drbd: Break a deadlock while concurrent fencing and establishing a connection
When we need to outdate the peer while being promoted to primary,
and the connection gets established at the same time, we deadlock
in drbd_try_outdate_peer() when trying to clear the susp_fen
bit.
Fix this by setting the STATE_SENT bit while holding the mutex.
Using drbd_change_state(.. , CS_HARD, ..) which does not block
until STATE_SENT is cleared, is only for clearness. It does
not contribute anything to the fix.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 68e3992..125c9e8 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1026,24 +1026,27 @@
if (drbd_send_protocol(connection) == -EOPNOTSUPP)
return -1;
+ /* Prevent a race between resync-handshake and
+ * being promoted to Primary.
+ *
+ * Grab and release the state mutex, so we know that any current
+ * drbd_set_role() is finished, and any incoming drbd_set_role
+ * will see the STATE_SENT flag, and wait for it to be cleared.
+ */
+ idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
+ mutex_lock(peer_device->device->state_mutex);
+
set_bit(STATE_SENT, &connection->flags);
+ idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
+ mutex_unlock(peer_device->device->state_mutex);
+
rcu_read_lock();
idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
struct drbd_device *device = peer_device->device;
kref_get(&device->kref);
rcu_read_unlock();
- /* Prevent a race between resync-handshake and
- * being promoted to Primary.
- *
- * Grab and release the state mutex, so we know that any current
- * drbd_set_role() is finished, and any incoming drbd_set_role
- * will see the STATE_SENT flag, and wait for it to be cleared.
- */
- mutex_lock(device->state_mutex);
- mutex_unlock(device->state_mutex);
-
if (discard_my_data)
set_bit(DISCARD_MY_DATA, &device->flags);
else