[PATCH v5 0/5] MAP_DIRECT and block-map-atomic files
From: Dan Williams
Date: Wed Aug 16 2017 - 03:50:37 EST
Changes since v4 [1]:
* Drop the new vma ->fs_flags field, it can be replaced by just checking
->vm_ops locally in the filesystem. This approach also allows
non-MAP_DIRECT vmas to be vma_merge() capable since vmas with
vm_ops->close() disable vma merging. (Jan)
* Drop the new ->fmmap() operation, instead convert all ->mmap()
implementations tree-wide to take an extra 'map_flags' parameter.
(Jan)
* Drop the cute (MAP_SHARED|MAP_PRIVATE) hack/mechanism to add new
validated flags mmap(2) and instead just define a new mmap syscall
variant (sys_mmap_pgoff_strict). (Andy)
* Fix the fact that MAP_PRIVATE|MAP_DIRECT would silently fallback to
MAP_SHARED (addressed by the new syscall). (Kirill)
* Require CAP_LINUX_IMMUTABLE for MAP_DIRECT to close any unforeseen
denial of service for unmanaged + unprivileged MAP_DIRECT usage.
(Kirill)
* Switch MAP_DIRECT fault failures to SIGBUS (Kirill)
* Add an fcntl mechanism to allow an unprivileged process to use
MAP_DIRECT on an fd setup by a privileged process.
* Rework the MAP_DIRECT description to allow for future hardware where
it may not be required to software-pin the file offset to physical
address relationship.
Given the tree-wide touches in this revision the patchset is starting to
feel more like -mm material than strictly xfs.
[1]: https://lkml.org/lkml/2017/8/15/39
---
This is the next revision of a patch series that aims to enable
applications that otherwise need to resort to DAX mapping a raw device
file to instead move to a filesystem.
In the course of reviewing a previous posting, Christoph said:
That being said I think we absolutely should support RDMA memory
registrations for DAX mappings. I'm just not sure how S_IOMAP_IMMUTABLE
helps with that. We'll want a MAP_SYNC | MAP_POPULATE to make sure all
the blocks are populated and all ptes are set up. Second we need to
make sure get_user_page works, which for now means we'll need a struct
page mapping for the region (which will be really annoying for PCIe
mappings, like the upcoming NVMe persistent memory region), and we need
to guarantee that the extent mapping won't change while the
get_user_pages holds the pages inside it. I think that is true due to
side effects even with the current DAX code, but we'll need to make it
explicit. And maybe that's where we need to converge - "sealing" the
extent map makes sense as such a temporary measure that is not persisted
on disk, which automatically gets released when the holding process
exits, because we sort of already do this implicitly. It might also
make sense to have explicitly breakable seals similar to what I do for
the pNFS blocks kernel server, as any userspace RDMA file server would
also need those semantics.
So, this is an attempt to converge on the idea that we need an explicit
and process-lifetime-temporary mechanism for a process to be able to
make assumptions about the mapping to physical page to dax-file-offset
relationship. The "explicitly breakable seals" aspect is not addressed
in these patches, but I wonder if it might be a voluntary mechanism that
can implemented via userfaultfd.
---
Dan Williams (5):
vfs: add flags parameter to ->mmap() in 'struct file_operations'
fs, xfs: introduce S_IOMAP_SEALED
mm: introduce mmap3 for safely defining new mmap flags
fs, xfs: introduce MAP_DIRECT for creating block-map-atomic file ranges
fs, fcntl: add F_MAP_DIRECT
Diffstat without patch1:
arch/x86/entry/syscalls/syscall_32.tbl | 1 +
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
fs/attr.c | 10 +++
fs/fcntl.c | 15 +++++
fs/open.c | 6 ++
fs/read_write.c | 3 +
fs/xfs/libxfs/xfs_bmap.c | 5 ++
fs/xfs/xfs_bmap_util.c | 3 +
fs/xfs/xfs_file.c | 115 +++++++++++++++++++++++++++++++--
fs/xfs/xfs_inode.h | 1 +
fs/xfs/xfs_ioctl.c | 6 ++
fs/xfs/xfs_super.c | 1 +
include/linux/fs.h | 10 ++-
include/linux/mm.h | 2 +-
include/linux/mman.h | 25 +++++++
include/linux/syscalls.h | 3 +
include/uapi/asm-generic/mman.h | 1 +
include/uapi/linux/fcntl.h | 5 ++
mm/filemap.c | 5 ++
mm/mmap.c | 56 +++++++++++++++-
20 files changed, 263 insertions(+), 11 deletions(-)
Diffstat with patch1:
arch/arc/kernel/arc_hostlink.c | 3 -
arch/powerpc/kernel/proc_powerpc.c | 3 -
arch/powerpc/kvm/book3s_64_vio.c | 3 -
arch/powerpc/platforms/cell/spufs/file.c | 21 +++-
arch/powerpc/platforms/powernv/opal-prd.c | 3 -
arch/um/drivers/mmapper_kern.c | 3 -
arch/x86/entry/syscalls/syscall_32.tbl | 1
arch/x86/entry/syscalls/syscall_64.tbl | 1
drivers/android/binder.c | 3 -
drivers/char/agp/frontend.c | 3 -
drivers/char/bsr.c | 3 -
drivers/char/hpet.c | 6 +
drivers/char/mbcs.c | 3 -
drivers/char/mem.c | 11 +-
drivers/char/mspec.c | 9 +-
drivers/char/uv_mmtimer.c | 6 +
drivers/dax/device.c | 3 -
drivers/dma-buf/dma-buf.c | 4 +
drivers/firewire/core-cdev.c | 3 -
drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 5 +
drivers/gpu/drm/arc/arcpgu_drv.c | 5 +
drivers/gpu/drm/ast/ast_drv.h | 3 -
drivers/gpu/drm/ast/ast_ttm.c | 3 -
drivers/gpu/drm/drm_gem.c | 3 -
drivers/gpu/drm/drm_gem_cma_helper.c | 2
drivers/gpu/drm/etnaviv/etnaviv_gem.c | 2
drivers/gpu/drm/exynos/exynos_drm_gem.c | 2
drivers/gpu/drm/i810/i810_dma.c | 3 -
drivers/gpu/drm/i915/i915_gem_dmabuf.c | 2
drivers/gpu/drm/mediatek/mtk_drm_gem.c | 2
drivers/gpu/drm/mgag200/mgag200_drv.h | 3 -
drivers/gpu/drm/mgag200/mgag200_ttm.c | 3 -
drivers/gpu/drm/msm/msm_gem.c | 2
drivers/gpu/drm/omapdrm/omap_gem.c | 2
drivers/gpu/drm/radeon/radeon_drv.c | 3 -
drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 2
drivers/gpu/drm/tegra/gem.c | 2
drivers/gpu/drm/udl/udl_gem.c | 2
drivers/gpu/drm/vc4/vc4_bo.c | 2
drivers/gpu/drm/vgem/vgem_drv.c | 7 +
drivers/gpu/drm/vmwgfx/vmwgfx_drv.h | 3 -
drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c | 3 -
drivers/hsi/clients/cmt_speech.c | 3 -
drivers/hwtracing/intel_th/msu.c | 3 -
drivers/hwtracing/stm/core.c | 3 -
drivers/infiniband/core/uverbs_main.c | 3 -
drivers/infiniband/hw/hfi1/file_ops.c | 6 +
drivers/infiniband/hw/qib/qib_file_ops.c | 5 +
drivers/media/v4l2-core/v4l2-dev.c | 3 -
drivers/misc/aspeed-lpc-ctrl.c | 3 -
drivers/misc/cxl/file.c | 3 -
drivers/misc/genwqe/card_dev.c | 3 -
drivers/misc/mic/scif/scif_fd.c | 3 -
drivers/misc/mic/vop/vop_vringh.c | 3 -
drivers/misc/sgi-gru/grufile.c | 3 -
drivers/mtd/mtdchar.c | 3 -
drivers/pci/proc.c | 3 -
drivers/rapidio/devices/rio_mport_cdev.c | 3 -
drivers/sbus/char/flash.c | 3 -
drivers/sbus/char/jsflash.c | 3 -
drivers/scsi/cxlflash/superpipe.c | 3 -
drivers/scsi/sg.c | 3 -
drivers/staging/android/ashmem.c | 3 -
drivers/staging/comedi/comedi_fops.c | 3 -
drivers/staging/lustre/lustre/llite/llite_mmap.c | 2
drivers/staging/vme/devices/vme_user.c | 3 -
drivers/uio/uio.c | 3 -
drivers/usb/core/devio.c | 3 -
drivers/usb/mon/mon_bin.c | 3 -
drivers/vfio/vfio.c | 7 +
drivers/video/fbdev/core/fbmem.c | 3 -
drivers/video/fbdev/pxa3xx-gcu.c | 3 -
drivers/xen/gntalloc.c | 3 -
drivers/xen/gntdev.c | 3 -
drivers/xen/privcmd.c | 3 -
drivers/xen/xenbus/xenbus_dev_backend.c | 3 -
drivers/xen/xenfs/xenstored.c | 3 -
fs/9p/vfs_file.c | 10 +-
fs/aio.c | 3 -
fs/attr.c | 10 ++
fs/btrfs/file.c | 3 -
fs/cifs/file.c | 4 -
fs/coda/file.c | 5 +
fs/ecryptfs/file.c | 5 +
fs/ext2/file.c | 5 +
fs/ext4/file.c | 3 -
fs/f2fs/file.c | 3 -
fs/fcntl.c | 15 +++
fs/fuse/file.c | 8 +-
fs/gfs2/file.c | 3 -
fs/hugetlbfs/inode.c | 3 -
fs/kernfs/file.c | 3 -
fs/nfs/file.c | 5 +
fs/nfs/internal.h | 2
fs/nilfs2/file.c | 3 -
fs/open.c | 6 +
fs/orangefs/file.c | 5 +
fs/proc/inode.c | 7 +
fs/proc/vmcore.c | 6 +
fs/ramfs/file-nommu.c | 6 +
fs/read_write.c | 3 +
fs/romfs/mmap-nommu.c | 3 -
fs/ubifs/file.c | 5 +
fs/xfs/libxfs/xfs_bmap.c | 5 +
fs/xfs/xfs_bmap_util.c | 3 +
fs/xfs/xfs_file.c | 114 +++++++++++++++++++++-
fs/xfs/xfs_inode.h | 1
fs/xfs/xfs_ioctl.c | 6 +
fs/xfs/xfs_super.c | 1
include/drm/drm_gem.h | 3 -
include/linux/fs.h | 21 +++-
include/linux/mm.h | 2
include/linux/mman.h | 25 +++++
include/linux/syscalls.h | 3 +
include/uapi/asm-generic/mman.h | 1
include/uapi/linux/fcntl.h | 5 +
ipc/shm.c | 5 +
kernel/events/core.c | 3 -
kernel/kcov.c | 3 -
kernel/relay.c | 3 -
mm/filemap.c | 19 +++-
mm/mmap.c | 56 ++++++++++-
mm/nommu.c | 4 -
mm/shmem.c | 3 -
net/socket.c | 6 +
security/selinux/selinuxfs.c | 6 +
sound/core/compress_offload.c | 3 -
sound/core/hwdep.c | 3 -
sound/core/info.c | 3 -
sound/core/init.c | 3 -
sound/core/oss/pcm_oss.c | 3 -
sound/oss/soundcard.c | 3 -
sound/oss/swarm_cs4297a.c | 3 -
virt/kvm/kvm_main.c | 3 -
134 files changed, 553 insertions(+), 174 deletions(-)