On Fri 13-04-18 12:35:22, Kirill Tkhai wrote: > On 13.04.2018 11:55, Michal Hocko wrote: > > On Thu 12-04-18 17:52:04, Kirill Tkhai wrote: > > [...] > >> @@ -4471,6 +4477,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) > >> > >> return &memcg->css; > >> fail: > >> + mem_cgroup_id_remove(memcg); > >> mem_cgroup_free(memcg); > >> return ERR_PTR(-ENOMEM); > >> } > > > > The only path which jumps to fail: here (in the current mmotm tree) is > > error = memcg_online_kmem(memcg); > > if (error) > > goto fail; > > > > AFAICS and the only failure path in memcg_online_kmem > > memcg_id = memcg_alloc_cache_id(); > > if (memcg_id < 0) > > return memcg_id; > > > > I am not entirely clear on memcg_alloc_cache_id but it seems we do clean > > up properly. Or am I missing something? > > memcg_alloc_cache_id() may allocate a lot of memory, in case of the system reached > memcg_nr_cache_ids cgroups. In this case it iterates over all LRU lists, and double > size of every of them. In case of memory pressure it can fail. If this occurs, > mem_cgroup::id is not unhashed from IDR and we leak this id. OK, my bad I was looking at the bad code path. So you want to clean up after mem_cgroup_alloc not memcg_online_kmem. Now it makes much more sense. Sorry for the confusion on my end. Anyway, shouldn't we do the thing in mem_cgroup_free() to be symmetric to mem_cgroup_alloc? -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
