nfsd4: allow backchannel recovery

Now that we have a list of connections to choose from, we can teach the
callback code to just pick a suitable connection and use that, instead
of insisting on forever using the connection that the first
create_session was sent with.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index dd183af..18b740b 100644 (file)
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -473,8 +473,7 @@ static int max_cb_time(void)
 /* Reference counting, callback cleanup, etc., all look racy as heck.
  * And why is cl_cb_set an atomic? */
 
-static int setup_callback_client(struct nfs4_client *clp,
-               struct nfs4_cb_conn *conn)
+static int setup_callback_client(struct nfs4_client *clp, struct nfs4_cb_conn *conn, struct nfsd4_session *ses)
 {
        struct rpc_timeout      timeparms = {
                .to_initval     = max_cb_time(),
@@ -501,6 +500,10 @@ static int setup_callback_client(struct nfs4_client *clp,
                args.protocol = XPRT_TRANSPORT_TCP;
                clp->cl_cb_ident = conn->cb_ident;
        } else {
+               if (!conn->cb_xprt)
+                       return -EINVAL;
+               clp->cl_cb_conn.cb_xprt = conn->cb_xprt;
+               clp->cl_cb_session = ses;
                args.bc_xprt = conn->cb_xprt;
                args.prognumber = clp->cl_cb_session->se_cb_prog;
                args.protocol = XPRT_TRANSPORT_BC_TCP;
@@ -756,10 +759,27 @@ static void nfsd4_release_cb(struct nfsd4_callback *cb)
                cb->cb_ops->rpc_release(cb);
 }
 
+/* requires cl_lock: */
+static struct nfsd4_conn * __nfsd4_find_backchannel(struct nfs4_client *clp)
+{
+       struct nfsd4_session *s;
+       struct nfsd4_conn *c;
+
+       list_for_each_entry(s, &clp->cl_sessions, se_perclnt) {
+               list_for_each_entry(c, &s->se_conns, cn_persession) {
+                       if (c->cn_flags & NFS4_CDFC4_BACK)
+                               return c;
+               }
+       }
+       return NULL;
+}
+
 static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
 {
        struct nfs4_cb_conn conn;
        struct nfs4_client *clp = cb->cb_clp;
+       struct nfsd4_session *ses = NULL;
+       struct nfsd4_conn *c;
        int err;
 
        /*
@@ -770,6 +790,10 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
                rpc_shutdown_client(clp->cl_cb_client);
                clp->cl_cb_client = NULL;
        }
+       if (clp->cl_cb_conn.cb_xprt) {
+               svc_xprt_put(clp->cl_cb_conn.cb_xprt);
+               clp->cl_cb_conn.cb_xprt = NULL;
+       }
        if (test_bit(NFSD4_CLIENT_KILL, &clp->cl_cb_flags))
                return;
        spin_lock(&clp->cl_lock);
@@ -780,9 +804,15 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
        BUG_ON(!clp->cl_cb_flags);
        clear_bit(NFSD4_CLIENT_CB_UPDATE, &clp->cl_cb_flags);
        memcpy(&conn, &cb->cb_clp->cl_cb_conn, sizeof(struct nfs4_cb_conn));
+       c = __nfsd4_find_backchannel(clp);
+       if (c) {
+               svc_xprt_get(c->cn_xprt);
+               conn.cb_xprt = c->cn_xprt;
+               ses = c->cn_session;
+       }
        spin_unlock(&clp->cl_lock);
 
-       err = setup_callback_client(clp, &conn);
+       err = setup_callback_client(clp, &conn, ses);
        if (err)
                warn_no_callback_path(clp, err);
 }

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 956174f..290370b 100644 (file)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -642,6 +642,7 @@ static void nfsd4_conn_lost(struct svc_xpt_user *u)
                free_conn(c);
        }
        spin_unlock(&clp->cl_lock);
+       /* XXX: mark callback for update, probe callback */
 }
 
 static struct nfsd4_conn *alloc_conn(struct svc_rqst *rqstp, u32 flags)
@@ -790,16 +791,19 @@ static struct nfsd4_session *alloc_init_session(struct svc_rqst *rqstp, struct n
                free_session(&new->se_ref);
                return NULL;
        }
-       if (!clp->cl_cb_session && (cses->flags & SESSION4_BACK_CHAN)) {
+       if (cses->flags & SESSION4_BACK_CHAN) {
                struct sockaddr *sa = svc_addr(rqstp);
-
-               clp->cl_cb_session = new;
-               clp->cl_cb_conn.cb_xprt = rqstp->rq_xprt;
-               svc_xprt_get(rqstp->rq_xprt);
+               /*
+                * This is a little silly; with sessions there's no real
+                * use for the callback address.  Use the peer address
+                * as a reasonable default for now, but consider fixing
+                * the rpc client not to require an address in the
+                * future:
+                */
                rpc_copy_addr((struct sockaddr *)&clp->cl_cb_conn.cb_addr, sa);
                clp->cl_cb_conn.cb_addrlen = svc_addr_len(sa);
-               nfsd4_probe_callback(clp);
        }
+       nfsd4_probe_callback(clp);
        return new;
 }