Re: Add operation vcache_rekey

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

   Date: Wed, 25 Jun 2014 12:04:30 +0200
   From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>

   Using "memcpy(__UNCONST(node->vn_key.vk_key), new_key, new_key_len)"
   works but I'm not sure if __UNCONST is the right way to go.

I think __UNCONST is the right way to go -- removing const from the
API itself is certainly not right.  I would put the __UNCONST in the
initialization of temporary vcache keys used to look things up, e.g.
in vcache_get:

struct vcache_key {
        struct mount *vk_mount;
        void *vk_key;
        size_t vk_key_len;
};

int
vcache_get(struct mount *mp, const void *key, size_t key_len,
   struct vnode *vpp)
{
        ...
        struct vcache_key vcache_key;
        ...

        vcache_key.vk_mount = mp;
        vcache_key.vk_key = __UNCONST(key);
        vcache_key.vk_key_len = key_len;
        ....
}