bdrv_append() is not quite good for inserting filters: it does extra
permission update in intermediate state, where filter get it filtered
child but is not yet replace it in a backing chain.
Some filters (for example backup-top) may want permissions even when
have no parents. And described intermediate state becomes invalid.
That's (half a) reason, why we need "inactive" state for backup-top
filter.
bdrv_append() will be improved later, now let's add a unit test.
Now test fails, so it runs only with -d flag. To run do
./test-bdrv-graph-mod -d -p /bdrv-graph-mod/append-greedy-filter
from <build-directory>/tests.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210428151804.439460-4-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
