linux-kernel - [PATCH v4 2/3] nvme: handle connectivity loss in nvme_set_queue

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Message-Id: <20250109-nvme-fc-handle-com-lost-v4-2-fe5cae17b492@kernel.org>
Date: Thu, 09 Jan 2025 14:30:48 +0100
From: Daniel Wagner <wagi@...nel.org>
To: James Smart <james.smart@...adcom.com>, Keith Busch <kbusch@...nel.org>, 
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
 Hannes Reinecke <hare@...e.de>, Paul Ely <paul.ely@...adcom.com>
Cc: linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Daniel Wagner <wagi@...nel.org>
Subject: [PATCH v4 2/3] nvme: handle connectivity loss in
 nvme_set_queue_count

When the set feature attempts fails with any NVME status code set in
nvme_set_queue_count, the function still report success. Though the
numbers of queues set to 0. This is done to support controllers in
degraded state (the admin queue is still up and running but no IO
queues).

Though there is an exception. When nvme_set_features reports an host
path error, nvme_set_queue_count should propagate this error as the
connectivity is lost, which means also the admin queue is not working
anymore.

Fixes: 9a0be7abb62f ("nvme: refactor set_queue_count")
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Hannes Reinecke <hare@...e.de>
Reviewed-by: Sagi Grimberg <sagi@...mberg.me>
Signed-off-by: Daniel Wagner <wagi@...nel.org>
---
 drivers/nvme/host/core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index b72b0e06801490f2c14e7fa09a45a870045a221d..a08ff8b362d0b7bd1a8a343e26d564b089c6bad3 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1695,7 +1695,13 @@ int nvme_set_queue_count(struct nvme_ctrl *ctrl, int *count)
 
 	status = nvme_set_features(ctrl, NVME_FEAT_NUM_QUEUES, q_count, NULL, 0,
 			&result);
-	if (status < 0)
+
+	/*
+	 * It's either a kernel error or the host observed a connection
+	 * lost. In either case it's not possible communicate with the
+	 * controller and thus enter the error code path.
+	 */
+	if (status < 0 || status == NVME_SC_HOST_PATH_ERROR)
 		return status;
 
 	/*

-- 
2.47.1