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>
29 #include <linux/device.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 unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
50 enum wb_reason reason; /* why was writeback initiated? */
52 struct list_head list; /* pending work list */
53 struct completion *done; /* set if the caller waits */
57 * writeback_in_progress - determine whether there is writeback in progress
58 * @bdi: the device's backing_dev_info structure.
60 * Determine whether there is writeback waiting to be handled against a
63 int writeback_in_progress(struct backing_dev_info *bdi)
65 return test_bit(BDI_writeback_running, &bdi->state);
67 EXPORT_SYMBOL(writeback_in_progress);
69 struct backing_dev_info *inode_to_bdi(struct inode *inode)
71 struct super_block *sb;
74 return &noop_backing_dev_info;
78 if (sb_is_blkdev_sb(sb))
79 return blk_get_backing_dev_info(I_BDEV(inode));
83 EXPORT_SYMBOL_GPL(inode_to_bdi);
85 static inline struct inode *wb_inode(struct list_head *head)
87 return list_entry(head, struct inode, i_wb_list);
91 * Include the creation of the trace points after defining the
92 * wb_writeback_work structure and inline functions so that the definition
93 * remains local to this file.
95 #define CREATE_TRACE_POINTS
96 #include <trace/events/writeback.h>
98 EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
100 static void bdi_wakeup_thread(struct backing_dev_info *bdi)
102 spin_lock_bh(&bdi->wb_lock);
103 if (test_bit(BDI_registered, &bdi->state))
104 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
105 spin_unlock_bh(&bdi->wb_lock);
108 static void bdi_queue_work(struct backing_dev_info *bdi,
109 struct wb_writeback_work *work)
111 trace_writeback_queue(bdi, work);
113 spin_lock_bh(&bdi->wb_lock);
114 if (!test_bit(BDI_registered, &bdi->state)) {
116 complete(work->done);
119 list_add_tail(&work->list, &bdi->work_list);
120 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
122 spin_unlock_bh(&bdi->wb_lock);
126 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
127 bool range_cyclic, enum wb_reason reason)
129 struct wb_writeback_work *work;
132 * This is WB_SYNC_NONE writeback, so if allocation fails just
133 * wakeup the thread for old dirty data writeback
135 work = kzalloc(sizeof(*work), GFP_ATOMIC);
137 trace_writeback_nowork(bdi);
138 bdi_wakeup_thread(bdi);
142 work->sync_mode = WB_SYNC_NONE;
143 work->nr_pages = nr_pages;
144 work->range_cyclic = range_cyclic;
145 work->reason = reason;
147 bdi_queue_work(bdi, work);
151 * bdi_start_writeback - start writeback
152 * @bdi: the backing device to write from
153 * @nr_pages: the number of pages to write
154 * @reason: reason why some writeback work was initiated
157 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
158 * started when this function returns, we make no guarantees on
159 * completion. Caller need not hold sb s_umount semaphore.
162 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
163 enum wb_reason reason)
165 __bdi_start_writeback(bdi, nr_pages, true, reason);
169 * bdi_start_background_writeback - start background writeback
170 * @bdi: the backing device to write from
173 * This makes sure WB_SYNC_NONE background writeback happens. When
174 * this function returns, it is only guaranteed that for given BDI
175 * some IO is happening if we are over background dirty threshold.
176 * Caller need not hold sb s_umount semaphore.
178 void bdi_start_background_writeback(struct backing_dev_info *bdi)
181 * We just wake up the flusher thread. It will perform background
182 * writeback as soon as there is no other work to do.
184 trace_writeback_wake_background(bdi);
185 bdi_wakeup_thread(bdi);
189 * Remove the inode from the writeback list it is on.
191 void inode_wb_list_del(struct inode *inode)
193 struct backing_dev_info *bdi = inode_to_bdi(inode);
195 spin_lock(&bdi->wb.list_lock);
196 list_del_init(&inode->i_wb_list);
197 spin_unlock(&bdi->wb.list_lock);
201 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
202 * furthest end of its superblock's dirty-inode list.
204 * Before stamping the inode's ->dirtied_when, we check to see whether it is
205 * already the most-recently-dirtied inode on the b_dirty list. If that is
206 * the case then the inode must have been redirtied while it was being written
207 * out and we don't reset its dirtied_when.
209 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
211 assert_spin_locked(&wb->list_lock);
212 if (!list_empty(&wb->b_dirty)) {
215 tail = wb_inode(wb->b_dirty.next);
216 if (time_before(inode->dirtied_when, tail->dirtied_when))
217 inode->dirtied_when = jiffies;
219 list_move(&inode->i_wb_list, &wb->b_dirty);
223 * requeue inode for re-scanning after bdi->b_io list is exhausted.
225 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
227 assert_spin_locked(&wb->list_lock);
228 list_move(&inode->i_wb_list, &wb->b_more_io);
231 static void inode_sync_complete(struct inode *inode)
233 inode->i_state &= ~I_SYNC;
234 /* If inode is clean an unused, put it into LRU now... */
235 inode_add_lru(inode);
236 /* Waiters must see I_SYNC cleared before being woken up */
238 wake_up_bit(&inode->i_state, __I_SYNC);
241 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
243 bool ret = time_after(inode->dirtied_when, t);
246 * For inodes being constantly redirtied, dirtied_when can get stuck.
247 * It _appears_ to be in the future, but is actually in distant past.
248 * This test is necessary to prevent such wrapped-around relative times
249 * from permanently stopping the whole bdi writeback.
251 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
257 * Move expired (dirtied before work->older_than_this) dirty inodes from
258 * @delaying_queue to @dispatch_queue.
260 static int move_expired_inodes(struct list_head *delaying_queue,
261 struct list_head *dispatch_queue,
262 struct wb_writeback_work *work)
265 struct list_head *pos, *node;
266 struct super_block *sb = NULL;
271 while (!list_empty(delaying_queue)) {
272 inode = wb_inode(delaying_queue->prev);
273 if (work->older_than_this &&
274 inode_dirtied_after(inode, *work->older_than_this))
276 list_move(&inode->i_wb_list, &tmp);
278 if (sb_is_blkdev_sb(inode->i_sb))
280 if (sb && sb != inode->i_sb)
285 /* just one sb in list, splice to dispatch_queue and we're done */
287 list_splice(&tmp, dispatch_queue);
291 /* Move inodes from one superblock together */
292 while (!list_empty(&tmp)) {
293 sb = wb_inode(tmp.prev)->i_sb;
294 list_for_each_prev_safe(pos, node, &tmp) {
295 inode = wb_inode(pos);
296 if (inode->i_sb == sb)
297 list_move(&inode->i_wb_list, dispatch_queue);
305 * Queue all expired dirty inodes for io, eldest first.
307 * newly dirtied b_dirty b_io b_more_io
308 * =============> gf edc BA
310 * newly dirtied b_dirty b_io b_more_io
311 * =============> g fBAedc
313 * +--> dequeue for IO
315 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
318 assert_spin_locked(&wb->list_lock);
319 list_splice_init(&wb->b_more_io, &wb->b_io);
320 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
321 trace_writeback_queue_io(wb, work, moved);
324 static int write_inode(struct inode *inode, struct writeback_control *wbc)
328 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
329 trace_writeback_write_inode_start(inode, wbc);
330 ret = inode->i_sb->s_op->write_inode(inode, wbc);
331 trace_writeback_write_inode(inode, wbc);
338 * Wait for writeback on an inode to complete. Called with i_lock held.
339 * Caller must make sure inode cannot go away when we drop i_lock.
341 static void __inode_wait_for_writeback(struct inode *inode)
342 __releases(inode->i_lock)
343 __acquires(inode->i_lock)
345 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
346 wait_queue_head_t *wqh;
348 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
349 while (inode->i_state & I_SYNC) {
350 spin_unlock(&inode->i_lock);
351 __wait_on_bit(wqh, &wq, bit_wait,
352 TASK_UNINTERRUPTIBLE);
353 spin_lock(&inode->i_lock);
358 * Wait for writeback on an inode to complete. Caller must have inode pinned.
360 void inode_wait_for_writeback(struct inode *inode)
362 spin_lock(&inode->i_lock);
363 __inode_wait_for_writeback(inode);
364 spin_unlock(&inode->i_lock);
368 * Sleep until I_SYNC is cleared. This function must be called with i_lock
369 * held and drops it. It is aimed for callers not holding any inode reference
370 * so once i_lock is dropped, inode can go away.
372 static void inode_sleep_on_writeback(struct inode *inode)
373 __releases(inode->i_lock)
376 wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
379 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
380 sleep = inode->i_state & I_SYNC;
381 spin_unlock(&inode->i_lock);
384 finish_wait(wqh, &wait);
388 * Find proper writeback list for the inode depending on its current state and
389 * possibly also change of its state while we were doing writeback. Here we
390 * handle things such as livelock prevention or fairness of writeback among
391 * inodes. This function can be called only by flusher thread - noone else
392 * processes all inodes in writeback lists and requeueing inodes behind flusher
393 * thread's back can have unexpected consequences.
395 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
396 struct writeback_control *wbc)
398 if (inode->i_state & I_FREEING)
402 * Sync livelock prevention. Each inode is tagged and synced in one
403 * shot. If still dirty, it will be redirty_tail()'ed below. Update
404 * the dirty time to prevent enqueue and sync it again.
406 if ((inode->i_state & I_DIRTY) &&
407 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
408 inode->dirtied_when = jiffies;
410 if (wbc->pages_skipped) {
412 * writeback is not making progress due to locked
413 * buffers. Skip this inode for now.
415 redirty_tail(inode, wb);
419 if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
421 * We didn't write back all the pages. nfs_writepages()
422 * sometimes bales out without doing anything.
424 if (wbc->nr_to_write <= 0) {
425 /* Slice used up. Queue for next turn. */
426 requeue_io(inode, wb);
429 * Writeback blocked by something other than
430 * congestion. Delay the inode for some time to
431 * avoid spinning on the CPU (100% iowait)
432 * retrying writeback of the dirty page/inode
433 * that cannot be performed immediately.
435 redirty_tail(inode, wb);
437 } else if (inode->i_state & I_DIRTY) {
439 * Filesystems can dirty the inode during writeback operations,
440 * such as delayed allocation during submission or metadata
441 * updates after data IO completion.
443 redirty_tail(inode, wb);
445 /* The inode is clean. Remove from writeback lists. */
446 list_del_init(&inode->i_wb_list);
451 * Write out an inode and its dirty pages. Do not update the writeback list
452 * linkage. That is left to the caller. The caller is also responsible for
453 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
456 __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
458 struct address_space *mapping = inode->i_mapping;
459 long nr_to_write = wbc->nr_to_write;
463 WARN_ON(!(inode->i_state & I_SYNC));
465 trace_writeback_single_inode_start(inode, wbc, nr_to_write);
467 ret = do_writepages(mapping, wbc);
470 * Make sure to wait on the data before writing out the metadata.
471 * This is important for filesystems that modify metadata on data
472 * I/O completion. We don't do it for sync(2) writeback because it has a
473 * separate, external IO completion path and ->sync_fs for guaranteeing
474 * inode metadata is written back correctly.
476 if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
477 int err = filemap_fdatawait(mapping);
483 * Some filesystems may redirty the inode during the writeback
484 * due to delalloc, clear dirty metadata flags right before
487 spin_lock(&inode->i_lock);
489 dirty = inode->i_state & I_DIRTY;
490 inode->i_state &= ~I_DIRTY;
493 * Paired with smp_mb() in __mark_inode_dirty(). This allows
494 * __mark_inode_dirty() to test i_state without grabbing i_lock -
495 * either they see the I_DIRTY bits cleared or we see the dirtied
498 * I_DIRTY_PAGES is always cleared together above even if @mapping
499 * still has dirty pages. The flag is reinstated after smp_mb() if
500 * necessary. This guarantees that either __mark_inode_dirty()
501 * sees clear I_DIRTY_PAGES or we see PAGECACHE_TAG_DIRTY.
505 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
506 inode->i_state |= I_DIRTY_PAGES;
508 spin_unlock(&inode->i_lock);
510 /* Don't write the inode if only I_DIRTY_PAGES was set */
511 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
512 int err = write_inode(inode, wbc);
516 trace_writeback_single_inode(inode, wbc, nr_to_write);
521 * Write out an inode's dirty pages. Either the caller has an active reference
522 * on the inode or the inode has I_WILL_FREE set.
524 * This function is designed to be called for writing back one inode which
525 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
526 * and does more profound writeback list handling in writeback_sb_inodes().
529 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
530 struct writeback_control *wbc)
534 spin_lock(&inode->i_lock);
535 if (!atomic_read(&inode->i_count))
536 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
538 WARN_ON(inode->i_state & I_WILL_FREE);
540 if (inode->i_state & I_SYNC) {
541 if (wbc->sync_mode != WB_SYNC_ALL)
544 * It's a data-integrity sync. We must wait. Since callers hold
545 * inode reference or inode has I_WILL_FREE set, it cannot go
548 __inode_wait_for_writeback(inode);
550 WARN_ON(inode->i_state & I_SYNC);
552 * Skip inode if it is clean and we have no outstanding writeback in
553 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
554 * function since flusher thread may be doing for example sync in
555 * parallel and if we move the inode, it could get skipped. So here we
556 * make sure inode is on some writeback list and leave it there unless
557 * we have completely cleaned the inode.
559 if (!(inode->i_state & I_DIRTY) &&
560 (wbc->sync_mode != WB_SYNC_ALL ||
561 !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
563 inode->i_state |= I_SYNC;
564 spin_unlock(&inode->i_lock);
566 ret = __writeback_single_inode(inode, wbc);
568 spin_lock(&wb->list_lock);
569 spin_lock(&inode->i_lock);
571 * If inode is clean, remove it from writeback lists. Otherwise don't
572 * touch it. See comment above for explanation.
574 if (!(inode->i_state & I_DIRTY))
575 list_del_init(&inode->i_wb_list);
576 spin_unlock(&wb->list_lock);
577 inode_sync_complete(inode);
579 spin_unlock(&inode->i_lock);
583 static long writeback_chunk_size(struct backing_dev_info *bdi,
584 struct wb_writeback_work *work)
589 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
590 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
591 * here avoids calling into writeback_inodes_wb() more than once.
593 * The intended call sequence for WB_SYNC_ALL writeback is:
596 * writeback_sb_inodes() <== called only once
597 * write_cache_pages() <== called once for each inode
598 * (quickly) tag currently dirty pages
599 * (maybe slowly) sync all tagged pages
601 if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
604 pages = min(bdi->avg_write_bandwidth / 2,
605 global_dirty_limit / DIRTY_SCOPE);
606 pages = min(pages, work->nr_pages);
607 pages = round_down(pages + MIN_WRITEBACK_PAGES,
608 MIN_WRITEBACK_PAGES);
615 * Write a portion of b_io inodes which belong to @sb.
617 * Return the number of pages and/or inodes written.
619 static long writeback_sb_inodes(struct super_block *sb,
620 struct bdi_writeback *wb,
621 struct wb_writeback_work *work)
623 struct writeback_control wbc = {
624 .sync_mode = work->sync_mode,
625 .tagged_writepages = work->tagged_writepages,
626 .for_kupdate = work->for_kupdate,
627 .for_background = work->for_background,
628 .for_sync = work->for_sync,
629 .range_cyclic = work->range_cyclic,
631 .range_end = LLONG_MAX,
633 unsigned long start_time = jiffies;
635 long wrote = 0; /* count both pages and inodes */
637 while (!list_empty(&wb->b_io)) {
638 struct inode *inode = wb_inode(wb->b_io.prev);
640 if (inode->i_sb != sb) {
643 * We only want to write back data for this
644 * superblock, move all inodes not belonging
645 * to it back onto the dirty list.
647 redirty_tail(inode, wb);
652 * The inode belongs to a different superblock.
653 * Bounce back to the caller to unpin this and
654 * pin the next superblock.
660 * Don't bother with new inodes or inodes being freed, first
661 * kind does not need periodic writeout yet, and for the latter
662 * kind writeout is handled by the freer.
664 spin_lock(&inode->i_lock);
665 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
666 spin_unlock(&inode->i_lock);
667 redirty_tail(inode, wb);
670 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
672 * If this inode is locked for writeback and we are not
673 * doing writeback-for-data-integrity, move it to
674 * b_more_io so that writeback can proceed with the
675 * other inodes on s_io.
677 * We'll have another go at writing back this inode
678 * when we completed a full scan of b_io.
680 spin_unlock(&inode->i_lock);
681 requeue_io(inode, wb);
682 trace_writeback_sb_inodes_requeue(inode);
685 spin_unlock(&wb->list_lock);
688 * We already requeued the inode if it had I_SYNC set and we
689 * are doing WB_SYNC_NONE writeback. So this catches only the
692 if (inode->i_state & I_SYNC) {
693 /* Wait for I_SYNC. This function drops i_lock... */
694 inode_sleep_on_writeback(inode);
695 /* Inode may be gone, start again */
696 spin_lock(&wb->list_lock);
699 inode->i_state |= I_SYNC;
700 spin_unlock(&inode->i_lock);
702 write_chunk = writeback_chunk_size(wb->bdi, work);
703 wbc.nr_to_write = write_chunk;
704 wbc.pages_skipped = 0;
707 * We use I_SYNC to pin the inode in memory. While it is set
708 * evict_inode() will wait so the inode cannot be freed.
710 __writeback_single_inode(inode, &wbc);
712 work->nr_pages -= write_chunk - wbc.nr_to_write;
713 wrote += write_chunk - wbc.nr_to_write;
714 spin_lock(&wb->list_lock);
715 spin_lock(&inode->i_lock);
716 if (!(inode->i_state & I_DIRTY))
718 requeue_inode(inode, wb, &wbc);
719 inode_sync_complete(inode);
720 spin_unlock(&inode->i_lock);
721 cond_resched_lock(&wb->list_lock);
723 * bail out to wb_writeback() often enough to check
724 * background threshold and other termination conditions.
727 if (time_is_before_jiffies(start_time + HZ / 10UL))
729 if (work->nr_pages <= 0)
736 static long __writeback_inodes_wb(struct bdi_writeback *wb,
737 struct wb_writeback_work *work)
739 unsigned long start_time = jiffies;
742 while (!list_empty(&wb->b_io)) {
743 struct inode *inode = wb_inode(wb->b_io.prev);
744 struct super_block *sb = inode->i_sb;
746 if (!grab_super_passive(sb)) {
748 * grab_super_passive() may fail consistently due to
749 * s_umount being grabbed by someone else. Don't use
750 * requeue_io() to avoid busy retrying the inode/sb.
752 redirty_tail(inode, wb);
755 wrote += writeback_sb_inodes(sb, wb, work);
758 /* refer to the same tests at the end of writeback_sb_inodes */
760 if (time_is_before_jiffies(start_time + HZ / 10UL))
762 if (work->nr_pages <= 0)
766 /* Leave any unwritten inodes on b_io */
770 static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
771 enum wb_reason reason)
773 struct wb_writeback_work work = {
774 .nr_pages = nr_pages,
775 .sync_mode = WB_SYNC_NONE,
780 spin_lock(&wb->list_lock);
781 if (list_empty(&wb->b_io))
783 __writeback_inodes_wb(wb, &work);
784 spin_unlock(&wb->list_lock);
786 return nr_pages - work.nr_pages;
789 static bool over_bground_thresh(struct backing_dev_info *bdi)
791 unsigned long background_thresh, dirty_thresh;
793 global_dirty_limits(&background_thresh, &dirty_thresh);
795 if (global_page_state(NR_FILE_DIRTY) +
796 global_page_state(NR_UNSTABLE_NFS) > background_thresh)
799 if (bdi_stat(bdi, BDI_RECLAIMABLE) >
800 bdi_dirty_limit(bdi, background_thresh))
807 * Called under wb->list_lock. If there are multiple wb per bdi,
808 * only the flusher working on the first wb should do it.
810 static void wb_update_bandwidth(struct bdi_writeback *wb,
811 unsigned long start_time)
813 __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
817 * Explicit flushing or periodic writeback of "old" data.
819 * Define "old": the first time one of an inode's pages is dirtied, we mark the
820 * dirtying-time in the inode's address_space. So this periodic writeback code
821 * just walks the superblock inode list, writing back any inodes which are
822 * older than a specific point in time.
824 * Try to run once per dirty_writeback_interval. But if a writeback event
825 * takes longer than a dirty_writeback_interval interval, then leave a
828 * older_than_this takes precedence over nr_to_write. So we'll only write back
829 * all dirty pages if they are all attached to "old" mappings.
831 static long wb_writeback(struct bdi_writeback *wb,
832 struct wb_writeback_work *work)
834 unsigned long wb_start = jiffies;
835 long nr_pages = work->nr_pages;
836 unsigned long oldest_jif;
840 oldest_jif = jiffies;
841 work->older_than_this = &oldest_jif;
843 spin_lock(&wb->list_lock);
846 * Stop writeback when nr_pages has been consumed
848 if (work->nr_pages <= 0)
852 * Background writeout and kupdate-style writeback may
853 * run forever. Stop them if there is other work to do
854 * so that e.g. sync can proceed. They'll be restarted
855 * after the other works are all done.
857 if ((work->for_background || work->for_kupdate) &&
858 !list_empty(&wb->bdi->work_list))
862 * For background writeout, stop when we are below the
863 * background dirty threshold
865 if (work->for_background && !over_bground_thresh(wb->bdi))
869 * Kupdate and background works are special and we want to
870 * include all inodes that need writing. Livelock avoidance is
871 * handled by these works yielding to any other work so we are
874 if (work->for_kupdate) {
875 oldest_jif = jiffies -
876 msecs_to_jiffies(dirty_expire_interval * 10);
877 } else if (work->for_background)
878 oldest_jif = jiffies;
880 trace_writeback_start(wb->bdi, work);
881 if (list_empty(&wb->b_io))
884 progress = writeback_sb_inodes(work->sb, wb, work);
886 progress = __writeback_inodes_wb(wb, work);
887 trace_writeback_written(wb->bdi, work);
889 wb_update_bandwidth(wb, wb_start);
892 * Did we write something? Try for more
894 * Dirty inodes are moved to b_io for writeback in batches.
895 * The completion of the current batch does not necessarily
896 * mean the overall work is done. So we keep looping as long
897 * as made some progress on cleaning pages or inodes.
902 * No more inodes for IO, bail
904 if (list_empty(&wb->b_more_io))
907 * Nothing written. Wait for some inode to
908 * become available for writeback. Otherwise
909 * we'll just busyloop.
911 if (!list_empty(&wb->b_more_io)) {
912 trace_writeback_wait(wb->bdi, work);
913 inode = wb_inode(wb->b_more_io.prev);
914 spin_lock(&inode->i_lock);
915 spin_unlock(&wb->list_lock);
916 /* This function drops i_lock... */
917 inode_sleep_on_writeback(inode);
918 spin_lock(&wb->list_lock);
921 spin_unlock(&wb->list_lock);
923 return nr_pages - work->nr_pages;
927 * Return the next wb_writeback_work struct that hasn't been processed yet.
929 static struct wb_writeback_work *
930 get_next_work_item(struct backing_dev_info *bdi)
932 struct wb_writeback_work *work = NULL;
934 spin_lock_bh(&bdi->wb_lock);
935 if (!list_empty(&bdi->work_list)) {
936 work = list_entry(bdi->work_list.next,
937 struct wb_writeback_work, list);
938 list_del_init(&work->list);
940 spin_unlock_bh(&bdi->wb_lock);
945 * Add in the number of potentially dirty inodes, because each inode
946 * write can dirty pagecache in the underlying blockdev.
948 static unsigned long get_nr_dirty_pages(void)
950 return global_page_state(NR_FILE_DIRTY) +
951 global_page_state(NR_UNSTABLE_NFS) +
952 get_nr_dirty_inodes();
955 static long wb_check_background_flush(struct bdi_writeback *wb)
957 if (over_bground_thresh(wb->bdi)) {
959 struct wb_writeback_work work = {
960 .nr_pages = LONG_MAX,
961 .sync_mode = WB_SYNC_NONE,
964 .reason = WB_REASON_BACKGROUND,
967 return wb_writeback(wb, &work);
973 static long wb_check_old_data_flush(struct bdi_writeback *wb)
975 unsigned long expired;
979 * When set to zero, disable periodic writeback
981 if (!dirty_writeback_interval)
984 expired = wb->last_old_flush +
985 msecs_to_jiffies(dirty_writeback_interval * 10);
986 if (time_before(jiffies, expired))
989 wb->last_old_flush = jiffies;
990 nr_pages = get_nr_dirty_pages();
993 struct wb_writeback_work work = {
994 .nr_pages = nr_pages,
995 .sync_mode = WB_SYNC_NONE,
998 .reason = WB_REASON_PERIODIC,
1001 return wb_writeback(wb, &work);
1008 * Retrieve work items and do the writeback they describe
1010 static long wb_do_writeback(struct bdi_writeback *wb)
1012 struct backing_dev_info *bdi = wb->bdi;
1013 struct wb_writeback_work *work;
1016 set_bit(BDI_writeback_running, &wb->bdi->state);
1017 while ((work = get_next_work_item(bdi)) != NULL) {
1019 trace_writeback_exec(bdi, work);
1021 wrote += wb_writeback(wb, work);
1024 * Notify the caller of completion if this is a synchronous
1025 * work item, otherwise just free it.
1028 complete(work->done);
1034 * Check for periodic writeback, kupdated() style
1036 wrote += wb_check_old_data_flush(wb);
1037 wrote += wb_check_background_flush(wb);
1038 clear_bit(BDI_writeback_running, &wb->bdi->state);
1044 * Handle writeback of dirty data for the device backed by this bdi. Also
1045 * reschedules periodically and does kupdated style flushing.
1047 void bdi_writeback_workfn(struct work_struct *work)
1049 struct bdi_writeback *wb = container_of(to_delayed_work(work),
1050 struct bdi_writeback, dwork);
1051 struct backing_dev_info *bdi = wb->bdi;
1054 set_worker_desc("flush-%s", dev_name(bdi->dev));
1055 current->flags |= PF_SWAPWRITE;
1057 if (likely(!current_is_workqueue_rescuer() ||
1058 !test_bit(BDI_registered, &bdi->state))) {
1060 * The normal path. Keep writing back @bdi until its
1061 * work_list is empty. Note that this path is also taken
1062 * if @bdi is shutting down even when we're running off the
1063 * rescuer as work_list needs to be drained.
1066 pages_written = wb_do_writeback(wb);
1067 trace_writeback_pages_written(pages_written);
1068 } while (!list_empty(&bdi->work_list));
1071 * bdi_wq can't get enough workers and we're running off
1072 * the emergency worker. Don't hog it. Hopefully, 1024 is
1073 * enough for efficient IO.
1075 pages_written = writeback_inodes_wb(&bdi->wb, 1024,
1076 WB_REASON_FORKER_THREAD);
1077 trace_writeback_pages_written(pages_written);
1080 if (!list_empty(&bdi->work_list))
1081 mod_delayed_work(bdi_wq, &wb->dwork, 0);
1082 else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1083 bdi_wakeup_thread_delayed(bdi);
1085 current->flags &= ~PF_SWAPWRITE;
1089 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
1092 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1094 struct backing_dev_info *bdi;
1097 nr_pages = get_nr_dirty_pages();
1100 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1101 if (!bdi_has_dirty_io(bdi))
1103 __bdi_start_writeback(bdi, nr_pages, false, reason);
1108 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1110 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1111 struct dentry *dentry;
1112 const char *name = "?";
1114 dentry = d_find_alias(inode);
1116 spin_lock(&dentry->d_lock);
1117 name = (const char *) dentry->d_name.name;
1120 "%s(%d): dirtied inode %lu (%s) on %s\n",
1121 current->comm, task_pid_nr(current), inode->i_ino,
1122 name, inode->i_sb->s_id);
1124 spin_unlock(&dentry->d_lock);
1131 * __mark_inode_dirty - internal function
1132 * @inode: inode to mark
1133 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1134 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1135 * mark_inode_dirty_sync.
1137 * Put the inode on the super block's dirty list.
1139 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1140 * dirty list only if it is hashed or if it refers to a blockdev.
1141 * If it was not hashed, it will never be added to the dirty list
1142 * even if it is later hashed, as it will have been marked dirty already.
1144 * In short, make sure you hash any inodes _before_ you start marking
1147 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1148 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1149 * the kernel-internal blockdev inode represents the dirtying time of the
1150 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1151 * page->mapping->host, so the page-dirtying time is recorded in the internal
1154 void __mark_inode_dirty(struct inode *inode, int flags)
1156 struct super_block *sb = inode->i_sb;
1157 struct backing_dev_info *bdi = NULL;
1160 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1161 * dirty the inode itself
1163 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1164 trace_writeback_dirty_inode_start(inode, flags);
1166 if (sb->s_op->dirty_inode)
1167 sb->s_op->dirty_inode(inode, flags);
1169 trace_writeback_dirty_inode(inode, flags);
1173 * Paired with smp_mb() in __writeback_single_inode() for the
1174 * following lockless i_state test. See there for details.
1178 if ((inode->i_state & flags) == flags)
1181 if (unlikely(block_dump))
1182 block_dump___mark_inode_dirty(inode);
1184 spin_lock(&inode->i_lock);
1185 if ((inode->i_state & flags) != flags) {
1186 const int was_dirty = inode->i_state & I_DIRTY;
1188 inode->i_state |= flags;
1191 * If the inode is being synced, just update its dirty state.
1192 * The unlocker will place the inode on the appropriate
1193 * superblock list, based upon its state.
1195 if (inode->i_state & I_SYNC)
1196 goto out_unlock_inode;
1199 * Only add valid (hashed) inodes to the superblock's
1200 * dirty list. Add blockdev inodes as well.
1202 if (!S_ISBLK(inode->i_mode)) {
1203 if (inode_unhashed(inode))
1204 goto out_unlock_inode;
1206 if (inode->i_state & I_FREEING)
1207 goto out_unlock_inode;
1210 * If the inode was already on b_dirty/b_io/b_more_io, don't
1211 * reposition it (that would break b_dirty time-ordering).
1214 bool wakeup_bdi = false;
1215 bdi = inode_to_bdi(inode);
1217 spin_unlock(&inode->i_lock);
1218 spin_lock(&bdi->wb.list_lock);
1219 if (bdi_cap_writeback_dirty(bdi)) {
1220 WARN(!test_bit(BDI_registered, &bdi->state),
1221 "bdi-%s not registered\n", bdi->name);
1224 * If this is the first dirty inode for this
1225 * bdi, we have to wake-up the corresponding
1226 * bdi thread to make sure background
1227 * write-back happens later.
1229 if (!wb_has_dirty_io(&bdi->wb))
1233 inode->dirtied_when = jiffies;
1234 list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1235 spin_unlock(&bdi->wb.list_lock);
1238 bdi_wakeup_thread_delayed(bdi);
1243 spin_unlock(&inode->i_lock);
1246 EXPORT_SYMBOL(__mark_inode_dirty);
1248 static void wait_sb_inodes(struct super_block *sb)
1250 struct inode *inode, *old_inode = NULL;
1253 * We need to be protected against the filesystem going from
1254 * r/o to r/w or vice versa.
1256 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1258 spin_lock(&inode_sb_list_lock);
1261 * Data integrity sync. Must wait for all pages under writeback,
1262 * because there may have been pages dirtied before our sync
1263 * call, but which had writeout started before we write it out.
1264 * In which case, the inode may not be on the dirty list, but
1265 * we still have to wait for that writeout.
1267 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1268 struct address_space *mapping = inode->i_mapping;
1270 spin_lock(&inode->i_lock);
1271 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1272 (mapping->nrpages == 0)) {
1273 spin_unlock(&inode->i_lock);
1277 spin_unlock(&inode->i_lock);
1278 spin_unlock(&inode_sb_list_lock);
1281 * We hold a reference to 'inode' so it couldn't have been
1282 * removed from s_inodes list while we dropped the
1283 * inode_sb_list_lock. We cannot iput the inode now as we can
1284 * be holding the last reference and we cannot iput it under
1285 * inode_sb_list_lock. So we keep the reference and iput it
1291 filemap_fdatawait(mapping);
1295 spin_lock(&inode_sb_list_lock);
1297 spin_unlock(&inode_sb_list_lock);
1302 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1303 * @sb: the superblock
1304 * @nr: the number of pages to write
1305 * @reason: reason why some writeback work initiated
1307 * Start writeback on some inodes on this super_block. No guarantees are made
1308 * on how many (if any) will be written, and this function does not wait
1309 * for IO completion of submitted IO.
1311 void writeback_inodes_sb_nr(struct super_block *sb,
1313 enum wb_reason reason)
1315 DECLARE_COMPLETION_ONSTACK(done);
1316 struct wb_writeback_work work = {
1318 .sync_mode = WB_SYNC_NONE,
1319 .tagged_writepages = 1,
1325 if (sb->s_bdi == &noop_backing_dev_info)
1327 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1328 bdi_queue_work(sb->s_bdi, &work);
1329 wait_for_completion(&done);
1331 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1334 * writeback_inodes_sb - writeback dirty inodes from given super_block
1335 * @sb: the superblock
1336 * @reason: reason why some writeback work was initiated
1338 * Start writeback on some inodes on this super_block. No guarantees are made
1339 * on how many (if any) will be written, and this function does not wait
1340 * for IO completion of submitted IO.
1342 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1344 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1346 EXPORT_SYMBOL(writeback_inodes_sb);
1349 * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
1350 * @sb: the superblock
1351 * @nr: the number of pages to write
1352 * @reason: the reason of writeback
1354 * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
1355 * Returns 1 if writeback was started, 0 if not.
1357 int try_to_writeback_inodes_sb_nr(struct super_block *sb,
1359 enum wb_reason reason)
1361 if (writeback_in_progress(sb->s_bdi))
1364 if (!down_read_trylock(&sb->s_umount))
1367 writeback_inodes_sb_nr(sb, nr, reason);
1368 up_read(&sb->s_umount);
1371 EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
1374 * try_to_writeback_inodes_sb - try to start writeback if none underway
1375 * @sb: the superblock
1376 * @reason: reason why some writeback work was initiated
1378 * Implement by try_to_writeback_inodes_sb_nr()
1379 * Returns 1 if writeback was started, 0 if not.
1381 int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1383 return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1385 EXPORT_SYMBOL(try_to_writeback_inodes_sb);
1388 * sync_inodes_sb - sync sb inode pages
1389 * @sb: the superblock
1391 * This function writes and waits on any dirty inode belonging to this
1394 void sync_inodes_sb(struct super_block *sb)
1396 DECLARE_COMPLETION_ONSTACK(done);
1397 struct wb_writeback_work work = {
1399 .sync_mode = WB_SYNC_ALL,
1400 .nr_pages = LONG_MAX,
1403 .reason = WB_REASON_SYNC,
1407 /* Nothing to do? */
1408 if (sb->s_bdi == &noop_backing_dev_info)
1410 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1412 bdi_queue_work(sb->s_bdi, &work);
1413 wait_for_completion(&done);
1417 EXPORT_SYMBOL(sync_inodes_sb);
1420 * write_inode_now - write an inode to disk
1421 * @inode: inode to write to disk
1422 * @sync: whether the write should be synchronous or not
1424 * This function commits an inode to disk immediately if it is dirty. This is
1425 * primarily needed by knfsd.
1427 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1429 int write_inode_now(struct inode *inode, int sync)
1431 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1432 struct writeback_control wbc = {
1433 .nr_to_write = LONG_MAX,
1434 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1436 .range_end = LLONG_MAX,
1439 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1440 wbc.nr_to_write = 0;
1443 return writeback_single_inode(inode, wb, &wbc);
1445 EXPORT_SYMBOL(write_inode_now);
1448 * sync_inode - write an inode and its pages to disk.
1449 * @inode: the inode to sync
1450 * @wbc: controls the writeback mode
1452 * sync_inode() will write an inode and its pages to disk. It will also
1453 * correctly update the inode on its superblock's dirty inode lists and will
1454 * update inode->i_state.
1456 * The caller must have a ref on the inode.
1458 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1460 return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1462 EXPORT_SYMBOL(sync_inode);
1465 * sync_inode_metadata - write an inode to disk
1466 * @inode: the inode to sync
1467 * @wait: wait for I/O to complete.
1469 * Write an inode to disk and adjust its dirty state after completion.
1471 * Note: only writes the actual inode, no associated data or other metadata.
1473 int sync_inode_metadata(struct inode *inode, int wait)
1475 struct writeback_control wbc = {
1476 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1477 .nr_to_write = 0, /* metadata-only */
1480 return sync_inode(inode, &wbc);
1482 EXPORT_SYMBOL(sync_inode_metadata);