*/
 struct rpc_task *rpc_new_task(const struct rpc_task_setup *);
 struct rpc_task *rpc_run_task(const struct rpc_task_setup *);
+struct rpc_task *rpc_run_bc_task(struct rpc_rqst *req,
+                               const struct rpc_call_ops *ops);
 void           rpc_put_task(struct rpc_task *);
 void           rpc_exit_task(struct rpc_task *);
 void           rpc_release_calldata(const struct rpc_call_ops *, void *);
 
                                                /* buffer in use */
 #endif /* CONFIG_NFS_V4_1 */
 
+#if defined(CONFIG_NFS_V4_1)
+static inline int bc_prealloc(struct rpc_rqst *req)
+{
+       return test_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
+}
+#else
+static inline int bc_prealloc(struct rpc_rqst *req)
+{
+       return 0;
+}
+#endif /* CONFIG_NFS_V4_1 */
+
 struct xprt_create {
        int                     ident;          /* XPRT_TRANSPORT identifier */
        struct sockaddr *       srcaddr;        /* optional local address */
 
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/rpc_pipe_fs.h>
 #include <linux/sunrpc/metrics.h>
+#include <linux/sunrpc/bc_xprt.h>
 
+#include "sunrpc.h"
 
 #ifdef RPC_DEBUG
 # define RPCDBG_FACILITY       RPCDBG_CALL
 static void    call_bind(struct rpc_task *task);
 static void    call_bind_status(struct rpc_task *task);
 static void    call_transmit(struct rpc_task *task);
+#if defined(CONFIG_NFS_V4_1)
+static void    call_bc_transmit(struct rpc_task *task);
+#endif /* CONFIG_NFS_V4_1 */
 static void    call_status(struct rpc_task *task);
 static void    call_transmit_status(struct rpc_task *task);
 static void    call_refresh(struct rpc_task *task);
 }
 EXPORT_SYMBOL_GPL(rpc_call_async);
 
+#if defined(CONFIG_NFS_V4_1)
+/**
+ * rpc_run_bc_task - Allocate a new RPC task for backchannel use, then run
+ * rpc_execute against it
+ * @ops: RPC call ops
+ */
+struct rpc_task *rpc_run_bc_task(struct rpc_rqst *req,
+                                       const struct rpc_call_ops *tk_ops)
+{
+       struct rpc_task *task;
+       struct xdr_buf *xbufp = &req->rq_snd_buf;
+       struct rpc_task_setup task_setup_data = {
+               .callback_ops = tk_ops,
+       };
+
+       dprintk("RPC: rpc_run_bc_task req= %p\n", req);
+       /*
+        * Create an rpc_task to send the data
+        */
+       task = rpc_new_task(&task_setup_data);
+       if (!task) {
+               xprt_free_bc_request(req);
+               goto out;
+       }
+       task->tk_rqstp = req;
+
+       /*
+        * Set up the xdr_buf length.
+        * This also indicates that the buffer is XDR encoded already.
+        */
+       xbufp->len = xbufp->head[0].iov_len + xbufp->page_len +
+                       xbufp->tail[0].iov_len;
+
+       task->tk_action = call_bc_transmit;
+       atomic_inc(&task->tk_count);
+       BUG_ON(atomic_read(&task->tk_count) != 2);
+       rpc_execute(task);
+
+out:
+       dprintk("RPC: rpc_run_bc_task: task= %p\n", task);
+       return task;
+}
+#endif /* CONFIG_NFS_V4_1 */
+
 void
 rpc_call_start(struct rpc_task *task)
 {
         * in order to allow access to the socket to other RPC requests.
         */
        call_transmit_status(task);
-       if (task->tk_msg.rpc_proc->p_decode != NULL)
+       if (rpc_reply_expected(task))
                return;
        task->tk_action = rpc_exit_task;
        rpc_wake_up_queued_task(&task->tk_xprt->pending, task);
        }
 }
 
+#if defined(CONFIG_NFS_V4_1)
+/*
+ * 5b. Send the backchannel RPC reply.  On error, drop the reply.  In
+ * addition, disconnect on connectivity errors.
+ */
+static void
+call_bc_transmit(struct rpc_task *task)
+{
+       struct rpc_rqst *req = task->tk_rqstp;
+
+       BUG_ON(task->tk_status != 0);
+       task->tk_status = xprt_prepare_transmit(task);
+       if (task->tk_status == -EAGAIN) {
+               /*
+                * Could not reserve the transport. Try again after the
+                * transport is released.
+                */
+               task->tk_status = 0;
+               task->tk_action = call_bc_transmit;
+               return;
+       }
+
+       task->tk_action = rpc_exit_task;
+       if (task->tk_status < 0) {
+               printk(KERN_NOTICE "RPC: Could not send backchannel reply "
+                       "error: %d\n", task->tk_status);
+               return;
+       }
+
+       xprt_transmit(task);
+       xprt_end_transmit(task);
+       dprint_status(task);
+       switch (task->tk_status) {
+       case 0:
+               /* Success */
+               break;
+       case -EHOSTDOWN:
+       case -EHOSTUNREACH:
+       case -ENETUNREACH:
+       case -ETIMEDOUT:
+               /*
+                * Problem reaching the server.  Disconnect and let the
+                * forechannel reestablish the connection.  The server will
+                * have to retransmit the backchannel request and we'll
+                * reprocess it.  Since these ops are idempotent, there's no
+                * need to cache our reply at this time.
+                */
+               printk(KERN_NOTICE "RPC: Could not send backchannel reply "
+                       "error: %d\n", task->tk_status);
+               xprt_conditional_disconnect(task->tk_xprt,
+                       req->rq_connect_cookie);
+               break;
+       default:
+               /*
+                * We were unable to reply and will have to drop the
+                * request.  The server should reconnect and retransmit.
+                */
+               BUG_ON(task->tk_status == -EAGAIN);
+               printk(KERN_NOTICE "RPC: Could not send backchannel reply "
+                       "error: %d\n", task->tk_status);
+               break;
+       }
+       rpc_wake_up_queued_task(&req->rq_xprt->pending, task);
+}
+#endif /* CONFIG_NFS_V4_1 */
+
 /*
  * 6.  Sort out the RPC call status
  */
 
 void rpc_count_iostats(struct rpc_task *task)
 {
        struct rpc_rqst *req = task->tk_rqstp;
-       struct rpc_iostats *stats = task->tk_client->cl_metrics;
+       struct rpc_iostats *stats;
        struct rpc_iostats *op_metrics;
        long rtt, execute, queue;
 
-       if (!stats || !req)
+       if (!task->tk_client || !task->tk_client->cl_metrics || !req)
                return;
+
+       stats = task->tk_client->cl_metrics;
        op_metrics = &stats[task->tk_msg.rpc_proc->p_statidx];
 
        op_metrics->om_ops++;
 
--- /dev/null
+/******************************************************************************
+
+(c) 2008 NetApp.  All Rights Reserved.
+
+NetApp provides this source code under the GPL v2 License.
+The GPL v2 license is available at
+http://opensource.org/licenses/gpl-license.php.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+******************************************************************************/
+
+/*
+ * Functions and macros used internally by RPC
+ */
+
+#ifndef _NET_SUNRPC_SUNRPC_H
+#define _NET_SUNRPC_SUNRPC_H
+
+static inline int rpc_reply_expected(struct rpc_task *task)
+{
+       return (task->tk_msg.rpc_proc != NULL) &&
+               (task->tk_msg.rpc_proc->p_decode != NULL);
+}
+
+#endif /* _NET_SUNRPC_SUNRPC_H */
+
 
  *  -  Next, the caller puts together the RPC message, stuffs it into
  *     the request struct, and calls xprt_transmit().
  *  -  xprt_transmit sends the message and installs the caller on the
- *     transport's wait list. At the same time, it installs a timer that
- *     is run after the packet's timeout has expired.
+ *     transport's wait list. At the same time, if a reply is expected,
+ *     it installs a timer that is run after the packet's timeout has
+ *     expired.
  *  -  When a packet arrives, the data_ready handler walks the list of
  *     pending requests for that transport. If a matching XID is found, the
  *     caller is woken up, and the timer removed.
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/metrics.h>
 
+#include "sunrpc.h"
+
 /*
  * Local variables
  */
        dprintk("RPC: %5u xprt_transmit(%u)\n", task->tk_pid, req->rq_slen);
 
        if (!req->rq_received) {
-               if (list_empty(&req->rq_list)) {
+               if (list_empty(&req->rq_list) && rpc_reply_expected(task)) {
+                       /*
+                        * Add to the list only if we're expecting a reply
+                        */
                        spin_lock_bh(&xprt->transport_lock);
                        /* Update the softirq receive buffer */
                        memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
        /* Don't race with disconnect */
        if (!xprt_connected(xprt))
                task->tk_status = -ENOTCONN;
-       else if (!req->rq_received)
+       else if (!req->rq_received && rpc_reply_expected(task)) {
+               /*
+                * Sleep on the pending queue since
+                * we're expecting a reply.
+                */
                rpc_sleep_on(&xprt->pending, task, xprt_timer);
+       }
        spin_unlock_bh(&xprt->transport_lock);
 }
 
  */
 void xprt_release(struct rpc_task *task)
 {
-       struct rpc_xprt *xprt = task->tk_xprt;
+       struct rpc_xprt *xprt;
        struct rpc_rqst *req;
+       int is_bc_request;
 
        if (!(req = task->tk_rqstp))
                return;
+
+       /* Preallocated backchannel request? */
+       is_bc_request = bc_prealloc(req);
+
+       xprt = req->rq_xprt;
        rpc_count_iostats(task);
        spin_lock_bh(&xprt->transport_lock);
        xprt->ops->release_xprt(xprt, task);
                mod_timer(&xprt->timer,
                                xprt->last_used + xprt->idle_timeout);
        spin_unlock_bh(&xprt->transport_lock);
-       xprt->ops->buf_free(req->rq_buffer);
+       if (!bc_prealloc(req))
+               xprt->ops->buf_free(req->rq_buffer);
        task->tk_rqstp = NULL;
        if (req->rq_release_snd_buf)
                req->rq_release_snd_buf(req);
+
+       /*
+        * Early exit if this is a backchannel preallocated request.
+        * There is no need to have it added to the RPC slot list.
+        */
+       if (is_bc_request)
+               return;
+
        memset(req, 0, sizeof(*req));   /* mark unused */
 
        dprintk("RPC: %5u release request %p\n", task->tk_pid, req);