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Re: [Qemu-block] [PATCH 0/6] block: Fix slow pre-zeroing in qemu-img con

From: Nir Soffer
Subject: Re: [Qemu-block] [PATCH 0/6] block: Fix slow pre-zeroing in qemu-img convert
Date: Sun, 24 Mar 2019 01:11:19 +0200

On Fri, Mar 22, 2019 at 10:47 PM Eric Blake <address@hidden> wrote:
On 3/22/19 3:22 PM, Nir Soffer wrote:

> Thanks for fixing this! This will be a very important performance fix for
> importing
> VMs.
> The change description sounds good to me.
> Can you make these patches available on some git repo to make it easy to
> test?

Based on commit titles, this branch looks reasonably close (at the moment):


I tested the patches and they work correctly with NBD server (tested both nbdkit
and qemu-nbd), skipping pre zero step, and zeroing only the unallocated areas.

However zeroing is always done without BDRV_REQ_MAY_UNMAP, creating 
fully allocated images when the expected result is sparse image.

I posted a patch with possible fix, explaining this issue with mode details.
I don't see it yest in mail archive, but the patch is available here:


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