Re: [PATCH v3 2/2] kexec: Use min_t to simplify logic

[Zhang Yanfei <zhangyanfei@cn.fujitsu.com>]

于 2013年02月26日 16:38, Joe Perches 写道:
> On Tue, 2013-02-26 at 13:30 +0800, Zhang Yanfei wrote:
>> This is just a tweak: using min_t to simplify logic of variable
>> assignments.
>>
>> v3:
>> - cast type of (PAGE_SIZE - (maddr & ~PAGE_MASK)) into size_t.
> 
> Why?  Isn't this just a redundant cast?
> 
>> diff --git a/kernel/kexec.c b/kernel/kexec.c
> []
>> @@ -822,13 +822,9 @@ static int kimage_load_normal_segment(struct kimage *image,
> []
>> +		mchunk = min_t(size_t, mbytes,
>> +			       (size_t)(PAGE_SIZE - (maddr & ~PAGE_MASK)));
> 
> #define min_t(type, x, y) ({			\
> 	type __min1 = (x);			\
> 	type __min2 = (y);			\
> 	__min1 < __min2 ? __min1: __min2; })
> 
> 
> 

Hmm, from the definition, the cast is redundant.

Maybe I misunderstood what Andrew meant in the mail related to v2:

"The types of PAGE_SIZE and PAGE_MASK are vague - iirc they once had
different types on different architectures, so some form of casting is
unavoidable here."

Andrew, could you please explain the casting you meant above?

Thanks
Zhang