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=-8.5 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 07F15C282CE for ; Tue, 4 Jun 2019 14:30:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8AFC24999 for ; Tue, 4 Jun 2019 14:30:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727661AbfFDOa0 (ORCPT ); Tue, 4 Jun 2019 10:30:26 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:45294 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727347AbfFDOaZ (ORCPT ); Tue, 4 Jun 2019 10:30:25 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 41343341; Tue, 4 Jun 2019 07:30:25 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2C5B83F690; Tue, 4 Jun 2019 07:30:23 -0700 (PDT) Date: Tue, 4 Jun 2019 15:30:20 +0100 From: Mark Rutland To: Qian Cai , rppt@linux.ibm.com Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, will.deacon@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: <20190604143020.GD24467@lakrids.cambridge.arm.com> References: <1559656836-24940-1-git-send-email-cai@lca.pw> <20190604142338.GC24467@lakrids.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190604142338.GC24467@lakrids.cambridge.arm.com> 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 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. I see that since [1], pgd_alloc() was updated to special-case the init_mm, which is not sufficient for cases like: efi_mm.pgd = pgd_alloc(&efi_mm) ... which occurs in a kthread. So let's have a pgd_alloc_kernel() to make that explicit. Thanks, Mark.