Introduce a code path in the rpcrdma_reply_handler() to catch
incoming backward direction RPC calls and route them to the ULP's
backchannel server.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
net/sunrpc/xprtrdma/backchannel.c | 115 +++++++++++++++++++++++++++++++++++++
net/sunrpc/xprtrdma/rpc_rdma.c | 41 +++++++++++++
net/sunrpc/xprtrdma/xprt_rdma.h | 2 +
3 files changed, 158 insertions(+)
diff --git a/net/sunrpc/xprtrdma/backchannel.c b/net/sunrpc/xprtrdma/backchannel.c
index cc9c762..2eee18a 100644
--- a/net/sunrpc/xprtrdma/backchannel.c
+++ b/net/sunrpc/xprtrdma/backchannel.c
@@ -5,6 +5,8 @@
*/
#include <linux/module.h>
+#include <linux/sunrpc/xprt.h>
+#include <linux/sunrpc/svc.h>
#include "xprt_rdma.h"
@@ -12,6 +14,8 @@
# define RPCDBG_FACILITY RPCDBG_TRANS
#endif
+#define RPCRDMA_BACKCHANNEL_DEBUG
+
static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
struct rpc_rqst *rqst)
{
@@ -251,3 +255,114 @@ void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
spin_unlock_bh(&xprt->bc_pa_lock);
}
+
+/**
+ * rpcrdma_bc_receive_call - Handle a backward direction call
+ * @xprt: transport receiving the call
+ * @rep: receive buffer containing the call
+ *
+ * Called in the RPC reply handler, which runs in a tasklet.
+ * Be quick about it.
+ *
+ * Operational assumptions:
+ * o Backchannel credits are ignored, just as the NFS server
+ * forechannel currently does
+ * o The ULP manages a replay cache (eg, NFSv4.1 sessions).
+ * No replay detection is done at the transport level
+ */
+void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
+ struct rpcrdma_rep *rep)
+{
+ struct rpc_xprt *xprt = &r_xprt->rx_xprt;
+ struct rpcrdma_msg *headerp;
+ struct svc_serv *bc_serv;
+ struct rpcrdma_req *req;
+ struct rpc_rqst *rqst;
+ struct xdr_buf *buf;
+ size_t size;
+ __be32 *p;
+
+ headerp = rdmab_to_msg(rep->rr_rdmabuf);
+#ifdef RPCRDMA_BACKCHANNEL_DEBUG
+ pr_info("RPC: %s: callback XID %08x, length=%u\n",
+ __func__, be32_to_cpu(headerp->rm_xid), rep->rr_len);
+ pr_info("RPC: %s: %*ph\n", __func__, rep->rr_len, headerp);
+#endif
+
+ /* Sanity check:
+ * Need at least enough bytes for RPC/RDMA header, as code
+ * here references the header fields by array offset. Also,
+ * backward calls are always inline, so ensure there
+ * are some bytes beyond the RPC/RDMA header.
+ */
+ if (rep->rr_len < RPCRDMA_HDRLEN_MIN + 24)
+ goto out_short;
+ p = (__be32 *)((unsigned char *)headerp + RPCRDMA_HDRLEN_MIN);
+ size = rep->rr_len - RPCRDMA_HDRLEN_MIN;
+
+ /* Grab a free bc rqst */
+ spin_lock(&xprt->bc_pa_lock);
+ if (list_empty(&xprt->bc_pa_list)) {
+ spin_unlock(&xprt->bc_pa_lock);
+ goto out_overflow;
+ }
+ rqst = list_first_entry(&xprt->bc_pa_list,
+ struct rpc_rqst, rq_bc_pa_list);
+ list_del(&rqst->rq_bc_pa_list);
+ spin_unlock(&xprt->bc_pa_lock);
+#ifdef RPCRDMA_BACKCHANNEL_DEBUG
+ pr_info("RPC: %s: using rqst %p\n", __func__, rqst);
+#endif
+
+ /* Prepare rqst */
+ rqst->rq_reply_bytes_recvd = 0;
+ rqst->rq_bytes_sent = 0;
+ rqst->rq_xid = headerp->rm_xid;
+ set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
+
+ buf = &rqst->rq_rcv_buf;
+ memset(buf, 0, sizeof(*buf));
+ buf->head[0].iov_base = p;
+ buf->head[0].iov_len = size;
+ buf->len = size;
+
+ /* The receive buffer has to be hooked to the rpcrdma_req so that
+ * it can be reposted after the server is done parsing it but just
+ * before sending the backward direction reply. */
+ req = rpcr_to_rdmar(rqst);
+#ifdef RPCRDMA_BACKCHANNEL_DEBUG
+ pr_info("RPC: %s: attaching rep %p to req %p\n",
+ __func__, rep, req);
+#endif
+ req->rl_reply = rep;
+
+ /* Defeat the retransmit detection logic in send_request */
+ req->rl_connect_cookie = 0;
+
+ /* Queue rqst for ULP's callback service */
+ bc_serv = xprt->bc_serv;
+ spin_lock(&bc_serv->sv_cb_lock);
+ list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
+ spin_unlock(&bc_serv->sv_cb_lock);
+
+ wake_up(&bc_serv->sv_cb_waitq);
+
+ r_xprt->rx_stats.bcall_count++;
+ return;
+
+out_overflow:
+ pr_warn("RPC/RDMA backchannel overflow\n");
+ xprt_disconnect_done(xprt);
+ /* This receive buffer gets reposted automatically
+ * when the connection is re-established. */
+ return;
+
+out_short:
+ pr_warn("RPC/RDMA short backward direction call\n");
+
+ if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, &r_xprt->rx_ep, rep))
+ xprt_disconnect_done(xprt);
+ else
+ pr_warn("RPC: %s: reposting rep %p\n",
+ __func__, rep);
+}
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index d0dbbf7..3830250 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -716,6 +716,37 @@ rpcrdma_connect_worker(struct work_struct *work)
spin_unlock_bh(&xprt->transport_lock);
}
+#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
+rpcrdma_is_bcall(struct rpcrdma_msg *headerp)
+{
+ __be32 *p = (__be32 *)headerp;
+
+ if (headerp->rm_type != rdma_msg)
+ return false;
+ if (headerp->rm_body.rm_chunks[0] != xdr_zero)
+ return false;
+ if (headerp->rm_body.rm_chunks[1] != xdr_zero)
+ return false;
+ if (headerp->rm_body.rm_chunks[2] != xdr_zero)
+ return false;
+
+ /* sanity */
+ if (p[7] != headerp->rm_xid)
+ return false;
+ /* call direction */
+ if (p[8] != cpu_to_be32(RPC_CALL))
+ return false;
+
+ return true;
+}
+#endif /* CONFIG_SUNRPC_BACKCHANNEL */
+
/*
* This function is called when an async event is posted to
* the connection which changes the connection state. All it
@@ -756,6 +787,10 @@ rpcrdma_reply_handler(struct rpcrdma_rep *rep)
headerp = rdmab_to_msg(rep->rr_rdmabuf);
if (headerp->rm_vers != rpcrdma_version)
goto out_badversion;
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+ if (rpcrdma_is_bcall(headerp))
+ goto out_bcall;
+#endif
/* Get XID and try for a match. */
spin_lock(&xprt->transport_lock);
@@ -877,6 +912,12 @@ out_badstatus:
}
return;
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+out_bcall:
+ rpcrdma_bc_receive_call(r_xprt, rep);
+ return;
+#endif
+
out_shortreply:
dprintk("RPC: %s: short/invalid reply\n", __func__);
goto repost;
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index a59ce18..3e513e7c 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -352,6 +352,7 @@ struct rpcrdma_stats {
unsigned long failed_marshal_count;
unsigned long bad_reply_count;
unsigned long nomsg_call_count;
+ unsigned long bcall_count;
};
/*
@@ -516,6 +517,7 @@ void xprt_rdma_cleanup(void);
#if defined(CONFIG_SUNRPC_BACKCHANNEL)
int xprt_rdma_bc_setup(struct rpc_xprt *, unsigned int);
int rpcrdma_bc_post_recv(struct rpcrdma_xprt *, unsigned int);
+void rpcrdma_bc_receive_call(struct rpcrdma_xprt *, struct rpcrdma_rep *);
int rpcrdma_bc_marshal_reply(struct rpc_rqst *);
void xprt_rdma_bc_free_rqst(struct rpc_rqst *);
void xprt_rdma_bc_destroy(struct rpc_xprt *, unsigned int);
--
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