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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@redhat.com>
cc: David Ahern <dsahern@kernel.org>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
David Howells 2023-05-22 13:11:13 +01:00 committed by Jakub Kicinski
parent 2e910b9532
commit 270a1c3de4
1 changed files with 36 additions and 7 deletions
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43
net/ipv4/tcp.c
View File

@ -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 @@ restart:
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 @@ new_segment:
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 @@ new_segment:
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 @@ new_segment:
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)