Re: [PATCH v5 27/27] scsi: sd: add mpath_queue_depth dev attribute

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The sysfs show function `sd_mpath_queue_depth_show` returns 0 when the iopolicy is not QD, causing reads to return EOF (0 bytes).
--

--- Patch [27]: [PATCH v5 27/27] scsi: sd: add mpath_queue_depth dev attribute ---
commit a1c72efbc115f45170fc3510049d2e925ee24a95
Author: John Garry <[email protected]>

scsi: sd: add mpath_queue_depth dev attribute

Add a queue_depth file so that the multipath dynamic queue depth can be
looked up from per-path gendisk (scsi_disk) directory.

> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 6b6aef361ae22..fbf9da686f25d 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -4159,9 +4159,28 @@ static ssize_t sd_mpath_numa_nodes_show(struct device *dev,
>  }
>  static DEVICE_ATTR(mpath_numa_nodes, 0444, sd_mpath_numa_nodes_show, NULL);
>  
> +static ssize_t sd_mpath_queue_depth_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	struct gendisk *gd = dev_to_disk(dev);
> +	struct scsi_disk *sdkp = gd->private_data;
> +	struct scsi_device *sdev = sdkp->device;
> +	struct scsi_mpath_device *scsi_mpath_dev = sdev->scsi_mpath_dev;
> +	struct scsi_mpath_head *scsi_mpath_head =
> +				scsi_mpath_dev->scsi_mpath_head;
> +	struct Scsi_Host *shost = sdev->host;
> +
> +	if (!mpath_qd_iopolicy(&scsi_mpath_head->iopolicy))
> +		return 0;

[Severity: Medium]
Should this return a standard negative error code like -EOPNOTSUPP instead of 0?

Returning 0 from a sysfs show callback means zero bytes were written to the
output buffer, causing user-space reads to receive an immediate EOF and see a
completely empty file instead of parsing an integer or receiving an error.

> +
> +	return sysfs_emit(buf, "%d\n", atomic_read(&shost->mpath_nr_active));
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=27