drbd: Break a deadlock while concurrent fencing and establishing a connection (31007745) · Commits · 戴 / test

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>

drivers/block/drbd/drbd_receiver.c

+13 −10

Original line number	Diff line number	Diff line
		@@ -1026,14 +1026,6 @@ randomize:
		if (drbd_send_protocol(connection) == -EOPNOTSUPP)
		return -1;

		set_bit(STATE_SENT, &connection->flags);

		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.
		*
		@@ -1041,8 +1033,19 @@ randomize:
		* 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);
		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();

		if (discard_my_data)
		set_bit(DISCARD_MY_DATA, &device->flags);

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