xref: /linux/fs/dlm/recover.c (revision ab52c59103002b49f2455371e4b9c56ba3ef1781)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /******************************************************************************
3 *******************************************************************************
4 **
5 **  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
6 **  Copyright (C) 2004-2005 Red Hat, Inc.  All rights reserved.
7 **
8 **
9 *******************************************************************************
10 ******************************************************************************/
11 
12 #include "dlm_internal.h"
13 #include "lockspace.h"
14 #include "dir.h"
15 #include "config.h"
16 #include "ast.h"
17 #include "memory.h"
18 #include "rcom.h"
19 #include "lock.h"
20 #include "lowcomms.h"
21 #include "member.h"
22 #include "recover.h"
23 
24 
25 /*
26  * Recovery waiting routines: these functions wait for a particular reply from
27  * a remote node, or for the remote node to report a certain status.  They need
28  * to abort if the lockspace is stopped indicating a node has failed (perhaps
29  * the one being waited for).
30  */
31 
32 /*
33  * Wait until given function returns non-zero or lockspace is stopped
34  * (LS_RECOVERY_STOP set due to failure of a node in ls_nodes).  When another
35  * function thinks it could have completed the waited-on task, they should wake
36  * up ls_wait_general to get an immediate response rather than waiting for the
37  * timeout.  This uses a timeout so it can check periodically if the wait
38  * should abort due to node failure (which doesn't cause a wake_up).
39  * This should only be called by the dlm_recoverd thread.
40  */
41 
42 int dlm_wait_function(struct dlm_ls *ls, int (*testfn) (struct dlm_ls *ls))
43 {
44 	int error = 0;
45 	int rv;
46 
47 	while (1) {
48 		rv = wait_event_timeout(ls->ls_wait_general,
49 					testfn(ls) || dlm_recovery_stopped(ls),
50 					dlm_config.ci_recover_timer * HZ);
51 		if (rv)
52 			break;
53 		if (test_bit(LSFL_RCOM_WAIT, &ls->ls_flags)) {
54 			log_debug(ls, "dlm_wait_function timed out");
55 			return -ETIMEDOUT;
56 		}
57 	}
58 
59 	if (dlm_recovery_stopped(ls)) {
60 		log_debug(ls, "dlm_wait_function aborted");
61 		error = -EINTR;
62 	}
63 	return error;
64 }
65 
66 /*
67  * An efficient way for all nodes to wait for all others to have a certain
68  * status.  The node with the lowest nodeid polls all the others for their
69  * status (wait_status_all) and all the others poll the node with the low id
70  * for its accumulated result (wait_status_low).  When all nodes have set
71  * status flag X, then status flag X_ALL will be set on the low nodeid.
72  */
73 
74 uint32_t dlm_recover_status(struct dlm_ls *ls)
75 {
76 	uint32_t status;
77 	spin_lock_bh(&ls->ls_recover_lock);
78 	status = ls->ls_recover_status;
79 	spin_unlock_bh(&ls->ls_recover_lock);
80 	return status;
81 }
82 
83 static void _set_recover_status(struct dlm_ls *ls, uint32_t status)
84 {
85 	ls->ls_recover_status |= status;
86 }
87 
88 void dlm_set_recover_status(struct dlm_ls *ls, uint32_t status)
89 {
90 	spin_lock_bh(&ls->ls_recover_lock);
91 	_set_recover_status(ls, status);
92 	spin_unlock_bh(&ls->ls_recover_lock);
93 }
94 
95 static int wait_status_all(struct dlm_ls *ls, uint32_t wait_status,
96 			   int save_slots, uint64_t seq)
97 {
98 	struct dlm_rcom *rc = ls->ls_recover_buf;
99 	struct dlm_member *memb;
100 	int error = 0, delay;
101 
102 	list_for_each_entry(memb, &ls->ls_nodes, list) {
103 		delay = 0;
104 		for (;;) {
105 			if (dlm_recovery_stopped(ls)) {
106 				error = -EINTR;
107 				goto out;
108 			}
109 
110 			error = dlm_rcom_status(ls, memb->nodeid, 0, seq);
111 			if (error)
112 				goto out;
113 
114 			if (save_slots)
115 				dlm_slot_save(ls, rc, memb);
116 
117 			if (le32_to_cpu(rc->rc_result) & wait_status)
118 				break;
119 			if (delay < 1000)
120 				delay += 20;
121 			msleep(delay);
122 		}
123 	}
124  out:
125 	return error;
126 }
127 
128 static int wait_status_low(struct dlm_ls *ls, uint32_t wait_status,
129 			   uint32_t status_flags, uint64_t seq)
130 {
131 	struct dlm_rcom *rc = ls->ls_recover_buf;
132 	int error = 0, delay = 0, nodeid = ls->ls_low_nodeid;
133 
134 	for (;;) {
135 		if (dlm_recovery_stopped(ls)) {
136 			error = -EINTR;
137 			goto out;
138 		}
139 
140 		error = dlm_rcom_status(ls, nodeid, status_flags, seq);
141 		if (error)
142 			break;
143 
144 		if (le32_to_cpu(rc->rc_result) & wait_status)
145 			break;
146 		if (delay < 1000)
147 			delay += 20;
148 		msleep(delay);
149 	}
150  out:
151 	return error;
152 }
153 
154 static int wait_status(struct dlm_ls *ls, uint32_t status, uint64_t seq)
155 {
156 	uint32_t status_all = status << 1;
157 	int error;
158 
159 	if (ls->ls_low_nodeid == dlm_our_nodeid()) {
160 		error = wait_status_all(ls, status, 0, seq);
161 		if (!error)
162 			dlm_set_recover_status(ls, status_all);
163 	} else
164 		error = wait_status_low(ls, status_all, 0, seq);
165 
166 	return error;
167 }
168 
169 int dlm_recover_members_wait(struct dlm_ls *ls, uint64_t seq)
170 {
171 	struct dlm_member *memb;
172 	struct dlm_slot *slots;
173 	int num_slots, slots_size;
174 	int error, rv;
175 	uint32_t gen;
176 
177 	list_for_each_entry(memb, &ls->ls_nodes, list) {
178 		memb->slot = -1;
179 		memb->generation = 0;
180 	}
181 
182 	if (ls->ls_low_nodeid == dlm_our_nodeid()) {
183 		error = wait_status_all(ls, DLM_RS_NODES, 1, seq);
184 		if (error)
185 			goto out;
186 
187 		/* slots array is sparse, slots_size may be > num_slots */
188 
189 		rv = dlm_slots_assign(ls, &num_slots, &slots_size, &slots, &gen);
190 		if (!rv) {
191 			spin_lock_bh(&ls->ls_recover_lock);
192 			_set_recover_status(ls, DLM_RS_NODES_ALL);
193 			ls->ls_num_slots = num_slots;
194 			ls->ls_slots_size = slots_size;
195 			ls->ls_slots = slots;
196 			ls->ls_generation = gen;
197 			spin_unlock_bh(&ls->ls_recover_lock);
198 		} else {
199 			dlm_set_recover_status(ls, DLM_RS_NODES_ALL);
200 		}
201 	} else {
202 		error = wait_status_low(ls, DLM_RS_NODES_ALL,
203 					DLM_RSF_NEED_SLOTS, seq);
204 		if (error)
205 			goto out;
206 
207 		dlm_slots_copy_in(ls);
208 	}
209  out:
210 	return error;
211 }
212 
213 int dlm_recover_directory_wait(struct dlm_ls *ls, uint64_t seq)
214 {
215 	return wait_status(ls, DLM_RS_DIR, seq);
216 }
217 
218 int dlm_recover_locks_wait(struct dlm_ls *ls, uint64_t seq)
219 {
220 	return wait_status(ls, DLM_RS_LOCKS, seq);
221 }
222 
223 int dlm_recover_done_wait(struct dlm_ls *ls, uint64_t seq)
224 {
225 	return wait_status(ls, DLM_RS_DONE, seq);
226 }
227 
228 /*
229  * The recover_list contains all the rsb's for which we've requested the new
230  * master nodeid.  As replies are returned from the resource directories the
231  * rsb's are removed from the list.  When the list is empty we're done.
232  *
233  * The recover_list is later similarly used for all rsb's for which we've sent
234  * new lkb's and need to receive new corresponding lkid's.
235  *
236  * We use the address of the rsb struct as a simple local identifier for the
237  * rsb so we can match an rcom reply with the rsb it was sent for.
238  */
239 
240 static int recover_list_empty(struct dlm_ls *ls)
241 {
242 	int empty;
243 
244 	spin_lock_bh(&ls->ls_recover_list_lock);
245 	empty = list_empty(&ls->ls_recover_list);
246 	spin_unlock_bh(&ls->ls_recover_list_lock);
247 
248 	return empty;
249 }
250 
251 static void recover_list_add(struct dlm_rsb *r)
252 {
253 	struct dlm_ls *ls = r->res_ls;
254 
255 	spin_lock_bh(&ls->ls_recover_list_lock);
256 	if (list_empty(&r->res_recover_list)) {
257 		list_add_tail(&r->res_recover_list, &ls->ls_recover_list);
258 		ls->ls_recover_list_count++;
259 		dlm_hold_rsb(r);
260 	}
261 	spin_unlock_bh(&ls->ls_recover_list_lock);
262 }
263 
264 static void recover_list_del(struct dlm_rsb *r)
265 {
266 	struct dlm_ls *ls = r->res_ls;
267 
268 	spin_lock_bh(&ls->ls_recover_list_lock);
269 	list_del_init(&r->res_recover_list);
270 	ls->ls_recover_list_count--;
271 	spin_unlock_bh(&ls->ls_recover_list_lock);
272 
273 	dlm_put_rsb(r);
274 }
275 
276 static void recover_list_clear(struct dlm_ls *ls)
277 {
278 	struct dlm_rsb *r, *s;
279 
280 	spin_lock_bh(&ls->ls_recover_list_lock);
281 	list_for_each_entry_safe(r, s, &ls->ls_recover_list, res_recover_list) {
282 		list_del_init(&r->res_recover_list);
283 		r->res_recover_locks_count = 0;
284 		dlm_put_rsb(r);
285 		ls->ls_recover_list_count--;
286 	}
287 
288 	if (ls->ls_recover_list_count != 0) {
289 		log_error(ls, "warning: recover_list_count %d",
290 			  ls->ls_recover_list_count);
291 		ls->ls_recover_list_count = 0;
292 	}
293 	spin_unlock_bh(&ls->ls_recover_list_lock);
294 }
295 
296 static int recover_idr_empty(struct dlm_ls *ls)
297 {
298 	int empty = 1;
299 
300 	spin_lock_bh(&ls->ls_recover_idr_lock);
301 	if (ls->ls_recover_list_count)
302 		empty = 0;
303 	spin_unlock_bh(&ls->ls_recover_idr_lock);
304 
305 	return empty;
306 }
307 
308 static int recover_idr_add(struct dlm_rsb *r)
309 {
310 	struct dlm_ls *ls = r->res_ls;
311 	int rv;
312 
313 	spin_lock_bh(&ls->ls_recover_idr_lock);
314 	if (r->res_id) {
315 		rv = -1;
316 		goto out_unlock;
317 	}
318 	rv = idr_alloc(&ls->ls_recover_idr, r, 1, 0, GFP_NOWAIT);
319 	if (rv < 0)
320 		goto out_unlock;
321 
322 	r->res_id = rv;
323 	ls->ls_recover_list_count++;
324 	dlm_hold_rsb(r);
325 	rv = 0;
326 out_unlock:
327 	spin_unlock_bh(&ls->ls_recover_idr_lock);
328 	return rv;
329 }
330 
331 static void recover_idr_del(struct dlm_rsb *r)
332 {
333 	struct dlm_ls *ls = r->res_ls;
334 
335 	spin_lock_bh(&ls->ls_recover_idr_lock);
336 	idr_remove(&ls->ls_recover_idr, r->res_id);
337 	r->res_id = 0;
338 	ls->ls_recover_list_count--;
339 	spin_unlock_bh(&ls->ls_recover_idr_lock);
340 
341 	dlm_put_rsb(r);
342 }
343 
344 static struct dlm_rsb *recover_idr_find(struct dlm_ls *ls, uint64_t id)
345 {
346 	struct dlm_rsb *r;
347 
348 	spin_lock_bh(&ls->ls_recover_idr_lock);
349 	r = idr_find(&ls->ls_recover_idr, (int)id);
350 	spin_unlock_bh(&ls->ls_recover_idr_lock);
351 	return r;
352 }
353 
354 static void recover_idr_clear(struct dlm_ls *ls)
355 {
356 	struct dlm_rsb *r;
357 	int id;
358 
359 	spin_lock_bh(&ls->ls_recover_idr_lock);
360 
361 	idr_for_each_entry(&ls->ls_recover_idr, r, id) {
362 		idr_remove(&ls->ls_recover_idr, id);
363 		r->res_id = 0;
364 		r->res_recover_locks_count = 0;
365 		ls->ls_recover_list_count--;
366 
367 		dlm_put_rsb(r);
368 	}
369 
370 	if (ls->ls_recover_list_count != 0) {
371 		log_error(ls, "warning: recover_list_count %d",
372 			  ls->ls_recover_list_count);
373 		ls->ls_recover_list_count = 0;
374 	}
375 	spin_unlock_bh(&ls->ls_recover_idr_lock);
376 }
377 
378 
379 /* Master recovery: find new master node for rsb's that were
380    mastered on nodes that have been removed.
381 
382    dlm_recover_masters
383    recover_master
384    dlm_send_rcom_lookup            ->  receive_rcom_lookup
385                                        dlm_dir_lookup
386    receive_rcom_lookup_reply       <-
387    dlm_recover_master_reply
388    set_new_master
389    set_master_lkbs
390    set_lock_master
391 */
392 
393 /*
394  * Set the lock master for all LKBs in a lock queue
395  * If we are the new master of the rsb, we may have received new
396  * MSTCPY locks from other nodes already which we need to ignore
397  * when setting the new nodeid.
398  */
399 
400 static void set_lock_master(struct list_head *queue, int nodeid)
401 {
402 	struct dlm_lkb *lkb;
403 
404 	list_for_each_entry(lkb, queue, lkb_statequeue) {
405 		if (!test_bit(DLM_IFL_MSTCPY_BIT, &lkb->lkb_iflags)) {
406 			lkb->lkb_nodeid = nodeid;
407 			lkb->lkb_remid = 0;
408 		}
409 	}
410 }
411 
412 static void set_master_lkbs(struct dlm_rsb *r)
413 {
414 	set_lock_master(&r->res_grantqueue, r->res_nodeid);
415 	set_lock_master(&r->res_convertqueue, r->res_nodeid);
416 	set_lock_master(&r->res_waitqueue, r->res_nodeid);
417 }
418 
419 /*
420  * Propagate the new master nodeid to locks
421  * The NEW_MASTER flag tells dlm_recover_locks() which rsb's to consider.
422  * The NEW_MASTER2 flag tells recover_lvb() and recover_grant() which
423  * rsb's to consider.
424  */
425 
426 static void set_new_master(struct dlm_rsb *r)
427 {
428 	set_master_lkbs(r);
429 	rsb_set_flag(r, RSB_NEW_MASTER);
430 	rsb_set_flag(r, RSB_NEW_MASTER2);
431 }
432 
433 /*
434  * We do async lookups on rsb's that need new masters.  The rsb's
435  * waiting for a lookup reply are kept on the recover_list.
436  *
437  * Another node recovering the master may have sent us a rcom lookup,
438  * and our dlm_master_lookup() set it as the new master, along with
439  * NEW_MASTER so that we'll recover it here (this implies dir_nodeid
440  * equals our_nodeid below).
441  */
442 
443 static int recover_master(struct dlm_rsb *r, unsigned int *count, uint64_t seq)
444 {
445 	struct dlm_ls *ls = r->res_ls;
446 	int our_nodeid, dir_nodeid;
447 	int is_removed = 0;
448 	int error;
449 
450 	if (is_master(r))
451 		return 0;
452 
453 	is_removed = dlm_is_removed(ls, r->res_nodeid);
454 
455 	if (!is_removed && !rsb_flag(r, RSB_NEW_MASTER))
456 		return 0;
457 
458 	our_nodeid = dlm_our_nodeid();
459 	dir_nodeid = dlm_dir_nodeid(r);
460 
461 	if (dir_nodeid == our_nodeid) {
462 		if (is_removed) {
463 			r->res_master_nodeid = our_nodeid;
464 			r->res_nodeid = 0;
465 		}
466 
467 		/* set master of lkbs to ourself when is_removed, or to
468 		   another new master which we set along with NEW_MASTER
469 		   in dlm_master_lookup */
470 		set_new_master(r);
471 		error = 0;
472 	} else {
473 		recover_idr_add(r);
474 		error = dlm_send_rcom_lookup(r, dir_nodeid, seq);
475 	}
476 
477 	(*count)++;
478 	return error;
479 }
480 
481 /*
482  * All MSTCPY locks are purged and rebuilt, even if the master stayed the same.
483  * This is necessary because recovery can be started, aborted and restarted,
484  * causing the master nodeid to briefly change during the aborted recovery, and
485  * change back to the original value in the second recovery.  The MSTCPY locks
486  * may or may not have been purged during the aborted recovery.  Another node
487  * with an outstanding request in waiters list and a request reply saved in the
488  * requestqueue, cannot know whether it should ignore the reply and resend the
489  * request, or accept the reply and complete the request.  It must do the
490  * former if the remote node purged MSTCPY locks, and it must do the later if
491  * the remote node did not.  This is solved by always purging MSTCPY locks, in
492  * which case, the request reply would always be ignored and the request
493  * resent.
494  */
495 
496 static int recover_master_static(struct dlm_rsb *r, unsigned int *count)
497 {
498 	int dir_nodeid = dlm_dir_nodeid(r);
499 	int new_master = dir_nodeid;
500 
501 	if (dir_nodeid == dlm_our_nodeid())
502 		new_master = 0;
503 
504 	dlm_purge_mstcpy_locks(r);
505 	r->res_master_nodeid = dir_nodeid;
506 	r->res_nodeid = new_master;
507 	set_new_master(r);
508 	(*count)++;
509 	return 0;
510 }
511 
512 /*
513  * Go through local root resources and for each rsb which has a master which
514  * has departed, get the new master nodeid from the directory.  The dir will
515  * assign mastery to the first node to look up the new master.  That means
516  * we'll discover in this lookup if we're the new master of any rsb's.
517  *
518  * We fire off all the dir lookup requests individually and asynchronously to
519  * the correct dir node.
520  */
521 
522 int dlm_recover_masters(struct dlm_ls *ls, uint64_t seq,
523 			const struct list_head *root_list)
524 {
525 	struct dlm_rsb *r;
526 	unsigned int total = 0;
527 	unsigned int count = 0;
528 	int nodir = dlm_no_directory(ls);
529 	int error;
530 
531 	log_rinfo(ls, "dlm_recover_masters");
532 
533 	list_for_each_entry(r, root_list, res_root_list) {
534 		if (dlm_recovery_stopped(ls)) {
535 			error = -EINTR;
536 			goto out;
537 		}
538 
539 		lock_rsb(r);
540 		if (nodir)
541 			error = recover_master_static(r, &count);
542 		else
543 			error = recover_master(r, &count, seq);
544 		unlock_rsb(r);
545 		cond_resched();
546 		total++;
547 
548 		if (error)
549 			goto out;
550 	}
551 
552 	log_rinfo(ls, "dlm_recover_masters %u of %u", count, total);
553 
554 	error = dlm_wait_function(ls, &recover_idr_empty);
555  out:
556 	if (error)
557 		recover_idr_clear(ls);
558 	return error;
559 }
560 
561 int dlm_recover_master_reply(struct dlm_ls *ls, const struct dlm_rcom *rc)
562 {
563 	struct dlm_rsb *r;
564 	int ret_nodeid, new_master;
565 
566 	r = recover_idr_find(ls, le64_to_cpu(rc->rc_id));
567 	if (!r) {
568 		log_error(ls, "dlm_recover_master_reply no id %llx",
569 			  (unsigned long long)le64_to_cpu(rc->rc_id));
570 		goto out;
571 	}
572 
573 	ret_nodeid = le32_to_cpu(rc->rc_result);
574 
575 	if (ret_nodeid == dlm_our_nodeid())
576 		new_master = 0;
577 	else
578 		new_master = ret_nodeid;
579 
580 	lock_rsb(r);
581 	r->res_master_nodeid = ret_nodeid;
582 	r->res_nodeid = new_master;
583 	set_new_master(r);
584 	unlock_rsb(r);
585 	recover_idr_del(r);
586 
587 	if (recover_idr_empty(ls))
588 		wake_up(&ls->ls_wait_general);
589  out:
590 	return 0;
591 }
592 
593 
594 /* Lock recovery: rebuild the process-copy locks we hold on a
595    remastered rsb on the new rsb master.
596 
597    dlm_recover_locks
598    recover_locks
599    recover_locks_queue
600    dlm_send_rcom_lock              ->  receive_rcom_lock
601                                        dlm_recover_master_copy
602    receive_rcom_lock_reply         <-
603    dlm_recover_process_copy
604 */
605 
606 
607 /*
608  * keep a count of the number of lkb's we send to the new master; when we get
609  * an equal number of replies then recovery for the rsb is done
610  */
611 
612 static int recover_locks_queue(struct dlm_rsb *r, struct list_head *head,
613 			       uint64_t seq)
614 {
615 	struct dlm_lkb *lkb;
616 	int error = 0;
617 
618 	list_for_each_entry(lkb, head, lkb_statequeue) {
619 		error = dlm_send_rcom_lock(r, lkb, seq);
620 		if (error)
621 			break;
622 		r->res_recover_locks_count++;
623 	}
624 
625 	return error;
626 }
627 
628 static int recover_locks(struct dlm_rsb *r, uint64_t seq)
629 {
630 	int error = 0;
631 
632 	lock_rsb(r);
633 
634 	DLM_ASSERT(!r->res_recover_locks_count, dlm_dump_rsb(r););
635 
636 	error = recover_locks_queue(r, &r->res_grantqueue, seq);
637 	if (error)
638 		goto out;
639 	error = recover_locks_queue(r, &r->res_convertqueue, seq);
640 	if (error)
641 		goto out;
642 	error = recover_locks_queue(r, &r->res_waitqueue, seq);
643 	if (error)
644 		goto out;
645 
646 	if (r->res_recover_locks_count)
647 		recover_list_add(r);
648 	else
649 		rsb_clear_flag(r, RSB_NEW_MASTER);
650  out:
651 	unlock_rsb(r);
652 	return error;
653 }
654 
655 int dlm_recover_locks(struct dlm_ls *ls, uint64_t seq,
656 		      const struct list_head *root_list)
657 {
658 	struct dlm_rsb *r;
659 	int error, count = 0;
660 
661 	list_for_each_entry(r, root_list, res_root_list) {
662 		if (is_master(r)) {
663 			rsb_clear_flag(r, RSB_NEW_MASTER);
664 			continue;
665 		}
666 
667 		if (!rsb_flag(r, RSB_NEW_MASTER))
668 			continue;
669 
670 		if (dlm_recovery_stopped(ls)) {
671 			error = -EINTR;
672 			goto out;
673 		}
674 
675 		error = recover_locks(r, seq);
676 		if (error)
677 			goto out;
678 
679 		count += r->res_recover_locks_count;
680 	}
681 
682 	log_rinfo(ls, "dlm_recover_locks %d out", count);
683 
684 	error = dlm_wait_function(ls, &recover_list_empty);
685  out:
686 	if (error)
687 		recover_list_clear(ls);
688 	return error;
689 }
690 
691 void dlm_recovered_lock(struct dlm_rsb *r)
692 {
693 	DLM_ASSERT(rsb_flag(r, RSB_NEW_MASTER), dlm_dump_rsb(r););
694 
695 	r->res_recover_locks_count--;
696 	if (!r->res_recover_locks_count) {
697 		rsb_clear_flag(r, RSB_NEW_MASTER);
698 		recover_list_del(r);
699 	}
700 
701 	if (recover_list_empty(r->res_ls))
702 		wake_up(&r->res_ls->ls_wait_general);
703 }
704 
705 /*
706  * The lvb needs to be recovered on all master rsb's.  This includes setting
707  * the VALNOTVALID flag if necessary, and determining the correct lvb contents
708  * based on the lvb's of the locks held on the rsb.
709  *
710  * RSB_VALNOTVALID is set in two cases:
711  *
712  * 1. we are master, but not new, and we purged an EX/PW lock held by a
713  * failed node (in dlm_recover_purge which set RSB_RECOVER_LVB_INVAL)
714  *
715  * 2. we are a new master, and there are only NL/CR locks left.
716  * (We could probably improve this by only invaliding in this way when
717  * the previous master left uncleanly.  VMS docs mention that.)
718  *
719  * The LVB contents are only considered for changing when this is a new master
720  * of the rsb (NEW_MASTER2).  Then, the rsb's lvb is taken from any lkb with
721  * mode > CR.  If no lkb's exist with mode above CR, the lvb contents are taken
722  * from the lkb with the largest lvb sequence number.
723  */
724 
725 static void recover_lvb(struct dlm_rsb *r)
726 {
727 	struct dlm_lkb *big_lkb = NULL, *iter, *high_lkb = NULL;
728 	uint32_t high_seq = 0;
729 	int lock_lvb_exists = 0;
730 	int lvblen = r->res_ls->ls_lvblen;
731 
732 	if (!rsb_flag(r, RSB_NEW_MASTER2) &&
733 	    rsb_flag(r, RSB_RECOVER_LVB_INVAL)) {
734 		/* case 1 above */
735 		rsb_set_flag(r, RSB_VALNOTVALID);
736 		return;
737 	}
738 
739 	if (!rsb_flag(r, RSB_NEW_MASTER2))
740 		return;
741 
742 	/* we are the new master, so figure out if VALNOTVALID should
743 	   be set, and set the rsb lvb from the best lkb available. */
744 
745 	list_for_each_entry(iter, &r->res_grantqueue, lkb_statequeue) {
746 		if (!(iter->lkb_exflags & DLM_LKF_VALBLK))
747 			continue;
748 
749 		lock_lvb_exists = 1;
750 
751 		if (iter->lkb_grmode > DLM_LOCK_CR) {
752 			big_lkb = iter;
753 			goto setflag;
754 		}
755 
756 		if (((int)iter->lkb_lvbseq - (int)high_seq) >= 0) {
757 			high_lkb = iter;
758 			high_seq = iter->lkb_lvbseq;
759 		}
760 	}
761 
762 	list_for_each_entry(iter, &r->res_convertqueue, lkb_statequeue) {
763 		if (!(iter->lkb_exflags & DLM_LKF_VALBLK))
764 			continue;
765 
766 		lock_lvb_exists = 1;
767 
768 		if (iter->lkb_grmode > DLM_LOCK_CR) {
769 			big_lkb = iter;
770 			goto setflag;
771 		}
772 
773 		if (((int)iter->lkb_lvbseq - (int)high_seq) >= 0) {
774 			high_lkb = iter;
775 			high_seq = iter->lkb_lvbseq;
776 		}
777 	}
778 
779  setflag:
780 	if (!lock_lvb_exists)
781 		goto out;
782 
783 	/* lvb is invalidated if only NL/CR locks remain */
784 	if (!big_lkb)
785 		rsb_set_flag(r, RSB_VALNOTVALID);
786 
787 	if (!r->res_lvbptr) {
788 		r->res_lvbptr = dlm_allocate_lvb(r->res_ls);
789 		if (!r->res_lvbptr)
790 			goto out;
791 	}
792 
793 	if (big_lkb) {
794 		r->res_lvbseq = big_lkb->lkb_lvbseq;
795 		memcpy(r->res_lvbptr, big_lkb->lkb_lvbptr, lvblen);
796 	} else if (high_lkb) {
797 		r->res_lvbseq = high_lkb->lkb_lvbseq;
798 		memcpy(r->res_lvbptr, high_lkb->lkb_lvbptr, lvblen);
799 	} else {
800 		r->res_lvbseq = 0;
801 		memset(r->res_lvbptr, 0, lvblen);
802 	}
803  out:
804 	return;
805 }
806 
807 /* All master rsb's flagged RECOVER_CONVERT need to be looked at.  The locks
808    converting PR->CW or CW->PR need to have their lkb_grmode set. */
809 
810 static void recover_conversion(struct dlm_rsb *r)
811 {
812 	struct dlm_ls *ls = r->res_ls;
813 	struct dlm_lkb *lkb;
814 	int grmode = -1;
815 
816 	list_for_each_entry(lkb, &r->res_grantqueue, lkb_statequeue) {
817 		if (lkb->lkb_grmode == DLM_LOCK_PR ||
818 		    lkb->lkb_grmode == DLM_LOCK_CW) {
819 			grmode = lkb->lkb_grmode;
820 			break;
821 		}
822 	}
823 
824 	list_for_each_entry(lkb, &r->res_convertqueue, lkb_statequeue) {
825 		if (lkb->lkb_grmode != DLM_LOCK_IV)
826 			continue;
827 		if (grmode == -1) {
828 			log_debug(ls, "recover_conversion %x set gr to rq %d",
829 				  lkb->lkb_id, lkb->lkb_rqmode);
830 			lkb->lkb_grmode = lkb->lkb_rqmode;
831 		} else {
832 			log_debug(ls, "recover_conversion %x set gr %d",
833 				  lkb->lkb_id, grmode);
834 			lkb->lkb_grmode = grmode;
835 		}
836 	}
837 }
838 
839 /* We've become the new master for this rsb and waiting/converting locks may
840    need to be granted in dlm_recover_grant() due to locks that may have
841    existed from a removed node. */
842 
843 static void recover_grant(struct dlm_rsb *r)
844 {
845 	if (!list_empty(&r->res_waitqueue) || !list_empty(&r->res_convertqueue))
846 		rsb_set_flag(r, RSB_RECOVER_GRANT);
847 }
848 
849 void dlm_recover_rsbs(struct dlm_ls *ls, const struct list_head *root_list)
850 {
851 	struct dlm_rsb *r;
852 	unsigned int count = 0;
853 
854 	list_for_each_entry(r, root_list, res_root_list) {
855 		lock_rsb(r);
856 		if (is_master(r)) {
857 			if (rsb_flag(r, RSB_RECOVER_CONVERT))
858 				recover_conversion(r);
859 
860 			/* recover lvb before granting locks so the updated
861 			   lvb/VALNOTVALID is presented in the completion */
862 			recover_lvb(r);
863 
864 			if (rsb_flag(r, RSB_NEW_MASTER2))
865 				recover_grant(r);
866 			count++;
867 		} else {
868 			rsb_clear_flag(r, RSB_VALNOTVALID);
869 		}
870 		rsb_clear_flag(r, RSB_RECOVER_CONVERT);
871 		rsb_clear_flag(r, RSB_RECOVER_LVB_INVAL);
872 		rsb_clear_flag(r, RSB_NEW_MASTER2);
873 		unlock_rsb(r);
874 	}
875 
876 	if (count)
877 		log_rinfo(ls, "dlm_recover_rsbs %d done", count);
878 }
879 
880 /* Create a single list of all root rsb's to be used during recovery */
881 
882 void dlm_clear_toss(struct dlm_ls *ls)
883 {
884 	struct dlm_rsb *r, *safe;
885 	unsigned int count = 0;
886 
887 	write_lock_bh(&ls->ls_rsbtbl_lock);
888 	list_for_each_entry_safe(r, safe, &ls->ls_toss, res_rsbs_list) {
889 		list_del(&r->res_rsbs_list);
890 		rhashtable_remove_fast(&ls->ls_rsbtbl, &r->res_node,
891 				       dlm_rhash_rsb_params);
892 
893 		/* remove it from the toss queue if its part of it */
894 		if (!list_empty(&r->res_toss_q_list))
895 			list_del_init(&r->res_toss_q_list);
896 
897 		free_toss_rsb(r);
898 		count++;
899 	}
900 	write_unlock_bh(&ls->ls_rsbtbl_lock);
901 
902 	if (count)
903 		log_rinfo(ls, "dlm_clear_toss %u done", count);
904 }
905 
906