On Tue 07-12-21 19:40:33, Nico Pache wrote: > > > On 12/7/21 18:44, Andrew Morton wrote: > > On Tue, 7 Dec 2021 17:40:13 -0500 Nico Pache <npache@xxxxxxxxxx> wrote: > > > >> We have run into a panic caused by a shrinker allocation being attempted > >> on an offlined node. > >> > >> Our crash analysis has determined that the issue originates from trying > >> to allocate pages on an offlined node in expand_one_shrinker_info. This > >> function makes the incorrect assumption that we can allocate on any node. > >> To correct this we make sure the node is online before tempting an > >> allocation. If it is not online choose the closest node. > > > > This isn't fully accurate, is it? We could allocate on a node which is > > presently offline but which was previously onlined, by testing > > NODE_DATA(nid). > > Thanks for the review! I took your changes below into consideration for my V3. > > My knowledge of offlined/onlined nodes is quite limited but after looking into > it it doesnt seem like anything clears the state of NODE_DATA(nid) after a > try_offline_node is attempted. So theoretically the panic we saw would not > happen. What is the expected behavior of trying to allocate a page on a offline > node? To fall back (in the zonelist order) into the other node. If __GFP_THISNODE is specified then simply fail the allocation. -- Michal Hocko SUSE Labs
