[PATCH v2 1/2] cgroup/cpuset: reset DL migration state on can_attach() failure

[Guopeng Zhang]

cpuset_can_attach() accumulates temporary SCHED_DEADLINE migration
state in the destination cpuset while walking the taskset.

If a later task_can_attach() or security_task_setscheduler() check
fails, cgroup_migrate_execute() treats cpuset as the failing subsystem
and does not call cpuset_cancel_attach() for it. The partially
accumulated state is then left behind and can be consumed by a later
attach, corrupting cpuset DL task accounting and pending DL bandwidth
accounting.

Reset the pending DL migration state before returning from those
per-task failure paths.

Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Signed-off-by: Guopeng Zhang <zhangguopeng@xxxxxxxxxx>
---
 kernel/cgroup/cpuset.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index e3a081a07c6d..ae41736399a1 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3029,12 +3029,12 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
 	cgroup_taskset_for_each(task, css, tset) {
 		ret = task_can_attach(task);
 		if (ret)
-			goto out_unlock;
+			goto out_reset_dl_data;
 
 		if (setsched_check) {
 			ret = security_task_setscheduler(task);
 			if (ret)
-				goto out_unlock;
+				goto out_reset_dl_data;
 		}
 
 		if (dl_task(task)) {
@@ -3070,6 +3070,10 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
 	 * changes which zero cpus/mems_allowed.
 	 */
 	cs->attach_in_progress++;
+	goto out_unlock;
+
+out_reset_dl_data:
+	reset_migrate_dl_data(cs);
 out_unlock:
 	mutex_unlock(&cpuset_mutex);
 	return ret;
-- 
2.43.0