mm: use pfn_swap_entry_to_folio() in zap_huge_pmd()

Call pfn_swap_entry_to_folio() in zap_huge_pmd() as preparation for
converting mm counter functions to take a folio.  Saves a call to
compound_head() embedded inside PageAnon().

Link: https://lkml.kernel.org/r/20240111152429.3374566-7-willy@infradead.orgSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/huge_memory.c

@@ -1905,12 +1905,14 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		zap_deposited_table(tlb->mm, pmd);
 		spin_unlock(ptl);
 	} else {
-		struct page *page = NULL;
+		struct folio *folio = NULL;
 		int flush_needed = 1;
 
 		if (pmd_present(orig_pmd)) {
-			page = pmd_page(orig_pmd);
-			folio_remove_rmap_pmd(page_folio(page), page, vma);
+			struct page *page = pmd_page(orig_pmd);
+
+			folio = page_folio(page);
+			folio_remove_rmap_pmd(folio, page, vma);
 			VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
 			VM_BUG_ON_PAGE(!PageHead(page), page);
 		} else if (thp_migration_supported()) {
@@ -1918,23 +1920,24 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 
 			VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
 			entry = pmd_to_swp_entry(orig_pmd);
-			page = pfn_swap_entry_to_page(entry);
+			folio = pfn_swap_entry_folio(entry);
 			flush_needed = 0;
 		} else
 			WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
 
-		if (PageAnon(page)) {
+		if (folio_test_anon(folio)) {
 			zap_deposited_table(tlb->mm, pmd);
 			add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
 		} else {
 			if (arch_needs_pgtable_deposit())
 				zap_deposited_table(tlb->mm, pmd);
-			add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
+			add_mm_counter(tlb->mm, mm_counter_file(&folio->page),
+				       -HPAGE_PMD_NR);
 		}
 
 		spin_unlock(ptl);
 		if (flush_needed)
-			tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
+			tlb_remove_page_size(tlb, &folio->page, HPAGE_PMD_SIZE);
 	}
 	return 1;
 }