Re: [PATCH v1] mm/shrinker: simplify shrinker_memcg_alloc() using guard()

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

Hi wangxuewen,

kernel test robot noticed the following build warnings:

[auto build test WARNING on v7.1-rc3]
[also build test WARNING on linus/master next-20260508]
[cannot apply to akpm-mm/mm-everything]
[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/wangxuewen/mm-shrinker-simplify-shrinker_memcg_alloc-using-guard/20260515-014803
base:   v7.1-rc3
patch link:    https://lore.kernel.org/r/20260512085546.368911-1-18810879172%40163.com
patch subject: [PATCH v1] mm/shrinker: simplify shrinker_memcg_alloc() using guard()
config: sh-allyesconfig (https://download.01.org/0day-ci/archive/20260515/202605151100.lH0pRo2I-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260515/202605151100.lH0pRo2I-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/202605151100.lH0pRo2I-lkp@intel.com/

All warnings (new ones prefixed by >>):

   mm/shrinker.c: In function 'shrinker_memcg_alloc':
>> mm/shrinker.c:218:17: warning: unused variable 'ret' [-Wunused-variable]
     218 |         int id, ret = -ENOMEM;
         |                 ^~~


vim +/ret +218 mm/shrinker.c

96f7b2b9bbb1d68 Qi Zheng      2023-09-11  215  
48a7a0996a0089f Qi Zheng      2023-09-11  216  static int shrinker_memcg_alloc(struct shrinker *shrinker)
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  217  {
96f7b2b9bbb1d68 Qi Zheng      2023-09-11 @218  	int id, ret = -ENOMEM;
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  219  
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  220  	if (mem_cgroup_disabled())
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  221  		return -ENOSYS;
03375203e1da8f4 Michal Koutný 2026-02-25  222  	if (mem_cgroup_kmem_disabled() && !(shrinker->flags & SHRINKER_NONSLAB))
03375203e1da8f4 Michal Koutný 2026-02-25  223  		return -ENOSYS;
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  224  
5ce02a6f6282d95 wangxuewen    2026-05-12  225  	guard(mutex)(&shrinker_mutex);
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  226  	id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  227  	if (id < 0)
5ce02a6f6282d95 wangxuewen    2026-05-12  228  		return id;
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  229  
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  230  	if (id >= shrinker_nr_max) {
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  231  		if (expand_shrinker_info(id)) {
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  232  			idr_remove(&shrinker_idr, id);
5ce02a6f6282d95 wangxuewen    2026-05-12  233  			return -ENOMEM;
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  234  		}
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  235  	}
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  236  	shrinker->id = id;
5ce02a6f6282d95 wangxuewen    2026-05-12  237  	return 0;
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  238  }
96f7b2b9bbb1d68 Qi Zheng      2023-09-11  239  

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