[PATCH 00/19] pin_user_pages(): reduced-risk series for Linux 5.5

John Hubbard
2019-11-25T04:21:38Z

Hi,

Here is a set of well-reviewed (expect for one patch), lower-risk items
that can go into Linux 5.5. The one patch that wasn't reviewed is the
powerpc conversion, and it's still at this point a no-op, because
tracking isn't yet activated.

This is based on linux-next: b9d3d01405061bb42358fe53f824e894a1922ced
("Add linux-next specific files for 20191122").

This is essentially a cut-down v8 of "mm/gup: track dma-pinned pages:
FOLL_PIN" [1], and with one of the VFIO patches split into two patches.
The idea here is to get this long list of "noise" checked into 5.5, so
that the actual, higher-risk "track FOLL_PIN pages" (which is deferred:
not part of this series) will be a much shorter patchset to review.

For the v4l2-core changes, I've left those here (instead of sending
them separately to the -media tree), in order to get the name change
done now (put_user_page --> unpin_user_page). However, I've added a Cc
stable, as recommended during the last round of reviews.

Here are the relevant notes from the original cover letter, edited to
match the current situation:

This is a prerequisite to tracking dma-pinned pages. That in turn is a
prerequisite to solving the larger 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)
put_user_page()

Because there are interdependencies with FOLL_LONGTERM, a similar
conversion as for FOLL_PIN, was applied. The change was from this:

get_user_pages(FOLL_LONGTERM) (also sets FOLL_GET)
put_page()

to this:
pin_longterm_pages() (sets FOLL_PIN | FOLL_LONGTERM)
put_user_page()

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

thanks,
John Hubbard
NVIDIA

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

John Hubbard (18):
mm/gup: factor out duplicate code from four routines
mm/gup: move try_get_compound_head() to top, fix minor issues
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: 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*()

Documentation/core-api/index.rst | 1 +
Documentation/core-api/pin_user_pages.rst | 233 ++++++++++++++
arch/powerpc/mm/book3s64/iommu_api.c | 12 +-
drivers/gpu/drm/via/via_dmablit.c | 6 +-
drivers/infiniband/core/umem.c | 4 +-
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 | 77 +++--
mm/gup.c | 332 +++++++++++++-------
mm/gup_benchmark.c | 9 +-
mm/memremap.c | 80 ++---
mm/process_vm_access.c | 28 +-
net/xdp/xdp_umem.c | 4 +-
tools/testing/selftests/vm/gup_benchmark.c | 6 +-
24 files changed, 642 insertions(+), 285 deletions(-)
create mode 100644 Documentation/core-api/pin_user_pages.rst

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2.24.0