SG: Change sg_set_page() to take length and offset argument

[safe/jmp/linux-2.6] / 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/file.h>
#include <linux/blkdev.h>
#include <linux/crypto.h>
#include <linux/delay.h>
#include <linux/kfifo.h>
#include <linux/scatterlist.h>
#include <net/tcp.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi.h>
#include <scsi/scsi_transport_iscsi.h>

#include "iscsi_tcp.h"

MODULE_AUTHOR("Dmitry Yusupov <dmitry_yus@yahoo.com>, "
              "Alex Aizman <itn780@yahoo.com>");
MODULE_DESCRIPTION("iSCSI/TCP data-path");
MODULE_LICENSE("GPL");
/* #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)
{
        sg_init_one(&ibuf->sg, vbuf, size);
        ibuf->sent = 0;
        ibuf->use_sendmsg = 1;
}

static inline void
iscsi_buf_init_sg(struct iscsi_buf *ibuf, struct scatterlist *sg)
{
        sg_init_table(&ibuf->sg, 1);
        sg_set_page(&ibuf->sg, sg_page(sg), sg->length, sg->offset);
        /*
         * Fastpath: sg element fits into single page
         */
        if (sg->length + sg->offset <= PAGE_SIZE && !PageSlab(sg_page(sg)))
                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_hash_digest(&tcp_conn->tx_hash, &buf->sg, buf->sg.length, crc);
        buf->sg.length += sizeof(u32);
}

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_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;
        struct scsi_cmnd *sc;

        /* 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*));
                debug_scsi("iscsi_tcp_cleanup_ctask pending r2t dropped\n");
        }

        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)
{
        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;
        struct scsi_cmnd *sc = ctask->sc;
        int datasn = be32_to_cpu(rhdr->datasn);

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

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

        if (tcp_ctask->exp_datasn != datasn) {
                debug_tcp("%s: ctask->exp_datasn(%d) != rhdr->datasn(%d)\n",
                          __FUNCTION__, tcp_ctask->exp_datasn, datasn);
                return ISCSI_ERR_DATASN;
        }

        tcp_ctask->exp_datasn++;

        tcp_ctask->data_offset = be32_to_cpu(rhdr->offset);
        if (tcp_ctask->data_offset + tcp_conn->in.datalen > scsi_bufflen(sc)) {
                debug_tcp("%s: data_offset(%d) + data_len(%d) > total_length_in(%d)\n",
                          __FUNCTION__, tcp_ctask->data_offset,
                          tcp_conn->in.datalen, scsi_bufflen(sc));
                return ISCSI_ERR_DATA_OFFSET;
        }

        if (rhdr->flags & ISCSI_FLAG_DATA_STATUS) {
                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 <= scsi_bufflen(sc)) {
                                scsi_set_resid(sc, 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) {
                        scsi_set_resid(sc, 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;
        int i, sg_count = 0;
        struct scatterlist *sg;

        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));

        sg = scsi_sglist(sc);
        r2t->sg = NULL;
        for (i = 0; i < scsi_sg_count(sc); 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);
}

/**
 * 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) {
                printk(KERN_ERR "iscsi_tcp: invalid R2t with datalen %d\n",
                       tcp_conn->in.datalen);
                return ISCSI_ERR_DATALEN;
        }

        if (tcp_ctask->exp_datasn != r2tsn){
                debug_tcp("%s: ctask->exp_datasn(%d) != rhdr->r2tsn(%d)\n",
                          __FUNCTION__, tcp_ctask->exp_datasn, r2tsn);
                return ISCSI_ERR_R2TSN;
        }

        /* fill-in new R2T associated with the task */
        spin_lock(&session->lock);
        iscsi_update_cmdsn(session, (struct iscsi_nopin*)rhdr);

        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) {
                printk(KERN_ERR "iscsi_tcp: invalid R2T with zero data len\n");
                spin_unlock(&session->lock);
                return ISCSI_ERR_DATALEN;
        }

        if (r2t->data_length > session->max_burst)
                debug_scsi("invalid R2T with data len %u and max burst %u."
                           "Attempting to execute request.\n",
                            r2t->data_length, session->max_burst);

        r2t->data_offset = be32_to_cpu(rhdr->data_offset);
        if (r2t->data_offset + r2t->data_length > scsi_bufflen(ctask->sc)) {
                spin_unlock(&session->lock);
                printk(KERN_ERR "iscsi_tcp: invalid R2T with data len %u at "
                       "offset %u and total length %d\n", r2t->data_length,
                       r2t->data_offset, scsi_bufflen(ctask->sc));
                return ISCSI_ERR_DATALEN;
        }

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

        iscsi_solicit_data_init(conn, ctask, r2t);

        tcp_ctask->exp_datasn = r2tsn + 1;
        __kfifo_put(tcp_ctask->r2tqueue, (void*)&r2t, sizeof(void*));
        tcp_ctask->xmstate |= XMSTATE_SOL_HDR_INIT;
        list_move_tail(&ctask->running, &conn->xmitqueue);

        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_hash_digest(&tcp_conn->rx_hash, &sg, sg.length,
                                   (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);
                if (rc)
                        return rc;
                /* 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);
                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_REJECT:
        case ISCSI_OP_ASYNC_EVENT:
                /*
                 * It is possible that we could get a PDU with a buffer larger
                 * than 8K, but there are no targets that currently do this.
                 * For now we fail until we find a vendor that needs it
                 */
                if (ISCSI_DEF_MAX_RECV_SEG_LEN <
                    tcp_conn->in.datalen) {
                        printk(KERN_ERR "iscsi_tcp: received buffer of len %u "
                              "but conn buffer is only %u (opcode %0x)\n",
                              tcp_conn->in.datalen,
                              ISCSI_DEF_MAX_RECV_SEG_LEN, opcode);
                        rc = ISCSI_ERR_PROTO;
                        break;
                }

                if (tcp_conn->in.datalen)
                        goto copy_hdr;
        /* fall through */
        case ISCSI_OP_LOGOUT_RSP:
        case ISCSI_OP_NOOP_IN:
        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);
        unsigned 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 > scsi_bufflen(ctask->sc));

        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_conn *conn, int buf_size)
{
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        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*)conn->data + 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 hash_desc *desc, struct scatterlist *sg,
                         int offset, int length)
{
        struct scatterlist temp;

        memcpy(&temp, sg, sizeof(struct scatterlist));
        temp.offset = offset;
        temp.length = length;
        crypto_hash_update(desc, &temp, length);
}

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_hash_update(&tcp_conn->rx_hash, &tmp, len);
}

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);

        offset = tcp_ctask->data_offset;
        sg = scsi_sglist(sc);

        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 < scsi_sg_count(sc); i++) {
                char *dest;

                dest = kmap_atomic(sg_page(&sg[i]), 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_hash_update(
                                                        &tcp_conn->rx_hash,
                                                        &sg[i], sg[i].length);
                                else
                                        partial_sg_digest_update(
                                                        &tcp_conn->rx_hash,
                                                        &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->rx_hash,
                                                         &sg[i],
                                                         sg[i].offset,
                                                         sg[i].length-rc);
                        rc = 0;
                        break;
                }

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

        /* 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 flags 0x%x]\n",
                           (long)sc, sc->result, ctask->itt,
                           tcp_conn->in.hdr->flags);
                spin_lock(&conn->session->lock);
                __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:
        case ISCSI_OP_TEXT_RSP:
        case ISCSI_OP_LOGIN_RSP:
        case ISCSI_OP_ASYNC_EVENT:
        case ISCSI_OP_REJECT:
                /*
                 * Collect data segment to the connection's data
                 * placeholder
                 */
                if (iscsi_tcp_copy(conn, tcp_conn->in.datalen)) {
                        rc = -EAGAIN;
                        goto exit;
                }

                rc = iscsi_complete_pdu(conn, tcp_conn->in.hdr, conn->data,
                                        tcp_conn->in.datalen);
                if (!rc && conn->datadgst_en && opcode != ISCSI_OP_LOGIN_RSP)
                        iscsi_recv_digest_update(tcp_conn, 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, ISCSI_ERR_CONN_FAILED);
                                return 0;
                       }
                }

                /*
                 * Verify and process incoming PDU header.
                 */
                rc = iscsi_tcp_hdr_recv(conn);
                if (!rc && tcp_conn->in.datalen) {
                        if (conn->datadgst_en)
                                crypto_hash_init(&tcp_conn->rx_hash);
                        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 &&
            tcp_conn->in.copy) {
                uint32_t recv_digest;

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

                if (!tcp_conn->data_copied) {
                        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_hash_update(&tcp_conn->rx_hash,
                                                   &sg, sg.length);
                        }
                        crypto_hash_final(&tcp_conn->rx_hash,
                                          (u8 *) &tcp_conn->in.datadgst);
                        debug_tcp("rx digest 0x%x\n", tcp_conn->in.datadgst);
                }

                rc = iscsi_tcp_copy(conn, sizeof(uint32_t));
                if (rc) {
                        if (rc == -EAGAIN)
                                goto again;
                        iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
                        return 0;
                }

                memcpy(&recv_digest, conn->data, sizeof(uint32_t));
                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, ISCSI_ERR_CONN_FAILED);
                        return 0;
                }

                if (tcp_conn->in.padding)
                        tcp_conn->in_progress = IN_PROGRESS_PAD_RECV;
                else if (conn->datadgst_en)
                        tcp_conn->in_progress = IN_PROGRESS_DDIGEST_RECV;
                else
                        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
                tcp_conn->data_copied = 0;
        }

        if (tcp_conn->in_progress == IN_PROGRESS_PAD_RECV &&
            tcp_conn->in.copy) {
                int copylen = min(tcp_conn->in.padding - tcp_conn->data_copied,
                                  tcp_conn->in.copy);

                tcp_conn->in.copy -= copylen;
                tcp_conn->in.offset += copylen;
                tcp_conn->data_copied += copylen;

                if (tcp_conn->data_copied != tcp_conn->in.padding)
                        tcp_conn->in_progress = IN_PROGRESS_PAD_RECV;
                else if (conn->datadgst_en)
                        tcp_conn->in_progress = IN_PROGRESS_DDIGEST_RECV;
                else
                        tcp_conn->in_progress = IN_PROGRESS_WAIT_HEADER;
                tcp_conn->data_copied = 0;
        }

        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);
        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_tcp_conn *tcp_conn)
{
        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, res;

        /*
         * 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)
                res = sock_no_sendpage(sk, sg_page(&buf->sg), offset, size, flags);
        else
                res = tcp_conn->sendpage(sk, sg_page(&buf->sg), offset, size, flags);

        if (res >= 0) {
                conn->txdata_octets += res;
                buf->sent += res;
                return res;
        }

        tcp_conn->sendpage_failures_cnt++;
        if (res == -EAGAIN)
                res = -ENOBUFS;
        else
                iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
        return res;
}

/**
 * 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)
{
        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) {
                if (size != res)
                        return -EAGAIN;
                return 0;
        }

        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)
{
        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) {
                *count -= res;
                *sent += res;
                if (size != res)
                        return -EAGAIN;
                return 0;
        }

        return res;
}

static inline void
iscsi_data_digest_init(struct iscsi_tcp_conn *tcp_conn,
                      struct iscsi_tcp_cmd_task *tcp_ctask)
{
        crypto_hash_init(&tcp_conn->tx_hash);
        tcp_ctask->digest_count = 4;
}

/**
 * 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_data *hdr;
        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 (iscsi_buf_left(&r2t->sendbuf))
                return;

        iscsi_buf_init_sg(&r2t->sendbuf, r2t->sg);
        r2t->sg += 1;
}

static void iscsi_set_padding(struct iscsi_tcp_cmd_task *tcp_ctask,
                              unsigned long len)
{
        tcp_ctask->pad_count = len & (ISCSI_PAD_LEN - 1);
        if (!tcp_ctask->pad_count)
                return;

        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;
}

/**
 * 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 iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;

        BUG_ON(__kfifo_len(tcp_ctask->r2tqueue));
        tcp_ctask->xmstate = XMSTATE_CMD_HDR_INIT;
}

/**
 * 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 these states:
 *              XMSTATE_IMM_HDR_INIT    - calculate digest of PDU Header
 *              XMSTATE_IMM_HDR         - PDU Header xmit in progress
 *              XMSTATE_IMM_DATA        - PDU Data xmit in progress
 *              XMSTATE_IDLE            - management PDU is done
 **/
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;
        int rc;

        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_INIT) {
                iscsi_buf_init_iov(&tcp_mtask->headbuf, (char*)mtask->hdr,
                                   sizeof(struct iscsi_hdr));

                if (mtask->data_count) {
                        tcp_mtask->xmstate |= XMSTATE_IMM_DATA;
                        iscsi_buf_init_iov(&tcp_mtask->sendbuf,
                                           (char*)mtask->data,
                                           mtask->data_count);
                }

                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);

                tcp_mtask->sent = 0;
                tcp_mtask->xmstate &= ~XMSTATE_IMM_HDR_INIT;
                tcp_mtask->xmstate |= XMSTATE_IMM_HDR;
        }

        if (tcp_mtask->xmstate & XMSTATE_IMM_HDR) {
                rc = iscsi_sendhdr(conn, &tcp_mtask->headbuf,
                                   mtask->data_count);
                if (rc)
                        return rc;
                tcp_mtask->xmstate &= ~XMSTATE_IMM_HDR;
        }

        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 {
                        int rc;

                        rc = iscsi_sendpage(conn, &tcp_mtask->sendbuf,
                                        &mtask->data_count, &tcp_mtask->sent);
                        if (rc) {
                                tcp_mtask->xmstate |= XMSTATE_IMM_DATA;
                                return rc;
                        }
                } while (mtask->data_count);
        }

        BUG_ON(tcp_mtask->xmstate != XMSTATE_IDLE);
        if (mtask->hdr->itt == RESERVED_ITT) {
                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 int
iscsi_send_cmd_hdr(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
        struct scsi_cmnd *sc = ctask->sc;
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        int rc = 0;

        if (tcp_ctask->xmstate & XMSTATE_CMD_HDR_INIT) {
                tcp_ctask->sent = 0;
                tcp_ctask->sg_count = 0;
                tcp_ctask->exp_datasn = 0;

                if (sc->sc_data_direction == DMA_TO_DEVICE) {
                        struct scatterlist *sg = scsi_sglist(sc);

                        iscsi_buf_init_sg(&tcp_ctask->sendbuf, sg);
                        tcp_ctask->sg = sg + 1;
                        tcp_ctask->bad_sg = sg + scsi_sg_count(sc);

                        debug_scsi("cmd [itt 0x%x total %d imm_data %d "
                                   "unsol count %d, unsol offset %d]\n",
                                   ctask->itt, scsi_bufflen(sc),
                                   ctask->imm_count, ctask->unsol_count,
                                   ctask->unsol_offset);
                }

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

                if (conn->hdrdgst_en)
                        iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
                                         (u8*)tcp_ctask->hdrext);
                tcp_ctask->xmstate &= ~XMSTATE_CMD_HDR_INIT;
                tcp_ctask->xmstate |= XMSTATE_CMD_HDR_XMIT;
        }

        if (tcp_ctask->xmstate & XMSTATE_CMD_HDR_XMIT) {
                rc = iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->imm_count);
                if (rc)
                        return rc;
                tcp_ctask->xmstate &= ~XMSTATE_CMD_HDR_XMIT;

                if (sc->sc_data_direction != DMA_TO_DEVICE)
                        return 0;

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

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

                if (ctask->unsol_count)
                        tcp_ctask->xmstate |=
                                        XMSTATE_UNS_HDR | XMSTATE_UNS_INIT;
        }
        return rc;
}

static int
iscsi_send_padding(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;
        int sent = 0, rc;

        if (tcp_ctask->xmstate & XMSTATE_W_PAD) {
                iscsi_buf_init_iov(&tcp_ctask->sendbuf, (char*)&tcp_ctask->pad,
                                   tcp_ctask->pad_count);
                if (conn->datadgst_en)
                        crypto_hash_update(&tcp_conn->tx_hash,
                                           &tcp_ctask->sendbuf.sg,
                                           tcp_ctask->sendbuf.sg.length);
        } else if (!(tcp_ctask->xmstate & XMSTATE_W_RESEND_PAD))
                return 0;

        tcp_ctask->xmstate &= ~XMSTATE_W_PAD;
        tcp_ctask->xmstate &= ~XMSTATE_W_RESEND_PAD;
        debug_scsi("sending %d pad bytes for itt 0x%x\n",
                   tcp_ctask->pad_count, ctask->itt);
        rc = iscsi_sendpage(conn, &tcp_ctask->sendbuf, &tcp_ctask->pad_count,
                           &sent);
        if (rc) {
                debug_scsi("padding send failed %d\n", rc);
                tcp_ctask->xmstate |= XMSTATE_W_RESEND_PAD;
        }
        return rc;
}

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

        if (!conn->datadgst_en)
                return 0;

        tcp_ctask = ctask->dd_data;
        tcp_conn = conn->dd_data;

        if (!(tcp_ctask->xmstate & XMSTATE_W_RESEND_DATA_DIGEST)) {
                crypto_hash_final(&tcp_conn->tx_hash, (u8*)digest);
                iscsi_buf_init_iov(buf, (char*)digest, 4);
        }
        tcp_ctask->xmstate &= ~XMSTATE_W_RESEND_DATA_DIGEST;

        rc = iscsi_sendpage(conn, buf, &tcp_ctask->digest_count, &sent);
        if (!rc)
                debug_scsi("sent digest 0x%x for itt 0x%x\n", *digest,
                          ctask->itt);
        else {
                debug_scsi("sending digest 0x%x failed for itt 0x%x!\n",
                          *digest, ctask->itt);
                tcp_ctask->xmstate |= XMSTATE_W_RESEND_DATA_DIGEST;
        }
        return rc;
}

static int
iscsi_send_data(struct iscsi_cmd_task *ctask, struct iscsi_buf *sendbuf,
                struct scatterlist **sg, int *sent, int *count,
                struct iscsi_buf *digestbuf, uint32_t *digest)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_conn *conn = ctask->conn;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        int rc, buf_sent, offset;

        while (*count) {
                buf_sent = 0;
                offset = sendbuf->sent;

                rc = iscsi_sendpage(conn, sendbuf, count, &buf_sent);
                *sent = *sent + buf_sent;
                if (buf_sent && conn->datadgst_en)
                        partial_sg_digest_update(&tcp_conn->tx_hash,
                                &sendbuf->sg, sendbuf->sg.offset + offset,
                                buf_sent);
                if (!iscsi_buf_left(sendbuf) && *sg != tcp_ctask->bad_sg) {
                        iscsi_buf_init_sg(sendbuf, *sg);
                        *sg = *sg + 1;
                }

                if (rc)
                        return rc;
        }

        rc = iscsi_send_padding(conn, ctask);
        if (rc)
                return rc;

        return iscsi_send_digest(conn, ctask, digestbuf, digest);
}

static int
iscsi_send_unsol_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;
        int rc;

        tcp_ctask->xmstate |= XMSTATE_UNS_DATA;
        if (tcp_ctask->xmstate & XMSTATE_UNS_INIT) {
                dtask = &tcp_ctask->unsol_dtask;

                iscsi_prep_unsolicit_data_pdu(ctask, &dtask->hdr);
                iscsi_buf_init_iov(&tcp_ctask->headbuf, (char*)&dtask->hdr,
                                   sizeof(struct iscsi_hdr));
                if (conn->hdrdgst_en)
                        iscsi_hdr_digest(conn, &tcp_ctask->headbuf,
                                        (u8*)dtask->hdrext);

                tcp_ctask->xmstate &= ~XMSTATE_UNS_INIT;
                iscsi_set_padding(tcp_ctask, ctask->data_count);
        }

        rc = iscsi_sendhdr(conn, &tcp_ctask->headbuf, ctask->data_count);
        if (rc) {
                tcp_ctask->xmstate &= ~XMSTATE_UNS_DATA;
                tcp_ctask->xmstate |= XMSTATE_UNS_HDR;
                return rc;
        }

        if (conn->datadgst_en) {
                dtask = &tcp_ctask->unsol_dtask;
                iscsi_data_digest_init(ctask->conn->dd_data, tcp_ctask);
                dtask->digest = 0;
        }

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

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

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

        if (tcp_ctask->xmstate & XMSTATE_UNS_DATA) {
                struct iscsi_data_task *dtask = &tcp_ctask->unsol_dtask;
                int start = tcp_ctask->sent;

                rc = iscsi_send_data(ctask, &tcp_ctask->sendbuf, &tcp_ctask->sg,
                                     &tcp_ctask->sent, &ctask->data_count,
                                     &dtask->digestbuf, &dtask->digest);
                ctask->unsol_count -= tcp_ctask->sent - start;
                if (rc)
                        return rc;
                tcp_ctask->xmstate &= ~XMSTATE_UNS_DATA;
                /*
                 * Done with the Data-Out. Next, check if we need
                 * to send another unsolicited Data-Out.
                 */
                if (ctask->unsol_count) {
                        debug_scsi("sending more uns\n");
                        tcp_ctask->xmstate |= XMSTATE_UNS_INIT;
                        goto send_hdr;
                }
        }
        return 0;
}

static int iscsi_send_sol_pdu(struct iscsi_conn *conn,
                              struct iscsi_cmd_task *ctask)
{
        struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
        struct iscsi_session *session = conn->session;
        struct iscsi_r2t_info *r2t;
        struct iscsi_data_task *dtask;
        int left, rc;

        if (tcp_ctask->xmstate & XMSTATE_SOL_HDR_INIT) {
                if (!tcp_ctask->r2t) {
                        spin_lock_bh(&session->lock);
                        __kfifo_get(tcp_ctask->r2tqueue, (void*)&tcp_ctask->r2t,
                                    sizeof(void*));
                        spin_unlock_bh(&session->lock);
                }
send_hdr:
                r2t = tcp_ctask->r2t;
                dtask = &r2t->dtask;

                if (conn->hdrdgst_en)
                        iscsi_hdr_digest(conn, &r2t->headbuf,
                                        (u8*)dtask->hdrext);
                tcp_ctask->xmstate &= ~XMSTATE_SOL_HDR_INIT;
                tcp_ctask->xmstate |= XMSTATE_SOL_HDR;
        }

        if (tcp_ctask->xmstate & XMSTATE_SOL_HDR) {
                r2t = tcp_ctask->r2t;
                dtask = &r2t->dtask;

                rc = iscsi_sendhdr(conn, &r2t->headbuf, r2t->data_count);
                if (rc)
                        return rc;
                tcp_ctask->xmstate &= ~XMSTATE_SOL_HDR;
                tcp_ctask->xmstate |= XMSTATE_SOL_DATA;

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

                iscsi_set_padding(tcp_ctask, r2t->data_count);
                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) {
                r2t = tcp_ctask->r2t;
                dtask = &r2t->dtask;

                rc = iscsi_send_data(ctask, &r2t->sendbuf, &r2t->sg,
                                     &r2t->sent, &r2t->data_count,
                                     &dtask->digestbuf, &dtask->digest);
                if (rc)
                        return rc;
                tcp_ctask->xmstate &= ~XMSTATE_SOL_DATA;

                /*
                 * 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) {
                        iscsi_solicit_data_cont(conn, ctask, r2t, left);
                        goto send_hdr;
                }

                /*
                 * Done with this R2T. Check if there are more
                 * outstanding R2Ts ready to be processed.
                 */
                spin_lock_bh(&session->lock);
                tcp_ctask->r2t = NULL;
                __kfifo_put(tcp_ctask->r2tpool.queue, (void*)&r2t,
                            sizeof(void*));
                if (__kfifo_get(tcp_ctask->r2tqueue, (void*)&r2t,
                                sizeof(void*))) {
                        tcp_ctask->r2t = r2t;
                        spin_unlock_bh(&session->lock);
                        goto send_hdr;
                }
                spin_unlock_bh(&session->lock);
        }
        return 0;
}

/**
 * iscsi_tcp_ctask_xmit - xmit normal PDU task
 * @conn: iscsi connection
 * @ctask: iscsi command task
 *
 * Notes:
 *      The function can return -EAGAIN in which case caller must
 *      call it again later, or recover. '0' return code means successful
 *      xmit.
 *      The function is devided to logical helpers (above) for the different
 *      xmit stages.
 *
 *iscsi_send_cmd_hdr()
 *      XMSTATE_CMD_HDR_INIT - prepare Header and Data buffers Calculate
 *                             Header Digest
 *      XMSTATE_CMD_HDR_XMIT - Transmit header in progress
 *
 *iscsi_send_padding
 *      XMSTATE_W_PAD        - Prepare and send pading
 *      XMSTATE_W_RESEND_PAD - retry send pading
 *
 *iscsi_send_digest
 *      XMSTATE_W_RESEND_DATA_DIGEST - Finalize and send Data Digest
 *      XMSTATE_W_RESEND_DATA_DIGEST - retry sending digest
 *
 *iscsi_send_unsol_hdr
 *      XMSTATE_UNS_INIT     - prepare un-solicit data header and digest
 *      XMSTATE_UNS_HDR      - send un-solicit header
 *
 *iscsi_send_unsol_pdu
 *      XMSTATE_UNS_DATA     - send un-solicit data in progress
 *
 *iscsi_send_sol_pdu
 *      XMSTATE_SOL_HDR_INIT - solicit data header and digest initialize
 *      XMSTATE_SOL_HDR      - send solicit header
 *      XMSTATE_SOL_DATA     - send solicit data
 *
 *iscsi_tcp_ctask_xmit
 *      XMSTATE_IMM_DATA     - xmit managment data (??)
 **/
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);

        rc = iscsi_send_cmd_hdr(conn, ctask);
        if (rc)
                return rc;
        if (ctask->sc->sc_data_direction != DMA_TO_DEVICE)
                return 0;

        if (tcp_ctask->xmstate & XMSTATE_IMM_DATA) {
                rc = iscsi_send_data(ctask, &tcp_ctask->sendbuf, &tcp_ctask->sg,
                                     &tcp_ctask->sent, &ctask->imm_count,
                                     &tcp_ctask->immbuf, &tcp_ctask->immdigest);
                if (rc)
                        return rc;
                tcp_ctask->xmstate &= ~XMSTATE_IMM_DATA;
        }

        rc = iscsi_send_unsol_pdu(conn, ctask);
        if (rc)
                return rc;

        rc = iscsi_send_sol_pdu(conn, ctask);
        if (rc)
                return rc;

        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 = ISCSI_DEF_MAX_RECV_SEG_LEN;

        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->tx_hash.tfm = crypto_alloc_hash("crc32c", 0,
                                                  CRYPTO_ALG_ASYNC);
        tcp_conn->tx_hash.flags = 0;
        if (IS_ERR(tcp_conn->tx_hash.tfm)) {
                printk(KERN_ERR "Could not create connection due to crc32c "
                       "loading error %ld. Make sure the crc32c module is "
                       "built as a module or into the kernel\n",
                        PTR_ERR(tcp_conn->tx_hash.tfm));
                goto free_tcp_conn;
        }

        tcp_conn->rx_hash.tfm = crypto_alloc_hash("crc32c", 0,
                                                  CRYPTO_ALG_ASYNC);
        tcp_conn->rx_hash.flags = 0;
        if (IS_ERR(tcp_conn->rx_hash.tfm)) {
                printk(KERN_ERR "Could not create connection due to crc32c "
                       "loading error %ld. Make sure the crc32c module is "
                       "built as a module or into the kernel\n",
                        PTR_ERR(tcp_conn->rx_hash.tfm));
                goto free_tx_tfm;
        }

        return cls_conn;

free_tx_tfm:
        crypto_free_hash(tcp_conn->tx_hash.tfm);
free_tcp_conn:
        kfree(tcp_conn);
tcp_conn_alloc_fail:
        iscsi_conn_teardown(cls_conn);
        return NULL;
}

static void
iscsi_tcp_release_conn(struct iscsi_conn *conn)
{
        struct iscsi_session *session = conn->session;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        struct socket *sock = tcp_conn->sock;

        if (!sock)
                return;

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

        spin_lock_bh(&session->lock);
        tcp_conn->sock = NULL;
        conn->recv_lock = NULL;
        spin_unlock_bh(&session->lock);
        sockfd_put(sock);
}

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;

        iscsi_tcp_release_conn(conn);
        iscsi_conn_teardown(cls_conn);

        if (tcp_conn->tx_hash.tfm)
                crypto_free_hash(tcp_conn->tx_hash.tfm);
        if (tcp_conn->rx_hash.tfm)
                crypto_free_hash(tcp_conn->rx_hash.tfm);

        kfree(tcp_conn);
}

static void
iscsi_tcp_conn_stop(struct iscsi_cls_conn *cls_conn, int flag)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;

        iscsi_conn_stop(cls_conn, flag);
        iscsi_tcp_release_conn(conn);
        tcp_conn->hdr_size = sizeof(struct iscsi_hdr);
}

static int iscsi_tcp_get_addr(struct iscsi_conn *conn, struct socket *sock,
                              char *buf, int *port,
                              int (*getname)(struct socket *, struct sockaddr *,
                                        int *addrlen))
{
        struct sockaddr_storage *addr;
        struct sockaddr_in6 *sin6;
        struct sockaddr_in *sin;
        int rc = 0, len;

        addr = kmalloc(sizeof(*addr), GFP_KERNEL);
        if (!addr)
                return -ENOMEM;

        if (getname(sock, (struct sockaddr *) addr, &len)) {
                rc = -ENODEV;
                goto free_addr;
        }

        switch (addr->ss_family) {
        case AF_INET:
                sin = (struct sockaddr_in *)addr;
                spin_lock_bh(&conn->session->lock);
                sprintf(buf, NIPQUAD_FMT, NIPQUAD(sin->sin_addr.s_addr));
                *port = be16_to_cpu(sin->sin_port);
                spin_unlock_bh(&conn->session->lock);
                break;
        case AF_INET6:
                sin6 = (struct sockaddr_in6 *)addr;
                spin_lock_bh(&conn->session->lock);
                sprintf(buf, NIP6_FMT, NIP6(sin6->sin6_addr));
                *port = be16_to_cpu(sin6->sin6_port);
                spin_unlock_bh(&conn->session->lock);
                break;
        }
free_addr:
        kfree(addr);
        return rc;
}

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;
        }
        /*
         * copy these values now because if we drop the session
         * userspace may still want to query the values since we will
         * be using them for the reconnect
         */
        err = iscsi_tcp_get_addr(conn, sock, conn->portal_address,
                                 &conn->portal_port, kernel_getpeername);
        if (err)
                goto free_socket;

        err = iscsi_tcp_get_addr(conn, sock, conn->local_address,
                                &conn->local_port, kernel_getsockname);
        if (err)
                goto free_socket;

        err = iscsi_conn_bind(cls_session, cls_conn, is_leading);
        if (err)
                goto free_socket;

        /* 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;

free_socket:
        sockfd_put(sock);
        return err;
}

/* called with host lock */
static void
iscsi_tcp_mgmt_init(struct iscsi_conn *conn, struct iscsi_mgmt_task *mtask)
{
        struct iscsi_tcp_mgmt_task *tcp_mtask = mtask->dd_data;
        tcp_mtask->xmstate = XMSTATE_IMM_HDR_INIT;
}

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,
                     char *buf, int buflen)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        struct iscsi_session *session = conn->session;
        struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
        int value;

        switch(param) {
        case ISCSI_PARAM_HDRDGST_EN:
                iscsi_set_param(cls_conn, param, buf, buflen);
                tcp_conn->hdr_size = sizeof(struct iscsi_hdr);
                if (conn->hdrdgst_en)
                        tcp_conn->hdr_size += sizeof(__u32);
                break;
        case ISCSI_PARAM_DATADGST_EN:
                iscsi_set_param(cls_conn, param, buf, buflen);
                tcp_conn->sendpage = conn->datadgst_en ?
                        sock_no_sendpage : tcp_conn->sock->ops->sendpage;
                break;
        case ISCSI_PARAM_MAX_R2T:
                sscanf(buf, "%d", &value);
                if (session->max_r2t == roundup_pow_of_two(value))
                        break;
                iscsi_r2tpool_free(session);
                iscsi_set_param(cls_conn, param, buf, buflen);
                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;
        default:
                return iscsi_set_param(cls_conn, param, buf, buflen);
        }

        return 0;
}

static int
iscsi_tcp_conn_get_param(struct iscsi_cls_conn *cls_conn,
                         enum iscsi_param param, char *buf)
{
        struct iscsi_conn *conn = cls_conn->dd_data;
        int len;

        switch(param) {
        case ISCSI_PARAM_CONN_PORT:
                spin_lock_bh(&conn->session->lock);
                len = sprintf(buf, "%hu\n", conn->portal_port);
                spin_unlock_bh(&conn->session->lock);
                break;
        case ISCSI_PARAM_CONN_ADDRESS:
                spin_lock_bh(&conn->session->lock);
                len = sprintf(buf, "%s\n", conn->portal_address);
                spin_unlock_bh(&conn->session->lock);
                break;
        default:
                return iscsi_conn_get_param(cls_conn, param, buf);
        }

        return len;
}

static int
iscsi_tcp_host_get_param(struct Scsi_Host *shost, enum iscsi_host_param param,
                         char *buf)
{
        struct iscsi_session *session = iscsi_hostdata(shost->hostdata);
        int len;

        switch (param) {
        case ISCSI_HOST_PARAM_IPADDRESS:
                spin_lock_bh(&session->lock);
                if (!session->leadconn)
                        len = -ENODEV;
                else
                        len = sprintf(buf, "%s\n",
                                     session->leadconn->local_address);
                spin_unlock_bh(&session->lock);
                break;
        default:
                return iscsi_host_get_param(shost, param, buf);
        }
        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,
                         uint16_t cmds_max, uint16_t qdepth,
                         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, cmds_max, qdepth,
                                         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 int iscsi_tcp_slave_configure(struct scsi_device *sdev)
{
        blk_queue_bounce_limit(sdev->request_queue, BLK_BOUNCE_ANY);
        blk_queue_dma_alignment(sdev->request_queue, 0);
        return 0;
}

static struct scsi_host_template iscsi_sht = {
        .module                 = THIS_MODULE,
        .name                   = "iSCSI Initiator over TCP/IP",
        .queuecommand           = iscsi_queuecommand,
        .change_queue_depth     = iscsi_change_queue_depth,
        .can_queue              = ISCSI_DEF_XMIT_CMDS_MAX - 1,
        .sg_tablesize           = ISCSI_SG_TABLESIZE,
        .max_sectors            = 0xFFFF,
        .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,
        .slave_configure        = iscsi_tcp_slave_configure,
        .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 |
                                  ISCSI_PERSISTENT_PORT |
                                  ISCSI_PERSISTENT_ADDRESS |
                                  ISCSI_TARGET_NAME | ISCSI_TPGT |
                                  ISCSI_USERNAME | ISCSI_PASSWORD |
                                  ISCSI_USERNAME_IN | ISCSI_PASSWORD_IN,
        .host_param_mask        = ISCSI_HOST_HWADDRESS | ISCSI_HOST_IPADDRESS |
                                  ISCSI_HOST_INITIATOR_NAME |
                                  ISCSI_HOST_NETDEV_NAME,
        .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_tcp_conn_get_param,
        .get_session_param      = iscsi_session_get_param,
        .start_conn             = iscsi_conn_start,
        .stop_conn              = iscsi_tcp_conn_stop,
        /* iscsi host params */
        .get_host_param         = iscsi_tcp_host_get_param,
        .set_host_param         = iscsi_host_set_param,
        /* 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);