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SubjectRe: [PATCH BUGFIX 1/1] block, bfq: add requeue-request hook
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> Il giorno 06 feb 2018, alle ore 08:56, Mike Galbraith <efault@gmx.de> ha scritto:
>
> On Tue, 2018-02-06 at 08:44 +0100, Oleksandr Natalenko wrote:
>> Hi, Paolo.
>>
>> I can confirm that this patch fixes cfdisk hang for me. I've also tried
>> to trigger the issue Mike has encountered, but with no luck (maybe, I
>> wasn't insistent enough, just was doing dd on usb-storage device in the
>> VM).
>
> I was doing kbuilds, and it blew up on me twice. Switching back to cfq
> seemed to confirm it was indeed the patch causing trouble, but that's
> by no means a certainty.
>

Hi Mike,
as you can imagine, I didn't get any failure in my pre-submission
tests on this patch. In addition, it is not that easy to link this
patch, which just adds some internal bfq housekeeping in case of a
requeue, with a corruption of external lists for general I/O
management.

In this respect, as Oleksandr comments point out, by switching from
cfq to bfq, you switch between much more than two schedulers. Anyway,
who knows ...

Maybe this report will ring a bell with some block-layer expert, or,
hopefully, next feedback will help puzzle this out.

Thanks,
Paolo


> -Mike

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