kernel/bpf/kmem_cache_iter.c:25:1: warning: 'retain' attribute ignored

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   76b6905c11fd3c6dc4562aefc3e8c4429fefae1e
commit: 2e9a548009c2d804e55cdd5b0e9903756cf7d9b3 bpf: Add open coded version of kmem_cache iterator
date:   5 months ago
config: mips-allmodconfig (https://download.01.org/0day-ci/archive/20250318/202503181537.syuSFzVo-lkp@xxxxxxxxx/config)
compiler: mips-linux-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250318/202503181537.syuSFzVo-lkp@xxxxxxxxx/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@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202503181537.syuSFzVo-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

>> kernel/bpf/kmem_cache_iter.c:25:1: warning: 'retain' attribute ignored [-Wattributes]
      25 | {
         | ^
   kernel/bpf/kmem_cache_iter.c:36:1: warning: 'retain' attribute ignored [-Wattributes]
      36 | {
         | ^
   kernel/bpf/kmem_cache_iter.c:81:1: warning: 'retain' attribute ignored [-Wattributes]
      81 | {
         | ^

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 +25 kernel/bpf/kmem_cache_iter.c

    23	
    24	__bpf_kfunc int bpf_iter_kmem_cache_new(struct bpf_iter_kmem_cache *it)
  > 25	{
    26		struct bpf_iter_kmem_cache_kern *kit = (void *)it;
    27	
    28		BUILD_BUG_ON(sizeof(*kit) > sizeof(*it));
    29		BUILD_BUG_ON(__alignof__(*kit) != __alignof__(*it));
    30	
    31		kit->pos = KMEM_CACHE_POS_START;
    32		return 0;
    33	}
    34	

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