/*
 * 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"

static DEFINE_IDR(dnbd3_index_idr);
static DEFINE_MUTEX(dnbd3_index_mutex);

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


static int dnbd3_open(struct block_device *bdev, fmode_t mode)
{
	printk(KERN_DEBUG "dnbd3: dnbd3_open");

	return 0;
}

static void dnbd3_release(struct gendisk *disk, fmode_t mode)
{
	printk(KERN_DEBUG "dnbd3: dnbd3_release");

}


void dnbd3_blk_fail_all_requests(dnbd3_device_t *dev)
{
	printk(KERN_DEBUG "dnbd3: dnbd3_blk_fail_all_requests");
}


int dnbd3_net_connect(dnbd3_device_t *dev)
{
	return 0;
}


int dnbd3_net_disconnect(dnbd3_device_t *dev)
{
	return 0;
}

static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd, unsigned long arg)
{
	printk(KERN_DEBUG "dnbd3: dnbd3_ioctl");

	int result = -100;
	dnbd3_device_t *dev = bdev->bd_disk->private_data;
	char *imgname = NULL;
	dnbd3_ioctl_t *msg = NULL;
	//unsigned long irqflags;

	while (dev->disconnecting)
	{
		// do nothing
	}

	if (arg != 0)
	{
		msg = kmalloc(sizeof(*msg), GFP_KERNEL);
		if (msg == NULL) return -ENOMEM;
		if (copy_from_user((char *)msg, (char *)arg, 2) != 0 || msg->len != sizeof(*msg))
		{
			result = -ENOEXEC;
			goto cleanup_return;
		}
		if (copy_from_user((char *)msg, (char *)arg, sizeof(*msg)) != 0)
		{
			result = -ENOENT;
			goto cleanup_return;
		}
		if (msg->imgname != NULL && msg->imgnamelen > 0)
		{
			imgname = kmalloc(msg->imgnamelen + 1, GFP_KERNEL);
			if (imgname == NULL)
			{
				result = -ENOMEM;
				goto cleanup_return;
			}
			if (copy_from_user(imgname, msg->imgname, msg->imgnamelen) != 0)
			{
				result = -ENOENT;
				goto cleanup_return;
			}
			imgname[msg->imgnamelen] = '\0';
			//printk("IOCTL Image name of len %d is %s\n", (int)msg->imgnamelen, imgname);
		}
	}


	switch (cmd)
	{
	case IOCTL_OPEN:
		if (dev->imgname != NULL)
		{
			result = -EBUSY;
		}
		else if (imgname == NULL)
		{
			result = -EINVAL;
		}
		else if (msg == NULL)
		{
			result = -EINVAL;
		}
		else
		{
			if (sizeof(msg->host) != sizeof(dev->cur_server.host))
				printk("Odd size bug#1 triggered in IOCTL\n");
			memcpy(&dev->cur_server.host, &msg->host, sizeof(msg->host));
			dev->cur_server.failures = 0;
			memcpy(&dev->initial_server, &dev->cur_server, sizeof(dev->initial_server));
			dev->imgname = imgname;
			dev->rid = msg->rid;
			dev->use_server_provided_alts = msg->use_server_provided_alts;
			// Forget all alt servers on explicit connect, set first al server to initial server
			memset(dev->alt_servers, 0, sizeof(dev->alt_servers[0])*NUMBER_SERVERS);
			memcpy(dev->alt_servers, &dev->initial_server, sizeof(dev->alt_servers[0]));
//#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 11, 0)
//			if (blk_queue->backing_dev_info != NULL) {
//				blk_queue->backing_dev_info->ra_pages = (msg->read_ahead_kb * 1024) / PAGE_SIZE;
//			}
//#else
//			blk_queue->backing_dev_info.ra_pages = (msg->read_ahead_kb * 1024) / PAGE_SIZE;
//#endif
			if (dnbd3_net_connect(dev) == 0)
			{
				result = 0;
				imgname = NULL; // Prevent kfree at the end
			}
			else
			{
				result = -ENOENT;
				dev->imgname = NULL;
			}
		}
		break;

	case IOCTL_CLOSE:
		dnbd3_blk_fail_all_requests(dev);
		result = dnbd3_net_disconnect(dev);
		dnbd3_blk_fail_all_requests(dev);
		set_capacity(dev->disk, 0);
		if (dev->imgname)
		{
			kfree(dev->imgname);
			dev->imgname = NULL;
		}
		break;

	case IOCTL_SWITCH:
		result = -EINVAL;
		break;

	case IOCTL_ADD_SRV:
	case IOCTL_REM_SRV:
		if (dev->imgname == NULL)
		{
			result = -ENOENT;
		}
		else if (dev->new_servers_num >= NUMBER_SERVERS)
		{
			result = -EAGAIN;
		}
		else if (msg == NULL)
		{
			result = -EINVAL;
		}
		else
		{
			memcpy(&dev->new_servers[dev->new_servers_num].host, &msg->host, sizeof(msg->host));
			dev->new_servers[dev->new_servers_num].failures = (cmd == IOCTL_ADD_SRV ? 0 : 1); // 0 = ADD, 1 = REM
			++dev->new_servers_num;
			result = 0;
		}
		break;

	case BLKFLSBUF:
		result = 0;
		break;

	default:
		result = -EIO;
		break;
	}

cleanup_return:
	if (msg) kfree(msg);
	if (imgname) kfree(imgname);
	return result;

}

static const struct block_device_operations dnbd3_fops =
{
	.owner = THIS_MODULE,
	.open = dnbd3_open,
	.release = dnbd3_release,
	.ioctl = dnbd3_ioctl,
	.compat_ioctl =	dnbd3_ioctl,
};

static blk_status_t dnbd3_queue_rq(struct blk_mq_hw_ctx *hctx, const struct blk_mq_queue_data *bd)
{
	printk(KERN_DEBUG "dnbd3: dnbd3_queue_rq");
	return 0;
}

static void dnbd3_complete_rq(struct request *req)
{
	printk(KERN_DEBUG "dnbd3: dnbd3_complete_rq");

}

static int dnbd3_init_request(struct blk_mq_tag_set *set, struct request *rq, unsigned int hctx_idx, unsigned int numa_node)
{
	struct dnbd3_cmd *cmd = blk_mq_rq_to_pdu(rq);
	cmd->dnbd3 = set->driver_data;
	cmd->flags = 0;
	mutex_init(&cmd->lock);
	return 0;
}
static enum blk_eh_timer_return dnbd3_xmit_timeout(struct request *req, bool reserved)
{
	printk(KERN_DEBUG "dnbd3: dnbd3_xmit_timeout");
	return BLK_EH_DONE;
}


static const struct blk_mq_ops dnbd3_mq_ops = {
	.queue_rq = dnbd3_queue_rq,
	.complete = dnbd3_complete_rq,
	.init_request = dnbd3_init_request,
	.timeout = dnbd3_xmit_timeout,
};


static int dnbd3_blk_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", minor);


	disk = alloc_disk(1);
	if (!disk) {
		printk(KERN_DEBUG "dnbd3: alloc_disc failed, device %i", minor);
		goto out_free_nbd;
	}

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

	mutex_init(&dev->config_lock);
	refcount_set(&dev->config_refs, 0);
	refcount_set(&dev->refs, 1);
	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%d", minor);
//	sprintf(disk->disk_name, "dnbd3%d", minor);
	printk(KERN_DEBUG "dnbd3: add disk, device %s", 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_nbd:
	kfree(dev);
	printk(KERN_DEBUG "dnbd3: destroy device %i", minor);
	return err;
}



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

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


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

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

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

	// add MAX_NUMBER_DEVICES devices
	mutex_lock(&dnbd3_index_mutex);
	for (i = 0; i < max_devs; i++) {
		dnbd3_blk_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);
		disk->private_data = NULL;
		put_disk(disk);
	}
}

static void dnbd3_put(struct dnbd3_device_t *dnbd3)
{
	if (refcount_dec_and_mutex_lock(&dnbd3->refs, &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");

	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);
		if (refcount_read(&dnbd3->refs) != 1) {
			printk(KERN_ERR "dnbd3: possibly leaking a device\n");
		}
		dnbd3_put(dnbd3);
	}

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

	kfree(dnbd3_device);

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


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)");