Re: [PATCH v6 mm-new 01/10] mm: thp: add support for BPF based THP order selection

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

Hi Yafang,

kernel test robot noticed the following build warnings:

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

url:    https://github.com/intel-lab-lkp/linux/commits/Yafang-Shao/mm-thp-add-support-for-BPF-based-THP-order-selection/20250826-152415
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250826071948.2618-2-laoar.shao%40gmail.com
patch subject: [PATCH v6 mm-new 01/10] mm: thp: add support for BPF based THP order selection
config: loongarch-randconfig-r113-20250827 (https://download.01.org/0day-ci/archive/20250827/202508271009.5neOZ0OG-lkp@intel.com/config)
compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
reproduce: (https://download.01.org/0day-ci/archive/20250827/202508271009.5neOZ0OG-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/202508271009.5neOZ0OG-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> mm/bpf_thp.c:47:31: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:47:31: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:47:31: sparse:    int ( * )( ... )
   mm/bpf_thp.c:101:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:101:9: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:101:9: sparse:    int ( * )( ... )
   mm/bpf_thp.c:102:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:102:9: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:102:9: sparse:    int ( * )( ... )
   mm/bpf_thp.c:111:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:111:9: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:111:9: sparse:    int ( * )( ... )
   mm/bpf_thp.c:112:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:112:9: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:112:9: sparse:    int ( * )( ... )
   mm/bpf_thp.c:112:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:112:9: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:112:9: sparse:    int ( * )( ... )
   mm/bpf_thp.c:133:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:133:9: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:133:9: sparse:    int ( * )( ... )
   mm/bpf_thp.c:134:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:134:9: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:134:9: sparse:    int ( * )( ... )
   mm/bpf_thp.c:134:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   mm/bpf_thp.c:134:9: sparse:    int ( [noderef] __rcu * )( ... )
   mm/bpf_thp.c:134:9: sparse:    int ( * )( ... )
>> mm/bpf_thp.c:102:9: sparse: sparse: dereference of noderef expression
>> mm/bpf_thp.c:102:9: sparse: sparse: dereference of noderef expression
   mm/bpf_thp.c:112:9: sparse: sparse: dereference of noderef expression
   mm/bpf_thp.c:134:9: sparse: sparse: dereference of noderef expression
   mm/bpf_thp.c:134:9: sparse: sparse: dereference of noderef expression
   mm/bpf_thp.c:134:9: sparse: sparse: dereference of noderef expression
   mm/bpf_thp.c:148:14: sparse: sparse: dereference of noderef expression

vim +47 mm/bpf_thp.c

    33	
    34	int get_suggested_order(struct mm_struct *mm, struct vm_area_struct *vma__nullable,
    35				u64 vma_flags, enum tva_type tva_flags, int orders)
    36	{
    37		int (*bpf_suggested_order)(struct mm_struct *mm, struct vm_area_struct *vma__nullable,
    38					   u64 vma_flags, enum tva_type tva_flags, int orders);
    39		int suggested_orders = orders;
    40	
    41		/* No BPF program is attached */
    42		if (!test_bit(TRANSPARENT_HUGEPAGE_BPF_ATTACHED,
    43			      &transparent_hugepage_flags))
    44			return suggested_orders;
    45	
    46		rcu_read_lock();
  > 47		bpf_suggested_order = rcu_dereference(bpf_thp.get_suggested_order);
    48		if (!bpf_suggested_order)
    49			goto out;
    50	
    51		suggested_orders = bpf_suggested_order(mm, vma__nullable, vma_flags, tva_flags, orders);
    52		if (highest_order(suggested_orders) > highest_order(orders))
    53			suggested_orders = orders;
    54	
    55	out:
    56		rcu_read_unlock();
    57		return suggested_orders;
    58	}
    59	
    60	static bool bpf_thp_ops_is_valid_access(int off, int size,
    61						enum bpf_access_type type,
    62						const struct bpf_prog *prog,
    63						struct bpf_insn_access_aux *info)
    64	{
    65		return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
    66	}
    67	
    68	static const struct bpf_func_proto *
    69	bpf_thp_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
    70	{
    71		return bpf_base_func_proto(func_id, prog);
    72	}
    73	
    74	static const struct bpf_verifier_ops thp_bpf_verifier_ops = {
    75		.get_func_proto = bpf_thp_get_func_proto,
    76		.is_valid_access = bpf_thp_ops_is_valid_access,
    77	};
    78	
    79	static int bpf_thp_init(struct btf *btf)
    80	{
    81		return 0;
    82	}
    83	
    84	static int bpf_thp_init_member(const struct btf_type *t,
    85				       const struct btf_member *member,
    86				       void *kdata, const void *udata)
    87	{
    88		return 0;
    89	}
    90	
    91	static int bpf_thp_reg(void *kdata, struct bpf_link *link)
    92	{
    93		struct bpf_thp_ops *ops = kdata;
    94	
    95		spin_lock(&thp_ops_lock);
    96		if (test_and_set_bit(TRANSPARENT_HUGEPAGE_BPF_ATTACHED,
    97				     &transparent_hugepage_flags)) {
    98			spin_unlock(&thp_ops_lock);
    99			return -EBUSY;
   100		}
   101		WARN_ON_ONCE(rcu_access_pointer(bpf_thp.get_suggested_order));
 > 102		rcu_assign_pointer(bpf_thp.get_suggested_order, ops->get_suggested_order);
   103		spin_unlock(&thp_ops_lock);
   104		return 0;
   105	}
   106	

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