On Fri, Mar 04, 2016 at 10:58:15AM +0800, Anand Jain wrote: > > > On 04/18/2015 01:29 AM, David Sterba wrote: > > On Fri, Apr 17, 2015 at 09:19:11AM +0000, Hugo Mills wrote: > >>> In, some article i read that future there will be more chunk tree/ extent > >>> tree for single btrfs. Is this true. > >> > >> I recall, many moons ago, Chris saying that there probably wouldn't > >> be. > > > > More extent trees tied to a set of fs trees/subvolumes would be very > > useful for certain usecases *cough*encryption*cough*. > > I didn't understand in full what's the idea here, but let met try.. > would it not defeat the purpose of encryption which is not to let > disk have the un-encrypted data ? Looks like I am missing something > here. Depends how the encryption is designed. The separate extent trees would allow to have mixed data in the filesystem, encrypted or not. I can start with a normal filesystem, and then create encrypted subvolumes any time later. The idea of multiple extent trees: Currently we have only one, all subvolume share the extent tree, can do reflinks freely. We can create a subvolume (S1) and ask for a separate extent tree (E1). Now we can create snapshots of S1 that would share E1, and reflink accross snapshots that share E1. Why is this useful to encryption: all data _and_ metadata blocks tied to E1 and the attached subvolums are encrypted, the plain text is not accessible without the key. But the separate extent trees are useful on itself. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
