Re: [PATCH v4 3/4] mm: memcontrol: add interfaces for swap tier selection

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

Hi Youngjun,

kernel test robot noticed the following build errors:

[auto build test ERROR on 776250964cbaa49ebe6b8bb2870765cc89cece59]

url:    https://github.com/intel-lab-lkp/linux/commits/Youngjun-Park/mm-swap-introduce-swap-tier-infrastructure/20260217-121406
base:   776250964cbaa49ebe6b8bb2870765cc89cece59
patch link:    https://lore.kernel.org/r/20260217000950.4015880-4-youngjun.park%40lge.com
patch subject: [PATCH v4 3/4] mm: memcontrol: add interfaces for swap tier selection
config: powerpc64-randconfig-001-20260217 (https://download.01.org/0day-ci/archive/20260217/202602172046.jWVum2TN-lkp@intel.com/config)
compiler: powerpc64-linux-gcc (GCC) 8.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260217/202602172046.jWVum2TN-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/202602172046.jWVum2TN-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/swap_tier.c: In function 'swap_tier_memcg_propagate':
>> mm/swap_tier.c:342:8: error: dereferencing pointer to incomplete type 'struct mem_cgroup'
      child->tier_mask |= mask;
           ^~


vim +342 mm/swap_tier.c

   330	
   331	/*
   332	 * When a tier is removed, set its bit in every memcg's tier_mask and
   333	 * tier_effective_mask. This prevents stale tier indices from being
   334	 * silently filtered out if the same index is reused later.
   335	 */
   336	static void swap_tier_memcg_propagate(int mask)
   337	{
   338		struct mem_cgroup *child;
   339	
   340		rcu_read_lock();
   341		for_each_mem_cgroup_tree(child, root_mem_cgroup) {
 > 342			child->tier_mask |= mask;
   343			child->tier_effective_mask |= mask;
   344		}
   345		rcu_read_unlock();
   346	}
   347	

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