From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752573Ab3AWWze (ORCPT ); Wed, 23 Jan 2013 17:55:34 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:48964 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752332Ab3AWWz0 (ORCPT ); Wed, 23 Jan 2013 17:55:26 -0500 Date: Wed, 23 Jan 2013 22:55:24 +0000 From: Al Viro To: Mathieu Desnoyers Cc: linux-kernel@vger.kernel.org, Linus Torvalds Subject: [tracepoint] cargo-culting considered harmful... Message-ID: <20130123225523.GY4939@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In samples/tracepoints/tracepoint-probe-sample.c: /* * Here the caller only guarantees locking for struct file and struct inode. * Locking must therefore be done in the probe to use the dentry. */ static void probe_subsys_event(void *ignore, struct inode *inode, struct file *file) { path_get(&file->f_path); dget(file->f_path.dentry); printk(KERN_INFO "Event is encountered with filename %s\n", file->f_path.dentry->d_name.name); dput(file->f_path.dentry); path_put(&file->f_path); } note that * file->f_path is already pinned down by open(), path_get() does not provide anything extra. * file->f_path.dentry is already pinned by open() *and* path_get() just above that dget(). * ->d_name.name *IS* *NOT* *PROTECTED* by pinning dentry down, whether it's done once or thrice. I do realize that it's just an example, but perhaps we should rename that file to match the contents? The only question is whether it should be git mv samples/tracepoints/{tracepoint-probe-sample,cargo-cult}.c or git mv samples cargo-cult... Al, seriously peeved.