ocfs2/dlm: return EINVAL when the lockres on migration target is in DROPPING_REF state

If master migrate this lock resource to node when it happened to purge
it, a new lock resource will be created and inserted into hash list.  If
then master goes down, the lock resource being purged is recovered, so
there exist two lock resource with different owner.  So return error to
master if the lock resource is in DROPPING state, master will retry to
migrate this lock resource.
Signed-off-by: xuejiufei <xuejiufei@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Joseph Qi <joseph.qi@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/dlm/dlmrecovery.c

@@ -1403,12 +1403,24 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
 	 * and RECOVERY flag changed when it completes. */
 	hash = dlm_lockid_hash(mres->lockname, mres->lockname_len);
 	spin_lock(&dlm->spinlock);
-	res = __dlm_lookup_lockres(dlm, mres->lockname, mres->lockname_len,
+	res = __dlm_lookup_lockres_full(dlm, mres->lockname, mres->lockname_len,
 			hash);
 	if (res) {
 	 	/* this will get a ref on res */
 		/* mark it as recovering/migrating and hash it */
 		spin_lock(&res->spinlock);
+		if (res->state & DLM_LOCK_RES_DROPPING_REF) {
+			mlog(0, "%s: node is attempting to migrate "
+				"lockres %.*s, but marked as dropping "
+				" ref!\n", dlm->name,
+				mres->lockname_len, mres->lockname);
+			ret = -EINVAL;
+			spin_unlock(&res->spinlock);
+			spin_unlock(&dlm->spinlock);
+			dlm_lockres_put(res);
+			goto leave;
+		}
+
 		if (mres->flags & DLM_MRES_RECOVERY) {
 			res->state |= DLM_LOCK_RES_RECOVERING;
 		} else {