The patch titled Subject: mm/page_alloc.c: avoid infinite retries caused by cpuset race has been added to the -mm mm-new branch. Its filename is mm-page_allocc-avoid-infinite-retries-caused-by-cpuset-race.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Tianyang Zhang zhangtianyang@loongson.cn Subject: mm/page_alloc.c: avoid infinite retries caused by cpuset race Date: Wed, 16 Apr 2025 16:24:05 +0800

__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 Signed-off-by: Tianyang Zhang zhangtianyang@loongson.cn Cc: Vlastimil Babka vbabka@suse.cz Cc: Suren Baghdasaryan surenb@google.com 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 ---

mm/page_alloc.c | 8 ++++++++ 1 file changed, 8 insertions(+)

--- a/mm/page_alloc.c~mm-page_allocc-avoid-infinite-retries-caused-by-cpuset-race +++ a/mm/page_alloc.c @@ -4555,6 +4555,14 @@ 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); _

Patches currently in -mm which might be from zhangtianyang@loongson.cn are

mm-page_allocc-avoid-infinite-retries-caused-by-cpuset-race.patch