cregit-Linux how code gets into the kernel

Release 4.11 drivers/scsi/libiscsi.c

Directory: drivers/scsi
/*
 * 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/sched/signal.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);
}

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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;
}


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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));
}

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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++;
}

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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;
}


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/*
 * 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\n", cmd->cmd_len, rlen, pad_len, ahslength,
		          task->hdr_len);
	return 0;
}


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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)\n",
		          be32_to_cpu(rlen_ahdr->read_length),
		          be16_to_cpu(rlen_ahdr->ahslength));
	return 0;
}


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/**
 * 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;
	u64 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.\n",
					  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.\n",
					  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\n", task->itt,
					  task->hdr_itt);
			return -EACCES;
		}
		break;
	}

	return 0;
}


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/**
 * 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, transfer_length;
	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 (scsi_get_prot_op(sc) != SCSI_PROT_NORMAL)
		task->protected = true;

	transfer_length = scsi_transfer_length(sc);
	hdr->data_length = cpu_to_be32(transfer_length);
	if (sc->sc_data_direction == DMA_TO_DEVICE) {
		struct iscsi_r2t_info *r2t = &task->unsol_r2t;

		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 (transfer_length >= session->first_burst)
				task->imm_count = min(session->first_burst,
							conn->max_xmit_dlength);
			else
				task->imm_count = min(transfer_length,
						      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,
					       transfer_length) -
					       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);

		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]\n",
			  scsi_bidi_cmnd(sc) ? "bidirectional" :
			  sc->sc_data_direction == DMA_TO_DEVICE ?
			  "write" : "read", conn->id, sc, sc->cmnd[0],
			  task->itt, transfer_length,
			  scsi_bidi_cmnd(sc) ? scsi_in(sc)->length : 0,
			  session->cmdsn,
			  session->max_cmdsn - session->exp_cmdsn + 1);
	return 0;
}


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/**
 * iscsi_free_task - free a task
 * @task: iscsi cmd task
 *
 * Must be called with session back_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\n",
			  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) {
		/* 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);
	}
}


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void __iscsi_get_task(struct iscsi_task *task)
{
	atomic_inc(&task->refcount);
}

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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);
}

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EXPORT_SYMBOL_GPL(__iscsi_put_task);




void iscsi_put_task(struct iscsi_task *task)
{
	struct iscsi_session *session = task->conn->session;

	/* regular RX path uses back_lock */
	spin_lock_bh(&session->back_lock);
	__iscsi_put_task(task);
	spin_unlock_bh(&session->back_lock);
}

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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 back_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\n",
			  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;

	spin_lock_bh(&conn->taskqueuelock);
	if (!list_empty(&task->running)) {
		pr_debug_once("%s while task on list", __func__);
		list_del_init(&task->running);
	}
	spin_unlock_bh(&conn->taskqueuelock);

	if (conn->task == task)
		conn->task = NULL;

	if (conn->ping_task == task)
		conn->ping_task = NULL;

	/* release get from queueing */
	__iscsi_put_task(task);
}


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/**
 * 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 back_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]\n", task->itt);

	conn->last_recv = jiffies;
	__iscsi_update_cmdsn(conn->session, exp_cmdsn, max_cmdsn);
	iscsi_complete_task(task, ISCSI_TASK_COMPLETED);
}

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EXPORT_SYMBOL_GPL(iscsi_complete_scsi_task);


/*
 * session back_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;
	}

	/* regular RX path uses back_lock */
	spin_lock_bh(&conn->session->back_lock);
	iscsi_complete_task(task, state);
	spin_unlock_bh(&conn->session->back_lock);
}


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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]\n", hdr->opcode & ISCSI_OPCODE_MASK,
			  hdr->itt, task->data_count);
	return 0;
}


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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.\n");
			return NULL;
		}

		if (data_size > ISCSI_DEF_MAX_RECV_SEG_LEN) {
			iscsi_conn_printk(KERN_ERR, conn, "Invalid buffer len of %u for login task. Max len is %u\n", data_size, ISCSI_DEF_MAX_RECV_SEG_LEN);
			return NULL;
		}

		task = conn->login_task;
	} else {
		if (session->state != ISCSI_STATE_LOGGED_IN)
			return NULL;

		if (data_size != 0) {
			iscsi_conn_printk(KERN_ERR, conn, "Can not send data buffer of len %u for op 0x%x\n", data_size, opcode);