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 * Passed into wb_writeback(), essentially a subset of writeback_control
35 struct wb_writeback_work
{
37 struct super_block
*sb
;
38 enum writeback_sync_modes sync_mode
;
39 unsigned int for_kupdate
:1;
40 unsigned int range_cyclic
:1;
41 unsigned int for_background
:1;
43 struct list_head list
; /* pending work list */
44 struct completion
*done
; /* set if the caller waits */
48 * Include the creation of the trace points after defining the
49 * wb_writeback_work structure so that the definition remains local to this
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/writeback.h>
56 * We don't actually have pdflush, but this one is exported though /proc...
58 int nr_pdflush_threads
;
61 * writeback_in_progress - determine whether there is writeback in progress
62 * @bdi: the device's backing_dev_info structure.
64 * Determine whether there is writeback waiting to be handled against a
67 int writeback_in_progress(struct backing_dev_info
*bdi
)
69 return test_bit(BDI_writeback_running
, &bdi
->state
);
72 static inline struct backing_dev_info
*inode_to_bdi(struct inode
*inode
)
74 struct super_block
*sb
= inode
->i_sb
;
76 if (strcmp(sb
->s_type
->name
, "bdev") == 0)
77 return inode
->i_mapping
->backing_dev_info
;
82 static inline struct inode
*wb_inode(struct list_head
*head
)
84 return list_entry(head
, struct inode
, i_wb_list
);
87 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
88 static void bdi_wakeup_flusher(struct backing_dev_info
*bdi
)
91 wake_up_process(bdi
->wb
.task
);
94 * The bdi thread isn't there, wake up the forker thread which
95 * will create and run it.
97 wake_up_process(default_backing_dev_info
.wb
.task
);
101 static void bdi_queue_work(struct backing_dev_info
*bdi
,
102 struct wb_writeback_work
*work
)
104 trace_writeback_queue(bdi
, work
);
106 spin_lock_bh(&bdi
->wb_lock
);
107 list_add_tail(&work
->list
, &bdi
->work_list
);
109 trace_writeback_nothread(bdi
, work
);
110 bdi_wakeup_flusher(bdi
);
111 spin_unlock_bh(&bdi
->wb_lock
);
115 __bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
,
118 struct wb_writeback_work
*work
;
121 * This is WB_SYNC_NONE writeback, so if allocation fails just
122 * wakeup the thread for old dirty data writeback
124 work
= kzalloc(sizeof(*work
), GFP_ATOMIC
);
127 trace_writeback_nowork(bdi
);
128 wake_up_process(bdi
->wb
.task
);
133 work
->sync_mode
= WB_SYNC_NONE
;
134 work
->nr_pages
= nr_pages
;
135 work
->range_cyclic
= range_cyclic
;
137 bdi_queue_work(bdi
, work
);
141 * bdi_start_writeback - start writeback
142 * @bdi: the backing device to write from
143 * @nr_pages: the number of pages to write
146 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
147 * started when this function returns, we make no guarentees on
148 * completion. Caller need not hold sb s_umount semaphore.
151 void bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
)
153 __bdi_start_writeback(bdi
, nr_pages
, true);
157 * bdi_start_background_writeback - start background writeback
158 * @bdi: the backing device to write from
161 * This makes sure WB_SYNC_NONE background writeback happens. When
162 * this function returns, it is only guaranteed that for given BDI
163 * some IO is happening if we are over background dirty threshold.
164 * Caller need not hold sb s_umount semaphore.
166 void bdi_start_background_writeback(struct backing_dev_info
*bdi
)
169 * We just wake up the flusher thread. It will perform background
170 * writeback as soon as there is no other work to do.
172 trace_writeback_wake_background(bdi
);
173 spin_lock_bh(&bdi
->wb_lock
);
174 bdi_wakeup_flusher(bdi
);
175 spin_unlock_bh(&bdi
->wb_lock
);
179 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
180 * furthest end of its superblock's dirty-inode list.
182 * Before stamping the inode's ->dirtied_when, we check to see whether it is
183 * already the most-recently-dirtied inode on the b_dirty list. If that is
184 * the case then the inode must have been redirtied while it was being written
185 * out and we don't reset its dirtied_when.
187 static void redirty_tail(struct inode
*inode
)
189 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
191 if (!list_empty(&wb
->b_dirty
)) {
194 tail
= wb_inode(wb
->b_dirty
.next
);
195 if (time_before(inode
->dirtied_when
, tail
->dirtied_when
))
196 inode
->dirtied_when
= jiffies
;
198 list_move(&inode
->i_wb_list
, &wb
->b_dirty
);
202 * requeue inode for re-scanning after bdi->b_io list is exhausted.
204 static void requeue_io(struct inode
*inode
)
206 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
208 list_move(&inode
->i_wb_list
, &wb
->b_more_io
);
211 static void inode_sync_complete(struct inode
*inode
)
214 * Prevent speculative execution through spin_unlock(&inode_lock);
217 wake_up_bit(&inode
->i_state
, __I_SYNC
);
220 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
222 bool ret
= time_after(inode
->dirtied_when
, t
);
225 * For inodes being constantly redirtied, dirtied_when can get stuck.
226 * It _appears_ to be in the future, but is actually in distant past.
227 * This test is necessary to prevent such wrapped-around relative times
228 * from permanently stopping the whole bdi writeback.
230 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
236 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
238 static void move_expired_inodes(struct list_head
*delaying_queue
,
239 struct list_head
*dispatch_queue
,
240 unsigned long *older_than_this
)
243 struct list_head
*pos
, *node
;
244 struct super_block
*sb
= NULL
;
248 while (!list_empty(delaying_queue
)) {
249 inode
= wb_inode(delaying_queue
->prev
);
250 if (older_than_this
&&
251 inode_dirtied_after(inode
, *older_than_this
))
253 if (sb
&& sb
!= inode
->i_sb
)
256 list_move(&inode
->i_wb_list
, &tmp
);
259 /* just one sb in list, splice to dispatch_queue and we're done */
261 list_splice(&tmp
, dispatch_queue
);
265 /* Move inodes from one superblock together */
266 while (!list_empty(&tmp
)) {
267 sb
= wb_inode(tmp
.prev
)->i_sb
;
268 list_for_each_prev_safe(pos
, node
, &tmp
) {
269 inode
= wb_inode(pos
);
270 if (inode
->i_sb
== sb
)
271 list_move(&inode
->i_wb_list
, dispatch_queue
);
277 * Queue all expired dirty inodes for io, eldest first.
279 * newly dirtied b_dirty b_io b_more_io
280 * =============> gf edc BA
282 * newly dirtied b_dirty b_io b_more_io
283 * =============> g fBAedc
285 * +--> dequeue for IO
287 static void queue_io(struct bdi_writeback
*wb
, unsigned long *older_than_this
)
289 list_splice_init(&wb
->b_more_io
, &wb
->b_io
);
290 move_expired_inodes(&wb
->b_dirty
, &wb
->b_io
, older_than_this
);
293 static int write_inode(struct inode
*inode
, struct writeback_control
*wbc
)
295 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
))
296 return inode
->i_sb
->s_op
->write_inode(inode
, wbc
);
301 * Wait for writeback on an inode to complete.
303 static void inode_wait_for_writeback(struct inode
*inode
)
305 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
306 wait_queue_head_t
*wqh
;
308 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
309 while (inode
->i_state
& I_SYNC
) {
310 spin_unlock(&inode_lock
);
311 __wait_on_bit(wqh
, &wq
, inode_wait
, TASK_UNINTERRUPTIBLE
);
312 spin_lock(&inode_lock
);
317 * Write out an inode's dirty pages. Called under inode_lock. Either the
318 * caller has ref on the inode (either via __iget or via syscall against an fd)
319 * or the inode has I_WILL_FREE set (via generic_forget_inode)
321 * If `wait' is set, wait on the writeout.
323 * The whole writeout design is quite complex and fragile. We want to avoid
324 * starvation of particular inodes when others are being redirtied, prevent
327 * Called under inode_lock.
330 writeback_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
332 struct address_space
*mapping
= inode
->i_mapping
;
336 if (!atomic_read(&inode
->i_count
))
337 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
339 WARN_ON(inode
->i_state
& I_WILL_FREE
);
341 if (inode
->i_state
& I_SYNC
) {
343 * If this inode is locked for writeback and we are not doing
344 * writeback-for-data-integrity, move it to b_more_io so that
345 * writeback can proceed with the other inodes on s_io.
347 * We'll have another go at writing back this inode when we
348 * completed a full scan of b_io.
350 if (wbc
->sync_mode
!= WB_SYNC_ALL
) {
356 * It's a data-integrity sync. We must wait.
358 inode_wait_for_writeback(inode
);
361 BUG_ON(inode
->i_state
& I_SYNC
);
363 /* Set I_SYNC, reset I_DIRTY_PAGES */
364 inode
->i_state
|= I_SYNC
;
365 inode
->i_state
&= ~I_DIRTY_PAGES
;
366 spin_unlock(&inode_lock
);
368 ret
= do_writepages(mapping
, wbc
);
371 * Make sure to wait on the data before writing out the metadata.
372 * This is important for filesystems that modify metadata on data
375 if (wbc
->sync_mode
== WB_SYNC_ALL
) {
376 int err
= filemap_fdatawait(mapping
);
382 * Some filesystems may redirty the inode during the writeback
383 * due to delalloc, clear dirty metadata flags right before
386 spin_lock(&inode_lock
);
387 dirty
= inode
->i_state
& I_DIRTY
;
388 inode
->i_state
&= ~(I_DIRTY_SYNC
| I_DIRTY_DATASYNC
);
389 spin_unlock(&inode_lock
);
390 /* Don't write the inode if only I_DIRTY_PAGES was set */
391 if (dirty
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
392 int err
= write_inode(inode
, wbc
);
397 spin_lock(&inode_lock
);
398 inode
->i_state
&= ~I_SYNC
;
399 if (!(inode
->i_state
& I_FREEING
)) {
400 if (mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
)) {
402 * We didn't write back all the pages. nfs_writepages()
403 * sometimes bales out without doing anything.
405 inode
->i_state
|= I_DIRTY_PAGES
;
406 if (wbc
->nr_to_write
<= 0) {
408 * slice used up: queue for next turn
413 * Writeback blocked by something other than
414 * congestion. Delay the inode for some time to
415 * avoid spinning on the CPU (100% iowait)
416 * retrying writeback of the dirty page/inode
417 * that cannot be performed immediately.
421 } else if (inode
->i_state
& I_DIRTY
) {
423 * Filesystems can dirty the inode during writeback
424 * operations, such as delayed allocation during
425 * submission or metadata updates after data IO
431 * The inode is clean. At this point we either have
432 * a reference to the inode or it's on it's way out.
433 * No need to add it back to the LRU.
435 list_del_init(&inode
->i_wb_list
);
438 inode_sync_complete(inode
);
443 * For background writeback the caller does not have the sb pinned
444 * before calling writeback. So make sure that we do pin it, so it doesn't
445 * go away while we are writing inodes from it.
447 static bool pin_sb_for_writeback(struct super_block
*sb
)
450 if (list_empty(&sb
->s_instances
)) {
451 spin_unlock(&sb_lock
);
456 spin_unlock(&sb_lock
);
458 if (down_read_trylock(&sb
->s_umount
)) {
461 up_read(&sb
->s_umount
);
469 * Write a portion of b_io inodes which belong to @sb.
471 * If @only_this_sb is true, then find and write all such
472 * inodes. Otherwise write only ones which go sequentially
475 * Return 1, if the caller writeback routine should be
476 * interrupted. Otherwise return 0.
478 static int writeback_sb_inodes(struct super_block
*sb
, struct bdi_writeback
*wb
,
479 struct writeback_control
*wbc
, bool only_this_sb
)
481 while (!list_empty(&wb
->b_io
)) {
483 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
485 if (inode
->i_sb
!= sb
) {
488 * We only want to write back data for this
489 * superblock, move all inodes not belonging
490 * to it back onto the dirty list.
497 * The inode belongs to a different superblock.
498 * Bounce back to the caller to unpin this and
499 * pin the next superblock.
505 * Don't bother with new inodes or inodes beeing freed, first
506 * kind does not need peridic writeout yet, and for the latter
507 * kind writeout is handled by the freer.
509 if (inode
->i_state
& (I_NEW
| I_FREEING
| I_WILL_FREE
)) {
515 * Was this inode dirtied after sync_sb_inodes was called?
516 * This keeps sync from extra jobs and livelock.
518 if (inode_dirtied_after(inode
, wbc
->wb_start
))
522 pages_skipped
= wbc
->pages_skipped
;
523 writeback_single_inode(inode
, wbc
);
524 if (wbc
->pages_skipped
!= pages_skipped
) {
526 * writeback is not making progress due to locked
527 * buffers. Skip this inode for now.
531 spin_unlock(&inode_lock
);
534 spin_lock(&inode_lock
);
535 if (wbc
->nr_to_write
<= 0) {
539 if (!list_empty(&wb
->b_more_io
))
546 void writeback_inodes_wb(struct bdi_writeback
*wb
,
547 struct writeback_control
*wbc
)
552 wbc
->wb_start
= jiffies
; /* livelock avoidance */
553 spin_lock(&inode_lock
);
554 if (!wbc
->for_kupdate
|| list_empty(&wb
->b_io
))
555 queue_io(wb
, wbc
->older_than_this
);
557 while (!list_empty(&wb
->b_io
)) {
558 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
559 struct super_block
*sb
= inode
->i_sb
;
561 if (!pin_sb_for_writeback(sb
)) {
565 ret
= writeback_sb_inodes(sb
, wb
, wbc
, false);
571 spin_unlock(&inode_lock
);
572 /* Leave any unwritten inodes on b_io */
575 static void __writeback_inodes_sb(struct super_block
*sb
,
576 struct bdi_writeback
*wb
, struct writeback_control
*wbc
)
578 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
580 spin_lock(&inode_lock
);
581 if (!wbc
->for_kupdate
|| list_empty(&wb
->b_io
))
582 queue_io(wb
, wbc
->older_than_this
);
583 writeback_sb_inodes(sb
, wb
, wbc
, true);
584 spin_unlock(&inode_lock
);
588 * The maximum number of pages to writeout in a single bdi flush/kupdate
589 * operation. We do this so we don't hold I_SYNC against an inode for
590 * enormous amounts of time, which would block a userspace task which has
591 * been forced to throttle against that inode. Also, the code reevaluates
592 * the dirty each time it has written this many pages.
594 #define MAX_WRITEBACK_PAGES 1024
596 static inline bool over_bground_thresh(void)
598 unsigned long background_thresh
, dirty_thresh
;
600 global_dirty_limits(&background_thresh
, &dirty_thresh
);
602 return (global_page_state(NR_FILE_DIRTY
) +
603 global_page_state(NR_UNSTABLE_NFS
) > background_thresh
);
607 * Explicit flushing or periodic writeback of "old" data.
609 * Define "old": the first time one of an inode's pages is dirtied, we mark the
610 * dirtying-time in the inode's address_space. So this periodic writeback code
611 * just walks the superblock inode list, writing back any inodes which are
612 * older than a specific point in time.
614 * Try to run once per dirty_writeback_interval. But if a writeback event
615 * takes longer than a dirty_writeback_interval interval, then leave a
618 * older_than_this takes precedence over nr_to_write. So we'll only write back
619 * all dirty pages if they are all attached to "old" mappings.
621 static long wb_writeback(struct bdi_writeback
*wb
,
622 struct wb_writeback_work
*work
)
624 struct writeback_control wbc
= {
625 .sync_mode
= work
->sync_mode
,
626 .older_than_this
= NULL
,
627 .for_kupdate
= work
->for_kupdate
,
628 .for_background
= work
->for_background
,
629 .range_cyclic
= work
->range_cyclic
,
631 unsigned long oldest_jif
;
635 if (wbc
.for_kupdate
) {
636 wbc
.older_than_this
= &oldest_jif
;
637 oldest_jif
= jiffies
-
638 msecs_to_jiffies(dirty_expire_interval
* 10);
640 if (!wbc
.range_cyclic
) {
642 wbc
.range_end
= LLONG_MAX
;
645 wbc
.wb_start
= jiffies
; /* livelock avoidance */
648 * Stop writeback when nr_pages has been consumed
650 if (work
->nr_pages
<= 0)
654 * Background writeout and kupdate-style writeback may
655 * run forever. Stop them if there is other work to do
656 * so that e.g. sync can proceed. They'll be restarted
657 * after the other works are all done.
659 if ((work
->for_background
|| work
->for_kupdate
) &&
660 !list_empty(&wb
->bdi
->work_list
))
664 * For background writeout, stop when we are below the
665 * background dirty threshold
667 if (work
->for_background
&& !over_bground_thresh())
671 wbc
.nr_to_write
= MAX_WRITEBACK_PAGES
;
672 wbc
.pages_skipped
= 0;
674 trace_wbc_writeback_start(&wbc
, wb
->bdi
);
676 __writeback_inodes_sb(work
->sb
, wb
, &wbc
);
678 writeback_inodes_wb(wb
, &wbc
);
679 trace_wbc_writeback_written(&wbc
, wb
->bdi
);
681 work
->nr_pages
-= MAX_WRITEBACK_PAGES
- wbc
.nr_to_write
;
682 wrote
+= MAX_WRITEBACK_PAGES
- wbc
.nr_to_write
;
685 * If we consumed everything, see if we have more
687 if (wbc
.nr_to_write
<= 0)
690 * Didn't write everything and we don't have more IO, bail
695 * Did we write something? Try for more
697 if (wbc
.nr_to_write
< MAX_WRITEBACK_PAGES
)
700 * Nothing written. Wait for some inode to
701 * become available for writeback. Otherwise
702 * we'll just busyloop.
704 spin_lock(&inode_lock
);
705 if (!list_empty(&wb
->b_more_io
)) {
706 inode
= wb_inode(wb
->b_more_io
.prev
);
707 trace_wbc_writeback_wait(&wbc
, wb
->bdi
);
708 inode_wait_for_writeback(inode
);
710 spin_unlock(&inode_lock
);
717 * Return the next wb_writeback_work struct that hasn't been processed yet.
719 static struct wb_writeback_work
*
720 get_next_work_item(struct backing_dev_info
*bdi
)
722 struct wb_writeback_work
*work
= NULL
;
724 spin_lock_bh(&bdi
->wb_lock
);
725 if (!list_empty(&bdi
->work_list
)) {
726 work
= list_entry(bdi
->work_list
.next
,
727 struct wb_writeback_work
, list
);
728 list_del_init(&work
->list
);
730 spin_unlock_bh(&bdi
->wb_lock
);
735 * Add in the number of potentially dirty inodes, because each inode
736 * write can dirty pagecache in the underlying blockdev.
738 static unsigned long get_nr_dirty_pages(void)
740 return global_page_state(NR_FILE_DIRTY
) +
741 global_page_state(NR_UNSTABLE_NFS
) +
742 get_nr_dirty_inodes();
745 static long wb_check_background_flush(struct bdi_writeback
*wb
)
747 if (over_bground_thresh()) {
749 struct wb_writeback_work work
= {
750 .nr_pages
= LONG_MAX
,
751 .sync_mode
= WB_SYNC_NONE
,
756 return wb_writeback(wb
, &work
);
762 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
764 unsigned long expired
;
768 * When set to zero, disable periodic writeback
770 if (!dirty_writeback_interval
)
773 expired
= wb
->last_old_flush
+
774 msecs_to_jiffies(dirty_writeback_interval
* 10);
775 if (time_before(jiffies
, expired
))
778 wb
->last_old_flush
= jiffies
;
779 nr_pages
= get_nr_dirty_pages();
782 struct wb_writeback_work work
= {
783 .nr_pages
= nr_pages
,
784 .sync_mode
= WB_SYNC_NONE
,
789 return wb_writeback(wb
, &work
);
796 * Retrieve work items and do the writeback they describe
798 long wb_do_writeback(struct bdi_writeback
*wb
, int force_wait
)
800 struct backing_dev_info
*bdi
= wb
->bdi
;
801 struct wb_writeback_work
*work
;
804 set_bit(BDI_writeback_running
, &wb
->bdi
->state
);
805 while ((work
= get_next_work_item(bdi
)) != NULL
) {
807 * Override sync mode, in case we must wait for completion
808 * because this thread is exiting now.
811 work
->sync_mode
= WB_SYNC_ALL
;
813 trace_writeback_exec(bdi
, work
);
815 wrote
+= wb_writeback(wb
, work
);
818 * Notify the caller of completion if this is a synchronous
819 * work item, otherwise just free it.
822 complete(work
->done
);
828 * Check for periodic writeback, kupdated() style
830 wrote
+= wb_check_old_data_flush(wb
);
831 wrote
+= wb_check_background_flush(wb
);
832 clear_bit(BDI_writeback_running
, &wb
->bdi
->state
);
838 * Handle writeback of dirty data for the device backed by this bdi. Also
839 * wakes up periodically and does kupdated style flushing.
841 int bdi_writeback_thread(void *data
)
843 struct bdi_writeback
*wb
= data
;
844 struct backing_dev_info
*bdi
= wb
->bdi
;
847 current
->flags
|= PF_SWAPWRITE
;
849 wb
->last_active
= jiffies
;
852 * Our parent may run at a different priority, just set us to normal
854 set_user_nice(current
, 0);
856 trace_writeback_thread_start(bdi
);
858 while (!kthread_should_stop()) {
860 * Remove own delayed wake-up timer, since we are already awake
861 * and we'll take care of the preriodic write-back.
863 del_timer(&wb
->wakeup_timer
);
865 pages_written
= wb_do_writeback(wb
, 0);
867 trace_writeback_pages_written(pages_written
);
870 wb
->last_active
= jiffies
;
872 set_current_state(TASK_INTERRUPTIBLE
);
873 if (!list_empty(&bdi
->work_list
) || kthread_should_stop()) {
874 __set_current_state(TASK_RUNNING
);
878 if (wb_has_dirty_io(wb
) && dirty_writeback_interval
)
879 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval
* 10));
882 * We have nothing to do, so can go sleep without any
883 * timeout and save power. When a work is queued or
884 * something is made dirty - we will be woken up.
892 /* Flush any work that raced with us exiting */
893 if (!list_empty(&bdi
->work_list
))
894 wb_do_writeback(wb
, 1);
896 trace_writeback_thread_stop(bdi
);
902 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
905 void wakeup_flusher_threads(long nr_pages
)
907 struct backing_dev_info
*bdi
;
910 nr_pages
= global_page_state(NR_FILE_DIRTY
) +
911 global_page_state(NR_UNSTABLE_NFS
);
915 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
916 if (!bdi_has_dirty_io(bdi
))
918 __bdi_start_writeback(bdi
, nr_pages
, false);
923 static noinline
void block_dump___mark_inode_dirty(struct inode
*inode
)
925 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev")) {
926 struct dentry
*dentry
;
927 const char *name
= "?";
929 dentry
= d_find_alias(inode
);
931 spin_lock(&dentry
->d_lock
);
932 name
= (const char *) dentry
->d_name
.name
;
935 "%s(%d): dirtied inode %lu (%s) on %s\n",
936 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
937 name
, inode
->i_sb
->s_id
);
939 spin_unlock(&dentry
->d_lock
);
946 * __mark_inode_dirty - internal function
947 * @inode: inode to mark
948 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
949 * Mark an inode as dirty. Callers should use mark_inode_dirty or
950 * mark_inode_dirty_sync.
952 * Put the inode on the super block's dirty list.
954 * CAREFUL! We mark it dirty unconditionally, but move it onto the
955 * dirty list only if it is hashed or if it refers to a blockdev.
956 * If it was not hashed, it will never be added to the dirty list
957 * even if it is later hashed, as it will have been marked dirty already.
959 * In short, make sure you hash any inodes _before_ you start marking
962 * This function *must* be atomic for the I_DIRTY_PAGES case -
963 * set_page_dirty() is called under spinlock in several places.
965 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
966 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
967 * the kernel-internal blockdev inode represents the dirtying time of the
968 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
969 * page->mapping->host, so the page-dirtying time is recorded in the internal
972 void __mark_inode_dirty(struct inode
*inode
, int flags
)
974 struct super_block
*sb
= inode
->i_sb
;
975 struct backing_dev_info
*bdi
= NULL
;
976 bool wakeup_bdi
= false;
979 * Don't do this for I_DIRTY_PAGES - that doesn't actually
980 * dirty the inode itself
982 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
983 if (sb
->s_op
->dirty_inode
)
984 sb
->s_op
->dirty_inode(inode
);
988 * make sure that changes are seen by all cpus before we test i_state
993 /* avoid the locking if we can */
994 if ((inode
->i_state
& flags
) == flags
)
997 if (unlikely(block_dump
))
998 block_dump___mark_inode_dirty(inode
);
1000 spin_lock(&inode_lock
);
1001 if ((inode
->i_state
& flags
) != flags
) {
1002 const int was_dirty
= inode
->i_state
& I_DIRTY
;
1004 inode
->i_state
|= flags
;
1007 * If the inode is being synced, just update its dirty state.
1008 * The unlocker will place the inode on the appropriate
1009 * superblock list, based upon its state.
1011 if (inode
->i_state
& I_SYNC
)
1015 * Only add valid (hashed) inodes to the superblock's
1016 * dirty list. Add blockdev inodes as well.
1018 if (!S_ISBLK(inode
->i_mode
)) {
1019 if (inode_unhashed(inode
))
1022 if (inode
->i_state
& I_FREEING
)
1026 * If the inode was already on b_dirty/b_io/b_more_io, don't
1027 * reposition it (that would break b_dirty time-ordering).
1030 bdi
= inode_to_bdi(inode
);
1032 if (bdi_cap_writeback_dirty(bdi
)) {
1033 WARN(!test_bit(BDI_registered
, &bdi
->state
),
1034 "bdi-%s not registered\n", bdi
->name
);
1037 * If this is the first dirty inode for this
1038 * bdi, we have to wake-up the corresponding
1039 * bdi thread to make sure background
1040 * write-back happens later.
1042 if (!wb_has_dirty_io(&bdi
->wb
))
1046 inode
->dirtied_when
= jiffies
;
1047 list_move(&inode
->i_wb_list
, &bdi
->wb
.b_dirty
);
1051 spin_unlock(&inode_lock
);
1054 bdi_wakeup_thread_delayed(bdi
);
1056 EXPORT_SYMBOL(__mark_inode_dirty
);
1059 * Write out a superblock's list of dirty inodes. A wait will be performed
1060 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1062 * If older_than_this is non-NULL, then only write out inodes which
1063 * had their first dirtying at a time earlier than *older_than_this.
1065 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1066 * This function assumes that the blockdev superblock's inodes are backed by
1067 * a variety of queues, so all inodes are searched. For other superblocks,
1068 * assume that all inodes are backed by the same queue.
1070 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1071 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1072 * on the writer throttling path, and we get decent balancing between many
1073 * throttled threads: we don't want them all piling up on inode_sync_wait.
1075 static void wait_sb_inodes(struct super_block
*sb
)
1077 struct inode
*inode
, *old_inode
= NULL
;
1080 * We need to be protected against the filesystem going from
1081 * r/o to r/w or vice versa.
1083 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1085 spin_lock(&inode_lock
);
1088 * Data integrity sync. Must wait for all pages under writeback,
1089 * because there may have been pages dirtied before our sync
1090 * call, but which had writeout started before we write it out.
1091 * In which case, the inode may not be on the dirty list, but
1092 * we still have to wait for that writeout.
1094 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
1095 struct address_space
*mapping
;
1097 if (inode
->i_state
& (I_FREEING
|I_WILL_FREE
|I_NEW
))
1099 mapping
= inode
->i_mapping
;
1100 if (mapping
->nrpages
== 0)
1103 spin_unlock(&inode_lock
);
1105 * We hold a reference to 'inode' so it couldn't have
1106 * been removed from s_inodes list while we dropped the
1107 * inode_lock. We cannot iput the inode now as we can
1108 * be holding the last reference and we cannot iput it
1109 * under inode_lock. So we keep the reference and iput
1115 filemap_fdatawait(mapping
);
1119 spin_lock(&inode_lock
);
1121 spin_unlock(&inode_lock
);
1126 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1127 * @sb: the superblock
1128 * @nr: the number of pages to write
1130 * Start writeback on some inodes on this super_block. No guarantees are made
1131 * on how many (if any) will be written, and this function does not wait
1132 * for IO completion of submitted IO.
1134 void writeback_inodes_sb_nr(struct super_block
*sb
, unsigned long nr
)
1136 DECLARE_COMPLETION_ONSTACK(done
);
1137 struct wb_writeback_work work
= {
1139 .sync_mode
= WB_SYNC_NONE
,
1144 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1145 bdi_queue_work(sb
->s_bdi
, &work
);
1146 wait_for_completion(&done
);
1148 EXPORT_SYMBOL(writeback_inodes_sb_nr
);
1151 * writeback_inodes_sb - writeback dirty inodes from given super_block
1152 * @sb: the superblock
1154 * Start writeback on some inodes on this super_block. No guarantees are made
1155 * on how many (if any) will be written, and this function does not wait
1156 * for IO completion of submitted IO.
1158 void writeback_inodes_sb(struct super_block
*sb
)
1160 return writeback_inodes_sb_nr(sb
, get_nr_dirty_pages());
1162 EXPORT_SYMBOL(writeback_inodes_sb
);
1165 * writeback_inodes_sb_if_idle - start writeback if none underway
1166 * @sb: the superblock
1168 * Invoke writeback_inodes_sb if no writeback is currently underway.
1169 * Returns 1 if writeback was started, 0 if not.
1171 int writeback_inodes_sb_if_idle(struct super_block
*sb
)
1173 if (!writeback_in_progress(sb
->s_bdi
)) {
1174 down_read(&sb
->s_umount
);
1175 writeback_inodes_sb(sb
);
1176 up_read(&sb
->s_umount
);
1181 EXPORT_SYMBOL(writeback_inodes_sb_if_idle
);
1184 * writeback_inodes_sb_if_idle - start writeback if none underway
1185 * @sb: the superblock
1186 * @nr: the number of pages to write
1188 * Invoke writeback_inodes_sb if no writeback is currently underway.
1189 * Returns 1 if writeback was started, 0 if not.
1191 int writeback_inodes_sb_nr_if_idle(struct super_block
*sb
,
1194 if (!writeback_in_progress(sb
->s_bdi
)) {
1195 down_read(&sb
->s_umount
);
1196 writeback_inodes_sb_nr(sb
, nr
);
1197 up_read(&sb
->s_umount
);
1202 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle
);
1205 * sync_inodes_sb - sync sb inode pages
1206 * @sb: the superblock
1208 * This function writes and waits on any dirty inode belonging to this
1209 * super_block. The number of pages synced is returned.
1211 void sync_inodes_sb(struct super_block
*sb
)
1213 DECLARE_COMPLETION_ONSTACK(done
);
1214 struct wb_writeback_work work
= {
1216 .sync_mode
= WB_SYNC_ALL
,
1217 .nr_pages
= LONG_MAX
,
1222 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1224 bdi_queue_work(sb
->s_bdi
, &work
);
1225 wait_for_completion(&done
);
1229 EXPORT_SYMBOL(sync_inodes_sb
);
1232 * write_inode_now - write an inode to disk
1233 * @inode: inode to write to disk
1234 * @sync: whether the write should be synchronous or not
1236 * This function commits an inode to disk immediately if it is dirty. This is
1237 * primarily needed by knfsd.
1239 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1241 int write_inode_now(struct inode
*inode
, int sync
)
1244 struct writeback_control wbc
= {
1245 .nr_to_write
= LONG_MAX
,
1246 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1248 .range_end
= LLONG_MAX
,
1251 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
1252 wbc
.nr_to_write
= 0;
1255 spin_lock(&inode_lock
);
1256 ret
= writeback_single_inode(inode
, &wbc
);
1257 spin_unlock(&inode_lock
);
1259 inode_sync_wait(inode
);
1262 EXPORT_SYMBOL(write_inode_now
);
1265 * sync_inode - write an inode and its pages to disk.
1266 * @inode: the inode to sync
1267 * @wbc: controls the writeback mode
1269 * sync_inode() will write an inode and its pages to disk. It will also
1270 * correctly update the inode on its superblock's dirty inode lists and will
1271 * update inode->i_state.
1273 * The caller must have a ref on the inode.
1275 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1279 spin_lock(&inode_lock
);
1280 ret
= writeback_single_inode(inode
, wbc
);
1281 spin_unlock(&inode_lock
);
1284 EXPORT_SYMBOL(sync_inode
);
1287 * sync_inode - write an inode to disk
1288 * @inode: the inode to sync
1289 * @wait: wait for I/O to complete.
1291 * Write an inode to disk and adjust it's dirty state after completion.
1293 * Note: only writes the actual inode, no associated data or other metadata.
1295 int sync_inode_metadata(struct inode
*inode
, int wait
)
1297 struct writeback_control wbc
= {
1298 .sync_mode
= wait
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1299 .nr_to_write
= 0, /* metadata-only */
1302 return sync_inode(inode
, &wbc
);
1304 EXPORT_SYMBOL(sync_inode_metadata
);