4.15-stable review patch. If anyone has any objections, please let me know.
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From: Tejun Heo tj@kernel.org
commit c53593e5cb693d59d9e8b64fb3a79436bf99c3b3 upstream.
While adding cgroup2 interface for the cpu controller, 0d5936344f30 ("sched: Implement interface for cgroup unified hierarchy") forgot to update input validation and left it to reject cpu.max config if any descendant has set a higher value.
cgroup2 officially supports delegation and a descendant must not be able to restrict what its ancestors can configure. For absolute limits such as cpu.max and memory.max, this means that the config at each level should only act as the upper limit at that level and shouldn't interfere with what other cgroups can configure.
This patch updates config validation on cgroup2 so that the cpu controller follows the same convention.
Signed-off-by: Tejun Heo tj@kernel.org Fixes: 0d5936344f30 ("sched: Implement interface for cgroup unified hierarchy") Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org # v4.15+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/sched/core.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6611,13 +6611,18 @@ static int tg_cfs_schedulable_down(struc parent_quota = parent_b->hierarchical_quota;
/* - * Ensure max(child_quota) <= parent_quota, inherit when no + * Ensure max(child_quota) <= parent_quota. On cgroup2, + * always take the min. On cgroup1, only inherit when no * limit is set: */ - if (quota == RUNTIME_INF) - quota = parent_quota; - else if (parent_quota != RUNTIME_INF && quota > parent_quota) - return -EINVAL; + if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) { + quota = min(quota, parent_quota); + } else { + if (quota == RUNTIME_INF) + quota = parent_quota; + else if (parent_quota != RUNTIME_INF && quota > parent_quota) + return -EINVAL; + } } cfs_b->hierarchical_quota = quota;