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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D7DBC433F5 for ; Wed, 30 Mar 2022 01:47:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8E64D8D0002; Tue, 29 Mar 2022 21:47:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 897878D0001; Tue, 29 Mar 2022 21:47:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 75D218D0002; Tue, 29 Mar 2022 21:47:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0251.hostedemail.com [216.40.44.251]) by kanga.kvack.org (Postfix) with ESMTP id 632408D0001 for ; Tue, 29 Mar 2022 21:47:05 -0400 (EDT) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 17A4E182A3A41 for ; Wed, 30 Mar 2022 01:47:05 +0000 (UTC) X-FDA: 79299364410.31.626CBDA Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf11.hostedemail.com (Postfix) with ESMTP id E489740005 for ; Wed, 30 Mar 2022 01:47:03 +0000 (UTC) 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 Authentication-Results: imf11.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf11.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Stat-Signature: uhcdxwa8myrdob49bdmttyugumdfpopz X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: E489740005 X-HE-Tag: 1648604823-73053 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 >> >> > > . >