drivers/target/target_core_rd.c - maze/linux - Git at Google

 /*******************************************************************************
  * Filename:  target_core_rd.c
  *
  * This file contains the Storage Engine <-> Ramdisk transport
  * specific functions.
  *
  * (c) Copyright 2003-2012 RisingTide Systems LLC.
  *
  * Nicholas A. Bellinger <nab@kernel.org>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  *
  ******************************************************************************/

 #include <linux/string.h>
 #include <linux/parser.h>
 #include <linux/timer.h>
 #include <linux/blkdev.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_host.h>

 #include <target/target_core_base.h>
 #include <target/target_core_backend.h>

 #include "target_core_rd.h"

 static inline struct rd_dev *RD_DEV(struct se_device *dev)
 {
 	return container_of(dev, struct rd_dev, dev);
 }

 /*	rd_attach_hba(): (Part of se_subsystem_api_t template)
  *
  *
  */
 static int rd_attach_hba(struct se_hba *hba, u32 host_id)
 {
 	struct rd_host *rd_host;

 	rd_host = kzalloc(sizeof(struct rd_host), GFP_KERNEL);
 	if (!rd_host) {
 		pr_err("Unable to allocate memory for struct rd_host\n");
 		return -ENOMEM;
 	}

 	rd_host->rd_host_id = host_id;

 	hba->hba_ptr = rd_host;

 	pr_debug("CORE_HBA[%d] - TCM Ramdisk HBA Driver %s on"
 		" Generic Target Core Stack %s\n", hba->hba_id,
 		RD_HBA_VERSION, TARGET_CORE_MOD_VERSION);

 	return 0;
 }

 static void rd_detach_hba(struct se_hba *hba)
 {
 	struct rd_host *rd_host = hba->hba_ptr;

 	pr_debug("CORE_HBA[%d] - Detached Ramdisk HBA: %u from"
 		" Generic Target Core\n", hba->hba_id, rd_host->rd_host_id);

 	kfree(rd_host);
 	hba->hba_ptr = NULL;
 }

 /*	rd_release_device_space():
  *
  *
  */
 static void rd_release_device_space(struct rd_dev *rd_dev)
 {
 	u32 i, j, page_count = 0, sg_per_table;
 	struct rd_dev_sg_table *sg_table;
 	struct page *pg;
 	struct scatterlist *sg;

 	if (!rd_dev->sg_table_array || !rd_dev->sg_table_count)
 		return;

 	sg_table = rd_dev->sg_table_array;

 	for (i = 0; i < rd_dev->sg_table_count; i++) {
 		sg = sg_table[i].sg_table;
 		sg_per_table = sg_table[i].rd_sg_count;

 		for (j = 0; j < sg_per_table; j++) {
 			pg = sg_page(&sg[j]);
 			if (pg) {
 				__free_page(pg);
 				page_count++;
 			}
 		}

 		kfree(sg);
 	}

 	pr_debug("CORE_RD[%u] - Released device space for Ramdisk"
 		" Device ID: %u, pages %u in %u tables total bytes %lu\n",
 		rd_dev->rd_host->rd_host_id, rd_dev->rd_dev_id, page_count,
 		rd_dev->sg_table_count, (unsigned long)page_count * PAGE_SIZE);

 	kfree(sg_table);
 	rd_dev->sg_table_array = NULL;
 	rd_dev->sg_table_count = 0;
 }


 /*	rd_build_device_space():
  *
  *
  */
 static int rd_build_device_space(struct rd_dev *rd_dev)
 {
 	u32 i = 0, j, page_offset = 0, sg_per_table, sg_tables, total_sg_needed;
 	u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE /
 				sizeof(struct scatterlist));
 	struct rd_dev_sg_table *sg_table;
 	struct page *pg;
 	struct scatterlist *sg;

 	if (rd_dev->rd_page_count <= 0) {
 		pr_err("Illegal page count: %u for Ramdisk device\n",
 			rd_dev->rd_page_count);
 		return -EINVAL;
 	}
 	total_sg_needed = rd_dev->rd_page_count;

 	sg_tables = (total_sg_needed / max_sg_per_table) + 1;

 	sg_table = kzalloc(sg_tables * sizeof(struct rd_dev_sg_table), GFP_KERNEL);
 	if (!sg_table) {
 		pr_err("Unable to allocate memory for Ramdisk"
 			" scatterlist tables\n");
 		return -ENOMEM;
 	}

 	rd_dev->sg_table_array = sg_table;
 	rd_dev->sg_table_count = sg_tables;

 	while (total_sg_needed) {
 		sg_per_table = (total_sg_needed > max_sg_per_table) ?
 			max_sg_per_table : total_sg_needed;

 		sg = kzalloc(sg_per_table * sizeof(struct scatterlist),
 				GFP_KERNEL);
 		if (!sg) {
 			pr_err("Unable to allocate scatterlist array"
 				" for struct rd_dev\n");
 			return -ENOMEM;
 		}

 		sg_init_table(sg, sg_per_table);

 		sg_table[i].sg_table = sg;
 		sg_table[i].rd_sg_count = sg_per_table;
 		sg_table[i].page_start_offset = page_offset;
 		sg_table[i++].page_end_offset = (page_offset + sg_per_table)
 						- 1;

 		for (j = 0; j < sg_per_table; j++) {
 			pg = alloc_pages(GFP_KERNEL, 0);
 			if (!pg) {
 				pr_err("Unable to allocate scatterlist"
 					" pages for struct rd_dev_sg_table\n");
 				return -ENOMEM;
 			}
 			sg_assign_page(&sg[j], pg);
 			sg[j].length = PAGE_SIZE;
 		}

 		page_offset += sg_per_table;
 		total_sg_needed -= sg_per_table;
 	}

 	pr_debug("CORE_RD[%u] - Built Ramdisk Device ID: %u space of"
 		" %u pages in %u tables\n", rd_dev->rd_host->rd_host_id,
 		rd_dev->rd_dev_id, rd_dev->rd_page_count,
 		rd_dev->sg_table_count);

 	return 0;
 }

 static struct se_device *rd_alloc_device(struct se_hba *hba, const char *name)
 {
 	struct rd_dev *rd_dev;
 	struct rd_host *rd_host = hba->hba_ptr;

 	rd_dev = kzalloc(sizeof(struct rd_dev), GFP_KERNEL);
 	if (!rd_dev) {
 		pr_err("Unable to allocate memory for struct rd_dev\n");
 		return NULL;
 	}

 	rd_dev->rd_host = rd_host;

 	return &rd_dev->dev;
 }

 static int rd_configure_device(struct se_device *dev)
 {
 	struct rd_dev *rd_dev = RD_DEV(dev);
 	struct rd_host *rd_host = dev->se_hba->hba_ptr;
 	int ret;

 	if (!(rd_dev->rd_flags & RDF_HAS_PAGE_COUNT)) {
 		pr_debug("Missing rd_pages= parameter\n");
 		return -EINVAL;
 	}

 	ret = rd_build_device_space(rd_dev);
 	if (ret < 0)
 		goto fail;

 	dev->dev_attrib.hw_block_size = RD_BLOCKSIZE;
 	dev->dev_attrib.hw_max_sectors = UINT_MAX;
 	dev->dev_attrib.hw_queue_depth = RD_MAX_DEVICE_QUEUE_DEPTH;

 	rd_dev->rd_dev_id = rd_host->rd_host_dev_id_count++;

 	pr_debug("CORE_RD[%u] - Added TCM MEMCPY Ramdisk Device ID: %u of"
 		" %u pages in %u tables, %lu total bytes\n",
 		rd_host->rd_host_id, rd_dev->rd_dev_id, rd_dev->rd_page_count,
 		rd_dev->sg_table_count,
 		(unsigned long)(rd_dev->rd_page_count * PAGE_SIZE));

 	return 0;

 fail:
 	rd_release_device_space(rd_dev);
 	return ret;
 }

 static void rd_free_device(struct se_device *dev)
 {
 	struct rd_dev *rd_dev = RD_DEV(dev);

 	rd_release_device_space(rd_dev);
 	kfree(rd_dev);
 }

 static struct rd_dev_sg_table *rd_get_sg_table(struct rd_dev *rd_dev, u32 page)
 {
 	u32 i;
 	struct rd_dev_sg_table *sg_table;

 	for (i = 0; i < rd_dev->sg_table_count; i++) {
 		sg_table = &rd_dev->sg_table_array[i];
 		if ((sg_table->page_start_offset <= page) &&
 		    (sg_table->page_end_offset >= page))
 			return sg_table;
 	}

 	pr_err("Unable to locate struct rd_dev_sg_table for page: %u\n",
 			page);

 	return NULL;
 }

 static sense_reason_t
 rd_execute_rw(struct se_cmd *cmd)
 {
 	struct scatterlist *sgl = cmd->t_data_sg;
 	u32 sgl_nents = cmd->t_data_nents;
 	enum dma_data_direction data_direction = cmd->data_direction;
 	struct se_device *se_dev = cmd->se_dev;
 	struct rd_dev *dev = RD_DEV(se_dev);
 	struct rd_dev_sg_table *table;
 	struct scatterlist *rd_sg;
 	struct sg_mapping_iter m;
 	u32 rd_offset;
 	u32 rd_size;
 	u32 rd_page;
 	u32 src_len;
 	u64 tmp;

 	tmp = cmd->t_task_lba * se_dev->dev_attrib.block_size;
 	rd_offset = do_div(tmp, PAGE_SIZE);
 	rd_page = tmp;
 	rd_size = cmd->data_length;

 	table = rd_get_sg_table(dev, rd_page);
 	if (!table)
 		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

 	rd_sg = &table->sg_table[rd_page - table->page_start_offset];

 	pr_debug("RD[%u]: %s LBA: %llu, Size: %u Page: %u, Offset: %u\n",
 			dev->rd_dev_id,
 			data_direction == DMA_FROM_DEVICE ? "Read" : "Write",
 			cmd->t_task_lba, rd_size, rd_page, rd_offset);

 	src_len = PAGE_SIZE - rd_offset;
 	sg_miter_start(&m, sgl, sgl_nents,
 			data_direction == DMA_FROM_DEVICE ?
 				SG_MITER_TO_SG : SG_MITER_FROM_SG);
 	while (rd_size) {
 		u32 len;
 		void *rd_addr;

 		sg_miter_next(&m);
 		len = min((u32)m.length, src_len);
 		m.consumed = len;

 		rd_addr = sg_virt(rd_sg) + rd_offset;

 		if (data_direction == DMA_FROM_DEVICE)
 			memcpy(m.addr, rd_addr, len);
 		else
 			memcpy(rd_addr, m.addr, len);

 		rd_size -= len;
 		if (!rd_size)
 			continue;

 		src_len -= len;
 		if (src_len) {
 			rd_offset += len;
 			continue;
 		}

 		/* rd page completed, next one please */
 		rd_page++;
 		rd_offset = 0;
 		src_len = PAGE_SIZE;
 		if (rd_page <= table->page_end_offset) {
 			rd_sg++;
 			continue;
 		}

 		table = rd_get_sg_table(dev, rd_page);
 		if (!table) {
 			sg_miter_stop(&m);
 			return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 		}

 		/* since we increment, the first sg entry is correct */
 		rd_sg = table->sg_table;
 	}
 	sg_miter_stop(&m);

 	target_complete_cmd(cmd, SAM_STAT_GOOD);
 	return 0;
 }

 enum {
 	Opt_rd_pages, Opt_err
 };

 static match_table_t tokens = {
 	{Opt_rd_pages, "rd_pages=%d"},
 	{Opt_err, NULL}
 };

 static ssize_t rd_set_configfs_dev_params(struct se_device *dev,
 		const char *page, ssize_t count)
 {
 	struct rd_dev *rd_dev = RD_DEV(dev);
 	char *orig, *ptr, *opts;
 	substring_t args[MAX_OPT_ARGS];
 	int ret = 0, arg, 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_rd_pages:
 			match_int(args, &arg);
 			rd_dev->rd_page_count = arg;
 			pr_debug("RAMDISK: Referencing Page"
 				" Count: %u\n", rd_dev->rd_page_count);
 			rd_dev->rd_flags |= RDF_HAS_PAGE_COUNT;
 			break;
 		default:
 			break;
 		}
 	}

 	kfree(orig);
 	return (!ret) ? count : ret;
 }

 static ssize_t rd_show_configfs_dev_params(struct se_device *dev, char *b)
 {
 	struct rd_dev *rd_dev = RD_DEV(dev);

 	ssize_t bl = sprintf(b, "TCM RamDisk ID: %u  RamDisk Makeup: rd_mcp\n",
 			rd_dev->rd_dev_id);
 	bl += sprintf(b + bl, "        PAGES/PAGE_SIZE: %u*%lu"
 			"  SG_table_count: %u\n", rd_dev->rd_page_count,
 			PAGE_SIZE, rd_dev->sg_table_count);
 	return bl;
 }

 static sector_t rd_get_blocks(struct se_device *dev)
 {
 	struct rd_dev *rd_dev = RD_DEV(dev);

 	unsigned long long blocks_long = ((rd_dev->rd_page_count * PAGE_SIZE) /
 			dev->dev_attrib.block_size) - 1;

 	return blocks_long;
 }

 static struct sbc_ops rd_sbc_ops = {
 	.execute_rw		= rd_execute_rw,
 };

 static sense_reason_t
 rd_parse_cdb(struct se_cmd *cmd)
 {
 	return sbc_parse_cdb(cmd, &rd_sbc_ops);
 }

 static struct se_subsystem_api rd_mcp_template = {
 	.name			= "rd_mcp",
 	.inquiry_prod		= "RAMDISK-MCP",
 	.inquiry_rev		= RD_MCP_VERSION,
 	.transport_type		= TRANSPORT_PLUGIN_VHBA_VDEV,
 	.attach_hba		= rd_attach_hba,
 	.detach_hba		= rd_detach_hba,
 	.alloc_device		= rd_alloc_device,
 	.configure_device	= rd_configure_device,
 	.free_device		= rd_free_device,
 	.parse_cdb		= rd_parse_cdb,
 	.set_configfs_dev_params = rd_set_configfs_dev_params,
 	.show_configfs_dev_params = rd_show_configfs_dev_params,
 	.get_device_type	= sbc_get_device_type,
 	.get_blocks		= rd_get_blocks,
 };

 int __init rd_module_init(void)
 {
 	int ret;

 	ret = transport_subsystem_register(&rd_mcp_template);
 	if (ret < 0) {
 		return ret;
 	}

 	return 0;
 }

 void rd_module_exit(void)
 {
 	transport_subsystem_release(&rd_mcp_template);
 }
	/*******************************************************************************
	* Filename: target_core_rd.c
	*
	* This file contains the Storage Engine <-> Ramdisk transport
	* specific functions.
	*
	* (c) Copyright 2003-2012 RisingTide Systems LLC.
	*
	* Nicholas A. Bellinger <nab@kernel.org>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	*
	******************************************************************************/

	#include <linux/string.h>
	#include <linux/parser.h>
	#include <linux/timer.h>
	#include <linux/blkdev.h>
	#include <linux/slab.h>
	#include <linux/spinlock.h>
	#include <scsi/scsi.h>
	#include <scsi/scsi_host.h>

	#include <target/target_core_base.h>
	#include <target/target_core_backend.h>

	#include "target_core_rd.h"

	static inline struct rd_dev RD_DEV(struct se_device dev)
	{
	return container_of(dev, struct rd_dev, dev);
	}

	/* rd_attach_hba(): (Part of se_subsystem_api_t template)
	*
	*
	*/
	static int rd_attach_hba(struct se_hba *hba, u32 host_id)
	{
	struct rd_host *rd_host;

	rd_host = kzalloc(sizeof(struct rd_host), GFP_KERNEL);
	if (!rd_host) {
	pr_err("Unable to allocate memory for struct rd_host\n");
	return -ENOMEM;
	}

	rd_host->rd_host_id = host_id;

	hba->hba_ptr = rd_host;

	pr_debug("CORE_HBA[%d] - TCM Ramdisk HBA Driver %s on"
	" Generic Target Core Stack %s\n", hba->hba_id,
	RD_HBA_VERSION, TARGET_CORE_MOD_VERSION);

	return 0;
	}

	static void rd_detach_hba(struct se_hba *hba)
	{
	struct rd_host *rd_host = hba->hba_ptr;

	pr_debug("CORE_HBA[%d] - Detached Ramdisk HBA: %u from"
	" Generic Target Core\n", hba->hba_id, rd_host->rd_host_id);

	kfree(rd_host);
	hba->hba_ptr = NULL;
	}

	/* rd_release_device_space():
	*
	*
	*/
	static void rd_release_device_space(struct rd_dev *rd_dev)
	{
	u32 i, j, page_count = 0, sg_per_table;
	struct rd_dev_sg_table *sg_table;
	struct page *pg;
	struct scatterlist *sg;

	if (!rd_dev->sg_table_array \|\| !rd_dev->sg_table_count)
	return;

	sg_table = rd_dev->sg_table_array;

	for (i = 0; i < rd_dev->sg_table_count; i++) {
	sg = sg_table[i].sg_table;
	sg_per_table = sg_table[i].rd_sg_count;

	for (j = 0; j < sg_per_table; j++) {
	pg = sg_page(&sg[j]);
	if (pg) {
	__free_page(pg);
	page_count++;
	}
	}

	kfree(sg);
	}

	pr_debug("CORE_RD[%u] - Released device space for Ramdisk"
	" Device ID: %u, pages %u in %u tables total bytes %lu\n",
	rd_dev->rd_host->rd_host_id, rd_dev->rd_dev_id, page_count,
	rd_dev->sg_table_count, (unsigned long)page_count * PAGE_SIZE);

	kfree(sg_table);
	rd_dev->sg_table_array = NULL;
	rd_dev->sg_table_count = 0;
	}


	/* rd_build_device_space():
	*
	*
	*/
	static int rd_build_device_space(struct rd_dev *rd_dev)
	{
	u32 i = 0, j, page_offset = 0, sg_per_table, sg_tables, total_sg_needed;
	u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE /
	sizeof(struct scatterlist));
	struct rd_dev_sg_table *sg_table;
	struct page *pg;
	struct scatterlist *sg;

	if (rd_dev->rd_page_count <= 0) {
	pr_err("Illegal page count: %u for Ramdisk device\n",
	rd_dev->rd_page_count);
	return -EINVAL;
	}
	total_sg_needed = rd_dev->rd_page_count;

	sg_tables = (total_sg_needed / max_sg_per_table) + 1;

	sg_table = kzalloc(sg_tables * sizeof(struct rd_dev_sg_table), GFP_KERNEL);
	if (!sg_table) {
	pr_err("Unable to allocate memory for Ramdisk"
	" scatterlist tables\n");
	return -ENOMEM;
	}

	rd_dev->sg_table_array = sg_table;
	rd_dev->sg_table_count = sg_tables;

	while (total_sg_needed) {
	sg_per_table = (total_sg_needed > max_sg_per_table) ?
	max_sg_per_table : total_sg_needed;

	sg = kzalloc(sg_per_table * sizeof(struct scatterlist),
	GFP_KERNEL);
	if (!sg) {
	pr_err("Unable to allocate scatterlist array"
	" for struct rd_dev\n");
	return -ENOMEM;
	}

	sg_init_table(sg, sg_per_table);

	sg_table[i].sg_table = sg;
	sg_table[i].rd_sg_count = sg_per_table;
	sg_table[i].page_start_offset = page_offset;
	sg_table[i++].page_end_offset = (page_offset + sg_per_table)
	- 1;

	for (j = 0; j < sg_per_table; j++) {
	pg = alloc_pages(GFP_KERNEL, 0);
	if (!pg) {
	pr_err("Unable to allocate scatterlist"
	" pages for struct rd_dev_sg_table\n");
	return -ENOMEM;
	}
	sg_assign_page(&sg[j], pg);
	sg[j].length = PAGE_SIZE;
	}

	page_offset += sg_per_table;
	total_sg_needed -= sg_per_table;
	}

	pr_debug("CORE_RD[%u] - Built Ramdisk Device ID: %u space of"
	" %u pages in %u tables\n", rd_dev->rd_host->rd_host_id,
	rd_dev->rd_dev_id, rd_dev->rd_page_count,
	rd_dev->sg_table_count);

	return 0;
	}

	static struct se_device rd_alloc_device(struct se_hba hba, const char *name)
	{
	struct rd_dev *rd_dev;
	struct rd_host *rd_host = hba->hba_ptr;

	rd_dev = kzalloc(sizeof(struct rd_dev), GFP_KERNEL);
	if (!rd_dev) {
	pr_err("Unable to allocate memory for struct rd_dev\n");
	return NULL;
	}

	rd_dev->rd_host = rd_host;

	return &rd_dev->dev;
	}

	static int rd_configure_device(struct se_device *dev)
	{
	struct rd_dev *rd_dev = RD_DEV(dev);
	struct rd_host *rd_host = dev->se_hba->hba_ptr;
	int ret;

	if (!(rd_dev->rd_flags & RDF_HAS_PAGE_COUNT)) {
	pr_debug("Missing rd_pages= parameter\n");
	return -EINVAL;
	}

	ret = rd_build_device_space(rd_dev);
	if (ret < 0)
	goto fail;

	dev->dev_attrib.hw_block_size = RD_BLOCKSIZE;
	dev->dev_attrib.hw_max_sectors = UINT_MAX;
	dev->dev_attrib.hw_queue_depth = RD_MAX_DEVICE_QUEUE_DEPTH;

	rd_dev->rd_dev_id = rd_host->rd_host_dev_id_count++;

	pr_debug("CORE_RD[%u] - Added TCM MEMCPY Ramdisk Device ID: %u of"
	" %u pages in %u tables, %lu total bytes\n",
	rd_host->rd_host_id, rd_dev->rd_dev_id, rd_dev->rd_page_count,
	rd_dev->sg_table_count,
	(unsigned long)(rd_dev->rd_page_count * PAGE_SIZE));

	return 0;

	fail:
	rd_release_device_space(rd_dev);
	return ret;
	}

	static void rd_free_device(struct se_device *dev)
	{
	struct rd_dev *rd_dev = RD_DEV(dev);

	rd_release_device_space(rd_dev);
	kfree(rd_dev);
	}

	static struct rd_dev_sg_table rd_get_sg_table(struct rd_dev rd_dev, u32 page)
	{
	u32 i;
	struct rd_dev_sg_table *sg_table;

	for (i = 0; i < rd_dev->sg_table_count; i++) {
	sg_table = &rd_dev->sg_table_array[i];
	if ((sg_table->page_start_offset <= page) &&
	(sg_table->page_end_offset >= page))
	return sg_table;
	}

	pr_err("Unable to locate struct rd_dev_sg_table for page: %u\n",
	page);

	return NULL;
	}

	static sense_reason_t
	rd_execute_rw(struct se_cmd *cmd)
	{
	struct scatterlist *sgl = cmd->t_data_sg;
	u32 sgl_nents = cmd->t_data_nents;
	enum dma_data_direction data_direction = cmd->data_direction;
	struct se_device *se_dev = cmd->se_dev;
	struct rd_dev *dev = RD_DEV(se_dev);
	struct rd_dev_sg_table *table;
	struct scatterlist *rd_sg;
	struct sg_mapping_iter m;
	u32 rd_offset;
	u32 rd_size;
	u32 rd_page;
	u32 src_len;
	u64 tmp;

	tmp = cmd->t_task_lba * se_dev->dev_attrib.block_size;
	rd_offset = do_div(tmp, PAGE_SIZE);
	rd_page = tmp;
	rd_size = cmd->data_length;

	table = rd_get_sg_table(dev, rd_page);
	if (!table)
	return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	rd_sg = &table->sg_table[rd_page - table->page_start_offset];

	pr_debug("RD[%u]: %s LBA: %llu, Size: %u Page: %u, Offset: %u\n",
	dev->rd_dev_id,
	data_direction == DMA_FROM_DEVICE ? "Read" : "Write",
	cmd->t_task_lba, rd_size, rd_page, rd_offset);

	src_len = PAGE_SIZE - rd_offset;
	sg_miter_start(&m, sgl, sgl_nents,
	data_direction == DMA_FROM_DEVICE ?
	SG_MITER_TO_SG : SG_MITER_FROM_SG);
	while (rd_size) {
	u32 len;
	void *rd_addr;

	sg_miter_next(&m);
	len = min((u32)m.length, src_len);
	m.consumed = len;

	rd_addr = sg_virt(rd_sg) + rd_offset;

	if (data_direction == DMA_FROM_DEVICE)
	memcpy(m.addr, rd_addr, len);
	else
	memcpy(rd_addr, m.addr, len);

	rd_size -= len;
	if (!rd_size)
	continue;

	src_len -= len;
	if (src_len) {
	rd_offset += len;
	continue;
	}

	/* rd page completed, next one please */
	rd_page++;
	rd_offset = 0;
	src_len = PAGE_SIZE;
	if (rd_page <= table->page_end_offset) {
	rd_sg++;
	continue;
	}

	table = rd_get_sg_table(dev, rd_page);
	if (!table) {
	sg_miter_stop(&m);
	return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
	}

	/* since we increment, the first sg entry is correct */
	rd_sg = table->sg_table;
	}
	sg_miter_stop(&m);

	target_complete_cmd(cmd, SAM_STAT_GOOD);
	return 0;
	}

	enum {
	Opt_rd_pages, Opt_err
	};

	static match_table_t tokens = {
	{Opt_rd_pages, "rd_pages=%d"},
	{Opt_err, NULL}
	};

	static ssize_t rd_set_configfs_dev_params(struct se_device *dev,
	const char *page, ssize_t count)
	{
	struct rd_dev *rd_dev = RD_DEV(dev);
	char orig, ptr, *opts;
	substring_t args[MAX_OPT_ARGS];
	int ret = 0, arg, 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_rd_pages:
	match_int(args, &arg);
	rd_dev->rd_page_count = arg;
	pr_debug("RAMDISK: Referencing Page"
	" Count: %u\n", rd_dev->rd_page_count);
	rd_dev->rd_flags \|= RDF_HAS_PAGE_COUNT;
	break;
	default:
	break;
	}
	}

	kfree(orig);
	return (!ret) ? count : ret;
	}

	static ssize_t rd_show_configfs_dev_params(struct se_device dev, char b)
	{
	struct rd_dev *rd_dev = RD_DEV(dev);

	ssize_t bl = sprintf(b, "TCM RamDisk ID: %u RamDisk Makeup: rd_mcp\n",
	rd_dev->rd_dev_id);
	bl += sprintf(b + bl, " PAGES/PAGE_SIZE: %u*%lu"
	" SG_table_count: %u\n", rd_dev->rd_page_count,
	PAGE_SIZE, rd_dev->sg_table_count);
	return bl;
	}

	static sector_t rd_get_blocks(struct se_device *dev)
	{
	struct rd_dev *rd_dev = RD_DEV(dev);

	unsigned long long blocks_long = ((rd_dev->rd_page_count * PAGE_SIZE) /
	dev->dev_attrib.block_size) - 1;

	return blocks_long;
	}

	static struct sbc_ops rd_sbc_ops = {
	.execute_rw = rd_execute_rw,
	};

	static sense_reason_t
	rd_parse_cdb(struct se_cmd *cmd)
	{
	return sbc_parse_cdb(cmd, &rd_sbc_ops);
	}

	static struct se_subsystem_api rd_mcp_template = {
	.name = "rd_mcp",
	.inquiry_prod = "RAMDISK-MCP",
	.inquiry_rev = RD_MCP_VERSION,
	.transport_type = TRANSPORT_PLUGIN_VHBA_VDEV,
	.attach_hba = rd_attach_hba,
	.detach_hba = rd_detach_hba,
	.alloc_device = rd_alloc_device,
	.configure_device = rd_configure_device,
	.free_device = rd_free_device,
	.parse_cdb = rd_parse_cdb,
	.set_configfs_dev_params = rd_set_configfs_dev_params,
	.show_configfs_dev_params = rd_show_configfs_dev_params,
	.get_device_type = sbc_get_device_type,
	.get_blocks = rd_get_blocks,
	};

	int __init rd_module_init(void)
	{
	int ret;

	ret = transport_subsystem_register(&rd_mcp_template);
	if (ret < 0) {
	return ret;
	}

	return 0;
	}

	void rd_module_exit(void)
	{
	transport_subsystem_release(&rd_mcp_template);
	}