[hare-scsi-devel:nvme-mpath-bpf 5/6] drivers/nvme/host/bpf_ops.c:36:39: warning: variable 'nit' set but not used

[hare-scsi-devel:nvme-mpath-bpf 5/6] drivers/nvme/host/bpf_ops.c:36:39: warning: variable 'nit' set but not used

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/hare/scsi-devel.git nvme-mpath-bpf
head:   7e438588a7436fb1145593e81e9cd827bde45af9
commit: 85207b99a33685a9fde16be6d130fe5fd8442545 [5/6] nvme-bpf: eBPF struct_ops path selectors
config: x86_64-randconfig-004-20250730 (https://download.01.org/0day-ci/archive/20250730/202507300512.inemb73W-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14+deb12u1) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250730/202507300512.inemb73W-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/202507300512.inemb73W-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/nvme/host/bpf_ops.c: In function 'nvme_bpf_ops_btf_struct_access':
>> drivers/nvme/host/bpf_ops.c:36:39: warning: variable 'nit' set but not used [-Wunused-but-set-variable]
      36 |         const struct btf_type *nhit, *nit, *niter, *t;
         |                                       ^~~
   In file included from include/linux/bpf_verifier.h:7,
                    from drivers/nvme/host/bpf_ops.c:4:
   drivers/nvme/host/bpf_ops.c: In function 'nvme_bpf_struct_ops_init':
>> include/linux/bpf.h:1966:50: warning: statement with no effect [-Wunused-value]
    1966 | #define register_bpf_struct_ops(st_ops, type) ({ (void *)(st_ops); 0; })
         |                                                  ^~~~~~~~~~~~~~~~
   drivers/nvme/host/bpf_ops.c:341:15: note: in expansion of macro 'register_bpf_struct_ops'
     341 |         ret = register_bpf_struct_ops(&bpf_nvme_bpf_ops, nvme_bpf_ops);
         |               ^~~~~~~~~~~~~~~~~~~~~~~


vim +/nit +36 drivers/nvme/host/bpf_ops.c

    31	
    32	static int nvme_bpf_ops_btf_struct_access(struct bpf_verifier_log *log,
    33						  const struct bpf_reg_state *reg,
    34						  int off, int size)
    35	{
  > 36		const struct btf_type *nhit, *nit, *niter, *t;
    37	
    38		nhit = btf_type_by_id(reg->btf, nvme_bpf_ops_args_ids[0]);
    39		nit = btf_type_by_id(reg->btf, nvme_bpf_ops_args_ids[1]);
    40		niter = btf_type_by_id(reg->btf, nvme_bpf_ops_args_ids[2]);
    41	
    42		t = btf_type_by_id(reg->btf, reg->btf_id);
    43		if (t != nhit && t != niter) {
    44			bpf_log(log, "write access to struct %d is not supported\n", reg->btf_id);
    45			return -EACCES;
    46		}
    47		if (t == niter) {
    48			/* Allow writes to the 'head' element */
    49			if (off >= offsetof(struct nvme_bpf_iter, head) &&
    50			    off + size < offsetofend(struct nvme_bpf_iter, head))
    51				return NOT_INIT;
    52		} else {
    53			/* Allow writes to the 'bpf_ops' element */
    54			if (off >= offsetof(struct nvme_ns_head, bpf_ops) &&
    55			    off + size < offsetofend(struct nvme_ns_head, bpf_ops)) {
    56				return NOT_INIT;
    57			}
    58		}
    59		bpf_log(log, "write access for struct %s at off %d with size %d\n",
    60			nvme_bpf_ops_name, off, size);
    61		return -EACCES;
    62	}
    63	

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