123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591592593594595596597598599600601602603604605606607608609610611612613614615616617618619620621622623624625626627628629630631632633634635636637638639640641642643644645646647648649650651652653654655656657658659660661662663664665666667668669670671672673674675676677678679680681682683684685686687688689690691692693694695696697698699700701702703704705706707708709710711712713714715716717718719720721722723724725726727728729730731732733734735736737738739740741742743744745746747748749750751752753754755756757758759760761762763764765766767768769770771772773774775776777778779780781782783784785786787788789790791792793794795796797798799800801802803804805806807808809810811812813814815816817818819820821822823824825826827828829830831832833834835836837838839840841842843844845846847848849850851852853854855856857858859860861862863864865866867868869870871872873874875876877878879880881882883884885886887888889890891892893894/*******************************************************************************
 * Filename:  target_core_iblock.c
 *
 * This file contains the Storage Engine  <-> Linux BlockIO transport
 * specific functions.
 *
 * (c) Copyright 2003-2013 Datera, Inc.
 *
 * 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/fs.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/bio.h>
#include <linux/genhd.h>
#include <linux/file.h>
#include <linux/module.h>
#include <scsi/scsi_proto.h>
#include <asm/unaligned.h>

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

#include "target_core_iblock.h"

#define IBLOCK_MAX_BIO_PER_TASK	 32	/* max # of bios to submit at a time */
#define IBLOCK_BIO_POOL_SIZE	128

static inline struct iblock_dev *IBLOCK_DEV(struct se_device *dev)
{
	return container_of(dev, struct iblock_dev, dev);
}


static int iblock_attach_hba(struct se_hba *hba, u32 host_id)
{
	pr_debug("CORE_HBA[%d] - TCM iBlock HBA Driver %s on"
		" Generic Target Core Stack %s\n", hba->hba_id,
		IBLOCK_VERSION, TARGET_CORE_VERSION);
	return 0;
}

static void iblock_detach_hba(struct se_hba *hba)
{
}

static struct se_device *iblock_alloc_device(struct se_hba *hba, const char *name)
{
	struct iblock_dev *ib_dev = NULL;

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

	pr_debug( "IBLOCK: Allocated ib_dev for %s\n", name);

	return &ib_dev->dev;
}

static int iblock_configure_device(struct se_device *dev)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct request_queue *q;
	struct block_device *bd = NULL;
	struct blk_integrity *bi;
	fmode_t mode;
	unsigned int max_write_zeroes_sectors;
	int ret = -ENOMEM;

	if (!(ib_dev->ibd_flags & IBDF_HAS_UDEV_PATH)) {
		pr_err("Missing udev_path= parameters for IBLOCK\n");
		return -EINVAL;
	}

	ib_dev->ibd_bio_set = bioset_create(IBLOCK_BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
	if (!ib_dev->ibd_bio_set) {
		pr_err("IBLOCK: Unable to create bioset\n");
		goto out;
	}

	pr_debug( "IBLOCK: Claiming struct block_device: %s\n",
			ib_dev->ibd_udev_path);

	mode = FMODE_READ|FMODE_EXCL;
	if (!ib_dev->ibd_readonly)
		mode |= FMODE_WRITE;
	else
		dev->dev_flags |= DF_READ_ONLY;

	bd = blkdev_get_by_path(ib_dev->ibd_udev_path, mode, ib_dev);
	if (IS_ERR(bd)) {
		ret = PTR_ERR(bd);
		goto out_free_bioset;
	}
	ib_dev->ibd_bd = bd;

	q = bdev_get_queue(bd);

	dev->dev_attrib.hw_block_size = bdev_logical_block_size(bd);
	dev->dev_attrib.hw_max_sectors = queue_max_hw_sectors(q);
	dev->dev_attrib.hw_queue_depth = q->nr_requests;

	if (target_configure_unmap_from_queue(&dev->dev_attrib, q))
		pr_debug("IBLOCK: BLOCK Discard support available,"
			 " disabled by default\n");

	/*
	 * Enable write same emulation for IBLOCK and use 0xFFFF as
	 * the smaller WRITE_SAME(10) only has a two-byte block count.
	 */
	max_write_zeroes_sectors = bdev_write_zeroes_sectors(bd);
	if (max_write_zeroes_sectors)
		dev->dev_attrib.max_write_same_len = max_write_zeroes_sectors;
	else
		dev->dev_attrib.max_write_same_len = 0xFFFF;

	if (blk_queue_nonrot(q))
		dev->dev_attrib.is_nonrot = 1;

	bi = bdev_get_integrity(bd);
	if (bi) {
		struct bio_set *bs = ib_dev->ibd_bio_set;

		if (!strcmp(bi->profile->name, "T10-DIF-TYPE3-IP") ||
		    !strcmp(bi->profile->name, "T10-DIF-TYPE1-IP")) {
			pr_err("IBLOCK export of blk_integrity: %s not"
			       " supported\n", bi->profile->name);
			ret = -ENOSYS;
			goto out_blkdev_put;
		}

		if (!strcmp(bi->profile->name, "T10-DIF-TYPE3-CRC")) {
			dev->dev_attrib.pi_prot_type = TARGET_DIF_TYPE3_PROT;
		} else if (!strcmp(bi->profile->name, "T10-DIF-TYPE1-CRC")) {
			dev->dev_attrib.pi_prot_type = TARGET_DIF_TYPE1_PROT;
		}

		if (dev->dev_attrib.pi_prot_type) {
			if (bioset_integrity_create(bs, IBLOCK_BIO_POOL_SIZE) < 0) {
				pr_err("Unable to allocate bioset for PI\n");
				ret = -ENOMEM;
				goto out_blkdev_put;
			}
			pr_debug("IBLOCK setup BIP bs->bio_integrity_pool: %p\n",
				 bs->bio_integrity_pool);
		}
		dev->dev_attrib.hw_pi_prot_type = dev->dev_attrib.pi_prot_type;
	}

	return 0;

out_blkdev_put:
	blkdev_put(ib_dev->ibd_bd, FMODE_WRITE|FMODE_READ|FMODE_EXCL);
out_free_bioset:
	bioset_free(ib_dev->ibd_bio_set);
	ib_dev->ibd_bio_set = NULL;
out:
	return ret;
}

static void iblock_dev_call_rcu(struct rcu_head *p)
{
	struct se_device *dev = container_of(p, struct se_device, rcu_head);
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);

	kfree(ib_dev);
}

static void iblock_free_device(struct se_device *dev)
{
	call_rcu(&dev->rcu_head, iblock_dev_call_rcu);
}

static void iblock_destroy_device(struct se_device *dev)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);

	if (ib_dev->ibd_bd != NULL)
		blkdev_put(ib_dev->ibd_bd, FMODE_WRITE|FMODE_READ|FMODE_EXCL);
	if (ib_dev->ibd_bio_set != NULL)
		bioset_free(ib_dev->ibd_bio_set);
}

static unsigned long long iblock_emulate_read_cap_with_block_size(
	struct se_device *dev,
	struct block_device *bd,
	struct request_queue *q)
{
	unsigned long long blocks_long = (div_u64(i_size_read(bd->bd_inode),
					bdev_logical_block_size(bd)) - 1);
	u32 block_size = bdev_logical_block_size(bd);

	if (block_size == dev->dev_attrib.block_size)
		return blocks_long;

	switch (block_size) {
	case 4096:
		switch (dev->dev_attrib.block_size) {
		case 2048:
			blocks_long <<= 1;
			break;
		case 1024:
			blocks_long <<= 2;
			break;
		case 512:
			blocks_long <<= 3;
		default:
			break;
		}
		break;
	case 2048:
		switch (dev->dev_attrib.block_size) {
		case 4096:
			blocks_long >>= 1;
			break;
		case 1024:
			blocks_long <<= 1;
			break;
		case 512:
			blocks_long <<= 2;
			break;
		default:
			break;
		}
		break;
	case 1024:
		switch (dev->dev_attrib.block_size) {
		case 4096:
			blocks_long >>= 2;
			break;
		case 2048:
			blocks_long >>= 1;
			break;
		case 512:
			blocks_long <<= 1;
			break;
		default:
			break;
		}
		break;
	case 512:
		switch (dev->dev_attrib.block_size) {
		case 4096:
			blocks_long >>= 3;
			break;
		case 2048:
			blocks_long >>= 2;
			break;
		case 1024:
			blocks_long >>= 1;
			break;
		default:
			break;
		}
		break;
	default:
		break;
	}

	return blocks_long;
}

static void iblock_complete_cmd(struct se_cmd *cmd)
{
	struct iblock_req *ibr = cmd->priv;
	u8 status;

	if (!refcount_dec_and_test(&ibr->pending))
		return;

	if (atomic_read(&ibr->ib_bio_err_cnt))
		status = SAM_STAT_CHECK_CONDITION;
	else
		status = SAM_STAT_GOOD;

	target_complete_cmd(cmd, status);
	kfree(ibr);
}

static void iblock_bio_done(struct bio *bio)
{
	struct se_cmd *cmd = bio->bi_private;
	struct iblock_req *ibr = cmd->priv;

	if (bio->bi_status) {
		pr_err("bio error: %p,  err: %d\n", bio, bio->bi_status);
		/*
		 * Bump the ib_bio_err_cnt and release bio.
		 */
		atomic_inc(&ibr->ib_bio_err_cnt);
		smp_mb__after_atomic();
	}

	bio_put(bio);

	iblock_complete_cmd(cmd);
}

static struct bio *
iblock_get_bio(struct se_cmd *cmd, sector_t lba, u32 sg_num, int op,
	       int op_flags)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(cmd->se_dev);
	struct bio *bio;

	/*
	 * Only allocate as many vector entries as the bio code allows us to,
	 * we'll loop later on until we have handled the whole request.
	 */
	if (sg_num > BIO_MAX_PAGES)
		sg_num = BIO_MAX_PAGES;

	bio = bio_alloc_bioset(GFP_NOIO, sg_num, ib_dev->ibd_bio_set);
	if (!bio) {
		pr_err("Unable to allocate memory for bio\n");
		return NULL;
	}

	bio_set_dev(bio, ib_dev->ibd_bd);
	bio->bi_private = cmd;
	bio->bi_end_io = &iblock_bio_done;
	bio->bi_iter.bi_sector = lba;
	bio_set_op_attrs(bio, op, op_flags);

	return bio;
}

static void iblock_submit_bios(struct bio_list *list)
{
	struct blk_plug plug;
	struct bio *bio;

	blk_start_plug(&plug);
	while ((bio = bio_list_pop(list)))
		submit_bio(bio);
	blk_finish_plug(&plug);
}

static void iblock_end_io_flush(struct bio *bio)
{
	struct se_cmd *cmd = bio->bi_private;

	if (bio->bi_status)
		pr_err("IBLOCK: cache flush failed: %d\n", bio->bi_status);

	if (cmd) {
		if (bio->bi_status)
			target_complete_cmd(cmd, SAM_STAT_CHECK_CONDITION);
		else
			target_complete_cmd(cmd, SAM_STAT_GOOD);
	}

	bio_put(bio);
}

/*
 * Implement SYCHRONIZE CACHE.  Note that we can't handle lba ranges and must
 * always flush the whole cache.
 */
static sense_reason_t
iblock_execute_sync_cache(struct se_cmd *cmd)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(cmd->se_dev);
	int immed = (cmd->t_task_cdb[1] & 0x2);
	struct bio *bio;

	/*
	 * If the Immediate bit is set, queue up the GOOD response
	 * for this SYNCHRONIZE_CACHE op.
	 */
	if (immed)
		target_complete_cmd(cmd, SAM_STAT_GOOD);

	bio = bio_alloc(GFP_KERNEL, 0);
	bio->bi_end_io = iblock_end_io_flush;
	bio_set_dev(bio, ib_dev->ibd_bd);
	bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
	if (!immed)
		bio->bi_private = cmd;
	submit_bio(bio);
	return 0;
}

static sense_reason_t
iblock_execute_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
{
	struct block_device *bdev = IBLOCK_DEV(cmd->se_dev)->ibd_bd;
	struct se_device *dev = cmd->se_dev;
	int ret;

	ret = blkdev_issue_discard(bdev,
				   target_to_linux_sector(dev, lba),
				   target_to_linux_sector(dev,  nolb),
				   GFP_KERNEL, 0);
	if (ret < 0) {
		pr_err("blkdev_issue_discard() failed: %d\n", ret);
		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
	}

	return 0;
}

static sense_reason_t
iblock_execute_zero_out(struct block_device *bdev, struct se_cmd *cmd)
{
	struct se_device *dev = cmd->se_dev;
	struct scatterlist *sg = &cmd->t_data_sg[0];
	unsigned char *buf, zero = 0x00, *p = &zero;
	int rc, ret;

	buf = kmap(sg_page(sg)) + sg->offset;
	if (!buf)
		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
	/*
	 * Fall back to block_execute_write_same() slow-path if
	 * incoming WRITE_SAME payload does not contain zeros.
	 */
	rc = memcmp(buf, p, cmd->data_length);
	kunmap(sg_page(sg));

	if (rc)
		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	ret = blkdev_issue_zeroout(bdev,
				target_to_linux_sector(dev, cmd->t_task_lba),
				target_to_linux_sector(dev,
					sbc_get_write_same_sectors(cmd)),
				GFP_KERNEL, false);
	if (ret)
		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	target_complete_cmd(cmd, GOOD);
	return 0;
}

static sense_reason_t
iblock_execute_write_same(struct se_cmd *cmd)
{
	struct block_device *bdev = IBLOCK_DEV(cmd->se_dev)->ibd_bd;
	struct iblock_req *ibr;
	struct scatterlist *sg;
	struct bio *bio;
	struct bio_list list;
	struct se_device *dev = cmd->se_dev;
	sector_t block_lba = target_to_linux_sector(dev, cmd->t_task_lba);
	sector_t sectors = target_to_linux_sector(dev,
					sbc_get_write_same_sectors(cmd));

	if (cmd->prot_op) {
		pr_err("WRITE_SAME: Protection information with IBLOCK"
		       " backends not supported\n");
		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
	}
	sg = &cmd->t_data_sg[0];

	if (cmd->t_data_nents > 1 ||
	    sg->length != cmd->se_dev->dev_attrib.block_size) {
		pr_err("WRITE_SAME: Illegal SGL t_data_nents: %u length: %u"
			" block_size: %u\n", cmd->t_data_nents, sg->length,
			cmd->se_dev->dev_attrib.block_size);
		return TCM_INVALID_CDB_FIELD;
	}

	if (bdev_write_zeroes_sectors(bdev)) {
		if (!iblock_execute_zero_out(bdev, cmd))
			return 0;
	}

	ibr = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);
	if (!ibr)
		goto fail;
	cmd->priv = ibr;

	bio = iblock_get_bio(cmd, block_lba, 1, REQ_OP_WRITE, 0);
	if (!bio)
		goto fail_free_ibr;

	bio_list_init(&list);
	bio_list_add(&list, bio);

	refcount_set(&ibr->pending, 1);

	while (sectors) {
		while (bio_add_page(bio, sg_page(sg), sg->length, sg->offset)
				!= sg->length) {

			bio = iblock_get_bio(cmd, block_lba, 1, REQ_OP_WRITE,
					     0);
			if (!bio)
				goto fail_put_bios;

			refcount_inc(&ibr->pending);
			bio_list_add(&list, bio);
		}

		/* Always in 512 byte units for Linux/Block */
		block_lba += sg->length >> IBLOCK_LBA_SHIFT;
		sectors -= 1;
	}

	iblock_submit_bios(&list);
	return 0;

fail_put_bios:
	while ((bio = bio_list_pop(&list)))
		bio_put(bio);
fail_free_ibr:
	kfree(ibr);
fail:
	return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
}

enum {
	Opt_udev_path, Opt_readonly, Opt_force, Opt_err
};

static match_table_t tokens = {
	{Opt_udev_path, "udev_path=%s"},
	{Opt_readonly, "readonly=%d"},
	{Opt_force, "force=%d"},
	{Opt_err, NULL}
};

static ssize_t iblock_set_configfs_dev_params(struct se_device *dev,
		const char *page, ssize_t count)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	char *orig, *ptr, *arg_p, *opts;
	substring_t args[MAX_OPT_ARGS];
	int ret = 0, token;
	unsigned long tmp_readonly;

	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_udev_path:
			if (ib_dev->ibd_bd) {
				pr_err("Unable to set udev_path= while"
					" ib_dev->ibd_bd exists\n");
				ret = -EEXIST;
				goto out;
			}
			if (match_strlcpy(ib_dev->ibd_udev_path, &args[0],
				SE_UDEV_PATH_LEN) == 0) {
				ret = -EINVAL;
				break;
			}
			pr_debug("IBLOCK: Referencing UDEV path: %s\n",
					ib_dev->ibd_udev_path);
			ib_dev->ibd_flags |= IBDF_HAS_UDEV_PATH;
			break;
		case Opt_readonly:
			arg_p = match_strdup(&args[0]);
			if (!arg_p) {
				ret = -ENOMEM;
				break;
			}
			ret = kstrtoul(arg_p, 0, &tmp_readonly);
			kfree(arg_p);
			if (ret < 0) {
				pr_err("kstrtoul() failed for"
						" readonly=\n");
				goto out;
			}
			ib_dev->ibd_readonly = tmp_readonly;
			pr_debug("IBLOCK: readonly: %d\n", ib_dev->ibd_readonly);
			break;
		case Opt_force:
			break;
		default:
			break;
		}
	}

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

static ssize_t iblock_show_configfs_dev_params(struct se_device *dev, char *b)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct block_device *bd = ib_dev->ibd_bd;
	char buf[BDEVNAME_SIZE];
	ssize_t bl = 0;

	if (bd)
		bl += sprintf(b + bl, "iBlock device: %s",
				bdevname(bd, buf));
	if (ib_dev->ibd_flags & IBDF_HAS_UDEV_PATH)
		bl += sprintf(b + bl, "  UDEV PATH: %s",
				ib_dev->ibd_udev_path);
	bl += sprintf(b + bl, "  readonly: %d\n", ib_dev->ibd_readonly);

	bl += sprintf(b + bl, "        ");
	if (bd) {
		bl += sprintf(b + bl, "Major: %d Minor: %d  %s\n",
			MAJOR(bd->bd_dev), MINOR(bd->bd_dev), (!bd->bd_contains) ?
			"" : (bd->bd_holder == ib_dev) ?
			"CLAIMED: IBLOCK" : "CLAIMED: OS");
	} else {
		bl += sprintf(b + bl, "Major: 0 Minor: 0\n");
	}

	return bl;
}

static int
iblock_alloc_bip(struct se_cmd *cmd, struct bio *bio)
{
	struct se_device *dev = cmd->se_dev;
	struct blk_integrity *bi;
	struct bio_integrity_payload *bip;
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct scatterlist *sg;
	int i, rc;

	bi = bdev_get_integrity(ib_dev->ibd_bd);
	if (!bi) {
		pr_err("Unable to locate bio_integrity\n");
		return -ENODEV;
	}

	bip = bio_integrity_alloc(bio, GFP_NOIO, cmd->t_prot_nents);
	if (IS_ERR(bip)) {
		pr_err("Unable to allocate bio_integrity_payload\n");
		return PTR_ERR(bip);
	}

	bip->bip_iter.bi_size = (cmd->data_length / dev->dev_attrib.block_size) *
			 dev->prot_length;
	bip->bip_iter.bi_sector = bio->bi_iter.bi_sector;

	pr_debug("IBLOCK BIP Size: %u Sector: %llu\n", bip->bip_iter.bi_size,
		 (unsigned long long)bip->bip_iter.bi_sector);

	for_each_sg(cmd->t_prot_sg, sg, cmd->t_prot_nents, i) {

		rc = bio_integrity_add_page(bio, sg_page(sg), sg->length,
					    sg->offset);
		if (rc != sg->length) {
			pr_err("bio_integrity_add_page() failed; %d\n", rc);
			return -ENOMEM;
		}

		pr_debug("Added bio integrity page: %p length: %d offset; %d\n",
			 sg_page(sg), sg->length, sg->offset);
	}

	return 0;
}

static sense_reason_t
iblock_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
		  enum dma_data_direction data_direction)
{
	struct se_device *dev = cmd->se_dev;
	sector_t block_lba = target_to_linux_sector(dev, cmd->t_task_lba);
	struct iblock_req *ibr;
	struct bio *bio, *bio_start;
	struct bio_list list;
	struct scatterlist *sg;
	u32 sg_num = sgl_nents;
	unsigned bio_cnt;
	int i, op, op_flags = 0;

	if (data_direction == DMA_TO_DEVICE) {
		struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
		struct request_queue *q = bdev_get_queue(ib_dev->ibd_bd);
		/*
		 * Force writethrough using REQ_FUA if a volatile write cache
		 * is not enabled, or if initiator set the Force Unit Access bit.
		 */
		op = REQ_OP_WRITE;
		if (test_bit(QUEUE_FLAG_FUA, &q->queue_flags)) {
			if (cmd->se_cmd_flags & SCF_FUA)
				op_flags = REQ_FUA;
			else if (!test_bit(QUEUE_FLAG_WC, &q->queue_flags))
				op_flags = REQ_FUA;
		}
	} else {
		op = REQ_OP_READ;
	}

	ibr = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);
	if (!ibr)
		goto fail;
	cmd->priv = ibr;

	if (!sgl_nents) {
		refcount_set(&ibr->pending, 1);
		iblock_complete_cmd(cmd);
		return 0;
	}

	bio = iblock_get_bio(cmd, block_lba, sgl_nents, op, op_flags);
	if (!bio)
		goto fail_free_ibr;

	bio_start = bio;
	bio_list_init(&list);
	bio_list_add(&list, bio);

	refcount_set(&ibr->pending, 2);
	bio_cnt = 1;

	for_each_sg(sgl, sg, sgl_nents, i) {
		/*
		 * XXX: if the length the device accepts is shorter than the
		 *	length of the S/G list entry this will cause and
		 *	endless loop.  Better hope no driver uses huge pages.
		 */
		while (bio_add_page(bio, sg_page(sg), sg->length, sg->offset)
				!= sg->length) {
			if (bio_cnt >= IBLOCK_MAX_BIO_PER_TASK) {
				iblock_submit_bios(&list);
				bio_cnt = 0;
			}

			bio = iblock_get_bio(cmd, block_lba, sg_num, op,
					     op_flags);
			if (!bio)
				goto fail_put_bios;

			refcount_inc(&ibr->pending);
			bio_list_add(&list, bio);
			bio_cnt++;
		}

		/* Always in 512 byte units for Linux/Block */
		block_lba += sg->length >> IBLOCK_LBA_SHIFT;
		sg_num--;
	}

	if (cmd->prot_type && dev->dev_attrib.pi_prot_type) {
		int rc = iblock_alloc_bip(cmd, bio_start);
		if (rc)
			goto fail_put_bios;
	}

	iblock_submit_bios(&list);
	iblock_complete_cmd(cmd);
	return 0;

fail_put_bios:
	while ((bio = bio_list_pop(&list)))
		bio_put(bio);
fail_free_ibr:
	kfree(ibr);
fail:
	return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
}

static sector_t iblock_get_blocks(struct se_device *dev)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct block_device *bd = ib_dev->ibd_bd;
	struct request_queue *q = bdev_get_queue(bd);

	return iblock_emulate_read_cap_with_block_size(dev, bd, q);
}

static sector_t iblock_get_alignment_offset_lbas(struct se_device *dev)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct block_device *bd = ib_dev->ibd_bd;
	int ret;

	ret = bdev_alignment_offset(bd);
	if (ret == -1)
		return 0;

	/* convert offset-bytes to offset-lbas */
	return ret / bdev_logical_block_size(bd);
}

static unsigned int iblock_get_lbppbe(struct se_device *dev)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct block_device *bd = ib_dev->ibd_bd;
	int logs_per_phys = bdev_physical_block_size(bd) / bdev_logical_block_size(bd);

	return ilog2(logs_per_phys);
}

static unsigned int iblock_get_io_min(struct se_device *dev)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct block_device *bd = ib_dev->ibd_bd;

	return bdev_io_min(bd);
}

static unsigned int iblock_get_io_opt(struct se_device *dev)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct block_device *bd = ib_dev->ibd_bd;

	return bdev_io_opt(bd);
}

static struct sbc_ops iblock_sbc_ops = {
	.execute_rw		= iblock_execute_rw,
	.execute_sync_cache	= iblock_execute_sync_cache,
	.execute_write_same	= iblock_execute_write_same,
	.execute_unmap		= iblock_execute_unmap,
};

static sense_reason_t
iblock_parse_cdb(struct se_cmd *cmd)
{
	return sbc_parse_cdb(cmd, &iblock_sbc_ops);
}

static bool iblock_get_write_cache(struct se_device *dev)
{
	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
	struct block_device *bd = ib_dev->ibd_bd;
	struct request_queue *q = bdev_get_queue(bd);

	return test_bit(QUEUE_FLAG_WC, &q->queue_flags);
}

static const struct target_backend_ops iblock_ops = {
	.name			= "iblock",
	.inquiry_prod		= "IBLOCK",
	.inquiry_rev		= IBLOCK_VERSION,
	.owner			= THIS_MODULE,
	.attach_hba		= iblock_attach_hba,
	.detach_hba		= iblock_detach_hba,
	.alloc_device		= iblock_alloc_device,
	.configure_device	= iblock_configure_device,
	.destroy_device		= iblock_destroy_device,
	.free_device		= iblock_free_device,
	.parse_cdb		= iblock_parse_cdb,
	.set_configfs_dev_params = iblock_set_configfs_dev_params,
	.show_configfs_dev_params = iblock_show_configfs_dev_params,
	.get_device_type	= sbc_get_device_type,
	.get_blocks		= iblock_get_blocks,
	.get_alignment_offset_lbas = iblock_get_alignment_offset_lbas,
	.get_lbppbe		= iblock_get_lbppbe,
	.get_io_min		= iblock_get_io_min,
	.get_io_opt		= iblock_get_io_opt,
	.get_write_cache	= iblock_get_write_cache,
	.tb_dev_attrib_attrs	= sbc_attrib_attrs,
};

static int __init iblock_module_init(void)
{
	return transport_backend_register(&iblock_ops);
}

static void __exit iblock_module_exit(void)
{
	target_backend_unregister(&iblock_ops);
}

MODULE_DESCRIPTION("TCM IBLOCK subsystem plugin");
MODULE_AUTHOR("nab@Linux-iSCSI.org");
MODULE_LICENSE("GPL");

module_init(iblock_module_init);
module_exit