drivers/mtd/ubi/fastmap-wl.c - third_party/kernel - Git at Google

 // 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 || (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, 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;
 }

 /* 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;
 	}

 	/* No luck, trigger wear leveling to produce a new anchor PEB */
 	ubi->fm_do_produce_anchor = 1;
 	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->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;

 	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;
 	}

 	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;
 }
	// 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 \|\| (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, 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;
	}

	/* 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;
	}

	/* No luck, trigger wear leveling to produce a new anchor PEB */
	ubi->fm_do_produce_anchor = 1;
	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->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;

	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;
	}

	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;
	}