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 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Copyright (c) International Business Machines Corp., 2006
  *
  * 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;
 }
 
 /**
  * in_pq - check if a wear-leveling entry is present in the protection queue.
  * @ubi: UBI device description object
  * @e: the wear-leveling entry to check
  *
  * This function returns non-zero if @e is in the protection queue and zero
  * if it is not.
  */
 static inline int in_pq(const struct ubi_device *ubi, struct ubi_wl_entry *e)
 {
     struct ubi_wl_entry *p;
     int i;
 
     for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i)
         list_for_each_entry(p, &ubi->pq[i], u.list)
             if (p == e)
                 return 1;
 
     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;
     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;
             e = e1;
         }
     }
 
     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
  * @nested: denotes whether the work_sem is already held in read mode
  *
  * 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, bool nested)
 {
     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;
 
     if (nested)
         __schedule_ubi_work(ubi, wl_wrk);
     else
         schedule_ubi_work(ubi, wl_wrk);
     return 0;
 }
 
 static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk);
 /**
  * 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.e = e;
     wl_wrk.vol_id = vol_id;
     wl_wrk.lnum = lnum;
     wl_wrk.torture = torture;
 
     return __erase_worker(ubi, &wl_wrk);
 }
 
 static int ensure_wear_leveling(struct ubi_device *ubi, int nested);
 /**
  * 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 erase = 0, keep = 0, vol_id = -1, lnum = -1;
     struct ubi_wl_entry *e1, *e2;
     struct ubi_vid_io_buf *vidb;
     struct ubi_vid_hdr *vid_hdr;
     int dst_leb_clean = 0;
 
     kfree(wrk);
     if (shutdown)
         return 0;
 
     vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
     if (!vidb)
         return -ENOMEM;
 
     vid_hdr = ubi_get_vid_hdr(vidb);
 
     down_read(&ubi->fm_eba_sem);
     mutex_lock(&ubi->move_mutex);
     spin_lock(&ubi->wl_lock);
     ubi_assert(!ubi->move_from && !ubi->move_to);
     ubi_assert(!ubi->move_to_put);
 
 #ifdef CONFIG_MTD_UBI_FASTMAP
     if (!next_peb_for_wl(ubi) ||
 #else
     if (!ubi->free.rb_node ||
 #endif
         (!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
     e1 = find_anchor_wl_entry(&ubi->used);
     if (e1 && ubi->fm_anchor &&
         (ubi->fm_anchor->ec - e1->ec >= UBI_WL_THRESHOLD)) {
         ubi->fm_do_produce_anchor = 1;
         /*
          * fm_anchor is no longer considered a good anchor.
          * NULL assignment also prevents multiple wear level checks
          * of this PEB.
          */
         wl_tree_add(ubi->fm_anchor, &ubi->free);
         ubi->fm_anchor = NULL;
         ubi->free_count++;
     }
 
     if (ubi->fm_do_produce_anchor) {
         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);
         ubi->fm_do_produce_anchor = 0;
     } 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, vidb, 0);
     if (err && err != UBI_IO_BITFLIPS) {
         dst_leb_clean = 1;
         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;
         } else if (ubi->fast_attach && err == UBI_IO_BAD_HDR_EBADMSG) {
             /*
              * While a full scan would detect interrupted erasures
              * at attach time we can face them here when attached from
              * Fastmap.
              */
             dbg_wl("PEB %d has ECC errors, maybe from an interrupted erasure",
                    e1->pnum);
             erase = 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, vidb);
     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;
             dst_leb_clean = 1;
             goto out_not_moved;
         }
         if (err == MOVE_RETRY) {
             scrubbing = 1;
             dst_leb_clean = 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;
             keep = 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;
             }
             dst_leb_clean = 1;
             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_buf(vidb);
 
     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);
     up_read(&ubi->fm_eba_sem);
     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 if (keep)
         wl_tree_add(e1, &ubi->used);
     if (dst_leb_clean) {
         wl_tree_add(e2, &ubi->free);
         ubi->free_count++;
     }
 
     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_buf(vidb);
     if (dst_leb_clean) {
         ensure_wear_leveling(ubi, 1);
     } else {
         err = do_sync_erase(ubi, e2, vol_id, lnum, torture);
         if (err)
             goto out_ro;
     }
 
     if (erase) {
         err = do_sync_erase(ubi, e1, vol_id, lnum, 1);
         if (err)
             goto out_ro;
     }
 
     mutex_unlock(&ubi->move_mutex);
     up_read(&ubi->fm_eba_sem);
     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_buf(vidb);
     wl_entry_destroy(ubi, e1);
     wl_entry_destroy(ubi, e2);
 
 out_ro:
     ubi_ro_mode(ubi);
     mutex_unlock(&ubi->move_mutex);
     up_read(&ubi->fm_eba_sem);
     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);
     up_read(&ubi->fm_eba_sem);
     ubi_free_vid_buf(vidb);
     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_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) {
 #ifdef CONFIG_MTD_UBI_FASTMAP
         if (!need_wear_leveling(ubi))
             goto out_unlock;
 #else
         struct ubi_wl_entry *e1;
         struct ubi_wl_entry *e2;
 
         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;
 #endif
         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->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
  *
  * 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)
 {
     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;
 
     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) {
         spin_lock(&ubi->wl_lock);
 
         if (!ubi->fm_disabled && !ubi->fm_anchor &&
             e->pnum < UBI_FM_MAX_START) {
             /*
              * Abort anchor production, if needed it will be
              * enabled again in the wear leveling started below.
              */
             ubi->fm_anchor = e;
             ubi->fm_do_produce_anchor = 0;
         } else {
             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);
 
     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, false);
         if (err1) {
             wl_entry_destroy(ubi, e);
             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;
 }
 
 static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk,
               int shutdown)
 {
     int ret;
 
     if (shutdown) {
         struct ubi_wl_entry *e = wl_wrk->e;
 
         dbg_wl("cancel erasure of PEB %d EC %d", e->pnum, e->ec);
         kfree(wl_wrk);
         wl_entry_destroy(ubi, e);
         return 0;
     }
 
     ret = __erase_worker(ubi, wl_wrk);
     kfree(wl_wrk);
     return ret;
 }
 
 /**
  * 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, false);
     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;
 }
 
 static bool scrub_possible(struct ubi_device *ubi, struct ubi_wl_entry *e)
 {
     if (in_wl_tree(e, &ubi->scrub))
         return false;
     else if (in_wl_tree(e, &ubi->erroneous))
         return false;
     else if (ubi->move_from == e)
         return false;
     else if (ubi->move_to == e)
         return false;
 
     return true;
 }
 
 /**
  * ubi_bitflip_check - Check an eraseblock for bitflips and scrub it if needed.
  * @ubi: UBI device description object
  * @pnum: the physical eraseblock to schedule
  * @force: dont't read the block, assume bitflips happened and take action.
  *
  * This function reads the given eraseblock and checks if bitflips occured.
  * In case of bitflips, the eraseblock is scheduled for scrubbing.
  * If scrubbing is forced with @force, the eraseblock is not read,
  * but scheduled for scrubbing right away.
  *
  * Returns:
  * %EINVAL, PEB is out of range
  * %ENOENT, PEB is no longer used by UBI
  * %EBUSY, PEB cannot be checked now or a check is currently running on it
  * %EAGAIN, bit flips happened but scrubbing is currently not possible
  * %EUCLEAN, bit flips happened and PEB is scheduled for scrubbing
  * %0, no bit flips detected
  */
 int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
 {
     int err = 0;
     struct ubi_wl_entry *e;
 
     if (pnum < 0 || pnum >= ubi->peb_count) {
         err = -EINVAL;
         goto out;
     }
 
     /*
      * Pause all parallel work, otherwise it can happen that the
      * erase worker frees a wl entry under us.
      */
     down_write(&ubi->work_sem);
 
     /*
      * Make sure that the wl entry does not change state while
      * inspecting it.
      */
     spin_lock(&ubi->wl_lock);
     e = ubi->lookuptbl[pnum];
     if (!e) {
         spin_unlock(&ubi->wl_lock);
         err = -ENOENT;
         goto out_resume;
     }
 
     /*
      * Does it make sense to check this PEB?
      */
     if (!scrub_possible(ubi, e)) {
         spin_unlock(&ubi->wl_lock);
         err = -EBUSY;
         goto out_resume;
     }
     spin_unlock(&ubi->wl_lock);
 
     if (!force) {
         mutex_lock(&ubi->buf_mutex);
         err = ubi_io_read(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
         mutex_unlock(&ubi->buf_mutex);
     }
 
     if (force || err == UBI_IO_BITFLIPS) {
         /*
          * Okay, bit flip happened, let's figure out what we can do.
          */
         spin_lock(&ubi->wl_lock);
 
         /*
          * Recheck. We released wl_lock, UBI might have killed the
          * wl entry under us.
          */
         e = ubi->lookuptbl[pnum];
         if (!e) {
             spin_unlock(&ubi->wl_lock);
             err = -ENOENT;
             goto out_resume;
         }
 
         /*
          * Need to re-check state
          */
         if (!scrub_possible(ubi, e)) {
             spin_unlock(&ubi->wl_lock);
             err = -EBUSY;
             goto out_resume;
         }
 
         if (in_pq(ubi, e)) {
             prot_queue_del(ubi, e->pnum);
             wl_tree_add(e, &ubi->scrub);
             spin_unlock(&ubi->wl_lock);
 
             err = ensure_wear_leveling(ubi, 1);
         } else if (in_wl_tree(e, &ubi->used)) {
             rb_erase(&e->u.rb, &ubi->used);
             wl_tree_add(e, &ubi->scrub);
             spin_unlock(&ubi->wl_lock);
 
             err = ensure_wear_leveling(ubi, 1);
         } else if (in_wl_tree(e, &ubi->free)) {
             rb_erase(&e->u.rb, &ubi->free);
             ubi->free_count--;
             spin_unlock(&ubi->wl_lock);
 
             /*
              * This PEB is empty we can schedule it for
              * erasure right away. No wear leveling needed.
              */
             err = schedule_erase(ubi, e, UBI_UNKNOWN, UBI_UNKNOWN,
                          force ? 0 : 1, true);
         } else {
             spin_unlock(&ubi->wl_lock);
             err = -EAGAIN;
         }
 
         if (!err && !force)
             err = -EUCLEAN;
     } else {
         err = 0;
     }
 
 out_resume:
     up_write(&ubi->work_sem);
 out:
 
     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);
 
             /*
              * Check kthread_should_stop() after we set the task
              * state to guarantee that we either see the stop bit
              * and exit or the task state is reset to runnable such
              * that it's not scheduled out indefinitely and detects
              * the stop bit at kthread_should_stop().
              */
             if (kthread_should_stop()) {
                 set_current_state(TASK_RUNNING);
                 break;
             }
 
             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);
     ubi->thread_enabled = 0;
     return 0;
 }
 
 /**
  * shutdown_work - shutdown all pending works.
  * @ubi: UBI device description object
  */
 static void shutdown_work(struct ubi_device *ubi)
 {
     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);
     }
 }
 
 /**
  * erase_aeb - erase a PEB given in UBI attach info PEB
  * @ubi: UBI device description object
  * @aeb: UBI attach info PEB
  * @sync: If true, erase synchronously. Otherwise schedule for erasure
  */
 static int erase_aeb(struct ubi_device *ubi, struct ubi_ainf_peb *aeb, bool sync)
 {
     struct ubi_wl_entry *e;
     int err;
 
     e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
     if (!e)
         return -ENOMEM;
 
     e->pnum = aeb->pnum;
     e->ec = aeb->ec;
     ubi->lookuptbl[e->pnum] = e;
 
     if (sync) {
         err = sync_erase(ubi, e, false);
         if (err)
             goto out_free;
 
         wl_tree_add(e, &ubi->free);
         ubi->free_count++;
     } else {
         err = schedule_erase(ubi, e, aeb->vol_id, aeb->lnum, 0, false);
         if (err)
             goto out_free;
     }
 
     return 0;
 
 out_free:
     wl_entry_destroy(ubi, e);
 
     return err;
 }
 
 /**
  * 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 = kcalloc(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;
 
     ubi->free_count = 0;
     list_for_each_entry_safe(aeb, tmp, &ai->erase, u.list) {
         cond_resched();
 
         err = erase_aeb(ubi, aeb, false);
         if (err)
             goto out_free;
 
         found_pebs++;
     }
 
     list_for_each_entry(aeb, &ai->free, u.list) {
         cond_resched();
 
         e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
         if (!e) {
             err = -ENOMEM;
             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) {
                 err = -ENOMEM;
                 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++;
         }
     }
 
     list_for_each_entry(aeb, &ai->fastmap, u.list) {
         cond_resched();
 
         e = ubi_find_fm_block(ubi, aeb->pnum);
 
         if (e) {
             ubi_assert(!ubi->lookuptbl[e->pnum]);
             ubi->lookuptbl[e->pnum] = e;
         } else {
             bool sync = false;
 
             /*
              * Usually old Fastmap PEBs are scheduled for erasure
              * and we don't have to care about them but if we face
              * an power cut before scheduling them we need to
              * take care of them here.
              */
             if (ubi->lookuptbl[aeb->pnum])
                 continue;
 
             /*
              * The fastmap update code might not find a free PEB for
              * writing the fastmap anchor to and then reuses the
              * current fastmap anchor PEB. When this PEB gets erased
              * and a power cut happens before it is written again we
              * must make sure that the fastmap attach code doesn't
              * find any outdated fastmap anchors, hence we erase the
              * outdated fastmap anchor PEBs synchronously here.
              */
             if (aeb->vol_id == UBI_FM_SB_VOLUME_ID)
                 sync = true;
 
             err = erase_aeb(ubi, aeb, sync);
             if (err)
                 goto out_free;
         }
 
         found_pebs++;
     }
 
     dbg_wl("found %i PEBs", found_pebs);
 
     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);
         err = -ENOSPC;
         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;
 
 #ifdef CONFIG_MTD_UBI_FASTMAP
     if (!ubi->ro_mode && !ubi->fm_disabled)
         ubi_ensure_anchor_pebs(ubi);
 #endif
     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)
 {
     if (!ubi_dbg_chk_gen(ubi))
         return 0;
 
     if (in_pq(ubi, 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

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