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* [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN
@ 2019-12-16 22:25 John Hubbard
  2019-12-16 22:25 ` [PATCH v11 01/25] mm/gup: factor out duplicate code from four routines John Hubbard
                   ` (26 more replies)
  0 siblings, 27 replies; 67+ messages in thread
From: John Hubbard @ 2019-12-16 22:25 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Al Viro, Alex Williamson, Benjamin Herrenschmidt,
	Björn Töpel, Christoph Hellwig, Dan Williams,
	Daniel Vetter, Dave Chinner, David Airlie, David S . Miller,
	Ira Weiny, Jan Kara, Jason Gunthorpe, Jens Axboe,
	Jonathan Corbet, Jérôme Glisse, Magnus Karlsson,
	Mauro Carvalho Chehab, Michael Ellerman, Michal Hocko,
	Mike Kravetz, Paul Mackerras, Shuah Khan, Vlastimil Babka, bpf,
	dri-devel, kvm, linux-block, linux-doc, linux-fsdevel,
	linux-kselftest, linux-media, linux-rdma, linuxppc-dev, netdev,
	linux-mm, LKML, John Hubbard

Hi,

This implements an API naming change (put_user_page*() -->
unpin_user_page*()), and also implements tracking of FOLL_PIN pages. It
extends that tracking to a few select subsystems. More subsystems will
be added in follow up work.

Christoph Hellwig, a point of interest:

a) I've moved the bulk of the code out of the inline functions, as
   requested, for the devmap changes (patch 4: "mm: devmap: refactor
   1-based refcounting for ZONE_DEVICE pages").

Changes since v10: Remaining fixes resulting from Jan Kara's reviews:

* Shifted to using the sign bit in page_dma_pinned() to allow accurate
  results even in the overflow case. See the comments in that routine
  for details. This allowed getting rid of the new
  page_ref_zero_or_close_to_bias_overflow(), in favor of a simple
  sign check via "page_ref_count() <= 0").

* Simplified some of the huge_memory.c changes, and simplified a gup.c
  WARN invocation.

* Now using a standard -ENOMEM for most try_grab_page() failures.

* Got rid of tabs in the comment headers (I had thought they were
  required there, but it's actually the reverse: they are not
  allowed there).

* Rebased against 5.5-rc2 and retested.

* Added Jan Kara's reviewed-by tag for patch 23 (the main patch of the
  series).

Changes since v9: Fixes resulting from Jan Kara's and Jonathan Corbet's
reviews:

* Removed reviewed-by tags from the "mm/gup: track FOLL_PIN pages" (those
  were improperly inherited from the much smaller refactoring patch that
  was merged into it).

* Made try_grab_compound_head() and try_grab_page() behavior similar in
  their behavior with flags, in order to avoid "gotchas" later.

* follow_trans_huge_pmd(): moved the try_grab_page() to earlier in the
  routine, in order to avoid having to undo mlock_vma_page().

* follow_hugetlb_page(): removed a refcount overflow check that is now
  extraneous (and weaker than what try_grab_page() provides a few lines
  further down).

* Fixed up two Documentation flaws, pointed out by Jonathan Corbet's
  review.

Changes since v8:

* Merged the "mm/gup: pass flags arg to __gup_device_* functions" patch
  into the "mm/gup: track FOLL_PIN pages" patch, as requested by
  Christoph and Jan.

* Changed void grab_page() to bool try_grab_page(), and handled errors
  at the call sites. (From Jan's review comments.) try_grab_page()
  attempts to avoid page refcount overflows, even when counting up with
  GUP_PIN_COUNTING_BIAS increments.

* Fixed a bug that I'd introduced, when changing a BUG() to a WARN().

* Added Jan's reviewed-by tag to the " mm/gup: allow FOLL_FORCE for
  get_user_pages_fast()" patch.

* Documentation: pin_user_pages.rst: fixed an incorrect gup_benchmark
  invocation, left over from the pin_longterm days, spotted while preparing
  this version.

* Rebased onto today's linux.git (-rc1), and re-tested.

Changes since v7:

* Rebased onto Linux 5.5-rc1

* Reworked the grab_page() and try_grab_compound_head(), for API
  consistency and less diffs (thanks to Jan Kara's reviews).

* Added Leon Romanovsky's reviewed-by tags for two of the IB-related
  patches.

* patch 4 refactoring changes, as mentioned above.

There is a git repo and branch, for convenience:

    git@github.com:johnhubbard/linux.git pin_user_pages_tracking_v8

For the remaining list of "changes since version N", those are all in
v7, which is here:

  https://lore.kernel.org/r/20191121071354.456618-1-jhubbard@nvidia.com

============================================================
Overview:

This is a prerequisite to solving the problem of proper interactions
between file-backed pages, and [R]DMA activities, as discussed in [1],
[2], [3], and in a remarkable number of email threads since about
2017. :)

A new internal gup flag, FOLL_PIN is introduced, and thoroughly
documented in the last patch's Documentation/vm/pin_user_pages.rst.

I believe that this will provide a good starting point for doing the
layout lease work that Ira Weiny has been working on. That's because
these new wrapper functions provide a clean, constrained, systematically
named set of functionality that, again, is required in order to even
know if a page is "dma-pinned".

In contrast to earlier approaches, the page tracking can be
incrementally applied to the kernel call sites that, until now, have
been simply calling get_user_pages() ("gup"). In other words, opt-in by
changing from this:

    get_user_pages() (sets FOLL_GET)
    put_page()

to this:
    pin_user_pages() (sets FOLL_PIN)
    unpin_user_page()

============================================================
Testing:

* I've done some overall kernel testing (LTP, and a few other goodies),
  and some directed testing to exercise some of the changes. And as you
  can see, gup_benchmark is enhanced to exercise this. Basically, I've
  been able to runtime test the core get_user_pages() and
  pin_user_pages() and related routines, but not so much on several of
  the call sites--but those are generally just a couple of lines
  changed, each.

  Not much of the kernel is actually using this, which on one hand
  reduces risk quite a lot. But on the other hand, testing coverage
  is low. So I'd love it if, in particular, the Infiniband and PowerPC
  folks could do a smoke test of this series for me.

  Runtime testing for the call sites so far is pretty light:

    * io_uring: Some directed tests from liburing exercise this, and
                they pass.
    * process_vm_access.c: A small directed test passes.
    * gup_benchmark: the enhanced version hits the new gup.c code, and
                     passes.
    * infiniband: ran "ib_write_bw", which exercises the umem.c changes,
                  but not the other changes.
    * VFIO: compiles (I'm vowing to set up a run time test soon, but it's
                      not ready just yet)
    * powerpc: it compiles...
    * drm/via: compiles...
    * goldfish: compiles...
    * net/xdp: compiles...
    * media/v4l2: compiles...

[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/

Dan Williams (1):
  mm: Cleanup __put_devmap_managed_page() vs ->page_free()

John Hubbard (24):
  mm/gup: factor out duplicate code from four routines
  mm/gup: move try_get_compound_head() to top, fix minor issues
  mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages
  goldish_pipe: rename local pin_user_pages() routine
  mm: fix get_user_pages_remote()'s handling of FOLL_LONGTERM
  vfio: fix FOLL_LONGTERM use, simplify get_user_pages_remote() call
  mm/gup: allow FOLL_FORCE for get_user_pages_fast()
  IB/umem: use get_user_pages_fast() to pin DMA pages
  mm/gup: introduce pin_user_pages*() and FOLL_PIN
  goldish_pipe: convert to pin_user_pages() and put_user_page()
  IB/{core,hw,umem}: set FOLL_PIN via pin_user_pages*(), fix up ODP
  mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote()
  drm/via: set FOLL_PIN via pin_user_pages_fast()
  fs/io_uring: set FOLL_PIN via pin_user_pages()
  net/xdp: set FOLL_PIN via pin_user_pages()
  media/v4l2-core: set pages dirty upon releasing DMA buffers
  media/v4l2-core: pin_user_pages (FOLL_PIN) and put_user_page()
    conversion
  vfio, mm: pin_user_pages (FOLL_PIN) and put_user_page() conversion
  powerpc: book3s64: convert to pin_user_pages() and put_user_page()
  mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding
    "1"
  mm, tree-wide: rename put_user_page*() to unpin_user_page*()
  mm/gup: track FOLL_PIN pages
  mm/gup_benchmark: support pin_user_pages() and related calls
  selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN
    coverage

 Documentation/core-api/index.rst            |   1 +
 Documentation/core-api/pin_user_pages.rst   | 232 ++++++++
 arch/powerpc/mm/book3s64/iommu_api.c        |  10 +-
 drivers/gpu/drm/via/via_dmablit.c           |   6 +-
 drivers/infiniband/core/umem.c              |  19 +-
 drivers/infiniband/core/umem_odp.c          |  13 +-
 drivers/infiniband/hw/hfi1/user_pages.c     |   4 +-
 drivers/infiniband/hw/mthca/mthca_memfree.c |   8 +-
 drivers/infiniband/hw/qib/qib_user_pages.c  |   4 +-
 drivers/infiniband/hw/qib/qib_user_sdma.c   |   8 +-
 drivers/infiniband/hw/usnic/usnic_uiom.c    |   4 +-
 drivers/infiniband/sw/siw/siw_mem.c         |   4 +-
 drivers/media/v4l2-core/videobuf-dma-sg.c   |   8 +-
 drivers/nvdimm/pmem.c                       |   6 -
 drivers/platform/goldfish/goldfish_pipe.c   |  35 +-
 drivers/vfio/vfio_iommu_type1.c             |  35 +-
 fs/io_uring.c                               |   6 +-
 include/linux/mm.h                          | 155 ++++-
 include/linux/mmzone.h                      |   2 +
 include/linux/page_ref.h                    |  10 +
 mm/gup.c                                    | 626 +++++++++++++++-----
 mm/gup_benchmark.c                          |  74 ++-
 mm/huge_memory.c                            |  29 +-
 mm/hugetlb.c                                |  38 +-
 mm/memremap.c                               |  76 ++-
 mm/process_vm_access.c                      |  28 +-
 mm/swap.c                                   |  24 +
 mm/vmstat.c                                 |   2 +
 net/xdp/xdp_umem.c                          |   4 +-
 tools/testing/selftests/vm/gup_benchmark.c  |  21 +-
 tools/testing/selftests/vm/run_vmtests      |  22 +
 31 files changed, 1145 insertions(+), 369 deletions(-)
 create mode 100644 Documentation/core-api/pin_user_pages.rst

--
2.24.1


^ permalink raw reply	[flat|nested] 67+ messages in thread

end of thread, other threads:[~2020-01-07  1:29 UTC | newest]

Thread overview: 67+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-16 22:25 [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN John Hubbard
2019-12-16 22:25 ` [PATCH v11 01/25] mm/gup: factor out duplicate code from four routines John Hubbard
2019-12-18 15:52   ` Kirill A. Shutemov
2019-12-18 22:15     ` John Hubbard
2019-12-18 22:45       ` Kirill A. Shutemov
2019-12-16 22:25 ` [PATCH v11 02/25] mm/gup: move try_get_compound_head() to top, fix minor issues John Hubbard
2019-12-16 22:25 ` [PATCH v11 03/25] mm: Cleanup __put_devmap_managed_page() vs ->page_free() John Hubbard
2019-12-16 22:25 ` [PATCH v11 04/25] mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages John Hubbard
2019-12-18 16:04   ` Kirill A. Shutemov
2019-12-19  0:32     ` John Hubbard
2019-12-19  0:40     ` [PATCH v12] " John Hubbard
2019-12-19  5:27   ` [PATCH v11 04/25] " Dan Williams
2019-12-19  5:48     ` John Hubbard
2019-12-19  6:52       ` Dan Williams
2019-12-19  7:33         ` John Hubbard
2019-12-16 22:25 ` [PATCH v11 05/25] goldish_pipe: rename local pin_user_pages() routine John Hubbard
2019-12-16 22:25 ` [PATCH v11 06/25] mm: fix get_user_pages_remote()'s handling of FOLL_LONGTERM John Hubbard
2019-12-18 16:19   ` Kirill A. Shutemov
2019-12-18 22:15     ` John Hubbard
2019-12-16 22:25 ` [PATCH v11 07/25] vfio: fix FOLL_LONGTERM use, simplify get_user_pages_remote() call John Hubbard
2019-12-16 22:25 ` [PATCH v11 08/25] mm/gup: allow FOLL_FORCE for get_user_pages_fast() John Hubbard
2019-12-16 22:25 ` [PATCH v11 09/25] IB/umem: use get_user_pages_fast() to pin DMA pages John Hubbard
2019-12-16 22:25 ` [PATCH v11 10/25] mm/gup: introduce pin_user_pages*() and FOLL_PIN John Hubbard
2019-12-16 22:25 ` [PATCH v11 11/25] goldish_pipe: convert to pin_user_pages() and put_user_page() John Hubbard
2019-12-16 22:25 ` [PATCH v11 12/25] IB/{core,hw,umem}: set FOLL_PIN via pin_user_pages*(), fix up ODP John Hubbard
2019-12-16 22:25 ` [PATCH v11 13/25] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() John Hubbard
2019-12-16 22:25 ` [PATCH v11 14/25] drm/via: set FOLL_PIN via pin_user_pages_fast() John Hubbard
2019-12-16 22:25 ` [PATCH v11 15/25] fs/io_uring: set FOLL_PIN via pin_user_pages() John Hubbard
2019-12-16 22:25 ` [PATCH v11 16/25] net/xdp: " John Hubbard
2019-12-16 22:25 ` [PATCH v11 17/25] media/v4l2-core: set pages dirty upon releasing DMA buffers John Hubbard
2019-12-16 22:25 ` [PATCH v11 18/25] media/v4l2-core: pin_user_pages (FOLL_PIN) and put_user_page() conversion John Hubbard
2019-12-16 22:25 ` [PATCH v11 19/25] vfio, mm: " John Hubbard
2019-12-16 22:25 ` [PATCH v11 20/25] powerpc: book3s64: convert to pin_user_pages() and put_user_page() John Hubbard
2019-12-16 22:25 ` [PATCH v11 21/25] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" John Hubbard
2019-12-16 22:25 ` [PATCH v11 22/25] mm, tree-wide: rename put_user_page*() to unpin_user_page*() John Hubbard
2019-12-16 22:25 ` [PATCH v11 23/25] mm/gup: track FOLL_PIN pages John Hubbard
2019-12-17 14:19   ` [PATCH v12 " John Hubbard
2019-12-16 22:25 ` [PATCH v11 24/25] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2019-12-16 22:25 ` [PATCH v11 25/25] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
2019-12-17  7:39 ` [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN Jan Kara
2019-12-19 13:26 ` Leon Romanovsky
2019-12-19 20:30   ` John Hubbard
2019-12-19 21:07     ` Jason Gunthorpe
2019-12-19 21:13       ` John Hubbard
2019-12-20 13:34         ` Jason Gunthorpe
2019-12-21  0:32           ` Dan Williams
2019-12-23 18:24             ` Jason Gunthorpe
2019-12-19 22:58       ` John Hubbard
2019-12-20 18:48         ` Leon Romanovsky
2019-12-20 23:13           ` John Hubbard
2019-12-20 18:29       ` Leon Romanovsky
2019-12-20 23:54         ` John Hubbard
2019-12-21 10:08           ` Leon Romanovsky
2019-12-21 23:59             ` John Hubbard
2019-12-22 13:23           ` Leon Romanovsky
2019-12-25  2:03             ` John Hubbard
2019-12-25  5:26               ` Leon Romanovsky
2019-12-27 21:56                 ` John Hubbard
2019-12-29  4:33                   ` John Hubbard
2020-01-06  9:01                     ` Jan Kara
2020-01-07  1:26                       ` John Hubbard
2019-12-20  9:21     ` Jan Kara
2019-12-21  0:02       ` John Hubbard
2019-12-21  0:33       ` Dan Williams
2019-12-21  0:41         ` John Hubbard
2019-12-21  0:51           ` Dan Williams
2019-12-21  0:53             ` John Hubbard

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