Changes since v6 [1]: * Abandon the concept of immutable files and rework the implementation to reuse same FL_LAYOUT file lease mechanism that coordinates pnfsd layouts vs local filesystem changes. This establishes an interface where the kernel is always in control of the block-map and is free to invalidate MAP_DIRECT mappings when a lease breaker arrives. (Christoph) * Introduce a new ->mmap_validate() file operation since we need both the original @flags and @fd passed to mmap(2) to setup a MAP_DIRECT mapping. * Introduce a ->lease_direct() vm operation to allow the RDMA core to safely register memory against DAX and tear down the mapping when the lease is broken. This can be reused by any sub-system that follows a memory registration semantic. [1]: https://lkml.org/lkml/2017/8/23/754 --- MAP_DIRECT is a mechanism that allows an application to establish a mapping where the kernel will not change the block-map, or otherwise dirty the block-map metadata of a file without notification. It supports a "flush from userspace" model where persistent memory applications can bypass the overhead of ongoing coordination of writes with the filesystem, and it provides safety to RDMA operations involving DAX mappings. The kernel always has the ability to revoke access and convert the file back to normal operation after performing a "lease break". Similar to fcntl leases, there is no way for userspace to to cancel the lease break process once it has started, it can only delay it via the /proc/sys/fs/lease-break-time setting. MAP_DIRECT enables XFS to supplant the device-dax interface for mmap-write access to persistent memory with no ongoing coordination with the filesystem via fsync/msync syscalls. --- Dan Williams (12): mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags fs, mm: pass fd to ->mmap_validate() fs: introduce i_mapdcount fs: MAP_DIRECT core xfs: prepare xfs_break_layouts() for reuse with MAP_DIRECT xfs: wire up MAP_DIRECT dma-mapping: introduce dma_has_iommu() fs, mapdirect: introduce ->lease_direct() xfs: wire up ->lease_direct() device-dax: wire up ->lease_direct() IB/core: use MAP_DIRECT to fix / enable RDMA to DAX mappings tools/testing/nvdimm: enable rdma unit tests arch/alpha/include/uapi/asm/mman.h | 1 arch/mips/include/uapi/asm/mman.h | 1 arch/mips/kernel/vdso.c | 2 arch/parisc/include/uapi/asm/mman.h | 1 arch/tile/mm/elf.c | 3 arch/x86/mm/mpx.c | 3 arch/xtensa/include/uapi/asm/mman.h | 1 drivers/base/dma-mapping.c | 10 + drivers/dax/device.c | 4 drivers/infiniband/core/umem.c | 90 ++++++- drivers/iommu/amd_iommu.c | 6 drivers/iommu/intel-iommu.c | 6 fs/Kconfig | 4 fs/Makefile | 1 fs/aio.c | 2 fs/mapdirect.c | 349 ++++++++++++++++++++++++++ fs/xfs/Kconfig | 4 fs/xfs/Makefile | 1 fs/xfs/xfs_file.c | 130 ++++++++++ fs/xfs/xfs_iomap.c | 9 + fs/xfs/xfs_layout.c | 42 +++ fs/xfs/xfs_layout.h | 13 + fs/xfs/xfs_pnfs.c | 30 -- fs/xfs/xfs_pnfs.h | 10 - include/linux/dma-mapping.h | 3 include/linux/fs.h | 33 ++ include/linux/mapdirect.h | 68 +++++ include/linux/mm.h | 15 + include/linux/mman.h | 42 +++ include/rdma/ib_umem.h | 8 + include/uapi/asm-generic/mman-common.h | 1 include/uapi/asm-generic/mman.h | 1 ipc/shm.c | 3 mm/internal.h | 2 mm/mmap.c | 28 ++ mm/nommu.c | 5 mm/util.c | 7 - tools/include/uapi/asm-generic/mman-common.h | 1 tools/testing/nvdimm/Kbuild | 31 ++ tools/testing/nvdimm/config_check.c | 2 tools/testing/nvdimm/test/iomap.c | 6 41 files changed, 906 insertions(+), 73 deletions(-) create mode 100644 fs/mapdirect.c create mode 100644 fs/xfs/xfs_layout.c create mode 100644 fs/xfs/xfs_layout.h create mode 100644 include/linux/mapdirect.h
