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/config.h>
22 #include <linux/kernel.h>
23 #include <linux/syscalls.h>
26 #include <linux/percpu.h>
27 #include <linux/slab.h>
28 #include <linux/smp_lock.h>
29 #include <linux/blkdev.h>
30 #include <linux/file.h>
31 #include <linux/quotaops.h>
32 #include <linux/highmem.h>
33 #include <linux/module.h>
34 #include <linux/writeback.h>
35 #include <linux/hash.h>
36 #include <linux/suspend.h>
37 #include <linux/buffer_head.h>
38 #include <linux/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
);
46 static void invalidate_bh_lrus(void);
48 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
51 init_buffer(struct buffer_head
*bh
, bh_end_io_t
*handler
, void *private)
53 bh
->b_end_io
= handler
;
54 bh
->b_private
= private;
57 static int sync_buffer(void *word
)
59 struct block_device
*bd
;
60 struct buffer_head
*bh
61 = container_of(word
, struct buffer_head
, b_state
);
66 blk_run_address_space(bd
->bd_inode
->i_mapping
);
71 void fastcall
__lock_buffer(struct buffer_head
*bh
)
73 wait_on_bit_lock(&bh
->b_state
, BH_Lock
, sync_buffer
,
74 TASK_UNINTERRUPTIBLE
);
76 EXPORT_SYMBOL(__lock_buffer
);
78 void fastcall
unlock_buffer(struct buffer_head
*bh
)
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
);
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 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
114 * unlock the buffer. This is what ll_rw_block uses too.
116 void end_buffer_read_sync(struct buffer_head
*bh
, int uptodate
)
119 set_buffer_uptodate(bh
);
121 /* This happens, due to failed READA attempts. */
122 clear_buffer_uptodate(bh
);
128 void end_buffer_write_sync(struct buffer_head
*bh
, int uptodate
)
130 char b
[BDEVNAME_SIZE
];
133 set_buffer_uptodate(bh
);
135 if (!buffer_eopnotsupp(bh
) && printk_ratelimit()) {
137 printk(KERN_WARNING
"lost page write due to "
139 bdevname(bh
->b_bdev
, b
));
141 set_buffer_write_io_error(bh
);
142 clear_buffer_uptodate(bh
);
149 * Write out and wait upon all the dirty data associated with a block
150 * device via its mapping. Does not take the superblock lock.
152 int sync_blockdev(struct block_device
*bdev
)
159 ret
= filemap_fdatawrite(bdev
->bd_inode
->i_mapping
);
160 err
= filemap_fdatawait(bdev
->bd_inode
->i_mapping
);
166 EXPORT_SYMBOL(sync_blockdev
);
169 * Write out and wait upon all dirty data associated with this
170 * superblock. Filesystem data as well as the underlying block
171 * device. Takes the superblock lock.
173 int fsync_super(struct super_block
*sb
)
175 sync_inodes_sb(sb
, 0);
178 if (sb
->s_dirt
&& sb
->s_op
->write_super
)
179 sb
->s_op
->write_super(sb
);
181 if (sb
->s_op
->sync_fs
)
182 sb
->s_op
->sync_fs(sb
, 1);
183 sync_blockdev(sb
->s_bdev
);
184 sync_inodes_sb(sb
, 1);
186 return sync_blockdev(sb
->s_bdev
);
190 * Write out and wait upon all dirty data associated with this
191 * device. Filesystem data as well as the underlying block
192 * device. Takes the superblock lock.
194 int fsync_bdev(struct block_device
*bdev
)
196 struct super_block
*sb
= get_super(bdev
);
198 int res
= fsync_super(sb
);
202 return sync_blockdev(bdev
);
206 * freeze_bdev -- lock a filesystem and force it into a consistent state
207 * @bdev: blockdevice to lock
209 * This takes the block device bd_mount_sem to make sure no new mounts
210 * happen on bdev until thaw_bdev() is called.
211 * If a superblock is found on this device, we take the s_umount semaphore
212 * on it to make sure nobody unmounts until the snapshot creation is done.
214 struct super_block
*freeze_bdev(struct block_device
*bdev
)
216 struct super_block
*sb
;
218 down(&bdev
->bd_mount_sem
);
219 sb
= get_super(bdev
);
220 if (sb
&& !(sb
->s_flags
& MS_RDONLY
)) {
221 sb
->s_frozen
= SB_FREEZE_WRITE
;
224 sync_inodes_sb(sb
, 0);
228 if (sb
->s_dirt
&& sb
->s_op
->write_super
)
229 sb
->s_op
->write_super(sb
);
232 if (sb
->s_op
->sync_fs
)
233 sb
->s_op
->sync_fs(sb
, 1);
235 sync_blockdev(sb
->s_bdev
);
236 sync_inodes_sb(sb
, 1);
238 sb
->s_frozen
= SB_FREEZE_TRANS
;
241 sync_blockdev(sb
->s_bdev
);
243 if (sb
->s_op
->write_super_lockfs
)
244 sb
->s_op
->write_super_lockfs(sb
);
248 return sb
; /* thaw_bdev releases s->s_umount and bd_mount_sem */
250 EXPORT_SYMBOL(freeze_bdev
);
253 * thaw_bdev -- unlock filesystem
254 * @bdev: blockdevice to unlock
255 * @sb: associated superblock
257 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
259 void thaw_bdev(struct block_device
*bdev
, struct super_block
*sb
)
262 BUG_ON(sb
->s_bdev
!= bdev
);
264 if (sb
->s_op
->unlockfs
)
265 sb
->s_op
->unlockfs(sb
);
266 sb
->s_frozen
= SB_UNFROZEN
;
268 wake_up(&sb
->s_wait_unfrozen
);
272 up(&bdev
->bd_mount_sem
);
274 EXPORT_SYMBOL(thaw_bdev
);
277 * sync everything. Start out by waking pdflush, because that writes back
278 * all queues in parallel.
280 static void do_sync(unsigned long wait
)
283 sync_inodes(0); /* All mappings, inodes and their blockdevs */
285 sync_supers(); /* Write the superblocks */
286 sync_filesystems(0); /* Start syncing the filesystems */
287 sync_filesystems(wait
); /* Waitingly sync the filesystems */
288 sync_inodes(wait
); /* Mappings, inodes and blockdevs, again. */
290 printk("Emergency Sync complete\n");
291 if (unlikely(laptop_mode
))
292 laptop_sync_completion();
295 asmlinkage
long sys_sync(void)
301 void emergency_sync(void)
303 pdflush_operation(do_sync
, 0);
307 * Generic function to fsync a file.
309 * filp may be NULL if called via the msync of a vma.
312 int file_fsync(struct file
*filp
, struct dentry
*dentry
, int datasync
)
314 struct inode
* inode
= dentry
->d_inode
;
315 struct super_block
* sb
;
318 /* sync the inode to buffers */
319 ret
= write_inode_now(inode
, 0);
321 /* sync the superblock to buffers */
324 if (sb
->s_op
->write_super
)
325 sb
->s_op
->write_super(sb
);
328 /* .. finally sync the buffers to disk */
329 err
= sync_blockdev(sb
->s_bdev
);
335 static long do_fsync(unsigned int fd
, int datasync
)
338 struct address_space
*mapping
;
347 if (!file
->f_op
|| !file
->f_op
->fsync
) {
348 /* Why? We can still call filemap_fdatawrite */
352 mapping
= file
->f_mapping
;
354 current
->flags
|= PF_SYNCWRITE
;
355 ret
= filemap_fdatawrite(mapping
);
358 * We need to protect against concurrent writers,
359 * which could cause livelocks in fsync_buffers_list
361 down(&mapping
->host
->i_sem
);
362 err
= file
->f_op
->fsync(file
, file
->f_dentry
, datasync
);
365 up(&mapping
->host
->i_sem
);
366 err
= filemap_fdatawait(mapping
);
369 current
->flags
&= ~PF_SYNCWRITE
;
377 asmlinkage
long sys_fsync(unsigned int fd
)
379 return do_fsync(fd
, 0);
382 asmlinkage
long sys_fdatasync(unsigned int fd
)
384 return do_fsync(fd
, 1);
388 * Various filesystems appear to want __find_get_block to be non-blocking.
389 * But it's the page lock which protects the buffers. To get around this,
390 * we get exclusion from try_to_free_buffers with the blockdev mapping's
393 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
394 * may be quite high. This code could TryLock the page, and if that
395 * succeeds, there is no need to take private_lock. (But if
396 * private_lock is contended then so is mapping->tree_lock).
398 static struct buffer_head
*
399 __find_get_block_slow(struct block_device
*bdev
, sector_t block
, int unused
)
401 struct inode
*bd_inode
= bdev
->bd_inode
;
402 struct address_space
*bd_mapping
= bd_inode
->i_mapping
;
403 struct buffer_head
*ret
= NULL
;
405 struct buffer_head
*bh
;
406 struct buffer_head
*head
;
410 index
= block
>> (PAGE_CACHE_SHIFT
- bd_inode
->i_blkbits
);
411 page
= find_get_page(bd_mapping
, index
);
415 spin_lock(&bd_mapping
->private_lock
);
416 if (!page_has_buffers(page
))
418 head
= page_buffers(page
);
421 if (bh
->b_blocknr
== block
) {
426 if (!buffer_mapped(bh
))
428 bh
= bh
->b_this_page
;
429 } while (bh
!= head
);
431 /* we might be here because some of the buffers on this page are
432 * not mapped. This is due to various races between
433 * file io on the block device and getblk. It gets dealt with
434 * elsewhere, don't buffer_error if we had some unmapped buffers
437 printk("__find_get_block_slow() failed. "
438 "block=%llu, b_blocknr=%llu\n",
439 (unsigned long long)block
, (unsigned long long)bh
->b_blocknr
);
440 printk("b_state=0x%08lx, b_size=%u\n", bh
->b_state
, bh
->b_size
);
441 printk("device blocksize: %d\n", 1 << bd_inode
->i_blkbits
);
444 spin_unlock(&bd_mapping
->private_lock
);
445 page_cache_release(page
);
450 /* If invalidate_buffers() will trash dirty buffers, it means some kind
451 of fs corruption is going on. Trashing dirty data always imply losing
452 information that was supposed to be just stored on the physical layer
455 Thus invalidate_buffers in general usage is not allwowed to trash
456 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
457 be preserved. These buffers are simply skipped.
459 We also skip buffers which are still in use. For example this can
460 happen if a userspace program is reading the block device.
462 NOTE: In the case where the user removed a removable-media-disk even if
463 there's still dirty data not synced on disk (due a bug in the device driver
464 or due an error of the user), by not destroying the dirty buffers we could
465 generate corruption also on the next media inserted, thus a parameter is
466 necessary to handle this case in the most safe way possible (trying
467 to not corrupt also the new disk inserted with the data belonging to
468 the old now corrupted disk). Also for the ramdisk the natural thing
469 to do in order to release the ramdisk memory is to destroy dirty buffers.
471 These are two special cases. Normal usage imply the device driver
472 to issue a sync on the device (without waiting I/O completion) and
473 then an invalidate_buffers call that doesn't trash dirty buffers.
475 For handling cache coherency with the blkdev pagecache the 'update' case
476 is been introduced. It is needed to re-read from disk any pinned
477 buffer. NOTE: re-reading from disk is destructive so we can do it only
478 when we assume nobody is changing the buffercache under our I/O and when
479 we think the disk contains more recent information than the buffercache.
480 The update == 1 pass marks the buffers we need to update, the update == 2
481 pass does the actual I/O. */
482 void invalidate_bdev(struct block_device
*bdev
, int destroy_dirty_buffers
)
484 invalidate_bh_lrus();
486 * FIXME: what about destroy_dirty_buffers?
487 * We really want to use invalidate_inode_pages2() for
488 * that, but not until that's cleaned up.
490 invalidate_inode_pages(bdev
->bd_inode
->i_mapping
);
494 * Kick pdflush then try to free up some ZONE_NORMAL memory.
496 static void free_more_memory(void)
501 wakeup_pdflush(1024);
504 for_each_pgdat(pgdat
) {
505 zones
= pgdat
->node_zonelists
[gfp_zone(GFP_NOFS
)].zones
;
507 try_to_free_pages(zones
, GFP_NOFS
);
512 * I/O completion handler for block_read_full_page() - pages
513 * which come unlocked at the end of I/O.
515 static void end_buffer_async_read(struct buffer_head
*bh
, int uptodate
)
518 struct buffer_head
*first
;
519 struct buffer_head
*tmp
;
521 int page_uptodate
= 1;
523 BUG_ON(!buffer_async_read(bh
));
527 set_buffer_uptodate(bh
);
529 clear_buffer_uptodate(bh
);
530 if (printk_ratelimit())
536 * Be _very_ careful from here on. Bad things can happen if
537 * two buffer heads end IO at almost the same time and both
538 * decide that the page is now completely done.
540 first
= page_buffers(page
);
541 local_irq_save(flags
);
542 bit_spin_lock(BH_Uptodate_Lock
, &first
->b_state
);
543 clear_buffer_async_read(bh
);
547 if (!buffer_uptodate(tmp
))
549 if (buffer_async_read(tmp
)) {
550 BUG_ON(!buffer_locked(tmp
));
553 tmp
= tmp
->b_this_page
;
555 bit_spin_unlock(BH_Uptodate_Lock
, &first
->b_state
);
556 local_irq_restore(flags
);
559 * If none of the buffers had errors and they are all
560 * uptodate then we can set the page uptodate.
562 if (page_uptodate
&& !PageError(page
))
563 SetPageUptodate(page
);
568 bit_spin_unlock(BH_Uptodate_Lock
, &first
->b_state
);
569 local_irq_restore(flags
);
574 * Completion handler for block_write_full_page() - pages which are unlocked
575 * during I/O, and which have PageWriteback cleared upon I/O completion.
577 void end_buffer_async_write(struct buffer_head
*bh
, int uptodate
)
579 char b
[BDEVNAME_SIZE
];
581 struct buffer_head
*first
;
582 struct buffer_head
*tmp
;
585 BUG_ON(!buffer_async_write(bh
));
589 set_buffer_uptodate(bh
);
591 if (printk_ratelimit()) {
593 printk(KERN_WARNING
"lost page write due to "
595 bdevname(bh
->b_bdev
, b
));
597 set_bit(AS_EIO
, &page
->mapping
->flags
);
598 clear_buffer_uptodate(bh
);
602 first
= page_buffers(page
);
603 local_irq_save(flags
);
604 bit_spin_lock(BH_Uptodate_Lock
, &first
->b_state
);
606 clear_buffer_async_write(bh
);
608 tmp
= bh
->b_this_page
;
610 if (buffer_async_write(tmp
)) {
611 BUG_ON(!buffer_locked(tmp
));
614 tmp
= tmp
->b_this_page
;
616 bit_spin_unlock(BH_Uptodate_Lock
, &first
->b_state
);
617 local_irq_restore(flags
);
618 end_page_writeback(page
);
622 bit_spin_unlock(BH_Uptodate_Lock
, &first
->b_state
);
623 local_irq_restore(flags
);
628 * If a page's buffers are under async readin (end_buffer_async_read
629 * completion) then there is a possibility that another thread of
630 * control could lock one of the buffers after it has completed
631 * but while some of the other buffers have not completed. This
632 * locked buffer would confuse end_buffer_async_read() into not unlocking
633 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
634 * that this buffer is not under async I/O.
636 * The page comes unlocked when it has no locked buffer_async buffers
639 * PageLocked prevents anyone starting new async I/O reads any of
642 * PageWriteback is used to prevent simultaneous writeout of the same
645 * PageLocked prevents anyone from starting writeback of a page which is
646 * under read I/O (PageWriteback is only ever set against a locked page).
648 static void mark_buffer_async_read(struct buffer_head
*bh
)
650 bh
->b_end_io
= end_buffer_async_read
;
651 set_buffer_async_read(bh
);
654 void mark_buffer_async_write(struct buffer_head
*bh
)
656 bh
->b_end_io
= end_buffer_async_write
;
657 set_buffer_async_write(bh
);
659 EXPORT_SYMBOL(mark_buffer_async_write
);
663 * fs/buffer.c contains helper functions for buffer-backed address space's
664 * fsync functions. A common requirement for buffer-based filesystems is
665 * that certain data from the backing blockdev needs to be written out for
666 * a successful fsync(). For example, ext2 indirect blocks need to be
667 * written back and waited upon before fsync() returns.
669 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
670 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
671 * management of a list of dependent buffers at ->i_mapping->private_list.
673 * Locking is a little subtle: try_to_free_buffers() will remove buffers
674 * from their controlling inode's queue when they are being freed. But
675 * try_to_free_buffers() will be operating against the *blockdev* mapping
676 * at the time, not against the S_ISREG file which depends on those buffers.
677 * So the locking for private_list is via the private_lock in the address_space
678 * which backs the buffers. Which is different from the address_space
679 * against which the buffers are listed. So for a particular address_space,
680 * mapping->private_lock does *not* protect mapping->private_list! In fact,
681 * mapping->private_list will always be protected by the backing blockdev's
684 * Which introduces a requirement: all buffers on an address_space's
685 * ->private_list must be from the same address_space: the blockdev's.
687 * address_spaces which do not place buffers at ->private_list via these
688 * utility functions are free to use private_lock and private_list for
689 * whatever they want. The only requirement is that list_empty(private_list)
690 * be true at clear_inode() time.
692 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
693 * filesystems should do that. invalidate_inode_buffers() should just go
694 * BUG_ON(!list_empty).
696 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
697 * take an address_space, not an inode. And it should be called
698 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
701 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
702 * list if it is already on a list. Because if the buffer is on a list,
703 * it *must* already be on the right one. If not, the filesystem is being
704 * silly. This will save a ton of locking. But first we have to ensure
705 * that buffers are taken *off* the old inode's list when they are freed
706 * (presumably in truncate). That requires careful auditing of all
707 * filesystems (do it inside bforget()). It could also be done by bringing
712 * The buffer's backing address_space's private_lock must be held
714 static inline void __remove_assoc_queue(struct buffer_head
*bh
)
716 list_del_init(&bh
->b_assoc_buffers
);
719 int inode_has_buffers(struct inode
*inode
)
721 return !list_empty(&inode
->i_data
.private_list
);
725 * osync is designed to support O_SYNC io. It waits synchronously for
726 * all already-submitted IO to complete, but does not queue any new
727 * writes to the disk.
729 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
730 * you dirty the buffers, and then use osync_inode_buffers to wait for
731 * completion. Any other dirty buffers which are not yet queued for
732 * write will not be flushed to disk by the osync.
734 static int osync_buffers_list(spinlock_t
*lock
, struct list_head
*list
)
736 struct buffer_head
*bh
;
742 list_for_each_prev(p
, list
) {
744 if (buffer_locked(bh
)) {
748 if (!buffer_uptodate(bh
))
760 * sync_mapping_buffers - write out and wait upon a mapping's "associated"
762 * @mapping: the mapping which wants those buffers written
764 * Starts I/O against the buffers at mapping->private_list, and waits upon
767 * Basically, this is a convenience function for fsync().
768 * @mapping is a file or directory which needs those buffers to be written for
769 * a successful fsync().
771 int sync_mapping_buffers(struct address_space
*mapping
)
773 struct address_space
*buffer_mapping
= mapping
->assoc_mapping
;
775 if (buffer_mapping
== NULL
|| list_empty(&mapping
->private_list
))
778 return fsync_buffers_list(&buffer_mapping
->private_lock
,
779 &mapping
->private_list
);
781 EXPORT_SYMBOL(sync_mapping_buffers
);
784 * Called when we've recently written block `bblock', and it is known that
785 * `bblock' was for a buffer_boundary() buffer. This means that the block at
786 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
787 * dirty, schedule it for IO. So that indirects merge nicely with their data.
789 void write_boundary_block(struct block_device
*bdev
,
790 sector_t bblock
, unsigned blocksize
)
792 struct buffer_head
*bh
= __find_get_block(bdev
, bblock
+ 1, blocksize
);
794 if (buffer_dirty(bh
))
795 ll_rw_block(WRITE
, 1, &bh
);
800 void mark_buffer_dirty_inode(struct buffer_head
*bh
, struct inode
*inode
)
802 struct address_space
*mapping
= inode
->i_mapping
;
803 struct address_space
*buffer_mapping
= bh
->b_page
->mapping
;
805 mark_buffer_dirty(bh
);
806 if (!mapping
->assoc_mapping
) {
807 mapping
->assoc_mapping
= buffer_mapping
;
809 if (mapping
->assoc_mapping
!= buffer_mapping
)
812 if (list_empty(&bh
->b_assoc_buffers
)) {
813 spin_lock(&buffer_mapping
->private_lock
);
814 list_move_tail(&bh
->b_assoc_buffers
,
815 &mapping
->private_list
);
816 spin_unlock(&buffer_mapping
->private_lock
);
819 EXPORT_SYMBOL(mark_buffer_dirty_inode
);
822 * Add a page to the dirty page list.
824 * It is a sad fact of life that this function is called from several places
825 * deeply under spinlocking. It may not sleep.
827 * If the page has buffers, the uptodate buffers are set dirty, to preserve
828 * dirty-state coherency between the page and the buffers. It the page does
829 * not have buffers then when they are later attached they will all be set
832 * The buffers are dirtied before the page is dirtied. There's a small race
833 * window in which a writepage caller may see the page cleanness but not the
834 * buffer dirtiness. That's fine. If this code were to set the page dirty
835 * before the buffers, a concurrent writepage caller could clear the page dirty
836 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
837 * page on the dirty page list.
839 * We use private_lock to lock against try_to_free_buffers while using the
840 * page's buffer list. Also use this to protect against clean buffers being
841 * added to the page after it was set dirty.
843 * FIXME: may need to call ->reservepage here as well. That's rather up to the
844 * address_space though.
846 int __set_page_dirty_buffers(struct page
*page
)
848 struct address_space
* const mapping
= page
->mapping
;
850 spin_lock(&mapping
->private_lock
);
851 if (page_has_buffers(page
)) {
852 struct buffer_head
*head
= page_buffers(page
);
853 struct buffer_head
*bh
= head
;
856 set_buffer_dirty(bh
);
857 bh
= bh
->b_this_page
;
858 } while (bh
!= head
);
860 spin_unlock(&mapping
->private_lock
);
862 if (!TestSetPageDirty(page
)) {
863 write_lock_irq(&mapping
->tree_lock
);
864 if (page
->mapping
) { /* Race with truncate? */
865 if (mapping_cap_account_dirty(mapping
))
866 inc_page_state(nr_dirty
);
867 radix_tree_tag_set(&mapping
->page_tree
,
869 PAGECACHE_TAG_DIRTY
);
871 write_unlock_irq(&mapping
->tree_lock
);
872 __mark_inode_dirty(mapping
->host
, I_DIRTY_PAGES
);
877 EXPORT_SYMBOL(__set_page_dirty_buffers
);
880 * Write out and wait upon a list of buffers.
882 * We have conflicting pressures: we want to make sure that all
883 * initially dirty buffers get waited on, but that any subsequently
884 * dirtied buffers don't. After all, we don't want fsync to last
885 * forever if somebody is actively writing to the file.
887 * Do this in two main stages: first we copy dirty buffers to a
888 * temporary inode list, queueing the writes as we go. Then we clean
889 * up, waiting for those writes to complete.
891 * During this second stage, any subsequent updates to the file may end
892 * up refiling the buffer on the original inode's dirty list again, so
893 * there is a chance we will end up with a buffer queued for write but
894 * not yet completed on that list. So, as a final cleanup we go through
895 * the osync code to catch these locked, dirty buffers without requeuing
896 * any newly dirty buffers for write.
898 static int fsync_buffers_list(spinlock_t
*lock
, struct list_head
*list
)
900 struct buffer_head
*bh
;
901 struct list_head tmp
;
904 INIT_LIST_HEAD(&tmp
);
907 while (!list_empty(list
)) {
908 bh
= BH_ENTRY(list
->next
);
909 list_del_init(&bh
->b_assoc_buffers
);
910 if (buffer_dirty(bh
) || buffer_locked(bh
)) {
911 list_add(&bh
->b_assoc_buffers
, &tmp
);
912 if (buffer_dirty(bh
)) {
916 * Ensure any pending I/O completes so that
917 * ll_rw_block() actually writes the current
918 * contents - it is a noop if I/O is still in
919 * flight on potentially older contents.
921 ll_rw_block(SWRITE
, 1, &bh
);
928 while (!list_empty(&tmp
)) {
929 bh
= BH_ENTRY(tmp
.prev
);
930 __remove_assoc_queue(bh
);
934 if (!buffer_uptodate(bh
))
941 err2
= osync_buffers_list(lock
, list
);
949 * Invalidate any and all dirty buffers on a given inode. We are
950 * probably unmounting the fs, but that doesn't mean we have already
951 * done a sync(). Just drop the buffers from the inode list.
953 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
954 * assumes that all the buffers are against the blockdev. Not true
957 void invalidate_inode_buffers(struct inode
*inode
)
959 if (inode_has_buffers(inode
)) {
960 struct address_space
*mapping
= &inode
->i_data
;
961 struct list_head
*list
= &mapping
->private_list
;
962 struct address_space
*buffer_mapping
= mapping
->assoc_mapping
;
964 spin_lock(&buffer_mapping
->private_lock
);
965 while (!list_empty(list
))
966 __remove_assoc_queue(BH_ENTRY(list
->next
));
967 spin_unlock(&buffer_mapping
->private_lock
);
972 * Remove any clean buffers from the inode's buffer list. This is called
973 * when we're trying to free the inode itself. Those buffers can pin it.
975 * Returns true if all buffers were removed.
977 int remove_inode_buffers(struct inode
*inode
)
981 if (inode_has_buffers(inode
)) {
982 struct address_space
*mapping
= &inode
->i_data
;
983 struct list_head
*list
= &mapping
->private_list
;
984 struct address_space
*buffer_mapping
= mapping
->assoc_mapping
;
986 spin_lock(&buffer_mapping
->private_lock
);
987 while (!list_empty(list
)) {
988 struct buffer_head
*bh
= BH_ENTRY(list
->next
);
989 if (buffer_dirty(bh
)) {
993 __remove_assoc_queue(bh
);
995 spin_unlock(&buffer_mapping
->private_lock
);
1001 * Create the appropriate buffers when given a page for data area and
1002 * the size of each buffer.. Use the bh->b_this_page linked list to
1003 * follow the buffers created. Return NULL if unable to create more
1006 * The retry flag is used to differentiate async IO (paging, swapping)
1007 * which may not fail from ordinary buffer allocations.
1009 struct buffer_head
*alloc_page_buffers(struct page
*page
, unsigned long size
,
1012 struct buffer_head
*bh
, *head
;
1018 while ((offset
-= size
) >= 0) {
1019 bh
= alloc_buffer_head(GFP_NOFS
);
1024 bh
->b_this_page
= head
;
1029 atomic_set(&bh
->b_count
, 0);
1032 /* Link the buffer to its page */
1033 set_bh_page(bh
, page
, offset
);
1035 bh
->b_end_io
= NULL
;
1039 * In case anything failed, we just free everything we got.
1045 head
= head
->b_this_page
;
1046 free_buffer_head(bh
);
1051 * Return failure for non-async IO requests. Async IO requests
1052 * are not allowed to fail, so we have to wait until buffer heads
1053 * become available. But we don't want tasks sleeping with
1054 * partially complete buffers, so all were released above.
1059 /* We're _really_ low on memory. Now we just
1060 * wait for old buffer heads to become free due to
1061 * finishing IO. Since this is an async request and
1062 * the reserve list is empty, we're sure there are
1063 * async buffer heads in use.
1068 EXPORT_SYMBOL_GPL(alloc_page_buffers
);
1071 link_dev_buffers(struct page
*page
, struct buffer_head
*head
)
1073 struct buffer_head
*bh
, *tail
;
1078 bh
= bh
->b_this_page
;
1080 tail
->b_this_page
= head
;
1081 attach_page_buffers(page
, head
);
1085 * Initialise the state of a blockdev page's buffers.
1088 init_page_buffers(struct page
*page
, struct block_device
*bdev
,
1089 sector_t block
, int size
)
1091 struct buffer_head
*head
= page_buffers(page
);
1092 struct buffer_head
*bh
= head
;
1093 int uptodate
= PageUptodate(page
);
1096 if (!buffer_mapped(bh
)) {
1097 init_buffer(bh
, NULL
, NULL
);
1099 bh
->b_blocknr
= block
;
1101 set_buffer_uptodate(bh
);
1102 set_buffer_mapped(bh
);
1105 bh
= bh
->b_this_page
;
1106 } while (bh
!= head
);
1110 * Create the page-cache page that contains the requested block.
1112 * This is user purely for blockdev mappings.
1114 static struct page
*
1115 grow_dev_page(struct block_device
*bdev
, sector_t block
,
1116 pgoff_t index
, int size
)
1118 struct inode
*inode
= bdev
->bd_inode
;
1120 struct buffer_head
*bh
;
1122 page
= find_or_create_page(inode
->i_mapping
, index
, GFP_NOFS
);
1126 if (!PageLocked(page
))
1129 if (page_has_buffers(page
)) {
1130 bh
= page_buffers(page
);
1131 if (bh
->b_size
== size
) {
1132 init_page_buffers(page
, bdev
, block
, size
);
1135 if (!try_to_free_buffers(page
))
1140 * Allocate some buffers for this page
1142 bh
= alloc_page_buffers(page
, size
, 0);
1147 * Link the page to the buffers and initialise them. Take the
1148 * lock to be atomic wrt __find_get_block(), which does not
1149 * run under the page lock.
1151 spin_lock(&inode
->i_mapping
->private_lock
);
1152 link_dev_buffers(page
, bh
);
1153 init_page_buffers(page
, bdev
, block
, size
);
1154 spin_unlock(&inode
->i_mapping
->private_lock
);
1160 page_cache_release(page
);
1165 * Create buffers for the specified block device block's page. If
1166 * that page was dirty, the buffers are set dirty also.
1168 * Except that's a bug. Attaching dirty buffers to a dirty
1169 * blockdev's page can result in filesystem corruption, because
1170 * some of those buffers may be aliases of filesystem data.
1171 * grow_dev_page() will go BUG() if this happens.
1174 grow_buffers(struct block_device
*bdev
, sector_t block
, int size
)
1183 } while ((size
<< sizebits
) < PAGE_SIZE
);
1185 index
= block
>> sizebits
;
1186 block
= index
<< sizebits
;
1188 /* Create a page with the proper size buffers.. */
1189 page
= grow_dev_page(bdev
, block
, index
, size
);
1193 page_cache_release(page
);
1197 static struct buffer_head
*
1198 __getblk_slow(struct block_device
*bdev
, sector_t block
, int size
)
1200 /* Size must be multiple of hard sectorsize */
1201 if (unlikely(size
& (bdev_hardsect_size(bdev
)-1) ||
1202 (size
< 512 || size
> PAGE_SIZE
))) {
1203 printk(KERN_ERR
"getblk(): invalid block size %d requested\n",
1205 printk(KERN_ERR
"hardsect size: %d\n",
1206 bdev_hardsect_size(bdev
));
1213 struct buffer_head
* bh
;
1215 bh
= __find_get_block(bdev
, block
, size
);
1219 if (!grow_buffers(bdev
, block
, size
))
1225 * The relationship between dirty buffers and dirty pages:
1227 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1228 * the page is tagged dirty in its radix tree.
1230 * At all times, the dirtiness of the buffers represents the dirtiness of
1231 * subsections of the page. If the page has buffers, the page dirty bit is
1232 * merely a hint about the true dirty state.
1234 * When a page is set dirty in its entirety, all its buffers are marked dirty
1235 * (if the page has buffers).
1237 * When a buffer is marked dirty, its page is dirtied, but the page's other
1240 * Also. When blockdev buffers are explicitly read with bread(), they
1241 * individually become uptodate. But their backing page remains not
1242 * uptodate - even if all of its buffers are uptodate. A subsequent
1243 * block_read_full_page() against that page will discover all the uptodate
1244 * buffers, will set the page uptodate and will perform no I/O.
1248 * mark_buffer_dirty - mark a buffer_head as needing writeout
1249 * @bh: the buffer_head to mark dirty
1251 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1252 * backing page dirty, then tag the page as dirty in its address_space's radix
1253 * tree and then attach the address_space's inode to its superblock's dirty
1256 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1257 * mapping->tree_lock and the global inode_lock.
1259 void fastcall
mark_buffer_dirty(struct buffer_head
*bh
)
1261 if (!buffer_dirty(bh
) && !test_set_buffer_dirty(bh
))
1262 __set_page_dirty_nobuffers(bh
->b_page
);
1266 * Decrement a buffer_head's reference count. If all buffers against a page
1267 * have zero reference count, are clean and unlocked, and if the page is clean
1268 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1269 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1270 * a page but it ends up not being freed, and buffers may later be reattached).
1272 void __brelse(struct buffer_head
* buf
)
1274 if (atomic_read(&buf
->b_count
)) {
1278 printk(KERN_ERR
"VFS: brelse: Trying to free free buffer\n");
1283 * bforget() is like brelse(), except it discards any
1284 * potentially dirty data.
1286 void __bforget(struct buffer_head
*bh
)
1288 clear_buffer_dirty(bh
);
1289 if (!list_empty(&bh
->b_assoc_buffers
)) {
1290 struct address_space
*buffer_mapping
= bh
->b_page
->mapping
;
1292 spin_lock(&buffer_mapping
->private_lock
);
1293 list_del_init(&bh
->b_assoc_buffers
);
1294 spin_unlock(&buffer_mapping
->private_lock
);
1299 static struct buffer_head
*__bread_slow(struct buffer_head
*bh
)
1302 if (buffer_uptodate(bh
)) {
1307 bh
->b_end_io
= end_buffer_read_sync
;
1308 submit_bh(READ
, bh
);
1310 if (buffer_uptodate(bh
))
1318 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1319 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1320 * refcount elevated by one when they're in an LRU. A buffer can only appear
1321 * once in a particular CPU's LRU. A single buffer can be present in multiple
1322 * CPU's LRUs at the same time.
1324 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1325 * sb_find_get_block().
1327 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1328 * a local interrupt disable for that.
1331 #define BH_LRU_SIZE 8
1334 struct buffer_head
*bhs
[BH_LRU_SIZE
];
1337 static DEFINE_PER_CPU(struct bh_lru
, bh_lrus
) = {{ NULL
}};
1340 #define bh_lru_lock() local_irq_disable()
1341 #define bh_lru_unlock() local_irq_enable()
1343 #define bh_lru_lock() preempt_disable()
1344 #define bh_lru_unlock() preempt_enable()
1347 static inline void check_irqs_on(void)
1349 #ifdef irqs_disabled
1350 BUG_ON(irqs_disabled());
1355 * The LRU management algorithm is dopey-but-simple. Sorry.
1357 static void bh_lru_install(struct buffer_head
*bh
)
1359 struct buffer_head
*evictee
= NULL
;
1364 lru
= &__get_cpu_var(bh_lrus
);
1365 if (lru
->bhs
[0] != bh
) {
1366 struct buffer_head
*bhs
[BH_LRU_SIZE
];
1372 for (in
= 0; in
< BH_LRU_SIZE
; in
++) {
1373 struct buffer_head
*bh2
= lru
->bhs
[in
];
1378 if (out
>= BH_LRU_SIZE
) {
1379 BUG_ON(evictee
!= NULL
);
1386 while (out
< BH_LRU_SIZE
)
1388 memcpy(lru
->bhs
, bhs
, sizeof(bhs
));
1397 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1399 static inline struct buffer_head
*
1400 lookup_bh_lru(struct block_device
*bdev
, sector_t block
, int size
)
1402 struct buffer_head
*ret
= NULL
;
1408 lru
= &__get_cpu_var(bh_lrus
);
1409 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1410 struct buffer_head
*bh
= lru
->bhs
[i
];
1412 if (bh
&& bh
->b_bdev
== bdev
&&
1413 bh
->b_blocknr
== block
&& bh
->b_size
== size
) {
1416 lru
->bhs
[i
] = lru
->bhs
[i
- 1];
1431 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1432 * it in the LRU and mark it as accessed. If it is not present then return
1435 struct buffer_head
*
1436 __find_get_block(struct block_device
*bdev
, sector_t block
, int size
)
1438 struct buffer_head
*bh
= lookup_bh_lru(bdev
, block
, size
);
1441 bh
= __find_get_block_slow(bdev
, block
, size
);
1449 EXPORT_SYMBOL(__find_get_block
);
1452 * __getblk will locate (and, if necessary, create) the buffer_head
1453 * which corresponds to the passed block_device, block and size. The
1454 * returned buffer has its reference count incremented.
1456 * __getblk() cannot fail - it just keeps trying. If you pass it an
1457 * illegal block number, __getblk() will happily return a buffer_head
1458 * which represents the non-existent block. Very weird.
1460 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1461 * attempt is failing. FIXME, perhaps?
1463 struct buffer_head
*
1464 __getblk(struct block_device
*bdev
, sector_t block
, int size
)
1466 struct buffer_head
*bh
= __find_get_block(bdev
, block
, size
);
1470 bh
= __getblk_slow(bdev
, block
, size
);
1473 EXPORT_SYMBOL(__getblk
);
1476 * Do async read-ahead on a buffer..
1478 void __breadahead(struct block_device
*bdev
, sector_t block
, int size
)
1480 struct buffer_head
*bh
= __getblk(bdev
, block
, size
);
1481 ll_rw_block(READA
, 1, &bh
);
1484 EXPORT_SYMBOL(__breadahead
);
1487 * __bread() - reads a specified block and returns the bh
1488 * @bdev: the block_device to read from
1489 * @block: number of block
1490 * @size: size (in bytes) to read
1492 * Reads a specified block, and returns buffer head that contains it.
1493 * It returns NULL if the block was unreadable.
1495 struct buffer_head
*
1496 __bread(struct block_device
*bdev
, sector_t block
, int size
)
1498 struct buffer_head
*bh
= __getblk(bdev
, block
, size
);
1500 if (!buffer_uptodate(bh
))
1501 bh
= __bread_slow(bh
);
1504 EXPORT_SYMBOL(__bread
);
1507 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1508 * This doesn't race because it runs in each cpu either in irq
1509 * or with preempt disabled.
1511 static void invalidate_bh_lru(void *arg
)
1513 struct bh_lru
*b
= &get_cpu_var(bh_lrus
);
1516 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
1520 put_cpu_var(bh_lrus
);
1523 static void invalidate_bh_lrus(void)
1525 on_each_cpu(invalidate_bh_lru
, NULL
, 1, 1);
1528 void set_bh_page(struct buffer_head
*bh
,
1529 struct page
*page
, unsigned long offset
)
1532 if (offset
>= PAGE_SIZE
)
1534 if (PageHighMem(page
))
1536 * This catches illegal uses and preserves the offset:
1538 bh
->b_data
= (char *)(0 + offset
);
1540 bh
->b_data
= page_address(page
) + offset
;
1542 EXPORT_SYMBOL(set_bh_page
);
1545 * Called when truncating a buffer on a page completely.
1547 static inline void discard_buffer(struct buffer_head
* bh
)
1550 clear_buffer_dirty(bh
);
1552 clear_buffer_mapped(bh
);
1553 clear_buffer_req(bh
);
1554 clear_buffer_new(bh
);
1555 clear_buffer_delay(bh
);
1560 * try_to_release_page() - release old fs-specific metadata on a page
1562 * @page: the page which the kernel is trying to free
1563 * @gfp_mask: memory allocation flags (and I/O mode)
1565 * The address_space is to try to release any data against the page
1566 * (presumably at page->private). If the release was successful, return `1'.
1567 * Otherwise return zero.
1569 * The @gfp_mask argument specifies whether I/O may be performed to release
1570 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
1572 * NOTE: @gfp_mask may go away, and this function may become non-blocking.
1574 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
1576 struct address_space
* const mapping
= page
->mapping
;
1578 BUG_ON(!PageLocked(page
));
1579 if (PageWriteback(page
))
1582 if (mapping
&& mapping
->a_ops
->releasepage
)
1583 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
1584 return try_to_free_buffers(page
);
1586 EXPORT_SYMBOL(try_to_release_page
);
1589 * block_invalidatepage - invalidate part of all of a buffer-backed page
1591 * @page: the page which is affected
1592 * @offset: the index of the truncation point
1594 * block_invalidatepage() is called when all or part of the page has become
1595 * invalidatedby a truncate operation.
1597 * block_invalidatepage() does not have to release all buffers, but it must
1598 * ensure that no dirty buffer is left outside @offset and that no I/O
1599 * is underway against any of the blocks which are outside the truncation
1600 * point. Because the caller is about to free (and possibly reuse) those
1603 int block_invalidatepage(struct page
*page
, unsigned long offset
)
1605 struct buffer_head
*head
, *bh
, *next
;
1606 unsigned int curr_off
= 0;
1609 BUG_ON(!PageLocked(page
));
1610 if (!page_has_buffers(page
))
1613 head
= page_buffers(page
);
1616 unsigned int next_off
= curr_off
+ bh
->b_size
;
1617 next
= bh
->b_this_page
;
1620 * is this block fully invalidated?
1622 if (offset
<= curr_off
)
1624 curr_off
= next_off
;
1626 } while (bh
!= head
);
1629 * We release buffers only if the entire page is being invalidated.
1630 * The get_block cached value has been unconditionally invalidated,
1631 * so real IO is not possible anymore.
1634 ret
= try_to_release_page(page
, 0);
1638 EXPORT_SYMBOL(block_invalidatepage
);
1641 * We attach and possibly dirty the buffers atomically wrt
1642 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1643 * is already excluded via the page lock.
1645 void create_empty_buffers(struct page
*page
,
1646 unsigned long blocksize
, unsigned long b_state
)
1648 struct buffer_head
*bh
, *head
, *tail
;
1650 head
= alloc_page_buffers(page
, blocksize
, 1);
1653 bh
->b_state
|= b_state
;
1655 bh
= bh
->b_this_page
;
1657 tail
->b_this_page
= head
;
1659 spin_lock(&page
->mapping
->private_lock
);
1660 if (PageUptodate(page
) || PageDirty(page
)) {
1663 if (PageDirty(page
))
1664 set_buffer_dirty(bh
);
1665 if (PageUptodate(page
))
1666 set_buffer_uptodate(bh
);
1667 bh
= bh
->b_this_page
;
1668 } while (bh
!= head
);
1670 attach_page_buffers(page
, head
);
1671 spin_unlock(&page
->mapping
->private_lock
);
1673 EXPORT_SYMBOL(create_empty_buffers
);
1676 * We are taking a block for data and we don't want any output from any
1677 * buffer-cache aliases starting from return from that function and
1678 * until the moment when something will explicitly mark the buffer
1679 * dirty (hopefully that will not happen until we will free that block ;-)
1680 * We don't even need to mark it not-uptodate - nobody can expect
1681 * anything from a newly allocated buffer anyway. We used to used
1682 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1683 * don't want to mark the alias unmapped, for example - it would confuse
1684 * anyone who might pick it with bread() afterwards...
1686 * Also.. Note that bforget() doesn't lock the buffer. So there can
1687 * be writeout I/O going on against recently-freed buffers. We don't
1688 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1689 * only if we really need to. That happens here.
1691 void unmap_underlying_metadata(struct block_device
*bdev
, sector_t block
)
1693 struct buffer_head
*old_bh
;
1697 old_bh
= __find_get_block_slow(bdev
, block
, 0);
1699 clear_buffer_dirty(old_bh
);
1700 wait_on_buffer(old_bh
);
1701 clear_buffer_req(old_bh
);
1705 EXPORT_SYMBOL(unmap_underlying_metadata
);
1708 * NOTE! All mapped/uptodate combinations are valid:
1710 * Mapped Uptodate Meaning
1712 * No No "unknown" - must do get_block()
1713 * No Yes "hole" - zero-filled
1714 * Yes No "allocated" - allocated on disk, not read in
1715 * Yes Yes "valid" - allocated and up-to-date in memory.
1717 * "Dirty" is valid only with the last case (mapped+uptodate).
1721 * While block_write_full_page is writing back the dirty buffers under
1722 * the page lock, whoever dirtied the buffers may decide to clean them
1723 * again at any time. We handle that by only looking at the buffer
1724 * state inside lock_buffer().
1726 * If block_write_full_page() is called for regular writeback
1727 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1728 * locked buffer. This only can happen if someone has written the buffer
1729 * directly, with submit_bh(). At the address_space level PageWriteback
1730 * prevents this contention from occurring.
1732 static int __block_write_full_page(struct inode
*inode
, struct page
*page
,
1733 get_block_t
*get_block
, struct writeback_control
*wbc
)
1737 sector_t last_block
;
1738 struct buffer_head
*bh
, *head
;
1739 int nr_underway
= 0;
1741 BUG_ON(!PageLocked(page
));
1743 last_block
= (i_size_read(inode
) - 1) >> inode
->i_blkbits
;
1745 if (!page_has_buffers(page
)) {
1746 create_empty_buffers(page
, 1 << inode
->i_blkbits
,
1747 (1 << BH_Dirty
)|(1 << BH_Uptodate
));
1751 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1752 * here, and the (potentially unmapped) buffers may become dirty at
1753 * any time. If a buffer becomes dirty here after we've inspected it
1754 * then we just miss that fact, and the page stays dirty.
1756 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1757 * handle that here by just cleaning them.
1760 block
= page
->index
<< (PAGE_CACHE_SHIFT
- inode
->i_blkbits
);
1761 head
= page_buffers(page
);
1765 * Get all the dirty buffers mapped to disk addresses and
1766 * handle any aliases from the underlying blockdev's mapping.
1769 if (block
> last_block
) {
1771 * mapped buffers outside i_size will occur, because
1772 * this page can be outside i_size when there is a
1773 * truncate in progress.
1776 * The buffer was zeroed by block_write_full_page()
1778 clear_buffer_dirty(bh
);
1779 set_buffer_uptodate(bh
);
1780 } else if (!buffer_mapped(bh
) && buffer_dirty(bh
)) {
1781 err
= get_block(inode
, block
, bh
, 1);
1784 if (buffer_new(bh
)) {
1785 /* blockdev mappings never come here */
1786 clear_buffer_new(bh
);
1787 unmap_underlying_metadata(bh
->b_bdev
,
1791 bh
= bh
->b_this_page
;
1793 } while (bh
!= head
);
1796 if (!buffer_mapped(bh
))
1799 * If it's a fully non-blocking write attempt and we cannot
1800 * lock the buffer then redirty the page. Note that this can
1801 * potentially cause a busy-wait loop from pdflush and kswapd
1802 * activity, but those code paths have their own higher-level
1805 if (wbc
->sync_mode
!= WB_SYNC_NONE
|| !wbc
->nonblocking
) {
1807 } else if (test_set_buffer_locked(bh
)) {
1808 redirty_page_for_writepage(wbc
, page
);
1811 if (test_clear_buffer_dirty(bh
)) {
1812 mark_buffer_async_write(bh
);
1816 } while ((bh
= bh
->b_this_page
) != head
);
1819 * The page and its buffers are protected by PageWriteback(), so we can
1820 * drop the bh refcounts early.
1822 BUG_ON(PageWriteback(page
));
1823 set_page_writeback(page
);
1826 struct buffer_head
*next
= bh
->b_this_page
;
1827 if (buffer_async_write(bh
)) {
1828 submit_bh(WRITE
, bh
);
1832 } while (bh
!= head
);
1837 if (nr_underway
== 0) {
1839 * The page was marked dirty, but the buffers were
1840 * clean. Someone wrote them back by hand with
1841 * ll_rw_block/submit_bh. A rare case.
1845 if (!buffer_uptodate(bh
)) {
1849 bh
= bh
->b_this_page
;
1850 } while (bh
!= head
);
1852 SetPageUptodate(page
);
1853 end_page_writeback(page
);
1855 * The page and buffer_heads can be released at any time from
1858 wbc
->pages_skipped
++; /* We didn't write this page */
1864 * ENOSPC, or some other error. We may already have added some
1865 * blocks to the file, so we need to write these out to avoid
1866 * exposing stale data.
1867 * The page is currently locked and not marked for writeback
1870 /* Recovery: lock and submit the mapped buffers */
1872 if (buffer_mapped(bh
) && buffer_dirty(bh
)) {
1874 mark_buffer_async_write(bh
);
1877 * The buffer may have been set dirty during
1878 * attachment to a dirty page.
1880 clear_buffer_dirty(bh
);
1882 } while ((bh
= bh
->b_this_page
) != head
);
1884 BUG_ON(PageWriteback(page
));
1885 set_page_writeback(page
);
1888 struct buffer_head
*next
= bh
->b_this_page
;
1889 if (buffer_async_write(bh
)) {
1890 clear_buffer_dirty(bh
);
1891 submit_bh(WRITE
, bh
);
1895 } while (bh
!= head
);
1899 static int __block_prepare_write(struct inode
*inode
, struct page
*page
,
1900 unsigned from
, unsigned to
, get_block_t
*get_block
)
1902 unsigned block_start
, block_end
;
1905 unsigned blocksize
, bbits
;
1906 struct buffer_head
*bh
, *head
, *wait
[2], **wait_bh
=wait
;
1908 BUG_ON(!PageLocked(page
));
1909 BUG_ON(from
> PAGE_CACHE_SIZE
);
1910 BUG_ON(to
> PAGE_CACHE_SIZE
);
1913 blocksize
= 1 << inode
->i_blkbits
;
1914 if (!page_has_buffers(page
))
1915 create_empty_buffers(page
, blocksize
, 0);
1916 head
= page_buffers(page
);
1918 bbits
= inode
->i_blkbits
;
1919 block
= (sector_t
)page
->index
<< (PAGE_CACHE_SHIFT
- bbits
);
1921 for(bh
= head
, block_start
= 0; bh
!= head
|| !block_start
;
1922 block
++, block_start
=block_end
, bh
= bh
->b_this_page
) {
1923 block_end
= block_start
+ blocksize
;
1924 if (block_end
<= from
|| block_start
>= to
) {
1925 if (PageUptodate(page
)) {
1926 if (!buffer_uptodate(bh
))
1927 set_buffer_uptodate(bh
);
1932 clear_buffer_new(bh
);
1933 if (!buffer_mapped(bh
)) {
1934 err
= get_block(inode
, block
, bh
, 1);
1937 if (buffer_new(bh
)) {
1938 unmap_underlying_metadata(bh
->b_bdev
,
1940 if (PageUptodate(page
)) {
1941 set_buffer_uptodate(bh
);
1944 if (block_end
> to
|| block_start
< from
) {
1947 kaddr
= kmap_atomic(page
, KM_USER0
);
1951 if (block_start
< from
)
1952 memset(kaddr
+block_start
,
1953 0, from
-block_start
);
1954 flush_dcache_page(page
);
1955 kunmap_atomic(kaddr
, KM_USER0
);
1960 if (PageUptodate(page
)) {
1961 if (!buffer_uptodate(bh
))
1962 set_buffer_uptodate(bh
);
1965 if (!buffer_uptodate(bh
) && !buffer_delay(bh
) &&
1966 (block_start
< from
|| block_end
> to
)) {
1967 ll_rw_block(READ
, 1, &bh
);
1972 * If we issued read requests - let them complete.
1974 while(wait_bh
> wait
) {
1975 wait_on_buffer(*--wait_bh
);
1976 if (!buffer_uptodate(*wait_bh
))
1983 clear_buffer_new(bh
);
1984 } while ((bh
= bh
->b_this_page
) != head
);
1989 * Zero out any newly allocated blocks to avoid exposing stale
1990 * data. If BH_New is set, we know that the block was newly
1991 * allocated in the above loop.
1996 block_end
= block_start
+blocksize
;
1997 if (block_end
<= from
)
1999 if (block_start
>= to
)
2001 if (buffer_new(bh
)) {
2004 clear_buffer_new(bh
);
2005 kaddr
= kmap_atomic(page
, KM_USER0
);
2006 memset(kaddr
+block_start
, 0, bh
->b_size
);
2007 kunmap_atomic(kaddr
, KM_USER0
);
2008 set_buffer_uptodate(bh
);
2009 mark_buffer_dirty(bh
);
2012 block_start
= block_end
;
2013 bh
= bh
->b_this_page
;
2014 } while (bh
!= head
);
2018 static int __block_commit_write(struct inode
*inode
, struct page
*page
,
2019 unsigned from
, unsigned to
)
2021 unsigned block_start
, block_end
;
2024 struct buffer_head
*bh
, *head
;
2026 blocksize
= 1 << inode
->i_blkbits
;
2028 for(bh
= head
= page_buffers(page
), block_start
= 0;
2029 bh
!= head
|| !block_start
;
2030 block_start
=block_end
, bh
= bh
->b_this_page
) {
2031 block_end
= block_start
+ blocksize
;
2032 if (block_end
<= from
|| block_start
>= to
) {
2033 if (!buffer_uptodate(bh
))
2036 set_buffer_uptodate(bh
);
2037 mark_buffer_dirty(bh
);
2042 * If this is a partial write which happened to make all buffers
2043 * uptodate then we can optimize away a bogus readpage() for
2044 * the next read(). Here we 'discover' whether the page went
2045 * uptodate as a result of this (potentially partial) write.
2048 SetPageUptodate(page
);
2053 * Generic "read page" function for block devices that have the normal
2054 * get_block functionality. This is most of the block device filesystems.
2055 * Reads the page asynchronously --- the unlock_buffer() and
2056 * set/clear_buffer_uptodate() functions propagate buffer state into the
2057 * page struct once IO has completed.
2059 int block_read_full_page(struct page
*page
, get_block_t
*get_block
)
2061 struct inode
*inode
= page
->mapping
->host
;
2062 sector_t iblock
, lblock
;
2063 struct buffer_head
*bh
, *head
, *arr
[MAX_BUF_PER_PAGE
];
2064 unsigned int blocksize
;
2066 int fully_mapped
= 1;
2068 BUG_ON(!PageLocked(page
));
2069 blocksize
= 1 << inode
->i_blkbits
;
2070 if (!page_has_buffers(page
))
2071 create_empty_buffers(page
, blocksize
, 0);
2072 head
= page_buffers(page
);
2074 iblock
= (sector_t
)page
->index
<< (PAGE_CACHE_SHIFT
- inode
->i_blkbits
);
2075 lblock
= (i_size_read(inode
)+blocksize
-1) >> inode
->i_blkbits
;
2081 if (buffer_uptodate(bh
))
2084 if (!buffer_mapped(bh
)) {
2088 if (iblock
< lblock
) {
2089 err
= get_block(inode
, iblock
, bh
, 0);
2093 if (!buffer_mapped(bh
)) {
2094 void *kaddr
= kmap_atomic(page
, KM_USER0
);
2095 memset(kaddr
+ i
* blocksize
, 0, blocksize
);
2096 flush_dcache_page(page
);
2097 kunmap_atomic(kaddr
, KM_USER0
);
2099 set_buffer_uptodate(bh
);
2103 * get_block() might have updated the buffer
2106 if (buffer_uptodate(bh
))
2110 } while (i
++, iblock
++, (bh
= bh
->b_this_page
) != head
);
2113 SetPageMappedToDisk(page
);
2117 * All buffers are uptodate - we can set the page uptodate
2118 * as well. But not if get_block() returned an error.
2120 if (!PageError(page
))
2121 SetPageUptodate(page
);
2126 /* Stage two: lock the buffers */
2127 for (i
= 0; i
< nr
; i
++) {
2130 mark_buffer_async_read(bh
);
2134 * Stage 3: start the IO. Check for uptodateness
2135 * inside the buffer lock in case another process reading
2136 * the underlying blockdev brought it uptodate (the sct fix).
2138 for (i
= 0; i
< nr
; i
++) {
2140 if (buffer_uptodate(bh
))
2141 end_buffer_async_read(bh
, 1);
2143 submit_bh(READ
, bh
);
2148 /* utility function for filesystems that need to do work on expanding
2149 * truncates. Uses prepare/commit_write to allow the filesystem to
2150 * deal with the hole.
2152 int generic_cont_expand(struct inode
*inode
, loff_t size
)
2154 struct address_space
*mapping
= inode
->i_mapping
;
2156 unsigned long index
, offset
, limit
;
2160 limit
= current
->signal
->rlim
[RLIMIT_FSIZE
].rlim_cur
;
2161 if (limit
!= RLIM_INFINITY
&& size
> (loff_t
)limit
) {
2162 send_sig(SIGXFSZ
, current
, 0);
2165 if (size
> inode
->i_sb
->s_maxbytes
)
2168 offset
= (size
& (PAGE_CACHE_SIZE
-1)); /* Within page */
2170 /* ugh. in prepare/commit_write, if from==to==start of block, we
2171 ** skip the prepare. make sure we never send an offset for the start
2174 if ((offset
& (inode
->i_sb
->s_blocksize
- 1)) == 0) {
2177 index
= size
>> PAGE_CACHE_SHIFT
;
2179 page
= grab_cache_page(mapping
, index
);
2182 err
= mapping
->a_ops
->prepare_write(NULL
, page
, offset
, offset
);
2184 err
= mapping
->a_ops
->commit_write(NULL
, page
, offset
, offset
);
2187 page_cache_release(page
);
2195 * For moronic filesystems that do not allow holes in file.
2196 * We may have to extend the file.
2199 int cont_prepare_write(struct page
*page
, unsigned offset
,
2200 unsigned to
, get_block_t
*get_block
, loff_t
*bytes
)
2202 struct address_space
*mapping
= page
->mapping
;
2203 struct inode
*inode
= mapping
->host
;
2204 struct page
*new_page
;
2208 unsigned blocksize
= 1 << inode
->i_blkbits
;
2211 while(page
->index
> (pgpos
= *bytes
>>PAGE_CACHE_SHIFT
)) {
2213 new_page
= grab_cache_page(mapping
, pgpos
);
2216 /* we might sleep */
2217 if (*bytes
>>PAGE_CACHE_SHIFT
!= pgpos
) {
2218 unlock_page(new_page
);
2219 page_cache_release(new_page
);
2222 zerofrom
= *bytes
& ~PAGE_CACHE_MASK
;
2223 if (zerofrom
& (blocksize
-1)) {
2224 *bytes
|= (blocksize
-1);
2227 status
= __block_prepare_write(inode
, new_page
, zerofrom
,
2228 PAGE_CACHE_SIZE
, get_block
);
2231 kaddr
= kmap_atomic(new_page
, KM_USER0
);
2232 memset(kaddr
+zerofrom
, 0, PAGE_CACHE_SIZE
-zerofrom
);
2233 flush_dcache_page(new_page
);
2234 kunmap_atomic(kaddr
, KM_USER0
);
2235 generic_commit_write(NULL
, new_page
, zerofrom
, PAGE_CACHE_SIZE
);
2236 unlock_page(new_page
);
2237 page_cache_release(new_page
);
2240 if (page
->index
< pgpos
) {
2241 /* completely inside the area */
2244 /* page covers the boundary, find the boundary offset */
2245 zerofrom
= *bytes
& ~PAGE_CACHE_MASK
;
2247 /* if we will expand the thing last block will be filled */
2248 if (to
> zerofrom
&& (zerofrom
& (blocksize
-1))) {
2249 *bytes
|= (blocksize
-1);
2253 /* starting below the boundary? Nothing to zero out */
2254 if (offset
<= zerofrom
)
2257 status
= __block_prepare_write(inode
, page
, zerofrom
, to
, get_block
);
2260 if (zerofrom
< offset
) {
2261 kaddr
= kmap_atomic(page
, KM_USER0
);
2262 memset(kaddr
+zerofrom
, 0, offset
-zerofrom
);
2263 flush_dcache_page(page
);
2264 kunmap_atomic(kaddr
, KM_USER0
);
2265 __block_commit_write(inode
, page
, zerofrom
, offset
);
2269 ClearPageUptodate(page
);
2273 ClearPageUptodate(new_page
);
2274 unlock_page(new_page
);
2275 page_cache_release(new_page
);
2280 int block_prepare_write(struct page
*page
, unsigned from
, unsigned to
,
2281 get_block_t
*get_block
)
2283 struct inode
*inode
= page
->mapping
->host
;
2284 int err
= __block_prepare_write(inode
, page
, from
, to
, get_block
);
2286 ClearPageUptodate(page
);
2290 int block_commit_write(struct page
*page
, unsigned from
, unsigned to
)
2292 struct inode
*inode
= page
->mapping
->host
;
2293 __block_commit_write(inode
,page
,from
,to
);
2297 int generic_commit_write(struct file
*file
, struct page
*page
,
2298 unsigned from
, unsigned to
)
2300 struct inode
*inode
= page
->mapping
->host
;
2301 loff_t pos
= ((loff_t
)page
->index
<< PAGE_CACHE_SHIFT
) + to
;
2302 __block_commit_write(inode
,page
,from
,to
);
2304 * No need to use i_size_read() here, the i_size
2305 * cannot change under us because we hold i_sem.
2307 if (pos
> inode
->i_size
) {
2308 i_size_write(inode
, pos
);
2309 mark_inode_dirty(inode
);
2316 * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
2317 * immediately, while under the page lock. So it needs a special end_io
2318 * handler which does not touch the bh after unlocking it.
2320 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
2321 * a race there is benign: unlock_buffer() only use the bh's address for
2322 * hashing after unlocking the buffer, so it doesn't actually touch the bh
2325 static void end_buffer_read_nobh(struct buffer_head
*bh
, int uptodate
)
2328 set_buffer_uptodate(bh
);
2330 /* This happens, due to failed READA attempts. */
2331 clear_buffer_uptodate(bh
);
2337 * On entry, the page is fully not uptodate.
2338 * On exit the page is fully uptodate in the areas outside (from,to)
2340 int nobh_prepare_write(struct page
*page
, unsigned from
, unsigned to
,
2341 get_block_t
*get_block
)
2343 struct inode
*inode
= page
->mapping
->host
;
2344 const unsigned blkbits
= inode
->i_blkbits
;
2345 const unsigned blocksize
= 1 << blkbits
;
2346 struct buffer_head map_bh
;
2347 struct buffer_head
*read_bh
[MAX_BUF_PER_PAGE
];
2348 unsigned block_in_page
;
2349 unsigned block_start
;
2350 sector_t block_in_file
;
2355 int is_mapped_to_disk
= 1;
2358 if (PageMappedToDisk(page
))
2361 block_in_file
= (sector_t
)page
->index
<< (PAGE_CACHE_SHIFT
- blkbits
);
2362 map_bh
.b_page
= page
;
2365 * We loop across all blocks in the page, whether or not they are
2366 * part of the affected region. This is so we can discover if the
2367 * page is fully mapped-to-disk.
2369 for (block_start
= 0, block_in_page
= 0;
2370 block_start
< PAGE_CACHE_SIZE
;
2371 block_in_page
++, block_start
+= blocksize
) {
2372 unsigned block_end
= block_start
+ blocksize
;
2377 if (block_start
>= to
)
2379 ret
= get_block(inode
, block_in_file
+ block_in_page
,
2383 if (!buffer_mapped(&map_bh
))
2384 is_mapped_to_disk
= 0;
2385 if (buffer_new(&map_bh
))
2386 unmap_underlying_metadata(map_bh
.b_bdev
,
2388 if (PageUptodate(page
))
2390 if (buffer_new(&map_bh
) || !buffer_mapped(&map_bh
)) {
2391 kaddr
= kmap_atomic(page
, KM_USER0
);
2392 if (block_start
< from
) {
2393 memset(kaddr
+block_start
, 0, from
-block_start
);
2396 if (block_end
> to
) {
2397 memset(kaddr
+ to
, 0, block_end
- to
);
2400 flush_dcache_page(page
);
2401 kunmap_atomic(kaddr
, KM_USER0
);
2404 if (buffer_uptodate(&map_bh
))
2405 continue; /* reiserfs does this */
2406 if (block_start
< from
|| block_end
> to
) {
2407 struct buffer_head
*bh
= alloc_buffer_head(GFP_NOFS
);
2413 bh
->b_state
= map_bh
.b_state
;
2414 atomic_set(&bh
->b_count
, 0);
2415 bh
->b_this_page
= NULL
;
2417 bh
->b_blocknr
= map_bh
.b_blocknr
;
2418 bh
->b_size
= blocksize
;
2419 bh
->b_data
= (char *)(long)block_start
;
2420 bh
->b_bdev
= map_bh
.b_bdev
;
2421 bh
->b_private
= NULL
;
2422 read_bh
[nr_reads
++] = bh
;
2427 struct buffer_head
*bh
;
2430 * The page is locked, so these buffers are protected from
2431 * any VM or truncate activity. Hence we don't need to care
2432 * for the buffer_head refcounts.
2434 for (i
= 0; i
< nr_reads
; i
++) {
2437 bh
->b_end_io
= end_buffer_read_nobh
;
2438 submit_bh(READ
, bh
);
2440 for (i
= 0; i
< nr_reads
; i
++) {
2443 if (!buffer_uptodate(bh
))
2445 free_buffer_head(bh
);
2452 if (is_mapped_to_disk
)
2453 SetPageMappedToDisk(page
);
2454 SetPageUptodate(page
);
2457 * Setting the page dirty here isn't necessary for the prepare_write
2458 * function - commit_write will do that. But if/when this function is
2459 * used within the pagefault handler to ensure that all mmapped pages
2460 * have backing space in the filesystem, we will need to dirty the page
2461 * if its contents were altered.
2464 set_page_dirty(page
);
2469 for (i
= 0; i
< nr_reads
; i
++) {
2471 free_buffer_head(read_bh
[i
]);
2475 * Error recovery is pretty slack. Clear the page and mark it dirty
2476 * so we'll later zero out any blocks which _were_ allocated.
2478 kaddr
= kmap_atomic(page
, KM_USER0
);
2479 memset(kaddr
, 0, PAGE_CACHE_SIZE
);
2480 kunmap_atomic(kaddr
, KM_USER0
);
2481 SetPageUptodate(page
);
2482 set_page_dirty(page
);
2485 EXPORT_SYMBOL(nobh_prepare_write
);
2487 int nobh_commit_write(struct file
*file
, struct page
*page
,
2488 unsigned from
, unsigned to
)
2490 struct inode
*inode
= page
->mapping
->host
;
2491 loff_t pos
= ((loff_t
)page
->index
<< PAGE_CACHE_SHIFT
) + to
;
2493 set_page_dirty(page
);
2494 if (pos
> inode
->i_size
) {
2495 i_size_write(inode
, pos
);
2496 mark_inode_dirty(inode
);
2500 EXPORT_SYMBOL(nobh_commit_write
);
2503 * nobh_writepage() - based on block_full_write_page() except
2504 * that it tries to operate without attaching bufferheads to
2507 int nobh_writepage(struct page
*page
, get_block_t
*get_block
,
2508 struct writeback_control
*wbc
)
2510 struct inode
* const inode
= page
->mapping
->host
;
2511 loff_t i_size
= i_size_read(inode
);
2512 const pgoff_t end_index
= i_size
>> PAGE_CACHE_SHIFT
;
2517 /* Is the page fully inside i_size? */
2518 if (page
->index
< end_index
)
2521 /* Is the page fully outside i_size? (truncate in progress) */
2522 offset
= i_size
& (PAGE_CACHE_SIZE
-1);
2523 if (page
->index
>= end_index
+1 || !offset
) {
2525 * The page may have dirty, unmapped buffers. For example,
2526 * they may have been added in ext3_writepage(). Make them
2527 * freeable here, so the page does not leak.
2530 /* Not really sure about this - do we need this ? */
2531 if (page
->mapping
->a_ops
->invalidatepage
)
2532 page
->mapping
->a_ops
->invalidatepage(page
, offset
);
2535 return 0; /* don't care */
2539 * The page straddles i_size. It must be zeroed out on each and every
2540 * writepage invocation because it may be mmapped. "A file is mapped
2541 * in multiples of the page size. For a file that is not a multiple of
2542 * the page size, the remaining memory is zeroed when mapped, and
2543 * writes to that region are not written out to the file."
2545 kaddr
= kmap_atomic(page
, KM_USER0
);
2546 memset(kaddr
+ offset
, 0, PAGE_CACHE_SIZE
- offset
);
2547 flush_dcache_page(page
);
2548 kunmap_atomic(kaddr
, KM_USER0
);
2550 ret
= mpage_writepage(page
, get_block
, wbc
);
2552 ret
= __block_write_full_page(inode
, page
, get_block
, wbc
);
2555 EXPORT_SYMBOL(nobh_writepage
);
2558 * This function assumes that ->prepare_write() uses nobh_prepare_write().
2560 int nobh_truncate_page(struct address_space
*mapping
, loff_t from
)
2562 struct inode
*inode
= mapping
->host
;
2563 unsigned blocksize
= 1 << inode
->i_blkbits
;
2564 pgoff_t index
= from
>> PAGE_CACHE_SHIFT
;
2565 unsigned offset
= from
& (PAGE_CACHE_SIZE
-1);
2568 struct address_space_operations
*a_ops
= mapping
->a_ops
;
2572 if ((offset
& (blocksize
- 1)) == 0)
2576 page
= grab_cache_page(mapping
, index
);
2580 to
= (offset
+ blocksize
) & ~(blocksize
- 1);
2581 ret
= a_ops
->prepare_write(NULL
, page
, offset
, to
);
2583 kaddr
= kmap_atomic(page
, KM_USER0
);
2584 memset(kaddr
+ offset
, 0, PAGE_CACHE_SIZE
- offset
);
2585 flush_dcache_page(page
);
2586 kunmap_atomic(kaddr
, KM_USER0
);
2587 set_page_dirty(page
);
2590 page_cache_release(page
);
2594 EXPORT_SYMBOL(nobh_truncate_page
);
2596 int block_truncate_page(struct address_space
*mapping
,
2597 loff_t from
, get_block_t
*get_block
)
2599 pgoff_t index
= from
>> PAGE_CACHE_SHIFT
;
2600 unsigned offset
= from
& (PAGE_CACHE_SIZE
-1);
2603 unsigned length
, pos
;
2604 struct inode
*inode
= mapping
->host
;
2606 struct buffer_head
*bh
;
2610 blocksize
= 1 << inode
->i_blkbits
;
2611 length
= offset
& (blocksize
- 1);
2613 /* Block boundary? Nothing to do */
2617 length
= blocksize
- length
;
2618 iblock
= index
<< (PAGE_CACHE_SHIFT
- inode
->i_blkbits
);
2620 page
= grab_cache_page(mapping
, index
);
2625 if (!page_has_buffers(page
))
2626 create_empty_buffers(page
, blocksize
, 0);
2628 /* Find the buffer that contains "offset" */
2629 bh
= page_buffers(page
);
2631 while (offset
>= pos
) {
2632 bh
= bh
->b_this_page
;
2638 if (!buffer_mapped(bh
)) {
2639 err
= get_block(inode
, iblock
, bh
, 0);
2642 /* unmapped? It's a hole - nothing to do */
2643 if (!buffer_mapped(bh
))
2647 /* Ok, it's mapped. Make sure it's up-to-date */
2648 if (PageUptodate(page
))
2649 set_buffer_uptodate(bh
);
2651 if (!buffer_uptodate(bh
) && !buffer_delay(bh
)) {
2653 ll_rw_block(READ
, 1, &bh
);
2655 /* Uhhuh. Read error. Complain and punt. */
2656 if (!buffer_uptodate(bh
))
2660 kaddr
= kmap_atomic(page
, KM_USER0
);
2661 memset(kaddr
+ offset
, 0, length
);
2662 flush_dcache_page(page
);
2663 kunmap_atomic(kaddr
, KM_USER0
);
2665 mark_buffer_dirty(bh
);
2670 page_cache_release(page
);
2676 * The generic ->writepage function for buffer-backed address_spaces
2678 int block_write_full_page(struct page
*page
, get_block_t
*get_block
,
2679 struct writeback_control
*wbc
)
2681 struct inode
* const inode
= page
->mapping
->host
;
2682 loff_t i_size
= i_size_read(inode
);
2683 const pgoff_t end_index
= i_size
>> PAGE_CACHE_SHIFT
;
2687 /* Is the page fully inside i_size? */
2688 if (page
->index
< end_index
)
2689 return __block_write_full_page(inode
, page
, get_block
, wbc
);
2691 /* Is the page fully outside i_size? (truncate in progress) */
2692 offset
= i_size
& (PAGE_CACHE_SIZE
-1);
2693 if (page
->index
>= end_index
+1 || !offset
) {
2695 * The page may have dirty, unmapped buffers. For example,
2696 * they may have been added in ext3_writepage(). Make them
2697 * freeable here, so the page does not leak.
2699 block_invalidatepage(page
, 0);
2701 return 0; /* don't care */
2705 * The page straddles i_size. It must be zeroed out on each and every
2706 * writepage invokation because it may be mmapped. "A file is mapped
2707 * in multiples of the page size. For a file that is not a multiple of
2708 * the page size, the remaining memory is zeroed when mapped, and
2709 * writes to that region are not written out to the file."
2711 kaddr
= kmap_atomic(page
, KM_USER0
);
2712 memset(kaddr
+ offset
, 0, PAGE_CACHE_SIZE
- offset
);
2713 flush_dcache_page(page
);
2714 kunmap_atomic(kaddr
, KM_USER0
);
2715 return __block_write_full_page(inode
, page
, get_block
, wbc
);
2718 sector_t
generic_block_bmap(struct address_space
*mapping
, sector_t block
,
2719 get_block_t
*get_block
)
2721 struct buffer_head tmp
;
2722 struct inode
*inode
= mapping
->host
;
2725 get_block(inode
, block
, &tmp
, 0);
2726 return tmp
.b_blocknr
;
2729 static int end_bio_bh_io_sync(struct bio
*bio
, unsigned int bytes_done
, int err
)
2731 struct buffer_head
*bh
= bio
->bi_private
;
2736 if (err
== -EOPNOTSUPP
) {
2737 set_bit(BIO_EOPNOTSUPP
, &bio
->bi_flags
);
2738 set_bit(BH_Eopnotsupp
, &bh
->b_state
);
2741 bh
->b_end_io(bh
, test_bit(BIO_UPTODATE
, &bio
->bi_flags
));
2746 int submit_bh(int rw
, struct buffer_head
* bh
)
2751 BUG_ON(!buffer_locked(bh
));
2752 BUG_ON(!buffer_mapped(bh
));
2753 BUG_ON(!bh
->b_end_io
);
2755 if (buffer_ordered(bh
) && (rw
== WRITE
))
2759 * Only clear out a write error when rewriting, should this
2760 * include WRITE_SYNC as well?
2762 if (test_set_buffer_req(bh
) && (rw
== WRITE
|| rw
== WRITE_BARRIER
))
2763 clear_buffer_write_io_error(bh
);
2766 * from here on down, it's all bio -- do the initial mapping,
2767 * submit_bio -> generic_make_request may further map this bio around
2769 bio
= bio_alloc(GFP_NOIO
, 1);
2771 bio
->bi_sector
= bh
->b_blocknr
* (bh
->b_size
>> 9);
2772 bio
->bi_bdev
= bh
->b_bdev
;
2773 bio
->bi_io_vec
[0].bv_page
= bh
->b_page
;
2774 bio
->bi_io_vec
[0].bv_len
= bh
->b_size
;
2775 bio
->bi_io_vec
[0].bv_offset
= bh_offset(bh
);
2779 bio
->bi_size
= bh
->b_size
;
2781 bio
->bi_end_io
= end_bio_bh_io_sync
;
2782 bio
->bi_private
= bh
;
2785 submit_bio(rw
, bio
);
2787 if (bio_flagged(bio
, BIO_EOPNOTSUPP
))
2795 * ll_rw_block: low-level access to block devices (DEPRECATED)
2796 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
2797 * @nr: number of &struct buffer_heads in the array
2798 * @bhs: array of pointers to &struct buffer_head
2800 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2801 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2802 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2803 * are sent to disk. The fourth %READA option is described in the documentation
2804 * for generic_make_request() which ll_rw_block() calls.
2806 * This function drops any buffer that it cannot get a lock on (with the
2807 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2808 * clean when doing a write request, and any buffer that appears to be
2809 * up-to-date when doing read request. Further it marks as clean buffers that
2810 * are processed for writing (the buffer cache won't assume that they are
2811 * actually clean until the buffer gets unlocked).
2813 * ll_rw_block sets b_end_io to simple completion handler that marks
2814 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2817 * All of the buffers must be for the same device, and must also be a
2818 * multiple of the current approved size for the device.
2820 void ll_rw_block(int rw
, int nr
, struct buffer_head
*bhs
[])
2824 for (i
= 0; i
< nr
; i
++) {
2825 struct buffer_head
*bh
= bhs
[i
];
2829 else if (test_set_buffer_locked(bh
))
2833 if (rw
== WRITE
|| rw
== SWRITE
) {
2834 if (test_clear_buffer_dirty(bh
)) {
2835 bh
->b_end_io
= end_buffer_write_sync
;
2836 submit_bh(WRITE
, bh
);
2840 if (!buffer_uptodate(bh
)) {
2841 bh
->b_end_io
= end_buffer_read_sync
;
2852 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2853 * and then start new I/O and then wait upon it. The caller must have a ref on
2856 int sync_dirty_buffer(struct buffer_head
*bh
)
2860 WARN_ON(atomic_read(&bh
->b_count
) < 1);
2862 if (test_clear_buffer_dirty(bh
)) {
2864 bh
->b_end_io
= end_buffer_write_sync
;
2865 ret
= submit_bh(WRITE
, bh
);
2867 if (buffer_eopnotsupp(bh
)) {
2868 clear_buffer_eopnotsupp(bh
);
2871 if (!ret
&& !buffer_uptodate(bh
))
2880 * try_to_free_buffers() checks if all the buffers on this particular page
2881 * are unused, and releases them if so.
2883 * Exclusion against try_to_free_buffers may be obtained by either
2884 * locking the page or by holding its mapping's private_lock.
2886 * If the page is dirty but all the buffers are clean then we need to
2887 * be sure to mark the page clean as well. This is because the page
2888 * may be against a block device, and a later reattachment of buffers
2889 * to a dirty page will set *all* buffers dirty. Which would corrupt
2890 * filesystem data on the same device.
2892 * The same applies to regular filesystem pages: if all the buffers are
2893 * clean then we set the page clean and proceed. To do that, we require
2894 * total exclusion from __set_page_dirty_buffers(). That is obtained with
2897 * try_to_free_buffers() is non-blocking.
2899 static inline int buffer_busy(struct buffer_head
*bh
)
2901 return atomic_read(&bh
->b_count
) |
2902 (bh
->b_state
& ((1 << BH_Dirty
) | (1 << BH_Lock
)));
2906 drop_buffers(struct page
*page
, struct buffer_head
**buffers_to_free
)
2908 struct buffer_head
*head
= page_buffers(page
);
2909 struct buffer_head
*bh
;
2913 if (buffer_write_io_error(bh
) && page
->mapping
)
2914 set_bit(AS_EIO
, &page
->mapping
->flags
);
2915 if (buffer_busy(bh
))
2917 bh
= bh
->b_this_page
;
2918 } while (bh
!= head
);
2921 struct buffer_head
*next
= bh
->b_this_page
;
2923 if (!list_empty(&bh
->b_assoc_buffers
))
2924 __remove_assoc_queue(bh
);
2926 } while (bh
!= head
);
2927 *buffers_to_free
= head
;
2928 __clear_page_buffers(page
);
2934 int try_to_free_buffers(struct page
*page
)
2936 struct address_space
* const mapping
= page
->mapping
;
2937 struct buffer_head
*buffers_to_free
= NULL
;
2940 BUG_ON(!PageLocked(page
));
2941 if (PageWriteback(page
))
2944 if (mapping
== NULL
) { /* can this still happen? */
2945 ret
= drop_buffers(page
, &buffers_to_free
);
2949 spin_lock(&mapping
->private_lock
);
2950 ret
= drop_buffers(page
, &buffers_to_free
);
2953 * If the filesystem writes its buffers by hand (eg ext3)
2954 * then we can have clean buffers against a dirty page. We
2955 * clean the page here; otherwise later reattachment of buffers
2956 * could encounter a non-uptodate page, which is unresolvable.
2957 * This only applies in the rare case where try_to_free_buffers
2958 * succeeds but the page is not freed.
2960 clear_page_dirty(page
);
2962 spin_unlock(&mapping
->private_lock
);
2964 if (buffers_to_free
) {
2965 struct buffer_head
*bh
= buffers_to_free
;
2968 struct buffer_head
*next
= bh
->b_this_page
;
2969 free_buffer_head(bh
);
2971 } while (bh
!= buffers_to_free
);
2975 EXPORT_SYMBOL(try_to_free_buffers
);
2977 int block_sync_page(struct page
*page
)
2979 struct address_space
*mapping
;
2982 mapping
= page_mapping(page
);
2984 blk_run_backing_dev(mapping
->backing_dev_info
, page
);
2989 * There are no bdflush tunables left. But distributions are
2990 * still running obsolete flush daemons, so we terminate them here.
2992 * Use of bdflush() is deprecated and will be removed in a future kernel.
2993 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
2995 asmlinkage
long sys_bdflush(int func
, long data
)
2997 static int msg_count
;
2999 if (!capable(CAP_SYS_ADMIN
))
3002 if (msg_count
< 5) {
3005 "warning: process `%s' used the obsolete bdflush"
3006 " system call\n", current
->comm
);
3007 printk(KERN_INFO
"Fix your initscripts?\n");
3016 * Buffer-head allocation
3018 static kmem_cache_t
*bh_cachep
;
3021 * Once the number of bh's in the machine exceeds this level, we start
3022 * stripping them in writeback.
3024 static int max_buffer_heads
;
3026 int buffer_heads_over_limit
;
3028 struct bh_accounting
{
3029 int nr
; /* Number of live bh's */
3030 int ratelimit
; /* Limit cacheline bouncing */
3033 static DEFINE_PER_CPU(struct bh_accounting
, bh_accounting
) = {0, 0};
3035 static void recalc_bh_state(void)
3040 if (__get_cpu_var(bh_accounting
).ratelimit
++ < 4096)
3042 __get_cpu_var(bh_accounting
).ratelimit
= 0;
3044 tot
+= per_cpu(bh_accounting
, i
).nr
;
3045 buffer_heads_over_limit
= (tot
> max_buffer_heads
);
3048 struct buffer_head
*alloc_buffer_head(gfp_t gfp_flags
)
3050 struct buffer_head
*ret
= kmem_cache_alloc(bh_cachep
, gfp_flags
);
3052 get_cpu_var(bh_accounting
).nr
++;
3054 put_cpu_var(bh_accounting
);
3058 EXPORT_SYMBOL(alloc_buffer_head
);
3060 void free_buffer_head(struct buffer_head
*bh
)
3062 BUG_ON(!list_empty(&bh
->b_assoc_buffers
));
3063 kmem_cache_free(bh_cachep
, bh
);
3064 get_cpu_var(bh_accounting
).nr
--;
3066 put_cpu_var(bh_accounting
);
3068 EXPORT_SYMBOL(free_buffer_head
);
3071 init_buffer_head(void *data
, kmem_cache_t
*cachep
, unsigned long flags
)
3073 if ((flags
& (SLAB_CTOR_VERIFY
|SLAB_CTOR_CONSTRUCTOR
)) ==
3074 SLAB_CTOR_CONSTRUCTOR
) {
3075 struct buffer_head
* bh
= (struct buffer_head
*)data
;
3077 memset(bh
, 0, sizeof(*bh
));
3078 INIT_LIST_HEAD(&bh
->b_assoc_buffers
);
3082 #ifdef CONFIG_HOTPLUG_CPU
3083 static void buffer_exit_cpu(int cpu
)
3086 struct bh_lru
*b
= &per_cpu(bh_lrus
, cpu
);
3088 for (i
= 0; i
< BH_LRU_SIZE
; i
++) {
3094 static int buffer_cpu_notify(struct notifier_block
*self
,
3095 unsigned long action
, void *hcpu
)
3097 if (action
== CPU_DEAD
)
3098 buffer_exit_cpu((unsigned long)hcpu
);
3101 #endif /* CONFIG_HOTPLUG_CPU */
3103 void __init
buffer_init(void)
3107 bh_cachep
= kmem_cache_create("buffer_head",
3108 sizeof(struct buffer_head
), 0,
3109 SLAB_RECLAIM_ACCOUNT
|SLAB_PANIC
, init_buffer_head
, NULL
);
3112 * Limit the bh occupancy to 10% of ZONE_NORMAL
3114 nrpages
= (nr_free_buffer_pages() * 10) / 100;
3115 max_buffer_heads
= nrpages
* (PAGE_SIZE
/ sizeof(struct buffer_head
));
3116 hotcpu_notifier(buffer_cpu_notify
, 0);
3119 EXPORT_SYMBOL(__bforget
);
3120 EXPORT_SYMBOL(__brelse
);
3121 EXPORT_SYMBOL(__wait_on_buffer
);
3122 EXPORT_SYMBOL(block_commit_write
);
3123 EXPORT_SYMBOL(block_prepare_write
);
3124 EXPORT_SYMBOL(block_read_full_page
);
3125 EXPORT_SYMBOL(block_sync_page
);
3126 EXPORT_SYMBOL(block_truncate_page
);
3127 EXPORT_SYMBOL(block_write_full_page
);
3128 EXPORT_SYMBOL(cont_prepare_write
);
3129 EXPORT_SYMBOL(end_buffer_async_write
);
3130 EXPORT_SYMBOL(end_buffer_read_sync
);
3131 EXPORT_SYMBOL(end_buffer_write_sync
);
3132 EXPORT_SYMBOL(file_fsync
);
3133 EXPORT_SYMBOL(fsync_bdev
);
3134 EXPORT_SYMBOL(generic_block_bmap
);
3135 EXPORT_SYMBOL(generic_commit_write
);
3136 EXPORT_SYMBOL(generic_cont_expand
);
3137 EXPORT_SYMBOL(init_buffer
);
3138 EXPORT_SYMBOL(invalidate_bdev
);
3139 EXPORT_SYMBOL(ll_rw_block
);
3140 EXPORT_SYMBOL(mark_buffer_dirty
);
3141 EXPORT_SYMBOL(submit_bh
);
3142 EXPORT_SYMBOL(sync_dirty_buffer
);
3143 EXPORT_SYMBOL(unlock_buffer
);