linux-kernel - [PATCH v2 03/21] mm: memcontrol: remove the kmem states

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Date:   Thu, 27 May 2021 14:21:30 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     willy@...radead.org, akpm@...ux-foundation.org, hannes@...xchg.org,
        mhocko@...nel.org, vdavydov.dev@...il.com, shakeelb@...gle.com,
        guro@...com, shy828301@...il.com, alexs@...nel.org,
        richard.weiyang@...il.com, david@...morbit.com,
        trond.myklebust@...merspace.com, anna.schumaker@...app.com
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-nfs@...r.kernel.org,
        zhengqi.arch@...edance.com, duanxiongchun@...edance.com,
        fam.zheng@...edance.com, Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v2 03/21] mm: memcontrol: remove the kmem states

Now the kmem states is only used to indicate whether the kmem is
offline. Because css_alloc() could fail, then we didn't make the
kmem offline. In this case, we need the kmem state to mark this
so that memcg_free_kmem() can make the kmem offline.

However, we can set ->kmemcg_id to -1 to indicate the kmem has
been offline. So we can remove the kmem states to simplify the
code.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 include/linux/memcontrol.h | 7 -------
 mm/memcontrol.c            | 9 +++------
 2 files changed, 3 insertions(+), 13 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 0ce97eff79e2..6d0638e13fc1 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -182,12 +182,6 @@ 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];
@@ -320,7 +314,6 @@ 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 9add859f69d7..23a9fc8dc143 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3630,7 +3630,6 @@ 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)
@@ -3647,7 +3646,6 @@ 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;
 }
@@ -3657,11 +3655,9 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
 	struct mem_cgroup *parent;
 	int kmemcg_id;
 
-	if (memcg->kmem_state != KMEM_ONLINE)
+	if (cgroup_memory_nokmem)
 		return;
 
-	memcg->kmem_state = KMEM_ALLOCATED;
-
 	parent = parent_mem_cgroup(memcg);
 	if (!parent)
 		parent = root_mem_cgroup;
@@ -3675,12 +3671,13 @@ 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;
 }
 
 static void memcg_free_kmem(struct mem_cgroup *memcg)
 {
 	/* css_alloc() failed, offlining didn't happen */
-	if (unlikely(memcg->kmem_state == KMEM_ONLINE))
+	if (unlikely(memcg->kmemcg_id != -1))
 		memcg_offline_kmem(memcg);
 }
 #else
-- 
2.11.0