--- a/include/uapi/linux/target_core_user.h
+++ b/include/uapi/linux/target_core_user.h
@@ -43,6 +43,7 @@
 #define TCMU_MAILBOX_VERSION 2
 #define ALIGN_SIZE 64 /* Should be enough for most CPUs */
 #define TCMU_MAILBOX_FLAG_CAP_OOOC (1 << 0) /* Out-of-order completions */
+#define TCMU_MAILBOX_FLAG_CAP_READ_LEN (1 << 1) /* Read data length */
 
 struct tcmu_mailbox {
 	__u16 version;
@@ -70,6 +71,7 @@ struct tcmu_cmd_entry_hdr {
 	__u16 cmd_id;
 	__u8 kflags;
 #define TCMU_UFLAG_UNKNOWN_OP 0x1
+#define TCMU_UFLAG_READ_LEN   0x2
 	__u8 uflags;
 
 } __packed;
@@ -118,7 +120,7 @@ struct tcmu_cmd_entry {
 			__u8 scsi_status;
 			__u8 __pad1;
 			__u16 __pad2;
-			__u32 __pad3;
+			__u32 read_len;
 			char sense_buffer[TCMU_SENSE_BUFFERSIZE];
 		} rsp;
 	};
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -576,7 +576,7 @@ static int scatter_data_area(struct tcmu
 }
 
 static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
-			     bool bidi)
+			     bool bidi, uint32_t read_len)
 {
 	struct se_cmd *se_cmd = cmd->se_cmd;
 	int i, dbi;
@@ -609,7 +609,7 @@ static void gather_data_area(struct tcmu
 	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) {
+		while (sg_remaining > 0 && read_len > 0) {
 			if (block_remaining == 0) {
 				if (from)
 					kunmap_atomic(from);
@@ -621,6 +621,8 @@ static void gather_data_area(struct tcmu
 			}
 			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,
@@ -628,8 +630,11 @@ static void gather_data_area(struct tcmu
 
 			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);
@@ -947,6 +952,8 @@ static void tcmu_handle_completion(struc
 {
 	struct se_cmd *se_cmd = cmd->se_cmd;
 	struct tcmu_dev *udev = cmd->tcmu_dev;
+	bool read_len_valid = false;
+	uint32_t read_len = se_cmd->data_length;
 
 	/*
 	 * cmd has been completed already from timeout, just reclaim
@@ -961,13 +968,28 @@ static void tcmu_handle_completion(struc
 		pr_warn("TCMU: Userspace set UNKNOWN_OP flag on se_cmd %p\n",
 			cmd->se_cmd);
 		entry->rsp.scsi_status = SAM_STAT_CHECK_CONDITION;
-	} else if (entry->rsp.scsi_status == SAM_STAT_CHECK_CONDITION) {
+		goto done;
+	}
+
+	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);
-	} else if (se_cmd->se_cmd_flags & SCF_BIDI) {
+		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);
+		gather_data_area(udev, cmd, true, read_len);
 	} else if (se_cmd->data_direction == DMA_FROM_DEVICE) {
-		gather_data_area(udev, cmd, false);
+		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) {
@@ -975,7 +997,13 @@ static void tcmu_handle_completion(struc
 			se_cmd->data_direction);
 	}
 
-	target_complete_cmd(cmd->se_cmd, entry->rsp.scsi_status);
+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;
@@ -1532,7 +1560,7 @@ static int tcmu_configure_device(struct
 	/* Initialise the mailbox of the ring buffer */
 	mb = udev->mb_addr;
 	mb->version = TCMU_MAILBOX_VERSION;
-	mb->flags = TCMU_MAILBOX_FLAG_CAP_OOOC;
+	mb->flags = TCMU_MAILBOX_FLAG_CAP_OOOC | TCMU_MAILBOX_FLAG_CAP_READ_LEN;
 	mb->cmdr_off = CMDR_OFF;
 	mb->cmdr_size = udev->cmdr_size;
 
