[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: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

3 files changed, 786 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
new file mode 100644
index 000000000000..39da5cd6fb6f
--- /dev/null
+++ b/drivers/scsi/scsi_tgt_lib.c
@@ -0,0 +1,742 @@
+/*
+ * 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");
diff --git a/drivers/scsi/scsi_tgt_priv.h b/drivers/scsi/scsi_tgt_priv.h
new file mode 100644
index 000000000000..84488c51ff62
--- /dev/null
+++ b/drivers/scsi/scsi_tgt_priv.h
@@ -0,0 +1,25 @@
+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);
diff --git a/include/scsi/scsi_tgt.h b/include/scsi/scsi_tgt.h
new file mode 100644
index 000000000000..4f4427937af2
--- /dev/null
+++ b/include/scsi/scsi_tgt.h
@@ -0,0 +1,19 @@
+/*
+ * 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 *);