Initial import

1 files changed, 1844 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
new file mode 100644
index 000000000..16214d3d5
--- /dev/null
+++ b/drivers/mtd/ubi/wl.c
@@ -0,0 +1,1844 @@
+/*
+ * Copyright (c) International Business Machines Corp., 2006
+ *
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * Authors: Artem Bityutskiy (Битюцкий Артём), Thomas Gleixner
+ */
+
+/*
+ * UBI wear-leveling sub-system.
+ *
+ * This sub-system is responsible for wear-leveling. It works in terms of
+ * physical eraseblocks and erase counters and knows nothing about logical
+ * eraseblocks, volumes, etc. From this sub-system's perspective all physical
+ * eraseblocks are of two types - used and free. Used physical eraseblocks are
+ * those that were "get" by the 'ubi_wl_get_peb()' function, and free physical
+ * eraseblocks are those that were put by the 'ubi_wl_put_peb()' function.
+ *
+ * Physical eraseblocks returned by 'ubi_wl_get_peb()' have only erase counter
+ * header. The rest of the physical eraseblock contains only %0xFF bytes.
+ *
+ * When physical eraseblocks are returned to the WL sub-system by means of the
+ * 'ubi_wl_put_peb()' function, they are scheduled for erasure. The erasure is
+ * done asynchronously in context of the per-UBI device background thread,
+ * which is also managed by the WL sub-system.
+ *
+ * The wear-leveling is ensured by means of moving the contents of used
+ * physical eraseblocks with low erase counter to free physical eraseblocks
+ * with high erase counter.
+ *
+ * If the WL sub-system fails to erase a physical eraseblock, it marks it as
+ * bad.
+ *
+ * This sub-system is also responsible for scrubbing. If a bit-flip is detected
+ * in a physical eraseblock, it has to be moved. Technically this is the same
+ * as moving it for wear-leveling reasons.
+ *
+ * As it was said, for the UBI sub-system all physical eraseblocks are either
+ * "free" or "used". Free eraseblock are kept in the @wl->free RB-tree, while
+ * used eraseblocks are kept in @wl->used, @wl->erroneous, or @wl->scrub
+ * RB-trees, as well as (temporarily) in the @wl->pq queue.
+ *
+ * When the WL sub-system returns a physical eraseblock, the physical
+ * eraseblock is protected from being moved for some "time". For this reason,
+ * the physical eraseblock is not directly moved from the @wl->free tree to the
+ * @wl->used tree. There is a protection queue in between where this
+ * physical eraseblock is temporarily stored (@wl->pq).
+ *
+ * All this protection stuff is needed because:
+ *  o we don't want to move physical eraseblocks just after we have given them
+ *    to the user; instead, we first want to let users fill them up with data;
+ *
+ *  o there is a chance that the user will put the physical eraseblock very
+ *    soon, so it makes sense not to move it for some time, but wait.
+ *
+ * Physical eraseblocks stay protected only for limited time. But the "time" is
+ * measured in erase cycles in this case. This is implemented with help of the
+ * protection queue. Eraseblocks are put to the tail of this queue when they
+ * are returned by the 'ubi_wl_get_peb()', and eraseblocks are removed from the
+ * head of the queue on each erase operation (for any eraseblock). So the
+ * length of the queue defines how may (global) erase cycles PEBs are protected.
+ *
+ * To put it differently, each physical eraseblock has 2 main states: free and
+ * used. The former state corresponds to the @wl->free tree. The latter state
+ * is split up on several sub-states:
+ * o the WL movement is allowed (@wl->used tree);
+ * o the WL movement is disallowed (@wl->erroneous) because the PEB is
+ *   erroneous - e.g., there was a read error;
+ * o the WL movement is temporarily prohibited (@wl->pq queue);
+ * o scrubbing is needed (@wl->scrub tree).
+ *
+ * Depending on the sub-state, wear-leveling entries of the used physical
+ * eraseblocks may be kept in one of those structures.
+ *
+ * Note, in this implementation, we keep a small in-RAM object for each physical
+ * eraseblock. This is surely not a scalable solution. But it appears to be good
+ * enough for moderately large flashes and it is simple. In future, one may
+ * re-work this sub-system and make it more scalable.
+ *
+ * At the moment this sub-system does not utilize the sequence number, which
+ * was introduced relatively recently. But it would be wise to do this because
+ * the sequence number of a logical eraseblock characterizes how old is it. For
+ * example, when we move a PEB with low erase counter, and we need to pick the
+ * target PEB, we pick a PEB with the highest EC if our PEB is "old" and we
+ * pick target PEB with an average EC if our PEB is not very "old". This is a
+ * room for future re-works of the WL sub-system.
+ */
+
+#include <linux/slab.h>
+#include <linux/crc32.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include "ubi.h"
+#include "wl.h"
+
+/* Number of physical eraseblocks reserved for wear-leveling purposes */
+#define WL_RESERVED_PEBS 1
+
+/*
+ * Maximum difference between two erase counters. If this threshold is
+ * exceeded, the WL sub-system starts moving data from used physical
+ * eraseblocks with low erase counter to free physical eraseblocks with high
+ * erase counter.
+ */
+#define UBI_WL_THRESHOLD CONFIG_MTD_UBI_WL_THRESHOLD
+
+/*
+ * When a physical eraseblock is moved, the WL sub-system has to pick the target
+ * physical eraseblock to move to. The simplest way would be just to pick the
+ * one with the highest erase counter. But in certain workloads this could lead
+ * to an unlimited wear of one or few physical eraseblock. Indeed, imagine a
+ * situation when the picked physical eraseblock is constantly erased after the
+ * data is written to it. So, we have a constant which limits the highest erase
+ * counter of the free physical eraseblock to pick. Namely, the WL sub-system
+ * does not pick eraseblocks with erase counter greater than the lowest erase
+ * counter plus %WL_FREE_MAX_DIFF.
+ */
+#define WL_FREE_MAX_DIFF (2*UBI_WL_THRESHOLD)
+
+/*
+ * Maximum number of consecutive background thread failures which is enough to
+ * switch to read-only mode.
+ */
+#define WL_MAX_FAILURES 32
+
+static int self_check_ec(struct ubi_device *ubi, int pnum, int ec);
+static int self_check_in_wl_tree(const struct ubi_device *ubi,
+				 struct ubi_wl_entry *e, struct rb_root *root);
+static int self_check_in_pq(const struct ubi_device *ubi,
+			    struct ubi_wl_entry *e);
+
+/**
+ * wl_tree_add - add a wear-leveling entry to a WL RB-tree.
+ * @e: the wear-leveling entry to add
+ * @root: the root of the tree
+ *
+ * Note, we use (erase counter, physical eraseblock number) pairs as keys in
+ * the @ubi->used and @ubi->free RB-trees.
+ */
+static void wl_tree_add(struct ubi_wl_entry *e, struct rb_root *root)
+{
+	struct rb_node **p, *parent = NULL;
+
+	p = &root->rb_node;
+	while (*p) {
+		struct ubi_wl_entry *e1;
+
+		parent = *p;
+		e1 = rb_entry(parent, struct ubi_wl_entry, u.rb);
+
+		if (e->ec < e1->ec)
+			p = &(*p)->rb_left;
+		else if (e->ec > e1->ec)
+			p = &(*p)->rb_right;
+		else {
+			ubi_assert(e->pnum != e1->pnum);
+			if (e->pnum < e1->pnum)
+				p = &(*p)->rb_left;
+			else
+				p = &(*p)->rb_right;
+		}
+	}
+
+	rb_link_node(&e->u.rb, parent, p);
+	rb_insert_color(&e->u.rb, root);
+}
+
+/**
+ * wl_tree_destroy - destroy a wear-leveling entry.
+ * @ubi: UBI device description object
+ * @e: the wear-leveling entry to add
+ *
+ * This function destroys a wear leveling entry and removes
+ * the reference from the lookup table.
+ */
+static void wl_entry_destroy(struct ubi_device *ubi, struct ubi_wl_entry *e)
+{
+	ubi->lookuptbl[e->pnum] = NULL;
+	kmem_cache_free(ubi_wl_entry_slab, e);
+}
+
+/**
+ * do_work - do one pending work.
+ * @ubi: UBI device description object
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
+ */
+static int do_work(struct ubi_device *ubi)
+{
+	int err;
+	struct ubi_work *wrk;
+
+	cond_resched();
+
+	/*
+	 * @ubi->work_sem is used to synchronize with the workers. Workers take
+	 * it in read mode, so many of them may be doing works at a time. But
+	 * the queue flush code has to be sure the whole queue of works is
+	 * done, and it takes the mutex in write mode.
+	 */
+	down_read(&ubi->work_sem);
+	spin_lock(&ubi->wl_lock);
+	if (list_empty(&ubi->works)) {
+		spin_unlock(&ubi->wl_lock);
+		up_read(&ubi->work_sem);
+		return 0;
+	}
+
+	wrk = list_entry(ubi->works.next, struct ubi_work, list);
+	list_del(&wrk->list);
+	ubi->works_count -= 1;
+	ubi_assert(ubi->works_count >= 0);
+	spin_unlock(&ubi->wl_lock);
+
+	/*
+	 * Call the worker function. Do not touch the work structure
+	 * after this call as it will have been freed or reused by that
+	 * time by the worker function.
+	 */
+	err = wrk->func(ubi, wrk, 0);
+	if (err)
+		ubi_err(ubi, "work failed with error code %d", err);
+	up_read(&ubi->work_sem);
+
+	return err;
+}
+
+/**
+ * in_wl_tree - check if wear-leveling entry is present in a WL RB-tree.
+ * @e: the wear-leveling entry to check
+ * @root: the root of the tree
+ *
+ * This function returns non-zero if @e is in the @root RB-tree and zero if it
+ * is not.
+ */
+static int in_wl_tree(struct ubi_wl_entry *e, struct rb_root *root)
+{
+	struct rb_node *p;
+
+	p = root->rb_node;
+	while (p) {
+		struct ubi_wl_entry *e1;
+
+		e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
+
+		if (e->pnum == e1->pnum) {
+			ubi_assert(e == e1);
+			return 1;
+		}
+
+		if (e->ec < e1->ec)
+			p = p->rb_left;
+		else if (e->ec > e1->ec)
+			p = p->rb_right;
+		else {
+			ubi_assert(e->pnum != e1->pnum);
+			if (e->pnum < e1->pnum)
+				p = p->rb_left;
+			else
+				p = p->rb_right;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * prot_queue_add - add physical eraseblock to the protection queue.
+ * @ubi: UBI device description object
+ * @e: the physical eraseblock to add
+ *
+ * This function adds @e to the tail of the protection queue @ubi->pq, where
+ * @e will stay for %UBI_PROT_QUEUE_LEN erase operations and will be
+ * temporarily protected from the wear-leveling worker. Note, @wl->lock has to
+ * be locked.
+ */
+static void prot_queue_add(struct ubi_device *ubi, struct ubi_wl_entry *e)
+{
+	int pq_tail = ubi->pq_head - 1;
+
+	if (pq_tail < 0)
+		pq_tail = UBI_PROT_QUEUE_LEN - 1;
+	ubi_assert(pq_tail >= 0 && pq_tail < UBI_PROT_QUEUE_LEN);
+	list_add_tail(&e->u.list, &ubi->pq[pq_tail]);
+	dbg_wl("added PEB %d EC %d to the protection queue", e->pnum, e->ec);
+}
+
+/**
+ * find_wl_entry - find wear-leveling entry closest to certain erase counter.
+ * @ubi: UBI device description object
+ * @root: the RB-tree where to look for
+ * @diff: maximum possible difference from the smallest erase counter
+ *
+ * This function looks for a wear leveling entry with erase counter closest to
+ * min + @diff, where min is the smallest erase counter.
+ */
+static struct ubi_wl_entry *find_wl_entry(struct ubi_device *ubi,
+					  struct rb_root *root, int diff)
+{
+	struct rb_node *p;
+	struct ubi_wl_entry *e, *prev_e = NULL;
+	int max;
+
+	e = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
+	max = e->ec + diff;
+
+	p = root->rb_node;
+	while (p) {
+		struct ubi_wl_entry *e1;
+
+		e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
+		if (e1->ec >= max)
+			p = p->rb_left;
+		else {
+			p = p->rb_right;
+			prev_e = e;
+			e = e1;
+		}
+	}
+
+	/* If no fastmap has been written and this WL entry can be used
+	 * as anchor PEB, hold it back and return the second best WL entry
+	 * such that fastmap can use the anchor PEB later. */
+	if (prev_e && !ubi->fm_disabled &&
+	    !ubi->fm && e->pnum < UBI_FM_MAX_START)
+		return prev_e;
+
+	return e;
+}
+
+/**
+ * find_mean_wl_entry - find wear-leveling entry with medium erase counter.
+ * @ubi: UBI device description object
+ * @root: the RB-tree where to look for
+ *
+ * This function looks for a wear leveling entry with medium erase counter,
+ * but not greater or equivalent than the lowest erase counter plus
+ * %WL_FREE_MAX_DIFF/2.
+ */
+static struct ubi_wl_entry *find_mean_wl_entry(struct ubi_device *ubi,
+					       struct rb_root *root)
+{
+	struct ubi_wl_entry *e, *first, *last;
+
+	first = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
+	last = rb_entry(rb_last(root), struct ubi_wl_entry, u.rb);
+
+	if (last->ec - first->ec < WL_FREE_MAX_DIFF) {
+		e = rb_entry(root->rb_node, struct ubi_wl_entry, u.rb);
+
+		/* If no fastmap has been written and this WL entry can be used
+		 * as anchor PEB, hold it back and return the second best
+		 * WL entry such that fastmap can use the anchor PEB later. */
+		e = may_reserve_for_fm(ubi, e, root);
+	} else
+		e = find_wl_entry(ubi, root, WL_FREE_MAX_DIFF/2);
+
+	return e;
+}
+
+/**
+ * wl_get_wle - get a mean wl entry to be used by ubi_wl_get_peb() or
+ * refill_wl_user_pool().
+ * @ubi: UBI device description object
+ *
+ * This function returns a a wear leveling entry in case of success and
+ * NULL in case of failure.
+ */
+static struct ubi_wl_entry *wl_get_wle(struct ubi_device *ubi)
+{
+	struct ubi_wl_entry *e;
+
+	e = find_mean_wl_entry(ubi, &ubi->free);
+	if (!e) {
+		ubi_err(ubi, "no free eraseblocks");
+		return NULL;
+	}
+
+	self_check_in_wl_tree(ubi, e, &ubi->free);
+
+	/*
+	 * Move the physical eraseblock to the protection queue where it will
+	 * be protected from being moved for some time.
+	 */
+	rb_erase(&e->u.rb, &ubi->free);
+	ubi->free_count--;
+	dbg_wl("PEB %d EC %d", e->pnum, e->ec);
+
+	return e;
+}
+
+/**
+ * prot_queue_del - remove a physical eraseblock from the protection queue.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock to remove
+ *
+ * This function deletes PEB @pnum from the protection queue and returns zero
+ * in case of success and %-ENODEV if the PEB was not found.
+ */
+static int prot_queue_del(struct ubi_device *ubi, int pnum)
+{
+	struct ubi_wl_entry *e;
+
+	e = ubi->lookuptbl[pnum];
+	if (!e)
+		return -ENODEV;
+
+	if (self_check_in_pq(ubi, e))
+		return -ENODEV;
+
+	list_del(&e->u.list);
+	dbg_wl("deleted PEB %d from the protection queue", e->pnum);
+	return 0;
+}
+
+/**
+ * sync_erase - synchronously erase a physical eraseblock.
+ * @ubi: UBI device description object
+ * @e: the the physical eraseblock to erase
+ * @torture: if the physical eraseblock has to be tortured
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
+ */
+static int sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
+		      int torture)
+{
+	int err;
+	struct ubi_ec_hdr *ec_hdr;
+	unsigned long long ec = e->ec;
+
+	dbg_wl("erase PEB %d, old EC %llu", e->pnum, ec);
+
+	err = self_check_ec(ubi, e->pnum, e->ec);
+	if (err)
+		return -EINVAL;
+
+	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
+	if (!ec_hdr)
+		return -ENOMEM;
+
+	err = ubi_io_sync_erase(ubi, e->pnum, torture);
+	if (err < 0)
+		goto out_free;
+
+	ec += err;
+	if (ec > UBI_MAX_ERASECOUNTER) {
+		/*
+		 * Erase counter overflow. Upgrade UBI and use 64-bit
+		 * erase counters internally.
+		 */
+		ubi_err(ubi, "erase counter overflow at PEB %d, EC %llu",
+			e->pnum, ec);
+		err = -EINVAL;
+		goto out_free;
+	}
+
+	dbg_wl("erased PEB %d, new EC %llu", e->pnum, ec);
+
+	ec_hdr->ec = cpu_to_be64(ec);
+
+	err = ubi_io_write_ec_hdr(ubi, e->pnum, ec_hdr);
+	if (err)
+		goto out_free;
+
+	e->ec = ec;
+	spin_lock(&ubi->wl_lock);
+	if (e->ec > ubi->max_ec)
+		ubi->max_ec = e->ec;
+	spin_unlock(&ubi->wl_lock);
+
+out_free:
+	kfree(ec_hdr);
+	return err;
+}
+
+/**
+ * serve_prot_queue - check if it is time to stop protecting PEBs.
+ * @ubi: UBI device description object
+ *
+ * This function is called after each erase operation and removes PEBs from the
+ * tail of the protection queue. These PEBs have been protected for long enough
+ * and should be moved to the used tree.
+ */
+static void serve_prot_queue(struct ubi_device *ubi)
+{
+	struct ubi_wl_entry *e, *tmp;
+	int count;
+
+	/*
+	 * There may be several protected physical eraseblock to remove,
+	 * process them all.
+	 */
+repeat:
+	count = 0;
+	spin_lock(&ubi->wl_lock);
+	list_for_each_entry_safe(e, tmp, &ubi->pq[ubi->pq_head], u.list) {
+		dbg_wl("PEB %d EC %d protection over, move to used tree",
+			e->pnum, e->ec);
+
+		list_del(&e->u.list);
+		wl_tree_add(e, &ubi->used);
+		if (count++ > 32) {
+			/*
+			 * Let's be nice and avoid holding the spinlock for
+			 * too long.
+			 */
+			spin_unlock(&ubi->wl_lock);
+			cond_resched();
+			goto repeat;
+		}
+	}
+
+	ubi->pq_head += 1;
+	if (ubi->pq_head == UBI_PROT_QUEUE_LEN)
+		ubi->pq_head = 0;
+	ubi_assert(ubi->pq_head >= 0 && ubi->pq_head < UBI_PROT_QUEUE_LEN);
+	spin_unlock(&ubi->wl_lock);
+}
+
+/**
+ * __schedule_ubi_work - schedule a work.
+ * @ubi: UBI device description object
+ * @wrk: the work to schedule
+ *
+ * This function adds a work defined by @wrk to the tail of the pending works
+ * list. Can only be used if ubi->work_sem is already held in read mode!
+ */
+static void __schedule_ubi_work(struct ubi_device *ubi, struct ubi_work *wrk)
+{
+	spin_lock(&ubi->wl_lock);
+	list_add_tail(&wrk->list, &ubi->works);
+	ubi_assert(ubi->works_count >= 0);
+	ubi->works_count += 1;
+	if (ubi->thread_enabled && !ubi_dbg_is_bgt_disabled(ubi))
+		wake_up_process(ubi->bgt_thread);
+	spin_unlock(&ubi->wl_lock);
+}
+
+/**
+ * schedule_ubi_work - schedule a work.
+ * @ubi: UBI device description object
+ * @wrk: the work to schedule
+ *
+ * This function adds a work defined by @wrk to the tail of the pending works
+ * list.
+ */
+static void schedule_ubi_work(struct ubi_device *ubi, struct ubi_work *wrk)
+{
+	down_read(&ubi->work_sem);
+	__schedule_ubi_work(ubi, wrk);
+	up_read(&ubi->work_sem);
+}
+
+static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk,
+			int shutdown);
+
+/**
+ * schedule_erase - schedule an erase work.
+ * @ubi: UBI device description object
+ * @e: the WL entry of the physical eraseblock to erase
+ * @vol_id: the volume ID that last used this PEB
+ * @lnum: the last used logical eraseblock number for the PEB
+ * @torture: if the physical eraseblock has to be tortured
+ *
+ * This function returns zero in case of success and a %-ENOMEM in case of
+ * failure.
+ */
+static int schedule_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
+			  int vol_id, int lnum, int torture)
+{
+	struct ubi_work *wl_wrk;
+
+	ubi_assert(e);
+
+	dbg_wl("schedule erasure of PEB %d, EC %d, torture %d",
+	       e->pnum, e->ec, torture);
+
+	wl_wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
+	if (!wl_wrk)
+		return -ENOMEM;
+
+	wl_wrk->func = &erase_worker;
+	wl_wrk->e = e;
+	wl_wrk->vol_id = vol_id;
+	wl_wrk->lnum = lnum;
+	wl_wrk->torture = torture;
+
+	schedule_ubi_work(ubi, wl_wrk);
+	return 0;
+}
+
+/**
+ * do_sync_erase - run the erase worker synchronously.
+ * @ubi: UBI device description object
+ * @e: the WL entry of the physical eraseblock to erase
+ * @vol_id: the volume ID that last used this PEB
+ * @lnum: the last used logical eraseblock number for the PEB
+ * @torture: if the physical eraseblock has to be tortured
+ *
+ */
+static int do_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
+			 int vol_id, int lnum, int torture)
+{
+	struct ubi_work *wl_wrk;
+
+	dbg_wl("sync erase of PEB %i", e->pnum);
+
+	wl_wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
+	if (!wl_wrk)
+		return -ENOMEM;
+
+	wl_wrk->e = e;
+	wl_wrk->vol_id = vol_id;
+	wl_wrk->lnum = lnum;
+	wl_wrk->torture = torture;
+
+	return erase_worker(ubi, wl_wrk, 0);
+}
+
+/**
+ * wear_leveling_worker - wear-leveling worker function.
+ * @ubi: UBI device description object
+ * @wrk: the work object
+ * @shutdown: non-zero if the worker has to free memory and exit
+ * because the WL-subsystem is shutting down
+ *
+ * This function copies a more worn out physical eraseblock to a less worn out
+ * one. Returns zero in case of success and a negative error code in case of
+ * failure.
+ */
+static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
+				int shutdown)
+{
+	int err, scrubbing = 0, torture = 0, protect = 0, erroneous = 0;
+	int vol_id = -1, lnum = -1;
+#ifdef CONFIG_MTD_UBI_FASTMAP
+	int anchor = wrk->anchor;
+#endif
+	struct ubi_wl_entry *e1, *e2;
+	struct ubi_vid_hdr *vid_hdr;
+
+	kfree(wrk);
+	if (shutdown)
+		return 0;
+
+	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
+	if (!vid_hdr)
+		return -ENOMEM;
+
+	mutex_lock(&ubi->move_mutex);
+	spin_lock(&ubi->wl_lock);
+	ubi_assert(!ubi->move_from && !ubi->move_to);
+	ubi_assert(!ubi->move_to_put);
+
+	if (!ubi->free.rb_node ||
+	    (!ubi->used.rb_node && !ubi->scrub.rb_node)) {
+		/*
+		 * No free physical eraseblocks? Well, they must be waiting in
+		 * the queue to be erased. Cancel movement - it will be
+		 * triggered again when a free physical eraseblock appears.
+		 *
+		 * No used physical eraseblocks? They must be temporarily
+		 * protected from being moved. They will be moved to the
+		 * @ubi->used tree later and the wear-leveling will be
+		 * triggered again.
+		 */
+		dbg_wl("cancel WL, a list is empty: free %d, used %d",
+		       !ubi->free.rb_node, !ubi->used.rb_node);
+		goto out_cancel;
+	}
+
+#ifdef CONFIG_MTD_UBI_FASTMAP
+	/* Check whether we need to produce an anchor PEB */
+	if (!anchor)
+		anchor = !anchor_pebs_avalible(&ubi->free);
+
+	if (anchor) {
+		e1 = find_anchor_wl_entry(&ubi->used);
+		if (!e1)
+			goto out_cancel;
+		e2 = get_peb_for_wl(ubi);
+		if (!e2)
+			goto out_cancel;
+
+		self_check_in_wl_tree(ubi, e1, &ubi->used);
+		rb_erase(&e1->u.rb, &ubi->used);
+		dbg_wl("anchor-move PEB %d to PEB %d", e1->pnum, e2->pnum);
+	} else if (!ubi->scrub.rb_node) {
+#else
+	if (!ubi->scrub.rb_node) {
+#endif
+		/*
+		 * Now pick the least worn-out used physical eraseblock and a
+		 * highly worn-out free physical eraseblock. If the erase
+		 * counters differ much enough, start wear-leveling.
+		 */
+		e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
+		e2 = get_peb_for_wl(ubi);
+		if (!e2)
+			goto out_cancel;
+
+		if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD)) {
+			dbg_wl("no WL needed: min used EC %d, max free EC %d",
+			       e1->ec, e2->ec);
+
+			/* Give the unused PEB back */
+			wl_tree_add(e2, &ubi->free);
+			ubi->free_count++;
+			goto out_cancel;
+		}
+		self_check_in_wl_tree(ubi, e1, &ubi->used);
+		rb_erase(&e1->u.rb, &ubi->used);
+		dbg_wl("move PEB %d EC %d to PEB %d EC %d",
+		       e1->pnum, e1->ec, e2->pnum, e2->ec);
+	} else {
+		/* Perform scrubbing */
+		scrubbing = 1;
+		e1 = rb_entry(rb_first(&ubi->scrub), struct ubi_wl_entry, u.rb);
+		e2 = get_peb_for_wl(ubi);
+		if (!e2)
+			goto out_cancel;
+
+		self_check_in_wl_tree(ubi, e1, &ubi->scrub);
+		rb_erase(&e1->u.rb, &ubi->scrub);
+		dbg_wl("scrub PEB %d to PEB %d", e1->pnum, e2->pnum);
+	}
+
+	ubi->move_from = e1;
+	ubi->move_to = e2;
+	spin_unlock(&ubi->wl_lock);
+
+	/*
+	 * Now we are going to copy physical eraseblock @e1->pnum to @e2->pnum.
+	 * We so far do not know which logical eraseblock our physical
+	 * eraseblock (@e1) belongs to. We have to read the volume identifier
+	 * header first.
+	 *
+	 * Note, we are protected from this PEB being unmapped and erased. The
+	 * 'ubi_wl_put_peb()' would wait for moving to be finished if the PEB
+	 * which is being moved was unmapped.
+	 */
+
+	err = ubi_io_read_vid_hdr(ubi, e1->pnum, vid_hdr, 0);
+	if (err && err != UBI_IO_BITFLIPS) {
+		if (err == UBI_IO_FF) {
+			/*
+			 * We are trying to move PEB without a VID header. UBI
+			 * always write VID headers shortly after the PEB was
+			 * given, so we have a situation when it has not yet
+			 * had a chance to write it, because it was preempted.
+			 * So add this PEB to the protection queue so far,
+			 * because presumably more data will be written there
+			 * (including the missing VID header), and then we'll
+			 * move it.
+			 */
+			dbg_wl("PEB %d has no VID header", e1->pnum);
+			protect = 1;
+			goto out_not_moved;
+		} else if (err == UBI_IO_FF_BITFLIPS) {
+			/*
+			 * The same situation as %UBI_IO_FF, but bit-flips were
+			 * detected. It is better to schedule this PEB for
+			 * scrubbing.
+			 */
+			dbg_wl("PEB %d has no VID header but has bit-flips",
+			       e1->pnum);
+			scrubbing = 1;
+			goto out_not_moved;
+		}
+
+		ubi_err(ubi, "error %d while reading VID header from PEB %d",
+			err, e1->pnum);
+		goto out_error;
+	}
+
+	vol_id = be32_to_cpu(vid_hdr->vol_id);
+	lnum = be32_to_cpu(vid_hdr->lnum);
+
+	err = ubi_eba_copy_leb(ubi, e1->pnum, e2->pnum, vid_hdr);
+	if (err) {
+		if (err == MOVE_CANCEL_RACE) {
+			/*
+			 * The LEB has not been moved because the volume is
+			 * being deleted or the PEB has been put meanwhile. We
+			 * should prevent this PEB from being selected for
+			 * wear-leveling movement again, so put it to the
+			 * protection queue.
+			 */
+			protect = 1;
+			goto out_not_moved;
+		}
+		if (err == MOVE_RETRY) {
+			scrubbing = 1;
+			goto out_not_moved;
+		}
+		if (err == MOVE_TARGET_BITFLIPS || err == MOVE_TARGET_WR_ERR ||
+		    err == MOVE_TARGET_RD_ERR) {
+			/*
+			 * Target PEB had bit-flips or write error - torture it.
+			 */
+			torture = 1;
+			goto out_not_moved;
+		}
+
+		if (err == MOVE_SOURCE_RD_ERR) {
+			/*
+			 * An error happened while reading the source PEB. Do
+			 * not switch to R/O mode in this case, and give the
+			 * upper layers a possibility to recover from this,
+			 * e.g. by unmapping corresponding LEB. Instead, just
+			 * put this PEB to the @ubi->erroneous list to prevent
+			 * UBI from trying to move it over and over again.
+			 */
+			if (ubi->erroneous_peb_count > ubi->max_erroneous) {
+				ubi_err(ubi, "too many erroneous eraseblocks (%d)",
+					ubi->erroneous_peb_count);
+				goto out_error;
+			}
+			erroneous = 1;
+			goto out_not_moved;
+		}
+
+		if (err < 0)
+			goto out_error;
+
+		ubi_assert(0);
+	}
+
+	/* The PEB has been successfully moved */
+	if (scrubbing)
+		ubi_msg(ubi, "scrubbed PEB %d (LEB %d:%d), data moved to PEB %d",
+			e1->pnum, vol_id, lnum, e2->pnum);
+	ubi_free_vid_hdr(ubi, vid_hdr);
+
+	spin_lock(&ubi->wl_lock);
+	if (!ubi->move_to_put) {
+		wl_tree_add(e2, &ubi->used);
+		e2 = NULL;
+	}
+	ubi->move_from = ubi->move_to = NULL;
+	ubi->move_to_put = ubi->wl_scheduled = 0;
+	spin_unlock(&ubi->wl_lock);
+
+	err = do_sync_erase(ubi, e1, vol_id, lnum, 0);
+	if (err) {
+		if (e2)
+			wl_entry_destroy(ubi, e2);
+		goto out_ro;
+	}
+
+	if (e2) {
+		/*
+		 * Well, the target PEB was put meanwhile, schedule it for
+		 * erasure.
+		 */
+		dbg_wl("PEB %d (LEB %d:%d) was put meanwhile, erase",
+		       e2->pnum, vol_id, lnum);
+		err = do_sync_erase(ubi, e2, vol_id, lnum, 0);
+		if (err)
+			goto out_ro;
+	}
+
+	dbg_wl("done");
+	mutex_unlock(&ubi->move_mutex);
+	return 0;
+
+	/*
+	 * For some reasons the LEB was not moved, might be an error, might be
+	 * something else. @e1 was not changed, so return it back. @e2 might
+	 * have been changed, schedule it for erasure.
+	 */
+out_not_moved:
+	if (vol_id != -1)
+		dbg_wl("cancel moving PEB %d (LEB %d:%d) to PEB %d (%d)",
+		       e1->pnum, vol_id, lnum, e2->pnum, err);
+	else
+		dbg_wl("cancel moving PEB %d to PEB %d (%d)",
+		       e1->pnum, e2->pnum, err);
+	spin_lock(&ubi->wl_lock);
+	if (protect)
+		prot_queue_add(ubi, e1);
+	else if (erroneous) {
+		wl_tree_add(e1, &ubi->erroneous);
+		ubi->erroneous_peb_count += 1;
+	} else if (scrubbing)
+		wl_tree_add(e1, &ubi->scrub);
+	else
+		wl_tree_add(e1, &ubi->used);
+	ubi_assert(!ubi->move_to_put);
+	ubi->move_from = ubi->move_to = NULL;
+	ubi->wl_scheduled = 0;
+	spin_unlock(&ubi->wl_lock);
+
+	ubi_free_vid_hdr(ubi, vid_hdr);
+	err = do_sync_erase(ubi, e2, vol_id, lnum, torture);
+	if (err)
+		goto out_ro;
+
+	mutex_unlock(&ubi->move_mutex);
+	return 0;
+
+out_error:
+	if (vol_id != -1)
+		ubi_err(ubi, "error %d while moving PEB %d to PEB %d",
+			err, e1->pnum, e2->pnum);
+	else
+		ubi_err(ubi, "error %d while moving PEB %d (LEB %d:%d) to PEB %d",
+			err, e1->pnum, vol_id, lnum, e2->pnum);
+	spin_lock(&ubi->wl_lock);
+	ubi->move_from = ubi->move_to = NULL;
+	ubi->move_to_put = ubi->wl_scheduled = 0;
+	spin_unlock(&ubi->wl_lock);
+
+	ubi_free_vid_hdr(ubi, vid_hdr);
+	wl_entry_destroy(ubi, e1);
+	wl_entry_destroy(ubi, e2);
+
+out_ro:
+	ubi_ro_mode(ubi);
+	mutex_unlock(&ubi->move_mutex);
+	ubi_assert(err != 0);
+	return err < 0 ? err : -EIO;
+
+out_cancel:
+	ubi->wl_scheduled = 0;
+	spin_unlock(&ubi->wl_lock);
+	mutex_unlock(&ubi->move_mutex);
+	ubi_free_vid_hdr(ubi, vid_hdr);
+	return 0;
+}
+
+/**
+ * ensure_wear_leveling - schedule wear-leveling if it is needed.
+ * @ubi: UBI device description object
+ * @nested: set to non-zero if this function is called from UBI worker
+ *
+ * This function checks if it is time to start wear-leveling and schedules it
+ * if yes. This function returns zero in case of success and a negative error
+ * code in case of failure.
+ */
+static int ensure_wear_leveling(struct ubi_device *ubi, int nested)
+{
+	int err = 0;
+	struct ubi_wl_entry *e1;
+	struct ubi_wl_entry *e2;
+	struct ubi_work *wrk;
+
+	spin_lock(&ubi->wl_lock);
+	if (ubi->wl_scheduled)
+		/* Wear-leveling is already in the work queue */
+		goto out_unlock;
+
+	/*
+	 * If the ubi->scrub tree is not empty, scrubbing is needed, and the
+	 * the WL worker has to be scheduled anyway.
+	 */
+	if (!ubi->scrub.rb_node) {
+		if (!ubi->used.rb_node || !ubi->free.rb_node)
+			/* No physical eraseblocks - no deal */
+			goto out_unlock;
+
+		/*
+		 * We schedule wear-leveling only if the difference between the
+		 * lowest erase counter of used physical eraseblocks and a high
+		 * erase counter of free physical eraseblocks is greater than
+		 * %UBI_WL_THRESHOLD.
+		 */
+		e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
+		e2 = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
+
+		if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD))
+			goto out_unlock;
+		dbg_wl("schedule wear-leveling");
+	} else
+		dbg_wl("schedule scrubbing");
+
+	ubi->wl_scheduled = 1;
+	spin_unlock(&ubi->wl_lock);
+
+	wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
+	if (!wrk) {
+		err = -ENOMEM;
+		goto out_cancel;
+	}
+
+	wrk->anchor = 0;
+	wrk->func = &wear_leveling_worker;
+	if (nested)
+		__schedule_ubi_work(ubi, wrk);
+	else
+		schedule_ubi_work(ubi, wrk);
+	return err;
+
+out_cancel:
+	spin_lock(&ubi->wl_lock);
+	ubi->wl_scheduled = 0;
+out_unlock:
+	spin_unlock(&ubi->wl_lock);
+	return err;
+}
+
+/**
+ * erase_worker - physical eraseblock erase worker function.
+ * @ubi: UBI device description object
+ * @wl_wrk: the work object
+ * @shutdown: non-zero if the worker has to free memory and exit
+ * because the WL sub-system is shutting down
+ *
+ * This function erases a physical eraseblock and perform torture testing if
+ * needed. It also takes care about marking the physical eraseblock bad if
+ * needed. Returns zero in case of success and a negative error code in case of
+ * failure.
+ */
+static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk,
+			int shutdown)
+{
+	struct ubi_wl_entry *e = wl_wrk->e;
+	int pnum = e->pnum;
+	int vol_id = wl_wrk->vol_id;
+	int lnum = wl_wrk->lnum;
+	int err, available_consumed = 0;
+
+	if (shutdown) {
+		dbg_wl("cancel erasure of PEB %d EC %d", pnum, e->ec);
+		kfree(wl_wrk);
+		wl_entry_destroy(ubi, e);
+		return 0;
+	}
+
+	dbg_wl("erase PEB %d EC %d LEB %d:%d",
+	       pnum, e->ec, wl_wrk->vol_id, wl_wrk->lnum);
+
+	err = sync_erase(ubi, e, wl_wrk->torture);
+	if (!err) {
+		/* Fine, we've erased it successfully */
+		kfree(wl_wrk);
+
+		spin_lock(&ubi->wl_lock);
+		wl_tree_add(e, &ubi->free);
+		ubi->free_count++;
+		spin_unlock(&ubi->wl_lock);
+
+		/*
+		 * One more erase operation has happened, take care about
+		 * protected physical eraseblocks.
+		 */
+		serve_prot_queue(ubi);
+
+		/* And take care about wear-leveling */
+		err = ensure_wear_leveling(ubi, 1);
+		return err;
+	}
+
+	ubi_err(ubi, "failed to erase PEB %d, error %d", pnum, err);
+	kfree(wl_wrk);
+
+	if (err == -EINTR || err == -ENOMEM || err == -EAGAIN ||
+	    err == -EBUSY) {
+		int err1;
+
+		/* Re-schedule the LEB for erasure */
+		err1 = schedule_erase(ubi, e, vol_id, lnum, 0);
+		if (err1) {
+			err = err1;
+			goto out_ro;
+		}
+		return err;
+	}
+
+	wl_entry_destroy(ubi, e);
+	if (err != -EIO)
+		/*
+		 * If this is not %-EIO, we have no idea what to do. Scheduling
+		 * this physical eraseblock for erasure again would cause
+		 * errors again and again. Well, lets switch to R/O mode.
+		 */
+		goto out_ro;
+
+	/* It is %-EIO, the PEB went bad */
+
+	if (!ubi->bad_allowed) {
+		ubi_err(ubi, "bad physical eraseblock %d detected", pnum);
+		goto out_ro;
+	}
+
+	spin_lock(&ubi->volumes_lock);
+	if (ubi->beb_rsvd_pebs == 0) {
+		if (ubi->avail_pebs == 0) {
+			spin_unlock(&ubi->volumes_lock);
+			ubi_err(ubi, "no reserved/available physical eraseblocks");
+			goto out_ro;
+		}
+		ubi->avail_pebs -= 1;
+		available_consumed = 1;
+	}
+	spin_unlock(&ubi->volumes_lock);
+
+	ubi_msg(ubi, "mark PEB %d as bad", pnum);
+	err = ubi_io_mark_bad(ubi, pnum);
+	if (err)
+		goto out_ro;
+
+	spin_lock(&ubi->volumes_lock);
+	if (ubi->beb_rsvd_pebs > 0) {
+		if (available_consumed) {
+			/*
+			 * The amount of reserved PEBs increased since we last
+			 * checked.
+			 */
+			ubi->avail_pebs += 1;
+			available_consumed = 0;
+		}
+		ubi->beb_rsvd_pebs -= 1;
+	}
+	ubi->bad_peb_count += 1;
+	ubi->good_peb_count -= 1;
+	ubi_calculate_reserved(ubi);
+	if (available_consumed)
+		ubi_warn(ubi, "no PEBs in the reserved pool, used an available PEB");
+	else if (ubi->beb_rsvd_pebs)
+		ubi_msg(ubi, "%d PEBs left in the reserve",
+			ubi->beb_rsvd_pebs);
+	else
+		ubi_warn(ubi, "last PEB from the reserve was used");
+	spin_unlock(&ubi->volumes_lock);
+
+	return err;
+
+out_ro:
+	if (available_consumed) {
+		spin_lock(&ubi->volumes_lock);
+		ubi->avail_pebs += 1;
+		spin_unlock(&ubi->volumes_lock);
+	}
+	ubi_ro_mode(ubi);
+	return err;
+}
+
+/**
+ * ubi_wl_put_peb - return a PEB to the wear-leveling sub-system.
+ * @ubi: UBI device description object
+ * @vol_id: the volume ID that last used this PEB
+ * @lnum: the last used logical eraseblock number for the PEB
+ * @pnum: physical eraseblock to return
+ * @torture: if this physical eraseblock has to be tortured
+ *
+ * This function is called to return physical eraseblock @pnum to the pool of
+ * free physical eraseblocks. The @torture flag has to be set if an I/O error
+ * occurred to this @pnum and it has to be tested. This function returns zero
+ * in case of success, and a negative error code in case of failure.
+ */
+int ubi_wl_put_peb(struct ubi_device *ubi, int vol_id, int lnum,
+		   int pnum, int torture)
+{
+	int err;
+	struct ubi_wl_entry *e;
+
+	dbg_wl("PEB %d", pnum);
+	ubi_assert(pnum >= 0);
+	ubi_assert(pnum < ubi->peb_count);
+
+	down_read(&ubi->fm_protect);
+
+retry:
+	spin_lock(&ubi->wl_lock);
+	e = ubi->lookuptbl[pnum];
+	if (e == ubi->move_from) {
+		/*
+		 * User is putting the physical eraseblock which was selected to
+		 * be moved. It will be scheduled for erasure in the
+		 * wear-leveling worker.
+		 */
+		dbg_wl("PEB %d is being moved, wait", pnum);
+		spin_unlock(&ubi->wl_lock);
+
+		/* Wait for the WL worker by taking the @ubi->move_mutex */
+		mutex_lock(&ubi->move_mutex);
+		mutex_unlock(&ubi->move_mutex);
+		goto retry;
+	} else if (e == ubi->move_to) {
+		/*
+		 * User is putting the physical eraseblock which was selected
+		 * as the target the data is moved to. It may happen if the EBA
+		 * sub-system already re-mapped the LEB in 'ubi_eba_copy_leb()'
+		 * but the WL sub-system has not put the PEB to the "used" tree
+		 * yet, but it is about to do this. So we just set a flag which
+		 * will tell the WL worker that the PEB is not needed anymore
+		 * and should be scheduled for erasure.
+		 */
+		dbg_wl("PEB %d is the target of data moving", pnum);
+		ubi_assert(!ubi->move_to_put);
+		ubi->move_to_put = 1;
+		spin_unlock(&ubi->wl_lock);
+		up_read(&ubi->fm_protect);
+		return 0;
+	} else {
+		if (in_wl_tree(e, &ubi->used)) {
+			self_check_in_wl_tree(ubi, e, &ubi->used);
+			rb_erase(&e->u.rb, &ubi->used);
+		} else if (in_wl_tree(e, &ubi->scrub)) {
+			self_check_in_wl_tree(ubi, e, &ubi->scrub);
+			rb_erase(&e->u.rb, &ubi->scrub);
+		} else if (in_wl_tree(e, &ubi->erroneous)) {
+			self_check_in_wl_tree(ubi, e, &ubi->erroneous);
+			rb_erase(&e->u.rb, &ubi->erroneous);
+			ubi->erroneous_peb_count -= 1;
+			ubi_assert(ubi->erroneous_peb_count >= 0);
+			/* Erroneous PEBs should be tortured */
+			torture = 1;
+		} else {
+			err = prot_queue_del(ubi, e->pnum);
+			if (err) {
+				ubi_err(ubi, "PEB %d not found", pnum);
+				ubi_ro_mode(ubi);
+				spin_unlock(&ubi->wl_lock);
+				up_read(&ubi->fm_protect);
+				return err;
+			}
+		}
+	}
+	spin_unlock(&ubi->wl_lock);
+
+	err = schedule_erase(ubi, e, vol_id, lnum, torture);
+	if (err) {
+		spin_lock(&ubi->wl_lock);
+		wl_tree_add(e, &ubi->used);
+		spin_unlock(&ubi->wl_lock);
+	}
+
+	up_read(&ubi->fm_protect);
+	return err;
+}
+
+/**
+ * ubi_wl_scrub_peb - schedule a physical eraseblock for scrubbing.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock to schedule
+ *
+ * If a bit-flip in a physical eraseblock is detected, this physical eraseblock
+ * needs scrubbing. This function schedules a physical eraseblock for
+ * scrubbing which is done in background. This function returns zero in case of
+ * success and a negative error code in case of failure.
+ */
+int ubi_wl_scrub_peb(struct ubi_device *ubi, int pnum)
+{
+	struct ubi_wl_entry *e;
+
+	ubi_msg(ubi, "schedule PEB %d for scrubbing", pnum);
+
+retry:
+	spin_lock(&ubi->wl_lock);
+	e = ubi->lookuptbl[pnum];
+	if (e == ubi->move_from || in_wl_tree(e, &ubi->scrub) ||
+				   in_wl_tree(e, &ubi->erroneous)) {
+		spin_unlock(&ubi->wl_lock);
+		return 0;
+	}
+
+	if (e == ubi->move_to) {
+		/*
+		 * This physical eraseblock was used to move data to. The data
+		 * was moved but the PEB was not yet inserted to the proper
+		 * tree. We should just wait a little and let the WL worker
+		 * proceed.
+		 */
+		spin_unlock(&ubi->wl_lock);
+		dbg_wl("the PEB %d is not in proper tree, retry", pnum);
+		yield();
+		goto retry;
+	}
+
+	if (in_wl_tree(e, &ubi->used)) {
+		self_check_in_wl_tree(ubi, e, &ubi->used);
+		rb_erase(&e->u.rb, &ubi->used);
+	} else {
+		int err;
+
+		err = prot_queue_del(ubi, e->pnum);
+		if (err) {
+			ubi_err(ubi, "PEB %d not found", pnum);
+			ubi_ro_mode(ubi);
+			spin_unlock(&ubi->wl_lock);
+			return err;
+		}
+	}
+
+	wl_tree_add(e, &ubi->scrub);
+	spin_unlock(&ubi->wl_lock);
+
+	/*
+	 * Technically scrubbing is the same as wear-leveling, so it is done
+	 * by the WL worker.
+	 */
+	return ensure_wear_leveling(ubi, 0);
+}
+
+/**
+ * ubi_wl_flush - flush all pending works.
+ * @ubi: UBI device description object
+ * @vol_id: the volume id to flush for
+ * @lnum: the logical eraseblock number to flush for
+ *
+ * This function executes all pending works for a particular volume id /
+ * logical eraseblock number pair. If either value is set to %UBI_ALL, then it
+ * acts as a wildcard for all of the corresponding volume numbers or logical
+ * eraseblock numbers. It returns zero in case of success and a negative error
+ * code in case of failure.
+ */
+int ubi_wl_flush(struct ubi_device *ubi, int vol_id, int lnum)
+{
+	int err = 0;
+	int found = 1;
+
+	/*
+	 * Erase while the pending works queue is not empty, but not more than
+	 * the number of currently pending works.
+	 */
+	dbg_wl("flush pending work for LEB %d:%d (%d pending works)",
+	       vol_id, lnum, ubi->works_count);
+
+	while (found) {
+		struct ubi_work *wrk, *tmp;
+		found = 0;
+
+		down_read(&ubi->work_sem);
+		spin_lock(&ubi->wl_lock);
+		list_for_each_entry_safe(wrk, tmp, &ubi->works, list) {
+			if ((vol_id == UBI_ALL || wrk->vol_id == vol_id) &&
+			    (lnum == UBI_ALL || wrk->lnum == lnum)) {
+				list_del(&wrk->list);
+				ubi->works_count -= 1;
+				ubi_assert(ubi->works_count >= 0);
+				spin_unlock(&ubi->wl_lock);
+
+				err = wrk->func(ubi, wrk, 0);
+				if (err) {
+					up_read(&ubi->work_sem);
+					return err;
+				}
+
+				spin_lock(&ubi->wl_lock);
+				found = 1;
+				break;
+			}
+		}
+		spin_unlock(&ubi->wl_lock);
+		up_read(&ubi->work_sem);
+	}
+
+	/*
+	 * Make sure all the works which have been done in parallel are
+	 * finished.
+	 */
+	down_write(&ubi->work_sem);
+	up_write(&ubi->work_sem);
+
+	return err;
+}
+
+/**
+ * tree_destroy - destroy an RB-tree.
+ * @ubi: UBI device description object
+ * @root: the root of the tree to destroy
+ */
+static void tree_destroy(struct ubi_device *ubi, struct rb_root *root)
+{
+	struct rb_node *rb;
+	struct ubi_wl_entry *e;
+
+	rb = root->rb_node;
+	while (rb) {
+		if (rb->rb_left)
+			rb = rb->rb_left;
+		else if (rb->rb_right)
+			rb = rb->rb_right;
+		else {
+			e = rb_entry(rb, struct ubi_wl_entry, u.rb);
+
+			rb = rb_parent(rb);
+			if (rb) {
+				if (rb->rb_left == &e->u.rb)
+					rb->rb_left = NULL;
+				else
+					rb->rb_right = NULL;
+			}
+
+			wl_entry_destroy(ubi, e);
+		}
+	}
+}
+
+/**
+ * ubi_thread - UBI background thread.
+ * @u: the UBI device description object pointer
+ */
+int ubi_thread(void *u)
+{
+	int failures = 0;
+	struct ubi_device *ubi = u;
+
+	ubi_msg(ubi, "background thread \"%s\" started, PID %d",
+		ubi->bgt_name, task_pid_nr(current));
+
+	set_freezable();
+	for (;;) {
+		int err;
+
+		if (kthread_should_stop())
+			break;
+
+		if (try_to_freeze())
+			continue;
+
+		spin_lock(&ubi->wl_lock);
+		if (list_empty(&ubi->works) || ubi->ro_mode ||
+		    !ubi->thread_enabled || ubi_dbg_is_bgt_disabled(ubi)) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			spin_unlock(&ubi->wl_lock);
+			schedule();
+			continue;
+		}
+		spin_unlock(&ubi->wl_lock);
+
+		err = do_work(ubi);
+		if (err) {
+			ubi_err(ubi, "%s: work failed with error code %d",
+				ubi->bgt_name, err);
+			if (failures++ > WL_MAX_FAILURES) {
+				/*
+				 * Too many failures, disable the thread and
+				 * switch to read-only mode.
+				 */
+				ubi_msg(ubi, "%s: %d consecutive failures",
+					ubi->bgt_name, WL_MAX_FAILURES);
+				ubi_ro_mode(ubi);
+				ubi->thread_enabled = 0;
+				continue;
+			}
+		} else
+			failures = 0;
+
+		cond_resched();
+	}
+
+	dbg_wl("background thread \"%s\" is killed", ubi->bgt_name);
+	return 0;
+}
+
+/**
+ * shutdown_work - shutdown all pending works.
+ * @ubi: UBI device description object
+ */
+static void shutdown_work(struct ubi_device *ubi)
+{
+#ifdef CONFIG_MTD_UBI_FASTMAP
+	flush_work(&ubi->fm_work);
+#endif
+	while (!list_empty(&ubi->works)) {
+		struct ubi_work *wrk;
+
+		wrk = list_entry(ubi->works.next, struct ubi_work, list);
+		list_del(&wrk->list);
+		wrk->func(ubi, wrk, 1);
+		ubi->works_count -= 1;
+		ubi_assert(ubi->works_count >= 0);
+	}
+}
+
+/**
+ * ubi_wl_init - initialize the WL sub-system using attaching information.
+ * @ubi: UBI device description object
+ * @ai: attaching information
+ *
+ * This function returns zero in case of success, and a negative error code in
+ * case of failure.
+ */
+int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
+{
+	int err, i, reserved_pebs, found_pebs = 0;
+	struct rb_node *rb1, *rb2;
+	struct ubi_ainf_volume *av;
+	struct ubi_ainf_peb *aeb, *tmp;
+	struct ubi_wl_entry *e;
+
+	ubi->used = ubi->erroneous = ubi->free = ubi->scrub = RB_ROOT;
+	spin_lock_init(&ubi->wl_lock);
+	mutex_init(&ubi->move_mutex);
+	init_rwsem(&ubi->work_sem);
+	ubi->max_ec = ai->max_ec;
+	INIT_LIST_HEAD(&ubi->works);
+
+	sprintf(ubi->bgt_name, UBI_BGT_NAME_PATTERN, ubi->ubi_num);
+
+	err = -ENOMEM;
+	ubi->lookuptbl = kzalloc(ubi->peb_count * sizeof(void *), GFP_KERNEL);
+	if (!ubi->lookuptbl)
+		return err;
+
+	for (i = 0; i < UBI_PROT_QUEUE_LEN; i++)
+		INIT_LIST_HEAD(&ubi->pq[i]);
+	ubi->pq_head = 0;
+
+	list_for_each_entry_safe(aeb, tmp, &ai->erase, u.list) {
+		cond_resched();
+
+		e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
+		if (!e)
+			goto out_free;
+
+		e->pnum = aeb->pnum;
+		e->ec = aeb->ec;
+		ubi->lookuptbl[e->pnum] = e;
+		if (schedule_erase(ubi, e, aeb->vol_id, aeb->lnum, 0)) {
+			wl_entry_destroy(ubi, e);
+			goto out_free;
+		}
+
+		found_pebs++;
+	}
+
+	ubi->free_count = 0;
+	list_for_each_entry(aeb, &ai->free, u.list) {
+		cond_resched();
+
+		e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
+		if (!e)
+			goto out_free;
+
+		e->pnum = aeb->pnum;
+		e->ec = aeb->ec;
+		ubi_assert(e->ec >= 0);
+
+		wl_tree_add(e, &ubi->free);
+		ubi->free_count++;
+
+		ubi->lookuptbl[e->pnum] = e;
+
+		found_pebs++;
+	}
+
+	ubi_rb_for_each_entry(rb1, av, &ai->volumes, rb) {
+		ubi_rb_for_each_entry(rb2, aeb, &av->root, u.rb) {
+			cond_resched();
+
+			e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
+			if (!e)
+				goto out_free;
+
+			e->pnum = aeb->pnum;
+			e->ec = aeb->ec;
+			ubi->lookuptbl[e->pnum] = e;
+
+			if (!aeb->scrub) {
+				dbg_wl("add PEB %d EC %d to the used tree",
+				       e->pnum, e->ec);
+				wl_tree_add(e, &ubi->used);
+			} else {
+				dbg_wl("add PEB %d EC %d to the scrub tree",
+				       e->pnum, e->ec);
+				wl_tree_add(e, &ubi->scrub);
+			}
+
+			found_pebs++;
+		}
+	}
+
+	dbg_wl("found %i PEBs", found_pebs);
+
+	if (ubi->fm) {
+		ubi_assert(ubi->good_peb_count == \
+			   found_pebs + ubi->fm->used_blocks);
+
+		for (i = 0; i < ubi->fm->used_blocks; i++) {
+			e = ubi->fm->e[i];
+			ubi->lookuptbl[e->pnum] = e;
+		}
+	}
+	else
+		ubi_assert(ubi->good_peb_count == found_pebs);
+
+	reserved_pebs = WL_RESERVED_PEBS;
+	ubi_fastmap_init(ubi, &reserved_pebs);
+
+	if (ubi->avail_pebs < reserved_pebs) {
+		ubi_err(ubi, "no enough physical eraseblocks (%d, need %d)",
+			ubi->avail_pebs, reserved_pebs);
+		if (ubi->corr_peb_count)
+			ubi_err(ubi, "%d PEBs are corrupted and not used",
+				ubi->corr_peb_count);
+		goto out_free;
+	}
+	ubi->avail_pebs -= reserved_pebs;
+	ubi->rsvd_pebs += reserved_pebs;
+
+	/* Schedule wear-leveling if needed */
+	err = ensure_wear_leveling(ubi, 0);
+	if (err)
+		goto out_free;
+
+	return 0;
+
+out_free:
+	shutdown_work(ubi);
+	tree_destroy(ubi, &ubi->used);
+	tree_destroy(ubi, &ubi->free);
+	tree_destroy(ubi, &ubi->scrub);
+	kfree(ubi->lookuptbl);
+	return err;
+}
+
+/**
+ * protection_queue_destroy - destroy the protection queue.
+ * @ubi: UBI device description object
+ */
+static void protection_queue_destroy(struct ubi_device *ubi)
+{
+	int i;
+	struct ubi_wl_entry *e, *tmp;
+
+	for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i) {
+		list_for_each_entry_safe(e, tmp, &ubi->pq[i], u.list) {
+			list_del(&e->u.list);
+			wl_entry_destroy(ubi, e);
+		}
+	}
+}
+
+/**
+ * ubi_wl_close - close the wear-leveling sub-system.
+ * @ubi: UBI device description object
+ */
+void ubi_wl_close(struct ubi_device *ubi)
+{
+	dbg_wl("close the WL sub-system");
+	ubi_fastmap_close(ubi);
+	shutdown_work(ubi);
+	protection_queue_destroy(ubi);
+	tree_destroy(ubi, &ubi->used);
+	tree_destroy(ubi, &ubi->erroneous);
+	tree_destroy(ubi, &ubi->free);
+	tree_destroy(ubi, &ubi->scrub);
+	kfree(ubi->lookuptbl);
+}
+
+/**
+ * self_check_ec - make sure that the erase counter of a PEB is correct.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ * @ec: the erase counter to check
+ *
+ * This function returns zero if the erase counter of physical eraseblock @pnum
+ * is equivalent to @ec, and a negative error code if not or if an error
+ * occurred.
+ */
+static int self_check_ec(struct ubi_device *ubi, int pnum, int ec)
+{
+	int err;
+	long long read_ec;
+	struct ubi_ec_hdr *ec_hdr;
+
+	if (!ubi_dbg_chk_gen(ubi))
+		return 0;
+
+	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
+	if (!ec_hdr)
+		return -ENOMEM;
+
+	err = ubi_io_read_ec_hdr(ubi, pnum, ec_hdr, 0);
+	if (err && err != UBI_IO_BITFLIPS) {
+		/* The header does not have to exist */
+		err = 0;
+		goto out_free;
+	}
+
+	read_ec = be64_to_cpu(ec_hdr->ec);
+	if (ec != read_ec && read_ec - ec > 1) {
+		ubi_err(ubi, "self-check failed for PEB %d", pnum);
+		ubi_err(ubi, "read EC is %lld, should be %d", read_ec, ec);
+		dump_stack();
+		err = 1;
+	} else
+		err = 0;
+
+out_free:
+	kfree(ec_hdr);
+	return err;
+}
+
+/**
+ * self_check_in_wl_tree - check that wear-leveling entry is in WL RB-tree.
+ * @ubi: UBI device description object
+ * @e: the wear-leveling entry to check
+ * @root: the root of the tree
+ *
+ * This function returns zero if @e is in the @root RB-tree and %-EINVAL if it
+ * is not.
+ */
+static int self_check_in_wl_tree(const struct ubi_device *ubi,
+				 struct ubi_wl_entry *e, struct rb_root *root)
+{
+	if (!ubi_dbg_chk_gen(ubi))
+		return 0;
+
+	if (in_wl_tree(e, root))
+		return 0;
+
+	ubi_err(ubi, "self-check failed for PEB %d, EC %d, RB-tree %p ",
+		e->pnum, e->ec, root);
+	dump_stack();
+	return -EINVAL;
+}
+
+/**
+ * self_check_in_pq - check if wear-leveling entry is in the protection
+ *                        queue.
+ * @ubi: UBI device description object
+ * @e: the wear-leveling entry to check
+ *
+ * This function returns zero if @e is in @ubi->pq and %-EINVAL if it is not.
+ */
+static int self_check_in_pq(const struct ubi_device *ubi,
+			    struct ubi_wl_entry *e)
+{
+	struct ubi_wl_entry *p;
+	int i;
+
+	if (!ubi_dbg_chk_gen(ubi))
+		return 0;
+
+	for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i)
+		list_for_each_entry(p, &ubi->pq[i], u.list)
+			if (p == e)
+				return 0;
+
+	ubi_err(ubi, "self-check failed for PEB %d, EC %d, Protect queue",
+		e->pnum, e->ec);
+	dump_stack();
+	return -EINVAL;
+}
+#ifndef CONFIG_MTD_UBI_FASTMAP
+static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
+{
+	struct ubi_wl_entry *e;
+
+	e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
+	self_check_in_wl_tree(ubi, e, &ubi->free);
+	ubi->free_count--;
+	ubi_assert(ubi->free_count >= 0);
+	rb_erase(&e->u.rb, &ubi->free);
+
+	return e;
+}
+
+/**
+ * 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) {
+		spin_unlock(&ubi->wl_lock);
+
+		dbg_wl("do one work synchronously");
+		err = do_work(ubi);
+
+		spin_lock(&ubi->wl_lock);
+		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 err;
+	struct ubi_wl_entry *e;
+
+retry:
+	down_read(&ubi->fm_eba_sem);
+	spin_lock(&ubi->wl_lock);
+	if (!ubi->free.rb_node) {
+		if (ubi->works_count == 0) {
+			ubi_err(ubi, "no free eraseblocks");
+			ubi_assert(list_empty(&ubi->works));
+			spin_unlock(&ubi->wl_lock);
+			return -ENOSPC;
+		}
+
+		err = produce_free_peb(ubi);
+		if (err < 0) {
+			spin_unlock(&ubi->wl_lock);
+			return err;
+		}
+		spin_unlock(&ubi->wl_lock);
+		up_read(&ubi->fm_eba_sem);
+		goto retry;
+
+	}
+	e = wl_get_wle(ubi);
+	prot_queue_add(ubi, e);
+	spin_unlock(&ubi->wl_lock);
+
+	err = ubi_self_check_all_ff(ubi, e->pnum, ubi->vid_hdr_aloffset,
+				    ubi->peb_size - ubi->vid_hdr_aloffset);
+	if (err) {
+		ubi_err(ubi, "new PEB %d does not contain all 0xFF bytes", e->pnum);
+		return err;
+	}
+
+	return e->pnum;
+}
+#else
+#include "fastmap-wl.c"
+#endif