f2fs: use the updated test_dummy_encryption helper functions

Switch f2fs over to the functions that are replacing
fscrypt_set_test_dummy_encryption().  Since f2fs hasn't been converted
to the new mount API yet, this doesn't really provide a benefit for
f2fs.  But it allows fscrypt_set_test_dummy_encryption() to be removed.

Also take the opportunity to eliminate an #ifdef.
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -8,6 +8,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/fs.h>
+#include <linux/fs_context.h>
 #include <linux/sched/mm.h>
 #include <linux/statfs.h>
 #include <linux/buffer_head.h>
@@ -492,9 +493,19 @@ static int f2fs_set_test_dummy_encryption(struct super_block *sb,
 					  bool is_remount)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(sb);
-#ifdef CONFIG_FS_ENCRYPTION
+	struct fs_parameter param = {
+		.type = fs_value_is_string,
+		.string = arg->from ? arg->from : "",
+	};
+	struct fscrypt_dummy_policy *policy =
+		&F2FS_OPTION(sbi).dummy_enc_policy;
 	int err;
 
+	if (!IS_ENABLED(CONFIG_FS_ENCRYPTION)) {
+		f2fs_warn(sbi, "test_dummy_encryption option not supported");
+		return -EINVAL;
+	}
+
 	if (!f2fs_sb_has_encrypt(sbi)) {
 		f2fs_err(sbi, "Encrypt feature is off");
 		return -EINVAL;
@@ -506,12 +517,12 @@ static int f2fs_set_test_dummy_encryption(struct super_block *sb,
 	 * needed to allow it to be set or changed during remount.  We do allow
 	 * it to be specified during remount, but only if there is no change.
 	 */
-	if (is_remount && !F2FS_OPTION(sbi).dummy_enc_policy.policy) {
+	if (is_remount && !fscrypt_is_dummy_policy_set(policy)) {
 		f2fs_warn(sbi, "Can't set test_dummy_encryption on remount");
 		return -EINVAL;
 	}
-	err = fscrypt_set_test_dummy_encryption(
-		sb, arg->from, &F2FS_OPTION(sbi).dummy_enc_policy);
+
+	err = fscrypt_parse_test_dummy_encryption(&param, policy);
 	if (err) {
 		if (err == -EEXIST)
 			f2fs_warn(sbi,
@@ -524,12 +535,14 @@ static int f2fs_set_test_dummy_encryption(struct super_block *sb,
 				  opt, err);
 		return -EINVAL;
 	}
+	err = fscrypt_add_test_dummy_key(sb, policy);
+	if (err) {
+		f2fs_warn(sbi, "Error adding test dummy encryption key [%d]",
+			  err);
+		return err;
+	}
 	f2fs_warn(sbi, "Test dummy encryption mode enabled");
 	return 0;
-#else
-	f2fs_warn(sbi, "test_dummy_encryption option not supported");
-	return -EINVAL;
-#endif
 }
 
 #ifdef CONFIG_F2FS_FS_COMPRESSION