/*
 * 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,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * 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.
 */

/*
 * rpc_rdma.c
 *
 * This file contains the guts of the RPC RDMA protocol, and
 * does marshaling/unmarshaling, etc. It is also where interfacing
 * to the Linux RPC framework lives.
 */

#include "xprt_rdma.h"

#include <linux/highmem.h>

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# define RPCDBG_FACILITY        RPCDBG_TRANS
#endif

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

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
static const char transfertypes[][12] = {
        "pure inline",  /* no chunks */
        " read chunk",  /* some argument via rdma read */
        "*read chunk",  /* entire request via rdma read */
        "write chunk",  /* some result via rdma write */
        "reply chunk"   /* entire reply via rdma write */
};
#endif

/* The client can send a request inline as long as the RPCRDMA header
 * plus the RPC call fit under the transport's inline limit. If the
 * combined call message size exceeds that limit, the client must use
 * the read chunk list for this operation.
 */
static bool rpcrdma_args_inline(struct rpc_rqst *rqst)
{
        unsigned int callsize = RPCRDMA_HDRLEN_MIN + rqst->rq_snd_buf.len;

        return callsize <= RPCRDMA_INLINE_WRITE_THRESHOLD(rqst);
}

/* The client can't know how large the actual reply will be. Thus it
 * plans for the largest possible reply for that particular ULP
 * operation. If the maximum combined reply message size exceeds that
 * limit, the client must provide a write list or a reply chunk for
 * this request.
 */
static bool rpcrdma_results_inline(struct rpc_rqst *rqst)
{
        unsigned int repsize = RPCRDMA_HDRLEN_MIN + rqst->rq_rcv_buf.buflen;

        return repsize <= RPCRDMA_INLINE_READ_THRESHOLD(rqst);
}

static int
rpcrdma_tail_pullup(struct xdr_buf *buf)
{
        size_t tlen = buf->tail[0].iov_len;
        size_t skip = tlen & 3;

        /* Do not include the tail if it is only an XDR pad */
        if (tlen < 4)
                return 0;

        /* xdr_write_pages() adds a pad at the beginning of the tail
         * if the content in "buf->pages" is unaligned. Force the
         * tail's actual content to land at the next XDR position
         * after the head instead.
         */
        if (skip) {
                unsigned char *src, *dst;
                unsigned int count;

                src = buf->tail[0].iov_base;
                dst = buf->head[0].iov_base;
                dst += buf->head[0].iov_len;

                src += skip;
                tlen -= skip;

                dprintk("RPC:       %s: skip=%zu, memmove(%p, %p, %zu)\n",
                        __func__, skip, dst, src, tlen);

                for (count = tlen; count; count--)
                        *dst++ = *src++;
        }

        return tlen;
}

/* Split "vec" on page boundaries into segments. FMR registers pages,
 * not a byte range. Other modes coalesce these segments into a single
 * MR when they can.
 */
static int
rpcrdma_convert_kvec(struct kvec *vec, struct rpcrdma_mr_seg *seg,
                     int n, int nsegs)
{
        size_t page_offset;
        u32 remaining;
        char *base;

        base = vec->iov_base;
        page_offset = offset_in_page(base);
        remaining = vec->iov_len;
        while (remaining && n < nsegs) {
                seg[n].mr_page = NULL;
                seg[n].mr_offset = base;
                seg[n].mr_len = min_t(u32, PAGE_SIZE - page_offset, remaining);
                remaining -= seg[n].mr_len;
                base += seg[n].mr_len;
                ++n;
                page_offset = 0;
        }
        return n;
}

/*
 * Chunk assembly from upper layer xdr_buf.
 *
 * Prepare the passed-in xdr_buf into representation as RPC/RDMA chunk
 * elements. Segments are then coalesced when registered, if possible
 * within the selected memreg mode.
 *
 * Returns positive number of segments converted, or a negative errno.
 */

static int
rpcrdma_convert_iovs(struct xdr_buf *xdrbuf, unsigned int pos,
        enum rpcrdma_chunktype type, struct rpcrdma_mr_seg *seg, int nsegs)
{
        int len, n = 0, p;
        int page_base;
        struct page **ppages;

        if (pos == 0) {
                n = rpcrdma_convert_kvec(&xdrbuf->head[0], seg, n, nsegs);
                if (n == nsegs)
                        return -EIO;
        }

        len = xdrbuf->page_len;
        ppages = xdrbuf->pages + (xdrbuf->page_base >> PAGE_SHIFT);
        page_base = xdrbuf->page_base & ~PAGE_MASK;
        p = 0;
        while (len && n < nsegs) {
                if (!ppages[p]) {
                        /* alloc the pagelist for receiving buffer */
                        ppages[p] = alloc_page(GFP_ATOMIC);
                        if (!ppages[p])
                                return -ENOMEM;
                }
                seg[n].mr_page = ppages[p];
                seg[n].mr_offset = (void *)(unsigned long) page_base;
                seg[n].mr_len = min_t(u32, PAGE_SIZE - page_base, len);
                if (seg[n].mr_len > PAGE_SIZE)
                        return -EIO;
                len -= seg[n].mr_len;
                ++n;
                ++p;
                page_base = 0;  /* page offset only applies to first page */
        }

        /* Message overflows the seg array */
        if (len && n == nsegs)
                return -EIO;

        /* When encoding the read list, the tail is always sent inline */
        if (type == rpcrdma_readch)
                return n;

        if (xdrbuf->tail[0].iov_len) {
                /* the rpcrdma protocol allows us to omit any trailing
                 * xdr pad bytes, saving the server an RDMA operation. */
                if (xdrbuf->tail[0].iov_len < 4 && xprt_rdma_pad_optimize)
                        return n;
                n = rpcrdma_convert_kvec(&xdrbuf->tail[0], seg, n, nsegs);
                if (n == nsegs)
                        return -EIO;
        }

        return n;
}

/*
 * Create read/write chunk lists, and reply chunks, for RDMA
 *
 *   Assume check against THRESHOLD has been done, and chunks are required.
 *   Assume only encoding one list entry for read|write chunks. The NFSv3
 *     protocol is simple enough to allow this as it only has a single "bulk
 *     result" in each procedure - complicated NFSv4 COMPOUNDs are not. (The
 *     RDMA/Sessions NFSv4 proposal addresses this for future v4 revs.)
 *
 * When used for a single reply chunk (which is a special write
 * chunk used for the entire reply, rather than just the data), it
 * is used primarily for READDIR and READLINK which would otherwise
 * be severely size-limited by a small rdma inline read max. The server
 * response will come back as an RDMA Write, followed by a message
 * of type RDMA_NOMSG carrying the xid and length. As a result, reply
 * chunks do not provide data alignment, however they do not require
 * "fixup" (moving the response to the upper layer buffer) either.
 *
 * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
 *
 *  Read chunklist (a linked list):
 *   N elements, position P (same P for all chunks of same arg!):
 *    1 - PHLOO - 1 - PHLOO - ... - 1 - PHLOO - 0
 *
 *  Write chunklist (a list of (one) counted array):
 *   N elements:
 *    1 - N - HLOO - HLOO - ... - HLOO - 0
 *
 *  Reply chunk (a counted array):
 *   N elements:
 *    1 - N - HLOO - HLOO - ... - HLOO
 *
 * Returns positive RPC/RDMA header size, or negative errno.
 */

static ssize_t
rpcrdma_create_chunks(struct rpc_rqst *rqst, struct xdr_buf *target,
                struct rpcrdma_msg *headerp, enum rpcrdma_chunktype type)
{
        struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
        struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
        int n, nsegs, nchunks = 0;
        unsigned int pos;
        struct rpcrdma_mr_seg *seg = req->rl_segments;
        struct rpcrdma_read_chunk *cur_rchunk = NULL;
        struct rpcrdma_write_array *warray = NULL;
        struct rpcrdma_write_chunk *cur_wchunk = NULL;
        __be32 *iptr = headerp->rm_body.rm_chunks;
        int (*map)(struct rpcrdma_xprt *, struct rpcrdma_mr_seg *, int, bool);

        if (type == rpcrdma_readch || type == rpcrdma_areadch) {
                /* a read chunk - server will RDMA Read our memory */
                cur_rchunk = (struct rpcrdma_read_chunk *) iptr;
        } else {
                /* a write or reply chunk - server will RDMA Write our memory */
                *iptr++ = xdr_zero;     /* encode a NULL read chunk list */
                if (type == rpcrdma_replych)
                        *iptr++ = xdr_zero;     /* a NULL write chunk list */
                warray = (struct rpcrdma_write_array *) iptr;
                cur_wchunk = (struct rpcrdma_write_chunk *) (warray + 1);
        }

        if (type == rpcrdma_replych || type == rpcrdma_areadch)
                pos = 0;
        else
                pos = target->head[0].iov_len;

        nsegs = rpcrdma_convert_iovs(target, pos, type, seg, RPCRDMA_MAX_SEGS);
        if (nsegs < 0)
                return nsegs;

        map = r_xprt->rx_ia.ri_ops->ro_map;
        do {
                n = map(r_xprt, seg, nsegs, cur_wchunk != NULL);
                if (n <= 0)
                        goto out;
                if (cur_rchunk) {       /* read */
                        cur_rchunk->rc_discrim = xdr_one;
                        /* all read chunks have the same "position" */
                        cur_rchunk->rc_position = cpu_to_be32(pos);
                        cur_rchunk->rc_target.rs_handle =
                                                cpu_to_be32(seg->mr_rkey);
                        cur_rchunk->rc_target.rs_length =
                                                cpu_to_be32(seg->mr_len);
                        xdr_encode_hyper(
                                        (__be32 *)&cur_rchunk->rc_target.rs_offset,
                                        seg->mr_base);
                        dprintk("RPC:       %s: read chunk "
                                "elem %d@0x%llx:0x%x pos %u (%s)\n", __func__,
                                seg->mr_len, (unsigned long long)seg->mr_base,
                                seg->mr_rkey, pos, n < nsegs ? "more" : "last");
                        cur_rchunk++;
                        r_xprt->rx_stats.read_chunk_count++;
                } else {                /* write/reply */
                        cur_wchunk->wc_target.rs_handle =
                                                cpu_to_be32(seg->mr_rkey);
                        cur_wchunk->wc_target.rs_length =
                                                cpu_to_be32(seg->mr_len);
                        xdr_encode_hyper(
                                        (__be32 *)&cur_wchunk->wc_target.rs_offset,
                                        seg->mr_base);
                        dprintk("RPC:       %s: %s chunk "
                                "elem %d@0x%llx:0x%x (%s)\n", __func__,
                                (type == rpcrdma_replych) ? "reply" : "write",
                                seg->mr_len, (unsigned long long)seg->mr_base,
                                seg->mr_rkey, n < nsegs ? "more" : "last");
                        cur_wchunk++;
                        if (type == rpcrdma_replych)
                                r_xprt->rx_stats.reply_chunk_count++;
                        else
                                r_xprt->rx_stats.write_chunk_count++;
                        r_xprt->rx_stats.total_rdma_request += seg->mr_len;
                }
                nchunks++;
                seg   += n;
                nsegs -= n;
        } while (nsegs);

        /* success. all failures return above */
        req->rl_nchunks = nchunks;

        /*
         * finish off header. If write, marshal discrim and nchunks.
         */
        if (cur_rchunk) {
                iptr = (__be32 *) cur_rchunk;
                *iptr++ = xdr_zero;     /* finish the read chunk list */
                *iptr++ = xdr_zero;     /* encode a NULL write chunk list */
                *iptr++ = xdr_zero;     /* encode a NULL reply chunk */
        } else {
                warray->wc_discrim = xdr_one;
                warray->wc_nchunks = cpu_to_be32(nchunks);
                iptr = (__be32 *) cur_wchunk;
                if (type == rpcrdma_writech) {
                        *iptr++ = xdr_zero; /* finish the write chunk list */
                        *iptr++ = xdr_zero; /* encode a NULL reply chunk */
                }
        }

        /*
         * Return header size.
         */
        return (unsigned char *)iptr - (unsigned char *)headerp;

out:
        for (pos = 0; nchunks--;)
                pos += r_xprt->rx_ia.ri_ops->ro_unmap(r_xprt,
                                                      &req->rl_segments[pos]);
        return n;
}

/*
 * Copy write data inline.
 * This function is used for "small" requests. Data which is passed
 * to RPC via iovecs (or page list) is copied directly into the
 * pre-registered memory buffer for this request. For small amounts
 * of data, this is efficient. The cutoff value is tunable.
 */
static void rpcrdma_inline_pullup(struct rpc_rqst *rqst)
{
        int i, npages, curlen;
        int copy_len;
        unsigned char *srcp, *destp;
        struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
        int page_base;
        struct page **ppages;

        destp = rqst->rq_svec[0].iov_base;
        curlen = rqst->rq_svec[0].iov_len;
        destp += curlen;

        dprintk("RPC:       %s: destp 0x%p len %d hdrlen %d\n",
                __func__, destp, rqst->rq_slen, curlen);

        copy_len = rqst->rq_snd_buf.page_len;

        if (rqst->rq_snd_buf.tail[0].iov_len) {
                curlen = rqst->rq_snd_buf.tail[0].iov_len;
                if (destp + copy_len != rqst->rq_snd_buf.tail[0].iov_base) {
                        memmove(destp + copy_len,
                                rqst->rq_snd_buf.tail[0].iov_base, curlen);
                        r_xprt->rx_stats.pullup_copy_count += curlen;
                }
                dprintk("RPC:       %s: tail destp 0x%p len %d\n",
                        __func__, destp + copy_len, curlen);
                rqst->rq_svec[0].iov_len += curlen;
        }
        r_xprt->rx_stats.pullup_copy_count += copy_len;

        page_base = rqst->rq_snd_buf.page_base;
        ppages = rqst->rq_snd_buf.pages + (page_base >> PAGE_SHIFT);
        page_base &= ~PAGE_MASK;
        npages = PAGE_ALIGN(page_base+copy_len) >> PAGE_SHIFT;
        for (i = 0; copy_len && i < npages; i++) {
                curlen = PAGE_SIZE - page_base;
                if (curlen > copy_len)
                        curlen = copy_len;
                dprintk("RPC:       %s: page %d destp 0x%p len %d curlen %d\n",
                        __func__, i, destp, copy_len, curlen);
                srcp = kmap_atomic(ppages[i]);
                memcpy(destp, srcp+page_base, curlen);
                kunmap_atomic(srcp);
                rqst->rq_svec[0].iov_len += curlen;
                destp += curlen;
                copy_len -= curlen;
                page_base = 0;
        }
        /* header now contains entire send message */
}

/*
 * Marshal a request: the primary job of this routine is to choose
 * the transfer modes. See comments below.
 *
 * Uses multiple RDMA IOVs for a request:
 *  [0] -- RPC RDMA header, which uses memory from the *start* of the
 *         preregistered buffer that already holds the RPC data in
 *         its middle.
 *  [1] -- the RPC header/data, marshaled by RPC and the NFS protocol.
 *  [2] -- optional padding.
 *  [3] -- if padded, header only in [1] and data here.
 *
 * Returns zero on success, otherwise a negative errno.
 */

int
rpcrdma_marshal_req(struct rpc_rqst *rqst)
{
        struct rpc_xprt *xprt = rqst->rq_xprt;
        struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
        struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
        char *base;
        size_t rpclen;
        ssize_t hdrlen;
        enum rpcrdma_chunktype rtype, wtype;
        struct rpcrdma_msg *headerp;

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
        if (test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state))
                return rpcrdma_bc_marshal_reply(rqst);
#endif

        /*
         * rpclen gets amount of data in first buffer, which is the
         * pre-registered buffer.
         */
        base = rqst->rq_svec[0].iov_base;
        rpclen = rqst->rq_svec[0].iov_len;

        headerp = rdmab_to_msg(req->rl_rdmabuf);
        /* don't byte-swap XID, it's already done in request */
        headerp->rm_xid = rqst->rq_xid;
        headerp->rm_vers = rpcrdma_version;
        headerp->rm_credit = cpu_to_be32(r_xprt->rx_buf.rb_max_requests);
        headerp->rm_type = rdma_msg;

        /*
         * Chunks needed for results?
         *
         * o Read ops return data as write chunk(s), header as inline.
         * o If the expected result is under the inline threshold, all ops
         *   return as inline.
         * o Large non-read ops return as a single reply chunk.
         */
        if (rqst->rq_rcv_buf.flags & XDRBUF_READ)
                wtype = rpcrdma_writech;
        else if (rpcrdma_results_inline(rqst))
                wtype = rpcrdma_noch;
        else
                wtype = rpcrdma_replych;

        /*
         * Chunks needed for arguments?
         *
         * o If the total request is under the inline threshold, all ops
         *   are sent as inline.
         * o Large write ops transmit data as read chunk(s), header as
         *   inline.
         * o Large non-write ops are sent with the entire message as a
         *   single read chunk (protocol 0-position special case).
         *
         * This assumes that the upper layer does not present a request
         * that both has a data payload, and whose non-data arguments
         * by themselves are larger than the inline threshold.
         */
        if (rpcrdma_args_inline(rqst)) {
                rtype = rpcrdma_noch;
        } else if (rqst->rq_snd_buf.flags & XDRBUF_WRITE) {
                rtype = rpcrdma_readch;
        } else {
                r_xprt->rx_stats.nomsg_call_count++;
                headerp->rm_type = htonl(RDMA_NOMSG);
                rtype = rpcrdma_areadch;
                rpclen = 0;
        }

        /* The following simplification is not true forever */
        if (rtype != rpcrdma_noch && wtype == rpcrdma_replych)
                wtype = rpcrdma_noch;
        if (rtype != rpcrdma_noch && wtype != rpcrdma_noch) {
                dprintk("RPC:       %s: cannot marshal multiple chunk lists\n",
                        __func__);
                return -EIO;
        }

        hdrlen = RPCRDMA_HDRLEN_MIN;

        /*
         * Pull up any extra send data into the preregistered buffer.
         * When padding is in use and applies to the transfer, insert
         * it and change the message type.
         */
        if (rtype == rpcrdma_noch) {

                rpcrdma_inline_pullup(rqst);

                headerp->rm_body.rm_nochunks.rm_empty[0] = xdr_zero;
                headerp->rm_body.rm_nochunks.rm_empty[1] = xdr_zero;
                headerp->rm_body.rm_nochunks.rm_empty[2] = xdr_zero;
                /* new length after pullup */
                rpclen = rqst->rq_svec[0].iov_len;
        } else if (rtype == rpcrdma_readch)
                rpclen += rpcrdma_tail_pullup(&rqst->rq_snd_buf);
        if (rtype != rpcrdma_noch) {
                hdrlen = rpcrdma_create_chunks(rqst, &rqst->rq_snd_buf,
                                               headerp, rtype);
                wtype = rtype;  /* simplify dprintk */

        } else if (wtype != rpcrdma_noch) {
                hdrlen = rpcrdma_create_chunks(rqst, &rqst->rq_rcv_buf,
                                               headerp, wtype);
        }
        if (hdrlen < 0)
                return hdrlen;

        dprintk("RPC:       %s: %s: hdrlen %zd rpclen %zd"
                " headerp 0x%p base 0x%p lkey 0x%x\n",
                __func__, transfertypes[wtype], hdrlen, rpclen,
                headerp, base, rdmab_lkey(req->rl_rdmabuf));

        /*
         * initialize send_iov's - normally only two: rdma chunk header and
         * single preregistered RPC header buffer, but if padding is present,
         * then use a preregistered (and zeroed) pad buffer between the RPC
         * header and any write data. In all non-rdma cases, any following
         * data has been copied into the RPC header buffer.
         */
        req->rl_send_iov[0].addr = rdmab_addr(req->rl_rdmabuf);
        req->rl_send_iov[0].length = hdrlen;
        req->rl_send_iov[0].lkey = rdmab_lkey(req->rl_rdmabuf);

        req->rl_niovs = 1;
        if (rtype == rpcrdma_areadch)
                return 0;

        req->rl_send_iov[1].addr = rdmab_addr(req->rl_sendbuf);
        req->rl_send_iov[1].length = rpclen;
        req->rl_send_iov[1].lkey = rdmab_lkey(req->rl_sendbuf);

        req->rl_niovs = 2;
        return 0;
}

/*
 * Chase down a received write or reply chunklist to get length
 * RDMA'd by server. See map at rpcrdma_create_chunks()! :-)
 */
static int
rpcrdma_count_chunks(struct rpcrdma_rep *rep, unsigned int max, int wrchunk, __be32 **iptrp)
{
        unsigned int i, total_len;
        struct rpcrdma_write_chunk *cur_wchunk;
        char *base = (char *)rdmab_to_msg(rep->rr_rdmabuf);

        i = be32_to_cpu(**iptrp);
        if (i > max)
                return -1;
        cur_wchunk = (struct rpcrdma_write_chunk *) (*iptrp + 1);
        total_len = 0;
        while (i--) {
                struct rpcrdma_segment *seg = &cur_wchunk->wc_target;
                ifdebug(FACILITY) {
                        u64 off;
                        xdr_decode_hyper((__be32 *)&seg->rs_offset, &off);
                        dprintk("RPC:       %s: chunk %d@0x%llx:0x%x\n",
                                __func__,
                                be32_to_cpu(seg->rs_length),
                                (unsigned long long)off,
                                be32_to_cpu(seg->rs_handle));
                }
                total_len += be32_to_cpu(seg->rs_length);
                ++cur_wchunk;
        }
        /* check and adjust for properly terminated write chunk */
        if (wrchunk) {
                __be32 *w = (__be32 *) cur_wchunk;
                if (*w++ != xdr_zero)
                        return -1;
                cur_wchunk = (struct rpcrdma_write_chunk *) w;
        }
        if ((char *)cur_wchunk > base + rep->rr_len)
                return -1;

        *iptrp = (__be32 *) cur_wchunk;
        return total_len;
}

/*
 * Scatter inline received data back into provided iov's.
 */
static void
rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
{
        int i, npages, curlen, olen;
        char *destp;
        struct page **ppages;
        int page_base;

        curlen = rqst->rq_rcv_buf.head[0].iov_len;
        if (curlen > copy_len) {        /* write chunk header fixup */
                curlen = copy_len;
                rqst->rq_rcv_buf.head[0].iov_len = curlen;
        }

        dprintk("RPC:       %s: srcp 0x%p len %d hdrlen %d\n",
                __func__, srcp, copy_len, curlen);

        /* Shift pointer for first receive segment only */
        rqst->rq_rcv_buf.head[0].iov_base = srcp;
        srcp += curlen;
        copy_len -= curlen;

        olen = copy_len;
        i = 0;
        rpcx_to_rdmax(rqst->rq_xprt)->rx_stats.fixup_copy_count += olen;
        page_base = rqst->rq_rcv_buf.page_base;
        ppages = rqst->rq_rcv_buf.pages + (page_base >> PAGE_SHIFT);
        page_base &= ~PAGE_MASK;

        if (copy_len && rqst->rq_rcv_buf.page_len) {
                npages = PAGE_ALIGN(page_base +
                        rqst->rq_rcv_buf.page_len) >> PAGE_SHIFT;
                for (; i < npages; i++) {
                        curlen = PAGE_SIZE - page_base;
                        if (curlen > copy_len)
                                curlen = copy_len;
                        dprintk("RPC:       %s: page %d"
                                " srcp 0x%p len %d curlen %d\n",
                                __func__, i, srcp, copy_len, curlen);
                        destp = kmap_atomic(ppages[i]);
                        memcpy(destp + page_base, srcp, curlen);
                        flush_dcache_page(ppages[i]);
                        kunmap_atomic(destp);
                        srcp += curlen;
                        copy_len -= curlen;
                        if (copy_len == 0)
                                break;
                        page_base = 0;
                }
        }

        if (copy_len && rqst->rq_rcv_buf.tail[0].iov_len) {
                curlen = copy_len;
                if (curlen > rqst->rq_rcv_buf.tail[0].iov_len)
                        curlen = rqst->rq_rcv_buf.tail[0].iov_len;
                if (rqst->rq_rcv_buf.tail[0].iov_base != srcp)
                        memmove(rqst->rq_rcv_buf.tail[0].iov_base, srcp, curlen);
                dprintk("RPC:       %s: tail srcp 0x%p len %d curlen %d\n",
                        __func__, srcp, copy_len, curlen);
                rqst->rq_rcv_buf.tail[0].iov_len = curlen;
                copy_len -= curlen; ++i;
        } else
                rqst->rq_rcv_buf.tail[0].iov_len = 0;

        if (pad) {
                /* implicit padding on terminal chunk */
                unsigned char *p = rqst->rq_rcv_buf.tail[0].iov_base;
                while (pad--)
                        p[rqst->rq_rcv_buf.tail[0].iov_len++] = 0;
        }

        if (copy_len)
                dprintk("RPC:       %s: %d bytes in"
                        " %d extra segments (%d lost)\n",
                        __func__, olen, i, copy_len);

        /* TBD avoid a warning from call_decode() */
        rqst->rq_private_buf = rqst->rq_rcv_buf;
}

void
rpcrdma_connect_worker(struct work_struct *work)
{
        struct rpcrdma_ep *ep =
                container_of(work, struct rpcrdma_ep, rep_connect_worker.work);
        struct rpcrdma_xprt *r_xprt =
                container_of(ep, struct rpcrdma_xprt, rx_ep);
        struct rpc_xprt *xprt = &r_xprt->rx_xprt;

        spin_lock_bh(&xprt->transport_lock);
        if (++xprt->connect_cookie == 0)        /* maintain a reserved value */
                ++xprt->connect_cookie;
        if (ep->rep_connected > 0) {
                if (!xprt_test_and_set_connected(xprt))
                        xprt_wake_pending_tasks(xprt, 0);
        } else {
                if (xprt_test_and_clear_connected(xprt))
                        xprt_wake_pending_tasks(xprt, -ENOTCONN);
        }
        spin_unlock_bh(&xprt->transport_lock);
}

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
/* By convention, backchannel calls arrive via rdma_msg type
 * messages, and never populate the chunk lists. This makes
 * the RPC/RDMA header small and fixed in size, so it is
 * straightforward to check the RPC header's direction field.
 */
static bool
rpcrdma_is_bcall(struct rpcrdma_msg *headerp)
{
        __be32 *p = (__be32 *)headerp;

        if (headerp->rm_type != rdma_msg)
                return false;
        if (headerp->rm_body.rm_chunks[0] != xdr_zero)
                return false;
        if (headerp->rm_body.rm_chunks[1] != xdr_zero)
                return false;
        if (headerp->rm_body.rm_chunks[2] != xdr_zero)
                return false;

        /* sanity */
        if (p[7] != headerp->rm_xid)
                return false;
        /* call direction */
        if (p[8] != cpu_to_be32(RPC_CALL))
                return false;

        return true;
}
#endif  /* CONFIG_SUNRPC_BACKCHANNEL */

/*
 * This function is called when an async event is posted to
 * the connection which changes the connection state. All it
 * does at this point is mark the connection up/down, the rpc
 * timers do the rest.
 */
void
rpcrdma_conn_func(struct rpcrdma_ep *ep)
{
        schedule_delayed_work(&ep->rep_connect_worker, 0);
}

/* Process received RPC/RDMA messages.
 *
 * Errors must result in the RPC task either being awakened, or
 * allowed to timeout, to discover the errors at that time.
 */
void
rpcrdma_reply_handler(struct rpcrdma_rep *rep)
{
        struct rpcrdma_msg *headerp;
        struct rpcrdma_req *req;
        struct rpc_rqst *rqst;
        struct rpcrdma_xprt *r_xprt = rep->rr_rxprt;
        struct rpc_xprt *xprt = &r_xprt->rx_xprt;
        __be32 *iptr;
        int rdmalen, status, rmerr;
        unsigned long cwnd;

        dprintk("RPC:       %s: incoming rep %p\n", __func__, rep);

        if (rep->rr_len == RPCRDMA_BAD_LEN)
                goto out_badstatus;
        if (rep->rr_len < RPCRDMA_HDRLEN_ERR)
                goto out_shortreply;

        headerp = rdmab_to_msg(rep->rr_rdmabuf);
#if defined(CONFIG_SUNRPC_BACKCHANNEL)
        if (rpcrdma_is_bcall(headerp))
                goto out_bcall;
#endif

        /* Match incoming rpcrdma_rep to an rpcrdma_req to
         * get context for handling any incoming chunks.
         */
        spin_lock_bh(&xprt->transport_lock);
        rqst = xprt_lookup_rqst(xprt, headerp->rm_xid);
        if (!rqst)
                goto out_nomatch;

        req = rpcr_to_rdmar(rqst);
        if (req->rl_reply)
                goto out_duplicate;

        /* Sanity checking has passed. We are now committed
         * to complete this transaction.
         */
        list_del_init(&rqst->rq_list);
        spin_unlock_bh(&xprt->transport_lock);
        dprintk("RPC:       %s: reply %p completes request %p (xid 0x%08x)\n",
                __func__, rep, req, be32_to_cpu(headerp->rm_xid));

        /* from here on, the reply is no longer an orphan */
        req->rl_reply = rep;
        xprt->reestablish_timeout = 0;

        if (headerp->rm_vers != rpcrdma_version)
                goto out_badversion;

        /* check for expected message types */
        /* The order of some of these tests is important. */
        switch (headerp->rm_type) {
        case rdma_msg:
                /* never expect read chunks */
                /* never expect reply chunks (two ways to check) */
                /* never expect write chunks without having offered RDMA */
                if (headerp->rm_body.rm_chunks[0] != xdr_zero ||
                    (headerp->rm_body.rm_chunks[1] == xdr_zero &&
                     headerp->rm_body.rm_chunks[2] != xdr_zero) ||
                    (headerp->rm_body.rm_chunks[1] != xdr_zero &&
                     req->rl_nchunks == 0))
                        goto badheader;
                if (headerp->rm_body.rm_chunks[1] != xdr_zero) {
                        /* count any expected write chunks in read reply */
                        /* start at write chunk array count */
                        iptr = &headerp->rm_body.rm_chunks[2];
                        rdmalen = rpcrdma_count_chunks(rep,
                                                req->rl_nchunks, 1, &iptr);
                        /* check for validity, and no reply chunk after */
                        if (rdmalen < 0 || *iptr++ != xdr_zero)
                                goto badheader;
                        rep->rr_len -=
                            ((unsigned char *)iptr - (unsigned char *)headerp);
                        status = rep->rr_len + rdmalen;
                        r_xprt->rx_stats.total_rdma_reply += rdmalen;
                        /* special case - last chunk may omit padding */
                        if (rdmalen &= 3) {
                                rdmalen = 4 - rdmalen;
                                status += rdmalen;
                        }
                } else {
                        /* else ordinary inline */
                        rdmalen = 0;
                        iptr = (__be32 *)((unsigned char *)headerp +
                                                        RPCRDMA_HDRLEN_MIN);
                        rep->rr_len -= RPCRDMA_HDRLEN_MIN;
                        status = rep->rr_len;
                }
                /* Fix up the rpc results for upper layer */
                rpcrdma_inline_fixup(rqst, (char *)iptr, rep->rr_len, rdmalen);
                break;

        case rdma_nomsg:
                /* never expect read or write chunks, always reply chunks */
                if (headerp->rm_body.rm_chunks[0] != xdr_zero ||
                    headerp->rm_body.rm_chunks[1] != xdr_zero ||
                    headerp->rm_body.rm_chunks[2] != xdr_one ||
                    req->rl_nchunks == 0)
                        goto badheader;
                iptr = (__be32 *)((unsigned char *)headerp +
                                                        RPCRDMA_HDRLEN_MIN);
                rdmalen = rpcrdma_count_chunks(rep, req->rl_nchunks, 0, &iptr);
                if (rdmalen < 0)
                        goto badheader;
                r_xprt->rx_stats.total_rdma_reply += rdmalen;
                /* Reply chunk buffer already is the reply vector - no fixup. */
                status = rdmalen;
                break;

        case rdma_error:
                goto out_rdmaerr;

badheader:
        default:
                dprintk("%s: invalid rpcrdma reply header (type %d):"
                                " chunks[012] == %d %d %d"
                                " expected chunks <= %d\n",
                                __func__, be32_to_cpu(headerp->rm_type),
                                headerp->rm_body.rm_chunks[0],
                                headerp->rm_body.rm_chunks[1],
                                headerp->rm_body.rm_chunks[2],
                                req->rl_nchunks);
                status = -EIO;
                r_xprt->rx_stats.bad_reply_count++;
                break;
        }

out:
        /* Invalidate and flush the data payloads before waking the
         * waiting application. This guarantees the memory region is
         * properly fenced from the server before the application
         * accesses the data. It also ensures proper send flow
         * control: waking the next RPC waits until this RPC has
         * relinquished all its Send Queue entries.
         */
        if (req->rl_nchunks)
                r_xprt->rx_ia.ri_ops->ro_unmap_sync(r_xprt, req);

        spin_lock_bh(&xprt->transport_lock);
        cwnd = xprt->cwnd;
        xprt->cwnd = atomic_read(&r_xprt->rx_buf.rb_credits) << RPC_CWNDSHIFT;
        if (xprt->cwnd > cwnd)
                xprt_release_rqst_cong(rqst->rq_task);

        xprt_complete_rqst(rqst->rq_task, status);
        spin_unlock_bh(&xprt->transport_lock);
        dprintk("RPC:       %s: xprt_complete_rqst(0x%p, 0x%p, %d)\n",
                        __func__, xprt, rqst, status);
        return;

out_badstatus:
        rpcrdma_recv_buffer_put(rep);
        if (r_xprt->rx_ep.rep_connected == 1) {
                r_xprt->rx_ep.rep_connected = -EIO;
                rpcrdma_conn_func(&r_xprt->rx_ep);
        }
        return;

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
out_bcall:
        rpcrdma_bc_receive_call(r_xprt, rep);
        return;
#endif

/* If the incoming reply terminated a pending RPC, the next
 * RPC call will post a replacement receive buffer as it is
 * being marshaled.
 */
out_badversion:
        dprintk("RPC:       %s: invalid version %d\n",
                __func__, be32_to_cpu(headerp->rm_vers));
        status = -EIO;
        r_xprt->rx_stats.bad_reply_count++;
        goto out;

out_rdmaerr:
        rmerr = be32_to_cpu(headerp->rm_body.rm_error.rm_err);
        switch (rmerr) {
        case ERR_VERS:
                pr_err("%s: server reports header version error (%u-%u)\n",
                       __func__,
                       be32_to_cpu(headerp->rm_body.rm_error.rm_vers_low),
                       be32_to_cpu(headerp->rm_body.rm_error.rm_vers_high));
                break;
        case ERR_CHUNK:
                pr_err("%s: server reports header decoding error\n",
                       __func__);
                break;
        default:
                pr_err("%s: server reports unknown error %d\n",
                       __func__, rmerr);
        }
        status = -EREMOTEIO;
        r_xprt->rx_stats.bad_reply_count++;
        goto out;

/* If no pending RPC transaction was matched, post a replacement
 * receive buffer before returning.
 */
out_shortreply:
        dprintk("RPC:       %s: short/invalid reply\n", __func__);
        goto repost;

out_nomatch:
        spin_unlock_bh(&xprt->transport_lock);
        dprintk("RPC:       %s: no match for incoming xid 0x%08x len %d\n",
                __func__, be32_to_cpu(headerp->rm_xid),
                rep->rr_len);
        goto repost;

out_duplicate:
        spin_unlock_bh(&xprt->transport_lock);
        dprintk("RPC:       %s: "
                "duplicate reply %p to RPC request %p: xid 0x%08x\n",
                __func__, rep, req, be32_to_cpu(headerp->rm_xid));

repost:
        r_xprt->rx_stats.bad_reply_count++;
        if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, &r_xprt->rx_ep, rep))
                rpcrdma_recv_buffer_put(rep);
}