nilfs2: separate initializer of metadata file inode

This separates a part of initialization code of metadata file inode,
and makes it available from the nilfs iget function that a later patch
will add to.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/mdt.h b/fs/nilfs2/mdt.h
index 6c4bbb0..f445602 100644
--- a/fs/nilfs2/mdt.h
+++ b/fs/nilfs2/mdt.h
@@ -76,10 +76,12 @@
 int nilfs_mdt_mark_block_dirty(struct inode *, unsigned long);
 int nilfs_mdt_fetch_dirty(struct inode *);
 
+int nilfs_mdt_init(struct inode *inode, struct the_nilfs *nilfs,
+		   gfp_t gfp_mask, size_t objsz);
 struct inode *nilfs_mdt_new(struct the_nilfs *, struct super_block *, ino_t,
 			    size_t);
 struct inode *nilfs_mdt_new_common(struct the_nilfs *, struct super_block *,
-				   ino_t, gfp_t, size_t);
+				   ino_t);
 void nilfs_mdt_destroy(struct inode *);
 void nilfs_mdt_set_entry_size(struct inode *, unsigned, unsigned);
 void nilfs_mdt_set_shadow(struct inode *, struct inode *);