HAMMER 61F/Many: Stabilization w/ simultanious pruning and reblocking
[dragonfly.git] / sys / vfs / hammer / hammer_flusher.c
1 /*
2  * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
3  * 
4  * This code is derived from software contributed to The DragonFly Project
5  * by Matthew Dillon <dillon@backplane.com>
6  * 
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 
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
16  *    distribution.
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.
20  * 
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
32  * SUCH DAMAGE.
33  * 
34  * $DragonFly: src/sys/vfs/hammer/hammer_flusher.c,v 1.40 2008/07/14 03:20:49 dillon Exp $
35  */
36 /*
37  * HAMMER dependancy flusher thread
38  *
39  * Meta data updates create buffer dependancies which are arranged as a
40  * hierarchy of lists.
41  */
42
43 #include "hammer.h"
44
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);
50
51 /*
52  * Support structures for the flusher threads.
53  */
54 struct hammer_flusher_info {
55         TAILQ_ENTRY(hammer_flusher_info) entry;
56         struct hammer_mount *hmp;
57         thread_t        td;
58         int             runstate;
59         int             count;
60         hammer_flush_group_t flg;
61         hammer_inode_t  work_array[HAMMER_FLUSH_GROUP_SIZE];
62 };
63
64 typedef struct hammer_flusher_info *hammer_flusher_info_t;
65
66 /*
67  * Sync all inodes pending on the flusher.
68  *
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!
71  */
72 void
73 hammer_flusher_sync(hammer_mount_t hmp)
74 {
75         int seq;
76
77         seq = hammer_flusher_async(hmp, NULL);
78         while ((int)(seq - hmp->flusher.done) > 0)
79                 tsleep(&hmp->flusher.done, 0, "hmrfls", 0);
80 }
81
82 /*
83  * Sync all inodes pending on the flusher - return immediately.
84  *
85  * All flush groups will be flushed.
86  */
87 int
88 hammer_flusher_async(hammer_mount_t hmp, hammer_flush_group_t close_flg)
89 {
90         hammer_flush_group_t flg;
91         int seq = hmp->flusher.next;
92
93         TAILQ_FOREACH(flg, &hmp->flush_group_list, flush_entry) {
94                 if (flg->running == 0)
95                         ++seq;
96                 flg->closed = 1;
97                 if (flg == close_flg)
98                         break;
99         }
100         if (hmp->flusher.td) {
101                 if (hmp->flusher.signal++ == 0)
102                         wakeup(&hmp->flusher.signal);
103         } else {
104                 seq = hmp->flusher.done;
105         }
106         return(seq);
107 }
108
109 int
110 hammer_flusher_async_one(hammer_mount_t hmp)
111 {
112         int seq;
113
114         if (hmp->flusher.td) {
115                 seq = hmp->flusher.next;
116                 if (hmp->flusher.signal++ == 0)
117                         wakeup(&hmp->flusher.signal);
118         } else {
119                 seq = hmp->flusher.done;
120         }
121         return(seq);
122 }
123
124 void
125 hammer_flusher_wait(hammer_mount_t hmp, int seq)
126 {
127         while ((int)(seq - hmp->flusher.done) > 0)
128                 tsleep(&hmp->flusher.done, 0, "hmrfls", 0);
129 }
130
131 void
132 hammer_flusher_create(hammer_mount_t hmp)
133 {
134         hammer_flusher_info_t info;
135         int i;
136
137         hmp->flusher.signal = 0;
138         hmp->flusher.act = 0;
139         hmp->flusher.done = 0;
140         hmp->flusher.next = 1;
141         hammer_ref(&hmp->flusher.finalize_lock);
142         TAILQ_INIT(&hmp->flusher.run_list);
143         TAILQ_INIT(&hmp->flusher.ready_list);
144
145         lwkt_create(hammer_flusher_master_thread, hmp,
146                     &hmp->flusher.td, NULL, 0, -1, "hammer-M");
147         for (i = 0; i < HAMMER_MAX_FLUSHERS; ++i) {
148                 info = kmalloc(sizeof(*info), M_HAMMER, M_WAITOK|M_ZERO);
149                 info->hmp = hmp;
150                 TAILQ_INSERT_TAIL(&hmp->flusher.ready_list, info, entry);
151                 lwkt_create(hammer_flusher_slave_thread, info,
152                             &info->td, NULL, 0, -1, "hammer-S%d", i);
153         }
154 }
155
156 void
157 hammer_flusher_destroy(hammer_mount_t hmp)
158 {
159         hammer_flusher_info_t info;
160
161         /*
162          * Kill the master
163          */
164         hmp->flusher.exiting = 1;
165         while (hmp->flusher.td) {
166                 ++hmp->flusher.signal;
167                 wakeup(&hmp->flusher.signal);
168                 tsleep(&hmp->flusher.exiting, 0, "hmrwex", hz);
169         }
170
171         /*
172          * Kill the slaves
173          */
174         while ((info = TAILQ_FIRST(&hmp->flusher.ready_list)) != NULL) {
175                 KKASSERT(info->runstate == 0);
176                 TAILQ_REMOVE(&hmp->flusher.ready_list, info, entry);
177                 info->runstate = -1;
178                 wakeup(&info->runstate);
179                 while (info->td)
180                         tsleep(&info->td, 0, "hmrwwc", 0);
181                 TAILQ_REMOVE(&hmp->flusher.ready_list, info, entry);
182                 kfree(info, M_HAMMER);
183         }
184 }
185
186 /*
187  * The master flusher thread manages the flusher sequence id and
188  * synchronization with the slave work threads.
189  */
190 static void
191 hammer_flusher_master_thread(void *arg)
192 {
193         hammer_flush_group_t flg;
194         hammer_mount_t hmp;
195
196         hmp = arg;
197
198         for (;;) {
199                 /*
200                  * Do at least one flush cycle.  We may have to update the
201                  * UNDO FIFO even if no inodes are queued.
202                  */
203                 for (;;) {
204                         while (hmp->flusher.group_lock)
205                                 tsleep(&hmp->flusher.group_lock, 0, "hmrhld", 0);
206                         hmp->flusher.act = hmp->flusher.next;
207                         ++hmp->flusher.next;
208                         hammer_flusher_clean_loose_ios(hmp);
209                         hammer_flusher_flush(hmp);
210                         hmp->flusher.done = hmp->flusher.act;
211                         wakeup(&hmp->flusher.done);
212                         flg = TAILQ_FIRST(&hmp->flush_group_list);
213                         if (flg == NULL || flg->closed == 0)
214                                 break;
215                 }
216
217                 /*
218                  * Wait for activity.
219                  */
220                 if (hmp->flusher.exiting && TAILQ_EMPTY(&hmp->flush_group_list))
221                         break;
222                 while (hmp->flusher.signal == 0)
223                         tsleep(&hmp->flusher.signal, 0, "hmrwwa", 0);
224                 hmp->flusher.signal = 0;
225         }
226
227         /*
228          * And we are done.
229          */
230         hmp->flusher.td = NULL;
231         wakeup(&hmp->flusher.exiting);
232         lwkt_exit();
233 }
234
235 /*
236  * Flush all inodes in the current flush group.
237  */
238 static void
239 hammer_flusher_flush(hammer_mount_t hmp)
240 {
241         hammer_flusher_info_t info;
242         hammer_flush_group_t flg;
243         hammer_reserve_t resv;
244         hammer_inode_t ip;
245         hammer_inode_t next_ip;
246         int slave_index;
247         int count;
248
249         /*
250          * Just in-case there's a flush race on mount
251          */
252         if (TAILQ_FIRST(&hmp->flusher.ready_list) == NULL)
253                 return;
254
255         /*
256          * We only do one flg but we may have to loop/retry.
257          */
258         count = 0;
259         while ((flg = TAILQ_FIRST(&hmp->flush_group_list)) != NULL) {
260                 ++count;
261                 if (hammer_debug_general & 0x0001) {
262                         kprintf("hammer_flush %d ttl=%d recs=%d\n",
263                                 hmp->flusher.act,
264                                 flg->total_count, flg->refs);
265                 }
266                 hammer_start_transaction_fls(&hmp->flusher.trans, hmp);
267                 if (hammer_debug_general & 0x0001)
268                         kprintf("T");
269
270                 /*
271                  * If the previous flush cycle just about exhausted our
272                  * UNDO space we may have to do a dummy cycle to move the
273                  * first_offset up before actually digging into a new cycle,
274                  * or the new cycle will not have sufficient undo space.
275                  */
276                 if (hammer_flusher_undo_exhausted(&hmp->flusher.trans, 3))
277                         hammer_flusher_finalize(&hmp->flusher.trans, 0);
278
279                 /*
280                  * Iterate the inodes in the flg's flush_list and assign
281                  * them to slaves.
282                  */
283                 flg->running = 1;
284                 slave_index = 0;
285                 info = TAILQ_FIRST(&hmp->flusher.ready_list);
286                 next_ip = TAILQ_FIRST(&flg->flush_list);
287
288                 while ((ip = next_ip) != NULL) {
289                         next_ip = TAILQ_NEXT(ip, flush_entry);
290
291                         /*
292                          * Add ip to the slave's work array.  The slave is
293                          * not currently running.
294                          */
295                         info->work_array[info->count++] = ip;
296                         if (info->count != HAMMER_FLUSH_GROUP_SIZE)
297                                 continue;
298
299                         /*
300                          * Get the slave running
301                          */
302                         TAILQ_REMOVE(&hmp->flusher.ready_list, info, entry);
303                         TAILQ_INSERT_TAIL(&hmp->flusher.run_list, info, entry);
304                         info->flg = flg;
305                         info->runstate = 1;
306                         wakeup(&info->runstate);
307
308                         /*
309                          * Get a new slave.  We may have to wait for one to
310                          * finish running.
311                          */
312                         while ((info = TAILQ_FIRST(&hmp->flusher.ready_list)) == NULL) {
313                                 tsleep(&hmp->flusher.ready_list, 0, "hmrfcc", 0);
314                         }
315                 }
316
317                 /*
318                  * Run the current slave if necessary
319                  */
320                 if (info->count) {
321                         TAILQ_REMOVE(&hmp->flusher.ready_list, info, entry);
322                         TAILQ_INSERT_TAIL(&hmp->flusher.run_list, info, entry);
323                         info->flg = flg;
324                         info->runstate = 1;
325                         wakeup(&info->runstate);
326                 }
327
328                 /*
329                  * Wait for all slaves to finish running
330                  */
331                 while (TAILQ_FIRST(&hmp->flusher.run_list) != NULL)
332                         tsleep(&hmp->flusher.ready_list, 0, "hmrfcc", 0);
333
334                 /*
335                  * Do the final finalization, clean up
336                  */
337                 hammer_flusher_finalize(&hmp->flusher.trans, 1);
338                 hmp->flusher.tid = hmp->flusher.trans.tid;
339
340                 hammer_done_transaction(&hmp->flusher.trans);
341
342                 /*
343                  * Loop up on the same flg.  If the flg is done clean it up
344                  * and break out.  We only flush one flg.
345                  */
346                 if (TAILQ_FIRST(&flg->flush_list) == NULL) {
347                         KKASSERT(TAILQ_EMPTY(&flg->flush_list));
348                         KKASSERT(flg->refs == 0);
349                         TAILQ_REMOVE(&hmp->flush_group_list, flg, flush_entry);
350                         kfree(flg, M_HAMMER);
351                         break;
352                 }
353         }
354
355         /*
356          * We may have pure meta-data to flush, or we may have to finish
357          * cycling the UNDO FIFO, even if there were no flush groups.
358          */
359         if (count == 0 && hammer_flusher_haswork(hmp)) {
360                 hammer_start_transaction_fls(&hmp->flusher.trans, hmp);
361                 hammer_flusher_finalize(&hmp->flusher.trans, 1);
362                 hammer_done_transaction(&hmp->flusher.trans);
363         }
364
365         /*
366          * Clean up any freed big-blocks (typically zone-2). 
367          * resv->flush_group is typically set several flush groups ahead
368          * of the free to ensure that the freed block is not reused until
369          * it can no longer be reused.
370          */
371         while ((resv = TAILQ_FIRST(&hmp->delay_list)) != NULL) {
372                 if (resv->flush_group != hmp->flusher.act)
373                         break;
374                 hammer_reserve_clrdelay(hmp, resv);
375         }
376 }
377
378
379 /*
380  * The slave flusher thread pulls work off the master flush_list until no
381  * work is left.
382  */
383 static void
384 hammer_flusher_slave_thread(void *arg)
385 {
386         hammer_flush_group_t flg;
387         hammer_flusher_info_t info;
388         hammer_mount_t hmp;
389         hammer_inode_t ip;
390         int i;
391
392         info = arg;
393         hmp = info->hmp;
394
395         for (;;) {
396                 while (info->runstate == 0)
397                         tsleep(&info->runstate, 0, "hmrssw", 0);
398                 if (info->runstate < 0)
399                         break;
400                 flg = info->flg;
401
402                 for (i = 0; i < info->count; ++i) {
403                         ip = info->work_array[i];
404                         hammer_flusher_flush_inode(ip, &hmp->flusher.trans);
405                 }
406                 info->count = 0;
407                 info->runstate = 0;
408                 TAILQ_REMOVE(&hmp->flusher.run_list, info, entry);
409                 TAILQ_INSERT_TAIL(&hmp->flusher.ready_list, info, entry);
410                 wakeup(&hmp->flusher.ready_list);
411         }
412         info->td = NULL;
413         wakeup(&info->td);
414         lwkt_exit();
415 }
416
417 void
418 hammer_flusher_clean_loose_ios(hammer_mount_t hmp)
419 {
420         hammer_buffer_t buffer;
421         hammer_io_t io;
422
423         /*
424          * loose ends - buffers without bp's aren't tracked by the kernel
425          * and can build up, so clean them out.  This can occur when an
426          * IO completes on a buffer with no references left.
427          */
428         if ((io = TAILQ_FIRST(&hmp->lose_list)) != NULL) {
429                 crit_enter();   /* biodone() race */
430                 while ((io = TAILQ_FIRST(&hmp->lose_list)) != NULL) {
431                         KKASSERT(io->mod_list == &hmp->lose_list);
432                         TAILQ_REMOVE(&hmp->lose_list, io, mod_entry);
433                         io->mod_list = NULL;
434                         if (io->lock.refs == 0)
435                                 ++hammer_count_refedbufs;
436                         hammer_ref(&io->lock);
437                         buffer = (void *)io;
438                         hammer_rel_buffer(buffer, 0);
439                 }
440                 crit_exit();
441         }
442 }
443
444 /*
445  * Flush a single inode that is part of a flush group.
446  *
447  * NOTE!  The sync code can return EWOULDBLOCK if the flush operation
448  * would otherwise blow out the buffer cache.  hammer_flush_inode_done()
449  * will re-queue the inode for the next flush sequence and force the
450  * flusher to run again if this occurs.
451  */
452 static
453 void
454 hammer_flusher_flush_inode(hammer_inode_t ip, hammer_transaction_t trans)
455 {
456         hammer_mount_t hmp = ip->hmp;
457         int error;
458
459         hammer_flusher_clean_loose_ios(hmp);
460         error = hammer_sync_inode(trans, ip);
461         if (error != EWOULDBLOCK)
462                 ip->error = error;
463         hammer_flush_inode_done(ip);
464         while (hmp->flusher.finalize_want)
465                 tsleep(&hmp->flusher.finalize_want, 0, "hmrsxx", 0);
466         if (hammer_flusher_undo_exhausted(trans, 1)) {
467                 kprintf("HAMMER: Warning: UNDO area too small!\n");
468                 hammer_flusher_finalize(trans, 1);
469         } else if (hammer_flusher_meta_limit(trans->hmp)) {
470                 hammer_flusher_finalize(trans, 0);
471         }
472 }
473
474 /*
475  * Return non-zero if the UNDO area has less then (QUARTER / 4) of its
476  * space left.
477  *
478  * 1/4 - Emergency free undo space level.  Below this point the flusher
479  *       will finalize even if directory dependancies have not been resolved.
480  *
481  * 2/4 - Used by the pruning and reblocking code.  These functions may be
482  *       running in parallel with a flush and cannot be allowed to drop
483  *       available undo space to emergency levels.
484  *
485  * 3/4 - Used at the beginning of a flush to force-sync the volume header
486  *       to give the flush plenty of runway to work in.
487  */
488 int
489 hammer_flusher_undo_exhausted(hammer_transaction_t trans, int quarter)
490 {
491         if (hammer_undo_space(trans) <
492             hammer_undo_max(trans->hmp) * quarter / 4) {
493                 return(1);
494         } else {
495                 return(0);
496         }
497 }
498
499 /*
500  * Flush all pending UNDOs, wait for write completion, update the volume
501  * header with the new UNDO end position, and flush it.  Then
502  * asynchronously flush the meta-data.
503  *
504  * If this is the last finalization in a flush group we also synchronize
505  * our cached blockmap and set hmp->flusher_undo_start and our cached undo
506  * fifo first_offset so the next flush resets the FIFO pointers.
507  *
508  * If this is not final it is being called because too many dirty meta-data
509  * buffers have built up and must be flushed with UNDO synchronization to
510  * avoid a buffer cache deadlock.
511  */
512 void
513 hammer_flusher_finalize(hammer_transaction_t trans, int final)
514 {
515         hammer_volume_t root_volume;
516         hammer_blockmap_t cundomap, dundomap;
517         hammer_mount_t hmp;
518         hammer_io_t io;
519         int count;
520         int i;
521
522         hmp = trans->hmp;
523         root_volume = trans->rootvol;
524
525         /*
526          * Exclusively lock the flusher.  This guarantees that all dirty
527          * buffers will be idled (have a mod-count of 0).
528          */
529         ++hmp->flusher.finalize_want;
530         hammer_lock_ex(&hmp->flusher.finalize_lock);
531
532         /*
533          * If this isn't the final sync several threads may have hit the
534          * meta-limit at the same time and raced.  Only sync if we really
535          * have to, after acquiring the lock.
536          */
537         if (final == 0 && !hammer_flusher_meta_limit(hmp))
538                 goto done;
539
540         /*
541          * Flush data buffers.  This can occur asynchronously and at any
542          * time.  We must interlock against the frontend direct-data write
543          * but do not have to acquire the sync-lock yet.
544          */
545         count = 0;
546         while ((io = TAILQ_FIRST(&hmp->data_list)) != NULL) {
547                 if (io->lock.refs == 0)
548                         ++hammer_count_refedbufs;
549                 hammer_ref(&io->lock);
550                 hammer_io_write_interlock(io);
551                 KKASSERT(io->type != HAMMER_STRUCTURE_VOLUME);
552                 hammer_io_flush(io);
553                 hammer_io_done_interlock(io);
554                 hammer_rel_buffer((hammer_buffer_t)io, 0);
555                 ++count;
556         }
557
558         /*
559          * The sync-lock is required for the remaining sequence.  This lock
560          * prevents meta-data from being modified.
561          */
562         hammer_sync_lock_ex(trans);
563
564         /*
565          * If we have been asked to finalize the volume header sync the
566          * cached blockmap to the on-disk blockmap.  Generate an UNDO
567          * record for the update.
568          */
569         if (final) {
570                 cundomap = &hmp->blockmap[0];
571                 dundomap = &root_volume->ondisk->vol0_blockmap[0];
572                 if (root_volume->io.modified) {
573                         hammer_modify_volume(trans, root_volume,
574                                              dundomap, sizeof(hmp->blockmap));
575                         for (i = 0; i < HAMMER_MAX_ZONES; ++i)
576                                 hammer_crc_set_blockmap(&cundomap[i]);
577                         bcopy(cundomap, dundomap, sizeof(hmp->blockmap));
578                         hammer_modify_volume_done(root_volume);
579                 }
580         }
581
582         /*
583          * Flush UNDOs
584          */
585         count = 0;
586         while ((io = TAILQ_FIRST(&hmp->undo_list)) != NULL) {
587                 KKASSERT(io->modify_refs == 0);
588                 if (io->lock.refs == 0)
589                         ++hammer_count_refedbufs;
590                 hammer_ref(&io->lock);
591                 KKASSERT(io->type != HAMMER_STRUCTURE_VOLUME);
592                 hammer_io_flush(io);
593                 hammer_rel_buffer((hammer_buffer_t)io, 0);
594                 ++count;
595         }
596
597         /*
598          * Wait for I/Os to complete
599          */
600         hammer_flusher_clean_loose_ios(hmp);
601         hammer_io_wait_all(hmp, "hmrfl1");
602
603         /*
604          * Update the on-disk volume header with new UNDO FIFO end position
605          * (do not generate new UNDO records for this change).  We have to
606          * do this for the UNDO FIFO whether (final) is set or not.
607          *
608          * Also update the on-disk next_tid field.  This does not require
609          * an UNDO.  However, because our TID is generated before we get
610          * the sync lock another sync may have beat us to the punch.
611          *
612          * This also has the side effect of updating first_offset based on
613          * a prior finalization when the first finalization of the next flush
614          * cycle occurs, removing any undo info from the prior finalization
615          * from consideration.
616          *
617          * The volume header will be flushed out synchronously.
618          */
619         dundomap = &root_volume->ondisk->vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];
620         cundomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
621
622         if (dundomap->first_offset != cundomap->first_offset ||
623             dundomap->next_offset != cundomap->next_offset) {
624                 hammer_modify_volume(NULL, root_volume, NULL, 0);
625                 dundomap->first_offset = cundomap->first_offset;
626                 dundomap->next_offset = cundomap->next_offset;
627                 hammer_crc_set_blockmap(dundomap);
628                 hammer_modify_volume_done(root_volume);
629         }
630
631         if (root_volume->io.modified) {
632                 hammer_modify_volume(NULL, root_volume, NULL, 0);
633                 if (root_volume->ondisk->vol0_next_tid < trans->tid)
634                         root_volume->ondisk->vol0_next_tid = trans->tid;
635                 hammer_crc_set_volume(root_volume->ondisk);
636                 hammer_modify_volume_done(root_volume);
637                 hammer_io_flush(&root_volume->io);
638         }
639
640         /*
641          * Wait for I/Os to complete
642          */
643         hammer_flusher_clean_loose_ios(hmp);
644         hammer_io_wait_all(hmp, "hmrfl2");
645
646         /*
647          * Flush meta-data.  The meta-data will be undone if we crash
648          * so we can safely flush it asynchronously.
649          *
650          * Repeated catchups will wind up flushing this update's meta-data
651          * and the UNDO buffers for the next update simultaniously.  This
652          * is ok.
653          */
654         count = 0;
655         while ((io = TAILQ_FIRST(&hmp->meta_list)) != NULL) {
656                 KKASSERT(io->modify_refs == 0);
657                 if (io->lock.refs == 0)
658                         ++hammer_count_refedbufs;
659                 hammer_ref(&io->lock);
660                 KKASSERT(io->type != HAMMER_STRUCTURE_VOLUME);
661                 hammer_io_flush(io);
662                 hammer_rel_buffer((hammer_buffer_t)io, 0);
663                 ++count;
664         }
665
666         /*
667          * If this is the final finalization for the flush group set
668          * up for the next sequence by setting a new first_offset in
669          * our cached blockmap and clearing the undo history.
670          *
671          * Even though we have updated our cached first_offset, the on-disk
672          * first_offset still governs available-undo-space calculations.
673          */
674         if (final) {
675                 cundomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
676                 if (cundomap->first_offset == cundomap->next_offset) {
677                         hmp->hflags &= ~HMNT_UNDO_DIRTY;
678                 } else {
679                         cundomap->first_offset = cundomap->next_offset;
680                         hmp->hflags |= HMNT_UNDO_DIRTY;
681                 }
682                 hammer_clear_undo_history(hmp);
683         }
684
685         hammer_sync_unlock(trans);
686
687 done:
688         hammer_unlock(&hmp->flusher.finalize_lock);
689         if (--hmp->flusher.finalize_want == 0)
690                 wakeup(&hmp->flusher.finalize_want);
691 }
692
693 /*
694  * Return non-zero if too many dirty meta-data buffers have built up.
695  *
696  * Since we cannot allow such buffers to flush until we have dealt with
697  * the UNDOs, we risk deadlocking the kernel's buffer cache.
698  */
699 int
700 hammer_flusher_meta_limit(hammer_mount_t hmp)
701 {
702         if (hmp->locked_dirty_space + hmp->io_running_space >
703             hammer_limit_dirtybufspace) {
704                 return(1);
705         }
706         return(0);
707 }
708
709 /*
710  * Return non-zero if too many dirty meta-data buffers have built up.
711  *
712  * This version is used by background operations (mirror, prune, reblock)
713  * to leave room for foreground operations.
714  */
715 int
716 hammer_flusher_meta_halflimit(hammer_mount_t hmp)
717 {
718         if (hmp->locked_dirty_space + hmp->io_running_space >
719             hammer_limit_dirtybufspace / 2) {
720                 return(1);
721         }
722         return(0);
723 }
724
725 /*
726  * Return non-zero if the flusher still has something to flush.
727  */
728 int
729 hammer_flusher_haswork(hammer_mount_t hmp)
730 {
731         if (TAILQ_FIRST(&hmp->flush_group_list) ||      /* dirty inodes */
732             TAILQ_FIRST(&hmp->volu_list) ||             /* dirty bufffers */
733             TAILQ_FIRST(&hmp->undo_list) ||
734             TAILQ_FIRST(&hmp->data_list) ||
735             TAILQ_FIRST(&hmp->meta_list) ||
736             (hmp->hflags & HMNT_UNDO_DIRTY)             /* UNDO FIFO sync */
737         ) {
738                 return(1);
739         }
740         return(0);
741 }
742