Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754344AbZJGDy2 (ORCPT ); Tue, 6 Oct 2009 23:54:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753691AbZJGDy2 (ORCPT ); Tue, 6 Oct 2009 23:54:28 -0400 Received: from cantor.suse.de ([195.135.220.2]:33313 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753519AbZJGDy1 (ORCPT ); Tue, 6 Oct 2009 23:54:27 -0400 Message-ID: <4ACC111A.8020500@suse.de> Date: Wed, 07 Oct 2009 09:25:06 +0530 From: Suresh Jayaraman User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Hugh Dickins Cc: Rafael Wysocki , Jens Axboe , LKML , Andrew Morton Subject: Re: [PATCH] swapfile: avoid NULL pointer dereference in swapon when s_bdev is NULL References: <4AC1FC41.2060807@suse.de> <4AC492E2.7060205@suse.de> <4AC49B95.2040504@suse.de> In-Reply-To: X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2008 Lines: 46 Hugh Dickins wrote: > On Thu, 1 Oct 2009, Suresh Jayaraman wrote: >> Hugh Dickins wrote: >>> On Thu, 1 Oct 2009, Suresh Jayaraman wrote: >>>> The call sequence is add_to_swap() -> get_swap_page() -> scan_swap_map() >>>> -> discard_swap_cluster() -> blkdev_issue_discard(). >>>> >>>> Wrapping the code around a NULL check fixes the Oops for me. >>> That's odd: scan_swap_map() should only discard_swap_cluster() if >>> SWP_DISCARDABLE got set, and your first patch made sure that it wasn't. >> I forgot to mention, this is not on loopback NFS mount but an remote NFS >> mount (so possibly s_bdev is not NULL) when doing swapon. The oops was >> triggered when memhog program tries to use the swap space on the newly >> created swapfile on NFS. I have not completely investigated the issue, >> perhaps s_bdev is not being set when it ought to be.. > > I'm happy to see your first patch already in 2.6.32-rc3, but still > suspicious of this second patch you sent afterwards. A quick skim > through your patchset suggests 23/31 is probably responsible: Thanks for skimming through those patches. I noticed this already during my review and thought I had already fixed this, but apparently I missed out. I'll test after fixing this and report. > --- mmotm.orig/include/linux/swap.h > +++ mmotm/include/linux/swap.h > @@ -120,6 +120,7 @@ struct swap_extent { > enum { > SWP_USED = (1 << 0), /* is slot in swap_info[] used? */ > SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */ > + SWP_FILE = (1 << 2), /* file swap area */ > SWP_DISCARDABLE = (1 << 2), /* blkdev supports discard */ > SWP_DISCARDING = (1 << 3), /* now discarding a free cluster */ > SWP_SOLIDSTATE = (1 << 4), /* blkdev seeks are cheap */ > > Hugh Thanks, -- Suresh Jayaraman -- 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/