• Neil Brown's avatar
    [PATCH] kNFSd 3: Increase separation between lockd and nfsd. · 151ddf2e
    Neil Brown authored
    lockd currently asks nfsd for a 'client handle' for each
    request.
    
    This is used as a key for finding (or creating) a 'nlm_host'
    structure, so that there is only one of these per client...almost.
    There can currently be up to 4 nlm_hosts for a given client,
    depending on protocol (udp/tcp) or version (v1 or v4).
    
    But this isn't handled very well.
    
    So the question is: is there any advantage in having only on
    nlm_host per real host, or have we simply have one for each IP
    address that makes requests, whether they are separate hosts or not.
    
    The nlm_host structure is used:
     1/ to hold a lockd rpc client for talking to the
        remote lockd.  Having multiple lockd clients cannot hurt
        except possibly to waste a little space.
     2/ to identify resources to free when we receive notification
        from statd that a client has restarted.
        As statd gets a hostname and looks up all IP addresses,
        and then sends a notification for each IP for which it has
        a registration, there is no need to minimise the number
        of nlm_host structures (each of which register for monitoring).
     3/ to identify resources to free when a client sends a
        "free_all" request.  If a client uses multiple IP addresses to
        create locks, and then sends free_all from just one IP address
        we will loose here.
        However it is not clear that a client would ever want to send
        a free_all request, and the linux client doesn't seem to, so
        there is unlikely to be any loss here.
    
    This patch does not ask nfsd for a client identifier, but rather
    finds an nlm_host based on IP, version, protocol (udp/tcp) and
    whether we are acting as NFS server or client.
    
    All of this information is then placed in the cookie that is
    passed to statd and returned by statd when the client restarts.
    Previously only the IP address was passing the cookie, so possibly
    not all nlm_host structures would have been found.
    
    Because of these changes, lockd does not need to know
    anything about the nfsd export table, so the interface to
    nfsd is much more narrow.
    
    Another consequence is that when nfsd is told to delete a client,
    it cannot tell lockd to forget all the locks for that client.
    However it is not clear that lockd should ever forget any locks
    unless it is told to shutdown (or simulate a shutdown), and in
    anycase, the current nfsd admin tools never tell nfsd to delete
    a client anyway.
    151ddf2e
lockd.c 1.81 KB