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 int submit_bh_wbc(int op
, int op_flags
, struct buffer_head
*bh
,
56 enum rw_hint hint
, 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 page has dirty or writeback buffers. If all the buffers
83 * are unlocked and clean then the PageDirty information is stale. If
84 * any of the pages are locked, it is assumed they are locked for IO.
86 void buffer_check_dirty_writeback(struct page
*page
,
87 bool *dirty
, bool *writeback
)
89 struct buffer_head
*head
, *bh
;
93 BUG_ON(!PageLocked(page
));
95 if (!page_has_buffers(page
))
98 if (PageWriteback(page
))
101 head
= page_buffers(page
);
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
155 * unlock the buffer. This is what ll_rw_block uses too.
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 none of the buffers had errors and they are all
286 * uptodate then we can set the page uptodate.
288 if (page_uptodate
&& !PageError(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_page() - 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 ll_rw_block as
495 * you dirty the buffers, and then use osync_inode_buffers to wait for
496 * completion. Any other dirty buffers which are not yet queued for
497 * write will not be flushed to disk by the osync.
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 ll_rw_block(REQ_OP_WRITE
, 0, 1, &bh
);
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 int __set_page_dirty_buffers(struct page
*page
)
619 struct address_space
*mapping
= page_mapping(page
);
621 if (unlikely(!mapping
))
622 return !TestSetPageDirty(page
);
624 spin_lock(&mapping
->private_lock
);
625 if (page_has_buffers(page
)) {
626 struct buffer_head
*head
= page_buffers(page
);
627 struct buffer_head
*bh
= head
;
630 set_buffer_dirty(bh
);
631 bh
= bh
->b_this_page
;
632 } while (bh
!= head
);
635 * Lock out page's memcg migration to keep PageDirty
636 * synchronized with per-memcg dirty page counters.
638 lock_page_memcg(page
);
639 newly_dirty
= !TestSetPageDirty(page
);
640 spin_unlock(&mapping
->private_lock
);
643 __set_page_dirty(page
, mapping
, 1);
645 unlock_page_memcg(page
);
648 __mark_inode_dirty(mapping
->host
, I_DIRTY_PAGES
);
652 EXPORT_SYMBOL(__set_page_dirty_buffers
);
655 * Write out and wait upon a list of buffers.
657 * We have conflicting pressures: we want to make sure that all
658 * initially dirty buffers get waited on, but that any subsequently
659 * dirtied buffers don't. After all, we don't want fsync to last
660 * forever if somebody is actively writing to the file.
662 * Do this in two main stages: first we copy dirty buffers to a
663 * temporary inode list, queueing the writes as we go. Then we clean
664 * up, waiting for those writes to complete.
666 * During this second stage, any subsequent updates to the file may end
667 * up refiling the buffer on the original inode's dirty list again, so
668 * there is a chance we will end up with a buffer queued for write but
669 * not yet completed on that list. So, as a final cleanup we go through
670 * the osync code to catch these locked, dirty buffers without requeuing
671 * any newly dirty buffers for write.
673 static int fsync_buffers_list(spinlock_t
*lock
, struct list_head
*list
)
675 struct buffer_head
*bh
;
676 struct list_head tmp
;
677 struct address_space
*mapping
;
679 struct blk_plug plug
;
681 INIT_LIST_HEAD(&tmp
);
682 blk_start_plug(&plug
);
685 while (!list_empty(list
)) {
686 bh
= BH_ENTRY(list
->next
);
687 mapping
= bh
->b_assoc_map
;
688 __remove_assoc_queue(bh
);
689 /* Avoid race with mark_buffer_dirty_inode() which does
690 * a lockless check and we rely on seeing the dirty bit */
692 if (buffer_dirty(bh
) || buffer_locked(bh
)) {
693 list_add(&bh
->b_assoc_buffers
, &tmp
);
694 bh
->b_assoc_map
= mapping
;
695 if (buffer_dirty(bh
)) {
699 * Ensure any pending I/O completes so that
700 * write_dirty_buffer() actually writes the
701 * current contents - it is a noop if I/O is
702 * still in flight on potentially older
705 write_dirty_buffer(bh
, REQ_SYNC
);
708 * Kick off IO for the previous mapping. Note
709 * that we will not run the very last mapping,
710 * wait_on_buffer() will do that for us
711 * through sync_buffer().
720 blk_finish_plug(&plug
);
723 while (!list_empty(&tmp
)) {
724 bh
= BH_ENTRY(tmp
.prev
);
726 mapping
= bh
->b_assoc_map
;
727 __remove_assoc_queue(bh
);
728 /* Avoid race with mark_buffer_dirty_inode() which does
729 * a lockless check and we rely on seeing the dirty bit */
731 if (buffer_dirty(bh
)) {
732 list_add(&bh
->b_assoc_buffers
,
733 &mapping
->private_list
);
734 bh
->b_assoc_map
= mapping
;
738 if (!buffer_uptodate(bh
))
745 err2
= osync_buffers_list(lock
, list
);
753 * Invalidate any and all dirty buffers on a given inode. We are
754 * probably unmounting the fs, but that doesn't mean we have already
755 * done a sync(). Just drop the buffers from the inode list.
757 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
758 * assumes that all the buffers are against the blockdev. Not true
761 void invalidate_inode_buffers(struct inode
*inode
)
763 if (inode_has_buffers(inode
)) {
764 struct address_space
*mapping
= &inode
->i_data
;
765 struct list_head
*list
= &mapping
->private_list
;
766 struct address_space
*buffer_mapping
= mapping
->private_data
;
768 spin_lock(&buffer_mapping
->private_lock
);
769 while (!list_empty(list
))
770 __remove_assoc_queue(BH_ENTRY(list
->next
));
771 spin_unlock(&buffer_mapping
->private_lock
);
774 EXPORT_SYMBOL(invalidate_inode_buffers
);
777 * Remove any clean buffers from the inode's buffer list. This is called
778 * when we're trying to free the inode itself. Those buffers can pin it.
780 * Returns true if all buffers were removed.
782 int remove_inode_buffers(struct inode
*inode
)
786 if (inode_has_buffers(inode
)) {
787 struct address_space
*mapping
= &inode
->i_data
;
788 struct list_head
*list
= &mapping
->private_list
;
789 struct address_space
*buffer_mapping
= mapping
->private_data
;
791 spin_lock(&buffer_mapping
->private_lock
);
792 while (!list_empty(list
)) {
793 struct buffer_head
*bh
= BH_ENTRY(list
->next
);
794 if (buffer_dirty(bh
)) {
798 __remove_assoc_queue(bh
);
800 spin_unlock(&buffer_mapping
->private_lock
);
806 * Create the appropriate buffers when given a page for data area and
807 * the size of each buffer.. Use the bh->b_this_page linked list to
808 * follow the buffers created. Return NULL if unable to create more
811 * The retry flag is used to differentiate async IO (paging, swapping)
812 * which may not fail from ordinary buffer allocations.
814 struct buffer_head
*alloc_page_buffers(struct page
*page
, unsigned long size
,
817 struct buffer_head
*bh
, *head
;
818 gfp_t gfp
= GFP_NOFS
| __GFP_ACCOUNT
;
820 struct mem_cgroup
*memcg
, *old_memcg
;
825 /* The page lock pins the memcg */
826 memcg
= page_memcg(page
);
827 old_memcg
= set_active_memcg(memcg
);
831 while ((offset
-= size
) >= 0) {
832 bh
= alloc_buffer_head(gfp
);
836 bh
->b_this_page
= head
;
842 /* Link the buffer to its page */
843 set_bh_page(bh
, page
, offset
);
846 set_active_memcg(old_memcg
);
849 * In case anything failed, we just free everything we got.
855 head
= head
->b_this_page
;
856 free_buffer_head(bh
);
862 EXPORT_SYMBOL_GPL(alloc_page_buffers
);
865 link_dev_buffers(struct page
*page
, struct buffer_head
*head
)
867 struct buffer_head
*bh
, *tail
;
872 bh
= bh
->b_this_page
;
874 tail
->b_this_page
= head
;
875 attach_page_private(page
, head
);
878 static sector_t
blkdev_max_block(struct block_device
*bdev
, unsigned int size
)
880 sector_t retval
= ~((sector_t
)0);
881 loff_t sz
= i_size_read(bdev
->bd_inode
);
884 unsigned int sizebits
= blksize_bits(size
);
885 retval
= (sz
>> sizebits
);
891 * Initialise the state of a blockdev page's buffers.
894 init_page_buffers(struct page
*page
, struct block_device
*bdev
,
895 sector_t block
, int size
)
897 struct buffer_head
*head
= page_buffers(page
);
898 struct buffer_head
*bh
= head
;
899 int uptodate
= PageUptodate(page
);
900 sector_t end_block
= blkdev_max_block(I_BDEV(bdev
->bd_inode
), size
);
903 if (!buffer_mapped(bh
)) {
905 bh
->b_private
= NULL
;
907 bh
->b_blocknr
= block
;
909 set_buffer_uptodate(bh
);
910 if (block
< end_block
)
911 set_buffer_mapped(bh
);
914 bh
= bh
->b_this_page
;
915 } while (bh
!= head
);
918 * Caller needs to validate requested block against end of device.
924 * Create the page-cache page that contains the requested block.
926 * This is used purely for blockdev mappings.
929 grow_dev_page(struct block_device
*bdev
, sector_t block
,
930 pgoff_t index
, int size
, int sizebits
, gfp_t gfp
)
932 struct inode
*inode
= bdev
->bd_inode
;
934 struct buffer_head
*bh
;
939 gfp_mask
= mapping_gfp_constraint(inode
->i_mapping
, ~__GFP_FS
) | gfp
;
942 * XXX: __getblk_slow() can not really deal with failure and
943 * will endlessly loop on improvised global reclaim. Prefer
944 * looping in the allocator rather than here, at least that
945 * code knows what it's doing.
947 gfp_mask
|= __GFP_NOFAIL
;
949 page
= find_or_create_page(inode
->i_mapping
, index
, gfp_mask
);
951 BUG_ON(!PageLocked(page
));
953 if (page_has_buffers(page
)) {
954 bh
= page_buffers(page
);
955 if (bh
->b_size
== size
) {
956 end_block
= init_page_buffers(page
, bdev
,
957 (sector_t
)index
<< sizebits
,
961 if (!try_to_free_buffers(page
))
966 * Allocate some buffers for this page
968 bh
= alloc_page_buffers(page
, size
, true);
971 * Link the page to the buffers and initialise them. Take the
972 * lock to be atomic wrt __find_get_block(), which does not
973 * run under the page lock.
975 spin_lock(&inode
->i_mapping
->private_lock
);
976 link_dev_buffers(page
, bh
);
977 end_block
= init_page_buffers(page
, bdev
, (sector_t
)index
<< sizebits
,
979 spin_unlock(&inode
->i_mapping
->private_lock
);
981 ret
= (block
< end_block
) ? 1 : -ENXIO
;
989 * Create buffers for the specified block device block's page. If
990 * that page was dirty, the buffers are set dirty also.
993 grow_buffers(struct block_device
*bdev
, sector_t block
, int size
, gfp_t gfp
)
998 sizebits
= PAGE_SHIFT
- __ffs(size
);
999 index
= block
>> sizebits
;
1002 * Check for a block which wants to lie outside our maximum possible
1003 * pagecache index. (this comparison is done using sector_t types).
1005 if (unlikely(index
!= block
>> sizebits
)) {
1006 printk(KERN_ERR
"%s: requested out-of-range block %llu for "
1008 __func__
, (unsigned long long)block
,
1013 /* Create a page with the proper size buffers.. */
1014 return grow_dev_page(bdev
, block
, index
, size
, sizebits
, gfp
);
1017 static struct buffer_head
*
1018 __getblk_slow(struct block_device
*bdev
, sector_t block
,
1019 unsigned size
, gfp_t gfp
)
1021 /* Size must be multiple of hard sectorsize */
1022 if (unlikely(size
& (bdev_logical_block_size(bdev
)-1) ||
1023 (size
< 512 || size
> PAGE_SIZE
))) {
1024 printk(KERN_ERR
"getblk(): invalid block size %d requested\n",
1026 printk(KERN_ERR
"logical block size: %d\n",
1027 bdev_logical_block_size(bdev
));
1034 struct buffer_head
*bh
;
1037 bh
= __find_get_block(bdev
, block
, size
);
1041 ret
= grow_buffers(bdev
, block
, size
, gfp
);
1048 * The relationship between dirty buffers and dirty pages:
1050 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1051 * the page is tagged dirty in the page cache.
1053 * At all times, the dirtiness of the buffers represents the dirtiness of
1054 * subsections of the page. If the page has buffers, the page dirty bit is
1055 * merely a hint about the true dirty state.
1057 * When a page is set dirty in its entirety, all its buffers are marked dirty
1058 * (if the page has buffers).
1060 * When a buffer is marked dirty, its page is dirtied, but the page's other
1063 * Also. When blockdev buffers are explicitly read with bread(), they
1064 * individually become uptodate. But their backing page remains not
1065 * uptodate - even if all of its buffers are uptodate. A subsequent
1066 * block_read_full_page() against that page will discover all the uptodate
1067 * buffers, will set the page uptodate and will perform no I/O.
1071 * mark_buffer_dirty - mark a buffer_head as needing writeout
1072 * @bh: the buffer_head to mark dirty
1074 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1075 * its backing page dirty, then tag the page as dirty in the page cache
1076 * and then attach the address_space's inode to its superblock's dirty
1079 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1080 * i_pages lock and mapping->host->i_lock.
1082 void mark_buffer_dirty(struct buffer_head
*bh
)
1084 WARN_ON_ONCE(!buffer_uptodate(bh
));
1086 trace_block_dirty_buffer(bh
);
1089 * Very *carefully* optimize the it-is-already-dirty case.
1091 * Don't let the final "is it dirty" escape to before we
1092 * perhaps modified the buffer.
1094 if (buffer_dirty(bh
)) {
1096 if (buffer_dirty(bh
))
1100 if (!test_set_buffer_dirty(bh
)) {
1101 struct page
*page
= bh
->b_page
;
1102 struct address_space
*mapping
= NULL
;
1104 lock_page_memcg(page
);
1105 if (!TestSetPageDirty(page
)) {
1106 mapping
= page_mapping(page
);
1108 __set_page_dirty(page
, mapping
, 0);
1110 unlock_page_memcg(page
);
1112 __mark_inode_dirty(mapping
->host
, I_DIRTY_PAGES
);
1115 EXPORT_SYMBOL(mark_buffer_dirty
);
1117 void mark_buffer_write_io_error(struct buffer_head
*bh
)
1119 struct super_block
*sb
;
1121 set_buffer_write_io_error(bh
);
1122 /* FIXME: do we need to set this in both places? */
1123 if (bh
->b_page
&& bh
->b_page
->mapping
)
1124 mapping_set_error(bh
->b_page
->mapping
, -EIO
);
1125 if (bh
->b_assoc_map
)
1126 mapping_set_error(bh
->b_assoc_map
, -EIO
);
1128 sb
= READ_ONCE(bh
->b_bdev
->bd_super
);
1130 errseq_set(&sb
->s_wb_err
, -EIO
);
1133 EXPORT_SYMBOL(mark_buffer_write_io_error
);
1136 * Decrement a buffer_head's reference count. If all buffers against a page
1137 * have zero reference count, are clean and unlocked, and if the page is clean
1138 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1139 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1140 * a page but it ends up not being freed, and buffers may later be reattached).
1142 void __brelse(struct buffer_head
* buf
)
1144 if (atomic_read(&buf
->b_count
)) {
1148 WARN(1, KERN_ERR
"VFS: brelse: Trying to free free buffer\n");
1150 EXPORT_SYMBOL(__brelse
);
1153 * bforget() is like brelse(), except it discards any
1154 * potentially dirty data.
1156 void __bforget(struct buffer_head
*bh
)
1158 clear_buffer_dirty(bh
);
1159 if (bh
->b_assoc_map
) {
1160 struct address_space
*buffer_mapping
= bh
->b_page
->mapping
;
1162 spin_lock(&buffer_mapping
->private_lock
);
1163 list_del_init(&bh
->b_assoc_buffers
);
1164 bh
->b_assoc_map
= NULL
;
1165 spin_unlock(&buffer_mapping
->private_lock
);
1169 EXPORT_SYMBOL(__bforget
);
1171 static struct buffer_head
*__bread_slow(struct buffer_head
*bh
)
1174 if (buffer_uptodate(bh
)) {
1179 bh
->b_end_io
= end_buffer_read_sync
;
1180 submit_bh(REQ_OP_READ
, 0, bh
);
1182 if (buffer_uptodate(bh
))
1190 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1191 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1192 * refcount elevated by one when they're in an LRU. A buffer can only appear
1193 * once in a particular CPU's LRU. A single buffer can be present in multiple
1194 * CPU's LRUs at the same time.
1196 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1197 * sb_find_get_block().
1199 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1200 * a local interrupt disable for that.
1203 #define BH_LRU_SIZE 16
1206 struct buffer_head
*bhs
[BH_LRU_SIZE
];
1209 static DEFINE_PER_CPU(struct bh_lru
, bh_lrus
) = {{ NULL
}};
1212 #define bh_lru_lock() local_irq_disable()
1213 #define bh_lru_unlock() local_irq_enable()
1215 #define bh_lru_lock() preempt_disable()
1216 #define bh_lru_unlock() preempt_enable()
1219 static inline void check_irqs_on(void)
1221 #ifdef irqs_disabled
1222 BUG_ON(irqs_disabled());
1227 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1228 * inserted at the front, and the buffer_head at the back if any is evicted.
1229 * Or, if already in the LRU it is moved to the front.
1231 static void bh_lru_install(struct buffer_head
*bh
)
1233 struct buffer_head
*evictee
= bh
;
1239 * the refcount of buffer_head in bh_lru prevents dropping the
1240 * attached page(i.e., try_to_free_buffers) so it could cause
1241 * failing page migration.
1242 * Skip putting upcoming bh into bh_lru until migration is done.
1244 if (lru_cache_disabled())
1249 b
= this_cpu_ptr(&bh_lrus
);
1250 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1251 swap(evictee
, b
->bhs
[i
]);
1252 if (evictee
== bh
) {
1264 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1266 static struct buffer_head
*
1267 lookup_bh_lru(struct block_device
*bdev
, sector_t block
, unsigned size
)
1269 struct buffer_head
*ret
= NULL
;
1274 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1275 struct buffer_head
*bh
= __this_cpu_read(bh_lrus
.bhs
[i
]);
1277 if (bh
&& bh
->b_blocknr
== block
&& bh
->b_bdev
== bdev
&&
1278 bh
->b_size
== size
) {
1281 __this_cpu_write(bh_lrus
.bhs
[i
],
1282 __this_cpu_read(bh_lrus
.bhs
[i
- 1]));
1285 __this_cpu_write(bh_lrus
.bhs
[0], bh
);
1297 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1298 * it in the LRU and mark it as accessed. If it is not present then return
1301 struct buffer_head
*
1302 __find_get_block(struct block_device
*bdev
, sector_t block
, unsigned size
)
1304 struct buffer_head
*bh
= lookup_bh_lru(bdev
, block
, size
);
1307 /* __find_get_block_slow will mark the page accessed */
1308 bh
= __find_get_block_slow(bdev
, block
);
1316 EXPORT_SYMBOL(__find_get_block
);
1319 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1320 * which corresponds to the passed block_device, block and size. The
1321 * returned buffer has its reference count incremented.
1323 * __getblk_gfp() will lock up the machine if grow_dev_page's
1324 * try_to_free_buffers() attempt is failing. FIXME, perhaps?
1326 struct buffer_head
*
1327 __getblk_gfp(struct block_device
*bdev
, sector_t block
,
1328 unsigned size
, gfp_t gfp
)
1330 struct buffer_head
*bh
= __find_get_block(bdev
, block
, size
);
1334 bh
= __getblk_slow(bdev
, block
, size
, gfp
);
1337 EXPORT_SYMBOL(__getblk_gfp
);
1340 * Do async read-ahead on a buffer..
1342 void __breadahead(struct block_device
*bdev
, sector_t block
, unsigned size
)
1344 struct buffer_head
*bh
= __getblk(bdev
, block
, size
);
1346 ll_rw_block(REQ_OP_READ
, REQ_RAHEAD
, 1, &bh
);
1350 EXPORT_SYMBOL(__breadahead
);
1352 void __breadahead_gfp(struct block_device
*bdev
, sector_t block
, unsigned size
,
1355 struct buffer_head
*bh
= __getblk_gfp(bdev
, block
, size
, gfp
);
1357 ll_rw_block(REQ_OP_READ
, REQ_RAHEAD
, 1, &bh
);
1361 EXPORT_SYMBOL(__breadahead_gfp
);
1364 * __bread_gfp() - reads a specified block and returns the bh
1365 * @bdev: the block_device to read from
1366 * @block: number of block
1367 * @size: size (in bytes) to read
1368 * @gfp: page allocation flag
1370 * Reads a specified block, and returns buffer head that contains it.
1371 * The page cache can be allocated from non-movable area
1372 * not to prevent page migration if you set gfp to zero.
1373 * It returns NULL if the block was unreadable.
1375 struct buffer_head
*
1376 __bread_gfp(struct block_device
*bdev
, sector_t block
,
1377 unsigned size
, gfp_t gfp
)
1379 struct buffer_head
*bh
= __getblk_gfp(bdev
, block
, size
, gfp
);
1381 if (likely(bh
) && !buffer_uptodate(bh
))
1382 bh
= __bread_slow(bh
);
1385 EXPORT_SYMBOL(__bread_gfp
);
1387 static void __invalidate_bh_lrus(struct bh_lru
*b
)
1391 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1397 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1398 * This doesn't race because it runs in each cpu either in irq
1399 * or with preempt disabled.
1401 static void invalidate_bh_lru(void *arg
)
1403 struct bh_lru
*b
= &get_cpu_var(bh_lrus
);
1405 __invalidate_bh_lrus(b
);
1406 put_cpu_var(bh_lrus
);
1409 bool has_bh_in_lru(int cpu
, void *dummy
)
1411 struct bh_lru
*b
= per_cpu_ptr(&bh_lrus
, cpu
);
1414 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1422 void invalidate_bh_lrus(void)
1424 on_each_cpu_cond(has_bh_in_lru
, invalidate_bh_lru
, NULL
, 1);
1426 EXPORT_SYMBOL_GPL(invalidate_bh_lrus
);
1428 void invalidate_bh_lrus_cpu(int cpu
)
1433 b
= per_cpu_ptr(&bh_lrus
, cpu
);
1434 __invalidate_bh_lrus(b
);
1438 void set_bh_page(struct buffer_head
*bh
,
1439 struct page
*page
, unsigned long offset
)
1442 BUG_ON(offset
>= PAGE_SIZE
);
1443 if (PageHighMem(page
))
1445 * This catches illegal uses and preserves the offset:
1447 bh
->b_data
= (char *)(0 + offset
);
1449 bh
->b_data
= page_address(page
) + offset
;
1451 EXPORT_SYMBOL(set_bh_page
);
1454 * Called when truncating a buffer on a page completely.
1457 /* Bits that are cleared during an invalidate */
1458 #define BUFFER_FLAGS_DISCARD \
1459 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1460 1 << BH_Delay | 1 << BH_Unwritten)
1462 static void discard_buffer(struct buffer_head
* bh
)
1464 unsigned long b_state
, b_state_old
;
1467 clear_buffer_dirty(bh
);
1469 b_state
= bh
->b_state
;
1471 b_state_old
= cmpxchg(&bh
->b_state
, b_state
,
1472 (b_state
& ~BUFFER_FLAGS_DISCARD
));
1473 if (b_state_old
== b_state
)
1475 b_state
= b_state_old
;
1481 * block_invalidatepage - invalidate part or all of a buffer-backed page
1483 * @page: the page which is affected
1484 * @offset: start of the range to invalidate
1485 * @length: length of the range to invalidate
1487 * block_invalidatepage() is called when all or part of the page has become
1488 * invalidated by a truncate operation.
1490 * block_invalidatepage() does not have to release all buffers, but it must
1491 * ensure that no dirty buffer is left outside @offset and that no I/O
1492 * is underway against any of the blocks which are outside the truncation
1493 * point. Because the caller is about to free (and possibly reuse) those
1496 void block_invalidatepage(struct page
*page
, unsigned int offset
,
1497 unsigned int length
)
1499 struct buffer_head
*head
, *bh
, *next
;
1500 unsigned int curr_off
= 0;
1501 unsigned int stop
= length
+ offset
;
1503 BUG_ON(!PageLocked(page
));
1504 if (!page_has_buffers(page
))
1508 * Check for overflow
1510 BUG_ON(stop
> PAGE_SIZE
|| stop
< length
);
1512 head
= page_buffers(page
);
1515 unsigned int next_off
= curr_off
+ bh
->b_size
;
1516 next
= bh
->b_this_page
;
1519 * Are we still fully in range ?
1521 if (next_off
> stop
)
1525 * is this block fully invalidated?
1527 if (offset
<= curr_off
)
1529 curr_off
= next_off
;
1531 } while (bh
!= head
);
1534 * We release buffers only if the entire page is being invalidated.
1535 * The get_block cached value has been unconditionally invalidated,
1536 * so real IO is not possible anymore.
1538 if (length
== PAGE_SIZE
)
1539 try_to_release_page(page
, 0);
1543 EXPORT_SYMBOL(block_invalidatepage
);
1547 * We attach and possibly dirty the buffers atomically wrt
1548 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1549 * is already excluded via the page lock.
1551 void create_empty_buffers(struct page
*page
,
1552 unsigned long blocksize
, unsigned long b_state
)
1554 struct buffer_head
*bh
, *head
, *tail
;
1556 head
= alloc_page_buffers(page
, blocksize
, true);
1559 bh
->b_state
|= b_state
;
1561 bh
= bh
->b_this_page
;
1563 tail
->b_this_page
= head
;
1565 spin_lock(&page
->mapping
->private_lock
);
1566 if (PageUptodate(page
) || PageDirty(page
)) {
1569 if (PageDirty(page
))
1570 set_buffer_dirty(bh
);
1571 if (PageUptodate(page
))
1572 set_buffer_uptodate(bh
);
1573 bh
= bh
->b_this_page
;
1574 } while (bh
!= head
);
1576 attach_page_private(page
, head
);
1577 spin_unlock(&page
->mapping
->private_lock
);
1579 EXPORT_SYMBOL(create_empty_buffers
);
1582 * clean_bdev_aliases: clean a range of buffers in block device
1583 * @bdev: Block device to clean buffers in
1584 * @block: Start of a range of blocks to clean
1585 * @len: Number of blocks to clean
1587 * We are taking a range of blocks for data and we don't want writeback of any
1588 * buffer-cache aliases starting from return from this function and until the
1589 * moment when something will explicitly mark the buffer dirty (hopefully that
1590 * will not happen until we will free that block ;-) We don't even need to mark
1591 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1592 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1593 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1594 * would confuse anyone who might pick it with bread() afterwards...
1596 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1597 * writeout I/O going on against recently-freed buffers. We don't wait on that
1598 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1599 * need to. That happens here.
1601 void clean_bdev_aliases(struct block_device
*bdev
, sector_t block
, sector_t len
)
1603 struct inode
*bd_inode
= bdev
->bd_inode
;
1604 struct address_space
*bd_mapping
= bd_inode
->i_mapping
;
1605 struct pagevec pvec
;
1606 pgoff_t index
= block
>> (PAGE_SHIFT
- bd_inode
->i_blkbits
);
1609 struct buffer_head
*bh
;
1610 struct buffer_head
*head
;
1612 end
= (block
+ len
- 1) >> (PAGE_SHIFT
- bd_inode
->i_blkbits
);
1613 pagevec_init(&pvec
);
1614 while (pagevec_lookup_range(&pvec
, bd_mapping
, &index
, end
)) {
1615 count
= pagevec_count(&pvec
);
1616 for (i
= 0; i
< count
; i
++) {
1617 struct page
*page
= pvec
.pages
[i
];
1619 if (!page_has_buffers(page
))
1622 * We use page lock instead of bd_mapping->private_lock
1623 * to pin buffers here since we can afford to sleep and
1624 * it scales better than a global spinlock lock.
1627 /* Recheck when the page is locked which pins bhs */
1628 if (!page_has_buffers(page
))
1630 head
= page_buffers(page
);
1633 if (!buffer_mapped(bh
) || (bh
->b_blocknr
< block
))
1635 if (bh
->b_blocknr
>= block
+ len
)
1637 clear_buffer_dirty(bh
);
1639 clear_buffer_req(bh
);
1641 bh
= bh
->b_this_page
;
1642 } while (bh
!= head
);
1646 pagevec_release(&pvec
);
1648 /* End of range already reached? */
1649 if (index
> end
|| !index
)
1653 EXPORT_SYMBOL(clean_bdev_aliases
);
1656 * Size is a power-of-two in the range 512..PAGE_SIZE,
1657 * and the case we care about most is PAGE_SIZE.
1659 * So this *could* possibly be written with those
1660 * constraints in mind (relevant mostly if some
1661 * architecture has a slow bit-scan instruction)
1663 static inline int block_size_bits(unsigned int blocksize
)
1665 return ilog2(blocksize
);
1668 static struct buffer_head
*create_page_buffers(struct page
*page
, struct inode
*inode
, unsigned int b_state
)
1670 BUG_ON(!PageLocked(page
));
1672 if (!page_has_buffers(page
))
1673 create_empty_buffers(page
, 1 << READ_ONCE(inode
->i_blkbits
),
1675 return page_buffers(page
);
1679 * NOTE! All mapped/uptodate combinations are valid:
1681 * Mapped Uptodate Meaning
1683 * No No "unknown" - must do get_block()
1684 * No Yes "hole" - zero-filled
1685 * Yes No "allocated" - allocated on disk, not read in
1686 * Yes Yes "valid" - allocated and up-to-date in memory.
1688 * "Dirty" is valid only with the last case (mapped+uptodate).
1692 * While block_write_full_page is writing back the dirty buffers under
1693 * the page lock, whoever dirtied the buffers may decide to clean them
1694 * again at any time. We handle that by only looking at the buffer
1695 * state inside lock_buffer().
1697 * If block_write_full_page() is called for regular writeback
1698 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1699 * locked buffer. This only can happen if someone has written the buffer
1700 * directly, with submit_bh(). At the address_space level PageWriteback
1701 * prevents this contention from occurring.
1703 * If block_write_full_page() is called with wbc->sync_mode ==
1704 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1705 * causes the writes to be flagged as synchronous writes.
1707 int __block_write_full_page(struct inode
*inode
, struct page
*page
,
1708 get_block_t
*get_block
, struct writeback_control
*wbc
,
1709 bh_end_io_t
*handler
)
1713 sector_t last_block
;
1714 struct buffer_head
*bh
, *head
;
1715 unsigned int blocksize
, bbits
;
1716 int nr_underway
= 0;
1717 int write_flags
= wbc_to_write_flags(wbc
);
1719 head
= create_page_buffers(page
, inode
,
1720 (1 << BH_Dirty
)|(1 << BH_Uptodate
));
1723 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1724 * here, and the (potentially unmapped) buffers may become dirty at
1725 * any time. If a buffer becomes dirty here after we've inspected it
1726 * then we just miss that fact, and the page stays dirty.
1728 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1729 * handle that here by just cleaning them.
1733 blocksize
= bh
->b_size
;
1734 bbits
= block_size_bits(blocksize
);
1736 block
= (sector_t
)page
->index
<< (PAGE_SHIFT
- bbits
);
1737 last_block
= (i_size_read(inode
) - 1) >> bbits
;
1740 * Get all the dirty buffers mapped to disk addresses and
1741 * handle any aliases from the underlying blockdev's mapping.
1744 if (block
> last_block
) {
1746 * mapped buffers outside i_size will occur, because
1747 * this page can be outside i_size when there is a
1748 * truncate in progress.
1751 * The buffer was zeroed by block_write_full_page()
1753 clear_buffer_dirty(bh
);
1754 set_buffer_uptodate(bh
);
1755 } else if ((!buffer_mapped(bh
) || buffer_delay(bh
)) &&
1757 WARN_ON(bh
->b_size
!= blocksize
);
1758 err
= get_block(inode
, block
, bh
, 1);
1761 clear_buffer_delay(bh
);
1762 if (buffer_new(bh
)) {
1763 /* blockdev mappings never come here */
1764 clear_buffer_new(bh
);
1765 clean_bdev_bh_alias(bh
);
1768 bh
= bh
->b_this_page
;
1770 } while (bh
!= head
);
1773 if (!buffer_mapped(bh
))
1776 * If it's a fully non-blocking write attempt and we cannot
1777 * lock the buffer then redirty the page. Note that this can
1778 * potentially cause a busy-wait loop from writeback threads
1779 * and kswapd activity, but those code paths have their own
1780 * higher-level throttling.
1782 if (wbc
->sync_mode
!= WB_SYNC_NONE
) {
1784 } else if (!trylock_buffer(bh
)) {
1785 redirty_page_for_writepage(wbc
, page
);
1788 if (test_clear_buffer_dirty(bh
)) {
1789 mark_buffer_async_write_endio(bh
, handler
);
1793 } while ((bh
= bh
->b_this_page
) != head
);
1796 * The page and its buffers are protected by PageWriteback(), so we can
1797 * drop the bh refcounts early.
1799 BUG_ON(PageWriteback(page
));
1800 set_page_writeback(page
);
1803 struct buffer_head
*next
= bh
->b_this_page
;
1804 if (buffer_async_write(bh
)) {
1805 submit_bh_wbc(REQ_OP_WRITE
, write_flags
, bh
,
1806 inode
->i_write_hint
, wbc
);
1810 } while (bh
!= head
);
1815 if (nr_underway
== 0) {
1817 * The page was marked dirty, but the buffers were
1818 * clean. Someone wrote them back by hand with
1819 * ll_rw_block/submit_bh. A rare case.
1821 end_page_writeback(page
);
1824 * The page and buffer_heads can be released at any time from
1832 * ENOSPC, or some other error. We may already have added some
1833 * blocks to the file, so we need to write these out to avoid
1834 * exposing stale data.
1835 * The page is currently locked and not marked for writeback
1838 /* Recovery: lock and submit the mapped buffers */
1840 if (buffer_mapped(bh
) && buffer_dirty(bh
) &&
1841 !buffer_delay(bh
)) {
1843 mark_buffer_async_write_endio(bh
, handler
);
1846 * The buffer may have been set dirty during
1847 * attachment to a dirty page.
1849 clear_buffer_dirty(bh
);
1851 } while ((bh
= bh
->b_this_page
) != head
);
1853 BUG_ON(PageWriteback(page
));
1854 mapping_set_error(page
->mapping
, err
);
1855 set_page_writeback(page
);
1857 struct buffer_head
*next
= bh
->b_this_page
;
1858 if (buffer_async_write(bh
)) {
1859 clear_buffer_dirty(bh
);
1860 submit_bh_wbc(REQ_OP_WRITE
, write_flags
, bh
,
1861 inode
->i_write_hint
, wbc
);
1865 } while (bh
!= head
);
1869 EXPORT_SYMBOL(__block_write_full_page
);
1872 * If a page has any new buffers, zero them out here, and mark them uptodate
1873 * and dirty so they'll be written out (in order to prevent uninitialised
1874 * block data from leaking). And clear the new bit.
1876 void page_zero_new_buffers(struct page
*page
, unsigned from
, unsigned to
)
1878 unsigned int block_start
, block_end
;
1879 struct buffer_head
*head
, *bh
;
1881 BUG_ON(!PageLocked(page
));
1882 if (!page_has_buffers(page
))
1885 bh
= head
= page_buffers(page
);
1888 block_end
= block_start
+ bh
->b_size
;
1890 if (buffer_new(bh
)) {
1891 if (block_end
> from
&& block_start
< to
) {
1892 if (!PageUptodate(page
)) {
1893 unsigned start
, size
;
1895 start
= max(from
, block_start
);
1896 size
= min(to
, block_end
) - start
;
1898 zero_user(page
, start
, size
);
1899 set_buffer_uptodate(bh
);
1902 clear_buffer_new(bh
);
1903 mark_buffer_dirty(bh
);
1907 block_start
= block_end
;
1908 bh
= bh
->b_this_page
;
1909 } while (bh
!= head
);
1911 EXPORT_SYMBOL(page_zero_new_buffers
);
1914 iomap_to_bh(struct inode
*inode
, sector_t block
, struct buffer_head
*bh
,
1915 struct iomap
*iomap
)
1917 loff_t offset
= block
<< inode
->i_blkbits
;
1919 bh
->b_bdev
= iomap
->bdev
;
1922 * Block points to offset in file we need to map, iomap contains
1923 * the offset at which the map starts. If the map ends before the
1924 * current block, then do not map the buffer and let the caller
1927 BUG_ON(offset
>= iomap
->offset
+ iomap
->length
);
1929 switch (iomap
->type
) {
1932 * If the buffer is not up to date or beyond the current EOF,
1933 * we need to mark it as new to ensure sub-block zeroing is
1934 * executed if necessary.
1936 if (!buffer_uptodate(bh
) ||
1937 (offset
>= i_size_read(inode
)))
1940 case IOMAP_DELALLOC
:
1941 if (!buffer_uptodate(bh
) ||
1942 (offset
>= i_size_read(inode
)))
1944 set_buffer_uptodate(bh
);
1945 set_buffer_mapped(bh
);
1946 set_buffer_delay(bh
);
1948 case IOMAP_UNWRITTEN
:
1950 * For unwritten regions, we always need to ensure that regions
1951 * in the block we are not writing to are zeroed. Mark the
1952 * buffer as new to ensure this.
1955 set_buffer_unwritten(bh
);
1958 if ((iomap
->flags
& IOMAP_F_NEW
) ||
1959 offset
>= i_size_read(inode
))
1961 bh
->b_blocknr
= (iomap
->addr
+ offset
- iomap
->offset
) >>
1963 set_buffer_mapped(bh
);
1968 int __block_write_begin_int(struct page
*page
, loff_t pos
, unsigned len
,
1969 get_block_t
*get_block
, struct iomap
*iomap
)
1971 unsigned from
= pos
& (PAGE_SIZE
- 1);
1972 unsigned to
= from
+ len
;
1973 struct inode
*inode
= page
->mapping
->host
;
1974 unsigned block_start
, block_end
;
1977 unsigned blocksize
, bbits
;
1978 struct buffer_head
*bh
, *head
, *wait
[2], **wait_bh
=wait
;
1980 BUG_ON(!PageLocked(page
));
1981 BUG_ON(from
> PAGE_SIZE
);
1982 BUG_ON(to
> PAGE_SIZE
);
1985 head
= create_page_buffers(page
, inode
, 0);
1986 blocksize
= head
->b_size
;
1987 bbits
= block_size_bits(blocksize
);
1989 block
= (sector_t
)page
->index
<< (PAGE_SHIFT
- bbits
);
1991 for(bh
= head
, block_start
= 0; bh
!= head
|| !block_start
;
1992 block
++, block_start
=block_end
, bh
= bh
->b_this_page
) {
1993 block_end
= block_start
+ blocksize
;
1994 if (block_end
<= from
|| block_start
>= to
) {
1995 if (PageUptodate(page
)) {
1996 if (!buffer_uptodate(bh
))
1997 set_buffer_uptodate(bh
);
2002 clear_buffer_new(bh
);
2003 if (!buffer_mapped(bh
)) {
2004 WARN_ON(bh
->b_size
!= blocksize
);
2006 err
= get_block(inode
, block
, bh
, 1);
2010 iomap_to_bh(inode
, block
, bh
, iomap
);
2013 if (buffer_new(bh
)) {
2014 clean_bdev_bh_alias(bh
);
2015 if (PageUptodate(page
)) {
2016 clear_buffer_new(bh
);
2017 set_buffer_uptodate(bh
);
2018 mark_buffer_dirty(bh
);
2021 if (block_end
> to
|| block_start
< from
)
2022 zero_user_segments(page
,
2028 if (PageUptodate(page
)) {
2029 if (!buffer_uptodate(bh
))
2030 set_buffer_uptodate(bh
);
2033 if (!buffer_uptodate(bh
) && !buffer_delay(bh
) &&
2034 !buffer_unwritten(bh
) &&
2035 (block_start
< from
|| block_end
> to
)) {
2036 ll_rw_block(REQ_OP_READ
, 0, 1, &bh
);
2041 * If we issued read requests - let them complete.
2043 while(wait_bh
> wait
) {
2044 wait_on_buffer(*--wait_bh
);
2045 if (!buffer_uptodate(*wait_bh
))
2049 page_zero_new_buffers(page
, from
, to
);
2053 int __block_write_begin(struct page
*page
, loff_t pos
, unsigned len
,
2054 get_block_t
*get_block
)
2056 return __block_write_begin_int(page
, pos
, len
, get_block
, NULL
);
2058 EXPORT_SYMBOL(__block_write_begin
);
2060 static int __block_commit_write(struct inode
*inode
, struct page
*page
,
2061 unsigned from
, unsigned to
)
2063 unsigned block_start
, block_end
;
2066 struct buffer_head
*bh
, *head
;
2068 bh
= head
= page_buffers(page
);
2069 blocksize
= bh
->b_size
;
2073 block_end
= block_start
+ blocksize
;
2074 if (block_end
<= from
|| block_start
>= to
) {
2075 if (!buffer_uptodate(bh
))
2078 set_buffer_uptodate(bh
);
2079 mark_buffer_dirty(bh
);
2082 clear_buffer_new(bh
);
2084 block_start
= block_end
;
2085 bh
= bh
->b_this_page
;
2086 } while (bh
!= head
);
2089 * If this is a partial write which happened to make all buffers
2090 * uptodate then we can optimize away a bogus readpage() for
2091 * the next read(). Here we 'discover' whether the page went
2092 * uptodate as a result of this (potentially partial) write.
2095 SetPageUptodate(page
);
2100 * block_write_begin takes care of the basic task of block allocation and
2101 * bringing partial write blocks uptodate first.
2103 * The filesystem needs to handle block truncation upon failure.
2105 int block_write_begin(struct address_space
*mapping
, loff_t pos
, unsigned len
,
2106 unsigned flags
, struct page
**pagep
, get_block_t
*get_block
)
2108 pgoff_t index
= pos
>> PAGE_SHIFT
;
2112 page
= grab_cache_page_write_begin(mapping
, index
, flags
);
2116 status
= __block_write_begin(page
, pos
, len
, get_block
);
2117 if (unlikely(status
)) {
2126 EXPORT_SYMBOL(block_write_begin
);
2128 int block_write_end(struct file
*file
, struct address_space
*mapping
,
2129 loff_t pos
, unsigned len
, unsigned copied
,
2130 struct page
*page
, void *fsdata
)
2132 struct inode
*inode
= mapping
->host
;
2135 start
= pos
& (PAGE_SIZE
- 1);
2137 if (unlikely(copied
< len
)) {
2139 * The buffers that were written will now be uptodate, so we
2140 * don't have to worry about a readpage reading them and
2141 * overwriting a partial write. However if we have encountered
2142 * a short write and only partially written into a buffer, it
2143 * will not be marked uptodate, so a readpage might come in and
2144 * destroy our partial write.
2146 * Do the simplest thing, and just treat any short write to a
2147 * non uptodate page as a zero-length write, and force the
2148 * caller to redo the whole thing.
2150 if (!PageUptodate(page
))
2153 page_zero_new_buffers(page
, start
+copied
, start
+len
);
2155 flush_dcache_page(page
);
2157 /* This could be a short (even 0-length) commit */
2158 __block_commit_write(inode
, page
, start
, start
+copied
);
2162 EXPORT_SYMBOL(block_write_end
);
2164 int generic_write_end(struct file
*file
, struct address_space
*mapping
,
2165 loff_t pos
, unsigned len
, unsigned copied
,
2166 struct page
*page
, void *fsdata
)
2168 struct inode
*inode
= mapping
->host
;
2169 loff_t old_size
= inode
->i_size
;
2170 bool i_size_changed
= false;
2172 copied
= block_write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2175 * No need to use i_size_read() here, the i_size cannot change under us
2176 * because we hold i_rwsem.
2178 * But it's important to update i_size while still holding page lock:
2179 * page writeout could otherwise come in and zero beyond i_size.
2181 if (pos
+ copied
> inode
->i_size
) {
2182 i_size_write(inode
, pos
+ copied
);
2183 i_size_changed
= true;
2190 pagecache_isize_extended(inode
, old_size
, pos
);
2192 * Don't mark the inode dirty under page lock. First, it unnecessarily
2193 * makes the holding time of page lock longer. Second, it forces lock
2194 * ordering of page lock and transaction start for journaling
2198 mark_inode_dirty(inode
);
2201 EXPORT_SYMBOL(generic_write_end
);
2204 * block_is_partially_uptodate checks whether buffers within a page are
2207 * Returns true if all buffers which correspond to a file portion
2208 * we want to read are uptodate.
2210 int block_is_partially_uptodate(struct page
*page
, unsigned long from
,
2211 unsigned long count
)
2213 unsigned block_start
, block_end
, blocksize
;
2215 struct buffer_head
*bh
, *head
;
2218 if (!page_has_buffers(page
))
2221 head
= page_buffers(page
);
2222 blocksize
= head
->b_size
;
2223 to
= min_t(unsigned, PAGE_SIZE
- from
, count
);
2225 if (from
< blocksize
&& to
> PAGE_SIZE
- blocksize
)
2231 block_end
= block_start
+ blocksize
;
2232 if (block_end
> from
&& block_start
< to
) {
2233 if (!buffer_uptodate(bh
)) {
2237 if (block_end
>= to
)
2240 block_start
= block_end
;
2241 bh
= bh
->b_this_page
;
2242 } while (bh
!= head
);
2246 EXPORT_SYMBOL(block_is_partially_uptodate
);
2249 * Generic "read page" function for block devices that have the normal
2250 * get_block functionality. This is most of the block device filesystems.
2251 * Reads the page asynchronously --- the unlock_buffer() and
2252 * set/clear_buffer_uptodate() functions propagate buffer state into the
2253 * page struct once IO has completed.
2255 int block_read_full_page(struct page
*page
, get_block_t
*get_block
)
2257 struct inode
*inode
= page
->mapping
->host
;
2258 sector_t iblock
, lblock
;
2259 struct buffer_head
*bh
, *head
, *arr
[MAX_BUF_PER_PAGE
];
2260 unsigned int blocksize
, bbits
;
2262 int fully_mapped
= 1;
2264 head
= create_page_buffers(page
, inode
, 0);
2265 blocksize
= head
->b_size
;
2266 bbits
= block_size_bits(blocksize
);
2268 iblock
= (sector_t
)page
->index
<< (PAGE_SHIFT
- bbits
);
2269 lblock
= (i_size_read(inode
)+blocksize
-1) >> bbits
;
2275 if (buffer_uptodate(bh
))
2278 if (!buffer_mapped(bh
)) {
2282 if (iblock
< lblock
) {
2283 WARN_ON(bh
->b_size
!= blocksize
);
2284 err
= get_block(inode
, iblock
, bh
, 0);
2288 if (!buffer_mapped(bh
)) {
2289 zero_user(page
, i
* blocksize
, blocksize
);
2291 set_buffer_uptodate(bh
);
2295 * get_block() might have updated the buffer
2298 if (buffer_uptodate(bh
))
2302 } while (i
++, iblock
++, (bh
= bh
->b_this_page
) != head
);
2305 SetPageMappedToDisk(page
);
2309 * All buffers are uptodate - we can set the page uptodate
2310 * as well. But not if get_block() returned an error.
2312 if (!PageError(page
))
2313 SetPageUptodate(page
);
2318 /* Stage two: lock the buffers */
2319 for (i
= 0; i
< nr
; i
++) {
2322 mark_buffer_async_read(bh
);
2326 * Stage 3: start the IO. Check for uptodateness
2327 * inside the buffer lock in case another process reading
2328 * the underlying blockdev brought it uptodate (the sct fix).
2330 for (i
= 0; i
< nr
; i
++) {
2332 if (buffer_uptodate(bh
))
2333 end_buffer_async_read(bh
, 1);
2335 submit_bh(REQ_OP_READ
, 0, bh
);
2339 EXPORT_SYMBOL(block_read_full_page
);
2341 /* utility function for filesystems that need to do work on expanding
2342 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2343 * deal with the hole.
2345 int generic_cont_expand_simple(struct inode
*inode
, loff_t size
)
2347 struct address_space
*mapping
= inode
->i_mapping
;
2352 err
= inode_newsize_ok(inode
, size
);
2356 err
= pagecache_write_begin(NULL
, mapping
, size
, 0,
2357 AOP_FLAG_CONT_EXPAND
, &page
, &fsdata
);
2361 err
= pagecache_write_end(NULL
, mapping
, size
, 0, 0, page
, fsdata
);
2367 EXPORT_SYMBOL(generic_cont_expand_simple
);
2369 static int cont_expand_zero(struct file
*file
, struct address_space
*mapping
,
2370 loff_t pos
, loff_t
*bytes
)
2372 struct inode
*inode
= mapping
->host
;
2373 unsigned int blocksize
= i_blocksize(inode
);
2376 pgoff_t index
, curidx
;
2378 unsigned zerofrom
, offset
, len
;
2381 index
= pos
>> PAGE_SHIFT
;
2382 offset
= pos
& ~PAGE_MASK
;
2384 while (index
> (curidx
= (curpos
= *bytes
)>>PAGE_SHIFT
)) {
2385 zerofrom
= curpos
& ~PAGE_MASK
;
2386 if (zerofrom
& (blocksize
-1)) {
2387 *bytes
|= (blocksize
-1);
2390 len
= PAGE_SIZE
- zerofrom
;
2392 err
= pagecache_write_begin(file
, mapping
, curpos
, len
, 0,
2396 zero_user(page
, zerofrom
, len
);
2397 err
= pagecache_write_end(file
, mapping
, curpos
, len
, len
,
2404 balance_dirty_pages_ratelimited(mapping
);
2406 if (fatal_signal_pending(current
)) {
2412 /* page covers the boundary, find the boundary offset */
2413 if (index
== curidx
) {
2414 zerofrom
= curpos
& ~PAGE_MASK
;
2415 /* if we will expand the thing last block will be filled */
2416 if (offset
<= zerofrom
) {
2419 if (zerofrom
& (blocksize
-1)) {
2420 *bytes
|= (blocksize
-1);
2423 len
= offset
- zerofrom
;
2425 err
= pagecache_write_begin(file
, mapping
, curpos
, len
, 0,
2429 zero_user(page
, zerofrom
, len
);
2430 err
= pagecache_write_end(file
, mapping
, curpos
, len
, len
,
2442 * For moronic filesystems that do not allow holes in file.
2443 * We may have to extend the file.
2445 int cont_write_begin(struct file
*file
, struct address_space
*mapping
,
2446 loff_t pos
, unsigned len
, unsigned flags
,
2447 struct page
**pagep
, void **fsdata
,
2448 get_block_t
*get_block
, loff_t
*bytes
)
2450 struct inode
*inode
= mapping
->host
;
2451 unsigned int blocksize
= i_blocksize(inode
);
2452 unsigned int zerofrom
;
2455 err
= cont_expand_zero(file
, mapping
, pos
, bytes
);
2459 zerofrom
= *bytes
& ~PAGE_MASK
;
2460 if (pos
+len
> *bytes
&& zerofrom
& (blocksize
-1)) {
2461 *bytes
|= (blocksize
-1);
2465 return block_write_begin(mapping
, pos
, len
, flags
, pagep
, get_block
);
2467 EXPORT_SYMBOL(cont_write_begin
);
2469 int block_commit_write(struct page
*page
, unsigned from
, unsigned to
)
2471 struct inode
*inode
= page
->mapping
->host
;
2472 __block_commit_write(inode
,page
,from
,to
);
2475 EXPORT_SYMBOL(block_commit_write
);
2478 * block_page_mkwrite() is not allowed to change the file size as it gets
2479 * called from a page fault handler when a page is first dirtied. Hence we must
2480 * be careful to check for EOF conditions here. We set the page up correctly
2481 * for a written page which means we get ENOSPC checking when writing into
2482 * holes and correct delalloc and unwritten extent mapping on filesystems that
2483 * support these features.
2485 * We are not allowed to take the i_mutex here so we have to play games to
2486 * protect against truncate races as the page could now be beyond EOF. Because
2487 * truncate writes the inode size before removing pages, once we have the
2488 * page lock we can determine safely if the page is beyond EOF. If it is not
2489 * beyond EOF, then the page is guaranteed safe against truncation until we
2492 * Direct callers of this function should protect against filesystem freezing
2493 * using sb_start_pagefault() - sb_end_pagefault() functions.
2495 int block_page_mkwrite(struct vm_area_struct
*vma
, struct vm_fault
*vmf
,
2496 get_block_t get_block
)
2498 struct page
*page
= vmf
->page
;
2499 struct inode
*inode
= file_inode(vma
->vm_file
);
2505 size
= i_size_read(inode
);
2506 if ((page
->mapping
!= inode
->i_mapping
) ||
2507 (page_offset(page
) > size
)) {
2508 /* We overload EFAULT to mean page got truncated */
2513 /* page is wholly or partially inside EOF */
2514 if (((page
->index
+ 1) << PAGE_SHIFT
) > size
)
2515 end
= size
& ~PAGE_MASK
;
2519 ret
= __block_write_begin(page
, 0, end
, get_block
);
2521 ret
= block_commit_write(page
, 0, end
);
2523 if (unlikely(ret
< 0))
2525 set_page_dirty(page
);
2526 wait_for_stable_page(page
);
2532 EXPORT_SYMBOL(block_page_mkwrite
);
2535 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2536 * immediately, while under the page lock. So it needs a special end_io
2537 * handler which does not touch the bh after unlocking it.
2539 static void end_buffer_read_nobh(struct buffer_head
*bh
, int uptodate
)
2541 __end_buffer_read_notouch(bh
, uptodate
);
2545 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2546 * the page (converting it to circular linked list and taking care of page
2549 static void attach_nobh_buffers(struct page
*page
, struct buffer_head
*head
)
2551 struct buffer_head
*bh
;
2553 BUG_ON(!PageLocked(page
));
2555 spin_lock(&page
->mapping
->private_lock
);
2558 if (PageDirty(page
))
2559 set_buffer_dirty(bh
);
2560 if (!bh
->b_this_page
)
2561 bh
->b_this_page
= head
;
2562 bh
= bh
->b_this_page
;
2563 } while (bh
!= head
);
2564 attach_page_private(page
, head
);
2565 spin_unlock(&page
->mapping
->private_lock
);
2569 * On entry, the page is fully not uptodate.
2570 * On exit the page is fully uptodate in the areas outside (from,to)
2571 * The filesystem needs to handle block truncation upon failure.
2573 int nobh_write_begin(struct address_space
*mapping
,
2574 loff_t pos
, unsigned len
, unsigned flags
,
2575 struct page
**pagep
, void **fsdata
,
2576 get_block_t
*get_block
)
2578 struct inode
*inode
= mapping
->host
;
2579 const unsigned blkbits
= inode
->i_blkbits
;
2580 const unsigned blocksize
= 1 << blkbits
;
2581 struct buffer_head
*head
, *bh
;
2585 unsigned block_in_page
;
2586 unsigned block_start
, block_end
;
2587 sector_t block_in_file
;
2590 int is_mapped_to_disk
= 1;
2592 index
= pos
>> PAGE_SHIFT
;
2593 from
= pos
& (PAGE_SIZE
- 1);
2596 page
= grab_cache_page_write_begin(mapping
, index
, flags
);
2602 if (page_has_buffers(page
)) {
2603 ret
= __block_write_begin(page
, pos
, len
, get_block
);
2609 if (PageMappedToDisk(page
))
2613 * Allocate buffers so that we can keep track of state, and potentially
2614 * attach them to the page if an error occurs. In the common case of
2615 * no error, they will just be freed again without ever being attached
2616 * to the page (which is all OK, because we're under the page lock).
2618 * Be careful: the buffer linked list is a NULL terminated one, rather
2619 * than the circular one we're used to.
2621 head
= alloc_page_buffers(page
, blocksize
, false);
2627 block_in_file
= (sector_t
)page
->index
<< (PAGE_SHIFT
- blkbits
);
2630 * We loop across all blocks in the page, whether or not they are
2631 * part of the affected region. This is so we can discover if the
2632 * page is fully mapped-to-disk.
2634 for (block_start
= 0, block_in_page
= 0, bh
= head
;
2635 block_start
< PAGE_SIZE
;
2636 block_in_page
++, block_start
+= blocksize
, bh
= bh
->b_this_page
) {
2639 block_end
= block_start
+ blocksize
;
2642 if (block_start
>= to
)
2644 ret
= get_block(inode
, block_in_file
+ block_in_page
,
2648 if (!buffer_mapped(bh
))
2649 is_mapped_to_disk
= 0;
2651 clean_bdev_bh_alias(bh
);
2652 if (PageUptodate(page
)) {
2653 set_buffer_uptodate(bh
);
2656 if (buffer_new(bh
) || !buffer_mapped(bh
)) {
2657 zero_user_segments(page
, block_start
, from
,
2661 if (buffer_uptodate(bh
))
2662 continue; /* reiserfs does this */
2663 if (block_start
< from
|| block_end
> to
) {
2665 bh
->b_end_io
= end_buffer_read_nobh
;
2666 submit_bh(REQ_OP_READ
, 0, bh
);
2673 * The page is locked, so these buffers are protected from
2674 * any VM or truncate activity. Hence we don't need to care
2675 * for the buffer_head refcounts.
2677 for (bh
= head
; bh
; bh
= bh
->b_this_page
) {
2679 if (!buffer_uptodate(bh
))
2686 if (is_mapped_to_disk
)
2687 SetPageMappedToDisk(page
);
2689 *fsdata
= head
; /* to be released by nobh_write_end */
2696 * Error recovery is a bit difficult. We need to zero out blocks that
2697 * were newly allocated, and dirty them to ensure they get written out.
2698 * Buffers need to be attached to the page at this point, otherwise
2699 * the handling of potential IO errors during writeout would be hard
2700 * (could try doing synchronous writeout, but what if that fails too?)
2702 attach_nobh_buffers(page
, head
);
2703 page_zero_new_buffers(page
, from
, to
);
2712 EXPORT_SYMBOL(nobh_write_begin
);
2714 int nobh_write_end(struct file
*file
, struct address_space
*mapping
,
2715 loff_t pos
, unsigned len
, unsigned copied
,
2716 struct page
*page
, void *fsdata
)
2718 struct inode
*inode
= page
->mapping
->host
;
2719 struct buffer_head
*head
= fsdata
;
2720 struct buffer_head
*bh
;
2721 BUG_ON(fsdata
!= NULL
&& page_has_buffers(page
));
2723 if (unlikely(copied
< len
) && head
)
2724 attach_nobh_buffers(page
, head
);
2725 if (page_has_buffers(page
))
2726 return generic_write_end(file
, mapping
, pos
, len
,
2727 copied
, page
, fsdata
);
2729 SetPageUptodate(page
);
2730 set_page_dirty(page
);
2731 if (pos
+copied
> inode
->i_size
) {
2732 i_size_write(inode
, pos
+copied
);
2733 mark_inode_dirty(inode
);
2741 head
= head
->b_this_page
;
2742 free_buffer_head(bh
);
2747 EXPORT_SYMBOL(nobh_write_end
);
2750 * nobh_writepage() - based on block_full_write_page() except
2751 * that it tries to operate without attaching bufferheads to
2754 int nobh_writepage(struct page
*page
, get_block_t
*get_block
,
2755 struct writeback_control
*wbc
)
2757 struct inode
* const inode
= page
->mapping
->host
;
2758 loff_t i_size
= i_size_read(inode
);
2759 const pgoff_t end_index
= i_size
>> PAGE_SHIFT
;
2763 /* Is the page fully inside i_size? */
2764 if (page
->index
< end_index
)
2767 /* Is the page fully outside i_size? (truncate in progress) */
2768 offset
= i_size
& (PAGE_SIZE
-1);
2769 if (page
->index
>= end_index
+1 || !offset
) {
2771 return 0; /* don't care */
2775 * The page straddles i_size. It must be zeroed out on each and every
2776 * writepage invocation because it may be mmapped. "A file is mapped
2777 * in multiples of the page size. For a file that is not a multiple of
2778 * the page size, the remaining memory is zeroed when mapped, and
2779 * writes to that region are not written out to the file."
2781 zero_user_segment(page
, offset
, PAGE_SIZE
);
2783 ret
= mpage_writepage(page
, get_block
, wbc
);
2785 ret
= __block_write_full_page(inode
, page
, get_block
, wbc
,
2786 end_buffer_async_write
);
2789 EXPORT_SYMBOL(nobh_writepage
);
2791 int nobh_truncate_page(struct address_space
*mapping
,
2792 loff_t from
, get_block_t
*get_block
)
2794 pgoff_t index
= from
>> PAGE_SHIFT
;
2795 unsigned offset
= from
& (PAGE_SIZE
-1);
2798 unsigned length
, pos
;
2799 struct inode
*inode
= mapping
->host
;
2801 struct buffer_head map_bh
;
2804 blocksize
= i_blocksize(inode
);
2805 length
= offset
& (blocksize
- 1);
2807 /* Block boundary? Nothing to do */
2811 length
= blocksize
- length
;
2812 iblock
= (sector_t
)index
<< (PAGE_SHIFT
- inode
->i_blkbits
);
2814 page
= grab_cache_page(mapping
, index
);
2819 if (page_has_buffers(page
)) {
2823 return block_truncate_page(mapping
, from
, get_block
);
2826 /* Find the buffer that contains "offset" */
2828 while (offset
>= pos
) {
2833 map_bh
.b_size
= blocksize
;
2835 err
= get_block(inode
, iblock
, &map_bh
, 0);
2838 /* unmapped? It's a hole - nothing to do */
2839 if (!buffer_mapped(&map_bh
))
2842 /* Ok, it's mapped. Make sure it's up-to-date */
2843 if (!PageUptodate(page
)) {
2844 err
= mapping
->a_ops
->readpage(NULL
, page
);
2850 if (!PageUptodate(page
)) {
2854 if (page_has_buffers(page
))
2857 zero_user(page
, offset
, length
);
2858 set_page_dirty(page
);
2867 EXPORT_SYMBOL(nobh_truncate_page
);
2869 int block_truncate_page(struct address_space
*mapping
,
2870 loff_t from
, get_block_t
*get_block
)
2872 pgoff_t index
= from
>> PAGE_SHIFT
;
2873 unsigned offset
= from
& (PAGE_SIZE
-1);
2876 unsigned length
, pos
;
2877 struct inode
*inode
= mapping
->host
;
2879 struct buffer_head
*bh
;
2882 blocksize
= i_blocksize(inode
);
2883 length
= offset
& (blocksize
- 1);
2885 /* Block boundary? Nothing to do */
2889 length
= blocksize
- length
;
2890 iblock
= (sector_t
)index
<< (PAGE_SHIFT
- inode
->i_blkbits
);
2892 page
= grab_cache_page(mapping
, index
);
2897 if (!page_has_buffers(page
))
2898 create_empty_buffers(page
, blocksize
, 0);
2900 /* Find the buffer that contains "offset" */
2901 bh
= page_buffers(page
);
2903 while (offset
>= pos
) {
2904 bh
= bh
->b_this_page
;
2910 if (!buffer_mapped(bh
)) {
2911 WARN_ON(bh
->b_size
!= blocksize
);
2912 err
= get_block(inode
, iblock
, bh
, 0);
2915 /* unmapped? It's a hole - nothing to do */
2916 if (!buffer_mapped(bh
))
2920 /* Ok, it's mapped. Make sure it's up-to-date */
2921 if (PageUptodate(page
))
2922 set_buffer_uptodate(bh
);
2924 if (!buffer_uptodate(bh
) && !buffer_delay(bh
) && !buffer_unwritten(bh
)) {
2926 ll_rw_block(REQ_OP_READ
, 0, 1, &bh
);
2928 /* Uhhuh. Read error. Complain and punt. */
2929 if (!buffer_uptodate(bh
))
2933 zero_user(page
, offset
, length
);
2934 mark_buffer_dirty(bh
);
2943 EXPORT_SYMBOL(block_truncate_page
);
2946 * The generic ->writepage function for buffer-backed address_spaces
2948 int block_write_full_page(struct page
*page
, get_block_t
*get_block
,
2949 struct writeback_control
*wbc
)
2951 struct inode
* const inode
= page
->mapping
->host
;
2952 loff_t i_size
= i_size_read(inode
);
2953 const pgoff_t end_index
= i_size
>> PAGE_SHIFT
;
2956 /* Is the page fully inside i_size? */
2957 if (page
->index
< end_index
)
2958 return __block_write_full_page(inode
, page
, get_block
, wbc
,
2959 end_buffer_async_write
);
2961 /* Is the page fully outside i_size? (truncate in progress) */
2962 offset
= i_size
& (PAGE_SIZE
-1);
2963 if (page
->index
>= end_index
+1 || !offset
) {
2965 return 0; /* don't care */
2969 * The page straddles i_size. It must be zeroed out on each and every
2970 * writepage invocation because it may be mmapped. "A file is mapped
2971 * in multiples of the page size. For a file that is not a multiple of
2972 * the page size, the remaining memory is zeroed when mapped, and
2973 * writes to that region are not written out to the file."
2975 zero_user_segment(page
, offset
, PAGE_SIZE
);
2976 return __block_write_full_page(inode
, page
, get_block
, wbc
,
2977 end_buffer_async_write
);
2979 EXPORT_SYMBOL(block_write_full_page
);
2981 sector_t
generic_block_bmap(struct address_space
*mapping
, sector_t block
,
2982 get_block_t
*get_block
)
2984 struct inode
*inode
= mapping
->host
;
2985 struct buffer_head tmp
= {
2986 .b_size
= i_blocksize(inode
),
2989 get_block(inode
, block
, &tmp
, 0);
2990 return tmp
.b_blocknr
;
2992 EXPORT_SYMBOL(generic_block_bmap
);
2994 static void end_bio_bh_io_sync(struct bio
*bio
)
2996 struct buffer_head
*bh
= bio
->bi_private
;
2998 if (unlikely(bio_flagged(bio
, BIO_QUIET
)))
2999 set_bit(BH_Quiet
, &bh
->b_state
);
3001 bh
->b_end_io(bh
, !bio
->bi_status
);
3005 static int submit_bh_wbc(int op
, int op_flags
, struct buffer_head
*bh
,
3006 enum rw_hint write_hint
, struct writeback_control
*wbc
)
3010 BUG_ON(!buffer_locked(bh
));
3011 BUG_ON(!buffer_mapped(bh
));
3012 BUG_ON(!bh
->b_end_io
);
3013 BUG_ON(buffer_delay(bh
));
3014 BUG_ON(buffer_unwritten(bh
));
3017 * Only clear out a write error when rewriting
3019 if (test_set_buffer_req(bh
) && (op
== REQ_OP_WRITE
))
3020 clear_buffer_write_io_error(bh
);
3022 bio
= bio_alloc(GFP_NOIO
, 1);
3024 fscrypt_set_bio_crypt_ctx_bh(bio
, bh
, GFP_NOIO
);
3026 bio
->bi_iter
.bi_sector
= bh
->b_blocknr
* (bh
->b_size
>> 9);
3027 bio_set_dev(bio
, bh
->b_bdev
);
3028 bio
->bi_write_hint
= write_hint
;
3030 bio_add_page(bio
, bh
->b_page
, bh
->b_size
, bh_offset(bh
));
3031 BUG_ON(bio
->bi_iter
.bi_size
!= bh
->b_size
);
3033 bio
->bi_end_io
= end_bio_bh_io_sync
;
3034 bio
->bi_private
= bh
;
3036 if (buffer_meta(bh
))
3037 op_flags
|= REQ_META
;
3038 if (buffer_prio(bh
))
3039 op_flags
|= REQ_PRIO
;
3040 bio_set_op_attrs(bio
, op
, op_flags
);
3042 /* Take care of bh's that straddle the end of the device */
3046 wbc_init_bio(wbc
, bio
);
3047 wbc_account_cgroup_owner(wbc
, bh
->b_page
, bh
->b_size
);
3054 int submit_bh(int op
, int op_flags
, struct buffer_head
*bh
)
3056 return submit_bh_wbc(op
, op_flags
, bh
, 0, NULL
);
3058 EXPORT_SYMBOL(submit_bh
);
3061 * ll_rw_block: low-level access to block devices (DEPRECATED)
3062 * @op: whether to %READ or %WRITE
3063 * @op_flags: req_flag_bits
3064 * @nr: number of &struct buffer_heads in the array
3065 * @bhs: array of pointers to &struct buffer_head
3067 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3068 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
3069 * @op_flags contains flags modifying the detailed I/O behavior, most notably
3072 * This function drops any buffer that it cannot get a lock on (with the
3073 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3074 * request, and any buffer that appears to be up-to-date when doing read
3075 * request. Further it marks as clean buffers that are processed for
3076 * writing (the buffer cache won't assume that they are actually clean
3077 * until the buffer gets unlocked).
3079 * ll_rw_block sets b_end_io to simple completion handler that marks
3080 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3083 * All of the buffers must be for the same device, and must also be a
3084 * multiple of the current approved size for the device.
3086 void ll_rw_block(int op
, int op_flags
, int nr
, struct buffer_head
*bhs
[])
3090 for (i
= 0; i
< nr
; i
++) {
3091 struct buffer_head
*bh
= bhs
[i
];
3093 if (!trylock_buffer(bh
))
3096 if (test_clear_buffer_dirty(bh
)) {
3097 bh
->b_end_io
= end_buffer_write_sync
;
3099 submit_bh(op
, op_flags
, bh
);
3103 if (!buffer_uptodate(bh
)) {
3104 bh
->b_end_io
= end_buffer_read_sync
;
3106 submit_bh(op
, op_flags
, bh
);
3113 EXPORT_SYMBOL(ll_rw_block
);
3115 void write_dirty_buffer(struct buffer_head
*bh
, int op_flags
)
3118 if (!test_clear_buffer_dirty(bh
)) {
3122 bh
->b_end_io
= end_buffer_write_sync
;
3124 submit_bh(REQ_OP_WRITE
, op_flags
, bh
);
3126 EXPORT_SYMBOL(write_dirty_buffer
);
3129 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3130 * and then start new I/O and then wait upon it. The caller must have a ref on
3133 int __sync_dirty_buffer(struct buffer_head
*bh
, int op_flags
)
3137 WARN_ON(atomic_read(&bh
->b_count
) < 1);
3139 if (test_clear_buffer_dirty(bh
)) {
3141 * The bh should be mapped, but it might not be if the
3142 * device was hot-removed. Not much we can do but fail the I/O.
3144 if (!buffer_mapped(bh
)) {
3150 bh
->b_end_io
= end_buffer_write_sync
;
3151 ret
= submit_bh(REQ_OP_WRITE
, op_flags
, bh
);
3153 if (!ret
&& !buffer_uptodate(bh
))
3160 EXPORT_SYMBOL(__sync_dirty_buffer
);
3162 int sync_dirty_buffer(struct buffer_head
*bh
)
3164 return __sync_dirty_buffer(bh
, REQ_SYNC
);
3166 EXPORT_SYMBOL(sync_dirty_buffer
);
3169 * try_to_free_buffers() checks if all the buffers on this particular page
3170 * are unused, and releases them if so.
3172 * Exclusion against try_to_free_buffers may be obtained by either
3173 * locking the page or by holding its mapping's private_lock.
3175 * If the page is dirty but all the buffers are clean then we need to
3176 * be sure to mark the page clean as well. This is because the page
3177 * may be against a block device, and a later reattachment of buffers
3178 * to a dirty page will set *all* buffers dirty. Which would corrupt
3179 * filesystem data on the same device.
3181 * The same applies to regular filesystem pages: if all the buffers are
3182 * clean then we set the page clean and proceed. To do that, we require
3183 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3186 * try_to_free_buffers() is non-blocking.
3188 static inline int buffer_busy(struct buffer_head
*bh
)
3190 return atomic_read(&bh
->b_count
) |
3191 (bh
->b_state
& ((1 << BH_Dirty
) | (1 << BH_Lock
)));
3195 drop_buffers(struct page
*page
, struct buffer_head
**buffers_to_free
)
3197 struct buffer_head
*head
= page_buffers(page
);
3198 struct buffer_head
*bh
;
3202 if (buffer_busy(bh
))
3204 bh
= bh
->b_this_page
;
3205 } while (bh
!= head
);
3208 struct buffer_head
*next
= bh
->b_this_page
;
3210 if (bh
->b_assoc_map
)
3211 __remove_assoc_queue(bh
);
3213 } while (bh
!= head
);
3214 *buffers_to_free
= head
;
3215 detach_page_private(page
);
3221 int try_to_free_buffers(struct page
*page
)
3223 struct address_space
* const mapping
= page
->mapping
;
3224 struct buffer_head
*buffers_to_free
= NULL
;
3227 BUG_ON(!PageLocked(page
));
3228 if (PageWriteback(page
))
3231 if (mapping
== NULL
) { /* can this still happen? */
3232 ret
= drop_buffers(page
, &buffers_to_free
);
3236 spin_lock(&mapping
->private_lock
);
3237 ret
= drop_buffers(page
, &buffers_to_free
);
3240 * If the filesystem writes its buffers by hand (eg ext3)
3241 * then we can have clean buffers against a dirty page. We
3242 * clean the page here; otherwise the VM will never notice
3243 * that the filesystem did any IO at all.
3245 * Also, during truncate, discard_buffer will have marked all
3246 * the page's buffers clean. We discover that here and clean
3249 * private_lock must be held over this entire operation in order
3250 * to synchronise against __set_page_dirty_buffers and prevent the
3251 * dirty bit from being lost.
3254 cancel_dirty_page(page
);
3255 spin_unlock(&mapping
->private_lock
);
3257 if (buffers_to_free
) {
3258 struct buffer_head
*bh
= buffers_to_free
;
3261 struct buffer_head
*next
= bh
->b_this_page
;
3262 free_buffer_head(bh
);
3264 } while (bh
!= buffers_to_free
);
3268 EXPORT_SYMBOL(try_to_free_buffers
);
3271 * There are no bdflush tunables left. But distributions are
3272 * still running obsolete flush daemons, so we terminate them here.
3274 * Use of bdflush() is deprecated and will be removed in a future kernel.
3275 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3277 SYSCALL_DEFINE2(bdflush
, int, func
, long, data
)
3279 static int msg_count
;
3281 if (!capable(CAP_SYS_ADMIN
))
3284 if (msg_count
< 5) {
3287 "warning: process `%s' used the obsolete bdflush"
3288 " system call\n", current
->comm
);
3289 printk(KERN_INFO
"Fix your initscripts?\n");
3298 * Buffer-head allocation
3300 static struct kmem_cache
*bh_cachep __read_mostly
;
3303 * Once the number of bh's in the machine exceeds this level, we start
3304 * stripping them in writeback.
3306 static unsigned long max_buffer_heads
;
3308 int buffer_heads_over_limit
;
3310 struct bh_accounting
{
3311 int nr
; /* Number of live bh's */
3312 int ratelimit
; /* Limit cacheline bouncing */
3315 static DEFINE_PER_CPU(struct bh_accounting
, bh_accounting
) = {0, 0};
3317 static void recalc_bh_state(void)
3322 if (__this_cpu_inc_return(bh_accounting
.ratelimit
) - 1 < 4096)
3324 __this_cpu_write(bh_accounting
.ratelimit
, 0);
3325 for_each_online_cpu(i
)
3326 tot
+= per_cpu(bh_accounting
, i
).nr
;
3327 buffer_heads_over_limit
= (tot
> max_buffer_heads
);
3330 struct buffer_head
*alloc_buffer_head(gfp_t gfp_flags
)
3332 struct buffer_head
*ret
= kmem_cache_zalloc(bh_cachep
, gfp_flags
);
3334 INIT_LIST_HEAD(&ret
->b_assoc_buffers
);
3335 spin_lock_init(&ret
->b_uptodate_lock
);
3337 __this_cpu_inc(bh_accounting
.nr
);
3343 EXPORT_SYMBOL(alloc_buffer_head
);
3345 void free_buffer_head(struct buffer_head
*bh
)
3347 BUG_ON(!list_empty(&bh
->b_assoc_buffers
));
3348 kmem_cache_free(bh_cachep
, bh
);
3350 __this_cpu_dec(bh_accounting
.nr
);
3354 EXPORT_SYMBOL(free_buffer_head
);
3356 static int buffer_exit_cpu_dead(unsigned int cpu
)
3359 struct bh_lru
*b
= &per_cpu(bh_lrus
, cpu
);
3361 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
3365 this_cpu_add(bh_accounting
.nr
, per_cpu(bh_accounting
, cpu
).nr
);
3366 per_cpu(bh_accounting
, cpu
).nr
= 0;
3371 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3372 * @bh: struct buffer_head
3374 * Return true if the buffer is up-to-date and false,
3375 * with the buffer locked, if not.
3377 int bh_uptodate_or_lock(struct buffer_head
*bh
)
3379 if (!buffer_uptodate(bh
)) {
3381 if (!buffer_uptodate(bh
))
3387 EXPORT_SYMBOL(bh_uptodate_or_lock
);
3390 * bh_submit_read - Submit a locked buffer for reading
3391 * @bh: struct buffer_head
3393 * Returns zero on success and -EIO on error.
3395 int bh_submit_read(struct buffer_head
*bh
)
3397 BUG_ON(!buffer_locked(bh
));
3399 if (buffer_uptodate(bh
)) {
3405 bh
->b_end_io
= end_buffer_read_sync
;
3406 submit_bh(REQ_OP_READ
, 0, bh
);
3408 if (buffer_uptodate(bh
))
3412 EXPORT_SYMBOL(bh_submit_read
);
3414 void __init
buffer_init(void)
3416 unsigned long nrpages
;
3419 bh_cachep
= kmem_cache_create("buffer_head",
3420 sizeof(struct buffer_head
), 0,
3421 (SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|
3426 * Limit the bh occupancy to 10% of ZONE_NORMAL
3428 nrpages
= (nr_free_buffer_pages() * 10) / 100;
3429 max_buffer_heads
= nrpages
* (PAGE_SIZE
/ sizeof(struct buffer_head
));
3430 ret
= cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD
, "fs/buffer:dead",
3431 NULL
, buffer_exit_cpu_dead
);