[RFC] Read access to /config/dlm/<cluster>/comms/<comm>/addr

[Masatake YAMATO <yamato@xxxxxxxxxx>]

Hi,

I've found /config/dlm/<cluster>/comms/<comm>/addr is readable 
(in meaning of ls -l) but no handler(comm_addr_read) is defined in 
dlm/fs/dlm/config.c.

If cat command works fine with /config/dlm/<cluster>/comms/<comm>/addr,
it will be nice to understand the status of dlm. So I'm thinking about
writing a patch.

But after reading the source code, I've found its difficulties;
/config/dlm/<cluster>/comms/<comm>/addr holds 'struct
sockaddr_storage'.

I'd like to get your comment before going ahead.
I think we have three choice. Which do you think the best?

    1. When 'cat /config/dlm/<cluster>/comms/<comm>/addr' is invoked,
       it converts the held sockaddr_storage to human readable text and
       provids it to userland.
       e.g.

	    # cat /config/dlm/<cluster>/comms/<comm>/addr
	    AF_INET
	    192.168.151.1
	    #

       Advantage: human readable
       Disadvantage: data asymmetry in writing and reading
		     When writing to
		     /config/dlm/<cluster>/comms/<comm>/addr, it expects
		     binary format of sockaddr_storage.

    2. When 'cat /config/dlm/<cluster>/comms/<comm>/addr' is invoked,
       it provides the held sockaddr_storage to userland. 

       Advantage: data symmetry in writing and reading.
       Disadvantage: not human readable. It needs something effort to
		     understanding the returned binary data.

    3. Make /config/dlm/<cluster>/comms/<comm>/addr unreadable (in meaning of ls -l)

       e.g.
       # ls -l /config/dlm/<cluster>/comms/<comm>/addr
       --w-------. 1 root root 4096 Jun  9 08:51 /config/dlm/<cluster>/comms/<comm>/addr

       Advantage: easy to implement.
       Disadvantage: no way to know the value of node addr of dlm view.

Regards,
Masatake YAMATO

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