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[linux-ginger.git] / net / sunrpc / xprtrdma / rpc_rdma.c

/*
 * 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;

        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;
        }

        if (xdrbuf->page_len && (xdrbuf->pages[0] != NULL)) {
                if (n == nsegs)
                        return 0;
                seg[n].mr_page = xdrbuf->pages[0];
                seg[n].mr_offset = (void *)(unsigned long) xdrbuf->page_base;
                seg[n].mr_len = min_t(u32,
                        PAGE_SIZE - xdrbuf->page_base, xdrbuf->page_len);
                len = xdrbuf->page_len - seg[n].mr_len;
                ++n;
                p = 1;
                while (len > 0) {
                        if (n == nsegs)
                                return 0;
                        seg[n].mr_page = xdrbuf->pages[p];
                        seg[n].mr_offset = NULL;
                        seg[n].mr_len = min_t(u32, PAGE_SIZE, len);
                        len -= seg[n].mr_len;
                        ++n;
                        ++p;
                }
        }

        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)
                        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);

        /*
         * 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);

        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;
        npages = PAGE_ALIGN(rqst->rq_snd_buf.page_base+copy_len) >> PAGE_SHIFT;
        for (i = 0; copy_len && i < npages; i++) {
                if (i == 0)
                        curlen = PAGE_SIZE - rqst->rq_snd_buf.page_base;
                else
                        curlen = PAGE_SIZE;
                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(rqst->rq_snd_buf.pages[i],
                                        KM_SKB_SUNRPC_DATA);
                if (i == 0)
                        memcpy(destp, srcp+rqst->rq_snd_buf.page_base, curlen);
                else
                        memcpy(destp, srcp, curlen);
                kunmap_atomic(srcp, KM_SKB_SUNRPC_DATA);
                rqst->rq_svec[0].iov_len += curlen;
                destp += curlen;
                copy_len -= curlen;
        }
        /* 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;

        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;
        if (copy_len && rqst->rq_rcv_buf.page_len) {
                npages = PAGE_ALIGN(rqst->rq_rcv_buf.page_base +
                        rqst->rq_rcv_buf.page_len) >> PAGE_SHIFT;
                for (; i < npages; i++) {
                        if (i == 0)
                                curlen = PAGE_SIZE - rqst->rq_rcv_buf.page_base;
                        else
                                curlen = PAGE_SIZE;
                        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(rqst->rq_rcv_buf.pages[i],
                                                KM_SKB_SUNRPC_DATA);
                        if (i == 0)
                                memcpy(destp + rqst->rq_rcv_buf.page_base,
                                                srcp, curlen);
                        else
                                memcpy(destp, srcp, curlen);
                        flush_dcache_page(rqst->rq_rcv_buf.pages[i]);
                        kunmap_atomic(destp, KM_SKB_SUNRPC_DATA);
                        srcp += curlen;
                        copy_len -= curlen;
                        if (copy_len == 0)
                                break;
                }
                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);

        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);

        BUG_ON(!req || req->rl_reply);

        /* 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);
}