[PATCH] nvme: avoid missing db ring during reset

Linjun Bao
2025-04-25T12:01:52Z

During nvme reset, there is a rare case, when user admin cmd such
as smart-log and nvme_admin_create_sq from nvme_setup_io_queues
happen to in the same blk_mq dispatch list, and the user cmd is
the last one. nvme_admin_create_sq is dispatched first in
nvme_queue_rq(), nvme_write_sq_db() is called but immediately
returns without writing the doorbell because it's not masked
"last". The subsequent smart-log ioctl fails fast hitting
nvme_fail_nonready_cmd(), skipping both nvme_sq_copy_cmd() and
nvme_write_sq_db(), so no doorbell write ever occurs. The
nvme_admin_create_sq fails timeout finally.

The proposal is that do not treat user admin cmd during
RECONNECTING as non-ready, through it to the drive, thus no
doorbell missing happens in case above.

Signed-off-by: Linjun Bao <meljbao@gmail.com>
---
drivers/nvme/host/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 3cc79817e4d7..fc550226ed77 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -750,7 +750,8 @@ bool __nvme_check_ready(struct nvme_ctrl *ctrl, struct request *rq,
* sequence. until the controller will be LIVE, fail with
* BLK_STS_RESOURCE so that they will be rescheduled.
*/
- if (rq->q == ctrl->admin_q && (req->flags & NVME_REQ_USERCMD))
+ if (rq->q == ctrl->admin_q && (req->flags & NVME_REQ_USERCMD) &&
+ (nvme_ctrl_state(ctrl) != NVME_CTRL_CONNECTING))
return false;

if (ctrl->ops->flags & NVME_F_FABRICS) {
--
2.25.1