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=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,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 620AAC56201 for ; Wed, 11 Nov 2020 09:06:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E824C2075A for ; Wed, 11 Nov 2020 09:06:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="VatQ7YkQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726255AbgKKJGc (ORCPT ); Wed, 11 Nov 2020 04:06:32 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:23777 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726036AbgKKJGa (ORCPT ); Wed, 11 Nov 2020 04:06:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605085588; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MweZ+zDjGfskRd7/rs12EFNBHUajWWPBiHREeUxcr1E=; b=VatQ7YkQM5yuvwtWjxBBQmct0wbpy8moN436dfSvo95q7Fw021BwyYUZ1i+hEdnpnlI0Mm 2yIrc17H9rl0AaQwSWqLNJ7MjiMD3IT7kFhJRtliwKzypU98A5HNsGFSvIAr8qdTDAK9vT LzTbdbocatOzuK3zPDcZFOpgbpDZSxk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-196-W0ZwdTqeNTS5jCcAKWO8Lg-1; Wed, 11 Nov 2020 04:06:26 -0500 X-MC-Unique: W0ZwdTqeNTS5jCcAKWO8Lg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C6F0F1017DC3; Wed, 11 Nov 2020 09:06:23 +0000 (UTC) Received: from [10.36.114.151] (ovpn-114-151.ams2.redhat.com [10.36.114.151]) by smtp.corp.redhat.com (Postfix) with ESMTP id 773225B4B6; Wed, 11 Nov 2020 09:06:21 +0000 (UTC) Subject: Re: [PATCH v1] mm/page_alloc: clear pages in alloc_contig_pages() with init_on_alloc=1 or __GFP_ZERO To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Alexander Potapenko , Mike Kravetz , Vlastimil Babka , Mike Rapoport , Oscar Salvador , Kees Cook , Michael Ellerman References: <20201110193240.25401-1-david@redhat.com> <20201111084738.GT12240@dhcp22.suse.cz> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <4ebc711e-7fbc-62aa-b88f-3d6ffa9379ff@redhat.com> Date: Wed, 11 Nov 2020 10:06:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20201111084738.GT12240@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11.11.20 09:47, Michal Hocko wrote: > On Tue 10-11-20 20:32:40, David Hildenbrand wrote: >> commit 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and >> init_on_free=1 boot options") resulted with init_on_alloc=1 in all pages >> leaving the buddy via alloc_pages() and friends to be >> initialized/cleared/zeroed on allocation. >> >> However, the same logic is currently not applied to >> alloc_contig_pages(): allocated pages leaving the buddy aren't cleared >> with init_on_alloc=1 and init_on_free=0. Let's also properly clear >> pages on that allocation path and add support for __GFP_ZERO. > > AFAIR we do not have any user for __GFP_ZERO right? Not that this is Sorry, I had extended information under "---" but accidentally regenerated the patch before sending it out. __GFP_ZERO is not used yet. It's intended to be used in https://lkml.kernel.org/r/20201029162718.29910-1-david@redhat.com and I can move that change into a separate patch if desired. > harmful but it is better to call that explicitly because a missing > implementation would be a real problem and as such a bug fix. > > I am also not sure handling init_on_free at the higher level is good. > As we have discussed recently the primary point of this feature is to > add clearing at very few well defined entry points rather than spill it over > many places. In this case the entry point for the allocator is > __isolate_free_page which removes pages from the page allocator. I > haven't checked how much this is used elsewhere but I would expect > init_on_alloc to be handled there. Well, this is the entry point to our range allocator, which lives in page_alloc.c - used by actual high-level allocators (CMA, gigantic pages, etc). It's just a matter of taste where we want to have that handling exactly inside our allocator. isolate_freepages_range()->split_map_pages() does the post_alloc_hook call. As we certainly don't want to zero pages during compaction, we could either pass the gfp_mask/"bool clear" down to that functions and handle it in there, or handle it in isolate_freepages_range(), after the ->split_map_pages() call. Whatever you prefer. Thanks! -- Thanks, David / dhildenb