On Fri, Oct 13, 2017 at 04:02:09PM -0700, David Ahern wrote:
> ipv6_add_addr is called in process context with rtnl lock held
> (e.g., manual config of an address) or during softirq processing
> (e.g., autoconf and address from a router advertisement).
>
> Currently, ipv6_add_addr calls rcu_read_lock_bh shortly after entry
> and does not call unlock until exit, minus the call around the address
> validator notifier. Similarly, addrconf_hash_lock is taken after the
> validator notifier and held until exit. This forces the allocation of
> inet6_ifaddr to always be atomic.
>
> Refactor ipv6_add_addr as follows:
> 1. add an input boolean to discriminate the call path (process context
> or softirq). This new flag controls whether the alloc can be done
> with GFP_KERNEL or GFP_ATOMIC.
>
> 2. Move the rcu_read_lock_bh and unlock calls only around functions that
> do rcu updates.
>
> 3. Remove the in6_dev_hold and put added by 3ad7d2468f79f ("Ipvlan should
> return an error when an address is already in use."). This was done
> presumably because rcu_read_unlock_bh needs to be called before calling
> the validator. Since rcu_read_lock is not needed before the validator
> runs revert the hold and put added by 3ad7d2468f79f and only do the
> hold when setting ifp->idev.
>
> 4. move duplicate address check and insertion of new address in the global
> address hash into a helper. The helper is called after an ifa is
> allocated and filled in.
>
> This allows the ifa for manually configured addresses to be done with
> GFP_KERNEL and reduces the overall amount of time with rcu_read_lock held
> and hash table spinlock held.
>
> Signed-off-by: David Ahern <dsah...@gmail.com>
[...]
> @@ -1073,21 +1085,19 @@ ipv6_add_addr(struct inet6_dev *idev, const struct
> in6_addr *addr,
>
> in6_ifa_hold(ifa);
> write_unlock(&idev->lock);
> -out2:
> +
> rcu_read_unlock_bh();
>
> - if (likely(err == 0))
> - inet6addr_notifier_call_chain(NETDEV_UP, ifa);
> - else {
> + inet6addr_notifier_call_chain(NETDEV_UP, ifa);
> +out:
> + if (unlikely(err < 0)) {
> + if (rt)
> + ip6_rt_put(rt);
I believe 'rt' needs to be set to NULL after addrconf_dst_alloc()
fails.
> kfree(ifa);
> - in6_dev_put(idev);
> ifa = ERR_PTR(err);
> }
>
> return ifa;
> -out:
> - spin_unlock(&addrconf_hash_lock);
> - goto out2;
> }
