On 12/7/21 19:26, Yang Shi wrote: > On Tue, Dec 7, 2021 at 3:44 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> 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). >> >> It isn't entirely clear to me from the v1 discussion why this approach >> isn't being taken? >> >> AFAICT the proposed patch is *already* taking this approach, by having >> no protection against a concurrent or subsequent node offlining? > > AFAICT, we have not reached agreement on how to fix it yet. I saw 3 > proposals at least: > > 1. From Michal, allocate node data for all possible nodes. > https://lore.kernel.org/all/Ya89aqij6nMwJrIZ@xxxxxxxxxxxxxx/T/#u > > 2. What this patch does. Proposed originally from > https://lore.kernel.org/all/20211108202325.20304-1-amakhalov@xxxxxxxxxx/T/#u Correct me if im wrong, but isn't that a different caller? This patch fixes the issue in expand_one_shrinker_info. > 3. From David, fix in node_zonelist(). > https://lore.kernel.org/all/51c65635-1dae-6ba4-daf9-db9df0ec35d8@xxxxxxxxxx/T/#u > >> >>> --- a/mm/vmscan.c >>> +++ b/mm/vmscan.c >>> @@ -222,13 +222,16 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg, >>> int size = map_size + defer_size; >>> >>> for_each_node(nid) { >>> + int tmp = nid; >> >> Not `tmp', please. Better to use an identifier which explains the >> variable's use. target_nid? >> >> And a newline after defining locals, please. >> >>> pn = memcg->nodeinfo[nid]; >>> old = shrinker_info_protected(memcg, nid); >>> /* Not yet online memcg */ >>> if (!old) >>> return 0; >>> >>> - new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid); >>> + if(!node_online(nid)) >> >> s/if(/if (/ >> >>> + tmp = numa_mem_id(); >>> + new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, tmp); >>> if (!new) >>> return -ENOMEM; >>> >> >> And a code comment fully explaining what's going on here? >
