Re: [PATCH v2] scsi: core: Disable CDL by default

[Niklas Cassel <cassel@kernel.org>]

On Fri, Jun 07, 2024 at 10:25:07AM +0900, Damien Le Moal wrote:
> For scsi devices supporting the Command Duration Limits feature set, the
> user can enable/disable this feature use through the sysfs device
> attribute cdl_enable. This attribute modification triggers a call to
> scsi_cdl_enable() to enable and disable the feature for ATA devices and
> set the scsi device cdl_enable field to the user provided bool value.
> For SCSI devices supporting CDL, the feature set is always enabled and
> scsi_cdl_enable() is reduced to setting the cdl_enable field.
> 
> However, for ATA devices, a drive may spin-up with the CDL feature
> enabled by default. But the scsi device cdl_enable field is always
> initialized to false (CDL disabled), regardless of the actual device
> CDL feature state. For ATA devices managed by libata (or libsas),
> libata-core always disables the CDL feature set when the device is
> attached, thus syncing the state of the CDL feature on the device and of
> the scsi device cdl_enable field. However, for ATA devices connected to
> a SAS HBA, the CDL feature is not disabled on scan for ATA devices that
> have this feature enabled by default, leading to an inconsistent state
> of the feature on the device with the scsi device cdl_enable field.
> 
> Avoid this inconsistency by adding a call to scsi_cdl_enable() in
> scsi_cdl_check() to make sure that the device-side state of the CDL
> feature set always matches the scsi device cdl_enable field state.
> This implies that CDL will always be disabled for ATA devices connected
> to SAS HBAs, which is consistent with libata/libsas initialization of
> the device.
> 
> Reported-by: Scott McCoy <scott.mccoy@wdc.com>
> Fixes: 1b22cfb14142 ("scsi: core: Allow enabling and disabling command duration limits")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---

Reviewed-by: Niklas Cassel <cassel@kernel.org>