4 * Copyright (C) 2002, Linus Torvalds.
6 * Contains all the functions related to writing back and waiting
7 * upon dirty inodes against superblocks, and writing back dirty
8 * pages against inodes. ie: data writeback. Writeout of the
9 * inode itself is not handled here.
11 * 10Apr2002 Andrew Morton
12 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/spinlock.h>
19 #include <linux/slab.h>
20 #include <linux/sched.h>
23 #include <linux/kthread.h>
24 #include <linux/freezer.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/buffer_head.h>
29 #include <linux/tracepoint.h>
33 * Passed into wb_writeback(), essentially a subset of writeback_control
35 struct wb_writeback_work {
37 struct super_block *sb;
38 enum writeback_sync_modes sync_mode;
39 unsigned int tagged_writepages:1;
40 unsigned int for_kupdate:1;
41 unsigned int range_cyclic:1;
42 unsigned int for_background:1;
44 struct list_head list; /* pending work list */
45 struct completion *done; /* set if the caller waits */
49 * Include the creation of the trace points after defining the
50 * wb_writeback_work structure so that the definition remains local to this
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/writeback.h>
57 * We don't actually have pdflush, but this one is exported though /proc...
59 int nr_pdflush_threads;
62 * writeback_in_progress - determine whether there is writeback in progress
63 * @bdi: the device's backing_dev_info structure.
65 * Determine whether there is writeback waiting to be handled against a
68 int writeback_in_progress(struct backing_dev_info *bdi)
70 return test_bit(BDI_writeback_running, &bdi->state);
73 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
75 struct super_block *sb = inode->i_sb;
77 if (strcmp(sb->s_type->name, "bdev") == 0)
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);
88 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
89 static void bdi_wakeup_flusher(struct backing_dev_info *bdi)
92 wake_up_process(bdi->wb.task);
95 * The bdi thread isn't there, wake up the forker thread which
96 * will create and run it.
98 wake_up_process(default_backing_dev_info.wb.task);
102 static void bdi_queue_work(struct backing_dev_info *bdi,
103 struct wb_writeback_work *work)
105 trace_writeback_queue(bdi, work);
107 spin_lock_bh(&bdi->wb_lock);
108 list_add_tail(&work->list, &bdi->work_list);
110 trace_writeback_nothread(bdi, work);
111 bdi_wakeup_flusher(bdi);
112 spin_unlock_bh(&bdi->wb_lock);
116 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
119 struct wb_writeback_work *work;
122 * This is WB_SYNC_NONE writeback, so if allocation fails just
123 * wakeup the thread for old dirty data writeback
125 work = kzalloc(sizeof(*work), GFP_ATOMIC);
128 trace_writeback_nowork(bdi);
129 wake_up_process(bdi->wb.task);
134 work->sync_mode = WB_SYNC_NONE;
135 work->nr_pages = nr_pages;
136 work->range_cyclic = range_cyclic;
138 bdi_queue_work(bdi, work);
142 * bdi_start_writeback - start writeback
143 * @bdi: the backing device to write from
144 * @nr_pages: the number of pages to write
147 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
148 * started when this function returns, we make no guarantees on
149 * completion. Caller need not hold sb s_umount semaphore.
152 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
154 __bdi_start_writeback(bdi, nr_pages, true);
158 * bdi_start_background_writeback - start background writeback
159 * @bdi: the backing device to write from
162 * This makes sure WB_SYNC_NONE background writeback happens. When
163 * this function returns, it is only guaranteed that for given BDI
164 * some IO is happening if we are over background dirty threshold.
165 * Caller need not hold sb s_umount semaphore.
167 void bdi_start_background_writeback(struct backing_dev_info *bdi)
170 * We just wake up the flusher thread. It will perform background
171 * writeback as soon as there is no other work to do.
173 trace_writeback_wake_background(bdi);
174 spin_lock_bh(&bdi->wb_lock);
175 bdi_wakeup_flusher(bdi);
176 spin_unlock_bh(&bdi->wb_lock);
180 * Remove the inode from the writeback list it is on.
182 void inode_wb_list_del(struct inode *inode)
184 struct backing_dev_info *bdi = inode_to_bdi(inode);
186 spin_lock(&bdi->wb.list_lock);
187 list_del_init(&inode->i_wb_list);
188 spin_unlock(&bdi->wb.list_lock);
192 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
193 * furthest end of its superblock's dirty-inode list.
195 * Before stamping the inode's ->dirtied_when, we check to see whether it is
196 * already the most-recently-dirtied inode on the b_dirty list. If that is
197 * the case then the inode must have been redirtied while it was being written
198 * out and we don't reset its dirtied_when.
200 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
202 assert_spin_locked(&wb->list_lock);
203 if (!list_empty(&wb->b_dirty)) {
206 tail = wb_inode(wb->b_dirty.next);
207 if (time_before(inode->dirtied_when, tail->dirtied_when))
208 inode->dirtied_when = jiffies;
210 list_move(&inode->i_wb_list, &wb->b_dirty);
214 * requeue inode for re-scanning after bdi->b_io list is exhausted.
216 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
218 assert_spin_locked(&wb->list_lock);
219 list_move(&inode->i_wb_list, &wb->b_more_io);
222 static void inode_sync_complete(struct inode *inode)
225 * Prevent speculative execution through
226 * spin_unlock(&wb->list_lock);
230 wake_up_bit(&inode->i_state, __I_SYNC);
233 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
235 bool ret = time_after(inode->dirtied_when, t);
238 * For inodes being constantly redirtied, dirtied_when can get stuck.
239 * It _appears_ to be in the future, but is actually in distant past.
240 * This test is necessary to prevent such wrapped-around relative times
241 * from permanently stopping the whole bdi writeback.
243 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
249 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
251 static int move_expired_inodes(struct list_head *delaying_queue,
252 struct list_head *dispatch_queue,
253 unsigned long *older_than_this)
256 struct list_head *pos, *node;
257 struct super_block *sb = NULL;
262 while (!list_empty(delaying_queue)) {
263 inode = wb_inode(delaying_queue->prev);
264 if (older_than_this &&
265 inode_dirtied_after(inode, *older_than_this))
267 if (sb && sb != inode->i_sb)
270 list_move(&inode->i_wb_list, &tmp);
274 /* just one sb in list, splice to dispatch_queue and we're done */
276 list_splice(&tmp, dispatch_queue);
280 /* Move inodes from one superblock together */
281 while (!list_empty(&tmp)) {
282 sb = wb_inode(tmp.prev)->i_sb;
283 list_for_each_prev_safe(pos, node, &tmp) {
284 inode = wb_inode(pos);
285 if (inode->i_sb == sb)
286 list_move(&inode->i_wb_list, dispatch_queue);
294 * Queue all expired dirty inodes for io, eldest first.
296 * newly dirtied b_dirty b_io b_more_io
297 * =============> gf edc BA
299 * newly dirtied b_dirty b_io b_more_io
300 * =============> g fBAedc
302 * +--> dequeue for IO
304 static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
307 assert_spin_locked(&wb->list_lock);
308 list_splice_init(&wb->b_more_io, &wb->b_io);
309 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
310 trace_writeback_queue_io(wb, older_than_this, moved);
313 static int write_inode(struct inode *inode, struct writeback_control *wbc)
315 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
316 return inode->i_sb->s_op->write_inode(inode, wbc);
321 * Wait for writeback on an inode to complete.
323 static void inode_wait_for_writeback(struct inode *inode,
324 struct bdi_writeback *wb)
326 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
327 wait_queue_head_t *wqh;
329 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
330 while (inode->i_state & I_SYNC) {
331 spin_unlock(&inode->i_lock);
332 spin_unlock(&wb->list_lock);
333 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
334 spin_lock(&wb->list_lock);
335 spin_lock(&inode->i_lock);
340 * Write out an inode's dirty pages. Called under wb->list_lock and
341 * inode->i_lock. Either the caller has an active reference on the inode or
342 * the inode has I_WILL_FREE set.
344 * If `wait' is set, wait on the writeout.
346 * The whole writeout design is quite complex and fragile. We want to avoid
347 * starvation of particular inodes when others are being redirtied, prevent
351 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
352 struct writeback_control *wbc)
354 struct address_space *mapping = inode->i_mapping;
355 long nr_to_write = wbc->nr_to_write;
359 assert_spin_locked(&wb->list_lock);
360 assert_spin_locked(&inode->i_lock);
362 if (!atomic_read(&inode->i_count))
363 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
365 WARN_ON(inode->i_state & I_WILL_FREE);
367 if (inode->i_state & I_SYNC) {
369 * If this inode is locked for writeback and we are not doing
370 * writeback-for-data-integrity, move it to b_more_io so that
371 * writeback can proceed with the other inodes on s_io.
373 * We'll have another go at writing back this inode when we
374 * completed a full scan of b_io.
376 if (wbc->sync_mode != WB_SYNC_ALL) {
377 requeue_io(inode, wb);
378 trace_writeback_single_inode_requeue(inode, wbc,
384 * It's a data-integrity sync. We must wait.
386 inode_wait_for_writeback(inode, wb);
389 BUG_ON(inode->i_state & I_SYNC);
391 /* Set I_SYNC, reset I_DIRTY_PAGES */
392 inode->i_state |= I_SYNC;
393 inode->i_state &= ~I_DIRTY_PAGES;
394 spin_unlock(&inode->i_lock);
395 spin_unlock(&wb->list_lock);
397 ret = do_writepages(mapping, wbc);
400 * Make sure to wait on the data before writing out the metadata.
401 * This is important for filesystems that modify metadata on data
404 if (wbc->sync_mode == WB_SYNC_ALL) {
405 int err = filemap_fdatawait(mapping);
411 * Some filesystems may redirty the inode during the writeback
412 * due to delalloc, clear dirty metadata flags right before
415 spin_lock(&inode->i_lock);
416 dirty = inode->i_state & I_DIRTY;
417 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
418 spin_unlock(&inode->i_lock);
419 /* Don't write the inode if only I_DIRTY_PAGES was set */
420 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
421 int err = write_inode(inode, wbc);
426 spin_lock(&wb->list_lock);
427 spin_lock(&inode->i_lock);
428 inode->i_state &= ~I_SYNC;
429 if (!(inode->i_state & I_FREEING)) {
431 * Sync livelock prevention. Each inode is tagged and synced in
432 * one shot. If still dirty, it will be redirty_tail()'ed below.
433 * Update the dirty time to prevent enqueue and sync it again.
435 if ((inode->i_state & I_DIRTY) &&
436 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
437 inode->dirtied_when = jiffies;
439 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
441 * We didn't write back all the pages. nfs_writepages()
442 * sometimes bales out without doing anything.
444 inode->i_state |= I_DIRTY_PAGES;
445 if (wbc->nr_to_write <= 0) {
447 * slice used up: queue for next turn
449 requeue_io(inode, wb);
452 * Writeback blocked by something other than
453 * congestion. Delay the inode for some time to
454 * avoid spinning on the CPU (100% iowait)
455 * retrying writeback of the dirty page/inode
456 * that cannot be performed immediately.
458 redirty_tail(inode, wb);
460 } else if (inode->i_state & I_DIRTY) {
462 * Filesystems can dirty the inode during writeback
463 * operations, such as delayed allocation during
464 * submission or metadata updates after data IO
467 redirty_tail(inode, wb);
470 * The inode is clean. At this point we either have
471 * a reference to the inode or it's on it's way out.
472 * No need to add it back to the LRU.
474 list_del_init(&inode->i_wb_list);
475 wbc->inodes_written++;
478 inode_sync_complete(inode);
479 trace_writeback_single_inode(inode, wbc, nr_to_write);
484 * For background writeback the caller does not have the sb pinned
485 * before calling writeback. So make sure that we do pin it, so it doesn't
486 * go away while we are writing inodes from it.
488 static bool pin_sb_for_writeback(struct super_block *sb)
491 if (list_empty(&sb->s_instances)) {
492 spin_unlock(&sb_lock);
497 spin_unlock(&sb_lock);
499 if (down_read_trylock(&sb->s_umount)) {
502 up_read(&sb->s_umount);
510 * Write a portion of b_io inodes which belong to @sb.
512 * If @only_this_sb is true, then find and write all such
513 * inodes. Otherwise write only ones which go sequentially
516 * Return 1, if the caller writeback routine should be
517 * interrupted. Otherwise return 0.
519 static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
520 struct writeback_control *wbc, bool only_this_sb)
522 while (!list_empty(&wb->b_io)) {
524 struct inode *inode = wb_inode(wb->b_io.prev);
526 if (inode->i_sb != sb) {
529 * We only want to write back data for this
530 * superblock, move all inodes not belonging
531 * to it back onto the dirty list.
533 redirty_tail(inode, wb);
538 * The inode belongs to a different superblock.
539 * Bounce back to the caller to unpin this and
540 * pin the next superblock.
546 * Don't bother with new inodes or inodes beeing freed, first
547 * kind does not need peridic writeout yet, and for the latter
548 * kind writeout is handled by the freer.
550 spin_lock(&inode->i_lock);
551 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
552 spin_unlock(&inode->i_lock);
553 requeue_io(inode, wb);
559 pages_skipped = wbc->pages_skipped;
560 writeback_single_inode(inode, wb, wbc);
561 if (wbc->pages_skipped != pages_skipped) {
563 * writeback is not making progress due to locked
564 * buffers. Skip this inode for now.
566 redirty_tail(inode, wb);
568 spin_unlock(&inode->i_lock);
569 spin_unlock(&wb->list_lock);
572 spin_lock(&wb->list_lock);
573 if (wbc->nr_to_write <= 0)
580 static void __writeback_inodes_wb(struct bdi_writeback *wb,
581 struct writeback_control *wbc)
585 while (!list_empty(&wb->b_io)) {
586 struct inode *inode = wb_inode(wb->b_io.prev);
587 struct super_block *sb = inode->i_sb;
589 if (!pin_sb_for_writeback(sb)) {
590 requeue_io(inode, wb);
593 ret = writeback_sb_inodes(sb, wb, wbc, false);
599 /* Leave any unwritten inodes on b_io */
602 void writeback_inodes_wb(struct bdi_writeback *wb,
603 struct writeback_control *wbc)
605 spin_lock(&wb->list_lock);
606 if (list_empty(&wb->b_io))
607 queue_io(wb, wbc->older_than_this);
608 __writeback_inodes_wb(wb, wbc);
609 spin_unlock(&wb->list_lock);
613 * The maximum number of pages to writeout in a single bdi flush/kupdate
614 * operation. We do this so we don't hold I_SYNC against an inode for
615 * enormous amounts of time, which would block a userspace task which has
616 * been forced to throttle against that inode. Also, the code reevaluates
617 * the dirty each time it has written this many pages.
619 #define MAX_WRITEBACK_PAGES 1024
621 static inline bool over_bground_thresh(void)
623 unsigned long background_thresh, dirty_thresh;
625 global_dirty_limits(&background_thresh, &dirty_thresh);
627 return (global_page_state(NR_FILE_DIRTY) +
628 global_page_state(NR_UNSTABLE_NFS) > background_thresh);
632 * Explicit flushing or periodic writeback of "old" data.
634 * Define "old": the first time one of an inode's pages is dirtied, we mark the
635 * dirtying-time in the inode's address_space. So this periodic writeback code
636 * just walks the superblock inode list, writing back any inodes which are
637 * older than a specific point in time.
639 * Try to run once per dirty_writeback_interval. But if a writeback event
640 * takes longer than a dirty_writeback_interval interval, then leave a
643 * older_than_this takes precedence over nr_to_write. So we'll only write back
644 * all dirty pages if they are all attached to "old" mappings.
646 static long wb_writeback(struct bdi_writeback *wb,
647 struct wb_writeback_work *work)
649 struct writeback_control wbc = {
650 .sync_mode = work->sync_mode,
651 .tagged_writepages = work->tagged_writepages,
652 .older_than_this = NULL,
653 .for_kupdate = work->for_kupdate,
654 .for_background = work->for_background,
655 .range_cyclic = work->range_cyclic,
657 unsigned long oldest_jif;
659 long write_chunk = MAX_WRITEBACK_PAGES;
662 if (!wbc.range_cyclic) {
664 wbc.range_end = LLONG_MAX;
668 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
669 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
670 * here avoids calling into writeback_inodes_wb() more than once.
672 * The intended call sequence for WB_SYNC_ALL writeback is:
675 * writeback_sb_inodes() <== called only once
676 * write_cache_pages() <== called once for each inode
677 * (quickly) tag currently dirty pages
678 * (maybe slowly) sync all tagged pages
680 if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_writepages)
681 write_chunk = LONG_MAX;
683 oldest_jif = jiffies;
684 wbc.older_than_this = &oldest_jif;
686 spin_lock(&wb->list_lock);
689 * Stop writeback when nr_pages has been consumed
691 if (work->nr_pages <= 0)
695 * Background writeout and kupdate-style writeback may
696 * run forever. Stop them if there is other work to do
697 * so that e.g. sync can proceed. They'll be restarted
698 * after the other works are all done.
700 if ((work->for_background || work->for_kupdate) &&
701 !list_empty(&wb->bdi->work_list))
705 * For background writeout, stop when we are below the
706 * background dirty threshold
708 if (work->for_background && !over_bground_thresh())
711 if (work->for_kupdate) {
712 oldest_jif = jiffies -
713 msecs_to_jiffies(dirty_expire_interval * 10);
714 wbc.older_than_this = &oldest_jif;
717 wbc.nr_to_write = write_chunk;
718 wbc.pages_skipped = 0;
719 wbc.inodes_written = 0;
721 trace_wbc_writeback_start(&wbc, wb->bdi);
722 if (list_empty(&wb->b_io))
723 queue_io(wb, wbc.older_than_this);
725 writeback_sb_inodes(work->sb, wb, &wbc, true);
727 __writeback_inodes_wb(wb, &wbc);
728 trace_wbc_writeback_written(&wbc, wb->bdi);
730 work->nr_pages -= write_chunk - wbc.nr_to_write;
731 wrote += write_chunk - wbc.nr_to_write;
734 * Did we write something? Try for more
736 * Dirty inodes are moved to b_io for writeback in batches.
737 * The completion of the current batch does not necessarily
738 * mean the overall work is done. So we keep looping as long
739 * as made some progress on cleaning pages or inodes.
741 if (wbc.nr_to_write < write_chunk)
743 if (wbc.inodes_written)
746 * No more inodes for IO, bail
748 if (list_empty(&wb->b_more_io))
751 * Nothing written. Wait for some inode to
752 * become available for writeback. Otherwise
753 * we'll just busyloop.
755 if (!list_empty(&wb->b_more_io)) {
756 inode = wb_inode(wb->b_more_io.prev);
757 trace_wbc_writeback_wait(&wbc, wb->bdi);
758 spin_lock(&inode->i_lock);
759 inode_wait_for_writeback(inode, wb);
760 spin_unlock(&inode->i_lock);
763 spin_unlock(&wb->list_lock);
769 * Return the next wb_writeback_work struct that hasn't been processed yet.
771 static struct wb_writeback_work *
772 get_next_work_item(struct backing_dev_info *bdi)
774 struct wb_writeback_work *work = NULL;
776 spin_lock_bh(&bdi->wb_lock);
777 if (!list_empty(&bdi->work_list)) {
778 work = list_entry(bdi->work_list.next,
779 struct wb_writeback_work, list);
780 list_del_init(&work->list);
782 spin_unlock_bh(&bdi->wb_lock);
787 * Add in the number of potentially dirty inodes, because each inode
788 * write can dirty pagecache in the underlying blockdev.
790 static unsigned long get_nr_dirty_pages(void)
792 return global_page_state(NR_FILE_DIRTY) +
793 global_page_state(NR_UNSTABLE_NFS) +
794 get_nr_dirty_inodes();
797 static long wb_check_background_flush(struct bdi_writeback *wb)
799 if (over_bground_thresh()) {
801 struct wb_writeback_work work = {
802 .nr_pages = LONG_MAX,
803 .sync_mode = WB_SYNC_NONE,
808 return wb_writeback(wb, &work);
814 static long wb_check_old_data_flush(struct bdi_writeback *wb)
816 unsigned long expired;
820 * When set to zero, disable periodic writeback
822 if (!dirty_writeback_interval)
825 expired = wb->last_old_flush +
826 msecs_to_jiffies(dirty_writeback_interval * 10);
827 if (time_before(jiffies, expired))
830 wb->last_old_flush = jiffies;
831 nr_pages = get_nr_dirty_pages();
834 struct wb_writeback_work work = {
835 .nr_pages = nr_pages,
836 .sync_mode = WB_SYNC_NONE,
841 return wb_writeback(wb, &work);
848 * Retrieve work items and do the writeback they describe
850 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
852 struct backing_dev_info *bdi = wb->bdi;
853 struct wb_writeback_work *work;
856 set_bit(BDI_writeback_running, &wb->bdi->state);
857 while ((work = get_next_work_item(bdi)) != NULL) {
859 * Override sync mode, in case we must wait for completion
860 * because this thread is exiting now.
863 work->sync_mode = WB_SYNC_ALL;
865 trace_writeback_exec(bdi, work);
867 wrote += wb_writeback(wb, work);
870 * Notify the caller of completion if this is a synchronous
871 * work item, otherwise just free it.
874 complete(work->done);
880 * Check for periodic writeback, kupdated() style
882 wrote += wb_check_old_data_flush(wb);
883 wrote += wb_check_background_flush(wb);
884 clear_bit(BDI_writeback_running, &wb->bdi->state);
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_thread(void *data)
895 struct bdi_writeback *wb = data;
896 struct backing_dev_info *bdi = wb->bdi;
899 current->flags |= PF_SWAPWRITE;
901 wb->last_active = jiffies;
904 * Our parent may run at a different priority, just set us to normal
906 set_user_nice(current, 0);
908 trace_writeback_thread_start(bdi);
910 while (!kthread_should_stop()) {
912 * Remove own delayed wake-up timer, since we are already awake
913 * and we'll take care of the preriodic write-back.
915 del_timer(&wb->wakeup_timer);
917 pages_written = wb_do_writeback(wb, 0);
919 trace_writeback_pages_written(pages_written);
922 wb->last_active = jiffies;
924 set_current_state(TASK_INTERRUPTIBLE);
925 if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
926 __set_current_state(TASK_RUNNING);
930 if (wb_has_dirty_io(wb) && dirty_writeback_interval)
931 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
934 * We have nothing to do, so can go sleep without any
935 * timeout and save power. When a work is queued or
936 * something is made dirty - we will be woken up.
944 /* Flush any work that raced with us exiting */
945 if (!list_empty(&bdi->work_list))
946 wb_do_writeback(wb, 1);
948 trace_writeback_thread_stop(bdi);
954 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
957 void wakeup_flusher_threads(long nr_pages)
959 struct backing_dev_info *bdi;
962 nr_pages = global_page_state(NR_FILE_DIRTY) +
963 global_page_state(NR_UNSTABLE_NFS);
967 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
968 if (!bdi_has_dirty_io(bdi))
970 __bdi_start_writeback(bdi, nr_pages, false);
975 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
977 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
978 struct dentry *dentry;
979 const char *name = "?";
981 dentry = d_find_alias(inode);
983 spin_lock(&dentry->d_lock);
984 name = (const char *) dentry->d_name.name;
987 "%s(%d): dirtied inode %lu (%s) on %s\n",
988 current->comm, task_pid_nr(current), inode->i_ino,
989 name, inode->i_sb->s_id);
991 spin_unlock(&dentry->d_lock);
998 * __mark_inode_dirty - internal function
999 * @inode: inode to mark
1000 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1001 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1002 * mark_inode_dirty_sync.
1004 * Put the inode on the super block's dirty list.
1006 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1007 * dirty list only if it is hashed or if it refers to a blockdev.
1008 * If it was not hashed, it will never be added to the dirty list
1009 * even if it is later hashed, as it will have been marked dirty already.
1011 * In short, make sure you hash any inodes _before_ you start marking
1014 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1015 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1016 * the kernel-internal blockdev inode represents the dirtying time of the
1017 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1018 * page->mapping->host, so the page-dirtying time is recorded in the internal
1021 void __mark_inode_dirty(struct inode *inode, int flags)
1023 struct super_block *sb = inode->i_sb;
1024 struct backing_dev_info *bdi = NULL;
1027 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1028 * dirty the inode itself
1030 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1031 if (sb->s_op->dirty_inode)
1032 sb->s_op->dirty_inode(inode, flags);
1036 * make sure that changes are seen by all cpus before we test i_state
1041 /* avoid the locking if we can */
1042 if ((inode->i_state & flags) == flags)
1045 if (unlikely(block_dump))
1046 block_dump___mark_inode_dirty(inode);
1048 spin_lock(&inode->i_lock);
1049 if ((inode->i_state & flags) != flags) {
1050 const int was_dirty = inode->i_state & I_DIRTY;
1052 inode->i_state |= flags;
1055 * If the inode is being synced, just update its dirty state.
1056 * The unlocker will place the inode on the appropriate
1057 * superblock list, based upon its state.
1059 if (inode->i_state & I_SYNC)
1060 goto out_unlock_inode;
1063 * Only add valid (hashed) inodes to the superblock's
1064 * dirty list. Add blockdev inodes as well.
1066 if (!S_ISBLK(inode->i_mode)) {
1067 if (inode_unhashed(inode))
1068 goto out_unlock_inode;
1070 if (inode->i_state & I_FREEING)
1071 goto out_unlock_inode;
1074 * If the inode was already on b_dirty/b_io/b_more_io, don't
1075 * reposition it (that would break b_dirty time-ordering).
1078 bool wakeup_bdi = false;
1079 bdi = inode_to_bdi(inode);
1081 if (bdi_cap_writeback_dirty(bdi)) {
1082 WARN(!test_bit(BDI_registered, &bdi->state),
1083 "bdi-%s not registered\n", bdi->name);
1086 * If this is the first dirty inode for this
1087 * bdi, we have to wake-up the corresponding
1088 * bdi thread to make sure background
1089 * write-back happens later.
1091 if (!wb_has_dirty_io(&bdi->wb))
1095 spin_unlock(&inode->i_lock);
1096 spin_lock(&bdi->wb.list_lock);
1097 inode->dirtied_when = jiffies;
1098 list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1099 spin_unlock(&bdi->wb.list_lock);
1102 bdi_wakeup_thread_delayed(bdi);
1107 spin_unlock(&inode->i_lock);
1110 EXPORT_SYMBOL(__mark_inode_dirty);
1113 * Write out a superblock's list of dirty inodes. A wait will be performed
1114 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1116 * If older_than_this is non-NULL, then only write out inodes which
1117 * had their first dirtying at a time earlier than *older_than_this.
1119 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1120 * This function assumes that the blockdev superblock's inodes are backed by
1121 * a variety of queues, so all inodes are searched. For other superblocks,
1122 * assume that all inodes are backed by the same queue.
1124 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1125 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1126 * on the writer throttling path, and we get decent balancing between many
1127 * throttled threads: we don't want them all piling up on inode_sync_wait.
1129 static void wait_sb_inodes(struct super_block *sb)
1131 struct inode *inode, *old_inode = NULL;
1134 * We need to be protected against the filesystem going from
1135 * r/o to r/w or vice versa.
1137 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1139 spin_lock(&inode_sb_list_lock);
1142 * Data integrity sync. Must wait for all pages under writeback,
1143 * because there may have been pages dirtied before our sync
1144 * call, but which had writeout started before we write it out.
1145 * In which case, the inode may not be on the dirty list, but
1146 * we still have to wait for that writeout.
1148 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1149 struct address_space *mapping = inode->i_mapping;
1151 spin_lock(&inode->i_lock);
1152 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1153 (mapping->nrpages == 0)) {
1154 spin_unlock(&inode->i_lock);
1158 spin_unlock(&inode->i_lock);
1159 spin_unlock(&inode_sb_list_lock);
1162 * We hold a reference to 'inode' so it couldn't have been
1163 * removed from s_inodes list while we dropped the
1164 * inode_sb_list_lock. We cannot iput the inode now as we can
1165 * be holding the last reference and we cannot iput it under
1166 * inode_sb_list_lock. So we keep the reference and iput it
1172 filemap_fdatawait(mapping);
1176 spin_lock(&inode_sb_list_lock);
1178 spin_unlock(&inode_sb_list_lock);
1183 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1184 * @sb: the superblock
1185 * @nr: the number of pages to write
1187 * Start writeback on some inodes on this super_block. No guarantees are made
1188 * on how many (if any) will be written, and this function does not wait
1189 * for IO completion of submitted IO.
1191 void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr)
1193 DECLARE_COMPLETION_ONSTACK(done);
1194 struct wb_writeback_work work = {
1196 .sync_mode = WB_SYNC_NONE,
1197 .tagged_writepages = 1,
1202 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1203 bdi_queue_work(sb->s_bdi, &work);
1204 wait_for_completion(&done);
1206 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1209 * writeback_inodes_sb - writeback dirty inodes from given super_block
1210 * @sb: the superblock
1212 * Start writeback on some inodes on this super_block. No guarantees are made
1213 * on how many (if any) will be written, and this function does not wait
1214 * for IO completion of submitted IO.
1216 void writeback_inodes_sb(struct super_block *sb)
1218 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages());
1220 EXPORT_SYMBOL(writeback_inodes_sb);
1223 * writeback_inodes_sb_if_idle - start writeback if none underway
1224 * @sb: the superblock
1226 * Invoke writeback_inodes_sb if no writeback is currently underway.
1227 * Returns 1 if writeback was started, 0 if not.
1229 int writeback_inodes_sb_if_idle(struct super_block *sb)
1231 if (!writeback_in_progress(sb->s_bdi)) {
1232 down_read(&sb->s_umount);
1233 writeback_inodes_sb(sb);
1234 up_read(&sb->s_umount);
1239 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1242 * writeback_inodes_sb_if_idle - start writeback if none underway
1243 * @sb: the superblock
1244 * @nr: the number of pages to write
1246 * Invoke writeback_inodes_sb if no writeback is currently underway.
1247 * Returns 1 if writeback was started, 0 if not.
1249 int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
1252 if (!writeback_in_progress(sb->s_bdi)) {
1253 down_read(&sb->s_umount);
1254 writeback_inodes_sb_nr(sb, nr);
1255 up_read(&sb->s_umount);
1260 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
1263 * sync_inodes_sb - sync sb inode pages
1264 * @sb: the superblock
1266 * This function writes and waits on any dirty inode belonging to this
1269 void sync_inodes_sb(struct super_block *sb)
1271 DECLARE_COMPLETION_ONSTACK(done);
1272 struct wb_writeback_work work = {
1274 .sync_mode = WB_SYNC_ALL,
1275 .nr_pages = LONG_MAX,
1280 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1282 bdi_queue_work(sb->s_bdi, &work);
1283 wait_for_completion(&done);
1287 EXPORT_SYMBOL(sync_inodes_sb);
1290 * write_inode_now - write an inode to disk
1291 * @inode: inode to write to disk
1292 * @sync: whether the write should be synchronous or not
1294 * This function commits an inode to disk immediately if it is dirty. This is
1295 * primarily needed by knfsd.
1297 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1299 int write_inode_now(struct inode *inode, int sync)
1301 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1303 struct writeback_control wbc = {
1304 .nr_to_write = LONG_MAX,
1305 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1307 .range_end = LLONG_MAX,
1310 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1311 wbc.nr_to_write = 0;
1314 spin_lock(&wb->list_lock);
1315 spin_lock(&inode->i_lock);
1316 ret = writeback_single_inode(inode, wb, &wbc);
1317 spin_unlock(&inode->i_lock);
1318 spin_unlock(&wb->list_lock);
1320 inode_sync_wait(inode);
1323 EXPORT_SYMBOL(write_inode_now);
1326 * sync_inode - write an inode and its pages to disk.
1327 * @inode: the inode to sync
1328 * @wbc: controls the writeback mode
1330 * sync_inode() will write an inode and its pages to disk. It will also
1331 * correctly update the inode on its superblock's dirty inode lists and will
1332 * update inode->i_state.
1334 * The caller must have a ref on the inode.
1336 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1338 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1341 spin_lock(&wb->list_lock);
1342 spin_lock(&inode->i_lock);
1343 ret = writeback_single_inode(inode, wb, wbc);
1344 spin_unlock(&inode->i_lock);
1345 spin_unlock(&wb->list_lock);
1348 EXPORT_SYMBOL(sync_inode);
1351 * sync_inode_metadata - write an inode to disk
1352 * @inode: the inode to sync
1353 * @wait: wait for I/O to complete.
1355 * Write an inode to disk and adjust its dirty state after completion.
1357 * Note: only writes the actual inode, no associated data or other metadata.
1359 int sync_inode_metadata(struct inode *inode, int wait)
1361 struct writeback_control wbc = {
1362 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1363 .nr_to_write = 0, /* metadata-only */
1366 return sync_inode(inode, &wbc);
1368 EXPORT_SYMBOL(sync_inode_metadata);