On Wed, May 04, 2016 at 11:20:22PM -0400, Theodore Ts'o wrote:

On Mon, Apr 25, 2016 at 05:15:36PM -0700, Jaegeuk Kim wrote:

quoted

This patch removes the most parts of internal crypto codes.
And then, it modifies and adds some ext4-specific crypt codes to use the generic
facility.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

So I just tried this patch, and one big problem with it is that it
breaks backwards compatibility with existing userspace code, which
assumes that the name of the keys are prefixed with "ext4:".  I see
that in fs/crypto.h you've changed it to be "fscrypto:".  Which is
more general, perhaps, but the problem is that it's not what the
existing shipping code (for example, in the Android N preview release)
and what e2fsprogs's e4crypto is using.

I also worried about that before, but I thought there was no shipped
fs_encryption-enabled product.
Actually, f2fs has the same issue as well, since "f2fs:" was used before. :(

If we want to use fscrypto: as a more general prefix, I could see
doing that, but we need to provide for backwards compatibility ---
which means that at least for ext4, we will need to look for keys
using both the new and old prefix, and we would also want change
e4crypto to set keys with both the "ext4" and the more general
"fscrypto" prefix.

Got it. Let me add (*key_prefix(inode)) in fscrypt_operations so that filesystem
can give a specific prefix additionally.
Once fscrypto supports both of prefixes, does e4crypto have to set "fscrypto"?
The "ext4" should work all the time tho.

Thanks,

Cheers,

					- Ted