3 files changed, 64 insertions, 0 deletions

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index f31175717c1a..25a09069e458 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -501,6 +501,67 @@ nfsd4_probe_callback(struct nfs4_client *clp)
         do_probe_callback(clp);
 }
 
+/*
+ * There's currently a single callback channel slot.
+ * If the slot is available, then mark it busy.  Otherwise, set the
+ * thread for sleeping on the callback RPC wait queue.
+ */
+static int nfsd41_cb_setup_sequence(struct nfs4_client *clp,
+                struct rpc_task *task)
+{
+        struct nfs4_rpc_args *args = task->tk_msg.rpc_argp;
+        u32 *ptr = (u32 *)clp->cl_sessionid.data;
+        int status = 0;
+
+        dprintk("%s: %u:%u:%u:%u\n", __func__,
+                ptr[0], ptr[1], ptr[2], ptr[3]);
+
+        if (test_and_set_bit(0, &clp->cl_cb_slot_busy) != 0) {
+                rpc_sleep_on(&clp->cl_cb_waitq, task, NULL);
+                dprintk("%s slot is busy\n", __func__);
+                status = -EAGAIN;
+                goto out;
+        }
+
+        /*
+         * We'll need the clp during XDR encoding and decoding,
+         * and the sequence during decoding to verify the reply
+         */
+        args->args_seq.cbs_clp = clp;
+        task->tk_msg.rpc_resp = &args->args_seq;
+
+out:
+        dprintk("%s status=%d\n", __func__, status);
+        return status;
+}
+
+/*
+ * TODO: cb_sequence should support referring call lists, cachethis, multiple
+ * slots, and mark callback channel down on communication errors.
+ */
+static void nfsd4_cb_prepare(struct rpc_task *task, void *calldata)
+{
+        struct nfs4_delegation *dp = calldata;
+        struct nfs4_client *clp = dp->dl_client;
+        struct nfs4_rpc_args *args = task->tk_msg.rpc_argp;
+        u32 minorversion = clp->cl_cb_conn.cb_minorversion;
+        int status = 0;
+
+        args->args_seq.cbs_minorversion = minorversion;
+        if (minorversion) {
+                status = nfsd41_cb_setup_sequence(clp, task);
+                if (status) {
+                        if (status != -EAGAIN) {
+                                /* terminate rpc task */
+                                task->tk_status = status;
+                                task->tk_action = NULL;
+                        }
+                        return;
+                }
+        }
+        rpc_call_start(task);
+}
+
 static void nfsd4_cb_recall_done(struct rpc_task *task, void *calldata)
 {
         struct nfs4_delegation *dp = calldata;
@@ -540,6 +601,7 @@ static void nfsd4_cb_recall_release(void *calldata)
 }
 
 static const struct rpc_call_ops nfsd4_cb_recall_ops = {
+        .rpc_call_prepare = nfsd4_cb_prepare,
         .rpc_call_done = nfsd4_cb_recall_done,
         .rpc_release = nfsd4_cb_recall_release,
 };
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index f4cebd9016bc..76b7bcbb3f20 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1331,6 +1331,7 @@ nfsd4_create_session(struct svc_rqst *rqstp,
                         unconf->cl_cb_conn.cb_minorversion =
                                 cstate->minorversion;
                         unconf->cl_cb_conn.cb_prog = cr_ses->callback_prog;
+                        unconf->cl_cb_seq_nr = 1;
                         nfsd4_probe_callback(unconf);
                 }
                 conf = unconf;
diff --git a/include/linux/nfsd/state.h b/include/linux/nfsd/state.h
index 9cc40a137c34..b38d11324189 100644
--- a/include/linux/nfsd/state.h
+++ b/include/linux/nfsd/state.h
@@ -221,6 +221,7 @@ struct nfs4_client {
         /* for nfs41 callbacks */
         /* We currently support a single back channel with a single slot */
         unsigned long           cl_cb_slot_busy;
+        u32                     cl_cb_seq_nr;
         struct svc_xprt         *cl_cb_xprt;    /* 4.1 callback transport */
         struct rpc_wait_queue   cl_cb_waitq;    /* backchannel callers may */
                                                 /* wait here for slots */