memcg: use a folio in get_mctgt_type

Replace seven calls to compound_head() with one.  We still use the page as
page_mapped() is different from folio_mapped().

Link: https://lkml.kernel.org/r/20240111181219.3462852-4-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memcontrol.c

@@ -6109,6 +6109,7 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 		unsigned long addr, pte_t ptent, union mc_target *target)
 {
 	struct page *page = NULL;
+	struct folio *folio;
 	enum mc_target_type ret = MC_TARGET_NONE;
 	swp_entry_t ent = { .val = 0 };
 
@@ -6123,9 +6124,11 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 	else if (is_swap_pte(ptent))
 		page = mc_handle_swap_pte(vma, ptent, &ent);
 
+	if (page)
+		folio = page_folio(page);
 	if (target && page) {
-		if (!trylock_page(page)) {
-			put_page(page);
+		if (!folio_trylock(folio)) {
+			folio_put(folio);
 			return ret;
 		}
 		/*
@@ -6140,8 +6143,8 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 		 * Alas, skip moving the page in this case.
 		 */
 		if (!pte_present(ptent) && page_mapped(page)) {
-			unlock_page(page);
-			put_page(page);
+			folio_unlock(folio);
+			folio_put(folio);
 			return ret;
 		}
 	}
@@ -6154,18 +6157,18 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 		 * mem_cgroup_move_account() checks the page is valid or
 		 * not under LRU exclusion.
 		 */
-		if (page_memcg(page) == mc.from) {
+		if (folio_memcg(folio) == mc.from) {
 			ret = MC_TARGET_PAGE;
-			if (is_device_private_page(page) ||
-			    is_device_coherent_page(page))
+			if (folio_is_device_private(folio) ||
+			    folio_is_device_coherent(folio))
 				ret = MC_TARGET_DEVICE;
 			if (target)
-				target->folio = page_folio(page);
+				target->folio = folio;
 		}
 		if (!ret || !target) {
 			if (target)
-				unlock_page(page);
-			put_page(page);
+				folio_unlock(folio);
+			folio_put(folio);
 		}
 	}
 	/*