From af56d6acf494f7a003737b59e785a4e8e5e5b66a Mon Sep 17 00:00:00 2001 From: Dev Jain Date: Thu, 30 Jul 2026 09:45:52 +0000 Subject: [PATCH] mm/rmap: convert page -> folio for hwpoison checks Patch series "mm/rmap: Refactor try_to_unmap_one", v4. In preparation for batching anonymous large folio unmapping to optimize it, refactor try_to_unmap_one. This series refactors hugetlb, anon-lazyfree and anon-swapbacked logic into their own functions, significantly reducing the length of the huge try_to_unmap_one. This patch (of 5): try_to_unmap() receives hugetlb folios only from the hwpoison path. hugetlb_update_hwpoison() sets the hugetlb folio's head-page hwpoison bit, and page_vma_mapped_walk() reports the hugetlb mapping at the head PFN, so the previous PageHWPoison(subpage) check happened to work for hugetlb. For non-hugetlb folios, unmap_poisoned_folio() currently rejects large folios before calling try_to_unmap(). Hence it is always the case that if try_to_unmap_one() handles an hwpoisoned folio, then the head page is marked with the poison bit. Therefore, convert the poisoned subpage checks to folio_test_hwpoison(). No functional change intended, except that, while at it, convert VM_BUG_* to VM_WARN_*. Link: https://lore.kernel.org/20260730094559.418003-1-dev.jain@arm.com Link: https://lore.kernel.org/20260730094559.418003-2-dev.jain@arm.com Signed-off-by: Dev Jain Reviewed-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Reviewed-by: Anshuman Khandual Cc: Harry Yoo Cc: Jann Horn Cc: Lance Yang Cc: Liam R. Howlett Cc: Muchun Song Cc: Oscar Salvador Cc: Rik van Riel Cc: Ryan Roberts Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/rmap.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index e854679553b9..77be9fcffa99 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2122,10 +2122,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, bool anon = folio_test_anon(folio); /* - * The try_to_unmap() is only passed a hugetlb page - * in the case where the hugetlb page is poisoned. + * The try_to_unmap() is only passed a hugetlb folio + * in the case where the hugetlb folio contains a + * poisoned page. */ - VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage); + VM_WARN_ON_FOLIO(!folio_test_hwpoison(folio), folio); /* * huge_pmd_unshare may unmap an entire PMD page. * There is no way of knowing exactly which PMDs may @@ -2204,7 +2205,8 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, /* Update high watermark before we lower rss */ update_hiwater_rss(mm); - if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) { + /* unmap_poisoned_folio() only refs order-0 or hugetlb folios */ + if (folio_test_hwpoison(folio) && (flags & TTU_HWPOISON)) { pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); if (folio_test_hugetlb(folio)) { hugetlb_count_sub(folio_nr_pages(folio), mm);