hi all
the codes about filesystem in the kernel is:
static inline struct list_head * d_hash(struct dentry *parent, unsigned long hash)
{
hash += (unsigned long)parent / L1_CACHE_BYTES;
hash = hash^(hash>>D_HASHBITS)^(hash>>D_HASHBITS*2);
return dentry_hashtable + (hash & D_HASHMASK);
}
I know the function parameter of hash belongs to the qstr string is looking up, and the local variableshash should add the address of the dentry of parent.
Why count the hash value use "L1_CACHE_BYTES" , "D_HASHBITS" and "D_HASHMASK"?
And How to understand the codes following ?
hash += (unsigned long)parent / L1_CACHE_BYTES;
hash = hash^(hash>>D_HASHBITS)^(hash>>D_HASHBITS*2);
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