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This causes underutilized THPs to escape the shrinker after > NUMA migration, since they silently drop off the deferred split list. > > Fix this by recording whether the source folio was on the deferred split > queue and its partially mapped state before move_to_new_folio() unqueues > it, and re-queuing the destination folio after a successful migration if > it was. > > By the time migrate_folio_move() runs, partially mapped folios without a > pin have already been split by migrate_pages_batch(). So only two cases > remain on the deferred list at this point: > 1. Partially mapped folios with a pin (split failed). > 2. Fully mapped but potentially underused folios. > The recorded partially_mapped state is forwarded to deferred_split_folio() > so that the destination folio is correctly re-queued in both cases. > > Reported-by: Johannes Weiner > Fixes: dafff3f4c850 ("mm: split underused THPs") > Signed-off-by: Usama Arif > --- > v1 -> v2: > - record whether source folio was on the deferred split queue before > move_to_folio() (David) > - record partially mapped state and update commit message (Zi) > --- > mm/migrate.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > LGTM. Acked-by: Zi Yan Best Regards, Yan, Zi