Re: [PATCH v2 2/2] kernel.h: Split out mathematical helpers

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

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Hi Andy,

I love your patch! Yet something to improve:

[auto build test ERROR on next-20200203]
[cannot apply to nfs/linux-next rcu/dev linux/master linus/master v5.5 v5.5-rc7 v5.5-rc6 v5.5]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Andy-Shevchenko/kernel-h-Split-out-min-max-et-al-helpers/20200205-040141
base:    cee5a42837d4a6c4189f06f7bf355b97a24c3c93
config: m68k-multi_defconfig (attached as .config)
compiler: m68k-linux-gcc (GCC) 7.5.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.5.0 make.cross ARCH=m68k 

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

All errors (new ones prefixed by >>):

   lib/math/div64.c: In function 'div64_u64_rem':
>> lib/math/div64.c:112:11: error: implicit declaration of function 'fls' [-Werror=implicit-function-declaration]
      int n = fls(high);
              ^~~
   cc1: some warnings being treated as errors

vim +/fls +112 lib/math/div64.c

2418f4f28f8467 lib/div64.c Roman Zippel      2008-05-01   89  
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   90  /**
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   91   * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   92   * @dividend:	64bit dividend
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   93   * @divisor:	64bit divisor
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   94   * @remainder:  64bit remainder
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   95   *
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   96   * This implementation is a comparable to algorithm used by div64_u64.
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   97   * But this operation, which includes math for calculating the remainder,
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   98   * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20   99   * systems.
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  100   */
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  101  #ifndef div64_u64_rem
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  102  u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  103  {
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  104  	u32 high = divisor >> 32;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  105  	u64 quot;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  106  
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  107  	if (high == 0) {
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  108  		u32 rem32;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  109  		quot = div_u64_rem(dividend, divisor, &rem32);
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  110  		*remainder = rem32;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  111  	} else {
cdc94a37493135 lib/div64.c Stanislaw Gruszka 2019-03-07 @112  		int n = fls(high);
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  113  		quot = div_u64(dividend >> n, divisor >> n);
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  114  
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  115  		if (quot != 0)
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  116  			quot--;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  117  
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  118  		*remainder = dividend - quot * divisor;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  119  		if (*remainder >= divisor) {
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  120  			quot++;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  121  			*remainder -= divisor;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  122  		}
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  123  	}
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  124  
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  125  	return quot;
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  126  }
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  127  EXPORT_SYMBOL(div64_u64_rem);
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  128  #endif
eb18cba78c2b92 lib/div64.c Mike Snitzer      2013-08-20  129  

:::::: The code at line 112 was first introduced by commit
:::::: cdc94a37493135e355dfc0b0e086d84e3eadb50d lib/div64.c: off by one in shift

:::::: TO: Stanislaw Gruszka <sgruszka@redhat.com>
:::::: CC: Linus Torvalds <torvalds@linux-foundation.org>

---
0-DAY kernel test infrastructure                 Open Source Technology Center
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org Intel Corporation

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