Re: [PATCH 3/3] iotests/283: Check that finalize drops backup-top

[Kevin Wolf <kwolf@redhat.com>]

Am 19.02.2021 um 16:59 hat Max Reitz geschrieben:
> On 19.02.21 16:33, Max Reitz wrote:
> > Without any of HEAD^ or HEAD^^ applied, qemu will most likely crash on
> > the qemu-io invocation, for a variety of immediate reasons.  The
> > underlying problem is generally a use-after-free access into
> > backup-top's BlockCopyState.
> > 
> > With only HEAD^ applied, qemu-io will run into an EIO (which is not
> > capture by the output, but you can see that the qemu-io invocation will
> > be accepted (i.e., qemu-io will run) in contrast to the reference
> > output, where the node name cannot be found), and qemu will then crash
> > in query-named-block-nodes: bdrv_get_allocated_file_size() detects
> > backup-top to be a filter and passes the request through to its child.
> > However, after bdrv_backup_top_drop(), that child is NULL, so the
> > recursive call crashes.
> > 
> > With HEAD^^ applied, this test should pass.
> > 
> > Signed-off-by: Max Reitz <mreitz@redhat.com>
> > ---
> >   tests/qemu-iotests/283     | 55 ++++++++++++++++++++++++++++++++++++++
> >   tests/qemu-iotests/283.out | 15 +++++++++++
> >   2 files changed, 70 insertions(+)
> > 
> > diff --git a/tests/qemu-iotests/283 b/tests/qemu-iotests/283
> > index 79643e375b..509dcbbcf4 100755
> > --- a/tests/qemu-iotests/283
> > +++ b/tests/qemu-iotests/283
> > @@ -97,3 +97,58 @@ vm.qmp_log('blockdev-add', **{
> >   vm.qmp_log('blockdev-backup', sync='full', device='source', target='target')
> >   vm.shutdown()
> > +
> > +
> > +"""
> > +Check that the backup-top node is gone after job-finalize.
> > +
> > +During finalization, the node becomes inactive and can no longer
> > +function.  If it is still present, new parents might be attached, and
> > +there would be no meaningful way to handle their I/O requests.
> > +"""
> 
> Oh no, 297/pylint complains that this “string statement has no effect”.
> Guess it should be a normal comment under the following print() then...

Thanks, fixed up the comment as you suggest and applied to the block
branch.

Kevin