13.06.2019 1:09, Max Reitz wrote: > This allows us to differentiate between filters and nodes with COW > backing files: Filters cannot be used as overlays at all (for this > function). > > Signed-off-by: Max Reitz <mre...@redhat.com>
Overlay created in snapshot operation assumed to consume following writes and it's filtered child becomes readonly.. And filter works in completely another way. Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> [hmm, I start to like using "filtered child" collocation when I say about this thing. didn't you think about renaming backing chain to filtered chain?] > --- > blockdev.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/blockdev.c b/blockdev.c > index b5c0fd3c49..0f0cf0d9ae 100644 > --- a/blockdev.c > +++ b/blockdev.c > @@ -1665,7 +1665,12 @@ static void external_snapshot_prepare(BlkActionState > *common, > goto out; > } > > - if (state->new_bs->backing != NULL) { > + if (state->new_bs->drv->is_filter) { > + error_setg(errp, "Filters cannot be used as overlays"); > + goto out; > + } > + > + if (bdrv_filtered_cow_child(state->new_bs)) { > error_setg(errp, "The overlay already has a backing image"); > goto out; > } > -- Best regards, Vladimir