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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 B1257CA9EA0 for ; Tue, 22 Oct 2019 07:57:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 912C420B7C for ; Tue, 22 Oct 2019 07:57:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731072AbfJVH5t (ORCPT ); Tue, 22 Oct 2019 03:57:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:48178 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726978AbfJVH5t (ORCPT ); Tue, 22 Oct 2019 03:57:49 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7B15CB85D; Tue, 22 Oct 2019 07:57:47 +0000 (UTC) Date: Tue, 22 Oct 2019 09:57:45 +0200 From: Oscar Salvador To: David Hildenbrand Cc: n-horiguchi@ah.jp.nec.com, mhocko@kernel.org, mike.kravetz@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 15/16] mm/hwpoison-inject: Rip off duplicated checks Message-ID: <20191022075745.GC19060@linux> References: <20191017142123.24245-1-osalvador@suse.de> <20191017142123.24245-16-osalvador@suse.de> <1aa1f09a-1210-d0bc-86ac-9674828bff49@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1aa1f09a-1210-d0bc-86ac-9674828bff49@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 21, 2019 at 11:40:39AM +0200, David Hildenbrand wrote: > I explored somewhere already why this code was added: > > > commit 31d3d3484f9bd263925ecaa341500ac2df3a5d9b > Author: Wu Fengguang > Date: Wed Dec 16 12:19:59 2009 +0100 > > HWPOISON: limit hwpoison injector to known page types > > __memory_failure()'s workflow is > > set PG_hwpoison > //... > unset PG_hwpoison if didn't pass hwpoison filter > > That could kill unrelated process if it happens to page fault on the > page with the (temporary) PG_hwpoison. The race should be big enough to > appear in stress tests. > > Fix it by grabbing the page and checking filter at inject time. This > also avoids the very noisy "Injecting memory failure..." messages. > > - we don't touch madvise() based injection, because the filters are > generally not necessary for it. > - if we want to apply the filters to h/w aided injection, we'd better to > rearrange the logic in __memory_failure() instead of this patch. > > AK: fix documentation, use drain all, cleanups > > > You should justify why it is okay to do rip that code out now. > It's not just duplicate checks. > > Was the documented race fixed? > Will we fix the race within memory_failure() later? > Don't we care? > > Also, you should add that this fixes the access of uninitialized memmaps > now and makes the interface work correctly with devmem. Thanks for bringuing this up David. I guess I was carried away. Since I have to do another re-spin to re-work a couple of things, I will work on this as well. -- Oscar Salvador SUSE L3