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 CF08CC433EF for ; Wed, 15 Dec 2021 15:40:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4CC696B0078; Wed, 15 Dec 2021 10:40:18 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4552A6B007B; Wed, 15 Dec 2021 10:40:18 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2CE866B007D; Wed, 15 Dec 2021 10:40:18 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay030.a.hostedemail.com [64.99.140.30]) by kanga.kvack.org (Postfix) with ESMTP id 17DB26B0078 for ; Wed, 15 Dec 2021 10:40:18 -0500 (EST) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id D298D12061F for ; Wed, 15 Dec 2021 15:40:07 +0000 (UTC) X-FDA: 78920439654.03.C656B1A Received: from alexa-out-sd-01.qualcomm.com (alexa-out-sd-01.qualcomm.com [199.106.114.38]) by imf30.hostedemail.com (Postfix) with ESMTP id 6603480011 for ; Wed, 15 Dec 2021 15:40:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1639582806; x=1671118806; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=vPTxXWtyQPQZHHx15OGOUNr+WYx9qR2s8gHmDJ1KQ10=; b=udw+5FZl6xRgHW/DZ1X+0X31uU2n3uzUEeBlrf9St2W26r/QmT2p7q1w qTAZ+vfeP+sO9tYLz3nTXZBIBRIKch5Q1ORCjXSYnUjiokSKhURp9sOfq TtUUBFpKV8zwsBhEpCq7H00TBamDlA5k7knwXWx+v9QjLR3VtbwHuLW7G E=; Received: from unknown (HELO ironmsg04-sd.qualcomm.com) ([10.53.140.144]) by alexa-out-sd-01.qualcomm.com with ESMTP; 15 Dec 2021 07:40:04 -0800 X-QCInternal: smtphost Received: from nasanex01c.na.qualcomm.com ([10.47.97.222]) by ironmsg04-sd.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Dec 2021 07:40:04 -0800 Received: from nalasex01a.na.qualcomm.com (10.47.209.196) by nasanex01c.na.qualcomm.com (10.47.97.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.922.19; Wed, 15 Dec 2021 07:40:04 -0800 Received: from [10.216.54.238] (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.922.19; Wed, 15 Dec 2021 07:40:01 -0800 Subject: Re: [PATCH] mm/madvise: elevate page refcount while isolating in process_madvise() To: Matthew Wilcox CC: , , , , , , References: <1639571019-30043-1-git-send-email-quic_charante@quicinc.com> From: Charan Teja Kalla Message-ID: <297f6c6b-657c-451f-1458-bff96f803c36@quicinc.com> Date: Wed, 15 Dec 2021 21:09:57 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 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: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nalasex01a.na.qualcomm.com (10.47.209.196) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=quicinc.com header.s=qcdkim header.b=udw+5FZl; dmarc=pass (policy=none) header.from=quicinc.com; spf=pass (imf30.hostedemail.com: domain of quic_charante@quicinc.com designates 199.106.114.38 as permitted sender) smtp.mailfrom=quic_charante@quicinc.com X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6603480011 X-Stat-Signature: xksthwojswe4d18ckautzau1ff96ie3i X-HE-Tag: 1639582806-349937 X-Bogosity: Ham, tests=bogofilter, spamicity=0.001083, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/15/2021 7:25 PM, Matthew Wilcox wrote: > On Wed, Dec 15, 2021 at 05:53:39PM +0530, Charan Teja Reddy wrote: >> The documentation of isolate_lru_page() says that, "it must be called >> with an elevated refcount on the page", which is not followed while >> isolating pages in process_madvise() system call with advise >> MADV_PAGEOUT. Fix it. > > We hold the mmap_lock over the call to this function, so the reference > to the page from the page tables cannot go away. There's no need to > grab an extra reference here. Thanks Matthew for clearing such fundamentals. >