/*******************************************************************************
   * Filename:  target_core_iblock.c
   *
   * This file contains the Storage Engine  <-> Linux BlockIO transport
   * specific functions.
   *
   * Copyright (c) 2003, 2004, 2005 PyX Technologies, Inc.
   * Copyright (c) 2005, 2006, 2007 SBE, Inc.
   * Copyright (c) 2007-2010 Rising Tide Systems
   * Copyright (c) 2008-2010 Linux-iSCSI.org
   *
   * 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.h>
  #include <scsi/scsi_host.h>
  
  #include <target/target_core_base.h>
  #include <target/target_core_device.h>
  #include <target/target_core_transport.h>
  
  #include "target_core_iblock.h"

  static struct se_subsystem_api iblock_template;
  
  static void iblock_bio_done(struct bio *, int);
  
  /*	iblock_attach_hba(): (Part of se_subsystem_api_t template)
   *
   *
   */
  static int iblock_attach_hba(struct se_hba *hba, u32 host_id)
  {
  	struct iblock_hba *ib_host;
  
  	ib_host = kzalloc(sizeof(struct iblock_hba), GFP_KERNEL);

  	if (!ib_host) {
  		pr_err("Unable to allocate memory for"

  				" struct iblock_hba
  ");
  		return -ENOMEM;
  	}
  
  	ib_host->iblock_host_id = host_id;

  	hba->hba_ptr = ib_host;

  	pr_debug("CORE_HBA[%d] - TCM iBlock HBA Driver %s on"

  		" Generic Target Core Stack %s
  ", hba->hba_id,
  		IBLOCK_VERSION, TARGET_CORE_MOD_VERSION);

  	pr_debug("CORE_HBA[%d] - Attached iBlock HBA: %u to Generic
  ",

  		hba->hba_id, ib_host->iblock_host_id);

  
  	return 0;
  }
  
  static void iblock_detach_hba(struct se_hba *hba)
  {
  	struct iblock_hba *ib_host = hba->hba_ptr;

  	pr_debug("CORE_HBA[%d] - Detached iBlock HBA: %u from Generic"

  		" Target Core
  ", hba->hba_id, ib_host->iblock_host_id);
  
  	kfree(ib_host);
  	hba->hba_ptr = NULL;
  }
  
  static void *iblock_allocate_virtdevice(struct se_hba *hba, const char *name)
  {
  	struct iblock_dev *ib_dev = NULL;
  	struct iblock_hba *ib_host = hba->hba_ptr;
  
  	ib_dev = kzalloc(sizeof(struct iblock_dev), GFP_KERNEL);

  	if (!ib_dev) {
  		pr_err("Unable to allocate struct iblock_dev
  ");

  		return NULL;
  	}
  	ib_dev->ibd_host = ib_host;

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

  
  	return ib_dev;
  }
  
  static struct se_device *iblock_create_virtdevice(
  	struct se_hba *hba,
  	struct se_subsystem_dev *se_dev,
  	void *p)
  {
  	struct iblock_dev *ib_dev = p;
  	struct se_device *dev;
  	struct se_dev_limits dev_limits;
  	struct block_device *bd = NULL;
  	struct request_queue *q;
  	struct queue_limits *limits;
  	u32 dev_flags = 0;

  	int ret = -EINVAL;

  	if (!ib_dev) {
  		pr_err("Unable to locate struct iblock_dev parameter
  ");

  		return ERR_PTR(ret);

  	}
  	memset(&dev_limits, 0, sizeof(struct se_dev_limits));
  	/*
  	 * These settings need to be made tunable..
  	 */
  	ib_dev->ibd_bio_set = bioset_create(32, 64);

  	if (!ib_dev->ibd_bio_set) {
  		pr_err("IBLOCK: Unable to create bioset()
  ");

  		return ERR_PTR(-ENOMEM);

  	}

  	pr_debug("IBLOCK: Created bio_set()
  ");

  	/*
  	 * iblock_check_configfs_dev_params() ensures that ib_dev->ibd_udev_path
  	 * must already have been set in order for echo 1 > $HBA/$DEV/enable to run.
  	 */

  	pr_debug( "IBLOCK: Claiming struct block_device: %s
  ",

  			ib_dev->ibd_udev_path);
  
  	bd = blkdev_get_by_path(ib_dev->ibd_udev_path,
  				FMODE_WRITE|FMODE_READ|FMODE_EXCL, ib_dev);

  	if (IS_ERR(bd)) {
  		ret = PTR_ERR(bd);

  		goto failed;

  	}

  	/*
  	 * Setup the local scope queue_limits from struct request_queue->limits
  	 * to pass into transport_add_device_to_core_hba() as struct se_dev_limits.
  	 */
  	q = bdev_get_queue(bd);
  	limits = &dev_limits.limits;
  	limits->logical_block_size = bdev_logical_block_size(bd);
  	limits->max_hw_sectors = queue_max_hw_sectors(q);
  	limits->max_sectors = queue_max_sectors(q);

  	dev_limits.hw_queue_depth = q->nr_requests;
  	dev_limits.queue_depth = q->nr_requests;

  	ib_dev->ibd_bd = bd;
  
  	dev = transport_add_device_to_core_hba(hba,

  			&iblock_template, se_dev, dev_flags, ib_dev,

  			&dev_limits, "IBLOCK", IBLOCK_VERSION);

  	if (!dev)

  		goto failed;

  	/*
  	 * Check if the underlying struct block_device request_queue supports
  	 * the QUEUE_FLAG_DISCARD bit for UNMAP/WRITE_SAME in SCSI + TRIM
  	 * in ATA and we need to set TPE=1
  	 */

  	if (blk_queue_discard(q)) {

  		dev->se_sub_dev->se_dev_attrib.max_unmap_lba_count =

  				q->limits.max_discard_sectors;
  		/*
  		 * Currently hardcoded to 1 in Linux/SCSI code..
  		 */

  		dev->se_sub_dev->se_dev_attrib.max_unmap_block_desc_count = 1;
  		dev->se_sub_dev->se_dev_attrib.unmap_granularity =

  				q->limits.discard_granularity;

  		dev->se_sub_dev->se_dev_attrib.unmap_granularity_alignment =

  				q->limits.discard_alignment;

  		pr_debug("IBLOCK: BLOCK Discard support available,"

  				" disabled by default
  ");
  	}

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

  	return dev;
  
  failed:
  	if (ib_dev->ibd_bio_set) {
  		bioset_free(ib_dev->ibd_bio_set);
  		ib_dev->ibd_bio_set = NULL;
  	}
  	ib_dev->ibd_bd = NULL;

  	return ERR_PTR(ret);

  }
  
  static void iblock_free_device(void *p)
  {
  	struct iblock_dev *ib_dev = p;

  	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);

  	kfree(ib_dev);
  }
  
  static inline struct iblock_req *IBLOCK_REQ(struct se_task *task)
  {
  	return container_of(task, struct iblock_req, ib_task);
  }
  
  static struct se_task *

  iblock_alloc_task(unsigned char *cdb)

  {
  	struct iblock_req *ib_req;
  
  	ib_req = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);

  	if (!ib_req) {
  		pr_err("Unable to allocate memory for struct iblock_req
  ");

  		return NULL;
  	}

  	atomic_set(&ib_req->ib_bio_cnt, 0);
  	return &ib_req->ib_task;
  }
  
  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->se_sub_dev->se_dev_attrib.block_size)

  		return blocks_long;
  
  	switch (block_size) {
  	case 4096:

  		switch (dev->se_sub_dev->se_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->se_sub_dev->se_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->se_sub_dev->se_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->se_sub_dev->se_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_end_io_flush(struct bio *bio, int err)
  {
  	struct se_cmd *cmd = bio->bi_private;
  
  	if (err)
  		pr_err("IBLOCK: cache flush failed: %d
  ", err);
  
  	if (cmd)
  		transport_complete_sync_cache(cmd, err == 0);
  	bio_put(bio);
  }

  /*

   * Implement SYCHRONIZE CACHE.  Note that we can't handle lba ranges and must
   * always flush the whole cache.

   */
  static void iblock_emulate_sync_cache(struct se_task *task)
  {

  	struct se_cmd *cmd = task->task_se_cmd;

  	struct iblock_dev *ib_dev = cmd->se_dev->dev_ptr;

  	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)
  		transport_complete_sync_cache(cmd, 1);

  	bio = bio_alloc(GFP_KERNEL, 0);
  	bio->bi_end_io = iblock_end_io_flush;
  	bio->bi_bdev = ib_dev->ibd_bd;

  	if (!immed)

  		bio->bi_private = cmd;
  	submit_bio(WRITE_FLUSH, bio);

  }

  static int iblock_do_discard(struct se_device *dev, sector_t lba, u32 range)
  {
  	struct iblock_dev *ibd = dev->dev_ptr;
  	struct block_device *bd = ibd->ibd_bd;
  	int barrier = 0;
  
  	return blkdev_issue_discard(bd, lba, range, GFP_KERNEL, barrier);
  }
  
  static void iblock_free_task(struct se_task *task)
  {

  	kfree(IBLOCK_REQ(task));

  }
  
  enum {
  	Opt_udev_path, Opt_force, Opt_err
  };
  
  static match_table_t tokens = {
  	{Opt_udev_path, "udev_path=%s"},
  	{Opt_force, "force=%d"},
  	{Opt_err, NULL}
  };
  
  static ssize_t iblock_set_configfs_dev_params(struct se_hba *hba,
  					       struct se_subsystem_dev *se_dev,
  					       const char *page, ssize_t count)
  {
  	struct iblock_dev *ib_dev = se_dev->se_dev_su_ptr;

  	char *orig, *ptr, *arg_p, *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, ",")) != 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
  ");
  				ret = -EEXIST;
  				goto out;
  			}

  			arg_p = match_strdup(&args[0]);
  			if (!arg_p) {
  				ret = -ENOMEM;
  				break;
  			}
  			snprintf(ib_dev->ibd_udev_path, SE_UDEV_PATH_LEN,
  					"%s", arg_p);
  			kfree(arg_p);

  			pr_debug("IBLOCK: Referencing UDEV path: %s
  ",

  					ib_dev->ibd_udev_path);
  			ib_dev->ibd_flags |= IBDF_HAS_UDEV_PATH;
  			break;
  		case Opt_force:

  			break;
  		default:
  			break;
  		}
  	}
  
  out:
  	kfree(orig);
  	return (!ret) ? count : ret;
  }
  
  static ssize_t iblock_check_configfs_dev_params(
  	struct se_hba *hba,
  	struct se_subsystem_dev *se_dev)
  {
  	struct iblock_dev *ibd = se_dev->se_dev_su_ptr;
  
  	if (!(ibd->ibd_flags & IBDF_HAS_UDEV_PATH)) {

  		pr_err("Missing udev_path= parameters for IBLOCK
  ");

  		return -EINVAL;

  	}
  
  	return 0;
  }
  
  static ssize_t iblock_show_configfs_dev_params(
  	struct se_hba *hba,
  	struct se_subsystem_dev *se_dev,
  	char *b)
  {
  	struct iblock_dev *ibd = se_dev->se_dev_su_ptr;
  	struct block_device *bd = ibd->ibd_bd;
  	char buf[BDEVNAME_SIZE];
  	ssize_t bl = 0;
  
  	if (bd)
  		bl += sprintf(b + bl, "iBlock device: %s",
  				bdevname(bd, buf));
  	if (ibd->ibd_flags & IBDF_HAS_UDEV_PATH) {
  		bl += sprintf(b + bl, "  UDEV PATH: %s
  ",
  				ibd->ibd_udev_path);
  	} else
  		bl += sprintf(b + bl, "
  ");
  
  	bl += sprintf(b + bl, "        ");
  	if (bd) {
  		bl += sprintf(b + bl, "Major: %d Minor: %d  %s
  ",

  			MAJOR(bd->bd_dev), MINOR(bd->bd_dev), (!bd->bd_contains) ?

  			"" : (bd->bd_holder == (struct iblock_dev *)ibd) ?
  			"CLAIMED: IBLOCK" : "CLAIMED: OS");
  	} else {

  		bl += sprintf(b + bl, "Major: 0 Minor: 0
  ");

  	}
  
  	return bl;
  }
  
  static void iblock_bio_destructor(struct bio *bio)
  {
  	struct se_task *task = bio->bi_private;

  	struct iblock_dev *ib_dev = task->task_se_cmd->se_dev->dev_ptr;

  
  	bio_free(bio, ib_dev->ibd_bio_set);
  }

  static struct bio *
  iblock_get_bio(struct se_task *task, sector_t lba, u32 sg_num)

  {

  	struct iblock_dev *ib_dev = task->task_se_cmd->se_dev->dev_ptr;

  	struct iblock_req *ib_req = IBLOCK_REQ(task);

  	struct bio *bio;
  
  	bio = bio_alloc_bioset(GFP_NOIO, sg_num, ib_dev->ibd_bio_set);

  	if (!bio) {
  		pr_err("Unable to allocate memory for bio
  ");

  		return NULL;
  	}

  	pr_debug("Allocated bio: %p task_sg_nents: %u using ibd_bio_set:"
  		" %p
  ", bio, task->task_sg_nents, ib_dev->ibd_bio_set);
  	pr_debug("Allocated bio: %p task_size: %u
  ", bio, task->task_size);

  
  	bio->bi_bdev = ib_dev->ibd_bd;

  	bio->bi_private = task;

  	bio->bi_destructor = iblock_bio_destructor;
  	bio->bi_end_io = &iblock_bio_done;
  	bio->bi_sector = lba;
  	atomic_inc(&ib_req->ib_bio_cnt);

  	pr_debug("Set bio->bi_sector: %llu
  ", (unsigned long long)bio->bi_sector);
  	pr_debug("Set ib_req->ib_bio_cnt: %d
  ",

  			atomic_read(&ib_req->ib_bio_cnt));
  	return bio;
  }

  static int iblock_do_task(struct se_task *task)

  {
  	struct se_cmd *cmd = task->task_se_cmd;

  	struct se_device *dev = cmd->se_dev;

  	struct bio *bio;
  	struct bio_list list;

  	struct scatterlist *sg;

  	u32 i, sg_num = task->task_sg_nents;

  	sector_t block_lba;

  	struct blk_plug plug;
  	int rw;
  
  	if (task->task_data_direction == DMA_TO_DEVICE) {
  		/*
  		 * Force data to disk if we pretend to not have a volatile
  		 * write cache, or the initiator set the Force Unit Access bit.
  		 */
  		if (dev->se_sub_dev->se_dev_attrib.emulate_write_cache == 0 ||
  		    (dev->se_sub_dev->se_dev_attrib.emulate_fua_write > 0 &&

  		     (cmd->se_cmd_flags & SCF_FUA)))

  			rw = WRITE_FUA;
  		else
  			rw = WRITE;
  	} else {
  		rw = READ;
  	}

  	/*
  	 * Do starting conversion up from non 512-byte blocksize with
  	 * struct se_task SCSI blocksize into Linux/Block 512 units for BIO.
  	 */

  	if (dev->se_sub_dev->se_dev_attrib.block_size == 4096)

  		block_lba = (task->task_lba << 3);

  	else if (dev->se_sub_dev->se_dev_attrib.block_size == 2048)

  		block_lba = (task->task_lba << 2);

  	else if (dev->se_sub_dev->se_dev_attrib.block_size == 1024)

  		block_lba = (task->task_lba << 1);

  	else if (dev->se_sub_dev->se_dev_attrib.block_size == 512)

  		block_lba = task->task_lba;
  	else {

  		pr_err("Unsupported SCSI -> BLOCK LBA conversion:"

  				" %u
  ", dev->se_sub_dev->se_dev_attrib.block_size);

  		cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
  		return -ENOSYS;

  	}

  	bio = iblock_get_bio(task, block_lba, sg_num);

  	if (!bio) {
  		cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
  		return -ENOMEM;
  	}

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

  	for_each_sg(task->task_sg, sg, task->task_sg_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) {
  			bio = iblock_get_bio(task, block_lba, sg_num);

  			if (!bio)

  				goto fail;

  			bio_list_add(&list, bio);

  		}

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

  	}

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

  	return 0;

  fail:

  	while ((bio = bio_list_pop(&list)))

  		bio_put(bio);

  	cmd->scsi_sense_reason = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
  	return -ENOMEM;

  }

  static u32 iblock_get_device_rev(struct se_device *dev)
  {
  	return SCSI_SPC_2; /* Returns SPC-3 in Initiator Data */
  }
  
  static u32 iblock_get_device_type(struct se_device *dev)
  {
  	return TYPE_DISK;
  }
  
  static sector_t iblock_get_blocks(struct se_device *dev)
  {
  	struct iblock_dev *ibd = dev->dev_ptr;
  	struct block_device *bd = ibd->ibd_bd;
  	struct request_queue *q = bdev_get_queue(bd);
  
  	return iblock_emulate_read_cap_with_block_size(dev, bd, q);
  }
  
  static void iblock_bio_done(struct bio *bio, int err)
  {
  	struct se_task *task = bio->bi_private;
  	struct iblock_req *ibr = IBLOCK_REQ(task);

  	/*
  	 * Set -EIO if !BIO_UPTODATE and the passed is still err=0
  	 */

  	if (!test_bit(BIO_UPTODATE, &bio->bi_flags) && !err)

  		err = -EIO;
  
  	if (err != 0) {

  		pr_err("test_bit(BIO_UPTODATE) failed for bio: %p,"

  			" err: %d
  ", bio, err);
  		/*
  		 * Bump the ib_bio_err_cnt and release bio.
  		 */
  		atomic_inc(&ibr->ib_bio_err_cnt);
  		smp_mb__after_atomic_inc();

  	}

  	bio_put(bio);

  	if (!atomic_dec_and_test(&ibr->ib_bio_cnt))

  		return;

  
  	pr_debug("done[%p] bio: %p task_lba: %llu bio_lba: %llu err=%d
  ",
  		 task, bio, task->task_lba,
  		 (unsigned long long)bio->bi_sector, err);
  
  	transport_complete_task(task, !atomic_read(&ibr->ib_bio_err_cnt));

  }
  
  static struct se_subsystem_api iblock_template = {
  	.name			= "iblock",
  	.owner			= THIS_MODULE,
  	.transport_type		= TRANSPORT_PLUGIN_VHBA_PDEV,

  	.write_cache_emulated	= 1,
  	.fua_write_emulated	= 1,

  	.attach_hba		= iblock_attach_hba,
  	.detach_hba		= iblock_detach_hba,
  	.allocate_virtdevice	= iblock_allocate_virtdevice,
  	.create_virtdevice	= iblock_create_virtdevice,
  	.free_device		= iblock_free_device,

  	.alloc_task		= iblock_alloc_task,
  	.do_task		= iblock_do_task,
  	.do_discard		= iblock_do_discard,
  	.do_sync_cache		= iblock_emulate_sync_cache,
  	.free_task		= iblock_free_task,
  	.check_configfs_dev_params = iblock_check_configfs_dev_params,
  	.set_configfs_dev_params = iblock_set_configfs_dev_params,
  	.show_configfs_dev_params = iblock_show_configfs_dev_params,

  	.get_device_rev		= iblock_get_device_rev,
  	.get_device_type	= iblock_get_device_type,
  	.get_blocks		= iblock_get_blocks,
  };
  
  static int __init iblock_module_init(void)
  {
  	return transport_subsystem_register(&iblock_template);
  }
  
  static void iblock_module_exit(void)
  {
  	transport_subsystem_release(&iblock_template);
  }
  
  MODULE_DESCRIPTION("TCM IBLOCK subsystem plugin");
  MODULE_AUTHOR("nab@Linux-iSCSI.org");
  MODULE_LICENSE("GPL");
  
  module_init(iblock_module_init);
  module_exit(iblock_module_exit);