Am Mittwoch 01 Dezember 2010 schrieb Mike Hommey: > On Wed, Dec 01, 2010 at 11:01:37AM -0500, Chris Mason wrote: > > Excerpts from C Anthony Risinger's message of 2010-12-01 09:51:55 -0500: > > > On Wed, Dec 1, 2010 at 8:21 AM, Josef Bacik <josef@xxxxxxxxxx> wrote: > > > > === How do we want subvolumes to work from a user perspective? > > > > === > > > > > > > > 1) Users need to be able to create their own subvolumes. Â The > > > > permission semantics will be absolutely the same as creating > > > > directories, so I don't think this is too tricky. Â We want this > > > > because you can only take snapshots of subvolumes, and so it is > > > > important that users be able to create their own discrete > > > > snapshottable targets. > > > > > > > > 2) Users need to be able to snapshot their subvolumes. Â This is > > > > basically the same as #1, but it bears repeating. > > > > > > could it be possible to convert a directory into a volume? or at > > > least base a snapshot off it? > > > > I'm afraid this turns into the same complexity as creating a new > > volume and copying all the files/dirs in by hand. > > Except you wouldn't have to copy data, only metadata. And it could probably be race-free. If I'd cp -reflink or rsync stuff from a real directory to a subvolume and then rename the old directory to an other name and the subvolume to the directory name then I might be missing files that have been created during the copy process and missing changes to files that have been already copied. What I would like is an easy way to make ~/.kde or whatever a subvolume to be able to snapshot it independently while KDE applications or whatever is using and writing to it, *without* any userland even noticing it and without - except for metadata for managing the subvolume - any additional space consumption. So deepdance:/#12> btrfs subvolume create /home/martin/.kde ERROR: '/home/martin/.kde' exists would just make a subvolume out of ~/.kde even if it needs splitting out the tree or even copying the tree data into a new tree. There are other filesystem operations like btrfs filesystem balance that can be expensive as well. All that said from a user point of view. Maybe technical its not feasible. But it would be nice if it can be made feasible without loosing existing advantages. And maybe deepdance:/> btrfs subvolume create . ERROR: '.' exists should really remain this way ;). -- Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7
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