Add Btrfs to fs/Kconfig and fs/Makefile

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/Kconfig b/fs/Kconfig
index abccb5da..18f5a85 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -497,6 +497,23 @@
 	  this option for debugging only as it is likely to decrease
 	  performance of the filesystem.
 
+config BTRFS_FS
+	tristate "Btrfs filesystem (EXPERIMENTAL) Unstable disk format"
+	depends on EXPERIMENTAL
+	select LIBCRC32C
+	help
+	  Btrfs is a new filesystem with extents, writable snapshotting,
+	  support for multiple devices and many more features.
+
+	  Btrfs is highly experimental, and THE DISK FORMAT IS NOT YET
+	  FINALIZED.  You should say N here unless you are interested in
+	  testing Btrfs with non-critical data.
+
+	  To compile this file system support as a module, choose M here. The
+	  module will be called btrfs.
+
+	  If unsure, say N.
+
 endif # BLOCK
 
 config DNOTIFY