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-lkp@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-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 [off-list ref]
| Closes: https://lore.kernel.org/oe-kbuild-all/202308120029.elW3y1RM-lkp@intel.com/ (local)

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);
         |                                                       ~~~~~~~~~~ ^

quoted

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

quoted

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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https://github.com/intel/lkp-tests/wiki