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/export.h>
18 #include <linux/spinlock.h>
19 #include <linux/slab.h>
20 #include <linux/sched.h>
23 #include <linux/pagemap.h>
24 #include <linux/kthread.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/tracepoint.h>
32 * 4MB minimal write chunk size
34 #define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
37 * Passed into wb_writeback(), essentially a subset of writeback_control
39 struct wb_writeback_work
{
41 struct super_block
*sb
;
43 * Write only inodes dirtied before this time. Don't forget to set
44 * older_than_this_is_set when you set this.
46 unsigned long older_than_this
;
47 enum writeback_sync_modes sync_mode
;
48 unsigned int tagged_writepages
:1;
49 unsigned int for_kupdate
:1;
50 unsigned int range_cyclic
:1;
51 unsigned int for_background
:1;
52 unsigned int for_sync
:1; /* sync(2) WB_SYNC_ALL writeback */
53 unsigned int older_than_this_is_set
:1;
54 enum wb_reason reason
; /* why was writeback initiated? */
56 struct list_head list
; /* pending work list */
57 struct completion
*done
; /* set if the caller waits */
61 * writeback_in_progress - determine whether there is writeback in progress
62 * @bdi: the device's backing_dev_info structure.
64 * Determine whether there is writeback waiting to be handled against a
67 int writeback_in_progress(struct backing_dev_info
*bdi
)
69 return test_bit(BDI_writeback_running
, &bdi
->state
);
71 EXPORT_SYMBOL(writeback_in_progress
);
73 static inline struct backing_dev_info
*inode_to_bdi(struct inode
*inode
)
75 struct super_block
*sb
= inode
->i_sb
;
77 if (sb_is_blkdev_sb(sb
))
78 return inode
->i_mapping
->backing_dev_info
;
83 static inline struct inode
*wb_inode(struct list_head
*head
)
85 return list_entry(head
, struct inode
, i_wb_list
);
89 * Include the creation of the trace points after defining the
90 * wb_writeback_work structure and inline functions so that the definition
91 * remains local to this file.
93 #define CREATE_TRACE_POINTS
94 #include <trace/events/writeback.h>
96 static void bdi_queue_work(struct backing_dev_info
*bdi
,
97 struct wb_writeback_work
*work
)
99 trace_writeback_queue(bdi
, work
);
101 spin_lock_bh(&bdi
->wb_lock
);
102 list_add_tail(&work
->list
, &bdi
->work_list
);
103 spin_unlock_bh(&bdi
->wb_lock
);
105 mod_delayed_work(bdi_wq
, &bdi
->wb
.dwork
, 0);
109 __bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
,
110 bool range_cyclic
, enum wb_reason reason
)
112 struct wb_writeback_work
*work
;
115 * This is WB_SYNC_NONE writeback, so if allocation fails just
116 * wakeup the thread for old dirty data writeback
118 work
= kzalloc(sizeof(*work
), GFP_ATOMIC
);
120 trace_writeback_nowork(bdi
);
121 mod_delayed_work(bdi_wq
, &bdi
->wb
.dwork
, 0);
125 work
->sync_mode
= WB_SYNC_NONE
;
126 work
->nr_pages
= nr_pages
;
127 work
->range_cyclic
= range_cyclic
;
128 work
->reason
= reason
;
130 bdi_queue_work(bdi
, work
);
134 * bdi_start_writeback - start writeback
135 * @bdi: the backing device to write from
136 * @nr_pages: the number of pages to write
137 * @reason: reason why some writeback work was initiated
140 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
141 * started when this function returns, we make no guarantees on
142 * completion. Caller need not hold sb s_umount semaphore.
145 void bdi_start_writeback(struct backing_dev_info
*bdi
, long nr_pages
,
146 enum wb_reason reason
)
148 __bdi_start_writeback(bdi
, nr_pages
, true, reason
);
152 * bdi_start_background_writeback - start background writeback
153 * @bdi: the backing device to write from
156 * This makes sure WB_SYNC_NONE background writeback happens. When
157 * this function returns, it is only guaranteed that for given BDI
158 * some IO is happening if we are over background dirty threshold.
159 * Caller need not hold sb s_umount semaphore.
161 void bdi_start_background_writeback(struct backing_dev_info
*bdi
)
164 * We just wake up the flusher thread. It will perform background
165 * writeback as soon as there is no other work to do.
167 trace_writeback_wake_background(bdi
);
168 mod_delayed_work(bdi_wq
, &bdi
->wb
.dwork
, 0);
172 * Remove the inode from the writeback list it is on.
174 void inode_wb_list_del(struct inode
*inode
)
176 struct backing_dev_info
*bdi
= inode_to_bdi(inode
);
178 spin_lock(&bdi
->wb
.list_lock
);
179 list_del_init(&inode
->i_wb_list
);
180 spin_unlock(&bdi
->wb
.list_lock
);
184 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
185 * furthest end of its superblock's dirty-inode list.
187 * Before stamping the inode's ->dirtied_when, we check to see whether it is
188 * already the most-recently-dirtied inode on the b_dirty list. If that is
189 * the case then the inode must have been redirtied while it was being written
190 * out and we don't reset its dirtied_when.
192 static void redirty_tail(struct inode
*inode
, struct bdi_writeback
*wb
)
194 assert_spin_locked(&wb
->list_lock
);
195 if (!list_empty(&wb
->b_dirty
)) {
198 tail
= wb_inode(wb
->b_dirty
.next
);
199 if (time_before(inode
->dirtied_when
, tail
->dirtied_when
))
200 inode
->dirtied_when
= jiffies
;
202 list_move(&inode
->i_wb_list
, &wb
->b_dirty
);
206 * requeue inode for re-scanning after bdi->b_io list is exhausted.
208 static void requeue_io(struct inode
*inode
, struct bdi_writeback
*wb
)
210 assert_spin_locked(&wb
->list_lock
);
211 list_move(&inode
->i_wb_list
, &wb
->b_more_io
);
214 static void inode_sync_complete(struct inode
*inode
)
216 inode
->i_state
&= ~I_SYNC
;
217 /* If inode is clean an unused, put it into LRU now... */
218 inode_add_lru(inode
);
219 /* Waiters must see I_SYNC cleared before being woken up */
221 wake_up_bit(&inode
->i_state
, __I_SYNC
);
224 static bool inode_dirtied_after(struct inode
*inode
, unsigned long t
)
226 bool ret
= time_after(inode
->dirtied_when
, t
);
229 * For inodes being constantly redirtied, dirtied_when can get stuck.
230 * It _appears_ to be in the future, but is actually in distant past.
231 * This test is necessary to prevent such wrapped-around relative times
232 * from permanently stopping the whole bdi writeback.
234 ret
= ret
&& time_before_eq(inode
->dirtied_when
, jiffies
);
240 * Move expired (dirtied before work->older_than_this) dirty inodes from
241 * @delaying_queue to @dispatch_queue.
243 static int move_expired_inodes(struct list_head
*delaying_queue
,
244 struct list_head
*dispatch_queue
,
245 struct wb_writeback_work
*work
)
248 struct list_head
*pos
, *node
;
249 struct super_block
*sb
= NULL
;
254 WARN_ON_ONCE(!work
->older_than_this_is_set
);
255 while (!list_empty(delaying_queue
)) {
256 inode
= wb_inode(delaying_queue
->prev
);
257 if (inode_dirtied_after(inode
, work
->older_than_this
))
259 list_move(&inode
->i_wb_list
, &tmp
);
261 if (sb_is_blkdev_sb(inode
->i_sb
))
263 if (sb
&& sb
!= inode
->i_sb
)
268 /* just one sb in list, splice to dispatch_queue and we're done */
270 list_splice(&tmp
, dispatch_queue
);
274 /* Move inodes from one superblock together */
275 while (!list_empty(&tmp
)) {
276 sb
= wb_inode(tmp
.prev
)->i_sb
;
277 list_for_each_prev_safe(pos
, node
, &tmp
) {
278 inode
= wb_inode(pos
);
279 if (inode
->i_sb
== sb
)
280 list_move(&inode
->i_wb_list
, dispatch_queue
);
288 * Queue all expired dirty inodes for io, eldest first.
290 * newly dirtied b_dirty b_io b_more_io
291 * =============> gf edc BA
293 * newly dirtied b_dirty b_io b_more_io
294 * =============> g fBAedc
296 * +--> dequeue for IO
298 static void queue_io(struct bdi_writeback
*wb
, struct wb_writeback_work
*work
)
301 assert_spin_locked(&wb
->list_lock
);
302 list_splice_init(&wb
->b_more_io
, &wb
->b_io
);
303 moved
= move_expired_inodes(&wb
->b_dirty
, &wb
->b_io
, work
);
304 trace_writeback_queue_io(wb
, work
, moved
);
307 static int write_inode(struct inode
*inode
, struct writeback_control
*wbc
)
311 if (inode
->i_sb
->s_op
->write_inode
&& !is_bad_inode(inode
)) {
312 trace_writeback_write_inode_start(inode
, wbc
);
313 ret
= inode
->i_sb
->s_op
->write_inode(inode
, wbc
);
314 trace_writeback_write_inode(inode
, wbc
);
321 * Wait for writeback on an inode to complete. Called with i_lock held.
322 * Caller must make sure inode cannot go away when we drop i_lock.
324 static void __inode_wait_for_writeback(struct inode
*inode
)
325 __releases(inode
->i_lock
)
326 __acquires(inode
->i_lock
)
328 DEFINE_WAIT_BIT(wq
, &inode
->i_state
, __I_SYNC
);
329 wait_queue_head_t
*wqh
;
331 wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
332 while (inode
->i_state
& I_SYNC
) {
333 spin_unlock(&inode
->i_lock
);
334 __wait_on_bit(wqh
, &wq
, inode_wait
, TASK_UNINTERRUPTIBLE
);
335 spin_lock(&inode
->i_lock
);
340 * Wait for writeback on an inode to complete. Caller must have inode pinned.
342 void inode_wait_for_writeback(struct inode
*inode
)
344 spin_lock(&inode
->i_lock
);
345 __inode_wait_for_writeback(inode
);
346 spin_unlock(&inode
->i_lock
);
350 * Sleep until I_SYNC is cleared. This function must be called with i_lock
351 * held and drops it. It is aimed for callers not holding any inode reference
352 * so once i_lock is dropped, inode can go away.
354 static void inode_sleep_on_writeback(struct inode
*inode
)
355 __releases(inode
->i_lock
)
358 wait_queue_head_t
*wqh
= bit_waitqueue(&inode
->i_state
, __I_SYNC
);
361 prepare_to_wait(wqh
, &wait
, TASK_UNINTERRUPTIBLE
);
362 sleep
= inode
->i_state
& I_SYNC
;
363 spin_unlock(&inode
->i_lock
);
366 finish_wait(wqh
, &wait
);
370 * Find proper writeback list for the inode depending on its current state and
371 * possibly also change of its state while we were doing writeback. Here we
372 * handle things such as livelock prevention or fairness of writeback among
373 * inodes. This function can be called only by flusher thread - noone else
374 * processes all inodes in writeback lists and requeueing inodes behind flusher
375 * thread's back can have unexpected consequences.
377 static void requeue_inode(struct inode
*inode
, struct bdi_writeback
*wb
,
378 struct writeback_control
*wbc
)
380 if (inode
->i_state
& I_FREEING
)
384 * Sync livelock prevention. Each inode is tagged and synced in one
385 * shot. If still dirty, it will be redirty_tail()'ed below. Update
386 * the dirty time to prevent enqueue and sync it again.
388 if ((inode
->i_state
& I_DIRTY
) &&
389 (wbc
->sync_mode
== WB_SYNC_ALL
|| wbc
->tagged_writepages
))
390 inode
->dirtied_when
= jiffies
;
392 if (wbc
->pages_skipped
) {
394 * writeback is not making progress due to locked
395 * buffers. Skip this inode for now.
397 redirty_tail(inode
, wb
);
401 if (mapping_tagged(inode
->i_mapping
, PAGECACHE_TAG_DIRTY
)) {
403 * We didn't write back all the pages. nfs_writepages()
404 * sometimes bales out without doing anything.
406 if (wbc
->nr_to_write
<= 0) {
407 /* Slice used up. Queue for next turn. */
408 requeue_io(inode
, wb
);
411 * Writeback blocked by something other than
412 * congestion. Delay the inode for some time to
413 * avoid spinning on the CPU (100% iowait)
414 * retrying writeback of the dirty page/inode
415 * that cannot be performed immediately.
417 redirty_tail(inode
, wb
);
419 } else if (inode
->i_state
& I_DIRTY
) {
421 * Filesystems can dirty the inode during writeback operations,
422 * such as delayed allocation during submission or metadata
423 * updates after data IO completion.
425 redirty_tail(inode
, wb
);
427 /* The inode is clean. Remove from writeback lists. */
428 list_del_init(&inode
->i_wb_list
);
433 * Write out an inode and its dirty pages. Do not update the writeback list
434 * linkage. That is left to the caller. The caller is also responsible for
435 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
438 __writeback_single_inode(struct inode
*inode
, struct writeback_control
*wbc
)
440 struct address_space
*mapping
= inode
->i_mapping
;
441 long nr_to_write
= wbc
->nr_to_write
;
445 WARN_ON(!(inode
->i_state
& I_SYNC
));
447 trace_writeback_single_inode_start(inode
, wbc
, nr_to_write
);
449 ret
= do_writepages(mapping
, wbc
);
452 * Make sure to wait on the data before writing out the metadata.
453 * This is important for filesystems that modify metadata on data
454 * I/O completion. We don't do it for sync(2) writeback because it has a
455 * separate, external IO completion path and ->sync_fs for guaranteeing
456 * inode metadata is written back correctly.
458 if (wbc
->sync_mode
== WB_SYNC_ALL
&& !wbc
->for_sync
) {
459 int err
= filemap_fdatawait(mapping
);
465 * Some filesystems may redirty the inode during the writeback
466 * due to delalloc, clear dirty metadata flags right before
469 spin_lock(&inode
->i_lock
);
470 /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
471 if (!mapping_tagged(mapping
, PAGECACHE_TAG_DIRTY
))
472 inode
->i_state
&= ~I_DIRTY_PAGES
;
473 dirty
= inode
->i_state
& I_DIRTY
;
474 inode
->i_state
&= ~(I_DIRTY_SYNC
| I_DIRTY_DATASYNC
);
475 spin_unlock(&inode
->i_lock
);
476 /* Don't write the inode if only I_DIRTY_PAGES was set */
477 if (dirty
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
478 int err
= write_inode(inode
, wbc
);
482 trace_writeback_single_inode(inode
, wbc
, nr_to_write
);
487 * Write out an inode's dirty pages. Either the caller has an active reference
488 * on the inode or the inode has I_WILL_FREE set.
490 * This function is designed to be called for writing back one inode which
491 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
492 * and does more profound writeback list handling in writeback_sb_inodes().
495 writeback_single_inode(struct inode
*inode
, struct bdi_writeback
*wb
,
496 struct writeback_control
*wbc
)
500 spin_lock(&inode
->i_lock
);
501 if (!atomic_read(&inode
->i_count
))
502 WARN_ON(!(inode
->i_state
& (I_WILL_FREE
|I_FREEING
)));
504 WARN_ON(inode
->i_state
& I_WILL_FREE
);
506 if (inode
->i_state
& I_SYNC
) {
507 if (wbc
->sync_mode
!= WB_SYNC_ALL
)
510 * It's a data-integrity sync. We must wait. Since callers hold
511 * inode reference or inode has I_WILL_FREE set, it cannot go
514 __inode_wait_for_writeback(inode
);
516 WARN_ON(inode
->i_state
& I_SYNC
);
518 * Skip inode if it is clean. We don't want to mess with writeback
519 * lists in this function since flusher thread may be doing for example
520 * sync in parallel and if we move the inode, it could get skipped. So
521 * here we make sure inode is on some writeback list and leave it there
522 * unless we have completely cleaned the inode.
524 if (!(inode
->i_state
& I_DIRTY
))
526 inode
->i_state
|= I_SYNC
;
527 spin_unlock(&inode
->i_lock
);
529 ret
= __writeback_single_inode(inode
, wbc
);
531 spin_lock(&wb
->list_lock
);
532 spin_lock(&inode
->i_lock
);
534 * If inode is clean, remove it from writeback lists. Otherwise don't
535 * touch it. See comment above for explanation.
537 if (!(inode
->i_state
& I_DIRTY
))
538 list_del_init(&inode
->i_wb_list
);
539 spin_unlock(&wb
->list_lock
);
540 inode_sync_complete(inode
);
542 spin_unlock(&inode
->i_lock
);
546 static long writeback_chunk_size(struct backing_dev_info
*bdi
,
547 struct wb_writeback_work
*work
)
552 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
553 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
554 * here avoids calling into writeback_inodes_wb() more than once.
556 * The intended call sequence for WB_SYNC_ALL writeback is:
559 * writeback_sb_inodes() <== called only once
560 * write_cache_pages() <== called once for each inode
561 * (quickly) tag currently dirty pages
562 * (maybe slowly) sync all tagged pages
564 if (work
->sync_mode
== WB_SYNC_ALL
|| work
->tagged_writepages
)
567 pages
= min(bdi
->avg_write_bandwidth
/ 2,
568 global_dirty_limit
/ DIRTY_SCOPE
);
569 pages
= min(pages
, work
->nr_pages
);
570 pages
= round_down(pages
+ MIN_WRITEBACK_PAGES
,
571 MIN_WRITEBACK_PAGES
);
578 * Write a portion of b_io inodes which belong to @sb.
580 * Return the number of pages and/or inodes written.
582 static long writeback_sb_inodes(struct super_block
*sb
,
583 struct bdi_writeback
*wb
,
584 struct wb_writeback_work
*work
)
586 struct writeback_control wbc
= {
587 .sync_mode
= work
->sync_mode
,
588 .tagged_writepages
= work
->tagged_writepages
,
589 .for_kupdate
= work
->for_kupdate
,
590 .for_background
= work
->for_background
,
591 .for_sync
= work
->for_sync
,
592 .range_cyclic
= work
->range_cyclic
,
594 .range_end
= LLONG_MAX
,
596 unsigned long start_time
= jiffies
;
598 long wrote
= 0; /* count both pages and inodes */
600 while (!list_empty(&wb
->b_io
)) {
601 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
603 if (inode
->i_sb
!= sb
) {
606 * We only want to write back data for this
607 * superblock, move all inodes not belonging
608 * to it back onto the dirty list.
610 redirty_tail(inode
, wb
);
615 * The inode belongs to a different superblock.
616 * Bounce back to the caller to unpin this and
617 * pin the next superblock.
623 * Don't bother with new inodes or inodes being freed, first
624 * kind does not need periodic writeout yet, and for the latter
625 * kind writeout is handled by the freer.
627 spin_lock(&inode
->i_lock
);
628 if (inode
->i_state
& (I_NEW
| I_FREEING
| I_WILL_FREE
)) {
629 spin_unlock(&inode
->i_lock
);
630 redirty_tail(inode
, wb
);
633 if ((inode
->i_state
& I_SYNC
) && wbc
.sync_mode
!= WB_SYNC_ALL
) {
635 * If this inode is locked for writeback and we are not
636 * doing writeback-for-data-integrity, move it to
637 * b_more_io so that writeback can proceed with the
638 * other inodes on s_io.
640 * We'll have another go at writing back this inode
641 * when we completed a full scan of b_io.
643 spin_unlock(&inode
->i_lock
);
644 requeue_io(inode
, wb
);
645 trace_writeback_sb_inodes_requeue(inode
);
648 spin_unlock(&wb
->list_lock
);
651 * We already requeued the inode if it had I_SYNC set and we
652 * are doing WB_SYNC_NONE writeback. So this catches only the
655 if (inode
->i_state
& I_SYNC
) {
656 /* Wait for I_SYNC. This function drops i_lock... */
657 inode_sleep_on_writeback(inode
);
658 /* Inode may be gone, start again */
659 spin_lock(&wb
->list_lock
);
662 inode
->i_state
|= I_SYNC
;
663 spin_unlock(&inode
->i_lock
);
665 write_chunk
= writeback_chunk_size(wb
->bdi
, work
);
666 wbc
.nr_to_write
= write_chunk
;
667 wbc
.pages_skipped
= 0;
670 * We use I_SYNC to pin the inode in memory. While it is set
671 * evict_inode() will wait so the inode cannot be freed.
673 __writeback_single_inode(inode
, &wbc
);
675 work
->nr_pages
-= write_chunk
- wbc
.nr_to_write
;
676 wrote
+= write_chunk
- wbc
.nr_to_write
;
677 spin_lock(&wb
->list_lock
);
678 spin_lock(&inode
->i_lock
);
679 if (!(inode
->i_state
& I_DIRTY
))
681 requeue_inode(inode
, wb
, &wbc
);
682 inode_sync_complete(inode
);
683 spin_unlock(&inode
->i_lock
);
684 cond_resched_lock(&wb
->list_lock
);
686 * bail out to wb_writeback() often enough to check
687 * background threshold and other termination conditions.
690 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
692 if (work
->nr_pages
<= 0)
699 static long __writeback_inodes_wb(struct bdi_writeback
*wb
,
700 struct wb_writeback_work
*work
)
702 unsigned long start_time
= jiffies
;
705 while (!list_empty(&wb
->b_io
)) {
706 struct inode
*inode
= wb_inode(wb
->b_io
.prev
);
707 struct super_block
*sb
= inode
->i_sb
;
709 if (!grab_super_passive(sb
)) {
711 * grab_super_passive() may fail consistently due to
712 * s_umount being grabbed by someone else. Don't use
713 * requeue_io() to avoid busy retrying the inode/sb.
715 redirty_tail(inode
, wb
);
718 wrote
+= writeback_sb_inodes(sb
, wb
, work
);
721 /* refer to the same tests at the end of writeback_sb_inodes */
723 if (time_is_before_jiffies(start_time
+ HZ
/ 10UL))
725 if (work
->nr_pages
<= 0)
729 /* Leave any unwritten inodes on b_io */
733 static long writeback_inodes_wb(struct bdi_writeback
*wb
, long nr_pages
,
734 enum wb_reason reason
)
736 struct wb_writeback_work work
= {
737 .nr_pages
= nr_pages
,
738 .sync_mode
= WB_SYNC_NONE
,
741 .older_than_this
= jiffies
,
742 .older_than_this_is_set
= 1,
745 spin_lock(&wb
->list_lock
);
746 if (list_empty(&wb
->b_io
))
748 __writeback_inodes_wb(wb
, &work
);
749 spin_unlock(&wb
->list_lock
);
751 return nr_pages
- work
.nr_pages
;
754 static bool over_bground_thresh(struct backing_dev_info
*bdi
)
756 unsigned long background_thresh
, dirty_thresh
;
758 global_dirty_limits(&background_thresh
, &dirty_thresh
);
760 if (global_page_state(NR_FILE_DIRTY
) +
761 global_page_state(NR_UNSTABLE_NFS
) > background_thresh
)
764 if (bdi_stat(bdi
, BDI_RECLAIMABLE
) >
765 bdi_dirty_limit(bdi
, background_thresh
))
772 * Called under wb->list_lock. If there are multiple wb per bdi,
773 * only the flusher working on the first wb should do it.
775 static void wb_update_bandwidth(struct bdi_writeback
*wb
,
776 unsigned long start_time
)
778 __bdi_update_bandwidth(wb
->bdi
, 0, 0, 0, 0, 0, start_time
);
782 * Explicit flushing or periodic writeback of "old" data.
784 * Define "old": the first time one of an inode's pages is dirtied, we mark the
785 * dirtying-time in the inode's address_space. So this periodic writeback code
786 * just walks the superblock inode list, writing back any inodes which are
787 * older than a specific point in time.
789 * Try to run once per dirty_writeback_interval. But if a writeback event
790 * takes longer than a dirty_writeback_interval interval, then leave a
793 * older_than_this takes precedence over nr_to_write. So we'll only write back
794 * all dirty pages if they are all attached to "old" mappings.
796 static long wb_writeback(struct bdi_writeback
*wb
,
797 struct wb_writeback_work
*work
)
799 unsigned long wb_start
= jiffies
;
800 long nr_pages
= work
->nr_pages
;
804 if (!work
->older_than_this_is_set
) {
805 work
->older_than_this
= jiffies
;
806 work
->older_than_this_is_set
= 1;
809 spin_lock(&wb
->list_lock
);
812 * Stop writeback when nr_pages has been consumed
814 if (work
->nr_pages
<= 0)
818 * Background writeout and kupdate-style writeback may
819 * run forever. Stop them if there is other work to do
820 * so that e.g. sync can proceed. They'll be restarted
821 * after the other works are all done.
823 if ((work
->for_background
|| work
->for_kupdate
) &&
824 !list_empty(&wb
->bdi
->work_list
))
828 * For background writeout, stop when we are below the
829 * background dirty threshold
831 if (work
->for_background
&& !over_bground_thresh(wb
->bdi
))
835 * Kupdate and background works are special and we want to
836 * include all inodes that need writing. Livelock avoidance is
837 * handled by these works yielding to any other work so we are
840 if (work
->for_kupdate
) {
841 work
->older_than_this
= jiffies
-
842 msecs_to_jiffies(dirty_expire_interval
* 10);
843 } else if (work
->for_background
)
844 work
->older_than_this
= jiffies
;
846 trace_writeback_start(wb
->bdi
, work
);
847 if (list_empty(&wb
->b_io
))
850 progress
= writeback_sb_inodes(work
->sb
, wb
, work
);
852 progress
= __writeback_inodes_wb(wb
, work
);
853 trace_writeback_written(wb
->bdi
, work
);
855 wb_update_bandwidth(wb
, wb_start
);
858 * Did we write something? Try for more
860 * Dirty inodes are moved to b_io for writeback in batches.
861 * The completion of the current batch does not necessarily
862 * mean the overall work is done. So we keep looping as long
863 * as made some progress on cleaning pages or inodes.
868 * No more inodes for IO, bail
870 if (list_empty(&wb
->b_more_io
))
873 * Nothing written. Wait for some inode to
874 * become available for writeback. Otherwise
875 * we'll just busyloop.
877 if (!list_empty(&wb
->b_more_io
)) {
878 trace_writeback_wait(wb
->bdi
, work
);
879 inode
= wb_inode(wb
->b_more_io
.prev
);
880 spin_lock(&inode
->i_lock
);
881 spin_unlock(&wb
->list_lock
);
882 /* This function drops i_lock... */
883 inode_sleep_on_writeback(inode
);
884 spin_lock(&wb
->list_lock
);
887 spin_unlock(&wb
->list_lock
);
889 return nr_pages
- work
->nr_pages
;
893 * Return the next wb_writeback_work struct that hasn't been processed yet.
895 static struct wb_writeback_work
*
896 get_next_work_item(struct backing_dev_info
*bdi
)
898 struct wb_writeback_work
*work
= NULL
;
900 spin_lock_bh(&bdi
->wb_lock
);
901 if (!list_empty(&bdi
->work_list
)) {
902 work
= list_entry(bdi
->work_list
.next
,
903 struct wb_writeback_work
, list
);
904 list_del_init(&work
->list
);
906 spin_unlock_bh(&bdi
->wb_lock
);
911 * Add in the number of potentially dirty inodes, because each inode
912 * write can dirty pagecache in the underlying blockdev.
914 static unsigned long get_nr_dirty_pages(void)
916 return global_page_state(NR_FILE_DIRTY
) +
917 global_page_state(NR_UNSTABLE_NFS
) +
918 get_nr_dirty_inodes();
921 static long wb_check_background_flush(struct bdi_writeback
*wb
)
923 if (over_bground_thresh(wb
->bdi
)) {
925 struct wb_writeback_work work
= {
926 .nr_pages
= LONG_MAX
,
927 .sync_mode
= WB_SYNC_NONE
,
930 .reason
= WB_REASON_BACKGROUND
,
933 return wb_writeback(wb
, &work
);
939 static long wb_check_old_data_flush(struct bdi_writeback
*wb
)
941 unsigned long expired
;
945 * When set to zero, disable periodic writeback
947 if (!dirty_writeback_interval
)
950 expired
= wb
->last_old_flush
+
951 msecs_to_jiffies(dirty_writeback_interval
* 10);
952 if (time_before(jiffies
, expired
))
955 wb
->last_old_flush
= jiffies
;
956 nr_pages
= get_nr_dirty_pages();
959 struct wb_writeback_work work
= {
960 .nr_pages
= nr_pages
,
961 .sync_mode
= WB_SYNC_NONE
,
964 .reason
= WB_REASON_PERIODIC
,
967 return wb_writeback(wb
, &work
);
974 * Retrieve work items and do the writeback they describe
976 static long wb_do_writeback(struct bdi_writeback
*wb
)
978 struct backing_dev_info
*bdi
= wb
->bdi
;
979 struct wb_writeback_work
*work
;
982 set_bit(BDI_writeback_running
, &wb
->bdi
->state
);
983 while ((work
= get_next_work_item(bdi
)) != NULL
) {
985 trace_writeback_exec(bdi
, work
);
987 wrote
+= wb_writeback(wb
, work
);
990 * Notify the caller of completion if this is a synchronous
991 * work item, otherwise just free it.
994 complete(work
->done
);
1000 * Check for periodic writeback, kupdated() style
1002 wrote
+= wb_check_old_data_flush(wb
);
1003 wrote
+= wb_check_background_flush(wb
);
1004 clear_bit(BDI_writeback_running
, &wb
->bdi
->state
);
1010 * Handle writeback of dirty data for the device backed by this bdi. Also
1011 * reschedules periodically and does kupdated style flushing.
1013 void bdi_writeback_workfn(struct work_struct
*work
)
1015 struct bdi_writeback
*wb
= container_of(to_delayed_work(work
),
1016 struct bdi_writeback
, dwork
);
1017 struct backing_dev_info
*bdi
= wb
->bdi
;
1020 set_worker_desc("flush-%s", dev_name(bdi
->dev
));
1021 current
->flags
|= PF_SWAPWRITE
;
1023 if (likely(!current_is_workqueue_rescuer() ||
1024 list_empty(&bdi
->bdi_list
))) {
1026 * The normal path. Keep writing back @bdi until its
1027 * work_list is empty. Note that this path is also taken
1028 * if @bdi is shutting down even when we're running off the
1029 * rescuer as work_list needs to be drained.
1032 pages_written
= wb_do_writeback(wb
);
1033 trace_writeback_pages_written(pages_written
);
1034 } while (!list_empty(&bdi
->work_list
));
1037 * bdi_wq can't get enough workers and we're running off
1038 * the emergency worker. Don't hog it. Hopefully, 1024 is
1039 * enough for efficient IO.
1041 pages_written
= writeback_inodes_wb(&bdi
->wb
, 1024,
1042 WB_REASON_FORKER_THREAD
);
1043 trace_writeback_pages_written(pages_written
);
1046 if (!list_empty(&bdi
->work_list
) ||
1047 (wb_has_dirty_io(wb
) && dirty_writeback_interval
))
1048 queue_delayed_work(bdi_wq
, &wb
->dwork
,
1049 msecs_to_jiffies(dirty_writeback_interval
* 10));
1051 current
->flags
&= ~PF_SWAPWRITE
;
1055 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
1058 void wakeup_flusher_threads(long nr_pages
, enum wb_reason reason
)
1060 struct backing_dev_info
*bdi
;
1063 nr_pages
= get_nr_dirty_pages();
1066 list_for_each_entry_rcu(bdi
, &bdi_list
, bdi_list
) {
1067 if (!bdi_has_dirty_io(bdi
))
1069 __bdi_start_writeback(bdi
, nr_pages
, false, reason
);
1074 static noinline
void block_dump___mark_inode_dirty(struct inode
*inode
)
1076 if (inode
->i_ino
|| strcmp(inode
->i_sb
->s_id
, "bdev")) {
1077 struct dentry
*dentry
;
1078 const char *name
= "?";
1080 dentry
= d_find_alias(inode
);
1082 spin_lock(&dentry
->d_lock
);
1083 name
= (const char *) dentry
->d_name
.name
;
1086 "%s(%d): dirtied inode %lu (%s) on %s\n",
1087 current
->comm
, task_pid_nr(current
), inode
->i_ino
,
1088 name
, inode
->i_sb
->s_id
);
1090 spin_unlock(&dentry
->d_lock
);
1097 * __mark_inode_dirty - internal function
1098 * @inode: inode to mark
1099 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1100 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1101 * mark_inode_dirty_sync.
1103 * Put the inode on the super block's dirty list.
1105 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1106 * dirty list only if it is hashed or if it refers to a blockdev.
1107 * If it was not hashed, it will never be added to the dirty list
1108 * even if it is later hashed, as it will have been marked dirty already.
1110 * In short, make sure you hash any inodes _before_ you start marking
1113 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1114 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1115 * the kernel-internal blockdev inode represents the dirtying time of the
1116 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1117 * page->mapping->host, so the page-dirtying time is recorded in the internal
1120 void __mark_inode_dirty(struct inode
*inode
, int flags
)
1122 struct super_block
*sb
= inode
->i_sb
;
1123 struct backing_dev_info
*bdi
= NULL
;
1126 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1127 * dirty the inode itself
1129 if (flags
& (I_DIRTY_SYNC
| I_DIRTY_DATASYNC
)) {
1130 trace_writeback_dirty_inode_start(inode
, flags
);
1132 if (sb
->s_op
->dirty_inode
)
1133 sb
->s_op
->dirty_inode(inode
, flags
);
1135 trace_writeback_dirty_inode(inode
, flags
);
1139 * make sure that changes are seen by all cpus before we test i_state
1144 /* avoid the locking if we can */
1145 if ((inode
->i_state
& flags
) == flags
)
1148 if (unlikely(block_dump
))
1149 block_dump___mark_inode_dirty(inode
);
1151 spin_lock(&inode
->i_lock
);
1152 if ((inode
->i_state
& flags
) != flags
) {
1153 const int was_dirty
= inode
->i_state
& I_DIRTY
;
1155 inode
->i_state
|= flags
;
1158 * If the inode is being synced, just update its dirty state.
1159 * The unlocker will place the inode on the appropriate
1160 * superblock list, based upon its state.
1162 if (inode
->i_state
& I_SYNC
)
1163 goto out_unlock_inode
;
1166 * Only add valid (hashed) inodes to the superblock's
1167 * dirty list. Add blockdev inodes as well.
1169 if (!S_ISBLK(inode
->i_mode
)) {
1170 if (inode_unhashed(inode
))
1171 goto out_unlock_inode
;
1173 if (inode
->i_state
& I_FREEING
)
1174 goto out_unlock_inode
;
1177 * If the inode was already on b_dirty/b_io/b_more_io, don't
1178 * reposition it (that would break b_dirty time-ordering).
1181 bool wakeup_bdi
= false;
1182 bdi
= inode_to_bdi(inode
);
1184 spin_unlock(&inode
->i_lock
);
1185 spin_lock(&bdi
->wb
.list_lock
);
1186 if (bdi_cap_writeback_dirty(bdi
)) {
1187 WARN(!test_bit(BDI_registered
, &bdi
->state
),
1188 "bdi-%s not registered\n", bdi
->name
);
1191 * If this is the first dirty inode for this
1192 * bdi, we have to wake-up the corresponding
1193 * bdi thread to make sure background
1194 * write-back happens later.
1196 if (!wb_has_dirty_io(&bdi
->wb
))
1200 inode
->dirtied_when
= jiffies
;
1201 list_move(&inode
->i_wb_list
, &bdi
->wb
.b_dirty
);
1202 spin_unlock(&bdi
->wb
.list_lock
);
1205 bdi_wakeup_thread_delayed(bdi
);
1210 spin_unlock(&inode
->i_lock
);
1213 EXPORT_SYMBOL(__mark_inode_dirty
);
1215 static void wait_sb_inodes(struct super_block
*sb
)
1217 struct inode
*inode
, *old_inode
= NULL
;
1220 * We need to be protected against the filesystem going from
1221 * r/o to r/w or vice versa.
1223 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1225 spin_lock(&inode_sb_list_lock
);
1228 * Data integrity sync. Must wait for all pages under writeback,
1229 * because there may have been pages dirtied before our sync
1230 * call, but which had writeout started before we write it out.
1231 * In which case, the inode may not be on the dirty list, but
1232 * we still have to wait for that writeout.
1234 list_for_each_entry(inode
, &sb
->s_inodes
, i_sb_list
) {
1235 struct address_space
*mapping
= inode
->i_mapping
;
1237 spin_lock(&inode
->i_lock
);
1238 if ((inode
->i_state
& (I_FREEING
|I_WILL_FREE
|I_NEW
)) ||
1239 (mapping
->nrpages
== 0)) {
1240 spin_unlock(&inode
->i_lock
);
1244 spin_unlock(&inode
->i_lock
);
1245 spin_unlock(&inode_sb_list_lock
);
1248 * We hold a reference to 'inode' so it couldn't have been
1249 * removed from s_inodes list while we dropped the
1250 * inode_sb_list_lock. We cannot iput the inode now as we can
1251 * be holding the last reference and we cannot iput it under
1252 * inode_sb_list_lock. So we keep the reference and iput it
1258 filemap_fdatawait(mapping
);
1262 spin_lock(&inode_sb_list_lock
);
1264 spin_unlock(&inode_sb_list_lock
);
1269 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1270 * @sb: the superblock
1271 * @nr: the number of pages to write
1272 * @reason: reason why some writeback work initiated
1274 * Start writeback on some inodes on this super_block. No guarantees are made
1275 * on how many (if any) will be written, and this function does not wait
1276 * for IO completion of submitted IO.
1278 void writeback_inodes_sb_nr(struct super_block
*sb
,
1280 enum wb_reason reason
)
1282 DECLARE_COMPLETION_ONSTACK(done
);
1283 struct wb_writeback_work work
= {
1285 .sync_mode
= WB_SYNC_NONE
,
1286 .tagged_writepages
= 1,
1292 if (sb
->s_bdi
== &noop_backing_dev_info
)
1294 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1295 bdi_queue_work(sb
->s_bdi
, &work
);
1296 wait_for_completion(&done
);
1298 EXPORT_SYMBOL(writeback_inodes_sb_nr
);
1301 * writeback_inodes_sb - writeback dirty inodes from given super_block
1302 * @sb: the superblock
1303 * @reason: reason why some writeback work was initiated
1305 * Start writeback on some inodes on this super_block. No guarantees are made
1306 * on how many (if any) will be written, and this function does not wait
1307 * for IO completion of submitted IO.
1309 void writeback_inodes_sb(struct super_block
*sb
, enum wb_reason reason
)
1311 return writeback_inodes_sb_nr(sb
, get_nr_dirty_pages(), reason
);
1313 EXPORT_SYMBOL(writeback_inodes_sb
);
1316 * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
1317 * @sb: the superblock
1318 * @nr: the number of pages to write
1319 * @reason: the reason of writeback
1321 * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
1322 * Returns 1 if writeback was started, 0 if not.
1324 int try_to_writeback_inodes_sb_nr(struct super_block
*sb
,
1326 enum wb_reason reason
)
1328 if (writeback_in_progress(sb
->s_bdi
))
1331 if (!down_read_trylock(&sb
->s_umount
))
1334 writeback_inodes_sb_nr(sb
, nr
, reason
);
1335 up_read(&sb
->s_umount
);
1338 EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr
);
1341 * try_to_writeback_inodes_sb - try to start writeback if none underway
1342 * @sb: the superblock
1343 * @reason: reason why some writeback work was initiated
1345 * Implement by try_to_writeback_inodes_sb_nr()
1346 * Returns 1 if writeback was started, 0 if not.
1348 int try_to_writeback_inodes_sb(struct super_block
*sb
, enum wb_reason reason
)
1350 return try_to_writeback_inodes_sb_nr(sb
, get_nr_dirty_pages(), reason
);
1352 EXPORT_SYMBOL(try_to_writeback_inodes_sb
);
1355 * sync_inodes_sb - sync sb inode pages
1356 * @sb: the superblock
1357 * @older_than_this: timestamp
1359 * This function writes and waits on any dirty inode belonging to this
1360 * superblock that has been dirtied before given timestamp.
1362 void sync_inodes_sb(struct super_block
*sb
, unsigned long older_than_this
)
1364 DECLARE_COMPLETION_ONSTACK(done
);
1365 struct wb_writeback_work work
= {
1367 .sync_mode
= WB_SYNC_ALL
,
1368 .nr_pages
= LONG_MAX
,
1369 .older_than_this
= older_than_this
,
1370 .older_than_this_is_set
= 1,
1373 .reason
= WB_REASON_SYNC
,
1377 /* Nothing to do? */
1378 if (sb
->s_bdi
== &noop_backing_dev_info
)
1380 WARN_ON(!rwsem_is_locked(&sb
->s_umount
));
1382 bdi_queue_work(sb
->s_bdi
, &work
);
1383 wait_for_completion(&done
);
1387 EXPORT_SYMBOL(sync_inodes_sb
);
1390 * write_inode_now - write an inode to disk
1391 * @inode: inode to write to disk
1392 * @sync: whether the write should be synchronous or not
1394 * This function commits an inode to disk immediately if it is dirty. This is
1395 * primarily needed by knfsd.
1397 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1399 int write_inode_now(struct inode
*inode
, int sync
)
1401 struct bdi_writeback
*wb
= &inode_to_bdi(inode
)->wb
;
1402 struct writeback_control wbc
= {
1403 .nr_to_write
= LONG_MAX
,
1404 .sync_mode
= sync
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1406 .range_end
= LLONG_MAX
,
1409 if (!mapping_cap_writeback_dirty(inode
->i_mapping
))
1410 wbc
.nr_to_write
= 0;
1413 return writeback_single_inode(inode
, wb
, &wbc
);
1415 EXPORT_SYMBOL(write_inode_now
);
1418 * sync_inode - write an inode and its pages to disk.
1419 * @inode: the inode to sync
1420 * @wbc: controls the writeback mode
1422 * sync_inode() will write an inode and its pages to disk. It will also
1423 * correctly update the inode on its superblock's dirty inode lists and will
1424 * update inode->i_state.
1426 * The caller must have a ref on the inode.
1428 int sync_inode(struct inode
*inode
, struct writeback_control
*wbc
)
1430 return writeback_single_inode(inode
, &inode_to_bdi(inode
)->wb
, wbc
);
1432 EXPORT_SYMBOL(sync_inode
);
1435 * sync_inode_metadata - write an inode to disk
1436 * @inode: the inode to sync
1437 * @wait: wait for I/O to complete.
1439 * Write an inode to disk and adjust its dirty state after completion.
1441 * Note: only writes the actual inode, no associated data or other metadata.
1443 int sync_inode_metadata(struct inode
*inode
, int wait
)
1445 struct writeback_control wbc
= {
1446 .sync_mode
= wait
? WB_SYNC_ALL
: WB_SYNC_NONE
,
1447 .nr_to_write
= 0, /* metadata-only */
1450 return sync_inode(inode
, &wbc
);
1452 EXPORT_SYMBOL(sync_inode_metadata
);