To support the NFSv4.1 backchannel on RDMA connections, add a
capability for receiving an RPC/RDMA reply on a connection
established by a client.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
net/sunrpc/xprtrdma/rpc_rdma.c | 76 +++++++++++++++++++++++++++++++
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 60 ++++++++++++++++++++++++
net/sunrpc/xprtrdma/xprt_rdma.h | 4 ++
3 files changed, 140 insertions(+)
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 3830250..b728f6f 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -946,3 +946,79 @@ repost:
if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, &r_xprt->rx_ep, rep))
rpcrdma_recv_buffer_put(rep);
}
+
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+
+int
+rpcrdma_handle_bc_reply(struct rpc_xprt *xprt, struct rpcrdma_msg *rmsgp,
+ struct xdr_buf *rcvbuf)
+{
+ struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
+ struct kvec *dst, *src = &rcvbuf->head[0];
+ struct rpc_rqst *req;
+ unsigned long cwnd;
+ u32 credits;
+ size_t len;
+ __be32 xid;
+ __be32 *p;
+ int ret;
+
+ p = (__be32 *)src->iov_base;
+ len = src->iov_len;
+ xid = rmsgp->rm_xid;
+
+ pr_info("%s: xid=%08x, length=%zu\n",
+ __func__, be32_to_cpu(xid), len);
+ pr_info("%s: RPC/RDMA: %*ph\n",
+ __func__, (int)RPCRDMA_HDRLEN_MIN, rmsgp);
+ pr_info("%s: RPC: %*ph\n",
+ __func__, (int)len, p);
+
+ ret = -EAGAIN;
+ if (src->iov_len < 24)
+ goto out_shortreply;
+
+ spin_lock_bh(&xprt->transport_lock);
+ req = xprt_lookup_rqst(xprt, xid);
+ if (!req)
+ goto out_notfound;
+
+ dst = &req->rq_private_buf.head[0];
+ memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
+ if (dst->iov_len < len)
+ goto out_unlock;
+ memcpy(dst->iov_base, p, len);
+
+ credits = be32_to_cpu(rmsgp->rm_credit);
+ if (credits == 0)
+ credits = 1; /* don't deadlock */
+ else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
+ credits = r_xprt->rx_buf.rb_bc_max_requests;
+
+ cwnd = xprt->cwnd;
+ xprt->cwnd = credits << RPC_CWNDSHIFT;
+ if (xprt->cwnd > cwnd)
+ xprt_release_rqst_cong(req->rq_task);
+
+ ret = 0;
+ xprt_complete_rqst(req->rq_task, rcvbuf->len);
+ rcvbuf->len = 0;
+
+out_unlock:
+ spin_unlock_bh(&xprt->transport_lock);
+out:
+ return ret;
+
+out_shortreply:
+ pr_info("svcrdma: short bc reply: xprt=%p, len=%zu\n",
+ xprt, src->iov_len);
+ goto out;
+
+out_notfound:
+ pr_info("svcrdma: unrecognized bc reply: xprt=%p, xid=%08x\n",
+ xprt, be32_to_cpu(xid));
+
+ goto out_unlock;
+}
+
+#endif /* CONFIG_SUNRPC_BACKCHANNEL */
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index 5f6ca47..be75abba 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -47,6 +47,7 @@
#include <rdma/ib_verbs.h>
#include <rdma/rdma_cm.h>
#include <linux/sunrpc/svc_rdma.h>
+#include "xprt_rdma.h"
#define RPCDBG_FACILITY RPCDBG_SVCXPRT
@@ -560,6 +561,42 @@ static int rdma_read_complete(struct svc_rqst *rqstp,
return ret;
}
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+
+/* By convention, backchannel calls arrive via rdma_msg type
+ * messages, and never populate the chunk lists. This makes
+ * the RPC/RDMA header small and fixed in size, so it is
+ * straightforward to check the RPC header's direction field.
+ */
+static bool
+svc_rdma_is_backchannel_reply(struct svc_xprt *xprt, struct rpcrdma_msg *rmsgp)
+{
+ __be32 *p = (__be32 *)rmsgp;
+
+ if (!xprt->xpt_bc_xprt)
+ return false;
+
+ if (rmsgp->rm_type != rdma_msg)
+ return false;
+ if (rmsgp->rm_body.rm_chunks[0] != xdr_zero)
+ return false;
+ if (rmsgp->rm_body.rm_chunks[1] != xdr_zero)
+ return false;
+ if (rmsgp->rm_body.rm_chunks[2] != xdr_zero)
+ return false;
+
+ /* sanity */
+ if (p[7] != rmsgp->rm_xid)
+ return false;
+ /* call direction */
+ if (p[8] == cpu_to_be32(RPC_CALL))
+ return false;
+
+ return true;
+}
+
+#endif /* CONFIG_SUNRPC_BACKCHANNEL */
+
/*
* Set up the rqstp thread context to point to the RQ buffer. If
* necessary, pull additional data from the client with an RDMA_READ
@@ -625,6 +662,17 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
goto close_out;
}
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+ if (svc_rdma_is_backchannel_reply(xprt, rmsgp)) {
+ ret = rpcrdma_handle_bc_reply(xprt->xpt_bc_xprt, rmsgp,
+ &rqstp->rq_arg);
+ svc_rdma_put_context(ctxt, 0);
+ if (ret)
+ goto repost;
+ return ret;
+ }
+#endif
+
/* Read read-list data. */
ret = rdma_read_chunks(rdma_xprt, rmsgp, rqstp, ctxt);
if (ret > 0) {
@@ -661,4 +709,16 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
set_bit(XPT_CLOSE, &xprt->xpt_flags);
defer:
return 0;
+
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+repost:
+ ret = svc_rdma_post_recv(rdma_xprt);
+ if (ret) {
+ pr_info("svcrdma: could not post a receive buffer, err=%d."
+ "Closing transport %p.\n", ret, rdma_xprt);
+ set_bit(XPT_CLOSE, &rdma_xprt->sc_xprt.xpt_flags);
+ ret = -ENOTCONN;
+ }
+ return ret;
+#endif
}
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 3e513e7c..45a8b70 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -307,6 +307,8 @@ struct rpcrdma_buffer {
u32 rb_bc_srv_max_requests;
spinlock_t rb_reqslock; /* protect rb_allreqs */
struct list_head rb_allreqs;
+
+ u32 rb_bc_max_requests;
};
#define rdmab_to_ia(b) (&container_of((b), struct rpcrdma_xprt, rx_buf)->rx_ia)
@@ -506,6 +508,8 @@ void rpcrdma_reply_handler(struct rpcrdma_rep *);
* RPC/RDMA protocol calls - xprtrdma/rpc_rdma.c
*/
int rpcrdma_marshal_req(struct rpc_rqst *);
+int rpcrdma_handle_bc_reply(struct rpc_xprt *, struct rpcrdma_msg *,
+ struct xdr_buf *);
/* RPC/RDMA module init - xprtrdma/transport.c
*/
--
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