]>
git.proxmox.com Git - mirror_ubuntu-bionic-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 Andrew Morton
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>
30 * writeback_acquire - attempt to get exclusive writeback access to a device
31 * @bdi: the device's backing_dev_info structure
33 * It is a waste of resources to have more than one pdflush thread blocked on
34 * a single request queue. Exclusion at the request_queue level is obtained
35 * via a flag in the request_queue's backing_dev_info.state.
37 * Non-request_queue-backed address_spaces will share default_backing_dev_info,
38 * unless they implement their own. Which is somewhat inefficient, as this
39 * may prevent concurrent writeback against multiple devices.
41 static int writeback_acquire(struct backing_dev_info
*bdi
)
43 return !test_and_set_bit(BDI_pdflush
, &bdi
->state
);
47 * writeback_in_progress - determine whether there is writeback in progress
48 * @bdi: the device's backing_dev_info structure.
50 * Determine whether there is writeback in progress against a backing device.
52 int writeback_in_progress(struct backing_dev_info
*bdi
)
54 return test_bit(BDI_pdflush
, &bdi
->state
);
58 * writeback_release - relinquish exclusive writeback access against a device.
59 * @bdi: the device's backing_dev_info structure
61 static void writeback_release(struct backing_dev_info
*bdi
)
63 BUG_ON(!writeback_in_progress(bdi
));
64 clear_bit(BDI_pdflush
, &bdi
->state
);
68 * __mark_inode_dirty - internal function
69 * @inode: inode to mark
70 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
71 * Mark an inode as dirty. Callers should use mark_inode_dirty or
72 * mark_inode_dirty_sync.
74 * Put the inode on the super block's dirty list.
76 * CAREFUL! We mark it dirty unconditionally, but move it onto the
77 * dirty list only if it is hashed or if it refers to a blockdev.
78 * If it was not hashed, it will never be added to the dirty list
79 * even if it is later hashed, as it will have been marked dirty already.
81 * In short, make sure you hash any inodes _before_ you start marking
84 * This function *must* be atomic for the I_DIRTY_PAGES case -
85 * set_page_dirty() is called under spinlock in several places.
87 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
88 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
89 * the kernel-internal blockdev inode represents the dirtying time of the
90 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
91 * page->mapping->host, so the page-dirtying time is recorded in the internal
94 void __mark_inode_dirty(struct inode
*inode
, int flags
)
96 struct super_block
*sb
= inode
->i_sb
;
99 * Don't do this for I_DIRTY_PAGES - that doesn't actually
100 * dirty the inode itself
102 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
103 if (sb
->s_op
->dirty_inode
)
104 sb
->s_op
->dirty_inode(inode
);
108 * make sure that changes are seen by all cpus before we test i_state
113 /* avoid the locking if we can */
114 if ((inode
->i_state
& flags
) == flags
)
117 if (unlikely(block_dump
)) {
118 struct dentry
*dentry
= NULL
;
119 const char *name
= "?";
121 if (!list_empty(&inode
->i_dentry
)) {
122 dentry
= list_entry(inode
->i_dentry
.next
,
123 struct dentry
, d_alias
);
124 if (dentry
&& dentry
->d_name
.name
)
125 name
= (const char *) dentry
->d_name
.name
;
128 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev"))
130 "%s(%d): dirtied inode %lu (%s) on %s\n",
131 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
132 name
, inode
->i_sb
->s_id
);
135 spin_lock(&inode_lock
);
136 if ((inode
->i_state
& flags
) != flags
) {
137 const int was_dirty
= inode
->i_state
& I_DIRTY
;
139 inode
->i_state
|= flags
;
142 * If the inode is being synced, just update its dirty state.
143 * The unlocker will place the inode on the appropriate
144 * superblock list, based upon its state.
146 if (inode
->i_state
& I_SYNC
)
150 * Only add valid (hashed) inodes to the superblock's
151 * dirty list. Add blockdev inodes as well.
153 if (!S_ISBLK(inode
->i_mode
)) {
154 if (hlist_unhashed(&inode
->i_hash
))
157 if (inode
->i_state
& (I_FREEING
|I_CLEAR
))
161 * If the inode was already on s_dirty/s_io/s_more_io, don't
162 * reposition it (that would break s_dirty time-ordering).
165 inode
->dirtied_when
= jiffies
;
166 list_move(&inode
->i_list
, &sb
->s_dirty
);
170 spin_unlock(&inode_lock
);
173 EXPORT_SYMBOL(__mark_inode_dirty
);
175 static int write_inode(struct inode
*inode
, int sync
)
177 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
))
178 return inode
->i_sb
->s_op
->write_inode(inode
, sync
);
183 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
184 * furthest end of its superblock's dirty-inode list.
186 * Before stamping the inode's ->dirtied_when, we check to see whether it is
187 * already the most-recently-dirtied inode on the s_dirty list. If that is
188 * the case then the inode must have been redirtied while it was being written
189 * out and we don't reset its dirtied_when.
191 static void redirty_tail(struct inode
*inode
)
193 struct super_block
*sb
= inode
->i_sb
;
195 if (!list_empty(&sb
->s_dirty
)) {
196 struct inode
*tail_inode
;
198 tail_inode
= list_entry(sb
->s_dirty
.next
, struct inode
, i_list
);
199 if (time_before(inode
->dirtied_when
,
200 tail_inode
->dirtied_when
))
201 inode
->dirtied_when
= jiffies
;
203 list_move(&inode
->i_list
, &sb
->s_dirty
);
207 * requeue inode for re-scanning after sb->s_io list is exhausted.
209 static void requeue_io(struct inode
*inode
)
211 list_move(&inode
->i_list
, &inode
->i_sb
->s_more_io
);
214 static void inode_sync_complete(struct inode
*inode
)
217 * Prevent speculative execution through spin_unlock(&inode_lock);
220 wake_up_bit(&inode
->i_state
, __I_SYNC
);
223 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
225 bool ret
= time_after(inode
->dirtied_when
, t
);
228 * For inodes being constantly redirtied, dirtied_when can get stuck.
229 * It _appears_ to be in the future, but is actually in distant past.
230 * This test is necessary to prevent such wrapped-around relative times
231 * from permanently stopping the whole pdflush writeback.
233 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
239 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
241 static void move_expired_inodes(struct list_head
*delaying_queue
,
242 struct list_head
*dispatch_queue
,
243 unsigned long *older_than_this
)
245 while (!list_empty(delaying_queue
)) {
246 struct inode
*inode
= list_entry(delaying_queue
->prev
,
247 struct inode
, i_list
);
248 if (older_than_this
&&
249 inode_dirtied_after(inode
, *older_than_this
))
251 list_move(&inode
->i_list
, dispatch_queue
);
256 * Queue all expired dirty inodes for io, eldest first.
258 static void queue_io(struct super_block
*sb
,
259 unsigned long *older_than_this
)
261 list_splice_init(&sb
->s_more_io
, sb
->s_io
.prev
);
262 move_expired_inodes(&sb
->s_dirty
, &sb
->s_io
, older_than_this
);
265 int sb_has_dirty_inodes(struct super_block
*sb
)
267 return !list_empty(&sb
->s_dirty
) ||
268 !list_empty(&sb
->s_io
) ||
269 !list_empty(&sb
->s_more_io
);
271 EXPORT_SYMBOL(sb_has_dirty_inodes
);
274 * Write a single inode's dirty pages and inode data out to disk.
275 * If `wait' is set, wait on the writeout.
277 * The whole writeout design is quite complex and fragile. We want to avoid
278 * starvation of particular inodes when others are being redirtied, prevent
281 * Called under inode_lock.
284 __sync_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
287 struct address_space
*mapping
= inode
->i_mapping
;
288 int wait
= wbc
->sync_mode
== WB_SYNC_ALL
;
291 BUG_ON(inode
->i_state
& I_SYNC
);
292 WARN_ON(inode
->i_state
& I_NEW
);
294 /* Set I_SYNC, reset I_DIRTY */
295 dirty
= inode
->i_state
& I_DIRTY
;
296 inode
->i_state
|= I_SYNC
;
297 inode
->i_state
&= ~I_DIRTY
;
299 spin_unlock(&inode_lock
);
301 ret
= do_writepages(mapping
, wbc
);
303 /* Don't write the inode if only I_DIRTY_PAGES was set */
304 if (dirty
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
305 int err
= write_inode(inode
, wait
);
311 int err
= filemap_fdatawait(mapping
);
316 spin_lock(&inode_lock
);
317 WARN_ON(inode
->i_state
& I_NEW
);
318 inode
->i_state
&= ~I_SYNC
;
319 if (!(inode
->i_state
& I_FREEING
)) {
320 if (!(inode
->i_state
& I_DIRTY
) &&
321 mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
)) {
323 * We didn't write back all the pages. nfs_writepages()
324 * sometimes bales out without doing anything. Redirty
325 * the inode; Move it from s_io onto s_more_io/s_dirty.
328 * akpm: if the caller was the kupdate function we put
329 * this inode at the head of s_dirty so it gets first
330 * consideration. Otherwise, move it to the tail, for
331 * the reasons described there. I'm not really sure
332 * how much sense this makes. Presumably I had a good
333 * reasons for doing it this way, and I'd rather not
334 * muck with it at present.
336 if (wbc
->for_kupdate
) {
338 * For the kupdate function we move the inode
339 * to s_more_io so it will get more writeout as
340 * soon as the queue becomes uncongested.
342 inode
->i_state
|= I_DIRTY_PAGES
;
343 if (wbc
->nr_to_write
<= 0) {
345 * slice used up: queue for next turn
350 * somehow blocked: retry later
356 * Otherwise fully redirty the inode so that
357 * other inodes on this superblock will get some
358 * writeout. Otherwise heavy writing to one
359 * file would indefinitely suspend writeout of
360 * all the other files.
362 inode
->i_state
|= I_DIRTY_PAGES
;
365 } else if (inode
->i_state
& I_DIRTY
) {
367 * Someone redirtied the inode while were writing back
371 } else if (atomic_read(&inode
->i_count
)) {
373 * The inode is clean, inuse
375 list_move(&inode
->i_list
, &inode_in_use
);
378 * The inode is clean, unused
380 list_move(&inode
->i_list
, &inode_unused
);
383 inode_sync_complete(inode
);
388 * Write out an inode's dirty pages. Called under inode_lock. Either the
389 * caller has ref on the inode (either via __iget or via syscall against an fd)
390 * or the inode has I_WILL_FREE set (via generic_forget_inode)
393 __writeback_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
395 wait_queue_head_t
*wqh
;
397 if (!atomic_read(&inode
->i_count
))
398 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
400 WARN_ON(inode
->i_state
& I_WILL_FREE
);
402 if ((wbc
->sync_mode
!= WB_SYNC_ALL
) && (inode
->i_state
& I_SYNC
)) {
404 * We're skipping this inode because it's locked, and we're not
405 * doing writeback-for-data-integrity. Move it to s_more_io so
406 * that writeback can proceed with the other inodes on s_io.
407 * We'll have another go at writing back this inode when we
408 * completed a full scan of s_io.
415 * It's a data-integrity sync. We must wait.
417 if (inode
->i_state
& I_SYNC
) {
418 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
420 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
422 spin_unlock(&inode_lock
);
423 __wait_on_bit(wqh
, &wq
, inode_wait
,
424 TASK_UNINTERRUPTIBLE
);
425 spin_lock(&inode_lock
);
426 } while (inode
->i_state
& I_SYNC
);
428 return __sync_single_inode(inode
, wbc
);
432 * Write out a superblock's list of dirty inodes. A wait will be performed
433 * upon no inodes, all inodes or the final one, depending upon sync_mode.
435 * If older_than_this is non-NULL, then only write out inodes which
436 * had their first dirtying at a time earlier than *older_than_this.
438 * If we're a pdflush thread, then implement pdflush collision avoidance
439 * against the entire list.
441 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
442 * This function assumes that the blockdev superblock's inodes are backed by
443 * a variety of queues, so all inodes are searched. For other superblocks,
444 * assume that all inodes are backed by the same queue.
446 * FIXME: this linear search could get expensive with many fileystems. But
447 * how to fix? We need to go from an address_space to all inodes which share
448 * a queue with that address_space. (Easy: have a global "dirty superblocks"
451 * The inodes to be written are parked on sb->s_io. They are moved back onto
452 * sb->s_dirty as they are selected for writing. This way, none can be missed
453 * on the writer throttling path, and we get decent balancing between many
454 * throttled threads: we don't want them all piling up on inode_sync_wait.
456 void generic_sync_sb_inodes(struct super_block
*sb
,
457 struct writeback_control
*wbc
)
459 const unsigned long start
= jiffies
; /* livelock avoidance */
460 int sync
= wbc
->sync_mode
== WB_SYNC_ALL
;
462 spin_lock(&inode_lock
);
463 if (!wbc
->for_kupdate
|| list_empty(&sb
->s_io
))
464 queue_io(sb
, wbc
->older_than_this
);
466 while (!list_empty(&sb
->s_io
)) {
467 struct inode
*inode
= list_entry(sb
->s_io
.prev
,
468 struct inode
, i_list
);
469 struct address_space
*mapping
= inode
->i_mapping
;
470 struct backing_dev_info
*bdi
= mapping
->backing_dev_info
;
473 if (!bdi_cap_writeback_dirty(bdi
)) {
475 if (sb_is_blkdev_sb(sb
)) {
477 * Dirty memory-backed blockdev: the ramdisk
478 * driver does this. Skip just this inode
483 * Dirty memory-backed inode against a filesystem other
484 * than the kernel-internal bdev filesystem. Skip the
490 if (inode
->i_state
& I_NEW
) {
495 if (wbc
->nonblocking
&& bdi_write_congested(bdi
)) {
496 wbc
->encountered_congestion
= 1;
497 if (!sb_is_blkdev_sb(sb
))
498 break; /* Skip a congested fs */
500 continue; /* Skip a congested blockdev */
503 if (wbc
->bdi
&& bdi
!= wbc
->bdi
) {
504 if (!sb_is_blkdev_sb(sb
))
505 break; /* fs has the wrong queue */
507 continue; /* blockdev has wrong queue */
511 * Was this inode dirtied after sync_sb_inodes was called?
512 * This keeps sync from extra jobs and livelock.
514 if (inode_dirtied_after(inode
, start
))
517 /* Is another pdflush already flushing this queue? */
518 if (current_is_pdflush() && !writeback_acquire(bdi
))
521 BUG_ON(inode
->i_state
& I_FREEING
);
523 pages_skipped
= wbc
->pages_skipped
;
524 __writeback_single_inode(inode
, wbc
);
525 if (current_is_pdflush())
526 writeback_release(bdi
);
527 if (wbc
->pages_skipped
!= pages_skipped
) {
529 * writeback is not making progress due to locked
530 * buffers. Skip this inode for now.
534 spin_unlock(&inode_lock
);
537 spin_lock(&inode_lock
);
538 if (wbc
->nr_to_write
<= 0) {
542 if (!list_empty(&sb
->s_more_io
))
547 struct inode
*inode
, *old_inode
= NULL
;
550 * Data integrity sync. Must wait for all pages under writeback,
551 * because there may have been pages dirtied before our sync
552 * call, but which had writeout started before we write it out.
553 * In which case, the inode may not be on the dirty list, but
554 * we still have to wait for that writeout.
556 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
557 struct address_space
*mapping
;
560 (I_FREEING
|I_CLEAR
|I_WILL_FREE
|I_NEW
))
562 mapping
= inode
->i_mapping
;
563 if (mapping
->nrpages
== 0)
566 spin_unlock(&inode_lock
);
568 * We hold a reference to 'inode' so it couldn't have
569 * been removed from s_inodes list while we dropped the
570 * inode_lock. We cannot iput the inode now as we can
571 * be holding the last reference and we cannot iput it
572 * under inode_lock. So we keep the reference and iput
578 filemap_fdatawait(mapping
);
582 spin_lock(&inode_lock
);
584 spin_unlock(&inode_lock
);
587 spin_unlock(&inode_lock
);
589 return; /* Leave any unwritten inodes on s_io */
591 EXPORT_SYMBOL_GPL(generic_sync_sb_inodes
);
593 static void sync_sb_inodes(struct super_block
*sb
,
594 struct writeback_control
*wbc
)
596 generic_sync_sb_inodes(sb
, wbc
);
600 * Start writeback of dirty pagecache data against all unlocked inodes.
603 * We don't need to grab a reference to superblock here. If it has non-empty
604 * ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
605 * past sync_inodes_sb() until the ->s_dirty/s_io/s_more_io lists are all
606 * empty. Since __sync_single_inode() regains inode_lock before it finally moves
607 * inode from superblock lists we are OK.
609 * If `older_than_this' is non-zero then only flush inodes which have a
610 * flushtime older than *older_than_this.
612 * If `bdi' is non-zero then we will scan the first inode against each
613 * superblock until we find the matching ones. One group will be the dirty
614 * inodes against a filesystem. Then when we hit the dummy blockdev superblock,
615 * sync_sb_inodes will seekout the blockdev which matches `bdi'. Maybe not
616 * super-efficient but we're about to do a ton of I/O...
619 writeback_inodes(struct writeback_control
*wbc
)
621 struct super_block
*sb
;
626 list_for_each_entry_reverse(sb
, &super_blocks
, s_list
) {
627 if (sb_has_dirty_inodes(sb
)) {
628 /* we're making our own get_super here */
630 spin_unlock(&sb_lock
);
632 * If we can't get the readlock, there's no sense in
633 * waiting around, most of the time the FS is going to
634 * be unmounted by the time it is released.
636 if (down_read_trylock(&sb
->s_umount
)) {
638 sync_sb_inodes(sb
, wbc
);
639 up_read(&sb
->s_umount
);
642 if (__put_super_and_need_restart(sb
))
645 if (wbc
->nr_to_write
<= 0)
648 spin_unlock(&sb_lock
);
652 * writeback and wait upon the filesystem's dirty inodes. The caller will
653 * do this in two passes - one to write, and one to wait.
655 * A finite limit is set on the number of pages which will be written.
656 * To prevent infinite livelock of sys_sync().
658 * We add in the number of potentially dirty inodes, because each inode write
659 * can dirty pagecache in the underlying blockdev.
661 void sync_inodes_sb(struct super_block
*sb
, int wait
)
663 struct writeback_control wbc
= {
664 .sync_mode
= wait
? WB_SYNC_ALL
: WB_SYNC_NONE
,
666 .range_end
= LLONG_MAX
,
670 unsigned long nr_dirty
= global_page_state(NR_FILE_DIRTY
);
671 unsigned long nr_unstable
= global_page_state(NR_UNSTABLE_NFS
);
673 wbc
.nr_to_write
= nr_dirty
+ nr_unstable
+
674 (inodes_stat
.nr_inodes
- inodes_stat
.nr_unused
);
676 wbc
.nr_to_write
= LONG_MAX
; /* doesn't actually matter */
678 sync_sb_inodes(sb
, &wbc
);
682 * write_inode_now - write an inode to disk
683 * @inode: inode to write to disk
684 * @sync: whether the write should be synchronous or not
686 * This function commits an inode to disk immediately if it is dirty. This is
687 * primarily needed by knfsd.
689 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
691 int write_inode_now(struct inode
*inode
, int sync
)
694 struct writeback_control wbc
= {
695 .nr_to_write
= LONG_MAX
,
696 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
698 .range_end
= LLONG_MAX
,
701 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
705 spin_lock(&inode_lock
);
706 ret
= __writeback_single_inode(inode
, &wbc
);
707 spin_unlock(&inode_lock
);
709 inode_sync_wait(inode
);
712 EXPORT_SYMBOL(write_inode_now
);
715 * sync_inode - write an inode and its pages to disk.
716 * @inode: the inode to sync
717 * @wbc: controls the writeback mode
719 * sync_inode() will write an inode and its pages to disk. It will also
720 * correctly update the inode on its superblock's dirty inode lists and will
721 * update inode->i_state.
723 * The caller must have a ref on the inode.
725 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
729 spin_lock(&inode_lock
);
730 ret
= __writeback_single_inode(inode
, wbc
);
731 spin_unlock(&inode_lock
);
734 EXPORT_SYMBOL(sync_inode
);
737 * generic_osync_inode - flush all dirty data for a given inode to disk
738 * @inode: inode to write
739 * @mapping: the address_space that should be flushed
740 * @what: what to write and wait upon
742 * This can be called by file_write functions for files which have the
743 * O_SYNC flag set, to flush dirty writes to disk.
745 * @what is a bitmask, specifying which part of the inode's data should be
746 * written and waited upon.
748 * OSYNC_DATA: i_mapping's dirty data
749 * OSYNC_METADATA: the buffers at i_mapping->private_list
750 * OSYNC_INODE: the inode itself
753 int generic_osync_inode(struct inode
*inode
, struct address_space
*mapping
, int what
)
756 int need_write_inode_now
= 0;
759 if (what
& OSYNC_DATA
)
760 err
= filemap_fdatawrite(mapping
);
761 if (what
& (OSYNC_METADATA
|OSYNC_DATA
)) {
762 err2
= sync_mapping_buffers(mapping
);
766 if (what
& OSYNC_DATA
) {
767 err2
= filemap_fdatawait(mapping
);
772 spin_lock(&inode_lock
);
773 if ((inode
->i_state
& I_DIRTY
) &&
774 ((what
& OSYNC_INODE
) || (inode
->i_state
& I_DIRTY_DATASYNC
)))
775 need_write_inode_now
= 1;
776 spin_unlock(&inode_lock
);
778 if (need_write_inode_now
) {
779 err2
= write_inode_now(inode
, 1);
784 inode_sync_wait(inode
);
788 EXPORT_SYMBOL(generic_osync_inode
);