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[209.132.180.67]) by mx.google.com with ESMTP id 66si4753481plc.428.2019.08.16.15.00.58; Fri, 16 Aug 2019 15:01:14 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727734AbfHPWAY (ORCPT + 99 others); Fri, 16 Aug 2019 18:00:24 -0400 Received: from mga18.intel.com ([134.134.136.126]:24559 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727682AbfHPWAY (ORCPT ); Fri, 16 Aug 2019 18:00:24 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Aug 2019 14:59:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,394,1559545200"; d="scan'208";a="201663215" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by fmsmga004.fm.intel.com with ESMTP; 16 Aug 2019 14:59:54 -0700 Date: Fri, 16 Aug 2019 14:59:54 -0700 From: Ira Weiny To: John Hubbard Cc: Jan Kara , Andrew Morton , Christoph Hellwig , Dan Williams , Dave Chinner , Jason Gunthorpe , =?iso-8859-1?B?Suly9G1l?= Glisse , LKML , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages_remote() Message-ID: <20190816215954.GA19549@iweiny-DESK2.sc.intel.com> References: <2cbdf599-2226-99ae-b4d5-8909a0a1eadf@nvidia.com> <20190815132622.GG14313@quack2.suse.cz> <20190815133510.GA21302@quack2.suse.cz> <20190815173237.GA30924@iweiny-DESK2.sc.intel.com> <58b75fa9-1272-b683-cb9f-722cc316bf8f@nvidia.com> <20190816154108.GE3041@quack2.suse.cz> <20190816183337.GA371@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 16, 2019 at 11:50:09AM -0700, John Hubbard wrote: > On 8/16/19 11:33 AM, Ira Weiny wrote: > > On Fri, Aug 16, 2019 at 05:41:08PM +0200, Jan Kara wrote: > > > On Thu 15-08-19 19:14:08, John Hubbard wrote: > > > > On 8/15/19 10:41 AM, John Hubbard wrote: > > > > > On 8/15/19 10:32 AM, Ira Weiny wrote: > > > > > > On Thu, Aug 15, 2019 at 03:35:10PM +0200, Jan Kara wrote: > > > > > > > On Thu 15-08-19 15:26:22, Jan Kara wrote: > > > > > > > > On Wed 14-08-19 20:01:07, John Hubbard wrote: > > > > > > > > > On 8/14/19 5:02 PM, John Hubbard wrote: > > > > ... > > > > > > > > OK, there was only process_vm_access.c, plus (sort of) Bharath's sgi-gru > > > > patch, maybe eventually [1]. But looking at process_vm_access.c, I think > > > > it is one of the patches that is no longer applicable, and I can just > > > > drop it entirely...I'd welcome a second opinion on that... > > > > > > I don't think you can drop the patch. process_vm_rw_pages() clearly touches > > > page contents and does not synchronize with page_mkclean(). So it is case > > > 1) and needs FOLL_PIN semantics. > > > > John could you send a formal patch using vaddr_pin* and I'll add it to the > > tree? > > > > Yes...hints about which struct file to use here are very welcome, btw. This part > of mm is fairly new to me. I'm still working out the final semantics of vaddr_pin*. But right now you don't need a vaddr_pin if you don't specify FOLL_LONGTERM. Since case 1, this case, does not need FOLL_LONGTERM I think it is safe to simply pass NULL here. OTOH we could just track this against the mm_struct. But I don't think we need to because this pin should be transient. And this is why I keep leaning toward _not_ putting these flags in the vaddr_pin*() calls. I know this is what I did but I think I'm wrong. It should be the caller specifying what they want and the vaddr_pin*() calls check that what they are asking for is correct. Ira > > thanks, > -- > John Hubbard > NVIDIA