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 003FCC433F5 for ; Fri, 18 Feb 2022 01:15:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231203AbiBRBPa (ORCPT ); Thu, 17 Feb 2022 20:15:30 -0500 Received: from gmail-smtp-in.l.google.com ([23.128.96.19]:37012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229567AbiBRBP3 (ORCPT ); Thu, 17 Feb 2022 20:15:29 -0500 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB39AD2 for ; Thu, 17 Feb 2022 17:15:13 -0800 (PST) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4K0DCW57gwz1FD8j; Fri, 18 Feb 2022 09:10:47 +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; Fri, 18 Feb 2022 09:15:11 +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> <5d904bee-3faf-374a-090c-ce7c99c84ea9@huawei.com> <49a1bc35-7505-bc82-2931-e57f7b959cb3@suse.cz> From: Miaohe Lin Message-ID: <554115ed-3908-c970-aa1a-693b1c768551@huawei.com> Date: Fri, 18 Feb 2022 09:15:10 +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: <49a1bc35-7505-bc82-2931-e57f7b959cb3@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: dggems702-chm.china.huawei.com (10.3.19.179) 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 2022/2/18 1:04, Vlastimil Babka wrote: > On 2/17/22 11:44, Miaohe Lin wrote: >> 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. > > I'll add this to the slab tree and linux-next and we'll see if wider testing > uncovers such compilers. Should be unlikely. Many thanks! :) > >> 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); >>> >>> . >>> >> > > . >