[karo-tx-linux.git] / drivers / vhost / scsi.c

/*******************************************************************************
 * Vhost kernel TCM fabric driver for virtio SCSI initiators
 *
 * (C) Copyright 2010-2013 Datera, Inc.
 * (C) Copyright 2010-2012 IBM Corp.
 *
 * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
 *
 * Authors: Nicholas A. Bellinger <nab@daterainc.com>
 *          Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 ****************************************************************************/

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <generated/utsrelease.h>
#include <linux/utsname.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/configfs.h>
#include <linux/ctype.h>
#include <linux/compat.h>
#include <linux/eventfd.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <asm/unaligned.h>
#include <scsi/scsi.h>
#include <target/target_core_base.h>
#include <target/target_core_fabric.h>
#include <target/target_core_fabric_configfs.h>
#include <target/target_core_configfs.h>
#include <target/configfs_macros.h>
#include <linux/vhost.h>
#include <linux/virtio_scsi.h>
#include <linux/llist.h>
#include <linux/bitmap.h>
#include <linux/percpu_ida.h>

#include "vhost.h"

#define VHOST_SCSI_VERSION  "v0.1"
#define VHOST_SCSI_NAMELEN 256
#define VHOST_SCSI_MAX_CDB_SIZE 32
#define VHOST_SCSI_DEFAULT_TAGS 256
#define VHOST_SCSI_PREALLOC_SGLS 2048
#define VHOST_SCSI_PREALLOC_UPAGES 2048
#define VHOST_SCSI_PREALLOC_PROT_SGLS 512

struct vhost_scsi_inflight {
        /* Wait for the flush operation to finish */
        struct completion comp;
        /* Refcount for the inflight reqs */
        struct kref kref;
};

struct vhost_scsi_cmd {
        /* Descriptor from vhost_get_vq_desc() for virt_queue segment */
        int tvc_vq_desc;
        /* virtio-scsi initiator task attribute */
        int tvc_task_attr;
        /* virtio-scsi response incoming iovecs */
        int tvc_in_iovs;
        /* virtio-scsi initiator data direction */
        enum dma_data_direction tvc_data_direction;
        /* Expected data transfer length from virtio-scsi header */
        u32 tvc_exp_data_len;
        /* The Tag from include/linux/virtio_scsi.h:struct virtio_scsi_cmd_req */
        u64 tvc_tag;
        /* The number of scatterlists associated with this cmd */
        u32 tvc_sgl_count;
        u32 tvc_prot_sgl_count;
        /* Saved unpacked SCSI LUN for vhost_scsi_submission_work() */
        u32 tvc_lun;
        /* Pointer to the SGL formatted memory from virtio-scsi */
        struct scatterlist *tvc_sgl;
        struct scatterlist *tvc_prot_sgl;
        struct page **tvc_upages;
        /* Pointer to response header iovec */
        struct iovec *tvc_resp_iov;
        /* Pointer to vhost_scsi for our device */
        struct vhost_scsi *tvc_vhost;
        /* Pointer to vhost_virtqueue for the cmd */
        struct vhost_virtqueue *tvc_vq;
        /* Pointer to vhost nexus memory */
        struct vhost_scsi_nexus *tvc_nexus;
        /* The TCM I/O descriptor that is accessed via container_of() */
        struct se_cmd tvc_se_cmd;
        /* work item used for cmwq dispatch to vhost_scsi_submission_work() */
        struct work_struct work;
        /* Copy of the incoming SCSI command descriptor block (CDB) */
        unsigned char tvc_cdb[VHOST_SCSI_MAX_CDB_SIZE];
        /* Sense buffer that will be mapped into outgoing status */
        unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
        /* Completed commands list, serviced from vhost worker thread */
        struct llist_node tvc_completion_list;
        /* Used to track inflight cmd */
        struct vhost_scsi_inflight *inflight;
};

struct vhost_scsi_nexus {
        /* Pointer to TCM session for I_T Nexus */
        struct se_session *tvn_se_sess;
};

struct vhost_scsi_tpg {
        /* Vhost port target portal group tag for TCM */
        u16 tport_tpgt;
        /* Used to track number of TPG Port/Lun Links wrt to explict I_T Nexus shutdown */
        int tv_tpg_port_count;
        /* Used for vhost_scsi device reference to tpg_nexus, protected by tv_tpg_mutex */
        int tv_tpg_vhost_count;
        /* Used for enabling T10-PI with legacy devices */
        int tv_fabric_prot_type;
        /* list for vhost_scsi_list */
        struct list_head tv_tpg_list;
        /* Used to protect access for tpg_nexus */
        struct mutex tv_tpg_mutex;
        /* Pointer to the TCM VHost I_T Nexus for this TPG endpoint */
        struct vhost_scsi_nexus *tpg_nexus;
        /* Pointer back to vhost_scsi_tport */
        struct vhost_scsi_tport *tport;
        /* Returned by vhost_scsi_make_tpg() */
        struct se_portal_group se_tpg;
        /* Pointer back to vhost_scsi, protected by tv_tpg_mutex */
        struct vhost_scsi *vhost_scsi;
};

struct vhost_scsi_tport {
        /* SCSI protocol the tport is providing */
        u8 tport_proto_id;
        /* Binary World Wide unique Port Name for Vhost Target port */
        u64 tport_wwpn;
        /* ASCII formatted WWPN for Vhost Target port */
        char tport_name[VHOST_SCSI_NAMELEN];
        /* Returned by vhost_scsi_make_tport() */
        struct se_wwn tport_wwn;
};

struct vhost_scsi_evt {
        /* event to be sent to guest */
        struct virtio_scsi_event event;
        /* event list, serviced from vhost worker thread */
        struct llist_node list;
};

enum {
        VHOST_SCSI_VQ_CTL = 0,
        VHOST_SCSI_VQ_EVT = 1,
        VHOST_SCSI_VQ_IO = 2,
};

/* Note: can't set VIRTIO_F_VERSION_1 yet, since that implies ANY_LAYOUT. */
enum {
        VHOST_SCSI_FEATURES = VHOST_FEATURES | (1ULL << VIRTIO_SCSI_F_HOTPLUG) |
                                               (1ULL << VIRTIO_SCSI_F_T10_PI) |
                                               (1ULL << VIRTIO_F_ANY_LAYOUT) |
                                               (1ULL << VIRTIO_F_VERSION_1)
};

#define VHOST_SCSI_MAX_TARGET   256
#define VHOST_SCSI_MAX_VQ       128
#define VHOST_SCSI_MAX_EVENT    128

struct vhost_scsi_virtqueue {
        struct vhost_virtqueue vq;
        /*
         * Reference counting for inflight reqs, used for flush operation. At
         * each time, one reference tracks new commands submitted, while we
         * wait for another one to reach 0.
         */
        struct vhost_scsi_inflight inflights[2];
        /*
         * Indicate current inflight in use, protected by vq->mutex.
         * Writers must also take dev mutex and flush under it.
         */
        int inflight_idx;
};

struct vhost_scsi {
        /* Protected by vhost_scsi->dev.mutex */
        struct vhost_scsi_tpg **vs_tpg;
        char vs_vhost_wwpn[TRANSPORT_IQN_LEN];

        struct vhost_dev dev;
        struct vhost_scsi_virtqueue vqs[VHOST_SCSI_MAX_VQ];

        struct vhost_work vs_completion_work; /* cmd completion work item */
        struct llist_head vs_completion_list; /* cmd completion queue */

        struct vhost_work vs_event_work; /* evt injection work item */
        struct llist_head vs_event_list; /* evt injection queue */

        bool vs_events_missed; /* any missed events, protected by vq->mutex */
        int vs_events_nr; /* num of pending events, protected by vq->mutex */
};

static struct target_core_fabric_ops vhost_scsi_ops;
static struct workqueue_struct *vhost_scsi_workqueue;

/* Global spinlock to protect vhost_scsi TPG list for vhost IOCTL access */
static DEFINE_MUTEX(vhost_scsi_mutex);
static LIST_HEAD(vhost_scsi_list);

static int iov_num_pages(void __user *iov_base, size_t iov_len)
{
        return (PAGE_ALIGN((unsigned long)iov_base + iov_len) -
               ((unsigned long)iov_base & PAGE_MASK)) >> PAGE_SHIFT;
}

static void vhost_scsi_done_inflight(struct kref *kref)
{
        struct vhost_scsi_inflight *inflight;

        inflight = container_of(kref, struct vhost_scsi_inflight, kref);
        complete(&inflight->comp);
}

static void vhost_scsi_init_inflight(struct vhost_scsi *vs,
                                    struct vhost_scsi_inflight *old_inflight[])
{
        struct vhost_scsi_inflight *new_inflight;
        struct vhost_virtqueue *vq;
        int idx, i;

        for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
                vq = &vs->vqs[i].vq;

                mutex_lock(&vq->mutex);

                /* store old infight */
                idx = vs->vqs[i].inflight_idx;
                if (old_inflight)
                        old_inflight[i] = &vs->vqs[i].inflights[idx];

                /* setup new infight */
                vs->vqs[i].inflight_idx = idx ^ 1;
                new_inflight = &vs->vqs[i].inflights[idx ^ 1];
                kref_init(&new_inflight->kref);
                init_completion(&new_inflight->comp);

                mutex_unlock(&vq->mutex);
        }
}

static struct vhost_scsi_inflight *
vhost_scsi_get_inflight(struct vhost_virtqueue *vq)
{
        struct vhost_scsi_inflight *inflight;
        struct vhost_scsi_virtqueue *svq;

        svq = container_of(vq, struct vhost_scsi_virtqueue, vq);
        inflight = &svq->inflights[svq->inflight_idx];
        kref_get(&inflight->kref);

        return inflight;
}

static void vhost_scsi_put_inflight(struct vhost_scsi_inflight *inflight)
{
        kref_put(&inflight->kref, vhost_scsi_done_inflight);
}

static int vhost_scsi_check_true(struct se_portal_group *se_tpg)
{
        return 1;
}

static int vhost_scsi_check_false(struct se_portal_group *se_tpg)
{
        return 0;
}

static char *vhost_scsi_get_fabric_name(void)
{
        return "vhost";
}

static u8 vhost_scsi_get_fabric_proto_ident(struct se_portal_group *se_tpg)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        struct vhost_scsi_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 *vhost_scsi_get_fabric_wwn(struct se_portal_group *se_tpg)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        struct vhost_scsi_tport *tport = tpg->tport;

        return &tport->tport_name[0];
}

static u16 vhost_scsi_get_tpgt(struct se_portal_group *se_tpg)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        return tpg->tport_tpgt;
}

static u32
vhost_scsi_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 vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        struct vhost_scsi_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
vhost_scsi_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 vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        struct vhost_scsi_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 *
vhost_scsi_parse_pr_out_transport_id(struct se_portal_group *se_tpg,
                                    const char *buf,
                                    u32 *out_tid_len,
                                    char **port_nexus_ptr)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        struct vhost_scsi_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 int vhost_scsi_check_prot_fabric_only(struct se_portal_group *se_tpg)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);

        return tpg->tv_fabric_prot_type;
}

static struct se_node_acl *
vhost_scsi_alloc_fabric_acl(struct se_portal_group *se_tpg)
{
        return kzalloc(sizeof(struct se_node_acl), GFP_KERNEL);
}

static void
vhost_scsi_release_fabric_acl(struct se_portal_group *se_tpg,
                             struct se_node_acl *se_nacl)
{
        kfree(se_nacl);
}

static u32 vhost_scsi_tpg_get_inst_index(struct se_portal_group *se_tpg)
{
        return 1;
}

static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
{
        struct vhost_scsi_cmd *tv_cmd = container_of(se_cmd,
                                struct vhost_scsi_cmd, tvc_se_cmd);
        struct se_session *se_sess = tv_cmd->tvc_nexus->tvn_se_sess;
        int i;

        if (tv_cmd->tvc_sgl_count) {
                for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
                        put_page(sg_page(&tv_cmd->tvc_sgl[i]));
        }
        if (tv_cmd->tvc_prot_sgl_count) {
                for (i = 0; i < tv_cmd->tvc_prot_sgl_count; i++)
                        put_page(sg_page(&tv_cmd->tvc_prot_sgl[i]));
        }

        vhost_scsi_put_inflight(tv_cmd->inflight);
        percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
}

static int vhost_scsi_shutdown_session(struct se_session *se_sess)
{
        return 0;
}

static void vhost_scsi_close_session(struct se_session *se_sess)
{
        return;
}

static u32 vhost_scsi_sess_get_index(struct se_session *se_sess)
{
        return 0;
}

static int vhost_scsi_write_pending(struct se_cmd *se_cmd)
{
        /* Go ahead and process the write immediately */
        target_execute_cmd(se_cmd);
        return 0;
}

static int vhost_scsi_write_pending_status(struct se_cmd *se_cmd)
{
        return 0;
}

static void vhost_scsi_set_default_node_attrs(struct se_node_acl *nacl)
{
        return;
}

static u32 vhost_scsi_get_task_tag(struct se_cmd *se_cmd)
{
        return 0;
}

static int vhost_scsi_get_cmd_state(struct se_cmd *se_cmd)
{
        return 0;
}

static void vhost_scsi_complete_cmd(struct vhost_scsi_cmd *cmd)
{
        struct vhost_scsi *vs = cmd->tvc_vhost;

        llist_add(&cmd->tvc_completion_list, &vs->vs_completion_list);

        vhost_work_queue(&vs->dev, &vs->vs_completion_work);
}

static int vhost_scsi_queue_data_in(struct se_cmd *se_cmd)
{
        struct vhost_scsi_cmd *cmd = container_of(se_cmd,
                                struct vhost_scsi_cmd, tvc_se_cmd);
        vhost_scsi_complete_cmd(cmd);
        return 0;
}

static int vhost_scsi_queue_status(struct se_cmd *se_cmd)
{
        struct vhost_scsi_cmd *cmd = container_of(se_cmd,
                                struct vhost_scsi_cmd, tvc_se_cmd);
        vhost_scsi_complete_cmd(cmd);
        return 0;
}

static void vhost_scsi_queue_tm_rsp(struct se_cmd *se_cmd)
{
        return;
}

static void vhost_scsi_aborted_task(struct se_cmd *se_cmd)
{
        return;
}

static void vhost_scsi_free_evt(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
{
        vs->vs_events_nr--;
        kfree(evt);
}

static struct vhost_scsi_evt *
vhost_scsi_allocate_evt(struct vhost_scsi *vs,
                       u32 event, u32 reason)
{
        struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
        struct vhost_scsi_evt *evt;

        if (vs->vs_events_nr > VHOST_SCSI_MAX_EVENT) {
                vs->vs_events_missed = true;
                return NULL;
        }

        evt = kzalloc(sizeof(*evt), GFP_KERNEL);
        if (!evt) {
                vq_err(vq, "Failed to allocate vhost_scsi_evt\n");
                vs->vs_events_missed = true;
                return NULL;
        }

        evt->event.event = cpu_to_vhost32(vq, event);
        evt->event.reason = cpu_to_vhost32(vq, reason);
        vs->vs_events_nr++;

        return evt;
}

static void vhost_scsi_free_cmd(struct vhost_scsi_cmd *cmd)
{
        struct se_cmd *se_cmd = &cmd->tvc_se_cmd;

        /* TODO locking against target/backend threads? */
        transport_generic_free_cmd(se_cmd, 0);

}

static int vhost_scsi_check_stop_free(struct se_cmd *se_cmd)
{
        return target_put_sess_cmd(se_cmd);
}

static void
vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
{
        struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
        struct virtio_scsi_event *event = &evt->event;
        struct virtio_scsi_event __user *eventp;
        unsigned out, in;
        int head, ret;

        if (!vq->private_data) {
                vs->vs_events_missed = true;
                return;
        }

again:
        vhost_disable_notify(&vs->dev, vq);
        head = vhost_get_vq_desc(vq, vq->iov,
                        ARRAY_SIZE(vq->iov), &out, &in,
                        NULL, NULL);
        if (head < 0) {
                vs->vs_events_missed = true;
                return;
        }
        if (head == vq->num) {
                if (vhost_enable_notify(&vs->dev, vq))
                        goto again;
                vs->vs_events_missed = true;
                return;
        }

        if ((vq->iov[out].iov_len != sizeof(struct virtio_scsi_event))) {
                vq_err(vq, "Expecting virtio_scsi_event, got %zu bytes\n",
                                vq->iov[out].iov_len);
                vs->vs_events_missed = true;
                return;
        }

        if (vs->vs_events_missed) {
                event->event |= cpu_to_vhost32(vq, VIRTIO_SCSI_T_EVENTS_MISSED);
                vs->vs_events_missed = false;
        }

        eventp = vq->iov[out].iov_base;
        ret = __copy_to_user(eventp, event, sizeof(*event));
        if (!ret)
                vhost_add_used_and_signal(&vs->dev, vq, head, 0);
        else
                vq_err(vq, "Faulted on vhost_scsi_send_event\n");
}

static void vhost_scsi_evt_work(struct vhost_work *work)
{
        struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
                                        vs_event_work);
        struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
        struct vhost_scsi_evt *evt;
        struct llist_node *llnode;

        mutex_lock(&vq->mutex);
        llnode = llist_del_all(&vs->vs_event_list);
        while (llnode) {
                evt = llist_entry(llnode, struct vhost_scsi_evt, list);
                llnode = llist_next(llnode);
                vhost_scsi_do_evt_work(vs, evt);
                vhost_scsi_free_evt(vs, evt);
        }
        mutex_unlock(&vq->mutex);
}

/* Fill in status and signal that we are done processing this command
 *
 * This is scheduled in the vhost work queue so we are called with the owner
 * process mm and can access the vring.
 */
static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
{
        struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
                                        vs_completion_work);
        DECLARE_BITMAP(signal, VHOST_SCSI_MAX_VQ);
        struct virtio_scsi_cmd_resp v_rsp;
        struct vhost_scsi_cmd *cmd;
        struct llist_node *llnode;
        struct se_cmd *se_cmd;
        struct iov_iter iov_iter;
        int ret, vq;

        bitmap_zero(signal, VHOST_SCSI_MAX_VQ);
        llnode = llist_del_all(&vs->vs_completion_list);
        while (llnode) {
                cmd = llist_entry(llnode, struct vhost_scsi_cmd,
                                     tvc_completion_list);
                llnode = llist_next(llnode);
                se_cmd = &cmd->tvc_se_cmd;

                pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,
                        cmd, se_cmd->residual_count, se_cmd->scsi_status);

                memset(&v_rsp, 0, sizeof(v_rsp));
                v_rsp.resid = cpu_to_vhost32(cmd->tvc_vq, se_cmd->residual_count);
                /* TODO is status_qualifier field needed? */
                v_rsp.status = se_cmd->scsi_status;
                v_rsp.sense_len = cpu_to_vhost32(cmd->tvc_vq,
                                                 se_cmd->scsi_sense_length);
                memcpy(v_rsp.sense, cmd->tvc_sense_buf,
                       se_cmd->scsi_sense_length);

                iov_iter_init(&iov_iter, READ, cmd->tvc_resp_iov,
                              cmd->tvc_in_iovs, sizeof(v_rsp));
                ret = copy_to_iter(&v_rsp, sizeof(v_rsp), &iov_iter);
                if (likely(ret == sizeof(v_rsp))) {
                        struct vhost_scsi_virtqueue *q;
                        vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
                        q = container_of(cmd->tvc_vq, struct vhost_scsi_virtqueue, vq);
                        vq = q - vs->vqs;
                        __set_bit(vq, signal);
                } else
                        pr_err("Faulted on virtio_scsi_cmd_resp\n");

                vhost_scsi_free_cmd(cmd);
        }

        vq = -1;
        while ((vq = find_next_bit(signal, VHOST_SCSI_MAX_VQ, vq + 1))
                < VHOST_SCSI_MAX_VQ)
                vhost_signal(&vs->dev, &vs->vqs[vq].vq);
}

static struct vhost_scsi_cmd *
vhost_scsi_get_tag(struct vhost_virtqueue *vq, struct vhost_scsi_tpg *tpg,
                   unsigned char *cdb, u64 scsi_tag, u16 lun, u8 task_attr,
                   u32 exp_data_len, int data_direction)
{
        struct vhost_scsi_cmd *cmd;
        struct vhost_scsi_nexus *tv_nexus;
        struct se_session *se_sess;
        struct scatterlist *sg, *prot_sg;
        struct page **pages;
        int tag;

        tv_nexus = tpg->tpg_nexus;
        if (!tv_nexus) {
                pr_err("Unable to locate active struct vhost_scsi_nexus\n");
                return ERR_PTR(-EIO);
        }
        se_sess = tv_nexus->tvn_se_sess;

        tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
        if (tag < 0) {
                pr_err("Unable to obtain tag for vhost_scsi_cmd\n");
                return ERR_PTR(-ENOMEM);
        }

        cmd = &((struct vhost_scsi_cmd *)se_sess->sess_cmd_map)[tag];
        sg = cmd->tvc_sgl;
        prot_sg = cmd->tvc_prot_sgl;
        pages = cmd->tvc_upages;
        memset(cmd, 0, sizeof(struct vhost_scsi_cmd));

        cmd->tvc_sgl = sg;
        cmd->tvc_prot_sgl = prot_sg;
        cmd->tvc_upages = pages;
        cmd->tvc_se_cmd.map_tag = tag;
        cmd->tvc_tag = scsi_tag;
        cmd->tvc_lun = lun;
        cmd->tvc_task_attr = task_attr;
        cmd->tvc_exp_data_len = exp_data_len;
        cmd->tvc_data_direction = data_direction;
        cmd->tvc_nexus = tv_nexus;
        cmd->inflight = vhost_scsi_get_inflight(vq);

        memcpy(cmd->tvc_cdb, cdb, VHOST_SCSI_MAX_CDB_SIZE);

        return cmd;
}

/*
 * Map a user memory range into a scatterlist
 *
 * Returns the number of scatterlist entries used or -errno on error.
 */
static int
vhost_scsi_map_to_sgl(struct vhost_scsi_cmd *cmd,
                      void __user *ptr,
                      size_t len,
                      struct scatterlist *sgl,
                      bool write)
{
        unsigned int npages = 0, offset, nbytes;
        unsigned int pages_nr = iov_num_pages(ptr, len);
        struct scatterlist *sg = sgl;
        struct page **pages = cmd->tvc_upages;
        int ret, i;

        if (pages_nr > VHOST_SCSI_PREALLOC_UPAGES) {
                pr_err("vhost_scsi_map_to_sgl() pages_nr: %u greater than"
                       " preallocated VHOST_SCSI_PREALLOC_UPAGES: %u\n",
                        pages_nr, VHOST_SCSI_PREALLOC_UPAGES);
                return -ENOBUFS;
        }

        ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages);
        /* No pages were pinned */
        if (ret < 0)
                goto out;
        /* Less pages pinned than wanted */
        if (ret != pages_nr) {
                for (i = 0; i < ret; i++)
                        put_page(pages[i]);
                ret = -EFAULT;
                goto out;
        }

        while (len > 0) {
                offset = (uintptr_t)ptr & ~PAGE_MASK;
                nbytes = min_t(unsigned int, PAGE_SIZE - offset, len);
                sg_set_page(sg, pages[npages], nbytes, offset);
                ptr += nbytes;
                len -= nbytes;
                sg++;
                npages++;
        }

out:
        return ret;
}

static int
vhost_scsi_calc_sgls(struct iov_iter *iter, size_t bytes, int max_sgls)
{
        int sgl_count = 0;

        if (!iter || !iter->iov) {
                pr_err("%s: iter->iov is NULL, but expected bytes: %zu"
                       " present\n", __func__, bytes);
                return -EINVAL;
        }

        sgl_count = iov_iter_npages(iter, 0xffff);
        if (sgl_count > max_sgls) {
                pr_err("%s: requested sgl_count: %d exceeds pre-allocated"
                       " max_sgls: %d\n", __func__, sgl_count, max_sgls);
                return -EINVAL;
        }
        return sgl_count;
}

static int
vhost_scsi_iov_to_sgl(struct vhost_scsi_cmd *cmd, bool write,
                      struct iov_iter *iter,
                      struct scatterlist *sg, int sg_count)
{
        size_t off = iter->iov_offset;
        int i, ret;

        for (i = 0; i < iter->nr_segs; i++) {
                void __user *base = iter->iov[i].iov_base + off;
                size_t len = iter->iov[i].iov_len - off;

                ret = vhost_scsi_map_to_sgl(cmd, base, len, sg, write);
                if (ret < 0) {
                        for (i = 0; i < sg_count; i++) {
                                struct page *page = sg_page(&sg[i]);
                                if (page)
                                        put_page(page);
                        }
                        return ret;
                }
                sg += ret;
                off = 0;
        }
        return 0;
}

static int
vhost_scsi_mapal(struct vhost_scsi_cmd *cmd,
                 size_t prot_bytes, struct iov_iter *prot_iter,
                 size_t data_bytes, struct iov_iter *data_iter)
{
        int sgl_count, ret;
        bool write = (cmd->tvc_data_direction == DMA_FROM_DEVICE);

        if (prot_bytes) {
                sgl_count = vhost_scsi_calc_sgls(prot_iter, prot_bytes,
                                                 VHOST_SCSI_PREALLOC_PROT_SGLS);
                if (sgl_count < 0)
                        return sgl_count;

                sg_init_table(cmd->tvc_prot_sgl, sgl_count);
                cmd->tvc_prot_sgl_count = sgl_count;
                pr_debug("%s prot_sg %p prot_sgl_count %u\n", __func__,
                         cmd->tvc_prot_sgl, cmd->tvc_prot_sgl_count);

                ret = vhost_scsi_iov_to_sgl(cmd, write, prot_iter,
                                            cmd->tvc_prot_sgl,
                                            cmd->tvc_prot_sgl_count);
                if (ret < 0) {
                        cmd->tvc_prot_sgl_count = 0;
                        return ret;
                }
        }
        sgl_count = vhost_scsi_calc_sgls(data_iter, data_bytes,
                                         VHOST_SCSI_PREALLOC_SGLS);
        if (sgl_count < 0)
                return sgl_count;

        sg_init_table(cmd->tvc_sgl, sgl_count);
        cmd->tvc_sgl_count = sgl_count;
        pr_debug("%s data_sg %p data_sgl_count %u\n", __func__,
                  cmd->tvc_sgl, cmd->tvc_sgl_count);

        ret = vhost_scsi_iov_to_sgl(cmd, write, data_iter,
                                    cmd->tvc_sgl, cmd->tvc_sgl_count);
        if (ret < 0) {
                cmd->tvc_sgl_count = 0;
                return ret;
        }
        return 0;
}

static int vhost_scsi_to_tcm_attr(int attr)
{
        switch (attr) {
        case VIRTIO_SCSI_S_SIMPLE:
                return TCM_SIMPLE_TAG;
        case VIRTIO_SCSI_S_ORDERED:
                return TCM_ORDERED_TAG;
        case VIRTIO_SCSI_S_HEAD:
                return TCM_HEAD_TAG;
        case VIRTIO_SCSI_S_ACA:
                return TCM_ACA_TAG;
        default:
                break;
        }
        return TCM_SIMPLE_TAG;
}

static void vhost_scsi_submission_work(struct work_struct *work)
{
        struct vhost_scsi_cmd *cmd =
                container_of(work, struct vhost_scsi_cmd, work);
        struct vhost_scsi_nexus *tv_nexus;
        struct se_cmd *se_cmd = &cmd->tvc_se_cmd;
        struct scatterlist *sg_ptr, *sg_prot_ptr = NULL;
        int rc;

        /* FIXME: BIDI operation */
        if (cmd->tvc_sgl_count) {
                sg_ptr = cmd->tvc_sgl;

                if (cmd->tvc_prot_sgl_count)
                        sg_prot_ptr = cmd->tvc_prot_sgl;
                else
                        se_cmd->prot_pto = true;
        } else {
                sg_ptr = NULL;
        }
        tv_nexus = cmd->tvc_nexus;

        rc = target_submit_cmd_map_sgls(se_cmd, tv_nexus->tvn_se_sess,
                        cmd->tvc_cdb, &cmd->tvc_sense_buf[0],
                        cmd->tvc_lun, cmd->tvc_exp_data_len,
                        vhost_scsi_to_tcm_attr(cmd->tvc_task_attr),
                        cmd->tvc_data_direction, TARGET_SCF_ACK_KREF,
                        sg_ptr, cmd->tvc_sgl_count, NULL, 0, sg_prot_ptr,
                        cmd->tvc_prot_sgl_count);
        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 void
vhost_scsi_send_bad_target(struct vhost_scsi *vs,
                           struct vhost_virtqueue *vq,
                           int head, unsigned out)
{
        struct virtio_scsi_cmd_resp __user *resp;
        struct virtio_scsi_cmd_resp rsp;
        int ret;

        memset(&rsp, 0, sizeof(rsp));
        rsp.response = VIRTIO_SCSI_S_BAD_TARGET;
        resp = vq->iov[out].iov_base;
        ret = __copy_to_user(resp, &rsp, sizeof(rsp));
        if (!ret)
                vhost_add_used_and_signal(&vs->dev, vq, head, 0);
        else
                pr_err("Faulted on virtio_scsi_cmd_resp\n");
}

static void
vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
{
        struct vhost_scsi_tpg **vs_tpg, *tpg;
        struct virtio_scsi_cmd_req v_req;
        struct virtio_scsi_cmd_req_pi v_req_pi;
        struct vhost_scsi_cmd *cmd;
        struct iov_iter out_iter, in_iter, prot_iter, data_iter;
        u64 tag;
        u32 exp_data_len, data_direction;
        unsigned out, in;
        int head, ret, prot_bytes;
        size_t req_size, rsp_size = sizeof(struct virtio_scsi_cmd_resp);
        size_t out_size, in_size;
        u16 lun;
        u8 *target, *lunp, task_attr;
        bool t10_pi = vhost_has_feature(vq, VIRTIO_SCSI_F_T10_PI);
        void *req, *cdb;

        mutex_lock(&vq->mutex);
        /*
         * We can handle the vq only after the endpoint is setup by calling the
         * VHOST_SCSI_SET_ENDPOINT ioctl.
         */
        vs_tpg = vq->private_data;
        if (!vs_tpg)
                goto out;

        vhost_disable_notify(&vs->dev, vq);

        for (;;) {
                head = vhost_get_vq_desc(vq, vq->iov,
                                         ARRAY_SIZE(vq->iov), &out, &in,
                                         NULL, NULL);
                pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
                         head, out, in);
                /* On error, stop handling until the next kick. */
                if (unlikely(head < 0))
                        break;
                /* Nothing new?  Wait for eventfd to tell us they refilled. */
                if (head == vq->num) {
                        if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
                                vhost_disable_notify(&vs->dev, vq);
                                continue;
                        }
                        break;
                }
                /*
                 * Check for a sane response buffer so we can report early
                 * errors back to the guest.
                 */
                if (unlikely(vq->iov[out].iov_len < rsp_size)) {
                        vq_err(vq, "Expecting at least virtio_scsi_cmd_resp"
                                " size, got %zu bytes\n", vq->iov[out].iov_len);
                        break;
                }
                /*
                 * Setup pointers and values based upon different virtio-scsi
                 * request header if T10_PI is enabled in KVM guest.
                 */
                if (t10_pi) {
                        req = &v_req_pi;
                        req_size = sizeof(v_req_pi);
                        lunp = &v_req_pi.lun[0];
                        target = &v_req_pi.lun[1];
                } else {
                        req = &v_req;
                        req_size = sizeof(v_req);
                        lunp = &v_req.lun[0];
                        target = &v_req.lun[1];
                }
                /*
                 * FIXME: Not correct for BIDI operation
                 */
                out_size = iov_length(vq->iov, out);
                in_size = iov_length(&vq->iov[out], in);

                /*
                 * Copy over the virtio-scsi request header, which for a
                 * ANY_LAYOUT enabled guest may span multiple iovecs, or a
                 * single iovec may contain both the header + outgoing
                 * WRITE payloads.
                 *
                 * copy_from_iter() will advance out_iter, so that it will
                 * point at the start of the outgoing WRITE payload, if
                 * DMA_TO_DEVICE is set.
                 */
                iov_iter_init(&out_iter, WRITE, vq->iov, out, out_size);

                ret = copy_from_iter(req, req_size, &out_iter);
                if (unlikely(ret != req_size)) {
                        vq_err(vq, "Faulted on copy_from_iter\n");
                        vhost_scsi_send_bad_target(vs, vq, head, out);
                        continue;
                }
                /* virtio-scsi spec requires byte 0 of the lun to be 1 */
                if (unlikely(*lunp != 1)) {
                        vq_err(vq, "Illegal virtio-scsi lun: %u\n", *lunp);
                        vhost_scsi_send_bad_target(vs, vq, head, out);
                        continue;
                }

                tpg = ACCESS_ONCE(vs_tpg[*target]);
                if (unlikely(!tpg)) {
                        /* Target does not exist, fail the request */
                        vhost_scsi_send_bad_target(vs, vq, head, out);
                        continue;
                }
                /*
                 * Determine data_direction by calculating the total outgoing
                 * iovec sizes + incoming iovec sizes vs. virtio-scsi request +
                 * response headers respectively.
                 *
                 * For DMA_TO_DEVICE this is out_iter, which is already pointing
                 * to the right place.
                 *
                 * For DMA_FROM_DEVICE, the iovec will be just past the end
                 * of the virtio-scsi response header in either the same
                 * or immediately following iovec.
                 *
                 * Any associated T10_PI bytes for the outgoing / incoming
                 * payloads are included in calculation of exp_data_len here.
                 */
                prot_bytes = 0;

                if (out_size > req_size) {
                        data_direction = DMA_TO_DEVICE;
                        exp_data_len = out_size - req_size;
                        data_iter = out_iter;
                } else if (in_size > rsp_size) {
                        data_direction = DMA_FROM_DEVICE;
                        exp_data_len = in_size - rsp_size;

                        iov_iter_init(&in_iter, READ, &vq->iov[out], in,
                                      rsp_size + exp_data_len);
                        iov_iter_advance(&in_iter, rsp_size);
                        data_iter = in_iter;
                } else {
                        data_direction = DMA_NONE;
                        exp_data_len = 0;
                }
                /*
                 * If T10_PI header + payload is present, setup prot_iter values
                 * and recalculate data_iter for vhost_scsi_mapal() mapping to
                 * host scatterlists via get_user_pages_fast().
                 */
                if (t10_pi) {
                        if (v_req_pi.pi_bytesout) {
                                if (data_direction != DMA_TO_DEVICE) {
                                        vq_err(vq, "Received non zero pi_bytesout,"
                                                " but wrong data_direction\n");
                                        vhost_scsi_send_bad_target(vs, vq, head, out);
                                        continue;
                                }
                                prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesout);
                        } else if (v_req_pi.pi_bytesin) {
                                if (data_direction != DMA_FROM_DEVICE) {
                                        vq_err(vq, "Received non zero pi_bytesin,"
                                                " but wrong data_direction\n");
                                        vhost_scsi_send_bad_target(vs, vq, head, out);
                                        continue;
                                }
                                prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesin);
                        }
                        /*
                         * Set prot_iter to data_iter, and advance past any
                         * preceeding prot_bytes that may be present.
                         *
                         * Also fix up the exp_data_len to reflect only the
                         * actual data payload length.
                         */
                        if (prot_bytes) {
                                exp_data_len -= prot_bytes;
                                prot_iter = data_iter;
                                iov_iter_advance(&data_iter, prot_bytes);
                        }
                        tag = vhost64_to_cpu(vq, v_req_pi.tag);
                        task_attr = v_req_pi.task_attr;
                        cdb = &v_req_pi.cdb[0];
                        lun = ((v_req_pi.lun[2] << 8) | v_req_pi.lun[3]) & 0x3FFF;
                } else {
                        tag = vhost64_to_cpu(vq, v_req.tag);
                        task_attr = v_req.task_attr;
                        cdb = &v_req.cdb[0];
                        lun = ((v_req.lun[2] << 8) | v_req.lun[3]) & 0x3FFF;
                }
                /*
                 * Check that the received CDB size does not exceeded our
                 * hardcoded max for vhost-scsi, then get a pre-allocated
                 * cmd descriptor for the new virtio-scsi tag.
                 *
                 * TODO what if cdb was too small for varlen cdb header?
                 */
                if (unlikely(scsi_command_size(cdb) > VHOST_SCSI_MAX_CDB_SIZE)) {
                        vq_err(vq, "Received SCSI CDB with command_size: %d that"
                                " exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
                                scsi_command_size(cdb), VHOST_SCSI_MAX_CDB_SIZE);
                        vhost_scsi_send_bad_target(vs, vq, head, out);
                        continue;
                }
                cmd = vhost_scsi_get_tag(vq, tpg, cdb, tag, lun, task_attr,
                                         exp_data_len + prot_bytes,
                                         data_direction);
                if (IS_ERR(cmd)) {
                        vq_err(vq, "vhost_scsi_get_tag failed %ld\n",
                               PTR_ERR(cmd));
                        vhost_scsi_send_bad_target(vs, vq, head, out);
                        continue;
                }
                cmd->tvc_vhost = vs;
                cmd->tvc_vq = vq;
                cmd->tvc_resp_iov = &vq->iov[out];
                cmd->tvc_in_iovs = in;

                pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
                         cmd->tvc_cdb[0], cmd->tvc_lun);
                pr_debug("cmd: %p exp_data_len: %d, prot_bytes: %d data_direction:"
                         " %d\n", cmd, exp_data_len, prot_bytes, data_direction);

                if (data_direction != DMA_NONE) {
                        ret = vhost_scsi_mapal(cmd,
                                               prot_bytes, &prot_iter,
                                               exp_data_len, &data_iter);
                        if (unlikely(ret)) {
                                vq_err(vq, "Failed to map iov to sgl\n");
                                vhost_scsi_release_cmd(&cmd->tvc_se_cmd);
                                vhost_scsi_send_bad_target(vs, vq, head, out);
                                continue;
                        }
                }
                /*
                 * Save the descriptor from vhost_get_vq_desc() to be used to
                 * complete the virtio-scsi request in TCM callback context via
                 * vhost_scsi_queue_data_in() and vhost_scsi_queue_status()
                 */
                cmd->tvc_vq_desc = head;
                /*
                 * Dispatch cmd descriptor for cmwq execution in process
                 * context provided by vhost_scsi_workqueue.  This also ensures
                 * cmd is executed on the same kworker CPU as this vhost
                 * thread to gain positive L2 cache locality effects.
                 */
                INIT_WORK(&cmd->work, vhost_scsi_submission_work);
                queue_work(vhost_scsi_workqueue, &cmd->work);
        }
out:
        mutex_unlock(&vq->mutex);
}

static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
{
        pr_debug("%s: The handling func for control queue.\n", __func__);
}

static void
vhost_scsi_send_evt(struct vhost_scsi *vs,
                   struct vhost_scsi_tpg *tpg,
                   struct se_lun *lun,
                   u32 event,
                   u32 reason)
{
        struct vhost_scsi_evt *evt;

        evt = vhost_scsi_allocate_evt(vs, event, reason);
        if (!evt)
                return;

        if (tpg && lun) {
                /* TODO: share lun setup code with virtio-scsi.ko */
                /*
                 * Note: evt->event is zeroed when we allocate it and
                 * lun[4-7] need to be zero according to virtio-scsi spec.
                 */
                evt->event.lun[0] = 0x01;
                evt->event.lun[1] = tpg->tport_tpgt;
                if (lun->unpacked_lun >= 256)
                        evt->event.lun[2] = lun->unpacked_lun >> 8 | 0x40 ;
                evt->event.lun[3] = lun->unpacked_lun & 0xFF;
        }

        llist_add(&evt->list, &vs->vs_event_list);
        vhost_work_queue(&vs->dev, &vs->vs_event_work);
}

static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
{
        struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
                                                poll.work);
        struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);

        mutex_lock(&vq->mutex);
        if (!vq->private_data)
                goto out;

        if (vs->vs_events_missed)
                vhost_scsi_send_evt(vs, NULL, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
out:
        mutex_unlock(&vq->mutex);
}

static void vhost_scsi_handle_kick(struct vhost_work *work)
{
        struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
                                                poll.work);
        struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);

        vhost_scsi_handle_vq(vs, vq);
}

static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)
{
        vhost_poll_flush(&vs->vqs[index].vq.poll);
}

/* Callers must hold dev mutex */
static void vhost_scsi_flush(struct vhost_scsi *vs)
{
        struct vhost_scsi_inflight *old_inflight[VHOST_SCSI_MAX_VQ];
        int i;

        /* Init new inflight and remember the old inflight */
        vhost_scsi_init_inflight(vs, old_inflight);

        /*
         * The inflight->kref was initialized to 1. We decrement it here to
         * indicate the start of the flush operation so that it will reach 0
         * when all the reqs are finished.
         */
        for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
                kref_put(&old_inflight[i]->kref, vhost_scsi_done_inflight);

        /* Flush both the vhost poll and vhost work */
        for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
                vhost_scsi_flush_vq(vs, i);
        vhost_work_flush(&vs->dev, &vs->vs_completion_work);
        vhost_work_flush(&vs->dev, &vs->vs_event_work);

        /* Wait for all reqs issued before the flush to be finished */
        for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
                wait_for_completion(&old_inflight[i]->comp);
}

/*
 * Called from vhost_scsi_ioctl() context to walk the list of available
 * vhost_scsi_tpg with an active struct vhost_scsi_nexus
 *
 *  The lock nesting rule is:
 *    vhost_scsi_mutex -> vs->dev.mutex -> tpg->tv_tpg_mutex -> vq->mutex
 */
static int
vhost_scsi_set_endpoint(struct vhost_scsi *vs,
                        struct vhost_scsi_target *t)
{
        struct se_portal_group *se_tpg;
        struct vhost_scsi_tport *tv_tport;
        struct vhost_scsi_tpg *tpg;
        struct vhost_scsi_tpg **vs_tpg;
        struct vhost_virtqueue *vq;
        int index, ret, i, len;
        bool match = false;

        mutex_lock(&vhost_scsi_mutex);
        mutex_lock(&vs->dev.mutex);

        /* Verify that ring has been setup correctly. */
        for (index = 0; index < vs->dev.nvqs; ++index) {
                /* Verify that ring has been setup correctly. */
                if (!vhost_vq_access_ok(&vs->vqs[index].vq)) {
                        ret = -EFAULT;
                        goto out;
                }
        }

        len = sizeof(vs_tpg[0]) * VHOST_SCSI_MAX_TARGET;
        vs_tpg = kzalloc(len, GFP_KERNEL);
        if (!vs_tpg) {
                ret = -ENOMEM;
                goto out;
        }
        if (vs->vs_tpg)
                memcpy(vs_tpg, vs->vs_tpg, len);

        list_for_each_entry(tpg, &vhost_scsi_list, tv_tpg_list) {
                mutex_lock(&tpg->tv_tpg_mutex);
                if (!tpg->tpg_nexus) {
                        mutex_unlock(&tpg->tv_tpg_mutex);
                        continue;
                }
                if (tpg->tv_tpg_vhost_count != 0) {
                        mutex_unlock(&tpg->tv_tpg_mutex);
                        continue;
                }
                tv_tport = tpg->tport;

                if (!strcmp(tv_tport->tport_name, t->vhost_wwpn)) {
                        if (vs->vs_tpg && vs->vs_tpg[tpg->tport_tpgt]) {
                                kfree(vs_tpg);
                                mutex_unlock(&tpg->tv_tpg_mutex);
                                ret = -EEXIST;
                                goto out;
                        }
                        /*
                         * In order to ensure individual vhost-scsi configfs
                         * groups cannot be removed while in use by vhost ioctl,
                         * go ahead and take an explicit se_tpg->tpg_group.cg_item
                         * dependency now.
                         */
                        se_tpg = &tpg->se_tpg;
                        ret = target_depend_item(&se_tpg->tpg_group.cg_item);
                        if (ret) {
                                pr_warn("configfs_depend_item() failed: %d\n", ret);
                                kfree(vs_tpg);
                                mutex_unlock(&tpg->tv_tpg_mutex);
                                goto out;
                        }
                        tpg->tv_tpg_vhost_count++;
                        tpg->vhost_scsi = vs;
                        vs_tpg[tpg->tport_tpgt] = tpg;
                        smp_mb__after_atomic();
                        match = true;
                }
                mutex_unlock(&tpg->tv_tpg_mutex);
        }

        if (match) {
                memcpy(vs->vs_vhost_wwpn, t->vhost_wwpn,
                       sizeof(vs->vs_vhost_wwpn));
                for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
                        vq = &vs->vqs[i].vq;
                        mutex_lock(&vq->mutex);
                        vq->private_data = vs_tpg;
                        vhost_init_used(vq);
                        mutex_unlock(&vq->mutex);
                }
                ret = 0;
        } else {
                ret = -EEXIST;
        }

        /*
         * Act as synchronize_rcu to make sure access to
         * old vs->vs_tpg is finished.
         */
        vhost_scsi_flush(vs);
        kfree(vs->vs_tpg);
        vs->vs_tpg = vs_tpg;

out:
        mutex_unlock(&vs->dev.mutex);
        mutex_unlock(&vhost_scsi_mutex);
        return ret;
}

static int
vhost_scsi_clear_endpoint(struct vhost_scsi *vs,
                          struct vhost_scsi_target *t)
{
        struct se_portal_group *se_tpg;
        struct vhost_scsi_tport *tv_tport;
        struct vhost_scsi_tpg *tpg;
        struct vhost_virtqueue *vq;
        bool match = false;
        int index, ret, i;
        u8 target;

        mutex_lock(&vhost_scsi_mutex);
        mutex_lock(&vs->dev.mutex);
        /* Verify that ring has been setup correctly. */
        for (index = 0; index < vs->dev.nvqs; ++index) {
                if (!vhost_vq_access_ok(&vs->vqs[index].vq)) {
                        ret = -EFAULT;
                        goto err_dev;
                }
        }

        if (!vs->vs_tpg) {
                ret = 0;
                goto err_dev;
        }

        for (i = 0; i < VHOST_SCSI_MAX_TARGET; i++) {
                target = i;
                tpg = vs->vs_tpg[target];
                if (!tpg)
                        continue;

                mutex_lock(&tpg->tv_tpg_mutex);
                tv_tport = tpg->tport;
                if (!tv_tport) {
                        ret = -ENODEV;
                        goto err_tpg;
                }

                if (strcmp(tv_tport->tport_name, t->vhost_wwpn)) {
                        pr_warn("tv_tport->tport_name: %s, tpg->tport_tpgt: %hu"
                                " does not match t->vhost_wwpn: %s, t->vhost_tpgt: %hu\n",
                                tv_tport->tport_name, tpg->tport_tpgt,
                                t->vhost_wwpn, t->vhost_tpgt);
                        ret = -EINVAL;
                        goto err_tpg;
                }
                tpg->tv_tpg_vhost_count--;
                tpg->vhost_scsi = NULL;
                vs->vs_tpg[target] = NULL;
                match = true;
                mutex_unlock(&tpg->tv_tpg_mutex);
                /*
                 * Release se_tpg->tpg_group.cg_item configfs dependency now
                 * to allow vhost-scsi WWPN se_tpg->tpg_group shutdown to occur.
                 */
                se_tpg = &tpg->se_tpg;
                target_undepend_item(&se_tpg->tpg_group.cg_item);
        }
        if (match) {
                for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
                        vq = &vs->vqs[i].vq;
                        mutex_lock(&vq->mutex);
                        vq->private_data = NULL;
                        mutex_unlock(&vq->mutex);
                }
        }
        /*
         * Act as synchronize_rcu to make sure access to
         * old vs->vs_tpg is finished.
         */
        vhost_scsi_flush(vs);
        kfree(vs->vs_tpg);
        vs->vs_tpg = NULL;
        WARN_ON(vs->vs_events_nr);
        mutex_unlock(&vs->dev.mutex);
        mutex_unlock(&vhost_scsi_mutex);
        return 0;

err_tpg:
        mutex_unlock(&tpg->tv_tpg_mutex);
err_dev:
        mutex_unlock(&vs->dev.mutex);
        mutex_unlock(&vhost_scsi_mutex);
        return ret;
}

static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
{
        struct vhost_virtqueue *vq;
        int i;

        if (features & ~VHOST_SCSI_FEATURES)
                return -EOPNOTSUPP;

        mutex_lock(&vs->dev.mutex);
        if ((features & (1 << VHOST_F_LOG_ALL)) &&
            !vhost_log_access_ok(&vs->dev)) {
                mutex_unlock(&vs->dev.mutex);
                return -EFAULT;
        }

        for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
                vq = &vs->vqs[i].vq;
                mutex_lock(&vq->mutex);
                vq->acked_features = features;
                mutex_unlock(&vq->mutex);
        }
        mutex_unlock(&vs->dev.mutex);
        return 0;
}

static int vhost_scsi_open(struct inode *inode, struct file *f)
{
        struct vhost_scsi *vs;
        struct vhost_virtqueue **vqs;
        int r = -ENOMEM, i;

        vs = kzalloc(sizeof(*vs), GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
        if (!vs) {
                vs = vzalloc(sizeof(*vs));
                if (!vs)
                        goto err_vs;
        }

        vqs = kmalloc(VHOST_SCSI_MAX_VQ * sizeof(*vqs), GFP_KERNEL);
        if (!vqs)
                goto err_vqs;

        vhost_work_init(&vs->vs_completion_work, vhost_scsi_complete_cmd_work);
        vhost_work_init(&vs->vs_event_work, vhost_scsi_evt_work);

        vs->vs_events_nr = 0;
        vs->vs_events_missed = false;

        vqs[VHOST_SCSI_VQ_CTL] = &vs->vqs[VHOST_SCSI_VQ_CTL].vq;
        vqs[VHOST_SCSI_VQ_EVT] = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
        vs->vqs[VHOST_SCSI_VQ_CTL].vq.handle_kick = vhost_scsi_ctl_handle_kick;
        vs->vqs[VHOST_SCSI_VQ_EVT].vq.handle_kick = vhost_scsi_evt_handle_kick;
        for (i = VHOST_SCSI_VQ_IO; i < VHOST_SCSI_MAX_VQ; i++) {
                vqs[i] = &vs->vqs[i].vq;
                vs->vqs[i].vq.handle_kick = vhost_scsi_handle_kick;
        }
        vhost_dev_init(&vs->dev, vqs, VHOST_SCSI_MAX_VQ);

        vhost_scsi_init_inflight(vs, NULL);

        f->private_data = vs;
        return 0;

err_vqs:
        kvfree(vs);
err_vs:
        return r;
}

static int vhost_scsi_release(struct inode *inode, struct file *f)
{
        struct vhost_scsi *vs = f->private_data;
        struct vhost_scsi_target t;

        mutex_lock(&vs->dev.mutex);
        memcpy(t.vhost_wwpn, vs->vs_vhost_wwpn, sizeof(t.vhost_wwpn));
        mutex_unlock(&vs->dev.mutex);
        vhost_scsi_clear_endpoint(vs, &t);
        vhost_dev_stop(&vs->dev);
        vhost_dev_cleanup(&vs->dev, false);
        /* Jobs can re-queue themselves in evt kick handler. Do extra flush. */
        vhost_scsi_flush(vs);
        kfree(vs->dev.vqs);
        kvfree(vs);
        return 0;
}

static long
vhost_scsi_ioctl(struct file *f,
                 unsigned int ioctl,
                 unsigned long arg)
{
        struct vhost_scsi *vs = f->private_data;
        struct vhost_scsi_target backend;
        void __user *argp = (void __user *)arg;
        u64 __user *featurep = argp;
        u32 __user *eventsp = argp;
        u32 events_missed;
        u64 features;
        int r, abi_version = VHOST_SCSI_ABI_VERSION;
        struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;

        switch (ioctl) {
        case VHOST_SCSI_SET_ENDPOINT:
                if (copy_from_user(&backend, argp, sizeof backend))
                        return -EFAULT;
                if (backend.reserved != 0)
                        return -EOPNOTSUPP;

                return vhost_scsi_set_endpoint(vs, &backend);
        case VHOST_SCSI_CLEAR_ENDPOINT:
                if (copy_from_user(&backend, argp, sizeof backend))
                        return -EFAULT;
                if (backend.reserved != 0)
                        return -EOPNOTSUPP;

                return vhost_scsi_clear_endpoint(vs, &backend);
        case VHOST_SCSI_GET_ABI_VERSION:
                if (copy_to_user(argp, &abi_version, sizeof abi_version))
                        return -EFAULT;
                return 0;
        case VHOST_SCSI_SET_EVENTS_MISSED:
                if (get_user(events_missed, eventsp))
                        return -EFAULT;
                mutex_lock(&vq->mutex);
                vs->vs_events_missed = events_missed;
                mutex_unlock(&vq->mutex);
                return 0;
        case VHOST_SCSI_GET_EVENTS_MISSED:
                mutex_lock(&vq->mutex);
                events_missed = vs->vs_events_missed;
                mutex_unlock(&vq->mutex);
                if (put_user(events_missed, eventsp))
                        return -EFAULT;
                return 0;
        case VHOST_GET_FEATURES:
                features = VHOST_SCSI_FEATURES;
                if (copy_to_user(featurep, &features, sizeof features))
                        return -EFAULT;
                return 0;
        case VHOST_SET_FEATURES:
                if (copy_from_user(&features, featurep, sizeof features))
                        return -EFAULT;
                return vhost_scsi_set_features(vs, features);
        default:
                mutex_lock(&vs->dev.mutex);
                r = vhost_dev_ioctl(&vs->dev, ioctl, argp);
                /* TODO: flush backend after dev ioctl. */
                if (r == -ENOIOCTLCMD)
                        r = vhost_vring_ioctl(&vs->dev, ioctl, argp);
                mutex_unlock(&vs->dev.mutex);
                return r;
        }
}

#ifdef CONFIG_COMPAT
static long vhost_scsi_compat_ioctl(struct file *f, unsigned int ioctl,
                                unsigned long arg)
{
        return vhost_scsi_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
}
#endif

static const struct file_operations vhost_scsi_fops = {
        .owner          = THIS_MODULE,
        .release        = vhost_scsi_release,
        .unlocked_ioctl = vhost_scsi_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = vhost_scsi_compat_ioctl,
#endif
        .open           = vhost_scsi_open,
        .llseek         = noop_llseek,
};

static struct miscdevice vhost_scsi_misc = {
        MISC_DYNAMIC_MINOR,
        "vhost-scsi",
        &vhost_scsi_fops,
};

static int __init vhost_scsi_register(void)
{
        return misc_register(&vhost_scsi_misc);
}

static int vhost_scsi_deregister(void)
{
        return misc_deregister(&vhost_scsi_misc);
}

static char *vhost_scsi_dump_proto_id(struct vhost_scsi_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 void
vhost_scsi_do_plug(struct vhost_scsi_tpg *tpg,
                  struct se_lun *lun, bool plug)
{

        struct vhost_scsi *vs = tpg->vhost_scsi;
        struct vhost_virtqueue *vq;
        u32 reason;

        if (!vs)
                return;

        mutex_lock(&vs->dev.mutex);

        if (plug)
                reason = VIRTIO_SCSI_EVT_RESET_RESCAN;
        else
                reason = VIRTIO_SCSI_EVT_RESET_REMOVED;

        vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
        mutex_lock(&vq->mutex);
        if (vhost_has_feature(vq, VIRTIO_SCSI_F_HOTPLUG))
                vhost_scsi_send_evt(vs, tpg, lun,
                                   VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
        mutex_unlock(&vq->mutex);
        mutex_unlock(&vs->dev.mutex);
}

static void vhost_scsi_hotplug(struct vhost_scsi_tpg *tpg, struct se_lun *lun)
{
        vhost_scsi_do_plug(tpg, lun, true);
}

static void vhost_scsi_hotunplug(struct vhost_scsi_tpg *tpg, struct se_lun *lun)
{
        vhost_scsi_do_plug(tpg, lun, false);
}

static int vhost_scsi_port_link(struct se_portal_group *se_tpg,
                               struct se_lun *lun)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);

        mutex_lock(&vhost_scsi_mutex);

        mutex_lock(&tpg->tv_tpg_mutex);
        tpg->tv_tpg_port_count++;
        mutex_unlock(&tpg->tv_tpg_mutex);

        vhost_scsi_hotplug(tpg, lun);

        mutex_unlock(&vhost_scsi_mutex);

        return 0;
}

static void vhost_scsi_port_unlink(struct se_portal_group *se_tpg,
                                  struct se_lun *lun)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);

        mutex_lock(&vhost_scsi_mutex);

        mutex_lock(&tpg->tv_tpg_mutex);
        tpg->tv_tpg_port_count--;
        mutex_unlock(&tpg->tv_tpg_mutex);

        vhost_scsi_hotunplug(tpg, lun);

        mutex_unlock(&vhost_scsi_mutex);
}

static struct se_node_acl *
vhost_scsi_make_nodeacl(struct se_portal_group *se_tpg,
                       struct config_group *group,
                       const char *name)
{
        struct se_node_acl *se_nacl, *se_nacl_new;
        u32 nexus_depth;

        /* vhost_scsi_parse_wwn(name, &wwpn, 1) < 0)
                return ERR_PTR(-EINVAL); */
        se_nacl_new = vhost_scsi_alloc_fabric_acl(se_tpg);
        if (!se_nacl_new)
                return ERR_PTR(-ENOMEM);

        nexus_depth = 1;
        /*
         * se_nacl_new may be released by core_tpg_add_initiator_node_acl()
         * when converting a NodeACL from demo mode -> explict
         */
        se_nacl = core_tpg_add_initiator_node_acl(se_tpg, se_nacl_new,
                                name, nexus_depth);
        if (IS_ERR(se_nacl)) {
                vhost_scsi_release_fabric_acl(se_tpg, se_nacl_new);
                return se_nacl;
        }

        return se_nacl;
}

static void vhost_scsi_drop_nodeacl(struct se_node_acl *se_acl)
{
        core_tpg_del_initiator_node_acl(se_acl->se_tpg, se_acl, 1);
        kfree(se_acl);
}

static void vhost_scsi_free_cmd_map_res(struct vhost_scsi_nexus *nexus,
                                       struct se_session *se_sess)
{
        struct vhost_scsi_cmd *tv_cmd;
        unsigned int i;

        if (!se_sess->sess_cmd_map)
                return;

        for (i = 0; i < VHOST_SCSI_DEFAULT_TAGS; i++) {
                tv_cmd = &((struct vhost_scsi_cmd *)se_sess->sess_cmd_map)[i];

                kfree(tv_cmd->tvc_sgl);
                kfree(tv_cmd->tvc_prot_sgl);
                kfree(tv_cmd->tvc_upages);
        }
}

static ssize_t vhost_scsi_tpg_attrib_store_fabric_prot_type(
        struct se_portal_group *se_tpg,
        const char *page,
        size_t count)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        unsigned long val;
        int ret = kstrtoul(page, 0, &val);

        if (ret) {
                pr_err("kstrtoul() returned %d for fabric_prot_type\n", ret);
                return ret;
        }
        if (val != 0 && val != 1 && val != 3) {
                pr_err("Invalid vhost_scsi fabric_prot_type: %lu\n", val);
                return -EINVAL;
        }
        tpg->tv_fabric_prot_type = val;

        return count;
}

static ssize_t vhost_scsi_tpg_attrib_show_fabric_prot_type(
        struct se_portal_group *se_tpg,
        char *page)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);

        return sprintf(page, "%d\n", tpg->tv_fabric_prot_type);
}
TF_TPG_ATTRIB_ATTR(vhost_scsi, fabric_prot_type, S_IRUGO | S_IWUSR);

static struct configfs_attribute *vhost_scsi_tpg_attrib_attrs[] = {
        &vhost_scsi_tpg_attrib_fabric_prot_type.attr,
        NULL,
};

static int vhost_scsi_make_nexus(struct vhost_scsi_tpg *tpg,
                                const char *name)
{
        struct se_portal_group *se_tpg;
        struct se_session *se_sess;
        struct vhost_scsi_nexus *tv_nexus;
        struct vhost_scsi_cmd *tv_cmd;
        unsigned int i;

        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 vhost_scsi_nexus), GFP_KERNEL);
        if (!tv_nexus) {
                mutex_unlock(&tpg->tv_tpg_mutex);
                pr_err("Unable to allocate struct vhost_scsi_nexus\n");
                return -ENOMEM;
        }
        /*
         *  Initialize the struct se_session pointer and setup tagpool
         *  for struct vhost_scsi_cmd descriptors
         */
        tv_nexus->tvn_se_sess = transport_init_session_tags(
                                        VHOST_SCSI_DEFAULT_TAGS,
                                        sizeof(struct vhost_scsi_cmd),
                                        TARGET_PROT_DIN_PASS | TARGET_PROT_DOUT_PASS);
        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;
        for (i = 0; i < VHOST_SCSI_DEFAULT_TAGS; i++) {
                tv_cmd = &((struct vhost_scsi_cmd *)se_sess->sess_cmd_map)[i];

                tv_cmd->tvc_sgl = kzalloc(sizeof(struct scatterlist) *
                                        VHOST_SCSI_PREALLOC_SGLS, GFP_KERNEL);
                if (!tv_cmd->tvc_sgl) {
                        mutex_unlock(&tpg->tv_tpg_mutex);
                        pr_err("Unable to allocate tv_cmd->tvc_sgl\n");
                        goto out;
                }

                tv_cmd->tvc_upages = kzalloc(sizeof(struct page *) *
                                        VHOST_SCSI_PREALLOC_UPAGES, GFP_KERNEL);
                if (!tv_cmd->tvc_upages) {
                        mutex_unlock(&tpg->tv_tpg_mutex);
                        pr_err("Unable to allocate tv_cmd->tvc_upages\n");
                        goto out;
                }

                tv_cmd->tvc_prot_sgl = kzalloc(sizeof(struct scatterlist) *
                                        VHOST_SCSI_PREALLOC_PROT_SGLS, GFP_KERNEL);
                if (!tv_cmd->tvc_prot_sgl) {
                        mutex_unlock(&tpg->tv_tpg_mutex);
                        pr_err("Unable to allocate tv_cmd->tvc_prot_sgl\n");
                        goto out;
                }
        }
        /*
         * Since we are running in 'demo mode' this call with generate a
         * struct se_node_acl for the vhost_scsi 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 vhost 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:
        vhost_scsi_free_cmd_map_res(tv_nexus, se_sess);
        transport_free_session(se_sess);
        kfree(tv_nexus);
        return -ENOMEM;
}

static int vhost_scsi_drop_nexus(struct vhost_scsi_tpg *tpg)
{
        struct se_session *se_sess;
        struct vhost_scsi_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 TCM_vhost I_T Nexus with"
                        " active TPG port count: %d\n",
                        tpg->tv_tpg_port_count);
                return -EBUSY;
        }

        if (tpg->tv_tpg_vhost_count != 0) {
                mutex_unlock(&tpg->tv_tpg_mutex);
                pr_err("Unable to remove TCM_vhost I_T Nexus with"
                        " active TPG vhost count: %d\n",
                        tpg->tv_tpg_vhost_count);
                return -EBUSY;
        }

        pr_debug("TCM_vhost_ConfigFS: Removing I_T Nexus to emulated"
                " %s Initiator Port: %s\n", vhost_scsi_dump_proto_id(tpg->tport),
                tv_nexus->tvn_se_sess->se_node_acl->initiatorname);

        vhost_scsi_free_cmd_map_res(tv_nexus, se_sess);
        /*
         * Release the SCSI I_T Nexus to the emulated vhost 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 vhost_scsi_tpg_show_nexus(struct se_portal_group *se_tpg,
                                        char *page)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        struct vhost_scsi_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 vhost_scsi_tpg_store_nexus(struct se_portal_group *se_tpg,
                                         const char *page,
                                         size_t count)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);
        struct vhost_scsi_tport *tport_wwn = tpg->tport;
        unsigned char i_port[VHOST_SCSI_NAMELEN], *ptr, *port_ptr;
        int ret;
        /*
         * Shutdown the active I_T nexus if 'NULL' is passed..
         */
        if (!strncmp(page, "NULL", 4)) {
                ret = vhost_scsi_drop_nexus(tpg);
                return (!ret) ? count : ret;
        }
        /*
         * Otherwise make sure the passed virtual Initiator port WWN matches
         * the fabric protocol_id set in vhost_scsi_make_tport(), and call
         * vhost_scsi_make_nexus().
         */
        if (strlen(page) >= VHOST_SCSI_NAMELEN) {
                pr_err("Emulated NAA Sas Address: %s, exceeds"
                                " max: %d\n", page, VHOST_SCSI_NAMELEN);
                return -EINVAL;
        }
        snprintf(&i_port[0], VHOST_SCSI_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,
                                vhost_scsi_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,
                                vhost_scsi_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,
                                vhost_scsi_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 = vhost_scsi_make_nexus(tpg, port_ptr);
        if (ret < 0)
                return ret;

        return count;
}

TF_TPG_BASE_ATTR(vhost_scsi, nexus, S_IRUGO | S_IWUSR);

static struct configfs_attribute *vhost_scsi_tpg_attrs[] = {
        &vhost_scsi_tpg_nexus.attr,
        NULL,
};

static struct se_portal_group *
vhost_scsi_make_tpg(struct se_wwn *wwn,
                   struct config_group *group,
                   const char *name)
{
        struct vhost_scsi_tport *tport = container_of(wwn,
                        struct vhost_scsi_tport, tport_wwn);

        struct vhost_scsi_tpg *tpg;
        u16 tpgt;
        int ret;

        if (strstr(name, "tpgt_") != name)
                return ERR_PTR(-EINVAL);
        if (kstrtou16(name + 5, 10, &tpgt) || tpgt >= VHOST_SCSI_MAX_TARGET)
                return ERR_PTR(-EINVAL);

        tpg = kzalloc(sizeof(struct vhost_scsi_tpg), GFP_KERNEL);
        if (!tpg) {
                pr_err("Unable to allocate struct vhost_scsi_tpg");
                return ERR_PTR(-ENOMEM);
        }
        mutex_init(&tpg->tv_tpg_mutex);
        INIT_LIST_HEAD(&tpg->tv_tpg_list);
        tpg->tport = tport;
        tpg->tport_tpgt = tpgt;

        ret = core_tpg_register(&vhost_scsi_ops, wwn,
                                &tpg->se_tpg, tpg, TRANSPORT_TPG_TYPE_NORMAL);
        if (ret < 0) {
                kfree(tpg);
                return NULL;
        }
        mutex_lock(&vhost_scsi_mutex);
        list_add_tail(&tpg->tv_tpg_list, &vhost_scsi_list);
        mutex_unlock(&vhost_scsi_mutex);

        return &tpg->se_tpg;
}

static void vhost_scsi_drop_tpg(struct se_portal_group *se_tpg)
{
        struct vhost_scsi_tpg *tpg = container_of(se_tpg,
                                struct vhost_scsi_tpg, se_tpg);

        mutex_lock(&vhost_scsi_mutex);
        list_del(&tpg->tv_tpg_list);
        mutex_unlock(&vhost_scsi_mutex);
        /*
         * Release the virtual I_T Nexus for this vhost TPG
         */
        vhost_scsi_drop_nexus(tpg);
        /*
         * Deregister the se_tpg from TCM..
         */
        core_tpg_deregister(se_tpg);
        kfree(tpg);
}

static struct se_wwn *
vhost_scsi_make_tport(struct target_fabric_configfs *tf,
                     struct config_group *group,
                     const char *name)
{
        struct vhost_scsi_tport *tport;
        char *ptr;
        u64 wwpn = 0;
        int off = 0;

        /* if (vhost_scsi_parse_wwn(name, &wwpn, 1) < 0)
                return ERR_PTR(-EINVAL); */

        tport = kzalloc(sizeof(struct vhost_scsi_tport), GFP_KERNEL);
        if (!tport) {
                pr_err("Unable to allocate struct vhost_scsi_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) >= VHOST_SCSI_NAMELEN) {
                pr_err("Emulated %s Address: %s, exceeds"
                        " max: %d\n", name, vhost_scsi_dump_proto_id(tport),
                        VHOST_SCSI_NAMELEN);
                kfree(tport);
                return ERR_PTR(-EINVAL);
        }
        snprintf(&tport->tport_name[0], VHOST_SCSI_NAMELEN, "%s", &name[off]);

        pr_debug("TCM_VHost_ConfigFS: Allocated emulated Target"
                " %s Address: %s\n", vhost_scsi_dump_proto_id(tport), name);

        return &tport->tport_wwn;
}

static void vhost_scsi_drop_tport(struct se_wwn *wwn)
{
        struct vhost_scsi_tport *tport = container_of(wwn,
                                struct vhost_scsi_tport, tport_wwn);

        pr_debug("TCM_VHost_ConfigFS: Deallocating emulated Target"
                " %s Address: %s\n", vhost_scsi_dump_proto_id(tport),
                tport->tport_name);

        kfree(tport);
}

static ssize_t
vhost_scsi_wwn_show_attr_version(struct target_fabric_configfs *tf,
                                char *page)
{
        return sprintf(page, "TCM_VHOST fabric module %s on %s/%s"
                "on "UTS_RELEASE"\n", VHOST_SCSI_VERSION, utsname()->sysname,
                utsname()->machine);
}

TF_WWN_ATTR_RO(vhost_scsi, version);

static struct configfs_attribute *vhost_scsi_wwn_attrs[] = {
        &vhost_scsi_wwn_version.attr,
        NULL,
};

static struct target_core_fabric_ops vhost_scsi_ops = {
        .module                         = THIS_MODULE,
        .name                           = "vhost",
        .get_fabric_name                = vhost_scsi_get_fabric_name,
        .get_fabric_proto_ident         = vhost_scsi_get_fabric_proto_ident,
        .tpg_get_wwn                    = vhost_scsi_get_fabric_wwn,
        .tpg_get_tag                    = vhost_scsi_get_tpgt,
        .tpg_get_pr_transport_id        = vhost_scsi_get_pr_transport_id,
        .tpg_get_pr_transport_id_len    = vhost_scsi_get_pr_transport_id_len,
        .tpg_parse_pr_out_transport_id  = vhost_scsi_parse_pr_out_transport_id,
        .tpg_check_demo_mode            = vhost_scsi_check_true,
        .tpg_check_demo_mode_cache      = vhost_scsi_check_true,
        .tpg_check_demo_mode_write_protect = vhost_scsi_check_false,
        .tpg_check_prod_mode_write_protect = vhost_scsi_check_false,
        .tpg_check_prot_fabric_only     = vhost_scsi_check_prot_fabric_only,
        .tpg_alloc_fabric_acl           = vhost_scsi_alloc_fabric_acl,
        .tpg_release_fabric_acl         = vhost_scsi_release_fabric_acl,
        .tpg_get_inst_index             = vhost_scsi_tpg_get_inst_index,
        .release_cmd                    = vhost_scsi_release_cmd,
        .check_stop_free                = vhost_scsi_check_stop_free,
        .shutdown_session               = vhost_scsi_shutdown_session,
        .close_session                  = vhost_scsi_close_session,
        .sess_get_index                 = vhost_scsi_sess_get_index,
        .sess_get_initiator_sid         = NULL,
        .write_pending                  = vhost_scsi_write_pending,
        .write_pending_status           = vhost_scsi_write_pending_status,
        .set_default_node_attributes    = vhost_scsi_set_default_node_attrs,
        .get_task_tag                   = vhost_scsi_get_task_tag,
        .get_cmd_state                  = vhost_scsi_get_cmd_state,
        .queue_data_in                  = vhost_scsi_queue_data_in,
        .queue_status                   = vhost_scsi_queue_status,
        .queue_tm_rsp                   = vhost_scsi_queue_tm_rsp,
        .aborted_task                   = vhost_scsi_aborted_task,
        /*
         * Setup callers for generic logic in target_core_fabric_configfs.c
         */
        .fabric_make_wwn                = vhost_scsi_make_tport,
        .fabric_drop_wwn                = vhost_scsi_drop_tport,
        .fabric_make_tpg                = vhost_scsi_make_tpg,
        .fabric_drop_tpg                = vhost_scsi_drop_tpg,
        .fabric_post_link               = vhost_scsi_port_link,
        .fabric_pre_unlink              = vhost_scsi_port_unlink,
        .fabric_make_np                 = NULL,
        .fabric_drop_np                 = NULL,
        .fabric_make_nodeacl            = vhost_scsi_make_nodeacl,
        .fabric_drop_nodeacl            = vhost_scsi_drop_nodeacl,

        .tfc_wwn_attrs                  = vhost_scsi_wwn_attrs,
        .tfc_tpg_base_attrs             = vhost_scsi_tpg_attrs,
        .tfc_tpg_attrib_attrs           = vhost_scsi_tpg_attrib_attrs,
};

static int __init vhost_scsi_init(void)
{
        int ret = -ENOMEM;

        pr_debug("TCM_VHOST fabric module %s on %s/%s"
                " on "UTS_RELEASE"\n", VHOST_SCSI_VERSION, utsname()->sysname,
                utsname()->machine);

        /*
         * Use our own dedicated workqueue for submitting I/O into
         * target core to avoid contention within system_wq.
         */
        vhost_scsi_workqueue = alloc_workqueue("vhost_scsi", 0, 0);
        if (!vhost_scsi_workqueue)
                goto out;

        ret = vhost_scsi_register();
        if (ret < 0)
                goto out_destroy_workqueue;

        ret = target_register_template(&vhost_scsi_ops);
        if (ret < 0)
                goto out_vhost_scsi_deregister;

        return 0;

out_vhost_scsi_deregister:
        vhost_scsi_deregister();
out_destroy_workqueue:
        destroy_workqueue(vhost_scsi_workqueue);
out:
        return ret;
};

static void vhost_scsi_exit(void)
{
        target_unregister_template(&vhost_scsi_ops);
        vhost_scsi_deregister();
        destroy_workqueue(vhost_scsi_workqueue);
};

MODULE_DESCRIPTION("VHOST_SCSI series fabric driver");
MODULE_ALIAS("tcm_vhost");
MODULE_LICENSE("GPL");
module_init(vhost_scsi_init);
module_exit(vhost_scsi_exit);