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    SubjectRe: [PATCH v7 01/14] mm: Add F_SEAL_AUTO_ALLOCATE seal to memfd
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    On 7/21/22 11:44, David Hildenbrand wrote:
    >
    > Also, I*think* you can place pages via userfaultfd into shmem. Not
    > sure if that would count "auto alloc", but it would certainly bypass
    > fallocate().

    Yeah, userfaultfd_register would probably have to forbid this for
    F_SEAL_AUTO_ALLOCATE vmas. Maybe the memfile_node can be reused for
    this, adding a new MEMFILE_F_NO_AUTO_ALLOCATE flags? Then
    userfault_register would do something like
    memfile_node_get_flags(vma->vm_file) and check the result.

    This means moving this patch later, after "mm: Introduce memfile_notifier".

    Thanks,

    Paolo

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