drm/i915: use new macros to access the ring start register
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / fs-writeback.c
blob81e086d8aa5733c7a86a966827bf7ea18d29baa4
1 /*
2 * fs/fs-writeback.c
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>
21 #include <linux/fs.h>
22 #include <linux/mm.h>
23 #include <linux/kthread.h>
24 #include <linux/freezer.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/buffer_head.h>
29 #include <linux/tracepoint.h>
30 #include "internal.h"
33 * Passed into wb_writeback(), essentially a subset of writeback_control
35 struct wb_writeback_work {
36 long nr_pages;
37 struct super_block *sb;
38 enum writeback_sync_modes sync_mode;
39 unsigned int for_kupdate:1;
40 unsigned int range_cyclic:1;
41 unsigned int for_background:1;
43 struct list_head list; /* pending work list */
44 struct completion *done; /* set if the caller waits */
48 * Include the creation of the trace points after defining the
49 * wb_writeback_work structure so that the definition remains local to this
50 * file.
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/writeback.h>
55 #define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
58 * We don't actually have pdflush, but this one is exported though /proc...
60 int nr_pdflush_threads;
62 /**
63 * writeback_in_progress - determine whether there is writeback in progress
64 * @bdi: the device's backing_dev_info structure.
66 * Determine whether there is writeback waiting to be handled against a
67 * backing device.
69 int writeback_in_progress(struct backing_dev_info *bdi)
71 return test_bit(BDI_writeback_running, &bdi->state);
74 static void bdi_queue_work(struct backing_dev_info *bdi,
75 struct wb_writeback_work *work)
77 trace_writeback_queue(bdi, work);
79 spin_lock_bh(&bdi->wb_lock);
80 list_add_tail(&work->list, &bdi->work_list);
81 if (bdi->wb.task) {
82 wake_up_process(bdi->wb.task);
83 } else {
85 * The bdi thread isn't there, wake up the forker thread which
86 * will create and run it.
88 trace_writeback_nothread(bdi, work);
89 wake_up_process(default_backing_dev_info.wb.task);
91 spin_unlock_bh(&bdi->wb_lock);
94 static void
95 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
96 bool range_cyclic, bool for_background)
98 struct wb_writeback_work *work;
101 * This is WB_SYNC_NONE writeback, so if allocation fails just
102 * wakeup the thread for old dirty data writeback
104 work = kzalloc(sizeof(*work), GFP_ATOMIC);
105 if (!work) {
106 if (bdi->wb.task) {
107 trace_writeback_nowork(bdi);
108 wake_up_process(bdi->wb.task);
110 return;
113 work->sync_mode = WB_SYNC_NONE;
114 work->nr_pages = nr_pages;
115 work->range_cyclic = range_cyclic;
116 work->for_background = for_background;
118 bdi_queue_work(bdi, work);
122 * bdi_start_writeback - start writeback
123 * @bdi: the backing device to write from
124 * @nr_pages: the number of pages to write
126 * Description:
127 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
128 * started when this function returns, we make no guarentees on
129 * completion. Caller need not hold sb s_umount semaphore.
132 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
134 __bdi_start_writeback(bdi, nr_pages, true, false);
138 * bdi_start_background_writeback - start background writeback
139 * @bdi: the backing device to write from
141 * Description:
142 * This does WB_SYNC_NONE background writeback. The IO is only
143 * started when this function returns, we make no guarentees on
144 * completion. Caller need not hold sb s_umount semaphore.
146 void bdi_start_background_writeback(struct backing_dev_info *bdi)
148 __bdi_start_writeback(bdi, LONG_MAX, true, true);
152 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
153 * furthest end of its superblock's dirty-inode list.
155 * Before stamping the inode's ->dirtied_when, we check to see whether it is
156 * already the most-recently-dirtied inode on the b_dirty list. If that is
157 * the case then the inode must have been redirtied while it was being written
158 * out and we don't reset its dirtied_when.
160 static void redirty_tail(struct inode *inode)
162 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
164 if (!list_empty(&wb->b_dirty)) {
165 struct inode *tail;
167 tail = list_entry(wb->b_dirty.next, struct inode, i_list);
168 if (time_before(inode->dirtied_when, tail->dirtied_when))
169 inode->dirtied_when = jiffies;
171 list_move(&inode->i_list, &wb->b_dirty);
175 * requeue inode for re-scanning after bdi->b_io list is exhausted.
177 static void requeue_io(struct inode *inode)
179 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
181 list_move(&inode->i_list, &wb->b_more_io);
184 static void inode_sync_complete(struct inode *inode)
187 * Prevent speculative execution through spin_unlock(&inode_lock);
189 smp_mb();
190 wake_up_bit(&inode->i_state, __I_SYNC);
193 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
195 bool ret = time_after(inode->dirtied_when, t);
196 #ifndef CONFIG_64BIT
198 * For inodes being constantly redirtied, dirtied_when can get stuck.
199 * It _appears_ to be in the future, but is actually in distant past.
200 * This test is necessary to prevent such wrapped-around relative times
201 * from permanently stopping the whole bdi writeback.
203 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
204 #endif
205 return ret;
209 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
211 static void move_expired_inodes(struct list_head *delaying_queue,
212 struct list_head *dispatch_queue,
213 unsigned long *older_than_this)
215 LIST_HEAD(tmp);
216 struct list_head *pos, *node;
217 struct super_block *sb = NULL;
218 struct inode *inode;
219 int do_sb_sort = 0;
221 while (!list_empty(delaying_queue)) {
222 inode = list_entry(delaying_queue->prev, struct inode, i_list);
223 if (older_than_this &&
224 inode_dirtied_after(inode, *older_than_this))
225 break;
226 if (sb && sb != inode->i_sb)
227 do_sb_sort = 1;
228 sb = inode->i_sb;
229 list_move(&inode->i_list, &tmp);
232 /* just one sb in list, splice to dispatch_queue and we're done */
233 if (!do_sb_sort) {
234 list_splice(&tmp, dispatch_queue);
235 return;
238 /* Move inodes from one superblock together */
239 while (!list_empty(&tmp)) {
240 inode = list_entry(tmp.prev, struct inode, i_list);
241 sb = inode->i_sb;
242 list_for_each_prev_safe(pos, node, &tmp) {
243 inode = list_entry(pos, struct inode, i_list);
244 if (inode->i_sb == sb)
245 list_move(&inode->i_list, dispatch_queue);
251 * Queue all expired dirty inodes for io, eldest first.
252 * Before
253 * newly dirtied b_dirty b_io b_more_io
254 * =============> gf edc BA
255 * After
256 * newly dirtied b_dirty b_io b_more_io
257 * =============> g fBAedc
259 * +--> dequeue for IO
261 static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
263 list_splice_init(&wb->b_more_io, &wb->b_io);
264 move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
267 static int write_inode(struct inode *inode, struct writeback_control *wbc)
269 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
270 return inode->i_sb->s_op->write_inode(inode, wbc);
271 return 0;
275 * Wait for writeback on an inode to complete.
277 static void inode_wait_for_writeback(struct inode *inode)
279 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
280 wait_queue_head_t *wqh;
282 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
283 while (inode->i_state & I_SYNC) {
284 spin_unlock(&inode_lock);
285 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
286 spin_lock(&inode_lock);
291 * Write out an inode's dirty pages. Called under inode_lock. Either the
292 * caller has ref on the inode (either via __iget or via syscall against an fd)
293 * or the inode has I_WILL_FREE set (via generic_forget_inode)
295 * If `wait' is set, wait on the writeout.
297 * The whole writeout design is quite complex and fragile. We want to avoid
298 * starvation of particular inodes when others are being redirtied, prevent
299 * livelocks, etc.
301 * Called under inode_lock.
303 static int
304 writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
306 struct address_space *mapping = inode->i_mapping;
307 unsigned dirty;
308 int ret;
310 if (!atomic_read(&inode->i_count))
311 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
312 else
313 WARN_ON(inode->i_state & I_WILL_FREE);
315 if (inode->i_state & I_SYNC) {
317 * If this inode is locked for writeback and we are not doing
318 * writeback-for-data-integrity, move it to b_more_io so that
319 * writeback can proceed with the other inodes on s_io.
321 * We'll have another go at writing back this inode when we
322 * completed a full scan of b_io.
324 if (wbc->sync_mode != WB_SYNC_ALL) {
325 requeue_io(inode);
326 return 0;
330 * It's a data-integrity sync. We must wait.
332 inode_wait_for_writeback(inode);
335 BUG_ON(inode->i_state & I_SYNC);
337 /* Set I_SYNC, reset I_DIRTY_PAGES */
338 inode->i_state |= I_SYNC;
339 inode->i_state &= ~I_DIRTY_PAGES;
340 spin_unlock(&inode_lock);
342 ret = do_writepages(mapping, wbc);
345 * Make sure to wait on the data before writing out the metadata.
346 * This is important for filesystems that modify metadata on data
347 * I/O completion.
349 if (wbc->sync_mode == WB_SYNC_ALL) {
350 int err = filemap_fdatawait(mapping);
351 if (ret == 0)
352 ret = err;
356 * Some filesystems may redirty the inode during the writeback
357 * due to delalloc, clear dirty metadata flags right before
358 * write_inode()
360 spin_lock(&inode_lock);
361 dirty = inode->i_state & I_DIRTY;
362 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
363 spin_unlock(&inode_lock);
364 /* Don't write the inode if only I_DIRTY_PAGES was set */
365 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
366 int err = write_inode(inode, wbc);
367 if (ret == 0)
368 ret = err;
371 spin_lock(&inode_lock);
372 inode->i_state &= ~I_SYNC;
373 if (!(inode->i_state & I_FREEING)) {
374 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
376 * We didn't write back all the pages. nfs_writepages()
377 * sometimes bales out without doing anything.
379 inode->i_state |= I_DIRTY_PAGES;
380 if (wbc->nr_to_write <= 0) {
382 * slice used up: queue for next turn
384 requeue_io(inode);
385 } else {
387 * Writeback blocked by something other than
388 * congestion. Delay the inode for some time to
389 * avoid spinning on the CPU (100% iowait)
390 * retrying writeback of the dirty page/inode
391 * that cannot be performed immediately.
393 redirty_tail(inode);
395 } else if (inode->i_state & I_DIRTY) {
397 * Filesystems can dirty the inode during writeback
398 * operations, such as delayed allocation during
399 * submission or metadata updates after data IO
400 * completion.
402 redirty_tail(inode);
403 } else if (atomic_read(&inode->i_count)) {
405 * The inode is clean, inuse
407 list_move(&inode->i_list, &inode_in_use);
408 } else {
410 * The inode is clean, unused
412 list_move(&inode->i_list, &inode_unused);
415 inode_sync_complete(inode);
416 return ret;
420 * For background writeback the caller does not have the sb pinned
421 * before calling writeback. So make sure that we do pin it, so it doesn't
422 * go away while we are writing inodes from it.
424 static bool pin_sb_for_writeback(struct super_block *sb)
426 spin_lock(&sb_lock);
427 if (list_empty(&sb->s_instances)) {
428 spin_unlock(&sb_lock);
429 return false;
432 sb->s_count++;
433 spin_unlock(&sb_lock);
435 if (down_read_trylock(&sb->s_umount)) {
436 if (sb->s_root)
437 return true;
438 up_read(&sb->s_umount);
441 put_super(sb);
442 return false;
446 * Write a portion of b_io inodes which belong to @sb.
448 * If @only_this_sb is true, then find and write all such
449 * inodes. Otherwise write only ones which go sequentially
450 * in reverse order.
452 * Return 1, if the caller writeback routine should be
453 * interrupted. Otherwise return 0.
455 static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
456 struct writeback_control *wbc, bool only_this_sb)
458 while (!list_empty(&wb->b_io)) {
459 long pages_skipped;
460 struct inode *inode = list_entry(wb->b_io.prev,
461 struct inode, i_list);
463 if (inode->i_sb != sb) {
464 if (only_this_sb) {
466 * We only want to write back data for this
467 * superblock, move all inodes not belonging
468 * to it back onto the dirty list.
470 redirty_tail(inode);
471 continue;
475 * The inode belongs to a different superblock.
476 * Bounce back to the caller to unpin this and
477 * pin the next superblock.
479 return 0;
482 if (inode->i_state & (I_NEW | I_WILL_FREE)) {
483 requeue_io(inode);
484 continue;
487 * Was this inode dirtied after sync_sb_inodes was called?
488 * This keeps sync from extra jobs and livelock.
490 if (inode_dirtied_after(inode, wbc->wb_start))
491 return 1;
493 BUG_ON(inode->i_state & I_FREEING);
494 __iget(inode);
495 pages_skipped = wbc->pages_skipped;
496 writeback_single_inode(inode, wbc);
497 if (wbc->pages_skipped != pages_skipped) {
499 * writeback is not making progress due to locked
500 * buffers. Skip this inode for now.
502 redirty_tail(inode);
504 spin_unlock(&inode_lock);
505 iput(inode);
506 cond_resched();
507 spin_lock(&inode_lock);
508 if (wbc->nr_to_write <= 0) {
509 wbc->more_io = 1;
510 return 1;
512 if (!list_empty(&wb->b_more_io))
513 wbc->more_io = 1;
515 /* b_io is empty */
516 return 1;
519 void writeback_inodes_wb(struct bdi_writeback *wb,
520 struct writeback_control *wbc)
522 int ret = 0;
524 if (!wbc->wb_start)
525 wbc->wb_start = jiffies; /* livelock avoidance */
526 spin_lock(&inode_lock);
527 if (!wbc->for_kupdate || list_empty(&wb->b_io))
528 queue_io(wb, wbc->older_than_this);
530 while (!list_empty(&wb->b_io)) {
531 struct inode *inode = list_entry(wb->b_io.prev,
532 struct inode, i_list);
533 struct super_block *sb = inode->i_sb;
535 if (!pin_sb_for_writeback(sb)) {
536 requeue_io(inode);
537 continue;
539 ret = writeback_sb_inodes(sb, wb, wbc, false);
540 drop_super(sb);
542 if (ret)
543 break;
545 spin_unlock(&inode_lock);
546 /* Leave any unwritten inodes on b_io */
549 static void __writeback_inodes_sb(struct super_block *sb,
550 struct bdi_writeback *wb, struct writeback_control *wbc)
552 WARN_ON(!rwsem_is_locked(&sb->s_umount));
554 spin_lock(&inode_lock);
555 if (!wbc->for_kupdate || list_empty(&wb->b_io))
556 queue_io(wb, wbc->older_than_this);
557 writeback_sb_inodes(sb, wb, wbc, true);
558 spin_unlock(&inode_lock);
562 * The maximum number of pages to writeout in a single bdi flush/kupdate
563 * operation. We do this so we don't hold I_SYNC against an inode for
564 * enormous amounts of time, which would block a userspace task which has
565 * been forced to throttle against that inode. Also, the code reevaluates
566 * the dirty each time it has written this many pages.
568 #define MAX_WRITEBACK_PAGES 1024
570 static inline bool over_bground_thresh(void)
572 unsigned long background_thresh, dirty_thresh;
574 global_dirty_limits(&background_thresh, &dirty_thresh);
576 return (global_page_state(NR_FILE_DIRTY) +
577 global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
581 * Explicit flushing or periodic writeback of "old" data.
583 * Define "old": the first time one of an inode's pages is dirtied, we mark the
584 * dirtying-time in the inode's address_space. So this periodic writeback code
585 * just walks the superblock inode list, writing back any inodes which are
586 * older than a specific point in time.
588 * Try to run once per dirty_writeback_interval. But if a writeback event
589 * takes longer than a dirty_writeback_interval interval, then leave a
590 * one-second gap.
592 * older_than_this takes precedence over nr_to_write. So we'll only write back
593 * all dirty pages if they are all attached to "old" mappings.
595 static long wb_writeback(struct bdi_writeback *wb,
596 struct wb_writeback_work *work)
598 struct writeback_control wbc = {
599 .sync_mode = work->sync_mode,
600 .older_than_this = NULL,
601 .for_kupdate = work->for_kupdate,
602 .for_background = work->for_background,
603 .range_cyclic = work->range_cyclic,
605 unsigned long oldest_jif;
606 long wrote = 0;
607 struct inode *inode;
609 if (wbc.for_kupdate) {
610 wbc.older_than_this = &oldest_jif;
611 oldest_jif = jiffies -
612 msecs_to_jiffies(dirty_expire_interval * 10);
614 if (!wbc.range_cyclic) {
615 wbc.range_start = 0;
616 wbc.range_end = LLONG_MAX;
619 wbc.wb_start = jiffies; /* livelock avoidance */
620 for (;;) {
622 * Stop writeback when nr_pages has been consumed
624 if (work->nr_pages <= 0)
625 break;
628 * For background writeout, stop when we are below the
629 * background dirty threshold
631 if (work->for_background && !over_bground_thresh())
632 break;
634 wbc.more_io = 0;
635 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
636 wbc.pages_skipped = 0;
638 trace_wbc_writeback_start(&wbc, wb->bdi);
639 if (work->sb)
640 __writeback_inodes_sb(work->sb, wb, &wbc);
641 else
642 writeback_inodes_wb(wb, &wbc);
643 trace_wbc_writeback_written(&wbc, wb->bdi);
645 work->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
646 wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
649 * If we consumed everything, see if we have more
651 if (wbc.nr_to_write <= 0)
652 continue;
654 * Didn't write everything and we don't have more IO, bail
656 if (!wbc.more_io)
657 break;
659 * Did we write something? Try for more
661 if (wbc.nr_to_write < MAX_WRITEBACK_PAGES)
662 continue;
664 * Nothing written. Wait for some inode to
665 * become available for writeback. Otherwise
666 * we'll just busyloop.
668 spin_lock(&inode_lock);
669 if (!list_empty(&wb->b_more_io)) {
670 inode = list_entry(wb->b_more_io.prev,
671 struct inode, i_list);
672 trace_wbc_writeback_wait(&wbc, wb->bdi);
673 inode_wait_for_writeback(inode);
675 spin_unlock(&inode_lock);
678 return wrote;
682 * Return the next wb_writeback_work struct that hasn't been processed yet.
684 static struct wb_writeback_work *
685 get_next_work_item(struct backing_dev_info *bdi)
687 struct wb_writeback_work *work = NULL;
689 spin_lock_bh(&bdi->wb_lock);
690 if (!list_empty(&bdi->work_list)) {
691 work = list_entry(bdi->work_list.next,
692 struct wb_writeback_work, list);
693 list_del_init(&work->list);
695 spin_unlock_bh(&bdi->wb_lock);
696 return work;
699 static long wb_check_old_data_flush(struct bdi_writeback *wb)
701 unsigned long expired;
702 long nr_pages;
705 * When set to zero, disable periodic writeback
707 if (!dirty_writeback_interval)
708 return 0;
710 expired = wb->last_old_flush +
711 msecs_to_jiffies(dirty_writeback_interval * 10);
712 if (time_before(jiffies, expired))
713 return 0;
715 wb->last_old_flush = jiffies;
716 nr_pages = global_page_state(NR_FILE_DIRTY) +
717 global_page_state(NR_UNSTABLE_NFS) +
718 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
720 if (nr_pages) {
721 struct wb_writeback_work work = {
722 .nr_pages = nr_pages,
723 .sync_mode = WB_SYNC_NONE,
724 .for_kupdate = 1,
725 .range_cyclic = 1,
728 return wb_writeback(wb, &work);
731 return 0;
735 * Retrieve work items and do the writeback they describe
737 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
739 struct backing_dev_info *bdi = wb->bdi;
740 struct wb_writeback_work *work;
741 long wrote = 0;
743 set_bit(BDI_writeback_running, &wb->bdi->state);
744 while ((work = get_next_work_item(bdi)) != NULL) {
746 * Override sync mode, in case we must wait for completion
747 * because this thread is exiting now.
749 if (force_wait)
750 work->sync_mode = WB_SYNC_ALL;
752 trace_writeback_exec(bdi, work);
754 wrote += wb_writeback(wb, work);
757 * Notify the caller of completion if this is a synchronous
758 * work item, otherwise just free it.
760 if (work->done)
761 complete(work->done);
762 else
763 kfree(work);
767 * Check for periodic writeback, kupdated() style
769 wrote += wb_check_old_data_flush(wb);
770 clear_bit(BDI_writeback_running, &wb->bdi->state);
772 return wrote;
776 * Handle writeback of dirty data for the device backed by this bdi. Also
777 * wakes up periodically and does kupdated style flushing.
779 int bdi_writeback_thread(void *data)
781 struct bdi_writeback *wb = data;
782 struct backing_dev_info *bdi = wb->bdi;
783 long pages_written;
785 current->flags |= PF_FLUSHER | PF_SWAPWRITE;
786 set_freezable();
787 wb->last_active = jiffies;
790 * Our parent may run at a different priority, just set us to normal
792 set_user_nice(current, 0);
794 trace_writeback_thread_start(bdi);
796 while (!kthread_should_stop()) {
798 * Remove own delayed wake-up timer, since we are already awake
799 * and we'll take care of the preriodic write-back.
801 del_timer(&wb->wakeup_timer);
803 pages_written = wb_do_writeback(wb, 0);
805 trace_writeback_pages_written(pages_written);
807 if (pages_written)
808 wb->last_active = jiffies;
810 set_current_state(TASK_INTERRUPTIBLE);
811 if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
812 __set_current_state(TASK_RUNNING);
813 continue;
816 if (wb_has_dirty_io(wb) && dirty_writeback_interval)
817 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
818 else {
820 * We have nothing to do, so can go sleep without any
821 * timeout and save power. When a work is queued or
822 * something is made dirty - we will be woken up.
824 schedule();
827 try_to_freeze();
830 /* Flush any work that raced with us exiting */
831 if (!list_empty(&bdi->work_list))
832 wb_do_writeback(wb, 1);
834 trace_writeback_thread_stop(bdi);
835 return 0;
840 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
841 * the whole world.
843 void wakeup_flusher_threads(long nr_pages)
845 struct backing_dev_info *bdi;
847 if (!nr_pages) {
848 nr_pages = global_page_state(NR_FILE_DIRTY) +
849 global_page_state(NR_UNSTABLE_NFS);
852 rcu_read_lock();
853 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
854 if (!bdi_has_dirty_io(bdi))
855 continue;
856 __bdi_start_writeback(bdi, nr_pages, false, false);
858 rcu_read_unlock();
861 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
863 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
864 struct dentry *dentry;
865 const char *name = "?";
867 dentry = d_find_alias(inode);
868 if (dentry) {
869 spin_lock(&dentry->d_lock);
870 name = (const char *) dentry->d_name.name;
872 printk(KERN_DEBUG
873 "%s(%d): dirtied inode %lu (%s) on %s\n",
874 current->comm, task_pid_nr(current), inode->i_ino,
875 name, inode->i_sb->s_id);
876 if (dentry) {
877 spin_unlock(&dentry->d_lock);
878 dput(dentry);
884 * __mark_inode_dirty - internal function
885 * @inode: inode to mark
886 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
887 * Mark an inode as dirty. Callers should use mark_inode_dirty or
888 * mark_inode_dirty_sync.
890 * Put the inode on the super block's dirty list.
892 * CAREFUL! We mark it dirty unconditionally, but move it onto the
893 * dirty list only if it is hashed or if it refers to a blockdev.
894 * If it was not hashed, it will never be added to the dirty list
895 * even if it is later hashed, as it will have been marked dirty already.
897 * In short, make sure you hash any inodes _before_ you start marking
898 * them dirty.
900 * This function *must* be atomic for the I_DIRTY_PAGES case -
901 * set_page_dirty() is called under spinlock in several places.
903 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
904 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
905 * the kernel-internal blockdev inode represents the dirtying time of the
906 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
907 * page->mapping->host, so the page-dirtying time is recorded in the internal
908 * blockdev inode.
910 void __mark_inode_dirty(struct inode *inode, int flags)
912 struct super_block *sb = inode->i_sb;
913 struct backing_dev_info *bdi = NULL;
914 bool wakeup_bdi = false;
917 * Don't do this for I_DIRTY_PAGES - that doesn't actually
918 * dirty the inode itself
920 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
921 if (sb->s_op->dirty_inode)
922 sb->s_op->dirty_inode(inode);
926 * make sure that changes are seen by all cpus before we test i_state
927 * -- mikulas
929 smp_mb();
931 /* avoid the locking if we can */
932 if ((inode->i_state & flags) == flags)
933 return;
935 if (unlikely(block_dump))
936 block_dump___mark_inode_dirty(inode);
938 spin_lock(&inode_lock);
939 if ((inode->i_state & flags) != flags) {
940 const int was_dirty = inode->i_state & I_DIRTY;
942 inode->i_state |= flags;
945 * If the inode is being synced, just update its dirty state.
946 * The unlocker will place the inode on the appropriate
947 * superblock list, based upon its state.
949 if (inode->i_state & I_SYNC)
950 goto out;
953 * Only add valid (hashed) inodes to the superblock's
954 * dirty list. Add blockdev inodes as well.
956 if (!S_ISBLK(inode->i_mode)) {
957 if (hlist_unhashed(&inode->i_hash))
958 goto out;
960 if (inode->i_state & I_FREEING)
961 goto out;
964 * If the inode was already on b_dirty/b_io/b_more_io, don't
965 * reposition it (that would break b_dirty time-ordering).
967 if (!was_dirty) {
968 bdi = inode_to_bdi(inode);
970 if (bdi_cap_writeback_dirty(bdi)) {
971 WARN(!test_bit(BDI_registered, &bdi->state),
972 "bdi-%s not registered\n", bdi->name);
975 * If this is the first dirty inode for this
976 * bdi, we have to wake-up the corresponding
977 * bdi thread to make sure background
978 * write-back happens later.
980 if (!wb_has_dirty_io(&bdi->wb))
981 wakeup_bdi = true;
984 inode->dirtied_when = jiffies;
985 list_move(&inode->i_list, &bdi->wb.b_dirty);
988 out:
989 spin_unlock(&inode_lock);
991 if (wakeup_bdi)
992 bdi_wakeup_thread_delayed(bdi);
994 EXPORT_SYMBOL(__mark_inode_dirty);
997 * Write out a superblock's list of dirty inodes. A wait will be performed
998 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1000 * If older_than_this is non-NULL, then only write out inodes which
1001 * had their first dirtying at a time earlier than *older_than_this.
1003 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1004 * This function assumes that the blockdev superblock's inodes are backed by
1005 * a variety of queues, so all inodes are searched. For other superblocks,
1006 * assume that all inodes are backed by the same queue.
1008 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1009 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1010 * on the writer throttling path, and we get decent balancing between many
1011 * throttled threads: we don't want them all piling up on inode_sync_wait.
1013 static void wait_sb_inodes(struct super_block *sb)
1015 struct inode *inode, *old_inode = NULL;
1018 * We need to be protected against the filesystem going from
1019 * r/o to r/w or vice versa.
1021 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1023 spin_lock(&inode_lock);
1026 * Data integrity sync. Must wait for all pages under writeback,
1027 * because there may have been pages dirtied before our sync
1028 * call, but which had writeout started before we write it out.
1029 * In which case, the inode may not be on the dirty list, but
1030 * we still have to wait for that writeout.
1032 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1033 struct address_space *mapping;
1035 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
1036 continue;
1037 mapping = inode->i_mapping;
1038 if (mapping->nrpages == 0)
1039 continue;
1040 __iget(inode);
1041 spin_unlock(&inode_lock);
1043 * We hold a reference to 'inode' so it couldn't have
1044 * been removed from s_inodes list while we dropped the
1045 * inode_lock. We cannot iput the inode now as we can
1046 * be holding the last reference and we cannot iput it
1047 * under inode_lock. So we keep the reference and iput
1048 * it later.
1050 iput(old_inode);
1051 old_inode = inode;
1053 filemap_fdatawait(mapping);
1055 cond_resched();
1057 spin_lock(&inode_lock);
1059 spin_unlock(&inode_lock);
1060 iput(old_inode);
1064 * writeback_inodes_sb - writeback dirty inodes from given super_block
1065 * @sb: the superblock
1067 * Start writeback on some inodes on this super_block. No guarantees are made
1068 * on how many (if any) will be written, and this function does not wait
1069 * for IO completion of submitted IO. The number of pages submitted is
1070 * returned.
1072 void writeback_inodes_sb(struct super_block *sb)
1074 unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
1075 unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
1076 DECLARE_COMPLETION_ONSTACK(done);
1077 struct wb_writeback_work work = {
1078 .sb = sb,
1079 .sync_mode = WB_SYNC_NONE,
1080 .done = &done,
1083 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1085 work.nr_pages = nr_dirty + nr_unstable +
1086 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
1088 bdi_queue_work(sb->s_bdi, &work);
1089 wait_for_completion(&done);
1091 EXPORT_SYMBOL(writeback_inodes_sb);
1094 * writeback_inodes_sb_if_idle - start writeback if none underway
1095 * @sb: the superblock
1097 * Invoke writeback_inodes_sb if no writeback is currently underway.
1098 * Returns 1 if writeback was started, 0 if not.
1100 int writeback_inodes_sb_if_idle(struct super_block *sb)
1102 if (!writeback_in_progress(sb->s_bdi)) {
1103 down_read(&sb->s_umount);
1104 writeback_inodes_sb(sb);
1105 up_read(&sb->s_umount);
1106 return 1;
1107 } else
1108 return 0;
1110 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1113 * sync_inodes_sb - sync sb inode pages
1114 * @sb: the superblock
1116 * This function writes and waits on any dirty inode belonging to this
1117 * super_block. The number of pages synced is returned.
1119 void sync_inodes_sb(struct super_block *sb)
1121 DECLARE_COMPLETION_ONSTACK(done);
1122 struct wb_writeback_work work = {
1123 .sb = sb,
1124 .sync_mode = WB_SYNC_ALL,
1125 .nr_pages = LONG_MAX,
1126 .range_cyclic = 0,
1127 .done = &done,
1130 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1132 bdi_queue_work(sb->s_bdi, &work);
1133 wait_for_completion(&done);
1135 wait_sb_inodes(sb);
1137 EXPORT_SYMBOL(sync_inodes_sb);
1140 * write_inode_now - write an inode to disk
1141 * @inode: inode to write to disk
1142 * @sync: whether the write should be synchronous or not
1144 * This function commits an inode to disk immediately if it is dirty. This is
1145 * primarily needed by knfsd.
1147 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1149 int write_inode_now(struct inode *inode, int sync)
1151 int ret;
1152 struct writeback_control wbc = {
1153 .nr_to_write = LONG_MAX,
1154 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1155 .range_start = 0,
1156 .range_end = LLONG_MAX,
1159 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1160 wbc.nr_to_write = 0;
1162 might_sleep();
1163 spin_lock(&inode_lock);
1164 ret = writeback_single_inode(inode, &wbc);
1165 spin_unlock(&inode_lock);
1166 if (sync)
1167 inode_sync_wait(inode);
1168 return ret;
1170 EXPORT_SYMBOL(write_inode_now);
1173 * sync_inode - write an inode and its pages to disk.
1174 * @inode: the inode to sync
1175 * @wbc: controls the writeback mode
1177 * sync_inode() will write an inode and its pages to disk. It will also
1178 * correctly update the inode on its superblock's dirty inode lists and will
1179 * update inode->i_state.
1181 * The caller must have a ref on the inode.
1183 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1185 int ret;
1187 spin_lock(&inode_lock);
1188 ret = writeback_single_inode(inode, wbc);
1189 spin_unlock(&inode_lock);
1190 return ret;
1192 EXPORT_SYMBOL(sync_inode);