text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (c) 2015-2018 Oracle.  All rights reserved.
   *
   * Support for backward direction RPCs on RPC/RDMA (server-side).
   */
  
  #include <linux/sunrpc/svc_rdma.h>
  
  #include "xprt_rdma.h"
  #include <trace/events/rpcrdma.h>
  
  #define RPCDBG_FACILITY	RPCDBG_SVCXPRT
  
  #undef SVCRDMA_BACKCHANNEL_DEBUG
  
  /**
   * svc_rdma_handle_bc_reply - Process incoming backchannel reply
   * @xprt: controlling backchannel transport
   * @rdma_resp: pointer to incoming transport header
   * @rcvbuf: XDR buffer into which to decode the reply
   *
   * Returns:
   *	%0 if @rcvbuf is filled in, xprt_complete_rqst called,
   *	%-EAGAIN if server should call ->recvfrom again.
   */
  int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
  			     struct xdr_buf *rcvbuf)
  {
  	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  	struct kvec *dst, *src = &rcvbuf->head[0];
  	struct rpc_rqst *req;
  	u32 credits;
  	size_t len;
  	__be32 xid;
  	__be32 *p;
  	int ret;
  
  	p = (__be32 *)src->iov_base;
  	len = src->iov_len;
  	xid = *rdma_resp;
  
  #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, rdma_resp);
  	pr_info("%s:      RPC: %*ph\n",
  		__func__, (int)len, p);
  #endif
  
  	ret = -EAGAIN;
  	if (src->iov_len < 24)
  		goto out_shortreply;
  
  	spin_lock(&xprt->queue_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);
  	xprt_pin_rqst(req);
  	spin_unlock(&xprt->queue_lock);
  
  	credits = be32_to_cpup(rdma_resp + 2);
  	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;
  
  	spin_lock(&xprt->transport_lock);
  	xprt->cwnd = credits << RPC_CWNDSHIFT;
  	spin_unlock(&xprt->transport_lock);
  
  	spin_lock(&xprt->queue_lock);
  	ret = 0;
  	xprt_complete_rqst(req->rq_task, rcvbuf->len);
  	xprt_unpin_rqst(req);
  	rcvbuf->len = 0;
  
  out_unlock:
  	spin_unlock(&xprt->queue_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_send_reply_msg, but takes a struct
   * 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 svc_rdma_send_ctxt *ctxt)
  {
  	int ret;
  
  	ret = svc_rdma_map_reply_msg(rdma, ctxt, &rqst->rq_snd_buf, NULL);
  	if (ret < 0)
  		return -EIO;
  
  	/* Bump page refcnt so Send completion doesn't release
  	 * the rq_buffer before all retransmits are complete.
  	 */
  	get_page(virt_to_page(rqst->rq_buffer));
  	ctxt->sc_send_wr.opcode = IB_WR_SEND;
  	return svc_rdma_send(rdma, &ctxt->sc_send_wr);
  }
  
  /* 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.
   */
  static int
  xprt_rdma_bc_allocate(struct rpc_task *task)
  {
  	struct rpc_rqst *rqst = task->tk_rqstp;
  	size_t size = rqst->rq_callsize;
  	struct page *page;
  
  	if (size > PAGE_SIZE) {
  		WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
  			  size);
  		return -EINVAL;
  	}
  
  	page = alloc_page(RPCRDMA_DEF_GFP);
  	if (!page)
  		return -ENOMEM;
  	rqst->rq_buffer = page_address(page);
  
  	rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, RPCRDMA_DEF_GFP);
  	if (!rqst->rq_rbuffer) {
  		put_page(page);
  		return -ENOMEM;
  	}
  	return 0;
  }
  
  static void
  xprt_rdma_bc_free(struct rpc_task *task)
  {
  	struct rpc_rqst *rqst = task->tk_rqstp;
  
  	put_page(virt_to_page(rqst->rq_buffer));
  	kfree(rqst->rq_rbuffer);
  }
  
  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 svc_rdma_send_ctxt *ctxt;
  	__be32 *p;
  	int rc;
  
  	ctxt = svc_rdma_send_ctxt_get(rdma);
  	if (!ctxt)
  		goto drop_connection;
  
  	p = ctxt->sc_xprt_buf;
  	*p++ = rqst->rq_xid;
  	*p++ = rpcrdma_version;
  	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
  	*p++ = rdma_msg;
  	*p++ = xdr_zero;
  	*p++ = xdr_zero;
  	*p   = xdr_zero;
  	svc_rdma_sync_reply_hdr(rdma, ctxt, RPCRDMA_HDRLEN_MIN);
  
  #ifdef SVCRDMA_BACKCHANNEL_DEBUG
  	pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
  #endif
  
  	rc = svc_rdma_bc_sendto(rdma, rqst, ctxt);
  	if (rc) {
  		svc_rdma_send_ctxt_put(rdma, ctxt);
  		goto drop_connection;
  	}
  	return 0;
  
  drop_connection:
  	dprintk("svcrdma: failed to send bc call\n");
  	return -ENOTCONN;
  }
  
  /* Send an RPC call on the passive end of a transport
   * connection.
   */
  static int
  xprt_rdma_bc_send_request(struct rpc_rqst *rqst)
  {
  	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));
  
  	mutex_lock(&sxprt->xpt_mutex);
  
  	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);
  		if (ret == -ENOTCONN)
  			svc_close_xprt(sxprt);
  	}
  
  	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);
  	xprt->cwnd = RPC_CWNDSHIFT;
  }
  
  static void
  xprt_rdma_bc_put(struct rpc_xprt *xprt)
  {
  	dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
  
  	xprt_free(xprt);
  }
  
  static const 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,
  	.free_slot		= xprt_free_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,
  	.wait_for_reply_request	= xprt_wait_for_reply_request_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->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;
  
  	/* Final put for backchannel xprt is in __svc_rdma_free */
  	xprt_get(xprt);
  	return xprt;
  }
  
  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,
  };
  