f2fs: introduce f2fs_journal struct to wrap journal info

Introduce a new structure f2fs_journal to wrap journal info in struct
f2fs_summary_block for readability.

struct f2fs_journal {
	union {
		__le16 n_nats;
		__le16 n_sits;
	};
	union {
		struct nat_journal nat_j;
		struct sit_journal sit_j;
		struct f2fs_extra_info info;
	};
} __packed;

struct f2fs_summary_block {
	struct f2fs_summary entries[ENTRIES_IN_SUM];
	struct f2fs_journal journal;
	struct summary_footer footer;
} __packed;

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index f43e6a0..9eb215a 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -398,9 +398,7 @@
 	__u8 reserved[EXTRA_INFO_RESERVED];
 } __packed;
 
-/* 4KB-sized summary block structure */
-struct f2fs_summary_block {
-	struct f2fs_summary entries[ENTRIES_IN_SUM];
+struct f2fs_journal {
 	union {
 		__le16 n_nats;
 		__le16 n_sits;
@@ -411,6 +409,12 @@
 		struct sit_journal sit_j;
 		struct f2fs_extra_info info;
 	};
+} __packed;
+
+/* 4KB-sized summary block structure */
+struct f2fs_summary_block {
+	struct f2fs_summary entries[ENTRIES_IN_SUM];
+	struct f2fs_journal journal;
 	struct summary_footer footer;
 } __packed;