diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 9926a1d6..70e8613 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -367,17 +367,12 @@
 
 	down_write(&nilfs->ns_sem);
 	if (!(sb->s_flags & MS_RDONLY)) {
-		struct nilfs_super_block **sbp = nilfs->ns_sbp;
-		u64 t = get_seconds();
-		int dupsb;
-
-		if (!nilfs_discontinued(nilfs) && t >= nilfs->ns_sbwtime[0] &&
-		    t < nilfs->ns_sbwtime[0] + NILFS_SB_FREQ) {
+		if (!nilfs_discontinued(nilfs) &&
+		    !nilfs_sb_need_update(nilfs)) {
 			up_write(&nilfs->ns_sem);
 			return;
 		}
-		dupsb = sbp[1] && t > nilfs->ns_sbwtime[1] + NILFS_ALTSB_FREQ;
-		nilfs_commit_super(sbi, dupsb);
+		nilfs_commit_super(sbi, nilfs_altsb_need_update(nilfs));
 	}
 	sb->s_dirt = 0;
 	up_write(&nilfs->ns_sem);
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index fa3a1df..68e9626 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -200,6 +200,20 @@
 #define NILFS_SB_FREQ		10
 #define NILFS_ALTSB_FREQ	60  /* spare superblock */
 
+static inline int nilfs_sb_need_update(struct the_nilfs *nilfs)
+{
+	u64 t = get_seconds();
+	return t < nilfs->ns_sbwtime[0] ||
+		 t > nilfs->ns_sbwtime[0] + NILFS_SB_FREQ;
+}
+
+static inline int nilfs_altsb_need_update(struct the_nilfs *nilfs)
+{
+	u64 t = get_seconds();
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	return sbp[1] && t > nilfs->ns_sbwtime[1] + NILFS_ALTSB_FREQ;
+}
+
 void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);
 struct the_nilfs *find_or_create_nilfs(struct block_device *);
 void put_nilfs(struct the_nilfs *);