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    SubjectRe: [PATCH v6 1/8] SUNRPC: introduce helpers for reference counted rpcbind clients
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    On Tue, 2011-10-25 at 14:16 +0300, Stanislav Kinsbursky wrote: 
    > v6:
    > 1) added write memory barrier to rpcb_set_local to make sure, that rpcbind
    > clients become valid before rpcb_users assignment
    > 2) explicitly set rpcb_users to 1 instead of incrementing it (looks clearer from
    > my pow).
    >
    > v5: fixed races with rpcb_users in rpcb_get_local()
    >
    > This helpers will be used for dynamical creation and destruction of rpcbind
    > clients.
    > Variable rpcb_users is actually a counter of lauched RPC services. If rpcbind
    > clients has been created already, then we just increase rpcb_users.
    >
    > Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
    >
    > ---
    > net/sunrpc/rpcb_clnt.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
    > 1 files changed, 54 insertions(+), 0 deletions(-)
    >
    > diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
    > index e45d2fb..9fcdb42 100644
    > --- a/net/sunrpc/rpcb_clnt.c
    > +++ b/net/sunrpc/rpcb_clnt.c
    > @@ -114,6 +114,9 @@ static struct rpc_program rpcb_program;
    > static struct rpc_clnt * rpcb_local_clnt;
    > static struct rpc_clnt * rpcb_local_clnt4;
    >
    > +DEFINE_SPINLOCK(rpcb_clnt_lock);
    > +unsigned int rpcb_users;
    > +
    > struct rpcbind_args {
    > struct rpc_xprt * r_xprt;
    >
    > @@ -161,6 +164,57 @@ static void rpcb_map_release(void *data)
    > kfree(map);
    > }
    >
    > +static int rpcb_get_local(void)
    > +{
    > + int cnt;
    > +
    > + spin_lock(&rpcb_clnt_lock);
    > + if (rpcb_users)
    > + rpcb_users++;
    > + cnt = rpcb_users;
    > + spin_unlock(&rpcb_clnt_lock);
    > +
    > + return cnt;
    > +}
    > +
    > +void rpcb_put_local(void)
    > +{
    > + struct rpc_clnt *clnt = rpcb_local_clnt;
    > + struct rpc_clnt *clnt4 = rpcb_local_clnt4;
    > + int shutdown;
    > +
    > + spin_lock(&rpcb_clnt_lock);
    > + if (--rpcb_users == 0) {
    > + rpcb_local_clnt = NULL;
    > + rpcb_local_clnt4 = NULL;
    > + }
    > + shutdown = !rpcb_users;
    > + spin_unlock(&rpcb_clnt_lock);
    > +
    > + if (shutdown) {
    > + /*
    > + * cleanup_rpcb_clnt - remove xprtsock's sysctls, unregister
    > + */
    > + if (clnt4)
    > + rpc_shutdown_client(clnt4);
    > + if (clnt)
    > + rpc_shutdown_client(clnt);
    > + }
    > + return;

    I'm removing this before applying...

    > +}
    > +

    --
    Trond Myklebust
    Linux NFS client maintainer

    NetApp
    Trond.Myklebust@netapp.com
    www.netapp.com



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