[PATCH -next] cgroup/cpuset: Do not clear xcpus when clearing cpus

[Chen Ridong]

After commit 737bb142a00d ("cgroup/cpuset: Make cpuset.cpus.exclusive
independent of cpuset.cpus"), cpuset.cpus.exclusive and cpuset.cpus
became independent. However we found that cpuset.cpus.exclusive.effective
is cleared when cpuset.cpus is clear. To fix this issue, just remove xcpus
clearing when cpuset.cpus is being cleared.

It can be reproduced as below:
cd /sys/fs/cgroup/
mkdir test
echo +cpuset > cgroup.subtree_control
cd test
echo 3 > cpuset.cpus.exclusive
cat cpuset.cpus.exclusive.effective
3
echo > cpuset.cpus
cat cpuset.cpus.exclusive.effective // was cleared

Signed-off-by: Chen Ridong <chenridong@xxxxxxxxxx>
---
 kernel/cgroup/cpuset.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index a9b6d56eeffa..248c39bebbe9 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2523,10 +2523,9 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 	 * that parsing.  The validate_change() call ensures that cpusets
 	 * with tasks have cpus.
 	 */
-	if (!*buf) {
+	if (!*buf)
 		cpumask_clear(trialcs->cpus_allowed);
-		cpumask_clear(trialcs->effective_xcpus);
-	} else {
+	else {
 		retval = cpulist_parse(buf, trialcs->cpus_allowed);
 		if (retval < 0)
 			return retval;
-- 
2.34.1