[PATCH v2] nvmet: force reconnect when number of queue changes

[Daniel Wagner <dwagner@suse.de>]

In order to be able to test queue number changes we need to make sure
that the host reconnects.

The initial idea was to disable and re-enable the ports and have the
host to wait until the KATO timer expires and enter error
recovery. But in this scenario the host could see DNR for a connection
attempt which results in the host dropping the connection completely.

We can force to reconnect the host by deleting all controllers
connected to subsystem, which results the host observing a failing
command and tries to reconnect.

Also, the item passed into nvmet_subsys_attr_qid_max_show is not a
member of struct nvmet_port, it is part of nvmet_subsys. Hence,
don't try to dereference it as struct nvme_ctrl pointer.

Fixes: 2c4282742d04 ("nvmet: Expose max queues to configfs")
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://lore.kernel.org/r/20220913064203.133536-1-dwagner@suse.de
Signed-off-by: Daniel Wagner <dwagner@suse.de>
---
v2:
  - instead preventing changes, force reconnect by delete ctrls
  - renamed patch

v1:
  - initial verison
  - https://lore.kernel.org/linux-nvme/20220913064203.133536-1-dwagner@suse.de/

 drivers/nvme/target/configfs.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index e34a2896fedb..051a420d818e 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -1290,12 +1290,10 @@ static ssize_t nvmet_subsys_attr_qid_max_show(struct config_item *item,
 static ssize_t nvmet_subsys_attr_qid_max_store(struct config_item *item,
 					       const char *page, size_t cnt)
 {
-	struct nvmet_port *port = to_nvmet_port(item);
+	struct nvmet_subsys *subsys = to_subsys(item);
+	struct nvmet_ctrl *ctrl;
 	u16 qid_max;
 
-	if (nvmet_is_port_enabled(port, __func__))
-		return -EACCES;
-
 	if (sscanf(page, "%hu\n", &qid_max) != 1)
 		return -EINVAL;
 
@@ -1303,8 +1301,13 @@ static ssize_t nvmet_subsys_attr_qid_max_store(struct config_item *item,
 		return -EINVAL;
 
 	down_write(&nvmet_config_sem);
-	to_subsys(item)->max_qid = qid_max;
+	subsys->max_qid = qid_max;
+
+	/* Force reconnect */
+	list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry)
+		ctrl->ops->delete_ctrl(ctrl);
 	up_write(&nvmet_config_sem);
+
 	return cnt;
 }
 CONFIGFS_ATTR(nvmet_subsys_, attr_qid_max);
-- 
2.37.3