From: Max Reitz <mreitz@redhat.com>
To: Anton Nefedov <anton.nefedov@virtuozzo.com>,
Qemu-block <qemu-block@nongnu.org>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
Alberto Garcia <berto@igalia.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Subject: Re: Problems with c8bb23cbdbe3 on ppc64le
Date: Fri, 11 Oct 2019 09:49:11 +0200 [thread overview]
Message-ID: <cd53cd86-e93c-297a-c08e-3fc1ae2618ac@redhat.com> (raw)
In-Reply-To: <5ba5d289-4450-135c-f058-a7e498725058@virtuozzo.com>
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On 10.10.19 18:15, Anton Nefedov wrote:
> On 10/10/2019 6:17 PM, Max Reitz wrote:
>> Hi everyone,
>>
>> (CCs just based on tags in the commit in question)
>>
>> I have two bug reports which claim problems of qcow2 on XFS on ppc64le
>> machines since qemu 4.1.0. One of those is about bad performance
>> (sorry, is isn’t public :-/), the other about data corruption
>> (https://bugzilla.redhat.com/show_bug.cgi?id=1751934).
>>
>> It looks like in both cases reverting c8bb23cbdbe3 solves the problem
>> (which optimized COW of unallocated areas).
>>
>> I think I’ve looked at every angle but can‘t find what could be wrong
>> with it. Do any of you have any idea? :-/
>>
>
> hi,
>
> oh, that patch strikes again..
>
> I don't quite follow, was this bug confirmed to happen on x86? Comment 8
> (https://bugzilla.redhat.com/show_bug.cgi?id=1751934#c8) mentioned that
> (or was that mixed up with the old xfsctl bug?)
I think that was mixed up with the xfsctl bug, yes.
> Regardless of the platform, does it reproduce? That's comforting
> already; worst case we can trace each and every request then (unless it
> will stop to reproduce this way).
I haven’t been able to reproduce it yet (wrestling with the test system
and getting ppc64 machines provisioned), but as far as I know it
reproduces reliably on ppc64, but only there.
> Also, perhaps it's worth to try to replace fallocate with write(0)?
> Either in qcow2 (in the patch, bdrv_co_pwrite_zeroes -> bdrv_co_pwritev)
> or in the file driver. It might hint whether it's misbehaving fallocate
> (in qemu or in kernel) or something else.
Good idea, that should at least tell us something about the corruption.
Max
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next prev parent reply other threads:[~2019-10-11 7:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-10 15:17 Problems with c8bb23cbdbe3 on ppc64le Max Reitz
2019-10-10 16:15 ` Anton Nefedov
2019-10-11 7:49 ` Max Reitz [this message]
2019-10-21 11:40 ` Max Reitz
2019-10-21 13:33 ` Max Reitz
2019-10-21 16:24 ` Max Reitz
2019-10-24 9:08 ` Max Reitz
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