/*
 * Copyright (c) 2014 Ezequiel Garcia
 * Copyright (c) 2011 Free Electrons
 *
 * Driver parameter handling strongly based on drivers/mtd/ubi/build.c
 *   Copyright (c) International Business Machines Corp., 2006
 *   Copyright (c) Nokia Corporation, 2007
 *   Authors: Artem Bityutskiy, Frank Haverkamp
 *
 * 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, version 2.
 *
 * 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.
 */

/*
 * Read-only block devices on top of UBI volumes
 *
 * A simple implementation to allow a block device to be layered on top of a
 * UBI volume. The implementation is provided by creating a static 1-to-1
 * mapping between the block device and the UBI volume.
 *
 * The addressed byte is obtained from the addressed block sector, which is
 * mapped linearly into the corresponding LEB:
 *
 *   LEB number = addressed byte / LEB size
 *
 * This feature is compiled in the UBI core, and adds a 'block' parameter
 * to allow early creation of block devices on top of UBI volumes. Runtime
 * block creation/removal for UBI volumes is provided through two UBI ioctls:
 * UBI_IOCVOLCRBLK and UBI_IOCVOLRMBLK.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/mtd/ubi.h>
#include <linux/workqueue.h>
#include <linux/blkdev.h>
#include <linux/blk-mq.h>
#include <linux/hdreg.h>
#include <linux/scatterlist.h>
#include <linux/idr.h>
#include <asm/div64.h>

#include "ubi-media.h"
#include "ubi.h"

/* Maximum number of supported devices */
#define UBIBLOCK_MAX_DEVICES 32

/* Maximum length of the 'block=' parameter */
#define UBIBLOCK_PARAM_LEN 63

/* Maximum number of comma-separated items in the 'block=' parameter */
#define UBIBLOCK_PARAM_COUNT 2

struct ubiblock_param {
        int ubi_num;
        int vol_id;
        char name[UBIBLOCK_PARAM_LEN+1];
};

struct ubiblock_pdu {
        struct work_struct work;
        struct ubi_sgl usgl;
};

/* Numbers of elements set in the @ubiblock_param array */
static int ubiblock_devs __initdata;

/* MTD devices specification parameters */
static struct ubiblock_param ubiblock_param[UBIBLOCK_MAX_DEVICES] __initdata;

struct ubiblock {
        struct ubi_volume_desc *desc;
        int ubi_num;
        int vol_id;
        int refcnt;
        int leb_size;

        struct gendisk *gd;
        struct request_queue *rq;

        struct workqueue_struct *wq;

        struct mutex dev_mutex;
        struct list_head list;
        struct blk_mq_tag_set tag_set;
};

/* Linked list of all ubiblock instances */
static LIST_HEAD(ubiblock_devices);
static DEFINE_MUTEX(devices_mutex);
static int ubiblock_major;

static int __init ubiblock_set_param(const char *val,
                                     const struct kernel_param *kp)
{
        int i, ret;
        size_t len;
        struct ubiblock_param *param;
        char buf[UBIBLOCK_PARAM_LEN];
        char *pbuf = &buf[0];
        char *tokens[UBIBLOCK_PARAM_COUNT];

        if (!val)
                return -EINVAL;

        len = strnlen(val, UBIBLOCK_PARAM_LEN);
        if (len == 0) {
                pr_warn("UBI: block: empty 'block=' parameter - ignored\n");
                return 0;
        }

        if (len == UBIBLOCK_PARAM_LEN) {
                pr_err("UBI: block: parameter \"%s\" is too long, max. is %d\n",
                       val, UBIBLOCK_PARAM_LEN);
                return -EINVAL;
        }

        strcpy(buf, val);

        /* Get rid of the final newline */
        if (buf[len - 1] == '\n')
                buf[len - 1] = '\0';

        for (i = 0; i < UBIBLOCK_PARAM_COUNT; i++)
                tokens[i] = strsep(&pbuf, ",");

        param = &ubiblock_param[ubiblock_devs];
        if (tokens[1]) {
                /* Two parameters: can be 'ubi, vol_id' or 'ubi, vol_name' */
                ret = kstrtoint(tokens[0], 10, &param->ubi_num);
                if (ret < 0)
                        return -EINVAL;

                /* Second param can be a number or a name */
                ret = kstrtoint(tokens[1], 10, &param->vol_id);
                if (ret < 0) {
                        param->vol_id = -1;
                        strcpy(param->name, tokens[1]);
                }

        } else {
                /* One parameter: must be device path */
                strcpy(param->name, tokens[0]);
                param->ubi_num = -1;
                param->vol_id = -1;
        }

        ubiblock_devs++;

        return 0;
}

static const struct kernel_param_ops ubiblock_param_ops = {
        .set    = ubiblock_set_param,
};
module_param_cb(block, &ubiblock_param_ops, NULL, 0);
MODULE_PARM_DESC(block, "Attach block devices to UBI volumes. Parameter format: block=<path|dev,num|dev,name>.\n"
                        "Multiple \"block\" parameters may be specified.\n"
                        "UBI volumes may be specified by their number, name, or path to the device node.\n"
                        "Examples\n"
                        "Using the UBI volume path:\n"
                        "ubi.block=/dev/ubi0_0\n"
                        "Using the UBI device, and the volume name:\n"
                        "ubi.block=0,rootfs\n"
                        "Using both UBI device number and UBI volume number:\n"
                        "ubi.block=0,0\n");

static struct ubiblock *find_dev_nolock(int ubi_num, int vol_id)
{
        struct ubiblock *dev;

        list_for_each_entry(dev, &ubiblock_devices, list)
                if (dev->ubi_num == ubi_num && dev->vol_id == vol_id)
                        return dev;
        return NULL;
}

static int ubiblock_read(struct ubiblock_pdu *pdu)
{
        int ret, leb, offset, bytes_left, to_read;
        u64 pos;
        struct request *req = blk_mq_rq_from_pdu(pdu);
        struct ubiblock *dev = req->q->queuedata;

        to_read = blk_rq_bytes(req);
        pos = blk_rq_pos(req) << 9;

        /* Get LEB:offset address to read from */
        offset = do_div(pos, dev->leb_size);
        leb = pos;
        bytes_left = to_read;

        while (bytes_left) {
                /*
                 * We can only read one LEB at a time. Therefore if the read
                 * length is larger than one LEB size, we split the operation.
                 */
                if (offset + to_read > dev->leb_size)
                        to_read = dev->leb_size - offset;

                ret = ubi_read_sg(dev->desc, leb, &pdu->usgl, offset, to_read);
                if (ret < 0)
                        return ret;

                bytes_left -= to_read;
                to_read = bytes_left;
                leb += 1;
                offset = 0;
        }
        return 0;
}

static int ubiblock_open(struct block_device *bdev, fmode_t mode)
{
        struct ubiblock *dev = bdev->bd_disk->private_data;
        int ret;

        mutex_lock(&dev->dev_mutex);
        if (dev->refcnt > 0) {
                /*
                 * The volume is already open, just increase the reference
                 * counter.
                 */
                goto out_done;
        }

        /*
         * We want users to be aware they should only mount us as read-only.
         * It's just a paranoid check, as write requests will get rejected
         * in any case.
         */
        if (mode & FMODE_WRITE) {
                ret = -EPERM;
                goto out_unlock;
        }

        dev->desc = ubi_open_volume(dev->ubi_num, dev->vol_id, UBI_READONLY);
        if (IS_ERR(dev->desc)) {
                dev_err(disk_to_dev(dev->gd), "failed to open ubi volume %d_%d",
                        dev->ubi_num, dev->vol_id);
                ret = PTR_ERR(dev->desc);
                dev->desc = NULL;
                goto out_unlock;
        }

out_done:
        dev->refcnt++;
        mutex_unlock(&dev->dev_mutex);
        return 0;

out_unlock:
        mutex_unlock(&dev->dev_mutex);
        return ret;
}

static void ubiblock_release(struct gendisk *gd, fmode_t mode)
{
        struct ubiblock *dev = gd->private_data;

        mutex_lock(&dev->dev_mutex);
        dev->refcnt--;
        if (dev->refcnt == 0) {
                ubi_close_volume(dev->desc);
                dev->desc = NULL;
        }
        mutex_unlock(&dev->dev_mutex);
}

static int ubiblock_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
        /* Some tools might require this information */
        geo->heads = 1;
        geo->cylinders = 1;
        geo->sectors = get_capacity(bdev->bd_disk);
        geo->start = 0;
        return 0;
}

static const struct block_device_operations ubiblock_ops = {
        .owner = THIS_MODULE,
        .open = ubiblock_open,
        .release = ubiblock_release,
        .getgeo = ubiblock_getgeo,
};

static void ubiblock_do_work(struct work_struct *work)
{
        int ret;
        struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work);
        struct request *req = blk_mq_rq_from_pdu(pdu);

        blk_mq_start_request(req);

        /*
         * It is safe to ignore the return value of blk_rq_map_sg() because
         * the number of sg entries is limited to UBI_MAX_SG_COUNT
         * and ubi_read_sg() will check that limit.
         */
        blk_rq_map_sg(req->q, req, pdu->usgl.sg);

        ret = ubiblock_read(pdu);
        rq_flush_dcache_pages(req);

        blk_mq_end_request(req, ret);
}

static int ubiblock_queue_rq(struct blk_mq_hw_ctx *hctx,
                             const struct blk_mq_queue_data *bd)
{
        struct request *req = bd->rq;
        struct ubiblock *dev = hctx->queue->queuedata;
        struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);

        if (req->cmd_type != REQ_TYPE_FS)
                return BLK_MQ_RQ_QUEUE_ERROR;

        if (rq_data_dir(req) != READ)
                return BLK_MQ_RQ_QUEUE_ERROR; /* Write not implemented */

        ubi_sgl_init(&pdu->usgl);
        queue_work(dev->wq, &pdu->work);

        return BLK_MQ_RQ_QUEUE_OK;
}

static int ubiblock_init_request(void *data, struct request *req,
                                 unsigned int hctx_idx,
                                 unsigned int request_idx,
                                 unsigned int numa_node)
{
        struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);

        sg_init_table(pdu->usgl.sg, UBI_MAX_SG_COUNT);
        INIT_WORK(&pdu->work, ubiblock_do_work);

        return 0;
}

static struct blk_mq_ops ubiblock_mq_ops = {
        .queue_rq       = ubiblock_queue_rq,
        .init_request   = ubiblock_init_request,
        .map_queue      = blk_mq_map_queue,
};

static DEFINE_IDR(ubiblock_minor_idr);

int ubiblock_create(struct ubi_volume_info *vi)
{
        struct ubiblock *dev;
        struct gendisk *gd;
        u64 disk_capacity = vi->used_bytes >> 9;
        int ret;

        if ((sector_t)disk_capacity != disk_capacity)
                return -EFBIG;
        /* Check that the volume isn't already handled */
        mutex_lock(&devices_mutex);
        if (find_dev_nolock(vi->ubi_num, vi->vol_id)) {
                mutex_unlock(&devices_mutex);
                return -EEXIST;
        }
        mutex_unlock(&devices_mutex);

        dev = kzalloc(sizeof(struct ubiblock), GFP_KERNEL);
        if (!dev)
                return -ENOMEM;

        mutex_init(&dev->dev_mutex);

        dev->ubi_num = vi->ubi_num;
        dev->vol_id = vi->vol_id;
        dev->leb_size = vi->usable_leb_size;

        /* Initialize the gendisk of this ubiblock device */
        gd = alloc_disk(1);
        if (!gd) {
                pr_err("UBI: block: alloc_disk failed");
                ret = -ENODEV;
                goto out_free_dev;
        }

        gd->fops = &ubiblock_ops;
        gd->major = ubiblock_major;
        gd->first_minor = idr_alloc(&ubiblock_minor_idr, dev, 0, 0, GFP_KERNEL);
        if (gd->first_minor < 0) {
                dev_err(disk_to_dev(gd),
                        "block: dynamic minor allocation failed");
                ret = -ENODEV;
                goto out_put_disk;
        }
        gd->private_data = dev;
        sprintf(gd->disk_name, "ubiblock%d_%d", dev->ubi_num, dev->vol_id);
        set_capacity(gd, disk_capacity);
        dev->gd = gd;

        dev->tag_set.ops = &ubiblock_mq_ops;
        dev->tag_set.queue_depth = 64;
        dev->tag_set.numa_node = NUMA_NO_NODE;
        dev->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
        dev->tag_set.cmd_size = sizeof(struct ubiblock_pdu);
        dev->tag_set.driver_data = dev;
        dev->tag_set.nr_hw_queues = 1;

        ret = blk_mq_alloc_tag_set(&dev->tag_set);
        if (ret) {
                dev_err(disk_to_dev(dev->gd), "blk_mq_alloc_tag_set failed");
                goto out_remove_minor;
        }

        dev->rq = blk_mq_init_queue(&dev->tag_set);
        if (IS_ERR(dev->rq)) {
                dev_err(disk_to_dev(gd), "blk_mq_init_queue failed");
                ret = PTR_ERR(dev->rq);
                goto out_free_tags;
        }
        blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT);

        dev->rq->queuedata = dev;
        dev->gd->queue = dev->rq;

        /*
         * Create one workqueue per volume (per registered block device).
         * Rembember workqueues are cheap, they're not threads.
         */
        dev->wq = alloc_workqueue("%s", 0, 0, gd->disk_name);
        if (!dev->wq) {
                ret = -ENOMEM;
                goto out_free_queue;
        }

        mutex_lock(&devices_mutex);
        list_add_tail(&dev->list, &ubiblock_devices);
        mutex_unlock(&devices_mutex);

        /* Must be the last step: anyone can call file ops from now on */
        add_disk(dev->gd);
        dev_info(disk_to_dev(dev->gd), "created from ubi%d:%d(%s)",
                 dev->ubi_num, dev->vol_id, vi->name);
        return 0;

out_free_queue:
        blk_cleanup_queue(dev->rq);
out_free_tags:
        blk_mq_free_tag_set(&dev->tag_set);
out_remove_minor:
        idr_remove(&ubiblock_minor_idr, gd->first_minor);
out_put_disk:
        put_disk(dev->gd);
out_free_dev:
        kfree(dev);

        return ret;
}

static void ubiblock_cleanup(struct ubiblock *dev)
{
        /* Stop new requests to arrive */
        del_gendisk(dev->gd);
        /* Flush pending work */
        destroy_workqueue(dev->wq);
        /* Finally destroy the blk queue */
        blk_cleanup_queue(dev->rq);
        blk_mq_free_tag_set(&dev->tag_set);
        dev_info(disk_to_dev(dev->gd), "released");
        idr_remove(&ubiblock_minor_idr, dev->gd->first_minor);
        put_disk(dev->gd);
}

int ubiblock_remove(struct ubi_volume_info *vi)
{
        struct ubiblock *dev;

        mutex_lock(&devices_mutex);
        dev = find_dev_nolock(vi->ubi_num, vi->vol_id);
        if (!dev) {
                mutex_unlock(&devices_mutex);
                return -ENODEV;
        }

        /* Found a device, let's lock it so we can check if it's busy */
        mutex_lock(&dev->dev_mutex);
        if (dev->refcnt > 0) {
                mutex_unlock(&dev->dev_mutex);
                mutex_unlock(&devices_mutex);
                return -EBUSY;
        }

        /* Remove from device list */
        list_del(&dev->list);
        mutex_unlock(&devices_mutex);

        ubiblock_cleanup(dev);
        mutex_unlock(&dev->dev_mutex);
        kfree(dev);
        return 0;
}

static int ubiblock_resize(struct ubi_volume_info *vi)
{
        struct ubiblock *dev;
        u64 disk_capacity = vi->used_bytes >> 9;

        /*
         * Need to lock the device list until we stop using the device,
         * otherwise the device struct might get released in
         * 'ubiblock_remove()'.
         */
        mutex_lock(&devices_mutex);
        dev = find_dev_nolock(vi->ubi_num, vi->vol_id);
        if (!dev) {
                mutex_unlock(&devices_mutex);
                return -ENODEV;
        }
        if ((sector_t)disk_capacity != disk_capacity) {
                mutex_unlock(&devices_mutex);
                dev_warn(disk_to_dev(dev->gd), "the volume is too big (%d LEBs), cannot resize",
                         vi->size);
                return -EFBIG;
        }

        mutex_lock(&dev->dev_mutex);

        if (get_capacity(dev->gd) != disk_capacity) {
                set_capacity(dev->gd, disk_capacity);
                dev_info(disk_to_dev(dev->gd), "resized to %lld bytes",
                         vi->used_bytes);
        }
        mutex_unlock(&dev->dev_mutex);
        mutex_unlock(&devices_mutex);
        return 0;
}

static int ubiblock_notify(struct notifier_block *nb,
                         unsigned long notification_type, void *ns_ptr)
{
        struct ubi_notification *nt = ns_ptr;

        switch (notification_type) {
        case UBI_VOLUME_ADDED:
                /*
                 * We want to enforce explicit block device creation for
                 * volumes, so when a volume is added we do nothing.
                 */
                break;
        case UBI_VOLUME_REMOVED:
                ubiblock_remove(&nt->vi);
                break;
        case UBI_VOLUME_RESIZED:
                ubiblock_resize(&nt->vi);
                break;
        case UBI_VOLUME_UPDATED:
                /*
                 * If the volume is static, a content update might mean the
                 * size (i.e. used_bytes) was also changed.
                 */
                if (nt->vi.vol_type == UBI_STATIC_VOLUME)
                        ubiblock_resize(&nt->vi);
                break;
        default:
                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block ubiblock_notifier = {
        .notifier_call = ubiblock_notify,
};

static struct ubi_volume_desc * __init
open_volume_desc(const char *name, int ubi_num, int vol_id)
{
        if (ubi_num == -1)
                /* No ubi num, name must be a vol device path */
                return ubi_open_volume_path(name, UBI_READONLY);
        else if (vol_id == -1)
                /* No vol_id, must be vol_name */
                return ubi_open_volume_nm(ubi_num, name, UBI_READONLY);
        else
                return ubi_open_volume(ubi_num, vol_id, UBI_READONLY);
}

static void __init ubiblock_create_from_param(void)
{
        int i, ret = 0;
        struct ubiblock_param *p;
        struct ubi_volume_desc *desc;
        struct ubi_volume_info vi;

        /*
         * If there is an error creating one of the ubiblocks, continue on to
         * create the following ubiblocks. This helps in a circumstance where
         * the kernel command-line specifies multiple block devices and some
         * may be broken, but we still want the working ones to come up.
         */
        for (i = 0; i < ubiblock_devs; i++) {
                p = &ubiblock_param[i];

                desc = open_volume_desc(p->name, p->ubi_num, p->vol_id);
                if (IS_ERR(desc)) {
                        pr_err(
                               "UBI: block: can't open volume on ubi%d_%d, err=%ld",
                               p->ubi_num, p->vol_id, PTR_ERR(desc));
                        continue;
                }

                ubi_get_volume_info(desc, &vi);
                ubi_close_volume(desc);

                ret = ubiblock_create(&vi);
                if (ret) {
                        pr_err(
                               "UBI: block: can't add '%s' volume on ubi%d_%d, err=%d",
                               vi.name, p->ubi_num, p->vol_id, ret);
                        continue;
                }
        }
}

static void ubiblock_remove_all(void)
{
        struct ubiblock *next;
        struct ubiblock *dev;

        list_for_each_entry_safe(dev, next, &ubiblock_devices, list) {
                /* The module is being forcefully removed */
                WARN_ON(dev->desc);
                /* Remove from device list */
                list_del(&dev->list);
                ubiblock_cleanup(dev);
                kfree(dev);
        }
}

int __init ubiblock_init(void)
{
        int ret;

        ubiblock_major = register_blkdev(0, "ubiblock");
        if (ubiblock_major < 0)
                return ubiblock_major;

        /*
         * Attach block devices from 'block=' module param.
         * Even if one block device in the param list fails to come up,
         * still allow the module to load and leave any others up.
         */
        ubiblock_create_from_param();

        /*
         * Block devices are only created upon user requests, so we ignore
         * existing volumes.
         */
        ret = ubi_register_volume_notifier(&ubiblock_notifier, 1);
        if (ret)
                goto err_unreg;
        return 0;

err_unreg:
        unregister_blkdev(ubiblock_major, "ubiblock");
        ubiblock_remove_all();
        return ret;
}

void __exit ubiblock_exit(void)
{
        ubi_unregister_volume_notifier(&ubiblock_notifier);
        ubiblock_remove_all();
        unregister_blkdev(ubiblock_major, "ubiblock");
}