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=-13.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 9B4BBC4320A for ; Tue, 27 Jul 2021 06:28:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7C9F661132 for ; Tue, 27 Jul 2021 06:28:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235502AbhG0G2K (ORCPT ); Tue, 27 Jul 2021 02:28:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235063AbhG0G2J (ORCPT ); Tue, 27 Jul 2021 02:28:09 -0400 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 43CAFC061757 for ; Mon, 26 Jul 2021 23:28:09 -0700 (PDT) Received: by mail-pj1-x102b.google.com with SMTP id u9-20020a17090a1f09b029017554809f35so2653277pja.5 for ; Mon, 26 Jul 2021 23:28:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=C0G+NqzAvfTHBs08uzNiyXIWeT1GpRd5xZS7if6Ooo4=; b=FrPUfnll9HAo8rg3rm1L8BgZvinjoYNWLsCe8VF6qjOOpOkkykOA87p1JbNe/822c3 BwYbIlrg8BRC6k8XpCLXK+/4ZGkbcaGyfWweHzMUeNy8zaiBIcCZtPG/J3ppVZWCHF+K VpZsA6Wd3wtvbSnt484EkAVs2ZPXD/LAUHRdzPQMCRxmaHp5KuJNXJ2u3QuIJmEqK5Yb nbJuWO6wvlAUDc+XnhL8dwUCbZsRep7k4YnwN1BPkQeZA8PzKMK5MNN98jUF0oc0ISsV athIfcL1cNF89Rt5dKWaJ2tKqjh6+bvpmVTwg7X5vJjnTRrLIGrfU6SBSfP+SrzZ5dQK pB5A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=C0G+NqzAvfTHBs08uzNiyXIWeT1GpRd5xZS7if6Ooo4=; b=I/bZWlEFo0AmsyVx2hQG4tw5z98mrPIhZJzDHegk2VQqhuBIwBW6rBlmUcjzC09Vtl n9eJCPhAkuNr+uL/OkVw8aXZUcaMAxIE9jpht9RqxzbS4fqq/UNZrUo5fsXCrbglkIp/ KEniC5p2cKc8XOSU6jVFbnvvSRDyn7U3TbMi0h/fdogGJQQC3+kdT1J8BsDv17AiW2s9 rSpuNpvpc87IiFKlW60iPY/Xstfvxc7+I7+EL9uStHXi5NfZedJCZVUuMEIrmTtF3wGB EEfDGLCt7WBo5XkS9PsnfkEo6kGdQZs2Rz35qOQLGgQyit9EBiDo6B6lIbPSujpooI1Z O48Q== X-Gm-Message-State: AOAM533nfIIWu7ewMqFFbS1pTUqy8rrljgcJjvcDH2etA6xHgQVF+d2G 0CBi/HOXH7r/e6QiyQAQXj5A0MawImG7lkYZfrd/zQ== X-Google-Smtp-Source: ABdhPJzuYi4yIxwR2z/828VWqqpEpUF8Kpv2lA+SMK6YDA0+3Ql9hzanK7UNiIoyuHmfgc7y3xVI6zP3wXj+lYX+3Ic= X-Received: by 2002:a05:6a00:1508:b029:332:3aab:d842 with SMTP id q8-20020a056a001508b02903323aabd842mr21474337pfu.59.1627367288681; Mon, 26 Jul 2021 23:28:08 -0700 (PDT) MIME-Version: 1.0 References: <20210714091800.42645-1-songmuchun@bytedance.com> <20210714091800.42645-2-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Tue, 27 Jul 2021 14:27:31 +0800 Message-ID: Subject: Re: [PATCH 1/5] mm: introduce PAGEFLAGS_MASK to replace ((1UL << NR_PAGEFLAGS) - 1) To: Mike Kravetz Cc: Andrew Morton , Oscar Salvador , Michal Hocko , "Song Bao Hua (Barry Song)" , David Hildenbrand , Chen Huang , "Bodeddula, Balasubramaniam" , Jonathan Corbet , Xiongchun duan , fam.zheng@bytedance.com, linux-doc@vger.kernel.org, LKML , Linux Memory Management List , Qi Zheng Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Tue, Jul 27, 2021 at 5:04 AM Mike Kravetz wrote: > > On 7/14/21 2:17 AM, Muchun Song wrote: > > Instead of hard-coding ((1UL << NR_PAGEFLAGS) - 1) everywhere, introducing > > PAGEFLAGS_MASK to make the code clear to get the page flags. > > > > Signed-off-by: Muchun Song > > --- > > include/linux/page-flags.h | 4 +++- > > include/trace/events/page_ref.h | 4 ++-- > > lib/test_printf.c | 2 +- > > lib/vsprintf.c | 2 +- > > 4 files changed, 7 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > > index 5922031ffab6..358d3f6fa976 100644 > > --- a/include/linux/page-flags.h > > +++ b/include/linux/page-flags.h > > @@ -178,6 +178,8 @@ enum pageflags { > > PG_reported = PG_uptodate, > > }; > > > > +#define PAGEFLAGS_MASK (~((1UL << NR_PAGEFLAGS) - 1)) > > Can you explain why you chose this definition instead of > > #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1) > > and mostly use ~PAGEFLAGS_MASK below? Hi Mike, Actually, I learned from PAGE_MASK. So I thought the macro like xxx_MASK should be the format of 0x00...00ff...ff. I don't know if this is an unwritten rule. Please correct me if I am wrong. Thanks. > -- > Mike Kravetz