GRO is very optimistic in skb truesize estimates, only taking into
account the used part of fragments.

Be conservative, and use more precise computation, so that bloated GRO
skbs can be collapsed eventually.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: NAlexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>