Re: [RFC PATCH 10/14] SCSI: use the dedicated admin queue to send admin commands

[Bart Van Assche <Bart.VanAssche@wdc.com>]

On Wed, 2018-08-08 at 01:44 +0800, Ming Lei wrote:
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -278,16 +278,16 @@ int __scsi_execute(struc=
t scsi_device *sdev, const unsigned char *cmd,
>  	struct request *req;
>  	struct scsi_request *rq;
>  	int ret = DRIVER_ERROR << 24;
> +	struct request_queue *q = sdev->host->admin=
8-q;
> =20
> -	req = blk_get_request(sdev->request_queue,
> +	req = blk_get_request(q,
>  			data_direction == DMA_TO_DEVICE ?
>  			REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, BLK_=
-MQ_REQ_PREEMPT);

The above looks weird to me. Why are all RQF_PREEMPT requests sent to t=
he admin
queue instead of only RQF_PM requests?

> @@ -299,6 +299,8 @@ int __scsi_execute(struct =
scsi_device *sdev, const unsigned char *cmd,
>  	req->cmd_flags |= flags;
>  	req->rq_flags |= rq_flags | RQF_QUIET;=
-
> =20
> +	atomic_inc(&sdev->nr_admin_pending);

Why has a new counter been introduced to keep track of admin requests inste=
ad of
using q_usage_counter?

Thanks,

Bart.