[mirror_ubuntu-zesty-kernel.git] / drivers / target / iscsi / iscsi_target_tmr.c

/*******************************************************************************
 * This file contains the iSCSI Target specific Task Management functions.
 *
 * \u00a9 Copyright 2007-2011 RisingTide Systems LLC.
 *
 * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
 *
 * Author: Nicholas A. Bellinger <nab@linux-iscsi.org>
 *
 * 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.
 ******************************************************************************/

#include <asm/unaligned.h>
#include <scsi/iscsi_proto.h>
#include <target/target_core_base.h>
#include <target/target_core_transport.h>

#include "iscsi_target_core.h"
#include "iscsi_target_seq_pdu_list.h"
#include "iscsi_target_datain_values.h"
#include "iscsi_target_device.h"
#include "iscsi_target_erl0.h"
#include "iscsi_target_erl1.h"
#include "iscsi_target_erl2.h"
#include "iscsi_target_tmr.h"
#include "iscsi_target_tpg.h"
#include "iscsi_target_util.h"
#include "iscsi_target.h"

u8 iscsit_tmr_abort_task(
        struct iscsi_cmd *cmd,
        unsigned char *buf)
{
        struct iscsi_cmd *ref_cmd;
        struct iscsi_conn *conn = cmd->conn;
        struct iscsi_tmr_req *tmr_req = cmd->tmr_req;
        struct se_tmr_req *se_tmr = cmd->se_cmd.se_tmr_req;
        struct iscsi_tm *hdr = (struct iscsi_tm *) buf;

        ref_cmd = iscsit_find_cmd_from_itt(conn, hdr->rtt);
        if (!ref_cmd) {
                pr_err("Unable to locate RefTaskTag: 0x%08x on CID:"
                        " %hu.\n", hdr->rtt, conn->cid);
                return ((hdr->refcmdsn >= conn->sess->exp_cmd_sn) &&
                        (hdr->refcmdsn <= conn->sess->max_cmd_sn)) ?
                        ISCSI_TMF_RSP_COMPLETE : ISCSI_TMF_RSP_NO_TASK;
        }
        if (ref_cmd->cmd_sn != hdr->refcmdsn) {
                pr_err("RefCmdSN 0x%08x does not equal"
                        " task's CmdSN 0x%08x. Rejecting ABORT_TASK.\n",
                        hdr->refcmdsn, ref_cmd->cmd_sn);
                return ISCSI_TMF_RSP_REJECTED;
        }

        se_tmr->ref_task_tag            = hdr->rtt;
        se_tmr->ref_cmd                 = &ref_cmd->se_cmd;
        tmr_req->ref_cmd_sn             = hdr->refcmdsn;
        tmr_req->exp_data_sn            = hdr->exp_datasn;

        return ISCSI_TMF_RSP_COMPLETE;
}

/*
 *      Called from iscsit_handle_task_mgt_cmd().
 */
int iscsit_tmr_task_warm_reset(
        struct iscsi_conn *conn,
        struct iscsi_tmr_req *tmr_req,
        unsigned char *buf)
{
        struct iscsi_session *sess = conn->sess;
        struct iscsi_node_attrib *na = iscsit_tpg_get_node_attrib(sess);
#if 0
        struct iscsi_init_task_mgt_cmnd *hdr =
                (struct iscsi_init_task_mgt_cmnd *) buf;
#endif
        if (!na->tmr_warm_reset) {
                pr_err("TMR Opcode TARGET_WARM_RESET authorization"
                        " failed for Initiator Node: %s\n",
                        sess->se_sess->se_node_acl->initiatorname);
                 return -1;
        }
        /*
         * Do the real work in transport_generic_do_tmr().
         */
        return 0;
}

int iscsit_tmr_task_cold_reset(
        struct iscsi_conn *conn,
        struct iscsi_tmr_req *tmr_req,
        unsigned char *buf)
{
        struct iscsi_session *sess = conn->sess;
        struct iscsi_node_attrib *na = iscsit_tpg_get_node_attrib(sess);

        if (!na->tmr_cold_reset) {
                pr_err("TMR Opcode TARGET_COLD_RESET authorization"
                        " failed for Initiator Node: %s\n",
                        sess->se_sess->se_node_acl->initiatorname);
                return -1;
        }
        /*
         * Do the real work in transport_generic_do_tmr().
         */
        return 0;
}

u8 iscsit_tmr_task_reassign(
        struct iscsi_cmd *cmd,
        unsigned char *buf)
{
        struct iscsi_cmd *ref_cmd = NULL;
        struct iscsi_conn *conn = cmd->conn;
        struct iscsi_conn_recovery *cr = NULL;
        struct iscsi_tmr_req *tmr_req = cmd->tmr_req;
        struct se_tmr_req *se_tmr = cmd->se_cmd.se_tmr_req;
        struct iscsi_tm *hdr = (struct iscsi_tm *) buf;
        int ret;

        pr_debug("Got TASK_REASSIGN TMR ITT: 0x%08x,"
                " RefTaskTag: 0x%08x, ExpDataSN: 0x%08x, CID: %hu\n",
                hdr->itt, hdr->rtt, hdr->exp_datasn, conn->cid);

        if (conn->sess->sess_ops->ErrorRecoveryLevel != 2) {
                pr_err("TMR TASK_REASSIGN not supported in ERL<2,"
                                " ignoring request.\n");
                return ISCSI_TMF_RSP_NOT_SUPPORTED;
        }

        ret = iscsit_find_cmd_for_recovery(conn->sess, &ref_cmd, &cr, hdr->rtt);
        if (ret == -2) {
                pr_err("Command ITT: 0x%08x is still alligent to CID:"
                        " %hu\n", ref_cmd->init_task_tag, cr->cid);
                return ISCSI_TMF_RSP_TASK_ALLEGIANT;
        } else if (ret == -1) {
                pr_err("Unable to locate RefTaskTag: 0x%08x in"
                        " connection recovery command list.\n", hdr->rtt);
                return ISCSI_TMF_RSP_NO_TASK;
        }
        /*
         * Temporary check to prevent connection recovery for
         * connections with a differing MaxRecvDataSegmentLength.
         */
        if (cr->maxrecvdatasegmentlength !=
            conn->conn_ops->MaxRecvDataSegmentLength) {
                pr_err("Unable to perform connection recovery for"
                        " differing MaxRecvDataSegmentLength, rejecting"
                        " TMR TASK_REASSIGN.\n");
                return ISCSI_TMF_RSP_REJECTED;
        }

        se_tmr->ref_task_tag            = hdr->rtt;
        se_tmr->ref_cmd                 = &ref_cmd->se_cmd;
        se_tmr->ref_task_lun            = get_unaligned_le64(&hdr->lun);
        tmr_req->ref_cmd_sn             = hdr->refcmdsn;
        tmr_req->exp_data_sn            = hdr->exp_datasn;
        tmr_req->conn_recovery          = cr;
        tmr_req->task_reassign          = 1;
        /*
         * Command can now be reassigned to a new connection.
         * The task management response must be sent before the
         * reassignment actually happens.  See iscsi_tmr_post_handler().
         */
        return ISCSI_TMF_RSP_COMPLETE;
}

static void iscsit_task_reassign_remove_cmd(
        struct iscsi_cmd *cmd,
        struct iscsi_conn_recovery *cr,
        struct iscsi_session *sess)
{
        int ret;

        spin_lock(&cr->conn_recovery_cmd_lock);
        ret = iscsit_remove_cmd_from_connection_recovery(cmd, sess);
        spin_unlock(&cr->conn_recovery_cmd_lock);
        if (!ret) {
                pr_debug("iSCSI connection recovery successful for CID:"
                        " %hu on SID: %u\n", cr->cid, sess->sid);
                iscsit_remove_active_connection_recovery_entry(cr, sess);
        }
}

static int iscsit_task_reassign_complete_nop_out(
        struct iscsi_tmr_req *tmr_req,
        struct iscsi_conn *conn)
{
        struct se_tmr_req *se_tmr = tmr_req->se_tmr_req;
        struct se_cmd *se_cmd = se_tmr->ref_cmd;
        struct iscsi_cmd *cmd = container_of(se_cmd, struct iscsi_cmd, se_cmd);
        struct iscsi_conn_recovery *cr;

        if (!cmd->cr) {
                pr_err("struct iscsi_conn_recovery pointer for ITT: 0x%08x"
                        " is NULL!\n", cmd->init_task_tag);
                return -1;
        }
        cr = cmd->cr;

        /*
         * Reset the StatSN so a new one for this commands new connection
         * will be assigned.
         * Reset the ExpStatSN as well so we may receive Status SNACKs.
         */
        cmd->stat_sn = cmd->exp_stat_sn = 0;

        iscsit_task_reassign_remove_cmd(cmd, cr, conn->sess);

        spin_lock_bh(&conn->cmd_lock);
        list_add_tail(&cmd->i_list, &conn->conn_cmd_list);
        spin_unlock_bh(&conn->cmd_lock);

        cmd->i_state = ISTATE_SEND_NOPIN;
        iscsit_add_cmd_to_response_queue(cmd, conn, cmd->i_state);
        return 0;
}

static int iscsit_task_reassign_complete_write(
        struct iscsi_cmd *cmd,
        struct iscsi_tmr_req *tmr_req)
{
        int no_build_r2ts = 0;
        u32 length = 0, offset = 0;
        struct iscsi_conn *conn = cmd->conn;
        struct se_cmd *se_cmd = &cmd->se_cmd;
        /*
         * The Initiator must not send a R2T SNACK with a Begrun less than
         * the TMR TASK_REASSIGN's ExpDataSN.
         */
        if (!tmr_req->exp_data_sn) {
                cmd->cmd_flags &= ~ICF_GOT_DATACK_SNACK;
                cmd->acked_data_sn = 0;
        } else {
                cmd->cmd_flags |= ICF_GOT_DATACK_SNACK;
                cmd->acked_data_sn = (tmr_req->exp_data_sn - 1);
        }

        /*
         * The TMR TASK_REASSIGN's ExpDataSN contains the next R2TSN the
         * Initiator is expecting.  The Target controls all WRITE operations
         * so if we have received all DataOUT we can safety ignore Initiator.
         */
        if (cmd->cmd_flags & ICF_GOT_LAST_DATAOUT) {
                if (!atomic_read(&cmd->se_cmd.t_transport_sent)) {
                        pr_debug("WRITE ITT: 0x%08x: t_state: %d"
                                " never sent to transport\n",
                                cmd->init_task_tag, cmd->se_cmd.t_state);
                        return transport_generic_handle_data(se_cmd);
                }

                cmd->i_state = ISTATE_SEND_STATUS;
                iscsit_add_cmd_to_response_queue(cmd, conn, cmd->i_state);
                return 0;
        }

        /*
         * Special case to deal with DataSequenceInOrder=No and Non-Immeidate
         * Unsolicited DataOut.
         */
        if (cmd->unsolicited_data) {
                cmd->unsolicited_data = 0;

                offset = cmd->next_burst_len = cmd->write_data_done;

                if ((conn->sess->sess_ops->FirstBurstLength - offset) >=
                     cmd->data_length) {
                        no_build_r2ts = 1;
                        length = (cmd->data_length - offset);
                } else
                        length = (conn->sess->sess_ops->FirstBurstLength - offset);

                spin_lock_bh(&cmd->r2t_lock);
                if (iscsit_add_r2t_to_list(cmd, offset, length, 0, 0) < 0) {
                        spin_unlock_bh(&cmd->r2t_lock);
                        return -1;
                }
                cmd->outstanding_r2ts++;
                spin_unlock_bh(&cmd->r2t_lock);

                if (no_build_r2ts)
                        return 0;
        }
        /*
         * iscsit_build_r2ts_for_cmd() can handle the rest from here.
         */
        return iscsit_build_r2ts_for_cmd(cmd, conn, 2);
}

static int iscsit_task_reassign_complete_read(
        struct iscsi_cmd *cmd,
        struct iscsi_tmr_req *tmr_req)
{
        struct iscsi_conn *conn = cmd->conn;
        struct iscsi_datain_req *dr;
        struct se_cmd *se_cmd = &cmd->se_cmd;
        /*
         * The Initiator must not send a Data SNACK with a BegRun less than
         * the TMR TASK_REASSIGN's ExpDataSN.
         */
        if (!tmr_req->exp_data_sn) {
                cmd->cmd_flags &= ~ICF_GOT_DATACK_SNACK;
                cmd->acked_data_sn = 0;
        } else {
                cmd->cmd_flags |= ICF_GOT_DATACK_SNACK;
                cmd->acked_data_sn = (tmr_req->exp_data_sn - 1);
        }

        if (!atomic_read(&cmd->se_cmd.t_transport_sent)) {
                pr_debug("READ ITT: 0x%08x: t_state: %d never sent to"
                        " transport\n", cmd->init_task_tag,
                        cmd->se_cmd.t_state);
                transport_handle_cdb_direct(se_cmd);
                return 0;
        }

        if (!atomic_read(&se_cmd->t_transport_complete)) {
                pr_err("READ ITT: 0x%08x: t_state: %d, never returned"
                        " from transport\n", cmd->init_task_tag,
                        cmd->se_cmd.t_state);
                return -1;
        }

        dr = iscsit_allocate_datain_req();
        if (!dr)
                return -1;
        /*
         * The TMR TASK_REASSIGN's ExpDataSN contains the next DataSN the
         * Initiator is expecting.
         */
        dr->data_sn = dr->begrun = tmr_req->exp_data_sn;
        dr->runlength = 0;
        dr->generate_recovery_values = 1;
        dr->recovery = DATAIN_CONNECTION_RECOVERY;

        iscsit_attach_datain_req(cmd, dr);

        cmd->i_state = ISTATE_SEND_DATAIN;
        iscsit_add_cmd_to_response_queue(cmd, conn, cmd->i_state);
        return 0;
}

static int iscsit_task_reassign_complete_none(
        struct iscsi_cmd *cmd,
        struct iscsi_tmr_req *tmr_req)
{
        struct iscsi_conn *conn = cmd->conn;

        cmd->i_state = ISTATE_SEND_STATUS;
        iscsit_add_cmd_to_response_queue(cmd, conn, cmd->i_state);
        return 0;
}

static int iscsit_task_reassign_complete_scsi_cmnd(
        struct iscsi_tmr_req *tmr_req,
        struct iscsi_conn *conn)
{
        struct se_tmr_req *se_tmr = tmr_req->se_tmr_req;
        struct se_cmd *se_cmd = se_tmr->ref_cmd;
        struct iscsi_cmd *cmd = container_of(se_cmd, struct iscsi_cmd, se_cmd);
        struct iscsi_conn_recovery *cr;

        if (!cmd->cr) {
                pr_err("struct iscsi_conn_recovery pointer for ITT: 0x%08x"
                        " is NULL!\n", cmd->init_task_tag);
                return -1;
        }
        cr = cmd->cr;

        /*
         * Reset the StatSN so a new one for this commands new connection
         * will be assigned.
         * Reset the ExpStatSN as well so we may receive Status SNACKs.
         */
        cmd->stat_sn = cmd->exp_stat_sn = 0;

        iscsit_task_reassign_remove_cmd(cmd, cr, conn->sess);

        spin_lock_bh(&conn->cmd_lock);
        list_add_tail(&cmd->i_list, &conn->conn_cmd_list);
        spin_unlock_bh(&conn->cmd_lock);

        if (se_cmd->se_cmd_flags & SCF_SENT_CHECK_CONDITION) {
                cmd->i_state = ISTATE_SEND_STATUS;
                iscsit_add_cmd_to_response_queue(cmd, conn, cmd->i_state);
                return 0;
        }

        switch (cmd->data_direction) {
        case DMA_TO_DEVICE:
                return iscsit_task_reassign_complete_write(cmd, tmr_req);
        case DMA_FROM_DEVICE:
                return iscsit_task_reassign_complete_read(cmd, tmr_req);
        case DMA_NONE:
                return iscsit_task_reassign_complete_none(cmd, tmr_req);
        default:
                pr_err("Unknown cmd->data_direction: 0x%02x\n",
                                cmd->data_direction);
                return -1;
        }

        return 0;
}

static int iscsit_task_reassign_complete(
        struct iscsi_tmr_req *tmr_req,
        struct iscsi_conn *conn)
{
        struct se_tmr_req *se_tmr = tmr_req->se_tmr_req;
        struct se_cmd *se_cmd;
        struct iscsi_cmd *cmd;
        int ret = 0;

        if (!se_tmr->ref_cmd) {
                pr_err("TMR Request is missing a RefCmd struct iscsi_cmd.\n");
                return -1;
        }
        se_cmd = se_tmr->ref_cmd;
        cmd = container_of(se_cmd, struct iscsi_cmd, se_cmd);

        cmd->conn = conn;

        switch (cmd->iscsi_opcode) {
        case ISCSI_OP_NOOP_OUT:
                ret = iscsit_task_reassign_complete_nop_out(tmr_req, conn);
                break;
        case ISCSI_OP_SCSI_CMD:
                ret = iscsit_task_reassign_complete_scsi_cmnd(tmr_req, conn);
                break;
        default:
                 pr_err("Illegal iSCSI Opcode 0x%02x during"
                        " command realligence\n", cmd->iscsi_opcode);
                return -1;
        }

        if (ret != 0)
                return ret;

        pr_debug("Completed connection realligence for Opcode: 0x%02x,"
                " ITT: 0x%08x to CID: %hu.\n", cmd->iscsi_opcode,
                        cmd->init_task_tag, conn->cid);

        return 0;
}

/*
 *      Handles special after-the-fact actions related to TMRs.
 *      Right now the only one that its really needed for is
 *      connection recovery releated TASK_REASSIGN.
 */
extern int iscsit_tmr_post_handler(struct iscsi_cmd *cmd, struct iscsi_conn *conn)
{
        struct iscsi_tmr_req *tmr_req = cmd->tmr_req;
        struct se_tmr_req *se_tmr = cmd->se_cmd.se_tmr_req;

        if (tmr_req->task_reassign &&
           (se_tmr->response == ISCSI_TMF_RSP_COMPLETE))
                return iscsit_task_reassign_complete(tmr_req, conn);

        return 0;
}

/*
 *      Nothing to do here, but leave it for good measure. :-)
 */
int iscsit_task_reassign_prepare_read(
        struct iscsi_tmr_req *tmr_req,
        struct iscsi_conn *conn)
{
        return 0;
}

static void iscsit_task_reassign_prepare_unsolicited_dataout(
        struct iscsi_cmd *cmd,
        struct iscsi_conn *conn)
{
        int i, j;
        struct iscsi_pdu *pdu = NULL;
        struct iscsi_seq *seq = NULL;

        if (conn->sess->sess_ops->DataSequenceInOrder) {
                cmd->data_sn = 0;

                if (cmd->immediate_data)
                        cmd->r2t_offset += (cmd->first_burst_len -
                                cmd->seq_start_offset);

                if (conn->sess->sess_ops->DataPDUInOrder) {
                        cmd->write_data_done -= (cmd->immediate_data) ?
                                                (cmd->first_burst_len -
                                                 cmd->seq_start_offset) :
                                                 cmd->first_burst_len;
                        cmd->first_burst_len = 0;
                        return;
                }

                for (i = 0; i < cmd->pdu_count; i++) {
                        pdu = &cmd->pdu_list[i];

                        if (pdu->status != ISCSI_PDU_RECEIVED_OK)
                                continue;

                        if ((pdu->offset >= cmd->seq_start_offset) &&
                           ((pdu->offset + pdu->length) <=
                             cmd->seq_end_offset)) {
                                cmd->first_burst_len -= pdu->length;
                                cmd->write_data_done -= pdu->length;
                                pdu->status = ISCSI_PDU_NOT_RECEIVED;
                        }
                }
        } else {
                for (i = 0; i < cmd->seq_count; i++) {
                        seq = &cmd->seq_list[i];

                        if (seq->type != SEQTYPE_UNSOLICITED)
                                continue;

                        cmd->write_data_done -=
                                        (seq->offset - seq->orig_offset);
                        cmd->first_burst_len = 0;
                        seq->data_sn = 0;
                        seq->offset = seq->orig_offset;
                        seq->next_burst_len = 0;
                        seq->status = DATAOUT_SEQUENCE_WITHIN_COMMAND_RECOVERY;

                        if (conn->sess->sess_ops->DataPDUInOrder)
                                continue;

                        for (j = 0; j < seq->pdu_count; j++) {
                                pdu = &cmd->pdu_list[j+seq->pdu_start];

                                if (pdu->status != ISCSI_PDU_RECEIVED_OK)
                                        continue;

                                pdu->status = ISCSI_PDU_NOT_RECEIVED;
                        }
                }
        }
}

int iscsit_task_reassign_prepare_write(
        struct iscsi_tmr_req *tmr_req,
        struct iscsi_conn *conn)
{
        struct se_tmr_req *se_tmr = tmr_req->se_tmr_req;
        struct se_cmd *se_cmd = se_tmr->ref_cmd;
        struct iscsi_cmd *cmd = container_of(se_cmd, struct iscsi_cmd, se_cmd);
        struct iscsi_pdu *pdu = NULL;
        struct iscsi_r2t *r2t = NULL, *r2t_tmp;
        int first_incomplete_r2t = 1, i = 0;

        /*
         * The command was in the process of receiving Unsolicited DataOUT when
         * the connection failed.
         */
        if (cmd->unsolicited_data)
                iscsit_task_reassign_prepare_unsolicited_dataout(cmd, conn);

        /*
         * The Initiator is requesting R2Ts starting from zero,  skip
         * checking acknowledged R2Ts and start checking struct iscsi_r2ts
         * greater than zero.
         */
        if (!tmr_req->exp_data_sn)
                goto drop_unacknowledged_r2ts;

        /*
         * We now check that the PDUs in DataOUT sequences below
         * the TMR TASK_REASSIGN ExpDataSN (R2TSN the Initiator is
         * expecting next) have all the DataOUT they require to complete
         * the DataOUT sequence.  First scan from R2TSN 0 to TMR
         * TASK_REASSIGN ExpDataSN-1.
         *
         * If we have not received all DataOUT in question,  we must
         * make sure to make the appropriate changes to values in
         * struct iscsi_cmd (and elsewhere depending on session parameters)
         * so iscsit_build_r2ts_for_cmd() in iscsit_task_reassign_complete_write()
         * will resend a new R2T for the DataOUT sequences in question.
         */
        spin_lock_bh(&cmd->r2t_lock);
        if (list_empty(&cmd->cmd_r2t_list)) {
                spin_unlock_bh(&cmd->r2t_lock);
                return -1;
        }

        list_for_each_entry(r2t, &cmd->cmd_r2t_list, r2t_list) {

                if (r2t->r2t_sn >= tmr_req->exp_data_sn)
                        continue;
                /*
                 * Safely ignore Recovery R2Ts and R2Ts that have completed
                 * DataOUT sequences.
                 */
                if (r2t->seq_complete)
                        continue;

                if (r2t->recovery_r2t)
                        continue;

                /*
                 *                 DataSequenceInOrder=Yes:
                 *
                 * Taking into account the iSCSI implementation requirement of
                 * MaxOutstandingR2T=1 while ErrorRecoveryLevel>0 and
                 * DataSequenceInOrder=Yes, we must take into consideration
                 * the following:
                 *
                 *                  DataSequenceInOrder=No:
                 *
                 * Taking into account that the Initiator controls the (possibly
                 * random) PDU Order in (possibly random) Sequence Order of
                 * DataOUT the target requests with R2Ts,  we must take into
                 * consideration the following:
                 *
                 *      DataPDUInOrder=Yes for DataSequenceInOrder=[Yes,No]:
                 *
                 * While processing non-complete R2T DataOUT sequence requests
                 * the Target will re-request only the total sequence length
                 * minus current received offset.  This is because we must
                 * assume the initiator will continue sending DataOUT from the
                 * last PDU before the connection failed.
                 *
                 *      DataPDUInOrder=No for DataSequenceInOrder=[Yes,No]:
                 *
                 * While processing non-complete R2T DataOUT sequence requests
                 * the Target will re-request the entire DataOUT sequence if
                 * any single PDU is missing from the sequence.  This is because
                 * we have no logical method to determine the next PDU offset,
                 * and we must assume the Initiator will be sending any random
                 * PDU offset in the current sequence after TASK_REASSIGN
                 * has completed.
                 */
                if (conn->sess->sess_ops->DataSequenceInOrder) {
                        if (!first_incomplete_r2t) {
                                cmd->r2t_offset -= r2t->xfer_len;
                                goto next;
                        }

                        if (conn->sess->sess_ops->DataPDUInOrder) {
                                cmd->data_sn = 0;
                                cmd->r2t_offset -= (r2t->xfer_len -
                                        cmd->next_burst_len);
                                first_incomplete_r2t = 0;
                                goto next;
                        }

                        cmd->data_sn = 0;
                        cmd->r2t_offset -= r2t->xfer_len;

                        for (i = 0; i < cmd->pdu_count; i++) {
                                pdu = &cmd->pdu_list[i];

                                if (pdu->status != ISCSI_PDU_RECEIVED_OK)
                                        continue;

                                if ((pdu->offset >= r2t->offset) &&
                                    (pdu->offset < (r2t->offset +
                                                r2t->xfer_len))) {
                                        cmd->next_burst_len -= pdu->length;
                                        cmd->write_data_done -= pdu->length;
                                        pdu->status = ISCSI_PDU_NOT_RECEIVED;
                                }
                        }

                        first_incomplete_r2t = 0;
                } else {
                        struct iscsi_seq *seq;

                        seq = iscsit_get_seq_holder(cmd, r2t->offset,
                                        r2t->xfer_len);
                        if (!seq) {
                                spin_unlock_bh(&cmd->r2t_lock);
                                return -1;
                        }

                        cmd->write_data_done -=
                                        (seq->offset - seq->orig_offset);
                        seq->data_sn = 0;
                        seq->offset = seq->orig_offset;
                        seq->next_burst_len = 0;
                        seq->status = DATAOUT_SEQUENCE_WITHIN_COMMAND_RECOVERY;

                        cmd->seq_send_order--;

                        if (conn->sess->sess_ops->DataPDUInOrder)
                                goto next;

                        for (i = 0; i < seq->pdu_count; i++) {
                                pdu = &cmd->pdu_list[i+seq->pdu_start];

                                if (pdu->status != ISCSI_PDU_RECEIVED_OK)
                                        continue;

                                pdu->status = ISCSI_PDU_NOT_RECEIVED;
                        }
                }

next:
                cmd->outstanding_r2ts--;
        }
        spin_unlock_bh(&cmd->r2t_lock);

        /*
         * We now drop all unacknowledged R2Ts, ie: ExpDataSN from TMR
         * TASK_REASSIGN to the last R2T in the list..  We are also careful
         * to check that the Initiator is not requesting R2Ts for DataOUT
         * sequences it has already completed.
         *
         * Free each R2T in question and adjust values in struct iscsi_cmd
         * accordingly so iscsit_build_r2ts_for_cmd() do the rest of
         * the work after the TMR TASK_REASSIGN Response is sent.
         */
drop_unacknowledged_r2ts:

        cmd->cmd_flags &= ~ICF_SENT_LAST_R2T;
        cmd->r2t_sn = tmr_req->exp_data_sn;

        spin_lock_bh(&cmd->r2t_lock);
        list_for_each_entry_safe(r2t, r2t_tmp, &cmd->cmd_r2t_list, r2t_list) {
                /*
                 * Skip up to the R2T Sequence number provided by the
                 * iSCSI TASK_REASSIGN TMR
                 */
                if (r2t->r2t_sn < tmr_req->exp_data_sn)
                        continue;

                if (r2t->seq_complete) {
                        pr_err("Initiator is requesting R2Ts from"
                                " R2TSN: 0x%08x, but R2TSN: 0x%08x, Offset: %u,"
                                " Length: %u is already complete."
                                "   BAD INITIATOR ERL=2 IMPLEMENTATION!\n",
                                tmr_req->exp_data_sn, r2t->r2t_sn,
                                r2t->offset, r2t->xfer_len);
                        spin_unlock_bh(&cmd->r2t_lock);
                        return -1;
                }

                if (r2t->recovery_r2t) {
                        iscsit_free_r2t(r2t, cmd);
                        continue;
                }

                /*                 DataSequenceInOrder=Yes:
                 *
                 * Taking into account the iSCSI implementation requirement of
                 * MaxOutstandingR2T=1 while ErrorRecoveryLevel>0 and
                 * DataSequenceInOrder=Yes, it's safe to subtract the R2Ts
                 * entire transfer length from the commands R2T offset marker.
                 *
                 *                 DataSequenceInOrder=No:
                 *
                 * We subtract the difference from struct iscsi_seq between the
                 * current offset and original offset from cmd->write_data_done
                 * for account for DataOUT PDUs already received.  Then reset
                 * the current offset to the original and zero out the current
                 * burst length,  to make sure we re-request the entire DataOUT
                 * sequence.
                 */
                if (conn->sess->sess_ops->DataSequenceInOrder)
                        cmd->r2t_offset -= r2t->xfer_len;
                else
                        cmd->seq_send_order--;

                cmd->outstanding_r2ts--;
                iscsit_free_r2t(r2t, cmd);
        }
        spin_unlock_bh(&cmd->r2t_lock);

        return 0;
}

/*
 *      Performs sanity checks TMR TASK_REASSIGN's ExpDataSN for
 *      a given struct iscsi_cmd.
 */
int iscsit_check_task_reassign_expdatasn(
        struct iscsi_tmr_req *tmr_req,
        struct iscsi_conn *conn)
{
        struct se_tmr_req *se_tmr = tmr_req->se_tmr_req;
        struct se_cmd *se_cmd = se_tmr->ref_cmd;
        struct iscsi_cmd *ref_cmd = container_of(se_cmd, struct iscsi_cmd, se_cmd);

        if (ref_cmd->iscsi_opcode != ISCSI_OP_SCSI_CMD)
                return 0;

        if (se_cmd->se_cmd_flags & SCF_SENT_CHECK_CONDITION)
                return 0;

        if (ref_cmd->data_direction == DMA_NONE)
                return 0;

        /*
         * For READs the TMR TASK_REASSIGNs ExpDataSN contains the next DataSN
         * of DataIN the Initiator is expecting.
         *
         * Also check that the Initiator is not re-requesting DataIN that has
         * already been acknowledged with a DataAck SNACK.
         */
        if (ref_cmd->data_direction == DMA_FROM_DEVICE) {
                if (tmr_req->exp_data_sn > ref_cmd->data_sn) {
                        pr_err("Received ExpDataSN: 0x%08x for READ"
                                " in TMR TASK_REASSIGN greater than command's"
                                " DataSN: 0x%08x.\n", tmr_req->exp_data_sn,
                                ref_cmd->data_sn);
                        return -1;
                }
                if ((ref_cmd->cmd_flags & ICF_GOT_DATACK_SNACK) &&
                    (tmr_req->exp_data_sn <= ref_cmd->acked_data_sn)) {
                        pr_err("Received ExpDataSN: 0x%08x for READ"
                                " in TMR TASK_REASSIGN for previously"
                                " acknowledged DataIN: 0x%08x,"
                                " protocol error\n", tmr_req->exp_data_sn,
                                ref_cmd->acked_data_sn);
                        return -1;
                }
                return iscsit_task_reassign_prepare_read(tmr_req, conn);
        }

        /*
         * For WRITEs the TMR TASK_REASSIGNs ExpDataSN contains the next R2TSN
         * for R2Ts the Initiator is expecting.
         *
         * Do the magic in iscsit_task_reassign_prepare_write().
         */
        if (ref_cmd->data_direction == DMA_TO_DEVICE) {
                if (tmr_req->exp_data_sn > ref_cmd->r2t_sn) {
                        pr_err("Received ExpDataSN: 0x%08x for WRITE"
                                " in TMR TASK_REASSIGN greater than command's"
                                " R2TSN: 0x%08x.\n", tmr_req->exp_data_sn,
                                        ref_cmd->r2t_sn);
                        return -1;
                }
                return iscsit_task_reassign_prepare_write(tmr_req, conn);
        }

        pr_err("Unknown iSCSI data_direction: 0x%02x\n",
                        ref_cmd->data_direction);

        return -1;
}