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=-4.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 68A56C433DF for ; Fri, 26 Jun 2020 03:29:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43DA9208C7 for ; Fri, 26 Jun 2020 03:29:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593142191; bh=gJqVhnGNRkoppN0akj2ko9FC074SEW8dDzmzxOpPOyw=; h=Date:From:To:Subject:In-Reply-To:List-ID:From; b=AULL++TKyrJiv3ys7f911TIb9k3npKjaXG47vv7XF1+ihco/xTOLwtbommJbGaorD qHWZh5NwFN//vFBnTxWajSsY9GmrbKlVY4YDU24Kdjijq/3ICr0xPLtSdWFya3v81f /ORHAwW93HZxOh2jT6XDDbpqeqPeqdb0ppqsfbO8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728351AbgFZD3u (ORCPT ); Thu, 25 Jun 2020 23:29:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:48170 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728333AbgFZD3u (ORCPT ); Thu, 25 Jun 2020 23:29:50 -0400 Received: from localhost.localdomain (c-71-198-47-131.hsd1.ca.comcast.net [71.198.47.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B82202081A; Fri, 26 Jun 2020 03:29:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593142190; bh=gJqVhnGNRkoppN0akj2ko9FC074SEW8dDzmzxOpPOyw=; h=Date:From:To:Subject:In-Reply-To:From; b=GLwMvNfVfOKx6rEDgkMeix6rOpqfVHDJ1Q0wCk9vp0NAu6SUWLMNiwX8ZscAYGHU0 RL4UGYzSeyDXQx+fqIEW5X+uejqyFRrxawCkphJ+YhJq3vgth9A9afrzyOkQx2ZM1U kEQ9276MMg7f5oLlNX9PLlDD63X0IaETNSETG1TA= Date: Thu, 25 Jun 2020 20:29:49 -0700 From: Andrew Morton To: akpm@linux-foundation.org, cl@linux.com, guro@fb.com, hannes@cmpxchg.org, iamjoonsoo.kim@lge.com, longman@redhat.com, mhocko@kernel.org, mm-commits@vger.kernel.org, penberg@kernel.org, rientjes@google.com, shakeelb@google.com, stable@vger.kernel.org, torvalds@linux-foundation.org, vdavydov.dev@gmail.com Subject: [patch 11/32] mm, slab: fix sign conversion problem in memcg_uncharge_slab() Message-ID: <20200626032949.NrLuc32Sk%akpm@linux-foundation.org> In-Reply-To: <20200625202807.b630829d6fa55388148bee7d@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Waiman Long Subject: mm, slab: fix sign conversion problem in memcg_uncharge_slab() It was found that running the LTP test on a PowerPC system could produce erroneous values in /proc/meminfo, like: MemTotal: 531915072 kB MemFree: 507962176 kB MemAvailable: 1100020596352 kB Using bisection, the problem is tracked down to commit 9c315e4d7d8c ("mm: memcg/slab: cache page number in memcg_(un)charge_slab()"). In memcg_uncharge_slab() with a "int order" argument: unsigned int nr_pages = 1 << order; : mod_lruvec_state(lruvec, cache_vmstat_idx(s), -nr_pages); The mod_lruvec_state() function will eventually call the __mod_zone_page_state() which accepts a long argument. Depending on the compiler and how inlining is done, "-nr_pages" may be treated as a negative number or a very large positive number. Apparently, it was treated as a large positive number in that PowerPC system leading to incorrect stat counts. This problem hasn't been seen in x86-64 yet, perhaps the gcc compiler there has some slight difference in behavior. It is fixed by making nr_pages a signed value. For consistency, a similar change is applied to memcg_charge_slab() as well. Link: http://lkml.kernel.org/r/20200620184719.10994-1-longman@redhat.com Fixes: 9c315e4d7d8c ("mm: memcg/slab: cache page number in memcg_(un)charge_slab()"). Signed-off-by: Waiman Long Acked-by: Roman Gushchin Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Shakeel Butt Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Cc: Signed-off-by: Andrew Morton --- mm/slab.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/slab.h~mm-slab-fix-sign-conversion-problem-in-memcg_uncharge_slab +++ a/mm/slab.h @@ -348,7 +348,7 @@ static __always_inline int memcg_charge_ gfp_t gfp, int order, struct kmem_cache *s) { - unsigned int nr_pages = 1 << order; + int nr_pages = 1 << order; struct mem_cgroup *memcg; struct lruvec *lruvec; int ret; @@ -388,7 +388,7 @@ out: static __always_inline void memcg_uncharge_slab(struct page *page, int order, struct kmem_cache *s) { - unsigned int nr_pages = 1 << order; + int nr_pages = 1 << order; struct mem_cgroup *memcg; struct lruvec *lruvec; _