/*
 * Copyright (c) 2015 Oracle.  All rights reserved.
 *
 * Support for backward direction RPCs on RPC/RDMA (server-side).
 */

#include <linux/sunrpc/svc_rdma.h>
#include "xprt_rdma.h"

#define RPCDBG_FACILITY RPCDBG_SVCXPRT

#undef SVCRDMA_BACKCHANNEL_DEBUG

int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, struct rpcrdma_msg *rmsgp,
                             struct xdr_buf *rcvbuf)
{
        struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
        struct kvec *dst, *src = &rcvbuf->head[0];
        struct rpc_rqst *req;
        unsigned long cwnd;
        u32 credits;
        size_t len;
        __be32 xid;
        __be32 *p;
        int ret;

        p = (__be32 *)src->iov_base;
        len = src->iov_len;
        xid = rmsgp->rm_xid;

#ifdef SVCRDMA_BACKCHANNEL_DEBUG
        pr_info("%s: xid=%08x, length=%zu\n",
                __func__, be32_to_cpu(xid), len);
        pr_info("%s: RPC/RDMA: %*ph\n",
                __func__, (int)RPCRDMA_HDRLEN_MIN, rmsgp);
        pr_info("%s:      RPC: %*ph\n",
                __func__, (int)len, p);
#endif

        ret = -EAGAIN;
        if (src->iov_len < 24)
                goto out_shortreply;

        spin_lock_bh(&xprt->transport_lock);
        req = xprt_lookup_rqst(xprt, xid);
        if (!req)
                goto out_notfound;

        dst = &req->rq_private_buf.head[0];
        memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
        if (dst->iov_len < len)
                goto out_unlock;
        memcpy(dst->iov_base, p, len);

        credits = be32_to_cpu(rmsgp->rm_credit);
        if (credits == 0)
                credits = 1;    /* don't deadlock */
        else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
                credits = r_xprt->rx_buf.rb_bc_max_requests;

        cwnd = xprt->cwnd;
        xprt->cwnd = credits << RPC_CWNDSHIFT;
        if (xprt->cwnd > cwnd)
                xprt_release_rqst_cong(req->rq_task);

        ret = 0;
        xprt_complete_rqst(req->rq_task, rcvbuf->len);
        rcvbuf->len = 0;

out_unlock:
        spin_unlock_bh(&xprt->transport_lock);
out:
        return ret;

out_shortreply:
        dprintk("svcrdma: short bc reply: xprt=%p, len=%zu\n",
                xprt, src->iov_len);
        goto out;

out_notfound:
        dprintk("svcrdma: unrecognized bc reply: xprt=%p, xid=%08x\n",
                xprt, be32_to_cpu(xid));

        goto out_unlock;
}

/* Send a backwards direction RPC call.
 *
 * Caller holds the connection's mutex and has already marshaled
 * the RPC/RDMA request.
 *
 * This is similar to svc_rdma_reply, but takes an rpc_rqst
 * instead, does not support chunks, and avoids blocking memory
 * allocation.
 *
 * XXX: There is still an opportunity to block in svc_rdma_send()
 * if there are no SQ entries to post the Send. This may occur if
 * the adapter has a small maximum SQ depth.
 */
static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
                              struct rpc_rqst *rqst)
{
        struct xdr_buf *sndbuf = &rqst->rq_snd_buf;
        struct svc_rdma_op_ctxt *ctxt;
        struct svc_rdma_req_map *vec;
        struct ib_send_wr send_wr;
        int ret;

        vec = svc_rdma_get_req_map(rdma);
        ret = svc_rdma_map_xdr(rdma, sndbuf, vec, false);
        if (ret)
                goto out_err;

        ret = svc_rdma_repost_recv(rdma, GFP_NOIO);
        if (ret)
                goto out_err;

        ctxt = svc_rdma_get_context(rdma);
        ctxt->pages[0] = virt_to_page(rqst->rq_buffer);
        ctxt->count = 1;

        ctxt->direction = DMA_TO_DEVICE;
        ctxt->sge[0].lkey = rdma->sc_pd->local_dma_lkey;
        ctxt->sge[0].length = sndbuf->len;
        ctxt->sge[0].addr =
            ib_dma_map_page(rdma->sc_cm_id->device, ctxt->pages[0], 0,
                            sndbuf->len, DMA_TO_DEVICE);
        if (ib_dma_mapping_error(rdma->sc_cm_id->device, ctxt->sge[0].addr)) {
                ret = -EIO;
                goto out_unmap;
        }
        atomic_inc(&rdma->sc_dma_used);

        memset(&send_wr, 0, sizeof(send_wr));
        ctxt->cqe.done = svc_rdma_wc_send;
        send_wr.wr_cqe = &ctxt->cqe;
        send_wr.sg_list = ctxt->sge;
        send_wr.num_sge = 1;
        send_wr.opcode = IB_WR_SEND;
        send_wr.send_flags = IB_SEND_SIGNALED;

        ret = svc_rdma_send(rdma, &send_wr);
        if (ret) {
                ret = -EIO;
                goto out_unmap;
        }

out_err:
        svc_rdma_put_req_map(rdma, vec);
        dprintk("svcrdma: %s returns %d\n", __func__, ret);
        return ret;

out_unmap:
        svc_rdma_unmap_dma(ctxt);
        svc_rdma_put_context(ctxt, 1);
        goto out_err;
}

/* Server-side transport endpoint wants a whole page for its send
 * buffer. The client RPC code constructs the RPC header in this
 * buffer before it invokes ->send_request.
 *
 * Returns NULL if there was a temporary allocation failure.
 */
static void *
xprt_rdma_bc_allocate(struct rpc_task *task, size_t size)
{
        struct rpc_rqst *rqst = task->tk_rqstp;
        struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
        struct svcxprt_rdma *rdma;
        struct page *page;

        rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);

        /* Prevent an infinite loop: try to make this case work */
        if (size > PAGE_SIZE)
                WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
                          size);

        page = alloc_page(RPCRDMA_DEF_GFP);
        if (!page)
                return NULL;

        return page_address(page);
}

static void
xprt_rdma_bc_free(void *buffer)
{
        /* No-op: ctxt and page have already been freed. */
}

static int
rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst)
{
        struct rpc_xprt *xprt = rqst->rq_xprt;
        struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
        struct rpcrdma_msg *headerp = (struct rpcrdma_msg *)rqst->rq_buffer;
        int rc;

        /* Space in the send buffer for an RPC/RDMA header is reserved
         * via xprt->tsh_size.
         */
        headerp->rm_xid = rqst->rq_xid;
        headerp->rm_vers = rpcrdma_version;
        headerp->rm_credit = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
        headerp->rm_type = rdma_msg;
        headerp->rm_body.rm_chunks[0] = xdr_zero;
        headerp->rm_body.rm_chunks[1] = xdr_zero;
        headerp->rm_body.rm_chunks[2] = xdr_zero;

#ifdef SVCRDMA_BACKCHANNEL_DEBUG
        pr_info("%s: %*ph\n", __func__, 64, rqst->rq_buffer);
#endif

        rc = svc_rdma_bc_sendto(rdma, rqst);
        if (rc)
                goto drop_connection;
        return rc;

drop_connection:
        dprintk("svcrdma: failed to send bc call\n");
        xprt_disconnect_done(xprt);
        return -ENOTCONN;
}

/* Send an RPC call on the passive end of a transport
 * connection.
 */
static int
xprt_rdma_bc_send_request(struct rpc_task *task)
{
        struct rpc_rqst *rqst = task->tk_rqstp;
        struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
        struct svcxprt_rdma *rdma;
        int ret;

        dprintk("svcrdma: sending bc call with xid: %08x\n",
                be32_to_cpu(rqst->rq_xid));

        if (!mutex_trylock(&sxprt->xpt_mutex)) {
                rpc_sleep_on(&sxprt->xpt_bc_pending, task, NULL);
                if (!mutex_trylock(&sxprt->xpt_mutex))
                        return -EAGAIN;
                rpc_wake_up_queued_task(&sxprt->xpt_bc_pending, task);
        }

        ret = -ENOTCONN;
        rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt);
        if (!test_bit(XPT_DEAD, &sxprt->xpt_flags))
                ret = rpcrdma_bc_send_request(rdma, rqst);

        mutex_unlock(&sxprt->xpt_mutex);

        if (ret < 0)
                return ret;
        return 0;
}

static void
xprt_rdma_bc_close(struct rpc_xprt *xprt)
{
        dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);
}

static void
xprt_rdma_bc_put(struct rpc_xprt *xprt)
{
        dprintk("svcrdma: %s: xprt %p\n", __func__, xprt);

        xprt_free(xprt);
        module_put(THIS_MODULE);
}

static struct rpc_xprt_ops xprt_rdma_bc_procs = {
        .reserve_xprt           = xprt_reserve_xprt_cong,
        .release_xprt           = xprt_release_xprt_cong,
        .alloc_slot             = xprt_alloc_slot,
        .release_request        = xprt_release_rqst_cong,
        .buf_alloc              = xprt_rdma_bc_allocate,
        .buf_free               = xprt_rdma_bc_free,
        .send_request           = xprt_rdma_bc_send_request,
        .set_retrans_timeout    = xprt_set_retrans_timeout_def,
        .close                  = xprt_rdma_bc_close,
        .destroy                = xprt_rdma_bc_put,
        .print_stats            = xprt_rdma_print_stats
};

static const struct rpc_timeout xprt_rdma_bc_timeout = {
        .to_initval = 60 * HZ,
        .to_maxval = 60 * HZ,
};

/* It shouldn't matter if the number of backchannel session slots
 * doesn't match the number of RPC/RDMA credits. That just means
 * one or the other will have extra slots that aren't used.
 */
static struct rpc_xprt *
xprt_setup_rdma_bc(struct xprt_create *args)
{
        struct rpc_xprt *xprt;
        struct rpcrdma_xprt *new_xprt;

        if (args->addrlen > sizeof(xprt->addr)) {
                dprintk("RPC:       %s: address too large\n", __func__);
                return ERR_PTR(-EBADF);
        }

        xprt = xprt_alloc(args->net, sizeof(*new_xprt),
                          RPCRDMA_MAX_BC_REQUESTS,
                          RPCRDMA_MAX_BC_REQUESTS);
        if (!xprt) {
                dprintk("RPC:       %s: couldn't allocate rpc_xprt\n",
                        __func__);
                return ERR_PTR(-ENOMEM);
        }

        xprt->timeout = &xprt_rdma_bc_timeout;
        xprt_set_bound(xprt);
        xprt_set_connected(xprt);
        xprt->bind_timeout = RPCRDMA_BIND_TO;
        xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
        xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;

        xprt->prot = XPRT_TRANSPORT_BC_RDMA;
        xprt->tsh_size = RPCRDMA_HDRLEN_MIN / sizeof(__be32);
        xprt->ops = &xprt_rdma_bc_procs;

        memcpy(&xprt->addr, args->dstaddr, args->addrlen);
        xprt->addrlen = args->addrlen;
        xprt_rdma_format_addresses(xprt, (struct sockaddr *)&xprt->addr);
        xprt->resvport = 0;

        xprt->max_payload = xprt_rdma_max_inline_read;

        new_xprt = rpcx_to_rdmax(xprt);
        new_xprt->rx_buf.rb_bc_max_requests = xprt->max_reqs;

        xprt_get(xprt);
        args->bc_xprt->xpt_bc_xprt = xprt;
        xprt->bc_xprt = args->bc_xprt;

        if (!try_module_get(THIS_MODULE))
                goto out_fail;

        /* Final put for backchannel xprt is in __svc_rdma_free */
        xprt_get(xprt);
        return xprt;

out_fail:
        xprt_rdma_free_addresses(xprt);
        args->bc_xprt->xpt_bc_xprt = NULL;
        xprt_put(xprt);
        xprt_free(xprt);
        return ERR_PTR(-EINVAL);
}

struct xprt_class xprt_rdma_bc = {
        .list                   = LIST_HEAD_INIT(xprt_rdma_bc.list),
        .name                   = "rdma backchannel",
        .owner                  = THIS_MODULE,
        .ident                  = XPRT_TRANSPORT_BC_RDMA,
        .setup                  = xprt_setup_rdma_bc,
};