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Re: [Qemu-block] [Qemu-devel] [PATCH] block/mirror: fix fail to cancel w
From: |
Liang Li |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH] block/mirror: fix fail to cancel when VM has heavy BLK IO |
Date: |
Fri, 26 Jan 2018 14:46:50 +0800 |
User-agent: |
Mutt/1.7.2 (2016-11-26) |
On Thu, Jan 25, 2018 at 08:48:22AM -0600, Eric Blake wrote:
> On 01/24/2018 10:59 PM, Liang Li wrote:
> >>
> >> There's ongoing work on adding async mirroring; this may be a better
> >> solution to the issue you are seeing.
> >>
> >> https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg05419.html
> >>
> > Hi Eric,
> >
> > Thinks for your information, I didn't know libvirt depends on
> > 'block-job-cancel'
> > for some of the block related operations.
> >
> > It's seems a new interface should provided by qemu for use case that just
> > for aborting block job and don't care abort the mirror data integrality, and
> > libvirt can make use of this new interface.
> >
> > Do you think this is the right direction?
>
> I don't know if it is better to wait for the new async mirroring code to
> land, or to just propose a new QMP command that can force-quit an
> ongoing mirror in the READY state, but you are correct that the only
> safe way to do it is by adding a new command (or a new optional flag to
> the existing block-job-cancel command).
>
Active sync does not conflict with the new QMP command, no need to wait.
The current QMP command is:
{ 'command': 'block-job-cancel', 'data': { 'device': 'str', '*force': 'bool' } }
'force' has other meaning which is not used by libvirt, for the change, there
are 3 options:
a. Now that 'force' is not used by libvirt and it current semantic is not very
useful,
we can change it's semantic to force-quit without syncing.
b. change 'force' from bool to flag, and bit 0 is used for it's original
meaning.
c. add another bool parameter.
which is the best one?
Thanks!
Liang
> --
> Eric Blake, Principal Software Engineer
> Red Hat, Inc. +1-919-301-3266
> Virtualization: qemu.org | libvirt.org
>
Re: [Qemu-block] [Qemu-devel] [PATCH] block/mirror: fix fail to cancel when VM has heavy BLK IO, John Snow, 2018/01/26