[PATCH v4 01/12] mm/rmap: convert page -> folio for hwpoison checks

[Dev Jain <dev.jain@arm.com>]

If any page of a folio is poisoned, try_to_unmap() is called with the
intent to remove any mappings pointing to any part of the folio.

Therefore, an hwpoison check on a single page does not make sense
(although everything works out because the memory-failure path sets
hwpoison on the head page too). Convert these checks to check whether
the folio has at least one hwpoisoned page.

While at it, convert VM_BUG_* to VM_WARN_*.

Signed-off-by: Dev Jain <dev.jain@arm.com>
---
 mm/rmap.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index fb3c351f8c458..430c91c8fe2ae 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2116,10 +2116,11 @@ 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_contain_hwpoisoned_page(folio), folio);
 			/*
 			 * huge_pmd_unshare may unmap an entire PMD page.
 			 * There is no way of knowing exactly which PMDs may
@@ -2198,7 +2199,7 @@ 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)) {
+		if (folio_contain_hwpoisoned_page(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);
-- 
2.34.1