tty/n_gsm: fix bug in CRC calculation for gsm1 mode
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / fs-writeback.c
blob34591ee804b58ad8e81ee04b3754dba1bcf77f8c
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>
56 * We don't actually have pdflush, but this one is exported though /proc...
58 int nr_pdflush_threads;
60 /**
61 * writeback_in_progress - determine whether there is writeback in progress
62 * @bdi: the device's backing_dev_info structure.
64 * Determine whether there is writeback waiting to be handled against a
65 * backing device.
67 int writeback_in_progress(struct backing_dev_info *bdi)
69 return test_bit(BDI_writeback_running, &bdi->state);
72 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
74 struct super_block *sb = inode->i_sb;
76 if (strcmp(sb->s_type->name, "bdev") == 0)
77 return inode->i_mapping->backing_dev_info;
79 return sb->s_bdi;
82 static inline struct inode *wb_inode(struct list_head *head)
84 return list_entry(head, struct inode, i_wb_list);
87 /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */
88 static void bdi_wakeup_flusher(struct backing_dev_info *bdi)
90 if (bdi->wb.task) {
91 wake_up_process(bdi->wb.task);
92 } else {
94 * The bdi thread isn't there, wake up the forker thread which
95 * will create and run it.
97 wake_up_process(default_backing_dev_info.wb.task);
101 static void bdi_queue_work(struct backing_dev_info *bdi,
102 struct wb_writeback_work *work)
104 trace_writeback_queue(bdi, work);
106 spin_lock_bh(&bdi->wb_lock);
107 list_add_tail(&work->list, &bdi->work_list);
108 if (!bdi->wb.task)
109 trace_writeback_nothread(bdi, work);
110 bdi_wakeup_flusher(bdi);
111 spin_unlock_bh(&bdi->wb_lock);
114 static void
115 __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
116 bool range_cyclic)
118 struct wb_writeback_work *work;
121 * This is WB_SYNC_NONE writeback, so if allocation fails just
122 * wakeup the thread for old dirty data writeback
124 work = kzalloc(sizeof(*work), GFP_ATOMIC);
125 if (!work) {
126 if (bdi->wb.task) {
127 trace_writeback_nowork(bdi);
128 wake_up_process(bdi->wb.task);
130 return;
133 work->sync_mode = WB_SYNC_NONE;
134 work->nr_pages = nr_pages;
135 work->range_cyclic = range_cyclic;
137 bdi_queue_work(bdi, work);
141 * bdi_start_writeback - start writeback
142 * @bdi: the backing device to write from
143 * @nr_pages: the number of pages to write
145 * Description:
146 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
147 * started when this function returns, we make no guarantees on
148 * completion. Caller need not hold sb s_umount semaphore.
151 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
153 __bdi_start_writeback(bdi, nr_pages, true);
157 * bdi_start_background_writeback - start background writeback
158 * @bdi: the backing device to write from
160 * Description:
161 * This makes sure WB_SYNC_NONE background writeback happens. When
162 * this function returns, it is only guaranteed that for given BDI
163 * some IO is happening if we are over background dirty threshold.
164 * Caller need not hold sb s_umount semaphore.
166 void bdi_start_background_writeback(struct backing_dev_info *bdi)
169 * We just wake up the flusher thread. It will perform background
170 * writeback as soon as there is no other work to do.
172 trace_writeback_wake_background(bdi);
173 spin_lock_bh(&bdi->wb_lock);
174 bdi_wakeup_flusher(bdi);
175 spin_unlock_bh(&bdi->wb_lock);
179 * Remove the inode from the writeback list it is on.
181 void inode_wb_list_del(struct inode *inode)
183 spin_lock(&inode_wb_list_lock);
184 list_del_init(&inode->i_wb_list);
185 spin_unlock(&inode_wb_list_lock);
190 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
191 * furthest end of its superblock's dirty-inode list.
193 * Before stamping the inode's ->dirtied_when, we check to see whether it is
194 * already the most-recently-dirtied inode on the b_dirty list. If that is
195 * the case then the inode must have been redirtied while it was being written
196 * out and we don't reset its dirtied_when.
198 static void redirty_tail(struct inode *inode)
200 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
202 assert_spin_locked(&inode_wb_list_lock);
203 if (!list_empty(&wb->b_dirty)) {
204 struct inode *tail;
206 tail = wb_inode(wb->b_dirty.next);
207 if (time_before(inode->dirtied_when, tail->dirtied_when))
208 inode->dirtied_when = jiffies;
210 list_move(&inode->i_wb_list, &wb->b_dirty);
214 * requeue inode for re-scanning after bdi->b_io list is exhausted.
216 static void requeue_io(struct inode *inode)
218 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
220 assert_spin_locked(&inode_wb_list_lock);
221 list_move(&inode->i_wb_list, &wb->b_more_io);
224 static void inode_sync_complete(struct inode *inode)
227 * Prevent speculative execution through
228 * spin_unlock(&inode_wb_list_lock);
231 smp_mb();
232 wake_up_bit(&inode->i_state, __I_SYNC);
235 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
237 bool ret = time_after(inode->dirtied_when, t);
238 #ifndef CONFIG_64BIT
240 * For inodes being constantly redirtied, dirtied_when can get stuck.
241 * It _appears_ to be in the future, but is actually in distant past.
242 * This test is necessary to prevent such wrapped-around relative times
243 * from permanently stopping the whole bdi writeback.
245 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
246 #endif
247 return ret;
251 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
253 static void move_expired_inodes(struct list_head *delaying_queue,
254 struct list_head *dispatch_queue,
255 unsigned long *older_than_this)
257 LIST_HEAD(tmp);
258 struct list_head *pos, *node;
259 struct super_block *sb = NULL;
260 struct inode *inode;
261 int do_sb_sort = 0;
263 while (!list_empty(delaying_queue)) {
264 inode = wb_inode(delaying_queue->prev);
265 if (older_than_this &&
266 inode_dirtied_after(inode, *older_than_this))
267 break;
268 if (sb && sb != inode->i_sb)
269 do_sb_sort = 1;
270 sb = inode->i_sb;
271 list_move(&inode->i_wb_list, &tmp);
274 /* just one sb in list, splice to dispatch_queue and we're done */
275 if (!do_sb_sort) {
276 list_splice(&tmp, dispatch_queue);
277 return;
280 /* Move inodes from one superblock together */
281 while (!list_empty(&tmp)) {
282 sb = wb_inode(tmp.prev)->i_sb;
283 list_for_each_prev_safe(pos, node, &tmp) {
284 inode = wb_inode(pos);
285 if (inode->i_sb == sb)
286 list_move(&inode->i_wb_list, dispatch_queue);
292 * Queue all expired dirty inodes for io, eldest first.
293 * Before
294 * newly dirtied b_dirty b_io b_more_io
295 * =============> gf edc BA
296 * After
297 * newly dirtied b_dirty b_io b_more_io
298 * =============> g fBAedc
300 * +--> dequeue for IO
302 static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
304 assert_spin_locked(&inode_wb_list_lock);
305 list_splice_init(&wb->b_more_io, &wb->b_io);
306 move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
309 static int write_inode(struct inode *inode, struct writeback_control *wbc)
311 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
312 return inode->i_sb->s_op->write_inode(inode, wbc);
313 return 0;
317 * Wait for writeback on an inode to complete.
319 static void inode_wait_for_writeback(struct inode *inode)
321 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
322 wait_queue_head_t *wqh;
324 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
325 while (inode->i_state & I_SYNC) {
326 spin_unlock(&inode->i_lock);
327 spin_unlock(&inode_wb_list_lock);
328 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
329 spin_lock(&inode_wb_list_lock);
330 spin_lock(&inode->i_lock);
335 * Write out an inode's dirty pages. Called under inode_wb_list_lock and
336 * inode->i_lock. Either the caller has an active reference on the inode or
337 * the inode has I_WILL_FREE set.
339 * If `wait' is set, wait on the writeout.
341 * The whole writeout design is quite complex and fragile. We want to avoid
342 * starvation of particular inodes when others are being redirtied, prevent
343 * livelocks, etc.
345 static int
346 writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
348 struct address_space *mapping = inode->i_mapping;
349 unsigned dirty;
350 int ret;
352 assert_spin_locked(&inode_wb_list_lock);
353 assert_spin_locked(&inode->i_lock);
355 if (!atomic_read(&inode->i_count))
356 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
357 else
358 WARN_ON(inode->i_state & I_WILL_FREE);
360 if (inode->i_state & I_SYNC) {
362 * If this inode is locked for writeback and we are not doing
363 * writeback-for-data-integrity, move it to b_more_io so that
364 * writeback can proceed with the other inodes on s_io.
366 * We'll have another go at writing back this inode when we
367 * completed a full scan of b_io.
369 if (wbc->sync_mode != WB_SYNC_ALL) {
370 requeue_io(inode);
371 return 0;
375 * It's a data-integrity sync. We must wait.
377 inode_wait_for_writeback(inode);
380 BUG_ON(inode->i_state & I_SYNC);
382 /* Set I_SYNC, reset I_DIRTY_PAGES */
383 inode->i_state |= I_SYNC;
384 inode->i_state &= ~I_DIRTY_PAGES;
385 spin_unlock(&inode->i_lock);
386 spin_unlock(&inode_wb_list_lock);
388 ret = do_writepages(mapping, wbc);
391 * Make sure to wait on the data before writing out the metadata.
392 * This is important for filesystems that modify metadata on data
393 * I/O completion.
395 if (wbc->sync_mode == WB_SYNC_ALL) {
396 int err = filemap_fdatawait(mapping);
397 if (ret == 0)
398 ret = err;
402 * Some filesystems may redirty the inode during the writeback
403 * due to delalloc, clear dirty metadata flags right before
404 * write_inode()
406 spin_lock(&inode->i_lock);
407 dirty = inode->i_state & I_DIRTY;
408 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
409 spin_unlock(&inode->i_lock);
410 /* Don't write the inode if only I_DIRTY_PAGES was set */
411 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
412 int err = write_inode(inode, wbc);
413 if (ret == 0)
414 ret = err;
417 spin_lock(&inode_wb_list_lock);
418 spin_lock(&inode->i_lock);
419 inode->i_state &= ~I_SYNC;
420 if (!(inode->i_state & I_FREEING)) {
421 if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
423 * We didn't write back all the pages. nfs_writepages()
424 * sometimes bales out without doing anything.
426 inode->i_state |= I_DIRTY_PAGES;
427 if (wbc->nr_to_write <= 0) {
429 * slice used up: queue for next turn
431 requeue_io(inode);
432 } else {
434 * Writeback blocked by something other than
435 * congestion. Delay the inode for some time to
436 * avoid spinning on the CPU (100% iowait)
437 * retrying writeback of the dirty page/inode
438 * that cannot be performed immediately.
440 redirty_tail(inode);
442 } else if (inode->i_state & I_DIRTY) {
444 * Filesystems can dirty the inode during writeback
445 * operations, such as delayed allocation during
446 * submission or metadata updates after data IO
447 * completion.
449 redirty_tail(inode);
450 } else {
452 * The inode is clean. At this point we either have
453 * a reference to the inode or it's on it's way out.
454 * No need to add it back to the LRU.
456 list_del_init(&inode->i_wb_list);
459 inode_sync_complete(inode);
460 return ret;
464 * For background writeback the caller does not have the sb pinned
465 * before calling writeback. So make sure that we do pin it, so it doesn't
466 * go away while we are writing inodes from it.
468 static bool pin_sb_for_writeback(struct super_block *sb)
470 spin_lock(&sb_lock);
471 if (list_empty(&sb->s_instances)) {
472 spin_unlock(&sb_lock);
473 return false;
476 sb->s_count++;
477 spin_unlock(&sb_lock);
479 if (down_read_trylock(&sb->s_umount)) {
480 if (sb->s_root)
481 return true;
482 up_read(&sb->s_umount);
485 put_super(sb);
486 return false;
490 * Write a portion of b_io inodes which belong to @sb.
492 * If @only_this_sb is true, then find and write all such
493 * inodes. Otherwise write only ones which go sequentially
494 * in reverse order.
496 * Return 1, if the caller writeback routine should be
497 * interrupted. Otherwise return 0.
499 static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
500 struct writeback_control *wbc, bool only_this_sb)
502 while (!list_empty(&wb->b_io)) {
503 long pages_skipped;
504 struct inode *inode = wb_inode(wb->b_io.prev);
506 if (inode->i_sb != sb) {
507 if (only_this_sb) {
509 * We only want to write back data for this
510 * superblock, move all inodes not belonging
511 * to it back onto the dirty list.
513 redirty_tail(inode);
514 continue;
518 * The inode belongs to a different superblock.
519 * Bounce back to the caller to unpin this and
520 * pin the next superblock.
522 return 0;
526 * Don't bother with new inodes or inodes beeing freed, first
527 * kind does not need peridic writeout yet, and for the latter
528 * kind writeout is handled by the freer.
530 spin_lock(&inode->i_lock);
531 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
532 spin_unlock(&inode->i_lock);
533 requeue_io(inode);
534 continue;
538 * Was this inode dirtied after sync_sb_inodes was called?
539 * This keeps sync from extra jobs and livelock.
541 if (inode_dirtied_after(inode, wbc->wb_start)) {
542 spin_unlock(&inode->i_lock);
543 return 1;
546 __iget(inode);
548 pages_skipped = wbc->pages_skipped;
549 writeback_single_inode(inode, wbc);
550 if (wbc->pages_skipped != pages_skipped) {
552 * writeback is not making progress due to locked
553 * buffers. Skip this inode for now.
555 redirty_tail(inode);
557 spin_unlock(&inode->i_lock);
558 spin_unlock(&inode_wb_list_lock);
559 iput(inode);
560 cond_resched();
561 spin_lock(&inode_wb_list_lock);
562 if (wbc->nr_to_write <= 0) {
563 wbc->more_io = 1;
564 return 1;
566 if (!list_empty(&wb->b_more_io))
567 wbc->more_io = 1;
569 /* b_io is empty */
570 return 1;
573 void writeback_inodes_wb(struct bdi_writeback *wb,
574 struct writeback_control *wbc)
576 int ret = 0;
578 if (!wbc->wb_start)
579 wbc->wb_start = jiffies; /* livelock avoidance */
580 spin_lock(&inode_wb_list_lock);
581 if (!wbc->for_kupdate || list_empty(&wb->b_io))
582 queue_io(wb, wbc->older_than_this);
584 while (!list_empty(&wb->b_io)) {
585 struct inode *inode = wb_inode(wb->b_io.prev);
586 struct super_block *sb = inode->i_sb;
588 if (!pin_sb_for_writeback(sb)) {
589 requeue_io(inode);
590 continue;
592 ret = writeback_sb_inodes(sb, wb, wbc, false);
593 drop_super(sb);
595 if (ret)
596 break;
598 spin_unlock(&inode_wb_list_lock);
599 /* Leave any unwritten inodes on b_io */
602 static void __writeback_inodes_sb(struct super_block *sb,
603 struct bdi_writeback *wb, struct writeback_control *wbc)
605 WARN_ON(!rwsem_is_locked(&sb->s_umount));
607 spin_lock(&inode_wb_list_lock);
608 if (!wbc->for_kupdate || list_empty(&wb->b_io))
609 queue_io(wb, wbc->older_than_this);
610 writeback_sb_inodes(sb, wb, wbc, true);
611 spin_unlock(&inode_wb_list_lock);
615 * The maximum number of pages to writeout in a single bdi flush/kupdate
616 * operation. We do this so we don't hold I_SYNC against an inode for
617 * enormous amounts of time, which would block a userspace task which has
618 * been forced to throttle against that inode. Also, the code reevaluates
619 * the dirty each time it has written this many pages.
621 #define MAX_WRITEBACK_PAGES 1024
623 static inline bool over_bground_thresh(void)
625 unsigned long background_thresh, dirty_thresh;
627 global_dirty_limits(&background_thresh, &dirty_thresh);
629 return (global_page_state(NR_FILE_DIRTY) +
630 global_page_state(NR_UNSTABLE_NFS) > background_thresh);
634 * Explicit flushing or periodic writeback of "old" data.
636 * Define "old": the first time one of an inode's pages is dirtied, we mark the
637 * dirtying-time in the inode's address_space. So this periodic writeback code
638 * just walks the superblock inode list, writing back any inodes which are
639 * older than a specific point in time.
641 * Try to run once per dirty_writeback_interval. But if a writeback event
642 * takes longer than a dirty_writeback_interval interval, then leave a
643 * one-second gap.
645 * older_than_this takes precedence over nr_to_write. So we'll only write back
646 * all dirty pages if they are all attached to "old" mappings.
648 static long wb_writeback(struct bdi_writeback *wb,
649 struct wb_writeback_work *work)
651 struct writeback_control wbc = {
652 .sync_mode = work->sync_mode,
653 .older_than_this = NULL,
654 .for_kupdate = work->for_kupdate,
655 .for_background = work->for_background,
656 .range_cyclic = work->range_cyclic,
658 unsigned long oldest_jif;
659 long wrote = 0;
660 long write_chunk;
661 struct inode *inode;
663 if (wbc.for_kupdate) {
664 wbc.older_than_this = &oldest_jif;
665 oldest_jif = jiffies -
666 msecs_to_jiffies(dirty_expire_interval * 10);
668 if (!wbc.range_cyclic) {
669 wbc.range_start = 0;
670 wbc.range_end = LLONG_MAX;
674 * WB_SYNC_ALL mode does livelock avoidance by syncing dirty
675 * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX
676 * here avoids calling into writeback_inodes_wb() more than once.
678 * The intended call sequence for WB_SYNC_ALL writeback is:
680 * wb_writeback()
681 * __writeback_inodes_sb() <== called only once
682 * write_cache_pages() <== called once for each inode
683 * (quickly) tag currently dirty pages
684 * (maybe slowly) sync all tagged pages
686 if (wbc.sync_mode == WB_SYNC_NONE)
687 write_chunk = MAX_WRITEBACK_PAGES;
688 else
689 write_chunk = LONG_MAX;
691 wbc.wb_start = jiffies; /* livelock avoidance */
692 for (;;) {
694 * Stop writeback when nr_pages has been consumed
696 if (work->nr_pages <= 0)
697 break;
700 * Background writeout and kupdate-style writeback may
701 * run forever. Stop them if there is other work to do
702 * so that e.g. sync can proceed. They'll be restarted
703 * after the other works are all done.
705 if ((work->for_background || work->for_kupdate) &&
706 !list_empty(&wb->bdi->work_list))
707 break;
710 * For background writeout, stop when we are below the
711 * background dirty threshold
713 if (work->for_background && !over_bground_thresh())
714 break;
716 wbc.more_io = 0;
717 wbc.nr_to_write = write_chunk;
718 wbc.pages_skipped = 0;
720 trace_wbc_writeback_start(&wbc, wb->bdi);
721 if (work->sb)
722 __writeback_inodes_sb(work->sb, wb, &wbc);
723 else
724 writeback_inodes_wb(wb, &wbc);
725 trace_wbc_writeback_written(&wbc, wb->bdi);
727 work->nr_pages -= write_chunk - wbc.nr_to_write;
728 wrote += write_chunk - wbc.nr_to_write;
731 * If we consumed everything, see if we have more
733 if (wbc.nr_to_write <= 0)
734 continue;
736 * Didn't write everything and we don't have more IO, bail
738 if (!wbc.more_io)
739 break;
741 * Did we write something? Try for more
743 if (wbc.nr_to_write < write_chunk)
744 continue;
746 * Nothing written. Wait for some inode to
747 * become available for writeback. Otherwise
748 * we'll just busyloop.
750 spin_lock(&inode_wb_list_lock);
751 if (!list_empty(&wb->b_more_io)) {
752 inode = wb_inode(wb->b_more_io.prev);
753 trace_wbc_writeback_wait(&wbc, wb->bdi);
754 spin_lock(&inode->i_lock);
755 inode_wait_for_writeback(inode);
756 spin_unlock(&inode->i_lock);
758 spin_unlock(&inode_wb_list_lock);
761 return wrote;
765 * Return the next wb_writeback_work struct that hasn't been processed yet.
767 static struct wb_writeback_work *
768 get_next_work_item(struct backing_dev_info *bdi)
770 struct wb_writeback_work *work = NULL;
772 spin_lock_bh(&bdi->wb_lock);
773 if (!list_empty(&bdi->work_list)) {
774 work = list_entry(bdi->work_list.next,
775 struct wb_writeback_work, list);
776 list_del_init(&work->list);
778 spin_unlock_bh(&bdi->wb_lock);
779 return work;
783 * Add in the number of potentially dirty inodes, because each inode
784 * write can dirty pagecache in the underlying blockdev.
786 static unsigned long get_nr_dirty_pages(void)
788 return global_page_state(NR_FILE_DIRTY) +
789 global_page_state(NR_UNSTABLE_NFS) +
790 get_nr_dirty_inodes();
793 static long wb_check_background_flush(struct bdi_writeback *wb)
795 if (over_bground_thresh()) {
797 struct wb_writeback_work work = {
798 .nr_pages = LONG_MAX,
799 .sync_mode = WB_SYNC_NONE,
800 .for_background = 1,
801 .range_cyclic = 1,
804 return wb_writeback(wb, &work);
807 return 0;
810 static long wb_check_old_data_flush(struct bdi_writeback *wb)
812 unsigned long expired;
813 long nr_pages;
816 * When set to zero, disable periodic writeback
818 if (!dirty_writeback_interval)
819 return 0;
821 expired = wb->last_old_flush +
822 msecs_to_jiffies(dirty_writeback_interval * 10);
823 if (time_before(jiffies, expired))
824 return 0;
826 wb->last_old_flush = jiffies;
827 nr_pages = get_nr_dirty_pages();
829 if (nr_pages) {
830 struct wb_writeback_work work = {
831 .nr_pages = nr_pages,
832 .sync_mode = WB_SYNC_NONE,
833 .for_kupdate = 1,
834 .range_cyclic = 1,
837 return wb_writeback(wb, &work);
840 return 0;
844 * Retrieve work items and do the writeback they describe
846 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
848 struct backing_dev_info *bdi = wb->bdi;
849 struct wb_writeback_work *work;
850 long wrote = 0;
852 set_bit(BDI_writeback_running, &wb->bdi->state);
853 while ((work = get_next_work_item(bdi)) != NULL) {
855 * Override sync mode, in case we must wait for completion
856 * because this thread is exiting now.
858 if (force_wait)
859 work->sync_mode = WB_SYNC_ALL;
861 trace_writeback_exec(bdi, work);
863 wrote += wb_writeback(wb, work);
866 * Notify the caller of completion if this is a synchronous
867 * work item, otherwise just free it.
869 if (work->done)
870 complete(work->done);
871 else
872 kfree(work);
876 * Check for periodic writeback, kupdated() style
878 wrote += wb_check_old_data_flush(wb);
879 wrote += wb_check_background_flush(wb);
880 clear_bit(BDI_writeback_running, &wb->bdi->state);
882 return wrote;
886 * Handle writeback of dirty data for the device backed by this bdi. Also
887 * wakes up periodically and does kupdated style flushing.
889 int bdi_writeback_thread(void *data)
891 struct bdi_writeback *wb = data;
892 struct backing_dev_info *bdi = wb->bdi;
893 long pages_written;
895 current->flags |= PF_SWAPWRITE;
896 set_freezable();
897 wb->last_active = jiffies;
900 * Our parent may run at a different priority, just set us to normal
902 set_user_nice(current, 0);
904 trace_writeback_thread_start(bdi);
906 while (!kthread_should_stop()) {
908 * Remove own delayed wake-up timer, since we are already awake
909 * and we'll take care of the preriodic write-back.
911 del_timer(&wb->wakeup_timer);
913 pages_written = wb_do_writeback(wb, 0);
915 trace_writeback_pages_written(pages_written);
917 if (pages_written)
918 wb->last_active = jiffies;
920 set_current_state(TASK_INTERRUPTIBLE);
921 if (!list_empty(&bdi->work_list) || kthread_should_stop()) {
922 __set_current_state(TASK_RUNNING);
923 continue;
926 if (wb_has_dirty_io(wb) && dirty_writeback_interval)
927 schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
928 else {
930 * We have nothing to do, so can go sleep without any
931 * timeout and save power. When a work is queued or
932 * something is made dirty - we will be woken up.
934 schedule();
937 try_to_freeze();
940 /* Flush any work that raced with us exiting */
941 if (!list_empty(&bdi->work_list))
942 wb_do_writeback(wb, 1);
944 trace_writeback_thread_stop(bdi);
945 return 0;
950 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
951 * the whole world.
953 void wakeup_flusher_threads(long nr_pages)
955 struct backing_dev_info *bdi;
957 if (!nr_pages) {
958 nr_pages = global_page_state(NR_FILE_DIRTY) +
959 global_page_state(NR_UNSTABLE_NFS);
962 rcu_read_lock();
963 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
964 if (!bdi_has_dirty_io(bdi))
965 continue;
966 __bdi_start_writeback(bdi, nr_pages, false);
968 rcu_read_unlock();
971 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
973 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
974 struct dentry *dentry;
975 const char *name = "?";
977 dentry = d_find_alias(inode);
978 if (dentry) {
979 spin_lock(&dentry->d_lock);
980 name = (const char *) dentry->d_name.name;
982 printk(KERN_DEBUG
983 "%s(%d): dirtied inode %lu (%s) on %s\n",
984 current->comm, task_pid_nr(current), inode->i_ino,
985 name, inode->i_sb->s_id);
986 if (dentry) {
987 spin_unlock(&dentry->d_lock);
988 dput(dentry);
994 * __mark_inode_dirty - internal function
995 * @inode: inode to mark
996 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
997 * Mark an inode as dirty. Callers should use mark_inode_dirty or
998 * mark_inode_dirty_sync.
1000 * Put the inode on the super block's dirty list.
1002 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1003 * dirty list only if it is hashed or if it refers to a blockdev.
1004 * If it was not hashed, it will never be added to the dirty list
1005 * even if it is later hashed, as it will have been marked dirty already.
1007 * In short, make sure you hash any inodes _before_ you start marking
1008 * them dirty.
1010 * This function *must* be atomic for the I_DIRTY_PAGES case -
1011 * set_page_dirty() is called under spinlock in several places.
1013 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1014 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1015 * the kernel-internal blockdev inode represents the dirtying time of the
1016 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1017 * page->mapping->host, so the page-dirtying time is recorded in the internal
1018 * blockdev inode.
1020 void __mark_inode_dirty(struct inode *inode, int flags)
1022 struct super_block *sb = inode->i_sb;
1023 struct backing_dev_info *bdi = NULL;
1026 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1027 * dirty the inode itself
1029 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1030 if (sb->s_op->dirty_inode)
1031 sb->s_op->dirty_inode(inode);
1035 * make sure that changes are seen by all cpus before we test i_state
1036 * -- mikulas
1038 smp_mb();
1040 /* avoid the locking if we can */
1041 if ((inode->i_state & flags) == flags)
1042 return;
1044 if (unlikely(block_dump))
1045 block_dump___mark_inode_dirty(inode);
1047 spin_lock(&inode->i_lock);
1048 if ((inode->i_state & flags) != flags) {
1049 const int was_dirty = inode->i_state & I_DIRTY;
1051 inode->i_state |= flags;
1054 * If the inode is being synced, just update its dirty state.
1055 * The unlocker will place the inode on the appropriate
1056 * superblock list, based upon its state.
1058 if (inode->i_state & I_SYNC)
1059 goto out_unlock_inode;
1062 * Only add valid (hashed) inodes to the superblock's
1063 * dirty list. Add blockdev inodes as well.
1065 if (!S_ISBLK(inode->i_mode)) {
1066 if (inode_unhashed(inode))
1067 goto out_unlock_inode;
1069 if (inode->i_state & I_FREEING)
1070 goto out_unlock_inode;
1073 * If the inode was already on b_dirty/b_io/b_more_io, don't
1074 * reposition it (that would break b_dirty time-ordering).
1076 if (!was_dirty) {
1077 bool wakeup_bdi = false;
1078 bdi = inode_to_bdi(inode);
1080 if (bdi_cap_writeback_dirty(bdi)) {
1081 WARN(!test_bit(BDI_registered, &bdi->state),
1082 "bdi-%s not registered\n", bdi->name);
1085 * If this is the first dirty inode for this
1086 * bdi, we have to wake-up the corresponding
1087 * bdi thread to make sure background
1088 * write-back happens later.
1090 if (!wb_has_dirty_io(&bdi->wb))
1091 wakeup_bdi = true;
1094 spin_unlock(&inode->i_lock);
1095 spin_lock(&inode_wb_list_lock);
1096 inode->dirtied_when = jiffies;
1097 list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
1098 spin_unlock(&inode_wb_list_lock);
1100 if (wakeup_bdi)
1101 bdi_wakeup_thread_delayed(bdi);
1102 return;
1105 out_unlock_inode:
1106 spin_unlock(&inode->i_lock);
1109 EXPORT_SYMBOL(__mark_inode_dirty);
1112 * Write out a superblock's list of dirty inodes. A wait will be performed
1113 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1115 * If older_than_this is non-NULL, then only write out inodes which
1116 * had their first dirtying at a time earlier than *older_than_this.
1118 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1119 * This function assumes that the blockdev superblock's inodes are backed by
1120 * a variety of queues, so all inodes are searched. For other superblocks,
1121 * assume that all inodes are backed by the same queue.
1123 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1124 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1125 * on the writer throttling path, and we get decent balancing between many
1126 * throttled threads: we don't want them all piling up on inode_sync_wait.
1128 static void wait_sb_inodes(struct super_block *sb)
1130 struct inode *inode, *old_inode = NULL;
1133 * We need to be protected against the filesystem going from
1134 * r/o to r/w or vice versa.
1136 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1138 spin_lock(&inode_sb_list_lock);
1141 * Data integrity sync. Must wait for all pages under writeback,
1142 * because there may have been pages dirtied before our sync
1143 * call, but which had writeout started before we write it out.
1144 * In which case, the inode may not be on the dirty list, but
1145 * we still have to wait for that writeout.
1147 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1148 struct address_space *mapping = inode->i_mapping;
1150 spin_lock(&inode->i_lock);
1151 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
1152 (mapping->nrpages == 0)) {
1153 spin_unlock(&inode->i_lock);
1154 continue;
1156 __iget(inode);
1157 spin_unlock(&inode->i_lock);
1158 spin_unlock(&inode_sb_list_lock);
1161 * We hold a reference to 'inode' so it couldn't have been
1162 * removed from s_inodes list while we dropped the
1163 * inode_sb_list_lock. We cannot iput the inode now as we can
1164 * be holding the last reference and we cannot iput it under
1165 * inode_sb_list_lock. So we keep the reference and iput it
1166 * later.
1168 iput(old_inode);
1169 old_inode = inode;
1171 filemap_fdatawait(mapping);
1173 cond_resched();
1175 spin_lock(&inode_sb_list_lock);
1177 spin_unlock(&inode_sb_list_lock);
1178 iput(old_inode);
1182 * writeback_inodes_sb_nr - writeback dirty inodes from given super_block
1183 * @sb: the superblock
1184 * @nr: the number of pages to write
1186 * Start writeback on some inodes on this super_block. No guarantees are made
1187 * on how many (if any) will be written, and this function does not wait
1188 * for IO completion of submitted IO.
1190 void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr)
1192 DECLARE_COMPLETION_ONSTACK(done);
1193 struct wb_writeback_work work = {
1194 .sb = sb,
1195 .sync_mode = WB_SYNC_NONE,
1196 .done = &done,
1197 .nr_pages = nr,
1200 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1201 bdi_queue_work(sb->s_bdi, &work);
1202 wait_for_completion(&done);
1204 EXPORT_SYMBOL(writeback_inodes_sb_nr);
1207 * writeback_inodes_sb - writeback dirty inodes from given super_block
1208 * @sb: the superblock
1210 * Start writeback on some inodes on this super_block. No guarantees are made
1211 * on how many (if any) will be written, and this function does not wait
1212 * for IO completion of submitted IO.
1214 void writeback_inodes_sb(struct super_block *sb)
1216 return writeback_inodes_sb_nr(sb, get_nr_dirty_pages());
1218 EXPORT_SYMBOL(writeback_inodes_sb);
1221 * writeback_inodes_sb_if_idle - start writeback if none underway
1222 * @sb: the superblock
1224 * Invoke writeback_inodes_sb if no writeback is currently underway.
1225 * Returns 1 if writeback was started, 0 if not.
1227 int writeback_inodes_sb_if_idle(struct super_block *sb)
1229 if (!writeback_in_progress(sb->s_bdi)) {
1230 down_read(&sb->s_umount);
1231 writeback_inodes_sb(sb);
1232 up_read(&sb->s_umount);
1233 return 1;
1234 } else
1235 return 0;
1237 EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1240 * writeback_inodes_sb_if_idle - start writeback if none underway
1241 * @sb: the superblock
1242 * @nr: the number of pages to write
1244 * Invoke writeback_inodes_sb if no writeback is currently underway.
1245 * Returns 1 if writeback was started, 0 if not.
1247 int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
1248 unsigned long nr)
1250 if (!writeback_in_progress(sb->s_bdi)) {
1251 down_read(&sb->s_umount);
1252 writeback_inodes_sb_nr(sb, nr);
1253 up_read(&sb->s_umount);
1254 return 1;
1255 } else
1256 return 0;
1258 EXPORT_SYMBOL(writeback_inodes_sb_nr_if_idle);
1261 * sync_inodes_sb - sync sb inode pages
1262 * @sb: the superblock
1264 * This function writes and waits on any dirty inode belonging to this
1265 * super_block.
1267 void sync_inodes_sb(struct super_block *sb)
1269 DECLARE_COMPLETION_ONSTACK(done);
1270 struct wb_writeback_work work = {
1271 .sb = sb,
1272 .sync_mode = WB_SYNC_ALL,
1273 .nr_pages = LONG_MAX,
1274 .range_cyclic = 0,
1275 .done = &done,
1278 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1280 bdi_queue_work(sb->s_bdi, &work);
1281 wait_for_completion(&done);
1283 wait_sb_inodes(sb);
1285 EXPORT_SYMBOL(sync_inodes_sb);
1288 * write_inode_now - write an inode to disk
1289 * @inode: inode to write to disk
1290 * @sync: whether the write should be synchronous or not
1292 * This function commits an inode to disk immediately if it is dirty. This is
1293 * primarily needed by knfsd.
1295 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1297 int write_inode_now(struct inode *inode, int sync)
1299 int ret;
1300 struct writeback_control wbc = {
1301 .nr_to_write = LONG_MAX,
1302 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1303 .range_start = 0,
1304 .range_end = LLONG_MAX,
1307 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1308 wbc.nr_to_write = 0;
1310 might_sleep();
1311 spin_lock(&inode_wb_list_lock);
1312 spin_lock(&inode->i_lock);
1313 ret = writeback_single_inode(inode, &wbc);
1314 spin_unlock(&inode->i_lock);
1315 spin_unlock(&inode_wb_list_lock);
1316 if (sync)
1317 inode_sync_wait(inode);
1318 return ret;
1320 EXPORT_SYMBOL(write_inode_now);
1323 * sync_inode - write an inode and its pages to disk.
1324 * @inode: the inode to sync
1325 * @wbc: controls the writeback mode
1327 * sync_inode() will write an inode and its pages to disk. It will also
1328 * correctly update the inode on its superblock's dirty inode lists and will
1329 * update inode->i_state.
1331 * The caller must have a ref on the inode.
1333 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1335 int ret;
1337 spin_lock(&inode_wb_list_lock);
1338 spin_lock(&inode->i_lock);
1339 ret = writeback_single_inode(inode, wbc);
1340 spin_unlock(&inode->i_lock);
1341 spin_unlock(&inode_wb_list_lock);
1342 return ret;
1344 EXPORT_SYMBOL(sync_inode);
1347 * sync_inode_metadata - write an inode to disk
1348 * @inode: the inode to sync
1349 * @wait: wait for I/O to complete.
1351 * Write an inode to disk and adjust its dirty state after completion.
1353 * Note: only writes the actual inode, no associated data or other metadata.
1355 int sync_inode_metadata(struct inode *inode, int wait)
1357 struct writeback_control wbc = {
1358 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
1359 .nr_to_write = 0, /* metadata-only */
1362 return sync_inode(inode, &wbc);
1364 EXPORT_SYMBOL(sync_inode_metadata);