Re: [PATCH] include: mman: Use bool instead of int for the return value of arch_validate_prot

On 7/12/16 12:20, Michael Ellerman wrote:

Chen Gang [off-list ref] writes:

quoted

On 7/11/16 07:47, Dave Hansen wrote:

quoted

On 07/09/2016 09:29 AM, chengang@emindsoft.com.cn wrote:

quoted

-static inline int arch_validate_prot(unsigned long prot)
+static inline bool arch_validate_prot(unsigned long prot)
 {
 	if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | PROT_SAO))
-		return 0;
-	if ((prot & PROT_SAO) && !cpu_has_feature(CPU_FTR_SAO))
-		return 0;
-	return 1;
+		return false;
+	return (prot & PROT_SAO) == 0 || cpu_has_feature(CPU_FTR_SAO);
 }
 #define arch_validate_prot(prot) arch_validate_prot(prot)

Please don't do things like this.  They're not obviously correct and
also have no obvious benefit.  You also don't mention why you bothered
to alter the logical structure of these checks.

For all cases, bool is equal or a little better than int, and they are
equal in our case (2 final outputs are same). So for me, it may belong
to trivial patch, which can be skipped by the normal patch maintainers.

As a 'trivial' patch:

 - For a pure Boolean function, bool return value is more readable than
   int.

Agreed.

Please send a patch that does that and only that.

OK, thanks.

After check the assembly output, for some cases, merging 3 lines to 1
line may be a little more readable, but compiler will generate a little
bad output code.

I shall send patch v2 for it within this weekend.

Thanks.
-- 
Chen Gang (陈刚)

Managing Natural Environments is the Duty of Human Beings.