kernel hash function algorithm

[Onkar Mahajan <kern.devel@xxxxxxxxx>]

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