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 * @sb: write inodes from this super_block
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 static 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 */
663 void writeback_inodes_wbc(struct writeback_control
*wbc
)
665 struct backing_dev_info
*bdi
= wbc
->bdi
;
667 writeback_inodes_wb(&bdi
->wb
, wbc
);
671 * The maximum number of pages to writeout in a single bdi flush/kupdate
672 * operation. We do this so we don't hold I_SYNC against an inode for
673 * enormous amounts of time, which would block a userspace task which has
674 * been forced to throttle against that inode. Also, the code reevaluates
675 * the dirty each time it has written this many pages.
677 #define MAX_WRITEBACK_PAGES 1024
679 static inline bool over_bground_thresh(void)
681 unsigned long background_thresh
, dirty_thresh
;
683 get_dirty_limits(&background_thresh
, &dirty_thresh
, NULL
, NULL
);
685 return (global_page_state(NR_FILE_DIRTY
) +
686 global_page_state(NR_UNSTABLE_NFS
) >= background_thresh
);
690 * Explicit flushing or periodic writeback of "old" data.
692 * Define "old": the first time one of an inode's pages is dirtied, we mark the
693 * dirtying-time in the inode's address_space. So this periodic writeback code
694 * just walks the superblock inode list, writing back any inodes which are
695 * older than a specific point in time.
697 * Try to run once per dirty_writeback_interval. But if a writeback event
698 * takes longer than a dirty_writeback_interval interval, then leave a
701 * older_than_this takes precedence over nr_to_write. So we'll only write back
702 * all dirty pages if they are all attached to "old" mappings.
704 static long wb_writeback(struct bdi_writeback
*wb
,
705 struct wb_writeback_args
*args
)
707 struct writeback_control wbc
= {
710 .sync_mode
= args
->sync_mode
,
711 .older_than_this
= NULL
,
712 .for_kupdate
= args
->for_kupdate
,
713 .for_background
= args
->for_background
,
714 .range_cyclic
= args
->range_cyclic
,
716 unsigned long oldest_jif
;
720 if (wbc
.for_kupdate
) {
721 wbc
.older_than_this
= &oldest_jif
;
722 oldest_jif
= jiffies
-
723 msecs_to_jiffies(dirty_expire_interval
* 10);
725 if (!wbc
.range_cyclic
) {
727 wbc
.range_end
= LLONG_MAX
;
732 * Stop writeback when nr_pages has been consumed
734 if (args
->nr_pages
<= 0)
738 * For background writeout, stop when we are below the
739 * background dirty threshold
741 if (args
->for_background
&& !over_bground_thresh())
745 wbc
.nr_to_write
= MAX_WRITEBACK_PAGES
;
746 wbc
.pages_skipped
= 0;
747 writeback_inodes_wb(wb
, &wbc
);
748 args
->nr_pages
-= MAX_WRITEBACK_PAGES
- wbc
.nr_to_write
;
749 wrote
+= MAX_WRITEBACK_PAGES
- wbc
.nr_to_write
;
752 * If we consumed everything, see if we have more
754 if (wbc
.nr_to_write
<= 0)
757 * Didn't write everything and we don't have more IO, bail
762 * Did we write something? Try for more
764 if (wbc
.nr_to_write
< MAX_WRITEBACK_PAGES
)
767 * Nothing written. Wait for some inode to
768 * become available for writeback. Otherwise
769 * we'll just busyloop.
771 spin_lock(&inode_lock
);
772 if (!list_empty(&wb
->b_more_io
)) {
773 inode
= list_entry(wb
->b_more_io
.prev
,
774 struct inode
, i_list
);
775 inode_wait_for_writeback(inode
);
777 spin_unlock(&inode_lock
);
784 * Return the next bdi_work struct that hasn't been processed by this
785 * wb thread yet. ->seen is initially set for each thread that exists
786 * for this device, when a thread first notices a piece of work it
787 * clears its bit. Depending on writeback type, the thread will notify
788 * completion on either receiving the work (WB_SYNC_NONE) or after
789 * it is done (WB_SYNC_ALL).
791 static struct bdi_work
*get_next_work_item(struct backing_dev_info
*bdi
,
792 struct bdi_writeback
*wb
)
794 struct bdi_work
*work
, *ret
= NULL
;
798 list_for_each_entry_rcu(work
, &bdi
->work_list
, list
) {
799 if (!test_bit(wb
->nr
, &work
->seen
))
801 clear_bit(wb
->nr
, &work
->seen
);
811 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
813 unsigned long expired
;
817 * When set to zero, disable periodic writeback
819 if (!dirty_writeback_interval
)
822 expired
= wb
->last_old_flush
+
823 msecs_to_jiffies(dirty_writeback_interval
* 10);
824 if (time_before(jiffies
, expired
))
827 wb
->last_old_flush
= jiffies
;
828 nr_pages
= global_page_state(NR_FILE_DIRTY
) +
829 global_page_state(NR_UNSTABLE_NFS
) +
830 (inodes_stat
.nr_inodes
- inodes_stat
.nr_unused
);
833 struct wb_writeback_args args
= {
834 .nr_pages
= nr_pages
,
835 .sync_mode
= WB_SYNC_NONE
,
840 return wb_writeback(wb
, &args
);
847 * Retrieve work items and do the writeback they describe
849 long wb_do_writeback(struct bdi_writeback
*wb
, int force_wait
)
851 struct backing_dev_info
*bdi
= wb
->bdi
;
852 struct bdi_work
*work
;
855 while ((work
= get_next_work_item(bdi
, wb
)) != NULL
) {
856 struct wb_writeback_args args
= work
->args
;
859 * Override sync mode, in case we must wait for completion
862 work
->args
.sync_mode
= args
.sync_mode
= WB_SYNC_ALL
;
865 * If this isn't a data integrity operation, just notify
866 * that we have seen this work and we are now starting it.
868 if (!test_bit(WS_ONSTACK
, &work
->state
))
869 wb_clear_pending(wb
, work
);
871 wrote
+= wb_writeback(wb
, &args
);
874 * This is a data integrity writeback, so only do the
875 * notification when we have completed the work.
877 if (test_bit(WS_ONSTACK
, &work
->state
))
878 wb_clear_pending(wb
, work
);
882 * Check for periodic writeback, kupdated() style
884 wrote
+= wb_check_old_data_flush(wb
);
890 * Handle writeback of dirty data for the device backed by this bdi. Also
891 * wakes up periodically and does kupdated style flushing.
893 int bdi_writeback_task(struct bdi_writeback
*wb
)
895 unsigned long last_active
= jiffies
;
896 unsigned long wait_jiffies
= -1UL;
899 while (!kthread_should_stop()) {
900 pages_written
= wb_do_writeback(wb
, 0);
903 last_active
= jiffies
;
904 else if (wait_jiffies
!= -1UL) {
905 unsigned long max_idle
;
908 * Longest period of inactivity that we tolerate. If we
909 * see dirty data again later, the task will get
910 * recreated automatically.
912 max_idle
= max(5UL * 60 * HZ
, wait_jiffies
);
913 if (time_after(jiffies
, max_idle
+ last_active
))
917 if (dirty_writeback_interval
) {
918 wait_jiffies
= msecs_to_jiffies(dirty_writeback_interval
* 10);
919 schedule_timeout_interruptible(wait_jiffies
);
921 set_current_state(TASK_INTERRUPTIBLE
);
922 if (list_empty_careful(&wb
->bdi
->work_list
) &&
923 !kthread_should_stop())
925 __set_current_state(TASK_RUNNING
);
935 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
938 void wakeup_flusher_threads(long nr_pages
)
940 struct backing_dev_info
*bdi
;
941 struct wb_writeback_args args
= {
942 .sync_mode
= WB_SYNC_NONE
,
946 args
.nr_pages
= nr_pages
;
948 args
.nr_pages
= global_page_state(NR_FILE_DIRTY
) +
949 global_page_state(NR_UNSTABLE_NFS
);
953 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
954 if (!bdi_has_dirty_io(bdi
))
956 bdi_alloc_queue_work(bdi
, &args
);
961 static noinline
void block_dump___mark_inode_dirty(struct inode
*inode
)
963 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev")) {
964 struct dentry
*dentry
;
965 const char *name
= "?";
967 dentry
= d_find_alias(inode
);
969 spin_lock(&dentry
->d_lock
);
970 name
= (const char *) dentry
->d_name
.name
;
973 "%s(%d): dirtied inode %lu (%s) on %s\n",
974 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
975 name
, inode
->i_sb
->s_id
);
977 spin_unlock(&dentry
->d_lock
);
984 * __mark_inode_dirty - internal function
985 * @inode: inode to mark
986 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
987 * Mark an inode as dirty. Callers should use mark_inode_dirty or
988 * mark_inode_dirty_sync.
990 * Put the inode on the super block's dirty list.
992 * CAREFUL! We mark it dirty unconditionally, but move it onto the
993 * dirty list only if it is hashed or if it refers to a blockdev.
994 * If it was not hashed, it will never be added to the dirty list
995 * even if it is later hashed, as it will have been marked dirty already.
997 * In short, make sure you hash any inodes _before_ you start marking
1000 * This function *must* be atomic for the I_DIRTY_PAGES case -
1001 * set_page_dirty() is called under spinlock in several places.
1003 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1004 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1005 * the kernel-internal blockdev inode represents the dirtying time of the
1006 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1007 * page->mapping->host, so the page-dirtying time is recorded in the internal
1010 void __mark_inode_dirty(struct inode
*inode
, int flags
)
1012 struct super_block
*sb
= inode
->i_sb
;
1015 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1016 * dirty the inode itself
1018 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
1019 if (sb
->s_op
->dirty_inode
)
1020 sb
->s_op
->dirty_inode(inode
);
1024 * make sure that changes are seen by all cpus before we test i_state
1029 /* avoid the locking if we can */
1030 if ((inode
->i_state
& flags
) == flags
)
1033 if (unlikely(block_dump
))
1034 block_dump___mark_inode_dirty(inode
);
1036 spin_lock(&inode_lock
);
1037 if ((inode
->i_state
& flags
) != flags
) {
1038 const int was_dirty
= inode
->i_state
& I_DIRTY
;
1040 inode
->i_state
|= flags
;
1043 * If the inode is being synced, just update its dirty state.
1044 * The unlocker will place the inode on the appropriate
1045 * superblock list, based upon its state.
1047 if (inode
->i_state
& I_SYNC
)
1051 * Only add valid (hashed) inodes to the superblock's
1052 * dirty list. Add blockdev inodes as well.
1054 if (!S_ISBLK(inode
->i_mode
)) {
1055 if (hlist_unhashed(&inode
->i_hash
))
1058 if (inode
->i_state
& (I_FREEING
|I_CLEAR
))
1062 * If the inode was already on b_dirty/b_io/b_more_io, don't
1063 * reposition it (that would break b_dirty time-ordering).
1066 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
1067 struct backing_dev_info
*bdi
= wb
->bdi
;
1069 if (bdi_cap_writeback_dirty(bdi
) &&
1070 !test_bit(BDI_registered
, &bdi
->state
)) {
1072 printk(KERN_ERR
"bdi-%s not registered\n",
1076 inode
->dirtied_when
= jiffies
;
1077 list_move(&inode
->i_list
, &wb
->b_dirty
);
1081 spin_unlock(&inode_lock
);
1083 EXPORT_SYMBOL(__mark_inode_dirty
);
1086 * Write out a superblock's list of dirty inodes. A wait will be performed
1087 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1089 * If older_than_this is non-NULL, then only write out inodes which
1090 * had their first dirtying at a time earlier than *older_than_this.
1092 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1093 * This function assumes that the blockdev superblock's inodes are backed by
1094 * a variety of queues, so all inodes are searched. For other superblocks,
1095 * assume that all inodes are backed by the same queue.
1097 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1098 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1099 * on the writer throttling path, and we get decent balancing between many
1100 * throttled threads: we don't want them all piling up on inode_sync_wait.
1102 static void wait_sb_inodes(struct super_block
*sb
)
1104 struct inode
*inode
, *old_inode
= NULL
;
1107 * We need to be protected against the filesystem going from
1108 * r/o to r/w or vice versa.
1110 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1112 spin_lock(&inode_lock
);
1115 * Data integrity sync. Must wait for all pages under writeback,
1116 * because there may have been pages dirtied before our sync
1117 * call, but which had writeout started before we write it out.
1118 * In which case, the inode may not be on the dirty list, but
1119 * we still have to wait for that writeout.
1121 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
1122 struct address_space
*mapping
;
1124 if (inode
->i_state
& (I_FREEING
|I_CLEAR
|I_WILL_FREE
|I_NEW
))
1126 mapping
= inode
->i_mapping
;
1127 if (mapping
->nrpages
== 0)
1130 spin_unlock(&inode_lock
);
1132 * We hold a reference to 'inode' so it couldn't have
1133 * been removed from s_inodes list while we dropped the
1134 * inode_lock. We cannot iput the inode now as we can
1135 * be holding the last reference and we cannot iput it
1136 * under inode_lock. So we keep the reference and iput
1142 filemap_fdatawait(mapping
);
1146 spin_lock(&inode_lock
);
1148 spin_unlock(&inode_lock
);
1153 * writeback_inodes_sb - writeback dirty inodes from given super_block
1154 * @sb: the superblock
1156 * Start writeback on some inodes on this super_block. No guarantees are made
1157 * on how many (if any) will be written, and this function does not wait
1158 * for IO completion of submitted IO. The number of pages submitted is
1161 void writeback_inodes_sb(struct super_block
*sb
)
1163 unsigned long nr_dirty
= global_page_state(NR_FILE_DIRTY
);
1164 unsigned long nr_unstable
= global_page_state(NR_UNSTABLE_NFS
);
1165 struct wb_writeback_args args
= {
1167 .sync_mode
= WB_SYNC_NONE
,
1170 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1172 args
.nr_pages
= nr_dirty
+ nr_unstable
+
1173 (inodes_stat
.nr_inodes
- inodes_stat
.nr_unused
);
1175 bdi_queue_work_onstack(&args
);
1177 EXPORT_SYMBOL(writeback_inodes_sb
);
1180 * writeback_inodes_sb_if_idle - start writeback if none underway
1181 * @sb: the superblock
1183 * Invoke writeback_inodes_sb if no writeback is currently underway.
1184 * Returns 1 if writeback was started, 0 if not.
1186 int writeback_inodes_sb_if_idle(struct super_block
*sb
)
1188 if (!writeback_in_progress(sb
->s_bdi
)) {
1189 down_read(&sb
->s_umount
);
1190 writeback_inodes_sb(sb
);
1191 up_read(&sb
->s_umount
);
1196 EXPORT_SYMBOL(writeback_inodes_sb_if_idle
);
1199 * sync_inodes_sb - sync sb inode pages
1200 * @sb: the superblock
1202 * This function writes and waits on any dirty inode belonging to this
1203 * super_block. The number of pages synced is returned.
1205 void sync_inodes_sb(struct super_block
*sb
)
1207 struct wb_writeback_args args
= {
1209 .sync_mode
= WB_SYNC_ALL
,
1210 .nr_pages
= LONG_MAX
,
1214 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1216 bdi_queue_work_onstack(&args
);
1219 EXPORT_SYMBOL(sync_inodes_sb
);
1222 * write_inode_now - write an inode to disk
1223 * @inode: inode to write to disk
1224 * @sync: whether the write should be synchronous or not
1226 * This function commits an inode to disk immediately if it is dirty. This is
1227 * primarily needed by knfsd.
1229 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1231 int write_inode_now(struct inode
*inode
, int sync
)
1234 struct writeback_control wbc
= {
1235 .nr_to_write
= LONG_MAX
,
1236 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1238 .range_end
= LLONG_MAX
,
1241 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
1242 wbc
.nr_to_write
= 0;
1245 spin_lock(&inode_lock
);
1246 ret
= writeback_single_inode(inode
, &wbc
);
1247 spin_unlock(&inode_lock
);
1249 inode_sync_wait(inode
);
1252 EXPORT_SYMBOL(write_inode_now
);
1255 * sync_inode - write an inode and its pages to disk.
1256 * @inode: the inode to sync
1257 * @wbc: controls the writeback mode
1259 * sync_inode() will write an inode and its pages to disk. It will also
1260 * correctly update the inode on its superblock's dirty inode lists and will
1261 * update inode->i_state.
1263 * The caller must have a ref on the inode.
1265 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1269 spin_lock(&inode_lock
);
1270 ret
= writeback_single_inode(inode
, wbc
);
1271 spin_unlock(&inode_lock
);
1274 EXPORT_SYMBOL(sync_inode
);