[PATCH v6 09/37] slab: objext: introduce objext_flags as extension to page_memcg_data_flags

[Suren Baghdasaryan <surenb@xxxxxxxxxx>]

Introduce objext_flags to store additional objext flags unrelated to memcg.

Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 include/linux/memcontrol.h | 29 ++++++++++++++++++++++-------
 mm/slab.h                  |  5 +----
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 99f423742324..12afc2647cf0 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -357,7 +357,22 @@ enum page_memcg_data_flags {
 	__NR_MEMCG_DATA_FLAGS  = (1UL << 2),
 };
 
-#define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1)
+#define __FIRST_OBJEXT_FLAG	__NR_MEMCG_DATA_FLAGS
+
+#else /* CONFIG_MEMCG */
+
+#define __FIRST_OBJEXT_FLAG	(1UL << 0)
+
+#endif /* CONFIG_MEMCG */
+
+enum objext_flags {
+	/* the next bit after the last actual flag */
+	__NR_OBJEXTS_FLAGS  = __FIRST_OBJEXT_FLAG,
+};
+
+#define OBJEXTS_FLAGS_MASK (__NR_OBJEXTS_FLAGS - 1)
+
+#ifdef CONFIG_MEMCG
 
 static inline bool folio_memcg_kmem(struct folio *folio);
 
@@ -391,7 +406,7 @@ static inline struct mem_cgroup *__folio_memcg(struct folio *folio)
 	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_OBJEXTS, folio);
 	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_KMEM, folio);
 
-	return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+	return (struct mem_cgroup *)(memcg_data & ~OBJEXTS_FLAGS_MASK);
 }
 
 /*
@@ -412,7 +427,7 @@ static inline struct obj_cgroup *__folio_objcg(struct folio *folio)
 	VM_BUG_ON_FOLIO(memcg_data & MEMCG_DATA_OBJEXTS, folio);
 	VM_BUG_ON_FOLIO(!(memcg_data & MEMCG_DATA_KMEM), folio);
 
-	return (struct obj_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+	return (struct obj_cgroup *)(memcg_data & ~OBJEXTS_FLAGS_MASK);
 }
 
 /*
@@ -469,11 +484,11 @@ static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio)
 	if (memcg_data & MEMCG_DATA_KMEM) {
 		struct obj_cgroup *objcg;
 
-		objcg = (void *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+		objcg = (void *)(memcg_data & ~OBJEXTS_FLAGS_MASK);
 		return obj_cgroup_memcg(objcg);
 	}
 
-	return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+	return (struct mem_cgroup *)(memcg_data & ~OBJEXTS_FLAGS_MASK);
 }
 
 /*
@@ -512,11 +527,11 @@ static inline struct mem_cgroup *folio_memcg_check(struct folio *folio)
 	if (memcg_data & MEMCG_DATA_KMEM) {
 		struct obj_cgroup *objcg;
 
-		objcg = (void *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+		objcg = (void *)(memcg_data & ~OBJEXTS_FLAGS_MASK);
 		return obj_cgroup_memcg(objcg);
 	}
 
-	return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
+	return (struct mem_cgroup *)(memcg_data & ~OBJEXTS_FLAGS_MASK);
 }
 
 static inline struct mem_cgroup *page_memcg_check(struct page *page)
diff --git a/mm/slab.h b/mm/slab.h
index 1c16dc8344fa..65db525e93af 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -554,11 +554,8 @@ static inline struct slabobj_ext *slab_obj_exts(struct slab *slab)
 	VM_BUG_ON_PAGE(obj_exts && !(obj_exts & MEMCG_DATA_OBJEXTS),
 							slab_page(slab));
 	VM_BUG_ON_PAGE(obj_exts & MEMCG_DATA_KMEM, slab_page(slab));
-
-	return (struct slabobj_ext *)(obj_exts & ~MEMCG_DATA_FLAGS_MASK);
-#else
-	return (struct slabobj_ext *)obj_exts;
 #endif
+	return (struct slabobj_ext *)(obj_exts & ~OBJEXTS_FLAGS_MASK);
 }
 
 #else /* CONFIG_SLAB_OBJ_EXT */
-- 
2.44.0.291.gc1ea87d7ee-goog