nfsd4: allow 4.0 clients to change callback path

The rfc allows a client to change the callback parameters, but we didn't
previously implement it.

Teach the callbacks to rerun themselves (by placing themselves on a
workqueue) when they recognize that their rpc task has been killed and
that the callback connection has changed.

Then we can change the callback connection by setting up a new rpc
client, modifying the nfs4 client to point at it, waiting for any work
in progress to complete, and then shutting down the old client.

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

3 files changed, 24 insertions, 14 deletions

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index d6c46a9de422..ea77aa63754a 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -457,9 +457,8 @@ static int max_cb_time(void)
 /* Reference counting, callback cleanup, etc., all look racy as heck.
  * And why is cl_cb_set an atomic? */
 
-int setup_callback_client(struct nfs4_client *clp)
+int setup_callback_client(struct nfs4_client *clp, struct nfs4_cb_conn *cb)
 {
-        struct nfs4_cb_conn *cb = &clp->cl_cb_conn;
         struct rpc_timeout      timeparms = {
                 .to_initval     = max_cb_time(),
                 .to_retries     = 0,
@@ -481,7 +480,7 @@ int setup_callback_client(struct nfs4_client *clp)
         if (!clp->cl_principal && (clp->cl_flavor >= RPC_AUTH_GSS_KRB5))
                 return -EINVAL;
         if (cb->cb_minorversion) {
-                args.bc_xprt = clp->cl_cb_conn.cb_xprt;
+                args.bc_xprt = cb->cb_xprt;
                 args.protocol = XPRT_TRANSPORT_BC_TCP;
         }
         /* Create RPC client */
@@ -491,7 +490,7 @@ int setup_callback_client(struct nfs4_client *clp)
                         PTR_ERR(client));
                 return PTR_ERR(client);
         }
-        clp->cl_cb_client = client;
+        nfsd4_set_callback_client(clp, client);
         return 0;
 
 }
@@ -548,14 +547,13 @@ void do_probe_callback(struct nfs4_client *clp)
 /*
  * Set up the callback client and put a NFSPROC4_CB_NULL on the wire...
  */
-void
-nfsd4_probe_callback(struct nfs4_client *clp)
+void nfsd4_probe_callback(struct nfs4_client *clp, struct nfs4_cb_conn *cb)
 {
         int status;
 
         BUG_ON(atomic_read(&clp->cl_cb_set));
 
-        status = setup_callback_client(clp);
+        status = setup_callback_client(clp, cb);
         if (status) {
                 warn_no_callback_path(clp, status);
                 return;
@@ -645,18 +643,32 @@ static void nfsd4_cb_done(struct rpc_task *task, void *calldata)
         }
 }
 
+
 static void nfsd4_cb_recall_done(struct rpc_task *task, void *calldata)
 {
         struct nfs4_delegation *dp = calldata;
         struct nfs4_client *clp = dp->dl_client;
+        struct rpc_clnt *current_rpc_client = clp->cl_cb_client;
 
         nfsd4_cb_done(task, calldata);
 
+        if (current_rpc_client == NULL) {
+                /* We're shutting down; give up. */
+                /* XXX: err, or is it ok just to fall through
+                 * and rpc_restart_call? */
+                return;
+        }
+
         switch (task->tk_status) {
         case -EIO:
                 /* Network partition? */
                 atomic_set(&clp->cl_cb_set, 0);
                 warn_no_callback_path(clp, task->tk_status);
+                if (current_rpc_client != task->tk_client) {
+                        /* queue a callback on the new connection: */
+                        nfsd4_cb_recall(dp);
+                        return;
+                }
         case -EBADHANDLE:
         case -NFS4ERR_BAD_STATEID:
                 /* Race: client probably got cb_recall
@@ -705,8 +717,7 @@ void nfsd4_destroy_callback_queue(void)
         destroy_workqueue(callback_wq);
 }
 
-void nfsd4_set_callback_client(struct nfs4_client *clp, struct rpc_clnt
-*new)
+void nfsd4_set_callback_client(struct nfs4_client *clp, struct rpc_clnt *new)
 {
         struct rpc_clnt *old = clp->cl_cb_client;
 
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 59c9bd4c89e1..4300d9ffe95f 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1312,7 +1312,7 @@ nfsd4_create_session(struct svc_rqst *rqstp,
                                 cstate->minorversion;
                         unconf->cl_cb_conn.cb_prog = cr_ses->callback_prog;
                         unconf->cl_cb_seq_nr = 1;
-                        nfsd4_probe_callback(unconf);
+                        nfsd4_probe_callback(unconf, &unconf->cl_cb_conn);
                 }
                 conf = unconf;
         } else {
@@ -1605,9 +1605,8 @@ nfsd4_setclientid_confirm(struct svc_rqst *rqstp,
                 if (!same_creds(&conf->cl_cred, &unconf->cl_cred))
                         status = nfserr_clid_inuse;
                 else {
-                        /* XXX: We just turn off callbacks until we can handle
-                          * change request correctly. */
                         atomic_set(&conf->cl_cb_set, 0);
+                        nfsd4_probe_callback(conf, &unconf->cl_cb_conn);
                         expire_client(unconf);
                         status = nfs_ok;
 
@@ -1641,7 +1640,7 @@ nfsd4_setclientid_confirm(struct svc_rqst *rqstp,
                         }
                         move_to_confirmed(unconf);
                         conf = unconf;
-                        nfsd4_probe_callback(conf);
+                        nfsd4_probe_callback(conf, &conf->cl_cb_conn);
                         status = nfs_ok;
                 }
         } else if ((!conf || (conf && !same_verf(&conf->cl_confirm, &confirm)))
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index cf43812e6da5..98836fd87f69 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -390,7 +390,7 @@ extern int nfs4_in_grace(void);
 extern __be32 nfs4_check_open_reclaim(clientid_t *clid);
 extern void nfs4_free_stateowner(struct kref *kref);
 extern int set_callback_cred(void);
-extern void nfsd4_probe_callback(struct nfs4_client *clp);
+extern void nfsd4_probe_callback(struct nfs4_client *clp, struct nfs4_cb_conn *);
 extern void nfsd4_do_callback_rpc(struct work_struct *);
 extern void nfsd4_cb_recall(struct nfs4_delegation *dp);
 extern int nfsd4_create_callback_queue(void);