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    SubjectRe: [PATCH v2] mm/swapfile: unuse_pte can map random data if swap read fails
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    On 2022/4/19 20:12, David Hildenbrand wrote:
    > On 19.04.22 14:00, Miaohe Lin wrote:
    >> On 2022/4/19 19:46, David Hildenbrand wrote:
    >> ...
    >>>> Do you mean that we should set the pfn to 0 for the hwpoison marker so that we can
    >>>> distinguish swapin error case from real hwpoison case?
    >>>
    >>> I am not sure if we really have to distinguish. However, "0" seems to
    >>> make sense to indicate "this is not an actual problematic PFN, the
    >>> information is simply no longer around due to a hardware issue.
    >>>
    >>
    >> IMHO, we have to distinguish. For example, we might need to return VM_FAULT_SIGBUS
    >> instead of VM_FAULT_HWPOISON when user accesses the error page. Or should we simply
    >> return VM_FAULT_HWPOISON to simplify the handling?
    >
    > Hm, you're right. In e.g., x86 do_sigbus() we would send an BUS_MCEERR_AR.
    >
    > So yes, if we reuse is_hwpoison_entry() we'd have to convert to either
    > VM_FAULT_HWPOISON or VM_FAULT_SIGBUS.
    >
    > Something like "is_error_entry()" that can further be refined to
    > hwpoison or swapin could make sense. But what you have here is straight
    > forward to me as well. Whatever you/others prefer.

    IMHO, I prefer to use the separated swapin error maker because reusing hwpoison entry
    might make things more complicated and looks somewhat obscure.

    >
    > Acked-by: David Hildenbrand <david@redhat.com>

    Many thanks for your Acked-by tag!

    >
    >
    > NIT: I'd make the terminology make_swapin_error_entry() consistent with
    > SWAP_READ_ERROR and especially existing SWP_.
    >
    > For example, calling the latter SWP_SWAPIN_ERROR

    This looks better. Thanks! Will change to rename the relevant terminology in next
    version if no one has an objection. :)

    >

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