RE: [PATCH v2 3/3] [SCSI] Make LBP quirk skip lbpme checks tests

From: KY Srinivasan
Date: Sat Jul 26 2014 - 09:44:16 EST

> -----Original Message-----
> From: Martin K. Petersen [mailto:martin.petersen@xxxxxxxxxx]
> Sent: Friday, July 25, 2014 9:57 AM
> To: KY Srinivasan
> Cc: Martin K. Petersen; Sitsofe Wheeler; Christoph Hellwig;
> gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; ohering@xxxxxxxx; apw@xxxxxxxxxxxxx;
> jasowang@xxxxxxxxxx; jbottomley@xxxxxxxxxxxxx; linux-
> scsi@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 3/3] [SCSI] Make LBP quirk skip lbpme checks tests
> >>>>> "KY" == KY Srinivasan <kys@xxxxxxxxxxxxx> writes:
> KY> For the pass through case, the host validates the request and passes
> KY> the request to the device. However, not all scsi commands are
> KY> passed through even though the device it is being passed through may
> KY> support the command. WRITE_SAME is one such command.
> Consequently,
> KY> in the EVPD page, we will set state indicating that WRITE_SAME is
> KY> not supported (even if the device supports it).
> The LBP VPD page flags UNMAP as being supported. Do you actually support
> UNMAP to DSM TRIM SCSI-ATA translation?


I have been told by the Windows folks that this is done. I am trying to get
additional details.

K. Y
> One challenge in that department is that a single UNMAP command may turn
> into many, many, many DSM TRIM commands on the underlying SATA
> device.
> That's why we went with WRITE SAME for the internal Linux SATL, capping
> the maximum number of blocks to what we can fit in a single DSM TRIM
> command.
> --
> Martin K. Petersen Oracle Linux Engineering
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