GNU Linux-libre 5.4.241-gnu1

[releases.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/idr.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/parser.h>
#include <linux/vmalloc.h>
#include <linux/uio_driver.h>
#include <linux/radix-tree.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 cmd area, the size is fixed 8MB */
#define CMDR_SIZE (8 * 1024 * 1024)

/*
 * For data area, the block size is PAGE_SIZE and
 * the total size is 256K * PAGE_SIZE.
 */
#define DATA_BLOCK_SIZE PAGE_SIZE
#define DATA_BLOCK_SHIFT PAGE_SHIFT
#define DATA_BLOCK_BITS_DEF (256 * 1024)

#define TCMU_MBS_TO_BLOCKS(_mbs) (_mbs << (20 - DATA_BLOCK_SHIFT))
#define TCMU_BLOCKS_TO_MBS(_blocks) (_blocks >> (20 - DATA_BLOCK_SHIFT))

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

        char *name;
        struct se_hba *hba;

#define TCMU_DEV_BIT_OPEN 0
#define TCMU_DEV_BIT_BROKEN 1
#define TCMU_DEV_BIT_BLOCKED 2
        unsigned long flags;

        struct uio_info uio_info;

        struct inode *inode;

        struct tcmu_mailbox *mb_addr;
        uint64_t dev_size;
        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;
        size_t data_size;
        uint32_t max_blocks;
        size_t ring_size;

        struct mutex cmdr_lock;
        struct list_head qfull_queue;

        uint32_t dbi_max;
        uint32_t dbi_thresh;
        unsigned long *data_bitmap;
        struct radix_tree_root data_blocks;

        struct idr 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)

#define CMDR_OFF sizeof(struct tcmu_mailbox)

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_cur;
        uint32_t *dbi;

        unsigned long deadline;

#define TCMU_CMD_BIT_EXPIRED 0
#define TCMU_CMD_BIT_INFLIGHT 1
        unsigned long flags;
};
/*
 * 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_db_count = ATOMIC_INIT(0);
static struct delayed_work tcmu_unmap_work;
static int tcmu_global_max_blocks = TCMU_GLOBAL_MAX_BLOCKS_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_blocks = TCMU_MBS_TO_BLOCKS(max_area_mb);
        if (atomic_read(&global_db_count) > tcmu_global_max_blocks)
                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", TCMU_BLOCKS_TO_MBS(tcmu_global_max_blocks));
}

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_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,
        .ops = tcmu_genl_ops,
        .n_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 bool tcmu_get_empty_block(struct tcmu_dev *udev,
                                        struct tcmu_cmd *tcmu_cmd)
{
        struct page *page;
        int ret, dbi;

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

        page = radix_tree_lookup(&udev->data_blocks, dbi);
        if (!page) {
                if (atomic_add_return(1, &global_db_count) >
                                      tcmu_global_max_blocks)
                        schedule_delayed_work(&tcmu_unmap_work, 0);

                /* try to get new page from the mm */
                page = alloc_page(GFP_KERNEL);
                if (!page)
                        goto err_alloc;

                ret = radix_tree_insert(&udev->data_blocks, dbi, page);
                if (ret)
                        goto err_insert;
        }

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

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

        return true;
err_insert:
        __free_page(page);
err_alloc:
        atomic_dec(&global_db_count);
        return false;
}

static bool tcmu_get_empty_blocks(struct tcmu_dev *udev,
                                  struct tcmu_cmd *tcmu_cmd)
{
        int i;

        for (i = tcmu_cmd->dbi_cur; i < tcmu_cmd->dbi_cnt; i++) {
                if (!tcmu_get_empty_block(udev, tcmu_cmd))
                        return false;
        }
        return true;
}

static inline struct page *
tcmu_get_block_page(struct tcmu_dev *udev, uint32_t dbi)
{
        return radix_tree_lookup(&udev->data_blocks, dbi);
}

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 size_t tcmu_cmd_get_data_length(struct tcmu_cmd *tcmu_cmd)
{
        struct se_cmd *se_cmd = tcmu_cmd->se_cmd;
        size_t data_length = round_up(se_cmd->data_length, DATA_BLOCK_SIZE);

        if (se_cmd->se_cmd_flags & SCF_BIDI) {
                BUG_ON(!(se_cmd->t_bidi_data_sg && se_cmd->t_bidi_data_nents));
                data_length += round_up(se_cmd->t_bidi_data_sg->length,
                                DATA_BLOCK_SIZE);
        }

        return data_length;
}

static inline uint32_t tcmu_cmd_get_block_cnt(struct tcmu_cmd *tcmu_cmd)
{
        size_t data_length = tcmu_cmd_get_data_length(tcmu_cmd);

        return data_length / DATA_BLOCK_SIZE;
}

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_KERNEL);
        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_reset_dbi_cur(tcmu_cmd);
        tcmu_cmd->dbi_cnt = tcmu_cmd_get_block_cnt(tcmu_cmd);
        tcmu_cmd->dbi = kcalloc(tcmu_cmd->dbi_cnt, sizeof(uint32_t),
                                GFP_KERNEL);
        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;
}

static inline void new_iov(struct iovec **iov, int *iov_cnt)
{
        struct iovec *iovec;

        if (*iov_cnt != 0)
                (*iov)++;
        (*iov_cnt)++;

        iovec = *iov;
        memset(iovec, 0, sizeof(struct iovec));
}

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

/* offset is relative to mb_addr */
static inline size_t get_block_offset_user(struct tcmu_dev *dev,
                int dbi, int remaining)
{
        return dev->data_off + dbi * DATA_BLOCK_SIZE +
                DATA_BLOCK_SIZE - remaining;
}

static inline size_t iov_tail(struct iovec *iov)
{
        return (size_t)iov->iov_base + iov->iov_len;
}

static void scatter_data_area(struct tcmu_dev *udev,
        struct tcmu_cmd *tcmu_cmd, struct scatterlist *data_sg,
        unsigned int data_nents, struct iovec **iov,
        int *iov_cnt, bool copy_data)
{
        int i, dbi;
        int block_remaining = 0;
        void *from, *to = NULL;
        size_t copy_bytes, to_offset, offset;
        struct scatterlist *sg;
        struct page *page = NULL;

        for_each_sg(data_sg, sg, data_nents, i) {
                int sg_remaining = sg->length;
                from = kmap_atomic(sg_page(sg)) + sg->offset;
                while (sg_remaining > 0) {
                        if (block_remaining == 0) {
                                if (to) {
                                        flush_dcache_page(page);
                                        kunmap_atomic(to);
                                }

                                block_remaining = DATA_BLOCK_SIZE;
                                dbi = tcmu_cmd_get_dbi(tcmu_cmd);
                                page = tcmu_get_block_page(udev, dbi);
                                to = kmap_atomic(page);
                        }

                        /*
                         * Covert to virtual offset of the ring data area.
                         */
                        to_offset = get_block_offset_user(udev, dbi,
                                        block_remaining);

                        /*
                         * The following code will gather and map the blocks
                         * to the same iovec when the blocks are all next to
                         * each other.
                         */
                        copy_bytes = min_t(size_t, sg_remaining,
                                        block_remaining);
                        if (*iov_cnt != 0 &&
                            to_offset == iov_tail(*iov)) {
                                /*
                                 * Will append to the current iovec, because
                                 * the current block page is next to the
                                 * previous one.
                                 */
                                (*iov)->iov_len += copy_bytes;
                        } else {
                                /*
                                 * Will allocate a new iovec because we are
                                 * first time here or the current block page
                                 * is not next to the previous one.
                                 */
                                new_iov(iov, iov_cnt);
                                (*iov)->iov_base = (void __user *)to_offset;
                                (*iov)->iov_len = copy_bytes;
                        }

                        if (copy_data) {
                                offset = DATA_BLOCK_SIZE - block_remaining;
                                memcpy(to + offset,
                                       from + sg->length - sg_remaining,
                                       copy_bytes);
                        }

                        sg_remaining -= copy_bytes;
                        block_remaining -= copy_bytes;
                }
                kunmap_atomic(from - sg->offset);
        }

        if (to) {
                flush_dcache_page(page);
                kunmap_atomic(to);
        }
}

static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                             bool bidi, uint32_t read_len)
{
        struct se_cmd *se_cmd = cmd->se_cmd;
        int i, dbi;
        int block_remaining = 0;
        void *from = NULL, *to;
        size_t copy_bytes, offset;
        struct scatterlist *sg, *data_sg;
        struct page *page;
        unsigned int data_nents;
        uint32_t count = 0;

        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 discarded.
                 */
                count = DIV_ROUND_UP(se_cmd->data_length, DATA_BLOCK_SIZE);

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

        tcmu_cmd_set_dbi_cur(cmd, count);

        for_each_sg(data_sg, sg, data_nents, i) {
                int sg_remaining = sg->length;
                to = kmap_atomic(sg_page(sg)) + sg->offset;
                while (sg_remaining > 0 && read_len > 0) {
                        if (block_remaining == 0) {
                                if (from)
                                        kunmap_atomic(from);

                                block_remaining = DATA_BLOCK_SIZE;
                                dbi = tcmu_cmd_get_dbi(cmd);
                                page = tcmu_get_block_page(udev, dbi);
                                from = kmap_atomic(page);
                                flush_dcache_page(page);
                        }
                        copy_bytes = min_t(size_t, sg_remaining,
                                        block_remaining);
                        if (read_len < copy_bytes)
                                copy_bytes = read_len;
                        offset = DATA_BLOCK_SIZE - block_remaining;
                        memcpy(to + sg->length - sg_remaining, from + offset,
                                        copy_bytes);

                        sg_remaining -= copy_bytes;
                        block_remaining -= copy_bytes;
                        read_len -= copy_bytes;
                }
                kunmap_atomic(to - sg->offset);
                if (read_len == 0)
                        break;
        }
        if (from)
                kunmap_atomic(from);
}

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 *and*
 * space available on the data area.
 *
 * Called with ring lock held.
 */
static bool is_ring_space_avail(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                size_t cmd_size, size_t data_needed)
{
        struct tcmu_mailbox *mb = udev->mb_addr;
        uint32_t blocks_needed = (data_needed + DATA_BLOCK_SIZE - 1)
                                / DATA_BLOCK_SIZE;
        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;
        }

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

                if (blocks_left < blocks_needed) {
                        pr_debug("no data space: only %lu available, but ask for %zu\n",
                                        blocks_left * DATA_BLOCK_SIZE,
                                        data_needed);
                        return false;
                }

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

        return tcmu_get_empty_blocks(udev, cmd);
}

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;
}

/**
 * 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;
        struct tcmu_cmd_entry *entry;
        struct iovec *iov;
        int iov_cnt, cmd_id;
        uint32_t cmd_head;
        uint64_t cdb_off;
        bool copy_to_data_area;
        size_t data_length = tcmu_cmd_get_data_length(tcmu_cmd);

        *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;
        }

        /*
         * Must be a certain minimum size for response sense info, but
         * also may be larger if the iov array is large.
         *
         * We prepare as many iovs as possbile for potential uses here,
         * because it's expensive to tell how many regions are freed in
         * the bitmap & global data pool, as the size calculated here
         * will only be used to do the checks.
         *
         * The size will be recalculated later as actually needed to save
         * cmd area memories.
         */
        base_command_size = tcmu_cmd_get_base_cmd_size(tcmu_cmd->dbi_cnt);
        command_size = tcmu_cmd_get_cmd_size(tcmu_cmd, base_command_size);

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

        mb = udev->mb_addr;
        cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */
        if ((command_size > (udev->cmdr_size / 2)) ||
            data_length > udev->data_size) {
                pr_warn("TCMU: Request of size %zu/%zu is too big for %u/%zu "
                        "cmd ring/data area\n", command_size, data_length,
                        udev->cmdr_size, udev->data_size);
                *scsi_err = TCM_INVALID_CDB_FIELD;
                return -1;
        }

        if (!is_ring_space_avail(udev, tcmu_cmd, command_size, data_length)) {
                /*
                 * Don't leave commands partially setup because the unmap
                 * thread might need the blocks to make forward progress.
                 */
                tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cur);
                tcmu_cmd_reset_dbi_cur(tcmu_cmd);
                goto queue;
        }

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

                entry = (void *) mb + CMDR_OFF + cmd_head;
                tcmu_hdr_set_op(&entry->hdr.len_op, TCMU_OP_PAD);
                tcmu_hdr_set_len(&entry->hdr.len_op, pad_size);
                entry->hdr.cmd_id = 0; /* not used for PAD */
                entry->hdr.kflags = 0;
                entry->hdr.uflags = 0;
                tcmu_flush_dcache_range(entry, sizeof(entry->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);
        }

        entry = (void *) mb + CMDR_OFF + cmd_head;
        memset(entry, 0, command_size);
        tcmu_hdr_set_op(&entry->hdr.len_op, TCMU_OP_CMD);

        /* Handle allocating space from the data area */
        tcmu_cmd_reset_dbi_cur(tcmu_cmd);
        iov = &entry->req.iov[0];
        iov_cnt = 0;
        copy_to_data_area = (se_cmd->data_direction == DMA_TO_DEVICE
                || se_cmd->se_cmd_flags & SCF_BIDI);
        scatter_data_area(udev, tcmu_cmd, se_cmd->t_data_sg,
                          se_cmd->t_data_nents, &iov, &iov_cnt,
                          copy_to_data_area);
        entry->req.iov_cnt = iov_cnt;

        /* Handle BIDI commands */
        iov_cnt = 0;
        if (se_cmd->se_cmd_flags & SCF_BIDI) {
                iov++;
                scatter_data_area(udev, tcmu_cmd, se_cmd->t_bidi_data_sg,
                                  se_cmd->t_bidi_data_nents, &iov, &iov_cnt,
                                  false);
        }
        entry->req.iov_bidi_cnt = iov_cnt;

        cmd_id = idr_alloc(&udev->commands, tcmu_cmd, 1, USHRT_MAX, GFP_NOWAIT);
        if (cmd_id < 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);

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

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

        /*
         * Recalaulate the command's base size and size according
         * to the actual needs
         */
        base_command_size = tcmu_cmd_get_base_cmd_size(entry->req.iov_cnt +
                                                       entry->req.iov_bidi_cnt);
        command_size = tcmu_cmd_get_cmd_size(tcmu_cmd, base_command_size);

        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);
        set_bit(TCMU_CMD_BIT_INFLIGHT, &tcmu_cmd->flags);

        /* TODO: only if FLUSH and FUA? */
        uio_event_notify(&udev->uio_info);

        return 0;

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

        return 1;
}

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;
        int ret;

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

        mutex_lock(&udev->cmdr_lock);
        ret = queue_cmd_ring(tcmu_cmd, &scsi_ret);
        mutex_unlock(&udev->cmdr_lock);
        if (ret < 0)
                tcmu_free_cmd(tcmu_cmd);
        return scsi_ret;
}

static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *entry)
{
        struct se_cmd *se_cmd = cmd->se_cmd;
        struct tcmu_dev *udev = cmd->tcmu_dev;
        bool read_len_valid = false;
        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;
        }

        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:
        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:
        cmd->se_cmd = NULL;
        tcmu_cmd_free_data(cmd, cmd->dbi_cnt);
        tcmu_free_cmd(cmd);
}

static void tcmu_set_next_deadline(struct list_head *queue,
                                   struct timer_list *timer)
{
        struct tcmu_cmd *tcmu_cmd, *tmp_cmd;
        unsigned long deadline = 0;

        list_for_each_entry_safe(tcmu_cmd, tmp_cmd, queue, queue_entry) {
                if (!time_after(jiffies, tcmu_cmd->deadline)) {
                        deadline = tcmu_cmd->deadline;
                        break;
                }
        }

        if (deadline)
                mod_timer(timer, deadline);
        else
                del_timer(timer);
}

static bool tcmu_handle_completions(struct tcmu_dev *udev)
{
        struct tcmu_mailbox *mb;
        struct tcmu_cmd *cmd;
        int handled = 0;

        if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags)) {
                pr_err("ring broken, not handling completions\n");
                return 0;
        }

        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 = (void *) mb + CMDR_OFF + udev->cmdr_last_cleaned;

                /*
                 * 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));

                if (tcmu_hdr_get_op(entry->hdr.len_op) == TCMU_OP_PAD) {
                        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);

                cmd = idr_remove(&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;
                }

                tcmu_handle_completion(cmd, entry);

                UPDATE_HEAD(udev->cmdr_last_cleaned,
                            tcmu_hdr_get_len(entry->hdr.len_op),
                            udev->cmdr_size);

                handled++;
        }

        if (mb->cmd_tail == mb->cmd_head) {
                /* no more pending commands */
                del_timer(&udev->cmd_timer);

                if (list_empty(&udev->qfull_queue)) {
                        /*
                         * no more pending or waiting commands so try to
                         * reclaim blocks if needed.
                         */
                        if (atomic_read(&global_db_count) >
                            tcmu_global_max_blocks)
                                schedule_delayed_work(&tcmu_unmap_work, 0);
                }
        } else if (udev->cmd_time_out) {
                tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer);
        }

        return handled;
}

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

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

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

        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->max_blocks = DATA_BLOCK_BITS_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->inflight_queue);
        idr_init(&udev->commands);

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

        INIT_RADIX_TREE(&udev->data_blocks, GFP_KERNEL);

        return &udev->se_dev;
}

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.
                         */
                        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.
                         */
                        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);
        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_block_page(struct tcmu_dev *udev, uint32_t dbi)
{
        struct page *page;

        mutex_lock(&udev->cmdr_lock);
        page = tcmu_get_block_page(udev, dbi);
        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 block mapping  (dbi %u) on device %s\n",
               dbi, udev->name);
        page = NULL;
        mutex_unlock(&udev->cmdr_lock);

        return page;
}

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 dbi;

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

        vmf->page = page;
        return 0;
}

static const struct vm_operations_struct tcmu_vm_ops = {
        .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->ring_size >> PAGE_SHIFT))
                return -EINVAL;

        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;
        kref_get(&udev->kref);

        pr_debug("open\n");

        return 0;
}

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)) {
                kmem_cache_free(tcmu_cmd_cache, cmd);
                return 0;
        }
        return -EINVAL;
}

static void tcmu_blocks_release(struct radix_tree_root *blocks,
                                int start, int end)
{
        int i;
        struct page *page;

        for (i = start; i < end; i++) {
                page = radix_tree_delete(blocks, i);
                if (page) {
                        __free_page(page);
                        atomic_dec(&global_db_count);
                }
        }
}

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;
        int 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);
        idr_for_each_entry(&udev->commands, cmd, i) {
                if (tcmu_check_and_free_pending_cmd(cmd) != 0)
                        all_expired = false;
        }
        if (!list_empty(&udev->qfull_queue))
                all_expired = false;
        idr_destroy(&udev->commands);
        WARN_ON(!all_expired);

        tcmu_blocks_release(&udev->data_blocks, 0, udev->dbi_max + 1);
        bitmap_free(udev->data_bitmap);
        mutex_unlock(&udev->cmdr_lock);

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

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

        clear_bit(TCMU_DEV_BIT_OPEN, &udev->flags);

        pr_debug("close\n");
        /* release ref from open */
        kref_put(&udev->kref, tcmu_dev_kref_release);
        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;
        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;
        }

        udev->mb_addr = vzalloc(CMDR_SIZE);
        if (!udev->mb_addr) {
                ret = -ENOMEM;
                goto err_vzalloc;
        }

        /* mailbox fits in first part of CMDR space */
        udev->cmdr_size = CMDR_SIZE - CMDR_OFF;
        udev->data_off = CMDR_SIZE;
        udev->data_size = udev->max_blocks * DATA_BLOCK_SIZE;
        udev->dbi_thresh = 0; /* Default in Idle state */

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

        WARN_ON(!PAGE_ALIGNED(udev->data_off));
        WARN_ON(udev->data_size % PAGE_SIZE);
        WARN_ON(udev->data_size % DATA_BLOCK_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 = udev->ring_size = udev->data_size + 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;
        int i;

        mutex_lock(&udev->cmdr_lock);

        idr_for_each_entry(&udev->commands, cmd, i) {
                pr_debug("removing cmd %u on dev %s from ring (is expired %d)\n",
                          cmd->cmd_id, udev->name,
                          test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags));

                idr_remove(&udev->commands, i);
                if (!test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) {
                        WARN_ON(!cmd->se_cmd);
                        list_del_init(&cmd->queue_entry);
                        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);

        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_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_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;

        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;
        }

        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->max_blocks = TCMU_MBS_TO_BLOCKS(val);
        if (udev->max_blocks > tcmu_global_max_blocks) {
                pr_err("%d is too large. Adjusting max_data_area_mb to global limit of %u\n",
                       val, TCMU_BLOCKS_TO_MBS(tcmu_global_max_blocks));
                udev->max_blocks = tcmu_global_max_blocks;
        }

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;
                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\n",
                      TCMU_BLOCKS_TO_MBS(udev->max_blocks));

        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",
                        TCMU_BLOCKS_TO_MBS(udev->max_blocks));
}
CONFIGFS_ATTR_RO(tcmu_, max_data_area_mb);

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_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 struct configfs_attribute *tcmu_attrib_attrs[] = {
        &tcmu_attr_cmd_time_out,
        &tcmu_attr_qfull_time_out,
        &tcmu_attr_max_data_area_mb,
        &tcmu_attr_dev_config,
        &tcmu_attr_dev_size,
        &tcmu_attr_emulate_write_cache,
        &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,
        NULL,
};

static struct target_backend_ops tcmu_ops = {
        .name                   = "user",
        .owner                  = THIS_MODULE,
        .transport_flags        = TRANSPORT_FLAG_PASSTHROUGH,
        .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,
        .parse_cdb              = tcmu_parse_cdb,
        .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 start, end, block, total_freed = 0;

        if (atomic_read(&global_db_count) <= tcmu_global_max_blocks)
                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 */
                tcmu_handle_completions(udev);

                /* 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 + start * DATA_BLOCK_SIZE;
                unmap_mapping_range(udev->inode->i_mapping, off, 0, 1);

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

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

        if (atomic_read(&global_db_count) > tcmu_global_max_blocks)
                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; 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; tcmu_attrib_attrs[k] != NULL; k++) {
                tcmu_attrs[i] = tcmu_attrib_attrs[k];
                i++;
        }
        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);