Re: [PATCH 3/3] scsi: Improve CDL control

[Niklas Cassel <cassel@kernel.org>]

On Wed, Apr 16, 2025 at 05:42:38PM +0900, Damien Le Moal wrote:
> With ATA devices supporting the CDL feature, using CDL requires that the
> feature be enabled with a SET FEATURES command. This command is issued
> as the translated command for the MODE SELECT command issued by
> scsi_cdl_enable() when the user enables CDL through the device
> cdl_enable sysfs attribute.
> 
> However, the implementation of scsi_cdl_enable() always issues a MODE
> SELECT command for ATA devices when the enable argument is true, even if
> CDL is already enabled on the device. While this does not cause any
> issue with using CDL descriptors with read/write commands (the CDL
> feature will be enabled on the drive), issuing the MODE SELECT command
> even when the device CDL feature is already enabled will cause a reset
> of the ATA device CDL statistics log page (as defined in ACS, any CDL
> enable action must reset the device statistics).
> 
> Avoid this needless actions (and the implied statistics log page reset)
> by modifying scsi_cdl_enable() to issue the MODE SELECT command to
> enable CDL if and only if CDL is not reported as already enabled on the
> device.
> 
> And while at it, simplify the initialization of the is_ata boolean
> variable and move the declaration of the scsi mode data and sense header
> variables to within the scope of ATA device handling.
> 
> 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>