ocfs2/dlm: dlm_thread should not sleep while holding the dlm_spinlock

This patch addresses the bug in which the dlm_thread could go to sleep
while holding the dlm_spinlock.
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/dlm/dlmthread.c

@@ -176,12 +176,14 @@ static int dlm_purge_lockres(struct dlm_ctxt *dlm,
 	     res->lockname.name, master);
 
 	if (!master) {
+		/* drop spinlock...  retake below */
+		spin_unlock(&dlm->spinlock);
+
 		spin_lock(&res->spinlock);
 		/* This ensures that clear refmap is sent after the set */
 		__dlm_wait_on_lockres_flags(res, DLM_LOCK_RES_SETREF_INPROG);
 		spin_unlock(&res->spinlock);
-		/* drop spinlock to do messaging, retake below */
-		spin_unlock(&dlm->spinlock);
+
 		/* clear our bit from the master's refmap, ignore errors */
 		ret = dlm_drop_lockres_ref(dlm, res);
 		if (ret < 0) {