diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 02cf543..0b29e4f 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -31,6 +31,8 @@
 #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>
@@ -67,17 +69,24 @@
 
 #define TCMU_TIME_OUT (30 * MSEC_PER_SEC)
 
-/* For cmd area, the size is fixed 2M */
-#define CMDR_SIZE (2 * 1024 * 1024)
+/* For cmd area, the size is fixed 8MB */
+#define CMDR_SIZE (8 * 1024 * 1024)
 
-/* For data area, the size is fixed 32M */
-#define DATA_BLOCK_BITS (8 * 1024)
-#define DATA_BLOCK_SIZE 4096
+/*
+ * 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 ring buffer size is 34M */
+/* 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 struct device *tcmu_root_device;
 
 struct tcmu_hba {
@@ -87,6 +96,8 @@ struct tcmu_hba {
 #define TCMU_CONFIG_LEN 256
 
 struct tcmu_dev {
+	struct list_head node;
+
 	struct se_device se_dev;
 
 	char *name;
@@ -98,6 +109,8 @@ struct tcmu_dev {
 
 	struct uio_info uio_info;
 
+	struct inode *inode;
+
 	struct tcmu_mailbox *mb_addr;
 	size_t dev_size;
 	u32 cmdr_size;
@@ -108,10 +121,11 @@ struct tcmu_dev {
 	size_t data_size;
 
 	wait_queue_head_t wait_cmdr;
-	/* TODO should this be a mutex? */
-	spinlock_t cmdr_lock;
+	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;
 
@@ -146,6 +160,13 @@ struct tcmu_cmd {
 	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 */
@@ -174,48 +195,78 @@ enum tcmu_multicast_groups {
 #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)
+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 < tcmu_cmd->dbi_cnt; i++)
+	for (i = 0; i < len; i++)
 		clear_bit(tcmu_cmd->dbi[i], udev->data_bitmap);
 }
 
-static int tcmu_get_empty_block(struct tcmu_dev *udev, void **addr)
+static inline bool tcmu_get_empty_block(struct tcmu_dev *udev,
+					struct tcmu_cmd *tcmu_cmd)
 {
-	void *p;
-	uint32_t dbi;
-	int ret;
+	struct page *page;
+	int ret, dbi;
 
-	dbi = find_first_zero_bit(udev->data_bitmap, DATA_BLOCK_BITS);
-	if (dbi > udev->dbi_max)
-		udev->dbi_max = dbi;
+	dbi = find_first_zero_bit(udev->data_bitmap, udev->dbi_thresh);
+	if (dbi == udev->dbi_thresh)
+		return false;
 
-	set_bit(dbi, udev->data_bitmap);
+	page = radix_tree_lookup(&udev->data_blocks, dbi);
+	if (!page) {
 
-	p = radix_tree_lookup(&udev->data_blocks, dbi);
-	if (!p) {
-		p = kzalloc(DATA_BLOCK_SIZE, GFP_ATOMIC);
-		if (!p) {
-			clear_bit(dbi, udev->data_bitmap);
-			return -ENOMEM;
+		if (atomic_add_return(1, &global_db_count) >
+					TCMU_GLOBAL_MAX_BLOCKS) {
+			atomic_dec(&global_db_count);
+			return false;
 		}
 
-		ret = radix_tree_insert(&udev->data_blocks, dbi, p);
+		/* try to get new page from the mm */
+		page = alloc_page(GFP_KERNEL);
+		if (!page)
+			return false;
+
+		ret = radix_tree_insert(&udev->data_blocks, dbi, page);
 		if (ret) {
-			kfree(p);
-			clear_bit(dbi, udev->data_bitmap);
-			return ret;
+			__free_page(page);
+			return false;
 		}
+
 	}
 
-	*addr = p;
-	return dbi;
+	if (dbi > udev->dbi_max)
+		udev->dbi_max = dbi;
+
+	set_bit(dbi, udev->data_bitmap);
+	tcmu_cmd_set_dbi(tcmu_cmd, dbi);
+
+	return true;
 }
 
-static void *tcmu_get_block_addr(struct tcmu_dev *udev, uint32_t dbi)
+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);
 }
@@ -355,7 +406,7 @@ static inline size_t iov_tail(struct tcmu_dev *udev, struct iovec *iov)
 	return (size_t)iov->iov_base + iov->iov_len;
 }
 
-static int alloc_and_scatter_data_area(struct tcmu_dev *udev,
+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)
@@ -365,19 +416,20 @@ static int alloc_and_scatter_data_area(struct tcmu_dev *udev,
 	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_get_empty_block(udev, &to);
-				if (dbi < 0) {
-					kunmap_atomic(from - sg->offset);
-					return dbi;
-				}
-				tcmu_cmd_set_dbi(tcmu_cmd, dbi);
+				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,
@@ -405,6 +457,8 @@ static int alloc_and_scatter_data_area(struct tcmu_dev *udev,
 		}
 		kunmap_atomic(from - sg->offset);
 	}
+	if (to)
+		kunmap_atomic(to);
 
 	return 0;
 }
@@ -415,9 +469,10 @@ static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
 	struct se_cmd *se_cmd = cmd->se_cmd;
 	int i, dbi;
 	int block_remaining = 0;
-	void *from, *to;
+	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;
 
@@ -444,9 +499,13 @@ static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
 		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);
-				from = tcmu_get_block_addr(udev, dbi);
+				page = tcmu_get_block_page(udev, dbi);
+				from = kmap_atomic(page);
 			}
 			copy_bytes = min_t(size_t, sg_remaining,
 					block_remaining);
@@ -461,12 +520,13 @@ static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
 		}
 		kunmap_atomic(to - sg->offset);
 	}
+	if (from)
+		kunmap_atomic(from);
 }
 
-static inline size_t spc_bitmap_free(unsigned long *bitmap)
+static inline size_t spc_bitmap_free(unsigned long *bitmap, uint32_t thresh)
 {
-	return DATA_BLOCK_SIZE * (DATA_BLOCK_BITS -
-			bitmap_weight(bitmap, DATA_BLOCK_BITS));
+	return DATA_BLOCK_SIZE * (thresh - bitmap_weight(bitmap, thresh));
 }
 
 /*
@@ -475,9 +535,12 @@ static inline size_t spc_bitmap_free(unsigned long *bitmap)
  *
  * Called with ring lock held.
  */
-static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t data_needed)
+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;
 
@@ -501,13 +564,41 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t d
 		return false;
 	}
 
-	space = spc_bitmap_free(udev->data_bitmap);
+	/* try to check and get the data blocks as needed */
+	space = spc_bitmap_free(udev->data_bitmap, udev->dbi_thresh);
 	if (space < data_needed) {
-		pr_debug("no data space: only %zu available, but ask for %zu\n",
-				space, data_needed);
-		return false;
+		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;
+		}
 	}
 
+	if (!tcmu_get_empty_blocks(udev, cmd))
+		return false;
+
 	return true;
 }
 
@@ -544,7 +635,7 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t d
 
 	WARN_ON(command_size & (TCMU_OP_ALIGN_SIZE-1));
 
-	spin_lock_irq(&udev->cmdr_lock);
+	mutex_lock(&udev->cmdr_lock);
 
 	mb = udev->mb_addr;
 	cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */
@@ -553,18 +644,18 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t d
 		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);
-		spin_unlock_irq(&udev->cmdr_lock);
+		mutex_unlock(&udev->cmdr_lock);
 		return TCM_INVALID_CDB_FIELD;
 	}
 
-	while (!is_ring_space_avail(udev, command_size, data_length)) {
+	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");
-		spin_unlock_irq(&udev->cmdr_lock);
+		mutex_unlock(&udev->cmdr_lock);
 		if (udev->cmd_time_out)
 			ret = schedule_timeout(
 					msecs_to_jiffies(udev->cmd_time_out));
@@ -576,7 +667,7 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t d
 			return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 		}
 
-		spin_lock_irq(&udev->cmdr_lock);
+		mutex_lock(&udev->cmdr_lock);
 
 		/* We dropped cmdr_lock, cmd_head is stale */
 		cmd_head = mb->cmd_head % udev->cmdr_size; /* UAM */
@@ -609,15 +700,18 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t d
 	entry->hdr.uflags = 0;
 
 	/* 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 = alloc_and_scatter_data_area(udev, tcmu_cmd,
-			se_cmd->t_data_sg, se_cmd->t_data_nents,
-			&iov, &iov_cnt, copy_to_data_area);
+	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) {
-		spin_unlock_irq(&udev->cmdr_lock);
+		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;
 	}
@@ -628,12 +722,14 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t d
 	if (se_cmd->se_cmd_flags & SCF_BIDI) {
 		iov_cnt = 0;
 		iov++;
-		ret = alloc_and_scatter_data_area(udev, tcmu_cmd,
+		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) {
-			spin_unlock_irq(&udev->cmdr_lock);
+			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;
 		}
@@ -648,8 +744,7 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, size_t cmd_size, size_t d
 
 	UPDATE_HEAD(mb->cmd_head, command_size, udev->cmdr_size);
 	tcmu_flush_dcache_range(mb, sizeof(*mb));
-
-	spin_unlock_irq(&udev->cmdr_lock);
+	mutex_unlock(&udev->cmdr_lock);
 
 	/* TODO: only if FLUSH and FUA? */
 	uio_event_notify(&udev->uio_info);
@@ -723,14 +818,13 @@ static void tcmu_handle_completion(struct tcmu_cmd *cmd, struct tcmu_cmd_entry *
 
 out:
 	cmd->se_cmd = NULL;
-	tcmu_cmd_free_data(cmd);
+	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;
-	unsigned long flags;
 	int handled = 0;
 
 	if (test_bit(TCMU_DEV_BIT_BROKEN, &udev->flags)) {
@@ -738,8 +832,6 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
 		return 0;
 	}
 
-	spin_lock_irqsave(&udev->cmdr_lock, flags);
-
 	mb = udev->mb_addr;
 	tcmu_flush_dcache_range(mb, sizeof(*mb));
 
@@ -780,8 +872,6 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
 	if (mb->cmd_tail == mb->cmd_head)
 		del_timer(&udev->timeout); /* no more pending cmds */
 
-	spin_unlock_irqrestore(&udev->cmdr_lock, flags);
-
 	wake_up(&udev->wait_cmdr);
 
 	return handled;
@@ -808,16 +898,14 @@ static void tcmu_device_timedout(unsigned long data)
 {
 	struct tcmu_dev *udev = (struct tcmu_dev *)data;
 	unsigned long flags;
-	int handled;
-
-	handled = tcmu_handle_completions(udev);
-
-	pr_warn("%d completions handled from timeout\n", handled);
 
 	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.
@@ -862,7 +950,7 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 	udev->cmd_time_out = TCMU_TIME_OUT;
 
 	init_waitqueue_head(&udev->wait_cmdr);
-	spin_lock_init(&udev->cmdr_lock);
+	mutex_init(&udev->cmdr_lock);
 
 	idr_init(&udev->commands);
 	spin_lock_init(&udev->commands_lock);
@@ -877,59 +965,13 @@ 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;
 }
 
-static void tcmu_blocks_release(struct tcmu_dev *udev, bool release_pending)
-{
-	uint32_t dbi, end;
-	void *addr;
-
-	spin_lock_irq(&udev->cmdr_lock);
-
-	end = udev->dbi_max + 1;
-
-	/* try to release all unused blocks */
-	dbi = find_first_zero_bit(udev->data_bitmap, end);
-	if (dbi >= end) {
-		spin_unlock_irq(&udev->cmdr_lock);
-		return;
-	}
-	do {
-		addr = radix_tree_delete(&udev->data_blocks, dbi);
-		kfree(addr);
-
-		dbi = find_next_zero_bit(udev->data_bitmap, end, dbi + 1);
-	} while (dbi < end);
-
-	if (!release_pending)
-		return;
-
-	/* try to release all pending blocks */
-	dbi = find_first_bit(udev->data_bitmap, end);
-	if (dbi >= end) {
-		spin_unlock_irq(&udev->cmdr_lock);
-		return;
-	}
-	do {
-		addr = radix_tree_delete(&udev->data_blocks, dbi);
-		kfree(addr);
-
-		dbi = find_next_bit(udev->data_bitmap, end, dbi + 1);
-	} while (dbi < end);
-
-	spin_unlock_irq(&udev->cmdr_lock);
-}
-
-static void tcmu_vma_close(struct vm_area_struct *vma)
-{
-	struct tcmu_dev *udev = vma->vm_private_data;
-
-	tcmu_blocks_release(udev, false);
-}
-
 /*
  * mmap code from uio.c. Copied here because we want to hook mmap()
  * and this stuff must come along.
@@ -947,6 +989,60 @@ static int tcmu_find_mem_index(struct vm_area_struct *vma)
 	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;
@@ -970,14 +1066,13 @@ static int tcmu_vma_fault(struct vm_fault *vmf)
 		addr = (void *)(unsigned long)info->mem[mi].addr + offset;
 		page = vmalloc_to_page(addr);
 	} else {
-		/* For the dynamically growing data area pages */
 		uint32_t dbi;
 
+		/* For the dynamically growing data area pages */
 		dbi = (offset - udev->data_off) / DATA_BLOCK_SIZE;
-		addr = tcmu_get_block_addr(udev, dbi);
-		if (!addr)
+		page = tcmu_try_get_block_page(udev, dbi);
+		if (!page)
 			return VM_FAULT_NOPAGE;
-		page = virt_to_page(addr);
 	}
 
 	get_page(page);
@@ -986,7 +1081,6 @@ static int tcmu_vma_fault(struct vm_fault *vmf)
 }
 
 static const struct vm_operations_struct tcmu_vm_ops = {
-	.close = tcmu_vma_close,
 	.fault = tcmu_vma_fault,
 };
 
@@ -1014,6 +1108,8 @@ static int tcmu_open(struct uio_info *info, struct inode *inode)
 	if (test_and_set_bit(TCMU_DEV_BIT_OPEN, &udev->flags))
 		return -EBUSY;
 
+	udev->inode = inode;
+
 	pr_debug("open\n");
 
 	return 0;
@@ -1104,6 +1200,8 @@ static int tcmu_configure_device(struct se_device *dev)
 	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;
@@ -1116,7 +1214,7 @@ static int tcmu_configure_device(struct se_device *dev)
 	WARN_ON(udev->data_size % PAGE_SIZE);
 	WARN_ON(udev->data_size % DATA_BLOCK_SIZE);
 
-	INIT_RADIX_TREE(&udev->data_blocks, GFP_ATOMIC);
+	INIT_RADIX_TREE(&udev->data_blocks, GFP_KERNEL);
 
 	info->version = __stringify(TCMU_MAILBOX_VERSION);
 
@@ -1149,6 +1247,10 @@ static int tcmu_configure_device(struct se_device *dev)
 	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:
@@ -1183,6 +1285,23 @@ 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);
@@ -1192,6 +1311,10 @@ static void tcmu_free_device(struct se_device *dev)
 
 	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 */
@@ -1204,7 +1327,7 @@ static void tcmu_free_device(struct se_device *dev)
 	spin_unlock_irq(&udev->commands_lock);
 	WARN_ON(!all_expired);
 
-	tcmu_blocks_release(udev, true);
+	tcmu_blocks_release(udev);
 
 	if (tcmu_dev_configured(udev)) {
 		tcmu_netlink_event(TCMU_CMD_REMOVED_DEVICE, udev->uio_info.name,
@@ -1392,6 +1515,81 @@ static ssize_t tcmu_cmd_time_out_store(struct config_item *item, const char *pag
 	.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 (1) {
+		DEFINE_WAIT(__wait);
+
+		prepare_to_wait(&unmap_wait, &__wait, TASK_INTERRUPTIBLE);
+		schedule();
+		finish_wait(&unmap_wait, &__wait);
+
+		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, len = 0;
@@ -1437,8 +1635,17 @@ static int __init tcmu_module_init(void)
 	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:
@@ -1453,6 +1660,7 @@ static int __init tcmu_module_init(void)
 
 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);
