20.09.2019 18:27, Max Reitz wrote: > There is no good reason why we would allow external snapshots only on > the first non-filter node in a chain. Parent BDSs should not care > whether their child is replaced by a snapshot. (If they do care, they > should announce that via freezing the chain, which is checked in > bdrv_append() through bdrv_set_backing_hd().) > > Before we had bdrv_is_first_non_filter() here (since 212a5a8f095), there > was a special function bdrv_check_ext_snapshot() that allowed snapshots > by default, but block drivers could override this. Only blkverify did > so, however. > > It is not clear to me why blkverify would do so; maybe just so that the > testee block driver would not be replaced. The introducing commit > f6186f49e2c does not explain why. Maybe because 08b24cfe376 would have > been the correct solution? (Which adds a .supports_backing check.) > > Signed-off-by: Max Reitz<mre...@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> -- Best regards, Vladimir
