[PATCH 09/22 take 3] UBI: wear-leveling unit

Artem Bityutskiy
2007-03-14T15:34:07Z

diff -auNrp tmp-from/drivers/mtd/ubi/wl.c tmp-to/drivers/mtd/ubi/wl.c
--- tmp-from/drivers/mtd/ubi/wl.c 1970-01-01 02:00:00.000000000 +0200
+++ tmp-to/drivers/mtd/ubi/wl.c 2007-03-14 17:15:50.000000000 +0200
@@ -0,0 +1,1761 @@
+/*
+ * 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 B. Bityutskiy, Thomas Gleixner
+ */
+
+/*
+ * UBI wear-leveling unit.
+ *
+ * This unit 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 unit'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 unit 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 unit.
+ *
+ * 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.
+ *
+ * The 'ubi_wl_get_peb()' function accepts data type hints which help to pick
+ * an "optimal" physical eraseblock. For example, when it is known that the
+ * physical eraseblock will be "put" soon because it contains short-term data,
+ * the WL unit may pick a free physical eraseblock with low erase counter, and
+ * so forth.
+ *
+ * If the WL unit fails to erase a physical eraseblock, it marks it as bad.
+ *
+ * This unit 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 unit all physical eraseblocks are either "free"
+ * or "used". Free eraseblock are kept in the @wl->free RB-tree, while used
+ * eraseblocks are kept in a set of different RB-trees: @wl->used,
+ * @wl->prot.pnum, @wl->prot.aec, and @wl->scrub.
+ *
+ * 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 unit and make it more scalable.
+ *
+ * At the moment this unit 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 unit.
+ */
+
+#include <linux/slab.h>
+#include <linux/crc32.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include "ubi.h"
+
+/* Number of physical eraseblocks reserved for wear-leveling purposes */
+#define WL_RESERVED_PEBS 1
+
+/*
+ * How many erase cycles are short term, unknown, and long term physical
+ * eraseblocks protected.
+ */
+#define ST_PROTECTION 16
+#define U_PROTECTION 10
+#define LT_PROTECTION 4
+
+/*
+ * Maximum difference between two erase counters. If this threshold is
+ * exceeded, the WL unit 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 unit 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 unit does
+ * not pick eraseblocks with erase counter greater then the lowest erase
+ * counter plus %WL_FREE_MAX_DIFF.
+ */
+#define WL_FREE_MAX_DIFF (2*UBI_WL_THRESHOLD)
+
+/* Background thread name pattern */
+#define WL_NAME_PATTERN "ubi_bgt%dd"
+
+/*
+ * Maximum number of consecutive background thread failures which is enough to
+ * switch to read-only mode.
+ */
+#define WL_MAX_FAILURES 32
+
+/**
+ * struct ubi_wl_entry - wear-leveling entry.
+ *
+ * @rb: link in the corresponding RB-tree
+ * @ec: erase counter
+ * @pnum: physical eraseblock number
+ *
+ * Each physical eraseblock has a corresponding &struct wl_entry object which
+ * may be kept in different RB-trees.
+ */
+struct ubi_wl_entry {
+ struct rb_node rb;
+ int ec;
+ int pnum;
+};
+
+/**
+ * struct ubi_wl_prot_entry - PEB protection entry.
+ *
+ * @rb_pnum: link in the @wl->prot.pnum RB-tree
+ * @rb_aec: link in the @wl->prot.aec RB-tree
+ * @abs_ec: the absolute erase counter value when the protection ends
+ * @e: the wear-leveling entry of the physical eraseblock under protection
+ *
+ * When the WL unit 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 one more tree in between where this physical eraseblock is
+ * temporarily stored (@wl->prot).
+ *
+ * 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; this is
+ * especially important in case of "short term" physical eraseblocks.
+ *
+ * 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
+ * absolute erase counter (@wl->abs_ec). When it reaches certain value, the
+ * physical eraseblocks are moved from the protection trees (@wl->prot.*) to
+ * the @wl->used tree.
+ *
+ * Protected physical eraseblocks are searched by physical eraseblock number
+ * (when they are put) and by the absolute erase counter (to check if it is
+ * time to move them to the @wl->used tree). So there are actually 2 RB-trees
+ * storing the protected physical eraseblocks: @wl->prot.pnum and
+ * @wl->prot.aec. They are referred to as the "protection" trees. The
+ * first one is indexed by the physical eraseblock number. The second one is
+ * indexed by the absolute erase counter. Both trees store
+ * &struct ubi_wl_prot_entry objects.
+ *
+ * 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 temporarily prohibited (@wl->prot.pnum and
+ * @wl->prot.aec trees);
+ * 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 trees.
+ */
+struct ubi_wl_prot_entry {
+ struct rb_node rb_pnum;
+ struct rb_node rb_aec;
+ unsigned long long abs_ec;
+ struct ubi_wl_entry *e;
+};
+
+/**
+ * struct ubi_work - UBI work description data structure.
+ *
+ * @list: a link in the list of pending works
+ * @func: worker function
+ * @priv: private data of the worker function
+ *
+ * @e: physical eraseblock to erase
+ * @torture: if the physical eraseblock has to be tortured
+ *
+ * The @func pointer points to the worker function. If the @cancel argument is
+ * not zero, the worker has to free the resources and exit immediately. The
+ * worker has to return zero in case of success and a negative error code in
+ * case of failure.
+ */
+struct ubi_work {
+ struct list_head list;
+ int (*func)(struct ubi_info *ubi, struct ubi_work *wrk, int cancel);
+ /* The below fields are only relevant to erasure works */
+ struct ubi_wl_entry *e;
+ int torture;
+};
+
+#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID_WL
+static int paranoid_check_ec(const struct ubi_info *ubi, int pnum, int ec);
+static int paranoid_check_in_wl_tree(struct ubi_wl_entry *e,
+ struct rb_root *root);
+#else
+#define paranoid_check_ec(ubi, pnum, ec) 0
+#define paranoid_check_in_wl_tree(e, root)
+#endif
+
+/* Slab cache for wear-leveling entries */
+static struct kmem_cache *wl_entries_slab;
+
+/**
+ * tree_empty - a helper function to check if an RB-tree is empty.
+ *
+ * @root: the root of the tree
+ *
+ * This function returns non-zero if the RB-tree is empty and zero if not.
+ */
+static inline int tree_empty(struct rb_root *root)
+{
+ return root->rb_node == NULL;
+}
+
+/**
+ * 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->wl.used and @ubi->wl.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, 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->rb, parent, p);
+ rb_insert_color(&e->rb, root);
+}
+
+
+/*
+ * Helper functions to add and delete wear-leveling entries from different
+ * trees.
+ */
+
+static inline void free_tree_add(struct ubi_info *ubi,
+ struct ubi_wl_entry *e)
+{
+ wl_tree_add(e, &ubi->wl.free);
+}
+static inline void used_tree_add(struct ubi_info *ubi,
+ struct ubi_wl_entry *e)
+{
+ wl_tree_add(e, &ubi->wl.used);
+}
+static inline void scrub_tree_add(struct ubi_info *ubi,
+ struct ubi_wl_entry *e)
+{
+ wl_tree_add(e, &ubi->wl.scrub);
+}
+static inline void free_tree_del(struct ubi_info *ubi,
+ struct ubi_wl_entry *e)
+{
+ paranoid_check_in_wl_tree(e, &ubi->wl.free);
+ rb_erase(&e->rb, &ubi->wl.free);
+}
+static inline void used_tree_del(struct ubi_info *ubi,
+ struct ubi_wl_entry *e)
+{
+ paranoid_check_in_wl_tree(e, &ubi->wl.used);
+ rb_erase(&e->rb, &ubi->wl.used);
+}
+static inline void scrub_tree_del(struct ubi_info *ubi,
+ struct ubi_wl_entry *e)
+{
+ paranoid_check_in_wl_tree(e, &ubi->wl.scrub);
+ rb_erase(&e->rb, &ubi->wl.scrub);
+}
+
+/**
+ * do_work - do one pending work.
+ *
+ * @ubi: the 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_info *ubi)
+{
+ int err;
+ struct ubi_work *wrk;
+
+ spin_lock(&ubi->wl.lock);
+
+ if (list_empty(&ubi->wl.pending_works)) {
+ spin_unlock(&ubi->wl.lock);
+ return 0;
+ }
+
+ wrk = list_entry(ubi->wl.pending_works.next, struct ubi_work, list);
+ list_del(&wrk->list);
+ 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 (unlikely(err))
+ ubi_err("work failed with error code %d", err);
+
+ spin_lock(&ubi->wl.lock);
+ ubi->wl.pending_works_count -= 1;
+ ubi_assert(ubi->wl.pending_works_count >= 0);
+ spin_unlock(&ubi->wl.lock);
+ return err;
+}
+
+/**
+ * produce_free_peb - produce a free physical eraseblock.
+ *
+ * @ubi: the 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_info *ubi)
+{
+ int err;
+
+ spin_lock(&ubi->wl.lock);
+ while (tree_empty(&ubi->wl.free)) {
+ spin_unlock(&ubi->wl.lock);
+
+ dbg_wl("do one work synchronously");
+ err = do_work(ubi);
+ if (unlikely(err))
+ return err;
+
+ spin_lock(&ubi->wl.lock);
+ }
+ spin_unlock(&ubi->wl.lock);
+
+ return 0;
+}
+
+/**
+ * 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, 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_tree_add - add physical eraseblock to protection trees.
+ *
+ * @ubi: the UBI device description object
+ * @e: the physical eraseblock to add
+ * @pe: protection entry object to use
+ * @abs_ec: absolute erase counter value when this physical eraseblock has
+ * to be removed from the protection trees.
+ *
+ * @wl->lock has to be locked.
+ */
+static void prot_tree_add(struct ubi_info *ubi, struct ubi_wl_entry *e,
+ struct ubi_wl_prot_entry *pe, int abs_ec)
+{
+ struct rb_node **p, *parent = NULL;
+ struct ubi_wl_prot_entry *pe1;
+
+ pe->e = e;
+ pe->abs_ec = ubi->wl.abs_ec + abs_ec;
+
+ p = &ubi->wl.prot.pnum.rb_node;
+ while (*p) {
+ parent = *p;
+ pe1 = rb_entry(parent, struct ubi_wl_prot_entry, rb_pnum);
+
+ if (e->pnum < pe1->e->pnum)
+ p = &(*p)->rb_left;
+ else
+ p = &(*p)->rb_right;
+ }
+ rb_link_node(&pe->rb_pnum, parent, p);
+ rb_insert_color(&pe->rb_pnum, &ubi->wl.prot.pnum);
+
+ p = &ubi->wl.prot.aec.rb_node;
+ parent = NULL;
+ while (*p) {
+ parent = *p;
+ pe1 = rb_entry(parent, struct ubi_wl_prot_entry, rb_aec);
+
+ if (pe->abs_ec < pe1->abs_ec)
+ p = &(*p)->rb_left;
+ else
+ p = &(*p)->rb_right;
+ }
+ rb_link_node(&pe->rb_aec, parent, p);
+ rb_insert_color(&pe->rb_aec, &ubi->wl.prot.aec);
+}
+
+/**
+ * find_wl_entry - find wear-leveling entry closest to certain erase counter.
+ *
+ * @root: the RB-tree where to look for
+ * @max: highest possible erase counter
+ *
+ * This function looks for a wear leveling entry with erase counter closest to
+ * @max and less then @max.
+ */
+static struct ubi_wl_entry *find_wl_entry(struct rb_root *root, int max)
+{
+ struct rb_node *p;
+ struct ubi_wl_entry *e;
+
+ e = rb_entry(rb_first(root), struct ubi_wl_entry, rb);
+ max += e->ec;
+
+ p = root->rb_node;
+ while (p) {
+ struct ubi_wl_entry *e1;
+
+ e1 = rb_entry(p, struct ubi_wl_entry, rb);
+ if (e1->ec >= max)
+ p = p->rb_left;
+ else {
+ p = p->rb_right;
+ e = e1;
+ }
+ }
+
+ return e;
+}
+
+/**
+ * pick_unknown - select an "unknown" physical eraseblock.
+ *
+ * @ubi: the UBI device description object
+ *
+ * This function returns a physical eraseblock for "unknown" data. The wl->lock
+ * must be locked. The @wl->free list must not be empty.
+ */
+static struct ubi_wl_entry *pick_unknown(struct ubi_info *ubi)
+{
+ int medium_ec;
+ struct rb_node *p;
+ struct ubi_wl_entry *first, *last, *e;
+
+ /*
+ * For unknown data we are trying to pick a physical eraseblock with
+ * medium erase counter. But we by no means can pick a physical
+ * eraseblock with erase counter greater or equivalent then the the
+ * lowest erase counter plus %WL_FREE_MAX_DIFF.
+ */
+
+ first = rb_entry(rb_first(&ubi->wl.free), struct ubi_wl_entry, rb);
+ last = rb_entry(rb_last(&ubi->wl.free), struct ubi_wl_entry, rb);
+
+ if (last->ec - first->ec < WL_FREE_MAX_DIFF)
+ return rb_entry(ubi->wl.free.rb_node, struct ubi_wl_entry, rb);
+
+ medium_ec = (first->ec + WL_FREE_MAX_DIFF)/2;
+ e = first;
+
+ p = ubi->wl.free.rb_node;
+ while (p) {
+ struct ubi_wl_entry *e1;
+
+ e1 = rb_entry(p, struct ubi_wl_entry, rb);
+ if (e1->ec >= medium_ec)
+ p = p->rb_left;
+ else {
+ p = p->rb_right;
+ e = e1;
+ }
+ }
+
+ return e;
+}
+
+/**
+ * ubi_wl_get_peb - get a physical eraseblock.
+ *
+ * @ubi: the UBI device description object
+ * @dtype: type of data which will be stored in this physical eraseblock
+ *
+ * This function returns a physical eraseblock in case of success and a
+ * negative error code in case of failure. Might sleep.
+ */
+int ubi_wl_get_peb(struct ubi_info *ubi, enum ubi_data_type dtype)
+{
+ int err, protect;
+ struct ubi_wl_entry *e;
+ struct ubi_wl_prot_entry *pe;
+
+ ubi_assert(dtype == UBI_DATA_LONGTERM || dtype == UBI_DATA_SHORTTERM ||
+ dtype == UBI_DATA_UNKNOWN);
+
+ pe = kmalloc(sizeof(struct ubi_wl_prot_entry), GFP_KERNEL);
+ if (unlikely(!pe))
+ return -ENOMEM;
+
+retry:
+ spin_lock(&ubi->wl.lock);
+ if (unlikely(tree_empty(&ubi->wl.free))) {
+ if (unlikely(ubi->wl.pending_works_count == 0)) {
+ ubi_assert(list_empty(&ubi->wl.pending_works));
+ ubi_err("no free eraseblocks");
+ spin_unlock(&ubi->wl.lock);
+ kfree(pe);
+ return -ENOSPC;
+ }
+ spin_unlock(&ubi->wl.lock);
+
+ err = produce_free_peb(ubi);
+ if (unlikely(err < 0)) {
+ kfree(pe);
+ return err;
+ }
+ goto retry;
+ }
+
+ switch (dtype) {
+ case UBI_DATA_LONGTERM:
+ /*
+ * For long term data we pick a physical eraseblock
+ * with high erase counter. But the highest erase
+ * counter we can pick is bounded by the the lowest
+ * erase counter plus %WL_FREE_MAX_DIFF.
+ */
+ e = find_wl_entry(&ubi->wl.free, WL_FREE_MAX_DIFF);
+ protect = LT_PROTECTION;
+ break;
+ case UBI_DATA_UNKNOWN:
+ e = pick_unknown(ubi);
+ protect = U_PROTECTION;
+ break;
+ case UBI_DATA_SHORTTERM:
+ /*
+ * For short term data we pick a physical eraseblock
+ * with the lowest erase counter as we expect it will
+ * be erased soon.
+ */
+ e = rb_entry(rb_first(&ubi->wl.free),
+ struct ubi_wl_entry, rb);
+ protect = ST_PROTECTION;
+ break;
+ default:
+ protect = 0;
+ e = NULL;
+ BUG();
+ }
+
+ /*
+ * Move the physical eraseblock to the protection trees where it will
+ * be protected from being moved for some time.
+ */
+ free_tree_del(ubi, e);
+ prot_tree_add(ubi, e, pe, protect);
+
+ dbg_wl("PEB %d EC %d, protection %d", e->pnum, e->ec, protect);
+ spin_unlock(&ubi->wl.lock);
+
+ return e->pnum;
+}
+
+/**
+ * prot_tree_del - remove a physical eraseblock from the protection trees
+ *
+ * @ubi: the UBI device description object
+ * @pnum: the physical eraseblock to remove
+ */
+static void prot_tree_del(struct ubi_info *ubi, int pnum)
+{
+ struct rb_node *p;
+ struct ubi_wl_prot_entry *pe = NULL;
+
+ p = ubi->wl.prot.pnum.rb_node;
+ while (p) {
+
+ pe = rb_entry(p, struct ubi_wl_prot_entry, rb_pnum);
+
+ if (pnum == pe->e->pnum)
+ break;
+
+ if (pnum < pe->e->pnum)
+ p = p->rb_left;
+ else
+ p = p->rb_right;
+ }
+
+ ubi_assert(pe->e->pnum == pnum);
+ rb_erase(&pe->rb_aec, &ubi->wl.prot.aec);
+ rb_erase(&pe->rb_pnum, &ubi->wl.prot.pnum);
+ kfree(pe);
+}
+
+/**
+ * sync_erase - synchronously erase a physical eraseblock.
+ *
+ * @ubi: the 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_info *ubi, struct ubi_wl_entry *e, int torture)
+{
+ int err;
+ struct ubi_ec_hdr *ec_hdr;
+ uint64_t ec = e->ec;
+
+ dbg_wl("erase PEB %d, old EC %llu", e->pnum, (unsigned long long)ec);
+
+ err = paranoid_check_ec(ubi, e->pnum, e->ec);
+ if (unlikely(err > 0))
+ return -EINVAL;
+
+ ec_hdr = kzalloc(ubi->io.ec_hdr_alsize, GFP_KERNEL);
+ if (unlikely(!ec_hdr))
+ return -ENOMEM;
+
+ err = ubi_io_sync_erase(ubi, e->pnum, torture);
+ if (unlikely(err < 0))
+ goto out_free;
+
+ ec += err;
+ if (unlikely(ec > UBI_MAX_ERASECOUNTER)) {
+ /*
+ * Erase counter overflow. Upgrade UBI and use 64-bit
+ * erase counters internally.
+ */
+ ubi_err("erase counter overflow at PEB %d, EC %llu",
+ e->pnum, (unsigned long long)ec);
+ err = -EINVAL;
+ goto out_free;
+ }
+
+ dbg_wl("erased PEB %d, new EC %llu", e->pnum, (unsigned long long)ec);
+
+ ec_hdr->ec = cpu_to_ubi64(ec);
+
+ err = ubi_io_write_ec_hdr(ubi, e->pnum, ec_hdr);
+ if (unlikely(err))
+ goto out_free;
+
+ e->ec = ec;
+ spin_lock(&ubi->wl.lock);
+ if (e->ec > ubi->wl.max_ec)
+ ubi->wl.max_ec = e->ec;
+ spin_unlock(&ubi->wl.lock);
+
+out_free:
+ kfree(ec_hdr);
+ return err;
+}
+
+/**
+ * check_protection_over - check if it is time to stop protecting some
+ * physical eraseblocks.
+ *
+ * @ubi: the UBI device description object
+ *
+ * This function is called after each erase operation, when the absolute erase
+ * counter is incremented, to check if some physical eraseblock have not to be
+ * protected any longer. These physical eraseblocks are moved from the
+ * protection trees to the used tree.
+ */
+static void check_protection_over(struct ubi_info *ubi)
+{
+ struct ubi_wl_prot_entry *pe;
+
+ /*
+ * There may be several protected physical eraseblock to remove,
+ * process them all.
+ */
+ while (1) {
+ spin_lock(&ubi->wl.lock);
+ if (tree_empty(&ubi->wl.prot.aec)) {
+ spin_unlock(&ubi->wl.lock);
+ break;
+ }
+
+ pe = rb_entry(rb_first(&ubi->wl.prot.aec),
+ struct ubi_wl_prot_entry, rb_aec);
+
+ if (pe->abs_ec > ubi->wl.abs_ec) {
+ spin_unlock(&ubi->wl.lock);
+ break;
+ }
+
+ dbg_wl("PEB %d protection over, abs_ec %llu, PEB abs_ec %llu",
+ pe->e->pnum, ubi->wl.abs_ec, pe->abs_ec);
+ rb_erase(&pe->rb_aec, &ubi->wl.prot.aec);
+ rb_erase(&pe->rb_pnum, &ubi->wl.prot.pnum);
+ used_tree_add(ubi, pe->e);
+ spin_unlock(&ubi->wl.lock);
+
+ kfree(pe);
+ cond_resched();
+ }
+}
+
+/**
+ * schedule_ubi_work - schedule a work.
+ *
+ * @ubi: the UBI device description object
+ * @wrk: the work to schedule
+ *
+ * This function enqueues a work defined by @wrk to the tail of the pending
+ * works list.
+ */
+static void schedule_ubi_work(struct ubi_info *ubi, struct ubi_work *wrk)
+{
+ spin_lock(&ubi->wl.lock);
+ list_add_tail(&wrk->list, &ubi->wl.pending_works);
+ ubi_assert(ubi->wl.pending_works_count >= 0);
+ ubi->wl.pending_works_count += 1;
+ if (ubi->wl.thread_enabled)
+ wake_up_process(ubi->wl.task);
+ spin_unlock(&ubi->wl.lock);
+}
+
+/**
+ * reschedule_ubi_work - re-schedule a work.
+ *
+ * @ubi: the UBI device description object
+ * @wrk: the work to re-schedule.
+ *
+ * This function enqueues a work defined by @wrk to the tail of the pending
+ * works list.
+ */
+static void reschedule_ubi_work(struct ubi_info *ubi, struct ubi_work *wrk)
+{
+ spin_lock(&ubi->wl.lock);
+ list_add_tail(&wrk->list, &ubi->wl.pending_works);
+ ubi_assert(ubi->wl.pending_works_count >= 0);
+ ubi->wl.pending_works_count += 1;
+ if (ubi->wl.thread_enabled)
+ wake_up_process(ubi->wl.task);
+ spin_unlock(&ubi->wl.lock);
+}
+
+static int erase_worker(struct ubi_info *ubi, struct ubi_work *wl_wrk,
+ int cancel);
+
+/**
+ * schedule_erase - schedule an erase work.
+ *
+ * @ubi: the UBI device description object
+ * @e: the WL entry of 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 schedule_erase(struct ubi_info *ubi, struct ubi_wl_entry *e,
+ int torture)
+{
+ struct ubi_work *wl_wrk;
+
+ dbg_wl("schedule erasure of PEB %d, EC %d, torture %d",
+ e->pnum, e->ec, torture);
+
+ wl_wrk = kmalloc(sizeof(struct ubi_work), GFP_KERNEL);
+ if (unlikely(!wl_wrk))
+ return -ENOMEM;
+
+ wl_wrk->func = &erase_worker;
+ wl_wrk->e = e;
+ wl_wrk->torture = torture;
+
+ schedule_ubi_work(ubi, wl_wrk);
+ return 0;
+}
+
+/**
+ * wear_leveling_worker - wear-leveling worker function.
+ *
+ * @ubi: the UBI device description object
+ * @wrk: the work object
+ * @cancel: non-zero if the worker has to free memory and exit
+ *
+ * This function copies a less worn out physical eraseblock to a more 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_info *ubi, struct ubi_work *wrk,
+ int cancel)
+{
+ int err, put = 0;
+ struct ubi_wl_entry *e1, *e2;
+ struct ubi_vid_hdr *vid_hdr;
+
+ kfree(wrk);
+
+ if (unlikely(cancel))
+ return 0;
+
+ vid_hdr = ubi_zalloc_vid_hdr(ubi);
+ if (unlikely(!vid_hdr))
+ return -ENOMEM;
+
+ spin_lock(&ubi->wl.lock);
+
+ /*
+ * Only one WL worker at a time is supported at this implementation, so
+ * make sure a PEB is not being moved already.
+ */
+ if (ubi->wl.move_to || tree_empty(&ubi->wl.free) ||
+ (tree_empty(&ubi->wl.used) && tree_empty(&ubi->wl.scrub))) {
+ /*
+ * Only one WL worker at a time is supported at this
+ * implementation, so if a LEB is already being moved, cancel.
+ *
+ * No free physical eraseblocks? Well, we cancel wear-leveling
+ * then. 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->wl.used tree later and the wear-leveling will be
+ * triggered again.
+ */
+ dbg_wl("cancel WL, a list is empty: free %d, used %d",
+ tree_empty(&ubi->wl.free), tree_empty(&ubi->wl.used));
+ ubi->wl.wl_scheduled = 0;
+ spin_unlock(&ubi->wl.lock);
+ ubi_free_vid_hdr(ubi, vid_hdr);
+ return 0;
+ }
+
+ if (tree_empty(&ubi->wl.scrub)) {
+ /*
+ * 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->wl.used), struct ubi_wl_entry, rb);
+ e2 = find_wl_entry(&ubi->wl.free, WL_FREE_MAX_DIFF);
+
+ 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);
+ ubi->wl.wl_scheduled = 0;
+ spin_unlock(&ubi->wl.lock);
+ ubi_free_vid_hdr(ubi, vid_hdr);
+ return 0;
+ }
+ used_tree_del(ubi, e1);
+ dbg_wl("move PEB %d EC %d to PEB %d EC %d",
+ e1->pnum, e1->ec, e2->pnum, e2->ec);
+ } else {
+ e1 = rb_entry(rb_first(&ubi->wl.scrub), struct ubi_wl_entry, rb);
+ e2 = find_wl_entry(&ubi->wl.free, WL_FREE_MAX_DIFF);
+ scrub_tree_del(ubi, e1);
+ dbg_wl("scrub PEB %d to PEB %d", e1->pnum, e2->pnum);
+ }
+
+ free_tree_del(ubi, e2);
+ ubi_assert(!ubi->wl.move_from && !ubi->wl.move_to);
+ ubi_assert(!ubi->wl.move_to_put && !ubi->wl.move_from_put);
+ ubi->wl.move_from = e1;
+ ubi->wl.move_to = e1;
+ 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.
+ */
+
+ err = ubi_io_read_vid_hdr(ubi, e1->pnum, vid_hdr, 0);
+ if (unlikely(err && err != UBI_IO_BITFLIPS)) {
+ if (err == UBI_IO_PEB_FREE) {
+ /*
+ * 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 did not have
+ * chance to write it down because it was preempted.
+ * Just re-schedule the task, so that next time it will
+ * likely have the VID header in place.
+ */
+ dbg_wl("PEB %d has no VID header", e1->pnum);
+ err = 0;
+ } else {
+ ubi_err("error %d while reading VID header from PEB %d",
+ err, e1->pnum);
+ if (err > 0)
+ err = -EIO;
+ }
+ goto error;
+ }
+
+ err = ubi_eba_copy_leb(ubi, e1->pnum, e2->pnum, vid_hdr);
+ if (unlikely(err)) {
+ if (err == UBI_IO_BITFLIPS)
+ err = 0;
+ goto error;
+ }
+
+ ubi_free_vid_hdr(ubi, vid_hdr);
+ spin_lock(&ubi->wl.lock);
+ if (unlikely(!ubi->wl.move_to_put))
+ used_tree_add(ubi, e2);
+ else
+ put = 1;
+ ubi->wl.move_from = ubi->wl.move_to = NULL;
+ ubi->wl.move_from_put = ubi->wl.move_to_put = 0;
+ ubi->wl.wl_scheduled = 0;
+ spin_unlock(&ubi->wl.lock);
+
+ if (unlikely(put)) {
+ /*
+ * Well, the target PEB was put meanwhile, schedule it for
+ * erasure.
+ */
+ dbg_wl("PEB %d was put meanwhile, erase", e2->pnum);
+ err = schedule_erase(ubi, e2, 0);
+ if (unlikely(err)) {
+ kmem_cache_free(wl_entries_slab, e2);
+ ubi_ro_mode(ubi);
+ }
+ }
+
+ err = schedule_erase(ubi, e1, 0);
+ if (unlikely(err)) {
+ kmem_cache_free(wl_entries_slab, e1);
+ ubi_ro_mode(ubi);
+ }
+
+ dbg_wl("done");
+ return err;
+
+ /*
+ * Some error occurred. @e1 was not changed, so return it back. @e2
+ * might be changed, schedule it for erasure.
+ */
+error:
+ if (err)
+ dbg_wl("error %d occurred, cancel operation", err);
+ ubi_assert(err <= 0);
+
+ ubi_free_vid_hdr(ubi, vid_hdr);
+ spin_lock(&ubi->wl.lock);
+ ubi->wl.wl_scheduled = 0;
+ if (ubi->wl.move_from_put)
+ put = 1;
+ else
+ used_tree_add(ubi, e1);
+ ubi->wl.move_from = ubi->wl.move_to = NULL;
+ ubi->wl.move_from_put = ubi->wl.move_to_put = 0;
+ spin_unlock(&ubi->wl.lock);
+
+ if (put) {
+ /*
+ * Well, the target PEB was put meanwhile, schedule it for
+ * erasure.
+ */
+ dbg_wl("PEB %d was put meanwhile, erase", e1->pnum);
+ err = schedule_erase(ubi, e1, 0);
+ if (unlikely(err)) {
+ kmem_cache_free(wl_entries_slab, e1);
+ ubi_ro_mode(ubi);
+ }
+ }
+
+ err = schedule_erase(ubi, e2, 0);
+ if (unlikely(err)) {
+ kmem_cache_free(wl_entries_slab, e2);
+ ubi_ro_mode(ubi);
+ }
+
+ yield();
+ return err;
+}
+
+/**
+ * ensure_wear_leveling - schedule wear-leveling if it is needed.
+ *
+ * @ubi: the UBI device description object
+ *
+ * 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_info *ubi)
+{
+ 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.wl_scheduled)
+ /* Wear-leveling is already in the work queue */
+ goto out_unlock;
+
+ /*
+ * If the ubi->wl.scrub tree is not empty, scrubbing is needed, and the
+ * the WL worker has to be scheduled anyway.
+ */
+ if (tree_empty(&ubi->wl.scrub)) {
+ if (tree_empty(&ubi->wl.used) || tree_empty(&ubi->wl.free))
+ /* 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 then
+ * %UBI_WL_THRESHOLD.
+ */
+ e1 = rb_entry(rb_first(&ubi->wl.used), struct ubi_wl_entry, rb);
+ e2 = find_wl_entry(&ubi->wl.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.wl_scheduled = 1;
+ spin_unlock(&ubi->wl.lock);
+
+ wrk = kmalloc(sizeof(struct ubi_work), GFP_KERNEL);
+ if (unlikely(!wrk)) {
+ err = -ENOMEM;
+ goto out_cancel;
+ }
+
+ wrk->func = &wear_leveling_worker;
+ schedule_ubi_work(ubi, wrk);
+ return err;
+
+out_cancel:
+ spin_lock(&ubi->wl.lock);
+ ubi->wl.wl_scheduled = 0;
+out_unlock:
+ spin_unlock(&ubi->wl.lock);
+ return err;
+}
+
+/**
+ * erase_worker - physical eraseblock erase worker function.
+ *
+ * @ubi: the UBI device description object
+ * @wl_wrk: the work object
+ * @cancel: non-zero if the worker has to free memory and exit
+ *
+ * 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_info *ubi, struct ubi_work *wl_wrk,
+ int cancel)
+{
+ int err;
+ struct ubi_wl_entry *e = wl_wrk->e;
+ int pnum = e->pnum;
+
+ if (unlikely(cancel)) {
+ dbg_wl("cancel erasure of PEB %d EC %d", pnum, e->ec);
+ kfree(wl_wrk);
+ kmem_cache_free(wl_entries_slab, e);
+ return 0;
+ }
+
+ dbg_wl("erase PEB %d EC %d", pnum, e->ec);
+
+ err = sync_erase(ubi, e, wl_wrk->torture);
+ if (likely(!err)) {
+ /* Fine, we've erased it successfully */
+ kfree(wl_wrk);
+
+ spin_lock(&ubi->wl.lock);
+ ubi->wl.abs_ec += 1;
+ free_tree_add(ubi, e);
+ spin_unlock(&ubi->wl.lock);
+
+ /*
+ * One more erase operation has happened, take care about protected
+ * physical eraseblocks.
+ */
+ check_protection_over(ubi);
+
+ /* And take care about wear-leveling */
+ err = ensure_wear_leveling(ubi);
+ return err;
+ }
+
+ /*
+ * Some error occurred during erasure. If this is something like
+ * %-EINTR, we just re-schedule this physical eraseblock for
+ * erasure.
+ */
+
+ if (err == -EINTR || err == -EAGAIN || err == -ENOMEM ||
+ err == -EBUSY) {
+ reschedule_ubi_work(ubi, wl_wrk);
+ return err;
+ }
+
+ kfree(wl_wrk);
+ kmem_cache_free(wl_entries_slab, 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 RO mode.
+ */
+ ubi_ro_mode(ubi);
+ return err;
+ }
+
+ /* It is %-EIO, the PEB went bad */
+
+ if (!ubi->io.bad_allowed) {
+ ubi_err("flash device is severely bad");
+ ubi_ro_mode(ubi);
+ err = -EIO;
+ } else {
+ err = ubi_io_mark_bad(ubi, pnum);
+ if (err) {
+ ubi_ro_mode(ubi);
+ return err;
+ }
+ ubi->io.bad_peb_count += 1;
+ ubi->io.good_peb_count -= 1;
+ ubi_msg("PEB %d was mark as bad", pnum);
+ }
+
+ return err;
+}
+
+/**
+ * ubi_wl_put_peb - return a physical eraseblock to the wear-leveling
+ * unit.
+ *
+ * @ubi: the UBI device description object
+ * @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_info *ubi, int pnum, int torture)
+{
+ int err;
+ struct ubi_wl_entry *e;
+
+ dbg_wl("PEB %d", pnum);
+ ubi_assert(pnum >= 0);
+ ubi_assert(pnum < ubi->io.peb_count);
+
+ spin_lock(&ubi->wl.lock);
+
+ e = ubi->wl.lookuptbl[pnum];
+ if (unlikely(e == ubi->wl.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", pnum);
+ ubi_assert(!ubi->wl.move_from_put);
+ ubi->wl.move_from_put = 1;
+ spin_unlock(&ubi->wl.lock);
+ return 0;
+ } else if (unlikely(e == ubi->wl.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
+ * unit already re-mapped the LEB but the WL unit did has not
+ * put the PEB to the "used" tree.
+ */
+ dbg_wl("PEB %d is the target of data moving", pnum);
+ ubi_assert(!ubi->wl.move_to_put);
+ ubi->wl.move_to_put = 1;
+ spin_unlock(&ubi->wl.lock);
+ return 0;
+ } else {
+ if (in_wl_tree(e, &ubi->wl.used))
+ used_tree_del(ubi, e);
+ else if (unlikely(in_wl_tree(e, &ubi->wl.scrub)))
+ scrub_tree_del(ubi, e);
+ else
+ prot_tree_del(ubi, e->pnum);
+ }
+ spin_unlock(&ubi->wl.lock);
+
+ err = schedule_erase(ubi, e, torture);
+ if (unlikely(err)) {
+ spin_lock(&ubi->wl.lock);
+ used_tree_add(ubi, e);
+ spin_unlock(&ubi->wl.lock);
+ }
+
+ return err;
+}
+
+/**
+ * ubi_wl_scrub_peb - schedule a physical eraseblock for scrubbing.
+ *
+ * @ubi: the 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_info *ubi, int pnum)
+{
+ struct ubi_wl_entry *e;
+
+ dbg_wl("schedule PEB %d for scrubbing", pnum);
+
+retry:
+ spin_lock(&ubi->wl.lock);
+ e = ubi->wl.lookuptbl[pnum];
+ if (unlikely(e == ubi->wl.move_from) || in_wl_tree(e, &ubi->wl.scrub)) {
+ spin_unlock(&ubi->wl.lock);
+ return 0;
+ }
+
+ if (unlikely(e == ubi->wl.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->wl.used))
+ used_tree_del(ubi, e);
+ else
+ prot_tree_del(ubi, pnum);
+
+ scrub_tree_add(ubi, e);
+ 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);
+}
+
+/**
+ * ubi_wl_flush - flush all pending works.
+ *
+ * @ubi: the UBI device description object
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
+ */
+int ubi_wl_flush(struct ubi_info *ubi)
+{
+ int err, pending_count;
+
+ pending_count = ubi->wl.pending_works_count;
+
+ dbg_wl("flush (%d pending works)", pending_count);
+
+ /*
+ * Erase while the pending works queue is not empty, but not more then
+ * the number of currently pending works.
+ */
+ while (pending_count-- > 0) {
+ err = do_work(ubi);
+ if (unlikely(err))
+ return err;
+ }
+
+ return 0;
+}
+
+/**
+ * tree_destroy - destroy an RB-tree.
+ *
+ * @root: the root of the tree to destroy
+ */
+static void tree_destroy(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, rb);
+
+ rb = rb_parent(rb);
+ if (rb) {
+ if (rb->rb_left == &e->rb)
+ rb->rb_left = NULL;
+ else
+ rb->rb_right = NULL;
+ }
+
+ kmem_cache_free(wl_entries_slab, e);
+ }
+ }
+}
+
+/**
+ * ubi_thread - UBI background thread.
+ *
+ * @u: the UBI device description object pointer
+ */
+static int ubi_thread(void *u)
+{
+ int failures = 0;
+ struct ubi_info *ubi = u;
+
+ ubi_msg("background thread \"%s\" started, PID %d",
+ ubi->wl.bgt_name, current->pid);
+
+ for (;;) {
+ int err;
+
+ if (kthread_should_stop())
+ goto out;
+
+ if (try_to_freeze())
+ continue;
+
+ spin_lock(&ubi->wl.lock);
+ if (list_empty(&ubi->wl.pending_works) ||
+ ubi->io.ro_mode || !ubi->wl.thread_enabled) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ spin_unlock(&ubi->wl.lock);
+ schedule();
+ continue;
+ }
+ spin_unlock(&ubi->wl.lock);
+
+ err = do_work(ubi);
+ if (unlikely(err)) {
+ ubi_err("%s: work failed with error code %d",
+ ubi->wl.bgt_name, err);
+ if (failures++ > WL_MAX_FAILURES) {
+ /*
+ * Too many failures, disable the thread and
+ * switch to read-only mode.
+ */
+ ubi_msg("%s: %d consecutive failures",
+ ubi->wl.bgt_name, WL_MAX_FAILURES);
+ ubi_ro_mode(ubi);
+ break;
+ }
+ } else
+ failures = 0;
+
+ cond_resched();
+ }
+
+out:
+ dbg_wl("killing background thread \"%s\"", ubi->wl.bgt_name);
+
+ /* Cancel all pending works before exiting */
+ spin_lock(&ubi->wl.lock);
+ ubi->wl.task = NULL;
+
+ while (!list_empty(&ubi->wl.pending_works)) {
+ struct ubi_work *wrk;
+
+ wrk = list_entry(ubi->wl.pending_works.next,
+ struct ubi_work, list);
+ list_del(&wrk->list);
+ spin_unlock(&ubi->wl.lock);
+ wrk->func(ubi, wrk, 1);
+ spin_lock(&ubi->wl.lock);
+ ubi->wl.pending_works_count -= 1;
+ ubi_assert(ubi->wl.pending_works_count >= 0);
+ }
+ spin_unlock(&ubi->wl.lock);
+
+ return 0;
+}
+
+/**
+ * ubi_wl_init_scan - initialize the wear-leveling unit using scanning
+ * information.
+ *
+ * @ubi: the UBI device description object
+ * @si: a pointer to the scanning information
+ *
+ * This function returns zero in case of success, and a negative error code in
+ * case of failure.
+ */
+int ubi_wl_init_scan(struct ubi_info *ubi, struct ubi_scan_info *si)
+{
+ int err;
+ struct rb_node *rb1, *rb2;
+ struct ubi_scan_volume *sv;
+ struct ubi_scan_leb *seb, *tmp;
+ struct ubi_wl_entry *e;
+
+
+ ubi->wl.used = ubi->wl.free = ubi->wl.scrub = RB_ROOT;
+ ubi->wl.prot.pnum = ubi->wl.prot.aec = RB_ROOT;
+ spin_lock_init(&ubi->wl.lock);
+ ubi->wl.max_ec = si->max_ec;
+ INIT_LIST_HEAD(&ubi->wl.pending_works);
+
+ ubi->wl.bgt_name = kmalloc(sizeof(WL_NAME_PATTERN) + 20, GFP_KERNEL);
+ if (!ubi->wl.bgt_name)
+ return -ENOMEM;
+ sprintf(ubi->wl.bgt_name, WL_NAME_PATTERN, ubi->ubi_num);
+
+ ubi->wl.task = kthread_create(ubi_thread, ubi, ubi->wl.bgt_name);
+ if (IS_ERR(ubi->wl.task)) {
+ err = PTR_ERR(ubi->wl.task);
+ ubi_err("cannot spawn \"%s\", error %d", ubi->wl.bgt_name,
+ err);
+ goto out_free;
+ }
+
+ if (ubis_num == 0) {
+ wl_entries_slab = kmem_cache_create("ubi_wl_entry_slab",
+ sizeof(struct ubi_wl_entry),
+ 0, 0, NULL, NULL);
+ if (!wl_entries_slab)
+ return -ENOMEM;
+ }
+
+ ubi->wl.lookuptbl = kzalloc(ubi->io.peb_count * sizeof(void *), GFP_KERNEL);
+ if (!ubi->wl.lookuptbl) {
+ err = -ENOMEM;
+ goto out_free;
+ }
+
+ list_for_each_entry_safe(seb, tmp, &si->erase, u.list) {
+ cond_resched();
+
+ e = kmem_cache_alloc(wl_entries_slab, GFP_KERNEL);
+ if (unlikely(!e)) {
+ err = -ENOMEM;
+ goto out_free;
+ }
+
+ e->pnum = seb->pnum;
+ e->ec = seb->ec;
+ ubi->wl.lookuptbl[e->pnum] = e;
+ err = schedule_erase(ubi, e, 0);
+ if (unlikely(err)) {
+ kmem_cache_free(wl_entries_slab, e);
+ goto out_free;
+ }
+ }
+
+ err = -ENOMEM;
+ list_for_each_entry(seb, &si->free, u.list) {
+ cond_resched();
+
+ e = kmem_cache_alloc(wl_entries_slab, GFP_KERNEL);
+ if (unlikely(!e))
+ goto out_free;
+
+ e->pnum = seb->pnum;
+ e->ec = seb->ec;
+ ubi_assert(e->ec >= 0);
+ free_tree_add(ubi, e);
+ ubi->wl.lookuptbl[e->pnum] = e;
+ }
+
+ list_for_each_entry(seb, &si->corr, u.list) {
+ cond_resched();
+
+ e = kmem_cache_alloc(wl_entries_slab, GFP_KERNEL);
+ if (unlikely(!e)) {
+ err = -ENOMEM;
+ goto out_free;
+ }
+
+ e->pnum = seb->pnum;
+ e->ec = seb->ec;
+ ubi->wl.lookuptbl[e->pnum] = e;
+ err = schedule_erase(ubi, e, 0);
+ if (unlikely(err)) {
+ kmem_cache_free(wl_entries_slab, e);
+ goto out_free;
+ }
+ }
+
+ err = -ENOMEM;
+ rb_for_each_entry(rb1, sv, &si->volumes, rb) {
+ rb_for_each_entry(rb2, seb, &sv->root, u.rb) {
+ cond_resched();
+
+ e = kmem_cache_alloc(wl_entries_slab, GFP_KERNEL);
+ if (unlikely(!e))
+ goto out_free;
+
+ e->pnum = seb->pnum;
+ e->ec = seb->ec;
+ ubi->wl.lookuptbl[e->pnum] = e;
+ if (!seb->scrub) {
+ dbg_wl("add PEB %d EC %d to the used tree",
+ e->pnum, e->ec);
+ used_tree_add(ubi, e);
+ } else {
+ dbg_wl("add PEB %d EC %d to the scrub tree",
+ e->pnum, e->ec);
+ scrub_tree_add(ubi, e);
+ }
+ }
+ }
+
+ err = ubi_acc_reserve(ubi, WL_RESERVED_PEBS);
+ if (err)
+ goto out_free;
+
+ /* Schedule wear-leveling if needed */
+ err = ensure_wear_leveling(ubi);
+ if (err)
+ goto out_free;
+
+ return 0;
+
+out_free:
+ kfree(ubi->wl.bgt_name);
+ tree_destroy(&ubi->wl.used);
+ tree_destroy(&ubi->wl.free);
+ tree_destroy(&ubi->wl.scrub);
+ kfree(ubi->wl.lookuptbl);
+ if (ubis_num == 0)
+ kmem_cache_destroy(wl_entries_slab);
+ return err;
+}
+
+/**
+ * protection_trees_destroy - destroy the protection RB-trees.
+ *
+ * @ubi: the UBI device description object
+ */
+static void protection_trees_destroy(struct ubi_info *ubi)
+{
+ struct rb_node *rb;
+ struct ubi_wl_prot_entry *pe;
+
+ rb = ubi->wl.prot.aec.rb_node;
+ while (rb) {
+ if (rb->rb_left)
+ rb = rb->rb_left;
+ else if (rb->rb_right)
+ rb = rb->rb_right;
+ else {
+ pe = rb_entry(rb, struct ubi_wl_prot_entry, rb_aec);
+
+ rb = rb_parent(rb);
+ if (rb) {
+ if (rb->rb_left == &pe->rb_aec)
+ rb->rb_left = NULL;
+ else
+ rb->rb_right = NULL;
+ }
+
+ kmem_cache_free(wl_entries_slab, pe->e);
+ kfree(pe);
+ }
+ }
+}
+
+/**
+ * ubi_wl_close - close the wear-leveling unit.
+ *
+ * @ubi: the UBI device description object
+ */
+void ubi_wl_close(struct ubi_info *ubi)
+{
+ dbg_wl("disable \"%s\"", ubi->wl.bgt_name);
+ if (ubi->wl.task)
+ kthread_stop(ubi->wl.task);
+
+ dbg_wl("close the UBI wear-leveling unit");
+
+ ubi_assert(ubi->wl.pending_works_count == 0);
+ ubi_assert(list_empty(&ubi->wl.pending_works));
+
+ kfree(ubi->wl.bgt_name);
+ protection_trees_destroy(ubi);
+ tree_destroy(&ubi->wl.used);
+ tree_destroy(&ubi->wl.free);
+ tree_destroy(&ubi->wl.scrub);
+ kfree(ubi->wl.lookuptbl);
+ if (ubis_num == 1)
+ kmem_cache_destroy(wl_entries_slab);
+}
+
+/**
+ *
+ * ubi_wl_enable_thread - enable the background thread.
+ *
+ * @ubi: the UBI device description object
+ */
+void ubi_wl_enable_thread(struct ubi_info *ubi)
+{
+ if (!DBG_DISABLE_BGT) {
+ dbg_wl("enable the background thread");
+ ubi->wl.thread_enabled = 1;
+ wake_up_process(ubi->wl.task);
+ }
+}
+
+#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID_WL
+
+/**
+ * paranoid_check_ec - make sure that the erase counter of a physical eraseblock
+ * is correct.
+ *
+ * @ubi: the 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, %1 if not, and a negative error code if an error
+ * occurred.
+ */
+static int paranoid_check_ec(const struct ubi_info *ubi, int pnum, int ec)
+{
+ int err;
+ long long read_ec;
+ struct ubi_ec_hdr *ec_hdr;
+
+ ec_hdr = kzalloc(ubi->io.ec_hdr_alsize, GFP_KERNEL);
+ if (unlikely(!ec_hdr))
+ return -ENOMEM;
+
+ err = ubi_io_read_ec_hdr(ubi, pnum, ec_hdr, 0);
+ if (unlikely(err) && err != UBI_IO_BITFLIPS) {
+ /* The header does not have to exist */
+ err = 0;
+ goto out_free;
+ }
+
+ read_ec = ubi64_to_cpu(ec_hdr->ec);
+ if (unlikely(ec != read_ec)) {
+ ubi_err("paranoid check failed for PEB %d", pnum);
+ ubi_err("read EC is %lld, should be %d", read_ec, ec);
+ ubi_dbg_dump_stack();
+ err = 1;
+ } else
+ err = 0;
+
+out_free:
+ kfree(ec_hdr);
+ return err;
+}
+
+/**
+ * paranoid_check_in_wl_tree - make sure that a 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 zero if @e is in the @root RB-tree and %1 if it
+ * is not.
+ */
+static int paranoid_check_in_wl_tree(struct ubi_wl_entry *e,
+ struct rb_root *root)
+{
+ if (likely(in_wl_tree(e, root)))
+ return 0;
+
+ ubi_err("paranoid check failed for PEB %d, EC %d, RB-tree %p ",
+ e->pnum, e->ec, root);
+ ubi_dbg_dump_stack();
+ return 1;
+}
+
+#endif /* CONFIG_MTD_UBI_DEBUG_PARANOID_WL */