Merge tag 'renesas-boards-for-v3.13' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6.git] / fs / fs-writeback.c
blob9f4935b8f2087eb44475bf7fb8aab20f44889e86
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/export.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/pagemap.h>
24 #include <linux/kthread.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/backing-dev.h>
28 #include <linux/tracepoint.h>
29 #include "internal.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 {
40 long nr_pages;
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 unsigned int for_sync:1; /* sync(2) WB_SYNC_ALL writeback */
49 enum wb_reason reason; /* why was writeback initiated? */
51 struct list_head list; /* pending work list */
52 struct completion *done; /* set if the caller waits */
55 /**
56 * writeback_in_progress - determine whether there is writeback in progress
57 * @bdi: the device's backing_dev_info structure.
59 * Determine whether there is writeback waiting to be handled against a
60 * backing device.
62 int writeback_in_progress(struct backing_dev_info *bdi)
64 return test_bit(BDI_writeback_running, &bdi->state);
66 EXPORT_SYMBOL(writeback_in_progress);
68 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
70 struct super_block *sb = inode->i_sb;
72 if (sb_is_blkdev_sb(sb))
73 return inode->i_mapping->backing_dev_info;
75 return sb->s_bdi;
78 static inline struct inode *wb_inode(struct list_head *head)
80 return list_entry(head, struct inode, i_wb_list);
84 * Include the creation of the trace points after defining the
85 * wb_writeback_work structure and inline functions so that the definition
86 * remains local to this file.
88 #define CREATE_TRACE_POINTS
89 #include <trace/events/writeback.h>
91 static void bdi_queue_work(struct backing_dev_info *bdi,
92 struct wb_writeback_work *work)
94 trace_writeback_queue(bdi, work);
96 spin_lock_bh(&bdi->wb_lock);
97 list_add_tail(&work->list, &bdi->work_list);
98 spin_unlock_bh(&bdi->wb_lock);
100 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
103 static void
104 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
105 bool range_cyclic, enum wb_reason reason)
107 struct wb_writeback_work *work;
110 * This is WB_SYNC_NONE writeback, so if allocation fails just
111 * wakeup the thread for old dirty data writeback
113 work = kzalloc(sizeof(*work), GFP_ATOMIC);
114 if (!work) {
115 trace_writeback_nowork(bdi);
116 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
117 return;
120 work->sync_mode = WB_SYNC_NONE;
121 work->nr_pages = nr_pages;
122 work->range_cyclic = range_cyclic;
123 work->reason = reason;
125 bdi_queue_work(bdi, work);
129 * bdi_start_writeback - start writeback
130 * @bdi: the backing device to write from
131 * @nr_pages: the number of pages to write
132 * @reason: reason why some writeback work was initiated
134 * Description:
135 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
136 * started when this function returns, we make no guarantees on
137 * completion. Caller need not hold sb s_umount semaphore.
140 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
141 enum wb_reason reason)
143 __bdi_start_writeback(bdi, nr_pages, true, reason);
147 * bdi_start_background_writeback - start background writeback
148 * @bdi: the backing device to write from
150 * Description:
151 * This makes sure WB_SYNC_NONE background writeback happens. When
152 * this function returns, it is only guaranteed that for given BDI
153 * some IO is happening if we are over background dirty threshold.
154 * Caller need not hold sb s_umount semaphore.
156 void bdi_start_background_writeback(struct backing_dev_info *bdi)
159 * We just wake up the flusher thread. It will perform background
160 * writeback as soon as there is no other work to do.
162 trace_writeback_wake_background(bdi);
163 mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
167 * Remove the inode from the writeback list it is on.
169 void inode_wb_list_del(struct inode *inode)
171 struct backing_dev_info *bdi = inode_to_bdi(inode);
173 spin_lock(&bdi->wb.list_lock);
174 list_del_init(&inode->i_wb_list);
175 spin_unlock(&bdi->wb.list_lock);
179 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
180 * furthest end of its superblock's dirty-inode list.
182 * Before stamping the inode's ->dirtied_when, we check to see whether it is
183 * already the most-recently-dirtied inode on the b_dirty list. If that is
184 * the case then the inode must have been redirtied while it was being written
185 * out and we don't reset its dirtied_when.
187 static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
189 assert_spin_locked(&wb->list_lock);
190 if (!list_empty(&wb->b_dirty)) {
191 struct inode *tail;
193 tail = wb_inode(wb->b_dirty.next);
194 if (time_before(inode->dirtied_when, tail->dirtied_when))
195 inode->dirtied_when = jiffies;
197 list_move(&inode->i_wb_list, &wb->b_dirty);
201 * requeue inode for re-scanning after bdi->b_io list is exhausted.
203 static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
205 assert_spin_locked(&wb->list_lock);
206 list_move(&inode->i_wb_list, &wb->b_more_io);
209 static void inode_sync_complete(struct inode *inode)
211 inode->i_state &= ~I_SYNC;
212 /* If inode is clean an unused, put it into LRU now... */
213 inode_add_lru(inode);
214 /* Waiters must see I_SYNC cleared before being woken up */
215 smp_mb();
216 wake_up_bit(&inode->i_state, __I_SYNC);
219 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
221 bool ret = time_after(inode->dirtied_when, t);
222 #ifndef CONFIG_64BIT
224 * For inodes being constantly redirtied, dirtied_when can get stuck.
225 * It _appears_ to be in the future, but is actually in distant past.
226 * This test is necessary to prevent such wrapped-around relative times
227 * from permanently stopping the whole bdi writeback.
229 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
230 #endif
231 return ret;
235 * Move expired (dirtied before work->older_than_this) dirty inodes from
236 * @delaying_queue to @dispatch_queue.
238 static int move_expired_inodes(struct list_head *delaying_queue,
239 struct list_head *dispatch_queue,
240 struct wb_writeback_work *work)
242 LIST_HEAD(tmp);
243 struct list_head *pos, *node;
244 struct super_block *sb = NULL;
245 struct inode *inode;
246 int do_sb_sort = 0;
247 int moved = 0;
249 while (!list_empty(delaying_queue)) {
250 inode = wb_inode(delaying_queue->prev);
251 if (work->older_than_this &&
252 inode_dirtied_after(inode, *work->older_than_this))
253 break;
254 list_move(&inode->i_wb_list, &tmp);
255 moved++;
256 if (sb_is_blkdev_sb(inode->i_sb))
257 continue;
258 if (sb && sb != inode->i_sb)
259 do_sb_sort = 1;
260 sb = inode->i_sb;
263 /* just one sb in list, splice to dispatch_queue and we're done */
264 if (!do_sb_sort) {
265 list_splice(&tmp, dispatch_queue);
266 goto out;
269 /* Move inodes from one superblock together */
270 while (!list_empty(&tmp)) {
271 sb = wb_inode(tmp.prev)->i_sb;
272 list_for_each_prev_safe(pos, node, &tmp) {
273 inode = wb_inode(pos);
274 if (inode->i_sb == sb)
275 list_move(&inode->i_wb_list, dispatch_queue);
278 out:
279 return moved;
283 * Queue all expired dirty inodes for io, eldest first.
284 * Before
285 * newly dirtied b_dirty b_io b_more_io
286 * =============> gf edc BA
287 * After
288 * newly dirtied b_dirty b_io b_more_io
289 * =============> g fBAedc
291 * +--> dequeue for IO
293 static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
295 int moved;
296 assert_spin_locked(&wb->list_lock);
297 list_splice_init(&wb->b_more_io, &wb->b_io);
298 moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
299 trace_writeback_queue_io(wb, work, moved);
302 static int write_inode(struct inode *inode, struct writeback_control *wbc)
304 int ret;
306 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) {
307 trace_writeback_write_inode_start(inode, wbc);
308 ret = inode->i_sb->s_op->write_inode(inode, wbc);
309 trace_writeback_write_inode(inode, wbc);
310 return ret;
312 return 0;
316 * Wait for writeback on an inode to complete. Called with i_lock held.
317 * Caller must make sure inode cannot go away when we drop i_lock.
319 static void __inode_wait_for_writeback(struct inode *inode)
320 __releases(inode->i_lock)
321 __acquires(inode->i_lock)
323 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
324 wait_queue_head_t *wqh;
326 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
327 while (inode->i_state & I_SYNC) {
328 spin_unlock(&inode->i_lock);
329 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
330 spin_lock(&inode->i_lock);
335 * Wait for writeback on an inode to complete. Caller must have inode pinned.
337 void inode_wait_for_writeback(struct inode *inode)
339 spin_lock(&inode->i_lock);
340 __inode_wait_for_writeback(inode);
341 spin_unlock(&inode->i_lock);
345 * Sleep until I_SYNC is cleared. This function must be called with i_lock
346 * held and drops it. It is aimed for callers not holding any inode reference
347 * so once i_lock is dropped, inode can go away.
349 static void inode_sleep_on_writeback(struct inode *inode)
350 __releases(inode->i_lock)
352 DEFINE_WAIT(wait);
353 wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
354 int sleep;
356 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
357 sleep = inode->i_state & I_SYNC;
358 spin_unlock(&inode->i_lock);
359 if (sleep)
360 schedule();
361 finish_wait(wqh, &wait);
365 * Find proper writeback list for the inode depending on its current state and
366 * possibly also change of its state while we were doing writeback. Here we
367 * handle things such as livelock prevention or fairness of writeback among
368 * inodes. This function can be called only by flusher thread - noone else
369 * processes all inodes in writeback lists and requeueing inodes behind flusher
370 * thread's back can have unexpected consequences.
372 static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
373 struct writeback_control *wbc)
375 if (inode->i_state & I_FREEING)
376 return;
379 * Sync livelock prevention. Each inode is tagged and synced in one
380 * shot. If still dirty, it will be redirty_tail()'ed below. Update
381 * the dirty time to prevent enqueue and sync it again.
383 if ((inode->i_state & I_DIRTY) &&
384 (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
385 inode->dirtied_when = jiffies;
387 if (wbc->pages_skipped) {
389 * writeback is not making progress due to locked
390 * buffers. Skip this inode for now.
392 redirty_tail(inode, wb);
393 return;
396 if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
398 * We didn't write back all the pages. nfs_writepages()
399 * sometimes bales out without doing anything.
401 if (wbc->nr_to_write <= 0) {
402 /* Slice used up. Queue for next turn. */
403 requeue_io(inode, wb);
404 } else {
406 * Writeback blocked by something other than
407 * congestion. Delay the inode for some time to
408 * avoid spinning on the CPU (100% iowait)
409 * retrying writeback of the dirty page/inode
410 * that cannot be performed immediately.
412 redirty_tail(inode, wb);
414 } else if (inode->i_state & I_DIRTY) {
416 * Filesystems can dirty the inode during writeback operations,
417 * such as delayed allocation during submission or metadata
418 * updates after data IO completion.
420 redirty_tail(inode, wb);
421 } else {
422 /* The inode is clean. Remove from writeback lists. */
423 list_del_init(&inode->i_wb_list);
428 * Write out an inode and its dirty pages. Do not update the writeback list
429 * linkage. That is left to the caller. The caller is also responsible for
430 * setting I_SYNC flag and calling inode_sync_complete() to clear it.
432 static int
433 __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
435 struct address_space *mapping = inode->i_mapping;
436 long nr_to_write = wbc->nr_to_write;
437 unsigned dirty;
438 int ret;
440 WARN_ON(!(inode->i_state & I_SYNC));
442 trace_writeback_single_inode_start(inode, wbc, nr_to_write);
444 ret = do_writepages(mapping, wbc);
447 * Make sure to wait on the data before writing out the metadata.
448 * This is important for filesystems that modify metadata on data
449 * I/O completion. We don't do it for sync(2) writeback because it has a
450 * separate, external IO completion path and ->sync_fs for guaranteeing
451 * inode metadata is written back correctly.
453 if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
454 int err = filemap_fdatawait(mapping);
455 if (ret == 0)
456 ret = err;
460 * Some filesystems may redirty the inode during the writeback
461 * due to delalloc, clear dirty metadata flags right before
462 * write_inode()
464 spin_lock(&inode->i_lock);
465 /* Clear I_DIRTY_PAGES if we've written out all dirty pages */
466 if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
467 inode->i_state &= ~I_DIRTY_PAGES;
468 dirty = inode->i_state & I_DIRTY;
469 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
470 spin_unlock(&inode->i_lock);
471 /* Don't write the inode if only I_DIRTY_PAGES was set */
472 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
473 int err = write_inode(inode, wbc);
474 if (ret == 0)
475 ret = err;
477 trace_writeback_single_inode(inode, wbc, nr_to_write);
478 return ret;
482 * Write out an inode's dirty pages. Either the caller has an active reference
483 * on the inode or the inode has I_WILL_FREE set.
485 * This function is designed to be called for writing back one inode which
486 * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
487 * and does more profound writeback list handling in writeback_sb_inodes().
489 static int
490 writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
491 struct writeback_control *wbc)
493 int ret = 0;
495 spin_lock(&inode->i_lock);
496 if (!atomic_read(&inode->i_count))
497 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
498 else
499 WARN_ON(inode->i_state & I_WILL_FREE);
501 if (inode->i_state & I_SYNC) {
502 if (wbc->sync_mode != WB_SYNC_ALL)
503 goto out;
505 * It's a data-integrity sync. We must wait. Since callers hold
506 * inode reference or inode has I_WILL_FREE set, it cannot go
507 * away under us.
509 __inode_wait_for_writeback(inode);
511 WARN_ON(inode->i_state & I_SYNC);
513 * Skip inode if it is clean. We don't want to mess with writeback
514 * lists in this function since flusher thread may be doing for example
515 * sync in parallel and if we move the inode, it could get skipped. So
516 * here we make sure inode is on some writeback list and leave it there
517 * unless we have completely cleaned the inode.
519 if (!(inode->i_state & I_DIRTY))
520 goto out;
521 inode->i_state |= I_SYNC;
522 spin_unlock(&inode->i_lock);
524 ret = __writeback_single_inode(inode, wbc);
526 spin_lock(&wb->list_lock);
527 spin_lock(&inode->i_lock);
529 * If inode is clean, remove it from writeback lists. Otherwise don't
530 * touch it. See comment above for explanation.
532 if (!(inode->i_state & I_DIRTY))
533 list_del_init(&inode->i_wb_list);
534 spin_unlock(&wb->list_lock);
535 inode_sync_complete(inode);
536 out:
537 spin_unlock(&inode->i_lock);
538 return ret;
541 static long writeback_chunk_size(struct backing_dev_info *bdi,
542 struct wb_writeback_work *work)
544 long pages;
547 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
548 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
549 * here avoids calling into writeback_inodes_wb() more than once.
551 * The intended call sequence for WB_SYNC_ALL writeback is:
553 * wb_writeback()
554 * writeback_sb_inodes() <== called only once
555 * write_cache_pages() <== called once for each inode
556 * (quickly) tag currently dirty pages
557 * (maybe slowly) sync all tagged pages
559 if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
560 pages = LONG_MAX;
561 else {
562 pages = min(bdi->avg_write_bandwidth / 2,
563 global_dirty_limit / DIRTY_SCOPE);
564 pages = min(pages, work->nr_pages);
565 pages = round_down(pages + MIN_WRITEBACK_PAGES,
566 MIN_WRITEBACK_PAGES);
569 return pages;
573 * Write a portion of b_io inodes which belong to @sb.
575 * Return the number of pages and/or inodes written.
577 static long writeback_sb_inodes(struct super_block *sb,
578 struct bdi_writeback *wb,
579 struct wb_writeback_work *work)
581 struct writeback_control wbc = {
582 .sync_mode = work->sync_mode,
583 .tagged_writepages = work->tagged_writepages,
584 .for_kupdate = work->for_kupdate,
585 .for_background = work->for_background,
586 .for_sync = work->for_sync,
587 .range_cyclic = work->range_cyclic,
588 .range_start = 0,
589 .range_end = LLONG_MAX,
591 unsigned long start_time = jiffies;
592 long write_chunk;
593 long wrote = 0; /* count both pages and inodes */
595 while (!list_empty(&wb->b_io)) {
596 struct inode *inode = wb_inode(wb->b_io.prev);
598 if (inode->i_sb != sb) {
599 if (work->sb) {
601 * We only want to write back data for this
602 * superblock, move all inodes not belonging
603 * to it back onto the dirty list.
605 redirty_tail(inode, wb);
606 continue;
610 * The inode belongs to a different superblock.
611 * Bounce back to the caller to unpin this and
612 * pin the next superblock.
614 break;
618 * Don't bother with new inodes or inodes being freed, first
619 * kind does not need periodic writeout yet, and for the latter
620 * kind writeout is handled by the freer.
622 spin_lock(&inode->i_lock);
623 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
624 spin_unlock(&inode->i_lock);
625 redirty_tail(inode, wb);
626 continue;
628 if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
630 * If this inode is locked for writeback and we are not
631 * doing writeback-for-data-integrity, move it to
632 * b_more_io so that writeback can proceed with the
633 * other inodes on s_io.
635 * We'll have another go at writing back this inode
636 * when we completed a full scan of b_io.
638 spin_unlock(&inode->i_lock);
639 requeue_io(inode, wb);
640 trace_writeback_sb_inodes_requeue(inode);
641 continue;
643 spin_unlock(&wb->list_lock);
646 * We already requeued the inode if it had I_SYNC set and we
647 * are doing WB_SYNC_NONE writeback. So this catches only the
648 * WB_SYNC_ALL case.
650 if (inode->i_state & I_SYNC) {
651 /* Wait for I_SYNC. This function drops i_lock... */
652 inode_sleep_on_writeback(inode);
653 /* Inode may be gone, start again */
654 spin_lock(&wb->list_lock);
655 continue;
657 inode->i_state |= I_SYNC;
658 spin_unlock(&inode->i_lock);
660 write_chunk = writeback_chunk_size(wb->bdi, work);
661 wbc.nr_to_write = write_chunk;
662 wbc.pages_skipped = 0;
665 * We use I_SYNC to pin the inode in memory. While it is set
666 * evict_inode() will wait so the inode cannot be freed.
668 __writeback_single_inode(inode, &wbc);
670 work->nr_pages -= write_chunk - wbc.nr_to_write;
671 wrote += write_chunk - wbc.nr_to_write;
672 spin_lock(&wb->list_lock);
673 spin_lock(&inode->i_lock);
674 if (!(inode->i_state & I_DIRTY))
675 wrote++;
676 requeue_inode(inode, wb, &wbc);
677 inode_sync_complete(inode);
678 spin_unlock(&inode->i_lock);
679 cond_resched_lock(&wb->list_lock);
681 * bail out to wb_writeback() often enough to check
682 * background threshold and other termination conditions.
684 if (wrote) {
685 if (time_is_before_jiffies(start_time + HZ / 10UL))
686 break;
687 if (work->nr_pages <= 0)
688 break;
691 return wrote;
694 static long __writeback_inodes_wb(struct bdi_writeback *wb,
695 struct wb_writeback_work *work)
697 unsigned long start_time = jiffies;
698 long wrote = 0;
700 while (!list_empty(&wb->b_io)) {
701 struct inode *inode = wb_inode(wb->b_io.prev);
702 struct super_block *sb = inode->i_sb;
704 if (!grab_super_passive(sb)) {
706 * grab_super_passive() may fail consistently due to
707 * s_umount being grabbed by someone else. Don't use
708 * requeue_io() to avoid busy retrying the inode/sb.
710 redirty_tail(inode, wb);
711 continue;
713 wrote += writeback_sb_inodes(sb, wb, work);
714 drop_super(sb);
716 /* refer to the same tests at the end of writeback_sb_inodes */
717 if (wrote) {
718 if (time_is_before_jiffies(start_time + HZ / 10UL))
719 break;
720 if (work->nr_pages <= 0)
721 break;
724 /* Leave any unwritten inodes on b_io */
725 return wrote;
728 static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
729 enum wb_reason reason)
731 struct wb_writeback_work work = {
732 .nr_pages = nr_pages,
733 .sync_mode = WB_SYNC_NONE,
734 .range_cyclic = 1,
735 .reason = reason,
738 spin_lock(&wb->list_lock);
739 if (list_empty(&wb->b_io))
740 queue_io(wb, &work);
741 __writeback_inodes_wb(wb, &work);
742 spin_unlock(&wb->list_lock);
744 return nr_pages - work.nr_pages;
747 static bool over_bground_thresh(struct backing_dev_info *bdi)
749 unsigned long background_thresh, dirty_thresh;
751 global_dirty_limits(&background_thresh, &dirty_thresh);
753 if (global_page_state(NR_FILE_DIRTY) +
754 global_page_state(NR_UNSTABLE_NFS) > background_thresh)
755 return true;
757 if (bdi_stat(bdi, BDI_RECLAIMABLE) >
758 bdi_dirty_limit(bdi, background_thresh))
759 return true;
761 return false;
765 * Called under wb->list_lock. If there are multiple wb per bdi,
766 * only the flusher working on the first wb should do it.
768 static void wb_update_bandwidth(struct bdi_writeback *wb,
769 unsigned long start_time)
771 __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
775 * Explicit flushing or periodic writeback of "old" data.
777 * Define "old": the first time one of an inode's pages is dirtied, we mark the
778 * dirtying-time in the inode's address_space. So this periodic writeback code
779 * just walks the superblock inode list, writing back any inodes which are
780 * older than a specific point in time.
782 * Try to run once per dirty_writeback_interval. But if a writeback event
783 * takes longer than a dirty_writeback_interval interval, then leave a
784 * one-second gap.
786 * older_than_this takes precedence over nr_to_write. So we'll only write back
787 * all dirty pages if they are all attached to "old" mappings.
789 static long wb_writeback(struct bdi_writeback *wb,
790 struct wb_writeback_work *work)
792 unsigned long wb_start = jiffies;
793 long nr_pages = work->nr_pages;
794 unsigned long oldest_jif;
795 struct inode *inode;
796 long progress;
798 oldest_jif = jiffies;
799 work->older_than_this = &oldest_jif;
801 spin_lock(&wb->list_lock);
802 for (;;) {
804 * Stop writeback when nr_pages has been consumed
806 if (work->nr_pages <= 0)
807 break;
810 * Background writeout and kupdate-style writeback may
811 * run forever. Stop them if there is other work to do
812 * so that e.g. sync can proceed. They'll be restarted
813 * after the other works are all done.
815 if ((work->for_background || work->for_kupdate) &&
816 !list_empty(&wb->bdi->work_list))
817 break;
820 * For background writeout, stop when we are below the
821 * background dirty threshold
823 if (work->for_background && !over_bground_thresh(wb->bdi))
824 break;
827 * Kupdate and background works are special and we want to
828 * include all inodes that need writing. Livelock avoidance is
829 * handled by these works yielding to any other work so we are
830 * safe.
832 if (work->for_kupdate) {
833 oldest_jif = jiffies -
834 msecs_to_jiffies(dirty_expire_interval * 10);
835 } else if (work->for_background)
836 oldest_jif = jiffies;
838 trace_writeback_start(wb->bdi, work);
839 if (list_empty(&wb->b_io))
840 queue_io(wb, work);
841 if (work->sb)
842 progress = writeback_sb_inodes(work->sb, wb, work);
843 else
844 progress = __writeback_inodes_wb(wb, work);
845 trace_writeback_written(wb->bdi, work);
847 wb_update_bandwidth(wb, wb_start);
850 * Did we write something? Try for more
852 * Dirty inodes are moved to b_io for writeback in batches.
853 * The completion of the current batch does not necessarily
854 * mean the overall work is done. So we keep looping as long
855 * as made some progress on cleaning pages or inodes.
857 if (progress)
858 continue;
860 * No more inodes for IO, bail
862 if (list_empty(&wb->b_more_io))
863 break;
865 * Nothing written. Wait for some inode to
866 * become available for writeback. Otherwise
867 * we'll just busyloop.
869 if (!list_empty(&wb->b_more_io)) {
870 trace_writeback_wait(wb->bdi, work);
871 inode = wb_inode(wb->b_more_io.prev);
872 spin_lock(&inode->i_lock);
873 spin_unlock(&wb->list_lock);
874 /* This function drops i_lock... */
875 inode_sleep_on_writeback(inode);
876 spin_lock(&wb->list_lock);
879 spin_unlock(&wb->list_lock);
881 return nr_pages - work->nr_pages;
885 * Return the next wb_writeback_work struct that hasn't been processed yet.
887 static struct wb_writeback_work *
888 get_next_work_item(struct backing_dev_info *bdi)
890 struct wb_writeback_work *work = NULL;
892 spin_lock_bh(&bdi->wb_lock);
893 if (!list_empty(&bdi->work_list)) {
894 work = list_entry(bdi->work_list.next,
895 struct wb_writeback_work, list);
896 list_del_init(&work->list);
898 spin_unlock_bh(&bdi->wb_lock);
899 return work;
903 * Add in the number of potentially dirty inodes, because each inode
904 * write can dirty pagecache in the underlying blockdev.
906 static unsigned long get_nr_dirty_pages(void)
908 return global_page_state(NR_FILE_DIRTY) +
909 global_page_state(NR_UNSTABLE_NFS) +
910 get_nr_dirty_inodes();
913 static long wb_check_background_flush(struct bdi_writeback *wb)
915 if (over_bground_thresh(wb->bdi)) {
917 struct wb_writeback_work work = {
918 .nr_pages = LONG_MAX,
919 .sync_mode = WB_SYNC_NONE,
920 .for_background = 1,
921 .range_cyclic = 1,
922 .reason = WB_REASON_BACKGROUND,
925 return wb_writeback(wb, &work);
928 return 0;
931 static long wb_check_old_data_flush(struct bdi_writeback *wb)
933 unsigned long expired;
934 long nr_pages;
937 * When set to zero, disable periodic writeback
939 if (!dirty_writeback_interval)
940 return 0;
942 expired = wb->last_old_flush +
943 msecs_to_jiffies(dirty_writeback_interval * 10);
944 if (time_before(jiffies, expired))
945 return 0;
947 wb->last_old_flush = jiffies;
948 nr_pages = get_nr_dirty_pages();
950 if (nr_pages) {
951 struct wb_writeback_work work = {
952 .nr_pages = nr_pages,
953 .sync_mode = WB_SYNC_NONE,
954 .for_kupdate = 1,
955 .range_cyclic = 1,
956 .reason = WB_REASON_PERIODIC,
959 return wb_writeback(wb, &work);
962 return 0;
966 * Retrieve work items and do the writeback they describe
968 static long wb_do_writeback(struct bdi_writeback *wb)
970 struct backing_dev_info *bdi = wb->bdi;
971 struct wb_writeback_work *work;
972 long wrote = 0;
974 set_bit(BDI_writeback_running, &wb->bdi->state);
975 while ((work = get_next_work_item(bdi)) != NULL) {
977 trace_writeback_exec(bdi, work);
979 wrote += wb_writeback(wb, work);
982 * Notify the caller of completion if this is a synchronous
983 * work item, otherwise just free it.
985 if (work->done)
986 complete(work->done);
987 else
988 kfree(work);
992 * Check for periodic writeback, kupdated() style
994 wrote += wb_check_old_data_flush(wb);
995 wrote += wb_check_background_flush(wb);
996 clear_bit(BDI_writeback_running, &wb->bdi->state);
998 return wrote;
1002 * Handle writeback of dirty data for the device backed by this bdi. Also
1003 * reschedules periodically and does kupdated style flushing.
1005 void bdi_writeback_workfn(struct work_struct *work)
1007 struct bdi_writeback *wb = container_of(to_delayed_work(work),
1008 struct bdi_writeback, dwork);
1009 struct backing_dev_info *bdi = wb->bdi;
1010 long pages_written;
1012 set_worker_desc("flush-%s", dev_name(bdi->dev));
1013 current->flags |= PF_SWAPWRITE;
1015 if (likely(!current_is_workqueue_rescuer() ||
1016 list_empty(&bdi->bdi_list))) {
1018 * The normal path. Keep writing back @bdi until its
1019 * work_list is empty. Note that this path is also taken
1020 * if @bdi is shutting down even when we're running off the
1021 * rescuer as work_list needs to be drained.
1023 do {
1024 pages_written = wb_do_writeback(wb);
1025 trace_writeback_pages_written(pages_written);
1026 } while (!list_empty(&bdi->work_list));
1027 } else {
1029 * bdi_wq can't get enough workers and we're running off
1030 * the emergency worker. Don't hog it. Hopefully, 1024 is
1031 * enough for efficient IO.
1033 pages_written = writeback_inodes_wb(&bdi->wb, 1024,
1034 WB_REASON_FORKER_THREAD);
1035 trace_writeback_pages_written(pages_written);
1038 if (!list_empty(&bdi->work_list) ||
1039 (wb_has_dirty_io(wb) && dirty_writeback_interval))
1040 queue_delayed_work(bdi_wq, &wb->dwork,
1041 msecs_to_jiffies(dirty_writeback_interval * 10));
1043 current->flags &= ~PF_SWAPWRITE;
1047 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
1048 * the whole world.
1050 void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
1052 struct backing_dev_info *bdi;
1054 if (!nr_pages)
1055 nr_pages = get_nr_dirty_pages();
1057 rcu_read_lock();
1058 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
1059 if (!bdi_has_dirty_io(bdi))
1060 continue;
1061 __bdi_start_writeback(bdi, nr_pages, false, reason);
1063 rcu_read_unlock();
1066 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
1068 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
1069 struct dentry *dentry;
1070 const char *name = "?";
1072 dentry = d_find_alias(inode);
1073 if (dentry) {
1074 spin_lock(&dentry->d_lock);
1075 name = (const char *) dentry->d_name.name;
1077 printk(KERN_DEBUG
1078 "%s(%d): dirtied inode %lu (%s) on %s\n",
1079 current->comm, task_pid_nr(current), inode->i_ino,
1080 name, inode->i_sb->s_id);
1081 if (dentry) {
1082 spin_unlock(&dentry->d_lock);
1083 dput(dentry);
1089 * __mark_inode_dirty - internal function
1090 * @inode: inode to mark
1091 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1092 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1093 * mark_inode_dirty_sync.
1095 * Put the inode on the super block's dirty list.
1097 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1098 * dirty list only if it is hashed or if it refers to a blockdev.
1099 * If it was not hashed, it will never be added to the dirty list
1100 * even if it is later hashed, as it will have been marked dirty already.
1102 * In short, make sure you hash any inodes _before_ you start marking
1103 * them dirty.
1105 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1106 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1107 * the kernel-internal blockdev inode represents the dirtying time of the
1108 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1109 * page->mapping->host, so the page-dirtying time is recorded in the internal
1110 * blockdev inode.
1112 void __mark_inode_dirty(struct inode *inode, int flags)
1114 struct super_block *sb = inode->i_sb;
1115 struct backing_dev_info *bdi = NULL;
1118 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1119 * dirty the inode itself
1121 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1122 trace_writeback_dirty_inode_start(inode, flags);
1124 if (sb->s_op->dirty_inode)
1125 sb->s_op->dirty_inode(inode, flags);
1127 trace_writeback_dirty_inode(inode, flags);
1131 * make sure that changes are seen by all cpus before we test i_state
1132 * -- mikulas
1134 smp_mb();
1136 /* avoid the locking if we can */
1137 if ((inode->i_state & flags) == flags)
1138 return;
1140 if (unlikely(block_dump))
1141 block_dump___mark_inode_dirty(inode);
1143 spin_lock(&inode->i_lock);
1144 if ((inode->i_state & flags) != flags) {
1145 const int was_dirty = inode->i_state & I_DIRTY;
1147 inode->i_state |= flags;
1150 * If the inode is being synced, just update its dirty state.
1151 * The unlocker will place the inode on the appropriate
1152 * superblock list, based upon its state.
1154 if (inode->i_state & I_SYNC)
1155 goto out_unlock_inode;
1158 * Only add valid (hashed) inodes to the superblock's
1159 * dirty list. Add blockdev inodes as well.
1161 if (!S_ISBLK(inode->i_mode)) {
1162 if (inode_unhashed(inode))
1163 goto out_unlock_inode;
1165 if (inode->i_state & I_FREEING)
1166 goto out_unlock_inode;
1169 * If the inode was already on b_dirty/b_io/b_more_io, don't
1170 * reposition it (that would break b_dirty time-ordering).
1172 if (!was_dirty) {
1173 bool wakeup_bdi = false;
1174 bdi = inode_to_bdi(inode);
1176 spin_unlock(&inode->i_lock);
1177 spin_lock(&bdi->wb.list_lock);
1178 if (bdi_cap_writeback_dirty(bdi)) {
1179 WARN(!test_bit(BDI_registered, &bdi->state),
1180 "bdi-%s not registered\n", bdi->name);
1183 * If this is the first dirty inode for this
1184 * bdi, we have to wake-up the corresponding
1185 * bdi thread to make sure background
1186 * write-back happens later.
1188 if (!wb_has_dirty_io(&bdi->wb))
1189 wakeup_bdi = true;
1192 inode->dirtied_when = jiffies;
1193 list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1194 spin_unlock(&bdi->wb.list_lock);
1196 if (wakeup_bdi)
1197 bdi_wakeup_thread_delayed(bdi);
1198 return;
1201 out_unlock_inode:
1202 spin_unlock(&inode->i_lock);
1205 EXPORT_SYMBOL(__mark_inode_dirty);
1207 static void wait_sb_inodes(struct super_block *sb)
1209 struct inode *inode, *old_inode = NULL;
1212 * We need to be protected against the filesystem going from
1213 * r/o to r/w or vice versa.
1215 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1217 spin_lock(&inode_sb_list_lock);
1220 * Data integrity sync. Must wait for all pages under writeback,
1221 * because there may have been pages dirtied before our sync
1222 * call, but which had writeout started before we write it out.
1223 * In which case, the inode may not be on the dirty list, but
1224 * we still have to wait for that writeout.
1226 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1227 struct address_space *mapping = inode->i_mapping;
1229 spin_lock(&inode->i_lock);
1230 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1231 (mapping->nrpages == 0)) {
1232 spin_unlock(&inode->i_lock);
1233 continue;
1235 __iget(inode);
1236 spin_unlock(&inode->i_lock);
1237 spin_unlock(&inode_sb_list_lock);
1240 * We hold a reference to 'inode' so it couldn't have been
1241 * removed from s_inodes list while we dropped the
1242 * inode_sb_list_lock. We cannot iput the inode now as we can
1243 * be holding the last reference and we cannot iput it under
1244 * inode_sb_list_lock. So we keep the reference and iput it
1245 * later.
1247 iput(old_inode);
1248 old_inode = inode;
1250 filemap_fdatawait(mapping);
1252 cond_resched();
1254 spin_lock(&inode_sb_list_lock);
1256 spin_unlock(&inode_sb_list_lock);
1257 iput(old_inode);
1261 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1262 * @sb: the superblock
1263 * @nr: the number of pages to write
1264 * @reason: reason why some writeback work initiated
1266 * Start writeback on some inodes on this super_block. No guarantees are made
1267 * on how many (if any) will be written, and this function does not wait
1268 * for IO completion of submitted IO.
1270 void writeback_inodes_sb_nr(struct super_block *sb,
1271 unsigned long nr,
1272 enum wb_reason reason)
1274 DECLARE_COMPLETION_ONSTACK(done);
1275 struct wb_writeback_work work = {
1276 .sb = sb,
1277 .sync_mode = WB_SYNC_NONE,
1278 .tagged_writepages = 1,
1279 .done = &done,
1280 .nr_pages = nr,
1281 .reason = reason,
1284 if (sb->s_bdi == &noop_backing_dev_info)
1285 return;
1286 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1287 bdi_queue_work(sb->s_bdi, &work);
1288 wait_for_completion(&done);
1290 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1293 * writeback_inodes_sb - writeback dirty inodes from given super_block
1294 * @sb: the superblock
1295 * @reason: reason why some writeback work was initiated
1297 * Start writeback on some inodes on this super_block. No guarantees are made
1298 * on how many (if any) will be written, and this function does not wait
1299 * for IO completion of submitted IO.
1301 void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1303 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1305 EXPORT_SYMBOL(writeback_inodes_sb);
1308 * try_to_writeback_inodes_sb_nr - try to start writeback if none underway
1309 * @sb: the superblock
1310 * @nr: the number of pages to write
1311 * @reason: the reason of writeback
1313 * Invoke writeback_inodes_sb_nr if no writeback is currently underway.
1314 * Returns 1 if writeback was started, 0 if not.
1316 int try_to_writeback_inodes_sb_nr(struct super_block *sb,
1317 unsigned long nr,
1318 enum wb_reason reason)
1320 if (writeback_in_progress(sb->s_bdi))
1321 return 1;
1323 if (!down_read_trylock(&sb->s_umount))
1324 return 0;
1326 writeback_inodes_sb_nr(sb, nr, reason);
1327 up_read(&sb->s_umount);
1328 return 1;
1330 EXPORT_SYMBOL(try_to_writeback_inodes_sb_nr);
1333 * try_to_writeback_inodes_sb - try to start writeback if none underway
1334 * @sb: the superblock
1335 * @reason: reason why some writeback work was initiated
1337 * Implement by try_to_writeback_inodes_sb_nr()
1338 * Returns 1 if writeback was started, 0 if not.
1340 int try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
1342 return try_to_writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
1344 EXPORT_SYMBOL(try_to_writeback_inodes_sb);
1347 * sync_inodes_sb - sync sb inode pages
1348 * @sb: the superblock
1350 * This function writes and waits on any dirty inode belonging to this
1351 * super_block.
1353 void sync_inodes_sb(struct super_block *sb)
1355 DECLARE_COMPLETION_ONSTACK(done);
1356 struct wb_writeback_work work = {
1357 .sb = sb,
1358 .sync_mode = WB_SYNC_ALL,
1359 .nr_pages = LONG_MAX,
1360 .range_cyclic = 0,
1361 .done = &done,
1362 .reason = WB_REASON_SYNC,
1363 .for_sync = 1,
1366 /* Nothing to do? */
1367 if (sb->s_bdi == &noop_backing_dev_info)
1368 return;
1369 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1371 bdi_queue_work(sb->s_bdi, &work);
1372 wait_for_completion(&done);
1374 wait_sb_inodes(sb);
1376 EXPORT_SYMBOL(sync_inodes_sb);
1379 * write_inode_now - write an inode to disk
1380 * @inode: inode to write to disk
1381 * @sync: whether the write should be synchronous or not
1383 * This function commits an inode to disk immediately if it is dirty. This is
1384 * primarily needed by knfsd.
1386 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1388 int write_inode_now(struct inode *inode, int sync)
1390 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1391 struct writeback_control wbc = {
1392 .nr_to_write = LONG_MAX,
1393 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1394 .range_start = 0,
1395 .range_end = LLONG_MAX,
1398 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1399 wbc.nr_to_write = 0;
1401 might_sleep();
1402 return writeback_single_inode(inode, wb, &wbc);
1404 EXPORT_SYMBOL(write_inode_now);
1407 * sync_inode - write an inode and its pages to disk.
1408 * @inode: the inode to sync
1409 * @wbc: controls the writeback mode
1411 * sync_inode() will write an inode and its pages to disk. It will also
1412 * correctly update the inode on its superblock's dirty inode lists and will
1413 * update inode->i_state.
1415 * The caller must have a ref on the inode.
1417 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1419 return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
1421 EXPORT_SYMBOL(sync_inode);
1424 * sync_inode_metadata - write an inode to disk
1425 * @inode: the inode to sync
1426 * @wait: wait for I/O to complete.
1428 * Write an inode to disk and adjust its dirty state after completion.
1430 * Note: only writes the actual inode, no associated data or other metadata.
1432 int sync_inode_metadata(struct inode *inode, int wait)
1434 struct writeback_control wbc = {
1435 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1436 .nr_to_write = 0, /* metadata-only */
1439 return sync_inode(inode, &wbc);
1441 EXPORT_SYMBOL(sync_inode_metadata);