tree:   https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git dm-5.20
head:   0c74b0ed6fe1cb42ccb81a2a7ada32231b080b68
commit: 27223586ee34d658d7da8226ab7df1f481b21a51 [4/5] block: add bio_rewind() API
config: i386-randconfig-a005
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?id=27223586ee34d658d7da8226ab7df1f481b21a51
        git remote add device-mapper-dm https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git
        git fetch --no-tags device-mapper-dm dm-5.20
        git checkout 27223586ee34d658d7da8226ab7df1f481b21a51
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

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 >>):

>> block/blk-crypto.c:138:6: warning: no previous prototype for 'bio_crypt_dun_decrement' [-Wmissing-prototypes]
     138 | void bio_crypt_dun_decrement(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
         |      ^~~~~~~~~~~~~~~~~~~~~~~


vim +/bio_crypt_dun_decrement +138 block/blk-crypto.c

   136	
   137	/* Decrements @dun by @dec, treating @dun as a multi-limb integer. */
 > 138	void bio_crypt_dun_decrement(u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE],
   139				     unsigned int dec)
   140	{
   141		int i;
   142	
   143		for (i = 0; dec && i < BLK_CRYPTO_DUN_ARRAY_SIZE; i++) {
   144			u64 prev = dun[i];
   145	
   146			dun[i] -= dec;
   147			if (dun[i] > prev)
   148				dec = 1;
   149			else
   150				dec = 0;
   151		}
   152	}
   153	

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