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Date: Tue, 27 Sep 2016 06:15:11 -0400 (EDT)
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] proto: add 'shift' extension.
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To: "Denis V. Lunev" <den@virtuozzo.com>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>, qemu-devel@nongnu.org, qemu-block@nongnu.org, nbd-general@lists.sourceforge.net, alex@alex.org.uk, eblake@redhat.com, kwolf@redhat.com, stefanha@redhat.com, w@uter.be

> We could go in a different direction and export flag
> 'has_zero_init' which will report that the storage is
> initialized with all zeroes at the moment. In this
> case mirroring code will not fall into this
> branch.

Why don't you add the zero_init flag to QEMU's NBD driver instead?

Thanks,

Paolo