f2fs: introduce f2fs_change_bit to simplify the change bit logic

Introduce f2fs_change_bit to simplify the change bit logic in
function set_to_next_nat{sit}.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1073,6 +1073,15 @@ static inline int f2fs_clear_bit(unsigned int nr, char *addr)
 	return ret;
 }
 
+static inline void f2fs_change_bit(unsigned int nr, char *addr)
+{
+	int mask;
+
+	addr += (nr >> 3);
+	mask = 1 << (7 - (nr & 0x07));
+	*addr ^= mask;
+}
+
 /* used for f2fs_inode_info->flags */
 enum {
 	FI_NEW_INODE,		/* indicate newly allocated inode */

fs/f2fs/node.h

@@ -192,10 +192,7 @@ static inline void set_to_next_nat(struct f2fs_nm_info *nm_i, nid_t start_nid)
 {
 	unsigned int block_off = NAT_BLOCK_OFFSET(start_nid);
 
-	if (f2fs_test_bit(block_off, nm_i->nat_bitmap))
-		f2fs_clear_bit(block_off, nm_i->nat_bitmap);
-	else
-		f2fs_set_bit(block_off, nm_i->nat_bitmap);
+	f2fs_change_bit(block_off, nm_i->nat_bitmap);
 }
 
 static inline void fill_node_footer(struct page *page, nid_t nid,

fs/f2fs/segment.h

@@ -657,10 +657,7 @@ static inline void set_to_next_sit(struct sit_info *sit_i, unsigned int start)
 {
 	unsigned int block_off = SIT_BLOCK_OFFSET(start);
 
-	if (f2fs_test_bit(block_off, sit_i->sit_bitmap))
-		f2fs_clear_bit(block_off, sit_i->sit_bitmap);
-	else
-		f2fs_set_bit(block_off, sit_i->sit_bitmap);
+	f2fs_change_bit(block_off, sit_i->sit_bitmap);
 }
 
 static inline unsigned long long get_mtime(struct f2fs_sb_info *sbi)