do_last(): collapse the call of path_to_nameidata()

... and shift filling struct path to just before the call of
handle_mounts().  All callers of handle_mounts() are
immediately preceded by path->mnt = nd->path.mnt now.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -3362,8 +3362,6 @@ static int do_last(struct nameidata *nd,
 		error = PTR_ERR(dentry);
 		goto out;
 	}
-	path.mnt = nd->path.mnt;
-	path.dentry = dentry;
 
 	if (file->f_mode & FMODE_OPENED) {
 		if ((file->f_mode & FMODE_CREATED) ||
@@ -3380,7 +3378,8 @@ static int do_last(struct nameidata *nd,
 		open_flag &= ~O_TRUNC;
 		will_truncate = false;
 		acc_mode = 0;
-		path_to_nameidata(&path, nd);
+		dput(nd->path.dentry);
+		nd->path.dentry = dentry;
 		goto finish_open_created;
 	}
 
@@ -3394,6 +3393,8 @@ static int do_last(struct nameidata *nd,
 		got_write = false;
 	}
 
+	path.mnt = nd->path.mnt;
+	path.dentry = dentry;
 	error = handle_mounts(&path, nd, &inode, &seq);
 	if (unlikely(error < 0))
 		return error;