From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71586C433F5 for ; Tue, 12 Oct 2021 23:22:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F5B660F11 for ; Tue, 12 Oct 2021 23:22:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235469AbhJLXY7 (ORCPT ); Tue, 12 Oct 2021 19:24:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:46014 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229588AbhJLXY6 (ORCPT ); Tue, 12 Oct 2021 19:24:58 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id DC82E60E0C; Tue, 12 Oct 2021 23:22:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1634080976; bh=19NERmz1OqKhIhpjNbFrKpQAyB+6CWRvPQ5u6HEy1lg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eZQXhhZqPtEhDAbDT69+mDQw8CryvBAxGrDUcNYq+M5YfmJkgPp51lyCcAzgMtZEt 7TbOEw0t0kMIbkf3Z5bSlywAm9JONFZB5KB1TNf7yLezBFhHrV1fc6vdPbRteHtvJi nnhMhvvvMPaaBKjRWb37CLwCxyOnj0GYxS30cro3ff2RuT64lKd5aEzH6Yd+up3OaH HQVGdst1F0TFZ9vO5MpC4Th1gmnarMLVmZ3qzDvsAammTQomu51Lm/h8YoIxo6gwi0 Xzo8Gn/yQ1XN4VSJ7a3hFIVcM2lEAqgwGj/+siE20Dz8VVFusSRxHmWdVH/pXc+ZrH 5kNamSSFyjrFQ== Date: Tue, 12 Oct 2021 16:22:55 -0700 From: "Darrick J. Wong" To: Vlastimil Babka Cc: David Rientjes , Rustam Kovhaev , Dave Chinner , linux-xfs@vger.kernel.org, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, Al Viro , dvyukov@google.com Subject: Re: [PATCH] xfs: use kmem_cache_free() for kmem_cache objects Message-ID: <20211012232255.GS24307@magnolia> References: <20210929212347.1139666-1-rkovhaev@gmail.com> <20210930044202.GP2361455@dread.disaster.area> <17f537b3-e2eb-5d0a-1465-20f3d3c960e2@suse.cz> <1e0df91-556e-cee5-76f7-285d28fe31@google.com> <20211012204320.GP24307@magnolia> <20211012204345.GQ24307@magnolia> <9db5d16a-2999-07a4-c49d-7417601f834f@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9db5d16a-2999-07a4-c49d-7417601f834f@suse.cz> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 12, 2021 at 11:32:25PM +0200, Vlastimil Babka wrote: > On 10/12/2021 10:43 PM, Darrick J. Wong wrote: > > On Tue, Oct 12, 2021 at 01:43:20PM -0700, Darrick J. Wong wrote: > >> On Sun, Oct 03, 2021 at 06:07:20PM -0700, David Rientjes wrote: > >>> On Thu, 30 Sep 2021, Rustam Kovhaev wrote: > >>> > >>>>>>> I think it's fair if something like XFS (not meant for tiny systems AFAIK?) > >>>>>>> excludes SLOB (meant for tiny systems). Clearly nobody tried to use these > >>>>>>> two together last 5 years anyway. > >>>>>> > >>>>>> +1 for adding Kconfig option, it seems like some things are not meant to > >>>>>> be together. > >>>>> > >>>>> But if we patch SLOB, we won't need it. > >>>> > >>>> OK, so we consider XFS on SLOB a supported configuration that might be > >>>> used and should be tested. > >>>> I'll look into maybe adding a config with CONFIG_SLOB and CONFIG_XFS_FS > >>>> to syzbot. > >>>> > >>>> It seems that we need to patch SLOB anyway, because any other code can > >>>> hit the very same issue. > >>>> > >>> > >>> It's probably best to introduce both (SLOB fix and Kconfig change for > >>> XFS), at least in the interim because the combo of XFS and SLOB could be > >>> broken in other ways. If syzbot doesn't complain with a patched kernel to > >>> allow SLOB to be used with XFS, then we could potentially allow them to be > >>> used together. > >>> > >>> (I'm not sure that this freeing issue is the *only* thing that is broken, > >>> nor that we have sufficient information to make that determination right > >>> now..) > >> > >> I audited the entire xfs (kernel) codebase and didn't find any other > >> usage errors. Thanks for the patch; I'll apply it to for-next. > > Which patch, the one that started this thread and uses kmem_cache_free() instead > of kfree()? I thought we said it's not the best way? It's probably better to fix slob to be able to tell that a kmem_free'd object actually belongs to a cache and should get freed that way, just like its larger sl[ua]b cousins. However, even if that does come to pass, anybody /else/ who wants to start(?) using XFS on a SLOB system will need this patch to fix the minor papercut. Now that I've checked the rest of the codebase, I don't find it reasonable to make XFS mutually exclusive with SLOB over two instances of slab cache misuse. Hence the RVB. :) --D > > Also, the obligatory > > > > Reviewed-by: Darrick J. Wong > > > > --D > > > >> > >> --D >