Some fields are only used when the crypto_ctx is being used on the
read path, some are only used on the write path, and some are only
used when the structure is on free list. Optimize memory use by using
a union.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This takes code from fs/mpage.c and optimizes it for ext4. Its
primary reason is to allow us to more easily add encryption to ext4's
read path in an efficient manner.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>