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    SubjectRe: [PATCH] mm,memory_hotplug: Explicitly pass the head to isolate_huge_page
    On Wed, Feb 13, 2019 at 01:33:39PM +0100, Michal Hocko wrote:
    > Why isn't our check in has_unmovable_pages sufficient?

    Taking a closer look, it should be enough.
    I was mainly confused by the fact that if the zone is ZONE_MOVABLE,
    we do not keep checking in has_unmovable_pages():

    if (zone_idx(zone) == ZONE_MOVABLE)
    continue;

    But I overlooked that htlb_alloc_mask() checks whether the allocation
    cand end up in a movable zone.
    hugepage_movable_supported() checks that and if the hstate does not
    support migration at all, we skip __GFP_MOVABLE.

    So I think that the check in has_unmovable_pages() should be more than enough,
    so we could strip the checks from do_migrate_ranges() and
    scan_movable_pages() regarding hugepage migratability.

    I will run some tests just to make sure this holds and then
    I will send a patch.

    Thanks
    --
    Oscar Salvador
    SUSE L3

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