Re: [PATCH v3] mm/vmscan: fix demotion targets checks in reclaim/demotion

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

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Hi Bing,

kernel test robot noticed the following build warnings:

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

url:    https://github.com/intel-lab-lkp/linux/commits/Bing-Jiao/mm-vmscan-fix-demotion-targets-checks-in-reclaim-demotion/20251224-052216
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20251223212032.665731-1-bingjiao%40google.com
patch subject: [PATCH v3] mm/vmscan: fix demotion targets checks in reclaim/demotion
:::::: branch date: 4 days ago
:::::: commit date: 4 days ago
config: arm-randconfig-r071-20251224 (https://download.01.org/0day-ci/archive/20251228/202512280348.PQDhLdXM-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 8.5.0

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>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202512280348.PQDhLdXM-lkp@intel.com/

smatch warnings:
mm/vmscan.c:1075 demote_folio_list() error: uninitialized symbol 'nr_succeeded'.

vim +/nr_succeeded +1075 mm/vmscan.c

26aa2d199d6f2c Dave Hansen             2021-09-02  1032  
26aa2d199d6f2c Dave Hansen             2021-09-02  1033  /*
49fd9b6df54e61 Matthew Wilcox (Oracle  2022-09-02  1034)  * Take folios on @demote_folios and attempt to demote them to another node.
49fd9b6df54e61 Matthew Wilcox (Oracle  2022-09-02  1035)  * Folios which are not demoted are left on @demote_folios.
26aa2d199d6f2c Dave Hansen             2021-09-02  1036   */
49fd9b6df54e61 Matthew Wilcox (Oracle  2022-09-02  1037) static unsigned int demote_folio_list(struct list_head *demote_folios,
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1038  				      struct pglist_data *pgdat,
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1039  				      struct mem_cgroup *memcg)
26aa2d199d6f2c Dave Hansen             2021-09-02  1040  {
26aa2d199d6f2c Dave Hansen             2021-09-02  1041  	int target_nid = next_demotion_node(pgdat->node_id);
26aa2d199d6f2c Dave Hansen             2021-09-02  1042  	unsigned int nr_succeeded;
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1043  	nodemask_t allowed_mask, allowed_mems;
32008027289239 Jagdish Gediya          2022-08-18  1044  
32008027289239 Jagdish Gediya          2022-08-18  1045  	struct migration_target_control mtc = {
32008027289239 Jagdish Gediya          2022-08-18  1046  		/*
32008027289239 Jagdish Gediya          2022-08-18  1047  		 * Allocate from 'node', or fail quickly and quietly.
32008027289239 Jagdish Gediya          2022-08-18  1048  		 * When this happens, 'page' will likely just be discarded
32008027289239 Jagdish Gediya          2022-08-18  1049  		 * instead of migrated.
32008027289239 Jagdish Gediya          2022-08-18  1050  		 */
bd63d0fde2a2c3 Fushuai Wang            2025-10-06  1051  		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) |
32008027289239 Jagdish Gediya          2022-08-18  1052  			__GFP_NOMEMALLOC | GFP_NOWAIT,
e42dfe4e0a51b4 Baolin Wang             2024-03-06  1053  		.nmask = &allowed_mask,
e42dfe4e0a51b4 Baolin Wang             2024-03-06  1054  		.reason = MR_DEMOTION,
32008027289239 Jagdish Gediya          2022-08-18  1055  	};
26aa2d199d6f2c Dave Hansen             2021-09-02  1056  
49fd9b6df54e61 Matthew Wilcox (Oracle  2022-09-02  1057) 	if (list_empty(demote_folios))
26aa2d199d6f2c Dave Hansen             2021-09-02  1058  		return 0;
26aa2d199d6f2c Dave Hansen             2021-09-02  1059  
32008027289239 Jagdish Gediya          2022-08-18  1060  	node_get_allowed_targets(pgdat, &allowed_mask);
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1061  	allowed_mems = mem_cgroup_node_get_allowed(memcg);
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1062  	nodes_and(allowed_mask, allowed_mask, allowed_mems);
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1063  	if (nodes_empty(allowed_mask))
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1064  		return false;
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1065  
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1066  	if (target_nid == NUMA_NO_NODE || !node_isset(target_nid, allowed_mask))
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1067  		target_nid = node_random(&allowed_mask);
80ef4b3f9c7c95 Bing Jiao               2025-12-23  1068  	mtc.nid = target_nid;
32008027289239 Jagdish Gediya          2022-08-18  1069  
26aa2d199d6f2c Dave Hansen             2021-09-02  1070  	/* Demotion ignores all cpuset and mempolicy settings */
29ea04095b9697 SeongJae Park           2025-06-16  1071  	migrate_pages(demote_folios, alloc_demote_folio, NULL,
32008027289239 Jagdish Gediya          2022-08-18  1072  		      (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
26aa2d199d6f2c Dave Hansen             2021-09-02  1073  		      &nr_succeeded);
26aa2d199d6f2c Dave Hansen             2021-09-02  1074  
26aa2d199d6f2c Dave Hansen             2021-09-02 @1075  	return nr_succeeded;
26aa2d199d6f2c Dave Hansen             2021-09-02  1076  }
26aa2d199d6f2c Dave Hansen             2021-09-02  1077  

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