s390/qeth: tighten ucast IP locking

The programming of ucast IPs via qeth_l3_modify_ip() is driven
independently from any of our typical locking mechanisms (eg. detaching
the netdevice, or holding the conf_mutex).
So when we inspect the card state to check whether the required cmd IO
should be deferred, there is no protection against concurrent state
changes.

But by slightly re-ordering the teardown sequence, we can rely on the
ip_lock to sufficiently serialize things:

1. when running concurrently to qeth_l3_set_online(), any instance of
   qeth_l3_modify_ip() that aquires the ip_lock _after_
   qeth_l3_recover_ip() will observe the state as CARD_STATE_SOFTSETUP
   and not defer the IO.
2. when running concurrently to qeth_l3_set_offline(), any instance of
   qeth_l3_modify_ip() that aquires the ip_lock _after_
   qeth_l3_clear_ip_htable() will observe the state as CARD_STATE_DOWN
   and defer the IO.

These guarantees in mind, we can now drop the conf_mutex from the
qeth_l3_modify_rxip_vipa() wrapper.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index 876a21d..0815b64 100644 (file)
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -591,7 +591,6 @@ int qeth_l3_modify_rxip_vipa(struct qeth_card *card, bool add, const u8 *ip,
                             enum qeth_prot_versions proto)
 {
        struct qeth_ipaddr addr;
-       int rc;
 
        qeth_l3_init_ipaddr(&addr, type, proto);
        if (proto == QETH_PROT_IPV4)
@@ -599,11 +598,7 @@ int qeth_l3_modify_rxip_vipa(struct qeth_card *card, bool add, const u8 *ip,
        else
                memcpy(&addr.u.a6.addr, ip, 16);
 
-       mutex_lock(&card->conf_mutex);
-       rc = qeth_l3_modify_ip(card, &addr, add);
-       mutex_unlock(&card->conf_mutex);
-
-       return rc;
+       return qeth_l3_modify_ip(card, &addr, add);
 }
 
 int qeth_l3_modify_hsuid(struct qeth_card *card, bool add)
@@ -1161,9 +1156,9 @@ static void qeth_l3_stop_card(struct qeth_card *card)
                qeth_diags_trace(card, QETH_DIAGS_CMD_TRACE_DISABLE);
 
        if (card->state == CARD_STATE_SOFTSETUP) {
+               card->state = CARD_STATE_DOWN;
                qeth_l3_clear_ip_htable(card, 1);
                qeth_clear_ipacmd_list(card);
-               card->state = CARD_STATE_DOWN;
        }
 
        qeth_qdio_clear_card(card, 0);