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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 75B75C2D0E2 for ; Tue, 22 Sep 2020 09:03:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32D342399A for ; Tue, 22 Sep 2020 09:03:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726515AbgIVJDx (ORCPT ); Tue, 22 Sep 2020 05:03:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:55800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726419AbgIVJDw (ORCPT ); Tue, 22 Sep 2020 05:03:52 -0400 Received: from gaia (unknown [31.124.44.166]) (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 0B5AC20715; Tue, 22 Sep 2020 09:03:50 +0000 (UTC) Date: Tue, 22 Sep 2020 10:03:48 +0100 From: Catalin Marinas To: Chen Jun Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, rui.xiang@huawei.com, weiyongjun1@huawei.com Subject: Re: [PATCH -next 2/5] mm/kmemleak: skip update_checksum for OBJECT_NO_SCAN objects Message-ID: <20200922090346.GA15643@gaia> References: <20200921020007.35803-1-chenjun102@huawei.com> <20200921020007.35803-3-chenjun102@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200921020007.35803-3-chenjun102@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 21, 2020 at 02:00:04AM +0000, Chen Jun wrote: > From: Wei Yongjun > > Objects marked with OBJECT_NO_SCAN are never scanned. > So there is no need to update checksum for them. > > Signed-off-by: Wei Yongjun > Signed-off-by: Chen Jun > --- > mm/kmemleak.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index b3f603fd9fc3..c09c6b59eda6 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -1166,6 +1166,10 @@ static bool update_checksum(struct kmemleak_object *object) > { > u32 old_csum = object->checksum; > > + /* always return false for not scan object */ > + if (object->flags & OBJECT_NO_SCAN) > + return false; The reason for OBJECT_NO_SCAN is to avoid introducing more false negatives. The point of the checksum is to reduce the false positives - i.e. an object that is being modified between scans won't be considered a (transient) leak even if kmemleak couldn't find a reference pointer to it. So please drop this patch. -- Catalin