[Btrfs-devel] Selective Compression/Encryption

[Christian Hesse]

Hi there,

Currently compression and I assume if encryption is implemented it is
turned on or off during mount. There are however many times when a user
may want to select which files/directories they want to compress or
encrypt. This will also be helpful when implementing btrfs support in
grub for example. We can say the disk can be compressed/encrypted except
for /boot so compression/encryption doesn't have to be implemented in
grub.

You could just use an additional partition for /boot that has compression an
encryption disabled...

I was thinking of adding this functionality to the userspace application
btrfstune. The way I was thinking of doing this is when btrfstune +c is
applied to a directory or file the directory(and all its contents) or
file will always be compressed reguardless of how the filesystem is
mounted. The opposite would happen when btrfstune -c is used.
Would this be a reasonable thing to implement? Any suggestions before I
start doing this?

Things like compression or encription should be used at the "volume" level.

That was what I said some time ago when I asked why encryption support for
btrfs is planned. On a volume level you can use dm-crypt and the fs can
ignore that part completely.

The answer was that different users on a home partition could use their own
encryption key. That sounds like volume level is out of bet. ;)

So.. if a user wants a specific set of files or dirs ..they should
private_vol
bigarchives_vol
and set those volumes as compressed or encripted volumes
Regarding usability, the best would be for the sub-volume creation
tool to optionally allow passing encription/compression arguments.
should mount those volumes somewhere like: ~/Confidential or ~/Archives.
Basically, do it at the directory level (which in btrfs is at the
sub-volume level).
File-level granularity is totally unmanageable in the long term.
Kind regards,