From: Dan Williams <dan.j.williams@intel.com>
To: akpm@linux-foundation.org
Cc: Inki Dae <inki.dae@samsung.com>, Jan Kara <jack@suse.cz>,
Joonyoung Shim <jy0922.shim@samsung.com>,
linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org,
linux-kernel@vger.kernel.org,
Seung-Woo Kim <sw0312.kim@samsung.com>,
Jeff Moyer <jmoyer@redhat.com>,
stable@vger.kernel.org, Hal Rosenstock <hal.rosenstock@gmail.com>,
Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
linux-mm@kvack.org, Doug Ledford <dledford@redhat.com>,
Mel Gorman <mgorman@suse.de>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
Sean Hefty <sean.hefty@intel.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Christoph Hellwig <hch@lst.de>, Vlastimil Babka <vbabka@suse.cz>,
linux-media@vger.kernel.org
Subject: [PATCH v2 0/4] introduce get_user_pages_longterm()
Date: Tue, 14 Nov 2017 11:56:29 -0800 [thread overview]
Message-ID: <151068938905.7446.12333914805308312313.stgit@dwillia2-desk3.amr.corp.intel.com> (raw)
Changes since v1 [1]:
* Cleanup local 'vmas' argument (Christoph)
* Replace inline IS_ENABLED(CONFIG_FS_DAX) in C code with ifdef
versions of get_user_pages_longterm() for the FS_DAX on/off cases
(Christoph)
* Add a new patch for the get_vaddr_frames() case, this impacts users
like V4L2, and the Exynos driver.
* Collect Christoph's reviewed-by for the rdma change
[1]: https://lwn.net/Articles/738323/
---
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 (4):
mm: introduce get_user_pages_longterm
mm: fail get_vaddr_frames() for filesystem-dax mappings
[media] v4l2: disable filesystem-dax mapping support
IB/core: disable memory registration of fileystem-dax vmas
drivers/infiniband/core/umem.c | 2 -
drivers/media/v4l2-core/videobuf-dma-sg.c | 5 +-
include/linux/fs.h | 14 ++++++
include/linux/mm.h | 13 ++++++
mm/frame_vector.c | 4 ++
mm/gup.c | 64 +++++++++++++++++++++++++++++
6 files changed, 99 insertions(+), 3 deletions(-)
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next reply other threads:[~2017-11-14 20:04 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-14 19:56 Dan Williams [this message]
2017-11-14 19:56 ` [PATCH v2 1/4] mm: introduce get_user_pages_longterm Dan Williams
2017-11-21 23:05 ` Andrew Morton
2017-11-21 23:26 ` Dan Williams
2017-11-21 23:11 ` Andrew Morton
2017-11-14 19:56 ` [PATCH v2 2/4] mm: fail get_vaddr_frames() for filesystem-dax mappings Dan Williams
2017-11-27 16:15 ` Jan Kara
2017-11-27 16:19 ` Dan Williams
2017-11-14 19:56 ` [PATCH v2 3/4] [media] v4l2: disable filesystem-dax mapping support Dan Williams
2017-11-27 16:17 ` Jan Kara
2017-11-14 19:56 ` [PATCH v2 4/4] IB/core: disable memory registration of fileystem-dax vmas Dan Williams
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