop = length + offset;
1606
1607 BUG_ON(!folio_test_locked(folio));
1608
1609 /*
1610 * Check for overflow
1611 */
1612 BUG_ON(stop > folio_size(folio) || stop < length);
1613
1614 head = folio_buffers(folio);
1615 if (!head)
1616 return;
1617
1618 bh = head;
1619 do {
1620 size_t next_off = curr_off + bh->b_size;
1621 next = bh->b_this_page;
1622
1623 /*
1624 * Are we still fully in range ?
1625 */
1626 if (next_off > stop)
1627 goto out;
1628
1629 /*
1630 * is this block fully invalidated?
1631 */
1632 if (offset <= curr_off)
1633 discard_buffer(bh);
1634 curr_off = next_off;
1635 bh = next;
1636 } while (bh != head);
1637
1638 /*
1639 * We release buffers only if the entire folio is being invalidated.
1640 * The get_block cached value has been unconditionally invalidated,
1641 * so real IO is not possible anymore.
1642 */
1643 if (length == folio_size(folio))
1644 filemap_release_folio(folio, 0);
1645out:
1646 folio_clear_mappedtodisk(folio);
1647 return;
1648}
1649EXPORT_SYMBOL(block_invalidate_folio);
1650
1651/*
1652 * We attach and possibly dirty the buffers atomically wrt
1653 * block_dirty_folio() via i_private_lock. try_to_free_buffers
1654 * is already excluded via the folio lock.
1655 */
1656struct buffer_head *create_empty_buffers(struct folio *folio,
1657 unsigned long blocksize, unsigned long b_state)
1658{
1659 struct buffer_head *bh, *head, *tail;
1660 gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT | __GFP_NOFAIL;
1661
1662 head = folio_alloc_buffers(folio, blocksize, gfp);
1663 bh = head;
1664 do {
1665 bh->b_state |= b_state;
1666 tail = bh;
1667 bh = bh->b_this_page;
1668 } while (bh);
1669 tail->b_this_page = head;
1670
1671 spin_lock(&folio->mapping->i_private_lock);
1672 if (folio_test_uptodate(folio) || folio_test_dirty(folio)) {
1673 bh = head;
1674 do {
1675 if (folio_test_dirty(folio))
1676 set_buffer_dirty(bh);
1677 if (folio_test_uptodate(folio))
1678 set_buffer_uptodate(bh);
1679 bh = bh->b_this_page;
1680 } while (bh != head);
1681 }
1682 folio_attach_private(folio, head);
1683 spin_unlock(&folio->mapping->i_private_lock);
1684
1685 return head;
1686}
1687EXPORT_SYMBOL(create_empty_buffers);
1688
1689/**
1690 * clean_bdev_aliases: clean a range of buffers in block device
1691 * @bdev: Block device to clean buffers in
1692 * @block: Start of a range of blocks to clean
1693 * @len: Number of blocks to clean
1694 *
1695 * We are taking a range of blocks for data and we don't want writeback of any
1696 * buffer-cache aliases starting from return from this function and until the
1697 * moment when something will explicitly mark the buffer dirty (hopefully that
1698 * will not happen until we will free that block ;-) We don't even need to mark
1699 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1700 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1701 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1702 * would confuse anyone who might pick it with bread() afterwards...
1703 *
1704 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1705 * writeout I/O going on against recently-freed buffers. We don't wait on that
1706 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1707 * need to. That happens here.
1708 */
1709void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1710{
1711 struct address_space *bd_mapping = bdev->bd_mapping;
1712 const int blkbits = bd_mapping->host->i_blkbits;
1713 struct folio_batch fbatch;
1714 pgoff_t index = ((loff_t)block << blkbits) / PAGE_SIZE;
1715 pgoff_t end;
1716 int i, count;
1717 struct buffer_head *bh;
1718 struct buffer_head *head;
1719
1720 end = ((loff_t)(block + len - 1) << blkbits) / PAGE_SIZE;
1721 folio_batch_init(&fbatch);
1722 while (filemap_get_folios(bd_mapping, &index, end, &fbatch)) {
1723 count = folio_batch_count(&fbatch);
1724 for (i = 0; i < count; i++) {
1725 struct folio *folio = fbatch.folios[i];
1726
1727 if (!folio_buffers(folio))
1728 continue;
1729 /*
1730 * We use folio lock instead of bd_mapping->i_private_lock
1731 * to pin buffers here since we can afford to sleep and
1732 * it scales better than a global spinlock lock.
1733 */
1734 folio_lock(folio);
1735 /* Recheck when the folio is locked which pins bhs */
1736 head = folio_buffers(folio);
1737 if (!head)
1738 goto unlock_page;
1739 bh = head;
1740 do {
1741 if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1742 goto next;
1743 if (bh->b_blocknr >= block + len)
1744 break;
1745 clear_buffer_dirty(bh);
1746 wait_on_buffer(bh);
1747 clear_buffer_req(bh);
1748next:
1749 bh = bh->b_this_page;
1750 } while (bh != head);
1751unlock_page:
1752 folio_unlock(folio);
1753 }
1754 folio_batch_release(&fbatch);
1755 cond_resched();
1756 /* End of range already reached? */
1757 if (index > end || !index)
1758 break;
1759 }
1760}
1761EXPORT_SYMBOL(clean_bdev_aliases);
1762
1763static struct buffer_head *folio_create_buffers(struct folio *folio,
1764 struct inode *inode,
1765 unsigned int b_state)
1766{
1767 struct buffer_head *bh;
1768
1769 BUG_ON(!folio_test_locked(folio));
1770
1771 bh = folio_buffers(folio);
1772 if (!bh)
1773 bh = create_empty_buffers(folio,
1774 1 << READ_ONCE(inode->i_blkbits), b_state);
1775 return bh;
1776}
1777
1778/*
1779 * NOTE! All mapped/uptodate combinations are valid:
1780 *
1781 * Mapped Uptodate Meaning
1782 *
1783 * No No "unknown" - must do get_block()
1784 * No Yes "hole" - zero-filled
1785 * Yes No "allocated" - allocated on disk, not read in
1786 * Yes Yes "valid" - allocated and up-to-date in memory.
1787 *
1788 * "Dirty" is valid only with the last case (mapped+uptodate).
1789 */
1790
1791/*
1792 * While block_write_full_folio is writing back the dirty buffers under
1793 * the page lock, whoever dirtied the buffers may decide to clean them
1794 * again at any time. We handle that by only looking at the buffer
1795 * state inside lock_buffer().
1796 *
1797 * If block_write_full_folio() is called for regular writeback
1798 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1799 * locked buffer. This only can happen if someone has written the buffer
1800 * directly, with submit_bh(). At the address_space level PageWriteback
1801 * prevents this contention from occurring.
1802 *
1803 * If block_write_full_folio() is called with wbc->sync_mode ==
1804 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1805 * causes the writes to be flagged as synchronous writes.
1806 */
1807int __block_write_full_folio(struct inode *inode, struct folio *folio,
1808 get_block_t *get_block, struct writeback_control *wbc)
1809{
1810 int err;
1811 sector_t block;
1812 sector_t last_block;
1813 struct buffer_head *bh, *head;
1814 size_t blocksize;
1815 int nr_underway = 0;
1816 blk_opf_t write_flags = wbc_to_write_flags(wbc);
1817
1818 head = folio_create_buffers(folio, inode,
1819 (1 << BH_Dirty) | (1 << BH_Uptodate));
1820
1821 /*
1822 * Be very careful. We have no exclusion from block_dirty_folio
1823 * here, and the (potentially unmapped) buffers may become dirty at
1824 * any time. If a buffer becomes dirty here after we've inspected it
1825 * then we just miss that fact, and the folio stays dirty.
1826 *
1827 * Buffers outside i_size may be dirtied by block_dirty_folio;
1828 * handle that here by just cleaning them.
1829 */
1830
1831 bh = head;
1832 blocksize = bh->b_size;
1833
1834 block = div_u64(folio_pos(folio), blocksize);
1835 last_block = div_u64(i_size_read(inode) - 1, blocksize);
1836
1837 /*
1838 * Get all the dirty buffers mapped to disk addresses and
1839 * handle any aliases from the underlying blockdev's mapping.
1840 */
1841 do {
1842 if (block > last_block) {
1843 /*
1844 * mapped buffers outside i_size will occur, because
1845 * this folio can be outside i_size when there is a
1846 * truncate in progress.
1847 */
1848 /*
1849 * The buffer was zeroed by block_write_full_folio()
1850 */
1851 clear_buffer_dirty(bh);
1852 set_buffer_uptodate(bh);
1853 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1854 buffer_dirty(bh)) {
1855 WARN_ON(bh->b_size != blocksize);
1856 err = get_block(inode, block, bh, 1);
1857 if (err)
1858 goto recover;
1859 clear_buffer_delay(bh);
1860 if (buffer_new(bh)) {
1861 /* blockdev mappings never come here */
1862 clear_buffer_new(bh);
1863 clean_bdev_bh_alias(bh);
1864 }
1865 }
1866 bh = bh->b_this_page;
1867 block++;
1868 } while (bh != head);
1869
1870 do {
1871 if (!buffer_mapped(bh))
1872 continue;
1873 /*
1874 * If it's a fully non-blocking write attempt and we cannot
1875 * lock the buffer then redirty the folio. Note that this can
1876 * potentially cause a busy-wait loop from writeback threads
1877 * and kswapd activity, but those code paths have their own
1878 * higher-level throttling.
1879 */
1880 if (wbc->sync_mode != WB_SYNC_NONE) {
1881 lock_buffer(bh);
1882 } else if (!trylock_buffer(bh)) {
1883 folio_redirty_for_writepage(wbc, folio);
1884 continue;
1885 }
1886 if (test_clear_buffer_dirty(bh)) {
1887 mark_buffer_async_write_endio(bh,
1888 end_buffer_async_write);
1889 } else {
1890 unlock_buffer(bh);
1891 }
1892 } while ((bh = bh->b_this_page) != head);
1893
1894 /*
1895 * The folio and its buffers are protected by the writeback flag,
1896 * so we can drop the bh refcounts early.
1897 */
1898 BUG_ON(folio_test_writeback(folio));
1899 folio_start_writeback(folio);
1900
1901 do {
1902 struct buffer_head *next = bh->b_this_page;
1903 if (buffer_async_write(bh)) {
1904 submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
1905 inode->i_write_hint, wbc);
1906 nr_underway++;
1907 }
1908 bh = next;
1909 } while (bh != head);
1910 folio_unlock(folio);
1911
1912 err = 0;
1913done:
1914 if (nr_underway == 0) {
1915 /*
1916 * The folio was marked dirty, but the buffers were
1917 * clean. Someone wrote them back by hand with
1918 * write_dirty_buffer/submit_bh. A rare case.
1919 */
1920 folio_end_writeback(folio);
1921
1922 /*
1923 * The folio and buffer_heads can be released at any time from
1924 * here on.
1925 */
1926 }
1927 return err;
1928
1929recover:
1930 /*
1931 * ENOSPC, or some other error. We may already have added some
1932 * blocks to the file, so we need to write these out to avoid
1933 * exposing stale data.
1934 * The folio is currently locked and not marked for writeback
1935 */
1936 bh = head;
1937 /* Recovery: lock and submit the mapped buffers */
1938 do {
1939 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1940 !buffer_delay(bh)) {
1941 lock_buffer(bh);
1942 mark_buffer_async_write_endio(bh,
1943 end_buffer_async_write);
1944 } else {
1945 /*
1946 * The buffer may have been set dirty during
1947 * attachment to a dirty folio.
1948 */
1949 clear_buffer_dirty(bh);
1950 }
1951 } while ((bh = bh->b_this_page) != head);
1952 BUG_ON(folio_test_writeback(folio));
1953 mapping_set_error(folio->mapping, err);
1954 folio_start_writeback(folio);
1955 do {
1956 struct buffer_head *next = bh->b_this_page;
1957 if (buffer_async_write(bh)) {
1958 clear_buffer_dirty(bh);
1959 submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
1960 inode->i_write_hint, wbc);
1961 nr_underway++;
1962 }
1963 bh = next;
1964 } while (bh != head);
1965 folio_unlock(folio);
1966 goto done;
1967}
1968EXPORT_SYMBOL(__block_write_full_folio);
1969
1970/*
1971 * If a folio has any new buffers, zero them out here, and mark them uptodate
1972 * and dirty so they'll be written out (in order to prevent uninitialised
1973 * block data from leaking). And clear the new bit.
1974 */
1975void folio_zero_new_buffers(struct folio *folio, size_t from, size_t to)
1976{
1977 size_t block_start, block_end;
1978 struct buffer_head *head, *bh;
1979
1980 BUG_ON(!folio_test_locked(folio));
1981 head = folio_buffers(folio);
1982 if (!head)
1983 return;
1984
1985 bh = head;
1986 block_start = 0;
1987 do {
1988 block_end = block_start + bh->b_size;
1989
1990 if (buffer_new(bh)) {
1991 if (block_end > from && block_start < to) {
1992 if (!folio_test_uptodate(folio)) {
1993 size_t start, xend;
1994
1995 start = max(from, block_start);
1996 xend = min(to, block_end);
1997
1998 folio_zero_segment(folio, start, xend);
1999 set_buffer_uptodate(bh);
2000 }
2001
2002 clear_buffer_new(bh);
2003 mark_buffer_dirty(bh);
2004 }
2005 }
2006
2007 block_start = block_end;
2008 bh = bh->b_this_page;
2009 } while (bh != head);
2010}
2011EXPORT_SYMBOL(folio_zero_new_buffers);
2012
2013static int
2014iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
2015 const struct iomap *iomap)
2016{
2017 loff_t offset = (loff_t)block << inode->i_blkbits;
2018
2019 bh->b_bdev = iomap->bdev;
2020
2021 /*
2022 * Block points to offset in file we need to map, iomap contains
2023 * the offset at which the map starts. If the map ends before the
2024 * current block, then do not map the buffer and let the caller
2025 * handle it.
2026 */
2027 if (offset >= iomap->offset + iomap->length)
2028 return -EIO;
2029
2030 switch (iomap->type) {
2031 case IOMAP_HOLE:
2032 /*
2033 * If the buffer is not up to date or beyond the current EOF,
2034 * we need to mark it as new to ensure sub-block zeroing is
2035 * executed if necessary.
2036 */
2037 if (!buffer_uptodate(bh) ||
2038 (offset >= i_size_read(inode)))
2039 set_buffer_new(bh);
2040 return 0;
2041 case IOMAP_DELALLOC:
2042 if (!buffer_uptodate(bh) ||
2043 (offset >= i_size_read(inode)))
2044 set_buffer_new(bh);
2045 set_buffer_uptodate(bh);
2046 set_buffer_mapped(bh);
2047 set_buffer_delay(bh);
2048 return 0;
2049 case IOMAP_UNWRITTEN:
2050 /*
2051 * For unwritten regions, we always need to ensure that regions
2052 * in the block we are not writing to are zeroed. Mark the
2053 * buffer as new to ensure this.
2054 */
2055 set_buffer_new(bh);
2056 set_buffer_unwritten(bh);
2057 fallthrough;
2058 case IOMAP_MAPPED:
2059 if ((iomap->flags & IOMAP_F_NEW) ||
2060 offset >= i_size_read(inode)) {
2061 /*
2062 * This can happen if truncating the block device races
2063 * with the check in the caller as i_size updates on
2064 * block devices aren't synchronized by i_rwsem for
2065 * block devices.
2066 */
2067 if (S_ISBLK(inode->i_mode))
2068 return -EIO;
2069 set_buffer_new(bh);
2070 }
2071 bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
2072 inode->i_blkbits;
2073 set_buffer_mapped(bh);
2074 return 0;
2075 default:
2076 WARN_ON_ONCE(1);
2077 return -EIO;
2078 }
2079}
2080
2081int __block_write_begin_int(struct folio *folio, loff_t pos, unsigned len,
2082 get_block_t *get_block, const struct iomap *iomap)
2083{
2084 size_t from = offset_in_folio(folio, pos);
2085 size_t to = from + len;
2086 struct inode *inode = folio->mapping->host;
2087 size_t block_start, block_end;
2088 sector_t block;
2089 int err = 0;
2090 size_t blocksize;
2091 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
2092
2093 BUG_ON(!folio_test_locked(folio));
2094 BUG_ON(to > folio_size(folio));
2095 BUG_ON(from > to);
2096
2097 head = folio_create_buffers(folio, inode, 0);
2098 blocksize = head->b_size;
2099 block = div_u64(folio_pos(folio), blocksize);
2100
2101 for (bh = head, block_start = 0; bh != head || !block_start;
2102 block++, block_start=block_end, bh = bh->b_this_page) {
2103 block_end = block_start + blocksize;
2104 if (block_end <= from || block_start >= to) {
2105 if (folio_test_uptodate(folio)) {
2106 if (!buffer_uptodate(bh))
2107 set_buffer_uptodate(bh);
2108 }
2109 continue;
2110 }
2111 if (buffer_new(bh))
2112 clear_buffer_new(bh);
2113 if (!buffer_mapped(bh)) {
2114 WARN_ON(bh->b_size != blocksize);
2115 if (get_block)
2116 err = get_block(inode, block, bh, 1);
2117 else
2118 err = iomap_to_bh(inode, block, bh, iomap);
2119 if (err)
2120 break;
2121
2122 if (buffer_new(bh)) {
2123 clean_bdev_bh_alias(bh);
2124 if (folio_test_uptodate(folio)) {
2125 clear_buffer_new(bh);
2126 set_buffer_uptodate(bh);
2127 mark_buffer_dirty(bh);
2128 continue;
2129 }
2130 if (block_end > to || block_start < from)
2131 folio_zero_segments(folio,
2132 to, block_end,
2133 block_start, from);
2134 continue;
2135 }
2136 }
2137 if (folio_test_uptodate(folio)) {
2138 if (!buffer_uptodate(bh))
2139 set_buffer_uptodate(bh);
2140 continue;
2141 }
2142 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2143 !buffer_unwritten(bh) &&
2144 (block_start < from || block_end > to)) {
2145 bh_read_nowait(bh, 0);
2146 *wait_bh++=bh;
2147 }
2148 }
2149 /*
2150 * If we issued read requests - let them complete.
2151 */
2152 while(wait_bh > wait) {
2153 wait_on_buffer(*--wait_bh);
2154 if (!buffer_uptodate(*wait_bh))
2155 err = -EIO;
2156 }
2157 if (unlikely(err))
2158 folio_zero_new_buffers(folio, from, to);
2159 return err;
2160}
2161
2162int __block_write_begin(struct folio *folio, loff_t pos, unsigned len,
2163 get_block_t *get_block)
2164{
2165 return __block_write_begin_int(folio, pos, len, get_block, NULL);
2166}
2167EXPORT_SYMBOL(__block_write_begin);
2168
2169static void __block_commit_write(struct folio *folio, size_t from, size_t to)
2170{
2171 size_t block_start, block_end;
2172 bool partial = false;
2173 unsigned blocksize;
2174 struct buffer_head *bh, *head;
2175
2176 bh = head = folio_buffers(folio);
2177 if (!bh)
2178 return;
2179 blocksize = bh->b_size;
2180
2181 block_start = 0;
2182 do {
2183 block_end = block_start + blocksize;
2184 if (block_end <= from || block_start >= to) {
2185 if (!buffer_uptodate(bh))
2186 partial = true;
2187 } else {
2188 set_buffer_uptodate(bh);
2189 mark_buffer_dirty(bh);
2190 }
2191 if (buffer_new(bh))
2192 clear_buffer_new(bh);
2193
2194 block_start = block_end;
2195 bh = bh->b_this_page;
2196 } while (bh != head);
2197
2198 /*
2199 * If this is a partial write which happened to make all buffers
2200 * uptodate then we can optimize away a bogus read_folio() for
2201 * the next read(). Here we 'discover' whether the folio went
2202 * uptodate as a result of this (potentially partial) write.
2203 */
2204 if (!partial)
2205 folio_mark_uptodate(folio);
2206}
2207
2208/*
2209 * block_write_begin takes care of the basic task of block allocation and
2210 * bringing partial write blocks uptodate first.
2211 *
2212 * The filesystem needs to handle block truncation upon failure.
2213 */
2214int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2215 struct folio **foliop, get_block_t *get_block)
2216{
2217 pgoff_t index = pos >> PAGE_SHIFT;
2218 struct folio *folio;
2219 int status;
2220
2221 folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
2222 mapping_gfp_mask(mapping));
2223 if (IS_ERR(folio))
2224 return PTR_ERR(folio);
2225
2226 status = __block_write_begin_int(folio, pos, len, get_block, NULL);
2227 if (unlikely(status)) {
2228 folio_unlock(folio);
2229 folio_put(folio);
2230 folio = NULL;
2231 }
2232
2233 *foliop = folio;
2234 return status;
2235}
2236EXPORT_SYMBOL(block_write_begin);
2237
2238int block_write_end(struct file *file, struct address_space *mapping,
2239 loff_t pos, unsigned len, unsigned copied,
2240 struct folio *folio, void *fsdata)
2241{
2242 size_t start = pos - folio_pos(folio);
2243
2244 if (unlikely(copied < len)) {
2245 /*
2246 * The buffers that were written will now be uptodate, so
2247 * we don't have to worry about a read_folio reading them
2248 * and overwriting a partial write. However if we have
2249 * encountered a short write and only partially written
2250 * into a buffer, it will not be marked uptodate, so a
2251 * read_folio might come in and destroy our partial write.
2252 *
2253 * Do the simplest thing, and just treat any short write to a
2254 * non uptodate folio as a zero-length write, and force the
2255 * caller to redo the whole thing.
2256 */
2257 if (!folio_test_uptodate(folio))
2258 copied = 0;
2259
2260 folio_zero_new_buffers(folio, start+copied, start+len);
2261 }
2262 flush_dcache_folio(folio);
2263
2264 /* This could be a short (even 0-length) commit */
2265 __block_commit_write(folio, start, start + copied);
2266
2267 return copied;
2268}
2269EXPORT_SYMBOL(block_write_end);
2270
2271int generic_write_end(struct file *file, struct address_space *mapping,
2272 loff_t pos, unsigned len, unsigned copied,
2273 struct folio *folio, void *fsdata)
2274{
2275 struct inode *inode = mapping->host;
2276 loff_t old_size = inode->i_size;
2277 bool i_size_changed = false;
2278
2279 copied = block_write_end(file, mapping, pos, len, copied, folio, fsdata);
2280
2281 /*
2282 * No need to use i_size_read() here, the i_size cannot change under us
2283 * because we hold i_rwsem.
2284 *
2285 * But it's important to update i_size while still holding folio lock:
2286 * page writeout could otherwise come in and zero beyond i_size.
2287 */
2288 if (pos + copied > inode->i_size) {
2289 i_size_write(inode, pos + copied);
2290 i_size_changed = true;
2291 }
2292
2293 folio_unlock(folio);
2294 folio_put(folio);
2295
2296 if (old_size < pos)
2297 pagecache_isize_extended(inode, old_size, pos);
2298 /*
2299 * Don't mark the inode dirty under page lock. First, it unnecessarily
2300 * makes the holding time of page lock longer. Second, it forces lock
2301 * ordering of page lock and transaction start for journaling
2302 * filesystems.
2303 */
2304 if (i_size_changed)
2305 mark_inode_dirty(inode);
2306 return copied;
2307}
2308EXPORT_SYMBOL(generic_write_end);
2309
2310/*
2311 * block_is_partially_uptodate checks whether buffers within a folio are
2312 * uptodate or not.
2313 *
2314 * Returns true if all buffers which correspond to the specified part
2315 * of the folio are uptodate.
2316 */
2317bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
2318{
2319 unsigned block_start, block_end, blocksize;
2320 unsigned to;
2321 struct buffer_head *bh, *head;
2322 bool ret = true;
2323
2324 head = folio_buffers(folio);
2325 if (!head)
2326 return false;
2327 blocksize = head->b_size;
2328 to = min_t(unsigned, folio_size(folio) - from, count);
2329 to = from + to;
2330 if (from < blocksize && to > folio_size(folio) - blocksize)
2331 return false;
2332
2333 bh = head;
2334 block_start = 0;
2335 do {
2336 block_end = block_start + blocksize;
2337 if (block_end > from && block_start < to) {
2338 if (!buffer_uptodate(bh)) {
2339 ret = false;
2340 break;
2341 }
2342 if (block_end >= to)
2343 break;
2344 }
2345 block_start = block_end;
2346 bh = bh->b_this_page;
2347 } while (bh != head);
2348
2349 return ret;
2350}
2351EXPORT_SYMBOL(block_is_partially_uptodate);
2352
2353/*
2354 * Generic "read_folio" function for block devices that have the normal
2355 * get_block functionality. This is most of the block device filesystems.
2356 * Reads the folio asynchronously --- the unlock_buffer() and
2357 * set/clear_buffer_uptodate() functions propagate buffer state into the
2358 * folio once IO has completed.
2359 */
2360int block_read_full_folio(struct folio *folio, get_block_t *get_block)
2361{
2362 struct inode *inode = folio->mapping->host;
2363 sector_t iblock, lblock;
2364 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2365 size_t blocksize;
2366 int nr, i;
2367 int fully_mapped = 1;
2368 bool page_error = false;
2369 loff_t limit = i_size_read(inode);
2370
2371 /* This is needed for ext4. */
2372 if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
2373 limit = inode->i_sb->s_maxbytes;
2374
2375 VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
2376
2377 head = folio_create_buffers(folio, inode, 0);
2378 blocksize = head->b_size;
2379
2380 iblock = div_u64(folio_pos(folio), blocksize);
2381 lblock = div_u64(limit + blocksize - 1, blocksize);
2382 bh = head;
2383 nr = 0;
2384 i = 0;
2385
2386 do {
2387 if (buffer_uptodate(bh))
2388 continue;
2389
2390 if (!buffer_mapped(bh)) {
2391 int err = 0;
2392
2393 fully_mapped = 0;
2394 if (iblock < lblock) {
2395 WARN_ON(bh->b_size != blocksize);
2396 err = get_block(inode, iblock, bh, 0);
2397 if (err)
2398 page_error = true;
2399 }
2400 if (!buffer_mapped(bh)) {
2401 folio_zero_range(folio, i * blocksize,
2402 blocksize);
2403 if (!err)
2404 set_buffer_uptodate(bh);
2405 continue;
2406 }
2407 /*
2408 * get_block() might have updated the buffer
2409 * synchronously
2410 */
2411 if (buffer_uptodate(bh))
2412 continue;
2413 }
2414 arr[nr++] = bh;
2415 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2416
2417 if (fully_mapped)
2418 folio_set_mappedtodisk(folio);
2419
2420 if (!nr) {
2421 /*
2422 * All buffers are uptodate or get_block() returned an
2423 * error when trying to map them - we can finish the read.
2424 */
2425 folio_end_read(folio, !page_error);
2426 return 0;
2427 }
2428
2429 /* Stage two: lock the buffers */
2430 for (i = 0; i < nr; i++) {
2431 bh = arr[i];
2432 lock_buffer(bh);
2433 mark_buffer_async_read(bh);
2434 }
2435
2436 /*
2437 * Stage 3: start the IO. Check for uptodateness
2438 * inside the buffer lock in case another process reading
2439 * the underlying blockdev brought it uptodate (the sct fix).
2440 */
2441 for (i = 0; i < nr; i++) {
2442 bh = arr[i];
2443 if (buffer_uptodate(bh))
2444 end_buffer_async_read(bh, 1);
2445 else
2446 submit_bh(REQ_OP_READ, bh);
2447 }
2448 return 0;
2449}
2450EXPORT_SYMBOL(block_read_full_folio);
2451
2452/* utility function for filesystems that need to do work on expanding
2453 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2454 * deal with the hole.
2455 */
2456int generic_cont_expand_simple(struct inode *inode, loff_t size)
2457{
2458 struct address_space *mapping = inode->i_mapping;
2459 const struct address_space_operations *aops = mapping->a_ops;
2460 struct folio *folio;
2461 void *fsdata = NULL;
2462 int err;
2463
2464 err = inode_newsize_ok(inode, size);
2465 if (err)
2466 goto out;
2467
2468 err = aops->write_begin(NULL, mapping, size, 0, &folio, &fsdata);
2469 if (err)
2470 goto out;
2471
2472 err = aops->write_end(NULL, mapping, size, 0, 0, folio, fsdata);
2473 BUG_ON(err > 0);
2474
2475out:
2476 return err;
2477}
2478EXPORT_SYMBOL(generic_cont_expand_simple);
2479
2480static int cont_expand_zero(struct file *file, struct address_space *mapping,
2481 loff_t pos, loff_t *bytes)
2482{
2483 struct inode *inode = mapping->host;
2484 const struct address_space_operations *aops = mapping->a_ops;
2485 unsigned int blocksize = i_blocksize(inode);
2486 struct folio *folio;
2487 void *fsdata = NULL;
2488 pgoff_t index, curidx;
2489 loff_t curpos;
2490 unsigned zerofrom, offset, len;
2491 int err = 0;
2492
2493 index = pos >> PAGE_SHIFT;
2494 offset = pos & ~PAGE_MASK;
2495
2496 while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2497 zerofrom = curpos & ~PAGE_MASK;
2498 if (zerofrom & (blocksize-1)) {
2499 *bytes |= (blocksize-1);
2500 (*bytes)++;
2501 }
2502 len = PAGE_SIZE - zerofrom;
2503
2504 err = aops->write_begin(file, mapping, curpos, len,
2505 &folio, &fsdata);
2506 if (err)
2507 goto out;
2508 folio_zero_range(folio, offset_in_folio(folio, curpos), len);
2509 err = aops->write_end(file, mapping, curpos, len, len,
2510 folio, fsdata);
2511 if (err < 0)
2512 goto out;
2513 BUG_ON(err != len);
2514 err = 0;
2515
2516 balance_dirty_pages_ratelimited(mapping);
2517
2518 if (fatal_signal_pending(current)) {
2519 err = -EINTR;
2520 goto out;
2521 }
2522 }
2523
2524 /* page covers the boundary, find the boundary offset */
2525 if (index == curidx) {
2526 zerofrom = curpos & ~PAGE_MASK;
2527 /* if we will expand the thing last block will be filled */
2528 if (offset <= zerofrom) {
2529 goto out;
2530 }
2531 if (zerofrom & (blocksize-1)) {
2532 *bytes |= (blocksize-1);
2533 (*bytes)++;
2534 }
2535 len = offset - zerofrom;
2536
2537 err = aops->write_begin(file, mapping, curpos, len,
2538 &folio, &fsdata);
2539 if (err)
2540 goto out;
2541 folio_zero_range(folio, offset_in_folio(folio, curpos), len);
2542 err = aops->write_end(file, mapping, curpos, len, len,
2543 folio, fsdata);
2544 if (err < 0)
2545 goto out;
2546 BUG_ON(err != len);
2547 err = 0;
2548 }
2549out:
2550 return err;
2551}
2552
2553/*
2554 * For moronic filesystems that do not allow holes in file.
2555 * We may have to extend the file.
2556 */
2557int cont_write_begin(struct file *file, struct address_space *mapping,
2558 loff_t pos, unsigned len,
2559 struct folio **foliop, void **fsdata,
2560 get_block_t *get_block, loff_t *bytes)
2561{
2562 struct inode *inode = mapping->host;
2563 unsigned int blocksize = i_blocksize(inode);
2564 unsigned int zerofrom;
2565 int err;
2566
2567 err = cont_expand_zero(file, mapping, pos, bytes);
2568 if (err)
2569 return err;
2570
2571 zerofrom = *bytes & ~PAGE_MASK;
2572 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2573 *bytes |= (blocksize-1);
2574 (*bytes)++;
2575 }
2576
2577 return block_write_begin(mapping, pos, len, foliop, get_block);
2578}
2579EXPORT_SYMBOL(cont_write_begin);
2580
2581void block_commit_write(struct page *page, unsigned from, unsigned to)
2582{
2583 struct folio *folio = page_folio(page);
2584 __block_commit_write(folio, from, to);
2585}
2586EXPORT_SYMBOL(block_commit_write);
2587
2588/*
2589 * block_page_mkwrite() is not allowed to change the file size as it gets
2590 * called from a page fault handler when a page is first dirtied. Hence we must
2591 * be careful to check for EOF conditions here. We set the page up correctly
2592 * for a written page which means we get ENOSPC checking when writing into
2593 * holes and correct delalloc and unwritten extent mapping on filesystems that
2594 * support these features.
2595 *
2596 * We are not allowed to take the i_mutex here so we have to play games to
2597 * protect against truncate races as the page could now be beyond EOF. Because
2598 * truncate writes the inode size before removing pages, once we have the
2599 * page lock we can determine safely if the page is beyond EOF. If it is not
2600 * beyond EOF, then the page is guaranteed safe against truncation until we
2601 * unlock the page.
2602 *
2603 * Direct callers of this function should protect against filesystem freezing
2604 * using sb_start_pagefault() - sb_end_pagefault() functions.
2605 */
2606int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2607 get_block_t get_block)
2608{
2609 struct folio *folio = page_folio(vmf->page);
2610 struct inode *inode = file_inode(vma->vm_file);
2611 unsigned long end;
2612 loff_t size;
2613 int ret;
2614
2615 folio_lock(folio);
2616 size = i_size_read(inode);
2617 if ((folio->mapping != inode->i_mapping) ||
2618 (folio_pos(folio) >= size)) {
2619 /* We overload EFAULT to mean page got truncated */
2620 ret = -EFAULT;
2621 goto out_unlock;
2622 }
2623
2624 end = folio_size(folio);
2625 /* folio is wholly or partially inside EOF */
2626 if (folio_pos(folio) + end > size)
2627 end = size - folio_pos(folio);
2628
2629 ret = __block_write_begin_int(folio, 0, end, get_block, NULL);
2630 if (unlikely(ret))
2631 goto out_unlock;
2632
2633 __block_commit_write(folio, 0, end);
2634
2635 folio_mark_dirty(folio);
2636 folio_wait_stable(folio);
2637 return 0;
2638out_unlock:
2639 folio_unlock(folio);
2640 return ret;
2641}
2642EXPORT_SYMBOL(block_page_mkwrite);
2643
2644int block_truncate_page(struct address_space *mapping,
2645 loff_t from, get_block_t *get_block)
2646{
2647 pgoff_t index = from >> PAGE_SHIFT;
2648 unsigned blocksize;
2649 sector_t iblock;
2650 size_t offset, length, pos;
2651 struct inode *inode = mapping->host;
2652 struct folio *folio;
2653 struct buffer_head *bh;
2654 int err = 0;
2655
2656 blocksize = i_blocksize(inode);
2657 length = from & (blocksize - 1);
2658
2659 /* Block boundary? Nothing to do */
2660 if (!length)
2661 return 0;
2662
2663 length = blocksize - length;
2664 iblock = ((loff_t)index * PAGE_SIZE) >> inode->i_blkbits;
2665
2666 folio = filemap_grab_folio(mapping, index);
2667 if (IS_ERR(folio))
2668 return PTR_ERR(folio);
2669
2670 bh = folio_buffers(folio);
2671 if (!bh)
2672 bh = create_empty_buffers(folio, blocksize, 0);
2673
2674 /* Find the buffer that contains "offset" */
2675 offset = offset_in_folio(folio, from);
2676 pos = blocksize;
2677 while (offset >= pos) {
2678 bh = bh->b_this_page;
2679 iblock++;
2680 pos += blocksize;
2681 }
2682
2683 if (!buffer_mapped(bh)) {
2684 WARN_ON(bh->b_size != blocksize);
2685 err = get_block(inode, iblock, bh, 0);
2686 if (err)
2687 goto unlock;
2688 /* unmapped? It's a hole - nothing to do */
2689 if (!buffer_mapped(bh))
2690 goto unlock;
2691 }
2692
2693 /* Ok, it's mapped. Make sure it's up-to-date */
2694 if (folio_test_uptodate(folio))
2695 set_buffer_uptodate(bh);
2696
2697 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2698 err = bh_read(bh, 0);
2699 /* Uhhuh. Read error. Complain and punt. */
2700 if (err < 0)
2701 goto unlock;
2702 }
2703
2704 folio_zero_range(folio, offset, length);
2705 mark_buffer_dirty(bh);
2706
2707unlock:
2708 folio_unlock(folio);
2709 folio_put(folio);
2710
2711 return err;
2712}
2713EXPORT_SYMBOL(block_truncate_page);
2714
2715/*
2716 * The generic ->writepage function for buffer-backed address_spaces
2717 */
2718int block_write_full_folio(struct folio *folio, struct writeback_control *wbc,
2719 void *get_block)
2720{
2721 struct inode * const inode = folio->mapping->host;
2722 loff_t i_size = i_size_read(inode);
2723
2724 /* Is the folio fully inside i_size? */
2725 if (folio_pos(folio) + folio_size(folio) <= i_size)
2726 return __block_write_full_folio(inode, folio, get_block, wbc);
2727
2728 /* Is the folio fully outside i_size? (truncate in progress) */
2729 if (folio_pos(folio) >= i_size) {
2730 folio_unlock(folio);
2731 return 0; /* don't care */
2732 }
2733
2734 /*
2735 * The folio straddles i_size. It must be zeroed out on each and every
2736 * writepage invocation because it may be mmapped. "A file is mapped
2737 * in multiples of the page size. For a file that is not a multiple of
2738 * the page size, the remaining memory is zeroed when mapped, and
2739 * writes to that region are not written out to the file."
2740 */
2741 folio_zero_segment(folio, offset_in_folio(folio, i_size),
2742 folio_size(folio));
2743 return __block_write_full_folio(inode, folio, get_block, wbc);
2744}
2745
2746sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2747 get_block_t *get_block)
2748{
2749 struct inode *inode = mapping->host;
2750 struct buffer_head tmp = {
2751 .b_size = i_blocksize(inode),
2752 };
2753
2754 get_block(inode, block, &tmp, 0);
2755 return tmp.b_blocknr;
2756}
2757EXPORT_SYMBOL(generic_block_bmap);
2758
2759static void end_bio_bh_io_sync(struct bio *bio)
2760{
2761 struct buffer_head *bh = bio->bi_private;
2762
2763 if (unlikely(bio_flagged(bio, BIO_QUIET)))
2764 set_bit(BH_Quiet, &bh->b_state);
2765
2766 bh->b_end_io(bh, !bio->bi_status);
2767 bio_put(bio);
2768}
2769
2770static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
2771 enum rw_hint write_hint,
2772 struct writeback_control *wbc)
2773{
2774 const enum req_op op = opf & REQ_OP_MASK;
2775 struct bio *bio;
2776
2777 BUG_ON(!buffer_locked(bh));
2778 BUG_ON(!buffer_mapped(bh));
2779 BUG_ON(!bh->b_end_io);
2780 BUG_ON(buffer_delay(bh));
2781 BUG_ON(buffer_unwritten(bh));
2782
2783 /*
2784 * Only clear out a write error when rewriting
2785 */
2786 if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
2787 clear_buffer_write_io_error(bh);
2788
2789 if (buffer_meta(bh))
2790 opf |= REQ_META;
2791 if (buffer_prio(bh))
2792 opf |= REQ_PRIO;
2793
2794 bio = bio_alloc(bh->b_bdev, 1, opf, GFP_NOIO);
2795
2796 fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
2797
2798 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2799 bio->bi_write_hint = write_hint;
2800
2801 bio_add_folio_nofail(bio, bh->b_folio, bh->b_size, bh_offset(bh));
2802
2803 bio->bi_end_io = end_bio_bh_io_sync;
2804 bio->bi_private = bh;
2805
2806 /* Take care of bh's that straddle the end of the device */
2807 guard_bio_eod(bio);
2808
2809 if (wbc) {
2810 wbc_init_bio(wbc, bio);
2811 wbc_account_cgroup_owner(wbc, bh->b_folio, bh->b_size);
2812 }
2813
2814 submit_bio(bio);
2815}
2816
2817void submit_bh(blk_opf_t opf, struct buffer_head *bh)
2818{
2819 submit_bh_wbc(opf, bh, WRITE_LIFE_NOT_SET, NULL);
2820}
2821EXPORT_SYMBOL(submit_bh);
2822
2823void write_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2824{
2825 lock_buffer(bh);
2826 if (!test_clear_buffer_dirty(bh)) {
2827 unlock_buffer(bh);
2828 return;
2829 }
2830 bh->b_end_io = end_buffer_write_sync;
2831 get_bh(bh);
2832 submit_bh(REQ_OP_WRITE | op_flags, bh);
2833}
2834EXPORT_SYMBOL(write_dirty_buffer);
2835
2836/*
2837 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2838 * and then start new I/O and then wait upon it. The caller must have a ref on
2839 * the buffer_head.
2840 */
2841int __sync_dirty_buffer(struct buffer_head *bh, blk_opf_t op_flags)
2842{
2843 WARN_ON(atomic_read(&bh->b_count) < 1);
2844 lock_buffer(bh);
2845 if (test_clear_buffer_dirty(bh)) {
2846 /*
2847 * The bh should be mapped, but it might not be if the
2848 * device was hot-removed. Not much we can do but fail the I/O.
2849 */
2850 if (!buffer_mapped(bh)) {
2851 unlock_buffer(bh);
2852 return -EIO;
2853 }
2854
2855 get_bh(bh);
2856 bh->b_end_io = end_buffer_write_sync;
2857 submit_bh(REQ_OP_WRITE | op_flags, bh);
2858 wait_on_buffer(bh);
2859 if (!buffer_uptodate(bh))
2860 return -EIO;
2861 } else {
2862 unlock_buffer(bh);
2863 }
2864 return 0;
2865}
2866EXPORT_SYMBOL(__sync_dirty_buffer);
2867
2868int sync_dirty_buffer(struct buffer_head *bh)
2869{
2870 return __sync_dirty_buffer(bh, REQ_SYNC);
2871}
2872EXPORT_SYMBOL(sync_dirty_buffer);
2873
2874static inline int buffer_busy(struct buffer_head *bh)
2875{
2876 return atomic_read(&bh->b_count) |
2877 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2878}
2879
2880static bool
2881drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
2882{
2883 struct buffer_head *head = folio_buffers(folio);
2884 struct buffer_head *bh;
2885
2886 bh = head;
2887 do {
2888 if (buffer_busy(bh))
2889 goto failed;
2890 bh = bh->b_this_page;
2891 } while (bh != head);
2892
2893 do {
2894 struct buffer_head *next = bh->b_this_page;
2895
2896 if (bh->b_assoc_map)
2897 __remove_assoc_queue(bh);
2898 bh = next;
2899 } while (bh != head);
2900 *buffers_to_free = head;
2901 folio_detach_private(folio);
2902 return true;
2903failed:
2904 return false;
2905}
2906
2907/**
2908 * try_to_free_buffers - Release buffers attached to this folio.
2909 * @folio: The folio.
2910 *
2911 * If any buffers are in use (dirty, under writeback, elevated refcount),
2912 * no buffers will be freed.
2913 *
2914 * If the folio is dirty but all the buffers are clean then we need to
2915 * be sure to mark the folio clean as well. This is because the folio
2916 * may be against a block device, and a later reattachment of buffers
2917 * to a dirty folio will set *all* buffers dirty. Which would corrupt
2918 * filesystem data on the same device.
2919 *
2920 * The same applies to regular filesystem folios: if all the buffers are
2921 * clean then we set the folio clean and proceed. To do that, we require
2922 * total exclusion from block_dirty_folio(). That is obtained with
2923 * i_private_lock.
2924 *
2925 * Exclusion against try_to_free_buffers may be obtained by either
2926 * locking the folio or by holding its mapping's i_private_lock.
2927 *
2928 * Context: Process context. @folio must be locked. Will not sleep.
2929 * Return: true if all buffers attached to this folio were freed.
2930 */
2931bool try_to_free_buffers(struct folio *folio)
2932{
2933 struct address_space * const mapping = folio->mapping;
2934 struct buffer_head *buffers_to_free = NULL;
2935 bool ret = 0;
2936
2937 BUG_ON(!folio_test_locked(folio));
2938 if (folio_test_writeback(folio))
2939 return false;
2940
2941 if (mapping == NULL) { /* can this still happen? */
2942 ret = drop_buffers(folio, &buffers_to_free);
2943 goto out;
2944 }
2945
2946 spin_lock(&mapping->i_private_lock);
2947 ret = drop_buffers(folio, &buffers_to_free);
2948
2949 /*
2950 * If the filesystem writes its buffers by hand (eg ext3)
2951 * then we can have clean buffers against a dirty folio. We
2952 * clean the folio here; otherwise the VM will never notice
2953 * that the filesystem did any IO at all.
2954 *
2955 * Also, during truncate, discard_buffer will have marked all
2956 * the folio's buffers clean. We discover that here and clean
2957 * the folio also.
2958 *
2959 * i_private_lock must be held over this entire operation in order
2960 * to synchronise against block_dirty_folio and prevent the
2961 * dirty bit from being lost.
2962 */
2963 if (ret)
2964 folio_cancel_dirty(folio);
2965 spin_unlock(&mapping->i_private_lock);
2966out:
2967 if (buffers_to_free) {
2968 struct buffer_head *bh = buffers_to_free;
2969
2970 do {
2971 struct buffer_head *next = bh->b_this_page;
2972 free_buffer_head(bh);
2973 bh = next;
2974 } while (bh != buffers_to_free);
2975 }
2976 return ret;
2977}
2978EXPORT_SYMBOL(try_to_free_buffers);
2979
2980/*
2981 * Buffer-head allocation
2982 */
2983static struct kmem_cache *bh_cachep __ro_after_init;
2984
2985/*
2986 * Once the number of bh's in the machine exceeds this level, we start
2987 * stripping them in writeback.
2988 */
2989static unsigned long max_buffer_heads __ro_after_init;
2990
2991int buffer_heads_over_limit;
2992
2993struct bh_accounting {
2994 int nr; /* Number of live bh's */
2995 int ratelimit; /* Limit cacheline bouncing */
2996};
2997
2998static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
2999
3000static void recalc_bh_state(void)
3001{
3002 int i;
3003 int tot = 0;
3004
3005 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3006 return;
3007 __this_cpu_write(bh_accounting.ratelimit, 0);
3008 for_each_online_cpu(i)
3009 tot += per_cpu(bh_accounting, i).nr;
3010 buffer_heads_over_limit = (tot > max_buffer_heads);
3011}
3012
3013struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3014{
3015 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3016 if (ret) {
3017 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3018 spin_lock_init(&ret->b_uptodate_lock);
3019 preempt_disable();
3020 __this_cpu_inc(bh_accounting.nr);
3021 recalc_bh_state();
3022 preempt_enable();
3023 }
3024 return ret;
3025}
3026EXPORT_SYMBOL(alloc_buffer_head);
3027
3028void free_buffer_head(struct buffer_head *bh)
3029{
3030 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3031 kmem_cache_free(bh_cachep, bh);
3032 preempt_disable();
3033 __this_cpu_dec(bh_accounting.nr);
3034 recalc_bh_state();
3035 preempt_enable();
3036}
3037EXPORT_SYMBOL(free_buffer_head);
3038
3039static int buffer_exit_cpu_dead(unsigned int cpu)
3040{
3041 int i;
3042 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3043
3044 for (i = 0; i < BH_LRU_SIZE; i++) {
3045 brelse(b->bhs[i]);
3046 b->bhs[i] = NULL;
3047 }
3048 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3049 per_cpu(bh_accounting, cpu).nr = 0;
3050 return 0;
3051}
3052
3053/**
3054 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3055 * @bh: struct buffer_head
3056 *
3057 * Return true if the buffer is up-to-date and false,
3058 * with the buffer locked, if not.
3059 */
3060int bh_uptodate_or_lock(struct buffer_head *bh)
3061{
3062 if (!buffer_uptodate(bh)) {
3063 lock_buffer(bh);
3064 if (!buffer_uptodate(bh))
3065 return 0;
3066 unlock_buffer(bh);
3067 }
3068 return 1;
3069}
3070EXPORT_SYMBOL(bh_uptodate_or_lock);
3071
3072/**
3073 * __bh_read - Submit read for a locked buffer
3074 * @bh: struct buffer_head
3075 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3076 * @wait: wait until reading finish
3077 *
3078 * Returns zero on success or don't wait, and -EIO on error.
3079 */
3080int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
3081{
3082 int ret = 0;
3083
3084 BUG_ON(!buffer_locked(bh));
3085
3086 get_bh(bh);
3087 bh->b_end_io = end_buffer_read_sync;
3088 submit_bh(REQ_OP_READ | op_flags, bh);
3089 if (wait) {
3090 wait_on_buffer(bh);
3091 if (!buffer_uptodate(bh))
3092 ret = -EIO;
3093 }
3094 return ret;
3095}
3096EXPORT_SYMBOL(__bh_read);
3097
3098/**
3099 * __bh_read_batch - Submit read for a batch of unlocked buffers
3100 * @nr: entry number of the buffer batch
3101 * @bhs: a batch of struct buffer_head
3102 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
3103 * @force_lock: force to get a lock on the buffer if set, otherwise drops any
3104 * buffer that cannot lock.
3105 *
3106 * Returns zero on success or don't wait, and -EIO on error.
3107 */
3108void __bh_read_batch(int nr, struct buffer_head *bhs[],
3109 blk_opf_t op_flags, bool force_lock)
3110{
3111 int i;
3112
3113 for (i = 0; i < nr; i++) {
3114 struct buffer_head *bh = bhs[i];
3115
3116 if (buffer_uptodate(bh))
3117 continue;
3118
3119 if (force_lock)
3120 lock_buffer(bh);
3121 else
3122 if (!trylock_buffer(bh))
3123 continue;
3124
3125 if (buffer_uptodate(bh)) {
3126 unlock_buffer(bh);
3127 continue;
3128 }
3129
3130 bh->b_end_io = end_buffer_read_sync;
3131 get_bh(bh);
3132 submit_bh(REQ_OP_READ | op_flags, bh);
3133 }
3134}
3135EXPORT_SYMBOL(__bh_read_batch);
3136
3137void __init buffer_init(void)
3138{
3139 unsigned long nrpages;
3140 int ret;
3141
3142 bh_cachep = KMEM_CACHE(buffer_head,
3143 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC);
3144 /*
3145 * Limit the bh occupancy to 10% of ZONE_NORMAL
3146 */
3147 nrpages = (nr_free_buffer_pages() * 10) / 100;
3148 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3149 ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3150 NULL, buffer_exit_cpu_dead);
3151 WARN_ON(ret < 0);
3152}
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
52#include "internal.h"
53
54static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
55static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
56 enum rw_hint hint, struct writeback_control *wbc);
57
58#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
59
60inline void touch_buffer(struct buffer_head *bh)
61{
62 trace_block_touch_buffer(bh);
63 mark_page_accessed(bh->b_page);
64}
65EXPORT_SYMBOL(touch_buffer);
66
67void __lock_buffer(struct buffer_head *bh)
68{
69 wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
70}
71EXPORT_SYMBOL(__lock_buffer);
72
73void unlock_buffer(struct buffer_head *bh)
74{
75 clear_bit_unlock(BH_Lock, &bh->b_state);
76 smp_mb__after_atomic();
77 wake_up_bit(&bh->b_state, BH_Lock);
78}
79EXPORT_SYMBOL(unlock_buffer);
80
81/*
82 * Returns if the page has dirty or writeback buffers. If all the buffers
83 * are unlocked and clean then the PageDirty information is stale. If
84 * any of the pages are locked, it is assumed they are locked for IO.
85 */
86void buffer_check_dirty_writeback(struct page *page,
87 bool *dirty, bool *writeback)
88{
89 struct buffer_head *head, *bh;
90 *dirty = false;
91 *writeback = false;
92
93 BUG_ON(!PageLocked(page));
94
95 if (!page_has_buffers(page))
96 return;
97
98 if (PageWriteback(page))
99 *writeback = true;
100
101 head = page_buffers(page);
102 bh = head;
103 do {
104 if (buffer_locked(bh))
105 *writeback = true;
106
107 if (buffer_dirty(bh))
108 *dirty = true;
109
110 bh = bh->b_this_page;
111 } while (bh != head);
112}
113EXPORT_SYMBOL(buffer_check_dirty_writeback);
114
115/*
116 * Block until a buffer comes unlocked. This doesn't stop it
117 * from becoming locked again - you have to lock it yourself
118 * if you want to preserve its state.
119 */
120void __wait_on_buffer(struct buffer_head * bh)
121{
122 wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
123}
124EXPORT_SYMBOL(__wait_on_buffer);
125
126static void buffer_io_error(struct buffer_head *bh, char *msg)
127{
128 if (!test_bit(BH_Quiet, &bh->b_state))
129 printk_ratelimited(KERN_ERR
130 "Buffer I/O error on dev %pg, logical block %llu%s\n",
131 bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
132}
133
134/*
135 * End-of-IO handler helper function which does not touch the bh after
136 * unlocking it.
137 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
138 * a race there is benign: unlock_buffer() only use the bh's address for
139 * hashing after unlocking the buffer, so it doesn't actually touch the bh
140 * itself.
141 */
142static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
143{
144 if (uptodate) {
145 set_buffer_uptodate(bh);
146 } else {
147 /* This happens, due to failed read-ahead attempts. */
148 clear_buffer_uptodate(bh);
149 }
150 unlock_buffer(bh);
151}
152
153/*
154 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
155 * unlock the buffer. This is what ll_rw_block uses too.
156 */
157void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
158{
159 __end_buffer_read_notouch(bh, uptodate);
160 put_bh(bh);
161}
162EXPORT_SYMBOL(end_buffer_read_sync);
163
164void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
165{
166 if (uptodate) {
167 set_buffer_uptodate(bh);
168 } else {
169 buffer_io_error(bh, ", lost sync page write");
170 mark_buffer_write_io_error(bh);
171 clear_buffer_uptodate(bh);
172 }
173 unlock_buffer(bh);
174 put_bh(bh);
175}
176EXPORT_SYMBOL(end_buffer_write_sync);
177
178/*
179 * Various filesystems appear to want __find_get_block to be non-blocking.
180 * But it's the page lock which protects the buffers. To get around this,
181 * we get exclusion from try_to_free_buffers with the blockdev mapping's
182 * private_lock.
183 *
184 * Hack idea: for the blockdev mapping, private_lock contention
185 * may be quite high. This code could TryLock the page, and if that
186 * succeeds, there is no need to take private_lock.
187 */
188static struct buffer_head *
189__find_get_block_slow(struct block_device *bdev, sector_t block)
190{
191 struct inode *bd_inode = bdev->bd_inode;
192 struct address_space *bd_mapping = bd_inode->i_mapping;
193 struct buffer_head *ret = NULL;
194 pgoff_t index;
195 struct buffer_head *bh;
196 struct buffer_head *head;
197 struct page *page;
198 int all_mapped = 1;
199 static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
200
201 index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
202 page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
203 if (!page)
204 goto out;
205
206 spin_lock(&bd_mapping->private_lock);
207 if (!page_has_buffers(page))
208 goto out_unlock;
209 head = page_buffers(page);
210 bh = head;
211 do {
212 if (!buffer_mapped(bh))
213 all_mapped = 0;
214 else if (bh->b_blocknr == block) {
215 ret = bh;
216 get_bh(bh);
217 goto out_unlock;
218 }
219 bh = bh->b_this_page;
220 } while (bh != head);
221
222 /* we might be here because some of the buffers on this page are
223 * not mapped. This is due to various races between
224 * file io on the block device and getblk. It gets dealt with
225 * elsewhere, don't buffer_error if we had some unmapped buffers
226 */
227 ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
228 if (all_mapped && __ratelimit(&last_warned)) {
229 printk("__find_get_block_slow() failed. block=%llu, "
230 "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
231 "device %pg blocksize: %d\n",
232 (unsigned long long)block,
233 (unsigned long long)bh->b_blocknr,
234 bh->b_state, bh->b_size, bdev,
235 1 << bd_inode->i_blkbits);
236 }
237out_unlock:
238 spin_unlock(&bd_mapping->private_lock);
239 put_page(page);
240out:
241 return ret;
242}
243
244static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
245{
246 unsigned long flags;
247 struct buffer_head *first;
248 struct buffer_head *tmp;
249 struct page *page;
250 int page_uptodate = 1;
251
252 BUG_ON(!buffer_async_read(bh));
253
254 page = bh->b_page;
255 if (uptodate) {
256 set_buffer_uptodate(bh);
257 } else {
258 clear_buffer_uptodate(bh);
259 buffer_io_error(bh, ", async page read");
260 SetPageError(page);
261 }
262
263 /*
264 * Be _very_ careful from here on. Bad things can happen if
265 * two buffer heads end IO at almost the same time and both
266 * decide that the page is now completely done.
267 */
268 first = page_buffers(page);
269 spin_lock_irqsave(&first->b_uptodate_lock, flags);
270 clear_buffer_async_read(bh);
271 unlock_buffer(bh);
272 tmp = bh;
273 do {
274 if (!buffer_uptodate(tmp))
275 page_uptodate = 0;
276 if (buffer_async_read(tmp)) {
277 BUG_ON(!buffer_locked(tmp));
278 goto still_busy;
279 }
280 tmp = tmp->b_this_page;
281 } while (tmp != bh);
282 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
283
284 /*
285 * If none of the buffers had errors and they are all
286 * uptodate then we can set the page uptodate.
287 */
288 if (page_uptodate && !PageError(page))
289 SetPageUptodate(page);
290 unlock_page(page);
291 return;
292
293still_busy:
294 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
295 return;
296}
297
298struct decrypt_bh_ctx {
299 struct work_struct work;
300 struct buffer_head *bh;
301};
302
303static void decrypt_bh(struct work_struct *work)
304{
305 struct decrypt_bh_ctx *ctx =
306 container_of(work, struct decrypt_bh_ctx, work);
307 struct buffer_head *bh = ctx->bh;
308 int err;
309
310 err = fscrypt_decrypt_pagecache_blocks(bh->b_page, bh->b_size,
311 bh_offset(bh));
312 end_buffer_async_read(bh, err == 0);
313 kfree(ctx);
314}
315
316/*
317 * I/O completion handler for block_read_full_page() - pages
318 * which come unlocked at the end of I/O.
319 */
320static void end_buffer_async_read_io(struct buffer_head *bh, int uptodate)
321{
322 /* Decrypt if needed */
323 if (uptodate &&
324 fscrypt_inode_uses_fs_layer_crypto(bh->b_page->mapping->host)) {
325 struct decrypt_bh_ctx *ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
326
327 if (ctx) {
328 INIT_WORK(&ctx->work, decrypt_bh);
329 ctx->bh = bh;
330 fscrypt_enqueue_decrypt_work(&ctx->work);
331 return;
332 }
333 uptodate = 0;
334 }
335 end_buffer_async_read(bh, uptodate);
336}
337
338/*
339 * Completion handler for block_write_full_page() - pages which are unlocked
340 * during I/O, and which have PageWriteback cleared upon I/O completion.
341 */
342void end_buffer_async_write(struct buffer_head *bh, int uptodate)
343{
344 unsigned long flags;
345 struct buffer_head *first;
346 struct buffer_head *tmp;
347 struct page *page;
348
349 BUG_ON(!buffer_async_write(bh));
350
351 page = bh->b_page;
352 if (uptodate) {
353 set_buffer_uptodate(bh);
354 } else {
355 buffer_io_error(bh, ", lost async page write");
356 mark_buffer_write_io_error(bh);
357 clear_buffer_uptodate(bh);
358 SetPageError(page);
359 }
360
361 first = page_buffers(page);
362 spin_lock_irqsave(&first->b_uptodate_lock, flags);
363
364 clear_buffer_async_write(bh);
365 unlock_buffer(bh);
366 tmp = bh->b_this_page;
367 while (tmp != bh) {
368 if (buffer_async_write(tmp)) {
369 BUG_ON(!buffer_locked(tmp));
370 goto still_busy;
371 }
372 tmp = tmp->b_this_page;
373 }
374 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
375 end_page_writeback(page);
376 return;
377
378still_busy:
379 spin_unlock_irqrestore(&first->b_uptodate_lock, flags);
380 return;
381}
382EXPORT_SYMBOL(end_buffer_async_write);
383
384/*
385 * If a page's buffers are under async readin (end_buffer_async_read
386 * completion) then there is a possibility that another thread of
387 * control could lock one of the buffers after it has completed
388 * but while some of the other buffers have not completed. This
389 * locked buffer would confuse end_buffer_async_read() into not unlocking
390 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
391 * that this buffer is not under async I/O.
392 *
393 * The page comes unlocked when it has no locked buffer_async buffers
394 * left.
395 *
396 * PageLocked prevents anyone starting new async I/O reads any of
397 * the buffers.
398 *
399 * PageWriteback is used to prevent simultaneous writeout of the same
400 * page.
401 *
402 * PageLocked prevents anyone from starting writeback of a page which is
403 * under read I/O (PageWriteback is only ever set against a locked page).
404 */
405static void mark_buffer_async_read(struct buffer_head *bh)
406{
407 bh->b_end_io = end_buffer_async_read_io;
408 set_buffer_async_read(bh);
409}
410
411static void mark_buffer_async_write_endio(struct buffer_head *bh,
412 bh_end_io_t *handler)
413{
414 bh->b_end_io = handler;
415 set_buffer_async_write(bh);
416}
417
418void mark_buffer_async_write(struct buffer_head *bh)
419{
420 mark_buffer_async_write_endio(bh, end_buffer_async_write);
421}
422EXPORT_SYMBOL(mark_buffer_async_write);
423
424
425/*
426 * fs/buffer.c contains helper functions for buffer-backed address space's
427 * fsync functions. A common requirement for buffer-based filesystems is
428 * that certain data from the backing blockdev needs to be written out for
429 * a successful fsync(). For example, ext2 indirect blocks need to be
430 * written back and waited upon before fsync() returns.
431 *
432 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
433 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
434 * management of a list of dependent buffers at ->i_mapping->private_list.
435 *
436 * Locking is a little subtle: try_to_free_buffers() will remove buffers
437 * from their controlling inode's queue when they are being freed. But
438 * try_to_free_buffers() will be operating against the *blockdev* mapping
439 * at the time, not against the S_ISREG file which depends on those buffers.
440 * So the locking for private_list is via the private_lock in the address_space
441 * which backs the buffers. Which is different from the address_space
442 * against which the buffers are listed. So for a particular address_space,
443 * mapping->private_lock does *not* protect mapping->private_list! In fact,
444 * mapping->private_list will always be protected by the backing blockdev's
445 * ->private_lock.
446 *
447 * Which introduces a requirement: all buffers on an address_space's
448 * ->private_list must be from the same address_space: the blockdev's.
449 *
450 * address_spaces which do not place buffers at ->private_list via these
451 * utility functions are free to use private_lock and private_list for
452 * whatever they want. The only requirement is that list_empty(private_list)
453 * be true at clear_inode() time.
454 *
455 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
456 * filesystems should do that. invalidate_inode_buffers() should just go
457 * BUG_ON(!list_empty).
458 *
459 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
460 * take an address_space, not an inode. And it should be called
461 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
462 * queued up.
463 *
464 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
465 * list if it is already on a list. Because if the buffer is on a list,
466 * it *must* already be on the right one. If not, the filesystem is being
467 * silly. This will save a ton of locking. But first we have to ensure
468 * that buffers are taken *off* the old inode's list when they are freed
469 * (presumably in truncate). That requires careful auditing of all
470 * filesystems (do it inside bforget()). It could also be done by bringing
471 * b_inode back.
472 */
473
474/*
475 * The buffer's backing address_space's private_lock must be held
476 */
477static void __remove_assoc_queue(struct buffer_head *bh)
478{
479 list_del_init(&bh->b_assoc_buffers);
480 WARN_ON(!bh->b_assoc_map);
481 bh->b_assoc_map = NULL;
482}
483
484int inode_has_buffers(struct inode *inode)
485{
486 return !list_empty(&inode->i_data.private_list);
487}
488
489/*
490 * osync is designed to support O_SYNC io. It waits synchronously for
491 * all already-submitted IO to complete, but does not queue any new
492 * writes to the disk.
493 *
494 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
495 * you dirty the buffers, and then use osync_inode_buffers to wait for
496 * completion. Any other dirty buffers which are not yet queued for
497 * write will not be flushed to disk by the osync.
498 */
499static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
500{
501 struct buffer_head *bh;
502 struct list_head *p;
503 int err = 0;
504
505 spin_lock(lock);
506repeat:
507 list_for_each_prev(p, list) {
508 bh = BH_ENTRY(p);
509 if (buffer_locked(bh)) {
510 get_bh(bh);
511 spin_unlock(lock);
512 wait_on_buffer(bh);
513 if (!buffer_uptodate(bh))
514 err = -EIO;
515 brelse(bh);
516 spin_lock(lock);
517 goto repeat;
518 }
519 }
520 spin_unlock(lock);
521 return err;
522}
523
524void emergency_thaw_bdev(struct super_block *sb)
525{
526 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
527 printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
528}
529
530/**
531 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
532 * @mapping: the mapping which wants those buffers written
533 *
534 * Starts I/O against the buffers at mapping->private_list, and waits upon
535 * that I/O.
536 *
537 * Basically, this is a convenience function for fsync().
538 * @mapping is a file or directory which needs those buffers to be written for
539 * a successful fsync().
540 */
541int sync_mapping_buffers(struct address_space *mapping)
542{
543 struct address_space *buffer_mapping = mapping->private_data;
544
545 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
546 return 0;
547
548 return fsync_buffers_list(&buffer_mapping->private_lock,
549 &mapping->private_list);
550}
551EXPORT_SYMBOL(sync_mapping_buffers);
552
553/*
554 * Called when we've recently written block `bblock', and it is known that
555 * `bblock' was for a buffer_boundary() buffer. This means that the block at
556 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
557 * dirty, schedule it for IO. So that indirects merge nicely with their data.
558 */
559void write_boundary_block(struct block_device *bdev,
560 sector_t bblock, unsigned blocksize)
561{
562 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
563 if (bh) {
564 if (buffer_dirty(bh))
565 ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
566 put_bh(bh);
567 }
568}
569
570void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
571{
572 struct address_space *mapping = inode->i_mapping;
573 struct address_space *buffer_mapping = bh->b_page->mapping;
574
575 mark_buffer_dirty(bh);
576 if (!mapping->private_data) {
577 mapping->private_data = buffer_mapping;
578 } else {
579 BUG_ON(mapping->private_data != buffer_mapping);
580 }
581 if (!bh->b_assoc_map) {
582 spin_lock(&buffer_mapping->private_lock);
583 list_move_tail(&bh->b_assoc_buffers,
584 &mapping->private_list);
585 bh->b_assoc_map = mapping;
586 spin_unlock(&buffer_mapping->private_lock);
587 }
588}
589EXPORT_SYMBOL(mark_buffer_dirty_inode);
590
591/*
592 * Mark the page dirty, and set it dirty in the page cache, and mark the inode
593 * dirty.
594 *
595 * If warn is true, then emit a warning if the page is not uptodate and has
596 * not been truncated.
597 *
598 * The caller must hold lock_page_memcg().
599 */
600void __set_page_dirty(struct page *page, struct address_space *mapping,
601 int warn)
602{
603 unsigned long flags;
604
605 xa_lock_irqsave(&mapping->i_pages, flags);
606 if (page->mapping) { /* Race with truncate? */
607 WARN_ON_ONCE(warn && !PageUptodate(page));
608 account_page_dirtied(page, mapping);
609 __xa_set_mark(&mapping->i_pages, page_index(page),
610 PAGECACHE_TAG_DIRTY);
611 }
612 xa_unlock_irqrestore(&mapping->i_pages, flags);
613}
614EXPORT_SYMBOL_GPL(__set_page_dirty);
615
616/*
617 * Add a page to the dirty page list.
618 *
619 * It is a sad fact of life that this function is called from several places
620 * deeply under spinlocking. It may not sleep.
621 *
622 * If the page has buffers, the uptodate buffers are set dirty, to preserve
623 * dirty-state coherency between the page and the buffers. It the page does
624 * not have buffers then when they are later attached they will all be set
625 * dirty.
626 *
627 * The buffers are dirtied before the page is dirtied. There's a small race
628 * window in which a writepage caller may see the page cleanness but not the
629 * buffer dirtiness. That's fine. If this code were to set the page dirty
630 * before the buffers, a concurrent writepage caller could clear the page dirty
631 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
632 * page on the dirty page list.
633 *
634 * We use private_lock to lock against try_to_free_buffers while using the
635 * page's buffer list. Also use this to protect against clean buffers being
636 * added to the page after it was set dirty.
637 *
638 * FIXME: may need to call ->reservepage here as well. That's rather up to the
639 * address_space though.
640 */
641int __set_page_dirty_buffers(struct page *page)
642{
643 int newly_dirty;
644 struct address_space *mapping = page_mapping(page);
645
646 if (unlikely(!mapping))
647 return !TestSetPageDirty(page);
648
649 spin_lock(&mapping->private_lock);
650 if (page_has_buffers(page)) {
651 struct buffer_head *head = page_buffers(page);
652 struct buffer_head *bh = head;
653
654 do {
655 set_buffer_dirty(bh);
656 bh = bh->b_this_page;
657 } while (bh != head);
658 }
659 /*
660 * Lock out page->mem_cgroup migration to keep PageDirty
661 * synchronized with per-memcg dirty page counters.
662 */
663 lock_page_memcg(page);
664 newly_dirty = !TestSetPageDirty(page);
665 spin_unlock(&mapping->private_lock);
666
667 if (newly_dirty)
668 __set_page_dirty(page, mapping, 1);
669
670 unlock_page_memcg(page);
671
672 if (newly_dirty)
673 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
674
675 return newly_dirty;
676}
677EXPORT_SYMBOL(__set_page_dirty_buffers);
678
679/*
680 * Write out and wait upon a list of buffers.
681 *
682 * We have conflicting pressures: we want to make sure that all
683 * initially dirty buffers get waited on, but that any subsequently
684 * dirtied buffers don't. After all, we don't want fsync to last
685 * forever if somebody is actively writing to the file.
686 *
687 * Do this in two main stages: first we copy dirty buffers to a
688 * temporary inode list, queueing the writes as we go. Then we clean
689 * up, waiting for those writes to complete.
690 *
691 * During this second stage, any subsequent updates to the file may end
692 * up refiling the buffer on the original inode's dirty list again, so
693 * there is a chance we will end up with a buffer queued for write but
694 * not yet completed on that list. So, as a final cleanup we go through
695 * the osync code to catch these locked, dirty buffers without requeuing
696 * any newly dirty buffers for write.
697 */
698static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
699{
700 struct buffer_head *bh;
701 struct list_head tmp;
702 struct address_space *mapping;
703 int err = 0, err2;
704 struct blk_plug plug;
705
706 INIT_LIST_HEAD(&tmp);
707 blk_start_plug(&plug);
708
709 spin_lock(lock);
710 while (!list_empty(list)) {
711 bh = BH_ENTRY(list->next);
712 mapping = bh->b_assoc_map;
713 __remove_assoc_queue(bh);
714 /* Avoid race with mark_buffer_dirty_inode() which does
715 * a lockless check and we rely on seeing the dirty bit */
716 smp_mb();
717 if (buffer_dirty(bh) || buffer_locked(bh)) {
718 list_add(&bh->b_assoc_buffers, &tmp);
719 bh->b_assoc_map = mapping;
720 if (buffer_dirty(bh)) {
721 get_bh(bh);
722 spin_unlock(lock);
723 /*
724 * Ensure any pending I/O completes so that
725 * write_dirty_buffer() actually writes the
726 * current contents - it is a noop if I/O is
727 * still in flight on potentially older
728 * contents.
729 */
730 write_dirty_buffer(bh, REQ_SYNC);
731
732 /*
733 * Kick off IO for the previous mapping. Note
734 * that we will not run the very last mapping,
735 * wait_on_buffer() will do that for us
736 * through sync_buffer().
737 */
738 brelse(bh);
739 spin_lock(lock);
740 }
741 }
742 }
743
744 spin_unlock(lock);
745 blk_finish_plug(&plug);
746 spin_lock(lock);
747
748 while (!list_empty(&tmp)) {
749 bh = BH_ENTRY(tmp.prev);
750 get_bh(bh);
751 mapping = bh->b_assoc_map;
752 __remove_assoc_queue(bh);
753 /* Avoid race with mark_buffer_dirty_inode() which does
754 * a lockless check and we rely on seeing the dirty bit */
755 smp_mb();
756 if (buffer_dirty(bh)) {
757 list_add(&bh->b_assoc_buffers,
758 &mapping->private_list);
759 bh->b_assoc_map = mapping;
760 }
761 spin_unlock(lock);
762 wait_on_buffer(bh);
763 if (!buffer_uptodate(bh))
764 err = -EIO;
765 brelse(bh);
766 spin_lock(lock);
767 }
768
769 spin_unlock(lock);
770 err2 = osync_buffers_list(lock, list);
771 if (err)
772 return err;
773 else
774 return err2;
775}
776
777/*
778 * Invalidate any and all dirty buffers on a given inode. We are
779 * probably unmounting the fs, but that doesn't mean we have already
780 * done a sync(). Just drop the buffers from the inode list.
781 *
782 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
783 * assumes that all the buffers are against the blockdev. Not true
784 * for reiserfs.
785 */
786void invalidate_inode_buffers(struct inode *inode)
787{
788 if (inode_has_buffers(inode)) {
789 struct address_space *mapping = &inode->i_data;
790 struct list_head *list = &mapping->private_list;
791 struct address_space *buffer_mapping = mapping->private_data;
792
793 spin_lock(&buffer_mapping->private_lock);
794 while (!list_empty(list))
795 __remove_assoc_queue(BH_ENTRY(list->next));
796 spin_unlock(&buffer_mapping->private_lock);
797 }
798}
799EXPORT_SYMBOL(invalidate_inode_buffers);
800
801/*
802 * Remove any clean buffers from the inode's buffer list. This is called
803 * when we're trying to free the inode itself. Those buffers can pin it.
804 *
805 * Returns true if all buffers were removed.
806 */
807int remove_inode_buffers(struct inode *inode)
808{
809 int ret = 1;
810
811 if (inode_has_buffers(inode)) {
812 struct address_space *mapping = &inode->i_data;
813 struct list_head *list = &mapping->private_list;
814 struct address_space *buffer_mapping = mapping->private_data;
815
816 spin_lock(&buffer_mapping->private_lock);
817 while (!list_empty(list)) {
818 struct buffer_head *bh = BH_ENTRY(list->next);
819 if (buffer_dirty(bh)) {
820 ret = 0;
821 break;
822 }
823 __remove_assoc_queue(bh);
824 }
825 spin_unlock(&buffer_mapping->private_lock);
826 }
827 return ret;
828}
829
830/*
831 * Create the appropriate buffers when given a page for data area and
832 * the size of each buffer.. Use the bh->b_this_page linked list to
833 * follow the buffers created. Return NULL if unable to create more
834 * buffers.
835 *
836 * The retry flag is used to differentiate async IO (paging, swapping)
837 * which may not fail from ordinary buffer allocations.
838 */
839struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
840 bool retry)
841{
842 struct buffer_head *bh, *head;
843 gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
844 long offset;
845 struct mem_cgroup *memcg;
846
847 if (retry)
848 gfp |= __GFP_NOFAIL;
849
850 memcg = get_mem_cgroup_from_page(page);
851 memalloc_use_memcg(memcg);
852
853 head = NULL;
854 offset = PAGE_SIZE;
855 while ((offset -= size) >= 0) {
856 bh = alloc_buffer_head(gfp);
857 if (!bh)
858 goto no_grow;
859
860 bh->b_this_page = head;
861 bh->b_blocknr = -1;
862 head = bh;
863
864 bh->b_size = size;
865
866 /* Link the buffer to its page */
867 set_bh_page(bh, page, offset);
868 }
869out:
870 memalloc_unuse_memcg();
871 mem_cgroup_put(memcg);
872 return head;
873/*
874 * In case anything failed, we just free everything we got.
875 */
876no_grow:
877 if (head) {
878 do {
879 bh = head;
880 head = head->b_this_page;
881 free_buffer_head(bh);
882 } while (head);
883 }
884
885 goto out;
886}
887EXPORT_SYMBOL_GPL(alloc_page_buffers);
888
889static inline void
890link_dev_buffers(struct page *page, struct buffer_head *head)
891{
892 struct buffer_head *bh, *tail;
893
894 bh = head;
895 do {
896 tail = bh;
897 bh = bh->b_this_page;
898 } while (bh);
899 tail->b_this_page = head;
900 attach_page_private(page, head);
901}
902
903static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
904{
905 sector_t retval = ~((sector_t)0);
906 loff_t sz = i_size_read(bdev->bd_inode);
907
908 if (sz) {
909 unsigned int sizebits = blksize_bits(size);
910 retval = (sz >> sizebits);
911 }
912 return retval;
913}
914
915/*
916 * Initialise the state of a blockdev page's buffers.
917 */
918static sector_t
919init_page_buffers(struct page *page, struct block_device *bdev,
920 sector_t block, int size)
921{
922 struct buffer_head *head = page_buffers(page);
923 struct buffer_head *bh = head;
924 int uptodate = PageUptodate(page);
925 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
926
927 do {
928 if (!buffer_mapped(bh)) {
929 bh->b_end_io = NULL;
930 bh->b_private = NULL;
931 bh->b_bdev = bdev;
932 bh->b_blocknr = block;
933 if (uptodate)
934 set_buffer_uptodate(bh);
935 if (block < end_block)
936 set_buffer_mapped(bh);
937 }
938 block++;
939 bh = bh->b_this_page;
940 } while (bh != head);
941
942 /*
943 * Caller needs to validate requested block against end of device.
944 */
945 return end_block;
946}
947
948/*
949 * Create the page-cache page that contains the requested block.
950 *
951 * This is used purely for blockdev mappings.
952 */
953static int
954grow_dev_page(struct block_device *bdev, sector_t block,
955 pgoff_t index, int size, int sizebits, gfp_t gfp)
956{
957 struct inode *inode = bdev->bd_inode;
958 struct page *page;
959 struct buffer_head *bh;
960 sector_t end_block;
961 int ret = 0;
962 gfp_t gfp_mask;
963
964 gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
965
966 /*
967 * XXX: __getblk_slow() can not really deal with failure and
968 * will endlessly loop on improvised global reclaim. Prefer
969 * looping in the allocator rather than here, at least that
970 * code knows what it's doing.
971 */
972 gfp_mask |= __GFP_NOFAIL;
973
974 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
975
976 BUG_ON(!PageLocked(page));
977
978 if (page_has_buffers(page)) {
979 bh = page_buffers(page);
980 if (bh->b_size == size) {
981 end_block = init_page_buffers(page, bdev,
982 (sector_t)index << sizebits,
983 size);
984 goto done;
985 }
986 if (!try_to_free_buffers(page))
987 goto failed;
988 }
989
990 /*
991 * Allocate some buffers for this page
992 */
993 bh = alloc_page_buffers(page, size, true);
994
995 /*
996 * Link the page to the buffers and initialise them. Take the
997 * lock to be atomic wrt __find_get_block(), which does not
998 * run under the page lock.
999 */
1000 spin_lock(&inode->i_mapping->private_lock);
1001 link_dev_buffers(page, bh);
1002 end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
1003 size);
1004 spin_unlock(&inode->i_mapping->private_lock);
1005done:
1006 ret = (block < end_block) ? 1 : -ENXIO;
1007failed:
1008 unlock_page(page);
1009 put_page(page);
1010 return ret;
1011}
1012
1013/*
1014 * Create buffers for the specified block device block's page. If
1015 * that page was dirty, the buffers are set dirty also.
1016 */
1017static int
1018grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
1019{
1020 pgoff_t index;
1021 int sizebits;
1022
1023 sizebits = -1;
1024 do {
1025 sizebits++;
1026 } while ((size << sizebits) < PAGE_SIZE);
1027
1028 index = block >> sizebits;
1029
1030 /*
1031 * Check for a block which wants to lie outside our maximum possible
1032 * pagecache index. (this comparison is done using sector_t types).
1033 */
1034 if (unlikely(index != block >> sizebits)) {
1035 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1036 "device %pg\n",
1037 __func__, (unsigned long long)block,
1038 bdev);
1039 return -EIO;
1040 }
1041
1042 /* Create a page with the proper size buffers.. */
1043 return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1044}
1045
1046static struct buffer_head *
1047__getblk_slow(struct block_device *bdev, sector_t block,
1048 unsigned size, gfp_t gfp)
1049{
1050 /* Size must be multiple of hard sectorsize */
1051 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1052 (size < 512 || size > PAGE_SIZE))) {
1053 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1054 size);
1055 printk(KERN_ERR "logical block size: %d\n",
1056 bdev_logical_block_size(bdev));
1057
1058 dump_stack();
1059 return NULL;
1060 }
1061
1062 for (;;) {
1063 struct buffer_head *bh;
1064 int ret;
1065
1066 bh = __find_get_block(bdev, block, size);
1067 if (bh)
1068 return bh;
1069
1070 ret = grow_buffers(bdev, block, size, gfp);
1071 if (ret < 0)
1072 return NULL;
1073 }
1074}
1075
1076/*
1077 * The relationship between dirty buffers and dirty pages:
1078 *
1079 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1080 * the page is tagged dirty in the page cache.
1081 *
1082 * At all times, the dirtiness of the buffers represents the dirtiness of
1083 * subsections of the page. If the page has buffers, the page dirty bit is
1084 * merely a hint about the true dirty state.
1085 *
1086 * When a page is set dirty in its entirety, all its buffers are marked dirty
1087 * (if the page has buffers).
1088 *
1089 * When a buffer is marked dirty, its page is dirtied, but the page's other
1090 * buffers are not.
1091 *
1092 * Also. When blockdev buffers are explicitly read with bread(), they
1093 * individually become uptodate. But their backing page remains not
1094 * uptodate - even if all of its buffers are uptodate. A subsequent
1095 * block_read_full_page() against that page will discover all the uptodate
1096 * buffers, will set the page uptodate and will perform no I/O.
1097 */
1098
1099/**
1100 * mark_buffer_dirty - mark a buffer_head as needing writeout
1101 * @bh: the buffer_head to mark dirty
1102 *
1103 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1104 * its backing page dirty, then tag the page as dirty in the page cache
1105 * and then attach the address_space's inode to its superblock's dirty
1106 * inode list.
1107 *
1108 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1109 * i_pages lock and mapping->host->i_lock.
1110 */
1111void mark_buffer_dirty(struct buffer_head *bh)
1112{
1113 WARN_ON_ONCE(!buffer_uptodate(bh));
1114
1115 trace_block_dirty_buffer(bh);
1116
1117 /*
1118 * Very *carefully* optimize the it-is-already-dirty case.
1119 *
1120 * Don't let the final "is it dirty" escape to before we
1121 * perhaps modified the buffer.
1122 */
1123 if (buffer_dirty(bh)) {
1124 smp_mb();
1125 if (buffer_dirty(bh))
1126 return;
1127 }
1128
1129 if (!test_set_buffer_dirty(bh)) {
1130 struct page *page = bh->b_page;
1131 struct address_space *mapping = NULL;
1132
1133 lock_page_memcg(page);
1134 if (!TestSetPageDirty(page)) {
1135 mapping = page_mapping(page);
1136 if (mapping)
1137 __set_page_dirty(page, mapping, 0);
1138 }
1139 unlock_page_memcg(page);
1140 if (mapping)
1141 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1142 }
1143}
1144EXPORT_SYMBOL(mark_buffer_dirty);
1145
1146void mark_buffer_write_io_error(struct buffer_head *bh)
1147{
1148 struct super_block *sb;
1149
1150 set_buffer_write_io_error(bh);
1151 /* FIXME: do we need to set this in both places? */
1152 if (bh->b_page && bh->b_page->mapping)
1153 mapping_set_error(bh->b_page->mapping, -EIO);
1154 if (bh->b_assoc_map)
1155 mapping_set_error(bh->b_assoc_map, -EIO);
1156 rcu_read_lock();
1157 sb = READ_ONCE(bh->b_bdev->bd_super);
1158 if (sb)
1159 errseq_set(&sb->s_wb_err, -EIO);
1160 rcu_read_unlock();
1161}
1162EXPORT_SYMBOL(mark_buffer_write_io_error);
1163
1164/*
1165 * Decrement a buffer_head's reference count. If all buffers against a page
1166 * have zero reference count, are clean and unlocked, and if the page is clean
1167 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1168 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1169 * a page but it ends up not being freed, and buffers may later be reattached).
1170 */
1171void __brelse(struct buffer_head * buf)
1172{
1173 if (atomic_read(&buf->b_count)) {
1174 put_bh(buf);
1175 return;
1176 }
1177 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1178}
1179EXPORT_SYMBOL(__brelse);
1180
1181/*
1182 * bforget() is like brelse(), except it discards any
1183 * potentially dirty data.
1184 */
1185void __bforget(struct buffer_head *bh)
1186{
1187 clear_buffer_dirty(bh);
1188 if (bh->b_assoc_map) {
1189 struct address_space *buffer_mapping = bh->b_page->mapping;
1190
1191 spin_lock(&buffer_mapping->private_lock);
1192 list_del_init(&bh->b_assoc_buffers);
1193 bh->b_assoc_map = NULL;
1194 spin_unlock(&buffer_mapping->private_lock);
1195 }
1196 __brelse(bh);
1197}
1198EXPORT_SYMBOL(__bforget);
1199
1200static struct buffer_head *__bread_slow(struct buffer_head *bh)
1201{
1202 lock_buffer(bh);
1203 if (buffer_uptodate(bh)) {
1204 unlock_buffer(bh);
1205 return bh;
1206 } else {
1207 get_bh(bh);
1208 bh->b_end_io = end_buffer_read_sync;
1209 submit_bh(REQ_OP_READ, 0, bh);
1210 wait_on_buffer(bh);
1211 if (buffer_uptodate(bh))
1212 return bh;
1213 }
1214 brelse(bh);
1215 return NULL;
1216}
1217
1218/*
1219 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1220 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1221 * refcount elevated by one when they're in an LRU. A buffer can only appear
1222 * once in a particular CPU's LRU. A single buffer can be present in multiple
1223 * CPU's LRUs at the same time.
1224 *
1225 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1226 * sb_find_get_block().
1227 *
1228 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1229 * a local interrupt disable for that.
1230 */
1231
1232#define BH_LRU_SIZE 16
1233
1234struct bh_lru {
1235 struct buffer_head *bhs[BH_LRU_SIZE];
1236};
1237
1238static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1239
1240#ifdef CONFIG_SMP
1241#define bh_lru_lock() local_irq_disable()
1242#define bh_lru_unlock() local_irq_enable()
1243#else
1244#define bh_lru_lock() preempt_disable()
1245#define bh_lru_unlock() preempt_enable()
1246#endif
1247
1248static inline void check_irqs_on(void)
1249{
1250#ifdef irqs_disabled
1251 BUG_ON(irqs_disabled());
1252#endif
1253}
1254
1255/*
1256 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1257 * inserted at the front, and the buffer_head at the back if any is evicted.
1258 * Or, if already in the LRU it is moved to the front.
1259 */
1260static void bh_lru_install(struct buffer_head *bh)
1261{
1262 struct buffer_head *evictee = bh;
1263 struct bh_lru *b;
1264 int i;
1265
1266 check_irqs_on();
1267 bh_lru_lock();
1268
1269 b = this_cpu_ptr(&bh_lrus);
1270 for (i = 0; i < BH_LRU_SIZE; i++) {
1271 swap(evictee, b->bhs[i]);
1272 if (evictee == bh) {
1273 bh_lru_unlock();
1274 return;
1275 }
1276 }
1277
1278 get_bh(bh);
1279 bh_lru_unlock();
1280 brelse(evictee);
1281}
1282
1283/*
1284 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1285 */
1286static struct buffer_head *
1287lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1288{
1289 struct buffer_head *ret = NULL;
1290 unsigned int i;
1291
1292 check_irqs_on();
1293 bh_lru_lock();
1294 for (i = 0; i < BH_LRU_SIZE; i++) {
1295 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1296
1297 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1298 bh->b_size == size) {
1299 if (i) {
1300 while (i) {
1301 __this_cpu_write(bh_lrus.bhs[i],
1302 __this_cpu_read(bh_lrus.bhs[i - 1]));
1303 i--;
1304 }
1305 __this_cpu_write(bh_lrus.bhs[0], bh);
1306 }
1307 get_bh(bh);
1308 ret = bh;
1309 break;
1310 }
1311 }
1312 bh_lru_unlock();
1313 return ret;
1314}
1315
1316/*
1317 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1318 * it in the LRU and mark it as accessed. If it is not present then return
1319 * NULL
1320 */
1321struct buffer_head *
1322__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1323{
1324 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1325
1326 if (bh == NULL) {
1327 /* __find_get_block_slow will mark the page accessed */
1328 bh = __find_get_block_slow(bdev, block);
1329 if (bh)
1330 bh_lru_install(bh);
1331 } else
1332 touch_buffer(bh);
1333
1334 return bh;
1335}
1336EXPORT_SYMBOL(__find_get_block);
1337
1338/*
1339 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1340 * which corresponds to the passed block_device, block and size. The
1341 * returned buffer has its reference count incremented.
1342 *
1343 * __getblk_gfp() will lock up the machine if grow_dev_page's
1344 * try_to_free_buffers() attempt is failing. FIXME, perhaps?
1345 */
1346struct buffer_head *
1347__getblk_gfp(struct block_device *bdev, sector_t block,
1348 unsigned size, gfp_t gfp)
1349{
1350 struct buffer_head *bh = __find_get_block(bdev, block, size);
1351
1352 might_sleep();
1353 if (bh == NULL)
1354 bh = __getblk_slow(bdev, block, size, gfp);
1355 return bh;
1356}
1357EXPORT_SYMBOL(__getblk_gfp);
1358
1359/*
1360 * Do async read-ahead on a buffer..
1361 */
1362void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1363{
1364 struct buffer_head *bh = __getblk(bdev, block, size);
1365 if (likely(bh)) {
1366 ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1367 brelse(bh);
1368 }
1369}
1370EXPORT_SYMBOL(__breadahead);
1371
1372void __breadahead_gfp(struct block_device *bdev, sector_t block, unsigned size,
1373 gfp_t gfp)
1374{
1375 struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1376 if (likely(bh)) {
1377 ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1378 brelse(bh);
1379 }
1380}
1381EXPORT_SYMBOL(__breadahead_gfp);
1382
1383/**
1384 * __bread_gfp() - reads a specified block and returns the bh
1385 * @bdev: the block_device to read from
1386 * @block: number of block
1387 * @size: size (in bytes) to read
1388 * @gfp: page allocation flag
1389 *
1390 * Reads a specified block, and returns buffer head that contains it.
1391 * The page cache can be allocated from non-movable area
1392 * not to prevent page migration if you set gfp to zero.
1393 * It returns NULL if the block was unreadable.
1394 */
1395struct buffer_head *
1396__bread_gfp(struct block_device *bdev, sector_t block,
1397 unsigned size, gfp_t gfp)
1398{
1399 struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1400
1401 if (likely(bh) && !buffer_uptodate(bh))
1402 bh = __bread_slow(bh);
1403 return bh;
1404}
1405EXPORT_SYMBOL(__bread_gfp);
1406
1407/*
1408 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1409 * This doesn't race because it runs in each cpu either in irq
1410 * or with preempt disabled.
1411 */
1412static void invalidate_bh_lru(void *arg)
1413{
1414 struct bh_lru *b = &get_cpu_var(bh_lrus);
1415 int i;
1416
1417 for (i = 0; i < BH_LRU_SIZE; i++) {
1418 brelse(b->bhs[i]);
1419 b->bhs[i] = NULL;
1420 }
1421 put_cpu_var(bh_lrus);
1422}
1423
1424static bool has_bh_in_lru(int cpu, void *dummy)
1425{
1426 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1427 int i;
1428
1429 for (i = 0; i < BH_LRU_SIZE; i++) {
1430 if (b->bhs[i])
1431 return true;
1432 }
1433
1434 return false;
1435}
1436
1437void invalidate_bh_lrus(void)
1438{
1439 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1);
1440}
1441EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1442
1443void set_bh_page(struct buffer_head *bh,
1444 struct page *page, unsigned long offset)
1445{
1446 bh->b_page = page;
1447 BUG_ON(offset >= PAGE_SIZE);
1448 if (PageHighMem(page))
1449 /*
1450 * This catches illegal uses and preserves the offset:
1451 */
1452 bh->b_data = (char *)(0 + offset);
1453 else
1454 bh->b_data = page_address(page) + offset;
1455}
1456EXPORT_SYMBOL(set_bh_page);
1457
1458/*
1459 * Called when truncating a buffer on a page completely.
1460 */
1461
1462/* Bits that are cleared during an invalidate */
1463#define BUFFER_FLAGS_DISCARD \
1464 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1465 1 << BH_Delay | 1 << BH_Unwritten)
1466
1467static void discard_buffer(struct buffer_head * bh)
1468{
1469 unsigned long b_state, b_state_old;
1470
1471 lock_buffer(bh);
1472 clear_buffer_dirty(bh);
1473 bh->b_bdev = NULL;
1474 b_state = bh->b_state;
1475 for (;;) {
1476 b_state_old = cmpxchg(&bh->b_state, b_state,
1477 (b_state & ~BUFFER_FLAGS_DISCARD));
1478 if (b_state_old == b_state)
1479 break;
1480 b_state = b_state_old;
1481 }
1482 unlock_buffer(bh);
1483}
1484
1485/**
1486 * block_invalidatepage - invalidate part or all of a buffer-backed page
1487 *
1488 * @page: the page which is affected
1489 * @offset: start of the range to invalidate
1490 * @length: length of the range to invalidate
1491 *
1492 * block_invalidatepage() is called when all or part of the page has become
1493 * invalidated by a truncate operation.
1494 *
1495 * block_invalidatepage() does not have to release all buffers, but it must
1496 * ensure that no dirty buffer is left outside @offset and that no I/O
1497 * is underway against any of the blocks which are outside the truncation
1498 * point. Because the caller is about to free (and possibly reuse) those
1499 * blocks on-disk.
1500 */
1501void block_invalidatepage(struct page *page, unsigned int offset,
1502 unsigned int length)
1503{
1504 struct buffer_head *head, *bh, *next;
1505 unsigned int curr_off = 0;
1506 unsigned int stop = length + offset;
1507
1508 BUG_ON(!PageLocked(page));
1509 if (!page_has_buffers(page))
1510 goto out;
1511
1512 /*
1513 * Check for overflow
1514 */
1515 BUG_ON(stop > PAGE_SIZE || stop < length);
1516
1517 head = page_buffers(page);
1518 bh = head;
1519 do {
1520 unsigned int next_off = curr_off + bh->b_size;
1521 next = bh->b_this_page;
1522
1523 /*
1524 * Are we still fully in range ?
1525 */
1526 if (next_off > stop)
1527 goto out;
1528
1529 /*
1530 * is this block fully invalidated?
1531 */
1532 if (offset <= curr_off)
1533 discard_buffer(bh);
1534 curr_off = next_off;
1535 bh = next;
1536 } while (bh != head);
1537
1538 /*
1539 * We release buffers only if the entire page is being invalidated.
1540 * The get_block cached value has been unconditionally invalidated,
1541 * so real IO is not possible anymore.
1542 */
1543 if (length == PAGE_SIZE)
1544 try_to_release_page(page, 0);
1545out:
1546 return;
1547}
1548EXPORT_SYMBOL(block_invalidatepage);
1549
1550
1551/*
1552 * We attach and possibly dirty the buffers atomically wrt
1553 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1554 * is already excluded via the page lock.
1555 */
1556void create_empty_buffers(struct page *page,
1557 unsigned long blocksize, unsigned long b_state)
1558{
1559 struct buffer_head *bh, *head, *tail;
1560
1561 head = alloc_page_buffers(page, blocksize, true);
1562 bh = head;
1563 do {
1564 bh->b_state |= b_state;
1565 tail = bh;
1566 bh = bh->b_this_page;
1567 } while (bh);
1568 tail->b_this_page = head;
1569
1570 spin_lock(&page->mapping->private_lock);
1571 if (PageUptodate(page) || PageDirty(page)) {
1572 bh = head;
1573 do {
1574 if (PageDirty(page))
1575 set_buffer_dirty(bh);
1576 if (PageUptodate(page))
1577 set_buffer_uptodate(bh);
1578 bh = bh->b_this_page;
1579 } while (bh != head);
1580 }
1581 attach_page_private(page, head);
1582 spin_unlock(&page->mapping->private_lock);
1583}
1584EXPORT_SYMBOL(create_empty_buffers);
1585
1586/**
1587 * clean_bdev_aliases: clean a range of buffers in block device
1588 * @bdev: Block device to clean buffers in
1589 * @block: Start of a range of blocks to clean
1590 * @len: Number of blocks to clean
1591 *
1592 * We are taking a range of blocks for data and we don't want writeback of any
1593 * buffer-cache aliases starting from return from this function and until the
1594 * moment when something will explicitly mark the buffer dirty (hopefully that
1595 * will not happen until we will free that block ;-) We don't even need to mark
1596 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1597 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1598 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1599 * would confuse anyone who might pick it with bread() afterwards...
1600 *
1601 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1602 * writeout I/O going on against recently-freed buffers. We don't wait on that
1603 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1604 * need to. That happens here.
1605 */
1606void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1607{
1608 struct inode *bd_inode = bdev->bd_inode;
1609 struct address_space *bd_mapping = bd_inode->i_mapping;
1610 struct pagevec pvec;
1611 pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
1612 pgoff_t end;
1613 int i, count;
1614 struct buffer_head *bh;
1615 struct buffer_head *head;
1616
1617 end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1618 pagevec_init(&pvec);
1619 while (pagevec_lookup_range(&pvec, bd_mapping, &index, end)) {
1620 count = pagevec_count(&pvec);
1621 for (i = 0; i < count; i++) {
1622 struct page *page = pvec.pages[i];
1623
1624 if (!page_has_buffers(page))
1625 continue;
1626 /*
1627 * We use page lock instead of bd_mapping->private_lock
1628 * to pin buffers here since we can afford to sleep and
1629 * it scales better than a global spinlock lock.
1630 */
1631 lock_page(page);
1632 /* Recheck when the page is locked which pins bhs */
1633 if (!page_has_buffers(page))
1634 goto unlock_page;
1635 head = page_buffers(page);
1636 bh = head;
1637 do {
1638 if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1639 goto next;
1640 if (bh->b_blocknr >= block + len)
1641 break;
1642 clear_buffer_dirty(bh);
1643 wait_on_buffer(bh);
1644 clear_buffer_req(bh);
1645next:
1646 bh = bh->b_this_page;
1647 } while (bh != head);
1648unlock_page:
1649 unlock_page(page);
1650 }
1651 pagevec_release(&pvec);
1652 cond_resched();
1653 /* End of range already reached? */
1654 if (index > end || !index)
1655 break;
1656 }
1657}
1658EXPORT_SYMBOL(clean_bdev_aliases);
1659
1660/*
1661 * Size is a power-of-two in the range 512..PAGE_SIZE,
1662 * and the case we care about most is PAGE_SIZE.
1663 *
1664 * So this *could* possibly be written with those
1665 * constraints in mind (relevant mostly if some
1666 * architecture has a slow bit-scan instruction)
1667 */
1668static inline int block_size_bits(unsigned int blocksize)
1669{
1670 return ilog2(blocksize);
1671}
1672
1673static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1674{
1675 BUG_ON(!PageLocked(page));
1676
1677 if (!page_has_buffers(page))
1678 create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
1679 b_state);
1680 return page_buffers(page);
1681}
1682
1683/*
1684 * NOTE! All mapped/uptodate combinations are valid:
1685 *
1686 * Mapped Uptodate Meaning
1687 *
1688 * No No "unknown" - must do get_block()
1689 * No Yes "hole" - zero-filled
1690 * Yes No "allocated" - allocated on disk, not read in
1691 * Yes Yes "valid" - allocated and up-to-date in memory.
1692 *
1693 * "Dirty" is valid only with the last case (mapped+uptodate).
1694 */
1695
1696/*
1697 * While block_write_full_page is writing back the dirty buffers under
1698 * the page lock, whoever dirtied the buffers may decide to clean them
1699 * again at any time. We handle that by only looking at the buffer
1700 * state inside lock_buffer().
1701 *
1702 * If block_write_full_page() is called for regular writeback
1703 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1704 * locked buffer. This only can happen if someone has written the buffer
1705 * directly, with submit_bh(). At the address_space level PageWriteback
1706 * prevents this contention from occurring.
1707 *
1708 * If block_write_full_page() is called with wbc->sync_mode ==
1709 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1710 * causes the writes to be flagged as synchronous writes.
1711 */
1712int __block_write_full_page(struct inode *inode, struct page *page,
1713 get_block_t *get_block, struct writeback_control *wbc,
1714 bh_end_io_t *handler)
1715{
1716 int err;
1717 sector_t block;
1718 sector_t last_block;
1719 struct buffer_head *bh, *head;
1720 unsigned int blocksize, bbits;
1721 int nr_underway = 0;
1722 int write_flags = wbc_to_write_flags(wbc);
1723
1724 head = create_page_buffers(page, inode,
1725 (1 << BH_Dirty)|(1 << BH_Uptodate));
1726
1727 /*
1728 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1729 * here, and the (potentially unmapped) buffers may become dirty at
1730 * any time. If a buffer becomes dirty here after we've inspected it
1731 * then we just miss that fact, and the page stays dirty.
1732 *
1733 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1734 * handle that here by just cleaning them.
1735 */
1736
1737 bh = head;
1738 blocksize = bh->b_size;
1739 bbits = block_size_bits(blocksize);
1740
1741 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1742 last_block = (i_size_read(inode) - 1) >> bbits;
1743
1744 /*
1745 * Get all the dirty buffers mapped to disk addresses and
1746 * handle any aliases from the underlying blockdev's mapping.
1747 */
1748 do {
1749 if (block > last_block) {
1750 /*
1751 * mapped buffers outside i_size will occur, because
1752 * this page can be outside i_size when there is a
1753 * truncate in progress.
1754 */
1755 /*
1756 * The buffer was zeroed by block_write_full_page()
1757 */
1758 clear_buffer_dirty(bh);
1759 set_buffer_uptodate(bh);
1760 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1761 buffer_dirty(bh)) {
1762 WARN_ON(bh->b_size != blocksize);
1763 err = get_block(inode, block, bh, 1);
1764 if (err)
1765 goto recover;
1766 clear_buffer_delay(bh);
1767 if (buffer_new(bh)) {
1768 /* blockdev mappings never come here */
1769 clear_buffer_new(bh);
1770 clean_bdev_bh_alias(bh);
1771 }
1772 }
1773 bh = bh->b_this_page;
1774 block++;
1775 } while (bh != head);
1776
1777 do {
1778 if (!buffer_mapped(bh))
1779 continue;
1780 /*
1781 * If it's a fully non-blocking write attempt and we cannot
1782 * lock the buffer then redirty the page. Note that this can
1783 * potentially cause a busy-wait loop from writeback threads
1784 * and kswapd activity, but those code paths have their own
1785 * higher-level throttling.
1786 */
1787 if (wbc->sync_mode != WB_SYNC_NONE) {
1788 lock_buffer(bh);
1789 } else if (!trylock_buffer(bh)) {
1790 redirty_page_for_writepage(wbc, page);
1791 continue;
1792 }
1793 if (test_clear_buffer_dirty(bh)) {
1794 mark_buffer_async_write_endio(bh, handler);
1795 } else {
1796 unlock_buffer(bh);
1797 }
1798 } while ((bh = bh->b_this_page) != head);
1799
1800 /*
1801 * The page and its buffers are protected by PageWriteback(), so we can
1802 * drop the bh refcounts early.
1803 */
1804 BUG_ON(PageWriteback(page));
1805 set_page_writeback(page);
1806
1807 do {
1808 struct buffer_head *next = bh->b_this_page;
1809 if (buffer_async_write(bh)) {
1810 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1811 inode->i_write_hint, wbc);
1812 nr_underway++;
1813 }
1814 bh = next;
1815 } while (bh != head);
1816 unlock_page(page);
1817
1818 err = 0;
1819done:
1820 if (nr_underway == 0) {
1821 /*
1822 * The page was marked dirty, but the buffers were
1823 * clean. Someone wrote them back by hand with
1824 * ll_rw_block/submit_bh. A rare case.
1825 */
1826 end_page_writeback(page);
1827
1828 /*
1829 * The page and buffer_heads can be released at any time from
1830 * here on.
1831 */
1832 }
1833 return err;
1834
1835recover:
1836 /*
1837 * ENOSPC, or some other error. We may already have added some
1838 * blocks to the file, so we need to write these out to avoid
1839 * exposing stale data.
1840 * The page is currently locked and not marked for writeback
1841 */
1842 bh = head;
1843 /* Recovery: lock and submit the mapped buffers */
1844 do {
1845 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1846 !buffer_delay(bh)) {
1847 lock_buffer(bh);
1848 mark_buffer_async_write_endio(bh, handler);
1849 } else {
1850 /*
1851 * The buffer may have been set dirty during
1852 * attachment to a dirty page.
1853 */
1854 clear_buffer_dirty(bh);
1855 }
1856 } while ((bh = bh->b_this_page) != head);
1857 SetPageError(page);
1858 BUG_ON(PageWriteback(page));
1859 mapping_set_error(page->mapping, err);
1860 set_page_writeback(page);
1861 do {
1862 struct buffer_head *next = bh->b_this_page;
1863 if (buffer_async_write(bh)) {
1864 clear_buffer_dirty(bh);
1865 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1866 inode->i_write_hint, wbc);
1867 nr_underway++;
1868 }
1869 bh = next;
1870 } while (bh != head);
1871 unlock_page(page);
1872 goto done;
1873}
1874EXPORT_SYMBOL(__block_write_full_page);
1875
1876/*
1877 * If a page has any new buffers, zero them out here, and mark them uptodate
1878 * and dirty so they'll be written out (in order to prevent uninitialised
1879 * block data from leaking). And clear the new bit.
1880 */
1881void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1882{
1883 unsigned int block_start, block_end;
1884 struct buffer_head *head, *bh;
1885
1886 BUG_ON(!PageLocked(page));
1887 if (!page_has_buffers(page))
1888 return;
1889
1890 bh = head = page_buffers(page);
1891 block_start = 0;
1892 do {
1893 block_end = block_start + bh->b_size;
1894
1895 if (buffer_new(bh)) {
1896 if (block_end > from && block_start < to) {
1897 if (!PageUptodate(page)) {
1898 unsigned start, size;
1899
1900 start = max(from, block_start);
1901 size = min(to, block_end) - start;
1902
1903 zero_user(page, start, size);
1904 set_buffer_uptodate(bh);
1905 }
1906
1907 clear_buffer_new(bh);
1908 mark_buffer_dirty(bh);
1909 }
1910 }
1911
1912 block_start = block_end;
1913 bh = bh->b_this_page;
1914 } while (bh != head);
1915}
1916EXPORT_SYMBOL(page_zero_new_buffers);
1917
1918static void
1919iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
1920 struct iomap *iomap)
1921{
1922 loff_t offset = block << inode->i_blkbits;
1923
1924 bh->b_bdev = iomap->bdev;
1925
1926 /*
1927 * Block points to offset in file we need to map, iomap contains
1928 * the offset at which the map starts. If the map ends before the
1929 * current block, then do not map the buffer and let the caller
1930 * handle it.
1931 */
1932 BUG_ON(offset >= iomap->offset + iomap->length);
1933
1934 switch (iomap->type) {
1935 case IOMAP_HOLE:
1936 /*
1937 * If the buffer is not up to date or beyond the current EOF,
1938 * we need to mark it as new to ensure sub-block zeroing is
1939 * executed if necessary.
1940 */
1941 if (!buffer_uptodate(bh) ||
1942 (offset >= i_size_read(inode)))
1943 set_buffer_new(bh);
1944 break;
1945 case IOMAP_DELALLOC:
1946 if (!buffer_uptodate(bh) ||
1947 (offset >= i_size_read(inode)))
1948 set_buffer_new(bh);
1949 set_buffer_uptodate(bh);
1950 set_buffer_mapped(bh);
1951 set_buffer_delay(bh);
1952 break;
1953 case IOMAP_UNWRITTEN:
1954 /*
1955 * For unwritten regions, we always need to ensure that regions
1956 * in the block we are not writing to are zeroed. Mark the
1957 * buffer as new to ensure this.
1958 */
1959 set_buffer_new(bh);
1960 set_buffer_unwritten(bh);
1961 fallthrough;
1962 case IOMAP_MAPPED:
1963 if ((iomap->flags & IOMAP_F_NEW) ||
1964 offset >= i_size_read(inode))
1965 set_buffer_new(bh);
1966 bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
1967 inode->i_blkbits;
1968 set_buffer_mapped(bh);
1969 break;
1970 }
1971}
1972
1973int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
1974 get_block_t *get_block, struct iomap *iomap)
1975{
1976 unsigned from = pos & (PAGE_SIZE - 1);
1977 unsigned to = from + len;
1978 struct inode *inode = page->mapping->host;
1979 unsigned block_start, block_end;
1980 sector_t block;
1981 int err = 0;
1982 unsigned blocksize, bbits;
1983 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1984
1985 BUG_ON(!PageLocked(page));
1986 BUG_ON(from > PAGE_SIZE);
1987 BUG_ON(to > PAGE_SIZE);
1988 BUG_ON(from > to);
1989
1990 head = create_page_buffers(page, inode, 0);
1991 blocksize = head->b_size;
1992 bbits = block_size_bits(blocksize);
1993
1994 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1995
1996 for(bh = head, block_start = 0; bh != head || !block_start;
1997 block++, block_start=block_end, bh = bh->b_this_page) {
1998 block_end = block_start + blocksize;
1999 if (block_end <= from || block_start >= to) {
2000 if (PageUptodate(page)) {
2001 if (!buffer_uptodate(bh))
2002 set_buffer_uptodate(bh);
2003 }
2004 continue;
2005 }
2006 if (buffer_new(bh))
2007 clear_buffer_new(bh);
2008 if (!buffer_mapped(bh)) {
2009 WARN_ON(bh->b_size != blocksize);
2010 if (get_block) {
2011 err = get_block(inode, block, bh, 1);
2012 if (err)
2013 break;
2014 } else {
2015 iomap_to_bh(inode, block, bh, iomap);
2016 }
2017
2018 if (buffer_new(bh)) {
2019 clean_bdev_bh_alias(bh);
2020 if (PageUptodate(page)) {
2021 clear_buffer_new(bh);
2022 set_buffer_uptodate(bh);
2023 mark_buffer_dirty(bh);
2024 continue;
2025 }
2026 if (block_end > to || block_start < from)
2027 zero_user_segments(page,
2028 to, block_end,
2029 block_start, from);
2030 continue;
2031 }
2032 }
2033 if (PageUptodate(page)) {
2034 if (!buffer_uptodate(bh))
2035 set_buffer_uptodate(bh);
2036 continue;
2037 }
2038 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2039 !buffer_unwritten(bh) &&
2040 (block_start < from || block_end > to)) {
2041 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2042 *wait_bh++=bh;
2043 }
2044 }
2045 /*
2046 * If we issued read requests - let them complete.
2047 */
2048 while(wait_bh > wait) {
2049 wait_on_buffer(*--wait_bh);
2050 if (!buffer_uptodate(*wait_bh))
2051 err = -EIO;
2052 }
2053 if (unlikely(err))
2054 page_zero_new_buffers(page, from, to);
2055 return err;
2056}
2057
2058int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2059 get_block_t *get_block)
2060{
2061 return __block_write_begin_int(page, pos, len, get_block, NULL);
2062}
2063EXPORT_SYMBOL(__block_write_begin);
2064
2065static int __block_commit_write(struct inode *inode, struct page *page,
2066 unsigned from, unsigned to)
2067{
2068 unsigned block_start, block_end;
2069 int partial = 0;
2070 unsigned blocksize;
2071 struct buffer_head *bh, *head;
2072
2073 bh = head = page_buffers(page);
2074 blocksize = bh->b_size;
2075
2076 block_start = 0;
2077 do {
2078 block_end = block_start + blocksize;
2079 if (block_end <= from || block_start >= to) {
2080 if (!buffer_uptodate(bh))
2081 partial = 1;
2082 } else {
2083 set_buffer_uptodate(bh);
2084 mark_buffer_dirty(bh);
2085 }
2086 clear_buffer_new(bh);
2087
2088 block_start = block_end;
2089 bh = bh->b_this_page;
2090 } while (bh != head);
2091
2092 /*
2093 * If this is a partial write which happened to make all buffers
2094 * uptodate then we can optimize away a bogus readpage() for
2095 * the next read(). Here we 'discover' whether the page went
2096 * uptodate as a result of this (potentially partial) write.
2097 */
2098 if (!partial)
2099 SetPageUptodate(page);
2100 return 0;
2101}
2102
2103/*
2104 * block_write_begin takes care of the basic task of block allocation and
2105 * bringing partial write blocks uptodate first.
2106 *
2107 * The filesystem needs to handle block truncation upon failure.
2108 */
2109int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2110 unsigned flags, struct page **pagep, get_block_t *get_block)
2111{
2112 pgoff_t index = pos >> PAGE_SHIFT;
2113 struct page *page;
2114 int status;
2115
2116 page = grab_cache_page_write_begin(mapping, index, flags);
2117 if (!page)
2118 return -ENOMEM;
2119
2120 status = __block_write_begin(page, pos, len, get_block);
2121 if (unlikely(status)) {
2122 unlock_page(page);
2123 put_page(page);
2124 page = NULL;
2125 }
2126
2127 *pagep = page;
2128 return status;
2129}
2130EXPORT_SYMBOL(block_write_begin);
2131
2132int block_write_end(struct file *file, struct address_space *mapping,
2133 loff_t pos, unsigned len, unsigned copied,
2134 struct page *page, void *fsdata)
2135{
2136 struct inode *inode = mapping->host;
2137 unsigned start;
2138
2139 start = pos & (PAGE_SIZE - 1);
2140
2141 if (unlikely(copied < len)) {
2142 /*
2143 * The buffers that were written will now be uptodate, so we
2144 * don't have to worry about a readpage reading them and
2145 * overwriting a partial write. However if we have encountered
2146 * a short write and only partially written into a buffer, it
2147 * will not be marked uptodate, so a readpage might come in and
2148 * destroy our partial write.
2149 *
2150 * Do the simplest thing, and just treat any short write to a
2151 * non uptodate page as a zero-length write, and force the
2152 * caller to redo the whole thing.
2153 */
2154 if (!PageUptodate(page))
2155 copied = 0;
2156
2157 page_zero_new_buffers(page, start+copied, start+len);
2158 }
2159 flush_dcache_page(page);
2160
2161 /* This could be a short (even 0-length) commit */
2162 __block_commit_write(inode, page, start, start+copied);
2163
2164 return copied;
2165}
2166EXPORT_SYMBOL(block_write_end);
2167
2168int generic_write_end(struct file *file, struct address_space *mapping,
2169 loff_t pos, unsigned len, unsigned copied,
2170 struct page *page, void *fsdata)
2171{
2172 struct inode *inode = mapping->host;
2173 loff_t old_size = inode->i_size;
2174 bool i_size_changed = false;
2175
2176 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2177
2178 /*
2179 * No need to use i_size_read() here, the i_size cannot change under us
2180 * because we hold i_rwsem.
2181 *
2182 * But it's important to update i_size while still holding page lock:
2183 * page writeout could otherwise come in and zero beyond i_size.
2184 */
2185 if (pos + copied > inode->i_size) {
2186 i_size_write(inode, pos + copied);
2187 i_size_changed = true;
2188 }
2189
2190 unlock_page(page);
2191 put_page(page);
2192
2193 if (old_size < pos)
2194 pagecache_isize_extended(inode, old_size, pos);
2195 /*
2196 * Don't mark the inode dirty under page lock. First, it unnecessarily
2197 * makes the holding time of page lock longer. Second, it forces lock
2198 * ordering of page lock and transaction start for journaling
2199 * filesystems.
2200 */
2201 if (i_size_changed)
2202 mark_inode_dirty(inode);
2203 return copied;
2204}
2205EXPORT_SYMBOL(generic_write_end);
2206
2207/*
2208 * block_is_partially_uptodate checks whether buffers within a page are
2209 * uptodate or not.
2210 *
2211 * Returns true if all buffers which correspond to a file portion
2212 * we want to read are uptodate.
2213 */
2214int block_is_partially_uptodate(struct page *page, unsigned long from,
2215 unsigned long count)
2216{
2217 unsigned block_start, block_end, blocksize;
2218 unsigned to;
2219 struct buffer_head *bh, *head;
2220 int ret = 1;
2221
2222 if (!page_has_buffers(page))
2223 return 0;
2224
2225 head = page_buffers(page);
2226 blocksize = head->b_size;
2227 to = min_t(unsigned, PAGE_SIZE - from, count);
2228 to = from + to;
2229 if (from < blocksize && to > PAGE_SIZE - blocksize)
2230 return 0;
2231
2232 bh = head;
2233 block_start = 0;
2234 do {
2235 block_end = block_start + blocksize;
2236 if (block_end > from && block_start < to) {
2237 if (!buffer_uptodate(bh)) {
2238 ret = 0;
2239 break;
2240 }
2241 if (block_end >= to)
2242 break;
2243 }
2244 block_start = block_end;
2245 bh = bh->b_this_page;
2246 } while (bh != head);
2247
2248 return ret;
2249}
2250EXPORT_SYMBOL(block_is_partially_uptodate);
2251
2252/*
2253 * Generic "read page" function for block devices that have the normal
2254 * get_block functionality. This is most of the block device filesystems.
2255 * Reads the page asynchronously --- the unlock_buffer() and
2256 * set/clear_buffer_uptodate() functions propagate buffer state into the
2257 * page struct once IO has completed.
2258 */
2259int block_read_full_page(struct page *page, get_block_t *get_block)
2260{
2261 struct inode *inode = page->mapping->host;
2262 sector_t iblock, lblock;
2263 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2264 unsigned int blocksize, bbits;
2265 int nr, i;
2266 int fully_mapped = 1;
2267
2268 head = create_page_buffers(page, inode, 0);
2269 blocksize = head->b_size;
2270 bbits = block_size_bits(blocksize);
2271
2272 iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2273 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2274 bh = head;
2275 nr = 0;
2276 i = 0;
2277
2278 do {
2279 if (buffer_uptodate(bh))
2280 continue;
2281
2282 if (!buffer_mapped(bh)) {
2283 int err = 0;
2284
2285 fully_mapped = 0;
2286 if (iblock < lblock) {
2287 WARN_ON(bh->b_size != blocksize);
2288 err = get_block(inode, iblock, bh, 0);
2289 if (err)
2290 SetPageError(page);
2291 }
2292 if (!buffer_mapped(bh)) {
2293 zero_user(page, i * blocksize, blocksize);
2294 if (!err)
2295 set_buffer_uptodate(bh);
2296 continue;
2297 }
2298 /*
2299 * get_block() might have updated the buffer
2300 * synchronously
2301 */
2302 if (buffer_uptodate(bh))
2303 continue;
2304 }
2305 arr[nr++] = bh;
2306 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2307
2308 if (fully_mapped)
2309 SetPageMappedToDisk(page);
2310
2311 if (!nr) {
2312 /*
2313 * All buffers are uptodate - we can set the page uptodate
2314 * as well. But not if get_block() returned an error.
2315 */
2316 if (!PageError(page))
2317 SetPageUptodate(page);
2318 unlock_page(page);
2319 return 0;
2320 }
2321
2322 /* Stage two: lock the buffers */
2323 for (i = 0; i < nr; i++) {
2324 bh = arr[i];
2325 lock_buffer(bh);
2326 mark_buffer_async_read(bh);
2327 }
2328
2329 /*
2330 * Stage 3: start the IO. Check for uptodateness
2331 * inside the buffer lock in case another process reading
2332 * the underlying blockdev brought it uptodate (the sct fix).
2333 */
2334 for (i = 0; i < nr; i++) {
2335 bh = arr[i];
2336 if (buffer_uptodate(bh))
2337 end_buffer_async_read(bh, 1);
2338 else
2339 submit_bh(REQ_OP_READ, 0, bh);
2340 }
2341 return 0;
2342}
2343EXPORT_SYMBOL(block_read_full_page);
2344
2345/* utility function for filesystems that need to do work on expanding
2346 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2347 * deal with the hole.
2348 */
2349int generic_cont_expand_simple(struct inode *inode, loff_t size)
2350{
2351 struct address_space *mapping = inode->i_mapping;
2352 struct page *page;
2353 void *fsdata;
2354 int err;
2355
2356 err = inode_newsize_ok(inode, size);
2357 if (err)
2358 goto out;
2359
2360 err = pagecache_write_begin(NULL, mapping, size, 0,
2361 AOP_FLAG_CONT_EXPAND, &page, &fsdata);
2362 if (err)
2363 goto out;
2364
2365 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2366 BUG_ON(err > 0);
2367
2368out:
2369 return err;
2370}
2371EXPORT_SYMBOL(generic_cont_expand_simple);
2372
2373static int cont_expand_zero(struct file *file, struct address_space *mapping,
2374 loff_t pos, loff_t *bytes)
2375{
2376 struct inode *inode = mapping->host;
2377 unsigned int blocksize = i_blocksize(inode);
2378 struct page *page;
2379 void *fsdata;
2380 pgoff_t index, curidx;
2381 loff_t curpos;
2382 unsigned zerofrom, offset, len;
2383 int err = 0;
2384
2385 index = pos >> PAGE_SHIFT;
2386 offset = pos & ~PAGE_MASK;
2387
2388 while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2389 zerofrom = curpos & ~PAGE_MASK;
2390 if (zerofrom & (blocksize-1)) {
2391 *bytes |= (blocksize-1);
2392 (*bytes)++;
2393 }
2394 len = PAGE_SIZE - zerofrom;
2395
2396 err = pagecache_write_begin(file, mapping, curpos, len, 0,
2397 &page, &fsdata);
2398 if (err)
2399 goto out;
2400 zero_user(page, zerofrom, len);
2401 err = pagecache_write_end(file, mapping, curpos, len, len,
2402 page, fsdata);
2403 if (err < 0)
2404 goto out;
2405 BUG_ON(err != len);
2406 err = 0;
2407
2408 balance_dirty_pages_ratelimited(mapping);
2409
2410 if (fatal_signal_pending(current)) {
2411 err = -EINTR;
2412 goto out;
2413 }
2414 }
2415
2416 /* page covers the boundary, find the boundary offset */
2417 if (index == curidx) {
2418 zerofrom = curpos & ~PAGE_MASK;
2419 /* if we will expand the thing last block will be filled */
2420 if (offset <= zerofrom) {
2421 goto out;
2422 }
2423 if (zerofrom & (blocksize-1)) {
2424 *bytes |= (blocksize-1);
2425 (*bytes)++;
2426 }
2427 len = offset - zerofrom;
2428
2429 err = pagecache_write_begin(file, mapping, curpos, len, 0,
2430 &page, &fsdata);
2431 if (err)
2432 goto out;
2433 zero_user(page, zerofrom, len);
2434 err = pagecache_write_end(file, mapping, curpos, len, len,
2435 page, fsdata);
2436 if (err < 0)
2437 goto out;
2438 BUG_ON(err != len);
2439 err = 0;
2440 }
2441out:
2442 return err;
2443}
2444
2445/*
2446 * For moronic filesystems that do not allow holes in file.
2447 * We may have to extend the file.
2448 */
2449int cont_write_begin(struct file *file, struct address_space *mapping,
2450 loff_t pos, unsigned len, unsigned flags,
2451 struct page **pagep, void **fsdata,
2452 get_block_t *get_block, loff_t *bytes)
2453{
2454 struct inode *inode = mapping->host;
2455 unsigned int blocksize = i_blocksize(inode);
2456 unsigned int zerofrom;
2457 int err;
2458
2459 err = cont_expand_zero(file, mapping, pos, bytes);
2460 if (err)
2461 return err;
2462
2463 zerofrom = *bytes & ~PAGE_MASK;
2464 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2465 *bytes |= (blocksize-1);
2466 (*bytes)++;
2467 }
2468
2469 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2470}
2471EXPORT_SYMBOL(cont_write_begin);
2472
2473int block_commit_write(struct page *page, unsigned from, unsigned to)
2474{
2475 struct inode *inode = page->mapping->host;
2476 __block_commit_write(inode,page,from,to);
2477 return 0;
2478}
2479EXPORT_SYMBOL(block_commit_write);
2480
2481/*
2482 * block_page_mkwrite() is not allowed to change the file size as it gets
2483 * called from a page fault handler when a page is first dirtied. Hence we must
2484 * be careful to check for EOF conditions here. We set the page up correctly
2485 * for a written page which means we get ENOSPC checking when writing into
2486 * holes and correct delalloc and unwritten extent mapping on filesystems that
2487 * support these features.
2488 *
2489 * We are not allowed to take the i_mutex here so we have to play games to
2490 * protect against truncate races as the page could now be beyond EOF. Because
2491 * truncate writes the inode size before removing pages, once we have the
2492 * page lock we can determine safely if the page is beyond EOF. If it is not
2493 * beyond EOF, then the page is guaranteed safe against truncation until we
2494 * unlock the page.
2495 *
2496 * Direct callers of this function should protect against filesystem freezing
2497 * using sb_start_pagefault() - sb_end_pagefault() functions.
2498 */
2499int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2500 get_block_t get_block)
2501{
2502 struct page *page = vmf->page;
2503 struct inode *inode = file_inode(vma->vm_file);
2504 unsigned long end;
2505 loff_t size;
2506 int ret;
2507
2508 lock_page(page);
2509 size = i_size_read(inode);
2510 if ((page->mapping != inode->i_mapping) ||
2511 (page_offset(page) > size)) {
2512 /* We overload EFAULT to mean page got truncated */
2513 ret = -EFAULT;
2514 goto out_unlock;
2515 }
2516
2517 /* page is wholly or partially inside EOF */
2518 if (((page->index + 1) << PAGE_SHIFT) > size)
2519 end = size & ~PAGE_MASK;
2520 else
2521 end = PAGE_SIZE;
2522
2523 ret = __block_write_begin(page, 0, end, get_block);
2524 if (!ret)
2525 ret = block_commit_write(page, 0, end);
2526
2527 if (unlikely(ret < 0))
2528 goto out_unlock;
2529 set_page_dirty(page);
2530 wait_for_stable_page(page);
2531 return 0;
2532out_unlock:
2533 unlock_page(page);
2534 return ret;
2535}
2536EXPORT_SYMBOL(block_page_mkwrite);
2537
2538/*
2539 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2540 * immediately, while under the page lock. So it needs a special end_io
2541 * handler which does not touch the bh after unlocking it.
2542 */
2543static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2544{
2545 __end_buffer_read_notouch(bh, uptodate);
2546}
2547
2548/*
2549 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2550 * the page (converting it to circular linked list and taking care of page
2551 * dirty races).
2552 */
2553static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2554{
2555 struct buffer_head *bh;
2556
2557 BUG_ON(!PageLocked(page));
2558
2559 spin_lock(&page->mapping->private_lock);
2560 bh = head;
2561 do {
2562 if (PageDirty(page))
2563 set_buffer_dirty(bh);
2564 if (!bh->b_this_page)
2565 bh->b_this_page = head;
2566 bh = bh->b_this_page;
2567 } while (bh != head);
2568 attach_page_private(page, head);
2569 spin_unlock(&page->mapping->private_lock);
2570}
2571
2572/*
2573 * On entry, the page is fully not uptodate.
2574 * On exit the page is fully uptodate in the areas outside (from,to)
2575 * The filesystem needs to handle block truncation upon failure.
2576 */
2577int nobh_write_begin(struct address_space *mapping,
2578 loff_t pos, unsigned len, unsigned flags,
2579 struct page **pagep, void **fsdata,
2580 get_block_t *get_block)
2581{
2582 struct inode *inode = mapping->host;
2583 const unsigned blkbits = inode->i_blkbits;
2584 const unsigned blocksize = 1 << blkbits;
2585 struct buffer_head *head, *bh;
2586 struct page *page;
2587 pgoff_t index;
2588 unsigned from, to;
2589 unsigned block_in_page;
2590 unsigned block_start, block_end;
2591 sector_t block_in_file;
2592 int nr_reads = 0;
2593 int ret = 0;
2594 int is_mapped_to_disk = 1;
2595
2596 index = pos >> PAGE_SHIFT;
2597 from = pos & (PAGE_SIZE - 1);
2598 to = from + len;
2599
2600 page = grab_cache_page_write_begin(mapping, index, flags);
2601 if (!page)
2602 return -ENOMEM;
2603 *pagep = page;
2604 *fsdata = NULL;
2605
2606 if (page_has_buffers(page)) {
2607 ret = __block_write_begin(page, pos, len, get_block);
2608 if (unlikely(ret))
2609 goto out_release;
2610 return ret;
2611 }
2612
2613 if (PageMappedToDisk(page))
2614 return 0;
2615
2616 /*
2617 * Allocate buffers so that we can keep track of state, and potentially
2618 * attach them to the page if an error occurs. In the common case of
2619 * no error, they will just be freed again without ever being attached
2620 * to the page (which is all OK, because we're under the page lock).
2621 *
2622 * Be careful: the buffer linked list is a NULL terminated one, rather
2623 * than the circular one we're used to.
2624 */
2625 head = alloc_page_buffers(page, blocksize, false);
2626 if (!head) {
2627 ret = -ENOMEM;
2628 goto out_release;
2629 }
2630
2631 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
2632
2633 /*
2634 * We loop across all blocks in the page, whether or not they are
2635 * part of the affected region. This is so we can discover if the
2636 * page is fully mapped-to-disk.
2637 */
2638 for (block_start = 0, block_in_page = 0, bh = head;
2639 block_start < PAGE_SIZE;
2640 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2641 int create;
2642
2643 block_end = block_start + blocksize;
2644 bh->b_state = 0;
2645 create = 1;
2646 if (block_start >= to)
2647 create = 0;
2648 ret = get_block(inode, block_in_file + block_in_page,
2649 bh, create);
2650 if (ret)
2651 goto failed;
2652 if (!buffer_mapped(bh))
2653 is_mapped_to_disk = 0;
2654 if (buffer_new(bh))
2655 clean_bdev_bh_alias(bh);
2656 if (PageUptodate(page)) {
2657 set_buffer_uptodate(bh);
2658 continue;
2659 }
2660 if (buffer_new(bh) || !buffer_mapped(bh)) {
2661 zero_user_segments(page, block_start, from,
2662 to, block_end);
2663 continue;
2664 }
2665 if (buffer_uptodate(bh))
2666 continue; /* reiserfs does this */
2667 if (block_start < from || block_end > to) {
2668 lock_buffer(bh);
2669 bh->b_end_io = end_buffer_read_nobh;
2670 submit_bh(REQ_OP_READ, 0, bh);
2671 nr_reads++;
2672 }
2673 }
2674
2675 if (nr_reads) {
2676 /*
2677 * The page is locked, so these buffers are protected from
2678 * any VM or truncate activity. Hence we don't need to care
2679 * for the buffer_head refcounts.
2680 */
2681 for (bh = head; bh; bh = bh->b_this_page) {
2682 wait_on_buffer(bh);
2683 if (!buffer_uptodate(bh))
2684 ret = -EIO;
2685 }
2686 if (ret)
2687 goto failed;
2688 }
2689
2690 if (is_mapped_to_disk)
2691 SetPageMappedToDisk(page);
2692
2693 *fsdata = head; /* to be released by nobh_write_end */
2694
2695 return 0;
2696
2697failed:
2698 BUG_ON(!ret);
2699 /*
2700 * Error recovery is a bit difficult. We need to zero out blocks that
2701 * were newly allocated, and dirty them to ensure they get written out.
2702 * Buffers need to be attached to the page at this point, otherwise
2703 * the handling of potential IO errors during writeout would be hard
2704 * (could try doing synchronous writeout, but what if that fails too?)
2705 */
2706 attach_nobh_buffers(page, head);
2707 page_zero_new_buffers(page, from, to);
2708
2709out_release:
2710 unlock_page(page);
2711 put_page(page);
2712 *pagep = NULL;
2713
2714 return ret;
2715}
2716EXPORT_SYMBOL(nobh_write_begin);
2717
2718int nobh_write_end(struct file *file, struct address_space *mapping,
2719 loff_t pos, unsigned len, unsigned copied,
2720 struct page *page, void *fsdata)
2721{
2722 struct inode *inode = page->mapping->host;
2723 struct buffer_head *head = fsdata;
2724 struct buffer_head *bh;
2725 BUG_ON(fsdata != NULL && page_has_buffers(page));
2726
2727 if (unlikely(copied < len) && head)
2728 attach_nobh_buffers(page, head);
2729 if (page_has_buffers(page))
2730 return generic_write_end(file, mapping, pos, len,
2731 copied, page, fsdata);
2732
2733 SetPageUptodate(page);
2734 set_page_dirty(page);
2735 if (pos+copied > inode->i_size) {
2736 i_size_write(inode, pos+copied);
2737 mark_inode_dirty(inode);
2738 }
2739
2740 unlock_page(page);
2741 put_page(page);
2742
2743 while (head) {
2744 bh = head;
2745 head = head->b_this_page;
2746 free_buffer_head(bh);
2747 }
2748
2749 return copied;
2750}
2751EXPORT_SYMBOL(nobh_write_end);
2752
2753/*
2754 * nobh_writepage() - based on block_full_write_page() except
2755 * that it tries to operate without attaching bufferheads to
2756 * the page.
2757 */
2758int nobh_writepage(struct page *page, get_block_t *get_block,
2759 struct writeback_control *wbc)
2760{
2761 struct inode * const inode = page->mapping->host;
2762 loff_t i_size = i_size_read(inode);
2763 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2764 unsigned offset;
2765 int ret;
2766
2767 /* Is the page fully inside i_size? */
2768 if (page->index < end_index)
2769 goto out;
2770
2771 /* Is the page fully outside i_size? (truncate in progress) */
2772 offset = i_size & (PAGE_SIZE-1);
2773 if (page->index >= end_index+1 || !offset) {
2774 /*
2775 * The page may have dirty, unmapped buffers. For example,
2776 * they may have been added in ext3_writepage(). Make them
2777 * freeable here, so the page does not leak.
2778 */
2779#if 0
2780 /* Not really sure about this - do we need this ? */
2781 if (page->mapping->a_ops->invalidatepage)
2782 page->mapping->a_ops->invalidatepage(page, offset);
2783#endif
2784 unlock_page(page);
2785 return 0; /* don't care */
2786 }
2787
2788 /*
2789 * The page straddles i_size. It must be zeroed out on each and every
2790 * writepage invocation because it may be mmapped. "A file is mapped
2791 * in multiples of the page size. For a file that is not a multiple of
2792 * the page size, the remaining memory is zeroed when mapped, and
2793 * writes to that region are not written out to the file."
2794 */
2795 zero_user_segment(page, offset, PAGE_SIZE);
2796out:
2797 ret = mpage_writepage(page, get_block, wbc);
2798 if (ret == -EAGAIN)
2799 ret = __block_write_full_page(inode, page, get_block, wbc,
2800 end_buffer_async_write);
2801 return ret;
2802}
2803EXPORT_SYMBOL(nobh_writepage);
2804
2805int nobh_truncate_page(struct address_space *mapping,
2806 loff_t from, get_block_t *get_block)
2807{
2808 pgoff_t index = from >> PAGE_SHIFT;
2809 unsigned offset = from & (PAGE_SIZE-1);
2810 unsigned blocksize;
2811 sector_t iblock;
2812 unsigned length, pos;
2813 struct inode *inode = mapping->host;
2814 struct page *page;
2815 struct buffer_head map_bh;
2816 int err;
2817
2818 blocksize = i_blocksize(inode);
2819 length = offset & (blocksize - 1);
2820
2821 /* Block boundary? Nothing to do */
2822 if (!length)
2823 return 0;
2824
2825 length = blocksize - length;
2826 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2827
2828 page = grab_cache_page(mapping, index);
2829 err = -ENOMEM;
2830 if (!page)
2831 goto out;
2832
2833 if (page_has_buffers(page)) {
2834has_buffers:
2835 unlock_page(page);
2836 put_page(page);
2837 return block_truncate_page(mapping, from, get_block);
2838 }
2839
2840 /* Find the buffer that contains "offset" */
2841 pos = blocksize;
2842 while (offset >= pos) {
2843 iblock++;
2844 pos += blocksize;
2845 }
2846
2847 map_bh.b_size = blocksize;
2848 map_bh.b_state = 0;
2849 err = get_block(inode, iblock, &map_bh, 0);
2850 if (err)
2851 goto unlock;
2852 /* unmapped? It's a hole - nothing to do */
2853 if (!buffer_mapped(&map_bh))
2854 goto unlock;
2855
2856 /* Ok, it's mapped. Make sure it's up-to-date */
2857 if (!PageUptodate(page)) {
2858 err = mapping->a_ops->readpage(NULL, page);
2859 if (err) {
2860 put_page(page);
2861 goto out;
2862 }
2863 lock_page(page);
2864 if (!PageUptodate(page)) {
2865 err = -EIO;
2866 goto unlock;
2867 }
2868 if (page_has_buffers(page))
2869 goto has_buffers;
2870 }
2871 zero_user(page, offset, length);
2872 set_page_dirty(page);
2873 err = 0;
2874
2875unlock:
2876 unlock_page(page);
2877 put_page(page);
2878out:
2879 return err;
2880}
2881EXPORT_SYMBOL(nobh_truncate_page);
2882
2883int block_truncate_page(struct address_space *mapping,
2884 loff_t from, get_block_t *get_block)
2885{
2886 pgoff_t index = from >> PAGE_SHIFT;
2887 unsigned offset = from & (PAGE_SIZE-1);
2888 unsigned blocksize;
2889 sector_t iblock;
2890 unsigned length, pos;
2891 struct inode *inode = mapping->host;
2892 struct page *page;
2893 struct buffer_head *bh;
2894 int err;
2895
2896 blocksize = i_blocksize(inode);
2897 length = offset & (blocksize - 1);
2898
2899 /* Block boundary? Nothing to do */
2900 if (!length)
2901 return 0;
2902
2903 length = blocksize - length;
2904 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2905
2906 page = grab_cache_page(mapping, index);
2907 err = -ENOMEM;
2908 if (!page)
2909 goto out;
2910
2911 if (!page_has_buffers(page))
2912 create_empty_buffers(page, blocksize, 0);
2913
2914 /* Find the buffer that contains "offset" */
2915 bh = page_buffers(page);
2916 pos = blocksize;
2917 while (offset >= pos) {
2918 bh = bh->b_this_page;
2919 iblock++;
2920 pos += blocksize;
2921 }
2922
2923 err = 0;
2924 if (!buffer_mapped(bh)) {
2925 WARN_ON(bh->b_size != blocksize);
2926 err = get_block(inode, iblock, bh, 0);
2927 if (err)
2928 goto unlock;
2929 /* unmapped? It's a hole - nothing to do */
2930 if (!buffer_mapped(bh))
2931 goto unlock;
2932 }
2933
2934 /* Ok, it's mapped. Make sure it's up-to-date */
2935 if (PageUptodate(page))
2936 set_buffer_uptodate(bh);
2937
2938 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2939 err = -EIO;
2940 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2941 wait_on_buffer(bh);
2942 /* Uhhuh. Read error. Complain and punt. */
2943 if (!buffer_uptodate(bh))
2944 goto unlock;
2945 }
2946
2947 zero_user(page, offset, length);
2948 mark_buffer_dirty(bh);
2949 err = 0;
2950
2951unlock:
2952 unlock_page(page);
2953 put_page(page);
2954out:
2955 return err;
2956}
2957EXPORT_SYMBOL(block_truncate_page);
2958
2959/*
2960 * The generic ->writepage function for buffer-backed address_spaces
2961 */
2962int block_write_full_page(struct page *page, get_block_t *get_block,
2963 struct writeback_control *wbc)
2964{
2965 struct inode * const inode = page->mapping->host;
2966 loff_t i_size = i_size_read(inode);
2967 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2968 unsigned offset;
2969
2970 /* Is the page fully inside i_size? */
2971 if (page->index < end_index)
2972 return __block_write_full_page(inode, page, get_block, wbc,
2973 end_buffer_async_write);
2974
2975 /* Is the page fully outside i_size? (truncate in progress) */
2976 offset = i_size & (PAGE_SIZE-1);
2977 if (page->index >= end_index+1 || !offset) {
2978 /*
2979 * The page may have dirty, unmapped buffers. For example,
2980 * they may have been added in ext3_writepage(). Make them
2981 * freeable here, so the page does not leak.
2982 */
2983 do_invalidatepage(page, 0, PAGE_SIZE);
2984 unlock_page(page);
2985 return 0; /* don't care */
2986 }
2987
2988 /*
2989 * The page straddles i_size. It must be zeroed out on each and every
2990 * writepage invocation because it may be mmapped. "A file is mapped
2991 * in multiples of the page size. For a file that is not a multiple of
2992 * the page size, the remaining memory is zeroed when mapped, and
2993 * writes to that region are not written out to the file."
2994 */
2995 zero_user_segment(page, offset, PAGE_SIZE);
2996 return __block_write_full_page(inode, page, get_block, wbc,
2997 end_buffer_async_write);
2998}
2999EXPORT_SYMBOL(block_write_full_page);
3000
3001sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
3002 get_block_t *get_block)
3003{
3004 struct inode *inode = mapping->host;
3005 struct buffer_head tmp = {
3006 .b_size = i_blocksize(inode),
3007 };
3008
3009 get_block(inode, block, &tmp, 0);
3010 return tmp.b_blocknr;
3011}
3012EXPORT_SYMBOL(generic_block_bmap);
3013
3014static void end_bio_bh_io_sync(struct bio *bio)
3015{
3016 struct buffer_head *bh = bio->bi_private;
3017
3018 if (unlikely(bio_flagged(bio, BIO_QUIET)))
3019 set_bit(BH_Quiet, &bh->b_state);
3020
3021 bh->b_end_io(bh, !bio->bi_status);
3022 bio_put(bio);
3023}
3024
3025static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3026 enum rw_hint write_hint, struct writeback_control *wbc)
3027{
3028 struct bio *bio;
3029
3030 BUG_ON(!buffer_locked(bh));
3031 BUG_ON(!buffer_mapped(bh));
3032 BUG_ON(!bh->b_end_io);
3033 BUG_ON(buffer_delay(bh));
3034 BUG_ON(buffer_unwritten(bh));
3035
3036 /*
3037 * Only clear out a write error when rewriting
3038 */
3039 if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
3040 clear_buffer_write_io_error(bh);
3041
3042 bio = bio_alloc(GFP_NOIO, 1);
3043
3044 fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
3045
3046 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3047 bio_set_dev(bio, bh->b_bdev);
3048 bio->bi_write_hint = write_hint;
3049
3050 bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
3051 BUG_ON(bio->bi_iter.bi_size != bh->b_size);
3052
3053 bio->bi_end_io = end_bio_bh_io_sync;
3054 bio->bi_private = bh;
3055
3056 if (buffer_meta(bh))
3057 op_flags |= REQ_META;
3058 if (buffer_prio(bh))
3059 op_flags |= REQ_PRIO;
3060 bio_set_op_attrs(bio, op, op_flags);
3061
3062 /* Take care of bh's that straddle the end of the device */
3063 guard_bio_eod(bio);
3064
3065 if (wbc) {
3066 wbc_init_bio(wbc, bio);
3067 wbc_account_cgroup_owner(wbc, bh->b_page, bh->b_size);
3068 }
3069
3070 submit_bio(bio);
3071 return 0;
3072}
3073
3074int submit_bh(int op, int op_flags, struct buffer_head *bh)
3075{
3076 return submit_bh_wbc(op, op_flags, bh, 0, NULL);
3077}
3078EXPORT_SYMBOL(submit_bh);
3079
3080/**
3081 * ll_rw_block: low-level access to block devices (DEPRECATED)
3082 * @op: whether to %READ or %WRITE
3083 * @op_flags: req_flag_bits
3084 * @nr: number of &struct buffer_heads in the array
3085 * @bhs: array of pointers to &struct buffer_head
3086 *
3087 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3088 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
3089 * @op_flags contains flags modifying the detailed I/O behavior, most notably
3090 * %REQ_RAHEAD.
3091 *
3092 * This function drops any buffer that it cannot get a lock on (with the
3093 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3094 * request, and any buffer that appears to be up-to-date when doing read
3095 * request. Further it marks as clean buffers that are processed for
3096 * writing (the buffer cache won't assume that they are actually clean
3097 * until the buffer gets unlocked).
3098 *
3099 * ll_rw_block sets b_end_io to simple completion handler that marks
3100 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3101 * any waiters.
3102 *
3103 * All of the buffers must be for the same device, and must also be a
3104 * multiple of the current approved size for the device.
3105 */
3106void ll_rw_block(int op, int op_flags, int nr, struct buffer_head *bhs[])
3107{
3108 int i;
3109
3110 for (i = 0; i < nr; i++) {
3111 struct buffer_head *bh = bhs[i];
3112
3113 if (!trylock_buffer(bh))
3114 continue;
3115 if (op == WRITE) {
3116 if (test_clear_buffer_dirty(bh)) {
3117 bh->b_end_io = end_buffer_write_sync;
3118 get_bh(bh);
3119 submit_bh(op, op_flags, bh);
3120 continue;
3121 }
3122 } else {
3123 if (!buffer_uptodate(bh)) {
3124 bh->b_end_io = end_buffer_read_sync;
3125 get_bh(bh);
3126 submit_bh(op, op_flags, bh);
3127 continue;
3128 }
3129 }
3130 unlock_buffer(bh);
3131 }
3132}
3133EXPORT_SYMBOL(ll_rw_block);
3134
3135void write_dirty_buffer(struct buffer_head *bh, int op_flags)
3136{
3137 lock_buffer(bh);
3138 if (!test_clear_buffer_dirty(bh)) {
3139 unlock_buffer(bh);
3140 return;
3141 }
3142 bh->b_end_io = end_buffer_write_sync;
3143 get_bh(bh);
3144 submit_bh(REQ_OP_WRITE, op_flags, bh);
3145}
3146EXPORT_SYMBOL(write_dirty_buffer);
3147
3148/*
3149 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3150 * and then start new I/O and then wait upon it. The caller must have a ref on
3151 * the buffer_head.
3152 */
3153int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
3154{
3155 int ret = 0;
3156
3157 WARN_ON(atomic_read(&bh->b_count) < 1);
3158 lock_buffer(bh);
3159 if (test_clear_buffer_dirty(bh)) {
3160 /*
3161 * The bh should be mapped, but it might not be if the
3162 * device was hot-removed. Not much we can do but fail the I/O.
3163 */
3164 if (!buffer_mapped(bh)) {
3165 unlock_buffer(bh);
3166 return -EIO;
3167 }
3168
3169 get_bh(bh);
3170 bh->b_end_io = end_buffer_write_sync;
3171 ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
3172 wait_on_buffer(bh);
3173 if (!ret && !buffer_uptodate(bh))
3174 ret = -EIO;
3175 } else {
3176 unlock_buffer(bh);
3177 }
3178 return ret;
3179}
3180EXPORT_SYMBOL(__sync_dirty_buffer);
3181
3182int sync_dirty_buffer(struct buffer_head *bh)
3183{
3184 return __sync_dirty_buffer(bh, REQ_SYNC);
3185}
3186EXPORT_SYMBOL(sync_dirty_buffer);
3187
3188/*
3189 * try_to_free_buffers() checks if all the buffers on this particular page
3190 * are unused, and releases them if so.
3191 *
3192 * Exclusion against try_to_free_buffers may be obtained by either
3193 * locking the page or by holding its mapping's private_lock.
3194 *
3195 * If the page is dirty but all the buffers are clean then we need to
3196 * be sure to mark the page clean as well. This is because the page
3197 * may be against a block device, and a later reattachment of buffers
3198 * to a dirty page will set *all* buffers dirty. Which would corrupt
3199 * filesystem data on the same device.
3200 *
3201 * The same applies to regular filesystem pages: if all the buffers are
3202 * clean then we set the page clean and proceed. To do that, we require
3203 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3204 * private_lock.
3205 *
3206 * try_to_free_buffers() is non-blocking.
3207 */
3208static inline int buffer_busy(struct buffer_head *bh)
3209{
3210 return atomic_read(&bh->b_count) |
3211 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3212}
3213
3214static int
3215drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3216{
3217 struct buffer_head *head = page_buffers(page);
3218 struct buffer_head *bh;
3219
3220 bh = head;
3221 do {
3222 if (buffer_busy(bh))
3223 goto failed;
3224 bh = bh->b_this_page;
3225 } while (bh != head);
3226
3227 do {
3228 struct buffer_head *next = bh->b_this_page;
3229
3230 if (bh->b_assoc_map)
3231 __remove_assoc_queue(bh);
3232 bh = next;
3233 } while (bh != head);
3234 *buffers_to_free = head;
3235 detach_page_private(page);
3236 return 1;
3237failed:
3238 return 0;
3239}
3240
3241int try_to_free_buffers(struct page *page)
3242{
3243 struct address_space * const mapping = page->mapping;
3244 struct buffer_head *buffers_to_free = NULL;
3245 int ret = 0;
3246
3247 BUG_ON(!PageLocked(page));
3248 if (PageWriteback(page))
3249 return 0;
3250
3251 if (mapping == NULL) { /* can this still happen? */
3252 ret = drop_buffers(page, &buffers_to_free);
3253 goto out;
3254 }
3255
3256 spin_lock(&mapping->private_lock);
3257 ret = drop_buffers(page, &buffers_to_free);
3258
3259 /*
3260 * If the filesystem writes its buffers by hand (eg ext3)
3261 * then we can have clean buffers against a dirty page. We
3262 * clean the page here; otherwise the VM will never notice
3263 * that the filesystem did any IO at all.
3264 *
3265 * Also, during truncate, discard_buffer will have marked all
3266 * the page's buffers clean. We discover that here and clean
3267 * the page also.
3268 *
3269 * private_lock must be held over this entire operation in order
3270 * to synchronise against __set_page_dirty_buffers and prevent the
3271 * dirty bit from being lost.
3272 */
3273 if (ret)
3274 cancel_dirty_page(page);
3275 spin_unlock(&mapping->private_lock);
3276out:
3277 if (buffers_to_free) {
3278 struct buffer_head *bh = buffers_to_free;
3279
3280 do {
3281 struct buffer_head *next = bh->b_this_page;
3282 free_buffer_head(bh);
3283 bh = next;
3284 } while (bh != buffers_to_free);
3285 }
3286 return ret;
3287}
3288EXPORT_SYMBOL(try_to_free_buffers);
3289
3290/*
3291 * There are no bdflush tunables left. But distributions are
3292 * still running obsolete flush daemons, so we terminate them here.
3293 *
3294 * Use of bdflush() is deprecated and will be removed in a future kernel.
3295 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3296 */
3297SYSCALL_DEFINE2(bdflush, int, func, long, data)
3298{
3299 static int msg_count;
3300
3301 if (!capable(CAP_SYS_ADMIN))
3302 return -EPERM;
3303
3304 if (msg_count < 5) {
3305 msg_count++;
3306 printk(KERN_INFO
3307 "warning: process `%s' used the obsolete bdflush"
3308 " system call\n", current->comm);
3309 printk(KERN_INFO "Fix your initscripts?\n");
3310 }
3311
3312 if (func == 1)
3313 do_exit(0);
3314 return 0;
3315}
3316
3317/*
3318 * Buffer-head allocation
3319 */
3320static struct kmem_cache *bh_cachep __read_mostly;
3321
3322/*
3323 * Once the number of bh's in the machine exceeds this level, we start
3324 * stripping them in writeback.
3325 */
3326static unsigned long max_buffer_heads;
3327
3328int buffer_heads_over_limit;
3329
3330struct bh_accounting {
3331 int nr; /* Number of live bh's */
3332 int ratelimit; /* Limit cacheline bouncing */
3333};
3334
3335static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3336
3337static void recalc_bh_state(void)
3338{
3339 int i;
3340 int tot = 0;
3341
3342 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3343 return;
3344 __this_cpu_write(bh_accounting.ratelimit, 0);
3345 for_each_online_cpu(i)
3346 tot += per_cpu(bh_accounting, i).nr;
3347 buffer_heads_over_limit = (tot > max_buffer_heads);
3348}
3349
3350struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3351{
3352 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3353 if (ret) {
3354 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3355 spin_lock_init(&ret->b_uptodate_lock);
3356 preempt_disable();
3357 __this_cpu_inc(bh_accounting.nr);
3358 recalc_bh_state();
3359 preempt_enable();
3360 }
3361 return ret;
3362}
3363EXPORT_SYMBOL(alloc_buffer_head);
3364
3365void free_buffer_head(struct buffer_head *bh)
3366{
3367 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3368 kmem_cache_free(bh_cachep, bh);
3369 preempt_disable();
3370 __this_cpu_dec(bh_accounting.nr);
3371 recalc_bh_state();
3372 preempt_enable();
3373}
3374EXPORT_SYMBOL(free_buffer_head);
3375
3376static int buffer_exit_cpu_dead(unsigned int cpu)
3377{
3378 int i;
3379 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3380
3381 for (i = 0; i < BH_LRU_SIZE; i++) {
3382 brelse(b->bhs[i]);
3383 b->bhs[i] = NULL;
3384 }
3385 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3386 per_cpu(bh_accounting, cpu).nr = 0;
3387 return 0;
3388}
3389
3390/**
3391 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3392 * @bh: struct buffer_head
3393 *
3394 * Return true if the buffer is up-to-date and false,
3395 * with the buffer locked, if not.
3396 */
3397int bh_uptodate_or_lock(struct buffer_head *bh)
3398{
3399 if (!buffer_uptodate(bh)) {
3400 lock_buffer(bh);
3401 if (!buffer_uptodate(bh))
3402 return 0;
3403 unlock_buffer(bh);
3404 }
3405 return 1;
3406}
3407EXPORT_SYMBOL(bh_uptodate_or_lock);
3408
3409/**
3410 * bh_submit_read - Submit a locked buffer for reading
3411 * @bh: struct buffer_head
3412 *
3413 * Returns zero on success and -EIO on error.
3414 */
3415int bh_submit_read(struct buffer_head *bh)
3416{
3417 BUG_ON(!buffer_locked(bh));
3418
3419 if (buffer_uptodate(bh)) {
3420 unlock_buffer(bh);
3421 return 0;
3422 }
3423
3424 get_bh(bh);
3425 bh->b_end_io = end_buffer_read_sync;
3426 submit_bh(REQ_OP_READ, 0, bh);
3427 wait_on_buffer(bh);
3428 if (buffer_uptodate(bh))
3429 return 0;
3430 return -EIO;
3431}
3432EXPORT_SYMBOL(bh_submit_read);
3433
3434void __init buffer_init(void)
3435{
3436 unsigned long nrpages;
3437 int ret;
3438
3439 bh_cachep = kmem_cache_create("buffer_head",
3440 sizeof(struct buffer_head), 0,
3441 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3442 SLAB_MEM_SPREAD),
3443 NULL);
3444
3445 /*
3446 * Limit the bh occupancy to 10% of ZONE_NORMAL
3447 */
3448 nrpages = (nr_free_buffer_pages() * 10) / 100;
3449 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3450 ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3451 NULL, buffer_exit_cpu_dead);
3452 WARN_ON(ret < 0);
3453}