eCryptfs: Use the ablkcipher crypto API

Make the switch from the blkcipher kernel crypto interface to the
ablkcipher interface.

encrypt_scatterlist() and decrypt_scatterlist() now use the ablkcipher
interface but, from the eCryptfs standpoint, still treat the crypto
operation as a synchronous operation. They submit the async request and
then wait until the operation is finished before they return. Most of
the changes are contained inside those two functions.

Despite waiting for the completion of the crypto operation, the
ablkcipher interface provides performance increases in most cases when
used on AES-NI capable hardware.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Colin King <colin.king@canonical.com>
Reviewed-by: Zeev Zilberman <zeev@annapurnaLabs.com>
Cc: Dustin Kirkland <dustin.kirkland@gazzang.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Ying Huang <ying.huang@intel.com>
Cc: Thieu Le <thieule@google.com>
Cc: Li Wang <dragonylffly@163.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@iki.fi>

fs/ecryptfs/ecryptfs_kernel.h

@@ -38,6 +38,7 @@
 #include <linux/nsproxy.h>
 #include <linux/backing-dev.h>
 #include <linux/ecryptfs.h>
+#include <linux/crypto.h>
 
 #define ECRYPTFS_DEFAULT_IV_BYTES 16
 #define ECRYPTFS_DEFAULT_EXTENT_SIZE 4096
@@ -233,7 +234,7 @@ struct ecryptfs_crypt_stat {
 	size_t extent_shift;
 	unsigned int extent_mask;
 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
-	struct crypto_blkcipher *tfm;
+	struct crypto_ablkcipher *tfm;
 	struct crypto_hash *hash_tfm; /* Crypto context for generating
 				       * the initialization vectors */
 	unsigned char cipher[ECRYPTFS_MAX_CIPHER_NAME_SIZE];