Re: [RFC PATCH 5/6] mm/memcontrol, page_counter: Make memory.low tier-aware

[kernel test robot <lkp@intel.com>]

Hi Joshua,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Joshua-Hahn/mm-page_counter-Introduce-tiered-memory-awareness-to-page_counter/20260224-073845
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260223223830.586018-6-joshua.hahnjy%40gmail.com
patch subject: [RFC PATCH 5/6] mm/memcontrol, page_counter: Make memory.low tier-aware
config: m68k-allmodconfig (https://download.01.org/0day-ci/archive/20260224/202602241138.vaT8Mo2z-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260224/202602241138.vaT8Mo2z-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602241138.vaT8Mo2z-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/vmscan.c: In function 'shrink_one':
>> mm/vmscan.c:4909:24: error: 'tier_aware_memcg_limits' undeclared (first use in this function)
    4909 |         bool toptier = tier_aware_memcg_limits &&
         |                        ^~~~~~~~~~~~~~~~~~~~~~~
   mm/vmscan.c:4909:24: note: each undeclared identifier is reported only once for each function it appears in
   mm/vmscan.c: In function 'shrink_node_memcgs':
   mm/vmscan.c:6003:41: error: 'tier_aware_memcg_limits' undeclared (first use in this function)
    6003 |                                         tier_aware_memcg_limits && toptier)) {
         |                                         ^~~~~~~~~~~~~~~~~~~~~~~


vim +/tier_aware_memcg_limits +4909 mm/vmscan.c

  4901	
  4902	static int shrink_one(struct lruvec *lruvec, struct scan_control *sc)
  4903	{
  4904		bool success;
  4905		unsigned long scanned = sc->nr_scanned;
  4906		unsigned long reclaimed = sc->nr_reclaimed;
  4907		struct mem_cgroup *memcg = lruvec_memcg(lruvec);
  4908		struct pglist_data *pgdat = lruvec_pgdat(lruvec);
> 4909		bool toptier = tier_aware_memcg_limits &&
  4910			       node_is_toptier(pgdat->node_id);
  4911	
  4912		/* lru_gen_age_node() called mem_cgroup_calculate_protection() */
  4913		if (mem_cgroup_below_min(NULL, memcg))
  4914			return MEMCG_LRU_YOUNG;
  4915	
  4916		if (mem_cgroup_below_low(NULL, memcg, toptier)) {
  4917			/* see the comment on MEMCG_NR_GENS */
  4918			if (READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_TAIL)
  4919				return MEMCG_LRU_TAIL;
  4920	
  4921			memcg_memory_event(memcg, MEMCG_LOW);
  4922		}
  4923	
  4924		success = try_to_shrink_lruvec(lruvec, sc);
  4925	
  4926		shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, sc->priority);
  4927	
  4928		if (!sc->proactive)
  4929			vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned,
  4930				   sc->nr_reclaimed - reclaimed);
  4931	
  4932		flush_reclaim_state(sc);
  4933	
  4934		if (success && mem_cgroup_online(memcg))
  4935			return MEMCG_LRU_YOUNG;
  4936	
  4937		if (!success && lruvec_is_sizable(lruvec, sc))
  4938			return 0;
  4939	
  4940		/* one retry if offlined or too small */
  4941		return READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_TAIL ?
  4942		       MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG;
  4943	}
  4944	

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