Re: [PATCH 2/4] mm: multi-gen LRU: MGLRU unbalance reclaim

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

Hi Huan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on tj-cgroup/for-next linus/master v6.6 next-20231109]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Huan-Yang/mm-vmscan-LRU-unbalance-cgroup-reclaim/20231108-151757
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20231108065818.19932-3-link%40vivo.com
patch subject: [PATCH 2/4] mm: multi-gen LRU: MGLRU unbalance reclaim
config: x86_64-randconfig-013-20231108 (https://download.01.org/0day-ci/archive/20231109/202311091842.AqdVBQwL-lkp@intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231109/202311091842.AqdVBQwL-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/202311091842.AqdVBQwL-lkp@intel.com/

All warnings (new ones prefixed by >>):

   mm/vmscan.c: In function 'isolate_folios':
>> mm/vmscan.c:4518:15: warning: 'unbalance' is used uninitialized in this function [-Wuninitialized]
    4518 |   if (scanned || unbalance)
         |       ~~~~~~~~^~~~~~~~~~~~


vim +/unbalance +4518 mm/vmscan.c

  4480	
  4481	static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
  4482				  int *type_scanned, struct list_head *list)
  4483	{
  4484		int i;
  4485		int type;
  4486		int scanned;
  4487		int tier = -1;
  4488		bool unbalance;
  4489		DEFINE_MIN_SEQ(lruvec);
  4490	
  4491		/*
  4492		 * Try to make the obvious choice first. When anon and file are both
  4493		 * available from the same generation, interpret swappiness 1 as file
  4494		 * first and 200 as anon first.
  4495		 */
  4496		if (unlikely(unbalance_file_reclaim(sc, swappiness))) {
  4497			unbalance = true;
  4498			type = LRU_GEN_FILE;
  4499		} else if (unlikely(unbalance_anon_reclaim(sc, swappiness))) {
  4500			unbalance = true;
  4501			type = LRU_GEN_ANON;
  4502		} else if (!swappiness)
  4503			type = LRU_GEN_FILE;
  4504		else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE])
  4505			type = LRU_GEN_ANON;
  4506		else if (swappiness == 1)
  4507			type = LRU_GEN_FILE;
  4508		else if (swappiness == 200)
  4509			type = LRU_GEN_ANON;
  4510		else
  4511			type = get_type_to_scan(lruvec, swappiness, &tier);
  4512	
  4513		for (i = !swappiness; i < ANON_AND_FILE; i++) {
  4514			if (tier < 0)
  4515				tier = get_tier_idx(lruvec, type);
  4516	
  4517			scanned = scan_folios(lruvec, sc, type, tier, list);
> 4518			if (scanned || unbalance)
  4519				break;
  4520	
  4521			type = !type;
  4522			tier = -1;
  4523		}
  4524	
  4525		*type_scanned = type;
  4526	
  4527		return scanned;
  4528	}
  4529	

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