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/sched.h>
22 #include <linux/kthread.h>
23 #include <linux/freezer.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/backing-dev.h>
27 #include <linux/buffer_head.h>
30 #define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
33 * We don't actually have pdflush, but this one is exported though /proc...
35 int nr_pdflush_threads
;
38 * Passed into wb_writeback(), essentially a subset of writeback_control
40 struct wb_writeback_args
{
42 struct super_block
*sb
;
43 enum writeback_sync_modes sync_mode
;
50 * Work items for the bdi_writeback threads
53 struct list_head list
; /* pending work list */
54 struct rcu_head rcu_head
; /* for RCU free/clear of work */
56 unsigned long seen
; /* threads that have seen this work */
57 atomic_t pending
; /* number of threads still to do work */
59 struct wb_writeback_args args
; /* writeback arguments */
61 unsigned long state
; /* flag bits, see WS_* */
69 #define WS_USED (1 << WS_USED_B)
70 #define WS_ONSTACK (1 << WS_ONSTACK_B)
72 static inline bool bdi_work_on_stack(struct bdi_work
*work
)
74 return test_bit(WS_ONSTACK_B
, &work
->state
);
77 static inline void bdi_work_init(struct bdi_work
*work
,
78 struct wb_writeback_args
*args
)
80 INIT_RCU_HEAD(&work
->rcu_head
);
82 work
->state
= WS_USED
;
86 * writeback_in_progress - determine whether there is writeback in progress
87 * @bdi: the device's backing_dev_info structure.
89 * Determine whether there is writeback waiting to be handled against a
92 int writeback_in_progress(struct backing_dev_info
*bdi
)
94 return !list_empty(&bdi
->work_list
);
97 static void bdi_work_clear(struct bdi_work
*work
)
99 clear_bit(WS_USED_B
, &work
->state
);
100 smp_mb__after_clear_bit();
102 * work can have disappeared at this point. bit waitq functions
103 * should be able to tolerate this, provided bdi_sched_wait does
104 * not dereference it's pointer argument.
106 wake_up_bit(&work
->state
, WS_USED_B
);
109 static void bdi_work_free(struct rcu_head
*head
)
111 struct bdi_work
*work
= container_of(head
, struct bdi_work
, rcu_head
);
113 if (!bdi_work_on_stack(work
))
116 bdi_work_clear(work
);
119 static void wb_work_complete(struct bdi_work
*work
)
121 const enum writeback_sync_modes sync_mode
= work
->args
.sync_mode
;
122 int onstack
= bdi_work_on_stack(work
);
125 * For allocated work, we can clear the done/seen bit right here.
126 * For on-stack work, we need to postpone both the clear and free
127 * to after the RCU grace period, since the stack could be invalidated
128 * as soon as bdi_work_clear() has done the wakeup.
131 bdi_work_clear(work
);
132 if (sync_mode
== WB_SYNC_NONE
|| onstack
)
133 call_rcu(&work
->rcu_head
, bdi_work_free
);
136 static void wb_clear_pending(struct bdi_writeback
*wb
, struct bdi_work
*work
)
139 * The caller has retrieved the work arguments from this work,
140 * drop our reference. If this is the last ref, delete and free it
142 if (atomic_dec_and_test(&work
->pending
)) {
143 struct backing_dev_info
*bdi
= wb
->bdi
;
145 spin_lock(&bdi
->wb_lock
);
146 list_del_rcu(&work
->list
);
147 spin_unlock(&bdi
->wb_lock
);
149 wb_work_complete(work
);
153 static void bdi_queue_work(struct backing_dev_info
*bdi
, struct bdi_work
*work
)
155 work
->seen
= bdi
->wb_mask
;
157 atomic_set(&work
->pending
, bdi
->wb_cnt
);
158 BUG_ON(!bdi
->wb_cnt
);
161 * list_add_tail_rcu() contains the necessary barriers to
162 * make sure the above stores are seen before the item is
163 * noticed on the list
165 spin_lock(&bdi
->wb_lock
);
166 list_add_tail_rcu(&work
->list
, &bdi
->work_list
);
167 spin_unlock(&bdi
->wb_lock
);
170 * If the default thread isn't there, make sure we add it. When
171 * it gets created and wakes up, we'll run this work.
173 if (unlikely(list_empty_careful(&bdi
->wb_list
)))
174 wake_up_process(default_backing_dev_info
.wb
.task
);
176 struct bdi_writeback
*wb
= &bdi
->wb
;
179 wake_up_process(wb
->task
);
184 * Used for on-stack allocated work items. The caller needs to wait until
185 * the wb threads have acked the work before it's safe to continue.
187 static void bdi_wait_on_work_clear(struct bdi_work
*work
)
189 wait_on_bit(&work
->state
, WS_USED_B
, bdi_sched_wait
,
190 TASK_UNINTERRUPTIBLE
);
193 static void bdi_alloc_queue_work(struct backing_dev_info
*bdi
,
194 struct wb_writeback_args
*args
)
196 struct bdi_work
*work
;
199 * This is WB_SYNC_NONE writeback, so if allocation fails just
200 * wakeup the thread for old dirty data writeback
202 work
= kmalloc(sizeof(*work
), GFP_ATOMIC
);
204 bdi_work_init(work
, args
);
205 bdi_queue_work(bdi
, work
);
207 struct bdi_writeback
*wb
= &bdi
->wb
;
210 wake_up_process(wb
->task
);
215 * bdi_sync_writeback - start and wait for writeback
216 * @bdi: the backing device to write from
217 * @sb: write inodes from this super_block
220 * This does WB_SYNC_ALL data integrity writeback and waits for the
221 * IO to complete. Callers must hold the sb s_umount semaphore for
222 * reading, to avoid having the super disappear before we are done.
224 static void bdi_sync_writeback(struct backing_dev_info
*bdi
,
225 struct super_block
*sb
)
227 struct wb_writeback_args args
= {
229 .sync_mode
= WB_SYNC_ALL
,
230 .nr_pages
= LONG_MAX
,
233 struct bdi_work work
;
235 bdi_work_init(&work
, &args
);
236 work
.state
|= WS_ONSTACK
;
238 bdi_queue_work(bdi
, &work
);
239 bdi_wait_on_work_clear(&work
);
243 * bdi_start_writeback - start writeback
244 * @bdi: the backing device to write from
245 * @nr_pages: the number of pages to write
248 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
249 * started when this function returns, we make no guarentees on
250 * completion. Caller need not hold sb s_umount semaphore.
253 void bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
)
255 struct wb_writeback_args args
= {
256 .sync_mode
= WB_SYNC_NONE
,
257 .nr_pages
= nr_pages
,
262 * We treat @nr_pages=0 as the special case to do background writeback,
263 * ie. to sync pages until the background dirty threshold is reached.
266 args
.nr_pages
= LONG_MAX
;
267 args
.for_background
= 1;
270 bdi_alloc_queue_work(bdi
, &args
);
274 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
275 * furthest end of its superblock's dirty-inode list.
277 * Before stamping the inode's ->dirtied_when, we check to see whether it is
278 * already the most-recently-dirtied inode on the b_dirty list. If that is
279 * the case then the inode must have been redirtied while it was being written
280 * out and we don't reset its dirtied_when.
282 static void redirty_tail(struct inode
*inode
)
284 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
286 if (!list_empty(&wb
->b_dirty
)) {
289 tail
= list_entry(wb
->b_dirty
.next
, struct inode
, i_list
);
290 if (time_before(inode
->dirtied_when
, tail
->dirtied_when
))
291 inode
->dirtied_when
= jiffies
;
293 list_move(&inode
->i_list
, &wb
->b_dirty
);
297 * requeue inode for re-scanning after bdi->b_io list is exhausted.
299 static void requeue_io(struct inode
*inode
)
301 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
303 list_move(&inode
->i_list
, &wb
->b_more_io
);
306 static void inode_sync_complete(struct inode
*inode
)
309 * Prevent speculative execution through spin_unlock(&inode_lock);
312 wake_up_bit(&inode
->i_state
, __I_SYNC
);
315 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
317 bool ret
= time_after(inode
->dirtied_when
, t
);
320 * For inodes being constantly redirtied, dirtied_when can get stuck.
321 * It _appears_ to be in the future, but is actually in distant past.
322 * This test is necessary to prevent such wrapped-around relative times
323 * from permanently stopping the whole pdflush writeback.
325 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
331 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
333 static void move_expired_inodes(struct list_head
*delaying_queue
,
334 struct list_head
*dispatch_queue
,
335 unsigned long *older_than_this
)
337 while (!list_empty(delaying_queue
)) {
338 struct inode
*inode
= list_entry(delaying_queue
->prev
,
339 struct inode
, i_list
);
340 if (older_than_this
&&
341 inode_dirtied_after(inode
, *older_than_this
))
343 list_move(&inode
->i_list
, dispatch_queue
);
348 * Queue all expired dirty inodes for io, eldest first.
350 static void queue_io(struct bdi_writeback
*wb
, unsigned long *older_than_this
)
352 list_splice_init(&wb
->b_more_io
, wb
->b_io
.prev
);
353 move_expired_inodes(&wb
->b_dirty
, &wb
->b_io
, older_than_this
);
356 static int write_inode(struct inode
*inode
, int sync
)
358 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
))
359 return inode
->i_sb
->s_op
->write_inode(inode
, sync
);
364 * Wait for writeback on an inode to complete.
366 static void inode_wait_for_writeback(struct inode
*inode
)
368 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
369 wait_queue_head_t
*wqh
;
371 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
373 spin_unlock(&inode_lock
);
374 __wait_on_bit(wqh
, &wq
, inode_wait
, TASK_UNINTERRUPTIBLE
);
375 spin_lock(&inode_lock
);
376 } while (inode
->i_state
& I_SYNC
);
380 * Write out an inode's dirty pages. Called under inode_lock. Either the
381 * caller has ref on the inode (either via __iget or via syscall against an fd)
382 * or the inode has I_WILL_FREE set (via generic_forget_inode)
384 * If `wait' is set, wait on the writeout.
386 * The whole writeout design is quite complex and fragile. We want to avoid
387 * starvation of particular inodes when others are being redirtied, prevent
390 * Called under inode_lock.
393 writeback_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
395 struct address_space
*mapping
= inode
->i_mapping
;
396 int wait
= wbc
->sync_mode
== WB_SYNC_ALL
;
400 if (!atomic_read(&inode
->i_count
))
401 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
403 WARN_ON(inode
->i_state
& I_WILL_FREE
);
405 if (inode
->i_state
& I_SYNC
) {
407 * If this inode is locked for writeback and we are not doing
408 * writeback-for-data-integrity, move it to b_more_io so that
409 * writeback can proceed with the other inodes on s_io.
411 * We'll have another go at writing back this inode when we
412 * completed a full scan of b_io.
420 * It's a data-integrity sync. We must wait.
422 inode_wait_for_writeback(inode
);
425 BUG_ON(inode
->i_state
& I_SYNC
);
427 /* Set I_SYNC, reset I_DIRTY */
428 dirty
= inode
->i_state
& I_DIRTY
;
429 inode
->i_state
|= I_SYNC
;
430 inode
->i_state
&= ~I_DIRTY
;
432 spin_unlock(&inode_lock
);
434 ret
= do_writepages(mapping
, wbc
);
436 /* Don't write the inode if only I_DIRTY_PAGES was set */
437 if (dirty
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
438 int err
= write_inode(inode
, wait
);
444 int err
= filemap_fdatawait(mapping
);
449 spin_lock(&inode_lock
);
450 inode
->i_state
&= ~I_SYNC
;
451 if (!(inode
->i_state
& (I_FREEING
| I_CLEAR
))) {
452 if (inode
->i_state
& I_DIRTY
) {
454 * Someone redirtied the inode while were writing back
458 } else if (mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
)) {
460 * We didn't write back all the pages. nfs_writepages()
461 * sometimes bales out without doing anything. Redirty
462 * the inode; Move it from b_io onto b_more_io/b_dirty.
465 * akpm: if the caller was the kupdate function we put
466 * this inode at the head of b_dirty so it gets first
467 * consideration. Otherwise, move it to the tail, for
468 * the reasons described there. I'm not really sure
469 * how much sense this makes. Presumably I had a good
470 * reasons for doing it this way, and I'd rather not
471 * muck with it at present.
473 if (wbc
->for_kupdate
) {
475 * For the kupdate function we move the inode
476 * to b_more_io so it will get more writeout as
477 * soon as the queue becomes uncongested.
479 inode
->i_state
|= I_DIRTY_PAGES
;
480 if (wbc
->nr_to_write
<= 0) {
482 * slice used up: queue for next turn
487 * somehow blocked: retry later
493 * Otherwise fully redirty the inode so that
494 * other inodes on this superblock will get some
495 * writeout. Otherwise heavy writing to one
496 * file would indefinitely suspend writeout of
497 * all the other files.
499 inode
->i_state
|= I_DIRTY_PAGES
;
502 } else if (atomic_read(&inode
->i_count
)) {
504 * The inode is clean, inuse
506 list_move(&inode
->i_list
, &inode_in_use
);
509 * The inode is clean, unused
511 list_move(&inode
->i_list
, &inode_unused
);
514 inode_sync_complete(inode
);
519 * For WB_SYNC_NONE writeback, the caller does not have the sb pinned
520 * before calling writeback. So make sure that we do pin it, so it doesn't
521 * go away while we are writing inodes from it.
523 * Returns 0 if the super was successfully pinned (or pinning wasn't needed),
526 static int pin_sb_for_writeback(struct writeback_control
*wbc
,
529 struct super_block
*sb
= inode
->i_sb
;
532 * Caller must already hold the ref for this
534 if (wbc
->sync_mode
== WB_SYNC_ALL
) {
535 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
541 if (down_read_trylock(&sb
->s_umount
)) {
543 spin_unlock(&sb_lock
);
547 * umounted, drop rwsem again and fall through to failure
549 up_read(&sb
->s_umount
);
553 spin_unlock(&sb_lock
);
557 static void unpin_sb_for_writeback(struct writeback_control
*wbc
,
560 struct super_block
*sb
= inode
->i_sb
;
562 if (wbc
->sync_mode
== WB_SYNC_ALL
)
565 up_read(&sb
->s_umount
);
569 static void writeback_inodes_wb(struct bdi_writeback
*wb
,
570 struct writeback_control
*wbc
)
572 struct super_block
*sb
= wbc
->sb
;
573 const int is_blkdev_sb
= sb_is_blkdev_sb(sb
);
574 const unsigned long start
= jiffies
; /* livelock avoidance */
576 spin_lock(&inode_lock
);
578 if (!wbc
->for_kupdate
|| list_empty(&wb
->b_io
))
579 queue_io(wb
, wbc
->older_than_this
);
581 while (!list_empty(&wb
->b_io
)) {
582 struct inode
*inode
= list_entry(wb
->b_io
.prev
,
583 struct inode
, i_list
);
587 * super block given and doesn't match, skip this inode
589 if (sb
&& sb
!= inode
->i_sb
) {
594 if (!bdi_cap_writeback_dirty(wb
->bdi
)) {
598 * Dirty memory-backed blockdev: the ramdisk
599 * driver does this. Skip just this inode
604 * Dirty memory-backed inode against a filesystem other
605 * than the kernel-internal bdev filesystem. Skip the
611 if (inode
->i_state
& (I_NEW
| I_WILL_FREE
)) {
616 if (wbc
->nonblocking
&& bdi_write_congested(wb
->bdi
)) {
617 wbc
->encountered_congestion
= 1;
619 break; /* Skip a congested fs */
621 continue; /* Skip a congested blockdev */
625 * Was this inode dirtied after sync_sb_inodes was called?
626 * This keeps sync from extra jobs and livelock.
628 if (inode_dirtied_after(inode
, start
))
631 if (pin_sb_for_writeback(wbc
, inode
)) {
636 BUG_ON(inode
->i_state
& (I_FREEING
| I_CLEAR
));
638 pages_skipped
= wbc
->pages_skipped
;
639 writeback_single_inode(inode
, wbc
);
640 unpin_sb_for_writeback(wbc
, inode
);
641 if (wbc
->pages_skipped
!= pages_skipped
) {
643 * writeback is not making progress due to locked
644 * buffers. Skip this inode for now.
648 spin_unlock(&inode_lock
);
651 spin_lock(&inode_lock
);
652 if (wbc
->nr_to_write
<= 0) {
656 if (!list_empty(&wb
->b_more_io
))
660 spin_unlock(&inode_lock
);
661 /* Leave any unwritten inodes on b_io */
664 void writeback_inodes_wbc(struct writeback_control
*wbc
)
666 struct backing_dev_info
*bdi
= wbc
->bdi
;
668 writeback_inodes_wb(&bdi
->wb
, wbc
);
672 * The maximum number of pages to writeout in a single bdi flush/kupdate
673 * operation. We do this so we don't hold I_SYNC against an inode for
674 * enormous amounts of time, which would block a userspace task which has
675 * been forced to throttle against that inode. Also, the code reevaluates
676 * the dirty each time it has written this many pages.
678 #define MAX_WRITEBACK_PAGES 1024
680 static inline bool over_bground_thresh(void)
682 unsigned long background_thresh
, dirty_thresh
;
684 get_dirty_limits(&background_thresh
, &dirty_thresh
, NULL
, NULL
);
686 return (global_page_state(NR_FILE_DIRTY
) +
687 global_page_state(NR_UNSTABLE_NFS
) >= background_thresh
);
691 * Explicit flushing or periodic writeback of "old" data.
693 * Define "old": the first time one of an inode's pages is dirtied, we mark the
694 * dirtying-time in the inode's address_space. So this periodic writeback code
695 * just walks the superblock inode list, writing back any inodes which are
696 * older than a specific point in time.
698 * Try to run once per dirty_writeback_interval. But if a writeback event
699 * takes longer than a dirty_writeback_interval interval, then leave a
702 * older_than_this takes precedence over nr_to_write. So we'll only write back
703 * all dirty pages if they are all attached to "old" mappings.
705 static long wb_writeback(struct bdi_writeback
*wb
,
706 struct wb_writeback_args
*args
)
708 struct writeback_control wbc
= {
711 .sync_mode
= args
->sync_mode
,
712 .older_than_this
= NULL
,
713 .for_kupdate
= args
->for_kupdate
,
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
.encountered_congestion
= 0;
746 wbc
.nr_to_write
= MAX_WRITEBACK_PAGES
;
747 wbc
.pages_skipped
= 0;
748 writeback_inodes_wb(wb
, &wbc
);
749 args
->nr_pages
-= MAX_WRITEBACK_PAGES
- wbc
.nr_to_write
;
750 wrote
+= MAX_WRITEBACK_PAGES
- wbc
.nr_to_write
;
753 * If we ran out of stuff to write, bail unless more_io got set
755 if (wbc
.nr_to_write
> 0) {
757 if (wbc
.nr_to_write
< MAX_WRITEBACK_PAGES
)
760 * Nothing written. Wait for some inode to
761 * become available for writeback. Otherwise
762 * we'll just busyloop.
764 spin_lock(&inode_lock
);
765 if (!list_empty(&wb
->b_more_io
)) {
768 struct inode
, i_list
);
769 inode_wait_for_writeback(inode
);
771 spin_unlock(&inode_lock
);
782 * Return the next bdi_work struct that hasn't been processed by this
783 * wb thread yet. ->seen is initially set for each thread that exists
784 * for this device, when a thread first notices a piece of work it
785 * clears its bit. Depending on writeback type, the thread will notify
786 * completion on either receiving the work (WB_SYNC_NONE) or after
787 * it is done (WB_SYNC_ALL).
789 static struct bdi_work
*get_next_work_item(struct backing_dev_info
*bdi
,
790 struct bdi_writeback
*wb
)
792 struct bdi_work
*work
, *ret
= NULL
;
796 list_for_each_entry_rcu(work
, &bdi
->work_list
, list
) {
797 if (!test_bit(wb
->nr
, &work
->seen
))
799 clear_bit(wb
->nr
, &work
->seen
);
809 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
811 unsigned long expired
;
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 (args
.sync_mode
== WB_SYNC_NONE
)
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 (args
.sync_mode
== WB_SYNC_ALL
)
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 wait_jiffies
= msecs_to_jiffies(dirty_writeback_interval
* 10);
910 schedule_timeout_interruptible(wait_jiffies
);
918 * Schedule writeback for all backing devices. This does WB_SYNC_NONE
919 * writeback, for integrity writeback see bdi_sync_writeback().
921 static void bdi_writeback_all(struct super_block
*sb
, long nr_pages
)
923 struct wb_writeback_args args
= {
925 .nr_pages
= nr_pages
,
926 .sync_mode
= WB_SYNC_NONE
,
928 struct backing_dev_info
*bdi
;
932 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
933 if (!bdi_has_dirty_io(bdi
))
936 bdi_alloc_queue_work(bdi
, &args
);
943 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
946 void wakeup_flusher_threads(long nr_pages
)
949 nr_pages
= global_page_state(NR_FILE_DIRTY
) +
950 global_page_state(NR_UNSTABLE_NFS
);
951 bdi_writeback_all(NULL
, nr_pages
);
954 static noinline
void block_dump___mark_inode_dirty(struct inode
*inode
)
956 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev")) {
957 struct dentry
*dentry
;
958 const char *name
= "?";
960 dentry
= d_find_alias(inode
);
962 spin_lock(&dentry
->d_lock
);
963 name
= (const char *) dentry
->d_name
.name
;
966 "%s(%d): dirtied inode %lu (%s) on %s\n",
967 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
968 name
, inode
->i_sb
->s_id
);
970 spin_unlock(&dentry
->d_lock
);
977 * __mark_inode_dirty - internal function
978 * @inode: inode to mark
979 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
980 * Mark an inode as dirty. Callers should use mark_inode_dirty or
981 * mark_inode_dirty_sync.
983 * Put the inode on the super block's dirty list.
985 * CAREFUL! We mark it dirty unconditionally, but move it onto the
986 * dirty list only if it is hashed or if it refers to a blockdev.
987 * If it was not hashed, it will never be added to the dirty list
988 * even if it is later hashed, as it will have been marked dirty already.
990 * In short, make sure you hash any inodes _before_ you start marking
993 * This function *must* be atomic for the I_DIRTY_PAGES case -
994 * set_page_dirty() is called under spinlock in several places.
996 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
997 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
998 * the kernel-internal blockdev inode represents the dirtying time of the
999 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1000 * page->mapping->host, so the page-dirtying time is recorded in the internal
1003 void __mark_inode_dirty(struct inode
*inode
, int flags
)
1005 struct super_block
*sb
= inode
->i_sb
;
1008 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1009 * dirty the inode itself
1011 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
1012 if (sb
->s_op
->dirty_inode
)
1013 sb
->s_op
->dirty_inode(inode
);
1017 * make sure that changes are seen by all cpus before we test i_state
1022 /* avoid the locking if we can */
1023 if ((inode
->i_state
& flags
) == flags
)
1026 if (unlikely(block_dump
))
1027 block_dump___mark_inode_dirty(inode
);
1029 spin_lock(&inode_lock
);
1030 if ((inode
->i_state
& flags
) != flags
) {
1031 const int was_dirty
= inode
->i_state
& I_DIRTY
;
1033 inode
->i_state
|= flags
;
1036 * If the inode is being synced, just update its dirty state.
1037 * The unlocker will place the inode on the appropriate
1038 * superblock list, based upon its state.
1040 if (inode
->i_state
& I_SYNC
)
1044 * Only add valid (hashed) inodes to the superblock's
1045 * dirty list. Add blockdev inodes as well.
1047 if (!S_ISBLK(inode
->i_mode
)) {
1048 if (hlist_unhashed(&inode
->i_hash
))
1051 if (inode
->i_state
& (I_FREEING
|I_CLEAR
))
1055 * If the inode was already on b_dirty/b_io/b_more_io, don't
1056 * reposition it (that would break b_dirty time-ordering).
1059 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
1060 struct backing_dev_info
*bdi
= wb
->bdi
;
1062 if (bdi_cap_writeback_dirty(bdi
) &&
1063 !test_bit(BDI_registered
, &bdi
->state
)) {
1065 printk(KERN_ERR
"bdi-%s not registered\n",
1069 inode
->dirtied_when
= jiffies
;
1070 list_move(&inode
->i_list
, &wb
->b_dirty
);
1074 spin_unlock(&inode_lock
);
1076 EXPORT_SYMBOL(__mark_inode_dirty
);
1079 * Write out a superblock's list of dirty inodes. A wait will be performed
1080 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1082 * If older_than_this is non-NULL, then only write out inodes which
1083 * had their first dirtying at a time earlier than *older_than_this.
1085 * If we're a pdlfush thread, then implement pdflush collision avoidance
1086 * against the entire list.
1088 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1089 * This function assumes that the blockdev superblock's inodes are backed by
1090 * a variety of queues, so all inodes are searched. For other superblocks,
1091 * assume that all inodes are backed by the same queue.
1093 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1094 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1095 * on the writer throttling path, and we get decent balancing between many
1096 * throttled threads: we don't want them all piling up on inode_sync_wait.
1098 static void wait_sb_inodes(struct super_block
*sb
)
1100 struct inode
*inode
, *old_inode
= NULL
;
1103 * We need to be protected against the filesystem going from
1104 * r/o to r/w or vice versa.
1106 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1108 spin_lock(&inode_lock
);
1111 * Data integrity sync. Must wait for all pages under writeback,
1112 * because there may have been pages dirtied before our sync
1113 * call, but which had writeout started before we write it out.
1114 * In which case, the inode may not be on the dirty list, but
1115 * we still have to wait for that writeout.
1117 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
1118 struct address_space
*mapping
;
1120 if (inode
->i_state
& (I_FREEING
|I_CLEAR
|I_WILL_FREE
|I_NEW
))
1122 mapping
= inode
->i_mapping
;
1123 if (mapping
->nrpages
== 0)
1126 spin_unlock(&inode_lock
);
1128 * We hold a reference to 'inode' so it couldn't have
1129 * been removed from s_inodes list while we dropped the
1130 * inode_lock. We cannot iput the inode now as we can
1131 * be holding the last reference and we cannot iput it
1132 * under inode_lock. So we keep the reference and iput
1138 filemap_fdatawait(mapping
);
1142 spin_lock(&inode_lock
);
1144 spin_unlock(&inode_lock
);
1149 * writeback_inodes_sb - writeback dirty inodes from given super_block
1150 * @sb: the superblock
1152 * Start writeback on some inodes on this super_block. No guarantees are made
1153 * on how many (if any) will be written, and this function does not wait
1154 * for IO completion of submitted IO. The number of pages submitted is
1157 void writeback_inodes_sb(struct super_block
*sb
)
1159 unsigned long nr_dirty
= global_page_state(NR_FILE_DIRTY
);
1160 unsigned long nr_unstable
= global_page_state(NR_UNSTABLE_NFS
);
1163 nr_to_write
= nr_dirty
+ nr_unstable
+
1164 (inodes_stat
.nr_inodes
- inodes_stat
.nr_unused
);
1166 bdi_writeback_all(sb
, nr_to_write
);
1168 EXPORT_SYMBOL(writeback_inodes_sb
);
1171 * sync_inodes_sb - sync sb inode pages
1172 * @sb: the superblock
1174 * This function writes and waits on any dirty inode belonging to this
1175 * super_block. The number of pages synced is returned.
1177 void sync_inodes_sb(struct super_block
*sb
)
1179 bdi_sync_writeback(sb
->s_bdi
, sb
);
1182 EXPORT_SYMBOL(sync_inodes_sb
);
1185 * write_inode_now - write an inode to disk
1186 * @inode: inode to write to disk
1187 * @sync: whether the write should be synchronous or not
1189 * This function commits an inode to disk immediately if it is dirty. This is
1190 * primarily needed by knfsd.
1192 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1194 int write_inode_now(struct inode
*inode
, int sync
)
1197 struct writeback_control wbc
= {
1198 .nr_to_write
= LONG_MAX
,
1199 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1201 .range_end
= LLONG_MAX
,
1204 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
1205 wbc
.nr_to_write
= 0;
1208 spin_lock(&inode_lock
);
1209 ret
= writeback_single_inode(inode
, &wbc
);
1210 spin_unlock(&inode_lock
);
1212 inode_sync_wait(inode
);
1215 EXPORT_SYMBOL(write_inode_now
);
1218 * sync_inode - write an inode and its pages to disk.
1219 * @inode: the inode to sync
1220 * @wbc: controls the writeback mode
1222 * sync_inode() will write an inode and its pages to disk. It will also
1223 * correctly update the inode on its superblock's dirty inode lists and will
1224 * update inode->i_state.
1226 * The caller must have a ref on the inode.
1228 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1232 spin_lock(&inode_lock
);
1233 ret
= writeback_single_inode(inode
, wbc
);
1234 spin_unlock(&inode_lock
);
1237 EXPORT_SYMBOL(sync_inode
);