ppp: fix BUG on non-linear SKB (multilink receive)
[linux-2.6/mini2440.git] / fs / fs-writeback.c
blob8e1e5e19d21e1fd60c9f99b3988fee0191c3e901
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/sched.h>
20 #include <linux/fs.h>
21 #include <linux/mm.h>
22 #include <linux/kthread.h>
23 #include <linux/freezer.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/backing-dev.h>
27 #include <linux/buffer_head.h>
28 #include "internal.h"
30 #define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
33 * We don't actually have pdflush, but this one is exported though /proc...
35 int nr_pdflush_threads;
38 * Passed into wb_writeback(), essentially a subset of writeback_control
40 struct wb_writeback_args {
41 long nr_pages;
42 struct super_block *sb;
43 enum writeback_sync_modes sync_mode;
44 int for_kupdate;
45 int range_cyclic;
49 * Work items for the bdi_writeback threads
51 struct bdi_work {
52 struct list_head list; /* pending work list */
53 struct rcu_head rcu_head; /* for RCU free/clear of work */
55 unsigned long seen; /* threads that have seen this work */
56 atomic_t pending; /* number of threads still to do work */
58 struct wb_writeback_args args; /* writeback arguments */
60 unsigned long state; /* flag bits, see WS_* */
63 enum {
64 WS_USED_B = 0,
65 WS_ONSTACK_B,
68 #define WS_USED (1 << WS_USED_B)
69 #define WS_ONSTACK (1 << WS_ONSTACK_B)
71 static inline bool bdi_work_on_stack(struct bdi_work *work)
73 return test_bit(WS_ONSTACK_B, &work->state);
76 static inline void bdi_work_init(struct bdi_work *work,
77 struct wb_writeback_args *args)
79 INIT_RCU_HEAD(&work->rcu_head);
80 work->args = *args;
81 work->state = WS_USED;
84 /**
85 * writeback_in_progress - determine whether there is writeback in progress
86 * @bdi: the device's backing_dev_info structure.
88 * Determine whether there is writeback waiting to be handled against a
89 * backing device.
91 int writeback_in_progress(struct backing_dev_info *bdi)
93 return !list_empty(&bdi->work_list);
96 static void bdi_work_clear(struct bdi_work *work)
98 clear_bit(WS_USED_B, &work->state);
99 smp_mb__after_clear_bit();
101 * work can have disappeared at this point. bit waitq functions
102 * should be able to tolerate this, provided bdi_sched_wait does
103 * not dereference it's pointer argument.
105 wake_up_bit(&work->state, WS_USED_B);
108 static void bdi_work_free(struct rcu_head *head)
110 struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
112 if (!bdi_work_on_stack(work))
113 kfree(work);
114 else
115 bdi_work_clear(work);
118 static void wb_work_complete(struct bdi_work *work)
120 const enum writeback_sync_modes sync_mode = work->args.sync_mode;
121 int onstack = bdi_work_on_stack(work);
124 * For allocated work, we can clear the done/seen bit right here.
125 * For on-stack work, we need to postpone both the clear and free
126 * to after the RCU grace period, since the stack could be invalidated
127 * as soon as bdi_work_clear() has done the wakeup.
129 if (!onstack)
130 bdi_work_clear(work);
131 if (sync_mode == WB_SYNC_NONE || onstack)
132 call_rcu(&work->rcu_head, bdi_work_free);
135 static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
138 * The caller has retrieved the work arguments from this work,
139 * drop our reference. If this is the last ref, delete and free it
141 if (atomic_dec_and_test(&work->pending)) {
142 struct backing_dev_info *bdi = wb->bdi;
144 spin_lock(&bdi->wb_lock);
145 list_del_rcu(&work->list);
146 spin_unlock(&bdi->wb_lock);
148 wb_work_complete(work);
152 static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
154 work->seen = bdi->wb_mask;
155 BUG_ON(!work->seen);
156 atomic_set(&work->pending, bdi->wb_cnt);
157 BUG_ON(!bdi->wb_cnt);
160 * list_add_tail_rcu() contains the necessary barriers to
161 * make sure the above stores are seen before the item is
162 * noticed on the list
164 spin_lock(&bdi->wb_lock);
165 list_add_tail_rcu(&work->list, &bdi->work_list);
166 spin_unlock(&bdi->wb_lock);
169 * If the default thread isn't there, make sure we add it. When
170 * it gets created and wakes up, we'll run this work.
172 if (unlikely(list_empty_careful(&bdi->wb_list)))
173 wake_up_process(default_backing_dev_info.wb.task);
174 else {
175 struct bdi_writeback *wb = &bdi->wb;
177 if (wb->task)
178 wake_up_process(wb->task);
183 * Used for on-stack allocated work items. The caller needs to wait until
184 * the wb threads have acked the work before it's safe to continue.
186 static void bdi_wait_on_work_clear(struct bdi_work *work)
188 wait_on_bit(&work->state, WS_USED_B, bdi_sched_wait,
189 TASK_UNINTERRUPTIBLE);
192 static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
193 struct wb_writeback_args *args)
195 struct bdi_work *work;
198 * This is WB_SYNC_NONE writeback, so if allocation fails just
199 * wakeup the thread for old dirty data writeback
201 work = kmalloc(sizeof(*work), GFP_ATOMIC);
202 if (work) {
203 bdi_work_init(work, args);
204 bdi_queue_work(bdi, work);
205 } else {
206 struct bdi_writeback *wb = &bdi->wb;
208 if (wb->task)
209 wake_up_process(wb->task);
214 * bdi_sync_writeback - start and wait for writeback
215 * @bdi: the backing device to write from
216 * @sb: write inodes from this super_block
218 * Description:
219 * This does WB_SYNC_ALL data integrity writeback and waits for the
220 * IO to complete. Callers must hold the sb s_umount semaphore for
221 * reading, to avoid having the super disappear before we are done.
223 static void bdi_sync_writeback(struct backing_dev_info *bdi,
224 struct super_block *sb)
226 struct wb_writeback_args args = {
227 .sb = sb,
228 .sync_mode = WB_SYNC_ALL,
229 .nr_pages = LONG_MAX,
230 .range_cyclic = 0,
232 struct bdi_work work;
234 bdi_work_init(&work, &args);
235 work.state |= WS_ONSTACK;
237 bdi_queue_work(bdi, &work);
238 bdi_wait_on_work_clear(&work);
242 * bdi_start_writeback - start writeback
243 * @bdi: the backing device to write from
244 * @nr_pages: the number of pages to write
246 * Description:
247 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
248 * started when this function returns, we make no guarentees on
249 * completion. Caller need not hold sb s_umount semaphore.
252 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
254 struct wb_writeback_args args = {
255 .sync_mode = WB_SYNC_NONE,
256 .nr_pages = nr_pages,
257 .range_cyclic = 1,
260 bdi_alloc_queue_work(bdi, &args);
264 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
265 * furthest end of its superblock's dirty-inode list.
267 * Before stamping the inode's ->dirtied_when, we check to see whether it is
268 * already the most-recently-dirtied inode on the b_dirty list. If that is
269 * the case then the inode must have been redirtied while it was being written
270 * out and we don't reset its dirtied_when.
272 static void redirty_tail(struct inode *inode)
274 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
276 if (!list_empty(&wb->b_dirty)) {
277 struct inode *tail;
279 tail = list_entry(wb->b_dirty.next, struct inode, i_list);
280 if (time_before(inode->dirtied_when, tail->dirtied_when))
281 inode->dirtied_when = jiffies;
283 list_move(&inode->i_list, &wb->b_dirty);
287 * requeue inode for re-scanning after bdi->b_io list is exhausted.
289 static void requeue_io(struct inode *inode)
291 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
293 list_move(&inode->i_list, &wb->b_more_io);
296 static void inode_sync_complete(struct inode *inode)
299 * Prevent speculative execution through spin_unlock(&inode_lock);
301 smp_mb();
302 wake_up_bit(&inode->i_state, __I_SYNC);
305 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
307 bool ret = time_after(inode->dirtied_when, t);
308 #ifndef CONFIG_64BIT
310 * For inodes being constantly redirtied, dirtied_when can get stuck.
311 * It _appears_ to be in the future, but is actually in distant past.
312 * This test is necessary to prevent such wrapped-around relative times
313 * from permanently stopping the whole pdflush writeback.
315 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
316 #endif
317 return ret;
321 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
323 static void move_expired_inodes(struct list_head *delaying_queue,
324 struct list_head *dispatch_queue,
325 unsigned long *older_than_this)
327 while (!list_empty(delaying_queue)) {
328 struct inode *inode = list_entry(delaying_queue->prev,
329 struct inode, i_list);
330 if (older_than_this &&
331 inode_dirtied_after(inode, *older_than_this))
332 break;
333 list_move(&inode->i_list, dispatch_queue);
338 * Queue all expired dirty inodes for io, eldest first.
340 static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
342 list_splice_init(&wb->b_more_io, wb->b_io.prev);
343 move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
346 static int write_inode(struct inode *inode, int sync)
348 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
349 return inode->i_sb->s_op->write_inode(inode, sync);
350 return 0;
354 * Wait for writeback on an inode to complete.
356 static void inode_wait_for_writeback(struct inode *inode)
358 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
359 wait_queue_head_t *wqh;
361 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
362 do {
363 spin_unlock(&inode_lock);
364 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
365 spin_lock(&inode_lock);
366 } while (inode->i_state & I_SYNC);
370 * Write out an inode's dirty pages. Called under inode_lock. Either the
371 * caller has ref on the inode (either via __iget or via syscall against an fd)
372 * or the inode has I_WILL_FREE set (via generic_forget_inode)
374 * If `wait' is set, wait on the writeout.
376 * The whole writeout design is quite complex and fragile. We want to avoid
377 * starvation of particular inodes when others are being redirtied, prevent
378 * livelocks, etc.
380 * Called under inode_lock.
382 static int
383 writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
385 struct address_space *mapping = inode->i_mapping;
386 int wait = wbc->sync_mode == WB_SYNC_ALL;
387 unsigned dirty;
388 int ret;
390 if (!atomic_read(&inode->i_count))
391 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
392 else
393 WARN_ON(inode->i_state & I_WILL_FREE);
395 if (inode->i_state & I_SYNC) {
397 * If this inode is locked for writeback and we are not doing
398 * writeback-for-data-integrity, move it to b_more_io so that
399 * writeback can proceed with the other inodes on s_io.
401 * We'll have another go at writing back this inode when we
402 * completed a full scan of b_io.
404 if (!wait) {
405 requeue_io(inode);
406 return 0;
410 * It's a data-integrity sync. We must wait.
412 inode_wait_for_writeback(inode);
415 BUG_ON(inode->i_state & I_SYNC);
417 /* Set I_SYNC, reset I_DIRTY */
418 dirty = inode->i_state & I_DIRTY;
419 inode->i_state |= I_SYNC;
420 inode->i_state &= ~I_DIRTY;
422 spin_unlock(&inode_lock);
424 ret = do_writepages(mapping, wbc);
426 /* Don't write the inode if only I_DIRTY_PAGES was set */
427 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
428 int err = write_inode(inode, wait);
429 if (ret == 0)
430 ret = err;
433 if (wait) {
434 int err = filemap_fdatawait(mapping);
435 if (ret == 0)
436 ret = err;
439 spin_lock(&inode_lock);
440 inode->i_state &= ~I_SYNC;
441 if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
442 if (!(inode->i_state & I_DIRTY) &&
443 mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
445 * We didn't write back all the pages. nfs_writepages()
446 * sometimes bales out without doing anything. Redirty
447 * the inode; Move it from b_io onto b_more_io/b_dirty.
450 * akpm: if the caller was the kupdate function we put
451 * this inode at the head of b_dirty so it gets first
452 * consideration. Otherwise, move it to the tail, for
453 * the reasons described there. I'm not really sure
454 * how much sense this makes. Presumably I had a good
455 * reasons for doing it this way, and I'd rather not
456 * muck with it at present.
458 if (wbc->for_kupdate) {
460 * For the kupdate function we move the inode
461 * to b_more_io so it will get more writeout as
462 * soon as the queue becomes uncongested.
464 inode->i_state |= I_DIRTY_PAGES;
465 if (wbc->nr_to_write <= 0) {
467 * slice used up: queue for next turn
469 requeue_io(inode);
470 } else {
472 * somehow blocked: retry later
474 redirty_tail(inode);
476 } else {
478 * Otherwise fully redirty the inode so that
479 * other inodes on this superblock will get some
480 * writeout. Otherwise heavy writing to one
481 * file would indefinitely suspend writeout of
482 * all the other files.
484 inode->i_state |= I_DIRTY_PAGES;
485 redirty_tail(inode);
487 } else if (inode->i_state & I_DIRTY) {
489 * Someone redirtied the inode while were writing back
490 * the pages.
492 redirty_tail(inode);
493 } else if (atomic_read(&inode->i_count)) {
495 * The inode is clean, inuse
497 list_move(&inode->i_list, &inode_in_use);
498 } else {
500 * The inode is clean, unused
502 list_move(&inode->i_list, &inode_unused);
505 inode_sync_complete(inode);
506 return ret;
510 * For WB_SYNC_NONE writeback, the caller does not have the sb pinned
511 * before calling writeback. So make sure that we do pin it, so it doesn't
512 * go away while we are writing inodes from it.
514 * Returns 0 if the super was successfully pinned (or pinning wasn't needed),
515 * 1 if we failed.
517 static int pin_sb_for_writeback(struct writeback_control *wbc,
518 struct inode *inode)
520 struct super_block *sb = inode->i_sb;
523 * Caller must already hold the ref for this
525 if (wbc->sync_mode == WB_SYNC_ALL) {
526 WARN_ON(!rwsem_is_locked(&sb->s_umount));
527 return 0;
530 spin_lock(&sb_lock);
531 sb->s_count++;
532 if (down_read_trylock(&sb->s_umount)) {
533 if (sb->s_root) {
534 spin_unlock(&sb_lock);
535 return 0;
538 * umounted, drop rwsem again and fall through to failure
540 up_read(&sb->s_umount);
543 sb->s_count--;
544 spin_unlock(&sb_lock);
545 return 1;
548 static void unpin_sb_for_writeback(struct writeback_control *wbc,
549 struct inode *inode)
551 struct super_block *sb = inode->i_sb;
553 if (wbc->sync_mode == WB_SYNC_ALL)
554 return;
556 up_read(&sb->s_umount);
557 put_super(sb);
560 static void writeback_inodes_wb(struct bdi_writeback *wb,
561 struct writeback_control *wbc)
563 struct super_block *sb = wbc->sb;
564 const int is_blkdev_sb = sb_is_blkdev_sb(sb);
565 const unsigned long start = jiffies; /* livelock avoidance */
567 spin_lock(&inode_lock);
569 if (!wbc->for_kupdate || list_empty(&wb->b_io))
570 queue_io(wb, wbc->older_than_this);
572 while (!list_empty(&wb->b_io)) {
573 struct inode *inode = list_entry(wb->b_io.prev,
574 struct inode, i_list);
575 long pages_skipped;
578 * super block given and doesn't match, skip this inode
580 if (sb && sb != inode->i_sb) {
581 redirty_tail(inode);
582 continue;
585 if (!bdi_cap_writeback_dirty(wb->bdi)) {
586 redirty_tail(inode);
587 if (is_blkdev_sb) {
589 * Dirty memory-backed blockdev: the ramdisk
590 * driver does this. Skip just this inode
592 continue;
595 * Dirty memory-backed inode against a filesystem other
596 * than the kernel-internal bdev filesystem. Skip the
597 * entire superblock.
599 break;
602 if (inode->i_state & (I_NEW | I_WILL_FREE)) {
603 requeue_io(inode);
604 continue;
607 if (wbc->nonblocking && bdi_write_congested(wb->bdi)) {
608 wbc->encountered_congestion = 1;
609 if (!is_blkdev_sb)
610 break; /* Skip a congested fs */
611 requeue_io(inode);
612 continue; /* Skip a congested blockdev */
616 * Was this inode dirtied after sync_sb_inodes was called?
617 * This keeps sync from extra jobs and livelock.
619 if (inode_dirtied_after(inode, start))
620 break;
622 if (pin_sb_for_writeback(wbc, inode)) {
623 requeue_io(inode);
624 continue;
627 BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
628 __iget(inode);
629 pages_skipped = wbc->pages_skipped;
630 writeback_single_inode(inode, wbc);
631 unpin_sb_for_writeback(wbc, inode);
632 if (wbc->pages_skipped != pages_skipped) {
634 * writeback is not making progress due to locked
635 * buffers. Skip this inode for now.
637 redirty_tail(inode);
639 spin_unlock(&inode_lock);
640 iput(inode);
641 cond_resched();
642 spin_lock(&inode_lock);
643 if (wbc->nr_to_write <= 0) {
644 wbc->more_io = 1;
645 break;
647 if (!list_empty(&wb->b_more_io))
648 wbc->more_io = 1;
651 spin_unlock(&inode_lock);
652 /* Leave any unwritten inodes on b_io */
655 void writeback_inodes_wbc(struct writeback_control *wbc)
657 struct backing_dev_info *bdi = wbc->bdi;
659 writeback_inodes_wb(&bdi->wb, wbc);
663 * The maximum number of pages to writeout in a single bdi flush/kupdate
664 * operation. We do this so we don't hold I_SYNC against an inode for
665 * enormous amounts of time, which would block a userspace task which has
666 * been forced to throttle against that inode. Also, the code reevaluates
667 * the dirty each time it has written this many pages.
669 #define MAX_WRITEBACK_PAGES 1024
671 static inline bool over_bground_thresh(void)
673 unsigned long background_thresh, dirty_thresh;
675 get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
677 return (global_page_state(NR_FILE_DIRTY) +
678 global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
682 * Explicit flushing or periodic writeback of "old" data.
684 * Define "old": the first time one of an inode's pages is dirtied, we mark the
685 * dirtying-time in the inode's address_space. So this periodic writeback code
686 * just walks the superblock inode list, writing back any inodes which are
687 * older than a specific point in time.
689 * Try to run once per dirty_writeback_interval. But if a writeback event
690 * takes longer than a dirty_writeback_interval interval, then leave a
691 * one-second gap.
693 * older_than_this takes precedence over nr_to_write. So we'll only write back
694 * all dirty pages if they are all attached to "old" mappings.
696 static long wb_writeback(struct bdi_writeback *wb,
697 struct wb_writeback_args *args)
699 struct writeback_control wbc = {
700 .bdi = wb->bdi,
701 .sb = args->sb,
702 .sync_mode = args->sync_mode,
703 .older_than_this = NULL,
704 .for_kupdate = args->for_kupdate,
705 .range_cyclic = args->range_cyclic,
707 unsigned long oldest_jif;
708 long wrote = 0;
710 if (wbc.for_kupdate) {
711 wbc.older_than_this = &oldest_jif;
712 oldest_jif = jiffies -
713 msecs_to_jiffies(dirty_expire_interval * 10);
715 if (!wbc.range_cyclic) {
716 wbc.range_start = 0;
717 wbc.range_end = LLONG_MAX;
720 for (;;) {
722 * Don't flush anything for non-integrity writeback where
723 * no nr_pages was given
725 if (!args->for_kupdate && args->nr_pages <= 0 &&
726 args->sync_mode == WB_SYNC_NONE)
727 break;
730 * If no specific pages were given and this is just a
731 * periodic background writeout and we are below the
732 * background dirty threshold, don't do anything
734 if (args->for_kupdate && args->nr_pages <= 0 &&
735 !over_bground_thresh())
736 break;
738 wbc.more_io = 0;
739 wbc.encountered_congestion = 0;
740 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
741 wbc.pages_skipped = 0;
742 writeback_inodes_wb(wb, &wbc);
743 args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
744 wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
747 * If we ran out of stuff to write, bail unless more_io got set
749 if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
750 if (wbc.more_io && !wbc.for_kupdate)
751 continue;
752 break;
756 return wrote;
760 * Return the next bdi_work struct that hasn't been processed by this
761 * wb thread yet. ->seen is initially set for each thread that exists
762 * for this device, when a thread first notices a piece of work it
763 * clears its bit. Depending on writeback type, the thread will notify
764 * completion on either receiving the work (WB_SYNC_NONE) or after
765 * it is done (WB_SYNC_ALL).
767 static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
768 struct bdi_writeback *wb)
770 struct bdi_work *work, *ret = NULL;
772 rcu_read_lock();
774 list_for_each_entry_rcu(work, &bdi->work_list, list) {
775 if (!test_bit(wb->nr, &work->seen))
776 continue;
777 clear_bit(wb->nr, &work->seen);
779 ret = work;
780 break;
783 rcu_read_unlock();
784 return ret;
787 static long wb_check_old_data_flush(struct bdi_writeback *wb)
789 unsigned long expired;
790 long nr_pages;
792 expired = wb->last_old_flush +
793 msecs_to_jiffies(dirty_writeback_interval * 10);
794 if (time_before(jiffies, expired))
795 return 0;
797 wb->last_old_flush = jiffies;
798 nr_pages = global_page_state(NR_FILE_DIRTY) +
799 global_page_state(NR_UNSTABLE_NFS) +
800 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
802 if (nr_pages) {
803 struct wb_writeback_args args = {
804 .nr_pages = nr_pages,
805 .sync_mode = WB_SYNC_NONE,
806 .for_kupdate = 1,
807 .range_cyclic = 1,
810 return wb_writeback(wb, &args);
813 return 0;
817 * Retrieve work items and do the writeback they describe
819 long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
821 struct backing_dev_info *bdi = wb->bdi;
822 struct bdi_work *work;
823 long wrote = 0;
825 while ((work = get_next_work_item(bdi, wb)) != NULL) {
826 struct wb_writeback_args args = work->args;
829 * Override sync mode, in case we must wait for completion
831 if (force_wait)
832 work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
835 * If this isn't a data integrity operation, just notify
836 * that we have seen this work and we are now starting it.
838 if (args.sync_mode == WB_SYNC_NONE)
839 wb_clear_pending(wb, work);
841 wrote += wb_writeback(wb, &args);
844 * This is a data integrity writeback, so only do the
845 * notification when we have completed the work.
847 if (args.sync_mode == WB_SYNC_ALL)
848 wb_clear_pending(wb, work);
852 * Check for periodic writeback, kupdated() style
854 wrote += wb_check_old_data_flush(wb);
856 return wrote;
860 * Handle writeback of dirty data for the device backed by this bdi. Also
861 * wakes up periodically and does kupdated style flushing.
863 int bdi_writeback_task(struct bdi_writeback *wb)
865 unsigned long last_active = jiffies;
866 unsigned long wait_jiffies = -1UL;
867 long pages_written;
869 while (!kthread_should_stop()) {
870 pages_written = wb_do_writeback(wb, 0);
872 if (pages_written)
873 last_active = jiffies;
874 else if (wait_jiffies != -1UL) {
875 unsigned long max_idle;
878 * Longest period of inactivity that we tolerate. If we
879 * see dirty data again later, the task will get
880 * recreated automatically.
882 max_idle = max(5UL * 60 * HZ, wait_jiffies);
883 if (time_after(jiffies, max_idle + last_active))
884 break;
887 wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
888 schedule_timeout_interruptible(wait_jiffies);
889 try_to_freeze();
892 return 0;
896 * Schedule writeback for all backing devices. This does WB_SYNC_NONE
897 * writeback, for integrity writeback see bdi_sync_writeback().
899 static void bdi_writeback_all(struct super_block *sb, long nr_pages)
901 struct wb_writeback_args args = {
902 .sb = sb,
903 .nr_pages = nr_pages,
904 .sync_mode = WB_SYNC_NONE,
906 struct backing_dev_info *bdi;
908 rcu_read_lock();
910 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
911 if (!bdi_has_dirty_io(bdi))
912 continue;
914 bdi_alloc_queue_work(bdi, &args);
917 rcu_read_unlock();
921 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
922 * the whole world.
924 void wakeup_flusher_threads(long nr_pages)
926 if (nr_pages == 0)
927 nr_pages = global_page_state(NR_FILE_DIRTY) +
928 global_page_state(NR_UNSTABLE_NFS);
929 bdi_writeback_all(NULL, nr_pages);
932 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
934 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
935 struct dentry *dentry;
936 const char *name = "?";
938 dentry = d_find_alias(inode);
939 if (dentry) {
940 spin_lock(&dentry->d_lock);
941 name = (const char *) dentry->d_name.name;
943 printk(KERN_DEBUG
944 "%s(%d): dirtied inode %lu (%s) on %s\n",
945 current->comm, task_pid_nr(current), inode->i_ino,
946 name, inode->i_sb->s_id);
947 if (dentry) {
948 spin_unlock(&dentry->d_lock);
949 dput(dentry);
955 * __mark_inode_dirty - internal function
956 * @inode: inode to mark
957 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
958 * Mark an inode as dirty. Callers should use mark_inode_dirty or
959 * mark_inode_dirty_sync.
961 * Put the inode on the super block's dirty list.
963 * CAREFUL! We mark it dirty unconditionally, but move it onto the
964 * dirty list only if it is hashed or if it refers to a blockdev.
965 * If it was not hashed, it will never be added to the dirty list
966 * even if it is later hashed, as it will have been marked dirty already.
968 * In short, make sure you hash any inodes _before_ you start marking
969 * them dirty.
971 * This function *must* be atomic for the I_DIRTY_PAGES case -
972 * set_page_dirty() is called under spinlock in several places.
974 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
975 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
976 * the kernel-internal blockdev inode represents the dirtying time of the
977 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
978 * page->mapping->host, so the page-dirtying time is recorded in the internal
979 * blockdev inode.
981 void __mark_inode_dirty(struct inode *inode, int flags)
983 struct super_block *sb = inode->i_sb;
986 * Don't do this for I_DIRTY_PAGES - that doesn't actually
987 * dirty the inode itself
989 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
990 if (sb->s_op->dirty_inode)
991 sb->s_op->dirty_inode(inode);
995 * make sure that changes are seen by all cpus before we test i_state
996 * -- mikulas
998 smp_mb();
1000 /* avoid the locking if we can */
1001 if ((inode->i_state & flags) == flags)
1002 return;
1004 if (unlikely(block_dump))
1005 block_dump___mark_inode_dirty(inode);
1007 spin_lock(&inode_lock);
1008 if ((inode->i_state & flags) != flags) {
1009 const int was_dirty = inode->i_state & I_DIRTY;
1011 inode->i_state |= flags;
1014 * If the inode is being synced, just update its dirty state.
1015 * The unlocker will place the inode on the appropriate
1016 * superblock list, based upon its state.
1018 if (inode->i_state & I_SYNC)
1019 goto out;
1022 * Only add valid (hashed) inodes to the superblock's
1023 * dirty list. Add blockdev inodes as well.
1025 if (!S_ISBLK(inode->i_mode)) {
1026 if (hlist_unhashed(&inode->i_hash))
1027 goto out;
1029 if (inode->i_state & (I_FREEING|I_CLEAR))
1030 goto out;
1033 * If the inode was already on b_dirty/b_io/b_more_io, don't
1034 * reposition it (that would break b_dirty time-ordering).
1036 if (!was_dirty) {
1037 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
1038 struct backing_dev_info *bdi = wb->bdi;
1040 if (bdi_cap_writeback_dirty(bdi) &&
1041 !test_bit(BDI_registered, &bdi->state)) {
1042 WARN_ON(1);
1043 printk(KERN_ERR "bdi-%s not registered\n",
1044 bdi->name);
1047 inode->dirtied_when = jiffies;
1048 list_move(&inode->i_list, &wb->b_dirty);
1051 out:
1052 spin_unlock(&inode_lock);
1054 EXPORT_SYMBOL(__mark_inode_dirty);
1057 * Write out a superblock's list of dirty inodes. A wait will be performed
1058 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1060 * If older_than_this is non-NULL, then only write out inodes which
1061 * had their first dirtying at a time earlier than *older_than_this.
1063 * If we're a pdlfush thread, then implement pdflush collision avoidance
1064 * against the entire list.
1066 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1067 * This function assumes that the blockdev superblock's inodes are backed by
1068 * a variety of queues, so all inodes are searched. For other superblocks,
1069 * assume that all inodes are backed by the same queue.
1071 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1072 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1073 * on the writer throttling path, and we get decent balancing between many
1074 * throttled threads: we don't want them all piling up on inode_sync_wait.
1076 static void wait_sb_inodes(struct super_block *sb)
1078 struct inode *inode, *old_inode = NULL;
1081 * We need to be protected against the filesystem going from
1082 * r/o to r/w or vice versa.
1084 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1086 spin_lock(&inode_lock);
1089 * Data integrity sync. Must wait for all pages under writeback,
1090 * because there may have been pages dirtied before our sync
1091 * call, but which had writeout started before we write it out.
1092 * In which case, the inode may not be on the dirty list, but
1093 * we still have to wait for that writeout.
1095 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
1096 struct address_space *mapping;
1098 if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
1099 continue;
1100 mapping = inode->i_mapping;
1101 if (mapping->nrpages == 0)
1102 continue;
1103 __iget(inode);
1104 spin_unlock(&inode_lock);
1106 * We hold a reference to 'inode' so it couldn't have
1107 * been removed from s_inodes list while we dropped the
1108 * inode_lock. We cannot iput the inode now as we can
1109 * be holding the last reference and we cannot iput it
1110 * under inode_lock. So we keep the reference and iput
1111 * it later.
1113 iput(old_inode);
1114 old_inode = inode;
1116 filemap_fdatawait(mapping);
1118 cond_resched();
1120 spin_lock(&inode_lock);
1122 spin_unlock(&inode_lock);
1123 iput(old_inode);
1127 * writeback_inodes_sb - writeback dirty inodes from given super_block
1128 * @sb: the superblock
1130 * Start writeback on some inodes on this super_block. No guarantees are made
1131 * on how many (if any) will be written, and this function does not wait
1132 * for IO completion of submitted IO. The number of pages submitted is
1133 * returned.
1135 void writeback_inodes_sb(struct super_block *sb)
1137 unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
1138 unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
1139 long nr_to_write;
1141 nr_to_write = nr_dirty + nr_unstable +
1142 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
1144 bdi_writeback_all(sb, nr_to_write);
1146 EXPORT_SYMBOL(writeback_inodes_sb);
1149 * sync_inodes_sb - sync sb inode pages
1150 * @sb: the superblock
1152 * This function writes and waits on any dirty inode belonging to this
1153 * super_block. The number of pages synced is returned.
1155 void sync_inodes_sb(struct super_block *sb)
1157 bdi_sync_writeback(sb->s_bdi, sb);
1158 wait_sb_inodes(sb);
1160 EXPORT_SYMBOL(sync_inodes_sb);
1163 * write_inode_now - write an inode to disk
1164 * @inode: inode to write to disk
1165 * @sync: whether the write should be synchronous or not
1167 * This function commits an inode to disk immediately if it is dirty. This is
1168 * primarily needed by knfsd.
1170 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
1172 int write_inode_now(struct inode *inode, int sync)
1174 int ret;
1175 struct writeback_control wbc = {
1176 .nr_to_write = LONG_MAX,
1177 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
1178 .range_start = 0,
1179 .range_end = LLONG_MAX,
1182 if (!mapping_cap_writeback_dirty(inode->i_mapping))
1183 wbc.nr_to_write = 0;
1185 might_sleep();
1186 spin_lock(&inode_lock);
1187 ret = writeback_single_inode(inode, &wbc);
1188 spin_unlock(&inode_lock);
1189 if (sync)
1190 inode_sync_wait(inode);
1191 return ret;
1193 EXPORT_SYMBOL(write_inode_now);
1196 * sync_inode - write an inode and its pages to disk.
1197 * @inode: the inode to sync
1198 * @wbc: controls the writeback mode
1200 * sync_inode() will write an inode and its pages to disk. It will also
1201 * correctly update the inode on its superblock's dirty inode lists and will
1202 * update inode->i_state.
1204 * The caller must have a ref on the inode.
1206 int sync_inode(struct inode *inode, struct writeback_control *wbc)
1208 int ret;
1210 spin_lock(&inode_lock);
1211 ret = writeback_single_inode(inode, wbc);
1212 spin_unlock(&inode_lock);
1213 return ret;
1215 EXPORT_SYMBOL(sync_inode);