From 265792d0dede9259f0ca56bb3efcc23eceee7d01 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Wed, 27 Jul 2022 20:58:15 -0400 Subject: [PATCH] cgroup: Skip subtree root in cgroup_update_dfl_csses() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The cgroup_update_dfl_csses() function updates css associations when a cgroup's subtree_control file is modified. Any changes made to a cgroup's subtree_control file, however, will only affect its descendants but not the cgroup itself. So there is no point in migrating csses associated with that cgroup. We can skip them instead. Signed-off-by: Waiman Long Reviewed-by: Michal Koutný Signed-off-by: Tejun Heo --- kernel/cgroup/cgroup.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index c85dadf0d53b..85fa4c8587a8 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -2971,6 +2971,15 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp) cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) { struct cgrp_cset_link *link; + /* + * As cgroup_update_dfl_csses() is only called by + * cgroup_apply_control(). The csses associated with the + * given cgrp will not be affected by changes made to + * its subtree_control file. We can skip them. + */ + if (dsct == cgrp) + continue; + list_for_each_entry(link, &dsct->cset_links, cset_link) cgroup_migrate_add_src(link->cset, dsct, &mgctx); }