Re: [PATCH v5 4/6] scsi: add BLIST_NO_LUN_1F blacklist flag

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The BLIST_NO_LUN_1F flag fails to suppress the spurious 'No Device' entry for an unpopulated LUN 0, violating the primary goal of the commit.
--

commit 3370505ee70b7e5a5de5aa8aad7a378c9144aa38
Author: Phil Pemberton <philpem@philpem.me.uk>

scsi: add BLIST_NO_LUN_1F blacklist flag

Some multi-LUN devices respond to INQUIRY on unpopulated LUNs with
PQ=0 / PDT=0x1f instead of the standard PQ=3. The SCSI scan layer
normally adds such devices, producing spurious No Device entries.

This commit adds a BLIST_NO_LUN_1F flag to scsi_devinfo. It sets the
target flag pdt_1f_for_no_lun during scsi_add_lun() to suppress these
spurious entries.

> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index ef22a4228b855..bfbbf9be05d21 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -1069,6 +1069,8 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
>  	transport_configure_device(&sdev->sdev_gendev);
>  
>  	sdev->sdev_bflags = *bflags;
> +	if (sdev->sdev_bflags & BLIST_NO_LUN_1F)
> +		sdev->sdev_target->pdt_1f_for_no_lun = 1;

Could this cause a regression by failing to suppress the spurious No Device
entry for an unpopulated LUN 0?

In scsi_probe_and_add_lun(), the check to skip unpopulated LUNs occurs
before scsi_add_lun() is called:

drivers/scsi/scsi_scan.c:scsi_probe_and_add_lun() {
    ...
	if (((result[0] >> 5) == 1 || starget->pdt_1f_for_no_lun) &&
	    (result[0] & 0x1f) == 0x1f &&
	    !scsi_is_wlun(lun)) {
		SCSI_LOG_SCAN_BUS(3, sdev_printk(KERN_INFO, sdev,
					"scsi scan: peripheral device type"
					" of 31, no device added\n"));
		res = SCSI_SCAN_TARGET_PRESENT;
		goto out_free_result;
	}

	res = scsi_add_lun(sdev, result, &bflags, shost->async_scan);
    ...
}

If LUN 0 is unpopulated, scsi_probe_and_add_lun() will evaluate this skip
condition while starget->pdt_1f_for_no_lun is still 0.

The skip condition will evaluate to false, and scsi_add_lun() will be
invoked. This erroneously adds LUN 0 as a spurious No Device entry.

Should starget->pdt_1f_for_no_lun be updated directly from the local bflags
inside scsi_probe_and_add_lun() before the skip condition is evaluated?

>  
>  	if (scsi_device_is_pseudo_dev(sdev))
>  		return SCSI_SCAN_LUN_PRESENT;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512202728.299414-1-philpem@philpem.me.uk?part=4