David Howells wrote:
> When transmitting data, call down into TCP using a single sendmsg with
> MSG_SPLICE_PAGES to indicate that content should be spliced rather than
> performing several sendmsg and sendpage calls to transmit header, data
> pages and trailer.
>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: Keith Busch <kbusch@xxxxxxxxxx>
> cc: Jens Axboe <axboe@xxxxxx>
> cc: Christoph Hellwig <hch@xxxxxx>
> cc: Sagi Grimberg <sagi@xxxxxxxxxxx>
> cc: Chaitanya Kulkarni <kch@xxxxxxxxxx>
> cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> cc: Jens Axboe <axboe@xxxxxxxxx>
> cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> cc: linux-nvme@xxxxxxxxxxxxxxxxxxx
> cc: netdev@xxxxxxxxxxxxxxx
> ---
>
> Notes:
> ver #2)
> - Wrap lines at 80.
>
> drivers/nvme/host/tcp.c | 46 ++++++++++++++++++++-------------------
> drivers/nvme/target/tcp.c | 46 ++++++++++++++++++++++++---------------
> 2 files changed, 53 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index bf0230442d57..6f31cdbb696a 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -997,25 +997,25 @@ static int nvme_tcp_try_send_data(struct nvme_tcp_request *req)
> u32 h2cdata_left = req->h2cdata_left;
>
> while (true) {
> + struct bio_vec bvec;
> + struct msghdr msg = {
> + .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES,
> + };
> struct page *page = nvme_tcp_req_cur_page(req);
> size_t offset = nvme_tcp_req_cur_offset(req);
> size_t len = nvme_tcp_req_cur_length(req);
> bool last = nvme_tcp_pdu_last_send(req, len);
> int req_data_sent = req->data_sent;
> - int ret, flags = MSG_DONTWAIT;
> + int ret;
>
> if (last && !queue->data_digest && !nvme_tcp_queue_more(queue))
> - flags |= MSG_EOR;
> + msg.msg_flags |= MSG_EOR;
> else
> - flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
> + msg.msg_flags |= MSG_MORE;
>
> - if (sendpage_ok(page)) {
> - ret = kernel_sendpage(queue->sock, page, offset, len,
> - flags);
> - } else {
> - ret = sock_no_sendpage(queue->sock, page, offset, len,
> - flags);
> - }
> + bvec_set_page(&bvec, page, len, offset);
> + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, len);
> + ret = sock_sendmsg(queue->sock, &msg);
> if (ret <= 0)
> return ret;
>
> @@ -1054,22 +1054,24 @@ static int nvme_tcp_try_send_cmd_pdu(struct nvme_tcp_request *req)
> {
> struct nvme_tcp_queue *queue = req->queue;
> struct nvme_tcp_cmd_pdu *pdu = nvme_tcp_req_cmd_pdu(req);
> + struct bio_vec bvec;
> + struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES, };
> bool inline_data = nvme_tcp_has_inline_data(req);
> u8 hdgst = nvme_tcp_hdgst_len(queue);
> int len = sizeof(*pdu) + hdgst - req->offset;
> - int flags = MSG_DONTWAIT;
> int ret;
>
> if (inline_data || nvme_tcp_queue_more(queue))
> - flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
> + msg.msg_flags |= MSG_MORE;
> else
> - flags |= MSG_EOR;
> + msg.msg_flags |= MSG_EOR;
>
> if (queue->hdr_digest && !req->offset)
> nvme_tcp_hdgst(queue->snd_hash, pdu, sizeof(*pdu));
>
> - ret = kernel_sendpage(queue->sock, virt_to_page(pdu),
> - offset_in_page(pdu) + req->offset, len, flags);
> + bvec_set_virt(&bvec, (void *)pdu + req->offset, len);
> + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, len);
> + ret = sock_sendmsg(queue->sock, &msg);
> if (unlikely(ret <= 0))
> return ret;
>
struct bio_vec bvec;
struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES | ... };
..
bvec_set_virt
iov_iter_bvec
sock_sendmsg
is a frequent pattern. Does it make sense to define a wrapper? Same for bvec_set_page.
