The default root is allocated and initialized at boot, so we
shouldn't destroy the default root when it's umounted, otherwise
it will lead to disaster.
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
---
kernel/cgroup.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a5f75ac..f73fe48 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1027,12 +1027,14 @@ static umode_t cgroup_file_mode(const struct cftype *cft)
static void cgroup_get(struct cgroup *cgrp)
{
WARN_ON_ONCE(cgroup_is_dead(cgrp));
- css_get(&cgrp->self);
+ if (!(cgrp->self.flags & CSS_NO_REF))
+ css_get(&cgrp->self);
}
static void cgroup_put(struct cgroup *cgrp)
{
- css_put(&cgrp->self);
+ if (!(cgrp->self.flags & CSS_NO_REF))
+ css_put(&cgrp->self);
}
/**
@@ -1781,10 +1783,12 @@ static void cgroup_kill_sb(struct super_block *sb)
* This prevents new mounts by disabling percpu_ref_tryget_live().
* cgroup_mount() may wait for @root's release.
*/
- if (css_has_online_children(&root->cgrp.self))
+ if (css_has_online_children(&root->cgrp.self)) {
cgroup_put(&root->cgrp);
- else
- percpu_ref_kill(&root->cgrp.self.refcnt);
+ } else {
+ if (root != &cgrp_dfl_root)
+ percpu_ref_kill(&root->cgrp.self.refcnt);
+ }
kernfs_kill_sb(sb);
}
--
1.8.0.2
--
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