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>
31 #define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
34 * We don't actually have pdflush, but this one is exported though /proc...
36 int nr_pdflush_threads
;
39 * Passed into wb_writeback(), essentially a subset of writeback_control
41 struct wb_writeback_args
{
43 struct super_block
*sb
;
44 enum writeback_sync_modes sync_mode
;
45 unsigned int for_kupdate
:1;
46 unsigned int range_cyclic
:1;
47 unsigned int for_background
:1;
51 * Work items for the bdi_writeback threads
54 struct list_head list
; /* pending work list */
55 struct rcu_head rcu_head
; /* for RCU free/clear of work */
57 unsigned long seen
; /* threads that have seen this work */
58 atomic_t pending
; /* number of threads still to do work */
60 struct wb_writeback_args args
; /* writeback arguments */
62 unsigned long state
; /* flag bits, see WS_* */
70 static inline void bdi_work_init(struct bdi_work
*work
,
71 struct wb_writeback_args
*args
)
73 INIT_RCU_HEAD(&work
->rcu_head
);
75 __set_bit(WS_INPROGRESS
, &work
->state
);
79 * writeback_in_progress - determine whether there is writeback in progress
80 * @bdi: the device's backing_dev_info structure.
82 * Determine whether there is writeback waiting to be handled against a
85 int writeback_in_progress(struct backing_dev_info
*bdi
)
87 return !list_empty(&bdi
->work_list
);
90 static void bdi_work_free(struct rcu_head
*head
)
92 struct bdi_work
*work
= container_of(head
, struct bdi_work
, rcu_head
);
94 clear_bit(WS_INPROGRESS
, &work
->state
);
95 smp_mb__after_clear_bit();
96 wake_up_bit(&work
->state
, WS_INPROGRESS
);
98 if (!test_bit(WS_ONSTACK
, &work
->state
))
102 static void wb_clear_pending(struct bdi_writeback
*wb
, struct bdi_work
*work
)
105 * The caller has retrieved the work arguments from this work,
106 * drop our reference. If this is the last ref, delete and free it
108 if (atomic_dec_and_test(&work
->pending
)) {
109 struct backing_dev_info
*bdi
= wb
->bdi
;
111 spin_lock(&bdi
->wb_lock
);
112 list_del_rcu(&work
->list
);
113 spin_unlock(&bdi
->wb_lock
);
115 call_rcu(&work
->rcu_head
, bdi_work_free
);
119 static void bdi_queue_work(struct backing_dev_info
*bdi
, struct bdi_work
*work
)
121 work
->seen
= bdi
->wb_mask
;
123 atomic_set(&work
->pending
, bdi
->wb_cnt
);
124 BUG_ON(!bdi
->wb_cnt
);
127 * list_add_tail_rcu() contains the necessary barriers to
128 * make sure the above stores are seen before the item is
129 * noticed on the list
131 spin_lock(&bdi
->wb_lock
);
132 list_add_tail_rcu(&work
->list
, &bdi
->work_list
);
133 spin_unlock(&bdi
->wb_lock
);
136 * If the default thread isn't there, make sure we add it. When
137 * it gets created and wakes up, we'll run this work.
139 if (unlikely(list_empty_careful(&bdi
->wb_list
)))
140 wake_up_process(default_backing_dev_info
.wb
.task
);
142 struct bdi_writeback
*wb
= &bdi
->wb
;
145 wake_up_process(wb
->task
);
150 * Used for on-stack allocated work items. The caller needs to wait until
151 * the wb threads have acked the work before it's safe to continue.
153 static void bdi_wait_on_work_done(struct bdi_work
*work
)
155 wait_on_bit(&work
->state
, WS_INPROGRESS
, bdi_sched_wait
,
156 TASK_UNINTERRUPTIBLE
);
159 static void bdi_alloc_queue_work(struct backing_dev_info
*bdi
,
160 struct wb_writeback_args
*args
)
162 struct bdi_work
*work
;
165 * This is WB_SYNC_NONE writeback, so if allocation fails just
166 * wakeup the thread for old dirty data writeback
168 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
170 bdi_work_init(work
, args
);
171 bdi_queue_work(bdi
, work
);
173 struct bdi_writeback
*wb
= &bdi
->wb
;
176 wake_up_process(wb
->task
);
181 * bdi_queue_work_onstack - start and wait for writeback
182 * @args: parameters to control the work queue writeback
185 * This function initiates writeback and waits for the operation to
186 * complete. Callers must hold the sb s_umount semaphore for
187 * reading, to avoid having the super disappear before we are done.
189 static void bdi_queue_work_onstack(struct wb_writeback_args
*args
)
191 struct bdi_work work
;
193 bdi_work_init(&work
, args
);
194 __set_bit(WS_ONSTACK
, &work
.state
);
196 bdi_queue_work(args
->sb
->s_bdi
, &work
);
197 bdi_wait_on_work_done(&work
);
201 * bdi_start_writeback - start writeback
202 * @bdi: the backing device to write from
203 * @nr_pages: the number of pages to write
206 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
207 * started when this function returns, we make no guarentees on
208 * completion. Caller need not hold sb s_umount semaphore.
211 void bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
)
213 struct wb_writeback_args args
= {
214 .sync_mode
= WB_SYNC_NONE
,
215 .nr_pages
= nr_pages
,
219 bdi_alloc_queue_work(bdi
, &args
);
223 * bdi_start_background_writeback - start background writeback
224 * @bdi: the backing device to write from
227 * This does WB_SYNC_NONE background writeback. The IO is only
228 * started when this function returns, we make no guarentees on
229 * completion. Caller need not hold sb s_umount semaphore.
231 void bdi_start_background_writeback(struct backing_dev_info
*bdi
)
233 struct wb_writeback_args args
= {
234 .sync_mode
= WB_SYNC_NONE
,
235 .nr_pages
= LONG_MAX
,
239 bdi_alloc_queue_work(bdi
, &args
);
243 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
244 * furthest end of its superblock's dirty-inode list.
246 * Before stamping the inode's ->dirtied_when, we check to see whether it is
247 * already the most-recently-dirtied inode on the b_dirty list. If that is
248 * the case then the inode must have been redirtied while it was being written
249 * out and we don't reset its dirtied_when.
251 static void redirty_tail(struct inode
*inode
)
253 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
255 if (!list_empty(&wb
->b_dirty
)) {
258 tail
= list_entry(wb
->b_dirty
.next
, struct inode
, i_list
);
259 if (time_before(inode
->dirtied_when
, tail
->dirtied_when
))
260 inode
->dirtied_when
= jiffies
;
262 list_move(&inode
->i_list
, &wb
->b_dirty
);
266 * requeue inode for re-scanning after bdi->b_io list is exhausted.
268 static void requeue_io(struct inode
*inode
)
270 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
272 list_move(&inode
->i_list
, &wb
->b_more_io
);
275 static void inode_sync_complete(struct inode
*inode
)
278 * Prevent speculative execution through spin_unlock(&inode_lock);
281 wake_up_bit(&inode
->i_state
, __I_SYNC
);
284 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
286 bool ret
= time_after(inode
->dirtied_when
, t
);
289 * For inodes being constantly redirtied, dirtied_when can get stuck.
290 * It _appears_ to be in the future, but is actually in distant past.
291 * This test is necessary to prevent such wrapped-around relative times
292 * from permanently stopping the whole bdi writeback.
294 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
300 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
302 static void move_expired_inodes(struct list_head
*delaying_queue
,
303 struct list_head
*dispatch_queue
,
304 unsigned long *older_than_this
)
307 struct list_head
*pos
, *node
;
308 struct super_block
*sb
= NULL
;
312 while (!list_empty(delaying_queue
)) {
313 inode
= list_entry(delaying_queue
->prev
, struct inode
, i_list
);
314 if (older_than_this
&&
315 inode_dirtied_after(inode
, *older_than_this
))
317 if (sb
&& sb
!= inode
->i_sb
)
320 list_move(&inode
->i_list
, &tmp
);
323 /* just one sb in list, splice to dispatch_queue and we're done */
325 list_splice(&tmp
, dispatch_queue
);
329 /* Move inodes from one superblock together */
330 while (!list_empty(&tmp
)) {
331 inode
= list_entry(tmp
.prev
, struct inode
, i_list
);
333 list_for_each_prev_safe(pos
, node
, &tmp
) {
334 inode
= list_entry(pos
, struct inode
, i_list
);
335 if (inode
->i_sb
== sb
)
336 list_move(&inode
->i_list
, dispatch_queue
);
342 * Queue all expired dirty inodes for io, eldest first.
344 static void queue_io(struct bdi_writeback
*wb
, unsigned long *older_than_this
)
346 list_splice_init(&wb
->b_more_io
, wb
->b_io
.prev
);
347 move_expired_inodes(&wb
->b_dirty
, &wb
->b_io
, older_than_this
);
350 static int write_inode(struct inode
*inode
, struct writeback_control
*wbc
)
352 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
))
353 return inode
->i_sb
->s_op
->write_inode(inode
, wbc
);
358 * Wait for writeback on an inode to complete.
360 static void inode_wait_for_writeback(struct inode
*inode
)
362 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
363 wait_queue_head_t
*wqh
;
365 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
366 while (inode
->i_state
& I_SYNC
) {
367 spin_unlock(&inode_lock
);
368 __wait_on_bit(wqh
, &wq
, inode_wait
, TASK_UNINTERRUPTIBLE
);
369 spin_lock(&inode_lock
);
374 * Write out an inode's dirty pages. Called under inode_lock. Either the
375 * caller has ref on the inode (either via __iget or via syscall against an fd)
376 * or the inode has I_WILL_FREE set (via generic_forget_inode)
378 * If `wait' is set, wait on the writeout.
380 * The whole writeout design is quite complex and fragile. We want to avoid
381 * starvation of particular inodes when others are being redirtied, prevent
384 * Called under inode_lock.
387 writeback_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
389 struct address_space
*mapping
= inode
->i_mapping
;
393 if (!atomic_read(&inode
->i_count
))
394 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
396 WARN_ON(inode
->i_state
& I_WILL_FREE
);
398 if (inode
->i_state
& I_SYNC
) {
400 * If this inode is locked for writeback and we are not doing
401 * writeback-for-data-integrity, move it to b_more_io so that
402 * writeback can proceed with the other inodes on s_io.
404 * We'll have another go at writing back this inode when we
405 * completed a full scan of b_io.
407 if (wbc
->sync_mode
!= WB_SYNC_ALL
) {
413 * It's a data-integrity sync. We must wait.
415 inode_wait_for_writeback(inode
);
418 BUG_ON(inode
->i_state
& I_SYNC
);
420 /* Set I_SYNC, reset I_DIRTY_PAGES */
421 inode
->i_state
|= I_SYNC
;
422 inode
->i_state
&= ~I_DIRTY_PAGES
;
423 spin_unlock(&inode_lock
);
425 ret
= do_writepages(mapping
, wbc
);
428 * Make sure to wait on the data before writing out the metadata.
429 * This is important for filesystems that modify metadata on data
432 if (wbc
->sync_mode
== WB_SYNC_ALL
) {
433 int err
= filemap_fdatawait(mapping
);
439 * Some filesystems may redirty the inode during the writeback
440 * due to delalloc, clear dirty metadata flags right before
443 spin_lock(&inode_lock
);
444 dirty
= inode
->i_state
& I_DIRTY
;
445 inode
->i_state
&= ~(I_DIRTY_SYNC
| I_DIRTY_DATASYNC
);
446 spin_unlock(&inode_lock
);
447 /* Don't write the inode if only I_DIRTY_PAGES was set */
448 if (dirty
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
449 int err
= write_inode(inode
, wbc
);
454 spin_lock(&inode_lock
);
455 inode
->i_state
&= ~I_SYNC
;
456 if (!(inode
->i_state
& (I_FREEING
| I_CLEAR
))) {
457 if ((inode
->i_state
& I_DIRTY_PAGES
) && wbc
->for_kupdate
) {
459 * More pages get dirtied by a fast dirtier.
462 } else if (inode
->i_state
& I_DIRTY
) {
464 * At least XFS will redirty the inode during the
465 * writeback (delalloc) and on io completion (isize).
468 } else if (mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
)) {
470 * We didn't write back all the pages. nfs_writepages()
471 * sometimes bales out without doing anything. Redirty
472 * the inode; Move it from b_io onto b_more_io/b_dirty.
475 * akpm: if the caller was the kupdate function we put
476 * this inode at the head of b_dirty so it gets first
477 * consideration. Otherwise, move it to the tail, for
478 * the reasons described there. I'm not really sure
479 * how much sense this makes. Presumably I had a good
480 * reasons for doing it this way, and I'd rather not
481 * muck with it at present.
483 if (wbc
->for_kupdate
) {
485 * For the kupdate function we move the inode
486 * to b_more_io so it will get more writeout as
487 * soon as the queue becomes uncongested.
489 inode
->i_state
|= I_DIRTY_PAGES
;
491 if (wbc
->nr_to_write
<= 0) {
493 * slice used up: queue for next turn
498 * somehow blocked: retry later
504 * Otherwise fully redirty the inode so that
505 * other inodes on this superblock will get some
506 * writeout. Otherwise heavy writing to one
507 * file would indefinitely suspend writeout of
508 * all the other files.
510 inode
->i_state
|= I_DIRTY_PAGES
;
513 } else if (atomic_read(&inode
->i_count
)) {
515 * The inode is clean, inuse
517 list_move(&inode
->i_list
, &inode_in_use
);
520 * The inode is clean, unused
522 list_move(&inode
->i_list
, &inode_unused
);
525 inode_sync_complete(inode
);
530 * For background writeback the caller does not have the sb pinned
531 * before calling writeback. So make sure that we do pin it, so it doesn't
532 * go away while we are writing inodes from it.
534 static bool pin_sb_for_writeback(struct super_block
*sb
)
537 if (list_empty(&sb
->s_instances
)) {
538 spin_unlock(&sb_lock
);
543 spin_unlock(&sb_lock
);
545 if (down_read_trylock(&sb
->s_umount
)) {
548 up_read(&sb
->s_umount
);
556 * Write a portion of b_io inodes which belong to @sb.
557 * If @wbc->sb != NULL, then find and write all such
558 * inodes. Otherwise write only ones which go sequentially
560 * Return 1, if the caller writeback routine should be
561 * interrupted. Otherwise return 0.
563 static int writeback_sb_inodes(struct super_block
*sb
,
564 struct bdi_writeback
*wb
,
565 struct writeback_control
*wbc
)
567 while (!list_empty(&wb
->b_io
)) {
569 struct inode
*inode
= list_entry(wb
->b_io
.prev
,
570 struct inode
, i_list
);
571 if (wbc
->sb
&& sb
!= inode
->i_sb
) {
572 /* super block given and doesn't
573 match, skip this inode */
577 if (sb
!= inode
->i_sb
)
578 /* finish with this superblock */
580 if (inode
->i_state
& (I_NEW
| I_WILL_FREE
)) {
585 * Was this inode dirtied after sync_sb_inodes was called?
586 * This keeps sync from extra jobs and livelock.
588 if (inode_dirtied_after(inode
, wbc
->wb_start
))
591 BUG_ON(inode
->i_state
& (I_FREEING
| I_CLEAR
));
593 pages_skipped
= wbc
->pages_skipped
;
594 writeback_single_inode(inode
, wbc
);
595 if (wbc
->pages_skipped
!= pages_skipped
) {
597 * writeback is not making progress due to locked
598 * buffers. Skip this inode for now.
602 spin_unlock(&inode_lock
);
605 spin_lock(&inode_lock
);
606 if (wbc
->nr_to_write
<= 0) {
610 if (!list_empty(&wb
->b_more_io
))
617 void writeback_inodes_wb(struct bdi_writeback
*wb
,
618 struct writeback_control
*wbc
)
622 wbc
->wb_start
= jiffies
; /* livelock avoidance */
623 spin_lock(&inode_lock
);
624 if (!wbc
->for_kupdate
|| list_empty(&wb
->b_io
))
625 queue_io(wb
, wbc
->older_than_this
);
627 while (!list_empty(&wb
->b_io
)) {
628 struct inode
*inode
= list_entry(wb
->b_io
.prev
,
629 struct inode
, i_list
);
630 struct super_block
*sb
= inode
->i_sb
;
634 * We are requested to write out inodes for a specific
635 * superblock. This means we already have s_umount
636 * taken by the caller which also waits for us to
637 * complete the writeout.
644 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
646 ret
= writeback_sb_inodes(sb
, wb
, wbc
);
648 if (!pin_sb_for_writeback(sb
)) {
652 ret
= writeback_sb_inodes(sb
, wb
, wbc
);
659 spin_unlock(&inode_lock
);
660 /* Leave any unwritten inodes on b_io */
664 * The maximum number of pages to writeout in a single bdi flush/kupdate
665 * operation. We do this so we don't hold I_SYNC against an inode for
666 * enormous amounts of time, which would block a userspace task which has
667 * been forced to throttle against that inode. Also, the code reevaluates
668 * the dirty each time it has written this many pages.
670 #define MAX_WRITEBACK_PAGES 1024
672 static inline bool over_bground_thresh(void)
674 unsigned long background_thresh
, dirty_thresh
;
676 get_dirty_limits(&background_thresh
, &dirty_thresh
, NULL
, NULL
);
678 return (global_page_state(NR_FILE_DIRTY
) +
679 global_page_state(NR_UNSTABLE_NFS
) >= background_thresh
);
683 * Explicit flushing or periodic writeback of "old" data.
685 * Define "old": the first time one of an inode's pages is dirtied, we mark the
686 * dirtying-time in the inode's address_space. So this periodic writeback code
687 * just walks the superblock inode list, writing back any inodes which are
688 * older than a specific point in time.
690 * Try to run once per dirty_writeback_interval. But if a writeback event
691 * takes longer than a dirty_writeback_interval interval, then leave a
694 * older_than_this takes precedence over nr_to_write. So we'll only write back
695 * all dirty pages if they are all attached to "old" mappings.
697 static long wb_writeback(struct bdi_writeback
*wb
,
698 struct wb_writeback_args
*args
)
700 struct writeback_control wbc
= {
702 .sync_mode
= args
->sync_mode
,
703 .older_than_this
= NULL
,
704 .for_kupdate
= args
->for_kupdate
,
705 .for_background
= args
->for_background
,
706 .range_cyclic
= args
->range_cyclic
,
708 unsigned long oldest_jif
;
712 if (wbc
.for_kupdate
) {
713 wbc
.older_than_this
= &oldest_jif
;
714 oldest_jif
= jiffies
-
715 msecs_to_jiffies(dirty_expire_interval
* 10);
717 if (!wbc
.range_cyclic
) {
719 wbc
.range_end
= LLONG_MAX
;
724 * Stop writeback when nr_pages has been consumed
726 if (args
->nr_pages
<= 0)
730 * For background writeout, stop when we are below the
731 * background dirty threshold
733 if (args
->for_background
&& !over_bground_thresh())
737 wbc
.nr_to_write
= MAX_WRITEBACK_PAGES
;
738 wbc
.pages_skipped
= 0;
739 writeback_inodes_wb(wb
, &wbc
);
740 args
->nr_pages
-= MAX_WRITEBACK_PAGES
- wbc
.nr_to_write
;
741 wrote
+= MAX_WRITEBACK_PAGES
- wbc
.nr_to_write
;
744 * If we consumed everything, see if we have more
746 if (wbc
.nr_to_write
<= 0)
749 * Didn't write everything and we don't have more IO, bail
754 * Did we write something? Try for more
756 if (wbc
.nr_to_write
< MAX_WRITEBACK_PAGES
)
759 * Nothing written. Wait for some inode to
760 * become available for writeback. Otherwise
761 * we'll just busyloop.
763 spin_lock(&inode_lock
);
764 if (!list_empty(&wb
->b_more_io
)) {
765 inode
= list_entry(wb
->b_more_io
.prev
,
766 struct inode
, i_list
);
767 inode_wait_for_writeback(inode
);
769 spin_unlock(&inode_lock
);
776 * Return the next bdi_work struct that hasn't been processed by this
777 * wb thread yet. ->seen is initially set for each thread that exists
778 * for this device, when a thread first notices a piece of work it
779 * clears its bit. Depending on writeback type, the thread will notify
780 * completion on either receiving the work (WB_SYNC_NONE) or after
781 * it is done (WB_SYNC_ALL).
783 static struct bdi_work
*get_next_work_item(struct backing_dev_info
*bdi
,
784 struct bdi_writeback
*wb
)
786 struct bdi_work
*work
, *ret
= NULL
;
790 list_for_each_entry_rcu(work
, &bdi
->work_list
, list
) {
791 if (!test_bit(wb
->nr
, &work
->seen
))
793 clear_bit(wb
->nr
, &work
->seen
);
803 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
805 unsigned long expired
;
809 * When set to zero, disable periodic writeback
811 if (!dirty_writeback_interval
)
814 expired
= wb
->last_old_flush
+
815 msecs_to_jiffies(dirty_writeback_interval
* 10);
816 if (time_before(jiffies
, expired
))
819 wb
->last_old_flush
= jiffies
;
820 nr_pages
= global_page_state(NR_FILE_DIRTY
) +
821 global_page_state(NR_UNSTABLE_NFS
) +
822 (inodes_stat
.nr_inodes
- inodes_stat
.nr_unused
);
825 struct wb_writeback_args args
= {
826 .nr_pages
= nr_pages
,
827 .sync_mode
= WB_SYNC_NONE
,
832 return wb_writeback(wb
, &args
);
839 * Retrieve work items and do the writeback they describe
841 long wb_do_writeback(struct bdi_writeback
*wb
, int force_wait
)
843 struct backing_dev_info
*bdi
= wb
->bdi
;
844 struct bdi_work
*work
;
847 while ((work
= get_next_work_item(bdi
, wb
)) != NULL
) {
848 struct wb_writeback_args args
= work
->args
;
851 * Override sync mode, in case we must wait for completion
854 work
->args
.sync_mode
= args
.sync_mode
= WB_SYNC_ALL
;
857 * If this isn't a data integrity operation, just notify
858 * that we have seen this work and we are now starting it.
860 if (!test_bit(WS_ONSTACK
, &work
->state
))
861 wb_clear_pending(wb
, work
);
863 wrote
+= wb_writeback(wb
, &args
);
866 * This is a data integrity writeback, so only do the
867 * notification when we have completed the work.
869 if (test_bit(WS_ONSTACK
, &work
->state
))
870 wb_clear_pending(wb
, work
);
874 * Check for periodic writeback, kupdated() style
876 wrote
+= wb_check_old_data_flush(wb
);
882 * Handle writeback of dirty data for the device backed by this bdi. Also
883 * wakes up periodically and does kupdated style flushing.
885 int bdi_writeback_task(struct bdi_writeback
*wb
)
887 unsigned long last_active
= jiffies
;
888 unsigned long wait_jiffies
= -1UL;
891 while (!kthread_should_stop()) {
892 pages_written
= wb_do_writeback(wb
, 0);
895 last_active
= jiffies
;
896 else if (wait_jiffies
!= -1UL) {
897 unsigned long max_idle
;
900 * Longest period of inactivity that we tolerate. If we
901 * see dirty data again later, the task will get
902 * recreated automatically.
904 max_idle
= max(5UL * 60 * HZ
, wait_jiffies
);
905 if (time_after(jiffies
, max_idle
+ last_active
))
909 if (dirty_writeback_interval
) {
910 wait_jiffies
= msecs_to_jiffies(dirty_writeback_interval
* 10);
911 schedule_timeout_interruptible(wait_jiffies
);
913 set_current_state(TASK_INTERRUPTIBLE
);
914 if (list_empty_careful(&wb
->bdi
->work_list
) &&
915 !kthread_should_stop())
917 __set_current_state(TASK_RUNNING
);
927 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
930 void wakeup_flusher_threads(long nr_pages
)
932 struct backing_dev_info
*bdi
;
933 struct wb_writeback_args args
= {
934 .sync_mode
= WB_SYNC_NONE
,
938 args
.nr_pages
= nr_pages
;
940 args
.nr_pages
= global_page_state(NR_FILE_DIRTY
) +
941 global_page_state(NR_UNSTABLE_NFS
);
945 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
946 if (!bdi_has_dirty_io(bdi
))
948 bdi_alloc_queue_work(bdi
, &args
);
953 static noinline
void block_dump___mark_inode_dirty(struct inode
*inode
)
955 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev")) {
956 struct dentry
*dentry
;
957 const char *name
= "?";
959 dentry
= d_find_alias(inode
);
961 spin_lock(&dentry
->d_lock
);
962 name
= (const char *) dentry
->d_name
.name
;
965 "%s(%d): dirtied inode %lu (%s) on %s\n",
966 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
967 name
, inode
->i_sb
->s_id
);
969 spin_unlock(&dentry
->d_lock
);
976 * __mark_inode_dirty - internal function
977 * @inode: inode to mark
978 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
979 * Mark an inode as dirty. Callers should use mark_inode_dirty or
980 * mark_inode_dirty_sync.
982 * Put the inode on the super block's dirty list.
984 * CAREFUL! We mark it dirty unconditionally, but move it onto the
985 * dirty list only if it is hashed or if it refers to a blockdev.
986 * If it was not hashed, it will never be added to the dirty list
987 * even if it is later hashed, as it will have been marked dirty already.
989 * In short, make sure you hash any inodes _before_ you start marking
992 * This function *must* be atomic for the I_DIRTY_PAGES case -
993 * set_page_dirty() is called under spinlock in several places.
995 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
996 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
997 * the kernel-internal blockdev inode represents the dirtying time of the
998 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
999 * page->mapping->host, so the page-dirtying time is recorded in the internal
1002 void __mark_inode_dirty(struct inode
*inode
, int flags
)
1004 struct super_block
*sb
= inode
->i_sb
;
1007 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1008 * dirty the inode itself
1010 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
1011 if (sb
->s_op
->dirty_inode
)
1012 sb
->s_op
->dirty_inode(inode
);
1016 * make sure that changes are seen by all cpus before we test i_state
1021 /* avoid the locking if we can */
1022 if ((inode
->i_state
& flags
) == flags
)
1025 if (unlikely(block_dump
))
1026 block_dump___mark_inode_dirty(inode
);
1028 spin_lock(&inode_lock
);
1029 if ((inode
->i_state
& flags
) != flags
) {
1030 const int was_dirty
= inode
->i_state
& I_DIRTY
;
1032 inode
->i_state
|= flags
;
1035 * If the inode is being synced, just update its dirty state.
1036 * The unlocker will place the inode on the appropriate
1037 * superblock list, based upon its state.
1039 if (inode
->i_state
& I_SYNC
)
1043 * Only add valid (hashed) inodes to the superblock's
1044 * dirty list. Add blockdev inodes as well.
1046 if (!S_ISBLK(inode
->i_mode
)) {
1047 if (hlist_unhashed(&inode
->i_hash
))
1050 if (inode
->i_state
& (I_FREEING
|I_CLEAR
))
1054 * If the inode was already on b_dirty/b_io/b_more_io, don't
1055 * reposition it (that would break b_dirty time-ordering).
1058 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
1059 struct backing_dev_info
*bdi
= wb
->bdi
;
1061 if (bdi_cap_writeback_dirty(bdi
) &&
1062 !test_bit(BDI_registered
, &bdi
->state
)) {
1064 printk(KERN_ERR
"bdi-%s not registered\n",
1068 inode
->dirtied_when
= jiffies
;
1069 list_move(&inode
->i_list
, &wb
->b_dirty
);
1073 spin_unlock(&inode_lock
);
1075 EXPORT_SYMBOL(__mark_inode_dirty
);
1078 * Write out a superblock's list of dirty inodes. A wait will be performed
1079 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1081 * If older_than_this is non-NULL, then only write out inodes which
1082 * had their first dirtying at a time earlier than *older_than_this.
1084 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1085 * This function assumes that the blockdev superblock's inodes are backed by
1086 * a variety of queues, so all inodes are searched. For other superblocks,
1087 * assume that all inodes are backed by the same queue.
1089 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1090 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1091 * on the writer throttling path, and we get decent balancing between many
1092 * throttled threads: we don't want them all piling up on inode_sync_wait.
1094 static void wait_sb_inodes(struct super_block
*sb
)
1096 struct inode
*inode
, *old_inode
= NULL
;
1099 * We need to be protected against the filesystem going from
1100 * r/o to r/w or vice versa.
1102 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1104 spin_lock(&inode_lock
);
1107 * Data integrity sync. Must wait for all pages under writeback,
1108 * because there may have been pages dirtied before our sync
1109 * call, but which had writeout started before we write it out.
1110 * In which case, the inode may not be on the dirty list, but
1111 * we still have to wait for that writeout.
1113 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
1114 struct address_space
*mapping
;
1116 if (inode
->i_state
& (I_FREEING
|I_CLEAR
|I_WILL_FREE
|I_NEW
))
1118 mapping
= inode
->i_mapping
;
1119 if (mapping
->nrpages
== 0)
1122 spin_unlock(&inode_lock
);
1124 * We hold a reference to 'inode' so it couldn't have
1125 * been removed from s_inodes list while we dropped the
1126 * inode_lock. We cannot iput the inode now as we can
1127 * be holding the last reference and we cannot iput it
1128 * under inode_lock. So we keep the reference and iput
1134 filemap_fdatawait(mapping
);
1138 spin_lock(&inode_lock
);
1140 spin_unlock(&inode_lock
);
1145 * writeback_inodes_sb - writeback dirty inodes from given super_block
1146 * @sb: the superblock
1148 * Start writeback on some inodes on this super_block. No guarantees are made
1149 * on how many (if any) will be written, and this function does not wait
1150 * for IO completion of submitted IO. The number of pages submitted is
1153 void writeback_inodes_sb(struct super_block
*sb
)
1155 unsigned long nr_dirty
= global_page_state(NR_FILE_DIRTY
);
1156 unsigned long nr_unstable
= global_page_state(NR_UNSTABLE_NFS
);
1157 struct wb_writeback_args args
= {
1159 .sync_mode
= WB_SYNC_NONE
,
1162 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1164 args
.nr_pages
= nr_dirty
+ nr_unstable
+
1165 (inodes_stat
.nr_inodes
- inodes_stat
.nr_unused
);
1167 bdi_queue_work_onstack(&args
);
1169 EXPORT_SYMBOL(writeback_inodes_sb
);
1172 * writeback_inodes_sb_if_idle - start writeback if none underway
1173 * @sb: the superblock
1175 * Invoke writeback_inodes_sb if no writeback is currently underway.
1176 * Returns 1 if writeback was started, 0 if not.
1178 int writeback_inodes_sb_if_idle(struct super_block
*sb
)
1180 if (!writeback_in_progress(sb
->s_bdi
)) {
1181 down_read(&sb
->s_umount
);
1182 writeback_inodes_sb(sb
);
1183 up_read(&sb
->s_umount
);
1188 EXPORT_SYMBOL(writeback_inodes_sb_if_idle
);
1191 * sync_inodes_sb - sync sb inode pages
1192 * @sb: the superblock
1194 * This function writes and waits on any dirty inode belonging to this
1195 * super_block. The number of pages synced is returned.
1197 void sync_inodes_sb(struct super_block
*sb
)
1199 struct wb_writeback_args args
= {
1201 .sync_mode
= WB_SYNC_ALL
,
1202 .nr_pages
= LONG_MAX
,
1206 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1208 bdi_queue_work_onstack(&args
);
1211 EXPORT_SYMBOL(sync_inodes_sb
);
1214 * write_inode_now - write an inode to disk
1215 * @inode: inode to write to disk
1216 * @sync: whether the write should be synchronous or not
1218 * This function commits an inode to disk immediately if it is dirty. This is
1219 * primarily needed by knfsd.
1221 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1223 int write_inode_now(struct inode
*inode
, int sync
)
1226 struct writeback_control wbc
= {
1227 .nr_to_write
= LONG_MAX
,
1228 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1230 .range_end
= LLONG_MAX
,
1233 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
1234 wbc
.nr_to_write
= 0;
1237 spin_lock(&inode_lock
);
1238 ret
= writeback_single_inode(inode
, &wbc
);
1239 spin_unlock(&inode_lock
);
1241 inode_sync_wait(inode
);
1244 EXPORT_SYMBOL(write_inode_now
);
1247 * sync_inode - write an inode and its pages to disk.
1248 * @inode: the inode to sync
1249 * @wbc: controls the writeback mode
1251 * sync_inode() will write an inode and its pages to disk. It will also
1252 * correctly update the inode on its superblock's dirty inode lists and will
1253 * update inode->i_state.
1255 * The caller must have a ref on the inode.
1257 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1261 spin_lock(&inode_lock
);
1262 ret
= writeback_single_inode(inode
, wbc
);
1263 spin_unlock(&inode_lock
);
1266 EXPORT_SYMBOL(sync_inode
);