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_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 5B30BC2D0BF for ; Mon, 16 Dec 2019 12:54:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B70E206CB for ; Mon, 16 Dec 2019 12:54:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727657AbfLPMyA (ORCPT ); Mon, 16 Dec 2019 07:54:00 -0500 Received: from mx2.suse.de ([195.135.220.15]:39022 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727550AbfLPMx7 (ORCPT ); Mon, 16 Dec 2019 07:53:59 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 29D62AFAF; Mon, 16 Dec 2019 12:53:55 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 69B531E0B2E; Mon, 16 Dec 2019 13:53:53 +0100 (CET) Date: Mon, 16 Dec 2019 13:53:53 +0100 From: Jan Kara To: John Hubbard Cc: Andrew Morton , Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Christoph Hellwig , Dan Williams , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?iso-8859-1?B?Suly9G1l?= Glisse , Magnus Karlsson , Mauro Carvalho Chehab , Michael Ellerman , Michal Hocko , Mike Kravetz , Paul Mackerras , Shuah Khan , Vlastimil Babka , bpf@vger.kernel.org, dri-devel@lists.freedesktop.org, kvm@vger.kernel.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-media@vger.kernel.org, linux-rdma@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-mm@kvack.org, LKML , "Kirill A . Shutemov" Subject: Re: [PATCH v11 23/25] mm/gup: track FOLL_PIN pages Message-ID: <20191216125353.GF22157@quack2.suse.cz> References: <20191212101741.GD10065@quack2.suse.cz> <20191214032617.1670759-1-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20191214032617.1670759-1-jhubbard@nvidia.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Fri 13-12-19 19:26:17, John Hubbard wrote: > Add tracking of pages that were pinned via FOLL_PIN. > > As mentioned in the FOLL_PIN documentation, callers who effectively set > FOLL_PIN are required to ultimately free such pages via unpin_user_page(). > The effect is similar to FOLL_GET, and may be thought of as "FOLL_GET > for DIO and/or RDMA use". > > Pages that have been pinned via FOLL_PIN are identifiable via a > new function call: > > bool page_dma_pinned(struct page *page); > > What to do in response to encountering such a page, is left to later > patchsets. There is discussion about this in [1], [2], and [3]. > > This also changes a BUG_ON(), to a WARN_ON(), in follow_page_mask(). > > [1] Some slow progress on get_user_pages() (Apr 2, 2019): > https://lwn.net/Articles/784574/ > [2] DMA and get_user_pages() (LPC: Dec 12, 2018): > https://lwn.net/Articles/774411/ > [3] The trouble with get_user_pages() (Apr 30, 2018): > https://lwn.net/Articles/753027/ > > Suggested-by: Jan Kara > Suggested-by: Jérôme Glisse > Cc: Kirill A. Shutemov > Signed-off-by: John Hubbard > --- > > Hi Jan, > > This should address all of your comments for patch 23! Thanks. One comment below: > @@ -1486,6 +1500,10 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, > VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); > if (flags & FOLL_TOUCH) > touch_pmd(vma, addr, pmd, flags); > + > + if (!try_grab_page(page, flags)) > + return ERR_PTR(-ENOMEM); > + > if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { > /* > * We don't mlock() pte-mapped THPs. This way we can avoid I'd move this still a bit higher - just after VM_BUG_ON_PAGE() and before if (flags & FOLL_TOUCH) test. Because touch_pmd() can update page tables and we don't won't that if we're going to fail the fault. With this fixed, the patch looks good to me so you can then add: Reviewed-by: Jan Kara Honza -- Jan Kara SUSE Labs, CR