mm: convert mem_cgroup_css_from_page() to mem_cgroup_css_from_folio()

Only one caller doesn't have a folio, so move the page_folio() call to
that one caller from mem_cgroup_css_from_folio().

Link: https://lkml.kernel.org/r/20230116192507.2146150-3-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/fs-writeback.c

@@ -246,7 +246,7 @@ void __inode_attach_wb(struct inode *inode, struct folio *folio)
 		struct cgroup_subsys_state *memcg_css;
 
 		if (folio) {
-			memcg_css = mem_cgroup_css_from_page(&folio->page);
+			memcg_css = mem_cgroup_css_from_folio(folio);
 			wb = wb_get_create(bdi, memcg_css, GFP_ATOMIC);
 		} else {
 			/* must pin memcg_css, see wb_get_create() */
@@ -859,6 +859,7 @@ EXPORT_SYMBOL_GPL(wbc_detach_inode);
 void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
 			      size_t bytes)
 {
+	struct folio *folio;
 	struct cgroup_subsys_state *css;
 	int id;
 
@@ -871,7 +872,8 @@ void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
 	if (!wbc->wb || wbc->no_cgroup_owner)
 		return;
 
-	css = mem_cgroup_css_from_page(page);
+	folio = page_folio(page);
+	css = mem_cgroup_css_from_folio(folio);
 	/* dead cgroups shouldn't contribute to inode ownership arbitration */
 	if (!(css->flags & CSS_ONLINE))
 		return;

include/linux/memcontrol.h

@@ -890,7 +890,7 @@ static inline bool mm_match_cgroup(struct mm_struct *mm,
 	return match;
 }
 
-struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page);
+struct cgroup_subsys_state *mem_cgroup_css_from_folio(struct folio *folio);
 ino_t page_cgroup_ino(struct page *page);
 
 static inline bool mem_cgroup_online(struct mem_cgroup *memcg)

mm/memcontrol.c

@@ -350,21 +350,19 @@ EXPORT_SYMBOL(memcg_kmem_enabled_key);
 #endif
 
 /**
- * mem_cgroup_css_from_page - css of the memcg associated with a page
- * @page: page of interest
+ * mem_cgroup_css_from_folio - css of the memcg associated with a folio
+ * @folio: folio of interest
  *
  * If memcg is bound to the default hierarchy, css of the memcg associated
- * with @page is returned.  The returned css remains associated with @page
+ * with @folio is returned.  The returned css remains associated with @folio
  * until it is released.
  *
  * If memcg is bound to a traditional hierarchy, the css of root_mem_cgroup
  * is returned.
  */
-struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page)
+struct cgroup_subsys_state *mem_cgroup_css_from_folio(struct folio *folio)
 {
-	struct mem_cgroup *memcg;
-
-	memcg = page_memcg(page);
+	struct mem_cgroup *memcg = folio_memcg(folio);
 
 	if (!memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		memcg = root_mem_cgroup;