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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham 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 3CADAC43142 for ; Wed, 27 Jun 2018 17:02:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E736426039 for ; Wed, 27 Jun 2018 17:02:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E736426039 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965911AbeF0RCw (ORCPT ); Wed, 27 Jun 2018 13:02:52 -0400 Received: from mx2.suse.de ([195.135.220.15]:44387 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932406AbeF0RCu (ORCPT ); Wed, 27 Jun 2018 13:02:50 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext-too.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id A7EE1AD6A; Wed, 27 Jun 2018 17:02:48 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 906941E3C15; Wed, 27 Jun 2018 19:02:46 +0200 (CEST) Date: Wed, 27 Jun 2018 19:02:46 +0200 From: Jan Kara To: Jason Gunthorpe Cc: Jan Kara , Michal Hocko , Dan Williams , John Hubbard , Christoph Hellwig , John Hubbard , Matthew Wilcox , Christopher Lameter , Linux MM , LKML , linux-rdma Subject: Re: [PATCH 2/2] mm: set PG_dma_pinned on get_user_pages*() Message-ID: <20180627170246.qfvucs72seqabaef@quack2.suse.cz> References: <3898ef6b-2fa0-e852-a9ac-d904b47320d5@nvidia.com> <20180626134757.GY28965@dhcp22.suse.cz> <20180626164825.fz4m2lv6hydbdrds@quack2.suse.cz> <20180627113221.GO32348@dhcp22.suse.cz> <20180627115349.cu2k3ainqqdrrepz@quack2.suse.cz> <20180627115927.GQ32348@dhcp22.suse.cz> <20180627124255.np2a6rxy6rb6v7mm@quack2.suse.cz> <20180627145718.GB20171@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180627145718.GB20171@ziepe.ca> User-Agent: NeoMutt/20170912 (1.9.0) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 27-06-18 08:57:18, Jason Gunthorpe wrote: > On Wed, Jun 27, 2018 at 02:42:55PM +0200, Jan Kara wrote: > > On Wed 27-06-18 13:59:27, Michal Hocko wrote: > > > On Wed 27-06-18 13:53:49, Jan Kara wrote: > > > > On Wed 27-06-18 13:32:21, Michal Hocko wrote: > > > [...] > > > > > Appart from that, do we really care about 32b here? Big DIO, IB users > > > > > seem to be 64b only AFAIU. > > > > > > > > IMO it is a bad habit to leave unpriviledged-user-triggerable oops in the > > > > kernel even for uncommon platforms... > > > > > > Absolutely agreed! I didn't mean to keep the blow up for 32b. I just > > > wanted to say that we can stay with a simple solution for 32b. I thought > > > the g-u-p-longterm has plugged the most obvious breakage already. But > > > maybe I just misunderstood. > > > > Most yes, but if you try hard enough, you can still trigger the oops e.g. > > with appropriately set up direct IO when racing with writeback / reclaim. > > gup longterm is only different from normal gup if you have DAX and few > people do, which really means it doesn't help at all.. AFAIK?? Right, what I wrote works only for DAX. For non-DAX situation g-u-p longterm does not currently help at all. Sorry for confusion. Honza -- Jan Kara SUSE Labs, CR