From: Markus Armbruster <armbru@redhat.com>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>,
qemu-trivial@nongnu.org, qemu-devel@nongnu.org,
Stefan Hajnoczi <stefanha@redhat.com>,
Arthur Gautier <baloo@gandi.net>
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH] vmdk: Fix cylinders number during convert
Date: Thu, 23 Oct 2014 10:03:25 +0200 [thread overview]
Message-ID: <87egtzusaa.fsf@blackfin.pond.sub.org> (raw)
In-Reply-To: <5448A656.6030204@msgid.tls.msk.ru> (Michael Tokarev's message of "Thu, 23 Oct 2014 10:55:18 +0400")
Michael Tokarev <mjt@tls.msk.ru> writes:
> On 10/22/2014 05:25 PM, Arthur Gautier wrote:
>> We can not rely on int cast to get a correct number of cylinders. The
>> cylinders information was wrong in 49.9999% of cases.
>>
>> This ensures the cylinders always gets the ceiling value.
>
> Good thing, especially the good probability :), and also a good patch
> which comes with a test.
>
> But I wonder if anything can break this way? Migration, windows guest
> being unable to find its partitions, something else?
>
> And more. What-if our drive size in cylinders will be larger than
> the size in bytes? The proposed div_round_up() will increase number
> of cylinders, so size in CHS will be larger than size in bytes. Maybe
> there was a reason why originally the size in cylinders was calculated
> by truncating extra fractional part? What-if guest will try to access
> the very last CHS which is incomplete?
Too many questions for -trivial, copying VMDK maintainers.
WARNING: multiple messages have this Message-ID (diff)
From: Markus Armbruster <armbru@redhat.com>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>,
qemu-trivial@nongnu.org, qemu-devel@nongnu.org,
Stefan Hajnoczi <stefanha@redhat.com>,
Arthur Gautier <baloo@gandi.net>
Subject: Re: [Qemu-devel] [Qemu-trivial] [PATCH] vmdk: Fix cylinders number during convert
Date: Thu, 23 Oct 2014 10:03:25 +0200 [thread overview]
Message-ID: <87egtzusaa.fsf@blackfin.pond.sub.org> (raw)
In-Reply-To: <5448A656.6030204@msgid.tls.msk.ru> (Michael Tokarev's message of "Thu, 23 Oct 2014 10:55:18 +0400")
Michael Tokarev <mjt@tls.msk.ru> writes:
> On 10/22/2014 05:25 PM, Arthur Gautier wrote:
>> We can not rely on int cast to get a correct number of cylinders. The
>> cylinders information was wrong in 49.9999% of cases.
>>
>> This ensures the cylinders always gets the ceiling value.
>
> Good thing, especially the good probability :), and also a good patch
> which comes with a test.
>
> But I wonder if anything can break this way? Migration, windows guest
> being unable to find its partitions, something else?
>
> And more. What-if our drive size in cylinders will be larger than
> the size in bytes? The proposed div_round_up() will increase number
> of cylinders, so size in CHS will be larger than size in bytes. Maybe
> there was a reason why originally the size in cylinders was calculated
> by truncating extra fractional part? What-if guest will try to access
> the very last CHS which is incomplete?
Too many questions for -trivial, copying VMDK maintainers.
next prev parent reply other threads:[~2014-10-23 8:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-22 13:25 [Qemu-trivial] [PATCH] vmdk: Fix cylinders number during convert Arthur Gautier
2014-10-22 13:25 ` [Qemu-devel] " Arthur Gautier
2014-10-23 6:55 ` [Qemu-trivial] " Michael Tokarev
2014-10-23 6:55 ` [Qemu-devel] " Michael Tokarev
2014-10-23 8:03 ` Markus Armbruster [this message]
2014-10-23 8:03 ` Markus Armbruster
2014-10-28 16:00 ` [Qemu-trivial] [Qemu-devel] " Stefan Hajnoczi
2014-10-28 16:00 ` [Qemu-devel] [Qemu-trivial] " Stefan Hajnoczi
2014-10-29 1:28 ` [Qemu-trivial] [Qemu-devel] " Fam Zheng
2014-10-29 1:28 ` [Qemu-devel] [Qemu-trivial] " Fam Zheng
2014-10-30 9:09 ` [Qemu-trivial] [Qemu-devel] " Arthur Gautier
2014-10-30 9:09 ` [Qemu-devel] [Qemu-trivial] " Arthur Gautier
2014-10-30 10:27 ` [Qemu-trivial] [Qemu-devel] " Fam Zheng
2014-10-30 10:27 ` [Qemu-devel] [Qemu-trivial] " Fam Zheng
2014-10-30 14:28 ` [Qemu-trivial] [Qemu-devel] " Arthur Gautier
2014-10-30 14:28 ` [Qemu-devel] [Qemu-trivial] " Arthur Gautier
2014-10-31 2:52 ` [Qemu-trivial] [Qemu-devel] " Fam Zheng
2014-10-31 2:52 ` [Qemu-devel] [Qemu-trivial] " Fam Zheng
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