This patch applies the following ext4 patch:

  ext4 crypto: use per-inode tfm structure

As suggested by Herbert Xu, we shouldn't allocate a new tfm each time
we read or write a page.  Instead we can use a single tfm hanging off
the inode's crypt_info structure for all of our encryption needs for
that inode, since the tfm can be used by multiple crypto requests in
parallel.

Also use cmpxchg() to avoid races that could result in crypt_info
structure getting doubly allocated or doubly freed.
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

This patch splits f2fs_crypto_init/exit with two parts: base initialization and
memory allocation.

Firstly, f2fs module declares the base encryption memory pointers.
Then, allocating internal memories is done at the first encrypted inode access.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

This patch integrates the below patch into f2fs.

"ext4 crypto: get rid of ci_mode from struct ext4_crypt_info

The ci_mode field was superfluous, and getting rid of it gets rid of
an unused hole in the structure."
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

This patch integrates the below patch into f2fs.

"ext4 crypto: use slab caches

Use slab caches the ext4_crypto_ctx and ext4_crypt_info structures for
slighly better memory efficiency and debuggability."
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

This patch copies from encrypt_key.c in ext4, and modifies for f2fs.

Use GFP_NOFS, since _f2fs_get_encryption_info is called under f2fs_lock_op.
Signed-off-by: NMichael Halcrow <mhalcrow@google.com>
Signed-off-by: NIldar Muslukhov <muslukhovi@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>