4 * Copyright (C) 2002, Linus Torvalds.
6 * Contains all the functions related to writing back and waiting
7 * upon dirty inodes against superblocks, and writing back dirty
8 * pages against inodes. ie: data writeback. Writeout of the
9 * inode itself is not handled here.
11 * 10Apr2002 Andrew Morton
12 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
16 #include <linux/kernel.h>
17 #include <linux/export.h>
18 #include <linux/spinlock.h>
19 #include <linux/slab.h>
20 #include <linux/sched.h>
23 #include <linux/pagemap.h>
24 #include <linux/kthread.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/tracepoint.h>
32 * 4MB minimal write chunk size
34 #define MIN_WRITEBACK_PAGES (4096UL >> (PAGE_CACHE_SHIFT - 10))
37 * Passed into wb_writeback(), essentially a subset of writeback_control
39 struct wb_writeback_work {
41 struct super_block *sb;
42 unsigned long *older_than_this;
43 enum writeback_sync_modes sync_mode;
44 unsigned int tagged_writepages:1;
45 unsigned int for_kupdate:1;
46 unsigned int range_cyclic:1;
47 unsigned int for_background:1;
48 enum wb_reason reason; /* why was writeback initiated? */
50 struct list_head list; /* pending work list */
51 struct completion *done; /* set if the caller waits */
55 * writeback_in_progress - determine whether there is writeback in progress
56 * @bdi: the device's backing_dev_info structure.
58 * Determine whether there is writeback waiting to be handled against a
61 int writeback_in_progress(struct backing_dev_info *bdi)
63 return test_bit(BDI_writeback_running, &bdi->state);
65 EXPORT_SYMBOL(writeback_in_progress);
67 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
69 struct super_block *sb = inode->i_sb;
71 if (strcmp(sb->s_type->name, "bdev") == 0)
72 return inode->i_mapping->backing_dev_info;
77 static inline struct inode *wb_inode(struct list_head *head)
79 return list_entry(head, struct inode, i_wb_list);
83 * Include the creation of the trace points after defining the
84 * wb_writeback_work structure and inline functions so that the definition
85 * remains local to this file.
87 #define CREATE_TRACE_POINTS
88 #include <trace/events/writeback.h>
90 static void bdi_wakeup_thread(struct backing_dev_info *bdi)
92 spin_lock_bh(&bdi->wb_lock);
93 if (test_bit(BDI_registered, &bdi->state))
94 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
95 spin_unlock_bh(&bdi->wb_lock);
98 static void bdi_queue_work(struct backing_dev_info *bdi,
99 struct wb_writeback_work *work)
101 trace_writeback_queue(bdi, work);
103 spin_lock_bh(&bdi->wb_lock);
104 if (!test_bit(BDI_registered, &bdi->state)) {
106 complete(work->done);
109 list_add_tail(&work->list, &bdi->work_list);
110 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
112 spin_unlock_bh(&bdi->wb_lock);
116 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
117 bool range_cyclic, enum wb_reason reason)
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);
127 trace_writeback_nowork(bdi);
128 bdi_wakeup_thread(bdi);
132 work->sync_mode = WB_SYNC_NONE;
133 work->nr_pages = nr_pages;
134 work->range_cyclic = range_cyclic;
135 work->reason = reason;
137 bdi_queue_work(bdi, work);
141 * bdi_start_writeback - start writeback
142 * @bdi: the backing device to write from
143 * @nr_pages: the number of pages to write
144 * @reason: reason why some writeback work was initiated
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,
153 enum wb_reason reason)
155 __bdi_start_writeback(bdi, nr_pages, true, reason);
159 * bdi_start_background_writeback - start background writeback
160 * @bdi: the backing device to write from
163 * This makes sure WB_SYNC_NONE background writeback happens. When
164 * this function returns, it is only guaranteed that for given BDI
165 * some IO is happening if we are over background dirty threshold.
166 * Caller need not hold sb s_umount semaphore.
168 void bdi_start_background_writeback(struct backing_dev_info *bdi)
171 * We just wake up the flusher thread. It will perform background
172 * writeback as soon as there is no other work to do.
174 trace_writeback_wake_background(bdi);
175 bdi_wakeup_thread(bdi);
179 * Remove the inode from the writeback list it is on.
181 void inode_wb_list_del(struct inode *inode)
183 struct backing_dev_info *bdi = inode_to_bdi(inode);
185 spin_lock(&bdi->wb.list_lock);
186 list_del_init(&inode->i_wb_list);
187 spin_unlock(&bdi->wb.list_lock);
191 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
192 * furthest end of its superblock's dirty-inode list.
194 * Before stamping the inode's ->dirtied_when, we check to see whether it is
195 * already the most-recently-dirtied inode on the b_dirty list. If that is
196 * the case then the inode must have been redirtied while it was being written
197 * out and we don't reset its dirtied_when.
199 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
201 assert_spin_locked(&wb->list_lock);
202 if (!list_empty(&wb->b_dirty)) {
205 tail = wb_inode(wb->b_dirty.next);
206 if (time_before(inode->dirtied_when, tail->dirtied_when))
207 inode->dirtied_when = jiffies;
209 list_move(&inode->i_wb_list, &wb->b_dirty);
213 * requeue inode for re-scanning after bdi->b_io list is exhausted.
215 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
217 assert_spin_locked(&wb->list_lock);
218 list_move(&inode->i_wb_list, &wb->b_more_io);
221 static void inode_sync_complete(struct inode *inode)
223 inode->i_state &= ~I_SYNC;
224 /* If inode is clean an unused, put it into LRU now... */
225 inode_add_lru(inode);
226 /* Waiters must see I_SYNC cleared before being woken up */
228 wake_up_bit(&inode->i_state, __I_SYNC);
231 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
233 bool ret = time_after(inode->dirtied_when, t);
236 * For inodes being constantly redirtied, dirtied_when can get stuck.
237 * It _appears_ to be in the future, but is actually in distant past.
238 * This test is necessary to prevent such wrapped-around relative times
239 * from permanently stopping the whole bdi writeback.
241 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
247 * Move expired (dirtied before work->older_than_this) dirty inodes from
248 * @delaying_queue to @dispatch_queue.
250 static int move_expired_inodes(struct list_head *delaying_queue,
251 struct list_head *dispatch_queue,
252 struct wb_writeback_work *work)
255 struct list_head *pos, *node;
256 struct super_block *sb = NULL;
261 while (!list_empty(delaying_queue)) {
262 inode = wb_inode(delaying_queue->prev);
263 if (work->older_than_this &&
264 inode_dirtied_after(inode, *work->older_than_this))
266 if (sb && sb != inode->i_sb)
269 list_move(&inode->i_wb_list, &tmp);
273 /* just one sb in list, splice to dispatch_queue and we're done */
275 list_splice(&tmp, dispatch_queue);
279 /* Move inodes from one superblock together */
280 while (!list_empty(&tmp)) {
281 sb = wb_inode(tmp.prev)->i_sb;
282 list_for_each_prev_safe(pos, node, &tmp) {
283 inode = wb_inode(pos);
284 if (inode->i_sb == sb)
285 list_move(&inode->i_wb_list, dispatch_queue);
293 * Queue all expired dirty inodes for io, eldest first.
295 * newly dirtied b_dirty b_io b_more_io
296 * =============> gf edc BA
298 * newly dirtied b_dirty b_io b_more_io
299 * =============> g fBAedc
301 * +--> dequeue for IO
303 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
306 assert_spin_locked(&wb->list_lock);
307 list_splice_init(&wb->b_more_io, &wb->b_io);
308 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
309 trace_writeback_queue_io(wb, work, moved);
312 static int write_inode(struct inode *inode, struct writeback_control *wbc)
316 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
317 trace_writeback_write_inode_start(inode, wbc);
318 ret = inode->i_sb->s_op->write_inode(inode, wbc);
319 trace_writeback_write_inode(inode, wbc);
326 * Wait for writeback on an inode to complete. Called with i_lock held.
327 * Caller must make sure inode cannot go away when we drop i_lock.
329 static void __inode_wait_for_writeback(struct inode *inode)
330 __releases(inode->i_lock)
331 __acquires(inode->i_lock)
333 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
334 wait_queue_head_t *wqh;
336 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
337 while (inode->i_state & I_SYNC) {
338 spin_unlock(&inode->i_lock);
339 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
340 spin_lock(&inode->i_lock);
345 * Wait for writeback on an inode to complete. Caller must have inode pinned.
347 void inode_wait_for_writeback(struct inode *inode)
349 spin_lock(&inode->i_lock);
350 __inode_wait_for_writeback(inode);
351 spin_unlock(&inode->i_lock);
355 * Sleep until I_SYNC is cleared. This function must be called with i_lock
356 * held and drops it. It is aimed for callers not holding any inode reference
357 * so once i_lock is dropped, inode can go away.
359 static void inode_sleep_on_writeback(struct inode *inode)
360 __releases(inode->i_lock)
363 wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
366 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
367 sleep = inode->i_state & I_SYNC;
368 spin_unlock(&inode->i_lock);
371 finish_wait(wqh, &wait);
375 * Find proper writeback list for the inode depending on its current state and
376 * possibly also change of its state while we were doing writeback. Here we
377 * handle things such as livelock prevention or fairness of writeback among
378 * inodes. This function can be called only by flusher thread - noone else
379 * processes all inodes in writeback lists and requeueing inodes behind flusher
380 * thread's back can have unexpected consequences.
382 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
383 struct writeback_control *wbc)
385 if (inode->i_state & I_FREEING)
389 * Sync livelock prevention. Each inode is tagged and synced in one
390 * shot. If still dirty, it will be redirty_tail()'ed below. Update
391 * the dirty time to prevent enqueue and sync it again.
393 if ((inode->i_state & I_DIRTY) &&
394 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
395 inode->dirtied_when = jiffies;
397 if (wbc->pages_skipped) {
399 * writeback is not making progress due to locked
400 * buffers. Skip this inode for now.
402 redirty_tail(inode, wb);
406 if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
408 * We didn't write back all the pages. nfs_writepages()
409 * sometimes bales out without doing anything.
411 if (wbc->nr_to_write <= 0) {
412 /* Slice used up. Queue for next turn. */
413 requeue_io(inode, wb);
416 * Writeback blocked by something other than
417 * congestion. Delay the inode for some time to
418 * avoid spinning on the CPU (100% iowait)
419 * retrying writeback of the dirty page/inode
420 * that cannot be performed immediately.
422 redirty_tail(inode, wb);
424 } else if (inode->i_state & I_DIRTY) {
426 * Filesystems can dirty the inode during writeback operations,
427 * such as delayed allocation during submission or metadata
428 * updates after data IO completion.
430 redirty_tail(inode, wb);
432 /* The inode is clean. Remove from writeback lists. */
433 list_del_init(&inode->i_wb_list);
438 * Write out an inode and its dirty pages. Do not update the writeback list
439 * linkage. That is left to the caller. The caller is also responsible for
440 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
443 __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
445 struct address_space *mapping = inode->i_mapping;
446 long nr_to_write = wbc->nr_to_write;
450 WARN_ON(!(inode->i_state & I_SYNC));
452 trace_writeback_single_inode_start(inode, wbc, nr_to_write);
454 ret = do_writepages(mapping, wbc);
457 * Make sure to wait on the data before writing out the metadata.
458 * This is important for filesystems that modify metadata on data
461 if (wbc->sync_mode == WB_SYNC_ALL) {
462 int err = filemap_fdatawait(mapping);
468 * Some filesystems may redirty the inode during the writeback
469 * due to delalloc, clear dirty metadata flags right before
472 spin_lock(&inode->i_lock);
473 /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
474 if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
475 inode->i_state &= ~I_DIRTY_PAGES;
476 dirty = inode->i_state & I_DIRTY;
477 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
478 spin_unlock(&inode->i_lock);
479 /* Don't write the inode if only I_DIRTY_PAGES was set */
480 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
481 int err = write_inode(inode, wbc);
485 trace_writeback_single_inode(inode, wbc, nr_to_write);
490 * Write out an inode's dirty pages. Either the caller has an active reference
491 * on the inode or the inode has I_WILL_FREE set.
493 * This function is designed to be called for writing back one inode which
494 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
495 * and does more profound writeback list handling in writeback_sb_inodes().
498 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
499 struct writeback_control *wbc)
503 spin_lock(&inode->i_lock);
504 if (!atomic_read(&inode->i_count))
505 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
507 WARN_ON(inode->i_state & I_WILL_FREE);
509 if (inode->i_state & I_SYNC) {
510 if (wbc->sync_mode != WB_SYNC_ALL)
513 * It's a data-integrity sync. We must wait. Since callers hold
514 * inode reference or inode has I_WILL_FREE set, it cannot go
517 __inode_wait_for_writeback(inode);
519 WARN_ON(inode->i_state & I_SYNC);
521 * Skip inode if it is clean and we have no outstanding writeback in
522 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
523 * function since flusher thread may be doing for example sync in
524 * parallel and if we move the inode, it could get skipped. So here we
525 * make sure inode is on some writeback list and leave it there unless
526 * we have completely cleaned the inode.
528 if (!(inode->i_state & I_DIRTY) &&
529 (wbc->sync_mode != WB_SYNC_ALL ||
530 !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
532 inode->i_state |= I_SYNC;
533 spin_unlock(&inode->i_lock);
535 ret = __writeback_single_inode(inode, wbc);
537 spin_lock(&wb->list_lock);
538 spin_lock(&inode->i_lock);
540 * If inode is clean, remove it from writeback lists. Otherwise don't
541 * touch it. See comment above for explanation.
543 if (!(inode->i_state & I_DIRTY))
544 list_del_init(&inode->i_wb_list);
545 spin_unlock(&wb->list_lock);
546 inode_sync_complete(inode);
548 spin_unlock(&inode->i_lock);
552 static long writeback_chunk_size(struct backing_dev_info *bdi,
553 struct wb_writeback_work *work)
558 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
559 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
560 * here avoids calling into writeback_inodes_wb() more than once.
562 * The intended call sequence for WB_SYNC_ALL writeback is:
565 * writeback_sb_inodes() <== called only once
566 * write_cache_pages() <== called once for each inode
567 * (quickly) tag currently dirty pages
568 * (maybe slowly) sync all tagged pages
570 if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
573 pages = min(bdi->avg_write_bandwidth / 2,
574 global_dirty_limit / DIRTY_SCOPE);
575 pages = min(pages, work->nr_pages);
576 pages = round_down(pages + MIN_WRITEBACK_PAGES,
577 MIN_WRITEBACK_PAGES);
584 * Write a portion of b_io inodes which belong to @sb.
586 * Return the number of pages and/or inodes written.
588 static long writeback_sb_inodes(struct super_block *sb,
589 struct bdi_writeback *wb,
590 struct wb_writeback_work *work)
592 struct writeback_control wbc = {
593 .sync_mode = work->sync_mode,
594 .tagged_writepages = work->tagged_writepages,
595 .for_kupdate = work->for_kupdate,
596 .for_background = work->for_background,
597 .range_cyclic = work->range_cyclic,
599 .range_end = LLONG_MAX,
601 unsigned long start_time = jiffies;
603 long wrote = 0; /* count both pages and inodes */
605 while (!list_empty(&wb->b_io)) {
606 struct inode *inode = wb_inode(wb->b_io.prev);
608 if (inode->i_sb != sb) {
611 * We only want to write back data for this
612 * superblock, move all inodes not belonging
613 * to it back onto the dirty list.
615 redirty_tail(inode, wb);
620 * The inode belongs to a different superblock.
621 * Bounce back to the caller to unpin this and
622 * pin the next superblock.
628 * Don't bother with new inodes or inodes being freed, first
629 * kind does not need periodic writeout yet, and for the latter
630 * kind writeout is handled by the freer.
632 spin_lock(&inode->i_lock);
633 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
634 spin_unlock(&inode->i_lock);
635 redirty_tail(inode, wb);
638 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
640 * If this inode is locked for writeback and we are not
641 * doing writeback-for-data-integrity, move it to
642 * b_more_io so that writeback can proceed with the
643 * other inodes on s_io.
645 * We'll have another go at writing back this inode
646 * when we completed a full scan of b_io.
648 spin_unlock(&inode->i_lock);
649 requeue_io(inode, wb);
650 trace_writeback_sb_inodes_requeue(inode);
653 spin_unlock(&wb->list_lock);
656 * We already requeued the inode if it had I_SYNC set and we
657 * are doing WB_SYNC_NONE writeback. So this catches only the
660 if (inode->i_state & I_SYNC) {
661 /* Wait for I_SYNC. This function drops i_lock... */
662 inode_sleep_on_writeback(inode);
663 /* Inode may be gone, start again */
664 spin_lock(&wb->list_lock);
667 inode->i_state |= I_SYNC;
668 spin_unlock(&inode->i_lock);
670 write_chunk = writeback_chunk_size(wb->bdi, work);
671 wbc.nr_to_write = write_chunk;
672 wbc.pages_skipped = 0;
675 * We use I_SYNC to pin the inode in memory. While it is set
676 * evict_inode() will wait so the inode cannot be freed.
678 __writeback_single_inode(inode, &wbc);
680 work->nr_pages -= write_chunk - wbc.nr_to_write;
681 wrote += write_chunk - wbc.nr_to_write;
682 spin_lock(&wb->list_lock);
683 spin_lock(&inode->i_lock);
684 if (!(inode->i_state & I_DIRTY))
686 requeue_inode(inode, wb, &wbc);
687 inode_sync_complete(inode);
688 spin_unlock(&inode->i_lock);
689 cond_resched_lock(&wb->list_lock);
691 * bail out to wb_writeback() often enough to check
692 * background threshold and other termination conditions.
695 if (time_is_before_jiffies(start_time + HZ / 10UL))
697 if (work->nr_pages <= 0)
704 static long __writeback_inodes_wb(struct bdi_writeback *wb,
705 struct wb_writeback_work *work)
707 unsigned long start_time = jiffies;
710 while (!list_empty(&wb->b_io)) {
711 struct inode *inode = wb_inode(wb->b_io.prev);
712 struct super_block *sb = inode->i_sb;
714 if (!grab_super_passive(sb)) {
716 * grab_super_passive() may fail consistently due to
717 * s_umount being grabbed by someone else. Don't use
718 * requeue_io() to avoid busy retrying the inode/sb.
720 redirty_tail(inode, wb);
723 wrote += writeback_sb_inodes(sb, wb, work);
726 /* refer to the same tests at the end of writeback_sb_inodes */
728 if (time_is_before_jiffies(start_time + HZ / 10UL))
730 if (work->nr_pages <= 0)
734 /* Leave any unwritten inodes on b_io */
738 long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
739 enum wb_reason reason)
741 struct wb_writeback_work work = {
742 .nr_pages = nr_pages,
743 .sync_mode = WB_SYNC_NONE,
748 spin_lock(&wb->list_lock);
749 if (list_empty(&wb->b_io))
751 __writeback_inodes_wb(wb, &work);
752 spin_unlock(&wb->list_lock);
754 return nr_pages - work.nr_pages;
757 static bool over_bground_thresh(struct backing_dev_info *bdi)
759 unsigned long background_thresh, dirty_thresh;
761 global_dirty_limits(&background_thresh, &dirty_thresh);
763 if (global_page_state(NR_FILE_DIRTY) +
764 global_page_state(NR_UNSTABLE_NFS) > background_thresh)
767 if (bdi_stat(bdi, BDI_RECLAIMABLE) >
768 bdi_dirty_limit(bdi, background_thresh))
775 * Called under wb->list_lock. If there are multiple wb per bdi,
776 * only the flusher working on the first wb should do it.
778 static void wb_update_bandwidth(struct bdi_writeback *wb,
779 unsigned long start_time)
781 __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
785 * Explicit flushing or periodic writeback of "old" data.
787 * Define "old": the first time one of an inode's pages is dirtied, we mark the
788 * dirtying-time in the inode's address_space. So this periodic writeback code
789 * just walks the superblock inode list, writing back any inodes which are
790 * older than a specific point in time.
792 * Try to run once per dirty_writeback_interval. But if a writeback event
793 * takes longer than a dirty_writeback_interval interval, then leave a
796 * older_than_this takes precedence over nr_to_write. So we'll only write back
797 * all dirty pages if they are all attached to "old" mappings.
799 static long wb_writeback(struct bdi_writeback *wb,
800 struct wb_writeback_work *work)
802 unsigned long wb_start = jiffies;
803 long nr_pages = work->nr_pages;
804 unsigned long oldest_jif;
808 oldest_jif = jiffies;
809 work->older_than_this = &oldest_jif;
811 spin_lock(&wb->list_lock);
814 * Stop writeback when nr_pages has been consumed
816 if (work->nr_pages <= 0)
820 * Background writeout and kupdate-style writeback may
821 * run forever. Stop them if there is other work to do
822 * so that e.g. sync can proceed. They'll be restarted
823 * after the other works are all done.
825 if ((work->for_background || work->for_kupdate) &&
826 !list_empty(&wb->bdi->work_list))
830 * For background writeout, stop when we are below the
831 * background dirty threshold
833 if (work->for_background && !over_bground_thresh(wb->bdi))
837 * Kupdate and background works are special and we want to
838 * include all inodes that need writing. Livelock avoidance is
839 * handled by these works yielding to any other work so we are
842 if (work->for_kupdate) {
843 oldest_jif = jiffies -
844 msecs_to_jiffies(dirty_expire_interval * 10);
845 } else if (work->for_background)
846 oldest_jif = jiffies;
848 trace_writeback_start(wb->bdi, work);
849 if (list_empty(&wb->b_io))
852 progress = writeback_sb_inodes(work->sb, wb, work);
854 progress = __writeback_inodes_wb(wb, work);
855 trace_writeback_written(wb->bdi, work);
857 wb_update_bandwidth(wb, wb_start);
860 * Did we write something? Try for more
862 * Dirty inodes are moved to b_io for writeback in batches.
863 * The completion of the current batch does not necessarily
864 * mean the overall work is done. So we keep looping as long
865 * as made some progress on cleaning pages or inodes.
870 * No more inodes for IO, bail
872 if (list_empty(&wb->b_more_io))
875 * Nothing written. Wait for some inode to
876 * become available for writeback. Otherwise
877 * we'll just busyloop.
879 if (!list_empty(&wb->b_more_io)) {
880 trace_writeback_wait(wb->bdi, work);
881 inode = wb_inode(wb->b_more_io.prev);
882 spin_lock(&inode->i_lock);
883 spin_unlock(&wb->list_lock);
884 /* This function drops i_lock... */
885 inode_sleep_on_writeback(inode);
886 spin_lock(&wb->list_lock);
889 spin_unlock(&wb->list_lock);
891 return nr_pages - work->nr_pages;
895 * Return the next wb_writeback_work struct that hasn't been processed yet.
897 static struct wb_writeback_work *
898 get_next_work_item(struct backing_dev_info *bdi)
900 struct wb_writeback_work *work = NULL;
902 spin_lock_bh(&bdi->wb_lock);
903 if (!list_empty(&bdi->work_list)) {
904 work = list_entry(bdi->work_list.next,
905 struct wb_writeback_work, list);
906 list_del_init(&work->list);
908 spin_unlock_bh(&bdi->wb_lock);
913 * Add in the number of potentially dirty inodes, because each inode
914 * write can dirty pagecache in the underlying blockdev.
916 static unsigned long get_nr_dirty_pages(void)
918 return global_page_state(NR_FILE_DIRTY) +
919 global_page_state(NR_UNSTABLE_NFS) +
920 get_nr_dirty_inodes();
923 static long wb_check_background_flush(struct bdi_writeback *wb)
925 if (over_bground_thresh(wb->bdi)) {
927 struct wb_writeback_work work = {
928 .nr_pages = LONG_MAX,
929 .sync_mode = WB_SYNC_NONE,
932 .reason = WB_REASON_BACKGROUND,
935 return wb_writeback(wb, &work);
941 static long wb_check_old_data_flush(struct bdi_writeback *wb)
943 unsigned long expired;
947 * When set to zero, disable periodic writeback
949 if (!dirty_writeback_interval)
952 expired = wb->last_old_flush +
953 msecs_to_jiffies(dirty_writeback_interval * 10);
954 if (time_before(jiffies, expired))
957 wb->last_old_flush = jiffies;
958 nr_pages = get_nr_dirty_pages();
961 struct wb_writeback_work work = {
962 .nr_pages = nr_pages,
963 .sync_mode = WB_SYNC_NONE,
966 .reason = WB_REASON_PERIODIC,
969 return wb_writeback(wb, &work);
976 * Retrieve work items and do the writeback they describe
978 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
980 struct backing_dev_info *bdi = wb->bdi;
981 struct wb_writeback_work *work;
984 set_bit(BDI_writeback_running, &wb->bdi->state);
985 while ((work = get_next_work_item(bdi)) != NULL) {
987 * Override sync mode, in case we must wait for completion
988 * because this thread is exiting now.
991 work->sync_mode = WB_SYNC_ALL;
993 trace_writeback_exec(bdi, work);
995 wrote += wb_writeback(wb, work);
998 * Notify the caller of completion if this is a synchronous
999 * work item, otherwise just free it.
1002 complete(work->done);
1008 * Check for periodic writeback, kupdated() style
1010 wrote += wb_check_old_data_flush(wb);
1011 wrote += wb_check_background_flush(wb);
1012 clear_bit(BDI_writeback_running, &wb->bdi->state);
1018 * Handle writeback of dirty data for the device backed by this bdi. Also
1019 * reschedules periodically and does kupdated style flushing.
1021 void bdi_writeback_workfn(struct work_struct *work)
1023 struct bdi_writeback *wb = container_of(to_delayed_work(work),
1024 struct bdi_writeback, dwork);
1025 struct backing_dev_info *bdi = wb->bdi;
1028 set_worker_desc("flush-%s", dev_name(bdi->dev));
1029 current->flags |= PF_SWAPWRITE;
1031 if (likely(!current_is_workqueue_rescuer() ||
1032 !test_bit(BDI_registered, &bdi->state))) {
1034 * The normal path. Keep writing back @bdi until its
1035 * work_list is empty. Note that this path is also taken
1036 * if @bdi is shutting down even when we're running off the
1037 * rescuer as work_list needs to be drained.
1040 pages_written = wb_do_writeback(wb, 0);
1041 trace_writeback_pages_written(pages_written);
1042 } while (!list_empty(&bdi->work_list));
1045 * bdi_wq can't get enough workers and we're running off
1046 * the emergency worker. Don't hog it. Hopefully, 1024 is
1047 * enough for efficient IO.
1049 pages_written = writeback_inodes_wb(&bdi->wb, 1024,
1050 WB_REASON_FORKER_THREAD);
1051 trace_writeback_pages_written(pages_written);
1054 if (!list_empty(&bdi->work_list))
1055 mod_delayed_work(bdi_wq, &wb->dwork, 0);
1056 else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
1057 bdi_wakeup_thread_delayed(bdi);
1059 current->flags &= ~PF_SWAPWRITE;
1063 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
1066 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1068 struct backing_dev_info *bdi;
1071 nr_pages = global_page_state(NR_FILE_DIRTY) +
1072 global_page_state(NR_UNSTABLE_NFS);
1076 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1077 if (!bdi_has_dirty_io(bdi))
1079 __bdi_start_writeback(bdi, nr_pages, false, reason);
1084 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1086 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1087 struct dentry *dentry;
1088 const char *name = "?";
1090 dentry = d_find_alias(inode);
1092 spin_lock(&dentry->d_lock);
1093 name = (const char *) dentry->d_name.name;
1096 "%s(%d): dirtied inode %lu (%s) on %s\n",
1097 current->comm, task_pid_nr(current), inode->i_ino,
1098 name, inode->i_sb->s_id);
1100 spin_unlock(&dentry->d_lock);
1107 * __mark_inode_dirty - internal function
1108 * @inode: inode to mark
1109 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1110 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1111 * mark_inode_dirty_sync.
1113 * Put the inode on the super block's dirty list.
1115 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1116 * dirty list only if it is hashed or if it refers to a blockdev.
1117 * If it was not hashed, it will never be added to the dirty list
1118 * even if it is later hashed, as it will have been marked dirty already.
1120 * In short, make sure you hash any inodes _before_ you start marking
1123 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1124 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1125 * the kernel-internal blockdev inode represents the dirtying time of the
1126 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1127 * page->mapping->host, so the page-dirtying time is recorded in the internal
1130 void __mark_inode_dirty(struct inode *inode, int flags)
1132 struct super_block *sb = inode->i_sb;
1133 struct backing_dev_info *bdi = NULL;
1136 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1137 * dirty the inode itself
1139 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1140 trace_writeback_dirty_inode_start(inode, flags);
1142 if (sb->s_op->dirty_inode)
1143 sb->s_op->dirty_inode(inode, flags);
1145 trace_writeback_dirty_inode(inode, flags);
1149 * make sure that changes are seen by all cpus before we test i_state
1154 /* avoid the locking if we can */
1155 if ((inode->i_state & flags) == flags)
1158 if (unlikely(block_dump > 1))
1159 block_dump___mark_inode_dirty(inode);
1161 spin_lock(&inode->i_lock);
1162 if ((inode->i_state & flags) != flags) {
1163 const int was_dirty = inode->i_state & I_DIRTY;
1165 inode->i_state |= flags;
1168 * If the inode is being synced, just update its dirty state.
1169 * The unlocker will place the inode on the appropriate
1170 * superblock list, based upon its state.
1172 if (inode->i_state & I_SYNC)
1173 goto out_unlock_inode;
1176 * Only add valid (hashed) inodes to the superblock's
1177 * dirty list. Add blockdev inodes as well.
1179 if (!S_ISBLK(inode->i_mode)) {
1180 if (inode_unhashed(inode))
1181 goto out_unlock_inode;
1183 if (inode->i_state & I_FREEING)
1184 goto out_unlock_inode;
1187 * If the inode was already on b_dirty/b_io/b_more_io, don't
1188 * reposition it (that would break b_dirty time-ordering).
1191 bool wakeup_bdi = false;
1192 bdi = inode_to_bdi(inode);
1194 if (bdi_cap_writeback_dirty(bdi)) {
1195 WARN(!test_bit(BDI_registered, &bdi->state),
1196 "bdi-%s not registered\n", bdi->name);
1199 * If this is the first dirty inode for this
1200 * bdi, we have to wake-up the corresponding
1201 * bdi thread to make sure background
1202 * write-back happens later.
1204 if (!wb_has_dirty_io(&bdi->wb))
1208 spin_unlock(&inode->i_lock);
1209 spin_lock(&bdi->wb.list_lock);
1210 inode->dirtied_when = jiffies;
1211 list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1212 spin_unlock(&bdi->wb.list_lock);
1215 bdi_wakeup_thread_delayed(bdi);
1220 spin_unlock(&inode->i_lock);
1223 EXPORT_SYMBOL(__mark_inode_dirty);
1225 static void wait_sb_inodes(struct super_block *sb)
1227 struct inode *inode, *old_inode = NULL;
1230 * We need to be protected against the filesystem going from
1231 * r/o to r/w or vice versa.
1233 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1235 spin_lock(&inode_sb_list_lock);
1238 * Data integrity sync. Must wait for all pages under writeback,
1239 * because there may have been pages dirtied before our sync
1240 * call, but which had writeout started before we write it out.
1241 * In which case, the inode may not be on the dirty list, but
1242 * we still have to wait for that writeout.
1244 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1245 struct address_space *mapping = inode->i_mapping;
1247 spin_lock(&inode->i_lock);
1248 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1249 (mapping->nrpages == 0)) {
1250 spin_unlock(&inode->i_lock);
1254 spin_unlock(&inode->i_lock);
1255 spin_unlock(&inode_sb_list_lock);
1258 * We hold a reference to 'inode' so it couldn't have been
1259 * removed from s_inodes list while we dropped the
1260 * inode_sb_list_lock. We cannot iput the inode now as we can
1261 * be holding the last reference and we cannot iput it under
1262 * inode_sb_list_lock. So we keep the reference and iput it
1268 filemap_fdatawait(mapping);
1272 spin_lock(&inode_sb_list_lock);
1274 spin_unlock(&inode_sb_list_lock);
1279 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1280 * @sb: the superblock
1281 * @nr: the number of pages to write
1282 * @reason: reason why some writeback work initiated
1284 * Start writeback on some inodes on this super_block. No guarantees are made
1285 * on how many (if any) will be written, and this function does not wait
1286 * for IO completion of submitted IO.
1288 void writeback_inodes_sb_nr(struct super_block *sb,
1290 enum wb_reason reason)
1292 DECLARE_COMPLETION_ONSTACK(done);
1293 struct wb_writeback_work work = {
1295 .sync_mode = WB_SYNC_NONE,
1296 .tagged_writepages = 1,
1302 if (sb->s_bdi == &noop_backing_dev_info)
1304 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1305 bdi_queue_work(sb->s_bdi, &work);
1306 wait_for_completion(&done);
1308 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1311 * writeback_inodes_sb - writeback dirty inodes from given super_block
1312 * @sb: the superblock
1313 * @reason: reason why some writeback work was initiated
1315 * Start writeback on some inodes on this super_block. No guarantees are made
1316 * on how many (if any) will be written, and this function does not wait
1317 * for IO completion of submitted IO.
1319 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1321 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1323 EXPORT_SYMBOL(writeback_inodes_sb);
1326 * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
1327 * @sb: the superblock
1328 * @nr: the number of pages to write
1329 * @reason: the reason of writeback
1331 * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
1332 * Returns 1 if writeback was started, 0 if not.
1334 int try_to_writeback_inodes_sb_nr(struct super_block *sb,
1336 enum wb_reason reason)
1338 if (writeback_in_progress(sb->s_bdi))
1341 if (!down_read_trylock(&sb->s_umount))
1344 writeback_inodes_sb_nr(sb, nr, reason);
1345 up_read(&sb->s_umount);
1348 EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
1351 * try_to_writeback_inodes_sb - try to start writeback if none underway
1352 * @sb: the superblock
1353 * @reason: reason why some writeback work was initiated
1355 * Implement by try_to_writeback_inodes_sb_nr()
1356 * Returns 1 if writeback was started, 0 if not.
1358 int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1360 return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1362 EXPORT_SYMBOL(try_to_writeback_inodes_sb);
1365 * sync_inodes_sb - sync sb inode pages
1366 * @sb: the superblock
1368 * This function writes and waits on any dirty inode belonging to this
1371 void sync_inodes_sb(struct super_block *sb)
1373 DECLARE_COMPLETION_ONSTACK(done);
1374 struct wb_writeback_work work = {
1376 .sync_mode = WB_SYNC_ALL,
1377 .nr_pages = LONG_MAX,
1380 .reason = WB_REASON_SYNC,
1383 /* Nothing to do? */
1384 if (sb->s_bdi == &noop_backing_dev_info)
1386 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1388 bdi_queue_work(sb->s_bdi, &work);
1389 wait_for_completion(&done);
1393 EXPORT_SYMBOL(sync_inodes_sb);
1396 * write_inode_now - write an inode to disk
1397 * @inode: inode to write to disk
1398 * @sync: whether the write should be synchronous or not
1400 * This function commits an inode to disk immediately if it is dirty. This is
1401 * primarily needed by knfsd.
1403 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1405 int write_inode_now(struct inode *inode, int sync)
1407 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1408 struct writeback_control wbc = {
1409 .nr_to_write = LONG_MAX,
1410 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1412 .range_end = LLONG_MAX,
1415 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1416 wbc.nr_to_write = 0;
1419 return writeback_single_inode(inode, wb, &wbc);
1421 EXPORT_SYMBOL(write_inode_now);
1424 * sync_inode - write an inode and its pages to disk.
1425 * @inode: the inode to sync
1426 * @wbc: controls the writeback mode
1428 * sync_inode() will write an inode and its pages to disk. It will also
1429 * correctly update the inode on its superblock's dirty inode lists and will
1430 * update inode->i_state.
1432 * The caller must have a ref on the inode.
1434 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1436 return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1438 EXPORT_SYMBOL(sync_inode);
1441 * sync_inode_metadata - write an inode to disk
1442 * @inode: the inode to sync
1443 * @wait: wait for I/O to complete.
1445 * Write an inode to disk and adjust its dirty state after completion.
1447 * Note: only writes the actual inode, no associated data or other metadata.
1449 int sync_inode_metadata(struct inode *inode, int wait)
1451 struct writeback_control wbc = {
1452 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1453 .nr_to_write = 0, /* metadata-only */
1456 return sync_inode(inode, &wbc);
1458 EXPORT_SYMBOL(sync_inode_metadata);