[PATCH v2 27/46] mm: rmap: update try_to_{migrate,unmap} to handle mapcount for HGM

[James Houghton <jthoughton@xxxxxxxxxx>]

Make use of the new pvmw->pte_order field to determine the size of the
PTE we're unmapping/migrating.

Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx>

diff --git a/mm/migrate.c b/mm/migrate.c
index 9b4a7e75f6e6..616afcc40fdc 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -247,7 +247,7 @@ 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 c010d0af3a82..0a019ae32f04 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1609,7 +1609,7 @@ 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));
@@ -1757,7 +1757,13 @@ 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))
+			hugetlb_remove_rmap(subpage,
+					pvmw.pte_order + PAGE_SHIFT,
+					hstate_vma(vma), vma);
+		else
+			page_remove_rmap(subpage, vma, false);
+
 		if (vma->vm_flags & VM_LOCKED)
 			mlock_drain_local();
 		folio_put(folio);
@@ -2020,7 +2026,7 @@ 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));
@@ -2112,7 +2118,12 @@ 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))
+			hugetlb_remove_rmap(subpage,
+					pvmw.pte_order + PAGE_SHIFT,
+					hstate_vma(vma), vma);
+		else
+			page_remove_rmap(subpage, vma, false);
 		if (vma->vm_flags & VM_LOCKED)
 			mlock_drain_local();
 		folio_put(folio);
@@ -2196,6 +2207,8 @@ 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);
-- 
2.39.2.637.g21b0678d19-goog