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 B321DC61D97 for ; Fri, 24 Nov 2023 02:04:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F08B66B06E5; Thu, 23 Nov 2023 21:04:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EB8756B06E6; Thu, 23 Nov 2023 21:04:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D80206B06E7; Thu, 23 Nov 2023 21:04:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id CCC746B06E5 for ; Thu, 23 Nov 2023 21:04:28 -0500 (EST) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 9EB55C11B0 for ; Fri, 24 Nov 2023 02:04:28 +0000 (UTC) X-FDA: 81491203416.17.BBABC72 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf15.hostedemail.com (Postfix) with ESMTP id 0A527A0002 for ; Fri, 24 Nov 2023 02:04:24 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf15.hostedemail.com: domain of zhangpeng362@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=zhangpeng362@huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1700791466; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=PJC0t4imf3ScaFhci06w11OkwWmxUzVZZuhrKSVWxOw=; b=AbazcBgclCB9AeNvDa2t+t3HHHVlzQkjDFvrVG8oIHzskS1MxWNsuhufzq20A6MLDoj0aL iqsbbLzuI1fwQ3CpTNl/XUAhBUDL01SbenEHncRIwJgepUUktkqMtPE8AcnEhDn0BjciAy 7bfAKviP15rSpeub8DjP9MsfaJEktZM= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf15.hostedemail.com: domain of zhangpeng362@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=zhangpeng362@huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1700791466; a=rsa-sha256; cv=none; b=QpB/csTPdnEydQS+O1agpX0e9A0vVR8PaVfjTnL7gDL3CVMNzryub5LDoNq0ex9zKpdFeA hDkLTIa3w/4bw46mJoW/NYvQN7g9YGMmD52Dsl8JVbt0darSx/P1Tau5jssJqid2RBm0QO UFjKcrOMtmQqlWOC3/NVjKbCrygCcfs= Received: from kwepemm000020.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4SbyvD4YXCzvR5d; Fri, 24 Nov 2023 10:03:36 +0800 (CST) Received: from [10.174.179.160] (10.174.179.160) by kwepemm000020.china.huawei.com (7.193.23.93) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Fri, 24 Nov 2023 10:04:01 +0800 Message-ID: Date: Fri, 24 Nov 2023 10:04:00 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [RFC PATCH] mm: filemap: avoid unnecessary major faults in filemap_fault() Content-Language: en-US To: Matthew Wilcox CC: "Huang, Ying" , , , , , , , , , , References: <20231122140052.4092083-1-zhangpeng362@huawei.com> <87a5r4988r.fsf@yhuang6-desk2.ccr.corp.intel.com> <5b0e168a-dd43-80d4-2eeb-5c8a5d470f5e@huawei.com> From: "zhangpeng (AS)" In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.160] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemm000020.china.huawei.com (7.193.23.93) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 0A527A0002 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ny5f74x8taeexe7hkeowbecxrc77g478 X-HE-Tag: 1700791464-332733 X-HE-Meta: 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 mKK6/8Yt wA7QfcvviPz2MhYrSS1Rp0zICGJYQYhukP+9CHgjjwBGhTwqUP9vBPhXdpsdR4lkeadQiDs7QFktJ2VyReeEkPFlpc15nCQqN1107aV4qrh6asdoeLxaHAO6ew1Bh7cFgqQFbN6q6rxa9DcYpQ5sXAX/zsAsNgTtlBwYhAw3qK4J+2LRONzdAPtCjoQ== 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: List-Subscribe: List-Unsubscribe: On 2023/11/23 23:33, Matthew Wilcox wrote: > On Thu, Nov 23, 2023 at 05:09:04PM +0800, zhangpeng (AS) wrote: >>>> + pte_t *ptep = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, >>>> + vmf->address, &vmf->ptl); >>>> + if (ptep) { >>>> + /* >>>> + * Recheck pte with ptl locked as the pte can be cleared >>>> + * temporarily during a read/modify/write update. >>>> + */ >>>> + if (unlikely(!pte_none(ptep_get(ptep)))) >>>> + ret = VM_FAULT_NOPAGE; >>>> + pte_unmap_unlock(ptep, vmf->ptl); >>>> + if (unlikely(ret)) >>>> + return ret; >>>> + } >>>> + >>> Need to deal with ptep == NULL. Although that is high impossible. >> If ptep == NULL, we may just need to return VM_FAULT_SIGBUS. >> I'll add it in the next version. > no? wouldn't ptep being NULL mean that the ptep has been replaced with > a PMD entry, and thus should return NOPAGE? Yes, ptep == NULL means that the ptep has been replaced with a PMD entry. I'll add return NOPAGE in the next version. Thanks! -- Best Regards, Peng