Re: [PATCH v2 2/2] btrfs: qgroup: add sysfs interface for debug

[Qu Wenruo <wqu@suse.com>]

On 2020/6/30 上午5:30, David Sterba wrote:
> On Sun, Jun 28, 2020 at 01:07:15PM +0800, Qu Wenruo wrote:
>> +QGROUP_ATTR(rfer, reference);
> 
> Note that this is 'referenced'.
> 
>> +QGROUP_ATTR(excl, exclusive);
>> +QGROUP_ATTR(max_rfer, max_reference);
> 
> And here max_referenced.
> 
>> +QGROUP_ATTR(max_excl, max_exclusive);
>> +QGROUP_ATTR(lim_flags, limit_flags);
>> +QGROUP_RSV_ATTR(data, BTRFS_QGROUP_RSV_DATA);
>> +QGROUP_RSV_ATTR(meta_pertrans, BTRFS_QGROUP_RSV_META_PERTRANS);
>> +QGROUP_RSV_ATTR(meta_prealloc, BTRFS_QGROUP_RSV_META_PREALLOC);
> 
> The two above fixed but otherwise it's good, thanks.
> 
> The qgroup membership and relations could be added to the sysfs export
> too, but we're limited by the PAGE_SIZE output buffer so the information
> could be incomplete.
> 
Yep, PAGE_SIZE is one limitation.
But we can also go another direction, just using a new dir for related
qgroups, then we can workaround the limitation.

But personally speaking, the main objective is still the rsv_* members
for debug.
I don't really want to turn the sysfs interface into a way to export all
qgroup info yet.


But if this inspired us to explore more usage of sysfs other than adding
new ioctls to get information from btrfs, then I can't be more happier.

Thanks,
Qu