vfs: add file_path() helper

Turn
	d_path(&file->f_path, ...);
into
	file_path(file, ...);

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/open.c

diff --git a/fs/open.c b/fs/open.c
index b1c5823..1dbc793 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -823,6 +823,12 @@
 }
 EXPORT_SYMBOL(finish_no_open);
 
+char *file_path(struct file *filp, char *buf, int buflen)
+{
+	return d_path(&filp->f_path, buf, buflen);
+}
+EXPORT_SYMBOL(file_path);
+
 /**
  * vfs_open - open the file at the given path
  * @path: path to open