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-rw-r--r--mm/memcontrol.c22
1 files changed, 17 insertions, 5 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b29b850cf399..a4d3282493b6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5326,7 +5326,6 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
INIT_LIST_HEAD(&memcg->deferred_split_queue.split_queue);
memcg->deferred_split_queue.split_queue_len = 0;
#endif
- idr_replace(&mem_cgroup_idr, memcg, memcg->id.id);
lru_gen_init_memcg(memcg);
return memcg;
fail:
@@ -5398,14 +5397,27 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
if (alloc_shrinker_info(memcg))
goto offline_kmem;
- /* Online state pins memcg ID, memcg ID pins CSS */
- refcount_set(&memcg->id.ref, 1);
- css_get(css);
-
if (unlikely(mem_cgroup_is_root(memcg)))
queue_delayed_work(system_unbound_wq, &stats_flush_dwork,
FLUSH_TIME);
lru_gen_online_memcg(memcg);
+
+ /* Online state pins memcg ID, memcg ID pins CSS */
+ refcount_set(&memcg->id.ref, 1);
+ css_get(css);
+
+ /*
+ * Ensure mem_cgroup_from_id() works once we're fully online.
+ *
+ * We could do this earlier and require callers to filter with
+ * css_tryget_online(). But right now there are no users that
+ * need earlier access, and the workingset code relies on the
+ * cgroup tree linkage (mem_cgroup_get_nr_swap_pages()). So
+ * publish it here at the end of onlining. This matches the
+ * regular ID destruction during offlining.
+ */
+ idr_replace(&mem_cgroup_idr, memcg, memcg->id.id);
+
return 0;
offline_kmem:
memcg_offline_kmem(memcg);