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 14:49:46 +0200
From:   Stefan Metzmacher <metze@...ba.org>
To:     Pavel Begunkov <asml.silence@...il.com>,
        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

Am 21.10.22 um 12:42 schrieb Pavel Begunkov:
> 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 

That's good or SOCK_SUPPORT_ZC_MSGHDR_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.

I meant as a separate change to replace the hard coded logic in
sk_setsockopt()... But I don't care much about it, it's unlikely
that I ever want to use SO_ZEROCOPY...

metze