linux-kernel - [PATCH 5.12 019/127] nvme-tcp: rerun io_work if req

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Date:   Mon, 24 May 2021 17:25:36 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Keith Busch <kbusch@...nel.org>,
        Sagi Grimberg <sagi@...mberg.me>,
        Christoph Hellwig <hch@....de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 019/127] nvme-tcp: rerun io_work if req_list is not empty

From: Keith Busch <kbusch@...nel.org>

[ Upstream commit a0fdd1418007f83565d3f2e04b47923ba93a9b8c ]

A possible race condition exists where the request to send data is
enqueued from nvme_tcp_handle_r2t()'s will not be observed by
nvme_tcp_send_all() if it happens to be running. The driver relies on
io_work to send the enqueued request when it is runs again, but the
concurrently running nvme_tcp_send_all() may not have released the
send_mutex at that time. If no future commands are enqueued to re-kick
the io_work, the request will timeout in the SEND_H2C state, resulting
in a timeout error like:

  nvme nvme0: queue 1: timeout request 0x3 type 6

Ensure the io_work continues to run as long as the req_list is not empty.

Fixes: db5ad6b7f8cdd ("nvme-tcp: try to send request in queue_rq context")
Signed-off-by: Keith Busch <kbusch@...nel.org>
Reviewed-by: Sagi Grimberg <sagi@...mberg.me>
Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/nvme/host/tcp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index d7d7c81d0701..f8ef1faaf5e4 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1137,7 +1137,8 @@ static void nvme_tcp_io_work(struct work_struct *w)
 				pending = true;
 			else if (unlikely(result < 0))
 				break;
-		}
+		} else
+			pending = !llist_empty(&queue->req_list);
 
 		result = nvme_tcp_try_recv(queue);
 		if (result > 0)
-- 
2.30.2