From patchwork Mon Dec 9 22:53:24 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11280675 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7E06C138D for ; Mon, 9 Dec 2019 22:54:33 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 618F6206D5 for ; Mon, 9 Dec 2019 22:54:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 618F6206D5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D67D76E5C5; Mon, 9 Dec 2019 22:54:15 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from hqnvemgate24.nvidia.com (hqnvemgate24.nvidia.com [216.228.121.143]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9FF676E5A0 for ; Mon, 9 Dec 2019 22:54:00 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 09 Dec 2019 14:53:39 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 09 Dec 2019 14:53:59 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 09 Dec 2019 14:53:59 -0800 Received: from HQMAIL105.nvidia.com (172.20.187.12) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 9 Dec 2019 22:53:55 +0000 Received: from rnnvemgw01.nvidia.com (10.128.109.123) by HQMAIL105.nvidia.com (172.20.187.12) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Mon, 9 Dec 2019 22:53:55 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by rnnvemgw01.nvidia.com with Trustwave SEG (v7, 5, 8, 10121) id ; Mon, 09 Dec 2019 14:53:55 -0800 From: John Hubbard To: Andrew Morton Subject: [PATCH v8 06/26] mm: fix get_user_pages_remote()'s handling of FOLL_LONGTERM Date: Mon, 9 Dec 2019 14:53:24 -0800 Message-ID: <20191209225344.99740-7-jhubbard@nvidia.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191209225344.99740-1-jhubbard@nvidia.com> References: <20191209225344.99740-1-jhubbard@nvidia.com> MIME-Version: 1.0 X-NVConfidentiality: public X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1575932020; bh=l4ZzqtVW71Fwvoz1qyCbd1xWWEz8EY4C2cUJdAbaFHs=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:X-NVConfidentiality: Content-Transfer-Encoding:Content-Type; b=Tc6ngqtdaDUUYOEZpgVNwCPnzvZKNYykbtQ3tPQgJ7XL23fY0QNCULxxFBi+lsPXX XDwVnw0tTtpKy6Q50IbDLdmOKpfug+eTUgstYjxxdNqJGPfcK1R+lI+5xfXnCrKk0h vR7xtB6lCCRfunBcDYw1DbHdsr0FBJMLzidLxFUIkiQFwApLbu29Qe7bVy66Vi9Ym/ PqOy+2DjkhicWrqQZHOf88SY1f6fnW6jHiELsn5krAapqoIQggFqkgj7gX9eBl+1jj iD6MPf75Y/JAw17r9Na4KGxBjHvJhbxC3DCszYkpTwv5V2JBI/+6JQhenmBAUJjLZW 7qHI+gx7vSotQ== X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Hocko , Jan Kara , kvm@vger.kernel.org, linux-doc@vger.kernel.org, David Airlie , Dave Chinner , dri-devel@lists.freedesktop.org, LKML , linux-mm@kvack.org, Paul Mackerras , linux-kselftest@vger.kernel.org, Ira Weiny , Jonathan Corbet , linux-rdma@vger.kernel.org, Michael Ellerman , Christoph Hellwig , Jason Gunthorpe , Jason Gunthorpe , Vlastimil Babka , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , linux-media@vger.kernel.org, Shuah Khan , John Hubbard , linux-block@vger.kernel.org, =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Al Viro , Dan Williams , Mauro Carvalho Chehab , Magnus Karlsson , Jens Axboe , netdev@vger.kernel.org, Alex Williamson , linux-fsdevel@vger.kernel.org, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, "David S . Miller" , Mike Kravetz Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" As it says in the updated comment in gup.c: current FOLL_LONGTERM behavior is incompatible with FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on vmas. However, the corresponding restriction in get_user_pages_remote() was slightly stricter than is actually required: it forbade all FOLL_LONGTERM callers, but we can actually allow FOLL_LONGTERM callers that do not set the "locked" arg. Update the code and comments to loosen the restriction, allowing FOLL_LONGTERM in some cases. Also, copy the DAX check ("if a VMA is DAX, don't allow long term pinning") from the VFIO call site, all the way into the internals of get_user_pages_remote() and __gup_longterm_locked(). That is: get_user_pages_remote() calls __gup_longterm_locked(), which in turn calls check_dax_vmas(). This check will then be removed from the VFIO call site in a subsequent patch. Thanks to Jason Gunthorpe for pointing out a clean way to fix this, and to Dan Williams for helping clarify the DAX refactoring. Tested-by: Alex Williamson Acked-by: Alex Williamson Reviewed-by: Jason Gunthorpe Reviewed-by: Ira Weiny Suggested-by: Jason Gunthorpe Cc: Dan Williams Cc: Jerome Glisse Signed-off-by: John Hubbard --- mm/gup.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 3ecce297a47f..c0c56888e7cc 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -29,6 +29,13 @@ struct follow_page_context { unsigned int page_mask; }; +static __always_inline long __gup_longterm_locked(struct task_struct *tsk, + struct mm_struct *mm, + unsigned long start, + unsigned long nr_pages, + struct page **pages, + struct vm_area_struct **vmas, + unsigned int flags); /* * Return the compound head page with ref appropriately incremented, * or NULL if that failed. @@ -1179,13 +1186,23 @@ long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, struct vm_area_struct **vmas, int *locked) { /* - * FIXME: Current FOLL_LONGTERM behavior is incompatible with + * Parts of FOLL_LONGTERM behavior are incompatible with * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on - * vmas. As there are no users of this flag in this call we simply - * disallow this option for now. + * vmas. However, this only comes up if locked is set, and there are + * callers that do request FOLL_LONGTERM, but do not set locked. So, + * allow what we can. */ - if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) - return -EINVAL; + if (gup_flags & FOLL_LONGTERM) { + if (WARN_ON_ONCE(locked)) + return -EINVAL; + /* + * This will check the vmas (even if our vmas arg is NULL) + * and return -ENOTSUPP if DAX isn't allowed in this case: + */ + return __gup_longterm_locked(tsk, mm, start, nr_pages, pages, + vmas, gup_flags | FOLL_TOUCH | + FOLL_REMOTE); + } return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas, locked,