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Date: Mon, 20 Aug 2012 09:34:07 +0200
From: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
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Subject: Re: [Qemu-devel] [PATCH RFT 0/3] iscsi: fix NULL dereferences /
 races between task completion and abort
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, ronniesahlberg@gmail.com

Am 20.08.2012 09:22, schrieb Paolo Bonzini:
> Il 19/08/2012 21:22, Stefan Priebe - Profihost AG ha scritto:
>>
>>> No problem, my fault---I'm just back and I haven't really started again
>>> all my stuff, so the patch was not tested.
>>>
>>> This should fix it, though.
>>
>> Booting works fine now. But the VM starts to hang after trying to unmap
>> large regions. No segfault or so just not reacting anymore.
>
> This is expected; unfortunately cancellation right now is a synchronous
> operation in the block layer.  SCSI is the first big user of
> cancellation, and it would indeed benefit from asynchronous cancellation.
>
> Without these three patches, you risk corruption in case the following
> happens:
>
>      qemu                 target
>    -----------------------------------
>      send unmap -------->
>      cancel unmap ------>
>      send write -------->
>         <---------------- complete write
>                           <unmap just written sector>
>         <---------------- complete unmap
>         <---------------- cancellation done (unmap complete)

mhm OK that makes sense. But i cannot even login via SSH and i also see 
no cancellation message in kernel log.

So what is the right way to test these patches? With my version i can 
still work via SSH.

Stefan