1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
9 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
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
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
17 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
19 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
22 #include <linux/kernel.h>
23 #include <linux/sched/signal.h>
24 #include <linux/syscalls.h>
26 #include <linux/iomap.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>
54 static int fsync_buffers_list(spinlock_t
*lock
, struct list_head
*list
);
55 static void submit_bh_wbc(blk_opf_t opf
, struct buffer_head
*bh
,
56 struct writeback_control
*wbc
);
58 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
60 inline void touch_buffer(struct buffer_head
*bh
)
62 trace_block_touch_buffer(bh
);
63 mark_page_accessed(bh
->b_page
);
65 EXPORT_SYMBOL(touch_buffer
);
67 void __lock_buffer(struct buffer_head
*bh
)
69 wait_on_bit_lock_io(&bh
->b_state
, BH_Lock
, TASK_UNINTERRUPTIBLE
);
71 EXPORT_SYMBOL(__lock_buffer
);
73 void unlock_buffer(struct buffer_head
*bh
)
75 clear_bit_unlock(BH_Lock
, &bh
->b_state
);
76 smp_mb__after_atomic();
77 wake_up_bit(&bh
->b_state
, BH_Lock
);
79 EXPORT_SYMBOL(unlock_buffer
);
82 * Returns if the folio has dirty or writeback buffers. If all the buffers
83 * are unlocked and clean then the folio_test_dirty information is stale. If
84 * any of the buffers are locked, it is assumed they are locked for IO.
86 void buffer_check_dirty_writeback(struct folio
*folio
,
87 bool *dirty
, bool *writeback
)
89 struct buffer_head
*head
, *bh
;
93 BUG_ON(!folio_test_locked(folio
));
95 head
= folio_buffers(folio
);
99 if (folio_test_writeback(folio
))
104 if (buffer_locked(bh
))
107 if (buffer_dirty(bh
))
110 bh
= bh
->b_this_page
;
111 } while (bh
!= head
);
113 EXPORT_SYMBOL(buffer_check_dirty_writeback
);
116 * Block until a buffer comes unlocked. This doesn't stop it
117 * from becoming locked again - you have to lock it yourself
118 * if you want to preserve its state.
120 void __wait_on_buffer(struct buffer_head
* bh
)
122 wait_on_bit_io(&bh
->b_state
, BH_Lock
, TASK_UNINTERRUPTIBLE
);
124 EXPORT_SYMBOL(__wait_on_buffer
);
126 static void buffer_io_error(struct buffer_head
*bh
, char *msg
)
128 if (!test_bit(BH_Quiet
, &bh
->b_state
))
129 printk_ratelimited(KERN_ERR
130 "Buffer I/O error on dev %pg, logical block %llu%s\n",
131 bh
->b_bdev
, (unsigned long long)bh
->b_blocknr
, msg
);
135 * End-of-IO handler helper function which does not touch the bh after
137 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
138 * a race there is benign: unlock_buffer() only use the bh's address for
139 * hashing after unlocking the buffer, so it doesn't actually touch the bh
142 static void __end_buffer_read_notouch(struct buffer_head
*bh
, int uptodate
)
145 set_buffer_uptodate(bh
);
147 /* This happens, due to failed read-ahead attempts. */
148 clear_buffer_uptodate(bh
);
154 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
157 void end_buffer_read_sync(struct buffer_head
*bh
, int uptodate
)
159 __end_buffer_read_notouch(bh
, uptodate
);
162 EXPORT_SYMBOL(end_buffer_read_sync
);
164 void end_buffer_write_sync(struct buffer_head
*bh
, int uptodate
)
167 set_buffer_uptodate(bh
);
169 buffer_io_error(bh
, ", lost sync page write");
170 mark_buffer_write_io_error(bh
);
171 clear_buffer_uptodate(bh
);
176 EXPORT_SYMBOL(end_buffer_write_sync
);
179 * Various filesystems appear to want __find_get_block to be non-blocking.
180 * But it's the page lock which protects the buffers. To get around this,
181 * we get exclusion from try_to_free_buffers with the blockdev mapping's
184 * Hack idea: for the blockdev mapping, private_lock contention
185 * may be quite high. This code could TryLock the page, and if that
186 * succeeds, there is no need to take private_lock.
188 static struct buffer_head
*
189 __find_get_block_slow(struct block_device
*bdev
, sector_t block
)
191 struct inode
*bd_inode
= bdev
->bd_inode
;
192 struct address_space
*bd_mapping
= bd_inode
->i_mapping
;
193 struct buffer_head
*ret
= NULL
;
195 struct buffer_head
*bh
;
196 struct buffer_head
*head
;
199 static DEFINE_RATELIMIT_STATE(last_warned
, HZ
, 1);
201 index
= block
>> (PAGE_SHIFT
- bd_inode
->i_blkbits
);
202 page
= find_get_page_flags(bd_mapping
, index
, FGP_ACCESSED
);
206 spin_lock(&bd_mapping
->private_lock
);
207 if (!page_has_buffers(page
))
209 head
= page_buffers(page
);
212 if (!buffer_mapped(bh
))
214 else if (bh
->b_blocknr
== block
) {
219 bh
= bh
->b_this_page
;
220 } while (bh
!= head
);
222 /* we might be here because some of the buffers on this page are
223 * not mapped. This is due to various races between
224 * file io on the block device and getblk. It gets dealt with
225 * elsewhere, don't buffer_error if we had some unmapped buffers
227 ratelimit_set_flags(&last_warned
, RATELIMIT_MSG_ON_RELEASE
);
228 if (all_mapped
&& __ratelimit(&last_warned
)) {
229 printk("__find_get_block_slow() failed. block=%llu, "
230 "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
231 "device %pg blocksize: %d\n",
232 (unsigned long long)block
,
233 (unsigned long long)bh
->b_blocknr
,
234 bh
->b_state
, bh
->b_size
, bdev
,
235 1 << bd_inode
->i_blkbits
);
238 spin_unlock(&bd_mapping
->private_lock
);
244 static void end_buffer_async_read(struct buffer_head
*bh
, int uptodate
)
247 struct buffer_head
*first
;
248 struct buffer_head
*tmp
;
250 int page_uptodate
= 1;
252 BUG_ON(!buffer_async_read(bh
));
256 set_buffer_uptodate(bh
);
258 clear_buffer_uptodate(bh
);
259 buffer_io_error(bh
, ", async page read");
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.
268 first
= page_buffers(page
);
269 spin_lock_irqsave(&first
->b_uptodate_lock
, flags
);
270 clear_buffer_async_read(bh
);
274 if (!buffer_uptodate(tmp
))
276 if (buffer_async_read(tmp
)) {
277 BUG_ON(!buffer_locked(tmp
));
280 tmp
= tmp
->b_this_page
;
282 spin_unlock_irqrestore(&first
->b_uptodate_lock
, flags
);
285 * If all of the buffers are uptodate then we can set the page
289 SetPageUptodate(page
);
294 spin_unlock_irqrestore(&first
->b_uptodate_lock
, flags
);
298 struct decrypt_bh_ctx
{
299 struct work_struct work
;
300 struct buffer_head
*bh
;
303 static void decrypt_bh(struct work_struct
*work
)
305 struct decrypt_bh_ctx
*ctx
=
306 container_of(work
, struct decrypt_bh_ctx
, work
);
307 struct buffer_head
*bh
= ctx
->bh
;
310 err
= fscrypt_decrypt_pagecache_blocks(bh
->b_page
, bh
->b_size
,
312 end_buffer_async_read(bh
, err
== 0);
317 * I/O completion handler for block_read_full_folio() - pages
318 * which come unlocked at the end of I/O.
320 static void end_buffer_async_read_io(struct buffer_head
*bh
, int uptodate
)
322 /* Decrypt if needed */
324 fscrypt_inode_uses_fs_layer_crypto(bh
->b_page
->mapping
->host
)) {
325 struct decrypt_bh_ctx
*ctx
= kmalloc(sizeof(*ctx
), GFP_ATOMIC
);
328 INIT_WORK(&ctx
->work
, decrypt_bh
);
330 fscrypt_enqueue_decrypt_work(&ctx
->work
);
335 end_buffer_async_read(bh
, uptodate
);
339 * Completion handler for block_write_full_page() - pages which are unlocked
340 * during I/O, and which have PageWriteback cleared upon I/O completion.
342 void end_buffer_async_write(struct buffer_head
*bh
, int uptodate
)
345 struct buffer_head
*first
;
346 struct buffer_head
*tmp
;
349 BUG_ON(!buffer_async_write(bh
));
353 set_buffer_uptodate(bh
);
355 buffer_io_error(bh
, ", lost async page write");
356 mark_buffer_write_io_error(bh
);
357 clear_buffer_uptodate(bh
);
361 first
= page_buffers(page
);
362 spin_lock_irqsave(&first
->b_uptodate_lock
, flags
);
364 clear_buffer_async_write(bh
);
366 tmp
= bh
->b_this_page
;
368 if (buffer_async_write(tmp
)) {
369 BUG_ON(!buffer_locked(tmp
));
372 tmp
= tmp
->b_this_page
;
374 spin_unlock_irqrestore(&first
->b_uptodate_lock
, flags
);
375 end_page_writeback(page
);
379 spin_unlock_irqrestore(&first
->b_uptodate_lock
, flags
);
382 EXPORT_SYMBOL(end_buffer_async_write
);
385 * If a page's buffers are under async readin (end_buffer_async_read
386 * completion) then there is a possibility that another thread of
387 * control could lock one of the buffers after it has completed
388 * but while some of the other buffers have not completed. This
389 * locked buffer would confuse end_buffer_async_read() into not unlocking
390 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
391 * that this buffer is not under async I/O.
393 * The page comes unlocked when it has no locked buffer_async buffers
396 * PageLocked prevents anyone starting new async I/O reads any of
399 * PageWriteback is used to prevent simultaneous writeout of the same
402 * PageLocked prevents anyone from starting writeback of a page which is
403 * under read I/O (PageWriteback is only ever set against a locked page).
405 static void mark_buffer_async_read(struct buffer_head
*bh
)
407 bh
->b_end_io
= end_buffer_async_read_io
;
408 set_buffer_async_read(bh
);
411 static void mark_buffer_async_write_endio(struct buffer_head
*bh
,
412 bh_end_io_t
*handler
)
414 bh
->b_end_io
= handler
;
415 set_buffer_async_write(bh
);
418 void mark_buffer_async_write(struct buffer_head
*bh
)
420 mark_buffer_async_write_endio(bh
, end_buffer_async_write
);
422 EXPORT_SYMBOL(mark_buffer_async_write
);
426 * fs/buffer.c contains helper functions for buffer-backed address space's
427 * fsync functions. A common requirement for buffer-based filesystems is
428 * that certain data from the backing blockdev needs to be written out for
429 * a successful fsync(). For example, ext2 indirect blocks need to be
430 * written back and waited upon before fsync() returns.
432 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
433 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
434 * management of a list of dependent buffers at ->i_mapping->private_list.
436 * Locking is a little subtle: try_to_free_buffers() will remove buffers
437 * from their controlling inode's queue when they are being freed. But
438 * try_to_free_buffers() will be operating against the *blockdev* mapping
439 * at the time, not against the S_ISREG file which depends on those buffers.
440 * So the locking for private_list is via the private_lock in the address_space
441 * which backs the buffers. Which is different from the address_space
442 * against which the buffers are listed. So for a particular address_space,
443 * mapping->private_lock does *not* protect mapping->private_list! In fact,
444 * mapping->private_list will always be protected by the backing blockdev's
447 * Which introduces a requirement: all buffers on an address_space's
448 * ->private_list must be from the same address_space: the blockdev's.
450 * address_spaces which do not place buffers at ->private_list via these
451 * utility functions are free to use private_lock and private_list for
452 * whatever they want. The only requirement is that list_empty(private_list)
453 * be true at clear_inode() time.
455 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
456 * filesystems should do that. invalidate_inode_buffers() should just go
457 * BUG_ON(!list_empty).
459 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
460 * take an address_space, not an inode. And it should be called
461 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
464 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
465 * list if it is already on a list. Because if the buffer is on a list,
466 * it *must* already be on the right one. If not, the filesystem is being
467 * silly. This will save a ton of locking. But first we have to ensure
468 * that buffers are taken *off* the old inode's list when they are freed
469 * (presumably in truncate). That requires careful auditing of all
470 * filesystems (do it inside bforget()). It could also be done by bringing
475 * The buffer's backing address_space's private_lock must be held
477 static void __remove_assoc_queue(struct buffer_head
*bh
)
479 list_del_init(&bh
->b_assoc_buffers
);
480 WARN_ON(!bh
->b_assoc_map
);
481 bh
->b_assoc_map
= NULL
;
484 int inode_has_buffers(struct inode
*inode
)
486 return !list_empty(&inode
->i_data
.private_list
);
490 * osync is designed to support O_SYNC io. It waits synchronously for
491 * all already-submitted IO to complete, but does not queue any new
492 * writes to the disk.
494 * To do O_SYNC writes, just queue the buffer writes with write_dirty_buffer
495 * as you dirty the buffers, and then use osync_inode_buffers to wait for
496 * completion. Any other dirty buffers which are not yet queued for
497 * write will not be flushed to disk by the osync.
499 static int osync_buffers_list(spinlock_t
*lock
, struct list_head
*list
)
501 struct buffer_head
*bh
;
507 list_for_each_prev(p
, list
) {
509 if (buffer_locked(bh
)) {
513 if (!buffer_uptodate(bh
))
524 void emergency_thaw_bdev(struct super_block
*sb
)
526 while (sb
->s_bdev
&& !thaw_bdev(sb
->s_bdev
))
527 printk(KERN_WARNING
"Emergency Thaw on %pg\n", sb
->s_bdev
);
531 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
532 * @mapping: the mapping which wants those buffers written
534 * Starts I/O against the buffers at mapping->private_list, and waits upon
537 * Basically, this is a convenience function for fsync().
538 * @mapping is a file or directory which needs those buffers to be written for
539 * a successful fsync().
541 int sync_mapping_buffers(struct address_space
*mapping
)
543 struct address_space
*buffer_mapping
= mapping
->private_data
;
545 if (buffer_mapping
== NULL
|| list_empty(&mapping
->private_list
))
548 return fsync_buffers_list(&buffer_mapping
->private_lock
,
549 &mapping
->private_list
);
551 EXPORT_SYMBOL(sync_mapping_buffers
);
554 * Called when we've recently written block `bblock', and it is known that
555 * `bblock' was for a buffer_boundary() buffer. This means that the block at
556 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
557 * dirty, schedule it for IO. So that indirects merge nicely with their data.
559 void write_boundary_block(struct block_device
*bdev
,
560 sector_t bblock
, unsigned blocksize
)
562 struct buffer_head
*bh
= __find_get_block(bdev
, bblock
+ 1, blocksize
);
564 if (buffer_dirty(bh
))
565 write_dirty_buffer(bh
, 0);
570 void mark_buffer_dirty_inode(struct buffer_head
*bh
, struct inode
*inode
)
572 struct address_space
*mapping
= inode
->i_mapping
;
573 struct address_space
*buffer_mapping
= bh
->b_page
->mapping
;
575 mark_buffer_dirty(bh
);
576 if (!mapping
->private_data
) {
577 mapping
->private_data
= buffer_mapping
;
579 BUG_ON(mapping
->private_data
!= buffer_mapping
);
581 if (!bh
->b_assoc_map
) {
582 spin_lock(&buffer_mapping
->private_lock
);
583 list_move_tail(&bh
->b_assoc_buffers
,
584 &mapping
->private_list
);
585 bh
->b_assoc_map
= mapping
;
586 spin_unlock(&buffer_mapping
->private_lock
);
589 EXPORT_SYMBOL(mark_buffer_dirty_inode
);
592 * Add a page to the dirty page list.
594 * It is a sad fact of life that this function is called from several places
595 * deeply under spinlocking. It may not sleep.
597 * If the page has buffers, the uptodate buffers are set dirty, to preserve
598 * dirty-state coherency between the page and the buffers. It the page does
599 * not have buffers then when they are later attached they will all be set
602 * The buffers are dirtied before the page is dirtied. There's a small race
603 * window in which a writepage caller may see the page cleanness but not the
604 * buffer dirtiness. That's fine. If this code were to set the page dirty
605 * before the buffers, a concurrent writepage caller could clear the page dirty
606 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
607 * page on the dirty page list.
609 * We use private_lock to lock against try_to_free_buffers while using the
610 * page's buffer list. Also use this to protect against clean buffers being
611 * added to the page after it was set dirty.
613 * FIXME: may need to call ->reservepage here as well. That's rather up to the
614 * address_space though.
616 bool block_dirty_folio(struct address_space
*mapping
, struct folio
*folio
)
618 struct buffer_head
*head
;
621 spin_lock(&mapping
->private_lock
);
622 head
= folio_buffers(folio
);
624 struct buffer_head
*bh
= head
;
627 set_buffer_dirty(bh
);
628 bh
= bh
->b_this_page
;
629 } while (bh
!= head
);
632 * Lock out page's memcg migration to keep PageDirty
633 * synchronized with per-memcg dirty page counters.
635 folio_memcg_lock(folio
);
636 newly_dirty
= !folio_test_set_dirty(folio
);
637 spin_unlock(&mapping
->private_lock
);
640 __folio_mark_dirty(folio
, mapping
, 1);
642 folio_memcg_unlock(folio
);
645 __mark_inode_dirty(mapping
->host
, I_DIRTY_PAGES
);
649 EXPORT_SYMBOL(block_dirty_folio
);
652 * Write out and wait upon a list of buffers.
654 * We have conflicting pressures: we want to make sure that all
655 * initially dirty buffers get waited on, but that any subsequently
656 * dirtied buffers don't. After all, we don't want fsync to last
657 * forever if somebody is actively writing to the file.
659 * Do this in two main stages: first we copy dirty buffers to a
660 * temporary inode list, queueing the writes as we go. Then we clean
661 * up, waiting for those writes to complete.
663 * During this second stage, any subsequent updates to the file may end
664 * up refiling the buffer on the original inode's dirty list again, so
665 * there is a chance we will end up with a buffer queued for write but
666 * not yet completed on that list. So, as a final cleanup we go through
667 * the osync code to catch these locked, dirty buffers without requeuing
668 * any newly dirty buffers for write.
670 static int fsync_buffers_list(spinlock_t
*lock
, struct list_head
*list
)
672 struct buffer_head
*bh
;
673 struct list_head tmp
;
674 struct address_space
*mapping
;
676 struct blk_plug plug
;
678 INIT_LIST_HEAD(&tmp
);
679 blk_start_plug(&plug
);
682 while (!list_empty(list
)) {
683 bh
= BH_ENTRY(list
->next
);
684 mapping
= bh
->b_assoc_map
;
685 __remove_assoc_queue(bh
);
686 /* Avoid race with mark_buffer_dirty_inode() which does
687 * a lockless check and we rely on seeing the dirty bit */
689 if (buffer_dirty(bh
) || buffer_locked(bh
)) {
690 list_add(&bh
->b_assoc_buffers
, &tmp
);
691 bh
->b_assoc_map
= mapping
;
692 if (buffer_dirty(bh
)) {
696 * Ensure any pending I/O completes so that
697 * write_dirty_buffer() actually writes the
698 * current contents - it is a noop if I/O is
699 * still in flight on potentially older
702 write_dirty_buffer(bh
, REQ_SYNC
);
705 * Kick off IO for the previous mapping. Note
706 * that we will not run the very last mapping,
707 * wait_on_buffer() will do that for us
708 * through sync_buffer().
717 blk_finish_plug(&plug
);
720 while (!list_empty(&tmp
)) {
721 bh
= BH_ENTRY(tmp
.prev
);
723 mapping
= bh
->b_assoc_map
;
724 __remove_assoc_queue(bh
);
725 /* Avoid race with mark_buffer_dirty_inode() which does
726 * a lockless check and we rely on seeing the dirty bit */
728 if (buffer_dirty(bh
)) {
729 list_add(&bh
->b_assoc_buffers
,
730 &mapping
->private_list
);
731 bh
->b_assoc_map
= mapping
;
735 if (!buffer_uptodate(bh
))
742 err2
= osync_buffers_list(lock
, list
);
750 * Invalidate any and all dirty buffers on a given inode. We are
751 * probably unmounting the fs, but that doesn't mean we have already
752 * done a sync(). Just drop the buffers from the inode list.
754 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
755 * assumes that all the buffers are against the blockdev. Not true
758 void invalidate_inode_buffers(struct inode
*inode
)
760 if (inode_has_buffers(inode
)) {
761 struct address_space
*mapping
= &inode
->i_data
;
762 struct list_head
*list
= &mapping
->private_list
;
763 struct address_space
*buffer_mapping
= mapping
->private_data
;
765 spin_lock(&buffer_mapping
->private_lock
);
766 while (!list_empty(list
))
767 __remove_assoc_queue(BH_ENTRY(list
->next
));
768 spin_unlock(&buffer_mapping
->private_lock
);
771 EXPORT_SYMBOL(invalidate_inode_buffers
);
774 * Remove any clean buffers from the inode's buffer list. This is called
775 * when we're trying to free the inode itself. Those buffers can pin it.
777 * Returns true if all buffers were removed.
779 int remove_inode_buffers(struct inode
*inode
)
783 if (inode_has_buffers(inode
)) {
784 struct address_space
*mapping
= &inode
->i_data
;
785 struct list_head
*list
= &mapping
->private_list
;
786 struct address_space
*buffer_mapping
= mapping
->private_data
;
788 spin_lock(&buffer_mapping
->private_lock
);
789 while (!list_empty(list
)) {
790 struct buffer_head
*bh
= BH_ENTRY(list
->next
);
791 if (buffer_dirty(bh
)) {
795 __remove_assoc_queue(bh
);
797 spin_unlock(&buffer_mapping
->private_lock
);
803 * Create the appropriate buffers when given a page for data area and
804 * the size of each buffer.. Use the bh->b_this_page linked list to
805 * follow the buffers created. Return NULL if unable to create more
808 * The retry flag is used to differentiate async IO (paging, swapping)
809 * which may not fail from ordinary buffer allocations.
811 struct buffer_head
*alloc_page_buffers(struct page
*page
, unsigned long size
,
814 struct buffer_head
*bh
, *head
;
815 gfp_t gfp
= GFP_NOFS
| __GFP_ACCOUNT
;
817 struct mem_cgroup
*memcg
, *old_memcg
;
822 /* The page lock pins the memcg */
823 memcg
= page_memcg(page
);
824 old_memcg
= set_active_memcg(memcg
);
828 while ((offset
-= size
) >= 0) {
829 bh
= alloc_buffer_head(gfp
);
833 bh
->b_this_page
= head
;
839 /* Link the buffer to its page */
840 set_bh_page(bh
, page
, offset
);
843 set_active_memcg(old_memcg
);
846 * In case anything failed, we just free everything we got.
852 head
= head
->b_this_page
;
853 free_buffer_head(bh
);
859 EXPORT_SYMBOL_GPL(alloc_page_buffers
);
862 link_dev_buffers(struct page
*page
, struct buffer_head
*head
)
864 struct buffer_head
*bh
, *tail
;
869 bh
= bh
->b_this_page
;
871 tail
->b_this_page
= head
;
872 attach_page_private(page
, head
);
875 static sector_t
blkdev_max_block(struct block_device
*bdev
, unsigned int size
)
877 sector_t retval
= ~((sector_t
)0);
878 loff_t sz
= bdev_nr_bytes(bdev
);
881 unsigned int sizebits
= blksize_bits(size
);
882 retval
= (sz
>> sizebits
);
888 * Initialise the state of a blockdev page's buffers.
891 init_page_buffers(struct page
*page
, struct block_device
*bdev
,
892 sector_t block
, int size
)
894 struct buffer_head
*head
= page_buffers(page
);
895 struct buffer_head
*bh
= head
;
896 int uptodate
= PageUptodate(page
);
897 sector_t end_block
= blkdev_max_block(bdev
, size
);
900 if (!buffer_mapped(bh
)) {
902 bh
->b_private
= NULL
;
904 bh
->b_blocknr
= block
;
906 set_buffer_uptodate(bh
);
907 if (block
< end_block
)
908 set_buffer_mapped(bh
);
911 bh
= bh
->b_this_page
;
912 } while (bh
!= head
);
915 * Caller needs to validate requested block against end of device.
921 * Create the page-cache page that contains the requested block.
923 * This is used purely for blockdev mappings.
926 grow_dev_page(struct block_device
*bdev
, sector_t block
,
927 pgoff_t index
, int size
, int sizebits
, gfp_t gfp
)
929 struct inode
*inode
= bdev
->bd_inode
;
931 struct buffer_head
*bh
;
936 gfp_mask
= mapping_gfp_constraint(inode
->i_mapping
, ~__GFP_FS
) | gfp
;
939 * XXX: __getblk_slow() can not really deal with failure and
940 * will endlessly loop on improvised global reclaim. Prefer
941 * looping in the allocator rather than here, at least that
942 * code knows what it's doing.
944 gfp_mask
|= __GFP_NOFAIL
;
946 page
= find_or_create_page(inode
->i_mapping
, index
, gfp_mask
);
948 BUG_ON(!PageLocked(page
));
950 if (page_has_buffers(page
)) {
951 bh
= page_buffers(page
);
952 if (bh
->b_size
== size
) {
953 end_block
= init_page_buffers(page
, bdev
,
954 (sector_t
)index
<< sizebits
,
958 if (!try_to_free_buffers(page_folio(page
)))
963 * Allocate some buffers for this page
965 bh
= alloc_page_buffers(page
, size
, true);
968 * Link the page to the buffers and initialise them. Take the
969 * lock to be atomic wrt __find_get_block(), which does not
970 * run under the page lock.
972 spin_lock(&inode
->i_mapping
->private_lock
);
973 link_dev_buffers(page
, bh
);
974 end_block
= init_page_buffers(page
, bdev
, (sector_t
)index
<< sizebits
,
976 spin_unlock(&inode
->i_mapping
->private_lock
);
978 ret
= (block
< end_block
) ? 1 : -ENXIO
;
986 * Create buffers for the specified block device block's page. If
987 * that page was dirty, the buffers are set dirty also.
990 grow_buffers(struct block_device
*bdev
, sector_t block
, int size
, gfp_t gfp
)
995 sizebits
= PAGE_SHIFT
- __ffs(size
);
996 index
= block
>> sizebits
;
999 * Check for a block which wants to lie outside our maximum possible
1000 * pagecache index. (this comparison is done using sector_t types).
1002 if (unlikely(index
!= block
>> sizebits
)) {
1003 printk(KERN_ERR
"%s: requested out-of-range block %llu for "
1005 __func__
, (unsigned long long)block
,
1010 /* Create a page with the proper size buffers.. */
1011 return grow_dev_page(bdev
, block
, index
, size
, sizebits
, gfp
);
1014 static struct buffer_head
*
1015 __getblk_slow(struct block_device
*bdev
, sector_t block
,
1016 unsigned size
, gfp_t gfp
)
1018 /* Size must be multiple of hard sectorsize */
1019 if (unlikely(size
& (bdev_logical_block_size(bdev
)-1) ||
1020 (size
< 512 || size
> PAGE_SIZE
))) {
1021 printk(KERN_ERR
"getblk(): invalid block size %d requested\n",
1023 printk(KERN_ERR
"logical block size: %d\n",
1024 bdev_logical_block_size(bdev
));
1031 struct buffer_head
*bh
;
1034 bh
= __find_get_block(bdev
, block
, size
);
1038 ret
= grow_buffers(bdev
, block
, size
, gfp
);
1045 * The relationship between dirty buffers and dirty pages:
1047 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1048 * the page is tagged dirty in the page cache.
1050 * At all times, the dirtiness of the buffers represents the dirtiness of
1051 * subsections of the page. If the page has buffers, the page dirty bit is
1052 * merely a hint about the true dirty state.
1054 * When a page is set dirty in its entirety, all its buffers are marked dirty
1055 * (if the page has buffers).
1057 * When a buffer is marked dirty, its page is dirtied, but the page's other
1060 * Also. When blockdev buffers are explicitly read with bread(), they
1061 * individually become uptodate. But their backing page remains not
1062 * uptodate - even if all of its buffers are uptodate. A subsequent
1063 * block_read_full_folio() against that folio will discover all the uptodate
1064 * buffers, will set the folio uptodate and will perform no I/O.
1068 * mark_buffer_dirty - mark a buffer_head as needing writeout
1069 * @bh: the buffer_head to mark dirty
1071 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1072 * its backing page dirty, then tag the page as dirty in the page cache
1073 * and then attach the address_space's inode to its superblock's dirty
1076 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1077 * i_pages lock and mapping->host->i_lock.
1079 void mark_buffer_dirty(struct buffer_head
*bh
)
1081 WARN_ON_ONCE(!buffer_uptodate(bh
));
1083 trace_block_dirty_buffer(bh
);
1086 * Very *carefully* optimize the it-is-already-dirty case.
1088 * Don't let the final "is it dirty" escape to before we
1089 * perhaps modified the buffer.
1091 if (buffer_dirty(bh
)) {
1093 if (buffer_dirty(bh
))
1097 if (!test_set_buffer_dirty(bh
)) {
1098 struct page
*page
= bh
->b_page
;
1099 struct address_space
*mapping
= NULL
;
1101 lock_page_memcg(page
);
1102 if (!TestSetPageDirty(page
)) {
1103 mapping
= page_mapping(page
);
1105 __set_page_dirty(page
, mapping
, 0);
1107 unlock_page_memcg(page
);
1109 __mark_inode_dirty(mapping
->host
, I_DIRTY_PAGES
);
1112 EXPORT_SYMBOL(mark_buffer_dirty
);
1114 void mark_buffer_write_io_error(struct buffer_head
*bh
)
1116 struct super_block
*sb
;
1118 set_buffer_write_io_error(bh
);
1119 /* FIXME: do we need to set this in both places? */
1120 if (bh
->b_page
&& bh
->b_page
->mapping
)
1121 mapping_set_error(bh
->b_page
->mapping
, -EIO
);
1122 if (bh
->b_assoc_map
)
1123 mapping_set_error(bh
->b_assoc_map
, -EIO
);
1125 sb
= READ_ONCE(bh
->b_bdev
->bd_super
);
1127 errseq_set(&sb
->s_wb_err
, -EIO
);
1130 EXPORT_SYMBOL(mark_buffer_write_io_error
);
1133 * Decrement a buffer_head's reference count. If all buffers against a page
1134 * have zero reference count, are clean and unlocked, and if the page is clean
1135 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1136 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1137 * a page but it ends up not being freed, and buffers may later be reattached).
1139 void __brelse(struct buffer_head
* buf
)
1141 if (atomic_read(&buf
->b_count
)) {
1145 WARN(1, KERN_ERR
"VFS: brelse: Trying to free free buffer\n");
1147 EXPORT_SYMBOL(__brelse
);
1150 * bforget() is like brelse(), except it discards any
1151 * potentially dirty data.
1153 void __bforget(struct buffer_head
*bh
)
1155 clear_buffer_dirty(bh
);
1156 if (bh
->b_assoc_map
) {
1157 struct address_space
*buffer_mapping
= bh
->b_page
->mapping
;
1159 spin_lock(&buffer_mapping
->private_lock
);
1160 list_del_init(&bh
->b_assoc_buffers
);
1161 bh
->b_assoc_map
= NULL
;
1162 spin_unlock(&buffer_mapping
->private_lock
);
1166 EXPORT_SYMBOL(__bforget
);
1168 static struct buffer_head
*__bread_slow(struct buffer_head
*bh
)
1171 if (buffer_uptodate(bh
)) {
1176 bh
->b_end_io
= end_buffer_read_sync
;
1177 submit_bh(REQ_OP_READ
, bh
);
1179 if (buffer_uptodate(bh
))
1187 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1188 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1189 * refcount elevated by one when they're in an LRU. A buffer can only appear
1190 * once in a particular CPU's LRU. A single buffer can be present in multiple
1191 * CPU's LRUs at the same time.
1193 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1194 * sb_find_get_block().
1196 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1197 * a local interrupt disable for that.
1200 #define BH_LRU_SIZE 16
1203 struct buffer_head
*bhs
[BH_LRU_SIZE
];
1206 static DEFINE_PER_CPU(struct bh_lru
, bh_lrus
) = {{ NULL
}};
1209 #define bh_lru_lock() local_irq_disable()
1210 #define bh_lru_unlock() local_irq_enable()
1212 #define bh_lru_lock() preempt_disable()
1213 #define bh_lru_unlock() preempt_enable()
1216 static inline void check_irqs_on(void)
1218 #ifdef irqs_disabled
1219 BUG_ON(irqs_disabled());
1224 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1225 * inserted at the front, and the buffer_head at the back if any is evicted.
1226 * Or, if already in the LRU it is moved to the front.
1228 static void bh_lru_install(struct buffer_head
*bh
)
1230 struct buffer_head
*evictee
= bh
;
1238 * the refcount of buffer_head in bh_lru prevents dropping the
1239 * attached page(i.e., try_to_free_buffers) so it could cause
1240 * failing page migration.
1241 * Skip putting upcoming bh into bh_lru until migration is done.
1243 if (lru_cache_disabled()) {
1248 b
= this_cpu_ptr(&bh_lrus
);
1249 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1250 swap(evictee
, b
->bhs
[i
]);
1251 if (evictee
== bh
) {
1263 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1265 static struct buffer_head
*
1266 lookup_bh_lru(struct block_device
*bdev
, sector_t block
, unsigned size
)
1268 struct buffer_head
*ret
= NULL
;
1273 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1274 struct buffer_head
*bh
= __this_cpu_read(bh_lrus
.bhs
[i
]);
1276 if (bh
&& bh
->b_blocknr
== block
&& bh
->b_bdev
== bdev
&&
1277 bh
->b_size
== size
) {
1280 __this_cpu_write(bh_lrus
.bhs
[i
],
1281 __this_cpu_read(bh_lrus
.bhs
[i
- 1]));
1284 __this_cpu_write(bh_lrus
.bhs
[0], bh
);
1296 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1297 * it in the LRU and mark it as accessed. If it is not present then return
1300 struct buffer_head
*
1301 __find_get_block(struct block_device
*bdev
, sector_t block
, unsigned size
)
1303 struct buffer_head
*bh
= lookup_bh_lru(bdev
, block
, size
);
1306 /* __find_get_block_slow will mark the page accessed */
1307 bh
= __find_get_block_slow(bdev
, block
);
1315 EXPORT_SYMBOL(__find_get_block
);
1318 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1319 * which corresponds to the passed block_device, block and size. The
1320 * returned buffer has its reference count incremented.
1322 * __getblk_gfp() will lock up the machine if grow_dev_page's
1323 * try_to_free_buffers() attempt is failing. FIXME, perhaps?
1325 struct buffer_head
*
1326 __getblk_gfp(struct block_device
*bdev
, sector_t block
,
1327 unsigned size
, gfp_t gfp
)
1329 struct buffer_head
*bh
= __find_get_block(bdev
, block
, size
);
1333 bh
= __getblk_slow(bdev
, block
, size
, gfp
);
1336 EXPORT_SYMBOL(__getblk_gfp
);
1339 * Do async read-ahead on a buffer..
1341 void __breadahead(struct block_device
*bdev
, sector_t block
, unsigned size
)
1343 struct buffer_head
*bh
= __getblk(bdev
, block
, size
);
1345 bh_readahead(bh
, REQ_RAHEAD
);
1349 EXPORT_SYMBOL(__breadahead
);
1352 * __bread_gfp() - reads a specified block and returns the bh
1353 * @bdev: the block_device to read from
1354 * @block: number of block
1355 * @size: size (in bytes) to read
1356 * @gfp: page allocation flag
1358 * Reads a specified block, and returns buffer head that contains it.
1359 * The page cache can be allocated from non-movable area
1360 * not to prevent page migration if you set gfp to zero.
1361 * It returns NULL if the block was unreadable.
1363 struct buffer_head
*
1364 __bread_gfp(struct block_device
*bdev
, sector_t block
,
1365 unsigned size
, gfp_t gfp
)
1367 struct buffer_head
*bh
= __getblk_gfp(bdev
, block
, size
, gfp
);
1369 if (likely(bh
) && !buffer_uptodate(bh
))
1370 bh
= __bread_slow(bh
);
1373 EXPORT_SYMBOL(__bread_gfp
);
1375 static void __invalidate_bh_lrus(struct bh_lru
*b
)
1379 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1385 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1386 * This doesn't race because it runs in each cpu either in irq
1387 * or with preempt disabled.
1389 static void invalidate_bh_lru(void *arg
)
1391 struct bh_lru
*b
= &get_cpu_var(bh_lrus
);
1393 __invalidate_bh_lrus(b
);
1394 put_cpu_var(bh_lrus
);
1397 bool has_bh_in_lru(int cpu
, void *dummy
)
1399 struct bh_lru
*b
= per_cpu_ptr(&bh_lrus
, cpu
);
1402 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1410 void invalidate_bh_lrus(void)
1412 on_each_cpu_cond(has_bh_in_lru
, invalidate_bh_lru
, NULL
, 1);
1414 EXPORT_SYMBOL_GPL(invalidate_bh_lrus
);
1417 * It's called from workqueue context so we need a bh_lru_lock to close
1418 * the race with preemption/irq.
1420 void invalidate_bh_lrus_cpu(void)
1425 b
= this_cpu_ptr(&bh_lrus
);
1426 __invalidate_bh_lrus(b
);
1430 void set_bh_page(struct buffer_head
*bh
,
1431 struct page
*page
, unsigned long offset
)
1434 BUG_ON(offset
>= PAGE_SIZE
);
1435 if (PageHighMem(page
))
1437 * This catches illegal uses and preserves the offset:
1439 bh
->b_data
= (char *)(0 + offset
);
1441 bh
->b_data
= page_address(page
) + offset
;
1443 EXPORT_SYMBOL(set_bh_page
);
1446 * Called when truncating a buffer on a page completely.
1449 /* Bits that are cleared during an invalidate */
1450 #define BUFFER_FLAGS_DISCARD \
1451 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1452 1 << BH_Delay | 1 << BH_Unwritten)
1454 static void discard_buffer(struct buffer_head
* bh
)
1456 unsigned long b_state
;
1459 clear_buffer_dirty(bh
);
1461 b_state
= READ_ONCE(bh
->b_state
);
1463 } while (!try_cmpxchg(&bh
->b_state
, &b_state
,
1464 b_state
& ~BUFFER_FLAGS_DISCARD
));
1469 * block_invalidate_folio - Invalidate part or all of a buffer-backed folio.
1470 * @folio: The folio which is affected.
1471 * @offset: start of the range to invalidate
1472 * @length: length of the range to invalidate
1474 * block_invalidate_folio() is called when all or part of the folio has been
1475 * invalidated by a truncate operation.
1477 * block_invalidate_folio() does not have to release all buffers, but it must
1478 * ensure that no dirty buffer is left outside @offset and that no I/O
1479 * is underway against any of the blocks which are outside the truncation
1480 * point. Because the caller is about to free (and possibly reuse) those
1483 void block_invalidate_folio(struct folio
*folio
, size_t offset
, size_t length
)
1485 struct buffer_head
*head
, *bh
, *next
;
1486 size_t curr_off
= 0;
1487 size_t stop
= length
+ offset
;
1489 BUG_ON(!folio_test_locked(folio
));
1492 * Check for overflow
1494 BUG_ON(stop
> folio_size(folio
) || stop
< length
);
1496 head
= folio_buffers(folio
);
1502 size_t next_off
= curr_off
+ bh
->b_size
;
1503 next
= bh
->b_this_page
;
1506 * Are we still fully in range ?
1508 if (next_off
> stop
)
1512 * is this block fully invalidated?
1514 if (offset
<= curr_off
)
1516 curr_off
= next_off
;
1518 } while (bh
!= head
);
1521 * We release buffers only if the entire folio is being invalidated.
1522 * The get_block cached value has been unconditionally invalidated,
1523 * so real IO is not possible anymore.
1525 if (length
== folio_size(folio
))
1526 filemap_release_folio(folio
, 0);
1530 EXPORT_SYMBOL(block_invalidate_folio
);
1534 * We attach and possibly dirty the buffers atomically wrt
1535 * block_dirty_folio() via private_lock. try_to_free_buffers
1536 * is already excluded via the page lock.
1538 void create_empty_buffers(struct page
*page
,
1539 unsigned long blocksize
, unsigned long b_state
)
1541 struct buffer_head
*bh
, *head
, *tail
;
1543 head
= alloc_page_buffers(page
, blocksize
, true);
1546 bh
->b_state
|= b_state
;
1548 bh
= bh
->b_this_page
;
1550 tail
->b_this_page
= head
;
1552 spin_lock(&page
->mapping
->private_lock
);
1553 if (PageUptodate(page
) || PageDirty(page
)) {
1556 if (PageDirty(page
))
1557 set_buffer_dirty(bh
);
1558 if (PageUptodate(page
))
1559 set_buffer_uptodate(bh
);
1560 bh
= bh
->b_this_page
;
1561 } while (bh
!= head
);
1563 attach_page_private(page
, head
);
1564 spin_unlock(&page
->mapping
->private_lock
);
1566 EXPORT_SYMBOL(create_empty_buffers
);
1569 * clean_bdev_aliases: clean a range of buffers in block device
1570 * @bdev: Block device to clean buffers in
1571 * @block: Start of a range of blocks to clean
1572 * @len: Number of blocks to clean
1574 * We are taking a range of blocks for data and we don't want writeback of any
1575 * buffer-cache aliases starting from return from this function and until the
1576 * moment when something will explicitly mark the buffer dirty (hopefully that
1577 * will not happen until we will free that block ;-) We don't even need to mark
1578 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1579 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1580 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1581 * would confuse anyone who might pick it with bread() afterwards...
1583 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1584 * writeout I/O going on against recently-freed buffers. We don't wait on that
1585 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1586 * need to. That happens here.
1588 void clean_bdev_aliases(struct block_device
*bdev
, sector_t block
, sector_t len
)
1590 struct inode
*bd_inode
= bdev
->bd_inode
;
1591 struct address_space
*bd_mapping
= bd_inode
->i_mapping
;
1592 struct folio_batch fbatch
;
1593 pgoff_t index
= block
>> (PAGE_SHIFT
- bd_inode
->i_blkbits
);
1596 struct buffer_head
*bh
;
1597 struct buffer_head
*head
;
1599 end
= (block
+ len
- 1) >> (PAGE_SHIFT
- bd_inode
->i_blkbits
);
1600 folio_batch_init(&fbatch
);
1601 while (filemap_get_folios(bd_mapping
, &index
, end
, &fbatch
)) {
1602 count
= folio_batch_count(&fbatch
);
1603 for (i
= 0; i
< count
; i
++) {
1604 struct folio
*folio
= fbatch
.folios
[i
];
1606 if (!folio_buffers(folio
))
1609 * We use folio lock instead of bd_mapping->private_lock
1610 * to pin buffers here since we can afford to sleep and
1611 * it scales better than a global spinlock lock.
1614 /* Recheck when the folio is locked which pins bhs */
1615 head
= folio_buffers(folio
);
1620 if (!buffer_mapped(bh
) || (bh
->b_blocknr
< block
))
1622 if (bh
->b_blocknr
>= block
+ len
)
1624 clear_buffer_dirty(bh
);
1626 clear_buffer_req(bh
);
1628 bh
= bh
->b_this_page
;
1629 } while (bh
!= head
);
1631 folio_unlock(folio
);
1633 folio_batch_release(&fbatch
);
1635 /* End of range already reached? */
1636 if (index
> end
|| !index
)
1640 EXPORT_SYMBOL(clean_bdev_aliases
);
1643 * Size is a power-of-two in the range 512..PAGE_SIZE,
1644 * and the case we care about most is PAGE_SIZE.
1646 * So this *could* possibly be written with those
1647 * constraints in mind (relevant mostly if some
1648 * architecture has a slow bit-scan instruction)
1650 static inline int block_size_bits(unsigned int blocksize
)
1652 return ilog2(blocksize
);
1655 static struct buffer_head
*create_page_buffers(struct page
*page
, struct inode
*inode
, unsigned int b_state
)
1657 BUG_ON(!PageLocked(page
));
1659 if (!page_has_buffers(page
))
1660 create_empty_buffers(page
, 1 << READ_ONCE(inode
->i_blkbits
),
1662 return page_buffers(page
);
1666 * NOTE! All mapped/uptodate combinations are valid:
1668 * Mapped Uptodate Meaning
1670 * No No "unknown" - must do get_block()
1671 * No Yes "hole" - zero-filled
1672 * Yes No "allocated" - allocated on disk, not read in
1673 * Yes Yes "valid" - allocated and up-to-date in memory.
1675 * "Dirty" is valid only with the last case (mapped+uptodate).
1679 * While block_write_full_page is writing back the dirty buffers under
1680 * the page lock, whoever dirtied the buffers may decide to clean them
1681 * again at any time. We handle that by only looking at the buffer
1682 * state inside lock_buffer().
1684 * If block_write_full_page() is called for regular writeback
1685 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1686 * locked buffer. This only can happen if someone has written the buffer
1687 * directly, with submit_bh(). At the address_space level PageWriteback
1688 * prevents this contention from occurring.
1690 * If block_write_full_page() is called with wbc->sync_mode ==
1691 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1692 * causes the writes to be flagged as synchronous writes.
1694 int __block_write_full_page(struct inode
*inode
, struct page
*page
,
1695 get_block_t
*get_block
, struct writeback_control
*wbc
,
1696 bh_end_io_t
*handler
)
1700 sector_t last_block
;
1701 struct buffer_head
*bh
, *head
;
1702 unsigned int blocksize
, bbits
;
1703 int nr_underway
= 0;
1704 blk_opf_t write_flags
= wbc_to_write_flags(wbc
);
1706 head
= create_page_buffers(page
, inode
,
1707 (1 << BH_Dirty
)|(1 << BH_Uptodate
));
1710 * Be very careful. We have no exclusion from block_dirty_folio
1711 * here, and the (potentially unmapped) buffers may become dirty at
1712 * any time. If a buffer becomes dirty here after we've inspected it
1713 * then we just miss that fact, and the page stays dirty.
1715 * Buffers outside i_size may be dirtied by block_dirty_folio;
1716 * handle that here by just cleaning them.
1720 blocksize
= bh
->b_size
;
1721 bbits
= block_size_bits(blocksize
);
1723 block
= (sector_t
)page
->index
<< (PAGE_SHIFT
- bbits
);
1724 last_block
= (i_size_read(inode
) - 1) >> bbits
;
1727 * Get all the dirty buffers mapped to disk addresses and
1728 * handle any aliases from the underlying blockdev's mapping.
1731 if (block
> last_block
) {
1733 * mapped buffers outside i_size will occur, because
1734 * this page can be outside i_size when there is a
1735 * truncate in progress.
1738 * The buffer was zeroed by block_write_full_page()
1740 clear_buffer_dirty(bh
);
1741 set_buffer_uptodate(bh
);
1742 } else if ((!buffer_mapped(bh
) || buffer_delay(bh
)) &&
1744 WARN_ON(bh
->b_size
!= blocksize
);
1745 err
= get_block(inode
, block
, bh
, 1);
1748 clear_buffer_delay(bh
);
1749 if (buffer_new(bh
)) {
1750 /* blockdev mappings never come here */
1751 clear_buffer_new(bh
);
1752 clean_bdev_bh_alias(bh
);
1755 bh
= bh
->b_this_page
;
1757 } while (bh
!= head
);
1760 if (!buffer_mapped(bh
))
1763 * If it's a fully non-blocking write attempt and we cannot
1764 * lock the buffer then redirty the page. Note that this can
1765 * potentially cause a busy-wait loop from writeback threads
1766 * and kswapd activity, but those code paths have their own
1767 * higher-level throttling.
1769 if (wbc
->sync_mode
!= WB_SYNC_NONE
) {
1771 } else if (!trylock_buffer(bh
)) {
1772 redirty_page_for_writepage(wbc
, page
);
1775 if (test_clear_buffer_dirty(bh
)) {
1776 mark_buffer_async_write_endio(bh
, handler
);
1780 } while ((bh
= bh
->b_this_page
) != head
);
1783 * The page and its buffers are protected by PageWriteback(), so we can
1784 * drop the bh refcounts early.
1786 BUG_ON(PageWriteback(page
));
1787 set_page_writeback(page
);
1790 struct buffer_head
*next
= bh
->b_this_page
;
1791 if (buffer_async_write(bh
)) {
1792 submit_bh_wbc(REQ_OP_WRITE
| write_flags
, bh
, wbc
);
1796 } while (bh
!= head
);
1801 if (nr_underway
== 0) {
1803 * The page was marked dirty, but the buffers were
1804 * clean. Someone wrote them back by hand with
1805 * write_dirty_buffer/submit_bh. A rare case.
1807 end_page_writeback(page
);
1810 * The page and buffer_heads can be released at any time from
1818 * ENOSPC, or some other error. We may already have added some
1819 * blocks to the file, so we need to write these out to avoid
1820 * exposing stale data.
1821 * The page is currently locked and not marked for writeback
1824 /* Recovery: lock and submit the mapped buffers */
1826 if (buffer_mapped(bh
) && buffer_dirty(bh
) &&
1827 !buffer_delay(bh
)) {
1829 mark_buffer_async_write_endio(bh
, handler
);
1832 * The buffer may have been set dirty during
1833 * attachment to a dirty page.
1835 clear_buffer_dirty(bh
);
1837 } while ((bh
= bh
->b_this_page
) != head
);
1839 BUG_ON(PageWriteback(page
));
1840 mapping_set_error(page
->mapping
, err
);
1841 set_page_writeback(page
);
1843 struct buffer_head
*next
= bh
->b_this_page
;
1844 if (buffer_async_write(bh
)) {
1845 clear_buffer_dirty(bh
);
1846 submit_bh_wbc(REQ_OP_WRITE
| write_flags
, bh
, wbc
);
1850 } while (bh
!= head
);
1854 EXPORT_SYMBOL(__block_write_full_page
);
1857 * If a page has any new buffers, zero them out here, and mark them uptodate
1858 * and dirty so they'll be written out (in order to prevent uninitialised
1859 * block data from leaking). And clear the new bit.
1861 void page_zero_new_buffers(struct page
*page
, unsigned from
, unsigned to
)
1863 unsigned int block_start
, block_end
;
1864 struct buffer_head
*head
, *bh
;
1866 BUG_ON(!PageLocked(page
));
1867 if (!page_has_buffers(page
))
1870 bh
= head
= page_buffers(page
);
1873 block_end
= block_start
+ bh
->b_size
;
1875 if (buffer_new(bh
)) {
1876 if (block_end
> from
&& block_start
< to
) {
1877 if (!PageUptodate(page
)) {
1878 unsigned start
, size
;
1880 start
= max(from
, block_start
);
1881 size
= min(to
, block_end
) - start
;
1883 zero_user(page
, start
, size
);
1884 set_buffer_uptodate(bh
);
1887 clear_buffer_new(bh
);
1888 mark_buffer_dirty(bh
);
1892 block_start
= block_end
;
1893 bh
= bh
->b_this_page
;
1894 } while (bh
!= head
);
1896 EXPORT_SYMBOL(page_zero_new_buffers
);
1899 iomap_to_bh(struct inode
*inode
, sector_t block
, struct buffer_head
*bh
,
1900 const struct iomap
*iomap
)
1902 loff_t offset
= block
<< inode
->i_blkbits
;
1904 bh
->b_bdev
= iomap
->bdev
;
1907 * Block points to offset in file we need to map, iomap contains
1908 * the offset at which the map starts. If the map ends before the
1909 * current block, then do not map the buffer and let the caller
1912 BUG_ON(offset
>= iomap
->offset
+ iomap
->length
);
1914 switch (iomap
->type
) {
1917 * If the buffer is not up to date or beyond the current EOF,
1918 * we need to mark it as new to ensure sub-block zeroing is
1919 * executed if necessary.
1921 if (!buffer_uptodate(bh
) ||
1922 (offset
>= i_size_read(inode
)))
1925 case IOMAP_DELALLOC
:
1926 if (!buffer_uptodate(bh
) ||
1927 (offset
>= i_size_read(inode
)))
1929 set_buffer_uptodate(bh
);
1930 set_buffer_mapped(bh
);
1931 set_buffer_delay(bh
);
1933 case IOMAP_UNWRITTEN
:
1935 * For unwritten regions, we always need to ensure that regions
1936 * in the block we are not writing to are zeroed. Mark the
1937 * buffer as new to ensure this.
1940 set_buffer_unwritten(bh
);
1943 if ((iomap
->flags
& IOMAP_F_NEW
) ||
1944 offset
>= i_size_read(inode
))
1946 bh
->b_blocknr
= (iomap
->addr
+ offset
- iomap
->offset
) >>
1948 set_buffer_mapped(bh
);
1953 int __block_write_begin_int(struct folio
*folio
, loff_t pos
, unsigned len
,
1954 get_block_t
*get_block
, const struct iomap
*iomap
)
1956 unsigned from
= pos
& (PAGE_SIZE
- 1);
1957 unsigned to
= from
+ len
;
1958 struct inode
*inode
= folio
->mapping
->host
;
1959 unsigned block_start
, block_end
;
1962 unsigned blocksize
, bbits
;
1963 struct buffer_head
*bh
, *head
, *wait
[2], **wait_bh
=wait
;
1965 BUG_ON(!folio_test_locked(folio
));
1966 BUG_ON(from
> PAGE_SIZE
);
1967 BUG_ON(to
> PAGE_SIZE
);
1970 head
= create_page_buffers(&folio
->page
, inode
, 0);
1971 blocksize
= head
->b_size
;
1972 bbits
= block_size_bits(blocksize
);
1974 block
= (sector_t
)folio
->index
<< (PAGE_SHIFT
- bbits
);
1976 for(bh
= head
, block_start
= 0; bh
!= head
|| !block_start
;
1977 block
++, block_start
=block_end
, bh
= bh
->b_this_page
) {
1978 block_end
= block_start
+ blocksize
;
1979 if (block_end
<= from
|| block_start
>= to
) {
1980 if (folio_test_uptodate(folio
)) {
1981 if (!buffer_uptodate(bh
))
1982 set_buffer_uptodate(bh
);
1987 clear_buffer_new(bh
);
1988 if (!buffer_mapped(bh
)) {
1989 WARN_ON(bh
->b_size
!= blocksize
);
1991 err
= get_block(inode
, block
, bh
, 1);
1995 iomap_to_bh(inode
, block
, bh
, iomap
);
1998 if (buffer_new(bh
)) {
1999 clean_bdev_bh_alias(bh
);
2000 if (folio_test_uptodate(folio
)) {
2001 clear_buffer_new(bh
);
2002 set_buffer_uptodate(bh
);
2003 mark_buffer_dirty(bh
);
2006 if (block_end
> to
|| block_start
< from
)
2007 folio_zero_segments(folio
,
2013 if (folio_test_uptodate(folio
)) {
2014 if (!buffer_uptodate(bh
))
2015 set_buffer_uptodate(bh
);
2018 if (!buffer_uptodate(bh
) && !buffer_delay(bh
) &&
2019 !buffer_unwritten(bh
) &&
2020 (block_start
< from
|| block_end
> to
)) {
2021 bh_read_nowait(bh
, 0);
2026 * If we issued read requests - let them complete.
2028 while(wait_bh
> wait
) {
2029 wait_on_buffer(*--wait_bh
);
2030 if (!buffer_uptodate(*wait_bh
))
2034 page_zero_new_buffers(&folio
->page
, from
, to
);
2038 int __block_write_begin(struct page
*page
, loff_t pos
, unsigned len
,
2039 get_block_t
*get_block
)
2041 return __block_write_begin_int(page_folio(page
), pos
, len
, get_block
,
2044 EXPORT_SYMBOL(__block_write_begin
);
2046 static int __block_commit_write(struct inode
*inode
, struct page
*page
,
2047 unsigned from
, unsigned to
)
2049 unsigned block_start
, block_end
;
2052 struct buffer_head
*bh
, *head
;
2054 bh
= head
= page_buffers(page
);
2055 blocksize
= bh
->b_size
;
2059 block_end
= block_start
+ blocksize
;
2060 if (block_end
<= from
|| block_start
>= to
) {
2061 if (!buffer_uptodate(bh
))
2064 set_buffer_uptodate(bh
);
2065 mark_buffer_dirty(bh
);
2068 clear_buffer_new(bh
);
2070 block_start
= block_end
;
2071 bh
= bh
->b_this_page
;
2072 } while (bh
!= head
);
2075 * If this is a partial write which happened to make all buffers
2076 * uptodate then we can optimize away a bogus read_folio() for
2077 * the next read(). Here we 'discover' whether the page went
2078 * uptodate as a result of this (potentially partial) write.
2081 SetPageUptodate(page
);
2086 * block_write_begin takes care of the basic task of block allocation and
2087 * bringing partial write blocks uptodate first.
2089 * The filesystem needs to handle block truncation upon failure.
2091 int block_write_begin(struct address_space
*mapping
, loff_t pos
, unsigned len
,
2092 struct page
**pagep
, get_block_t
*get_block
)
2094 pgoff_t index
= pos
>> PAGE_SHIFT
;
2098 page
= grab_cache_page_write_begin(mapping
, index
);
2102 status
= __block_write_begin(page
, pos
, len
, get_block
);
2103 if (unlikely(status
)) {
2112 EXPORT_SYMBOL(block_write_begin
);
2114 int block_write_end(struct file
*file
, struct address_space
*mapping
,
2115 loff_t pos
, unsigned len
, unsigned copied
,
2116 struct page
*page
, void *fsdata
)
2118 struct inode
*inode
= mapping
->host
;
2121 start
= pos
& (PAGE_SIZE
- 1);
2123 if (unlikely(copied
< len
)) {
2125 * The buffers that were written will now be uptodate, so
2126 * we don't have to worry about a read_folio reading them
2127 * and overwriting a partial write. However if we have
2128 * encountered a short write and only partially written
2129 * into a buffer, it will not be marked uptodate, so a
2130 * read_folio might come in and destroy our partial write.
2132 * Do the simplest thing, and just treat any short write to a
2133 * non uptodate page as a zero-length write, and force the
2134 * caller to redo the whole thing.
2136 if (!PageUptodate(page
))
2139 page_zero_new_buffers(page
, start
+copied
, start
+len
);
2141 flush_dcache_page(page
);
2143 /* This could be a short (even 0-length) commit */
2144 __block_commit_write(inode
, page
, start
, start
+copied
);
2148 EXPORT_SYMBOL(block_write_end
);
2150 int generic_write_end(struct file
*file
, struct address_space
*mapping
,
2151 loff_t pos
, unsigned len
, unsigned copied
,
2152 struct page
*page
, void *fsdata
)
2154 struct inode
*inode
= mapping
->host
;
2155 loff_t old_size
= inode
->i_size
;
2156 bool i_size_changed
= false;
2158 copied
= block_write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2161 * No need to use i_size_read() here, the i_size cannot change under us
2162 * because we hold i_rwsem.
2164 * But it's important to update i_size while still holding page lock:
2165 * page writeout could otherwise come in and zero beyond i_size.
2167 if (pos
+ copied
> inode
->i_size
) {
2168 i_size_write(inode
, pos
+ copied
);
2169 i_size_changed
= true;
2176 pagecache_isize_extended(inode
, old_size
, pos
);
2178 * Don't mark the inode dirty under page lock. First, it unnecessarily
2179 * makes the holding time of page lock longer. Second, it forces lock
2180 * ordering of page lock and transaction start for journaling
2184 mark_inode_dirty(inode
);
2187 EXPORT_SYMBOL(generic_write_end
);
2190 * block_is_partially_uptodate checks whether buffers within a folio are
2193 * Returns true if all buffers which correspond to the specified part
2194 * of the folio are uptodate.
2196 bool block_is_partially_uptodate(struct folio
*folio
, size_t from
, size_t count
)
2198 unsigned block_start
, block_end
, blocksize
;
2200 struct buffer_head
*bh
, *head
;
2203 head
= folio_buffers(folio
);
2206 blocksize
= head
->b_size
;
2207 to
= min_t(unsigned, folio_size(folio
) - from
, count
);
2209 if (from
< blocksize
&& to
> folio_size(folio
) - blocksize
)
2215 block_end
= block_start
+ blocksize
;
2216 if (block_end
> from
&& block_start
< to
) {
2217 if (!buffer_uptodate(bh
)) {
2221 if (block_end
>= to
)
2224 block_start
= block_end
;
2225 bh
= bh
->b_this_page
;
2226 } while (bh
!= head
);
2230 EXPORT_SYMBOL(block_is_partially_uptodate
);
2233 * Generic "read_folio" function for block devices that have the normal
2234 * get_block functionality. This is most of the block device filesystems.
2235 * Reads the folio asynchronously --- the unlock_buffer() and
2236 * set/clear_buffer_uptodate() functions propagate buffer state into the
2237 * folio once IO has completed.
2239 int block_read_full_folio(struct folio
*folio
, get_block_t
*get_block
)
2241 struct inode
*inode
= folio
->mapping
->host
;
2242 sector_t iblock
, lblock
;
2243 struct buffer_head
*bh
, *head
, *arr
[MAX_BUF_PER_PAGE
];
2244 unsigned int blocksize
, bbits
;
2246 int fully_mapped
= 1;
2247 bool page_error
= false;
2249 VM_BUG_ON_FOLIO(folio_test_large(folio
), folio
);
2251 head
= create_page_buffers(&folio
->page
, inode
, 0);
2252 blocksize
= head
->b_size
;
2253 bbits
= block_size_bits(blocksize
);
2255 iblock
= (sector_t
)folio
->index
<< (PAGE_SHIFT
- bbits
);
2256 lblock
= (i_size_read(inode
)+blocksize
-1) >> bbits
;
2262 if (buffer_uptodate(bh
))
2265 if (!buffer_mapped(bh
)) {
2269 if (iblock
< lblock
) {
2270 WARN_ON(bh
->b_size
!= blocksize
);
2271 err
= get_block(inode
, iblock
, bh
, 0);
2273 folio_set_error(folio
);
2277 if (!buffer_mapped(bh
)) {
2278 folio_zero_range(folio
, i
* blocksize
,
2281 set_buffer_uptodate(bh
);
2285 * get_block() might have updated the buffer
2288 if (buffer_uptodate(bh
))
2292 } while (i
++, iblock
++, (bh
= bh
->b_this_page
) != head
);
2295 folio_set_mappedtodisk(folio
);
2299 * All buffers are uptodate - we can set the folio uptodate
2300 * as well. But not if get_block() returned an error.
2303 folio_mark_uptodate(folio
);
2304 folio_unlock(folio
);
2308 /* Stage two: lock the buffers */
2309 for (i
= 0; i
< nr
; i
++) {
2312 mark_buffer_async_read(bh
);
2316 * Stage 3: start the IO. Check for uptodateness
2317 * inside the buffer lock in case another process reading
2318 * the underlying blockdev brought it uptodate (the sct fix).
2320 for (i
= 0; i
< nr
; i
++) {
2322 if (buffer_uptodate(bh
))
2323 end_buffer_async_read(bh
, 1);
2325 submit_bh(REQ_OP_READ
, bh
);
2329 EXPORT_SYMBOL(block_read_full_folio
);
2331 /* utility function for filesystems that need to do work on expanding
2332 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2333 * deal with the hole.
2335 int generic_cont_expand_simple(struct inode
*inode
, loff_t size
)
2337 struct address_space
*mapping
= inode
->i_mapping
;
2338 const struct address_space_operations
*aops
= mapping
->a_ops
;
2340 void *fsdata
= NULL
;
2343 err
= inode_newsize_ok(inode
, size
);
2347 err
= aops
->write_begin(NULL
, mapping
, size
, 0, &page
, &fsdata
);
2351 err
= aops
->write_end(NULL
, mapping
, size
, 0, 0, page
, fsdata
);
2357 EXPORT_SYMBOL(generic_cont_expand_simple
);
2359 static int cont_expand_zero(struct file
*file
, struct address_space
*mapping
,
2360 loff_t pos
, loff_t
*bytes
)
2362 struct inode
*inode
= mapping
->host
;
2363 const struct address_space_operations
*aops
= mapping
->a_ops
;
2364 unsigned int blocksize
= i_blocksize(inode
);
2366 void *fsdata
= NULL
;
2367 pgoff_t index
, curidx
;
2369 unsigned zerofrom
, offset
, len
;
2372 index
= pos
>> PAGE_SHIFT
;
2373 offset
= pos
& ~PAGE_MASK
;
2375 while (index
> (curidx
= (curpos
= *bytes
)>>PAGE_SHIFT
)) {
2376 zerofrom
= curpos
& ~PAGE_MASK
;
2377 if (zerofrom
& (blocksize
-1)) {
2378 *bytes
|= (blocksize
-1);
2381 len
= PAGE_SIZE
- zerofrom
;
2383 err
= aops
->write_begin(file
, mapping
, curpos
, len
,
2387 zero_user(page
, zerofrom
, len
);
2388 err
= aops
->write_end(file
, mapping
, curpos
, len
, len
,
2395 balance_dirty_pages_ratelimited(mapping
);
2397 if (fatal_signal_pending(current
)) {
2403 /* page covers the boundary, find the boundary offset */
2404 if (index
== curidx
) {
2405 zerofrom
= curpos
& ~PAGE_MASK
;
2406 /* if we will expand the thing last block will be filled */
2407 if (offset
<= zerofrom
) {
2410 if (zerofrom
& (blocksize
-1)) {
2411 *bytes
|= (blocksize
-1);
2414 len
= offset
- zerofrom
;
2416 err
= aops
->write_begin(file
, mapping
, curpos
, len
,
2420 zero_user(page
, zerofrom
, len
);
2421 err
= aops
->write_end(file
, mapping
, curpos
, len
, len
,
2433 * For moronic filesystems that do not allow holes in file.
2434 * We may have to extend the file.
2436 int cont_write_begin(struct file
*file
, struct address_space
*mapping
,
2437 loff_t pos
, unsigned len
,
2438 struct page
**pagep
, void **fsdata
,
2439 get_block_t
*get_block
, loff_t
*bytes
)
2441 struct inode
*inode
= mapping
->host
;
2442 unsigned int blocksize
= i_blocksize(inode
);
2443 unsigned int zerofrom
;
2446 err
= cont_expand_zero(file
, mapping
, pos
, bytes
);
2450 zerofrom
= *bytes
& ~PAGE_MASK
;
2451 if (pos
+len
> *bytes
&& zerofrom
& (blocksize
-1)) {
2452 *bytes
|= (blocksize
-1);
2456 return block_write_begin(mapping
, pos
, len
, pagep
, get_block
);
2458 EXPORT_SYMBOL(cont_write_begin
);
2460 int block_commit_write(struct page
*page
, unsigned from
, unsigned to
)
2462 struct inode
*inode
= page
->mapping
->host
;
2463 __block_commit_write(inode
,page
,from
,to
);
2466 EXPORT_SYMBOL(block_commit_write
);
2469 * block_page_mkwrite() is not allowed to change the file size as it gets
2470 * called from a page fault handler when a page is first dirtied. Hence we must
2471 * be careful to check for EOF conditions here. We set the page up correctly
2472 * for a written page which means we get ENOSPC checking when writing into
2473 * holes and correct delalloc and unwritten extent mapping on filesystems that
2474 * support these features.
2476 * We are not allowed to take the i_mutex here so we have to play games to
2477 * protect against truncate races as the page could now be beyond EOF. Because
2478 * truncate writes the inode size before removing pages, once we have the
2479 * page lock we can determine safely if the page is beyond EOF. If it is not
2480 * beyond EOF, then the page is guaranteed safe against truncation until we
2483 * Direct callers of this function should protect against filesystem freezing
2484 * using sb_start_pagefault() - sb_end_pagefault() functions.
2486 int block_page_mkwrite(struct vm_area_struct
*vma
, struct vm_fault
*vmf
,
2487 get_block_t get_block
)
2489 struct page
*page
= vmf
->page
;
2490 struct inode
*inode
= file_inode(vma
->vm_file
);
2496 size
= i_size_read(inode
);
2497 if ((page
->mapping
!= inode
->i_mapping
) ||
2498 (page_offset(page
) > size
)) {
2499 /* We overload EFAULT to mean page got truncated */
2504 /* page is wholly or partially inside EOF */
2505 if (((page
->index
+ 1) << PAGE_SHIFT
) > size
)
2506 end
= size
& ~PAGE_MASK
;
2510 ret
= __block_write_begin(page
, 0, end
, get_block
);
2512 ret
= block_commit_write(page
, 0, end
);
2514 if (unlikely(ret
< 0))
2516 set_page_dirty(page
);
2517 wait_for_stable_page(page
);
2523 EXPORT_SYMBOL(block_page_mkwrite
);
2525 int block_truncate_page(struct address_space
*mapping
,
2526 loff_t from
, get_block_t
*get_block
)
2528 pgoff_t index
= from
>> PAGE_SHIFT
;
2529 unsigned offset
= from
& (PAGE_SIZE
-1);
2532 unsigned length
, pos
;
2533 struct inode
*inode
= mapping
->host
;
2535 struct buffer_head
*bh
;
2538 blocksize
= i_blocksize(inode
);
2539 length
= offset
& (blocksize
- 1);
2541 /* Block boundary? Nothing to do */
2545 length
= blocksize
- length
;
2546 iblock
= (sector_t
)index
<< (PAGE_SHIFT
- inode
->i_blkbits
);
2548 page
= grab_cache_page(mapping
, index
);
2553 if (!page_has_buffers(page
))
2554 create_empty_buffers(page
, blocksize
, 0);
2556 /* Find the buffer that contains "offset" */
2557 bh
= page_buffers(page
);
2559 while (offset
>= pos
) {
2560 bh
= bh
->b_this_page
;
2566 if (!buffer_mapped(bh
)) {
2567 WARN_ON(bh
->b_size
!= blocksize
);
2568 err
= get_block(inode
, iblock
, bh
, 0);
2571 /* unmapped? It's a hole - nothing to do */
2572 if (!buffer_mapped(bh
))
2576 /* Ok, it's mapped. Make sure it's up-to-date */
2577 if (PageUptodate(page
))
2578 set_buffer_uptodate(bh
);
2580 if (!buffer_uptodate(bh
) && !buffer_delay(bh
) && !buffer_unwritten(bh
)) {
2581 err
= bh_read(bh
, 0);
2582 /* Uhhuh. Read error. Complain and punt. */
2587 zero_user(page
, offset
, length
);
2588 mark_buffer_dirty(bh
);
2597 EXPORT_SYMBOL(block_truncate_page
);
2600 * The generic ->writepage function for buffer-backed address_spaces
2602 int block_write_full_page(struct page
*page
, get_block_t
*get_block
,
2603 struct writeback_control
*wbc
)
2605 struct inode
* const inode
= page
->mapping
->host
;
2606 loff_t i_size
= i_size_read(inode
);
2607 const pgoff_t end_index
= i_size
>> PAGE_SHIFT
;
2610 /* Is the page fully inside i_size? */
2611 if (page
->index
< end_index
)
2612 return __block_write_full_page(inode
, page
, get_block
, wbc
,
2613 end_buffer_async_write
);
2615 /* Is the page fully outside i_size? (truncate in progress) */
2616 offset
= i_size
& (PAGE_SIZE
-1);
2617 if (page
->index
>= end_index
+1 || !offset
) {
2619 return 0; /* don't care */
2623 * The page straddles i_size. It must be zeroed out on each and every
2624 * writepage invocation because it may be mmapped. "A file is mapped
2625 * in multiples of the page size. For a file that is not a multiple of
2626 * the page size, the remaining memory is zeroed when mapped, and
2627 * writes to that region are not written out to the file."
2629 zero_user_segment(page
, offset
, PAGE_SIZE
);
2630 return __block_write_full_page(inode
, page
, get_block
, wbc
,
2631 end_buffer_async_write
);
2633 EXPORT_SYMBOL(block_write_full_page
);
2635 sector_t
generic_block_bmap(struct address_space
*mapping
, sector_t block
,
2636 get_block_t
*get_block
)
2638 struct inode
*inode
= mapping
->host
;
2639 struct buffer_head tmp
= {
2640 .b_size
= i_blocksize(inode
),
2643 get_block(inode
, block
, &tmp
, 0);
2644 return tmp
.b_blocknr
;
2646 EXPORT_SYMBOL(generic_block_bmap
);
2648 static void end_bio_bh_io_sync(struct bio
*bio
)
2650 struct buffer_head
*bh
= bio
->bi_private
;
2652 if (unlikely(bio_flagged(bio
, BIO_QUIET
)))
2653 set_bit(BH_Quiet
, &bh
->b_state
);
2655 bh
->b_end_io(bh
, !bio
->bi_status
);
2659 static void submit_bh_wbc(blk_opf_t opf
, struct buffer_head
*bh
,
2660 struct writeback_control
*wbc
)
2662 const enum req_op op
= opf
& REQ_OP_MASK
;
2665 BUG_ON(!buffer_locked(bh
));
2666 BUG_ON(!buffer_mapped(bh
));
2667 BUG_ON(!bh
->b_end_io
);
2668 BUG_ON(buffer_delay(bh
));
2669 BUG_ON(buffer_unwritten(bh
));
2672 * Only clear out a write error when rewriting
2674 if (test_set_buffer_req(bh
) && (op
== REQ_OP_WRITE
))
2675 clear_buffer_write_io_error(bh
);
2677 if (buffer_meta(bh
))
2679 if (buffer_prio(bh
))
2682 bio
= bio_alloc(bh
->b_bdev
, 1, opf
, GFP_NOIO
);
2684 fscrypt_set_bio_crypt_ctx_bh(bio
, bh
, GFP_NOIO
);
2686 bio
->bi_iter
.bi_sector
= bh
->b_blocknr
* (bh
->b_size
>> 9);
2688 bio_add_page(bio
, bh
->b_page
, bh
->b_size
, bh_offset(bh
));
2689 BUG_ON(bio
->bi_iter
.bi_size
!= bh
->b_size
);
2691 bio
->bi_end_io
= end_bio_bh_io_sync
;
2692 bio
->bi_private
= bh
;
2694 /* Take care of bh's that straddle the end of the device */
2698 wbc_init_bio(wbc
, bio
);
2699 wbc_account_cgroup_owner(wbc
, bh
->b_page
, bh
->b_size
);
2705 void submit_bh(blk_opf_t opf
, struct buffer_head
*bh
)
2707 submit_bh_wbc(opf
, bh
, NULL
);
2709 EXPORT_SYMBOL(submit_bh
);
2711 void write_dirty_buffer(struct buffer_head
*bh
, blk_opf_t op_flags
)
2714 if (!test_clear_buffer_dirty(bh
)) {
2718 bh
->b_end_io
= end_buffer_write_sync
;
2720 submit_bh(REQ_OP_WRITE
| op_flags
, bh
);
2722 EXPORT_SYMBOL(write_dirty_buffer
);
2725 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2726 * and then start new I/O and then wait upon it. The caller must have a ref on
2729 int __sync_dirty_buffer(struct buffer_head
*bh
, blk_opf_t op_flags
)
2731 WARN_ON(atomic_read(&bh
->b_count
) < 1);
2733 if (test_clear_buffer_dirty(bh
)) {
2735 * The bh should be mapped, but it might not be if the
2736 * device was hot-removed. Not much we can do but fail the I/O.
2738 if (!buffer_mapped(bh
)) {
2744 bh
->b_end_io
= end_buffer_write_sync
;
2745 submit_bh(REQ_OP_WRITE
| op_flags
, bh
);
2747 if (!buffer_uptodate(bh
))
2754 EXPORT_SYMBOL(__sync_dirty_buffer
);
2756 int sync_dirty_buffer(struct buffer_head
*bh
)
2758 return __sync_dirty_buffer(bh
, REQ_SYNC
);
2760 EXPORT_SYMBOL(sync_dirty_buffer
);
2763 * try_to_free_buffers() checks if all the buffers on this particular folio
2764 * are unused, and releases them if so.
2766 * Exclusion against try_to_free_buffers may be obtained by either
2767 * locking the folio or by holding its mapping's private_lock.
2769 * If the folio is dirty but all the buffers are clean then we need to
2770 * be sure to mark the folio clean as well. This is because the folio
2771 * may be against a block device, and a later reattachment of buffers
2772 * to a dirty folio will set *all* buffers dirty. Which would corrupt
2773 * filesystem data on the same device.
2775 * The same applies to regular filesystem folios: if all the buffers are
2776 * clean then we set the folio clean and proceed. To do that, we require
2777 * total exclusion from block_dirty_folio(). That is obtained with
2780 * try_to_free_buffers() is non-blocking.
2782 static inline int buffer_busy(struct buffer_head
*bh
)
2784 return atomic_read(&bh
->b_count
) |
2785 (bh
->b_state
& ((1 << BH_Dirty
) | (1 << BH_Lock
)));
2789 drop_buffers(struct folio
*folio
, struct buffer_head
**buffers_to_free
)
2791 struct buffer_head
*head
= folio_buffers(folio
);
2792 struct buffer_head
*bh
;
2796 if (buffer_busy(bh
))
2798 bh
= bh
->b_this_page
;
2799 } while (bh
!= head
);
2802 struct buffer_head
*next
= bh
->b_this_page
;
2804 if (bh
->b_assoc_map
)
2805 __remove_assoc_queue(bh
);
2807 } while (bh
!= head
);
2808 *buffers_to_free
= head
;
2809 folio_detach_private(folio
);
2815 bool try_to_free_buffers(struct folio
*folio
)
2817 struct address_space
* const mapping
= folio
->mapping
;
2818 struct buffer_head
*buffers_to_free
= NULL
;
2821 BUG_ON(!folio_test_locked(folio
));
2822 if (folio_test_writeback(folio
))
2825 if (mapping
== NULL
) { /* can this still happen? */
2826 ret
= drop_buffers(folio
, &buffers_to_free
);
2830 spin_lock(&mapping
->private_lock
);
2831 ret
= drop_buffers(folio
, &buffers_to_free
);
2834 * If the filesystem writes its buffers by hand (eg ext3)
2835 * then we can have clean buffers against a dirty folio. We
2836 * clean the folio here; otherwise the VM will never notice
2837 * that the filesystem did any IO at all.
2839 * Also, during truncate, discard_buffer will have marked all
2840 * the folio's buffers clean. We discover that here and clean
2843 * private_lock must be held over this entire operation in order
2844 * to synchronise against block_dirty_folio and prevent the
2845 * dirty bit from being lost.
2848 folio_cancel_dirty(folio
);
2849 spin_unlock(&mapping
->private_lock
);
2851 if (buffers_to_free
) {
2852 struct buffer_head
*bh
= buffers_to_free
;
2855 struct buffer_head
*next
= bh
->b_this_page
;
2856 free_buffer_head(bh
);
2858 } while (bh
!= buffers_to_free
);
2862 EXPORT_SYMBOL(try_to_free_buffers
);
2865 * Buffer-head allocation
2867 static struct kmem_cache
*bh_cachep __read_mostly
;
2870 * Once the number of bh's in the machine exceeds this level, we start
2871 * stripping them in writeback.
2873 static unsigned long max_buffer_heads
;
2875 int buffer_heads_over_limit
;
2877 struct bh_accounting
{
2878 int nr
; /* Number of live bh's */
2879 int ratelimit
; /* Limit cacheline bouncing */
2882 static DEFINE_PER_CPU(struct bh_accounting
, bh_accounting
) = {0, 0};
2884 static void recalc_bh_state(void)
2889 if (__this_cpu_inc_return(bh_accounting
.ratelimit
) - 1 < 4096)
2891 __this_cpu_write(bh_accounting
.ratelimit
, 0);
2892 for_each_online_cpu(i
)
2893 tot
+= per_cpu(bh_accounting
, i
).nr
;
2894 buffer_heads_over_limit
= (tot
> max_buffer_heads
);
2897 struct buffer_head
*alloc_buffer_head(gfp_t gfp_flags
)
2899 struct buffer_head
*ret
= kmem_cache_zalloc(bh_cachep
, gfp_flags
);
2901 INIT_LIST_HEAD(&ret
->b_assoc_buffers
);
2902 spin_lock_init(&ret
->b_uptodate_lock
);
2904 __this_cpu_inc(bh_accounting
.nr
);
2910 EXPORT_SYMBOL(alloc_buffer_head
);
2912 void free_buffer_head(struct buffer_head
*bh
)
2914 BUG_ON(!list_empty(&bh
->b_assoc_buffers
));
2915 kmem_cache_free(bh_cachep
, bh
);
2917 __this_cpu_dec(bh_accounting
.nr
);
2921 EXPORT_SYMBOL(free_buffer_head
);
2923 static int buffer_exit_cpu_dead(unsigned int cpu
)
2926 struct bh_lru
*b
= &per_cpu(bh_lrus
, cpu
);
2928 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
2932 this_cpu_add(bh_accounting
.nr
, per_cpu(bh_accounting
, cpu
).nr
);
2933 per_cpu(bh_accounting
, cpu
).nr
= 0;
2938 * bh_uptodate_or_lock - Test whether the buffer is uptodate
2939 * @bh: struct buffer_head
2941 * Return true if the buffer is up-to-date and false,
2942 * with the buffer locked, if not.
2944 int bh_uptodate_or_lock(struct buffer_head
*bh
)
2946 if (!buffer_uptodate(bh
)) {
2948 if (!buffer_uptodate(bh
))
2954 EXPORT_SYMBOL(bh_uptodate_or_lock
);
2957 * __bh_read - Submit read for a locked buffer
2958 * @bh: struct buffer_head
2959 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
2960 * @wait: wait until reading finish
2962 * Returns zero on success or don't wait, and -EIO on error.
2964 int __bh_read(struct buffer_head
*bh
, blk_opf_t op_flags
, bool wait
)
2968 BUG_ON(!buffer_locked(bh
));
2971 bh
->b_end_io
= end_buffer_read_sync
;
2972 submit_bh(REQ_OP_READ
| op_flags
, bh
);
2975 if (!buffer_uptodate(bh
))
2980 EXPORT_SYMBOL(__bh_read
);
2983 * __bh_read_batch - Submit read for a batch of unlocked buffers
2984 * @nr: entry number of the buffer batch
2985 * @bhs: a batch of struct buffer_head
2986 * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
2987 * @force_lock: force to get a lock on the buffer if set, otherwise drops any
2988 * buffer that cannot lock.
2990 * Returns zero on success or don't wait, and -EIO on error.
2992 void __bh_read_batch(int nr
, struct buffer_head
*bhs
[],
2993 blk_opf_t op_flags
, bool force_lock
)
2997 for (i
= 0; i
< nr
; i
++) {
2998 struct buffer_head
*bh
= bhs
[i
];
3000 if (buffer_uptodate(bh
))
3006 if (!trylock_buffer(bh
))
3009 if (buffer_uptodate(bh
)) {
3014 bh
->b_end_io
= end_buffer_read_sync
;
3016 submit_bh(REQ_OP_READ
| op_flags
, bh
);
3019 EXPORT_SYMBOL(__bh_read_batch
);
3021 void __init
buffer_init(void)
3023 unsigned long nrpages
;
3026 bh_cachep
= kmem_cache_create("buffer_head",
3027 sizeof(struct buffer_head
), 0,
3028 (SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|
3033 * Limit the bh occupancy to 10% of ZONE_NORMAL
3035 nrpages
= (nr_free_buffer_pages() * 10) / 100;
3036 max_buffer_heads
= nrpages
* (PAGE_SIZE
/ sizeof(struct buffer_head
));
3037 ret
= cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD
, "fs/buffer:dead",
3038 NULL
, buffer_exit_cpu_dead
);