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 ABE44C433FE for ; Wed, 19 Oct 2022 23:18:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BA8236B0071; Wed, 19 Oct 2022 19:18:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B57D76B0073; Wed, 19 Oct 2022 19:18:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9F8206B0074; Wed, 19 Oct 2022 19:18:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8C1426B0071 for ; Wed, 19 Oct 2022 19:18:13 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 5B418140B1D for ; Wed, 19 Oct 2022 23:18:13 +0000 (UTC) X-FDA: 80039264466.01.77A5BB8 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf26.hostedemail.com (Postfix) with ESMTP id ECA83140038 for ; Wed, 19 Oct 2022 23:18:12 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 13ACD61962; Wed, 19 Oct 2022 23:18:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4E22FC433D6; Wed, 19 Oct 2022 23:18:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1666221491; bh=PQpDdjCNhgH/SV9g2/UI3EyVE4IUuose3w4ZZPETCZE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=iX+GyCvTyHxKlLGc4DPMWUDKazCf8F3gxd4aWuRFaCC1MN6GMNAkS9onWpNJ6+ohV pOJdhmLadfgJXoXOOnkpK39orQ63j/79kuXaiS5rxgCUHlS7u50fw7t6mbOCaw8t+C pRZUpAbckhlnTJzeXvhTqmDdxwYVtf5IBj1z9VuQ= Date: Wed, 19 Oct 2022 16:18:10 -0700 From: Andrew Morton To: Yang Shi Cc: Mel Gorman , Matthew Wilcox , Linux-MM , LKML Subject: Re: [RFC PATCH] mm/huge_memory: Do not clobber swp_entry_t during THP split Message-Id: <20221019161810.7510df1f37658a2b71c5e3a7@linux-foundation.org> In-Reply-To: References: <20221019134156.zjyyn5aownakvztf@techsingularity.net> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666221493; 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:dkim-signature; bh=oTKnll5qAfEqL/kTmHzW68SLmbcIKONxvCsQlkSz6Qo=; b=BmhSJ+2epMZKegFX+p6u7PSKpj2YwMdsmDn4VH9n5vpi9DbLAcmJBH5FwQhIVZOeT6sbYf 4qqJiaebAr8a93GvTap53xKMiNRzhT02kb/HqpRafQ002MpkuqWv2tAz93O7jXAaeAigC2 RLKiM9/UWPHT5srSyb/FZqvQmktOEFs= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=iX+GyCvT; dmarc=none; spf=pass (imf26.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666221493; a=rsa-sha256; cv=none; b=nLsWyFi6heoZcmj5uq+4c2hnr0DN2NSkMM2Ssz0z54MYcNh7VnUyJte+s6usCaOX1B0BBn vteMOms39SrFW4Et9M5D7n4YLDJm44VzYyV0HdgxJyLWVch5dF634XmGeVE0G+/+zk3LUF 4e5P6K+IXcFsda0wvU9yARlFfboYG7Q= Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=iX+GyCvT; dmarc=none; spf=pass (imf26.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: ECA83140038 X-Rspam-User: X-Stat-Signature: pcb5bbx33oadwgy8kpfm8jcp188onade X-HE-Tag: 1666221492-778876 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, 19 Oct 2022 11:17:14 -0700 Yang Shi wrote: > > The intent of commit b653db77350c patch was to avoid the case where > > PG_private is clear but folio->private is not-NULL. However, THP tail > > pages uses page->private for "swp_entry_t if folio_test_swapcache()" as > > stated in the documentation for struct folio. This patch only clobbers > > page->private for tail pages if the head page was not in swapcache and > > warns once if page->private had an unexpected value. > > It looks like the same issue fixed by > https://lore.kernel.org/linux-mm/20220906190602.1626037-1-bfoster@redhat.com/ It is. As I asked earlier this week, what about reverting b653db77350c? Why do we care about the value of ->private for non-PG_private pages?