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 A8972C433E2 for ; Wed, 9 Sep 2020 20:16:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 10E0121D7D for ; Wed, 9 Sep 2020 20:16:01 +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="iG6nBaZ2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10E0121D7D 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 1D6766B005C; Wed, 9 Sep 2020 16:16:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 161FA6B0075; Wed, 9 Sep 2020 16:16:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 000336B0080; Wed, 9 Sep 2020 16:16:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0073.hostedemail.com [216.40.44.73]) by kanga.kvack.org (Postfix) with ESMTP id D938D6B005C for ; Wed, 9 Sep 2020 16:16:00 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 91669824805A for ; Wed, 9 Sep 2020 20:16:00 +0000 (UTC) X-FDA: 77244629280.13.shop82_2807d4a270e0 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id 5DEAE18140B70 for ; Wed, 9 Sep 2020 20:16:00 +0000 (UTC) X-HE-Tag: shop82_2807d4a270e0 X-Filterd-Recvd-Size: 3824 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Wed, 9 Sep 2020 20:15:59 +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=Bw4rIJZLeK5WfU3TO9eMUF05YqQkLW/1cl+vzePNNf8=; b=iG6nBaZ2r0xjMc/5udrwMFgvVe zUDTE0FRIJKDA3f55Mj+WKsuMCkMrHGPVAgxs+CjEBF9K8DMTByr2eV/wyFcPvmVaNAeY9xTIqlOZ EH3nLSyN/oT93H3UyjXf1yValOLopcbpn3LFJsMi9LuSJgOzAT2F6nzyrkEgzOtPM85Kl/yajl+JY TL5tEsH6XBNI8KDUZBqbcFBznLuljUyY+vW9YlFRSz3iHlAQQ4a5F2JcCPtjiX1A+qizt0Ml+g35b CTKkt5fMZoPqXZNp7Sd7GqfcOLTiF/ol3aMbBxVvzoWXh/c3yqIjpa+1S7EGo6JxiWVpbEkf/03wb ciR5lr9g==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kG6V8-0002Y4-CZ; Wed, 09 Sep 2020 20:15:30 +0000 Date: Wed, 9 Sep 2020 21:15:30 +0100 From: Matthew Wilcox To: Hugh Dickins Cc: Alexander Duyck , Alex Shi , Andrew Morton , Mel Gorman , Tejun Heo , Konstantin Khlebnikov , Daniel Jordan , Johannes Weiner , kbuild test robot , linux-mm , LKML , cgroups@vger.kernel.org, Shakeel Butt , Joonsoo Kim , Wei Yang , "Kirill A. Shutemov" , Rong Chen , Michal Hocko , Vladimir Davydov , 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: <20200909201530.GM6583@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> <20200909010118.GB6583@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 5DEAE18140B70 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 Wed, Sep 09, 2020 at 11:24:14AM -0700, Hugh Dickins wrote: > After overnight reflection, my own preference would be simply to > drop this patch. I think we are making altogether too much of a > fuss here over what was simply correct as plain put_page() > (and further from correct if we change it to leak the page in an > unforeseen circumstance). > > And if Alex's comment was not quite grammatically correct, never mind, > it said as much as was worth saying. I got more worried by his > placement of the "busy:" label, but that does appear to work correctly. > > There's probably a thousand places where put_page() is used, where > it would be troublesome if it were the final put_page(): this one > bothered you because you'd been looking at isolate_migratepages_block(), > and its necessary avoidance of lru_lock recursion on put_page(); > but let's just just leave this put_page() as is. My problem with put_page() is that it's no longer the simple decrement-and-branch-to-slow-path-if-zero that it used to be. It has the awful devmap excrement in it so it really expands into a lot of code. I really wish that "feature" could be backed out again. It clearly wasn't ready for merge.