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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 04B5CC433B4 for ; Wed, 14 Apr 2021 06:04:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2CCF611C9 for ; Wed, 14 Apr 2021 06:04:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348555AbhDNGEv (ORCPT ); Wed, 14 Apr 2021 02:04:51 -0400 Received: from mx2.suse.de ([195.135.220.15]:50460 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348556AbhDNGEq (ORCPT ); Wed, 14 Apr 2021 02:04:46 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1618380262; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=u+2Ssby07S60nylEFaEVC0kcFk8cqBXASSGiNOFJJrU=; b=aWs2owsBfcMfFsA6IhkWMGFmirqk8xYxoZ0kB9aAKkrbWFD8JCBrZue4VBgq1wIvNZqMPZ D0/nE+9oUBv8qZknzhEV4iyTQJ3U1V9KbfTfTrKOmBrb6oJsn1/Ga97ceTgbc2QHence/2 2XopKsvIDA7NAFXG/vEquobGIQGsCgo= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2CF8DAD77; Wed, 14 Apr 2021 06:04:22 +0000 (UTC) Date: Wed, 14 Apr 2021 08:04:21 +0200 From: Michal Hocko To: Mike Kravetz Cc: Oscar Salvador , 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: References: <20210413104747.12177-1-osalvador@suse.de> <20210413104747.12177-4-osalvador@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 13-04-21 14:19:03, Mike Kravetz wrote: > On 4/13/21 6:23 AM, Michal Hocko wrote: > > On Tue 13-04-21 12:47:43, Oscar Salvador wrote: [...] > > Or do we need it for giga pages which are not allocated by the page > > allocator? If yes then moving it to prep_compound_gigantic_page would be > > better. > > I am pretty sure dynamically allocated giga pages have page->Private > cleared as well. It is not obvious, but the alloc_contig_range code > used to put together giga pages will end up calling isolate_freepages_range > that will call split_map_pages and then post_alloc_hook for each MAX_ORDER > block. Thanks for saving me from crawling that code. > As mentioned, this is not obvious and I would hate to rely on this > behavior not changing. Thinking about it some more, having some (page granularity) allocator not clearing page private would be a serious problem for anybody relying on its state. So I am not sure this can change. > > So should we just drop it here? > > The only place where page->private may not be initialized is when we do > allocations at boot time from memblock. In this case, we will add the > pages to the free list via put_page/free_huge_page so the appropriate > flags will be cleared before anyone notices. Pages allocated by the bootmem should be pre initialized from the boot, no? > I'm wondering if we should just do a set_page_private(page, 0) here in > prep_new_huge_page since we now use that field for flags. Or, is that > overkill? I would rather not duplicate the work done by underlying allocators. I do not think other users of the allocator want to do the same so why should hugetlb be any different. -- Michal Hocko SUSE Labs