Use of list_head struct

[Pranay Srivastava]

On Fri, Jun 17, 2016 at 3:41 PM, Martin Houry <martinhoury at gmail.com> wrote:
> 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"?

some magic value perhaps?

>
> I'm new here, thank you for your help!
> Martin
>
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-- 
        ---P.K.S