linux-kernel - [PATCH v2 19/21] mm: memcontrol: fix cannot alloc the maximum memcg ID

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Message-Id: <20210527062148.9361-20-songmuchun@bytedance.com>
Date:   Thu, 27 May 2021 14:21:46 +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 19/21] mm: memcontrol: fix cannot alloc the maximum memcg ID

The idr_alloc() does not include @max ID. So in the current implementation,
the maximum memcg ID is 65534 instead of 65535. It seems a bug. So fix this.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ae3ad1001824..a1c8ec858593 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5044,7 +5044,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 		return ERR_PTR(error);
 
 	memcg->id.id = idr_alloc(&mem_cgroup_idr, NULL,
-				 1, MEM_CGROUP_ID_MAX,
+				 1, MEM_CGROUP_ID_MAX + 1,
 				 GFP_KERNEL);
 	if (memcg->id.id < 0) {
 		error = memcg->id.id;
-- 
2.11.0