mm/slab_common.c:1331:1: warning: 'retain' attribute ignored

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   76b6905c11fd3c6dc4562aefc3e8c4429fefae1e
commit: a992d7a3979120fbd7c13435d27b3da8d9ed095a mm/bpf: Add bpf_get_kmem_cache() kfunc
date:   5 months ago
config: mips-allmodconfig (https://download.01.org/0day-ci/archive/20250319/202503190112.kVuDUqV8-lkp@intel.com/config)
compiler: mips-linux-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250319/202503190112.kVuDUqV8-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/202503190112.kVuDUqV8-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/slab_common.c:1331:1: warning: 'retain' attribute ignored [-Wattributes]
    1331 | {
         | ^

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for GET_FREE_REGION
   Depends on [n]: SPARSEMEM [=n]
   Selected by [m]:
   - RESOURCE_KUNIT_TEST [=m] && RUNTIME_TESTING_MENU [=y] && KUNIT [=m]


vim +/retain +1331 mm/slab_common.c

  1329	
  1330	__bpf_kfunc struct kmem_cache *bpf_get_kmem_cache(u64 addr)
> 1331	{
  1332		struct slab *slab;
  1333	
  1334		if (!virt_addr_valid((void *)(long)addr))
  1335			return NULL;
  1336	
  1337		slab = virt_to_slab((void *)(long)addr);
  1338		return slab ? slab->slab_cache : NULL;
  1339	}
  1340	

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