On Wed, May 5, 2010 at 6:28 PM, Isaac Dupree <ml@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > On 05/05/10 19:10, C Anthony Risinger wrote: >> >> subvolumes can be mounted two ways via a mount option: >> >> 1) subvol=<subvolume_name> >> 2) subvol=<subvolume_id> >> >> 1 can only be used if the subvolume is in the root of the FS, i.e. >> /__active would work, but /root/__active would NOT... the mount option >> cannot have slashes and i don't know if this will change. > > since we control the structure, why not the (slightly uglier) > > /root__active > /root__rollback > /root__20090807 > /home__active > /home__... > > just remove the slashes or replace them with some other character like dash > or underscore. `ls` will still sort things alphabetically so there will > still be some semblance of order for the humans, and it would behave nearly > the same to the machine. And it will be easier for debugging purposes if > all these subvolumes are accessible by name. (Do you think you can ask > upstream whether they want to change or keep the restriction on slashes(i.e. > volumes in subdirectories), in light of our '.' organizational ideas?) ah, yeah thanks, i meant to mention that too but got lost in the myriad of letters i had written :). this would work just fine, and has the benefit of working on pretty much any recent-ish kernel/btrfs version. the end user should never see any of this anyway. iirc, this is how fedora does it (something like yum_snapshot_20090807). but fedora installs into the default "." subvolume, so each time you take a snapshot you get a bunch of empty folders from previous snapshots (the snapshot yum_snapshot_20090808 would have an empty folder yum_snapshot_20090807 [snapshots not recursive]); we can stop this by not installing into the "." subvolume and using an actual mount point for operations, plus it keep the real root "device" (root__active) nice and clean. as for upstream, they are pretty receptive to changes right now. im not sure if the slash thing is a limit of the mount command/something else, or just was not implemented. afiak, the <id> mounting was implemented to replace the name mounting [and for setting a new default], i'm not sure if <name> mounting will be dropped or not. also even if they did implement, we prob wouldn't see it until 2.6.35 :(. any other ideas besides rollbacks and an original snapshot that btrfs could be used for? C Anthony
