// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2015-2020, Oracle and/or its affiliates.
*
* Support for reverse-direction RPCs on RPC/RDMA.
*/
#include <linux/sunrpc/xprt.h>
#include <linux/sunrpc/svc.h>
#include <linux/sunrpc/svc_xprt.h>
#include <linux/sunrpc/svc_rdma.h>
#include "xprt_rdma.h"
#include <trace/events/rpcrdma.h>
#undef RPCRDMA_BACKCHANNEL_DEBUG
/**
* xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
* @xprt: transport associated with these backchannel resources
* @reqs: number of concurrent incoming requests to expect
*
* Returns 0 on success; otherwise a negative errno
*/
int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
{
struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
r_xprt->rx_buf.rb_bc_srv_max_requests = RPCRDMA_BACKWARD_WRS >> 1;
trace_xprtrdma_cb_setup(r_xprt, reqs);
return 0;
}
/**
* xprt_rdma_bc_maxpayload - Return maximum backchannel message size
* @xprt: transport
*
* Returns maximum size, in bytes, of a backchannel message
*/
size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
{
struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
struct rpcrdma_ep *ep = r_xprt->rx_ep;
size_t maxmsg;
maxmsg = min_t(unsigned int, ep->re_inline_send, ep->re_inline_recv);
maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
return maxmsg - RPCRDMA_HDRLEN_MIN;
}
unsigned int xprt_rdma_bc_max_slots(struct rpc_xprt *xprt)
{
return RPCRDMA_BACKWARD_WRS >> 1;
}
static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
{
struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
__be32 *p;
rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
rdmab_data(req->rl_rdmabuf), rqst);
p = xdr_reserve_space(&req->rl_stream, 28);
if (unlikely(!p))
return -EIO;
*p++ = rqst->rq_xid;
*p++ = rpcrdma_version;
*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
*p++ = rdma_msg;
*p++ = xdr_zero;
*p++ = xdr_zero;
*p = xdr_zero;
if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
&rqst->rq_snd_buf, rpcrdma_noch_pullup))
return -EIO;
trace_xprtrdma_cb_reply(r_xprt, rqst);
return 0;
}
/**
* xprt_rdma_bc_send_reply - marshal and send a backchannel reply
* @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
*
* Caller holds the transport's write lock.
*
* Returns:
* %0 if the RPC message has been sent
* %-ENOTCONN if the caller should reconnect and call again
* %-EIO if a permanent error occurred and the request was not
* sent. Do not try to send this message again.
*/
int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
{
struct rpc_xprt *xprt = rqst->rq_xprt;
struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
int rc;
if (!xprt_connected(xprt))
return -ENOTCONN;
if (!xprt_request_get_cong(xprt, rqst))
return -EBADSLT;
rc = rpcrdma_bc_marshal_reply(rqst);
if (rc < 0)
goto failed_marshal;
if (frwr_send(r_xprt, req))
goto drop_connection;
return 0;
failed_marshal:
if (rc != -ENOTCONN)
return rc;
drop_connection:
xprt_rdma_close(xprt);
return -ENOTCONN;
}
/**
* xprt_rdma_bc_destroy - Release resources for handling backchannel requests
* @xprt: transport associated with these backchannel resources
* @reqs: number of incoming requests to destroy; ignored
*/
void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
{
struct rpc_rqst *rqst, *tmp;
spin_lock(&xprt->bc_pa_lock);
list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
list_del(&rqst->rq_bc_pa_list);
spin_unlock(&xprt->bc_pa_lock);
rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
spin_lock(&xprt->bc_pa_lock);
}
spin_unlock(&xprt->bc_pa_lock);
}
/**
* xprt_rdma_bc_free_rqst - Release a backchannel rqst
* @rqst: request to release
*/
void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
{
struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
struct rpcrdma_rep *rep = req->rl_reply;
struct rpc_xprt *xprt = rqst->rq_xprt;
struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
rpcrdma_rep_put(&r_xprt->rx_buf, rep);
req->rl_reply = NULL;
spin_lock(&xprt->bc_pa_lock);
list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
spin_unlock(&xprt->bc_pa_lock);
xprt_put(xprt);
}
static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
{
struct rpc_xprt *xprt = &r_xprt->rx_xprt;
struct rpcrdma_req *req;
struct rpc_rqst *rqst;
size_t size;
spin_lock(&xprt->bc_pa_lock);
rqst = list_first_entry_or_null(&xprt->bc_pa_list, struct rpc_rqst,
rq_bc_pa_list);
if (!rqst)
goto create_req;
list_del(&rqst->rq_bc_pa_list);
spin_unlock(&xprt->bc_pa_lock);
return rqst;
create_req:
spin_unlock(&xprt->bc_pa_lock);
/* Set a limit to prevent a remote from overrunning our resources.
*/
if (xprt->bc_alloc_count >= RPCRDMA_BACKWARD_WRS)
return NULL;
size = min_t(size_t, r_xprt->rx_ep->re_inline_recv, PAGE_SIZE);
req = rpcrdma_req_create(r_xprt, size);
if (!req)
return NULL;
if (rpcrdma_req_setup(r_xprt, req)) {
rpcrdma_req_destroy(req);
return NULL;
}
xprt->bc_alloc_count++;
rqst = &req->rl_slot;
rqst->rq_xprt = xprt;
__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
xdr_buf_init(&rqst->rq_snd_buf, rdmab_data(req->rl_sendbuf), size);
return rqst;
}
/**
* rpcrdma_bc_receive_call - Handle a reverse-direction Call
* @r_xprt: transport receiving the call
* @rep: receive buffer containing the call
*
* 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 svc_serv *bc_serv;
struct rpcrdma_req *req;
struct rpc_rqst *rqst;
struct xdr_buf *buf;
size_t size;
__be32 *p;
p = xdr_inline_decode(&rep->rr_stream, 0);
size = xdr_stream_remaining(&rep->rr_stream);
#ifdef RPCRDMA_BACKCHANNEL_DEBUG
pr_info("RPC: %s: callback XID %08x, length=%u\n",
__func__, be32_to_cpup(p), size);
pr_info("RPC: %s: %*ph\n", __func__, size, p);
#endif
rqst = rpcrdma_bc_rqst_get(r_xprt);
if (!rqst)
goto out_overflow;
rqst->rq_reply_bytes_recvd = 0;
rqst->rq_xid = *p;
rqst->rq_private_buf.len = size;
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 is not released while the req is pointing
* to its buffer, and so that it can be reposted after
* the Upper Layer is done decoding it.
*/
req = rpcr_to_rdmar(rqst);
req->rl_reply = rep;
trace_xprtrdma_cb_call(r_xprt, rqst);
/* Queue rqst for ULP's callback service */
bc_serv = xprt->bc_serv;
xprt_get(xprt);
lwq_enqueue(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]);
r_xprt->rx_stats.bcall_count++;
return;
out_overflow:
pr_warn("RPC/RDMA backchannel overflow\n");
xprt_force_disconnect(xprt);
/* This receive buffer gets reposted automatically
* when the connection is re-established.
*/
return;
}
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