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

[Nir Soffer]

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):

https://repo.or.cz/qemu/kevin.git/shortlog/refs/heads/qcow2-data-file

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:

https://github.com/nirs/qemu/commit/5023405ee42dc0d8e9a03ac03d247079f719b455

Nir