This changeset adds extent-based data encryption to fscrypt.
Some filesystems need to encrypt data based on extents, rather than on
inodes, due to features incompatible with inode-based encryption. For
instance, btrfs can have multiple inodes referencing a single block of
data, and moves logical data blocks to different physical locations on
disk in the background.
As per discussion last year in [1] and later in [2], we would like to
allow the use of fscrypt with btrfs, with authenticated encryption. This
is the first step of that work, adding extent-based encryption to
fscrypt; authenticated encryption is the next step. Extent-based
encryption should be usable by other filesystems which wish to support
snapshotting or background data rearrangement also, but btrfs is the
first user.
This changeset requires extent encryption to use inlinecrypt, as
discussed previously. There are two questionable parts: the
forget_extent_info hook is not yet in use by btrfs, as I haven't yet
written a test exercising a race where it would be relevant; and saving
the session key credentials just to enable v1 session-based policies is
perhaps less good than
This applies atop [3], which itself is based on kdave/misc-next. It
passes most encryption fstests with suitable changes to btrfs-progs, but
not generic/580 or generic/595 due to different timing involved in
extent encryption. Tests and btrfs progs updates to follow.
[1] https://docs.google.com/document/d/1janjxewlewtVPqctkWOjSa7OhCgB8Gdx7iDaCDQQNZA/edit?usp=sharing
[2] https://lore.kernel.org/linux-fscrypt/[email protected]/T/#t
[3]
https://lore.kernel.org/linux-fscrypt/[email protected]/