linux-kernel - Re: [RFC PATCH 01/21] crypto: scomp - Revert "add support for deflate rfc1950 (zlib)"

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Message-ID: <CAMj1kXGn70sGAHgOttKkC6n6jfVZ9Y61NZ9ffLmJV8MK2Kh8nQ@mail.gmail.com>
Date:   Thu, 3 Aug 2023 11:59:00 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Giovanni Cabiddu <giovanni.cabiddu@...el.com>
Cc:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Eric Biggers <ebiggers@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Haren Myneni <haren@...ibm.com>,
        Nick Terrell <terrelln@...com>,
        Minchan Kim <minchan@...nel.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Jens Axboe <axboe@...nel.dk>,
        Richard Weinberger <richard@....at>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        qat-linux <qat-linux@...el.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC PATCH 01/21] crypto: scomp - Revert "add support for deflate
 rfc1950 (zlib)"

Hello Giovanni,

On Thu, 3 Aug 2023 at 11:51, Giovanni Cabiddu
<giovanni.cabiddu@...el.com> wrote:
>
> Hi Ard,
>
> On Tue, Jul 18, 2023 at 01:58:27PM +0100, Ard Biesheuvel wrote:
> > This reverts commit a368f43d6e3a001e684e9191a27df384fbff12f5.
> >
> > "zlib-deflate" was introduced 6 years ago, but it does not have any
> > users. So let's remove the generic implementation and the test vectors,
> > but retain the "zlib-deflate" entry in the testmgr code to avoid
> > introducing warning messages on systems that implement zlib-deflate in
> > hardware.
> >
> > Note that RFC 1950 which forms the basis of this algorithm dates back to
> > 1996, and predates RFC 1951, on which the existing IPcomp is based and
> > which we have supported in the kernel since 2003. So it seems rather
> > unlikely that we will ever grow the need to support zlib-deflate.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> Support for zlib-deflate was added for [1] but that work was not
> completed.
>

Any clue why zlib_deflate was chosen in this case?

/me also notes that this is another occurrence of the antipattern
where we use an asynchronous API and subsequently sleep on the
completion.

> Based on [2], either we leave this SW implementation or we remove the HW
> implementations in the QAT [3] and in the Hisilicon Zip [4] drivers.
>

That would work for me as well - dead code is just busywork.

> [1] https://patchwork.kernel.org/project/linux-btrfs/patch/1467083180-111750-1-git-send-email-weigang.li@intel.com/
> [2] https://lore.kernel.org/lkml/ZIw%2Fjtxdg6O1O0j3@gondor.apana.org.au/
> [3] https://elixir.bootlin.com/linux/latest/source/drivers/crypto/intel/qat/qat_common/qat_comp_algs.c#L457
> [4] https://elixir.bootlin.com/linux/latest/source/drivers/crypto/hisilicon/zip/zip_crypto.c#L754
>
> Regards,
>
> --
> Giovanni