[PATCH] BTRFS-PROG: recursively subvolume snapshot and delete

[Goffredo Baroncelli <kreijack@gmail.com>]

Hi All,

the following patches implement the recursively snapshotting and
deleting of a subvolume. 

To snapshot recursively you must pass the -R switch:

# btrfs subvolume create sub1
Create subvolume './sub1'
# btrfs subvolume create sub1/sub2
Create subvolume 'sub1/sub2'

# btrfs subvolume snapshot -R sub1 sub1-snap
Create a snapshot of 'sub1' in './sub1-snap'
Create a snapshot of 'sub1/sub2' in './sub1-snap/sub2'

To recursively delete subvolumes, you must pass the switch '-R':

# btrfs subvolume create sub1
Create subvolume './sub1'
# btrfs subvolume create sub1/sub2
Create subvolume 'sub1/sub2'

# btrfs subvolume delete -R sub1
Delete subvolume '/root/sub1/sub2'
Delete subvolume '/root/sub1'


Some caveats:
1) the recursively behaviour need the root capability
This because how the subvolume are discovered

2) it is not possible to recursively snapshot a subvolume
in read-only mode
This because when a subvolume is snapshotted, its 
nested subvolumes appear as directory in the snapshot.
These directories are removed before snapshotting the 
nested subvolumes. This is incompatible with a read
only subvolume.

BR
G.Baroncelli