// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2015-2018 Oracle.  All rights reserved.
 *
 * Support for reverse-direction RPCs on RPC/RDMA (server-side).
 */

#include <linux/sunrpc/svc_rdma.h>

#include "xprt_rdma.h"
#include <trace/events/rpcrdma.h>

/**
 * svc_rdma_handle_bc_reply - Process incoming backchannel Reply
 * @rqstp: resources for handling the Reply
 * @rctxt: Received message
 *
 */
void svc_rdma_handle_bc_reply(struct svc_rqst *rqstp,
                              struct svc_rdma_recv_ctxt *rctxt)
{
        struct svc_xprt *sxprt = rqstp->rq_xprt;
        struct rpc_xprt *xprt = sxprt->xpt_bc_xprt;
        struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
        struct xdr_buf *rcvbuf = &rqstp->rq_arg;
        struct kvec *dst, *src = &rcvbuf->head[0];
        __be32 *rdma_resp = rctxt->rc_recv_buf;
        struct rpc_rqst *req;
        u32 credits;

        spin_lock(&xprt->queue_lock);
        req = xprt_lookup_rqst(xprt, *rdma_resp);
        if (!req)
                goto out_unlock;

        dst = &req->rq_private_buf.head[0];
        memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
        if (dst->iov_len < src->iov_len)
                goto out_unlock;
        memcpy(dst->iov_base, src->iov_base, src->iov_len);
        xprt_pin_rqst(req);
        spin_unlock(&xprt->queue_lock);

        credits = be32_to_cpup(rdma_resp + 2);
        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;
        spin_lock(&xprt->transport_lock);
        xprt->cwnd = credits << RPC_CWNDSHIFT;
        spin_unlock(&xprt->transport_lock);

        spin_lock(&xprt->queue_lock);
        xprt_complete_rqst(req->rq_task, rcvbuf->len);
        xprt_unpin_rqst(req);
        rcvbuf->len = 0;

out_unlock:
        spin_unlock(&xprt->queue_lock);
}

/* Send a reverse-direction RPC Call.
 *
 * Caller holds the connection's mutex and has already marshaled
 * the RPC/RDMA request.
 *
 * This is similar to svc_rdma_send_reply_msg, but takes a struct
 * 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 svc_rdma_send_ctxt *sctxt)
{
        struct svc_rdma_pcl empty_pcl;
        int ret;

        pcl_init(&empty_pcl);
        ret = svc_rdma_map_reply_msg(rdma, sctxt, &empty_pcl, &empty_pcl,
                                     &rqst->rq_snd_buf);
        if (ret < 0)
                return -EIO;

        /* Bump page refcnt so Send completion doesn't release
         * the rq_buffer before all retransmits are complete.
         */
        get_page(virt_to_page(rqst->rq_buffer));
        sctxt->sc_send_wr.opcode = IB_WR_SEND;
        return svc_rdma_post_send(rdma, sctxt);
}

/* 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.
 */
static int
xprt_rdma_bc_allocate(struct rpc_task *task)
{
        struct rpc_rqst *rqst = task->tk_rqstp;
        size_t size = rqst->rq_callsize;
        struct page *page;

        if (size > PAGE_SIZE) {
                WARN_ONCE(1, "svcrdma: large bc buffer request (size %zu)\n",
                          size);
                return -EINVAL;
        }

        page = alloc_page(GFP_NOIO | __GFP_NOWARN);
        if (!page)
                return -ENOMEM;
        rqst->rq_buffer = page_address(page);

        rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, GFP_NOIO | __GFP_NOWARN);
        if (!rqst->rq_rbuffer) {
                put_page(page);
                return -ENOMEM;
        }
        return 0;
}

static void
xprt_rdma_bc_free(struct rpc_task *task)
{
        struct rpc_rqst *rqst = task->tk_rqstp;

        put_page(virt_to_page(rqst->rq_buffer));
        kfree(rqst->rq_rbuffer);
}

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 svc_rdma_send_ctxt *ctxt;
        __be32 *p;
        int rc;

        ctxt = svc_rdma_send_ctxt_get(rdma);
        if (!ctxt)
                goto drop_connection;

        p = xdr_reserve_space(&ctxt->sc_stream, RPCRDMA_HDRLEN_MIN);
        if (!p)
                goto put_ctxt;
        *p++ = rqst->rq_xid;
        *p++ = rpcrdma_version;
        *p++ = cpu_to_be32(r_xprt->rx_buf.rb_bc_max_requests);
        *p++ = rdma_msg;
        *p++ = xdr_zero;
        *p++ = xdr_zero;
        *p   = xdr_zero;

        rqst->rq_xtime = ktime_get();
        rc = svc_rdma_bc_sendto(rdma, rqst, ctxt);
        if (rc)
                goto put_ctxt;
        return 0;

put_ctxt:
        svc_rdma_send_ctxt_put(rdma, ctxt);

drop_connection:
        return -ENOTCONN;
}

/**
 * xprt_rdma_bc_send_request - Send a reverse-direction Call
 * @rqst: rpc_rqst containing Call message to be sent
 *
 * Return values:
 *   %0 if the message was sent successfully
 *   %ENOTCONN if the message was not sent
 */
static int xprt_rdma_bc_send_request(struct rpc_rqst *rqst)
{
        struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt;
        struct svcxprt_rdma *rdma =
                container_of(sxprt, struct svcxprt_rdma, sc_xprt);
        int ret;

        if (test_bit(XPT_DEAD, &sxprt->xpt_flags))
                return -ENOTCONN;

        ret = rpcrdma_bc_send_request(rdma, rqst);
        if (ret == -ENOTCONN)
                svc_xprt_close(sxprt);
        return ret;
}

static void
xprt_rdma_bc_close(struct rpc_xprt *xprt)
{
        xprt_disconnect_done(xprt);
        xprt->cwnd = RPC_CWNDSHIFT;
}

static void
xprt_rdma_bc_put(struct rpc_xprt *xprt)
{
        xprt_rdma_free_addresses(xprt);
        xprt_free(xprt);
}

static const 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,
        .free_slot              = xprt_free_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,
        .wait_for_reply_request = xprt_wait_for_reply_request_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))
                return ERR_PTR(-EBADF);

        xprt = xprt_alloc(args->net, sizeof(*new_xprt),
                          RPCRDMA_MAX_BC_REQUESTS,
                          RPCRDMA_MAX_BC_REQUESTS);
        if (!xprt)
                return ERR_PTR(-ENOMEM);

        xprt->timeout = &xprt_rdma_bc_timeout;
        xprt_set_bound(xprt);
        xprt_set_connected(xprt);
        xprt->bind_timeout = 0;
        xprt->reestablish_timeout = 0;
        xprt->idle_timeout = 0;

        xprt->prot = XPRT_TRANSPORT_BC_RDMA;
        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;

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

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,
};