scsi: target: tcmu: Fix possible page UAF

[mirror_ubuntu-jammy-kernel.git] / drivers / target / target_core_user.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2013 Shaohua Li <shli@kernel.org>
 * Copyright (C) 2014 Red Hat, Inc.
 * Copyright (C) 2015 Arrikto, Inc.
 * Copyright (C) 2017 Chinamobile, Inc.
 */

#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/parser.h>
#include <linux/vmalloc.h>
#include <linux/uio_driver.h>
#include <linux/xarray.h>
#include <linux/stringify.h>
#include <linux/bitops.h>
#include <linux/highmem.h>
#include <linux/configfs.h>
#include <linux/mutex.h>
#include <linux/workqueue.h>
#include <net/genetlink.h>
#include <scsi/scsi_common.h>
#include <scsi/scsi_proto.h>
#include <target/target_core_base.h>
#include <target/target_core_fabric.h>
#include <target/target_core_backend.h>

#include <linux/target_core_user.h>

/**
 * DOC: Userspace I/O
 * Userspace I/O
 * -------------
 *
 * Define a shared-memory interface for LIO to pass SCSI commands and
 * data to userspace for processing. This is to allow backends that
 * are too complex for in-kernel support to be possible.
 *
 * It uses the UIO framework to do a lot of the device-creation and
 * introspection work for us.
 *
 * See the .h file for how the ring is laid out. Note that while the
 * command ring is defined, the particulars of the data area are
 * not. Offset values in the command entry point to other locations
 * internal to the mmap-ed area. There is separate space outside the
 * command ring for data buffers. This leaves maximum flexibility for
 * moving buffer allocations, or even page flipping or other
 * allocation techniques, without altering the command ring layout.
 *
 * SECURITY:
 * The user process must be assumed to be malicious. There's no way to
 * prevent it breaking the command ring protocol if it wants, but in
 * order to prevent other issues we must only ever read *data* from
 * the shared memory area, not offsets or sizes. This applies to
 * command ring entries as well as the mailbox. Extra code needed for
 * this may have a 'UAM' comment.
 */

#define TCMU_TIME_OUT (30 * MSEC_PER_SEC)

/* For mailbox plus cmd ring, the size is fixed 8MB */
#define MB_CMDR_SIZE (8 * 1024 * 1024)
/* Offset of cmd ring is size of mailbox */
#define CMDR_OFF sizeof(struct tcmu_mailbox)
#define CMDR_SIZE (MB_CMDR_SIZE - CMDR_OFF)

/*
 * For data area, the default block size is PAGE_SIZE and
 * the default total size is 256K * PAGE_SIZE.
 */
#define DATA_PAGES_PER_BLK_DEF 1
#define DATA_AREA_PAGES_DEF (256 * 1024)

#define TCMU_MBS_TO_PAGES(_mbs) ((size_t)_mbs << (20 - PAGE_SHIFT))
#define TCMU_PAGES_TO_MBS(_pages) (_pages >> (20 - PAGE_SHIFT))

/*
 * Default number of global data blocks(512K * PAGE_SIZE)
 * when the unmap thread will be started.
 */
#define TCMU_GLOBAL_MAX_PAGES_DEF (512 * 1024)

static u8 tcmu_kern_cmd_reply_supported;
static u8 tcmu_netlink_blocked;

static struct device *tcmu_root_device;

struct tcmu_hba {
        u32 host_id;
};

#define TCMU_CONFIG_LEN 256

static DEFINE_MUTEX(tcmu_nl_cmd_mutex);
static LIST_HEAD(tcmu_nl_cmd_list);

struct tcmu_dev;

struct tcmu_nl_cmd {
        /* wake up thread waiting for reply */
        struct completion complete;
        struct list_head nl_list;
        struct tcmu_dev *udev;
        int cmd;
        int status;
};

struct tcmu_dev {
        struct list_head node;
        struct kref kref;

        struct se_device se_dev;
        struct se_dev_plug se_plug;

        char *name;
        struct se_hba *hba;

#define TCMU_DEV_BIT_OPEN 0
#define TCMU_DEV_BIT_BROKEN 1
#define TCMU_DEV_BIT_BLOCKED 2
#define TCMU_DEV_BIT_TMR_NOTIFY 3
#define TCMU_DEV_BIT_PLUGGED 4
        unsigned long flags;

        struct uio_info uio_info;

        struct inode *inode;

        uint64_t dev_size;

        struct tcmu_mailbox *mb_addr;
        void *cmdr;
        u32 cmdr_size;
        u32 cmdr_last_cleaned;
        /* Offset of data area from start of mb */
        /* Must add data_off and mb_addr to get the address */
        size_t data_off;
        int data_area_mb;
        uint32_t max_blocks;
        size_t mmap_pages;

        struct mutex cmdr_lock;
        struct list_head qfull_queue;
        struct list_head tmr_queue;

        uint32_t dbi_max;
        uint32_t dbi_thresh;
        unsigned long *data_bitmap;
        struct xarray data_pages;
        uint32_t data_pages_per_blk;
        uint32_t data_blk_size;

        struct xarray commands;

        struct timer_list cmd_timer;
        unsigned int cmd_time_out;
        struct list_head inflight_queue;

        struct timer_list qfull_timer;
        int qfull_time_out;

        struct list_head timedout_entry;

        struct tcmu_nl_cmd curr_nl_cmd;

        char dev_config[TCMU_CONFIG_LEN];

        int nl_reply_supported;
};

#define TCMU_DEV(_se_dev) container_of(_se_dev, struct tcmu_dev, se_dev)

struct tcmu_cmd {
        struct se_cmd *se_cmd;
        struct tcmu_dev *tcmu_dev;
        struct list_head queue_entry;

        uint16_t cmd_id;

        /* Can't use se_cmd when cleaning up expired cmds, because if
           cmd has been completed then accessing se_cmd is off limits */
        uint32_t dbi_cnt;
        uint32_t dbi_bidi_cnt;
        uint32_t dbi_cur;
        uint32_t *dbi;

        uint32_t data_len_bidi;

        unsigned long deadline;

#define TCMU_CMD_BIT_EXPIRED 0
#define TCMU_CMD_BIT_KEEP_BUF 1
        unsigned long flags;
};

struct tcmu_tmr {
        struct list_head queue_entry;

        uint8_t tmr_type;
        uint32_t tmr_cmd_cnt;
        int16_t tmr_cmd_ids[];
};

/*
 * To avoid dead lock the mutex lock order should always be:
 *
 * mutex_lock(&root_udev_mutex);
 * ...
 * mutex_lock(&tcmu_dev->cmdr_lock);
 * mutex_unlock(&tcmu_dev->cmdr_lock);
 * ...
 * mutex_unlock(&root_udev_mutex);
 */
static DEFINE_MUTEX(root_udev_mutex);
static LIST_HEAD(root_udev);

static DEFINE_SPINLOCK(timed_out_udevs_lock);
static LIST_HEAD(timed_out_udevs);

static struct kmem_cache *tcmu_cmd_cache;

static atomic_t global_page_count = ATOMIC_INIT(0);
static struct delayed_work tcmu_unmap_work;
static int tcmu_global_max_pages = TCMU_GLOBAL_MAX_PAGES_DEF;

static int tcmu_set_global_max_data_area(const char *str,
                                         const struct kernel_param *kp)
{
        int ret, max_area_mb;

        ret = kstrtoint(str, 10, &max_area_mb);
        if (ret)
                return -EINVAL;

        if (max_area_mb <= 0) {
                pr_err("global_max_data_area must be larger than 0.\n");
                return -EINVAL;
        }

        tcmu_global_max_pages = TCMU_MBS_TO_PAGES(max_area_mb);
        if (atomic_read(&global_page_count) > tcmu_global_max_pages)
                schedule_delayed_work(&tcmu_unmap_work, 0);
        else
                cancel_delayed_work_sync(&tcmu_unmap_work);

        return 0;
}

static int tcmu_get_global_max_data_area(char *buffer,
                                         const struct kernel_param *kp)
{
        return sprintf(buffer, "%d\n", TCMU_PAGES_TO_MBS(tcmu_global_max_pages));
}

static const struct kernel_param_ops tcmu_global_max_data_area_op = {
        .set = tcmu_set_global_max_data_area,
        .get = tcmu_get_global_max_data_area,
};

module_param_cb(global_max_data_area_mb, &tcmu_global_max_data_area_op, NULL,
                S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(global_max_data_area_mb,
                 "Max MBs allowed to be allocated to all the tcmu device's "
                 "data areas.");

static int tcmu_get_block_netlink(char *buffer,
                                  const struct kernel_param *kp)
{
        return sprintf(buffer, "%s\n", tcmu_netlink_blocked ?
                       "blocked" : "unblocked");
}

static int tcmu_set_block_netlink(const char *str,
                                  const struct kernel_param *kp)
{
        int ret;
        u8 val;

        ret = kstrtou8(str, 0, &val);
        if (ret < 0)
                return ret;

        if (val > 1) {
                pr_err("Invalid block netlink value %u\n", val);
                return -EINVAL;
        }

        tcmu_netlink_blocked = val;
        return 0;
}

static const struct kernel_param_ops tcmu_block_netlink_op = {
        .set = tcmu_set_block_netlink,
        .get = tcmu_get_block_netlink,
};

module_param_cb(block_netlink, &tcmu_block_netlink_op, NULL, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(block_netlink, "Block new netlink commands.");

static int tcmu_fail_netlink_cmd(struct tcmu_nl_cmd *nl_cmd)
{
        struct tcmu_dev *udev = nl_cmd->udev;

        if (!tcmu_netlink_blocked) {
                pr_err("Could not reset device's netlink interface. Netlink is not blocked.\n");
                return -EBUSY;
        }

        if (nl_cmd->cmd != TCMU_CMD_UNSPEC) {
                pr_debug("Aborting nl cmd %d on %s\n", nl_cmd->cmd, udev->name);
                nl_cmd->status = -EINTR;
                list_del(&nl_cmd->nl_list);
                complete(&nl_cmd->complete);
        }
        return 0;
}

static int tcmu_set_reset_netlink(const char *str,
                                  const struct kernel_param *kp)
{
        struct tcmu_nl_cmd *nl_cmd, *tmp_cmd;
        int ret;
        u8 val;

        ret = kstrtou8(str, 0, &val);
        if (ret < 0)
                return ret;

        if (val != 1) {
                pr_err("Invalid reset netlink value %u\n", val);
                return -EINVAL;
        }

        mutex_lock(&tcmu_nl_cmd_mutex);
        list_for_each_entry_safe(nl_cmd, tmp_cmd, &tcmu_nl_cmd_list, nl_list) {
                ret = tcmu_fail_netlink_cmd(nl_cmd);
                if (ret)
                        break;
        }
        mutex_unlock(&tcmu_nl_cmd_mutex);

        return ret;
}

static const struct kernel_param_ops tcmu_reset_netlink_op = {
        .set = tcmu_set_reset_netlink,
};

module_param_cb(reset_netlink, &tcmu_reset_netlink_op, NULL, S_IWUSR);
MODULE_PARM_DESC(reset_netlink, "Reset netlink commands.");

/* multicast group */
enum tcmu_multicast_groups {
        TCMU_MCGRP_CONFIG,
};

static const struct genl_multicast_group tcmu_mcgrps[] = {
        [TCMU_MCGRP_CONFIG] = { .name = "config", },
};

static struct nla_policy tcmu_attr_policy[TCMU_ATTR_MAX+1] = {
        [TCMU_ATTR_DEVICE]      = { .type = NLA_STRING },
        [TCMU_ATTR_MINOR]       = { .type = NLA_U32 },
        [TCMU_ATTR_CMD_STATUS]  = { .type = NLA_S32 },
        [TCMU_ATTR_DEVICE_ID]   = { .type = NLA_U32 },
        [TCMU_ATTR_SUPP_KERN_CMD_REPLY] = { .type = NLA_U8 },
};

static int tcmu_genl_cmd_done(struct genl_info *info, int completed_cmd)
{
        struct tcmu_dev *udev = NULL;
        struct tcmu_nl_cmd *nl_cmd;
        int dev_id, rc, ret = 0;

        if (!info->attrs[TCMU_ATTR_CMD_STATUS] ||
            !info->attrs[TCMU_ATTR_DEVICE_ID]) {
                printk(KERN_ERR "TCMU_ATTR_CMD_STATUS or TCMU_ATTR_DEVICE_ID not set, doing nothing\n");
                return -EINVAL;
        }

        dev_id = nla_get_u32(info->attrs[TCMU_ATTR_DEVICE_ID]);
        rc = nla_get_s32(info->attrs[TCMU_ATTR_CMD_STATUS]);

        mutex_lock(&tcmu_nl_cmd_mutex);
        list_for_each_entry(nl_cmd, &tcmu_nl_cmd_list, nl_list) {
                if (nl_cmd->udev->se_dev.dev_index == dev_id) {
                        udev = nl_cmd->udev;
                        break;
                }
        }

        if (!udev) {
                pr_err("tcmu nl cmd %u/%d completion could not find device with dev id %u.\n",
                       completed_cmd, rc, dev_id);
                ret = -ENODEV;
                goto unlock;
        }
        list_del(&nl_cmd->nl_list);

        pr_debug("%s genl cmd done got id %d curr %d done %d rc %d stat %d\n",
                 udev->name, dev_id, nl_cmd->cmd, completed_cmd, rc,
                 nl_cmd->status);

        if (nl_cmd->cmd != completed_cmd) {
                pr_err("Mismatched commands on %s (Expecting reply for %d. Current %d).\n",
                       udev->name, completed_cmd, nl_cmd->cmd);
                ret = -EINVAL;
                goto unlock;
        }

        nl_cmd->status = rc;
        complete(&nl_cmd->complete);
unlock:
        mutex_unlock(&tcmu_nl_cmd_mutex);
        return ret;
}

static int tcmu_genl_rm_dev_done(struct sk_buff *skb, struct genl_info *info)
{
        return tcmu_genl_cmd_done(info, TCMU_CMD_REMOVED_DEVICE);
}

static int tcmu_genl_add_dev_done(struct sk_buff *skb, struct genl_info *info)
{
        return tcmu_genl_cmd_done(info, TCMU_CMD_ADDED_DEVICE);
}

static int tcmu_genl_reconfig_dev_done(struct sk_buff *skb,
                                       struct genl_info *info)
{
        return tcmu_genl_cmd_done(info, TCMU_CMD_RECONFIG_DEVICE);
}

static int tcmu_genl_set_features(struct sk_buff *skb, struct genl_info *info)
{
        if (info->attrs[TCMU_ATTR_SUPP_KERN_CMD_REPLY]) {
                tcmu_kern_cmd_reply_supported  =
                        nla_get_u8(info->attrs[TCMU_ATTR_SUPP_KERN_CMD_REPLY]);
                printk(KERN_INFO "tcmu daemon: command reply support %u.\n",
                       tcmu_kern_cmd_reply_supported);
        }

        return 0;
}

static const struct genl_small_ops tcmu_genl_ops[] = {
        {
                .cmd    = TCMU_CMD_SET_FEATURES,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .flags  = GENL_ADMIN_PERM,
                .doit   = tcmu_genl_set_features,
        },
        {
                .cmd    = TCMU_CMD_ADDED_DEVICE_DONE,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .flags  = GENL_ADMIN_PERM,
                .doit   = tcmu_genl_add_dev_done,
        },
        {
                .cmd    = TCMU_CMD_REMOVED_DEVICE_DONE,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .flags  = GENL_ADMIN_PERM,
                .doit   = tcmu_genl_rm_dev_done,
        },
        {
                .cmd    = TCMU_CMD_RECONFIG_DEVICE_DONE,
                .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
                .flags  = GENL_ADMIN_PERM,
                .doit   = tcmu_genl_reconfig_dev_done,
        },
};

/* Our generic netlink family */
static struct genl_family tcmu_genl_family __ro_after_init = {
        .module = THIS_MODULE,
        .hdrsize = 0,
        .name = "TCM-USER",
        .version = 2,
        .maxattr = TCMU_ATTR_MAX,
        .policy = tcmu_attr_policy,
        .mcgrps = tcmu_mcgrps,
        .n_mcgrps = ARRAY_SIZE(tcmu_mcgrps),
        .netnsok = true,
        .small_ops = tcmu_genl_ops,
        .n_small_ops = ARRAY_SIZE(tcmu_genl_ops),
};

#define tcmu_cmd_set_dbi_cur(cmd, index) ((cmd)->dbi_cur = (index))
#define tcmu_cmd_reset_dbi_cur(cmd) tcmu_cmd_set_dbi_cur(cmd, 0)
#define tcmu_cmd_set_dbi(cmd, index) ((cmd)->dbi[(cmd)->dbi_cur++] = (index))
#define tcmu_cmd_get_dbi(cmd) ((cmd)->dbi[(cmd)->dbi_cur++])

static void tcmu_cmd_free_data(struct tcmu_cmd *tcmu_cmd, uint32_t len)
{
        struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
        uint32_t i;

        for (i = 0; i < len; i++)
                clear_bit(tcmu_cmd->dbi[i], udev->data_bitmap);
}

static inline int tcmu_get_empty_block(struct tcmu_dev *udev,
                                       struct tcmu_cmd *tcmu_cmd,
                                       int prev_dbi, int length, int *iov_cnt)
{
        XA_STATE(xas, &udev->data_pages, 0);
        struct page *page;
        int i, cnt, dbi, dpi;
        int page_cnt = DIV_ROUND_UP(length, PAGE_SIZE);

        dbi = find_first_zero_bit(udev->data_bitmap, udev->dbi_thresh);
        if (dbi == udev->dbi_thresh)
                return -1;

        dpi = dbi * udev->data_pages_per_blk;
        /* Count the number of already allocated pages */
        xas_set(&xas, dpi);
        rcu_read_lock();
        for (cnt = 0; xas_next(&xas) && cnt < page_cnt;)
                cnt++;
        rcu_read_unlock();

        for (i = cnt; i < page_cnt; i++) {
                /* try to get new page from the mm */
                page = alloc_page(GFP_NOIO);
                if (!page)
                        break;

                if (xa_store(&udev->data_pages, dpi + i, page, GFP_NOIO)) {
                        __free_page(page);
                        break;
                }
        }
        if (atomic_add_return(i - cnt, &global_page_count) >
                              tcmu_global_max_pages)
                schedule_delayed_work(&tcmu_unmap_work, 0);

        if (i && dbi > udev->dbi_max)
                udev->dbi_max = dbi;

        set_bit(dbi, udev->data_bitmap);
        tcmu_cmd_set_dbi(tcmu_cmd, dbi);

        if (dbi != prev_dbi + 1)
                *iov_cnt += 1;

        return i == page_cnt ? dbi : -1;
}

static int tcmu_get_empty_blocks(struct tcmu_dev *udev,
                                 struct tcmu_cmd *tcmu_cmd, int length)
{
        /* start value of dbi + 1 must not be a valid dbi */
        int dbi = -2;
        int blk_data_len, iov_cnt = 0;
        uint32_t blk_size = udev->data_blk_size;

        for (; length > 0; length -= blk_size) {
                blk_data_len = min_t(uint32_t, length, blk_size);
                dbi = tcmu_get_empty_block(udev, tcmu_cmd, dbi, blk_data_len,
                                           &iov_cnt);
                if (dbi < 0)
                        return -1;
        }
        return iov_cnt;
}

static inline void tcmu_free_cmd(struct tcmu_cmd *tcmu_cmd)
{
        kfree(tcmu_cmd->dbi);
        kmem_cache_free(tcmu_cmd_cache, tcmu_cmd);
}

static inline void tcmu_cmd_set_block_cnts(struct tcmu_cmd *cmd)
{
        int i, len;
        struct se_cmd *se_cmd = cmd->se_cmd;
        uint32_t blk_size = cmd->tcmu_dev->data_blk_size;

        cmd->dbi_cnt = DIV_ROUND_UP(se_cmd->data_length, blk_size);

        if (se_cmd->se_cmd_flags & SCF_BIDI) {
                BUG_ON(!(se_cmd->t_bidi_data_sg && se_cmd->t_bidi_data_nents));
                for (i = 0, len = 0; i < se_cmd->t_bidi_data_nents; i++)
                        len += se_cmd->t_bidi_data_sg[i].length;
                cmd->dbi_bidi_cnt = DIV_ROUND_UP(len, blk_size);
                cmd->dbi_cnt += cmd->dbi_bidi_cnt;
                cmd->data_len_bidi = len;
        }
}

static int new_block_to_iov(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                            struct iovec **iov, int prev_dbi, int len)
{
        /* Get the next dbi */
        int dbi = tcmu_cmd_get_dbi(cmd);

        /* Do not add more than udev->data_blk_size to iov */
        len = min_t(int,  len, udev->data_blk_size);

        /*
         * The following code will gather and map the blocks to the same iovec
         * when the blocks are all next to each other.
         */
        if (dbi != prev_dbi + 1) {
                /* dbi is not next to previous dbi, so start new iov */
                if (prev_dbi >= 0)
                        (*iov)++;
                /* write offset relative to mb_addr */
                (*iov)->iov_base = (void __user *)
                                   (udev->data_off + dbi * udev->data_blk_size);
        }
        (*iov)->iov_len += len;

        return dbi;
}

static void tcmu_setup_iovs(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                            struct iovec **iov, int data_length)
{
        /* start value of dbi + 1 must not be a valid dbi */
        int dbi = -2;

        /* We prepare the IOVs for DMA_FROM_DEVICE transfer direction */
        for (; data_length > 0; data_length -= udev->data_blk_size)
                dbi = new_block_to_iov(udev, cmd, iov, dbi, data_length);
}

static struct tcmu_cmd *tcmu_alloc_cmd(struct se_cmd *se_cmd)
{
        struct se_device *se_dev = se_cmd->se_dev;
        struct tcmu_dev *udev = TCMU_DEV(se_dev);
        struct tcmu_cmd *tcmu_cmd;

        tcmu_cmd = kmem_cache_zalloc(tcmu_cmd_cache, GFP_NOIO);
        if (!tcmu_cmd)
                return NULL;

        INIT_LIST_HEAD(&tcmu_cmd->queue_entry);
        tcmu_cmd->se_cmd = se_cmd;
        tcmu_cmd->tcmu_dev = udev;

        tcmu_cmd_set_block_cnts(tcmu_cmd);
        tcmu_cmd->dbi = kcalloc(tcmu_cmd->dbi_cnt, sizeof(uint32_t),
                                GFP_NOIO);
        if (!tcmu_cmd->dbi) {
                kmem_cache_free(tcmu_cmd_cache, tcmu_cmd);
                return NULL;
        }

        return tcmu_cmd;
}

static inline void tcmu_flush_dcache_range(void *vaddr, size_t size)
{
        unsigned long offset = offset_in_page(vaddr);
        void *start = vaddr - offset;

        size = round_up(size+offset, PAGE_SIZE);

        while (size) {
                flush_dcache_page(vmalloc_to_page(start));
                start += PAGE_SIZE;
                size -= PAGE_SIZE;
        }
}

/*
 * Some ring helper functions. We don't assume size is a power of 2 so
 * we can't use circ_buf.h.
 */
static inline size_t spc_used(size_t head, size_t tail, size_t size)
{
        int diff = head - tail;

        if (diff >= 0)
                return diff;
        else
                return size + diff;
}

static inline size_t spc_free(size_t head, size_t tail, size_t size)
{
        /* Keep 1 byte unused or we can't tell full from empty */
        return (size - spc_used(head, tail, size) - 1);
}

static inline size_t head_to_end(size_t head, size_t size)
{
        return size - head;
}

#define UPDATE_HEAD(head, used, size) smp_store_release(&head, ((head % size) + used) % size)

#define TCMU_SG_TO_DATA_AREA 1
#define TCMU_DATA_AREA_TO_SG 2

static inline void tcmu_copy_data(struct tcmu_dev *udev,
                                  struct tcmu_cmd *tcmu_cmd, uint32_t direction,
                                  struct scatterlist *sg, unsigned int sg_nents,
                                  struct iovec **iov, size_t data_len)
{
        /* start value of dbi + 1 must not be a valid dbi */
        int dbi = -2;
        size_t page_remaining, cp_len;
        int page_cnt, page_inx, dpi;
        struct sg_mapping_iter sg_iter;
        unsigned int sg_flags;
        struct page *page;
        void *data_page_start, *data_addr;

        if (direction == TCMU_SG_TO_DATA_AREA)
                sg_flags = SG_MITER_ATOMIC | SG_MITER_FROM_SG;
        else
                sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;
        sg_miter_start(&sg_iter, sg, sg_nents, sg_flags);

        while (data_len) {
                if (direction == TCMU_SG_TO_DATA_AREA)
                        dbi = new_block_to_iov(udev, tcmu_cmd, iov, dbi,
                                               data_len);
                else
                        dbi = tcmu_cmd_get_dbi(tcmu_cmd);

                page_cnt = DIV_ROUND_UP(data_len, PAGE_SIZE);
                if (page_cnt > udev->data_pages_per_blk)
                        page_cnt = udev->data_pages_per_blk;

                dpi = dbi * udev->data_pages_per_blk;
                for (page_inx = 0; page_inx < page_cnt && data_len;
                     page_inx++, dpi++) {
                        page = xa_load(&udev->data_pages, dpi);

                        if (direction == TCMU_DATA_AREA_TO_SG)
                                flush_dcache_page(page);
                        data_page_start = kmap_atomic(page);
                        page_remaining = PAGE_SIZE;

                        while (page_remaining && data_len) {
                                if (!sg_miter_next(&sg_iter)) {
                                        /* set length to 0 to abort outer loop */
                                        data_len = 0;
                                        pr_debug("%s: aborting data copy due to exhausted sg_list\n",
                                                 __func__);
                                        break;
                                }
                                cp_len = min3(sg_iter.length, page_remaining,
                                              data_len);

                                data_addr = data_page_start +
                                            PAGE_SIZE - page_remaining;
                                if (direction == TCMU_SG_TO_DATA_AREA)
                                        memcpy(data_addr, sg_iter.addr, cp_len);
                                else
                                        memcpy(sg_iter.addr, data_addr, cp_len);

                                data_len -= cp_len;
                                page_remaining -= cp_len;
                                sg_iter.consumed = cp_len;
                        }
                        sg_miter_stop(&sg_iter);

                        kunmap_atomic(data_page_start);
                        if (direction == TCMU_SG_TO_DATA_AREA)
                                flush_dcache_page(page);
                }
        }
}

static void scatter_data_area(struct tcmu_dev *udev, struct tcmu_cmd *tcmu_cmd,
                              struct iovec **iov)
{
        struct se_cmd *se_cmd = tcmu_cmd->se_cmd;

        tcmu_copy_data(udev, tcmu_cmd, TCMU_SG_TO_DATA_AREA, se_cmd->t_data_sg,
                       se_cmd->t_data_nents, iov, se_cmd->data_length);
}

static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *tcmu_cmd,
                             bool bidi, uint32_t read_len)
{
        struct se_cmd *se_cmd = tcmu_cmd->se_cmd;
        struct scatterlist *data_sg;
        unsigned int data_nents;

        if (!bidi) {
                data_sg = se_cmd->t_data_sg;
                data_nents = se_cmd->t_data_nents;
        } else {
                /*
                 * For bidi case, the first count blocks are for Data-Out
                 * buffer blocks, and before gathering the Data-In buffer
                 * the Data-Out buffer blocks should be skipped.
                 */
                tcmu_cmd_set_dbi_cur(tcmu_cmd,
                                     tcmu_cmd->dbi_cnt - tcmu_cmd->dbi_bidi_cnt);

                data_sg = se_cmd->t_bidi_data_sg;
                data_nents = se_cmd->t_bidi_data_nents;
        }

        tcmu_copy_data(udev, tcmu_cmd, TCMU_DATA_AREA_TO_SG, data_sg,
                       data_nents, NULL, read_len);
}

static inline size_t spc_bitmap_free(unsigned long *bitmap, uint32_t thresh)
{
        return thresh - bitmap_weight(bitmap, thresh);
}

/*
 * We can't queue a command until we have space available on the cmd ring.
 *
 * Called with ring lock held.
 */
static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size)
{
        struct tcmu_mailbox *mb = udev->mb_addr;
        size_t space, cmd_needed;
        u32 cmd_head;

        tcmu_flush_dcache_range(mb, sizeof(*mb));

        cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */

        /*
         * If cmd end-of-ring space is too small then we need space for a NOP plus
         * original cmd - cmds are internally contiguous.
         */
        if (head_to_end(cmd_head, udev->cmdr_size) >= cmd_size)
                cmd_needed = cmd_size;
        else
                cmd_needed = cmd_size + head_to_end(cmd_head, udev->cmdr_size);

        space = spc_free(cmd_head, udev->cmdr_last_cleaned, udev->cmdr_size);
        if (space < cmd_needed) {
                pr_debug("no cmd space: %u %u %u\n", cmd_head,
                       udev->cmdr_last_cleaned, udev->cmdr_size);
                return false;
        }
        return true;
}

/*
 * We have to allocate data buffers before we can queue a command.
 * Returns -1 on error (not enough space) or number of needed iovs on success
 *
 * Called with ring lock held.
 */
static int tcmu_alloc_data_space(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                                  int *iov_bidi_cnt)
{
        int space, iov_cnt = 0, ret = 0;

        if (!cmd->dbi_cnt)
                goto wr_iov_cnts;

        /* try to check and get the data blocks as needed */
        space = spc_bitmap_free(udev->data_bitmap, udev->dbi_thresh);
        if (space < cmd->dbi_cnt) {
                unsigned long blocks_left =
                                (udev->max_blocks - udev->dbi_thresh) + space;

                if (blocks_left < cmd->dbi_cnt) {
                        pr_debug("no data space: only %lu available, but ask for %u\n",
                                        blocks_left * udev->data_blk_size,
                                        cmd->dbi_cnt * udev->data_blk_size);
                        return -1;
                }

                udev->dbi_thresh += cmd->dbi_cnt;
                if (udev->dbi_thresh > udev->max_blocks)
                        udev->dbi_thresh = udev->max_blocks;
        }

        iov_cnt = tcmu_get_empty_blocks(udev, cmd, cmd->se_cmd->data_length);
        if (iov_cnt < 0)
                return -1;

        if (cmd->dbi_bidi_cnt) {
                ret = tcmu_get_empty_blocks(udev, cmd, cmd->data_len_bidi);
                if (ret < 0)
                        return -1;
        }
wr_iov_cnts:
        *iov_bidi_cnt = ret;
        return iov_cnt + ret;
}

static inline size_t tcmu_cmd_get_base_cmd_size(size_t iov_cnt)
{
        return max(offsetof(struct tcmu_cmd_entry, req.iov[iov_cnt]),
                        sizeof(struct tcmu_cmd_entry));
}

static inline size_t tcmu_cmd_get_cmd_size(struct tcmu_cmd *tcmu_cmd,
                                           size_t base_command_size)
{
        struct se_cmd *se_cmd = tcmu_cmd->se_cmd;
        size_t command_size;

        command_size = base_command_size +
                round_up(scsi_command_size(se_cmd->t_task_cdb),
                                TCMU_OP_ALIGN_SIZE);

        WARN_ON(command_size & (TCMU_OP_ALIGN_SIZE-1));

        return command_size;
}

static void tcmu_setup_cmd_timer(struct tcmu_cmd *tcmu_cmd, unsigned int tmo,
                                 struct timer_list *timer)
{
        if (!tmo)
                return;

        tcmu_cmd->deadline = round_jiffies_up(jiffies + msecs_to_jiffies(tmo));
        if (!timer_pending(timer))
                mod_timer(timer, tcmu_cmd->deadline);

        pr_debug("Timeout set up for cmd %p, dev = %s, tmo = %lu\n", tcmu_cmd,
                 tcmu_cmd->tcmu_dev->name, tmo / MSEC_PER_SEC);
}

static int add_to_qfull_queue(struct tcmu_cmd *tcmu_cmd)
{
        struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
        unsigned int tmo;

        /*
         * For backwards compat if qfull_time_out is not set use
         * cmd_time_out and if that's not set use the default time out.
         */
        if (!udev->qfull_time_out)
                return -ETIMEDOUT;
        else if (udev->qfull_time_out > 0)
                tmo = udev->qfull_time_out;
        else if (udev->cmd_time_out)
                tmo = udev->cmd_time_out;
        else
                tmo = TCMU_TIME_OUT;

        tcmu_setup_cmd_timer(tcmu_cmd, tmo, &udev->qfull_timer);

        list_add_tail(&tcmu_cmd->queue_entry, &udev->qfull_queue);
        pr_debug("adding cmd %p on dev %s to ring space wait queue\n",
                 tcmu_cmd, udev->name);
        return 0;
}

static uint32_t ring_insert_padding(struct tcmu_dev *udev, size_t cmd_size)
{
        struct tcmu_cmd_entry_hdr *hdr;
        struct tcmu_mailbox *mb = udev->mb_addr;
        uint32_t cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */

        /* Insert a PAD if end-of-ring space is too small */
        if (head_to_end(cmd_head, udev->cmdr_size) < cmd_size) {
                size_t pad_size = head_to_end(cmd_head, udev->cmdr_size);

                hdr = udev->cmdr + cmd_head;
                tcmu_hdr_set_op(&hdr->len_op, TCMU_OP_PAD);
                tcmu_hdr_set_len(&hdr->len_op, pad_size);
                hdr->cmd_id = 0; /* not used for PAD */
                hdr->kflags = 0;
                hdr->uflags = 0;
                tcmu_flush_dcache_range(hdr, sizeof(*hdr));

                UPDATE_HEAD(mb->cmd_head, pad_size, udev->cmdr_size);
                tcmu_flush_dcache_range(mb, sizeof(*mb));

                cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */
                WARN_ON(cmd_head != 0);
        }

        return cmd_head;
}

static void tcmu_unplug_device(struct se_dev_plug *se_plug)
{
        struct se_device *se_dev = se_plug->se_dev;
        struct tcmu_dev *udev = TCMU_DEV(se_dev);

        clear_bit(TCMU_DEV_BIT_PLUGGED, &udev->flags);
        uio_event_notify(&udev->uio_info);
}

static struct se_dev_plug *tcmu_plug_device(struct se_device *se_dev)
{
        struct tcmu_dev *udev = TCMU_DEV(se_dev);

        if (!test_and_set_bit(TCMU_DEV_BIT_PLUGGED, &udev->flags))
                return &udev->se_plug;

        return NULL;
}

/**
 * queue_cmd_ring - queue cmd to ring or internally
 * @tcmu_cmd: cmd to queue
 * @scsi_err: TCM error code if failure (-1) returned.
 *
 * Returns:
 * -1 we cannot queue internally or to the ring.
 *  0 success
 *  1 internally queued to wait for ring memory to free.
 */
static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err)
{
        struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
        struct se_cmd *se_cmd = tcmu_cmd->se_cmd;
        size_t base_command_size, command_size;
        struct tcmu_mailbox *mb = udev->mb_addr;
        struct tcmu_cmd_entry *entry;
        struct iovec *iov;
        int iov_cnt, iov_bidi_cnt;
        uint32_t cmd_id, cmd_head;
        uint64_t cdb_off;
        uint32_t blk_size = udev->data_blk_size;
        /* size of data buffer needed */
        size_t data_length = (size_t)tcmu_cmd->dbi_cnt * blk_size;

        *scsi_err = TCM_NO_SENSE;

        if (test_bit(TCMU_DEV_BIT_BLOCKED, &udev->flags)) {
                *scsi_err = TCM_LUN_BUSY;
                return -1;
        }

        if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags)) {
                *scsi_err = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                return -1;
        }

        if (!list_empty(&udev->qfull_queue))
                goto queue;

        if (data_length > (size_t)udev->max_blocks * blk_size) {
                pr_warn("TCMU: Request of size %zu is too big for %zu data area\n",
                        data_length, (size_t)udev->max_blocks * blk_size);
                *scsi_err = TCM_INVALID_CDB_FIELD;
                return -1;
        }

        iov_cnt = tcmu_alloc_data_space(udev, tcmu_cmd, &iov_bidi_cnt);
        if (iov_cnt < 0)
                goto free_and_queue;

        /*
         * Must be a certain minimum size for response sense info, but
         * also may be larger if the iov array is large.
         */
        base_command_size = tcmu_cmd_get_base_cmd_size(iov_cnt);
        command_size = tcmu_cmd_get_cmd_size(tcmu_cmd, base_command_size);

        if (command_size > (udev->cmdr_size / 2)) {
                pr_warn("TCMU: Request of size %zu is too big for %u cmd ring\n",
                        command_size, udev->cmdr_size);
                tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cur);
                *scsi_err = TCM_INVALID_CDB_FIELD;
                return -1;
        }

        if (!is_ring_space_avail(udev, command_size))
                /*
                 * Don't leave commands partially setup because the unmap
                 * thread might need the blocks to make forward progress.
                 */
                goto free_and_queue;

        if (xa_alloc(&udev->commands, &cmd_id, tcmu_cmd, XA_LIMIT(1, 0xffff),
                     GFP_NOWAIT) < 0) {
                pr_err("tcmu: Could not allocate cmd id.\n");

                tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cnt);
                *scsi_err = TCM_OUT_OF_RESOURCES;
                return -1;
        }
        tcmu_cmd->cmd_id = cmd_id;

        pr_debug("allocated cmd id %u for cmd %p dev %s\n", tcmu_cmd->cmd_id,
                 tcmu_cmd, udev->name);

        cmd_head = ring_insert_padding(udev, command_size);

        entry = udev->cmdr + cmd_head;
        memset(entry, 0, command_size);
        tcmu_hdr_set_op(&entry->hdr.len_op, TCMU_OP_CMD);

        /* prepare iov list and copy data to data area if necessary */
        tcmu_cmd_reset_dbi_cur(tcmu_cmd);
        iov = &entry->req.iov[0];

        if (se_cmd->data_direction == DMA_TO_DEVICE ||
            se_cmd->se_cmd_flags & SCF_BIDI)
                scatter_data_area(udev, tcmu_cmd, &iov);
        else
                tcmu_setup_iovs(udev, tcmu_cmd, &iov, se_cmd->data_length);

        entry->req.iov_cnt = iov_cnt - iov_bidi_cnt;

        /* Handle BIDI commands */
        if (se_cmd->se_cmd_flags & SCF_BIDI) {
                iov++;
                tcmu_setup_iovs(udev, tcmu_cmd, &iov, tcmu_cmd->data_len_bidi);
                entry->req.iov_bidi_cnt = iov_bidi_cnt;
        }

        tcmu_setup_cmd_timer(tcmu_cmd, udev->cmd_time_out, &udev->cmd_timer);

        entry->hdr.cmd_id = tcmu_cmd->cmd_id;

        tcmu_hdr_set_len(&entry->hdr.len_op, command_size);

        /* All offsets relative to mb_addr, not start of entry! */
        cdb_off = CMDR_OFF + cmd_head + base_command_size;
        memcpy((void *) mb + cdb_off, se_cmd->t_task_cdb, scsi_command_size(se_cmd->t_task_cdb));
        entry->req.cdb_off = cdb_off;
        tcmu_flush_dcache_range(entry, command_size);

        UPDATE_HEAD(mb->cmd_head, command_size, udev->cmdr_size);
        tcmu_flush_dcache_range(mb, sizeof(*mb));

        list_add_tail(&tcmu_cmd->queue_entry, &udev->inflight_queue);

        if (!test_bit(TCMU_DEV_BIT_PLUGGED, &udev->flags))
                uio_event_notify(&udev->uio_info);

        return 0;

free_and_queue:
        tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cur);
        tcmu_cmd_reset_dbi_cur(tcmu_cmd);

queue:
        if (add_to_qfull_queue(tcmu_cmd)) {
                *scsi_err = TCM_OUT_OF_RESOURCES;
                return -1;
        }

        return 1;
}

/**
 * queue_tmr_ring - queue tmr info to ring or internally
 * @udev: related tcmu_dev
 * @tmr: tcmu_tmr containing tmr info to queue
 *
 * Returns:
 *  0 success
 *  1 internally queued to wait for ring memory to free.
 */
static int
queue_tmr_ring(struct tcmu_dev *udev, struct tcmu_tmr *tmr)
{
        struct tcmu_tmr_entry *entry;
        int cmd_size;
        int id_list_sz;
        struct tcmu_mailbox *mb = udev->mb_addr;
        uint32_t cmd_head;

        if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags))
                goto out_free;

        id_list_sz = sizeof(tmr->tmr_cmd_ids[0]) * tmr->tmr_cmd_cnt;
        cmd_size = round_up(sizeof(*entry) + id_list_sz, TCMU_OP_ALIGN_SIZE);

        if (!list_empty(&udev->tmr_queue) ||
            !is_ring_space_avail(udev, cmd_size)) {
                list_add_tail(&tmr->queue_entry, &udev->tmr_queue);
                pr_debug("adding tmr %p on dev %s to TMR ring space wait queue\n",
                         tmr, udev->name);
                return 1;
        }

        cmd_head = ring_insert_padding(udev, cmd_size);

        entry = udev->cmdr + cmd_head;
        memset(entry, 0, cmd_size);
        tcmu_hdr_set_op(&entry->hdr.len_op, TCMU_OP_TMR);
        tcmu_hdr_set_len(&entry->hdr.len_op, cmd_size);
        entry->tmr_type = tmr->tmr_type;
        entry->cmd_cnt = tmr->tmr_cmd_cnt;
        memcpy(&entry->cmd_ids[0], &tmr->tmr_cmd_ids[0], id_list_sz);
        tcmu_flush_dcache_range(entry, cmd_size);

        UPDATE_HEAD(mb->cmd_head, cmd_size, udev->cmdr_size);
        tcmu_flush_dcache_range(mb, sizeof(*mb));

        uio_event_notify(&udev->uio_info);

out_free:
        kfree(tmr);

        return 0;
}

static sense_reason_t
tcmu_queue_cmd(struct se_cmd *se_cmd)
{
        struct se_device *se_dev = se_cmd->se_dev;
        struct tcmu_dev *udev = TCMU_DEV(se_dev);
        struct tcmu_cmd *tcmu_cmd;
        sense_reason_t scsi_ret = TCM_CHECK_CONDITION_ABORT_CMD;
        int ret = -1;

        tcmu_cmd = tcmu_alloc_cmd(se_cmd);
        if (!tcmu_cmd)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        mutex_lock(&udev->cmdr_lock);
        if (!(se_cmd->transport_state & CMD_T_ABORTED))
                ret = queue_cmd_ring(tcmu_cmd, &scsi_ret);
        if (ret < 0)
                tcmu_free_cmd(tcmu_cmd);
        else
                se_cmd->priv = tcmu_cmd;
        mutex_unlock(&udev->cmdr_lock);
        return scsi_ret;
}

static void tcmu_set_next_deadline(struct list_head *queue,
                                   struct timer_list *timer)
{
        struct tcmu_cmd *cmd;

        if (!list_empty(queue)) {
                cmd = list_first_entry(queue, struct tcmu_cmd, queue_entry);
                mod_timer(timer, cmd->deadline);
        } else
                del_timer(timer);
}

static int
tcmu_tmr_type(enum tcm_tmreq_table tmf)
{
        switch (tmf) {
        case TMR_ABORT_TASK:            return TCMU_TMR_ABORT_TASK;
        case TMR_ABORT_TASK_SET:        return TCMU_TMR_ABORT_TASK_SET;
        case TMR_CLEAR_ACA:             return TCMU_TMR_CLEAR_ACA;
        case TMR_CLEAR_TASK_SET:        return TCMU_TMR_CLEAR_TASK_SET;
        case TMR_LUN_RESET:             return TCMU_TMR_LUN_RESET;
        case TMR_TARGET_WARM_RESET:     return TCMU_TMR_TARGET_WARM_RESET;
        case TMR_TARGET_COLD_RESET:     return TCMU_TMR_TARGET_COLD_RESET;
        case TMR_LUN_RESET_PRO:         return TCMU_TMR_LUN_RESET_PRO;
        default:                        return TCMU_TMR_UNKNOWN;
        }
}

static void
tcmu_tmr_notify(struct se_device *se_dev, enum tcm_tmreq_table tmf,
                struct list_head *cmd_list)
{
        int i = 0, cmd_cnt = 0;
        bool unqueued = false;
        uint16_t *cmd_ids = NULL;
        struct tcmu_cmd *cmd;
        struct se_cmd *se_cmd;
        struct tcmu_tmr *tmr;
        struct tcmu_dev *udev = TCMU_DEV(se_dev);

        mutex_lock(&udev->cmdr_lock);

        /* First we check for aborted commands in qfull_queue */
        list_for_each_entry(se_cmd, cmd_list, state_list) {
                i++;
                if (!se_cmd->priv)
                        continue;
                cmd = se_cmd->priv;
                /* Commands on qfull queue have no id yet */
                if (cmd->cmd_id) {
                        cmd_cnt++;
                        continue;
                }
                pr_debug("Removing aborted command %p from queue on dev %s.\n",
                         cmd, udev->name);

                list_del_init(&cmd->queue_entry);
                tcmu_free_cmd(cmd);
                se_cmd->priv = NULL;
                target_complete_cmd(se_cmd, SAM_STAT_TASK_ABORTED);
                unqueued = true;
        }
        if (unqueued)
                tcmu_set_next_deadline(&udev->qfull_queue, &udev->qfull_timer);

        if (!test_bit(TCMU_DEV_BIT_TMR_NOTIFY, &udev->flags))
                goto unlock;

        pr_debug("TMR event %d on dev %s, aborted cmds %d, afflicted cmd_ids %d\n",
                 tcmu_tmr_type(tmf), udev->name, i, cmd_cnt);

        tmr = kmalloc(sizeof(*tmr) + cmd_cnt * sizeof(*cmd_ids), GFP_NOIO);
        if (!tmr)
                goto unlock;

        tmr->tmr_type = tcmu_tmr_type(tmf);
        tmr->tmr_cmd_cnt = cmd_cnt;

        if (cmd_cnt != 0) {
                cmd_cnt = 0;
                list_for_each_entry(se_cmd, cmd_list, state_list) {
                        if (!se_cmd->priv)
                                continue;
                        cmd = se_cmd->priv;
                        if (cmd->cmd_id)
                                tmr->tmr_cmd_ids[cmd_cnt++] = cmd->cmd_id;
                }
        }

        queue_tmr_ring(udev, tmr);

unlock:
        mutex_unlock(&udev->cmdr_lock);
}

static bool tcmu_handle_completion(struct tcmu_cmd *cmd,
                                   struct tcmu_cmd_entry *entry, bool keep_buf)
{
        struct se_cmd *se_cmd = cmd->se_cmd;
        struct tcmu_dev *udev = cmd->tcmu_dev;
        bool read_len_valid = false;
        bool ret = true;
        uint32_t read_len;

        /*
         * cmd has been completed already from timeout, just reclaim
         * data area space and free cmd
         */
        if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
                WARN_ON_ONCE(se_cmd);
                goto out;
        }
        if (test_bit(TCMU_CMD_BIT_KEEP_BUF, &cmd->flags)) {
                pr_err("cmd_id %u already completed with KEEP_BUF, ring is broken\n",
                       entry->hdr.cmd_id);
                set_bit(TCMU_DEV_BIT_BROKEN, &udev->flags);
                ret = false;
                goto out;
        }

        list_del_init(&cmd->queue_entry);

        tcmu_cmd_reset_dbi_cur(cmd);

        if (entry->hdr.uflags & TCMU_UFLAG_UNKNOWN_OP) {
                pr_warn("TCMU: Userspace set UNKNOWN_OP flag on se_cmd %p\n",
                        cmd->se_cmd);
                entry->rsp.scsi_status = SAM_STAT_CHECK_CONDITION;
                goto done;
        }

        read_len = se_cmd->data_length;
        if (se_cmd->data_direction == DMA_FROM_DEVICE &&
            (entry->hdr.uflags & TCMU_UFLAG_READ_LEN) && entry->rsp.read_len) {
                read_len_valid = true;
                if (entry->rsp.read_len < read_len)
                        read_len = entry->rsp.read_len;
        }

        if (entry->rsp.scsi_status == SAM_STAT_CHECK_CONDITION) {
                transport_copy_sense_to_cmd(se_cmd, entry->rsp.sense_buffer);
                if (!read_len_valid )
                        goto done;
                else
                        se_cmd->se_cmd_flags |= SCF_TREAT_READ_AS_NORMAL;
        }
        if (se_cmd->se_cmd_flags & SCF_BIDI) {
                /* Get Data-In buffer before clean up */
                gather_data_area(udev, cmd, true, read_len);
        } else if (se_cmd->data_direction == DMA_FROM_DEVICE) {
                gather_data_area(udev, cmd, false, read_len);
        } else if (se_cmd->data_direction == DMA_TO_DEVICE) {
                /* TODO: */
        } else if (se_cmd->data_direction != DMA_NONE) {
                pr_warn("TCMU: data direction was %d!\n",
                        se_cmd->data_direction);
        }

done:
        se_cmd->priv = NULL;
        if (read_len_valid) {
                pr_debug("read_len = %d\n", read_len);
                target_complete_cmd_with_length(cmd->se_cmd,
                                        entry->rsp.scsi_status, read_len);
        } else
                target_complete_cmd(cmd->se_cmd, entry->rsp.scsi_status);

out:
        if (!keep_buf) {
                tcmu_cmd_free_data(cmd, cmd->dbi_cnt);
                tcmu_free_cmd(cmd);
        } else {
                /*
                 * Keep this command after completion, since userspace still
                 * needs the data buffer. Mark it with TCMU_CMD_BIT_KEEP_BUF
                 * and reset potential TCMU_CMD_BIT_EXPIRED, so we don't accept
                 * a second completion later.
                 * Userspace can free the buffer later by writing the cmd_id
                 * to new action attribute free_kept_buf.
                 */
                clear_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
                set_bit(TCMU_CMD_BIT_KEEP_BUF, &cmd->flags);
        }
        return ret;
}

static int tcmu_run_tmr_queue(struct tcmu_dev *udev)
{
        struct tcmu_tmr *tmr, *tmp;
        LIST_HEAD(tmrs);

        if (list_empty(&udev->tmr_queue))
                return 1;

        pr_debug("running %s's tmr queue\n", udev->name);

        list_splice_init(&udev->tmr_queue, &tmrs);

        list_for_each_entry_safe(tmr, tmp, &tmrs, queue_entry) {
                list_del_init(&tmr->queue_entry);

                pr_debug("removing tmr %p on dev %s from queue\n",
                         tmr, udev->name);

                if (queue_tmr_ring(udev, tmr)) {
                        pr_debug("ran out of space during tmr queue run\n");
                        /*
                         * tmr was requeued, so just put all tmrs back in
                         * the queue
                         */
                        list_splice_tail(&tmrs, &udev->tmr_queue);
                        return 0;
                }
        }

        return 1;
}

static bool tcmu_handle_completions(struct tcmu_dev *udev)
{
        struct tcmu_mailbox *mb;
        struct tcmu_cmd *cmd;
        bool free_space = false;

        if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags)) {
                pr_err("ring broken, not handling completions\n");
                return false;
        }

        mb = udev->mb_addr;
        tcmu_flush_dcache_range(mb, sizeof(*mb));

        while (udev->cmdr_last_cleaned != READ_ONCE(mb->cmd_tail)) {

                struct tcmu_cmd_entry *entry = udev->cmdr + udev->cmdr_last_cleaned;
                bool keep_buf;

                /*
                 * Flush max. up to end of cmd ring since current entry might
                 * be a padding that is shorter than sizeof(*entry)
                 */
                size_t ring_left = head_to_end(udev->cmdr_last_cleaned,
                                               udev->cmdr_size);
                tcmu_flush_dcache_range(entry, ring_left < sizeof(*entry) ?
                                        ring_left : sizeof(*entry));

                free_space = true;

                if (tcmu_hdr_get_op(entry->hdr.len_op) == TCMU_OP_PAD ||
                    tcmu_hdr_get_op(entry->hdr.len_op) == TCMU_OP_TMR) {
                        UPDATE_HEAD(udev->cmdr_last_cleaned,
                                    tcmu_hdr_get_len(entry->hdr.len_op),
                                    udev->cmdr_size);
                        continue;
                }
                WARN_ON(tcmu_hdr_get_op(entry->hdr.len_op) != TCMU_OP_CMD);

                keep_buf = !!(entry->hdr.uflags & TCMU_UFLAG_KEEP_BUF);
                if (keep_buf)
                        cmd = xa_load(&udev->commands, entry->hdr.cmd_id);
                else
                        cmd = xa_erase(&udev->commands, entry->hdr.cmd_id);
                if (!cmd) {
                        pr_err("cmd_id %u not found, ring is broken\n",
                               entry->hdr.cmd_id);
                        set_bit(TCMU_DEV_BIT_BROKEN, &udev->flags);
                        return false;
                }

                if (!tcmu_handle_completion(cmd, entry, keep_buf))
                        break;

                UPDATE_HEAD(udev->cmdr_last_cleaned,
                            tcmu_hdr_get_len(entry->hdr.len_op),
                            udev->cmdr_size);
        }
        if (free_space)
                free_space = tcmu_run_tmr_queue(udev);

        if (atomic_read(&global_page_count) > tcmu_global_max_pages &&
            xa_empty(&udev->commands) && list_empty(&udev->qfull_queue)) {
                /*
                 * Allocated blocks exceeded global block limit, currently no
                 * more pending or waiting commands so try to reclaim blocks.
                 */
                schedule_delayed_work(&tcmu_unmap_work, 0);
        }
        if (udev->cmd_time_out)
                tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer);

        return free_space;
}

static void tcmu_check_expired_ring_cmd(struct tcmu_cmd *cmd)
{
        struct se_cmd *se_cmd;

        if (!time_after_eq(jiffies, cmd->deadline))
                return;

        set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
        list_del_init(&cmd->queue_entry);
        se_cmd = cmd->se_cmd;
        se_cmd->priv = NULL;
        cmd->se_cmd = NULL;

        pr_debug("Timing out inflight cmd %u on dev %s.\n",
                 cmd->cmd_id, cmd->tcmu_dev->name);

        target_complete_cmd(se_cmd, SAM_STAT_CHECK_CONDITION);
}

static void tcmu_check_expired_queue_cmd(struct tcmu_cmd *cmd)
{
        struct se_cmd *se_cmd;

        if (!time_after_eq(jiffies, cmd->deadline))
                return;

        pr_debug("Timing out queued cmd %p on dev %s.\n",
                  cmd, cmd->tcmu_dev->name);

        list_del_init(&cmd->queue_entry);
        se_cmd = cmd->se_cmd;
        tcmu_free_cmd(cmd);

        se_cmd->priv = NULL;
        target_complete_cmd(se_cmd, SAM_STAT_TASK_SET_FULL);
}

static void tcmu_device_timedout(struct tcmu_dev *udev)
{
        spin_lock(&timed_out_udevs_lock);
        if (list_empty(&udev->timedout_entry))
                list_add_tail(&udev->timedout_entry, &timed_out_udevs);
        spin_unlock(&timed_out_udevs_lock);

        schedule_delayed_work(&tcmu_unmap_work, 0);
}

static void tcmu_cmd_timedout(struct timer_list *t)
{
        struct tcmu_dev *udev = from_timer(udev, t, cmd_timer);

        pr_debug("%s cmd timeout has expired\n", udev->name);
        tcmu_device_timedout(udev);
}

static void tcmu_qfull_timedout(struct timer_list *t)
{
        struct tcmu_dev *udev = from_timer(udev, t, qfull_timer);

        pr_debug("%s qfull timeout has expired\n", udev->name);
        tcmu_device_timedout(udev);
}

static int tcmu_attach_hba(struct se_hba *hba, u32 host_id)
{
        struct tcmu_hba *tcmu_hba;

        tcmu_hba = kzalloc(sizeof(struct tcmu_hba), GFP_KERNEL);
        if (!tcmu_hba)
                return -ENOMEM;

        tcmu_hba->host_id = host_id;
        hba->hba_ptr = tcmu_hba;

        return 0;
}

static void tcmu_detach_hba(struct se_hba *hba)
{
        kfree(hba->hba_ptr);
        hba->hba_ptr = NULL;
}

static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
{
        struct tcmu_dev *udev;

        udev = kzalloc(sizeof(struct tcmu_dev), GFP_KERNEL);
        if (!udev)
                return NULL;
        kref_init(&udev->kref);

        udev->name = kstrdup(name, GFP_KERNEL);
        if (!udev->name) {
                kfree(udev);
                return NULL;
        }

        udev->hba = hba;
        udev->cmd_time_out = TCMU_TIME_OUT;
        udev->qfull_time_out = -1;

        udev->data_pages_per_blk = DATA_PAGES_PER_BLK_DEF;
        udev->max_blocks = DATA_AREA_PAGES_DEF / udev->data_pages_per_blk;
        udev->data_area_mb = TCMU_PAGES_TO_MBS(DATA_AREA_PAGES_DEF);

        mutex_init(&udev->cmdr_lock);

        INIT_LIST_HEAD(&udev->node);
        INIT_LIST_HEAD(&udev->timedout_entry);
        INIT_LIST_HEAD(&udev->qfull_queue);
        INIT_LIST_HEAD(&udev->tmr_queue);
        INIT_LIST_HEAD(&udev->inflight_queue);
        xa_init_flags(&udev->commands, XA_FLAGS_ALLOC1);

        timer_setup(&udev->qfull_timer, tcmu_qfull_timedout, 0);
        timer_setup(&udev->cmd_timer, tcmu_cmd_timedout, 0);

        xa_init(&udev->data_pages);

        return &udev->se_dev;
}

static void tcmu_dev_call_rcu(struct rcu_head *p)
{
        struct se_device *dev = container_of(p, struct se_device, rcu_head);
        struct tcmu_dev *udev = TCMU_DEV(dev);

        kfree(udev->uio_info.name);
        kfree(udev->name);
        kfree(udev);
}

static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd)
{
        if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags) ||
            test_bit(TCMU_CMD_BIT_KEEP_BUF, &cmd->flags)) {
                kmem_cache_free(tcmu_cmd_cache, cmd);
                return 0;
        }
        return -EINVAL;
}

static u32 tcmu_blocks_release(struct tcmu_dev *udev, unsigned long first,
                                unsigned long last)
{
        XA_STATE(xas, &udev->data_pages, first * udev->data_pages_per_blk);
        struct page *page;
        u32 pages_freed = 0;

        xas_lock(&xas);
        xas_for_each(&xas, page, (last + 1) * udev->data_pages_per_blk - 1) {
                xas_store(&xas, NULL);
                __free_page(page);
                pages_freed++;
        }
        xas_unlock(&xas);

        atomic_sub(pages_freed, &global_page_count);

        return pages_freed;
}

static void tcmu_remove_all_queued_tmr(struct tcmu_dev *udev)
{
        struct tcmu_tmr *tmr, *tmp;

        list_for_each_entry_safe(tmr, tmp, &udev->tmr_queue, queue_entry) {
                list_del_init(&tmr->queue_entry);
                kfree(tmr);
        }
}

static void tcmu_dev_kref_release(struct kref *kref)
{
        struct tcmu_dev *udev = container_of(kref, struct tcmu_dev, kref);
        struct se_device *dev = &udev->se_dev;
        struct tcmu_cmd *cmd;
        bool all_expired = true;
        unsigned long i;

        vfree(udev->mb_addr);
        udev->mb_addr = NULL;

        spin_lock_bh(&timed_out_udevs_lock);
        if (!list_empty(&udev->timedout_entry))
                list_del(&udev->timedout_entry);
        spin_unlock_bh(&timed_out_udevs_lock);

        /* Upper layer should drain all requests before calling this */
        mutex_lock(&udev->cmdr_lock);
        xa_for_each(&udev->commands, i, cmd) {
                if (tcmu_check_and_free_pending_cmd(cmd) != 0)
                        all_expired = false;
        }
        /* There can be left over TMR cmds. Remove them. */
        tcmu_remove_all_queued_tmr(udev);
        if (!list_empty(&udev->qfull_queue))
                all_expired = false;
        xa_destroy(&udev->commands);
        WARN_ON(!all_expired);

        tcmu_blocks_release(udev, 0, udev->dbi_max);
        bitmap_free(udev->data_bitmap);
        mutex_unlock(&udev->cmdr_lock);

        pr_debug("dev_kref_release\n");

        call_rcu(&dev->rcu_head, tcmu_dev_call_rcu);
}

static void run_qfull_queue(struct tcmu_dev *udev, bool fail)
{
        struct tcmu_cmd *tcmu_cmd, *tmp_cmd;
        LIST_HEAD(cmds);
        sense_reason_t scsi_ret;
        int ret;

        if (list_empty(&udev->qfull_queue))
                return;

        pr_debug("running %s's cmdr queue forcefail %d\n", udev->name, fail);

        list_splice_init(&udev->qfull_queue, &cmds);

        list_for_each_entry_safe(tcmu_cmd, tmp_cmd, &cmds, queue_entry) {
                list_del_init(&tcmu_cmd->queue_entry);

                pr_debug("removing cmd %p on dev %s from queue\n",
                         tcmu_cmd, udev->name);

                if (fail) {
                        /*
                         * We were not able to even start the command, so
                         * fail with busy to allow a retry in case runner
                         * was only temporarily down. If the device is being
                         * removed then LIO core will do the right thing and
                         * fail the retry.
                         */
                        tcmu_cmd->se_cmd->priv = NULL;
                        target_complete_cmd(tcmu_cmd->se_cmd, SAM_STAT_BUSY);
                        tcmu_free_cmd(tcmu_cmd);
                        continue;
                }

                ret = queue_cmd_ring(tcmu_cmd, &scsi_ret);
                if (ret < 0) {
                        pr_debug("cmd %p on dev %s failed with %u\n",
                                 tcmu_cmd, udev->name, scsi_ret);
                        /*
                         * Ignore scsi_ret for now. target_complete_cmd
                         * drops it.
                         */
                        tcmu_cmd->se_cmd->priv = NULL;
                        target_complete_cmd(tcmu_cmd->se_cmd,
                                            SAM_STAT_CHECK_CONDITION);
                        tcmu_free_cmd(tcmu_cmd);
                } else if (ret > 0) {
                        pr_debug("ran out of space during cmdr queue run\n");
                        /*
                         * cmd was requeued, so just put all cmds back in
                         * the queue
                         */
                        list_splice_tail(&cmds, &udev->qfull_queue);
                        break;
                }
        }

        tcmu_set_next_deadline(&udev->qfull_queue, &udev->qfull_timer);
}

static int tcmu_irqcontrol(struct uio_info *info, s32 irq_on)
{
        struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);

        mutex_lock(&udev->cmdr_lock);
        if (tcmu_handle_completions(udev))
                run_qfull_queue(udev, false);
        mutex_unlock(&udev->cmdr_lock);

        return 0;
}

/*
 * mmap code from uio.c. Copied here because we want to hook mmap()
 * and this stuff must come along.
 */
static int tcmu_find_mem_index(struct vm_area_struct *vma)
{
        struct tcmu_dev *udev = vma->vm_private_data;
        struct uio_info *info = &udev->uio_info;

        if (vma->vm_pgoff < MAX_UIO_MAPS) {
                if (info->mem[vma->vm_pgoff].size == 0)
                        return -1;
                return (int)vma->vm_pgoff;
        }
        return -1;
}

static struct page *tcmu_try_get_data_page(struct tcmu_dev *udev, uint32_t dpi)
{
        struct page *page;

        mutex_lock(&udev->cmdr_lock);
        page = xa_load(&udev->data_pages, dpi);
        if (likely(page)) {
                get_page(page);
                mutex_unlock(&udev->cmdr_lock);
                return page;
        }

        /*
         * Userspace messed up and passed in a address not in the
         * data iov passed to it.
         */
        pr_err("Invalid addr to data page mapping (dpi %u) on device %s\n",
               dpi, udev->name);
        mutex_unlock(&udev->cmdr_lock);

        return NULL;
}

static void tcmu_vma_open(struct vm_area_struct *vma)
{
        struct tcmu_dev *udev = vma->vm_private_data;

        pr_debug("vma_open\n");

        kref_get(&udev->kref);
}

static void tcmu_vma_close(struct vm_area_struct *vma)
{
        struct tcmu_dev *udev = vma->vm_private_data;

        pr_debug("vma_close\n");

        /* release ref from tcmu_vma_open */
        kref_put(&udev->kref, tcmu_dev_kref_release);
}

static vm_fault_t tcmu_vma_fault(struct vm_fault *vmf)
{
        struct tcmu_dev *udev = vmf->vma->vm_private_data;
        struct uio_info *info = &udev->uio_info;
        struct page *page;
        unsigned long offset;
        void *addr;

        int mi = tcmu_find_mem_index(vmf->vma);
        if (mi < 0)
                return VM_FAULT_SIGBUS;

        /*
         * We need to subtract mi because userspace uses offset = N*PAGE_SIZE
         * to use mem[N].
         */
        offset = (vmf->pgoff - mi) << PAGE_SHIFT;

        if (offset < udev->data_off) {
                /* For the vmalloc()ed cmd area pages */
                addr = (void *)(unsigned long)info->mem[mi].addr + offset;
                page = vmalloc_to_page(addr);
                get_page(page);
        } else {
                uint32_t dpi;

                /* For the dynamically growing data area pages */
                dpi = (offset - udev->data_off) / PAGE_SIZE;
                page = tcmu_try_get_data_page(udev, dpi);
                if (!page)
                        return VM_FAULT_SIGBUS;
        }

        vmf->page = page;
        return 0;
}

static const struct vm_operations_struct tcmu_vm_ops = {
        .open = tcmu_vma_open,
        .close = tcmu_vma_close,
        .fault = tcmu_vma_fault,
};

static int tcmu_mmap(struct uio_info *info, struct vm_area_struct *vma)
{
        struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);

        vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
        vma->vm_ops = &tcmu_vm_ops;

        vma->vm_private_data = udev;

        /* Ensure the mmap is exactly the right size */
        if (vma_pages(vma) != udev->mmap_pages)
                return -EINVAL;

        tcmu_vma_open(vma);

        return 0;
}

static int tcmu_open(struct uio_info *info, struct inode *inode)
{
        struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);

        /* O_EXCL not supported for char devs, so fake it? */
        if (test_and_set_bit(TCMU_DEV_BIT_OPEN, &udev->flags))
                return -EBUSY;

        udev->inode = inode;

        pr_debug("open\n");

        return 0;
}

static int tcmu_release(struct uio_info *info, struct inode *inode)
{
        struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);
        struct tcmu_cmd *cmd;
        unsigned long i;
        bool freed = false;

        mutex_lock(&udev->cmdr_lock);

        xa_for_each(&udev->commands, i, cmd) {
                /* Cmds with KEEP_BUF set are no longer on the ring, but
                 * userspace still holds the data buffer. If userspace closes
                 * we implicitly free these cmds and buffers, since after new
                 * open the (new ?) userspace cannot find the cmd in the ring
                 * and thus never will release the buffer by writing cmd_id to
                 * free_kept_buf action attribute.
                 */
                if (!test_bit(TCMU_CMD_BIT_KEEP_BUF, &cmd->flags))
                        continue;
                pr_debug("removing KEEP_BUF cmd %u on dev %s from ring\n",
                         cmd->cmd_id, udev->name);
                freed = true;

                xa_erase(&udev->commands, i);
                tcmu_cmd_free_data(cmd, cmd->dbi_cnt);
                tcmu_free_cmd(cmd);
        }
        /*
         * We only freed data space, not ring space. Therefore we dont call
         * run_tmr_queue, but call run_qfull_queue if tmr_list is empty.
         */
        if (freed && list_empty(&udev->tmr_queue))
                run_qfull_queue(udev, false);

        mutex_unlock(&udev->cmdr_lock);

        clear_bit(TCMU_DEV_BIT_OPEN, &udev->flags);

        pr_debug("close\n");

        return 0;
}

static int tcmu_init_genl_cmd_reply(struct tcmu_dev *udev, int cmd)
{
        struct tcmu_nl_cmd *nl_cmd = &udev->curr_nl_cmd;

        if (!tcmu_kern_cmd_reply_supported)
                return 0;

        if (udev->nl_reply_supported <= 0)
                return 0;

        mutex_lock(&tcmu_nl_cmd_mutex);

        if (tcmu_netlink_blocked) {
                mutex_unlock(&tcmu_nl_cmd_mutex);
                pr_warn("Failing nl cmd %d on %s. Interface is blocked.\n", cmd,
                        udev->name);
                return -EAGAIN;
        }

        if (nl_cmd->cmd != TCMU_CMD_UNSPEC) {
                mutex_unlock(&tcmu_nl_cmd_mutex);
                pr_warn("netlink cmd %d already executing on %s\n",
                         nl_cmd->cmd, udev->name);
                return -EBUSY;
        }

        memset(nl_cmd, 0, sizeof(*nl_cmd));
        nl_cmd->cmd = cmd;
        nl_cmd->udev = udev;
        init_completion(&nl_cmd->complete);
        INIT_LIST_HEAD(&nl_cmd->nl_list);

        list_add_tail(&nl_cmd->nl_list, &tcmu_nl_cmd_list);

        mutex_unlock(&tcmu_nl_cmd_mutex);
        return 0;
}

static void tcmu_destroy_genl_cmd_reply(struct tcmu_dev *udev)
{
        struct tcmu_nl_cmd *nl_cmd = &udev->curr_nl_cmd;

        if (!tcmu_kern_cmd_reply_supported)
                return;

        if (udev->nl_reply_supported <= 0)
                return;

        mutex_lock(&tcmu_nl_cmd_mutex);

        list_del(&nl_cmd->nl_list);
        memset(nl_cmd, 0, sizeof(*nl_cmd));

        mutex_unlock(&tcmu_nl_cmd_mutex);
}

static int tcmu_wait_genl_cmd_reply(struct tcmu_dev *udev)
{
        struct tcmu_nl_cmd *nl_cmd = &udev->curr_nl_cmd;
        int ret;

        if (!tcmu_kern_cmd_reply_supported)
                return 0;

        if (udev->nl_reply_supported <= 0)
                return 0;

        pr_debug("sleeping for nl reply\n");
        wait_for_completion(&nl_cmd->complete);

        mutex_lock(&tcmu_nl_cmd_mutex);
        nl_cmd->cmd = TCMU_CMD_UNSPEC;
        ret = nl_cmd->status;
        mutex_unlock(&tcmu_nl_cmd_mutex);

        return ret;
}

static int tcmu_netlink_event_init(struct tcmu_dev *udev,
                                   enum tcmu_genl_cmd cmd,
                                   struct sk_buff **buf, void **hdr)
{
        struct sk_buff *skb;
        void *msg_header;
        int ret = -ENOMEM;

        skb = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
        if (!skb)
                return ret;

        msg_header = genlmsg_put(skb, 0, 0, &tcmu_genl_family, 0, cmd);
        if (!msg_header)
                goto free_skb;

        ret = nla_put_string(skb, TCMU_ATTR_DEVICE, udev->uio_info.name);
        if (ret < 0)
                goto free_skb;

        ret = nla_put_u32(skb, TCMU_ATTR_MINOR, udev->uio_info.uio_dev->minor);
        if (ret < 0)
                goto free_skb;

        ret = nla_put_u32(skb, TCMU_ATTR_DEVICE_ID, udev->se_dev.dev_index);
        if (ret < 0)
                goto free_skb;

        *buf = skb;
        *hdr = msg_header;
        return ret;

free_skb:
        nlmsg_free(skb);
        return ret;
}

static int tcmu_netlink_event_send(struct tcmu_dev *udev,
                                   enum tcmu_genl_cmd cmd,
                                   struct sk_buff *skb, void *msg_header)
{
        int ret;

        genlmsg_end(skb, msg_header);

        ret = tcmu_init_genl_cmd_reply(udev, cmd);
        if (ret) {
                nlmsg_free(skb);
                return ret;
        }

        ret = genlmsg_multicast_allns(&tcmu_genl_family, skb, 0,
                                      TCMU_MCGRP_CONFIG, GFP_KERNEL);

        /* Wait during an add as the listener may not be up yet */
        if (ret == 0 ||
           (ret == -ESRCH && cmd == TCMU_CMD_ADDED_DEVICE))
                return tcmu_wait_genl_cmd_reply(udev);
        else
                tcmu_destroy_genl_cmd_reply(udev);

        return ret;
}

static int tcmu_send_dev_add_event(struct tcmu_dev *udev)
{
        struct sk_buff *skb = NULL;
        void *msg_header = NULL;
        int ret = 0;

        ret = tcmu_netlink_event_init(udev, TCMU_CMD_ADDED_DEVICE, &skb,
                                      &msg_header);
        if (ret < 0)
                return ret;
        return tcmu_netlink_event_send(udev, TCMU_CMD_ADDED_DEVICE, skb,
                                       msg_header);
}

static int tcmu_send_dev_remove_event(struct tcmu_dev *udev)
{
        struct sk_buff *skb = NULL;
        void *msg_header = NULL;
        int ret = 0;

        ret = tcmu_netlink_event_init(udev, TCMU_CMD_REMOVED_DEVICE,
                                      &skb, &msg_header);
        if (ret < 0)
                return ret;
        return tcmu_netlink_event_send(udev, TCMU_CMD_REMOVED_DEVICE,
                                       skb, msg_header);
}

static int tcmu_update_uio_info(struct tcmu_dev *udev)
{
        struct tcmu_hba *hba = udev->hba->hba_ptr;
        struct uio_info *info;
        char *str;

        info = &udev->uio_info;

        if (udev->dev_config[0])
                str = kasprintf(GFP_KERNEL, "tcm-user/%u/%s/%s", hba->host_id,
                                udev->name, udev->dev_config);
        else
                str = kasprintf(GFP_KERNEL, "tcm-user/%u/%s", hba->host_id,
                                udev->name);
        if (!str)
                return -ENOMEM;

        /* If the old string exists, free it */
        kfree(info->name);
        info->name = str;

        return 0;
}

static int tcmu_configure_device(struct se_device *dev)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);
        struct uio_info *info;
        struct tcmu_mailbox *mb;
        size_t data_size;
        int ret = 0;

        ret = tcmu_update_uio_info(udev);
        if (ret)
                return ret;

        info = &udev->uio_info;

        mutex_lock(&udev->cmdr_lock);
        udev->data_bitmap = bitmap_zalloc(udev->max_blocks, GFP_KERNEL);
        mutex_unlock(&udev->cmdr_lock);
        if (!udev->data_bitmap) {
                ret = -ENOMEM;
                goto err_bitmap_alloc;
        }

        mb = vzalloc(MB_CMDR_SIZE);
        if (!mb) {
                ret = -ENOMEM;
                goto err_vzalloc;
        }

        /* mailbox fits in first part of CMDR space */
        udev->mb_addr = mb;
        udev->cmdr = (void *)mb + CMDR_OFF;
        udev->cmdr_size = CMDR_SIZE;
        udev->data_off = MB_CMDR_SIZE;
        data_size = TCMU_MBS_TO_PAGES(udev->data_area_mb) << PAGE_SHIFT;
        udev->mmap_pages = (data_size + MB_CMDR_SIZE) >> PAGE_SHIFT;
        udev->data_blk_size = udev->data_pages_per_blk * PAGE_SIZE;
        udev->dbi_thresh = 0; /* Default in Idle state */

        /* Initialise the mailbox of the ring buffer */
        mb->version = TCMU_MAILBOX_VERSION;
        mb->flags = TCMU_MAILBOX_FLAG_CAP_OOOC |
                    TCMU_MAILBOX_FLAG_CAP_READ_LEN |
                    TCMU_MAILBOX_FLAG_CAP_TMR |
                    TCMU_MAILBOX_FLAG_CAP_KEEP_BUF;
        mb->cmdr_off = CMDR_OFF;
        mb->cmdr_size = udev->cmdr_size;

        WARN_ON(!PAGE_ALIGNED(udev->data_off));
        WARN_ON(data_size % PAGE_SIZE);

        info->version = __stringify(TCMU_MAILBOX_VERSION);

        info->mem[0].name = "tcm-user command & data buffer";
        info->mem[0].addr = (phys_addr_t)(uintptr_t)udev->mb_addr;
        info->mem[0].size = data_size + MB_CMDR_SIZE;
        info->mem[0].memtype = UIO_MEM_NONE;

        info->irqcontrol = tcmu_irqcontrol;
        info->irq = UIO_IRQ_CUSTOM;

        info->mmap = tcmu_mmap;
        info->open = tcmu_open;
        info->release = tcmu_release;

        ret = uio_register_device(tcmu_root_device, info);
        if (ret)
                goto err_register;

        /* User can set hw_block_size before enable the device */
        if (dev->dev_attrib.hw_block_size == 0)
                dev->dev_attrib.hw_block_size = 512;
        /* Other attributes can be configured in userspace */
        if (!dev->dev_attrib.hw_max_sectors)
                dev->dev_attrib.hw_max_sectors = 128;
        if (!dev->dev_attrib.emulate_write_cache)
                dev->dev_attrib.emulate_write_cache = 0;
        dev->dev_attrib.hw_queue_depth = 128;

        /* If user didn't explicitly disable netlink reply support, use
         * module scope setting.
         */
        if (udev->nl_reply_supported >= 0)
                udev->nl_reply_supported = tcmu_kern_cmd_reply_supported;

        /*
         * Get a ref incase userspace does a close on the uio device before
         * LIO has initiated tcmu_free_device.
         */
        kref_get(&udev->kref);

        ret = tcmu_send_dev_add_event(udev);
        if (ret)
                goto err_netlink;

        mutex_lock(&root_udev_mutex);
        list_add(&udev->node, &root_udev);
        mutex_unlock(&root_udev_mutex);

        return 0;

err_netlink:
        kref_put(&udev->kref, tcmu_dev_kref_release);
        uio_unregister_device(&udev->uio_info);
err_register:
        vfree(udev->mb_addr);
        udev->mb_addr = NULL;
err_vzalloc:
        bitmap_free(udev->data_bitmap);
        udev->data_bitmap = NULL;
err_bitmap_alloc:
        kfree(info->name);
        info->name = NULL;

        return ret;
}

static void tcmu_free_device(struct se_device *dev)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);

        /* release ref from init */
        kref_put(&udev->kref, tcmu_dev_kref_release);
}

static void tcmu_destroy_device(struct se_device *dev)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);

        del_timer_sync(&udev->cmd_timer);
        del_timer_sync(&udev->qfull_timer);

        mutex_lock(&root_udev_mutex);
        list_del(&udev->node);
        mutex_unlock(&root_udev_mutex);

        tcmu_send_dev_remove_event(udev);

        uio_unregister_device(&udev->uio_info);

        /* release ref from configure */
        kref_put(&udev->kref, tcmu_dev_kref_release);
}

static void tcmu_unblock_dev(struct tcmu_dev *udev)
{
        mutex_lock(&udev->cmdr_lock);
        clear_bit(TCMU_DEV_BIT_BLOCKED, &udev->flags);
        mutex_unlock(&udev->cmdr_lock);
}

static void tcmu_block_dev(struct tcmu_dev *udev)
{
        mutex_lock(&udev->cmdr_lock);

        if (test_and_set_bit(TCMU_DEV_BIT_BLOCKED, &udev->flags))
                goto unlock;

        /* complete IO that has executed successfully */
        tcmu_handle_completions(udev);
        /* fail IO waiting to be queued */
        run_qfull_queue(udev, true);

unlock:
        mutex_unlock(&udev->cmdr_lock);
}

static void tcmu_reset_ring(struct tcmu_dev *udev, u8 err_level)
{
        struct tcmu_mailbox *mb;
        struct tcmu_cmd *cmd;
        unsigned long i;

        mutex_lock(&udev->cmdr_lock);

        xa_for_each(&udev->commands, i, cmd) {
                pr_debug("removing cmd %u on dev %s from ring %s\n",
                         cmd->cmd_id, udev->name,
                         test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags) ?
                         "(is expired)" :
                         (test_bit(TCMU_CMD_BIT_KEEP_BUF, &cmd->flags) ?
                         "(is keep buffer)" : ""));

                xa_erase(&udev->commands, i);
                if (!test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags) &&
                    !test_bit(TCMU_CMD_BIT_KEEP_BUF, &cmd->flags)) {
                        WARN_ON(!cmd->se_cmd);
                        list_del_init(&cmd->queue_entry);
                        cmd->se_cmd->priv = NULL;
                        if (err_level == 1) {
                                /*
                                 * Userspace was not able to start the
                                 * command or it is retryable.
                                 */
                                target_complete_cmd(cmd->se_cmd, SAM_STAT_BUSY);
                        } else {
                                /* hard failure */
                                target_complete_cmd(cmd->se_cmd,
                                                    SAM_STAT_CHECK_CONDITION);
                        }
                }
                tcmu_cmd_free_data(cmd, cmd->dbi_cnt);
                tcmu_free_cmd(cmd);
        }

        mb = udev->mb_addr;
        tcmu_flush_dcache_range(mb, sizeof(*mb));
        pr_debug("mb last %u head %u tail %u\n", udev->cmdr_last_cleaned,
                 mb->cmd_tail, mb->cmd_head);

        udev->cmdr_last_cleaned = 0;
        mb->cmd_tail = 0;
        mb->cmd_head = 0;
        tcmu_flush_dcache_range(mb, sizeof(*mb));
        clear_bit(TCMU_DEV_BIT_BROKEN, &udev->flags);

        del_timer(&udev->cmd_timer);

        /*
         * ring is empty and qfull queue never contains aborted commands.
         * So TMRs in tmr queue do not contain relevant cmd_ids.
         * After a ring reset userspace should do a fresh start, so
         * even LUN RESET message is no longer relevant.
         * Therefore remove all TMRs from qfull queue
         */
        tcmu_remove_all_queued_tmr(udev);

        run_qfull_queue(udev, false);

        mutex_unlock(&udev->cmdr_lock);
}

enum {
        Opt_dev_config, Opt_dev_size, Opt_hw_block_size, Opt_hw_max_sectors,
        Opt_nl_reply_supported, Opt_max_data_area_mb, Opt_data_pages_per_blk,
        Opt_err,
};

static match_table_t tokens = {
        {Opt_dev_config, "dev_config=%s"},
        {Opt_dev_size, "dev_size=%s"},
        {Opt_hw_block_size, "hw_block_size=%d"},
        {Opt_hw_max_sectors, "hw_max_sectors=%d"},
        {Opt_nl_reply_supported, "nl_reply_supported=%d"},
        {Opt_max_data_area_mb, "max_data_area_mb=%d"},
        {Opt_data_pages_per_blk, "data_pages_per_blk=%d"},
        {Opt_err, NULL}
};

static int tcmu_set_dev_attrib(substring_t *arg, u32 *dev_attrib)
{
        int val, ret;

        ret = match_int(arg, &val);
        if (ret < 0) {
                pr_err("match_int() failed for dev attrib. Error %d.\n",
                       ret);
                return ret;
        }

        if (val <= 0) {
                pr_err("Invalid dev attrib value %d. Must be greater than zero.\n",
                       val);
                return -EINVAL;
        }
        *dev_attrib = val;
        return 0;
}

static int tcmu_set_max_blocks_param(struct tcmu_dev *udev, substring_t *arg)
{
        int val, ret;
        uint32_t pages_per_blk = udev->data_pages_per_blk;

        ret = match_int(arg, &val);
        if (ret < 0) {
                pr_err("match_int() failed for max_data_area_mb=. Error %d.\n",
                       ret);
                return ret;
        }
        if (val <= 0) {
                pr_err("Invalid max_data_area %d.\n", val);
                return -EINVAL;
        }
        if (val > TCMU_PAGES_TO_MBS(tcmu_global_max_pages)) {
                pr_err("%d is too large. Adjusting max_data_area_mb to global limit of %u\n",
                       val, TCMU_PAGES_TO_MBS(tcmu_global_max_pages));
                val = TCMU_PAGES_TO_MBS(tcmu_global_max_pages);
        }
        if (TCMU_MBS_TO_PAGES(val) < pages_per_blk) {
                pr_err("Invalid max_data_area %d (%zu pages): smaller than data_pages_per_blk (%u pages).\n",
                       val, TCMU_MBS_TO_PAGES(val), pages_per_blk);
                return -EINVAL;
        }

        mutex_lock(&udev->cmdr_lock);
        if (udev->data_bitmap) {
                pr_err("Cannot set max_data_area_mb after it has been enabled.\n");
                ret = -EINVAL;
                goto unlock;
        }

        udev->data_area_mb = val;
        udev->max_blocks = TCMU_MBS_TO_PAGES(val) / pages_per_blk;

unlock:
        mutex_unlock(&udev->cmdr_lock);
        return ret;
}

static int tcmu_set_data_pages_per_blk(struct tcmu_dev *udev, substring_t *arg)
{
        int val, ret;

        ret = match_int(arg, &val);
        if (ret < 0) {
                pr_err("match_int() failed for data_pages_per_blk=. Error %d.\n",
                       ret);
                return ret;
        }

        if (val > TCMU_MBS_TO_PAGES(udev->data_area_mb)) {
                pr_err("Invalid data_pages_per_blk %d: greater than max_data_area_mb %d -> %zd pages).\n",
                       val, udev->data_area_mb,
                       TCMU_MBS_TO_PAGES(udev->data_area_mb));
                return -EINVAL;
        }

        mutex_lock(&udev->cmdr_lock);
        if (udev->data_bitmap) {
                pr_err("Cannot set data_pages_per_blk after it has been enabled.\n");
                ret = -EINVAL;
                goto unlock;
        }

        udev->data_pages_per_blk = val;
        udev->max_blocks = TCMU_MBS_TO_PAGES(udev->data_area_mb) / val;

unlock:
        mutex_unlock(&udev->cmdr_lock);
        return ret;
}

static ssize_t tcmu_set_configfs_dev_params(struct se_device *dev,
                const char *page, ssize_t count)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);
        char *orig, *ptr, *opts;
        substring_t args[MAX_OPT_ARGS];
        int ret = 0, token;

        opts = kstrdup(page, GFP_KERNEL);
        if (!opts)
                return -ENOMEM;

        orig = opts;

        while ((ptr = strsep(&opts, ",\n")) != NULL) {
                if (!*ptr)
                        continue;

                token = match_token(ptr, tokens, args);
                switch (token) {
                case Opt_dev_config:
                        if (match_strlcpy(udev->dev_config, &args[0],
                                          TCMU_CONFIG_LEN) == 0) {
                                ret = -EINVAL;
                                break;
                        }
                        pr_debug("TCMU: Referencing Path: %s\n", udev->dev_config);
                        break;
                case Opt_dev_size:
                        ret = match_u64(&args[0], &udev->dev_size);
                        if (ret < 0)
                                pr_err("match_u64() failed for dev_size=. Error %d.\n",
                                       ret);
                        break;
                case Opt_hw_block_size:
                        ret = tcmu_set_dev_attrib(&args[0],
                                        &(dev->dev_attrib.hw_block_size));
                        break;
                case Opt_hw_max_sectors:
                        ret = tcmu_set_dev_attrib(&args[0],
                                        &(dev->dev_attrib.hw_max_sectors));
                        break;
                case Opt_nl_reply_supported:
                        ret = match_int(&args[0], &udev->nl_reply_supported);
                        if (ret < 0)
                                pr_err("match_int() failed for nl_reply_supported=. Error %d.\n",
                                       ret);
                        break;
                case Opt_max_data_area_mb:
                        ret = tcmu_set_max_blocks_param(udev, &args[0]);
                        break;
                case Opt_data_pages_per_blk:
                        ret = tcmu_set_data_pages_per_blk(udev, &args[0]);
                        break;
                default:
                        break;
                }

                if (ret)
                        break;
        }

        kfree(orig);
        return (!ret) ? count : ret;
}

static ssize_t tcmu_show_configfs_dev_params(struct se_device *dev, char *b)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);
        ssize_t bl = 0;

        bl = sprintf(b + bl, "Config: %s ",
                     udev->dev_config[0] ? udev->dev_config : "NULL");
        bl += sprintf(b + bl, "Size: %llu ", udev->dev_size);
        bl += sprintf(b + bl, "MaxDataAreaMB: %u ", udev->data_area_mb);
        bl += sprintf(b + bl, "DataPagesPerBlk: %u\n", udev->data_pages_per_blk);

        return bl;
}

static sector_t tcmu_get_blocks(struct se_device *dev)
{
        struct tcmu_dev *udev = TCMU_DEV(dev);

        return div_u64(udev->dev_size - dev->dev_attrib.block_size,
                       dev->dev_attrib.block_size);
}

static sense_reason_t
tcmu_parse_cdb(struct se_cmd *cmd)
{
        return passthrough_parse_cdb(cmd, tcmu_queue_cmd);
}

static ssize_t tcmu_cmd_time_out_show(struct config_item *item, char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                        struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);

        return snprintf(page, PAGE_SIZE, "%lu\n", udev->cmd_time_out / MSEC_PER_SEC);
}

static ssize_t tcmu_cmd_time_out_store(struct config_item *item, const char *page,
                                       size_t count)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                        struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = container_of(da->da_dev,
                                        struct tcmu_dev, se_dev);
        u32 val;
        int ret;

        if (da->da_dev->export_count) {
                pr_err("Unable to set tcmu cmd_time_out while exports exist\n");
                return -EINVAL;
        }

        ret = kstrtou32(page, 0, &val);
        if (ret < 0)
                return ret;

        udev->cmd_time_out = val * MSEC_PER_SEC;
        return count;
}
CONFIGFS_ATTR(tcmu_, cmd_time_out);

static ssize_t tcmu_qfull_time_out_show(struct config_item *item, char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);

        return snprintf(page, PAGE_SIZE, "%ld\n", udev->qfull_time_out <= 0 ?
                        udev->qfull_time_out :
                        udev->qfull_time_out / MSEC_PER_SEC);
}

static ssize_t tcmu_qfull_time_out_store(struct config_item *item,
                                         const char *page, size_t count)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                        struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
        s32 val;
        int ret;

        ret = kstrtos32(page, 0, &val);
        if (ret < 0)
                return ret;

        if (val >= 0) {
                udev->qfull_time_out = val * MSEC_PER_SEC;
        } else if (val == -1) {
                udev->qfull_time_out = val;
        } else {
                printk(KERN_ERR "Invalid qfull timeout value %d\n", val);
                return -EINVAL;
        }
        return count;
}
CONFIGFS_ATTR(tcmu_, qfull_time_out);

static ssize_t tcmu_max_data_area_mb_show(struct config_item *item, char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);

        return snprintf(page, PAGE_SIZE, "%u\n", udev->data_area_mb);
}
CONFIGFS_ATTR_RO(tcmu_, max_data_area_mb);

static ssize_t tcmu_data_pages_per_blk_show(struct config_item *item,
                                            char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);

        return snprintf(page, PAGE_SIZE, "%u\n", udev->data_pages_per_blk);
}
CONFIGFS_ATTR_RO(tcmu_, data_pages_per_blk);

static ssize_t tcmu_dev_config_show(struct config_item *item, char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);

        return snprintf(page, PAGE_SIZE, "%s\n", udev->dev_config);
}

static int tcmu_send_dev_config_event(struct tcmu_dev *udev,
                                      const char *reconfig_data)
{
        struct sk_buff *skb = NULL;
        void *msg_header = NULL;
        int ret = 0;

        ret = tcmu_netlink_event_init(udev, TCMU_CMD_RECONFIG_DEVICE,
                                      &skb, &msg_header);
        if (ret < 0)
                return ret;
        ret = nla_put_string(skb, TCMU_ATTR_DEV_CFG, reconfig_data);
        if (ret < 0) {
                nlmsg_free(skb);
                return ret;
        }
        return tcmu_netlink_event_send(udev, TCMU_CMD_RECONFIG_DEVICE,
                                       skb, msg_header);
}


static ssize_t tcmu_dev_config_store(struct config_item *item, const char *page,
                                     size_t count)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
        int ret, len;

        len = strlen(page);
        if (!len || len > TCMU_CONFIG_LEN - 1)
                return -EINVAL;

        /* Check if device has been configured before */
        if (target_dev_configured(&udev->se_dev)) {
                ret = tcmu_send_dev_config_event(udev, page);
                if (ret) {
                        pr_err("Unable to reconfigure device\n");
                        return ret;
                }
                strlcpy(udev->dev_config, page, TCMU_CONFIG_LEN);

                ret = tcmu_update_uio_info(udev);
                if (ret)
                        return ret;
                return count;
        }
        strlcpy(udev->dev_config, page, TCMU_CONFIG_LEN);

        return count;
}
CONFIGFS_ATTR(tcmu_, dev_config);

static ssize_t tcmu_dev_size_show(struct config_item *item, char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);

        return snprintf(page, PAGE_SIZE, "%llu\n", udev->dev_size);
}

static int tcmu_send_dev_size_event(struct tcmu_dev *udev, u64 size)
{
        struct sk_buff *skb = NULL;
        void *msg_header = NULL;
        int ret = 0;

        ret = tcmu_netlink_event_init(udev, TCMU_CMD_RECONFIG_DEVICE,
                                      &skb, &msg_header);
        if (ret < 0)
                return ret;
        ret = nla_put_u64_64bit(skb, TCMU_ATTR_DEV_SIZE,
                                size, TCMU_ATTR_PAD);
        if (ret < 0) {
                nlmsg_free(skb);
                return ret;
        }
        return tcmu_netlink_event_send(udev, TCMU_CMD_RECONFIG_DEVICE,
                                       skb, msg_header);
}

static ssize_t tcmu_dev_size_store(struct config_item *item, const char *page,
                                   size_t count)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
        u64 val;
        int ret;

        ret = kstrtou64(page, 0, &val);
        if (ret < 0)
                return ret;

        /* Check if device has been configured before */
        if (target_dev_configured(&udev->se_dev)) {
                ret = tcmu_send_dev_size_event(udev, val);
                if (ret) {
                        pr_err("Unable to reconfigure device\n");
                        return ret;
                }
        }
        udev->dev_size = val;
        return count;
}
CONFIGFS_ATTR(tcmu_, dev_size);

static ssize_t tcmu_nl_reply_supported_show(struct config_item *item,
                char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);

        return snprintf(page, PAGE_SIZE, "%d\n", udev->nl_reply_supported);
}

static ssize_t tcmu_nl_reply_supported_store(struct config_item *item,
                const char *page, size_t count)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                                struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
        s8 val;
        int ret;

        ret = kstrtos8(page, 0, &val);
        if (ret < 0)
                return ret;

        udev->nl_reply_supported = val;
        return count;
}
CONFIGFS_ATTR(tcmu_, nl_reply_supported);

static ssize_t tcmu_emulate_write_cache_show(struct config_item *item,
                                             char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                        struct se_dev_attrib, da_group);

        return snprintf(page, PAGE_SIZE, "%i\n", da->emulate_write_cache);
}

static int tcmu_send_emulate_write_cache(struct tcmu_dev *udev, u8 val)
{
        struct sk_buff *skb = NULL;
        void *msg_header = NULL;
        int ret = 0;

        ret = tcmu_netlink_event_init(udev, TCMU_CMD_RECONFIG_DEVICE,
                                      &skb, &msg_header);
        if (ret < 0)
                return ret;
        ret = nla_put_u8(skb, TCMU_ATTR_WRITECACHE, val);
        if (ret < 0) {
                nlmsg_free(skb);
                return ret;
        }
        return tcmu_netlink_event_send(udev, TCMU_CMD_RECONFIG_DEVICE,
                                       skb, msg_header);
}

static ssize_t tcmu_emulate_write_cache_store(struct config_item *item,
                                              const char *page, size_t count)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                        struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
        u8 val;
        int ret;

        ret = kstrtou8(page, 0, &val);
        if (ret < 0)
                return ret;

        /* Check if device has been configured before */
        if (target_dev_configured(&udev->se_dev)) {
                ret = tcmu_send_emulate_write_cache(udev, val);
                if (ret) {
                        pr_err("Unable to reconfigure device\n");
                        return ret;
                }
        }

        da->emulate_write_cache = val;
        return count;
}
CONFIGFS_ATTR(tcmu_, emulate_write_cache);

static ssize_t tcmu_tmr_notification_show(struct config_item *item, char *page)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                        struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);

        return snprintf(page, PAGE_SIZE, "%i\n",
                        test_bit(TCMU_DEV_BIT_TMR_NOTIFY, &udev->flags));
}

static ssize_t tcmu_tmr_notification_store(struct config_item *item,
                                           const char *page, size_t count)
{
        struct se_dev_attrib *da = container_of(to_config_group(item),
                                        struct se_dev_attrib, da_group);
        struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
        u8 val;
        int ret;

        ret = kstrtou8(page, 0, &val);
        if (ret < 0)
                return ret;
        if (val > 1)
                return -EINVAL;

        if (val)
                set_bit(TCMU_DEV_BIT_TMR_NOTIFY, &udev->flags);
        else
                clear_bit(TCMU_DEV_BIT_TMR_NOTIFY, &udev->flags);
        return count;
}
CONFIGFS_ATTR(tcmu_, tmr_notification);

static ssize_t tcmu_block_dev_show(struct config_item *item, char *page)
{
        struct se_device *se_dev = container_of(to_config_group(item),
                                                struct se_device,
                                                dev_action_group);
        struct tcmu_dev *udev = TCMU_DEV(se_dev);

        if (test_bit(TCMU_DEV_BIT_BLOCKED, &udev->flags))
                return snprintf(page, PAGE_SIZE, "%s\n", "blocked");
        else
                return snprintf(page, PAGE_SIZE, "%s\n", "unblocked");
}

static ssize_t tcmu_block_dev_store(struct config_item *item, const char *page,
                                    size_t count)
{
        struct se_device *se_dev = container_of(to_config_group(item),
                                                struct se_device,
                                                dev_action_group);
        struct tcmu_dev *udev = TCMU_DEV(se_dev);
        u8 val;
        int ret;

        if (!target_dev_configured(&udev->se_dev)) {
                pr_err("Device is not configured.\n");
                return -EINVAL;
        }

        ret = kstrtou8(page, 0, &val);
        if (ret < 0)
                return ret;

        if (val > 1) {
                pr_err("Invalid block value %d\n", val);
                return -EINVAL;
        }

        if (!val)
                tcmu_unblock_dev(udev);
        else
                tcmu_block_dev(udev);
        return count;
}
CONFIGFS_ATTR(tcmu_, block_dev);

static ssize_t tcmu_reset_ring_store(struct config_item *item, const char *page,
                                     size_t count)
{
        struct se_device *se_dev = container_of(to_config_group(item),
                                                struct se_device,
                                                dev_action_group);
        struct tcmu_dev *udev = TCMU_DEV(se_dev);
        u8 val;
        int ret;

        if (!target_dev_configured(&udev->se_dev)) {
                pr_err("Device is not configured.\n");
                return -EINVAL;
        }

        ret = kstrtou8(page, 0, &val);
        if (ret < 0)
                return ret;

        if (val != 1 && val != 2) {
                pr_err("Invalid reset ring value %d\n", val);
                return -EINVAL;
        }

        tcmu_reset_ring(udev, val);
        return count;
}
CONFIGFS_ATTR_WO(tcmu_, reset_ring);

static ssize_t tcmu_free_kept_buf_store(struct config_item *item, const char *page,
                                        size_t count)
{
        struct se_device *se_dev = container_of(to_config_group(item),
                                                struct se_device,
                                                dev_action_group);
        struct tcmu_dev *udev = TCMU_DEV(se_dev);
        struct tcmu_cmd *cmd;
        u16 cmd_id;
        int ret;

        if (!target_dev_configured(&udev->se_dev)) {
                pr_err("Device is not configured.\n");
                return -EINVAL;
        }

        ret = kstrtou16(page, 0, &cmd_id);
        if (ret < 0)
                return ret;

        mutex_lock(&udev->cmdr_lock);

        {
                XA_STATE(xas, &udev->commands, cmd_id);

                xas_lock(&xas);
                cmd = xas_load(&xas);
                if (!cmd) {
                        pr_err("free_kept_buf: cmd_id %d not found\n", cmd_id);
                        count = -EINVAL;
                        xas_unlock(&xas);
                        goto out_unlock;
                }
                if (!test_bit(TCMU_CMD_BIT_KEEP_BUF, &cmd->flags)) {
                        pr_err("free_kept_buf: cmd_id %d was not completed with KEEP_BUF\n",
                               cmd_id);
                        count = -EINVAL;
                        xas_unlock(&xas);
                        goto out_unlock;
                }
                xas_store(&xas, NULL);
                xas_unlock(&xas);
        }

        tcmu_cmd_free_data(cmd, cmd->dbi_cnt);
        tcmu_free_cmd(cmd);
        /*
         * We only freed data space, not ring space. Therefore we dont call
         * run_tmr_queue, but call run_qfull_queue if tmr_list is empty.
         */
        if (list_empty(&udev->tmr_queue))
                run_qfull_queue(udev, false);

out_unlock:
        mutex_unlock(&udev->cmdr_lock);
        return count;
}
CONFIGFS_ATTR_WO(tcmu_, free_kept_buf);

static struct configfs_attribute *tcmu_attrib_attrs[] = {
        &tcmu_attr_cmd_time_out,
        &tcmu_attr_qfull_time_out,
        &tcmu_attr_max_data_area_mb,
        &tcmu_attr_data_pages_per_blk,
        &tcmu_attr_dev_config,
        &tcmu_attr_dev_size,
        &tcmu_attr_emulate_write_cache,
        &tcmu_attr_tmr_notification,
        &tcmu_attr_nl_reply_supported,
        NULL,
};

static struct configfs_attribute **tcmu_attrs;

static struct configfs_attribute *tcmu_action_attrs[] = {
        &tcmu_attr_block_dev,
        &tcmu_attr_reset_ring,
        &tcmu_attr_free_kept_buf,
        NULL,
};

static struct target_backend_ops tcmu_ops = {
        .name                   = "user",
        .owner                  = THIS_MODULE,
        .transport_flags_default = TRANSPORT_FLAG_PASSTHROUGH,
        .transport_flags_changeable = TRANSPORT_FLAG_PASSTHROUGH_PGR |
                                      TRANSPORT_FLAG_PASSTHROUGH_ALUA,
        .attach_hba             = tcmu_attach_hba,
        .detach_hba             = tcmu_detach_hba,
        .alloc_device           = tcmu_alloc_device,
        .configure_device       = tcmu_configure_device,
        .destroy_device         = tcmu_destroy_device,
        .free_device            = tcmu_free_device,
        .unplug_device          = tcmu_unplug_device,
        .plug_device            = tcmu_plug_device,
        .parse_cdb              = tcmu_parse_cdb,
        .tmr_notify             = tcmu_tmr_notify,
        .set_configfs_dev_params = tcmu_set_configfs_dev_params,
        .show_configfs_dev_params = tcmu_show_configfs_dev_params,
        .get_device_type        = sbc_get_device_type,
        .get_blocks             = tcmu_get_blocks,
        .tb_dev_action_attrs    = tcmu_action_attrs,
};

static void find_free_blocks(void)
{
        struct tcmu_dev *udev;
        loff_t off;
        u32 pages_freed, total_pages_freed = 0;
        u32 start, end, block, total_blocks_freed = 0;

        if (atomic_read(&global_page_count) <= tcmu_global_max_pages)
                return;

        mutex_lock(&root_udev_mutex);
        list_for_each_entry(udev, &root_udev, node) {
                mutex_lock(&udev->cmdr_lock);

                if (!target_dev_configured(&udev->se_dev)) {
                        mutex_unlock(&udev->cmdr_lock);
                        continue;
                }

                /* Try to complete the finished commands first */
                if (tcmu_handle_completions(udev))
                        run_qfull_queue(udev, false);

                /* Skip the udevs in idle */
                if (!udev->dbi_thresh) {
                        mutex_unlock(&udev->cmdr_lock);
                        continue;
                }

                end = udev->dbi_max + 1;
                block = find_last_bit(udev->data_bitmap, end);
                if (block == udev->dbi_max) {
                        /*
                         * The last bit is dbi_max, so it is not possible
                         * reclaim any blocks.
                         */
                        mutex_unlock(&udev->cmdr_lock);
                        continue;
                } else if (block == end) {
                        /* The current udev will goto idle state */
                        udev->dbi_thresh = start = 0;
                        udev->dbi_max = 0;
                } else {
                        udev->dbi_thresh = start = block + 1;
                        udev->dbi_max = block;
                }

                /* Here will truncate the data area from off */
                off = udev->data_off + (loff_t)start * udev->data_blk_size;
                unmap_mapping_range(udev->inode->i_mapping, off, 0, 1);

                /* Release the block pages */
                pages_freed = tcmu_blocks_release(udev, start, end - 1);
                mutex_unlock(&udev->cmdr_lock);

                total_pages_freed += pages_freed;
                total_blocks_freed += end - start;
                pr_debug("Freed %u pages (total %u) from %u blocks (total %u) from %s.\n",
                         pages_freed, total_pages_freed, end - start,
                         total_blocks_freed, udev->name);
        }
        mutex_unlock(&root_udev_mutex);

        if (atomic_read(&global_page_count) > tcmu_global_max_pages)
                schedule_delayed_work(&tcmu_unmap_work, msecs_to_jiffies(5000));
}

static void check_timedout_devices(void)
{
        struct tcmu_dev *udev, *tmp_dev;
        struct tcmu_cmd *cmd, *tmp_cmd;
        LIST_HEAD(devs);

        spin_lock_bh(&timed_out_udevs_lock);
        list_splice_init(&timed_out_udevs, &devs);

        list_for_each_entry_safe(udev, tmp_dev, &devs, timedout_entry) {
                list_del_init(&udev->timedout_entry);
                spin_unlock_bh(&timed_out_udevs_lock);

                mutex_lock(&udev->cmdr_lock);

                /*
                 * If cmd_time_out is disabled but qfull is set deadline
                 * will only reflect the qfull timeout. Ignore it.
                 */
                if (udev->cmd_time_out) {
                        list_for_each_entry_safe(cmd, tmp_cmd,
                                                 &udev->inflight_queue,
                                                 queue_entry) {
                                tcmu_check_expired_ring_cmd(cmd);
                        }
                        tcmu_set_next_deadline(&udev->inflight_queue,
                                               &udev->cmd_timer);
                }
                list_for_each_entry_safe(cmd, tmp_cmd, &udev->qfull_queue,
                                         queue_entry) {
                        tcmu_check_expired_queue_cmd(cmd);
                }
                tcmu_set_next_deadline(&udev->qfull_queue, &udev->qfull_timer);

                mutex_unlock(&udev->cmdr_lock);

                spin_lock_bh(&timed_out_udevs_lock);
        }

        spin_unlock_bh(&timed_out_udevs_lock);
}

static void tcmu_unmap_work_fn(struct work_struct *work)
{
        check_timedout_devices();
        find_free_blocks();
}

static int __init tcmu_module_init(void)
{
        int ret, i, k, len = 0;

        BUILD_BUG_ON((sizeof(struct tcmu_cmd_entry) % TCMU_OP_ALIGN_SIZE) != 0);

        INIT_DELAYED_WORK(&tcmu_unmap_work, tcmu_unmap_work_fn);

        tcmu_cmd_cache = kmem_cache_create("tcmu_cmd_cache",
                                sizeof(struct tcmu_cmd),
                                __alignof__(struct tcmu_cmd),
                                0, NULL);
        if (!tcmu_cmd_cache)
                return -ENOMEM;

        tcmu_root_device = root_device_register("tcm_user");
        if (IS_ERR(tcmu_root_device)) {
                ret = PTR_ERR(tcmu_root_device);
                goto out_free_cache;
        }

        ret = genl_register_family(&tcmu_genl_family);
        if (ret < 0) {
                goto out_unreg_device;
        }

        for (i = 0; passthrough_attrib_attrs[i] != NULL; i++)
                len += sizeof(struct configfs_attribute *);
        for (i = 0; passthrough_pr_attrib_attrs[i] != NULL; i++)
                len += sizeof(struct configfs_attribute *);
        for (i = 0; tcmu_attrib_attrs[i] != NULL; i++)
                len += sizeof(struct configfs_attribute *);
        len += sizeof(struct configfs_attribute *);

        tcmu_attrs = kzalloc(len, GFP_KERNEL);
        if (!tcmu_attrs) {
                ret = -ENOMEM;
                goto out_unreg_genl;
        }

        for (i = 0; passthrough_attrib_attrs[i] != NULL; i++)
                tcmu_attrs[i] = passthrough_attrib_attrs[i];
        for (k = 0; passthrough_pr_attrib_attrs[k] != NULL; k++)
                tcmu_attrs[i++] = passthrough_pr_attrib_attrs[k];
        for (k = 0; tcmu_attrib_attrs[k] != NULL; k++)
                tcmu_attrs[i++] = tcmu_attrib_attrs[k];
        tcmu_ops.tb_dev_attrib_attrs = tcmu_attrs;

        ret = transport_backend_register(&tcmu_ops);
        if (ret)
                goto out_attrs;

        return 0;

out_attrs:
        kfree(tcmu_attrs);
out_unreg_genl:
        genl_unregister_family(&tcmu_genl_family);
out_unreg_device:
        root_device_unregister(tcmu_root_device);
out_free_cache:
        kmem_cache_destroy(tcmu_cmd_cache);

        return ret;
}

static void __exit tcmu_module_exit(void)
{
        cancel_delayed_work_sync(&tcmu_unmap_work);
        target_backend_unregister(&tcmu_ops);
        kfree(tcmu_attrs);
        genl_unregister_family(&tcmu_genl_family);
        root_device_unregister(tcmu_root_device);
        kmem_cache_destroy(tcmu_cmd_cache);
}

MODULE_DESCRIPTION("TCM USER subsystem plugin");
MODULE_AUTHOR("Shaohua Li <shli@kernel.org>");
MODULE_AUTHOR("Andy Grover <agrover@redhat.com>");
MODULE_LICENSE("GPL");

module_init(tcmu_module_init);
module_exit(tcmu_module_exit);