On 2/11/13 9:36 AM, Eric Sandeen wrote:
> 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.
As another thought, did you consider using dynamic debug for this, or is that
too much trickiness? Might be nice since usually a bug reporter won't have
a kernel built with CONFIG_EXT4_DEBUG . . .
-Eric
> 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); \
>>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
