On Sun, Apr 12, 2009 at 07:35, David Zeuthen <zeuthen@xxxxxxxxx> wrote:
> But we'd still need some kind of way of having the kernel tell user
> space what devices are currently claimed by the btrfs filesystem
> instance (and we'd need notifications on changes too). Otherwise we
> don't have enough information for the desktop shell and partitioning
> programs to let the user know that /dev/sdb2 or /dev/sdc1 or whatever
> is currently claimed by the 0:19 btrfs mount at /media/fedora-usb.
>
> One idea is to have a pollable file, /proc/fs/btrfs/devs, that maps
> from the dev_t of the btrfs filesystem instance (as used in
> /proc/self/mountinfo) to the set of dev_t for block devices currently
> claimed? E.g. for the example above we'd have
>
> /proc/fs/btrfs/devs:
> 0:19 8:18
Btrfs used to export some information in /sys/fs/btrfs/, this is
disabled for now. Maybe we can possibly make it export something like:
$ tree /sys/fs/btrfs/
/sys/fs/btrfs/
|-- 969d1386-a002-4c28-94f2-47be23f344e4
| |-- ba1532f3-849b-400b-9c76-2c9aee126c52
| | |-- device -> ../../../devices/.../block/sda/sda3
| | |-- attribute1
| | |-- ...
| `-- 45645656-849b-400b-9c76-2c9aee126c52
| |-- device -> ../../../devices/.../block/sdb/sdb3
| |-- attribute1
| ....
`-- 645645686-a002-4c28-94f2-47be23f344e4
|-- ...
So you could look for a "device" link at the subvolume devices? Or if
that does not fit for some reason, we could also add a "btrfs" class,
to export details about the subvolumes.
Thanks,
Kay
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