Re: [PATCH] scsi: introduce a quirk for false cache reporting

[Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org>]

On Wed, 2016-08-10 at 22:40 -0400, Martin K. Petersen wrote:
> >>>>> "Oliver" == Oliver Neukum <oneukum-IBi9RG/b67k@public.gmane.org> writes:
> 
> Oliver> Some SATA to USB bridges fail to cooperate with some drives
> Oliver> resulting in no cache being present being reported to the
> Oliver> host. That causes the host to skip sending a command to
> Oliver> synchronize caches. That causes data loss when the drive is
> Oliver> powered down.
> 
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index a6c346d..392d166 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -179,6 +179,7 @@ struct scsi_device {
>  	unsigned try_rc_10_first:1;	/* Try READ_CAPACACITY_10 first */
>  	unsigned is_visible:1;	/* is the device visible in sysfs */
>  	unsigned wce_default_on:1;	/* Cache is ON by default */
> +	unsigned always_sync:1;		/* synchronize cache in every case*/
>  	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
>  	unsigned broken_fua:1;		/* Don't set FUA bit */
>  	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
> 
> I must be missing something. How is always_sync different from just
> setting wce_default_on?

Hi,

wce_default_on controls the default if the device provides no
indication. The problem here is that the indication the device
provides must be overridden, as they are false.

	Regards
		Oliver


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