orangefs: add features op

This is a new userspace operation, which will be done if the client-core
version is greater than or equal to 2.9.6. This will provide a way to
implement optional features and to determine which features are
supported by the client-core. If the client-core version is older than
2.9.6, no optional features are supported and the op will not be done.

The intent is to allow protocol extensions without relying on the
client-core's current behavior of ignoring what it doesn't understand.

Signed-off-by: Martin Brandenburg <martin@omnibond.com>
diff --git a/fs/orangefs/orangefs-cache.c b/fs/orangefs/orangefs-cache.c
index eb0b6e0..aa3830b 100644
--- a/fs/orangefs/orangefs-cache.c
+++ b/fs/orangefs/orangefs-cache.c
@@ -97,6 +97,8 @@
 			return "OP_FSYNC";
 		else if (type == ORANGEFS_VFS_OP_FSKEY)
 			return "OP_FSKEY";
+		else if (type == ORANGEFS_VFS_OP_FEATURES)
+			return "OP_FEATURES";
 	}
 	return "OP_UNKNOWN?";
 }