xprtrdma: Handle incoming backward direction RPC calls
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@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Tested-By: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprtrdma/backchannel.c b/net/sunrpc/xprtrdma/backchannel.c
index ffc4853..0b3387f 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)
{
@@ -253,3 +257,117 @@
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);
+}