[PATCH] mm: memcontrol: remove the kmem states

[PATCH] mm: memcontrol: remove the kmem states

[Muchun Song]

Now the kmem states is only used to indicate whether the kmem is
offline. However, we can set ->kmemcg_id to -1 to indicate whether
the kmem is offline. Finally, we can remove the kmem states to
simplify the code.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 include/linux/memcontrol.h | 7 -------
 mm/memcontrol.c            | 7 ++-----
 2 files changed, 2 insertions(+), 12 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index e34bf0cbdf55..509e1480e3be 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -180,12 +180,6 @@ struct mem_cgroup_thresholds {
 	struct mem_cgroup_threshold_ary *spare;
 };
 
-enum memcg_kmem_state {
-	KMEM_NONE,
-	KMEM_ALLOCATED,
-	KMEM_ONLINE,
-};
-
 #if defined(CONFIG_SMP)
 struct memcg_padding {
 	char x[0];
@@ -318,7 +312,6 @@ struct mem_cgroup {
 
 #ifdef CONFIG_MEMCG_KMEM
 	int kmemcg_id;
-	enum memcg_kmem_state kmem_state;
 	struct obj_cgroup __rcu *objcg;
 	struct list_head objcg_list; /* list of inherited objcgs */
 #endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e26f87cd7e4c..760e3669a7c8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3621,7 +3621,6 @@ static int memcg_online_kmem(struct mem_cgroup *memcg)
 		return 0;
 
 	BUG_ON(memcg->kmemcg_id >= 0);
-	BUG_ON(memcg->kmem_state);
 
 	memcg_id = memcg_alloc_cache_id();
 	if (memcg_id < 0)
@@ -3638,7 +3637,6 @@ static int memcg_online_kmem(struct mem_cgroup *memcg)
 	static_branch_enable(&memcg_kmem_enabled_key);
 
 	memcg->kmemcg_id = memcg_id;
-	memcg->kmem_state = KMEM_ONLINE;
 
 	return 0;
 }
@@ -3648,11 +3646,9 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
 	struct mem_cgroup *parent;
 	int kmemcg_id;
 
-	if (memcg->kmem_state != KMEM_ONLINE)
+	if (memcg->kmemcg_id == -1)
 		return;
 
-	memcg->kmem_state = KMEM_ALLOCATED;
-
 	parent = parent_mem_cgroup(memcg);
 	if (!parent)
 		parent = root_mem_cgroup;
@@ -3671,6 +3667,7 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
 	memcg_drain_all_list_lrus(kmemcg_id, parent);
 
 	memcg_free_cache_id(kmemcg_id);
+	memcg->kmemcg_id = -1;
 }
 #else
 static int memcg_online_kmem(struct mem_cgroup *memcg)
-- 
2.11.0

Re: [PATCH] mm: memcontrol: remove the kmem states

[Roman Gushchin]

On Mon, Oct 25, 2021 at 08:52:59PM +0800, Muchun Song wrote:
> Now the kmem states is only used to indicate whether the kmem is
> offline. However, we can set ->kmemcg_id to -1 to indicate whether
> the kmem is offline. Finally, we can remove the kmem states to
> simplify the code.
> 
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>

Acked-by: Roman Gushchin <guro@fb.com>

Nice! These states made the code more complex without a good reason.

Thanks!