On Thu 29-07-21 20:12:43, Roman Gushchin wrote: > On Thu, Jul 29, 2021 at 08:57:54PM +0800, Miaohe Lin wrote: > > rtpn might be NULL in very rare case. We have better to check it before > > dereferencing it. Since memcg can live with NULL rb_tree_per_node in > > soft_limit_tree, warn this case and continue. > > > > Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> > > --- > > mm/memcontrol.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 5b4592d1e0f2..70a32174e7c4 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -7109,6 +7109,8 @@ static int __init mem_cgroup_init(void) > > rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, > > node_online(node) ? node : NUMA_NO_NODE); > > > > + if (WARN_ON_ONCE(!rtpn)) > > + continue; > > I also really doubt that it makes any sense to continue in this case. > If this allocations fails (at the very beginning of the system's life, it's an __init function), > something is terribly wrong and panic'ing on a NULL-pointer dereference sounds like > a perfect choice. Moreover this is 24B allocation during early boot. Kernel will OOM and panic when not being able to find any victim. I do not think we need to do any special handling here. -- Michal Hocko SUSE Labs
