Re: [PATCH 4/6] scsi: iscsi, ql4: Use per session workqueue for unbinding.

[Lee Duncan <lduncan@suse.com>]

On 2/26/22 15:04, Mike Christie wrote:
> We currently allocate a workqueue per host and only use it for removing
> the target. For the session per host case we could be using this workqueue
> to be able to do recoveries (block, unblock, timeout handling) in
> parallel. To also allow offload drivers to do their session recoveries in
> parallel, this drops the per host workqueue and replaces it with a per
> session one.
> 
> Signed-off-by: Mike Christie <michael.christie@oracle.com>
> ---
>   drivers/scsi/qla4xxx/ql4_os.c       |  2 +-
>   drivers/scsi/scsi_transport_iscsi.c | 19 ++++++++++++++-----
>   include/scsi/scsi_transport_iscsi.h |  2 ++
>   3 files changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/scsi/qla4xxx/ql4_os.c b/drivers/scsi/qla4xxx/ql4_os.c
> index 0ae936d839f1..955d8cb675f1 100644
> --- a/drivers/scsi/qla4xxx/ql4_os.c
> +++ b/drivers/scsi/qla4xxx/ql4_os.c
> @@ -5096,7 +5096,7 @@ int qla4xxx_unblock_flash_ddb(struct iscsi_cls_session *cls_session)
>   		ql4_printk(KERN_INFO, ha, "scsi%ld: %s: ddb[%d]"
>   			   " start scan\n", ha->host_no, __func__,
>   			   ddb_entry->fw_ddb_index);
> -		scsi_queue_work(ha->host, &ddb_entry->sess->scan_work);
> +		queue_work(ddb_entry->sess->workq, &ddb_entry->sess->scan_work);
>   	}
>   	return QLA_SUCCESS;
>   }
> diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
> index 05cd4bca979e..ecb592a70e03 100644
> --- a/drivers/scsi/scsi_transport_iscsi.c
> +++ b/drivers/scsi/scsi_transport_iscsi.c
> @@ -2032,19 +2032,27 @@ EXPORT_SYMBOL_GPL(iscsi_alloc_session);
>   
>   int iscsi_add_session(struct iscsi_cls_session *session, unsigned int target_id)
>   {
> +	struct Scsi_Host *shost = iscsi_session_to_shost(session);
>   	unsigned long flags;
>   	int id = 0;
>   	int err;
>   
>   	session->sid = atomic_add_return(1, &iscsi_session_nr);
>   
> +	session->workq = alloc_workqueue("iscsi_ctrl_%d:%d",
> +			WQ_SYSFS | WQ_MEM_RECLAIM | WQ_UNBOUND, 0,
> +			shost->host_no, session->sid);
> +	if (!session->workq)
> +		return -ENOMEM;
> +
>   	if (target_id == ISCSI_MAX_TARGET) {
>   		id = ida_simple_get(&iscsi_sess_ida, 0, 0, GFP_KERNEL);
>   
>   		if (id < 0) {
>   			iscsi_cls_session_printk(KERN_ERR, session,
>   					"Failure in Target ID Allocation\n");
> -			return id;
> +			err = id;
> +			goto destroy_wq;
>   		}
>   		session->target_id = (unsigned int)id;
>   		session->ida_used = true;
> @@ -2078,7 +2086,8 @@ int iscsi_add_session(struct iscsi_cls_session *session, unsigned int target_id)
>   release_ida:
>   	if (session->ida_used)
>   		ida_simple_remove(&iscsi_sess_ida, session->target_id);
> -
> +destroy_wq:
> +	destroy_workqueue(session->workq);
>   	return err;
>   }
>   EXPORT_SYMBOL_GPL(iscsi_add_session);
> @@ -2177,6 +2186,8 @@ void iscsi_remove_session(struct iscsi_cls_session *session)
>   
>   	transport_unregister_device(&session->dev);
>   
> +	destroy_workqueue(session->workq);
> +
>   	ISCSI_DBG_TRANS_SESSION(session, "Completing session removal\n");
>   	device_del(&session->dev);
>   }
> @@ -3833,8 +3844,7 @@ iscsi_if_recv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, uint32_t *group)
>   	case ISCSI_UEVENT_UNBIND_SESSION:
>   		session = iscsi_session_lookup(ev->u.d_session.sid);
>   		if (session)
> -			scsi_queue_work(iscsi_session_to_shost(session),
> -					&session->unbind_work);
> +			queue_work(session->workq, &session->unbind_work);
>   		else
>   			err = -EINVAL;
>   		break;
> @@ -4707,7 +4717,6 @@ iscsi_register_transport(struct iscsi_transport *tt)
>   	INIT_LIST_HEAD(&priv->list);
>   	priv->iscsi_transport = tt;
>   	priv->t.user_scan = iscsi_user_scan;
> -	priv->t.create_work_queue = 1;
>   
>   	priv->dev.class = &iscsi_transport_class;
>   	dev_set_name(&priv->dev, "%s", tt->name);
> diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
> index 90b55db46d7c..7a0d24d3b916 100644
> --- a/include/scsi/scsi_transport_iscsi.h
> +++ b/include/scsi/scsi_transport_iscsi.h
> @@ -251,6 +251,8 @@ struct iscsi_cls_session {
>   	bool recovery_tmo_sysfs_override;
>   	struct delayed_work recovery_work;
>   
> +	struct workqueue_struct *workq;
> +
>   	unsigned int target_id;
>   	bool ida_used;
>   

Reviewed-by: Lee Duncan <lduncan@suse.com>