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 31B86C43381 for ; Mon, 11 Jan 2021 16:16:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F165D2247F for ; Mon, 11 Jan 2021 16:16:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388654AbhAKQQg (ORCPT ); Mon, 11 Jan 2021 11:16:36 -0500 Received: from mx2.suse.de ([195.135.220.15]:57376 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730472AbhAKQQf (ORCPT ); Mon, 11 Jan 2021 11:16:35 -0500 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=1610381748; 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=/MLcYm9FTPYiWOWaeOX0MRtpZVUJ/LO/iqAkq7nU3CY=; b=sXOlN3lud62xh6d8BigmuKb+9U0y2dD+yQr4Q+H8DbazOec28y1mgWHeYDR0W5mzLVgghE kMsg2m8cmZStxuq63nDLzg3IjBwQzHWfGwhsoJTlMknXKSyEzEoC6VRM51ZnHqYo4uHmVA wfI/iL+JAeYDGdUPFnKMRYktUhyyhDQ= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AE32EAE89; Mon, 11 Jan 2021 16:15:48 +0000 (UTC) Date: Mon, 11 Jan 2021 17:15:47 +0100 From: Michal Hocko To: Jason Gunthorpe Cc: John Hubbard , Linus Torvalds , Andrea Arcangeli , Andrew Morton , Linux-MM , Linux Kernel Mailing List , Yu Zhao , Andy Lutomirski , Peter Xu , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , Minchan Kim , Will Deacon , Peter Zijlstra , Hugh Dickins , "Kirill A. Shutemov" , Matthew Wilcox , Oleg Nesterov , Jann Horn , Kees Cook , Leon Romanovsky , Jan Kara , Kirill Tkhai , Nadav Amit , Jens Axboe Subject: Re: [PATCH 0/1] mm: restore full accuracy in COW page reuse Message-ID: <20210111161547.GD22493@dhcp22.suse.cz> References: <20210110004435.26382-1-aarcange@redhat.com> <45806a5a-65c2-67ce-fc92-dc8c2144d766@nvidia.com> <20210111160549.GN504133@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210111160549.GN504133@ziepe.ca> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 11-01-21 12:05:49, Jason Gunthorpe wrote: > On Sun, Jan 10, 2021 at 11:26:57PM -0800, John Hubbard wrote: > > > So: > > > > FOLL_PIN: would use DMA_PIN_COUNTING_BIAS to increment page refcount. > > These are long term pins for dma. > > > > FOLL_GET: would use GUP_PIN_COUNTING_BIAS to increment page refcount. > > These are not long term pins. > > Do we have any places yet that care about the long-term-ness? I was hoping to use that information to distinguish ephemeral migration failures due to page reference from long term pins. The later would be a hard failure for the migration. -- Michal Hocko SUSE Labs