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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 DB34FC32750 for ; Tue, 13 Aug 2019 21:16:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9CFF2206C2 for ; Tue, 13 Aug 2019 21:16:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="OkG7Qgjo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9CFF2206C2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3CEB46B0010; Tue, 13 Aug 2019 17:16:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 37F206B02B2; Tue, 13 Aug 2019 17:16:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 297226B02B3; Tue, 13 Aug 2019 17:16:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0196.hostedemail.com [216.40.44.196]) by kanga.kvack.org (Postfix) with ESMTP id 08F836B0010 for ; Tue, 13 Aug 2019 17:16:33 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id A3F5F52C3 for ; Tue, 13 Aug 2019 21:16:32 +0000 (UTC) X-FDA: 75818663424.05.van26_90669d991b555 X-HE-Tag: van26_90669d991b555 X-Filterd-Recvd-Size: 3143 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Tue, 13 Aug 2019 21:16:32 +0000 (UTC) Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D5EA8205C9; Tue, 13 Aug 2019 21:16:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565730991; bh=5lO5nG45fLOHTgE1yvwYm5c55LUdkLb+cAFPTo7XcbE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=OkG7QgjoGy1/FLMnWjN6QVHtQGDQE7lx3AF09Wq1TzQirB9nW7PhsZgi97LYakzAS kpNmEhjjpIsqmSORExdEosdrLv2gJP/YeSBEFOMn1H5v5ee8hvFz/1qjptsMpcWS3X KSFzaA/tLs+FDl9iSVKMYNQ4/gNMWqHEiPVBbtww= Date: Tue, 13 Aug 2019 14:16:30 -0700 From: Andrew Morton To: David Rientjes Cc: Vlastimil Babka , Naoya Horiguchi , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch] mm, page_alloc: move_freepages should not examine struct page of reserved memory Message-Id: <20190813141630.bd8cee48e6a83ca77eead6ad@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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, 12 Aug 2019 20:37:11 -0700 (PDT) David Rientjes wrote: > After commit 907ec5fca3dc ("mm: zero remaining unavailable struct pages"), > struct page of reserved memory is zeroed. This causes page->flags to be 0 > and fixes issues related to reading /proc/kpageflags, for example, of > reserved memory. > > The VM_BUG_ON() in move_freepages_block(), however, assumes that > page_zone() is meaningful even for reserved memory. That assumption is no > longer true after the aforementioned commit. > > There's no reason why move_freepages_block() should be testing the > legitimacy of page_zone() for reserved memory; its scope is limited only > to pages on the zone's freelist. > > Note that pfn_valid() can be true for reserved memory: there is a backing > struct page. The check for page_to_nid(page) is also buggy but reserved > memory normally only appears on node 0 so the zeroing doesn't affect this. > > Move the debug checks to after verifying PageBuddy is true. This isolates > the scope of the checks to only be for buddy pages which are on the zone's > freelist which move_freepages_block() is operating on. In this case, an > incorrect node or zone is a bug worthy of being warned about (and the > examination of struct page is acceptable bcause this memory is not > reserved). I'm thinking Fixes:907ec5fca3dc and Cc:stable? But 907ec5fca3dc is almost a year old, so you were doing something special to trigger this?