Re: [PATCH v2 -next] mm/hugetlb_cgroup: register lockdep key for cftype

[SeongJae Park <sj@xxxxxxxxxx>]

Hi Xiu,


On Tue, 18 Jun 2024 07:19:22 +0000 Xiu Jianfeng <xiujianfeng@xxxxxxxxxx> wrote:

> When CONFIG_DEBUG_LOCK_ALLOC is enabled, the following commands can
> trigger a bug,
> 
> mount -t cgroup2 none /sys/fs/cgroup
> cd /sys/fs/cgroup
> echo "+hugetlb" > cgroup.subtree_control

[...]
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
> index 2b899c4ae968..4ff238ba1250 100644
> --- a/mm/hugetlb_cgroup.c
> +++ b/mm/hugetlb_cgroup.c
> @@ -836,6 +836,8 @@ hugetlb_cgroup_cfttypes_init(struct hstate *h, struct cftype *cft,
>  			cft->file_offset = MEMFILE_OFFSET0(offset) +
>  					   MEMFILE_FIELD_SIZE(offset) * idx;
>  		}
> +
> +		lockdep_register_key(&cft->lockdep_key);
>  	}
>  }

I found the latest mm-unstable tree fails build as below, and 'git bisect'
points this patch.

    linux/mm/hugetlb_cgroup.c: In function ‘hugetlb_cgroup_cfttypes_init’:
    linux/mm/hugetlb_cgroup.c:840:42: error: ‘struct cftype’ has no member named ‘lockdep_key’
      840 |                 lockdep_register_key(&cft->lockdep_key);
          |                                          ^~

Maybe we should take care of CONFIG_DEBUG_LOCK_ALLOC undefined case, like
below?


diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index a45065698419..9747c2e64e95 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -837,7 +837,9 @@ hugetlb_cgroup_cfttypes_init(struct hstate *h, struct cftype *cft,
                                           MEMFILE_FIELD_SIZE(offset) * idx;
                }

+#ifdef CONFIG_DEBUG_LOCK_ALLOC
                lockdep_register_key(&cft->lockdep_key);
+#endif
        }
 }

[...]


Thanks,
SJ