2 * Copyright (c) 2008 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * $DragonFly: src/sys/vfs/hammer/hammer_flusher.c,v 1.40.2.3 2008/07/18 00:21:09 dillon Exp $
37 * HAMMER dependancy flusher thread
39 * Meta data updates create buffer dependancies which are arranged as a
45 static void hammer_flusher_master_thread(void *arg
);
46 static void hammer_flusher_slave_thread(void *arg
);
47 static void hammer_flusher_flush(hammer_mount_t hmp
);
48 static void hammer_flusher_flush_inode(hammer_inode_t ip
,
49 hammer_transaction_t trans
);
52 * Support structures for the flusher threads.
54 struct hammer_flusher_info
{
55 TAILQ_ENTRY(hammer_flusher_info
) entry
;
56 struct hammer_mount
*hmp
;
60 hammer_flush_group_t flg
;
61 hammer_inode_t work_array
[HAMMER_FLUSH_GROUP_SIZE
];
64 typedef struct hammer_flusher_info
*hammer_flusher_info_t
;
67 * Sync all inodes pending on the flusher.
69 * All flush groups will be flushed. This does not queue dirty inodes
70 * to the flush groups, it just flushes out what has already been queued!
73 hammer_flusher_sync(hammer_mount_t hmp
)
77 seq
= hammer_flusher_async(hmp
, NULL
);
78 while ((int)(seq
- hmp
->flusher
.done
) > 0)
79 tsleep(&hmp
->flusher
.done
, 0, "hmrfls", 0);
83 * Sync all inodes pending on the flusher - return immediately.
85 * All flush groups will be flushed.
88 hammer_flusher_async(hammer_mount_t hmp
, hammer_flush_group_t close_flg
)
90 hammer_flush_group_t flg
;
91 int seq
= hmp
->flusher
.next
;
93 TAILQ_FOREACH(flg
, &hmp
->flush_group_list
, flush_entry
) {
94 if (flg
->running
== 0)
100 if (hmp
->flusher
.td
) {
101 if (hmp
->flusher
.signal
++ == 0)
102 wakeup(&hmp
->flusher
.signal
);
104 seq
= hmp
->flusher
.done
;
110 hammer_flusher_async_one(hammer_mount_t hmp
)
114 if (hmp
->flusher
.td
) {
115 seq
= hmp
->flusher
.next
;
116 if (hmp
->flusher
.signal
++ == 0)
117 wakeup(&hmp
->flusher
.signal
);
119 seq
= hmp
->flusher
.done
;
125 hammer_flusher_wait(hammer_mount_t hmp
, int seq
)
127 while ((int)(seq
- hmp
->flusher
.done
) > 0) {
128 tsleep(&hmp
->flusher
.done
, 0, "hmrfls", 0);
133 hammer_flusher_create(hammer_mount_t hmp
)
135 hammer_flusher_info_t info
;
138 hmp
->flusher
.signal
= 0;
139 hmp
->flusher
.act
= 0;
140 hmp
->flusher
.done
= 0;
141 hmp
->flusher
.next
= 1;
142 hammer_ref(&hmp
->flusher
.finalize_lock
);
143 TAILQ_INIT(&hmp
->flusher
.run_list
);
144 TAILQ_INIT(&hmp
->flusher
.ready_list
);
146 lwkt_create(hammer_flusher_master_thread
, hmp
,
147 &hmp
->flusher
.td
, NULL
, 0, -1, "hammer-M");
148 for (i
= 0; i
< HAMMER_MAX_FLUSHERS
; ++i
) {
149 info
= kmalloc(sizeof(*info
), M_HAMMER
, M_WAITOK
|M_ZERO
);
151 TAILQ_INSERT_TAIL(&hmp
->flusher
.ready_list
, info
, entry
);
152 lwkt_create(hammer_flusher_slave_thread
, info
,
153 &info
->td
, NULL
, 0, -1, "hammer-S%d", i
);
158 hammer_flusher_destroy(hammer_mount_t hmp
)
160 hammer_flusher_info_t info
;
165 hmp
->flusher
.exiting
= 1;
166 while (hmp
->flusher
.td
) {
167 ++hmp
->flusher
.signal
;
168 wakeup(&hmp
->flusher
.signal
);
169 tsleep(&hmp
->flusher
.exiting
, 0, "hmrwex", hz
);
175 while ((info
= TAILQ_FIRST(&hmp
->flusher
.ready_list
)) != NULL
) {
176 KKASSERT(info
->runstate
== 0);
177 TAILQ_REMOVE(&hmp
->flusher
.ready_list
, info
, entry
);
179 wakeup(&info
->runstate
);
181 tsleep(&info
->td
, 0, "hmrwwc", 0);
182 TAILQ_REMOVE(&hmp
->flusher
.ready_list
, info
, entry
);
183 kfree(info
, M_HAMMER
);
188 * The master flusher thread manages the flusher sequence id and
189 * synchronization with the slave work threads.
192 hammer_flusher_master_thread(void *arg
)
194 hammer_flush_group_t flg
;
201 * Do at least one flush cycle. We may have to update the
202 * UNDO FIFO even if no inodes are queued.
205 while (hmp
->flusher
.group_lock
)
206 tsleep(&hmp
->flusher
.group_lock
, 0, "hmrhld", 0);
207 hmp
->flusher
.act
= hmp
->flusher
.next
;
209 hammer_flusher_clean_loose_ios(hmp
);
210 hammer_flusher_flush(hmp
);
211 hmp
->flusher
.done
= hmp
->flusher
.act
;
212 wakeup(&hmp
->flusher
.done
);
213 flg
= TAILQ_FIRST(&hmp
->flush_group_list
);
214 if (flg
== NULL
|| flg
->closed
== 0)
216 if (hmp
->flags
& HAMMER_MOUNT_CRITICAL_ERROR
)
223 if (hmp
->flusher
.exiting
&& TAILQ_EMPTY(&hmp
->flush_group_list
))
225 while (hmp
->flusher
.signal
== 0)
226 tsleep(&hmp
->flusher
.signal
, 0, "hmrwwa", 0);
227 hmp
->flusher
.signal
= 0;
233 hmp
->flusher
.td
= NULL
;
234 wakeup(&hmp
->flusher
.exiting
);
239 * Flush all inodes in the current flush group.
242 hammer_flusher_flush(hammer_mount_t hmp
)
244 hammer_flusher_info_t info
;
245 hammer_flush_group_t flg
;
246 hammer_reserve_t resv
;
248 hammer_inode_t next_ip
;
253 * Just in-case there's a flush race on mount
255 if (TAILQ_FIRST(&hmp
->flusher
.ready_list
) == NULL
)
259 * We only do one flg but we may have to loop/retry.
262 while ((flg
= TAILQ_FIRST(&hmp
->flush_group_list
)) != NULL
) {
264 if (hammer_debug_general
& 0x0001) {
265 kprintf("hammer_flush %d ttl=%d recs=%d\n",
267 flg
->total_count
, flg
->refs
);
269 if (hmp
->flags
& HAMMER_MOUNT_CRITICAL_ERROR
)
271 hammer_start_transaction_fls(&hmp
->flusher
.trans
, hmp
);
274 * If the previous flush cycle just about exhausted our
275 * UNDO space we may have to do a dummy cycle to move the
276 * first_offset up before actually digging into a new cycle,
277 * or the new cycle will not have sufficient undo space.
279 if (hammer_flusher_undo_exhausted(&hmp
->flusher
.trans
, 3))
280 hammer_flusher_finalize(&hmp
->flusher
.trans
, 0);
283 * Ok, we are running this flush group now (this prevents new
287 if (hmp
->next_flush_group
== flg
)
288 hmp
->next_flush_group
= TAILQ_NEXT(flg
, flush_entry
);
291 * Iterate the inodes in the flg's flush_list and assign
295 info
= TAILQ_FIRST(&hmp
->flusher
.ready_list
);
296 next_ip
= TAILQ_FIRST(&flg
->flush_list
);
298 while ((ip
= next_ip
) != NULL
) {
299 next_ip
= TAILQ_NEXT(ip
, flush_entry
);
302 * Add ip to the slave's work array. The slave is
303 * not currently running.
305 info
->work_array
[info
->count
++] = ip
;
306 if (info
->count
!= HAMMER_FLUSH_GROUP_SIZE
)
310 * Get the slave running
312 TAILQ_REMOVE(&hmp
->flusher
.ready_list
, info
, entry
);
313 TAILQ_INSERT_TAIL(&hmp
->flusher
.run_list
, info
, entry
);
316 wakeup(&info
->runstate
);
319 * Get a new slave. We may have to wait for one to
322 while ((info
= TAILQ_FIRST(&hmp
->flusher
.ready_list
)) == NULL
) {
323 tsleep(&hmp
->flusher
.ready_list
, 0, "hmrfcc", 0);
328 * Run the current slave if necessary
331 TAILQ_REMOVE(&hmp
->flusher
.ready_list
, info
, entry
);
332 TAILQ_INSERT_TAIL(&hmp
->flusher
.run_list
, info
, entry
);
335 wakeup(&info
->runstate
);
339 * Wait for all slaves to finish running
341 while (TAILQ_FIRST(&hmp
->flusher
.run_list
) != NULL
)
342 tsleep(&hmp
->flusher
.ready_list
, 0, "hmrfcc", 0);
345 * Do the final finalization, clean up
347 hammer_flusher_finalize(&hmp
->flusher
.trans
, 1);
348 hmp
->flusher
.tid
= hmp
->flusher
.trans
.tid
;
350 hammer_done_transaction(&hmp
->flusher
.trans
);
353 * Loop up on the same flg. If the flg is done clean it up
354 * and break out. We only flush one flg.
356 if (TAILQ_FIRST(&flg
->flush_list
) == NULL
) {
357 KKASSERT(TAILQ_EMPTY(&flg
->flush_list
));
358 KKASSERT(flg
->refs
== 0);
359 TAILQ_REMOVE(&hmp
->flush_group_list
, flg
, flush_entry
);
360 kfree(flg
, M_HAMMER
);
366 * We may have pure meta-data to flush, or we may have to finish
367 * cycling the UNDO FIFO, even if there were no flush groups.
369 if (count
== 0 && hammer_flusher_haswork(hmp
)) {
370 hammer_start_transaction_fls(&hmp
->flusher
.trans
, hmp
);
371 hammer_flusher_finalize(&hmp
->flusher
.trans
, 1);
372 hammer_done_transaction(&hmp
->flusher
.trans
);
376 * Clean up any freed big-blocks (typically zone-2).
377 * resv->flush_group is typically set several flush groups ahead
378 * of the free to ensure that the freed block is not reused until
379 * it can no longer be reused.
381 while ((resv
= TAILQ_FIRST(&hmp
->delay_list
)) != NULL
) {
382 if (resv
->flush_group
!= hmp
->flusher
.act
)
384 hammer_reserve_clrdelay(hmp
, resv
);
390 * The slave flusher thread pulls work off the master flush_list until no
394 hammer_flusher_slave_thread(void *arg
)
396 hammer_flush_group_t flg
;
397 hammer_flusher_info_t info
;
406 while (info
->runstate
== 0)
407 tsleep(&info
->runstate
, 0, "hmrssw", 0);
408 if (info
->runstate
< 0)
412 for (i
= 0; i
< info
->count
; ++i
) {
413 ip
= info
->work_array
[i
];
414 hammer_flusher_flush_inode(ip
, &hmp
->flusher
.trans
);
415 ++hammer_stats_inode_flushes
;
419 TAILQ_REMOVE(&hmp
->flusher
.run_list
, info
, entry
);
420 TAILQ_INSERT_TAIL(&hmp
->flusher
.ready_list
, info
, entry
);
421 wakeup(&hmp
->flusher
.ready_list
);
429 hammer_flusher_clean_loose_ios(hammer_mount_t hmp
)
431 hammer_buffer_t buffer
;
435 * loose ends - buffers without bp's aren't tracked by the kernel
436 * and can build up, so clean them out. This can occur when an
437 * IO completes on a buffer with no references left.
439 if ((io
= TAILQ_FIRST(&hmp
->lose_list
)) != NULL
) {
440 crit_enter(); /* biodone() race */
441 while ((io
= TAILQ_FIRST(&hmp
->lose_list
)) != NULL
) {
442 KKASSERT(io
->mod_list
== &hmp
->lose_list
);
443 TAILQ_REMOVE(&hmp
->lose_list
, io
, mod_entry
);
445 if (io
->lock
.refs
== 0)
446 ++hammer_count_refedbufs
;
447 hammer_ref(&io
->lock
);
449 hammer_rel_buffer(buffer
, 0);
456 * Flush a single inode that is part of a flush group.
458 * Flusher errors are extremely serious, even ENOSPC shouldn't occur because
459 * the front-end should have reserved sufficient space on the media. Any
460 * error other then EWOULDBLOCK will force the mount to be read-only.
464 hammer_flusher_flush_inode(hammer_inode_t ip
, hammer_transaction_t trans
)
466 hammer_mount_t hmp
= ip
->hmp
;
469 hammer_flusher_clean_loose_ios(hmp
);
470 error
= hammer_sync_inode(trans
, ip
);
473 * EWOULDBLOCK can happen under normal operation, all other errors
474 * are considered extremely serious. We must set WOULDBLOCK
475 * mechanics to deal with the mess left over from the abort of the
479 ip
->flags
|= HAMMER_INODE_WOULDBLOCK
;
480 if (error
== EWOULDBLOCK
)
483 hammer_flush_inode_done(ip
, error
);
484 while (hmp
->flusher
.finalize_want
)
485 tsleep(&hmp
->flusher
.finalize_want
, 0, "hmrsxx", 0);
486 if (hammer_flusher_undo_exhausted(trans
, 1)) {
487 kprintf("HAMMER: Warning: UNDO area too small!\n");
488 hammer_flusher_finalize(trans
, 1);
489 } else if (hammer_flusher_meta_limit(trans
->hmp
)) {
490 hammer_flusher_finalize(trans
, 0);
495 * Return non-zero if the UNDO area has less then (QUARTER / 4) of its
498 * 1/4 - Emergency free undo space level. Below this point the flusher
499 * will finalize even if directory dependancies have not been resolved.
501 * 2/4 - Used by the pruning and reblocking code. These functions may be
502 * running in parallel with a flush and cannot be allowed to drop
503 * available undo space to emergency levels.
505 * 3/4 - Used at the beginning of a flush to force-sync the volume header
506 * to give the flush plenty of runway to work in.
509 hammer_flusher_undo_exhausted(hammer_transaction_t trans
, int quarter
)
511 if (hammer_undo_space(trans
) <
512 hammer_undo_max(trans
->hmp
) * quarter
/ 4) {
520 * Flush all pending UNDOs, wait for write completion, update the volume
521 * header with the new UNDO end position, and flush it. Then
522 * asynchronously flush the meta-data.
524 * If this is the last finalization in a flush group we also synchronize
525 * our cached blockmap and set hmp->flusher_undo_start and our cached undo
526 * fifo first_offset so the next flush resets the FIFO pointers.
528 * If this is not final it is being called because too many dirty meta-data
529 * buffers have built up and must be flushed with UNDO synchronization to
530 * avoid a buffer cache deadlock.
533 hammer_flusher_finalize(hammer_transaction_t trans
, int final
)
535 hammer_volume_t root_volume
;
536 hammer_blockmap_t cundomap
, dundomap
;
543 root_volume
= trans
->rootvol
;
546 * Exclusively lock the flusher. This guarantees that all dirty
547 * buffers will be idled (have a mod-count of 0).
549 ++hmp
->flusher
.finalize_want
;
550 hammer_lock_ex(&hmp
->flusher
.finalize_lock
);
553 * If this isn't the final sync several threads may have hit the
554 * meta-limit at the same time and raced. Only sync if we really
555 * have to, after acquiring the lock.
557 if (final
== 0 && !hammer_flusher_meta_limit(hmp
))
560 if (hmp
->flags
& HAMMER_MOUNT_CRITICAL_ERROR
)
564 * Flush data buffers. This can occur asynchronously and at any
565 * time. We must interlock against the frontend direct-data write
566 * but do not have to acquire the sync-lock yet.
569 while ((io
= TAILQ_FIRST(&hmp
->data_list
)) != NULL
) {
572 if (io
->lock
.refs
== 0)
573 ++hammer_count_refedbufs
;
574 hammer_ref(&io
->lock
);
575 hammer_io_write_interlock(io
);
576 KKASSERT(io
->type
!= HAMMER_STRUCTURE_VOLUME
);
578 hammer_io_done_interlock(io
);
579 hammer_rel_buffer((hammer_buffer_t
)io
, 0);
584 * The sync-lock is required for the remaining sequence. This lock
585 * prevents meta-data from being modified.
587 hammer_sync_lock_ex(trans
);
590 * If we have been asked to finalize the volume header sync the
591 * cached blockmap to the on-disk blockmap. Generate an UNDO
592 * record for the update.
595 cundomap
= &hmp
->blockmap
[0];
596 dundomap
= &root_volume
->ondisk
->vol0_blockmap
[0];
597 if (root_volume
->io
.modified
) {
598 hammer_modify_volume(trans
, root_volume
,
599 dundomap
, sizeof(hmp
->blockmap
));
600 for (i
= 0; i
< HAMMER_MAX_ZONES
; ++i
)
601 hammer_crc_set_blockmap(&cundomap
[i
]);
602 bcopy(cundomap
, dundomap
, sizeof(hmp
->blockmap
));
603 hammer_modify_volume_done(root_volume
);
611 while ((io
= TAILQ_FIRST(&hmp
->undo_list
)) != NULL
) {
614 KKASSERT(io
->modify_refs
== 0);
615 if (io
->lock
.refs
== 0)
616 ++hammer_count_refedbufs
;
617 hammer_ref(&io
->lock
);
618 KKASSERT(io
->type
!= HAMMER_STRUCTURE_VOLUME
);
620 hammer_rel_buffer((hammer_buffer_t
)io
, 0);
625 * Wait for I/Os to complete
627 hammer_flusher_clean_loose_ios(hmp
);
628 hammer_io_wait_all(hmp
, "hmrfl1");
630 if (hmp
->flags
& HAMMER_MOUNT_CRITICAL_ERROR
)
634 * Update the on-disk volume header with new UNDO FIFO end position
635 * (do not generate new UNDO records for this change). We have to
636 * do this for the UNDO FIFO whether (final) is set or not.
638 * Also update the on-disk next_tid field. This does not require
639 * an UNDO. However, because our TID is generated before we get
640 * the sync lock another sync may have beat us to the punch.
642 * This also has the side effect of updating first_offset based on
643 * a prior finalization when the first finalization of the next flush
644 * cycle occurs, removing any undo info from the prior finalization
645 * from consideration.
647 * The volume header will be flushed out synchronously.
649 dundomap
= &root_volume
->ondisk
->vol0_blockmap
[HAMMER_ZONE_UNDO_INDEX
];
650 cundomap
= &hmp
->blockmap
[HAMMER_ZONE_UNDO_INDEX
];
652 if (dundomap
->first_offset
!= cundomap
->first_offset
||
653 dundomap
->next_offset
!= cundomap
->next_offset
) {
654 hammer_modify_volume(NULL
, root_volume
, NULL
, 0);
655 dundomap
->first_offset
= cundomap
->first_offset
;
656 dundomap
->next_offset
= cundomap
->next_offset
;
657 hammer_crc_set_blockmap(dundomap
);
658 hammer_modify_volume_done(root_volume
);
661 if (root_volume
->io
.modified
) {
662 hammer_modify_volume(NULL
, root_volume
, NULL
, 0);
663 if (root_volume
->ondisk
->vol0_next_tid
< trans
->tid
)
664 root_volume
->ondisk
->vol0_next_tid
= trans
->tid
;
665 hammer_crc_set_volume(root_volume
->ondisk
);
666 hammer_modify_volume_done(root_volume
);
667 hammer_io_flush(&root_volume
->io
);
671 * Wait for I/Os to complete
673 hammer_flusher_clean_loose_ios(hmp
);
674 hammer_io_wait_all(hmp
, "hmrfl2");
676 if (hmp
->flags
& HAMMER_MOUNT_CRITICAL_ERROR
)
680 * Flush meta-data. The meta-data will be undone if we crash
681 * so we can safely flush it asynchronously.
683 * Repeated catchups will wind up flushing this update's meta-data
684 * and the UNDO buffers for the next update simultaniously. This
688 while ((io
= TAILQ_FIRST(&hmp
->meta_list
)) != NULL
) {
691 KKASSERT(io
->modify_refs
== 0);
692 if (io
->lock
.refs
== 0)
693 ++hammer_count_refedbufs
;
694 hammer_ref(&io
->lock
);
695 KKASSERT(io
->type
!= HAMMER_STRUCTURE_VOLUME
);
697 hammer_rel_buffer((hammer_buffer_t
)io
, 0);
702 * If this is the final finalization for the flush group set
703 * up for the next sequence by setting a new first_offset in
704 * our cached blockmap and clearing the undo history.
706 * Even though we have updated our cached first_offset, the on-disk
707 * first_offset still governs available-undo-space calculations.
710 cundomap
= &hmp
->blockmap
[HAMMER_ZONE_UNDO_INDEX
];
711 if (cundomap
->first_offset
== cundomap
->next_offset
) {
712 hmp
->hflags
&= ~HMNT_UNDO_DIRTY
;
714 cundomap
->first_offset
= cundomap
->next_offset
;
715 hmp
->hflags
|= HMNT_UNDO_DIRTY
;
717 hammer_clear_undo_history(hmp
);
721 * Cleanup. Report any critical errors.
724 hammer_sync_unlock(trans
);
726 if (hmp
->flags
& HAMMER_MOUNT_CRITICAL_ERROR
) {
727 kprintf("HAMMER(%s): Critical write error during flush, "
728 "refusing to sync UNDO FIFO\n",
729 root_volume
->ondisk
->vol_name
);
733 hammer_unlock(&hmp
->flusher
.finalize_lock
);
734 if (--hmp
->flusher
.finalize_want
== 0)
735 wakeup(&hmp
->flusher
.finalize_want
);
736 hammer_stats_commits
+= final
;
740 * Return non-zero if too many dirty meta-data buffers have built up.
742 * Since we cannot allow such buffers to flush until we have dealt with
743 * the UNDOs, we risk deadlocking the kernel's buffer cache.
746 hammer_flusher_meta_limit(hammer_mount_t hmp
)
748 if (hmp
->locked_dirty_space
+ hmp
->io_running_space
>
749 hammer_limit_dirtybufspace
) {
756 * Return non-zero if too many dirty meta-data buffers have built up.
758 * This version is used by background operations (mirror, prune, reblock)
759 * to leave room for foreground operations.
762 hammer_flusher_meta_halflimit(hammer_mount_t hmp
)
764 if (hmp
->locked_dirty_space
+ hmp
->io_running_space
>
765 hammer_limit_dirtybufspace
/ 2) {
772 * Return non-zero if the flusher still has something to flush.
775 hammer_flusher_haswork(hammer_mount_t hmp
)
777 if (hmp
->flags
& HAMMER_MOUNT_CRITICAL_ERROR
)
779 if (TAILQ_FIRST(&hmp
->flush_group_list
) || /* dirty inodes */
780 TAILQ_FIRST(&hmp
->volu_list
) || /* dirty bufffers */
781 TAILQ_FIRST(&hmp
->undo_list
) ||
782 TAILQ_FIRST(&hmp
->data_list
) ||
783 TAILQ_FIRST(&hmp
->meta_list
) ||
784 (hmp
->hflags
& HMNT_UNDO_DIRTY
) /* UNDO FIFO sync */