css_id should be committed after a css is brought online fully. This
is currently done form cgroup_populate_dir() but we're gonna reorder
operations such that cgroup_populate_dir() is called before css is
onlined. Let's move css_id commit from cgroup_populate_dir() to
online_css().
This change makes it possible for cgroup creation to fail after css_id
is committed; however, as css is already fully initialized, the
cleanup isn't different from the cgroup being removed.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
kernel/cgroup.c | 53 +++++++++++++++++++++++++----------------------------
1 file changed, 25 insertions(+), 28 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a65be0c..6a3ad20 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4244,7 +4244,7 @@ static struct cftype cgroup_base_files[] = {
static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
{
struct cgroup_subsys *ss;
- int i, ret = 0;
+ int i, ret;
/* process cftsets of each subsystem */
for_each_subsys(ss, i) {
@@ -4255,29 +4255,14 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
list_for_each_entry(set, &ss->cftsets, node) {
ret = cgroup_addrm_files(cgrp, set->cfts, true);
- if (ret < 0)
- goto err;
+ if (ret < 0) {
+ cgroup_clear_dir(cgrp, subsys_mask);
+ return ret;
+ }
}
}
- /* This cgroup is ready now */
- for_each_root_subsys(cgrp->root, ss) {
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
- struct css_id *id = rcu_dereference_protected(css->id, true);
-
- /*
- * Update id->css pointer and make this css visible from
- * CSS ID functions. This pointer will be dereferened
- * from RCU-read-side without locks.
- */
- if (id)
- rcu_assign_pointer(id->css, css);
- }
-
return 0;
-err:
- cgroup_clear_dir(cgrp, subsys_mask);
- return ret;
}
/*
@@ -4356,18 +4341,30 @@ static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
static int online_css(struct cgroup_subsys_state *css)
{
struct cgroup_subsys *ss = css->ss;
- int ret = 0;
+ struct css_id *id = rcu_dereference_protected(css->id, true);
+ int ret;
lockdep_assert_held(&cgroup_mutex);
- if (ss->css_online)
+ if (ss->css_online) {
ret = ss->css_online(css);
- if (!ret) {
- css->flags |= CSS_ONLINE;
- css->cgroup->nr_css++;
- rcu_assign_pointer(css->cgroup->subsys[ss->subsys_id], css);
+ if (ret)
+ return ret;
}
- return ret;
+
+ css->flags |= CSS_ONLINE;
+ css->cgroup->nr_css++;
+ rcu_assign_pointer(css->cgroup->subsys[ss->subsys_id], css);
+
+ /*
+ * Update id->css pointer and make this css visible from CSS ID
+ * functions. This pointer will be dereferened from RCU-read-side
+ * without locks.
+ */
+ if (id)
+ rcu_assign_pointer(id->css, css);
+
+ return 0;
}
/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
@@ -5678,7 +5675,7 @@ static int alloc_css_id(struct cgroup_subsys_state *child_css)
child_id->stack[depth] = child_id->id;
/*
* child_id->css pointer will be set after this cgroup is available
- * see cgroup_populate_dir()
+ * see online_css()
*/
rcu_assign_pointer(child_css->id, child_id);
--
1.8.3.1
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