Re: [RFC PATCH 2/5] scsi: ufs: Add UFS-feature layer

[Bart Van Assche <bvanassche@acm.org>]

On 2020-06-04 18:30, Daejun Park wrote:
> +inline void ufsf_slave_configure(struct ufs_hba *hba,
> +				 struct scsi_device *sdev)
> +{
> +	/* skip well-known LU */
> +	if (sdev->lun >= UFS_UPIU_MAX_UNIT_NUM_ID)
> +		return;
> +
> +	if (!(hba->dev_info.b_ufs_feature_sup & UFS_FEATURE_SUPPORT_HPB_BIT))
> +		return;
> +
> +	atomic_inc(&hba->ufsf.slave_conf_cnt);
> +	smp_mb__after_atomic(); /* for slave_conf_cnt */
> +
> +	/* waiting sdev init.*/
> +	if (waitqueue_active(&hba->ufsf.sdev_wait))
> +		wake_up(&hba->ufsf.sdev_wait);
> +}

Guarding a wake_up() call with a waitqueue_active() check is an
anti-pattern. Please don't do that and call wake_up() directly.
Additionally, wake_up() includes a barrier if it wakes up a kernel
thread so the smp_mb__after_atomic() can be left out if the
waitqueue_active() call is removed.

> +/**
> + * struct ufsf_operation - UFS feature specific callbacks
> + * @prep_fn: called after construct upiu structure
> + * @reset: called after proving hba
                           ^^^^^^^
Is this a typo? Should "proving" perhaps be changed into "probing"?

> +struct ufshpb_driver {
> +	struct device_driver drv;
> +	struct list_head lh_hpb_lu;
> +
> +	struct ufsf_operation ufshpb_ops;
> +
> +	/* memory management */
> +	struct kmem_cache *ufshpb_mctx_cache;
> +	mempool_t *ufshpb_mctx_pool;
> +	mempool_t *ufshpb_page_pool;
> +
> +	struct workqueue_struct *ufshpb_wq;
> +};

Why is a dedicated workqueue needed? Why are the standard workqueues not
good enough?

> @@ -2525,6 +2525,8 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
>  
>  	ufshcd_comp_scsi_upiu(hba, lrbp);
>  
> +	ufsf_ops_prep_fn(hba, lrbp);
> +
>  	err = ufshcd_map_sg(hba, lrbp);
>  	if (err) {
>  		lrbp->cmd = NULL;

What happens if a SCSI command is retried and hence ufsf_ops_prep_fn()
is called multiple times for the same SCSI command?

Thanks,

Bart.