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/freezer.h>
26 #include <linux/writeback.h>
27 #include <linux/blkdev.h>
28 #include <linux/backing-dev.h>
29 #include <linux/tracepoint.h>
33 * 4MB minimal write chunk size
35 #define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
38 * Passed into wb_writeback(), essentially a subset of writeback_control
40 struct wb_writeback_work {
42 struct super_block *sb;
43 unsigned long *older_than_this;
44 enum writeback_sync_modes sync_mode;
45 unsigned int tagged_writepages:1;
46 unsigned int for_kupdate:1;
47 unsigned int range_cyclic:1;
48 unsigned int for_background:1;
49 enum wb_reason reason; /* why was writeback initiated? */
51 struct list_head list; /* pending work list */
52 struct completion *done; /* set if the caller waits */
56 * We don't actually have pdflush, but this one is exported though /proc...
58 int nr_pdflush_threads;
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);
72 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
74 struct super_block *sb = inode->i_sb;
76 if (strcmp(sb->s_type->name, "bdev") == 0)
77 return inode->i_mapping->backing_dev_info;
82 static inline struct inode *wb_inode(struct list_head *head)
84 return list_entry(head, struct inode, i_wb_list);
88 * Include the creation of the trace points after defining the
89 * wb_writeback_work structure and inline functions so that the definition
90 * remains local to this file.
92 #define CREATE_TRACE_POINTS
93 #include <trace/events/writeback.h>
95 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
96 static void bdi_wakeup_flusher(struct backing_dev_info *bdi)
99 wake_up_process(bdi->wb.task);
102 * The bdi thread isn't there, wake up the forker thread which
103 * will create and run it.
105 wake_up_process(default_backing_dev_info.wb.task);
109 static void bdi_queue_work(struct backing_dev_info *bdi,
110 struct wb_writeback_work *work)
112 trace_writeback_queue(bdi, work);
114 spin_lock_bh(&bdi->wb_lock);
115 list_add_tail(&work->list, &bdi->work_list);
117 trace_writeback_nothread(bdi, work);
118 bdi_wakeup_flusher(bdi);
119 spin_unlock_bh(&bdi->wb_lock);
123 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
124 bool range_cyclic, enum wb_reason reason)
126 struct wb_writeback_work *work;
129 * This is WB_SYNC_NONE writeback, so if allocation fails just
130 * wakeup the thread for old dirty data writeback
132 work = kzalloc(sizeof(*work), GFP_ATOMIC);
135 trace_writeback_nowork(bdi);
136 wake_up_process(bdi->wb.task);
141 work->sync_mode = WB_SYNC_NONE;
142 work->nr_pages = nr_pages;
143 work->range_cyclic = range_cyclic;
144 work->reason = reason;
146 bdi_queue_work(bdi, work);
150 * bdi_start_writeback - start writeback
151 * @bdi: the backing device to write from
152 * @nr_pages: the number of pages to write
153 * @reason: reason why some writeback work was initiated
156 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
157 * started when this function returns, we make no guarantees on
158 * completion. Caller need not hold sb s_umount semaphore.
161 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
162 enum wb_reason reason)
164 __bdi_start_writeback(bdi, nr_pages, true, reason);
168 * bdi_start_background_writeback - start background writeback
169 * @bdi: the backing device to write from
172 * This makes sure WB_SYNC_NONE background writeback happens. When
173 * this function returns, it is only guaranteed that for given BDI
174 * some IO is happening if we are over background dirty threshold.
175 * Caller need not hold sb s_umount semaphore.
177 void bdi_start_background_writeback(struct backing_dev_info *bdi)
180 * We just wake up the flusher thread. It will perform background
181 * writeback as soon as there is no other work to do.
183 trace_writeback_wake_background(bdi);
184 spin_lock_bh(&bdi->wb_lock);
185 bdi_wakeup_flusher(bdi);
186 spin_unlock_bh(&bdi->wb_lock);
190 * Remove the inode from the writeback list it is on.
192 void inode_wb_list_del(struct inode *inode)
194 struct backing_dev_info *bdi = inode_to_bdi(inode);
196 spin_lock(&bdi->wb.list_lock);
197 list_del_init(&inode->i_wb_list);
198 spin_unlock(&bdi->wb.list_lock);
202 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
203 * furthest end of its superblock's dirty-inode list.
205 * Before stamping the inode's ->dirtied_when, we check to see whether it is
206 * already the most-recently-dirtied inode on the b_dirty list. If that is
207 * the case then the inode must have been redirtied while it was being written
208 * out and we don't reset its dirtied_when.
210 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
212 assert_spin_locked(&wb->list_lock);
213 if (!list_empty(&wb->b_dirty)) {
216 tail = wb_inode(wb->b_dirty.next);
217 if (time_before(inode->dirtied_when, tail->dirtied_when))
218 inode->dirtied_when = jiffies;
220 list_move(&inode->i_wb_list, &wb->b_dirty);
224 * requeue inode for re-scanning after bdi->b_io list is exhausted.
226 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
228 assert_spin_locked(&wb->list_lock);
229 list_move(&inode->i_wb_list, &wb->b_more_io);
232 static void inode_sync_complete(struct inode *inode)
234 inode->i_state &= ~I_SYNC;
235 /* Waiters must see I_SYNC cleared before being woken up */
237 wake_up_bit(&inode->i_state, __I_SYNC);
240 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
242 bool ret = time_after(inode->dirtied_when, t);
245 * For inodes being constantly redirtied, dirtied_when can get stuck.
246 * It _appears_ to be in the future, but is actually in distant past.
247 * This test is necessary to prevent such wrapped-around relative times
248 * from permanently stopping the whole bdi writeback.
250 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
256 * Move expired (dirtied after work->older_than_this) dirty inodes from
257 * @delaying_queue to @dispatch_queue.
259 static int move_expired_inodes(struct list_head *delaying_queue,
260 struct list_head *dispatch_queue,
261 struct wb_writeback_work *work)
264 struct list_head *pos, *node;
265 struct super_block *sb = NULL;
270 while (!list_empty(delaying_queue)) {
271 inode = wb_inode(delaying_queue->prev);
272 if (work->older_than_this &&
273 inode_dirtied_after(inode, *work->older_than_this))
275 if (sb && sb != inode->i_sb)
278 list_move(&inode->i_wb_list, &tmp);
282 /* just one sb in list, splice to dispatch_queue and we're done */
284 list_splice(&tmp, dispatch_queue);
288 /* Move inodes from one superblock together */
289 while (!list_empty(&tmp)) {
290 sb = wb_inode(tmp.prev)->i_sb;
291 list_for_each_prev_safe(pos, node, &tmp) {
292 inode = wb_inode(pos);
293 if (inode->i_sb == sb)
294 list_move(&inode->i_wb_list, dispatch_queue);
302 * Queue all expired dirty inodes for io, eldest first.
304 * newly dirtied b_dirty b_io b_more_io
305 * =============> gf edc BA
307 * newly dirtied b_dirty b_io b_more_io
308 * =============> g fBAedc
310 * +--> dequeue for IO
312 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
315 assert_spin_locked(&wb->list_lock);
316 list_splice_init(&wb->b_more_io, &wb->b_io);
317 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
318 trace_writeback_queue_io(wb, work, moved);
321 static int write_inode(struct inode *inode, struct writeback_control *wbc)
323 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
324 return inode->i_sb->s_op->write_inode(inode, wbc);
329 * Wait for writeback on an inode to complete.
331 static void inode_wait_for_writeback(struct inode *inode,
332 struct bdi_writeback *wb)
334 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
335 wait_queue_head_t *wqh;
337 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
338 while (inode->i_state & I_SYNC) {
339 spin_unlock(&inode->i_lock);
340 spin_unlock(&wb->list_lock);
341 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
342 spin_lock(&wb->list_lock);
343 spin_lock(&inode->i_lock);
348 * Write out an inode's dirty pages. Called under wb->list_lock and
349 * inode->i_lock. Either the caller has an active reference on the inode or
350 * the inode has I_WILL_FREE set.
352 * If `wait' is set, wait on the writeout.
354 * The whole writeout design is quite complex and fragile. We want to avoid
355 * starvation of particular inodes when others are being redirtied, prevent
359 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
360 struct writeback_control *wbc)
362 struct address_space *mapping = inode->i_mapping;
363 long nr_to_write = wbc->nr_to_write;
367 assert_spin_locked(&wb->list_lock);
368 assert_spin_locked(&inode->i_lock);
370 if (!atomic_read(&inode->i_count))
371 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
373 WARN_ON(inode->i_state & I_WILL_FREE);
375 if (inode->i_state & I_SYNC) {
377 * If this inode is locked for writeback and we are not doing
378 * writeback-for-data-integrity, move it to b_more_io so that
379 * writeback can proceed with the other inodes on s_io.
381 * We'll have another go at writing back this inode when we
382 * completed a full scan of b_io.
384 if (wbc->sync_mode != WB_SYNC_ALL) {
385 requeue_io(inode, wb);
386 trace_writeback_single_inode_requeue(inode, wbc,
392 * It's a data-integrity sync. We must wait.
394 inode_wait_for_writeback(inode, wb);
397 BUG_ON(inode->i_state & I_SYNC);
399 /* Set I_SYNC, reset I_DIRTY_PAGES */
400 inode->i_state |= I_SYNC;
401 inode->i_state &= ~I_DIRTY_PAGES;
402 spin_unlock(&inode->i_lock);
403 spin_unlock(&wb->list_lock);
405 ret = do_writepages(mapping, wbc);
408 * Make sure to wait on the data before writing out the metadata.
409 * This is important for filesystems that modify metadata on data
412 if (wbc->sync_mode == WB_SYNC_ALL) {
413 int err = filemap_fdatawait(mapping);
419 * Some filesystems may redirty the inode during the writeback
420 * due to delalloc, clear dirty metadata flags right before
423 spin_lock(&inode->i_lock);
424 dirty = inode->i_state & I_DIRTY;
425 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
426 spin_unlock(&inode->i_lock);
427 /* Don't write the inode if only I_DIRTY_PAGES was set */
428 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
429 int err = write_inode(inode, wbc);
434 spin_lock(&wb->list_lock);
435 spin_lock(&inode->i_lock);
436 if (!(inode->i_state & I_FREEING)) {
438 * Sync livelock prevention. Each inode is tagged and synced in
439 * one shot. If still dirty, it will be redirty_tail()'ed below.
440 * Update the dirty time to prevent enqueue and sync it again.
442 if ((inode->i_state & I_DIRTY) &&
443 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
444 inode->dirtied_when = jiffies;
446 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
448 * We didn't write back all the pages. nfs_writepages()
449 * sometimes bales out without doing anything.
451 inode->i_state |= I_DIRTY_PAGES;
452 if (wbc->nr_to_write <= 0) {
454 * slice used up: queue for next turn
456 requeue_io(inode, wb);
459 * Writeback blocked by something other than
460 * congestion. Delay the inode for some time to
461 * avoid spinning on the CPU (100% iowait)
462 * retrying writeback of the dirty page/inode
463 * that cannot be performed immediately.
465 redirty_tail(inode, wb);
467 } else if (inode->i_state & I_DIRTY) {
469 * Filesystems can dirty the inode during writeback
470 * operations, such as delayed allocation during
471 * submission or metadata updates after data IO
474 redirty_tail(inode, wb);
477 * The inode is clean. At this point we either have
478 * a reference to the inode or it's on it's way out.
479 * No need to add it back to the LRU.
481 list_del_init(&inode->i_wb_list);
484 inode_sync_complete(inode);
485 trace_writeback_single_inode(inode, wbc, nr_to_write);
489 static long writeback_chunk_size(struct backing_dev_info *bdi,
490 struct wb_writeback_work *work)
495 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
496 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
497 * here avoids calling into writeback_inodes_wb() more than once.
499 * The intended call sequence for WB_SYNC_ALL writeback is:
502 * writeback_sb_inodes() <== called only once
503 * write_cache_pages() <== called once for each inode
504 * (quickly) tag currently dirty pages
505 * (maybe slowly) sync all tagged pages
507 if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
510 pages = min(bdi->avg_write_bandwidth / 2,
511 global_dirty_limit / DIRTY_SCOPE);
512 pages = min(pages, work->nr_pages);
513 pages = round_down(pages + MIN_WRITEBACK_PAGES,
514 MIN_WRITEBACK_PAGES);
521 * Write a portion of b_io inodes which belong to @sb.
523 * If @only_this_sb is true, then find and write all such
524 * inodes. Otherwise write only ones which go sequentially
527 * Return the number of pages and/or inodes written.
529 static long writeback_sb_inodes(struct super_block *sb,
530 struct bdi_writeback *wb,
531 struct wb_writeback_work *work)
533 struct writeback_control wbc = {
534 .sync_mode = work->sync_mode,
535 .tagged_writepages = work->tagged_writepages,
536 .for_kupdate = work->for_kupdate,
537 .for_background = work->for_background,
538 .range_cyclic = work->range_cyclic,
540 .range_end = LLONG_MAX,
542 unsigned long start_time = jiffies;
544 long wrote = 0; /* count both pages and inodes */
546 while (!list_empty(&wb->b_io)) {
547 struct inode *inode = wb_inode(wb->b_io.prev);
549 if (inode->i_sb != sb) {
552 * We only want to write back data for this
553 * superblock, move all inodes not belonging
554 * to it back onto the dirty list.
556 redirty_tail(inode, wb);
561 * The inode belongs to a different superblock.
562 * Bounce back to the caller to unpin this and
563 * pin the next superblock.
569 * Don't bother with new inodes or inodes beeing freed, first
570 * kind does not need peridic writeout yet, and for the latter
571 * kind writeout is handled by the freer.
573 spin_lock(&inode->i_lock);
574 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
575 spin_unlock(&inode->i_lock);
576 redirty_tail(inode, wb);
580 write_chunk = writeback_chunk_size(wb->bdi, work);
581 wbc.nr_to_write = write_chunk;
582 wbc.pages_skipped = 0;
584 writeback_single_inode(inode, wb, &wbc);
586 work->nr_pages -= write_chunk - wbc.nr_to_write;
587 wrote += write_chunk - wbc.nr_to_write;
588 if (!(inode->i_state & I_DIRTY))
590 if (wbc.pages_skipped) {
592 * writeback is not making progress due to locked
593 * buffers. Skip this inode for now.
595 redirty_tail(inode, wb);
597 spin_unlock(&inode->i_lock);
598 spin_unlock(&wb->list_lock);
601 spin_lock(&wb->list_lock);
603 * bail out to wb_writeback() often enough to check
604 * background threshold and other termination conditions.
607 if (time_is_before_jiffies(start_time + HZ / 10UL))
609 if (work->nr_pages <= 0)
616 static long __writeback_inodes_wb(struct bdi_writeback *wb,
617 struct wb_writeback_work *work)
619 unsigned long start_time = jiffies;
622 while (!list_empty(&wb->b_io)) {
623 struct inode *inode = wb_inode(wb->b_io.prev);
624 struct super_block *sb = inode->i_sb;
626 if (!grab_super_passive(sb)) {
628 * grab_super_passive() may fail consistently due to
629 * s_umount being grabbed by someone else. Don't use
630 * requeue_io() to avoid busy retrying the inode/sb.
632 redirty_tail(inode, wb);
635 wrote += writeback_sb_inodes(sb, wb, work);
638 /* refer to the same tests at the end of writeback_sb_inodes */
640 if (time_is_before_jiffies(start_time + HZ / 10UL))
642 if (work->nr_pages <= 0)
646 /* Leave any unwritten inodes on b_io */
650 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
651 enum wb_reason reason)
653 struct wb_writeback_work work = {
654 .nr_pages = nr_pages,
655 .sync_mode = WB_SYNC_NONE,
660 spin_lock(&wb->list_lock);
661 if (list_empty(&wb->b_io))
663 __writeback_inodes_wb(wb, &work);
664 spin_unlock(&wb->list_lock);
666 return nr_pages - work.nr_pages;
669 static bool over_bground_thresh(struct backing_dev_info *bdi)
671 unsigned long background_thresh, dirty_thresh;
673 global_dirty_limits(&background_thresh, &dirty_thresh);
675 if (global_page_state(NR_FILE_DIRTY) +
676 global_page_state(NR_UNSTABLE_NFS) > background_thresh)
679 if (bdi_stat(bdi, BDI_RECLAIMABLE) >
680 bdi_dirty_limit(bdi, background_thresh))
687 * Called under wb->list_lock. If there are multiple wb per bdi,
688 * only the flusher working on the first wb should do it.
690 static void wb_update_bandwidth(struct bdi_writeback *wb,
691 unsigned long start_time)
693 __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
697 * Explicit flushing or periodic writeback of "old" data.
699 * Define "old": the first time one of an inode's pages is dirtied, we mark the
700 * dirtying-time in the inode's address_space. So this periodic writeback code
701 * just walks the superblock inode list, writing back any inodes which are
702 * older than a specific point in time.
704 * Try to run once per dirty_writeback_interval. But if a writeback event
705 * takes longer than a dirty_writeback_interval interval, then leave a
708 * older_than_this takes precedence over nr_to_write. So we'll only write back
709 * all dirty pages if they are all attached to "old" mappings.
711 static long wb_writeback(struct bdi_writeback *wb,
712 struct wb_writeback_work *work)
714 unsigned long wb_start = jiffies;
715 long nr_pages = work->nr_pages;
716 unsigned long oldest_jif;
720 oldest_jif = jiffies;
721 work->older_than_this = &oldest_jif;
723 spin_lock(&wb->list_lock);
726 * Stop writeback when nr_pages has been consumed
728 if (work->nr_pages <= 0)
732 * Background writeout and kupdate-style writeback may
733 * run forever. Stop them if there is other work to do
734 * so that e.g. sync can proceed. They'll be restarted
735 * after the other works are all done.
737 if ((work->for_background || work->for_kupdate) &&
738 !list_empty(&wb->bdi->work_list))
742 * For background writeout, stop when we are below the
743 * background dirty threshold
745 if (work->for_background && !over_bground_thresh(wb->bdi))
749 * Kupdate and background works are special and we want to
750 * include all inodes that need writing. Livelock avoidance is
751 * handled by these works yielding to any other work so we are
754 if (work->for_kupdate) {
755 oldest_jif = jiffies -
756 msecs_to_jiffies(dirty_expire_interval * 10);
757 } else if (work->for_background)
758 oldest_jif = jiffies;
760 trace_writeback_start(wb->bdi, work);
761 if (list_empty(&wb->b_io))
764 progress = writeback_sb_inodes(work->sb, wb, work);
766 progress = __writeback_inodes_wb(wb, work);
767 trace_writeback_written(wb->bdi, work);
769 wb_update_bandwidth(wb, wb_start);
772 * Did we write something? Try for more
774 * Dirty inodes are moved to b_io for writeback in batches.
775 * The completion of the current batch does not necessarily
776 * mean the overall work is done. So we keep looping as long
777 * as made some progress on cleaning pages or inodes.
782 * No more inodes for IO, bail
784 if (list_empty(&wb->b_more_io))
787 * Nothing written. Wait for some inode to
788 * become available for writeback. Otherwise
789 * we'll just busyloop.
791 if (!list_empty(&wb->b_more_io)) {
792 trace_writeback_wait(wb->bdi, work);
793 inode = wb_inode(wb->b_more_io.prev);
794 spin_lock(&inode->i_lock);
795 inode_wait_for_writeback(inode, wb);
796 spin_unlock(&inode->i_lock);
799 spin_unlock(&wb->list_lock);
801 return nr_pages - work->nr_pages;
805 * Return the next wb_writeback_work struct that hasn't been processed yet.
807 static struct wb_writeback_work *
808 get_next_work_item(struct backing_dev_info *bdi)
810 struct wb_writeback_work *work = NULL;
812 spin_lock_bh(&bdi->wb_lock);
813 if (!list_empty(&bdi->work_list)) {
814 work = list_entry(bdi->work_list.next,
815 struct wb_writeback_work, list);
816 list_del_init(&work->list);
818 spin_unlock_bh(&bdi->wb_lock);
823 * Add in the number of potentially dirty inodes, because each inode
824 * write can dirty pagecache in the underlying blockdev.
826 static unsigned long get_nr_dirty_pages(void)
828 return global_page_state(NR_FILE_DIRTY) +
829 global_page_state(NR_UNSTABLE_NFS) +
830 get_nr_dirty_inodes();
833 static long wb_check_background_flush(struct bdi_writeback *wb)
835 if (over_bground_thresh(wb->bdi)) {
837 struct wb_writeback_work work = {
838 .nr_pages = LONG_MAX,
839 .sync_mode = WB_SYNC_NONE,
842 .reason = WB_REASON_BACKGROUND,
845 return wb_writeback(wb, &work);
851 static long wb_check_old_data_flush(struct bdi_writeback *wb)
853 unsigned long expired;
857 * When set to zero, disable periodic writeback
859 if (!dirty_writeback_interval)
862 expired = wb->last_old_flush +
863 msecs_to_jiffies(dirty_writeback_interval * 10);
864 if (time_before(jiffies, expired))
867 wb->last_old_flush = jiffies;
868 nr_pages = get_nr_dirty_pages();
871 struct wb_writeback_work work = {
872 .nr_pages = nr_pages,
873 .sync_mode = WB_SYNC_NONE,
876 .reason = WB_REASON_PERIODIC,
879 return wb_writeback(wb, &work);
886 * Retrieve work items and do the writeback they describe
888 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
890 struct backing_dev_info *bdi = wb->bdi;
891 struct wb_writeback_work *work;
894 set_bit(BDI_writeback_running, &wb->bdi->state);
895 while ((work = get_next_work_item(bdi)) != NULL) {
897 * Override sync mode, in case we must wait for completion
898 * because this thread is exiting now.
901 work->sync_mode = WB_SYNC_ALL;
903 trace_writeback_exec(bdi, work);
905 wrote += wb_writeback(wb, work);
908 * Notify the caller of completion if this is a synchronous
909 * work item, otherwise just free it.
912 complete(work->done);
918 * Check for periodic writeback, kupdated() style
920 wrote += wb_check_old_data_flush(wb);
921 wrote += wb_check_background_flush(wb);
922 clear_bit(BDI_writeback_running, &wb->bdi->state);
928 * Handle writeback of dirty data for the device backed by this bdi. Also
929 * wakes up periodically and does kupdated style flushing.
931 int bdi_writeback_thread(void *data)
933 struct bdi_writeback *wb = data;
934 struct backing_dev_info *bdi = wb->bdi;
937 current->flags |= PF_SWAPWRITE;
939 wb->last_active = jiffies;
942 * Our parent may run at a different priority, just set us to normal
944 set_user_nice(current, 0);
946 trace_writeback_thread_start(bdi);
948 while (!kthread_freezable_should_stop(NULL)) {
950 * Remove own delayed wake-up timer, since we are already awake
951 * and we'll take care of the preriodic write-back.
953 del_timer(&wb->wakeup_timer);
955 pages_written = wb_do_writeback(wb, 0);
957 trace_writeback_pages_written(pages_written);
960 wb->last_active = jiffies;
962 set_current_state(TASK_INTERRUPTIBLE);
963 if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
964 __set_current_state(TASK_RUNNING);
968 if (wb_has_dirty_io(wb) && dirty_writeback_interval)
969 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
972 * We have nothing to do, so can go sleep without any
973 * timeout and save power. When a work is queued or
974 * something is made dirty - we will be woken up.
980 /* Flush any work that raced with us exiting */
981 if (!list_empty(&bdi->work_list))
982 wb_do_writeback(wb, 1);
984 trace_writeback_thread_stop(bdi);
990 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
993 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
995 struct backing_dev_info *bdi;
998 nr_pages = global_page_state(NR_FILE_DIRTY) +
999 global_page_state(NR_UNSTABLE_NFS);
1003 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1004 if (!bdi_has_dirty_io(bdi))
1006 __bdi_start_writeback(bdi, nr_pages, false, reason);
1011 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1013 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1014 struct dentry *dentry;
1015 const char *name = "?";
1017 dentry = d_find_alias(inode);
1019 spin_lock(&dentry->d_lock);
1020 name = (const char *) dentry->d_name.name;
1023 "%s(%d): dirtied inode %lu (%s) on %s\n",
1024 current->comm, task_pid_nr(current), inode->i_ino,
1025 name, inode->i_sb->s_id);
1027 spin_unlock(&dentry->d_lock);
1034 * __mark_inode_dirty - internal function
1035 * @inode: inode to mark
1036 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1037 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1038 * mark_inode_dirty_sync.
1040 * Put the inode on the super block's dirty list.
1042 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1043 * dirty list only if it is hashed or if it refers to a blockdev.
1044 * If it was not hashed, it will never be added to the dirty list
1045 * even if it is later hashed, as it will have been marked dirty already.
1047 * In short, make sure you hash any inodes _before_ you start marking
1050 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1051 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1052 * the kernel-internal blockdev inode represents the dirtying time of the
1053 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1054 * page->mapping->host, so the page-dirtying time is recorded in the internal
1057 void __mark_inode_dirty(struct inode *inode, int flags)
1059 struct super_block *sb = inode->i_sb;
1060 struct backing_dev_info *bdi = NULL;
1063 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1064 * dirty the inode itself
1066 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1067 if (sb->s_op->dirty_inode)
1068 sb->s_op->dirty_inode(inode, flags);
1072 * make sure that changes are seen by all cpus before we test i_state
1077 /* avoid the locking if we can */
1078 if ((inode->i_state & flags) == flags)
1081 if (unlikely(block_dump))
1082 block_dump___mark_inode_dirty(inode);
1084 spin_lock(&inode->i_lock);
1085 if ((inode->i_state & flags) != flags) {
1086 const int was_dirty = inode->i_state & I_DIRTY;
1088 inode->i_state |= flags;
1091 * If the inode is being synced, just update its dirty state.
1092 * The unlocker will place the inode on the appropriate
1093 * superblock list, based upon its state.
1095 if (inode->i_state & I_SYNC)
1096 goto out_unlock_inode;
1099 * Only add valid (hashed) inodes to the superblock's
1100 * dirty list. Add blockdev inodes as well.
1102 if (!S_ISBLK(inode->i_mode)) {
1103 if (inode_unhashed(inode))
1104 goto out_unlock_inode;
1106 if (inode->i_state & I_FREEING)
1107 goto out_unlock_inode;
1110 * If the inode was already on b_dirty/b_io/b_more_io, don't
1111 * reposition it (that would break b_dirty time-ordering).
1114 bool wakeup_bdi = false;
1115 bdi = inode_to_bdi(inode);
1117 if (bdi_cap_writeback_dirty(bdi)) {
1118 WARN(!test_bit(BDI_registered, &bdi->state),
1119 "bdi-%s not registered\n", bdi->name);
1122 * If this is the first dirty inode for this
1123 * bdi, we have to wake-up the corresponding
1124 * bdi thread to make sure background
1125 * write-back happens later.
1127 if (!wb_has_dirty_io(&bdi->wb))
1131 spin_unlock(&inode->i_lock);
1132 spin_lock(&bdi->wb.list_lock);
1133 inode->dirtied_when = jiffies;
1134 list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1135 spin_unlock(&bdi->wb.list_lock);
1138 bdi_wakeup_thread_delayed(bdi);
1143 spin_unlock(&inode->i_lock);
1146 EXPORT_SYMBOL(__mark_inode_dirty);
1148 static void wait_sb_inodes(struct super_block *sb)
1150 struct inode *inode, *old_inode = NULL;
1153 * We need to be protected against the filesystem going from
1154 * r/o to r/w or vice versa.
1156 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1158 spin_lock(&inode_sb_list_lock);
1161 * Data integrity sync. Must wait for all pages under writeback,
1162 * because there may have been pages dirtied before our sync
1163 * call, but which had writeout started before we write it out.
1164 * In which case, the inode may not be on the dirty list, but
1165 * we still have to wait for that writeout.
1167 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1168 struct address_space *mapping = inode->i_mapping;
1170 spin_lock(&inode->i_lock);
1171 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1172 (mapping->nrpages == 0)) {
1173 spin_unlock(&inode->i_lock);
1177 spin_unlock(&inode->i_lock);
1178 spin_unlock(&inode_sb_list_lock);
1181 * We hold a reference to 'inode' so it couldn't have been
1182 * removed from s_inodes list while we dropped the
1183 * inode_sb_list_lock. We cannot iput the inode now as we can
1184 * be holding the last reference and we cannot iput it under
1185 * inode_sb_list_lock. So we keep the reference and iput it
1191 filemap_fdatawait(mapping);
1195 spin_lock(&inode_sb_list_lock);
1197 spin_unlock(&inode_sb_list_lock);
1202 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1203 * @sb: the superblock
1204 * @nr: the number of pages to write
1205 * @reason: reason why some writeback work initiated
1207 * Start writeback on some inodes on this super_block. No guarantees are made
1208 * on how many (if any) will be written, and this function does not wait
1209 * for IO completion of submitted IO.
1211 void writeback_inodes_sb_nr(struct super_block *sb,
1213 enum wb_reason reason)
1215 DECLARE_COMPLETION_ONSTACK(done);
1216 struct wb_writeback_work work = {
1218 .sync_mode = WB_SYNC_NONE,
1219 .tagged_writepages = 1,
1225 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1226 bdi_queue_work(sb->s_bdi, &work);
1227 wait_for_completion(&done);
1229 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1232 * writeback_inodes_sb - writeback dirty inodes from given super_block
1233 * @sb: the superblock
1234 * @reason: reason why some writeback work was initiated
1236 * Start writeback on some inodes on this super_block. No guarantees are made
1237 * on how many (if any) will be written, and this function does not wait
1238 * for IO completion of submitted IO.
1240 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1242 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1244 EXPORT_SYMBOL(writeback_inodes_sb);
1247 * writeback_inodes_sb_if_idle - start writeback if none underway
1248 * @sb: the superblock
1249 * @reason: reason why some writeback work was initiated
1251 * Invoke writeback_inodes_sb if no writeback is currently underway.
1252 * Returns 1 if writeback was started, 0 if not.
1254 int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
1256 if (!writeback_in_progress(sb->s_bdi)) {
1257 down_read(&sb->s_umount);
1258 writeback_inodes_sb(sb, reason);
1259 up_read(&sb->s_umount);
1264 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1267 * writeback_inodes_sb_nr_if_idle - start writeback if none underway
1268 * @sb: the superblock
1269 * @nr: the number of pages to write
1270 * @reason: reason why some writeback work was initiated
1272 * Invoke writeback_inodes_sb if no writeback is currently underway.
1273 * Returns 1 if writeback was started, 0 if not.
1275 int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
1277 enum wb_reason reason)
1279 if (!writeback_in_progress(sb->s_bdi)) {
1280 down_read(&sb->s_umount);
1281 writeback_inodes_sb_nr(sb, nr, reason);
1282 up_read(&sb->s_umount);
1287 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
1290 * sync_inodes_sb - sync sb inode pages
1291 * @sb: the superblock
1293 * This function writes and waits on any dirty inode belonging to this
1296 void sync_inodes_sb(struct super_block *sb)
1298 DECLARE_COMPLETION_ONSTACK(done);
1299 struct wb_writeback_work work = {
1301 .sync_mode = WB_SYNC_ALL,
1302 .nr_pages = LONG_MAX,
1305 .reason = WB_REASON_SYNC,
1308 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1310 bdi_queue_work(sb->s_bdi, &work);
1311 wait_for_completion(&done);
1315 EXPORT_SYMBOL(sync_inodes_sb);
1318 * write_inode_now - write an inode to disk
1319 * @inode: inode to write to disk
1320 * @sync: whether the write should be synchronous or not
1322 * This function commits an inode to disk immediately if it is dirty. This is
1323 * primarily needed by knfsd.
1325 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1327 int write_inode_now(struct inode *inode, int sync)
1329 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1331 struct writeback_control wbc = {
1332 .nr_to_write = LONG_MAX,
1333 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1335 .range_end = LLONG_MAX,
1338 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1339 wbc.nr_to_write = 0;
1342 spin_lock(&wb->list_lock);
1343 spin_lock(&inode->i_lock);
1344 ret = writeback_single_inode(inode, wb, &wbc);
1345 spin_unlock(&inode->i_lock);
1346 spin_unlock(&wb->list_lock);
1349 EXPORT_SYMBOL(write_inode_now);
1352 * sync_inode - write an inode and its pages to disk.
1353 * @inode: the inode to sync
1354 * @wbc: controls the writeback mode
1356 * sync_inode() will write an inode and its pages to disk. It will also
1357 * correctly update the inode on its superblock's dirty inode lists and will
1358 * update inode->i_state.
1360 * The caller must have a ref on the inode.
1362 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1364 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1367 spin_lock(&wb->list_lock);
1368 spin_lock(&inode->i_lock);
1369 ret = writeback_single_inode(inode, wb, wbc);
1370 spin_unlock(&inode->i_lock);
1371 spin_unlock(&wb->list_lock);
1374 EXPORT_SYMBOL(sync_inode);
1377 * sync_inode_metadata - write an inode to disk
1378 * @inode: the inode to sync
1379 * @wait: wait for I/O to complete.
1381 * Write an inode to disk and adjust its dirty state after completion.
1383 * Note: only writes the actual inode, no associated data or other metadata.
1385 int sync_inode_metadata(struct inode *inode, int wait)
1387 struct writeback_control wbc = {
1388 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1389 .nr_to_write = 0, /* metadata-only */
1392 return sync_inode(inode, &wbc);
1394 EXPORT_SYMBOL(sync_inode_metadata);