mm/memcg: Convert uncharge_page() to uncharge_folio()

Use a folio rather than a page to ensure that we're only operating on
base or head pages, and not tail pages.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>

mm/memcontrol.c

@@ -6794,24 +6794,23 @@ static void uncharge_batch(const struct uncharge_gather *ug)
 	memcg_check_events(ug->memcg, ug->nid);
 	local_irq_restore(flags);
 
-	/* drop reference from uncharge_page */
+	/* drop reference from uncharge_folio */
 	css_put(&ug->memcg->css);
 }
 
-static void uncharge_page(struct page *page, struct uncharge_gather *ug)
+static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
 {
-	struct folio *folio = page_folio(page);
-	unsigned long nr_pages;
+	long nr_pages;
 	struct mem_cgroup *memcg;
 	struct obj_cgroup *objcg;
-	bool use_objcg = PageMemcgKmem(page);
+	bool use_objcg = folio_memcg_kmem(folio);
 
-	VM_BUG_ON_PAGE(PageLRU(page), page);
+	VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
 
 	/*
 	 * Nobody should be changing or seriously looking at
-	 * page memcg or objcg at this point, we have fully
-	 * exclusive access to the page.
+	 * folio memcg or objcg at this point, we have fully
+	 * exclusive access to the folio.
 	 */
 	if (use_objcg) {
 		objcg = __folio_objcg(folio);
@@ -6833,19 +6832,19 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 			uncharge_gather_clear(ug);
 		}
 		ug->memcg = memcg;
-		ug->nid = page_to_nid(page);
+		ug->nid = folio_nid(folio);
 
 		/* pairs with css_put in uncharge_batch */
 		css_get(&memcg->css);
 	}
 
-	nr_pages = compound_nr(page);
+	nr_pages = folio_nr_pages(folio);
 
 	if (use_objcg) {
 		ug->nr_memory += nr_pages;
 		ug->nr_kmem += nr_pages;
 
-		page->memcg_data = 0;
+		folio->memcg_data = 0;
 		obj_cgroup_put(objcg);
 	} else {
 		/* LRU pages aren't accounted at the root level */
@@ -6853,7 +6852,7 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 			ug->nr_memory += nr_pages;
 		ug->pgpgout++;
 
-		page->memcg_data = 0;
+		folio->memcg_data = 0;
 	}
 
 	css_put(&memcg->css);
@@ -6874,7 +6873,7 @@ void __mem_cgroup_uncharge(struct page *page)
 		return;
 
 	uncharge_gather_clear(&ug);
-	uncharge_page(page, &ug);
+	uncharge_folio(page_folio(page), &ug);
 	uncharge_batch(&ug);
 }
 
@@ -6888,11 +6887,11 @@ void __mem_cgroup_uncharge(struct page *page)
 void __mem_cgroup_uncharge_list(struct list_head *page_list)
 {
 	struct uncharge_gather ug;
-	struct page *page;
+	struct folio *folio;
 
 	uncharge_gather_clear(&ug);
-	list_for_each_entry(page, page_list, lru)
-		uncharge_page(page, &ug);
+	list_for_each_entry(folio, page_list, lru)
+		uncharge_folio(folio, &ug);
 	if (ug.memcg)
 		uncharge_batch(&ug);
 }