5be9d14f12cbcddf4ef51cab689d5ce53ea1f1db
[linux-2.6.git] / fs / ocfs2 / dlm / dlmthread.c
1 /* -*- mode: c; c-basic-offset: 8; -*-
2  * vim: noexpandtab sw=8 ts=8 sts=0:
3  *
4  * dlmthread.c
5  *
6  * standalone DLM module
7  *
8  * Copyright (C) 2004 Oracle.  All rights reserved.
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public
12  * License as published by the Free Software Foundation; either
13  * version 2 of the License, or (at your option) any later version.
14  *
15  * This program is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18  * General Public License for more details.
19  *
20  * You should have received a copy of the GNU General Public
21  * License along with this program; if not, write to the
22  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
23  * Boston, MA 021110-1307, USA.
24  *
25  */
26
27
28 #include <linux/module.h>
29 #include <linux/fs.h>
30 #include <linux/types.h>
31 #include <linux/slab.h>
32 #include <linux/highmem.h>
33 #include <linux/utsname.h>
34 #include <linux/init.h>
35 #include <linux/sysctl.h>
36 #include <linux/random.h>
37 #include <linux/blkdev.h>
38 #include <linux/socket.h>
39 #include <linux/inet.h>
40 #include <linux/timer.h>
41 #include <linux/kthread.h>
42
43
44 #include "cluster/heartbeat.h"
45 #include "cluster/nodemanager.h"
46 #include "cluster/tcp.h"
47
48 #include "dlmapi.h"
49 #include "dlmcommon.h"
50 #include "dlmdomain.h"
51
52 #define MLOG_MASK_PREFIX (ML_DLM|ML_DLM_THREAD)
53 #include "cluster/masklog.h"
54
55 static int dlm_thread(void *data);
56
57 static void dlm_flush_asts(struct dlm_ctxt *dlm);
58
59 #define dlm_lock_is_remote(dlm, lock)     ((lock)->ml.node != (dlm)->node_num)
60
61 /* will exit holding res->spinlock, but may drop in function */
62 /* waits until flags are cleared on res->state */
63 void __dlm_wait_on_lockres_flags(struct dlm_lock_resource *res, int flags)
64 {
65         DECLARE_WAITQUEUE(wait, current);
66
67         assert_spin_locked(&res->spinlock);
68
69         add_wait_queue(&res->wq, &wait);
70 repeat:
71         set_current_state(TASK_UNINTERRUPTIBLE);
72         if (res->state & flags) {
73                 spin_unlock(&res->spinlock);
74                 schedule();
75                 spin_lock(&res->spinlock);
76                 goto repeat;
77         }
78         remove_wait_queue(&res->wq, &wait);
79         current->state = TASK_RUNNING;
80 }
81
82
83 static int __dlm_lockres_unused(struct dlm_lock_resource *res)
84 {
85         if (list_empty(&res->granted) &&
86             list_empty(&res->converting) &&
87             list_empty(&res->blocked) &&
88             list_empty(&res->dirty))
89                 return 1;
90         return 0;
91 }
92
93
94 /* Call whenever you may have added or deleted something from one of
95  * the lockres queue's. This will figure out whether it belongs on the
96  * unused list or not and does the appropriate thing. */
97 void __dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
98                               struct dlm_lock_resource *res)
99 {
100         mlog_entry("%.*s\n", res->lockname.len, res->lockname.name);
101
102         assert_spin_locked(&dlm->spinlock);
103         assert_spin_locked(&res->spinlock);
104
105         if (__dlm_lockres_unused(res)){
106                 if (list_empty(&res->purge)) {
107                         mlog(0, "putting lockres %.*s from purge list\n",
108                              res->lockname.len, res->lockname.name);
109
110                         res->last_used = jiffies;
111                         list_add_tail(&res->purge, &dlm->purge_list);
112                         dlm->purge_count++;
113                 }
114         } else if (!list_empty(&res->purge)) {
115                 mlog(0, "removing lockres %.*s from purge list\n",
116                      res->lockname.len, res->lockname.name);
117
118                 list_del_init(&res->purge);
119                 dlm->purge_count--;
120         }
121 }
122
123 void dlm_lockres_calc_usage(struct dlm_ctxt *dlm,
124                             struct dlm_lock_resource *res)
125 {
126         mlog_entry("%.*s\n", res->lockname.len, res->lockname.name);
127         spin_lock(&dlm->spinlock);
128         spin_lock(&res->spinlock);
129
130         __dlm_lockres_calc_usage(dlm, res);
131
132         spin_unlock(&res->spinlock);
133         spin_unlock(&dlm->spinlock);
134 }
135
136 /* TODO: Eventual API: Called with the dlm spinlock held, may drop it
137  * to do migration, but will re-acquire before exit. */
138 void dlm_purge_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *lockres)
139 {
140         int master;
141         int ret;
142
143         spin_lock(&lockres->spinlock);
144         master = lockres->owner == dlm->node_num;
145         spin_unlock(&lockres->spinlock);
146
147         mlog(0, "purging lockres %.*s, master = %d\n", lockres->lockname.len,
148              lockres->lockname.name, master);
149
150         /* Non master is the easy case -- no migration required, just
151          * quit. */
152         if (!master)
153                 goto finish;
154
155         /* Wheee! Migrate lockres here! */
156         spin_unlock(&dlm->spinlock);
157 again:
158
159         ret = dlm_migrate_lockres(dlm, lockres, O2NM_MAX_NODES);
160         if (ret == -ENOTEMPTY) {
161                 mlog(ML_ERROR, "lockres %.*s still has local locks!\n",
162                      lockres->lockname.len, lockres->lockname.name);
163
164                 BUG();
165         } else if (ret < 0) {
166                 mlog(ML_NOTICE, "lockres %.*s: migrate failed, retrying\n",
167                      lockres->lockname.len, lockres->lockname.name);
168                 goto again;
169         }
170
171         spin_lock(&dlm->spinlock);
172
173 finish:
174         if (!list_empty(&lockres->purge)) {
175                 list_del_init(&lockres->purge);
176                 dlm->purge_count--;
177         }
178         __dlm_unhash_lockres(lockres);
179 }
180
181 static void dlm_run_purge_list(struct dlm_ctxt *dlm,
182                                int purge_now)
183 {
184         unsigned int run_max, unused;
185         unsigned long purge_jiffies;
186         struct dlm_lock_resource *lockres;
187
188         spin_lock(&dlm->spinlock);
189         run_max = dlm->purge_count;
190
191         while(run_max && !list_empty(&dlm->purge_list)) {
192                 run_max--;
193
194                 lockres = list_entry(dlm->purge_list.next,
195                                      struct dlm_lock_resource, purge);
196
197                 /* Status of the lockres *might* change so double
198                  * check. If the lockres is unused, holding the dlm
199                  * spinlock will prevent people from getting and more
200                  * refs on it -- there's no need to keep the lockres
201                  * spinlock. */
202                 spin_lock(&lockres->spinlock);
203                 unused = __dlm_lockres_unused(lockres);
204                 spin_unlock(&lockres->spinlock);
205
206                 if (!unused)
207                         continue;
208
209                 purge_jiffies = lockres->last_used +
210                         msecs_to_jiffies(DLM_PURGE_INTERVAL_MS);
211
212                 /* Make sure that we want to be processing this guy at
213                  * this time. */
214                 if (!purge_now && time_after(purge_jiffies, jiffies)) {
215                         /* Since resources are added to the purge list
216                          * in tail order, we can stop at the first
217                          * unpurgable resource -- anyone added after
218                          * him will have a greater last_used value */
219                         break;
220                 }
221
222                 list_del_init(&lockres->purge);
223                 dlm->purge_count--;
224
225                 /* This may drop and reacquire the dlm spinlock if it
226                  * has to do migration. */
227                 mlog(0, "calling dlm_purge_lockres!\n");
228                 dlm_purge_lockres(dlm, lockres);
229                 mlog(0, "DONE calling dlm_purge_lockres!\n");
230
231                 /* Avoid adding any scheduling latencies */
232                 cond_resched_lock(&dlm->spinlock);
233         }
234
235         spin_unlock(&dlm->spinlock);
236 }
237
238 static void dlm_shuffle_lists(struct dlm_ctxt *dlm,
239                               struct dlm_lock_resource *res)
240 {
241         struct dlm_lock *lock, *target;
242         struct list_head *iter;
243         struct list_head *head;
244         int can_grant = 1;
245
246         //mlog(0, "res->lockname.len=%d\n", res->lockname.len);
247         //mlog(0, "res->lockname.name=%p\n", res->lockname.name);
248         //mlog(0, "shuffle res %.*s\n", res->lockname.len,
249         //        res->lockname.name);
250
251         /* because this function is called with the lockres
252          * spinlock, and because we know that it is not migrating/
253          * recovering/in-progress, it is fine to reserve asts and
254          * basts right before queueing them all throughout */
255         assert_spin_locked(&res->spinlock);
256         BUG_ON((res->state & (DLM_LOCK_RES_MIGRATING|
257                               DLM_LOCK_RES_RECOVERING|
258                               DLM_LOCK_RES_IN_PROGRESS)));
259
260 converting:
261         if (list_empty(&res->converting))
262                 goto blocked;
263         mlog(0, "res %.*s has locks on a convert queue\n", res->lockname.len,
264              res->lockname.name);
265
266         target = list_entry(res->converting.next, struct dlm_lock, list);
267         if (target->ml.convert_type == LKM_IVMODE) {
268                 mlog(ML_ERROR, "%.*s: converting a lock with no "
269                      "convert_type!\n", res->lockname.len, res->lockname.name);
270                 BUG();
271         }
272         head = &res->granted;
273         list_for_each(iter, head) {
274                 lock = list_entry(iter, struct dlm_lock, list);
275                 if (lock==target)
276                         continue;
277                 if (!dlm_lock_compatible(lock->ml.type,
278                                          target->ml.convert_type)) {
279                         can_grant = 0;
280                         /* queue the BAST if not already */
281                         if (lock->ml.highest_blocked == LKM_IVMODE) {
282                                 __dlm_lockres_reserve_ast(res);
283                                 dlm_queue_bast(dlm, lock);
284                         }
285                         /* update the highest_blocked if needed */
286                         if (lock->ml.highest_blocked < target->ml.convert_type)
287                                 lock->ml.highest_blocked =
288                                         target->ml.convert_type;
289                 }
290         }
291         head = &res->converting;
292         list_for_each(iter, head) {
293                 lock = list_entry(iter, struct dlm_lock, list);
294                 if (lock==target)
295                         continue;
296                 if (!dlm_lock_compatible(lock->ml.type,
297                                          target->ml.convert_type)) {
298                         can_grant = 0;
299                         if (lock->ml.highest_blocked == LKM_IVMODE) {
300                                 __dlm_lockres_reserve_ast(res);
301                                 dlm_queue_bast(dlm, lock);
302                         }
303                         if (lock->ml.highest_blocked < target->ml.convert_type)
304                                 lock->ml.highest_blocked =
305                                         target->ml.convert_type;
306                 }
307         }
308
309         /* we can convert the lock */
310         if (can_grant) {
311                 spin_lock(&target->spinlock);
312                 BUG_ON(target->ml.highest_blocked != LKM_IVMODE);
313
314                 mlog(0, "calling ast for converting lock: %.*s, have: %d, "
315                      "granting: %d, node: %u\n", res->lockname.len,
316                      res->lockname.name, target->ml.type,
317                      target->ml.convert_type, target->ml.node);
318
319                 target->ml.type = target->ml.convert_type;
320                 target->ml.convert_type = LKM_IVMODE;
321                 list_del_init(&target->list);
322                 list_add_tail(&target->list, &res->granted);
323
324                 BUG_ON(!target->lksb);
325                 target->lksb->status = DLM_NORMAL;
326
327                 spin_unlock(&target->spinlock);
328
329                 __dlm_lockres_reserve_ast(res);
330                 dlm_queue_ast(dlm, target);
331                 /* go back and check for more */
332                 goto converting;
333         }
334
335 blocked:
336         if (list_empty(&res->blocked))
337                 goto leave;
338         target = list_entry(res->blocked.next, struct dlm_lock, list);
339
340         head = &res->granted;
341         list_for_each(iter, head) {
342                 lock = list_entry(iter, struct dlm_lock, list);
343                 if (lock==target)
344                         continue;
345                 if (!dlm_lock_compatible(lock->ml.type, target->ml.type)) {
346                         can_grant = 0;
347                         if (lock->ml.highest_blocked == LKM_IVMODE) {
348                                 __dlm_lockres_reserve_ast(res);
349                                 dlm_queue_bast(dlm, lock);
350                         }
351                         if (lock->ml.highest_blocked < target->ml.type)
352                                 lock->ml.highest_blocked = target->ml.type;
353                 }
354         }
355
356         head = &res->converting;
357         list_for_each(iter, head) {
358                 lock = list_entry(iter, struct dlm_lock, list);
359                 if (lock==target)
360                         continue;
361                 if (!dlm_lock_compatible(lock->ml.type, target->ml.type)) {
362                         can_grant = 0;
363                         if (lock->ml.highest_blocked == LKM_IVMODE) {
364                                 __dlm_lockres_reserve_ast(res);
365                                 dlm_queue_bast(dlm, lock);
366                         }
367                         if (lock->ml.highest_blocked < target->ml.type)
368                                 lock->ml.highest_blocked = target->ml.type;
369                 }
370         }
371
372         /* we can grant the blocked lock (only
373          * possible if converting list empty) */
374         if (can_grant) {
375                 spin_lock(&target->spinlock);
376                 BUG_ON(target->ml.highest_blocked != LKM_IVMODE);
377
378                 mlog(0, "calling ast for blocked lock: %.*s, granting: %d, "
379                      "node: %u\n", res->lockname.len, res->lockname.name,
380                      target->ml.type, target->ml.node);
381
382                 // target->ml.type is already correct
383                 list_del_init(&target->list);
384                 list_add_tail(&target->list, &res->granted);
385
386                 BUG_ON(!target->lksb);
387                 target->lksb->status = DLM_NORMAL;
388
389                 spin_unlock(&target->spinlock);
390
391                 __dlm_lockres_reserve_ast(res);
392                 dlm_queue_ast(dlm, target);
393                 /* go back and check for more */
394                 goto converting;
395         }
396
397 leave:
398         return;
399 }
400
401 /* must have NO locks when calling this with res !=NULL * */
402 void dlm_kick_thread(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
403 {
404         mlog_entry("dlm=%p, res=%p\n", dlm, res);
405         if (res) {
406                 spin_lock(&dlm->spinlock);
407                 spin_lock(&res->spinlock);
408                 __dlm_dirty_lockres(dlm, res);
409                 spin_unlock(&res->spinlock);
410                 spin_unlock(&dlm->spinlock);
411         }
412         wake_up(&dlm->dlm_thread_wq);
413 }
414
415 void __dlm_dirty_lockres(struct dlm_ctxt *dlm, struct dlm_lock_resource *res)
416 {
417         mlog_entry("dlm=%p, res=%p\n", dlm, res);
418
419         assert_spin_locked(&dlm->spinlock);
420         assert_spin_locked(&res->spinlock);
421
422         /* don't shuffle secondary queues */
423         if ((res->owner == dlm->node_num) &&
424             !(res->state & DLM_LOCK_RES_DIRTY)) {
425                 list_add_tail(&res->dirty, &dlm->dirty_list);
426                 res->state |= DLM_LOCK_RES_DIRTY;
427         }
428 }
429
430
431 /* Launch the NM thread for the mounted volume */
432 int dlm_launch_thread(struct dlm_ctxt *dlm)
433 {
434         mlog(0, "starting dlm thread...\n");
435
436         dlm->dlm_thread_task = kthread_run(dlm_thread, dlm, "dlm_thread");
437         if (IS_ERR(dlm->dlm_thread_task)) {
438                 mlog_errno(PTR_ERR(dlm->dlm_thread_task));
439                 dlm->dlm_thread_task = NULL;
440                 return -EINVAL;
441         }
442
443         return 0;
444 }
445
446 void dlm_complete_thread(struct dlm_ctxt *dlm)
447 {
448         if (dlm->dlm_thread_task) {
449                 mlog(ML_KTHREAD, "waiting for dlm thread to exit\n");
450                 kthread_stop(dlm->dlm_thread_task);
451                 dlm->dlm_thread_task = NULL;
452         }
453 }
454
455 static int dlm_dirty_list_empty(struct dlm_ctxt *dlm)
456 {
457         int empty;
458
459         spin_lock(&dlm->spinlock);
460         empty = list_empty(&dlm->dirty_list);
461         spin_unlock(&dlm->spinlock);
462
463         return empty;
464 }
465
466 static void dlm_flush_asts(struct dlm_ctxt *dlm)
467 {
468         int ret;
469         struct dlm_lock *lock;
470         struct dlm_lock_resource *res;
471         u8 hi;
472
473         spin_lock(&dlm->ast_lock);
474         while (!list_empty(&dlm->pending_asts)) {
475                 lock = list_entry(dlm->pending_asts.next,
476                                   struct dlm_lock, ast_list);
477                 /* get an extra ref on lock */
478                 dlm_lock_get(lock);
479                 res = lock->lockres;
480                 mlog(0, "delivering an ast for this lockres\n");
481
482                 BUG_ON(!lock->ast_pending);
483
484                 /* remove from list (including ref) */
485                 list_del_init(&lock->ast_list);
486                 dlm_lock_put(lock);
487                 spin_unlock(&dlm->ast_lock);
488
489                 if (lock->ml.node != dlm->node_num) {
490                         ret = dlm_do_remote_ast(dlm, res, lock);
491                         if (ret < 0)
492                                 mlog_errno(ret);
493                 } else
494                         dlm_do_local_ast(dlm, res, lock);
495
496                 spin_lock(&dlm->ast_lock);
497
498                 /* possible that another ast was queued while
499                  * we were delivering the last one */
500                 if (!list_empty(&lock->ast_list)) {
501                         mlog(0, "aha another ast got queued while "
502                              "we were finishing the last one.  will "
503                              "keep the ast_pending flag set.\n");
504                 } else
505                         lock->ast_pending = 0;
506
507                 /* drop the extra ref.
508                  * this may drop it completely. */
509                 dlm_lock_put(lock);
510                 dlm_lockres_release_ast(dlm, res);
511         }
512
513         while (!list_empty(&dlm->pending_basts)) {
514                 lock = list_entry(dlm->pending_basts.next,
515                                   struct dlm_lock, bast_list);
516                 /* get an extra ref on lock */
517                 dlm_lock_get(lock);
518                 res = lock->lockres;
519
520                 BUG_ON(!lock->bast_pending);
521
522                 /* get the highest blocked lock, and reset */
523                 spin_lock(&lock->spinlock);
524                 BUG_ON(lock->ml.highest_blocked <= LKM_IVMODE);
525                 hi = lock->ml.highest_blocked;
526                 lock->ml.highest_blocked = LKM_IVMODE;
527                 spin_unlock(&lock->spinlock);
528
529                 /* remove from list (including ref) */
530                 list_del_init(&lock->bast_list);
531                 dlm_lock_put(lock);
532                 spin_unlock(&dlm->ast_lock);
533
534                 mlog(0, "delivering a bast for this lockres "
535                      "(blocked = %d\n", hi);
536
537                 if (lock->ml.node != dlm->node_num) {
538                         ret = dlm_send_proxy_bast(dlm, res, lock, hi);
539                         if (ret < 0)
540                                 mlog_errno(ret);
541                 } else
542                         dlm_do_local_bast(dlm, res, lock, hi);
543
544                 spin_lock(&dlm->ast_lock);
545
546                 /* possible that another bast was queued while
547                  * we were delivering the last one */
548                 if (!list_empty(&lock->bast_list)) {
549                         mlog(0, "aha another bast got queued while "
550                              "we were finishing the last one.  will "
551                              "keep the bast_pending flag set.\n");
552                 } else
553                         lock->bast_pending = 0;
554
555                 /* drop the extra ref.
556                  * this may drop it completely. */
557                 dlm_lock_put(lock);
558                 dlm_lockres_release_ast(dlm, res);
559         }
560         wake_up(&dlm->ast_wq);
561         spin_unlock(&dlm->ast_lock);
562 }
563
564
565 #define DLM_THREAD_TIMEOUT_MS (4 * 1000)
566 #define DLM_THREAD_MAX_DIRTY  100
567 #define DLM_THREAD_MAX_ASTS   10
568
569 static int dlm_thread(void *data)
570 {
571         struct dlm_lock_resource *res;
572         struct dlm_ctxt *dlm = data;
573         unsigned long timeout = msecs_to_jiffies(DLM_THREAD_TIMEOUT_MS);
574
575         mlog(0, "dlm thread running for %s...\n", dlm->name);
576
577         while (!kthread_should_stop()) {
578                 int n = DLM_THREAD_MAX_DIRTY;
579
580                 /* dlm_shutting_down is very point-in-time, but that
581                  * doesn't matter as we'll just loop back around if we
582                  * get false on the leading edge of a state
583                  * transition. */
584                 dlm_run_purge_list(dlm, dlm_shutting_down(dlm));
585
586                 /* We really don't want to hold dlm->spinlock while
587                  * calling dlm_shuffle_lists on each lockres that
588                  * needs to have its queues adjusted and AST/BASTs
589                  * run.  So let's pull each entry off the dirty_list
590                  * and drop dlm->spinlock ASAP.  Once off the list,
591                  * res->spinlock needs to be taken again to protect
592                  * the queues while calling dlm_shuffle_lists.  */
593                 spin_lock(&dlm->spinlock);
594                 while (!list_empty(&dlm->dirty_list)) {
595                         int delay = 0;
596                         res = list_entry(dlm->dirty_list.next,
597                                          struct dlm_lock_resource, dirty);
598
599                         /* peel a lockres off, remove it from the list,
600                          * unset the dirty flag and drop the dlm lock */
601                         BUG_ON(!res);
602                         dlm_lockres_get(res);
603
604                         spin_lock(&res->spinlock);
605                         res->state &= ~DLM_LOCK_RES_DIRTY;
606                         list_del_init(&res->dirty);
607                         spin_unlock(&res->spinlock);
608                         spin_unlock(&dlm->spinlock);
609
610                         /* lockres can be re-dirtied/re-added to the
611                          * dirty_list in this gap, but that is ok */
612
613                         spin_lock(&res->spinlock);
614                         if (res->owner != dlm->node_num) {
615                                 __dlm_print_one_lock_resource(res);
616                                 mlog(ML_ERROR, "inprog:%s, mig:%s, reco:%s, dirty:%s\n",
617                                      res->state & DLM_LOCK_RES_IN_PROGRESS ? "yes" : "no",
618                                      res->state & DLM_LOCK_RES_MIGRATING ? "yes" : "no",
619                                      res->state & DLM_LOCK_RES_RECOVERING ? "yes" : "no",
620                                      res->state & DLM_LOCK_RES_DIRTY ? "yes" : "no");
621                         }
622                         BUG_ON(res->owner != dlm->node_num);
623
624                         /* it is now ok to move lockreses in these states
625                          * to the dirty list, assuming that they will only be
626                          * dirty for a short while. */
627                         if (res->state & (DLM_LOCK_RES_IN_PROGRESS |
628                                           DLM_LOCK_RES_MIGRATING |
629                                           DLM_LOCK_RES_RECOVERING)) {
630                                 /* move it to the tail and keep going */
631                                 spin_unlock(&res->spinlock);
632                                 mlog(0, "delaying list shuffling for in-"
633                                      "progress lockres %.*s, state=%d\n",
634                                      res->lockname.len, res->lockname.name,
635                                      res->state);
636                                 delay = 1;
637                                 goto in_progress;
638                         }
639
640                         /* at this point the lockres is not migrating/
641                          * recovering/in-progress.  we have the lockres
642                          * spinlock and do NOT have the dlm lock.
643                          * safe to reserve/queue asts and run the lists. */
644
645                         mlog(0, "calling dlm_shuffle_lists with dlm=%p, "
646                              "res=%p\n", dlm, res);
647
648                         /* called while holding lockres lock */
649                         dlm_shuffle_lists(dlm, res);
650                         spin_unlock(&res->spinlock);
651
652                         dlm_lockres_calc_usage(dlm, res);
653
654 in_progress:
655
656                         spin_lock(&dlm->spinlock);
657                         /* if the lock was in-progress, stick
658                          * it on the back of the list */
659                         if (delay) {
660                                 spin_lock(&res->spinlock);
661                                 list_add_tail(&res->dirty, &dlm->dirty_list);
662                                 res->state |= DLM_LOCK_RES_DIRTY;
663                                 spin_unlock(&res->spinlock);
664                         }
665                         dlm_lockres_put(res);
666
667                         /* unlikely, but we may need to give time to
668                          * other tasks */
669                         if (!--n) {
670                                 mlog(0, "throttling dlm_thread\n");
671                                 break;
672                         }
673                 }
674
675                 spin_unlock(&dlm->spinlock);
676                 dlm_flush_asts(dlm);
677
678                 /* yield and continue right away if there is more work to do */
679                 if (!n) {
680                         yield();
681                         continue;
682                 }
683
684                 wait_event_interruptible_timeout(dlm->dlm_thread_wq,
685                                                  !dlm_dirty_list_empty(dlm) ||
686                                                  kthread_should_stop(),
687                                                  timeout);
688         }
689
690         mlog(0, "quitting DLM thread\n");
691         return 0;
692 }