xref: /openbmc/linux/fs/ocfs2/dlm/dlmunlock.c (revision 31b90347)
1 /* -*- mode: c; c-basic-offset: 8; -*-
2  * vim: noexpandtab sw=8 ts=8 sts=0:
3  *
4  * dlmunlock.c
5  *
6  * underlying calls for unlocking locks
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/highmem.h>
32 #include <linux/init.h>
33 #include <linux/sysctl.h>
34 #include <linux/random.h>
35 #include <linux/blkdev.h>
36 #include <linux/socket.h>
37 #include <linux/inet.h>
38 #include <linux/spinlock.h>
39 #include <linux/delay.h>
40 
41 #include "cluster/heartbeat.h"
42 #include "cluster/nodemanager.h"
43 #include "cluster/tcp.h"
44 
45 #include "dlmapi.h"
46 #include "dlmcommon.h"
47 
48 #define MLOG_MASK_PREFIX ML_DLM
49 #include "cluster/masklog.h"
50 
51 #define DLM_UNLOCK_FREE_LOCK           0x00000001
52 #define DLM_UNLOCK_CALL_AST            0x00000002
53 #define DLM_UNLOCK_REMOVE_LOCK         0x00000004
54 #define DLM_UNLOCK_REGRANT_LOCK        0x00000008
55 #define DLM_UNLOCK_CLEAR_CONVERT_TYPE  0x00000010
56 
57 
58 static enum dlm_status dlm_get_cancel_actions(struct dlm_ctxt *dlm,
59 					      struct dlm_lock_resource *res,
60 					      struct dlm_lock *lock,
61 					      struct dlm_lockstatus *lksb,
62 					      int *actions);
63 static enum dlm_status dlm_get_unlock_actions(struct dlm_ctxt *dlm,
64 					      struct dlm_lock_resource *res,
65 					      struct dlm_lock *lock,
66 					      struct dlm_lockstatus *lksb,
67 					      int *actions);
68 
69 static enum dlm_status dlm_send_remote_unlock_request(struct dlm_ctxt *dlm,
70 						 struct dlm_lock_resource *res,
71 						 struct dlm_lock *lock,
72 						 struct dlm_lockstatus *lksb,
73 						 int flags,
74 						 u8 owner);
75 
76 
77 /*
78  * according to the spec:
79  * http://opendlm.sourceforge.net/cvsmirror/opendlm/docs/dlmbook_final.pdf
80  *
81  *  flags & LKM_CANCEL != 0: must be converting or blocked
82  *  flags & LKM_CANCEL == 0: must be granted
83  *
84  * So to unlock a converting lock, you must first cancel the
85  * convert (passing LKM_CANCEL in flags), then call the unlock
86  * again (with no LKM_CANCEL in flags).
87  */
88 
89 
90 /*
91  * locking:
92  *   caller needs:  none
93  *   taken:         res->spinlock and lock->spinlock taken and dropped
94  *   held on exit:  none
95  * returns: DLM_NORMAL, DLM_NOLOCKMGR, status from network
96  * all callers should have taken an extra ref on lock coming in
97  */
98 static enum dlm_status dlmunlock_common(struct dlm_ctxt *dlm,
99 					struct dlm_lock_resource *res,
100 					struct dlm_lock *lock,
101 					struct dlm_lockstatus *lksb,
102 					int flags, int *call_ast,
103 					int master_node)
104 {
105 	enum dlm_status status;
106 	int actions = 0;
107 	int in_use;
108         u8 owner;
109 
110 	mlog(0, "master_node = %d, valblk = %d\n", master_node,
111 	     flags & LKM_VALBLK);
112 
113 	if (master_node)
114 		BUG_ON(res->owner != dlm->node_num);
115 	else
116 		BUG_ON(res->owner == dlm->node_num);
117 
118 	spin_lock(&dlm->ast_lock);
119 	/* We want to be sure that we're not freeing a lock
120 	 * that still has AST's pending... */
121 	in_use = !list_empty(&lock->ast_list);
122 	spin_unlock(&dlm->ast_lock);
123 	if (in_use && !(flags & LKM_CANCEL)) {
124 	       mlog(ML_ERROR, "lockres %.*s: Someone is calling dlmunlock "
125 		    "while waiting for an ast!", res->lockname.len,
126 		    res->lockname.name);
127 		return DLM_BADPARAM;
128 	}
129 
130 	spin_lock(&res->spinlock);
131 	if (res->state & DLM_LOCK_RES_IN_PROGRESS) {
132 		if (master_node && !(flags & LKM_CANCEL)) {
133 			mlog(ML_ERROR, "lockres in progress!\n");
134 			spin_unlock(&res->spinlock);
135 			return DLM_FORWARD;
136 		}
137 		/* ok for this to sleep if not in a network handler */
138 		__dlm_wait_on_lockres(res);
139 		res->state |= DLM_LOCK_RES_IN_PROGRESS;
140 	}
141 	spin_lock(&lock->spinlock);
142 
143 	if (res->state & DLM_LOCK_RES_RECOVERING) {
144 		status = DLM_RECOVERING;
145 		goto leave;
146 	}
147 
148 	if (res->state & DLM_LOCK_RES_MIGRATING) {
149 		status = DLM_MIGRATING;
150 		goto leave;
151 	}
152 
153 	/* see above for what the spec says about
154 	 * LKM_CANCEL and the lock queue state */
155 	if (flags & LKM_CANCEL)
156 		status = dlm_get_cancel_actions(dlm, res, lock, lksb, &actions);
157 	else
158 		status = dlm_get_unlock_actions(dlm, res, lock, lksb, &actions);
159 
160 	if (status != DLM_NORMAL && (status != DLM_CANCELGRANT || !master_node))
161 		goto leave;
162 
163 	/* By now this has been masked out of cancel requests. */
164 	if (flags & LKM_VALBLK) {
165 		/* make the final update to the lvb */
166 		if (master_node)
167 			memcpy(res->lvb, lksb->lvb, DLM_LVB_LEN);
168 		else
169 			flags |= LKM_PUT_LVB; /* let the send function
170 					       * handle it. */
171 	}
172 
173 	if (!master_node) {
174 		owner = res->owner;
175 		/* drop locks and send message */
176 		if (flags & LKM_CANCEL)
177 			lock->cancel_pending = 1;
178 		else
179 			lock->unlock_pending = 1;
180 		spin_unlock(&lock->spinlock);
181 		spin_unlock(&res->spinlock);
182 		status = dlm_send_remote_unlock_request(dlm, res, lock, lksb,
183 							flags, owner);
184 		spin_lock(&res->spinlock);
185 		spin_lock(&lock->spinlock);
186 		/* if the master told us the lock was already granted,
187 		 * let the ast handle all of these actions */
188 		if (status == DLM_CANCELGRANT) {
189 			actions &= ~(DLM_UNLOCK_REMOVE_LOCK|
190 				     DLM_UNLOCK_REGRANT_LOCK|
191 				     DLM_UNLOCK_CLEAR_CONVERT_TYPE);
192 		} else if (status == DLM_RECOVERING ||
193 			   status == DLM_MIGRATING ||
194 			   status == DLM_FORWARD) {
195 			/* must clear the actions because this unlock
196 			 * is about to be retried.  cannot free or do
197 			 * any list manipulation. */
198 			mlog(0, "%s:%.*s: clearing actions, %s\n",
199 			     dlm->name, res->lockname.len,
200 			     res->lockname.name,
201 			     status==DLM_RECOVERING?"recovering":
202 			     (status==DLM_MIGRATING?"migrating":
203 			      "forward"));
204 			actions = 0;
205 		}
206 		if (flags & LKM_CANCEL)
207 			lock->cancel_pending = 0;
208 		else
209 			lock->unlock_pending = 0;
210 
211 	}
212 
213 	/* get an extra ref on lock.  if we are just switching
214 	 * lists here, we dont want the lock to go away. */
215 	dlm_lock_get(lock);
216 
217 	if (actions & DLM_UNLOCK_REMOVE_LOCK) {
218 		list_del_init(&lock->list);
219 		dlm_lock_put(lock);
220 	}
221 	if (actions & DLM_UNLOCK_REGRANT_LOCK) {
222 		dlm_lock_get(lock);
223 		list_add_tail(&lock->list, &res->granted);
224 	}
225 	if (actions & DLM_UNLOCK_CLEAR_CONVERT_TYPE) {
226 		mlog(0, "clearing convert_type at %smaster node\n",
227 		     master_node ? "" : "non-");
228 		lock->ml.convert_type = LKM_IVMODE;
229 	}
230 
231 	/* remove the extra ref on lock */
232 	dlm_lock_put(lock);
233 
234 leave:
235 	res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
236 	if (!dlm_lock_on_list(&res->converting, lock))
237 		BUG_ON(lock->ml.convert_type != LKM_IVMODE);
238 	else
239 		BUG_ON(lock->ml.convert_type == LKM_IVMODE);
240 	spin_unlock(&lock->spinlock);
241 	spin_unlock(&res->spinlock);
242 	wake_up(&res->wq);
243 
244 	/* let the caller's final dlm_lock_put handle the actual kfree */
245 	if (actions & DLM_UNLOCK_FREE_LOCK) {
246 		/* this should always be coupled with list removal */
247 		BUG_ON(!(actions & DLM_UNLOCK_REMOVE_LOCK));
248 		mlog(0, "lock %u:%llu should be gone now! refs=%d\n",
249 		     dlm_get_lock_cookie_node(be64_to_cpu(lock->ml.cookie)),
250 		     dlm_get_lock_cookie_seq(be64_to_cpu(lock->ml.cookie)),
251 		     atomic_read(&lock->lock_refs.refcount)-1);
252 		dlm_lock_put(lock);
253 	}
254 	if (actions & DLM_UNLOCK_CALL_AST)
255 		*call_ast = 1;
256 
257 	/* if cancel or unlock succeeded, lvb work is done */
258 	if (status == DLM_NORMAL)
259 		lksb->flags &= ~(DLM_LKSB_PUT_LVB|DLM_LKSB_GET_LVB);
260 
261 	return status;
262 }
263 
264 void dlm_commit_pending_unlock(struct dlm_lock_resource *res,
265 			       struct dlm_lock *lock)
266 {
267 	/* leave DLM_LKSB_PUT_LVB on the lksb so any final
268 	 * update of the lvb will be sent to the new master */
269 	list_del_init(&lock->list);
270 }
271 
272 void dlm_commit_pending_cancel(struct dlm_lock_resource *res,
273 			       struct dlm_lock *lock)
274 {
275 	list_move_tail(&lock->list, &res->granted);
276 	lock->ml.convert_type = LKM_IVMODE;
277 }
278 
279 
280 static inline enum dlm_status dlmunlock_master(struct dlm_ctxt *dlm,
281 					  struct dlm_lock_resource *res,
282 					  struct dlm_lock *lock,
283 					  struct dlm_lockstatus *lksb,
284 					  int flags,
285 					  int *call_ast)
286 {
287 	return dlmunlock_common(dlm, res, lock, lksb, flags, call_ast, 1);
288 }
289 
290 static inline enum dlm_status dlmunlock_remote(struct dlm_ctxt *dlm,
291 					  struct dlm_lock_resource *res,
292 					  struct dlm_lock *lock,
293 					  struct dlm_lockstatus *lksb,
294 					  int flags, int *call_ast)
295 {
296 	return dlmunlock_common(dlm, res, lock, lksb, flags, call_ast, 0);
297 }
298 
299 /*
300  * locking:
301  *   caller needs:  none
302  *   taken:         none
303  *   held on exit:  none
304  * returns: DLM_NORMAL, DLM_NOLOCKMGR, status from network
305  */
306 static enum dlm_status dlm_send_remote_unlock_request(struct dlm_ctxt *dlm,
307 						 struct dlm_lock_resource *res,
308 						 struct dlm_lock *lock,
309 						 struct dlm_lockstatus *lksb,
310 						 int flags,
311 						 u8 owner)
312 {
313 	struct dlm_unlock_lock unlock;
314 	int tmpret;
315 	enum dlm_status ret;
316 	int status = 0;
317 	struct kvec vec[2];
318 	size_t veclen = 1;
319 
320 	mlog(0, "%.*s\n", res->lockname.len, res->lockname.name);
321 
322 	if (owner == dlm->node_num) {
323 		/* ended up trying to contact ourself.  this means
324 		 * that the lockres had been remote but became local
325 		 * via a migration.  just retry it, now as local */
326 		mlog(0, "%s:%.*s: this node became the master due to a "
327 		     "migration, re-evaluate now\n", dlm->name,
328 		     res->lockname.len, res->lockname.name);
329 		return DLM_FORWARD;
330 	}
331 
332 	memset(&unlock, 0, sizeof(unlock));
333 	unlock.node_idx = dlm->node_num;
334 	unlock.flags = cpu_to_be32(flags);
335 	unlock.cookie = lock->ml.cookie;
336 	unlock.namelen = res->lockname.len;
337 	memcpy(unlock.name, res->lockname.name, unlock.namelen);
338 
339 	vec[0].iov_len = sizeof(struct dlm_unlock_lock);
340 	vec[0].iov_base = &unlock;
341 
342 	if (flags & LKM_PUT_LVB) {
343 		/* extra data to send if we are updating lvb */
344 		vec[1].iov_len = DLM_LVB_LEN;
345 		vec[1].iov_base = lock->lksb->lvb;
346 		veclen++;
347 	}
348 
349 	tmpret = o2net_send_message_vec(DLM_UNLOCK_LOCK_MSG, dlm->key,
350 					vec, veclen, owner, &status);
351 	if (tmpret >= 0) {
352 		// successfully sent and received
353 		if (status == DLM_FORWARD)
354 			mlog(0, "master was in-progress.  retry\n");
355 		ret = status;
356 	} else {
357 		mlog(ML_ERROR, "Error %d when sending message %u (key 0x%x) to "
358 		     "node %u\n", tmpret, DLM_UNLOCK_LOCK_MSG, dlm->key, owner);
359 		if (dlm_is_host_down(tmpret)) {
360 			/* NOTE: this seems strange, but it is what we want.
361 			 * when the master goes down during a cancel or
362 			 * unlock, the recovery code completes the operation
363 			 * as if the master had not died, then passes the
364 			 * updated state to the recovery master.  this thread
365 			 * just needs to finish out the operation and call
366 			 * the unlockast. */
367 			ret = DLM_NORMAL;
368 		} else {
369 			/* something bad.  this will BUG in ocfs2 */
370 			ret = dlm_err_to_dlm_status(tmpret);
371 		}
372 	}
373 
374 	return ret;
375 }
376 
377 /*
378  * locking:
379  *   caller needs:  none
380  *   taken:         takes and drops res->spinlock
381  *   held on exit:  none
382  * returns: DLM_NORMAL, DLM_BADARGS, DLM_IVLOCKID,
383  *          return value from dlmunlock_master
384  */
385 int dlm_unlock_lock_handler(struct o2net_msg *msg, u32 len, void *data,
386 			    void **ret_data)
387 {
388 	struct dlm_ctxt *dlm = data;
389 	struct dlm_unlock_lock *unlock = (struct dlm_unlock_lock *)msg->buf;
390 	struct dlm_lock_resource *res = NULL;
391 	struct dlm_lock *lock = NULL;
392 	enum dlm_status status = DLM_NORMAL;
393 	int found = 0, i;
394 	struct dlm_lockstatus *lksb = NULL;
395 	int ignore;
396 	u32 flags;
397 	struct list_head *queue;
398 
399 	flags = be32_to_cpu(unlock->flags);
400 
401 	if (flags & LKM_GET_LVB) {
402 		mlog(ML_ERROR, "bad args!  GET_LVB specified on unlock!\n");
403 		return DLM_BADARGS;
404 	}
405 
406 	if ((flags & (LKM_PUT_LVB|LKM_CANCEL)) == (LKM_PUT_LVB|LKM_CANCEL)) {
407 		mlog(ML_ERROR, "bad args!  cannot modify lvb on a CANCEL "
408 		     "request!\n");
409 		return DLM_BADARGS;
410 	}
411 
412 	if (unlock->namelen > DLM_LOCKID_NAME_MAX) {
413 		mlog(ML_ERROR, "Invalid name length in unlock handler!\n");
414 		return DLM_IVBUFLEN;
415 	}
416 
417 	if (!dlm_grab(dlm))
418 		return DLM_REJECTED;
419 
420 	mlog_bug_on_msg(!dlm_domain_fully_joined(dlm),
421 			"Domain %s not fully joined!\n", dlm->name);
422 
423 	mlog(0, "lvb: %s\n", flags & LKM_PUT_LVB ? "put lvb" : "none");
424 
425 	res = dlm_lookup_lockres(dlm, unlock->name, unlock->namelen);
426 	if (!res) {
427 		/* We assume here that a no lock resource simply means
428 		 * it was migrated away and destroyed before the other
429 		 * node could detect it. */
430 		mlog(0, "returning DLM_FORWARD -- res no longer exists\n");
431 		status = DLM_FORWARD;
432 		goto not_found;
433 	}
434 
435 	queue=&res->granted;
436 	found = 0;
437 	spin_lock(&res->spinlock);
438 	if (res->state & DLM_LOCK_RES_RECOVERING) {
439 		spin_unlock(&res->spinlock);
440 		mlog(0, "returning DLM_RECOVERING\n");
441 		status = DLM_RECOVERING;
442 		goto leave;
443 	}
444 
445 	if (res->state & DLM_LOCK_RES_MIGRATING) {
446 		spin_unlock(&res->spinlock);
447 		mlog(0, "returning DLM_MIGRATING\n");
448 		status = DLM_MIGRATING;
449 		goto leave;
450 	}
451 
452 	if (res->owner != dlm->node_num) {
453 		spin_unlock(&res->spinlock);
454 		mlog(0, "returning DLM_FORWARD -- not master\n");
455 		status = DLM_FORWARD;
456 		goto leave;
457 	}
458 
459 	for (i=0; i<3; i++) {
460 		list_for_each_entry(lock, queue, list) {
461 			if (lock->ml.cookie == unlock->cookie &&
462 		    	    lock->ml.node == unlock->node_idx) {
463 				dlm_lock_get(lock);
464 				found = 1;
465 				break;
466 			}
467 		}
468 		if (found)
469 			break;
470 		/* scan granted -> converting -> blocked queues */
471 		queue++;
472 	}
473 	spin_unlock(&res->spinlock);
474 	if (!found) {
475 		status = DLM_IVLOCKID;
476 		goto not_found;
477 	}
478 
479 	/* lock was found on queue */
480 	lksb = lock->lksb;
481 	if (flags & (LKM_VALBLK|LKM_PUT_LVB) &&
482 	    lock->ml.type != LKM_EXMODE)
483 		flags &= ~(LKM_VALBLK|LKM_PUT_LVB);
484 
485 	/* unlockast only called on originating node */
486 	if (flags & LKM_PUT_LVB) {
487 		lksb->flags |= DLM_LKSB_PUT_LVB;
488 		memcpy(&lksb->lvb[0], &unlock->lvb[0], DLM_LVB_LEN);
489 	}
490 
491 	/* if this is in-progress, propagate the DLM_FORWARD
492 	 * all the way back out */
493 	status = dlmunlock_master(dlm, res, lock, lksb, flags, &ignore);
494 	if (status == DLM_FORWARD)
495 		mlog(0, "lockres is in progress\n");
496 
497 	if (flags & LKM_PUT_LVB)
498 		lksb->flags &= ~DLM_LKSB_PUT_LVB;
499 
500 	dlm_lockres_calc_usage(dlm, res);
501 	dlm_kick_thread(dlm, res);
502 
503 not_found:
504 	if (!found)
505 		mlog(ML_ERROR, "failed to find lock to unlock! "
506 			       "cookie=%u:%llu\n",
507 		     dlm_get_lock_cookie_node(be64_to_cpu(unlock->cookie)),
508 		     dlm_get_lock_cookie_seq(be64_to_cpu(unlock->cookie)));
509 	else
510 		dlm_lock_put(lock);
511 
512 leave:
513 	if (res)
514 		dlm_lockres_put(res);
515 
516 	dlm_put(dlm);
517 
518 	return status;
519 }
520 
521 
522 static enum dlm_status dlm_get_cancel_actions(struct dlm_ctxt *dlm,
523 					      struct dlm_lock_resource *res,
524 					      struct dlm_lock *lock,
525 					      struct dlm_lockstatus *lksb,
526 					      int *actions)
527 {
528 	enum dlm_status status;
529 
530 	if (dlm_lock_on_list(&res->blocked, lock)) {
531 		/* cancel this outright */
532 		status = DLM_NORMAL;
533 		*actions = (DLM_UNLOCK_CALL_AST |
534 			    DLM_UNLOCK_REMOVE_LOCK);
535 	} else if (dlm_lock_on_list(&res->converting, lock)) {
536 		/* cancel the request, put back on granted */
537 		status = DLM_NORMAL;
538 		*actions = (DLM_UNLOCK_CALL_AST |
539 			    DLM_UNLOCK_REMOVE_LOCK |
540 			    DLM_UNLOCK_REGRANT_LOCK |
541 			    DLM_UNLOCK_CLEAR_CONVERT_TYPE);
542 	} else if (dlm_lock_on_list(&res->granted, lock)) {
543 		/* too late, already granted. */
544 		status = DLM_CANCELGRANT;
545 		*actions = DLM_UNLOCK_CALL_AST;
546 	} else {
547 		mlog(ML_ERROR, "lock to cancel is not on any list!\n");
548 		status = DLM_IVLOCKID;
549 		*actions = 0;
550 	}
551 	return status;
552 }
553 
554 static enum dlm_status dlm_get_unlock_actions(struct dlm_ctxt *dlm,
555 					      struct dlm_lock_resource *res,
556 					      struct dlm_lock *lock,
557 					      struct dlm_lockstatus *lksb,
558 					      int *actions)
559 {
560 	enum dlm_status status;
561 
562 	/* unlock request */
563 	if (!dlm_lock_on_list(&res->granted, lock)) {
564 		status = DLM_DENIED;
565 		dlm_error(status);
566 		*actions = 0;
567 	} else {
568 		/* unlock granted lock */
569 		status = DLM_NORMAL;
570 		*actions = (DLM_UNLOCK_FREE_LOCK |
571 			    DLM_UNLOCK_CALL_AST |
572 			    DLM_UNLOCK_REMOVE_LOCK);
573 	}
574 	return status;
575 }
576 
577 /* there seems to be no point in doing this async
578  * since (even for the remote case) there is really
579  * no work to queue up... so just do it and fire the
580  * unlockast by hand when done... */
581 enum dlm_status dlmunlock(struct dlm_ctxt *dlm, struct dlm_lockstatus *lksb,
582 			  int flags, dlm_astunlockfunc_t *unlockast, void *data)
583 {
584 	enum dlm_status status;
585 	struct dlm_lock_resource *res;
586 	struct dlm_lock *lock = NULL;
587 	int call_ast, is_master;
588 
589 	if (!lksb) {
590 		dlm_error(DLM_BADARGS);
591 		return DLM_BADARGS;
592 	}
593 
594 	if (flags & ~(LKM_CANCEL | LKM_VALBLK | LKM_INVVALBLK)) {
595 		dlm_error(DLM_BADPARAM);
596 		return DLM_BADPARAM;
597 	}
598 
599 	if ((flags & (LKM_VALBLK | LKM_CANCEL)) == (LKM_VALBLK | LKM_CANCEL)) {
600 		mlog(0, "VALBLK given with CANCEL: ignoring VALBLK\n");
601 		flags &= ~LKM_VALBLK;
602 	}
603 
604 	if (!lksb->lockid || !lksb->lockid->lockres) {
605 		dlm_error(DLM_BADPARAM);
606 		return DLM_BADPARAM;
607 	}
608 
609 	lock = lksb->lockid;
610 	BUG_ON(!lock);
611 	dlm_lock_get(lock);
612 
613 	res = lock->lockres;
614 	BUG_ON(!res);
615 	dlm_lockres_get(res);
616 retry:
617 	call_ast = 0;
618 	/* need to retry up here because owner may have changed */
619 	mlog(0, "lock=%p res=%p\n", lock, res);
620 
621 	spin_lock(&res->spinlock);
622 	is_master = (res->owner == dlm->node_num);
623 	if (flags & LKM_VALBLK && lock->ml.type != LKM_EXMODE)
624 		flags &= ~LKM_VALBLK;
625 	spin_unlock(&res->spinlock);
626 
627 	if (is_master) {
628 		status = dlmunlock_master(dlm, res, lock, lksb, flags,
629 					  &call_ast);
630 		mlog(0, "done calling dlmunlock_master: returned %d, "
631 		     "call_ast is %d\n", status, call_ast);
632 	} else {
633 		status = dlmunlock_remote(dlm, res, lock, lksb, flags,
634 					  &call_ast);
635 		mlog(0, "done calling dlmunlock_remote: returned %d, "
636 		     "call_ast is %d\n", status, call_ast);
637 	}
638 
639 	if (status == DLM_RECOVERING ||
640 	    status == DLM_MIGRATING ||
641 	    status == DLM_FORWARD) {
642 		/* We want to go away for a tiny bit to allow recovery
643 		 * / migration to complete on this resource. I don't
644 		 * know of any wait queue we could sleep on as this
645 		 * may be happening on another node. Perhaps the
646 		 * proper solution is to queue up requests on the
647 		 * other end? */
648 
649 		/* do we want to yield(); ?? */
650 		msleep(50);
651 
652 		mlog(0, "retrying unlock due to pending recovery/"
653 		     "migration/in-progress\n");
654 		goto retry;
655 	}
656 
657 	if (call_ast) {
658 		mlog(0, "calling unlockast(%p, %d)\n", data, status);
659 		if (is_master) {
660 			/* it is possible that there is one last bast
661 			 * pending.  make sure it is flushed, then
662 			 * call the unlockast.
663 			 * not an issue if this is a mastered remotely,
664 			 * since this lock has been removed from the
665 			 * lockres queues and cannot be found. */
666 			dlm_kick_thread(dlm, NULL);
667 			wait_event(dlm->ast_wq,
668 				   dlm_lock_basts_flushed(dlm, lock));
669 		}
670 		(*unlockast)(data, status);
671 	}
672 
673 	if (status == DLM_CANCELGRANT)
674 		status = DLM_NORMAL;
675 
676 	if (status == DLM_NORMAL) {
677 		mlog(0, "kicking the thread\n");
678 		dlm_kick_thread(dlm, res);
679 	} else
680 		dlm_error(status);
681 
682 	dlm_lockres_calc_usage(dlm, res);
683 	dlm_lockres_put(res);
684 	dlm_lock_put(lock);
685 
686 	mlog(0, "returning status=%d!\n", status);
687 	return status;
688 }
689 EXPORT_SYMBOL_GPL(dlmunlock);
690 
691