drdb: Switch to kvfree_rcu() API

Instead of invoking a synchronize_rcu() to free a pointer
after a grace period we can directly make use of new API
that does the same but in more efficient way.

TO: Jens Axboe <axboe@kernel.dk>
TO: Philipp Reisner <philipp.reisner@linbit.com>
TO: Jason Gunthorpe <jgg@nvidia.com>
TO: drbd-dev@lists.linbit.com
TO: linux-block@vger.kernel.org
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Link: https://lore.kernel.org/r/20220406190715.1938174-7-christoph.boehmwalder@linbit.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/drbd/drbd_nl.c

@@ -1602,8 +1602,7 @@ int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
 			drbd_send_sync_param(peer_device);
 	}
 
-	synchronize_rcu();
-	kfree(old_disk_conf);
+	kvfree_rcu(old_disk_conf);
 	kfree(old_plan);
 	mod_timer(&device->request_timer, jiffies + HZ);
 	goto success;
@@ -2434,8 +2433,7 @@ int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
 
 	mutex_unlock(&connection->resource->conf_update);
 	mutex_unlock(&connection->data.mutex);
-	synchronize_rcu();
-	kfree(old_net_conf);
+	kvfree_rcu(old_net_conf);
 
 	if (connection->cstate >= C_WF_REPORT_PARAMS) {
 		struct drbd_peer_device *peer_device;
@@ -2849,8 +2847,7 @@ int drbd_adm_resize(struct sk_buff *skb, struct genl_info *info)
 		new_disk_conf->disk_size = (sector_t)rs.resize_size;
 		rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
 		mutex_unlock(&device->resource->conf_update);
-		synchronize_rcu();
-		kfree(old_disk_conf);
+		kvfree_rcu(old_disk_conf);
 		new_disk_conf = NULL;
 	}
 

drivers/block/drbd/drbd_receiver.c

@@ -3750,8 +3750,7 @@ static int receive_protocol(struct drbd_connection *connection, struct packet_in
 		drbd_info(connection, "peer data-integrity-alg: %s\n",
 			  integrity_alg[0] ? integrity_alg : "(none)");
 
-	synchronize_rcu();
-	kfree(old_net_conf);
+	kvfree_rcu(old_net_conf);
 	return 0;
 
 disconnect_rcu_unlock:
@@ -4119,8 +4118,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
 
 			rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
 			mutex_unlock(&connection->resource->conf_update);
-			synchronize_rcu();
-			kfree(old_disk_conf);
+			kvfree_rcu(old_disk_conf);
 
 			drbd_info(device, "Peer sets u_size to %lu sectors (old: %lu)\n",
 				 (unsigned long)p_usize, (unsigned long)my_usize);

drivers/block/drbd/drbd_state.c

@@ -2071,8 +2071,7 @@ static int w_after_conn_state_ch(struct drbd_work *w, int unused)
 		conn_free_crypto(connection);
 		mutex_unlock(&connection->resource->conf_update);
 
-		synchronize_rcu();
-		kfree(old_conf);
+		kvfree_rcu(old_conf);
 	}
 
 	if (ns_max.susp_fen) {