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tcp: Convert do_tcp_sendpages() to use MSG_SPLICE_PAGES

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Convert do_tcp_sendpages() to use sendmsg() with MSG_SPLICE_PAGES rather
than directly splicing in the pages itself.  do_tcp_sendpages() can then be
inlined in subsequent patches into its callers.

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 13:11:14 +01:00 committed by Jakub Kicinski
parent 270a1c3de4
commit c5c37af6ec
1 changed files with 7 additions and 151 deletions
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158
net/ipv4/tcp.c
View File

@ -974,163 +974,19 @@ static int tcp_wmem_schedule(struct sock *sk, int copy)
return min(copy, sk->sk_forward_alloc);
}
static struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags,
struct page *page, int offset, size_t *size)
{
struct sk_buff *skb = tcp_write_queue_tail(sk);
struct tcp_sock *tp = tcp_sk(sk);
bool can_coalesce;
int copy, i;
if (!skb || (copy = size_goal - skb->len) <= 0 ||
!tcp_skb_can_collapse_to(skb)) {
new_segment:
if (!sk_stream_memory_free(sk))
return NULL;
skb = tcp_stream_alloc_skb(sk, 0, sk->sk_allocation,
tcp_rtx_and_write_queues_empty(sk));
if (!skb)
return NULL;
#ifdef CONFIG_TLS_DEVICE
skb->decrypted = !!(flags & MSG_SENDPAGE_DECRYPTED);
#endif
tcp_skb_entail(sk, skb);
copy = size_goal;
}
if (copy > *size)
copy = *size;
i = skb_shinfo(skb)->nr_frags;
can_coalesce = skb_can_coalesce(skb, i, page, offset);
if (!can_coalesce && i >= READ_ONCE(sysctl_max_skb_frags)) {
tcp_mark_push(tp, skb);
goto new_segment;
}
if (tcp_downgrade_zcopy_pure(sk, skb))
return NULL;
copy = tcp_wmem_schedule(sk, copy);
if (!copy)
return NULL;
if (can_coalesce) {
skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
} else {
get_page(page);
skb_fill_page_desc_noacc(skb, i, page, offset, copy);
}
if (!(flags & MSG_NO_SHARED_FRAGS))
skb_shinfo(skb)->flags |= SKBFL_SHARED_FRAG;
skb->len += copy;
skb->data_len += copy;
skb->truesize += copy;
sk_wmem_queued_add(sk, copy);
sk_mem_charge(sk, copy);
WRITE_ONCE(tp->write_seq, tp->write_seq + copy);
TCP_SKB_CB(skb)->end_seq += copy;
tcp_skb_pcount_set(skb, 0);
*size = copy;
return skb;
}
ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
size_t size, int flags)
{
struct tcp_sock *tp = tcp_sk(sk);
int mss_now, size_goal;
int err;
ssize_t copied;
long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
struct bio_vec bvec;
struct msghdr msg = { .msg_flags = flags | MSG_SPLICE_PAGES, };
if (IS_ENABLED(CONFIG_DEBUG_VM) &&
WARN_ONCE(!sendpage_ok(page),
"page must not be a Slab one and have page_count > 0"))
return -EINVAL;
bvec_set_page(&bvec, page, size, offset);
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
/* Wait for a connection to finish. One exception is TCP Fast Open
* (passive side) where data is allowed to be sent before a connection
* is fully established.
*/
if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
!tcp_passive_fastopen(sk)) {
err = sk_stream_wait_connect(sk, &timeo);
if (err != 0)
goto out_err;
}
if (flags & MSG_SENDPAGE_NOTLAST)
msg.msg_flags |= MSG_MORE;
sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
mss_now = tcp_send_mss(sk, &size_goal, flags);
copied = 0;
err = -EPIPE;
if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
goto out_err;
while (size > 0) {
struct sk_buff *skb;
size_t copy = size;
skb = tcp_build_frag(sk, size_goal, flags, page, offset, &copy);
if (!skb)
goto wait_for_space;
if (!copied)
TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_PSH;
copied += copy;
offset += copy;
size -= copy;
if (!size)
goto out;
if (skb->len < size_goal || (flags & MSG_OOB))
continue;
if (forced_push(tp)) {
tcp_mark_push(tp, skb);
__tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_PUSH);
} else if (skb == tcp_send_head(sk))
tcp_push_one(sk, mss_now);
continue;
wait_for_space:
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
tcp_push(sk, flags & ~MSG_MORE, mss_now,
TCP_NAGLE_PUSH, size_goal);
err = sk_stream_wait_memory(sk, &timeo);
if (err != 0)
goto do_error;
mss_now = tcp_send_mss(sk, &size_goal, flags);
}
out:
if (copied) {
tcp_tx_timestamp(sk, sk->sk_tsflags);
if (!(flags & MSG_SENDPAGE_NOTLAST))
tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
}
return copied;
do_error:
tcp_remove_empty_skb(sk);
if (copied)
goto out;
out_err:
/* make sure we wake any epoll edge trigger waiter */
if (unlikely(tcp_rtx_and_write_queues_empty(sk) && err == -EAGAIN)) {
sk->sk_write_space(sk);
tcp_chrono_stop(sk, TCP_CHRONO_SNDBUF_LIMITED);
}
return sk_stream_error(sk, flags, err);
return tcp_sendmsg_locked(sk, &msg, size);
}
EXPORT_SYMBOL_GPL(do_tcp_sendpages);