On Wed, Aug 27, 2025 at 10:58 AM kernel test robot <lkp@xxxxxxxxx> wrote: > > 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@xxxxxxxxx/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@xxxxxxxxx/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@xxxxxxxxx> > | Closes: https://lore.kernel.org/oe-kbuild-all/202508271009.5neOZ0OG-lkp@xxxxxxxxx/ Thanks for the report . It seems this sparse warning can be fixed with the below additional change, would you please test it again? diff --git a/mm/bpf_thp.c b/mm/bpf_thp.c index 46b3bc96359e..b2f97f9e930d 100644 --- a/mm/bpf_thp.c +++ b/mm/bpf_thp.c @@ -5,27 +5,32 @@ #include <linux/huge_mm.h> #include <linux/khugepaged.h> +/** + * @get_suggested_order: Get the suggested THP orders for allocation + * @mm: mm_struct associated with the THP allocation + * @vma__nullable: vm_area_struct associated with the THP allocation (may be NULL) + * When NULL, the decision should be based on @mm (i.e., when + * triggered from an mm-scope hook rather than a VMA-specific + * context). + * Must belong to @mm (guaranteed by the caller). + * @vma_flags: use these vm_flags instead of @vma->vm_flags (0 if @vma is NULL) + * @tva_flags: TVA flags for current @vma (-1 if @vma is NULL) + * @orders: Bitmask of requested THP orders for this allocation + * - PMD-mapped allocation if PMD_ORDER is set + * - mTHP allocation otherwise + * + * Rerurn: Bitmask of suggested THP orders for allocation. The highest + * suggested order will not exceed the highest requested order + * in @orders. + */ +typedef int suggested_order_fn_t(struct mm_struct *mm, + struct vm_area_struct *vma__nullable, + u64 vma_flags, + enum tva_type tva_flags, + int orders); + struct bpf_thp_ops { - /** - * @get_suggested_order: Get the suggested THP orders for allocation - * @mm: mm_struct associated with the THP allocation - * @vma__nullable: vm_area_struct associated with the THP allocation (may be NULL) - * When NULL, the decision should be based on @mm (i.e., when - * triggered from an mm-scope hook rather than a VMA-specific - * context). - * Must belong to @mm (guaranteed by the caller). - * @vma_flags: use these vm_flags instead of @vma->vm_flags (0 if @vma is NULL) - * @tva_flags: TVA flags for current @vma (-1 if @vma is NULL) - * @orders: Bitmask of requested THP orders for this allocation - * - PMD-mapped allocation if PMD_ORDER is set - * - mTHP allocation otherwise - * - * Rerurn: Bitmask of suggested THP orders for allocation. The highest - * suggested order will not exceed the highest requested order - * in @orders. - */ - int (*get_suggested_order)(struct mm_struct *mm, struct vm_area_struct *vma__nullable, - u64 vma_flags, enum tva_type tva_flags, int orders) __rcu; + suggested_order_fn_t __rcu *get_suggested_order; }; static struct bpf_thp_ops bpf_thp; @@ -34,8 +39,7 @@ static DEFINE_SPINLOCK(thp_ops_lock); int get_suggested_order(struct mm_struct *mm, struct vm_area_struct *vma__nullable, u64 vma_flags, enum tva_type tva_flags, int orders) { - int (*bpf_suggested_order)(struct mm_struct *mm, struct vm_area_struct *vma__nullable, - u64 vma_flags, enum tva_type tva_flags, int orders); + suggested_order_fn_t *bpf_suggested_order; int suggested_orders = orders; /* No BPF program is attached */ @@ -106,10 +110,12 @@ static int bpf_thp_reg(void *kdata, struct bpf_link *link) static void bpf_thp_unreg(void *kdata, struct bpf_link *link) { + suggested_order_fn_t *old_fn; + spin_lock(&thp_ops_lock); clear_bit(TRANSPARENT_HUGEPAGE_BPF_ATTACHED, &transparent_hugepage_flags); - WARN_ON_ONCE(!rcu_access_pointer(bpf_thp.get_suggested_order)); - rcu_replace_pointer(bpf_thp.get_suggested_order, NULL, lockdep_is_held(&thp_ops_lock)); + old_fn = rcu_replace_pointer(bpf_thp.get_suggested_order, NULL, lockdep_is_held(&thp_ops_lock)); + WARN_ON_ONCE(!old_fn); spin_unlock(&thp_ops_lock); synchronize_rcu(); @@ -117,8 +123,9 @@ static void bpf_thp_unreg(void *kdata, struct bpf_link *link) static int bpf_thp_update(void *kdata, void *old_kdata, struct bpf_link *link) { - struct bpf_thp_ops *ops = kdata; + suggested_order_fn_t *old_fn, *new_fn; struct bpf_thp_ops *old = old_kdata; + struct bpf_thp_ops *ops = kdata; int ret = 0; if (!ops || !old) @@ -130,9 +137,10 @@ static int bpf_thp_update(void *kdata, void *old_kdata, struct bpf_link *link) ret = -ENOENT; goto out; } - WARN_ON_ONCE(!rcu_access_pointer(bpf_thp.get_suggested_order)); - rcu_replace_pointer(bpf_thp.get_suggested_order, ops->get_suggested_order, - lockdep_is_held(&thp_ops_lock)); + + new_fn = rcu_dereference(ops->get_suggested_order); + old_fn = rcu_replace_pointer(bpf_thp.get_suggested_order, new_fn, lockdep_is_held(&thp_ops_lock)); + WARN_ON_ONCE(!old_fn || !new_fn); out: spin_unlock(&thp_ops_lock); @@ -159,7 +167,7 @@ static int suggested_order(struct mm_struct *mm, struct vm_area_struct *vma__nul } static struct bpf_thp_ops __bpf_thp_ops = { - .get_suggested_order = suggested_order, + .get_suggested_order = (suggested_order_fn_t __rcu *)suggested_order, }; static struct bpf_struct_ops bpf_bpf_thp_ops = { -- Regards Yafang
