Re: [PATCH 08/14] zram: check that backends array has at least one backend

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

Hi Sergey,

kernel test robot noticed the following build errors:

[auto build test ERROR on axboe-block/for-next]
[also build test ERROR on akpm-mm/mm-everything linus/master v6.9-rc6 next-20240503]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Sergey-Senozhatsky/zram-move-from-crypto-API-to-custom-comp-backends-API/20240503-172335
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
patch link:    https://lore.kernel.org/r/20240503091823.3616962-9-senozhatsky%40chromium.org
patch subject: [PATCH 08/14] zram: check that backends array has at least one backend
config: s390-defconfig (https://download.01.org/0day-ci/archive/20240504/202405041440.UTBQZAaf-lkp@intel.com/config)
compiler: clang version 19.0.0git (https://github.com/llvm/llvm-project 37ae4ad0eef338776c7e2cffb3896153d43dcd90)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240504/202405041440.UTBQZAaf-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/202405041440.UTBQZAaf-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/block/zram/zcomp.c:12:
   In file included from include/linux/cpu.h:17:
   In file included from include/linux/node.h:18:
   In file included from include/linux/device.h:32:
   In file included from include/linux/device/driver.h:21:
   In file included from include/linux/module.h:19:
   In file included from include/linux/elf.h:6:
   In file included from arch/s390/include/asm/elf.h:173:
   In file included from arch/s390/include/asm/mmu_context.h:11:
   In file included from arch/s390/include/asm/pgalloc.h:18:
   In file included from include/linux/mm.h:2208:
   include/linux/vmstat.h:508:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     508 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     509 |                            item];
         |                            ~~~~
   include/linux/vmstat.h:515:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     515 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     516 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:522:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     522 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
   include/linux/vmstat.h:527:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     527 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     528 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:536:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     536 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     537 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
>> drivers/block/zram/zcomp.c:214:2: error: call to '__compiletime_assert_285' declared with 'error' attribute: BUILD_BUG_ON failed: ARRAY_SIZE(backends) <= 1
     214 |         BUILD_BUG_ON(ARRAY_SIZE(backends) <= 1);
         |         ^
   include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
      50 |         BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
         |         ^
   include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
      39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
         |                                     ^
   include/linux/compiler_types.h:449:2: note: expanded from macro 'compiletime_assert'
     449 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
         |         ^
   include/linux/compiler_types.h:437:2: note: expanded from macro '_compiletime_assert'
     437 |         __compiletime_assert(condition, msg, prefix, suffix)
         |         ^
   include/linux/compiler_types.h:430:4: note: expanded from macro '__compiletime_assert'
     430 |                         prefix ## suffix();                             \
         |                         ^
   <scratch space>:97:1: note: expanded from here
      97 | __compiletime_assert_285
         | ^
   5 warnings and 1 error generated.


vim +214 drivers/block/zram/zcomp.c

   202	
   203	struct zcomp *zcomp_create(const char *alg)
   204	{
   205		struct zcomp *comp;
   206		int error;
   207	
   208		/*
   209		 * The backends array has a sentinel NULL value, so the minimum
   210		 * size is 1. In order to be valid the array, apart from the
   211		 * sentinel NULL element, should have at least one compression
   212		 * backend selected.
   213		 */
 > 214		BUILD_BUG_ON(ARRAY_SIZE(backends) <= 1);

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