From: Kevin Wolf <kwolf@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH for-1.2] qed: refuse unaligned zero writes with a backing file
Date: Tue, 28 Aug 2012 15:38:37 +0200 [thread overview]
Message-ID: <503CC9DD.8040608@redhat.com> (raw)
In-Reply-To: <503CC6BC.2030101@redhat.com>
Am 28.08.2012 15:25, schrieb Paolo Bonzini:
> Il 28/08/2012 15:04, Stefan Hajnoczi ha scritto:
>> Zero writes have cluster granularity in QED. Therefore they can only be
>> used to zero entire clusters.
>>
>> If the zero write request leaves sectors untouched, zeroing the entire
>> cluster would obscure the backing file. Instead return -ENOTSUP, which
>> is handled by block.c:bdrv_co_do_write_zeroes() and falls back to a
>> regular write.
>>
>> The qemu-iotests 034 test cases covers this scenario.
>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Thanks, applied to the block branch.
> Makes sense since both streaming and copy-on-read will do cluster-aligned writes.
>
> The "right fix" would not be much more complex though, something like this, right?
> (untested).
I think Stefan's fix is the right one. It does the same thing as yours
and it's much simpler.
Kevin
prev parent reply other threads:[~2012-08-28 13:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-28 13:04 [Qemu-devel] [PATCH for-1.2] qed: refuse unaligned zero writes with a backing file Stefan Hajnoczi
2012-08-28 13:25 ` Paolo Bonzini
2012-08-28 13:37 ` Stefan Hajnoczi
2012-08-28 14:23 ` Paolo Bonzini
2012-08-29 7:53 ` Stefan Hajnoczi
2012-08-29 9:09 ` Paolo Bonzini
2012-08-28 13:38 ` Kevin Wolf [this message]
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