linux-kernel - Re: [PATCH v5 1/9] lib: zstd: Add zstd compatibility wrapper

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Message-ID: <4ED61269-0F19-46EB-ACE3-C6D81E0A9136@fb.com>
Date:   Tue, 10 Nov 2020 14:24:35 -0500
From:   "Chris Mason" <clm@...com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     Nick Terrell <nickrterrell@...il.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        <linux-crypto@...r.kernel.org>, <linux-btrfs@...r.kernel.org>,
        <squashfs-devel@...ts.sourceforge.net>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, Kernel Team <Kernel-team@...com>,
        Nick Terrell <terrelln@...com>, Petr Malat <oss@...at.biz>,
        Johannes Weiner <jweiner@...com>,
        Niket Agarwal <niketa@...com>, Yann Collet <cyan@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v5 1/9] lib: zstd: Add zstd compatibility wrapper

On 10 Nov 2020, at 13:39, Christoph Hellwig wrote:

> On Mon, Nov 09, 2020 at 02:01:41PM -0500, Chris Mason wrote:
>> You do consistently ask for a shim layer, but you haven???t explained 
>> what
>> we gain by diverging from the documented and tested API of the 
>> upstream zstd
>> project.  It???s an important discussion given that we hope to 
>> regularly
>> update the kernel side as they make improvements in zstd.
>
> An API that looks like every other kernel API, and doesn't cause 
> endless
> amount of churn because someone decided they need a new API flavor of
> the day.  Btw, I'm not asking for a shim layer - that was the 
> compromise
> we ended up with.
>
> If zstd folks can't maintain a sane code base maybe we should just 
> drop
> this childish churning code base from the tree.

I think APIs change based on the needs of the project.  We do this all 
the time in the kernel, and we don’t think twice about updating users 
of the API as needed.  The zstd changes look awkward and large today 
because it’ a long time period, but we’ve all been pretty vocal in 
the past about the importance of being able to advance APIs.

-chris