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SubjectRe: [PATCH v2] libata: add support for NCQ commands for SG interface
On Mon, Nov 16, 2015 at 08:47:19AM -0500, Mark Lord wrote:
> On 15-10-27 01:49 AM, vinayak.kale@gmail.com wrote:
> >From: Vinayak Kale <vinayak.kale@seagate.com>
> >
> >This patch is needed to make NCQ commands with FPDMA protocol value
> >(eg READ/WRITE FPDMA) work over SCSI Generic (SG) interface.
> ..
> >+ /* For NCQ commands with FPDMA protocol, copy the tag value */
> >+ if (tf->protocol == ATA_PROT_NCQ)
> >+ tf->nsect = qc->tag << 3;
> >+
>
>
> What prevents the qc-tag value here from conflicting with in-flight I/O
> using the exact same qc-tag ??

The SG command doesn't set the tag, it's being set from an allocated
qc which can't otherwise be in-flight.

Thanks.

--
tejun


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