tree:   https://github.com/bvanassche/linux block-for-next
head:   481cfff256b6aa0e14e85749d199b26a17f26681
commit: 481cfff256b6aa0e14e85749d199b26a17f26681 [6/6] null_blk: Support configuring the maximum segment size
config: x86_64-randconfig-a012-20220926
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/bvanassche/linux/commit/481cfff256b6aa0e14e85749d199b26a17f26681
        git remote add bvanassche https://github.com/bvanassche/linux
        git fetch --no-tags bvanassche block-for-next
        git checkout 481cfff256b6aa0e14e85749d199b26a17f26681
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/block/null_blk/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> drivers/block/null_blk/main.c:1276:13: warning: variable 'len' is uninitialized when used here [-Wuninitialized]
                   sector += len >> SECTOR_SHIFT;
                             ^~~
   drivers/block/null_blk/main.c:1256:18: note: initialize the variable 'len' to silence this warning
           unsigned int len, i;
                           ^
                            = 0
   1 warning generated.


vim +/len +1276 drivers/block/null_blk/main.c

  1248	
  1249	static int null_handle_rq_sg(struct nullb_cmd *cmd)
  1250	{
  1251		struct request *rq = cmd->rq;
  1252		struct nullb *nullb = cmd->nq->dev->nullb;
  1253		sector_t sector = blk_rq_pos(rq);
  1254		unsigned int nr_seg = blk_rq_nr_phys_segments(rq);
  1255		struct scatterlist *sg, *sglist;
  1256		unsigned int len, i;
  1257		int err;
  1258	
  1259		sglist = kcalloc(nr_seg, sizeof(*sglist), GFP_KERNEL);
  1260		if (!sglist)
  1261			return -ENOMEM;
  1262	
  1263		sg_init_table(sglist, nr_seg);
  1264		nr_seg = blk_rq_map_sg(rq->q, rq, sglist);
  1265		WARN_ON_ONCE(nr_seg > blk_rq_nr_phys_segments(rq));
  1266	
  1267		spin_lock_irq(&nullb->lock);
  1268		for_each_sg(sglist, sg, nr_seg, i) {
  1269			err = null_transfer(nullb, sg_page(sg), sg->length,
  1270					    sg->offset, op_is_write(req_op(rq)), sector,
  1271					    rq->cmd_flags & REQ_FUA);
  1272			if (err) {
  1273				spin_unlock_irq(&nullb->lock);
  1274				goto out;
  1275			}
> 1276			sector += len >> SECTOR_SHIFT;
  1277		}
  1278		spin_unlock_irq(&nullb->lock);
  1279	
  1280		err = 0;
  1281	
  1282	out:
  1283		kfree(sglist);
  1284		return err;
  1285	}
  1286	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp