]>
git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - fs/fs-writeback.c
4 * Copyright (C) 2002, Linus Torvalds.
6 * Contains all the functions related to writing back and waiting
7 * upon dirty inodes against superblocks, and writing back dirty
8 * pages against inodes. ie: data writeback. Writeout of the
9 * inode itself is not handled here.
11 * 10Apr2002 akpm@zip.com.au
12 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/spinlock.h>
19 #include <linux/sched.h>
22 #include <linux/writeback.h>
23 #include <linux/blkdev.h>
24 #include <linux/backing-dev.h>
25 #include <linux/buffer_head.h>
29 * __mark_inode_dirty - internal function
30 * @inode: inode to mark
31 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
32 * Mark an inode as dirty. Callers should use mark_inode_dirty or
33 * mark_inode_dirty_sync.
35 * Put the inode on the super block's dirty list.
37 * CAREFUL! We mark it dirty unconditionally, but move it onto the
38 * dirty list only if it is hashed or if it refers to a blockdev.
39 * If it was not hashed, it will never be added to the dirty list
40 * even if it is later hashed, as it will have been marked dirty already.
42 * In short, make sure you hash any inodes _before_ you start marking
45 * This function *must* be atomic for the I_DIRTY_PAGES case -
46 * set_page_dirty() is called under spinlock in several places.
48 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
49 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
50 * the kernel-internal blockdev inode represents the dirtying time of the
51 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
52 * page->mapping->host, so the page-dirtying time is recorded in the internal
55 void __mark_inode_dirty(struct inode
*inode
, int flags
)
57 struct super_block
*sb
= inode
->i_sb
;
60 * Don't do this for I_DIRTY_PAGES - that doesn't actually
61 * dirty the inode itself
63 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
64 if (sb
->s_op
->dirty_inode
)
65 sb
->s_op
->dirty_inode(inode
);
69 * make sure that changes are seen by all cpus before we test i_state
74 /* avoid the locking if we can */
75 if ((inode
->i_state
& flags
) == flags
)
78 if (unlikely(block_dump
)) {
79 struct dentry
*dentry
= NULL
;
80 const char *name
= "?";
82 if (!list_empty(&inode
->i_dentry
)) {
83 dentry
= list_entry(inode
->i_dentry
.next
,
84 struct dentry
, d_alias
);
85 if (dentry
&& dentry
->d_name
.name
)
86 name
= (const char *) dentry
->d_name
.name
;
89 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev"))
91 "%s(%d): dirtied inode %lu (%s) on %s\n",
92 current
->comm
, current
->pid
, inode
->i_ino
,
93 name
, inode
->i_sb
->s_id
);
96 spin_lock(&inode_lock
);
97 if ((inode
->i_state
& flags
) != flags
) {
98 const int was_dirty
= inode
->i_state
& I_DIRTY
;
100 inode
->i_state
|= flags
;
103 * If the inode is locked, just update its dirty state.
104 * The unlocker will place the inode on the appropriate
105 * superblock list, based upon its state.
107 if (inode
->i_state
& I_LOCK
)
111 * Only add valid (hashed) inodes to the superblock's
112 * dirty list. Add blockdev inodes as well.
114 if (!S_ISBLK(inode
->i_mode
)) {
115 if (hlist_unhashed(&inode
->i_hash
))
118 if (inode
->i_state
& (I_FREEING
|I_CLEAR
))
122 * If the inode was already on s_dirty or s_io, don't
123 * reposition it (that would break s_dirty time-ordering).
126 inode
->dirtied_when
= jiffies
;
127 list_move(&inode
->i_list
, &sb
->s_dirty
);
131 spin_unlock(&inode_lock
);
134 EXPORT_SYMBOL(__mark_inode_dirty
);
136 static int write_inode(struct inode
*inode
, int sync
)
138 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
))
139 return inode
->i_sb
->s_op
->write_inode(inode
, sync
);
144 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
145 * furthest end of its superblock's dirty-inode list.
147 * Before stamping the inode's ->dirtied_when, we check to see whether it is
148 * already the most-recently-dirtied inode on the s_dirty list. If that is
149 * the case then the inode must have been redirtied while it was being written
150 * out and we don't reset its dirtied_when.
152 static void redirty_tail(struct inode
*inode
)
154 struct super_block
*sb
= inode
->i_sb
;
156 if (!list_empty(&sb
->s_dirty
)) {
157 struct inode
*tail_inode
;
159 tail_inode
= list_entry(sb
->s_dirty
.next
, struct inode
, i_list
);
160 if (!time_after_eq(inode
->dirtied_when
,
161 tail_inode
->dirtied_when
))
162 inode
->dirtied_when
= jiffies
;
164 list_move(&inode
->i_list
, &sb
->s_dirty
);
168 * Redirty an inode, but mark it as the very next-to-be-written inode on its
169 * superblock's dirty-inode list.
170 * We need to preserve s_dirty's reverse-time-orderedness, so we cheat by
171 * setting this inode's dirtied_when to the same value as that of the inode
172 * which is presently head-of-list, if present head-of-list is newer than this
173 * inode. (head-of-list is the least-recently-dirtied inode: the oldest one).
175 static void redirty_head(struct inode
*inode
)
177 struct super_block
*sb
= inode
->i_sb
;
179 if (!list_empty(&sb
->s_dirty
)) {
180 struct inode
*head_inode
;
182 head_inode
= list_entry(sb
->s_dirty
.prev
, struct inode
, i_list
);
183 if (time_after(inode
->dirtied_when
, head_inode
->dirtied_when
))
184 inode
->dirtied_when
= head_inode
->dirtied_when
;
186 list_move_tail(&inode
->i_list
, &sb
->s_dirty
);
190 * Write a single inode's dirty pages and inode data out to disk.
191 * If `wait' is set, wait on the writeout.
193 * The whole writeout design is quite complex and fragile. We want to avoid
194 * starvation of particular inodes when others are being redirtied, prevent
197 * Called under inode_lock.
200 __sync_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
203 struct address_space
*mapping
= inode
->i_mapping
;
204 int wait
= wbc
->sync_mode
== WB_SYNC_ALL
;
207 BUG_ON(inode
->i_state
& I_LOCK
);
209 /* Set I_LOCK, reset I_DIRTY */
210 dirty
= inode
->i_state
& I_DIRTY
;
211 inode
->i_state
|= I_LOCK
;
212 inode
->i_state
&= ~I_DIRTY
;
214 spin_unlock(&inode_lock
);
216 ret
= do_writepages(mapping
, wbc
);
218 /* Don't write the inode if only I_DIRTY_PAGES was set */
219 if (dirty
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
220 int err
= write_inode(inode
, wait
);
226 int err
= filemap_fdatawait(mapping
);
231 spin_lock(&inode_lock
);
232 inode
->i_state
&= ~I_LOCK
;
233 if (!(inode
->i_state
& I_FREEING
)) {
234 if (!(inode
->i_state
& I_DIRTY
) &&
235 mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
)) {
237 * We didn't write back all the pages. nfs_writepages()
238 * sometimes bales out without doing anything. Redirty
239 * the inode. It is moved from s_io onto s_dirty.
242 * akpm: if the caller was the kupdate function we put
243 * this inode at the head of s_dirty so it gets first
244 * consideration. Otherwise, move it to the tail, for
245 * the reasons described there. I'm not really sure
246 * how much sense this makes. Presumably I had a good
247 * reasons for doing it this way, and I'd rather not
248 * muck with it at present.
250 if (wbc
->for_kupdate
) {
252 * For the kupdate function we leave the inode
253 * at the head of sb_dirty so it will get more
254 * writeout as soon as the queue becomes
257 inode
->i_state
|= I_DIRTY_PAGES
;
261 * Otherwise fully redirty the inode so that
262 * other inodes on this superblock will get some
263 * writeout. Otherwise heavy writing to one
264 * file would indefinitely suspend writeout of
265 * all the other files.
267 inode
->i_state
|= I_DIRTY_PAGES
;
270 } else if (inode
->i_state
& I_DIRTY
) {
272 * Someone redirtied the inode while were writing back
276 } else if (atomic_read(&inode
->i_count
)) {
278 * The inode is clean, inuse
280 list_move(&inode
->i_list
, &inode_in_use
);
283 * The inode is clean, unused
285 list_move(&inode
->i_list
, &inode_unused
);
288 wake_up_inode(inode
);
293 * Write out an inode's dirty pages. Called under inode_lock. Either the
294 * caller has ref on the inode (either via __iget or via syscall against an fd)
295 * or the inode has I_WILL_FREE set (via generic_forget_inode)
298 __writeback_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
300 wait_queue_head_t
*wqh
;
302 if (!atomic_read(&inode
->i_count
))
303 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
305 WARN_ON(inode
->i_state
& I_WILL_FREE
);
307 if ((wbc
->sync_mode
!= WB_SYNC_ALL
) && (inode
->i_state
& I_LOCK
)) {
308 struct address_space
*mapping
= inode
->i_mapping
;
314 * Even if we don't actually write the inode itself here,
315 * we can at least start some of the data writeout..
317 spin_unlock(&inode_lock
);
318 ret
= do_writepages(mapping
, wbc
);
319 spin_lock(&inode_lock
);
324 * It's a data-integrity sync. We must wait.
326 if (inode
->i_state
& I_LOCK
) {
327 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_LOCK
);
329 wqh
= bit_waitqueue(&inode
->i_state
, __I_LOCK
);
331 spin_unlock(&inode_lock
);
332 __wait_on_bit(wqh
, &wq
, inode_wait
,
333 TASK_UNINTERRUPTIBLE
);
334 spin_lock(&inode_lock
);
335 } while (inode
->i_state
& I_LOCK
);
337 return __sync_single_inode(inode
, wbc
);
341 * Write out a superblock's list of dirty inodes. A wait will be performed
342 * upon no inodes, all inodes or the final one, depending upon sync_mode.
344 * If older_than_this is non-NULL, then only write out inodes which
345 * had their first dirtying at a time earlier than *older_than_this.
347 * If we're a pdlfush thread, then implement pdflush collision avoidance
348 * against the entire list.
350 * WB_SYNC_HOLD is a hack for sys_sync(): reattach the inode to sb->s_dirty so
351 * that it can be located for waiting on in __writeback_single_inode().
353 * Called under inode_lock.
355 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
356 * This function assumes that the blockdev superblock's inodes are backed by
357 * a variety of queues, so all inodes are searched. For other superblocks,
358 * assume that all inodes are backed by the same queue.
360 * FIXME: this linear search could get expensive with many fileystems. But
361 * how to fix? We need to go from an address_space to all inodes which share
362 * a queue with that address_space. (Easy: have a global "dirty superblocks"
365 * The inodes to be written are parked on sb->s_io. They are moved back onto
366 * sb->s_dirty as they are selected for writing. This way, none can be missed
367 * on the writer throttling path, and we get decent balancing between many
368 * throttled threads: we don't want them all piling up on __wait_on_inode.
371 sync_sb_inodes(struct super_block
*sb
, struct writeback_control
*wbc
)
373 const unsigned long start
= jiffies
; /* livelock avoidance */
375 if (!wbc
->for_kupdate
|| list_empty(&sb
->s_io
))
376 list_splice_init(&sb
->s_dirty
, &sb
->s_io
);
378 while (!list_empty(&sb
->s_io
)) {
379 struct inode
*inode
= list_entry(sb
->s_io
.prev
,
380 struct inode
, i_list
);
381 struct address_space
*mapping
= inode
->i_mapping
;
382 struct backing_dev_info
*bdi
= mapping
->backing_dev_info
;
385 if (!bdi_cap_writeback_dirty(bdi
)) {
387 if (sb_is_blkdev_sb(sb
)) {
389 * Dirty memory-backed blockdev: the ramdisk
390 * driver does this. Skip just this inode
395 * Dirty memory-backed inode against a filesystem other
396 * than the kernel-internal bdev filesystem. Skip the
402 if (wbc
->nonblocking
&& bdi_write_congested(bdi
)) {
403 wbc
->encountered_congestion
= 1;
404 if (!sb_is_blkdev_sb(sb
))
405 break; /* Skip a congested fs */
406 list_move(&inode
->i_list
, &sb
->s_dirty
);
407 continue; /* Skip a congested blockdev */
410 if (wbc
->bdi
&& bdi
!= wbc
->bdi
) {
411 if (!sb_is_blkdev_sb(sb
))
412 break; /* fs has the wrong queue */
413 list_move(&inode
->i_list
, &sb
->s_dirty
);
414 continue; /* blockdev has wrong queue */
417 /* Was this inode dirtied after sync_sb_inodes was called? */
418 if (time_after(inode
->dirtied_when
, start
))
421 /* Was this inode dirtied too recently? */
422 if (wbc
->older_than_this
&& time_after(inode
->dirtied_when
,
423 *wbc
->older_than_this
))
426 /* Is another pdflush already flushing this queue? */
427 if (current_is_pdflush() && !writeback_acquire(bdi
))
430 BUG_ON(inode
->i_state
& I_FREEING
);
432 pages_skipped
= wbc
->pages_skipped
;
433 __writeback_single_inode(inode
, wbc
);
434 if (wbc
->sync_mode
== WB_SYNC_HOLD
) {
435 inode
->dirtied_when
= jiffies
;
436 list_move(&inode
->i_list
, &sb
->s_dirty
);
438 if (current_is_pdflush())
439 writeback_release(bdi
);
440 if (wbc
->pages_skipped
!= pages_skipped
) {
442 * writeback is not making progress due to locked
443 * buffers. Skip this inode for now.
447 spin_unlock(&inode_lock
);
450 spin_lock(&inode_lock
);
451 if (wbc
->nr_to_write
<= 0)
454 return; /* Leave any unwritten inodes on s_io */
458 * Start writeback of dirty pagecache data against all unlocked inodes.
461 * We don't need to grab a reference to superblock here. If it has non-empty
462 * ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
463 * past sync_inodes_sb() until both the ->s_dirty and ->s_io lists are
464 * empty. Since __sync_single_inode() regains inode_lock before it finally moves
465 * inode from superblock lists we are OK.
467 * If `older_than_this' is non-zero then only flush inodes which have a
468 * flushtime older than *older_than_this.
470 * If `bdi' is non-zero then we will scan the first inode against each
471 * superblock until we find the matching ones. One group will be the dirty
472 * inodes against a filesystem. Then when we hit the dummy blockdev superblock,
473 * sync_sb_inodes will seekout the blockdev which matches `bdi'. Maybe not
474 * super-efficient but we're about to do a ton of I/O...
477 writeback_inodes(struct writeback_control
*wbc
)
479 struct super_block
*sb
;
484 sb
= sb_entry(super_blocks
.prev
);
485 for (; sb
!= sb_entry(&super_blocks
); sb
= sb_entry(sb
->s_list
.prev
)) {
486 if (!list_empty(&sb
->s_dirty
) || !list_empty(&sb
->s_io
)) {
487 /* we're making our own get_super here */
489 spin_unlock(&sb_lock
);
491 * If we can't get the readlock, there's no sense in
492 * waiting around, most of the time the FS is going to
493 * be unmounted by the time it is released.
495 if (down_read_trylock(&sb
->s_umount
)) {
497 spin_lock(&inode_lock
);
498 sync_sb_inodes(sb
, wbc
);
499 spin_unlock(&inode_lock
);
501 up_read(&sb
->s_umount
);
504 if (__put_super_and_need_restart(sb
))
507 if (wbc
->nr_to_write
<= 0)
510 spin_unlock(&sb_lock
);
514 * writeback and wait upon the filesystem's dirty inodes. The caller will
515 * do this in two passes - one to write, and one to wait. WB_SYNC_HOLD is
516 * used to park the written inodes on sb->s_dirty for the wait pass.
518 * A finite limit is set on the number of pages which will be written.
519 * To prevent infinite livelock of sys_sync().
521 * We add in the number of potentially dirty inodes, because each inode write
522 * can dirty pagecache in the underlying blockdev.
524 void sync_inodes_sb(struct super_block
*sb
, int wait
)
526 struct writeback_control wbc
= {
527 .sync_mode
= wait
? WB_SYNC_ALL
: WB_SYNC_HOLD
,
529 .range_end
= LLONG_MAX
,
531 unsigned long nr_dirty
= global_page_state(NR_FILE_DIRTY
);
532 unsigned long nr_unstable
= global_page_state(NR_UNSTABLE_NFS
);
534 wbc
.nr_to_write
= nr_dirty
+ nr_unstable
+
535 (inodes_stat
.nr_inodes
- inodes_stat
.nr_unused
) +
536 nr_dirty
+ nr_unstable
;
537 wbc
.nr_to_write
+= wbc
.nr_to_write
/ 2; /* Bit more for luck */
538 spin_lock(&inode_lock
);
539 sync_sb_inodes(sb
, &wbc
);
540 spin_unlock(&inode_lock
);
544 * Rather lame livelock avoidance.
546 static void set_sb_syncing(int val
)
548 struct super_block
*sb
;
550 sb
= sb_entry(super_blocks
.prev
);
551 for (; sb
!= sb_entry(&super_blocks
); sb
= sb_entry(sb
->s_list
.prev
)) {
554 spin_unlock(&sb_lock
);
558 * sync_inodes - writes all inodes to disk
559 * @wait: wait for completion
561 * sync_inodes() goes through each super block's dirty inode list, writes the
562 * inodes out, waits on the writeout and puts the inodes back on the normal
565 * This is for sys_sync(). fsync_dev() uses the same algorithm. The subtle
566 * part of the sync functions is that the blockdev "superblock" is processed
567 * last. This is because the write_inode() function of a typical fs will
568 * perform no I/O, but will mark buffers in the blockdev mapping as dirty.
569 * What we want to do is to perform all that dirtying first, and then write
570 * back all those inode blocks via the blockdev mapping in one sweep. So the
571 * additional (somewhat redundant) sync_blockdev() calls here are to make
572 * sure that really happens. Because if we call sync_inodes_sb(wait=1) with
573 * outstanding dirty inodes, the writeback goes block-at-a-time within the
574 * filesystem's write_inode(). This is extremely slow.
576 static void __sync_inodes(int wait
)
578 struct super_block
*sb
;
582 list_for_each_entry(sb
, &super_blocks
, s_list
) {
587 spin_unlock(&sb_lock
);
588 down_read(&sb
->s_umount
);
590 sync_inodes_sb(sb
, wait
);
591 sync_blockdev(sb
->s_bdev
);
593 up_read(&sb
->s_umount
);
595 if (__put_super_and_need_restart(sb
))
598 spin_unlock(&sb_lock
);
601 void sync_inodes(int wait
)
613 * write_inode_now - write an inode to disk
614 * @inode: inode to write to disk
615 * @sync: whether the write should be synchronous or not
617 * This function commits an inode to disk immediately if it is dirty. This is
618 * primarily needed by knfsd.
620 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
622 int write_inode_now(struct inode
*inode
, int sync
)
625 struct writeback_control wbc
= {
626 .nr_to_write
= LONG_MAX
,
627 .sync_mode
= WB_SYNC_ALL
,
629 .range_end
= LLONG_MAX
,
632 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
636 spin_lock(&inode_lock
);
637 ret
= __writeback_single_inode(inode
, &wbc
);
638 spin_unlock(&inode_lock
);
640 wait_on_inode(inode
);
643 EXPORT_SYMBOL(write_inode_now
);
646 * sync_inode - write an inode and its pages to disk.
647 * @inode: the inode to sync
648 * @wbc: controls the writeback mode
650 * sync_inode() will write an inode and its pages to disk. It will also
651 * correctly update the inode on its superblock's dirty inode lists and will
652 * update inode->i_state.
654 * The caller must have a ref on the inode.
656 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
660 spin_lock(&inode_lock
);
661 ret
= __writeback_single_inode(inode
, wbc
);
662 spin_unlock(&inode_lock
);
665 EXPORT_SYMBOL(sync_inode
);
668 * generic_osync_inode - flush all dirty data for a given inode to disk
669 * @inode: inode to write
670 * @mapping: the address_space that should be flushed
671 * @what: what to write and wait upon
673 * This can be called by file_write functions for files which have the
674 * O_SYNC flag set, to flush dirty writes to disk.
676 * @what is a bitmask, specifying which part of the inode's data should be
677 * written and waited upon.
679 * OSYNC_DATA: i_mapping's dirty data
680 * OSYNC_METADATA: the buffers at i_mapping->private_list
681 * OSYNC_INODE: the inode itself
684 int generic_osync_inode(struct inode
*inode
, struct address_space
*mapping
, int what
)
687 int need_write_inode_now
= 0;
690 if (what
& OSYNC_DATA
)
691 err
= filemap_fdatawrite(mapping
);
692 if (what
& (OSYNC_METADATA
|OSYNC_DATA
)) {
693 err2
= sync_mapping_buffers(mapping
);
697 if (what
& OSYNC_DATA
) {
698 err2
= filemap_fdatawait(mapping
);
703 spin_lock(&inode_lock
);
704 if ((inode
->i_state
& I_DIRTY
) &&
705 ((what
& OSYNC_INODE
) || (inode
->i_state
& I_DIRTY_DATASYNC
)))
706 need_write_inode_now
= 1;
707 spin_unlock(&inode_lock
);
709 if (need_write_inode_now
) {
710 err2
= write_inode_now(inode
, 1);
715 wait_on_inode(inode
);
720 EXPORT_SYMBOL(generic_osync_inode
);
723 * writeback_acquire: attempt to get exclusive writeback access to a device
724 * @bdi: the device's backing_dev_info structure
726 * It is a waste of resources to have more than one pdflush thread blocked on
727 * a single request queue. Exclusion at the request_queue level is obtained
728 * via a flag in the request_queue's backing_dev_info.state.
730 * Non-request_queue-backed address_spaces will share default_backing_dev_info,
731 * unless they implement their own. Which is somewhat inefficient, as this
732 * may prevent concurrent writeback against multiple devices.
734 int writeback_acquire(struct backing_dev_info
*bdi
)
736 return !test_and_set_bit(BDI_pdflush
, &bdi
->state
);
740 * writeback_in_progress: determine whether there is writeback in progress
741 * @bdi: the device's backing_dev_info structure.
743 * Determine whether there is writeback in progress against a backing device.
745 int writeback_in_progress(struct backing_dev_info
*bdi
)
747 return test_bit(BDI_pdflush
, &bdi
->state
);
751 * writeback_release: relinquish exclusive writeback access against a device.
752 * @bdi: the device's backing_dev_info structure
754 void writeback_release(struct backing_dev_info
*bdi
)
756 BUG_ON(!writeback_in_progress(bdi
));
757 clear_bit(BDI_pdflush
, &bdi
->state
);