// SPDX-License-Identifier: GPL-2.0

  /*
   *  Shared Memory Communications over RDMA (SMC-R) and RoCE
   *
   *  Basic Transport Functions exploiting Infiniband API
   *
   *  Copyright IBM Corp. 2016
   *
   *  Author(s):  Ursula Braun <ubraun@linux.vnet.ibm.com>
   */
  
  #include <linux/socket.h>
  #include <linux/if_vlan.h>
  #include <linux/random.h>
  #include <linux/workqueue.h>
  #include <net/tcp.h>
  #include <net/sock.h>
  #include <rdma/ib_verbs.h>
  
  #include "smc.h"
  #include "smc_clc.h"
  #include "smc_core.h"
  #include "smc_ib.h"

  #include "smc_wr.h"

  #include "smc_llc.h"

  #include "smc_cdc.h"

  #include "smc_close.h"

  #define SMC_LGR_NUM_INCR		256
  #define SMC_LGR_FREE_DELAY_SERV		(600 * HZ)
  #define SMC_LGR_FREE_DELAY_CLNT		(SMC_LGR_FREE_DELAY_SERV + 10)

  static u32 smc_lgr_num;			/* unique link group number */

  /* Register connection's alert token in our lookup structure.
   * To use rbtrees we have to implement our own insert core.
   * Requires @conns_lock
   * @smc		connection to register
   * Returns 0 on success, != otherwise.
   */
  static void smc_lgr_add_alert_token(struct smc_connection *conn)
  {
  	struct rb_node **link, *parent = NULL;
  	u32 token = conn->alert_token_local;
  
  	link = &conn->lgr->conns_all.rb_node;
  	while (*link) {
  		struct smc_connection *cur = rb_entry(*link,
  					struct smc_connection, alert_node);
  
  		parent = *link;
  		if (cur->alert_token_local > token)
  			link = &parent->rb_left;
  		else
  			link = &parent->rb_right;
  	}
  	/* Put the new node there */
  	rb_link_node(&conn->alert_node, parent, link);
  	rb_insert_color(&conn->alert_node, &conn->lgr->conns_all);
  }
  
  /* Register connection in link group by assigning an alert token
   * registered in a search tree.
   * Requires @conns_lock
   * Note that '0' is a reserved value and not assigned.
   */
  static void smc_lgr_register_conn(struct smc_connection *conn)
  {
  	struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
  	static atomic_t nexttoken = ATOMIC_INIT(0);
  
  	/* find a new alert_token_local value not yet used by some connection
  	 * in this link group
  	 */
  	sock_hold(&smc->sk); /* sock_put in smc_lgr_unregister_conn() */
  	while (!conn->alert_token_local) {
  		conn->alert_token_local = atomic_inc_return(&nexttoken);
  		if (smc_lgr_find_conn(conn->alert_token_local, conn->lgr))
  			conn->alert_token_local = 0;
  	}
  	smc_lgr_add_alert_token(conn);
  	conn->lgr->conns_num++;
  }
  
  /* Unregister connection and reset the alert token of the given connection<
   */
  static void __smc_lgr_unregister_conn(struct smc_connection *conn)
  {
  	struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
  	struct smc_link_group *lgr = conn->lgr;
  
  	rb_erase(&conn->alert_node, &lgr->conns_all);
  	lgr->conns_num--;
  	conn->alert_token_local = 0;
  	conn->lgr = NULL;
  	sock_put(&smc->sk); /* sock_hold in smc_lgr_register_conn() */
  }
  
  /* Unregister connection and trigger lgr freeing if applicable
   */
  static void smc_lgr_unregister_conn(struct smc_connection *conn)
  {
  	struct smc_link_group *lgr = conn->lgr;
  	int reduced = 0;
  
  	write_lock_bh(&lgr->conns_lock);
  	if (conn->alert_token_local) {
  		reduced = 1;
  		__smc_lgr_unregister_conn(conn);
  	}
  	write_unlock_bh(&lgr->conns_lock);

  	if (!reduced || lgr->conns_num)
  		return;
  	/* client link group creation always follows the server link group
  	 * creation. For client use a somewhat higher removal delay time,
  	 * otherwise there is a risk of out-of-sync link groups.
  	 */
  	mod_delayed_work(system_wq, &lgr->free_work,
  			 lgr->role == SMC_CLNT ? SMC_LGR_FREE_DELAY_CLNT :
  						 SMC_LGR_FREE_DELAY_SERV);

  }
  
  static void smc_lgr_free_work(struct work_struct *work)
  {
  	struct smc_link_group *lgr = container_of(to_delayed_work(work),
  						  struct smc_link_group,
  						  free_work);
  	bool conns;
  
  	spin_lock_bh(&smc_lgr_list.lock);
  	read_lock_bh(&lgr->conns_lock);
  	conns = RB_EMPTY_ROOT(&lgr->conns_all);
  	read_unlock_bh(&lgr->conns_lock);
  	if (!conns) { /* number of lgr connections is no longer zero */
  		spin_unlock_bh(&smc_lgr_list.lock);
  		return;
  	}
  	list_del_init(&lgr->list); /* remove from smc_lgr_list */
  	spin_unlock_bh(&smc_lgr_list.lock);
  	smc_lgr_free(lgr);
  }
  
  /* create a new SMC link group */
  static int smc_lgr_create(struct smc_sock *smc, __be32 peer_in_addr,
  			  struct smc_ib_device *smcibdev, u8 ibport,
  			  char *peer_systemid, unsigned short vlan_id)
  {
  	struct smc_link_group *lgr;
  	struct smc_link *lnk;
  	u8 rndvec[3];
  	int rc = 0;

  	int i;

  
  	lgr = kzalloc(sizeof(*lgr), GFP_KERNEL);
  	if (!lgr) {
  		rc = -ENOMEM;
  		goto out;
  	}
  	lgr->role = smc->listen_smc ? SMC_SERV : SMC_CLNT;
  	lgr->sync_err = false;
  	lgr->daddr = peer_in_addr;
  	memcpy(lgr->peer_systemid, peer_systemid, SMC_SYSTEMID_LEN);
  	lgr->vlan_id = vlan_id;

  	rwlock_init(&lgr->sndbufs_lock);
  	rwlock_init(&lgr->rmbs_lock);
  	for (i = 0; i < SMC_RMBE_SIZES; i++) {
  		INIT_LIST_HEAD(&lgr->sndbufs[i]);
  		INIT_LIST_HEAD(&lgr->rmbs[i]);
  	}

  	smc_lgr_num += SMC_LGR_NUM_INCR;
  	memcpy(&lgr->id, (u8 *)&smc_lgr_num, SMC_LGR_ID_SIZE);

  	INIT_DELAYED_WORK(&lgr->free_work, smc_lgr_free_work);
  	lgr->conns_all = RB_ROOT;
  
  	lnk = &lgr->lnk[SMC_SINGLE_LINK];
  	/* initialize link */

  	lnk->link_id = SMC_SINGLE_LINK;

  	lnk->smcibdev = smcibdev;
  	lnk->ibport = ibport;
  	lnk->path_mtu = smcibdev->pattr[ibport - 1].active_mtu;

  	if (!smcibdev->initialized)
  		smc_ib_setup_per_ibdev(smcibdev);

  	get_random_bytes(rndvec, sizeof(rndvec));
  	lnk->psn_initial = rndvec[0] + (rndvec[1] << 8) + (rndvec[2] << 16);

  	rc = smc_wr_alloc_link_mem(lnk);
  	if (rc)
  		goto free_lgr;

  	rc = smc_ib_create_protection_domain(lnk);
  	if (rc)
  		goto free_link_mem;
  	rc = smc_ib_create_queue_pair(lnk);
  	if (rc)
  		goto dealloc_pd;
  	rc = smc_wr_create_link(lnk);
  	if (rc)
  		goto destroy_qp;

  	init_completion(&lnk->llc_confirm);
  	init_completion(&lnk->llc_confirm_resp);

  
  	smc->conn.lgr = lgr;
  	rwlock_init(&lgr->conns_lock);
  	spin_lock_bh(&smc_lgr_list.lock);
  	list_add(&lgr->list, &smc_lgr_list.list);
  	spin_unlock_bh(&smc_lgr_list.lock);

  	return 0;

  destroy_qp:
  	smc_ib_destroy_queue_pair(lnk);
  dealloc_pd:
  	smc_ib_dealloc_protection_domain(lnk);
  free_link_mem:
  	smc_wr_free_link_mem(lnk);

  free_lgr:
  	kfree(lgr);

  out:
  	return rc;
  }

  static void smc_buf_unuse(struct smc_connection *conn)

  {
  	if (conn->sndbuf_desc) {
  		conn->sndbuf_desc->used = 0;
  		conn->sndbuf_size = 0;
  	}

  	if (conn->rmb_desc) {

  		conn->rmb_desc->reused = true;

  		conn->rmb_desc->used = 0;
  		conn->rmbe_size = 0;
  	}
  }

  /* remove a finished connection from its link group */
  void smc_conn_free(struct smc_connection *conn)
  {
  	struct smc_link_group *lgr = conn->lgr;
  
  	if (!lgr)
  		return;

  	smc_cdc_tx_dismiss_slots(conn);

  	smc_lgr_unregister_conn(conn);

  	smc_buf_unuse(conn);

  }
  
  static void smc_link_clear(struct smc_link *lnk)
  {
  	lnk->peer_qpn = 0;

  	smc_ib_modify_qp_reset(lnk);

  	smc_wr_free_link(lnk);

  	smc_ib_destroy_queue_pair(lnk);
  	smc_ib_dealloc_protection_domain(lnk);

  	smc_wr_free_link_mem(lnk);

  }

  static void smc_buf_free(struct smc_buf_desc *buf_desc, struct smc_link *lnk,
  			 bool is_rmb)

  {

  	if (is_rmb) {
  		if (buf_desc->mr_rx[SMC_SINGLE_LINK])
  			smc_ib_put_memory_region(
  					buf_desc->mr_rx[SMC_SINGLE_LINK]);
  		smc_ib_buf_unmap_sg(lnk->smcibdev, buf_desc,
  				    DMA_FROM_DEVICE);
  	} else {
  		smc_ib_buf_unmap_sg(lnk->smcibdev, buf_desc,
  				    DMA_TO_DEVICE);

  	}

  	sg_free_table(&buf_desc->sgt[SMC_SINGLE_LINK]);
  	if (buf_desc->cpu_addr)
  		free_pages((unsigned long)buf_desc->cpu_addr, buf_desc->order);
  	kfree(buf_desc);

  }

  static void __smc_lgr_free_bufs(struct smc_link_group *lgr, bool is_rmb)

  {

  	struct smc_link *lnk = &lgr->lnk[SMC_SINGLE_LINK];

  	struct smc_buf_desc *buf_desc, *bf_desc;
  	struct list_head *buf_list;

  	int i;
  
  	for (i = 0; i < SMC_RMBE_SIZES; i++) {

  		if (is_rmb)
  			buf_list = &lgr->rmbs[i];
  		else
  			buf_list = &lgr->sndbufs[i];
  		list_for_each_entry_safe(buf_desc, bf_desc, buf_list,

  					 list) {

  			list_del(&buf_desc->list);
  			smc_buf_free(buf_desc, lnk, is_rmb);

  		}
  	}
  }

  static void smc_lgr_free_bufs(struct smc_link_group *lgr)
  {
  	/* free send buffers */
  	__smc_lgr_free_bufs(lgr, false);
  	/* free rmbs */
  	__smc_lgr_free_bufs(lgr, true);
  }

  /* remove a link group */
  void smc_lgr_free(struct smc_link_group *lgr)
  {

  	smc_lgr_free_bufs(lgr);

  	smc_link_clear(&lgr->lnk[SMC_SINGLE_LINK]);
  	kfree(lgr);
  }
  
  /* terminate linkgroup abnormally */
  void smc_lgr_terminate(struct smc_link_group *lgr)
  {
  	struct smc_connection *conn;

  	struct smc_sock *smc;

  	struct rb_node *node;
  
  	spin_lock_bh(&smc_lgr_list.lock);
  	if (list_empty(&lgr->list)) {
  		/* termination already triggered */
  		spin_unlock_bh(&smc_lgr_list.lock);
  		return;
  	}
  	/* do not use this link group for new connections */
  	list_del_init(&lgr->list);
  	spin_unlock_bh(&smc_lgr_list.lock);
  
  	write_lock_bh(&lgr->conns_lock);
  	node = rb_first(&lgr->conns_all);
  	while (node) {
  		conn = rb_entry(node, struct smc_connection, alert_node);

  		smc = container_of(conn, struct smc_sock, conn);
  		sock_hold(&smc->sk);

  		__smc_lgr_unregister_conn(conn);

  		schedule_work(&conn->close_work);

  		sock_put(&smc->sk);

  		node = rb_first(&lgr->conns_all);
  	}
  	write_unlock_bh(&lgr->conns_lock);

  }
  
  /* Determine vlan of internal TCP socket.
   * @vlan_id: address to store the determined vlan id into
   */
  static int smc_vlan_by_tcpsk(struct socket *clcsock, unsigned short *vlan_id)
  {
  	struct dst_entry *dst = sk_dst_get(clcsock->sk);
  	int rc = 0;
  
  	*vlan_id = 0;
  	if (!dst) {
  		rc = -ENOTCONN;
  		goto out;
  	}
  	if (!dst->dev) {
  		rc = -ENODEV;
  		goto out_rel;
  	}
  
  	if (is_vlan_dev(dst->dev))
  		*vlan_id = vlan_dev_vlan_id(dst->dev);
  
  out_rel:
  	dst_release(dst);
  out:
  	return rc;
  }
  
  /* determine the link gid matching the vlan id of the link group */
  static int smc_link_determine_gid(struct smc_link_group *lgr)
  {
  	struct smc_link *lnk = &lgr->lnk[SMC_SINGLE_LINK];
  	struct ib_gid_attr gattr;
  	union ib_gid gid;
  	int i;
  
  	if (!lgr->vlan_id) {
  		lnk->gid = lnk->smcibdev->gid[lnk->ibport - 1];
  		return 0;
  	}
  
  	for (i = 0; i < lnk->smcibdev->pattr[lnk->ibport - 1].gid_tbl_len;
  	     i++) {
  		if (ib_query_gid(lnk->smcibdev->ibdev, lnk->ibport, i, &gid,
  				 &gattr))
  			continue;
  		if (gattr.ndev &&
  		    (vlan_dev_vlan_id(gattr.ndev) == lgr->vlan_id)) {
  			lnk->gid = gid;
  			return 0;
  		}
  	}
  	return -ENODEV;
  }
  
  /* create a new SMC connection (and a new link group if necessary) */
  int smc_conn_create(struct smc_sock *smc, __be32 peer_in_addr,
  		    struct smc_ib_device *smcibdev, u8 ibport,
  		    struct smc_clc_msg_local *lcl, int srv_first_contact)
  {
  	struct smc_connection *conn = &smc->conn;
  	struct smc_link_group *lgr;
  	unsigned short vlan_id;
  	enum smc_lgr_role role;
  	int local_contact = SMC_FIRST_CONTACT;
  	int rc = 0;
  
  	role = smc->listen_smc ? SMC_SERV : SMC_CLNT;
  	rc = smc_vlan_by_tcpsk(smc->clcsock, &vlan_id);
  	if (rc)
  		return rc;
  
  	if ((role == SMC_CLNT) && srv_first_contact)
  		/* create new link group as well */
  		goto create;
  
  	/* determine if an existing link group can be reused */
  	spin_lock_bh(&smc_lgr_list.lock);
  	list_for_each_entry(lgr, &smc_lgr_list.list, list) {
  		write_lock_bh(&lgr->conns_lock);
  		if (!memcmp(lgr->peer_systemid, lcl->id_for_peer,
  			    SMC_SYSTEMID_LEN) &&
  		    !memcmp(lgr->lnk[SMC_SINGLE_LINK].peer_gid, &lcl->gid,
  			    SMC_GID_SIZE) &&
  		    !memcmp(lgr->lnk[SMC_SINGLE_LINK].peer_mac, lcl->mac,
  			    sizeof(lcl->mac)) &&
  		    !lgr->sync_err &&
  		    (lgr->role == role) &&

  		    (lgr->vlan_id == vlan_id) &&
  		    ((role == SMC_CLNT) ||
  		     (lgr->conns_num < SMC_RMBS_PER_LGR_MAX))) {

  			/* link group found */
  			local_contact = SMC_REUSE_CONTACT;
  			conn->lgr = lgr;
  			smc_lgr_register_conn(conn); /* add smc conn to lgr */
  			write_unlock_bh(&lgr->conns_lock);
  			break;
  		}
  		write_unlock_bh(&lgr->conns_lock);
  	}
  	spin_unlock_bh(&smc_lgr_list.lock);
  
  	if (role == SMC_CLNT && !srv_first_contact &&
  	    (local_contact == SMC_FIRST_CONTACT)) {
  		/* Server reuses a link group, but Client wants to start
  		 * a new one
  		 * send out_of_sync decline, reason synchr. error
  		 */
  		return -ENOLINK;
  	}
  
  create:
  	if (local_contact == SMC_FIRST_CONTACT) {
  		rc = smc_lgr_create(smc, peer_in_addr, smcibdev, ibport,
  				    lcl->id_for_peer, vlan_id);
  		if (rc)
  			goto out;
  		smc_lgr_register_conn(conn); /* add smc conn to lgr */
  		rc = smc_link_determine_gid(conn->lgr);
  	}

  	conn->local_tx_ctrl.common.type = SMC_CDC_MSG_TYPE;
  	conn->local_tx_ctrl.len = sizeof(struct smc_cdc_msg);
  #ifndef KERNEL_HAS_ATOMIC64
  	spin_lock_init(&conn->acurs_lock);
  #endif

  
  out:
  	return rc ? rc : local_contact;
  }

  /* try to reuse a sndbuf or rmb description slot for a certain
   * buffer size; if not available, return NULL

   */
  static inline

  struct smc_buf_desc *smc_buf_get_slot(struct smc_link_group *lgr,
  				      int compressed_bufsize,
  				      rwlock_t *lock,
  				      struct list_head *buf_list)

  {

  	struct smc_buf_desc *buf_slot;

  	read_lock_bh(lock);
  	list_for_each_entry(buf_slot, buf_list, list) {
  		if (cmpxchg(&buf_slot->used, 0, 1) == 0) {
  			read_unlock_bh(lock);
  			return buf_slot;

  		}
  	}

  	read_unlock_bh(lock);

  	return NULL;
  }

  /* one of the conditions for announcing a receiver's current window size is
   * that it "results in a minimum increase in the window size of 10% of the
   * receive buffer space" [RFC7609]
   */
  static inline int smc_rmb_wnd_update_limit(int rmbe_size)
  {
  	return min_t(int, rmbe_size / 10, SOCK_MIN_SNDBUF / 2);
  }

  static struct smc_buf_desc *smc_new_buf_create(struct smc_link_group *lgr,
  					       bool is_rmb, int bufsize)
  {
  	struct smc_buf_desc *buf_desc;
  	struct smc_link *lnk;
  	int rc;
  
  	/* try to alloc a new buffer */
  	buf_desc = kzalloc(sizeof(*buf_desc), GFP_KERNEL);
  	if (!buf_desc)
  		return ERR_PTR(-ENOMEM);
  
  	buf_desc->cpu_addr =
  		(void *)__get_free_pages(GFP_KERNEL | __GFP_NOWARN |
  					 __GFP_NOMEMALLOC |
  					 __GFP_NORETRY | __GFP_ZERO,
  					 get_order(bufsize));
  	if (!buf_desc->cpu_addr) {
  		kfree(buf_desc);
  		return ERR_PTR(-EAGAIN);
  	}
  	buf_desc->order = get_order(bufsize);
  
  	/* build the sg table from the pages */
  	lnk = &lgr->lnk[SMC_SINGLE_LINK];
  	rc = sg_alloc_table(&buf_desc->sgt[SMC_SINGLE_LINK], 1,
  			    GFP_KERNEL);
  	if (rc) {
  		smc_buf_free(buf_desc, lnk, is_rmb);
  		return ERR_PTR(rc);
  	}
  	sg_set_buf(buf_desc->sgt[SMC_SINGLE_LINK].sgl,
  		   buf_desc->cpu_addr, bufsize);
  
  	/* map sg table to DMA address */
  	rc = smc_ib_buf_map_sg(lnk->smcibdev, buf_desc,
  			       is_rmb ? DMA_FROM_DEVICE : DMA_TO_DEVICE);
  	/* SMC protocol depends on mapping to one DMA address only */
  	if (rc != 1)  {
  		smc_buf_free(buf_desc, lnk, is_rmb);
  		return ERR_PTR(-EAGAIN);
  	}
  
  	/* create a new memory region for the RMB */
  	if (is_rmb) {
  		rc = smc_ib_get_memory_region(lnk->roce_pd,
  					      IB_ACCESS_REMOTE_WRITE |
  					      IB_ACCESS_LOCAL_WRITE,
  					      buf_desc);
  		if (rc) {
  			smc_buf_free(buf_desc, lnk, is_rmb);
  			return ERR_PTR(rc);
  		}
  	}
  
  	return buf_desc;
  }

  static int __smc_buf_create(struct smc_sock *smc, bool is_rmb)

  {
  	struct smc_connection *conn = &smc->conn;
  	struct smc_link_group *lgr = conn->lgr;

  	struct smc_buf_desc *buf_desc = NULL;
  	struct list_head *buf_list;

  	int bufsize, bufsize_short;

  	int sk_buf_size;
  	rwlock_t *lock;

  	if (is_rmb)
  		/* use socket recv buffer size (w/o overhead) as start value */
  		sk_buf_size = smc->sk.sk_rcvbuf / 2;
  	else
  		/* use socket send buffer size (w/o overhead) as start value */
  		sk_buf_size = smc->sk.sk_sndbuf / 2;

  	for (bufsize_short = smc_compress_bufsize(sk_buf_size);

  	     bufsize_short >= 0; bufsize_short--) {

  		if (is_rmb) {
  			lock = &lgr->rmbs_lock;
  			buf_list = &lgr->rmbs[bufsize_short];
  		} else {
  			lock = &lgr->sndbufs_lock;
  			buf_list = &lgr->sndbufs[bufsize_short];

  		}

  		bufsize = smc_uncompress_bufsize(bufsize_short);

  		if ((1 << get_order(bufsize)) > SG_MAX_SINGLE_ALLOC)
  			continue;

  		/* check for reusable slot in the link group */
  		buf_desc = smc_buf_get_slot(lgr, bufsize_short, lock, buf_list);
  		if (buf_desc) {
  			memset(buf_desc->cpu_addr, 0, bufsize);

  			break; /* found reusable slot */
  		}

  		buf_desc = smc_new_buf_create(lgr, is_rmb, bufsize);
  		if (PTR_ERR(buf_desc) == -ENOMEM)
  			break;
  		if (IS_ERR(buf_desc))

  			continue;

  		buf_desc->used = 1;
  		write_lock_bh(lock);
  		list_add(&buf_desc->list, buf_list);
  		write_unlock_bh(lock);
  		break; /* found */

  	}

  	if (IS_ERR(buf_desc))

  		return -ENOMEM;
  
  	if (is_rmb) {
  		conn->rmb_desc = buf_desc;

  		conn->rmbe_size = bufsize;
  		conn->rmbe_size_short = bufsize_short;
  		smc->sk.sk_rcvbuf = bufsize * 2;

  		atomic_set(&conn->bytes_to_rcv, 0);

  		conn->rmbe_update_limit = smc_rmb_wnd_update_limit(bufsize);

  	} else {

  		conn->sndbuf_desc = buf_desc;
  		conn->sndbuf_size = bufsize;
  		smc->sk.sk_sndbuf = bufsize * 2;
  		atomic_set(&conn->sndbuf_space, bufsize);

  	}

  	return 0;
  }

  void smc_sndbuf_sync_sg_for_cpu(struct smc_connection *conn)
  {
  	struct smc_link_group *lgr = conn->lgr;
  
  	smc_ib_sync_sg_for_cpu(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
  			       conn->sndbuf_desc, DMA_TO_DEVICE);
  }
  
  void smc_sndbuf_sync_sg_for_device(struct smc_connection *conn)
  {
  	struct smc_link_group *lgr = conn->lgr;
  
  	smc_ib_sync_sg_for_device(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
  				  conn->sndbuf_desc, DMA_TO_DEVICE);
  }
  
  void smc_rmb_sync_sg_for_cpu(struct smc_connection *conn)
  {
  	struct smc_link_group *lgr = conn->lgr;
  
  	smc_ib_sync_sg_for_cpu(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
  			       conn->rmb_desc, DMA_FROM_DEVICE);
  }
  
  void smc_rmb_sync_sg_for_device(struct smc_connection *conn)
  {
  	struct smc_link_group *lgr = conn->lgr;
  
  	smc_ib_sync_sg_for_device(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
  				  conn->rmb_desc, DMA_FROM_DEVICE);
  }

  /* create the send and receive buffer for an SMC socket;
   * receive buffers are called RMBs;
   * (even though the SMC protocol allows more than one RMB-element per RMB,
   * the Linux implementation uses just one RMB-element per RMB, i.e. uses an
   * extra RMB for every connection in a link group
   */
  int smc_buf_create(struct smc_sock *smc)
  {
  	int rc;
  
  	/* create send buffer */
  	rc = __smc_buf_create(smc, false);
  	if (rc)
  		return rc;
  	/* create rmb */
  	rc = __smc_buf_create(smc, true);
  	if (rc)
  		smc_buf_free(smc->conn.sndbuf_desc,
  			     &smc->conn.lgr->lnk[SMC_SINGLE_LINK], false);
  	return rc;

  }

  
  static inline int smc_rmb_reserve_rtoken_idx(struct smc_link_group *lgr)
  {
  	int i;
  
  	for_each_clear_bit(i, lgr->rtokens_used_mask, SMC_RMBS_PER_LGR_MAX) {
  		if (!test_and_set_bit(i, lgr->rtokens_used_mask))
  			return i;
  	}
  	return -ENOSPC;
  }
  
  /* save rkey and dma_addr received from peer during clc handshake */
  int smc_rmb_rtoken_handling(struct smc_connection *conn,
  			    struct smc_clc_msg_accept_confirm *clc)
  {
  	u64 dma_addr = be64_to_cpu(clc->rmb_dma_addr);
  	struct smc_link_group *lgr = conn->lgr;
  	u32 rkey = ntohl(clc->rmb_rkey);
  	int i;
  
  	for (i = 0; i < SMC_RMBS_PER_LGR_MAX; i++) {
  		if ((lgr->rtokens[i][SMC_SINGLE_LINK].rkey == rkey) &&

  		    (lgr->rtokens[i][SMC_SINGLE_LINK].dma_addr == dma_addr) &&

  		    test_bit(i, lgr->rtokens_used_mask)) {
  			conn->rtoken_idx = i;
  			return 0;
  		}
  	}
  	conn->rtoken_idx = smc_rmb_reserve_rtoken_idx(lgr);
  	if (conn->rtoken_idx < 0)
  		return conn->rtoken_idx;
  	lgr->rtokens[conn->rtoken_idx][SMC_SINGLE_LINK].rkey = rkey;
  	lgr->rtokens[conn->rtoken_idx][SMC_SINGLE_LINK].dma_addr = dma_addr;
  	return 0;
  }