mm/page_alloc.c: avoid infinite retries caused by cpuset race

__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/[email protected]
Fixes: c33d6c0 ("mm, page_alloc: avoid looking up the first zone in a zonelist twice")
Signed-off-by: Tianyang Zhang <[email protected]>
Reviewed-by: Suren Baghdasaryan <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Brendan Jackman <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: zhangtianyang-zty

mm/page_alloc.c

@@ -4562,6 +4562,14 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 	}
 
 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);