// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (c) 2015 Oracle. All rights reserved.
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*
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* Support for backward direction RPCs on RPC/RDMA.
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*/
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#include <linux/sunrpc/xprt.h>
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#include <linux/sunrpc/svc.h>
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#include <linux/sunrpc/svc_xprt.h>
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#include <linux/sunrpc/svc_rdma.h>
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#include "xprt_rdma.h"
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#include <trace/events/rpcrdma.h>
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#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
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# define RPCDBG_FACILITY RPCDBG_TRANS
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#endif
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#undef RPCRDMA_BACKCHANNEL_DEBUG
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/**
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* xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
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* @xprt: transport associated with these backchannel resources
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* @reqs: number of concurrent incoming requests to expect
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*
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* Returns 0 on success; otherwise a negative errno
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*/
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int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
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{
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struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
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r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
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trace_xprtrdma_cb_setup(r_xprt, reqs);
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return 0;
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}
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/**
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* xprt_rdma_bc_maxpayload - Return maximum backchannel message size
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* @xprt: transport
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*
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* Returns maximum size, in bytes, of a backchannel message
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*/
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size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
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{
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struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
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struct rpcrdma_ep *ep = r_xprt->rx_ep;
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size_t maxmsg;
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maxmsg = min_t(unsigned int, ep->re_inline_send, ep->re_inline_recv);
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maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
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return maxmsg - RPCRDMA_HDRLEN_MIN;
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}
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unsigned int xprt_rdma_bc_max_slots(struct rpc_xprt *xprt)
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{
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return RPCRDMA_BACKWARD_WRS >> 1;
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}
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static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
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{
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struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
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struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
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__be32 *p;
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rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
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xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
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rdmab_data(req->rl_rdmabuf), rqst);
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p = xdr_reserve_space(&req->rl_stream, 28);
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if (unlikely(!p))
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return -EIO;
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*p++ = rqst->rq_xid;
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*p++ = rpcrdma_version;
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*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
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*p++ = rdma_msg;
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*p++ = xdr_zero;
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*p++ = xdr_zero;
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*p = xdr_zero;
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if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
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&rqst->rq_snd_buf, rpcrdma_noch_pullup))
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return -EIO;
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trace_xprtrdma_cb_reply(rqst);
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return 0;
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}
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/**
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* xprt_rdma_bc_send_reply - marshal and send a backchannel reply
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* @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
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*
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* Caller holds the transport's write lock.
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*
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* Returns:
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* %0 if the RPC message has been sent
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* %-ENOTCONN if the caller should reconnect and call again
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* %-EIO if a permanent error occurred and the request was not
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* sent. Do not try to send this message again.
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*/
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int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
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{
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struct rpc_xprt *xprt = rqst->rq_xprt;
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struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
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struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
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int rc;
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if (!xprt_connected(xprt))
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return -ENOTCONN;
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if (!xprt_request_get_cong(xprt, rqst))
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return -EBADSLT;
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rc = rpcrdma_bc_marshal_reply(rqst);
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if (rc < 0)
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goto failed_marshal;
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if (rpcrdma_post_sends(r_xprt, req))
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goto drop_connection;
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return 0;
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failed_marshal:
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if (rc != -ENOTCONN)
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return rc;
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drop_connection:
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xprt_rdma_close(xprt);
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return -ENOTCONN;
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}
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/**
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* xprt_rdma_bc_destroy - Release resources for handling backchannel requests
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* @xprt: transport associated with these backchannel resources
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* @reqs: number of incoming requests to destroy; ignored
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*/
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void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
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{
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struct rpc_rqst *rqst, *tmp;
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spin_lock(&xprt->bc_pa_lock);
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list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
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list_del(&rqst->rq_bc_pa_list);
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spin_unlock(&xprt->bc_pa_lock);
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rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
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spin_lock(&xprt->bc_pa_lock);
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}
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spin_unlock(&xprt->bc_pa_lock);
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}
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/**
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* xprt_rdma_bc_free_rqst - Release a backchannel rqst
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* @rqst: request to release
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*/
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void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
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{
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struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
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struct rpc_xprt *xprt = rqst->rq_xprt;
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rpcrdma_recv_buffer_put(req->rl_reply);
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req->rl_reply = NULL;
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spin_lock(&xprt->bc_pa_lock);
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list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
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spin_unlock(&xprt->bc_pa_lock);
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xprt_put(xprt);
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}
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static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
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{
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struct rpc_xprt *xprt = &r_xprt->rx_xprt;
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struct rpcrdma_req *req;
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struct rpc_rqst *rqst;
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size_t size;
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spin_lock(&xprt->bc_pa_lock);
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rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
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rq_bc_pa_list);
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if (!rqst)
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goto create_req;
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list_del(&rqst->rq_bc_pa_list);
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spin_unlock(&xprt->bc_pa_lock);
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return rqst;
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create_req:
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spin_unlock(&xprt->bc_pa_lock);
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/* Set a limit to prevent a remote from overrunning our resources.
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*/
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if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
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return NULL;
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size = min_t(size_t, r_xprt->rx_ep->re_inline_recv, PAGE_SIZE);
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req = rpcrdma_req_create(r_xprt, size, GFP_KERNEL);
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if (!req)
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return NULL;
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if (rpcrdma_req_setup(r_xprt, req)) {
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rpcrdma_req_destroy(req);
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return NULL;
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}
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xprt->bc_alloc_count++;
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rqst = &req->rl_slot;
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rqst->rq_xprt = xprt;
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__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
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xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
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return rqst;
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}
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/**
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* rpcrdma_bc_receive_call - Handle a backward direction call
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* @r_xprt: transport receiving the call
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* @rep: receive buffer containing the call
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*
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* Operational assumptions:
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* o Backchannel credits are ignored, just as the NFS server
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* forechannel currently does
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* o The ULP manages a replay cache (eg, NFSv4.1 sessions).
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* No replay detection is done at the transport level
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*/
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void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
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struct rpcrdma_rep *rep)
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{
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struct rpc_xprt *xprt = &r_xprt->rx_xprt;
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struct svc_serv *bc_serv;
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struct rpcrdma_req *req;
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struct rpc_rqst *rqst;
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struct xdr_buf *buf;
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size_t size;
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__be32 *p;
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p = xdr_inline_decode(&rep->rr_stream, 0);
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size = xdr_stream_remaining(&rep->rr_stream);
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#ifdef RPCRDMA_BACKCHANNEL_DEBUG
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pr_info("RPC: %s: callback XID %08x, length=%u\n",
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__func__, be32_to_cpup(p), size);
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pr_info("RPC: %s: %*ph\n", __func__, size, p);
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#endif
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rqst = rpcrdma_bc_rqst_get(r_xprt);
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if (!rqst)
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goto out_overflow;
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rqst->rq_reply_bytes_recvd = 0;
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rqst->rq_xid = *p;
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rqst->rq_private_buf.len = size;
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buf = &rqst->rq_rcv_buf;
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memset(buf, 0, sizeof(*buf));
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buf->head[0].iov_base = p;
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buf->head[0].iov_len = size;
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buf->len = size;
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/* The receive buffer has to be hooked to the rpcrdma_req
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* so that it is not released while the req is pointing
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* to its buffer, and so that it can be reposted after
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* the Upper Layer is done decoding it.
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*/
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req = rpcr_to_rdmar(rqst);
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req->rl_reply = rep;
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trace_xprtrdma_cb_call(rqst);
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/* Queue rqst for ULP's callback service */
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bc_serv = xprt->bc_serv;
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xprt_get(xprt);
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spin_lock(&bc_serv->sv_cb_lock);
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list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
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spin_unlock(&bc_serv->sv_cb_lock);
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wake_up(&bc_serv->sv_cb_waitq);
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r_xprt->rx_stats.bcall_count++;
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return;
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out_overflow:
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pr_warn("RPC/RDMA backchannel overflow\n");
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xprt_force_disconnect(xprt);
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/* This receive buffer gets reposted automatically
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* when the connection is re-established.
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*/
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return;
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}
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