6.6-stable review patch. If anyone has any objections, please let me know.
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From: Tianyang Zhang zhangtianyang@loongson.cn
commit e05741fb10c38d70bbd7ec12b23c197b6355d519 upstream.
__alloc_pages_slowpath has no change detection for ac->nodemask in the part of retry path, while cpuset can modify it in parallel. For some processes that set mempolicy as MPOL_BIND, this results ac->nodemask changes, and then the should_reclaim_retry will judge based on the latest nodemask and jump to retry, while the get_page_from_freelist only traverses the zonelist from ac->preferred_zoneref, which selected by a expired nodemask and may cause infinite retries in some cases
cpu 64: __alloc_pages_slowpath { /* ..... */ retry: /* ac->nodemask = 0x1, ac->preferred->zone->nid = 1 */ if (alloc_flags & ALLOC_KSWAPD) wake_all_kswapds(order, gfp_mask, ac); /* cpu 1: cpuset_write_resmask update_nodemask update_nodemasks_hier update_tasks_nodemask mpol_rebind_task mpol_rebind_policy mpol_rebind_nodemask // mempolicy->nodes has been modified, // which ac->nodemask point to
*/ /* ac->nodemask = 0x3, ac->preferred->zone->nid = 1 */ if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags, did_some_progress > 0, &no_progress_loops)) goto retry; }
Simultaneously starting multiple cpuset01 from LTP can quickly reproduce this issue on a multi node server when the maximum memory pressure is reached and the swap is enabled
Link: https://lkml.kernel.org/r/20250416082405.20988-1-zhangtianyang@loongson.cn Fixes: c33d6c06f60f ("mm, page_alloc: avoid looking up the first zone in a zonelist twice") Signed-off-by: Tianyang Zhang zhangtianyang@loongson.cn Reviewed-by: Suren Baghdasaryan surenb@google.com Reviewed-by: Vlastimil Babka vbabka@suse.cz Cc: Michal Hocko mhocko@suse.com Cc: Brendan Jackman jackmanb@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Zi Yan ziy@nvidia.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/page_alloc.c | 8 ++++++++ 1 file changed, 8 insertions(+)
--- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4038,6 +4038,14 @@ restart: }
retry: + /* + * Deal with possible cpuset update races or zonelist updates to avoid + * infinite retries. + */ + if (check_retry_cpuset(cpuset_mems_cookie, ac) || + check_retry_zonelist(zonelist_iter_cookie)) + goto restart; + /* Ensure kswapd doesn't accidentally go to sleep as long as we loop */ if (alloc_flags & ALLOC_KSWAPD) wake_all_kswapds(order, gfp_mask, ac);