// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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>
 */

#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/file.h>
#include <linux/fs_context.h>
#include <linux/semaphore.h>
#include <linux/slab.h>
#include <linux/seq_file.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_RDMA_SEND_SGE        4
#define P9_RDMA_RECV_SGE        4
#define P9_RDMA_IRD             0
#define P9_RDMA_ORD             0
#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
 * @timeout: Number of uSecs to wait for connection management events
 * @privport: Whether a privileged port may be used
 * @port: The port to use
 * @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;
        long timeout;
        bool privport;
        u16 port;
        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;
};

struct p9_rdma_req;

/**
 * struct p9_rdma_context - Keeps track of in-process WR
 *
 * @cqe: completion queue entry
 * @busa: Bus address to unmap when the WR completes
 * @req: Keeps track of requests (send)
 * @rc: Keepts track of replies (receive)
 */
struct p9_rdma_context {
        struct ib_cqe cqe;
        dma_addr_t busa;
        union {
                struct p9_req_t *req;
                struct p9_fcall rc;
        };
};

static int p9_rdma_show_options(struct seq_file *m, struct p9_client *clnt)
{
        struct p9_trans_rdma *rdma = clnt->trans;

        if (rdma->port != P9_RDMA_PORT)
                seq_printf(m, ",port=%u", rdma->port);
        if (rdma->sq_depth != P9_RDMA_SQ_DEPTH)
                seq_printf(m, ",sq=%u", rdma->sq_depth);
        if (rdma->rq_depth != P9_RDMA_RQ_DEPTH)
                seq_printf(m, ",rq=%u", rdma->rq_depth);
        if (rdma->timeout != P9_RDMA_TIMEOUT)
                seq_printf(m, ",timeout=%lu", rdma->timeout);
        if (rdma->privport)
                seq_puts(m, ",privport");
        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;
                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
recv_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct p9_client *client = cq->cq_context;
        struct p9_trans_rdma *rdma = client->trans;
        struct p9_rdma_context *c =
                container_of(wc->wr_cqe, struct p9_rdma_context, cqe);
        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 (wc->status != IB_WC_SUCCESS)
                goto err_out;

        c->rc.size = wc->byte_len;
        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.sdata)) {
                pr_err("Duplicate reply for request %d", tag);
                goto err_out;
        }

        req->rc.size = c->rc.size;
        req->rc.sdata = c->rc.sdata;
        p9_client_cb(client, req, REQ_STATUS_RCVD);

 out:
        up(&rdma->rq_sem);
        kfree(c);
        return;

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

static void
send_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct p9_client *client = cq->cq_context;
        struct p9_trans_rdma *rdma = client->trans;
        struct p9_rdma_context *c =
                container_of(wc->wr_cqe, struct p9_rdma_context, cqe);

        ib_dma_unmap_single(rdma->cm_id->device,
                            c->busa, c->req->tc.size,
                            DMA_TO_DEVICE);
        up(&rdma->sq_sem);
        p9_req_put(client, c->req);
        kfree(c);
}

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

        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_free_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;
        struct ib_sge sge;
        int ret;

        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;

        c->cqe.done = recv_done;

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

        wr.next = NULL;
        wr.wr_cqe = &c->cqe;
        wr.sg_list = &sge;
        wr.num_sge = 1;

        ret = ib_post_recv(rdma->qp, &wr, NULL);
        if (ret)
                ib_dma_unmap_single(rdma->cm_id->device, c->busa,
                                    client->msize, DMA_FROM_DEVICE);
        return ret;

 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;
        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! */
                        p9_fcall_fini(&req->rc);
                        req->rc.sdata = 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_obj(*rpl_context, GFP_NOFS);
        if (!rpl_context) {
                err = -ENOMEM;
                goto recv_error;
        }
        rpl_context->rc.sdata = req->rc.sdata;

        /*
         * 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_ERROR, "POST RECV failed: %d\n", err);
                goto recv_error;
        }
        /* remove posted receive buffer from request structure */
        req->rc.sdata = NULL;

dont_need_post_recv:
        /* Post the request */
        c = kmalloc_obj(*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;
        }

        c->cqe.done = send_done;

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

        wr.next = NULL;
        wr.wr_cqe = &c->cqe;
        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 dma_unmap;
        }

        /* Mark request as `sent' *before* we actually send it,
         * because doing if after could erase the REQ_STATUS_RCVD
         * status in case of a very fast reply.
         */
        WRITE_ONCE(req->status, REQ_STATUS_SENT);
        err = ib_post_send(rdma->qp, &wr, NULL);
        if (err)
                goto dma_unmap;

        /* Success */
        return 0;

dma_unmap:
        ib_dma_unmap_single(rdma->cm_id->device, c->busa,
                            c->req->tc.size, DMA_TO_DEVICE);
 /* Handle errors that happened during or while preparing the send: */
 send_error:
        WRITE_ONCE(req->status, REQ_STATUS_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 (err != -EINTR && 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_obj(struct p9_trans_rdma);
        if (!rdma)
                return NULL;

        rdma->port = opts->port;
        rdma->privport = opts->privport;
        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;
}

static int rdma_cancel(struct p9_client *client, struct p9_req_t *req)
{
        /* Nothing to do here.
         * We will take care of it (if we have to) in rdma_cancelled()
         */
        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;
}

static int p9_rdma_bind_privport(struct p9_trans_rdma *rdma)
{
        struct sockaddr_in cl = {
                .sin_family = AF_INET,
                .sin_addr.s_addr = htonl(INADDR_ANY),
        };
        int port, err = -EINVAL;

        for (port = P9_DEF_MAX_RESVPORT; port >= P9_DEF_MIN_RESVPORT; port--) {
                cl.sin_port = htons((ushort)port);
                err = rdma_bind_addr(rdma->cm_id, (struct sockaddr *)&cl);
                if (err != -EADDRINUSE)
                        break;
        }
        return err;
}

/**
 * rdma_create_trans - Transport method for creating a transport instance
 * @client: client instance
 * @fc: The filesystem context
 */
static int
rdma_create_trans(struct p9_client *client, struct fs_context *fc)
{
        const char *addr = fc->source;
        struct v9fs_context *ctx = fc->fs_private;
        struct p9_rdma_opts opts = ctx->rdma_opts;
        int err;
        struct p9_trans_rdma *rdma;
        struct rdma_conn_param conn_param;
        struct ib_qp_init_attr qp_attr;

        if (addr == NULL)
                return -EINVAL;

        /* options are already parsed, in the fs context */
        opts = ctx->rdma_opts;

        /* 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(&init_net, 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;

        /* Bind to a privileged port if we need to */
        if (opts.privport) {
                err = p9_rdma_bind_privport(rdma);
                if (err < 0) {
                        pr_err("%s (%d): problem binding to privport: %d\n",
                               __func__, task_pid_nr(current), -err);
                        goto error;
                }
        }

        /* 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;

        /* Create the Completion Queue */
        rdma->cq = ib_alloc_cq_any(rdma->cm_id->device, client,
                                   opts.sq_depth + opts.rq_depth + 1,
                                   IB_POLL_SOFTIRQ);
        if (IS_ERR(rdma->cq))
                goto error;

        /* Create the Protection Domain */
        rdma->pd = ib_alloc_pd(rdma->cm_id->device, 0);
        if (IS_ERR(rdma->pd))
                goto error;

        /* 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,
        .pooled_rbuffers = true,
        .def = false,
        .supports_vmalloc = false,
        .owner = THIS_MODULE,
        .create = rdma_create_trans,
        .close = rdma_close,
        .request = rdma_request,
        .cancel = rdma_cancel,
        .cancelled = rdma_cancelled,
        .show_options = p9_rdma_show_options,
};

/**
 * 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_ALIAS_9P("rdma");

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