nilfs2: always set back pointer to host inode in mapping->host

In the current nilfs, page cache for btree nodes and meta data files
do not set a valid back pointer to the host inode in mapping->host.

This will change it so that every address space in nilfs uses
mapping->host to hold its host inode.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/page.h b/fs/nilfs2/page.h
index f827afa..e301e56 100644
--- a/fs/nilfs2/page.h
+++ b/fs/nilfs2/page.h
@@ -57,7 +57,7 @@
 int nilfs_copy_dirty_pages(struct address_space *, struct address_space *);
 void nilfs_copy_back_pages(struct address_space *, struct address_space *);
 void nilfs_clear_dirty_pages(struct address_space *);
-void nilfs_mapping_init(struct address_space *mapping,
+void nilfs_mapping_init(struct address_space *mapping, struct inode *inode,
 			struct backing_dev_info *bdi);
 unsigned nilfs_page_count_clean_buffers(struct page *, unsigned, unsigned);
 unsigned long nilfs_find_uncommitted_extent(struct inode *inode,