ext4 crypto: migrate into vfs's crypto engine

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>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index df44c87..4f615cd 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -303,10 +303,10 @@
 	struct inode *inode = file->f_mapping->host;
 
 	if (ext4_encrypted_inode(inode)) {
-		int err = ext4_get_encryption_info(inode);
+		int err = fscrypt_get_encryption_info(inode);
 		if (err)
 			return 0;
-		if (ext4_encryption_info(inode) == NULL)
+		if (!fscrypt_has_encryption_key(inode))
 			return -ENOKEY;
 	}
 	file_accessed(file);
@@ -362,16 +362,16 @@
 		}
 	}
 	if (ext4_encrypted_inode(inode)) {
-		ret = ext4_get_encryption_info(inode);
+		ret = fscrypt_get_encryption_info(inode);
 		if (ret)
 			return -EACCES;
-		if (ext4_encryption_info(inode) == NULL)
+		if (!fscrypt_has_encryption_key(inode))
 			return -ENOKEY;
 	}
 
 	dir = dget_parent(file_dentry(filp));
 	if (ext4_encrypted_inode(d_inode(dir)) &&
-	    !ext4_is_child_context_consistent_with_parent(d_inode(dir), inode)) {
+			!fscrypt_has_permitted_context(d_inode(dir), inode)) {
 		ext4_warning(inode->i_sb,
 			     "Inconsistent encryption contexts: %lu/%lu",
 			     (unsigned long) d_inode(dir)->i_ino,