new helper: file_inode(file)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
index 6194688..89dc088 100644
--- a/fs/nilfs2/file.c
+++ b/fs/nilfs2/file.c
@@ -67,7 +67,7 @@
 static int nilfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct page *page = vmf->page;
-	struct inode *inode = vma->vm_file->f_dentry->d_inode;
+	struct inode *inode = file_inode(vma->vm_file);
 	struct nilfs_transaction_info ti;
 	int ret = 0;