Am 16.01.2014 um 20:20 hat Jeff Cody geschrieben:
> On Thu, Jan 16, 2014 at 10:39:30AM +0100, Kevin Wolf wrote:
> > Am 14.01.2014 um 20:12 hat Jeff Cody geschrieben:
> > > Having both read-only=on and snapshot=on together does not make sense;
> > > currently, the read-only argument is effectively ignored for the
> > > temporary snapshot. To prevent confusion, disallow the usage of both
> > > 'snapshot=on' and 'read-only=on'.
> > >
> > > Signed-off-by: Jeff Cody <jc...@redhat.com>
> >
> > I believe the reason why this was allowed was so that you can use a
> > read-only file with -snapshot. It might not be necessary any more since
> > I switched -snapshot implementation to modify the options QDict instead
> > of manually doing a second bdrv_open().
> >
> > Did you test that this still works now?
>
> Yes, that still works.
Great. :-)
> > The other question is about this code in bdrv_open_flags():
> >
> > /*
> > * Snapshots should be writable.
> > */
> > if (bs->is_temporary) {
> > open_flags |= BDRV_O_RDWR;
> > }
> >
> > Is this dead code now because the flag is always already set?
> >
>
> Yes, that ends up being dead code. From later in blockdev_init():
>
> bdrv_flags |= ro ? 0 : BDRV_O_RDWR;
>
> QINCREF(bs_opts);
> ret = bdrv_open(dinfo->bdrv, file, bs_opts, bdrv_flags, drv, &error);
>
>
> And ro is set from the read-only QemuOpts, that we check in this
> patch in conjunction with snapshot. So if read-only=on is not
> specified, it is opened r/w by default.
Good, that was my impression as well. Can you send a follow-up patch to
remove the dead code?
Kevin
