[SCSI] scsi tgt: scsi target lib functionality

The core scsi target lib functions.

TODO:
- mv md/dm-bio-list.h to linux/bio-list.h so md and us do not have to
do that weird include.
- convert scsi_tgt_cmd's work struct to James's execute code. And try
to kill our scsi_tgt_cmd.
- add host state checking. We do refcouting so hotplug is partially
supported, but we need to add state checking to make it easier on
the LLD.
Signed-off-by: NMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/scsi_tgt_lib.c

+/*
+ * SCSI target lib functions
+ *
+ * Copyright (C) 2005 Mike Christie <michaelc@cs.wisc.edu>
+ * Copyright (C) 2005 FUJITA Tomonori <tomof@acm.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.
+ *
+ * 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., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+#include <linux/blkdev.h>
+#include <linux/hash.h>
+#include <linux/module.h>
+#include <linux/pagemap.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_tgt.h>
+#include <../drivers/md/dm-bio-list.h>
+
+#include "scsi_tgt_priv.h"
+
+static struct workqueue_struct *scsi_tgtd;
+static kmem_cache_t *scsi_tgt_cmd_cache;
+
+/*
+ * TODO: this struct will be killed when the block layer supports large bios
+ * and James's work struct code is in
+ */
+struct scsi_tgt_cmd {
+	/* TODO replace work with James b's code */
+	struct work_struct work;
+	/* TODO replace the lists with a large bio */
+	struct bio_list xfer_done_list;
+	struct bio_list xfer_list;
+
+	struct list_head hash_list;
+	struct request *rq;
+	u64 tag;
+
+	void *buffer;
+	unsigned bufflen;
+};
+
+#define TGT_HASH_ORDER	4
+#define cmd_hashfn(tag)	hash_long((unsigned long) (tag), TGT_HASH_ORDER)
+
+struct scsi_tgt_queuedata {
+	struct Scsi_Host *shost;
+	struct list_head cmd_hash[1 << TGT_HASH_ORDER];
+	spinlock_t cmd_hash_lock;
+};
+
+/*
+ * Function:	scsi_host_get_command()
+ *
+ * Purpose:	Allocate and setup a scsi command block and blk request
+ *
+ * Arguments:	shost	- scsi host
+ *		data_dir - dma data dir
+ *		gfp_mask- allocator flags
+ *
+ * Returns:	The allocated scsi command structure.
+ *
+ * This should be called by target LLDs to get a command.
+ */
+struct scsi_cmnd *scsi_host_get_command(struct Scsi_Host *shost,
+					enum dma_data_direction data_dir,
+					gfp_t gfp_mask)
+{
+	int write = (data_dir == DMA_TO_DEVICE);
+	struct request *rq;
+	struct scsi_cmnd *cmd;
+	struct scsi_tgt_cmd *tcmd;
+
+	/* Bail if we can't get a reference to the device */
+	if (!get_device(&shost->shost_gendev))
+		return NULL;
+
+	tcmd = kmem_cache_alloc(scsi_tgt_cmd_cache, GFP_ATOMIC);
+	if (!tcmd)
+		goto put_dev;
+
+	rq = blk_get_request(shost->uspace_req_q, write, gfp_mask);
+	if (!rq)
+		goto free_tcmd;
+
+	cmd = __scsi_get_command(shost, gfp_mask);
+	if (!cmd)
+		goto release_rq;
+
+	memset(cmd, 0, sizeof(*cmd));
+	cmd->sc_data_direction = data_dir;
+	cmd->jiffies_at_alloc = jiffies;
+	cmd->request = rq;
+
+	rq->special = cmd;
+	rq->cmd_type = REQ_TYPE_SPECIAL;
+	rq->cmd_flags |= REQ_TYPE_BLOCK_PC;
+	rq->end_io_data = tcmd;
+
+	bio_list_init(&tcmd->xfer_list);
+	bio_list_init(&tcmd->xfer_done_list);
+	tcmd->rq = rq;
+
+	return cmd;
+
+release_rq:
+	blk_put_request(rq);
+free_tcmd:
+	kmem_cache_free(scsi_tgt_cmd_cache, tcmd);
+put_dev:
+	put_device(&shost->shost_gendev);
+	return NULL;
+
+}
+EXPORT_SYMBOL_GPL(scsi_host_get_command);
+
+/*
+ * Function:	scsi_host_put_command()
+ *
+ * Purpose:	Free a scsi command block
+ *
+ * Arguments:	shost	- scsi host
+ * 		cmd	- command block to free
+ *
+ * Returns:	Nothing.
+ *
+ * Notes:	The command must not belong to any lists.
+ */
+void scsi_host_put_command(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
+{
+	struct request_queue *q = shost->uspace_req_q;
+	struct request *rq = cmd->request;
+	struct scsi_tgt_cmd *tcmd = rq->end_io_data;
+	unsigned long flags;
+
+	kmem_cache_free(scsi_tgt_cmd_cache, tcmd);
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	__blk_put_request(q, rq);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	__scsi_put_command(shost, cmd, &shost->shost_gendev);
+}
+EXPORT_SYMBOL_GPL(scsi_host_put_command);
+
+static void scsi_unmap_user_pages(struct scsi_tgt_cmd *tcmd)
+{
+	struct bio *bio;
+
+	/* must call bio_endio in case bio was bounced */
+	while ((bio = bio_list_pop(&tcmd->xfer_done_list))) {
+		bio_endio(bio, bio->bi_size, 0);
+		bio_unmap_user(bio);
+	}
+
+	while ((bio = bio_list_pop(&tcmd->xfer_list))) {
+		bio_endio(bio, bio->bi_size, 0);
+		bio_unmap_user(bio);
+	}
+}
+
+static void cmd_hashlist_del(struct scsi_cmnd *cmd)
+{
+	struct request_queue *q = cmd->request->q;
+	struct scsi_tgt_queuedata *qdata = q->queuedata;
+	unsigned long flags;
+	struct scsi_tgt_cmd *tcmd = cmd->request->end_io_data;
+
+	spin_lock_irqsave(&qdata->cmd_hash_lock, flags);
+	list_del(&tcmd->hash_list);
+	spin_unlock_irqrestore(&qdata->cmd_hash_lock, flags);
+}
+
+static void scsi_tgt_cmd_destroy(void *data)
+{
+	struct scsi_cmnd *cmd = data;
+	struct scsi_tgt_cmd *tcmd = cmd->request->end_io_data;
+
+	dprintk("cmd %p %d %lu\n", cmd, cmd->sc_data_direction,
+		rq_data_dir(cmd->request));
+	/*
+	 * We fix rq->cmd_flags here since when we told bio_map_user
+	 * to write vm for WRITE commands, blk_rq_bio_prep set
+	 * rq_data_dir the flags to READ.
+	 */
+	if (cmd->sc_data_direction == DMA_TO_DEVICE)
+		cmd->request->cmd_flags |= REQ_RW;
+	else
+		cmd->request->cmd_flags &= ~REQ_RW;
+
+	scsi_unmap_user_pages(tcmd);
+	scsi_host_put_command(scsi_tgt_cmd_to_host(cmd), cmd);
+}
+
+static void init_scsi_tgt_cmd(struct request *rq, struct scsi_tgt_cmd *tcmd,
+			      u64 tag)
+{
+	struct scsi_tgt_queuedata *qdata = rq->q->queuedata;
+	unsigned long flags;
+	struct list_head *head;
+
+	tcmd->tag = tag;
+	spin_lock_irqsave(&qdata->cmd_hash_lock, flags);
+	head = &qdata->cmd_hash[cmd_hashfn(tag)];
+	list_add(&tcmd->hash_list, head);
+	spin_unlock_irqrestore(&qdata->cmd_hash_lock, flags);
+}
+
+/*
+ * scsi_tgt_alloc_queue - setup queue used for message passing
+ * shost: scsi host
+ *
+ * This should be called by the LLD after host allocation.
+ * And will be released when the host is released.
+ */
+int scsi_tgt_alloc_queue(struct Scsi_Host *shost)
+{
+	struct scsi_tgt_queuedata *queuedata;
+	struct request_queue *q;
+	int err, i;
+
+	/*
+	 * Do we need to send a netlink event or should uspace
+	 * just respond to the hotplug event?
+	 */
+	q = __scsi_alloc_queue(shost, NULL);
+	if (!q)
+		return -ENOMEM;
+
+	queuedata = kzalloc(sizeof(*queuedata), GFP_KERNEL);
+	if (!queuedata) {
+		err = -ENOMEM;
+		goto cleanup_queue;
+	}
+	queuedata->shost = shost;
+	q->queuedata = queuedata;
+
+	/*
+	 * this is a silly hack. We should probably just queue as many
+	 * command as is recvd to userspace. uspace can then make
+	 * sure we do not overload the HBA
+	 */
+	q->nr_requests = shost->hostt->can_queue;
+	/*
+	 * We currently only support software LLDs so this does
+	 * not matter for now. Do we need this for the cards we support?
+	 * If so we should make it a host template value.
+	 */
+	blk_queue_dma_alignment(q, 0);
+	shost->uspace_req_q = q;
+
+	for (i = 0; i < ARRAY_SIZE(queuedata->cmd_hash); i++)
+		INIT_LIST_HEAD(&queuedata->cmd_hash[i]);
+	spin_lock_init(&queuedata->cmd_hash_lock);
+
+	return 0;
+
+cleanup_queue:
+	blk_cleanup_queue(q);
+	return err;
+}
+EXPORT_SYMBOL_GPL(scsi_tgt_alloc_queue);
+
+void scsi_tgt_free_queue(struct Scsi_Host *shost)
+{
+	int i;
+	unsigned long flags;
+	struct request_queue *q = shost->uspace_req_q;
+	struct scsi_cmnd *cmd;
+	struct scsi_tgt_queuedata *qdata = q->queuedata;
+	struct scsi_tgt_cmd *tcmd, *n;
+	LIST_HEAD(cmds);
+
+	spin_lock_irqsave(&qdata->cmd_hash_lock, flags);
+
+	for (i = 0; i < ARRAY_SIZE(qdata->cmd_hash); i++) {
+		list_for_each_entry_safe(tcmd, n, &qdata->cmd_hash[i],
+					 hash_list) {
+			list_del(&tcmd->hash_list);
+			list_add(&tcmd->hash_list, &cmds);
+		}
+	}
+
+	spin_unlock_irqrestore(&qdata->cmd_hash_lock, flags);
+
+	while (!list_empty(&cmds)) {
+		tcmd = list_entry(cmds.next, struct scsi_tgt_cmd, hash_list);
+		list_del(&tcmd->hash_list);
+		cmd = tcmd->rq->special;
+
+		shost->hostt->eh_abort_handler(cmd);
+		scsi_tgt_cmd_destroy(cmd);
+	}
+}
+EXPORT_SYMBOL_GPL(scsi_tgt_free_queue);
+
+struct Scsi_Host *scsi_tgt_cmd_to_host(struct scsi_cmnd *cmd)
+{
+	struct scsi_tgt_queuedata *queue = cmd->request->q->queuedata;
+	return queue->shost;
+}
+EXPORT_SYMBOL_GPL(scsi_tgt_cmd_to_host);
+
+/*
+ * scsi_tgt_queue_command - queue command for userspace processing
+ * @cmd:	scsi command
+ * @scsilun:	scsi lun
+ * @tag:	unique value to identify this command for tmf
+ */
+int scsi_tgt_queue_command(struct scsi_cmnd *cmd, struct scsi_lun *scsilun,
+			   u64 tag)
+{
+	struct scsi_tgt_cmd *tcmd = cmd->request->end_io_data;
+	int err;
+
+	init_scsi_tgt_cmd(cmd->request, tcmd, tag);
+	err = scsi_tgt_uspace_send_cmd(cmd, scsilun, tag);
+	if (err)
+		cmd_hashlist_del(cmd);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(scsi_tgt_queue_command);
+
+/*
+ * This is run from a interrpt handler normally and the unmap
+ * needs process context so we must queue
+ */
+static void scsi_tgt_cmd_done(struct scsi_cmnd *cmd)
+{
+	struct scsi_tgt_cmd *tcmd = cmd->request->end_io_data;
+
+	dprintk("cmd %p %lu\n", cmd, rq_data_dir(cmd->request));
+
+	scsi_tgt_uspace_send_status(cmd, tcmd->tag);
+	INIT_WORK(&tcmd->work, scsi_tgt_cmd_destroy, cmd);
+	queue_work(scsi_tgtd, &tcmd->work);
+}
+
+static int __scsi_tgt_transfer_response(struct scsi_cmnd *cmd)
+{
+	struct Scsi_Host *shost = scsi_tgt_cmd_to_host(cmd);
+	int err;
+
+	dprintk("cmd %p %lu\n", cmd, rq_data_dir(cmd->request));
+
+	err = shost->hostt->transfer_response(cmd, scsi_tgt_cmd_done);
+	switch (err) {
+	case SCSI_MLQUEUE_HOST_BUSY:
+	case SCSI_MLQUEUE_DEVICE_BUSY:
+		return -EAGAIN;
+	}
+
+	return 0;
+}
+
+static void scsi_tgt_transfer_response(struct scsi_cmnd *cmd)
+{
+	struct scsi_tgt_cmd *tcmd = cmd->request->end_io_data;
+	int err;
+
+	err = __scsi_tgt_transfer_response(cmd);
+	if (!err)
+		return;
+
+	cmd->result = DID_BUS_BUSY << 16;
+	err = scsi_tgt_uspace_send_status(cmd, tcmd->tag);
+	if (err <= 0)
+		/* the eh will have to pick this up */
+		printk(KERN_ERR "Could not send cmd %p status\n", cmd);
+}
+
+static int scsi_tgt_init_cmd(struct scsi_cmnd *cmd, gfp_t gfp_mask)
+{
+	struct request *rq = cmd->request;
+	struct scsi_tgt_cmd *tcmd = rq->end_io_data;
+	int count;
+
+	cmd->use_sg = rq->nr_phys_segments;
+	cmd->request_buffer = scsi_alloc_sgtable(cmd, gfp_mask);
+	if (!cmd->request_buffer)
+		return -ENOMEM;
+
+	cmd->request_bufflen = rq->data_len;
+
+	dprintk("cmd %p addr %p cnt %d %lu\n", cmd, tcmd->buffer, cmd->use_sg,
+		rq_data_dir(rq));
+	count = blk_rq_map_sg(rq->q, rq, cmd->request_buffer);
+	if (likely(count <= cmd->use_sg)) {
+		cmd->use_sg = count;
+		return 0;
+	}
+
+	eprintk("cmd %p addr %p cnt %d\n", cmd, tcmd->buffer, cmd->use_sg);
+	scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
+	return -EINVAL;
+}
+
+/* TODO: test this crap and replace bio_map_user with new interface maybe */
+static int scsi_map_user_pages(struct scsi_tgt_cmd *tcmd, struct scsi_cmnd *cmd,
+			       int rw)
+{
+	struct request_queue *q = cmd->request->q;
+	struct request *rq = cmd->request;
+	void *uaddr = tcmd->buffer;
+	unsigned int len = tcmd->bufflen;
+	struct bio *bio;
+	int err;
+
+	while (len > 0) {
+		dprintk("%lx %u\n", (unsigned long) uaddr, len);
+		bio = bio_map_user(q, NULL, (unsigned long) uaddr, len, rw);
+		if (IS_ERR(bio)) {
+			err = PTR_ERR(bio);
+			dprintk("fail to map %lx %u %d %x\n",
+				(unsigned long) uaddr, len, err, cmd->cmnd[0]);
+			goto unmap_bios;
+		}
+
+		uaddr += bio->bi_size;
+		len -= bio->bi_size;
+
+		/*
+		 * The first bio is added and merged. We could probably
+		 * try to add others using scsi_merge_bio() but for now
+		 * we keep it simple. The first bio should be pretty large
+		 * (either hitting the 1 MB bio pages limit or a queue limit)
+		 * already but for really large IO we may want to try and
+		 * merge these.
+		 */
+		if (!rq->bio) {
+			blk_rq_bio_prep(q, rq, bio);
+			rq->data_len = bio->bi_size;
+		} else
+			/* put list of bios to transfer in next go around */
+			bio_list_add(&tcmd->xfer_list, bio);
+	}
+
+	cmd->offset = 0;
+	err = scsi_tgt_init_cmd(cmd, GFP_KERNEL);
+	if (err)
+		goto unmap_bios;
+
+	return 0;
+
+unmap_bios:
+	if (rq->bio) {
+		bio_unmap_user(rq->bio);
+		while ((bio = bio_list_pop(&tcmd->xfer_list)))
+			bio_unmap_user(bio);
+	}
+
+	return err;
+}
+
+static int scsi_tgt_transfer_data(struct scsi_cmnd *);
+
+static void scsi_tgt_data_transfer_done(struct scsi_cmnd *cmd)
+{
+	struct scsi_tgt_cmd *tcmd = cmd->request->end_io_data;
+	struct bio *bio;
+	int err;
+
+	/* should we free resources here on error ? */
+	if (cmd->result) {
+send_uspace_err:
+		err = scsi_tgt_uspace_send_status(cmd, tcmd->tag);
+		if (err <= 0)
+			/* the tgt uspace eh will have to pick this up */
+			printk(KERN_ERR "Could not send cmd %p status\n", cmd);
+		return;
+	}
+
+	dprintk("cmd %p request_bufflen %u bufflen %u\n",
+		cmd, cmd->request_bufflen, tcmd->bufflen);
+
+	scsi_free_sgtable(cmd->request_buffer, cmd->sglist_len);
+	bio_list_add(&tcmd->xfer_done_list, cmd->request->bio);
+
+	tcmd->buffer += cmd->request_bufflen;
+	cmd->offset += cmd->request_bufflen;
+
+	if (!tcmd->xfer_list.head) {
+		scsi_tgt_transfer_response(cmd);
+		return;
+	}
+
+	dprintk("cmd2 %p request_bufflen %u bufflen %u\n",
+		cmd, cmd->request_bufflen, tcmd->bufflen);
+
+	bio = bio_list_pop(&tcmd->xfer_list);
+	BUG_ON(!bio);
+
+	blk_rq_bio_prep(cmd->request->q, cmd->request, bio);
+	cmd->request->data_len = bio->bi_size;
+	err = scsi_tgt_init_cmd(cmd, GFP_ATOMIC);
+	if (err) {
+		cmd->result = DID_ERROR << 16;
+		goto send_uspace_err;
+	}
+
+	if (scsi_tgt_transfer_data(cmd)) {
+		cmd->result = DID_NO_CONNECT << 16;
+		goto send_uspace_err;
+	}
+}
+
+static int scsi_tgt_transfer_data(struct scsi_cmnd *cmd)
+{
+	int err;
+	struct Scsi_Host *host = scsi_tgt_cmd_to_host(cmd);
+
+	err = host->hostt->transfer_data(cmd, scsi_tgt_data_transfer_done);
+	switch (err) {
+		case SCSI_MLQUEUE_HOST_BUSY:
+		case SCSI_MLQUEUE_DEVICE_BUSY:
+			return -EAGAIN;
+	default:
+		return 0;
+	}
+}
+
+static int scsi_tgt_copy_sense(struct scsi_cmnd *cmd, unsigned long uaddr,
+				unsigned len)
+{
+	char __user *p = (char __user *) uaddr;
+
+	if (copy_from_user(cmd->sense_buffer, p,
+			   min_t(unsigned, SCSI_SENSE_BUFFERSIZE, len))) {
+		printk(KERN_ERR "Could not copy the sense buffer\n");
+		return -EIO;
+	}
+	return 0;
+}
+
+static int scsi_tgt_abort_cmd(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
+{
+	int err;
+
+	err = shost->hostt->eh_abort_handler(cmd);
+	if (err)
+		eprintk("fail to abort %p\n", cmd);
+
+	scsi_tgt_cmd_destroy(cmd);
+	return err;
+}
+
+static struct request *tgt_cmd_hash_lookup(struct request_queue *q, u64 tag)
+{
+	struct scsi_tgt_queuedata *qdata = q->queuedata;
+	struct request *rq = NULL;
+	struct list_head *head;
+	struct scsi_tgt_cmd *tcmd;
+	unsigned long flags;
+
+	head = &qdata->cmd_hash[cmd_hashfn(tag)];
+	spin_lock_irqsave(&qdata->cmd_hash_lock, flags);
+	list_for_each_entry(tcmd, head, hash_list) {
+		if (tcmd->tag == tag) {
+			rq = tcmd->rq;
+			list_del(&tcmd->hash_list);
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&qdata->cmd_hash_lock, flags);
+
+	return rq;
+}
+
+int scsi_tgt_kspace_exec(int host_no, u64 tag, int result, u32 len,
+			 unsigned long uaddr, u8 rw)
+{
+	struct Scsi_Host *shost;
+	struct scsi_cmnd *cmd;
+	struct request *rq;
+	struct scsi_tgt_cmd *tcmd;
+	int err = 0;
+
+	dprintk("%d %llu %d %u %lx %u\n", host_no, (unsigned long long) tag,
+		result, len, uaddr, rw);
+
+	/* TODO: replace with a O(1) alg */
+	shost = scsi_host_lookup(host_no);
+	if (IS_ERR(shost)) {
+		printk(KERN_ERR "Could not find host no %d\n", host_no);
+		return -EINVAL;
+	}
+
+	if (!shost->uspace_req_q) {
+		printk(KERN_ERR "Not target scsi host %d\n", host_no);
+		goto done;
+	}
+
+	rq = tgt_cmd_hash_lookup(shost->uspace_req_q, tag);
+	if (!rq) {
+		printk(KERN_ERR "Could not find tag %llu\n",
+		       (unsigned long long) tag);
+		err = -EINVAL;
+		goto done;
+	}
+	cmd = rq->special;
+
+	dprintk("cmd %p result %d len %d bufflen %u %lu %x\n", cmd,
+		result, len, cmd->request_bufflen, rq_data_dir(rq), cmd->cmnd[0]);
+
+	if (result == TASK_ABORTED) {
+		scsi_tgt_abort_cmd(shost, cmd);
+		goto done;
+	}
+	/*
+	 * store the userspace values here, the working values are
+	 * in the request_* values
+	 */
+	tcmd = cmd->request->end_io_data;
+	tcmd->buffer = (void *)uaddr;
+	tcmd->bufflen = len;
+	cmd->result = result;
+
+	if (!tcmd->bufflen || cmd->request_buffer) {
+		err = __scsi_tgt_transfer_response(cmd);
+		goto done;
+	}
+
+	/*
+	 * TODO: Do we need to handle case where request does not
+	 * align with LLD.
+	 */
+	err = scsi_map_user_pages(rq->end_io_data, cmd, rw);
+	if (err) {
+		eprintk("%p %d\n", cmd, err);
+		err = -EAGAIN;
+		goto done;
+	}
+
+	/* userspace failure */
+	if (cmd->result) {
+		if (status_byte(cmd->result) == CHECK_CONDITION)
+			scsi_tgt_copy_sense(cmd, uaddr, len);
+		err = __scsi_tgt_transfer_response(cmd);
+		goto done;
+	}
+	/* ask the target LLD to transfer the data to the buffer */
+	err = scsi_tgt_transfer_data(cmd);
+
+done:
+	scsi_host_put(shost);
+	return err;
+}
+
+int scsi_tgt_tsk_mgmt_request(struct Scsi_Host *shost, int function, u64 tag,
+			      struct scsi_lun *scsilun, void *data)
+{
+	int err;
+
+	/* TODO: need to retry if this fails. */
+	err = scsi_tgt_uspace_send_tsk_mgmt(shost->host_no, function,
+					    tag, scsilun, data);
+	if (err < 0)
+		eprintk("The task management request lost!\n");
+	return err;
+}
+EXPORT_SYMBOL_GPL(scsi_tgt_tsk_mgmt_request);
+
+int scsi_tgt_kspace_tsk_mgmt(int host_no, u64 mid, int result)
+{
+	struct Scsi_Host *shost;
+	int err = -EINVAL;
+
+	dprintk("%d %d %llx\n", host_no, result, (unsigned long long) mid);
+
+	shost = scsi_host_lookup(host_no);
+	if (IS_ERR(shost)) {
+		printk(KERN_ERR "Could not find host no %d\n", host_no);
+		return err;
+	}
+
+	if (!shost->uspace_req_q) {
+		printk(KERN_ERR "Not target scsi host %d\n", host_no);
+		goto done;
+	}
+
+	err = shost->hostt->tsk_mgmt_response(mid, result);
+done:
+	scsi_host_put(shost);
+	return err;
+}
+
+static int __init scsi_tgt_init(void)
+{
+	int err;
+
+	scsi_tgt_cmd_cache = kmem_cache_create("scsi_tgt_cmd",
+					       sizeof(struct scsi_tgt_cmd),
+					       0, 0, NULL, NULL);
+	if (!scsi_tgt_cmd_cache)
+		return -ENOMEM;
+
+	scsi_tgtd = create_workqueue("scsi_tgtd");
+	if (!scsi_tgtd) {
+		err = -ENOMEM;
+		goto free_kmemcache;
+	}
+
+	err = scsi_tgt_if_init();
+	if (err)
+		goto destroy_wq;
+
+	return 0;
+
+destroy_wq:
+	destroy_workqueue(scsi_tgtd);
+free_kmemcache:
+	kmem_cache_destroy(scsi_tgt_cmd_cache);
+	return err;
+}
+
+static void __exit scsi_tgt_exit(void)
+{
+	destroy_workqueue(scsi_tgtd);
+	scsi_tgt_if_exit();
+	kmem_cache_destroy(scsi_tgt_cmd_cache);
+}
+
+module_init(scsi_tgt_init);
+module_exit(scsi_tgt_exit);
+
+MODULE_DESCRIPTION("SCSI target core");
+MODULE_LICENSE("GPL");

drivers/scsi/scsi_tgt_priv.h

+struct scsi_cmnd;
+struct scsi_lun;
+struct Scsi_Host;
+struct task_struct;
+
+/* tmp - will replace with SCSI logging stuff */
+#define eprintk(fmt, args...)					\
+do {								\
+	printk("%s(%d) " fmt, __FUNCTION__, __LINE__, ##args);	\
+} while (0)
+
+#define dprintk(fmt, args...)
+/* #define dprintk eprintk */
+
+extern void scsi_tgt_if_exit(void);
+extern int scsi_tgt_if_init(void);
+
+extern int scsi_tgt_uspace_send_cmd(struct scsi_cmnd *cmd, struct scsi_lun *lun,
+				    u64 tag);
+extern int scsi_tgt_uspace_send_status(struct scsi_cmnd *cmd, u64 tag);
+extern int scsi_tgt_kspace_exec(int host_no, u64 tag, int result, u32 len,
+				unsigned long uaddr, u8 rw);
+extern int scsi_tgt_uspace_send_tsk_mgmt(int host_no, int function, u64 tag,
+					 struct scsi_lun *scsilun, void *data);
+extern int scsi_tgt_kspace_tsk_mgmt(int host_no, u64 mid, int result);

include/scsi/scsi_tgt.h

+/*
+ * SCSI target definitions
+ */
+
+#include <linux/dma-mapping.h>
+
+struct Scsi_Host;
+struct scsi_cmnd;
+struct scsi_lun;
+
+extern struct Scsi_Host *scsi_tgt_cmd_to_host(struct scsi_cmnd *);
+extern int scsi_tgt_alloc_queue(struct Scsi_Host *);
+extern void scsi_tgt_free_queue(struct Scsi_Host *);
+extern int scsi_tgt_queue_command(struct scsi_cmnd *, struct scsi_lun *, u64);
+extern int scsi_tgt_tsk_mgmt_request(struct Scsi_Host *, int, u64, struct scsi_lun *,
+				     void *);
+extern struct scsi_cmnd *scsi_host_get_command(struct Scsi_Host *,
+					       enum dma_data_direction,	gfp_t);
+extern void scsi_host_put_command(struct Scsi_Host *, struct scsi_cmnd *);