Re: [PATCH v2 01/13] mm/vma: remove __private sparse decoration from vma_flags_t

* Lorenzo Stoakes <[email protected]> [260122 16:06]:
> We need to pass around these values and access them in a way that sparse
> does not allow, as __private implies noderef, i.e. disallowing dereference
> of the value, which manifests as sparse warnings even when passed around
> benignly.
> 
> Signed-off-by: Lorenzo Stoakes <[email protected]>

Reviewed-by: Liam R. Howlett <[email protected]>

> ---
>  include/linux/mm.h       |  4 ++--
>  include/linux/mm_types.h | 14 ++++++++------
>  2 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index d7ca837dd8a5..776a7e03f88b 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -943,7 +943,7 @@ static inline void vm_flags_reset_once(struct vm_area_struct *vma,
>  	 * system word.
>  	 */
>  	if (NUM_VMA_FLAG_BITS > BITS_PER_LONG) {
> -		unsigned long *bitmap = ACCESS_PRIVATE(&vma->flags, __vma_flags);
> +		unsigned long *bitmap = vma->flags.__vma_flags;
>  
>  		bitmap_zero(&bitmap[1], NUM_VMA_FLAG_BITS - BITS_PER_LONG);
>  	}
> @@ -1006,7 +1006,7 @@ static inline bool __vma_flag_atomic_valid(struct vm_area_struct *vma,
>  static inline void vma_flag_set_atomic(struct vm_area_struct *vma,
>  				       vma_flag_t bit)
>  {
> -	unsigned long *bitmap = ACCESS_PRIVATE(&vma->flags, __vma_flags);
> +	unsigned long *bitmap = vma->flags.__vma_flags;
>  
>  	vma_assert_stabilised(vma);
>  	if (__vma_flag_atomic_valid(vma, bit))
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index e5ee66f84d9a..592ad065fa75 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -866,7 +866,7 @@ struct mmap_action {
>  #define NUM_VMA_FLAG_BITS BITS_PER_LONG
>  typedef struct {
>  	DECLARE_BITMAP(__vma_flags, NUM_VMA_FLAG_BITS);
> -} __private vma_flags_t;
> +} vma_flags_t;
>  
>  /*
>   * Describes a VMA that is about to be mmap()'ed. Drivers may choose to
> @@ -1056,7 +1056,7 @@ struct vm_area_struct {
>  /* Clears all bits in the VMA flags bitmap, non-atomically. */
>  static inline void vma_flags_clear_all(vma_flags_t *flags)
>  {
> -	bitmap_zero(ACCESS_PRIVATE(flags, __vma_flags), NUM_VMA_FLAG_BITS);
> +	bitmap_zero(flags->__vma_flags, NUM_VMA_FLAG_BITS);
>  }
>  
>  /*
> @@ -1067,7 +1067,9 @@ static inline void vma_flags_clear_all(vma_flags_t *flags)
>   */
>  static inline void vma_flags_overwrite_word(vma_flags_t *flags, unsigned long value)
>  {
> -	*ACCESS_PRIVATE(flags, __vma_flags) = value;
> +	unsigned long *bitmap = flags->__vma_flags;
> +
> +	bitmap[0] = value;
>  }
>  
>  /*
> @@ -1078,7 +1080,7 @@ static inline void vma_flags_overwrite_word(vma_flags_t *flags, unsigned long va
>   */
>  static inline void vma_flags_overwrite_word_once(vma_flags_t *flags, unsigned long value)
>  {
> -	unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);
> +	unsigned long *bitmap = flags->__vma_flags;
>  
>  	WRITE_ONCE(*bitmap, value);
>  }
> @@ -1086,7 +1088,7 @@ static inline void vma_flags_overwrite_word_once(vma_flags_t *flags, unsigned lo
>  /* Update the first system word of VMA flags setting bits, non-atomically. */
>  static inline void vma_flags_set_word(vma_flags_t *flags, unsigned long value)
>  {
> -	unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);
> +	unsigned long *bitmap = flags->__vma_flags;
>  
>  	*bitmap |= value;
>  }
> @@ -1094,7 +1096,7 @@ static inline void vma_flags_set_word(vma_flags_t *flags, unsigned long value)
>  /* Update the first system word of VMA flags clearing bits, non-atomically. */
>  static inline void vma_flags_clear_word(vma_flags_t *flags, unsigned long value)
>  {
> -	unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);
> +	unsigned long *bitmap = flags->__vma_flags;
>  
>  	*bitmap &= ~value;
>  }
> -- 
> 2.52.0
>