From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 2C4056B0003 for ; Fri, 23 Feb 2018 03:55:53 -0500 (EST) Received: by mail-pf0-f197.google.com with SMTP id s17so3893152pfm.23 for ; Fri, 23 Feb 2018 00:55:53 -0800 (PST) Received: from mga06.intel.com (mga06.intel.com. [134.134.136.31]) by mx.google.com with ESMTPS id j61-v6si1485730plb.395.2018.02.23.00.55.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 23 Feb 2018 00:55:51 -0800 (PST) Date: Fri, 23 Feb 2018 16:55:47 +0800 From: Haozhong Zhang Subject: Re: [PATCH v2 0/5] vfio, dax: prevent long term filesystem-dax pins and other fixes Message-ID: <20180223085547.3kkbo5lbt3orkqqn@hz-desktop> References: <151937026001.18973.12034171121582300402.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <151937026001.18973.12034171121582300402.stgit@dwillia2-desk3.amr.corp.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: linux-nvdimm@lists.01.org, Michal Hocko , Jan Kara , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-mm@kvack.org, Alex Williamson , Gerd Rausch , Alexander Viro , linux-fsdevel@vger.kernel.org, kbuild test robot , Christoph Hellwig On 02/22/18 23:17 -0800, Dan Williams wrote: > Changes since v1 [1]: > > * Fix the detection of device-dax file instances in vma_is_fsdax(). > (Haozhong, Gerd) > > * Fix compile breakage in the FS_DAX=n and DEV_DAX=y case. (0day robot) > > [1]: https://lists.01.org/pipermail/linux-nvdimm/2018-February/014046.html > > --- > > The vfio interface, like RDMA, wants to setup long term (indefinite) > pins of the pages backing an address range so that a guest or userspace > driver can perform DMA to the with physical address. Given that this > pinning may lead to filesystem operations deadlocking in the > filesystem-dax case, the pinning request needs to be rejected. > > The longer term fix for vfio, RDMA, and any other long term pin user, is > to provide a 'pin with lease' mechanism. Similar to the leases that are > hold for pNFS RDMA layouts, this userspace lease gives the kernel a way > to notify userspace that the block layout of the file is changing and > the kernel is revoking access to pinned pages. > > --- > > Dan Williams (5): > dax: fix vma_is_fsdax() helper > dax: fix dax_mapping() definition in the FS_DAX=n + DEV_DAX=y case > dax: fix S_DAX definition > dax: short circuit vma_is_fsdax() in the CONFIG_FS_DAX=n case > vfio: disable filesystem-dax page pinning > > > drivers/vfio/vfio_iommu_type1.c | 18 +++++++++++++++--- > include/linux/dax.h | 9 ++++++--- > include/linux/fs.h | 6 ++++-- > 3 files changed, 25 insertions(+), 8 deletions(-) Tested on QEMU with fs-dax and device-dax as vNVDIMM backends respectively with vfio passthrough. The fs-dax case fails QEMU as expected, and the device-dax case works normally now. Tested-by: Haozhong Zhang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org