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    SubjectRe: [PATCH v1 1/2] mm/hugetlb: fix hugetlb not supporting write-notify
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    On 05.08.22 20:23, Mike Kravetz wrote:
    > On 08/05/22 14:14, Peter Xu wrote:
    >> On Fri, Aug 05, 2022 at 01:03:28PM +0200, David Hildenbrand wrote:
    >>> diff --git a/mm/mmap.c b/mm/mmap.c
    >>> index 61e6135c54ef..462a6b0344ac 100644
    >>> --- a/mm/mmap.c
    >>> +++ b/mm/mmap.c
    >>> @@ -1683,6 +1683,13 @@ int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
    >>> if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
    >>> return 0;
    >>>
    >>> + /*
    >>> + * Hugetlb does not require/support writenotify; especially, it does not
    >>> + * support softdirty tracking.
    >>> + */
    >>> + if (is_vm_hugetlb_page(vma))
    >>> + return 0;
    >>
    >> I'm kind of confused here.. you seems to be fixing up soft-dirty for
    >> hugetlb but here it's explicitly forbidden.
    >>
    >> Could you explain a bit more on why this patch is needed if (assume
    >> there'll be a working) patch 2 being provided?
    >>
    >
    > No comments on the patch, but ...
    >
    > Since it required little thought, I ran the test program on next-20220802 and
    > was surprised that the issue did not recreate. Even added a simple printk
    > to make sure we were getting into vma_wants_writenotify with a hugetlb vma.
    > We were.


    ... does your config have CONFIG_MEM_SOFT_DIRTY enabled?


    --
    Thanks,

    David / dhildenb

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