Re: [bug report] block: Non-NCQ commands will never be executed while fio is continuously running

[yangxingui]

On 2024/10/31 22:12, Niklas Cassel wrote:
> On Thu, Sep 19, 2024 at 04:14:15PM +0200, Damien Le Moal wrote:
> > On 2024/09/19 14:26, Yu Kuai wrote:
> > > Does libata return a specific value in this case? If so, maybe we can
> > > stop other hctx untill this IO is handled.
> > >
> > > For now, I think libata should use single hctx, it just doesn't support
> > > multiple hctx yet.
> >
> > libata does not care/know about hctx. It only issues commands to ATA devices,
> > which always are single queue. And pure SATA adapters like AHCI are always
> > single queue.
> >
> > The issue at hand can happen only for libsas based SAS HBAs that have multiple
> > command submission queues (with a shared tag set). Commands for the same device
> > may end up being submitted through different queues, and when the submitted
> > commands include a mix of NCQ and non-NCQ commands, the problem happens without
> > libata being able to easily do anything about it, and not possible control
> > possible at the scsi layer either since the commands submitted are SCSI (not yet
> > translated to ATA commands) which do not have any NCQ/non-NCQ exclusion
> > knowledge at all. NCQ is an ATA concept unknown to the scsi and block layer.
> >
> > We (Niklas and I) are trying to find a solution, but that may not be within
> > libata itself. It may need changes to libsas as well. Not sure yet. Still exploring.
>
> Hello Xingui,
>
> I send a proposed solution to this problem here:
> https://lore.kernel.org/linux-ide/20241031140731.224589-4-cassel@xxxxxxxxxx/
>
> Please test and see if it addresses your problem.
OK, thanks for following this issue and fixing it, we will verify it as 
soon as possible.

Thanks.
Xingui