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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2913CC433F5 for ; Thu, 17 Feb 2022 10:44:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239258AbiBQKo3 (ORCPT ); Thu, 17 Feb 2022 05:44:29 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:59466 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237461AbiBQKoX (ORCPT ); Thu, 17 Feb 2022 05:44:23 -0500 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29EE4293B76 for ; Thu, 17 Feb 2022 02:44:08 -0800 (PST) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4JzrtR3XpPz1FDJ3; Thu, 17 Feb 2022 18:39:43 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Thu, 17 Feb 2022 18:44:05 +0800 Subject: Re: [PATCH] mm/slab_common: use helper function is_power_of_2() To: Vlastimil Babka CC: , , Andrew Morton , Christoph Lameter , , , References: <20220217091609.8214-1-linmiaohe@huawei.com> <8f307e8a-5f97-cf5d-0a77-1c79b05abd60@suse.cz> From: Miaohe Lin Message-ID: <5d904bee-3faf-374a-090c-ce7c99c84ea9@huawei.com> Date: Thu, 17 Feb 2022 18:44:05 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <8f307e8a-5f97-cf5d-0a77-1c79b05abd60@suse.cz> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/2/17 17:23, Vlastimil Babka wrote: > On 2/17/22 10:16, Miaohe Lin wrote: >> Use helper function is_power_of_2() to check if KMALLOC_MIN_SIZE is power >> of two. Minor readability improvement. >> >> Signed-off-by: Miaohe Lin > > We can try, but in case some compiler will no longer able to perform the > check at build-time (although is_power_of_2() looks sufficiently trivial > too), we'll have to revert it. I see. I checked the compiler in my env but there might be some compilers can't perform the check at build-time. Many thanks for your reply. > >> --- >> mm/slab_common.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/slab_common.c b/mm/slab_common.c >> index 23f2ab0713b7..6ee64d6208b3 100644 >> --- a/mm/slab_common.c >> +++ b/mm/slab_common.c >> @@ -807,7 +807,7 @@ void __init setup_kmalloc_cache_index_table(void) >> unsigned int i; >> >> BUILD_BUG_ON(KMALLOC_MIN_SIZE > 256 || >> - (KMALLOC_MIN_SIZE & (KMALLOC_MIN_SIZE - 1))); >> + !is_power_of_2(KMALLOC_MIN_SIZE)); >> >> for (i = 8; i < KMALLOC_MIN_SIZE; i += 8) { >> unsigned int elem = size_index_elem(i); > > . >