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/slab.h>
20 #include <linux/sched.h>
23 #include <linux/kthread.h>
24 #include <linux/freezer.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/buffer_head.h>
29 #include <linux/tracepoint.h>
33 * The maximum number of pages to writeout in a single bdi flush/kupdate
34 * operation. We do this so we don't hold I_SYNC against an inode for
35 * enormous amounts of time, which would block a userspace task which has
36 * been forced to throttle against that inode. Also, the code reevaluates
37 * the dirty each time it has written this many pages.
39 #define MAX_WRITEBACK_PAGES 1024L
42 * Passed into wb_writeback(), essentially a subset of writeback_control
44 struct wb_writeback_work
{
46 struct super_block
*sb
;
47 unsigned long *older_than_this
;
48 enum writeback_sync_modes sync_mode
;
49 unsigned int tagged_writepages
:1;
50 unsigned int for_kupdate
:1;
51 unsigned int range_cyclic
:1;
52 unsigned int for_background
:1;
54 struct list_head list
; /* pending work list */
55 struct completion
*done
; /* set if the caller waits */
59 * Include the creation of the trace points after defining the
60 * wb_writeback_work structure so that the definition remains local to this
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/writeback.h>
67 * We don't actually have pdflush, but this one is exported though /proc...
69 int nr_pdflush_threads
;
72 * writeback_in_progress - determine whether there is writeback in progress
73 * @bdi: the device's backing_dev_info structure.
75 * Determine whether there is writeback waiting to be handled against a
78 int writeback_in_progress(struct backing_dev_info
*bdi
)
80 return test_bit(BDI_writeback_running
, &bdi
->state
);
83 static inline struct backing_dev_info
*inode_to_bdi(struct inode
*inode
)
85 struct super_block
*sb
= inode
->i_sb
;
87 if (strcmp(sb
->s_type
->name
, "bdev") == 0)
88 return inode
->i_mapping
->backing_dev_info
;
93 static inline struct inode
*wb_inode(struct list_head
*head
)
95 return list_entry(head
, struct inode
, i_wb_list
);
98 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
99 static void bdi_wakeup_flusher(struct backing_dev_info
*bdi
)
102 wake_up_process(bdi
->wb
.task
);
105 * The bdi thread isn't there, wake up the forker thread which
106 * will create and run it.
108 wake_up_process(default_backing_dev_info
.wb
.task
);
112 static void bdi_queue_work(struct backing_dev_info
*bdi
,
113 struct wb_writeback_work
*work
)
115 trace_writeback_queue(bdi
, work
);
117 spin_lock_bh(&bdi
->wb_lock
);
118 list_add_tail(&work
->list
, &bdi
->work_list
);
120 trace_writeback_nothread(bdi
, work
);
121 bdi_wakeup_flusher(bdi
);
122 spin_unlock_bh(&bdi
->wb_lock
);
126 __bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
,
129 struct wb_writeback_work
*work
;
132 * This is WB_SYNC_NONE writeback, so if allocation fails just
133 * wakeup the thread for old dirty data writeback
135 work
= kzalloc(sizeof(*work
), GFP_ATOMIC
);
138 trace_writeback_nowork(bdi
);
139 wake_up_process(bdi
->wb
.task
);
144 work
->sync_mode
= WB_SYNC_NONE
;
145 work
->nr_pages
= nr_pages
;
146 work
->range_cyclic
= range_cyclic
;
148 bdi_queue_work(bdi
, work
);
152 * bdi_start_writeback - start writeback
153 * @bdi: the backing device to write from
154 * @nr_pages: the number of pages to write
157 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
158 * started when this function returns, we make no guarantees on
159 * completion. Caller need not hold sb s_umount semaphore.
162 void bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
)
164 __bdi_start_writeback(bdi
, nr_pages
, true);
168 * bdi_start_background_writeback - start background writeback
169 * @bdi: the backing device to write from
172 * This makes sure WB_SYNC_NONE background writeback happens. When
173 * this function returns, it is only guaranteed that for given BDI
174 * some IO is happening if we are over background dirty threshold.
175 * Caller need not hold sb s_umount semaphore.
177 void bdi_start_background_writeback(struct backing_dev_info
*bdi
)
180 * We just wake up the flusher thread. It will perform background
181 * writeback as soon as there is no other work to do.
183 trace_writeback_wake_background(bdi
);
184 spin_lock_bh(&bdi
->wb_lock
);
185 bdi_wakeup_flusher(bdi
);
186 spin_unlock_bh(&bdi
->wb_lock
);
190 * Remove the inode from the writeback list it is on.
192 void inode_wb_list_del(struct inode
*inode
)
194 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
196 spin_lock(&bdi
->wb
.list_lock
);
197 list_del_init(&inode
->i_wb_list
);
198 spin_unlock(&bdi
->wb
.list_lock
);
202 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
203 * furthest end of its superblock's dirty-inode list.
205 * Before stamping the inode's ->dirtied_when, we check to see whether it is
206 * already the most-recently-dirtied inode on the b_dirty list. If that is
207 * the case then the inode must have been redirtied while it was being written
208 * out and we don't reset its dirtied_when.
210 static void redirty_tail(struct inode
*inode
, struct bdi_writeback
*wb
)
212 assert_spin_locked(&wb
->list_lock
);
213 if (!list_empty(&wb
->b_dirty
)) {
216 tail
= wb_inode(wb
->b_dirty
.next
);
217 if (time_before(inode
->dirtied_when
, tail
->dirtied_when
))
218 inode
->dirtied_when
= jiffies
;
220 list_move(&inode
->i_wb_list
, &wb
->b_dirty
);
224 * requeue inode for re-scanning after bdi->b_io list is exhausted.
226 static void requeue_io(struct inode
*inode
, struct bdi_writeback
*wb
)
228 assert_spin_locked(&wb
->list_lock
);
229 list_move(&inode
->i_wb_list
, &wb
->b_more_io
);
232 static void inode_sync_complete(struct inode
*inode
)
235 * Prevent speculative execution through
236 * spin_unlock(&wb->list_lock);
240 wake_up_bit(&inode
->i_state
, __I_SYNC
);
243 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
245 bool ret
= time_after(inode
->dirtied_when
, t
);
248 * For inodes being constantly redirtied, dirtied_when can get stuck.
249 * It _appears_ to be in the future, but is actually in distant past.
250 * This test is necessary to prevent such wrapped-around relative times
251 * from permanently stopping the whole bdi writeback.
253 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
259 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
261 static int move_expired_inodes(struct list_head
*delaying_queue
,
262 struct list_head
*dispatch_queue
,
263 unsigned long *older_than_this
)
266 struct list_head
*pos
, *node
;
267 struct super_block
*sb
= NULL
;
272 while (!list_empty(delaying_queue
)) {
273 inode
= wb_inode(delaying_queue
->prev
);
274 if (older_than_this
&&
275 inode_dirtied_after(inode
, *older_than_this
))
277 if (sb
&& sb
!= inode
->i_sb
)
280 list_move(&inode
->i_wb_list
, &tmp
);
284 /* just one sb in list, splice to dispatch_queue and we're done */
286 list_splice(&tmp
, dispatch_queue
);
290 /* Move inodes from one superblock together */
291 while (!list_empty(&tmp
)) {
292 sb
= wb_inode(tmp
.prev
)->i_sb
;
293 list_for_each_prev_safe(pos
, node
, &tmp
) {
294 inode
= wb_inode(pos
);
295 if (inode
->i_sb
== sb
)
296 list_move(&inode
->i_wb_list
, dispatch_queue
);
304 * Queue all expired dirty inodes for io, eldest first.
306 * newly dirtied b_dirty b_io b_more_io
307 * =============> gf edc BA
309 * newly dirtied b_dirty b_io b_more_io
310 * =============> g fBAedc
312 * +--> dequeue for IO
314 static void queue_io(struct bdi_writeback
*wb
, unsigned long *older_than_this
)
317 assert_spin_locked(&wb
->list_lock
);
318 list_splice_init(&wb
->b_more_io
, &wb
->b_io
);
319 moved
= move_expired_inodes(&wb
->b_dirty
, &wb
->b_io
, older_than_this
);
320 trace_writeback_queue_io(wb
, older_than_this
, moved
);
323 static int write_inode(struct inode
*inode
, struct writeback_control
*wbc
)
325 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
))
326 return inode
->i_sb
->s_op
->write_inode(inode
, wbc
);
331 * Wait for writeback on an inode to complete.
333 static void inode_wait_for_writeback(struct inode
*inode
,
334 struct bdi_writeback
*wb
)
336 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
337 wait_queue_head_t
*wqh
;
339 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
340 while (inode
->i_state
& I_SYNC
) {
341 spin_unlock(&inode
->i_lock
);
342 spin_unlock(&wb
->list_lock
);
343 __wait_on_bit(wqh
, &wq
, inode_wait
, TASK_UNINTERRUPTIBLE
);
344 spin_lock(&wb
->list_lock
);
345 spin_lock(&inode
->i_lock
);
350 * Write out an inode's dirty pages. Called under wb->list_lock and
351 * inode->i_lock. Either the caller has an active reference on the inode or
352 * the inode has I_WILL_FREE set.
354 * If `wait' is set, wait on the writeout.
356 * The whole writeout design is quite complex and fragile. We want to avoid
357 * starvation of particular inodes when others are being redirtied, prevent
361 writeback_single_inode(struct inode
*inode
, struct bdi_writeback
*wb
,
362 struct writeback_control
*wbc
)
364 struct address_space
*mapping
= inode
->i_mapping
;
365 long nr_to_write
= wbc
->nr_to_write
;
369 assert_spin_locked(&wb
->list_lock
);
370 assert_spin_locked(&inode
->i_lock
);
372 if (!atomic_read(&inode
->i_count
))
373 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
375 WARN_ON(inode
->i_state
& I_WILL_FREE
);
377 if (inode
->i_state
& I_SYNC
) {
379 * If this inode is locked for writeback and we are not doing
380 * writeback-for-data-integrity, move it to b_more_io so that
381 * writeback can proceed with the other inodes on s_io.
383 * We'll have another go at writing back this inode when we
384 * completed a full scan of b_io.
386 if (wbc
->sync_mode
!= WB_SYNC_ALL
) {
387 requeue_io(inode
, wb
);
388 trace_writeback_single_inode_requeue(inode
, wbc
,
394 * It's a data-integrity sync. We must wait.
396 inode_wait_for_writeback(inode
, wb
);
399 BUG_ON(inode
->i_state
& I_SYNC
);
401 /* Set I_SYNC, reset I_DIRTY_PAGES */
402 inode
->i_state
|= I_SYNC
;
403 inode
->i_state
&= ~I_DIRTY_PAGES
;
404 spin_unlock(&inode
->i_lock
);
405 spin_unlock(&wb
->list_lock
);
407 ret
= do_writepages(mapping
, wbc
);
410 * Make sure to wait on the data before writing out the metadata.
411 * This is important for filesystems that modify metadata on data
414 if (wbc
->sync_mode
== WB_SYNC_ALL
) {
415 int err
= filemap_fdatawait(mapping
);
421 * Some filesystems may redirty the inode during the writeback
422 * due to delalloc, clear dirty metadata flags right before
425 spin_lock(&inode
->i_lock
);
426 dirty
= inode
->i_state
& I_DIRTY
;
427 inode
->i_state
&= ~(I_DIRTY_SYNC
| I_DIRTY_DATASYNC
);
428 spin_unlock(&inode
->i_lock
);
429 /* Don't write the inode if only I_DIRTY_PAGES was set */
430 if (dirty
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
431 int err
= write_inode(inode
, wbc
);
436 spin_lock(&wb
->list_lock
);
437 spin_lock(&inode
->i_lock
);
438 inode
->i_state
&= ~I_SYNC
;
439 if (!(inode
->i_state
& I_FREEING
)) {
441 * Sync livelock prevention. Each inode is tagged and synced in
442 * one shot. If still dirty, it will be redirty_tail()'ed below.
443 * Update the dirty time to prevent enqueue and sync it again.
445 if ((inode
->i_state
& I_DIRTY
) &&
446 (wbc
->sync_mode
== WB_SYNC_ALL
|| wbc
->tagged_writepages
))
447 inode
->dirtied_when
= jiffies
;
449 if (mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
)) {
451 * We didn't write back all the pages. nfs_writepages()
452 * sometimes bales out without doing anything.
454 inode
->i_state
|= I_DIRTY_PAGES
;
455 if (wbc
->nr_to_write
<= 0) {
457 * slice used up: queue for next turn
459 requeue_io(inode
, wb
);
462 * Writeback blocked by something other than
463 * congestion. Delay the inode for some time to
464 * avoid spinning on the CPU (100% iowait)
465 * retrying writeback of the dirty page/inode
466 * that cannot be performed immediately.
468 redirty_tail(inode
, wb
);
470 } else if (inode
->i_state
& I_DIRTY
) {
472 * Filesystems can dirty the inode during writeback
473 * operations, such as delayed allocation during
474 * submission or metadata updates after data IO
477 redirty_tail(inode
, wb
);
480 * The inode is clean. At this point we either have
481 * a reference to the inode or it's on it's way out.
482 * No need to add it back to the LRU.
484 list_del_init(&inode
->i_wb_list
);
487 inode_sync_complete(inode
);
488 trace_writeback_single_inode(inode
, wbc
, nr_to_write
);
493 * For background writeback the caller does not have the sb pinned
494 * before calling writeback. So make sure that we do pin it, so it doesn't
495 * go away while we are writing inodes from it.
497 static bool pin_sb_for_writeback(struct super_block
*sb
)
500 if (list_empty(&sb
->s_instances
)) {
501 spin_unlock(&sb_lock
);
506 spin_unlock(&sb_lock
);
508 if (down_read_trylock(&sb
->s_umount
)) {
511 up_read(&sb
->s_umount
);
518 static long writeback_chunk_size(struct wb_writeback_work
*work
)
523 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
524 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
525 * here avoids calling into writeback_inodes_wb() more than once.
527 * The intended call sequence for WB_SYNC_ALL writeback is:
530 * writeback_sb_inodes() <== called only once
531 * write_cache_pages() <== called once for each inode
532 * (quickly) tag currently dirty pages
533 * (maybe slowly) sync all tagged pages
535 if (work
->sync_mode
== WB_SYNC_ALL
|| work
->tagged_writepages
)
538 pages
= min(MAX_WRITEBACK_PAGES
, work
->nr_pages
);
544 * Write a portion of b_io inodes which belong to @sb.
546 * If @only_this_sb is true, then find and write all such
547 * inodes. Otherwise write only ones which go sequentially
550 * Return the number of pages and/or inodes written.
552 static long writeback_sb_inodes(struct super_block
*sb
,
553 struct bdi_writeback
*wb
,
554 struct wb_writeback_work
*work
)
556 struct writeback_control wbc
= {
557 .sync_mode
= work
->sync_mode
,
558 .tagged_writepages
= work
->tagged_writepages
,
559 .for_kupdate
= work
->for_kupdate
,
560 .for_background
= work
->for_background
,
561 .range_cyclic
= work
->range_cyclic
,
563 .range_end
= LLONG_MAX
,
565 unsigned long start_time
= jiffies
;
567 long wrote
= 0; /* count both pages and inodes */
569 while (!list_empty(&wb
->b_io
)) {
570 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
572 if (inode
->i_sb
!= sb
) {
575 * We only want to write back data for this
576 * superblock, move all inodes not belonging
577 * to it back onto the dirty list.
579 redirty_tail(inode
, wb
);
584 * The inode belongs to a different superblock.
585 * Bounce back to the caller to unpin this and
586 * pin the next superblock.
592 * Don't bother with new inodes or inodes beeing freed, first
593 * kind does not need peridic writeout yet, and for the latter
594 * kind writeout is handled by the freer.
596 spin_lock(&inode
->i_lock
);
597 if (inode
->i_state
& (I_NEW
| I_FREEING
| I_WILL_FREE
)) {
598 spin_unlock(&inode
->i_lock
);
599 requeue_io(inode
, wb
);
603 write_chunk
= writeback_chunk_size(work
);
604 wbc
.nr_to_write
= write_chunk
;
605 wbc
.pages_skipped
= 0;
607 writeback_single_inode(inode
, wb
, &wbc
);
609 work
->nr_pages
-= write_chunk
- wbc
.nr_to_write
;
610 wrote
+= write_chunk
- wbc
.nr_to_write
;
611 if (!(inode
->i_state
& I_DIRTY
))
613 if (wbc
.pages_skipped
) {
615 * writeback is not making progress due to locked
616 * buffers. Skip this inode for now.
618 redirty_tail(inode
, wb
);
620 spin_unlock(&inode
->i_lock
);
621 spin_unlock(&wb
->list_lock
);
624 spin_lock(&wb
->list_lock
);
626 * bail out to wb_writeback() often enough to check
627 * background threshold and other termination conditions.
630 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
632 if (work
->nr_pages
<= 0)
639 static long __writeback_inodes_wb(struct bdi_writeback
*wb
,
640 struct wb_writeback_work
*work
)
642 unsigned long start_time
= jiffies
;
645 while (!list_empty(&wb
->b_io
)) {
646 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
647 struct super_block
*sb
= inode
->i_sb
;
649 if (!pin_sb_for_writeback(sb
)) {
650 requeue_io(inode
, wb
);
653 wrote
+= writeback_sb_inodes(sb
, wb
, work
);
656 /* refer to the same tests at the end of writeback_sb_inodes */
658 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
660 if (work
->nr_pages
<= 0)
664 /* Leave any unwritten inodes on b_io */
668 long writeback_inodes_wb(struct bdi_writeback
*wb
, long nr_pages
)
670 struct wb_writeback_work work
= {
671 .nr_pages
= nr_pages
,
672 .sync_mode
= WB_SYNC_NONE
,
676 spin_lock(&wb
->list_lock
);
677 if (list_empty(&wb
->b_io
))
679 __writeback_inodes_wb(wb
, &work
);
680 spin_unlock(&wb
->list_lock
);
682 return nr_pages
- work
.nr_pages
;
685 static inline bool over_bground_thresh(void)
687 unsigned long background_thresh
, dirty_thresh
;
689 global_dirty_limits(&background_thresh
, &dirty_thresh
);
691 return (global_page_state(NR_FILE_DIRTY
) +
692 global_page_state(NR_UNSTABLE_NFS
) > background_thresh
);
696 * Explicit flushing or periodic writeback of "old" data.
698 * Define "old": the first time one of an inode's pages is dirtied, we mark the
699 * dirtying-time in the inode's address_space. So this periodic writeback code
700 * just walks the superblock inode list, writing back any inodes which are
701 * older than a specific point in time.
703 * Try to run once per dirty_writeback_interval. But if a writeback event
704 * takes longer than a dirty_writeback_interval interval, then leave a
707 * older_than_this takes precedence over nr_to_write. So we'll only write back
708 * all dirty pages if they are all attached to "old" mappings.
710 static long wb_writeback(struct bdi_writeback
*wb
,
711 struct wb_writeback_work
*work
)
713 long nr_pages
= work
->nr_pages
;
714 unsigned long oldest_jif
;
718 oldest_jif
= jiffies
;
719 work
->older_than_this
= &oldest_jif
;
721 spin_lock(&wb
->list_lock
);
724 * Stop writeback when nr_pages has been consumed
726 if (work
->nr_pages
<= 0)
730 * Background writeout and kupdate-style writeback may
731 * run forever. Stop them if there is other work to do
732 * so that e.g. sync can proceed. They'll be restarted
733 * after the other works are all done.
735 if ((work
->for_background
|| work
->for_kupdate
) &&
736 !list_empty(&wb
->bdi
->work_list
))
740 * For background writeout, stop when we are below the
741 * background dirty threshold
743 if (work
->for_background
&& !over_bground_thresh())
746 if (work
->for_kupdate
) {
747 oldest_jif
= jiffies
-
748 msecs_to_jiffies(dirty_expire_interval
* 10);
749 work
->older_than_this
= &oldest_jif
;
752 trace_writeback_start(wb
->bdi
, work
);
753 if (list_empty(&wb
->b_io
))
754 queue_io(wb
, work
->older_than_this
);
756 progress
= writeback_sb_inodes(work
->sb
, wb
, work
);
758 progress
= __writeback_inodes_wb(wb
, work
);
759 trace_writeback_written(wb
->bdi
, work
);
762 * Did we write something? Try for more
764 * Dirty inodes are moved to b_io for writeback in batches.
765 * The completion of the current batch does not necessarily
766 * mean the overall work is done. So we keep looping as long
767 * as made some progress on cleaning pages or inodes.
772 * No more inodes for IO, bail
774 if (list_empty(&wb
->b_more_io
))
777 * Nothing written. Wait for some inode to
778 * become available for writeback. Otherwise
779 * we'll just busyloop.
781 if (!list_empty(&wb
->b_more_io
)) {
782 trace_writeback_wait(wb
->bdi
, work
);
783 inode
= wb_inode(wb
->b_more_io
.prev
);
784 spin_lock(&inode
->i_lock
);
785 inode_wait_for_writeback(inode
, wb
);
786 spin_unlock(&inode
->i_lock
);
789 spin_unlock(&wb
->list_lock
);
791 return nr_pages
- work
->nr_pages
;
795 * Return the next wb_writeback_work struct that hasn't been processed yet.
797 static struct wb_writeback_work
*
798 get_next_work_item(struct backing_dev_info
*bdi
)
800 struct wb_writeback_work
*work
= NULL
;
802 spin_lock_bh(&bdi
->wb_lock
);
803 if (!list_empty(&bdi
->work_list
)) {
804 work
= list_entry(bdi
->work_list
.next
,
805 struct wb_writeback_work
, list
);
806 list_del_init(&work
->list
);
808 spin_unlock_bh(&bdi
->wb_lock
);
813 * Add in the number of potentially dirty inodes, because each inode
814 * write can dirty pagecache in the underlying blockdev.
816 static unsigned long get_nr_dirty_pages(void)
818 return global_page_state(NR_FILE_DIRTY
) +
819 global_page_state(NR_UNSTABLE_NFS
) +
820 get_nr_dirty_inodes();
823 static long wb_check_background_flush(struct bdi_writeback
*wb
)
825 if (over_bground_thresh()) {
827 struct wb_writeback_work work
= {
828 .nr_pages
= LONG_MAX
,
829 .sync_mode
= WB_SYNC_NONE
,
834 return wb_writeback(wb
, &work
);
840 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
842 unsigned long expired
;
846 * When set to zero, disable periodic writeback
848 if (!dirty_writeback_interval
)
851 expired
= wb
->last_old_flush
+
852 msecs_to_jiffies(dirty_writeback_interval
* 10);
853 if (time_before(jiffies
, expired
))
856 wb
->last_old_flush
= jiffies
;
857 nr_pages
= get_nr_dirty_pages();
860 struct wb_writeback_work work
= {
861 .nr_pages
= nr_pages
,
862 .sync_mode
= WB_SYNC_NONE
,
867 return wb_writeback(wb
, &work
);
874 * Retrieve work items and do the writeback they describe
876 long wb_do_writeback(struct bdi_writeback
*wb
, int force_wait
)
878 struct backing_dev_info
*bdi
= wb
->bdi
;
879 struct wb_writeback_work
*work
;
882 set_bit(BDI_writeback_running
, &wb
->bdi
->state
);
883 while ((work
= get_next_work_item(bdi
)) != NULL
) {
885 * Override sync mode, in case we must wait for completion
886 * because this thread is exiting now.
889 work
->sync_mode
= WB_SYNC_ALL
;
891 trace_writeback_exec(bdi
, work
);
893 wrote
+= wb_writeback(wb
, work
);
896 * Notify the caller of completion if this is a synchronous
897 * work item, otherwise just free it.
900 complete(work
->done
);
906 * Check for periodic writeback, kupdated() style
908 wrote
+= wb_check_old_data_flush(wb
);
909 wrote
+= wb_check_background_flush(wb
);
910 clear_bit(BDI_writeback_running
, &wb
->bdi
->state
);
916 * Handle writeback of dirty data for the device backed by this bdi. Also
917 * wakes up periodically and does kupdated style flushing.
919 int bdi_writeback_thread(void *data
)
921 struct bdi_writeback
*wb
= data
;
922 struct backing_dev_info
*bdi
= wb
->bdi
;
925 current
->flags
|= PF_SWAPWRITE
;
927 wb
->last_active
= jiffies
;
930 * Our parent may run at a different priority, just set us to normal
932 set_user_nice(current
, 0);
934 trace_writeback_thread_start(bdi
);
936 while (!kthread_should_stop()) {
938 * Remove own delayed wake-up timer, since we are already awake
939 * and we'll take care of the preriodic write-back.
941 del_timer(&wb
->wakeup_timer
);
943 pages_written
= wb_do_writeback(wb
, 0);
945 trace_writeback_pages_written(pages_written
);
948 wb
->last_active
= jiffies
;
950 set_current_state(TASK_INTERRUPTIBLE
);
951 if (!list_empty(&bdi
->work_list
) || kthread_should_stop()) {
952 __set_current_state(TASK_RUNNING
);
956 if (wb_has_dirty_io(wb
) && dirty_writeback_interval
)
957 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval
* 10));
960 * We have nothing to do, so can go sleep without any
961 * timeout and save power. When a work is queued or
962 * something is made dirty - we will be woken up.
970 /* Flush any work that raced with us exiting */
971 if (!list_empty(&bdi
->work_list
))
972 wb_do_writeback(wb
, 1);
974 trace_writeback_thread_stop(bdi
);
980 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
983 void wakeup_flusher_threads(long nr_pages
)
985 struct backing_dev_info
*bdi
;
988 nr_pages
= global_page_state(NR_FILE_DIRTY
) +
989 global_page_state(NR_UNSTABLE_NFS
);
993 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
994 if (!bdi_has_dirty_io(bdi
))
996 __bdi_start_writeback(bdi
, nr_pages
, false);
1001 static noinline
void block_dump___mark_inode_dirty(struct inode
*inode
)
1003 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev")) {
1004 struct dentry
*dentry
;
1005 const char *name
= "?";
1007 dentry
= d_find_alias(inode
);
1009 spin_lock(&dentry
->d_lock
);
1010 name
= (const char *) dentry
->d_name
.name
;
1013 "%s(%d): dirtied inode %lu (%s) on %s\n",
1014 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
1015 name
, inode
->i_sb
->s_id
);
1017 spin_unlock(&dentry
->d_lock
);
1024 * __mark_inode_dirty - internal function
1025 * @inode: inode to mark
1026 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1027 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1028 * mark_inode_dirty_sync.
1030 * Put the inode on the super block's dirty list.
1032 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1033 * dirty list only if it is hashed or if it refers to a blockdev.
1034 * If it was not hashed, it will never be added to the dirty list
1035 * even if it is later hashed, as it will have been marked dirty already.
1037 * In short, make sure you hash any inodes _before_ you start marking
1040 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1041 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1042 * the kernel-internal blockdev inode represents the dirtying time of the
1043 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1044 * page->mapping->host, so the page-dirtying time is recorded in the internal
1047 void __mark_inode_dirty(struct inode
*inode
, int flags
)
1049 struct super_block
*sb
= inode
->i_sb
;
1050 struct backing_dev_info
*bdi
= NULL
;
1053 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1054 * dirty the inode itself
1056 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
1057 if (sb
->s_op
->dirty_inode
)
1058 sb
->s_op
->dirty_inode(inode
, flags
);
1062 * make sure that changes are seen by all cpus before we test i_state
1067 /* avoid the locking if we can */
1068 if ((inode
->i_state
& flags
) == flags
)
1071 if (unlikely(block_dump
))
1072 block_dump___mark_inode_dirty(inode
);
1074 spin_lock(&inode
->i_lock
);
1075 if ((inode
->i_state
& flags
) != flags
) {
1076 const int was_dirty
= inode
->i_state
& I_DIRTY
;
1078 inode
->i_state
|= flags
;
1081 * If the inode is being synced, just update its dirty state.
1082 * The unlocker will place the inode on the appropriate
1083 * superblock list, based upon its state.
1085 if (inode
->i_state
& I_SYNC
)
1086 goto out_unlock_inode
;
1089 * Only add valid (hashed) inodes to the superblock's
1090 * dirty list. Add blockdev inodes as well.
1092 if (!S_ISBLK(inode
->i_mode
)) {
1093 if (inode_unhashed(inode
))
1094 goto out_unlock_inode
;
1096 if (inode
->i_state
& I_FREEING
)
1097 goto out_unlock_inode
;
1100 * If the inode was already on b_dirty/b_io/b_more_io, don't
1101 * reposition it (that would break b_dirty time-ordering).
1104 bool wakeup_bdi
= false;
1105 bdi
= inode_to_bdi(inode
);
1107 if (bdi_cap_writeback_dirty(bdi
)) {
1108 WARN(!test_bit(BDI_registered
, &bdi
->state
),
1109 "bdi-%s not registered\n", bdi
->name
);
1112 * If this is the first dirty inode for this
1113 * bdi, we have to wake-up the corresponding
1114 * bdi thread to make sure background
1115 * write-back happens later.
1117 if (!wb_has_dirty_io(&bdi
->wb
))
1121 spin_unlock(&inode
->i_lock
);
1122 spin_lock(&bdi
->wb
.list_lock
);
1123 inode
->dirtied_when
= jiffies
;
1124 list_move(&inode
->i_wb_list
, &bdi
->wb
.b_dirty
);
1125 spin_unlock(&bdi
->wb
.list_lock
);
1128 bdi_wakeup_thread_delayed(bdi
);
1133 spin_unlock(&inode
->i_lock
);
1136 EXPORT_SYMBOL(__mark_inode_dirty
);
1139 * Write out a superblock's list of dirty inodes. A wait will be performed
1140 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1142 * If older_than_this is non-NULL, then only write out inodes which
1143 * had their first dirtying at a time earlier than *older_than_this.
1145 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1146 * This function assumes that the blockdev superblock's inodes are backed by
1147 * a variety of queues, so all inodes are searched. For other superblocks,
1148 * assume that all inodes are backed by the same queue.
1150 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1151 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1152 * on the writer throttling path, and we get decent balancing between many
1153 * throttled threads: we don't want them all piling up on inode_sync_wait.
1155 static void wait_sb_inodes(struct super_block
*sb
)
1157 struct inode
*inode
, *old_inode
= NULL
;
1160 * We need to be protected against the filesystem going from
1161 * r/o to r/w or vice versa.
1163 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1165 spin_lock(&inode_sb_list_lock
);
1168 * Data integrity sync. Must wait for all pages under writeback,
1169 * because there may have been pages dirtied before our sync
1170 * call, but which had writeout started before we write it out.
1171 * In which case, the inode may not be on the dirty list, but
1172 * we still have to wait for that writeout.
1174 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
1175 struct address_space
*mapping
= inode
->i_mapping
;
1177 spin_lock(&inode
->i_lock
);
1178 if ((inode
->i_state
& (I_FREEING
|I_WILL_FREE
|I_NEW
)) ||
1179 (mapping
->nrpages
== 0)) {
1180 spin_unlock(&inode
->i_lock
);
1184 spin_unlock(&inode
->i_lock
);
1185 spin_unlock(&inode_sb_list_lock
);
1188 * We hold a reference to 'inode' so it couldn't have been
1189 * removed from s_inodes list while we dropped the
1190 * inode_sb_list_lock. We cannot iput the inode now as we can
1191 * be holding the last reference and we cannot iput it under
1192 * inode_sb_list_lock. So we keep the reference and iput it
1198 filemap_fdatawait(mapping
);
1202 spin_lock(&inode_sb_list_lock
);
1204 spin_unlock(&inode_sb_list_lock
);
1209 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1210 * @sb: the superblock
1211 * @nr: the number of pages to write
1213 * Start writeback on some inodes on this super_block. No guarantees are made
1214 * on how many (if any) will be written, and this function does not wait
1215 * for IO completion of submitted IO.
1217 void writeback_inodes_sb_nr(struct super_block
*sb
, unsigned long nr
)
1219 DECLARE_COMPLETION_ONSTACK(done
);
1220 struct wb_writeback_work work
= {
1222 .sync_mode
= WB_SYNC_NONE
,
1223 .tagged_writepages
= 1,
1228 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1229 bdi_queue_work(sb
->s_bdi
, &work
);
1230 wait_for_completion(&done
);
1232 EXPORT_SYMBOL(writeback_inodes_sb_nr
);
1235 * writeback_inodes_sb - writeback dirty inodes from given super_block
1236 * @sb: the superblock
1238 * Start writeback on some inodes on this super_block. No guarantees are made
1239 * on how many (if any) will be written, and this function does not wait
1240 * for IO completion of submitted IO.
1242 void writeback_inodes_sb(struct super_block
*sb
)
1244 return writeback_inodes_sb_nr(sb
, get_nr_dirty_pages());
1246 EXPORT_SYMBOL(writeback_inodes_sb
);
1249 * writeback_inodes_sb_if_idle - start writeback if none underway
1250 * @sb: the superblock
1252 * Invoke writeback_inodes_sb if no writeback is currently underway.
1253 * Returns 1 if writeback was started, 0 if not.
1255 int writeback_inodes_sb_if_idle(struct super_block
*sb
)
1257 if (!writeback_in_progress(sb
->s_bdi
)) {
1258 down_read(&sb
->s_umount
);
1259 writeback_inodes_sb(sb
);
1260 up_read(&sb
->s_umount
);
1265 EXPORT_SYMBOL(writeback_inodes_sb_if_idle
);
1268 * writeback_inodes_sb_if_idle - start writeback if none underway
1269 * @sb: the superblock
1270 * @nr: the number of pages to write
1272 * Invoke writeback_inodes_sb if no writeback is currently underway.
1273 * Returns 1 if writeback was started, 0 if not.
1275 int writeback_inodes_sb_nr_if_idle(struct super_block
*sb
,
1278 if (!writeback_in_progress(sb
->s_bdi
)) {
1279 down_read(&sb
->s_umount
);
1280 writeback_inodes_sb_nr(sb
, nr
);
1281 up_read(&sb
->s_umount
);
1286 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle
);
1289 * sync_inodes_sb - sync sb inode pages
1290 * @sb: the superblock
1292 * This function writes and waits on any dirty inode belonging to this
1295 void sync_inodes_sb(struct super_block
*sb
)
1297 DECLARE_COMPLETION_ONSTACK(done
);
1298 struct wb_writeback_work work
= {
1300 .sync_mode
= WB_SYNC_ALL
,
1301 .nr_pages
= LONG_MAX
,
1306 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1308 bdi_queue_work(sb
->s_bdi
, &work
);
1309 wait_for_completion(&done
);
1313 EXPORT_SYMBOL(sync_inodes_sb
);
1316 * write_inode_now - write an inode to disk
1317 * @inode: inode to write to disk
1318 * @sync: whether the write should be synchronous or not
1320 * This function commits an inode to disk immediately if it is dirty. This is
1321 * primarily needed by knfsd.
1323 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1325 int write_inode_now(struct inode
*inode
, int sync
)
1327 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
1329 struct writeback_control wbc
= {
1330 .nr_to_write
= LONG_MAX
,
1331 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1333 .range_end
= LLONG_MAX
,
1336 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
1337 wbc
.nr_to_write
= 0;
1340 spin_lock(&wb
->list_lock
);
1341 spin_lock(&inode
->i_lock
);
1342 ret
= writeback_single_inode(inode
, wb
, &wbc
);
1343 spin_unlock(&inode
->i_lock
);
1344 spin_unlock(&wb
->list_lock
);
1346 inode_sync_wait(inode
);
1349 EXPORT_SYMBOL(write_inode_now
);
1352 * sync_inode - write an inode and its pages to disk.
1353 * @inode: the inode to sync
1354 * @wbc: controls the writeback mode
1356 * sync_inode() will write an inode and its pages to disk. It will also
1357 * correctly update the inode on its superblock's dirty inode lists and will
1358 * update inode->i_state.
1360 * The caller must have a ref on the inode.
1362 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1364 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
1367 spin_lock(&wb
->list_lock
);
1368 spin_lock(&inode
->i_lock
);
1369 ret
= writeback_single_inode(inode
, wb
, wbc
);
1370 spin_unlock(&inode
->i_lock
);
1371 spin_unlock(&wb
->list_lock
);
1374 EXPORT_SYMBOL(sync_inode
);
1377 * sync_inode_metadata - write an inode to disk
1378 * @inode: the inode to sync
1379 * @wait: wait for I/O to complete.
1381 * Write an inode to disk and adjust its dirty state after completion.
1383 * Note: only writes the actual inode, no associated data or other metadata.
1385 int sync_inode_metadata(struct inode
*inode
, int wait
)
1387 struct writeback_control wbc
= {
1388 .sync_mode
= wait
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1389 .nr_to_write
= 0, /* metadata-only */
1392 return sync_inode(inode
, &wbc
);
1394 EXPORT_SYMBOL(sync_inode_metadata
);