// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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
 */

/*
 * 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/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 ubi_sgl usgl;
};

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

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

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 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_IDR(ubiblock_minor_idr);
/* Protects ubiblock_devices and ubiblock_minor_idr */
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 blk_status_t ubiblock_read(struct request *req)
{
        struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);
        struct ubiblock *dev = req->q->queuedata;
        u64 pos = blk_rq_pos(req) << 9;
        int to_read = blk_rq_bytes(req);
        int bytes_left = to_read;
        /* Get LEB:offset address to read from */
        int offset = do_div(pos, dev->leb_size);
        int leb = pos;
        struct req_iterator iter;
        struct bio_vec bvec;
        int ret;

        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.
         */
        ubi_sgl_init(&pdu->usgl);
        blk_rq_map_sg(req, pdu->usgl.sg);

        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)
                        break;

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

        rq_for_each_segment(bvec, req, iter)
                flush_dcache_page(bvec.bv_page);

        blk_mq_end_request(req, errno_to_blk_status(ret));

        return BLK_STS_OK;
}

static int ubiblock_open(struct gendisk *disk, blk_mode_t mode)
{
        struct ubiblock *dev = 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 & BLK_OPEN_WRITE) {
                ret = -EROFS;
                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)
{
        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 gendisk *disk, struct hd_geometry *geo)
{
        /* Some tools might require this information */
        geo->heads = 1;
        geo->cylinders = 1;
        geo->sectors = get_capacity(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 blk_status_t ubiblock_queue_rq(struct blk_mq_hw_ctx *hctx,
                             const struct blk_mq_queue_data *bd)
{
        switch (req_op(bd->rq)) {
        case REQ_OP_READ:
                return ubiblock_read(bd->rq);
        default:
                return BLK_STS_IOERR;
        }
}

static int ubiblock_init_request(struct blk_mq_tag_set *set,
                struct request *req, unsigned int hctx_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);
        return 0;
}

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

static int calc_disk_capacity(struct ubi_volume_info *vi, u64 *disk_capacity)
{
        u64 size = vi->used_bytes >> 9;

        if (vi->used_bytes % 512) {
                if (vi->vol_type == UBI_DYNAMIC_VOLUME)
                        pr_warn("UBI: block: volume size is not a multiple of 512, last %llu bytes are ignored!\n",
                                vi->used_bytes - (size << 9));
                else
                        pr_info("UBI: block: volume size is not a multiple of 512, last %llu bytes are ignored!\n",
                                vi->used_bytes - (size << 9));
        }

        if ((sector_t)size != size)
                return -EFBIG;

        *disk_capacity = size;

        return 0;
}

int ubiblock_create(struct ubi_volume_info *vi)
{
        struct queue_limits lim = {
                .max_segments           = UBI_MAX_SG_COUNT,
        };
        struct ubiblock *dev;
        struct gendisk *gd;
        u64 disk_capacity;
        int ret;

        ret = calc_disk_capacity(vi, &disk_capacity);
        if (ret) {
                return ret;
        }

        /* Check that the volume isn't already handled */
        mutex_lock(&devices_mutex);
        if (find_dev_nolock(vi->ubi_num, vi->vol_id)) {
                ret = -EEXIST;
                goto out_unlock;
        }

        dev = kzalloc_obj(struct ubiblock);
        if (!dev) {
                ret = -ENOMEM;
                goto out_unlock;
        }

        mutex_init(&dev->dev_mutex);

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

        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_BLOCKING;
        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) {
                pr_err("ubiblock%d_%d: blk_mq_alloc_tag_set failed\n",
                        dev->ubi_num, dev->vol_id);
                goto out_free_dev;
        }


        /* Initialize the gendisk of this ubiblock device */
        gd = blk_mq_alloc_disk(&dev->tag_set, &lim, dev);
        if (IS_ERR(gd)) {
                ret = PTR_ERR(gd);
                goto out_free_tags;
        }

        gd->fops = &ubiblock_ops;
        gd->major = ubiblock_major;
        gd->minors = 1;
        gd->first_minor = idr_alloc(&ubiblock_minor_idr, dev, 0, 0, GFP_KERNEL);
        if (gd->first_minor < 0) {
                pr_err("ubiblock%d_%d: block: dynamic minor allocation failed\n",
                        dev->ubi_num, dev->vol_id);
                ret = -ENODEV;
                goto out_cleanup_disk;
        }
        gd->flags |= GENHD_FL_NO_PART;
        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->rq = gd->queue;

        list_add_tail(&dev->list, &ubiblock_devices);

        /* Must be the last step: anyone can call file ops from now on */
        ret = device_add_disk(vi->dev, dev->gd, NULL);
        if (ret)
                goto out_remove_minor;

        dev_info(disk_to_dev(dev->gd), "created from ubi%d:%d(%s)",
                 dev->ubi_num, dev->vol_id, vi->name);
        mutex_unlock(&devices_mutex);
        return 0;

out_remove_minor:
        list_del(&dev->list);
        idr_remove(&ubiblock_minor_idr, gd->first_minor);
out_cleanup_disk:
        put_disk(gd);
out_free_tags:
        blk_mq_free_tag_set(&dev->tag_set);
out_free_dev:
        kfree(dev);
out_unlock:
        mutex_unlock(&devices_mutex);

        return ret;
}

static void ubiblock_cleanup(struct ubiblock *dev)
{
        int id = dev->gd->first_minor;

        /* Stop new requests to arrive */
        del_gendisk(dev->gd);
        /* Finally destroy the blk queue */
        dev_info(disk_to_dev(dev->gd), "released");
        put_disk(dev->gd);
        blk_mq_free_tag_set(&dev->tag_set);
        idr_remove(&ubiblock_minor_idr, id);
}

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

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

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

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

        kfree(dev);
        return 0;

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

static int ubiblock_resize(struct ubi_volume_info *vi)
{
        struct ubiblock *dev;
        u64 disk_capacity;
        int ret;

        /*
         * 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;
        }

        ret = calc_disk_capacity(vi, &disk_capacity);
        if (ret) {
                mutex_unlock(&devices_mutex);
                if (ret == -EFBIG) {
                        dev_warn(disk_to_dev(dev->gd),
                                 "the volume is too big (%d LEBs), cannot resize",
                                 vi->size);
                }
                return ret;
        }

        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 bool
match_volume_desc(struct ubi_volume_info *vi, const char *name, int ubi_num, int vol_id)
{
        int err, len, cur_ubi_num, cur_vol_id;

        if (ubi_num == -1) {
                /* No ubi num, name must be a vol device path */
                err = ubi_get_num_by_path(name, &cur_ubi_num, &cur_vol_id);
                if (err || vi->ubi_num != cur_ubi_num || vi->vol_id != cur_vol_id)
                        return false;

                return true;
        }

        if (vol_id == -1) {
                /* Got ubi_num, but no vol_id, name must be volume name */
                if (vi->ubi_num != ubi_num)
                        return false;

                len = strnlen(name, UBI_VOL_NAME_MAX + 1);
                if (len < 1 || vi->name_len != len)
                        return false;

                if (strcmp(name, vi->name))
                        return false;

                return true;
        }

        if (vi->ubi_num != ubi_num)
                return false;

        if (vi->vol_id != vol_id)
                return false;

        return true;
}

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

        /*
         * Iterate over ubiblock cmdline parameters. If a parameter matches the
         * newly added volume create the ubiblock device for it.
         */
        for (i = 0; i < ubiblock_devs; i++) {
                p = &ubiblock_param[i];

                if (!match_volume_desc(vi, p->name, p->ubi_num, p->vol_id))
                        continue;

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

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:
                ubiblock_create_from_param(&nt->vi);
                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 void ubiblock_remove_all(void)
{
        struct ubiblock *next;
        struct ubiblock *dev;

        mutex_lock(&devices_mutex);
        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);
        }
        mutex_unlock(&devices_mutex);
}

int __init ubiblock_init(void)
{
        int ret;

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

        ret = ubi_register_volume_notifier(&ubiblock_notifier, 0);
        if (ret)
                goto err_unreg;
        return 0;

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

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