Re: [PATCH 4/4] mm: Apply vm_uffd_ops API to core mm

[Peter Xu <peterx@redhat.com>]

On Mon, Jun 23, 2025 at 03:09:13AM +0800, kernel test robot wrote:
> Hi Peter,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on next-20250620]
> [cannot apply to akpm-mm/mm-everything linus/master v6.16-rc2 v6.16-rc1 v6.15 v6.16-rc2]
> [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/Peter-Xu/mm-Introduce-vm_uffd_ops-API/20250621-030557
> base:   next-20250620
> patch link:    https://lore.kernel.org/r/20250620190342.1780170-5-peterx%40redhat.com
> patch subject: [PATCH 4/4] mm: Apply vm_uffd_ops API to core mm
> config: i386-randconfig-061-20250622 (https://download.01.org/0day-ci/archive/20250623/202506230216.JVgQj2Si-lkp@intel.com/config)
> compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250623/202506230216.JVgQj2Si-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/202506230216.JVgQj2Si-lkp@intel.com/
> 
> sparse warnings: (new ones prefixed by >>)
>    mm/shmem.c: note: in included file (through include/linux/shmem_fs.h):
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> --
>    mm/hugetlb.c:669:12: sparse: sparse: context imbalance in 'allocate_file_region_entries' - wrong count at exit
>    mm/hugetlb.c:740:13: sparse: sparse: context imbalance in 'region_add' - wrong count at exit
>    mm/hugetlb.c:807:13: sparse: sparse: context imbalance in 'region_chg' - wrong count at exit
>    mm/hugetlb.c:5798:20: sparse: sparse: context imbalance in 'move_huge_pte' - different lock contexts for basic block
>    mm/hugetlb.c: note: in included file:
>    include/linux/mm.h:1391:22: sparse: sparse: context imbalance in 'hugetlb_wp' - unexpected unlock
>    mm/hugetlb.c: note: in included file (through include/linux/hugetlb.h, include/linux/migrate.h):
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> --
>    mm/userfaultfd.c:270:9: sparse: sparse: context imbalance in 'mfill_atomic_install_pte' - different lock contexts for basic block
>    mm/userfaultfd.c:412:9: sparse: sparse: context imbalance in 'mfill_atomic_pte_zeropage' - different lock contexts for basic block
>    mm/userfaultfd.c:498:9: sparse: sparse: context imbalance in 'mfill_atomic_pte_poison' - different lock contexts for basic block
>    mm/userfaultfd.c: note: in included file:
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
> >> include/linux/userfaultfd_k.h:90:17: sparse: sparse: cast from restricted uffd_flags_t
>    mm/userfaultfd.c: note: in included file (through include/linux/rbtree.h, include/linux/mm_types.h, include/linux/mmzone.h, ...):
>    include/linux/rcupdate.h:871:25: sparse: sparse: context imbalance in 'move_pages_pte' - unexpected unlock
> 
> vim +90 include/linux/userfaultfd_k.h
> 
>     87	
>     88	static inline enum mfill_atomic_mode uffd_flags_get_mode(uffd_flags_t flags)
>     89	{
>   > 90		return (enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
>     91	}
>     92	

Sigh.. I thought the cast would helped to tell sparse on this.  Looks like
I need __force..

I'll squash below change when repost:

diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 6064f9542d5b..6c5ca68204dd 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -87,7 +87,7 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);

 static inline enum mfill_atomic_mode uffd_flags_get_mode(uffd_flags_t flags)
 {
-       return (enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
+       return (__force enum mfill_atomic_mode)(flags & MFILL_ATOMIC_MODE_MASK);
 }

 static inline bool uffd_flags_mode_is(uffd_flags_t flags, enum mfill_atomic_mode expected)

-- 
Peter Xu