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

Logan Gunthorpe
2022-10-21T17:42:29Z

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