/*
   * iSCSI lib functions
   *
   * Copyright (C) 2006 Red Hat, Inc.  All rights reserved.
   * Copyright (C) 2004 - 2006 Mike Christie
   * Copyright (C) 2004 - 2005 Dmitry Yusupov
   * Copyright (C) 2004 - 2005 Alex Aizman
   * 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
   */
  #include <linux/types.h>

  #include <linux/kfifo.h>
  #include <linux/delay.h>

  #include <linux/log2.h>

  #include <linux/slab.h>

  #include <linux/module.h>

  #include <asm/unaligned.h>

  #include <net/tcp.h>
  #include <scsi/scsi_cmnd.h>
  #include <scsi/scsi_device.h>
  #include <scsi/scsi_eh.h>
  #include <scsi/scsi_tcq.h>
  #include <scsi/scsi_host.h>
  #include <scsi/scsi.h>
  #include <scsi/iscsi_proto.h>
  #include <scsi/scsi_transport.h>
  #include <scsi/scsi_transport_iscsi.h>
  #include <scsi/libiscsi.h>

  static int iscsi_dbg_lib_conn;
  module_param_named(debug_libiscsi_conn, iscsi_dbg_lib_conn, int,
  		   S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(debug_libiscsi_conn,
  		 "Turn on debugging for connections in libiscsi module. "
  		 "Set to 1 to turn on, and zero to turn off. Default is off.");
  
  static int iscsi_dbg_lib_session;
  module_param_named(debug_libiscsi_session, iscsi_dbg_lib_session, int,
  		   S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(debug_libiscsi_session,
  		 "Turn on debugging for sessions in libiscsi module. "
  		 "Set to 1 to turn on, and zero to turn off. Default is off.");
  
  static int iscsi_dbg_lib_eh;
  module_param_named(debug_libiscsi_eh, iscsi_dbg_lib_eh, int,
  		   S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(debug_libiscsi_eh,
  		 "Turn on debugging for error handling in libiscsi module. "
  		 "Set to 1 to turn on, and zero to turn off. Default is off.");

  
  #define ISCSI_DBG_CONN(_conn, dbg_fmt, arg...)			\
  	do {							\

  		if (iscsi_dbg_lib_conn)				\

  			iscsi_conn_printk(KERN_INFO, _conn,	\
  					     "%s " dbg_fmt,	\
  					     __func__, ##arg);	\
  	} while (0);
  
  #define ISCSI_DBG_SESSION(_session, dbg_fmt, arg...)			\
  	do {								\

  		if (iscsi_dbg_lib_session)				\
  			iscsi_session_printk(KERN_INFO, _session,	\
  					     "%s " dbg_fmt,		\
  					     __func__, ##arg);		\
  	} while (0);
  
  #define ISCSI_DBG_EH(_session, dbg_fmt, arg...)				\
  	do {								\
  		if (iscsi_dbg_lib_eh)					\

  			iscsi_session_printk(KERN_INFO, _session,	\
  					     "%s " dbg_fmt,		\
  					     __func__, ##arg);		\
  	} while (0);

  inline void iscsi_conn_queue_work(struct iscsi_conn *conn)
  {
  	struct Scsi_Host *shost = conn->session->host;
  	struct iscsi_host *ihost = shost_priv(shost);

  	if (ihost->workq)
  		queue_work(ihost->workq, &conn->xmitwork);

  }
  EXPORT_SYMBOL_GPL(iscsi_conn_queue_work);

  static void __iscsi_update_cmdsn(struct iscsi_session *session,
  				 uint32_t exp_cmdsn, uint32_t max_cmdsn)

  {

  	/*
  	 * standard specifies this check for when to update expected and
  	 * max sequence numbers
  	 */
  	if (iscsi_sna_lt(max_cmdsn, exp_cmdsn - 1))
  		return;
  
  	if (exp_cmdsn != session->exp_cmdsn &&
  	    !iscsi_sna_lt(exp_cmdsn, session->exp_cmdsn))

  		session->exp_cmdsn = exp_cmdsn;

  	if (max_cmdsn != session->max_cmdsn &&
  	    !iscsi_sna_lt(max_cmdsn, session->max_cmdsn)) {
  		session->max_cmdsn = max_cmdsn;
  		/*
  		 * if the window closed with IO queued, then kick the
  		 * xmit thread
  		 */

  		if (!list_empty(&session->leadconn->cmdqueue) ||

  		    !list_empty(&session->leadconn->mgmtqueue))
  			iscsi_conn_queue_work(session->leadconn);

  	}

  }

  
  void iscsi_update_cmdsn(struct iscsi_session *session, struct iscsi_nopin *hdr)
  {
  	__iscsi_update_cmdsn(session, be32_to_cpu(hdr->exp_cmdsn),
  			     be32_to_cpu(hdr->max_cmdsn));
  }

  EXPORT_SYMBOL_GPL(iscsi_update_cmdsn);

  /**
   * iscsi_prep_data_out_pdu - initialize Data-Out
   * @task: scsi command task
   * @r2t: R2T info
   * @hdr: iscsi data in pdu
   *
   * Notes:
   *	Initialize Data-Out within this R2T sequence and finds
   *	proper data_offset within this SCSI command.
   *
   *	This function is called with connection lock taken.
   **/
  void iscsi_prep_data_out_pdu(struct iscsi_task *task, struct iscsi_r2t_info *r2t,
  			   struct iscsi_data *hdr)

  {

  	struct iscsi_conn *conn = task->conn;

  	unsigned int left = r2t->data_length - r2t->sent;
  
  	task->hdr_len = sizeof(struct iscsi_data);

  
  	memset(hdr, 0, sizeof(struct iscsi_data));

  	hdr->ttt = r2t->ttt;
  	hdr->datasn = cpu_to_be32(r2t->datasn);
  	r2t->datasn++;

  	hdr->opcode = ISCSI_OP_SCSI_DATA_OUT;

  	hdr->lun = task->lun;

  	hdr->itt = task->hdr_itt;
  	hdr->exp_statsn = r2t->exp_statsn;
  	hdr->offset = cpu_to_be32(r2t->data_offset + r2t->sent);
  	if (left > 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, left);
  		r2t->data_count = left;

  		hdr->flags = ISCSI_FLAG_CMD_FINAL;
  	}

  	conn->dataout_pdus_cnt++;

  }

  EXPORT_SYMBOL_GPL(iscsi_prep_data_out_pdu);

  static int iscsi_add_hdr(struct iscsi_task *task, unsigned len)

  {

  	unsigned exp_len = task->hdr_len + len;

  	if (exp_len > task->hdr_max) {

  		WARN_ON(1);
  		return -EINVAL;
  	}
  
  	WARN_ON(len & (ISCSI_PAD_LEN - 1)); /* caller must pad the AHS */

  	task->hdr_len = exp_len;

  	return 0;
  }

  /*
   * make an extended cdb AHS
   */

  static int iscsi_prep_ecdb_ahs(struct iscsi_task *task)

  {

  	struct scsi_cmnd *cmd = task->sc;

  	unsigned rlen, pad_len;
  	unsigned short ahslength;
  	struct iscsi_ecdb_ahdr *ecdb_ahdr;
  	int rc;

  	ecdb_ahdr = iscsi_next_hdr(task);

  	rlen = cmd->cmd_len - ISCSI_CDB_SIZE;
  
  	BUG_ON(rlen > sizeof(ecdb_ahdr->ecdb));
  	ahslength = rlen + sizeof(ecdb_ahdr->reserved);
  
  	pad_len = iscsi_padding(rlen);

  	rc = iscsi_add_hdr(task, sizeof(ecdb_ahdr->ahslength) +

  	                   sizeof(ecdb_ahdr->ahstype) + ahslength + pad_len);
  	if (rc)
  		return rc;
  
  	if (pad_len)
  		memset(&ecdb_ahdr->ecdb[rlen], 0, pad_len);
  
  	ecdb_ahdr->ahslength = cpu_to_be16(ahslength);
  	ecdb_ahdr->ahstype = ISCSI_AHSTYPE_CDB;
  	ecdb_ahdr->reserved = 0;
  	memcpy(ecdb_ahdr->ecdb, cmd->cmnd + ISCSI_CDB_SIZE, rlen);

  	ISCSI_DBG_SESSION(task->conn->session,
  			  "iscsi_prep_ecdb_ahs: varlen_cdb_len %d "
  		          "rlen %d pad_len %d ahs_length %d iscsi_headers_size "
  		          "%u
  ", cmd->cmd_len, rlen, pad_len, ahslength,
  		          task->hdr_len);

  	return 0;
  }

  static int iscsi_prep_bidi_ahs(struct iscsi_task *task)

  {

  	struct scsi_cmnd *sc = task->sc;

  	struct iscsi_rlength_ahdr *rlen_ahdr;
  	int rc;

  	rlen_ahdr = iscsi_next_hdr(task);
  	rc = iscsi_add_hdr(task, sizeof(*rlen_ahdr));

  	if (rc)
  		return rc;
  
  	rlen_ahdr->ahslength =
  		cpu_to_be16(sizeof(rlen_ahdr->read_length) +
  						  sizeof(rlen_ahdr->reserved));
  	rlen_ahdr->ahstype = ISCSI_AHSTYPE_RLENGTH;
  	rlen_ahdr->reserved = 0;
  	rlen_ahdr->read_length = cpu_to_be32(scsi_in(sc)->length);

  	ISCSI_DBG_SESSION(task->conn->session,
  			  "bidi-in rlen_ahdr->read_length(%d) "
  		          "rlen_ahdr->ahslength(%d)
  ",
  		          be32_to_cpu(rlen_ahdr->read_length),
  		          be16_to_cpu(rlen_ahdr->ahslength));

  	return 0;
  }

  /**

   * iscsi_check_tmf_restrictions - check if a task is affected by TMF
   * @task: iscsi task
   * @opcode: opcode to check for
   *
   * During TMF a task has to be checked if it's affected.
   * All unrelated I/O can be passed through, but I/O to the
   * affected LUN should be restricted.
   * If 'fast_abort' is set we won't be sending any I/O to the
   * affected LUN.
   * Otherwise the target is waiting for all TTTs to be completed,
   * so we have to send all outstanding Data-Out PDUs to the target.
   */
  static int iscsi_check_tmf_restrictions(struct iscsi_task *task, int opcode)
  {
  	struct iscsi_conn *conn = task->conn;
  	struct iscsi_tm *tmf = &conn->tmhdr;
  	unsigned int hdr_lun;
  
  	if (conn->tmf_state == TMF_INITIAL)
  		return 0;
  
  	if ((tmf->opcode & ISCSI_OPCODE_MASK) != ISCSI_OP_SCSI_TMFUNC)
  		return 0;
  
  	switch (ISCSI_TM_FUNC_VALUE(tmf)) {
  	case ISCSI_TM_FUNC_LOGICAL_UNIT_RESET:
  		/*
  		 * Allow PDUs for unrelated LUNs
  		 */

  		hdr_lun = scsilun_to_int(&tmf->lun);

  		if (hdr_lun != task->sc->device->lun)
  			return 0;

  		/* fall through */
  	case ISCSI_TM_FUNC_TARGET_WARM_RESET:

  		/*
  		 * Fail all SCSI cmd PDUs
  		 */
  		if (opcode != ISCSI_OP_SCSI_DATA_OUT) {
  			iscsi_conn_printk(KERN_INFO, conn,
  					  "task [op %x/%x itt "

  					  "0x%x/0x%x] "

  					  "rejected.
  ",
  					  task->hdr->opcode, opcode,

  					  task->itt, task->hdr_itt);

  			return -EACCES;
  		}
  		/*
  		 * And also all data-out PDUs in response to R2T
  		 * if fast_abort is set.
  		 */
  		if (conn->session->fast_abort) {
  			iscsi_conn_printk(KERN_INFO, conn,
  					  "task [op %x/%x itt "

  					  "0x%x/0x%x] fast abort.
  ",

  					  task->hdr->opcode, opcode,

  					  task->itt, task->hdr_itt);

  			return -EACCES;
  		}
  		break;
  	case ISCSI_TM_FUNC_ABORT_TASK:
  		/*
  		 * the caller has already checked if the task
  		 * they want to abort was in the pending queue so if
  		 * we are here the cmd pdu has gone out already, and
  		 * we will only hit this for data-outs
  		 */
  		if (opcode == ISCSI_OP_SCSI_DATA_OUT &&
  		    task->hdr_itt == tmf->rtt) {
  			ISCSI_DBG_SESSION(conn->session,
  					  "Preventing task %x/%x from sending "
  					  "data-out due to abort task in "
  					  "progress
  ", task->itt,
  					  task->hdr_itt);
  			return -EACCES;
  		}
  		break;
  	}
  
  	return 0;
  }
  
  /**

   * iscsi_prep_scsi_cmd_pdu - prep iscsi scsi cmd pdu

   * @task: iscsi task

   *
   * Prep basic iSCSI PDU fields for a scsi cmd pdu. The LLD should set
   * fields like dlength or final based on how much data it sends
   */

  static int iscsi_prep_scsi_cmd_pdu(struct iscsi_task *task)

  {

  	struct iscsi_conn *conn = task->conn;

  	struct iscsi_session *session = conn->session;

  	struct scsi_cmnd *sc = task->sc;

  	struct iscsi_scsi_req *hdr;

  	unsigned hdrlength, cmd_len;

  	itt_t itt;

  	int rc;

  	rc = iscsi_check_tmf_restrictions(task, ISCSI_OP_SCSI_CMD);
  	if (rc)
  		return rc;

  	if (conn->session->tt->alloc_pdu) {
  		rc = conn->session->tt->alloc_pdu(task, ISCSI_OP_SCSI_CMD);
  		if (rc)
  			return rc;
  	}

  	hdr = (struct iscsi_scsi_req *)task->hdr;

  	itt = hdr->itt;

  	memset(hdr, 0, sizeof(*hdr));

  	if (session->tt->parse_pdu_itt)
  		hdr->itt = task->hdr_itt = itt;
  	else
  		hdr->itt = task->hdr_itt = build_itt(task->itt,
  						     task->conn->session->age);

  	task->hdr_len = 0;
  	rc = iscsi_add_hdr(task, sizeof(*hdr));

  	if (rc)
  		return rc;

  	hdr->opcode = ISCSI_OP_SCSI_CMD;
  	hdr->flags = ISCSI_ATTR_SIMPLE;

  	int_to_scsilun(sc->device->lun, &hdr->lun);
  	task->lun = hdr->lun;

  	hdr->exp_statsn = cpu_to_be32(conn->exp_statsn);

  	cmd_len = sc->cmd_len;
  	if (cmd_len < ISCSI_CDB_SIZE)
  		memset(&hdr->cdb[cmd_len], 0, ISCSI_CDB_SIZE - cmd_len);
  	else if (cmd_len > ISCSI_CDB_SIZE) {

  		rc = iscsi_prep_ecdb_ahs(task);

  		if (rc)
  			return rc;
  		cmd_len = ISCSI_CDB_SIZE;
  	}
  	memcpy(hdr->cdb, sc->cmnd, cmd_len);

  	task->imm_count = 0;

  	if (scsi_bidi_cmnd(sc)) {
  		hdr->flags |= ISCSI_FLAG_CMD_READ;

  		rc = iscsi_prep_bidi_ahs(task);

  		if (rc)
  			return rc;
  	}

  	if (sc->sc_data_direction == DMA_TO_DEVICE) {

  		unsigned out_len = scsi_out(sc)->length;

  		struct iscsi_r2t_info *r2t = &task->unsol_r2t;

  		hdr->data_length = cpu_to_be32(out_len);

  		hdr->flags |= ISCSI_FLAG_CMD_WRITE;
  		/*
  		 * Write counters:
  		 *
  		 *	imm_count	bytes to be sent right after
  		 *			SCSI PDU Header
  		 *
  		 *	unsol_count	bytes(as Data-Out) to be sent
  		 *			without	R2T ack right after
  		 *			immediate data
  		 *

  		 *	r2t data_length bytes to be sent via R2T ack's

  		 *
  		 *      pad_count       bytes to be sent as zero-padding
  		 */

  		memset(r2t, 0, sizeof(*r2t));

  
  		if (session->imm_data_en) {

  			if (out_len >= session->first_burst)

  				task->imm_count = min(session->first_burst,

  							conn->max_xmit_dlength);
  			else

  				task->imm_count = min(out_len,

  							conn->max_xmit_dlength);

  			hton24(hdr->dlength, task->imm_count);

  		} else

  			zero_data(hdr->dlength);

  		if (!session->initial_r2t_en) {

  			r2t->data_length = min(session->first_burst, out_len) -
  					       task->imm_count;
  			r2t->data_offset = task->imm_count;
  			r2t->ttt = cpu_to_be32(ISCSI_RESERVED_TAG);
  			r2t->exp_statsn = cpu_to_be32(conn->exp_statsn);

  		}

  		if (!task->unsol_r2t.data_length)

  			/* No unsolicit Data-Out's */

  			hdr->flags |= ISCSI_FLAG_CMD_FINAL;

  	} else {

  		hdr->flags |= ISCSI_FLAG_CMD_FINAL;
  		zero_data(hdr->dlength);

  		hdr->data_length = cpu_to_be32(scsi_in(sc)->length);

  
  		if (sc->sc_data_direction == DMA_FROM_DEVICE)
  			hdr->flags |= ISCSI_FLAG_CMD_READ;
  	}

  	/* calculate size of additional header segments (AHSs) */

  	hdrlength = task->hdr_len - sizeof(*hdr);

  
  	WARN_ON(hdrlength & (ISCSI_PAD_LEN-1));
  	hdrlength /= ISCSI_PAD_LEN;
  
  	WARN_ON(hdrlength >= 256);
  	hdr->hlength = hdrlength & 0xFF;

  	hdr->cmdsn = task->cmdsn = cpu_to_be32(session->cmdsn);

  	if (session->tt->init_task && session->tt->init_task(task))

  		return -EIO;

  	task->state = ISCSI_TASK_RUNNING;

  	session->cmdsn++;

  	conn->scsicmd_pdus_cnt++;

  	ISCSI_DBG_SESSION(session, "iscsi prep [%s cid %d sc %p cdb 0x%x "
  			  "itt 0x%x len %d bidi_len %d cmdsn %d win %d]
  ",
  			  scsi_bidi_cmnd(sc) ? "bidirectional" :
  			  sc->sc_data_direction == DMA_TO_DEVICE ?
  			  "write" : "read", conn->id, sc, sc->cmnd[0],
  			  task->itt, scsi_bufflen(sc),
  			  scsi_bidi_cmnd(sc) ? scsi_in(sc)->length : 0,
  			  session->cmdsn,
  			  session->max_cmdsn - session->exp_cmdsn + 1);

  	return 0;

  }

  
  /**

   * iscsi_free_task - free a task

   * @task: iscsi cmd task

   *
   * Must be called with session lock.

   * This function returns the scsi command to scsi-ml or cleans
   * up mgmt tasks then returns the task to the pool.

   */

  static void iscsi_free_task(struct iscsi_task *task)

  {

  	struct iscsi_conn *conn = task->conn;

  	struct iscsi_session *session = conn->session;

  	struct scsi_cmnd *sc = task->sc;

  	int oldstate = task->state;

  	ISCSI_DBG_SESSION(session, "freeing task itt 0x%x state %d sc %p
  ",
  			  task->itt, task->state, task->sc);

  	session->tt->cleanup_task(task);

  	task->state = ISCSI_TASK_FREE;

  	task->sc = NULL;

  	/*

  	 * login task is preallocated so do not free

  	 */

  	if (conn->login_task == task)

  		return;

  	kfifo_in(&session->cmdpool.queue, (void*)&task, sizeof(void*));

  	if (sc) {

  		task->sc = NULL;

  		/* SCSI eh reuses commands to verify us */
  		sc->SCp.ptr = NULL;
  		/*

  		 * queue command may call this to free the task, so
  		 * it will decide how to return sc to scsi-ml.

  		 */

  		if (oldstate != ISCSI_TASK_REQUEUE_SCSIQ)

  			sc->scsi_done(sc);
  	}

  }

  void __iscsi_get_task(struct iscsi_task *task)

  {

  	atomic_inc(&task->refcount);

  }

  EXPORT_SYMBOL_GPL(__iscsi_get_task);

  void __iscsi_put_task(struct iscsi_task *task)

  {

  	if (atomic_dec_and_test(&task->refcount))

  		iscsi_free_task(task);

  }

  EXPORT_SYMBOL_GPL(__iscsi_put_task);

  void iscsi_put_task(struct iscsi_task *task)

  {

  	struct iscsi_session *session = task->conn->session;

  
  	spin_lock_bh(&session->lock);

  	__iscsi_put_task(task);

  	spin_unlock_bh(&session->lock);
  }

  EXPORT_SYMBOL_GPL(iscsi_put_task);

  /**
   * iscsi_complete_task - finish a task
   * @task: iscsi cmd task

   * @state: state to complete task with

   *
   * Must be called with session lock.
   */

  static void iscsi_complete_task(struct iscsi_task *task, int state)

  {
  	struct iscsi_conn *conn = task->conn;

  	ISCSI_DBG_SESSION(conn->session,
  			  "complete task itt 0x%x state %d sc %p
  ",
  			  task->itt, task->state, task->sc);

  	if (task->state == ISCSI_TASK_COMPLETED ||
  	    task->state == ISCSI_TASK_ABRT_TMF ||

  	    task->state == ISCSI_TASK_ABRT_SESS_RECOV ||
  	    task->state == ISCSI_TASK_REQUEUE_SCSIQ)

  		return;
  	WARN_ON_ONCE(task->state == ISCSI_TASK_FREE);

  	task->state = state;

  
  	if (!list_empty(&task->running))
  		list_del_init(&task->running);
  
  	if (conn->task == task)
  		conn->task = NULL;
  
  	if (conn->ping_task == task)
  		conn->ping_task = NULL;
  
  	/* release get from queueing */
  	__iscsi_put_task(task);
  }

  /**
   * iscsi_complete_scsi_task - finish scsi task normally
   * @task: iscsi task for scsi cmd
   * @exp_cmdsn: expected cmd sn in cpu format
   * @max_cmdsn: max cmd sn in cpu format
   *
   * This is used when drivers do not need or cannot perform
   * lower level pdu processing.
   *
   * Called with session lock
   */
  void iscsi_complete_scsi_task(struct iscsi_task *task,
  			      uint32_t exp_cmdsn, uint32_t max_cmdsn)
  {
  	struct iscsi_conn *conn = task->conn;
  
  	ISCSI_DBG_SESSION(conn->session, "[itt 0x%x]
  ", task->itt);
  
  	conn->last_recv = jiffies;
  	__iscsi_update_cmdsn(conn->session, exp_cmdsn, max_cmdsn);
  	iscsi_complete_task(task, ISCSI_TASK_COMPLETED);
  }
  EXPORT_SYMBOL_GPL(iscsi_complete_scsi_task);

  /*

   * session lock must be held and if not called for a task that is
   * still pending or from the xmit thread, then xmit thread must
   * be suspended.

   */

  static void fail_scsi_task(struct iscsi_task *task, int err)

  {

  	struct iscsi_conn *conn = task->conn;

  	struct scsi_cmnd *sc;

  	int state;

  	/*
  	 * if a command completes and we get a successful tmf response
  	 * we will hit this because the scsi eh abort code does not take
  	 * a ref to the task.
  	 */

  	sc = task->sc;

  	if (!sc)
  		return;

  	if (task->state == ISCSI_TASK_PENDING) {

  		/*
  		 * cmd never made it to the xmit thread, so we should not count
  		 * the cmd in the sequencing
  		 */
  		conn->session->queued_cmdsn--;

  		/* it was never sent so just complete like normal */
  		state = ISCSI_TASK_COMPLETED;
  	} else if (err == DID_TRANSPORT_DISRUPTED)
  		state = ISCSI_TASK_ABRT_SESS_RECOV;
  	else
  		state = ISCSI_TASK_ABRT_TMF;

  	sc->result = err << 16;

  	if (!scsi_bidi_cmnd(sc))
  		scsi_set_resid(sc, scsi_bufflen(sc));
  	else {
  		scsi_out(sc)->resid = scsi_out(sc)->length;
  		scsi_in(sc)->resid = scsi_in(sc)->length;
  	}

  	iscsi_complete_task(task, state);

  }

  static int iscsi_prep_mgmt_task(struct iscsi_conn *conn,

  				struct iscsi_task *task)

  {
  	struct iscsi_session *session = conn->session;

  	struct iscsi_hdr *hdr = task->hdr;

  	struct iscsi_nopout *nop = (struct iscsi_nopout *)hdr;

  	uint8_t opcode = hdr->opcode & ISCSI_OPCODE_MASK;

  
  	if (conn->session->state == ISCSI_STATE_LOGGING_OUT)
  		return -ENOTCONN;

  	if (opcode != ISCSI_OP_LOGIN && opcode != ISCSI_OP_TEXT)

  		nop->exp_statsn = cpu_to_be32(conn->exp_statsn);
  	/*
  	 * pre-format CmdSN for outgoing PDU.
  	 */
  	nop->cmdsn = cpu_to_be32(session->cmdsn);
  	if (hdr->itt != RESERVED_ITT) {

  		/*

  		 * TODO: We always use immediate for normal session pdus.

  		 * If we start to send tmfs or nops as non-immediate then
  		 * we should start checking the cmdsn numbers for mgmt tasks.

  		 *
  		 * During discovery sessions iscsid sends TEXT as non immediate,
  		 * but we always only send one PDU at a time.

  		 */
  		if (conn->c_stage == ISCSI_CONN_STARTED &&
  		    !(hdr->opcode & ISCSI_OP_IMMEDIATE)) {
  			session->queued_cmdsn++;
  			session->cmdsn++;
  		}
  	}

  	if (session->tt->init_task && session->tt->init_task(task))
  		return -EIO;

  
  	if ((hdr->opcode & ISCSI_OPCODE_MASK) == ISCSI_OP_LOGOUT)
  		session->state = ISCSI_STATE_LOGGING_OUT;

  	task->state = ISCSI_TASK_RUNNING;

  	ISCSI_DBG_SESSION(session, "mgmtpdu [op 0x%x hdr->itt 0x%x "
  			  "datalen %d]
  ", hdr->opcode & ISCSI_OPCODE_MASK,
  			  hdr->itt, task->data_count);

  	return 0;
  }

  static struct iscsi_task *

  __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
  		      char *data, uint32_t data_size)
  {
  	struct iscsi_session *session = conn->session;

  	struct iscsi_host *ihost = shost_priv(session->host);

  	uint8_t opcode = hdr->opcode & ISCSI_OPCODE_MASK;

  	struct iscsi_task *task;

  	itt_t itt;

  
  	if (session->state == ISCSI_STATE_TERMINATE)
  		return NULL;

  	if (opcode == ISCSI_OP_LOGIN || opcode == ISCSI_OP_TEXT) {

  		/*
  		 * Login and Text are sent serially, in
  		 * request-followed-by-response sequence.

  		 * Same task can be used. Same ITT must be used.
  		 * Note that login_task is preallocated at conn_create().

  		 */

  		if (conn->login_task->state != ISCSI_TASK_FREE) {
  			iscsi_conn_printk(KERN_ERR, conn, "Login/Text in "
  					  "progress. Cannot start new task.
  ");
  			return NULL;
  		}

  		task = conn->login_task;

  	} else {

  		if (session->state != ISCSI_STATE_LOGGED_IN)
  			return NULL;

  		BUG_ON(conn->c_stage == ISCSI_CONN_INITIAL_STAGE);
  		BUG_ON(conn->c_stage == ISCSI_CONN_STOPPED);

  		if (!kfifo_out(&session->cmdpool.queue,

  				 (void*)&task, sizeof(void*)))

  			return NULL;
  	}

  	/*
  	 * released in complete pdu for task we expect a response for, and
  	 * released by the lld when it has transmitted the task for
  	 * pdus we do not expect a response for.
  	 */

  	atomic_set(&task->refcount, 1);
  	task->conn = conn;
  	task->sc = NULL;

  	INIT_LIST_HEAD(&task->running);
  	task->state = ISCSI_TASK_PENDING;

  
  	if (data_size) {

  		memcpy(task->data, data, data_size);
  		task->data_count = data_size;

  	} else

  		task->data_count = 0;

  	if (conn->session->tt->alloc_pdu) {
  		if (conn->session->tt->alloc_pdu(task, hdr->opcode)) {
  			iscsi_conn_printk(KERN_ERR, conn, "Could not allocate "
  					 "pdu for mgmt task.
  ");

  			goto free_task;

  		}

  	}

  	itt = task->hdr->itt;

  	task->hdr_len = sizeof(struct iscsi_hdr);

  	memcpy(task->hdr, hdr, sizeof(struct iscsi_hdr));

  
  	if (hdr->itt != RESERVED_ITT) {
  		if (session->tt->parse_pdu_itt)
  			task->hdr->itt = itt;
  		else
  			task->hdr->itt = build_itt(task->itt,
  						   task->conn->session->age);
  	}

  	if (!ihost->workq) {

  		if (iscsi_prep_mgmt_task(conn, task))
  			goto free_task;

  		if (session->tt->xmit_task(task))

  			goto free_task;

  	} else {
  		list_add_tail(&task->running, &conn->mgmtqueue);

  		iscsi_conn_queue_work(conn);

  	}

  	return task;

  
  free_task:
  	__iscsi_put_task(task);
  	return NULL;

  }
  
  int iscsi_conn_send_pdu(struct iscsi_cls_conn *cls_conn, struct iscsi_hdr *hdr,
  			char *data, uint32_t data_size)
  {
  	struct iscsi_conn *conn = cls_conn->dd_data;
  	struct iscsi_session *session = conn->session;
  	int err = 0;
  
  	spin_lock_bh(&session->lock);
  	if (!__iscsi_conn_send_pdu(conn, hdr, data, data_size))
  		err = -EPERM;
  	spin_unlock_bh(&session->lock);

  	return err;
  }
  EXPORT_SYMBOL_GPL(iscsi_conn_send_pdu);

  /**
   * iscsi_cmd_rsp - SCSI Command Response processing
   * @conn: iscsi connection
   * @hdr: iscsi header

   * @task: scsi command task

   * @data: cmd data buffer
   * @datalen: len of buffer
   *
   * iscsi_cmd_rsp sets up the scsi_cmnd fields based on the PDU and

   * then completes the command and task.

   **/

  static void iscsi_scsi_cmd_rsp(struct iscsi_conn *conn, struct iscsi_hdr *hdr,

  			       struct iscsi_task *task, char *data,

  			       int datalen)

  {

  	struct iscsi_scsi_rsp *rhdr = (struct iscsi_scsi_rsp *)hdr;

  	struct iscsi_session *session = conn->session;

  	struct scsi_cmnd *sc = task->sc;

  	iscsi_update_cmdsn(session, (struct iscsi_nopin*)rhdr);

  	conn->exp_statsn = be32_to_cpu(rhdr->statsn) + 1;
  
  	sc->result = (DID_OK << 16) | rhdr->cmd_status;
  
  	if (rhdr->response != ISCSI_STATUS_CMD_COMPLETED) {
  		sc->result = DID_ERROR << 16;
  		goto out;
  	}
  
  	if (rhdr->cmd_status == SAM_STAT_CHECK_CONDITION) {

  		uint16_t senselen;

  
  		if (datalen < 2) {
  invalid_datalen:

  			iscsi_conn_printk(KERN_ERR,  conn,
  					 "Got CHECK_CONDITION but invalid data "
  					 "buffer size of %d
  ", datalen);

  			sc->result = DID_BAD_TARGET << 16;
  			goto out;
  		}

  		senselen = get_unaligned_be16(data);

  		if (datalen < senselen)
  			goto invalid_datalen;
  
  		memcpy(sc->sense_buffer, data + 2,

  		       min_t(uint16_t, senselen, SCSI_SENSE_BUFFERSIZE));

  		ISCSI_DBG_SESSION(session, "copied %d bytes of sense
  ",
  				  min_t(uint16_t, senselen,
  				  SCSI_SENSE_BUFFERSIZE));

  	}

  	if (rhdr->flags & (ISCSI_FLAG_CMD_BIDI_UNDERFLOW |
  			   ISCSI_FLAG_CMD_BIDI_OVERFLOW)) {
  		int res_count = be32_to_cpu(rhdr->bi_residual_count);
  
  		if (scsi_bidi_cmnd(sc) && res_count > 0 &&
  				(rhdr->flags & ISCSI_FLAG_CMD_BIDI_OVERFLOW ||
  				 res_count <= scsi_in(sc)->length))
  			scsi_in(sc)->resid = res_count;
  		else
  			sc->result = (DID_BAD_TARGET << 16) | rhdr->cmd_status;
  	}

  	if (rhdr->flags & (ISCSI_FLAG_CMD_UNDERFLOW |
  	                   ISCSI_FLAG_CMD_OVERFLOW)) {

  		int res_count = be32_to_cpu(rhdr->residual_count);

  		if (res_count > 0 &&
  		    (rhdr->flags & ISCSI_FLAG_CMD_OVERFLOW ||
  		     res_count <= scsi_bufflen(sc)))

  			/* write side for bidi or uni-io set_resid */

  			scsi_set_resid(sc, res_count);

  		else
  			sc->result = (DID_BAD_TARGET << 16) | rhdr->cmd_status;

  	}

  out:

  	ISCSI_DBG_SESSION(session, "cmd rsp done [sc %p res %d itt 0x%x]
  ",

  			  sc, sc->result, task->itt);

  	conn->scsirsp_pdus_cnt++;

  	iscsi_complete_task(task, ISCSI_TASK_COMPLETED);

  }

  /**
   * iscsi_data_in_rsp - SCSI Data-In Response processing
   * @conn: iscsi connection
   * @hdr:  iscsi pdu
   * @task: scsi command task
   **/
  static void
  iscsi_data_in_rsp(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
  		  struct iscsi_task *task)
  {
  	struct iscsi_data_rsp *rhdr = (struct iscsi_data_rsp *)hdr;
  	struct scsi_cmnd *sc = task->sc;
  
  	if (!(rhdr->flags & ISCSI_FLAG_DATA_STATUS))
  		return;

  	iscsi_update_cmdsn(conn->session, (struct iscsi_nopin *)hdr);

  	sc->result = (DID_OK << 16) | rhdr->cmd_status;
  	conn->exp_statsn = be32_to_cpu(rhdr->statsn) + 1;
  	if (rhdr->flags & (ISCSI_FLAG_DATA_UNDERFLOW |
  	                   ISCSI_FLAG_DATA_OVERFLOW)) {
  		int res_count = be32_to_cpu(rhdr->residual_count);
  
  		if (res_count > 0 &&
  		    (rhdr->flags & ISCSI_FLAG_CMD_OVERFLOW ||
  		     res_count <= scsi_in(sc)->length))
  			scsi_in(sc)->resid = res_count;
  		else
  			sc->result = (DID_BAD_TARGET << 16) | rhdr->cmd_status;
  	}

  	ISCSI_DBG_SESSION(conn->session, "data in with status done "
  			  "[sc %p res %d itt 0x%x]
  ",
  			  sc, sc->result, task->itt);

  	conn->scsirsp_pdus_cnt++;

  	iscsi_complete_task(task, ISCSI_TASK_COMPLETED);

  }

  static void iscsi_tmf_rsp(struct iscsi_conn *conn, struct iscsi_hdr *hdr)
  {
  	struct iscsi_tm_rsp *tmf = (struct iscsi_tm_rsp *)hdr;
  
  	conn->exp_statsn = be32_to_cpu(hdr->statsn) + 1;
  	conn->tmfrsp_pdus_cnt++;

  	if (conn->tmf_state != TMF_QUEUED)

  		return;
  
  	if (tmf->response == ISCSI_TMF_RSP_COMPLETE)

  		conn->tmf_state = TMF_SUCCESS;

  	else if (tmf->response == ISCSI_TMF_RSP_NO_TASK)

  		conn->tmf_state = TMF_NOT_FOUND;

  	else

  		conn->tmf_state = TMF_FAILED;

  	wake_up(&conn->ehwait);
  }

  static void iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
  {
          struct iscsi_nopout hdr;

  	struct iscsi_task *task;

  	if (!rhdr && conn->ping_task)

  		return;
  
  	memset(&hdr, 0, sizeof(struct iscsi_nopout));
  	hdr.opcode = ISCSI_OP_NOOP_OUT | ISCSI_OP_IMMEDIATE;
  	hdr.flags = ISCSI_FLAG_CMD_FINAL;
  
  	if (rhdr) {

  		hdr.lun = rhdr->lun;

  		hdr.ttt = rhdr->ttt;
  		hdr.itt = RESERVED_ITT;
  	} else
  		hdr.ttt = RESERVED_ITT;

  	task = __iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)&hdr, NULL, 0);
  	if (!task)

  		iscsi_conn_printk(KERN_ERR, conn, "Could not send nopout
  ");

  	else if (!rhdr) {
  		/* only track our nops */
  		conn->ping_task = task;
  		conn->last_ping = jiffies;
  	}

  }

  static int iscsi_nop_out_rsp(struct iscsi_task *task,
  			     struct iscsi_nopin *nop, char *data, int datalen)
  {
  	struct iscsi_conn *conn = task->conn;
  	int rc = 0;
  
  	if (conn->ping_task != task) {
  		/*
  		 * If this is not in response to one of our
  		 * nops then it must be from userspace.
  		 */
  		if (iscsi_recv_pdu(conn->cls_conn, (struct iscsi_hdr *)nop,
  				   data, datalen))
  			rc = ISCSI_ERR_CONN_FAILED;
  	} else
  		mod_timer(&conn->transport_timer, jiffies + conn->recv_timeout);
  	iscsi_complete_task(task, ISCSI_TASK_COMPLETED);
  	return rc;
  }

  static int iscsi_handle_reject(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
  			       char *data, int datalen)
  {
  	struct iscsi_reject *reject = (struct iscsi_reject *)hdr;
  	struct iscsi_hdr rejected_pdu;

  	int opcode, rc = 0;

  
  	conn->exp_statsn = be32_to_cpu(reject->statsn) + 1;

  	if (ntoh24(reject->dlength) > datalen ||
  	    ntoh24(reject->dlength) < sizeof(struct iscsi_hdr)) {
  		iscsi_conn_printk(KERN_ERR, conn, "Cannot handle rejected "
  				  "pdu. Invalid data length (pdu dlength "
  				  "%u, datalen %d
  ", ntoh24(reject->dlength),
  				  datalen);
  		return ISCSI_ERR_PROTO;
  	}
  	memcpy(&rejected_pdu, data, sizeof(struct iscsi_hdr));
  	opcode = rejected_pdu.opcode & ISCSI_OPCODE_MASK;
  
  	switch (reject->reason) {
  	case ISCSI_REASON_DATA_DIGEST_ERROR:
  		iscsi_conn_printk(KERN_ERR, conn,
  				  "pdu (op 0x%x itt 0x%x) rejected "
  				  "due to DataDigest error.
  ",
  				  rejected_pdu.itt, opcode);
  		break;
  	case ISCSI_REASON_IMM_CMD_REJECT:
  		iscsi_conn_printk(KERN_ERR, conn,
  				  "pdu (op 0x%x itt 0x%x) rejected. Too many "
  				  "immediate commands.
  ",
  				  rejected_pdu.itt, opcode);
  		/*
  		 * We only send one TMF at a time so if the target could not
  		 * handle it, then it should get fixed (RFC mandates that
  		 * a target can handle one immediate TMF per conn).
  		 *
  		 * For nops-outs, we could have sent more than one if
  		 * the target is sending us lots of nop-ins
  		 */
  		if (opcode != ISCSI_OP_NOOP_OUT)
  			return 0;

  		 if (rejected_pdu.itt == cpu_to_be32(ISCSI_RESERVED_TAG))
  			/*
  			 * nop-out in response to target's nop-out rejected.
  			 * Just resend.
  			 */
  			iscsi_send_nopout(conn,
  					  (struct iscsi_nopin*)&rejected_pdu);
  		else {
  			struct iscsi_task *task;
  			/*
  			 * Our nop as ping got dropped. We know the target
  			 * and transport are ok so just clean up
  			 */
  			task = iscsi_itt_to_task(conn, rejected_pdu.itt);
  			if (!task) {
  				iscsi_conn_printk(KERN_ERR, conn,
  						 "Invalid pdu reject. Could "
  						 "not lookup rejected task.
  ");
  				rc = ISCSI_ERR_BAD_ITT;
  			} else
  				rc = iscsi_nop_out_rsp(task,
  					(struct iscsi_nopin*)&rejected_pdu,
  					NULL, 0);

  		}

  		break;
  	default:
  		iscsi_conn_printk(KERN_ERR, conn,
  				  "pdu (op 0x%x itt 0x%x) rejected. Reason "
  				  "code 0x%x
  ", rejected_pdu.itt,
  				  rejected_pdu.opcode, reject->reason);
  		break;

  	}

  	return rc;

  }

  /**

   * iscsi_itt_to_task - look up task by itt
   * @conn: iscsi connection
   * @itt: itt
   *
   * This should be used for mgmt tasks like login and nops, or if
   * the LDD's itt space does not include the session age.
   *
   * The session lock must be held.
   */

  struct iscsi_task *iscsi_itt_to_task(struct iscsi_conn *conn, itt_t itt)

  {
  	struct iscsi_session *session = conn->session;

  	int i;

  
  	if (itt == RESERVED_ITT)
  		return NULL;

  	if (session->tt->parse_pdu_itt)
  		session->tt->parse_pdu_itt(conn, itt, &i, NULL);
  	else
  		i = get_itt(itt);

  	if (i >= session->cmds_max)
  		return NULL;
  
  	return session->cmds[i];
  }

  EXPORT_SYMBOL_GPL(iscsi_itt_to_task);

  
  /**

   * __iscsi_complete_pdu - complete pdu
   * @conn: iscsi conn
   * @hdr: iscsi header
   * @data: data buffer
   * @datalen: len of data buffer
   *
   * Completes pdu processing by freeing any resources allocated at
   * queuecommand or send generic. session lock must be held and verify
   * itt must have been called.
   */

  int __iscsi_complete_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
  			 char *data, int datalen)

  {
  	struct iscsi_session *session = conn->session;
  	int opcode = hdr->opcode & ISCSI_OPCODE_MASK, rc = 0;

  	struct iscsi_task *task;

  	uint32_t itt;

  	conn->last_recv = jiffies;

  	rc = iscsi_verify_itt(conn, hdr->itt);
  	if (rc)
  		return rc;

  	if (hdr->itt != RESERVED_ITT)
  		itt = get_itt(hdr->itt);

  	else

  		itt = ~0U;

  	ISCSI_DBG_SESSION(session, "[op 0x%x cid %d itt 0x%x len %d]
  ",
  			  opcode, conn->id, itt, datalen);

  	if (itt == ~0U) {

  		iscsi_update_cmdsn(session, (struct iscsi_nopin*)hdr);

  		switch(opcode) {
  		case ISCSI_OP_NOOP_IN:

  			if (datalen) {

  				rc = ISCSI_ERR_PROTO;

  				break;
  			}

  			if (hdr->ttt == cpu_to_be32(ISCSI_RESERVED_TAG))

  				break;

  			iscsi_send_nopout(conn, (struct iscsi_nopin*)hdr);

  			break;
  		case ISCSI_OP_REJECT:

  			rc = iscsi_handle_reject(conn, hdr, data, datalen);
  			break;

  		case ISCSI_OP_ASYNC_EVENT:

  			conn->exp_statsn = be32_to_cpu(hdr->statsn) + 1;

  			if (iscsi_recv_pdu(conn->cls_conn, hdr, data, datalen))
  				rc = ISCSI_ERR_CONN_FAILED;

  			break;
  		default:
  			rc = ISCSI_ERR_BAD_OPCODE;
  			break;
  		}

  		goto out;
  	}

  	switch(opcode) {
  	case ISCSI_OP_SCSI_CMD_RSP:

  	case ISCSI_OP_SCSI_DATA_IN:
  		task = iscsi_itt_to_ctask(conn, hdr->itt);
  		if (!task)
  			return ISCSI_ERR_BAD_ITT;

  		task->last_xfer = jiffies;

  		break;
  	case ISCSI_OP_R2T:
  		/*
  		 * LLD handles R2Ts if they need to.
  		 */
  		return 0;
  	case ISCSI_OP_LOGOUT_RSP:
  	case ISCSI_OP_LOGIN_RSP:
  	case ISCSI_OP_TEXT_RSP:
  	case ISCSI_OP_SCSI_TMFUNC_RSP:
  	case ISCSI_OP_NOOP_IN:
  		task = iscsi_itt_to_task(conn, hdr->itt);
  		if (!task)
  			return ISCSI_ERR_BAD_ITT;
  		break;
  	default:
  		return ISCSI_ERR_BAD_OPCODE;
  	}
  
  	switch(opcode) {
  	case ISCSI_OP_SCSI_CMD_RSP:

  		iscsi_scsi_cmd_rsp(conn, hdr, task, data, datalen);

  		break;
  	case ISCSI_OP_SCSI_DATA_IN:

  		iscsi_data_in_rsp(conn, hdr, task);

  		break;

  	case ISCSI_OP_LOGOUT_RSP:
  		iscsi_update_cmdsn(session, (struct iscsi_nopin*)hdr);
  		if (datalen) {
  			rc = ISCSI_ERR_PROTO;
  			break;
  		}
  		conn->exp_statsn = be32_to_cpu(hdr->statsn) + 1;
  		goto recv_pdu;
  	case ISCSI_OP_LOGIN_RSP:
  	case ISCSI_OP_TEXT_RSP:
  		iscsi_update_cmdsn(session, (struct iscsi_nopin*)hdr);
  		/*
  		 * login related PDU's exp_statsn is handled in
  		 * userspace
  		 */
  		goto recv_pdu;
  	case ISCSI_OP_SCSI_TMFUNC_RSP:
  		iscsi_update_cmdsn(session, (struct iscsi_nopin*)hdr);
  		if (datalen) {
  			rc = ISCSI_ERR_PROTO;
  			break;
  		}
  
  		iscsi_tmf_rsp(conn, hdr);

  		iscsi_complete_task(task, ISCSI_TASK_COMPLETED);

  		break;
  	case ISCSI_OP_NOOP_IN:
  		iscsi_update_cmdsn(session, (struct iscsi_nopin*)hdr);
  		if (hdr->ttt != cpu_to_be32(ISCSI_RESERVED_TAG) || datalen) {
  			rc = ISCSI_ERR_PROTO;
  			break;
  		}
  		conn->exp_statsn = be32_to_cpu(hdr->statsn) + 1;

  		rc = iscsi_nop_out_rsp(task, (struct iscsi_nopin*)hdr,
  				       data, datalen);

  		break;
  	default:
  		rc = ISCSI_ERR_BAD_OPCODE;
  		break;
  	}

  out:
  	return rc;
  recv_pdu:
  	if (iscsi_recv_pdu(conn->cls_conn, hdr, data, datalen))
  		rc = ISCSI_ERR_CONN_FAILED;

  	iscsi_complete_task(task, ISCSI_TASK_COMPLETED);

  	return rc;
  }

  EXPORT_SYMBOL_GPL(__iscsi_complete_pdu);

  
  int iscsi_complete_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
  		       char *data, int datalen)
  {
  	int rc;
  
  	spin_lock(&conn->session->lock);
  	rc = __iscsi_complete_pdu(conn, hdr, data, datalen);
  	spin_unlock(&conn->session->lock);
  	return rc;
  }
  EXPORT_SYMBOL_GPL(iscsi_complete_pdu);

  int iscsi_verify_itt(struct iscsi_conn *conn, itt_t itt)

  {
  	struct iscsi_session *session = conn->session;

  	int age = 0, i = 0;

  	if (itt == RESERVED_ITT)
  		return 0;

  	if (session->tt->parse_pdu_itt)
  		session->tt->parse_pdu_itt(conn, itt, &i, &age);
  	else {
  		i = get_itt(itt);
  		age = ((__force u32)itt >> ISCSI_AGE_SHIFT) & ISCSI_AGE_MASK;
  	}
  
  	if (age != session->age) {

  		iscsi_conn_printk(KERN_ERR, conn,
  				  "received itt %x expected session age (%x)
  ",

  				  (__force u32)itt, session->age);

  		return ISCSI_ERR_BAD_ITT;
  	}

  	if (i >= session->cmds_max) {
  		iscsi_conn_printk(KERN_ERR, conn,
  				  "received invalid itt index %u (max cmds "
  				   "%u.
  ", i, session->cmds_max);
  		return ISCSI_ERR_BAD_ITT;

  	}

  	return 0;
  }
  EXPORT_SYMBOL_GPL(iscsi_verify_itt);

  /**
   * iscsi_itt_to_ctask - look up ctask by itt
   * @conn: iscsi connection
   * @itt: itt
   *
   * This should be used for cmd tasks.
   *
   * The session lock must be held.
   */
  struct iscsi_task *iscsi_itt_to_ctask(struct iscsi_conn *conn, itt_t itt)

  {

  	struct iscsi_task *task;

  
  	if (iscsi_verify_itt(conn, itt))
  		return NULL;

  	task = iscsi_itt_to_task(conn, itt);
  	if (!task || !task->sc)

  		return NULL;

  	if (task->sc->SCp.phase != conn->session->age) {
  		iscsi_session_printk(KERN_ERR, conn->session,
  				  "task's session age %d, expected %d
  ",
  				  task->sc->SCp.phase, conn->session->age);

  		return NULL;

  	}

  	return task;

  }
  EXPORT_SYMBOL_GPL(iscsi_itt_to_ctask);

  void iscsi_session_failure(struct iscsi_session *session,

  			   enum iscsi_err err)
  {

  	struct iscsi_conn *conn;
  	struct device *dev;

  	spin_lock_bh(&session->lock);

  	conn = session->leadconn;
  	if (session->state == ISCSI_STATE_TERMINATE || !conn) {

  		spin_unlock_bh(&session->lock);

  		return;
  	}
  
  	dev = get_device(&conn->cls_conn->dev);

  	spin_unlock_bh(&session->lock);

  	if (!dev)
  	        return;
  	/*
  	 * if the host is being removed bypass the connection
  	 * recovery initialization because we are going to kill
  	 * the session.
  	 */
  	if (err == ISCSI_ERR_INVALID_HOST)
  		iscsi_conn_error_event(conn->cls_conn, err);
  	else
  		iscsi_conn_failure(conn, err);
  	put_device(dev);
  }
  EXPORT_SYMBOL_GPL(iscsi_session_failure);

  void iscsi_conn_failure(struct iscsi_conn *conn, enum iscsi_err err)
  {
  	struct iscsi_session *session = conn->session;

  	spin_lock_bh(&session->lock);

  	if (session->state == ISCSI_STATE_FAILED) {

  		spin_unlock_bh(&session->lock);

  		return;
  	}

  	if (conn->stop_stage == 0)

  		session->state = ISCSI_STATE_FAILED;

  	spin_unlock_bh(&session->lock);

  	set_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx);
  	set_bit(ISCSI_SUSPEND_BIT, &conn->suspend_rx);

  	iscsi_conn_error_event(conn->cls_conn, err);

  }
  EXPORT_SYMBOL_GPL(iscsi_conn_failure);

  static int iscsi_check_cmdsn_window_closed(struct iscsi_conn *conn)
  {
  	struct iscsi_session *session = conn->session;
  
  	/*
  	 * Check for iSCSI window and take care of CmdSN wrap-around
  	 */

  	if (!iscsi_sna_lte(session->queued_cmdsn, session->max_cmdsn)) {

  		ISCSI_DBG_SESSION(session, "iSCSI CmdSN closed. ExpCmdSn "
  				  "%u MaxCmdSN %u CmdSN %u/%u
  ",
  				  session->exp_cmdsn, session->max_cmdsn,
  				  session->cmdsn, session->queued_cmdsn);

  		return -ENOSPC;
  	}
  	return 0;
  }

  static int iscsi_xmit_task(struct iscsi_conn *conn)

  {

  	struct iscsi_task *task = conn->task;

  	int rc;

  	if (test_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx))
  		return -ENODATA;

  	__iscsi_get_task(task);

  	spin_unlock_bh(&conn->session->lock);

  	rc = conn->session->tt->xmit_task(task);

  	spin_lock_bh(&conn->session->lock);

  	if (!rc) {

  		/* done with this task */

  		task->last_xfer = jiffies;

  		conn->task = NULL;

  	}
  	__iscsi_put_task(task);

  	return rc;
  }

  /**

   * iscsi_requeue_task - requeue task to run from session workqueue
   * @task: task to requeue

   *

   * LLDs that need to run a task from the session workqueue should call

   * this. The session lock must be held. This should only be called
   * by software drivers.

   */

  void iscsi_requeue_task(struct iscsi_task *task)

  {

  	struct iscsi_conn *conn = task->conn;

  	/*
  	 * this may be on the requeue list already if the xmit_task callout
  	 * is handling the r2ts while we are adding new ones
  	 */
  	if (list_empty(&task->running))
  		list_add_tail(&task->running, &conn->requeue);

  	iscsi_conn_queue_work(conn);

  }

  EXPORT_SYMBOL_GPL(iscsi_requeue_task);

  
  /**

   * iscsi_data_xmit - xmit any command into the scheduled connection
   * @conn: iscsi connection
   *
   * Notes:
   *	The function can return -EAGAIN in which case the caller must
   *	re-schedule it again later or recover. '0' return code means
   *	successful xmit.
   **/
  static int iscsi_data_xmit(struct iscsi_conn *conn)
  {

  	struct iscsi_task *task;

  	int rc = 0;

  	spin_lock_bh(&conn->session->lock);

  	if (test_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx)) {

  		ISCSI_DBG_SESSION(conn->session, "Tx suspended!
  ");

  		spin_unlock_bh(&conn->session->lock);

  		return -ENODATA;

  	}

  	if (conn->task) {
  		rc = iscsi_xmit_task(conn);

  	        if (rc)

  		        goto done;

  	}

  	/*
  	 * process mgmt pdus like nops before commands since we should
  	 * only have one nop-out as a ping from us and targets should not
  	 * overflow us with nop-ins
  	 */
  check_mgmt:

  	while (!list_empty(&conn->mgmtqueue)) {

  		conn->task = list_entry(conn->mgmtqueue.next,
  					 struct iscsi_task, running);

  		list_del_init(&conn->task->running);

  		if (iscsi_prep_mgmt_task(conn, conn->task)) {
  			__iscsi_put_task(conn->task);
  			conn->task = NULL;

  			continue;
  		}

  		rc = iscsi_xmit_task(conn);

  		if (rc)

  			goto done;

  	}

  	/* process pending command queue */

  	while (!list_empty(&conn->cmdqueue)) {

  		conn->task = list_entry(conn->cmdqueue.next, struct iscsi_task,
  					running);

  		list_del_init(&conn->task->running);

  		if (conn->session->state == ISCSI_STATE_LOGGING_OUT) {

  			fail_scsi_task(conn->task, DID_IMM_RETRY);

  			continue;
  		}

  		rc = iscsi_prep_scsi_cmd_pdu(conn->task);
  		if (rc) {

  			if (rc == -ENOMEM || rc == -EACCES) {

  				list_add_tail(&conn->task->running,
  					      &conn->cmdqueue);

  				conn->task = NULL;

  				goto done;

  			} else

  				fail_scsi_task(conn->task, DID_ABORT);

  			continue;
  		}

  		rc = iscsi_xmit_task(conn);

  		if (rc)

  			goto done;

  		/*

  		 * we could continuously get new task requests so

  		 * we need to check the mgmt queue for nops that need to
  		 * be sent to aviod starvation
  		 */

  		if (!list_empty(&conn->mgmtqueue))
  			goto check_mgmt;
  	}
  
  	while (!list_empty(&conn->requeue)) {

  		/*
  		 * we always do fastlogout - conn stop code will clean up.
  		 */
  		if (conn->session->state == ISCSI_STATE_LOGGING_OUT)
  			break;

  		task = list_entry(conn->requeue.next, struct iscsi_task,
  				  running);
  		if (iscsi_check_tmf_restrictions(task, ISCSI_OP_SCSI_DATA_OUT))
  			break;
  
  		conn->task = task;

  		list_del_init(&conn->task->running);

  		conn->task->state = ISCSI_TASK_RUNNING;

  		rc = iscsi_xmit_task(conn);

  		if (rc)

  			goto done;

  		if (!list_empty(&conn->mgmtqueue))

  			goto check_mgmt;

  	}

  	spin_unlock_bh(&conn->session->lock);

  	return -ENODATA;

  done:

  	spin_unlock_bh(&conn->session->lock);

  	return rc;

  }

  static void iscsi_xmitworker(struct work_struct *work)

  {

  	struct iscsi_conn *conn =
  		container_of(work, struct iscsi_conn, xmitwork);

  	int rc;

  	/*
  	 * serialize Xmit worker on a per-connection basis.
  	 */

  	do {
  		rc = iscsi_data_xmit(conn);
  	} while (rc >= 0 || rc == -EAGAIN);

  }

  static inline struct iscsi_task *iscsi_alloc_task(struct iscsi_conn *conn,
  						  struct scsi_cmnd *sc)
  {
  	struct iscsi_task *task;

  	if (!kfifo_out(&conn->session->cmdpool.queue,

  			 (void *) &task, sizeof(void *)))
  		return NULL;
  
  	sc->SCp.phase = conn->session->age;
  	sc->SCp.ptr = (char *) task;
  
  	atomic_set(&task->refcount, 1);
  	task->state = ISCSI_TASK_PENDING;
  	task->conn = conn;
  	task->sc = sc;

  	task->have_checked_conn = false;
  	task->last_timeout = jiffies;
  	task->last_xfer = jiffies;

  	INIT_LIST_HEAD(&task->running);
  	return task;
  }

  enum {
  	FAILURE_BAD_HOST = 1,
  	FAILURE_SESSION_FAILED,
  	FAILURE_SESSION_FREED,
  	FAILURE_WINDOW_CLOSED,

  	FAILURE_OOM,

  	FAILURE_SESSION_TERMINATE,

  	FAILURE_SESSION_IN_RECOVERY,

  	FAILURE_SESSION_RECOVERY_TIMEOUT,

  	FAILURE_SESSION_LOGGING_OUT,

  	FAILURE_SESSION_NOT_READY,

  };

  int iscsi_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *sc)

  {

  	struct iscsi_cls_session *cls_session;

  	struct iscsi_host *ihost;

  	int reason = 0;
  	struct iscsi_session *session;
  	struct iscsi_conn *conn;

  	struct iscsi_task *task = NULL;

  	sc->result = 0;

  	sc->SCp.ptr = NULL;

  	ihost = shost_priv(host);

  	cls_session = starget_to_session(scsi_target(sc->device));
  	session = cls_session->dd_data;

  	spin_lock_bh(&session->lock);

  	reason = iscsi_session_chkready(cls_session);

  	if (reason) {
  		sc->result = reason;
  		goto fault;
  	}

  	if (session->state != ISCSI_STATE_LOGGED_IN) {

  		/*
  		 * to handle the race between when we set the recovery state
  		 * and block the session we requeue here (commands could
  		 * be entering our queuecommand while a block is starting
  		 * up because the block code is not locked)
  		 */

  		switch (session->state) {

  		case ISCSI_STATE_FAILED:

  		case ISCSI_STATE_IN_RECOVERY:

  			reason = FAILURE_SESSION_IN_RECOVERY;

  			sc->result = DID_IMM_RETRY << 16;
  			break;

  		case ISCSI_STATE_LOGGING_OUT:
  			reason = FAILURE_SESSION_LOGGING_OUT;

  			sc->result = DID_IMM_RETRY << 16;
  			break;

  		case ISCSI_STATE_RECOVERY_FAILED:

  			reason = FAILURE_SESSION_RECOVERY_TIMEOUT;

  			sc->result = DID_TRANSPORT_FAILFAST << 16;

  			break;
  		case ISCSI_STATE_TERMINATE:

  			reason = FAILURE_SESSION_TERMINATE;

  			sc->result = DID_NO_CONNECT << 16;

  			break;

  		default:

  			reason = FAILURE_SESSION_FREED;

  			sc->result = DID_NO_CONNECT << 16;

  		}

  		goto fault;
  	}

  	conn = session->leadconn;

  	if (!conn) {
  		reason = FAILURE_SESSION_FREED;

  		sc->result = DID_NO_CONNECT << 16;

  		goto fault;
  	}

  	if (test_bit(ISCSI_SUSPEND_BIT, &conn->suspend_tx)) {
  		reason = FAILURE_SESSION_IN_RECOVERY;
  		sc->result = DID_REQUEUE;
  		goto fault;
  	}