[PATCH net-next v3 11/18] nvme/target: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage

David Howells
2023-06-20T14:56:53Z

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@redhat.com>
Tested-by: Sagi Grimberg <sagi@grimberg.me>
Acked-by: Willem de Bruijn <willemb@google.com>
cc: Keith Busch <kbusch@kernel.org>
cc: Jens Axboe <axboe@fb.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Chaitanya Kulkarni <kch@nvidia.com>
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: linux-nvme@lists.infradead.org
cc: netdev@vger.kernel.org
---

Notes:
ver #3)
- Split nvme/host from nvme/target changes.

ver #2)
- Wrap lines at 80.

drivers/nvme/target/tcp.c | 46 ++++++++++++++++++++++++---------------
1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index ed98df72c76b..868aa4de2e4c 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -576,13 +576,17 @@ static void nvmet_tcp_execute_request(struct nvmet_tcp_cmd *cmd)

static int nvmet_try_send_data_pdu(struct nvmet_tcp_cmd *cmd)
{
+ struct msghdr msg = {
+ .msg_flags = MSG_DONTWAIT | MSG_MORE | MSG_SPLICE_PAGES,
+ };
+ struct bio_vec bvec;
u8 hdgst = nvmet_tcp_hdgst_len(cmd->queue);
int left = sizeof(*cmd->data_pdu) - cmd->offset + hdgst;
int ret;

- ret = kernel_sendpage(cmd->queue->sock, virt_to_page(cmd->data_pdu),
- offset_in_page(cmd->data_pdu) + cmd->offset,
- left, MSG_DONTWAIT | MSG_MORE | MSG_SENDPAGE_NOTLAST);
+ bvec_set_virt(&bvec, (void *)cmd->data_pdu + cmd->offset, left);
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, left);
+ ret = sock_sendmsg(cmd->queue->sock, &msg);
if (ret <= 0)
return ret;

@@ -603,17 +607,21 @@ static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
int ret;

while (cmd->cur_sg) {
+ struct msghdr msg = {
+ .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES,
+ };
struct page *page = sg_page(cmd->cur_sg);
+ struct bio_vec bvec;
u32 left = cmd->cur_sg->length - cmd->offset;
- int flags = MSG_DONTWAIT;

if ((!last_in_batch && cmd->queue->send_list_len) ||
cmd->wbytes_done + left < cmd->req.transfer_len ||
queue->data_digest || !queue->nvme_sq.sqhd_disabled)
- flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
+ msg.msg_flags |= MSG_MORE;

- ret = kernel_sendpage(cmd->queue->sock, page, cmd->offset,
- left, flags);
+ bvec_set_page(&bvec, page, left, cmd->offset);
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, left);
+ ret = sock_sendmsg(cmd->queue->sock, &msg);
if (ret <= 0)
return ret;

@@ -649,18 +657,20 @@ static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
static int nvmet_try_send_response(struct nvmet_tcp_cmd *cmd,
bool last_in_batch)
{
+ struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES, };
+ struct bio_vec bvec;
u8 hdgst = nvmet_tcp_hdgst_len(cmd->queue);
int left = sizeof(*cmd->rsp_pdu) - cmd->offset + hdgst;
- int flags = MSG_DONTWAIT;
int ret;

if (!last_in_batch && cmd->queue->send_list_len)
- flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
+ msg.msg_flags |= MSG_MORE;
else
- flags |= MSG_EOR;
+ msg.msg_flags |= MSG_EOR;

- ret = kernel_sendpage(cmd->queue->sock, virt_to_page(cmd->rsp_pdu),
- offset_in_page(cmd->rsp_pdu) + cmd->offset, left, flags);
+ bvec_set_virt(&bvec, (void *)cmd->rsp_pdu + cmd->offset, left);
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, left);
+ ret = sock_sendmsg(cmd->queue->sock, &msg);
if (ret <= 0)
return ret;
cmd->offset += ret;
@@ -677,18 +687,20 @@ static int nvmet_try_send_response(struct nvmet_tcp_cmd *cmd,

static int nvmet_try_send_r2t(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
{
+ struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES, };
+ struct bio_vec bvec;
u8 hdgst = nvmet_tcp_hdgst_len(cmd->queue);
int left = sizeof(*cmd->r2t_pdu) - cmd->offset + hdgst;
- int flags = MSG_DONTWAIT;
int ret;

if (!last_in_batch && cmd->queue->send_list_len)
- flags |= MSG_MORE | MSG_SENDPAGE_NOTLAST;
+ msg.msg_flags |= MSG_MORE;
else
- flags |= MSG_EOR;
+ msg.msg_flags |= MSG_EOR;

- ret = kernel_sendpage(cmd->queue->sock, virt_to_page(cmd->r2t_pdu),
- offset_in_page(cmd->r2t_pdu) + cmd->offset, left, flags);
+ bvec_set_virt(&bvec, (void *)cmd->r2t_pdu + cmd->offset, left);
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, left);
+ ret = sock_sendmsg(cmd->queue->sock, &msg);
if (ret <= 0)
return ret;
cmd->offset += ret;