Re: [PATCH 1/2] btrfs: remove MIXED_BACKREF sysfs file

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2022/7/11 23:23, David Sterba wrote:
> On Sat, Jun 25, 2022 at 01:53:47PM +0800, Qu Wenruo wrote:
>>> Removed functionality is documented, the sysfs feature files are in
>>> manual pages and we can add a notice in which version it was removed.
>>
>> Then have all the old features get removed one by one, until one day we
>> have a dozen of bits set, but only one or two still show in sysfs features?
>>
>> No, this definitely doesn't look sane to me.
>
> And nobody is suggesting that either,

Doesn't the patch just remove the sysfs file for both global and per-fs
features?
Or did I miss something?

> the big data and mixed backrefs
> are something that's exceptional in this regard. Removing other features
> would take some significant time to remove and a check if it would still
> not break some testing setups.
>
>> It's just trying to hide some bad behaviors which we didn't get it right
>> in the first place.
>> It's fine to didn't get those things done correct in the first place,
>> but not fine to hide them.
>>
>> Especially those sysfs is already hidden to most users, way less
>> invasive than the dmesg output/mkfs features/etc, why we still want to
>> remove them?
>
> To unclutter the namespace a bit, in case of the mixed_backrefs it's a
> bit confusing with the mixed block groups but I think I've mentioned
> that already.

If you're just to avoid the namespace conflicts/confusion, then just
rename them with some prefix like "__always_on_" or something similar.

Thanks,
Qu