From patchwork Thu Mar 11 14:41:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thadeu Lima de Souza Cascardo X-Patchwork-Id: 1451222 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lists.ubuntu.com (client-ip=91.189.94.19; helo=huckleberry.canonical.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=) Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 4DxBTp3JRkz9sRN; Fri, 12 Mar 2021 01:41:33 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.86_2) (envelope-from ) id 1lKMVB-0007Bj-Me; Thu, 11 Mar 2021 14:41:25 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1lKMVA-0007BY-Oa for kernel-team@lists.ubuntu.com; Thu, 11 Mar 2021 14:41:24 +0000 Received: from [179.93.213.27] (helo=localhost.localdomain) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1lKMVA-0000Th-3I for kernel-team@lists.ubuntu.com; Thu, 11 Mar 2021 14:41:24 +0000 From: Thadeu Lima de Souza Cascardo To: kernel-team@lists.ubuntu.com Subject: [SRU Groovy] UBUNTU: SAUCE: Revert "mm: memcg/slab: optimize objcg stock draining" Date: Thu, 11 Mar 2021 11:41:17 -0300 Message-Id: <20210311144117.1175073-1-cascardo@canonical.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" BugLink: https://bugs.launchpad.net/bugs/1918668 This reverts commit 482b2134fda0a74aff66147e777233caede3a0bc, which is commit 3de7d4f25a7438f09fef4e71ef111f1805cd8e7c upstream. It is supposed to fix f2fe7b09a52b ("mm: memcg/slab: charge individual slab objects instead of pages"), which is not present in groovy kernel at all. It leads to NULL pointer derefences like: [ 10.012503] BUG: kernel NULL pointer dereference, address: 0000000000000518 [ 10.030761] #PF: supervisor read access in kernel mode [ 10.042518] #PF: error_code(0x0000) - not-present page [ 10.050165] PGD 0 P4D 0 [ 10.077050] Oops: 0000 [#1] SMP PTI [ 10.081927] CPU: 0 PID: 516 Comm: kexec-load Tainted: G W 5.8.0-45-generic #51 [ 10.092486] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-1 04/01/2014 [ 10.103510] RIP: 0010:__mod_memcg_state.part.0+0xc/0x90 This is possibly caused by a refcount going past 0: [ 5.792689] percpu ref (css_release) <= 0 (-81) after switching to atomic [ 5.792747] WARNING: CPU: 2 PID: 24 at lib/percpu-refcount.c:161 percpu_ref_switch_to_atomic_rcu+0x147/0x160 Signed-off-by: Thadeu Lima de Souza Cascardo Acked-by: Kleber Sacilotto de Souza Acked-by: Tim Gardner --- mm/memcontrol.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index fdfae074ac91..bf0fc20ae20b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2936,7 +2936,9 @@ void __memcg_kmem_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages) if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) page_counter_uncharge(&memcg->kmem, nr_pages); - refill_stock(memcg, nr_pages); + page_counter_uncharge(&memcg->memory, nr_pages); + if (do_memsw_account()) + page_counter_uncharge(&memcg->memsw, nr_pages); } /**