4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
10 * Removed a lot of unnecessary code and simplified things now that
11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
13 * Speed up hash, lru, and free list operations. Use gfp() for allocating
14 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
21 #include <linux/kernel.h>
22 #include <linux/syscalls.h>
25 #include <linux/percpu.h>
26 #include <linux/slab.h>
27 #include <linux/capability.h>
28 #include <linux/blkdev.h>
29 #include <linux/file.h>
30 #include <linux/quotaops.h>
31 #include <linux/highmem.h>
32 #include <linux/module.h>
33 #include <linux/writeback.h>
34 #include <linux/hash.h>
35 #include <linux/suspend.h>
36 #include <linux/buffer_head.h>
37 #include <linux/task_io_accounting_ops.h>
38 #include <linux/bio.h>
39 #include <linux/notifier.h>
40 #include <linux/cpu.h>
41 #include <linux/bitops.h>
42 #include <linux/mpage.h>
43 #include <linux/bit_spinlock.h>
45 static int fsync_buffers_list(spinlock_t
*lock
, struct list_head
*list
);
47 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
50 init_buffer(struct buffer_head
*bh
, bh_end_io_t
*handler
, void *private)
52 bh
->b_end_io
= handler
;
53 bh
->b_private
= private;
56 static int sync_buffer(void *word
)
58 struct block_device
*bd
;
59 struct buffer_head
*bh
60 = container_of(word
, struct buffer_head
, b_state
);
65 blk_run_address_space(bd
->bd_inode
->i_mapping
);
70 void __lock_buffer(struct buffer_head
*bh
)
72 wait_on_bit_lock(&bh
->b_state
, BH_Lock
, sync_buffer
,
73 TASK_UNINTERRUPTIBLE
);
75 EXPORT_SYMBOL(__lock_buffer
);
77 void unlock_buffer(struct buffer_head
*bh
)
79 smp_mb__before_clear_bit();
80 clear_buffer_locked(bh
);
81 smp_mb__after_clear_bit();
82 wake_up_bit(&bh
->b_state
, BH_Lock
);
86 * Block until a buffer comes unlocked. This doesn't stop it
87 * from becoming locked again - you have to lock it yourself
88 * if you want to preserve its state.
90 void __wait_on_buffer(struct buffer_head
* bh
)
92 wait_on_bit(&bh
->b_state
, BH_Lock
, sync_buffer
, TASK_UNINTERRUPTIBLE
);
96 __clear_page_buffers(struct page
*page
)
98 ClearPagePrivate(page
);
99 set_page_private(page
, 0);
100 page_cache_release(page
);
103 static void buffer_io_error(struct buffer_head
*bh
)
105 char b
[BDEVNAME_SIZE
];
107 printk(KERN_ERR
"Buffer I/O error on device %s, logical block %Lu\n",
108 bdevname(bh
->b_bdev
, b
),
109 (unsigned long long)bh
->b_blocknr
);
113 * End-of-IO handler helper function which does not touch the bh after
115 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
116 * a race there is benign: unlock_buffer() only use the bh's address for
117 * hashing after unlocking the buffer, so it doesn't actually touch the bh
120 static void __end_buffer_read_notouch(struct buffer_head
*bh
, int uptodate
)
123 set_buffer_uptodate(bh
);
125 /* This happens, due to failed READA attempts. */
126 clear_buffer_uptodate(bh
);
132 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
133 * unlock the buffer. This is what ll_rw_block uses too.
135 void end_buffer_read_sync(struct buffer_head
*bh
, int uptodate
)
137 __end_buffer_read_notouch(bh
, uptodate
);
141 void end_buffer_write_sync(struct buffer_head
*bh
, int uptodate
)
143 char b
[BDEVNAME_SIZE
];
146 set_buffer_uptodate(bh
);
148 if (!buffer_eopnotsupp(bh
) && printk_ratelimit()) {
150 printk(KERN_WARNING
"lost page write due to "
152 bdevname(bh
->b_bdev
, b
));
154 set_buffer_write_io_error(bh
);
155 clear_buffer_uptodate(bh
);
162 * Write out and wait upon all the dirty data associated with a block
163 * device via its mapping. Does not take the superblock lock.
165 int sync_blockdev(struct block_device
*bdev
)
170 ret
= filemap_write_and_wait(bdev
->bd_inode
->i_mapping
);
173 EXPORT_SYMBOL(sync_blockdev
);
176 * Write out and wait upon all dirty data associated with this
177 * device. Filesystem data as well as the underlying block
178 * device. Takes the superblock lock.
180 int fsync_bdev(struct block_device
*bdev
)
182 struct super_block
*sb
= get_super(bdev
);
184 int res
= fsync_super(sb
);
188 return sync_blockdev(bdev
);
192 * freeze_bdev -- lock a filesystem and force it into a consistent state
193 * @bdev: blockdevice to lock
195 * This takes the block device bd_mount_sem to make sure no new mounts
196 * happen on bdev until thaw_bdev() is called.
197 * If a superblock is found on this device, we take the s_umount semaphore
198 * on it to make sure nobody unmounts until the snapshot creation is done.
200 struct super_block
*freeze_bdev(struct block_device
*bdev
)
202 struct super_block
*sb
;
204 down(&bdev
->bd_mount_sem
);
205 sb
= get_super(bdev
);
206 if (sb
&& !(sb
->s_flags
& MS_RDONLY
)) {
207 sb
->s_frozen
= SB_FREEZE_WRITE
;
212 sb
->s_frozen
= SB_FREEZE_TRANS
;
215 sync_blockdev(sb
->s_bdev
);
217 if (sb
->s_op
->write_super_lockfs
)
218 sb
->s_op
->write_super_lockfs(sb
);
222 return sb
; /* thaw_bdev releases s->s_umount and bd_mount_sem */
224 EXPORT_SYMBOL(freeze_bdev
);
227 * thaw_bdev -- unlock filesystem
228 * @bdev: blockdevice to unlock
229 * @sb: associated superblock
231 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
233 void thaw_bdev(struct block_device
*bdev
, struct super_block
*sb
)
236 BUG_ON(sb
->s_bdev
!= bdev
);
238 if (sb
->s_op
->unlockfs
)
239 sb
->s_op
->unlockfs(sb
);
240 sb
->s_frozen
= SB_UNFROZEN
;
242 wake_up(&sb
->s_wait_unfrozen
);
246 up(&bdev
->bd_mount_sem
);
248 EXPORT_SYMBOL(thaw_bdev
);
251 * Various filesystems appear to want __find_get_block to be non-blocking.
252 * But it's the page lock which protects the buffers. To get around this,
253 * we get exclusion from try_to_free_buffers with the blockdev mapping's
256 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
257 * may be quite high. This code could TryLock the page, and if that
258 * succeeds, there is no need to take private_lock. (But if
259 * private_lock is contended then so is mapping->tree_lock).
261 static struct buffer_head
*
262 __find_get_block_slow(struct block_device
*bdev
, sector_t block
)
264 struct inode
*bd_inode
= bdev
->bd_inode
;
265 struct address_space
*bd_mapping
= bd_inode
->i_mapping
;
266 struct buffer_head
*ret
= NULL
;
268 struct buffer_head
*bh
;
269 struct buffer_head
*head
;
273 index
= block
>> (PAGE_CACHE_SHIFT
- bd_inode
->i_blkbits
);
274 page
= find_get_page(bd_mapping
, index
);
278 spin_lock(&bd_mapping
->private_lock
);
279 if (!page_has_buffers(page
))
281 head
= page_buffers(page
);
284 if (bh
->b_blocknr
== block
) {
289 if (!buffer_mapped(bh
))
291 bh
= bh
->b_this_page
;
292 } while (bh
!= head
);
294 /* we might be here because some of the buffers on this page are
295 * not mapped. This is due to various races between
296 * file io on the block device and getblk. It gets dealt with
297 * elsewhere, don't buffer_error if we had some unmapped buffers
300 printk("__find_get_block_slow() failed. "
301 "block=%llu, b_blocknr=%llu\n",
302 (unsigned long long)block
,
303 (unsigned long long)bh
->b_blocknr
);
304 printk("b_state=0x%08lx, b_size=%zu\n",
305 bh
->b_state
, bh
->b_size
);
306 printk("device blocksize: %d\n", 1 << bd_inode
->i_blkbits
);
309 spin_unlock(&bd_mapping
->private_lock
);
310 page_cache_release(page
);
315 /* If invalidate_buffers() will trash dirty buffers, it means some kind
316 of fs corruption is going on. Trashing dirty data always imply losing
317 information that was supposed to be just stored on the physical layer
320 Thus invalidate_buffers in general usage is not allwowed to trash
321 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
322 be preserved. These buffers are simply skipped.
324 We also skip buffers which are still in use. For example this can
325 happen if a userspace program is reading the block device.
327 NOTE: In the case where the user removed a removable-media-disk even if
328 there's still dirty data not synced on disk (due a bug in the device driver
329 or due an error of the user), by not destroying the dirty buffers we could
330 generate corruption also on the next media inserted, thus a parameter is
331 necessary to handle this case in the most safe way possible (trying
332 to not corrupt also the new disk inserted with the data belonging to
333 the old now corrupted disk). Also for the ramdisk the natural thing
334 to do in order to release the ramdisk memory is to destroy dirty buffers.
336 These are two special cases. Normal usage imply the device driver
337 to issue a sync on the device (without waiting I/O completion) and
338 then an invalidate_buffers call that doesn't trash dirty buffers.
340 For handling cache coherency with the blkdev pagecache the 'update' case
341 is been introduced. It is needed to re-read from disk any pinned
342 buffer. NOTE: re-reading from disk is destructive so we can do it only
343 when we assume nobody is changing the buffercache under our I/O and when
344 we think the disk contains more recent information than the buffercache.
345 The update == 1 pass marks the buffers we need to update, the update == 2
346 pass does the actual I/O. */
347 void invalidate_bdev(struct block_device
*bdev
)
349 struct address_space
*mapping
= bdev
->bd_inode
->i_mapping
;
351 if (mapping
->nrpages
== 0)
354 invalidate_bh_lrus();
355 invalidate_mapping_pages(mapping
, 0, -1);
359 * Kick pdflush then try to free up some ZONE_NORMAL memory.
361 static void free_more_memory(void)
366 wakeup_pdflush(1024);
369 for_each_online_pgdat(pgdat
) {
370 zones
= pgdat
->node_zonelists
[gfp_zone(GFP_NOFS
)].zones
;
372 try_to_free_pages(zones
, 0, GFP_NOFS
);
377 * I/O completion handler for block_read_full_page() - pages
378 * which come unlocked at the end of I/O.
380 static void end_buffer_async_read(struct buffer_head
*bh
, int uptodate
)
383 struct buffer_head
*first
;
384 struct buffer_head
*tmp
;
386 int page_uptodate
= 1;
388 BUG_ON(!buffer_async_read(bh
));
392 set_buffer_uptodate(bh
);
394 clear_buffer_uptodate(bh
);
395 if (printk_ratelimit())
401 * Be _very_ careful from here on. Bad things can happen if
402 * two buffer heads end IO at almost the same time and both
403 * decide that the page is now completely done.
405 first
= page_buffers(page
);
406 local_irq_save(flags
);
407 bit_spin_lock(BH_Uptodate_Lock
, &first
->b_state
);
408 clear_buffer_async_read(bh
);
412 if (!buffer_uptodate(tmp
))
414 if (buffer_async_read(tmp
)) {
415 BUG_ON(!buffer_locked(tmp
));
418 tmp
= tmp
->b_this_page
;
420 bit_spin_unlock(BH_Uptodate_Lock
, &first
->b_state
);
421 local_irq_restore(flags
);
424 * If none of the buffers had errors and they are all
425 * uptodate then we can set the page uptodate.
427 if (page_uptodate
&& !PageError(page
))
428 SetPageUptodate(page
);
433 bit_spin_unlock(BH_Uptodate_Lock
, &first
->b_state
);
434 local_irq_restore(flags
);
439 * Completion handler for block_write_full_page() - pages which are unlocked
440 * during I/O, and which have PageWriteback cleared upon I/O completion.
442 static void end_buffer_async_write(struct buffer_head
*bh
, int uptodate
)
444 char b
[BDEVNAME_SIZE
];
446 struct buffer_head
*first
;
447 struct buffer_head
*tmp
;
450 BUG_ON(!buffer_async_write(bh
));
454 set_buffer_uptodate(bh
);
456 if (printk_ratelimit()) {
458 printk(KERN_WARNING
"lost page write due to "
460 bdevname(bh
->b_bdev
, b
));
462 set_bit(AS_EIO
, &page
->mapping
->flags
);
463 set_buffer_write_io_error(bh
);
464 clear_buffer_uptodate(bh
);
468 first
= page_buffers(page
);
469 local_irq_save(flags
);
470 bit_spin_lock(BH_Uptodate_Lock
, &first
->b_state
);
472 clear_buffer_async_write(bh
);
474 tmp
= bh
->b_this_page
;
476 if (buffer_async_write(tmp
)) {
477 BUG_ON(!buffer_locked(tmp
));
480 tmp
= tmp
->b_this_page
;
482 bit_spin_unlock(BH_Uptodate_Lock
, &first
->b_state
);
483 local_irq_restore(flags
);
484 end_page_writeback(page
);
488 bit_spin_unlock(BH_Uptodate_Lock
, &first
->b_state
);
489 local_irq_restore(flags
);
494 * If a page's buffers are under async readin (end_buffer_async_read
495 * completion) then there is a possibility that another thread of
496 * control could lock one of the buffers after it has completed
497 * but while some of the other buffers have not completed. This
498 * locked buffer would confuse end_buffer_async_read() into not unlocking
499 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
500 * that this buffer is not under async I/O.
502 * The page comes unlocked when it has no locked buffer_async buffers
505 * PageLocked prevents anyone starting new async I/O reads any of
508 * PageWriteback is used to prevent simultaneous writeout of the same
511 * PageLocked prevents anyone from starting writeback of a page which is
512 * under read I/O (PageWriteback is only ever set against a locked page).
514 static void mark_buffer_async_read(struct buffer_head
*bh
)
516 bh
->b_end_io
= end_buffer_async_read
;
517 set_buffer_async_read(bh
);
520 void mark_buffer_async_write(struct buffer_head
*bh
)
522 bh
->b_end_io
= end_buffer_async_write
;
523 set_buffer_async_write(bh
);
525 EXPORT_SYMBOL(mark_buffer_async_write
);
529 * fs/buffer.c contains helper functions for buffer-backed address space's
530 * fsync functions. A common requirement for buffer-based filesystems is
531 * that certain data from the backing blockdev needs to be written out for
532 * a successful fsync(). For example, ext2 indirect blocks need to be
533 * written back and waited upon before fsync() returns.
535 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
536 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
537 * management of a list of dependent buffers at ->i_mapping->private_list.
539 * Locking is a little subtle: try_to_free_buffers() will remove buffers
540 * from their controlling inode's queue when they are being freed. But
541 * try_to_free_buffers() will be operating against the *blockdev* mapping
542 * at the time, not against the S_ISREG file which depends on those buffers.
543 * So the locking for private_list is via the private_lock in the address_space
544 * which backs the buffers. Which is different from the address_space
545 * against which the buffers are listed. So for a particular address_space,
546 * mapping->private_lock does *not* protect mapping->private_list! In fact,
547 * mapping->private_list will always be protected by the backing blockdev's
550 * Which introduces a requirement: all buffers on an address_space's
551 * ->private_list must be from the same address_space: the blockdev's.
553 * address_spaces which do not place buffers at ->private_list via these
554 * utility functions are free to use private_lock and private_list for
555 * whatever they want. The only requirement is that list_empty(private_list)
556 * be true at clear_inode() time.
558 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
559 * filesystems should do that. invalidate_inode_buffers() should just go
560 * BUG_ON(!list_empty).
562 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
563 * take an address_space, not an inode. And it should be called
564 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
567 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
568 * list if it is already on a list. Because if the buffer is on a list,
569 * it *must* already be on the right one. If not, the filesystem is being
570 * silly. This will save a ton of locking. But first we have to ensure
571 * that buffers are taken *off* the old inode's list when they are freed
572 * (presumably in truncate). That requires careful auditing of all
573 * filesystems (do it inside bforget()). It could also be done by bringing
578 * The buffer's backing address_space's private_lock must be held
580 static inline void __remove_assoc_queue(struct buffer_head
*bh
)
582 list_del_init(&bh
->b_assoc_buffers
);
583 WARN_ON(!bh
->b_assoc_map
);
584 if (buffer_write_io_error(bh
))
585 set_bit(AS_EIO
, &bh
->b_assoc_map
->flags
);
586 bh
->b_assoc_map
= NULL
;
589 int inode_has_buffers(struct inode
*inode
)
591 return !list_empty(&inode
->i_data
.private_list
);
595 * osync is designed to support O_SYNC io. It waits synchronously for
596 * all already-submitted IO to complete, but does not queue any new
597 * writes to the disk.
599 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
600 * you dirty the buffers, and then use osync_inode_buffers to wait for
601 * completion. Any other dirty buffers which are not yet queued for
602 * write will not be flushed to disk by the osync.
604 static int osync_buffers_list(spinlock_t
*lock
, struct list_head
*list
)
606 struct buffer_head
*bh
;
612 list_for_each_prev(p
, list
) {
614 if (buffer_locked(bh
)) {
618 if (!buffer_uptodate(bh
))
630 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
631 * @mapping: the mapping which wants those buffers written
633 * Starts I/O against the buffers at mapping->private_list, and waits upon
636 * Basically, this is a convenience function for fsync().
637 * @mapping is a file or directory which needs those buffers to be written for
638 * a successful fsync().
640 int sync_mapping_buffers(struct address_space
*mapping
)
642 struct address_space
*buffer_mapping
= mapping
->assoc_mapping
;
644 if (buffer_mapping
== NULL
|| list_empty(&mapping
->private_list
))
647 return fsync_buffers_list(&buffer_mapping
->private_lock
,
648 &mapping
->private_list
);
650 EXPORT_SYMBOL(sync_mapping_buffers
);
653 * Called when we've recently written block `bblock', and it is known that
654 * `bblock' was for a buffer_boundary() buffer. This means that the block at
655 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
656 * dirty, schedule it for IO. So that indirects merge nicely with their data.
658 void write_boundary_block(struct block_device
*bdev
,
659 sector_t bblock
, unsigned blocksize
)
661 struct buffer_head
*bh
= __find_get_block(bdev
, bblock
+ 1, blocksize
);
663 if (buffer_dirty(bh
))
664 ll_rw_block(WRITE
, 1, &bh
);
669 void mark_buffer_dirty_inode(struct buffer_head
*bh
, struct inode
*inode
)
671 struct address_space
*mapping
= inode
->i_mapping
;
672 struct address_space
*buffer_mapping
= bh
->b_page
->mapping
;
674 mark_buffer_dirty(bh
);
675 if (!mapping
->assoc_mapping
) {
676 mapping
->assoc_mapping
= buffer_mapping
;
678 BUG_ON(mapping
->assoc_mapping
!= buffer_mapping
);
680 if (!bh
->b_assoc_map
) {
681 spin_lock(&buffer_mapping
->private_lock
);
682 list_move_tail(&bh
->b_assoc_buffers
,
683 &mapping
->private_list
);
684 bh
->b_assoc_map
= mapping
;
685 spin_unlock(&buffer_mapping
->private_lock
);
688 EXPORT_SYMBOL(mark_buffer_dirty_inode
);
691 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
694 * If warn is true, then emit a warning if the page is not uptodate and has
695 * not been truncated.
697 static int __set_page_dirty(struct page
*page
,
698 struct address_space
*mapping
, int warn
)
700 if (unlikely(!mapping
))
701 return !TestSetPageDirty(page
);
703 if (TestSetPageDirty(page
))
706 write_lock_irq(&mapping
->tree_lock
);
707 if (page
->mapping
) { /* Race with truncate? */
708 WARN_ON_ONCE(warn
&& !PageUptodate(page
));
710 if (mapping_cap_account_dirty(mapping
)) {
711 __inc_zone_page_state(page
, NR_FILE_DIRTY
);
712 __inc_bdi_stat(mapping
->backing_dev_info
,
714 task_io_account_write(PAGE_CACHE_SIZE
);
716 radix_tree_tag_set(&mapping
->page_tree
,
717 page_index(page
), PAGECACHE_TAG_DIRTY
);
719 write_unlock_irq(&mapping
->tree_lock
);
720 __mark_inode_dirty(mapping
->host
, I_DIRTY_PAGES
);
726 * Add a page to the dirty page list.
728 * It is a sad fact of life that this function is called from several places
729 * deeply under spinlocking. It may not sleep.
731 * If the page has buffers, the uptodate buffers are set dirty, to preserve
732 * dirty-state coherency between the page and the buffers. It the page does
733 * not have buffers then when they are later attached they will all be set
736 * The buffers are dirtied before the page is dirtied. There's a small race
737 * window in which a writepage caller may see the page cleanness but not the
738 * buffer dirtiness. That's fine. If this code were to set the page dirty
739 * before the buffers, a concurrent writepage caller could clear the page dirty
740 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
741 * page on the dirty page list.
743 * We use private_lock to lock against try_to_free_buffers while using the
744 * page's buffer list. Also use this to protect against clean buffers being
745 * added to the page after it was set dirty.
747 * FIXME: may need to call ->reservepage here as well. That's rather up to the
748 * address_space though.
750 int __set_page_dirty_buffers(struct page
*page
)
752 struct address_space
*mapping
= page_mapping(page
);
754 if (unlikely(!mapping
))
755 return !TestSetPageDirty(page
);
757 spin_lock(&mapping
->private_lock
);
758 if (page_has_buffers(page
)) {
759 struct buffer_head
*head
= page_buffers(page
);
760 struct buffer_head
*bh
= head
;
763 set_buffer_dirty(bh
);
764 bh
= bh
->b_this_page
;
765 } while (bh
!= head
);
767 spin_unlock(&mapping
->private_lock
);
769 return __set_page_dirty(page
, mapping
, 1);
771 EXPORT_SYMBOL(__set_page_dirty_buffers
);
774 * Write out and wait upon a list of buffers.
776 * We have conflicting pressures: we want to make sure that all
777 * initially dirty buffers get waited on, but that any subsequently
778 * dirtied buffers don't. After all, we don't want fsync to last
779 * forever if somebody is actively writing to the file.
781 * Do this in two main stages: first we copy dirty buffers to a
782 * temporary inode list, queueing the writes as we go. Then we clean
783 * up, waiting for those writes to complete.
785 * During this second stage, any subsequent updates to the file may end
786 * up refiling the buffer on the original inode's dirty list again, so
787 * there is a chance we will end up with a buffer queued for write but
788 * not yet completed on that list. So, as a final cleanup we go through
789 * the osync code to catch these locked, dirty buffers without requeuing
790 * any newly dirty buffers for write.
792 static int fsync_buffers_list(spinlock_t
*lock
, struct list_head
*list
)
794 struct buffer_head
*bh
;
795 struct list_head tmp
;
796 struct address_space
*mapping
;
799 INIT_LIST_HEAD(&tmp
);
802 while (!list_empty(list
)) {
803 bh
= BH_ENTRY(list
->next
);
804 mapping
= bh
->b_assoc_map
;
805 __remove_assoc_queue(bh
);
806 /* Avoid race with mark_buffer_dirty_inode() which does
807 * a lockless check and we rely on seeing the dirty bit */
809 if (buffer_dirty(bh
) || buffer_locked(bh
)) {
810 list_add(&bh
->b_assoc_buffers
, &tmp
);
811 bh
->b_assoc_map
= mapping
;
812 if (buffer_dirty(bh
)) {
816 * Ensure any pending I/O completes so that
817 * ll_rw_block() actually writes the current
818 * contents - it is a noop if I/O is still in
819 * flight on potentially older contents.
821 ll_rw_block(SWRITE_SYNC
, 1, &bh
);
828 while (!list_empty(&tmp
)) {
829 bh
= BH_ENTRY(tmp
.prev
);
831 mapping
= bh
->b_assoc_map
;
832 __remove_assoc_queue(bh
);
833 /* Avoid race with mark_buffer_dirty_inode() which does
834 * a lockless check and we rely on seeing the dirty bit */
836 if (buffer_dirty(bh
)) {
837 list_add(&bh
->b_assoc_buffers
,
838 &mapping
->private_list
);
839 bh
->b_assoc_map
= mapping
;
843 if (!buffer_uptodate(bh
))
850 err2
= osync_buffers_list(lock
, list
);
858 * Invalidate any and all dirty buffers on a given inode. We are
859 * probably unmounting the fs, but that doesn't mean we have already
860 * done a sync(). Just drop the buffers from the inode list.
862 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
863 * assumes that all the buffers are against the blockdev. Not true
866 void invalidate_inode_buffers(struct inode
*inode
)
868 if (inode_has_buffers(inode
)) {
869 struct address_space
*mapping
= &inode
->i_data
;
870 struct list_head
*list
= &mapping
->private_list
;
871 struct address_space
*buffer_mapping
= mapping
->assoc_mapping
;
873 spin_lock(&buffer_mapping
->private_lock
);
874 while (!list_empty(list
))
875 __remove_assoc_queue(BH_ENTRY(list
->next
));
876 spin_unlock(&buffer_mapping
->private_lock
);
881 * Remove any clean buffers from the inode's buffer list. This is called
882 * when we're trying to free the inode itself. Those buffers can pin it.
884 * Returns true if all buffers were removed.
886 int remove_inode_buffers(struct inode
*inode
)
890 if (inode_has_buffers(inode
)) {
891 struct address_space
*mapping
= &inode
->i_data
;
892 struct list_head
*list
= &mapping
->private_list
;
893 struct address_space
*buffer_mapping
= mapping
->assoc_mapping
;
895 spin_lock(&buffer_mapping
->private_lock
);
896 while (!list_empty(list
)) {
897 struct buffer_head
*bh
= BH_ENTRY(list
->next
);
898 if (buffer_dirty(bh
)) {
902 __remove_assoc_queue(bh
);
904 spin_unlock(&buffer_mapping
->private_lock
);
910 * Create the appropriate buffers when given a page for data area and
911 * the size of each buffer.. Use the bh->b_this_page linked list to
912 * follow the buffers created. Return NULL if unable to create more
915 * The retry flag is used to differentiate async IO (paging, swapping)
916 * which may not fail from ordinary buffer allocations.
918 struct buffer_head
*alloc_page_buffers(struct page
*page
, unsigned long size
,
921 struct buffer_head
*bh
, *head
;
927 while ((offset
-= size
) >= 0) {
928 bh
= alloc_buffer_head(GFP_NOFS
);
933 bh
->b_this_page
= head
;
938 atomic_set(&bh
->b_count
, 0);
939 bh
->b_private
= NULL
;
942 /* Link the buffer to its page */
943 set_bh_page(bh
, page
, offset
);
945 init_buffer(bh
, NULL
, NULL
);
949 * In case anything failed, we just free everything we got.
955 head
= head
->b_this_page
;
956 free_buffer_head(bh
);
961 * Return failure for non-async IO requests. Async IO requests
962 * are not allowed to fail, so we have to wait until buffer heads
963 * become available. But we don't want tasks sleeping with
964 * partially complete buffers, so all were released above.
969 /* We're _really_ low on memory. Now we just
970 * wait for old buffer heads to become free due to
971 * finishing IO. Since this is an async request and
972 * the reserve list is empty, we're sure there are
973 * async buffer heads in use.
978 EXPORT_SYMBOL_GPL(alloc_page_buffers
);
981 link_dev_buffers(struct page
*page
, struct buffer_head
*head
)
983 struct buffer_head
*bh
, *tail
;
988 bh
= bh
->b_this_page
;
990 tail
->b_this_page
= head
;
991 attach_page_buffers(page
, head
);
995 * Initialise the state of a blockdev page's buffers.
998 init_page_buffers(struct page
*page
, struct block_device
*bdev
,
999 sector_t block
, int size
)
1001 struct buffer_head
*head
= page_buffers(page
);
1002 struct buffer_head
*bh
= head
;
1003 int uptodate
= PageUptodate(page
);
1006 if (!buffer_mapped(bh
)) {
1007 init_buffer(bh
, NULL
, NULL
);
1009 bh
->b_blocknr
= block
;
1011 set_buffer_uptodate(bh
);
1012 set_buffer_mapped(bh
);
1015 bh
= bh
->b_this_page
;
1016 } while (bh
!= head
);
1020 * Create the page-cache page that contains the requested block.
1022 * This is user purely for blockdev mappings.
1024 static struct page
*
1025 grow_dev_page(struct block_device
*bdev
, sector_t block
,
1026 pgoff_t index
, int size
)
1028 struct inode
*inode
= bdev
->bd_inode
;
1030 struct buffer_head
*bh
;
1032 page
= find_or_create_page(inode
->i_mapping
, index
,
1033 (mapping_gfp_mask(inode
->i_mapping
) & ~__GFP_FS
)|__GFP_MOVABLE
);
1037 BUG_ON(!PageLocked(page
));
1039 if (page_has_buffers(page
)) {
1040 bh
= page_buffers(page
);
1041 if (bh
->b_size
== size
) {
1042 init_page_buffers(page
, bdev
, block
, size
);
1045 if (!try_to_free_buffers(page
))
1050 * Allocate some buffers for this page
1052 bh
= alloc_page_buffers(page
, size
, 0);
1057 * Link the page to the buffers and initialise them. Take the
1058 * lock to be atomic wrt __find_get_block(), which does not
1059 * run under the page lock.
1061 spin_lock(&inode
->i_mapping
->private_lock
);
1062 link_dev_buffers(page
, bh
);
1063 init_page_buffers(page
, bdev
, block
, size
);
1064 spin_unlock(&inode
->i_mapping
->private_lock
);
1070 page_cache_release(page
);
1075 * Create buffers for the specified block device block's page. If
1076 * that page was dirty, the buffers are set dirty also.
1079 grow_buffers(struct block_device
*bdev
, sector_t block
, int size
)
1088 } while ((size
<< sizebits
) < PAGE_SIZE
);
1090 index
= block
>> sizebits
;
1093 * Check for a block which wants to lie outside our maximum possible
1094 * pagecache index. (this comparison is done using sector_t types).
1096 if (unlikely(index
!= block
>> sizebits
)) {
1097 char b
[BDEVNAME_SIZE
];
1099 printk(KERN_ERR
"%s: requested out-of-range block %llu for "
1101 __FUNCTION__
, (unsigned long long)block
,
1105 block
= index
<< sizebits
;
1106 /* Create a page with the proper size buffers.. */
1107 page
= grow_dev_page(bdev
, block
, index
, size
);
1111 page_cache_release(page
);
1115 static struct buffer_head
*
1116 __getblk_slow(struct block_device
*bdev
, sector_t block
, int size
)
1118 /* Size must be multiple of hard sectorsize */
1119 if (unlikely(size
& (bdev_hardsect_size(bdev
)-1) ||
1120 (size
< 512 || size
> PAGE_SIZE
))) {
1121 printk(KERN_ERR
"getblk(): invalid block size %d requested\n",
1123 printk(KERN_ERR
"hardsect size: %d\n",
1124 bdev_hardsect_size(bdev
));
1131 struct buffer_head
* bh
;
1134 bh
= __find_get_block(bdev
, block
, size
);
1138 ret
= grow_buffers(bdev
, block
, size
);
1147 * The relationship between dirty buffers and dirty pages:
1149 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1150 * the page is tagged dirty in its radix tree.
1152 * At all times, the dirtiness of the buffers represents the dirtiness of
1153 * subsections of the page. If the page has buffers, the page dirty bit is
1154 * merely a hint about the true dirty state.
1156 * When a page is set dirty in its entirety, all its buffers are marked dirty
1157 * (if the page has buffers).
1159 * When a buffer is marked dirty, its page is dirtied, but the page's other
1162 * Also. When blockdev buffers are explicitly read with bread(), they
1163 * individually become uptodate. But their backing page remains not
1164 * uptodate - even if all of its buffers are uptodate. A subsequent
1165 * block_read_full_page() against that page will discover all the uptodate
1166 * buffers, will set the page uptodate and will perform no I/O.
1170 * mark_buffer_dirty - mark a buffer_head as needing writeout
1171 * @bh: the buffer_head to mark dirty
1173 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1174 * backing page dirty, then tag the page as dirty in its address_space's radix
1175 * tree and then attach the address_space's inode to its superblock's dirty
1178 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1179 * mapping->tree_lock and the global inode_lock.
1181 void mark_buffer_dirty(struct buffer_head
*bh
)
1183 WARN_ON_ONCE(!buffer_uptodate(bh
));
1186 * Very *carefully* optimize the it-is-already-dirty case.
1188 * Don't let the final "is it dirty" escape to before we
1189 * perhaps modified the buffer.
1191 if (buffer_dirty(bh
)) {
1193 if (buffer_dirty(bh
))
1197 if (!test_set_buffer_dirty(bh
))
1198 __set_page_dirty(bh
->b_page
, page_mapping(bh
->b_page
), 0);
1202 * Decrement a buffer_head's reference count. If all buffers against a page
1203 * have zero reference count, are clean and unlocked, and if the page is clean
1204 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1205 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1206 * a page but it ends up not being freed, and buffers may later be reattached).
1208 void __brelse(struct buffer_head
* buf
)
1210 if (atomic_read(&buf
->b_count
)) {
1214 printk(KERN_ERR
"VFS: brelse: Trying to free free buffer\n");
1219 * bforget() is like brelse(), except it discards any
1220 * potentially dirty data.
1222 void __bforget(struct buffer_head
*bh
)
1224 clear_buffer_dirty(bh
);
1225 if (bh
->b_assoc_map
) {
1226 struct address_space
*buffer_mapping
= bh
->b_page
->mapping
;
1228 spin_lock(&buffer_mapping
->private_lock
);
1229 list_del_init(&bh
->b_assoc_buffers
);
1230 bh
->b_assoc_map
= NULL
;
1231 spin_unlock(&buffer_mapping
->private_lock
);
1236 static struct buffer_head
*__bread_slow(struct buffer_head
*bh
)
1239 if (buffer_uptodate(bh
)) {
1244 bh
->b_end_io
= end_buffer_read_sync
;
1245 submit_bh(READ
, bh
);
1247 if (buffer_uptodate(bh
))
1255 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1256 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1257 * refcount elevated by one when they're in an LRU. A buffer can only appear
1258 * once in a particular CPU's LRU. A single buffer can be present in multiple
1259 * CPU's LRUs at the same time.
1261 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1262 * sb_find_get_block().
1264 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1265 * a local interrupt disable for that.
1268 #define BH_LRU_SIZE 8
1271 struct buffer_head
*bhs
[BH_LRU_SIZE
];
1274 static DEFINE_PER_CPU(struct bh_lru
, bh_lrus
) = {{ NULL
}};
1277 #define bh_lru_lock() local_irq_disable()
1278 #define bh_lru_unlock() local_irq_enable()
1280 #define bh_lru_lock() preempt_disable()
1281 #define bh_lru_unlock() preempt_enable()
1284 static inline void check_irqs_on(void)
1286 #ifdef irqs_disabled
1287 BUG_ON(irqs_disabled());
1292 * The LRU management algorithm is dopey-but-simple. Sorry.
1294 static void bh_lru_install(struct buffer_head
*bh
)
1296 struct buffer_head
*evictee
= NULL
;
1301 lru
= &__get_cpu_var(bh_lrus
);
1302 if (lru
->bhs
[0] != bh
) {
1303 struct buffer_head
*bhs
[BH_LRU_SIZE
];
1309 for (in
= 0; in
< BH_LRU_SIZE
; in
++) {
1310 struct buffer_head
*bh2
= lru
->bhs
[in
];
1315 if (out
>= BH_LRU_SIZE
) {
1316 BUG_ON(evictee
!= NULL
);
1323 while (out
< BH_LRU_SIZE
)
1325 memcpy(lru
->bhs
, bhs
, sizeof(bhs
));
1334 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1336 static struct buffer_head
*
1337 lookup_bh_lru(struct block_device
*bdev
, sector_t block
, unsigned size
)
1339 struct buffer_head
*ret
= NULL
;
1345 lru
= &__get_cpu_var(bh_lrus
);
1346 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1347 struct buffer_head
*bh
= lru
->bhs
[i
];
1349 if (bh
&& bh
->b_bdev
== bdev
&&
1350 bh
->b_blocknr
== block
&& bh
->b_size
== size
) {
1353 lru
->bhs
[i
] = lru
->bhs
[i
- 1];
1368 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1369 * it in the LRU and mark it as accessed. If it is not present then return
1372 struct buffer_head
*
1373 __find_get_block(struct block_device
*bdev
, sector_t block
, unsigned size
)
1375 struct buffer_head
*bh
= lookup_bh_lru(bdev
, block
, size
);
1378 bh
= __find_get_block_slow(bdev
, block
);
1386 EXPORT_SYMBOL(__find_get_block
);
1389 * __getblk will locate (and, if necessary, create) the buffer_head
1390 * which corresponds to the passed block_device, block and size. The
1391 * returned buffer has its reference count incremented.
1393 * __getblk() cannot fail - it just keeps trying. If you pass it an
1394 * illegal block number, __getblk() will happily return a buffer_head
1395 * which represents the non-existent block. Very weird.
1397 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1398 * attempt is failing. FIXME, perhaps?
1400 struct buffer_head
*
1401 __getblk(struct block_device
*bdev
, sector_t block
, unsigned size
)
1403 struct buffer_head
*bh
= __find_get_block(bdev
, block
, size
);
1407 bh
= __getblk_slow(bdev
, block
, size
);
1410 EXPORT_SYMBOL(__getblk
);
1413 * Do async read-ahead on a buffer..
1415 void __breadahead(struct block_device
*bdev
, sector_t block
, unsigned size
)
1417 struct buffer_head
*bh
= __getblk(bdev
, block
, size
);
1419 ll_rw_block(READA
, 1, &bh
);
1423 EXPORT_SYMBOL(__breadahead
);
1426 * __bread() - reads a specified block and returns the bh
1427 * @bdev: the block_device to read from
1428 * @block: number of block
1429 * @size: size (in bytes) to read
1431 * Reads a specified block, and returns buffer head that contains it.
1432 * It returns NULL if the block was unreadable.
1434 struct buffer_head
*
1435 __bread(struct block_device
*bdev
, sector_t block
, unsigned size
)
1437 struct buffer_head
*bh
= __getblk(bdev
, block
, size
);
1439 if (likely(bh
) && !buffer_uptodate(bh
))
1440 bh
= __bread_slow(bh
);
1443 EXPORT_SYMBOL(__bread
);
1446 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1447 * This doesn't race because it runs in each cpu either in irq
1448 * or with preempt disabled.
1450 static void invalidate_bh_lru(void *arg
)
1452 struct bh_lru
*b
= &get_cpu_var(bh_lrus
);
1455 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1459 put_cpu_var(bh_lrus
);
1462 void invalidate_bh_lrus(void)
1464 on_each_cpu(invalidate_bh_lru
, NULL
, 1, 1);
1466 EXPORT_SYMBOL_GPL(invalidate_bh_lrus
);
1468 void set_bh_page(struct buffer_head
*bh
,
1469 struct page
*page
, unsigned long offset
)
1472 BUG_ON(offset
>= PAGE_SIZE
);
1473 if (PageHighMem(page
))
1475 * This catches illegal uses and preserves the offset:
1477 bh
->b_data
= (char *)(0 + offset
);
1479 bh
->b_data
= page_address(page
) + offset
;
1481 EXPORT_SYMBOL(set_bh_page
);
1484 * Called when truncating a buffer on a page completely.
1486 static void discard_buffer(struct buffer_head
* bh
)
1489 clear_buffer_dirty(bh
);
1491 clear_buffer_mapped(bh
);
1492 clear_buffer_req(bh
);
1493 clear_buffer_new(bh
);
1494 clear_buffer_delay(bh
);
1495 clear_buffer_unwritten(bh
);
1500 * block_invalidatepage - invalidate part of all of a buffer-backed page
1502 * @page: the page which is affected
1503 * @offset: the index of the truncation point
1505 * block_invalidatepage() is called when all or part of the page has become
1506 * invalidatedby a truncate operation.
1508 * block_invalidatepage() does not have to release all buffers, but it must
1509 * ensure that no dirty buffer is left outside @offset and that no I/O
1510 * is underway against any of the blocks which are outside the truncation
1511 * point. Because the caller is about to free (and possibly reuse) those
1514 void block_invalidatepage(struct page
*page
, unsigned long offset
)
1516 struct buffer_head
*head
, *bh
, *next
;
1517 unsigned int curr_off
= 0;
1519 BUG_ON(!PageLocked(page
));
1520 if (!page_has_buffers(page
))
1523 head
= page_buffers(page
);
1526 unsigned int next_off
= curr_off
+ bh
->b_size
;
1527 next
= bh
->b_this_page
;
1530 * is this block fully invalidated?
1532 if (offset
<= curr_off
)
1534 curr_off
= next_off
;
1536 } while (bh
!= head
);
1539 * We release buffers only if the entire page is being invalidated.
1540 * The get_block cached value has been unconditionally invalidated,
1541 * so real IO is not possible anymore.
1544 try_to_release_page(page
, 0);
1548 EXPORT_SYMBOL(block_invalidatepage
);
1551 * We attach and possibly dirty the buffers atomically wrt
1552 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1553 * is already excluded via the page lock.
1555 void create_empty_buffers(struct page
*page
,
1556 unsigned long blocksize
, unsigned long b_state
)
1558 struct buffer_head
*bh
, *head
, *tail
;
1560 head
= alloc_page_buffers(page
, blocksize
, 1);
1563 bh
->b_state
|= b_state
;
1565 bh
= bh
->b_this_page
;
1567 tail
->b_this_page
= head
;
1569 spin_lock(&page
->mapping
->private_lock
);
1570 if (PageUptodate(page
) || PageDirty(page
)) {
1573 if (PageDirty(page
))
1574 set_buffer_dirty(bh
);
1575 if (PageUptodate(page
))
1576 set_buffer_uptodate(bh
);
1577 bh
= bh
->b_this_page
;
1578 } while (bh
!= head
);
1580 attach_page_buffers(page
, head
);
1581 spin_unlock(&page
->mapping
->private_lock
);
1583 EXPORT_SYMBOL(create_empty_buffers
);
1586 * We are taking a block for data and we don't want any output from any
1587 * buffer-cache aliases starting from return from that function and
1588 * until the moment when something will explicitly mark the buffer
1589 * dirty (hopefully that will not happen until we will free that block ;-)
1590 * We don't even need to mark it not-uptodate - nobody can expect
1591 * anything from a newly allocated buffer anyway. We used to used
1592 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1593 * don't want to mark the alias unmapped, for example - it would confuse
1594 * anyone who might pick it with bread() afterwards...
1596 * Also.. Note that bforget() doesn't lock the buffer. So there can
1597 * be writeout I/O going on against recently-freed buffers. We don't
1598 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1599 * only if we really need to. That happens here.
1601 void unmap_underlying_metadata(struct block_device
*bdev
, sector_t block
)
1603 struct buffer_head
*old_bh
;
1607 old_bh
= __find_get_block_slow(bdev
, block
);
1609 clear_buffer_dirty(old_bh
);
1610 wait_on_buffer(old_bh
);
1611 clear_buffer_req(old_bh
);
1615 EXPORT_SYMBOL(unmap_underlying_metadata
);
1618 * NOTE! All mapped/uptodate combinations are valid:
1620 * Mapped Uptodate Meaning
1622 * No No "unknown" - must do get_block()
1623 * No Yes "hole" - zero-filled
1624 * Yes No "allocated" - allocated on disk, not read in
1625 * Yes Yes "valid" - allocated and up-to-date in memory.
1627 * "Dirty" is valid only with the last case (mapped+uptodate).
1631 * While block_write_full_page is writing back the dirty buffers under
1632 * the page lock, whoever dirtied the buffers may decide to clean them
1633 * again at any time. We handle that by only looking at the buffer
1634 * state inside lock_buffer().
1636 * If block_write_full_page() is called for regular writeback
1637 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1638 * locked buffer. This only can happen if someone has written the buffer
1639 * directly, with submit_bh(). At the address_space level PageWriteback
1640 * prevents this contention from occurring.
1642 static int __block_write_full_page(struct inode
*inode
, struct page
*page
,
1643 get_block_t
*get_block
, struct writeback_control
*wbc
)
1647 sector_t last_block
;
1648 struct buffer_head
*bh
, *head
;
1649 const unsigned blocksize
= 1 << inode
->i_blkbits
;
1650 int nr_underway
= 0;
1652 BUG_ON(!PageLocked(page
));
1654 last_block
= (i_size_read(inode
) - 1) >> inode
->i_blkbits
;
1656 if (!page_has_buffers(page
)) {
1657 create_empty_buffers(page
, blocksize
,
1658 (1 << BH_Dirty
)|(1 << BH_Uptodate
));
1662 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1663 * here, and the (potentially unmapped) buffers may become dirty at
1664 * any time. If a buffer becomes dirty here after we've inspected it
1665 * then we just miss that fact, and the page stays dirty.
1667 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1668 * handle that here by just cleaning them.
1671 block
= (sector_t
)page
->index
<< (PAGE_CACHE_SHIFT
- inode
->i_blkbits
);
1672 head
= page_buffers(page
);
1676 * Get all the dirty buffers mapped to disk addresses and
1677 * handle any aliases from the underlying blockdev's mapping.
1680 if (block
> last_block
) {
1682 * mapped buffers outside i_size will occur, because
1683 * this page can be outside i_size when there is a
1684 * truncate in progress.
1687 * The buffer was zeroed by block_write_full_page()
1689 clear_buffer_dirty(bh
);
1690 set_buffer_uptodate(bh
);
1691 } else if (!buffer_mapped(bh
) && buffer_dirty(bh
)) {
1692 WARN_ON(bh
->b_size
!= blocksize
);
1693 err
= get_block(inode
, block
, bh
, 1);
1696 if (buffer_new(bh
)) {
1697 /* blockdev mappings never come here */
1698 clear_buffer_new(bh
);
1699 unmap_underlying_metadata(bh
->b_bdev
,
1703 bh
= bh
->b_this_page
;
1705 } while (bh
!= head
);
1708 if (!buffer_mapped(bh
))
1711 * If it's a fully non-blocking write attempt and we cannot
1712 * lock the buffer then redirty the page. Note that this can
1713 * potentially cause a busy-wait loop from pdflush and kswapd
1714 * activity, but those code paths have their own higher-level
1717 if (wbc
->sync_mode
!= WB_SYNC_NONE
|| !wbc
->nonblocking
) {
1719 } else if (test_set_buffer_locked(bh
)) {
1720 redirty_page_for_writepage(wbc
, page
);
1723 if (test_clear_buffer_dirty(bh
)) {
1724 mark_buffer_async_write(bh
);
1728 } while ((bh
= bh
->b_this_page
) != head
);
1731 * The page and its buffers are protected by PageWriteback(), so we can
1732 * drop the bh refcounts early.
1734 BUG_ON(PageWriteback(page
));
1735 set_page_writeback(page
);
1738 struct buffer_head
*next
= bh
->b_this_page
;
1739 if (buffer_async_write(bh
)) {
1740 submit_bh(WRITE
, bh
);
1744 } while (bh
!= head
);
1749 if (nr_underway
== 0) {
1751 * The page was marked dirty, but the buffers were
1752 * clean. Someone wrote them back by hand with
1753 * ll_rw_block/submit_bh. A rare case.
1755 end_page_writeback(page
);
1758 * The page and buffer_heads can be released at any time from
1766 * ENOSPC, or some other error. We may already have added some
1767 * blocks to the file, so we need to write these out to avoid
1768 * exposing stale data.
1769 * The page is currently locked and not marked for writeback
1772 /* Recovery: lock and submit the mapped buffers */
1774 if (buffer_mapped(bh
) && buffer_dirty(bh
)) {
1776 mark_buffer_async_write(bh
);
1779 * The buffer may have been set dirty during
1780 * attachment to a dirty page.
1782 clear_buffer_dirty(bh
);
1784 } while ((bh
= bh
->b_this_page
) != head
);
1786 BUG_ON(PageWriteback(page
));
1787 mapping_set_error(page
->mapping
, err
);
1788 set_page_writeback(page
);
1790 struct buffer_head
*next
= bh
->b_this_page
;
1791 if (buffer_async_write(bh
)) {
1792 clear_buffer_dirty(bh
);
1793 submit_bh(WRITE
, bh
);
1797 } while (bh
!= head
);
1803 * If a page has any new buffers, zero them out here, and mark them uptodate
1804 * and dirty so they'll be written out (in order to prevent uninitialised
1805 * block data from leaking). And clear the new bit.
1807 void page_zero_new_buffers(struct page
*page
, unsigned from
, unsigned to
)
1809 unsigned int block_start
, block_end
;
1810 struct buffer_head
*head
, *bh
;
1812 BUG_ON(!PageLocked(page
));
1813 if (!page_has_buffers(page
))
1816 bh
= head
= page_buffers(page
);
1819 block_end
= block_start
+ bh
->b_size
;
1821 if (buffer_new(bh
)) {
1822 if (block_end
> from
&& block_start
< to
) {
1823 if (!PageUptodate(page
)) {
1824 unsigned start
, size
;
1826 start
= max(from
, block_start
);
1827 size
= min(to
, block_end
) - start
;
1829 zero_user(page
, start
, size
);
1830 set_buffer_uptodate(bh
);
1833 clear_buffer_new(bh
);
1834 mark_buffer_dirty(bh
);
1838 block_start
= block_end
;
1839 bh
= bh
->b_this_page
;
1840 } while (bh
!= head
);
1842 EXPORT_SYMBOL(page_zero_new_buffers
);
1844 static int __block_prepare_write(struct inode
*inode
, struct page
*page
,
1845 unsigned from
, unsigned to
, get_block_t
*get_block
)
1847 unsigned block_start
, block_end
;
1850 unsigned blocksize
, bbits
;
1851 struct buffer_head
*bh
, *head
, *wait
[2], **wait_bh
=wait
;
1853 BUG_ON(!PageLocked(page
));
1854 BUG_ON(from
> PAGE_CACHE_SIZE
);
1855 BUG_ON(to
> PAGE_CACHE_SIZE
);
1858 blocksize
= 1 << inode
->i_blkbits
;
1859 if (!page_has_buffers(page
))
1860 create_empty_buffers(page
, blocksize
, 0);
1861 head
= page_buffers(page
);
1863 bbits
= inode
->i_blkbits
;
1864 block
= (sector_t
)page
->index
<< (PAGE_CACHE_SHIFT
- bbits
);
1866 for(bh
= head
, block_start
= 0; bh
!= head
|| !block_start
;
1867 block
++, block_start
=block_end
, bh
= bh
->b_this_page
) {
1868 block_end
= block_start
+ blocksize
;
1869 if (block_end
<= from
|| block_start
>= to
) {
1870 if (PageUptodate(page
)) {
1871 if (!buffer_uptodate(bh
))
1872 set_buffer_uptodate(bh
);
1877 clear_buffer_new(bh
);
1878 if (!buffer_mapped(bh
)) {
1879 WARN_ON(bh
->b_size
!= blocksize
);
1880 err
= get_block(inode
, block
, bh
, 1);
1883 if (buffer_new(bh
)) {
1884 unmap_underlying_metadata(bh
->b_bdev
,
1886 if (PageUptodate(page
)) {
1887 clear_buffer_new(bh
);
1888 set_buffer_uptodate(bh
);
1889 mark_buffer_dirty(bh
);
1892 if (block_end
> to
|| block_start
< from
)
1893 zero_user_segments(page
,
1899 if (PageUptodate(page
)) {
1900 if (!buffer_uptodate(bh
))
1901 set_buffer_uptodate(bh
);
1904 if (!buffer_uptodate(bh
) && !buffer_delay(bh
) &&
1905 !buffer_unwritten(bh
) &&
1906 (block_start
< from
|| block_end
> to
)) {
1907 ll_rw_block(READ
, 1, &bh
);
1912 * If we issued read requests - let them complete.
1914 while(wait_bh
> wait
) {
1915 wait_on_buffer(*--wait_bh
);
1916 if (!buffer_uptodate(*wait_bh
))
1920 page_zero_new_buffers(page
, from
, to
);
1924 static int __block_commit_write(struct inode
*inode
, struct page
*page
,
1925 unsigned from
, unsigned to
)
1927 unsigned block_start
, block_end
;
1930 struct buffer_head
*bh
, *head
;
1932 blocksize
= 1 << inode
->i_blkbits
;
1934 for(bh
= head
= page_buffers(page
), block_start
= 0;
1935 bh
!= head
|| !block_start
;
1936 block_start
=block_end
, bh
= bh
->b_this_page
) {
1937 block_end
= block_start
+ blocksize
;
1938 if (block_end
<= from
|| block_start
>= to
) {
1939 if (!buffer_uptodate(bh
))
1942 set_buffer_uptodate(bh
);
1943 mark_buffer_dirty(bh
);
1945 clear_buffer_new(bh
);
1949 * If this is a partial write which happened to make all buffers
1950 * uptodate then we can optimize away a bogus readpage() for
1951 * the next read(). Here we 'discover' whether the page went
1952 * uptodate as a result of this (potentially partial) write.
1955 SetPageUptodate(page
);
1960 * block_write_begin takes care of the basic task of block allocation and
1961 * bringing partial write blocks uptodate first.
1963 * If *pagep is not NULL, then block_write_begin uses the locked page
1964 * at *pagep rather than allocating its own. In this case, the page will
1965 * not be unlocked or deallocated on failure.
1967 int block_write_begin(struct file
*file
, struct address_space
*mapping
,
1968 loff_t pos
, unsigned len
, unsigned flags
,
1969 struct page
**pagep
, void **fsdata
,
1970 get_block_t
*get_block
)
1972 struct inode
*inode
= mapping
->host
;
1976 unsigned start
, end
;
1979 index
= pos
>> PAGE_CACHE_SHIFT
;
1980 start
= pos
& (PAGE_CACHE_SIZE
- 1);
1986 page
= __grab_cache_page(mapping
, index
);
1993 BUG_ON(!PageLocked(page
));
1995 status
= __block_prepare_write(inode
, page
, start
, end
, get_block
);
1996 if (unlikely(status
)) {
1997 ClearPageUptodate(page
);
2001 page_cache_release(page
);
2005 * prepare_write() may have instantiated a few blocks
2006 * outside i_size. Trim these off again. Don't need
2007 * i_size_read because we hold i_mutex.
2009 if (pos
+ len
> inode
->i_size
)
2010 vmtruncate(inode
, inode
->i_size
);
2018 EXPORT_SYMBOL(block_write_begin
);
2020 int block_write_end(struct file
*file
, struct address_space
*mapping
,
2021 loff_t pos
, unsigned len
, unsigned copied
,
2022 struct page
*page
, void *fsdata
)
2024 struct inode
*inode
= mapping
->host
;
2027 start
= pos
& (PAGE_CACHE_SIZE
- 1);
2029 if (unlikely(copied
< len
)) {
2031 * The buffers that were written will now be uptodate, so we
2032 * don't have to worry about a readpage reading them and
2033 * overwriting a partial write. However if we have encountered
2034 * a short write and only partially written into a buffer, it
2035 * will not be marked uptodate, so a readpage might come in and
2036 * destroy our partial write.
2038 * Do the simplest thing, and just treat any short write to a
2039 * non uptodate page as a zero-length write, and force the
2040 * caller to redo the whole thing.
2042 if (!PageUptodate(page
))
2045 page_zero_new_buffers(page
, start
+copied
, start
+len
);
2047 flush_dcache_page(page
);
2049 /* This could be a short (even 0-length) commit */
2050 __block_commit_write(inode
, page
, start
, start
+copied
);
2054 EXPORT_SYMBOL(block_write_end
);
2056 int generic_write_end(struct file
*file
, struct address_space
*mapping
,
2057 loff_t pos
, unsigned len
, unsigned copied
,
2058 struct page
*page
, void *fsdata
)
2060 struct inode
*inode
= mapping
->host
;
2062 copied
= block_write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2065 * No need to use i_size_read() here, the i_size
2066 * cannot change under us because we hold i_mutex.
2068 * But it's important to update i_size while still holding page lock:
2069 * page writeout could otherwise come in and zero beyond i_size.
2071 if (pos
+copied
> inode
->i_size
) {
2072 i_size_write(inode
, pos
+copied
);
2073 mark_inode_dirty(inode
);
2077 page_cache_release(page
);
2081 EXPORT_SYMBOL(generic_write_end
);
2084 * Generic "read page" function for block devices that have the normal
2085 * get_block functionality. This is most of the block device filesystems.
2086 * Reads the page asynchronously --- the unlock_buffer() and
2087 * set/clear_buffer_uptodate() functions propagate buffer state into the
2088 * page struct once IO has completed.
2090 int block_read_full_page(struct page
*page
, get_block_t
*get_block
)
2092 struct inode
*inode
= page
->mapping
->host
;
2093 sector_t iblock
, lblock
;
2094 struct buffer_head
*bh
, *head
, *arr
[MAX_BUF_PER_PAGE
];
2095 unsigned int blocksize
;
2097 int fully_mapped
= 1;
2099 BUG_ON(!PageLocked(page
));
2100 blocksize
= 1 << inode
->i_blkbits
;
2101 if (!page_has_buffers(page
))
2102 create_empty_buffers(page
, blocksize
, 0);
2103 head
= page_buffers(page
);
2105 iblock
= (sector_t
)page
->index
<< (PAGE_CACHE_SHIFT
- inode
->i_blkbits
);
2106 lblock
= (i_size_read(inode
)+blocksize
-1) >> inode
->i_blkbits
;
2112 if (buffer_uptodate(bh
))
2115 if (!buffer_mapped(bh
)) {
2119 if (iblock
< lblock
) {
2120 WARN_ON(bh
->b_size
!= blocksize
);
2121 err
= get_block(inode
, iblock
, bh
, 0);
2125 if (!buffer_mapped(bh
)) {
2126 zero_user(page
, i
* blocksize
, blocksize
);
2128 set_buffer_uptodate(bh
);
2132 * get_block() might have updated the buffer
2135 if (buffer_uptodate(bh
))
2139 } while (i
++, iblock
++, (bh
= bh
->b_this_page
) != head
);
2142 SetPageMappedToDisk(page
);
2146 * All buffers are uptodate - we can set the page uptodate
2147 * as well. But not if get_block() returned an error.
2149 if (!PageError(page
))
2150 SetPageUptodate(page
);
2155 /* Stage two: lock the buffers */
2156 for (i
= 0; i
< nr
; i
++) {
2159 mark_buffer_async_read(bh
);
2163 * Stage 3: start the IO. Check for uptodateness
2164 * inside the buffer lock in case another process reading
2165 * the underlying blockdev brought it uptodate (the sct fix).
2167 for (i
= 0; i
< nr
; i
++) {
2169 if (buffer_uptodate(bh
))
2170 end_buffer_async_read(bh
, 1);
2172 submit_bh(READ
, bh
);
2177 /* utility function for filesystems that need to do work on expanding
2178 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2179 * deal with the hole.
2181 int generic_cont_expand_simple(struct inode
*inode
, loff_t size
)
2183 struct address_space
*mapping
= inode
->i_mapping
;
2186 unsigned long limit
;
2190 limit
= current
->signal
->rlim
[RLIMIT_FSIZE
].rlim_cur
;
2191 if (limit
!= RLIM_INFINITY
&& size
> (loff_t
)limit
) {
2192 send_sig(SIGXFSZ
, current
, 0);
2195 if (size
> inode
->i_sb
->s_maxbytes
)
2198 err
= pagecache_write_begin(NULL
, mapping
, size
, 0,
2199 AOP_FLAG_UNINTERRUPTIBLE
|AOP_FLAG_CONT_EXPAND
,
2204 err
= pagecache_write_end(NULL
, mapping
, size
, 0, 0, page
, fsdata
);
2211 int cont_expand_zero(struct file
*file
, struct address_space
*mapping
,
2212 loff_t pos
, loff_t
*bytes
)
2214 struct inode
*inode
= mapping
->host
;
2215 unsigned blocksize
= 1 << inode
->i_blkbits
;
2218 pgoff_t index
, curidx
;
2220 unsigned zerofrom
, offset
, len
;
2223 index
= pos
>> PAGE_CACHE_SHIFT
;
2224 offset
= pos
& ~PAGE_CACHE_MASK
;
2226 while (index
> (curidx
= (curpos
= *bytes
)>>PAGE_CACHE_SHIFT
)) {
2227 zerofrom
= curpos
& ~PAGE_CACHE_MASK
;
2228 if (zerofrom
& (blocksize
-1)) {
2229 *bytes
|= (blocksize
-1);
2232 len
= PAGE_CACHE_SIZE
- zerofrom
;
2234 err
= pagecache_write_begin(file
, mapping
, curpos
, len
,
2235 AOP_FLAG_UNINTERRUPTIBLE
,
2239 zero_user(page
, zerofrom
, len
);
2240 err
= pagecache_write_end(file
, mapping
, curpos
, len
, len
,
2248 /* page covers the boundary, find the boundary offset */
2249 if (index
== curidx
) {
2250 zerofrom
= curpos
& ~PAGE_CACHE_MASK
;
2251 /* if we will expand the thing last block will be filled */
2252 if (offset
<= zerofrom
) {
2255 if (zerofrom
& (blocksize
-1)) {
2256 *bytes
|= (blocksize
-1);
2259 len
= offset
- zerofrom
;
2261 err
= pagecache_write_begin(file
, mapping
, curpos
, len
,
2262 AOP_FLAG_UNINTERRUPTIBLE
,
2266 zero_user(page
, zerofrom
, len
);
2267 err
= pagecache_write_end(file
, mapping
, curpos
, len
, len
,
2279 * For moronic filesystems that do not allow holes in file.
2280 * We may have to extend the file.
2282 int cont_write_begin(struct file
*file
, struct address_space
*mapping
,
2283 loff_t pos
, unsigned len
, unsigned flags
,
2284 struct page
**pagep
, void **fsdata
,
2285 get_block_t
*get_block
, loff_t
*bytes
)
2287 struct inode
*inode
= mapping
->host
;
2288 unsigned blocksize
= 1 << inode
->i_blkbits
;
2292 err
= cont_expand_zero(file
, mapping
, pos
, bytes
);
2296 zerofrom
= *bytes
& ~PAGE_CACHE_MASK
;
2297 if (pos
+len
> *bytes
&& zerofrom
& (blocksize
-1)) {
2298 *bytes
|= (blocksize
-1);
2303 err
= block_write_begin(file
, mapping
, pos
, len
,
2304 flags
, pagep
, fsdata
, get_block
);
2309 int block_prepare_write(struct page
*page
, unsigned from
, unsigned to
,
2310 get_block_t
*get_block
)
2312 struct inode
*inode
= page
->mapping
->host
;
2313 int err
= __block_prepare_write(inode
, page
, from
, to
, get_block
);
2315 ClearPageUptodate(page
);
2319 int block_commit_write(struct page
*page
, unsigned from
, unsigned to
)
2321 struct inode
*inode
= page
->mapping
->host
;
2322 __block_commit_write(inode
,page
,from
,to
);
2326 int generic_commit_write(struct file
*file
, struct page
*page
,
2327 unsigned from
, unsigned to
)
2329 struct inode
*inode
= page
->mapping
->host
;
2330 loff_t pos
= ((loff_t
)page
->index
<< PAGE_CACHE_SHIFT
) + to
;
2331 __block_commit_write(inode
,page
,from
,to
);
2333 * No need to use i_size_read() here, the i_size
2334 * cannot change under us because we hold i_mutex.
2336 if (pos
> inode
->i_size
) {
2337 i_size_write(inode
, pos
);
2338 mark_inode_dirty(inode
);
2344 * block_page_mkwrite() is not allowed to change the file size as it gets
2345 * called from a page fault handler when a page is first dirtied. Hence we must
2346 * be careful to check for EOF conditions here. We set the page up correctly
2347 * for a written page which means we get ENOSPC checking when writing into
2348 * holes and correct delalloc and unwritten extent mapping on filesystems that
2349 * support these features.
2351 * We are not allowed to take the i_mutex here so we have to play games to
2352 * protect against truncate races as the page could now be beyond EOF. Because
2353 * vmtruncate() writes the inode size before removing pages, once we have the
2354 * page lock we can determine safely if the page is beyond EOF. If it is not
2355 * beyond EOF, then the page is guaranteed safe against truncation until we
2359 block_page_mkwrite(struct vm_area_struct
*vma
, struct page
*page
,
2360 get_block_t get_block
)
2362 struct inode
*inode
= vma
->vm_file
->f_path
.dentry
->d_inode
;
2368 size
= i_size_read(inode
);
2369 if ((page
->mapping
!= inode
->i_mapping
) ||
2370 (page_offset(page
) > size
)) {
2371 /* page got truncated out from underneath us */
2375 /* page is wholly or partially inside EOF */
2376 if (((page
->index
+ 1) << PAGE_CACHE_SHIFT
) > size
)
2377 end
= size
& ~PAGE_CACHE_MASK
;
2379 end
= PAGE_CACHE_SIZE
;
2381 ret
= block_prepare_write(page
, 0, end
, get_block
);
2383 ret
= block_commit_write(page
, 0, end
);
2391 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2392 * immediately, while under the page lock. So it needs a special end_io
2393 * handler which does not touch the bh after unlocking it.
2395 static void end_buffer_read_nobh(struct buffer_head
*bh
, int uptodate
)
2397 __end_buffer_read_notouch(bh
, uptodate
);
2401 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2402 * the page (converting it to circular linked list and taking care of page
2405 static void attach_nobh_buffers(struct page
*page
, struct buffer_head
*head
)
2407 struct buffer_head
*bh
;
2409 BUG_ON(!PageLocked(page
));
2411 spin_lock(&page
->mapping
->private_lock
);
2414 if (PageDirty(page
))
2415 set_buffer_dirty(bh
);
2416 if (!bh
->b_this_page
)
2417 bh
->b_this_page
= head
;
2418 bh
= bh
->b_this_page
;
2419 } while (bh
!= head
);
2420 attach_page_buffers(page
, head
);
2421 spin_unlock(&page
->mapping
->private_lock
);
2425 * On entry, the page is fully not uptodate.
2426 * On exit the page is fully uptodate in the areas outside (from,to)
2428 int nobh_write_begin(struct file
*file
, struct address_space
*mapping
,
2429 loff_t pos
, unsigned len
, unsigned flags
,
2430 struct page
**pagep
, void **fsdata
,
2431 get_block_t
*get_block
)
2433 struct inode
*inode
= mapping
->host
;
2434 const unsigned blkbits
= inode
->i_blkbits
;
2435 const unsigned blocksize
= 1 << blkbits
;
2436 struct buffer_head
*head
, *bh
;
2440 unsigned block_in_page
;
2441 unsigned block_start
, block_end
;
2442 sector_t block_in_file
;
2445 int is_mapped_to_disk
= 1;
2447 index
= pos
>> PAGE_CACHE_SHIFT
;
2448 from
= pos
& (PAGE_CACHE_SIZE
- 1);
2451 page
= __grab_cache_page(mapping
, index
);
2457 if (page_has_buffers(page
)) {
2459 page_cache_release(page
);
2461 return block_write_begin(file
, mapping
, pos
, len
, flags
, pagep
,
2465 if (PageMappedToDisk(page
))
2469 * Allocate buffers so that we can keep track of state, and potentially
2470 * attach them to the page if an error occurs. In the common case of
2471 * no error, they will just be freed again without ever being attached
2472 * to the page (which is all OK, because we're under the page lock).
2474 * Be careful: the buffer linked list is a NULL terminated one, rather
2475 * than the circular one we're used to.
2477 head
= alloc_page_buffers(page
, blocksize
, 0);
2483 block_in_file
= (sector_t
)page
->index
<< (PAGE_CACHE_SHIFT
- blkbits
);
2486 * We loop across all blocks in the page, whether or not they are
2487 * part of the affected region. This is so we can discover if the
2488 * page is fully mapped-to-disk.
2490 for (block_start
= 0, block_in_page
= 0, bh
= head
;
2491 block_start
< PAGE_CACHE_SIZE
;
2492 block_in_page
++, block_start
+= blocksize
, bh
= bh
->b_this_page
) {
2495 block_end
= block_start
+ blocksize
;
2498 if (block_start
>= to
)
2500 ret
= get_block(inode
, block_in_file
+ block_in_page
,
2504 if (!buffer_mapped(bh
))
2505 is_mapped_to_disk
= 0;
2507 unmap_underlying_metadata(bh
->b_bdev
, bh
->b_blocknr
);
2508 if (PageUptodate(page
)) {
2509 set_buffer_uptodate(bh
);
2512 if (buffer_new(bh
) || !buffer_mapped(bh
)) {
2513 zero_user_segments(page
, block_start
, from
,
2517 if (buffer_uptodate(bh
))
2518 continue; /* reiserfs does this */
2519 if (block_start
< from
|| block_end
> to
) {
2521 bh
->b_end_io
= end_buffer_read_nobh
;
2522 submit_bh(READ
, bh
);
2529 * The page is locked, so these buffers are protected from
2530 * any VM or truncate activity. Hence we don't need to care
2531 * for the buffer_head refcounts.
2533 for (bh
= head
; bh
; bh
= bh
->b_this_page
) {
2535 if (!buffer_uptodate(bh
))
2542 if (is_mapped_to_disk
)
2543 SetPageMappedToDisk(page
);
2545 *fsdata
= head
; /* to be released by nobh_write_end */
2552 * Error recovery is a bit difficult. We need to zero out blocks that
2553 * were newly allocated, and dirty them to ensure they get written out.
2554 * Buffers need to be attached to the page at this point, otherwise
2555 * the handling of potential IO errors during writeout would be hard
2556 * (could try doing synchronous writeout, but what if that fails too?)
2558 attach_nobh_buffers(page
, head
);
2559 page_zero_new_buffers(page
, from
, to
);
2563 page_cache_release(page
);
2566 if (pos
+ len
> inode
->i_size
)
2567 vmtruncate(inode
, inode
->i_size
);
2571 EXPORT_SYMBOL(nobh_write_begin
);
2573 int nobh_write_end(struct file
*file
, struct address_space
*mapping
,
2574 loff_t pos
, unsigned len
, unsigned copied
,
2575 struct page
*page
, void *fsdata
)
2577 struct inode
*inode
= page
->mapping
->host
;
2578 struct buffer_head
*head
= fsdata
;
2579 struct buffer_head
*bh
;
2580 BUG_ON(fsdata
!= NULL
&& page_has_buffers(page
));
2582 if (unlikely(copied
< len
) && !page_has_buffers(page
))
2583 attach_nobh_buffers(page
, head
);
2584 if (page_has_buffers(page
))
2585 return generic_write_end(file
, mapping
, pos
, len
,
2586 copied
, page
, fsdata
);
2588 SetPageUptodate(page
);
2589 set_page_dirty(page
);
2590 if (pos
+copied
> inode
->i_size
) {
2591 i_size_write(inode
, pos
+copied
);
2592 mark_inode_dirty(inode
);
2596 page_cache_release(page
);
2600 head
= head
->b_this_page
;
2601 free_buffer_head(bh
);
2606 EXPORT_SYMBOL(nobh_write_end
);
2609 * nobh_writepage() - based on block_full_write_page() except
2610 * that it tries to operate without attaching bufferheads to
2613 int nobh_writepage(struct page
*page
, get_block_t
*get_block
,
2614 struct writeback_control
*wbc
)
2616 struct inode
* const inode
= page
->mapping
->host
;
2617 loff_t i_size
= i_size_read(inode
);
2618 const pgoff_t end_index
= i_size
>> PAGE_CACHE_SHIFT
;
2622 /* Is the page fully inside i_size? */
2623 if (page
->index
< end_index
)
2626 /* Is the page fully outside i_size? (truncate in progress) */
2627 offset
= i_size
& (PAGE_CACHE_SIZE
-1);
2628 if (page
->index
>= end_index
+1 || !offset
) {
2630 * The page may have dirty, unmapped buffers. For example,
2631 * they may have been added in ext3_writepage(). Make them
2632 * freeable here, so the page does not leak.
2635 /* Not really sure about this - do we need this ? */
2636 if (page
->mapping
->a_ops
->invalidatepage
)
2637 page
->mapping
->a_ops
->invalidatepage(page
, offset
);
2640 return 0; /* don't care */
2644 * The page straddles i_size. It must be zeroed out on each and every
2645 * writepage invocation because it may be mmapped. "A file is mapped
2646 * in multiples of the page size. For a file that is not a multiple of
2647 * the page size, the remaining memory is zeroed when mapped, and
2648 * writes to that region are not written out to the file."
2650 zero_user_segment(page
, offset
, PAGE_CACHE_SIZE
);
2652 ret
= mpage_writepage(page
, get_block
, wbc
);
2654 ret
= __block_write_full_page(inode
, page
, get_block
, wbc
);
2657 EXPORT_SYMBOL(nobh_writepage
);
2659 int nobh_truncate_page(struct address_space
*mapping
,
2660 loff_t from
, get_block_t
*get_block
)
2662 pgoff_t index
= from
>> PAGE_CACHE_SHIFT
;
2663 unsigned offset
= from
& (PAGE_CACHE_SIZE
-1);
2666 unsigned length
, pos
;
2667 struct inode
*inode
= mapping
->host
;
2669 struct buffer_head map_bh
;
2672 blocksize
= 1 << inode
->i_blkbits
;
2673 length
= offset
& (blocksize
- 1);
2675 /* Block boundary? Nothing to do */
2679 length
= blocksize
- length
;
2680 iblock
= (sector_t
)index
<< (PAGE_CACHE_SHIFT
- inode
->i_blkbits
);
2682 page
= grab_cache_page(mapping
, index
);
2687 if (page_has_buffers(page
)) {
2690 page_cache_release(page
);
2691 return block_truncate_page(mapping
, from
, get_block
);
2694 /* Find the buffer that contains "offset" */
2696 while (offset
>= pos
) {
2701 err
= get_block(inode
, iblock
, &map_bh
, 0);
2704 /* unmapped? It's a hole - nothing to do */
2705 if (!buffer_mapped(&map_bh
))
2708 /* Ok, it's mapped. Make sure it's up-to-date */
2709 if (!PageUptodate(page
)) {
2710 err
= mapping
->a_ops
->readpage(NULL
, page
);
2712 page_cache_release(page
);
2716 if (!PageUptodate(page
)) {
2720 if (page_has_buffers(page
))
2723 zero_user(page
, offset
, length
);
2724 set_page_dirty(page
);
2729 page_cache_release(page
);
2733 EXPORT_SYMBOL(nobh_truncate_page
);
2735 int block_truncate_page(struct address_space
*mapping
,
2736 loff_t from
, get_block_t
*get_block
)
2738 pgoff_t index
= from
>> PAGE_CACHE_SHIFT
;
2739 unsigned offset
= from
& (PAGE_CACHE_SIZE
-1);
2742 unsigned length
, pos
;
2743 struct inode
*inode
= mapping
->host
;
2745 struct buffer_head
*bh
;
2748 blocksize
= 1 << inode
->i_blkbits
;
2749 length
= offset
& (blocksize
- 1);
2751 /* Block boundary? Nothing to do */
2755 length
= blocksize
- length
;
2756 iblock
= (sector_t
)index
<< (PAGE_CACHE_SHIFT
- inode
->i_blkbits
);
2758 page
= grab_cache_page(mapping
, index
);
2763 if (!page_has_buffers(page
))
2764 create_empty_buffers(page
, blocksize
, 0);
2766 /* Find the buffer that contains "offset" */
2767 bh
= page_buffers(page
);
2769 while (offset
>= pos
) {
2770 bh
= bh
->b_this_page
;
2776 if (!buffer_mapped(bh
)) {
2777 WARN_ON(bh
->b_size
!= blocksize
);
2778 err
= get_block(inode
, iblock
, bh
, 0);
2781 /* unmapped? It's a hole - nothing to do */
2782 if (!buffer_mapped(bh
))
2786 /* Ok, it's mapped. Make sure it's up-to-date */
2787 if (PageUptodate(page
))
2788 set_buffer_uptodate(bh
);
2790 if (!buffer_uptodate(bh
) && !buffer_delay(bh
) && !buffer_unwritten(bh
)) {
2792 ll_rw_block(READ
, 1, &bh
);
2794 /* Uhhuh. Read error. Complain and punt. */
2795 if (!buffer_uptodate(bh
))
2799 zero_user(page
, offset
, length
);
2800 mark_buffer_dirty(bh
);
2805 page_cache_release(page
);
2811 * The generic ->writepage function for buffer-backed address_spaces
2813 int block_write_full_page(struct page
*page
, get_block_t
*get_block
,
2814 struct writeback_control
*wbc
)
2816 struct inode
* const inode
= page
->mapping
->host
;
2817 loff_t i_size
= i_size_read(inode
);
2818 const pgoff_t end_index
= i_size
>> PAGE_CACHE_SHIFT
;
2821 /* Is the page fully inside i_size? */
2822 if (page
->index
< end_index
)
2823 return __block_write_full_page(inode
, page
, get_block
, wbc
);
2825 /* Is the page fully outside i_size? (truncate in progress) */
2826 offset
= i_size
& (PAGE_CACHE_SIZE
-1);
2827 if (page
->index
>= end_index
+1 || !offset
) {
2829 * The page may have dirty, unmapped buffers. For example,
2830 * they may have been added in ext3_writepage(). Make them
2831 * freeable here, so the page does not leak.
2833 do_invalidatepage(page
, 0);
2835 return 0; /* don't care */
2839 * The page straddles i_size. It must be zeroed out on each and every
2840 * writepage invokation because it may be mmapped. "A file is mapped
2841 * in multiples of the page size. For a file that is not a multiple of
2842 * the page size, the remaining memory is zeroed when mapped, and
2843 * writes to that region are not written out to the file."
2845 zero_user_segment(page
, offset
, PAGE_CACHE_SIZE
);
2846 return __block_write_full_page(inode
, page
, get_block
, wbc
);
2849 sector_t
generic_block_bmap(struct address_space
*mapping
, sector_t block
,
2850 get_block_t
*get_block
)
2852 struct buffer_head tmp
;
2853 struct inode
*inode
= mapping
->host
;
2856 tmp
.b_size
= 1 << inode
->i_blkbits
;
2857 get_block(inode
, block
, &tmp
, 0);
2858 return tmp
.b_blocknr
;
2861 static void end_bio_bh_io_sync(struct bio
*bio
, int err
)
2863 struct buffer_head
*bh
= bio
->bi_private
;
2865 if (err
== -EOPNOTSUPP
) {
2866 set_bit(BIO_EOPNOTSUPP
, &bio
->bi_flags
);
2867 set_bit(BH_Eopnotsupp
, &bh
->b_state
);
2870 bh
->b_end_io(bh
, test_bit(BIO_UPTODATE
, &bio
->bi_flags
));
2874 int submit_bh(int rw
, struct buffer_head
* bh
)
2879 BUG_ON(!buffer_locked(bh
));
2880 BUG_ON(!buffer_mapped(bh
));
2881 BUG_ON(!bh
->b_end_io
);
2883 if (buffer_ordered(bh
) && (rw
== WRITE
))
2887 * Only clear out a write error when rewriting, should this
2888 * include WRITE_SYNC as well?
2890 if (test_set_buffer_req(bh
) && (rw
== WRITE
|| rw
== WRITE_BARRIER
))
2891 clear_buffer_write_io_error(bh
);
2894 * from here on down, it's all bio -- do the initial mapping,
2895 * submit_bio -> generic_make_request may further map this bio around
2897 bio
= bio_alloc(GFP_NOIO
, 1);
2899 bio
->bi_sector
= bh
->b_blocknr
* (bh
->b_size
>> 9);
2900 bio
->bi_bdev
= bh
->b_bdev
;
2901 bio
->bi_io_vec
[0].bv_page
= bh
->b_page
;
2902 bio
->bi_io_vec
[0].bv_len
= bh
->b_size
;
2903 bio
->bi_io_vec
[0].bv_offset
= bh_offset(bh
);
2907 bio
->bi_size
= bh
->b_size
;
2909 bio
->bi_end_io
= end_bio_bh_io_sync
;
2910 bio
->bi_private
= bh
;
2913 submit_bio(rw
, bio
);
2915 if (bio_flagged(bio
, BIO_EOPNOTSUPP
))
2923 * ll_rw_block: low-level access to block devices (DEPRECATED)
2924 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
2925 * @nr: number of &struct buffer_heads in the array
2926 * @bhs: array of pointers to &struct buffer_head
2928 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2929 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2930 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2931 * are sent to disk. The fourth %READA option is described in the documentation
2932 * for generic_make_request() which ll_rw_block() calls.
2934 * This function drops any buffer that it cannot get a lock on (with the
2935 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2936 * clean when doing a write request, and any buffer that appears to be
2937 * up-to-date when doing read request. Further it marks as clean buffers that
2938 * are processed for writing (the buffer cache won't assume that they are
2939 * actually clean until the buffer gets unlocked).
2941 * ll_rw_block sets b_end_io to simple completion handler that marks
2942 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2945 * All of the buffers must be for the same device, and must also be a
2946 * multiple of the current approved size for the device.
2948 void ll_rw_block(int rw
, int nr
, struct buffer_head
*bhs
[])
2952 for (i
= 0; i
< nr
; i
++) {
2953 struct buffer_head
*bh
= bhs
[i
];
2955 if (rw
== SWRITE
|| rw
== SWRITE_SYNC
)
2957 else if (test_set_buffer_locked(bh
))
2960 if (rw
== WRITE
|| rw
== SWRITE
|| rw
== SWRITE_SYNC
) {
2961 if (test_clear_buffer_dirty(bh
)) {
2962 bh
->b_end_io
= end_buffer_write_sync
;
2964 if (rw
== SWRITE_SYNC
)
2965 submit_bh(WRITE_SYNC
, bh
);
2967 submit_bh(WRITE
, bh
);
2971 if (!buffer_uptodate(bh
)) {
2972 bh
->b_end_io
= end_buffer_read_sync
;
2983 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2984 * and then start new I/O and then wait upon it. The caller must have a ref on
2987 int sync_dirty_buffer(struct buffer_head
*bh
)
2991 WARN_ON(atomic_read(&bh
->b_count
) < 1);
2993 if (test_clear_buffer_dirty(bh
)) {
2995 bh
->b_end_io
= end_buffer_write_sync
;
2996 ret
= submit_bh(WRITE_SYNC
, bh
);
2998 if (buffer_eopnotsupp(bh
)) {
2999 clear_buffer_eopnotsupp(bh
);
3002 if (!ret
&& !buffer_uptodate(bh
))
3011 * try_to_free_buffers() checks if all the buffers on this particular page
3012 * are unused, and releases them if so.
3014 * Exclusion against try_to_free_buffers may be obtained by either
3015 * locking the page or by holding its mapping's private_lock.
3017 * If the page is dirty but all the buffers are clean then we need to
3018 * be sure to mark the page clean as well. This is because the page
3019 * may be against a block device, and a later reattachment of buffers
3020 * to a dirty page will set *all* buffers dirty. Which would corrupt
3021 * filesystem data on the same device.
3023 * The same applies to regular filesystem pages: if all the buffers are
3024 * clean then we set the page clean and proceed. To do that, we require
3025 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3028 * try_to_free_buffers() is non-blocking.
3030 static inline int buffer_busy(struct buffer_head
*bh
)
3032 return atomic_read(&bh
->b_count
) |
3033 (bh
->b_state
& ((1 << BH_Dirty
) | (1 << BH_Lock
)));
3037 drop_buffers(struct page
*page
, struct buffer_head
**buffers_to_free
)
3039 struct buffer_head
*head
= page_buffers(page
);
3040 struct buffer_head
*bh
;
3044 if (buffer_write_io_error(bh
) && page
->mapping
)
3045 set_bit(AS_EIO
, &page
->mapping
->flags
);
3046 if (buffer_busy(bh
))
3048 bh
= bh
->b_this_page
;
3049 } while (bh
!= head
);
3052 struct buffer_head
*next
= bh
->b_this_page
;
3054 if (bh
->b_assoc_map
)
3055 __remove_assoc_queue(bh
);
3057 } while (bh
!= head
);
3058 *buffers_to_free
= head
;
3059 __clear_page_buffers(page
);
3065 int try_to_free_buffers(struct page
*page
)
3067 struct address_space
* const mapping
= page
->mapping
;
3068 struct buffer_head
*buffers_to_free
= NULL
;
3071 BUG_ON(!PageLocked(page
));
3072 if (PageWriteback(page
))
3075 if (mapping
== NULL
) { /* can this still happen? */
3076 ret
= drop_buffers(page
, &buffers_to_free
);
3080 spin_lock(&mapping
->private_lock
);
3081 ret
= drop_buffers(page
, &buffers_to_free
);
3084 * If the filesystem writes its buffers by hand (eg ext3)
3085 * then we can have clean buffers against a dirty page. We
3086 * clean the page here; otherwise the VM will never notice
3087 * that the filesystem did any IO at all.
3089 * Also, during truncate, discard_buffer will have marked all
3090 * the page's buffers clean. We discover that here and clean
3093 * private_lock must be held over this entire operation in order
3094 * to synchronise against __set_page_dirty_buffers and prevent the
3095 * dirty bit from being lost.
3098 cancel_dirty_page(page
, PAGE_CACHE_SIZE
);
3099 spin_unlock(&mapping
->private_lock
);
3101 if (buffers_to_free
) {
3102 struct buffer_head
*bh
= buffers_to_free
;
3105 struct buffer_head
*next
= bh
->b_this_page
;
3106 free_buffer_head(bh
);
3108 } while (bh
!= buffers_to_free
);
3112 EXPORT_SYMBOL(try_to_free_buffers
);
3114 void block_sync_page(struct page
*page
)
3116 struct address_space
*mapping
;
3119 mapping
= page_mapping(page
);
3121 blk_run_backing_dev(mapping
->backing_dev_info
, page
);
3125 * There are no bdflush tunables left. But distributions are
3126 * still running obsolete flush daemons, so we terminate them here.
3128 * Use of bdflush() is deprecated and will be removed in a future kernel.
3129 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3131 asmlinkage
long sys_bdflush(int func
, long data
)
3133 static int msg_count
;
3135 if (!capable(CAP_SYS_ADMIN
))
3138 if (msg_count
< 5) {
3141 "warning: process `%s' used the obsolete bdflush"
3142 " system call\n", current
->comm
);
3143 printk(KERN_INFO
"Fix your initscripts?\n");
3152 * Buffer-head allocation
3154 static struct kmem_cache
*bh_cachep
;
3157 * Once the number of bh's in the machine exceeds this level, we start
3158 * stripping them in writeback.
3160 static int max_buffer_heads
;
3162 int buffer_heads_over_limit
;
3164 struct bh_accounting
{
3165 int nr
; /* Number of live bh's */
3166 int ratelimit
; /* Limit cacheline bouncing */
3169 static DEFINE_PER_CPU(struct bh_accounting
, bh_accounting
) = {0, 0};
3171 static void recalc_bh_state(void)
3176 if (__get_cpu_var(bh_accounting
).ratelimit
++ < 4096)
3178 __get_cpu_var(bh_accounting
).ratelimit
= 0;
3179 for_each_online_cpu(i
)
3180 tot
+= per_cpu(bh_accounting
, i
).nr
;
3181 buffer_heads_over_limit
= (tot
> max_buffer_heads
);
3184 struct buffer_head
*alloc_buffer_head(gfp_t gfp_flags
)
3186 struct buffer_head
*ret
= kmem_cache_alloc(bh_cachep
,
3187 set_migrateflags(gfp_flags
, __GFP_RECLAIMABLE
));
3189 INIT_LIST_HEAD(&ret
->b_assoc_buffers
);
3190 get_cpu_var(bh_accounting
).nr
++;
3192 put_cpu_var(bh_accounting
);
3196 EXPORT_SYMBOL(alloc_buffer_head
);
3198 void free_buffer_head(struct buffer_head
*bh
)
3200 BUG_ON(!list_empty(&bh
->b_assoc_buffers
));
3201 kmem_cache_free(bh_cachep
, bh
);
3202 get_cpu_var(bh_accounting
).nr
--;
3204 put_cpu_var(bh_accounting
);
3206 EXPORT_SYMBOL(free_buffer_head
);
3208 static void buffer_exit_cpu(int cpu
)
3211 struct bh_lru
*b
= &per_cpu(bh_lrus
, cpu
);
3213 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
3217 get_cpu_var(bh_accounting
).nr
+= per_cpu(bh_accounting
, cpu
).nr
;
3218 per_cpu(bh_accounting
, cpu
).nr
= 0;
3219 put_cpu_var(bh_accounting
);
3222 static int buffer_cpu_notify(struct notifier_block
*self
,
3223 unsigned long action
, void *hcpu
)
3225 if (action
== CPU_DEAD
|| action
== CPU_DEAD_FROZEN
)
3226 buffer_exit_cpu((unsigned long)hcpu
);
3231 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3232 * @bh: struct buffer_head
3234 * Return true if the buffer is up-to-date and false,
3235 * with the buffer locked, if not.
3237 int bh_uptodate_or_lock(struct buffer_head
*bh
)
3239 if (!buffer_uptodate(bh
)) {
3241 if (!buffer_uptodate(bh
))
3247 EXPORT_SYMBOL(bh_uptodate_or_lock
);
3250 * bh_submit_read - Submit a locked buffer for reading
3251 * @bh: struct buffer_head
3253 * Returns zero on success and -EIO on error.
3255 int bh_submit_read(struct buffer_head
*bh
)
3257 BUG_ON(!buffer_locked(bh
));
3259 if (buffer_uptodate(bh
)) {
3265 bh
->b_end_io
= end_buffer_read_sync
;
3266 submit_bh(READ
, bh
);
3268 if (buffer_uptodate(bh
))
3272 EXPORT_SYMBOL(bh_submit_read
);
3275 init_buffer_head(struct kmem_cache
*cachep
, void *data
)
3277 struct buffer_head
*bh
= data
;
3279 memset(bh
, 0, sizeof(*bh
));
3280 INIT_LIST_HEAD(&bh
->b_assoc_buffers
);
3283 void __init
buffer_init(void)
3287 bh_cachep
= kmem_cache_create("buffer_head",
3288 sizeof(struct buffer_head
), 0,
3289 (SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
|
3294 * Limit the bh occupancy to 10% of ZONE_NORMAL
3296 nrpages
= (nr_free_buffer_pages() * 10) / 100;
3297 max_buffer_heads
= nrpages
* (PAGE_SIZE
/ sizeof(struct buffer_head
));
3298 hotcpu_notifier(buffer_cpu_notify
, 0);
3301 EXPORT_SYMBOL(__bforget
);
3302 EXPORT_SYMBOL(__brelse
);
3303 EXPORT_SYMBOL(__wait_on_buffer
);
3304 EXPORT_SYMBOL(block_commit_write
);
3305 EXPORT_SYMBOL(block_prepare_write
);
3306 EXPORT_SYMBOL(block_page_mkwrite
);
3307 EXPORT_SYMBOL(block_read_full_page
);
3308 EXPORT_SYMBOL(block_sync_page
);
3309 EXPORT_SYMBOL(block_truncate_page
);
3310 EXPORT_SYMBOL(block_write_full_page
);
3311 EXPORT_SYMBOL(cont_write_begin
);
3312 EXPORT_SYMBOL(end_buffer_read_sync
);
3313 EXPORT_SYMBOL(end_buffer_write_sync
);
3314 EXPORT_SYMBOL(file_fsync
);
3315 EXPORT_SYMBOL(fsync_bdev
);
3316 EXPORT_SYMBOL(generic_block_bmap
);
3317 EXPORT_SYMBOL(generic_commit_write
);
3318 EXPORT_SYMBOL(generic_cont_expand_simple
);
3319 EXPORT_SYMBOL(init_buffer
);
3320 EXPORT_SYMBOL(invalidate_bdev
);
3321 EXPORT_SYMBOL(ll_rw_block
);
3322 EXPORT_SYMBOL(mark_buffer_dirty
);
3323 EXPORT_SYMBOL(submit_bh
);
3324 EXPORT_SYMBOL(sync_dirty_buffer
);
3325 EXPORT_SYMBOL(unlock_buffer
);