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Subject[PATCH net-next v10 13/16] udp: Convert udp_sendpage() to use MSG_SPLICE_PAGES
Date
Convert udp_sendpage() to use sendmsg() with MSG_SPLICE_PAGES rather than
directly splicing in the pages itself.

This allows ->sendpage() to be replaced by something that can handle
multiple multipage folios in a single transaction.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
cc: David Ahern <dsahern@kernel.org>
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: netdev@vger.kernel.org
---

Notes:
ver #6)
- udp_sendpage() shouldn't lock the socket around udp_sendpage().
- udp_sendpage() should only set MSG_MORE if MSG_SENDPAGE_NOTLAST is set.

net/ipv4/udp.c | 51 ++++++--------------------------------------------
1 file changed, 6 insertions(+), 45 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index aa32afd871ee..2879dc6d66ea 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1332,54 +1332,15 @@ EXPORT_SYMBOL(udp_sendmsg);
int udp_sendpage(struct sock *sk, struct page *page, int offset,
size_t size, int flags)
{
- struct inet_sock *inet = inet_sk(sk);
- struct udp_sock *up = udp_sk(sk);
- int ret;
+ struct bio_vec bvec;
+ struct msghdr msg = { .msg_flags = flags | MSG_SPLICE_PAGES };

if (flags & MSG_SENDPAGE_NOTLAST)
- flags |= MSG_MORE;
-
- if (!up->pending) {
- struct msghdr msg = { .msg_flags = flags|MSG_MORE };
-
- /* Call udp_sendmsg to specify destination address which
- * sendpage interface can't pass.
- * This will succeed only when the socket is connected.
- */
- ret = udp_sendmsg(sk, &msg, 0);
- if (ret < 0)
- return ret;
- }
-
- lock_sock(sk);
+ msg.msg_flags |= MSG_MORE;

- if (unlikely(!up->pending)) {
- release_sock(sk);
-
- net_dbg_ratelimited("cork failed\n");
- return -EINVAL;
- }
-
- ret = ip_append_page(sk, &inet->cork.fl.u.ip4,
- page, offset, size, flags);
- if (ret == -EOPNOTSUPP) {
- release_sock(sk);
- return sock_no_sendpage(sk->sk_socket, page, offset,
- size, flags);
- }
- if (ret < 0) {
- udp_flush_pending_frames(sk);
- goto out;
- }
-
- up->len += size;
- if (!(READ_ONCE(up->corkflag) || (flags&MSG_MORE)))
- ret = udp_push_pending_frames(sk);
- if (!ret)
- ret = size;
-out:
- release_sock(sk);
- return ret;
+ bvec_set_page(&bvec, page, size, offset);
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
+ return udp_sendmsg(sk, &msg, size);
}

#define UDP_SKB_IS_STATELESS 0x80000000
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