[SCSI] iscsi: return task found during search

[mirror_ubuntu-bionic-kernel.git] / drivers / scsi / iscsi_tcp.c

/*
 * iSCSI Initiator over TCP/IP Data-Path
 *
 * Copyright (C) 2004 Dmitry Yusupov
 * Copyright (C) 2004 Alex Aizman
 * Copyright (C) 2005 - 2006 Mike Christie
 * Copyright (C) 2006 Red Hat, Inc.  All rights reserved.
 * maintained by open-iscsi@googlegroups.com
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * See the file COPYING included with this distribution for more details.
 *
 * Credits:
 *      Christoph Hellwig
 *      FUJITA Tomonori
 *      Arne Redlich
 *      Zhenyu Wang
 */

#include <linux/types.h>
#include <linux/list.h>
#include <linux/inet.h>
#include <linux/blkdev.h>
#include <linux/crypto.h>
#include <linux/delay.h>
#include <linux/kfifo.h>
#include <linux/scatterlist.h>
#include <linux/mutex.h>
#include <net/tcp.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi.h>
#include <scsi/scsi_transport_iscsi.h>

#include "iscsi_tcp.h"

#define ISCSI_TCP_VERSION "1.0-574"

MODULE_AUTHOR("Dmitry Yusupov <dmitry_yus@yahoo.com>, "
              "Alex Aizman <itn780@yahoo.com>");
MODULE_DESCRIPTION("iSCSI/TCP data-path");
MODULE_LICENSE("GPL");
MODULE_VERSION(ISCSI_TCP_VERSION);
/* #define DEBUG_TCP */
#define DEBUG_ASSERT

#ifdef DEBUG_TCP
#define debug_tcp(fmt...) printk(KERN_INFO "tcp: " fmt)
#else
#define debug_tcp(fmt...)
#endif

#ifndef DEBUG_ASSERT
#ifdef BUG_ON
#undef BUG_ON
#endif
#define BUG_ON(expr)
#endif

static unsigned int iscsi_max_lun = 512;
module_param_named(max_lun, iscsi_max_lun, uint, S_IRUGO);

static inline void
iscsi_buf_init_iov(struct iscsi_buf *ibuf, char *vbuf, int size)
{
        ibuf->sg.page = virt_to_page(vbuf);
        ibuf->sg.offset = offset_in_page(vbuf);
        ibuf->sg.length = size;
        ibuf->sent = 0;
        ibuf->use_sendmsg = 1;
}

static inline void
iscsi_buf_init_sg(struct iscsi_buf *ibuf, struct scatterlist *sg)
{
        ibuf->sg.page = sg->page;
        ibuf->sg.offset = sg->offset;
        ibuf->sg.length = sg->length;
        /*
         * Fastpath: sg element fits into single page
         */
        if (sg->length + sg->offset <= PAGE_SIZE && !PageSlab(sg->page))
                ibuf->use_sendmsg = 0;
        else
                ibuf->use_sendmsg = 1;
        ibuf->sent = 0;
}

static inline int
iscsi_buf_left(struct iscsi_buf *ibuf)
{
        int rc;

        rc = ibuf->sg.length - ibuf->sent;
        BUG_ON(rc < 0);
        return rc;
}

static inline void
iscsi_hdr_digest(struct iscsi_conn *conn, struct iscsi_buf *buf,
                 u8* crc)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

        crypto_digest_digest(tcp_conn->tx_tfm, &buf->sg, 1, crc);
        buf->sg.length += sizeof(uint32_t);
}

static inline int
iscsi_hdr_extract(struct iscsi_tcp_conn *tcp_conn)
{
        struct sk_buff *skb = tcp_conn->in.skb;

        tcp_conn->in.zero_copy_hdr = 0;

        if (tcp_conn->in.copy >= tcp_conn->hdr_size &&
            tcp_conn->in_progress == IN_PROGRESS_WAIT_HEADER) {
                /*
                 * Zero-copy PDU Header: using connection context
                 * to store header pointer.
                 */
                if (skb_shinfo(skb)->frag_list == NULL &&
                    !skb_shinfo(skb)->nr_frags) {
                        tcp_conn->in.hdr = (struct iscsi_hdr *)
                                ((char*)skb->data + tcp_conn->in.offset);
                        tcp_conn->in.zero_copy_hdr = 1;
                } else {
                        /* ignoring return code since we checked
                         * in.copy before */
                        skb_copy_bits(skb, tcp_conn->in.offset,
                                &tcp_conn->hdr, tcp_conn->hdr_size);
                        tcp_conn->in.hdr = &tcp_conn->hdr;
                }
                tcp_conn->in.offset += tcp_conn->hdr_size;
                tcp_conn->in.copy -= tcp_conn->hdr_size;
        } else {
                int hdr_remains;
                int copylen;

                /*
                 * PDU header scattered across SKB's,
                 * copying it... This'll happen quite rarely.
                 */

                if (tcp_conn->in_progress == IN_PROGRESS_WAIT_HEADER)
                        tcp_conn->in.hdr_offset = 0;

                hdr_remains = tcp_conn->hdr_size - tcp_conn->in.hdr_offset;
                BUG_ON(hdr_remains <= 0);

                copylen = min(tcp_conn->in.copy, hdr_remains);
                skb_copy_bits(skb, tcp_conn->in.offset,
                        (char*)&tcp_conn->hdr + tcp_conn->in.hdr_offset,
                        copylen);

                debug_tcp("PDU gather offset %d bytes %d in.offset %d "
                       "in.copy %d\n", tcp_conn->in.hdr_offset, copylen,
                       tcp_conn->in.offset, tcp_conn->in.copy);

                tcp_conn->in.offset += copylen;
                tcp_conn->in.copy -= copylen;
                if (copylen < hdr_remains)  {
                        tcp_conn->in_progress = IN_PROGRESS_HEADER_GATHER;
                        tcp_conn->in.hdr_offset += copylen;
                        return -EAGAIN;
                }
                tcp_conn->in.hdr = &tcp_conn->hdr;
                tcp_conn->discontiguous_hdr_cnt++;
                tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
        }

        return 0;
}

/*
 * must be called with session lock
 */
static void
__iscsi_ctask_cleanup(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct scsi_cmnd *sc;

        sc = ctask->sc;
        if (unlikely(!sc))
                return;

        tcp_ctask->xmstate = XMSTATE_IDLE;
        tcp_ctask->r2t = NULL;
}

/**
 * iscsi_data_rsp - SCSI Data-In Response processing
 * @conn: iscsi connection
 * @ctask: scsi command task
 **/
static int
iscsi_data_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        int rc;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_data_rsp *rhdr = (struct iscsi_data_rsp *)tcp_conn->in.hdr;
        struct iscsi_session *session = conn->session;
        int datasn = be32_to_cpu(rhdr->datasn);

        rc = iscsi_check_assign_cmdsn(session, (struct iscsi_nopin*)rhdr);
        if (rc)
                return rc;
        /*
         * setup Data-In byte counter (gets decremented..)
         */
        ctask->data_count = tcp_conn->in.datalen;

        if (tcp_conn->in.datalen == 0)
                return 0;

        if (ctask->datasn != datasn)
                return ISCSI_ERR_DATASN;

        ctask->datasn++;

        tcp_ctask->data_offset = be32_to_cpu(rhdr->offset);
        if (tcp_ctask->data_offset + tcp_conn->in.datalen > ctask->total_length)
                return ISCSI_ERR_DATA_OFFSET;

        if (rhdr->flags & ISCSI_FLAG_DATA_STATUS) {
                struct scsi_cmnd *sc = ctask->sc;

                conn->exp_statsn = be32_to_cpu(rhdr->statsn) + 1;
                if (rhdr->flags & ISCSI_FLAG_DATA_UNDERFLOW) {
                        int res_count = be32_to_cpu(rhdr->residual_count);

                        if (res_count > 0 &&
                            res_count <= sc->request_bufflen) {
                                sc->resid = res_count;
                                sc->result = (DID_OK << 16) | rhdr->cmd_status;
                        } else
                                sc->result = (DID_BAD_TARGET << 16) |
                                        rhdr->cmd_status;
                } else if (rhdr->flags & ISCSI_FLAG_DATA_OVERFLOW) {
                        sc->resid = be32_to_cpu(rhdr->residual_count);
                        sc->result = (DID_OK << 16) | rhdr->cmd_status;
                } else
                        sc->result = (DID_OK << 16) | rhdr->cmd_status;
        }

        conn->datain_pdus_cnt++;
        return 0;
}

/**
 * iscsi_solicit_data_init - initialize first Data-Out
 * @conn: iscsi connection
 * @ctask: scsi command task
 * @r2t: R2T info
 *
 * Notes:
 *      Initialize first Data-Out within this R2T sequence and finds
 *      proper data_offset within this SCSI command.
 *
 *      This function is called with connection lock taken.
 **/
static void
iscsi_solicit_data_init(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask,
                        struct iscsi_r2t_info *r2t)
{
        struct iscsi_data *hdr;
        struct scsi_cmnd *sc = ctask->sc;
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

        hdr = &r2t->dtask.hdr;
        memset(hdr, 0, sizeof(struct iscsi_data));
        hdr->ttt = r2t->ttt;
        hdr->datasn = cpu_to_be32(r2t->solicit_datasn);
        r2t->solicit_datasn++;
        hdr->opcode = ISCSI_OP_SCSI_DATA_OUT;
        memcpy(hdr->lun, ctask->hdr->lun, sizeof(hdr->lun));
        hdr->itt = ctask->hdr->itt;
        hdr->exp_statsn = r2t->exp_statsn;
        hdr->offset = cpu_to_be32(r2t->data_offset);
        if (r2t->data_length > conn->max_xmit_dlength) {
                hton24(hdr->dlength, conn->max_xmit_dlength);
                r2t->data_count = conn->max_xmit_dlength;
                hdr->flags = 0;
        } else {
                hton24(hdr->dlength, r2t->data_length);
                r2t->data_count = r2t->data_length;
                hdr->flags = ISCSI_FLAG_CMD_FINAL;
        }
        conn->dataout_pdus_cnt++;

        r2t->sent = 0;

        iscsi_buf_init_iov(&r2t->headbuf, (char*)hdr,
                           sizeof(struct iscsi_hdr));

        if (sc->use_sg) {
                int i, sg_count = 0;
                struct scatterlist *sg = sc->request_buffer;

                r2t->sg = NULL;
                for (i = 0; i < sc->use_sg; i++, sg += 1) {
                        /* FIXME: prefetch ? */
                        if (sg_count + sg->length > r2t->data_offset) {
                                int page_offset;

                                /* sg page found! */

                                /* offset within this page */
                                page_offset = r2t->data_offset - sg_count;

                                /* fill in this buffer */
                                iscsi_buf_init_sg(&r2t->sendbuf, sg);
                                r2t->sendbuf.sg.offset += page_offset;
                                r2t->sendbuf.sg.length -= page_offset;

                                /* xmit logic will continue with next one */
                                r2t->sg = sg + 1;
                                break;
                        }
                        sg_count += sg->length;
                }
                BUG_ON(r2t->sg == NULL);
        } else
                iscsi_buf_init_iov(&tcp_ctask->sendbuf,
                            (char*)sc->request_buffer + r2t->data_offset,
                            r2t->data_count);
}

/**
 * iscsi_r2t_rsp - iSCSI R2T Response processing
 * @conn: iscsi connection
 * @ctask: scsi command task
 **/
static int
iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_r2t_info *r2t;
        struct iscsi_session *session = conn->session;
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct iscsi_r2t_rsp *rhdr = (struct iscsi_r2t_rsp *)tcp_conn->in.hdr;
        int r2tsn = be32_to_cpu(rhdr->r2tsn);
        int rc;

        if (tcp_conn->in.datalen)
                return ISCSI_ERR_DATALEN;

        if (tcp_ctask->exp_r2tsn && tcp_ctask->exp_r2tsn != r2tsn)
                return ISCSI_ERR_R2TSN;

        rc = iscsi_check_assign_cmdsn(session, (struct iscsi_nopin*)rhdr);
        if (rc)
                return rc;

        /* FIXME: use R2TSN to detect missing R2T */

        /* fill-in new R2T associated with the task */
        spin_lock(&session->lock);
        if (!ctask->sc || ctask->mtask ||
             session->state != ISCSI_STATE_LOGGED_IN) {
                printk(KERN_INFO "iscsi_tcp: dropping R2T itt %d in "
                       "recovery...\n", ctask->itt);
                spin_unlock(&session->lock);
                return 0;
        }
        rc = __kfifo_get(tcp_ctask->r2tpool.queue, (void*)&r2t, sizeof(void*));
        BUG_ON(!rc);

        r2t->exp_statsn = rhdr->statsn;
        r2t->data_length = be32_to_cpu(rhdr->data_length);
        if (r2t->data_length == 0 ||
            r2t->data_length > session->max_burst) {
                spin_unlock(&session->lock);
                return ISCSI_ERR_DATALEN;
        }

        r2t->data_offset = be32_to_cpu(rhdr->data_offset);
        if (r2t->data_offset + r2t->data_length > ctask->total_length) {
                spin_unlock(&session->lock);
                return ISCSI_ERR_DATALEN;
        }

        r2t->ttt = rhdr->ttt; /* no flip */
        r2t->solicit_datasn = 0;

        iscsi_solicit_data_init(conn, ctask, r2t);

        tcp_ctask->exp_r2tsn = r2tsn + 1;
        tcp_ctask->xmstate |= XMSTATE_SOL_HDR;
        __kfifo_put(tcp_ctask->r2tqueue, (void*)&r2t, sizeof(void*));
        __kfifo_put(conn->xmitqueue, (void*)&ctask, sizeof(void*));

        scsi_queue_work(session->host, &conn->xmitwork);
        conn->r2t_pdus_cnt++;
        spin_unlock(&session->lock);

        return 0;
}

static int
iscsi_tcp_hdr_recv(struct iscsi_conn *conn)
{
        int rc = 0, opcode, ahslen;
        struct iscsi_hdr *hdr;
        struct iscsi_session *session = conn->session;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        uint32_t cdgst, rdgst = 0, itt;

        hdr = tcp_conn->in.hdr;

        /* verify PDU length */
        tcp_conn->in.datalen = ntoh24(hdr->dlength);
        if (tcp_conn->in.datalen > conn->max_recv_dlength) {
                printk(KERN_ERR "iscsi_tcp: datalen %d > %d\n",
                       tcp_conn->in.datalen, conn->max_recv_dlength);
                return ISCSI_ERR_DATALEN;
        }
        tcp_conn->data_copied = 0;

        /* read AHS */
        ahslen = hdr->hlength << 2;
        tcp_conn->in.offset += ahslen;
        tcp_conn->in.copy -= ahslen;
        if (tcp_conn->in.copy < 0) {
                printk(KERN_ERR "iscsi_tcp: can't handle AHS with length "
                       "%d bytes\n", ahslen);
                return ISCSI_ERR_AHSLEN;
        }

        /* calculate read padding */
        tcp_conn->in.padding = tcp_conn->in.datalen & (ISCSI_PAD_LEN-1);
        if (tcp_conn->in.padding) {
                tcp_conn->in.padding = ISCSI_PAD_LEN - tcp_conn->in.padding;
                debug_scsi("read padding %d bytes\n", tcp_conn->in.padding);
        }

        if (conn->hdrdgst_en) {
                struct scatterlist sg;

                sg_init_one(&sg, (u8 *)hdr,
                            sizeof(struct iscsi_hdr) + ahslen);
                crypto_digest_digest(tcp_conn->rx_tfm, &sg, 1, (u8 *)&cdgst);
                rdgst = *(uint32_t*)((char*)hdr + sizeof(struct iscsi_hdr) +
                                     ahslen);
                if (cdgst != rdgst) {
                        printk(KERN_ERR "iscsi_tcp: hdrdgst error "
                               "recv 0x%x calc 0x%x\n", rdgst, cdgst);
                        return ISCSI_ERR_HDR_DGST;
                }
        }

        opcode = hdr->opcode & ISCSI_OPCODE_MASK;
        /* verify itt (itt encoding: age+cid+itt) */
        rc = iscsi_verify_itt(conn, hdr, &itt);
        if (rc == ISCSI_ERR_NO_SCSI_CMD) {
                tcp_conn->in.datalen = 0; /* force drop */
                return 0;
        } else if (rc)
                return rc;

        debug_tcp("opcode 0x%x offset %d copy %d ahslen %d datalen %d\n",
                  opcode, tcp_conn->in.offset, tcp_conn->in.copy,
                  ahslen, tcp_conn->in.datalen);

        switch(opcode) {
        case ISCSI_OP_SCSI_DATA_IN:
                tcp_conn->in.ctask = session->cmds[itt];
                rc = iscsi_data_rsp(conn, tcp_conn->in.ctask);
                /* fall through */
        case ISCSI_OP_SCSI_CMD_RSP:
                tcp_conn->in.ctask = session->cmds[itt];
                if (tcp_conn->in.datalen)
                        goto copy_hdr;

                spin_lock(&session->lock);
                __iscsi_ctask_cleanup(conn, tcp_conn->in.ctask);
                rc = __iscsi_complete_pdu(conn, hdr, NULL, 0);
                spin_unlock(&session->lock);
                break;
        case ISCSI_OP_R2T:
                tcp_conn->in.ctask = session->cmds[itt];
                if (ahslen)
                        rc = ISCSI_ERR_AHSLEN;
                else if (tcp_conn->in.ctask->sc->sc_data_direction ==
                                                                DMA_TO_DEVICE)
                        rc = iscsi_r2t_rsp(conn, tcp_conn->in.ctask);
                else
                        rc = ISCSI_ERR_PROTO;
                break;
        case ISCSI_OP_LOGIN_RSP:
        case ISCSI_OP_TEXT_RSP:
        case ISCSI_OP_LOGOUT_RSP:
        case ISCSI_OP_NOOP_IN:
        case ISCSI_OP_REJECT:
        case ISCSI_OP_ASYNC_EVENT:
                if (tcp_conn->in.datalen)
                        goto copy_hdr;
        /* fall through */
        case ISCSI_OP_SCSI_TMFUNC_RSP:
                rc = iscsi_complete_pdu(conn, hdr, NULL, 0);
                break;
        default:
                rc = ISCSI_ERR_BAD_OPCODE;
                break;
        }

        return rc;

copy_hdr:
        /*
         * if we did zero copy for the header but we will need multiple
         * skbs to complete the command then we have to copy the header
         * for later use
         */
        if (tcp_conn->in.zero_copy_hdr && tcp_conn->in.copy <
           (tcp_conn->in.datalen + tcp_conn->in.padding +
            (conn->datadgst_en ? 4 : 0))) {
                debug_tcp("Copying header for later use. in.copy %d in.datalen"
                          " %d\n", tcp_conn->in.copy, tcp_conn->in.datalen);
                memcpy(&tcp_conn->hdr, tcp_conn->in.hdr,
                       sizeof(struct iscsi_hdr));
                tcp_conn->in.hdr = &tcp_conn->hdr;
                tcp_conn->in.zero_copy_hdr = 0;
        }
        return 0;
}

/**
 * iscsi_ctask_copy - copy skb bits to the destanation cmd task
 * @conn: iscsi tcp connection
 * @ctask: scsi command task
 * @buf: buffer to copy to
 * @buf_size: size of buffer
 * @offset: offset within the buffer
 *
 * Notes:
 *      The function calls skb_copy_bits() and updates per-connection and
 *      per-cmd byte counters.
 *
 *      Read counters (in bytes):
 *
 *      conn->in.offset         offset within in progress SKB
 *      conn->in.copy           left to copy from in progress SKB
 *                              including padding
 *      conn->in.copied         copied already from in progress SKB
 *      conn->data_copied       copied already from in progress buffer
 *      ctask->sent             total bytes sent up to the MidLayer
 *      ctask->data_count       left to copy from in progress Data-In
 *      buf_left                left to copy from in progress buffer
 **/
static inline int
iscsi_ctask_copy(struct iscsi_tcp_conn *tcp_conn, struct iscsi_cmd_task *ctask,
                void *buf, int buf_size, int offset)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        int buf_left = buf_size - (tcp_conn->data_copied + offset);
        int size = min(tcp_conn->in.copy, buf_left);
        int rc;

        size = min(size, ctask->data_count);

        debug_tcp("ctask_copy %d bytes at offset %d copied %d\n",
               size, tcp_conn->in.offset, tcp_conn->in.copied);

        BUG_ON(size <= 0);
        BUG_ON(tcp_ctask->sent + size > ctask->total_length);

        rc = skb_copy_bits(tcp_conn->in.skb, tcp_conn->in.offset,
                           (char*)buf + (offset + tcp_conn->data_copied), size);
        /* must fit into skb->len */
        BUG_ON(rc);

        tcp_conn->in.offset += size;
        tcp_conn->in.copy -= size;
        tcp_conn->in.copied += size;
        tcp_conn->data_copied += size;
        tcp_ctask->sent += size;
        ctask->data_count -= size;

        BUG_ON(tcp_conn->in.copy < 0);
        BUG_ON(ctask->data_count < 0);

        if (buf_size != (tcp_conn->data_copied + offset)) {
                if (!ctask->data_count) {
                        BUG_ON(buf_size - tcp_conn->data_copied < 0);
                        /* done with this PDU */
                        return buf_size - tcp_conn->data_copied;
                }
                return -EAGAIN;
        }

        /* done with this buffer or with both - PDU and buffer */
        tcp_conn->data_copied = 0;
        return 0;
}

/**
 * iscsi_tcp_copy - copy skb bits to the destanation buffer
 * @conn: iscsi tcp connection
 *
 * Notes:
 *      The function calls skb_copy_bits() and updates per-connection
 *      byte counters.
 **/
static inline int
iscsi_tcp_copy(struct iscsi_tcp_conn *tcp_conn)
{
        void *buf = tcp_conn->data;
        int buf_size = tcp_conn->in.datalen;
        int buf_left = buf_size - tcp_conn->data_copied;
        int size = min(tcp_conn->in.copy, buf_left);
        int rc;

        debug_tcp("tcp_copy %d bytes at offset %d copied %d\n",
               size, tcp_conn->in.offset, tcp_conn->data_copied);
        BUG_ON(size <= 0);

        rc = skb_copy_bits(tcp_conn->in.skb, tcp_conn->in.offset,
                           (char*)buf + tcp_conn->data_copied, size);
        BUG_ON(rc);

        tcp_conn->in.offset += size;
        tcp_conn->in.copy -= size;
        tcp_conn->in.copied += size;
        tcp_conn->data_copied += size;

        if (buf_size != tcp_conn->data_copied)
                return -EAGAIN;

        return 0;
}

static inline void
partial_sg_digest_update(struct iscsi_tcp_conn *tcp_conn,
                         struct scatterlist *sg, int offset, int length)
{
        struct scatterlist temp;

        memcpy(&temp, sg, sizeof(struct scatterlist));
        temp.offset = offset;
        temp.length = length;
        crypto_digest_update(tcp_conn->data_rx_tfm, &temp, 1);
}

static void
iscsi_recv_digest_update(struct iscsi_tcp_conn *tcp_conn, char* buf, int len)
{
        struct scatterlist tmp;

        sg_init_one(&tmp, buf, len);
        crypto_digest_update(tcp_conn->data_rx_tfm, &tmp, 1);
}

static int iscsi_scsi_data_in(struct iscsi_conn *conn)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct iscsi_cmd_task *ctask = tcp_conn->in.ctask;
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct scsi_cmnd *sc = ctask->sc;
        struct scatterlist *sg;
        int i, offset, rc = 0;

        BUG_ON((void*)ctask != sc->SCp.ptr);

        /*
         * copying Data-In into the Scsi_Cmnd
         */
        if (!sc->use_sg) {
                i = ctask->data_count;
                rc = iscsi_ctask_copy(tcp_conn, ctask, sc->request_buffer,
                                      sc->request_bufflen,
                                      tcp_ctask->data_offset);
                if (rc == -EAGAIN)
                        return rc;
                if (conn->datadgst_en)
                        iscsi_recv_digest_update(tcp_conn, sc->request_buffer,
                                                 i);
                rc = 0;
                goto done;
        }

        offset = tcp_ctask->data_offset;
        sg = sc->request_buffer;

        if (tcp_ctask->data_offset)
                for (i = 0; i < tcp_ctask->sg_count; i++)
                        offset -= sg[i].length;
        /* we've passed through partial sg*/
        if (offset < 0)
                offset = 0;

        for (i = tcp_ctask->sg_count; i < sc->use_sg; i++) {
                char *dest;

                dest = kmap_atomic(sg[i].page, KM_SOFTIRQ0);
                rc = iscsi_ctask_copy(tcp_conn, ctask, dest + sg[i].offset,
                                      sg[i].length, offset);
                kunmap_atomic(dest, KM_SOFTIRQ0);
                if (rc == -EAGAIN)
                        /* continue with the next SKB/PDU */
                        return rc;
                if (!rc) {
                        if (conn->datadgst_en) {
                                if (!offset)
                                        crypto_digest_update(
                                                        tcp_conn->data_rx_tfm,
                                                        &sg[i], 1);
                                else
                                        partial_sg_digest_update(tcp_conn,
                                                        &sg[i],
                                                        sg[i].offset + offset,
                                                        sg[i].length - offset);
                        }
                        offset = 0;
                        tcp_ctask->sg_count++;
                }

                if (!ctask->data_count) {
                        if (rc && conn->datadgst_en)
                                /*
                                 * data-in is complete, but buffer not...
                                 */
                                partial_sg_digest_update(tcp_conn, &sg[i],
                                                sg[i].offset, sg[i].length-rc);
                        rc = 0;
                        break;
                }

                if (!tcp_conn->in.copy)
                        return -EAGAIN;
        }
        BUG_ON(ctask->data_count);

done:
        /* check for non-exceptional status */
        if (tcp_conn->in.hdr->flags & ISCSI_FLAG_DATA_STATUS) {
                debug_scsi("done [sc %lx res %d itt 0x%x]\n",
                           (long)sc, sc->result, ctask->itt);
                spin_lock(&conn->session->lock);
                __iscsi_ctask_cleanup(conn, ctask);
                __iscsi_complete_pdu(conn, tcp_conn->in.hdr, NULL, 0);
                spin_unlock(&conn->session->lock);
        }

        return rc;
}

static int
iscsi_data_recv(struct iscsi_conn *conn)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        int rc = 0, opcode;

        opcode = tcp_conn->in.hdr->opcode & ISCSI_OPCODE_MASK;
        switch (opcode) {
        case ISCSI_OP_SCSI_DATA_IN:
                rc = iscsi_scsi_data_in(conn);
                break;
        case ISCSI_OP_SCSI_CMD_RSP:
                spin_lock(&conn->session->lock);
                __iscsi_ctask_cleanup(conn, tcp_conn->in.ctask);
                spin_unlock(&conn->session->lock);
        case ISCSI_OP_TEXT_RSP:
        case ISCSI_OP_LOGIN_RSP:
        case ISCSI_OP_NOOP_IN:
        case ISCSI_OP_ASYNC_EVENT:
        case ISCSI_OP_REJECT:
                /*
                 * Collect data segment to the connection's data
                 * placeholder
                 */
                if (iscsi_tcp_copy(tcp_conn)) {
                        rc = -EAGAIN;
                        goto exit;
                }

                rc = iscsi_complete_pdu(conn, tcp_conn->in.hdr, tcp_conn->data,
                                        tcp_conn->in.datalen);
                if (!rc && conn->datadgst_en && opcode != ISCSI_OP_LOGIN_RSP)
                        iscsi_recv_digest_update(tcp_conn, tcp_conn->data,
                                                tcp_conn->in.datalen);
                break;
        default:
                BUG_ON(1);
        }
exit:
        return rc;
}

/**
 * iscsi_tcp_data_recv - TCP receive in sendfile fashion
 * @rd_desc: read descriptor
 * @skb: socket buffer
 * @offset: offset in skb
 * @len: skb->len - offset
 **/
static int
iscsi_tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
                unsigned int offset, size_t len)
{
        int rc;
        struct iscsi_conn *conn = rd_desc->arg.data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        int processed;
        char pad[ISCSI_PAD_LEN];
        struct scatterlist sg;

        /*
         * Save current SKB and its offset in the corresponding
         * connection context.
         */
        tcp_conn->in.copy = skb->len - offset;
        tcp_conn->in.offset = offset;
        tcp_conn->in.skb = skb;
        tcp_conn->in.len = tcp_conn->in.copy;
        BUG_ON(tcp_conn->in.copy <= 0);
        debug_tcp("in %d bytes\n", tcp_conn->in.copy);

more:
        tcp_conn->in.copied = 0;
        rc = 0;

        if (unlikely(conn->suspend_rx)) {
                debug_tcp("conn %d Rx suspended!\n", conn->id);
                return 0;
        }

        if (tcp_conn->in_progress == IN_PROGRESS_WAIT_HEADER ||
            tcp_conn->in_progress == IN_PROGRESS_HEADER_GATHER) {
                rc = iscsi_hdr_extract(tcp_conn);
                if (rc) {
                       if (rc == -EAGAIN)
                                goto nomore;
                       else {
                                iscsi_conn_failure(conn, rc);
                                return 0;
                       }
                }

                /*
                 * Verify and process incoming PDU header.
                 */
                rc = iscsi_tcp_hdr_recv(conn);
                if (!rc && tcp_conn->in.datalen) {
                        if (conn->datadgst_en) {
                                BUG_ON(!tcp_conn->data_rx_tfm);
                                crypto_digest_init(tcp_conn->data_rx_tfm);
                        }
                        tcp_conn->in_progress = IN_PROGRESS_DATA_RECV;
                } else if (rc) {
                        iscsi_conn_failure(conn, rc);
                        return 0;
                }
        }

        if (tcp_conn->in_progress == IN_PROGRESS_DDIGEST_RECV) {
                uint32_t recv_digest;

                debug_tcp("extra data_recv offset %d copy %d\n",
                          tcp_conn->in.offset, tcp_conn->in.copy);
                skb_copy_bits(tcp_conn->in.skb, tcp_conn->in.offset,
                                &recv_digest, 4);
                tcp_conn->in.offset += 4;
                tcp_conn->in.copy -= 4;
                if (recv_digest != tcp_conn->in.datadgst) {
                        debug_tcp("iscsi_tcp: data digest error!"
                                  "0x%x != 0x%x\n", recv_digest,
                                  tcp_conn->in.datadgst);
                        iscsi_conn_failure(conn, ISCSI_ERR_DATA_DGST);
                        return 0;
                } else {
                        debug_tcp("iscsi_tcp: data digest match!"
                                  "0x%x == 0x%x\n", recv_digest,
                                  tcp_conn->in.datadgst);
                        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
                }
        }

        if (tcp_conn->in_progress == IN_PROGRESS_DATA_RECV &&
           tcp_conn->in.copy) {

                debug_tcp("data_recv offset %d copy %d\n",
                       tcp_conn->in.offset, tcp_conn->in.copy);

                rc = iscsi_data_recv(conn);
                if (rc) {
                        if (rc == -EAGAIN)
                                goto again;
                        iscsi_conn_failure(conn, rc);
                        return 0;
                }
                tcp_conn->in.copy -= tcp_conn->in.padding;
                tcp_conn->in.offset += tcp_conn->in.padding;
                if (conn->datadgst_en) {
                        if (tcp_conn->in.padding) {
                                debug_tcp("padding -> %d\n",
                                          tcp_conn->in.padding);
                                memset(pad, 0, tcp_conn->in.padding);
                                sg_init_one(&sg, pad, tcp_conn->in.padding);
                                crypto_digest_update(tcp_conn->data_rx_tfm,
                                                     &sg, 1);
                        }
                        crypto_digest_final(tcp_conn->data_rx_tfm,
                                            (u8 *) & tcp_conn->in.datadgst);
                        debug_tcp("rx digest 0x%x\n", tcp_conn->in.datadgst);
                        tcp_conn->in_progress = IN_PROGRESS_DDIGEST_RECV;
                } else
                        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
        }

        debug_tcp("f, processed %d from out of %d padding %d\n",
               tcp_conn->in.offset - offset, (int)len, tcp_conn->in.padding);
        BUG_ON(tcp_conn->in.offset - offset > len);

        if (tcp_conn->in.offset - offset != len) {
                debug_tcp("continue to process %d bytes\n",
                       (int)len - (tcp_conn->in.offset - offset));
                goto more;
        }

nomore:
        processed = tcp_conn->in.offset - offset;
        BUG_ON(processed == 0);
        return processed;

again:
        processed = tcp_conn->in.offset - offset;
        debug_tcp("c, processed %d from out of %d rd_desc_cnt %d\n",
                  processed, (int)len, (int)rd_desc->count);
        BUG_ON(processed == 0);
        BUG_ON(processed > len);

        conn->rxdata_octets += processed;
        return processed;
}

static void
iscsi_tcp_data_ready(struct sock *sk, int flag)
{
        struct iscsi_conn *conn = sk->sk_user_data;
        read_descriptor_t rd_desc;

        read_lock(&sk->sk_callback_lock);

        /*
         * Use rd_desc to pass 'conn' to iscsi_tcp_data_recv.
         * We set count to 1 because we want the network layer to
         * hand us all the skbs that are available. iscsi_tcp_data_recv
         * handled pdus that cross buffers or pdus that still need data.
         */
        rd_desc.arg.data = conn;
        rd_desc.count = 1;
        tcp_read_sock(sk, &rd_desc, iscsi_tcp_data_recv);

        read_unlock(&sk->sk_callback_lock);
}

static void
iscsi_tcp_state_change(struct sock *sk)
{
        struct iscsi_tcp_conn *tcp_conn;
        struct iscsi_conn *conn;
        struct iscsi_session *session;
        void (*old_state_change)(struct sock *);

        read_lock(&sk->sk_callback_lock);

        conn = (struct iscsi_conn*)sk->sk_user_data;
        session = conn->session;

        if ((sk->sk_state == TCP_CLOSE_WAIT ||
             sk->sk_state == TCP_CLOSE) &&
            !atomic_read(&sk->sk_rmem_alloc)) {
                debug_tcp("iscsi_tcp_state_change: TCP_CLOSE|TCP_CLOSE_WAIT\n");
                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
        }

        tcp_conn = conn->dd_data;
        old_state_change = tcp_conn->old_state_change;

        read_unlock(&sk->sk_callback_lock);

        old_state_change(sk);
}

/**
 * iscsi_write_space - Called when more output buffer space is available
 * @sk: socket space is available for
 **/
static void
iscsi_write_space(struct sock *sk)
{
        struct iscsi_conn *conn = (struct iscsi_conn*)sk->sk_user_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

        tcp_conn->old_write_space(sk);
        debug_tcp("iscsi_write_space: cid %d\n", conn->id);
        clear_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx);
        scsi_queue_work(conn->session->host, &conn->xmitwork);
}

static void
iscsi_conn_set_callbacks(struct iscsi_conn *conn)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct sock *sk = tcp_conn->sock->sk;

        /* assign new callbacks */
        write_lock_bh(&sk->sk_callback_lock);
        sk->sk_user_data = conn;
        tcp_conn->old_data_ready = sk->sk_data_ready;
        tcp_conn->old_state_change = sk->sk_state_change;
        tcp_conn->old_write_space = sk->sk_write_space;
        sk->sk_data_ready = iscsi_tcp_data_ready;
        sk->sk_state_change = iscsi_tcp_state_change;
        sk->sk_write_space = iscsi_write_space;
        write_unlock_bh(&sk->sk_callback_lock);
}

static void
iscsi_conn_restore_callbacks(struct iscsi_conn *conn)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct sock *sk = tcp_conn->sock->sk;

        /* restore socket callbacks, see also: iscsi_conn_set_callbacks() */
        write_lock_bh(&sk->sk_callback_lock);
        sk->sk_user_data    = NULL;
        sk->sk_data_ready   = tcp_conn->old_data_ready;
        sk->sk_state_change = tcp_conn->old_state_change;
        sk->sk_write_space  = tcp_conn->old_write_space;
        sk->sk_no_check  = 0;
        write_unlock_bh(&sk->sk_callback_lock);
}

/**
 * iscsi_send - generic send routine
 * @sk: kernel's socket
 * @buf: buffer to write from
 * @size: actual size to write
 * @flags: socket's flags
 */
static inline int
iscsi_send(struct iscsi_conn *conn, struct iscsi_buf *buf, int size, int flags)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct socket *sk = tcp_conn->sock;
        int offset = buf->sg.offset + buf->sent;

        /*
         * if we got use_sg=0 or are sending something we kmallocd
         * then we did not have to do kmap (kmap returns page_address)
         *
         * if we got use_sg > 0, but had to drop down, we do not
         * set clustering so this should only happen for that
         * slab case.
         */
        if (buf->use_sendmsg)
                return sock_no_sendpage(sk, buf->sg.page, offset, size, flags);
        else
                return tcp_conn->sendpage(sk, buf->sg.page, offset, size,
                                          flags);
}

/**
 * iscsi_sendhdr - send PDU Header via tcp_sendpage()
 * @conn: iscsi connection
 * @buf: buffer to write from
 * @datalen: lenght of data to be sent after the header
 *
 * Notes:
 *      (Tx, Fast Path)
 **/
static inline int
iscsi_sendhdr(struct iscsi_conn *conn, struct iscsi_buf *buf, int datalen)
{
        struct iscsi_tcp_conn *tcp_conn;
        int flags = 0; /* MSG_DONTWAIT; */
        int res, size;

        size = buf->sg.length - buf->sent;
        BUG_ON(buf->sent + size > buf->sg.length);
        if (buf->sent + size != buf->sg.length || datalen)
                flags |= MSG_MORE;

        res = iscsi_send(conn, buf, size, flags);
        debug_tcp("sendhdr %d bytes, sent %d res %d\n", size, buf->sent, res);
        if (res >= 0) {
                conn->txdata_octets += res;
                buf->sent += res;
                if (size != res)
                        return -EAGAIN;
                return 0;
        } else if (res == -EAGAIN) {
                tcp_conn = conn->dd_data;
                tcp_conn->sendpage_failures_cnt++;
                set_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx);
        } else if (res == -EPIPE)
                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);

        return res;
}

/**
 * iscsi_sendpage - send one page of iSCSI Data-Out.
 * @conn: iscsi connection
 * @buf: buffer to write from
 * @count: remaining data
 * @sent: number of bytes sent
 *
 * Notes:
 *      (Tx, Fast Path)
 **/
static inline int
iscsi_sendpage(struct iscsi_conn *conn, struct iscsi_buf *buf,
               int *count, int *sent)
{
        struct iscsi_tcp_conn *tcp_conn;
        int flags = 0; /* MSG_DONTWAIT; */
        int res, size;

        size = buf->sg.length - buf->sent;
        BUG_ON(buf->sent + size > buf->sg.length);
        if (size > *count)
                size = *count;
        if (buf->sent + size != buf->sg.length || *count != size)
                flags |= MSG_MORE;

        res = iscsi_send(conn, buf, size, flags);
        debug_tcp("sendpage: %d bytes, sent %d left %d sent %d res %d\n",
                  size, buf->sent, *count, *sent, res);
        if (res >= 0) {
                conn->txdata_octets += res;
                buf->sent += res;
                *count -= res;
                *sent += res;
                if (size != res)
                        return -EAGAIN;
                return 0;
        } else if (res == -EAGAIN) {
                tcp_conn = conn->dd_data;
                tcp_conn->sendpage_failures_cnt++;
                set_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx);
        } else if (res == -EPIPE)
                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);

        return res;
}

static inline void
iscsi_data_digest_init(struct iscsi_tcp_conn *tcp_conn,
                      struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

        BUG_ON(!tcp_conn->data_tx_tfm);
        crypto_digest_init(tcp_conn->data_tx_tfm);
        tcp_ctask->digest_count = 4;
}

static int
iscsi_digest_final_send(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask,
                        struct iscsi_buf *buf, uint32_t *digest, int final)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        int rc = 0;
        int sent = 0;

        if (final)
                crypto_digest_final(tcp_conn->data_tx_tfm, (u8*)digest);

        iscsi_buf_init_iov(buf, (char*)digest, 4);
        rc = iscsi_sendpage(conn, buf, &tcp_ctask->digest_count, &sent);
        if (rc) {
                tcp_ctask->datadigest = *digest;
                tcp_ctask->xmstate |= XMSTATE_DATA_DIGEST;
        } else
                tcp_ctask->digest_count = 4;
        return rc;
}

/**
 * iscsi_solicit_data_cont - initialize next Data-Out
 * @conn: iscsi connection
 * @ctask: scsi command task
 * @r2t: R2T info
 * @left: bytes left to transfer
 *
 * Notes:
 *      Initialize next Data-Out within this R2T sequence and continue
 *      to process next Scatter-Gather element(if any) of this SCSI command.
 *
 *      Called under connection lock.
 **/
static void
iscsi_solicit_data_cont(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask,
                        struct iscsi_r2t_info *r2t, int left)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_data *hdr;
        struct scsi_cmnd *sc = ctask->sc;
        int new_offset;

        hdr = &r2t->dtask.hdr;
        memset(hdr, 0, sizeof(struct iscsi_data));
        hdr->ttt = r2t->ttt;
        hdr->datasn = cpu_to_be32(r2t->solicit_datasn);
        r2t->solicit_datasn++;
        hdr->opcode = ISCSI_OP_SCSI_DATA_OUT;
        memcpy(hdr->lun, ctask->hdr->lun, sizeof(hdr->lun));
        hdr->itt = ctask->hdr->itt;
        hdr->exp_statsn = r2t->exp_statsn;
        new_offset = r2t->data_offset + r2t->sent;
        hdr->offset = cpu_to_be32(new_offset);
        if (left > conn->max_xmit_dlength) {
                hton24(hdr->dlength, conn->max_xmit_dlength);
                r2t->data_count = conn->max_xmit_dlength;
        } else {
                hton24(hdr->dlength, left);
                r2t->data_count = left;
                hdr->flags = ISCSI_FLAG_CMD_FINAL;
        }
        conn->dataout_pdus_cnt++;

        iscsi_buf_init_iov(&r2t->headbuf, (char*)hdr,
                           sizeof(struct iscsi_hdr));

        if (sc->use_sg && !iscsi_buf_left(&r2t->sendbuf)) {
                BUG_ON(tcp_ctask->bad_sg == r2t->sg);
                iscsi_buf_init_sg(&r2t->sendbuf, r2t->sg);
                r2t->sg += 1;
        } else
                iscsi_buf_init_iov(&tcp_ctask->sendbuf,
                            (char*)sc->request_buffer + new_offset,
                            r2t->data_count);
}

static void
iscsi_unsolicit_data_init(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_data_task *dtask;

        dtask = tcp_ctask->dtask = &tcp_ctask->unsol_dtask;
        iscsi_prep_unsolicit_data_pdu(ctask, &dtask->hdr,
                                      tcp_ctask->r2t_data_count);
        iscsi_buf_init_iov(&tcp_ctask->headbuf, (char*)&dtask->hdr,
                           sizeof(struct iscsi_hdr));
}

/**
 * iscsi_tcp_cmd_init - Initialize iSCSI SCSI_READ or SCSI_WRITE commands
 * @conn: iscsi connection
 * @ctask: scsi command task
 * @sc: scsi command
 **/
static void
iscsi_tcp_cmd_init(struct iscsi_cmd_task *ctask)
{
        struct scsi_cmnd *sc = ctask->sc;
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

        BUG_ON(__kfifo_len(tcp_ctask->r2tqueue));

        tcp_ctask->sent = 0;
        tcp_ctask->sg_count = 0;

        if (sc->sc_data_direction == DMA_TO_DEVICE) {
                tcp_ctask->xmstate = XMSTATE_W_HDR;
                tcp_ctask->exp_r2tsn = 0;
                BUG_ON(ctask->total_length == 0);

                if (sc->use_sg) {
                        struct scatterlist *sg = sc->request_buffer;

                        iscsi_buf_init_sg(&tcp_ctask->sendbuf,
                                          &sg[tcp_ctask->sg_count++]);
                        tcp_ctask->sg = sg;
                        tcp_ctask->bad_sg = sg + sc->use_sg;
                } else
                        iscsi_buf_init_iov(&tcp_ctask->sendbuf,
                                           sc->request_buffer,
                                           sc->request_bufflen);

                if (ctask->imm_count)
                        tcp_ctask->xmstate |= XMSTATE_IMM_DATA;

                tcp_ctask->pad_count = ctask->total_length & (ISCSI_PAD_LEN-1);
                if (tcp_ctask->pad_count) {
                        tcp_ctask->pad_count = ISCSI_PAD_LEN -
                                                        tcp_ctask->pad_count;
                        debug_scsi("write padding %d bytes\n",
                                   tcp_ctask->pad_count);
                        tcp_ctask->xmstate |= XMSTATE_W_PAD;
                }

                if (ctask->unsol_count)
                        tcp_ctask->xmstate |= XMSTATE_UNS_HDR |
                                                XMSTATE_UNS_INIT;
                tcp_ctask->r2t_data_count = ctask->total_length -
                                    ctask->imm_count -
                                    ctask->unsol_count;

                debug_scsi("cmd [itt %x total %d imm %d imm_data %d "
                           "r2t_data %d]\n",
                           ctask->itt, ctask->total_length, ctask->imm_count,
                           ctask->unsol_count, tcp_ctask->r2t_data_count);
        } else
                tcp_ctask->xmstate = XMSTATE_R_HDR;

        iscsi_buf_init_iov(&tcp_ctask->headbuf, (char*)ctask->hdr,
                            sizeof(struct iscsi_hdr));
}

/**
 * iscsi_tcp_mtask_xmit - xmit management(immediate) task
 * @conn: iscsi connection
 * @mtask: task management task
 *
 * Notes:
 *      The function can return -EAGAIN in which case caller must
 *      call it again later, or recover. '0' return code means successful
 *      xmit.
 *
 *      Management xmit state machine consists of two states:
 *              IN_PROGRESS_IMM_HEAD - PDU Header xmit in progress
 *              IN_PROGRESS_IMM_DATA - PDU Data xmit in progress
 **/
static int
iscsi_tcp_mtask_xmit(struct iscsi_conn *conn, struct iscsi_mgmt_task *mtask)
{
        struct iscsi_tcp_mgmt_task *tcp_mtask = mtask->dd_data;

        debug_scsi("mtask deq [cid %d state %x itt 0x%x]\n",
                conn->id, tcp_mtask->xmstate, mtask->itt);

        if (tcp_mtask->xmstate & XMSTATE_IMM_HDR) {
                tcp_mtask->xmstate &= ~XMSTATE_IMM_HDR;
                if (mtask->data_count)
                        tcp_mtask->xmstate |= XMSTATE_IMM_DATA;
                if (conn->c_stage != ISCSI_CONN_INITIAL_STAGE &&
                    conn->stop_stage != STOP_CONN_RECOVER &&
                    conn->hdrdgst_en)
                        iscsi_hdr_digest(conn, &tcp_mtask->headbuf,
                                        (u8*)tcp_mtask->hdrext);
                if (iscsi_sendhdr(conn, &tcp_mtask->headbuf,
                                  mtask->data_count)) {
                        tcp_mtask->xmstate |= XMSTATE_IMM_HDR;
                        if (mtask->data_count)
                                tcp_mtask->xmstate &= ~XMSTATE_IMM_DATA;
                        return -EAGAIN;
                }
        }

        if (tcp_mtask->xmstate & XMSTATE_IMM_DATA) {
                BUG_ON(!mtask->data_count);
                tcp_mtask->xmstate &= ~XMSTATE_IMM_DATA;
                /* FIXME: implement.
                 * Virtual buffer could be spreaded across multiple pages...
                 */
                do {
                        if (iscsi_sendpage(conn, &tcp_mtask->sendbuf,
                                   &mtask->data_count, &tcp_mtask->sent)) {
                                tcp_mtask->xmstate |= XMSTATE_IMM_DATA;
                                return -EAGAIN;
                        }
                } while (mtask->data_count);
        }

        BUG_ON(tcp_mtask->xmstate != XMSTATE_IDLE);
        if (mtask->hdr->itt == cpu_to_be32(ISCSI_RESERVED_TAG)) {
                struct iscsi_session *session = conn->session;

                spin_lock_bh(&session->lock);
                list_del(&conn->mtask->running);
                __kfifo_put(session->mgmtpool.queue, (void*)&conn->mtask,
                            sizeof(void*));
                spin_unlock_bh(&session->lock);
        }
        return 0;
}

static inline int
handle_xmstate_r_hdr(struct iscsi_conn *conn,
                     struct iscsi_tcp_cmd_task *tcp_ctask)
{
        tcp_ctask->xmstate &= ~XMSTATE_R_HDR;
        if (conn->hdrdgst_en)
                iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
                                 (u8*)tcp_ctask->hdrext);
        if (!iscsi_sendhdr(conn, &tcp_ctask->headbuf, 0)) {
                BUG_ON(tcp_ctask->xmstate != XMSTATE_IDLE);
                return 0; /* wait for Data-In */
        }
        tcp_ctask->xmstate |= XMSTATE_R_HDR;
        return -EAGAIN;
}

static inline int
handle_xmstate_w_hdr(struct iscsi_conn *conn,
                     struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

        tcp_ctask->xmstate &= ~XMSTATE_W_HDR;
        if (conn->hdrdgst_en)
                iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
                                 (u8*)tcp_ctask->hdrext);
        if (iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->imm_count)) {
                tcp_ctask->xmstate |= XMSTATE_W_HDR;
                return -EAGAIN;
        }
        return 0;
}

static inline int
handle_xmstate_data_digest(struct iscsi_conn *conn,
                           struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

        tcp_ctask->xmstate &= ~XMSTATE_DATA_DIGEST;
        debug_tcp("resent data digest 0x%x\n", tcp_ctask->datadigest);
        if (iscsi_digest_final_send(conn, ctask, &tcp_ctask->immbuf,
                                    &tcp_ctask->datadigest, 0)) {
                tcp_ctask->xmstate |= XMSTATE_DATA_DIGEST;
                debug_tcp("resent data digest 0x%x fail!\n",
                          tcp_ctask->datadigest);
                return -EAGAIN;
        }
        return 0;
}

static inline int
handle_xmstate_imm_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

        BUG_ON(!ctask->imm_count);
        tcp_ctask->xmstate &= ~XMSTATE_IMM_DATA;

        if (conn->datadgst_en) {
                iscsi_data_digest_init(tcp_conn, ctask);
                tcp_ctask->immdigest = 0;
        }

        for (;;) {
                if (iscsi_sendpage(conn, &tcp_ctask->sendbuf, &ctask->imm_count,
                                   &tcp_ctask->sent)) {
                        tcp_ctask->xmstate |= XMSTATE_IMM_DATA;
                        if (conn->datadgst_en) {
                                crypto_digest_final(tcp_conn->data_tx_tfm,
                                                (u8*)&tcp_ctask->immdigest);
                                debug_tcp("tx imm sendpage fail 0x%x\n",
                                          tcp_ctask->datadigest);
                        }
                        return -EAGAIN;
                }
                if (conn->datadgst_en)
                        crypto_digest_update(tcp_conn->data_tx_tfm,
                                             &tcp_ctask->sendbuf.sg, 1);

                if (!ctask->imm_count)
                        break;
                iscsi_buf_init_sg(&tcp_ctask->sendbuf,
                                  &tcp_ctask->sg[tcp_ctask->sg_count++]);
        }

        if (conn->datadgst_en && !(tcp_ctask->xmstate & XMSTATE_W_PAD)) {
                if (iscsi_digest_final_send(conn, ctask, &tcp_ctask->immbuf,
                                            &tcp_ctask->immdigest, 1)) {
                        debug_tcp("sending imm digest 0x%x fail!\n",
                                  tcp_ctask->immdigest);
                        return -EAGAIN;
                }
                debug_tcp("sending imm digest 0x%x\n", tcp_ctask->immdigest);
        }

        return 0;
}

static inline int
handle_xmstate_uns_hdr(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_data_task *dtask;

        tcp_ctask->xmstate |= XMSTATE_UNS_DATA;
        if (tcp_ctask->xmstate & XMSTATE_UNS_INIT) {
                iscsi_unsolicit_data_init(conn, ctask);
                dtask = tcp_ctask->dtask;
                if (conn->hdrdgst_en)
                        iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
                                        (u8*)dtask->hdrext);
                tcp_ctask->xmstate &= ~XMSTATE_UNS_INIT;
        }
        if (iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->data_count)) {
                tcp_ctask->xmstate &= ~XMSTATE_UNS_DATA;
                tcp_ctask->xmstate |= XMSTATE_UNS_HDR;
                return -EAGAIN;
        }

        debug_scsi("uns dout [itt 0x%x dlen %d sent %d]\n",
                   ctask->itt, ctask->unsol_count, tcp_ctask->sent);
        return 0;
}

static inline int
handle_xmstate_uns_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_data_task *dtask = tcp_ctask->dtask;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

        BUG_ON(!ctask->data_count);
        tcp_ctask->xmstate &= ~XMSTATE_UNS_DATA;

        if (conn->datadgst_en) {
                iscsi_data_digest_init(tcp_conn, ctask);
                dtask->digest = 0;
        }

        for (;;) {
                int start = tcp_ctask->sent;

                if (iscsi_sendpage(conn, &tcp_ctask->sendbuf,
                                   &ctask->data_count, &tcp_ctask->sent)) {
                        ctask->unsol_count -= tcp_ctask->sent - start;
                        tcp_ctask->xmstate |= XMSTATE_UNS_DATA;
                        /* will continue with this ctask later.. */
                        if (conn->datadgst_en) {
                                crypto_digest_final(tcp_conn->data_tx_tfm,
                                                (u8 *)&dtask->digest);
                                debug_tcp("tx uns data fail 0x%x\n",
                                          dtask->digest);
                        }
                        return -EAGAIN;
                }

                BUG_ON(tcp_ctask->sent > ctask->total_length);
                ctask->unsol_count -= tcp_ctask->sent - start;

                /*
                 * XXX:we may run here with un-initial sendbuf.
                 * so pass it
                 */
                if (conn->datadgst_en && tcp_ctask->sent - start > 0)
                        crypto_digest_update(tcp_conn->data_tx_tfm,
                                             &tcp_ctask->sendbuf.sg, 1);

                if (!ctask->data_count)
                        break;
                iscsi_buf_init_sg(&tcp_ctask->sendbuf,
                                  &tcp_ctask->sg[tcp_ctask->sg_count++]);
        }
        BUG_ON(ctask->unsol_count < 0);

        /*
         * Done with the Data-Out. Next, check if we need
         * to send another unsolicited Data-Out.
         */
        if (ctask->unsol_count) {
                if (conn->datadgst_en) {
                        if (iscsi_digest_final_send(conn, ctask,
                                                    &dtask->digestbuf,
                                                    &dtask->digest, 1)) {
                                debug_tcp("send uns digest 0x%x fail\n",
                                          dtask->digest);
                                return -EAGAIN;
                        }
                        debug_tcp("sending uns digest 0x%x, more uns\n",
                                  dtask->digest);
                }
                tcp_ctask->xmstate |= XMSTATE_UNS_INIT;
                return 1;
        }

        if (conn->datadgst_en && !(tcp_ctask->xmstate & XMSTATE_W_PAD)) {
                if (iscsi_digest_final_send(conn, ctask,
                                            &dtask->digestbuf,
                                            &dtask->digest, 1)) {
                        debug_tcp("send last uns digest 0x%x fail\n",
                                   dtask->digest);
                        return -EAGAIN;
                }
                debug_tcp("sending uns digest 0x%x\n",dtask->digest);
        }

        return 0;
}

static inline int
handle_xmstate_sol_data(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_session *session = conn->session;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_r2t_info *r2t = tcp_ctask->r2t;
        struct iscsi_data_task *dtask = &r2t->dtask;
        int left;

        tcp_ctask->xmstate &= ~XMSTATE_SOL_DATA;
        tcp_ctask->dtask = dtask;

        if (conn->datadgst_en) {
                iscsi_data_digest_init(tcp_conn, ctask);
                dtask->digest = 0;
        }
solicit_again:
        /*
         * send Data-Out whitnin this R2T sequence.
         */
        if (!r2t->data_count)
                goto data_out_done;

        if (iscsi_sendpage(conn, &r2t->sendbuf, &r2t->data_count, &r2t->sent)) {
                tcp_ctask->xmstate |= XMSTATE_SOL_DATA;
                /* will continue with this ctask later.. */
                if (conn->datadgst_en) {
                        crypto_digest_final(tcp_conn->data_tx_tfm,
                                          (u8 *)&dtask->digest);
                        debug_tcp("r2t data send fail 0x%x\n", dtask->digest);
                }
                return -EAGAIN;
        }

        BUG_ON(r2t->data_count < 0);
        if (conn->datadgst_en)
                crypto_digest_update(tcp_conn->data_tx_tfm, &r2t->sendbuf.sg,
                                     1);

        if (r2t->data_count) {
                BUG_ON(ctask->sc->use_sg == 0);
                if (!iscsi_buf_left(&r2t->sendbuf)) {
                        BUG_ON(tcp_ctask->bad_sg == r2t->sg);
                        iscsi_buf_init_sg(&r2t->sendbuf, r2t->sg);
                        r2t->sg += 1;
                }
                goto solicit_again;
        }

data_out_done:
        /*
         * Done with this Data-Out. Next, check if we have
         * to send another Data-Out for this R2T.
         */
        BUG_ON(r2t->data_length - r2t->sent < 0);
        left = r2t->data_length - r2t->sent;
        if (left) {
                if (conn->datadgst_en) {
                        if (iscsi_digest_final_send(conn, ctask,
                                                    &dtask->digestbuf,
                                                    &dtask->digest, 1)) {
                                debug_tcp("send r2t data digest 0x%x"
                                          "fail\n", dtask->digest);
                                return -EAGAIN;
                        }
                        debug_tcp("r2t data send digest 0x%x\n",
                                  dtask->digest);
                }
                iscsi_solicit_data_cont(conn, ctask, r2t, left);
                tcp_ctask->xmstate |= XMSTATE_SOL_DATA;
                tcp_ctask->xmstate &= ~XMSTATE_SOL_HDR;
                return 1;
        }

        /*
         * Done with this R2T. Check if there are more
         * outstanding R2Ts ready to be processed.
         */
        BUG_ON(tcp_ctask->r2t_data_count - r2t->data_length < 0);
        if (conn->datadgst_en) {
                if (iscsi_digest_final_send(conn, ctask, &dtask->digestbuf,
                                            &dtask->digest, 1)) {
                        debug_tcp("send last r2t data digest 0x%x"
                                  "fail\n", dtask->digest);
                        return -EAGAIN;
                }
                debug_tcp("r2t done dout digest 0x%x\n", dtask->digest);
        }

        tcp_ctask->r2t_data_count -= r2t->data_length;
        tcp_ctask->r2t = NULL;
        spin_lock_bh(&session->lock);
        __kfifo_put(tcp_ctask->r2tpool.queue, (void*)&r2t, sizeof(void*));
        spin_unlock_bh(&session->lock);
        if (__kfifo_get(tcp_ctask->r2tqueue, (void*)&r2t, sizeof(void*))) {
                tcp_ctask->r2t = r2t;
                tcp_ctask->xmstate |= XMSTATE_SOL_DATA;
                tcp_ctask->xmstate &= ~XMSTATE_SOL_HDR;
                return 1;
        }

        return 0;
}

static inline int
handle_xmstate_w_pad(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct iscsi_data_task *dtask = tcp_ctask->dtask;
        int sent;

        tcp_ctask->xmstate &= ~XMSTATE_W_PAD;
        iscsi_buf_init_iov(&tcp_ctask->sendbuf, (char*)&tcp_ctask->pad,
                            tcp_ctask->pad_count);
        if (iscsi_sendpage(conn, &tcp_ctask->sendbuf, &tcp_ctask->pad_count,
                           &sent)) {
                tcp_ctask->xmstate |= XMSTATE_W_PAD;
                return -EAGAIN;
        }

        if (conn->datadgst_en) {
                crypto_digest_update(tcp_conn->data_tx_tfm,
                                     &tcp_ctask->sendbuf.sg, 1);
                /* imm data? */
                if (!dtask) {
                        if (iscsi_digest_final_send(conn, ctask,
                                                    &tcp_ctask->immbuf,
                                                    &tcp_ctask->immdigest, 1)) {
                                debug_tcp("send padding digest 0x%x"
                                          "fail!\n", tcp_ctask->immdigest);
                                return -EAGAIN;
                        }
                        debug_tcp("done with padding, digest 0x%x\n",
                                  tcp_ctask->datadigest);
                } else {
                        if (iscsi_digest_final_send(conn, ctask,
                                                    &dtask->digestbuf,
                                                    &dtask->digest, 1)) {
                                debug_tcp("send padding digest 0x%x"
                                          "fail\n", dtask->digest);
                                return -EAGAIN;
                        }
                        debug_tcp("done with padding, digest 0x%x\n",
                                  dtask->digest);
                }
        }

        return 0;
}

static int
iscsi_tcp_ctask_xmit(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        int rc = 0;

        debug_scsi("ctask deq [cid %d xmstate %x itt 0x%x]\n",
                conn->id, tcp_ctask->xmstate, ctask->itt);

        /*
         * serialize with TMF AbortTask
         */
        if (ctask->mtask)
                return rc;

        if (tcp_ctask->xmstate & XMSTATE_R_HDR) {
                rc = handle_xmstate_r_hdr(conn, tcp_ctask);
                return rc;
        }

        if (tcp_ctask->xmstate & XMSTATE_W_HDR) {
                rc = handle_xmstate_w_hdr(conn, ctask);
                if (rc)
                        return rc;
        }

        /* XXX: for data digest xmit recover */
        if (tcp_ctask->xmstate & XMSTATE_DATA_DIGEST) {
                rc = handle_xmstate_data_digest(conn, ctask);
                if (rc)
                        return rc;
        }

        if (tcp_ctask->xmstate & XMSTATE_IMM_DATA) {
                rc = handle_xmstate_imm_data(conn, ctask);
                if (rc)
                        return rc;
        }

        if (tcp_ctask->xmstate & XMSTATE_UNS_HDR) {
                BUG_ON(!ctask->unsol_count);
                tcp_ctask->xmstate &= ~XMSTATE_UNS_HDR;
unsolicit_head_again:
                rc = handle_xmstate_uns_hdr(conn, ctask);
                if (rc)
                        return rc;
        }

        if (tcp_ctask->xmstate & XMSTATE_UNS_DATA) {
                rc = handle_xmstate_uns_data(conn, ctask);
                if (rc == 1)
                        goto unsolicit_head_again;
                else if (rc)
                        return rc;
                goto done;
        }

        if (tcp_ctask->xmstate & XMSTATE_SOL_HDR) {
                struct iscsi_r2t_info *r2t;

                tcp_ctask->xmstate &= ~XMSTATE_SOL_HDR;
                tcp_ctask->xmstate |= XMSTATE_SOL_DATA;
                if (!tcp_ctask->r2t)
                        __kfifo_get(tcp_ctask->r2tqueue, (void*)&tcp_ctask->r2t,
                                    sizeof(void*));
solicit_head_again:
                r2t = tcp_ctask->r2t;
                if (conn->hdrdgst_en)
                        iscsi_hdr_digest(conn, &r2t->headbuf,
                                        (u8*)r2t->dtask.hdrext);
                if (iscsi_sendhdr(conn, &r2t->headbuf, r2t->data_count)) {
                        tcp_ctask->xmstate &= ~XMSTATE_SOL_DATA;
                        tcp_ctask->xmstate |= XMSTATE_SOL_HDR;
                        return -EAGAIN;
                }

                debug_scsi("sol dout [dsn %d itt 0x%x dlen %d sent %d]\n",
                        r2t->solicit_datasn - 1, ctask->itt, r2t->data_count,
                        r2t->sent);
        }

        if (tcp_ctask->xmstate & XMSTATE_SOL_DATA) {
                rc = handle_xmstate_sol_data(conn, ctask);
                if (rc == 1)
                        goto solicit_head_again;
                if (rc)
                        return rc;
        }

done:
        /*
         * Last thing to check is whether we need to send write
         * padding. Note that we check for xmstate equality, not just the bit.
         */
        if (tcp_ctask->xmstate == XMSTATE_W_PAD)
                rc = handle_xmstate_w_pad(conn, ctask);

        return rc;
}

static struct iscsi_cls_conn *
iscsi_tcp_conn_create(struct iscsi_cls_session *cls_session, uint32_t conn_idx)
{
        struct iscsi_conn *conn;
        struct iscsi_cls_conn *cls_conn;
        struct iscsi_tcp_conn *tcp_conn;

        cls_conn = iscsi_conn_setup(cls_session, conn_idx);
        if (!cls_conn)
                return NULL;
        conn = cls_conn->dd_data;
        /*
         * due to strange issues with iser these are not set
         * in iscsi_conn_setup
         */
        conn->max_recv_dlength = DEFAULT_MAX_RECV_DATA_SEGMENT_LENGTH;

        tcp_conn = kzalloc(sizeof(*tcp_conn), GFP_KERNEL);
        if (!tcp_conn)
                goto tcp_conn_alloc_fail;

        conn->dd_data = tcp_conn;
        tcp_conn->iscsi_conn = conn;
        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
        /* initial operational parameters */
        tcp_conn->hdr_size = sizeof(struct iscsi_hdr);
        tcp_conn->data_size = DEFAULT_MAX_RECV_DATA_SEGMENT_LENGTH;

        /* allocate initial PDU receive place holder */
        if (tcp_conn->data_size <= PAGE_SIZE)
                tcp_conn->data = kmalloc(tcp_conn->data_size, GFP_KERNEL);
        else
                tcp_conn->data = (void*)__get_free_pages(GFP_KERNEL,
                                        get_order(tcp_conn->data_size));
        if (!tcp_conn->data)
                goto max_recv_dlenght_alloc_fail;

        return cls_conn;

max_recv_dlenght_alloc_fail:
        kfree(tcp_conn);
tcp_conn_alloc_fail:
        iscsi_conn_teardown(cls_conn);
        return NULL;
}

static void
iscsi_tcp_conn_destroy(struct iscsi_cls_conn *cls_conn)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        int digest = 0;

        if (conn->hdrdgst_en || conn->datadgst_en)
                digest = 1;

        iscsi_conn_teardown(cls_conn);

        /* now free tcp_conn */
        if (digest) {
                if (tcp_conn->tx_tfm)
                        crypto_free_tfm(tcp_conn->tx_tfm);
                if (tcp_conn->rx_tfm)
                        crypto_free_tfm(tcp_conn->rx_tfm);
                if (tcp_conn->data_tx_tfm)
                        crypto_free_tfm(tcp_conn->data_tx_tfm);
                if (tcp_conn->data_rx_tfm)
                        crypto_free_tfm(tcp_conn->data_rx_tfm);
        }

        /* free conn->data, size = MaxRecvDataSegmentLength */
        if (tcp_conn->data_size <= PAGE_SIZE)
                kfree(tcp_conn->data);
        else
                free_pages((unsigned long)tcp_conn->data,
                           get_order(tcp_conn->data_size));
        kfree(tcp_conn);
}

static int
iscsi_tcp_conn_bind(struct iscsi_cls_session *cls_session,
                    struct iscsi_cls_conn *cls_conn, uint64_t transport_eph,
                    int is_leading)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct sock *sk;
        struct socket *sock;
        int err;

        /* lookup for existing socket */
        sock = sockfd_lookup((int)transport_eph, &err);
        if (!sock) {
                printk(KERN_ERR "iscsi_tcp: sockfd_lookup failed %d\n", err);
                return -EEXIST;
        }

        err = iscsi_conn_bind(cls_session, cls_conn, is_leading);
        if (err)
                return err;

        /* bind iSCSI connection and socket */
        tcp_conn->sock = sock;

        /* setup Socket parameters */
        sk = sock->sk;
        sk->sk_reuse = 1;
        sk->sk_sndtimeo = 15 * HZ; /* FIXME: make it configurable */
        sk->sk_allocation = GFP_ATOMIC;

        /* FIXME: disable Nagle's algorithm */

        /*
         * Intercept TCP callbacks for sendfile like receive
         * processing.
         */
        conn->recv_lock = &sk->sk_callback_lock;
        iscsi_conn_set_callbacks(conn);
        tcp_conn->sendpage = tcp_conn->sock->ops->sendpage;
        /*
         * set receive state machine into initial state
         */
        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;

        return 0;
}

static void
iscsi_tcp_cleanup_ctask(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_r2t_info *r2t;

        /* flush ctask's r2t queues */
        while (__kfifo_get(tcp_ctask->r2tqueue, (void*)&r2t, sizeof(void*)))
                __kfifo_put(tcp_ctask->r2tpool.queue, (void*)&r2t,
                            sizeof(void*));

        __iscsi_ctask_cleanup(conn, ctask);
}

static void
iscsi_tcp_suspend_conn_rx(struct iscsi_conn *conn)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct sock *sk;

        if (!tcp_conn->sock)
                return;

        sk = tcp_conn->sock->sk;
        write_lock_bh(&sk->sk_callback_lock);
        set_bit(ISCSI_SUSPEND_BIT, &conn->suspend_rx);
        write_unlock_bh(&sk->sk_callback_lock);
}

static void
iscsi_tcp_terminate_conn(struct iscsi_conn *conn)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

        if (!tcp_conn->sock)
                return;

        sock_hold(tcp_conn->sock->sk);
        iscsi_conn_restore_callbacks(conn);
        sock_put(tcp_conn->sock->sk);

        sock_release(tcp_conn->sock);
        tcp_conn->sock = NULL;
        conn->recv_lock = NULL;
}

/* called with host lock */
static void
iscsi_tcp_mgmt_init(struct iscsi_conn *conn, struct iscsi_mgmt_task *mtask,
                    char *data, uint32_t data_size)
{
        struct iscsi_tcp_mgmt_task *tcp_mtask = mtask->dd_data;

        iscsi_buf_init_iov(&tcp_mtask->headbuf, (char*)mtask->hdr,
                           sizeof(struct iscsi_hdr));
        tcp_mtask->xmstate = XMSTATE_IMM_HDR;

        if (mtask->data_count)
                iscsi_buf_init_iov(&tcp_mtask->sendbuf, (char*)mtask->data,
                                    mtask->data_count);
}

static int
iscsi_r2tpool_alloc(struct iscsi_session *session)
{
        int i;
        int cmd_i;

        /*
         * initialize per-task: R2T pool and xmit queue
         */
        for (cmd_i = 0; cmd_i < session->cmds_max; cmd_i++) {
                struct iscsi_cmd_task *ctask = session->cmds[cmd_i];
                struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

                /*
                 * pre-allocated x4 as much r2ts to handle race when
                 * target acks DataOut faster than we data_xmit() queues
                 * could replenish r2tqueue.
                 */

                /* R2T pool */
                if (iscsi_pool_init(&tcp_ctask->r2tpool, session->max_r2t * 4,
                                    (void***)&tcp_ctask->r2ts,
                                    sizeof(struct iscsi_r2t_info))) {
                        goto r2t_alloc_fail;
                }

                /* R2T xmit queue */
                tcp_ctask->r2tqueue = kfifo_alloc(
                      session->max_r2t * 4 * sizeof(void*), GFP_KERNEL, NULL);
                if (tcp_ctask->r2tqueue == ERR_PTR(-ENOMEM)) {
                        iscsi_pool_free(&tcp_ctask->r2tpool,
                                        (void**)tcp_ctask->r2ts);
                        goto r2t_alloc_fail;
                }
        }

        return 0;

r2t_alloc_fail:
        for (i = 0; i < cmd_i; i++) {
                struct iscsi_cmd_task *ctask = session->cmds[i];
                struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

                kfifo_free(tcp_ctask->r2tqueue);
                iscsi_pool_free(&tcp_ctask->r2tpool,
                                (void**)tcp_ctask->r2ts);
        }
        return -ENOMEM;
}

static void
iscsi_r2tpool_free(struct iscsi_session *session)
{
        int i;

        for (i = 0; i < session->cmds_max; i++) {
                struct iscsi_cmd_task *ctask = session->cmds[i];
                struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

                kfifo_free(tcp_ctask->r2tqueue);
                iscsi_pool_free(&tcp_ctask->r2tpool,
                                (void**)tcp_ctask->r2ts);
        }
}

static int
iscsi_conn_set_param(struct iscsi_cls_conn *cls_conn, enum iscsi_param param,
                     uint32_t value)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        struct iscsi_session *session = conn->session;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

        switch(param) {
        case ISCSI_PARAM_MAX_RECV_DLENGTH: {
                char *saveptr = tcp_conn->data;
                gfp_t flags = GFP_KERNEL;

                if (tcp_conn->data_size >= value) {
                        conn->max_recv_dlength = value;
                        break;
                }

                spin_lock_bh(&session->lock);
                if (conn->stop_stage == STOP_CONN_RECOVER)
                        flags = GFP_ATOMIC;
                spin_unlock_bh(&session->lock);

                if (value <= PAGE_SIZE)
                        tcp_conn->data = kmalloc(value, flags);
                else
                        tcp_conn->data = (void*)__get_free_pages(flags,
                                                             get_order(value));
                if (tcp_conn->data == NULL) {
                        tcp_conn->data = saveptr;
                        return -ENOMEM;
                }
                if (tcp_conn->data_size <= PAGE_SIZE)
                        kfree(saveptr);
                else
                        free_pages((unsigned long)saveptr,
                                   get_order(tcp_conn->data_size));
                conn->max_recv_dlength = value;
                tcp_conn->data_size = value;
                }
                break;
        case ISCSI_PARAM_MAX_XMIT_DLENGTH:
                conn->max_xmit_dlength =  value;
                break;
        case ISCSI_PARAM_HDRDGST_EN:
                conn->hdrdgst_en = value;
                tcp_conn->hdr_size = sizeof(struct iscsi_hdr);
                if (conn->hdrdgst_en) {
                        tcp_conn->hdr_size += sizeof(__u32);
                        if (!tcp_conn->tx_tfm)
                                tcp_conn->tx_tfm = crypto_alloc_tfm("crc32c",
                                                                    0);
                        if (!tcp_conn->tx_tfm)
                                return -ENOMEM;
                        if (!tcp_conn->rx_tfm)
                                tcp_conn->rx_tfm = crypto_alloc_tfm("crc32c",
                                                                    0);
                        if (!tcp_conn->rx_tfm) {
                                crypto_free_tfm(tcp_conn->tx_tfm);
                                return -ENOMEM;
                        }
                } else {
                        if (tcp_conn->tx_tfm)
                                crypto_free_tfm(tcp_conn->tx_tfm);
                        if (tcp_conn->rx_tfm)
                                crypto_free_tfm(tcp_conn->rx_tfm);
                }
                break;
        case ISCSI_PARAM_DATADGST_EN:
                conn->datadgst_en = value;
                if (conn->datadgst_en) {
                        if (!tcp_conn->data_tx_tfm)
                                tcp_conn->data_tx_tfm =
                                    crypto_alloc_tfm("crc32c", 0);
                        if (!tcp_conn->data_tx_tfm)
                                return -ENOMEM;
                        if (!tcp_conn->data_rx_tfm)
                                tcp_conn->data_rx_tfm =
                                    crypto_alloc_tfm("crc32c", 0);
                        if (!tcp_conn->data_rx_tfm) {
                                crypto_free_tfm(tcp_conn->data_tx_tfm);
                                return -ENOMEM;
                        }
                } else {
                        if (tcp_conn->data_tx_tfm)
                                crypto_free_tfm(tcp_conn->data_tx_tfm);
                        if (tcp_conn->data_rx_tfm)
                                crypto_free_tfm(tcp_conn->data_rx_tfm);
                }
                tcp_conn->sendpage = conn->datadgst_en ?
                        sock_no_sendpage : tcp_conn->sock->ops->sendpage;
                break;
        case ISCSI_PARAM_INITIAL_R2T_EN:
                session->initial_r2t_en = value;
                break;
        case ISCSI_PARAM_MAX_R2T:
                if (session->max_r2t == roundup_pow_of_two(value))
                        break;
                iscsi_r2tpool_free(session);
                session->max_r2t = value;
                if (session->max_r2t & (session->max_r2t - 1))
                        session->max_r2t = roundup_pow_of_two(session->max_r2t);
                if (iscsi_r2tpool_alloc(session))
                        return -ENOMEM;
                break;
        case ISCSI_PARAM_IMM_DATA_EN:
                session->imm_data_en = value;
                break;
        case ISCSI_PARAM_FIRST_BURST:
                session->first_burst = value;
                break;
        case ISCSI_PARAM_MAX_BURST:
                session->max_burst = value;
                break;
        case ISCSI_PARAM_PDU_INORDER_EN:
                session->pdu_inorder_en = value;
                break;
        case ISCSI_PARAM_DATASEQ_INORDER_EN:
                session->dataseq_inorder_en = value;
                break;
        case ISCSI_PARAM_ERL:
                session->erl = value;
                break;
        case ISCSI_PARAM_IFMARKER_EN:
                BUG_ON(value);
                session->ifmarker_en = value;
                break;
        case ISCSI_PARAM_OFMARKER_EN:
                BUG_ON(value);
                session->ofmarker_en = value;
                break;
        case ISCSI_PARAM_EXP_STATSN:
                conn->exp_statsn = value;
                break;
        default:
                break;
        }

        return 0;
}

static int
iscsi_session_get_param(struct iscsi_cls_session *cls_session,
                        enum iscsi_param param, uint32_t *value)
{
        struct Scsi_Host *shost = iscsi_session_to_shost(cls_session);
        struct iscsi_session *session = iscsi_hostdata(shost->hostdata);

        switch(param) {
        case ISCSI_PARAM_INITIAL_R2T_EN:
                *value = session->initial_r2t_en;
                break;
        case ISCSI_PARAM_MAX_R2T:
                *value = session->max_r2t;
                break;
        case ISCSI_PARAM_IMM_DATA_EN:
                *value = session->imm_data_en;
                break;
        case ISCSI_PARAM_FIRST_BURST:
                *value = session->first_burst;
                break;
        case ISCSI_PARAM_MAX_BURST:
                *value = session->max_burst;
                break;
        case ISCSI_PARAM_PDU_INORDER_EN:
                *value = session->pdu_inorder_en;
                break;
        case ISCSI_PARAM_DATASEQ_INORDER_EN:
                *value = session->dataseq_inorder_en;
                break;
        case ISCSI_PARAM_ERL:
                *value = session->erl;
                break;
        case ISCSI_PARAM_IFMARKER_EN:
                *value = session->ifmarker_en;
                break;
        case ISCSI_PARAM_OFMARKER_EN:
                *value = session->ofmarker_en;
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int
iscsi_conn_get_param(struct iscsi_cls_conn *cls_conn,
                     enum iscsi_param param, uint32_t *value)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct inet_sock *inet;

        switch(param) {
        case ISCSI_PARAM_MAX_RECV_DLENGTH:
                *value = conn->max_recv_dlength;
                break;
        case ISCSI_PARAM_MAX_XMIT_DLENGTH:
                *value = conn->max_xmit_dlength;
                break;
        case ISCSI_PARAM_HDRDGST_EN:
                *value = conn->hdrdgst_en;
                break;
        case ISCSI_PARAM_DATADGST_EN:
                *value = conn->datadgst_en;
                break;
        case ISCSI_PARAM_CONN_PORT:
                mutex_lock(&conn->xmitmutex);
                if (!tcp_conn->sock) {
                        mutex_unlock(&conn->xmitmutex);
                        return -EINVAL;
                }

                inet = inet_sk(tcp_conn->sock->sk);
                *value = be16_to_cpu(inet->dport);
                mutex_unlock(&conn->xmitmutex);
        case ISCSI_PARAM_EXP_STATSN:
                *value = conn->exp_statsn;
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int
iscsi_conn_get_str_param(struct iscsi_cls_conn *cls_conn,
                         enum iscsi_param param, char *buf)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct sock *sk;
        struct inet_sock *inet;
        struct ipv6_pinfo *np;
        int len = 0;

        switch (param) {
        case ISCSI_PARAM_CONN_ADDRESS:
                mutex_lock(&conn->xmitmutex);
                if (!tcp_conn->sock) {
                        mutex_unlock(&conn->xmitmutex);
                        return -EINVAL;
                }

                sk = tcp_conn->sock->sk;
                if (sk->sk_family == PF_INET) {
                        inet = inet_sk(sk);
                        len = sprintf(buf, "%u.%u.%u.%u\n",
                                      NIPQUAD(inet->daddr));
                } else {
                        np = inet6_sk(sk);
                        len = sprintf(buf,
                                "%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x\n",
                                NIP6(np->daddr));
                }
                mutex_unlock(&conn->xmitmutex);
                break;
        default:
                return -EINVAL;
        }

        return len;
}

static void
iscsi_conn_get_stats(struct iscsi_cls_conn *cls_conn, struct iscsi_stats *stats)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

        stats->txdata_octets = conn->txdata_octets;
        stats->rxdata_octets = conn->rxdata_octets;
        stats->scsicmd_pdus = conn->scsicmd_pdus_cnt;
        stats->dataout_pdus = conn->dataout_pdus_cnt;
        stats->scsirsp_pdus = conn->scsirsp_pdus_cnt;
        stats->datain_pdus = conn->datain_pdus_cnt;
        stats->r2t_pdus = conn->r2t_pdus_cnt;
        stats->tmfcmd_pdus = conn->tmfcmd_pdus_cnt;
        stats->tmfrsp_pdus = conn->tmfrsp_pdus_cnt;
        stats->custom_length = 3;
        strcpy(stats->custom[0].desc, "tx_sendpage_failures");
        stats->custom[0].value = tcp_conn->sendpage_failures_cnt;
        strcpy(stats->custom[1].desc, "rx_discontiguous_hdr");
        stats->custom[1].value = tcp_conn->discontiguous_hdr_cnt;
        strcpy(stats->custom[2].desc, "eh_abort_cnt");
        stats->custom[2].value = conn->eh_abort_cnt;
}

static struct iscsi_cls_session *
iscsi_tcp_session_create(struct iscsi_transport *iscsit,
                         struct scsi_transport_template *scsit,
                         uint32_t initial_cmdsn, uint32_t *hostno)
{
        struct iscsi_cls_session *cls_session;
        struct iscsi_session *session;
        uint32_t hn;
        int cmd_i;

        cls_session = iscsi_session_setup(iscsit, scsit,
                                         sizeof(struct iscsi_tcp_cmd_task),
                                         sizeof(struct iscsi_tcp_mgmt_task),
                                         initial_cmdsn, &hn);
        if (!cls_session)
                return NULL;
        *hostno = hn;

        session = class_to_transport_session(cls_session);
        for (cmd_i = 0; cmd_i < session->cmds_max; cmd_i++) {
                struct iscsi_cmd_task *ctask = session->cmds[cmd_i];
                struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

                ctask->hdr = &tcp_ctask->hdr;
        }

        for (cmd_i = 0; cmd_i < session->mgmtpool_max; cmd_i++) {
                struct iscsi_mgmt_task *mtask = session->mgmt_cmds[cmd_i];
                struct iscsi_tcp_mgmt_task *tcp_mtask = mtask->dd_data;

                mtask->hdr = &tcp_mtask->hdr;
        }

        if (iscsi_r2tpool_alloc(class_to_transport_session(cls_session)))
                goto r2tpool_alloc_fail;

        return cls_session;

r2tpool_alloc_fail:
        iscsi_session_teardown(cls_session);
        return NULL;
}

static void iscsi_tcp_session_destroy(struct iscsi_cls_session *cls_session)
{
        iscsi_r2tpool_free(class_to_transport_session(cls_session));
        iscsi_session_teardown(cls_session);
}

static struct scsi_host_template iscsi_sht = {
        .name                   = "iSCSI Initiator over TCP/IP, v"
                                  ISCSI_TCP_VERSION,
        .queuecommand           = iscsi_queuecommand,
        .change_queue_depth     = iscsi_change_queue_depth,
        .can_queue              = ISCSI_XMIT_CMDS_MAX - 1,
        .sg_tablesize           = ISCSI_SG_TABLESIZE,
        .cmd_per_lun            = ISCSI_DEF_CMD_PER_LUN,
        .eh_abort_handler       = iscsi_eh_abort,
        .eh_host_reset_handler  = iscsi_eh_host_reset,
        .use_clustering         = DISABLE_CLUSTERING,
        .proc_name              = "iscsi_tcp",
        .this_id                = -1,
};

static struct iscsi_transport iscsi_tcp_transport = {
        .owner                  = THIS_MODULE,
        .name                   = "tcp",
        .caps                   = CAP_RECOVERY_L0 | CAP_MULTI_R2T | CAP_HDRDGST
                                  | CAP_DATADGST,
        .param_mask             = ISCSI_MAX_RECV_DLENGTH |
                                  ISCSI_MAX_XMIT_DLENGTH |
                                  ISCSI_HDRDGST_EN |
                                  ISCSI_DATADGST_EN |
                                  ISCSI_INITIAL_R2T_EN |
                                  ISCSI_MAX_R2T |
                                  ISCSI_IMM_DATA_EN |
                                  ISCSI_FIRST_BURST |
                                  ISCSI_MAX_BURST |
                                  ISCSI_PDU_INORDER_EN |
                                  ISCSI_DATASEQ_INORDER_EN |
                                  ISCSI_ERL |
                                  ISCSI_CONN_PORT |
                                  ISCSI_CONN_ADDRESS |
                                  ISCSI_EXP_STATSN,
        .host_template          = &iscsi_sht,
        .conndata_size          = sizeof(struct iscsi_conn),
        .max_conn               = 1,
        .max_cmd_len            = ISCSI_TCP_MAX_CMD_LEN,
        /* session management */
        .create_session         = iscsi_tcp_session_create,
        .destroy_session        = iscsi_tcp_session_destroy,
        /* connection management */
        .create_conn            = iscsi_tcp_conn_create,
        .bind_conn              = iscsi_tcp_conn_bind,
        .destroy_conn           = iscsi_tcp_conn_destroy,
        .set_param              = iscsi_conn_set_param,
        .get_conn_param         = iscsi_conn_get_param,
        .get_conn_str_param     = iscsi_conn_get_str_param,
        .get_session_param      = iscsi_session_get_param,
        .start_conn             = iscsi_conn_start,
        .stop_conn              = iscsi_conn_stop,
        /* these are called as part of conn recovery */
        .suspend_conn_recv      = iscsi_tcp_suspend_conn_rx,
        .terminate_conn         = iscsi_tcp_terminate_conn,
        /* IO */
        .send_pdu               = iscsi_conn_send_pdu,
        .get_stats              = iscsi_conn_get_stats,
        .init_cmd_task          = iscsi_tcp_cmd_init,
        .init_mgmt_task         = iscsi_tcp_mgmt_init,
        .xmit_cmd_task          = iscsi_tcp_ctask_xmit,
        .xmit_mgmt_task         = iscsi_tcp_mtask_xmit,
        .cleanup_cmd_task       = iscsi_tcp_cleanup_ctask,
        /* recovery */
        .session_recovery_timedout = iscsi_session_recovery_timedout,
};

static int __init
iscsi_tcp_init(void)
{
        if (iscsi_max_lun < 1) {
                printk(KERN_ERR "iscsi_tcp: Invalid max_lun value of %u\n",
                       iscsi_max_lun);
                return -EINVAL;
        }
        iscsi_tcp_transport.max_lun = iscsi_max_lun;

        if (!iscsi_register_transport(&iscsi_tcp_transport))
                return -ENODEV;

        return 0;
}

static void __exit
iscsi_tcp_exit(void)
{
        iscsi_unregister_transport(&iscsi_tcp_transport);
}

module_init(iscsi_tcp_init);
module_exit(iscsi_tcp_exit);