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s390/qeth: tighten ucast IP locking

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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>
This commit is contained in:
Julian Wiedmann 2020-09-23 10:36:56 +02:00 committed by David S. Miller
parent ab29c480b1
commit f3380b1edc
1 changed files with 2 additions and 7 deletions
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9
drivers/s390/net/qeth_l3_main.c
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@ -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);