Commit f3dfa40a authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
Browse files

drbd: fix race when forcefully disconnecting 



If a forced disconnect hits a restarting receiver right after it passed
its final "if (C_DISCONNECTING)" test in drbdd_init(), but before it was
actually restarted by drbd_thread_setup, we could be left with a
connection stuck in C_DISCONNECTING, never reaching C_STANDALONE,
which would be necessary to take it down or reconfigure it.

Move the last cleanup into w_after_conn_state_ch(), and do an additional
state change request in conn_try_disconnect(), just in case.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent 88104ca4

drivers/block/drbd/drbd_nl.c

+48 −37
Original line number Diff line number Diff line
@@ -2115,17 +2115,13 @@ int drbd_adm_connect(struct sk_buff *skb, struct genl_info *info) 
static enum drbd_state_rv conn_try_disconnect(struct drbd_tconn *tconn, bool force)

{

	enum drbd_state_rv rv;

	if (force) {

		spin_lock_irq(&tconn->req_lock);

		rv = _conn_request_state(tconn, NS(conn, C_DISCONNECTING), CS_HARD);

		spin_unlock_irq(&tconn->req_lock);

		return rv;

	}



	rv = conn_request_state(tconn, NS(conn, C_DISCONNECTING), 0);

	rv = conn_request_state(tconn, NS(conn, C_DISCONNECTING),

			force ? CS_HARD : 0);



	switch (rv) {

	case SS_NOTHING_TO_DO:

		break;

	case SS_ALREADY_STANDALONE:

		return SS_SUCCESS;

	case SS_PRIMARY_NOP:
@@ -2138,14 +2134,35 @@ static enum drbd_state_rv conn_try_disconnect(struct drbd_tconn *tconn, bool for 
		rv = conn_request_state(tconn, NS2(conn, C_DISCONNECTING,

							disk, D_OUTDATED), 0);

		if (rv == SS_IS_DISKLESS || rv == SS_LOWER_THAN_OUTDATED) {

			conn_request_state(tconn, NS(conn, C_DISCONNECTING), CS_HARD);

			rv = SS_SUCCESS;

			rv = conn_request_state(tconn, NS(conn, C_DISCONNECTING),

					CS_HARD);

		}

		break;

	default:;

		/* no special handling necessary */

	}



	if (rv >= SS_SUCCESS) {

		enum drbd_state_rv rv2;

		/* No one else can reconfigure the network while I am here.

		 * The state handling only uses drbd_thread_stop_nowait(),

		 * we want to really wait here until the receiver is no more.

		 */

		drbd_thread_stop(&adm_ctx.tconn->receiver);



		/* Race breaker.  This additional state change request may be

		 * necessary, if this was a forced disconnect during a receiver

		 * restart.  We may have "killed" the receiver thread just

		 * after drbdd_init() returned.  Typically, we should be

		 * C_STANDALONE already, now, and this becomes a no-op.

		 */

		rv2 = conn_request_state(tconn, NS(conn, C_STANDALONE),

				CS_VERBOSE | CS_HARD);

		if (rv2 < SS_SUCCESS)

			conn_err(tconn,

				"unexpected rv2=%d in conn_try_disconnect()\n",

				rv2);

	}

	return rv;

}
@@ -2176,18 +2193,8 @@ int drbd_adm_disconnect(struct sk_buff *skb, struct genl_info *info) 


	rv = conn_try_disconnect(tconn, parms.force_disconnect);

	if (rv < SS_SUCCESS)

		goto fail;



	/* No one else can reconfigure the network while I am here.

	 * The state handling only uses drbd_thread_stop_nowait(),

	 * we want to really wait here until the receiver is no more. */

	drbd_thread_stop(&tconn->receiver);

	if (wait_event_interruptible(tconn->ping_wait,

				     tconn->cstate == C_STANDALONE)) {

		retcode = ERR_INTR;

		goto fail;

	}



		retcode = rv;  /* FIXME: Type mismatch. */

	else

		retcode = NO_ERROR;

 fail:

	drbd_adm_finish(info, retcode);
@@ -3049,8 +3056,7 @@ int drbd_adm_delete_minor(struct sk_buff *skb, struct genl_info *info) 


int drbd_adm_down(struct sk_buff *skb, struct genl_info *info)

{

	enum drbd_ret_code retcode;

	enum drbd_state_rv rv;

	int retcode; /* enum drbd_ret_code rsp. enum drbd_state_rv */

	struct drbd_conf *mdev;

	unsigned i;
@@ -3074,30 +3080,35 @@ int drbd_adm_down(struct sk_buff *skb, struct genl_info *info) 
			goto out_unlock;

		}

	}

	up_read(&drbd_cfg_rwsem);



	/* disconnect */

	rv = conn_try_disconnect(adm_ctx.tconn, 0);

	if (rv < SS_SUCCESS) {

		retcode = rv; /* enum type mismatch! */

	/* disconnect; may stop the receiver;

	 * must not hold the drbd_cfg_rwsem */

	retcode = conn_try_disconnect(adm_ctx.tconn, 0);

	if (retcode < SS_SUCCESS) {

		drbd_msg_put_info("failed to disconnect");

		goto out_unlock;

		goto out;

	}



	/* Make sure the network threads have actually stopped,

	 * state handling only does drbd_thread_stop_nowait(). */

	drbd_thread_stop(&adm_ctx.tconn->receiver);



	down_read(&drbd_cfg_rwsem);

	/* detach */

	idr_for_each_entry(&adm_ctx.tconn->volumes, mdev, i) {

		rv = adm_detach(mdev);

		if (rv < SS_SUCCESS) {

			retcode = rv; /* enum type mismatch! */

		retcode = adm_detach(mdev);

		if (retcode < SS_SUCCESS) {

			drbd_msg_put_info("failed to detach");

			goto out_unlock;

		}

	}

	up_read(&drbd_cfg_rwsem);



	/* If we reach this, all volumes (of this tconn) are Secondary,

	 * Disconnected, Diskless, aka Unconfigured. Make sure all threads have

	 * actually stopped, state handling only does drbd_thread_stop_nowait().

	 * This needs to be done without holding drbd_cfg_rwsem. */

	drbd_thread_stop(&adm_ctx.tconn->worker);



	/* Now, nothing can fail anymore */



	/* delete volumes */

	down_write(&drbd_cfg_rwsem);

	idr_for_each_entry(&adm_ctx.tconn->volumes, mdev, i) {

drivers/block/drbd/drbd_receiver.c

+1 −13
Original line number Diff line number Diff line
@@ -4213,21 +4213,9 @@ static void drbd_disconnect(struct drbd_tconn *tconn) 


	spin_unlock_irq(&tconn->req_lock);



	if (oc == C_DISCONNECTING) {

		struct net_conf *old_conf;



		mutex_lock(&tconn->net_conf_update);

		old_conf = tconn->net_conf;

		rcu_assign_pointer(tconn->net_conf, NULL);

		conn_free_crypto(tconn);

		mutex_unlock(&tconn->net_conf_update);



		synchronize_rcu();

		kfree(old_conf);



	if (oc == C_DISCONNECTING)

		conn_request_state(tconn, NS(conn, C_STANDALONE), CS_VERBOSE | CS_HARD);

}

}



static int drbd_disconnected(int vnr, void *p, void *data)

{

drivers/block/drbd/drbd_state.c

+13 −0
Original line number Diff line number Diff line
@@ -1416,6 +1416,19 @@ static int w_after_conn_state_ch(struct drbd_work *w, int unused) 
	if (oc == C_STANDALONE && ns_max.conn == C_UNCONNECTED)

		drbd_thread_start(&tconn->receiver);



	if (oc == C_DISCONNECTING && ns_max.conn == C_STANDALONE) {

		struct net_conf *old_conf;



		mutex_lock(&tconn->net_conf_update);

		old_conf = tconn->net_conf;

		rcu_assign_pointer(tconn->net_conf, NULL);

		conn_free_crypto(tconn);

		mutex_unlock(&tconn->net_conf_update);



		synchronize_rcu();

		kfree(old_conf);

	}



	if (ns_max.susp_fen) {

		/* case1: The outdate peer handler is successful: */

		if (ns_max.pdsk <= D_OUTDATED) {