On 2/9/13 7:42 PM, Theodore Ts'o wrote:
> 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 ext4 module.
>
> Secondly, as a module paramter it can be specified as a boot option if
> ext4 is built into the kernel, or as a parameter when the module is
> loaded, and it can also be manipulated dynamically under
> /sys/module/ext4/parameters/mballoc_debug. So it is more flexible.
>
> Ultimately we want to move away from using mb_debug() towards
> tracepoints, but for now this is still a useful simplification of the
> code base.
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Good idea.
My only suggestion would be to add parameter information to the descriptions -
default value and permissible value range? I guess nothing enforces that
like for proc entries, right?
"Debugging level for ext4's mballoc: 0/1 (default 0)"
(hm, we never pass anything but "1" o_O)
It doesn't seem like the values need sanity checking at module load time,
but maybe it'd be worth it just out of paranoia.
Updating Documentation/filesystems/ext4.txt would be good too.
Thanks,
-Eric
-Eric
> ---
> fs/ext4/mballoc.c | 47 +++++++++--------------------------------------
> fs/ext4/mballoc.h | 4 ++--
> 2 files changed, 11 insertions(+), 40 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index e350885..6540ebe 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -23,11 +23,18 @@
>
> #include "ext4_jbd2.h"
> #include "mballoc.h"
> -#include <linux/debugfs.h>
> #include <linux/log2.h>
> +#include <linux/module.h>
> #include <linux/slab.h>
> #include <trace/events/ext4.h>
>
> +#ifdef CONFIG_EXT4_DEBUG
> +ushort ext4_mballoc_debug __read_mostly;
> +
> +module_param_named(mballoc_debug, ext4_mballoc_debug, ushort, 0644);
> +MODULE_PARM_DESC(mballoc_debug, "Debugging level for ext4's mballoc");
> +#endif
> +
> /*
> * MUSTDO:
> * - test ext4_ext_search_left() and ext4_ext_search_right()
> @@ -2660,40 +2667,6 @@ static void ext4_free_data_callback(struct super_block *sb,
> mb_debug(1, "freed %u blocks in %u structures\n", count, count2);
> }
>
> -#ifdef CONFIG_EXT4_DEBUG
> -u8 mb_enable_debug __read_mostly;
> -
> -static struct dentry *debugfs_dir;
> -static struct dentry *debugfs_debug;
> -
> -static void __init ext4_create_debugfs_entry(void)
> -{
> - debugfs_dir = debugfs_create_dir("ext4", NULL);
> - if (debugfs_dir)
> - debugfs_debug = debugfs_create_u8("mballoc-debug",
> - S_IRUGO | S_IWUSR,
> - debugfs_dir,
> - &mb_enable_debug);
> -}
> -
> -static void ext4_remove_debugfs_entry(void)
> -{
> - debugfs_remove(debugfs_debug);
> - debugfs_remove(debugfs_dir);
> -}
> -
> -#else
> -
> -static void __init ext4_create_debugfs_entry(void)
> -{
> -}
> -
> -static void ext4_remove_debugfs_entry(void)
> -{
> -}
> -
> -#endif
> -
> int __init ext4_init_mballoc(void)
> {
> ext4_pspace_cachep = KMEM_CACHE(ext4_prealloc_space,
> @@ -2715,7 +2688,6 @@ int __init ext4_init_mballoc(void)
> kmem_cache_destroy(ext4_ac_cachep);
> return -ENOMEM;
> }
> - ext4_create_debugfs_entry();
> return 0;
> }
>
> @@ -2730,7 +2702,6 @@ void ext4_exit_mballoc(void)
> kmem_cache_destroy(ext4_ac_cachep);
> kmem_cache_destroy(ext4_free_data_cachep);
> ext4_groupinfo_destroy_slabs();
> - ext4_remove_debugfs_entry();
> }
>
>
> @@ -3876,7 +3847,7 @@ static void ext4_mb_show_ac(struct ext4_allocation_context *ac)
> struct super_block *sb = ac->ac_sb;
> ext4_group_t ngroups, i;
>
> - if (!mb_enable_debug ||
> + if (!ext4_mballoc_debug ||
> (EXT4_SB(sb)->s_mount_flags & EXT4_MF_FS_ABORTED))
> return;
>
> diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
> index 3ccd889..08481ee 100644
> --- a/fs/ext4/mballoc.h
> +++ b/fs/ext4/mballoc.h
> @@ -37,11 +37,11 @@
> /*
> */
> #ifdef CONFIG_EXT4_DEBUG
> -extern u8 mb_enable_debug;
> +extern ushort ext4_mballoc_debug;
>
> #define mb_debug(n, fmt, a...) \
> do { \
> - if ((n) <= mb_enable_debug) { \
> + if ((n) <= ext4_mballoc_debug) { \
> printk(KERN_DEBUG "(%s, %d): %s: ", \
> __FILE__, __LINE__, __func__); \
> printk(fmt, ## a); \
>
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