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=-3.5 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 C3EEAC00A89 for ; Mon, 2 Nov 2020 14:49:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 56EE02084C for ; Mon, 2 Nov 2020 14:49:48 +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="Fc5EzzbP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 56EE02084C 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 E94B46B0070; Mon, 2 Nov 2020 09:49:47 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E45C86B0072; Mon, 2 Nov 2020 09:49:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D827B6B0073; Mon, 2 Nov 2020 09:49:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0229.hostedemail.com [216.40.44.229]) by kanga.kvack.org (Postfix) with ESMTP id ACFF16B0070 for ; Mon, 2 Nov 2020 09:49:47 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 52FA6181AC9C6 for ; Mon, 2 Nov 2020 14:49:47 +0000 (UTC) X-FDA: 77439762414.20.top78_24034fa272b0 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id 23FE3180C0609 for ; Mon, 2 Nov 2020 14:49:47 +0000 (UTC) X-HE-Tag: top78_24034fa272b0 X-Filterd-Recvd-Size: 3500 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf09.hostedemail.com (Postfix) with ESMTP for ; Mon, 2 Nov 2020 14:49:46 +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=9Y50BuvtY/Iv9iX09V09H3tcMOFeUq4GX0ITyW7hR88=; b=Fc5EzzbP5uGjYagLwVWe4N7rSc dT4LPqKUJQefMq0cWg6QZxnZyzdW0BT/rLNPNmIIzGjo6rnnJx/uNQnCaukD43QfeUz4egAOUJTEN EsUPSMhMJLUgnontgXLVFf1k9EJkUYkC4BpE+14S9u/W8QEbfXOis468N/nX2cczNVhkRsKScXYHY tpj4XWjN+CWDGuX9qefNrodCFBeuiTggLV5g0NTk4c+wGg7MWemnx0Wt1qSxG5lpOvgIFJITFzZ80 DB3MVpy1gEYCxw9T6tPp5HHxTX30xlGavqhM697UTSooTwW0jmx5PcZIOUmXva0C6VNnW2SiHnAfe ROmfwCBA==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kZb9D-0007ZT-TK; Mon, 02 Nov 2020 14:49:28 +0000 Date: Mon, 2 Nov 2020 14:49:27 +0000 From: Matthew Wilcox To: Johannes Weiner Cc: Alex Shi , akpm@linux-foundation.org, mgorman@techsingularity.net, tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, 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, Vlastimil Babka , Minchan Kim Subject: Re: [PATCH v20 08/20] mm: page_idle_get_page() does not need lru_lock Message-ID: <20201102144927.GN27442@casper.infradead.org> References: <1603968305-8026-1-git-send-email-alex.shi@linux.alibaba.com> <1603968305-8026-9-git-send-email-alex.shi@linux.alibaba.com> <20201102144110.GB724984@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201102144110.GB724984@cmpxchg.org> 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, Nov 02, 2020 at 09:41:10AM -0500, Johannes Weiner wrote: > On Thu, Oct 29, 2020 at 06:44:53PM +0800, Alex Shi wrote: > > From: Hugh Dickins > > > > It is necessary for page_idle_get_page() to recheck PageLRU() after > > get_page_unless_zero(), but holding lru_lock around that serves no > > useful purpose, and adds to lru_lock contention: delete it. > > > > See https://lore.kernel.org/lkml/20150504031722.GA2768@blaptop for the > > discussion that led to lru_lock there; but __page_set_anon_rmap() now > > uses WRITE_ONCE(), > > That doesn't seem to be the case in Linus's or Andrew's tree. Am I > missing a dependent patch series? > > > and I see no other risk in page_idle_clear_pte_refs() using > > rmap_walk() (beyond the risk of racing PageAnon->PageKsm, mostly but > > not entirely prevented by page_count() check in ksm.c's > > write_protect_page(): that risk being shared with page_referenced() > > and not helped by lru_lock). > > Isn't it possible, as per Minchan's description, for page->mapping to > point to a struct anon_vma without PAGE_MAPPING_ANON set, and rmap > thinking it's looking at a struct address_space? I don't think it can point to an anon_vma without the ANON bit set. Minchan's concern in that email was that it might still be NULL.