ocfs2/dlm: get mle inuse only when it is initialized

When dlm_add_migration_mle returns -EEXIST, previously input mle will
not be initialized.  So we can't use its associated dlm object.  And we
truly don't need this mle for already launched migration progress, since
oldmle has taken this role.

Link: http://lkml.kernel.org/r/63ADC13FD55D6546B7DECE290D39E373CED7AA61@H3CMLB14-EX.srv.huawei-3com.com
Signed-off-by: Changwei Ge <ge.changwei@h3c.com>
Reviewed-by: Joseph Qi <jiangqi903@gmail.com>
Cc: Mark Fasheh <mfasheh@versity.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/dlm/dlmmaster.c

@@ -2616,7 +2616,9 @@ static int dlm_migrate_lockres(struct dlm_ctxt *dlm,
 	 * otherwise the assert_master from the new
 	 * master will destroy this.
 	 */
-	dlm_get_mle_inuse(mle);
+	if (ret != -EEXIST)
+		dlm_get_mle_inuse(mle);
+
 	spin_unlock(&dlm->master_lock);
 	spin_unlock(&dlm->spinlock);