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 unsigned long *older_than_this
;
39 enum writeback_sync_modes sync_mode
;
40 unsigned int tagged_writepages
:1;
41 unsigned int for_kupdate
:1;
42 unsigned int range_cyclic
:1;
43 unsigned int for_background
:1;
44 enum wb_reason reason
; /* why was writeback initiated? */
46 struct list_head list
; /* pending work list */
47 struct completion
*done
; /* set if the caller waits */
50 const char *wb_reason_name
[] = {
51 [WB_REASON_BACKGROUND
] = "background",
52 [WB_REASON_TRY_TO_FREE_PAGES
] = "try_to_free_pages",
53 [WB_REASON_SYNC
] = "sync",
54 [WB_REASON_PERIODIC
] = "periodic",
55 [WB_REASON_LAPTOP_TIMER
] = "laptop_timer",
56 [WB_REASON_FREE_MORE_MEM
] = "free_more_memory",
57 [WB_REASON_FS_FREE_SPACE
] = "fs_free_space",
58 [WB_REASON_FORKER_THREAD
] = "forker_thread"
62 * Include the creation of the trace points after defining the
63 * wb_writeback_work structure so that the definition remains local to this
66 #define CREATE_TRACE_POINTS
67 #include <trace/events/writeback.h>
70 * We don't actually have pdflush, but this one is exported though /proc...
72 int nr_pdflush_threads
;
75 * writeback_in_progress - determine whether there is writeback in progress
76 * @bdi: the device's backing_dev_info structure.
78 * Determine whether there is writeback waiting to be handled against a
81 int writeback_in_progress(struct backing_dev_info
*bdi
)
83 return test_bit(BDI_writeback_running
, &bdi
->state
);
86 static inline struct backing_dev_info
*inode_to_bdi(struct inode
*inode
)
88 struct super_block
*sb
= inode
->i_sb
;
90 if (strcmp(sb
->s_type
->name
, "bdev") == 0)
91 return inode
->i_mapping
->backing_dev_info
;
96 static inline struct inode
*wb_inode(struct list_head
*head
)
98 return list_entry(head
, struct inode
, i_wb_list
);
101 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
102 static void bdi_wakeup_flusher(struct backing_dev_info
*bdi
)
105 wake_up_process(bdi
->wb
.task
);
108 * The bdi thread isn't there, wake up the forker thread which
109 * will create and run it.
111 wake_up_process(default_backing_dev_info
.wb
.task
);
115 static void bdi_queue_work(struct backing_dev_info
*bdi
,
116 struct wb_writeback_work
*work
)
118 trace_writeback_queue(bdi
, work
);
120 spin_lock_bh(&bdi
->wb_lock
);
121 list_add_tail(&work
->list
, &bdi
->work_list
);
123 trace_writeback_nothread(bdi
, work
);
124 bdi_wakeup_flusher(bdi
);
125 spin_unlock_bh(&bdi
->wb_lock
);
129 __bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
,
130 bool range_cyclic
, enum wb_reason reason
)
132 struct wb_writeback_work
*work
;
135 * This is WB_SYNC_NONE writeback, so if allocation fails just
136 * wakeup the thread for old dirty data writeback
138 work
= kzalloc(sizeof(*work
), GFP_ATOMIC
);
141 trace_writeback_nowork(bdi
);
142 wake_up_process(bdi
->wb
.task
);
147 work
->sync_mode
= WB_SYNC_NONE
;
148 work
->nr_pages
= nr_pages
;
149 work
->range_cyclic
= range_cyclic
;
150 work
->reason
= reason
;
152 bdi_queue_work(bdi
, work
);
156 * bdi_start_writeback - start writeback
157 * @bdi: the backing device to write from
158 * @nr_pages: the number of pages to write
159 * @reason: reason why some writeback work was initiated
162 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
163 * started when this function returns, we make no guarantees on
164 * completion. Caller need not hold sb s_umount semaphore.
167 void bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
,
168 enum wb_reason reason
)
170 __bdi_start_writeback(bdi
, nr_pages
, true, reason
);
174 * bdi_start_background_writeback - start background writeback
175 * @bdi: the backing device to write from
178 * This makes sure WB_SYNC_NONE background writeback happens. When
179 * this function returns, it is only guaranteed that for given BDI
180 * some IO is happening if we are over background dirty threshold.
181 * Caller need not hold sb s_umount semaphore.
183 void bdi_start_background_writeback(struct backing_dev_info
*bdi
)
186 * We just wake up the flusher thread. It will perform background
187 * writeback as soon as there is no other work to do.
189 trace_writeback_wake_background(bdi
);
190 spin_lock_bh(&bdi
->wb_lock
);
191 bdi_wakeup_flusher(bdi
);
192 spin_unlock_bh(&bdi
->wb_lock
);
196 * Remove the inode from the writeback list it is on.
198 void inode_wb_list_del(struct inode
*inode
)
200 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
202 spin_lock(&bdi
->wb
.list_lock
);
203 list_del_init(&inode
->i_wb_list
);
204 spin_unlock(&bdi
->wb
.list_lock
);
208 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
209 * furthest end of its superblock's dirty-inode list.
211 * Before stamping the inode's ->dirtied_when, we check to see whether it is
212 * already the most-recently-dirtied inode on the b_dirty list. If that is
213 * the case then the inode must have been redirtied while it was being written
214 * out and we don't reset its dirtied_when.
216 static void redirty_tail(struct inode
*inode
, struct bdi_writeback
*wb
)
218 assert_spin_locked(&wb
->list_lock
);
219 if (!list_empty(&wb
->b_dirty
)) {
222 tail
= wb_inode(wb
->b_dirty
.next
);
223 if (time_before(inode
->dirtied_when
, tail
->dirtied_when
))
224 inode
->dirtied_when
= jiffies
;
226 list_move(&inode
->i_wb_list
, &wb
->b_dirty
);
230 * requeue inode for re-scanning after bdi->b_io list is exhausted.
232 static void requeue_io(struct inode
*inode
, struct bdi_writeback
*wb
)
234 assert_spin_locked(&wb
->list_lock
);
235 list_move(&inode
->i_wb_list
, &wb
->b_more_io
);
238 static void inode_sync_complete(struct inode
*inode
)
241 * Prevent speculative execution through
242 * spin_unlock(&wb->list_lock);
246 wake_up_bit(&inode
->i_state
, __I_SYNC
);
249 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
251 bool ret
= time_after(inode
->dirtied_when
, t
);
254 * For inodes being constantly redirtied, dirtied_when can get stuck.
255 * It _appears_ to be in the future, but is actually in distant past.
256 * This test is necessary to prevent such wrapped-around relative times
257 * from permanently stopping the whole bdi writeback.
259 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
265 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
267 static int move_expired_inodes(struct list_head
*delaying_queue
,
268 struct list_head
*dispatch_queue
,
269 struct wb_writeback_work
*work
)
272 struct list_head
*pos
, *node
;
273 struct super_block
*sb
= NULL
;
278 while (!list_empty(delaying_queue
)) {
279 inode
= wb_inode(delaying_queue
->prev
);
280 if (work
->older_than_this
&&
281 inode_dirtied_after(inode
, *work
->older_than_this
))
283 if (sb
&& sb
!= inode
->i_sb
)
286 list_move(&inode
->i_wb_list
, &tmp
);
290 /* just one sb in list, splice to dispatch_queue and we're done */
292 list_splice(&tmp
, dispatch_queue
);
296 /* Move inodes from one superblock together */
297 while (!list_empty(&tmp
)) {
298 sb
= wb_inode(tmp
.prev
)->i_sb
;
299 list_for_each_prev_safe(pos
, node
, &tmp
) {
300 inode
= wb_inode(pos
);
301 if (inode
->i_sb
== sb
)
302 list_move(&inode
->i_wb_list
, dispatch_queue
);
310 * Queue all expired dirty inodes for io, eldest first.
312 * newly dirtied b_dirty b_io b_more_io
313 * =============> gf edc BA
315 * newly dirtied b_dirty b_io b_more_io
316 * =============> g fBAedc
318 * +--> dequeue for IO
320 static void queue_io(struct bdi_writeback
*wb
, struct wb_writeback_work
*work
)
323 assert_spin_locked(&wb
->list_lock
);
324 list_splice_init(&wb
->b_more_io
, &wb
->b_io
);
325 moved
= move_expired_inodes(&wb
->b_dirty
, &wb
->b_io
, work
);
326 trace_writeback_queue_io(wb
, work
, moved
);
329 static int write_inode(struct inode
*inode
, struct writeback_control
*wbc
)
331 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
))
332 return inode
->i_sb
->s_op
->write_inode(inode
, wbc
);
337 * Wait for writeback on an inode to complete.
339 static void inode_wait_for_writeback(struct inode
*inode
,
340 struct bdi_writeback
*wb
)
342 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
343 wait_queue_head_t
*wqh
;
345 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
346 while (inode
->i_state
& I_SYNC
) {
347 spin_unlock(&inode
->i_lock
);
348 spin_unlock(&wb
->list_lock
);
349 __wait_on_bit(wqh
, &wq
, inode_wait
, TASK_UNINTERRUPTIBLE
);
350 spin_lock(&wb
->list_lock
);
351 spin_lock(&inode
->i_lock
);
356 * Write out an inode's dirty pages. Called under wb->list_lock and
357 * inode->i_lock. Either the caller has an active reference on the inode or
358 * the inode has I_WILL_FREE set.
360 * If `wait' is set, wait on the writeout.
362 * The whole writeout design is quite complex and fragile. We want to avoid
363 * starvation of particular inodes when others are being redirtied, prevent
367 writeback_single_inode(struct inode
*inode
, struct bdi_writeback
*wb
,
368 struct writeback_control
*wbc
)
370 struct address_space
*mapping
= inode
->i_mapping
;
371 long nr_to_write
= wbc
->nr_to_write
;
375 assert_spin_locked(&wb
->list_lock
);
376 assert_spin_locked(&inode
->i_lock
);
378 if (!atomic_read(&inode
->i_count
))
379 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
381 WARN_ON(inode
->i_state
& I_WILL_FREE
);
383 if (inode
->i_state
& I_SYNC
) {
385 * If this inode is locked for writeback and we are not doing
386 * writeback-for-data-integrity, move it to b_more_io so that
387 * writeback can proceed with the other inodes on s_io.
389 * We'll have another go at writing back this inode when we
390 * completed a full scan of b_io.
392 if (wbc
->sync_mode
!= WB_SYNC_ALL
) {
393 requeue_io(inode
, wb
);
394 trace_writeback_single_inode_requeue(inode
, wbc
,
400 * It's a data-integrity sync. We must wait.
402 inode_wait_for_writeback(inode
, wb
);
405 BUG_ON(inode
->i_state
& I_SYNC
);
407 /* Set I_SYNC, reset I_DIRTY_PAGES */
408 inode
->i_state
|= I_SYNC
;
409 inode
->i_state
&= ~I_DIRTY_PAGES
;
410 spin_unlock(&inode
->i_lock
);
411 spin_unlock(&wb
->list_lock
);
413 ret
= do_writepages(mapping
, wbc
);
416 * Make sure to wait on the data before writing out the metadata.
417 * This is important for filesystems that modify metadata on data
420 if (wbc
->sync_mode
== WB_SYNC_ALL
) {
421 int err
= filemap_fdatawait(mapping
);
427 * Some filesystems may redirty the inode during the writeback
428 * due to delalloc, clear dirty metadata flags right before
431 spin_lock(&inode
->i_lock
);
432 dirty
= inode
->i_state
& I_DIRTY
;
433 inode
->i_state
&= ~(I_DIRTY_SYNC
| I_DIRTY_DATASYNC
);
434 spin_unlock(&inode
->i_lock
);
435 /* Don't write the inode if only I_DIRTY_PAGES was set */
436 if (dirty
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
437 int err
= write_inode(inode
, wbc
);
442 spin_lock(&wb
->list_lock
);
443 spin_lock(&inode
->i_lock
);
444 inode
->i_state
&= ~I_SYNC
;
445 if (!(inode
->i_state
& I_FREEING
)) {
447 * Sync livelock prevention. Each inode is tagged and synced in
448 * one shot. If still dirty, it will be redirty_tail()'ed below.
449 * Update the dirty time to prevent enqueue and sync it again.
451 if ((inode
->i_state
& I_DIRTY
) &&
452 (wbc
->sync_mode
== WB_SYNC_ALL
|| wbc
->tagged_writepages
))
453 inode
->dirtied_when
= jiffies
;
455 if (mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
)) {
457 * We didn't write back all the pages. nfs_writepages()
458 * sometimes bales out without doing anything.
460 inode
->i_state
|= I_DIRTY_PAGES
;
461 if (wbc
->nr_to_write
<= 0) {
463 * slice used up: queue for next turn
465 requeue_io(inode
, wb
);
468 * Writeback blocked by something other than
469 * congestion. Delay the inode for some time to
470 * avoid spinning on the CPU (100% iowait)
471 * retrying writeback of the dirty page/inode
472 * that cannot be performed immediately.
474 redirty_tail(inode
, wb
);
476 } else if (inode
->i_state
& I_DIRTY
) {
478 * Filesystems can dirty the inode during writeback
479 * operations, such as delayed allocation during
480 * submission or metadata updates after data IO
483 redirty_tail(inode
, wb
);
486 * The inode is clean. At this point we either have
487 * a reference to the inode or it's on it's way out.
488 * No need to add it back to the LRU.
490 list_del_init(&inode
->i_wb_list
);
493 inode_sync_complete(inode
);
494 trace_writeback_single_inode(inode
, wbc
, nr_to_write
);
498 static long writeback_chunk_size(struct backing_dev_info
*bdi
,
499 struct wb_writeback_work
*work
)
504 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
505 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
506 * here avoids calling into writeback_inodes_wb() more than once.
508 * The intended call sequence for WB_SYNC_ALL writeback is:
511 * writeback_sb_inodes() <== called only once
512 * write_cache_pages() <== called once for each inode
513 * (quickly) tag currently dirty pages
514 * (maybe slowly) sync all tagged pages
516 if (work
->sync_mode
== WB_SYNC_ALL
|| work
->tagged_writepages
)
519 pages
= min(bdi
->avg_write_bandwidth
/ 2,
520 global_dirty_limit
/ DIRTY_SCOPE
);
521 pages
= min(pages
, work
->nr_pages
);
522 pages
= round_down(pages
+ MIN_WRITEBACK_PAGES
,
523 MIN_WRITEBACK_PAGES
);
530 * Write a portion of b_io inodes which belong to @sb.
532 * If @only_this_sb is true, then find and write all such
533 * inodes. Otherwise write only ones which go sequentially
536 * Return the number of pages and/or inodes written.
538 static long writeback_sb_inodes(struct super_block
*sb
,
539 struct bdi_writeback
*wb
,
540 struct wb_writeback_work
*work
)
542 struct writeback_control wbc
= {
543 .sync_mode
= work
->sync_mode
,
544 .tagged_writepages
= work
->tagged_writepages
,
545 .for_kupdate
= work
->for_kupdate
,
546 .for_background
= work
->for_background
,
547 .range_cyclic
= work
->range_cyclic
,
549 .range_end
= LLONG_MAX
,
551 unsigned long start_time
= jiffies
;
553 long wrote
= 0; /* count both pages and inodes */
555 while (!list_empty(&wb
->b_io
)) {
556 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
558 if (inode
->i_sb
!= sb
) {
561 * We only want to write back data for this
562 * superblock, move all inodes not belonging
563 * to it back onto the dirty list.
565 redirty_tail(inode
, wb
);
570 * The inode belongs to a different superblock.
571 * Bounce back to the caller to unpin this and
572 * pin the next superblock.
578 * Don't bother with new inodes or inodes beeing freed, first
579 * kind does not need peridic writeout yet, and for the latter
580 * kind writeout is handled by the freer.
582 spin_lock(&inode
->i_lock
);
583 if (inode
->i_state
& (I_NEW
| I_FREEING
| I_WILL_FREE
)) {
584 spin_unlock(&inode
->i_lock
);
585 redirty_tail(inode
, wb
);
589 write_chunk
= writeback_chunk_size(wb
->bdi
, work
);
590 wbc
.nr_to_write
= write_chunk
;
591 wbc
.pages_skipped
= 0;
593 writeback_single_inode(inode
, wb
, &wbc
);
595 work
->nr_pages
-= write_chunk
- wbc
.nr_to_write
;
596 wrote
+= write_chunk
- wbc
.nr_to_write
;
597 if (!(inode
->i_state
& I_DIRTY
))
599 if (wbc
.pages_skipped
) {
601 * writeback is not making progress due to locked
602 * buffers. Skip this inode for now.
604 redirty_tail(inode
, wb
);
606 spin_unlock(&inode
->i_lock
);
607 spin_unlock(&wb
->list_lock
);
610 spin_lock(&wb
->list_lock
);
612 * bail out to wb_writeback() often enough to check
613 * background threshold and other termination conditions.
616 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
618 if (work
->nr_pages
<= 0)
625 static long __writeback_inodes_wb(struct bdi_writeback
*wb
,
626 struct wb_writeback_work
*work
)
628 unsigned long start_time
= jiffies
;
631 while (!list_empty(&wb
->b_io
)) {
632 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
633 struct super_block
*sb
= inode
->i_sb
;
635 if (!grab_super_passive(sb
)) {
637 * grab_super_passive() may fail consistently due to
638 * s_umount being grabbed by someone else. Don't use
639 * requeue_io() to avoid busy retrying the inode/sb.
641 redirty_tail(inode
, wb
);
644 wrote
+= writeback_sb_inodes(sb
, wb
, work
);
647 /* refer to the same tests at the end of writeback_sb_inodes */
649 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
651 if (work
->nr_pages
<= 0)
655 /* Leave any unwritten inodes on b_io */
659 long writeback_inodes_wb(struct bdi_writeback
*wb
, long nr_pages
,
660 enum wb_reason reason
)
662 struct wb_writeback_work work
= {
663 .nr_pages
= nr_pages
,
664 .sync_mode
= WB_SYNC_NONE
,
669 spin_lock(&wb
->list_lock
);
670 if (list_empty(&wb
->b_io
))
672 __writeback_inodes_wb(wb
, &work
);
673 spin_unlock(&wb
->list_lock
);
675 return nr_pages
- work
.nr_pages
;
678 static bool over_bground_thresh(struct backing_dev_info
*bdi
)
680 unsigned long background_thresh
, dirty_thresh
;
682 global_dirty_limits(&background_thresh
, &dirty_thresh
);
684 if (global_page_state(NR_FILE_DIRTY
) +
685 global_page_state(NR_UNSTABLE_NFS
) > background_thresh
)
688 if (bdi_stat(bdi
, BDI_RECLAIMABLE
) >
689 bdi_dirty_limit(bdi
, background_thresh
))
696 * Called under wb->list_lock. If there are multiple wb per bdi,
697 * only the flusher working on the first wb should do it.
699 static void wb_update_bandwidth(struct bdi_writeback
*wb
,
700 unsigned long start_time
)
702 __bdi_update_bandwidth(wb
->bdi
, 0, 0, 0, 0, 0, start_time
);
706 * Explicit flushing or periodic writeback of "old" data.
708 * Define "old": the first time one of an inode's pages is dirtied, we mark the
709 * dirtying-time in the inode's address_space. So this periodic writeback code
710 * just walks the superblock inode list, writing back any inodes which are
711 * older than a specific point in time.
713 * Try to run once per dirty_writeback_interval. But if a writeback event
714 * takes longer than a dirty_writeback_interval interval, then leave a
717 * older_than_this takes precedence over nr_to_write. So we'll only write back
718 * all dirty pages if they are all attached to "old" mappings.
720 static long wb_writeback(struct bdi_writeback
*wb
,
721 struct wb_writeback_work
*work
)
723 unsigned long wb_start
= jiffies
;
724 long nr_pages
= work
->nr_pages
;
725 unsigned long oldest_jif
;
729 oldest_jif
= jiffies
;
730 work
->older_than_this
= &oldest_jif
;
732 spin_lock(&wb
->list_lock
);
735 * Stop writeback when nr_pages has been consumed
737 if (work
->nr_pages
<= 0)
741 * Background writeout and kupdate-style writeback may
742 * run forever. Stop them if there is other work to do
743 * so that e.g. sync can proceed. They'll be restarted
744 * after the other works are all done.
746 if ((work
->for_background
|| work
->for_kupdate
) &&
747 !list_empty(&wb
->bdi
->work_list
))
751 * For background writeout, stop when we are below the
752 * background dirty threshold
754 if (work
->for_background
&& !over_bground_thresh(wb
->bdi
))
757 if (work
->for_kupdate
) {
758 oldest_jif
= jiffies
-
759 msecs_to_jiffies(dirty_expire_interval
* 10);
760 work
->older_than_this
= &oldest_jif
;
763 trace_writeback_start(wb
->bdi
, work
);
764 if (list_empty(&wb
->b_io
))
767 progress
= writeback_sb_inodes(work
->sb
, wb
, work
);
769 progress
= __writeback_inodes_wb(wb
, work
);
770 trace_writeback_written(wb
->bdi
, work
);
772 wb_update_bandwidth(wb
, wb_start
);
775 * Did we write something? Try for more
777 * Dirty inodes are moved to b_io for writeback in batches.
778 * The completion of the current batch does not necessarily
779 * mean the overall work is done. So we keep looping as long
780 * as made some progress on cleaning pages or inodes.
785 * No more inodes for IO, bail
787 if (list_empty(&wb
->b_more_io
))
790 * Nothing written. Wait for some inode to
791 * become available for writeback. Otherwise
792 * we'll just busyloop.
794 if (!list_empty(&wb
->b_more_io
)) {
795 trace_writeback_wait(wb
->bdi
, work
);
796 inode
= wb_inode(wb
->b_more_io
.prev
);
797 spin_lock(&inode
->i_lock
);
798 inode_wait_for_writeback(inode
, wb
);
799 spin_unlock(&inode
->i_lock
);
802 spin_unlock(&wb
->list_lock
);
804 return nr_pages
- work
->nr_pages
;
808 * Return the next wb_writeback_work struct that hasn't been processed yet.
810 static struct wb_writeback_work
*
811 get_next_work_item(struct backing_dev_info
*bdi
)
813 struct wb_writeback_work
*work
= NULL
;
815 spin_lock_bh(&bdi
->wb_lock
);
816 if (!list_empty(&bdi
->work_list
)) {
817 work
= list_entry(bdi
->work_list
.next
,
818 struct wb_writeback_work
, list
);
819 list_del_init(&work
->list
);
821 spin_unlock_bh(&bdi
->wb_lock
);
826 * Add in the number of potentially dirty inodes, because each inode
827 * write can dirty pagecache in the underlying blockdev.
829 static unsigned long get_nr_dirty_pages(void)
831 return global_page_state(NR_FILE_DIRTY
) +
832 global_page_state(NR_UNSTABLE_NFS
) +
833 get_nr_dirty_inodes();
836 static long wb_check_background_flush(struct bdi_writeback
*wb
)
838 if (over_bground_thresh(wb
->bdi
)) {
840 struct wb_writeback_work work
= {
841 .nr_pages
= LONG_MAX
,
842 .sync_mode
= WB_SYNC_NONE
,
845 .reason
= WB_REASON_BACKGROUND
,
848 return wb_writeback(wb
, &work
);
854 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
856 unsigned long expired
;
860 * When set to zero, disable periodic writeback
862 if (!dirty_writeback_interval
)
865 expired
= wb
->last_old_flush
+
866 msecs_to_jiffies(dirty_writeback_interval
* 10);
867 if (time_before(jiffies
, expired
))
870 wb
->last_old_flush
= jiffies
;
871 nr_pages
= get_nr_dirty_pages();
874 struct wb_writeback_work work
= {
875 .nr_pages
= nr_pages
,
876 .sync_mode
= WB_SYNC_NONE
,
879 .reason
= WB_REASON_PERIODIC
,
882 return wb_writeback(wb
, &work
);
889 * Retrieve work items and do the writeback they describe
891 long wb_do_writeback(struct bdi_writeback
*wb
, int force_wait
)
893 struct backing_dev_info
*bdi
= wb
->bdi
;
894 struct wb_writeback_work
*work
;
897 set_bit(BDI_writeback_running
, &wb
->bdi
->state
);
898 while ((work
= get_next_work_item(bdi
)) != NULL
) {
900 * Override sync mode, in case we must wait for completion
901 * because this thread is exiting now.
904 work
->sync_mode
= WB_SYNC_ALL
;
906 trace_writeback_exec(bdi
, work
);
908 wrote
+= wb_writeback(wb
, work
);
911 * Notify the caller of completion if this is a synchronous
912 * work item, otherwise just free it.
915 complete(work
->done
);
921 * Check for periodic writeback, kupdated() style
923 wrote
+= wb_check_old_data_flush(wb
);
924 wrote
+= wb_check_background_flush(wb
);
925 clear_bit(BDI_writeback_running
, &wb
->bdi
->state
);
931 * Handle writeback of dirty data for the device backed by this bdi. Also
932 * wakes up periodically and does kupdated style flushing.
934 int bdi_writeback_thread(void *data
)
936 struct bdi_writeback
*wb
= data
;
937 struct backing_dev_info
*bdi
= wb
->bdi
;
940 current
->flags
|= PF_SWAPWRITE
;
942 wb
->last_active
= jiffies
;
945 * Our parent may run at a different priority, just set us to normal
947 set_user_nice(current
, 0);
949 trace_writeback_thread_start(bdi
);
951 while (!kthread_freezable_should_stop(NULL
)) {
953 * Remove own delayed wake-up timer, since we are already awake
954 * and we'll take care of the preriodic write-back.
956 del_timer(&wb
->wakeup_timer
);
958 pages_written
= wb_do_writeback(wb
, 0);
960 trace_writeback_pages_written(pages_written
);
963 wb
->last_active
= jiffies
;
965 set_current_state(TASK_INTERRUPTIBLE
);
966 if (!list_empty(&bdi
->work_list
) || kthread_should_stop()) {
967 __set_current_state(TASK_RUNNING
);
971 if (wb_has_dirty_io(wb
) && dirty_writeback_interval
)
972 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval
* 10));
975 * We have nothing to do, so can go sleep without any
976 * timeout and save power. When a work is queued or
977 * something is made dirty - we will be woken up.
983 /* Flush any work that raced with us exiting */
984 if (!list_empty(&bdi
->work_list
))
985 wb_do_writeback(wb
, 1);
987 trace_writeback_thread_stop(bdi
);
993 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
996 void wakeup_flusher_threads(long nr_pages
, enum wb_reason reason
)
998 struct backing_dev_info
*bdi
;
1001 nr_pages
= global_page_state(NR_FILE_DIRTY
) +
1002 global_page_state(NR_UNSTABLE_NFS
);
1006 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
1007 if (!bdi_has_dirty_io(bdi
))
1009 __bdi_start_writeback(bdi
, nr_pages
, false, reason
);
1014 static noinline
void block_dump___mark_inode_dirty(struct inode
*inode
)
1016 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev")) {
1017 struct dentry
*dentry
;
1018 const char *name
= "?";
1020 dentry
= d_find_alias(inode
);
1022 spin_lock(&dentry
->d_lock
);
1023 name
= (const char *) dentry
->d_name
.name
;
1026 "%s(%d): dirtied inode %lu (%s) on %s\n",
1027 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
1028 name
, inode
->i_sb
->s_id
);
1030 spin_unlock(&dentry
->d_lock
);
1037 * __mark_inode_dirty - internal function
1038 * @inode: inode to mark
1039 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1040 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1041 * mark_inode_dirty_sync.
1043 * Put the inode on the super block's dirty list.
1045 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1046 * dirty list only if it is hashed or if it refers to a blockdev.
1047 * If it was not hashed, it will never be added to the dirty list
1048 * even if it is later hashed, as it will have been marked dirty already.
1050 * In short, make sure you hash any inodes _before_ you start marking
1053 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1054 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1055 * the kernel-internal blockdev inode represents the dirtying time of the
1056 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1057 * page->mapping->host, so the page-dirtying time is recorded in the internal
1060 void __mark_inode_dirty(struct inode
*inode
, int flags
)
1062 struct super_block
*sb
= inode
->i_sb
;
1063 struct backing_dev_info
*bdi
= NULL
;
1066 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1067 * dirty the inode itself
1069 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
1070 if (sb
->s_op
->dirty_inode
)
1071 sb
->s_op
->dirty_inode(inode
, flags
);
1075 * make sure that changes are seen by all cpus before we test i_state
1080 /* avoid the locking if we can */
1081 if ((inode
->i_state
& flags
) == flags
)
1084 if (unlikely(block_dump
))
1085 block_dump___mark_inode_dirty(inode
);
1087 spin_lock(&inode
->i_lock
);
1088 if ((inode
->i_state
& flags
) != flags
) {
1089 const int was_dirty
= inode
->i_state
& I_DIRTY
;
1091 inode
->i_state
|= flags
;
1094 * If the inode is being synced, just update its dirty state.
1095 * The unlocker will place the inode on the appropriate
1096 * superblock list, based upon its state.
1098 if (inode
->i_state
& I_SYNC
)
1099 goto out_unlock_inode
;
1102 * Only add valid (hashed) inodes to the superblock's
1103 * dirty list. Add blockdev inodes as well.
1105 if (!S_ISBLK(inode
->i_mode
)) {
1106 if (inode_unhashed(inode
))
1107 goto out_unlock_inode
;
1109 if (inode
->i_state
& I_FREEING
)
1110 goto out_unlock_inode
;
1113 * If the inode was already on b_dirty/b_io/b_more_io, don't
1114 * reposition it (that would break b_dirty time-ordering).
1117 bool wakeup_bdi
= false;
1118 bdi
= inode_to_bdi(inode
);
1120 if (bdi_cap_writeback_dirty(bdi
)) {
1121 WARN(!test_bit(BDI_registered
, &bdi
->state
),
1122 "bdi-%s not registered\n", bdi
->name
);
1125 * If this is the first dirty inode for this
1126 * bdi, we have to wake-up the corresponding
1127 * bdi thread to make sure background
1128 * write-back happens later.
1130 if (!wb_has_dirty_io(&bdi
->wb
))
1134 spin_unlock(&inode
->i_lock
);
1135 spin_lock(&bdi
->wb
.list_lock
);
1136 inode
->dirtied_when
= jiffies
;
1137 list_move(&inode
->i_wb_list
, &bdi
->wb
.b_dirty
);
1138 spin_unlock(&bdi
->wb
.list_lock
);
1141 bdi_wakeup_thread_delayed(bdi
);
1146 spin_unlock(&inode
->i_lock
);
1149 EXPORT_SYMBOL(__mark_inode_dirty
);
1152 * Write out a superblock's list of dirty inodes. A wait will be performed
1153 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1155 * If older_than_this is non-NULL, then only write out inodes which
1156 * had their first dirtying at a time earlier than *older_than_this.
1158 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1159 * This function assumes that the blockdev superblock's inodes are backed by
1160 * a variety of queues, so all inodes are searched. For other superblocks,
1161 * assume that all inodes are backed by the same queue.
1163 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1164 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1165 * on the writer throttling path, and we get decent balancing between many
1166 * throttled threads: we don't want them all piling up on inode_sync_wait.
1168 static void wait_sb_inodes(struct super_block
*sb
)
1170 struct inode
*inode
, *old_inode
= NULL
;
1173 * We need to be protected against the filesystem going from
1174 * r/o to r/w or vice versa.
1176 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1178 spin_lock(&inode_sb_list_lock
);
1181 * Data integrity sync. Must wait for all pages under writeback,
1182 * because there may have been pages dirtied before our sync
1183 * call, but which had writeout started before we write it out.
1184 * In which case, the inode may not be on the dirty list, but
1185 * we still have to wait for that writeout.
1187 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
1188 struct address_space
*mapping
= inode
->i_mapping
;
1190 spin_lock(&inode
->i_lock
);
1191 if ((inode
->i_state
& (I_FREEING
|I_WILL_FREE
|I_NEW
)) ||
1192 (mapping
->nrpages
== 0)) {
1193 spin_unlock(&inode
->i_lock
);
1197 spin_unlock(&inode
->i_lock
);
1198 spin_unlock(&inode_sb_list_lock
);
1201 * We hold a reference to 'inode' so it couldn't have been
1202 * removed from s_inodes list while we dropped the
1203 * inode_sb_list_lock. We cannot iput the inode now as we can
1204 * be holding the last reference and we cannot iput it under
1205 * inode_sb_list_lock. So we keep the reference and iput it
1211 filemap_fdatawait(mapping
);
1215 spin_lock(&inode_sb_list_lock
);
1217 spin_unlock(&inode_sb_list_lock
);
1222 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1223 * @sb: the superblock
1224 * @nr: the number of pages to write
1225 * @reason: reason why some writeback work initiated
1227 * Start writeback on some inodes on this super_block. No guarantees are made
1228 * on how many (if any) will be written, and this function does not wait
1229 * for IO completion of submitted IO.
1231 void writeback_inodes_sb_nr(struct super_block
*sb
,
1233 enum wb_reason reason
)
1235 DECLARE_COMPLETION_ONSTACK(done
);
1236 struct wb_writeback_work work
= {
1238 .sync_mode
= WB_SYNC_NONE
,
1239 .tagged_writepages
= 1,
1245 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1246 bdi_queue_work(sb
->s_bdi
, &work
);
1247 wait_for_completion(&done
);
1249 EXPORT_SYMBOL(writeback_inodes_sb_nr
);
1252 * writeback_inodes_sb - writeback dirty inodes from given super_block
1253 * @sb: the superblock
1254 * @reason: reason why some writeback work was initiated
1256 * Start writeback on some inodes on this super_block. No guarantees are made
1257 * on how many (if any) will be written, and this function does not wait
1258 * for IO completion of submitted IO.
1260 void writeback_inodes_sb(struct super_block
*sb
, enum wb_reason reason
)
1262 return writeback_inodes_sb_nr(sb
, get_nr_dirty_pages(), reason
);
1264 EXPORT_SYMBOL(writeback_inodes_sb
);
1267 * writeback_inodes_sb_if_idle - start writeback if none underway
1268 * @sb: the superblock
1269 * @reason: reason why some writeback work was initiated
1271 * Invoke writeback_inodes_sb if no writeback is currently underway.
1272 * Returns 1 if writeback was started, 0 if not.
1274 int writeback_inodes_sb_if_idle(struct super_block
*sb
, enum wb_reason reason
)
1276 if (!writeback_in_progress(sb
->s_bdi
)) {
1277 down_read(&sb
->s_umount
);
1278 writeback_inodes_sb(sb
, reason
);
1279 up_read(&sb
->s_umount
);
1284 EXPORT_SYMBOL(writeback_inodes_sb_if_idle
);
1287 * writeback_inodes_sb_if_idle - start writeback if none underway
1288 * @sb: the superblock
1289 * @nr: the number of pages to write
1290 * @reason: reason why some writeback work was initiated
1292 * Invoke writeback_inodes_sb if no writeback is currently underway.
1293 * Returns 1 if writeback was started, 0 if not.
1295 int writeback_inodes_sb_nr_if_idle(struct super_block
*sb
,
1297 enum wb_reason reason
)
1299 if (!writeback_in_progress(sb
->s_bdi
)) {
1300 down_read(&sb
->s_umount
);
1301 writeback_inodes_sb_nr(sb
, nr
, reason
);
1302 up_read(&sb
->s_umount
);
1307 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle
);
1310 * sync_inodes_sb - sync sb inode pages
1311 * @sb: the superblock
1313 * This function writes and waits on any dirty inode belonging to this
1316 void sync_inodes_sb(struct super_block
*sb
)
1318 DECLARE_COMPLETION_ONSTACK(done
);
1319 struct wb_writeback_work work
= {
1321 .sync_mode
= WB_SYNC_ALL
,
1322 .nr_pages
= LONG_MAX
,
1325 .reason
= WB_REASON_SYNC
,
1328 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1330 bdi_queue_work(sb
->s_bdi
, &work
);
1331 wait_for_completion(&done
);
1335 EXPORT_SYMBOL(sync_inodes_sb
);
1338 * write_inode_now - write an inode to disk
1339 * @inode: inode to write to disk
1340 * @sync: whether the write should be synchronous or not
1342 * This function commits an inode to disk immediately if it is dirty. This is
1343 * primarily needed by knfsd.
1345 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1347 int write_inode_now(struct inode
*inode
, int sync
)
1349 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
1351 struct writeback_control wbc
= {
1352 .nr_to_write
= LONG_MAX
,
1353 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1355 .range_end
= LLONG_MAX
,
1358 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
1359 wbc
.nr_to_write
= 0;
1362 spin_lock(&wb
->list_lock
);
1363 spin_lock(&inode
->i_lock
);
1364 ret
= writeback_single_inode(inode
, wb
, &wbc
);
1365 spin_unlock(&inode
->i_lock
);
1366 spin_unlock(&wb
->list_lock
);
1368 inode_sync_wait(inode
);
1371 EXPORT_SYMBOL(write_inode_now
);
1374 * sync_inode - write an inode and its pages to disk.
1375 * @inode: the inode to sync
1376 * @wbc: controls the writeback mode
1378 * sync_inode() will write an inode and its pages to disk. It will also
1379 * correctly update the inode on its superblock's dirty inode lists and will
1380 * update inode->i_state.
1382 * The caller must have a ref on the inode.
1384 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1386 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
1389 spin_lock(&wb
->list_lock
);
1390 spin_lock(&inode
->i_lock
);
1391 ret
= writeback_single_inode(inode
, wb
, wbc
);
1392 spin_unlock(&inode
->i_lock
);
1393 spin_unlock(&wb
->list_lock
);
1396 EXPORT_SYMBOL(sync_inode
);
1399 * sync_inode_metadata - write an inode to disk
1400 * @inode: the inode to sync
1401 * @wait: wait for I/O to complete.
1403 * Write an inode to disk and adjust its dirty state after completion.
1405 * Note: only writes the actual inode, no associated data or other metadata.
1407 int sync_inode_metadata(struct inode
*inode
, int wait
)
1409 struct writeback_control wbc
= {
1410 .sync_mode
= wait
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1411 .nr_to_write
= 0, /* metadata-only */
1414 return sync_inode(inode
, &wbc
);
1416 EXPORT_SYMBOL(sync_inode_metadata
);