ocfs2/dlm: Handle EAGAIN for compatibility - v2

Mainline commit aad1b15310b9bcd59fa81ab8f2b1513b59553ea8 made the
dlm_begin_reco_handler() return -EAGAIN instead of EAGAIN.

As this error is transmitted over the wire, we want the receiver,
dlm_send_begin_reco_message(), to understand both the older EAGAIN and
the newer -EAGAIN, to allow rolling upgrade of the cluster nodes.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/dlm/dlmrecovery.c

@@ -2639,7 +2639,13 @@ retry:
 			     "begin reco msg (%d)\n", dlm->name, nodenum, ret);
 			ret = 0;
 		}
-		if (ret == -EAGAIN) {
+
+		/*
+		 * Prior to commit aad1b15310b9bcd59fa81ab8f2b1513b59553ea8,
+		 * dlm_begin_reco_handler() returned EAGAIN and not -EAGAIN.
+		 * We are handling both for compatibility reasons.
+		 */
+		if (ret == -EAGAIN || ret == EAGAIN) {
 			mlog(0, "%s: trying to start recovery of node "
 			     "%u, but node %u is waiting for last recovery "
 			     "to complete, backoff for a bit\n", dlm->name,