linux-kernel - Re: [PATCH net-next v2 08/10] crypto: af_alg: Support MSG_SPLICE

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Date:   Thu, 01 Jun 2023 12:35:12 +0100
From:   David Howells <dhowells@...hat.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     dhowells@...hat.com, netdev@...r.kernel.org,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, linux-crypto@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 08/10] crypto: af_alg: Support MSG_SPLICE_PAGES

Paolo Abeni <pabeni@...hat.com> wrote:

> > +	if ((msg->msg_flags & MSG_SPLICE_PAGES) &&
> > +	    !iov_iter_is_bvec(&msg->msg_iter))
> > +		return -EINVAL;
> > +
> ...
> It looks like the above expect/supports only ITER_BVEC iterators, what
> about adding a WARN_ON_ONCE(<other iov type>)?

Meh.  I relaxed that requirement as I'm now using tools to extract stuff from
any iterator (extract_iter_to_sg() in this case) rather than walking the
bvec[] directly.  I forgot to remove the check from af_alg.  I can add an
extra patch to remove it.  Also, it probably doesn't matter for AF_ALG since
that's only likely to be called from userspace, either directly (which will
not set MSG_SPLICE_PAGES) or via splice (which will pass a BVEC).  Internal
kernel code will use crypto API directly.

> Also, I'm keeping this series a bit more in pw to allow Herbert or
> others to have a look.

Thanks.

David