Re: [PATCH v2 2/2] vhost-scsi: clamp max_io_vqs module parameter

On 8/2/26 12:24 PM, Dongli Zhang wrote:
> max_io_vqs is currently validated only when a vhost-scsi device is opened.
> This allows sysfs to show values larger than the driver will actually use,
> e.g. writing 2048 succeeds even though vhost_scsi_open() later clamps it to
> VHOST_SCSI_MAX_IO_VQ. This makes the sysfs value differ from the value that
> will actually be used.
> 
> hv# echo 2048 > /sys/module/vhost_scsi/parameters/max_io_vqs
> 
> hv# cat /sys/module/vhost_scsi/parameters/max_io_vqs
> 2048
> 
> [  315.630495] Invalid max_io_vqs of 2048. Using 1024.
> 
> Keep accepting out-of-range values for compatibility, but clamp them in the
> module parameter setter and store the effective value. This preserves the
> existing behavior that invalid values do not make module loading or sysfs
> writes fail. It also makes reads report the value that will actually be
> used.
> 
> With the parameter value kept in range, remove the duplicate validation
> from vhost_scsi_open().
> 
> Signed-off-by: Dongli Zhang <[email protected]>
> ---
> v1->v2:
>   - Access vhost_scsi_max_io_vqs with READ_ONCE().
>   - Clamp out-of-range max_io_vqs values instead of rejecting them.
> 
Reviewed-by: Mike Christie <[email protected]>