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