__split_folio_to_order() copies page flags from the original folio to newly created sub-folios using an explicit allowlist, but PG_dropbehind is not included. When a large folio with PG_dropbehind set is split, only the head sub-folio retains the flag; all tail sub-folios silently lose it and will not be reclaimed eagerly after writeback completes. Add PG_dropbehind to the flag copy mask so that the drop-behind hint is preserved across folio splits. Fixes: a323281cdfec ("mm: add PG_dropbehind folio flag") Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Jeff Layton --- mm/huge_memory.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 970e077019b7..e01917b14d1a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3642,6 +3642,7 @@ static void __split_folio_to_order(struct folio *folio, int old_order, (1L << PG_arch_3) | #endif (1L << PG_dirty) | + (1L << PG_dropbehind) | LRU_GEN_MASK | LRU_REFS_MASK)); if (handle_hwpoison && -- 2.54.0