From: David Teigland <teigland@redhat.com>
Subject: [RHEL5 PATCH] dlm: resend lock during recovery if master not ready
Date: Thu, 30 Nov 2006 16:03:08 -0600
Bugzilla: 215596
Message-Id: <20061130220308.GA31429@redhat.com>
Changelog: dlm: resend lock during recovery if master not ready


bz 215596
patch 1 of 3

There's a chance the new master of resource hasn't learned it's the new
master before another node sends it a lock during recovery.  The node
sending the lock needs to resend if this happens.

- A sends a master lookup for resource R to C
- B sends a master lookup for resource R to C
- C receives A's lookup, assigns A to be master of R and
  sends a reply back to A
- C receives B's lookup and sends a reply back to B saying
  that A is the master
- B receives lookup reply from C and sends its lock for R to A
- A receives lock from B, doesn't think it's the master of R
  and sends an error back to B
- A receives lookup reply from C and becomes master of R
- B gets error back from A and resends its lock back to A
  (this resending is what this patch does)
- A receives lock from B, it now sees it's the master of R
  and takes the lock

Index: latest/fs/dlm/lock.c
===================================================================
--- latest.orig/fs/dlm/lock.c
+++ latest/fs/dlm/lock.c
@@ -3571,6 +3571,14 @@ int dlm_recover_process_copy(struct dlm_
 	lock_rsb(r);
 
 	switch (error) {
+	case -EBADR:
+		/* There's a chance the new master received our lock before
+		   dlm_recover_master_reply(), this wouldn't happen if we did
+		   a barrier between recover_masters and recover_locks. */
+		log_debug(ls, "master copy not ready %x r %lx %s", lkb->lkb_id,
+			  (unsigned long)r, r->res_name);
+		dlm_send_rcom_lock(r, lkb);
+		goto out;
 	case -EEXIST:
 		log_debug(ls, "master copy exists %x", lkb->lkb_id);
 		/* fall through */
@@ -3585,7 +3593,7 @@ int dlm_recover_process_copy(struct dlm_
 	/* an ack for dlm_recover_locks() which waits for replies from
 	   all the locks it sends to new masters */
 	dlm_recovered_lock(r);
-
+ out:
 	unlock_rsb(r);
 	put_rsb(r);
 	dlm_put_lkb(lkb);