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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 57173C65C20 for ; Mon, 8 Oct 2018 16:49:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2622C2089D for ; Mon, 8 Oct 2018 16:49:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2622C2089D 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 S1726567AbeJIABt (ORCPT ); Mon, 8 Oct 2018 20:01:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:57020 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726291AbeJIABt (ORCPT ); Mon, 8 Oct 2018 20:01:49 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 1E014B04A; Mon, 8 Oct 2018 16:49:11 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 52C011E3614; Mon, 8 Oct 2018 18:49:07 +0200 (CEST) Date: Mon, 8 Oct 2018 18:49:07 +0200 From: Jan Kara To: john.hubbard@gmail.com Cc: Matthew Wilcox , Michal Hocko , Christopher Lameter , Jason Gunthorpe , Dan Williams , Jan Kara , linux-mm@kvack.org, LKML , linux-rdma , linux-fsdevel@vger.kernel.org, John Hubbard , Al Viro , Jerome Glisse , Christoph Hellwig , Ralph Campbell Subject: Re: [PATCH v3 2/3] mm: introduce put_user_page*(), placeholder versions Message-ID: <20181008164907.GA11150@quack2.suse.cz> References: <20181006024949.20691-1-jhubbard@nvidia.com> <20181006024949.20691-3-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181006024949.20691-3-jhubbard@nvidia.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 05-10-18 19:49:48, john.hubbard@gmail.com wrote: > From: John Hubbard > > Introduces put_user_page(), which simply calls put_page(). > This provides a way to update all get_user_pages*() callers, > so that they call put_user_page(), instead of put_page(). > > Also introduces put_user_pages(), and a few dirty/locked variations, > as a replacement for release_pages(), and also as a replacement > for open-coded loops that release multiple pages. > These may be used for subsequent performance improvements, > via batching of pages to be released. > > This prepares for eventually fixing the problem described > in [1], and is following a plan listed in [2], [3], [4]. > > [1] https://lwn.net/Articles/753027/ : "The Trouble with get_user_pages()" > > [2] https://lkml.kernel.org/r/20180709080554.21931-1-jhubbard@nvidia.com > Proposed steps for fixing get_user_pages() + DMA problems. > > [3]https://lkml.kernel.org/r/20180710082100.mkdwngdv5kkrcz6n@quack2.suse.cz > Bounce buffers (otherwise [2] is not really viable). > > [4] https://lkml.kernel.org/r/20181003162115.GG24030@quack2.suse.cz > Follow-up discussions. > > CC: Matthew Wilcox > CC: Michal Hocko > CC: Christopher Lameter > CC: Jason Gunthorpe > CC: Dan Williams > CC: Jan Kara > CC: Al Viro > CC: Jerome Glisse > CC: Christoph Hellwig > CC: Ralph Campbell > Signed-off-by: John Hubbard > --- > include/linux/mm.h | 48 ++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 46 insertions(+), 2 deletions(-) Looks good to me. You can add: Reviewed-by: Jan Kara Just one nit below: > +/* Pages that were pinned via get_user_pages*() should be released via > + * either put_user_page(), or one of the put_user_pages*() routines > + * below. > + */ Multi-line comments usually follow formatting: /* * Some text here * and more text here... */ Honza -- Jan Kara SUSE Labs, CR