[RFC PATCH v2 42/48] nvme: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage

David Howells
2023-03-29T14:22:58Z

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>
cc: Keith Busch <kbusch@kernel.org>
cc: Jens Axboe <axboe@fb.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Sagi Grimberg <sagi@grimberg.me>
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
---
drivers/nvme/host/tcp.c | 44 ++++++++++++++++++------------------
drivers/nvme/target/tcp.c | 47 +++++++++++++++++++++++++--------------
2 files changed, 52 insertions(+), 39 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index fa32969b532f..cc617692702d 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -979,25 +979,23 @@ 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 | MSG_SENDPAGE_NOTLAST;

- 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;

@@ -1036,22 +1034,24 @@ 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 = req->pdu;
+ 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 | MSG_SENDPAGE_NOTLAST;
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;

@@ -1075,6 +1075,8 @@ static int nvme_tcp_try_send_data_pdu(struct nvme_tcp_request *req)
{
struct nvme_tcp_queue *queue = req->queue;
struct nvme_tcp_data_pdu *pdu = req->pdu;
+ struct bio_vec bvec;
+ struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_MORE, };
u8 hdgst = nvme_tcp_hdgst_len(queue);
int len = sizeof(*pdu) - req->offset + hdgst;
int ret;
@@ -1083,13 +1085,11 @@ static int nvme_tcp_try_send_data_pdu(struct nvme_tcp_request *req)
nvme_tcp_hdgst(queue->snd_hash, pdu, sizeof(*pdu));

if (!req->h2cdata_left)
- ret = kernel_sendpage(queue->sock, virt_to_page(pdu),
- offset_in_page(pdu) + req->offset, len,
- MSG_DONTWAIT | MSG_MORE | MSG_SENDPAGE_NOTLAST);
- else
- ret = sock_no_sendpage(queue->sock, virt_to_page(pdu),
- offset_in_page(pdu) + req->offset, len,
- MSG_DONTWAIT | MSG_MORE);
+ msg.msg_flags |= MSG_SPLICE_PAGES | MSG_SENDPAGE_NOTLAST;
+
+ 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;

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index d6cc557cc539..00b491abf50f 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -548,13 +548,18 @@ static void nvmet_tcp_execute_request(struct nvmet_tcp_cmd *cmd)

static int nvmet_try_send_data_pdu(struct nvmet_tcp_cmd *cmd)
{
+ struct bio_vec bvec;
+ struct msghdr msg = {
+ .msg_flags = (MSG_DONTWAIT | MSG_MORE | MSG_SENDPAGE_NOTLAST |
+ MSG_SPLICE_PAGES),
+ };
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;

@@ -575,17 +580,21 @@ static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
int ret;

while (cmd->cur_sg) {
+ struct bio_vec bvec;
+ struct msghdr msg = {
+ .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES,
+ };
struct page *page = sg_page(cmd->cur_sg);
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 | MSG_SENDPAGE_NOTLAST;

- 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;

@@ -621,18 +630,20 @@ 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 bio_vec bvec;
+ struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES, };
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 | MSG_SENDPAGE_NOTLAST;
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;
@@ -649,18 +660,20 @@ 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 bio_vec bvec;
+ struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_SPLICE_PAGES, };
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 | MSG_SENDPAGE_NOTLAST;
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;