[mirror_ubuntu-eoan-kernel.git] / net / sunrpc / xprtrdma / backchannel.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2015 Oracle.  All rights reserved.
 *
 * Support for backward 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>

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# define RPCDBG_FACILITY	RPCDBG_TRANS
#endif

#undef RPCRDMA_BACKCHANNEL_DEBUG

static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
				 unsigned int count)
{
	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
	struct rpcrdma_req *req;
	struct rpc_rqst *rqst;
	unsigned int i;

	for (i = 0; i < (count << 1); i++) {
		struct rpcrdma_regbuf *rb;
		size_t size;

		req = rpcrdma_create_req(r_xprt);
		if (IS_ERR(req))
			return PTR_ERR(req);
		rqst = &req->rl_slot;

		rqst->rq_xprt = xprt;
		INIT_LIST_HEAD(&rqst->rq_bc_list);
		__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
		spin_lock(&xprt->bc_pa_lock);
		list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
		spin_unlock(&xprt->bc_pa_lock);

		size = r_xprt->rx_data.inline_rsize;
		rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
		if (IS_ERR(rb))
			goto out_fail;
		req->rl_sendbuf = rb;
		xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
			     min_t(size_t, size, PAGE_SIZE));
	}
	return 0;

out_fail:
	rpcrdma_req_destroy(req);
	return -ENOMEM;
}

/**
 * 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);
	int rc;

	/* The backchannel reply path returns each rpc_rqst to the
	 * bc_pa_list _after_ the reply is sent. If the server is
	 * faster than the client, it can send another backward
	 * direction request before the rpc_rqst is returned to the
	 * list. The client rejects the request in this case.
	 *
	 * Twice as many rpc_rqsts are prepared to ensure there is
	 * always an rpc_rqst available as soon as a reply is sent.
	 */
	if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
		goto out_err;

	rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
	if (rc)
		goto out_free;

	r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
	trace_xprtrdma_cb_setup(r_xprt, reqs);
	return 0;

out_free:
	xprt_rdma_bc_destroy(xprt, reqs);

out_err:
	pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
	return -ENOMEM;
}

/**
 * xprt_rdma_bc_up - Create transport endpoint for backchannel service
 * @serv: server endpoint
 * @net: network namespace
 *
 * The "xprt" is an implied argument: it supplies the name of the
 * backchannel transport class.
 *
 * Returns zero on success, negative errno on failure
 */
int xprt_rdma_bc_up(struct svc_serv *serv, struct net *net)
{
	int ret;

	ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
	if (ret < 0)
		return ret;
	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_create_data_internal *cdata = &r_xprt->rx_data;
	size_t maxmsg;

	maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
	maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
	return maxmsg - RPCRDMA_HDRLEN_MIN;
}

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,
			req->rl_rdmabuf->rg_base);

	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))
		return -EIO;

	trace_xprtrdma_cb_reply(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 (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, 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 rpc_xprt *xprt = rqst->rq_xprt;

	dprintk("RPC:       %s: freeing rqst %p (req %p)\n",
		__func__, rqst, req);

	rpcrdma_recv_buffer_put(req->rl_reply);
	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);
}

/**
 * rpcrdma_bc_receive_call - Handle a backward 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

	/* 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);

	/* Prepare rqst */
	rqst->rq_reply_bytes_recvd = 0;
	rqst->rq_bytes_sent = 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(rqst);

	/* 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_force_disconnect(xprt);
	/* This receive buffer gets reposted automatically
	 * when the connection is re-established.
	 */
	return;
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
f531a5db CL	2	/*
	3	* Copyright (c) 2015 Oracle. All rights reserved.
	4	*
	5	* Support for backward direction RPCs on RPC/RDMA.
	6	*/
	7
63cae470 CL	8	#include <linux/sunrpc/xprt.h>
63cae470 CL	9	#include <linux/sunrpc/svc.h>
76566773	10	#include <linux/sunrpc/svc_xprt.h>
bd2abef3	11	#include <linux/sunrpc/svc_rdma.h>
f531a5db CL	12
f531a5db CL	13	#include "xprt_rdma.h"
b6e717cb	14	#include <trace/events/rpcrdma.h>
f531a5db CL	15
	16	#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
	17	# define RPCDBG_FACILITY RPCDBG_TRANS
	18	#endif
	19
c8bbe0c7	20	#undef RPCRDMA_BACKCHANNEL_DEBUG
63cae470	21
edb41e61 CL	22	static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
edb41e61 CL	23	unsigned int count)
f531a5db	24	{
edb41e61	25	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
92f4433e	26	struct rpcrdma_req *req;
edb41e61 CL	27	struct rpc_rqst *rqst;
	28	unsigned int i;
	29
	30	for (i = 0; i < (count << 1); i++) {
	31	struct rpcrdma_regbuf *rb;
edb41e61 CL	32	size_t size;
	33
	34	req = rpcrdma_create_req(r_xprt);
	35	if (IS_ERR(req))
	36	return PTR_ERR(req);
	37	rqst = &req->rl_slot;
	38
	39	rqst->rq_xprt = xprt;
edb41e61 CL	40	INIT_LIST_HEAD(&rqst->rq_bc_list);
edb41e61 CL	41	__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
f7d46681	42	spin_lock(&xprt->bc_pa_lock);
edb41e61	43	list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
f7d46681	44	spin_unlock(&xprt->bc_pa_lock);
edb41e61 CL	45
	46	size = r_xprt->rx_data.inline_rsize;
	47	rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
	48	if (IS_ERR(rb))
	49	goto out_fail;
	50	req->rl_sendbuf = rb;
	51	xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
	52	min_t(size_t, size, PAGE_SIZE));
	53	}
f531a5db CL	54	return 0;
	55
	56	out_fail:
92f4433e	57	rpcrdma_req_destroy(req);
f531a5db CL	58	return -ENOMEM;
	59	}
	60
f531a5db CL	61	/**
	62	* xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
	63	* @xprt: transport associated with these backchannel resources
	64	* @reqs: number of concurrent incoming requests to expect
	65	*
	66	* Returns 0 on success; otherwise a negative errno
	67	*/
	68	int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
	69	{
	70	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
f531a5db CL	71	int rc;
	72
	73	/* The backchannel reply path returns each rpc_rqst to the
	74	* bc_pa_list _after_ the reply is sent. If the server is
	75	* faster than the client, it can send another backward
	76	* direction request before the rpc_rqst is returned to the
	77	* list. The client rejects the request in this case.
	78	*
	79	* Twice as many rpc_rqsts are prepared to ensure there is
	80	* always an rpc_rqst available as soon as a reply is sent.
	81	*/
124fa17d CL	82	if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
	83	goto out_err;
	84
edb41e61	85	rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
f531a5db CL	86	if (rc)
	87	goto out_free;
	88
edb41e61	89	r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
fc1eb807	90	trace_xprtrdma_cb_setup(r_xprt, reqs);
f531a5db CL	91	return 0;
	92
	93	out_free:
	94	xprt_rdma_bc_destroy(xprt, reqs);
	95
124fa17d	96	out_err:
f531a5db CL	97	pr_err("RPC: %s: setup backchannel transport failed\n", __func__);
	98	return -ENOMEM;
	99	}
	100
76566773 CL	101	/**
	102	* xprt_rdma_bc_up - Create transport endpoint for backchannel service
	103	* @serv: server endpoint
	104	* @net: network namespace
	105	*
	106	* The "xprt" is an implied argument: it supplies the name of the
	107	* backchannel transport class.
	108	*
	109	* Returns zero on success, negative errno on failure
	110	*/
	111	int xprt_rdma_bc_up(struct svc_serv serv, struct net net)
	112	{
	113	int ret;
	114
	115	ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
	116	if (ret < 0)
	117	return ret;
	118	return 0;
	119	}
	120
6b26cc8c CL	121	/**
	122	* xprt_rdma_bc_maxpayload - Return maximum backchannel message size
	123	* @xprt: transport
	124	*
	125	* Returns maximum size, in bytes, of a backchannel message
	126	*/
	127	size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
	128	{
	129	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	130	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
	131	size_t maxmsg;
	132
	133	maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
62aee0e3	134	maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
6b26cc8c CL	135	return maxmsg - RPCRDMA_HDRLEN_MIN;
	136	}
	137
cf73daf5	138	static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
83128a60	139	{
7ec910e7	140	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
83128a60	141	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
7ec910e7 CL	142	__be32 *p;
	143
	144	rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
	145	xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
	146	req->rl_rdmabuf->rg_base);
	147
	148	p = xdr_reserve_space(&req->rl_stream, 28);
	149	if (unlikely(!p))
	150	return -EIO;
	151	*p++ = rqst->rq_xid;
	152	*p++ = rpcrdma_version;
	153	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
	154	*p++ = rdma_msg;
	155	*p++ = xdr_zero;
	156	*p++ = xdr_zero;
	157	*p = xdr_zero;
83128a60	158
857f9aca CL	159	if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
857f9aca CL	160	&rqst->rq_snd_buf, rpcrdma_noch))
655fec69	161	return -EIO;
fc1eb807 CL	162
fc1eb807 CL	163	trace_xprtrdma_cb_reply(rqst);
83128a60 CL	164	return 0;
	165	}
	166
cf73daf5 CL	167	/**
	168	* xprt_rdma_bc_send_reply - marshal and send a backchannel reply
	169	* @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
	170	*
	171	* Caller holds the transport's write lock.
	172	*
	173	* Returns:
	174	* %0 if the RPC message has been sent
	175	* %-ENOTCONN if the caller should reconnect and call again
	176	* %-EIO if a permanent error occurred and the request was not
	177	* sent. Do not try to send this message again.
	178	*/
	179	int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
	180	{
0c0829bc CL	181	struct rpc_xprt *xprt = rqst->rq_xprt;
0c0829bc CL	182	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
cf73daf5 CL	183	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
	184	int rc;
	185
0c0829bc CL	186	if (!xprt_connected(xprt))
0c0829bc CL	187	return -ENOTCONN;
cf73daf5	188
0c0829bc	189	if (!xprt_request_get_cong(xprt, rqst))
75891f50 TM	190	return -EBADSLT;
75891f50 TM	191
cf73daf5 CL	192	rc = rpcrdma_bc_marshal_reply(rqst);
	193	if (rc < 0)
	194	goto failed_marshal;
	195
	196	if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
	197	goto drop_connection;
	198	return 0;
	199
	200	failed_marshal:
	201	if (rc != -ENOTCONN)
	202	return rc;
	203	drop_connection:
0c0829bc	204	xprt_rdma_close(xprt);
cf73daf5 CL	205	return -ENOTCONN;
	206	}
	207
f531a5db CL	208	/**
	209	* xprt_rdma_bc_destroy - Release resources for handling backchannel requests
	210	* @xprt: transport associated with these backchannel resources
	211	* @reqs: number of incoming requests to destroy; ignored
	212	*/
	213	void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
	214	{
f531a5db CL	215	struct rpc_rqst rqst, tmp;
f531a5db CL	216
f7d46681	217	spin_lock(&xprt->bc_pa_lock);
f531a5db CL	218	list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
f531a5db CL	219	list_del(&rqst->rq_bc_pa_list);
f7d46681	220	spin_unlock(&xprt->bc_pa_lock);
f531a5db	221
92f4433e	222	rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
f531a5db	223
f7d46681	224	spin_lock(&xprt->bc_pa_lock);
f531a5db	225	}
f7d46681	226	spin_unlock(&xprt->bc_pa_lock);
f531a5db CL	227	}
	228
	229	/**
	230	* xprt_rdma_bc_free_rqst - Release a backchannel rqst
	231	* @rqst: request to release
	232	*/
	233	void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
	234	{
7c8d9e7c	235	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
f531a5db CL	236	struct rpc_xprt *xprt = rqst->rq_xprt;
f531a5db CL	237
c8bbe0c7	238	dprintk("RPC: %s: freeing rqst %p (req %p)\n",
7c8d9e7c CL	239	__func__, rqst, req);
	240
	241	rpcrdma_recv_buffer_put(req->rl_reply);
	242	req->rl_reply = NULL;
c8bbe0c7	243
f7d46681	244	spin_lock(&xprt->bc_pa_lock);
f531a5db	245	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
f7d46681	246	spin_unlock(&xprt->bc_pa_lock);
f531a5db	247	}
63cae470 CL	248
	249	/**
	250	* rpcrdma_bc_receive_call - Handle a backward direction call
9ab6d89e	251	* @r_xprt: transport receiving the call
63cae470 CL	252	* @rep: receive buffer containing the call
63cae470 CL	253	*
63cae470 CL	254	* Operational assumptions:
	255	* o Backchannel credits are ignored, just as the NFS server
	256	* forechannel currently does
	257	* o The ULP manages a replay cache (eg, NFSv4.1 sessions).
	258	* No replay detection is done at the transport level
	259	*/
	260	void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
	261	struct rpcrdma_rep *rep)
	262	{
	263	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
63cae470 CL	264	struct svc_serv *bc_serv;
	265	struct rpcrdma_req *req;
	266	struct rpc_rqst *rqst;
	267	struct xdr_buf *buf;
	268	size_t size;
	269	__be32 *p;
	270
41c8f70f CL	271	p = xdr_inline_decode(&rep->rr_stream, 0);
	272	size = xdr_stream_remaining(&rep->rr_stream);
	273
63cae470 CL	274	#ifdef RPCRDMA_BACKCHANNEL_DEBUG
63cae470 CL	275	pr_info("RPC: %s: callback XID %08x, length=%u\n",
41c8f70f CL	276	__func__, be32_to_cpup(p), size);
41c8f70f CL	277	pr_info("RPC: %s: %*ph\n", __func__, size, p);
63cae470 CL	278	#endif
63cae470 CL	279
63cae470 CL	280	/* Grab a free bc rqst */
	281	spin_lock(&xprt->bc_pa_lock);
	282	if (list_empty(&xprt->bc_pa_list)) {
	283	spin_unlock(&xprt->bc_pa_lock);
	284	goto out_overflow;
	285	}
	286	rqst = list_first_entry(&xprt->bc_pa_list,
	287	struct rpc_rqst, rq_bc_pa_list);
	288	list_del(&rqst->rq_bc_pa_list);
	289	spin_unlock(&xprt->bc_pa_lock);
63cae470 CL	290
	291	/* Prepare rqst */
	292	rqst->rq_reply_bytes_recvd = 0;
	293	rqst->rq_bytes_sent = 0;
41c8f70f	294	rqst->rq_xid = *p;
9f74660b CL	295
9f74660b CL	296	rqst->rq_private_buf.len = size;
63cae470 CL	297
	298	buf = &rqst->rq_rcv_buf;
	299	memset(buf, 0, sizeof(*buf));
	300	buf->head[0].iov_base = p;
	301	buf->head[0].iov_len = size;
	302	buf->len = size;
	303
	304	/* The receive buffer has to be hooked to the rpcrdma_req
41c8f70f CL	305	* so that it is not released while the req is pointing
	306	* to its buffer, and so that it can be reposted after
	307	* the Upper Layer is done decoding it.
63cae470 CL	308	*/
63cae470 CL	309	req = rpcr_to_rdmar(rqst);
63cae470	310	req->rl_reply = rep;
fc1eb807	311	trace_xprtrdma_cb_call(rqst);
63cae470	312
63cae470 CL	313	/* Queue rqst for ULP's callback service */
	314	bc_serv = xprt->bc_serv;
	315	spin_lock(&bc_serv->sv_cb_lock);
	316	list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
	317	spin_unlock(&bc_serv->sv_cb_lock);
	318
	319	wake_up(&bc_serv->sv_cb_waitq);
	320
	321	r_xprt->rx_stats.bcall_count++;
	322	return;
	323
	324	out_overflow:
	325	pr_warn("RPC/RDMA backchannel overflow\n");
0c0829bc	326	xprt_force_disconnect(xprt);
63cae470 CL	327	/* This receive buffer gets reposted automatically
	328	* when the connection is re-established.
	329	*/
	330	return;
63cae470	331	}