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>

1 files changed, 20 insertions, 9 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;