/*
 * Copyright (c) 2005-2006 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.
 *
 * Author: Tom Tucker <tom@opengridcomputing.com>
 */

#include <linux/sunrpc/debug.h>
#include <linux/sunrpc/rpc_rdma.h>
#include <linux/spinlock.h>
#include <asm/unaligned.h>
#include <rdma/ib_verbs.h>
#include <rdma/rdma_cm.h>
#include <linux/sunrpc/svc_rdma.h>

#define RPCDBG_FACILITY RPCDBG_SVCXPRT

/*
 * Replace the pages in the rq_argpages array with the pages from the SGE in
 * the RDMA_RECV completion. The SGL should contain full pages up until the
 * last one.
 */
static void rdma_build_arg_xdr(struct svc_rqst *rqstp,
                               struct svc_rdma_op_ctxt *ctxt,
                               u32 byte_count)
{
        struct page *page;
        u32 bc;
        int sge_no;

        /* Swap the page in the SGE with the page in argpages */
        page = ctxt->pages[0];
        put_page(rqstp->rq_pages[0]);
        rqstp->rq_pages[0] = page;

        /* Set up the XDR head */
        rqstp->rq_arg.head[0].iov_base = page_address(page);
        rqstp->rq_arg.head[0].iov_len = min(byte_count, ctxt->sge[0].length);
        rqstp->rq_arg.len = byte_count;
        rqstp->rq_arg.buflen = byte_count;

        /* Compute bytes past head in the SGL */
        bc = byte_count - rqstp->rq_arg.head[0].iov_len;

        /* If data remains, store it in the pagelist */
        rqstp->rq_arg.page_len = bc;
        rqstp->rq_arg.page_base = 0;
        rqstp->rq_arg.pages = &rqstp->rq_pages[1];
        sge_no = 1;
        while (bc && sge_no < ctxt->count) {
                page = ctxt->pages[sge_no];
                put_page(rqstp->rq_pages[sge_no]);
                rqstp->rq_pages[sge_no] = page;
                bc -= min(bc, ctxt->sge[sge_no].length);
                rqstp->rq_arg.buflen += ctxt->sge[sge_no].length;
                sge_no++;
        }
        rqstp->rq_respages = &rqstp->rq_pages[sge_no];

        /* We should never run out of SGE because the limit is defined to
         * support the max allowed RPC data length
         */
        BUG_ON(bc && (sge_no == ctxt->count));
        BUG_ON((rqstp->rq_arg.head[0].iov_len + rqstp->rq_arg.page_len)
               != byte_count);
        BUG_ON(rqstp->rq_arg.len != byte_count);

        /* If not all pages were used from the SGL, free the remaining ones */
        bc = sge_no;
        while (sge_no < ctxt->count) {
                page = ctxt->pages[sge_no++];
                put_page(page);
        }
        ctxt->count = bc;

        /* Set up tail */
        rqstp->rq_arg.tail[0].iov_base = NULL;
        rqstp->rq_arg.tail[0].iov_len = 0;
}

/* Encode a read-chunk-list as an array of IB SGE
 *
 * Assumptions:
 * - chunk[0]->position points to pages[0] at an offset of 0
 * - pages[] is not physically or virtually contiguous and consists of
 *   PAGE_SIZE elements.
 *
 * Output:
 * - sge array pointing into pages[] array.
 * - chunk_sge array specifying sge index and count for each
 *   chunk in the read list
 *
 */
static int map_read_chunks(struct svcxprt_rdma *xprt,
                           struct svc_rqst *rqstp,
                           struct svc_rdma_op_ctxt *head,
                           struct rpcrdma_msg *rmsgp,
                           struct svc_rdma_req_map *rpl_map,
                           struct svc_rdma_req_map *chl_map,
                           int ch_count,
                           int byte_count)
{
        int sge_no;
        int sge_bytes;
        int page_off;
        int page_no;
        int ch_bytes;
        int ch_no;
        struct rpcrdma_read_chunk *ch;

        sge_no = 0;
        page_no = 0;
        page_off = 0;
        ch = (struct rpcrdma_read_chunk *)&rmsgp->rm_body.rm_chunks[0];
        ch_no = 0;
        ch_bytes = ntohl(ch->rc_target.rs_length);
        head->arg.head[0] = rqstp->rq_arg.head[0];
        head->arg.tail[0] = rqstp->rq_arg.tail[0];
        head->arg.pages = &head->pages[head->count];
        head->hdr_count = head->count; /* save count of hdr pages */
        head->arg.page_base = 0;
        head->arg.page_len = ch_bytes;
        head->arg.len = rqstp->rq_arg.len + ch_bytes;
        head->arg.buflen = rqstp->rq_arg.buflen + ch_bytes;
        head->count++;
        chl_map->ch[0].start = 0;
        while (byte_count) {
                rpl_map->sge[sge_no].iov_base =
                        page_address(rqstp->rq_arg.pages[page_no]) + page_off;
                sge_bytes = min_t(int, PAGE_SIZE-page_off, ch_bytes);
                rpl_map->sge[sge_no].iov_len = sge_bytes;
                /*
                 * Don't bump head->count here because the same page
                 * may be used by multiple SGE.
                 */
                head->arg.pages[page_no] = rqstp->rq_arg.pages[page_no];
                rqstp->rq_respages = &rqstp->rq_arg.pages[page_no+1];

                byte_count -= sge_bytes;
                ch_bytes -= sge_bytes;
                sge_no++;
                /*
                 * If all bytes for this chunk have been mapped to an
                 * SGE, move to the next SGE
                 */
                if (ch_bytes == 0) {
                        chl_map->ch[ch_no].count =
                                sge_no - chl_map->ch[ch_no].start;
                        ch_no++;
                        ch++;
                        chl_map->ch[ch_no].start = sge_no;
                        ch_bytes = ntohl(ch->rc_target.rs_length);
                        /* If bytes remaining account for next chunk */
                        if (byte_count) {
                                head->arg.page_len += ch_bytes;
                                head->arg.len += ch_bytes;
                                head->arg.buflen += ch_bytes;
                        }
                }
                /*
                 * If this SGE consumed all of the page, move to the
                 * next page
                 */
                if ((sge_bytes + page_off) == PAGE_SIZE) {
                        page_no++;
                        page_off = 0;
                        /*
                         * If there are still bytes left to map, bump
                         * the page count
                         */
                        if (byte_count)
                                head->count++;
                } else
                        page_off += sge_bytes;
        }
        BUG_ON(byte_count != 0);
        return sge_no;
}

/* Map a read-chunk-list to an XDR and fast register the page-list.
 *
 * Assumptions:
 * - chunk[0]   position points to pages[0] at an offset of 0
 * - pages[]    will be made physically contiguous by creating a one-off memory
 *              region using the fastreg verb.
 * - byte_count is # of bytes in read-chunk-list
 * - ch_count   is # of chunks in read-chunk-list
 *
 * Output:
 * - sge array pointing into pages[] array.
 * - chunk_sge array specifying sge index and count for each
 *   chunk in the read list
 */
static int fast_reg_read_chunks(struct svcxprt_rdma *xprt,
                                struct svc_rqst *rqstp,
                                struct svc_rdma_op_ctxt *head,
                                struct rpcrdma_msg *rmsgp,
                                struct svc_rdma_req_map *rpl_map,
                                struct svc_rdma_req_map *chl_map,
                                int ch_count,
                                int byte_count)
{
        int page_no;
        int ch_no;
        u32 offset;
        struct rpcrdma_read_chunk *ch;
        struct svc_rdma_fastreg_mr *frmr;
        int ret = 0;

        frmr = svc_rdma_get_frmr(xprt);
        if (IS_ERR(frmr))
                return -ENOMEM;

        head->frmr = frmr;
        head->arg.head[0] = rqstp->rq_arg.head[0];
        head->arg.tail[0] = rqstp->rq_arg.tail[0];
        head->arg.pages = &head->pages[head->count];
        head->hdr_count = head->count; /* save count of hdr pages */
        head->arg.page_base = 0;
        head->arg.page_len = byte_count;
        head->arg.len = rqstp->rq_arg.len + byte_count;
        head->arg.buflen = rqstp->rq_arg.buflen + byte_count;

        /* Fast register the page list */
        frmr->kva = page_address(rqstp->rq_arg.pages[0]);
        frmr->direction = DMA_FROM_DEVICE;
        frmr->access_flags = (IB_ACCESS_LOCAL_WRITE|IB_ACCESS_REMOTE_WRITE);
        frmr->map_len = byte_count;
        frmr->page_list_len = PAGE_ALIGN(byte_count) >> PAGE_SHIFT;
        for (page_no = 0; page_no < frmr->page_list_len; page_no++) {
                frmr->page_list->page_list[page_no] =
                        ib_dma_map_page(xprt->sc_cm_id->device,
                                        rqstp->rq_arg.pages[page_no], 0,
                                        PAGE_SIZE, DMA_FROM_DEVICE);
                if (ib_dma_mapping_error(xprt->sc_cm_id->device,
                                         frmr->page_list->page_list[page_no]))
                        goto fatal_err;
                atomic_inc(&xprt->sc_dma_used);
                head->arg.pages[page_no] = rqstp->rq_arg.pages[page_no];
        }
        head->count += page_no;

        /* rq_respages points one past arg pages */
        rqstp->rq_respages = &rqstp->rq_arg.pages[page_no];

        /* Create the reply and chunk maps */
        offset = 0;
        ch = (struct rpcrdma_read_chunk *)&rmsgp->rm_body.rm_chunks[0];
        for (ch_no = 0; ch_no < ch_count; ch_no++) {
                int len = ntohl(ch->rc_target.rs_length);
                rpl_map->sge[ch_no].iov_base = frmr->kva + offset;
                rpl_map->sge[ch_no].iov_len = len;
                chl_map->ch[ch_no].count = 1;
                chl_map->ch[ch_no].start = ch_no;
                offset += len;
                ch++;
        }

        ret = svc_rdma_fastreg(xprt, frmr);
        if (ret)
                goto fatal_err;

        return ch_no;

 fatal_err:
        printk("svcrdma: error fast registering xdr for xprt %p", xprt);
        svc_rdma_put_frmr(xprt, frmr);
        return -EIO;
}

static int rdma_set_ctxt_sge(struct svcxprt_rdma *xprt,
                             struct svc_rdma_op_ctxt *ctxt,
                             struct svc_rdma_fastreg_mr *frmr,
                             struct kvec *vec,
                             u64 *sgl_offset,
                             int count)
{
        int i;
        unsigned long off;

        ctxt->count = count;
        ctxt->direction = DMA_FROM_DEVICE;
        for (i = 0; i < count; i++) {
                ctxt->sge[i].length = 0; /* in case map fails */
                if (!frmr) {
                        BUG_ON(!virt_to_page(vec[i].iov_base));
                        off = (unsigned long)vec[i].iov_base & ~PAGE_MASK;
                        ctxt->sge[i].addr =
                                ib_dma_map_page(xprt->sc_cm_id->device,
                                                virt_to_page(vec[i].iov_base),
                                                off,
                                                vec[i].iov_len,
                                                DMA_FROM_DEVICE);
                        if (ib_dma_mapping_error(xprt->sc_cm_id->device,
                                                 ctxt->sge[i].addr))
                                return -EINVAL;
                        ctxt->sge[i].lkey = xprt->sc_dma_lkey;
                        atomic_inc(&xprt->sc_dma_used);
                } else {
                        ctxt->sge[i].addr = (unsigned long)vec[i].iov_base;
                        ctxt->sge[i].lkey = frmr->mr->lkey;
                }
                ctxt->sge[i].length = vec[i].iov_len;
                *sgl_offset = *sgl_offset + vec[i].iov_len;
        }
        return 0;
}

static int rdma_read_max_sge(struct svcxprt_rdma *xprt, int sge_count)
{
        if ((rdma_node_get_transport(xprt->sc_cm_id->device->node_type) ==
             RDMA_TRANSPORT_IWARP) &&
            sge_count > 1)
                return 1;
        else
                return min_t(int, sge_count, xprt->sc_max_sge);
}

/*
 * Use RDMA_READ to read data from the advertised client buffer into the
 * XDR stream starting at rq_arg.head[0].iov_base.
 * Each chunk in the array
 * contains the following fields:
 * discrim      - '1', This isn't used for data placement
 * position     - The xdr stream offset (the same for every chunk)
 * handle       - RMR for client memory region
 * length       - data transfer length
 * offset       - 64 bit tagged offset in remote memory region
 *
 * On our side, we need to read into a pagelist. The first page immediately
 * follows the RPC header.
 *
 * This function returns:
 * 0 - No error and no read-list found.
 *
 * 1 - Successful read-list processing. The data is not yet in
 * the pagelist and therefore the RPC request must be deferred. The
 * I/O completion will enqueue the transport again and
 * svc_rdma_recvfrom will complete the request.
 *
 * <0 - Error processing/posting read-list.
 *
 * NOTE: The ctxt must not be touched after the last WR has been posted
 * because the I/O completion processing may occur on another
 * processor and free / modify the context. Ne touche pas!
 */
static int rdma_read_xdr(struct svcxprt_rdma *xprt,
                         struct rpcrdma_msg *rmsgp,
                         struct svc_rqst *rqstp,
                         struct svc_rdma_op_ctxt *hdr_ctxt)
{
        struct ib_send_wr read_wr;
        struct ib_send_wr inv_wr;
        int err = 0;
        int ch_no;
        int ch_count;
        int byte_count;
        int sge_count;
        u64 sgl_offset;
        struct rpcrdma_read_chunk *ch;
        struct svc_rdma_op_ctxt *ctxt = NULL;
        struct svc_rdma_req_map *rpl_map;
        struct svc_rdma_req_map *chl_map;

        /* If no read list is present, return 0 */
        ch = svc_rdma_get_read_chunk(rmsgp);
        if (!ch)
                return 0;

        svc_rdma_rcl_chunk_counts(ch, &ch_count, &byte_count);
        if (ch_count > RPCSVC_MAXPAGES)
                return -EINVAL;

        /* Allocate temporary reply and chunk maps */
        rpl_map = svc_rdma_get_req_map();
        chl_map = svc_rdma_get_req_map();

        if (!xprt->sc_frmr_pg_list_len)
                sge_count = map_read_chunks(xprt, rqstp, hdr_ctxt, rmsgp,
                                            rpl_map, chl_map, ch_count,
                                            byte_count);
        else
                sge_count = fast_reg_read_chunks(xprt, rqstp, hdr_ctxt, rmsgp,
                                                 rpl_map, chl_map, ch_count,
                                                 byte_count);
        if (sge_count < 0) {
                err = -EIO;
                goto out;
        }

        sgl_offset = 0;
        ch_no = 0;

        for (ch = (struct rpcrdma_read_chunk *)&rmsgp->rm_body.rm_chunks[0];
             ch->rc_discrim != 0; ch++, ch_no++) {
                u64 rs_offset;
next_sge:
                ctxt = svc_rdma_get_context(xprt);
                ctxt->direction = DMA_FROM_DEVICE;
                ctxt->frmr = hdr_ctxt->frmr;
                ctxt->read_hdr = NULL;
                clear_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
                clear_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags);

                /* Prepare READ WR */
                memset(&read_wr, 0, sizeof read_wr);
                read_wr.wr_id = (unsigned long)ctxt;
                read_wr.opcode = IB_WR_RDMA_READ;
                ctxt->wr_op = read_wr.opcode;
                read_wr.send_flags = IB_SEND_SIGNALED;
                read_wr.wr.rdma.rkey = ntohl(ch->rc_target.rs_handle);
                xdr_decode_hyper((__be32 *)&ch->rc_target.rs_offset,
                                 &rs_offset);
                read_wr.wr.rdma.remote_addr = rs_offset + sgl_offset;
                read_wr.sg_list = ctxt->sge;
                read_wr.num_sge =
                        rdma_read_max_sge(xprt, chl_map->ch[ch_no].count);
                err = rdma_set_ctxt_sge(xprt, ctxt, hdr_ctxt->frmr,
                                        &rpl_map->sge[chl_map->ch[ch_no].start],
                                        &sgl_offset,
                                        read_wr.num_sge);
                if (err) {
                        svc_rdma_unmap_dma(ctxt);
                        svc_rdma_put_context(ctxt, 0);
                        goto out;
                }
                if (((ch+1)->rc_discrim == 0) &&
                    (read_wr.num_sge == chl_map->ch[ch_no].count)) {
                        /*
                         * Mark the last RDMA_READ with a bit to
                         * indicate all RPC data has been fetched from
                         * the client and the RPC needs to be enqueued.
                         */
                        set_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
                        if (hdr_ctxt->frmr) {
                                set_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags);
                                /*
                                 * Invalidate the local MR used to map the data
                                 * sink.
                                 */
                                if (xprt->sc_dev_caps &
                                    SVCRDMA_DEVCAP_READ_W_INV) {
                                        read_wr.opcode =
                                                IB_WR_RDMA_READ_WITH_INV;
                                        ctxt->wr_op = read_wr.opcode;
                                        read_wr.ex.invalidate_rkey =
                                                ctxt->frmr->mr->lkey;
                                } else {
                                        /* Prepare INVALIDATE WR */
                                        memset(&inv_wr, 0, sizeof inv_wr);
                                        inv_wr.opcode = IB_WR_LOCAL_INV;
                                        inv_wr.send_flags = IB_SEND_SIGNALED;
                                        inv_wr.ex.invalidate_rkey =
                                                hdr_ctxt->frmr->mr->lkey;
                                        read_wr.next = &inv_wr;
                                }
                        }
                        ctxt->read_hdr = hdr_ctxt;
                }
                /* Post the read */
                err = svc_rdma_send(xprt, &read_wr);
                if (err) {
                        printk(KERN_ERR "svcrdma: Error %d posting RDMA_READ\n",
                               err);
                        set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
                        svc_rdma_unmap_dma(ctxt);
                        svc_rdma_put_context(ctxt, 0);
                        goto out;
                }
                atomic_inc(&rdma_stat_read);

                if (read_wr.num_sge < chl_map->ch[ch_no].count) {
                        chl_map->ch[ch_no].count -= read_wr.num_sge;
                        chl_map->ch[ch_no].start += read_wr.num_sge;
                        goto next_sge;
                }
                sgl_offset = 0;
                err = 1;
        }

 out:
        svc_rdma_put_req_map(rpl_map);
        svc_rdma_put_req_map(chl_map);

        /* Detach arg pages. svc_recv will replenish them */
        for (ch_no = 0; &rqstp->rq_pages[ch_no] < rqstp->rq_respages; ch_no++)
                rqstp->rq_pages[ch_no] = NULL;

        /*
         * Detach res pages. If svc_release sees any it will attempt to
         * put them.
         */
        while (rqstp->rq_next_page != rqstp->rq_respages)
                *(--rqstp->rq_next_page) = NULL;

        return err;
}

static int rdma_read_complete(struct svc_rqst *rqstp,
                              struct svc_rdma_op_ctxt *head)
{
        int page_no;
        int ret;

        BUG_ON(!head);

        /* Copy RPC pages */
        for (page_no = 0; page_no < head->count; page_no++) {
                put_page(rqstp->rq_pages[page_no]);
                rqstp->rq_pages[page_no] = head->pages[page_no];
        }
        /* Point rq_arg.pages past header */
        rqstp->rq_arg.pages = &rqstp->rq_pages[head->hdr_count];
        rqstp->rq_arg.page_len = head->arg.page_len;
        rqstp->rq_arg.page_base = head->arg.page_base;

        /* rq_respages starts after the last arg page */
        rqstp->rq_respages = &rqstp->rq_arg.pages[page_no];
        rqstp->rq_next_page = &rqstp->rq_arg.pages[page_no];

        /* Rebuild rq_arg head and tail. */
        rqstp->rq_arg.head[0] = head->arg.head[0];
        rqstp->rq_arg.tail[0] = head->arg.tail[0];
        rqstp->rq_arg.len = head->arg.len;
        rqstp->rq_arg.buflen = head->arg.buflen;

        /* Free the context */
        svc_rdma_put_context(head, 0);

        /* XXX: What should this be? */
        rqstp->rq_prot = IPPROTO_MAX;
        svc_xprt_copy_addrs(rqstp, rqstp->rq_xprt);

        ret = rqstp->rq_arg.head[0].iov_len
                + rqstp->rq_arg.page_len
                + rqstp->rq_arg.tail[0].iov_len;
        dprintk("svcrdma: deferred read ret=%d, rq_arg.len =%d, "
                "rq_arg.head[0].iov_base=%p, rq_arg.head[0].iov_len = %zd\n",
                ret, rqstp->rq_arg.len, rqstp->rq_arg.head[0].iov_base,
                rqstp->rq_arg.head[0].iov_len);

        return ret;
}

/*
 * Set up the rqstp thread context to point to the RQ buffer. If
 * necessary, pull additional data from the client with an RDMA_READ
 * request.
 */
int svc_rdma_recvfrom(struct svc_rqst *rqstp)
{
        struct svc_xprt *xprt = rqstp->rq_xprt;
        struct svcxprt_rdma *rdma_xprt =
                container_of(xprt, struct svcxprt_rdma, sc_xprt);
        struct svc_rdma_op_ctxt *ctxt = NULL;
        struct rpcrdma_msg *rmsgp;
        int ret = 0;
        int len;

        dprintk("svcrdma: rqstp=%p\n", rqstp);

        spin_lock_bh(&rdma_xprt->sc_rq_dto_lock);
        if (!list_empty(&rdma_xprt->sc_read_complete_q)) {
                ctxt = list_entry(rdma_xprt->sc_read_complete_q.next,
                                  struct svc_rdma_op_ctxt,
                                  dto_q);
                list_del_init(&ctxt->dto_q);
        }
        if (ctxt) {
                spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock);
                return rdma_read_complete(rqstp, ctxt);
        }

        if (!list_empty(&rdma_xprt->sc_rq_dto_q)) {
                ctxt = list_entry(rdma_xprt->sc_rq_dto_q.next,
                                  struct svc_rdma_op_ctxt,
                                  dto_q);
                list_del_init(&ctxt->dto_q);
        } else {
                atomic_inc(&rdma_stat_rq_starve);
                clear_bit(XPT_DATA, &xprt->xpt_flags);
                ctxt = NULL;
        }
        spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock);
        if (!ctxt) {
                /* This is the EAGAIN path. The svc_recv routine will
                 * return -EAGAIN, the nfsd thread will go to call into
                 * svc_recv again and we shouldn't be on the active
                 * transport list
                 */
                if (test_bit(XPT_CLOSE, &xprt->xpt_flags))
                        goto close_out;

                BUG_ON(ret);
                goto out;
        }
        dprintk("svcrdma: processing ctxt=%p on xprt=%p, rqstp=%p, status=%d\n",
                ctxt, rdma_xprt, rqstp, ctxt->wc_status);
        BUG_ON(ctxt->wc_status != IB_WC_SUCCESS);
        atomic_inc(&rdma_stat_recv);

        /* Build up the XDR from the receive buffers. */
        rdma_build_arg_xdr(rqstp, ctxt, ctxt->byte_len);

        /* Decode the RDMA header. */
        len = svc_rdma_xdr_decode_req(&rmsgp, rqstp);
        rqstp->rq_xprt_hlen = len;

        /* If the request is invalid, reply with an error */
        if (len < 0) {
                if (len == -ENOSYS)
                        svc_rdma_send_error(rdma_xprt, rmsgp, ERR_VERS);
                goto close_out;
        }

        /* Read read-list data. */
        ret = rdma_read_xdr(rdma_xprt, rmsgp, rqstp, ctxt);
        if (ret > 0) {
                /* read-list posted, defer until data received from client. */
                goto defer;
        }
        if (ret < 0) {
                /* Post of read-list failed, free context. */
                svc_rdma_put_context(ctxt, 1);
                return 0;
        }

        ret = rqstp->rq_arg.head[0].iov_len
                + rqstp->rq_arg.page_len
                + rqstp->rq_arg.tail[0].iov_len;
        svc_rdma_put_context(ctxt, 0);
 out:
        dprintk("svcrdma: ret = %d, rq_arg.len =%d, "
                "rq_arg.head[0].iov_base=%p, rq_arg.head[0].iov_len = %zd\n",
                ret, rqstp->rq_arg.len,
                rqstp->rq_arg.head[0].iov_base,
                rqstp->rq_arg.head[0].iov_len);
        rqstp->rq_prot = IPPROTO_MAX;
        svc_xprt_copy_addrs(rqstp, xprt);
        return ret;

 close_out:
        if (ctxt)
                svc_rdma_put_context(ctxt, 1);
        dprintk("svcrdma: transport %p is closing\n", xprt);
        /*
         * Set the close bit and enqueue it. svc_recv will see the
         * close bit and call svc_xprt_delete
         */
        set_bit(XPT_CLOSE, &xprt->xpt_flags);
defer:
        return 0;
}