/*
 * Copyright (C) 2013 Shaohua Li <shli@kernel.org>
 * Copyright (C) 2014 Red Hat, Inc.
 * Copyright (C) 2015 Arrikto, Inc.
 * Copyright (C) 2017 Chinamobile, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <linux/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/kthread.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>

/*
 * 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_BITS (256 * 1024)
#define DATA_SIZE (DATA_BLOCK_BITS * DATA_BLOCK_SIZE)
#define DATA_BLOCK_INIT_BITS 128

/* The total size of the ring is 8M + 256K * PAGE_SIZE */
#define TCMU_RING_SIZE (CMDR_SIZE + DATA_SIZE)

/* Default maximum of the global data blocks(512K * PAGE_SIZE) */
#define TCMU_GLOBAL_MAX_BLOCKS (512 * 1024)

static u8 tcmu_kern_cmd_reply_supported;

static struct device *tcmu_root_device;

struct tcmu_hba {
        u32 host_id;
};

#define TCMU_CONFIG_LEN 256

struct tcmu_nl_cmd {
        /* wake up thread waiting for reply */
        struct completion complete;
        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
        unsigned long flags;

        struct uio_info uio_info;

        struct inode *inode;

        struct tcmu_mailbox *mb_addr;
        size_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;

        wait_queue_head_t wait_cmdr;
        struct mutex cmdr_lock;

        bool waiting_global;
        uint32_t dbi_max;
        uint32_t dbi_thresh;
        DECLARE_BITMAP(data_bitmap, DATA_BLOCK_BITS);
        struct radix_tree_root data_blocks;

        struct idr commands;
        spinlock_t commands_lock;

        struct timer_list timeout;
        unsigned int cmd_time_out;

        spinlock_t nl_cmd_lock;
        struct tcmu_nl_cmd curr_nl_cmd;
        /* wake up threads waiting on curr_nl_cmd */
        wait_queue_head_t nl_cmd_wq;

        char dev_config[TCMU_CONFIG_LEN];
};

#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;

        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
        unsigned long flags;
};

static struct task_struct *unmap_thread;
static wait_queue_head_t unmap_wait;
static DEFINE_MUTEX(root_udev_mutex);
static LIST_HEAD(root_udev);

static atomic_t global_db_count = ATOMIC_INIT(0);

static struct kmem_cache *tcmu_cmd_cache;

/* 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 se_device *dev;
        struct tcmu_dev *udev;
        struct tcmu_nl_cmd *nl_cmd;
        int dev_id, rc, ret = 0;
        bool is_removed = (completed_cmd == TCMU_CMD_REMOVED_DEVICE);

        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]);

        dev = target_find_device(dev_id, !is_removed);
        if (!dev) {
                printk(KERN_ERR "tcmu nl cmd %u/%u completion could not find device with dev id %u.\n",
                       completed_cmd, rc, dev_id);
                return -ENODEV;
        }
        udev = TCMU_DEV(dev);

        spin_lock(&udev->nl_cmd_lock);
        nl_cmd = &udev->curr_nl_cmd;

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

        if (nl_cmd->cmd != completed_cmd) {
                printk(KERN_ERR "Mismatched commands (Expecting reply for %d. Current %d).\n",
                       completed_cmd, nl_cmd->cmd);
                ret = -EINVAL;
        } else {
                nl_cmd->status = rc;
        }

        spin_unlock(&udev->nl_cmd_lock);
        if (!is_removed)
                 target_undepend_item(&dev->dev_group.cg_item);
        if (!ret)
                complete(&nl_cmd->complete);
        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,
                .flags  = GENL_ADMIN_PERM,
                .policy = tcmu_attr_policy,
                .doit   = tcmu_genl_set_features,
        },
        {
                .cmd    = TCMU_CMD_ADDED_DEVICE_DONE,
                .flags  = GENL_ADMIN_PERM,
                .policy = tcmu_attr_policy,
                .doit   = tcmu_genl_add_dev_done,
        },
        {
                .cmd    = TCMU_CMD_REMOVED_DEVICE_DONE,
                .flags  = GENL_ADMIN_PERM,
                .policy = tcmu_attr_policy,
                .doit   = tcmu_genl_rm_dev_done,
        },
        {
                .cmd    = TCMU_CMD_RECONFIG_DEVICE_DONE,
                .flags  = GENL_ADMIN_PERM,
                .policy = tcmu_attr_policy,
                .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,
        .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) {
                        atomic_dec(&global_db_count);
                        return false;
                }

                /* 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;

        udev->waiting_global = false;

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

err:
        udev->waiting_global = true;
        /* Try to wake up the unmap thread */
        wake_up(&unmap_wait);
        return false;
}

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;
        int cmd_id;

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

        tcmu_cmd->se_cmd = se_cmd;
        tcmu_cmd->tcmu_dev = udev;
        if (udev->cmd_time_out)
                tcmu_cmd->deadline = jiffies +
                                        msecs_to_jiffies(udev->cmd_time_out);

        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;
        }

        idr_preload(GFP_KERNEL);
        spin_lock_irq(&udev->commands_lock);
        cmd_id = idr_alloc(&udev->commands, tcmu_cmd, 0,
                USHRT_MAX, GFP_NOWAIT);
        spin_unlock_irq(&udev->commands_lock);
        idr_preload_end();

        if (cmd_id < 0) {
                tcmu_free_cmd(tcmu_cmd);
                return NULL;
        }
        tcmu_cmd->cmd_id = cmd_id;

        return tcmu_cmd;
}

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

        size = round_up(size+offset, PAGE_SIZE);
        vaddr -= offset;

        while (size) {
                flush_dcache_page(virt_to_page(vaddr));
                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 tcmu_dev *udev)
{
        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 int 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;

        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)
                                        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);
                        }

                        copy_bytes = min_t(size_t, sg_remaining,
                                        block_remaining);
                        to_offset = get_block_offset_user(udev, dbi,
                                        block_remaining);

                        if (*iov_cnt != 0 &&
                            to_offset == iov_tail(*iov)) {
                                (*iov)->iov_len += copy_bytes;
                        } else {
                                new_iov(iov, iov_cnt, udev);
                                (*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);
                                tcmu_flush_dcache_range(to, copy_bytes);
                        }
                        sg_remaining -= copy_bytes;
                        block_remaining -= copy_bytes;
                }
                kunmap_atomic(from - sg->offset);
        }
        if (to)
                kunmap_atomic(to);

        return 0;
}

static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                             bool bidi)
{
        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) {
                        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);
                        }
                        copy_bytes = min_t(size_t, sg_remaining,
                                        block_remaining);
                        offset = DATA_BLOCK_SIZE - block_remaining;
                        tcmu_flush_dcache_range(from, copy_bytes);
                        memcpy(to + sg->length - sg_remaining, from + offset,
                                        copy_bytes);

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

static inline size_t spc_bitmap_free(unsigned long *bitmap, uint32_t thresh)
{
        return DATA_BLOCK_SIZE * (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_needed) {
                unsigned long blocks_left = DATA_BLOCK_BITS - udev->dbi_thresh;
                unsigned long grow;

                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;
                }

                /* Try to expand the thresh */
                if (!udev->dbi_thresh) {
                        /* From idle state */
                        uint32_t init_thresh = DATA_BLOCK_INIT_BITS;

                        udev->dbi_thresh = max(blocks_needed, init_thresh);
                } else {
                        /*
                         * Grow the data area by max(blocks needed,
                         * dbi_thresh / 2), but limited to the max
                         * DATA_BLOCK_BITS size.
                         */
                        grow = max(blocks_needed, udev->dbi_thresh / 2);
                        udev->dbi_thresh += grow;
                        if (udev->dbi_thresh > DATA_BLOCK_BITS)
                                udev->dbi_thresh = DATA_BLOCK_BITS;
                }
        }

        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 sense_reason_t
tcmu_queue_cmd_ring(struct tcmu_cmd *tcmu_cmd)
{
        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, ret;
        uint32_t cmd_head;
        uint64_t cdb_off;
        bool copy_to_data_area;
        size_t data_length = tcmu_cmd_get_data_length(tcmu_cmd);

        if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags))
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

        /*
         * 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);

        mutex_lock(&udev->cmdr_lock);

        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);
                mutex_unlock(&udev->cmdr_lock);
                return TCM_INVALID_CDB_FIELD;
        }

        while (!is_ring_space_avail(udev, tcmu_cmd, command_size, data_length)) {
                int ret;
                DEFINE_WAIT(__wait);

                prepare_to_wait(&udev->wait_cmdr, &__wait, TASK_INTERRUPTIBLE);

                pr_debug("sleeping for ring space\n");
                mutex_unlock(&udev->cmdr_lock);
                if (udev->cmd_time_out)
                        ret = schedule_timeout(
                                        msecs_to_jiffies(udev->cmd_time_out));
                else
                        ret = schedule_timeout(msecs_to_jiffies(TCMU_TIME_OUT));
                finish_wait(&udev->wait_cmdr, &__wait);
                if (!ret) {
                        pr_warn("tcmu: command timed out\n");
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                }

                mutex_lock(&udev->cmdr_lock);

                /* We dropped cmdr_lock, cmd_head is stale */
                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) < 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));

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

        /* 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);
        ret = scatter_data_area(udev, tcmu_cmd, se_cmd->t_data_sg,
                                se_cmd->t_data_nents, &iov, &iov_cnt,
                                copy_to_data_area);
        if (ret) {
                tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cnt);
                mutex_unlock(&udev->cmdr_lock);

                pr_err("tcmu: alloc and scatter data failed\n");
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
        }
        entry->req.iov_cnt = iov_cnt;

        /* Handle BIDI commands */
        iov_cnt = 0;
        if (se_cmd->se_cmd_flags & SCF_BIDI) {
                iov++;
                ret = scatter_data_area(udev, tcmu_cmd,
                                        se_cmd->t_bidi_data_sg,
                                        se_cmd->t_bidi_data_nents,
                                        &iov, &iov_cnt, false);
                if (ret) {
                        tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cnt);
                        mutex_unlock(&udev->cmdr_lock);

                        pr_err("tcmu: alloc and scatter bidi data failed\n");
                        return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
                }
        }
        entry->req.iov_bidi_cnt = iov_cnt;

        /*
         * 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, sizeof(*entry));

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

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

        if (udev->cmd_time_out)
                mod_timer(&udev->timeout, round_jiffies_up(jiffies +
                          msecs_to_jiffies(udev->cmd_time_out)));

        return TCM_NO_SENSE;
}

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 ret;

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

        ret = tcmu_queue_cmd_ring(tcmu_cmd);
        if (ret != TCM_NO_SENSE) {
                pr_err("TCMU: Could not queue command\n");
                spin_lock_irq(&udev->commands_lock);
                idr_remove(&udev->commands, tcmu_cmd->cmd_id);
                spin_unlock_irq(&udev->commands_lock);

                tcmu_free_cmd(tcmu_cmd);
        }

        return 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;

        /*
         * cmd has been completed already from timeout, just reclaim
         * data area space and free cmd
         */
        if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags))
                goto out;

        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;
        } else if (entry->rsp.scsi_status == SAM_STAT_CHECK_CONDITION) {
                transport_copy_sense_to_cmd(se_cmd, entry->rsp.sense_buffer);
        } else if (se_cmd->se_cmd_flags & SCF_BIDI) {
                /* Get Data-In buffer before clean up */
                gather_data_area(udev, cmd, true);
        } else if (se_cmd->data_direction == DMA_FROM_DEVICE) {
                gather_data_area(udev, cmd, false);
        } 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);
        }

        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 unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
{
        struct tcmu_mailbox *mb;
        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 != ACCESS_ONCE(mb->cmd_tail)) {

                struct tcmu_cmd_entry *entry = (void *) mb + CMDR_OFF + udev->cmdr_last_cleaned;
                struct tcmu_cmd *cmd;

                tcmu_flush_dcache_range(entry, 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);

                spin_lock(&udev->commands_lock);
                cmd = idr_remove(&udev->commands, entry->hdr.cmd_id);
                spin_unlock(&udev->commands_lock);

                if (!cmd) {
                        pr_err("cmd_id not found, ring is broken\n");
                        set_bit(TCMU_DEV_BIT_BROKEN, &udev->flags);
                        break;
                }

                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)
                del_timer(&udev->timeout); /* no more pending cmds */

        wake_up(&udev->wait_cmdr);

        return handled;
}

static int tcmu_check_expired_cmd(int id, void *p, void *data)
{
        struct tcmu_cmd *cmd = p;

        if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags))
                return 0;

        if (!time_after(jiffies, cmd->deadline))
                return 0;

        set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
        target_complete_cmd(cmd->se_cmd, SAM_STAT_CHECK_CONDITION);
        cmd->se_cmd = NULL;

        return 0;
}

static void tcmu_device_timedout(unsigned long data)
{
        struct tcmu_dev *udev = (struct tcmu_dev *)data;
        unsigned long flags;

        spin_lock_irqsave(&udev->commands_lock, flags);
        idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);
        spin_unlock_irqrestore(&udev->commands_lock, flags);

        /* Try to wake up the ummap thread */
        wake_up(&unmap_wait);

        /*
         * We don't need to wakeup threads on wait_cmdr since they have their
         * own timeout.
         */
}

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;

        init_waitqueue_head(&udev->wait_cmdr);
        mutex_init(&udev->cmdr_lock);

        idr_init(&udev->commands);
        spin_lock_init(&udev->commands_lock);

        setup_timer(&udev->timeout, tcmu_device_timedout,
                (unsigned long)udev);

        init_waitqueue_head(&udev->nl_cmd_wq);
        spin_lock_init(&udev->nl_cmd_lock);

        return &udev->se_dev;
}

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

        mutex_lock(&tcmu_dev->cmdr_lock);
        tcmu_handle_completions(tcmu_dev);
        mutex_unlock(&tcmu_dev->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;
        int ret;

        mutex_lock(&udev->cmdr_lock);
        page = tcmu_get_block_page(udev, dbi);
        if (likely(page)) {
                mutex_unlock(&udev->cmdr_lock);
                return page;
        }

        /*
         * Normally it shouldn't be here:
         * Only when the userspace has touched the blocks which
         * are out of the tcmu_cmd's data iov[], and will return
         * one zeroed page.
         */
        pr_warn("Block(%u) out of cmd's iov[] has been touched!\n", dbi);
        pr_warn("Mostly it will be a bug of userspace, please have a check!\n");

        if (dbi >= udev->dbi_thresh) {
                /* Extern the udev->dbi_thresh to dbi + 1 */
                udev->dbi_thresh = dbi + 1;
                udev->dbi_max = dbi;
        }

        page = radix_tree_lookup(&udev->data_blocks, dbi);
        if (!page) {
                page = alloc_page(GFP_KERNEL | __GFP_ZERO);
                if (!page) {
                        mutex_unlock(&udev->cmdr_lock);
                        return NULL;
                }

                ret = radix_tree_insert(&udev->data_blocks, dbi, page);
                if (ret) {
                        mutex_unlock(&udev->cmdr_lock);
                        __free_page(page);
                        return NULL;
                }

                /*
                 * Since this case is rare in page fault routine, here we
                 * will allow the global_db_count >= TCMU_GLOBAL_MAX_BLOCKS
                 * to reduce possible page fault call trace.
                 */
                atomic_inc(&global_db_count);
        }
        mutex_unlock(&udev->cmdr_lock);

        return page;
}

static int 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);
        } 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_NOPAGE;
        }

        get_page(page);
        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) != (TCMU_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 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;

        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 void 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;
relock:
        spin_lock(&udev->nl_cmd_lock);

        if (nl_cmd->cmd != TCMU_CMD_UNSPEC) {
                spin_unlock(&udev->nl_cmd_lock);
                pr_debug("sleeping for open nl cmd\n");
                wait_event(udev->nl_cmd_wq, (nl_cmd->cmd == TCMU_CMD_UNSPEC));
                goto relock;
        }

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

        spin_unlock(&udev->nl_cmd_lock);
}

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

        if (!tcmu_kern_cmd_reply_supported)
                return 0;

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

        spin_lock(&udev->nl_cmd_lock);
        nl_cmd->cmd = TCMU_CMD_UNSPEC;
        ret = nl_cmd->status;
        nl_cmd->status = 0;
        spin_unlock(&udev->nl_cmd_lock);

        wake_up_all(&udev->nl_cmd_wq);

        return ret;;
}

static int tcmu_netlink_event(struct tcmu_dev *udev, enum tcmu_genl_cmd cmd,
                              int reconfig_attr, const void *reconfig_data)
{
        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;

        if (cmd == TCMU_CMD_RECONFIG_DEVICE) {
                switch (reconfig_attr) {
                case TCMU_ATTR_DEV_CFG:
                        ret = nla_put_string(skb, reconfig_attr, reconfig_data);
                        break;
                case TCMU_ATTR_DEV_SIZE:
                        ret = nla_put_u64_64bit(skb, reconfig_attr,
                                                *((u64 *)reconfig_data),
                                                TCMU_ATTR_PAD);
                        break;
                case TCMU_ATTR_WRITECACHE:
                        ret = nla_put_u8(skb, reconfig_attr,
                                          *((u8 *)reconfig_data));
                        break;
                default:
                        BUG();
                }

                if (ret < 0)
                        goto free_skb;
        }

        genlmsg_end(skb, msg_header);

        tcmu_init_genl_cmd_reply(udev, cmd);

        ret = genlmsg_multicast_allns(&tcmu_genl_family, skb, 0,
                                TCMU_MCGRP_CONFIG, GFP_KERNEL);
        /* We don't care if no one is listening */
        if (ret == -ESRCH)
                ret = 0;
        if (!ret)
                ret = tcmu_wait_genl_cmd_reply(udev);

        return ret;
free_skb:
        nlmsg_free(skb);
        return ret;
}

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

        info = &udev->uio_info;
        size = snprintf(NULL, 0, "tcm-user/%u/%s/%s", hba->host_id, udev->name,
                        udev->dev_config);
        size += 1; /* for \0 */
        str = kmalloc(size, GFP_KERNEL);
        if (!str)
                return -ENOMEM;

        used = snprintf(str, size, "tcm-user/%u/%s", hba->host_id, udev->name);
        if (udev->dev_config[0])
                snprintf(str + used, size - used, "/%s", udev->dev_config);

        /* 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;

        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 = DATA_SIZE;
        udev->dbi_thresh = 0; /* Default in Idle state */
        udev->waiting_global = false;

        /* Initialise the mailbox of the ring buffer */
        mb = udev->mb_addr;
        mb->version = TCMU_MAILBOX_VERSION;
        mb->flags = TCMU_MAILBOX_FLAG_CAP_OOOC;
        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);

        INIT_RADIX_TREE(&udev->data_blocks, GFP_KERNEL);

        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 = TCMU_RING_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;

        /*
         * 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_netlink_event(udev, TCMU_CMD_ADDED_DEVICE, 0, NULL);
        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);
err_vzalloc:
        kfree(info->name);
        info->name = NULL;

        return ret;
}

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 bool tcmu_dev_configured(struct tcmu_dev *udev)
{
        return udev->uio_info.uio_dev ? true : false;
}

static void tcmu_blocks_release(struct tcmu_dev *udev)
{
        int i;
        struct page *page;

        /* Try to release all block pages */
        mutex_lock(&udev->cmdr_lock);
        for (i = 0; i <= udev->dbi_max; i++) {
                page = radix_tree_delete(&udev->data_blocks, i);
                if (page) {
                        __free_page(page);
                        atomic_dec(&global_db_count);
                }
        }
        mutex_unlock(&udev->cmdr_lock);
}

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);
        struct tcmu_cmd *cmd;
        bool all_expired = true;
        int i;

        del_timer_sync(&udev->timeout);

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

        vfree(udev->mb_addr);

        /* Upper layer should drain all requests before calling this */
        spin_lock_irq(&udev->commands_lock);
        idr_for_each_entry(&udev->commands, cmd, i) {
                if (tcmu_check_and_free_pending_cmd(cmd) != 0)
                        all_expired = false;
        }
        idr_destroy(&udev->commands);
        spin_unlock_irq(&udev->commands_lock);
        WARN_ON(!all_expired);

        tcmu_blocks_release(udev);

        tcmu_netlink_event(udev, TCMU_CMD_REMOVED_DEVICE, 0, NULL);

        uio_unregister_device(&udev->uio_info);

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

enum {
        Opt_dev_config, Opt_dev_size, Opt_hw_block_size, Opt_hw_max_sectors,
        Opt_err,
};

static match_table_t tokens = {
        {Opt_dev_config, "dev_config=%s"},
        {Opt_dev_size, "dev_size=%u"},
        {Opt_hw_block_size, "hw_block_size=%u"},
        {Opt_hw_max_sectors, "hw_max_sectors=%u"},
        {Opt_err, NULL}
};

static int tcmu_set_dev_attrib(substring_t *arg, u32 *dev_attrib)
{
        unsigned long tmp_ul;
        char *arg_p;
        int ret;

        arg_p = match_strdup(arg);
        if (!arg_p)
                return -ENOMEM;

        ret = kstrtoul(arg_p, 0, &tmp_ul);
        kfree(arg_p);
        if (ret < 0) {
                pr_err("kstrtoul() failed for dev attrib\n");
                return ret;
        }
        if (!tmp_ul) {
                pr_err("dev attrib must be nonzero\n");
                return -EINVAL;
        }
        *dev_attrib = tmp_ul;
        return 0;
}

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, *arg_p;
        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:
                        arg_p = match_strdup(&args[0]);
                        if (!arg_p) {
                                ret = -ENOMEM;
                                break;
                        }
                        ret = kstrtoul(arg_p, 0, (unsigned long *) &udev->dev_size);
                        kfree(arg_p);
                        if (ret < 0)
                                pr_err("kstrtoul() failed for dev_size=\n");
                        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;
                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: %zu\n", udev->dev_size);

        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 = container_of(da->da_dev,
                                        struct tcmu_dev, se_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_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 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 (tcmu_dev_configured(udev)) {
                ret = tcmu_netlink_event(udev, TCMU_CMD_RECONFIG_DEVICE,
                                         TCMU_ATTR_DEV_CFG, 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, "%zu\n", udev->dev_size);
}

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 (tcmu_dev_configured(udev)) {
                ret = tcmu_netlink_event(udev, TCMU_CMD_RECONFIG_DEVICE,
                                         TCMU_ATTR_DEV_SIZE, &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_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 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 (tcmu_dev_configured(udev)) {
                ret = tcmu_netlink_event(udev, TCMU_CMD_RECONFIG_DEVICE,
                                         TCMU_ATTR_WRITECACHE, &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 struct configfs_attribute *tcmu_attrib_attrs[] = {
        &tcmu_attr_cmd_time_out,
        &tcmu_attr_dev_config,
        &tcmu_attr_dev_size,
        &tcmu_attr_emulate_write_cache,
        NULL,
};

static struct configfs_attribute **tcmu_attrs;

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_attrib_attrs    = NULL,
};

static int unmap_thread_fn(void *data)
{
        struct tcmu_dev *udev;
        loff_t off;
        uint32_t start, end, block;
        struct page *page;
        int i;

        while (!kthread_should_stop()) {
                DEFINE_WAIT(__wait);

                prepare_to_wait(&unmap_wait, &__wait, TASK_INTERRUPTIBLE);
                schedule();
                finish_wait(&unmap_wait, &__wait);

                if (kthread_should_stop())
                        break;

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

                        /* Try to complete the finished commands first */
                        tcmu_handle_completions(udev);

                        /* Skip the udevs waiting the global pool or in idle */
                        if (udev->waiting_global || !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 there is
                                 * no need to shrink 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 */
                        for (i = start; i < end; i++) {
                                page = radix_tree_delete(&udev->data_blocks, i);
                                if (page) {
                                        __free_page(page);
                                        atomic_dec(&global_db_count);
                                }
                        }
                        mutex_unlock(&udev->cmdr_lock);
                }

                /*
                 * Try to wake up the udevs who are waiting
                 * for the global data pool.
                 */
                list_for_each_entry(udev, &root_udev, node) {
                        if (udev->waiting_global)
                                wake_up(&udev->wait_cmdr);
                }
                mutex_unlock(&root_udev_mutex);
        }

        return 0;
}

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);

        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;

        init_waitqueue_head(&unmap_wait);
        unmap_thread = kthread_run(unmap_thread_fn, NULL, "tcmu_unmap");
        if (IS_ERR(unmap_thread)) {
                ret = PTR_ERR(unmap_thread);
                goto out_unreg_transport;
        }

        return 0;

out_unreg_transport:
        target_backend_unregister(&tcmu_ops);
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)
{
        kthread_stop(unmap_thread);
        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);