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Message-Id: <20230522121125.2595254-5-dhowells@redhat.com> Date: Mon, 22 May 2023 13:11:13 +0100 From: David Howells <dhowells@...hat.com> To: netdev@...r.kernel.org Cc: David Howells <dhowells@...hat.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Willem de Bruijn <willemdebruijn.kernel@...il.com>, David Ahern <dsahern@...nel.org>, Matthew Wilcox <willy@...radead.org>, Al Viro <viro@...iv.linux.org.uk>, Christoph Hellwig <hch@...radead.org>, Jens Axboe <axboe@...nel.dk>, Jeff Layton <jlayton@...nel.org>, Christian Brauner <brauner@...nel.org>, Chuck Lever III <chuck.lever@...cle.com>, Linus Torvalds <torvalds@...ux-foundation.org>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: [PATCH net-next v10 04/16] tcp: Support MSG_SPLICE_PAGES Make TCP's sendmsg() support MSG_SPLICE_PAGES. This causes pages to be spliced or copied (if it cannot be spliced) from the source iterator. This allows ->sendpage() to be replaced by something that can handle multiple multipage folios in a single transaction. Signed-off-by: David Howells <dhowells@...hat.com> cc: Eric Dumazet <edumazet@...gle.com> cc: "David S. Miller" <davem@...emloft.net> cc: David Ahern <dsahern@...nel.org> cc: Jakub Kicinski <kuba@...nel.org> cc: Paolo Abeni <pabeni@...hat.com> cc: Jens Axboe <axboe@...nel.dk> cc: Matthew Wilcox <willy@...radead.org> cc: netdev@...r.kernel.org --- Notes: ver #9) - Fix a merge conflict with commit eea96a3e2c909. ver #7) - Missed a "zc = 1" in tcp_sendmsg_locked(). ver #6) - Set zc to 0/MSG_ZEROCOPY/MSG_SPLICE_PAGES rather than 0/1/2. - Use common helper. net/ipv4/tcp.c | 43 ++++++++++++++++++++++++++++++++++++------- 1 file changed, 36 insertions(+), 7 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 3d18e295bb2f..2d61150d01f1 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1223,7 +1223,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) int flags, err, copied = 0; int mss_now = 0, size_goal, copied_syn = 0; int process_backlog = 0; - bool zc = false; + int zc = 0; long timeo; flags = msg->msg_flags; @@ -1231,7 +1231,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) if ((flags & MSG_ZEROCOPY) && size) { if (msg->msg_ubuf) { uarg = msg->msg_ubuf; - zc = sk->sk_route_caps & NETIF_F_SG; + if (sk->sk_route_caps & NETIF_F_SG) + zc = MSG_ZEROCOPY; } else if (sock_flag(sk, SOCK_ZEROCOPY)) { skb = tcp_write_queue_tail(sk); uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb)); @@ -1239,10 +1240,14 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) err = -ENOBUFS; goto out_err; } - zc = sk->sk_route_caps & NETIF_F_SG; - if (!zc) + if (sk->sk_route_caps & NETIF_F_SG) + zc = MSG_ZEROCOPY; + else uarg_to_msgzc(uarg)->zerocopy = 0; } + } else if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES) && size) { + if (sk->sk_route_caps & NETIF_F_SG) + zc = MSG_SPLICE_PAGES; } if (unlikely(flags & MSG_FASTOPEN || inet_sk(sk)->defer_connect) && @@ -1305,7 +1310,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) goto do_error; while (msg_data_left(msg)) { - int copy = 0; + ssize_t copy = 0; skb = tcp_write_queue_tail(sk); if (skb) @@ -1346,7 +1351,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) if (copy > msg_data_left(msg)) copy = msg_data_left(msg); - if (!zc) { + if (zc == 0) { bool merge = true; int i = skb_shinfo(skb)->nr_frags; struct page_frag *pfrag = sk_page_frag(sk); @@ -1391,7 +1396,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) page_ref_inc(pfrag->page); } pfrag->offset += copy; - } else { + } else if (zc == MSG_ZEROCOPY) { /* First append to a fragless skb builds initial * pure zerocopy skb */ @@ -1412,6 +1417,30 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) if (err < 0) goto do_error; copy = err; + } else if (zc == MSG_SPLICE_PAGES) { + /* Splice in data if we can; copy if we can't. */ + if (tcp_downgrade_zcopy_pure(sk, skb)) + goto wait_for_space; + copy = tcp_wmem_schedule(sk, copy); + if (!copy) + goto wait_for_space; + + err = skb_splice_from_iter(skb, &msg->msg_iter, copy, + sk->sk_allocation); + if (err < 0) { + if (err == -EMSGSIZE) { + tcp_mark_push(tp, skb); + goto new_segment; + } + goto do_error; + } + copy = err; + + if (!(flags & MSG_NO_SHARED_FRAGS)) + skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG; + + sk_wmem_queued_add(sk, copy); + sk_mem_charge(sk, copy); } if (!copied)
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