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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 B5042C433E1 for ; Sun, 23 Aug 2020 15:21:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C30120706 for ; Sun, 23 Aug 2020 15:21:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="IWPT+EnC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727910AbgHWPVr (ORCPT ); Sun, 23 Aug 2020 11:21:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44588 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726935AbgHWPVn (ORCPT ); Sun, 23 Aug 2020 11:21:43 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8078EC061573 for ; Sun, 23 Aug 2020 08:21:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=gm1l7LMMWkh8XudQNYEYGcqLPJBnhezkbfdutvBRAvQ=; b=IWPT+EnCVx+/a2LokrEVSSUtYT X/gyZpW0+IE9jiZvqtwsJy5omgmg3wmH5OniZg9R84dYUOYzlBCZDdZWI0IMiniWIYWP86tnMUx48 MAjQWdu8+Vu4VQrWnKfQv8SS1RgvljT+OWCfJvnJ71Zgx4XdHxLrAiOUf82qDBc/7E7eQ0GNrzkAU 9T82GFNby8NlDlHaDSL6Cgfu4S1opi9VM1G5kvNTe4981Ah/A7l1maBTQphbZTYZsoVjUzq2yzmGQ N3/vKzwoUHDArg5Ke06Mq36ZG2ZhiTa0Hx6OyezpaonT+i1RF8IJHSwmtpGJxlWAvUEfIybDRnPLa 8GEWnl/A==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1k9roJ-0007Hg-1f; Sun, 23 Aug 2020 15:21:31 +0000 Date: Sun, 23 Aug 2020 16:21:30 +0100 From: Matthew Wilcox To: Giuseppe Scrivano Cc: Andrew Morton , Xu Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Tejun Heo Subject: Re: [PATCH] hugetlb_cgroup: convert comma to semicolon Message-ID: <20200823152130.GA17456@casper.infradead.org> References: <20200818064333.21759-1-vulab@iscas.ac.cn> <20200818184036.d6c479446b2c3b231d1e3bff@linux-foundation.org> <87eeo32gto.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87eeo32gto.fsf@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 19, 2020 at 10:14:11AM +0200, Giuseppe Scrivano wrote: > >> - cft->file_offset = offsetof(struct hugetlb_cgroup, events_file[idx]), > >> + cft->file_offset = offsetof(struct hugetlb_cgroup, events_file[idx]); > >> cft->flags = CFTYPE_NOT_ON_ROOT; > > I think in this case having two expressions as part of the same > statement is equivalent to having two separate statements. Both > cft->file_offset and cft->flags get the expected value. That's not how the comma operator works. It will evaluate offsetof(struct hugetlb_cgroup, events_file[idx]) and then discard the result. Since it has no side-effects, this is effectively doing: cft->file_offset = cft->flags = CFTYPE_NOT_ON_ROOT;