whiterose

linux unikernel
Log | Files | Refs | README | LICENSE | git clone https://git.ne02ptzero.me/git/whiterose

backchannel.c (8136B)


      1 // SPDX-License-Identifier: GPL-2.0
      2 /*
      3  * Copyright (c) 2015 Oracle.  All rights reserved.
      4  *
      5  * Support for backward direction RPCs on RPC/RDMA.
      6  */
      7 
      8 #include <linux/sunrpc/xprt.h>
      9 #include <linux/sunrpc/svc.h>
     10 #include <linux/sunrpc/svc_xprt.h>
     11 #include <linux/sunrpc/svc_rdma.h>
     12 
     13 #include "xprt_rdma.h"
     14 #include <trace/events/rpcrdma.h>
     15 
     16 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
     17 # define RPCDBG_FACILITY	RPCDBG_TRANS
     18 #endif
     19 
     20 #undef RPCRDMA_BACKCHANNEL_DEBUG
     21 
     22 static int rpcrdma_bc_setup_reqs(struct rpcrdma_xprt *r_xprt,
     23 				 unsigned int count)
     24 {
     25 	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
     26 	struct rpcrdma_req *req;
     27 	struct rpc_rqst *rqst;
     28 	unsigned int i;
     29 
     30 	for (i = 0; i < (count << 1); i++) {
     31 		struct rpcrdma_regbuf *rb;
     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;
     40 		INIT_LIST_HEAD(&rqst->rq_bc_list);
     41 		__set_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state);
     42 		spin_lock(&xprt->bc_pa_lock);
     43 		list_add(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
     44 		spin_unlock(&xprt->bc_pa_lock);
     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 	}
     54 	return 0;
     55 
     56 out_fail:
     57 	rpcrdma_req_destroy(req);
     58 	return -ENOMEM;
     59 }
     60 
     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);
     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 	 */
     82 	if (reqs > RPCRDMA_BACKWARD_WRS >> 1)
     83 		goto out_err;
     84 
     85 	rc = rpcrdma_bc_setup_reqs(r_xprt, reqs);
     86 	if (rc)
     87 		goto out_free;
     88 
     89 	r_xprt->rx_buf.rb_bc_srv_max_requests = reqs;
     90 	trace_xprtrdma_cb_setup(r_xprt, reqs);
     91 	return 0;
     92 
     93 out_free:
     94 	xprt_rdma_bc_destroy(xprt, reqs);
     95 
     96 out_err:
     97 	pr_err("RPC:       %s: setup backchannel transport failed\n", __func__);
     98 	return -ENOMEM;
     99 }
    100 
    101 /**
    102  * xprt_rdma_bc_maxpayload - Return maximum backchannel message size
    103  * @xprt: transport
    104  *
    105  * Returns maximum size, in bytes, of a backchannel message
    106  */
    107 size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *xprt)
    108 {
    109 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
    110 	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
    111 	size_t maxmsg;
    112 
    113 	maxmsg = min_t(unsigned int, cdata->inline_rsize, cdata->inline_wsize);
    114 	maxmsg = min_t(unsigned int, maxmsg, PAGE_SIZE);
    115 	return maxmsg - RPCRDMA_HDRLEN_MIN;
    116 }
    117 
    118 static int rpcrdma_bc_marshal_reply(struct rpc_rqst *rqst)
    119 {
    120 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
    121 	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
    122 	__be32 *p;
    123 
    124 	rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
    125 	xdr_init_encode(&req->rl_stream, &req->rl_hdrbuf,
    126 			req->rl_rdmabuf->rg_base, rqst);
    127 
    128 	p = xdr_reserve_space(&req->rl_stream, 28);
    129 	if (unlikely(!p))
    130 		return -EIO;
    131 	*p++ = rqst->rq_xid;
    132 	*p++ = rpcrdma_version;
    133 	*p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_srv_max_requests);
    134 	*p++ = rdma_msg;
    135 	*p++ = xdr_zero;
    136 	*p++ = xdr_zero;
    137 	*p = xdr_zero;
    138 
    139 	if (rpcrdma_prepare_send_sges(r_xprt, req, RPCRDMA_HDRLEN_MIN,
    140 				      &rqst->rq_snd_buf, rpcrdma_noch))
    141 		return -EIO;
    142 
    143 	trace_xprtrdma_cb_reply(rqst);
    144 	return 0;
    145 }
    146 
    147 /**
    148  * xprt_rdma_bc_send_reply - marshal and send a backchannel reply
    149  * @rqst: RPC rqst with a backchannel RPC reply in rq_snd_buf
    150  *
    151  * Caller holds the transport's write lock.
    152  *
    153  * Returns:
    154  *	%0 if the RPC message has been sent
    155  *	%-ENOTCONN if the caller should reconnect and call again
    156  *	%-EIO if a permanent error occurred and the request was not
    157  *		sent. Do not try to send this message again.
    158  */
    159 int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst)
    160 {
    161 	struct rpc_xprt *xprt = rqst->rq_xprt;
    162 	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
    163 	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
    164 	int rc;
    165 
    166 	if (!xprt_connected(xprt))
    167 		return -ENOTCONN;
    168 
    169 	if (!xprt_request_get_cong(xprt, rqst))
    170 		return -EBADSLT;
    171 
    172 	rc = rpcrdma_bc_marshal_reply(rqst);
    173 	if (rc < 0)
    174 		goto failed_marshal;
    175 
    176 	if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
    177 		goto drop_connection;
    178 	return 0;
    179 
    180 failed_marshal:
    181 	if (rc != -ENOTCONN)
    182 		return rc;
    183 drop_connection:
    184 	xprt_rdma_close(xprt);
    185 	return -ENOTCONN;
    186 }
    187 
    188 /**
    189  * xprt_rdma_bc_destroy - Release resources for handling backchannel requests
    190  * @xprt: transport associated with these backchannel resources
    191  * @reqs: number of incoming requests to destroy; ignored
    192  */
    193 void xprt_rdma_bc_destroy(struct rpc_xprt *xprt, unsigned int reqs)
    194 {
    195 	struct rpc_rqst *rqst, *tmp;
    196 
    197 	spin_lock(&xprt->bc_pa_lock);
    198 	list_for_each_entry_safe(rqst, tmp, &xprt->bc_pa_list, rq_bc_pa_list) {
    199 		list_del(&rqst->rq_bc_pa_list);
    200 		spin_unlock(&xprt->bc_pa_lock);
    201 
    202 		rpcrdma_req_destroy(rpcr_to_rdmar(rqst));
    203 
    204 		spin_lock(&xprt->bc_pa_lock);
    205 	}
    206 	spin_unlock(&xprt->bc_pa_lock);
    207 }
    208 
    209 /**
    210  * xprt_rdma_bc_free_rqst - Release a backchannel rqst
    211  * @rqst: request to release
    212  */
    213 void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
    214 {
    215 	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
    216 	struct rpc_xprt *xprt = rqst->rq_xprt;
    217 
    218 	rpcrdma_recv_buffer_put(req->rl_reply);
    219 	req->rl_reply = NULL;
    220 
    221 	spin_lock(&xprt->bc_pa_lock);
    222 	list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
    223 	spin_unlock(&xprt->bc_pa_lock);
    224 }
    225 
    226 /**
    227  * rpcrdma_bc_receive_call - Handle a backward direction call
    228  * @r_xprt: transport receiving the call
    229  * @rep: receive buffer containing the call
    230  *
    231  * Operational assumptions:
    232  *    o Backchannel credits are ignored, just as the NFS server
    233  *      forechannel currently does
    234  *    o The ULP manages a replay cache (eg, NFSv4.1 sessions).
    235  *      No replay detection is done at the transport level
    236  */
    237 void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
    238 			     struct rpcrdma_rep *rep)
    239 {
    240 	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
    241 	struct svc_serv *bc_serv;
    242 	struct rpcrdma_req *req;
    243 	struct rpc_rqst *rqst;
    244 	struct xdr_buf *buf;
    245 	size_t size;
    246 	__be32 *p;
    247 
    248 	p = xdr_inline_decode(&rep->rr_stream, 0);
    249 	size = xdr_stream_remaining(&rep->rr_stream);
    250 
    251 #ifdef RPCRDMA_BACKCHANNEL_DEBUG
    252 	pr_info("RPC:       %s: callback XID %08x, length=%u\n",
    253 		__func__, be32_to_cpup(p), size);
    254 	pr_info("RPC:       %s: %*ph\n", __func__, size, p);
    255 #endif
    256 
    257 	/* Grab a free bc rqst */
    258 	spin_lock(&xprt->bc_pa_lock);
    259 	if (list_empty(&xprt->bc_pa_list)) {
    260 		spin_unlock(&xprt->bc_pa_lock);
    261 		goto out_overflow;
    262 	}
    263 	rqst = list_first_entry(&xprt->bc_pa_list,
    264 				struct rpc_rqst, rq_bc_pa_list);
    265 	list_del(&rqst->rq_bc_pa_list);
    266 	spin_unlock(&xprt->bc_pa_lock);
    267 
    268 	/* Prepare rqst */
    269 	rqst->rq_reply_bytes_recvd = 0;
    270 	rqst->rq_xid = *p;
    271 
    272 	rqst->rq_private_buf.len = size;
    273 
    274 	buf = &rqst->rq_rcv_buf;
    275 	memset(buf, 0, sizeof(*buf));
    276 	buf->head[0].iov_base = p;
    277 	buf->head[0].iov_len = size;
    278 	buf->len = size;
    279 
    280 	/* The receive buffer has to be hooked to the rpcrdma_req
    281 	 * so that it is not released while the req is pointing
    282 	 * to its buffer, and so that it can be reposted after
    283 	 * the Upper Layer is done decoding it.
    284 	 */
    285 	req = rpcr_to_rdmar(rqst);
    286 	req->rl_reply = rep;
    287 	trace_xprtrdma_cb_call(rqst);
    288 
    289 	/* Queue rqst for ULP's callback service */
    290 	bc_serv = xprt->bc_serv;
    291 	spin_lock(&bc_serv->sv_cb_lock);
    292 	list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
    293 	spin_unlock(&bc_serv->sv_cb_lock);
    294 
    295 	wake_up(&bc_serv->sv_cb_waitq);
    296 
    297 	r_xprt->rx_stats.bcall_count++;
    298 	return;
    299 
    300 out_overflow:
    301 	pr_warn("RPC/RDMA backchannel overflow\n");
    302 	xprt_force_disconnect(xprt);
    303 	/* This receive buffer gets reposted automatically
    304 	 * when the connection is re-established.
    305 	 */
    306 	return;
    307 }