blob: de0bdb6b729f8935023468f65472c7301ec4d9a1 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2015, 2017 Oracle. All rights reserved.
* Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
*/
/* Lightweight memory registration using Fast Registration Work
* Requests (FRWR).
*
* FRWR features ordered asynchronous registration and invalidation
* of arbitrarily-sized memory regions. This is the fastest and safest
* but most complex memory registration mode.
*/
/* Normal operation
*
* A Memory Region is prepared for RDMA Read or Write using a FAST_REG
* Work Request (frwr_map). When the RDMA operation is finished, this
* Memory Region is invalidated using a LOCAL_INV Work Request
* (frwr_unmap_async and frwr_unmap_sync).
*
* Typically FAST_REG Work Requests are not signaled, and neither are
* RDMA Send Work Requests (with the exception of signaling occasionally
* to prevent provider work queue overflows). This greatly reduces HCA
* interrupt workload.
*/
/* Transport recovery
*
* frwr_map and frwr_unmap_* cannot run at the same time the transport
* connect worker is running. The connect worker holds the transport
* send lock, just as ->send_request does. This prevents frwr_map and
* the connect worker from running concurrently. When a connection is
* closed, the Receive completion queue is drained before the allowing
* the connect worker to get control. This prevents frwr_unmap and the
* connect worker from running concurrently.
*
* When the underlying transport disconnects, MRs that are in flight
* are flushed and are likely unusable. Thus all MRs are destroyed.
* New MRs are created on demand.
*/
#include <linux/sunrpc/svc_rdma.h>
#include "xprt_rdma.h"
#include <trace/events/rpcrdma.h>
static void frwr_cid_init(struct rpcrdma_ep *ep,
struct rpcrdma_mr *mr)
{
struct rpc_rdma_cid *cid = &mr->mr_cid;
cid->ci_queue_id = ep->re_attr.send_cq->res.id;
cid->ci_completion_id = mr->mr_ibmr->res.id;
}
static void frwr_mr_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr *mr)
{
if (mr->mr_device) {
trace_xprtrdma_mr_unmap(mr);
ib_dma_unmap_sg(mr->mr_device, mr->mr_sg, mr->mr_nents,
mr->mr_dir);
mr->mr_device = NULL;
}
}
/**
* frwr_mr_release - Destroy one MR
* @mr: MR allocated by frwr_mr_init
*
*/
void frwr_mr_release(struct rpcrdma_mr *mr)
{
int rc;
frwr_mr_unmap(mr->mr_xprt, mr);
rc = ib_dereg_mr(mr->mr_ibmr);
if (rc)
trace_xprtrdma_frwr_dereg(mr, rc);
kfree(mr->mr_sg);
kfree(mr);
}
static void frwr_mr_put(struct rpcrdma_mr *mr)
{
frwr_mr_unmap(mr->mr_xprt, mr);
/* The MR is returned to the req's MR free list instead
* of to the xprt's MR free list. No spinlock is needed.
*/
rpcrdma_mr_push(mr, &mr->mr_req->rl_free_mrs);
}
/* frwr_reset - Place MRs back on the free list
* @req: request to reset
*
* Used after a failed marshal. For FRWR, this means the MRs
* don't have to be fully released and recreated.
*
* NB: This is safe only as long as none of @req's MRs are
* involved with an ongoing asynchronous FAST_REG or LOCAL_INV
* Work Request.
*/
void frwr_reset(struct rpcrdma_req *req)
{
struct rpcrdma_mr *mr;
while ((mr = rpcrdma_mr_pop(&req->rl_registered)))
frwr_mr_put(mr);
}
/**
* frwr_mr_init - Initialize one MR
* @r_xprt: controlling transport instance
* @mr: generic MR to prepare for FRWR
*
* Returns zero if successful. Otherwise a negative errno
* is returned.
*/
int frwr_mr_init(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr *mr)
{
struct rpcrdma_ep *ep = r_xprt->rx_ep;
unsigned int depth = ep->re_max_fr_depth;
struct scatterlist *sg;
struct ib_mr *frmr;
int rc;
frmr = ib_alloc_mr(ep->re_pd, ep->re_mrtype, depth);
if (IS_ERR(frmr))
goto out_mr_err;
sg = kmalloc_array(depth, sizeof(*sg), GFP_KERNEL);
if (!sg)
goto out_list_err;
mr->mr_xprt = r_xprt;
mr->mr_ibmr = frmr;
mr->mr_device = NULL;
INIT_LIST_HEAD(&mr->mr_list);
init_completion(&mr->mr_linv_done);
frwr_cid_init(ep, mr);
sg_init_table(sg, depth);
mr->mr_sg = sg;
return 0;
out_mr_err:
rc = PTR_ERR(frmr);
trace_xprtrdma_frwr_alloc(mr, rc);
return rc;
out_list_err:
ib_dereg_mr(frmr);
return -ENOMEM;
}
/**
* frwr_query_device - Prepare a transport for use with FRWR
* @ep: endpoint to fill in
* @device: RDMA device to query
*
* On success, sets:
* ep->re_attr
* ep->re_max_requests
* ep->re_max_rdma_segs
* ep->re_max_fr_depth
* ep->re_mrtype
*
* Return values:
* On success, returns zero.
* %-EINVAL - the device does not support FRWR memory registration
* %-ENOMEM - the device is not sufficiently capable for NFS/RDMA
*/
int frwr_query_device(struct rpcrdma_ep *ep, const struct ib_device *device)
{
const struct ib_device_attr *attrs = &device->attrs;
int max_qp_wr, depth, delta;
unsigned int max_sge;
if (!(attrs->device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS) ||
attrs->max_fast_reg_page_list_len == 0) {
pr_err("rpcrdma: 'frwr' mode is not supported by device %s\n",
device->name);
return -EINVAL;
}
max_sge = min_t(unsigned int, attrs->max_send_sge,
RPCRDMA_MAX_SEND_SGES);
if (max_sge < RPCRDMA_MIN_SEND_SGES) {
pr_err("rpcrdma: HCA provides only %u send SGEs\n", max_sge);
return -ENOMEM;
}
ep->re_attr.cap.max_send_sge = max_sge;
ep->re_attr.cap.max_recv_sge = 1;
ep->re_mrtype = IB_MR_TYPE_MEM_REG;
if (attrs->kernel_cap_flags & IBK_SG_GAPS_REG)
ep->re_mrtype = IB_MR_TYPE_SG_GAPS;
/* Quirk: Some devices advertise a large max_fast_reg_page_list_len
* capability, but perform optimally when the MRs are not larger
* than a page.
*/
if (attrs->max_sge_rd > RPCRDMA_MAX_HDR_SEGS)
ep->re_max_fr_depth = attrs->max_sge_rd;
else
ep->re_max_fr_depth = attrs->max_fast_reg_page_list_len;
if (ep->re_max_fr_depth > RPCRDMA_MAX_DATA_SEGS)
ep->re_max_fr_depth = RPCRDMA_MAX_DATA_SEGS;
/* Add room for frwr register and invalidate WRs.
* 1. FRWR reg WR for head
* 2. FRWR invalidate WR for head
* 3. N FRWR reg WRs for pagelist
* 4. N FRWR invalidate WRs for pagelist
* 5. FRWR reg WR for tail
* 6. FRWR invalidate WR for tail
* 7. The RDMA_SEND WR
*/
depth = 7;
/* Calculate N if the device max FRWR depth is smaller than
* RPCRDMA_MAX_DATA_SEGS.
*/
if (ep->re_max_fr_depth < RPCRDMA_MAX_DATA_SEGS) {
delta = RPCRDMA_MAX_DATA_SEGS - ep->re_max_fr_depth;
do {
depth += 2; /* FRWR reg + invalidate */
delta -= ep->re_max_fr_depth;
} while (delta > 0);
}
max_qp_wr = attrs->max_qp_wr;
max_qp_wr -= RPCRDMA_BACKWARD_WRS;
max_qp_wr -= 1;
if (max_qp_wr < RPCRDMA_MIN_SLOT_TABLE)
return -ENOMEM;
if (ep->re_max_requests > max_qp_wr)
ep->re_max_requests = max_qp_wr;
ep->re_attr.cap.max_send_wr = ep->re_max_requests * depth;
if (ep->re_attr.cap.max_send_wr > max_qp_wr) {
ep->re_max_requests = max_qp_wr / depth;
if (!ep->re_max_requests)
return -ENOMEM;
ep->re_attr.cap.max_send_wr = ep->re_max_requests * depth;
}
ep->re_attr.cap.max_send_wr += RPCRDMA_BACKWARD_WRS;
ep->re_attr.cap.max_send_wr += 1; /* for ib_drain_sq */
ep->re_attr.cap.max_recv_wr = ep->re_max_requests;
ep->re_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS;
ep->re_attr.cap.max_recv_wr += RPCRDMA_MAX_RECV_BATCH;
ep->re_attr.cap.max_recv_wr += 1; /* for ib_drain_rq */
ep->re_max_rdma_segs =
DIV_ROUND_UP(RPCRDMA_MAX_DATA_SEGS, ep->re_max_fr_depth);
/* Reply chunks require segments for head and tail buffers */
ep->re_max_rdma_segs += 2;
if (ep->re_max_rdma_segs > RPCRDMA_MAX_HDR_SEGS)
ep->re_max_rdma_segs = RPCRDMA_MAX_HDR_SEGS;
/* Ensure the underlying device is capable of conveying the
* largest r/wsize NFS will ask for. This guarantees that
* failing over from one RDMA device to another will not
* break NFS I/O.
*/
if ((ep->re_max_rdma_segs * ep->re_max_fr_depth) < RPCRDMA_MAX_SEGS)
return -ENOMEM;
return 0;
}
/**
* frwr_map - Register a memory region
* @r_xprt: controlling transport
* @seg: memory region co-ordinates
* @nsegs: number of segments remaining
* @writing: true when RDMA Write will be used
* @xid: XID of RPC using the registered memory
* @mr: MR to fill in
*
* Prepare a REG_MR Work Request to register a memory region
* for remote access via RDMA READ or RDMA WRITE.
*
* Returns the next segment or a negative errno pointer.
* On success, @mr is filled in.
*/
struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
struct rpcrdma_mr_seg *seg,
int nsegs, bool writing, __be32 xid,
struct rpcrdma_mr *mr)
{
struct rpcrdma_ep *ep = r_xprt->rx_ep;
struct ib_reg_wr *reg_wr;
int i, n, dma_nents;
struct ib_mr *ibmr;
u8 key;
if (nsegs > ep->re_max_fr_depth)
nsegs = ep->re_max_fr_depth;
for (i = 0; i < nsegs;) {
sg_set_page(&mr->mr_sg[i], seg->mr_page,
seg->mr_len, seg->mr_offset);
++seg;
++i;
if (ep->re_mrtype == IB_MR_TYPE_SG_GAPS)
continue;
if ((i < nsegs && seg->mr_offset) ||
offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
break;
}
mr->mr_dir = rpcrdma_data_dir(writing);
mr->mr_nents = i;
dma_nents = ib_dma_map_sg(ep->re_id->device, mr->mr_sg, mr->mr_nents,
mr->mr_dir);
if (!dma_nents)
goto out_dmamap_err;
mr->mr_device = ep->re_id->device;
ibmr = mr->mr_ibmr;
n = ib_map_mr_sg(ibmr, mr->mr_sg, dma_nents, NULL, PAGE_SIZE);
if (n != dma_nents)
goto out_mapmr_err;
ibmr->iova &= 0x00000000ffffffff;
ibmr->iova |= ((u64)be32_to_cpu(xid)) << 32;
key = (u8)(ibmr->rkey & 0x000000FF);
ib_update_fast_reg_key(ibmr, ++key);
reg_wr = &mr->mr_regwr;
reg_wr->mr = ibmr;
reg_wr->key = ibmr->rkey;
reg_wr->access = writing ?
IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
IB_ACCESS_REMOTE_READ;
mr->mr_handle = ibmr->rkey;
mr->mr_length = ibmr->length;
mr->mr_offset = ibmr->iova;
trace_xprtrdma_mr_map(mr);
return seg;
out_dmamap_err:
trace_xprtrdma_frwr_sgerr(mr, i);
return ERR_PTR(-EIO);
out_mapmr_err:
trace_xprtrdma_frwr_maperr(mr, n);
return ERR_PTR(-EIO);
}
/**
* frwr_wc_fastreg - Invoked by RDMA provider for a flushed FastReg WC
* @cq: completion queue
* @wc: WCE for a completed FastReg WR
*
* Each flushed MR gets destroyed after the QP has drained.
*/
static void frwr_wc_fastreg(struct ib_cq *cq, struct ib_wc *wc)
{
struct ib_cqe *cqe = wc->wr_cqe;
struct rpcrdma_mr *mr = container_of(cqe, struct rpcrdma_mr, mr_cqe);
/* WARNING: Only wr_cqe and status are reliable at this point */
trace_xprtrdma_wc_fastreg(wc, &mr->mr_cid);
rpcrdma_flush_disconnect(cq->cq_context, wc);
}
/**
* frwr_send - post Send WRs containing the RPC Call message
* @r_xprt: controlling transport instance
* @req: prepared RPC Call
*
* For FRWR, chain any FastReg WRs to the Send WR. Only a
* single ib_post_send call is needed to register memory
* and then post the Send WR.
*
* Returns the return code from ib_post_send.
*
* Caller must hold the transport send lock to ensure that the
* pointers to the transport's rdma_cm_id and QP are stable.
*/
int frwr_send(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
struct ib_send_wr *post_wr, *send_wr = &req->rl_wr;
struct rpcrdma_ep *ep = r_xprt->rx_ep;
struct rpcrdma_mr *mr;
unsigned int num_wrs;
int ret;
num_wrs = 1;
post_wr = send_wr;
list_for_each_entry(mr, &req->rl_registered, mr_list) {
trace_xprtrdma_mr_fastreg(mr);
mr->mr_cqe.done = frwr_wc_fastreg;
mr->mr_regwr.wr.next = post_wr;
mr->mr_regwr.wr.wr_cqe = &mr->mr_cqe;
mr->mr_regwr.wr.num_sge = 0;
mr->mr_regwr.wr.opcode = IB_WR_REG_MR;
mr->mr_regwr.wr.send_flags = 0;
post_wr = &mr->mr_regwr.wr;
++num_wrs;
}
if ((kref_read(&req->rl_kref) > 1) || num_wrs > ep->re_send_count) {
send_wr->send_flags |= IB_SEND_SIGNALED;
ep->re_send_count = min_t(unsigned int, ep->re_send_batch,
num_wrs - ep->re_send_count);
} else {
send_wr->send_flags &= ~IB_SEND_SIGNALED;
ep->re_send_count -= num_wrs;
}
trace_xprtrdma_post_send(req);
ret = ib_post_send(ep->re_id->qp, post_wr, NULL);
if (ret)
trace_xprtrdma_post_send_err(r_xprt, req, ret);
return ret;
}
/**
* frwr_reminv - handle a remotely invalidated mr on the @mrs list
* @rep: Received reply
* @mrs: list of MRs to check
*
*/
void frwr_reminv(struct rpcrdma_rep *rep, struct list_head *mrs)
{
struct rpcrdma_mr *mr;
list_for_each_entry(mr, mrs, mr_list)
if (mr->mr_handle == rep->rr_inv_rkey) {
list_del_init(&mr->mr_list);
trace_xprtrdma_mr_reminv(mr);
frwr_mr_put(mr);
break; /* only one invalidated MR per RPC */
}
}
static void frwr_mr_done(struct ib_wc *wc, struct rpcrdma_mr *mr)
{
if (likely(wc->status == IB_WC_SUCCESS))
frwr_mr_put(mr);
}
/**
* frwr_wc_localinv - Invoked by RDMA provider for a LOCAL_INV WC
* @cq: completion queue
* @wc: WCE for a completed LocalInv WR
*
*/
static void frwr_wc_localinv(struct ib_cq *cq, struct ib_wc *wc)
{
struct ib_cqe *cqe = wc->wr_cqe;
struct rpcrdma_mr *mr = container_of(cqe, struct rpcrdma_mr, mr_cqe);
/* WARNING: Only wr_cqe and status are reliable at this point */
trace_xprtrdma_wc_li(wc, &mr->mr_cid);
frwr_mr_done(wc, mr);
rpcrdma_flush_disconnect(cq->cq_context, wc);
}
/**
* frwr_wc_localinv_wake - Invoked by RDMA provider for a LOCAL_INV WC
* @cq: completion queue
* @wc: WCE for a completed LocalInv WR
*
* Awaken anyone waiting for an MR to finish being fenced.
*/
static void frwr_wc_localinv_wake(struct ib_cq *cq, struct ib_wc *wc)
{
struct ib_cqe *cqe = wc->wr_cqe;
struct rpcrdma_mr *mr = container_of(cqe, struct rpcrdma_mr, mr_cqe);
/* WARNING: Only wr_cqe and status are reliable at this point */
trace_xprtrdma_wc_li_wake(wc, &mr->mr_cid);
frwr_mr_done(wc, mr);
complete(&mr->mr_linv_done);
rpcrdma_flush_disconnect(cq->cq_context, wc);
}
/**
* frwr_unmap_sync - invalidate memory regions that were registered for @req
* @r_xprt: controlling transport instance
* @req: rpcrdma_req with a non-empty list of MRs to process
*
* Sleeps until it is safe for the host CPU to access the previously mapped
* memory regions. This guarantees that registered MRs are properly fenced
* from the server before the RPC consumer accesses the data in them. It
* also ensures proper Send flow control: waking the next RPC waits until
* this RPC has relinquished all its Send Queue entries.
*/
void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
struct ib_send_wr *first, **prev, *last;
struct rpcrdma_ep *ep = r_xprt->rx_ep;
const struct ib_send_wr *bad_wr;
struct rpcrdma_mr *mr;
int rc;
/* ORDER: Invalidate all of the MRs first
*
* Chain the LOCAL_INV Work Requests and post them with
* a single ib_post_send() call.
*/
prev = &first;
mr = rpcrdma_mr_pop(&req->rl_registered);
do {
trace_xprtrdma_mr_localinv(mr);
r_xprt->rx_stats.local_inv_needed++;
last = &mr->mr_invwr;
last->next = NULL;
last->wr_cqe = &mr->mr_cqe;
last->sg_list = NULL;
last->num_sge = 0;
last->opcode = IB_WR_LOCAL_INV;
last->send_flags = IB_SEND_SIGNALED;
last->ex.invalidate_rkey = mr->mr_handle;
last->wr_cqe->done = frwr_wc_localinv;
*prev = last;
prev = &last->next;
} while ((mr = rpcrdma_mr_pop(&req->rl_registered)));
mr = container_of(last, struct rpcrdma_mr, mr_invwr);
/* Strong send queue ordering guarantees that when the
* last WR in the chain completes, all WRs in the chain
* are complete.
*/
last->wr_cqe->done = frwr_wc_localinv_wake;
reinit_completion(&mr->mr_linv_done);
/* Transport disconnect drains the receive CQ before it
* replaces the QP. The RPC reply handler won't call us
* unless re_id->qp is a valid pointer.
*/
bad_wr = NULL;
rc = ib_post_send(ep->re_id->qp, first, &bad_wr);
/* The final LOCAL_INV WR in the chain is supposed to
* do the wake. If it was never posted, the wake will
* not happen, so don't wait in that case.
*/
if (bad_wr != first)
wait_for_completion(&mr->mr_linv_done);
if (!rc)
return;
/* On error, the MRs get destroyed once the QP has drained. */
trace_xprtrdma_post_linv_err(req, rc);
/* Force a connection loss to ensure complete recovery.
*/
rpcrdma_force_disconnect(ep);
}
/**
* frwr_wc_localinv_done - Invoked by RDMA provider for a signaled LOCAL_INV WC
* @cq: completion queue
* @wc: WCE for a completed LocalInv WR
*
*/
static void frwr_wc_localinv_done(struct ib_cq *cq, struct ib_wc *wc)
{
struct ib_cqe *cqe = wc->wr_cqe;
struct rpcrdma_mr *mr = container_of(cqe, struct rpcrdma_mr, mr_cqe);
struct rpcrdma_rep *rep;
/* WARNING: Only wr_cqe and status are reliable at this point */
trace_xprtrdma_wc_li_done(wc, &mr->mr_cid);
/* Ensure that @rep is generated before the MR is released */
rep = mr->mr_req->rl_reply;
smp_rmb();
if (wc->status != IB_WC_SUCCESS) {
if (rep)
rpcrdma_unpin_rqst(rep);
rpcrdma_flush_disconnect(cq->cq_context, wc);
return;
}
frwr_mr_put(mr);
rpcrdma_complete_rqst(rep);
}
/**
* frwr_unmap_async - invalidate memory regions that were registered for @req
* @r_xprt: controlling transport instance
* @req: rpcrdma_req with a non-empty list of MRs to process
*
* This guarantees that registered MRs are properly fenced from the
* server before the RPC consumer accesses the data in them. It also
* ensures proper Send flow control: waking the next RPC waits until
* this RPC has relinquished all its Send Queue entries.
*/
void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
{
struct ib_send_wr *first, *last, **prev;
struct rpcrdma_ep *ep = r_xprt->rx_ep;
struct rpcrdma_mr *mr;
int rc;
/* Chain the LOCAL_INV Work Requests and post them with
* a single ib_post_send() call.
*/
prev = &first;
mr = rpcrdma_mr_pop(&req->rl_registered);
do {
trace_xprtrdma_mr_localinv(mr);
r_xprt->rx_stats.local_inv_needed++;
last = &mr->mr_invwr;
last->next = NULL;
last->wr_cqe = &mr->mr_cqe;
last->sg_list = NULL;
last->num_sge = 0;
last->opcode = IB_WR_LOCAL_INV;
last->send_flags = IB_SEND_SIGNALED;
last->ex.invalidate_rkey = mr->mr_handle;
last->wr_cqe->done = frwr_wc_localinv;
*prev = last;
prev = &last->next;
} while ((mr = rpcrdma_mr_pop(&req->rl_registered)));
/* Strong send queue ordering guarantees that when the
* last WR in the chain completes, all WRs in the chain
* are complete. The last completion will wake up the
* RPC waiter.
*/
last->wr_cqe->done = frwr_wc_localinv_done;
/* Transport disconnect drains the receive CQ before it
* replaces the QP. The RPC reply handler won't call us
* unless re_id->qp is a valid pointer.
*/
rc = ib_post_send(ep->re_id->qp, first, NULL);
if (!rc)
return;
/* On error, the MRs get destroyed once the QP has drained. */
trace_xprtrdma_post_linv_err(req, rc);
/* The final LOCAL_INV WR in the chain is supposed to
* do the wake. If it was never posted, the wake does
* not happen. Unpin the rqst in preparation for its
* retransmission.
*/
rpcrdma_unpin_rqst(req->rl_reply);
/* Force a connection loss to ensure complete recovery.
*/
rpcrdma_force_disconnect(ep);
}
/**
* frwr_wp_create - Create an MR for padding Write chunks
* @r_xprt: transport resources to use
*
* Return 0 on success, negative errno on failure.
*/
int frwr_wp_create(struct rpcrdma_xprt *r_xprt)
{
struct rpcrdma_ep *ep = r_xprt->rx_ep;
struct rpcrdma_mr_seg seg;
struct rpcrdma_mr *mr;
mr = rpcrdma_mr_get(r_xprt);
if (!mr)
return -EAGAIN;
mr->mr_req = NULL;
ep->re_write_pad_mr = mr;
seg.mr_len = XDR_UNIT;
seg.mr_page = virt_to_page(ep->re_write_pad);
seg.mr_offset = offset_in_page(ep->re_write_pad);
if (IS_ERR(frwr_map(r_xprt, &seg, 1, true, xdr_zero, mr)))
return -EIO;
trace_xprtrdma_mr_fastreg(mr);
mr->mr_cqe.done = frwr_wc_fastreg;
mr->mr_regwr.wr.next = NULL;
mr->mr_regwr.wr.wr_cqe = &mr->mr_cqe;
mr->mr_regwr.wr.num_sge = 0;
mr->mr_regwr.wr.opcode = IB_WR_REG_MR;
mr->mr_regwr.wr.send_flags = 0;
return ib_post_send(ep->re_id->qp, &mr->mr_regwr.wr, NULL);
}