linux-kernel - Re: [PATCH 2/2] scsi: register sysfs for scsi/iscsi workqueues

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Date:   Mon, 22 Jun 2020 10:40:09 -0500
From:   Mike Christie <michael.christie@...cle.com>
To:     Bob Liu <bob.liu@...cle.com>, linux-kernel@...r.kernel.org
Cc:     tj@...nel.org, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, open-iscsi@...glegroups.com,
        lduncan@...e.com, lduncan@...e.com, maier@...ux.ibm.com,
        bblock@...ux.ibm.com
Subject: Re: [PATCH 2/2] scsi: register sysfs for scsi/iscsi workqueues

On 6/11/20 5:07 AM, Bob Liu wrote:
> This patch enable setting cpu affinity through "cpumask" for below
> scsi/iscsi workqueues, so as to get better isolation.
> - scsi_wq_*
> - scsi_tmf_*
> - iscsi_q_xx
> - iscsi_eh
> 
> Signed-off-by: Bob Liu <bob.liu@...cle.com>
> ---
>   drivers/scsi/hosts.c                | 4 ++--
>   drivers/scsi/libiscsi.c             | 2 +-
>   drivers/scsi/scsi_transport_iscsi.c | 2 +-
>   3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index 1d669e4..4b9f80d 100644
> --- a/drivers/scsi/hosts.c
> +++ b/drivers/scsi/hosts.c
> @@ -272,7 +272,7 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
>   	if (shost->transportt->create_work_queue) {
>   		snprintf(shost->work_q_name, sizeof(shost->work_q_name),
>   			 "scsi_wq_%d", shost->host_no);
> -		shost->work_q = create_singlethread_workqueue(
> +		shost->work_q = create_singlethread_workqueue_noorder(
>   					shost->work_q_name);
>   		if (!shost->work_q) {
>   			error = -EINVAL;

This patch seems ok for the iscsi, fc, tmf, and non transport class scan 
uses. We are either heavy handed with flushes or did not need ordering.

I don't know about the zfcp use though, so I cc'd  the developers listed 
as maintainers. It looks like for zfcp we can do:

zfcp_scsi_rport_register->fc_remote_port_add->fc_remote_port_create->scsi_queue_work 
to scan the scsi target on the rport.

and then zfcp_scsi_rport_register can call zfcp_unit_queue_scsi_scan->
scsi_queue_work which will scan for a specific lun.

It looks ok if those are not ordered, but I would get their review to 
make sure.