Subject: Re: [PATCH 14/14] powerpc: remove address space overrides using set_fs()

From: Christoph Hellwig <[email-masked]>
Date: Thu, 3 Sep 2020 17:49:09 +0200

On Thu, Sep 03, 2020 at 05:43:25PM +0200, Christophe Leroy wrote:
>
>
> Le 03/09/2020 à 16:22, Christoph Hellwig a écrit :
>> Stop providing the possibility to override the address space using
>> set_fs() now that there is no need for that any more.
>>
>> Signed-off-by: Christoph Hellwig <[email-masked]>
>> ---
>
>
>>   -static inline int __access_ok(unsigned long addr, unsigned long size,
>> -			mm_segment_t seg)
>> +static inline bool __access_ok(unsigned long addr, unsigned long size)
>>   {
>> -	if (addr > seg.seg)
>> -		return 0;
>> -	return (size == 0 || size - 1 <= seg.seg - addr);
>> +	if (addr >= TASK_SIZE_MAX)
>> +		return false;
>> +	return size == 0 || size <= TASK_SIZE_MAX - addr;
>>   }
>
> You don't need to test size == 0 anymore. It used to be necessary because 
> of the 'size - 1', as size is unsigned.
>
> Now you can directly do
>
> 	return size <= TASK_SIZE_MAX - addr;
>
> If size is 0, this will always be true (because you already know that addr 
> is not >= TASK_SIZE_MAX

True.  What do you think of Linus' comment about always using the
ppc32 version on ppc64 as well with this?