Re: [PATCH v3 5/6] mm/slab: Support disabling KMALLOC_PARTITION_CACHES at boot

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

Hi Chris,

kernel test robot noticed the following build warnings:

[auto build test WARNING on ce6518e61e3b4bf4f97f7ac6204049b9eba7eb75]

url:    https://github.com/intel-lab-lkp/linux/commits/Chris-Down/mm-slab-Enable-SLAB_FREELIST_HARDENED-by-default/20261113-005125
base:   ce6518e61e3b4bf4f97f7ac6204049b9eba7eb75
patch link:    https://lore.kernel.org/r/9a4caff0336c78a7adc746786c81c9c01f89c40b.1794506262.git.chris%40chrisdown.name
patch subject: [PATCH v3 5/6] mm/slab: Support disabling KMALLOC_PARTITION_CACHES at boot
config: arm-allnoconfig (https://download.01.org/0day-ci/archive/20261114/202611140551.XAyf9KWi-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261114/202611140551.XAyf9KWi-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/202611140551.XAyf9KWi-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/slab_common.c:1029:44: warning: overlapping comparisons always evaluate to false [-Wtautological-overlap-compare]
    1029 |         } else if (type > KMALLOC_PARTITION_START && type <= KMALLOC_PARTITION_END) {
         |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   1 warning generated.


vim +1029 mm/slab_common.c

   999	
  1000	static void __init
  1001	new_kmalloc_cache(int idx, enum kmalloc_cache_type type)
  1002	{
  1003		slab_flags_t flags = 0;
  1004		unsigned int minalign = __kmalloc_minalign();
  1005		unsigned int aligned_size = kmalloc_info[idx].size;
  1006		int aligned_idx = idx;
  1007	
  1008		if ((KMALLOC_RECLAIM != KMALLOC_NORMAL) && (type == KMALLOC_RECLAIM)) {
  1009			flags |= SLAB_RECLAIM_ACCOUNT;
  1010		} else if (IS_ENABLED(CONFIG_MEMCG) && (type == KMALLOC_CGROUP)) {
  1011			if (mem_cgroup_kmem_disabled()) {
  1012				kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
  1013				return;
  1014			}
  1015			flags |= SLAB_ACCOUNT;
  1016		} else if (IS_ENABLED(CONFIG_SLAB_OBJ_EXT) && type == KMALLOC_NO_OBJ_EXT) {
  1017			if (!need_kmalloc_no_objext()) {
  1018				kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
  1019				return;
  1020			}
  1021			flags |= SLAB_NO_OBJ_EXT | SLAB_NO_MERGE;
  1022		} else if (IS_ENABLED(CONFIG_ZONE_DMA) && (type == KMALLOC_DMA)) {
  1023			flags |= SLAB_CACHE_DMA;
  1024		}
  1025	
  1026		if (kmalloc_partition_enabled) {
  1027			if (type >= KMALLOC_PARTITION_START && type <= KMALLOC_PARTITION_END)
  1028				flags |= SLAB_NO_MERGE;
> 1029		} else if (type > KMALLOC_PARTITION_START && type <= KMALLOC_PARTITION_END) {
  1030			/* Use the normal caches, which have already been created. */
  1031			kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
  1032			return;
  1033		}
  1034	
  1035		/*
  1036		 * If memcg_kmem is enabled and this is a KMALLOC_NORMAL cache and not
  1037		 * aliased with any other type, make sure it's never merged with any other
  1038		 * cache.
  1039		 *
  1040		 * In other cases the kmalloc cache may end up being used for a
  1041		 * __GFP_ACCOUNT allocation so mark it as such. The exception is a
  1042		 * KMALLOC_NO_OBJ_EXT cache.
  1043		 */
  1044		if (!mem_cgroup_kmem_disabled()) {
  1045			if (type == KMALLOC_NORMAL && KMALLOC_RECLAIM != KMALLOC_NORMAL)
  1046				flags |= SLAB_NO_MERGE;
  1047			else if (!(flags & SLAB_NO_OBJ_EXT))
  1048				flags |= SLAB_MAY_ACCOUNT;
  1049		}
  1050	
  1051		if (minalign > ARCH_KMALLOC_MINALIGN) {
  1052			aligned_size = ALIGN(aligned_size, minalign);
  1053			aligned_idx = __kmalloc_index(aligned_size, false);
  1054		}
  1055	
  1056		if (!kmalloc_caches[type][aligned_idx])
  1057			kmalloc_caches[type][aligned_idx] = create_kmalloc_cache(
  1058						kmalloc_info[aligned_idx].name[type],
  1059						aligned_size, flags);
  1060		if (idx != aligned_idx)
  1061			kmalloc_caches[type][idx] = kmalloc_caches[type][aligned_idx];
  1062	}
  1063	

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