ext4: Add configurable run-time mballoc debugging

Allow mballoc debugging to be enabled at run-time instead of just at
compile time.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
index 15230462..d5c0ea2 100644
--- a/fs/ext4/Kconfig
+++ b/fs/ext4/Kconfig
@@ -77,3 +77,12 @@
 
 	  If you are not using a security module that requires using
 	  extended attributes for file security labels, say N.
+
+config EXT4_DEBUG
+	bool "EXT4 debugging support"
+	depends on EXT4_FS
+	help
+	  Enables run-time debugging support for the ext4 filesystem.
+
+	  If you select Y here, then you will be able to turn on debugging
+	  with a command such as "echo 1 > /sys/kernel/debug/ext4/mballoc-debug"