Re: [PATCH v3 v3 2/2] ext4: allow clearing mballoc stats through mb_stats

Theodore Tso
2026-04-23T16:21:30Z

On Wed, Apr 22, 2026 at 09:50:25AM +0800, Baolin Liu wrote:
> From: Baolin Liu <liubaolin@kylinos.cn>
>
> Make /proc/fs/ext4/<dev>/mb_stats writable and clear the runtime
> mballoc statistics when 0 is written.

At the moment to enable mb_stats the system administrator needs to
write "1" to /sys/fs/ext4/<dev>/mb_stats, and writing "0" to the sysfs
file will pauce the statistics colleciton (but not clear the
statistics). Adding a way to clear the statistics by writing to the
procfs file might be confusing to users.

So.... as a suggestion, if you're adding to the ability to write to
/proc/fs/.../mb_stats, what if we make things work by

* Write 1 to /proc/fs/.../mb_stats to enable statistics collection
* Write 0 to /proc/fs/.../mb_stats to disable statistics collection
* Write -1 to /proc/fs/.../mb_stats to clear statistics counters

And then deprecate the /sys/fs/.../mb_stats variable (but we probably
won't be able to remove it for at least a year or two).

- Ted