a question abount idmapd‏

[Trond Myklebust]

On Wed, 2009-09-23 at 18:44 +0800, hongpo gao wrote:
> 
> hello, 
> 
> I have a question about idmap. Should I send the mail to
> linux-nfs at vger.kernel.org?

The linux-nfs mailing list is preferred over nfsv4 at linux-nfs.org, if
that's what you mean.

> The question is as follows:
> 
> In Linux Kernel fs/nfs/idmap.c, 
> The process will call rpc_queue_upcall in the nfs_idmap_id function,
> then it will wait on the waitqueue util the userspace write msg into
> the idmap rpc_pipe. 
> 
> In userspace idmapd.c file,
> the nfscb will read the rpc_pipe by aiomicio(read, ...), write the
> rpc_pipe by atomicio(write,...) in the end.
> my question is : if the rpc.idmapd deamon is killed in the duration
> time that between atomicio(read,.. ) and atomic(write,...), will the
> kernel thread will always sleep on the wait_queue? That is to say,
> will the rpc_queue_upcall be never return ?

No. The kernel tracks whether or not a daemon is listening on the other
end of the rpc_pipe, and will therefore return an error should the above
scenario happen.

Cheers
  Trond