Merge tag 'linux-kselftest-4.13-rc6-fixes' of git://git.kernel.org/pub/scm/linux...

[mirror_ubuntu-artful-kernel.git] / drivers / infiniband / ulp / iser / iser_initiator.c

/*
 * Copyright (c) 2004, 2005, 2006 Voltaire, Inc. All rights reserved.
 * Copyright (c) 2013-2014 Mellanox Technologies. 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
 * OpenIB.org BSD 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.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/scatterlist.h>
#include <linux/kfifo.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_host.h>

#include "iscsi_iser.h"

/* Register user buffer memory and initialize passive rdma
 *  dto descriptor. Data size is stored in
 *  task->data[ISER_DIR_IN].data_len, Protection size
 *  os stored in task->prot[ISER_DIR_IN].data_len
 */
static int iser_prepare_read_cmd(struct iscsi_task *task)

{
        struct iscsi_iser_task *iser_task = task->dd_data;
        struct iser_mem_reg *mem_reg;
        int err;
        struct iser_ctrl *hdr = &iser_task->desc.iser_header;
        struct iser_data_buf *buf_in = &iser_task->data[ISER_DIR_IN];

        err = iser_dma_map_task_data(iser_task,
                                     buf_in,
                                     ISER_DIR_IN,
                                     DMA_FROM_DEVICE);
        if (err)
                return err;

        if (scsi_prot_sg_count(iser_task->sc)) {
                struct iser_data_buf *pbuf_in = &iser_task->prot[ISER_DIR_IN];

                err = iser_dma_map_task_data(iser_task,
                                             pbuf_in,
                                             ISER_DIR_IN,
                                             DMA_FROM_DEVICE);
                if (err)
                        return err;
        }

        err = iser_reg_rdma_mem(iser_task, ISER_DIR_IN, false);
        if (err) {
                iser_err("Failed to set up Data-IN RDMA\n");
                return err;
        }
        mem_reg = &iser_task->rdma_reg[ISER_DIR_IN];

        hdr->flags    |= ISER_RSV;
        hdr->read_stag = cpu_to_be32(mem_reg->rkey);
        hdr->read_va   = cpu_to_be64(mem_reg->sge.addr);

        iser_dbg("Cmd itt:%d READ tags RKEY:%#.4X VA:%#llX\n",
                 task->itt, mem_reg->rkey,
                 (unsigned long long)mem_reg->sge.addr);

        return 0;
}

/* Register user buffer memory and initialize passive rdma
 *  dto descriptor. Data size is stored in
 *  task->data[ISER_DIR_OUT].data_len, Protection size
 *  is stored at task->prot[ISER_DIR_OUT].data_len
 */
static int
iser_prepare_write_cmd(struct iscsi_task *task,
                       unsigned int imm_sz,
                       unsigned int unsol_sz,
                       unsigned int edtl)
{
        struct iscsi_iser_task *iser_task = task->dd_data;
        struct iser_mem_reg *mem_reg;
        int err;
        struct iser_ctrl *hdr = &iser_task->desc.iser_header;
        struct iser_data_buf *buf_out = &iser_task->data[ISER_DIR_OUT];
        struct ib_sge *tx_dsg = &iser_task->desc.tx_sg[1];

        err = iser_dma_map_task_data(iser_task,
                                     buf_out,
                                     ISER_DIR_OUT,
                                     DMA_TO_DEVICE);
        if (err)
                return err;

        if (scsi_prot_sg_count(iser_task->sc)) {
                struct iser_data_buf *pbuf_out = &iser_task->prot[ISER_DIR_OUT];

                err = iser_dma_map_task_data(iser_task,
                                             pbuf_out,
                                             ISER_DIR_OUT,
                                             DMA_TO_DEVICE);
                if (err)
                        return err;
        }

        err = iser_reg_rdma_mem(iser_task, ISER_DIR_OUT,
                                buf_out->data_len == imm_sz);
        if (err != 0) {
                iser_err("Failed to register write cmd RDMA mem\n");
                return err;
        }

        mem_reg = &iser_task->rdma_reg[ISER_DIR_OUT];

        if (unsol_sz < edtl) {
                hdr->flags     |= ISER_WSV;
                if (buf_out->data_len > imm_sz) {
                        hdr->write_stag = cpu_to_be32(mem_reg->rkey);
                        hdr->write_va = cpu_to_be64(mem_reg->sge.addr + unsol_sz);
                }

                iser_dbg("Cmd itt:%d, WRITE tags, RKEY:%#.4X "
                         "VA:%#llX + unsol:%d\n",
                         task->itt, mem_reg->rkey,
                         (unsigned long long)mem_reg->sge.addr, unsol_sz);
        }

        if (imm_sz > 0) {
                iser_dbg("Cmd itt:%d, WRITE, adding imm.data sz: %d\n",
                         task->itt, imm_sz);
                tx_dsg->addr = mem_reg->sge.addr;
                tx_dsg->length = imm_sz;
                tx_dsg->lkey = mem_reg->sge.lkey;
                iser_task->desc.num_sge = 2;
        }

        return 0;
}

/* creates a new tx descriptor and adds header regd buffer */
static void iser_create_send_desc(struct iser_conn      *iser_conn,
                                  struct iser_tx_desc   *tx_desc)
{
        struct iser_device *device = iser_conn->ib_conn.device;

        ib_dma_sync_single_for_cpu(device->ib_device,
                tx_desc->dma_addr, ISER_HEADERS_LEN, DMA_TO_DEVICE);

        memset(&tx_desc->iser_header, 0, sizeof(struct iser_ctrl));
        tx_desc->iser_header.flags = ISER_VER;
        tx_desc->num_sge = 1;
}

static void iser_free_login_buf(struct iser_conn *iser_conn)
{
        struct iser_device *device = iser_conn->ib_conn.device;
        struct iser_login_desc *desc = &iser_conn->login_desc;

        if (!desc->req)
                return;

        ib_dma_unmap_single(device->ib_device, desc->req_dma,
                            ISCSI_DEF_MAX_RECV_SEG_LEN, DMA_TO_DEVICE);

        ib_dma_unmap_single(device->ib_device, desc->rsp_dma,
                            ISER_RX_LOGIN_SIZE, DMA_FROM_DEVICE);

        kfree(desc->req);
        kfree(desc->rsp);

        /* make sure we never redo any unmapping */
        desc->req = NULL;
        desc->rsp = NULL;
}

static int iser_alloc_login_buf(struct iser_conn *iser_conn)
{
        struct iser_device *device = iser_conn->ib_conn.device;
        struct iser_login_desc *desc = &iser_conn->login_desc;

        desc->req = kmalloc(ISCSI_DEF_MAX_RECV_SEG_LEN, GFP_KERNEL);
        if (!desc->req)
                return -ENOMEM;

        desc->req_dma = ib_dma_map_single(device->ib_device, desc->req,
                                          ISCSI_DEF_MAX_RECV_SEG_LEN,
                                          DMA_TO_DEVICE);
        if (ib_dma_mapping_error(device->ib_device,
                                desc->req_dma))
                goto free_req;

        desc->rsp = kmalloc(ISER_RX_LOGIN_SIZE, GFP_KERNEL);
        if (!desc->rsp)
                goto unmap_req;

        desc->rsp_dma = ib_dma_map_single(device->ib_device, desc->rsp,
                                           ISER_RX_LOGIN_SIZE,
                                           DMA_FROM_DEVICE);
        if (ib_dma_mapping_error(device->ib_device,
                                desc->rsp_dma))
                goto free_rsp;

        return 0;

free_rsp:
        kfree(desc->rsp);
unmap_req:
        ib_dma_unmap_single(device->ib_device, desc->req_dma,
                            ISCSI_DEF_MAX_RECV_SEG_LEN,
                            DMA_TO_DEVICE);
free_req:
        kfree(desc->req);

        return -ENOMEM;
}

int iser_alloc_rx_descriptors(struct iser_conn *iser_conn,
                              struct iscsi_session *session)
{
        int i, j;
        u64 dma_addr;
        struct iser_rx_desc *rx_desc;
        struct ib_sge       *rx_sg;
        struct ib_conn *ib_conn = &iser_conn->ib_conn;
        struct iser_device *device = ib_conn->device;

        iser_conn->qp_max_recv_dtos = session->cmds_max;
        iser_conn->qp_max_recv_dtos_mask = session->cmds_max - 1; /* cmds_max is 2^N */
        iser_conn->min_posted_rx = iser_conn->qp_max_recv_dtos >> 2;

        if (device->reg_ops->alloc_reg_res(ib_conn, session->scsi_cmds_max,
                                           iser_conn->scsi_sg_tablesize))
                goto create_rdma_reg_res_failed;

        if (iser_alloc_login_buf(iser_conn))
                goto alloc_login_buf_fail;

        iser_conn->num_rx_descs = session->cmds_max;
        iser_conn->rx_descs = kmalloc(iser_conn->num_rx_descs *
                                sizeof(struct iser_rx_desc), GFP_KERNEL);
        if (!iser_conn->rx_descs)
                goto rx_desc_alloc_fail;

        rx_desc = iser_conn->rx_descs;

        for (i = 0; i < iser_conn->qp_max_recv_dtos; i++, rx_desc++)  {
                dma_addr = ib_dma_map_single(device->ib_device, (void *)rx_desc,
                                        ISER_RX_PAYLOAD_SIZE, DMA_FROM_DEVICE);
                if (ib_dma_mapping_error(device->ib_device, dma_addr))
                        goto rx_desc_dma_map_failed;

                rx_desc->dma_addr = dma_addr;
                rx_desc->cqe.done = iser_task_rsp;
                rx_sg = &rx_desc->rx_sg;
                rx_sg->addr = rx_desc->dma_addr;
                rx_sg->length = ISER_RX_PAYLOAD_SIZE;
                rx_sg->lkey = device->pd->local_dma_lkey;
        }

        iser_conn->rx_desc_head = 0;
        return 0;

rx_desc_dma_map_failed:
        rx_desc = iser_conn->rx_descs;
        for (j = 0; j < i; j++, rx_desc++)
                ib_dma_unmap_single(device->ib_device, rx_desc->dma_addr,
                                    ISER_RX_PAYLOAD_SIZE, DMA_FROM_DEVICE);
        kfree(iser_conn->rx_descs);
        iser_conn->rx_descs = NULL;
rx_desc_alloc_fail:
        iser_free_login_buf(iser_conn);
alloc_login_buf_fail:
        device->reg_ops->free_reg_res(ib_conn);
create_rdma_reg_res_failed:
        iser_err("failed allocating rx descriptors / data buffers\n");
        return -ENOMEM;
}

void iser_free_rx_descriptors(struct iser_conn *iser_conn)
{
        int i;
        struct iser_rx_desc *rx_desc;
        struct ib_conn *ib_conn = &iser_conn->ib_conn;
        struct iser_device *device = ib_conn->device;

        if (device->reg_ops->free_reg_res)
                device->reg_ops->free_reg_res(ib_conn);

        rx_desc = iser_conn->rx_descs;
        for (i = 0; i < iser_conn->qp_max_recv_dtos; i++, rx_desc++)
                ib_dma_unmap_single(device->ib_device, rx_desc->dma_addr,
                                    ISER_RX_PAYLOAD_SIZE, DMA_FROM_DEVICE);
        kfree(iser_conn->rx_descs);
        /* make sure we never redo any unmapping */
        iser_conn->rx_descs = NULL;

        iser_free_login_buf(iser_conn);
}

static int iser_post_rx_bufs(struct iscsi_conn *conn, struct iscsi_hdr *req)
{
        struct iser_conn *iser_conn = conn->dd_data;
        struct ib_conn *ib_conn = &iser_conn->ib_conn;
        struct iscsi_session *session = conn->session;

        iser_dbg("req op %x flags %x\n", req->opcode, req->flags);
        /* check if this is the last login - going to full feature phase */
        if ((req->flags & ISCSI_FULL_FEATURE_PHASE) != ISCSI_FULL_FEATURE_PHASE)
                return 0;

        /*
         * Check that there is one posted recv buffer
         * (for the last login response).
         */
        WARN_ON(ib_conn->post_recv_buf_count != 1);

        if (session->discovery_sess) {
                iser_info("Discovery session, re-using login RX buffer\n");
                return 0;
        } else
                iser_info("Normal session, posting batch of RX %d buffers\n",
                          iser_conn->min_posted_rx);

        /* Initial post receive buffers */
        if (iser_post_recvm(iser_conn, iser_conn->min_posted_rx))
                return -ENOMEM;

        return 0;
}

static inline bool iser_signal_comp(u8 sig_count)
{
        return ((sig_count % ISER_SIGNAL_CMD_COUNT) == 0);
}

/**
 * iser_send_command - send command PDU
 */
int iser_send_command(struct iscsi_conn *conn,
                      struct iscsi_task *task)
{
        struct iser_conn *iser_conn = conn->dd_data;
        struct iscsi_iser_task *iser_task = task->dd_data;
        unsigned long edtl;
        int err;
        struct iser_data_buf *data_buf, *prot_buf;
        struct iscsi_scsi_req *hdr = (struct iscsi_scsi_req *)task->hdr;
        struct scsi_cmnd *sc  =  task->sc;
        struct iser_tx_desc *tx_desc = &iser_task->desc;
        u8 sig_count = ++iser_conn->ib_conn.sig_count;

        edtl = ntohl(hdr->data_length);

        /* build the tx desc regd header and add it to the tx desc dto */
        tx_desc->type = ISCSI_TX_SCSI_COMMAND;
        tx_desc->cqe.done = iser_cmd_comp;
        iser_create_send_desc(iser_conn, tx_desc);

        if (hdr->flags & ISCSI_FLAG_CMD_READ) {
                data_buf = &iser_task->data[ISER_DIR_IN];
                prot_buf = &iser_task->prot[ISER_DIR_IN];
        } else {
                data_buf = &iser_task->data[ISER_DIR_OUT];
                prot_buf = &iser_task->prot[ISER_DIR_OUT];
        }

        if (scsi_sg_count(sc)) { /* using a scatter list */
                data_buf->sg = scsi_sglist(sc);
                data_buf->size = scsi_sg_count(sc);
        }
        data_buf->data_len = scsi_bufflen(sc);

        if (scsi_prot_sg_count(sc)) {
                prot_buf->sg  = scsi_prot_sglist(sc);
                prot_buf->size = scsi_prot_sg_count(sc);
                prot_buf->data_len = (data_buf->data_len >>
                                     ilog2(sc->device->sector_size)) * 8;
        }

        if (hdr->flags & ISCSI_FLAG_CMD_READ) {
                err = iser_prepare_read_cmd(task);
                if (err)
                        goto send_command_error;
        }
        if (hdr->flags & ISCSI_FLAG_CMD_WRITE) {
                err = iser_prepare_write_cmd(task,
                                             task->imm_count,
                                             task->imm_count +
                                             task->unsol_r2t.data_length,
                                             edtl);
                if (err)
                        goto send_command_error;
        }

        iser_task->status = ISER_TASK_STATUS_STARTED;

        err = iser_post_send(&iser_conn->ib_conn, tx_desc,
                             iser_signal_comp(sig_count));
        if (!err)
                return 0;

send_command_error:
        iser_err("conn %p failed task->itt %d err %d\n",conn, task->itt, err);
        return err;
}

/**
 * iser_send_data_out - send data out PDU
 */
int iser_send_data_out(struct iscsi_conn *conn,
                       struct iscsi_task *task,
                       struct iscsi_data *hdr)
{
        struct iser_conn *iser_conn = conn->dd_data;
        struct iscsi_iser_task *iser_task = task->dd_data;
        struct iser_tx_desc *tx_desc = NULL;
        struct iser_mem_reg *mem_reg;
        unsigned long buf_offset;
        unsigned long data_seg_len;
        uint32_t itt;
        int err;
        struct ib_sge *tx_dsg;

        itt = (__force uint32_t)hdr->itt;
        data_seg_len = ntoh24(hdr->dlength);
        buf_offset   = ntohl(hdr->offset);

        iser_dbg("%s itt %d dseg_len %d offset %d\n",
                 __func__,(int)itt,(int)data_seg_len,(int)buf_offset);

        tx_desc = kmem_cache_zalloc(ig.desc_cache, GFP_ATOMIC);
        if (tx_desc == NULL) {
                iser_err("Failed to alloc desc for post dataout\n");
                return -ENOMEM;
        }

        tx_desc->type = ISCSI_TX_DATAOUT;
        tx_desc->cqe.done = iser_dataout_comp;
        tx_desc->iser_header.flags = ISER_VER;
        memcpy(&tx_desc->iscsi_header, hdr, sizeof(struct iscsi_hdr));

        /* build the tx desc */
        err = iser_initialize_task_headers(task, tx_desc);
        if (err)
                goto send_data_out_error;

        mem_reg = &iser_task->rdma_reg[ISER_DIR_OUT];
        tx_dsg = &tx_desc->tx_sg[1];
        tx_dsg->addr = mem_reg->sge.addr + buf_offset;
        tx_dsg->length = data_seg_len;
        tx_dsg->lkey = mem_reg->sge.lkey;
        tx_desc->num_sge = 2;

        if (buf_offset + data_seg_len > iser_task->data[ISER_DIR_OUT].data_len) {
                iser_err("Offset:%ld & DSL:%ld in Data-Out "
                         "inconsistent with total len:%ld, itt:%d\n",
                         buf_offset, data_seg_len,
                         iser_task->data[ISER_DIR_OUT].data_len, itt);
                err = -EINVAL;
                goto send_data_out_error;
        }
        iser_dbg("data-out itt: %d, offset: %ld, sz: %ld\n",
                 itt, buf_offset, data_seg_len);


        err = iser_post_send(&iser_conn->ib_conn, tx_desc, true);
        if (!err)
                return 0;

send_data_out_error:
        kmem_cache_free(ig.desc_cache, tx_desc);
        iser_err("conn %p failed err %d\n", conn, err);
        return err;
}

int iser_send_control(struct iscsi_conn *conn,
                      struct iscsi_task *task)
{
        struct iser_conn *iser_conn = conn->dd_data;
        struct iscsi_iser_task *iser_task = task->dd_data;
        struct iser_tx_desc *mdesc = &iser_task->desc;
        unsigned long data_seg_len;
        int err = 0;
        struct iser_device *device;

        /* build the tx desc regd header and add it to the tx desc dto */
        mdesc->type = ISCSI_TX_CONTROL;
        mdesc->cqe.done = iser_ctrl_comp;
        iser_create_send_desc(iser_conn, mdesc);

        device = iser_conn->ib_conn.device;

        data_seg_len = ntoh24(task->hdr->dlength);

        if (data_seg_len > 0) {
                struct iser_login_desc *desc = &iser_conn->login_desc;
                struct ib_sge *tx_dsg = &mdesc->tx_sg[1];

                if (task != conn->login_task) {
                        iser_err("data present on non login task!!!\n");
                        goto send_control_error;
                }

                ib_dma_sync_single_for_cpu(device->ib_device, desc->req_dma,
                                           task->data_count, DMA_TO_DEVICE);

                memcpy(desc->req, task->data, task->data_count);

                ib_dma_sync_single_for_device(device->ib_device, desc->req_dma,
                                              task->data_count, DMA_TO_DEVICE);

                tx_dsg->addr = desc->req_dma;
                tx_dsg->length = task->data_count;
                tx_dsg->lkey = device->pd->local_dma_lkey;
                mdesc->num_sge = 2;
        }

        if (task == conn->login_task) {
                iser_dbg("op %x dsl %lx, posting login rx buffer\n",
                         task->hdr->opcode, data_seg_len);
                err = iser_post_recvl(iser_conn);
                if (err)
                        goto send_control_error;
                err = iser_post_rx_bufs(conn, task->hdr);
                if (err)
                        goto send_control_error;
        }

        err = iser_post_send(&iser_conn->ib_conn, mdesc, true);
        if (!err)
                return 0;

send_control_error:
        iser_err("conn %p failed err %d\n",conn, err);
        return err;
}

void iser_login_rsp(struct ib_cq *cq, struct ib_wc *wc)
{
        struct ib_conn *ib_conn = wc->qp->qp_context;
        struct iser_conn *iser_conn = to_iser_conn(ib_conn);
        struct iser_login_desc *desc = iser_login(wc->wr_cqe);
        struct iscsi_hdr *hdr;
        char *data;
        int length;

        if (unlikely(wc->status != IB_WC_SUCCESS)) {
                iser_err_comp(wc, "login_rsp");
                return;
        }

        ib_dma_sync_single_for_cpu(ib_conn->device->ib_device,
                                   desc->rsp_dma, ISER_RX_LOGIN_SIZE,
                                   DMA_FROM_DEVICE);

        hdr = desc->rsp + sizeof(struct iser_ctrl);
        data = desc->rsp + ISER_HEADERS_LEN;
        length = wc->byte_len - ISER_HEADERS_LEN;

        iser_dbg("op 0x%x itt 0x%x dlen %d\n", hdr->opcode,
                 hdr->itt, length);

        iscsi_iser_recv(iser_conn->iscsi_conn, hdr, data, length);

        ib_dma_sync_single_for_device(ib_conn->device->ib_device,
                                      desc->rsp_dma, ISER_RX_LOGIN_SIZE,
                                      DMA_FROM_DEVICE);

        ib_conn->post_recv_buf_count--;
}

static inline void
iser_inv_desc(struct iser_fr_desc *desc, u32 rkey)
{
        if (likely(rkey == desc->rsc.mr->rkey))
                desc->rsc.mr_valid = 0;
        else if (likely(rkey == desc->pi_ctx->sig_mr->rkey))
                desc->pi_ctx->sig_mr_valid = 0;
}

static int
iser_check_remote_inv(struct iser_conn *iser_conn,
                      struct ib_wc *wc,
                      struct iscsi_hdr *hdr)
{
        if (wc->wc_flags & IB_WC_WITH_INVALIDATE) {
                struct iscsi_task *task;
                u32 rkey = wc->ex.invalidate_rkey;

                iser_dbg("conn %p: remote invalidation for rkey %#x\n",
                         iser_conn, rkey);

                if (unlikely(!iser_conn->snd_w_inv)) {
                        iser_err("conn %p: unexpected remote invalidation, "
                                 "terminating connection\n", iser_conn);
                        return -EPROTO;
                }

                task = iscsi_itt_to_ctask(iser_conn->iscsi_conn, hdr->itt);
                if (likely(task)) {
                        struct iscsi_iser_task *iser_task = task->dd_data;
                        struct iser_fr_desc *desc;

                        if (iser_task->dir[ISER_DIR_IN]) {
                                desc = iser_task->rdma_reg[ISER_DIR_IN].mem_h;
                                iser_inv_desc(desc, rkey);
                        }

                        if (iser_task->dir[ISER_DIR_OUT]) {
                                desc = iser_task->rdma_reg[ISER_DIR_OUT].mem_h;
                                iser_inv_desc(desc, rkey);
                        }
                } else {
                        iser_err("failed to get task for itt=%d\n", hdr->itt);
                        return -EINVAL;
                }
        }

        return 0;
}


void iser_task_rsp(struct ib_cq *cq, struct ib_wc *wc)
{
        struct ib_conn *ib_conn = wc->qp->qp_context;
        struct iser_conn *iser_conn = to_iser_conn(ib_conn);
        struct iser_rx_desc *desc = iser_rx(wc->wr_cqe);
        struct iscsi_hdr *hdr;
        int length;
        int outstanding, count, err;

        if (unlikely(wc->status != IB_WC_SUCCESS)) {
                iser_err_comp(wc, "task_rsp");
                return;
        }

        ib_dma_sync_single_for_cpu(ib_conn->device->ib_device,
                                   desc->dma_addr, ISER_RX_PAYLOAD_SIZE,
                                   DMA_FROM_DEVICE);

        hdr = &desc->iscsi_header;
        length = wc->byte_len - ISER_HEADERS_LEN;

        iser_dbg("op 0x%x itt 0x%x dlen %d\n", hdr->opcode,
                 hdr->itt, length);

        if (iser_check_remote_inv(iser_conn, wc, hdr)) {
                iscsi_conn_failure(iser_conn->iscsi_conn,
                                   ISCSI_ERR_CONN_FAILED);
                return;
        }

        iscsi_iser_recv(iser_conn->iscsi_conn, hdr, desc->data, length);

        ib_dma_sync_single_for_device(ib_conn->device->ib_device,
                                      desc->dma_addr, ISER_RX_PAYLOAD_SIZE,
                                      DMA_FROM_DEVICE);

        /* decrementing conn->post_recv_buf_count only --after-- freeing the   *
         * task eliminates the need to worry on tasks which are completed in   *
         * parallel to the execution of iser_conn_term. So the code that waits *
         * for the posted rx bufs refcount to become zero handles everything   */
        ib_conn->post_recv_buf_count--;

        outstanding = ib_conn->post_recv_buf_count;
        if (outstanding + iser_conn->min_posted_rx <= iser_conn->qp_max_recv_dtos) {
                count = min(iser_conn->qp_max_recv_dtos - outstanding,
                            iser_conn->min_posted_rx);
                err = iser_post_recvm(iser_conn, count);
                if (err)
                        iser_err("posting %d rx bufs err %d\n", count, err);
        }
}

void iser_cmd_comp(struct ib_cq *cq, struct ib_wc *wc)
{
        if (unlikely(wc->status != IB_WC_SUCCESS))
                iser_err_comp(wc, "command");
}

void iser_ctrl_comp(struct ib_cq *cq, struct ib_wc *wc)
{
        struct iser_tx_desc *desc = iser_tx(wc->wr_cqe);
        struct iscsi_task *task;

        if (unlikely(wc->status != IB_WC_SUCCESS)) {
                iser_err_comp(wc, "control");
                return;
        }

        /* this arithmetic is legal by libiscsi dd_data allocation */
        task = (void *)desc - sizeof(struct iscsi_task);
        if (task->hdr->itt == RESERVED_ITT)
                iscsi_put_task(task);
}

void iser_dataout_comp(struct ib_cq *cq, struct ib_wc *wc)
{
        struct iser_tx_desc *desc = iser_tx(wc->wr_cqe);
        struct ib_conn *ib_conn = wc->qp->qp_context;
        struct iser_device *device = ib_conn->device;

        if (unlikely(wc->status != IB_WC_SUCCESS))
                iser_err_comp(wc, "dataout");

        ib_dma_unmap_single(device->ib_device, desc->dma_addr,
                            ISER_HEADERS_LEN, DMA_TO_DEVICE);
        kmem_cache_free(ig.desc_cache, desc);
}

void iser_task_rdma_init(struct iscsi_iser_task *iser_task)

{
        iser_task->status = ISER_TASK_STATUS_INIT;

        iser_task->dir[ISER_DIR_IN] = 0;
        iser_task->dir[ISER_DIR_OUT] = 0;

        iser_task->data[ISER_DIR_IN].data_len  = 0;
        iser_task->data[ISER_DIR_OUT].data_len = 0;

        iser_task->prot[ISER_DIR_IN].data_len  = 0;
        iser_task->prot[ISER_DIR_OUT].data_len = 0;

        memset(&iser_task->rdma_reg[ISER_DIR_IN], 0,
               sizeof(struct iser_mem_reg));
        memset(&iser_task->rdma_reg[ISER_DIR_OUT], 0,
               sizeof(struct iser_mem_reg));
}

void iser_task_rdma_finalize(struct iscsi_iser_task *iser_task)
{
        int prot_count = scsi_prot_sg_count(iser_task->sc);

        if (iser_task->dir[ISER_DIR_IN]) {
                iser_unreg_rdma_mem(iser_task, ISER_DIR_IN);
                iser_dma_unmap_task_data(iser_task,
                                         &iser_task->data[ISER_DIR_IN],
                                         DMA_FROM_DEVICE);
                if (prot_count)
                        iser_dma_unmap_task_data(iser_task,
                                                 &iser_task->prot[ISER_DIR_IN],
                                                 DMA_FROM_DEVICE);
        }

        if (iser_task->dir[ISER_DIR_OUT]) {
                iser_unreg_rdma_mem(iser_task, ISER_DIR_OUT);
                iser_dma_unmap_task_data(iser_task,
                                         &iser_task->data[ISER_DIR_OUT],
                                         DMA_TO_DEVICE);
                if (prot_count)
                        iser_dma_unmap_task_data(iser_task,
                                                 &iser_task->prot[ISER_DIR_OUT],
                                                 DMA_TO_DEVICE);
        }
}