text: /*
   * Xen SCSI backend driver
   *
   * Copyright (c) 2008, FUJITSU Limited
   *
   * Based on the blkback driver code.
   * Adaption to kernel taget core infrastructure taken from vhost/scsi.c
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License version 2
   * as published by the Free Software Foundation; or, when distributed
   * separately from the Linux kernel or incorporated into other
   * software packages, subject to the following license:
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this source file (the "Software"), to deal in the Software without
   * restriction, including without limitation the rights to use, copy, modify,
   * merge, publish, distribute, sublicense, and/or sell copies of the Software,
   * and to permit persons to whom the Software is furnished to do so, subject to
   * the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
   * IN THE SOFTWARE.
   */
  
  #define pr_fmt(fmt) "xen-pvscsi: " fmt
  
  #include <stdarg.h>
  
  #include <linux/module.h>
  #include <linux/utsname.h>
  #include <linux/interrupt.h>
  #include <linux/slab.h>
  #include <linux/wait.h>
  #include <linux/sched.h>
  #include <linux/list.h>
  #include <linux/gfp.h>
  #include <linux/delay.h>
  #include <linux/spinlock.h>
  #include <linux/configfs.h>
  
  #include <generated/utsrelease.h>
  
  #include <scsi/scsi.h>
  #include <scsi/scsi_dbg.h>
  #include <scsi/scsi_eh.h>
  #include <scsi/scsi_tcq.h>
  
  #include <target/target_core_base.h>
  #include <target/target_core_fabric.h>
  #include <target/target_core_configfs.h>
  #include <target/target_core_fabric_configfs.h>
  
  #include <asm/hypervisor.h>
  
  #include <xen/xen.h>
  #include <xen/balloon.h>
  #include <xen/events.h>
  #include <xen/xenbus.h>
  #include <xen/grant_table.h>
  #include <xen/page.h>
  
  #include <xen/interface/grant_table.h>
  #include <xen/interface/io/vscsiif.h>
  
  #define VSCSI_VERSION	"v0.1"
  #define VSCSI_NAMELEN	32
  
  struct ids_tuple {
  	unsigned int hst;		/* host    */
  	unsigned int chn;		/* channel */
  	unsigned int tgt;		/* target  */
  	unsigned int lun;		/* LUN     */
  };
  
  struct v2p_entry {
  	struct ids_tuple v;		/* translate from */
  	struct scsiback_tpg *tpg;	/* translate to   */
  	unsigned int lun;
  	struct kref kref;
  	struct list_head l;
  };
  
  struct vscsibk_info {
  	struct xenbus_device *dev;
  
  	domid_t domid;
  	unsigned int irq;
  
  	struct vscsiif_back_ring ring;
  	int ring_error;
  
  	spinlock_t ring_lock;
  	atomic_t nr_unreplied_reqs;
  
  	spinlock_t v2p_lock;
  	struct list_head v2p_entry_lists;
  
  	wait_queue_head_t waiting_to_free;
  };
  
  /* theoretical maximum of grants for one request */
  #define VSCSI_MAX_GRANTS	(SG_ALL + VSCSIIF_SG_TABLESIZE)
  
  /*
   * VSCSI_GRANT_BATCH is the maximum number of grants to be processed in one
   * call to map/unmap grants. Don't choose it too large, as there are arrays
   * with VSCSI_GRANT_BATCH elements allocated on the stack.
   */
  #define VSCSI_GRANT_BATCH	16
  
  struct vscsibk_pend {
  	uint16_t rqid;
  
  	uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE];
  	uint8_t cmd_len;
  
  	uint8_t sc_data_direction;
  	uint16_t n_sg;		/* real length of SG list */
  	uint16_t n_grants;	/* SG pages and potentially SG list */
  	uint32_t data_len;
  	uint32_t result;
  
  	struct vscsibk_info *info;
  	struct v2p_entry *v2p;
  	struct scatterlist *sgl;
  
  	uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
  
  	grant_handle_t grant_handles[VSCSI_MAX_GRANTS];
  	struct page *pages[VSCSI_MAX_GRANTS];
  
  	struct se_cmd se_cmd;
  };
  
  struct scsiback_tmr {
  	atomic_t tmr_complete;
  	wait_queue_head_t tmr_wait;
  };
  
  struct scsiback_nexus {
  	/* Pointer to TCM session for I_T Nexus */
  	struct se_session *tvn_se_sess;
  };
  
  struct scsiback_tport {
  	/* SCSI protocol the tport is providing */
  	u8 tport_proto_id;
  	/* Binary World Wide unique Port Name for pvscsi Target port */
  	u64 tport_wwpn;
  	/* ASCII formatted WWPN for pvscsi Target port */
  	char tport_name[VSCSI_NAMELEN];
  	/* Returned by scsiback_make_tport() */
  	struct se_wwn tport_wwn;
  };
  
  struct scsiback_tpg {
  	/* scsiback port target portal group tag for TCM */
  	u16 tport_tpgt;
  	/* track number of TPG Port/Lun Links wrt explicit I_T Nexus shutdown */
  	int tv_tpg_port_count;
  	/* xen-pvscsi references to tpg_nexus, protected by tv_tpg_mutex */
  	int tv_tpg_fe_count;
  	/* list for scsiback_list */
  	struct list_head tv_tpg_list;
  	/* Used to protect access for tpg_nexus */
  	struct mutex tv_tpg_mutex;
  	/* Pointer to the TCM pvscsi I_T Nexus for this TPG endpoint */
  	struct scsiback_nexus *tpg_nexus;
  	/* Pointer back to scsiback_tport */
  	struct scsiback_tport *tport;
  	/* Returned by scsiback_make_tpg() */
  	struct se_portal_group se_tpg;
  	/* alias used in xenstore */
  	char param_alias[VSCSI_NAMELEN];
  	/* list of info structures related to this target portal group */
  	struct list_head info_list;
  };
  
  #define SCSIBACK_INVALID_HANDLE (~0)
  
  static bool log_print_stat;
  module_param(log_print_stat, bool, 0644);
  
  static int scsiback_max_buffer_pages = 1024;
  module_param_named(max_buffer_pages, scsiback_max_buffer_pages, int, 0644);
  MODULE_PARM_DESC(max_buffer_pages,
  "Maximum number of free pages to keep in backend buffer");
  
  static struct kmem_cache *scsiback_cachep;
  static DEFINE_SPINLOCK(free_pages_lock);
  static int free_pages_num;
  static LIST_HEAD(scsiback_free_pages);
  
  /* Global spinlock to protect scsiback TPG list */
  static DEFINE_MUTEX(scsiback_mutex);
  static LIST_HEAD(scsiback_list);
  
  static const struct target_core_fabric_ops scsiback_ops;
  
  static void scsiback_get(struct vscsibk_info *info)
  {
  	atomic_inc(&info->nr_unreplied_reqs);
  }
  
  static void scsiback_put(struct vscsibk_info *info)
  {
  	if (atomic_dec_and_test(&info->nr_unreplied_reqs))
  		wake_up(&info->waiting_to_free);
  }
  
  static void put_free_pages(struct page **page, int num)
  {
  	unsigned long flags;
  	int i = free_pages_num + num, n = num;
  
  	if (num == 0)
  		return;
  	if (i > scsiback_max_buffer_pages) {
  		n = min(num, i - scsiback_max_buffer_pages);
  		gnttab_free_pages(n, page + num - n);
  		n = num - n;
  	}
  	spin_lock_irqsave(&free_pages_lock, flags);
  	for (i = 0; i < n; i++)
  		list_add(&page[i]->lru, &scsiback_free_pages);
  	free_pages_num += n;
  	spin_unlock_irqrestore(&free_pages_lock, flags);
  }
  
  static int get_free_page(struct page **page)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&free_pages_lock, flags);
  	if (list_empty(&scsiback_free_pages)) {
  		spin_unlock_irqrestore(&free_pages_lock, flags);
  		return gnttab_alloc_pages(1, page);
  	}
  	page[0] = list_first_entry(&scsiback_free_pages, struct page, lru);
  	list_del(&page[0]->lru);
  	free_pages_num--;
  	spin_unlock_irqrestore(&free_pages_lock, flags);
  	return 0;
  }
  
  static unsigned long vaddr_page(struct page *page)
  {
  	unsigned long pfn = page_to_pfn(page);
  
  	return (unsigned long)pfn_to_kaddr(pfn);
  }
  
  static unsigned long vaddr(struct vscsibk_pend *req, int seg)
  {
  	return vaddr_page(req->pages[seg]);
  }
  
  static void scsiback_print_status(char *sense_buffer, int errors,
  					struct vscsibk_pend *pending_req)
  {
  	struct scsiback_tpg *tpg = pending_req->v2p->tpg;
  
  	pr_err("[%s:%d] cmnd[0]=%02x -> st=%02x msg=%02x host=%02x drv=%02x\n",
  	       tpg->tport->tport_name, pending_req->v2p->lun,
  	       pending_req->cmnd[0], status_byte(errors), msg_byte(errors),
  	       host_byte(errors), driver_byte(errors));
  }
  
  static void scsiback_fast_flush_area(struct vscsibk_pend *req)
  {
  	struct gnttab_unmap_grant_ref unmap[VSCSI_GRANT_BATCH];
  	struct page *pages[VSCSI_GRANT_BATCH];
  	unsigned int i, invcount = 0;
  	grant_handle_t handle;
  	int err;
  
  	kfree(req->sgl);
  	req->sgl = NULL;
  	req->n_sg = 0;
  
  	if (!req->n_grants)
  		return;
  
  	for (i = 0; i < req->n_grants; i++) {
  		handle = req->grant_handles[i];
  		if (handle == SCSIBACK_INVALID_HANDLE)
  			continue;
  		gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i),
  				    GNTMAP_host_map, handle);
  		req->grant_handles[i] = SCSIBACK_INVALID_HANDLE;
  		pages[invcount] = req->pages[i];
  		put_page(pages[invcount]);
  		invcount++;
  		if (invcount < VSCSI_GRANT_BATCH)
  			continue;
  		err = gnttab_unmap_refs(unmap, NULL, pages, invcount);
  		BUG_ON(err);
  		invcount = 0;
  	}
  
  	if (invcount) {
  		err = gnttab_unmap_refs(unmap, NULL, pages, invcount);
  		BUG_ON(err);
  	}
  
  	put_free_pages(req->pages, req->n_grants);
  	req->n_grants = 0;
  }
  
  static void scsiback_free_translation_entry(struct kref *kref)
  {
  	struct v2p_entry *entry = container_of(kref, struct v2p_entry, kref);
  	struct scsiback_tpg *tpg = entry->tpg;
  
  	mutex_lock(&tpg->tv_tpg_mutex);
  	tpg->tv_tpg_fe_count--;
  	mutex_unlock(&tpg->tv_tpg_mutex);
  
  	kfree(entry);
  }
  
  static void scsiback_do_resp_with_sense(char *sense_buffer, int32_t result,
  			uint32_t resid, struct vscsibk_pend *pending_req)
  {
  	struct vscsiif_response *ring_res;
  	struct vscsibk_info *info = pending_req->info;
  	int notify;
  	struct scsi_sense_hdr sshdr;
  	unsigned long flags;
  	unsigned len;
  
  	spin_lock_irqsave(&info->ring_lock, flags);
  
  	ring_res = RING_GET_RESPONSE(&info->ring, info->ring.rsp_prod_pvt);
  	info->ring.rsp_prod_pvt++;
  
  	ring_res->rslt   = result;
  	ring_res->rqid   = pending_req->rqid;
  
  	if (sense_buffer != NULL &&
  	    scsi_normalize_sense(sense_buffer, VSCSIIF_SENSE_BUFFERSIZE,
  				 &sshdr)) {
  		len = min_t(unsigned, 8 + sense_buffer[7],
  			    VSCSIIF_SENSE_BUFFERSIZE);
  		memcpy(ring_res->sense_buffer, sense_buffer, len);
  		ring_res->sense_len = len;
  	} else {
  		ring_res->sense_len = 0;
  	}
  
  	ring_res->residual_len = resid;
  
  	RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&info->ring, notify);
  	spin_unlock_irqrestore(&info->ring_lock, flags);
  
  	if (notify)
  		notify_remote_via_irq(info->irq);
  
  	if (pending_req->v2p)
  		kref_put(&pending_req->v2p->kref,
  			 scsiback_free_translation_entry);
  }
  
  static void scsiback_cmd_done(struct vscsibk_pend *pending_req)
  {
  	struct vscsibk_info *info = pending_req->info;
  	unsigned char *sense_buffer;
  	unsigned int resid;
  	int errors;
  
  	sense_buffer = pending_req->sense_buffer;
  	resid        = pending_req->se_cmd.residual_count;
  	errors       = pending_req->result;
  
  	if (errors && log_print_stat)
  		scsiback_print_status(sense_buffer, errors, pending_req);
  
  	scsiback_fast_flush_area(pending_req);
  	scsiback_do_resp_with_sense(sense_buffer, errors, resid, pending_req);
  	scsiback_put(info);
  }
  
  static void scsiback_cmd_exec(struct vscsibk_pend *pending_req)
  {
  	struct se_cmd *se_cmd = &pending_req->se_cmd;
  	struct se_session *sess = pending_req->v2p->tpg->tpg_nexus->tvn_se_sess;
  	int rc;
  
  	memset(pending_req->sense_buffer, 0, VSCSIIF_SENSE_BUFFERSIZE);
  
  	memset(se_cmd, 0, sizeof(*se_cmd));
  
  	scsiback_get(pending_req->info);
  	rc = target_submit_cmd_map_sgls(se_cmd, sess, pending_req->cmnd,
  			pending_req->sense_buffer, pending_req->v2p->lun,
  			pending_req->data_len, 0,
  			pending_req->sc_data_direction, 0,
  			pending_req->sgl, pending_req->n_sg,
  			NULL, 0, NULL, 0);
  	if (rc < 0) {
  		transport_send_check_condition_and_sense(se_cmd,
  				TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, 0);
  		transport_generic_free_cmd(se_cmd, 0);
  	}
  }
  
  static int scsiback_gnttab_data_map_batch(struct gnttab_map_grant_ref *map,
  	struct page **pg, grant_handle_t *grant, int cnt)
  {
  	int err, i;
  
  	if (!cnt)
  		return 0;
  
  	err = gnttab_map_refs(map, NULL, pg, cnt);
  	BUG_ON(err);
  	for (i = 0; i < cnt; i++) {
  		if (unlikely(map[i].status != GNTST_okay)) {
  			pr_err("invalid buffer -- could not remap it\n");
  			map[i].handle = SCSIBACK_INVALID_HANDLE;
  			err = -ENOMEM;
  		} else {
  			get_page(pg[i]);
  		}
  		grant[i] = map[i].handle;
  	}
  	return err;
  }
  
  static int scsiback_gnttab_data_map_list(struct vscsibk_pend *pending_req,
  			struct scsiif_request_segment *seg, struct page **pg,
  			grant_handle_t *grant, int cnt, u32 flags)
  {
  	int mapcount = 0, i, err = 0;
  	struct gnttab_map_grant_ref map[VSCSI_GRANT_BATCH];
  	struct vscsibk_info *info = pending_req->info;
  
  	for (i = 0; i < cnt; i++) {
  		if (get_free_page(pg + mapcount)) {
  			put_free_pages(pg, mapcount);
  			pr_err("no grant page\n");
  			return -ENOMEM;
  		}
  		gnttab_set_map_op(&map[mapcount], vaddr_page(pg[mapcount]),
  				  flags, seg[i].gref, info->domid);
  		mapcount++;
  		if (mapcount < VSCSI_GRANT_BATCH)
  			continue;
  		err = scsiback_gnttab_data_map_batch(map, pg, grant, mapcount);
  		pg += mapcount;
  		grant += mapcount;
  		pending_req->n_grants += mapcount;
  		if (err)
  			return err;
  		mapcount = 0;
  	}
  	err = scsiback_gnttab_data_map_batch(map, pg, grant, mapcount);
  	pending_req->n_grants += mapcount;
  	return err;
  }
  
  static int scsiback_gnttab_data_map(struct vscsiif_request *ring_req,
  					struct vscsibk_pend *pending_req)
  {
  	u32 flags;
  	int i, err, n_segs, i_seg = 0;
  	struct page **pg;
  	struct scsiif_request_segment *seg;
  	unsigned long end_seg = 0;
  	unsigned int nr_segments = (unsigned int)ring_req->nr_segments;
  	unsigned int nr_sgl = 0;
  	struct scatterlist *sg;
  	grant_handle_t *grant;
  
  	pending_req->n_sg = 0;
  	pending_req->n_grants = 0;
  	pending_req->data_len = 0;
  
  	nr_segments &= ~VSCSIIF_SG_GRANT;
  	if (!nr_segments)
  		return 0;
  
  	if (nr_segments > VSCSIIF_SG_TABLESIZE) {
  		pr_debug("invalid parameter nr_seg = %d\n",
  			ring_req->nr_segments);
  		return -EINVAL;
  	}
  
  	if (ring_req->nr_segments & VSCSIIF_SG_GRANT) {
  		err = scsiback_gnttab_data_map_list(pending_req, ring_req->seg,
  			pending_req->pages, pending_req->grant_handles,
  			nr_segments, GNTMAP_host_map | GNTMAP_readonly);
  		if (err)
  			return err;
  		nr_sgl = nr_segments;
  		nr_segments = 0;
  		for (i = 0; i < nr_sgl; i++) {
  			n_segs = ring_req->seg[i].length /
  				 sizeof(struct scsiif_request_segment);
  			if ((unsigned)ring_req->seg[i].offset +
  			    (unsigned)ring_req->seg[i].length > PAGE_SIZE ||
  			    n_segs * sizeof(struct scsiif_request_segment) !=
  			    ring_req->seg[i].length)
  				return -EINVAL;
  			nr_segments += n_segs;
  		}
  		if (nr_segments > SG_ALL) {
  			pr_debug("invalid nr_seg = %d\n", nr_segments);
  			return -EINVAL;
  		}
  	}
  
  	/* free of (sgl) in fast_flush_area() */
  	pending_req->sgl = kmalloc_array(nr_segments,
  					sizeof(struct scatterlist), GFP_KERNEL);
  	if (!pending_req->sgl)
  		return -ENOMEM;
  
  	sg_init_table(pending_req->sgl, nr_segments);
  	pending_req->n_sg = nr_segments;
  
  	flags = GNTMAP_host_map;
  	if (pending_req->sc_data_direction == DMA_TO_DEVICE)
  		flags |= GNTMAP_readonly;
  
  	pg = pending_req->pages + nr_sgl;
  	grant = pending_req->grant_handles + nr_sgl;
  	if (!nr_sgl) {
  		seg = ring_req->seg;
  		err = scsiback_gnttab_data_map_list(pending_req, seg,
  			pg, grant, nr_segments, flags);
  		if (err)
  			return err;
  	} else {
  		for (i = 0; i < nr_sgl; i++) {
  			seg = (struct scsiif_request_segment *)(
  			      vaddr(pending_req, i) + ring_req->seg[i].offset);
  			n_segs = ring_req->seg[i].length /
  				 sizeof(struct scsiif_request_segment);
  			err = scsiback_gnttab_data_map_list(pending_req, seg,
  				pg, grant, n_segs, flags);
  			if (err)
  				return err;
  			pg += n_segs;
  			grant += n_segs;
  		}
  		end_seg = vaddr(pending_req, 0) + ring_req->seg[0].offset;
  		seg = (struct scsiif_request_segment *)end_seg;
  		end_seg += ring_req->seg[0].length;
  		pg = pending_req->pages + nr_sgl;
  	}
  
  	for_each_sg(pending_req->sgl, sg, nr_segments, i) {
  		sg_set_page(sg, pg[i], seg->length, seg->offset);
  		pending_req->data_len += seg->length;
  		seg++;
  		if (nr_sgl && (unsigned long)seg >= end_seg) {
  			i_seg++;
  			end_seg = vaddr(pending_req, i_seg) +
  				  ring_req->seg[i_seg].offset;
  			seg = (struct scsiif_request_segment *)end_seg;
  			end_seg += ring_req->seg[i_seg].length;
  		}
  		if (sg->offset >= PAGE_SIZE ||
  		    sg->length > PAGE_SIZE ||
  		    sg->offset + sg->length > PAGE_SIZE)
  			return -EINVAL;
  	}
  
  	return 0;
  }
  
  static void scsiback_disconnect(struct vscsibk_info *info)
  {
  	wait_event(info->waiting_to_free,
  		atomic_read(&info->nr_unreplied_reqs) == 0);
  
  	unbind_from_irqhandler(info->irq, info);
  	info->irq = 0;
  	xenbus_unmap_ring_vfree(info->dev, info->ring.sring);
  }
  
  static void scsiback_device_action(struct vscsibk_pend *pending_req,
  	enum tcm_tmreq_table act, int tag)
  {
  	int rc, err = FAILED;
  	struct scsiback_tpg *tpg = pending_req->v2p->tpg;
  	struct se_cmd *se_cmd = &pending_req->se_cmd;
  	struct scsiback_tmr *tmr;
  
  	tmr = kzalloc(sizeof(struct scsiback_tmr), GFP_KERNEL);
  	if (!tmr)
  		goto out;
  
  	init_waitqueue_head(&tmr->tmr_wait);
  
  	transport_init_se_cmd(se_cmd, tpg->se_tpg.se_tpg_tfo,
  		tpg->tpg_nexus->tvn_se_sess, 0, DMA_NONE, TCM_SIMPLE_TAG,
  		&pending_req->sense_buffer[0]);
  
  	rc = core_tmr_alloc_req(se_cmd, tmr, act, GFP_KERNEL);
  	if (rc < 0)
  		goto out;
  
  	se_cmd->se_tmr_req->ref_task_tag = tag;
  
  	if (transport_lookup_tmr_lun(se_cmd, pending_req->v2p->lun) < 0)
  		goto out;
  
  	transport_generic_handle_tmr(se_cmd);
  	wait_event(tmr->tmr_wait, atomic_read(&tmr->tmr_complete));
  
  	err = (se_cmd->se_tmr_req->response == TMR_FUNCTION_COMPLETE) ?
  		SUCCESS : FAILED;
  
  out:
  	if (tmr) {
  		transport_generic_free_cmd(&pending_req->se_cmd, 1);
  		kfree(tmr);
  	}
  
  	scsiback_do_resp_with_sense(NULL, err, 0, pending_req);
  
  	kmem_cache_free(scsiback_cachep, pending_req);
  }
  
  /*
    Perform virtual to physical translation
  */
  static struct v2p_entry *scsiback_do_translation(struct vscsibk_info *info,
  			struct ids_tuple *v)
  {
  	struct v2p_entry *entry;
  	struct list_head *head = &(info->v2p_entry_lists);
  	unsigned long flags;
  
  	spin_lock_irqsave(&info->v2p_lock, flags);
  	list_for_each_entry(entry, head, l) {
  		if ((entry->v.chn == v->chn) &&
  		    (entry->v.tgt == v->tgt) &&
  		    (entry->v.lun == v->lun)) {
  			kref_get(&entry->kref);
  			goto out;
  		}
  	}
  	entry = NULL;
  
  out:
  	spin_unlock_irqrestore(&info->v2p_lock, flags);
  	return entry;
  }
  
  static int prepare_pending_reqs(struct vscsibk_info *info,
  				struct vscsiif_request *ring_req,
  				struct vscsibk_pend *pending_req)
  {
  	struct v2p_entry *v2p;
  	struct ids_tuple vir;
  
  	pending_req->rqid       = ring_req->rqid;
  	pending_req->info       = info;
  
  	vir.chn = ring_req->channel;
  	vir.tgt = ring_req->id;
  	vir.lun = ring_req->lun;
  
  	v2p = scsiback_do_translation(info, &vir);
  	if (!v2p) {
  		pending_req->v2p = NULL;
  		pr_debug("the v2p of (chn:%d, tgt:%d, lun:%d) doesn't exist.\n",
  			vir.chn, vir.tgt, vir.lun);
  		return -ENODEV;
  	}
  	pending_req->v2p = v2p;
  
  	/* request range check from frontend */
  	pending_req->sc_data_direction = ring_req->sc_data_direction;
  	if ((pending_req->sc_data_direction != DMA_BIDIRECTIONAL) &&
  		(pending_req->sc_data_direction != DMA_TO_DEVICE) &&
  		(pending_req->sc_data_direction != DMA_FROM_DEVICE) &&
  		(pending_req->sc_data_direction != DMA_NONE)) {
  		pr_debug("invalid parameter data_dir = %d\n",
  			pending_req->sc_data_direction);
  		return -EINVAL;
  	}
  
  	pending_req->cmd_len = ring_req->cmd_len;
  	if (pending_req->cmd_len > VSCSIIF_MAX_COMMAND_SIZE) {
  		pr_debug("invalid parameter cmd_len = %d\n",
  			pending_req->cmd_len);
  		return -EINVAL;
  	}
  	memcpy(pending_req->cmnd, ring_req->cmnd, pending_req->cmd_len);
  
  	return 0;
  }
  
  static int scsiback_do_cmd_fn(struct vscsibk_info *info)
  {
  	struct vscsiif_back_ring *ring = &info->ring;
  	struct vscsiif_request ring_req;
  	struct vscsibk_pend *pending_req;
  	RING_IDX rc, rp;
  	int err, more_to_do;
  	uint32_t result;
  
  	rc = ring->req_cons;
  	rp = ring->sring->req_prod;
  	rmb();	/* guest system is accessing ring, too */
  
  	if (RING_REQUEST_PROD_OVERFLOW(ring, rp)) {
  		rc = ring->rsp_prod_pvt;
  		pr_warn("Dom%d provided bogus ring requests (%#x - %#x = %u). Halting ring processing\n",
  			   info->domid, rp, rc, rp - rc);
  		info->ring_error = 1;
  		return 0;
  	}
  
  	while ((rc != rp)) {
  		if (RING_REQUEST_CONS_OVERFLOW(ring, rc))
  			break;
  		pending_req = kmem_cache_alloc(scsiback_cachep, GFP_KERNEL);
  		if (!pending_req)
  			return 1;
  
  		ring_req = *RING_GET_REQUEST(ring, rc);
  		ring->req_cons = ++rc;
  
  		err = prepare_pending_reqs(info, &ring_req, pending_req);
  		if (err) {
  			switch (err) {
  			case -ENODEV:
  				result = DID_NO_CONNECT;
  				break;
  			default:
  				result = DRIVER_ERROR;
  				break;
  			}
  			scsiback_do_resp_with_sense(NULL, result << 24, 0,
  						    pending_req);
  			kmem_cache_free(scsiback_cachep, pending_req);
  			return 1;
  		}
  
  		switch (ring_req.act) {
  		case VSCSIIF_ACT_SCSI_CDB:
  			if (scsiback_gnttab_data_map(&ring_req, pending_req)) {
  				scsiback_fast_flush_area(pending_req);
  				scsiback_do_resp_with_sense(NULL,
  					DRIVER_ERROR << 24, 0, pending_req);
  				kmem_cache_free(scsiback_cachep, pending_req);
  			} else {
  				scsiback_cmd_exec(pending_req);
  			}
  			break;
  		case VSCSIIF_ACT_SCSI_ABORT:
  			scsiback_device_action(pending_req, TMR_ABORT_TASK,
  				ring_req.ref_rqid);
  			break;
  		case VSCSIIF_ACT_SCSI_RESET:
  			scsiback_device_action(pending_req, TMR_LUN_RESET, 0);
  			break;
  		default:
  			pr_err_ratelimited("invalid request\n");
  			scsiback_do_resp_with_sense(NULL, DRIVER_ERROR << 24,
  						    0, pending_req);
  			kmem_cache_free(scsiback_cachep, pending_req);
  			break;
  		}
  
  		/* Yield point for this unbounded loop. */
  		cond_resched();
  	}
  
  	RING_FINAL_CHECK_FOR_REQUESTS(&info->ring, more_to_do);
  	return more_to_do;
  }
  
  static irqreturn_t scsiback_irq_fn(int irq, void *dev_id)
  {
  	struct vscsibk_info *info = dev_id;
  
  	if (info->ring_error)
  		return IRQ_HANDLED;
  
  	while (scsiback_do_cmd_fn(info))
  		cond_resched();
  
  	return IRQ_HANDLED;
  }
  
  static int scsiback_init_sring(struct vscsibk_info *info, grant_ref_t ring_ref,
  			evtchn_port_t evtchn)
  {
  	void *area;
  	struct vscsiif_sring *sring;
  	int err;
  
  	if (info->irq)
  		return -1;
  
  	err = xenbus_map_ring_valloc(info->dev, &ring_ref, 1, &area);
  	if (err)
  		return err;
  
  	sring = (struct vscsiif_sring *)area;
  	BACK_RING_INIT(&info->ring, sring, PAGE_SIZE);
  
  	err = bind_interdomain_evtchn_to_irq(info->domid, evtchn);
  	if (err < 0)
  		goto unmap_page;
  
  	info->irq = err;
  
  	err = request_threaded_irq(info->irq, NULL, scsiback_irq_fn,
  				   IRQF_ONESHOT, "vscsiif-backend", info);
  	if (err)
  		goto free_irq;
  
  	return 0;
  
  free_irq:
  	unbind_from_irqhandler(info->irq, info);
  	info->irq = 0;
  unmap_page:
  	xenbus_unmap_ring_vfree(info->dev, area);
  
  	return err;
  }
  
  static int scsiback_map(struct vscsibk_info *info)
  {
  	struct xenbus_device *dev = info->dev;
  	unsigned int ring_ref, evtchn;
  	int err;
  
  	err = xenbus_gather(XBT_NIL, dev->otherend,
  			"ring-ref", "%u", &ring_ref,
  			"event-channel", "%u", &evtchn, NULL);
  	if (err) {
  		xenbus_dev_fatal(dev, err, "reading %s ring", dev->otherend);
  		return err;
  	}
  
  	return scsiback_init_sring(info, ring_ref, evtchn);
  }
  
  /*
    Add a new translation entry
  */
  static int scsiback_add_translation_entry(struct vscsibk_info *info,
  					  char *phy, struct ids_tuple *v)
  {
  	int err = 0;
  	struct v2p_entry *entry;
  	struct v2p_entry *new;
  	struct list_head *head = &(info->v2p_entry_lists);
  	unsigned long flags;
  	char *lunp;
  	unsigned int lun;
  	struct scsiback_tpg *tpg_entry, *tpg = NULL;
  	char *error = "doesn't exist";
  
  	lunp = strrchr(phy, ':');
  	if (!lunp) {
  		pr_err("illegal format of physical device %s\n", phy);
  		return -EINVAL;
  	}
  	*lunp = 0;
  	lunp++;
  	if (kstrtouint(lunp, 10, &lun) || lun >= TRANSPORT_MAX_LUNS_PER_TPG) {
  		pr_err("lun number not valid: %s\n", lunp);
  		return -EINVAL;
  	}
  
  	mutex_lock(&scsiback_mutex);
  	list_for_each_entry(tpg_entry, &scsiback_list, tv_tpg_list) {
  		if (!strcmp(phy, tpg_entry->tport->tport_name) ||
  		    !strcmp(phy, tpg_entry->param_alias)) {
  			spin_lock(&tpg_entry->se_tpg.tpg_lun_lock);
  			if (tpg_entry->se_tpg.tpg_lun_list[lun]->lun_status ==
  			    TRANSPORT_LUN_STATUS_ACTIVE) {
  				if (!tpg_entry->tpg_nexus)
  					error = "nexus undefined";
  				else
  					tpg = tpg_entry;
  			}
  			spin_unlock(&tpg_entry->se_tpg.tpg_lun_lock);
  			break;
  		}
  	}
  	if (tpg) {
  		mutex_lock(&tpg->tv_tpg_mutex);
  		tpg->tv_tpg_fe_count++;
  		mutex_unlock(&tpg->tv_tpg_mutex);
  	}
  	mutex_unlock(&scsiback_mutex);
  
  	if (!tpg) {
  		pr_err("%s:%d %s\n", phy, lun, error);
  		return -ENODEV;
  	}
  
  	new = kmalloc(sizeof(struct v2p_entry), GFP_KERNEL);
  	if (new == NULL) {
  		err = -ENOMEM;
  		goto out_free;
  	}
  
  	spin_lock_irqsave(&info->v2p_lock, flags);
  
  	/* Check double assignment to identical virtual ID */
  	list_for_each_entry(entry, head, l) {
  		if ((entry->v.chn == v->chn) &&
  		    (entry->v.tgt == v->tgt) &&
  		    (entry->v.lun == v->lun)) {
  			pr_warn("Virtual ID is already used. Assignment was not performed.\n");
  			err = -EEXIST;
  			goto out;
  		}
  
  	}
  
  	/* Create a new translation entry and add to the list */
  	kref_init(&new->kref);
  	new->v = *v;
  	new->tpg = tpg;
  	new->lun = lun;
  	list_add_tail(&new->l, head);
  
  out:
  	spin_unlock_irqrestore(&info->v2p_lock, flags);
  
  out_free:
  	mutex_lock(&tpg->tv_tpg_mutex);
  	tpg->tv_tpg_fe_count--;
  	mutex_unlock(&tpg->tv_tpg_mutex);
  
  	if (err)
  		kfree(new);
  
  	return err;
  }
  
  static void __scsiback_del_translation_entry(struct v2p_entry *entry)
  {
  	list_del(&entry->l);
  	kref_put(&entry->kref, scsiback_free_translation_entry);
  }
  
  /*
    Delete the translation entry specfied
  */
  static int scsiback_del_translation_entry(struct vscsibk_info *info,
  					  struct ids_tuple *v)
  {
  	struct v2p_entry *entry;
  	struct list_head *head = &(info->v2p_entry_lists);
  	unsigned long flags;
  
  	spin_lock_irqsave(&info->v2p_lock, flags);
  	/* Find out the translation entry specified */
  	list_for_each_entry(entry, head, l) {
  		if ((entry->v.chn == v->chn) &&
  		    (entry->v.tgt == v->tgt) &&
  		    (entry->v.lun == v->lun)) {
  			goto found;
  		}
  	}
  
  	spin_unlock_irqrestore(&info->v2p_lock, flags);
  	return 1;
  
  found:
  	/* Delete the translation entry specfied */
  	__scsiback_del_translation_entry(entry);
  
  	spin_unlock_irqrestore(&info->v2p_lock, flags);
  	return 0;
  }
  
  static void scsiback_do_add_lun(struct vscsibk_info *info, const char *state,
  				char *phy, struct ids_tuple *vir, int try)
  {
  	if (!scsiback_add_translation_entry(info, phy, vir)) {
  		if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
  				  "%d", XenbusStateInitialised)) {
  			pr_err("xenbus_printf error %s\n", state);
  			scsiback_del_translation_entry(info, vir);
  		}
  	} else if (!try) {
  		xenbus_printf(XBT_NIL, info->dev->nodename, state,
  			      "%d", XenbusStateClosed);
  	}
  }
  
  static void scsiback_do_del_lun(struct vscsibk_info *info, const char *state,
  				struct ids_tuple *vir)
  {
  	if (!scsiback_del_translation_entry(info, vir)) {
  		if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
  				  "%d", XenbusStateClosed))
  			pr_err("xenbus_printf error %s\n", state);
  	}
  }
  
  #define VSCSIBACK_OP_ADD_OR_DEL_LUN	1
  #define VSCSIBACK_OP_UPDATEDEV_STATE	2
  
  static void scsiback_do_1lun_hotplug(struct vscsibk_info *info, int op,
  				     char *ent)
  {
  	int err;
  	struct ids_tuple vir;
  	char *val;
  	int device_state;
  	char phy[VSCSI_NAMELEN];
  	char str[64];
  	char state[64];
  	struct xenbus_device *dev = info->dev;
  
  	/* read status */
  	snprintf(state, sizeof(state), "vscsi-devs/%s/state", ent);
  	err = xenbus_scanf(XBT_NIL, dev->nodename, state, "%u", &device_state);
  	if (XENBUS_EXIST_ERR(err))
  		return;
  
  	/* physical SCSI device */
  	snprintf(str, sizeof(str), "vscsi-devs/%s/p-dev", ent);
  	val = xenbus_read(XBT_NIL, dev->nodename, str, NULL);
  	if (IS_ERR(val)) {
  		xenbus_printf(XBT_NIL, dev->nodename, state,
  			      "%d", XenbusStateClosed);
  		return;
  	}
  	strlcpy(phy, val, VSCSI_NAMELEN);
  	kfree(val);
  
  	/* virtual SCSI device */
  	snprintf(str, sizeof(str), "vscsi-devs/%s/v-dev", ent);
  	err = xenbus_scanf(XBT_NIL, dev->nodename, str, "%u:%u:%u:%u",
  			   &vir.hst, &vir.chn, &vir.tgt, &vir.lun);
  	if (XENBUS_EXIST_ERR(err)) {
  		xenbus_printf(XBT_NIL, dev->nodename, state,
  			      "%d", XenbusStateClosed);
  		return;
  	}
  
  	switch (op) {
  	case VSCSIBACK_OP_ADD_OR_DEL_LUN:
  		switch (device_state) {
  		case XenbusStateInitialising:
  			scsiback_do_add_lun(info, state, phy, &vir, 0);
  			break;
  		case XenbusStateConnected:
  			scsiback_do_add_lun(info, state, phy, &vir, 1);
  			break;
  		case XenbusStateClosing:
  			scsiback_do_del_lun(info, state, &vir);
  			break;
  		default:
  			break;
  		}
  		break;
  
  	case VSCSIBACK_OP_UPDATEDEV_STATE:
  		if (device_state == XenbusStateInitialised) {
  			/* modify vscsi-devs/dev-x/state */
  			if (xenbus_printf(XBT_NIL, dev->nodename, state,
  					  "%d", XenbusStateConnected)) {
  				pr_err("xenbus_printf error %s\n", str);
  				scsiback_del_translation_entry(info, &vir);
  				xenbus_printf(XBT_NIL, dev->nodename, state,
  					      "%d", XenbusStateClosed);
  			}
  		}
  		break;
  	/* When it is necessary, processing is added here. */
  	default:
  		break;
  	}
  }
  
  static void scsiback_do_lun_hotplug(struct vscsibk_info *info, int op)
  {
  	int i;
  	char **dir;
  	unsigned int ndir = 0;
  
  	dir = xenbus_directory(XBT_NIL, info->dev->nodename, "vscsi-devs",
  			       &ndir);
  	if (IS_ERR(dir))
  		return;
  
  	for (i = 0; i < ndir; i++)
  		scsiback_do_1lun_hotplug(info, op, dir[i]);
  
  	kfree(dir);
  }
  
  static void scsiback_frontend_changed(struct xenbus_device *dev,
  					enum xenbus_state frontend_state)
  {
  	struct vscsibk_info *info = dev_get_drvdata(&dev->dev);
  
  	switch (frontend_state) {
  	case XenbusStateInitialising:
  		break;
  
  	case XenbusStateInitialised:
  		if (scsiback_map(info))
  			break;
  
  		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_ADD_OR_DEL_LUN);
  		xenbus_switch_state(dev, XenbusStateConnected);
  		break;
  
  	case XenbusStateConnected:
  		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_UPDATEDEV_STATE);
  
  		if (dev->state == XenbusStateConnected)
  			break;
  
  		xenbus_switch_state(dev, XenbusStateConnected);
  		break;
  
  	case XenbusStateClosing:
  		if (info->irq)
  			scsiback_disconnect(info);
  
  		xenbus_switch_state(dev, XenbusStateClosing);
  		break;
  
  	case XenbusStateClosed:
  		xenbus_switch_state(dev, XenbusStateClosed);
  		if (xenbus_dev_is_online(dev))
  			break;
  		/* fall through if not online */
  	case XenbusStateUnknown:
  		device_unregister(&dev->dev);
  		break;
  
  	case XenbusStateReconfiguring:
  		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_ADD_OR_DEL_LUN);
  		xenbus_switch_state(dev, XenbusStateReconfigured);
  
  		break;
  
  	default:
  		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
  					frontend_state);
  		break;
  	}
  }
  
  /*
    Release the translation entry specfied
  */
  static void scsiback_release_translation_entry(struct vscsibk_info *info)
  {
  	struct v2p_entry *entry, *tmp;
  	struct list_head *head = &(info->v2p_entry_lists);
  	unsigned long flags;
  
  	spin_lock_irqsave(&info->v2p_lock, flags);
  
  	list_for_each_entry_safe(entry, tmp, head, l)
  		__scsiback_del_translation_entry(entry);
  
  	spin_unlock_irqrestore(&info->v2p_lock, flags);
  }
  
  static int scsiback_remove(struct xenbus_device *dev)
  {
  	struct vscsibk_info *info = dev_get_drvdata(&dev->dev);
  
  	if (info->irq)
  		scsiback_disconnect(info);
  
  	scsiback_release_translation_entry(info);
  
  	dev_set_drvdata(&dev->dev, NULL);
  
  	return 0;
  }
  
  static int scsiback_probe(struct xenbus_device *dev,
  			   const struct xenbus_device_id *id)
  {
  	int err;
  
  	struct vscsibk_info *info = kzalloc(sizeof(struct vscsibk_info),
  					    GFP_KERNEL);
  
  	pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
  
  	if (!info) {
  		xenbus_dev_fatal(dev, -ENOMEM, "allocating backend structure");
  		return -ENOMEM;
  	}
  	info->dev = dev;
  	dev_set_drvdata(&dev->dev, info);
  
  	info->domid = dev->otherend_id;
  	spin_lock_init(&info->ring_lock);
  	info->ring_error = 0;
  	atomic_set(&info->nr_unreplied_reqs, 0);
  	init_waitqueue_head(&info->waiting_to_free);
  	info->dev = dev;
  	info->irq = 0;
  	INIT_LIST_HEAD(&info->v2p_entry_lists);
  	spin_lock_init(&info->v2p_lock);
  
  	err = xenbus_printf(XBT_NIL, dev->nodename, "feature-sg-grant", "%u",
  			    SG_ALL);
  	if (err)
  		xenbus_dev_error(dev, err, "writing feature-sg-grant");
  
  	err = xenbus_switch_state(dev, XenbusStateInitWait);
  	if (err)
  		goto fail;
  
  	return 0;
  
  fail:
  	pr_warn("%s failed\n", __func__);
  	scsiback_remove(dev);
  
  	return err;
  }
  
  static char *scsiback_dump_proto_id(struct scsiback_tport *tport)
  {
  	switch (tport->tport_proto_id) {
  	case SCSI_PROTOCOL_SAS:
  		return "SAS";
  	case SCSI_PROTOCOL_FCP:
  		return "FCP";
  	case SCSI_PROTOCOL_ISCSI:
  		return "iSCSI";
  	default:
  		break;
  	}
  
  	return "Unknown";
  }
  
  static u8 scsiback_get_fabric_proto_ident(struct se_portal_group *se_tpg)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  	struct scsiback_tport *tport = tpg->tport;
  
  	switch (tport->tport_proto_id) {
  	case SCSI_PROTOCOL_SAS:
  		return sas_get_fabric_proto_ident(se_tpg);
  	case SCSI_PROTOCOL_FCP:
  		return fc_get_fabric_proto_ident(se_tpg);
  	case SCSI_PROTOCOL_ISCSI:
  		return iscsi_get_fabric_proto_ident(se_tpg);
  	default:
  		pr_err("Unknown tport_proto_id: 0x%02x, using SAS emulation\n",
  			tport->tport_proto_id);
  		break;
  	}
  
  	return sas_get_fabric_proto_ident(se_tpg);
  }
  
  static char *scsiback_get_fabric_wwn(struct se_portal_group *se_tpg)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  	struct scsiback_tport *tport = tpg->tport;
  
  	return &tport->tport_name[0];
  }
  
  static u16 scsiback_get_tag(struct se_portal_group *se_tpg)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  	return tpg->tport_tpgt;
  }
  
  static u32 scsiback_get_default_depth(struct se_portal_group *se_tpg)
  {
  	return 1;
  }
  
  static u32
  scsiback_get_pr_transport_id(struct se_portal_group *se_tpg,
  			      struct se_node_acl *se_nacl,
  			      struct t10_pr_registration *pr_reg,
  			      int *format_code,
  			      unsigned char *buf)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  	struct scsiback_tport *tport = tpg->tport;
  
  	switch (tport->tport_proto_id) {
  	case SCSI_PROTOCOL_SAS:
  		return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
  					format_code, buf);
  	case SCSI_PROTOCOL_FCP:
  		return fc_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
  					format_code, buf);
  	case SCSI_PROTOCOL_ISCSI:
  		return iscsi_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
  					format_code, buf);
  	default:
  		pr_err("Unknown tport_proto_id: 0x%02x, using SAS emulation\n",
  			tport->tport_proto_id);
  		break;
  	}
  
  	return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
  			format_code, buf);
  }
  
  static u32
  scsiback_get_pr_transport_id_len(struct se_portal_group *se_tpg,
  				  struct se_node_acl *se_nacl,
  				  struct t10_pr_registration *pr_reg,
  				  int *format_code)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  	struct scsiback_tport *tport = tpg->tport;
  
  	switch (tport->tport_proto_id) {
  	case SCSI_PROTOCOL_SAS:
  		return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
  					format_code);
  	case SCSI_PROTOCOL_FCP:
  		return fc_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
  					format_code);
  	case SCSI_PROTOCOL_ISCSI:
  		return iscsi_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
  					format_code);
  	default:
  		pr_err("Unknown tport_proto_id: 0x%02x, using SAS emulation\n",
  			tport->tport_proto_id);
  		break;
  	}
  
  	return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
  			format_code);
  }
  
  static char *
  scsiback_parse_pr_out_transport_id(struct se_portal_group *se_tpg,
  				    const char *buf,
  				    u32 *out_tid_len,
  				    char **port_nexus_ptr)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  	struct scsiback_tport *tport = tpg->tport;
  
  	switch (tport->tport_proto_id) {
  	case SCSI_PROTOCOL_SAS:
  		return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
  					port_nexus_ptr);
  	case SCSI_PROTOCOL_FCP:
  		return fc_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
  					port_nexus_ptr);
  	case SCSI_PROTOCOL_ISCSI:
  		return iscsi_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
  					port_nexus_ptr);
  	default:
  		pr_err("Unknown tport_proto_id: 0x%02x, using SAS emulation\n",
  			tport->tport_proto_id);
  		break;
  	}
  
  	return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
  			port_nexus_ptr);
  }
  
  static struct se_wwn *
  scsiback_make_tport(struct target_fabric_configfs *tf,
  		     struct config_group *group,
  		     const char *name)
  {
  	struct scsiback_tport *tport;
  	char *ptr;
  	u64 wwpn = 0;
  	int off = 0;
  
  	tport = kzalloc(sizeof(struct scsiback_tport), GFP_KERNEL);
  	if (!tport)
  		return ERR_PTR(-ENOMEM);
  
  	tport->tport_wwpn = wwpn;
  	/*
  	 * Determine the emulated Protocol Identifier and Target Port Name
  	 * based on the incoming configfs directory name.
  	 */
  	ptr = strstr(name, "naa.");
  	if (ptr) {
  		tport->tport_proto_id = SCSI_PROTOCOL_SAS;
  		goto check_len;
  	}
  	ptr = strstr(name, "fc.");
  	if (ptr) {
  		tport->tport_proto_id = SCSI_PROTOCOL_FCP;
  		off = 3; /* Skip over "fc." */
  		goto check_len;
  	}
  	ptr = strstr(name, "iqn.");
  	if (ptr) {
  		tport->tport_proto_id = SCSI_PROTOCOL_ISCSI;
  		goto check_len;
  	}
  
  	pr_err("Unable to locate prefix for emulated Target Port: %s\n", name);
  	kfree(tport);
  	return ERR_PTR(-EINVAL);
  
  check_len:
  	if (strlen(name) >= VSCSI_NAMELEN) {
  		pr_err("Emulated %s Address: %s, exceeds max: %d\n", name,
  			scsiback_dump_proto_id(tport), VSCSI_NAMELEN);
  		kfree(tport);
  		return ERR_PTR(-EINVAL);
  	}
  	snprintf(&tport->tport_name[0], VSCSI_NAMELEN, "%s", &name[off]);
  
  	pr_debug("Allocated emulated Target %s Address: %s\n",
  		 scsiback_dump_proto_id(tport), name);
  
  	return &tport->tport_wwn;
  }
  
  static void scsiback_drop_tport(struct se_wwn *wwn)
  {
  	struct scsiback_tport *tport = container_of(wwn,
  				struct scsiback_tport, tport_wwn);
  
  	pr_debug("Deallocating emulated Target %s Address: %s\n",
  		 scsiback_dump_proto_id(tport), tport->tport_name);
  
  	kfree(tport);
  }
  
  static struct se_node_acl *
  scsiback_alloc_fabric_acl(struct se_portal_group *se_tpg)
  {
  	return kzalloc(sizeof(struct se_node_acl), GFP_KERNEL);
  }
  
  static void
  scsiback_release_fabric_acl(struct se_portal_group *se_tpg,
  			     struct se_node_acl *se_nacl)
  {
  	kfree(se_nacl);
  }
  
  static u32 scsiback_tpg_get_inst_index(struct se_portal_group *se_tpg)
  {
  	return 1;
  }
  
  static int scsiback_check_stop_free(struct se_cmd *se_cmd)
  {
  	/*
  	 * Do not release struct se_cmd's containing a valid TMR pointer.
  	 * These will be released directly in scsiback_device_action()
  	 * with transport_generic_free_cmd().
  	 */
  	if (se_cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)
  		return 0;
  
  	transport_generic_free_cmd(se_cmd, 0);
  	return 1;
  }
  
  static void scsiback_release_cmd(struct se_cmd *se_cmd)
  {
  	struct vscsibk_pend *pending_req = container_of(se_cmd,
  				struct vscsibk_pend, se_cmd);
  
  	kmem_cache_free(scsiback_cachep, pending_req);
  }
  
  static int scsiback_shutdown_session(struct se_session *se_sess)
  {
  	return 0;
  }
  
  static void scsiback_close_session(struct se_session *se_sess)
  {
  }
  
  static u32 scsiback_sess_get_index(struct se_session *se_sess)
  {
  	return 0;
  }
  
  static int scsiback_write_pending(struct se_cmd *se_cmd)
  {
  	/* Go ahead and process the write immediately */
  	target_execute_cmd(se_cmd);
  
  	return 0;
  }
  
  static int scsiback_write_pending_status(struct se_cmd *se_cmd)
  {
  	return 0;
  }
  
  static void scsiback_set_default_node_attrs(struct se_node_acl *nacl)
  {
  }
  
  static u32 scsiback_get_task_tag(struct se_cmd *se_cmd)
  {
  	struct vscsibk_pend *pending_req = container_of(se_cmd,
  				struct vscsibk_pend, se_cmd);
  
  	return pending_req->rqid;
  }
  
  static int scsiback_get_cmd_state(struct se_cmd *se_cmd)
  {
  	return 0;
  }
  
  static int scsiback_queue_data_in(struct se_cmd *se_cmd)
  {
  	struct vscsibk_pend *pending_req = container_of(se_cmd,
  				struct vscsibk_pend, se_cmd);
  
  	pending_req->result = SAM_STAT_GOOD;
  	scsiback_cmd_done(pending_req);
  	return 0;
  }
  
  static int scsiback_queue_status(struct se_cmd *se_cmd)
  {
  	struct vscsibk_pend *pending_req = container_of(se_cmd,
  				struct vscsibk_pend, se_cmd);
  
  	if (se_cmd->sense_buffer &&
  	    ((se_cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) ||
  	     (se_cmd->se_cmd_flags & SCF_EMULATED_TASK_SENSE)))
  		pending_req->result = (DRIVER_SENSE << 24) |
  				      SAM_STAT_CHECK_CONDITION;
  	else
  		pending_req->result = se_cmd->scsi_status;
  
  	scsiback_cmd_done(pending_req);
  	return 0;
  }
  
  static void scsiback_queue_tm_rsp(struct se_cmd *se_cmd)
  {
  	struct se_tmr_req *se_tmr = se_cmd->se_tmr_req;
  	struct scsiback_tmr *tmr = se_tmr->fabric_tmr_ptr;
  
  	atomic_set(&tmr->tmr_complete, 1);
  	wake_up(&tmr->tmr_wait);
  }
  
  static void scsiback_aborted_task(struct se_cmd *se_cmd)
  {
  }
  
  static ssize_t scsiback_tpg_param_show_alias(struct se_portal_group *se_tpg,
  					     char *page)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg, struct scsiback_tpg,
  						se_tpg);
  	ssize_t rb;
  
  	mutex_lock(&tpg->tv_tpg_mutex);
  	rb = snprintf(page, PAGE_SIZE, "%s\n", tpg->param_alias);
  	mutex_unlock(&tpg->tv_tpg_mutex);
  
  	return rb;
  }
  
  static ssize_t scsiback_tpg_param_store_alias(struct se_portal_group *se_tpg,
  					      const char *page, size_t count)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg, struct scsiback_tpg,
  						se_tpg);
  	int len;
  
  	if (strlen(page) >= VSCSI_NAMELEN) {
  		pr_err("param alias: %s, exceeds max: %d\n", page,
  			VSCSI_NAMELEN);
  		return -EINVAL;
  	}
  
  	mutex_lock(&tpg->tv_tpg_mutex);
  	len = snprintf(tpg->param_alias, VSCSI_NAMELEN, "%s", page);
  	if (tpg->param_alias[len - 1] == '\n')
  		tpg->param_alias[len - 1] = '\0';
  	mutex_unlock(&tpg->tv_tpg_mutex);
  
  	return count;
  }
  
  TF_TPG_PARAM_ATTR(scsiback, alias, S_IRUGO | S_IWUSR);
  
  static struct configfs_attribute *scsiback_param_attrs[] = {
  	&scsiback_tpg_param_alias.attr,
  	NULL,
  };
  
  static int scsiback_make_nexus(struct scsiback_tpg *tpg,
  				const char *name)
  {
  	struct se_portal_group *se_tpg;
  	struct se_session *se_sess;
  	struct scsiback_nexus *tv_nexus;
  
  	mutex_lock(&tpg->tv_tpg_mutex);
  	if (tpg->tpg_nexus) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		pr_debug("tpg->tpg_nexus already exists\n");
  		return -EEXIST;
  	}
  	se_tpg = &tpg->se_tpg;
  
  	tv_nexus = kzalloc(sizeof(struct scsiback_nexus), GFP_KERNEL);
  	if (!tv_nexus) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		return -ENOMEM;
  	}
  	/*
  	 * Initialize the struct se_session pointer
  	 */
  	tv_nexus->tvn_se_sess = transport_init_session(TARGET_PROT_NORMAL);
  	if (IS_ERR(tv_nexus->tvn_se_sess)) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		kfree(tv_nexus);
  		return -ENOMEM;
  	}
  	se_sess = tv_nexus->tvn_se_sess;
  	/*
  	 * Since we are running in 'demo mode' this call with generate a
  	 * struct se_node_acl for the scsiback struct se_portal_group with
  	 * the SCSI Initiator port name of the passed configfs group 'name'.
  	 */
  	tv_nexus->tvn_se_sess->se_node_acl = core_tpg_check_initiator_node_acl(
  				se_tpg, (unsigned char *)name);
  	if (!tv_nexus->tvn_se_sess->se_node_acl) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		pr_debug("core_tpg_check_initiator_node_acl() failed for %s\n",
  			 name);
  		goto out;
  	}
  	/* Now register the TCM pvscsi virtual I_T Nexus as active. */
  	transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
  			tv_nexus->tvn_se_sess, tv_nexus);
  	tpg->tpg_nexus = tv_nexus;
  
  	mutex_unlock(&tpg->tv_tpg_mutex);
  	return 0;
  
  out:
  	transport_free_session(se_sess);
  	kfree(tv_nexus);
  	return -ENOMEM;
  }
  
  static int scsiback_drop_nexus(struct scsiback_tpg *tpg)
  {
  	struct se_session *se_sess;
  	struct scsiback_nexus *tv_nexus;
  
  	mutex_lock(&tpg->tv_tpg_mutex);
  	tv_nexus = tpg->tpg_nexus;
  	if (!tv_nexus) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		return -ENODEV;
  	}
  
  	se_sess = tv_nexus->tvn_se_sess;
  	if (!se_sess) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		return -ENODEV;
  	}
  
  	if (tpg->tv_tpg_port_count != 0) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		pr_err("Unable to remove xen-pvscsi I_T Nexus with active TPG port count: %d\n",
  			tpg->tv_tpg_port_count);
  		return -EBUSY;
  	}
  
  	if (tpg->tv_tpg_fe_count != 0) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		pr_err("Unable to remove xen-pvscsi I_T Nexus with active TPG frontend count: %d\n",
  			tpg->tv_tpg_fe_count);
  		return -EBUSY;
  	}
  
  	pr_debug("Removing I_T Nexus to emulated %s Initiator Port: %s\n",
  		scsiback_dump_proto_id(tpg->tport),
  		tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
  
  	/*
  	 * Release the SCSI I_T Nexus to the emulated xen-pvscsi Target Port
  	 */
  	transport_deregister_session(tv_nexus->tvn_se_sess);
  	tpg->tpg_nexus = NULL;
  	mutex_unlock(&tpg->tv_tpg_mutex);
  
  	kfree(tv_nexus);
  	return 0;
  }
  
  static ssize_t scsiback_tpg_show_nexus(struct se_portal_group *se_tpg,
  					char *page)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  	struct scsiback_nexus *tv_nexus;
  	ssize_t ret;
  
  	mutex_lock(&tpg->tv_tpg_mutex);
  	tv_nexus = tpg->tpg_nexus;
  	if (!tv_nexus) {
  		mutex_unlock(&tpg->tv_tpg_mutex);
  		return -ENODEV;
  	}
  	ret = snprintf(page, PAGE_SIZE, "%s\n",
  			tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
  	mutex_unlock(&tpg->tv_tpg_mutex);
  
  	return ret;
  }
  
  static ssize_t scsiback_tpg_store_nexus(struct se_portal_group *se_tpg,
  					 const char *page,
  					 size_t count)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  	struct scsiback_tport *tport_wwn = tpg->tport;
  	unsigned char i_port[VSCSI_NAMELEN], *ptr, *port_ptr;
  	int ret;
  	/*
  	 * Shutdown the active I_T nexus if 'NULL' is passed.
  	 */
  	if (!strncmp(page, "NULL", 4)) {
  		ret = scsiback_drop_nexus(tpg);
  		return (!ret) ? count : ret;
  	}
  	/*
  	 * Otherwise make sure the passed virtual Initiator port WWN matches
  	 * the fabric protocol_id set in scsiback_make_tport(), and call
  	 * scsiback_make_nexus().
  	 */
  	if (strlen(page) >= VSCSI_NAMELEN) {
  		pr_err("Emulated NAA Sas Address: %s, exceeds max: %d\n",
  			page, VSCSI_NAMELEN);
  		return -EINVAL;
  	}
  	snprintf(&i_port[0], VSCSI_NAMELEN, "%s", page);
  
  	ptr = strstr(i_port, "naa.");
  	if (ptr) {
  		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_SAS) {
  			pr_err("Passed SAS Initiator Port %s does not match target port protoid: %s\n",
  				i_port, scsiback_dump_proto_id(tport_wwn));
  			return -EINVAL;
  		}
  		port_ptr = &i_port[0];
  		goto check_newline;
  	}
  	ptr = strstr(i_port, "fc.");
  	if (ptr) {
  		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_FCP) {
  			pr_err("Passed FCP Initiator Port %s does not match target port protoid: %s\n",
  				i_port, scsiback_dump_proto_id(tport_wwn));
  			return -EINVAL;
  		}
  		port_ptr = &i_port[3]; /* Skip over "fc." */
  		goto check_newline;
  	}
  	ptr = strstr(i_port, "iqn.");
  	if (ptr) {
  		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_ISCSI) {
  			pr_err("Passed iSCSI Initiator Port %s does not match target port protoid: %s\n",
  				i_port, scsiback_dump_proto_id(tport_wwn));
  			return -EINVAL;
  		}
  		port_ptr = &i_port[0];
  		goto check_newline;
  	}
  	pr_err("Unable to locate prefix for emulated Initiator Port: %s\n",
  		i_port);
  	return -EINVAL;
  	/*
  	 * Clear any trailing newline for the NAA WWN
  	 */
  check_newline:
  	if (i_port[strlen(i_port) - 1] == '\n')
  		i_port[strlen(i_port) - 1] = '\0';
  
  	ret = scsiback_make_nexus(tpg, port_ptr);
  	if (ret < 0)
  		return ret;
  
  	return count;
  }
  
  TF_TPG_BASE_ATTR(scsiback, nexus, S_IRUGO | S_IWUSR);
  
  static struct configfs_attribute *scsiback_tpg_attrs[] = {
  	&scsiback_tpg_nexus.attr,
  	NULL,
  };
  
  static ssize_t
  scsiback_wwn_show_attr_version(struct target_fabric_configfs *tf,
  				char *page)
  {
  	return sprintf(page, "xen-pvscsi fabric module %s on %s/%s on "
  		UTS_RELEASE"\n",
  		VSCSI_VERSION, utsname()->sysname, utsname()->machine);
  }
  
  TF_WWN_ATTR_RO(scsiback, version);
  
  static struct configfs_attribute *scsiback_wwn_attrs[] = {
  	&scsiback_wwn_version.attr,
  	NULL,
  };
  
  static char *scsiback_get_fabric_name(void)
  {
  	return "xen-pvscsi";
  }
  
  static int scsiback_port_link(struct se_portal_group *se_tpg,
  			       struct se_lun *lun)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  
  	mutex_lock(&tpg->tv_tpg_mutex);
  	tpg->tv_tpg_port_count++;
  	mutex_unlock(&tpg->tv_tpg_mutex);
  
  	return 0;
  }
  
  static void scsiback_port_unlink(struct se_portal_group *se_tpg,
  				  struct se_lun *lun)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  
  	mutex_lock(&tpg->tv_tpg_mutex);
  	tpg->tv_tpg_port_count--;
  	mutex_unlock(&tpg->tv_tpg_mutex);
  }
  
  static struct se_portal_group *
  scsiback_make_tpg(struct se_wwn *wwn,
  		   struct config_group *group,
  		   const char *name)
  {
  	struct scsiback_tport *tport = container_of(wwn,
  			struct scsiback_tport, tport_wwn);
  
  	struct scsiback_tpg *tpg;
  	u16 tpgt;
  	int ret;
  
  	if (strstr(name, "tpgt_") != name)
  		return ERR_PTR(-EINVAL);
  	ret = kstrtou16(name + 5, 10, &tpgt);
  	if (ret)
  		return ERR_PTR(ret);
  
  	tpg = kzalloc(sizeof(struct scsiback_tpg), GFP_KERNEL);
  	if (!tpg)
  		return ERR_PTR(-ENOMEM);
  
  	mutex_init(&tpg->tv_tpg_mutex);
  	INIT_LIST_HEAD(&tpg->tv_tpg_list);
  	INIT_LIST_HEAD(&tpg->info_list);
  	tpg->tport = tport;
  	tpg->tport_tpgt = tpgt;
  
  	ret = core_tpg_register(&scsiback_ops, wwn,
  				&tpg->se_tpg, tpg, TRANSPORT_TPG_TYPE_NORMAL);
  	if (ret < 0) {
  		kfree(tpg);
  		return NULL;
  	}
  	mutex_lock(&scsiback_mutex);
  	list_add_tail(&tpg->tv_tpg_list, &scsiback_list);
  	mutex_unlock(&scsiback_mutex);
  
  	return &tpg->se_tpg;
  }
  
  static void scsiback_drop_tpg(struct se_portal_group *se_tpg)
  {
  	struct scsiback_tpg *tpg = container_of(se_tpg,
  				struct scsiback_tpg, se_tpg);
  
  	mutex_lock(&scsiback_mutex);
  	list_del(&tpg->tv_tpg_list);
  	mutex_unlock(&scsiback_mutex);
  	/*
  	 * Release the virtual I_T Nexus for this xen-pvscsi TPG
  	 */
  	scsiback_drop_nexus(tpg);
  	/*
  	 * Deregister the se_tpg from TCM.
  	 */
  	core_tpg_deregister(se_tpg);
  	kfree(tpg);
  }
  
  static int scsiback_check_true(struct se_portal_group *se_tpg)
  {
  	return 1;
  }
  
  static int scsiback_check_false(struct se_portal_group *se_tpg)
  {
  	return 0;
  }
  
  static const struct target_core_fabric_ops scsiback_ops = {
  	.module				= THIS_MODULE,
  	.name				= "xen-pvscsi",
  	.get_fabric_name		= scsiback_get_fabric_name,
  	.get_fabric_proto_ident		= scsiback_get_fabric_proto_ident,
  	.tpg_get_wwn			= scsiback_get_fabric_wwn,
  	.tpg_get_tag			= scsiback_get_tag,
  	.tpg_get_default_depth		= scsiback_get_default_depth,
  	.tpg_get_pr_transport_id	= scsiback_get_pr_transport_id,
  	.tpg_get_pr_transport_id_len	= scsiback_get_pr_transport_id_len,
  	.tpg_parse_pr_out_transport_id	= scsiback_parse_pr_out_transport_id,
  	.tpg_check_demo_mode		= scsiback_check_true,
  	.tpg_check_demo_mode_cache	= scsiback_check_true,
  	.tpg_check_demo_mode_write_protect = scsiback_check_false,
  	.tpg_check_prod_mode_write_protect = scsiback_check_false,
  	.tpg_alloc_fabric_acl		= scsiback_alloc_fabric_acl,
  	.tpg_release_fabric_acl		= scsiback_release_fabric_acl,
  	.tpg_get_inst_index		= scsiback_tpg_get_inst_index,
  	.check_stop_free		= scsiback_check_stop_free,
  	.release_cmd			= scsiback_release_cmd,
  	.put_session			= NULL,
  	.shutdown_session		= scsiback_shutdown_session,
  	.close_session			= scsiback_close_session,
  	.sess_get_index			= scsiback_sess_get_index,
  	.sess_get_initiator_sid		= NULL,
  	.write_pending			= scsiback_write_pending,
  	.write_pending_status		= scsiback_write_pending_status,
  	.set_default_node_attributes	= scsiback_set_default_node_attrs,
  	.get_task_tag			= scsiback_get_task_tag,
  	.get_cmd_state			= scsiback_get_cmd_state,
  	.queue_data_in			= scsiback_queue_data_in,
  	.queue_status			= scsiback_queue_status,
  	.queue_tm_rsp			= scsiback_queue_tm_rsp,
  	.aborted_task			= scsiback_aborted_task,
  	/*
  	 * Setup callers for generic logic in target_core_fabric_configfs.c
  	 */
  	.fabric_make_wwn		= scsiback_make_tport,
  	.fabric_drop_wwn		= scsiback_drop_tport,
  	.fabric_make_tpg		= scsiback_make_tpg,
  	.fabric_drop_tpg		= scsiback_drop_tpg,
  	.fabric_post_link		= scsiback_port_link,
  	.fabric_pre_unlink		= scsiback_port_unlink,
  	.fabric_make_np			= NULL,
  	.fabric_drop_np			= NULL,
  #if 0
  	.fabric_make_nodeacl		= scsiback_make_nodeacl,
  	.fabric_drop_nodeacl		= scsiback_drop_nodeacl,
  #endif
  
  	.tfc_wwn_attrs			= scsiback_wwn_attrs,
  	.tfc_tpg_base_attrs		= scsiback_tpg_attrs,
  	.tfc_tpg_param_attrs		= scsiback_param_attrs,
  };
  
  static const struct xenbus_device_id scsiback_ids[] = {
  	{ "vscsi" },
  	{ "" }
  };
  
  static struct xenbus_driver scsiback_driver = {
  	.ids			= scsiback_ids,
  	.probe			= scsiback_probe,
  	.remove			= scsiback_remove,
  	.otherend_changed	= scsiback_frontend_changed
  };
  
  static void scsiback_init_pend(void *p)
  {
  	struct vscsibk_pend *pend = p;
  	int i;
  
  	memset(pend, 0, sizeof(*pend));
  	for (i = 0; i < VSCSI_MAX_GRANTS; i++)
  		pend->grant_handles[i] = SCSIBACK_INVALID_HANDLE;
  }
  
  static int __init scsiback_init(void)
  {
  	int ret;
  
  	if (!xen_domain())
  		return -ENODEV;
  
  	pr_debug("xen-pvscsi: fabric module %s on %s/%s on "UTS_RELEASE"\n",
  		 VSCSI_VERSION, utsname()->sysname, utsname()->machine);
  
  	scsiback_cachep = kmem_cache_create("vscsiif_cache",
  		sizeof(struct vscsibk_pend), 0, 0, scsiback_init_pend);
  	if (!scsiback_cachep)
  		return -ENOMEM;
  
  	ret = xenbus_register_backend(&scsiback_driver);
  	if (ret)
  		goto out_cache_destroy;
  
  	ret = target_register_template(&scsiback_ops);
  	if (ret)
  		goto out_unregister_xenbus;
  
  	return 0;
  
  out_unregister_xenbus:
  	xenbus_unregister_driver(&scsiback_driver);
  out_cache_destroy:
  	kmem_cache_destroy(scsiback_cachep);
  	pr_err("%s: error %d\n", __func__, ret);
  	return ret;
  }
  
  static void __exit scsiback_exit(void)
  {
  	struct page *page;
  
  	while (free_pages_num) {
  		if (get_free_page(&page))
  			BUG();
  		gnttab_free_pages(1, &page);
  	}
  	target_unregister_template(&scsiback_ops);
  	xenbus_unregister_driver(&scsiback_driver);
  	kmem_cache_destroy(scsiback_cachep);
  }
  
  module_init(scsiback_init);
  module_exit(scsiback_exit);
  
  MODULE_DESCRIPTION("Xen SCSI backend driver");
  MODULE_LICENSE("Dual BSD/GPL");
  MODULE_ALIAS("xen-backend:vscsi");
  MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
  