linux-kernel - Re: [PATCH v2 2/2] scsi: ufs: core: Cleanup ufshcd_slave

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Date:   Fri, 14 Oct 2022 14:05:48 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Bean Huo <beanhuo@...pp.de>, alim.akhtar@...sung.com,
        avri.altman@....com, asutoshd@...eaurora.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, stanley.chu@...iatek.com,
        beanhuo@...ron.com, tomas.winkler@...el.com, cang@...eaurora.org,
        daejun7.park@...sung.com
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] scsi: ufs: core: Cleanup ufshcd_slave_alloc()

On 10/10/22 02:29, Bean Huo wrote:
> From: Bean Huo <beanhuo@...ron.com>
> 
> Combine ufshcd_get_lu_power_on_wp_status() and ufshcd_set_queue_depth()
> into one single ufshcd_lu_init(), so that we only need to read the LUN
> descriptor once to replace the original twice.

The following part can probably be left out from the patch description 
without reducing clarity: " to replace the original twice".

> +/**
> + * ufshcd_lu_power_on_wp_init - Initialize LU's power on write protect state
> + * @hba: per-adapter instance
> + * @sdev: pointer to SCSI device
> + * @b_lu_write_protect: bLUWriteProtect value read from LU descriptor
> + */
> +static inline void ufshcd_lu_power_on_wp_init(struct ufs_hba *hba, const struct scsi_device *sdev,
> +					      u8 b_lu_write_protect)
> +{
> +	if (hba->dev_info.f_power_on_wp_en && !hba->dev_info.is_lu_power_on_wp &&
> +	    b_lu_write_protect == UFS_LU_POWER_ON_WP)
> +		hba->dev_info.is_lu_power_on_wp = true;
> +}

The body of this function is only three lines long and this function is 
only called once. Are you sure that you want a separate function instead 
of inlining this function in its only caller?

> +static void ufshcd_lu_init(struct ufs_hba *hba, struct scsi_device *sdev)
> +{
> +	int ret;
> +	int len;
> +	u8 lun;
> +	u8 lun_qdepth;
> +	u8 *desc_buf;

Most kernel developers these days order local variable declarations from 
longest to shortest line ("reverse Christmas tree").

> +	lun_qdepth = hba->nutrs;
> +	lun = ufshcd_scsi_to_upiu_lun(sdev->lun);
> +	len = hba->desc_size[QUERY_DESC_IDN_UNIT];
> +
> +	desc_buf = kmalloc(len, GFP_KERNEL);
> +	if (!desc_buf)
> +		goto set_qdepth;
> +
> +	ret = ufshcd_read_unit_desc_param(hba, lun, 0, desc_buf, len);
> +	if (ret == -EOPNOTSUPP)
> +		/* If LU doesn't support unit descriptor, its queue depth is set to 1 */
> +		lun_qdepth = 1;
> +	else if (desc_buf[UNIT_DESC_PARAM_LU_Q_DEPTH])
> +		lun_qdepth = min_t(int, desc_buf[UNIT_DESC_PARAM_LU_Q_DEPTH], hba->nutrs);

ufshcd_read_unit_desc_param() can return fewer bytes than requested. How 
about modifying ufshcd_read_unit_desc_param() such that it returns the 
number of bytes that has been copied and using that return value above 
to check whether at least UNIT_DESC_PARAM_LU_Q_DEPTH bytes have been 
initialized in desc_buf?

> +	/*
> +	 * According to UFS device spec, The write protection mode is only supported by normal LU,
> +	 * not supported by WLUN.
> +	 */
> +	if (!ret && lun < hba->dev_info.max_lu_supported)
> +		ufshcd_lu_power_on_wp_init(hba, sdev, desc_buf[UNIT_DESC_PARAM_LU_WR_PROTECT]);

Please insert an if (ret < 0) check after the 
ufshcd_read_unit_desc_param() call and jump to the kfree() statement if 
ret < 0 instead of checking several times whether or not ret < 0.

Thanks,

Bart.