From 267bede12d3b108ca29997ce280e927a570ec97f Mon Sep 17 00:00:00 2001 From: Longlong Xia Date: Fri, 14 Aug 2026 16:30:27 +0800 Subject: [PATCH] mm/hugetlb: keep max_huge_pages when dissolving surplus folios dissolve_free_hugetlb_folio() can remove a free folio as surplus when its node has surplus pages. In that case remove_hugetlb_folio() decrements both nr_huge_pages and surplus_huge_pages, leaving the persistent pool size unchanged. Updating max_huge_pages as if a persistent folio had been removed can therefore corrupt the persistent pool target and underflow it when max_huge_pages is zero. Keep max_huge_pages unchanged for surplus folios, including the vmemmap restoration rollback path. Link: https://lore.kernel.org/20260814083027.1419487-1-xialonglong2025@163.com Fixes: cb402bbdabca ("mm/hugetlb: fix surplus pages in dissolve_free_huge_page()") Assisted-by: Codex:gpt-5.6-sol Signed-off-by: Longlong Xia Reviewed-by: Muchun Song Cc: David Hildenbrand Cc: Jinjiang Tu Cc: Longlong Xia Cc: Oscar Salvador Cc: Signed-off-by: Andrew Morton --- mm/hugetlb.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 785772845795..885017e26fd4 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1992,7 +1992,8 @@ int dissolve_free_hugetlb_folio(struct folio *folio) if (h->surplus_huge_pages_node[folio_nid(folio)]) adjust_surplus = true; remove_hugetlb_folio(h, folio, adjust_surplus); - h->max_huge_pages--; + if (!adjust_surplus) + h->max_huge_pages--; spin_unlock_irq(&hugetlb_lock); /* @@ -2012,7 +2013,8 @@ int dissolve_free_hugetlb_folio(struct folio *folio) if (rc) { spin_lock_irq(&hugetlb_lock); add_hugetlb_folio(h, folio, adjust_surplus); - h->max_huge_pages++; + if (!adjust_surplus) + h->max_huge_pages++; goto out; } } else {