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Message-ID: <bd2750e52b47af1782233e254114eb8d627f1073.camel@redhat.com>
Subject: Re: [PATCH net-next v2 08/10] crypto: af_alg: Support
 MSG_SPLICE_PAGES
From:   Paolo Abeni <pabeni@redhat.com>
To:     David Howells <dhowells@redhat.com>, netdev@vger.kernel.org
Cc:     Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        David Ahern <dsahern@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jens Axboe <axboe@kernel.dk>, linux-crypto@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Date:   Thu, 01 Jun 2023 11:49:15 +0200
In-Reply-To: <20230530141635.136968-9-dhowells@redhat.com>
References: <20230530141635.136968-1-dhowells@redhat.com>
         <20230530141635.136968-9-dhowells@redhat.com>
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On Tue, 2023-05-30 at 15:16 +0100, David Howells wrote:
> Make AF_ALG sendmsg() support MSG_SPLICE_PAGES.  This causes pages to be
> spliced from the source iterator.
>=20
> This allows ->sendpage() to be replaced by something that can handle
> multiple multipage folios in a single transaction.
>=20
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Herbert Xu <herbert@gondor.apana.org.au>
> cc: "David S. Miller" <davem@davemloft.net>
> cc: Eric Dumazet <edumazet@google.com>
> cc: Jakub Kicinski <kuba@kernel.org>
> cc: Paolo Abeni <pabeni@redhat.com>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Matthew Wilcox <willy@infradead.org>
> cc: linux-crypto@vger.kernel.org
> cc: netdev@vger.kernel.org
> ---
>  crypto/af_alg.c         | 28 ++++++++++++++++++++++++++--
>  crypto/algif_aead.c     | 22 +++++++++++-----------
>  crypto/algif_skcipher.c |  8 ++++----
>  3 files changed, 41 insertions(+), 17 deletions(-)
>=20
> diff --git a/crypto/af_alg.c b/crypto/af_alg.c
> index fd56ccff6fed..62f4205d42e3 100644
> --- a/crypto/af_alg.c
> +++ b/crypto/af_alg.c
> @@ -940,6 +940,10 @@ int af_alg_sendmsg(struct socket *sock, struct msghd=
r *msg, size_t size,
>  	bool init =3D false;
>  	int err =3D 0;
> =20
> +	if ((msg->msg_flags & MSG_SPLICE_PAGES) &&
> +	    !iov_iter_is_bvec(&msg->msg_iter))
> +		return -EINVAL;
> +
>  	if (msg->msg_controllen) {
>  		err =3D af_alg_cmsg_send(msg, &con);
>  		if (err)
> @@ -985,7 +989,7 @@ int af_alg_sendmsg(struct socket *sock, struct msghdr=
 *msg, size_t size,
>  	while (size) {
>  		struct scatterlist *sg;
>  		size_t len =3D size;
> -		size_t plen;
> +		ssize_t plen;
> =20
>  		/* use the existing memory in an allocated page */
>  		if (ctx->merge) {
> @@ -1030,7 +1034,27 @@ int af_alg_sendmsg(struct socket *sock, struct msg=
hdr *msg, size_t size,
>  		if (sgl->cur)
>  			sg_unmark_end(sg + sgl->cur - 1);
> =20
> -		if (1 /* TODO check MSG_SPLICE_PAGES */) {
> +		if (msg->msg_flags & MSG_SPLICE_PAGES) {
> +			struct sg_table sgtable =3D {
> +				.sgl		=3D sg,
> +				.nents		=3D sgl->cur,
> +				.orig_nents	=3D sgl->cur,
> +			};
> +
> +			plen =3D extract_iter_to_sg(&msg->msg_iter, len, &sgtable,
> +						  MAX_SGL_ENTS, 0);

It looks like the above expect/supports only ITER_BVEC iterators, what
about adding a WARN_ON_ONCE(<other iov type>)?

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

Cheers,

Paolo