/*
 * Copyright (c) 2012 Linutronix GmbH
 * Copyright (c) 2014 sigma star gmbh
 * Author: Richard Weinberger <richard@nod.at>
 *
 * 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.
 *
 */

/**
 * update_fastmap_work_fn - calls ubi_update_fastmap from a work queue
 * @wrk: the work description object
 */
static void update_fastmap_work_fn(struct work_struct *wrk)
{
        struct ubi_device *ubi = container_of(wrk, struct ubi_device, fm_work);

        ubi_update_fastmap(ubi);
        spin_lock(&ubi->wl_lock);
        ubi->fm_work_scheduled = 0;
        spin_unlock(&ubi->wl_lock);
}

/**
 * find_anchor_wl_entry - find wear-leveling entry to used as anchor PEB.
 * @root: the RB-tree where to look for
 */
static struct ubi_wl_entry *find_anchor_wl_entry(struct rb_root *root)
{
        struct rb_node *p;
        struct ubi_wl_entry *e, *victim = NULL;
        int max_ec = UBI_MAX_ERASECOUNTER;

        ubi_rb_for_each_entry(p, e, root, u.rb) {
                if (e->pnum < UBI_FM_MAX_START && e->ec < max_ec) {
                        victim = e;
                        max_ec = e->ec;
                }
        }

        return victim;
}

/**
 * return_unused_pool_pebs - returns unused PEB to the free tree.
 * @ubi: UBI device description object
 * @pool: fastmap pool description object
 */
static void return_unused_pool_pebs(struct ubi_device *ubi,
                                    struct ubi_fm_pool *pool)
{
        int i;
        struct ubi_wl_entry *e;

        for (i = pool->used; i < pool->size; i++) {
                e = ubi->lookuptbl[pool->pebs[i]];
                wl_tree_add(e, &ubi->free);
                ubi->free_count++;
        }
}

static int anchor_pebs_avalible(struct rb_root *root)
{
        struct rb_node *p;
        struct ubi_wl_entry *e;

        ubi_rb_for_each_entry(p, e, root, u.rb)
                if (e->pnum < UBI_FM_MAX_START)
                        return 1;

        return 0;
}

/**
 * ubi_wl_get_fm_peb - find a physical erase block with a given maximal number.
 * @ubi: UBI device description object
 * @anchor: This PEB will be used as anchor PEB by fastmap
 *
 * The function returns a physical erase block with a given maximal number
 * and removes it from the wl subsystem.
 * Must be called with wl_lock held!
 */
struct ubi_wl_entry *ubi_wl_get_fm_peb(struct ubi_device *ubi, int anchor)
{
        struct ubi_wl_entry *e = NULL;

        if (!ubi->free.rb_node || (ubi->free_count - ubi->beb_rsvd_pebs < 1))
                goto out;

        if (anchor)
                e = find_anchor_wl_entry(&ubi->free);
        else
                e = find_mean_wl_entry(ubi, &ubi->free);

        if (!e)
                goto out;

        self_check_in_wl_tree(ubi, e, &ubi->free);

        /* remove it from the free list,
         * the wl subsystem does no longer know this erase block */
        rb_erase(&e->u.rb, &ubi->free);
        ubi->free_count--;
out:
        return e;
}

/**
 * ubi_refill_pools - refills all fastmap PEB pools.
 * @ubi: UBI device description object
 */
void ubi_refill_pools(struct ubi_device *ubi)
{
        struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool;
        struct ubi_fm_pool *pool = &ubi->fm_pool;
        struct ubi_wl_entry *e;
        int enough;

        spin_lock(&ubi->wl_lock);

        return_unused_pool_pebs(ubi, wl_pool);
        return_unused_pool_pebs(ubi, pool);

        wl_pool->size = 0;
        pool->size = 0;

        for (;;) {
                enough = 0;
                if (pool->size < pool->max_size) {
                        if (!ubi->free.rb_node)
                                break;

                        e = wl_get_wle(ubi);
                        if (!e)
                                break;

                        pool->pebs[pool->size] = e->pnum;
                        pool->size++;
                } else
                        enough++;

                if (wl_pool->size < wl_pool->max_size) {
                        if (!ubi->free.rb_node ||
                           (ubi->free_count - ubi->beb_rsvd_pebs < 5))
                                break;

                        e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
                        self_check_in_wl_tree(ubi, e, &ubi->free);
                        rb_erase(&e->u.rb, &ubi->free);
                        ubi->free_count--;

                        wl_pool->pebs[wl_pool->size] = e->pnum;
                        wl_pool->size++;
                } else
                        enough++;

                if (enough == 2)
                        break;
        }

        wl_pool->used = 0;
        pool->used = 0;

        spin_unlock(&ubi->wl_lock);
}

/**
 * produce_free_peb - produce a free physical eraseblock.
 * @ubi: UBI device description object
 *
 * This function tries to make a free PEB by means of synchronous execution of
 * pending works. This may be needed if, for example the background thread is
 * disabled. Returns zero in case of success and a negative error code in case
 * of failure.
 */
static int produce_free_peb(struct ubi_device *ubi)
{
        int err;

        while (!ubi->free.rb_node && ubi->works_count) {
                dbg_wl("do one work synchronously");
                err = do_work(ubi);

                if (err)
                        return err;
        }

        return 0;
}

/**
 * ubi_wl_get_peb - get a physical eraseblock.
 * @ubi: UBI device description object
 *
 * This function returns a physical eraseblock in case of success and a
 * negative error code in case of failure.
 * Returns with ubi->fm_eba_sem held in read mode!
 */
int ubi_wl_get_peb(struct ubi_device *ubi)
{
        int ret, retried = 0;
        struct ubi_fm_pool *pool = &ubi->fm_pool;
        struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool;

again:
        down_read(&ubi->fm_eba_sem);
        spin_lock(&ubi->wl_lock);

        /* We check here also for the WL pool because at this point we can
         * refill the WL pool synchronous. */
        if (pool->used == pool->size || wl_pool->used == wl_pool->size) {
                spin_unlock(&ubi->wl_lock);
                up_read(&ubi->fm_eba_sem);
                ret = ubi_update_fastmap(ubi);
                if (ret) {
                        ubi_msg(ubi, "Unable to write a new fastmap: %i", ret);
                        down_read(&ubi->fm_eba_sem);
                        return -ENOSPC;
                }
                down_read(&ubi->fm_eba_sem);
                spin_lock(&ubi->wl_lock);
        }

        if (pool->used == pool->size) {
                spin_unlock(&ubi->wl_lock);
                if (retried) {
                        ubi_err(ubi, "Unable to get a free PEB from user WL pool");
                        ret = -ENOSPC;
                        goto out;
                }
                retried = 1;
                up_read(&ubi->fm_eba_sem);
                ret = produce_free_peb(ubi);
                if (ret < 0) {
                        down_read(&ubi->fm_eba_sem);
                        goto out;
                }
                goto again;
        }

        ubi_assert(pool->used < pool->size);
        ret = pool->pebs[pool->used++];
        prot_queue_add(ubi, ubi->lookuptbl[ret]);
        spin_unlock(&ubi->wl_lock);
out:
        return ret;
}

/* get_peb_for_wl - returns a PEB to be used internally by the WL sub-system.
 *
 * @ubi: UBI device description object
 */
static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
{
        struct ubi_fm_pool *pool = &ubi->fm_wl_pool;
        int pnum;

        ubi_assert(rwsem_is_locked(&ubi->fm_eba_sem));

        if (pool->used == pool->size) {
                /* We cannot update the fastmap here because this
                 * function is called in atomic context.
                 * Let's fail here and refill/update it as soon as possible. */
                if (!ubi->fm_work_scheduled) {
                        ubi->fm_work_scheduled = 1;
                        schedule_work(&ubi->fm_work);
                }
                return NULL;
        }

        pnum = pool->pebs[pool->used++];
        return ubi->lookuptbl[pnum];
}

/**
 * ubi_ensure_anchor_pebs - schedule wear-leveling to produce an anchor PEB.
 * @ubi: UBI device description object
 */
int ubi_ensure_anchor_pebs(struct ubi_device *ubi)
{
        struct ubi_work *wrk;

        spin_lock(&ubi->wl_lock);
        if (ubi->wl_scheduled) {
                spin_unlock(&ubi->wl_lock);
                return 0;
        }
        ubi->wl_scheduled = 1;
        spin_unlock(&ubi->wl_lock);

        wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
        if (!wrk) {
                spin_lock(&ubi->wl_lock);
                ubi->wl_scheduled = 0;
                spin_unlock(&ubi->wl_lock);
                return -ENOMEM;
        }

        wrk->anchor = 1;
        wrk->func = &wear_leveling_worker;
        __schedule_ubi_work(ubi, wrk);
        return 0;
}

/**
 * ubi_wl_put_fm_peb - returns a PEB used in a fastmap to the wear-leveling
 * sub-system.
 * see: ubi_wl_put_peb()
 *
 * @ubi: UBI device description object
 * @fm_e: physical eraseblock to return
 * @lnum: the last used logical eraseblock number for the PEB
 * @torture: if this physical eraseblock has to be tortured
 */
int ubi_wl_put_fm_peb(struct ubi_device *ubi, struct ubi_wl_entry *fm_e,
                      int lnum, int torture)
{
        struct ubi_wl_entry *e;
        int vol_id, pnum = fm_e->pnum;

        dbg_wl("PEB %d", pnum);

        ubi_assert(pnum >= 0);
        ubi_assert(pnum < ubi->peb_count);

        spin_lock(&ubi->wl_lock);
        e = ubi->lookuptbl[pnum];

        /* This can happen if we recovered from a fastmap the very
         * first time and writing now a new one. In this case the wl system
         * has never seen any PEB used by the original fastmap.
         */
        if (!e) {
                e = fm_e;
                ubi_assert(e->ec >= 0);
                ubi->lookuptbl[pnum] = e;
        }

        spin_unlock(&ubi->wl_lock);

        vol_id = lnum ? UBI_FM_DATA_VOLUME_ID : UBI_FM_SB_VOLUME_ID;
        return schedule_erase(ubi, e, vol_id, lnum, torture, true);
}

/**
 * ubi_is_erase_work - checks whether a work is erase work.
 * @wrk: The work object to be checked
 */
int ubi_is_erase_work(struct ubi_work *wrk)
{
        return wrk->func == erase_worker;
}

static void ubi_fastmap_close(struct ubi_device *ubi)
{
        int i;

        flush_work(&ubi->fm_work);
        return_unused_pool_pebs(ubi, &ubi->fm_pool);
        return_unused_pool_pebs(ubi, &ubi->fm_wl_pool);

        if (ubi->fm) {
                for (i = 0; i < ubi->fm->used_blocks; i++)
                        kfree(ubi->fm->e[i]);
        }
        kfree(ubi->fm);
}

/**
 * may_reserve_for_fm - tests whether a PEB shall be reserved for fastmap.
 * See find_mean_wl_entry()
 *
 * @ubi: UBI device description object
 * @e: physical eraseblock to return
 * @root: RB tree to test against.
 */
static struct ubi_wl_entry *may_reserve_for_fm(struct ubi_device *ubi,
                                           struct ubi_wl_entry *e,
                                           struct rb_root *root) {
        if (e && !ubi->fm_disabled && !ubi->fm &&
            e->pnum < UBI_FM_MAX_START)
                e = rb_entry(rb_next(root->rb_node),
                             struct ubi_wl_entry, u.rb);

        return e;
}