mm/memcg: Add folio_memcg() and related functions

memcg information is only stored in the head page, so the memcg
subsystem needs to assure that all accesses are to the head page.
The first step is converting page_memcg() to folio_memcg().

The callers of page_memcg() and PageMemcgKmem() are not yet ready to be
converted to use folios, so retain them as wrappers around folio_memcg()
and folio_memcg_kmem().  They will be converted in a later patch set.

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>

1 files changed, 65 insertions, 45 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3096c9a0ee01..06659670db32 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -369,7 +369,7 @@ enum page_memcg_data_flags {
 
 #define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1)
 
-static inline bool PageMemcgKmem(struct page *page);
+static inline bool folio_memcg_kmem(struct folio *folio);
 
 /*
  * After the initialization objcg->memcg is always pointing at
@@ -384,73 +384,77 @@ static inline struct mem_cgroup *obj_cgroup_memcg(struct obj_cgroup *objcg)
 }
 
 /*
- * __page_memcg - get the memory cgroup associated with a non-kmem page
- * @page: a pointer to the page struct
+ * __folio_memcg - Get the memory cgroup associated with a non-kmem folio
+ * @folio: Pointer to the folio.
  *
- * Returns a pointer to the memory cgroup associated with the page,
- * or NULL. This function assumes that the page is known to have a
+ * Returns a pointer to the memory cgroup associated with the folio,
+ * or NULL. This function assumes that the folio is known to have a
  * proper memory cgroup pointer. It's not safe to call this function
- * against some type of pages, e.g. slab pages or ex-slab pages or
- * kmem pages.
+ * against some type of folios, e.g. slab folios or ex-slab folios or
+ * kmem folios.
  */
-static inline struct mem_cgroup *__page_memcg(struct page *page)
+static inline struct mem_cgroup *__folio_memcg(struct folio *folio)
 {
-	unsigned long memcg_data = page->memcg_data;
+	unsigned long memcg_data = folio->memcg_data;
 
-	VM_BUG_ON_PAGE(PageSlab(page), page);
-	VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_OBJCGS, page);
-	VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_KMEM, page);
+	VM_BUG_ON_FOLIO(folio_test_slab(folio), folio);
+	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_OBJCGS, folio);
+	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_KMEM, folio);
 
 	return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
 }
 
 /*
- * __page_objcg - get the object cgroup associated with a kmem page
- * @page: a pointer to the page struct
+ * __folio_objcg - get the object cgroup associated with a kmem folio.
+ * @folio: Pointer to the folio.
  *
- * Returns a pointer to the object cgroup associated with the page,
- * or NULL. This function assumes that the page is known to have a
+ * Returns a pointer to the object cgroup associated with the folio,
+ * or NULL. This function assumes that the folio is known to have a
  * proper object cgroup pointer. It's not safe to call this function
- * against some type of pages, e.g. slab pages or ex-slab pages or
- * LRU pages.
+ * against some type of folios, e.g. slab folios or ex-slab folios or
+ * LRU folios.
  */
-static inline struct obj_cgroup *__page_objcg(struct page *page)
+static inline struct obj_cgroup *__folio_objcg(struct folio *folio)
 {
-	unsigned long memcg_data = page->memcg_data;
+	unsigned long memcg_data = folio->memcg_data;
 
-	VM_BUG_ON_PAGE(PageSlab(page), page);
-	VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_OBJCGS, page);
-	VM_BUG_ON_PAGE(!(memcg_data & MEMCG_DATA_KMEM), page);
+	VM_BUG_ON_FOLIO(folio_test_slab(folio), folio);
+	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_OBJCGS, folio);
+	VM_BUG_ON_FOLIO(!(memcg_data & MEMCG_DATA_KMEM), folio);
 
 	return (struct obj_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
 }
 
 /*
- * page_memcg - get the memory cgroup associated with a page
- * @page: a pointer to the page struct
+ * folio_memcg - Get the memory cgroup associated with a folio.
+ * @folio: Pointer to the folio.
  *
- * Returns a pointer to the memory cgroup associated with the page,
- * or NULL. This function assumes that the page is known to have a
+ * Returns a pointer to the memory cgroup associated with the folio,
+ * or NULL. This function assumes that the folio is known to have a
  * proper memory cgroup pointer. It's not safe to call this function
- * against some type of pages, e.g. slab pages or ex-slab pages.
+ * against some type of folios, e.g. slab folios or ex-slab folios.
  *
- * For a non-kmem page any of the following ensures page and memcg binding
+ * For a non-kmem folio any of the following ensures folio and memcg binding
  * stability:
  *
- * - the page lock
+ * - the folio lock
  * - LRU isolation
  * - lock_page_memcg()
  * - exclusive reference
  *
- * For a kmem page a caller should hold an rcu read lock to protect memcg
- * associated with a kmem page from being released.
+ * For a kmem folio a caller should hold an rcu read lock to protect memcg
+ * associated with a kmem folio from being released.
  */
+static inline struct mem_cgroup *folio_memcg(struct folio *folio)
+{
+	if (folio_memcg_kmem(folio))
+		return obj_cgroup_memcg(__folio_objcg(folio));
+	return __folio_memcg(folio);
+}
+
 static inline struct mem_cgroup *page_memcg(struct page *page)
 {
-	if (PageMemcgKmem(page))
-		return obj_cgroup_memcg(__page_objcg(page));
-	else
-		return __page_memcg(page);
+	return folio_memcg(page_folio(page));
 }
 
 /*
@@ -523,17 +527,18 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
 
 #ifdef CONFIG_MEMCG_KMEM
 /*
- * PageMemcgKmem - check if the page has MemcgKmem flag set
- * @page: a pointer to the page struct
+ * folio_memcg_kmem - Check if the folio has the memcg_kmem flag set.
+ * @folio: Pointer to the folio.
  *
- * Checks if the page has MemcgKmem flag set. The caller must ensure that
- * the page has an associated memory cgroup. It's not safe to call this function
- * against some types of pages, e.g. slab pages.
+ * Checks if the folio has MemcgKmem flag set. The caller must ensure
+ * that the folio has an associated memory cgroup. It's not safe to call
+ * this function against some types of folios, e.g. slab folios.
  */
-static inline bool PageMemcgKmem(struct page *page)
+static inline bool folio_memcg_kmem(struct folio *folio)
 {
-	VM_BUG_ON_PAGE(page->memcg_data & MEMCG_DATA_OBJCGS, page);
-	return page->memcg_data & MEMCG_DATA_KMEM;
+	VM_BUG_ON_PGFLAGS(PageTail(&folio->page), &folio->page);
+	VM_BUG_ON_FOLIO(folio->memcg_data & MEMCG_DATA_OBJCGS, folio);
+	return folio->memcg_data & MEMCG_DATA_KMEM;
 }
 
 /*
@@ -577,7 +582,7 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page)
 }
 
 #else
-static inline bool PageMemcgKmem(struct page *page)
+static inline bool folio_memcg_kmem(struct folio *folio)
 {
 	return false;
 }
@@ -593,6 +598,11 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page)
 }
 #endif
 
+static inline bool PageMemcgKmem(struct page *page)
+{
+	return folio_memcg_kmem(page_folio(page));
+}
+
 static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
 {
 	return (memcg == root_mem_cgroup);
@@ -1115,6 +1125,11 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
 #define MEM_CGROUP_ID_SHIFT	0
 #define MEM_CGROUP_ID_MAX	0
 
+static inline struct mem_cgroup *folio_memcg(struct folio *folio)
+{
+	return NULL;
+}
+
 static inline struct mem_cgroup *page_memcg(struct page *page)
 {
 	return NULL;
@@ -1131,6 +1146,11 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page)
 	return NULL;
 }
 
+static inline bool folio_memcg_kmem(struct folio *folio)
+{
+	return false;
+}
+
 static inline bool PageMemcgKmem(struct page *page)
 {
 	return false;