powerpc/powernv: Report size of OPAL memcons log

[linux/fpc-iii.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>

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

static const char transfertypes[][12] = {
        "inline",       /* no chunks */
        "read list",    /* some argument via rdma read */
        "*read list",   /* entire request via rdma read */
        "write list",   /* some result via rdma write */
        "reply chunk"   /* entire reply via rdma write */
};

/* Returns size of largest RPC-over-RDMA header in a Call message
 *
 * The largest Call header contains a full-size Read list and a
 * minimal Reply chunk.
 */
static unsigned int rpcrdma_max_call_header_size(unsigned int maxsegs)
{
        unsigned int size;

        /* Fixed header fields and list discriminators */
        size = RPCRDMA_HDRLEN_MIN;

        /* Maximum Read list size */
        maxsegs += 2;   /* segment for head and tail buffers */
        size = maxsegs * sizeof(struct rpcrdma_read_chunk);

        /* Minimal Read chunk size */
        size += sizeof(__be32); /* segment count */
        size += sizeof(struct rpcrdma_segment);
        size += sizeof(__be32); /* list discriminator */

        dprintk("RPC:       %s: max call header size = %u\n",
                __func__, size);
        return size;
}

/* Returns size of largest RPC-over-RDMA header in a Reply message
 *
 * There is only one Write list or one Reply chunk per Reply
 * message.  The larger list is the Write list.
 */
static unsigned int rpcrdma_max_reply_header_size(unsigned int maxsegs)
{
        unsigned int size;

        /* Fixed header fields and list discriminators */
        size = RPCRDMA_HDRLEN_MIN;

        /* Maximum Write list size */
        maxsegs += 2;   /* segment for head and tail buffers */
        size = sizeof(__be32);          /* segment count */
        size += maxsegs * sizeof(struct rpcrdma_segment);
        size += sizeof(__be32); /* list discriminator */

        dprintk("RPC:       %s: max reply header size = %u\n",
                __func__, size);
        return size;
}

void rpcrdma_set_max_header_sizes(struct rpcrdma_xprt *r_xprt)
{
        struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
        struct rpcrdma_ia *ia = &r_xprt->rx_ia;
        unsigned int maxsegs = ia->ri_max_segs;

        ia->ri_max_inline_write = cdata->inline_wsize -
                                  rpcrdma_max_call_header_size(maxsegs);
        ia->ri_max_inline_read = cdata->inline_rsize -
                                 rpcrdma_max_reply_header_size(maxsegs);
}

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

        return rqst->rq_snd_buf.len <= ia->ri_max_inline_write;
}

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

        return rqst->rq_rcv_buf.buflen <= ia->ri_max_inline_read;
}

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

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

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

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

        n = 0;
        if (pos == 0) {
                n = rpcrdma_convert_kvec(&xdrbuf->head[0], seg, n);
                if (n == RPCRDMA_MAX_SEGS)
                        goto out_overflow;
        }

        len = xdrbuf->page_len;
        ppages = xdrbuf->pages + (xdrbuf->page_base >> PAGE_SHIFT);
        page_base = xdrbuf->page_base & ~PAGE_MASK;
        p = 0;
        while (len && n < RPCRDMA_MAX_SEGS) {
                if (!ppages[p]) {
                        /* alloc the pagelist for receiving buffer */
                        ppages[p] = alloc_page(GFP_ATOMIC);
                        if (!ppages[p])
                                return -EAGAIN;
                }
                seg[n].mr_page = ppages[p];
                seg[n].mr_offset = (void *)(unsigned long) page_base;
                seg[n].mr_len = min_t(u32, PAGE_SIZE - page_base, len);
                if (seg[n].mr_len > PAGE_SIZE)
                        goto out_overflow;
                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 == RPCRDMA_MAX_SEGS)
                goto out_overflow;

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

        /* When encoding the Write list, some servers need to see an extra
         * segment for odd-length Write chunks. The upper layer provides
         * space in the tail iovec for this purpose.
         */
        if (type == rpcrdma_writech && reminv_expected)
                return n;

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

        return n;

out_overflow:
        pr_err("rpcrdma: segment array overflow\n");
        return -EIO;
}

static inline __be32 *
xdr_encode_rdma_segment(__be32 *iptr, struct rpcrdma_mw *mw)
{
        *iptr++ = cpu_to_be32(mw->mw_handle);
        *iptr++ = cpu_to_be32(mw->mw_length);
        return xdr_encode_hyper(iptr, mw->mw_offset);
}

/* XDR-encode the Read list. Supports encoding a list of read
 * segments that belong to a single read chunk.
 *
 * 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
 *
 * Returns a pointer to the XDR word in the RDMA header following
 * the end of the Read list, or an error pointer.
 */
static __be32 *
rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt,
                         struct rpcrdma_req *req, struct rpc_rqst *rqst,
                         __be32 *iptr, enum rpcrdma_chunktype rtype)
{
        struct rpcrdma_mr_seg *seg;
        struct rpcrdma_mw *mw;
        unsigned int pos;
        int n, nsegs;

        if (rtype == rpcrdma_noch) {
                *iptr++ = xdr_zero;     /* item not present */
                return iptr;
        }

        pos = rqst->rq_snd_buf.head[0].iov_len;
        if (rtype == rpcrdma_areadch)
                pos = 0;
        seg = req->rl_segments;
        nsegs = rpcrdma_convert_iovs(&rqst->rq_snd_buf, pos, rtype, seg, false);
        if (nsegs < 0)
                return ERR_PTR(nsegs);

        do {
                n = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
                                                 false, &mw);
                if (n < 0)
                        return ERR_PTR(n);
                list_add(&mw->mw_list, &req->rl_registered);

                *iptr++ = xdr_one;      /* item present */

                /* All read segments in this chunk
                 * have the same "position".
                 */
                *iptr++ = cpu_to_be32(pos);
                iptr = xdr_encode_rdma_segment(iptr, mw);

                dprintk("RPC: %5u %s: pos %u %u@0x%016llx:0x%08x (%s)\n",
                        rqst->rq_task->tk_pid, __func__, pos,
                        mw->mw_length, (unsigned long long)mw->mw_offset,
                        mw->mw_handle, n < nsegs ? "more" : "last");

                r_xprt->rx_stats.read_chunk_count++;
                seg += n;
                nsegs -= n;
        } while (nsegs);

        /* Finish Read list */
        *iptr++ = xdr_zero;     /* Next item not present */
        return iptr;
}

/* XDR-encode the Write list. Supports encoding a list containing
 * one array of plain segments that belong to a single write chunk.
 *
 * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
 *
 *  Write chunklist (a list of (one) counted array):
 *   N elements:
 *    1 - N - HLOO - HLOO - ... - HLOO - 0
 *
 * Returns a pointer to the XDR word in the RDMA header following
 * the end of the Write list, or an error pointer.
 */
static __be32 *
rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
                          struct rpc_rqst *rqst, __be32 *iptr,
                          enum rpcrdma_chunktype wtype)
{
        struct rpcrdma_mr_seg *seg;
        struct rpcrdma_mw *mw;
        int n, nsegs, nchunks;
        __be32 *segcount;

        if (wtype != rpcrdma_writech) {
                *iptr++ = xdr_zero;     /* no Write list present */
                return iptr;
        }

        seg = req->rl_segments;
        nsegs = rpcrdma_convert_iovs(&rqst->rq_rcv_buf,
                                     rqst->rq_rcv_buf.head[0].iov_len,
                                     wtype, seg,
                                     r_xprt->rx_ia.ri_reminv_expected);
        if (nsegs < 0)
                return ERR_PTR(nsegs);

        *iptr++ = xdr_one;      /* Write list present */
        segcount = iptr++;      /* save location of segment count */

        nchunks = 0;
        do {
                n = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
                                                 true, &mw);
                if (n < 0)
                        return ERR_PTR(n);
                list_add(&mw->mw_list, &req->rl_registered);

                iptr = xdr_encode_rdma_segment(iptr, mw);

                dprintk("RPC: %5u %s: %u@0x016%llx:0x%08x (%s)\n",
                        rqst->rq_task->tk_pid, __func__,
                        mw->mw_length, (unsigned long long)mw->mw_offset,
                        mw->mw_handle, n < nsegs ? "more" : "last");

                r_xprt->rx_stats.write_chunk_count++;
                r_xprt->rx_stats.total_rdma_request += seg->mr_len;
                nchunks++;
                seg   += n;
                nsegs -= n;
        } while (nsegs);

        /* Update count of segments in this Write chunk */
        *segcount = cpu_to_be32(nchunks);

        /* Finish Write list */
        *iptr++ = xdr_zero;     /* Next item not present */
        return iptr;
}

/* XDR-encode the Reply chunk. Supports encoding an array of plain
 * segments that belong to a single write (reply) chunk.
 *
 * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
 *
 *  Reply chunk (a counted array):
 *   N elements:
 *    1 - N - HLOO - HLOO - ... - HLOO
 *
 * Returns a pointer to the XDR word in the RDMA header following
 * the end of the Reply chunk, or an error pointer.
 */
static __be32 *
rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt,
                           struct rpcrdma_req *req, struct rpc_rqst *rqst,
                           __be32 *iptr, enum rpcrdma_chunktype wtype)
{
        struct rpcrdma_mr_seg *seg;
        struct rpcrdma_mw *mw;
        int n, nsegs, nchunks;
        __be32 *segcount;

        if (wtype != rpcrdma_replych) {
                *iptr++ = xdr_zero;     /* no Reply chunk present */
                return iptr;
        }

        seg = req->rl_segments;
        nsegs = rpcrdma_convert_iovs(&rqst->rq_rcv_buf, 0, wtype, seg,
                                     r_xprt->rx_ia.ri_reminv_expected);
        if (nsegs < 0)
                return ERR_PTR(nsegs);

        *iptr++ = xdr_one;      /* Reply chunk present */
        segcount = iptr++;      /* save location of segment count */

        nchunks = 0;
        do {
                n = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
                                                 true, &mw);
                if (n < 0)
                        return ERR_PTR(n);
                list_add(&mw->mw_list, &req->rl_registered);

                iptr = xdr_encode_rdma_segment(iptr, mw);

                dprintk("RPC: %5u %s: %u@0x%016llx:0x%08x (%s)\n",
                        rqst->rq_task->tk_pid, __func__,
                        mw->mw_length, (unsigned long long)mw->mw_offset,
                        mw->mw_handle, n < nsegs ? "more" : "last");

                r_xprt->rx_stats.reply_chunk_count++;
                r_xprt->rx_stats.total_rdma_request += seg->mr_len;
                nchunks++;
                seg   += n;
                nsegs -= n;
        } while (nsegs);

        /* Update count of segments in the Reply chunk */
        *segcount = cpu_to_be32(nchunks);

        return iptr;
}

/* Prepare the RPC-over-RDMA header SGE.
 */
static bool
rpcrdma_prepare_hdr_sge(struct rpcrdma_ia *ia, struct rpcrdma_req *req,
                        u32 len)
{
        struct rpcrdma_regbuf *rb = req->rl_rdmabuf;
        struct ib_sge *sge = &req->rl_send_sge[0];

        if (unlikely(!rpcrdma_regbuf_is_mapped(rb))) {
                if (!__rpcrdma_dma_map_regbuf(ia, rb))
                        return false;
                sge->addr = rdmab_addr(rb);
                sge->lkey = rdmab_lkey(rb);
        }
        sge->length = len;

        ib_dma_sync_single_for_device(ia->ri_device, sge->addr,
                                      sge->length, DMA_TO_DEVICE);
        req->rl_send_wr.num_sge++;
        return true;
}

/* Prepare the Send SGEs. The head and tail iovec, and each entry
 * in the page list, gets its own SGE.
 */
static bool
rpcrdma_prepare_msg_sges(struct rpcrdma_ia *ia, struct rpcrdma_req *req,
                         struct xdr_buf *xdr, enum rpcrdma_chunktype rtype)
{
        unsigned int sge_no, page_base, len, remaining;
        struct rpcrdma_regbuf *rb = req->rl_sendbuf;
        struct ib_device *device = ia->ri_device;
        struct ib_sge *sge = req->rl_send_sge;
        u32 lkey = ia->ri_pd->local_dma_lkey;
        struct page *page, **ppages;

        /* The head iovec is straightforward, as it is already
         * DMA-mapped. Sync the content that has changed.
         */
        if (!rpcrdma_dma_map_regbuf(ia, rb))
                return false;
        sge_no = 1;
        sge[sge_no].addr = rdmab_addr(rb);
        sge[sge_no].length = xdr->head[0].iov_len;
        sge[sge_no].lkey = rdmab_lkey(rb);
        ib_dma_sync_single_for_device(device, sge[sge_no].addr,
                                      sge[sge_no].length, DMA_TO_DEVICE);

        /* If there is a Read chunk, the page list is being handled
         * via explicit RDMA, and thus is skipped here. However, the
         * tail iovec may include an XDR pad for the page list, as
         * well as additional content, and may not reside in the
         * same page as the head iovec.
         */
        if (rtype == rpcrdma_readch) {
                len = xdr->tail[0].iov_len;

                /* Do not include the tail if it is only an XDR pad */
                if (len < 4)
                        goto out;

                page = virt_to_page(xdr->tail[0].iov_base);
                page_base = (unsigned long)xdr->tail[0].iov_base & ~PAGE_MASK;

                /* If the content in the page list is an odd length,
                 * xdr_write_pages() has added a pad at the beginning
                 * of the tail iovec. Force the tail's non-pad content
                 * to land at the next XDR position in the Send message.
                 */
                page_base += len & 3;
                len -= len & 3;
                goto map_tail;
        }

        /* If there is a page list present, temporarily DMA map
         * and prepare an SGE for each page to be sent.
         */
        if (xdr->page_len) {
                ppages = xdr->pages + (xdr->page_base >> PAGE_SHIFT);
                page_base = xdr->page_base & ~PAGE_MASK;
                remaining = xdr->page_len;
                while (remaining) {
                        sge_no++;
                        if (sge_no > RPCRDMA_MAX_SEND_SGES - 2)
                                goto out_mapping_overflow;

                        len = min_t(u32, PAGE_SIZE - page_base, remaining);
                        sge[sge_no].addr = ib_dma_map_page(device, *ppages,
                                                           page_base, len,
                                                           DMA_TO_DEVICE);
                        if (ib_dma_mapping_error(device, sge[sge_no].addr))
                                goto out_mapping_err;
                        sge[sge_no].length = len;
                        sge[sge_no].lkey = lkey;

                        req->rl_mapped_sges++;
                        ppages++;
                        remaining -= len;
                        page_base = 0;
                }
        }

        /* The tail iovec is not always constructed in the same
         * page where the head iovec resides (see, for example,
         * gss_wrap_req_priv). To neatly accommodate that case,
         * DMA map it separately.
         */
        if (xdr->tail[0].iov_len) {
                page = virt_to_page(xdr->tail[0].iov_base);
                page_base = (unsigned long)xdr->tail[0].iov_base & ~PAGE_MASK;
                len = xdr->tail[0].iov_len;

map_tail:
                sge_no++;
                sge[sge_no].addr = ib_dma_map_page(device, page,
                                                   page_base, len,
                                                   DMA_TO_DEVICE);
                if (ib_dma_mapping_error(device, sge[sge_no].addr))
                        goto out_mapping_err;
                sge[sge_no].length = len;
                sge[sge_no].lkey = lkey;
                req->rl_mapped_sges++;
        }

out:
        req->rl_send_wr.num_sge = sge_no + 1;
        return true;

out_mapping_overflow:
        pr_err("rpcrdma: too many Send SGEs (%u)\n", sge_no);
        return false;

out_mapping_err:
        pr_err("rpcrdma: Send mapping error\n");
        return false;
}

bool
rpcrdma_prepare_send_sges(struct rpcrdma_ia *ia, struct rpcrdma_req *req,
                          u32 hdrlen, struct xdr_buf *xdr,
                          enum rpcrdma_chunktype rtype)
{
        req->rl_send_wr.num_sge = 0;
        req->rl_mapped_sges = 0;

        if (!rpcrdma_prepare_hdr_sge(ia, req, hdrlen))
                goto out_map;

        if (rtype != rpcrdma_areadch)
                if (!rpcrdma_prepare_msg_sges(ia, req, xdr, rtype))
                        goto out_map;

        return true;

out_map:
        pr_err("rpcrdma: failed to DMA map a Send buffer\n");
        return false;
}

void
rpcrdma_unmap_sges(struct rpcrdma_ia *ia, struct rpcrdma_req *req)
{
        struct ib_device *device = ia->ri_device;
        struct ib_sge *sge;
        int count;

        sge = &req->rl_send_sge[2];
        for (count = req->rl_mapped_sges; count--; sge++)
                ib_dma_unmap_page(device, sge->addr, sge->length,
                                  DMA_TO_DEVICE);
        req->rl_mapped_sges = 0;
}

/*
 * Marshal a request: the primary job of this routine is to choose
 * the transfer modes. See comments below.
 *
 * Returns zero on success, otherwise a negative errno.
 */

int
rpcrdma_marshal_req(struct rpc_rqst *rqst)
{
        struct rpc_xprt *xprt = rqst->rq_xprt;
        struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
        struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
        enum rpcrdma_chunktype rtype, wtype;
        struct rpcrdma_msg *headerp;
        bool ddp_allowed;
        ssize_t hdrlen;
        size_t rpclen;
        __be32 *iptr;

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

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

        /* When the ULP employs a GSS flavor that guarantees integrity
         * or privacy, direct data placement of individual data items
         * is not allowed.
         */
        ddp_allowed = !(rqst->rq_cred->cr_auth->au_flags &
                                                RPCAUTH_AUTH_DATATOUCH);

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

        /* This implementation supports the following combinations
         * of chunk lists in one RPC-over-RDMA Call message:
         *
         *   - Read list
         *   - Write list
         *   - Reply chunk
         *   - Read list + Reply chunk
         *
         * It might not yet support the following combinations:
         *
         *   - Read list + Write list
         *
         * It does not support the following combinations:
         *
         *   - Write list + Reply chunk
         *   - Read list + Write list + Reply chunk
         *
         * This implementation supports only a single chunk in each
         * Read or Write list. Thus for example the client cannot
         * send a Call message with a Position Zero Read chunk and a
         * regular Read chunk at the same time.
         */
        iptr = headerp->rm_body.rm_chunks;
        iptr = rpcrdma_encode_read_list(r_xprt, req, rqst, iptr, rtype);
        if (IS_ERR(iptr))
                goto out_unmap;
        iptr = rpcrdma_encode_write_list(r_xprt, req, rqst, iptr, wtype);
        if (IS_ERR(iptr))
                goto out_unmap;
        iptr = rpcrdma_encode_reply_chunk(r_xprt, req, rqst, iptr, wtype);
        if (IS_ERR(iptr))
                goto out_unmap;
        hdrlen = (unsigned char *)iptr - (unsigned char *)headerp;

        dprintk("RPC: %5u %s: %s/%s: hdrlen %zd rpclen %zd\n",
                rqst->rq_task->tk_pid, __func__,
                transfertypes[rtype], transfertypes[wtype],
                hdrlen, rpclen);

        if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, hdrlen,
                                       &rqst->rq_snd_buf, rtype)) {
                iptr = ERR_PTR(-EIO);
                goto out_unmap;
        }
        return 0;

out_unmap:
        r_xprt->rx_ia.ri_ops->ro_unmap_safe(r_xprt, req, false);
        return PTR_ERR(iptr);
}

/*
 * 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, int wrchunk, __be32 **iptrp)
{
        unsigned int i, total_len;
        struct rpcrdma_write_chunk *cur_wchunk;
        char *base = (char *)rdmab_to_msg(rep->rr_rdmabuf);

        i = be32_to_cpu(**iptrp);
        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%016llx:0x%08x\n",
                                __func__,
                                be32_to_cpu(seg->rs_length),
                                (unsigned long long)off,
                                be32_to_cpu(seg->rs_handle));
                }
                total_len += be32_to_cpu(seg->rs_length);
                ++cur_wchunk;
        }
        /* check and adjust for properly terminated write chunk */
        if (wrchunk) {
                __be32 *w = (__be32 *) cur_wchunk;
                if (*w++ != xdr_zero)
                        return -1;
                cur_wchunk = (struct rpcrdma_write_chunk *) w;
        }
        if ((char *)cur_wchunk > base + rep->rr_len)
                return -1;

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

/**
 * rpcrdma_inline_fixup - Scatter inline received data into rqst's iovecs
 * @rqst: controlling RPC request
 * @srcp: points to RPC message payload in receive buffer
 * @copy_len: remaining length of receive buffer content
 * @pad: Write chunk pad bytes needed (zero for pure inline)
 *
 * The upper layer has set the maximum number of bytes it can
 * receive in each component of rq_rcv_buf. These values are set in
 * the head.iov_len, page_len, tail.iov_len, and buflen fields.
 *
 * Unlike the TCP equivalent (xdr_partial_copy_from_skb), in
 * many cases this function simply updates iov_base pointers in
 * rq_rcv_buf to point directly to the received reply data, to
 * avoid copying reply data.
 *
 * Returns the count of bytes which had to be memcopied.
 */
static unsigned long
rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
{
        unsigned long fixup_copy_count;
        int i, npages, curlen;
        char *destp;
        struct page **ppages;
        int page_base;

        /* The head iovec is redirected to the RPC reply message
         * in the receive buffer, to avoid a memcopy.
         */
        rqst->rq_rcv_buf.head[0].iov_base = srcp;
        rqst->rq_private_buf.head[0].iov_base = srcp;

        /* The contents of the receive buffer that follow
         * head.iov_len bytes are copied into the page list.
         */
        curlen = rqst->rq_rcv_buf.head[0].iov_len;
        if (curlen > copy_len)
                curlen = copy_len;
        dprintk("RPC:       %s: srcp 0x%p len %d hdrlen %d\n",
                __func__, srcp, copy_len, curlen);
        srcp += curlen;
        copy_len -= curlen;

        page_base = rqst->rq_rcv_buf.page_base;
        ppages = rqst->rq_rcv_buf.pages + (page_base >> PAGE_SHIFT);
        page_base &= ~PAGE_MASK;
        fixup_copy_count = 0;
        if (copy_len && rqst->rq_rcv_buf.page_len) {
                int pagelist_len;

                pagelist_len = rqst->rq_rcv_buf.page_len;
                if (pagelist_len > copy_len)
                        pagelist_len = copy_len;
                npages = PAGE_ALIGN(page_base + pagelist_len) >> PAGE_SHIFT;
                for (i = 0; i < npages; i++) {
                        curlen = PAGE_SIZE - page_base;
                        if (curlen > pagelist_len)
                                curlen = pagelist_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;
                        fixup_copy_count += curlen;
                        pagelist_len -= curlen;
                        if (!pagelist_len)
                                break;
                        page_base = 0;
                }

                /* Implicit padding for the last segment in a Write
                 * chunk is inserted inline at the front of the tail
                 * iovec. The upper layer ignores the content of
                 * the pad. Simply ensure inline content in the tail
                 * that follows the Write chunk is properly aligned.
                 */
                if (pad)
                        srcp -= pad;
        }

        /* The tail iovec is redirected to the remaining data
         * in the receive buffer, to avoid a memcopy.
         */
        if (copy_len || pad) {
                rqst->rq_rcv_buf.tail[0].iov_base = srcp;
                rqst->rq_private_buf.tail[0].iov_base = srcp;
        }

        return fixup_copy_count;
}

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

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

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

        return true;
}
#endif  /* CONFIG_SUNRPC_BACKCHANNEL */

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

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

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

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

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

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

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

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

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

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

                r_xprt->rx_stats.fixup_copy_count +=
                        rpcrdma_inline_fixup(rqst, (char *)iptr, rep->rr_len,
                                             rdmalen);
                break;

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

        case rdma_error:
                goto out_rdmaerr;

badheader:
        default:
                dprintk("RPC: %5u %s: invalid rpcrdma reply (type %u)\n",
                        rqst->rq_task->tk_pid, __func__,
                        be32_to_cpu(headerp->rm_type));
                status = -EIO;
                r_xprt->rx_stats.bad_reply_count++;
                break;
        }

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

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

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

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

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

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

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

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

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

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

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