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[fs/lustre-release.git] / lustre / ptlrpc / recov_thread.c
1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
2  * vim:expandtab:shiftwidth=8:tabstop=8:
3  *
4  *  Copyright (C) 2003 Cluster File Systems, Inc.
5  *   Author: Andreas Dilger <adilger@clusterfs.com>
6  *
7  *   This file is part of Lustre, http://www.lustre.org.
8  *
9  *   Lustre is free software; you can redistribute it and/or
10  *   modify it under the terms of version 2 of the GNU General Public
11  *   License as published by the Free Software Foundation.
12  *
13  *   Lustre is distributed in the hope that it will be useful,
14  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
15  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  *   GNU General Public License for more details.
17  *
18  *   You should have received a copy of the GNU General Public License
19  *   along with Lustre; if not, write to the Free Software
20  *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21  *
22  * OST<->MDS recovery logging thread.
23  *
24  * Invariants in implementation:
25  * - we do not share logs among different OST<->MDS connections, so that
26  *   if an OST or MDS fails it need only look at log(s) relevant to itself
27  */
28
29 #define DEBUG_SUBSYSTEM S_LOG
30
31 #ifndef EXPORT_SYMTAB
32 # define EXPORT_SYMTAB
33 #endif
34
35 #ifdef __KERNEL__
36 #include <linux/fs.h>
37 #else
38 # include <portals/list.h>
39 # include <liblustre.h>
40 #endif
41
42 #include <linux/kp30.h>
43 #include <linux/obd_class.h>
44 #include <linux/lustre_commit_confd.h>
45 #include <linux/obd_support.h>
46 #include <linux/obd_class.h>
47 #include <linux/lustre_net.h>
48 #include <portals/types.h>
49 #include <portals/list.h>
50 #include <linux/lustre_log.h>
51 #include "ptlrpc_internal.h"
52
53 #define LLCD_SIZE 4096
54
55 #ifdef __KERNEL__
56
57 static struct llog_commit_master lustre_lcm;
58 static struct llog_commit_master *lcm = &lustre_lcm;
59
60 /* Allocate new commit structs in case we do not have enough */
61 static int llcd_alloc(void)
62 {
63         struct llog_canceld_ctxt *llcd;
64         int offset = offsetof(struct llog_canceld_ctxt, llcd_cookies);
65
66         OBD_ALLOC(llcd, LLCD_SIZE + offset);
67         if (llcd == NULL)
68                 return -ENOMEM;
69
70         llcd->llcd_lcm = lcm;
71
72         spin_lock(&lcm->lcm_llcd_lock);
73         list_add(&llcd->llcd_list, &lcm->lcm_llcd_free);
74         atomic_inc(&lcm->lcm_llcd_numfree);
75         spin_unlock(&lcm->lcm_llcd_lock);
76
77         return 0;
78 }
79
80 /* Get a free cookie struct from the list */
81 struct llog_canceld_ctxt *llcd_grab(void)
82 {
83         struct llog_canceld_ctxt *llcd;
84
85         spin_lock(&lcm->lcm_llcd_lock);
86         if (list_empty(&lcm->lcm_llcd_free)) {
87                 spin_unlock(&lcm->lcm_llcd_lock);
88                 if (llcd_alloc() < 0) {
89                         CERROR("unable to allocate log commit data!\n");
90                         return NULL;
91                 }
92                 spin_lock(&lcm->lcm_llcd_lock);
93         }
94
95         llcd = list_entry(lcm->lcm_llcd_free.next, typeof(*llcd), llcd_list);
96         list_del(&llcd->llcd_list);
97         atomic_dec(&lcm->lcm_llcd_numfree);
98         spin_unlock(&lcm->lcm_llcd_lock);
99
100         llcd->llcd_tries = 0;
101         llcd->llcd_cookiebytes = 0;
102
103         return llcd;
104 }
105 EXPORT_SYMBOL(llcd_grab);
106
107 static void llcd_put(struct llog_canceld_ctxt *llcd)
108 {
109         int offset = offsetof(struct llog_canceld_ctxt, llcd_cookies);
110
111         if (atomic_read(&lcm->lcm_llcd_numfree) >= lcm->lcm_llcd_maxfree) {
112                 OBD_FREE(llcd, LLCD_SIZE + offset);
113         } else {
114                 spin_lock(&lcm->lcm_llcd_lock);
115                 list_add(&llcd->llcd_list, &lcm->lcm_llcd_free);
116                 atomic_inc(&lcm->lcm_llcd_numfree);
117                 spin_unlock(&lcm->lcm_llcd_lock);
118         }
119 }
120
121 /* Send some cookies to the appropriate target */
122 void llcd_send(struct llog_canceld_ctxt *llcd)
123 {
124         spin_lock(&llcd->llcd_lcm->lcm_llcd_lock);
125         list_add_tail(&llcd->llcd_list, &llcd->llcd_lcm->lcm_llcd_pending);
126         spin_unlock(&llcd->llcd_lcm->lcm_llcd_lock);
127
128         wake_up_nr(&llcd->llcd_lcm->lcm_waitq, 1);
129 }
130 EXPORT_SYMBOL(llcd_send);
131
132 /* deleted objects have a commit callback that cancels the MDS
133  * log record for the deletion.  The commit callback calls this
134  * function
135  */
136 int llog_obd_repl_cancel(struct llog_ctxt *ctxt, int count,
137                          struct llog_cookie *cookies, int flags, void *data)
138 {
139         struct llog_canceld_ctxt *llcd;
140         int rc = 0;
141         ENTRY;
142
143         LASSERT(ctxt);
144
145         if (ctxt->loc_imp == NULL) {
146                 CWARN("no import for ctxt %p\n", ctxt);
147                 RETURN(0);
148         }
149
150         if (count == 0 || cookies == NULL) {
151                 down(&ctxt->loc_sem);
152                 if (ctxt->loc_llcd == NULL || !(flags & OBD_LLOG_FL_SENDNOW))
153                         GOTO(out, rc);
154
155                 llcd = ctxt->loc_llcd;
156                 GOTO(send_now, rc);
157         }
158
159         down(&ctxt->loc_sem);
160         llcd = ctxt->loc_llcd;
161         if (llcd == NULL) {
162                 llcd = llcd_grab();
163                 if (llcd == NULL) {
164                         CERROR("couldn't get an llcd - dropped "LPX64":%x+%u\n",
165                                cookies->lgc_lgl.lgl_oid,
166                                cookies->lgc_lgl.lgl_ogen, cookies->lgc_index);
167                         GOTO(out, rc = -ENOMEM);
168                 }
169                 llcd->llcd_ctxt = ctxt;
170                 ctxt->loc_llcd = llcd;
171         }
172
173         memcpy((char *)llcd->llcd_cookies + llcd->llcd_cookiebytes, cookies,
174                sizeof(*cookies));
175         llcd->llcd_cookiebytes += sizeof(*cookies);
176
177 send_now:
178         if ((LLCD_SIZE - llcd->llcd_cookiebytes < sizeof(*cookies) ||
179              flags & OBD_LLOG_FL_SENDNOW)) {
180                 CDEBUG(D_HA, "send llcd %p:%p\n", llcd, llcd->llcd_ctxt);
181                 ctxt->loc_llcd = NULL;
182                 llcd_send(llcd);
183         }
184 out:
185         up(&ctxt->loc_sem);
186         return rc;
187 }
188 EXPORT_SYMBOL(llog_obd_repl_cancel);
189
190 int llog_obd_repl_sync(struct llog_ctxt *ctxt, struct obd_export *exp)
191 {
192         int rc = 0;
193         ENTRY;
194
195         if (exp && (ctxt->loc_imp == exp->exp_imp_reverse)) {
196                 down(&ctxt->loc_sem);
197                 if (ctxt->loc_llcd != NULL) {
198                         CWARN("import will be destroyed, put "
199                               "llcd %p:%p\n", ctxt->loc_llcd, ctxt);
200                         llcd_put(ctxt->loc_llcd);
201                         ctxt->loc_llcd = NULL;
202                         ctxt->loc_imp = NULL;
203                 }
204                 up(&ctxt->loc_sem);
205         } else {
206                 rc = llog_cancel(ctxt, 0, NULL, OBD_LLOG_FL_SENDNOW, NULL);
207         }
208
209         RETURN(rc);
210 }
211 EXPORT_SYMBOL(llog_obd_repl_sync);
212
213 static int log_commit_thread(void *arg)
214 {
215         struct llog_commit_master *lcm = arg;
216         struct llog_commit_daemon *lcd;
217         struct llog_canceld_ctxt *llcd, *n;
218         unsigned long flags;
219         ENTRY;
220
221         OBD_ALLOC(lcd, sizeof(*lcd));
222         if (lcd == NULL)
223                 RETURN(-ENOMEM);
224
225         lock_kernel();
226         ptlrpc_daemonize(); /* thread never needs to do IO */
227
228         SIGNAL_MASK_LOCK(current, flags);
229         sigfillset(&current->blocked);
230         RECALC_SIGPENDING;
231         SIGNAL_MASK_UNLOCK(current, flags);
232
233         spin_lock(&lcm->lcm_thread_lock);
234
235         THREAD_NAME(current->comm, sizeof(current->comm) - 1,
236                     "ll_log_comt_%02d", atomic_read(&lcm->lcm_thread_total));
237         atomic_inc(&lcm->lcm_thread_total);
238         spin_unlock(&lcm->lcm_thread_lock);
239         unlock_kernel();
240
241         INIT_LIST_HEAD(&lcd->lcd_lcm_list);
242         INIT_LIST_HEAD(&lcd->lcd_llcd_list);
243         lcd->lcd_lcm = lcm;
244
245         CDEBUG(D_HA, "%s started\n", current->comm);
246         do {
247                 struct ptlrpc_request *request;
248                 struct obd_import *import = NULL;
249                 struct list_head *sending_list;
250                 int rc = 0;
251
252                 /* If we do not have enough pages available, allocate some */
253                 while (atomic_read(&lcm->lcm_llcd_numfree) <
254                        lcm->lcm_llcd_minfree) {
255                         if (llcd_alloc() < 0)
256                                 break;
257                 }
258
259                 spin_lock(&lcm->lcm_thread_lock);
260                 atomic_inc(&lcm->lcm_thread_numidle);
261                 list_move(&lcd->lcd_lcm_list, &lcm->lcm_thread_idle);
262                 spin_unlock(&lcm->lcm_thread_lock);
263
264                 wait_event_interruptible(lcm->lcm_waitq,
265                                          !list_empty(&lcm->lcm_llcd_pending) ||
266                                          lcm->lcm_flags & LLOG_LCM_FL_EXIT);
267
268                 /* If we are the last available thread, start a new one in case
269                  * we get blocked on an RPC (nobody else will start a new one)*/
270                 spin_lock(&lcm->lcm_thread_lock);
271                 atomic_dec(&lcm->lcm_thread_numidle);
272                 list_move(&lcd->lcd_lcm_list, &lcm->lcm_thread_busy);
273                 spin_unlock(&lcm->lcm_thread_lock);
274
275                 sending_list = &lcm->lcm_llcd_pending;
276         resend:
277                 if (lcm->lcm_flags & LLOG_LCM_FL_EXIT) {
278                         lcm->lcm_llcd_maxfree = 0;
279                         lcm->lcm_llcd_minfree = 0;
280                         lcm->lcm_thread_max = 0;
281
282                         if (list_empty(&lcm->lcm_llcd_pending) ||
283                             lcm->lcm_flags & LLOG_LCM_FL_EXIT_FORCE)
284                                 break;
285                 }
286
287                 if (atomic_read(&lcm->lcm_thread_numidle) <= 1 &&
288                     atomic_read(&lcm->lcm_thread_total) < lcm->lcm_thread_max) {
289                         rc = llog_start_commit_thread();
290                         if (rc < 0)
291                                 CERROR("error starting thread: rc %d\n", rc);
292                 }
293
294                 /* Move all of the pending cancels from the same OST off of
295                  * the list, so we don't get multiple threads blocked and/or
296                  * doing upcalls on the same OST in case of failure. */
297                 spin_lock(&lcm->lcm_llcd_lock);
298                 if (!list_empty(sending_list)) {
299                         list_move_tail(sending_list->next,
300                                        &lcd->lcd_llcd_list);
301                         llcd = list_entry(lcd->lcd_llcd_list.next,
302                                           typeof(*llcd), llcd_list);
303                         LASSERT(llcd->llcd_lcm == lcm);
304                         import = llcd->llcd_ctxt->loc_imp;
305                 }
306                 list_for_each_entry_safe(llcd, n, sending_list, llcd_list) {
307                         LASSERT(llcd->llcd_lcm == lcm);
308                         if (import == llcd->llcd_ctxt->loc_imp)
309                                 list_move_tail(&llcd->llcd_list,
310                                                &lcd->lcd_llcd_list);
311                 }
312                 if (sending_list != &lcm->lcm_llcd_resend) {
313                         list_for_each_entry_safe(llcd, n, &lcm->lcm_llcd_resend,
314                                                  llcd_list) {
315                                 LASSERT(llcd->llcd_lcm == lcm);
316                                 if (import == llcd->llcd_ctxt->loc_imp)
317                                         list_move_tail(&llcd->llcd_list,
318                                                        &lcd->lcd_llcd_list);
319                         }
320                 }
321                 spin_unlock(&lcm->lcm_llcd_lock);
322
323                 /* We are the only one manipulating our local list - no lock */
324                 list_for_each_entry_safe(llcd,n, &lcd->lcd_llcd_list,llcd_list){
325                         char *bufs[1] = {(char *)llcd->llcd_cookies};
326
327                         list_del(&llcd->llcd_list);
328                         if (llcd->llcd_cookiebytes == 0) {
329                                 CDEBUG(D_HA, "put empty llcd %p:%p\n",
330                                        llcd, llcd->llcd_ctxt);
331                                 llcd_put(llcd);
332                                 continue;
333                         }
334
335                         down(&llcd->llcd_ctxt->loc_sem);
336                         if (llcd->llcd_ctxt->loc_imp == NULL) {
337                                 up(&llcd->llcd_ctxt->loc_sem);
338                                 CWARN("import will be destroyed, put "
339                                       "llcd %p:%p\n", llcd, llcd->llcd_ctxt);
340                                 llcd_put(llcd);
341                                 continue;
342                         }
343
344                         request = ptlrpc_prep_req(import, OBD_LOG_CANCEL, 1,
345                                                   &llcd->llcd_cookiebytes,
346                                                   bufs);
347                         up(&llcd->llcd_ctxt->loc_sem);
348
349                         if (request == NULL) {
350                                 rc = -ENOMEM;
351                                 CERROR("error preparing commit: rc %d\n", rc);
352
353                                 spin_lock(&lcm->lcm_llcd_lock);
354                                 list_splice(&lcd->lcd_llcd_list,
355                                             &lcm->lcm_llcd_resend);
356                                 INIT_LIST_HEAD(&lcd->lcd_llcd_list);
357                                 spin_unlock(&lcm->lcm_llcd_lock);
358                                 break;
359                         }
360
361                         request->rq_replen = lustre_msg_size(0, NULL);
362                         down(&llcd->llcd_ctxt->loc_sem);
363                         if (llcd->llcd_ctxt->loc_imp == NULL) {
364                                 up(&llcd->llcd_ctxt->loc_sem);
365                                 CWARN("import will be destroyed, put "
366                                       "llcd %p:%p\n", llcd, llcd->llcd_ctxt);
367                                 llcd_put(llcd);
368                                 ptlrpc_req_finished(request);
369                                 continue;
370                         }
371                         rc = ptlrpc_queue_wait(request);
372                         ptlrpc_req_finished(request);
373                         up(&llcd->llcd_ctxt->loc_sem);
374
375                         /* If the RPC failed, we put this and the remaining
376                          * messages onto the resend list for another time. */
377                         if (rc == 0) {
378                                 llcd_put(llcd);
379                                 continue;
380                         }
381
382 #if 0                   /* FIXME just put llcd, not put it on resend list */
383                         spin_lock(&lcm->lcm_llcd_lock);
384                         list_splice(&lcd->lcd_llcd_list, &lcm->lcm_llcd_resend);
385                         if (++llcd->llcd_tries < 5) {
386                                 CERROR("commit %p failed on attempt %d: rc %d\n",
387                                        llcd, llcd->llcd_tries, rc);
388
389                                 list_add_tail(&llcd->llcd_list,
390                                               &lcm->lcm_llcd_resend);
391                                 spin_unlock(&lcm->lcm_llcd_lock);
392                         } else {
393                                 spin_unlock(&lcm->lcm_llcd_lock);
394 #endif
395                                 CERROR("commit %p:%p drop %d cookies: rc %d\n",
396                                        llcd, llcd->llcd_ctxt,
397                                        (int)(llcd->llcd_cookiebytes /
398                                              sizeof(*llcd->llcd_cookies)), rc);
399                                 llcd_put(llcd);
400 #if 0
401                         }
402                         break;
403 #endif
404                 }
405
406                 if (rc == 0) {
407                         sending_list = &lcm->lcm_llcd_resend;
408                         if (!list_empty(sending_list))
409                                 goto resend;
410                 }
411         } while(1);
412
413         /* If we are force exiting, just drop all of the cookies. */
414         if (lcm->lcm_flags & LLOG_LCM_FL_EXIT_FORCE) {
415                 spin_lock(&lcm->lcm_llcd_lock);
416                 list_splice(&lcm->lcm_llcd_pending, &lcd->lcd_llcd_list);
417                 list_splice(&lcm->lcm_llcd_resend, &lcd->lcd_llcd_list);
418                 list_splice(&lcm->lcm_llcd_free, &lcd->lcd_llcd_list);
419                 spin_unlock(&lcm->lcm_llcd_lock);
420
421                 list_for_each_entry_safe(llcd, n, &lcd->lcd_llcd_list,llcd_list)
422                         llcd_put(llcd);
423         }
424
425         spin_lock(&lcm->lcm_thread_lock);
426         list_del(&lcd->lcd_lcm_list);
427         spin_unlock(&lcm->lcm_thread_lock);
428         OBD_FREE(lcd, sizeof(*lcd));
429
430         spin_lock(&lcm->lcm_thread_lock);
431         atomic_dec(&lcm->lcm_thread_total);
432         spin_unlock(&lcm->lcm_thread_lock);
433         wake_up(&lcm->lcm_waitq);
434
435         CDEBUG(D_HA, "%s exiting\n", current->comm);
436         return 0;
437 }
438
439 int llog_start_commit_thread(void)
440 {
441         int rc;
442         ENTRY;
443
444         if (atomic_read(&lcm->lcm_thread_total) >= lcm->lcm_thread_max)
445                 RETURN(0);
446
447         rc = kernel_thread(log_commit_thread, lcm, CLONE_VM | CLONE_FILES);
448         if (rc < 0) {
449                 CERROR("error starting thread #%d: %d\n",
450                        atomic_read(&lcm->lcm_thread_total), rc);
451                 RETURN(rc);
452         }
453
454         RETURN(0);
455 }
456 EXPORT_SYMBOL(llog_start_commit_thread);
457
458 static struct llog_process_args {
459         struct semaphore         llpa_sem;
460         struct llog_ctxt        *llpa_ctxt;
461         void                    *llpa_cb;
462         void                    *llpa_arg;
463 } llpa;
464
465 int llog_init_commit_master(void)
466 {
467         INIT_LIST_HEAD(&lcm->lcm_thread_busy);
468         INIT_LIST_HEAD(&lcm->lcm_thread_idle);
469         spin_lock_init(&lcm->lcm_thread_lock);
470         atomic_set(&lcm->lcm_thread_numidle, 0);
471         init_waitqueue_head(&lcm->lcm_waitq);
472         INIT_LIST_HEAD(&lcm->lcm_llcd_pending);
473         INIT_LIST_HEAD(&lcm->lcm_llcd_resend);
474         INIT_LIST_HEAD(&lcm->lcm_llcd_free);
475         spin_lock_init(&lcm->lcm_llcd_lock);
476         atomic_set(&lcm->lcm_llcd_numfree, 0);
477         lcm->lcm_llcd_minfree = 0;
478         lcm->lcm_thread_max = 5;
479         /* FIXME initialize semaphore for llog_process_args */
480         sema_init(&llpa.llpa_sem, 1);
481         return 0;
482 }
483
484 int llog_cleanup_commit_master(int force)
485 {
486         lcm->lcm_flags |= LLOG_LCM_FL_EXIT;
487         if (force)
488                 lcm->lcm_flags |= LLOG_LCM_FL_EXIT_FORCE;
489         wake_up(&lcm->lcm_waitq);
490
491         wait_event_interruptible(lcm->lcm_waitq,
492                                  atomic_read(&lcm->lcm_thread_total) == 0);
493         return 0;
494 }
495
496 static int log_process_thread(void *args)
497 {
498         struct llog_process_args *data = args;
499         struct llog_ctxt *ctxt = data->llpa_ctxt;
500         void   *cb = data->llpa_cb;
501         struct llog_logid logid = *(struct llog_logid *)(data->llpa_arg);
502         struct llog_handle *llh = NULL;
503         unsigned long flags;
504         int rc;
505         ENTRY;
506
507         up(&data->llpa_sem);
508         lock_kernel();
509         ptlrpc_daemonize(); /* thread never needs to do IO */
510
511         SIGNAL_MASK_LOCK(current, flags);
512         sigfillset(&current->blocked);
513         RECALC_SIGPENDING;
514         SIGNAL_MASK_UNLOCK(current, flags);
515         unlock_kernel();
516
517         rc = llog_open(ctxt, &llh, &logid, NULL, 0);
518         if (rc) {
519                 CERROR("llog_create failed %d\n", rc);
520                 RETURN(rc);
521         }
522         rc = llog_init_handle(llh, LLOG_F_IS_CAT, NULL);
523         if (rc) {
524                 CERROR("llog_init_handle failed %d\n", rc);
525                 GOTO(out, rc);
526         }
527
528         if (cb) {
529                 rc = llog_cat_process(llh, (llog_cb_t)cb, NULL);
530                 if (rc != LLOG_PROC_BREAK)
531                         CERROR("llog_cat_process failed %d\n", rc);
532         } else {
533                 CWARN("no callback function for recovery\n");
534         }
535
536         CDEBUG(D_HA, "send llcd %p:%p forcibly after recovery\n",
537                ctxt->loc_llcd, ctxt);
538         llog_sync(ctxt, NULL);
539 out:
540         rc = llog_cat_put(llh);
541         if (rc)
542                 CERROR("llog_cat_put failed %d\n", rc);
543
544         RETURN(rc);
545 }
546
547 static int llog_recovery_generic(struct llog_ctxt *ctxt, void *handle,void *arg)
548 {
549         int rc;
550         ENTRY;
551
552         down(&llpa.llpa_sem);
553         llpa.llpa_ctxt = ctxt;
554         llpa.llpa_cb = handle;
555         llpa.llpa_arg = arg;
556
557         rc = kernel_thread(log_process_thread, &llpa, CLONE_VM | CLONE_FILES);
558         if (rc < 0)
559                 CERROR("error starting log_process_thread: %d\n", rc);
560         else {
561                 CDEBUG(D_HA, "log_process_thread: %d\n", rc);
562                 rc = 0;
563         }
564
565         RETURN(rc);
566 }
567
568 int llog_repl_connect(struct llog_ctxt *ctxt, int count,
569                       struct llog_logid *logid, struct llog_gen *gen,
570                       struct obd_uuid *uuid)
571 {
572         struct llog_canceld_ctxt *llcd;
573         int rc;
574         ENTRY;
575
576         /* send back llcd before recovery from llog */
577         if (ctxt->loc_llcd != NULL) {
578                 CWARN("llcd %p:%p not empty\n", ctxt->loc_llcd, ctxt);
579                 llog_sync(ctxt, NULL);
580         }
581
582         down(&ctxt->loc_sem);
583         ctxt->loc_gen = *gen;
584         llcd = llcd_grab();
585         if (llcd == NULL) {
586                 CERROR("couldn't get an llcd\n");
587                 up(&ctxt->loc_sem);
588                 RETURN(-ENOMEM);
589         }
590         llcd->llcd_ctxt = ctxt;
591         ctxt->loc_llcd = llcd;
592         up(&ctxt->loc_sem);
593
594         rc = llog_recovery_generic(ctxt, ctxt->llog_proc_cb, logid);
595         if (rc != 0)
596                 CERROR("error recovery process: %d\n", rc);
597
598         RETURN(rc);
599 }
600 EXPORT_SYMBOL(llog_repl_connect);
601
602 #else /* !__KERNEL__ */
603
604 int llog_obd_repl_cancel(struct llog_ctxt *ctxt, int count,
605                          struct llog_cookie *cookies, int flags, void *data)
606 {
607         return 0;
608 }
609 #endif