Re: [PATCH v13 9/9] null_blk: add support for copy offload

[kernel test robot <lkp@intel.com>]

Hi Nitesh,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 53cdf865f90ba922a854c65ed05b519f9d728424]

url:    https://github.com/intel-lab-lkp/linux/commits/Nitesh-Shetty/block-Introduce-queue-limits-for-copy-offload-support/20230628-163126
base:   53cdf865f90ba922a854c65ed05b519f9d728424
patch link:    https://lore.kernel.org/r/20230627183629.26571-10-nj.shetty%40samsung.com
patch subject: [PATCH v13 9/9] null_blk: add support for copy offload
config: hexagon-randconfig-r045-20230628 (https://download.01.org/0day-ci/archive/20230628/202306281909.TRNCf5eG-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/20230628/202306281909.TRNCf5eG-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/202306281909.TRNCf5eG-lkp@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:334:
   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:334:
   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:334:
   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:1295:2: warning: variable 'rem' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
    1295 |         __rq_for_each_bio(bio, req) {
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/blk-mq.h:1012:2: note: expanded from macro '__rq_for_each_bio'
    1012 |         if ((rq->bio))                  \
         |         ^~~~~~~~~~~~~~
   include/linux/compiler.h:55:28: note: expanded from macro 'if'
      55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
         |                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:57:30: note: expanded from macro '__trace_if_var'
      57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
         |                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/block/null_blk/main.c:1300:15: note: uninitialized use occurs here
    1300 |         if (WARN_ON(!rem))
         |                      ^~~
   include/asm-generic/bug.h:123:25: note: expanded from macro 'WARN_ON'
     123 |         int __ret_warn_on = !!(condition);                              \
         |                                ^~~~~~~~~
   include/linux/compiler.h:55:47: note: expanded from macro 'if'
      55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
         |                                               ^~~~
   include/linux/compiler.h:57:52: note: expanded from macro '__trace_if_var'
      57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
         |                                                    ^~~~
   drivers/block/null_blk/main.c:1295:2: note: remove the 'if' if its condition is always true
    1295 |         __rq_for_each_bio(bio, req) {
         |         ^
   include/linux/blk-mq.h:1012:2: note: expanded from macro '__rq_for_each_bio'
    1012 |         if ((rq->bio))                  \
         |         ^
   include/linux/compiler.h:55:23: note: expanded from macro 'if'
      55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
         |                       ^
   drivers/block/null_blk/main.c:1287:12: note: initialize the variable 'rem' to silence this warning
    1287 |         size_t rem, temp;
         |                   ^
         |                    = 0
   7 warnings generated.


vim +1295 drivers/block/null_blk/main.c

  1281	
  1282	static inline int nullb_setup_copy_write(struct nullb *nullb,
  1283			struct request *req, bool is_fua)
  1284	{
  1285		sector_t sector_in, sector_out;
  1286		void *in, *out;
  1287		size_t rem, temp;
  1288		struct bio *bio;
  1289		unsigned long offset_in, offset_out;
  1290		struct nullb_page *t_page_in, *t_page_out;
  1291		int ret = -EIO;
  1292	
  1293		sector_out = blk_rq_pos(req);
  1294	
> 1295		__rq_for_each_bio(bio, req) {
  1296			sector_in = bio->bi_iter.bi_sector;
  1297			rem = bio->bi_iter.bi_size;
  1298		}
  1299	
  1300		if (WARN_ON(!rem))
  1301			return BLK_STS_NOTSUPP;
  1302	
  1303		spin_lock_irq(&nullb->lock);
  1304		while (rem > 0) {
  1305			temp = min_t(size_t, nullb->dev->blocksize, rem);
  1306			offset_in = (sector_in & SECTOR_MASK) << SECTOR_SHIFT;
  1307			offset_out = (sector_out & SECTOR_MASK) << SECTOR_SHIFT;
  1308	
  1309			if (null_cache_active(nullb) && !is_fua)
  1310				null_make_cache_space(nullb, PAGE_SIZE);
  1311	
  1312			t_page_in = null_lookup_page(nullb, sector_in, false,
  1313				!null_cache_active(nullb));
  1314			if (!t_page_in)
  1315				goto err;
  1316			t_page_out = null_insert_page(nullb, sector_out,
  1317				!null_cache_active(nullb) || is_fua);
  1318			if (!t_page_out)
  1319				goto err;
  1320	
  1321			in = kmap_local_page(t_page_in->page);
  1322			out = kmap_local_page(t_page_out->page);
  1323	
  1324			memcpy(out + offset_out, in + offset_in, temp);
  1325			kunmap_local(out);
  1326			kunmap_local(in);
  1327			__set_bit(sector_out & SECTOR_MASK, t_page_out->bitmap);
  1328	
  1329			if (is_fua)
  1330				null_free_sector(nullb, sector_out, true);
  1331	
  1332			rem -= temp;
  1333			sector_in += temp >> SECTOR_SHIFT;
  1334			sector_out += temp >> SECTOR_SHIFT;
  1335		}
  1336	
  1337		ret = 0;
  1338	err:
  1339		spin_unlock_irq(&nullb->lock);
  1340		return ret;
  1341	}
  1342	

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