/*
 *  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      (600 * HZ)

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)
                schedule_delayed_work(&lgr->free_work, SMC_LGR_FREE_DELAY);
}

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->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;
        init_waitqueue_head(&lnk->wr_tx_wait);
        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_sndbuf_unuse(struct smc_connection *conn)
{
        if (conn->sndbuf_desc) {
                conn->sndbuf_desc->used = 0;
                conn->sndbuf_size = 0;
        }
}

static void smc_rmb_unuse(struct smc_connection *conn)
{
        if (conn->rmb_desc) {
                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_rmb_unuse(conn);
        smc_sndbuf_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_lgr_free_sndbufs(struct smc_link_group *lgr)
{
        struct smc_buf_desc *sndbuf_desc, *bf_desc;
        int i;

        for (i = 0; i < SMC_RMBE_SIZES; i++) {
                list_for_each_entry_safe(sndbuf_desc, bf_desc, &lgr->sndbufs[i],
                                         list) {
                        list_del(&sndbuf_desc->list);
                        smc_ib_buf_unmap(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
                                         smc_uncompress_bufsize(i),
                                         sndbuf_desc, DMA_TO_DEVICE);
                        kfree(sndbuf_desc->cpu_addr);
                        kfree(sndbuf_desc);
                }
        }
}

static void smc_lgr_free_rmbs(struct smc_link_group *lgr)
{
        struct smc_buf_desc *rmb_desc, *bf_desc;
        struct smc_link *lnk = &lgr->lnk[SMC_SINGLE_LINK];
        int i;

        for (i = 0; i < SMC_RMBE_SIZES; i++) {
                list_for_each_entry_safe(rmb_desc, bf_desc, &lgr->rmbs[i],
                                         list) {
                        list_del(&rmb_desc->list);
                        smc_ib_buf_unmap(lnk->smcibdev,
                                         smc_uncompress_bufsize(i),
                                         rmb_desc, DMA_FROM_DEVICE);
                        kfree(rmb_desc->cpu_addr);
                        kfree(rmb_desc);
                }
        }
}

/* remove a link group */
void smc_lgr_free(struct smc_link_group *lgr)
{
        smc_lgr_free_rmbs(lgr);
        smc_lgr_free_sndbufs(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 description slot of the sndbufs list for a certain
 * buf_size; if not available, return NULL
 */
static inline
struct smc_buf_desc *smc_sndbuf_get_slot(struct smc_link_group *lgr,
                                         int compressed_bufsize)
{
        struct smc_buf_desc *sndbuf_slot;

        read_lock_bh(&lgr->sndbufs_lock);
        list_for_each_entry(sndbuf_slot, &lgr->sndbufs[compressed_bufsize],
                            list) {
                if (cmpxchg(&sndbuf_slot->used, 0, 1) == 0) {
                        read_unlock_bh(&lgr->sndbufs_lock);
                        return sndbuf_slot;
                }
        }
        read_unlock_bh(&lgr->sndbufs_lock);
        return NULL;
}

/* try to reuse an rmb description slot of the rmbs list for a certain
 * rmbe_size; if not available, return NULL
 */
static inline
struct smc_buf_desc *smc_rmb_get_slot(struct smc_link_group *lgr,
                                      int compressed_bufsize)
{
        struct smc_buf_desc *rmb_slot;

        read_lock_bh(&lgr->rmbs_lock);
        list_for_each_entry(rmb_slot, &lgr->rmbs[compressed_bufsize],
                            list) {
                if (cmpxchg(&rmb_slot->used, 0, 1) == 0) {
                        read_unlock_bh(&lgr->rmbs_lock);
                        return rmb_slot;
                }
        }
        read_unlock_bh(&lgr->rmbs_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);
}

/* create the tx buffer for an SMC socket */
int smc_sndbuf_create(struct smc_sock *smc)
{
        struct smc_connection *conn = &smc->conn;
        struct smc_link_group *lgr = conn->lgr;
        int tmp_bufsize, tmp_bufsize_short;
        struct smc_buf_desc *sndbuf_desc;
        int rc;

        /* use socket send buffer size (w/o overhead) as start value */
        for (tmp_bufsize_short = smc_compress_bufsize(smc->sk.sk_sndbuf / 2);
             tmp_bufsize_short >= 0; tmp_bufsize_short--) {
                tmp_bufsize = smc_uncompress_bufsize(tmp_bufsize_short);
                /* check for reusable sndbuf_slot in the link group */
                sndbuf_desc = smc_sndbuf_get_slot(lgr, tmp_bufsize_short);
                if (sndbuf_desc) {
                        memset(sndbuf_desc->cpu_addr, 0, tmp_bufsize);
                        break; /* found reusable slot */
                }
                /* try to alloc a new send buffer */
                sndbuf_desc = kzalloc(sizeof(*sndbuf_desc), GFP_KERNEL);
                if (!sndbuf_desc)
                        break; /* give up with -ENOMEM */
                sndbuf_desc->cpu_addr = kzalloc(tmp_bufsize,
                                                GFP_KERNEL | __GFP_NOWARN |
                                                __GFP_NOMEMALLOC |
                                                __GFP_NORETRY);
                if (!sndbuf_desc->cpu_addr) {
                        kfree(sndbuf_desc);
                        sndbuf_desc = NULL;
                        /* if send buffer allocation has failed,
                         * try a smaller one
                         */
                        continue;
                }
                rc = smc_ib_buf_map(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
                                    tmp_bufsize, sndbuf_desc,
                                    DMA_TO_DEVICE);
                if (rc) {
                        kfree(sndbuf_desc->cpu_addr);
                        kfree(sndbuf_desc);
                        sndbuf_desc = NULL;
                        continue; /* if mapping failed, try smaller one */
                }
                sndbuf_desc->used = 1;
                write_lock_bh(&lgr->sndbufs_lock);
                list_add(&sndbuf_desc->list,
                         &lgr->sndbufs[tmp_bufsize_short]);
                write_unlock_bh(&lgr->sndbufs_lock);
                break;
        }
        if (sndbuf_desc && sndbuf_desc->cpu_addr) {
                conn->sndbuf_desc = sndbuf_desc;
                conn->sndbuf_size = tmp_bufsize;
                smc->sk.sk_sndbuf = tmp_bufsize * 2;
                atomic_set(&conn->sndbuf_space, tmp_bufsize);
                return 0;
        } else {
                return -ENOMEM;
        }
}

/* create the RMB for an SMC socket (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_rmb_create(struct smc_sock *smc)
{
        struct smc_connection *conn = &smc->conn;
        struct smc_link_group *lgr = conn->lgr;
        int tmp_bufsize, tmp_bufsize_short;
        struct smc_buf_desc *rmb_desc;
        int rc;

        /* use socket recv buffer size (w/o overhead) as start value */
        for (tmp_bufsize_short = smc_compress_bufsize(smc->sk.sk_rcvbuf / 2);
             tmp_bufsize_short >= 0; tmp_bufsize_short--) {
                tmp_bufsize = smc_uncompress_bufsize(tmp_bufsize_short);
                /* check for reusable rmb_slot in the link group */
                rmb_desc = smc_rmb_get_slot(lgr, tmp_bufsize_short);
                if (rmb_desc) {
                        memset(rmb_desc->cpu_addr, 0, tmp_bufsize);
                        break; /* found reusable slot */
                }
                /* try to alloc a new RMB */
                rmb_desc = kzalloc(sizeof(*rmb_desc), GFP_KERNEL);
                if (!rmb_desc)
                        break; /* give up with -ENOMEM */
                rmb_desc->cpu_addr = kzalloc(tmp_bufsize,
                                             GFP_KERNEL | __GFP_NOWARN |
                                             __GFP_NOMEMALLOC |
                                             __GFP_NORETRY);
                if (!rmb_desc->cpu_addr) {
                        kfree(rmb_desc);
                        rmb_desc = NULL;
                        /* if RMB allocation has failed,
                         * try a smaller one
                         */
                        continue;
                }
                rc = smc_ib_buf_map(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
                                    tmp_bufsize, rmb_desc,
                                    DMA_FROM_DEVICE);
                if (rc) {
                        kfree(rmb_desc->cpu_addr);
                        kfree(rmb_desc);
                        rmb_desc = NULL;
                        continue; /* if mapping failed, try smaller one */
                }
                rmb_desc->rkey[SMC_SINGLE_LINK] =
                        lgr->lnk[SMC_SINGLE_LINK].roce_pd->unsafe_global_rkey;
                rmb_desc->used = 1;
                write_lock_bh(&lgr->rmbs_lock);
                list_add(&rmb_desc->list,
                         &lgr->rmbs[tmp_bufsize_short]);
                write_unlock_bh(&lgr->rmbs_lock);
                break;
        }
        if (rmb_desc && rmb_desc->cpu_addr) {
                conn->rmb_desc = rmb_desc;
                conn->rmbe_size = tmp_bufsize;
                conn->rmbe_size_short = tmp_bufsize_short;
                smc->sk.sk_rcvbuf = tmp_bufsize * 2;
                atomic_set(&conn->bytes_to_rcv, 0);
                conn->rmbe_update_limit = smc_rmb_wnd_update_limit(tmp_bufsize);
                return 0;
        } else {
                return -ENOMEM;
        }
}

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;
}