rpc_rdma.c

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/*
 * 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>

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY    RPCDBG_TRANS
#endif

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

#ifdef RPC_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

/*
 * 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.
 *
 * Note, this routine is never called if the connection's memory
 * registration strategy is 0 (bounce buffers).
 */

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 && xdrbuf->head[0].iov_len) {
        seg[n].mr_page = NULL;
        seg[n].mr_offset = xdrbuf->head[0].iov_base;
        seg[n].mr_len = xdrbuf->head[0].iov_len;
        ++n;
    }

    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) {
        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);
        BUG_ON(seg[n].mr_len > PAGE_SIZE);
        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 0;

    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;
        if (n == nsegs)
            /* Tail remains, but we're out of segments */
            return 0;
        seg[n].mr_page = NULL;
        seg[n].mr_offset = xdrbuf->tail[0].iov_base;
        seg[n].mr_len = xdrbuf->tail[0].iov_len;
        ++n;
    }

    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
 */

static unsigned int
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_task->tk_xprt);
    int 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;

    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 0;

    do {
        /* bind/register the memory, then build chunk from result. */
        int n = rpcrdma_register_external(seg, nsegs,
                        cur_wchunk != NULL, r_xprt);
        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 = htonl(pos);
            cur_rchunk->rc_target.rs_handle = htonl(seg->mr_rkey);
            cur_rchunk->rc_target.rs_length = htonl(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 = htonl(seg->mr_rkey);
            cur_wchunk->wc_target.rs_length = htonl(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;

    BUG_ON(nchunks == 0);
    BUG_ON((r_xprt->rx_ia.ri_memreg_strategy == RPCRDMA_FRMR)
           && (nchunks > 3));

    /*
     * 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 = htonl(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 += rpcrdma_deregister_external(
                &req->rl_segments[pos], r_xprt, NULL);
    return 0;
}

/*
 * 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 int
rpcrdma_inline_pullup(struct rpc_rqst *rqst, int pad)
{
    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;
    /*
     * Do optional padding where it makes sense. Alignment of write
     * payload can help the server, if our setting is accurate.
     */
    pad -= (curlen + 36/*sizeof(struct rpcrdma_msg_padded)*/);
    if (pad < 0 || rqst->rq_slen - curlen < RPCRDMA_INLINE_PAD_THRESH)
        pad = 0;    /* don't pad this request */

    dprintk("RPC:       %s: pad %d destp 0x%p len %d hdrlen %d\n",
        __func__, pad, 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 */
    return pad;
}

/*
 * 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.
 */

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

    /*
     * 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;

    /* build RDMA header in private area at front */
    headerp = (struct rpcrdma_msg *) req->rl_base;
    /* don't htonl XID, it's already done in request */
    headerp->rm_xid = rqst->rq_xid;
    headerp->rm_vers = xdr_one;
    headerp->rm_credit = htonl(r_xprt->rx_buf.rb_max_requests);
    headerp->rm_type = htonl(RDMA_MSG);

    /*
     * Chunks needed for results?
     *
     * o If the expected result is under the inline threshold, all ops
     *   return as inline (but see later).
     * o Large non-read ops return as a single reply chunk.
     * o Large read ops return data as write chunk(s), header as inline.
     *
     * Note: the NFS code sending down multiple result segments implies
     * the op is one of read, readdir[plus], readlink or NFSv4 getacl.
     */

    /*
     * This code can handle read chunks, write chunks OR reply
     * chunks -- only one type. If the request is too big to fit
     * inline, then we will choose read chunks. If the request is
     * a READ, then use write chunks to separate the file data
     * into pages; otherwise use reply chunks.
     */
    if (rqst->rq_rcv_buf.buflen <= RPCRDMA_INLINE_READ_THRESHOLD(rqst))
        wtype = rpcrdma_noch;
    else if (rqst->rq_rcv_buf.page_len == 0)
        wtype = rpcrdma_replych;
    else if (rqst->rq_rcv_buf.flags & XDRBUF_READ)
        wtype = rpcrdma_writech;
    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 non-write ops are sent with the entire message as a
     *   single read chunk (protocol 0-position special case).
     * o Large write ops transmit data as read chunk(s), header as
     *   inline.
     *
     * Note: the NFS code sending down multiple argument segments
     * implies the op is a write.
     * TBD check NFSv4 setacl
     */
    if (rqst->rq_snd_buf.len <= RPCRDMA_INLINE_WRITE_THRESHOLD(rqst))
        rtype = rpcrdma_noch;
    else if (rqst->rq_snd_buf.page_len == 0)
        rtype = rpcrdma_areadch;
    else
        rtype = rpcrdma_readch;

    /* The following simplification is not true forever */
    if (rtype != rpcrdma_noch && wtype == rpcrdma_replych)
        wtype = rpcrdma_noch;
    BUG_ON(rtype != rpcrdma_noch && wtype != rpcrdma_noch);

    if (r_xprt->rx_ia.ri_memreg_strategy == RPCRDMA_BOUNCEBUFFERS &&
        (rtype != rpcrdma_noch || wtype != rpcrdma_noch)) {
        /* forced to "pure inline"? */
        dprintk("RPC:       %s: too much data (%d/%d) for inline\n",
            __func__, rqst->rq_rcv_buf.len, rqst->rq_snd_buf.len);
        return -1;
    }

    hdrlen = 28; /*sizeof *headerp;*/
    padlen = 0;

    /*
     * 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) {

        padlen = rpcrdma_inline_pullup(rqst,
                        RPCRDMA_INLINE_PAD_VALUE(rqst));

        if (padlen) {
            headerp->rm_type = htonl(RDMA_MSGP);
            headerp->rm_body.rm_padded.rm_align =
                htonl(RPCRDMA_INLINE_PAD_VALUE(rqst));
            headerp->rm_body.rm_padded.rm_thresh =
                htonl(RPCRDMA_INLINE_PAD_THRESH);
            headerp->rm_body.rm_padded.rm_pempty[0] = xdr_zero;
            headerp->rm_body.rm_padded.rm_pempty[1] = xdr_zero;
            headerp->rm_body.rm_padded.rm_pempty[2] = xdr_zero;
            hdrlen += 2 * sizeof(u32); /* extra words in padhdr */
            BUG_ON(wtype != rpcrdma_noch);

        } else {
            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;
            /*
             * Currently we try to not actually use read inline.
             * Reply chunks have the desirable property that
             * they land, packed, directly in the target buffers
             * without headers, so they require no fixup. The
             * additional RDMA Write op sends the same amount
             * of data, streams on-the-wire and adds no overhead
             * on receive. Therefore, we request a reply chunk
             * for non-writes wherever feasible and efficient.
             */
            if (wtype == rpcrdma_noch &&
                r_xprt->rx_ia.ri_memreg_strategy > RPCRDMA_REGISTER)
                wtype = rpcrdma_replych;
        }
    }

    /*
     * Marshal chunks. This routine will return the header length
     * consumed by marshaling.
     */
    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 -1;

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

    /*
     * 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 = req->rl_iov.addr;
    req->rl_send_iov[0].length = hdrlen;
    req->rl_send_iov[0].lkey = req->rl_iov.lkey;

    req->rl_send_iov[1].addr = req->rl_iov.addr + (base - req->rl_base);
    req->rl_send_iov[1].length = rpclen;
    req->rl_send_iov[1].lkey = req->rl_iov.lkey;

    req->rl_niovs = 2;

    if (padlen) {
        struct rpcrdma_ep *ep = &r_xprt->rx_ep;

        req->rl_send_iov[2].addr = ep->rep_pad.addr;
        req->rl_send_iov[2].length = padlen;
        req->rl_send_iov[2].lkey = ep->rep_pad.lkey;

        req->rl_send_iov[3].addr = req->rl_send_iov[1].addr + rpclen;
        req->rl_send_iov[3].length = rqst->rq_slen - rpclen;
        req->rl_send_iov[3].lkey = req->rl_iov.lkey;

        req->rl_niovs = 4;
    }

    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;

    i = ntohl(**iptrp); /* get array count */
    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__,
                ntohl(seg->rs_length),
                (unsigned long long)off,
                ntohl(seg->rs_handle));
        }
        total_len += ntohl(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 > rep->rr_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;
        }
        rqst->rq_rcv_buf.page_len = olen - copy_len;
    } else
        rqst->rq_rcv_buf.page_len = 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;
}

/*
 * 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)
{
    struct rpc_xprt *xprt = ep->rep_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);
}

/*
 * This function is called when memory window unbind which we are waiting
 * for completes. Just use rr_func (zeroed by upcall) to signal completion.
 */
static void
rpcrdma_unbind_func(struct rpcrdma_rep *rep)
{
    wake_up(&rep->rr_unbind);
}

/*
 * Called as a tasklet to do req/reply match and complete a request
 * 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 rpc_xprt *xprt = rep->rr_xprt;
    struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
    __be32 *iptr;
    int i, rdmalen, status;

    /* Check status. If bad, signal disconnect and return rep to pool */
    if (rep->rr_len == ~0U) {
        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 (rep->rr_len < 28) {
        dprintk("RPC:       %s: short/invalid reply\n", __func__);
        goto repost;
    }
    headerp = (struct rpcrdma_msg *) rep->rr_base;
    if (headerp->rm_vers != xdr_one) {
        dprintk("RPC:       %s: invalid version %d\n",
            __func__, ntohl(headerp->rm_vers));
        goto repost;
    }

    /* Get XID and try for a match. */
    spin_lock(&xprt->transport_lock);
    rqst = xprt_lookup_rqst(xprt, headerp->rm_xid);
    if (rqst == NULL) {
        spin_unlock(&xprt->transport_lock);
        dprintk("RPC:       %s: reply 0x%p failed "
            "to match any request xid 0x%08x len %d\n",
            __func__, rep, headerp->rm_xid, rep->rr_len);
repost:
        r_xprt->rx_stats.bad_reply_count++;
        rep->rr_func = rpcrdma_reply_handler;
        if (rpcrdma_ep_post_recv(&r_xprt->rx_ia, &r_xprt->rx_ep, rep))
            rpcrdma_recv_buffer_put(rep);

        return;
    }

    /* get request object */
    req = rpcr_to_rdmar(rqst);
    if (req->rl_reply) {
        spin_unlock(&xprt->transport_lock);
        dprintk("RPC:       %s: duplicate reply 0x%p to RPC "
            "request 0x%p: xid 0x%08x\n", __func__, rep, req,
            headerp->rm_xid);
        goto repost;
    }

    dprintk("RPC:       %s: reply 0x%p completes request 0x%p\n"
        "                   RPC request 0x%p xid 0x%08x\n",
            __func__, rep, req, rqst, headerp->rm_xid);

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

    /* check for expected message types */
    /* The order of some of these tests is important. */
    switch (headerp->rm_type) {
    case htonl(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 + 28);
            rep->rr_len -= 28; /*sizeof *headerp;*/
            status = rep->rr_len;
        }
        /* Fix up the rpc results for upper layer */
        rpcrdma_inline_fixup(rqst, (char *)iptr, rep->rr_len, rdmalen);
        break;

    case htonl(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 + 28);
        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;

badheader:
    default:
        dprintk("%s: invalid rpcrdma reply header (type %d):"
                " chunks[012] == %d %d %d"
                " expected chunks <= %d\n",
                __func__, ntohl(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;
    }

    /* If using mw bind, start the deregister process now. */
    /* (Note: if mr_free(), cannot perform it here, in tasklet context) */
    if (req->rl_nchunks) switch (r_xprt->rx_ia.ri_memreg_strategy) {
    case RPCRDMA_MEMWINDOWS:
        for (i = 0; req->rl_nchunks-- > 1;)
            i += rpcrdma_deregister_external(
                &req->rl_segments[i], r_xprt, NULL);
        /* Optionally wait (not here) for unbinds to complete */
        rep->rr_func = rpcrdma_unbind_func;
        (void) rpcrdma_deregister_external(&req->rl_segments[i],
                           r_xprt, rep);
        break;
    case RPCRDMA_MEMWINDOWS_ASYNC:
        for (i = 0; req->rl_nchunks--;)
            i += rpcrdma_deregister_external(&req->rl_segments[i],
                             r_xprt, NULL);
        break;
    default:
        break;
    }

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