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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0ACC5C433E2 for ; Wed, 9 Sep 2020 01:01:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6E05C21D43 for ; Wed, 9 Sep 2020 01:01:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="SNQjPYWH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6E05C21D43 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8F5856B0062; Tue, 8 Sep 2020 21:01:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8A5B06B0068; Tue, 8 Sep 2020 21:01:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7BB0B6B006C; Tue, 8 Sep 2020 21:01:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0129.hostedemail.com [216.40.44.129]) by kanga.kvack.org (Postfix) with ESMTP id 63A246B0062 for ; Tue, 8 Sep 2020 21:01:40 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 2D16C180AD81A for ; Wed, 9 Sep 2020 01:01:40 +0000 (UTC) X-FDA: 77241720360.09.loaf41_5b03f05270d9 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin09.hostedemail.com (Postfix) with ESMTP id 061AA180AD807 for ; Wed, 9 Sep 2020 01:01:39 +0000 (UTC) X-HE-Tag: loaf41_5b03f05270d9 X-Filterd-Recvd-Size: 3029 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Wed, 9 Sep 2020 01:01:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=fVCZ2gAQlCOU+3FQ8zVoZg2a2/Nz/JlYFnCb9jL8Xz0=; b=SNQjPYWHMmaFL7LKw4GX4WfZlG jqCZi08dIMAMm78xsBxjzttVxrreGfM/VkZblsnmw7u/IjfZA+8cVbKcrhuXgKI68/lQkiNTvpJaA u1d9lIuxE++qMUdBjM8NP9Nl1GoK2hBFIkf0ewekXxEkrV+ppWkaOTpuGF6WRGAQxKWB6whYUtJpo aT0MUfU+Bo51JVvUpzB7d6JWHzb0XJcx7osuTkygosX4d9xlTPLYgjwCgGJzFdjocTow9gyLfIPAB PO3jgrUt0dAMTn/b7ZVGH2K+aFTTflDztYCCY98ocrpLwT6fUGwc1K6lN2N7IPFzDI4Azpo4w8Ylu H/nmn/kA==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kFoUA-0006Dw-54; Wed, 09 Sep 2020 01:01:18 +0000 Date: Wed, 9 Sep 2020 02:01:18 +0100 From: Matthew Wilcox To: Alex Shi Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, hannes@cmpxchg.org, lkp@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, shakeelb@google.com, iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com, kirill@shutemov.name, alexander.duyck@gmail.com, rong.a.chen@intel.com, mhocko@suse.com, vdavydov.dev@gmail.com, shy828301@gmail.com, Alexander Duyck Subject: Re: [PATCH v18 31/32] mm: Add explicit page decrement in exception path for isolate_lru_pages Message-ID: <20200909010118.GB6583@casper.infradead.org> References: <1598273705-69124-1-git-send-email-alex.shi@linux.alibaba.com> <1598273705-69124-32-git-send-email-alex.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1598273705-69124-32-git-send-email-alex.shi@linux.alibaba.com> X-Rspamd-Queue-Id: 061AA180AD807 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 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 Mon, Aug 24, 2020 at 08:55:04PM +0800, Alex Shi wrote: > +++ b/mm/vmscan.c > @@ -1688,10 +1688,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, > > if (!TestClearPageLRU(page)) { > /* > - * This page may in other isolation path, > - * but we still hold lru_lock. > + * This page is being isolated in another > + * thread, but we still hold lru_lock. The > + * other thread must be holding a reference > + * to the page so this should never hit a > + * reference count of 0. > */ > - put_page(page); > + WARN_ON(put_page_testzero(page)); > goto busy; I read Hugh's review and that led me to take a look at this. We don't do it like this. Use the same pattern as elsewhere in mm: page_ref_sub(page, nr); VM_BUG_ON_PAGE(page_count(page) <= 0, page);