// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2012 Linutronix GmbH
 * Copyright (c) 2014 sigma star gmbh
 * Author: Richard Weinberger <richard@nod.at>
 */

/**
 * 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;
}

static inline void return_unused_peb(struct ubi_device *ubi,
                                     struct ubi_wl_entry *e)
{
        wl_tree_add(e, &ubi->free);
        ubi->free_count++;
}

/**
 * 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]];
                return_unused_peb(ubi, e);
        }
}

/**
 * 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)
                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;
}

/*
 * wait_free_pebs_for_pool - wait until there enough free pebs
 * @ubi: UBI device description object
 *
 * Wait and execute do_work until there are enough free pebs, fill pool
 * as much as we can. This will reduce pool refilling times, which can
 * reduce the fastmap updating frequency.
 */
static void wait_free_pebs_for_pool(struct ubi_device *ubi)
{
        struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool;
        struct ubi_fm_pool *pool = &ubi->fm_pool;
        int free, expect_free, executed;
        /*
         * There are at least following free pebs which reserved by UBI:
         * 1. WL_RESERVED_PEBS[1]
         * 2. EBA_RESERVED_PEBS[1]
         * 3. fm pebs - 1: Twice fastmap size deducted by fastmap and fm_anchor
         * 4. beb_rsvd_pebs: This value should be get under lock ubi->wl_lock
         */
        int reserved = WL_RESERVED_PEBS + EBA_RESERVED_PEBS +
                       ubi->fm_size / ubi->leb_size - 1 + ubi->fm_pool_rsv_cnt;

        do {
                spin_lock(&ubi->wl_lock);
                free = ubi->free_count;
                free += pool->size - pool->used + wl_pool->size - wl_pool->used;
                expect_free = reserved + ubi->beb_rsvd_pebs;
                spin_unlock(&ubi->wl_lock);

                /*
                 * Break out if there are no works or work is executed failure,
                 * given the fact that erase_worker will schedule itself when
                 * -EBUSY is returned from mtd layer caused by system shutdown.
                 */
                if (do_work(ubi, &executed) || !executed)
                        break;
        } while (free < expect_free);
}

/*
 * left_free_count - returns the number of free pebs to fill fm pools
 * @ubi: UBI device description object
 *
 * This helper function returns the number of free pebs (deducted
 * by fastmap pebs) to fill fm_pool and fm_wl_pool.
 */
static int left_free_count(struct ubi_device *ubi)
{
        int fm_used = 0;        // fastmap non anchor pebs.

        if (!ubi->free.rb_node)
                return 0;

        if (!ubi->ro_mode && !ubi->fm_disabled)
                fm_used = ubi->fm_size / ubi->leb_size - 1;

        return ubi->free_count - fm_used;
}

/*
 * can_fill_pools - whether free PEBs will be left after filling pools
 * @ubi: UBI device description object
 * @free: current number of free PEBs
 *
 * Return %1 if there are still left free PEBs after filling pools,
 * otherwise %0 is returned.
 */
static int can_fill_pools(struct ubi_device *ubi, int free)
{
        struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool;
        struct ubi_fm_pool *pool = &ubi->fm_pool;
        int pool_need = pool->max_size - pool->size +
                        wl_pool->max_size - wl_pool->size;

        if (free - pool_need < 1)
                return 0;

        return 1;
}

/**
 * ubi_refill_pools_and_lock - refills all fastmap PEB pools and takes fm locks.
 * @ubi: UBI device description object
 */
void ubi_refill_pools_and_lock(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;

        if (!ubi->ro_mode && !ubi->fm_disabled)
                wait_free_pebs_for_pool(ubi);

        down_write(&ubi->fm_protect);
        down_write(&ubi->work_sem);
        down_write(&ubi->fm_eba_sem);

        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;

        if (ubi->fm_anchor) {
                wl_tree_add(ubi->fm_anchor, &ubi->free);
                ubi->free_count++;
                ubi->fm_anchor = NULL;
        }

        if (!ubi->fm_disabled)
                /*
                 * All available PEBs are in ubi->free, now is the time to get
                 * the best anchor PEBs.
                 */
                ubi->fm_anchor = ubi_wl_get_fm_peb(ubi, 1);

        for (;;) {
                enough = 0;
                if (pool->size < pool->max_size) {
                        if (left_free_count(ubi) <= 0)
                                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) {
                        int left_free = left_free_count(ubi);

                        if (left_free <= 0)
                                break;

                        e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF,
                                          !can_fill_pools(ubi, left_free));
                        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, NULL);

                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, attempts = 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);
                attempts++;
                if (attempts == 10) {
                        ubi_err(ubi, "Unable to get a free PEB from user WL pool");
                        ret = -ENOSPC;
                        goto out;
                }
                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;
}

/**
 * next_peb_for_wl - returns next PEB to be used internally by the
 * WL sub-system.
 *
 * @ubi: UBI device description object
 * @need_fill: whether to fill wear-leveling pool when no PEBs are found
 */
static struct ubi_wl_entry *next_peb_for_wl(struct ubi_device *ubi,
                                            bool need_fill)
{
        struct ubi_fm_pool *pool = &ubi->fm_wl_pool;
        int pnum;

        if (pool->used == pool->size) {
                if (need_fill && !ubi->fm_work_scheduled) {
                        /*
                         * 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.
                         */
                        ubi->fm_work_scheduled = 1;
                        schedule_work(&ubi->fm_work);
                }
                return NULL;
        }

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

/**
 * need_wear_leveling - checks whether to trigger a wear leveling work.
 * UBI fetches free PEB from wl_pool, we check free PEBs from both 'wl_pool'
 * and 'ubi->free', because free PEB in 'ubi->free' tree maybe moved into
 * 'wl_pool' by ubi_refill_pools().
 *
 * @ubi: UBI device description object
 */
static bool need_wear_leveling(struct ubi_device *ubi)
{
        int ec;
        struct ubi_wl_entry *e;

        if (!ubi->used.rb_node)
                return false;

        e = next_peb_for_wl(ubi, false);
        if (!e) {
                if (!ubi->free.rb_node)
                        return false;
                e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF, 0);
                ec = e->ec;
        } else {
                ec = e->ec;
                if (ubi->free.rb_node) {
                        e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF, 0);
                        ec = max(ec, e->ec);
                }
        }
        e = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);

        return ec - e->ec >= UBI_WL_THRESHOLD;
}

/* 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;
        struct ubi_wl_entry *anchor;

        spin_lock(&ubi->wl_lock);

        /* Do we already have an anchor? */
        if (ubi->fm_anchor) {
                spin_unlock(&ubi->wl_lock);
                return 0;
        }

        /* See if we can find an anchor PEB on the list of free PEBs */
        anchor = ubi_wl_get_fm_peb(ubi, 1);
        if (anchor) {
                ubi->fm_anchor = anchor;
                spin_unlock(&ubi->wl_lock);
                return 0;
        }

        ubi->fm_do_produce_anchor = 1;
        /* No luck, trigger wear leveling to produce a new anchor PEB. */
        if (ubi->wl_scheduled) {
                spin_unlock(&ubi->wl_lock);
                return 0;
        }
        ubi->wl_scheduled = 1;
        spin_unlock(&ubi->wl_lock);

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

        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)
{
        return_unused_pool_pebs(ubi, &ubi->fm_pool);
        return_unused_pool_pebs(ubi, &ubi->fm_wl_pool);

        if (ubi->fm_anchor) {
                return_unused_peb(ubi, ubi->fm_anchor);
                ubi->fm_anchor = NULL;
        }

        ubi_free_fastmap(ubi);
}

/**
 * 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 && !ubi->fm_anchor &&
            e->pnum < UBI_FM_MAX_START)
                e = rb_entry(rb_next(root->rb_node),
                             struct ubi_wl_entry, u.rb);

        return e;
}