Re: [Qemu-devel] [PATCH 2/7] block: Set BDRV_O_ALLOW_RDWR and snapshot_options before storing the flags

[Kevin Wolf <kwolf@redhat.com>]

Am 15.09.2016 um 13:24 hat Alberto Garcia geschrieben:
> On Wed 14 Sep 2016 06:40:29 PM CEST, Kevin Wolf wrote:
> >> +    if (flags & BDRV_O_RDWR) {
> >> +        flags |= BDRV_O_ALLOW_RDWR;
> >> +    }
> >> +
> >> +    if (flags & BDRV_O_SNAPSHOT) {
> >> +        snapshot_options = qdict_new();
> >> +        bdrv_temp_snapshot_options(&snapshot_flags, snapshot_options,
> >> +                                   flags, options);
> >> +        bdrv_backing_options(&flags, options, flags, options);
> >> +    }
> >> +
> >>      bs->open_flags = flags;
> >>      bs->options = options;
> >>      options = qdict_clone_shallow(options);
> >
> > Here I think we get different semantics now: bdrv_backing_options()
> > only affected the cloned QDict before, and now it affects bs->options,
> > too.
> 
> The thing is that bdrv_backing_options() doesn't change the options in
> general, and in the case where it does (BDRV_OPT_READ_ONLY after the
> next patch) I think it makes sense that the options are changed.
> "snapshot=on" is a bit of a special case after all.

Fair enough, it is correct (as I suspected), but it's not a bug fix
because so far the options weren't changed, so there's no observable
difference.

I think mentioning this in the commit message wouldn't hurt, though.

Kevin