Re: [PATCH] btrfs: zstd: add `zstd-fast` alias mount option for fast modes

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

在 2025/4/2 19:07, Daniel Vacek 写道:
> On Tue, 1 Apr 2025 at 00:57, David Sterba <dsterba@suse.cz> wrote:
[...]
>>>> I thought this was solid. Or would you rather bail out with -EINVAL?
>>>
>>> I prefer to bail out with -EINVAL, but it's only my personal choice.
>>
>> I tend to agree with you, the idea for the alias was based on feedback
>> that upstream zstd calls the levels fast, not by the negative numbers.
>> So I think we stick to the zstd: and zstd-fast: prefixes followed only
>> by the positive numbers.
>
> Hmm, so for zlib and zstd if the level is out of range, it's just
> clipped and not failed as invalid. I guess zstd-fast should also do
> the same to be consistent.

Or we can change the zlib/zstd level checks so that it can return
-EINVAL when invalid levels are provided.

But to avoid huge surprise, I'd recommend to add warning/error messages
first.

I'm not a huge fan when invalid values are silently clamped, even it's
just an optional level parameter.

Thanks,
Qu

>
>> We can make this change before 6.15 final so it's not in any released
>> kernel and we don't have to deal with compatibility.
>