Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759946AbXIZQOq (ORCPT ); Wed, 26 Sep 2007 12:14:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753516AbXIZQOj (ORCPT ); Wed, 26 Sep 2007 12:14:39 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:41908 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751688AbXIZQOi (ORCPT ); Wed, 26 Sep 2007 12:14:38 -0400 Subject: Re: missing mnt_drop_write() on open error From: Dave Hansen To: Miklos Szeredi Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Christoph Hellwig In-Reply-To: References: <1190769669.26982.325.camel@localhost> Content-Type: text/plain Date: Wed, 26 Sep 2007 09:14:32 -0700 Message-Id: <1190823272.30530.16.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2124 Lines: 48 On Wed, 2007-09-26 at 10:38 +0200, Miklos Szeredi wrote: > > On Wed, 2007-09-26 at 01:14 +0200, Miklos Szeredi wrote: > > > I get this at umount, if there was a failed open(): > > > > > > WARNING: at fs/namespace.c:586 __mntput() > > > > > > I think the problem is that may_open() calls mnt_want_write(), but if > > > open doesn't succeed, mnt_drop_write() will not be called. > > > > Does this help? > > It didn't fix it for me, but the patch looks OK. > > In __dentry_open() there's still a few places where fput() won't be > called, notably when ->open fails, which is what I'm triggering I > think. > > Also even more horrible things can happen because of the > nd->intent.open.file thing. For example if the lookup routine calls > lookup_instantiate_filp(), and after this, but before may_open() some > error happens, then release_open_intent() will call fput() on the > file, which will cause mnt_drop_write() to be called, even though a > matching mnt_want_write() hasn't yet been called. Ugly, eh? I used to have a patch that didn't completely trust that all files with FMODE_WRITE set to have taken a write on the mnt. I think I used a flag to indicate whether or not a particular file had a mnt_want_write() done on its behalf. It somewhat artificially keeps the mnt write count balanced, but I think it will let us detect when things like this go on. > > I'm also thinking that we should change the open_namei* > > functions to simply return 'struct file *'. Those are the only users > > other than NFS, and forcing the return of a file like that will force > > users to do the fput() on it if they don't want it any more. We'd just > > need to make sure no new may_open() users pop up. Any thoughts on that? > > Yeah, something needs to be done with open, because currently it's way > too convoluted. Sounds like Christoph has some ideas... -- Dave - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/