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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51F8BC4321A for ; Tue, 11 Jun 2019 10:03:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2EFF92089E for ; Tue, 11 Jun 2019 10:03:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405157AbfFKKDy (ORCPT ); Tue, 11 Jun 2019 06:03:54 -0400 Received: from foss.arm.com ([217.140.110.172]:57280 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404889AbfFKKDy (ORCPT ); Tue, 11 Jun 2019 06:03:54 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3292A337; Tue, 11 Jun 2019 03:03:53 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F1B7C3F73C; Tue, 11 Jun 2019 03:05:33 -0700 (PDT) Date: Tue, 11 Jun 2019 11:03:49 +0100 From: Mark Rutland To: Qian Cai , rppt@linux.ibm.com Cc: Will Deacon , akpm@linux-foundation.org, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, mhocko@kernel.org, linux-mm@kvack.org, vdavydov.dev@gmail.com, hannes@cmpxchg.org, cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH -next] arm64/mm: fix a bogus GFP flag in pgd_alloc() Message-ID: <20190611100348.GB26409@lakrids.cambridge.arm.com> References: <1559656836-24940-1-git-send-email-cai@lca.pw> <20190604142338.GC24467@lakrids.cambridge.arm.com> <20190610114326.GF15979@fuggles.cambridge.arm.com> <1560187575.6132.70.camel@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1560187575.6132.70.camel@lca.pw> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 10, 2019 at 01:26:15PM -0400, Qian Cai wrote: > On Mon, 2019-06-10 at 12:43 +0100, Will Deacon wrote: > > On Tue, Jun 04, 2019 at 03:23:38PM +0100, Mark Rutland wrote: > > > On Tue, Jun 04, 2019 at 10:00:36AM -0400, Qian Cai wrote: > > > > The commit "arm64: switch to generic version of pte allocation" > > > > introduced endless failures during boot like, > > > > > > > > kobject_add_internal failed for pgd_cache(285:chronyd.service) (error: > > > > -2 parent: cgroup) > > > > > > > > It turns out __GFP_ACCOUNT is passed to kernel page table allocations > > > > and then later memcg finds out those don't belong to any cgroup. > > > > > > Mike, I understood from [1] that this wasn't expected to be a problem, > > > as the accounting should bypass kernel threads. > > > > > > Was that assumption wrong, or is something different happening here? > > > > > > > > > > > backtrace: > > > >   kobject_add_internal > > > >   kobject_init_and_add > > > >   sysfs_slab_add+0x1a8 > > > >   __kmem_cache_create > > > >   create_cache > > > >   memcg_create_kmem_cache > > > >   memcg_kmem_cache_create_func > > > >   process_one_work > > > >   worker_thread > > > >   kthread > > > > > > > > Signed-off-by: Qian Cai > > > > --- > > > >  arch/arm64/mm/pgd.c | 2 +- > > > >  1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/arch/arm64/mm/pgd.c b/arch/arm64/mm/pgd.c > > > > index 769516cb6677..53c48f5c8765 100644 > > > > --- a/arch/arm64/mm/pgd.c > > > > +++ b/arch/arm64/mm/pgd.c > > > > @@ -38,7 +38,7 @@ pgd_t *pgd_alloc(struct mm_struct *mm) > > > >   if (PGD_SIZE == PAGE_SIZE) > > > >   return (pgd_t *)__get_free_page(gfp); > > > >   else > > > > - return kmem_cache_alloc(pgd_cache, gfp); > > > > + return kmem_cache_alloc(pgd_cache, GFP_PGTABLE_KERNEL); > > > > > > This is used to allocate PGDs for both user and kernel pagetables (e.g. > > > for the efi runtime services), so while this may fix the regression, I'm > > > not sure it's the right fix. > > > > > > Do we need a separate pgd_alloc_kernel()? > > > > So can I take the above for -rc5, or is somebody else working on a different > > fix to implement pgd_alloc_kernel()? > > The offensive commit "arm64: switch to generic version of pte allocation" is not > yet in the mainline, but only in the Andrew's tree and linux-next, and I doubt > Andrew will push this out any time sooner given it is broken. I'd assumed that Mike would respin these patches to implement and use pgd_alloc_kernel() (or take gfp flags) and the updated patches would replace these in akpm's tree. Mike, could you confirm what your plan is? I'm happy to review/test updated patches for arm64. Thanks, Mark.