/*
 * linux/fs/9p/trans_rdma.c
 *
 * RDMA transport layer based on the trans_fd.c implementation.
 *
 *  Copyright (C) 2008 by Tom Tucker <tom@opengridcomputing.com>
 *  Copyright (C) 2006 by Russ Cox <rsc@swtch.com>
 *  Copyright (C) 2004-2005 by Latchesar Ionkov <lucho@ionkov.net>
 *  Copyright (C) 2004-2008 by Eric Van Hensbergen <ericvh@gmail.com>
 *  Copyright (C) 1997-2002 by Ron Minnich <rminnich@sarnoff.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/in.h>
#include <linux/module.h>
#include <linux/net.h>
#include <linux/ipv6.h>
#include <linux/kthread.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/un.h>
#include <linux/uaccess.h>
#include <linux/inet.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <linux/parser.h>
#include <linux/semaphore.h>
#include <linux/slab.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include <net/9p/transport.h>
#include <rdma/ib_verbs.h>
#include <rdma/rdma_cm.h>

#define P9_PORT                 5640
#define P9_RDMA_SQ_DEPTH        32
#define P9_RDMA_RQ_DEPTH        32
#define P9_RDMA_SEND_SGE        4
#define P9_RDMA_RECV_SGE        4
#define P9_RDMA_IRD             0
#define P9_RDMA_ORD             0
#define P9_RDMA_TIMEOUT         30000           /* 30 seconds */
#define P9_RDMA_MAXSIZE         (1024*1024)     /* 1MB */

/**
 * struct p9_trans_rdma - RDMA transport instance
 *
 * @state: tracks the transport state machine for connection setup and tear down
 * @cm_id: The RDMA CM ID
 * @pd: Protection Domain pointer
 * @qp: Queue Pair pointer
 * @cq: Completion Queue pointer
 * @dm_mr: DMA Memory Region pointer
 * @lkey: The local access only memory region key
 * @timeout: Number of uSecs to wait for connection management events
 * @sq_depth: The depth of the Send Queue
 * @sq_sem: Semaphore for the SQ
 * @rq_depth: The depth of the Receive Queue.
 * @rq_sem: Semaphore for the RQ
 * @excess_rc : Amount of posted Receive Contexts without a pending request.
 *              See rdma_request()
 * @addr: The remote peer's address
 * @req_lock: Protects the active request list
 * @cm_done: Completion event for connection management tracking
 */
struct p9_trans_rdma {
        enum {
                P9_RDMA_INIT,
                P9_RDMA_ADDR_RESOLVED,
                P9_RDMA_ROUTE_RESOLVED,
                P9_RDMA_CONNECTED,
                P9_RDMA_FLUSHING,
                P9_RDMA_CLOSING,
                P9_RDMA_CLOSED,
        } state;
        struct rdma_cm_id *cm_id;
        struct ib_pd *pd;
        struct ib_qp *qp;
        struct ib_cq *cq;
        struct ib_mr *dma_mr;
        u32 lkey;
        long timeout;
        int sq_depth;
        struct semaphore sq_sem;
        int rq_depth;
        struct semaphore rq_sem;
        atomic_t excess_rc;
        struct sockaddr_in addr;
        spinlock_t req_lock;

        struct completion cm_done;
};

/**
 * p9_rdma_context - Keeps track of in-process WR
 *
 * @wc_op: The original WR op for when the CQE completes in error.
 * @busa: Bus address to unmap when the WR completes
 * @req: Keeps track of requests (send)
 * @rc: Keepts track of replies (receive)
 */
struct p9_rdma_req;
struct p9_rdma_context {
        enum ib_wc_opcode wc_op;
        dma_addr_t busa;
        union {
                struct p9_req_t *req;
                struct p9_fcall *rc;
        };
};

/**
 * p9_rdma_opts - Collection of mount options
 * @port: port of connection
 * @sq_depth: The requested depth of the SQ. This really doesn't need
 * to be any deeper than the number of threads used in the client
 * @rq_depth: The depth of the RQ. Should be greater than or equal to SQ depth
 * @timeout: Time to wait in msecs for CM events
 */
struct p9_rdma_opts {
        short port;
        int sq_depth;
        int rq_depth;
        long timeout;
};

/*
 * Option Parsing (code inspired by NFS code)
 */
enum {
        /* Options that take integer arguments */
        Opt_port, Opt_rq_depth, Opt_sq_depth, Opt_timeout, Opt_err,
};

static match_table_t tokens = {
        {Opt_port, "port=%u"},
        {Opt_sq_depth, "sq=%u"},
        {Opt_rq_depth, "rq=%u"},
        {Opt_timeout, "timeout=%u"},
        {Opt_err, NULL},
};

/**
 * parse_opts - parse mount options into rdma options structure
 * @params: options string passed from mount
 * @opts: rdma transport-specific structure to parse options into
 *
 * Returns 0 upon success, -ERRNO upon failure
 */
static int parse_opts(char *params, struct p9_rdma_opts *opts)
{
        char *p;
        substring_t args[MAX_OPT_ARGS];
        int option;
        char *options, *tmp_options;

        opts->port = P9_PORT;
        opts->sq_depth = P9_RDMA_SQ_DEPTH;
        opts->rq_depth = P9_RDMA_RQ_DEPTH;
        opts->timeout = P9_RDMA_TIMEOUT;

        if (!params)
                return 0;

        tmp_options = kstrdup(params, GFP_KERNEL);
        if (!tmp_options) {
                p9_debug(P9_DEBUG_ERROR,
                         "failed to allocate copy of option string\n");
                return -ENOMEM;
        }
        options = tmp_options;

        while ((p = strsep(&options, ",")) != NULL) {
                int token;
                int r;
                if (!*p)
                        continue;
                token = match_token(p, tokens, args);
                r = match_int(&args[0], &option);
                if (r < 0) {
                        p9_debug(P9_DEBUG_ERROR,
                                 "integer field, but no integer?\n");
                        continue;
                }
                switch (token) {
                case Opt_port:
                        opts->port = option;
                        break;
                case Opt_sq_depth:
                        opts->sq_depth = option;
                        break;
                case Opt_rq_depth:
                        opts->rq_depth = option;
                        break;
                case Opt_timeout:
                        opts->timeout = option;
                        break;
                default:
                        continue;
                }
        }
        /* RQ must be at least as large as the SQ */
        opts->rq_depth = max(opts->rq_depth, opts->sq_depth);
        kfree(tmp_options);
        return 0;
}

static int
p9_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event)
{
        struct p9_client *c = id->context;
        struct p9_trans_rdma *rdma = c->trans;
        switch (event->event) {
        case RDMA_CM_EVENT_ADDR_RESOLVED:
                BUG_ON(rdma->state != P9_RDMA_INIT);
                rdma->state = P9_RDMA_ADDR_RESOLVED;
                break;

        case RDMA_CM_EVENT_ROUTE_RESOLVED:
                BUG_ON(rdma->state != P9_RDMA_ADDR_RESOLVED);
                rdma->state = P9_RDMA_ROUTE_RESOLVED;
                break;

        case RDMA_CM_EVENT_ESTABLISHED:
                BUG_ON(rdma->state != P9_RDMA_ROUTE_RESOLVED);
                rdma->state = P9_RDMA_CONNECTED;
                break;

        case RDMA_CM_EVENT_DISCONNECTED:
                if (rdma)
                        rdma->state = P9_RDMA_CLOSED;
                if (c)
                        c->status = Disconnected;
                break;

        case RDMA_CM_EVENT_TIMEWAIT_EXIT:
                break;

        case RDMA_CM_EVENT_ADDR_CHANGE:
        case RDMA_CM_EVENT_ROUTE_ERROR:
        case RDMA_CM_EVENT_DEVICE_REMOVAL:
        case RDMA_CM_EVENT_MULTICAST_JOIN:
        case RDMA_CM_EVENT_MULTICAST_ERROR:
        case RDMA_CM_EVENT_REJECTED:
        case RDMA_CM_EVENT_CONNECT_REQUEST:
        case RDMA_CM_EVENT_CONNECT_RESPONSE:
        case RDMA_CM_EVENT_CONNECT_ERROR:
        case RDMA_CM_EVENT_ADDR_ERROR:
        case RDMA_CM_EVENT_UNREACHABLE:
                c->status = Disconnected;
                rdma_disconnect(rdma->cm_id);
                break;
        default:
                BUG();
        }
        complete(&rdma->cm_done);
        return 0;
}

static void
handle_recv(struct p9_client *client, struct p9_trans_rdma *rdma,
            struct p9_rdma_context *c, enum ib_wc_status status, u32 byte_len)
{
        struct p9_req_t *req;
        int err = 0;
        int16_t tag;

        req = NULL;
        ib_dma_unmap_single(rdma->cm_id->device, c->busa, client->msize,
                                                         DMA_FROM_DEVICE);

        if (status != IB_WC_SUCCESS)
                goto err_out;

        err = p9_parse_header(c->rc, NULL, NULL, &tag, 1);
        if (err)
                goto err_out;

        req = p9_tag_lookup(client, tag);
        if (!req)
                goto err_out;

        /* Check that we have not yet received a reply for this request.
         */
        if (unlikely(req->rc)) {
                pr_err("Duplicate reply for request %d", tag);
                goto err_out;
        }

        req->rc = c->rc;
        req->status = REQ_STATUS_RCVD;
        p9_client_cb(client, req);

        return;

 err_out:
        p9_debug(P9_DEBUG_ERROR, "req %p err %d status %d\n", req, err, status);
        rdma->state = P9_RDMA_FLUSHING;
        client->status = Disconnected;
}

static void
handle_send(struct p9_client *client, struct p9_trans_rdma *rdma,
            struct p9_rdma_context *c, enum ib_wc_status status, u32 byte_len)
{
        ib_dma_unmap_single(rdma->cm_id->device,
                            c->busa, c->req->tc->size,
                            DMA_TO_DEVICE);
}

static void qp_event_handler(struct ib_event *event, void *context)
{
        p9_debug(P9_DEBUG_ERROR, "QP event %d context %p\n",
                 event->event, context);
}

static void cq_comp_handler(struct ib_cq *cq, void *cq_context)
{
        struct p9_client *client = cq_context;
        struct p9_trans_rdma *rdma = client->trans;
        int ret;
        struct ib_wc wc;

        ib_req_notify_cq(rdma->cq, IB_CQ_NEXT_COMP);
        while ((ret = ib_poll_cq(cq, 1, &wc)) > 0) {
                struct p9_rdma_context *c = (void *) (unsigned long) wc.wr_id;

                switch (c->wc_op) {
                case IB_WC_RECV:
                        handle_recv(client, rdma, c, wc.status, wc.byte_len);
                        up(&rdma->rq_sem);
                        break;

                case IB_WC_SEND:
                        handle_send(client, rdma, c, wc.status, wc.byte_len);
                        up(&rdma->sq_sem);
                        break;

                default:
                        pr_err("unexpected completion type, c->wc_op=%d, wc.opcode=%d, status=%d\n",
                               c->wc_op, wc.opcode, wc.status);
                        break;
                }
                kfree(c);
        }
}

static void cq_event_handler(struct ib_event *e, void *v)
{
        p9_debug(P9_DEBUG_ERROR, "CQ event %d context %p\n", e->event, v);
}

static void rdma_destroy_trans(struct p9_trans_rdma *rdma)
{
        if (!rdma)
                return;

        if (rdma->dma_mr && !IS_ERR(rdma->dma_mr))
                ib_dereg_mr(rdma->dma_mr);

        if (rdma->qp && !IS_ERR(rdma->qp))
                ib_destroy_qp(rdma->qp);

        if (rdma->pd && !IS_ERR(rdma->pd))
                ib_dealloc_pd(rdma->pd);

        if (rdma->cq && !IS_ERR(rdma->cq))
                ib_destroy_cq(rdma->cq);

        if (rdma->cm_id && !IS_ERR(rdma->cm_id))
                rdma_destroy_id(rdma->cm_id);

        kfree(rdma);
}

static int
post_recv(struct p9_client *client, struct p9_rdma_context *c)
{
        struct p9_trans_rdma *rdma = client->trans;
        struct ib_recv_wr wr, *bad_wr;
        struct ib_sge sge;

        c->busa = ib_dma_map_single(rdma->cm_id->device,
                                    c->rc->sdata, client->msize,
                                    DMA_FROM_DEVICE);
        if (ib_dma_mapping_error(rdma->cm_id->device, c->busa))
                goto error;

        sge.addr = c->busa;
        sge.length = client->msize;
        sge.lkey = rdma->lkey;

        wr.next = NULL;
        c->wc_op = IB_WC_RECV;
        wr.wr_id = (unsigned long) c;
        wr.sg_list = &sge;
        wr.num_sge = 1;
        return ib_post_recv(rdma->qp, &wr, &bad_wr);

 error:
        p9_debug(P9_DEBUG_ERROR, "EIO\n");
        return -EIO;
}

static int rdma_request(struct p9_client *client, struct p9_req_t *req)
{
        struct p9_trans_rdma *rdma = client->trans;
        struct ib_send_wr wr, *bad_wr;
        struct ib_sge sge;
        int err = 0;
        unsigned long flags;
        struct p9_rdma_context *c = NULL;
        struct p9_rdma_context *rpl_context = NULL;

        /* When an error occurs between posting the recv and the send,
         * there will be a receive context posted without a pending request.
         * Since there is no way to "un-post" it, we remember it and skip
         * post_recv() for the next request.
         * So here,
         * see if we are this `next request' and need to absorb an excess rc.
         * If yes, then drop and free our own, and do not recv_post().
         **/
        if (unlikely(atomic_read(&rdma->excess_rc) > 0)) {
                if ((atomic_sub_return(1, &rdma->excess_rc) >= 0)) {
                        /* Got one ! */
                        kfree(req->rc);
                        req->rc = NULL;
                        goto dont_need_post_recv;
                } else {
                        /* We raced and lost. */
                        atomic_inc(&rdma->excess_rc);
                }
        }

        /* Allocate an fcall for the reply */
        rpl_context = kmalloc(sizeof *rpl_context, GFP_NOFS);
        if (!rpl_context) {
                err = -ENOMEM;
                goto recv_error;
        }
        rpl_context->rc = req->rc;

        /*
         * Post a receive buffer for this request. We need to ensure
         * there is a reply buffer available for every outstanding
         * request. A flushed request can result in no reply for an
         * outstanding request, so we must keep a count to avoid
         * overflowing the RQ.
         */
        if (down_interruptible(&rdma->rq_sem)) {
                err = -EINTR;
                goto recv_error;
        }

        err = post_recv(client, rpl_context);
        if (err) {
                p9_debug(P9_DEBUG_FCALL, "POST RECV failed\n");
                goto recv_error;
        }
        /* remove posted receive buffer from request structure */
        req->rc = NULL;

dont_need_post_recv:
        /* Post the request */
        c = kmalloc(sizeof *c, GFP_NOFS);
        if (!c) {
                err = -ENOMEM;
                goto send_error;
        }
        c->req = req;

        c->busa = ib_dma_map_single(rdma->cm_id->device,
                                    c->req->tc->sdata, c->req->tc->size,
                                    DMA_TO_DEVICE);
        if (ib_dma_mapping_error(rdma->cm_id->device, c->busa)) {
                err = -EIO;
                goto send_error;
        }

        sge.addr = c->busa;
        sge.length = c->req->tc->size;
        sge.lkey = rdma->lkey;

        wr.next = NULL;
        c->wc_op = IB_WC_SEND;
        wr.wr_id = (unsigned long) c;
        wr.opcode = IB_WR_SEND;
        wr.send_flags = IB_SEND_SIGNALED;
        wr.sg_list = &sge;
        wr.num_sge = 1;

        if (down_interruptible(&rdma->sq_sem)) {
                err = -EINTR;
                goto send_error;
        }

        err = ib_post_send(rdma->qp, &wr, &bad_wr);
        if (err)
                goto send_error;

        /* Success */
        return 0;

 /* Handle errors that happened during or while preparing the send: */
 send_error:
        kfree(c);
        p9_debug(P9_DEBUG_ERROR, "Error %d in rdma_request()\n", err);

        /* Ach.
         *  We did recv_post(), but not send. We have one recv_post in excess.
         */
        atomic_inc(&rdma->excess_rc);
        return err;

 /* Handle errors that happened during or while preparing post_recv(): */
 recv_error:
        kfree(rpl_context);
        spin_lock_irqsave(&rdma->req_lock, flags);
        if (rdma->state < P9_RDMA_CLOSING) {
                rdma->state = P9_RDMA_CLOSING;
                spin_unlock_irqrestore(&rdma->req_lock, flags);
                rdma_disconnect(rdma->cm_id);
        } else
                spin_unlock_irqrestore(&rdma->req_lock, flags);
        return err;
}

static void rdma_close(struct p9_client *client)
{
        struct p9_trans_rdma *rdma;

        if (!client)
                return;

        rdma = client->trans;
        if (!rdma)
                return;

        client->status = Disconnected;
        rdma_disconnect(rdma->cm_id);
        rdma_destroy_trans(rdma);
}

/**
 * alloc_rdma - Allocate and initialize the rdma transport structure
 * @opts: Mount options structure
 */
static struct p9_trans_rdma *alloc_rdma(struct p9_rdma_opts *opts)
{
        struct p9_trans_rdma *rdma;

        rdma = kzalloc(sizeof(struct p9_trans_rdma), GFP_KERNEL);
        if (!rdma)
                return NULL;

        rdma->sq_depth = opts->sq_depth;
        rdma->rq_depth = opts->rq_depth;
        rdma->timeout = opts->timeout;
        spin_lock_init(&rdma->req_lock);
        init_completion(&rdma->cm_done);
        sema_init(&rdma->sq_sem, rdma->sq_depth);
        sema_init(&rdma->rq_sem, rdma->rq_depth);
        atomic_set(&rdma->excess_rc, 0);

        return rdma;
}

/* its not clear to me we can do anything after send has been posted */
static int rdma_cancel(struct p9_client *client, struct p9_req_t *req)
{
        return 1;
}

/* A request has been fully flushed without a reply.
 * That means we have posted one buffer in excess.
 */
static int rdma_cancelled(struct p9_client *client, struct p9_req_t *req)
{
        struct p9_trans_rdma *rdma = client->trans;

        atomic_inc(&rdma->excess_rc);
        return 0;
}

/**
 * trans_create_rdma - Transport method for creating atransport instance
 * @client: client instance
 * @addr: IP address string
 * @args: Mount options string
 */
static int
rdma_create_trans(struct p9_client *client, const char *addr, char *args)
{
        int err;
        struct p9_rdma_opts opts;
        struct p9_trans_rdma *rdma;
        struct rdma_conn_param conn_param;
        struct ib_qp_init_attr qp_attr;
        struct ib_device_attr devattr;

        /* Parse the transport specific mount options */
        err = parse_opts(args, &opts);
        if (err < 0)
                return err;

        /* Create and initialize the RDMA transport structure */
        rdma = alloc_rdma(&opts);
        if (!rdma)
                return -ENOMEM;

        /* Create the RDMA CM ID */
        rdma->cm_id = rdma_create_id(p9_cm_event_handler, client, RDMA_PS_TCP,
                                     IB_QPT_RC);
        if (IS_ERR(rdma->cm_id))
                goto error;

        /* Associate the client with the transport */
        client->trans = rdma;

        /* Resolve the server's address */
        rdma->addr.sin_family = AF_INET;
        rdma->addr.sin_addr.s_addr = in_aton(addr);
        rdma->addr.sin_port = htons(opts.port);
        err = rdma_resolve_addr(rdma->cm_id, NULL,
                                (struct sockaddr *)&rdma->addr,
                                rdma->timeout);
        if (err)
                goto error;
        err = wait_for_completion_interruptible(&rdma->cm_done);
        if (err || (rdma->state != P9_RDMA_ADDR_RESOLVED))
                goto error;

        /* Resolve the route to the server */
        err = rdma_resolve_route(rdma->cm_id, rdma->timeout);
        if (err)
                goto error;
        err = wait_for_completion_interruptible(&rdma->cm_done);
        if (err || (rdma->state != P9_RDMA_ROUTE_RESOLVED))
                goto error;

        /* Query the device attributes */
        err = ib_query_device(rdma->cm_id->device, &devattr);
        if (err)
                goto error;

        /* Create the Completion Queue */
        rdma->cq = ib_create_cq(rdma->cm_id->device, cq_comp_handler,
                                cq_event_handler, client,
                                opts.sq_depth + opts.rq_depth + 1, 0);
        if (IS_ERR(rdma->cq))
                goto error;
        ib_req_notify_cq(rdma->cq, IB_CQ_NEXT_COMP);

        /* Create the Protection Domain */
        rdma->pd = ib_alloc_pd(rdma->cm_id->device);
        if (IS_ERR(rdma->pd))
                goto error;

        /* Cache the DMA lkey in the transport */
        rdma->dma_mr = NULL;
        if (devattr.device_cap_flags & IB_DEVICE_LOCAL_DMA_LKEY)
                rdma->lkey = rdma->cm_id->device->local_dma_lkey;
        else {
                rdma->dma_mr = ib_get_dma_mr(rdma->pd, IB_ACCESS_LOCAL_WRITE);
                if (IS_ERR(rdma->dma_mr))
                        goto error;
                rdma->lkey = rdma->dma_mr->lkey;
        }

        /* Create the Queue Pair */
        memset(&qp_attr, 0, sizeof qp_attr);
        qp_attr.event_handler = qp_event_handler;
        qp_attr.qp_context = client;
        qp_attr.cap.max_send_wr = opts.sq_depth;
        qp_attr.cap.max_recv_wr = opts.rq_depth;
        qp_attr.cap.max_send_sge = P9_RDMA_SEND_SGE;
        qp_attr.cap.max_recv_sge = P9_RDMA_RECV_SGE;
        qp_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
        qp_attr.qp_type = IB_QPT_RC;
        qp_attr.send_cq = rdma->cq;
        qp_attr.recv_cq = rdma->cq;
        err = rdma_create_qp(rdma->cm_id, rdma->pd, &qp_attr);
        if (err)
                goto error;
        rdma->qp = rdma->cm_id->qp;

        /* Request a connection */
        memset(&conn_param, 0, sizeof(conn_param));
        conn_param.private_data = NULL;
        conn_param.private_data_len = 0;
        conn_param.responder_resources = P9_RDMA_IRD;
        conn_param.initiator_depth = P9_RDMA_ORD;
        err = rdma_connect(rdma->cm_id, &conn_param);
        if (err)
                goto error;
        err = wait_for_completion_interruptible(&rdma->cm_done);
        if (err || (rdma->state != P9_RDMA_CONNECTED))
                goto error;

        client->status = Connected;

        return 0;

error:
        rdma_destroy_trans(rdma);
        return -ENOTCONN;
}

static struct p9_trans_module p9_rdma_trans = {
        .name = "rdma",
        .maxsize = P9_RDMA_MAXSIZE,
        .def = 0,
        .owner = THIS_MODULE,
        .create = rdma_create_trans,
        .close = rdma_close,
        .request = rdma_request,
        .cancel = rdma_cancel,
};

/**
 * p9_trans_rdma_init - Register the 9P RDMA transport driver
 */
static int __init p9_trans_rdma_init(void)
{
        v9fs_register_trans(&p9_rdma_trans);
        return 0;
}

static void __exit p9_trans_rdma_exit(void)
{
        v9fs_unregister_trans(&p9_rdma_trans);
}

module_init(p9_trans_rdma_init);
module_exit(p9_trans_rdma_exit);

MODULE_AUTHOR("Tom Tucker <tom@opengridcomputing.com>");
MODULE_DESCRIPTION("RDMA Transport for 9P");
MODULE_LICENSE("Dual BSD/GPL");