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

Bart Van Assche
2020-06-10T04:16:06Z

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.