kernel/drivers/mtd/ubi/wl.c

   1 /*
   2  * Copyright (c) International Business Machines Corp., 2006
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
  12  * the GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  17  *
  18  * Authors: Artem Bityutskiy (Битюцкий Артём), Thomas Gleixner
  19  */
  20
  21 /*
  22  * UBI wear-leveling sub-system.
  23  *
  24  * This sub-system is responsible for wear-leveling. It works in terms of
  25  * physical eraseblocks and erase counters and knows nothing about logical
  26  * eraseblocks, volumes, etc. From this sub-system's perspective all physical
  27  * eraseblocks are of two types - used and free. Used physical eraseblocks are
  28  * those that were "get" by the 'ubi_wl_get_peb()' function, and free physical
  29  * eraseblocks are those that were put by the 'ubi_wl_put_peb()' function.
  30  *
  31  * Physical eraseblocks returned by 'ubi_wl_get_peb()' have only erase counter
  32  * header. The rest of the physical eraseblock contains only %0xFF bytes.
  33  *
  34  * When physical eraseblocks are returned to the WL sub-system by means of the
  35  * 'ubi_wl_put_peb()' function, they are scheduled for erasure. The erasure is
  36  * done asynchronously in context of the per-UBI device background thread,
  37  * which is also managed by the WL sub-system.
  38  *
  39  * The wear-leveling is ensured by means of moving the contents of used
  40  * physical eraseblocks with low erase counter to free physical eraseblocks
  41  * with high erase counter.
  42  *
  43  * If the WL sub-system fails to erase a physical eraseblock, it marks it as
  44  * bad.
  45  *
  46  * This sub-system is also responsible for scrubbing. If a bit-flip is detected
  47  * in a physical eraseblock, it has to be moved. Technically this is the same
  48  * as moving it for wear-leveling reasons.
  49  *
  50  * As it was said, for the UBI sub-system all physical eraseblocks are either
  51  * "free" or "used". Free eraseblock are kept in the @wl->free RB-tree, while
  52  * used eraseblocks are kept in @wl->used, @wl->erroneous, or @wl->scrub
  53  * RB-trees, as well as (temporarily) in the @wl->pq queue.
  54  *
  55  * When the WL sub-system returns a physical eraseblock, the physical
  56  * eraseblock is protected from being moved for some "time". For this reason,
  57  * the physical eraseblock is not directly moved from the @wl->free tree to the
  58  * @wl->used tree. There is a protection queue in between where this
  59  * physical eraseblock is temporarily stored (@wl->pq).
  60  *
  61  * All this protection stuff is needed because:
  62  *  o we don't want to move physical eraseblocks just after we have given them
  63  *    to the user; instead, we first want to let users fill them up with data;
  64  *
  65  *  o there is a chance that the user will put the physical eraseblock very
  66  *    soon, so it makes sense not to move it for some time, but wait.
  67  *
  68  * Physical eraseblocks stay protected only for limited time. But the "time" is
  69  * measured in erase cycles in this case. This is implemented with help of the
  70  * protection queue. Eraseblocks are put to the tail of this queue when they
  71  * are returned by the 'ubi_wl_get_peb()', and eraseblocks are removed from the
  72  * head of the queue on each erase operation (for any eraseblock). So the
  73  * length of the queue defines how may (global) erase cycles PEBs are protected.
  74  *
  75  * To put it differently, each physical eraseblock has 2 main states: free and
  76  * used. The former state corresponds to the @wl->free tree. The latter state
  77  * is split up on several sub-states:
  78  * o the WL movement is allowed (@wl->used tree);
  79  * o the WL movement is disallowed (@wl->erroneous) because the PEB is
  80  *   erroneous - e.g., there was a read error;
  81  * o the WL movement is temporarily prohibited (@wl->pq queue);
  82  * o scrubbing is needed (@wl->scrub tree).
  83  *
  84  * Depending on the sub-state, wear-leveling entries of the used physical
  85  * eraseblocks may be kept in one of those structures.
  86  *
  87  * Note, in this implementation, we keep a small in-RAM object for each physical
  88  * eraseblock. This is surely not a scalable solution. But it appears to be good
  89  * enough for moderately large flashes and it is simple. In future, one may
  90  * re-work this sub-system and make it more scalable.
  91  *
  92  * At the moment this sub-system does not utilize the sequence number, which
  93  * was introduced relatively recently. But it would be wise to do this because
  94  * the sequence number of a logical eraseblock characterizes how old is it. For
  95  * example, when we move a PEB with low erase counter, and we need to pick the
  96  * target PEB, we pick a PEB with the highest EC if our PEB is "old" and we
  97  * pick target PEB with an average EC if our PEB is not very "old". This is a
  98  * room for future re-works of the WL sub-system.
  99  */
 100
 101 #include <linux/slab.h>
 102 #include <linux/crc32.h>
 103 #include <linux/freezer.h>
 104 #include <linux/kthread.h>
 105 #include "ubi.h"
 106 #include "wl.h"
 107
 108 /* Number of physical eraseblocks reserved for wear-leveling purposes */
 109 #define WL_RESERVED_PEBS 1
 110
 111 /*
 112  * Maximum difference between two erase counters. If this threshold is
 113  * exceeded, the WL sub-system starts moving data from used physical
 114  * eraseblocks with low erase counter to free physical eraseblocks with high
 115  * erase counter.
 116  */
 117 #define UBI_WL_THRESHOLD CONFIG_MTD_UBI_WL_THRESHOLD
 118
 119 /*
 120  * When a physical eraseblock is moved, the WL sub-system has to pick the target
 121  * physical eraseblock to move to. The simplest way would be just to pick the
 122  * one with the highest erase counter. But in certain workloads this could lead
 123  * to an unlimited wear of one or few physical eraseblock. Indeed, imagine a
 124  * situation when the picked physical eraseblock is constantly erased after the
 125  * data is written to it. So, we have a constant which limits the highest erase
 126  * counter of the free physical eraseblock to pick. Namely, the WL sub-system
 127  * does not pick eraseblocks with erase counter greater than the lowest erase
 128  * counter plus %WL_FREE_MAX_DIFF.
 129  */
 130 #define WL_FREE_MAX_DIFF (2*UBI_WL_THRESHOLD)
 131
 132 /*
 133  * Maximum number of consecutive background thread failures which is enough to
 134  * switch to read-only mode.
 135  */
 136 #define WL_MAX_FAILURES 32
 137
 138 static int self_check_ec(struct ubi_device *ubi, int pnum, int ec);
 139 static int self_check_in_wl_tree(const struct ubi_device *ubi,
 140                                  struct ubi_wl_entry *e, struct rb_root *root);
 141 static int self_check_in_pq(const struct ubi_device *ubi,
 142                             struct ubi_wl_entry *e);
 143
 144 /**
 145  * wl_tree_add - add a wear-leveling entry to a WL RB-tree.
 146  * @e: the wear-leveling entry to add
 147  * @root: the root of the tree
 148  *
 149  * Note, we use (erase counter, physical eraseblock number) pairs as keys in
 150  * the @ubi->used and @ubi->free RB-trees.
 151  */
 152 static void wl_tree_add(struct ubi_wl_entry *e, struct rb_root *root)
 153 {
 154         struct rb_node **p, *parent = NULL;
 155
 156         p = &root->rb_node;
 157         while (*p) {
 158                 struct ubi_wl_entry *e1;
 159
 160                 parent = *p;
 161                 e1 = rb_entry(parent, struct ubi_wl_entry, u.rb);
 162
 163                 if (e->ec < e1->ec)
 164                         p = &(*p)->rb_left;
 165                 else if (e->ec > e1->ec)
 166                         p = &(*p)->rb_right;
 167                 else {
 168                         ubi_assert(e->pnum != e1->pnum);
 169                         if (e->pnum < e1->pnum)
 170                                 p = &(*p)->rb_left;
 171                         else
 172                                 p = &(*p)->rb_right;
 173                 }
 174         }
 175
 176         rb_link_node(&e->u.rb, parent, p);
 177         rb_insert_color(&e->u.rb, root);
 178 }
 179
 180 /**
 181  * wl_tree_destroy - destroy a wear-leveling entry.
 182  * @ubi: UBI device description object
 183  * @e: the wear-leveling entry to add
 184  *
 185  * This function destroys a wear leveling entry and removes
 186  * the reference from the lookup table.
 187  */
 188 static void wl_entry_destroy(struct ubi_device *ubi, struct ubi_wl_entry *e)
 189 {
 190         ubi->lookuptbl[e->pnum] = NULL;
 191         kmem_cache_free(ubi_wl_entry_slab, e);
 192 }
 193
 194 /**
 195  * do_work - do one pending work.
 196  * @ubi: UBI device description object
 197  *
 198  * This function returns zero in case of success and a negative error code in
 199  * case of failure.
 200  */
 201 static int do_work(struct ubi_device *ubi)
 202 {
 203         int err;
 204         struct ubi_work *wrk;
 205
 206         cond_resched();
 207
 208         /*
 209          * @ubi->work_sem is used to synchronize with the workers. Workers take
 210          * it in read mode, so many of them may be doing works at a time. But
 211          * the queue flush code has to be sure the whole queue of works is
 212          * done, and it takes the mutex in write mode.
 213          */
 214         down_read(&ubi->work_sem);
 215         spin_lock(&ubi->wl_lock);
 216         if (list_empty(&ubi->works)) {
 217                 spin_unlock(&ubi->wl_lock);
 218                 up_read(&ubi->work_sem);
 219                 return 0;
 220         }
 221
 222         wrk = list_entry(ubi->works.next, struct ubi_work, list);
 223         list_del(&wrk->list);
 224         ubi->works_count -= 1;
 225         ubi_assert(ubi->works_count >= 0);
 226         spin_unlock(&ubi->wl_lock);
 227
 228         /*
 229          * Call the worker function. Do not touch the work structure
 230          * after this call as it will have been freed or reused by that
 231          * time by the worker function.
 232          */
 233         err = wrk->func(ubi, wrk, 0);
 234         if (err)
 235                 ubi_err(ubi, "work failed with error code %d", err);
 236         up_read(&ubi->work_sem);
 237
 238         return err;
 239 }
 240
 241 /**
 242  * in_wl_tree - check if wear-leveling entry is present in a WL RB-tree.
 243  * @e: the wear-leveling entry to check
 244  * @root: the root of the tree
 245  *
 246  * This function returns non-zero if @e is in the @root RB-tree and zero if it
 247  * is not.
 248  */
 249 static int in_wl_tree(struct ubi_wl_entry *e, struct rb_root *root)
 250 {
 251         struct rb_node *p;
 252
 253         p = root->rb_node;
 254         while (p) {
 255                 struct ubi_wl_entry *e1;
 256
 257                 e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
 258
 259                 if (e->pnum == e1->pnum) {
 260                         ubi_assert(e == e1);
 261                         return 1;
 262                 }
 263
 264                 if (e->ec < e1->ec)
 265                         p = p->rb_left;
 266                 else if (e->ec > e1->ec)
 267                         p = p->rb_right;
 268                 else {
 269                         ubi_assert(e->pnum != e1->pnum);
 270                         if (e->pnum < e1->pnum)
 271                                 p = p->rb_left;
 272                         else
 273                                 p = p->rb_right;
 274                 }
 275         }
 276
 277         return 0;
 278 }
 279
 280 /**
 281  * prot_queue_add - add physical eraseblock to the protection queue.
 282  * @ubi: UBI device description object
 283  * @e: the physical eraseblock to add
 284  *
 285  * This function adds @e to the tail of the protection queue @ubi->pq, where
 286  * @e will stay for %UBI_PROT_QUEUE_LEN erase operations and will be
 287  * temporarily protected from the wear-leveling worker. Note, @wl->lock has to
 288  * be locked.
 289  */
 290 static void prot_queue_add(struct ubi_device *ubi, struct ubi_wl_entry *e)
 291 {
 292         int pq_tail = ubi->pq_head - 1;
 293
 294         if (pq_tail < 0)
 295                 pq_tail = UBI_PROT_QUEUE_LEN - 1;
 296         ubi_assert(pq_tail >= 0 && pq_tail < UBI_PROT_QUEUE_LEN);
 297         list_add_tail(&e->u.list, &ubi->pq[pq_tail]);
 298         dbg_wl("added PEB %d EC %d to the protection queue", e->pnum, e->ec);
 299 }
 300
 301 /**
 302  * find_wl_entry - find wear-leveling entry closest to certain erase counter.
 303  * @ubi: UBI device description object
 304  * @root: the RB-tree where to look for
 305  * @diff: maximum possible difference from the smallest erase counter
 306  *
 307  * This function looks for a wear leveling entry with erase counter closest to
 308  * min + @diff, where min is the smallest erase counter.
 309  */
 310 static struct ubi_wl_entry *find_wl_entry(struct ubi_device *ubi,
 311                                           struct rb_root *root, int diff)
 312 {
 313         struct rb_node *p;
 314         struct ubi_wl_entry *e, *prev_e = NULL;
 315         int max;
 316
 317         e = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
 318         max = e->ec + diff;
 319
 320         p = root->rb_node;
 321         while (p) {
 322                 struct ubi_wl_entry *e1;
 323
 324                 e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
 325                 if (e1->ec >= max)
 326                         p = p->rb_left;
 327                 else {
 328                         p = p->rb_right;
 329                         prev_e = e;
 330                         e = e1;
 331                 }
 332         }
 333
 334         /* If no fastmap has been written and this WL entry can be used
 335          * as anchor PEB, hold it back and return the second best WL entry
 336          * such that fastmap can use the anchor PEB later. */
 337         if (prev_e && !ubi->fm_disabled &&
 338             !ubi->fm && e->pnum < UBI_FM_MAX_START)
 339                 return prev_e;
 340
 341         return e;
 342 }
 343
 344 /**
 345  * find_mean_wl_entry - find wear-leveling entry with medium erase counter.
 346  * @ubi: UBI device description object
 347  * @root: the RB-tree where to look for
 348  *
 349  * This function looks for a wear leveling entry with medium erase counter,
 350  * but not greater or equivalent than the lowest erase counter plus
 351  * %WL_FREE_MAX_DIFF/2.
 352  */
 353 static struct ubi_wl_entry *find_mean_wl_entry(struct ubi_device *ubi,
 354                                                struct rb_root *root)
 355 {
 356         struct ubi_wl_entry *e, *first, *last;
 357
 358         first = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
 359         last = rb_entry(rb_last(root), struct ubi_wl_entry, u.rb);
 360
 361         if (last->ec - first->ec < WL_FREE_MAX_DIFF) {
 362                 e = rb_entry(root->rb_node, struct ubi_wl_entry, u.rb);
 363
 364                 /* If no fastmap has been written and this WL entry can be used
 365                  * as anchor PEB, hold it back and return the second best
 366                  * WL entry such that fastmap can use the anchor PEB later. */
 367                 e = may_reserve_for_fm(ubi, e, root);
 368         } else
 369                 e = find_wl_entry(ubi, root, WL_FREE_MAX_DIFF/2);
 370
 371         return e;
 372 }
 373
 374 /**
 375  * wl_get_wle - get a mean wl entry to be used by ubi_wl_get_peb() or
 376  * refill_wl_user_pool().
 377  * @ubi: UBI device description object
 378  *
 379  * This function returns a a wear leveling entry in case of success and
 380  * NULL in case of failure.
 381  */
 382 static struct ubi_wl_entry *wl_get_wle(struct ubi_device *ubi)
 383 {
 384         struct ubi_wl_entry *e;
 385
 386         e = find_mean_wl_entry(ubi, &ubi->free);
 387         if (!e) {
 388                 ubi_err(ubi, "no free eraseblocks");
 389                 return NULL;
 390         }
 391
 392         self_check_in_wl_tree(ubi, e, &ubi->free);
 393
 394         /*
 395          * Move the physical eraseblock to the protection queue where it will
 396          * be protected from being moved for some time.
 397          */
 398         rb_erase(&e->u.rb, &ubi->free);
 399         ubi->free_count--;
 400         dbg_wl("PEB %d EC %d", e->pnum, e->ec);
 401
 402         return e;
 403 }
 404
 405 /**
 406  * prot_queue_del - remove a physical eraseblock from the protection queue.
 407  * @ubi: UBI device description object
 408  * @pnum: the physical eraseblock to remove
 409  *
 410  * This function deletes PEB @pnum from the protection queue and returns zero
 411  * in case of success and %-ENODEV if the PEB was not found.
 412  */
 413 static int prot_queue_del(struct ubi_device *ubi, int pnum)
 414 {
 415         struct ubi_wl_entry *e;
 416
 417         e = ubi->lookuptbl[pnum];
 418         if (!e)
 419                 return -ENODEV;
 420
 421         if (self_check_in_pq(ubi, e))
 422                 return -ENODEV;
 423
 424         list_del(&e->u.list);
 425         dbg_wl("deleted PEB %d from the protection queue", e->pnum);
 426         return 0;
 427 }
 428
 429 /**
 430  * sync_erase - synchronously erase a physical eraseblock.
 431  * @ubi: UBI device description object
 432  * @e: the the physical eraseblock to erase
 433  * @torture: if the physical eraseblock has to be tortured
 434  *
 435  * This function returns zero in case of success and a negative error code in
 436  * case of failure.
 437  */
 438 static int sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
 439                       int torture)
 440 {
 441         int err;
 442         struct ubi_ec_hdr *ec_hdr;
 443         unsigned long long ec = e->ec;
 444
 445         dbg_wl("erase PEB %d, old EC %llu", e->pnum, ec);
 446
 447         err = self_check_ec(ubi, e->pnum, e->ec);
 448         if (err)
 449                 return -EINVAL;
 450
 451         ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
 452         if (!ec_hdr)
 453                 return -ENOMEM;
 454
 455         err = ubi_io_sync_erase(ubi, e->pnum, torture);
 456         if (err < 0)
 457                 goto out_free;
 458
 459         ec += err;
 460         if (ec > UBI_MAX_ERASECOUNTER) {
 461                 /*
 462                  * Erase counter overflow. Upgrade UBI and use 64-bit
 463                  * erase counters internally.
 464                  */
 465                 ubi_err(ubi, "erase counter overflow at PEB %d, EC %llu",
 466                         e->pnum, ec);
 467                 err = -EINVAL;
 468                 goto out_free;
 469         }
 470
 471         dbg_wl("erased PEB %d, new EC %llu", e->pnum, ec);
 472
 473         ec_hdr->ec = cpu_to_be64(ec);
 474
 475         err = ubi_io_write_ec_hdr(ubi, e->pnum, ec_hdr);
 476         if (err)
 477                 goto out_free;
 478
 479         e->ec = ec;
 480         spin_lock(&ubi->wl_lock);
 481         if (e->ec > ubi->max_ec)
 482                 ubi->max_ec = e->ec;
 483         spin_unlock(&ubi->wl_lock);
 484
 485 out_free:
 486         kfree(ec_hdr);
 487         return err;
 488 }
 489
 490 /**
 491  * serve_prot_queue - check if it is time to stop protecting PEBs.
 492  * @ubi: UBI device description object
 493  *
 494  * This function is called after each erase operation and removes PEBs from the
 495  * tail of the protection queue. These PEBs have been protected for long enough
 496  * and should be moved to the used tree.
 497  */
 498 static void serve_prot_queue(struct ubi_device *ubi)
 499 {
 500         struct ubi_wl_entry *e, *tmp;
 501         int count;
 502
 503         /*
 504          * There may be several protected physical eraseblock to remove,
 505          * process them all.
 506          */
 507 repeat:
 508         count = 0;
 509         spin_lock(&ubi->wl_lock);
 510         list_for_each_entry_safe(e, tmp, &ubi->pq[ubi->pq_head], u.list) {
 511                 dbg_wl("PEB %d EC %d protection over, move to used tree",
 512                         e->pnum, e->ec);
 513
 514                 list_del(&e->u.list);
 515                 wl_tree_add(e, &ubi->used);
 516                 if (count++ > 32) {
 517                         /*
 518                          * Let's be nice and avoid holding the spinlock for
 519                          * too long.
 520                          */
 521                         spin_unlock(&ubi->wl_lock);
 522                         cond_resched();
 523                         goto repeat;
 524                 }
 525         }
 526
 527         ubi->pq_head += 1;
 528         if (ubi->pq_head == UBI_PROT_QUEUE_LEN)
 529                 ubi->pq_head = 0;
 530         ubi_assert(ubi->pq_head >= 0 && ubi->pq_head < UBI_PROT_QUEUE_LEN);
 531         spin_unlock(&ubi->wl_lock);
 532 }
 533
 534 /**
 535  * __schedule_ubi_work - schedule a work.
 536  * @ubi: UBI device description object
 537  * @wrk: the work to schedule
 538  *
 539  * This function adds a work defined by @wrk to the tail of the pending works
 540  * list. Can only be used if ubi->work_sem is already held in read mode!
 541  */
 542 static void __schedule_ubi_work(struct ubi_device *ubi, struct ubi_work *wrk)
 543 {
 544         spin_lock(&ubi->wl_lock);
 545         list_add_tail(&wrk->list, &ubi->works);
 546         ubi_assert(ubi->works_count >= 0);
 547         ubi->works_count += 1;
 548         if (ubi->thread_enabled && !ubi_dbg_is_bgt_disabled(ubi))
 549                 wake_up_process(ubi->bgt_thread);
 550         spin_unlock(&ubi->wl_lock);
 551 }
 552
 553 /**
 554  * schedule_ubi_work - schedule a work.
 555  * @ubi: UBI device description object
 556  * @wrk: the work to schedule
 557  *
 558  * This function adds a work defined by @wrk to the tail of the pending works
 559  * list.
 560  */
 561 static void schedule_ubi_work(struct ubi_device *ubi, struct ubi_work *wrk)
 562 {
 563         down_read(&ubi->work_sem);
 564         __schedule_ubi_work(ubi, wrk);
 565         up_read(&ubi->work_sem);
 566 }
 567
 568 static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk,
 569                         int shutdown);
 570
 571 /**
 572  * schedule_erase - schedule an erase work.
 573  * @ubi: UBI device description object
 574  * @e: the WL entry of the physical eraseblock to erase
 575  * @vol_id: the volume ID that last used this PEB
 576  * @lnum: the last used logical eraseblock number for the PEB
 577  * @torture: if the physical eraseblock has to be tortured
 578  *
 579  * This function returns zero in case of success and a %-ENOMEM in case of
 580  * failure.
 581  */
 582 static int schedule_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
 583                           int vol_id, int lnum, int torture)
 584 {
 585         struct ubi_work *wl_wrk;
 586
 587         ubi_assert(e);
 588
 589         dbg_wl("schedule erasure of PEB %d, EC %d, torture %d",
 590                e->pnum, e->ec, torture);
 591
 592         wl_wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
 593         if (!wl_wrk)
 594                 return -ENOMEM;
 595
 596         wl_wrk->func = &erase_worker;
 597         wl_wrk->e = e;
 598         wl_wrk->vol_id = vol_id;
 599         wl_wrk->lnum = lnum;
 600         wl_wrk->torture = torture;
 601
 602         schedule_ubi_work(ubi, wl_wrk);
 603         return 0;
 604 }
 605
 606 static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk);
 607 /**
 608  * do_sync_erase - run the erase worker synchronously.
 609  * @ubi: UBI device description object
 610  * @e: the WL entry of the physical eraseblock to erase
 611  * @vol_id: the volume ID that last used this PEB
 612  * @lnum: the last used logical eraseblock number for the PEB
 613  * @torture: if the physical eraseblock has to be tortured
 614  *
 615  */
 616 static int do_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
 617                          int vol_id, int lnum, int torture)
 618 {
 619         struct ubi_work wl_wrk;
 620
 621         dbg_wl("sync erase of PEB %i", e->pnum);
 622
 623         wl_wrk.e = e;
 624         wl_wrk.vol_id = vol_id;
 625         wl_wrk.lnum = lnum;
 626         wl_wrk.torture = torture;
 627
 628         return __erase_worker(ubi, &wl_wrk);
 629 }
 630
 631 /**
 632  * wear_leveling_worker - wear-leveling worker function.
 633  * @ubi: UBI device description object
 634  * @wrk: the work object
 635  * @shutdown: non-zero if the worker has to free memory and exit
 636  * because the WL-subsystem is shutting down
 637  *
 638  * This function copies a more worn out physical eraseblock to a less worn out
 639  * one. Returns zero in case of success and a negative error code in case of
 640  * failure.
 641  */
 642 static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 643                                 int shutdown)
 644 {
 645         int err, scrubbing = 0, torture = 0, protect = 0, erroneous = 0;
 646         int vol_id = -1, lnum = -1;
 647 #ifdef CONFIG_MTD_UBI_FASTMAP
 648         int anchor = wrk->anchor;
 649 #endif
 650         struct ubi_wl_entry *e1, *e2;
 651         struct ubi_vid_hdr *vid_hdr;
 652
 653         kfree(wrk);
 654         if (shutdown)
 655                 return 0;
 656
 657         vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
 658         if (!vid_hdr)
 659                 return -ENOMEM;
 660
 661         mutex_lock(&ubi->move_mutex);
 662         spin_lock(&ubi->wl_lock);
 663         ubi_assert(!ubi->move_from && !ubi->move_to);
 664         ubi_assert(!ubi->move_to_put);
 665
 666         if (!ubi->free.rb_node ||
 667             (!ubi->used.rb_node && !ubi->scrub.rb_node)) {
 668                 /*
 669                  * No free physical eraseblocks? Well, they must be waiting in
 670                  * the queue to be erased. Cancel movement - it will be
 671                  * triggered again when a free physical eraseblock appears.
 672                  *
 673                  * No used physical eraseblocks? They must be temporarily
 674                  * protected from being moved. They will be moved to the
 675                  * @ubi->used tree later and the wear-leveling will be
 676                  * triggered again.
 677                  */
 678                 dbg_wl("cancel WL, a list is empty: free %d, used %d",
 679                        !ubi->free.rb_node, !ubi->used.rb_node);
 680                 goto out_cancel;
 681         }
 682
 683 #ifdef CONFIG_MTD_UBI_FASTMAP
 684         /* Check whether we need to produce an anchor PEB */
 685         if (!anchor)
 686                 anchor = !anchor_pebs_avalible(&ubi->free);
 687
 688         if (anchor) {
 689                 e1 = find_anchor_wl_entry(&ubi->used);
 690                 if (!e1)
 691                         goto out_cancel;
 692                 e2 = get_peb_for_wl(ubi);
 693                 if (!e2)
 694                         goto out_cancel;
 695
 696                 self_check_in_wl_tree(ubi, e1, &ubi->used);
 697                 rb_erase(&e1->u.rb, &ubi->used);
 698                 dbg_wl("anchor-move PEB %d to PEB %d", e1->pnum, e2->pnum);
 699         } else if (!ubi->scrub.rb_node) {
 700 #else
 701         if (!ubi->scrub.rb_node) {
 702 #endif
 703                 /*
 704                  * Now pick the least worn-out used physical eraseblock and a
 705                  * highly worn-out free physical eraseblock. If the erase
 706                  * counters differ much enough, start wear-leveling.
 707                  */
 708                 e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
 709                 e2 = get_peb_for_wl(ubi);
 710                 if (!e2)
 711                         goto out_cancel;
 712
 713                 if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD)) {
 714                         dbg_wl("no WL needed: min used EC %d, max free EC %d",
 715                                e1->ec, e2->ec);
 716
 717                         /* Give the unused PEB back */
 718                         wl_tree_add(e2, &ubi->free);
 719                         ubi->free_count++;
 720                         goto out_cancel;
 721                 }
 722                 self_check_in_wl_tree(ubi, e1, &ubi->used);
 723                 rb_erase(&e1->u.rb, &ubi->used);
 724                 dbg_wl("move PEB %d EC %d to PEB %d EC %d",
 725                        e1->pnum, e1->ec, e2->pnum, e2->ec);
 726         } else {
 727                 /* Perform scrubbing */
 728                 scrubbing = 1;
 729                 e1 = rb_entry(rb_first(&ubi->scrub), struct ubi_wl_entry, u.rb);
 730                 e2 = get_peb_for_wl(ubi);
 731                 if (!e2)
 732                         goto out_cancel;
 733
 734                 self_check_in_wl_tree(ubi, e1, &ubi->scrub);
 735                 rb_erase(&e1->u.rb, &ubi->scrub);
 736                 dbg_wl("scrub PEB %d to PEB %d", e1->pnum, e2->pnum);
 737         }
 738
 739         ubi->move_from = e1;
 740         ubi->move_to = e2;
 741         spin_unlock(&ubi->wl_lock);
 742
 743         /*
 744          * Now we are going to copy physical eraseblock @e1->pnum to @e2->pnum.
 745          * We so far do not know which logical eraseblock our physical
 746          * eraseblock (@e1) belongs to. We have to read the volume identifier
 747          * header first.
 748          *
 749          * Note, we are protected from this PEB being unmapped and erased. The
 750          * 'ubi_wl_put_peb()' would wait for moving to be finished if the PEB
 751          * which is being moved was unmapped.
 752          */
 753
 754         err = ubi_io_read_vid_hdr(ubi, e1->pnum, vid_hdr, 0);
 755         if (err && err != UBI_IO_BITFLIPS) {
 756                 if (err == UBI_IO_FF) {
 757                         /*
 758                          * We are trying to move PEB without a VID header. UBI
 759                          * always write VID headers shortly after the PEB was
 760                          * given, so we have a situation when it has not yet
 761                          * had a chance to write it, because it was preempted.
 762                          * So add this PEB to the protection queue so far,
 763                          * because presumably more data will be written there
 764                          * (including the missing VID header), and then we'll
 765                          * move it.
 766                          */
 767                         dbg_wl("PEB %d has no VID header", e1->pnum);
 768                         protect = 1;
 769                         goto out_not_moved;
 770                 } else if (err == UBI_IO_FF_BITFLIPS) {
 771                         /*
 772                          * The same situation as %UBI_IO_FF, but bit-flips were
 773                          * detected. It is better to schedule this PEB for
 774                          * scrubbing.
 775                          */
 776                         dbg_wl("PEB %d has no VID header but has bit-flips",
 777                                e1->pnum);
 778                         scrubbing = 1;
 779                         goto out_not_moved;
 780                 }
 781
 782                 ubi_err(ubi, "error %d while reading VID header from PEB %d",
 783                         err, e1->pnum);
 784                 goto out_error;
 785         }
 786
 787         vol_id = be32_to_cpu(vid_hdr->vol_id);
 788         lnum = be32_to_cpu(vid_hdr->lnum);
 789
 790         err = ubi_eba_copy_leb(ubi, e1->pnum, e2->pnum, vid_hdr);
 791         if (err) {
 792                 if (err == MOVE_CANCEL_RACE) {
 793                         /*
 794                          * The LEB has not been moved because the volume is
 795                          * being deleted or the PEB has been put meanwhile. We
 796                          * should prevent this PEB from being selected for
 797                          * wear-leveling movement again, so put it to the
 798                          * protection queue.
 799                          */
 800                         protect = 1;
 801                         goto out_not_moved;
 802                 }
 803                 if (err == MOVE_RETRY) {
 804                         scrubbing = 1;
 805                         goto out_not_moved;
 806                 }
 807                 if (err == MOVE_TARGET_BITFLIPS || err == MOVE_TARGET_WR_ERR ||
 808                     err == MOVE_TARGET_RD_ERR) {
 809                         /*
 810                          * Target PEB had bit-flips or write error - torture it.
 811                          */
 812                         torture = 1;
 813                         goto out_not_moved;
 814                 }
 815
 816                 if (err == MOVE_SOURCE_RD_ERR) {
 817                         /*
 818                          * An error happened while reading the source PEB. Do
 819                          * not switch to R/O mode in this case, and give the
 820                          * upper layers a possibility to recover from this,
 821                          * e.g. by unmapping corresponding LEB. Instead, just
 822                          * put this PEB to the @ubi->erroneous list to prevent
 823                          * UBI from trying to move it over and over again.
 824                          */
 825                         if (ubi->erroneous_peb_count > ubi->max_erroneous) {
 826                                 ubi_err(ubi, "too many erroneous eraseblocks (%d)",
 827                                         ubi->erroneous_peb_count);
 828                                 goto out_error;
 829                         }
 830                         erroneous = 1;
 831                         goto out_not_moved;
 832                 }
 833
 834                 if (err < 0)
 835                         goto out_error;
 836
 837                 ubi_assert(0);
 838         }
 839
 840         /* The PEB has been successfully moved */
 841         if (scrubbing)
 842                 ubi_msg(ubi, "scrubbed PEB %d (LEB %d:%d), data moved to PEB %d",
 843                         e1->pnum, vol_id, lnum, e2->pnum);
 844         ubi_free_vid_hdr(ubi, vid_hdr);
 845
 846         spin_lock(&ubi->wl_lock);
 847         if (!ubi->move_to_put) {
 848                 wl_tree_add(e2, &ubi->used);
 849                 e2 = NULL;
 850         }
 851         ubi->move_from = ubi->move_to = NULL;
 852         ubi->move_to_put = ubi->wl_scheduled = 0;
 853         spin_unlock(&ubi->wl_lock);
 854
 855         err = do_sync_erase(ubi, e1, vol_id, lnum, 0);
 856         if (err) {
 857                 if (e2)
 858                         wl_entry_destroy(ubi, e2);
 859                 goto out_ro;
 860         }
 861
 862         if (e2) {
 863                 /*
 864                  * Well, the target PEB was put meanwhile, schedule it for
 865                  * erasure.
 866                  */
 867                 dbg_wl("PEB %d (LEB %d:%d) was put meanwhile, erase",
 868                        e2->pnum, vol_id, lnum);
 869                 err = do_sync_erase(ubi, e2, vol_id, lnum, 0);
 870                 if (err)
 871                         goto out_ro;
 872         }
 873
 874         dbg_wl("done");
 875         mutex_unlock(&ubi->move_mutex);
 876         return 0;
 877
 878         /*
 879          * For some reasons the LEB was not moved, might be an error, might be
 880          * something else. @e1 was not changed, so return it back. @e2 might
 881          * have been changed, schedule it for erasure.
 882          */
 883 out_not_moved:
 884         if (vol_id != -1)
 885                 dbg_wl("cancel moving PEB %d (LEB %d:%d) to PEB %d (%d)",
 886                        e1->pnum, vol_id, lnum, e2->pnum, err);
 887         else
 888                 dbg_wl("cancel moving PEB %d to PEB %d (%d)",
 889                        e1->pnum, e2->pnum, err);
 890         spin_lock(&ubi->wl_lock);
 891         if (protect)
 892                 prot_queue_add(ubi, e1);
 893         else if (erroneous) {
 894                 wl_tree_add(e1, &ubi->erroneous);
 895                 ubi->erroneous_peb_count += 1;
 896         } else if (scrubbing)
 897                 wl_tree_add(e1, &ubi->scrub);
 898         else
 899                 wl_tree_add(e1, &ubi->used);
 900         ubi_assert(!ubi->move_to_put);
 901         ubi->move_from = ubi->move_to = NULL;
 902         ubi->wl_scheduled = 0;
 903         spin_unlock(&ubi->wl_lock);
 904
 905         ubi_free_vid_hdr(ubi, vid_hdr);
 906         err = do_sync_erase(ubi, e2, vol_id, lnum, torture);
 907         if (err)
 908                 goto out_ro;
 909
 910         mutex_unlock(&ubi->move_mutex);
 911         return 0;
 912
 913 out_error:
 914         if (vol_id != -1)
 915                 ubi_err(ubi, "error %d while moving PEB %d to PEB %d",
 916                         err, e1->pnum, e2->pnum);
 917         else
 918                 ubi_err(ubi, "error %d while moving PEB %d (LEB %d:%d) to PEB %d",
 919                         err, e1->pnum, vol_id, lnum, e2->pnum);
 920         spin_lock(&ubi->wl_lock);
 921         ubi->move_from = ubi->move_to = NULL;
 922         ubi->move_to_put = ubi->wl_scheduled = 0;
 923         spin_unlock(&ubi->wl_lock);
 924
 925         ubi_free_vid_hdr(ubi, vid_hdr);
 926         wl_entry_destroy(ubi, e1);
 927         wl_entry_destroy(ubi, e2);
 928
 929 out_ro:
 930         ubi_ro_mode(ubi);
 931         mutex_unlock(&ubi->move_mutex);
 932         ubi_assert(err != 0);
 933         return err < 0 ? err : -EIO;
 934
 935 out_cancel:
 936         ubi->wl_scheduled = 0;
 937         spin_unlock(&ubi->wl_lock);
 938         mutex_unlock(&ubi->move_mutex);
 939         ubi_free_vid_hdr(ubi, vid_hdr);
 940         return 0;
 941 }
 942
 943 /**
 944  * ensure_wear_leveling - schedule wear-leveling if it is needed.
 945  * @ubi: UBI device description object
 946  * @nested: set to non-zero if this function is called from UBI worker
 947  *
 948  * This function checks if it is time to start wear-leveling and schedules it
 949  * if yes. This function returns zero in case of success and a negative error
 950  * code in case of failure.
 951  */
 952 static int ensure_wear_leveling(struct ubi_device *ubi, int nested)
 953 {
 954         int err = 0;
 955         struct ubi_wl_entry *e1;
 956         struct ubi_wl_entry *e2;
 957         struct ubi_work *wrk;
 958
 959         spin_lock(&ubi->wl_lock);
 960         if (ubi->wl_scheduled)
 961                 /* Wear-leveling is already in the work queue */
 962                 goto out_unlock;
 963
 964         /*
 965          * If the ubi->scrub tree is not empty, scrubbing is needed, and the
 966          * the WL worker has to be scheduled anyway.
 967          */
 968         if (!ubi->scrub.rb_node) {
 969                 if (!ubi->used.rb_node || !ubi->free.rb_node)
 970                         /* No physical eraseblocks - no deal */
 971                         goto out_unlock;
 972
 973                 /*
 974                  * We schedule wear-leveling only if the difference between the
 975                  * lowest erase counter of used physical eraseblocks and a high
 976                  * erase counter of free physical eraseblocks is greater than
 977                  * %UBI_WL_THRESHOLD.
 978                  */
 979                 e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
 980                 e2 = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
 981
 982                 if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD))
 983                         goto out_unlock;
 984                 dbg_wl("schedule wear-leveling");
 985         } else
 986                 dbg_wl("schedule scrubbing");
 987
 988         ubi->wl_scheduled = 1;
 989         spin_unlock(&ubi->wl_lock);
 990
 991         wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
 992         if (!wrk) {
 993                 err = -ENOMEM;
 994                 goto out_cancel;
 995         }
 996
 997         wrk->anchor = 0;
 998         wrk->func = &wear_leveling_worker;
 999         if (nested)
1000                 __schedule_ubi_work(ubi, wrk);
1001         else
1002                 schedule_ubi_work(ubi, wrk);
1003         return err;
1004
1005 out_cancel:
1006         spin_lock(&ubi->wl_lock);
1007         ubi->wl_scheduled = 0;
1008 out_unlock:
1009         spin_unlock(&ubi->wl_lock);
1010         return err;
1011 }
1012
1013 /**
1014  * __erase_worker - physical eraseblock erase worker function.
1015  * @ubi: UBI device description object
1016  * @wl_wrk: the work object
1017  * @shutdown: non-zero if the worker has to free memory and exit
1018  * because the WL sub-system is shutting down
1019  *
1020  * This function erases a physical eraseblock and perform torture testing if
1021  * needed. It also takes care about marking the physical eraseblock bad if
1022  * needed. Returns zero in case of success and a negative error code in case of
1023  * failure.
1024  */
1025 static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk)
1026 {
1027         struct ubi_wl_entry *e = wl_wrk->e;
1028         int pnum = e->pnum;
1029         int vol_id = wl_wrk->vol_id;
1030         int lnum = wl_wrk->lnum;
1031         int err, available_consumed = 0;
1032
1033         dbg_wl("erase PEB %d EC %d LEB %d:%d",
1034                pnum, e->ec, wl_wrk->vol_id, wl_wrk->lnum);
1035
1036         err = sync_erase(ubi, e, wl_wrk->torture);
1037         if (!err) {
1038                 spin_lock(&ubi->wl_lock);
1039                 wl_tree_add(e, &ubi->free);
1040                 ubi->free_count++;
1041                 spin_unlock(&ubi->wl_lock);
1042
1043                 /*
1044                  * One more erase operation has happened, take care about
1045                  * protected physical eraseblocks.
1046                  */
1047                 serve_prot_queue(ubi);
1048
1049                 /* And take care about wear-leveling */
1050                 err = ensure_wear_leveling(ubi, 1);
1051                 return err;
1052         }
1053
1054         ubi_err(ubi, "failed to erase PEB %d, error %d", pnum, err);
1055
1056         if (err == -EINTR || err == -ENOMEM || err == -EAGAIN ||
1057             err == -EBUSY) {
1058                 int err1;
1059
1060                 /* Re-schedule the LEB for erasure */
1061                 err1 = schedule_erase(ubi, e, vol_id, lnum, 0);
1062                 if (err1) {
1063                         wl_entry_destroy(ubi, e);
1064                         err = err1;
1065                         goto out_ro;
1066                 }
1067                 return err;
1068         }
1069
1070         wl_entry_destroy(ubi, e);
1071         if (err != -EIO)
1072                 /*
1073                  * If this is not %-EIO, we have no idea what to do. Scheduling
1074                  * this physical eraseblock for erasure again would cause
1075                  * errors again and again. Well, lets switch to R/O mode.
1076                  */
1077                 goto out_ro;
1078
1079         /* It is %-EIO, the PEB went bad */
1080
1081         if (!ubi->bad_allowed) {
1082                 ubi_err(ubi, "bad physical eraseblock %d detected", pnum);
1083                 goto out_ro;
1084         }
1085
1086         spin_lock(&ubi->volumes_lock);
1087         if (ubi->beb_rsvd_pebs == 0) {
1088                 if (ubi->avail_pebs == 0) {
1089                         spin_unlock(&ubi->volumes_lock);
1090                         ubi_err(ubi, "no reserved/available physical eraseblocks");
1091                         goto out_ro;
1092                 }
1093                 ubi->avail_pebs -= 1;
1094                 available_consumed = 1;
1095         }
1096         spin_unlock(&ubi->volumes_lock);
1097
1098         ubi_msg(ubi, "mark PEB %d as bad", pnum);
1099         err = ubi_io_mark_bad(ubi, pnum);
1100         if (err)
1101                 goto out_ro;
1102
1103         spin_lock(&ubi->volumes_lock);
1104         if (ubi->beb_rsvd_pebs > 0) {
1105                 if (available_consumed) {
1106                         /*
1107                          * The amount of reserved PEBs increased since we last
1108                          * checked.
1109                          */
1110                         ubi->avail_pebs += 1;
1111                         available_consumed = 0;
1112                 }
1113                 ubi->beb_rsvd_pebs -= 1;
1114         }
1115         ubi->bad_peb_count += 1;
1116         ubi->good_peb_count -= 1;
1117         ubi_calculate_reserved(ubi);
1118         if (available_consumed)
1119                 ubi_warn(ubi, "no PEBs in the reserved pool, used an available PEB");
1120         else if (ubi->beb_rsvd_pebs)
1121                 ubi_msg(ubi, "%d PEBs left in the reserve",
1122                         ubi->beb_rsvd_pebs);
1123         else
1124                 ubi_warn(ubi, "last PEB from the reserve was used");
1125         spin_unlock(&ubi->volumes_lock);
1126
1127         return err;
1128
1129 out_ro:
1130         if (available_consumed) {
1131                 spin_lock(&ubi->volumes_lock);
1132                 ubi->avail_pebs += 1;
1133                 spin_unlock(&ubi->volumes_lock);
1134         }
1135         ubi_ro_mode(ubi);
1136         return err;
1137 }
1138
1139 static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk,
1140                           int shutdown)
1141 {
1142         int ret;
1143
1144         if (shutdown) {
1145                 struct ubi_wl_entry *e = wl_wrk->e;
1146
1147                 dbg_wl("cancel erasure of PEB %d EC %d", e->pnum, e->ec);
1148                 kfree(wl_wrk);
1149                 wl_entry_destroy(ubi, e);
1150                 return 0;
1151         }
1152
1153         ret = __erase_worker(ubi, wl_wrk);
1154         kfree(wl_wrk);
1155         return ret;
1156 }
1157
1158 /**
1159  * ubi_wl_put_peb - return a PEB to the wear-leveling sub-system.
1160  * @ubi: UBI device description object
1161  * @vol_id: the volume ID that last used this PEB
1162  * @lnum: the last used logical eraseblock number for the PEB
1163  * @pnum: physical eraseblock to return
1164  * @torture: if this physical eraseblock has to be tortured
1165  *
1166  * This function is called to return physical eraseblock @pnum to the pool of
1167  * free physical eraseblocks. The @torture flag has to be set if an I/O error
1168  * occurred to this @pnum and it has to be tested. This function returns zero
1169  * in case of success, and a negative error code in case of failure.
1170  */
1171 int ubi_wl_put_peb(struct ubi_device *ubi, int vol_id, int lnum,
1172                    int pnum, int torture)
1173 {
1174         int err;
1175         struct ubi_wl_entry *e;
1176
1177         dbg_wl("PEB %d", pnum);
1178         ubi_assert(pnum >= 0);
1179         ubi_assert(pnum < ubi->peb_count);
1180
1181         down_read(&ubi->fm_protect);
1182
1183 retry:
1184         spin_lock(&ubi->wl_lock);
1185         e = ubi->lookuptbl[pnum];
1186         if (e == ubi->move_from) {
1187                 /*
1188                  * User is putting the physical eraseblock which was selected to
1189                  * be moved. It will be scheduled for erasure in the
1190                  * wear-leveling worker.
1191                  */
1192                 dbg_wl("PEB %d is being moved, wait", pnum);
1193                 spin_unlock(&ubi->wl_lock);
1194
1195                 /* Wait for the WL worker by taking the @ubi->move_mutex */
1196                 mutex_lock(&ubi->move_mutex);
1197                 mutex_unlock(&ubi->move_mutex);
1198                 goto retry;
1199         } else if (e == ubi->move_to) {
1200                 /*
1201                  * User is putting the physical eraseblock which was selected
1202                  * as the target the data is moved to. It may happen if the EBA
1203                  * sub-system already re-mapped the LEB in 'ubi_eba_copy_leb()'
1204                  * but the WL sub-system has not put the PEB to the "used" tree
1205                  * yet, but it is about to do this. So we just set a flag which
1206                  * will tell the WL worker that the PEB is not needed anymore
1207                  * and should be scheduled for erasure.
1208                  */
1209                 dbg_wl("PEB %d is the target of data moving", pnum);
1210                 ubi_assert(!ubi->move_to_put);
1211                 ubi->move_to_put = 1;
1212                 spin_unlock(&ubi->wl_lock);
1213                 up_read(&ubi->fm_protect);
1214                 return 0;
1215         } else {
1216                 if (in_wl_tree(e, &ubi->used)) {
1217                         self_check_in_wl_tree(ubi, e, &ubi->used);
1218                         rb_erase(&e->u.rb, &ubi->used);
1219                 } else if (in_wl_tree(e, &ubi->scrub)) {
1220                         self_check_in_wl_tree(ubi, e, &ubi->scrub);
1221                         rb_erase(&e->u.rb, &ubi->scrub);
1222                 } else if (in_wl_tree(e, &ubi->erroneous)) {
1223                         self_check_in_wl_tree(ubi, e, &ubi->erroneous);
1224                         rb_erase(&e->u.rb, &ubi->erroneous);
1225                         ubi->erroneous_peb_count -= 1;
1226                         ubi_assert(ubi->erroneous_peb_count >= 0);
1227                         /* Erroneous PEBs should be tortured */
1228                         torture = 1;
1229                 } else {
1230                         err = prot_queue_del(ubi, e->pnum);
1231                         if (err) {
1232                                 ubi_err(ubi, "PEB %d not found", pnum);
1233                                 ubi_ro_mode(ubi);
1234                                 spin_unlock(&ubi->wl_lock);
1235                                 up_read(&ubi->fm_protect);
1236                                 return err;
1237                         }
1238                 }
1239         }
1240         spin_unlock(&ubi->wl_lock);
1241
1242         err = schedule_erase(ubi, e, vol_id, lnum, torture);
1243         if (err) {
1244                 spin_lock(&ubi->wl_lock);
1245                 wl_tree_add(e, &ubi->used);
1246                 spin_unlock(&ubi->wl_lock);
1247         }
1248
1249         up_read(&ubi->fm_protect);
1250         return err;
1251 }
1252
1253 /**
1254  * ubi_wl_scrub_peb - schedule a physical eraseblock for scrubbing.
1255  * @ubi: UBI device description object
1256  * @pnum: the physical eraseblock to schedule
1257  *
1258  * If a bit-flip in a physical eraseblock is detected, this physical eraseblock
1259  * needs scrubbing. This function schedules a physical eraseblock for
1260  * scrubbing which is done in background. This function returns zero in case of
1261  * success and a negative error code in case of failure.
1262  */
1263 int ubi_wl_scrub_peb(struct ubi_device *ubi, int pnum)
1264 {
1265         struct ubi_wl_entry *e;
1266
1267         ubi_msg(ubi, "schedule PEB %d for scrubbing", pnum);
1268
1269 retry:
1270         spin_lock(&ubi->wl_lock);
1271         e = ubi->lookuptbl[pnum];
1272         if (e == ubi->move_from || in_wl_tree(e, &ubi->scrub) ||
1273                                    in_wl_tree(e, &ubi->erroneous)) {
1274                 spin_unlock(&ubi->wl_lock);
1275                 return 0;
1276         }
1277
1278         if (e == ubi->move_to) {
1279                 /*
1280                  * This physical eraseblock was used to move data to. The data
1281                  * was moved but the PEB was not yet inserted to the proper
1282                  * tree. We should just wait a little and let the WL worker
1283                  * proceed.
1284                  */
1285                 spin_unlock(&ubi->wl_lock);
1286                 dbg_wl("the PEB %d is not in proper tree, retry", pnum);
1287                 yield();
1288                 goto retry;
1289         }
1290
1291         if (in_wl_tree(e, &ubi->used)) {
1292                 self_check_in_wl_tree(ubi, e, &ubi->used);
1293                 rb_erase(&e->u.rb, &ubi->used);
1294         } else {
1295                 int err;
1296
1297                 err = prot_queue_del(ubi, e->pnum);
1298                 if (err) {
1299                         ubi_err(ubi, "PEB %d not found", pnum);
1300                         ubi_ro_mode(ubi);
1301                         spin_unlock(&ubi->wl_lock);
1302                         return err;
1303                 }
1304         }
1305
1306         wl_tree_add(e, &ubi->scrub);
1307         spin_unlock(&ubi->wl_lock);
1308
1309         /*
1310          * Technically scrubbing is the same as wear-leveling, so it is done
1311          * by the WL worker.
1312          */
1313         return ensure_wear_leveling(ubi, 0);
1314 }
1315
1316 /**
1317  * ubi_wl_flush - flush all pending works.
1318  * @ubi: UBI device description object
1319  * @vol_id: the volume id to flush for
1320  * @lnum: the logical eraseblock number to flush for
1321  *
1322  * This function executes all pending works for a particular volume id /
1323  * logical eraseblock number pair. If either value is set to %UBI_ALL, then it
1324  * acts as a wildcard for all of the corresponding volume numbers or logical
1325  * eraseblock numbers. It returns zero in case of success and a negative error
1326  * code in case of failure.
1327  */
1328 int ubi_wl_flush(struct ubi_device *ubi, int vol_id, int lnum)
1329 {
1330         int err = 0;
1331         int found = 1;
1332
1333         /*
1334          * Erase while the pending works queue is not empty, but not more than
1335          * the number of currently pending works.
1336          */
1337         dbg_wl("flush pending work for LEB %d:%d (%d pending works)",
1338                vol_id, lnum, ubi->works_count);
1339
1340         while (found) {
1341                 struct ubi_work *wrk, *tmp;
1342                 found = 0;
1343
1344                 down_read(&ubi->work_sem);
1345                 spin_lock(&ubi->wl_lock);
1346                 list_for_each_entry_safe(wrk, tmp, &ubi->works, list) {
1347                         if ((vol_id == UBI_ALL || wrk->vol_id == vol_id) &&
1348                             (lnum == UBI_ALL || wrk->lnum == lnum)) {
1349                                 list_del(&wrk->list);
1350                                 ubi->works_count -= 1;
1351                                 ubi_assert(ubi->works_count >= 0);
1352                                 spin_unlock(&ubi->wl_lock);
1353
1354                                 err = wrk->func(ubi, wrk, 0);
1355                                 if (err) {
1356                                         up_read(&ubi->work_sem);
1357                                         return err;
1358                                 }
1359
1360                                 spin_lock(&ubi->wl_lock);
1361                                 found = 1;
1362                                 break;
1363                         }
1364                 }
1365                 spin_unlock(&ubi->wl_lock);
1366                 up_read(&ubi->work_sem);
1367         }
1368
1369         /*
1370          * Make sure all the works which have been done in parallel are
1371          * finished.
1372          */
1373         down_write(&ubi->work_sem);
1374         up_write(&ubi->work_sem);
1375
1376         return err;
1377 }
1378
1379 /**
1380  * tree_destroy - destroy an RB-tree.
1381  * @ubi: UBI device description object
1382  * @root: the root of the tree to destroy
1383  */
1384 static void tree_destroy(struct ubi_device *ubi, struct rb_root *root)
1385 {
1386         struct rb_node *rb;
1387         struct ubi_wl_entry *e;
1388
1389         rb = root->rb_node;
1390         while (rb) {
1391                 if (rb->rb_left)
1392                         rb = rb->rb_left;
1393                 else if (rb->rb_right)
1394                         rb = rb->rb_right;
1395                 else {
1396                         e = rb_entry(rb, struct ubi_wl_entry, u.rb);
1397
1398                         rb = rb_parent(rb);
1399                         if (rb) {
1400                                 if (rb->rb_left == &e->u.rb)
1401                                         rb->rb_left = NULL;
1402                                 else
1403                                         rb->rb_right = NULL;
1404                         }
1405
1406                         wl_entry_destroy(ubi, e);
1407                 }
1408         }
1409 }
1410
1411 /**
1412  * ubi_thread - UBI background thread.
1413  * @u: the UBI device description object pointer
1414  */
1415 int ubi_thread(void *u)
1416 {
1417         int failures = 0;
1418         struct ubi_device *ubi = u;
1419
1420         ubi_msg(ubi, "background thread \"%s\" started, PID %d",
1421                 ubi->bgt_name, task_pid_nr(current));
1422
1423         set_freezable();
1424         for (;;) {
1425                 int err;
1426
1427                 if (kthread_should_stop())
1428                         break;
1429
1430                 if (try_to_freeze())
1431                         continue;
1432
1433                 spin_lock(&ubi->wl_lock);
1434                 if (list_empty(&ubi->works) || ubi->ro_mode ||
1435                     !ubi->thread_enabled || ubi_dbg_is_bgt_disabled(ubi)) {
1436                         set_current_state(TASK_INTERRUPTIBLE);
1437                         spin_unlock(&ubi->wl_lock);
1438                         schedule();
1439                         continue;
1440                 }
1441                 spin_unlock(&ubi->wl_lock);
1442
1443                 err = do_work(ubi);
1444                 if (err) {
1445                         ubi_err(ubi, "%s: work failed with error code %d",
1446                                 ubi->bgt_name, err);
1447                         if (failures++ > WL_MAX_FAILURES) {
1448                                 /*
1449                                  * Too many failures, disable the thread and
1450                                  * switch to read-only mode.
1451                                  */
1452                                 ubi_msg(ubi, "%s: %d consecutive failures",
1453                                         ubi->bgt_name, WL_MAX_FAILURES);
1454                                 ubi_ro_mode(ubi);
1455                                 ubi->thread_enabled = 0;
1456                                 continue;
1457                         }
1458                 } else
1459                         failures = 0;
1460
1461                 cond_resched();
1462         }
1463
1464         dbg_wl("background thread \"%s\" is killed", ubi->bgt_name);
1465         return 0;
1466 }
1467
1468 /**
1469  * shutdown_work - shutdown all pending works.
1470  * @ubi: UBI device description object
1471  */
1472 static void shutdown_work(struct ubi_device *ubi)
1473 {
1474 #ifdef CONFIG_MTD_UBI_FASTMAP
1475         flush_work(&ubi->fm_work);
1476 #endif
1477         while (!list_empty(&ubi->works)) {
1478                 struct ubi_work *wrk;
1479
1480                 wrk = list_entry(ubi->works.next, struct ubi_work, list);
1481                 list_del(&wrk->list);
1482                 wrk->func(ubi, wrk, 1);
1483                 ubi->works_count -= 1;
1484                 ubi_assert(ubi->works_count >= 0);
1485         }
1486 }
1487
1488 /**
1489  * ubi_wl_init - initialize the WL sub-system using attaching information.
1490  * @ubi: UBI device description object
1491  * @ai: attaching information
1492  *
1493  * This function returns zero in case of success, and a negative error code in
1494  * case of failure.
1495  */
1496 int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
1497 {
1498         int err, i, reserved_pebs, found_pebs = 0;
1499         struct rb_node *rb1, *rb2;
1500         struct ubi_ainf_volume *av;
1501         struct ubi_ainf_peb *aeb, *tmp;
1502         struct ubi_wl_entry *e;
1503
1504         ubi->used = ubi->erroneous = ubi->free = ubi->scrub = RB_ROOT;
1505         spin_lock_init(&ubi->wl_lock);
1506         mutex_init(&ubi->move_mutex);
1507         init_rwsem(&ubi->work_sem);
1508         ubi->max_ec = ai->max_ec;
1509         INIT_LIST_HEAD(&ubi->works);
1510
1511         sprintf(ubi->bgt_name, UBI_BGT_NAME_PATTERN, ubi->ubi_num);
1512
1513         err = -ENOMEM;
1514         ubi->lookuptbl = kzalloc(ubi->peb_count * sizeof(void *), GFP_KERNEL);
1515         if (!ubi->lookuptbl)
1516                 return err;
1517
1518         for (i = 0; i < UBI_PROT_QUEUE_LEN; i++)
1519                 INIT_LIST_HEAD(&ubi->pq[i]);
1520         ubi->pq_head = 0;
1521
1522         list_for_each_entry_safe(aeb, tmp, &ai->erase, u.list) {
1523                 cond_resched();
1524
1525                 e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
1526                 if (!e)
1527                         goto out_free;
1528
1529                 e->pnum = aeb->pnum;
1530                 e->ec = aeb->ec;
1531                 ubi->lookuptbl[e->pnum] = e;
1532                 if (schedule_erase(ubi, e, aeb->vol_id, aeb->lnum, 0)) {
1533                         wl_entry_destroy(ubi, e);
1534                         goto out_free;
1535                 }
1536
1537                 found_pebs++;
1538         }
1539
1540         ubi->free_count = 0;
1541         list_for_each_entry(aeb, &ai->free, u.list) {
1542                 cond_resched();
1543
1544                 e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
1545                 if (!e)
1546                         goto out_free;
1547
1548                 e->pnum = aeb->pnum;
1549                 e->ec = aeb->ec;
1550                 ubi_assert(e->ec >= 0);
1551
1552                 wl_tree_add(e, &ubi->free);
1553                 ubi->free_count++;
1554
1555                 ubi->lookuptbl[e->pnum] = e;
1556
1557                 found_pebs++;
1558         }
1559
1560         ubi_rb_for_each_entry(rb1, av, &ai->volumes, rb) {
1561                 ubi_rb_for_each_entry(rb2, aeb, &av->root, u.rb) {
1562                         cond_resched();
1563
1564                         e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
1565                         if (!e)
1566                                 goto out_free;
1567
1568                         e->pnum = aeb->pnum;
1569                         e->ec = aeb->ec;
1570                         ubi->lookuptbl[e->pnum] = e;
1571
1572                         if (!aeb->scrub) {
1573                                 dbg_wl("add PEB %d EC %d to the used tree",
1574                                        e->pnum, e->ec);
1575                                 wl_tree_add(e, &ubi->used);
1576                         } else {
1577                                 dbg_wl("add PEB %d EC %d to the scrub tree",
1578                                        e->pnum, e->ec);
1579                                 wl_tree_add(e, &ubi->scrub);
1580                         }
1581
1582                         found_pebs++;
1583                 }
1584         }
1585
1586         dbg_wl("found %i PEBs", found_pebs);
1587
1588         if (ubi->fm) {
1589                 ubi_assert(ubi->good_peb_count ==
1590                            found_pebs + ubi->fm->used_blocks);
1591
1592                 for (i = 0; i < ubi->fm->used_blocks; i++) {
1593                         e = ubi->fm->e[i];
1594                         ubi->lookuptbl[e->pnum] = e;
1595                 }
1596         }
1597         else
1598                 ubi_assert(ubi->good_peb_count == found_pebs);
1599
1600         reserved_pebs = WL_RESERVED_PEBS;
1601         ubi_fastmap_init(ubi, &reserved_pebs);
1602
1603         if (ubi->avail_pebs < reserved_pebs) {
1604                 ubi_err(ubi, "no enough physical eraseblocks (%d, need %d)",
1605                         ubi->avail_pebs, reserved_pebs);
1606                 if (ubi->corr_peb_count)
1607                         ubi_err(ubi, "%d PEBs are corrupted and not used",
1608                                 ubi->corr_peb_count);
1609                 err = -ENOSPC;
1610                 goto out_free;
1611         }
1612         ubi->avail_pebs -= reserved_pebs;
1613         ubi->rsvd_pebs += reserved_pebs;
1614
1615         /* Schedule wear-leveling if needed */
1616         err = ensure_wear_leveling(ubi, 0);
1617         if (err)
1618                 goto out_free;
1619
1620         return 0;
1621
1622 out_free:
1623         shutdown_work(ubi);
1624         tree_destroy(ubi, &ubi->used);
1625         tree_destroy(ubi, &ubi->free);
1626         tree_destroy(ubi, &ubi->scrub);
1627         kfree(ubi->lookuptbl);
1628         return err;
1629 }
1630
1631 /**
1632  * protection_queue_destroy - destroy the protection queue.
1633  * @ubi: UBI device description object
1634  */
1635 static void protection_queue_destroy(struct ubi_device *ubi)
1636 {
1637         int i;
1638         struct ubi_wl_entry *e, *tmp;
1639
1640         for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i) {
1641                 list_for_each_entry_safe(e, tmp, &ubi->pq[i], u.list) {
1642                         list_del(&e->u.list);
1643                         wl_entry_destroy(ubi, e);
1644                 }
1645         }
1646 }
1647
1648 /**
1649  * ubi_wl_close - close the wear-leveling sub-system.
1650  * @ubi: UBI device description object
1651  */
1652 void ubi_wl_close(struct ubi_device *ubi)
1653 {
1654         dbg_wl("close the WL sub-system");
1655         ubi_fastmap_close(ubi);
1656         shutdown_work(ubi);
1657         protection_queue_destroy(ubi);
1658         tree_destroy(ubi, &ubi->used);
1659         tree_destroy(ubi, &ubi->erroneous);
1660         tree_destroy(ubi, &ubi->free);
1661         tree_destroy(ubi, &ubi->scrub);
1662         kfree(ubi->lookuptbl);
1663 }
1664
1665 /**
1666  * self_check_ec - make sure that the erase counter of a PEB is correct.
1667  * @ubi: UBI device description object
1668  * @pnum: the physical eraseblock number to check
1669  * @ec: the erase counter to check
1670  *
1671  * This function returns zero if the erase counter of physical eraseblock @pnum
1672  * is equivalent to @ec, and a negative error code if not or if an error
1673  * occurred.
1674  */
1675 static int self_check_ec(struct ubi_device *ubi, int pnum, int ec)
1676 {
1677         int err;
1678         long long read_ec;
1679         struct ubi_ec_hdr *ec_hdr;
1680
1681         if (!ubi_dbg_chk_gen(ubi))
1682                 return 0;
1683
1684         ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
1685         if (!ec_hdr)
1686                 return -ENOMEM;
1687
1688         err = ubi_io_read_ec_hdr(ubi, pnum, ec_hdr, 0);
1689         if (err && err != UBI_IO_BITFLIPS) {
1690                 /* The header does not have to exist */
1691                 err = 0;
1692                 goto out_free;
1693         }
1694
1695         read_ec = be64_to_cpu(ec_hdr->ec);
1696         if (ec != read_ec && read_ec - ec > 1) {
1697                 ubi_err(ubi, "self-check failed for PEB %d", pnum);
1698                 ubi_err(ubi, "read EC is %lld, should be %d", read_ec, ec);
1699                 dump_stack();
1700                 err = 1;
1701         } else
1702                 err = 0;
1703
1704 out_free:
1705         kfree(ec_hdr);
1706         return err;
1707 }
1708
1709 /**
1710  * self_check_in_wl_tree - check that wear-leveling entry is in WL RB-tree.
1711  * @ubi: UBI device description object
1712  * @e: the wear-leveling entry to check
1713  * @root: the root of the tree
1714  *
1715  * This function returns zero if @e is in the @root RB-tree and %-EINVAL if it
1716  * is not.
1717  */
1718 static int self_check_in_wl_tree(const struct ubi_device *ubi,
1719                                  struct ubi_wl_entry *e, struct rb_root *root)
1720 {
1721         if (!ubi_dbg_chk_gen(ubi))
1722                 return 0;
1723
1724         if (in_wl_tree(e, root))
1725                 return 0;
1726
1727         ubi_err(ubi, "self-check failed for PEB %d, EC %d, RB-tree %p ",
1728                 e->pnum, e->ec, root);
1729         dump_stack();
1730         return -EINVAL;
1731 }
1732
1733 /**
1734  * self_check_in_pq - check if wear-leveling entry is in the protection
1735  *                        queue.
1736  * @ubi: UBI device description object
1737  * @e: the wear-leveling entry to check
1738  *
1739  * This function returns zero if @e is in @ubi->pq and %-EINVAL if it is not.
1740  */
1741 static int self_check_in_pq(const struct ubi_device *ubi,
1742                             struct ubi_wl_entry *e)
1743 {
1744         struct ubi_wl_entry *p;
1745         int i;
1746
1747         if (!ubi_dbg_chk_gen(ubi))
1748                 return 0;
1749
1750         for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i)
1751                 list_for_each_entry(p, &ubi->pq[i], u.list)
1752                         if (p == e)
1753                                 return 0;
1754
1755         ubi_err(ubi, "self-check failed for PEB %d, EC %d, Protect queue",
1756                 e->pnum, e->ec);
1757         dump_stack();
1758         return -EINVAL;
1759 }
1760 #ifndef CONFIG_MTD_UBI_FASTMAP
1761 static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
1762 {
1763         struct ubi_wl_entry *e;
1764
1765         e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
1766         self_check_in_wl_tree(ubi, e, &ubi->free);
1767         ubi->free_count--;
1768         ubi_assert(ubi->free_count >= 0);
1769         rb_erase(&e->u.rb, &ubi->free);
1770
1771         return e;
1772 }
1773
1774 /**
1775  * produce_free_peb - produce a free physical eraseblock.
1776  * @ubi: UBI device description object
1777  *
1778  * This function tries to make a free PEB by means of synchronous execution of
1779  * pending works. This may be needed if, for example the background thread is
1780  * disabled. Returns zero in case of success and a negative error code in case
1781  * of failure.
1782  */
1783 static int produce_free_peb(struct ubi_device *ubi)
1784 {
1785         int err;
1786
1787         while (!ubi->free.rb_node && ubi->works_count) {
1788                 spin_unlock(&ubi->wl_lock);
1789
1790                 dbg_wl("do one work synchronously");
1791                 err = do_work(ubi);
1792
1793                 spin_lock(&ubi->wl_lock);
1794                 if (err)
1795                         return err;
1796         }
1797
1798         return 0;
1799 }
1800
1801 /**
1802  * ubi_wl_get_peb - get a physical eraseblock.
1803  * @ubi: UBI device description object
1804  *
1805  * This function returns a physical eraseblock in case of success and a
1806  * negative error code in case of failure.
1807  * Returns with ubi->fm_eba_sem held in read mode!
1808  */
1809 int ubi_wl_get_peb(struct ubi_device *ubi)
1810 {
1811         int err;
1812         struct ubi_wl_entry *e;
1813
1814 retry:
1815         down_read(&ubi->fm_eba_sem);
1816         spin_lock(&ubi->wl_lock);
1817         if (!ubi->free.rb_node) {
1818                 if (ubi->works_count == 0) {
1819                         ubi_err(ubi, "no free eraseblocks");
1820                         ubi_assert(list_empty(&ubi->works));
1821                         spin_unlock(&ubi->wl_lock);
1822                         return -ENOSPC;
1823                 }
1824
1825                 err = produce_free_peb(ubi);
1826                 if (err < 0) {
1827                         spin_unlock(&ubi->wl_lock);
1828                         return err;
1829                 }
1830                 spin_unlock(&ubi->wl_lock);
1831                 up_read(&ubi->fm_eba_sem);
1832                 goto retry;
1833
1834         }
1835         e = wl_get_wle(ubi);
1836         prot_queue_add(ubi, e);
1837         spin_unlock(&ubi->wl_lock);
1838
1839         err = ubi_self_check_all_ff(ubi, e->pnum, ubi->vid_hdr_aloffset,
1840                                     ubi->peb_size - ubi->vid_hdr_aloffset);
1841         if (err) {
1842                 ubi_err(ubi, "new PEB %d does not contain all 0xFF bytes", e->pnum);
1843                 return err;
1844         }
1845
1846         return e->pnum;
1847 }
1848 #else
1849 #include "fastmap-wl.c"
1850 #endif