[PATCH v10 0/8] Userspace P2PDMA with O_DIRECT NVMe devices

Logan Gunthorpe
2022-09-22T16:39:57Z

Hi,

This is the latest P2PDMA userspace patch set. This version includes
some cleanup from feedback of 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 v6.0-rc6. A git branch is available here:

https://github.com/sbates130272/linux-p2pmem/ p2pdma_user_cmb_v10

Thanks,

Logan

[1] https://lkml.kernel.org/r/20220825152425.6296-1-logang@deltatee.com

--

Changes since v8:
- 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 since v7:
- 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)

Changes since v6:
- Rebase onto v5.19-rc1
- Rework how the pages are stored in the VMA per Jason's suggestion

Changes since v5:
- 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 (8):
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 | 7 +-
drivers/pci/p2pdma.c | 124 ++++++++++++++++++++++++
include/linux/mm.h | 1 +
include/linux/mmzone.h | 24 +++++
include/linux/uio.h | 6 ++
lib/iov_iter.c | 32 ++++--
lib/scatterlist.c | 25 +++--
mm/gup.c | 22 ++++-
10 files changed, 240 insertions(+), 22 deletions(-)

base-commit: 521a547ced6477c54b4b0cc206000406c221b4d6
--
2.30.2