xref: /linux/fs/ocfs2/dlm/dlmunlock.c (revision 14b42963f64b98ab61fa9723c03d71aa5ef4f862)
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/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/spinlock.h>
41 #include <linux/delay.h>
42 
43 #include "cluster/heartbeat.h"
44 #include "cluster/nodemanager.h"
45 #include "cluster/tcp.h"
46 
47 #include "dlmapi.h"
48 #include "dlmcommon.h"
49 
50 #define MLOG_MASK_PREFIX ML_DLM
51 #include "cluster/masklog.h"
52 
53 #define DLM_UNLOCK_FREE_LOCK           0x00000001
54 #define DLM_UNLOCK_CALL_AST            0x00000002
55 #define DLM_UNLOCK_REMOVE_LOCK         0x00000004
56 #define DLM_UNLOCK_REGRANT_LOCK        0x00000008
57 #define DLM_UNLOCK_CLEAR_CONVERT_TYPE  0x00000010
58 
59 
60 static enum dlm_status dlm_get_cancel_actions(struct dlm_ctxt *dlm,
61 					      struct dlm_lock_resource *res,
62 					      struct dlm_lock *lock,
63 					      struct dlm_lockstatus *lksb,
64 					      int *actions);
65 static enum dlm_status dlm_get_unlock_actions(struct dlm_ctxt *dlm,
66 					      struct dlm_lock_resource *res,
67 					      struct dlm_lock *lock,
68 					      struct dlm_lockstatus *lksb,
69 					      int *actions);
70 
71 static enum dlm_status dlm_send_remote_unlock_request(struct dlm_ctxt *dlm,
72 						 struct dlm_lock_resource *res,
73 						 struct dlm_lock *lock,
74 						 struct dlm_lockstatus *lksb,
75 						 int flags,
76 						 u8 owner);
77 
78 
79 /*
80  * according to the spec:
81  * http://opendlm.sourceforge.net/cvsmirror/opendlm/docs/dlmbook_final.pdf
82  *
83  *  flags & LKM_CANCEL != 0: must be converting or blocked
84  *  flags & LKM_CANCEL == 0: must be granted
85  *
86  * So to unlock a converting lock, you must first cancel the
87  * convert (passing LKM_CANCEL in flags), then call the unlock
88  * again (with no LKM_CANCEL in flags).
89  */
90 
91 
92 /*
93  * locking:
94  *   caller needs:  none
95  *   taken:         res->spinlock and lock->spinlock taken and dropped
96  *   held on exit:  none
97  * returns: DLM_NORMAL, DLM_NOLOCKMGR, status from network
98  * all callers should have taken an extra ref on lock coming in
99  */
100 static enum dlm_status dlmunlock_common(struct dlm_ctxt *dlm,
101 					struct dlm_lock_resource *res,
102 					struct dlm_lock *lock,
103 					struct dlm_lockstatus *lksb,
104 					int flags, int *call_ast,
105 					int master_node)
106 {
107 	enum dlm_status status;
108 	int actions = 0;
109 	int in_use;
110         u8 owner;
111 
112 	mlog(0, "master_node = %d, valblk = %d\n", master_node,
113 	     flags & LKM_VALBLK);
114 
115 	if (master_node)
116 		BUG_ON(res->owner != dlm->node_num);
117 	else
118 		BUG_ON(res->owner == dlm->node_num);
119 
120 	spin_lock(&dlm->spinlock);
121 	/* We want to be sure that we're not freeing a lock
122 	 * that still has AST's pending... */
123 	in_use = !list_empty(&lock->ast_list);
124 	spin_unlock(&dlm->spinlock);
125 	if (in_use) {
126 	       mlog(ML_ERROR, "lockres %.*s: Someone is calling dlmunlock "
127 		    "while waiting for an ast!", res->lockname.len,
128 		    res->lockname.name);
129 		return DLM_BADPARAM;
130 	}
131 
132 	spin_lock(&res->spinlock);
133 	if (res->state & DLM_LOCK_RES_IN_PROGRESS) {
134 		if (master_node) {
135 			mlog(ML_ERROR, "lockres in progress!\n");
136 			spin_unlock(&res->spinlock);
137 			return DLM_FORWARD;
138 		}
139 		/* ok for this to sleep if not in a network handler */
140 		__dlm_wait_on_lockres(res);
141 		res->state |= DLM_LOCK_RES_IN_PROGRESS;
142 	}
143 	spin_lock(&lock->spinlock);
144 
145 	if (res->state & DLM_LOCK_RES_RECOVERING) {
146 		status = DLM_RECOVERING;
147 		goto leave;
148 	}
149 
150 
151 	/* see above for what the spec says about
152 	 * LKM_CANCEL and the lock queue state */
153 	if (flags & LKM_CANCEL)
154 		status = dlm_get_cancel_actions(dlm, res, lock, lksb, &actions);
155 	else
156 		status = dlm_get_unlock_actions(dlm, res, lock, lksb, &actions);
157 
158 	if (status != DLM_NORMAL)
159 		goto leave;
160 
161 	/* By now this has been masked out of cancel requests. */
162 	if (flags & LKM_VALBLK) {
163 		/* make the final update to the lvb */
164 		if (master_node)
165 			memcpy(res->lvb, lksb->lvb, DLM_LVB_LEN);
166 		else
167 			flags |= LKM_PUT_LVB; /* let the send function
168 					       * handle it. */
169 	}
170 
171 	if (!master_node) {
172 		owner = res->owner;
173 		/* drop locks and send message */
174 		if (flags & LKM_CANCEL)
175 			lock->cancel_pending = 1;
176 		else
177 			lock->unlock_pending = 1;
178 		spin_unlock(&lock->spinlock);
179 		spin_unlock(&res->spinlock);
180 		status = dlm_send_remote_unlock_request(dlm, res, lock, lksb,
181 							flags, owner);
182 		spin_lock(&res->spinlock);
183 		spin_lock(&lock->spinlock);
184 		/* if the master told us the lock was already granted,
185 		 * let the ast handle all of these actions */
186 		if (status == DLM_NORMAL &&
187 		    lksb->status == DLM_CANCELGRANT) {
188 			actions &= ~(DLM_UNLOCK_REMOVE_LOCK|
189 				     DLM_UNLOCK_REGRANT_LOCK|
190 				     DLM_UNLOCK_CLEAR_CONVERT_TYPE);
191 		} else if (status == DLM_RECOVERING ||
192 			   status == DLM_MIGRATING ||
193 			   status == DLM_FORWARD) {
194 			/* must clear the actions because this unlock
195 			 * is about to be retried.  cannot free or do
196 			 * any list manipulation. */
197 			mlog(0, "%s:%.*s: clearing actions, %s\n",
198 			     dlm->name, res->lockname.len,
199 			     res->lockname.name,
200 			     status==DLM_RECOVERING?"recovering":
201 			     (status==DLM_MIGRATING?"migrating":
202 			      "forward"));
203 			actions = 0;
204 		}
205 		if (flags & LKM_CANCEL)
206 			lock->cancel_pending = 0;
207 		else
208 			lock->unlock_pending = 0;
209 
210 	}
211 
212 	/* get an extra ref on lock.  if we are just switching
213 	 * lists here, we dont want the lock to go away. */
214 	dlm_lock_get(lock);
215 
216 	if (actions & DLM_UNLOCK_REMOVE_LOCK) {
217 		list_del_init(&lock->list);
218 		dlm_lock_put(lock);
219 	}
220 	if (actions & DLM_UNLOCK_REGRANT_LOCK) {
221 		dlm_lock_get(lock);
222 		list_add_tail(&lock->list, &res->granted);
223 	}
224 	if (actions & DLM_UNLOCK_CLEAR_CONVERT_TYPE) {
225 		mlog(0, "clearing convert_type at %smaster node\n",
226 		     master_node ? "" : "non-");
227 		lock->ml.convert_type = LKM_IVMODE;
228 	}
229 
230 	/* remove the extra ref on lock */
231 	dlm_lock_put(lock);
232 
233 leave:
234 	res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
235 	if (!dlm_lock_on_list(&res->converting, lock))
236 		BUG_ON(lock->ml.convert_type != LKM_IVMODE);
237 	else
238 		BUG_ON(lock->ml.convert_type == LKM_IVMODE);
239 	spin_unlock(&lock->spinlock);
240 	spin_unlock(&res->spinlock);
241 	wake_up(&res->wq);
242 
243 	/* let the caller's final dlm_lock_put handle the actual kfree */
244 	if (actions & DLM_UNLOCK_FREE_LOCK) {
245 		/* this should always be coupled with list removal */
246 		BUG_ON(!(actions & DLM_UNLOCK_REMOVE_LOCK));
247 		mlog(0, "lock %u:%llu should be gone now! refs=%d\n",
248 		     dlm_get_lock_cookie_node(lock->ml.cookie),
249 		     dlm_get_lock_cookie_seq(lock->ml.cookie),
250 		     atomic_read(&lock->lock_refs.refcount)-1);
251 		dlm_lock_put(lock);
252 	}
253 	if (actions & DLM_UNLOCK_CALL_AST)
254 		*call_ast = 1;
255 
256 	/* if cancel or unlock succeeded, lvb work is done */
257 	if (status == DLM_NORMAL)
258 		lksb->flags &= ~(DLM_LKSB_PUT_LVB|DLM_LKSB_GET_LVB);
259 
260 	return status;
261 }
262 
263 void dlm_commit_pending_unlock(struct dlm_lock_resource *res,
264 			       struct dlm_lock *lock)
265 {
266 	/* leave DLM_LKSB_PUT_LVB on the lksb so any final
267 	 * update of the lvb will be sent to the new master */
268 	list_del_init(&lock->list);
269 }
270 
271 void dlm_commit_pending_cancel(struct dlm_lock_resource *res,
272 			       struct dlm_lock *lock)
273 {
274 	list_move_tail(&lock->list, &res->granted);
275 	lock->ml.convert_type = LKM_IVMODE;
276 }
277 
278 
279 static inline enum dlm_status dlmunlock_master(struct dlm_ctxt *dlm,
280 					  struct dlm_lock_resource *res,
281 					  struct dlm_lock *lock,
282 					  struct dlm_lockstatus *lksb,
283 					  int flags,
284 					  int *call_ast)
285 {
286 	return dlmunlock_common(dlm, res, lock, lksb, flags, call_ast, 1);
287 }
288 
289 static inline enum dlm_status dlmunlock_remote(struct dlm_ctxt *dlm,
290 					  struct dlm_lock_resource *res,
291 					  struct dlm_lock *lock,
292 					  struct dlm_lockstatus *lksb,
293 					  int flags, int *call_ast)
294 {
295 	return dlmunlock_common(dlm, res, lock, lksb, flags, call_ast, 0);
296 }
297 
298 /*
299  * locking:
300  *   caller needs:  none
301  *   taken:         none
302  *   held on exit:  none
303  * returns: DLM_NORMAL, DLM_NOLOCKMGR, status from network
304  */
305 static enum dlm_status dlm_send_remote_unlock_request(struct dlm_ctxt *dlm,
306 						 struct dlm_lock_resource *res,
307 						 struct dlm_lock *lock,
308 						 struct dlm_lockstatus *lksb,
309 						 int flags,
310 						 u8 owner)
311 {
312 	struct dlm_unlock_lock unlock;
313 	int tmpret;
314 	enum dlm_status ret;
315 	int status = 0;
316 	struct kvec vec[2];
317 	size_t veclen = 1;
318 
319 	mlog_entry("%.*s\n", res->lockname.len, res->lockname.name);
320 
321 	if (owner == dlm->node_num) {
322 		/* ended up trying to contact ourself.  this means
323 		 * that the lockres had been remote but became local
324 		 * via a migration.  just retry it, now as local */
325 		mlog(0, "%s:%.*s: this node became the master due to a "
326 		     "migration, re-evaluate now\n", dlm->name,
327 		     res->lockname.len, res->lockname.name);
328 		return DLM_FORWARD;
329 	}
330 
331 	memset(&unlock, 0, sizeof(unlock));
332 	unlock.node_idx = dlm->node_num;
333 	unlock.flags = cpu_to_be32(flags);
334 	unlock.cookie = lock->ml.cookie;
335 	unlock.namelen = res->lockname.len;
336 	memcpy(unlock.name, res->lockname.name, unlock.namelen);
337 
338 	vec[0].iov_len = sizeof(struct dlm_unlock_lock);
339 	vec[0].iov_base = &unlock;
340 
341 	if (flags & LKM_PUT_LVB) {
342 		/* extra data to send if we are updating lvb */
343 		vec[1].iov_len = DLM_LVB_LEN;
344 		vec[1].iov_base = lock->lksb->lvb;
345 		veclen++;
346 	}
347 
348 	tmpret = o2net_send_message_vec(DLM_UNLOCK_LOCK_MSG, dlm->key,
349 					vec, veclen, owner, &status);
350 	if (tmpret >= 0) {
351 		// successfully sent and received
352 		if (status == DLM_CANCELGRANT)
353 			ret = DLM_NORMAL;
354 		else if (status == DLM_FORWARD) {
355 			mlog(0, "master was in-progress.  retry\n");
356 			ret = DLM_FORWARD;
357 		} else
358 			ret = status;
359 		lksb->status = status;
360 	} else {
361 		mlog_errno(tmpret);
362 		if (dlm_is_host_down(tmpret)) {
363 			/* NOTE: this seems strange, but it is what we want.
364 			 * when the master goes down during a cancel or
365 			 * unlock, the recovery code completes the operation
366 			 * as if the master had not died, then passes the
367 			 * updated state to the recovery master.  this thread
368 			 * just needs to finish out the operation and call
369 			 * the unlockast. */
370 			ret = DLM_NORMAL;
371 		} else {
372 			/* something bad.  this will BUG in ocfs2 */
373 			ret = dlm_err_to_dlm_status(tmpret);
374 		}
375 		lksb->status = ret;
376 	}
377 
378 	return ret;
379 }
380 
381 /*
382  * locking:
383  *   caller needs:  none
384  *   taken:         takes and drops res->spinlock
385  *   held on exit:  none
386  * returns: DLM_NORMAL, DLM_BADARGS, DLM_IVLOCKID,
387  *          return value from dlmunlock_master
388  */
389 int dlm_unlock_lock_handler(struct o2net_msg *msg, u32 len, void *data)
390 {
391 	struct dlm_ctxt *dlm = data;
392 	struct dlm_unlock_lock *unlock = (struct dlm_unlock_lock *)msg->buf;
393 	struct dlm_lock_resource *res = NULL;
394 	struct list_head *iter;
395 	struct dlm_lock *lock = NULL;
396 	enum dlm_status status = DLM_NORMAL;
397 	int found = 0, i;
398 	struct dlm_lockstatus *lksb = NULL;
399 	int ignore;
400 	u32 flags;
401 	struct list_head *queue;
402 
403 	flags = be32_to_cpu(unlock->flags);
404 
405 	if (flags & LKM_GET_LVB) {
406 		mlog(ML_ERROR, "bad args!  GET_LVB specified on unlock!\n");
407 		return DLM_BADARGS;
408 	}
409 
410 	if ((flags & (LKM_PUT_LVB|LKM_CANCEL)) == (LKM_PUT_LVB|LKM_CANCEL)) {
411 		mlog(ML_ERROR, "bad args!  cannot modify lvb on a CANCEL "
412 		     "request!\n");
413 		return DLM_BADARGS;
414 	}
415 
416 	if (unlock->namelen > DLM_LOCKID_NAME_MAX) {
417 		mlog(ML_ERROR, "Invalid name length in unlock handler!\n");
418 		return DLM_IVBUFLEN;
419 	}
420 
421 	if (!dlm_grab(dlm))
422 		return DLM_REJECTED;
423 
424 	mlog_bug_on_msg(!dlm_domain_fully_joined(dlm),
425 			"Domain %s not fully joined!\n", dlm->name);
426 
427 	mlog(0, "lvb: %s\n", flags & LKM_PUT_LVB ? "put lvb" : "none");
428 
429 	res = dlm_lookup_lockres(dlm, unlock->name, unlock->namelen);
430 	if (!res) {
431 		/* We assume here that a no lock resource simply means
432 		 * it was migrated away and destroyed before the other
433 		 * node could detect it. */
434 		mlog(0, "returning DLM_FORWARD -- res no longer exists\n");
435 		status = DLM_FORWARD;
436 		goto not_found;
437 	}
438 
439 	queue=&res->granted;
440 	found = 0;
441 	spin_lock(&res->spinlock);
442 	if (res->state & DLM_LOCK_RES_RECOVERING) {
443 		spin_unlock(&res->spinlock);
444 		mlog(0, "returning DLM_RECOVERING\n");
445 		status = DLM_RECOVERING;
446 		goto leave;
447 	}
448 
449 	if (res->state & DLM_LOCK_RES_MIGRATING) {
450 		spin_unlock(&res->spinlock);
451 		mlog(0, "returning DLM_MIGRATING\n");
452 		status = DLM_MIGRATING;
453 		goto leave;
454 	}
455 
456 	if (res->owner != dlm->node_num) {
457 		spin_unlock(&res->spinlock);
458 		mlog(0, "returning DLM_FORWARD -- not master\n");
459 		status = DLM_FORWARD;
460 		goto leave;
461 	}
462 
463 	for (i=0; i<3; i++) {
464 		list_for_each(iter, queue) {
465 			lock = list_entry(iter, struct dlm_lock, list);
466 			if (lock->ml.cookie == unlock->cookie &&
467 		    	    lock->ml.node == unlock->node_idx) {
468 				dlm_lock_get(lock);
469 				found = 1;
470 				break;
471 			}
472 		}
473 		if (found)
474 			break;
475 		/* scan granted -> converting -> blocked queues */
476 		queue++;
477 	}
478 	spin_unlock(&res->spinlock);
479 	if (!found) {
480 		status = DLM_IVLOCKID;
481 		goto not_found;
482 	}
483 
484 	/* lock was found on queue */
485 	lksb = lock->lksb;
486 	/* unlockast only called on originating node */
487 	if (flags & LKM_PUT_LVB) {
488 		lksb->flags |= DLM_LKSB_PUT_LVB;
489 		memcpy(&lksb->lvb[0], &unlock->lvb[0], DLM_LVB_LEN);
490 	}
491 
492 	/* if this is in-progress, propagate the DLM_FORWARD
493 	 * all the way back out */
494 	status = dlmunlock_master(dlm, res, lock, lksb, flags, &ignore);
495 	if (status == DLM_FORWARD)
496 		mlog(0, "lockres is in progress\n");
497 
498 	if (flags & LKM_PUT_LVB)
499 		lksb->flags &= ~DLM_LKSB_PUT_LVB;
500 
501 	dlm_lockres_calc_usage(dlm, res);
502 	dlm_kick_thread(dlm, res);
503 
504 not_found:
505 	if (!found)
506 		mlog(ML_ERROR, "failed to find lock to unlock! "
507 			       "cookie=%u:%llu\n",
508 			       dlm_get_lock_cookie_node(unlock->cookie),
509 			       dlm_get_lock_cookie_seq(unlock->cookie));
510 	else {
511 		/* send the lksb->status back to the other node */
512 		status = lksb->status;
513 		dlm_lock_put(lock);
514 	}
515 
516 leave:
517 	if (res)
518 		dlm_lockres_put(res);
519 
520 	dlm_put(dlm);
521 
522 	return status;
523 }
524 
525 
526 static enum dlm_status dlm_get_cancel_actions(struct dlm_ctxt *dlm,
527 					      struct dlm_lock_resource *res,
528 					      struct dlm_lock *lock,
529 					      struct dlm_lockstatus *lksb,
530 					      int *actions)
531 {
532 	enum dlm_status status;
533 
534 	if (dlm_lock_on_list(&res->blocked, lock)) {
535 		/* cancel this outright */
536 		lksb->status = DLM_NORMAL;
537 		status = DLM_NORMAL;
538 		*actions = (DLM_UNLOCK_CALL_AST |
539 			    DLM_UNLOCK_REMOVE_LOCK);
540 	} else if (dlm_lock_on_list(&res->converting, lock)) {
541 		/* cancel the request, put back on granted */
542 		lksb->status = DLM_NORMAL;
543 		status = DLM_NORMAL;
544 		*actions = (DLM_UNLOCK_CALL_AST |
545 			    DLM_UNLOCK_REMOVE_LOCK |
546 			    DLM_UNLOCK_REGRANT_LOCK |
547 			    DLM_UNLOCK_CLEAR_CONVERT_TYPE);
548 	} else if (dlm_lock_on_list(&res->granted, lock)) {
549 		/* too late, already granted.  DLM_CANCELGRANT */
550 		lksb->status = DLM_CANCELGRANT;
551 		status = DLM_NORMAL;
552 		*actions = DLM_UNLOCK_CALL_AST;
553 	} else {
554 		mlog(ML_ERROR, "lock to cancel is not on any list!\n");
555 		lksb->status = DLM_IVLOCKID;
556 		status = DLM_IVLOCKID;
557 		*actions = 0;
558 	}
559 	return status;
560 }
561 
562 static enum dlm_status dlm_get_unlock_actions(struct dlm_ctxt *dlm,
563 					      struct dlm_lock_resource *res,
564 					      struct dlm_lock *lock,
565 					      struct dlm_lockstatus *lksb,
566 					      int *actions)
567 {
568 	enum dlm_status status;
569 
570 	/* unlock request */
571 	if (!dlm_lock_on_list(&res->granted, lock)) {
572 		lksb->status = DLM_DENIED;
573 		status = DLM_DENIED;
574 		dlm_error(status);
575 		*actions = 0;
576 	} else {
577 		/* unlock granted lock */
578 		lksb->status = DLM_NORMAL;
579 		status = DLM_NORMAL;
580 		*actions = (DLM_UNLOCK_FREE_LOCK |
581 			    DLM_UNLOCK_CALL_AST |
582 			    DLM_UNLOCK_REMOVE_LOCK);
583 	}
584 	return status;
585 }
586 
587 /* there seems to be no point in doing this async
588  * since (even for the remote case) there is really
589  * no work to queue up... so just do it and fire the
590  * unlockast by hand when done... */
591 enum dlm_status dlmunlock(struct dlm_ctxt *dlm, struct dlm_lockstatus *lksb,
592 			  int flags, dlm_astunlockfunc_t *unlockast, void *data)
593 {
594 	enum dlm_status status;
595 	struct dlm_lock_resource *res;
596 	struct dlm_lock *lock = NULL;
597 	int call_ast, is_master;
598 
599 	mlog_entry_void();
600 
601 	if (!lksb) {
602 		dlm_error(DLM_BADARGS);
603 		return DLM_BADARGS;
604 	}
605 
606 	if (flags & ~(LKM_CANCEL | LKM_VALBLK | LKM_INVVALBLK)) {
607 		dlm_error(DLM_BADPARAM);
608 		return DLM_BADPARAM;
609 	}
610 
611 	if ((flags & (LKM_VALBLK | LKM_CANCEL)) == (LKM_VALBLK | LKM_CANCEL)) {
612 		mlog(0, "VALBLK given with CANCEL: ignoring VALBLK\n");
613 		flags &= ~LKM_VALBLK;
614 	}
615 
616 	if (!lksb->lockid || !lksb->lockid->lockres) {
617 		dlm_error(DLM_BADPARAM);
618 		return DLM_BADPARAM;
619 	}
620 
621 	lock = lksb->lockid;
622 	BUG_ON(!lock);
623 	dlm_lock_get(lock);
624 
625 	res = lock->lockres;
626 	BUG_ON(!res);
627 	dlm_lockres_get(res);
628 retry:
629 	call_ast = 0;
630 	/* need to retry up here because owner may have changed */
631 	mlog(0, "lock=%p res=%p\n", lock, res);
632 
633 	spin_lock(&res->spinlock);
634 	is_master = (res->owner == dlm->node_num);
635 	spin_unlock(&res->spinlock);
636 
637 	if (is_master) {
638 		status = dlmunlock_master(dlm, res, lock, lksb, flags,
639 					  &call_ast);
640 		mlog(0, "done calling dlmunlock_master: returned %d, "
641 		     "call_ast is %d\n", status, call_ast);
642 	} else {
643 		status = dlmunlock_remote(dlm, res, lock, lksb, flags,
644 					  &call_ast);
645 		mlog(0, "done calling dlmunlock_remote: returned %d, "
646 		     "call_ast is %d\n", status, call_ast);
647 	}
648 
649 	if (status == DLM_RECOVERING ||
650 	    status == DLM_MIGRATING ||
651 	    status == DLM_FORWARD) {
652 		/* We want to go away for a tiny bit to allow recovery
653 		 * / migration to complete on this resource. I don't
654 		 * know of any wait queue we could sleep on as this
655 		 * may be happening on another node. Perhaps the
656 		 * proper solution is to queue up requests on the
657 		 * other end? */
658 
659 		/* do we want to yield(); ?? */
660 		msleep(50);
661 
662 		mlog(0, "retrying unlock due to pending recovery/"
663 		     "migration/in-progress\n");
664 		goto retry;
665 	}
666 
667 	if (call_ast) {
668 		mlog(0, "calling unlockast(%p, %d)\n", data, lksb->status);
669 		if (is_master) {
670 			/* it is possible that there is one last bast
671 			 * pending.  make sure it is flushed, then
672 			 * call the unlockast.
673 			 * not an issue if this is a mastered remotely,
674 			 * since this lock has been removed from the
675 			 * lockres queues and cannot be found. */
676 			dlm_kick_thread(dlm, NULL);
677 			wait_event(dlm->ast_wq,
678 				   dlm_lock_basts_flushed(dlm, lock));
679 		}
680 		(*unlockast)(data, lksb->status);
681 	}
682 
683 	if (status == DLM_NORMAL) {
684 		mlog(0, "kicking the thread\n");
685 		dlm_kick_thread(dlm, res);
686 	} else
687 		dlm_error(status);
688 
689 	dlm_lockres_calc_usage(dlm, res);
690 	dlm_lockres_put(res);
691 	dlm_lock_put(lock);
692 
693 	mlog(0, "returning status=%d!\n", status);
694 	return status;
695 }
696 EXPORT_SYMBOL_GPL(dlmunlock);
697 
698