SUNRPC: skip dead but not buried clients on PipeFS events

These clients can't be safely dereferenced if their counter in 0.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 6797246..d10ebc4 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -218,7 +218,8 @@
 		if (((event == RPC_PIPEFS_MOUNT) && clnt->cl_dentry) ||
 		    ((event == RPC_PIPEFS_UMOUNT) && !clnt->cl_dentry))
 			continue;
-		atomic_inc(&clnt->cl_count);
+		if (atomic_inc_not_zero(&clnt->cl_count) == 0)
+			continue;
 		spin_unlock(&sn->rpc_client_lock);
 		return clnt;
 	}