[PATCH v11 0/9] Userspace P2PDMA with O_DIRECT NVMe devices

[Logan Gunthorpe <logang@deltatee.com>]

Hi,

This is the latest P2PDMA userspace patch set. This version includes
some cleanup from feedback from the last posting[1].

This patch set enables userspace P2PDMA by allowing userspace to mmap()
allocated chunks of the CMB. The resulting VMA can be passed only
to O_DIRECT IO on NVMe backed files or block devices. A flag is added
to GUP() in Patch 1, then Patches 2 through 6 wire this flag up based
on whether the block queue indicates P2PDMA support. Patches 7
creates the sysfs resource that can hand out the VMAs and Patch 8
adds brief documentation for the new interface.

Feedback welcome.

This series is based on v6.1-rc1. A git branch is available here:

  https://github.com/sbates130272/linux-p2pmem/  p2pdma_user_cmb_v11

Thanks,

Logan

[1] https://lkml.kernel.org/r/20220922163926.7077-1-logang@deltatee.com

--

Changes in v11:
  - Rebased onto v6.1-rc1, fixed minor conflict in bio_map_user_iov
  - The GUP test was moved to try_grab_page() and try_grab_folio().
    This ought to be a bit more future proof. It required adding a new
    cleanup patch to return a proper error code from try_grab_page().
    (Per Jason)

Changes in v10:
  - Rebased onto v6.0-rc6
  - Reworked iov iter changes to reuse the code better and
    name them without the _flags() prefix (per Christoph)
  - Renamed a number of flags variables to gup_flags (per John)
  - Minor fixups to the last documentation patch (from Greg and John)

Changes in v9:
  - Rebased onto v6.0-rc2, included reworking the iov_iter patch
    due to changes there
  - Drop the char device mmap implementation in favour of a sysfs
    based interface. (per Christoph)

 (v8 only included the first half of the series and was merged for v6.0)

Changes in v8:
  - Rebase onto v5.19-rc1
  - Rework how the pages are stored in the VMA per Jason's suggestion

Changes in v7:
  - Rebased onto v5.18-rc1 which includes Christophs cleanup to
    free_zone_device_page() (similar to Ralph's patch).
  - Fix bug with concurrent first calls to pci_p2pdma_vma_fault()
    that caused a double allocation and lost p2p memory. Noticed
    by Andrew Maier.
  - Collected a Reviewed-by tag from Chaitanya.
  - Numerous minor fixes to commit messages

--

Logan Gunthorpe (9):
  mm: allow multiple error returns in try_grab_page()
  mm: introduce FOLL_PCI_P2PDMA to gate getting PCI P2PDMA pages
  iov_iter: introduce iov_iter_get_pages_[alloc_]flags()
  block: add check when merging zone device pages
  lib/scatterlist: add check when merging zone device pages
  block: set FOLL_PCI_P2PDMA in __bio_iov_iter_get_pages()
  block: set FOLL_PCI_P2PDMA in bio_map_user_iov()
  PCI/P2PDMA: Allow userspace VMA allocations through sysfs
  ABI: sysfs-bus-pci: add documentation for p2pmem allocate

 Documentation/ABI/testing/sysfs-bus-pci |  10 ++
 block/bio.c                             |  11 ++-
 block/blk-map.c                         |  12 ++-
 drivers/pci/p2pdma.c                    | 124 ++++++++++++++++++++++++
 include/linux/mm.h                      |   3 +-
 include/linux/mmzone.h                  |  24 +++++
 include/linux/uio.h                     |   6 ++
 lib/iov_iter.c                          |  32 ++++--
 lib/scatterlist.c                       |  25 +++--
 mm/gup.c                                |  45 ++++++---
 mm/huge_memory.c                        |  19 ++--
 mm/hugetlb.c                            |  23 +++--
 12 files changed, 280 insertions(+), 54 deletions(-)


base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780
--
2.30.2