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