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

[Qu Wenruo]

在 2025/4/2 19:07, Daniel Vacek 写道:
> On Tue, 1 Apr 2025 at 00:57, David Sterba <dsterba@xxxxxxx> 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.