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Re: [Qemu-devel] [PATCH v2 08/17] block: make bdrv_has_zero_init return


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH v2 08/17] block: make bdrv_has_zero_init return false for copy-on-write-images
Date: Fri, 19 Jul 2013 15:23:39 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7

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Il 19/07/2013 15:21, Eric Blake ha scritto:
> Question (more for my understanding, not that you need to change
> code): must we blindly return 0 in the presence of a backing file,
> or is it possible to recursively query the backing_hd's zero_init
> status, allowing us to return 1 iff all files in the chain support
> zero_init.

No, it's really blind.  bdrv_has_zero_init is like "was the image all
zeros at creation time", and the answer is no because the content of
the image used to be the same as the backing_hd.

Paolo
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