exportfs: Return the minimum required handle size

The exportfs encode handle function should return the minimum required
handle size. This helps user to find out the handle size by passing 0
handle size in the first step and then redoing to the call again with
the returned handle size value.

Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/udf/namei.c

diff --git a/fs/udf/namei.c b/fs/udf/namei.c
index b7c338d..f1dce84 100644
--- a/fs/udf/namei.c
+++ b/fs/udf/namei.c
@@ -1286,8 +1286,13 @@
 	struct fid *fid = (struct fid *)fh;
 	int type = FILEID_UDF_WITHOUT_PARENT;
 
-	if (len < 3 || (connectable && len < 5))
+	if (connectable && (len < 5)) {
+		*lenp = 5;
 		return 255;
+	} else if (len < 3) {
+		*lenp = 3;
+		return 255;
+	}
 
 	*lenp = 3;
 	fid->udf.block = location.logicalBlockNum;