From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by kanga.kvack.org (Postfix) with ESMTP id 5AB748E0001 for ; Tue, 22 Jan 2019 12:19:13 -0500 (EST) Received: by mail-wr1-f69.google.com with SMTP id v16so12456425wru.8 for ; Tue, 22 Jan 2019 09:19:13 -0800 (PST) Received: from Galois.linutronix.de (Galois.linutronix.de. [2a01:7a0:2:106d:700::1]) by mx.google.com with ESMTPS id h133si35824998wmf.41.2019.01.22.09.19.11 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Tue, 22 Jan 2019 09:19:12 -0800 (PST) Date: Tue, 22 Jan 2019 18:19:08 +0100 From: Sebastian Andrzej Siewior Subject: Re: [PATCH] backing-dev: no need to check return value of debugfs_create functions Message-ID: <20190122171908.c7geuvluezkjp3s7@linutronix.de> References: <20190122152151.16139-8-gregkh@linuxfoundation.org> <20190122160759.mx3h7gjc23zmrvxc@linutronix.de> <20190122162503.GB22548@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190122162503.GB22548@kroah.com> Sender: owner-linux-mm@kvack.org List-ID: To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Andrew Morton , Anders Roxell , Arnd Bergmann , Michal Hocko , linux-mm@kvack.org On 2019-01-22 17:25:03 [+0100], Greg Kroah-Hartman wrote: > > > } > > > > > > static void bdi_debug_unregister(struct backing_dev_info *bdi) > > > { > > > - debugfs_remove(bdi->debug_stats); > > > - debugfs_remove(bdi->debug_dir); > > > + debugfs_remove_recursive(bdi->debug_dir); > > > > this won't remove it. > > Which is fine, you don't care. but if you cat the stats file then it will dereference the bdi struct which has been free(), right? > But step back, how could that original call be NULL? That only happens > if you pass it a bad parent dentry (which you didn't), or the system is > totally out of memory (in which case you don't care as everything else > is on fire). debugfs_get_inode() could do -ENOMEM and then the directory creation fails with NULL. > > If you return for "debug_dir == NULL" then it is a nice cleanup. > > No, that's not a valid thing to check for, you should not care as it > will not happen. And if it does happen, it's ok, it's only debugfs, no > one can rely on it, it is only for debugging. It might happen with ENOMEM as of now. It could happen for other reasons in future if the code changes. > thanks, > > greg k-h Sebastian