16.02.2019 23:26, Andrei Borzenkov пишет: ... >> Difference suggests the order does not matter. Increment suggests it >> does matter. >> >> btrfs sub create A >> cp somestuff A >> btrfs sub snap -r A a.1 >> cp morestuff A >> btrfs sub snap -r A a.2 >> >> The normal case of send is: >> >> btrfs send -p a.1 a.2 >> >> However, is it valid to do? >> >> btrfs send -p a.2 a1 >> > > Of course it is. Stream contains differences between the first and the > second stream, where order does matter. "Incremental" implies temporal > ordering between two snapshots which does not exist on "btrfs send" > level and must be ensured by tools that use "btrfs send/receive". There > is no inherent parent/child or temporal relationship implied by "btrfs > send" itself. "btrfs send" *will* compute differences from a.1 to a.2 > although a.2 is newer than a.1; it is up to you to ensure you apply this > stream to correct base on destination. >
And BTW your example can actually be useful to revert (roll back) content of volume to previous snapshot.
