mm, slab: clean up slab->obj_exts always

When memory allocation profiling is disabled at runtime or due to an
error, shutdown_mem_profiling() is called: slab->obj_exts which
previously allocated remains.
It won't be cleared by unaccount_slab() because of
mem_alloc_profiling_enabled() not true. It's incorrect, slab->obj_exts
should always be cleaned up in unaccount_slab() to avoid following error:

[...]BUG: Bad page state in process...
..
[...]page dumped because: page still charged to cgroup

[[email protected]: fold need_slab_obj_ext() into its only user]
Fixes: 21c690a ("mm: introduce slabobj_ext to support slab object extensions")
Cc: [email protected]
Signed-off-by: Zhenhua Huang <[email protected]>
Acked-by: David Rientjes <[email protected]>
Acked-by: Harry Yoo <[email protected]>
Tested-by: Harry Yoo <[email protected]>
Acked-by: Suren Baghdasaryan <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Vlastimil Babka <[email protected]>

Author: Zhenhua Huang

mm/slub.c

@@ -2028,8 +2028,7 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 	return 0;
 }
 
-/* Should be called only if mem_alloc_profiling_enabled() */
-static noinline void free_slab_obj_exts(struct slab *slab)
+static inline void free_slab_obj_exts(struct slab *slab)
 {
 	struct slabobj_ext *obj_exts;
 
@@ -2049,18 +2048,6 @@ static noinline void free_slab_obj_exts(struct slab *slab)
 	slab->obj_exts = 0;
 }
 
-static inline bool need_slab_obj_ext(void)
-{
-	if (mem_alloc_profiling_enabled())
-		return true;
-
-	/*
-	 * CONFIG_MEMCG creates vector of obj_cgroup objects conditionally
-	 * inside memcg_slab_post_alloc_hook. No other users for now.
-	 */
-	return false;
-}
-
 #else /* CONFIG_SLAB_OBJ_EXT */
 
 static inline void init_slab_obj_exts(struct slab *slab)
@@ -2077,11 +2064,6 @@ static inline void free_slab_obj_exts(struct slab *slab)
 {
 }
 
-static inline bool need_slab_obj_ext(void)
-{
-	return false;
-}
-
 #endif /* CONFIG_SLAB_OBJ_EXT */
 
 #ifdef CONFIG_MEM_ALLOC_PROFILING
@@ -2129,7 +2111,7 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags)
 static inline void
 alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags)
 {
-	if (need_slab_obj_ext())
+	if (mem_alloc_profiling_enabled())
 		__alloc_tagging_slab_alloc_hook(s, object, flags);
 }
 
@@ -2601,8 +2583,12 @@ static __always_inline void account_slab(struct slab *slab, int order,
 static __always_inline void unaccount_slab(struct slab *slab, int order,
 					   struct kmem_cache *s)
 {
-	if (memcg_kmem_online() || need_slab_obj_ext())
-		free_slab_obj_exts(slab);
+	/*
+	 * The slab object extensions should now be freed regardless of
+	 * whether mem_alloc_profiling_enabled() or not because profiling
+	 * might have been disabled after slab->obj_exts got allocated.
+	 */
+	free_slab_obj_exts(slab);
 
 	mod_node_page_state(slab_pgdat(slab), cache_vmstat_idx(s),
 			    -(PAGE_SIZE << order));