jbd2: Move jbd2-debug file to debugfs

The jbd2-debug file used to be located in /proc/sys/fs/jbd2-debug, but it
incorrectly used create_proc_entry() instead of the sysctl routines, and
no proc entry was ever created.

Instead of fixing this we might as well move the jbd2-debug file to
debugfs which would be the preferred location for this kind of tunable.
The new location is now /sys/kernel/debug/jbd2/jbd2-debug.

Signed-off-by: Jose R. Santos <jrs@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/Kconfig b/fs/Kconfig
index 613df55..6a64990 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -251,7 +251,7 @@
 
 config JBD2_DEBUG
 	bool "JBD2 (ext4dev/ext4) debugging support"
-	depends on JBD2
+	depends on JBD2 && DEBUG_FS
 	help
 	  If you are using the ext4dev/ext4 journaled file system (or
 	  potentially any other filesystem/device using JBD2), this option
@@ -260,10 +260,10 @@
 	  By default, the debugging output will be turned off.
 
 	  If you select Y here, then you will be able to turn on debugging
-	  with "echo N > /proc/sys/fs/jbd2-debug", where N is a number between
-	  1 and 5. The higher the number, the more debugging output is
-	  generated.  To turn debugging off again, do
-	  "echo 0 > /proc/sys/fs/jbd2-debug".
+	  with "echo N > /sys/kernel/debug/jbd2/jbd2-debug", where N is a
+	  number between 1 and 5. The higher the number, the more debugging
+	  output is generated.  To turn debugging off again, do
+	  "echo 0 > /sys/kernel/debug/jbd2/jbd2-debug".
 
 config FS_MBCACHE
 # Meta block cache for Extended Attributes (ext2/ext3/ext4)