Re: [PATCH v2 00/20] get_user_pages() for dax mappings

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Hi Dan,

We've tested this patch series (as pulled from your git repo) with our P2P work and everything is working great. The issues we found in v1 have been fixed and we have not found any new ones.

Tested-By: Logan Gunthorpe <logang@xxxxxxxxxxxx>

Thanks,

Logan



On 09/10/15 06:55 PM, Dan Williams wrote:
Changes since v1 [1]:
1/ Rebased on the accepted cleanups to the memremap() api and the NUMA
    hints for devm allocations. (see libnvdimm-for-next [2]).

2/ Rebased on DAX fixes from Ross [3], currently in -mm, and Dave [4],
    applied locally for now.

3/ Renamed __pfn_t to pfn_t and converted KVM and UM accordingly (Dave
    Hansen)

4/ Make pfn-to-pfn_t conversions a nop (binary identical) for typical
    mapped pfns (Dave Hansen)

5/ Fixed up the devm_memremap_pages() api to require passing in a
    percpu_ref object.  Addresses a crash reported-by Logan.

6/ Moved the back pointer from a page to its hosting 'struct
    dev_pagemap' to share storage with the 'lru' field rather than
    'mapping'.  Enables us to revoke mappings at devm_memunmap_page()
    time and addresses a crash reported-by Logan.

7/ Rework dax_map_bh() into dax_map_atomic() to avoid proliferating
    buffer_head usage deeper into the dax implementation.  Also addresses
    a crash reported by Logan (Dave Chinner)

8/ Include an initial, only lightly tested, implementation of revoking
    usages of ZONE_DEVICE pages when the driver disables the pmem device.
    This coordinates with blk_cleanup_queue() for the pmem gendisk, see
    patch 19.

9/ Include a cleaned up version of the vmem_altmap infrastructure
    allowing the struct page memmap to optionally be allocated from pmem
    itself.

[1]: https://lists.01.org/pipermail/linux-nvdimm/2015-September/002199.html
[2]: https://git.kernel.org/cgit/linux/kernel/git/nvdimm/nvdimm.git/log/?h=libnvdimm-for-next
[3]: https://git.kernel.org/cgit/linux/kernel/git/nvdimm/nvdimm.git/commit/?h=dax-fixes&id=93fdde069dce
[4]: https://lists.01.org/pipermail/linux-nvdimm/2015-October/002286.html

---
To date, we have implemented two I/O usage models for persistent memory,
PMEM (a persistent "ram disk") and DAX (mmap persistent memory into
userspace).  This series adds a third, DAX-GUP, that allows DAX mappings
to be the target of direct-i/o.  It allows userspace to coordinate
DMA/RDMA from/to persitent memory.

The implementation leverages the ZONE_DEVICE mm-zone that went into
4.3-rc1 to flag pages that are owned and dynamically mapped by a device
driver.  The pmem driver, after mapping a persistent memory range into
the system memmap via devm_memremap_pages(), arranges for DAX to
distinguish pfn-only versus page-backed pmem-pfns via flags in the new
__pfn_t type.  The DAX code, upon seeing a PFN_DEV+PFN_MAP flagged pfn,
flags the resulting pte(s) inserted into the process page tables with a
new _PAGE_DEVMAP flag.  Later, when get_user_pages() is walking ptes it
keys off _PAGE_DEVMAP to pin the device hosting the page range active.
Finally, get_page() and put_page() are modified to take references
against the device driver established page mapping.

This series is available via git here:

   git://git.kernel.org/pub/scm/linux/kernel/git/djbw/nvdimm libnvdimm-pending

---

Dan Williams (20):
       block: generic request_queue reference counting
       dax: increase granularity of dax_clear_blocks() operations
       block, dax: fix lifetime of in-kernel dax mappings with dax_map_atomic()
       mm: introduce __get_dev_pagemap()
       x86, mm: introduce vmem_altmap to augment vmemmap_populate()
       libnvdimm, pfn, pmem: allocate memmap array in persistent memory
       avr32: convert to asm-generic/memory_model.h
       hugetlb: fix compile error on tile
       frv: fix compiler warning from definition of __pmd()
       um: kill pfn_t
       kvm: rename pfn_t to kvm_pfn_t
       mips: fix PAGE_MASK definition
       mm, dax, pmem: introduce pfn_t
       mm, dax, gpu: convert vm_insert_mixed to pfn_t, introduce _PAGE_DEVMAP
       mm, dax: convert vmf_insert_pfn_pmd() to pfn_t
       list: introduce list_poison() and LIST_POISON3
       mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup
       block: notify queue death confirmation
       mm, pmem: devm_memunmap_pages(), truncate and unmap ZONE_DEVICE pages
       mm, x86: get_user_pages() for dax mappings


  arch/alpha/include/asm/pgtable.h        |    1
  arch/arm/include/asm/kvm_mmu.h          |    5 -
  arch/arm/kvm/mmu.c                      |   10 +
  arch/arm64/include/asm/kvm_mmu.h        |    3
  arch/avr32/include/asm/page.h           |    8 -
  arch/frv/include/asm/page.h             |    2
  arch/ia64/include/asm/pgtable.h         |    1
  arch/m68k/include/asm/page_mm.h         |    1
  arch/m68k/include/asm/page_no.h         |    1
  arch/mips/include/asm/kvm_host.h        |    6 -
  arch/mips/include/asm/page.h            |    2
  arch/mips/kvm/emulate.c                 |    2
  arch/mips/kvm/tlb.c                     |   14 +
  arch/parisc/include/asm/pgtable.h       |    1
  arch/powerpc/include/asm/kvm_book3s.h   |    4
  arch/powerpc/include/asm/kvm_ppc.h      |    2
  arch/powerpc/include/asm/pgtable.h      |    1
  arch/powerpc/kvm/book3s.c               |    6 -
  arch/powerpc/kvm/book3s_32_mmu_host.c   |    2
  arch/powerpc/kvm/book3s_64_mmu_host.c   |    2
  arch/powerpc/kvm/e500.h                 |    2
  arch/powerpc/kvm/e500_mmu_host.c        |    8 -
  arch/powerpc/kvm/trace_pr.h             |    2
  arch/powerpc/sysdev/axonram.c           |    8 -
  arch/sparc/include/asm/pgtable_64.h     |    2
  arch/tile/include/asm/pgtable.h         |    1
  arch/um/include/asm/page.h              |    6 -
  arch/um/include/asm/pgtable-3level.h    |    5 -
  arch/um/include/asm/pgtable.h           |    2
  arch/x86/include/asm/pgtable.h          |   24 ++
  arch/x86/include/asm/pgtable_types.h    |    7 +
  arch/x86/kvm/iommu.c                    |   11 +
  arch/x86/kvm/mmu.c                      |   37 ++--
  arch/x86/kvm/mmu_audit.c                |    2
  arch/x86/kvm/paging_tmpl.h              |    6 -
  arch/x86/kvm/vmx.c                      |    2
  arch/x86/kvm/x86.c                      |    2
  arch/x86/mm/gup.c                       |   56 +++++-
  arch/x86/mm/init_64.c                   |   32 +++
  arch/x86/mm/pat.c                       |    4
  block/blk-core.c                        |   79 +++++++-
  block/blk-mq-sysfs.c                    |    6 -
  block/blk-mq.c                          |   87 +++------
  block/blk-sysfs.c                       |    3
  block/blk.h                             |   12 +
  drivers/block/brd.c                     |    4
  drivers/gpu/drm/exynos/exynos_drm_gem.c |    3
  drivers/gpu/drm/gma500/framebuffer.c    |    3
  drivers/gpu/drm/msm/msm_gem.c           |    3
  drivers/gpu/drm/omapdrm/omap_gem.c      |    6 -
  drivers/gpu/drm/ttm/ttm_bo_vm.c         |    3
  drivers/nvdimm/pfn_devs.c               |    3
  drivers/nvdimm/pmem.c                   |  128 +++++++++----
  drivers/s390/block/dcssblk.c            |   10 -
  fs/block_dev.c                          |    2
  fs/dax.c                                |  199 +++++++++++++--------
  include/asm-generic/pgtable.h           |    6 -
  include/linux/blk-mq.h                  |    1
  include/linux/blkdev.h                  |   12 +
  include/linux/huge_mm.h                 |    2
  include/linux/hugetlb.h                 |    1
  include/linux/io.h                      |   17 --
  include/linux/kvm_host.h                |   37 ++--
  include/linux/kvm_types.h               |    2
  include/linux/list.h                    |   14 +
  include/linux/memory_hotplug.h          |    3
  include/linux/mm.h                      |  300 +++++++++++++++++++++++++++++--
  include/linux/mm_types.h                |    5 +
  include/linux/pfn.h                     |    9 +
  include/linux/poison.h                  |    1
  kernel/memremap.c                       |  187 +++++++++++++++++++
  lib/list_debug.c                        |    2
  mm/gup.c                                |   11 +
  mm/huge_memory.c                        |   10 +
  mm/hugetlb.c                            |   18 ++
  mm/memory.c                             |   17 +-
  mm/memory_hotplug.c                     |   66 +++++--
  mm/page_alloc.c                         |   10 +
  mm/sparse-vmemmap.c                     |   37 ++++
  mm/sparse.c                             |    8 +
  mm/swap.c                               |   15 ++
  virt/kvm/kvm_main.c                     |   47 ++---
  82 files changed, 1264 insertions(+), 418 deletions(-)

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