sctp: implement memory accounting on rx path

sk_forward_alloc's updating is also done on rx path, but to be consistent
we change to use sk_mem_charge() in sctp_skb_set_owner_r().

In sctp_eat_data(), it's not enough to check sctp_memory_pressure only,
which doesn't work for mem_cgroup_sockets_enabled, so we change to use
sk_under_memory_pressure().

When it's under memory pressure, sk_mem_reclaim() and sk_rmem_schedule()
should be called on both RENEGE or CHUNK DELIVERY path exit the memory
pressure status as soon as possible.

Note that sk_rmem_schedule() is using datalen to make things easy there.

Reported-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Matteo Croce <mcroce@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index c9ae340..7dfc34b 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -6412,13 +6412,15 @@ static int sctp_eat_data(const struct sctp_association *asoc,
 	 * in sctp_ulpevent_make_rcvmsg will drop the frame if we grow our
 	 * memory usage too much
 	 */
-	if (*sk->sk_prot_creator->memory_pressure) {
+	if (sk_under_memory_pressure(sk)) {
 		if (sctp_tsnmap_has_gap(map) &&
 		    (sctp_tsnmap_get_ctsn(map) + 1) == tsn) {
 			pr_debug("%s: under pressure, reneging for tsn:%u\n",
 				 __func__, tsn);
 			deliver = SCTP_CMD_RENEGE;
-		 }
+		} else {
+			sk_mem_reclaim(sk);
+		}
 	}
 
 	/*