Hi Nitesh,

kernel test robot noticed the following build warnings:

[auto build test WARNING on f7dc24b3413851109c4047b22997bd0d95ed52a2]

url:    
https://github.com/intel-lab-lkp/linux/commits/Nitesh-Shetty/block-Introduce-queue-limits-and-sysfs-for-copy-offload-support/20230811-192259
base:   f7dc24b3413851109c4047b22997bd0d95ed52a2
patch link:    
https://lore.kernel.org/r/20230811105300.15889-12-nj.shetty%40samsung.com
patch subject: [PATCH v14 11/11] null_blk: add support for copy offload
config: hexagon-randconfig-r032-20230811 
(https://download.01.org/0day-ci/archive/20230812/202308120029.elw3y1rm-...@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project.git 
4a5ac14ee968ff0ad5d2cc1ffa0299048db4c88a)
reproduce: 
(https://download.01.org/0day-ci/archive/20230812/202308120029.elw3y1rm-...@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 <l...@intel.com>
| Closes: 
https://lore.kernel.org/oe-kbuild-all/202308120029.elw3y1rm-...@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/block/null_blk/main.c:12:
   In file included from drivers/block/null_blk/null_blk.h:8:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:337:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a 
null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     547 |         val = __raw_readb(PCI_IOBASE + addr);
         |                           ~~~~~~~~~~ ^
   include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a 
null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     560 |         val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + 
addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from 
macro '__le16_to_cpu'
      37 | #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
         |                                                   ^
   In file included from drivers/block/null_blk/main.c:12:
   In file included from drivers/block/null_blk/null_blk.h:8:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:337:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a 
null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     573 |         val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + 
addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from 
macro '__le32_to_cpu'
      35 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
         |                                                   ^
   In file included from drivers/block/null_blk/main.c:12:
   In file included from drivers/block/null_blk/null_blk.h:8:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/hexagon/include/asm/io.h:337:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a 
null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     584 |         __raw_writeb(value, PCI_IOBASE + addr);
         |                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a 
null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     594 |         __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + 
addr);
         |                                                       ~~~~~~~~~~ ^
   include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a 
null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     604 |         __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + 
addr);
         |                                                       ~~~~~~~~~~ ^
>> drivers/block/null_blk/main.c:1303:2: warning: variable 'sector_in' is used 
>> uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
    1303 |         __rq_for_each_bio(bio, req) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/blk-mq.h:1008:6: note: expanded from macro '__rq_for_each_bio'
    1008 |         if ((rq->bio))                  \
         |             ^~~~~~~~~
   drivers/block/null_blk/main.c:1316:8: note: uninitialized use occurs here
    1316 |                             sector_in << SECTOR_SHIFT, rem);
         |                             ^~~~~~~~~
   drivers/block/null_blk/main.c:1303:2: note: remove the 'if' if its condition 
is always true
    1303 |         __rq_for_each_bio(bio, req) {
         |         ^
   include/linux/blk-mq.h:1008:2: note: expanded from macro '__rq_for_each_bio'
    1008 |         if ((rq->bio))                  \
         |         ^
   drivers/block/null_blk/main.c:1287:20: note: initialize the variable 
'sector_in' to silence this warning
    1287 |         sector_t sector_in, sector_out;
         |                           ^
         |                            = 0
>> drivers/block/null_blk/main.c:1303:2: warning: variable 'sector_out' is used 
>> uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
    1303 |         __rq_for_each_bio(bio, req) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/blk-mq.h:1008:6: note: expanded from macro '__rq_for_each_bio'
    1008 |         if ((rq->bio))                  \
         |             ^~~~~~~~~
   drivers/block/null_blk/main.c:1315:27: note: uninitialized use occurs here
    1315 |         trace_nullb_copy_op(req, sector_out << SECTOR_SHIFT,
         |                                  ^~~~~~~~~~
   drivers/block/null_blk/main.c:1303:2: note: remove the 'if' if its condition 
is always true
    1303 |         __rq_for_each_bio(bio, req) {
         |         ^
   include/linux/blk-mq.h:1008:2: note: expanded from macro '__rq_for_each_bio'
    1008 |         if ((rq->bio))                  \
         |         ^
   drivers/block/null_blk/main.c:1287:32: note: initialize the variable 
'sector_out' to silence this warning
    1287 |         sector_t sector_in, sector_out;
         |                                       ^
         |                                        = 0
   8 warnings generated.


vim +1303 drivers/block/null_blk/main.c

  1283  
  1284  static inline int nullb_setup_copy(struct nullb *nullb, struct request 
*req,
  1285                                     bool is_fua)
  1286  {
  1287          sector_t sector_in, sector_out;
  1288          loff_t offset_in, offset_out;
  1289          void *in, *out;
  1290          ssize_t chunk, rem = 0;
  1291          struct bio *bio;
  1292          struct nullb_page *t_page_in, *t_page_out;
  1293          u16 seg = 1;
  1294          int status = -EIO;
  1295  
  1296          if (blk_rq_nr_phys_segments(req) != COPY_MAX_SEGMENTS)
  1297                  return status;
  1298  
  1299          /*
  1300           * First bio contains information about source and last bio 
contains
  1301           * information about destination.
  1302           */
> 1303          __rq_for_each_bio(bio, req) {
  1304                  if (seg == blk_rq_nr_phys_segments(req)) {
  1305                          sector_out = bio->bi_iter.bi_sector;
  1306                          if (rem != bio->bi_iter.bi_size)
  1307                                  return status;
  1308                  } else {
  1309                          sector_in = bio->bi_iter.bi_sector;
  1310                          rem = bio->bi_iter.bi_size;
  1311                  }
  1312                  seg++;
  1313          }
  1314  
  1315          trace_nullb_copy_op(req, sector_out << SECTOR_SHIFT,
  1316                              sector_in << SECTOR_SHIFT, rem);
  1317  
  1318          spin_lock_irq(&nullb->lock);
  1319          while (rem > 0) {
  1320                  chunk = min_t(size_t, nullb->dev->blocksize, rem);
  1321                  offset_in = (sector_in & SECTOR_MASK) << SECTOR_SHIFT;
  1322                  offset_out = (sector_out & SECTOR_MASK) << SECTOR_SHIFT;
  1323  
  1324                  if (null_cache_active(nullb) && !is_fua)
  1325                          null_make_cache_space(nullb, PAGE_SIZE);
  1326  
  1327                  t_page_in = null_lookup_page(nullb, sector_in, false,
  1328                                               !null_cache_active(nullb));
  1329                  if (!t_page_in)
  1330                          goto err;
  1331                  t_page_out = null_insert_page(nullb, sector_out,
  1332                                                !null_cache_active(nullb) 
||
  1333                                                is_fua);
  1334                  if (!t_page_out)
  1335                          goto err;
  1336  
  1337                  in = kmap_local_page(t_page_in->page);
  1338                  out = kmap_local_page(t_page_out->page);
  1339  
  1340                  memcpy(out + offset_out, in + offset_in, chunk);
  1341                  kunmap_local(out);
  1342                  kunmap_local(in);
  1343                  __set_bit(sector_out & SECTOR_MASK, t_page_out->bitmap);
  1344  
  1345                  if (is_fua)
  1346                          null_free_sector(nullb, sector_out, true);
  1347  
  1348                  rem -= chunk;
  1349                  sector_in += chunk >> SECTOR_SHIFT;
  1350                  sector_out += chunk >> SECTOR_SHIFT;
  1351          }
  1352  
  1353          status = 0;
  1354  err:
  1355          spin_unlock_irq(&nullb->lock);
  1356          return status;
  1357  }
  1358  

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0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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