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    SubjectRe: [PATCH RFC 2/8] mm: introduce PG_offline
    On Fri 13-04-18 15:16:26, David Hildenbrand wrote:
    > online_pages()/offline_pages() theoretically allows us to work on
    > sub-section sizes. This is especially relevant in the context of
    > virtualization. It e.g. allows us to add/remove memory to Linux in a VM in
    > 4MB chunks.

    Well, theoretically possible but this would require a lot of auditing
    because the hotplug and per section assumption is quite a spread one.

    > While the whole section is marked as online/offline, we have to know
    > the state of each page. E.g. to not read memory that is not online
    > during kexec() or to properly mark a section as offline as soon as all
    > contained pages are offline.

    But you cannot use a page flag for that, I am afraid. Page flags are
    extremely scarce resource. I haven't looked at the rest of the series
    but _if_ we have a bit spare which I am not really sure about then you
    should prove there are no other ways around this.

    > Signed-off-by: David Hildenbrand <david@redhat.com>
    --
    Michal Hocko
    SUSE Labs

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