From 2273dea6b1e1fcdd06d207048a2cd563ed80111a Mon Sep 17 00:00:00 2001 From: Liu Shixin Date: Wed, 5 Mar 2025 11:54:09 +0800 Subject: [PATCH] mm/hugetlb: update nr_huge_pages and surplus_huge_pages together In alloc_surplus_hugetlb_folio(), we increase nr_huge_pages and surplus_huge_pages separately. In the middle window, if we set nr_hugepages to smaller and satisfy count < persistent_huge_pages(h), the surplus_huge_pages will be increased by adjust_pool_surplus(). After adding delay in the middle window, we can reproduce the problem easily by following step: 1. echo 3 > /proc/sys/vm/nr_overcommit_hugepages 2. mmap two hugepages. When nr_huge_pages=2 and surplus_huge_pages=1, goto step 3. 3. echo 0 > /proc/sys/vm/nr_huge_pages Finally, nr_huge_pages is less than surplus_huge_pages. To fix the problem, call only_alloc_fresh_hugetlb_folio() instead and move down __prep_account_new_huge_page() into the hugetlb_lock. Link: https://lkml.kernel.org/r/20250305035409.2391344-1-liushixin2@huawei.com Fixes: 0c397daea1d4 ("mm, hugetlb: further simplify hugetlb allocation API") Signed-off-by: Liu Shixin Acked-by: Peter Xu Acked-by: Oscar Salvador Cc: David Hildenbrand Cc: Kefeng Wang Cc: Liu Shixin Cc: Muchun Song Signed-off-by: Andrew Morton --- mm/hugetlb.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 438de55dd38d3..af9b8c1fca675 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2259,11 +2259,20 @@ static struct folio *alloc_surplus_hugetlb_folio(struct hstate *h, goto out_unlock; spin_unlock_irq(&hugetlb_lock); - folio = alloc_fresh_hugetlb_folio(h, gfp_mask, nid, nmask); + folio = only_alloc_fresh_hugetlb_folio(h, gfp_mask, nid, nmask, NULL); if (!folio) return NULL; + hugetlb_vmemmap_optimize_folio(h, folio); + spin_lock_irq(&hugetlb_lock); + /* + * nr_huge_pages needs to be adjusted within the same lock cycle + * as surplus_pages, otherwise it might confuse + * persistent_huge_pages() momentarily. + */ + __prep_account_new_huge_page(h, nid); + /* * We could have raced with the pool size change. * Double check that and simply deallocate the new page -- 2.39.5