Re: [PATCH] mm: mempolicy: N:M interleave policy for tiered memory nodes

[kernel test robot]

Hi Johannes,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Johannes-Weiner/mm-mempolicy-N-M-interleave-policy-for-tiered-memory-nodes/20220608-012652
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
config: x86_64-randconfig-a003 (https://download.01.org/0day-ci/archive/20220609/202206090708.jaGUnz8e-lkp@xxxxxxxxx/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project b92436efcb7813fc481b30f2593a4907568d917a)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/876d8daa0642d35f71ff504eeb3be4b950339a45
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Johannes-Weiner/mm-mempolicy-N-M-interleave-policy-for-tiered-memory-nodes/20220608-012652
        git checkout 876d8daa0642d35f71ff504eeb3be4b950339a45
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> mm/mempolicy.c:1890:11: warning: variable 'next' is used uninitialized whenever function 'next_node_tier' is called [-Wsometimes-uninitialized]
           unsigned next, start = nid;
           ~~~~~~~~~^~~~
   mm/mempolicy.c:1893:23: note: uninitialized use occurs here
                   next = next_node_in(next, policy->nodes);
                                       ^~~~
   include/linux/nodemask.h:278:46: note: expanded from macro 'next_node_in'
   #define next_node_in(n, src) __next_node_in((n), &(src))
                                                ^
   mm/mempolicy.c:1890:15: note: initialize the variable 'next' to silence this warning
           unsigned next, start = nid;
                        ^
                         = 0
   1 warning generated.


vim +1890 mm/mempolicy.c

  1887	
  1888	static unsigned next_node_tier(int nid, struct mempolicy *policy, bool toptier)
  1889	{
> 1890		unsigned next, start = nid;
  1891	
  1892		do {
  1893			next = next_node_in(next, policy->nodes);
  1894			if (next == MAX_NUMNODES)
  1895				break;
  1896			if (toptier == node_is_toptier(next))
  1897				break;
  1898		} while (next != start);
  1899		return next;
  1900	}
  1901	

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