On 20 December 2017 at 10:56, Joe Perches <joe@xxxxxxxxxxx> wrote:
> On Wed, 2017-12-20 at 10:33 +0100, Crt Mori wrote:
>> There is no option to perform 64bit integer sqrt on 32bit platform.
>> Added stronger typed int_sqrt64 enables the 64bit calculations to
>> be performed on 32bit platforms. Although int_sqrt() is a rough
>> approximation, the same algorithm is used in int_sqrt64() as good
>> enough on 32bit platform.
> []
>> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> []
>> @@ -459,6 +459,7 @@ extern int kernel_text_address(unsigned long addr);
>> extern int func_ptr_is_kernel_text(void *ptr);
>>
>> unsigned long int_sqrt(unsigned long);
>> +u32 int_sqrt64(u64 x);
>
> #ifdef BITS_PER_LONG == 64
> static inline u32 int_sqrt64(u64 x)
> {
> re
> turn (u32)int_sqrt(x);
> }
> #else
> u32 int_sqrt64(u64 x);
> #endif
>
> []
>
OK, fixing it in v10.
>> +#if BITS_PER_LONG < 64
>> +/**
>> + * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input
>> + * is expected.
>> + * @x: 64bit integer of which to calculate the sqrt
>> + */
>> +u32 int_sqrt64(u64 x)
>> +{
>> + u64 b, m, y = 0;
>> +
>> + if (x <= 1)
>> + return x;
>> +
>> + m = 1ULL << (fls64(x) & ~1ULL);
>> + while (m != 0) {
>> + b = y + m;
>> + y >>= 1;
>> +
>> + if (x >= b) {
>> + x -= b;
>> + y += m;
>> + }
>> + m >>= 2;
>> + }
>> +
>> + return y;
>> +}
>> +EXPORT_SYMBOL(int_sqrt64);
>> +#else
>> +u32 int_sqrt64(u64 x)
>> +{
>> + return int_sqrt(x);
>> +}
>> +EXPORT_SYMBOL(int_sqrt64);
>> +#endif
>
> This doesn't need to be EXPORT_SYMBOL for the
> BITS_PER_LONG == 64 case
>
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