Re: [PATCH 5/5] blk-cgroup: Fix an RCU warning in blkiocg_create()

Li Zefan
2010-05-07T06:54:19Z

Paul E. McKenney wrote:
> On Thu, Apr 22, 2010 at 05:32:28PM +0800, Li Zefan wrote:
>> with CONFIG_PROVE_RCU=y, a warning can be triggered:
>>
>> # mount -t cgroup -o blkio xxx /mnt
>> # mkdir /mnt/subgroup
>>
>> ...
>> kernel/cgroup.c:4442 invoked rcu_dereference_check() without protection!
>> ...
>>
>> To fix this, we avoid caling css_depth() here, which is a bit simpler
>> than the original code.
>
> Queued for 2.6.34, thank you!
>

Seems neither you nor Jens queued this patch...

> Thanx, Paul
>
>> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
>> ---
>> block/blk-cgroup.c | 8 ++++----
>> 1 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
>> index 5fe03de..2cc682b 100644
>> --- a/block/blk-cgroup.c
>> +++ b/block/blk-cgroup.c
>> @@ -286,16 +286,16 @@ done:
>> static struct cgroup_subsys_state *
>> blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
>> {
>> - struct blkio_cgroup *blkcg, *parent_blkcg;
>> + struct blkio_cgroup *blkcg;
>> + struct cgroup *parent = cgroup->parent;
>>
>> - if (!cgroup->parent) {
>> + if (!parent) {
>> blkcg = &blkio_root_cgroup;
>> goto done;
>> }
>>
>> /* Currently we do not support hierarchy deeper than two level (0,1) */
>> - parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
>> - if (css_depth(&parent_blkcg->css) > 0)
>> + if (parent != cgroup->top_cgroup)
>> return ERR_PTR(-EINVAL);
>>
>> blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
>> --
>> 1.6.3
>>
>> --
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>
>