ext4: don't fail remount if journalling mode didn't change

Switching to the new mount api introduced inconsistency in how the
journalling mode mount option (data=) is handled during a remount.

Ext4 always prevented changing the journalling mode during the remount,
however the new code always fails the remount when the journalling mode
is specified, even if it remains unchanged. Fix it.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Fixes: cebe85d ("ext4: switch to the new mount api")
Link: https://lore.kernel.org/r/20211220152657.101599-1-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -2155,19 +2155,22 @@ static int unnote_qf_name(struct fs_context *fc, int qtype)
 #endif
 
 #define EXT4_SET_CTX(name)						\
-static inline void ctx_set_##name(struct ext4_fs_context *ctx, int flag)\
+static inline void ctx_set_##name(struct ext4_fs_context *ctx,		\
+				  unsigned long flag)			\
 {									\
 	ctx->mask_s_##name |= flag;					\
 	ctx->vals_s_##name |= flag;					\
 }									\
-static inline void ctx_clear_##name(struct ext4_fs_context *ctx, int flag)\
+static inline void ctx_clear_##name(struct ext4_fs_context *ctx,	\
+				    unsigned long flag)			\
 {									\
 	ctx->mask_s_##name |= flag;					\
 	ctx->vals_s_##name &= ~flag;					\
 }									\
-static inline bool ctx_test_##name(struct ext4_fs_context *ctx, int flag)\
+static inline unsigned long						\
+ctx_test_##name(struct ext4_fs_context *ctx, unsigned long flag)	\
 {									\
-	return ((ctx->vals_s_##name & flag) != 0);			\
+	return (ctx->vals_s_##name & flag);				\
 }									\
 
 EXT4_SET_CTX(flags);
@@ -2828,7 +2831,8 @@ static int ext4_check_opt_consistency(struct fs_context *fc,
 				 "Remounting file system with no journal "
 				 "so ignoring journalled data option");
 			ctx_clear_mount_opt(ctx, EXT4_MOUNT_DATA_FLAGS);
-		} else if (ctx->mask_s_mount_opt & EXT4_MOUNT_DATA_FLAGS) {
+		} else if (ctx_test_mount_opt(ctx, EXT4_MOUNT_DATA_FLAGS) !=
+			   test_opt(sb, DATA_FLAGS)) {
 			ext4_msg(NULL, KERN_ERR, "Cannot change data mode "
 				 "on remount");
 			return -EINVAL;