/*
 * This file is part of the Distributed Network Block Device 3
 *
 * Copyright(c) 2019 Frederic Robra <frederic@robra.org>
 * Parts copyright 2011-2012 Johann Latocha <johann@latocha.de>
 *
 * This file may be licensed under the terms of of the
 * GNU General Public License Version 2 (the ``GPL'').
 *
 * Software distributed under the License is distributed
 * on an ``AS IS'' basis, WITHOUT WARRANTY OF ANY KIND, either
 * express or implied. See the GPL for the specific language
 * governing rights and limitations.
 *
 * You should have received a copy of the GPL along with this
 * program. If not, go to http://www.gnu.org/licenses/gpl.html
 * or write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */

#include <linux/major.h>

#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/fs.h>
#include <linux/bio.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/ioctl.h>
#include <linux/mutex.h>
#include <linux/compiler.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/net.h>
#include <linux/kthread.h>
#include <linux/types.h>
#include <linux/debugfs.h>
#include <linux/blk-mq.h>

#include <linux/uaccess.h>
#include <asm/types.h>

#include "dnbd3.h"
#include "clientconfig.h"
#include "sysfs.h"
#include "block.h"
#include "mq.h"

DEFINE_IDR(dnbd3_index_idr);
DEFINE_MUTEX(dnbd3_index_mutex);

static unsigned int max_devs = NUMBER_DEVICES;
static dnbd3_device_t *dnbd3_device;
int major;



static int dnbd3_add_device(dnbd3_device_t *dev, int minor)
{
	struct gendisk *disk;
	struct request_queue *q;
	int err = -ENOMEM;
	printk(KERN_DEBUG "dnbd3: adding device %i\n", minor);


	disk = alloc_disk(1);
	if (!disk) {
		printk(KERN_WARNING "dnbd3: alloc_disc failed device %i\n", minor);
		goto out_free_dnbd3;
	}

	err = idr_alloc(&dnbd3_index_idr, dev, minor, minor + 1, GFP_KERNEL);
	if (err == -ENOSPC) {
		printk(KERN_WARNING "dnbd3: idr_alloc failed device %i\n", minor);
		err = -EEXIST;
	}

	if (err < 0)
		goto out_free_disk;

	dev->minor = minor;
	dev->disk = disk;
	dev->tag_set.ops = &dnbd3_mq_ops;
	dev->tag_set.nr_hw_queues = 1; // this can be changed later with blk_mq_update_nr_hw_queues()
	dev->tag_set.queue_depth = 128;
	dev->tag_set.numa_node = NUMA_NO_NODE;
	dev->tag_set.cmd_size = sizeof(dnbd3_cmd);
	dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE |
		BLK_MQ_F_SG_MERGE | BLK_MQ_F_BLOCKING;
	dev->tag_set.driver_data = dev;

	err = blk_mq_alloc_tag_set(&dev->tag_set);
	if (err)
		goto out_free_idr;

	q = blk_mq_init_queue(&dev->tag_set);
	if (IS_ERR(q)) {
		err = PTR_ERR(q);
		goto out_free_tags;
	}
	disk->queue = q;

	/*
	 * Tell the block layer that we are not a rotational device
	 */
	blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);
	disk->queue->limits.discard_granularity = 0;
	disk->queue->limits.discard_alignment = 0;
	blk_queue_max_discard_sectors(disk->queue, 0);
	blk_queue_max_segment_size(disk->queue, UINT_MAX);
	blk_queue_max_segments(disk->queue, USHRT_MAX);
	blk_queue_max_hw_sectors(disk->queue, 65536);
	disk->queue->limits.max_sectors = 256;

	INIT_LIST_HEAD(&dev->list);
	disk->major = major;
	disk->first_minor = minor;
	disk->fops = &dnbd3_fops;
	disk->private_data = dev;
	sprintf(disk->disk_name, "dnbd%i", minor);
	printk(KERN_DEBUG "dnbd3: add disk device %s\n", disk->disk_name);
	add_disk(disk);
	dnbd3_sysfs_init(dev);
	return minor;

out_free_tags:
	blk_mq_free_tag_set(&dev->tag_set);
out_free_idr:
	idr_remove(&dnbd3_index_idr, minor);
out_free_disk:
	put_disk(disk);
out_free_dnbd3:
	kfree(dev);
	printk(KERN_DEBUG "dnbd3: destroy device %i\n", minor);
	return err;
}



static int __init dnbd3_init(void)
{
	int i;
	printk(KERN_DEBUG "dnbd3: starting kernel module\n");

	if (max_devs < 0) {
		printk(KERN_ERR "dnbd3: max_devs must be >= 0\n");
		return -EINVAL;
	}


	dnbd3_device = kcalloc(max_devs, sizeof(*dnbd3_device), GFP_KERNEL);
	if (!dnbd3_device) {
		printk(KERN_ERR "dnbd3: failed to create dnbd3 device\n");
		return -ENOMEM;
	}

	// initialize block device
	major = register_blkdev(0, "dnbd3");
	if (major == 0) {
		printk(KERN_ERR "dnbd3: register_blkdev failed\n");
		return -EIO;
	}

	printk(KERN_DEBUG "dnbd3: kernel module loaded. Machine type: " ENDIAN_MODE "\n");

	// add MAX_NUMBER_DEVICES devices
	mutex_lock(&dnbd3_index_mutex);
	for (i = 0; i < max_devs; i++) {
		dnbd3_add_device(&dnbd3_device[i], i);
	}
	mutex_unlock(&dnbd3_index_mutex);

	printk(KERN_INFO "dnbd3: init successful (%i devices).\n", max_devs);

	return 0;
}


static int dnbd3_exit_cb(int id, void *ptr, void *data)
{
	struct list_head *list = (struct list_head *)data;
	struct dnbd3_device_t *dnbd3 = ptr;

	list_add_tail(&dnbd3->list, list);
	return 0;
}

static void dnbd3_dev_remove(struct dnbd3_device_t *dnbd3)
{
	struct gendisk *disk = dnbd3->disk;
	struct request_queue *q;

	if (disk) {
		q = disk->queue;
		del_gendisk(disk);
		blk_cleanup_queue(q);
		blk_mq_free_tag_set(&dnbd3->tag_set);
		dnbd3_net_disconnect(dnbd3);
		disk->private_data = NULL;
		put_disk(disk);
	}
}

static void dnbd3_put(struct dnbd3_device_t *dnbd3)
{
	mutex_lock(&dnbd3_index_mutex);
	idr_remove(&dnbd3_index_idr, dnbd3->minor);
	mutex_unlock(&dnbd3_index_mutex);
	dnbd3_dev_remove(dnbd3);
}


static void __exit dnbd3_exit(void)
{
	dnbd3_device_t *dnbd3;
	LIST_HEAD(del_list);
	printk(KERN_DEBUG "dnbd3: stopping kernel module\n");

	mutex_lock(&dnbd3_index_mutex);
	idr_for_each(&dnbd3_index_idr, &dnbd3_exit_cb, &del_list);
	mutex_unlock(&dnbd3_index_mutex);

	while (!list_empty(&del_list)) {
		dnbd3 = list_first_entry(&del_list, struct dnbd3_device_t, list);
		dnbd3_sysfs_exit(dnbd3);
		list_del_init(&dnbd3->list);
		dnbd3_put(dnbd3);
	}

	idr_destroy(&dnbd3_index_idr);
	unregister_blkdev(major, "dnbd3");

	kfree(dnbd3_device);

	printk(KERN_INFO "dnbd3: stopped kernel module\n");
}


module_init(dnbd3_init);
module_exit(dnbd3_exit);

MODULE_DESCRIPTION("Distributed Network Block Device 3");
MODULE_LICENSE("GPL");

module_param(max_devs, int, 0444);
MODULE_PARM_DESC(max_devs, "number of network block devices to initialize (default: 8)");