RE: [PATCH 1/2] conf: add locking option to disk source

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Thank you for your comment.

I will try to write so that this will not be locking specific.

> On Wed, Feb 14, 2024 at 13:17:39 +0100, Peter Krempa wrote:
> > On Wed, Feb 14, 2024 at 14:17:57 +0900, Hiroki Narukawa wrote:
> > > There is a case that locking hits a bug and users wants to disable
> > > locking like bug in Linux kernel.
> > >
> > > This commit adds option to configure locking for file source.
> > >
> > > Signed-off-by: Hiroki Narukawa <hnarukaw@xxxxxxxxxxxxx>
> > > ---
> > >  docs/formatdomain.rst             | 5 +++++
> > >  src/conf/domain_conf.c            | 8 ++++++++
> > >  src/conf/schemas/domaincommon.rng | 5 +++++
> > >  src/conf/storage_source_conf.h    | 3 +++
> > >  4 files changed, 21 insertions(+)
> > >
> > > diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst index
> > > 0a4f9d9000..95869d573c 100644
> > > --- a/docs/formatdomain.rst
> > > +++ b/docs/formatdomain.rst
> > > @@ -2782,6 +2782,11 @@ paravirtualized driver is specified via the ``disk``
> element.
> > >        via the filesystem. The filename passed via ``file`` can still be used
> > >        to generate paths to write into image metadata when doing block
> operations
> > >        but libvirt will not access these natively.
> > > +
> > > +      :since:`Since 10.1.0` a new optional attribute ``locking`` can be
> added
> > > +      which can take "on" or "off". Basically this option should be kept
> > > +      default, but it can be used explicitly for workaround about bug in
> > > +      locking.
> >
> > This is not the first time this is being suggested and I'm still not
> > persuaded that we want this. We definitelly do not want this as a
> > generic production attribute.
> >
> > A possibility would be to do it as part of the qemu XML namespace
> > along with tainting the VM that such config is being used.
> >
> > https://libv/
> >
> irt.org%2Fdrvqemu.html%23pass-through-of-arbitrary-qemu-commands&data=
> >
> 05%7C02%7Chnarukaw%40yahoo-corp.jp%7Ce8a8b57666244c52e3b108dc2d58
> bcf2%
> >
> 7Ca208d369cd4e4f87b11998eaf31df2c3%7C1%7C0%7C638435106350299392%7
> CUnkn
> >
> own%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1h
> aWwi
> >
> LCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=MIFzrihGDgVq4XO8na2K%2F7c9q
> 708wMwKAZ
> > 0yKU1ZJVE%3D&reserved=0
> >
> > The main reason is that you never actually want to use this, except
> > for the very specific case of bugs you are mentioning.
>
> To elaborate on the qemu XML namespace integration:
>
>  Currently we parse the namespace elements only on a global scope, so
> per-disk XML attributes are not supported. Thus to add per-disk or  per-device
> XML namespace attributes a new parsing callback will be  needed.
>
>  A second option would be to do it similarly to how we allow override of  device
> parameters:
>
>
> https://libvirt.org/
> %2Fdrvqemu.html%23overriding-properties-of-qemu-devices&data=05%7C02%
> 7Chnarukaw%40yahoo-corp.jp%7Ce8a8b57666244c52e3b108dc2d58bcf2%7Ca2
> 08d369cd4e4f87b11998eaf31df2c3%7C1%7C0%7C638435106350305499%7CUnk
> nown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1
> haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=7eH0zujLapnHQRIQXqihwP
> ADhiAt77yInaSVjUdFez4%3D&reserved=0
>
>  The image to override would be identified using the TARGET[INDEX]  tuple (e.g.
> vda[1]) as declared in the XML.
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