2018-05-03 07:45:16

by Michal Hocko

Subject: Re: [PATCH] include/linux/gfp.h: use unsigned int in gfp_zone

On Thu 03-05-18 11:44:58, Huaisheng Ye wrote:
> Suggest using unsigned int instead of int for bit within gfp_zone.
>
> The value of bit comes from flags, which's type is gfp_t. And it
> indicates the number of bits in the right shift for GFP_ZONE_TABLE.
>
> Signed-off-by: Huaisheng Ye <[email protected]>

The patch looks OK but it misses the most important piece of
information. Why this is worth changing. Does it lead to a better code?
Silence a warning or...

> ---
> 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

2018-05-03 14:08:46

by Huaisheng HS1 Ye

Subject: RE: [PATCH] include/linux/gfp.h: use unsigned int in gfp_zone

> On Thu 03-05-18 11:44:58, Huaisheng Ye wrote:
> > Suggest using unsigned int instead of int for bit within gfp_zone.
> >
> > The value of bit comes from flags, which's type is gfp_t. And it
> > indicates the number of bits in the right shift for GFP_ZONE_TABLE.
> >
> > Signed-off-by: Huaisheng Ye <[email protected]>
>
> The patch looks OK but it misses the most important piece of
> information. Why this is worth changing. Does it lead to a better code?
> Silence a warning or...
>
Yes, thank you and I will rewrite the commit log later.

Sincerely,
Huaisheng, Ye
> > ---
> > 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