Re: [PATCH v2 6/7] block/copy-before-write: implement cbw-timeout option

[Hanna Reitz]

On 01.04.22 15:24, Hanna Reitz wrote:
> On 01.04.22 11:19, Vladimir Sementsov-Ogievskiy wrote:
> > In some scenarios, when copy-before-write operations lasts too long
> > time, it's better to cancel it.
> >
> > Most useful would be to use the new option together with
> > on-cbw-error=break-snapshot: this way if cbw operation takes too long
> > time we'll just cancel backup process but do not disturb the guest too
> > much.
> >
> > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
> > ---
> >   block/copy-before-write.c | 6 +++++-
> >   qapi/block-core.json      | 5 ++++-
> >   2 files changed, 9 insertions(+), 2 deletions(-)

[...]

> > diff --git a/qapi/block-core.json b/qapi/block-core.json
> > index 3f08025114..e077506e0f 100644
> > --- a/qapi/block-core.json
> > +++ b/qapi/block-core.json
> > @@ -4207,12 +4207,15 @@
> >   # @on-cbw-error: Behavior on failure of copy-before-write operation.
> >   #                Default is @break-guest-write. (Since 7.0)
> >   #
> > +# @cbw-timeout: Zero means no limit. Non-zero sets the timeout in 
> > seconds
> > +#               for copy-before-write operation. Default 0. (Since 7.0)
>
> *7.1, but:
>
> Reviewed-by: Hanna Reitz <hreitz@redhat.com>

On second thought, perhaps we should make an explicit note that a 
timeout means an error?  E.g. “When a timeout occurs, the respective 
copy-before-write operation will fail, and the @on-cbw-error parameter 
will decide how this failure is handled.”

(Optional, R-b stands without it, too)