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>

fs/Kconfig

@@ -251,7 +251,7 @@ config JBD2
 
 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 @@ config JBD2_DEBUG
 	  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)

fs/jbd2/journal.c

@@ -35,6 +35,7 @@
 #include <linux/kthread.h>
 #include <linux/poison.h>
 #include <linux/proc_fs.h>
+#include <linux/debugfs.h>
 
 #include <asm/uaccess.h>
 #include <asm/page.h>
@@ -1951,64 +1952,50 @@ void jbd2_journal_put_journal_head(struct journal_head *jh)
 }
 
 /*
- * /proc tunables
+ * debugfs tunables
  */
 #if defined(CONFIG_JBD2_DEBUG)
-int jbd2_journal_enable_debug;
+u8 jbd2_journal_enable_debug;
 EXPORT_SYMBOL(jbd2_journal_enable_debug);
 #endif
 
-#if defined(CONFIG_JBD2_DEBUG) && defined(CONFIG_PROC_FS)
+#if defined(CONFIG_JBD2_DEBUG) && defined(CONFIG_DEBUG_FS)
 
-static struct proc_dir_entry *proc_jbd_debug;
+#define JBD2_DEBUG_NAME "jbd2-debug"
 
-static int read_jbd_debug(char *page, char **start, off_t off,
-			  int count, int *eof, void *data)
-{
-	int ret;
+struct dentry *jbd2_debugfs_dir, *jbd2_debug;
 
-	ret = sprintf(page + off, "%d\n", jbd2_journal_enable_debug);
-	*eof = 1;
-	return ret;
+static void __init jbd2_create_debugfs_entry(void)
+{
+	jbd2_debugfs_dir = debugfs_create_dir("jbd2", NULL);
+	if (jbd2_debugfs_dir)
+		jbd2_debug = debugfs_create_u8(JBD2_DEBUG_NAME, S_IRUGO,
+					       jbd2_debugfs_dir,
+					       &jbd2_journal_enable_debug);
 }
 
-static int write_jbd_debug(struct file *file, const char __user *buffer,
-			   unsigned long count, void *data)
+static void __exit jbd2_remove_debugfs_entry(void)
 {
-	char buf[32];
-
-	if (count > ARRAY_SIZE(buf) - 1)
-		count = ARRAY_SIZE(buf) - 1;
-	if (copy_from_user(buf, buffer, count))
-		return -EFAULT;
-	buf[ARRAY_SIZE(buf) - 1] = '\0';
-	jbd2_journal_enable_debug = simple_strtoul(buf, NULL, 10);
-	return count;
+	if (jbd2_debug)
+		debugfs_remove(jbd2_debug);
+	if (jbd2_debugfs_dir)
+		debugfs_remove(jbd2_debugfs_dir);
 }
 
-#define JBD_PROC_NAME "sys/fs/jbd2-debug"
+#else
 
-static void __init create_jbd_proc_entry(void)
+static void __init jbd2_create_debugfs_entry(void)
 {
-	proc_jbd_debug = create_proc_entry(JBD_PROC_NAME, 0644, NULL);
-	if (proc_jbd_debug) {
-		/* Why is this so hard? */
-		proc_jbd_debug->read_proc = read_jbd_debug;
-		proc_jbd_debug->write_proc = write_jbd_debug;
-	}
+	do {
+	} while (0);
 }
 
-static void __exit jbd2_remove_jbd_proc_entry(void)
+static void __exit jbd2_remove_debugfs_entry(void)
 {
-	if (proc_jbd_debug)
-		remove_proc_entry(JBD_PROC_NAME, NULL);
+	do {
+	} while (0);
 }
 
-#else
-
-#define create_jbd_proc_entry() do {} while (0)
-#define jbd2_remove_jbd_proc_entry() do {} while (0)
-
 #endif
 
 struct kmem_cache *jbd2_handle_cache;
@@ -2067,7 +2054,7 @@ static int __init journal_init(void)
 	ret = journal_init_caches();
 	if (ret != 0)
 		jbd2_journal_destroy_caches();
-	create_jbd_proc_entry();
+	jbd2_create_debugfs_entry();
 	return ret;
 }
 
@@ -2078,7 +2065,7 @@ static void __exit journal_exit(void)
 	if (n)
 		printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
 #endif
-	jbd2_remove_jbd_proc_entry();
+	jbd2_remove_debugfs_entry();
 	jbd2_journal_destroy_caches();
 }
 

include/linux/jbd2.h

@@ -57,7 +57,7 @@
  * CONFIG_JBD2_DEBUG is on.
  */
 #define JBD_EXPENSIVE_CHECKING
-extern int jbd2_journal_enable_debug;
+extern u8 jbd2_journal_enable_debug;
 
 #define jbd_debug(n, f, a...)						\
 	do {								\