mm/memcg: Convert commit_charge() to take a folio

The memcg_data is only set on the head page, so enforce that by
typing it as a folio.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>

mm/memcontrol.c

@@ -2711,9 +2711,9 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
 }
 #endif
 
-static void commit_charge(struct page *page, struct mem_cgroup *memcg)
+static void commit_charge(struct folio *folio, struct mem_cgroup *memcg)
 {
-	VM_BUG_ON_PAGE(page_memcg(page), page);
+	VM_BUG_ON_FOLIO(folio_memcg(folio), folio);
 	/*
 	 * Any of the following ensures page's memcg stability:
 	 *
@@ -2722,7 +2722,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg)
 	 * - lock_page_memcg()
 	 * - exclusive reference
 	 */
-	page->memcg_data = (unsigned long)memcg;
+	folio->memcg_data = (unsigned long)memcg;
 }
 
 static struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *objcg)
@@ -6662,7 +6662,8 @@ void mem_cgroup_calculate_protection(struct mem_cgroup *root,
 
 static int charge_memcg(struct page *page, struct mem_cgroup *memcg, gfp_t gfp)
 {
-	unsigned int nr_pages = thp_nr_pages(page);
+	struct folio *folio = page_folio(page);
+	long nr_pages = folio_nr_pages(folio);
 	int ret;
 
 	ret = try_charge(memcg, gfp, nr_pages);
@@ -6670,7 +6671,7 @@ static int charge_memcg(struct page *page, struct mem_cgroup *memcg, gfp_t gfp)
 		goto out;
 
 	css_get(&memcg->css);
-	commit_charge(page, memcg);
+	commit_charge(folio, memcg);
 
 	local_irq_disable();
 	mem_cgroup_charge_statistics(memcg, nr_pages);
@@ -6922,21 +6923,21 @@ void __mem_cgroup_uncharge_list(struct list_head *page_list)
  */
 void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 {
+	struct folio *newfolio = page_folio(newpage);
 	struct mem_cgroup *memcg;
-	unsigned int nr_pages;
+	long nr_pages = folio_nr_pages(newfolio);
 	unsigned long flags;
 
 	VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
-	VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
-	VM_BUG_ON_PAGE(PageAnon(oldpage) != PageAnon(newpage), newpage);
-	VM_BUG_ON_PAGE(PageTransHuge(oldpage) != PageTransHuge(newpage),
-		       newpage);
+	VM_BUG_ON_FOLIO(!folio_test_locked(newfolio), newfolio);
+	VM_BUG_ON_FOLIO(PageAnon(oldpage) != folio_test_anon(newfolio), newfolio);
+	VM_BUG_ON_FOLIO(compound_nr(oldpage) != nr_pages, newfolio);
 
 	if (mem_cgroup_disabled())
 		return;
 
 	/* Page cache replacement: new page already charged? */
-	if (page_memcg(newpage))
+	if (folio_memcg(newfolio))
 		return;
 
 	memcg = page_memcg(oldpage);
@@ -6945,8 +6946,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 		return;
 
 	/* Force-charge the new page. The old one will be freed soon */
-	nr_pages = thp_nr_pages(newpage);
-
 	if (!mem_cgroup_is_root(memcg)) {
 		page_counter_charge(&memcg->memory, nr_pages);
 		if (do_memsw_account())
@@ -6954,7 +6953,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 	}
 
 	css_get(&memcg->css);
-	commit_charge(newpage, memcg);
+	commit_charge(newfolio, memcg);
 
 	local_irq_save(flags);
 	mem_cgroup_charge_statistics(memcg, nr_pages);