netdev - Re: [PATCH for-6.1 0/3] fail io_uring zc with sockets not supporting it

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Date:   Fri, 21 Oct 2022 11:42:07 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Stefan Metzmacher <metze@...ba.org>, Jens Axboe <axboe@...nel.dk>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     io-uring@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH for-6.1 0/3] fail io_uring zc with sockets not supporting
 it

On 10/21/22 11:27, Stefan Metzmacher wrote:
> Hi Pavel,
> 
>> Some sockets don't care about msghdr::ubuf_info and would execute the
>> request by copying data. Such fallback behaviour was always a pain in
>> my experience, so we'd rather want to fail such requests and have a more
>> robust api in the future.
>>
>> Mark struct socket that support it with a new SOCK_SUPPORT_ZC flag.
>> I'm not entirely sure it's the best place for the flag but at least
>> we don't have to do a bunch of extra dereferences in the hot path.
> 
> I'd give the flag another name that indicates msg_ubuf and

Could be renamed, e.g. SOCK_SUPPORT_MSGHDR_UBUF or maybe
SOCK_SUPPORT_EXTERNAL_UBUF

> have a 2nd flag that can indicate support for SO_ZEROCOPY in sk_setsockopt()

There is absolutely no reason to introduce a second flag here, it has
nothing to do with SO_ZEROCOPY.

> The SO_ZEROCOPY version is also provided by AF_RDS.

-- 
Pavel Begunkov