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

/*
 * Copyright (c) 2015 Oracle.  All rights reserved.
 *
 * Support for backward direction RPCs on RPC/RDMA.
 */

#include <linux/module.h>
#include <linux/sunrpc/xprt.h>
#include <linux/sunrpc/svc.h>
#include <linux/sunrpc/svc_xprt.h>

#include "xprt_rdma.h"

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

#undef RPCRDMA_BACKCHANNEL_DEBUG

static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
				 struct rpc_rqst *rqst)
{
	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);

	spin_lock(&buf->rb_reqslock);
	list_del(&req->rl_all);
	spin_unlock(&buf->rb_reqslock);

	rpcrdma_destroy_req(req);

	kfree(rqst);
}

static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
				 struct rpc_rqst *rqst)
{
	struct rpcrdma_regbuf *rb;
	struct rpcrdma_req *req;
	size_t size;

	req = rpcrdma_create_req(r_xprt);
	if (IS_ERR(req))
		return PTR_ERR(req);
	req->rl_backchannel = true;

	rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
				  DMA_TO_DEVICE, GFP_KERNEL);
	if (IS_ERR(rb))
		goto out_fail;
	req->rl_rdmabuf = rb;
	xdr_buf_init(&req->rl_hdrbuf, rb->rg_base, rdmab_length(rb));

	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));
	rpcrdma_set_xprtdata(rqst, req);
	return 0;

out_fail:
	rpcrdma_bc_free_rqst(r_xprt, rqst);
	return -ENOMEM;
}

/* Allocate and add receive buffers to the rpcrdma_buffer's
 * existing list of rep's. These are released when the
 * transport is destroyed.
 */
static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
				 unsigned int count)
{
	struct rpcrdma_rep *rep;
	int rc = 0;

	while (count--) {
		rep = rpcrdma_create_rep(r_xprt);
		if (IS_ERR(rep)) {
			pr_err("RPC:       %s: reply buffer alloc failed\n",
			       __func__);
			rc = PTR_ERR(rep);
			break;
		}

		rpcrdma_recv_buffer_put(rep);
	}

	return rc;
}

/**
 * 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);
	struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
	struct rpc_rqst *rqst;
	unsigned int i;
	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;

	for (i = 0; i < (reqs << 1); i++) {
		rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
		if (!rqst)
			goto out_free;

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

		rqst->rq_xprt = &r_xprt->rx_xprt;
		INIT_LIST_HEAD(&rqst->rq_list);
		INIT_LIST_HEAD(&rqst->rq_bc_list);

		if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
			goto out_free;

		spin_lock_bh(&xprt->bc_pa_lock);
		list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
		spin_unlock_bh(&xprt->bc_pa_lock);
	}

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

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

	buffer->rb_bc_srv_max_requests = reqs;
	request_module("svcrdma");

	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;
}

/**
 * rpcrdma_bc_marshal_reply - Send backwards direction reply
 * @rqst: buffer containing RPC reply data
 *
 * Returns zero on success.
 */
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;
	return 0;
}

/**
 * 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 rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	struct rpc_rqst *rqst, *tmp;

	spin_lock_bh(&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_bh(&xprt->bc_pa_lock);

		rpcrdma_bc_free_rqst(r_xprt, rqst);

		spin_lock_bh(&xprt->bc_pa_lock);
	}
	spin_unlock_bh(&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 rpc_xprt *xprt = rqst->rq_xprt;

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

	smp_mb__before_atomic();
	WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
	clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
	smp_mb__after_atomic();

	spin_lock_bh(&xprt->bc_pa_lock);
	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
	spin_unlock_bh(&xprt->bc_pa_lock);
}

/**
 * rpcrdma_bc_receive_call - Handle a backward direction call
 * @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);
	dprintk("RPC:       %s: using rqst %p\n", __func__, rqst);

	/* Prepare rqst */
	rqst->rq_reply_bytes_recvd = 0;
	rqst->rq_bytes_sent = 0;
	rqst->rq_xid = *p;

	rqst->rq_private_buf.len = size;
	set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);

	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);
	dprintk("RPC:       %s: attaching rep %p to req %p\n",
		__func__, rep, req);
	req->rl_reply = rep;

	/* Defeat the retransmit detection logic in send_request */
	req->rl_connect_cookie = 0;

	/* 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_disconnect_done(xprt);
	/* This receive buffer gets reposted automatically
	 * when the connection is re-established.
	 */
	return;
}
Commit	Line	Data
f531a5db CL	1	/*
	2	* Copyright (c) 2015 Oracle. All rights reserved.
	3	*
	4	* Support for backward direction RPCs on RPC/RDMA.
	5	*/
	6
	7	#include <linux/module.h>
63cae470 CL	8	#include <linux/sunrpc/xprt.h>
63cae470 CL	9	#include <linux/sunrpc/svc.h>
76566773	10	#include <linux/sunrpc/svc_xprt.h>
f531a5db CL	11
	12	#include "xprt_rdma.h"
	13
	14	#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
	15	# define RPCDBG_FACILITY RPCDBG_TRANS
	16	#endif
	17
c8bbe0c7	18	#undef RPCRDMA_BACKCHANNEL_DEBUG
63cae470	19
f531a5db CL	20	static void rpcrdma_bc_free_rqst(struct rpcrdma_xprt *r_xprt,
	21	struct rpc_rqst *rqst)
	22	{
	23	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
	24	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
	25
	26	spin_lock(&buf->rb_reqslock);
	27	list_del(&req->rl_all);
	28	spin_unlock(&buf->rb_reqslock);
	29
13650c23	30	rpcrdma_destroy_req(req);
f531a5db CL	31
	32	kfree(rqst);
	33	}
	34
	35	static int rpcrdma_bc_setup_rqst(struct rpcrdma_xprt *r_xprt,
	36	struct rpc_rqst *rqst)
	37	{
f531a5db CL	38	struct rpcrdma_regbuf *rb;
f531a5db CL	39	struct rpcrdma_req *req;
f531a5db CL	40	size_t size;
	41
	42	req = rpcrdma_create_req(r_xprt);
abfb6897 DC	43	if (IS_ERR(req))
abfb6897 DC	44	return PTR_ERR(req);
f531a5db CL	45	req->rl_backchannel = true;
f531a5db CL	46
13650c23	47	rb = rpcrdma_alloc_regbuf(RPCRDMA_HDRBUF_SIZE,
99ef4db3	48	DMA_TO_DEVICE, GFP_KERNEL);
f531a5db CL	49	if (IS_ERR(rb))
	50	goto out_fail;
	51	req->rl_rdmabuf = rb;
7ec910e7	52	xdr_buf_init(&req->rl_hdrbuf, rb->rg_base, rdmab_length(rb));
f531a5db	53
08cf2efd	54	size = r_xprt->rx_data.inline_rsize;
13650c23	55	rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, GFP_KERNEL);
f531a5db CL	56	if (IS_ERR(rb))
f531a5db CL	57	goto out_fail;
f531a5db	58	req->rl_sendbuf = rb;
62aee0e3 CL	59	xdr_buf_init(&rqst->rq_snd_buf, rb->rg_base,
62aee0e3 CL	60	min_t(size_t, size, PAGE_SIZE));
5a6d1db4	61	rpcrdma_set_xprtdata(rqst, req);
f531a5db CL	62	return 0;
	63
	64	out_fail:
	65	rpcrdma_bc_free_rqst(r_xprt, rqst);
	66	return -ENOMEM;
	67	}
	68
	69	/* Allocate and add receive buffers to the rpcrdma_buffer's
	70	* existing list of rep's. These are released when the
	71	* transport is destroyed.
	72	*/
	73	static int rpcrdma_bc_setup_reps(struct rpcrdma_xprt *r_xprt,
	74	unsigned int count)
	75	{
f531a5db	76	struct rpcrdma_rep *rep;
f531a5db CL	77	int rc = 0;
	78
	79	while (count--) {
	80	rep = rpcrdma_create_rep(r_xprt);
	81	if (IS_ERR(rep)) {
	82	pr_err("RPC: %s: reply buffer alloc failed\n",
	83	__func__);
	84	rc = PTR_ERR(rep);
	85	break;
	86	}
	87
9b06688b	88	rpcrdma_recv_buffer_put(rep);
f531a5db CL	89	}
	90
	91	return rc;
	92	}
	93
	94	/**
	95	* xprt_rdma_bc_setup - Pre-allocate resources for handling backchannel requests
	96	* @xprt: transport associated with these backchannel resources
	97	* @reqs: number of concurrent incoming requests to expect
	98	*
	99	* Returns 0 on success; otherwise a negative errno
	100	*/
	101	int xprt_rdma_bc_setup(struct rpc_xprt *xprt, unsigned int reqs)
	102	{
	103	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	104	struct rpcrdma_buffer *buffer = &r_xprt->rx_buf;
	105	struct rpc_rqst *rqst;
	106	unsigned int i;
	107	int rc;
	108
	109	/* The backchannel reply path returns each rpc_rqst to the
	110	* bc_pa_list _after_ the reply is sent. If the server is
	111	* faster than the client, it can send another backward
	112	* direction request before the rpc_rqst is returned to the
	113	* list. The client rejects the request in this case.
	114	*
	115	* Twice as many rpc_rqsts are prepared to ensure there is
	116	* always an rpc_rqst available as soon as a reply is sent.
	117	*/
124fa17d CL	118	if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
	119	goto out_err;
	120
f531a5db CL	121	for (i = 0; i < (reqs << 1); i++) {
f531a5db CL	122	rqst = kzalloc(sizeof(*rqst), GFP_KERNEL);
d2c23c00	123	if (!rqst)
f531a5db	124	goto out_free;
d2c23c00	125
c8bbe0c7	126	dprintk("RPC: %s: new rqst %p\n", __func__, rqst);
f531a5db CL	127
	128	rqst->rq_xprt = &r_xprt->rx_xprt;
	129	INIT_LIST_HEAD(&rqst->rq_list);
	130	INIT_LIST_HEAD(&rqst->rq_bc_list);
	131
	132	if (rpcrdma_bc_setup_rqst(r_xprt, rqst))
	133	goto out_free;
	134
	135	spin_lock_bh(&xprt->bc_pa_lock);
	136	list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
	137	spin_unlock_bh(&xprt->bc_pa_lock);
	138	}
	139
	140	rc = rpcrdma_bc_setup_reps(r_xprt, reqs);
	141	if (rc)
	142	goto out_free;
	143
	144	rc = rpcrdma_ep_post_extra_recv(r_xprt, reqs);
	145	if (rc)
	146	goto out_free;
	147
	148	buffer->rb_bc_srv_max_requests = reqs;
	149	request_module("svcrdma");
	150
	151	return 0;
	152
	153	out_free:
	154	xprt_rdma_bc_destroy(xprt, reqs);
	155
124fa17d	156	out_err:
f531a5db CL	157	pr_err("RPC: %s: setup backchannel transport failed\n", __func__);
	158	return -ENOMEM;
	159	}
	160
76566773 CL	161	/**
	162	* xprt_rdma_bc_up - Create transport endpoint for backchannel service
	163	* @serv: server endpoint
	164	* @net: network namespace
	165	*
	166	* The "xprt" is an implied argument: it supplies the name of the
	167	* backchannel transport class.
	168	*
	169	* Returns zero on success, negative errno on failure
	170	*/
	171	int xprt_rdma_bc_up(struct svc_serv serv, struct net net)
	172	{
	173	int ret;
	174
	175	ret = svc_create_xprt(serv, "rdma-bc", net, PF_INET, 0, 0);
	176	if (ret < 0)
	177	return ret;
	178	return 0;
	179	}
	180
6b26cc8c CL	181	/**
	182	* xprt_rdma_bc_maxpayload - Return maximum backchannel message size
	183	* @xprt: transport
	184	*
	185	* Returns maximum size, in bytes, of a backchannel message
	186	*/
	187	size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
	188	{
	189	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	190	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
	191	size_t maxmsg;
	192
	193	maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
62aee0e3	194	maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
6b26cc8c CL	195	return maxmsg - RPCRDMA_HDRLEN_MIN;
	196	}
	197
83128a60 CL	198	/**
	199	* rpcrdma_bc_marshal_reply - Send backwards direction reply
	200	* @rqst: buffer containing RPC reply data
	201	*
	202	* Returns zero on success.
	203	*/
	204	int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
	205	{
7ec910e7	206	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
83128a60	207	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
7ec910e7 CL	208	__be32 *p;
	209
	210	rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
	211	xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
	212	req->rl_rdmabuf->rg_base);
	213
	214	p = xdr_reserve_space(&req->rl_stream, 28);
	215	if (unlikely(!p))
	216	return -EIO;
	217	*p++ = rqst->rq_xid;
	218	*p++ = rpcrdma_version;
	219	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
	220	*p++ = rdma_msg;
	221	*p++ = xdr_zero;
	222	*p++ = xdr_zero;
	223	*p = xdr_zero;
83128a60	224
857f9aca CL	225	if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
857f9aca CL	226	&rqst->rq_snd_buf, rpcrdma_noch))
655fec69	227	return -EIO;
83128a60 CL	228	return 0;
	229	}
	230
f531a5db CL	231	/**
	232	* xprt_rdma_bc_destroy - Release resources for handling backchannel requests
	233	* @xprt: transport associated with these backchannel resources
	234	* @reqs: number of incoming requests to destroy; ignored
	235	*/
	236	void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
	237	{
	238	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	239	struct rpc_rqst rqst, tmp;
	240
	241	spin_lock_bh(&xprt->bc_pa_lock);
	242	list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
	243	list_del(&rqst->rq_bc_pa_list);
	244	spin_unlock_bh(&xprt->bc_pa_lock);
	245
	246	rpcrdma_bc_free_rqst(r_xprt, rqst);
	247
	248	spin_lock_bh(&xprt->bc_pa_lock);
	249	}
	250	spin_unlock_bh(&xprt->bc_pa_lock);
	251	}
	252
	253	/**
	254	* xprt_rdma_bc_free_rqst - Release a backchannel rqst
	255	* @rqst: request to release
	256	*/
	257	void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
	258	{
	259	struct rpc_xprt *xprt = rqst->rq_xprt;
	260
c8bbe0c7 CL	261	dprintk("RPC: %s: freeing rqst %p (req %p)\n",
	262	__func__, rqst, rpcr_to_rdmar(rqst));
	263
f531a5db CL	264	smp_mb__before_atomic();
	265	WARN_ON_ONCE(!test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state));
	266	clear_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
	267	smp_mb__after_atomic();
	268
	269	spin_lock_bh(&xprt->bc_pa_lock);
	270	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
	271	spin_unlock_bh(&xprt->bc_pa_lock);
	272	}
63cae470 CL	273
	274	/**
	275	* rpcrdma_bc_receive_call - Handle a backward direction call
	276	* @xprt: transport receiving the call
	277	* @rep: receive buffer containing the call
	278	*
63cae470 CL	279	* Operational assumptions:
	280	* o Backchannel credits are ignored, just as the NFS server
	281	* forechannel currently does
	282	* o The ULP manages a replay cache (eg, NFSv4.1 sessions).
	283	* No replay detection is done at the transport level
	284	*/
	285	void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
	286	struct rpcrdma_rep *rep)
	287	{
	288	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
63cae470 CL	289	struct svc_serv *bc_serv;
	290	struct rpcrdma_req *req;
	291	struct rpc_rqst *rqst;
	292	struct xdr_buf *buf;
	293	size_t size;
	294	__be32 *p;
	295
41c8f70f CL	296	p = xdr_inline_decode(&rep->rr_stream, 0);
	297	size = xdr_stream_remaining(&rep->rr_stream);
	298
63cae470 CL	299	#ifdef RPCRDMA_BACKCHANNEL_DEBUG
63cae470 CL	300	pr_info("RPC: %s: callback XID %08x, length=%u\n",
41c8f70f CL	301	__func__, be32_to_cpup(p), size);
41c8f70f CL	302	pr_info("RPC: %s: %*ph\n", __func__, size, p);
63cae470 CL	303	#endif
63cae470 CL	304
63cae470 CL	305	/* Grab a free bc rqst */
	306	spin_lock(&xprt->bc_pa_lock);
	307	if (list_empty(&xprt->bc_pa_list)) {
	308	spin_unlock(&xprt->bc_pa_lock);
	309	goto out_overflow;
	310	}
	311	rqst = list_first_entry(&xprt->bc_pa_list,
	312	struct rpc_rqst, rq_bc_pa_list);
	313	list_del(&rqst->rq_bc_pa_list);
	314	spin_unlock(&xprt->bc_pa_lock);
c8bbe0c7	315	dprintk("RPC: %s: using rqst %p\n", __func__, rqst);
63cae470 CL	316
	317	/* Prepare rqst */
	318	rqst->rq_reply_bytes_recvd = 0;
	319	rqst->rq_bytes_sent = 0;
41c8f70f	320	rqst->rq_xid = *p;
9f74660b CL	321
9f74660b CL	322	rqst->rq_private_buf.len = size;
63cae470 CL	323	set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
	324
	325	buf = &rqst->rq_rcv_buf;
	326	memset(buf, 0, sizeof(*buf));
	327	buf->head[0].iov_base = p;
	328	buf->head[0].iov_len = size;
	329	buf->len = size;
	330
	331	/* The receive buffer has to be hooked to the rpcrdma_req
41c8f70f CL	332	* so that it is not released while the req is pointing
	333	* to its buffer, and so that it can be reposted after
	334	* the Upper Layer is done decoding it.
63cae470 CL	335	*/
63cae470 CL	336	req = rpcr_to_rdmar(rqst);
c8bbe0c7	337	dprintk("RPC: %s: attaching rep %p to req %p\n",
63cae470	338	__func__, rep, req);
63cae470 CL	339	req->rl_reply = rep;
	340
	341	/* Defeat the retransmit detection logic in send_request */
	342	req->rl_connect_cookie = 0;
	343
	344	/* Queue rqst for ULP's callback service */
	345	bc_serv = xprt->bc_serv;
	346	spin_lock(&bc_serv->sv_cb_lock);
	347	list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
	348	spin_unlock(&bc_serv->sv_cb_lock);
	349
	350	wake_up(&bc_serv->sv_cb_waitq);
	351
	352	r_xprt->rx_stats.bcall_count++;
	353	return;
	354
	355	out_overflow:
	356	pr_warn("RPC/RDMA backchannel overflow\n");
	357	xprt_disconnect_done(xprt);
	358	/* This receive buffer gets reposted automatically
	359	* when the connection is re-established.
	360	*/
	361	return;
63cae470	362	}