Re: [PATCH v4 4/7] mm: replace vma->vm_flags direct modifications with modifier calls

From: Hyeonggon Yoo
Date: Tue Jan 31 2023 - 03:32:43 EST

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In reply to: Liam R. Howlett: "Re: [PATCH v4 4/7] mm: replace vma->vm_flags direct modifications with modifier calls"
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On Thu, Jan 26, 2023 at 11:37:49AM -0800, Suren Baghdasaryan wrote:
> Replace direct modifications to vma->vm_flags with calls to modifier
> functions to be able to track flag changes and to keep vma locking
> correctness.
>
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
> Acked-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
> ---
> arch/arm/kernel/process.c | 2 +-
> arch/ia64/mm/init.c | 8 ++++----
> arch/loongarch/include/asm/tlb.h | 2 +-
> arch/powerpc/kvm/book3s_xive_native.c | 2 +-
> arch/powerpc/mm/book3s64/subpage_prot.c | 2 +-
> arch/powerpc/platforms/book3s/vas-api.c | 2 +-
> arch/powerpc/platforms/cell/spufs/file.c | 14 +++++++-------
> arch/s390/mm/gmap.c | 3 +--
> arch/x86/entry/vsyscall/vsyscall_64.c | 2 +-
> arch/x86/kernel/cpu/sgx/driver.c | 2 +-
> arch/x86/kernel/cpu/sgx/virt.c | 2 +-
> arch/x86/mm/pat/memtype.c | 6 +++---
> arch/x86/um/mem_32.c | 2 +-
> drivers/acpi/pfr_telemetry.c | 2 +-
> drivers/android/binder.c | 3 +--
> drivers/char/mspec.c | 2 +-
> drivers/crypto/hisilicon/qm.c | 2 +-
> drivers/dax/device.c | 2 +-
> drivers/dma/idxd/cdev.c | 2 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 2 +-
> drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 4 ++--
> drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c | 4 ++--
> drivers/gpu/drm/amd/amdkfd/kfd_events.c | 4 ++--
> drivers/gpu/drm/amd/amdkfd/kfd_process.c | 4 ++--
> drivers/gpu/drm/drm_gem.c | 2 +-
> drivers/gpu/drm/drm_gem_dma_helper.c | 3 +--
> drivers/gpu/drm/drm_gem_shmem_helper.c | 2 +-
> drivers/gpu/drm/drm_vm.c | 8 ++++----
> drivers/gpu/drm/etnaviv/etnaviv_gem.c | 2 +-
> drivers/gpu/drm/exynos/exynos_drm_gem.c | 4 ++--
> drivers/gpu/drm/gma500/framebuffer.c | 2 +-
> drivers/gpu/drm/i810/i810_dma.c | 2 +-
> drivers/gpu/drm/i915/gem/i915_gem_mman.c | 4 ++--
> drivers/gpu/drm/mediatek/mtk_drm_gem.c | 2 +-
> drivers/gpu/drm/msm/msm_gem.c | 2 +-
> drivers/gpu/drm/omapdrm/omap_gem.c | 3 +--
> drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 3 +--
> drivers/gpu/drm/tegra/gem.c | 5 ++---
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 3 +--
> drivers/gpu/drm/virtio/virtgpu_vram.c | 2 +-
> drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c | 2 +-
> drivers/gpu/drm/xen/xen_drm_front_gem.c | 3 +--
> drivers/hsi/clients/cmt_speech.c | 2 +-
> drivers/hwtracing/intel_th/msu.c | 2 +-
> drivers/hwtracing/stm/core.c | 2 +-
> drivers/infiniband/hw/hfi1/file_ops.c | 4 ++--
> drivers/infiniband/hw/mlx5/main.c | 4 ++--
> drivers/infiniband/hw/qib/qib_file_ops.c | 13 ++++++-------
> drivers/infiniband/hw/usnic/usnic_ib_verbs.c | 2 +-
> drivers/infiniband/hw/vmw_pvrdma/pvrdma_verbs.c | 2 +-
> .../media/common/videobuf2/videobuf2-dma-contig.c | 2 +-
> drivers/media/common/videobuf2/videobuf2-vmalloc.c | 2 +-
> drivers/media/v4l2-core/videobuf-dma-contig.c | 2 +-
> drivers/media/v4l2-core/videobuf-dma-sg.c | 4 ++--
> drivers/media/v4l2-core/videobuf-vmalloc.c | 2 +-
> drivers/misc/cxl/context.c | 2 +-
> drivers/misc/habanalabs/common/memory.c | 2 +-
> drivers/misc/habanalabs/gaudi/gaudi.c | 4 ++--
> drivers/misc/habanalabs/gaudi2/gaudi2.c | 8 ++++----
> drivers/misc/habanalabs/goya/goya.c | 4 ++--
> drivers/misc/ocxl/context.c | 4 ++--
> drivers/misc/ocxl/sysfs.c | 2 +-
> drivers/misc/open-dice.c | 4 ++--
> drivers/misc/sgi-gru/grufile.c | 4 ++--
> drivers/misc/uacce/uacce.c | 2 +-
> drivers/sbus/char/oradax.c | 2 +-
> drivers/scsi/cxlflash/ocxl_hw.c | 2 +-
> drivers/scsi/sg.c | 2 +-
> drivers/staging/media/atomisp/pci/hmm/hmm_bo.c | 2 +-
> drivers/staging/media/deprecated/meye/meye.c | 4 ++--
> .../media/deprecated/stkwebcam/stk-webcam.c | 2 +-
> drivers/target/target_core_user.c | 2 +-
> drivers/uio/uio.c | 2 +-
> drivers/usb/core/devio.c | 3 +--
> drivers/usb/mon/mon_bin.c | 3 +--
> drivers/vdpa/vdpa_user/iova_domain.c | 2 +-
> drivers/vfio/pci/vfio_pci_core.c | 2 +-
> drivers/vhost/vdpa.c | 2 +-
> drivers/video/fbdev/68328fb.c | 2 +-
> drivers/video/fbdev/core/fb_defio.c | 4 ++--
> drivers/xen/gntalloc.c | 2 +-
> drivers/xen/gntdev.c | 4 ++--
> drivers/xen/privcmd-buf.c | 2 +-
> drivers/xen/privcmd.c | 4 ++--
> fs/aio.c | 2 +-
> fs/cramfs/inode.c | 2 +-
> fs/erofs/data.c | 2 +-
> fs/exec.c | 4 ++--
> fs/ext4/file.c | 2 +-
> fs/fuse/dax.c | 2 +-
> fs/hugetlbfs/inode.c | 4 ++--
> fs/orangefs/file.c | 3 +--
> fs/proc/task_mmu.c | 2 +-
> fs/proc/vmcore.c | 3 +--
> fs/userfaultfd.c | 2 +-
> fs/xfs/xfs_file.c | 2 +-
> include/linux/mm.h | 2 +-
> kernel/bpf/ringbuf.c | 4 ++--
> kernel/bpf/syscall.c | 4 ++--
> kernel/events/core.c | 2 +-
> kernel/kcov.c | 2 +-
> kernel/relay.c | 2 +-
> mm/madvise.c | 2 +-
> mm/memory.c | 6 +++---
> mm/mlock.c | 6 +++---
> mm/mmap.c | 10 +++++-----
> mm/mprotect.c | 2 +-
> mm/mremap.c | 6 +++---
> mm/nommu.c | 11 ++++++-----
> mm/secretmem.c | 2 +-
> mm/shmem.c | 2 +-
> mm/vmalloc.c | 2 +-
> net/ipv4/tcp.c | 4 ++--
> security/selinux/selinuxfs.c | 6 +++---
> sound/core/oss/pcm_oss.c | 2 +-
> sound/core/pcm_native.c | 9 +++++----
> sound/soc/pxa/mmp-sspa.c | 2 +-
> sound/usb/usx2y/us122l.c | 4 ++--
> sound/usb/usx2y/usX2Yhwdep.c | 2 +-
> sound/usb/usx2y/usx2yhwdeppcm.c | 2 +-
> 120 files changed, 188 insertions(+), 199 deletions(-)
>

Hello Suren,

[...]

Whoa, it's so long.
Mostly looks fine but two things I'm not sure about:

> diff --git a/drivers/misc/open-dice.c b/drivers/misc/open-dice.c
> index 9dda47b3fd70..7be4e6c9f120 100644
> --- a/drivers/misc/open-dice.c
> +++ b/drivers/misc/open-dice.c
> @@ -95,12 +95,12 @@ static int open_dice_mmap(struct file *filp, struct vm_area_struct *vma)
> if (vma->vm_flags & VM_WRITE)
> return -EPERM;
> /* Ensure userspace cannot acquire VM_WRITE later. */
> - vma->vm_flags &= ~VM_MAYWRITE;
> + vm_flags_clear(vma, VM_MAYSHARE);
> }

I think it should be:
s/VM_MAYSHARE/VM_MAYWRITE/

> diff --git a/mm/mlock.c b/mm/mlock.c
> index 5c4fff93cd6b..ed49459e343e 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -380,7 +380,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma,
> */
> if (newflags & VM_LOCKED)
> newflags |= VM_IO;
> - WRITE_ONCE(vma->vm_flags, newflags);
> + vm_flags_reset(vma, newflags);
>
> lru_add_drain();
> walk_page_range(vma->vm_mm, start, end, &mlock_walk_ops, NULL);
> @@ -388,7 +388,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma,
>
> if (newflags & VM_IO) {
> newflags &= ~VM_IO;
> - WRITE_ONCE(vma->vm_flags, newflags);
> + vm_flags_reset(vma, newflags);
> }
> }

wondering the if the comment above is still true?

/*
* There is a slight chance that concurrent page migration,
* or page reclaim finding a page of this now-VM_LOCKED vma,
* will call mlock_vma_folio() and raise page's mlock_count:
* double counting, leaving the page unevictable indefinitely.
* Communicate this danger to mlock_vma_folio() with VM_IO,
* which is a VM_SPECIAL flag not allowed on VM_LOCKED vmas.
* mmap_lock is held in write mode here, so this weird
* combination should not be visible to other mmap_lock users;
* but WRITE_ONCE so rmap walkers must see VM_IO if VM_LOCKED.
*/

does ACCESS_PRIVATE() still guarentee that compiler cannot mysteriously
optimize writes like WRITE_ONCE()?

Next message: Peter Zijlstra: "Re: [PATCH] x86/tdx: Do not corrupt frame-pointer in __tdx_hypercall()"
Previous message: Guo Ren: "Re: [PATCH] riscv: kprobe: Optimize kprobe with accurate atomicity"
In reply to: Liam R. Howlett: "Re: [PATCH v4 4/7] mm: replace vma->vm_flags direct modifications with modifier calls"
Next in thread: Suren Baghdasaryan: "Re: [PATCH v4 4/7] mm: replace vma->vm_flags direct modifications with modifier calls"
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