d_lookup -- search for a dentry
struct dentry * d_lookup
(struct dentry * parent, struct qstr * name);
qstr of name we wish to find
Searches the children of the parent dentry for the name in question. If
the dentry is found its reference count is incremented and the dentry
is returned. The caller must use d_put to free the entry when it has
finished using it. NULL is returned on failure.