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-rw-r--r--net/sunrpc/xprtrdma/frwr_ops.c696
1 files changed, 696 insertions, 0 deletions
diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
new file mode 100644
index 0000000000..ffbf998949
--- /dev/null
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -0,0 +1,696 @@
+// 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;
+
+ sg = kcalloc_node(depth, sizeof(*sg), XPRTRDMA_GFP_FLAGS,
+ ibdev_to_node(ep->re_id->device));
+ if (!sg)
+ return -ENOMEM;
+
+ frmr = ib_alloc_mr(ep->re_pd, ep->re_mrtype, depth);
+ if (IS_ERR(frmr))
+ goto out_mr_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:
+ kfree(sg);
+ trace_xprtrdma_frwr_alloc(mr, PTR_ERR(frmr));
+ return PTR_ERR(frmr);
+}
+
+/**
+ * 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);
+}