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 D45D7C433EF for ; Wed, 30 Mar 2022 01:47:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241719AbiC3Bsr (ORCPT ); Tue, 29 Mar 2022 21:48:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48940 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237034AbiC3Bsq (ORCPT ); Tue, 29 Mar 2022 21:48:46 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E0EFF13DD4 for ; Tue, 29 Mar 2022 18:47:01 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4KSq4H1hfDzDq5k; Wed, 30 Mar 2022 09:44:47 +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; Wed, 30 Mar 2022 09:46:59 +0800 Subject: Re: [PATCH 1/8] mm/vmscan: remove redundant folio_test_swapbacked check when folio is file lru To: Matthew Wilcox CC: , , References: <20220329132619.18689-1-linmiaohe@huawei.com> <20220329132619.18689-2-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Wed, 30 Mar 2022 09:46:59 +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: 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 2022/3/29 21:46, Matthew Wilcox wrote: > On Tue, Mar 29, 2022 at 09:26:12PM +0800, Miaohe Lin wrote: >> When folio is file lru, folio_test_swapbacked is guaranteed to be true. So >> it's unnecessary to check it here again. No functional change intended. > > ummm ... is your logic right here? The condition is: > > if (!a || (b && !c)) > Because a is !c, so c is !a. Then we have: !a || (b && !c) ==> !a || (b && !!a) ==> !a || (b && a) ==> !a || b. Or am I miss something? Thanks. > I don't see how it follows that a => c means we can do any > simplification at all. > >> Signed-off-by: Miaohe Lin >> --- >> mm/vmscan.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 1678802e03e7..7c1a9713bfc9 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -1434,8 +1434,7 @@ static void folio_check_dirty_writeback(struct folio *folio, >> * Anonymous pages are not handled by flushers and must be written >> * from reclaim context. Do not stall reclaim based on them >> */ >> - if (!folio_is_file_lru(folio) || >> - (folio_test_anon(folio) && !folio_test_swapbacked(folio))) { >> + if (!folio_is_file_lru(folio) || folio_test_anon(folio)) { >> *dirty = false; >> *writeback = false; >> return; >> -- >> 2.23.0 >> >> > > . >