Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754581AbYHOABU (ORCPT ); Thu, 14 Aug 2008 20:01:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751424AbYHOABM (ORCPT ); Thu, 14 Aug 2008 20:01:12 -0400 Received: from extu-mxob-2.symantec.com ([216.10.194.135]:59801 "EHLO extu-mxob-2.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751379AbYHOABL (ORCPT ); Thu, 14 Aug 2008 20:01:11 -0400 Date: Fri, 15 Aug 2008 01:00:54 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.site To: Johannes Weiner cc: Jeremy Fitzhardinge , Ian Campbell , linux-kernel@vger.kernel.org, Kel Modderman , Markus Armbruster , Peter Zijlstra Subject: Re: kernel BUG at lib/radix-tree.c:473! In-Reply-To: <871w0r5gw8.fsf@skyscraper.fehenstaub.lan> Message-ID: References: <1218697362.26014.9.camel@localhost.localdomain> <48A48879.2000309@goop.org> <48A4AC01.7040402@goop.org> <871w0r5gw8.fsf@skyscraper.fehenstaub.lan> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1563 Lines: 32 On Fri, 15 Aug 2008, Johannes Weiner wrote: > Jeremy Fitzhardinge writes: > > Hugh Dickins wrote: > > > >> An additional useful input would be: what happens if you replace > >> that /dev/fb0 by a symlink /dev/fb0 pointing to an fb0 device node in > >> one of your disk filesystems? I rather expect that to cause the same > >> trouble, which would argue that the driver is wrong and shmem right. > > > > I don't follow. Do you mean make /dev/fb0 a plain file on a > > filesystem? Or make it a disk device node? Something else? > > Creating a device node on a different filesystem to see if the driver > only worked with the safe shmem set_page_dirty and now breaks due to > exposure to the generic version. Or if the driver works with the > generic version through other mappings and the shmem code screws it up > somewhere else. Yes, that's it. I think it was ext2 I referred to, when I worried about this when making the change to tmpfs; and my reading of it was that ext2 left a device node's a_ops unset, as I was changing tmpfs to do. (Looking at it again, ext2 doesn't even specify its .set_page_dirty, so even if it had assigned an a_ops, it wouldn't have avoided the default behaviour.) But I'd like to hear what actually happens in practice, rather than relying on my reading. Hugh -- 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/