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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Keith Busch <kbusch@kernel.org>, Sasha Levin <sashal@kernel.org>,
	Mark Wunderlich <mark.wunderlich@intel.com>,
	Sagi Grimberg <sagi@grimberg.me>,
	linux-nvme@lists.infradead.org
Subject: [PATCH AUTOSEL 5.5 21/28] nvmet-tcp: set MSG_MORE only if we actually have more to send
Date: Thu, 26 Mar 2020 19:23:50 -0400
Message-ID: <20200326232357.7516-21-sashal@kernel.org> (raw)
In-Reply-To: <20200326232357.7516-1-sashal@kernel.org>

From: Sagi Grimberg <sagi@grimberg.me>

[ Upstream commit 98fd5c723730f560e5bea919a64ac5b83d45eb72 ]

When we send PDU data, we want to optimize the tcp stack
operation if we have more data to send. So when we set MSG_MORE
when:
- We have more fragments coming in the batch, or
- We have a more data to send in this PDU
- We don't have a data digest trailer
- We optimize with the SUCCESS flag and omit the NVMe completion
  (used if sq_head pointer update is disabled)

This addresses a regression in QD=1 with SUCCESS flag optimization
as we unconditionally set MSG_MORE when we didn't actually have
more data to send.

Fixes: 70583295388a ("nvmet-tcp: implement C2HData SUCCESS optimization")
Reported-by: Mark Wunderlich <mark.wunderlich@intel.com>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/nvme/target/tcp.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index af674fc0bb1e4..5bb5342b8d0c7 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -515,7 +515,7 @@ static int nvmet_try_send_data_pdu(struct nvmet_tcp_cmd *cmd)
 	return 1;
 }
 
-static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd)
+static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd, bool last_in_batch)
 {
 	struct nvmet_tcp_queue *queue = cmd->queue;
 	int ret;
@@ -523,9 +523,15 @@ static int nvmet_try_send_data(struct nvmet_tcp_cmd *cmd)
 	while (cmd->cur_sg) {
 		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;
 
 		ret = kernel_sendpage(cmd->queue->sock, page, cmd->offset,
-					left, MSG_DONTWAIT | MSG_MORE);
+					left, flags);
 		if (ret <= 0)
 			return ret;
 
@@ -660,7 +666,7 @@ static int nvmet_tcp_try_send_one(struct nvmet_tcp_queue *queue,
 	}
 
 	if (cmd->state == NVMET_TCP_SEND_DATA) {
-		ret = nvmet_try_send_data(cmd);
+		ret = nvmet_try_send_data(cmd, last_in_batch);
 		if (ret <= 0)
 			goto done_send;
 	}
-- 
2.20.1


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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200326232357.7516-1-sashal@kernel.org>
2020-03-26 23:23 ` [PATCH AUTOSEL 5.5 03/28] nvme-rdma: Avoid double freeing of async event data Sasha Levin
2020-03-26 23:23 ` Sasha Levin [this message]

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