[mirror_ubuntu-eoan-kernel.git] / net / sunrpc / xprtrdma / xprt_rdma.h

/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
/*
 * Copyright (c) 2014-2017 Oracle.  All rights reserved.
 * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the BSD-type
 * license below:
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *      Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *      Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer in the documentation and/or other materials provided
 *      with the distribution.
 *
 *      Neither the name of the Network Appliance, Inc. nor the names of
 *      its contributors may be used to endorse or promote products
 *      derived from this software without specific prior written
 *      permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _LINUX_SUNRPC_XPRT_RDMA_H
#define _LINUX_SUNRPC_XPRT_RDMA_H

#include <linux/wait.h>                 /* wait_queue_head_t, etc */
#include <linux/spinlock.h>             /* spinlock_t, etc */
#include <linux/atomic.h>                       /* atomic_t, etc */
#include <linux/workqueue.h>            /* struct work_struct */

#include <rdma/rdma_cm.h>               /* RDMA connection api */
#include <rdma/ib_verbs.h>              /* RDMA verbs api */

#include <linux/sunrpc/clnt.h>          /* rpc_xprt */
#include <linux/sunrpc/rpc_rdma.h>      /* RPC/RDMA protocol */
#include <linux/sunrpc/xprtrdma.h>      /* xprt parameters */

#define RDMA_RESOLVE_TIMEOUT    (5000)  /* 5 seconds */
#define RDMA_CONNECT_RETRY_MAX  (2)     /* retries if no listener backlog */

#define RPCRDMA_BIND_TO         (60U * HZ)
#define RPCRDMA_INIT_REEST_TO   (5U * HZ)
#define RPCRDMA_MAX_REEST_TO    (30U * HZ)
#define RPCRDMA_IDLE_DISC_TO    (5U * 60 * HZ)

/*
 * Interface Adapter -- one per transport instance
 */
struct rpcrdma_ia {
        struct ib_device        *ri_device;
        struct rdma_cm_id       *ri_id;
        struct ib_pd            *ri_pd;
        struct completion       ri_done;
        struct completion       ri_remove_done;
        int                     ri_async_rc;
        unsigned int            ri_max_segs;
        unsigned int            ri_max_frwr_depth;
        unsigned int            ri_max_inline_write;
        unsigned int            ri_max_inline_read;
        unsigned int            ri_max_send_sges;
        bool                    ri_implicit_roundup;
        enum ib_mr_type         ri_mrtype;
        unsigned long           ri_flags;
        struct ib_qp_attr       ri_qp_attr;
        struct ib_qp_init_attr  ri_qp_init_attr;
};

enum {
        RPCRDMA_IAF_REMOVING = 0,
};

/*
 * RDMA Endpoint -- one per transport instance
 */

struct rpcrdma_ep {
        unsigned int            rep_send_count;
        unsigned int            rep_send_batch;
        int                     rep_connected;
        struct ib_qp_init_attr  rep_attr;
        wait_queue_head_t       rep_connect_wait;
        struct rpcrdma_connect_private  rep_cm_private;
        struct rdma_conn_param  rep_remote_cma;
        int                     rep_receive_count;
};

/* Pre-allocate extra Work Requests for handling backward receives
 * and sends. This is a fixed value because the Work Queues are
 * allocated when the forward channel is set up.
 */
#if defined(CONFIG_SUNRPC_BACKCHANNEL)
#define RPCRDMA_BACKWARD_WRS            (8)
#else
#define RPCRDMA_BACKWARD_WRS            (0)
#endif

/* Registered buffer -- registered kmalloc'd memory for RDMA SEND/RECV
 *
 * The below structure appears at the front of a large region of kmalloc'd
 * memory, which always starts on a good alignment boundary.
 */

struct rpcrdma_regbuf {
        struct ib_sge           rg_iov;
        struct ib_device        *rg_device;
        enum dma_data_direction rg_direction;
        __be32                  rg_base[0] __attribute__ ((aligned(256)));
};

static inline u64
rdmab_addr(struct rpcrdma_regbuf *rb)
{
        return rb->rg_iov.addr;
}

static inline u32
rdmab_length(struct rpcrdma_regbuf *rb)
{
        return rb->rg_iov.length;
}

static inline u32
rdmab_lkey(struct rpcrdma_regbuf *rb)
{
        return rb->rg_iov.lkey;
}

static inline struct ib_device *
rdmab_device(struct rpcrdma_regbuf *rb)
{
        return rb->rg_device;
}

#define RPCRDMA_DEF_GFP         (GFP_NOIO | __GFP_NOWARN)

/* To ensure a transport can always make forward progress,
 * the number of RDMA segments allowed in header chunk lists
 * is capped at 8. This prevents less-capable devices and
 * memory registrations from overrunning the Send buffer
 * while building chunk lists.
 *
 * Elements of the Read list take up more room than the
 * Write list or Reply chunk. 8 read segments means the Read
 * list (or Write list or Reply chunk) cannot consume more
 * than
 *
 * ((8 + 2) * read segment size) + 1 XDR words, or 244 bytes.
 *
 * And the fixed part of the header is another 24 bytes.
 *
 * The smallest inline threshold is 1024 bytes, ensuring that
 * at least 750 bytes are available for RPC messages.
 */
enum {
        RPCRDMA_MAX_HDR_SEGS = 8,
        RPCRDMA_HDRBUF_SIZE = 256,
};

/*
 * struct rpcrdma_rep -- this structure encapsulates state required
 * to receive and complete an RPC Reply, asychronously. It needs
 * several pieces of state:
 *
 *   o receive buffer and ib_sge (donated to provider)
 *   o status of receive (success or not, length, inv rkey)
 *   o bookkeeping state to get run by reply handler (XDR stream)
 *
 * These structures are allocated during transport initialization.
 * N of these are associated with a transport instance, managed by
 * struct rpcrdma_buffer. N is the max number of outstanding RPCs.
 */

struct rpcrdma_rep {
        struct ib_cqe           rr_cqe;
        __be32                  rr_xid;
        __be32                  rr_vers;
        __be32                  rr_proc;
        int                     rr_wc_flags;
        u32                     rr_inv_rkey;
        bool                    rr_temp;
        struct rpcrdma_regbuf   *rr_rdmabuf;
        struct rpcrdma_xprt     *rr_rxprt;
        struct work_struct      rr_work;
        struct xdr_buf          rr_hdrbuf;
        struct xdr_stream       rr_stream;
        struct rpc_rqst         *rr_rqst;
        struct list_head        rr_list;
        struct ib_recv_wr       rr_recv_wr;
};

/* struct rpcrdma_sendctx - DMA mapped SGEs to unmap after Send completes
 */
struct rpcrdma_req;
struct rpcrdma_xprt;
struct rpcrdma_sendctx {
        struct ib_send_wr       sc_wr;
        struct ib_cqe           sc_cqe;
        struct rpcrdma_xprt     *sc_xprt;
        struct rpcrdma_req      *sc_req;
        unsigned int            sc_unmap_count;
        struct ib_sge           sc_sges[];
};

/* Limit the number of SGEs that can be unmapped during one
 * Send completion. This caps the amount of work a single
 * completion can do before returning to the provider.
 *
 * Setting this to zero disables Send completion batching.
 */
enum {
        RPCRDMA_MAX_SEND_BATCH = 7,
};

/*
 * struct rpcrdma_mr - external memory region metadata
 *
 * An external memory region is any buffer or page that is registered
 * on the fly (ie, not pre-registered).
 *
 * Each rpcrdma_buffer has a list of free MWs anchored in rb_mrs. During
 * call_allocate, rpcrdma_buffer_get() assigns one to each segment in
 * an rpcrdma_req. Then rpcrdma_register_external() grabs these to keep
 * track of registration metadata while each RPC is pending.
 * rpcrdma_deregister_external() uses this metadata to unmap and
 * release these resources when an RPC is complete.
 */
enum rpcrdma_frwr_state {
        FRWR_IS_INVALID,        /* ready to be used */
        FRWR_IS_VALID,          /* in use */
        FRWR_FLUSHED_FR,        /* flushed FASTREG WR */
        FRWR_FLUSHED_LI,        /* flushed LOCALINV WR */
};

struct rpcrdma_frwr {
        struct ib_mr                    *fr_mr;
        struct ib_cqe                   fr_cqe;
        enum rpcrdma_frwr_state         fr_state;
        struct completion               fr_linv_done;
        union {
                struct ib_reg_wr        fr_regwr;
                struct ib_send_wr       fr_invwr;
        };
};

struct rpcrdma_mr {
        struct list_head        mr_list;
        struct scatterlist      *mr_sg;
        int                     mr_nents;
        enum dma_data_direction mr_dir;
        struct rpcrdma_frwr     frwr;
        struct rpcrdma_xprt     *mr_xprt;
        u32                     mr_handle;
        u32                     mr_length;
        u64                     mr_offset;
        struct work_struct      mr_recycle;
        struct list_head        mr_all;
};

/*
 * struct rpcrdma_req -- structure central to the request/reply sequence.
 *
 * N of these are associated with a transport instance, and stored in
 * struct rpcrdma_buffer. N is the max number of outstanding requests.
 *
 * It includes pre-registered buffer memory for send AND recv.
 * The recv buffer, however, is not owned by this structure, and
 * is "donated" to the hardware when a recv is posted. When a
 * reply is handled, the recv buffer used is given back to the
 * struct rpcrdma_req associated with the request.
 *
 * In addition to the basic memory, this structure includes an array
 * of iovs for send operations. The reason is that the iovs passed to
 * ib_post_{send,recv} must not be modified until the work request
 * completes.
 */

/* Maximum number of page-sized "segments" per chunk list to be
 * registered or invalidated. Must handle a Reply chunk:
 */
enum {
        RPCRDMA_MAX_IOV_SEGS    = 3,
        RPCRDMA_MAX_DATA_SEGS   = ((1 * 1024 * 1024) / PAGE_SIZE) + 1,
        RPCRDMA_MAX_SEGS        = RPCRDMA_MAX_DATA_SEGS +
                                  RPCRDMA_MAX_IOV_SEGS,
};

struct rpcrdma_mr_seg {         /* chunk descriptors */
        u32             mr_len;         /* length of chunk or segment */
        struct page     *mr_page;       /* owning page, if any */
        char            *mr_offset;     /* kva if no page, else offset */
};

/* The Send SGE array is provisioned to send a maximum size
 * inline request:
 * - RPC-over-RDMA header
 * - xdr_buf head iovec
 * - RPCRDMA_MAX_INLINE bytes, in pages
 * - xdr_buf tail iovec
 *
 * The actual number of array elements consumed by each RPC
 * depends on the device's max_sge limit.
 */
enum {
        RPCRDMA_MIN_SEND_SGES = 3,
        RPCRDMA_MAX_PAGE_SGES = RPCRDMA_MAX_INLINE >> PAGE_SHIFT,
        RPCRDMA_MAX_SEND_SGES = 1 + 1 + RPCRDMA_MAX_PAGE_SGES + 1,
};

struct rpcrdma_buffer;
struct rpcrdma_req {
        struct list_head        rl_list;
        struct rpc_rqst         rl_slot;
        struct rpcrdma_buffer   *rl_buffer;
        struct rpcrdma_rep      *rl_reply;
        struct xdr_stream       rl_stream;
        struct xdr_buf          rl_hdrbuf;
        struct rpcrdma_sendctx  *rl_sendctx;
        struct rpcrdma_regbuf   *rl_rdmabuf;    /* xprt header */
        struct rpcrdma_regbuf   *rl_sendbuf;    /* rq_snd_buf */
        struct rpcrdma_regbuf   *rl_recvbuf;    /* rq_rcv_buf */

        struct list_head        rl_all;
        unsigned long           rl_flags;

        struct list_head        rl_registered;  /* registered segments */
        struct rpcrdma_mr_seg   rl_segments[RPCRDMA_MAX_SEGS];
};

/* rl_flags */
enum {
        RPCRDMA_REQ_F_PENDING = 0,
        RPCRDMA_REQ_F_TX_RESOURCES,
};

static inline struct rpcrdma_req *
rpcr_to_rdmar(const struct rpc_rqst *rqst)
{
        return container_of(rqst, struct rpcrdma_req, rl_slot);
}

static inline void
rpcrdma_mr_push(struct rpcrdma_mr *mr, struct list_head *list)
{
        list_add_tail(&mr->mr_list, list);
}

static inline struct rpcrdma_mr *
rpcrdma_mr_pop(struct list_head *list)
{
        struct rpcrdma_mr *mr;

        mr = list_first_entry(list, struct rpcrdma_mr, mr_list);
        list_del_init(&mr->mr_list);
        return mr;
}

/*
 * struct rpcrdma_buffer -- holds list/queue of pre-registered memory for
 * inline requests/replies, and client/server credits.
 *
 * One of these is associated with a transport instance
 */
struct rpcrdma_buffer {
        spinlock_t              rb_mrlock;      /* protect rb_mrs list */
        struct list_head        rb_mrs;
        struct list_head        rb_all;

        unsigned long           rb_sc_head;
        unsigned long           rb_sc_tail;
        unsigned long           rb_sc_last;
        struct rpcrdma_sendctx  **rb_sc_ctxs;

        spinlock_t              rb_lock;        /* protect buf lists */
        struct list_head        rb_send_bufs;
        struct list_head        rb_recv_bufs;
        unsigned long           rb_flags;
        u32                     rb_max_requests;
        u32                     rb_credits;     /* most recent credit grant */

        u32                     rb_bc_srv_max_requests;
        spinlock_t              rb_reqslock;    /* protect rb_allreqs */
        struct list_head        rb_allreqs;

        u32                     rb_bc_max_requests;

        struct workqueue_struct *rb_completion_wq;
        struct delayed_work     rb_refresh_worker;
};

/* rb_flags */
enum {
        RPCRDMA_BUF_F_EMPTY_SCQ = 0,
};

/*
 * Internal structure for transport instance creation. This
 * exists primarily for modularity.
 *
 * This data should be set with mount options
 */
struct rpcrdma_create_data_internal {
        unsigned int    max_requests;   /* max requests (slots) in flight */
        unsigned int    rsize;          /* mount rsize - max read hdr+data */
        unsigned int    wsize;          /* mount wsize - max write hdr+data */
        unsigned int    inline_rsize;   /* max non-rdma read data payload */
        unsigned int    inline_wsize;   /* max non-rdma write data payload */
};

/*
 * Statistics for RPCRDMA
 */
struct rpcrdma_stats {
        /* accessed when sending a call */
        unsigned long           read_chunk_count;
        unsigned long           write_chunk_count;
        unsigned long           reply_chunk_count;
        unsigned long long      total_rdma_request;

        /* rarely accessed error counters */
        unsigned long long      pullup_copy_count;
        unsigned long           hardway_register_count;
        unsigned long           failed_marshal_count;
        unsigned long           bad_reply_count;
        unsigned long           mrs_recycled;
        unsigned long           mrs_orphaned;
        unsigned long           mrs_allocated;
        unsigned long           empty_sendctx_q;

        /* accessed when receiving a reply */
        unsigned long long      total_rdma_reply;
        unsigned long long      fixup_copy_count;
        unsigned long           reply_waits_for_send;
        unsigned long           local_inv_needed;
        unsigned long           nomsg_call_count;
        unsigned long           bcall_count;
};

/*
 * RPCRDMA transport -- encapsulates the structures above for
 * integration with RPC.
 *
 * The contained structures are embedded, not pointers,
 * for convenience. This structure need not be visible externally.
 *
 * It is allocated and initialized during mount, and released
 * during unmount.
 */
struct rpcrdma_xprt {
        struct rpc_xprt         rx_xprt;
        struct rpcrdma_ia       rx_ia;
        struct rpcrdma_ep       rx_ep;
        struct rpcrdma_buffer   rx_buf;
        struct rpcrdma_create_data_internal rx_data;
        struct delayed_work     rx_connect_worker;
        struct rpcrdma_stats    rx_stats;
};

#define rpcx_to_rdmax(x) container_of(x, struct rpcrdma_xprt, rx_xprt)
#define rpcx_to_rdmad(x) (rpcx_to_rdmax(x)->rx_data)

static inline const char *
rpcrdma_addrstr(const struct rpcrdma_xprt *r_xprt)
{
        return r_xprt->rx_xprt.address_strings[RPC_DISPLAY_ADDR];
}

static inline const char *
rpcrdma_portstr(const struct rpcrdma_xprt *r_xprt)
{
        return r_xprt->rx_xprt.address_strings[RPC_DISPLAY_PORT];
}

/* Setting this to 0 ensures interoperability with early servers.
 * Setting this to 1 enhances certain unaligned read/write performance.
 * Default is 0, see sysctl entry and rpc_rdma.c rpcrdma_convert_iovs() */
extern int xprt_rdma_pad_optimize;

/* This setting controls the hunt for a supported memory
 * registration strategy.
 */
extern unsigned int xprt_rdma_memreg_strategy;

/*
 * Interface Adapter calls - xprtrdma/verbs.c
 */
int rpcrdma_ia_open(struct rpcrdma_xprt *xprt);
void rpcrdma_ia_remove(struct rpcrdma_ia *ia);
void rpcrdma_ia_close(struct rpcrdma_ia *);

/*
 * Endpoint calls - xprtrdma/verbs.c
 */
int rpcrdma_ep_create(struct rpcrdma_ep *, struct rpcrdma_ia *,
                                struct rpcrdma_create_data_internal *);
void rpcrdma_ep_destroy(struct rpcrdma_ep *, struct rpcrdma_ia *);
int rpcrdma_ep_connect(struct rpcrdma_ep *, struct rpcrdma_ia *);
void rpcrdma_ep_disconnect(struct rpcrdma_ep *, struct rpcrdma_ia *);

int rpcrdma_ep_post(struct rpcrdma_ia *, struct rpcrdma_ep *,
                                struct rpcrdma_req *);

/*
 * Buffer calls - xprtrdma/verbs.c
 */
struct rpcrdma_req *rpcrdma_create_req(struct rpcrdma_xprt *);
void rpcrdma_destroy_req(struct rpcrdma_req *);
int rpcrdma_buffer_create(struct rpcrdma_xprt *);
void rpcrdma_buffer_destroy(struct rpcrdma_buffer *);
struct rpcrdma_sendctx *rpcrdma_sendctx_get_locked(struct rpcrdma_buffer *buf);

struct rpcrdma_mr *rpcrdma_mr_get(struct rpcrdma_xprt *r_xprt);
void rpcrdma_mr_put(struct rpcrdma_mr *mr);
void rpcrdma_mr_unmap_and_put(struct rpcrdma_mr *mr);

static inline void
rpcrdma_mr_recycle(struct rpcrdma_mr *mr)
{
        schedule_work(&mr->mr_recycle);
}

struct rpcrdma_req *rpcrdma_buffer_get(struct rpcrdma_buffer *);
void rpcrdma_buffer_put(struct rpcrdma_req *);
void rpcrdma_recv_buffer_put(struct rpcrdma_rep *);

struct rpcrdma_regbuf *rpcrdma_alloc_regbuf(size_t, enum dma_data_direction,
                                            gfp_t);
bool __rpcrdma_dma_map_regbuf(struct rpcrdma_ia *, struct rpcrdma_regbuf *);
void rpcrdma_free_regbuf(struct rpcrdma_regbuf *);

static inline bool
rpcrdma_regbuf_is_mapped(struct rpcrdma_regbuf *rb)
{
        return rb->rg_device != NULL;
}

static inline bool
rpcrdma_dma_map_regbuf(struct rpcrdma_ia *ia, struct rpcrdma_regbuf *rb)
{
        if (likely(rpcrdma_regbuf_is_mapped(rb)))
                return true;
        return __rpcrdma_dma_map_regbuf(ia, rb);
}

/*
 * Wrappers for chunk registration, shared by read/write chunk code.
 */

static inline enum dma_data_direction
rpcrdma_data_dir(bool writing)
{
        return writing ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
}

/* Memory registration calls xprtrdma/frwr_ops.c
 */
bool frwr_is_supported(struct rpcrdma_ia *);
int frwr_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
              struct rpcrdma_create_data_internal *cdata);
int frwr_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mr *mr);
void frwr_release_mr(struct rpcrdma_mr *mr);
size_t frwr_maxpages(struct rpcrdma_xprt *r_xprt);
struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
                                struct rpcrdma_mr_seg *seg,
                                int nsegs, bool writing, u32 xid,
                                struct rpcrdma_mr **mr);
int frwr_send(struct rpcrdma_ia *ia, struct rpcrdma_req *req);
void frwr_reminv(struct rpcrdma_rep *rep, struct list_head *mrs);
void frwr_unmap_sync(struct rpcrdma_xprt *r_xprt,
                     struct list_head *mrs);

/*
 * RPC/RDMA protocol calls - xprtrdma/rpc_rdma.c
 */

enum rpcrdma_chunktype {
        rpcrdma_noch = 0,
        rpcrdma_readch,
        rpcrdma_areadch,
        rpcrdma_writech,
        rpcrdma_replych
};

int rpcrdma_prepare_send_sges(struct rpcrdma_xprt *r_xprt,
                              struct rpcrdma_req *req, u32 hdrlen,
                              struct xdr_buf *xdr,
                              enum rpcrdma_chunktype rtype);
void rpcrdma_unmap_sendctx(struct rpcrdma_sendctx *sc);
int rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst);
void rpcrdma_set_max_header_sizes(struct rpcrdma_xprt *);
void rpcrdma_complete_rqst(struct rpcrdma_rep *rep);
void rpcrdma_reply_handler(struct rpcrdma_rep *rep);
void rpcrdma_release_rqst(struct rpcrdma_xprt *r_xprt,
                          struct rpcrdma_req *req);
void rpcrdma_deferred_completion(struct work_struct *work);

static inline void rpcrdma_set_xdrlen(struct xdr_buf *xdr, size_t len)
{
        xdr->head[0].iov_len = len;
        xdr->len = len;
}

/* RPC/RDMA module init - xprtrdma/transport.c
 */
extern unsigned int xprt_rdma_max_inline_read;
void xprt_rdma_format_addresses(struct rpc_xprt *xprt, struct sockaddr *sap);
void xprt_rdma_free_addresses(struct rpc_xprt *xprt);
void xprt_rdma_close(struct rpc_xprt *xprt);
void xprt_rdma_print_stats(struct rpc_xprt *xprt, struct seq_file *seq);
int xprt_rdma_init(void);
void xprt_rdma_cleanup(void);

/* Backchannel calls - xprtrdma/backchannel.c
 */
#if defined(CONFIG_SUNRPC_BACKCHANNEL)
int xprt_rdma_bc_setup(struct rpc_xprt *, unsigned int);
int xprt_rdma_bc_up(struct svc_serv *, struct net *);
size_t xprt_rdma_bc_maxpayload(struct rpc_xprt *);
int rpcrdma_bc_post_recv(struct rpcrdma_xprt *, unsigned int);
void rpcrdma_bc_receive_call(struct rpcrdma_xprt *, struct rpcrdma_rep *);
int xprt_rdma_bc_send_reply(struct rpc_rqst *rqst);
void xprt_rdma_bc_free_rqst(struct rpc_rqst *);
void xprt_rdma_bc_destroy(struct rpc_xprt *, unsigned int);
#endif  /* CONFIG_SUNRPC_BACKCHANNEL */

extern struct xprt_class xprt_rdma_bc;

#endif                          /* _LINUX_SUNRPC_XPRT_RDMA_H */