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 31D51C388F9 for ; Wed, 11 Nov 2020 09:06:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4DE89205CB 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="Si0TmJPq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4DE89205CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A9E076B0068; Wed, 11 Nov 2020 04:06:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A4F026B006C; Wed, 11 Nov 2020 04:06:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 965156B006E; Wed, 11 Nov 2020 04:06:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0192.hostedemail.com [216.40.44.192]) by kanga.kvack.org (Postfix) with ESMTP id 6A3286B0068 for ; Wed, 11 Nov 2020 04:06:32 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 0E263181AC9CB for ; Wed, 11 Nov 2020 09:06:32 +0000 (UTC) X-FDA: 77471556624.07.head16_1d07ca8272fc Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id E7CC41803F9A4 for ; Wed, 11 Nov 2020 09:06:31 +0000 (UTC) X-HE-Tag: head16_1d07ca8272fc X-Filterd-Recvd-Size: 4887 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf42.hostedemail.com (Postfix) with ESMTP for ; Wed, 11 Nov 2020 09:06:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605085590; 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=Si0TmJPqkx3DLapqdecLhqtKs2x3TRd2oOzGIYZBR8KAh9yZC7BuuNdROdLWUoFytNi4Gy Zp4I4NahDv3vl/KIT67mE83OieGhcnaLJGCTyPjXa5sU27pYv4UkP4IC4Z77NvDD1QOCQC /pRVQjTJLIhQbn9lX7xxdlWwkwn8oCY= 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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