mm/slub: remove DEACTIVATE_TO_* stat items

The cpu slabs and their deactivations were removed, so remove the unused
stat items. Weirdly enough the values were also used to control
__add_partial() adding to head or tail of the list, so replace that with
a new enum add_mode, which is cleaner.

Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Hao Li <hao.li@linux.dev>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Author: tehcaster

mm/slub.c

@@ -329,6 +329,11 @@ static void debugfs_slab_add(struct kmem_cache *);
 static inline void debugfs_slab_add(struct kmem_cache *s) { }
 #endif
 
+enum add_mode {
+	ADD_TO_HEAD,
+	ADD_TO_TAIL,
+};
+
 enum stat_item {
 	ALLOC_PCS,		/* Allocation from percpu sheaf */
 	ALLOC_FASTPATH,		/* Allocation from cpu slab */
@@ -348,8 +353,6 @@ enum stat_item {
 	CPUSLAB_FLUSH,		/* Abandoning of the cpu slab */
 	DEACTIVATE_FULL,	/* Cpu slab was full when deactivated */
 	DEACTIVATE_EMPTY,	/* Cpu slab was empty when deactivated */
-	DEACTIVATE_TO_HEAD,	/* Cpu slab was moved to the head of partials */
-	DEACTIVATE_TO_TAIL,	/* Cpu slab was moved to the tail of partials */
 	DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */
 	DEACTIVATE_BYPASS,	/* Implicit deactivation */
 	ORDER_FALLBACK,		/* Number of times fallback was necessary */
@@ -3270,21 +3273,21 @@ static inline void slab_clear_node_partial(struct slab *slab)
  * Management of partially allocated slabs.
  */
 static inline void
-__add_partial(struct kmem_cache_node *n, struct slab *slab, int tail)
+__add_partial(struct kmem_cache_node *n, struct slab *slab, enum add_mode mode)
 {
 	n->nr_partial++;
-	if (tail == DEACTIVATE_TO_TAIL)
+	if (mode == ADD_TO_TAIL)
 		list_add_tail(&slab->slab_list, &n->partial);
 	else
 		list_add(&slab->slab_list, &n->partial);
 	slab_set_node_partial(slab);
 }
 
 static inline void add_partial(struct kmem_cache_node *n,
-				struct slab *slab, int tail)
+				struct slab *slab, enum add_mode mode)
 {
 	lockdep_assert_held(&n->list_lock);
-	__add_partial(n, slab, tail);
+	__add_partial(n, slab, mode);
 }
 
 static inline void remove_partial(struct kmem_cache_node *n,
@@ -3377,7 +3380,7 @@ static void *alloc_single_from_new_slab(struct kmem_cache *s, struct slab *slab,
 	if (slab->inuse == slab->objects)
 		add_full(s, n, slab);
 	else
-		add_partial(n, slab, DEACTIVATE_TO_HEAD);
+		add_partial(n, slab, ADD_TO_HEAD);
 
 	inc_slabs_node(s, nid, slab->objects);
 	spin_unlock_irqrestore(&n->list_lock, flags);
@@ -3999,7 +4002,7 @@ static unsigned int alloc_from_new_slab(struct kmem_cache *s, struct slab *slab,
 			n = get_node(s, slab_nid(slab));
 			spin_lock_irqsave(&n->list_lock, flags);
 		}
-		add_partial(n, slab, DEACTIVATE_TO_HEAD);
+		add_partial(n, slab, ADD_TO_HEAD);
 		spin_unlock_irqrestore(&n->list_lock, flags);
 	}
 
@@ -5070,7 +5073,7 @@ static noinline void free_to_partial_list(
 			/* was on full list */
 			remove_full(s, n, slab);
 			if (!slab_free) {
-				add_partial(n, slab, DEACTIVATE_TO_TAIL);
+				add_partial(n, slab, ADD_TO_TAIL);
 				stat(s, FREE_ADD_PARTIAL);
 			}
 		} else if (slab_free) {
@@ -5190,7 +5193,7 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
 	 * then add it.
 	 */
 	if (unlikely(was_full)) {
-		add_partial(n, slab, DEACTIVATE_TO_TAIL);
+		add_partial(n, slab, ADD_TO_TAIL);
 		stat(s, FREE_ADD_PARTIAL);
 	}
 	spin_unlock_irqrestore(&n->list_lock, flags);
@@ -6605,7 +6608,7 @@ __refill_objects_node(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int mi
 				continue;
 
 			list_del(&slab->slab_list);
-			add_partial(n, slab, DEACTIVATE_TO_HEAD);
+			add_partial(n, slab, ADD_TO_HEAD);
 		}
 
 		spin_unlock_irqrestore(&n->list_lock, flags);
@@ -7072,7 +7075,7 @@ static void early_kmem_cache_node_alloc(int node)
 	 * No locks need to be taken here as it has just been
 	 * initialized and there is no concurrent access.
 	 */
-	__add_partial(n, slab, DEACTIVATE_TO_HEAD);
+	__add_partial(n, slab, ADD_TO_HEAD);
 }
 
 static void free_kmem_cache_nodes(struct kmem_cache *s)
@@ -8764,8 +8767,6 @@ STAT_ATTR(FREE_SLAB, free_slab);
 STAT_ATTR(CPUSLAB_FLUSH, cpuslab_flush);
 STAT_ATTR(DEACTIVATE_FULL, deactivate_full);
 STAT_ATTR(DEACTIVATE_EMPTY, deactivate_empty);
-STAT_ATTR(DEACTIVATE_TO_HEAD, deactivate_to_head);
-STAT_ATTR(DEACTIVATE_TO_TAIL, deactivate_to_tail);
 STAT_ATTR(DEACTIVATE_REMOTE_FREES, deactivate_remote_frees);
 STAT_ATTR(DEACTIVATE_BYPASS, deactivate_bypass);
 STAT_ATTR(ORDER_FALLBACK, order_fallback);
@@ -8868,8 +8869,6 @@ static struct attribute *slab_attrs[] = {
 	&cpuslab_flush_attr.attr,
 	&deactivate_full_attr.attr,
 	&deactivate_empty_attr.attr,
-	&deactivate_to_head_attr.attr,
-	&deactivate_to_tail_attr.attr,
 	&deactivate_remote_frees_attr.attr,
 	&deactivate_bypass_attr.attr,
 	&order_fallback_attr.attr,