nilfs2: use bgl_lock_ptr()

Simplify nilfs_mdt_bgl_lock() by utilizing bgl_lock_ptr() helper in
<linux/blockgroup_lock.h>.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/mdt.h

@@ -111,7 +111,10 @@ static inline __u64 nilfs_mdt_cno(struct inode *inode)
 	return ((struct the_nilfs *)inode->i_sb->s_fs_info)->ns_cno;
 }
 
-#define nilfs_mdt_bgl_lock(inode, bg) \
-	(&NILFS_MDT(inode)->mi_bgl->locks[(bg) & (NR_BG_LOCKS-1)].lock)
+static inline spinlock_t *
+nilfs_mdt_bgl_lock(struct inode *inode, unsigned int block_group)
+{
+	return bgl_lock_ptr(NILFS_MDT(inode)->mi_bgl, block_group);
+}
 
 #endif /* _NILFS_MDT_H */