Re: [PATCH] cgroup: Kill the parent controller when its last child is killed

[kernel test robot <lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

Hi Bui,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on tj-cgroup/for-next]
[also build test ERROR on v5.17 next-20220401]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Bui-Quang-Minh/cgroup-Kill-the-parent-controller-when-its-last-child-is-killed/20220403-215911
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-next
config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20220403/202204032330.l2wsF3mf-lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org/config)
compiler: gcc-11 (Debian 11.2.0-19) 11.2.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/2bc22feae8a913c7f371bc79ef9967122d8d326c
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Bui-Quang-Minh/cgroup-Kill-the-parent-controller-when-its-last-child-is-killed/20220403-215911
        git checkout 2bc22feae8a913c7f371bc79ef9967122d8d326c
        # save the config file to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash kernel/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

All errors (new ones prefixed by >>):

   kernel/cgroup/cgroup.c: In function 'css_release_work_fn':
>> kernel/cgroup/cgroup.c:5169:52: error: 'struct cgroup_bpf' has no member named 'refcnt'
    5169 |                 if (!percpu_ref_is_dying(&cgrp->bpf.refcnt))
         |                                                    ^


vim +5169 kernel/cgroup/cgroup.c

  5148	
  5149	static void css_release_work_fn(struct work_struct *work)
  5150	{
  5151		struct cgroup_subsys_state *css =
  5152			container_of(work, struct cgroup_subsys_state, destroy_work);
  5153		struct cgroup_subsys *ss = css->ss;
  5154		struct cgroup *cgrp = css->cgroup;
  5155		struct cgroup *parent = cgroup_parent(cgrp);
  5156	
  5157		mutex_lock(&cgroup_mutex);
  5158	
  5159		css->flags |= CSS_RELEASED;
  5160		list_del_rcu(&css->sibling);
  5161	
  5162		/*
  5163		 * If parent doesn't have any children, start killing it.
  5164		 * And don't kill the default root.
  5165		 */
  5166		if (parent && list_empty(&parent->self.children) &&
  5167		    parent != &cgrp_dfl_root.cgrp &&
  5168		    !percpu_ref_is_dying(&parent->self.refcnt)) {
> 5169			if (!percpu_ref_is_dying(&cgrp->bpf.refcnt))
  5170				cgroup_bpf_offline(parent);
  5171			percpu_ref_kill(&parent->self.refcnt);
  5172		}
  5173	
  5174		if (ss) {
  5175			/* css release path */
  5176			if (!list_empty(&css->rstat_css_node)) {
  5177				cgroup_rstat_flush(cgrp);
  5178				list_del_rcu(&css->rstat_css_node);
  5179			}
  5180	
  5181			cgroup_idr_replace(&ss->css_idr, NULL, css->id);
  5182			if (ss->css_released)
  5183				ss->css_released(css);
  5184		} else {
  5185			struct cgroup *tcgrp;
  5186	
  5187			/* cgroup release path */
  5188			TRACE_CGROUP_PATH(release, cgrp);
  5189	
  5190			cgroup_rstat_flush(cgrp);
  5191	
  5192			spin_lock_irq(&css_set_lock);
  5193			for (tcgrp = cgroup_parent(cgrp); tcgrp;
  5194			     tcgrp = cgroup_parent(tcgrp))
  5195				tcgrp->nr_dying_descendants--;
  5196			spin_unlock_irq(&css_set_lock);
  5197	
  5198			/*
  5199			 * There are two control paths which try to determine
  5200			 * cgroup from dentry without going through kernfs -
  5201			 * cgroupstats_build() and css_tryget_online_from_dir().
  5202			 * Those are supported by RCU protecting clearing of
  5203			 * cgrp->kn->priv backpointer.
  5204			 */
  5205			if (cgrp->kn)
  5206				RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
  5207						 NULL);
  5208		}
  5209	
  5210		mutex_unlock(&cgroup_mutex);
  5211	
  5212		INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
  5213		queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
  5214	}
  5215	

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