[PATCH 1/2] nvme-core: add ctrl state transition debug helper

[Nitesh Shetty]

On 11/02/24 08:26PM, Chaitanya Kulkarni wrote:
>NVMe controller state machine has total 7 states and 13 state transition
>arcs. Debugging NVMeOF problems in the field is not straight-froward,
>since it involves complex combination of connect/reconnect/kato/timeout
>handlers etc scenarios.
>We already have a helper in sysfs.c that reads the controller state, but
>one has to constantly read the state in order understand the complete
>state transition which is very inconvenient.
>
>It is often helpful to know full state transition of controller when
>dealing with NVMeOF issues at the time of analyzing the trace.
>
>Add a helper that allows us to decode and print each controller state
>transition :-
>
>blktests (master) # dmesg -c | grep nvme_change_ctrl_state
>blktests (master) # nvme_trtype=tcp ./check nvme/048
>nvme/048 (Test queue count changes on reconnect)             [passed]
>    runtime  6.264s  ...  5.240s
>blktests (master) # dmesg -c | grep nvme_change_ctrl_state
>[17080.988689] nvme nvme0: nvme_change_ctrl_state new -> connecting
>[17081.006623] nvme nvme0: nvme_change_ctrl_state connecting -> live
>[17081.038313] nvme nvme0: nvme_change_ctrl_state live -> resetting
>[17081.040730] nvme nvme0: nvme_change_ctrl_state resetting -> connecting
>[17083.056750] nvme nvme0: nvme_change_ctrl_state connecting -> live
>[17083.075906] nvme nvme0: nvme_change_ctrl_state live -> resetting
>[17083.076112] nvme nvme0: nvme_change_ctrl_state resetting -> connecting
>[17085.105270] nvme nvme0: nvme_change_ctrl_state connecting -> live
>[17086.126484] nvme nvme0: nvme_change_ctrl_state live -> deleting
>[17086.126506] nvme nvme0: nvme_change_ctrl_state deleting -> deleting (no IO)
>blktests (master) #
>
>Signed-off-by: Chaitanya Kulkarni <kch at nvidia.com>
>---
>
> drivers/nvme/host/core.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
>diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>index 20c0c141fcc0..daeb2409f989 100644
>--- a/drivers/nvme/host/core.c
>+++ b/drivers/nvme/host/core.c
>@@ -544,6 +544,21 @@ void nvme_cancel_admin_tagset(struct nvme_ctrl *ctrl)
> }
> EXPORT_SYMBOL_GPL(nvme_cancel_admin_tagset);
>
>+static const char *nvme_ctrl_state_str(enum nvme_ctrl_state st)
>+{
>+	static const char *const str[] = {
>+		[NVME_CTRL_NEW]			= "new",
>+		[NVME_CTRL_LIVE]		= "live",
>+		[NVME_CTRL_RESETTING]		= "resetting",
>+		[NVME_CTRL_CONNECTING]		= "connecting",
>+		[NVME_CTRL_DELETING]		= "deleting",
>+		[NVME_CTRL_DELETING_NOIO]	= "deleting (no IO)",
>+		[NVME_CTRL_DEAD]		= "dead",
>+	};
>+
>+	return st < ARRAY_SIZE(str) && str[st] ? str[st] : "unknown state";
>+}
>+
> bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
> 		enum nvme_ctrl_state new_state)
> {
>@@ -621,6 +636,9 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
> 	}
>
> 	if (changed) {
>+		dev_dbg(ctrl->device, "%s %s -> %s\n", __func__,
>+			nvme_ctrl_state_str(old_state),
>+			nvme_ctrl_state_str(new_state));
> 		WRITE_ONCE(ctrl->state, new_state);
> 		wake_up_all(&ctrl->state_wq);
> 	}
>-- 
>2.40.0
>
>

Revieved-by: Nitesh Shetty <nj.shetty at samsung.com>