On Fri 04-05-18 14:52:08, Huaisheng Ye wrote:
> Suggest using unsigned int instead of int for bit within gfp_zone.
>
> Within function gfp_zone, the value of local variable bit comes from
> formal parameter flags, which's type is gfp_t. Local variable bit
> indicates the number of bits in the right shift for GFP_ZONE_TABLE
> with GFP_ZONES_SHIFT. So, variable bit shall always be unsigned
> integer, it doesn't make sense that forcing it to be a signed integer.
>
> Current GFP_ZONEMASK is just valid as low four bits, the largest
> value of bit shall be less or equal 0x0F. But in the future, as the
> mask expands to higher bits, there will be a risk of confusion.
I am highly skeptical we will ever grow the number of zones enough
that signed vs. unsigned would matter. So I guess this all boils down to
aesthetic. I do not care either way. The generated code seems the be the
same.
> Signed-off-by: Huaisheng Ye <yehs1@xxxxxxxxxx>
> ---
> include/linux/gfp.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 1a4582b..21551fc 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -401,7 +401,7 @@ static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags)
> static inline enum zone_type gfp_zone(gfp_t flags)
> {
> enum zone_type z;
> - int bit = (__force int) (flags & GFP_ZONEMASK);
> + unsigned int bit = (__force unsigned int) (flags & GFP_ZONEMASK);
>
> z = (GFP_ZONE_TABLE >> (bit * GFP_ZONES_SHIFT)) &
> ((1 << GFP_ZONES_SHIFT) - 1);
> --
> 1.8.3.1
>
--
Michal Hocko
SUSE Labs
