[PATCH 3.19.y-ckt 052/102] cpuset: use trialcs->mems_allowed as a temp variable

[Kamal Mostafa]

3.19.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alban Crequy <alban.crequy@xxxxxxxxx>

commit 24ee3cf89bef04e8bc23788aca4e029a3f0f06d9 upstream.

The comment says it's using trialcs->mems_allowed as a temp variable but
it didn't match the code. Change the code to match the comment.

This fixes an issue when writing in cpuset.mems when a sub-directory
exists: we need to write several times for the information to persist:

| root@alban:/sys/fs/cgroup/cpuset# mkdir footest9
| root@alban:/sys/fs/cgroup/cpuset# cd footest9
| root@alban:/sys/fs/cgroup/cpuset/footest9# mkdir aa
| root@alban:/sys/fs/cgroup/cpuset/footest9# cat cpuset.mems
|
| root@alban:/sys/fs/cgroup/cpuset/footest9# echo 0 > cpuset.mems
| root@alban:/sys/fs/cgroup/cpuset/footest9# cat cpuset.mems
|
| root@alban:/sys/fs/cgroup/cpuset/footest9# echo 0 > cpuset.mems
| root@alban:/sys/fs/cgroup/cpuset/footest9# cat cpuset.mems
| 0
| root@alban:/sys/fs/cgroup/cpuset/footest9# cat aa/cpuset.mems
|
| root@alban:/sys/fs/cgroup/cpuset/footest9# echo 0 > aa/cpuset.mems
| root@alban:/sys/fs/cgroup/cpuset/footest9# cat aa/cpuset.mems
| 0
| root@alban:/sys/fs/cgroup/cpuset/footest9#

This should help to fix the following issue in Docker:
https://github.com/opencontainers/runc/issues/133
In some conditions, a Docker container needs to be started twice in
order to work.

Signed-off-by: Alban Crequy <alban@xxxxxxxxxxxx>
Tested-by: Iago LÃpez Galeiras <iago@xxxxxxxxxxxx>
Acked-by: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
 kernel/cpuset.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 9e25599..c90edf6 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1214,7 +1214,7 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
 	spin_unlock_irq(&callback_lock);
 
 	/* use trialcs->mems_allowed as a temp variable */
-	update_nodemasks_hier(cs, &cs->mems_allowed);
+	update_nodemasks_hier(cs, &trialcs->mems_allowed);
 done:
 	return retval;
 }
-- 
1.9.1

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