nvme: don't unquiesce the admin queue in nvme_kill_queues

None of the callers of nvme_kill_queues needs it to unquiesce the
admin queues, as all of them already do it themselves:

 1) nvme_reset_work explicit call nvme_start_admin_queue toward the
    beginning of the function.  The extra call to nvme_start_admin_queue
    in nvme_reset_work this won't do anything as
    NVME_CTRL_ADMIN_Q_STOPPED will already be cleared.
 2) nvme_remove calls nvme_dev_disable with shutdown flag set to true at
    the very beginning of the function if the PCIe device was not present,
    which is the precondition for the call to nvme_kill_queues.
    nvme_dev_disable already calls nvme_start_admin_queue toward the
    end of the function when the shutdown flag is set to true, so the
    admin queue is already enabled at this point.
 3) nvme_remove_dead_ctrl schedules a workqueue to unbind the driver,
    which will end up in nvme_remove, which calls nvme_dev_disable with
    the shutdown flag.  This case will call nvme_start_admin_queue a bit
    later than before.
 4) apple_nvme_remove uses the same sequence as nvme_remove_dead_ctrl
    above.
 5) nvme_remove_namespaces only calls nvme_kill_queues when the
    controller is in the DEAD state.  That can only happen in the PCIe
    driver, and only from nvme_remove. See item 2) above for the
    conditions there.

So it is safe to just remove the call to nvme_start_admin_queue in
nvme_kill_queues without replacement.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20221101150050.3510-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/core.c

@@ -5135,10 +5135,6 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
 
 	down_read(&ctrl->namespaces_rwsem);
 
-	/* Forcibly unquiesce queues to avoid blocking dispatch */
-	if (ctrl->admin_q && !blk_queue_dying(ctrl->admin_q))
-		nvme_start_admin_queue(ctrl);
-
 	list_for_each_entry(ns, &ctrl->namespaces, list)
 		nvme_set_queue_dying(ns);