[RFC PATCH v2 22/47] mm: rmap: make page_vma_mapped_walk callers use pte_order

[James Houghton]

This also updates the callers' hugetlb mapcounting code to handle
mapcount properly for subpage-mapped hugetlb pages.

Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx>
---
 mm/migrate.c |  2 +-
 mm/rmap.c    | 17 +++++++++++++----
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index a0105fa6e3b2..8712b694c5a7 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -235,7 +235,7 @@ static bool remove_migration_pte(struct folio *folio,
 
 #ifdef CONFIG_HUGETLB_PAGE
 		if (folio_test_hugetlb(folio)) {
-			unsigned int shift = huge_page_shift(hstate_vma(vma));
+			unsigned int shift = pvmw.pte_order + PAGE_SHIFT;
 
 			pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
 			if (folio_test_anon(folio))
diff --git a/mm/rmap.c b/mm/rmap.c
index 9bba65b30e4d..19850d955aea 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1626,7 +1626,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 		if (PageHWPoison(subpage) && !(flags & TTU_IGNORE_HWPOISON)) {
 			pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
 			if (folio_test_hugetlb(folio)) {
-				hugetlb_count_sub(folio_nr_pages(folio), mm);
+				hugetlb_count_sub(1UL << pvmw.pte_order, mm);
 				set_huge_pte_at(mm, address, pvmw.pte, pteval);
 			} else {
 				dec_mm_counter(mm, mm_counter(&folio->page));
@@ -1785,7 +1785,11 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 		 *
 		 * See Documentation/mm/mmu_notifier.rst
 		 */
-		page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
+		if (folio_test_hugetlb(folio))
+			page_remove_rmap(&folio->page, vma, true);
+		else
+			page_remove_rmap(subpage, vma, false);
+
 		if (vma->vm_flags & VM_LOCKED)
 			mlock_page_drain_local();
 		folio_put(folio);
@@ -2034,7 +2038,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 		} else if (PageHWPoison(subpage)) {
 			pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
 			if (folio_test_hugetlb(folio)) {
-				hugetlb_count_sub(folio_nr_pages(folio), mm);
+				hugetlb_count_sub(1L << pvmw.pte_order, mm);
 				set_huge_pte_at(mm, address, pvmw.pte, pteval);
 			} else {
 				dec_mm_counter(mm, mm_counter(&folio->page));
@@ -2126,7 +2130,10 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 		 *
 		 * See Documentation/mm/mmu_notifier.rst
 		 */
-		page_remove_rmap(subpage, vma, folio_test_hugetlb(folio));
+		if (folio_test_hugetlb(folio))
+			page_remove_rmap(&folio->page, vma, true);
+		else
+			page_remove_rmap(subpage, vma, false);
 		if (vma->vm_flags & VM_LOCKED)
 			mlock_page_drain_local();
 		folio_put(folio);
@@ -2210,6 +2217,8 @@ static bool page_make_device_exclusive_one(struct folio *folio,
 				      args->owner);
 	mmu_notifier_invalidate_range_start(&range);
 
+	VM_BUG_ON_FOLIO(folio_test_hugetlb(folio), folio);
+
 	while (page_vma_mapped_walk(&pvmw)) {
 		/* Unexpected PMD-mapped THP? */
 		VM_BUG_ON_FOLIO(!pvmw.pte, folio);
-- 
2.38.0.135.g90850a2211-goog