[PATCH net-next v5 07/16] nvme-tcp: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage

From: David Howells
Date: Fri Jun 23 2023 - 18:57:06 EST


When transmitting data, call down into TCP using a sendmsg with
MSG_SPLICE_PAGES instead of sendpage.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Tested-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Acked-by: Willem de Bruijn <willemb@xxxxxxxxxx>
cc: Keith Busch <kbusch@xxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxx>
cc: Christoph Hellwig <hch@xxxxxx>
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 #4)
- Cancel MSG_SPLICE_PAGES if the page being sent fails sendpage_ok().

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

ver #2)
- Wrap lines at 80.

drivers/nvme/host/tcp.c | 49 +++++++++++++++++++++++------------------
1 file changed, 27 insertions(+), 22 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index bf0230442d57..47ae17f16c05 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -997,25 +997,28 @@ 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);
- }
+ if (!sendpage_ok(page))
+ msg.msg_flags &= ~MSG_SPLICE_PAGES,
+
+ 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 +1057,24 @@ 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;

@@ -1093,6 +1098,8 @@ 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 = nvme_tcp_req_data_pdu(req);
+ 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;
@@ -1101,13 +1108,11 @@ 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;
+
+ 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;