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The pages being migrated are already unmapp= ed >> and marked for migration during setup (via unmap). folio_split() and >> __split_unmapped_folio() take additional isolated arguments, to avoid >> unmapping and remaping these pages and unlocking/putting the folio. >> >> Since unmap/remap is avoided in these code paths, an extra reference >> count is added to the split folio pages, which will be dropped in >> the finalize phase. >> >> Signed-off-by: Balbir Singh >> --- > > [...] > >> remap_page(origin_folio, 1 << order, >> folio_test_anon(origin_folio) ? >> RMP_USE_SHARED_ZEROPAGE : 0); >> @@ -3808,6 +3823,7 @@ bool uniform_split_supported(struct folio *folio= , unsigned int new_order, >> * @lock_at: a page within @folio to be left locked to caller >> * @list: after-split folios will be put on it if non NULL >> * @uniform_split: perform uniform split or not (non-uniform split) >> + * @isolated: The pages are already unmapped > > Isolated -> unmapped? Huh? > > Can we just detect that state from the folio so we don't have to pass r= andom boolean variables around? > > For example, folio_mapped() can tell you if the folio is currently mapp= ed. My proposal is to clean up __split_unmapped_folio() to not include remap(), folio_ref_unfreeze(), lru_add_split_folio(), so that Balbir can use __split_unmapped_folio() directly. Since the folio is unmapped and all page table entries are migration entries, __folio_split(= ) code could be avoided. My clean up patch is at: https://lore.kernel.org/linux-mm/660F3BCC-0360-4= 58F-BFF5-92C797E165CC@nvidia.com/. I will make some polish and send it ou= t properly. Best Regards, Yan, Zi