Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c56c65fb67d6461f6059dd83b1750a1973a91185
Commit:     c56c65fb67d6461f6059dd83b1750a1973a91185
Parent:     e96018280cb36210f4c69663561825114a57e7e1
Author:     \"Talpey, Thomas\ <[EMAIL PROTECTED]>
AuthorDate: Mon Sep 10 13:51:18 2007 -0400
Committer:  Trond Myklebust <[EMAIL PROTECTED]>
CommitDate: Tue Oct 9 17:18:08 2007 -0400

    RPCRDMA: rpc rdma verbs interface implementation
    
    This implements the interface from rpcrdma to the RDMA verbs interface
    supported by Infniband and iWARP.
    
    Signed-off-by: Tom Talpey <[EMAIL PROTECTED]>
    Signed-off-by: James Lentini <[EMAIL PROTECTED]>
    Signed-off-by: Trond Myklebust <[EMAIL PROTECTED]>
---
 net/sunrpc/xprtrdma/verbs.c | 1663 ++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 1626 insertions(+), 37 deletions(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
dissimilarity index 97%
index 0baf533..9ec8ca4 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1,37 +1,1626 @@
-/*
- * Placeholders for subsequent patches
- */
-
-#include "xprt_rdma.h"
-
-int rpcrdma_ia_open(struct rpcrdma_xprt *a, struct sockaddr *b, int c)
-{ return EINVAL; }
-void rpcrdma_ia_close(struct rpcrdma_ia *a) { }
-int rpcrdma_ep_create(struct rpcrdma_ep *a, struct rpcrdma_ia *b,
-struct rpcrdma_create_data_internal *c) { return EINVAL; }
-int rpcrdma_ep_destroy(struct rpcrdma_ep *a, struct rpcrdma_ia *b)
-{ return EINVAL; }
-int rpcrdma_ep_connect(struct rpcrdma_ep *a, struct rpcrdma_ia *b)
-{ return EINVAL; }
-int rpcrdma_ep_disconnect(struct rpcrdma_ep *a, struct rpcrdma_ia *b)
-{ return EINVAL; }
-int rpcrdma_ep_post(struct rpcrdma_ia *a, struct rpcrdma_ep *b,
-struct rpcrdma_req *c) { return EINVAL; }
-int rpcrdma_ep_post_recv(struct rpcrdma_ia *a, struct rpcrdma_ep *b,
-struct rpcrdma_rep *c) { return EINVAL; }
-int rpcrdma_buffer_create(struct rpcrdma_buffer *a, struct rpcrdma_ep *b,
-struct rpcrdma_ia *c, struct rpcrdma_create_data_internal *d) { return EINVAL; 
}
-void rpcrdma_buffer_destroy(struct rpcrdma_buffer *a) { }
-struct rpcrdma_req *rpcrdma_buffer_get(struct rpcrdma_buffer *a)
-{ return NULL; }
-void rpcrdma_buffer_put(struct rpcrdma_req *a) { }
-void rpcrdma_recv_buffer_get(struct rpcrdma_req *a) { }
-void rpcrdma_recv_buffer_put(struct rpcrdma_rep *a) { }
-int rpcrdma_register_internal(struct rpcrdma_ia *a, void *b, int c,
-struct ib_mr **d, struct ib_sge *e) { return EINVAL; }
-int rpcrdma_deregister_internal(struct rpcrdma_ia *a, struct ib_mr *b,
-struct ib_sge *c) { return EINVAL; }
-int rpcrdma_register_external(struct rpcrdma_mr_seg *a, int b, int c,
-struct rpcrdma_xprt *d) { return EINVAL; }
-int rpcrdma_deregister_external(struct rpcrdma_mr_seg *a,
-struct rpcrdma_xprt *b, void *c) { return EINVAL; }
+/*
+ * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the BSD-type
+ * license below:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *      Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *
+ *      Redistributions in binary form must reproduce the above
+ *      copyright notice, this list of conditions and the following
+ *      disclaimer in the documentation and/or other materials provided
+ *      with the distribution.
+ *
+ *      Neither the name of the Network Appliance, Inc. nor the names of
+ *      its contributors may be used to endorse or promote products
+ *      derived from this software without specific prior written
+ *      permission.
+ *
+ * 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.
+ */
+
+/*
+ * verbs.c
+ *
+ * Encapsulates the major functions managing:
+ *  o adapters
+ *  o endpoints
+ *  o connections
+ *  o buffer memory
+ */
+
+#include <linux/pci.h> /* for Tavor hack below */
+
+#include "xprt_rdma.h"
+
+/*
+ * Globals/Macros
+ */
+
+#ifdef RPC_DEBUG
+# define RPCDBG_FACILITY       RPCDBG_TRANS
+#endif
+
+/*
+ * internal functions
+ */
+
+/*
+ * handle replies in tasklet context, using a single, global list
+ * rdma tasklet function -- just turn around and call the func
+ * for all replies on the list
+ */
+
+static DEFINE_SPINLOCK(rpcrdma_tk_lock_g);
+static LIST_HEAD(rpcrdma_tasklets_g);
+
+static void
+rpcrdma_run_tasklet(unsigned long data)
+{
+       struct rpcrdma_rep *rep;
+       void (*func)(struct rpcrdma_rep *);
+       unsigned long flags;
+
+       data = data;
+       spin_lock_irqsave(&rpcrdma_tk_lock_g, flags);
+       while (!list_empty(&rpcrdma_tasklets_g)) {
+               rep = list_entry(rpcrdma_tasklets_g.next,
+                                struct rpcrdma_rep, rr_list);
+               list_del(&rep->rr_list);
+               func = rep->rr_func;
+               rep->rr_func = NULL;
+               spin_unlock_irqrestore(&rpcrdma_tk_lock_g, flags);
+
+               if (func)
+                       func(rep);
+               else
+                       rpcrdma_recv_buffer_put(rep);
+
+               spin_lock_irqsave(&rpcrdma_tk_lock_g, flags);
+       }
+       spin_unlock_irqrestore(&rpcrdma_tk_lock_g, flags);
+}
+
+static DECLARE_TASKLET(rpcrdma_tasklet_g, rpcrdma_run_tasklet, 0UL);
+
+static inline void
+rpcrdma_schedule_tasklet(struct rpcrdma_rep *rep)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&rpcrdma_tk_lock_g, flags);
+       list_add_tail(&rep->rr_list, &rpcrdma_tasklets_g);
+       spin_unlock_irqrestore(&rpcrdma_tk_lock_g, flags);
+       tasklet_schedule(&rpcrdma_tasklet_g);
+}
+
+static void
+rpcrdma_qp_async_error_upcall(struct ib_event *event, void *context)
+{
+       struct rpcrdma_ep *ep = context;
+
+       dprintk("RPC:       %s: QP error %X on device %s ep %p\n",
+               __func__, event->event, event->device->name, context);
+       if (ep->rep_connected == 1) {
+               ep->rep_connected = -EIO;
+               ep->rep_func(ep);
+               wake_up_all(&ep->rep_connect_wait);
+       }
+}
+
+static void
+rpcrdma_cq_async_error_upcall(struct ib_event *event, void *context)
+{
+       struct rpcrdma_ep *ep = context;
+
+       dprintk("RPC:       %s: CQ error %X on device %s ep %p\n",
+               __func__, event->event, event->device->name, context);
+       if (ep->rep_connected == 1) {
+               ep->rep_connected = -EIO;
+               ep->rep_func(ep);
+               wake_up_all(&ep->rep_connect_wait);
+       }
+}
+
+static inline
+void rpcrdma_event_process(struct ib_wc *wc)
+{
+       struct rpcrdma_rep *rep =
+                       (struct rpcrdma_rep *)(unsigned long) wc->wr_id;
+
+       dprintk("RPC:       %s: event rep %p status %X opcode %X length %u\n",
+               __func__, rep, wc->status, wc->opcode, wc->byte_len);
+
+       if (!rep) /* send or bind completion that we don't care about */
+               return;
+
+       if (IB_WC_SUCCESS != wc->status) {
+               dprintk("RPC:       %s: %s WC status %X, connection lost\n",
+                       __func__, (wc->opcode & IB_WC_RECV) ? "recv" : "send",
+                        wc->status);
+               rep->rr_len = ~0U;
+               rpcrdma_schedule_tasklet(rep);
+               return;
+       }
+
+       switch (wc->opcode) {
+       case IB_WC_RECV:
+               rep->rr_len = wc->byte_len;
+               ib_dma_sync_single_for_cpu(
+                       rdmab_to_ia(rep->rr_buffer)->ri_id->device,
+                       rep->rr_iov.addr, rep->rr_len, DMA_FROM_DEVICE);
+               /* Keep (only) the most recent credits, after check validity */
+               if (rep->rr_len >= 16) {
+                       struct rpcrdma_msg *p =
+                                       (struct rpcrdma_msg *) rep->rr_base;
+                       unsigned int credits = ntohl(p->rm_credit);
+                       if (credits == 0) {
+                               dprintk("RPC:       %s: server"
+                                       " dropped credits to 0!\n", __func__);
+                               /* don't deadlock */
+                               credits = 1;
+                       } else if (credits > rep->rr_buffer->rb_max_requests) {
+                               dprintk("RPC:       %s: server"
+                                       " over-crediting: %d (%d)\n",
+                                       __func__, credits,
+                                       rep->rr_buffer->rb_max_requests);
+                               credits = rep->rr_buffer->rb_max_requests;
+                       }
+                       atomic_set(&rep->rr_buffer->rb_credits, credits);
+               }
+               /* fall through */
+       case IB_WC_BIND_MW:
+               rpcrdma_schedule_tasklet(rep);
+               break;
+       default:
+               dprintk("RPC:       %s: unexpected WC event %X\n",
+                       __func__, wc->opcode);
+               break;
+       }
+}
+
+static inline int
+rpcrdma_cq_poll(struct ib_cq *cq)
+{
+       struct ib_wc wc;
+       int rc;
+
+       for (;;) {
+               rc = ib_poll_cq(cq, 1, &wc);
+               if (rc < 0) {
+                       dprintk("RPC:       %s: ib_poll_cq failed %i\n",
+                               __func__, rc);
+                       return rc;
+               }
+               if (rc == 0)
+                       break;
+
+               rpcrdma_event_process(&wc);
+       }
+
+       return 0;
+}
+
+/*
+ * rpcrdma_cq_event_upcall
+ *
+ * This upcall handles recv, send, bind and unbind events.
+ * It is reentrant but processes single events in order to maintain
+ * ordering of receives to keep server credits.
+ *
+ * It is the responsibility of the scheduled tasklet to return
+ * recv buffers to the pool. NOTE: this affects synchronization of
+ * connection shutdown. That is, the structures required for
+ * the completion of the reply handler must remain intact until
+ * all memory has been reclaimed.
+ *
+ * Note that send events are suppressed and do not result in an upcall.
+ */
+static void
+rpcrdma_cq_event_upcall(struct ib_cq *cq, void *context)
+{
+       int rc;
+
+       rc = rpcrdma_cq_poll(cq);
+       if (rc)
+               return;
+
+       rc = ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
+       if (rc) {
+               dprintk("RPC:       %s: ib_req_notify_cq failed %i\n",
+                       __func__, rc);
+               return;
+       }
+
+       rpcrdma_cq_poll(cq);
+}
+
+#ifdef RPC_DEBUG
+static const char * const conn[] = {
+       "address resolved",
+       "address error",
+       "route resolved",
+       "route error",
+       "connect request",
+       "connect response",
+       "connect error",
+       "unreachable",
+       "rejected",
+       "established",
+       "disconnected",
+       "device removal"
+};
+#endif
+
+static int
+rpcrdma_conn_upcall(struct rdma_cm_id *id, struct rdma_cm_event *event)
+{
+       struct rpcrdma_xprt *xprt = id->context;
+       struct rpcrdma_ia *ia = &xprt->rx_ia;
+       struct rpcrdma_ep *ep = &xprt->rx_ep;
+       struct sockaddr_in *addr = (struct sockaddr_in *) &ep->rep_remote_addr;
+       struct ib_qp_attr attr;
+       struct ib_qp_init_attr iattr;
+       int connstate = 0;
+
+       switch (event->event) {
+       case RDMA_CM_EVENT_ADDR_RESOLVED:
+       case RDMA_CM_EVENT_ROUTE_RESOLVED:
+               complete(&ia->ri_done);
+               break;
+       case RDMA_CM_EVENT_ADDR_ERROR:
+               ia->ri_async_rc = -EHOSTUNREACH;
+               dprintk("RPC:       %s: CM address resolution error, ep 0x%p\n",
+                       __func__, ep);
+               complete(&ia->ri_done);
+               break;
+       case RDMA_CM_EVENT_ROUTE_ERROR:
+               ia->ri_async_rc = -ENETUNREACH;
+               dprintk("RPC:       %s: CM route resolution error, ep 0x%p\n",
+                       __func__, ep);
+               complete(&ia->ri_done);
+               break;
+       case RDMA_CM_EVENT_ESTABLISHED:
+               connstate = 1;
+               ib_query_qp(ia->ri_id->qp, &attr,
+                       IB_QP_MAX_QP_RD_ATOMIC | IB_QP_MAX_DEST_RD_ATOMIC,
+                       &iattr);
+               dprintk("RPC:       %s: %d responder resources"
+                       " (%d initiator)\n",
+                       __func__, attr.max_dest_rd_atomic, attr.max_rd_atomic);
+               goto connected;
+       case RDMA_CM_EVENT_CONNECT_ERROR:
+               connstate = -ENOTCONN;
+               goto connected;
+       case RDMA_CM_EVENT_UNREACHABLE:
+               connstate = -ENETDOWN;
+               goto connected;
+       case RDMA_CM_EVENT_REJECTED:
+               connstate = -ECONNREFUSED;
+               goto connected;
+       case RDMA_CM_EVENT_DISCONNECTED:
+               connstate = -ECONNABORTED;
+               goto connected;
+       case RDMA_CM_EVENT_DEVICE_REMOVAL:
+               connstate = -ENODEV;
+connected:
+               dprintk("RPC:       %s: %s: %u.%u.%u.%u:%u"
+                       " (ep 0x%p event 0x%x)\n",
+                       __func__,
+                       (event->event <= 11) ? conn[event->event] :
+                                               "unknown connection error",
+                       NIPQUAD(addr->sin_addr.s_addr),
+                       ntohs(addr->sin_port),
+                       ep, event->event);
+               atomic_set(&rpcx_to_rdmax(ep->rep_xprt)->rx_buf.rb_credits, 1);
+               dprintk("RPC:       %s: %sconnected\n",
+                                       __func__, connstate > 0 ? "" : "dis");
+               ep->rep_connected = connstate;
+               ep->rep_func(ep);
+               wake_up_all(&ep->rep_connect_wait);
+               break;
+       default:
+               ia->ri_async_rc = -EINVAL;
+               dprintk("RPC:       %s: unexpected CM event %X\n",
+                       __func__, event->event);
+               complete(&ia->ri_done);
+               break;
+       }
+
+       return 0;
+}
+
+static struct rdma_cm_id *
+rpcrdma_create_id(struct rpcrdma_xprt *xprt,
+                       struct rpcrdma_ia *ia, struct sockaddr *addr)
+{
+       struct rdma_cm_id *id;
+       int rc;
+
+       id = rdma_create_id(rpcrdma_conn_upcall, xprt, RDMA_PS_TCP);
+       if (IS_ERR(id)) {
+               rc = PTR_ERR(id);
+               dprintk("RPC:       %s: rdma_create_id() failed %i\n",
+                       __func__, rc);
+               return id;
+       }
+
+       ia->ri_async_rc = 0;
+       rc = rdma_resolve_addr(id, NULL, addr, RDMA_RESOLVE_TIMEOUT);
+       if (rc) {
+               dprintk("RPC:       %s: rdma_resolve_addr() failed %i\n",
+                       __func__, rc);
+               goto out;
+       }
+       wait_for_completion(&ia->ri_done);
+       rc = ia->ri_async_rc;
+       if (rc)
+               goto out;
+
+       ia->ri_async_rc = 0;
+       rc = rdma_resolve_route(id, RDMA_RESOLVE_TIMEOUT);
+       if (rc) {
+               dprintk("RPC:       %s: rdma_resolve_route() failed %i\n",
+                       __func__, rc);
+               goto out;
+       }
+       wait_for_completion(&ia->ri_done);
+       rc = ia->ri_async_rc;
+       if (rc)
+               goto out;
+
+       return id;
+
+out:
+       rdma_destroy_id(id);
+       return ERR_PTR(rc);
+}
+
+/*
+ * Drain any cq, prior to teardown.
+ */
+static void
+rpcrdma_clean_cq(struct ib_cq *cq)
+{
+       struct ib_wc wc;
+       int count = 0;
+
+       while (1 == ib_poll_cq(cq, 1, &wc))
+               ++count;
+
+       if (count)
+               dprintk("RPC:       %s: flushed %d events (last 0x%x)\n",
+                       __func__, count, wc.opcode);
+}
+
+/*
+ * Exported functions.
+ */
+
+/*
+ * Open and initialize an Interface Adapter.
+ *  o initializes fields of struct rpcrdma_ia, including
+ *    interface and provider attributes and protection zone.
+ */
+int
+rpcrdma_ia_open(struct rpcrdma_xprt *xprt, struct sockaddr *addr, int memreg)
+{
+       int rc;
+       struct rpcrdma_ia *ia = &xprt->rx_ia;
+
+       init_completion(&ia->ri_done);
+
+       ia->ri_id = rpcrdma_create_id(xprt, ia, addr);
+       if (IS_ERR(ia->ri_id)) {
+               rc = PTR_ERR(ia->ri_id);
+               goto out1;
+       }
+
+       ia->ri_pd = ib_alloc_pd(ia->ri_id->device);
+       if (IS_ERR(ia->ri_pd)) {
+               rc = PTR_ERR(ia->ri_pd);
+               dprintk("RPC:       %s: ib_alloc_pd() failed %i\n",
+                       __func__, rc);
+               goto out2;
+       }
+
+       /*
+        * Optionally obtain an underlying physical identity mapping in
+        * order to do a memory window-based bind. This base registration
+        * is protected from remote access - that is enabled only by binding
+        * for the specific bytes targeted during each RPC operation, and
+        * revoked after the corresponding completion similar to a storage
+        * adapter.
+        */
+       if (memreg > RPCRDMA_REGISTER) {
+               int mem_priv = IB_ACCESS_LOCAL_WRITE;
+               switch (memreg) {
+#if RPCRDMA_PERSISTENT_REGISTRATION
+               case RPCRDMA_ALLPHYSICAL:
+                       mem_priv |= IB_ACCESS_REMOTE_WRITE;
+                       mem_priv |= IB_ACCESS_REMOTE_READ;
+                       break;
+#endif
+               case RPCRDMA_MEMWINDOWS_ASYNC:
+               case RPCRDMA_MEMWINDOWS:
+                       mem_priv |= IB_ACCESS_MW_BIND;
+                       break;
+               default:
+                       break;
+               }
+               ia->ri_bind_mem = ib_get_dma_mr(ia->ri_pd, mem_priv);
+               if (IS_ERR(ia->ri_bind_mem)) {
+                       printk(KERN_ALERT "%s: ib_get_dma_mr for "
+                               "phys register failed with %lX\n\t"
+                               "Will continue with degraded performance\n",
+                               __func__, PTR_ERR(ia->ri_bind_mem));
+                       memreg = RPCRDMA_REGISTER;
+                       ia->ri_bind_mem = NULL;
+               }
+       }
+
+       /* Else will do memory reg/dereg for each chunk */
+       ia->ri_memreg_strategy = memreg;
+
+       return 0;
+out2:
+       rdma_destroy_id(ia->ri_id);
+out1:
+       return rc;
+}
+
+/*
+ * Clean up/close an IA.
+ *   o if event handles and PD have been initialized, free them.
+ *   o close the IA
+ */
+void
+rpcrdma_ia_close(struct rpcrdma_ia *ia)
+{
+       int rc;
+
+       dprintk("RPC:       %s: entering\n", __func__);
+       if (ia->ri_bind_mem != NULL) {
+               rc = ib_dereg_mr(ia->ri_bind_mem);
+               dprintk("RPC:       %s: ib_dereg_mr returned %i\n",
+                       __func__, rc);
+       }
+       if (ia->ri_id != NULL && !IS_ERR(ia->ri_id) && ia->ri_id->qp)
+               rdma_destroy_qp(ia->ri_id);
+       if (ia->ri_pd != NULL && !IS_ERR(ia->ri_pd)) {
+               rc = ib_dealloc_pd(ia->ri_pd);
+               dprintk("RPC:       %s: ib_dealloc_pd returned %i\n",
+                       __func__, rc);
+       }
+       if (ia->ri_id != NULL && !IS_ERR(ia->ri_id))
+               rdma_destroy_id(ia->ri_id);
+}
+
+/*
+ * Create unconnected endpoint.
+ */
+int
+rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
+                               struct rpcrdma_create_data_internal *cdata)
+{
+       struct ib_device_attr devattr;
+       int rc;
+
+       rc = ib_query_device(ia->ri_id->device, &devattr);
+       if (rc) {
+               dprintk("RPC:       %s: ib_query_device failed %d\n",
+                       __func__, rc);
+               return rc;
+       }
+
+       /* check provider's send/recv wr limits */
+       if (cdata->max_requests > devattr.max_qp_wr)
+               cdata->max_requests = devattr.max_qp_wr;
+
+       ep->rep_attr.event_handler = rpcrdma_qp_async_error_upcall;
+       ep->rep_attr.qp_context = ep;
+       /* send_cq and recv_cq initialized below */
+       ep->rep_attr.srq = NULL;
+       ep->rep_attr.cap.max_send_wr = cdata->max_requests;
+       switch (ia->ri_memreg_strategy) {
+       case RPCRDMA_MEMWINDOWS_ASYNC:
+       case RPCRDMA_MEMWINDOWS:
+               /* Add room for mw_binds+unbinds - overkill! */
+               ep->rep_attr.cap.max_send_wr++;
+               ep->rep_attr.cap.max_send_wr *= (2 * RPCRDMA_MAX_SEGS);
+               if (ep->rep_attr.cap.max_send_wr > devattr.max_qp_wr)
+                       return -EINVAL;
+               break;
+       default:
+               break;
+       }
+       ep->rep_attr.cap.max_recv_wr = cdata->max_requests;
+       ep->rep_attr.cap.max_send_sge = (cdata->padding ? 4 : 2);
+       ep->rep_attr.cap.max_recv_sge = 1;
+       ep->rep_attr.cap.max_inline_data = 0;
+       ep->rep_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
+       ep->rep_attr.qp_type = IB_QPT_RC;
+       ep->rep_attr.port_num = ~0;
+
+       dprintk("RPC:       %s: requested max: dtos: send %d recv %d; "
+               "iovs: send %d recv %d\n",
+               __func__,
+               ep->rep_attr.cap.max_send_wr,
+               ep->rep_attr.cap.max_recv_wr,
+               ep->rep_attr.cap.max_send_sge,
+               ep->rep_attr.cap.max_recv_sge);
+
+       /* set trigger for requesting send completion */
+       ep->rep_cqinit = ep->rep_attr.cap.max_send_wr/2 /*  - 1*/;
+       switch (ia->ri_memreg_strategy) {
+       case RPCRDMA_MEMWINDOWS_ASYNC:
+       case RPCRDMA_MEMWINDOWS:
+               ep->rep_cqinit -= RPCRDMA_MAX_SEGS;
+               break;
+       default:
+               break;
+       }
+       if (ep->rep_cqinit <= 2)
+               ep->rep_cqinit = 0;
+       INIT_CQCOUNT(ep);
+       ep->rep_ia = ia;
+       init_waitqueue_head(&ep->rep_connect_wait);
+
+       /*
+        * Create a single cq for receive dto and mw_bind (only ever
+        * care about unbind, really). Send completions are suppressed.
+        * Use single threaded tasklet upcalls to maintain ordering.
+        */
+       ep->rep_cq = ib_create_cq(ia->ri_id->device, rpcrdma_cq_event_upcall,
+                                 rpcrdma_cq_async_error_upcall, NULL,
+                                 ep->rep_attr.cap.max_recv_wr +
+                                 ep->rep_attr.cap.max_send_wr + 1, 0);
+       if (IS_ERR(ep->rep_cq)) {
+               rc = PTR_ERR(ep->rep_cq);
+               dprintk("RPC:       %s: ib_create_cq failed: %i\n",
+                       __func__, rc);
+               goto out1;
+       }
+
+       rc = ib_req_notify_cq(ep->rep_cq, IB_CQ_NEXT_COMP);
+       if (rc) {
+               dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",
+                       __func__, rc);
+               goto out2;
+       }
+
+       ep->rep_attr.send_cq = ep->rep_cq;
+       ep->rep_attr.recv_cq = ep->rep_cq;
+
+       /* Initialize cma parameters */
+
+       /* RPC/RDMA does not use private data */
+       ep->rep_remote_cma.private_data = NULL;
+       ep->rep_remote_cma.private_data_len = 0;
+
+       /* Client offers RDMA Read but does not initiate */
+       switch (ia->ri_memreg_strategy) {
+       case RPCRDMA_BOUNCEBUFFERS:
+               ep->rep_remote_cma.responder_resources = 0;
+               break;
+       case RPCRDMA_MTHCAFMR:
+       case RPCRDMA_REGISTER:
+               ep->rep_remote_cma.responder_resources = cdata->max_requests *
+                               (RPCRDMA_MAX_DATA_SEGS / 8);
+               break;
+       case RPCRDMA_MEMWINDOWS:
+       case RPCRDMA_MEMWINDOWS_ASYNC:
+#if RPCRDMA_PERSISTENT_REGISTRATION
+       case RPCRDMA_ALLPHYSICAL:
+#endif
+               ep->rep_remote_cma.responder_resources = cdata->max_requests *
+                               (RPCRDMA_MAX_DATA_SEGS / 2);
+               break;
+       default:
+               break;
+       }
+       if (ep->rep_remote_cma.responder_resources > devattr.max_qp_rd_atom)
+               ep->rep_remote_cma.responder_resources = devattr.max_qp_rd_atom;
+       ep->rep_remote_cma.initiator_depth = 0;
+
+       ep->rep_remote_cma.retry_count = 7;
+       ep->rep_remote_cma.flow_control = 0;
+       ep->rep_remote_cma.rnr_retry_count = 0;
+
+       return 0;
+
+out2:
+       if (ib_destroy_cq(ep->rep_cq))
+               ;
+out1:
+       return rc;
+}
+
+/*
+ * rpcrdma_ep_destroy
+ *
+ * Disconnect and destroy endpoint. After this, the only
+ * valid operations on the ep are to free it (if dynamically
+ * allocated) or re-create it.
+ *
+ * The caller's error handling must be sure to not leak the endpoint
+ * if this function fails.
+ */
+int
+rpcrdma_ep_destroy(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
+{
+       int rc;
+
+       dprintk("RPC:       %s: entering, connected is %d\n",
+               __func__, ep->rep_connected);
+
+       if (ia->ri_id->qp) {
+               rc = rpcrdma_ep_disconnect(ep, ia);
+               if (rc)
+                       dprintk("RPC:       %s: rpcrdma_ep_disconnect"
+                               " returned %i\n", __func__, rc);
+       }
+
+       ep->rep_func = NULL;
+
+       /* padding - could be done in rpcrdma_buffer_destroy... */
+       if (ep->rep_pad_mr) {
+               rpcrdma_deregister_internal(ia, ep->rep_pad_mr, &ep->rep_pad);
+               ep->rep_pad_mr = NULL;
+       }
+
+       if (ia->ri_id->qp) {
+               rdma_destroy_qp(ia->ri_id);
+               ia->ri_id->qp = NULL;
+       }
+
+       rpcrdma_clean_cq(ep->rep_cq);
+       rc = ib_destroy_cq(ep->rep_cq);
+       if (rc)
+               dprintk("RPC:       %s: ib_destroy_cq returned %i\n",
+                       __func__, rc);
+
+       return rc;
+}
+
+/*
+ * Connect unconnected endpoint.
+ */
+int
+rpcrdma_ep_connect(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
+{
+       struct rdma_cm_id *id;
+       int rc = 0;
+       int retry_count = 0;
+       int reconnect = (ep->rep_connected != 0);
+
+       if (reconnect) {
+               struct rpcrdma_xprt *xprt;
+retry:
+               rc = rpcrdma_ep_disconnect(ep, ia);
+               if (rc && rc != -ENOTCONN)
+                       dprintk("RPC:       %s: rpcrdma_ep_disconnect"
+                               " status %i\n", __func__, rc);
+               rpcrdma_clean_cq(ep->rep_cq);
+
+               xprt = container_of(ia, struct rpcrdma_xprt, rx_ia);
+               id = rpcrdma_create_id(xprt, ia,
+                               (struct sockaddr *)&xprt->rx_data.addr);
+               if (IS_ERR(id)) {
+                       rc = PTR_ERR(id);
+                       goto out;
+               }
+               /* TEMP TEMP TEMP - fail if new device:
+                * Deregister/remarshal *all* requests!
+                * Close and recreate adapter, pd, etc!
+                * Re-determine all attributes still sane!
+                * More stuff I haven't thought of!
+                * Rrrgh!
+                */
+               if (ia->ri_id->device != id->device) {
+                       printk("RPC:       %s: can't reconnect on "
+                               "different device!\n", __func__);
+                       rdma_destroy_id(id);
+                       rc = -ENETDOWN;
+                       goto out;
+               }
+               /* END TEMP */
+               rdma_destroy_id(ia->ri_id);
+               ia->ri_id = id;
+       }
+
+       rc = rdma_create_qp(ia->ri_id, ia->ri_pd, &ep->rep_attr);
+       if (rc) {
+               dprintk("RPC:       %s: rdma_create_qp failed %i\n",
+                       __func__, rc);
+               goto out;
+       }
+
+/* XXX Tavor device performs badly with 2K MTU! */
+if (strnicmp(ia->ri_id->device->dma_device->bus->name, "pci", 3) == 0) {
+       struct pci_dev *pcid = to_pci_dev(ia->ri_id->device->dma_device);
+       if (pcid->device == PCI_DEVICE_ID_MELLANOX_TAVOR &&
+           (pcid->vendor == PCI_VENDOR_ID_MELLANOX ||
+            pcid->vendor == PCI_VENDOR_ID_TOPSPIN)) {
+               struct ib_qp_attr attr = {
+                       .path_mtu = IB_MTU_1024
+               };
+               rc = ib_modify_qp(ia->ri_id->qp, &attr, IB_QP_PATH_MTU);
+       }
+}
+
+       /* Theoretically a client initiator_depth > 0 is not needed,
+        * but many peers fail to complete the connection unless they
+        * == responder_resources! */
+       if (ep->rep_remote_cma.initiator_depth !=
+                               ep->rep_remote_cma.responder_resources)
+               ep->rep_remote_cma.initiator_depth =
+                       ep->rep_remote_cma.responder_resources;
+
+       ep->rep_connected = 0;
+
+       rc = rdma_connect(ia->ri_id, &ep->rep_remote_cma);
+       if (rc) {
+               dprintk("RPC:       %s: rdma_connect() failed with %i\n",
+                               __func__, rc);
+               goto out;
+       }
+
+       if (reconnect)
+               return 0;
+
+       wait_event_interruptible(ep->rep_connect_wait, ep->rep_connected != 0);
+
+       /*
+        * Check state. A non-peer reject indicates no listener
+        * (ECONNREFUSED), which may be a transient state. All
+        * others indicate a transport condition which has already
+        * undergone a best-effort.
+        */
+       if (ep->rep_connected == -ECONNREFUSED
+           && ++retry_count <= RDMA_CONNECT_RETRY_MAX) {
+               dprintk("RPC:       %s: non-peer_reject, retry\n", __func__);
+               goto retry;
+       }
+       if (ep->rep_connected <= 0) {
+               /* Sometimes, the only way to reliably connect to remote
+                * CMs is to use same nonzero values for ORD and IRD. */
+               ep->rep_remote_cma.initiator_depth =
+                                       ep->rep_remote_cma.responder_resources;
+               if (ep->rep_remote_cma.initiator_depth == 0)
+                       ++ep->rep_remote_cma.initiator_depth;
+               if (ep->rep_remote_cma.responder_resources == 0)
+                       ++ep->rep_remote_cma.responder_resources;
+               if (retry_count++ == 0)
+                       goto retry;
+               rc = ep->rep_connected;
+       } else {
+               dprintk("RPC:       %s: connected\n", __func__);
+       }
+
+out:
+       if (rc)
+               ep->rep_connected = rc;
+       return rc;
+}
+
+/*
+ * rpcrdma_ep_disconnect
+ *
+ * This is separate from destroy to facilitate the ability
+ * to reconnect without recreating the endpoint.
+ *
+ * This call is not reentrant, and must not be made in parallel
+ * on the same endpoint.
+ */
+int
+rpcrdma_ep_disconnect(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
+{
+       int rc;
+
+       rpcrdma_clean_cq(ep->rep_cq);
+       rc = rdma_disconnect(ia->ri_id);
+       if (!rc) {
+               /* returns without wait if not connected */
+               wait_event_interruptible(ep->rep_connect_wait,
+                                                       ep->rep_connected != 1);
+               dprintk("RPC:       %s: after wait, %sconnected\n", __func__,
+                       (ep->rep_connected == 1) ? "still " : "dis");
+       } else {
+               dprintk("RPC:       %s: rdma_disconnect %i\n", __func__, rc);
+               ep->rep_connected = rc;
+       }
+       return rc;
+}
+
+/*
+ * Initialize buffer memory
+ */
+int
+rpcrdma_buffer_create(struct rpcrdma_buffer *buf, struct rpcrdma_ep *ep,
+       struct rpcrdma_ia *ia, struct rpcrdma_create_data_internal *cdata)
+{
+       char *p;
+       size_t len;
+       int i, rc;
+
+       buf->rb_max_requests = cdata->max_requests;
+       spin_lock_init(&buf->rb_lock);
+       atomic_set(&buf->rb_credits, 1);
+
+       /* Need to allocate:
+        *   1.  arrays for send and recv pointers
+        *   2.  arrays of struct rpcrdma_req to fill in pointers
+        *   3.  array of struct rpcrdma_rep for replies
+        *   4.  padding, if any
+        *   5.  mw's, if any
+        * Send/recv buffers in req/rep need to be registered
+        */
+
+       len = buf->rb_max_requests *
+               (sizeof(struct rpcrdma_req *) + sizeof(struct rpcrdma_rep *));
+       len += cdata->padding;
+       switch (ia->ri_memreg_strategy) {
+       case RPCRDMA_MTHCAFMR:
+               /* TBD we are perhaps overallocating here */
+               len += (buf->rb_max_requests + 1) * RPCRDMA_MAX_SEGS *
+                               sizeof(struct rpcrdma_mw);
+               break;
+       case RPCRDMA_MEMWINDOWS_ASYNC:
+       case RPCRDMA_MEMWINDOWS:
+               len += (buf->rb_max_requests + 1) * RPCRDMA_MAX_SEGS *
+                               sizeof(struct rpcrdma_mw);
+               break;
+       default:
+               break;
+       }
+
+       /* allocate 1, 4 and 5 in one shot */
+       p = kzalloc(len, GFP_KERNEL);
+       if (p == NULL) {
+               dprintk("RPC:       %s: req_t/rep_t/pad kzalloc(%zd) failed\n",
+                       __func__, len);
+               rc = -ENOMEM;
+               goto out;
+       }
+       buf->rb_pool = p;       /* for freeing it later */
+
+       buf->rb_send_bufs = (struct rpcrdma_req **) p;
+       p = (char *) &buf->rb_send_bufs[buf->rb_max_requests];
+       buf->rb_recv_bufs = (struct rpcrdma_rep **) p;
+       p = (char *) &buf->rb_recv_bufs[buf->rb_max_requests];
+
+       /*
+        * Register the zeroed pad buffer, if any.
+        */
+       if (cdata->padding) {
+               rc = rpcrdma_register_internal(ia, p, cdata->padding,
+                                           &ep->rep_pad_mr, &ep->rep_pad);
+               if (rc)
+                       goto out;
+       }
+       p += cdata->padding;
+
+       /*
+        * Allocate the fmr's, or mw's for mw_bind chunk registration.
+        * We "cycle" the mw's in order to minimize rkey reuse,
+        * and also reduce unbind-to-bind collision.
+        */
+       INIT_LIST_HEAD(&buf->rb_mws);
+       switch (ia->ri_memreg_strategy) {
+       case RPCRDMA_MTHCAFMR:
+               {
+               struct rpcrdma_mw *r = (struct rpcrdma_mw *)p;
+               struct ib_fmr_attr fa = {
+                       RPCRDMA_MAX_DATA_SEGS, 1, PAGE_SHIFT
+               };
+               /* TBD we are perhaps overallocating here */
+               for (i = (buf->rb_max_requests+1) * RPCRDMA_MAX_SEGS; i; i--) {
+                       r->r.fmr = ib_alloc_fmr(ia->ri_pd,
+                               IB_ACCESS_REMOTE_WRITE | IB_ACCESS_REMOTE_READ,
+                               &fa);
+                       if (IS_ERR(r->r.fmr)) {
+                               rc = PTR_ERR(r->r.fmr);
+                               dprintk("RPC:       %s: ib_alloc_fmr"
+                                       " failed %i\n", __func__, rc);
+                               goto out;
+                       }
+                       list_add(&r->mw_list, &buf->rb_mws);
+                       ++r;
+               }
+               }
+               break;
+       case RPCRDMA_MEMWINDOWS_ASYNC:
+       case RPCRDMA_MEMWINDOWS:
+               {
+               struct rpcrdma_mw *r = (struct rpcrdma_mw *)p;
+               /* Allocate one extra request's worth, for full cycling */
+               for (i = (buf->rb_max_requests+1) * RPCRDMA_MAX_SEGS; i; i--) {
+                       r->r.mw = ib_alloc_mw(ia->ri_pd);
+                       if (IS_ERR(r->r.mw)) {
+                               rc = PTR_ERR(r->r.mw);
+                               dprintk("RPC:       %s: ib_alloc_mw"
+                                       " failed %i\n", __func__, rc);
+                               goto out;
+                       }
+                       list_add(&r->mw_list, &buf->rb_mws);
+                       ++r;
+               }
+               }
+               break;
+       default:
+               break;
+       }
+
+       /*
+        * Allocate/init the request/reply buffers. Doing this
+        * using kmalloc for now -- one for each buf.
+        */
+       for (i = 0; i < buf->rb_max_requests; i++) {
+               struct rpcrdma_req *req;
+               struct rpcrdma_rep *rep;
+
+               len = cdata->inline_wsize + sizeof(struct rpcrdma_req);
+               /* RPC layer requests *double* size + 1K RPC_SLACK_SPACE! */
+               /* Typical ~2400b, so rounding up saves work later */
+               if (len < 4096)
+                       len = 4096;
+               req = kmalloc(len, GFP_KERNEL);
+               if (req == NULL) {
+                       dprintk("RPC:       %s: request buffer %d alloc"
+                               " failed\n", __func__, i);
+                       rc = -ENOMEM;
+                       goto out;
+               }
+               memset(req, 0, sizeof(struct rpcrdma_req));
+               buf->rb_send_bufs[i] = req;
+               buf->rb_send_bufs[i]->rl_buffer = buf;
+
+               rc = rpcrdma_register_internal(ia, req->rl_base,
+                               len - offsetof(struct rpcrdma_req, rl_base),
+                               &buf->rb_send_bufs[i]->rl_handle,
+                               &buf->rb_send_bufs[i]->rl_iov);
+               if (rc)
+                       goto out;
+
+               buf->rb_send_bufs[i]->rl_size = len-sizeof(struct rpcrdma_req);
+
+               len = cdata->inline_rsize + sizeof(struct rpcrdma_rep);
+               rep = kmalloc(len, GFP_KERNEL);
+               if (rep == NULL) {
+                       dprintk("RPC:       %s: reply buffer %d alloc failed\n",
+                               __func__, i);
+                       rc = -ENOMEM;
+                       goto out;
+               }
+               memset(rep, 0, sizeof(struct rpcrdma_rep));
+               buf->rb_recv_bufs[i] = rep;
+               buf->rb_recv_bufs[i]->rr_buffer = buf;
+               init_waitqueue_head(&rep->rr_unbind);
+
+               rc = rpcrdma_register_internal(ia, rep->rr_base,
+                               len - offsetof(struct rpcrdma_rep, rr_base),
+                               &buf->rb_recv_bufs[i]->rr_handle,
+                               &buf->rb_recv_bufs[i]->rr_iov);
+               if (rc)
+                       goto out;
+
+       }
+       dprintk("RPC:       %s: max_requests %d\n",
+               __func__, buf->rb_max_requests);
+       /* done */
+       return 0;
+out:
+       rpcrdma_buffer_destroy(buf);
+       return rc;
+}
+
+/*
+ * Unregister and destroy buffer memory. Need to deal with
+ * partial initialization, so it's callable from failed create.
+ * Must be called before destroying endpoint, as registrations
+ * reference it.
+ */
+void
+rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
+{
+       int rc, i;
+       struct rpcrdma_ia *ia = rdmab_to_ia(buf);
+
+       /* clean up in reverse order from create
+        *   1.  recv mr memory (mr free, then kfree)
+        *   1a. bind mw memory
+        *   2.  send mr memory (mr free, then kfree)
+        *   3.  padding (if any) [moved to rpcrdma_ep_destroy]
+        *   4.  arrays
+        */
+       dprintk("RPC:       %s: entering\n", __func__);
+
+       for (i = 0; i < buf->rb_max_requests; i++) {
+               if (buf->rb_recv_bufs && buf->rb_recv_bufs[i]) {
+                       rpcrdma_deregister_internal(ia,
+                                       buf->rb_recv_bufs[i]->rr_handle,
+                                       &buf->rb_recv_bufs[i]->rr_iov);
+                       kfree(buf->rb_recv_bufs[i]);
+               }
+               if (buf->rb_send_bufs && buf->rb_send_bufs[i]) {
+                       while (!list_empty(&buf->rb_mws)) {
+                               struct rpcrdma_mw *r;
+                               r = list_entry(buf->rb_mws.next,
+                                       struct rpcrdma_mw, mw_list);
+                               list_del(&r->mw_list);
+                               switch (ia->ri_memreg_strategy) {
+                               case RPCRDMA_MTHCAFMR:
+                                       rc = ib_dealloc_fmr(r->r.fmr);
+                                       if (rc)
+                                               dprintk("RPC:       %s:"
+                                                       " ib_dealloc_fmr"
+                                                       " failed %i\n",
+                                                       __func__, rc);
+                                       break;
+                               case RPCRDMA_MEMWINDOWS_ASYNC:
+                               case RPCRDMA_MEMWINDOWS:
+                                       rc = ib_dealloc_mw(r->r.mw);
+                                       if (rc)
+                                               dprintk("RPC:       %s:"
+                                                       " ib_dealloc_mw"
+                                                       " failed %i\n",
+                                                       __func__, rc);
+                                       break;
+                               default:
+                                       break;
+                               }
+                       }
+                       rpcrdma_deregister_internal(ia,
+                                       buf->rb_send_bufs[i]->rl_handle,
+                                       &buf->rb_send_bufs[i]->rl_iov);
+                       kfree(buf->rb_send_bufs[i]);
+               }
+       }
+
+       kfree(buf->rb_pool);
+}
+
+/*
+ * Get a set of request/reply buffers.
+ *
+ * Reply buffer (if needed) is attached to send buffer upon return.
+ * Rule:
+ *    rb_send_index and rb_recv_index MUST always be pointing to the
+ *    *next* available buffer (non-NULL). They are incremented after
+ *    removing buffers, and decremented *before* returning them.
+ */
+struct rpcrdma_req *
+rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
+{
+       struct rpcrdma_req *req;
+       unsigned long flags;
+
+       spin_lock_irqsave(&buffers->rb_lock, flags);
+       if (buffers->rb_send_index == buffers->rb_max_requests) {
+               spin_unlock_irqrestore(&buffers->rb_lock, flags);
+               dprintk("RPC:       %s: out of request buffers\n", __func__);
+               return ((struct rpcrdma_req *)NULL);
+       }
+
+       req = buffers->rb_send_bufs[buffers->rb_send_index];
+       if (buffers->rb_send_index < buffers->rb_recv_index) {
+               dprintk("RPC:       %s: %d extra receives outstanding (ok)\n",
+                       __func__,
+                       buffers->rb_recv_index - buffers->rb_send_index);
+               req->rl_reply = NULL;
+       } else {
+               req->rl_reply = buffers->rb_recv_bufs[buffers->rb_recv_index];
+               buffers->rb_recv_bufs[buffers->rb_recv_index++] = NULL;
+       }
+       buffers->rb_send_bufs[buffers->rb_send_index++] = NULL;
+       if (!list_empty(&buffers->rb_mws)) {
+               int i = RPCRDMA_MAX_SEGS - 1;
+               do {
+                       struct rpcrdma_mw *r;
+                       r = list_entry(buffers->rb_mws.next,
+                                       struct rpcrdma_mw, mw_list);
+                       list_del(&r->mw_list);
+                       req->rl_segments[i].mr_chunk.rl_mw = r;
+               } while (--i >= 0);
+       }
+       spin_unlock_irqrestore(&buffers->rb_lock, flags);
+       return req;
+}
+
+/*
+ * Put request/reply buffers back into pool.
+ * Pre-decrement counter/array index.
+ */
+void
+rpcrdma_buffer_put(struct rpcrdma_req *req)
+{
+       struct rpcrdma_buffer *buffers = req->rl_buffer;
+       struct rpcrdma_ia *ia = rdmab_to_ia(buffers);
+       int i;
+       unsigned long flags;
+
+       BUG_ON(req->rl_nchunks != 0);
+       spin_lock_irqsave(&buffers->rb_lock, flags);
+       buffers->rb_send_bufs[--buffers->rb_send_index] = req;
+       req->rl_niovs = 0;
+       if (req->rl_reply) {
+               buffers->rb_recv_bufs[--buffers->rb_recv_index] = req->rl_reply;
+               init_waitqueue_head(&req->rl_reply->rr_unbind);
+               req->rl_reply->rr_func = NULL;
+               req->rl_reply = NULL;
+       }
+       switch (ia->ri_memreg_strategy) {
+       case RPCRDMA_MTHCAFMR:
+       case RPCRDMA_MEMWINDOWS_ASYNC:
+       case RPCRDMA_MEMWINDOWS:
+               /*
+                * Cycle mw's back in reverse order, and "spin" them.
+                * This delays and scrambles reuse as much as possible.
+                */
+               i = 1;
+               do {
+                       struct rpcrdma_mw **mw;
+                       mw = &req->rl_segments[i].mr_chunk.rl_mw;
+                       list_add_tail(&(*mw)->mw_list, &buffers->rb_mws);
+                       *mw = NULL;
+               } while (++i < RPCRDMA_MAX_SEGS);
+               list_add_tail(&req->rl_segments[0].mr_chunk.rl_mw->mw_list,
+                                       &buffers->rb_mws);
+               req->rl_segments[0].mr_chunk.rl_mw = NULL;
+               break;
+       default:
+               break;
+       }
+       spin_unlock_irqrestore(&buffers->rb_lock, flags);
+}
+
+/*
+ * Recover reply buffers from pool.
+ * This happens when recovering from error conditions.
+ * Post-increment counter/array index.
+ */
+void
+rpcrdma_recv_buffer_get(struct rpcrdma_req *req)
+{
+       struct rpcrdma_buffer *buffers = req->rl_buffer;
+       unsigned long flags;
+
+       if (req->rl_iov.length == 0)    /* special case xprt_rdma_allocate() */
+               buffers = ((struct rpcrdma_req *) buffers)->rl_buffer;
+       spin_lock_irqsave(&buffers->rb_lock, flags);
+       if (buffers->rb_recv_index < buffers->rb_max_requests) {
+               req->rl_reply = buffers->rb_recv_bufs[buffers->rb_recv_index];
+               buffers->rb_recv_bufs[buffers->rb_recv_index++] = NULL;
+       }
+       spin_unlock_irqrestore(&buffers->rb_lock, flags);
+}
+
+/*
+ * Put reply buffers back into pool when not attached to
+ * request. This happens in error conditions, and when
+ * aborting unbinds. Pre-decrement counter/array index.
+ */
+void
+rpcrdma_recv_buffer_put(struct rpcrdma_rep *rep)
+{
+       struct rpcrdma_buffer *buffers = rep->rr_buffer;
+       unsigned long flags;
+
+       rep->rr_func = NULL;
+       spin_lock_irqsave(&buffers->rb_lock, flags);
+       buffers->rb_recv_bufs[--buffers->rb_recv_index] = rep;
+       spin_unlock_irqrestore(&buffers->rb_lock, flags);
+}
+
+/*
+ * Wrappers for internal-use kmalloc memory registration, used by buffer code.
+ */
+
+int
+rpcrdma_register_internal(struct rpcrdma_ia *ia, void *va, int len,
+                               struct ib_mr **mrp, struct ib_sge *iov)
+{
+       struct ib_phys_buf ipb;
+       struct ib_mr *mr;
+       int rc;
+
+       /*
+        * All memory passed here was kmalloc'ed, therefore phys-contiguous.
+        */
+       iov->addr = ib_dma_map_single(ia->ri_id->device,
+                       va, len, DMA_BIDIRECTIONAL);
+       iov->length = len;
+
+       if (ia->ri_bind_mem != NULL) {
+               *mrp = NULL;
+               iov->lkey = ia->ri_bind_mem->lkey;
+               return 0;
+       }
+
+       ipb.addr = iov->addr;
+       ipb.size = iov->length;
+       mr = ib_reg_phys_mr(ia->ri_pd, &ipb, 1,
+                       IB_ACCESS_LOCAL_WRITE, &iov->addr);
+
+       dprintk("RPC:       %s: phys convert: 0x%llx "
+                       "registered 0x%llx length %d\n",
+                       __func__, ipb.addr, iov->addr, len);
+
+       if (IS_ERR(mr)) {
+               *mrp = NULL;
+               rc = PTR_ERR(mr);
+               dprintk("RPC:       %s: failed with %i\n", __func__, rc);
+       } else {
+               *mrp = mr;
+               iov->lkey = mr->lkey;
+               rc = 0;
+       }
+
+       return rc;
+}
+
+int
+rpcrdma_deregister_internal(struct rpcrdma_ia *ia,
+                               struct ib_mr *mr, struct ib_sge *iov)
+{
+       int rc;
+
+       ib_dma_unmap_single(ia->ri_id->device,
+                       iov->addr, iov->length, DMA_BIDIRECTIONAL);
+
+       if (NULL == mr)
+               return 0;
+
+       rc = ib_dereg_mr(mr);
+       if (rc)
+               dprintk("RPC:       %s: ib_dereg_mr failed %i\n", __func__, rc);
+       return rc;
+}
+
+/*
+ * Wrappers for chunk registration, shared by read/write chunk code.
+ */
+
+static void
+rpcrdma_map_one(struct rpcrdma_ia *ia, struct rpcrdma_mr_seg *seg, int writing)
+{
+       seg->mr_dir = writing ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+       seg->mr_dmalen = seg->mr_len;
+       if (seg->mr_page)
+               seg->mr_dma = ib_dma_map_page(ia->ri_id->device,
+                               seg->mr_page, offset_in_page(seg->mr_offset),
+                               seg->mr_dmalen, seg->mr_dir);
+       else
+               seg->mr_dma = ib_dma_map_single(ia->ri_id->device,
+                               seg->mr_offset,
+                               seg->mr_dmalen, seg->mr_dir);
+}
+
+static void
+rpcrdma_unmap_one(struct rpcrdma_ia *ia, struct rpcrdma_mr_seg *seg)
+{
+       if (seg->mr_page)
+               ib_dma_unmap_page(ia->ri_id->device,
+                               seg->mr_dma, seg->mr_dmalen, seg->mr_dir);
+       else
+               ib_dma_unmap_single(ia->ri_id->device,
+                               seg->mr_dma, seg->mr_dmalen, seg->mr_dir);
+}
+
+int
+rpcrdma_register_external(struct rpcrdma_mr_seg *seg,
+                       int nsegs, int writing, struct rpcrdma_xprt *r_xprt)
+{
+       struct rpcrdma_ia *ia = &r_xprt->rx_ia;
+       int mem_priv = (writing ? IB_ACCESS_REMOTE_WRITE :
+                                 IB_ACCESS_REMOTE_READ);
+       struct rpcrdma_mr_seg *seg1 = seg;
+       int i;
+       int rc = 0;
+
+       switch (ia->ri_memreg_strategy) {
+
+#if RPCRDMA_PERSISTENT_REGISTRATION
+       case RPCRDMA_ALLPHYSICAL:
+               rpcrdma_map_one(ia, seg, writing);
+               seg->mr_rkey = ia->ri_bind_mem->rkey;
+               seg->mr_base = seg->mr_dma;
+               seg->mr_nsegs = 1;
+               nsegs = 1;
+               break;
+#endif
+
+       /* Registration using fast memory registration */
+       case RPCRDMA_MTHCAFMR:
+               {
+               u64 physaddrs[RPCRDMA_MAX_DATA_SEGS];
+               int len, pageoff = offset_in_page(seg->mr_offset);
+               seg1->mr_offset -= pageoff;     /* start of page */
+               seg1->mr_len += pageoff;
+               len = -pageoff;
+               if (nsegs > RPCRDMA_MAX_DATA_SEGS)
+                       nsegs = RPCRDMA_MAX_DATA_SEGS;
+               for (i = 0; i < nsegs;) {
+                       rpcrdma_map_one(ia, seg, writing);
+                       physaddrs[i] = seg->mr_dma;
+                       len += seg->mr_len;
+                       ++seg;
+                       ++i;
+                       /* Check for holes */
+                       if ((i < nsegs && offset_in_page(seg->mr_offset)) ||
+                           offset_in_page((seg-1)->mr_offset+(seg-1)->mr_len))
+                               break;
+               }
+               nsegs = i;
+               rc = ib_map_phys_fmr(seg1->mr_chunk.rl_mw->r.fmr,
+                                       physaddrs, nsegs, seg1->mr_dma);
+               if (rc) {
+                       dprintk("RPC:       %s: failed ib_map_phys_fmr "
+                               "[EMAIL PROTECTED] (%d)... status %i\n", 
__func__,
+                               len, (unsigned long long)seg1->mr_dma,
+                               pageoff, nsegs, rc);
+                       while (nsegs--)
+                               rpcrdma_unmap_one(ia, --seg);
+               } else {
+                       seg1->mr_rkey = seg1->mr_chunk.rl_mw->r.fmr->rkey;
+                       seg1->mr_base = seg1->mr_dma + pageoff;
+                       seg1->mr_nsegs = nsegs;
+                       seg1->mr_len = len;
+               }
+               }
+               break;
+
+       /* Registration using memory windows */
+       case RPCRDMA_MEMWINDOWS_ASYNC:
+       case RPCRDMA_MEMWINDOWS:
+               {
+               struct ib_mw_bind param;
+               rpcrdma_map_one(ia, seg, writing);
+               param.mr = ia->ri_bind_mem;
+               param.wr_id = 0ULL;     /* no send cookie */
+               param.addr = seg->mr_dma;
+               param.length = seg->mr_len;
+               param.send_flags = 0;
+               param.mw_access_flags = mem_priv;
+
+               DECR_CQCOUNT(&r_xprt->rx_ep);
+               rc = ib_bind_mw(ia->ri_id->qp,
+                                       seg->mr_chunk.rl_mw->r.mw, &param);
+               if (rc) {
+                       dprintk("RPC:       %s: failed ib_bind_mw "
+                               "[EMAIL PROTECTED] status %i\n",
+                               __func__, seg->mr_len,
+                               (unsigned long long)seg->mr_dma, rc);
+                       rpcrdma_unmap_one(ia, seg);
+               } else {
+                       seg->mr_rkey = seg->mr_chunk.rl_mw->r.mw->rkey;
+                       seg->mr_base = param.addr;
+                       seg->mr_nsegs = 1;
+                       nsegs = 1;
+               }
+               }
+               break;
+
+       /* Default registration each time */
+       default:
+               {
+               struct ib_phys_buf ipb[RPCRDMA_MAX_DATA_SEGS];
+               int len = 0;
+               if (nsegs > RPCRDMA_MAX_DATA_SEGS)
+                       nsegs = RPCRDMA_MAX_DATA_SEGS;
+               for (i = 0; i < nsegs;) {
+                       rpcrdma_map_one(ia, seg, writing);
+                       ipb[i].addr = seg->mr_dma;
+                       ipb[i].size = seg->mr_len;
+                       len += seg->mr_len;
+                       ++seg;
+                       ++i;
+                       /* Check for holes */
+                       if ((i < nsegs && offset_in_page(seg->mr_offset)) ||
+                           offset_in_page((seg-1)->mr_offset+(seg-1)->mr_len))
+                               break;
+               }
+               nsegs = i;
+               seg1->mr_base = seg1->mr_dma;
+               seg1->mr_chunk.rl_mr = ib_reg_phys_mr(ia->ri_pd,
+                                       ipb, nsegs, mem_priv, &seg1->mr_base);
+               if (IS_ERR(seg1->mr_chunk.rl_mr)) {
+                       rc = PTR_ERR(seg1->mr_chunk.rl_mr);
+                       dprintk("RPC:       %s: failed ib_reg_phys_mr "
+                               "[EMAIL PROTECTED] (%d)... status %i\n",
+                               __func__, len,
+                               (unsigned long long)seg1->mr_dma, nsegs, rc);
+                       while (nsegs--)
+                               rpcrdma_unmap_one(ia, --seg);
+               } else {
+                       seg1->mr_rkey = seg1->mr_chunk.rl_mr->rkey;
+                       seg1->mr_nsegs = nsegs;
+                       seg1->mr_len = len;
+               }
+               }
+               break;
+       }
+       if (rc)
+               return -1;
+
+       return nsegs;
+}
+
+int
+rpcrdma_deregister_external(struct rpcrdma_mr_seg *seg,
+               struct rpcrdma_xprt *r_xprt, void *r)
+{
+       struct rpcrdma_ia *ia = &r_xprt->rx_ia;
+       struct rpcrdma_mr_seg *seg1 = seg;
+       int nsegs = seg->mr_nsegs, rc;
+
+       switch (ia->ri_memreg_strategy) {
+
+#if RPCRDMA_PERSISTENT_REGISTRATION
+       case RPCRDMA_ALLPHYSICAL:
+               BUG_ON(nsegs != 1);
+               rpcrdma_unmap_one(ia, seg);
+               rc = 0;
+               break;
+#endif
+
+       case RPCRDMA_MTHCAFMR:
+               {
+               LIST_HEAD(l);
+               list_add(&seg->mr_chunk.rl_mw->r.fmr->list, &l);
+               rc = ib_unmap_fmr(&l);
+               while (seg1->mr_nsegs--)
+                       rpcrdma_unmap_one(ia, seg++);
+               }
+               if (rc)
+                       dprintk("RPC:       %s: failed ib_unmap_fmr,"
+                               " status %i\n", __func__, rc);
+               break;
+
+       case RPCRDMA_MEMWINDOWS_ASYNC:
+       case RPCRDMA_MEMWINDOWS:
+               {
+               struct ib_mw_bind param;
+               BUG_ON(nsegs != 1);
+               param.mr = ia->ri_bind_mem;
+               param.addr = 0ULL;      /* unbind */
+               param.length = 0;
+               param.mw_access_flags = 0;
+               if (r) {
+                       param.wr_id = (u64) (unsigned long) r;
+                       param.send_flags = IB_SEND_SIGNALED;
+                       INIT_CQCOUNT(&r_xprt->rx_ep);
+               } else {
+                       param.wr_id = 0ULL;
+                       param.send_flags = 0;
+                       DECR_CQCOUNT(&r_xprt->rx_ep);
+               }
+               rc = ib_bind_mw(ia->ri_id->qp,
+                               seg->mr_chunk.rl_mw->r.mw, &param);
+               rpcrdma_unmap_one(ia, seg);
+               }
+               if (rc)
+                       dprintk("RPC:       %s: failed ib_(un)bind_mw,"
+                               " status %i\n", __func__, rc);
+               else
+                       r = NULL;       /* will upcall on completion */
+               break;
+
+       default:
+               rc = ib_dereg_mr(seg1->mr_chunk.rl_mr);
+               seg1->mr_chunk.rl_mr = NULL;
+               while (seg1->mr_nsegs--)
+                       rpcrdma_unmap_one(ia, seg++);
+               if (rc)
+                       dprintk("RPC:       %s: failed ib_dereg_mr,"
+                               " status %i\n", __func__, rc);
+               break;
+       }
+       if (r) {
+               struct rpcrdma_rep *rep = r;
+               void (*func)(struct rpcrdma_rep *) = rep->rr_func;
+               rep->rr_func = NULL;
+               func(rep);      /* dereg done, callback now */
+       }
+       return nsegs;
+}
+
+/*
+ * Prepost any receive buffer, then post send.
+ *
+ * Receive buffer is donated to hardware, reclaimed upon recv completion.
+ */
+int
+rpcrdma_ep_post(struct rpcrdma_ia *ia,
+               struct rpcrdma_ep *ep,
+               struct rpcrdma_req *req)
+{
+       struct ib_send_wr send_wr, *send_wr_fail;
+       struct rpcrdma_rep *rep = req->rl_reply;
+       int rc;
+
+       if (rep) {
+               rc = rpcrdma_ep_post_recv(ia, ep, rep);
+               if (rc)
+                       goto out;
+               req->rl_reply = NULL;
+       }
+
+       send_wr.next = NULL;
+       send_wr.wr_id = 0ULL;   /* no send cookie */
+       send_wr.sg_list = req->rl_send_iov;
+       send_wr.num_sge = req->rl_niovs;
+       send_wr.opcode = IB_WR_SEND;
+       send_wr.imm_data = 0;
+       if (send_wr.num_sge == 4)       /* no need to sync any pad (constant) */
+               ib_dma_sync_single_for_device(ia->ri_id->device,
+                       req->rl_send_iov[3].addr, req->rl_send_iov[3].length,
+                       DMA_TO_DEVICE);
+       ib_dma_sync_single_for_device(ia->ri_id->device,
+               req->rl_send_iov[1].addr, req->rl_send_iov[1].length,
+               DMA_TO_DEVICE);
+       ib_dma_sync_single_for_device(ia->ri_id->device,
+               req->rl_send_iov[0].addr, req->rl_send_iov[0].length,
+               DMA_TO_DEVICE);
+
+       if (DECR_CQCOUNT(ep) > 0)
+               send_wr.send_flags = 0;
+       else { /* Provider must take a send completion every now and then */
+               INIT_CQCOUNT(ep);
+               send_wr.send_flags = IB_SEND_SIGNALED;
+       }
+
+       rc = ib_post_send(ia->ri_id->qp, &send_wr, &send_wr_fail);
+       if (rc)
+               dprintk("RPC:       %s: ib_post_send returned %i\n", __func__,
+                       rc);
+out:
+       return rc;
+}
+
+/*
+ * (Re)post a receive buffer.
+ */
+int
+rpcrdma_ep_post_recv(struct rpcrdma_ia *ia,
+                    struct rpcrdma_ep *ep,
+                    struct rpcrdma_rep *rep)
+{
+       struct ib_recv_wr recv_wr, *recv_wr_fail;
+       int rc;
+
+       recv_wr.next = NULL;
+       recv_wr.wr_id = (u64) (unsigned long) rep;
+       recv_wr.sg_list = &rep->rr_iov;
+       recv_wr.num_sge = 1;
+
+       ib_dma_sync_single_for_cpu(ia->ri_id->device,
+               rep->rr_iov.addr, rep->rr_iov.length, DMA_BIDIRECTIONAL);
+
+       DECR_CQCOUNT(ep);
+       rc = ib_post_recv(ia->ri_id->qp, &recv_wr, &recv_wr_fail);
+
+       if (rc)
+               dprintk("RPC:       %s: ib_post_recv returned %i\n", __func__,
+                       rc);
+       return rc;
+}
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