[Devel] [PATCH RHEL7 COMMIT] ve/cgroup: Get correct VE init css when ve init_task is moved to child cgroup

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-693.17.1.vz7.45.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.17.1.vz7.45.4
------>
commit 52d17a28f60d446da2159d486fbbedc197061a91
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Tue Feb 27 15:28:28 2018 +0300

    ve/cgroup: Get correct VE init css when ve init_task is moved to child cgroup
    
    Init task of container can be moved to any child cgroup.
    But ve_get_init_css() remains to return its cgroup as
    top of container. Fix that by finding of real top cgroup
    among init_task cgroup parents.
    
    https://jira.sw.ru/browse/PSBM-81572
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    Reviewed-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
    
    ======================================================
    Patchset description:
    sched/ve: Fix wrong loadavg accounting inside CT
    
    Three problems are fixed here:
    
    1)Tasks from child task groups are not propagated in CT's loadavg
    2)Loadavg of CT's init task cgroup is returned as CT's loadavg,
      while init task may be in child task group.
    3)In calc_load_ve() (from interrupt) we count loadavg for all cpu
      cgroups, which is slow and unneed.
    
    The patchset fixes all of them.
    
    https://jira.sw.ru/browse/PSBM-81572
    
    Kirill Tkhai (5):
          ve/cgroup: Get correct VE init css when ve init_task is moved to child cgroup
          sched/ve: Link VE root cpu cgroups in separate list
          sched/ve: Do not show loadavg in child VE cpu cgroups
          sched/ve: Iterate only VE root cpu cgroups to count loadavg
          sched/ve: Use cfs_rq::h_nr_running to count loadavg
---
 kernel/ve/ve.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
index ee043483c7e7..68f84797a840 100644
--- a/kernel/ve/ve.c
+++ b/kernel/ve/ve.c
@@ -111,8 +111,9 @@ EXPORT_SYMBOL(put_ve);
 
 struct cgroup_subsys_state *ve_get_init_css(struct ve_struct *ve, int subsys_id)
 {
-	struct cgroup_subsys_state *css;
+	struct cgroup_subsys_state *css, *tmp;
 	struct task_struct *task;
+	struct cgroup *cgroup;
 
 	rcu_read_lock();
 	task = ve->ve_ns ? ve->init_task : &init_task;
@@ -122,6 +123,18 @@ struct cgroup_subsys_state *ve_get_init_css(struct ve_struct *ve, int subsys_id)
 			break;
 		cpu_relax();
 	}
+
+	cgroup = css->cgroup;
+	while (!test_bit(CGRP_VE_ROOT, &cgroup->flags) && cgroup->parent)
+		cgroup = cgroup->parent;
+
+	if (cgroup != css->cgroup) {
+		tmp = cgroup->subsys[subsys_id];
+		css_get(tmp);
+		css_put(css);
+		css = tmp;
+	}
+
 	rcu_read_unlock();
 	return css;
 }