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Re: [Qemu-devel] [PATCH] block: change default of .has_zero_init to 0

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH] block: change default of .has_zero_init to 0
Date: Thu, 27 Jun 2013 09:12:55 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6

On 06/27/2013 07:52 AM, Peter Lieven wrote:
> .has_zero_init defaults to 1 for all formats and protocols.
> this is a dangerous default since this means that all
> new added drivers need to manually overwrite it to 0 if
> they do not ensure that a device is zero initialized
> after bdrv_create().
> if a driver needs to explicitly set this value to
> 1 its easier to verify the correctness in the review process.
> during review of the existing drivers it turned out
> that ssh and gluster had a wrong default of 1.
> both protocols support host_devices as backend
> which are not by default zero initialized. this
> wrong assumption will lead to possible corruption
> if qemu-img convert is used to write to such a backend.
> a similar problem with the wrong default existed for
> iscsi mose likely because the driver developer did


Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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