From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Subject: Re: linux-next: Tree for Jun 26 [ vfs | block | fuse (cpuidle) releated? ] Date: Wed, 26 Jun 2013 17:24:46 +0200 Message-ID: <20130626172446.51f0bd5f@skate> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org To: sedat.dilek@gmail.com Cc: linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, Al Viro , Jens Axboe , linux-fsdevel , Miklos Szeredi , fuse-devel@lists.sourceforge.net, Stephen Rothwell , Arnd Bergmann , Greg Kroah-Hartman List-Id: linux-next.vger.kernel.org Dear Sedat Dilek, On Wed, 26 Jun 2013 16:50:55 +0200, Sedat Dilek wrote: > [ TO/CC char-misc folks ] > > The CULPRIT commit [1] due to my git-bisecting is: > > commit 585d98e00ba7a5e2abe65f7a1eff631cb612289b > "char: misc: assign file->private_data in all cases" > > After reverting it, my system boots up fine again. > > Can someone from the char-misc folks look at that? Ok. My understanding is that the misc device registered by fs/fuse/dev.c:fuse_dev_init() makes the assumption that file->private_data == NULL when a misc device is opened. But I'm not sure to fully understand the code flow of the FUSE filesystem. And since it doesn't provide its own implementation of the ->open() operation, the misc infrastructure was leaving the file->private_data defined to NULL before my patch. With my patch, the file->private_data gets assigned unconditionally (regardless of whether the misc driver provides or does not provide a ->open() operation) which modifies the unwritten assumption that fuse was making about the initial value of file->private_data. I believe the assumption made by fuse over the initial value of this variable is a bit fragile. Maybe the FUSE code needs to be slightly adjusted to not make this assumption? Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com