text: // 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(virt_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;
  
  	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);
  			}
  
  			/*
  			 * 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);
  				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);
  }
  
  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);
  			}
  			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;
  			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;
  			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 int tcmu_setup_cmd_timer(struct tcmu_cmd *tcmu_cmd, unsigned int tmo,
  				struct timer_list *timer)
  {
  	struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
  	int cmd_id;
  
  	if (tcmu_cmd->cmd_id)
  		goto setup_timer;
  
  	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");
  		return cmd_id;
  	}
  	tcmu_cmd->cmd_id = cmd_id;
  
  	pr_debug("allocated cmd %u for dev %s tmo %lu\n", tcmu_cmd->cmd_id,
  		 udev->name, tmo / MSEC_PER_SEC);
  
  setup_timer:
  	if (!tmo)
  		return 0;
  
  	tcmu_cmd->deadline = round_jiffies_up(jiffies + msecs_to_jiffies(tmo));
  	if (!timer_pending(timer))
  		mod_timer(timer, tcmu_cmd->deadline);
  
  	return 0;
  }
  
  static int add_to_qfull_queue(struct tcmu_cmd *tcmu_cmd)
  {
  	struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
  	unsigned int tmo;
  	int ret;
  
  	/*
  	 * 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;
  
  	ret = tcmu_setup_cmd_timer(tcmu_cmd, tmo, &udev->qfull_timer);
  	if (ret)
  		return ret;
  
  	list_add_tail(&tcmu_cmd->queue_entry, &udev->qfull_queue);
  	pr_debug("adding cmd %u on dev %s to ring space wait queue\n",
  		 tcmu_cmd->cmd_id, 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, 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);
  
  	*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));
  
  		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;
  
  	ret = tcmu_setup_cmd_timer(tcmu_cmd, udev->cmd_time_out,
  				   &udev->cmd_timer);
  	if (ret) {
  		tcmu_cmd_free_data(tcmu_cmd, tcmu_cmd->dbi_cnt);
  
  		*scsi_err = TCM_OUT_OF_RESOURCES;
  		return -1;
  	}
  	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, sizeof(*entry));
  
  	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 unsigned int 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;
  
  		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);
  
  		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);
  			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) {
  		/* 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 int tcmu_check_expired_cmd(int id, void *p, void *data)
  {
  	struct tcmu_cmd *cmd = p;
  	struct tcmu_dev *udev = cmd->tcmu_dev;
  	u8 scsi_status;
  	struct se_cmd *se_cmd;
  	bool is_running;
  
  	if (test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags))
  		return 0;
  
  	if (!time_after(jiffies, cmd->deadline))
  		return 0;
  
  	is_running = test_bit(TCMU_CMD_BIT_INFLIGHT, &cmd->flags);
  	se_cmd = cmd->se_cmd;
  
  	if (is_running) {
  		/*
  		 * If cmd_time_out is disabled but qfull is set deadline
  		 * will only reflect the qfull timeout. Ignore it.
  		 */
  		if (!udev->cmd_time_out)
  			return 0;
  
  		set_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags);
  		/*
  		 * target_complete_cmd will translate this to LUN COMM FAILURE
  		 */
  		scsi_status = SAM_STAT_CHECK_CONDITION;
  		list_del_init(&cmd->queue_entry);
  		cmd->se_cmd = NULL;
  	} else {
  		list_del_init(&cmd->queue_entry);
  		idr_remove(&udev->commands, id);
  		tcmu_free_cmd(cmd);
  		scsi_status = SAM_STAT_TASK_SET_FULL;
  	}
  
  	pr_debug("Timing out cmd %u on dev %s that is %s.\n",
  		 id, udev->name, is_running ? "inflight" : "queued");
  
  	target_complete_cmd(se_cmd, scsi_status);
  	return 0;
  }
  
  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 bool run_qfull_queue(struct tcmu_dev *udev, bool fail)
  {
  	struct tcmu_cmd *tcmu_cmd, *tmp_cmd;
  	LIST_HEAD(cmds);
  	bool drained = true;
  	sense_reason_t scsi_ret;
  	int ret;
  
  	if (list_empty(&udev->qfull_queue))
  		return true;
  
  	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 %u on dev %s from queue\n",
  		         tcmu_cmd->cmd_id, udev->name);
  
  		if (fail) {
  			idr_remove(&udev->commands, tcmu_cmd->cmd_id);
  			/*
  			 * 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 %u on dev %s failed with %u\n",
  			         tcmu_cmd->cmd_id, udev->name, scsi_ret);
  
  			idr_remove(&udev->commands, tcmu_cmd->cmd_id);
  			/*
  			 * 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);
  			drained = false;
  			break;
  		}
  	}
  
  	tcmu_set_next_deadline(&udev->qfull_queue, &udev->qfull_timer);
  	return drained;
  }
  
  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)) {
  		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);
  	} 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;
  	}
  
  	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) != (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;
  	}
  	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) {
  		if (!test_bit(TCMU_CMD_BIT_INFLIGHT, &cmd->flags))
  			continue;
  
  		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));
  
  	del_timer(&udev->cmd_timer);
  
  	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;
  	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);
  		idr_for_each(&udev->commands, tcmu_check_expired_cmd, NULL);
  
  		tcmu_set_next_deadline(&udev->inflight_queue, &udev->cmd_timer);
  		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);
  