Use of list_head struct

Hello mailing list! I've read some code in the NFS4.1 client. I have trouble to access variables in a list_head. So I have : (include/linux/sunrpc/xprt.h line 168) struct rpc_xprt{ . . struct rpc_wait_queue pending; /* requests in flight */ . . } ==> struct rpc_wait_queue { . struct list_head tasks[RPC_NR_PRIORITY]; /* task queue for each priority level */ . } The struct "list_head" is a classical linked list. But How do I know the type of the struct in this list? I can maybe guess the struct in it : struct rpc_task {} But how can I be certain that "struct list_head tasks" contains some "struct rpc_task"? I'm new here, thank you for your help! Martin