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=-5.3 required=3.0 tests=BAYES_00, 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 9BA92C433ED for ; Wed, 14 Apr 2021 10:02:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AA3A610C8 for ; Wed, 14 Apr 2021 10:02:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348671AbhDNKDD (ORCPT ); Wed, 14 Apr 2021 06:03:03 -0400 Received: from mx2.suse.de ([195.135.220.15]:43884 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346091AbhDNKCP (ORCPT ); Wed, 14 Apr 2021 06:02:15 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 43ECCAED7; Wed, 14 Apr 2021 10:01:50 +0000 (UTC) Date: Wed, 14 Apr 2021 12:01:47 +0200 From: Oscar Salvador To: Michal Hocko Cc: Mike Kravetz , Andrew Morton , Vlastimil Babka , David Hildenbrand , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v7 3/7] mm,hugetlb: Clear HPageFreed outside of the lock Message-ID: <20210414100147.GD20886@linux> References: <20210413104747.12177-1-osalvador@suse.de> <20210413104747.12177-4-osalvador@suse.de> <20210414074132.GB20401@linux> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 14, 2021 at 10:28:33AM +0200, Michal Hocko wrote: > You are right it doesn't do it there. But all struct pages, even those > that are allocated by the bootmem allocator should initialize its struct > pages. They would be poisoned otherwise, right? I would have to look at > the exact code path but IIRC this should be around the time bootmem > allocator state transitions to the page allocator. Ok, you are right. struct pages are initialized a bit earlier through: start_kernel setup_arch paging_init zone_sizes_init free_area_init free_area_init_node free_area_init_core memmap_init_zone memmap_init_range __init_single_page While the allocation of bootmem hugetlb happens start_kernel parse_args ... hugepages_setup ... hugetlb_hstate_alloc_pages __alloc_bootmem_huge_page which is after the setup_arch() call. So by the time we get the page from __alloc_bootmem_huge_page(), fields are zeroed. I thought we might get in trouble because memblock_alloc_try_nid_raw() calls page_init_poison() which poisons the chunk with 0xff,e.g: [ 1.955471] boot: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff [ 1.955476] boot: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff but it seems that does not the memmap struct page. I checked, and when we get there in __alloc_bootmem_huge_page, page->private is still zeroed, so I guess it should be safe to assume that we do not really need to clear the flag in __prep_new_huge_page() routine? -- Oscar Salvador SUSE L3