svcrdma: Add class for RDMA backwards direction transport
To support the server-side of an NFSv4.1 backchannel on RDMA
connections, add a transport class that enables backward
direction messages on an existing forward channel connection.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Bruce Fields <bfields@fieldses.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
new file mode 100644
index 0000000..deff06a
--- /dev/null
+++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
@@ -0,0 +1,371 @@
+/*
+ * Copyright (c) 2015 Oracle. All rights reserved.
+ *
+ * Support for backward direction RPCs on RPC/RDMA (server-side).
+ */
+
+#include <linux/sunrpc/svc_rdma.h>
+#include "xprt_rdma.h"
+
+#define RPCDBG_FACILITY RPCDBG_SVCXPRT
+
+#undef SVCRDMA_BACKCHANNEL_DEBUG
+
+int svc_rdma_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;
+
+#ifdef SVCRDMA_BACKCHANNEL_DEBUG
+ 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);
+#endif
+
+ 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:
+ dprintk("svcrdma: short bc reply: xprt=%p, len=%zu\n",
+ xprt, src->iov_len);
+ goto out;
+
+out_notfound:
+ dprintk("svcrdma: unrecognized bc reply: xprt=%p, xid=%08x\n",
+ xprt, be32_to_cpu(xid));
+
+ goto out_unlock;
+}
+
+/* Send a backwards direction RPC call.
+ *
+ * Caller holds the connection's mutex and has already marshaled
+ * the RPC/RDMA request.
+ *
+ * This is similar to svc_rdma_reply, but takes an rpc_rqst
+ * instead, does not support chunks, and avoids blocking memory
+ * allocation.
+ *
+ * XXX: There is still an opportunity to block in svc_rdma_send()
+ * if there are no SQ entries to post the Send. This may occur if
+ * the adapter has a small maximum SQ depth.
+ */
+static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
+ struct rpc_rqst *rqst)
+{
+ struct xdr_buf *sndbuf = &rqst->rq_snd_buf;
+ struct svc_rdma_op_ctxt *ctxt;
+ struct svc_rdma_req_map *vec;
+ struct ib_send_wr send_wr;
+ int ret;
+
+ vec = svc_rdma_get_req_map(rdma);
+ ret = svc_rdma_map_xdr(rdma, sndbuf, vec);
+ if (ret)
+ goto out_err;
+
+ /* Post a recv buffer to handle the reply for this request. */
+ ret = svc_rdma_post_recv(rdma, GFP_NOIO);
+ if (ret) {
+ pr_err("svcrdma: Failed to post bc receive buffer, err=%d.\n",
+ ret);
+ pr_err("svcrdma: closing transport %p.\n", rdma);
+ set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
+ ret = -ENOTCONN;
+ goto out_err;
+ }
+
+ ctxt = svc_rdma_get_context(rdma);
+ ctxt->pages[0] = virt_to_page(rqst->rq_buffer);
+ ctxt->count = 1;
+
+ ctxt->wr_op = IB_WR_SEND;
+ ctxt->direction = DMA_TO_DEVICE;
+ ctxt->sge[0].lkey = rdma->sc_dma_lkey;
+ ctxt->sge[0].length = sndbuf->len;
+ ctxt->sge[0].addr =
+ ib_dma_map_page(rdma->sc_cm_id->device, ctxt->pages[0], 0,
+ sndbuf->len, DMA_TO_DEVICE);
+ if (ib_dma_mapping_error(rdma->sc_cm_id->device, ctxt->sge[0].addr)) {
+ ret = -EIO;
+ goto out_unmap;
+ }
+ atomic_inc(&rdma->sc_dma_used);
+
+ memset(&send_wr, 0, sizeof(send_wr));
+ send_wr.wr_id = (unsigned long)ctxt;
+ send_wr.sg_list = ctxt->sge;
+ send_wr.num_sge = 1;
+ send_wr.opcode = IB_WR_SEND;
+ send_wr.send_flags = IB_SEND_SIGNALED;
+
+ ret = svc_rdma_send(rdma, &send_wr);
+ if (ret) {
+ ret = -EIO;
+ goto out_unmap;
+ }
+
+out_err:
+ svc_rdma_put_req_map(rdma, vec);
+ dprintk("svcrdma: %s returns %d\n", __func__, ret);
+ return ret;
+
+out_unmap:
+ svc_rdma_unmap_dma(ctxt);
+ svc_rdma_put_context(ctxt, 1);
+ goto out_err;
+}
+
+/* Server-side transport endpoint wants a whole page for its send
+ * buffer. The client RPC code constructs the RPC header in this
+ * buffer before it invokes ->send_request.
+ *
+ * Returns NULL if there was a temporary allocation failure.
+ */
+static void *
+xprt_rdma_bc_allocate(struct rpc_task *task, size_t size)
+{
+ struct rpc_rqst *rqst = task->tk_rqstp;
+ struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
+ struct svcxprt_rdma *rdma;
+ struct page *page;
+
+ rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
+
+ /* Prevent an infinite loop: try to make this case work */
+ if (size > PAGE_SIZE)
+ WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
+ size);
+
+ page = alloc_page(RPCRDMA_DEF_GFP);
+ if (!page)
+ return NULL;
+
+ return page_address(page);
+}
+
+static void
+xprt_rdma_bc_free(void *buffer)
+{
+ /* No-op: ctxt and page have already been freed. */
+}
+
+static int
+rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
+{
+ struct rpc_xprt *xprt = rqst->rq_xprt;
+ struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
+ struct rpcrdma_msg *headerp = (struct rpcrdma_msg *)rqst->rq_buffer;
+ int rc;
+
+ /* Space in the send buffer for an RPC/RDMA header is reserved
+ * via xprt->tsh_size.
+ */
+ headerp->rm_xid = rqst->rq_xid;
+ headerp->rm_vers = rpcrdma_version;
+ headerp->rm_credit = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
+ headerp->rm_type = rdma_msg;
+ headerp->rm_body.rm_chunks[0] = xdr_zero;
+ headerp->rm_body.rm_chunks[1] = xdr_zero;
+ headerp->rm_body.rm_chunks[2] = xdr_zero;
+
+#ifdef SVCRDMA_BACKCHANNEL_DEBUG
+ pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
+#endif
+
+ rc = svc_rdma_bc_sendto(rdma, rqst);
+ if (rc)
+ goto drop_connection;
+ return rc;
+
+drop_connection:
+ dprintk("svcrdma: failed to send bc call\n");
+ xprt_disconnect_done(xprt);
+ return -ENOTCONN;
+}
+
+/* Send an RPC call on the passive end of a transport
+ * connection.
+ */
+static int
+xprt_rdma_bc_send_request(struct rpc_task *task)
+{
+ struct rpc_rqst *rqst = task->tk_rqstp;
+ struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
+ struct svcxprt_rdma *rdma;
+ int ret;
+
+ dprintk("svcrdma: sending bc call with xid: %08x\n",
+ be32_to_cpu(rqst->rq_xid));
+
+ if (!mutex_trylock(&sxprt->xpt_mutex)) {
+ rpc_sleep_on(&sxprt->xpt_bc_pending, task, NULL);
+ if (!mutex_trylock(&sxprt->xpt_mutex))
+ return -EAGAIN;
+ rpc_wake_up_queued_task(&sxprt->xpt_bc_pending, task);
+ }
+
+ ret = -ENOTCONN;
+ rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
+ if (!test_bit(XPT_DEAD, &sxprt->xpt_flags))
+ ret = rpcrdma_bc_send_request(rdma, rqst);
+
+ mutex_unlock(&sxprt->xpt_mutex);
+
+ if (ret < 0)
+ return ret;
+ return 0;
+}
+
+static void
+xprt_rdma_bc_close(struct rpc_xprt *xprt)
+{
+ dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
+}
+
+static void
+xprt_rdma_bc_put(struct rpc_xprt *xprt)
+{
+ dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
+
+ xprt_free(xprt);
+ module_put(THIS_MODULE);
+}
+
+static struct rpc_xprt_ops xprt_rdma_bc_procs = {
+ .reserve_xprt = xprt_reserve_xprt_cong,
+ .release_xprt = xprt_release_xprt_cong,
+ .alloc_slot = xprt_alloc_slot,
+ .release_request = xprt_release_rqst_cong,
+ .buf_alloc = xprt_rdma_bc_allocate,
+ .buf_free = xprt_rdma_bc_free,
+ .send_request = xprt_rdma_bc_send_request,
+ .set_retrans_timeout = xprt_set_retrans_timeout_def,
+ .close = xprt_rdma_bc_close,
+ .destroy = xprt_rdma_bc_put,
+ .print_stats = xprt_rdma_print_stats
+};
+
+static const struct rpc_timeout xprt_rdma_bc_timeout = {
+ .to_initval = 60 * HZ,
+ .to_maxval = 60 * HZ,
+};
+
+/* It shouldn't matter if the number of backchannel session slots
+ * doesn't match the number of RPC/RDMA credits. That just means
+ * one or the other will have extra slots that aren't used.
+ */
+static struct rpc_xprt *
+xprt_setup_rdma_bc(struct xprt_create *args)
+{
+ struct rpc_xprt *xprt;
+ struct rpcrdma_xprt *new_xprt;
+
+ if (args->addrlen > sizeof(xprt->addr)) {
+ dprintk("RPC: %s: address too large\n", __func__);
+ return ERR_PTR(-EBADF);
+ }
+
+ xprt = xprt_alloc(args->net, sizeof(*new_xprt),
+ RPCRDMA_MAX_BC_REQUESTS,
+ RPCRDMA_MAX_BC_REQUESTS);
+ if (!xprt) {
+ dprintk("RPC: %s: couldn't allocate rpc_xprt\n",
+ __func__);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ xprt->timeout = &xprt_rdma_bc_timeout;
+ xprt_set_bound(xprt);
+ xprt_set_connected(xprt);
+ xprt->bind_timeout = RPCRDMA_BIND_TO;
+ xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
+ xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
+
+ xprt->prot = XPRT_TRANSPORT_BC_RDMA;
+ xprt->tsh_size = RPCRDMA_HDRLEN_MIN / sizeof(__be32);
+ xprt->ops = &xprt_rdma_bc_procs;
+
+ memcpy(&xprt->addr, args->dstaddr, args->addrlen);
+ xprt->addrlen = args->addrlen;
+ xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
+ xprt->resvport = 0;
+
+ xprt->max_payload = xprt_rdma_max_inline_read;
+
+ new_xprt = rpcx_to_rdmax(xprt);
+ new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;
+
+ xprt_get(xprt);
+ args->bc_xprt->xpt_bc_xprt = xprt;
+ xprt->bc_xprt = args->bc_xprt;
+
+ if (!try_module_get(THIS_MODULE))
+ goto out_fail;
+
+ /* Final put for backchannel xprt is in __svc_rdma_free */
+ xprt_get(xprt);
+ return xprt;
+
+out_fail:
+ xprt_rdma_free_addresses(xprt);
+ args->bc_xprt->xpt_bc_xprt = NULL;
+ xprt_put(xprt);
+ xprt_free(xprt);
+ return ERR_PTR(-EINVAL);
+}
+
+struct xprt_class xprt_rdma_bc = {
+ .list = LIST_HEAD_INIT(xprt_rdma_bc.list),
+ .name = "rdma backchannel",
+ .owner = THIS_MODULE,
+ .ident = XPRT_TRANSPORT_BC_RDMA,
+ .setup = xprt_setup_rdma_bc,
+};