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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 5497CC433E0 for ; Sat, 20 Jun 2020 18:47:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0FF8024181 for ; Sat, 20 Jun 2020 18:47:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="GzG34s6g" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0FF8024181 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 73BF78D000F; Sat, 20 Jun 2020 14:47:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6EAD18D0008; Sat, 20 Jun 2020 14:47:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 601758D000F; Sat, 20 Jun 2020 14:47:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0044.hostedemail.com [216.40.44.44]) by kanga.kvack.org (Postfix) with ESMTP id 4646E8D0008 for ; Sat, 20 Jun 2020 14:47:43 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id B0D2E2DFC for ; Sat, 20 Jun 2020 18:47:42 +0000 (UTC) X-FDA: 76950473964.07.death15_1c0eeb826e23 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id 8B0BD1803F9B7 for ; Sat, 20 Jun 2020 18:47:42 +0000 (UTC) X-HE-Tag: death15_1c0eeb826e23 X-Filterd-Recvd-Size: 4104 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-1.mimecast.com [207.211.31.81]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Sat, 20 Jun 2020 18:47:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1592678861; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc; bh=mClg+dw3ex3SxKOKAQfa7c9Gaag31kwGFLnQSg16We4=; b=GzG34s6gY692Rgl9kT7XxlgBWanlLqRHnyVnFtk5SMJ279A3HqahZVfuLtYQA0W4SA8g8A gsjiRSjjhnmO9iLQf8MIkBSXTO/qIyc5NVAyk0WCSki4UUNKKxzqXMq1ORZ9lR4Cib4WF7 K1/dJFKXaK2jajqyhskgNdd8Vpey5UE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-63-i8PliEcoOT2WuuoRnpFgXA-1; Sat, 20 Jun 2020 14:47:39 -0400 X-MC-Unique: i8PliEcoOT2WuuoRnpFgXA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DE66F107ACCD; Sat, 20 Jun 2020 18:47:36 +0000 (UTC) Received: from llong.com (ovpn-112-81.rdu2.redhat.com [10.10.112.81]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9FB8A19C4F; Sat, 20 Jun 2020 18:47:31 +0000 (UTC) From: Waiman Long To: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Johannes Weiner , Shakeel Butt , Roman Gushchin Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Waiman Long Subject: [PATCH] mm, slab: Fix sign conversion problem in memcg_uncharge_slab() Date: Sat, 20 Jun 2020 14:47:19 -0400 Message-Id: <20200620184719.10994-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Rspamd-Queue-Id: 8B0BD1803F9B7 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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. Fixes: 9c315e4d7d8c ("mm: memcg/slab: cache page number in memcg_(un)charge_slab()"). Signed-off-by: Waiman Long --- mm/slab.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/slab.h b/mm/slab.h index 207c83ef6e06..74f7e09a7cfd 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -348,7 +348,7 @@ static __always_inline int memcg_charge_slab(struct page *page, 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 @@ static __always_inline int memcg_charge_slab(struct page *page, 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; -- 2.18.1