libceph: handle connection reopen race with callbacks
If a connection is closed and/or reopened (ceph_con_close, ceph_con_open)
it can race with a callback. con_work does various state checks for
closed or reopened sockets at the beginning, but drops con->mutex before
making callbacks. We need to check for state bit changes after retaking
the lock to ensure we restart con_work and execute those CLOSED/OPENING
tests or else we may end up operating under stale assumptions.
In Jim's case, this was causing 'bad tag' errors.
There are four cases where we re-take the con->mutex inside con_work: catch
them all and return EAGAIN from try_{read,write} so that we can restart
con_work.
Reported-by: Jim Schutt <jaschut@sandia.gov>
Tested-by: Jim Schutt <jaschut@sandia.gov>
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index e15a82c..b140dd3 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -598,7 +598,7 @@
* Connection negotiation.
*/
-static void prepare_connect_authorizer(struct ceph_connection *con)
+static int prepare_connect_authorizer(struct ceph_connection *con)
{
void *auth_buf;
int auth_len = 0;
@@ -612,6 +612,10 @@
con->auth_retry);
mutex_lock(&con->mutex);
+ if (test_bit(CLOSED, &con->state) ||
+ test_bit(OPENING, &con->state))
+ return -EAGAIN;
+
con->out_connect.authorizer_protocol = cpu_to_le32(auth_protocol);
con->out_connect.authorizer_len = cpu_to_le32(auth_len);
@@ -619,6 +623,8 @@
con->out_kvec[con->out_kvec_left].iov_len = auth_len;
con->out_kvec_left++;
con->out_kvec_bytes += auth_len;
+
+ return 0;
}
/*
@@ -640,9 +646,9 @@
set_bit(WRITE_PENDING, &con->state);
}
-static void prepare_write_connect(struct ceph_messenger *msgr,
- struct ceph_connection *con,
- int after_banner)
+static int prepare_write_connect(struct ceph_messenger *msgr,
+ struct ceph_connection *con,
+ int after_banner)
{
unsigned global_seq = get_global_seq(con->msgr, 0);
int proto;
@@ -683,7 +689,7 @@
con->out_more = 0;
set_bit(WRITE_PENDING, &con->state);
- prepare_connect_authorizer(con);
+ return prepare_connect_authorizer(con);
}
@@ -1216,6 +1222,7 @@
u64 sup_feat = con->msgr->supported_features;
u64 req_feat = con->msgr->required_features;
u64 server_feat = le64_to_cpu(con->in_reply.features);
+ int ret;
dout("process_connect on %p tag %d\n", con, (int)con->in_tag);
@@ -1250,7 +1257,9 @@
return -1;
}
con->auth_retry = 1;
- prepare_write_connect(con->msgr, con, 0);
+ ret = prepare_write_connect(con->msgr, con, 0);
+ if (ret < 0)
+ return ret;
prepare_read_connect(con);
break;
@@ -1277,6 +1286,9 @@
if (con->ops->peer_reset)
con->ops->peer_reset(con);
mutex_lock(&con->mutex);
+ if (test_bit(CLOSED, &con->state) ||
+ test_bit(OPENING, &con->state))
+ return -EAGAIN;
break;
case CEPH_MSGR_TAG_RETRY_SESSION:
@@ -1810,6 +1822,17 @@
more:
dout("try_read tag %d in_base_pos %d\n", (int)con->in_tag,
con->in_base_pos);
+
+ /*
+ * process_connect and process_message drop and re-take
+ * con->mutex. make sure we handle a racing close or reopen.
+ */
+ if (test_bit(CLOSED, &con->state) ||
+ test_bit(OPENING, &con->state)) {
+ ret = -EAGAIN;
+ goto out;
+ }
+
if (test_bit(CONNECTING, &con->state)) {
if (!test_bit(NEGOTIATING, &con->state)) {
dout("try_read connecting\n");
@@ -1938,8 +1961,10 @@
{
struct ceph_connection *con = container_of(work, struct ceph_connection,
work.work);
+ int ret;
mutex_lock(&con->mutex);
+restart:
if (test_and_clear_bit(BACKOFF, &con->state)) {
dout("con_work %p backing off\n", con);
if (queue_delayed_work(ceph_msgr_wq, &con->work,
@@ -1969,18 +1994,31 @@
con_close_socket(con);
}
- if (test_and_clear_bit(SOCK_CLOSED, &con->state) ||
- try_read(con) < 0 ||
- try_write(con) < 0) {
- mutex_unlock(&con->mutex);
- ceph_fault(con); /* error/fault path */
- goto done_unlocked;
- }
+ if (test_and_clear_bit(SOCK_CLOSED, &con->state))
+ goto fault;
+
+ ret = try_read(con);
+ if (ret == -EAGAIN)
+ goto restart;
+ if (ret < 0)
+ goto fault;
+
+ ret = try_write(con);
+ if (ret == -EAGAIN)
+ goto restart;
+ if (ret < 0)
+ goto fault;
done:
mutex_unlock(&con->mutex);
done_unlocked:
con->ops->put(con);
+ return;
+
+fault:
+ mutex_unlock(&con->mutex);
+ ceph_fault(con); /* error/fault path */
+ goto done_unlocked;
}