4 * Copyright (C) 2002, Linus Torvalds.
6 * Contains all the functions related to writing back and waiting
7 * upon dirty inodes against superblocks, and writing back dirty
8 * pages against inodes. ie: data writeback. Writeout of the
9 * inode itself is not handled here.
11 * 10Apr2002 Andrew Morton
12 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/spinlock.h>
19 #include <linux/slab.h>
20 #include <linux/sched.h>
23 #include <linux/kthread.h>
24 #include <linux/freezer.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/buffer_head.h>
31 #define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
34 * We don't actually have pdflush, but this one is exported though /proc...
36 int nr_pdflush_threads;
39 * Passed into wb_writeback(), essentially a subset of writeback_control
41 struct wb_writeback_args {
43 struct super_block *sb;
44 enum writeback_sync_modes sync_mode;
45 unsigned int for_kupdate:1;
46 unsigned int range_cyclic:1;
47 unsigned int for_background:1;
51 * Work items for the bdi_writeback threads
54 struct list_head list; /* pending work list */
55 struct rcu_head rcu_head; /* for RCU free/clear of work */
57 unsigned long seen; /* threads that have seen this work */
58 atomic_t pending; /* number of threads still to do work */
60 struct wb_writeback_args args; /* writeback arguments */
62 unsigned long state; /* flag bits, see WS_* */
70 static inline void bdi_work_init(struct bdi_work *work,
71 struct wb_writeback_args *args)
73 INIT_RCU_HEAD(&work->rcu_head);
75 __set_bit(WS_INPROGRESS, &work->state);
79 * writeback_in_progress - determine whether there is writeback in progress
80 * @bdi: the device's backing_dev_info structure.
82 * Determine whether there is writeback waiting to be handled against a
85 int writeback_in_progress(struct backing_dev_info *bdi)
87 return !list_empty(&bdi->work_list);
90 static void bdi_work_free(struct rcu_head *head)
92 struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
94 clear_bit(WS_INPROGRESS, &work->state);
95 smp_mb__after_clear_bit();
96 wake_up_bit(&work->state, WS_INPROGRESS);
98 if (!test_bit(WS_ONSTACK, &work->state))
102 static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
105 * The caller has retrieved the work arguments from this work,
106 * drop our reference. If this is the last ref, delete and free it
108 if (atomic_dec_and_test(&work->pending)) {
109 struct backing_dev_info *bdi = wb->bdi;
111 spin_lock(&bdi->wb_lock);
112 list_del_rcu(&work->list);
113 spin_unlock(&bdi->wb_lock);
115 call_rcu(&work->rcu_head, bdi_work_free);
119 static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
121 work->seen = bdi->wb_mask;
123 atomic_set(&work->pending, bdi->wb_cnt);
124 BUG_ON(!bdi->wb_cnt);
127 * list_add_tail_rcu() contains the necessary barriers to
128 * make sure the above stores are seen before the item is
129 * noticed on the list
131 spin_lock(&bdi->wb_lock);
132 list_add_tail_rcu(&work->list, &bdi->work_list);
133 spin_unlock(&bdi->wb_lock);
136 * If the default thread isn't there, make sure we add it. When
137 * it gets created and wakes up, we'll run this work.
139 if (unlikely(list_empty_careful(&bdi->wb_list)))
140 wake_up_process(default_backing_dev_info.wb.task);
142 struct bdi_writeback *wb = &bdi->wb;
145 wake_up_process(wb->task);
150 * Used for on-stack allocated work items. The caller needs to wait until
151 * the wb threads have acked the work before it's safe to continue.
153 static void bdi_wait_on_work_done(struct bdi_work *work)
155 wait_on_bit(&work->state, WS_INPROGRESS, bdi_sched_wait,
156 TASK_UNINTERRUPTIBLE);
159 static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
160 struct wb_writeback_args *args)
162 struct bdi_work *work;
165 * This is WB_SYNC_NONE writeback, so if allocation fails just
166 * wakeup the thread for old dirty data writeback
168 work = kmalloc(sizeof(*work), GFP_ATOMIC);
170 bdi_work_init(work, args);
171 bdi_queue_work(bdi, work);
173 struct bdi_writeback *wb = &bdi->wb;
176 wake_up_process(wb->task);
181 * bdi_queue_work_onstack - start and wait for writeback
182 * @args: parameters to control the work queue writeback
185 * This function initiates writeback and waits for the operation to
186 * complete. Callers must hold the sb s_umount semaphore for
187 * reading, to avoid having the super disappear before we are done.
189 static void bdi_queue_work_onstack(struct wb_writeback_args *args)
191 struct bdi_work work;
193 bdi_work_init(&work, args);
194 __set_bit(WS_ONSTACK, &work.state);
196 bdi_queue_work(args->sb->s_bdi, &work);
197 bdi_wait_on_work_done(&work);
201 * bdi_start_writeback - start writeback
202 * @bdi: the backing device to write from
203 * @nr_pages: the number of pages to write
206 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
207 * started when this function returns, we make no guarentees on
208 * completion. Caller need not hold sb s_umount semaphore.
211 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
213 struct wb_writeback_args args = {
214 .sync_mode = WB_SYNC_NONE,
215 .nr_pages = nr_pages,
219 bdi_alloc_queue_work(bdi, &args);
223 * bdi_start_background_writeback - start background writeback
224 * @bdi: the backing device to write from
227 * This does WB_SYNC_NONE background writeback. The IO is only
228 * started when this function returns, we make no guarentees on
229 * completion. Caller need not hold sb s_umount semaphore.
231 void bdi_start_background_writeback(struct backing_dev_info *bdi)
233 struct wb_writeback_args args = {
234 .sync_mode = WB_SYNC_NONE,
235 .nr_pages = LONG_MAX,
239 bdi_alloc_queue_work(bdi, &args);
243 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
244 * furthest end of its superblock's dirty-inode list.
246 * Before stamping the inode's ->dirtied_when, we check to see whether it is
247 * already the most-recently-dirtied inode on the b_dirty list. If that is
248 * the case then the inode must have been redirtied while it was being written
249 * out and we don't reset its dirtied_when.
251 static void redirty_tail(struct inode *inode)
253 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
255 if (!list_empty(&wb->b_dirty)) {
258 tail = list_entry(wb->b_dirty.next, struct inode, i_list);
259 if (time_before(inode->dirtied_when, tail->dirtied_when))
260 inode->dirtied_when = jiffies;
262 list_move(&inode->i_list, &wb->b_dirty);
266 * requeue inode for re-scanning after bdi->b_io list is exhausted.
268 static void requeue_io(struct inode *inode)
270 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
272 list_move(&inode->i_list, &wb->b_more_io);
275 static void inode_sync_complete(struct inode *inode)
278 * Prevent speculative execution through spin_unlock(&inode_lock);
281 wake_up_bit(&inode->i_state, __I_SYNC);
284 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
286 bool ret = time_after(inode->dirtied_when, t);
289 * For inodes being constantly redirtied, dirtied_when can get stuck.
290 * It _appears_ to be in the future, but is actually in distant past.
291 * This test is necessary to prevent such wrapped-around relative times
292 * from permanently stopping the whole bdi writeback.
294 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
300 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
302 static void move_expired_inodes(struct list_head *delaying_queue,
303 struct list_head *dispatch_queue,
304 unsigned long *older_than_this)
307 struct list_head *pos, *node;
308 struct super_block *sb = NULL;
312 while (!list_empty(delaying_queue)) {
313 inode = list_entry(delaying_queue->prev, struct inode, i_list);
314 if (older_than_this &&
315 inode_dirtied_after(inode, *older_than_this))
317 if (sb && sb != inode->i_sb)
320 list_move(&inode->i_list, &tmp);
323 /* just one sb in list, splice to dispatch_queue and we're done */
325 list_splice(&tmp, dispatch_queue);
329 /* Move inodes from one superblock together */
330 while (!list_empty(&tmp)) {
331 inode = list_entry(tmp.prev, struct inode, i_list);
333 list_for_each_prev_safe(pos, node, &tmp) {
334 inode = list_entry(pos, struct inode, i_list);
335 if (inode->i_sb == sb)
336 list_move(&inode->i_list, dispatch_queue);
342 * Queue all expired dirty inodes for io, eldest first.
344 static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
346 list_splice_init(&wb->b_more_io, wb->b_io.prev);
347 move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
350 static int write_inode(struct inode *inode, struct writeback_control *wbc)
352 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
353 return inode->i_sb->s_op->write_inode(inode, wbc);
358 * Wait for writeback on an inode to complete.
360 static void inode_wait_for_writeback(struct inode *inode)
362 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
363 wait_queue_head_t *wqh;
365 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
366 while (inode->i_state & I_SYNC) {
367 spin_unlock(&inode_lock);
368 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
369 spin_lock(&inode_lock);
374 * Write out an inode's dirty pages. Called under inode_lock. Either the
375 * caller has ref on the inode (either via __iget or via syscall against an fd)
376 * or the inode has I_WILL_FREE set (via generic_forget_inode)
378 * If `wait' is set, wait on the writeout.
380 * The whole writeout design is quite complex and fragile. We want to avoid
381 * starvation of particular inodes when others are being redirtied, prevent
384 * Called under inode_lock.
387 writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
389 struct address_space *mapping = inode->i_mapping;
393 if (!atomic_read(&inode->i_count))
394 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
396 WARN_ON(inode->i_state & I_WILL_FREE);
398 if (inode->i_state & I_SYNC) {
400 * If this inode is locked for writeback and we are not doing
401 * writeback-for-data-integrity, move it to b_more_io so that
402 * writeback can proceed with the other inodes on s_io.
404 * We'll have another go at writing back this inode when we
405 * completed a full scan of b_io.
407 if (wbc->sync_mode != WB_SYNC_ALL) {
413 * It's a data-integrity sync. We must wait.
415 inode_wait_for_writeback(inode);
418 BUG_ON(inode->i_state & I_SYNC);
420 /* Set I_SYNC, reset I_DIRTY_PAGES */
421 inode->i_state |= I_SYNC;
422 inode->i_state &= ~I_DIRTY_PAGES;
423 spin_unlock(&inode_lock);
425 ret = do_writepages(mapping, wbc);
428 * Make sure to wait on the data before writing out the metadata.
429 * This is important for filesystems that modify metadata on data
432 if (wbc->sync_mode == WB_SYNC_ALL) {
433 int err = filemap_fdatawait(mapping);
439 * Some filesystems may redirty the inode during the writeback
440 * due to delalloc, clear dirty metadata flags right before
443 spin_lock(&inode_lock);
444 dirty = inode->i_state & I_DIRTY;
445 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
446 spin_unlock(&inode_lock);
447 /* Don't write the inode if only I_DIRTY_PAGES was set */
448 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
449 int err = write_inode(inode, wbc);
454 spin_lock(&inode_lock);
455 inode->i_state &= ~I_SYNC;
456 if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
457 if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
459 * More pages get dirtied by a fast dirtier.
462 } else if (inode->i_state & I_DIRTY) {
464 * At least XFS will redirty the inode during the
465 * writeback (delalloc) and on io completion (isize).
468 } else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
470 * We didn't write back all the pages. nfs_writepages()
471 * sometimes bales out without doing anything. Redirty
472 * the inode; Move it from b_io onto b_more_io/b_dirty.
475 * akpm: if the caller was the kupdate function we put
476 * this inode at the head of b_dirty so it gets first
477 * consideration. Otherwise, move it to the tail, for
478 * the reasons described there. I'm not really sure
479 * how much sense this makes. Presumably I had a good
480 * reasons for doing it this way, and I'd rather not
481 * muck with it at present.
483 if (wbc->for_kupdate) {
485 * For the kupdate function we move the inode
486 * to b_more_io so it will get more writeout as
487 * soon as the queue becomes uncongested.
489 inode->i_state |= I_DIRTY_PAGES;
491 if (wbc->nr_to_write <= 0) {
493 * slice used up: queue for next turn
498 * somehow blocked: retry later
504 * Otherwise fully redirty the inode so that
505 * other inodes on this superblock will get some
506 * writeout. Otherwise heavy writing to one
507 * file would indefinitely suspend writeout of
508 * all the other files.
510 inode->i_state |= I_DIRTY_PAGES;
513 } else if (atomic_read(&inode->i_count)) {
515 * The inode is clean, inuse
517 list_move(&inode->i_list, &inode_in_use);
520 * The inode is clean, unused
522 list_move(&inode->i_list, &inode_unused);
525 inode_sync_complete(inode);
530 * For background writeback the caller does not have the sb pinned
531 * before calling writeback. So make sure that we do pin it, so it doesn't
532 * go away while we are writing inodes from it.
534 static bool pin_sb_for_writeback(struct super_block *sb)
537 if (list_empty(&sb->s_instances)) {
538 spin_unlock(&sb_lock);
543 spin_unlock(&sb_lock);
545 if (down_read_trylock(&sb->s_umount)) {
548 up_read(&sb->s_umount);
556 * Write a portion of b_io inodes which belong to @sb.
558 * If @only_this_sb is true, then find and write all such
559 * inodes. Otherwise write only ones which go sequentially
562 * Return 1, if the caller writeback routine should be
563 * interrupted. Otherwise return 0.
565 static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
566 struct writeback_control *wbc, bool only_this_sb)
568 while (!list_empty(&wb->b_io)) {
570 struct inode *inode = list_entry(wb->b_io.prev,
571 struct inode, i_list);
573 if (inode->i_sb != sb) {
576 * We only want to write back data for this
577 * superblock, move all inodes not belonging
578 * to it back onto the dirty list.
585 * The inode belongs to a different superblock.
586 * Bounce back to the caller to unpin this and
587 * pin the next superblock.
592 if (inode->i_state & (I_NEW | I_WILL_FREE)) {
597 * Was this inode dirtied after sync_sb_inodes was called?
598 * This keeps sync from extra jobs and livelock.
600 if (inode_dirtied_after(inode, wbc->wb_start))
603 BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
605 pages_skipped = wbc->pages_skipped;
606 writeback_single_inode(inode, wbc);
607 if (wbc->pages_skipped != pages_skipped) {
609 * writeback is not making progress due to locked
610 * buffers. Skip this inode for now.
614 spin_unlock(&inode_lock);
617 spin_lock(&inode_lock);
618 if (wbc->nr_to_write <= 0) {
622 if (!list_empty(&wb->b_more_io))
629 void writeback_inodes_wb(struct bdi_writeback *wb,
630 struct writeback_control *wbc)
634 wbc->wb_start = jiffies; /* livelock avoidance */
635 spin_lock(&inode_lock);
636 if (!wbc->for_kupdate || list_empty(&wb->b_io))
637 queue_io(wb, wbc->older_than_this);
639 while (!list_empty(&wb->b_io)) {
640 struct inode *inode = list_entry(wb->b_io.prev,
641 struct inode, i_list);
642 struct super_block *sb = inode->i_sb;
644 if (!pin_sb_for_writeback(sb)) {
648 ret = writeback_sb_inodes(sb, wb, wbc, false);
654 spin_unlock(&inode_lock);
655 /* Leave any unwritten inodes on b_io */
658 static void __writeback_inodes_sb(struct super_block *sb,
659 struct bdi_writeback *wb, struct writeback_control *wbc)
661 WARN_ON(!rwsem_is_locked(&sb->s_umount));
663 wbc->wb_start = jiffies; /* livelock avoidance */
664 spin_lock(&inode_lock);
665 if (!wbc->for_kupdate || list_empty(&wb->b_io))
666 queue_io(wb, wbc->older_than_this);
667 writeback_sb_inodes(sb, wb, wbc, true);
668 spin_unlock(&inode_lock);
672 * The maximum number of pages to writeout in a single bdi flush/kupdate
673 * operation. We do this so we don't hold I_SYNC against an inode for
674 * enormous amounts of time, which would block a userspace task which has
675 * been forced to throttle against that inode. Also, the code reevaluates
676 * the dirty each time it has written this many pages.
678 #define MAX_WRITEBACK_PAGES 1024
680 static inline bool over_bground_thresh(void)
682 unsigned long background_thresh, dirty_thresh;
684 get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
686 return (global_page_state(NR_FILE_DIRTY) +
687 global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
691 * Explicit flushing or periodic writeback of "old" data.
693 * Define "old": the first time one of an inode's pages is dirtied, we mark the
694 * dirtying-time in the inode's address_space. So this periodic writeback code
695 * just walks the superblock inode list, writing back any inodes which are
696 * older than a specific point in time.
698 * Try to run once per dirty_writeback_interval. But if a writeback event
699 * takes longer than a dirty_writeback_interval interval, then leave a
702 * older_than_this takes precedence over nr_to_write. So we'll only write back
703 * all dirty pages if they are all attached to "old" mappings.
705 static long wb_writeback(struct bdi_writeback *wb,
706 struct wb_writeback_args *args)
708 struct writeback_control wbc = {
709 .sync_mode = args->sync_mode,
710 .older_than_this = NULL,
711 .for_kupdate = args->for_kupdate,
712 .for_background = args->for_background,
713 .range_cyclic = args->range_cyclic,
715 unsigned long oldest_jif;
719 if (wbc.for_kupdate) {
720 wbc.older_than_this = &oldest_jif;
721 oldest_jif = jiffies -
722 msecs_to_jiffies(dirty_expire_interval * 10);
724 if (!wbc.range_cyclic) {
726 wbc.range_end = LLONG_MAX;
731 * Stop writeback when nr_pages has been consumed
733 if (args->nr_pages <= 0)
737 * For background writeout, stop when we are below the
738 * background dirty threshold
740 if (args->for_background && !over_bground_thresh())
744 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
745 wbc.pages_skipped = 0;
747 __writeback_inodes_sb(args->sb, wb, &wbc);
749 writeback_inodes_wb(wb, &wbc);
750 args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
751 wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
754 * If we consumed everything, see if we have more
756 if (wbc.nr_to_write <= 0)
759 * Didn't write everything and we don't have more IO, bail
764 * Did we write something? Try for more
766 if (wbc.nr_to_write < MAX_WRITEBACK_PAGES)
769 * Nothing written. Wait for some inode to
770 * become available for writeback. Otherwise
771 * we'll just busyloop.
773 spin_lock(&inode_lock);
774 if (!list_empty(&wb->b_more_io)) {
775 inode = list_entry(wb->b_more_io.prev,
776 struct inode, i_list);
777 inode_wait_for_writeback(inode);
779 spin_unlock(&inode_lock);
786 * Return the next bdi_work struct that hasn't been processed by this
787 * wb thread yet. ->seen is initially set for each thread that exists
788 * for this device, when a thread first notices a piece of work it
789 * clears its bit. Depending on writeback type, the thread will notify
790 * completion on either receiving the work (WB_SYNC_NONE) or after
791 * it is done (WB_SYNC_ALL).
793 static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
794 struct bdi_writeback *wb)
796 struct bdi_work *work, *ret = NULL;
800 list_for_each_entry_rcu(work, &bdi->work_list, list) {
801 if (!test_bit(wb->nr, &work->seen))
803 clear_bit(wb->nr, &work->seen);
813 static long wb_check_old_data_flush(struct bdi_writeback *wb)
815 unsigned long expired;
819 * When set to zero, disable periodic writeback
821 if (!dirty_writeback_interval)
824 expired = wb->last_old_flush +
825 msecs_to_jiffies(dirty_writeback_interval * 10);
826 if (time_before(jiffies, expired))
829 wb->last_old_flush = jiffies;
830 nr_pages = global_page_state(NR_FILE_DIRTY) +
831 global_page_state(NR_UNSTABLE_NFS) +
832 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
835 struct wb_writeback_args args = {
836 .nr_pages = nr_pages,
837 .sync_mode = WB_SYNC_NONE,
842 return wb_writeback(wb, &args);
849 * Retrieve work items and do the writeback they describe
851 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
853 struct backing_dev_info *bdi = wb->bdi;
854 struct bdi_work *work;
857 while ((work = get_next_work_item(bdi, wb)) != NULL) {
858 struct wb_writeback_args args = work->args;
861 * Override sync mode, in case we must wait for completion
864 work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
867 * If this isn't a data integrity operation, just notify
868 * that we have seen this work and we are now starting it.
870 if (!test_bit(WS_ONSTACK, &work->state))
871 wb_clear_pending(wb, work);
873 wrote += wb_writeback(wb, &args);
876 * This is a data integrity writeback, so only do the
877 * notification when we have completed the work.
879 if (test_bit(WS_ONSTACK, &work->state))
880 wb_clear_pending(wb, work);
884 * Check for periodic writeback, kupdated() style
886 wrote += wb_check_old_data_flush(wb);
892 * Handle writeback of dirty data for the device backed by this bdi. Also
893 * wakes up periodically and does kupdated style flushing.
895 int bdi_writeback_task(struct bdi_writeback *wb)
897 unsigned long last_active = jiffies;
898 unsigned long wait_jiffies = -1UL;
901 while (!kthread_should_stop()) {
902 pages_written = wb_do_writeback(wb, 0);
905 last_active = jiffies;
906 else if (wait_jiffies != -1UL) {
907 unsigned long max_idle;
910 * Longest period of inactivity that we tolerate. If we
911 * see dirty data again later, the task will get
912 * recreated automatically.
914 max_idle = max(5UL * 60 * HZ, wait_jiffies);
915 if (time_after(jiffies, max_idle + last_active))
919 if (dirty_writeback_interval) {
920 wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
921 schedule_timeout_interruptible(wait_jiffies);
923 set_current_state(TASK_INTERRUPTIBLE);
924 if (list_empty_careful(&wb->bdi->work_list) &&
925 !kthread_should_stop())
927 __set_current_state(TASK_RUNNING);
937 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
940 void wakeup_flusher_threads(long nr_pages)
942 struct backing_dev_info *bdi;
943 struct wb_writeback_args args = {
944 .sync_mode = WB_SYNC_NONE,
948 args.nr_pages = nr_pages;
950 args.nr_pages = global_page_state(NR_FILE_DIRTY) +
951 global_page_state(NR_UNSTABLE_NFS);
955 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
956 if (!bdi_has_dirty_io(bdi))
958 bdi_alloc_queue_work(bdi, &args);
963 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
965 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
966 struct dentry *dentry;
967 const char *name = "?";
969 dentry = d_find_alias(inode);
971 spin_lock(&dentry->d_lock);
972 name = (const char *) dentry->d_name.name;
975 "%s(%d): dirtied inode %lu (%s) on %s\n",
976 current->comm, task_pid_nr(current), inode->i_ino,
977 name, inode->i_sb->s_id);
979 spin_unlock(&dentry->d_lock);
986 * __mark_inode_dirty - internal function
987 * @inode: inode to mark
988 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
989 * Mark an inode as dirty. Callers should use mark_inode_dirty or
990 * mark_inode_dirty_sync.
992 * Put the inode on the super block's dirty list.
994 * CAREFUL! We mark it dirty unconditionally, but move it onto the
995 * dirty list only if it is hashed or if it refers to a blockdev.
996 * If it was not hashed, it will never be added to the dirty list
997 * even if it is later hashed, as it will have been marked dirty already.
999 * In short, make sure you hash any inodes _before_ you start marking
1002 * This function *must* be atomic for the I_DIRTY_PAGES case -
1003 * set_page_dirty() is called under spinlock in several places.
1005 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1006 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1007 * the kernel-internal blockdev inode represents the dirtying time of the
1008 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1009 * page->mapping->host, so the page-dirtying time is recorded in the internal
1012 void __mark_inode_dirty(struct inode *inode, int flags)
1014 struct super_block *sb = inode->i_sb;
1017 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1018 * dirty the inode itself
1020 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1021 if (sb->s_op->dirty_inode)
1022 sb->s_op->dirty_inode(inode);
1026 * make sure that changes are seen by all cpus before we test i_state
1031 /* avoid the locking if we can */
1032 if ((inode->i_state & flags) == flags)
1035 if (unlikely(block_dump))
1036 block_dump___mark_inode_dirty(inode);
1038 spin_lock(&inode_lock);
1039 if ((inode->i_state & flags) != flags) {
1040 const int was_dirty = inode->i_state & I_DIRTY;
1042 inode->i_state |= flags;
1045 * If the inode is being synced, just update its dirty state.
1046 * The unlocker will place the inode on the appropriate
1047 * superblock list, based upon its state.
1049 if (inode->i_state & I_SYNC)
1053 * Only add valid (hashed) inodes to the superblock's
1054 * dirty list. Add blockdev inodes as well.
1056 if (!S_ISBLK(inode->i_mode)) {
1057 if (hlist_unhashed(&inode->i_hash))
1060 if (inode->i_state & (I_FREEING|I_CLEAR))
1064 * If the inode was already on b_dirty/b_io/b_more_io, don't
1065 * reposition it (that would break b_dirty time-ordering).
1068 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1069 struct backing_dev_info *bdi = wb->bdi;
1071 if (bdi_cap_writeback_dirty(bdi) &&
1072 !test_bit(BDI_registered, &bdi->state)) {
1074 printk(KERN_ERR "bdi-%s not registered\n",
1078 inode->dirtied_when = jiffies;
1079 list_move(&inode->i_list, &wb->b_dirty);
1083 spin_unlock(&inode_lock);
1085 EXPORT_SYMBOL(__mark_inode_dirty);
1088 * Write out a superblock's list of dirty inodes. A wait will be performed
1089 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1091 * If older_than_this is non-NULL, then only write out inodes which
1092 * had their first dirtying at a time earlier than *older_than_this.
1094 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1095 * This function assumes that the blockdev superblock's inodes are backed by
1096 * a variety of queues, so all inodes are searched. For other superblocks,
1097 * assume that all inodes are backed by the same queue.
1099 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1100 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1101 * on the writer throttling path, and we get decent balancing between many
1102 * throttled threads: we don't want them all piling up on inode_sync_wait.
1104 static void wait_sb_inodes(struct super_block *sb)
1106 struct inode *inode, *old_inode = NULL;
1109 * We need to be protected against the filesystem going from
1110 * r/o to r/w or vice versa.
1112 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1114 spin_lock(&inode_lock);
1117 * Data integrity sync. Must wait for all pages under writeback,
1118 * because there may have been pages dirtied before our sync
1119 * call, but which had writeout started before we write it out.
1120 * In which case, the inode may not be on the dirty list, but
1121 * we still have to wait for that writeout.
1123 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1124 struct address_space *mapping;
1126 if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
1128 mapping = inode->i_mapping;
1129 if (mapping->nrpages == 0)
1132 spin_unlock(&inode_lock);
1134 * We hold a reference to 'inode' so it couldn't have
1135 * been removed from s_inodes list while we dropped the
1136 * inode_lock. We cannot iput the inode now as we can
1137 * be holding the last reference and we cannot iput it
1138 * under inode_lock. So we keep the reference and iput
1144 filemap_fdatawait(mapping);
1148 spin_lock(&inode_lock);
1150 spin_unlock(&inode_lock);
1155 * writeback_inodes_sb - writeback dirty inodes from given super_block
1156 * @sb: the superblock
1158 * Start writeback on some inodes on this super_block. No guarantees are made
1159 * on how many (if any) will be written, and this function does not wait
1160 * for IO completion of submitted IO. The number of pages submitted is
1163 void writeback_inodes_sb(struct super_block *sb)
1165 unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
1166 unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
1167 struct wb_writeback_args args = {
1169 .sync_mode = WB_SYNC_NONE,
1172 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1174 args.nr_pages = nr_dirty + nr_unstable +
1175 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
1177 bdi_queue_work_onstack(&args);
1179 EXPORT_SYMBOL(writeback_inodes_sb);
1182 * writeback_inodes_sb_if_idle - start writeback if none underway
1183 * @sb: the superblock
1185 * Invoke writeback_inodes_sb if no writeback is currently underway.
1186 * Returns 1 if writeback was started, 0 if not.
1188 int writeback_inodes_sb_if_idle(struct super_block *sb)
1190 if (!writeback_in_progress(sb->s_bdi)) {
1191 down_read(&sb->s_umount);
1192 writeback_inodes_sb(sb);
1193 up_read(&sb->s_umount);
1198 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1201 * sync_inodes_sb - sync sb inode pages
1202 * @sb: the superblock
1204 * This function writes and waits on any dirty inode belonging to this
1205 * super_block. The number of pages synced is returned.
1207 void sync_inodes_sb(struct super_block *sb)
1209 struct wb_writeback_args args = {
1211 .sync_mode = WB_SYNC_ALL,
1212 .nr_pages = LONG_MAX,
1216 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1218 bdi_queue_work_onstack(&args);
1221 EXPORT_SYMBOL(sync_inodes_sb);
1224 * write_inode_now - write an inode to disk
1225 * @inode: inode to write to disk
1226 * @sync: whether the write should be synchronous or not
1228 * This function commits an inode to disk immediately if it is dirty. This is
1229 * primarily needed by knfsd.
1231 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1233 int write_inode_now(struct inode *inode, int sync)
1236 struct writeback_control wbc = {
1237 .nr_to_write = LONG_MAX,
1238 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1240 .range_end = LLONG_MAX,
1243 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1244 wbc.nr_to_write = 0;
1247 spin_lock(&inode_lock);
1248 ret = writeback_single_inode(inode, &wbc);
1249 spin_unlock(&inode_lock);
1251 inode_sync_wait(inode);
1254 EXPORT_SYMBOL(write_inode_now);
1257 * sync_inode - write an inode and its pages to disk.
1258 * @inode: the inode to sync
1259 * @wbc: controls the writeback mode
1261 * sync_inode() will write an inode and its pages to disk. It will also
1262 * correctly update the inode on its superblock's dirty inode lists and will
1263 * update inode->i_state.
1265 * The caller must have a ref on the inode.
1267 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1271 spin_lock(&inode_lock);
1272 ret = writeback_single_inode(inode, wbc);
1273 spin_unlock(&inode_lock);
1276 EXPORT_SYMBOL(sync_inode);