Btrfs progs v4.2.1

Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/version.sh b/version.sh
index e7e83b1..7da1a2e 100755
--- a/version.sh
+++ b/version.sh
@@ -6,7 +6,7 @@
 # Copyright 2008, Oracle
 # Released under the GNU GPLv2
 
-v="v4.2"
+v="v4.2.1"
 
 opt=$1