[PATCH 1/4] jbd: use module parameters instead of debugfs for jbd_debug

[Paul Gortmaker <paul.gortmaker@windriver.com>]

This is a direct backport of commit b6e96d0067d81f6a300bedee
("jbd2: use module parameters instead of debugfs for jbd_debug")
from jbd2 into jbd.  The value is in making ext4 and ext3 user
experiences consistent with each other.  Quoting the original:

 --------------
 There are multiple reasons to move away from debugfs.  First of all,
 we are only using it for a single parameter, and it is much more
 complicated to set up (some 30 lines of code compared to 3), and one
 more thing that might fail while loading the jbd2 module.

 Secondly, as a module paramter it can be specified as a boot option if
 jbd2 is built into the kernel, or as a parameter when the module is
 loaded, and it can also be manipulated dynamically under
 /sys/module/jbd2/parameters/jbd2_debug.  So it is more flexible.

 Ultimately we want to move away from using jbd_debug() towards
 tracepoints, but for now this is still a useful simplification of the
 code base.
 --------------

It is worth noting that we use /sys/module/jbd/parameters/jbd1_debug
(i.e. the "1" might appear odd) for the module parameter in order to
avoid namespace collisions with the existing jbd_debug used as a
function call.

In addition, we combine the content of jbd2 commit 75497d0607b56e16e4
("jbd2: remove debug dependency on debug_fs and update Kconfig help text")
since they were only separate commits unintentionally in jbd2.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 fs/jbd/Kconfig      |  6 +++---
 fs/jbd/journal.c    | 49 ++++++++-----------------------------------------
 include/linux/jbd.h |  3 +--
 3 files changed, 12 insertions(+), 46 deletions(-)

diff --git a/fs/jbd/Kconfig b/fs/jbd/Kconfig
index 4e28bee..54cbb55 100644
--- a/fs/jbd/Kconfig
+++ b/fs/jbd/Kconfig
@@ -15,7 +15,7 @@ config JBD
 
 config JBD_DEBUG
 	bool "JBD (ext3) debugging support"
-	depends on JBD && DEBUG_FS
+	depends on JBD
 	help
 	  If you are using the ext3 journaled file system (or potentially any
 	  other file system/device using JBD), this option allows you to
@@ -24,7 +24,7 @@ config JBD_DEBUG
 	  debugging output will be turned off.
 
 	  If you select Y here, then you will be able to turn on debugging
-	  with "echo N > /sys/kernel/debug/jbd/jbd-debug", where N is a
+	  with "echo N > /sys/module/jbd/parameters/jbd1_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/jbd/jbd-debug".
+	  "echo 0 > /sys/module/jbd/parameters/jbd1_debug".
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index 6510d63..166263d 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -35,7 +35,6 @@
 #include <linux/kthread.h>
 #include <linux/poison.h>
 #include <linux/proc_fs.h>
-#include <linux/debugfs.h>
 #include <linux/ratelimit.h>
 
 #define CREATE_TRACE_POINTS
@@ -44,6 +43,14 @@
 #include <asm/uaccess.h>
 #include <asm/page.h>
 
+#ifdef CONFIG_JBD_DEBUG
+ushort jbd_journal_enable_debug __read_mostly;
+EXPORT_SYMBOL(jbd_journal_enable_debug);
+
+module_param_named(jbd1_debug, jbd_journal_enable_debug, ushort, 0644);
+MODULE_PARM_DESC(jbd1_debug, "Debugging level for jbd");
+#endif
+
 EXPORT_SYMBOL(journal_start);
 EXPORT_SYMBOL(journal_restart);
 EXPORT_SYMBOL(journal_extend);
@@ -2017,44 +2024,6 @@ void journal_put_journal_head(struct journal_head *jh)
 		jbd_unlock_bh_journal_head(bh);
 }
 
-/*
- * debugfs tunables
- */
-#ifdef CONFIG_JBD_DEBUG
-
-u8 journal_enable_debug __read_mostly;
-EXPORT_SYMBOL(journal_enable_debug);
-
-static struct dentry *jbd_debugfs_dir;
-static struct dentry *jbd_debug;
-
-static void __init jbd_create_debugfs_entry(void)
-{
-	jbd_debugfs_dir = debugfs_create_dir("jbd", NULL);
-	if (jbd_debugfs_dir)
-		jbd_debug = debugfs_create_u8("jbd-debug", S_IRUGO | S_IWUSR,
-					       jbd_debugfs_dir,
-					       &journal_enable_debug);
-}
-
-static void __exit jbd_remove_debugfs_entry(void)
-{
-	debugfs_remove(jbd_debug);
-	debugfs_remove(jbd_debugfs_dir);
-}
-
-#else
-
-static inline void jbd_create_debugfs_entry(void)
-{
-}
-
-static inline void jbd_remove_debugfs_entry(void)
-{
-}
-
-#endif
-
 struct kmem_cache *jbd_handle_cache;
 
 static int __init journal_init_handle_cache(void)
@@ -2109,7 +2078,6 @@ static int __init journal_init(void)
 	ret = journal_init_caches();
 	if (ret != 0)
 		journal_destroy_caches();
-	jbd_create_debugfs_entry();
 	return ret;
 }
 
@@ -2120,7 +2088,6 @@ static void __exit journal_exit(void)
 	if (n)
 		printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
 #endif
-	jbd_remove_debugfs_entry();
 	journal_destroy_caches();
 }
 
diff --git a/include/linux/jbd.h b/include/linux/jbd.h
index 8685d1b..e45b430 100644
--- a/include/linux/jbd.h
+++ b/include/linux/jbd.h
@@ -20,7 +20,6 @@
 #ifndef __KERNEL__
 #include "jfs_compat.h"
 #define JFS_DEBUG
-#define jfs_debug jbd_debug
 #else
 
 #include <linux/types.h>
@@ -55,7 +54,7 @@
  * CONFIG_JBD_DEBUG is on.
  */
 #define JBD_EXPENSIVE_CHECKING
-extern u8 journal_enable_debug;
+extern ushort journal_enable_debug;
 
 #define jbd_debug(n, f, a...)						\
 	do {								\
-- 
1.8.1.2