kernel hash function algorithm

[Onkar Mahajan]

Why is the hash calculated like this ?

*static unsigned long hash(struct super_block *sb, unsigned long hashval)**
{
    unsigned long tmp;

    tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
            L1_CACHE_BYTES;
    tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> I_HASHBITS);
    return tmp & I_HASHMASK;
}*


Regards,
Onkar