From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id B3D5A6B0033 for ; Mon, 6 Nov 2017 20:05:26 -0500 (EST) Received: by mail-pf0-f198.google.com with SMTP id e64so12714501pfk.0 for ; Mon, 06 Nov 2017 17:05:26 -0800 (PST) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTPS id g2si21576pgr.506.2017.11.06.17.05.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Nov 2017 17:05:25 -0800 (PST) Subject: [PATCH 0/3] introduce get_user_pages_longterm() From: Dan Williams Date: Mon, 06 Nov 2017 16:57:10 -0800 Message-ID: <151001623063.16354.14661493921524115663.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: Sean Hefty , Jan Kara , linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, Doug Ledford , stable@vger.kernel.org, Hal Rosenstock , Jason Gunthorpe , linux-mm@kvack.org, Jeff Moyer , Ross Zwisler , Mauro Carvalho Chehab , Christoph Hellwig , linux-media@vger.kernel.org Andrew, Here is a new get_user_pages api for cases where a driver intends to keep an elevated page count indefinitely. This is distinct from usages like iov_iter_get_pages where the elevated page counts are transient. The iov_iter_get_pages cases immediately turn around and submit the pages to a device driver which will put_page when the i/o operation completes (under kernel control). In the longterm case userspace is responsible for dropping the page reference at some undefined point in the future. This is untenable for filesystem-dax case where the filesystem is in control of the lifetime of the block / page and needs reasonable limits on how long it can wait for pages in a mapping to become idle. Fixing filesystems to actually wait for dax pages to be idle before blocks from a truncate/hole-punch operation are repurposed is saved for a later patch series. Also, allowing longterm registration of dax mappings is a future patch series that introduces a "map with lease" semantic where the kernel can revoke a lease and force userspace to drop its page references. I have also tagged these for -stable to purposely break cases that might assume that longterm memory registrations for filesystem-dax mappings were supported by the kernel. The behavior regression this policy change implies is one of the reasons we maintain the "dax enabled. Warning: EXPERIMENTAL, use at your own risk" notification when mounting a filesystem in dax mode. It is worth noting the device-dax interface does not suffer the same constraints since it does not support file space management operations like hole-punch. --- Dan Williams (3): mm: introduce get_user_pages_longterm IB/core: disable memory registration of fileystem-dax vmas [media] v4l2: disable filesystem-dax mapping support drivers/infiniband/core/umem.c | 2 - drivers/media/v4l2-core/videobuf-dma-sg.c | 5 +- include/linux/mm.h | 3 + mm/gup.c | 75 +++++++++++++++++++++++++++++ 4 files changed, 82 insertions(+), 3 deletions(-) -- 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