From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755287AbcESX0N (ORCPT ); Thu, 19 May 2016 19:26:13 -0400 Received: from mail-pa0-f44.google.com ([209.85.220.44]:36423 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751646AbcESX0M (ORCPT ); Thu, 19 May 2016 19:26:12 -0400 Subject: Re: [PATCH] mm: move page_ext_init after all struct pages are initialized To: Andrew Morton References: <1463693345-30842-1-git-send-email-yang.shi@linaro.org> <20160519153007.322150e4253656a3ac963656@linux-foundation.org> <6dd46bac-a0e4-d3c0-ded3-cbacc7f4a4ff@linaro.org> <20160519162107.372d19eac129d590ea160203@linux-foundation.org> Cc: iamjoonsoo.kim@lge.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linaro-kernel@lists.linaro.org From: "Shi, Yang" Message-ID: Date: Thu, 19 May 2016 16:26:09 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <20160519162107.372d19eac129d590ea160203@linux-foundation.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/19/2016 4:21 PM, Andrew Morton wrote: > On Thu, 19 May 2016 15:35:15 -0700 "Shi, Yang" wrote: > >> On 5/19/2016 3:30 PM, Andrew Morton wrote: >>> On Thu, 19 May 2016 14:29:05 -0700 Yang Shi wrote: >>> >>>> When DEFERRED_STRUCT_PAGE_INIT is enabled, just a subset of memmap at boot >>>> are initialized, then the rest are initialized in parallel by starting one-off >>>> "pgdatinitX" kernel thread for each node X. >>>> >>>> If page_ext_init is called before it, some pages will not have valid extension, >>>> so move page_ext_init() after it. >>>> >>> >>> When fixing a bug, please fully describe the end-user impact >>> of that bug >> >> The kernel ran into the below oops which is same with the oops reported >> in >> http://ozlabs.org/~akpm/mmots/broken-out/mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch. > > So this patch makes > mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch > obsolete? Actually, no. Checking the return value for lookup_page_ext() is still needed. But, the commit log need to be amended since that bootup oops won't happen anymore with this patch applied. Thanks, Yang >