Hi Shaohua,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.9-rc5]
[cannot apply to block/for-next next-20161114]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Shaohua-Li/blk-throttle-add-high-limit/20161115-063105
config: xtensa-allmodconfig (attached as .config)
compiler: xtensa-linux-gcc (GCC) 4.9.0
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=xtensa 

All warnings (new ones prefixed by >>):

   In file included from ./arch/xtensa/include/generated/asm/div64.h:1:0,
                    from include/linux/kernel.h:142,
                    from include/linux/list.h:8,
                    from include/linux/module.h:9,
                    from block/blk-throttle.c:7:
   block/blk-throttle.c: In function 'throtl_calculate_line_slope':
   include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast
     (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
                               ^
>> block/blk-throttle.c:2017:2: note: in expansion of macro 'do_div'
     do_div(xMean, valid_lat);
     ^
   include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast
     (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
                               ^
   block/blk-throttle.c:2019:2: note: in expansion of macro 'do_div'
     do_div(yMean, valid_lat);
     ^
   include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast
     (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
                               ^
   block/blk-throttle.c:2023:2: note: in expansion of macro 'do_div'
     do_div(slope, denominator);
     ^

vim +/do_div +2017 block/blk-throttle.c

  2001		for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
  2002			u64 x, y;
  2003	
  2004			if (td->avg_buckets[i].latency == 0)
  2005				continue;
  2006	
  2007			x = td->avg_buckets[i].size >> 10;
  2008			y = td->avg_buckets[i].latency;
  2009			sumX += x;
  2010			sumY += y;
  2011	
  2012			sumXY += x * y;
  2013			sumX2 += x * x;
  2014		}
  2015	
  2016		xMean = sumX;
> 2017		do_div(xMean, valid_lat);
  2018		yMean = sumY;
  2019		do_div(yMean, valid_lat);
  2020		denominator = sumX2 - sumX * xMean;
  2021	
  2022		slope = sumXY - sumX * yMean;
  2023		do_div(slope, denominator);
  2024		td->line_slope = slope;
  2025	}

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