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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/*
2 * linux/fs/buffer.c
3 *
4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
5 */
6
7/*
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
9 *
10 * Removed a lot of unnecessary code and simplified things now that
11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
12 *
13 * Speed up hash, lru, and free list operations. Use gfp() for allocating
14 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
15 *
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
17 *
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
19 */
20
21#include <linux/kernel.h>
22#include <linux/syscalls.h>
23#include <linux/fs.h>
24#include <linux/mm.h>
25#include <linux/percpu.h>
26#include <linux/slab.h>
27#include <linux/capability.h>
28#include <linux/blkdev.h>
29#include <linux/file.h>
30#include <linux/quotaops.h>
31#include <linux/highmem.h>
32#include <linux/export.h>
33#include <linux/writeback.h>
34#include <linux/hash.h>
35#include <linux/suspend.h>
36#include <linux/buffer_head.h>
37#include <linux/task_io_accounting_ops.h>
38#include <linux/bio.h>
39#include <linux/notifier.h>
40#include <linux/cpu.h>
41#include <linux/bitops.h>
42#include <linux/mpage.h>
43#include <linux/bit_spinlock.h>
44#include <trace/events/block.h>
45
46static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
47
48#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
49
50void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
51{
52 bh->b_end_io = handler;
53 bh->b_private = private;
54}
55EXPORT_SYMBOL(init_buffer);
56
57inline void touch_buffer(struct buffer_head *bh)
58{
59 trace_block_touch_buffer(bh);
60 mark_page_accessed(bh->b_page);
61}
62EXPORT_SYMBOL(touch_buffer);
63
64static int sleep_on_buffer(void *word)
65{
66 io_schedule();
67 return 0;
68}
69
70void __lock_buffer(struct buffer_head *bh)
71{
72 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
73 TASK_UNINTERRUPTIBLE);
74}
75EXPORT_SYMBOL(__lock_buffer);
76
77void unlock_buffer(struct buffer_head *bh)
78{
79 clear_bit_unlock(BH_Lock, &bh->b_state);
80 smp_mb__after_clear_bit();
81 wake_up_bit(&bh->b_state, BH_Lock);
82}
83EXPORT_SYMBOL(unlock_buffer);
84
85/*
86 * Returns if the page has dirty or writeback buffers. If all the buffers
87 * are unlocked and clean then the PageDirty information is stale. If
88 * any of the pages are locked, it is assumed they are locked for IO.
89 */
90void buffer_check_dirty_writeback(struct page *page,
91 bool *dirty, bool *writeback)
92{
93 struct buffer_head *head, *bh;
94 *dirty = false;
95 *writeback = false;
96
97 BUG_ON(!PageLocked(page));
98
99 if (!page_has_buffers(page))
100 return;
101
102 if (PageWriteback(page))
103 *writeback = true;
104
105 head = page_buffers(page);
106 bh = head;
107 do {
108 if (buffer_locked(bh))
109 *writeback = true;
110
111 if (buffer_dirty(bh))
112 *dirty = true;
113
114 bh = bh->b_this_page;
115 } while (bh != head);
116}
117EXPORT_SYMBOL(buffer_check_dirty_writeback);
118
119/*
120 * Block until a buffer comes unlocked. This doesn't stop it
121 * from becoming locked again - you have to lock it yourself
122 * if you want to preserve its state.
123 */
124void __wait_on_buffer(struct buffer_head * bh)
125{
126 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
127}
128EXPORT_SYMBOL(__wait_on_buffer);
129
130static void
131__clear_page_buffers(struct page *page)
132{
133 ClearPagePrivate(page);
134 set_page_private(page, 0);
135 page_cache_release(page);
136}
137
138
139static int quiet_error(struct buffer_head *bh)
140{
141 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
142 return 0;
143 return 1;
144}
145
146
147static void buffer_io_error(struct buffer_head *bh)
148{
149 char b[BDEVNAME_SIZE];
150 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
151 bdevname(bh->b_bdev, b),
152 (unsigned long long)bh->b_blocknr);
153}
154
155/*
156 * End-of-IO handler helper function which does not touch the bh after
157 * unlocking it.
158 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
159 * a race there is benign: unlock_buffer() only use the bh's address for
160 * hashing after unlocking the buffer, so it doesn't actually touch the bh
161 * itself.
162 */
163static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
164{
165 if (uptodate) {
166 set_buffer_uptodate(bh);
167 } else {
168 /* This happens, due to failed READA attempts. */
169 clear_buffer_uptodate(bh);
170 }
171 unlock_buffer(bh);
172}
173
174/*
175 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
176 * unlock the buffer. This is what ll_rw_block uses too.
177 */
178void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
179{
180 __end_buffer_read_notouch(bh, uptodate);
181 put_bh(bh);
182}
183EXPORT_SYMBOL(end_buffer_read_sync);
184
185void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
186{
187 char b[BDEVNAME_SIZE];
188
189 if (uptodate) {
190 set_buffer_uptodate(bh);
191 } else {
192 if (!quiet_error(bh)) {
193 buffer_io_error(bh);
194 printk(KERN_WARNING "lost page write due to "
195 "I/O error on %s\n",
196 bdevname(bh->b_bdev, b));
197 }
198 set_buffer_write_io_error(bh);
199 clear_buffer_uptodate(bh);
200 }
201 unlock_buffer(bh);
202 put_bh(bh);
203}
204EXPORT_SYMBOL(end_buffer_write_sync);
205
206/*
207 * Various filesystems appear to want __find_get_block to be non-blocking.
208 * But it's the page lock which protects the buffers. To get around this,
209 * we get exclusion from try_to_free_buffers with the blockdev mapping's
210 * private_lock.
211 *
212 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
213 * may be quite high. This code could TryLock the page, and if that
214 * succeeds, there is no need to take private_lock. (But if
215 * private_lock is contended then so is mapping->tree_lock).
216 */
217static struct buffer_head *
218__find_get_block_slow(struct block_device *bdev, sector_t block)
219{
220 struct inode *bd_inode = bdev->bd_inode;
221 struct address_space *bd_mapping = bd_inode->i_mapping;
222 struct buffer_head *ret = NULL;
223 pgoff_t index;
224 struct buffer_head *bh;
225 struct buffer_head *head;
226 struct page *page;
227 int all_mapped = 1;
228
229 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
230 page = find_get_page(bd_mapping, index);
231 if (!page)
232 goto out;
233
234 spin_lock(&bd_mapping->private_lock);
235 if (!page_has_buffers(page))
236 goto out_unlock;
237 head = page_buffers(page);
238 bh = head;
239 do {
240 if (!buffer_mapped(bh))
241 all_mapped = 0;
242 else if (bh->b_blocknr == block) {
243 ret = bh;
244 get_bh(bh);
245 goto out_unlock;
246 }
247 bh = bh->b_this_page;
248 } while (bh != head);
249
250 /* we might be here because some of the buffers on this page are
251 * not mapped. This is due to various races between
252 * file io on the block device and getblk. It gets dealt with
253 * elsewhere, don't buffer_error if we had some unmapped buffers
254 */
255 if (all_mapped) {
256 char b[BDEVNAME_SIZE];
257
258 printk("__find_get_block_slow() failed. "
259 "block=%llu, b_blocknr=%llu\n",
260 (unsigned long long)block,
261 (unsigned long long)bh->b_blocknr);
262 printk("b_state=0x%08lx, b_size=%zu\n",
263 bh->b_state, bh->b_size);
264 printk("device %s blocksize: %d\n", bdevname(bdev, b),
265 1 << bd_inode->i_blkbits);
266 }
267out_unlock:
268 spin_unlock(&bd_mapping->private_lock);
269 page_cache_release(page);
270out:
271 return ret;
272}
273
274/*
275 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
276 */
277static void free_more_memory(void)
278{
279 struct zone *zone;
280 int nid;
281
282 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
283 yield();
284
285 for_each_online_node(nid) {
286 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
287 gfp_zone(GFP_NOFS), NULL,
288 &zone);
289 if (zone)
290 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
291 GFP_NOFS, NULL);
292 }
293}
294
295/*
296 * I/O completion handler for block_read_full_page() - pages
297 * which come unlocked at the end of I/O.
298 */
299static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
300{
301 unsigned long flags;
302 struct buffer_head *first;
303 struct buffer_head *tmp;
304 struct page *page;
305 int page_uptodate = 1;
306
307 BUG_ON(!buffer_async_read(bh));
308
309 page = bh->b_page;
310 if (uptodate) {
311 set_buffer_uptodate(bh);
312 } else {
313 clear_buffer_uptodate(bh);
314 if (!quiet_error(bh))
315 buffer_io_error(bh);
316 SetPageError(page);
317 }
318
319 /*
320 * Be _very_ careful from here on. Bad things can happen if
321 * two buffer heads end IO at almost the same time and both
322 * decide that the page is now completely done.
323 */
324 first = page_buffers(page);
325 local_irq_save(flags);
326 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
327 clear_buffer_async_read(bh);
328 unlock_buffer(bh);
329 tmp = bh;
330 do {
331 if (!buffer_uptodate(tmp))
332 page_uptodate = 0;
333 if (buffer_async_read(tmp)) {
334 BUG_ON(!buffer_locked(tmp));
335 goto still_busy;
336 }
337 tmp = tmp->b_this_page;
338 } while (tmp != bh);
339 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
340 local_irq_restore(flags);
341
342 /*
343 * If none of the buffers had errors and they are all
344 * uptodate then we can set the page uptodate.
345 */
346 if (page_uptodate && !PageError(page))
347 SetPageUptodate(page);
348 unlock_page(page);
349 return;
350
351still_busy:
352 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
353 local_irq_restore(flags);
354 return;
355}
356
357/*
358 * Completion handler for block_write_full_page() - pages which are unlocked
359 * during I/O, and which have PageWriteback cleared upon I/O completion.
360 */
361void end_buffer_async_write(struct buffer_head *bh, int uptodate)
362{
363 char b[BDEVNAME_SIZE];
364 unsigned long flags;
365 struct buffer_head *first;
366 struct buffer_head *tmp;
367 struct page *page;
368
369 BUG_ON(!buffer_async_write(bh));
370
371 page = bh->b_page;
372 if (uptodate) {
373 set_buffer_uptodate(bh);
374 } else {
375 if (!quiet_error(bh)) {
376 buffer_io_error(bh);
377 printk(KERN_WARNING "lost page write due to "
378 "I/O error on %s\n",
379 bdevname(bh->b_bdev, b));
380 }
381 set_bit(AS_EIO, &page->mapping->flags);
382 set_buffer_write_io_error(bh);
383 clear_buffer_uptodate(bh);
384 SetPageError(page);
385 }
386
387 first = page_buffers(page);
388 local_irq_save(flags);
389 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
390
391 clear_buffer_async_write(bh);
392 unlock_buffer(bh);
393 tmp = bh->b_this_page;
394 while (tmp != bh) {
395 if (buffer_async_write(tmp)) {
396 BUG_ON(!buffer_locked(tmp));
397 goto still_busy;
398 }
399 tmp = tmp->b_this_page;
400 }
401 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
402 local_irq_restore(flags);
403 end_page_writeback(page);
404 return;
405
406still_busy:
407 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
408 local_irq_restore(flags);
409 return;
410}
411EXPORT_SYMBOL(end_buffer_async_write);
412
413/*
414 * If a page's buffers are under async readin (end_buffer_async_read
415 * completion) then there is a possibility that another thread of
416 * control could lock one of the buffers after it has completed
417 * but while some of the other buffers have not completed. This
418 * locked buffer would confuse end_buffer_async_read() into not unlocking
419 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
420 * that this buffer is not under async I/O.
421 *
422 * The page comes unlocked when it has no locked buffer_async buffers
423 * left.
424 *
425 * PageLocked prevents anyone starting new async I/O reads any of
426 * the buffers.
427 *
428 * PageWriteback is used to prevent simultaneous writeout of the same
429 * page.
430 *
431 * PageLocked prevents anyone from starting writeback of a page which is
432 * under read I/O (PageWriteback is only ever set against a locked page).
433 */
434static void mark_buffer_async_read(struct buffer_head *bh)
435{
436 bh->b_end_io = end_buffer_async_read;
437 set_buffer_async_read(bh);
438}
439
440static void mark_buffer_async_write_endio(struct buffer_head *bh,
441 bh_end_io_t *handler)
442{
443 bh->b_end_io = handler;
444 set_buffer_async_write(bh);
445}
446
447void mark_buffer_async_write(struct buffer_head *bh)
448{
449 mark_buffer_async_write_endio(bh, end_buffer_async_write);
450}
451EXPORT_SYMBOL(mark_buffer_async_write);
452
453
454/*
455 * fs/buffer.c contains helper functions for buffer-backed address space's
456 * fsync functions. A common requirement for buffer-based filesystems is
457 * that certain data from the backing blockdev needs to be written out for
458 * a successful fsync(). For example, ext2 indirect blocks need to be
459 * written back and waited upon before fsync() returns.
460 *
461 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
462 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
463 * management of a list of dependent buffers at ->i_mapping->private_list.
464 *
465 * Locking is a little subtle: try_to_free_buffers() will remove buffers
466 * from their controlling inode's queue when they are being freed. But
467 * try_to_free_buffers() will be operating against the *blockdev* mapping
468 * at the time, not against the S_ISREG file which depends on those buffers.
469 * So the locking for private_list is via the private_lock in the address_space
470 * which backs the buffers. Which is different from the address_space
471 * against which the buffers are listed. So for a particular address_space,
472 * mapping->private_lock does *not* protect mapping->private_list! In fact,
473 * mapping->private_list will always be protected by the backing blockdev's
474 * ->private_lock.
475 *
476 * Which introduces a requirement: all buffers on an address_space's
477 * ->private_list must be from the same address_space: the blockdev's.
478 *
479 * address_spaces which do not place buffers at ->private_list via these
480 * utility functions are free to use private_lock and private_list for
481 * whatever they want. The only requirement is that list_empty(private_list)
482 * be true at clear_inode() time.
483 *
484 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
485 * filesystems should do that. invalidate_inode_buffers() should just go
486 * BUG_ON(!list_empty).
487 *
488 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
489 * take an address_space, not an inode. And it should be called
490 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
491 * queued up.
492 *
493 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
494 * list if it is already on a list. Because if the buffer is on a list,
495 * it *must* already be on the right one. If not, the filesystem is being
496 * silly. This will save a ton of locking. But first we have to ensure
497 * that buffers are taken *off* the old inode's list when they are freed
498 * (presumably in truncate). That requires careful auditing of all
499 * filesystems (do it inside bforget()). It could also be done by bringing
500 * b_inode back.
501 */
502
503/*
504 * The buffer's backing address_space's private_lock must be held
505 */
506static void __remove_assoc_queue(struct buffer_head *bh)
507{
508 list_del_init(&bh->b_assoc_buffers);
509 WARN_ON(!bh->b_assoc_map);
510 if (buffer_write_io_error(bh))
511 set_bit(AS_EIO, &bh->b_assoc_map->flags);
512 bh->b_assoc_map = NULL;
513}
514
515int inode_has_buffers(struct inode *inode)
516{
517 return !list_empty(&inode->i_data.private_list);
518}
519
520/*
521 * osync is designed to support O_SYNC io. It waits synchronously for
522 * all already-submitted IO to complete, but does not queue any new
523 * writes to the disk.
524 *
525 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
526 * you dirty the buffers, and then use osync_inode_buffers to wait for
527 * completion. Any other dirty buffers which are not yet queued for
528 * write will not be flushed to disk by the osync.
529 */
530static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
531{
532 struct buffer_head *bh;
533 struct list_head *p;
534 int err = 0;
535
536 spin_lock(lock);
537repeat:
538 list_for_each_prev(p, list) {
539 bh = BH_ENTRY(p);
540 if (buffer_locked(bh)) {
541 get_bh(bh);
542 spin_unlock(lock);
543 wait_on_buffer(bh);
544 if (!buffer_uptodate(bh))
545 err = -EIO;
546 brelse(bh);
547 spin_lock(lock);
548 goto repeat;
549 }
550 }
551 spin_unlock(lock);
552 return err;
553}
554
555static void do_thaw_one(struct super_block *sb, void *unused)
556{
557 char b[BDEVNAME_SIZE];
558 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
559 printk(KERN_WARNING "Emergency Thaw on %s\n",
560 bdevname(sb->s_bdev, b));
561}
562
563static void do_thaw_all(struct work_struct *work)
564{
565 iterate_supers(do_thaw_one, NULL);
566 kfree(work);
567 printk(KERN_WARNING "Emergency Thaw complete\n");
568}
569
570/**
571 * emergency_thaw_all -- forcibly thaw every frozen filesystem
572 *
573 * Used for emergency unfreeze of all filesystems via SysRq
574 */
575void emergency_thaw_all(void)
576{
577 struct work_struct *work;
578
579 work = kmalloc(sizeof(*work), GFP_ATOMIC);
580 if (work) {
581 INIT_WORK(work, do_thaw_all);
582 schedule_work(work);
583 }
584}
585
586/**
587 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
588 * @mapping: the mapping which wants those buffers written
589 *
590 * Starts I/O against the buffers at mapping->private_list, and waits upon
591 * that I/O.
592 *
593 * Basically, this is a convenience function for fsync().
594 * @mapping is a file or directory which needs those buffers to be written for
595 * a successful fsync().
596 */
597int sync_mapping_buffers(struct address_space *mapping)
598{
599 struct address_space *buffer_mapping = mapping->private_data;
600
601 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
602 return 0;
603
604 return fsync_buffers_list(&buffer_mapping->private_lock,
605 &mapping->private_list);
606}
607EXPORT_SYMBOL(sync_mapping_buffers);
608
609/*
610 * Called when we've recently written block `bblock', and it is known that
611 * `bblock' was for a buffer_boundary() buffer. This means that the block at
612 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
613 * dirty, schedule it for IO. So that indirects merge nicely with their data.
614 */
615void write_boundary_block(struct block_device *bdev,
616 sector_t bblock, unsigned blocksize)
617{
618 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
619 if (bh) {
620 if (buffer_dirty(bh))
621 ll_rw_block(WRITE, 1, &bh);
622 put_bh(bh);
623 }
624}
625
626void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
627{
628 struct address_space *mapping = inode->i_mapping;
629 struct address_space *buffer_mapping = bh->b_page->mapping;
630
631 mark_buffer_dirty(bh);
632 if (!mapping->private_data) {
633 mapping->private_data = buffer_mapping;
634 } else {
635 BUG_ON(mapping->private_data != buffer_mapping);
636 }
637 if (!bh->b_assoc_map) {
638 spin_lock(&buffer_mapping->private_lock);
639 list_move_tail(&bh->b_assoc_buffers,
640 &mapping->private_list);
641 bh->b_assoc_map = mapping;
642 spin_unlock(&buffer_mapping->private_lock);
643 }
644}
645EXPORT_SYMBOL(mark_buffer_dirty_inode);
646
647/*
648 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
649 * dirty.
650 *
651 * If warn is true, then emit a warning if the page is not uptodate and has
652 * not been truncated.
653 */
654static void __set_page_dirty(struct page *page,
655 struct address_space *mapping, int warn)
656{
657 unsigned long flags;
658
659 spin_lock_irqsave(&mapping->tree_lock, flags);
660 if (page->mapping) { /* Race with truncate? */
661 WARN_ON_ONCE(warn && !PageUptodate(page));
662 account_page_dirtied(page, mapping);
663 radix_tree_tag_set(&mapping->page_tree,
664 page_index(page), PAGECACHE_TAG_DIRTY);
665 }
666 spin_unlock_irqrestore(&mapping->tree_lock, flags);
667 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
668}
669
670/*
671 * Add a page to the dirty page list.
672 *
673 * It is a sad fact of life that this function is called from several places
674 * deeply under spinlocking. It may not sleep.
675 *
676 * If the page has buffers, the uptodate buffers are set dirty, to preserve
677 * dirty-state coherency between the page and the buffers. It the page does
678 * not have buffers then when they are later attached they will all be set
679 * dirty.
680 *
681 * The buffers are dirtied before the page is dirtied. There's a small race
682 * window in which a writepage caller may see the page cleanness but not the
683 * buffer dirtiness. That's fine. If this code were to set the page dirty
684 * before the buffers, a concurrent writepage caller could clear the page dirty
685 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
686 * page on the dirty page list.
687 *
688 * We use private_lock to lock against try_to_free_buffers while using the
689 * page's buffer list. Also use this to protect against clean buffers being
690 * added to the page after it was set dirty.
691 *
692 * FIXME: may need to call ->reservepage here as well. That's rather up to the
693 * address_space though.
694 */
695int __set_page_dirty_buffers(struct page *page)
696{
697 int newly_dirty;
698 struct address_space *mapping = page_mapping(page);
699
700 if (unlikely(!mapping))
701 return !TestSetPageDirty(page);
702
703 spin_lock(&mapping->private_lock);
704 if (page_has_buffers(page)) {
705 struct buffer_head *head = page_buffers(page);
706 struct buffer_head *bh = head;
707
708 do {
709 set_buffer_dirty(bh);
710 bh = bh->b_this_page;
711 } while (bh != head);
712 }
713 newly_dirty = !TestSetPageDirty(page);
714 spin_unlock(&mapping->private_lock);
715
716 if (newly_dirty)
717 __set_page_dirty(page, mapping, 1);
718 return newly_dirty;
719}
720EXPORT_SYMBOL(__set_page_dirty_buffers);
721
722/*
723 * Write out and wait upon a list of buffers.
724 *
725 * We have conflicting pressures: we want to make sure that all
726 * initially dirty buffers get waited on, but that any subsequently
727 * dirtied buffers don't. After all, we don't want fsync to last
728 * forever if somebody is actively writing to the file.
729 *
730 * Do this in two main stages: first we copy dirty buffers to a
731 * temporary inode list, queueing the writes as we go. Then we clean
732 * up, waiting for those writes to complete.
733 *
734 * During this second stage, any subsequent updates to the file may end
735 * up refiling the buffer on the original inode's dirty list again, so
736 * there is a chance we will end up with a buffer queued for write but
737 * not yet completed on that list. So, as a final cleanup we go through
738 * the osync code to catch these locked, dirty buffers without requeuing
739 * any newly dirty buffers for write.
740 */
741static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
742{
743 struct buffer_head *bh;
744 struct list_head tmp;
745 struct address_space *mapping;
746 int err = 0, err2;
747 struct blk_plug plug;
748
749 INIT_LIST_HEAD(&tmp);
750 blk_start_plug(&plug);
751
752 spin_lock(lock);
753 while (!list_empty(list)) {
754 bh = BH_ENTRY(list->next);
755 mapping = bh->b_assoc_map;
756 __remove_assoc_queue(bh);
757 /* Avoid race with mark_buffer_dirty_inode() which does
758 * a lockless check and we rely on seeing the dirty bit */
759 smp_mb();
760 if (buffer_dirty(bh) || buffer_locked(bh)) {
761 list_add(&bh->b_assoc_buffers, &tmp);
762 bh->b_assoc_map = mapping;
763 if (buffer_dirty(bh)) {
764 get_bh(bh);
765 spin_unlock(lock);
766 /*
767 * Ensure any pending I/O completes so that
768 * write_dirty_buffer() actually writes the
769 * current contents - it is a noop if I/O is
770 * still in flight on potentially older
771 * contents.
772 */
773 write_dirty_buffer(bh, WRITE_SYNC);
774
775 /*
776 * Kick off IO for the previous mapping. Note
777 * that we will not run the very last mapping,
778 * wait_on_buffer() will do that for us
779 * through sync_buffer().
780 */
781 brelse(bh);
782 spin_lock(lock);
783 }
784 }
785 }
786
787 spin_unlock(lock);
788 blk_finish_plug(&plug);
789 spin_lock(lock);
790
791 while (!list_empty(&tmp)) {
792 bh = BH_ENTRY(tmp.prev);
793 get_bh(bh);
794 mapping = bh->b_assoc_map;
795 __remove_assoc_queue(bh);
796 /* Avoid race with mark_buffer_dirty_inode() which does
797 * a lockless check and we rely on seeing the dirty bit */
798 smp_mb();
799 if (buffer_dirty(bh)) {
800 list_add(&bh->b_assoc_buffers,
801 &mapping->private_list);
802 bh->b_assoc_map = mapping;
803 }
804 spin_unlock(lock);
805 wait_on_buffer(bh);
806 if (!buffer_uptodate(bh))
807 err = -EIO;
808 brelse(bh);
809 spin_lock(lock);
810 }
811
812 spin_unlock(lock);
813 err2 = osync_buffers_list(lock, list);
814 if (err)
815 return err;
816 else
817 return err2;
818}
819
820/*
821 * Invalidate any and all dirty buffers on a given inode. We are
822 * probably unmounting the fs, but that doesn't mean we have already
823 * done a sync(). Just drop the buffers from the inode list.
824 *
825 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
826 * assumes that all the buffers are against the blockdev. Not true
827 * for reiserfs.
828 */
829void invalidate_inode_buffers(struct inode *inode)
830{
831 if (inode_has_buffers(inode)) {
832 struct address_space *mapping = &inode->i_data;
833 struct list_head *list = &mapping->private_list;
834 struct address_space *buffer_mapping = mapping->private_data;
835
836 spin_lock(&buffer_mapping->private_lock);
837 while (!list_empty(list))
838 __remove_assoc_queue(BH_ENTRY(list->next));
839 spin_unlock(&buffer_mapping->private_lock);
840 }
841}
842EXPORT_SYMBOL(invalidate_inode_buffers);
843
844/*
845 * Remove any clean buffers from the inode's buffer list. This is called
846 * when we're trying to free the inode itself. Those buffers can pin it.
847 *
848 * Returns true if all buffers were removed.
849 */
850int remove_inode_buffers(struct inode *inode)
851{
852 int ret = 1;
853
854 if (inode_has_buffers(inode)) {
855 struct address_space *mapping = &inode->i_data;
856 struct list_head *list = &mapping->private_list;
857 struct address_space *buffer_mapping = mapping->private_data;
858
859 spin_lock(&buffer_mapping->private_lock);
860 while (!list_empty(list)) {
861 struct buffer_head *bh = BH_ENTRY(list->next);
862 if (buffer_dirty(bh)) {
863 ret = 0;
864 break;
865 }
866 __remove_assoc_queue(bh);
867 }
868 spin_unlock(&buffer_mapping->private_lock);
869 }
870 return ret;
871}
872
873/*
874 * Create the appropriate buffers when given a page for data area and
875 * the size of each buffer.. Use the bh->b_this_page linked list to
876 * follow the buffers created. Return NULL if unable to create more
877 * buffers.
878 *
879 * The retry flag is used to differentiate async IO (paging, swapping)
880 * which may not fail from ordinary buffer allocations.
881 */
882struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
883 int retry)
884{
885 struct buffer_head *bh, *head;
886 long offset;
887
888try_again:
889 head = NULL;
890 offset = PAGE_SIZE;
891 while ((offset -= size) >= 0) {
892 bh = alloc_buffer_head(GFP_NOFS);
893 if (!bh)
894 goto no_grow;
895
896 bh->b_this_page = head;
897 bh->b_blocknr = -1;
898 head = bh;
899
900 bh->b_size = size;
901
902 /* Link the buffer to its page */
903 set_bh_page(bh, page, offset);
904 }
905 return head;
906/*
907 * In case anything failed, we just free everything we got.
908 */
909no_grow:
910 if (head) {
911 do {
912 bh = head;
913 head = head->b_this_page;
914 free_buffer_head(bh);
915 } while (head);
916 }
917
918 /*
919 * Return failure for non-async IO requests. Async IO requests
920 * are not allowed to fail, so we have to wait until buffer heads
921 * become available. But we don't want tasks sleeping with
922 * partially complete buffers, so all were released above.
923 */
924 if (!retry)
925 return NULL;
926
927 /* We're _really_ low on memory. Now we just
928 * wait for old buffer heads to become free due to
929 * finishing IO. Since this is an async request and
930 * the reserve list is empty, we're sure there are
931 * async buffer heads in use.
932 */
933 free_more_memory();
934 goto try_again;
935}
936EXPORT_SYMBOL_GPL(alloc_page_buffers);
937
938static inline void
939link_dev_buffers(struct page *page, struct buffer_head *head)
940{
941 struct buffer_head *bh, *tail;
942
943 bh = head;
944 do {
945 tail = bh;
946 bh = bh->b_this_page;
947 } while (bh);
948 tail->b_this_page = head;
949 attach_page_buffers(page, head);
950}
951
952static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
953{
954 sector_t retval = ~((sector_t)0);
955 loff_t sz = i_size_read(bdev->bd_inode);
956
957 if (sz) {
958 unsigned int sizebits = blksize_bits(size);
959 retval = (sz >> sizebits);
960 }
961 return retval;
962}
963
964/*
965 * Initialise the state of a blockdev page's buffers.
966 */
967static sector_t
968init_page_buffers(struct page *page, struct block_device *bdev,
969 sector_t block, int size)
970{
971 struct buffer_head *head = page_buffers(page);
972 struct buffer_head *bh = head;
973 int uptodate = PageUptodate(page);
974 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
975
976 do {
977 if (!buffer_mapped(bh)) {
978 init_buffer(bh, NULL, NULL);
979 bh->b_bdev = bdev;
980 bh->b_blocknr = block;
981 if (uptodate)
982 set_buffer_uptodate(bh);
983 if (block < end_block)
984 set_buffer_mapped(bh);
985 }
986 block++;
987 bh = bh->b_this_page;
988 } while (bh != head);
989
990 /*
991 * Caller needs to validate requested block against end of device.
992 */
993 return end_block;
994}
995
996/*
997 * Create the page-cache page that contains the requested block.
998 *
999 * This is used purely for blockdev mappings.
1000 */
1001static int
1002grow_dev_page(struct block_device *bdev, sector_t block,
1003 pgoff_t index, int size, int sizebits)
1004{
1005 struct inode *inode = bdev->bd_inode;
1006 struct page *page;
1007 struct buffer_head *bh;
1008 sector_t end_block;
1009 int ret = 0; /* Will call free_more_memory() */
1010 gfp_t gfp_mask;
1011
1012 gfp_mask = mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS;
1013 gfp_mask |= __GFP_MOVABLE;
1014 /*
1015 * XXX: __getblk_slow() can not really deal with failure and
1016 * will endlessly loop on improvised global reclaim. Prefer
1017 * looping in the allocator rather than here, at least that
1018 * code knows what it's doing.
1019 */
1020 gfp_mask |= __GFP_NOFAIL;
1021
1022 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
1023 if (!page)
1024 return ret;
1025
1026 BUG_ON(!PageLocked(page));
1027
1028 if (page_has_buffers(page)) {
1029 bh = page_buffers(page);
1030 if (bh->b_size == size) {
1031 end_block = init_page_buffers(page, bdev,
1032 index << sizebits, size);
1033 goto done;
1034 }
1035 if (!try_to_free_buffers(page))
1036 goto failed;
1037 }
1038
1039 /*
1040 * Allocate some buffers for this page
1041 */
1042 bh = alloc_page_buffers(page, size, 0);
1043 if (!bh)
1044 goto failed;
1045
1046 /*
1047 * Link the page to the buffers and initialise them. Take the
1048 * lock to be atomic wrt __find_get_block(), which does not
1049 * run under the page lock.
1050 */
1051 spin_lock(&inode->i_mapping->private_lock);
1052 link_dev_buffers(page, bh);
1053 end_block = init_page_buffers(page, bdev, index << sizebits, size);
1054 spin_unlock(&inode->i_mapping->private_lock);
1055done:
1056 ret = (block < end_block) ? 1 : -ENXIO;
1057failed:
1058 unlock_page(page);
1059 page_cache_release(page);
1060 return ret;
1061}
1062
1063/*
1064 * Create buffers for the specified block device block's page. If
1065 * that page was dirty, the buffers are set dirty also.
1066 */
1067static int
1068grow_buffers(struct block_device *bdev, sector_t block, int size)
1069{
1070 pgoff_t index;
1071 int sizebits;
1072
1073 sizebits = -1;
1074 do {
1075 sizebits++;
1076 } while ((size << sizebits) < PAGE_SIZE);
1077
1078 index = block >> sizebits;
1079
1080 /*
1081 * Check for a block which wants to lie outside our maximum possible
1082 * pagecache index. (this comparison is done using sector_t types).
1083 */
1084 if (unlikely(index != block >> sizebits)) {
1085 char b[BDEVNAME_SIZE];
1086
1087 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1088 "device %s\n",
1089 __func__, (unsigned long long)block,
1090 bdevname(bdev, b));
1091 return -EIO;
1092 }
1093
1094 /* Create a page with the proper size buffers.. */
1095 return grow_dev_page(bdev, block, index, size, sizebits);
1096}
1097
1098static struct buffer_head *
1099__getblk_slow(struct block_device *bdev, sector_t block, int size)
1100{
1101 /* Size must be multiple of hard sectorsize */
1102 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1103 (size < 512 || size > PAGE_SIZE))) {
1104 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1105 size);
1106 printk(KERN_ERR "logical block size: %d\n",
1107 bdev_logical_block_size(bdev));
1108
1109 dump_stack();
1110 return NULL;
1111 }
1112
1113 for (;;) {
1114 struct buffer_head *bh;
1115 int ret;
1116
1117 bh = __find_get_block(bdev, block, size);
1118 if (bh)
1119 return bh;
1120
1121 ret = grow_buffers(bdev, block, size);
1122 if (ret < 0)
1123 return NULL;
1124 if (ret == 0)
1125 free_more_memory();
1126 }
1127}
1128
1129/*
1130 * The relationship between dirty buffers and dirty pages:
1131 *
1132 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1133 * the page is tagged dirty in its radix tree.
1134 *
1135 * At all times, the dirtiness of the buffers represents the dirtiness of
1136 * subsections of the page. If the page has buffers, the page dirty bit is
1137 * merely a hint about the true dirty state.
1138 *
1139 * When a page is set dirty in its entirety, all its buffers are marked dirty
1140 * (if the page has buffers).
1141 *
1142 * When a buffer is marked dirty, its page is dirtied, but the page's other
1143 * buffers are not.
1144 *
1145 * Also. When blockdev buffers are explicitly read with bread(), they
1146 * individually become uptodate. But their backing page remains not
1147 * uptodate - even if all of its buffers are uptodate. A subsequent
1148 * block_read_full_page() against that page will discover all the uptodate
1149 * buffers, will set the page uptodate and will perform no I/O.
1150 */
1151
1152/**
1153 * mark_buffer_dirty - mark a buffer_head as needing writeout
1154 * @bh: the buffer_head to mark dirty
1155 *
1156 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1157 * backing page dirty, then tag the page as dirty in its address_space's radix
1158 * tree and then attach the address_space's inode to its superblock's dirty
1159 * inode list.
1160 *
1161 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1162 * mapping->tree_lock and mapping->host->i_lock.
1163 */
1164void mark_buffer_dirty(struct buffer_head *bh)
1165{
1166 WARN_ON_ONCE(!buffer_uptodate(bh));
1167
1168 trace_block_dirty_buffer(bh);
1169
1170 /*
1171 * Very *carefully* optimize the it-is-already-dirty case.
1172 *
1173 * Don't let the final "is it dirty" escape to before we
1174 * perhaps modified the buffer.
1175 */
1176 if (buffer_dirty(bh)) {
1177 smp_mb();
1178 if (buffer_dirty(bh))
1179 return;
1180 }
1181
1182 if (!test_set_buffer_dirty(bh)) {
1183 struct page *page = bh->b_page;
1184 if (!TestSetPageDirty(page)) {
1185 struct address_space *mapping = page_mapping(page);
1186 if (mapping)
1187 __set_page_dirty(page, mapping, 0);
1188 }
1189 }
1190}
1191EXPORT_SYMBOL(mark_buffer_dirty);
1192
1193/*
1194 * Decrement a buffer_head's reference count. If all buffers against a page
1195 * have zero reference count, are clean and unlocked, and if the page is clean
1196 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1197 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1198 * a page but it ends up not being freed, and buffers may later be reattached).
1199 */
1200void __brelse(struct buffer_head * buf)
1201{
1202 if (atomic_read(&buf->b_count)) {
1203 put_bh(buf);
1204 return;
1205 }
1206 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1207}
1208EXPORT_SYMBOL(__brelse);
1209
1210/*
1211 * bforget() is like brelse(), except it discards any
1212 * potentially dirty data.
1213 */
1214void __bforget(struct buffer_head *bh)
1215{
1216 clear_buffer_dirty(bh);
1217 if (bh->b_assoc_map) {
1218 struct address_space *buffer_mapping = bh->b_page->mapping;
1219
1220 spin_lock(&buffer_mapping->private_lock);
1221 list_del_init(&bh->b_assoc_buffers);
1222 bh->b_assoc_map = NULL;
1223 spin_unlock(&buffer_mapping->private_lock);
1224 }
1225 __brelse(bh);
1226}
1227EXPORT_SYMBOL(__bforget);
1228
1229static struct buffer_head *__bread_slow(struct buffer_head *bh)
1230{
1231 lock_buffer(bh);
1232 if (buffer_uptodate(bh)) {
1233 unlock_buffer(bh);
1234 return bh;
1235 } else {
1236 get_bh(bh);
1237 bh->b_end_io = end_buffer_read_sync;
1238 submit_bh(READ, bh);
1239 wait_on_buffer(bh);
1240 if (buffer_uptodate(bh))
1241 return bh;
1242 }
1243 brelse(bh);
1244 return NULL;
1245}
1246
1247/*
1248 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1249 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1250 * refcount elevated by one when they're in an LRU. A buffer can only appear
1251 * once in a particular CPU's LRU. A single buffer can be present in multiple
1252 * CPU's LRUs at the same time.
1253 *
1254 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1255 * sb_find_get_block().
1256 *
1257 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1258 * a local interrupt disable for that.
1259 */
1260
1261#define BH_LRU_SIZE 8
1262
1263struct bh_lru {
1264 struct buffer_head *bhs[BH_LRU_SIZE];
1265};
1266
1267static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1268
1269#ifdef CONFIG_SMP
1270#define bh_lru_lock() local_irq_disable()
1271#define bh_lru_unlock() local_irq_enable()
1272#else
1273#define bh_lru_lock() preempt_disable()
1274#define bh_lru_unlock() preempt_enable()
1275#endif
1276
1277static inline void check_irqs_on(void)
1278{
1279#ifdef irqs_disabled
1280 BUG_ON(irqs_disabled());
1281#endif
1282}
1283
1284/*
1285 * The LRU management algorithm is dopey-but-simple. Sorry.
1286 */
1287static void bh_lru_install(struct buffer_head *bh)
1288{
1289 struct buffer_head *evictee = NULL;
1290
1291 check_irqs_on();
1292 bh_lru_lock();
1293 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
1294 struct buffer_head *bhs[BH_LRU_SIZE];
1295 int in;
1296 int out = 0;
1297
1298 get_bh(bh);
1299 bhs[out++] = bh;
1300 for (in = 0; in < BH_LRU_SIZE; in++) {
1301 struct buffer_head *bh2 =
1302 __this_cpu_read(bh_lrus.bhs[in]);
1303
1304 if (bh2 == bh) {
1305 __brelse(bh2);
1306 } else {
1307 if (out >= BH_LRU_SIZE) {
1308 BUG_ON(evictee != NULL);
1309 evictee = bh2;
1310 } else {
1311 bhs[out++] = bh2;
1312 }
1313 }
1314 }
1315 while (out < BH_LRU_SIZE)
1316 bhs[out++] = NULL;
1317 memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
1318 }
1319 bh_lru_unlock();
1320
1321 if (evictee)
1322 __brelse(evictee);
1323}
1324
1325/*
1326 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1327 */
1328static struct buffer_head *
1329lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1330{
1331 struct buffer_head *ret = NULL;
1332 unsigned int i;
1333
1334 check_irqs_on();
1335 bh_lru_lock();
1336 for (i = 0; i < BH_LRU_SIZE; i++) {
1337 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1338
1339 if (bh && bh->b_bdev == bdev &&
1340 bh->b_blocknr == block && bh->b_size == size) {
1341 if (i) {
1342 while (i) {
1343 __this_cpu_write(bh_lrus.bhs[i],
1344 __this_cpu_read(bh_lrus.bhs[i - 1]));
1345 i--;
1346 }
1347 __this_cpu_write(bh_lrus.bhs[0], bh);
1348 }
1349 get_bh(bh);
1350 ret = bh;
1351 break;
1352 }
1353 }
1354 bh_lru_unlock();
1355 return ret;
1356}
1357
1358/*
1359 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1360 * it in the LRU and mark it as accessed. If it is not present then return
1361 * NULL
1362 */
1363struct buffer_head *
1364__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1365{
1366 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1367
1368 if (bh == NULL) {
1369 bh = __find_get_block_slow(bdev, block);
1370 if (bh)
1371 bh_lru_install(bh);
1372 }
1373 if (bh)
1374 touch_buffer(bh);
1375 return bh;
1376}
1377EXPORT_SYMBOL(__find_get_block);
1378
1379/*
1380 * __getblk will locate (and, if necessary, create) the buffer_head
1381 * which corresponds to the passed block_device, block and size. The
1382 * returned buffer has its reference count incremented.
1383 *
1384 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1385 * attempt is failing. FIXME, perhaps?
1386 */
1387struct buffer_head *
1388__getblk(struct block_device *bdev, sector_t block, unsigned size)
1389{
1390 struct buffer_head *bh = __find_get_block(bdev, block, size);
1391
1392 might_sleep();
1393 if (bh == NULL)
1394 bh = __getblk_slow(bdev, block, size);
1395 return bh;
1396}
1397EXPORT_SYMBOL(__getblk);
1398
1399/*
1400 * Do async read-ahead on a buffer..
1401 */
1402void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1403{
1404 struct buffer_head *bh = __getblk(bdev, block, size);
1405 if (likely(bh)) {
1406 ll_rw_block(READA, 1, &bh);
1407 brelse(bh);
1408 }
1409}
1410EXPORT_SYMBOL(__breadahead);
1411
1412/**
1413 * __bread() - reads a specified block and returns the bh
1414 * @bdev: the block_device to read from
1415 * @block: number of block
1416 * @size: size (in bytes) to read
1417 *
1418 * Reads a specified block, and returns buffer head that contains it.
1419 * It returns NULL if the block was unreadable.
1420 */
1421struct buffer_head *
1422__bread(struct block_device *bdev, sector_t block, unsigned size)
1423{
1424 struct buffer_head *bh = __getblk(bdev, block, size);
1425
1426 if (likely(bh) && !buffer_uptodate(bh))
1427 bh = __bread_slow(bh);
1428 return bh;
1429}
1430EXPORT_SYMBOL(__bread);
1431
1432/*
1433 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1434 * This doesn't race because it runs in each cpu either in irq
1435 * or with preempt disabled.
1436 */
1437static void invalidate_bh_lru(void *arg)
1438{
1439 struct bh_lru *b = &get_cpu_var(bh_lrus);
1440 int i;
1441
1442 for (i = 0; i < BH_LRU_SIZE; i++) {
1443 brelse(b->bhs[i]);
1444 b->bhs[i] = NULL;
1445 }
1446 put_cpu_var(bh_lrus);
1447}
1448
1449static bool has_bh_in_lru(int cpu, void *dummy)
1450{
1451 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1452 int i;
1453
1454 for (i = 0; i < BH_LRU_SIZE; i++) {
1455 if (b->bhs[i])
1456 return 1;
1457 }
1458
1459 return 0;
1460}
1461
1462void invalidate_bh_lrus(void)
1463{
1464 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1465}
1466EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1467
1468void set_bh_page(struct buffer_head *bh,
1469 struct page *page, unsigned long offset)
1470{
1471 bh->b_page = page;
1472 BUG_ON(offset >= PAGE_SIZE);
1473 if (PageHighMem(page))
1474 /*
1475 * This catches illegal uses and preserves the offset:
1476 */
1477 bh->b_data = (char *)(0 + offset);
1478 else
1479 bh->b_data = page_address(page) + offset;
1480}
1481EXPORT_SYMBOL(set_bh_page);
1482
1483/*
1484 * Called when truncating a buffer on a page completely.
1485 */
1486static void discard_buffer(struct buffer_head * bh)
1487{
1488 lock_buffer(bh);
1489 clear_buffer_dirty(bh);
1490 bh->b_bdev = NULL;
1491 clear_buffer_mapped(bh);
1492 clear_buffer_req(bh);
1493 clear_buffer_new(bh);
1494 clear_buffer_delay(bh);
1495 clear_buffer_unwritten(bh);
1496 unlock_buffer(bh);
1497}
1498
1499/**
1500 * block_invalidatepage - invalidate part or all of a buffer-backed page
1501 *
1502 * @page: the page which is affected
1503 * @offset: start of the range to invalidate
1504 * @length: length of the range to invalidate
1505 *
1506 * block_invalidatepage() is called when all or part of the page has become
1507 * invalidated by a truncate operation.
1508 *
1509 * block_invalidatepage() does not have to release all buffers, but it must
1510 * ensure that no dirty buffer is left outside @offset and that no I/O
1511 * is underway against any of the blocks which are outside the truncation
1512 * point. Because the caller is about to free (and possibly reuse) those
1513 * blocks on-disk.
1514 */
1515void block_invalidatepage(struct page *page, unsigned int offset,
1516 unsigned int length)
1517{
1518 struct buffer_head *head, *bh, *next;
1519 unsigned int curr_off = 0;
1520 unsigned int stop = length + offset;
1521
1522 BUG_ON(!PageLocked(page));
1523 if (!page_has_buffers(page))
1524 goto out;
1525
1526 /*
1527 * Check for overflow
1528 */
1529 BUG_ON(stop > PAGE_CACHE_SIZE || stop < length);
1530
1531 head = page_buffers(page);
1532 bh = head;
1533 do {
1534 unsigned int next_off = curr_off + bh->b_size;
1535 next = bh->b_this_page;
1536
1537 /*
1538 * Are we still fully in range ?
1539 */
1540 if (next_off > stop)
1541 goto out;
1542
1543 /*
1544 * is this block fully invalidated?
1545 */
1546 if (offset <= curr_off)
1547 discard_buffer(bh);
1548 curr_off = next_off;
1549 bh = next;
1550 } while (bh != head);
1551
1552 /*
1553 * We release buffers only if the entire page is being invalidated.
1554 * The get_block cached value has been unconditionally invalidated,
1555 * so real IO is not possible anymore.
1556 */
1557 if (offset == 0)
1558 try_to_release_page(page, 0);
1559out:
1560 return;
1561}
1562EXPORT_SYMBOL(block_invalidatepage);
1563
1564
1565/*
1566 * We attach and possibly dirty the buffers atomically wrt
1567 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1568 * is already excluded via the page lock.
1569 */
1570void create_empty_buffers(struct page *page,
1571 unsigned long blocksize, unsigned long b_state)
1572{
1573 struct buffer_head *bh, *head, *tail;
1574
1575 head = alloc_page_buffers(page, blocksize, 1);
1576 bh = head;
1577 do {
1578 bh->b_state |= b_state;
1579 tail = bh;
1580 bh = bh->b_this_page;
1581 } while (bh);
1582 tail->b_this_page = head;
1583
1584 spin_lock(&page->mapping->private_lock);
1585 if (PageUptodate(page) || PageDirty(page)) {
1586 bh = head;
1587 do {
1588 if (PageDirty(page))
1589 set_buffer_dirty(bh);
1590 if (PageUptodate(page))
1591 set_buffer_uptodate(bh);
1592 bh = bh->b_this_page;
1593 } while (bh != head);
1594 }
1595 attach_page_buffers(page, head);
1596 spin_unlock(&page->mapping->private_lock);
1597}
1598EXPORT_SYMBOL(create_empty_buffers);
1599
1600/*
1601 * We are taking a block for data and we don't want any output from any
1602 * buffer-cache aliases starting from return from that function and
1603 * until the moment when something will explicitly mark the buffer
1604 * dirty (hopefully that will not happen until we will free that block ;-)
1605 * We don't even need to mark it not-uptodate - nobody can expect
1606 * anything from a newly allocated buffer anyway. We used to used
1607 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1608 * don't want to mark the alias unmapped, for example - it would confuse
1609 * anyone who might pick it with bread() afterwards...
1610 *
1611 * Also.. Note that bforget() doesn't lock the buffer. So there can
1612 * be writeout I/O going on against recently-freed buffers. We don't
1613 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1614 * only if we really need to. That happens here.
1615 */
1616void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1617{
1618 struct buffer_head *old_bh;
1619
1620 might_sleep();
1621
1622 old_bh = __find_get_block_slow(bdev, block);
1623 if (old_bh) {
1624 clear_buffer_dirty(old_bh);
1625 wait_on_buffer(old_bh);
1626 clear_buffer_req(old_bh);
1627 __brelse(old_bh);
1628 }
1629}
1630EXPORT_SYMBOL(unmap_underlying_metadata);
1631
1632/*
1633 * Size is a power-of-two in the range 512..PAGE_SIZE,
1634 * and the case we care about most is PAGE_SIZE.
1635 *
1636 * So this *could* possibly be written with those
1637 * constraints in mind (relevant mostly if some
1638 * architecture has a slow bit-scan instruction)
1639 */
1640static inline int block_size_bits(unsigned int blocksize)
1641{
1642 return ilog2(blocksize);
1643}
1644
1645static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1646{
1647 BUG_ON(!PageLocked(page));
1648
1649 if (!page_has_buffers(page))
1650 create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
1651 return page_buffers(page);
1652}
1653
1654/*
1655 * NOTE! All mapped/uptodate combinations are valid:
1656 *
1657 * Mapped Uptodate Meaning
1658 *
1659 * No No "unknown" - must do get_block()
1660 * No Yes "hole" - zero-filled
1661 * Yes No "allocated" - allocated on disk, not read in
1662 * Yes Yes "valid" - allocated and up-to-date in memory.
1663 *
1664 * "Dirty" is valid only with the last case (mapped+uptodate).
1665 */
1666
1667/*
1668 * While block_write_full_page is writing back the dirty buffers under
1669 * the page lock, whoever dirtied the buffers may decide to clean them
1670 * again at any time. We handle that by only looking at the buffer
1671 * state inside lock_buffer().
1672 *
1673 * If block_write_full_page() is called for regular writeback
1674 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1675 * locked buffer. This only can happen if someone has written the buffer
1676 * directly, with submit_bh(). At the address_space level PageWriteback
1677 * prevents this contention from occurring.
1678 *
1679 * If block_write_full_page() is called with wbc->sync_mode ==
1680 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1681 * causes the writes to be flagged as synchronous writes.
1682 */
1683static int __block_write_full_page(struct inode *inode, struct page *page,
1684 get_block_t *get_block, struct writeback_control *wbc,
1685 bh_end_io_t *handler)
1686{
1687 int err;
1688 sector_t block;
1689 sector_t last_block;
1690 struct buffer_head *bh, *head;
1691 unsigned int blocksize, bbits;
1692 int nr_underway = 0;
1693 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
1694 WRITE_SYNC : WRITE);
1695
1696 head = create_page_buffers(page, inode,
1697 (1 << BH_Dirty)|(1 << BH_Uptodate));
1698
1699 /*
1700 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1701 * here, and the (potentially unmapped) buffers may become dirty at
1702 * any time. If a buffer becomes dirty here after we've inspected it
1703 * then we just miss that fact, and the page stays dirty.
1704 *
1705 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1706 * handle that here by just cleaning them.
1707 */
1708
1709 bh = head;
1710 blocksize = bh->b_size;
1711 bbits = block_size_bits(blocksize);
1712
1713 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1714 last_block = (i_size_read(inode) - 1) >> bbits;
1715
1716 /*
1717 * Get all the dirty buffers mapped to disk addresses and
1718 * handle any aliases from the underlying blockdev's mapping.
1719 */
1720 do {
1721 if (block > last_block) {
1722 /*
1723 * mapped buffers outside i_size will occur, because
1724 * this page can be outside i_size when there is a
1725 * truncate in progress.
1726 */
1727 /*
1728 * The buffer was zeroed by block_write_full_page()
1729 */
1730 clear_buffer_dirty(bh);
1731 set_buffer_uptodate(bh);
1732 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1733 buffer_dirty(bh)) {
1734 WARN_ON(bh->b_size != blocksize);
1735 err = get_block(inode, block, bh, 1);
1736 if (err)
1737 goto recover;
1738 clear_buffer_delay(bh);
1739 if (buffer_new(bh)) {
1740 /* blockdev mappings never come here */
1741 clear_buffer_new(bh);
1742 unmap_underlying_metadata(bh->b_bdev,
1743 bh->b_blocknr);
1744 }
1745 }
1746 bh = bh->b_this_page;
1747 block++;
1748 } while (bh != head);
1749
1750 do {
1751 if (!buffer_mapped(bh))
1752 continue;
1753 /*
1754 * If it's a fully non-blocking write attempt and we cannot
1755 * lock the buffer then redirty the page. Note that this can
1756 * potentially cause a busy-wait loop from writeback threads
1757 * and kswapd activity, but those code paths have their own
1758 * higher-level throttling.
1759 */
1760 if (wbc->sync_mode != WB_SYNC_NONE) {
1761 lock_buffer(bh);
1762 } else if (!trylock_buffer(bh)) {
1763 redirty_page_for_writepage(wbc, page);
1764 continue;
1765 }
1766 if (test_clear_buffer_dirty(bh)) {
1767 mark_buffer_async_write_endio(bh, handler);
1768 } else {
1769 unlock_buffer(bh);
1770 }
1771 } while ((bh = bh->b_this_page) != head);
1772
1773 /*
1774 * The page and its buffers are protected by PageWriteback(), so we can
1775 * drop the bh refcounts early.
1776 */
1777 BUG_ON(PageWriteback(page));
1778 set_page_writeback(page);
1779
1780 do {
1781 struct buffer_head *next = bh->b_this_page;
1782 if (buffer_async_write(bh)) {
1783 submit_bh(write_op, bh);
1784 nr_underway++;
1785 }
1786 bh = next;
1787 } while (bh != head);
1788 unlock_page(page);
1789
1790 err = 0;
1791done:
1792 if (nr_underway == 0) {
1793 /*
1794 * The page was marked dirty, but the buffers were
1795 * clean. Someone wrote them back by hand with
1796 * ll_rw_block/submit_bh. A rare case.
1797 */
1798 end_page_writeback(page);
1799
1800 /*
1801 * The page and buffer_heads can be released at any time from
1802 * here on.
1803 */
1804 }
1805 return err;
1806
1807recover:
1808 /*
1809 * ENOSPC, or some other error. We may already have added some
1810 * blocks to the file, so we need to write these out to avoid
1811 * exposing stale data.
1812 * The page is currently locked and not marked for writeback
1813 */
1814 bh = head;
1815 /* Recovery: lock and submit the mapped buffers */
1816 do {
1817 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1818 !buffer_delay(bh)) {
1819 lock_buffer(bh);
1820 mark_buffer_async_write_endio(bh, handler);
1821 } else {
1822 /*
1823 * The buffer may have been set dirty during
1824 * attachment to a dirty page.
1825 */
1826 clear_buffer_dirty(bh);
1827 }
1828 } while ((bh = bh->b_this_page) != head);
1829 SetPageError(page);
1830 BUG_ON(PageWriteback(page));
1831 mapping_set_error(page->mapping, err);
1832 set_page_writeback(page);
1833 do {
1834 struct buffer_head *next = bh->b_this_page;
1835 if (buffer_async_write(bh)) {
1836 clear_buffer_dirty(bh);
1837 submit_bh(write_op, bh);
1838 nr_underway++;
1839 }
1840 bh = next;
1841 } while (bh != head);
1842 unlock_page(page);
1843 goto done;
1844}
1845
1846/*
1847 * If a page has any new buffers, zero them out here, and mark them uptodate
1848 * and dirty so they'll be written out (in order to prevent uninitialised
1849 * block data from leaking). And clear the new bit.
1850 */
1851void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1852{
1853 unsigned int block_start, block_end;
1854 struct buffer_head *head, *bh;
1855
1856 BUG_ON(!PageLocked(page));
1857 if (!page_has_buffers(page))
1858 return;
1859
1860 bh = head = page_buffers(page);
1861 block_start = 0;
1862 do {
1863 block_end = block_start + bh->b_size;
1864
1865 if (buffer_new(bh)) {
1866 if (block_end > from && block_start < to) {
1867 if (!PageUptodate(page)) {
1868 unsigned start, size;
1869
1870 start = max(from, block_start);
1871 size = min(to, block_end) - start;
1872
1873 zero_user(page, start, size);
1874 set_buffer_uptodate(bh);
1875 }
1876
1877 clear_buffer_new(bh);
1878 mark_buffer_dirty(bh);
1879 }
1880 }
1881
1882 block_start = block_end;
1883 bh = bh->b_this_page;
1884 } while (bh != head);
1885}
1886EXPORT_SYMBOL(page_zero_new_buffers);
1887
1888int __block_write_begin(struct page *page, loff_t pos, unsigned len,
1889 get_block_t *get_block)
1890{
1891 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1892 unsigned to = from + len;
1893 struct inode *inode = page->mapping->host;
1894 unsigned block_start, block_end;
1895 sector_t block;
1896 int err = 0;
1897 unsigned blocksize, bbits;
1898 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1899
1900 BUG_ON(!PageLocked(page));
1901 BUG_ON(from > PAGE_CACHE_SIZE);
1902 BUG_ON(to > PAGE_CACHE_SIZE);
1903 BUG_ON(from > to);
1904
1905 head = create_page_buffers(page, inode, 0);
1906 blocksize = head->b_size;
1907 bbits = block_size_bits(blocksize);
1908
1909 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1910
1911 for(bh = head, block_start = 0; bh != head || !block_start;
1912 block++, block_start=block_end, bh = bh->b_this_page) {
1913 block_end = block_start + blocksize;
1914 if (block_end <= from || block_start >= to) {
1915 if (PageUptodate(page)) {
1916 if (!buffer_uptodate(bh))
1917 set_buffer_uptodate(bh);
1918 }
1919 continue;
1920 }
1921 if (buffer_new(bh))
1922 clear_buffer_new(bh);
1923 if (!buffer_mapped(bh)) {
1924 WARN_ON(bh->b_size != blocksize);
1925 err = get_block(inode, block, bh, 1);
1926 if (err)
1927 break;
1928 if (buffer_new(bh)) {
1929 unmap_underlying_metadata(bh->b_bdev,
1930 bh->b_blocknr);
1931 if (PageUptodate(page)) {
1932 clear_buffer_new(bh);
1933 set_buffer_uptodate(bh);
1934 mark_buffer_dirty(bh);
1935 continue;
1936 }
1937 if (block_end > to || block_start < from)
1938 zero_user_segments(page,
1939 to, block_end,
1940 block_start, from);
1941 continue;
1942 }
1943 }
1944 if (PageUptodate(page)) {
1945 if (!buffer_uptodate(bh))
1946 set_buffer_uptodate(bh);
1947 continue;
1948 }
1949 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1950 !buffer_unwritten(bh) &&
1951 (block_start < from || block_end > to)) {
1952 ll_rw_block(READ, 1, &bh);
1953 *wait_bh++=bh;
1954 }
1955 }
1956 /*
1957 * If we issued read requests - let them complete.
1958 */
1959 while(wait_bh > wait) {
1960 wait_on_buffer(*--wait_bh);
1961 if (!buffer_uptodate(*wait_bh))
1962 err = -EIO;
1963 }
1964 if (unlikely(err))
1965 page_zero_new_buffers(page, from, to);
1966 return err;
1967}
1968EXPORT_SYMBOL(__block_write_begin);
1969
1970static int __block_commit_write(struct inode *inode, struct page *page,
1971 unsigned from, unsigned to)
1972{
1973 unsigned block_start, block_end;
1974 int partial = 0;
1975 unsigned blocksize;
1976 struct buffer_head *bh, *head;
1977
1978 bh = head = page_buffers(page);
1979 blocksize = bh->b_size;
1980
1981 block_start = 0;
1982 do {
1983 block_end = block_start + blocksize;
1984 if (block_end <= from || block_start >= to) {
1985 if (!buffer_uptodate(bh))
1986 partial = 1;
1987 } else {
1988 set_buffer_uptodate(bh);
1989 mark_buffer_dirty(bh);
1990 }
1991 clear_buffer_new(bh);
1992
1993 block_start = block_end;
1994 bh = bh->b_this_page;
1995 } while (bh != head);
1996
1997 /*
1998 * If this is a partial write which happened to make all buffers
1999 * uptodate then we can optimize away a bogus readpage() for
2000 * the next read(). Here we 'discover' whether the page went
2001 * uptodate as a result of this (potentially partial) write.
2002 */
2003 if (!partial)
2004 SetPageUptodate(page);
2005 return 0;
2006}
2007
2008/*
2009 * block_write_begin takes care of the basic task of block allocation and
2010 * bringing partial write blocks uptodate first.
2011 *
2012 * The filesystem needs to handle block truncation upon failure.
2013 */
2014int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2015 unsigned flags, struct page **pagep, get_block_t *get_block)
2016{
2017 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
2018 struct page *page;
2019 int status;
2020
2021 page = grab_cache_page_write_begin(mapping, index, flags);
2022 if (!page)
2023 return -ENOMEM;
2024
2025 status = __block_write_begin(page, pos, len, get_block);
2026 if (unlikely(status)) {
2027 unlock_page(page);
2028 page_cache_release(page);
2029 page = NULL;
2030 }
2031
2032 *pagep = page;
2033 return status;
2034}
2035EXPORT_SYMBOL(block_write_begin);
2036
2037int block_write_end(struct file *file, struct address_space *mapping,
2038 loff_t pos, unsigned len, unsigned copied,
2039 struct page *page, void *fsdata)
2040{
2041 struct inode *inode = mapping->host;
2042 unsigned start;
2043
2044 start = pos & (PAGE_CACHE_SIZE - 1);
2045
2046 if (unlikely(copied < len)) {
2047 /*
2048 * The buffers that were written will now be uptodate, so we
2049 * don't have to worry about a readpage reading them and
2050 * overwriting a partial write. However if we have encountered
2051 * a short write and only partially written into a buffer, it
2052 * will not be marked uptodate, so a readpage might come in and
2053 * destroy our partial write.
2054 *
2055 * Do the simplest thing, and just treat any short write to a
2056 * non uptodate page as a zero-length write, and force the
2057 * caller to redo the whole thing.
2058 */
2059 if (!PageUptodate(page))
2060 copied = 0;
2061
2062 page_zero_new_buffers(page, start+copied, start+len);
2063 }
2064 flush_dcache_page(page);
2065
2066 /* This could be a short (even 0-length) commit */
2067 __block_commit_write(inode, page, start, start+copied);
2068
2069 return copied;
2070}
2071EXPORT_SYMBOL(block_write_end);
2072
2073int generic_write_end(struct file *file, struct address_space *mapping,
2074 loff_t pos, unsigned len, unsigned copied,
2075 struct page *page, void *fsdata)
2076{
2077 struct inode *inode = mapping->host;
2078 int i_size_changed = 0;
2079
2080 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2081
2082 /*
2083 * No need to use i_size_read() here, the i_size
2084 * cannot change under us because we hold i_mutex.
2085 *
2086 * But it's important to update i_size while still holding page lock:
2087 * page writeout could otherwise come in and zero beyond i_size.
2088 */
2089 if (pos+copied > inode->i_size) {
2090 i_size_write(inode, pos+copied);
2091 i_size_changed = 1;
2092 }
2093
2094 unlock_page(page);
2095 page_cache_release(page);
2096
2097 /*
2098 * Don't mark the inode dirty under page lock. First, it unnecessarily
2099 * makes the holding time of page lock longer. Second, it forces lock
2100 * ordering of page lock and transaction start for journaling
2101 * filesystems.
2102 */
2103 if (i_size_changed)
2104 mark_inode_dirty(inode);
2105
2106 return copied;
2107}
2108EXPORT_SYMBOL(generic_write_end);
2109
2110/*
2111 * block_is_partially_uptodate checks whether buffers within a page are
2112 * uptodate or not.
2113 *
2114 * Returns true if all buffers which correspond to a file portion
2115 * we want to read are uptodate.
2116 */
2117int block_is_partially_uptodate(struct page *page, unsigned long from,
2118 unsigned long count)
2119{
2120 unsigned block_start, block_end, blocksize;
2121 unsigned to;
2122 struct buffer_head *bh, *head;
2123 int ret = 1;
2124
2125 if (!page_has_buffers(page))
2126 return 0;
2127
2128 head = page_buffers(page);
2129 blocksize = head->b_size;
2130 to = min_t(unsigned, PAGE_CACHE_SIZE - from, count);
2131 to = from + to;
2132 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2133 return 0;
2134
2135 bh = head;
2136 block_start = 0;
2137 do {
2138 block_end = block_start + blocksize;
2139 if (block_end > from && block_start < to) {
2140 if (!buffer_uptodate(bh)) {
2141 ret = 0;
2142 break;
2143 }
2144 if (block_end >= to)
2145 break;
2146 }
2147 block_start = block_end;
2148 bh = bh->b_this_page;
2149 } while (bh != head);
2150
2151 return ret;
2152}
2153EXPORT_SYMBOL(block_is_partially_uptodate);
2154
2155/*
2156 * Generic "read page" function for block devices that have the normal
2157 * get_block functionality. This is most of the block device filesystems.
2158 * Reads the page asynchronously --- the unlock_buffer() and
2159 * set/clear_buffer_uptodate() functions propagate buffer state into the
2160 * page struct once IO has completed.
2161 */
2162int block_read_full_page(struct page *page, get_block_t *get_block)
2163{
2164 struct inode *inode = page->mapping->host;
2165 sector_t iblock, lblock;
2166 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2167 unsigned int blocksize, bbits;
2168 int nr, i;
2169 int fully_mapped = 1;
2170
2171 head = create_page_buffers(page, inode, 0);
2172 blocksize = head->b_size;
2173 bbits = block_size_bits(blocksize);
2174
2175 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
2176 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2177 bh = head;
2178 nr = 0;
2179 i = 0;
2180
2181 do {
2182 if (buffer_uptodate(bh))
2183 continue;
2184
2185 if (!buffer_mapped(bh)) {
2186 int err = 0;
2187
2188 fully_mapped = 0;
2189 if (iblock < lblock) {
2190 WARN_ON(bh->b_size != blocksize);
2191 err = get_block(inode, iblock, bh, 0);
2192 if (err)
2193 SetPageError(page);
2194 }
2195 if (!buffer_mapped(bh)) {
2196 zero_user(page, i * blocksize, blocksize);
2197 if (!err)
2198 set_buffer_uptodate(bh);
2199 continue;
2200 }
2201 /*
2202 * get_block() might have updated the buffer
2203 * synchronously
2204 */
2205 if (buffer_uptodate(bh))
2206 continue;
2207 }
2208 arr[nr++] = bh;
2209 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2210
2211 if (fully_mapped)
2212 SetPageMappedToDisk(page);
2213
2214 if (!nr) {
2215 /*
2216 * All buffers are uptodate - we can set the page uptodate
2217 * as well. But not if get_block() returned an error.
2218 */
2219 if (!PageError(page))
2220 SetPageUptodate(page);
2221 unlock_page(page);
2222 return 0;
2223 }
2224
2225 /* Stage two: lock the buffers */
2226 for (i = 0; i < nr; i++) {
2227 bh = arr[i];
2228 lock_buffer(bh);
2229 mark_buffer_async_read(bh);
2230 }
2231
2232 /*
2233 * Stage 3: start the IO. Check for uptodateness
2234 * inside the buffer lock in case another process reading
2235 * the underlying blockdev brought it uptodate (the sct fix).
2236 */
2237 for (i = 0; i < nr; i++) {
2238 bh = arr[i];
2239 if (buffer_uptodate(bh))
2240 end_buffer_async_read(bh, 1);
2241 else
2242 submit_bh(READ, bh);
2243 }
2244 return 0;
2245}
2246EXPORT_SYMBOL(block_read_full_page);
2247
2248/* utility function for filesystems that need to do work on expanding
2249 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2250 * deal with the hole.
2251 */
2252int generic_cont_expand_simple(struct inode *inode, loff_t size)
2253{
2254 struct address_space *mapping = inode->i_mapping;
2255 struct page *page;
2256 void *fsdata;
2257 int err;
2258
2259 err = inode_newsize_ok(inode, size);
2260 if (err)
2261 goto out;
2262
2263 err = pagecache_write_begin(NULL, mapping, size, 0,
2264 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2265 &page, &fsdata);
2266 if (err)
2267 goto out;
2268
2269 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2270 BUG_ON(err > 0);
2271
2272out:
2273 return err;
2274}
2275EXPORT_SYMBOL(generic_cont_expand_simple);
2276
2277static int cont_expand_zero(struct file *file, struct address_space *mapping,
2278 loff_t pos, loff_t *bytes)
2279{
2280 struct inode *inode = mapping->host;
2281 unsigned blocksize = 1 << inode->i_blkbits;
2282 struct page *page;
2283 void *fsdata;
2284 pgoff_t index, curidx;
2285 loff_t curpos;
2286 unsigned zerofrom, offset, len;
2287 int err = 0;
2288
2289 index = pos >> PAGE_CACHE_SHIFT;
2290 offset = pos & ~PAGE_CACHE_MASK;
2291
2292 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2293 zerofrom = curpos & ~PAGE_CACHE_MASK;
2294 if (zerofrom & (blocksize-1)) {
2295 *bytes |= (blocksize-1);
2296 (*bytes)++;
2297 }
2298 len = PAGE_CACHE_SIZE - zerofrom;
2299
2300 err = pagecache_write_begin(file, mapping, curpos, len,
2301 AOP_FLAG_UNINTERRUPTIBLE,
2302 &page, &fsdata);
2303 if (err)
2304 goto out;
2305 zero_user(page, zerofrom, len);
2306 err = pagecache_write_end(file, mapping, curpos, len, len,
2307 page, fsdata);
2308 if (err < 0)
2309 goto out;
2310 BUG_ON(err != len);
2311 err = 0;
2312
2313 balance_dirty_pages_ratelimited(mapping);
2314 }
2315
2316 /* page covers the boundary, find the boundary offset */
2317 if (index == curidx) {
2318 zerofrom = curpos & ~PAGE_CACHE_MASK;
2319 /* if we will expand the thing last block will be filled */
2320 if (offset <= zerofrom) {
2321 goto out;
2322 }
2323 if (zerofrom & (blocksize-1)) {
2324 *bytes |= (blocksize-1);
2325 (*bytes)++;
2326 }
2327 len = offset - zerofrom;
2328
2329 err = pagecache_write_begin(file, mapping, curpos, len,
2330 AOP_FLAG_UNINTERRUPTIBLE,
2331 &page, &fsdata);
2332 if (err)
2333 goto out;
2334 zero_user(page, zerofrom, len);
2335 err = pagecache_write_end(file, mapping, curpos, len, len,
2336 page, fsdata);
2337 if (err < 0)
2338 goto out;
2339 BUG_ON(err != len);
2340 err = 0;
2341 }
2342out:
2343 return err;
2344}
2345
2346/*
2347 * For moronic filesystems that do not allow holes in file.
2348 * We may have to extend the file.
2349 */
2350int cont_write_begin(struct file *file, struct address_space *mapping,
2351 loff_t pos, unsigned len, unsigned flags,
2352 struct page **pagep, void **fsdata,
2353 get_block_t *get_block, loff_t *bytes)
2354{
2355 struct inode *inode = mapping->host;
2356 unsigned blocksize = 1 << inode->i_blkbits;
2357 unsigned zerofrom;
2358 int err;
2359
2360 err = cont_expand_zero(file, mapping, pos, bytes);
2361 if (err)
2362 return err;
2363
2364 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2365 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2366 *bytes |= (blocksize-1);
2367 (*bytes)++;
2368 }
2369
2370 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2371}
2372EXPORT_SYMBOL(cont_write_begin);
2373
2374int block_commit_write(struct page *page, unsigned from, unsigned to)
2375{
2376 struct inode *inode = page->mapping->host;
2377 __block_commit_write(inode,page,from,to);
2378 return 0;
2379}
2380EXPORT_SYMBOL(block_commit_write);
2381
2382/*
2383 * block_page_mkwrite() is not allowed to change the file size as it gets
2384 * called from a page fault handler when a page is first dirtied. Hence we must
2385 * be careful to check for EOF conditions here. We set the page up correctly
2386 * for a written page which means we get ENOSPC checking when writing into
2387 * holes and correct delalloc and unwritten extent mapping on filesystems that
2388 * support these features.
2389 *
2390 * We are not allowed to take the i_mutex here so we have to play games to
2391 * protect against truncate races as the page could now be beyond EOF. Because
2392 * truncate writes the inode size before removing pages, once we have the
2393 * page lock we can determine safely if the page is beyond EOF. If it is not
2394 * beyond EOF, then the page is guaranteed safe against truncation until we
2395 * unlock the page.
2396 *
2397 * Direct callers of this function should protect against filesystem freezing
2398 * using sb_start_write() - sb_end_write() functions.
2399 */
2400int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2401 get_block_t get_block)
2402{
2403 struct page *page = vmf->page;
2404 struct inode *inode = file_inode(vma->vm_file);
2405 unsigned long end;
2406 loff_t size;
2407 int ret;
2408
2409 lock_page(page);
2410 size = i_size_read(inode);
2411 if ((page->mapping != inode->i_mapping) ||
2412 (page_offset(page) > size)) {
2413 /* We overload EFAULT to mean page got truncated */
2414 ret = -EFAULT;
2415 goto out_unlock;
2416 }
2417
2418 /* page is wholly or partially inside EOF */
2419 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2420 end = size & ~PAGE_CACHE_MASK;
2421 else
2422 end = PAGE_CACHE_SIZE;
2423
2424 ret = __block_write_begin(page, 0, end, get_block);
2425 if (!ret)
2426 ret = block_commit_write(page, 0, end);
2427
2428 if (unlikely(ret < 0))
2429 goto out_unlock;
2430 set_page_dirty(page);
2431 wait_for_stable_page(page);
2432 return 0;
2433out_unlock:
2434 unlock_page(page);
2435 return ret;
2436}
2437EXPORT_SYMBOL(__block_page_mkwrite);
2438
2439int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2440 get_block_t get_block)
2441{
2442 int ret;
2443 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
2444
2445 sb_start_pagefault(sb);
2446
2447 /*
2448 * Update file times before taking page lock. We may end up failing the
2449 * fault so this update may be superfluous but who really cares...
2450 */
2451 file_update_time(vma->vm_file);
2452
2453 ret = __block_page_mkwrite(vma, vmf, get_block);
2454 sb_end_pagefault(sb);
2455 return block_page_mkwrite_return(ret);
2456}
2457EXPORT_SYMBOL(block_page_mkwrite);
2458
2459/*
2460 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2461 * immediately, while under the page lock. So it needs a special end_io
2462 * handler which does not touch the bh after unlocking it.
2463 */
2464static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2465{
2466 __end_buffer_read_notouch(bh, uptodate);
2467}
2468
2469/*
2470 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2471 * the page (converting it to circular linked list and taking care of page
2472 * dirty races).
2473 */
2474static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2475{
2476 struct buffer_head *bh;
2477
2478 BUG_ON(!PageLocked(page));
2479
2480 spin_lock(&page->mapping->private_lock);
2481 bh = head;
2482 do {
2483 if (PageDirty(page))
2484 set_buffer_dirty(bh);
2485 if (!bh->b_this_page)
2486 bh->b_this_page = head;
2487 bh = bh->b_this_page;
2488 } while (bh != head);
2489 attach_page_buffers(page, head);
2490 spin_unlock(&page->mapping->private_lock);
2491}
2492
2493/*
2494 * On entry, the page is fully not uptodate.
2495 * On exit the page is fully uptodate in the areas outside (from,to)
2496 * The filesystem needs to handle block truncation upon failure.
2497 */
2498int nobh_write_begin(struct address_space *mapping,
2499 loff_t pos, unsigned len, unsigned flags,
2500 struct page **pagep, void **fsdata,
2501 get_block_t *get_block)
2502{
2503 struct inode *inode = mapping->host;
2504 const unsigned blkbits = inode->i_blkbits;
2505 const unsigned blocksize = 1 << blkbits;
2506 struct buffer_head *head, *bh;
2507 struct page *page;
2508 pgoff_t index;
2509 unsigned from, to;
2510 unsigned block_in_page;
2511 unsigned block_start, block_end;
2512 sector_t block_in_file;
2513 int nr_reads = 0;
2514 int ret = 0;
2515 int is_mapped_to_disk = 1;
2516
2517 index = pos >> PAGE_CACHE_SHIFT;
2518 from = pos & (PAGE_CACHE_SIZE - 1);
2519 to = from + len;
2520
2521 page = grab_cache_page_write_begin(mapping, index, flags);
2522 if (!page)
2523 return -ENOMEM;
2524 *pagep = page;
2525 *fsdata = NULL;
2526
2527 if (page_has_buffers(page)) {
2528 ret = __block_write_begin(page, pos, len, get_block);
2529 if (unlikely(ret))
2530 goto out_release;
2531 return ret;
2532 }
2533
2534 if (PageMappedToDisk(page))
2535 return 0;
2536
2537 /*
2538 * Allocate buffers so that we can keep track of state, and potentially
2539 * attach them to the page if an error occurs. In the common case of
2540 * no error, they will just be freed again without ever being attached
2541 * to the page (which is all OK, because we're under the page lock).
2542 *
2543 * Be careful: the buffer linked list is a NULL terminated one, rather
2544 * than the circular one we're used to.
2545 */
2546 head = alloc_page_buffers(page, blocksize, 0);
2547 if (!head) {
2548 ret = -ENOMEM;
2549 goto out_release;
2550 }
2551
2552 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2553
2554 /*
2555 * We loop across all blocks in the page, whether or not they are
2556 * part of the affected region. This is so we can discover if the
2557 * page is fully mapped-to-disk.
2558 */
2559 for (block_start = 0, block_in_page = 0, bh = head;
2560 block_start < PAGE_CACHE_SIZE;
2561 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2562 int create;
2563
2564 block_end = block_start + blocksize;
2565 bh->b_state = 0;
2566 create = 1;
2567 if (block_start >= to)
2568 create = 0;
2569 ret = get_block(inode, block_in_file + block_in_page,
2570 bh, create);
2571 if (ret)
2572 goto failed;
2573 if (!buffer_mapped(bh))
2574 is_mapped_to_disk = 0;
2575 if (buffer_new(bh))
2576 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2577 if (PageUptodate(page)) {
2578 set_buffer_uptodate(bh);
2579 continue;
2580 }
2581 if (buffer_new(bh) || !buffer_mapped(bh)) {
2582 zero_user_segments(page, block_start, from,
2583 to, block_end);
2584 continue;
2585 }
2586 if (buffer_uptodate(bh))
2587 continue; /* reiserfs does this */
2588 if (block_start < from || block_end > to) {
2589 lock_buffer(bh);
2590 bh->b_end_io = end_buffer_read_nobh;
2591 submit_bh(READ, bh);
2592 nr_reads++;
2593 }
2594 }
2595
2596 if (nr_reads) {
2597 /*
2598 * The page is locked, so these buffers are protected from
2599 * any VM or truncate activity. Hence we don't need to care
2600 * for the buffer_head refcounts.
2601 */
2602 for (bh = head; bh; bh = bh->b_this_page) {
2603 wait_on_buffer(bh);
2604 if (!buffer_uptodate(bh))
2605 ret = -EIO;
2606 }
2607 if (ret)
2608 goto failed;
2609 }
2610
2611 if (is_mapped_to_disk)
2612 SetPageMappedToDisk(page);
2613
2614 *fsdata = head; /* to be released by nobh_write_end */
2615
2616 return 0;
2617
2618failed:
2619 BUG_ON(!ret);
2620 /*
2621 * Error recovery is a bit difficult. We need to zero out blocks that
2622 * were newly allocated, and dirty them to ensure they get written out.
2623 * Buffers need to be attached to the page at this point, otherwise
2624 * the handling of potential IO errors during writeout would be hard
2625 * (could try doing synchronous writeout, but what if that fails too?)
2626 */
2627 attach_nobh_buffers(page, head);
2628 page_zero_new_buffers(page, from, to);
2629
2630out_release:
2631 unlock_page(page);
2632 page_cache_release(page);
2633 *pagep = NULL;
2634
2635 return ret;
2636}
2637EXPORT_SYMBOL(nobh_write_begin);
2638
2639int nobh_write_end(struct file *file, struct address_space *mapping,
2640 loff_t pos, unsigned len, unsigned copied,
2641 struct page *page, void *fsdata)
2642{
2643 struct inode *inode = page->mapping->host;
2644 struct buffer_head *head = fsdata;
2645 struct buffer_head *bh;
2646 BUG_ON(fsdata != NULL && page_has_buffers(page));
2647
2648 if (unlikely(copied < len) && head)
2649 attach_nobh_buffers(page, head);
2650 if (page_has_buffers(page))
2651 return generic_write_end(file, mapping, pos, len,
2652 copied, page, fsdata);
2653
2654 SetPageUptodate(page);
2655 set_page_dirty(page);
2656 if (pos+copied > inode->i_size) {
2657 i_size_write(inode, pos+copied);
2658 mark_inode_dirty(inode);
2659 }
2660
2661 unlock_page(page);
2662 page_cache_release(page);
2663
2664 while (head) {
2665 bh = head;
2666 head = head->b_this_page;
2667 free_buffer_head(bh);
2668 }
2669
2670 return copied;
2671}
2672EXPORT_SYMBOL(nobh_write_end);
2673
2674/*
2675 * nobh_writepage() - based on block_full_write_page() except
2676 * that it tries to operate without attaching bufferheads to
2677 * the page.
2678 */
2679int nobh_writepage(struct page *page, get_block_t *get_block,
2680 struct writeback_control *wbc)
2681{
2682 struct inode * const inode = page->mapping->host;
2683 loff_t i_size = i_size_read(inode);
2684 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2685 unsigned offset;
2686 int ret;
2687
2688 /* Is the page fully inside i_size? */
2689 if (page->index < end_index)
2690 goto out;
2691
2692 /* Is the page fully outside i_size? (truncate in progress) */
2693 offset = i_size & (PAGE_CACHE_SIZE-1);
2694 if (page->index >= end_index+1 || !offset) {
2695 /*
2696 * The page may have dirty, unmapped buffers. For example,
2697 * they may have been added in ext3_writepage(). Make them
2698 * freeable here, so the page does not leak.
2699 */
2700#if 0
2701 /* Not really sure about this - do we need this ? */
2702 if (page->mapping->a_ops->invalidatepage)
2703 page->mapping->a_ops->invalidatepage(page, offset);
2704#endif
2705 unlock_page(page);
2706 return 0; /* don't care */
2707 }
2708
2709 /*
2710 * The page straddles i_size. It must be zeroed out on each and every
2711 * writepage invocation because it may be mmapped. "A file is mapped
2712 * in multiples of the page size. For a file that is not a multiple of
2713 * the page size, the remaining memory is zeroed when mapped, and
2714 * writes to that region are not written out to the file."
2715 */
2716 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2717out:
2718 ret = mpage_writepage(page, get_block, wbc);
2719 if (ret == -EAGAIN)
2720 ret = __block_write_full_page(inode, page, get_block, wbc,
2721 end_buffer_async_write);
2722 return ret;
2723}
2724EXPORT_SYMBOL(nobh_writepage);
2725
2726int nobh_truncate_page(struct address_space *mapping,
2727 loff_t from, get_block_t *get_block)
2728{
2729 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2730 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2731 unsigned blocksize;
2732 sector_t iblock;
2733 unsigned length, pos;
2734 struct inode *inode = mapping->host;
2735 struct page *page;
2736 struct buffer_head map_bh;
2737 int err;
2738
2739 blocksize = 1 << inode->i_blkbits;
2740 length = offset & (blocksize - 1);
2741
2742 /* Block boundary? Nothing to do */
2743 if (!length)
2744 return 0;
2745
2746 length = blocksize - length;
2747 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2748
2749 page = grab_cache_page(mapping, index);
2750 err = -ENOMEM;
2751 if (!page)
2752 goto out;
2753
2754 if (page_has_buffers(page)) {
2755has_buffers:
2756 unlock_page(page);
2757 page_cache_release(page);
2758 return block_truncate_page(mapping, from, get_block);
2759 }
2760
2761 /* Find the buffer that contains "offset" */
2762 pos = blocksize;
2763 while (offset >= pos) {
2764 iblock++;
2765 pos += blocksize;
2766 }
2767
2768 map_bh.b_size = blocksize;
2769 map_bh.b_state = 0;
2770 err = get_block(inode, iblock, &map_bh, 0);
2771 if (err)
2772 goto unlock;
2773 /* unmapped? It's a hole - nothing to do */
2774 if (!buffer_mapped(&map_bh))
2775 goto unlock;
2776
2777 /* Ok, it's mapped. Make sure it's up-to-date */
2778 if (!PageUptodate(page)) {
2779 err = mapping->a_ops->readpage(NULL, page);
2780 if (err) {
2781 page_cache_release(page);
2782 goto out;
2783 }
2784 lock_page(page);
2785 if (!PageUptodate(page)) {
2786 err = -EIO;
2787 goto unlock;
2788 }
2789 if (page_has_buffers(page))
2790 goto has_buffers;
2791 }
2792 zero_user(page, offset, length);
2793 set_page_dirty(page);
2794 err = 0;
2795
2796unlock:
2797 unlock_page(page);
2798 page_cache_release(page);
2799out:
2800 return err;
2801}
2802EXPORT_SYMBOL(nobh_truncate_page);
2803
2804int block_truncate_page(struct address_space *mapping,
2805 loff_t from, get_block_t *get_block)
2806{
2807 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2808 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2809 unsigned blocksize;
2810 sector_t iblock;
2811 unsigned length, pos;
2812 struct inode *inode = mapping->host;
2813 struct page *page;
2814 struct buffer_head *bh;
2815 int err;
2816
2817 blocksize = 1 << inode->i_blkbits;
2818 length = offset & (blocksize - 1);
2819
2820 /* Block boundary? Nothing to do */
2821 if (!length)
2822 return 0;
2823
2824 length = blocksize - length;
2825 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2826
2827 page = grab_cache_page(mapping, index);
2828 err = -ENOMEM;
2829 if (!page)
2830 goto out;
2831
2832 if (!page_has_buffers(page))
2833 create_empty_buffers(page, blocksize, 0);
2834
2835 /* Find the buffer that contains "offset" */
2836 bh = page_buffers(page);
2837 pos = blocksize;
2838 while (offset >= pos) {
2839 bh = bh->b_this_page;
2840 iblock++;
2841 pos += blocksize;
2842 }
2843
2844 err = 0;
2845 if (!buffer_mapped(bh)) {
2846 WARN_ON(bh->b_size != blocksize);
2847 err = get_block(inode, iblock, bh, 0);
2848 if (err)
2849 goto unlock;
2850 /* unmapped? It's a hole - nothing to do */
2851 if (!buffer_mapped(bh))
2852 goto unlock;
2853 }
2854
2855 /* Ok, it's mapped. Make sure it's up-to-date */
2856 if (PageUptodate(page))
2857 set_buffer_uptodate(bh);
2858
2859 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2860 err = -EIO;
2861 ll_rw_block(READ, 1, &bh);
2862 wait_on_buffer(bh);
2863 /* Uhhuh. Read error. Complain and punt. */
2864 if (!buffer_uptodate(bh))
2865 goto unlock;
2866 }
2867
2868 zero_user(page, offset, length);
2869 mark_buffer_dirty(bh);
2870 err = 0;
2871
2872unlock:
2873 unlock_page(page);
2874 page_cache_release(page);
2875out:
2876 return err;
2877}
2878EXPORT_SYMBOL(block_truncate_page);
2879
2880/*
2881 * The generic ->writepage function for buffer-backed address_spaces
2882 * this form passes in the end_io handler used to finish the IO.
2883 */
2884int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2885 struct writeback_control *wbc, bh_end_io_t *handler)
2886{
2887 struct inode * const inode = page->mapping->host;
2888 loff_t i_size = i_size_read(inode);
2889 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2890 unsigned offset;
2891
2892 /* Is the page fully inside i_size? */
2893 if (page->index < end_index)
2894 return __block_write_full_page(inode, page, get_block, wbc,
2895 handler);
2896
2897 /* Is the page fully outside i_size? (truncate in progress) */
2898 offset = i_size & (PAGE_CACHE_SIZE-1);
2899 if (page->index >= end_index+1 || !offset) {
2900 /*
2901 * The page may have dirty, unmapped buffers. For example,
2902 * they may have been added in ext3_writepage(). Make them
2903 * freeable here, so the page does not leak.
2904 */
2905 do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
2906 unlock_page(page);
2907 return 0; /* don't care */
2908 }
2909
2910 /*
2911 * The page straddles i_size. It must be zeroed out on each and every
2912 * writepage invocation because it may be mmapped. "A file is mapped
2913 * in multiples of the page size. For a file that is not a multiple of
2914 * the page size, the remaining memory is zeroed when mapped, and
2915 * writes to that region are not written out to the file."
2916 */
2917 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2918 return __block_write_full_page(inode, page, get_block, wbc, handler);
2919}
2920EXPORT_SYMBOL(block_write_full_page_endio);
2921
2922/*
2923 * The generic ->writepage function for buffer-backed address_spaces
2924 */
2925int block_write_full_page(struct page *page, get_block_t *get_block,
2926 struct writeback_control *wbc)
2927{
2928 return block_write_full_page_endio(page, get_block, wbc,
2929 end_buffer_async_write);
2930}
2931EXPORT_SYMBOL(block_write_full_page);
2932
2933sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2934 get_block_t *get_block)
2935{
2936 struct buffer_head tmp;
2937 struct inode *inode = mapping->host;
2938 tmp.b_state = 0;
2939 tmp.b_blocknr = 0;
2940 tmp.b_size = 1 << inode->i_blkbits;
2941 get_block(inode, block, &tmp, 0);
2942 return tmp.b_blocknr;
2943}
2944EXPORT_SYMBOL(generic_block_bmap);
2945
2946static void end_bio_bh_io_sync(struct bio *bio, int err)
2947{
2948 struct buffer_head *bh = bio->bi_private;
2949
2950 if (err == -EOPNOTSUPP) {
2951 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2952 }
2953
2954 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2955 set_bit(BH_Quiet, &bh->b_state);
2956
2957 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2958 bio_put(bio);
2959}
2960
2961/*
2962 * This allows us to do IO even on the odd last sectors
2963 * of a device, even if the bh block size is some multiple
2964 * of the physical sector size.
2965 *
2966 * We'll just truncate the bio to the size of the device,
2967 * and clear the end of the buffer head manually.
2968 *
2969 * Truly out-of-range accesses will turn into actual IO
2970 * errors, this only handles the "we need to be able to
2971 * do IO at the final sector" case.
2972 */
2973static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
2974{
2975 sector_t maxsector;
2976 unsigned bytes;
2977
2978 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
2979 if (!maxsector)
2980 return;
2981
2982 /*
2983 * If the *whole* IO is past the end of the device,
2984 * let it through, and the IO layer will turn it into
2985 * an EIO.
2986 */
2987 if (unlikely(bio->bi_iter.bi_sector >= maxsector))
2988 return;
2989
2990 maxsector -= bio->bi_iter.bi_sector;
2991 bytes = bio->bi_iter.bi_size;
2992 if (likely((bytes >> 9) <= maxsector))
2993 return;
2994
2995 /* Uhhuh. We've got a bh that straddles the device size! */
2996 bytes = maxsector << 9;
2997
2998 /* Truncate the bio.. */
2999 bio->bi_iter.bi_size = bytes;
3000 bio->bi_io_vec[0].bv_len = bytes;
3001
3002 /* ..and clear the end of the buffer for reads */
3003 if ((rw & RW_MASK) == READ) {
3004 void *kaddr = kmap_atomic(bh->b_page);
3005 memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes);
3006 kunmap_atomic(kaddr);
3007 flush_dcache_page(bh->b_page);
3008 }
3009}
3010
3011int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
3012{
3013 struct bio *bio;
3014 int ret = 0;
3015
3016 BUG_ON(!buffer_locked(bh));
3017 BUG_ON(!buffer_mapped(bh));
3018 BUG_ON(!bh->b_end_io);
3019 BUG_ON(buffer_delay(bh));
3020 BUG_ON(buffer_unwritten(bh));
3021
3022 /*
3023 * Only clear out a write error when rewriting
3024 */
3025 if (test_set_buffer_req(bh) && (rw & WRITE))
3026 clear_buffer_write_io_error(bh);
3027
3028 /*
3029 * from here on down, it's all bio -- do the initial mapping,
3030 * submit_bio -> generic_make_request may further map this bio around
3031 */
3032 bio = bio_alloc(GFP_NOIO, 1);
3033
3034 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3035 bio->bi_bdev = bh->b_bdev;
3036 bio->bi_io_vec[0].bv_page = bh->b_page;
3037 bio->bi_io_vec[0].bv_len = bh->b_size;
3038 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
3039
3040 bio->bi_vcnt = 1;
3041 bio->bi_iter.bi_size = bh->b_size;
3042
3043 bio->bi_end_io = end_bio_bh_io_sync;
3044 bio->bi_private = bh;
3045 bio->bi_flags |= bio_flags;
3046
3047 /* Take care of bh's that straddle the end of the device */
3048 guard_bh_eod(rw, bio, bh);
3049
3050 if (buffer_meta(bh))
3051 rw |= REQ_META;
3052 if (buffer_prio(bh))
3053 rw |= REQ_PRIO;
3054
3055 bio_get(bio);
3056 submit_bio(rw, bio);
3057
3058 if (bio_flagged(bio, BIO_EOPNOTSUPP))
3059 ret = -EOPNOTSUPP;
3060
3061 bio_put(bio);
3062 return ret;
3063}
3064EXPORT_SYMBOL_GPL(_submit_bh);
3065
3066int submit_bh(int rw, struct buffer_head *bh)
3067{
3068 return _submit_bh(rw, bh, 0);
3069}
3070EXPORT_SYMBOL(submit_bh);
3071
3072/**
3073 * ll_rw_block: low-level access to block devices (DEPRECATED)
3074 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
3075 * @nr: number of &struct buffer_heads in the array
3076 * @bhs: array of pointers to &struct buffer_head
3077 *
3078 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3079 * requests an I/O operation on them, either a %READ or a %WRITE. The third
3080 * %READA option is described in the documentation for generic_make_request()
3081 * which ll_rw_block() calls.
3082 *
3083 * This function drops any buffer that it cannot get a lock on (with the
3084 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3085 * request, and any buffer that appears to be up-to-date when doing read
3086 * request. Further it marks as clean buffers that are processed for
3087 * writing (the buffer cache won't assume that they are actually clean
3088 * until the buffer gets unlocked).
3089 *
3090 * ll_rw_block sets b_end_io to simple completion handler that marks
3091 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3092 * any waiters.
3093 *
3094 * All of the buffers must be for the same device, and must also be a
3095 * multiple of the current approved size for the device.
3096 */
3097void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3098{
3099 int i;
3100
3101 for (i = 0; i < nr; i++) {
3102 struct buffer_head *bh = bhs[i];
3103
3104 if (!trylock_buffer(bh))
3105 continue;
3106 if (rw == WRITE) {
3107 if (test_clear_buffer_dirty(bh)) {
3108 bh->b_end_io = end_buffer_write_sync;
3109 get_bh(bh);
3110 submit_bh(WRITE, bh);
3111 continue;
3112 }
3113 } else {
3114 if (!buffer_uptodate(bh)) {
3115 bh->b_end_io = end_buffer_read_sync;
3116 get_bh(bh);
3117 submit_bh(rw, bh);
3118 continue;
3119 }
3120 }
3121 unlock_buffer(bh);
3122 }
3123}
3124EXPORT_SYMBOL(ll_rw_block);
3125
3126void write_dirty_buffer(struct buffer_head *bh, int rw)
3127{
3128 lock_buffer(bh);
3129 if (!test_clear_buffer_dirty(bh)) {
3130 unlock_buffer(bh);
3131 return;
3132 }
3133 bh->b_end_io = end_buffer_write_sync;
3134 get_bh(bh);
3135 submit_bh(rw, bh);
3136}
3137EXPORT_SYMBOL(write_dirty_buffer);
3138
3139/*
3140 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3141 * and then start new I/O and then wait upon it. The caller must have a ref on
3142 * the buffer_head.
3143 */
3144int __sync_dirty_buffer(struct buffer_head *bh, int rw)
3145{
3146 int ret = 0;
3147
3148 WARN_ON(atomic_read(&bh->b_count) < 1);
3149 lock_buffer(bh);
3150 if (test_clear_buffer_dirty(bh)) {
3151 get_bh(bh);
3152 bh->b_end_io = end_buffer_write_sync;
3153 ret = submit_bh(rw, bh);
3154 wait_on_buffer(bh);
3155 if (!ret && !buffer_uptodate(bh))
3156 ret = -EIO;
3157 } else {
3158 unlock_buffer(bh);
3159 }
3160 return ret;
3161}
3162EXPORT_SYMBOL(__sync_dirty_buffer);
3163
3164int sync_dirty_buffer(struct buffer_head *bh)
3165{
3166 return __sync_dirty_buffer(bh, WRITE_SYNC);
3167}
3168EXPORT_SYMBOL(sync_dirty_buffer);
3169
3170/*
3171 * try_to_free_buffers() checks if all the buffers on this particular page
3172 * are unused, and releases them if so.
3173 *
3174 * Exclusion against try_to_free_buffers may be obtained by either
3175 * locking the page or by holding its mapping's private_lock.
3176 *
3177 * If the page is dirty but all the buffers are clean then we need to
3178 * be sure to mark the page clean as well. This is because the page
3179 * may be against a block device, and a later reattachment of buffers
3180 * to a dirty page will set *all* buffers dirty. Which would corrupt
3181 * filesystem data on the same device.
3182 *
3183 * The same applies to regular filesystem pages: if all the buffers are
3184 * clean then we set the page clean and proceed. To do that, we require
3185 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3186 * private_lock.
3187 *
3188 * try_to_free_buffers() is non-blocking.
3189 */
3190static inline int buffer_busy(struct buffer_head *bh)
3191{
3192 return atomic_read(&bh->b_count) |
3193 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3194}
3195
3196static int
3197drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3198{
3199 struct buffer_head *head = page_buffers(page);
3200 struct buffer_head *bh;
3201
3202 bh = head;
3203 do {
3204 if (buffer_write_io_error(bh) && page->mapping)
3205 set_bit(AS_EIO, &page->mapping->flags);
3206 if (buffer_busy(bh))
3207 goto failed;
3208 bh = bh->b_this_page;
3209 } while (bh != head);
3210
3211 do {
3212 struct buffer_head *next = bh->b_this_page;
3213
3214 if (bh->b_assoc_map)
3215 __remove_assoc_queue(bh);
3216 bh = next;
3217 } while (bh != head);
3218 *buffers_to_free = head;
3219 __clear_page_buffers(page);
3220 return 1;
3221failed:
3222 return 0;
3223}
3224
3225int try_to_free_buffers(struct page *page)
3226{
3227 struct address_space * const mapping = page->mapping;
3228 struct buffer_head *buffers_to_free = NULL;
3229 int ret = 0;
3230
3231 BUG_ON(!PageLocked(page));
3232 if (PageWriteback(page))
3233 return 0;
3234
3235 if (mapping == NULL) { /* can this still happen? */
3236 ret = drop_buffers(page, &buffers_to_free);
3237 goto out;
3238 }
3239
3240 spin_lock(&mapping->private_lock);
3241 ret = drop_buffers(page, &buffers_to_free);
3242
3243 /*
3244 * If the filesystem writes its buffers by hand (eg ext3)
3245 * then we can have clean buffers against a dirty page. We
3246 * clean the page here; otherwise the VM will never notice
3247 * that the filesystem did any IO at all.
3248 *
3249 * Also, during truncate, discard_buffer will have marked all
3250 * the page's buffers clean. We discover that here and clean
3251 * the page also.
3252 *
3253 * private_lock must be held over this entire operation in order
3254 * to synchronise against __set_page_dirty_buffers and prevent the
3255 * dirty bit from being lost.
3256 */
3257 if (ret)
3258 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3259 spin_unlock(&mapping->private_lock);
3260out:
3261 if (buffers_to_free) {
3262 struct buffer_head *bh = buffers_to_free;
3263
3264 do {
3265 struct buffer_head *next = bh->b_this_page;
3266 free_buffer_head(bh);
3267 bh = next;
3268 } while (bh != buffers_to_free);
3269 }
3270 return ret;
3271}
3272EXPORT_SYMBOL(try_to_free_buffers);
3273
3274/*
3275 * There are no bdflush tunables left. But distributions are
3276 * still running obsolete flush daemons, so we terminate them here.
3277 *
3278 * Use of bdflush() is deprecated and will be removed in a future kernel.
3279 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3280 */
3281SYSCALL_DEFINE2(bdflush, int, func, long, data)
3282{
3283 static int msg_count;
3284
3285 if (!capable(CAP_SYS_ADMIN))
3286 return -EPERM;
3287
3288 if (msg_count < 5) {
3289 msg_count++;
3290 printk(KERN_INFO
3291 "warning: process `%s' used the obsolete bdflush"
3292 " system call\n", current->comm);
3293 printk(KERN_INFO "Fix your initscripts?\n");
3294 }
3295
3296 if (func == 1)
3297 do_exit(0);
3298 return 0;
3299}
3300
3301/*
3302 * Buffer-head allocation
3303 */
3304static struct kmem_cache *bh_cachep __read_mostly;
3305
3306/*
3307 * Once the number of bh's in the machine exceeds this level, we start
3308 * stripping them in writeback.
3309 */
3310static unsigned long max_buffer_heads;
3311
3312int buffer_heads_over_limit;
3313
3314struct bh_accounting {
3315 int nr; /* Number of live bh's */
3316 int ratelimit; /* Limit cacheline bouncing */
3317};
3318
3319static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3320
3321static void recalc_bh_state(void)
3322{
3323 int i;
3324 int tot = 0;
3325
3326 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3327 return;
3328 __this_cpu_write(bh_accounting.ratelimit, 0);
3329 for_each_online_cpu(i)
3330 tot += per_cpu(bh_accounting, i).nr;
3331 buffer_heads_over_limit = (tot > max_buffer_heads);
3332}
3333
3334struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3335{
3336 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3337 if (ret) {
3338 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3339 preempt_disable();
3340 __this_cpu_inc(bh_accounting.nr);
3341 recalc_bh_state();
3342 preempt_enable();
3343 }
3344 return ret;
3345}
3346EXPORT_SYMBOL(alloc_buffer_head);
3347
3348void free_buffer_head(struct buffer_head *bh)
3349{
3350 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3351 kmem_cache_free(bh_cachep, bh);
3352 preempt_disable();
3353 __this_cpu_dec(bh_accounting.nr);
3354 recalc_bh_state();
3355 preempt_enable();
3356}
3357EXPORT_SYMBOL(free_buffer_head);
3358
3359static void buffer_exit_cpu(int cpu)
3360{
3361 int i;
3362 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3363
3364 for (i = 0; i < BH_LRU_SIZE; i++) {
3365 brelse(b->bhs[i]);
3366 b->bhs[i] = NULL;
3367 }
3368 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3369 per_cpu(bh_accounting, cpu).nr = 0;
3370}
3371
3372static int buffer_cpu_notify(struct notifier_block *self,
3373 unsigned long action, void *hcpu)
3374{
3375 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3376 buffer_exit_cpu((unsigned long)hcpu);
3377 return NOTIFY_OK;
3378}
3379
3380/**
3381 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3382 * @bh: struct buffer_head
3383 *
3384 * Return true if the buffer is up-to-date and false,
3385 * with the buffer locked, if not.
3386 */
3387int bh_uptodate_or_lock(struct buffer_head *bh)
3388{
3389 if (!buffer_uptodate(bh)) {
3390 lock_buffer(bh);
3391 if (!buffer_uptodate(bh))
3392 return 0;
3393 unlock_buffer(bh);
3394 }
3395 return 1;
3396}
3397EXPORT_SYMBOL(bh_uptodate_or_lock);
3398
3399/**
3400 * bh_submit_read - Submit a locked buffer for reading
3401 * @bh: struct buffer_head
3402 *
3403 * Returns zero on success and -EIO on error.
3404 */
3405int bh_submit_read(struct buffer_head *bh)
3406{
3407 BUG_ON(!buffer_locked(bh));
3408
3409 if (buffer_uptodate(bh)) {
3410 unlock_buffer(bh);
3411 return 0;
3412 }
3413
3414 get_bh(bh);
3415 bh->b_end_io = end_buffer_read_sync;
3416 submit_bh(READ, bh);
3417 wait_on_buffer(bh);
3418 if (buffer_uptodate(bh))
3419 return 0;
3420 return -EIO;
3421}
3422EXPORT_SYMBOL(bh_submit_read);
3423
3424void __init buffer_init(void)
3425{
3426 unsigned long nrpages;
3427
3428 bh_cachep = kmem_cache_create("buffer_head",
3429 sizeof(struct buffer_head), 0,
3430 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3431 SLAB_MEM_SPREAD),
3432 NULL);
3433
3434 /*
3435 * Limit the bh occupancy to 10% of ZONE_NORMAL
3436 */
3437 nrpages = (nr_free_buffer_pages() * 10) / 100;
3438 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3439 hotcpu_notifier(buffer_cpu_notify, 0);
3440}