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1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (c) International Business Machines Corp., 2006
4  *
5  * Authors: Artem Bityutskiy (Битюцкий Артём), Thomas Gleixner
6  */
7 
8 /*
9  * UBI wear-leveling sub-system.
10  *
11  * This sub-system is responsible for wear-leveling. It works in terms of
12  * physical eraseblocks and erase counters and knows nothing about logical
13  * eraseblocks, volumes, etc. From this sub-system's perspective all physical
14  * eraseblocks are of two types - used and free. Used physical eraseblocks are
15  * those that were "get" by the 'ubi_wl_get_peb()' function, and free physical
16  * eraseblocks are those that were put by the 'ubi_wl_put_peb()' function.
17  *
18  * Physical eraseblocks returned by 'ubi_wl_get_peb()' have only erase counter
19  * header. The rest of the physical eraseblock contains only %0xFF bytes.
20  *
21  * When physical eraseblocks are returned to the WL sub-system by means of the
22  * 'ubi_wl_put_peb()' function, they are scheduled for erasure. The erasure is
23  * done asynchronously in context of the per-UBI device background thread,
24  * which is also managed by the WL sub-system.
25  *
26  * The wear-leveling is ensured by means of moving the contents of used
27  * physical eraseblocks with low erase counter to free physical eraseblocks
28  * with high erase counter.
29  *
30  * If the WL sub-system fails to erase a physical eraseblock, it marks it as
31  * bad.
32  *
33  * This sub-system is also responsible for scrubbing. If a bit-flip is detected
34  * in a physical eraseblock, it has to be moved. Technically this is the same
35  * as moving it for wear-leveling reasons.
36  *
37  * As it was said, for the UBI sub-system all physical eraseblocks are either
38  * "free" or "used". Free eraseblock are kept in the @wl->free RB-tree, while
39  * used eraseblocks are kept in @wl->used, @wl->erroneous, or @wl->scrub
40  * RB-trees, as well as (temporarily) in the @wl->pq queue.
41  *
42  * When the WL sub-system returns a physical eraseblock, the physical
43  * eraseblock is protected from being moved for some "time". For this reason,
44  * the physical eraseblock is not directly moved from the @wl->free tree to the
45  * @wl->used tree. There is a protection queue in between where this
46  * physical eraseblock is temporarily stored (@wl->pq).
47  *
48  * All this protection stuff is needed because:
49  *  o we don't want to move physical eraseblocks just after we have given them
50  *    to the user; instead, we first want to let users fill them up with data;
51  *
52  *  o there is a chance that the user will put the physical eraseblock very
53  *    soon, so it makes sense not to move it for some time, but wait.
54  *
55  * Physical eraseblocks stay protected only for limited time. But the "time" is
56  * measured in erase cycles in this case. This is implemented with help of the
57  * protection queue. Eraseblocks are put to the tail of this queue when they
58  * are returned by the 'ubi_wl_get_peb()', and eraseblocks are removed from the
59  * head of the queue on each erase operation (for any eraseblock). So the
60  * length of the queue defines how may (global) erase cycles PEBs are protected.
61  *
62  * To put it differently, each physical eraseblock has 2 main states: free and
63  * used. The former state corresponds to the @wl->free tree. The latter state
64  * is split up on several sub-states:
65  * o the WL movement is allowed (@wl->used tree);
66  * o the WL movement is disallowed (@wl->erroneous) because the PEB is
67  *   erroneous - e.g., there was a read error;
68  * o the WL movement is temporarily prohibited (@wl->pq queue);
69  * o scrubbing is needed (@wl->scrub tree).
70  *
71  * Depending on the sub-state, wear-leveling entries of the used physical
72  * eraseblocks may be kept in one of those structures.
73  *
74  * Note, in this implementation, we keep a small in-RAM object for each physical
75  * eraseblock. This is surely not a scalable solution. But it appears to be good
76  * enough for moderately large flashes and it is simple. In future, one may
77  * re-work this sub-system and make it more scalable.
78  *
79  * At the moment this sub-system does not utilize the sequence number, which
80  * was introduced relatively recently. But it would be wise to do this because
81  * the sequence number of a logical eraseblock characterizes how old is it. For
82  * example, when we move a PEB with low erase counter, and we need to pick the
83  * target PEB, we pick a PEB with the highest EC if our PEB is "old" and we
84  * pick target PEB with an average EC if our PEB is not very "old". This is a
85  * room for future re-works of the WL sub-system.
86  */
87 
88 #include <linux/slab.h>
89 #include <linux/crc32.h>
90 #include <linux/freezer.h>
91 #include <linux/kthread.h>
92 #include "ubi.h"
93 #include "wl.h"
94 
95 /* Number of physical eraseblocks reserved for wear-leveling purposes */
96 #define WL_RESERVED_PEBS 1
97 
98 /*
99  * Maximum difference between two erase counters. If this threshold is
100  * exceeded, the WL sub-system starts moving data from used physical
101  * eraseblocks with low erase counter to free physical eraseblocks with high
102  * erase counter.
103  */
104 #define UBI_WL_THRESHOLD CONFIG_MTD_UBI_WL_THRESHOLD
105 
106 /*
107  * When a physical eraseblock is moved, the WL sub-system has to pick the target
108  * physical eraseblock to move to. The simplest way would be just to pick the
109  * one with the highest erase counter. But in certain workloads this could lead
110  * to an unlimited wear of one or few physical eraseblock. Indeed, imagine a
111  * situation when the picked physical eraseblock is constantly erased after the
112  * data is written to it. So, we have a constant which limits the highest erase
113  * counter of the free physical eraseblock to pick. Namely, the WL sub-system
114  * does not pick eraseblocks with erase counter greater than the lowest erase
115  * counter plus %WL_FREE_MAX_DIFF.
116  */
117 #define WL_FREE_MAX_DIFF (2*UBI_WL_THRESHOLD)
118 
119 /*
120  * Maximum number of consecutive background thread failures which is enough to
121  * switch to read-only mode.
122  */
123 #define WL_MAX_FAILURES 32
124 
125 static int self_check_ec(struct ubi_device *ubi, int pnum, int ec);
126 static int self_check_in_wl_tree(const struct ubi_device *ubi,
127 				 struct ubi_wl_entry *e, struct rb_root *root);
128 static int self_check_in_pq(const struct ubi_device *ubi,
129 			    struct ubi_wl_entry *e);
130 
131 /**
132  * wl_tree_add - add a wear-leveling entry to a WL RB-tree.
133  * @e: the wear-leveling entry to add
134  * @root: the root of the tree
135  *
136  * Note, we use (erase counter, physical eraseblock number) pairs as keys in
137  * the @ubi->used and @ubi->free RB-trees.
138  */
wl_tree_add(struct ubi_wl_entry * e,struct rb_root * root)139 static void wl_tree_add(struct ubi_wl_entry *e, struct rb_root *root)
140 {
141 	struct rb_node **p, *parent = NULL;
142 
143 	p = &root->rb_node;
144 	while (*p) {
145 		struct ubi_wl_entry *e1;
146 
147 		parent = *p;
148 		e1 = rb_entry(parent, struct ubi_wl_entry, u.rb);
149 
150 		if (e->ec < e1->ec)
151 			p = &(*p)->rb_left;
152 		else if (e->ec > e1->ec)
153 			p = &(*p)->rb_right;
154 		else {
155 			ubi_assert(e->pnum != e1->pnum);
156 			if (e->pnum < e1->pnum)
157 				p = &(*p)->rb_left;
158 			else
159 				p = &(*p)->rb_right;
160 		}
161 	}
162 
163 	rb_link_node(&e->u.rb, parent, p);
164 	rb_insert_color(&e->u.rb, root);
165 }
166 
167 /**
168  * wl_tree_destroy - destroy a wear-leveling entry.
169  * @ubi: UBI device description object
170  * @e: the wear-leveling entry to add
171  *
172  * This function destroys a wear leveling entry and removes
173  * the reference from the lookup table.
174  */
wl_entry_destroy(struct ubi_device * ubi,struct ubi_wl_entry * e)175 static void wl_entry_destroy(struct ubi_device *ubi, struct ubi_wl_entry *e)
176 {
177 	ubi->lookuptbl[e->pnum] = NULL;
178 	kmem_cache_free(ubi_wl_entry_slab, e);
179 }
180 
181 /**
182  * do_work - do one pending work.
183  * @ubi: UBI device description object
184  *
185  * This function returns zero in case of success and a negative error code in
186  * case of failure.
187  */
do_work(struct ubi_device * ubi)188 static int do_work(struct ubi_device *ubi)
189 {
190 	int err;
191 	struct ubi_work *wrk;
192 
193 	cond_resched();
194 
195 	/*
196 	 * @ubi->work_sem is used to synchronize with the workers. Workers take
197 	 * it in read mode, so many of them may be doing works at a time. But
198 	 * the queue flush code has to be sure the whole queue of works is
199 	 * done, and it takes the mutex in write mode.
200 	 */
201 	down_read(&ubi->work_sem);
202 	spin_lock(&ubi->wl_lock);
203 	if (list_empty(&ubi->works)) {
204 		spin_unlock(&ubi->wl_lock);
205 		up_read(&ubi->work_sem);
206 		return 0;
207 	}
208 
209 	wrk = list_entry(ubi->works.next, struct ubi_work, list);
210 	list_del(&wrk->list);
211 	ubi->works_count -= 1;
212 	ubi_assert(ubi->works_count >= 0);
213 	spin_unlock(&ubi->wl_lock);
214 
215 	/*
216 	 * Call the worker function. Do not touch the work structure
217 	 * after this call as it will have been freed or reused by that
218 	 * time by the worker function.
219 	 */
220 	err = wrk->func(ubi, wrk, 0);
221 	if (err)
222 		ubi_err(ubi, "work failed with error code %d", err);
223 	up_read(&ubi->work_sem);
224 
225 	return err;
226 }
227 
228 /**
229  * in_wl_tree - check if wear-leveling entry is present in a WL RB-tree.
230  * @e: the wear-leveling entry to check
231  * @root: the root of the tree
232  *
233  * This function returns non-zero if @e is in the @root RB-tree and zero if it
234  * is not.
235  */
in_wl_tree(struct ubi_wl_entry * e,struct rb_root * root)236 static int in_wl_tree(struct ubi_wl_entry *e, struct rb_root *root)
237 {
238 	struct rb_node *p;
239 
240 	p = root->rb_node;
241 	while (p) {
242 		struct ubi_wl_entry *e1;
243 
244 		e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
245 
246 		if (e->pnum == e1->pnum) {
247 			ubi_assert(e == e1);
248 			return 1;
249 		}
250 
251 		if (e->ec < e1->ec)
252 			p = p->rb_left;
253 		else if (e->ec > e1->ec)
254 			p = p->rb_right;
255 		else {
256 			ubi_assert(e->pnum != e1->pnum);
257 			if (e->pnum < e1->pnum)
258 				p = p->rb_left;
259 			else
260 				p = p->rb_right;
261 		}
262 	}
263 
264 	return 0;
265 }
266 
267 /**
268  * in_pq - check if a wear-leveling entry is present in the protection queue.
269  * @ubi: UBI device description object
270  * @e: the wear-leveling entry to check
271  *
272  * This function returns non-zero if @e is in the protection queue and zero
273  * if it is not.
274  */
in_pq(const struct ubi_device * ubi,struct ubi_wl_entry * e)275 static inline int in_pq(const struct ubi_device *ubi, struct ubi_wl_entry *e)
276 {
277 	struct ubi_wl_entry *p;
278 	int i;
279 
280 	for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i)
281 		list_for_each_entry(p, &ubi->pq[i], u.list)
282 			if (p == e)
283 				return 1;
284 
285 	return 0;
286 }
287 
288 /**
289  * prot_queue_add - add physical eraseblock to the protection queue.
290  * @ubi: UBI device description object
291  * @e: the physical eraseblock to add
292  *
293  * This function adds @e to the tail of the protection queue @ubi->pq, where
294  * @e will stay for %UBI_PROT_QUEUE_LEN erase operations and will be
295  * temporarily protected from the wear-leveling worker. Note, @wl->lock has to
296  * be locked.
297  */
prot_queue_add(struct ubi_device * ubi,struct ubi_wl_entry * e)298 static void prot_queue_add(struct ubi_device *ubi, struct ubi_wl_entry *e)
299 {
300 	int pq_tail = ubi->pq_head - 1;
301 
302 	if (pq_tail < 0)
303 		pq_tail = UBI_PROT_QUEUE_LEN - 1;
304 	ubi_assert(pq_tail >= 0 && pq_tail < UBI_PROT_QUEUE_LEN);
305 	list_add_tail(&e->u.list, &ubi->pq[pq_tail]);
306 	dbg_wl("added PEB %d EC %d to the protection queue", e->pnum, e->ec);
307 }
308 
309 /**
310  * find_wl_entry - find wear-leveling entry closest to certain erase counter.
311  * @ubi: UBI device description object
312  * @root: the RB-tree where to look for
313  * @diff: maximum possible difference from the smallest erase counter
314  *
315  * This function looks for a wear leveling entry with erase counter closest to
316  * min + @diff, where min is the smallest erase counter.
317  */
find_wl_entry(struct ubi_device * ubi,struct rb_root * root,int diff)318 static struct ubi_wl_entry *find_wl_entry(struct ubi_device *ubi,
319 					  struct rb_root *root, int diff)
320 {
321 	struct rb_node *p;
322 	struct ubi_wl_entry *e;
323 	int max;
324 
325 	e = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
326 	max = e->ec + diff;
327 
328 	p = root->rb_node;
329 	while (p) {
330 		struct ubi_wl_entry *e1;
331 
332 		e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
333 		if (e1->ec >= max)
334 			p = p->rb_left;
335 		else {
336 			p = p->rb_right;
337 			e = e1;
338 		}
339 	}
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  */
find_mean_wl_entry(struct ubi_device * ubi,struct rb_root * root)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  */
wl_get_wle(struct ubi_device * ubi)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  */
prot_queue_del(struct ubi_device * ubi,int pnum)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  */
sync_erase(struct ubi_device * ubi,struct ubi_wl_entry * e,int torture)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  */
serve_prot_queue(struct ubi_device * ubi)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  */
__schedule_ubi_work(struct ubi_device * ubi,struct ubi_work * wrk)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  */
schedule_ubi_work(struct ubi_device * ubi,struct ubi_work * wrk)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  * @nested: denotes whether the work_sem is already held
579  *
580  * This function returns zero in case of success and a %-ENOMEM in case of
581  * failure.
582  */
schedule_erase(struct ubi_device * ubi,struct ubi_wl_entry * e,int vol_id,int lnum,int torture,bool nested)583 static int schedule_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
584 			  int vol_id, int lnum, int torture, bool nested)
585 {
586 	struct ubi_work *wl_wrk;
587 
588 	ubi_assert(e);
589 
590 	dbg_wl("schedule erasure of PEB %d, EC %d, torture %d",
591 	       e->pnum, e->ec, torture);
592 
593 	wl_wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
594 	if (!wl_wrk)
595 		return -ENOMEM;
596 
597 	wl_wrk->func = &erase_worker;
598 	wl_wrk->e = e;
599 	wl_wrk->vol_id = vol_id;
600 	wl_wrk->lnum = lnum;
601 	wl_wrk->torture = torture;
602 
603 	if (nested)
604 		__schedule_ubi_work(ubi, wl_wrk);
605 	else
606 		schedule_ubi_work(ubi, wl_wrk);
607 	return 0;
608 }
609 
610 static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk);
611 /**
612  * do_sync_erase - run the erase worker synchronously.
613  * @ubi: UBI device description object
614  * @e: the WL entry of the physical eraseblock to erase
615  * @vol_id: the volume ID that last used this PEB
616  * @lnum: the last used logical eraseblock number for the PEB
617  * @torture: if the physical eraseblock has to be tortured
618  *
619  */
do_sync_erase(struct ubi_device * ubi,struct ubi_wl_entry * e,int vol_id,int lnum,int torture)620 static int do_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
621 			 int vol_id, int lnum, int torture)
622 {
623 	struct ubi_work wl_wrk;
624 
625 	dbg_wl("sync erase of PEB %i", e->pnum);
626 
627 	wl_wrk.e = e;
628 	wl_wrk.vol_id = vol_id;
629 	wl_wrk.lnum = lnum;
630 	wl_wrk.torture = torture;
631 
632 	return __erase_worker(ubi, &wl_wrk);
633 }
634 
635 static int ensure_wear_leveling(struct ubi_device *ubi, int nested);
636 /**
637  * wear_leveling_worker - wear-leveling worker function.
638  * @ubi: UBI device description object
639  * @wrk: the work object
640  * @shutdown: non-zero if the worker has to free memory and exit
641  * because the WL-subsystem is shutting down
642  *
643  * This function copies a more worn out physical eraseblock to a less worn out
644  * one. Returns zero in case of success and a negative error code in case of
645  * failure.
646  */
wear_leveling_worker(struct ubi_device * ubi,struct ubi_work * wrk,int shutdown)647 static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
648 				int shutdown)
649 {
650 	int err, scrubbing = 0, torture = 0, protect = 0, erroneous = 0;
651 	int erase = 0, keep = 0, vol_id = -1, lnum = -1;
652 	struct ubi_wl_entry *e1, *e2;
653 	struct ubi_vid_io_buf *vidb;
654 	struct ubi_vid_hdr *vid_hdr;
655 	int dst_leb_clean = 0;
656 
657 	kfree(wrk);
658 	if (shutdown)
659 		return 0;
660 
661 	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
662 	if (!vidb)
663 		return -ENOMEM;
664 
665 	vid_hdr = ubi_get_vid_hdr(vidb);
666 
667 	down_read(&ubi->fm_eba_sem);
668 	mutex_lock(&ubi->move_mutex);
669 	spin_lock(&ubi->wl_lock);
670 	ubi_assert(!ubi->move_from && !ubi->move_to);
671 	ubi_assert(!ubi->move_to_put);
672 
673 	if (!ubi->free.rb_node ||
674 	    (!ubi->used.rb_node && !ubi->scrub.rb_node)) {
675 		/*
676 		 * No free physical eraseblocks? Well, they must be waiting in
677 		 * the queue to be erased. Cancel movement - it will be
678 		 * triggered again when a free physical eraseblock appears.
679 		 *
680 		 * No used physical eraseblocks? They must be temporarily
681 		 * protected from being moved. They will be moved to the
682 		 * @ubi->used tree later and the wear-leveling will be
683 		 * triggered again.
684 		 */
685 		dbg_wl("cancel WL, a list is empty: free %d, used %d",
686 		       !ubi->free.rb_node, !ubi->used.rb_node);
687 		goto out_cancel;
688 	}
689 
690 #ifdef CONFIG_MTD_UBI_FASTMAP
691 	e1 = find_anchor_wl_entry(&ubi->used);
692 	if (e1 && ubi->fm_anchor &&
693 	    (ubi->fm_anchor->ec - e1->ec >= UBI_WL_THRESHOLD)) {
694 		ubi->fm_do_produce_anchor = 1;
695 		/*
696 		 * fm_anchor is no longer considered a good anchor.
697 		 * NULL assignment also prevents multiple wear level checks
698 		 * of this PEB.
699 		 */
700 		wl_tree_add(ubi->fm_anchor, &ubi->free);
701 		ubi->fm_anchor = NULL;
702 		ubi->free_count++;
703 	}
704 
705 	if (ubi->fm_do_produce_anchor) {
706 		if (!e1)
707 			goto out_cancel;
708 		e2 = get_peb_for_wl(ubi);
709 		if (!e2)
710 			goto out_cancel;
711 
712 		self_check_in_wl_tree(ubi, e1, &ubi->used);
713 		rb_erase(&e1->u.rb, &ubi->used);
714 		dbg_wl("anchor-move PEB %d to PEB %d", e1->pnum, e2->pnum);
715 		ubi->fm_do_produce_anchor = 0;
716 	} else if (!ubi->scrub.rb_node) {
717 #else
718 	if (!ubi->scrub.rb_node) {
719 #endif
720 		/*
721 		 * Now pick the least worn-out used physical eraseblock and a
722 		 * highly worn-out free physical eraseblock. If the erase
723 		 * counters differ much enough, start wear-leveling.
724 		 */
725 		e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
726 		e2 = get_peb_for_wl(ubi);
727 		if (!e2)
728 			goto out_cancel;
729 
730 		if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD)) {
731 			dbg_wl("no WL needed: min used EC %d, max free EC %d",
732 			       e1->ec, e2->ec);
733 
734 			/* Give the unused PEB back */
735 			wl_tree_add(e2, &ubi->free);
736 			ubi->free_count++;
737 			goto out_cancel;
738 		}
739 		self_check_in_wl_tree(ubi, e1, &ubi->used);
740 		rb_erase(&e1->u.rb, &ubi->used);
741 		dbg_wl("move PEB %d EC %d to PEB %d EC %d",
742 		       e1->pnum, e1->ec, e2->pnum, e2->ec);
743 	} else {
744 		/* Perform scrubbing */
745 		scrubbing = 1;
746 		e1 = rb_entry(rb_first(&ubi->scrub), struct ubi_wl_entry, u.rb);
747 		e2 = get_peb_for_wl(ubi);
748 		if (!e2)
749 			goto out_cancel;
750 
751 		self_check_in_wl_tree(ubi, e1, &ubi->scrub);
752 		rb_erase(&e1->u.rb, &ubi->scrub);
753 		dbg_wl("scrub PEB %d to PEB %d", e1->pnum, e2->pnum);
754 	}
755 
756 	ubi->move_from = e1;
757 	ubi->move_to = e2;
758 	spin_unlock(&ubi->wl_lock);
759 
760 	/*
761 	 * Now we are going to copy physical eraseblock @e1->pnum to @e2->pnum.
762 	 * We so far do not know which logical eraseblock our physical
763 	 * eraseblock (@e1) belongs to. We have to read the volume identifier
764 	 * header first.
765 	 *
766 	 * Note, we are protected from this PEB being unmapped and erased. The
767 	 * 'ubi_wl_put_peb()' would wait for moving to be finished if the PEB
768 	 * which is being moved was unmapped.
769 	 */
770 
771 	err = ubi_io_read_vid_hdr(ubi, e1->pnum, vidb, 0);
772 	if (err && err != UBI_IO_BITFLIPS) {
773 		dst_leb_clean = 1;
774 		if (err == UBI_IO_FF) {
775 			/*
776 			 * We are trying to move PEB without a VID header. UBI
777 			 * always write VID headers shortly after the PEB was
778 			 * given, so we have a situation when it has not yet
779 			 * had a chance to write it, because it was preempted.
780 			 * So add this PEB to the protection queue so far,
781 			 * because presumably more data will be written there
782 			 * (including the missing VID header), and then we'll
783 			 * move it.
784 			 */
785 			dbg_wl("PEB %d has no VID header", e1->pnum);
786 			protect = 1;
787 			goto out_not_moved;
788 		} else if (err == UBI_IO_FF_BITFLIPS) {
789 			/*
790 			 * The same situation as %UBI_IO_FF, but bit-flips were
791 			 * detected. It is better to schedule this PEB for
792 			 * scrubbing.
793 			 */
794 			dbg_wl("PEB %d has no VID header but has bit-flips",
795 			       e1->pnum);
796 			scrubbing = 1;
797 			goto out_not_moved;
798 		} else if (ubi->fast_attach && err == UBI_IO_BAD_HDR_EBADMSG) {
799 			/*
800 			 * While a full scan would detect interrupted erasures
801 			 * at attach time we can face them here when attached from
802 			 * Fastmap.
803 			 */
804 			dbg_wl("PEB %d has ECC errors, maybe from an interrupted erasure",
805 			       e1->pnum);
806 			erase = 1;
807 			goto out_not_moved;
808 		}
809 
810 		ubi_err(ubi, "error %d while reading VID header from PEB %d",
811 			err, e1->pnum);
812 		goto out_error;
813 	}
814 
815 	vol_id = be32_to_cpu(vid_hdr->vol_id);
816 	lnum = be32_to_cpu(vid_hdr->lnum);
817 
818 	err = ubi_eba_copy_leb(ubi, e1->pnum, e2->pnum, vidb);
819 	if (err) {
820 		if (err == MOVE_CANCEL_RACE) {
821 			/*
822 			 * The LEB has not been moved because the volume is
823 			 * being deleted or the PEB has been put meanwhile. We
824 			 * should prevent this PEB from being selected for
825 			 * wear-leveling movement again, so put it to the
826 			 * protection queue.
827 			 */
828 			protect = 1;
829 			dst_leb_clean = 1;
830 			goto out_not_moved;
831 		}
832 		if (err == MOVE_RETRY) {
833 			scrubbing = 1;
834 			dst_leb_clean = 1;
835 			goto out_not_moved;
836 		}
837 		if (err == MOVE_TARGET_BITFLIPS || err == MOVE_TARGET_WR_ERR ||
838 		    err == MOVE_TARGET_RD_ERR) {
839 			/*
840 			 * Target PEB had bit-flips or write error - torture it.
841 			 */
842 			torture = 1;
843 			keep = 1;
844 			goto out_not_moved;
845 		}
846 
847 		if (err == MOVE_SOURCE_RD_ERR) {
848 			/*
849 			 * An error happened while reading the source PEB. Do
850 			 * not switch to R/O mode in this case, and give the
851 			 * upper layers a possibility to recover from this,
852 			 * e.g. by unmapping corresponding LEB. Instead, just
853 			 * put this PEB to the @ubi->erroneous list to prevent
854 			 * UBI from trying to move it over and over again.
855 			 */
856 			if (ubi->erroneous_peb_count > ubi->max_erroneous) {
857 				ubi_err(ubi, "too many erroneous eraseblocks (%d)",
858 					ubi->erroneous_peb_count);
859 				goto out_error;
860 			}
861 			dst_leb_clean = 1;
862 			erroneous = 1;
863 			goto out_not_moved;
864 		}
865 
866 		if (err < 0)
867 			goto out_error;
868 
869 		ubi_assert(0);
870 	}
871 
872 	/* The PEB has been successfully moved */
873 	if (scrubbing)
874 		ubi_msg(ubi, "scrubbed PEB %d (LEB %d:%d), data moved to PEB %d",
875 			e1->pnum, vol_id, lnum, e2->pnum);
876 	ubi_free_vid_buf(vidb);
877 
878 	spin_lock(&ubi->wl_lock);
879 	if (!ubi->move_to_put) {
880 		wl_tree_add(e2, &ubi->used);
881 		e2 = NULL;
882 	}
883 	ubi->move_from = ubi->move_to = NULL;
884 	ubi->move_to_put = ubi->wl_scheduled = 0;
885 	spin_unlock(&ubi->wl_lock);
886 
887 	err = do_sync_erase(ubi, e1, vol_id, lnum, 0);
888 	if (err) {
889 		if (e2) {
890 			spin_lock(&ubi->wl_lock);
891 			wl_entry_destroy(ubi, e2);
892 			spin_unlock(&ubi->wl_lock);
893 		}
894 		goto out_ro;
895 	}
896 
897 	if (e2) {
898 		/*
899 		 * Well, the target PEB was put meanwhile, schedule it for
900 		 * erasure.
901 		 */
902 		dbg_wl("PEB %d (LEB %d:%d) was put meanwhile, erase",
903 		       e2->pnum, vol_id, lnum);
904 		err = do_sync_erase(ubi, e2, vol_id, lnum, 0);
905 		if (err)
906 			goto out_ro;
907 	}
908 
909 	dbg_wl("done");
910 	mutex_unlock(&ubi->move_mutex);
911 	up_read(&ubi->fm_eba_sem);
912 	return 0;
913 
914 	/*
915 	 * For some reasons the LEB was not moved, might be an error, might be
916 	 * something else. @e1 was not changed, so return it back. @e2 might
917 	 * have been changed, schedule it for erasure.
918 	 */
919 out_not_moved:
920 	if (vol_id != -1)
921 		dbg_wl("cancel moving PEB %d (LEB %d:%d) to PEB %d (%d)",
922 		       e1->pnum, vol_id, lnum, e2->pnum, err);
923 	else
924 		dbg_wl("cancel moving PEB %d to PEB %d (%d)",
925 		       e1->pnum, e2->pnum, err);
926 	spin_lock(&ubi->wl_lock);
927 	if (protect)
928 		prot_queue_add(ubi, e1);
929 	else if (erroneous) {
930 		wl_tree_add(e1, &ubi->erroneous);
931 		ubi->erroneous_peb_count += 1;
932 	} else if (scrubbing)
933 		wl_tree_add(e1, &ubi->scrub);
934 	else if (keep)
935 		wl_tree_add(e1, &ubi->used);
936 	if (dst_leb_clean) {
937 		wl_tree_add(e2, &ubi->free);
938 		ubi->free_count++;
939 	}
940 
941 	ubi_assert(!ubi->move_to_put);
942 	ubi->move_from = ubi->move_to = NULL;
943 	ubi->wl_scheduled = 0;
944 	spin_unlock(&ubi->wl_lock);
945 
946 	ubi_free_vid_buf(vidb);
947 	if (dst_leb_clean) {
948 		ensure_wear_leveling(ubi, 1);
949 	} else {
950 		err = do_sync_erase(ubi, e2, vol_id, lnum, torture);
951 		if (err)
952 			goto out_ro;
953 	}
954 
955 	if (erase) {
956 		err = do_sync_erase(ubi, e1, vol_id, lnum, 1);
957 		if (err)
958 			goto out_ro;
959 	}
960 
961 	mutex_unlock(&ubi->move_mutex);
962 	up_read(&ubi->fm_eba_sem);
963 	return 0;
964 
965 out_error:
966 	if (vol_id != -1)
967 		ubi_err(ubi, "error %d while moving PEB %d to PEB %d",
968 			err, e1->pnum, e2->pnum);
969 	else
970 		ubi_err(ubi, "error %d while moving PEB %d (LEB %d:%d) to PEB %d",
971 			err, e1->pnum, vol_id, lnum, e2->pnum);
972 	spin_lock(&ubi->wl_lock);
973 	ubi->move_from = ubi->move_to = NULL;
974 	ubi->move_to_put = ubi->wl_scheduled = 0;
975 	wl_entry_destroy(ubi, e1);
976 	wl_entry_destroy(ubi, e2);
977 	spin_unlock(&ubi->wl_lock);
978 
979 	ubi_free_vid_buf(vidb);
980 
981 out_ro:
982 	ubi_ro_mode(ubi);
983 	mutex_unlock(&ubi->move_mutex);
984 	up_read(&ubi->fm_eba_sem);
985 	ubi_assert(err != 0);
986 	return err < 0 ? err : -EIO;
987 
988 out_cancel:
989 	ubi->wl_scheduled = 0;
990 	spin_unlock(&ubi->wl_lock);
991 	mutex_unlock(&ubi->move_mutex);
992 	up_read(&ubi->fm_eba_sem);
993 	ubi_free_vid_buf(vidb);
994 	return 0;
995 }
996 
997 /**
998  * ensure_wear_leveling - schedule wear-leveling if it is needed.
999  * @ubi: UBI device description object
1000  * @nested: set to non-zero if this function is called from UBI worker
1001  *
1002  * This function checks if it is time to start wear-leveling and schedules it
1003  * if yes. This function returns zero in case of success and a negative error
1004  * code in case of failure.
1005  */
1006 static int ensure_wear_leveling(struct ubi_device *ubi, int nested)
1007 {
1008 	int err = 0;
1009 	struct ubi_wl_entry *e1;
1010 	struct ubi_wl_entry *e2;
1011 	struct ubi_work *wrk;
1012 
1013 	spin_lock(&ubi->wl_lock);
1014 	if (ubi->wl_scheduled)
1015 		/* Wear-leveling is already in the work queue */
1016 		goto out_unlock;
1017 
1018 	/*
1019 	 * If the ubi->scrub tree is not empty, scrubbing is needed, and the
1020 	 * the WL worker has to be scheduled anyway.
1021 	 */
1022 	if (!ubi->scrub.rb_node) {
1023 		if (!ubi->used.rb_node || !ubi->free.rb_node)
1024 			/* No physical eraseblocks - no deal */
1025 			goto out_unlock;
1026 
1027 		/*
1028 		 * We schedule wear-leveling only if the difference between the
1029 		 * lowest erase counter of used physical eraseblocks and a high
1030 		 * erase counter of free physical eraseblocks is greater than
1031 		 * %UBI_WL_THRESHOLD.
1032 		 */
1033 		e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
1034 		e2 = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
1035 
1036 		if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD))
1037 			goto out_unlock;
1038 		dbg_wl("schedule wear-leveling");
1039 	} else
1040 		dbg_wl("schedule scrubbing");
1041 
1042 	ubi->wl_scheduled = 1;
1043 	spin_unlock(&ubi->wl_lock);
1044 
1045 	wrk = kmalloc(sizeof(struct ubi_work), GFP_NOFS);
1046 	if (!wrk) {
1047 		err = -ENOMEM;
1048 		goto out_cancel;
1049 	}
1050 
1051 	wrk->func = &wear_leveling_worker;
1052 	if (nested)
1053 		__schedule_ubi_work(ubi, wrk);
1054 	else
1055 		schedule_ubi_work(ubi, wrk);
1056 	return err;
1057 
1058 out_cancel:
1059 	spin_lock(&ubi->wl_lock);
1060 	ubi->wl_scheduled = 0;
1061 out_unlock:
1062 	spin_unlock(&ubi->wl_lock);
1063 	return err;
1064 }
1065 
1066 /**
1067  * __erase_worker - physical eraseblock erase worker function.
1068  * @ubi: UBI device description object
1069  * @wl_wrk: the work object
1070  *
1071  * This function erases a physical eraseblock and perform torture testing if
1072  * needed. It also takes care about marking the physical eraseblock bad if
1073  * needed. Returns zero in case of success and a negative error code in case of
1074  * failure.
1075  */
1076 static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk)
1077 {
1078 	struct ubi_wl_entry *e = wl_wrk->e;
1079 	int pnum = e->pnum;
1080 	int vol_id = wl_wrk->vol_id;
1081 	int lnum = wl_wrk->lnum;
1082 	int err, available_consumed = 0;
1083 
1084 	dbg_wl("erase PEB %d EC %d LEB %d:%d",
1085 	       pnum, e->ec, wl_wrk->vol_id, wl_wrk->lnum);
1086 
1087 	err = sync_erase(ubi, e, wl_wrk->torture);
1088 	if (!err) {
1089 		spin_lock(&ubi->wl_lock);
1090 
1091 		if (!ubi->fm_disabled && !ubi->fm_anchor &&
1092 		    e->pnum < UBI_FM_MAX_START) {
1093 			/*
1094 			 * Abort anchor production, if needed it will be
1095 			 * enabled again in the wear leveling started below.
1096 			 */
1097 			ubi->fm_anchor = e;
1098 			ubi->fm_do_produce_anchor = 0;
1099 		} else {
1100 			wl_tree_add(e, &ubi->free);
1101 			ubi->free_count++;
1102 		}
1103 
1104 		spin_unlock(&ubi->wl_lock);
1105 
1106 		/*
1107 		 * One more erase operation has happened, take care about
1108 		 * protected physical eraseblocks.
1109 		 */
1110 		serve_prot_queue(ubi);
1111 
1112 		/* And take care about wear-leveling */
1113 		err = ensure_wear_leveling(ubi, 1);
1114 		return err;
1115 	}
1116 
1117 	ubi_err(ubi, "failed to erase PEB %d, error %d", pnum, err);
1118 
1119 	if (err == -EINTR || err == -ENOMEM || err == -EAGAIN ||
1120 	    err == -EBUSY) {
1121 		int err1;
1122 
1123 		/* Re-schedule the LEB for erasure */
1124 		err1 = schedule_erase(ubi, e, vol_id, lnum, 0, true);
1125 		if (err1) {
1126 			spin_lock(&ubi->wl_lock);
1127 			wl_entry_destroy(ubi, e);
1128 			spin_unlock(&ubi->wl_lock);
1129 			err = err1;
1130 			goto out_ro;
1131 		}
1132 		return err;
1133 	}
1134 
1135 	spin_lock(&ubi->wl_lock);
1136 	wl_entry_destroy(ubi, e);
1137 	spin_unlock(&ubi->wl_lock);
1138 	if (err != -EIO)
1139 		/*
1140 		 * If this is not %-EIO, we have no idea what to do. Scheduling
1141 		 * this physical eraseblock for erasure again would cause
1142 		 * errors again and again. Well, lets switch to R/O mode.
1143 		 */
1144 		goto out_ro;
1145 
1146 	/* It is %-EIO, the PEB went bad */
1147 
1148 	if (!ubi->bad_allowed) {
1149 		ubi_err(ubi, "bad physical eraseblock %d detected", pnum);
1150 		goto out_ro;
1151 	}
1152 
1153 	spin_lock(&ubi->volumes_lock);
1154 	if (ubi->beb_rsvd_pebs == 0) {
1155 		if (ubi->avail_pebs == 0) {
1156 			spin_unlock(&ubi->volumes_lock);
1157 			ubi_err(ubi, "no reserved/available physical eraseblocks");
1158 			goto out_ro;
1159 		}
1160 		ubi->avail_pebs -= 1;
1161 		available_consumed = 1;
1162 	}
1163 	spin_unlock(&ubi->volumes_lock);
1164 
1165 	ubi_msg(ubi, "mark PEB %d as bad", pnum);
1166 	err = ubi_io_mark_bad(ubi, pnum);
1167 	if (err)
1168 		goto out_ro;
1169 
1170 	spin_lock(&ubi->volumes_lock);
1171 	if (ubi->beb_rsvd_pebs > 0) {
1172 		if (available_consumed) {
1173 			/*
1174 			 * The amount of reserved PEBs increased since we last
1175 			 * checked.
1176 			 */
1177 			ubi->avail_pebs += 1;
1178 			available_consumed = 0;
1179 		}
1180 		ubi->beb_rsvd_pebs -= 1;
1181 	}
1182 	ubi->bad_peb_count += 1;
1183 	ubi->good_peb_count -= 1;
1184 	ubi_calculate_reserved(ubi);
1185 	if (available_consumed)
1186 		ubi_warn(ubi, "no PEBs in the reserved pool, used an available PEB");
1187 	else if (ubi->beb_rsvd_pebs)
1188 		ubi_msg(ubi, "%d PEBs left in the reserve",
1189 			ubi->beb_rsvd_pebs);
1190 	else
1191 		ubi_warn(ubi, "last PEB from the reserve was used");
1192 	spin_unlock(&ubi->volumes_lock);
1193 
1194 	return err;
1195 
1196 out_ro:
1197 	if (available_consumed) {
1198 		spin_lock(&ubi->volumes_lock);
1199 		ubi->avail_pebs += 1;
1200 		spin_unlock(&ubi->volumes_lock);
1201 	}
1202 	ubi_ro_mode(ubi);
1203 	return err;
1204 }
1205 
1206 static int erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk,
1207 			  int shutdown)
1208 {
1209 	int ret;
1210 
1211 	if (shutdown) {
1212 		struct ubi_wl_entry *e = wl_wrk->e;
1213 
1214 		dbg_wl("cancel erasure of PEB %d EC %d", e->pnum, e->ec);
1215 		kfree(wl_wrk);
1216 		wl_entry_destroy(ubi, e);
1217 		return 0;
1218 	}
1219 
1220 	ret = __erase_worker(ubi, wl_wrk);
1221 	kfree(wl_wrk);
1222 	return ret;
1223 }
1224 
1225 /**
1226  * ubi_wl_put_peb - return a PEB to the wear-leveling sub-system.
1227  * @ubi: UBI device description object
1228  * @vol_id: the volume ID that last used this PEB
1229  * @lnum: the last used logical eraseblock number for the PEB
1230  * @pnum: physical eraseblock to return
1231  * @torture: if this physical eraseblock has to be tortured
1232  *
1233  * This function is called to return physical eraseblock @pnum to the pool of
1234  * free physical eraseblocks. The @torture flag has to be set if an I/O error
1235  * occurred to this @pnum and it has to be tested. This function returns zero
1236  * in case of success, and a negative error code in case of failure.
1237  */
1238 int ubi_wl_put_peb(struct ubi_device *ubi, int vol_id, int lnum,
1239 		   int pnum, int torture)
1240 {
1241 	int err;
1242 	struct ubi_wl_entry *e;
1243 
1244 	dbg_wl("PEB %d", pnum);
1245 	ubi_assert(pnum >= 0);
1246 	ubi_assert(pnum < ubi->peb_count);
1247 
1248 	down_read(&ubi->fm_protect);
1249 
1250 retry:
1251 	spin_lock(&ubi->wl_lock);
1252 	e = ubi->lookuptbl[pnum];
1253 	if (!e) {
1254 		/*
1255 		 * This wl entry has been removed for some errors by other
1256 		 * process (eg. wear leveling worker), corresponding process
1257 		 * (except __erase_worker, which cannot concurrent with
1258 		 * ubi_wl_put_peb) will set ubi ro_mode at the same time,
1259 		 * just ignore this wl entry.
1260 		 */
1261 		spin_unlock(&ubi->wl_lock);
1262 		up_read(&ubi->fm_protect);
1263 		return 0;
1264 	}
1265 	if (e == ubi->move_from) {
1266 		/*
1267 		 * User is putting the physical eraseblock which was selected to
1268 		 * be moved. It will be scheduled for erasure in the
1269 		 * wear-leveling worker.
1270 		 */
1271 		dbg_wl("PEB %d is being moved, wait", pnum);
1272 		spin_unlock(&ubi->wl_lock);
1273 
1274 		/* Wait for the WL worker by taking the @ubi->move_mutex */
1275 		mutex_lock(&ubi->move_mutex);
1276 		mutex_unlock(&ubi->move_mutex);
1277 		goto retry;
1278 	} else if (e == ubi->move_to) {
1279 		/*
1280 		 * User is putting the physical eraseblock which was selected
1281 		 * as the target the data is moved to. It may happen if the EBA
1282 		 * sub-system already re-mapped the LEB in 'ubi_eba_copy_leb()'
1283 		 * but the WL sub-system has not put the PEB to the "used" tree
1284 		 * yet, but it is about to do this. So we just set a flag which
1285 		 * will tell the WL worker that the PEB is not needed anymore
1286 		 * and should be scheduled for erasure.
1287 		 */
1288 		dbg_wl("PEB %d is the target of data moving", pnum);
1289 		ubi_assert(!ubi->move_to_put);
1290 		ubi->move_to_put = 1;
1291 		spin_unlock(&ubi->wl_lock);
1292 		up_read(&ubi->fm_protect);
1293 		return 0;
1294 	} else {
1295 		if (in_wl_tree(e, &ubi->used)) {
1296 			self_check_in_wl_tree(ubi, e, &ubi->used);
1297 			rb_erase(&e->u.rb, &ubi->used);
1298 		} else if (in_wl_tree(e, &ubi->scrub)) {
1299 			self_check_in_wl_tree(ubi, e, &ubi->scrub);
1300 			rb_erase(&e->u.rb, &ubi->scrub);
1301 		} else if (in_wl_tree(e, &ubi->erroneous)) {
1302 			self_check_in_wl_tree(ubi, e, &ubi->erroneous);
1303 			rb_erase(&e->u.rb, &ubi->erroneous);
1304 			ubi->erroneous_peb_count -= 1;
1305 			ubi_assert(ubi->erroneous_peb_count >= 0);
1306 			/* Erroneous PEBs should be tortured */
1307 			torture = 1;
1308 		} else {
1309 			err = prot_queue_del(ubi, e->pnum);
1310 			if (err) {
1311 				ubi_err(ubi, "PEB %d not found", pnum);
1312 				ubi_ro_mode(ubi);
1313 				spin_unlock(&ubi->wl_lock);
1314 				up_read(&ubi->fm_protect);
1315 				return err;
1316 			}
1317 		}
1318 	}
1319 	spin_unlock(&ubi->wl_lock);
1320 
1321 	err = schedule_erase(ubi, e, vol_id, lnum, torture, false);
1322 	if (err) {
1323 		spin_lock(&ubi->wl_lock);
1324 		wl_tree_add(e, &ubi->used);
1325 		spin_unlock(&ubi->wl_lock);
1326 	}
1327 
1328 	up_read(&ubi->fm_protect);
1329 	return err;
1330 }
1331 
1332 /**
1333  * ubi_wl_scrub_peb - schedule a physical eraseblock for scrubbing.
1334  * @ubi: UBI device description object
1335  * @pnum: the physical eraseblock to schedule
1336  *
1337  * If a bit-flip in a physical eraseblock is detected, this physical eraseblock
1338  * needs scrubbing. This function schedules a physical eraseblock for
1339  * scrubbing which is done in background. This function returns zero in case of
1340  * success and a negative error code in case of failure.
1341  */
1342 int ubi_wl_scrub_peb(struct ubi_device *ubi, int pnum)
1343 {
1344 	struct ubi_wl_entry *e;
1345 
1346 	ubi_msg(ubi, "schedule PEB %d for scrubbing", pnum);
1347 
1348 retry:
1349 	spin_lock(&ubi->wl_lock);
1350 	e = ubi->lookuptbl[pnum];
1351 	if (e == ubi->move_from || in_wl_tree(e, &ubi->scrub) ||
1352 				   in_wl_tree(e, &ubi->erroneous)) {
1353 		spin_unlock(&ubi->wl_lock);
1354 		return 0;
1355 	}
1356 
1357 	if (e == ubi->move_to) {
1358 		/*
1359 		 * This physical eraseblock was used to move data to. The data
1360 		 * was moved but the PEB was not yet inserted to the proper
1361 		 * tree. We should just wait a little and let the WL worker
1362 		 * proceed.
1363 		 */
1364 		spin_unlock(&ubi->wl_lock);
1365 		dbg_wl("the PEB %d is not in proper tree, retry", pnum);
1366 		yield();
1367 		goto retry;
1368 	}
1369 
1370 	if (in_wl_tree(e, &ubi->used)) {
1371 		self_check_in_wl_tree(ubi, e, &ubi->used);
1372 		rb_erase(&e->u.rb, &ubi->used);
1373 	} else {
1374 		int err;
1375 
1376 		err = prot_queue_del(ubi, e->pnum);
1377 		if (err) {
1378 			ubi_err(ubi, "PEB %d not found", pnum);
1379 			ubi_ro_mode(ubi);
1380 			spin_unlock(&ubi->wl_lock);
1381 			return err;
1382 		}
1383 	}
1384 
1385 	wl_tree_add(e, &ubi->scrub);
1386 	spin_unlock(&ubi->wl_lock);
1387 
1388 	/*
1389 	 * Technically scrubbing is the same as wear-leveling, so it is done
1390 	 * by the WL worker.
1391 	 */
1392 	return ensure_wear_leveling(ubi, 0);
1393 }
1394 
1395 /**
1396  * ubi_wl_flush - flush all pending works.
1397  * @ubi: UBI device description object
1398  * @vol_id: the volume id to flush for
1399  * @lnum: the logical eraseblock number to flush for
1400  *
1401  * This function executes all pending works for a particular volume id /
1402  * logical eraseblock number pair. If either value is set to %UBI_ALL, then it
1403  * acts as a wildcard for all of the corresponding volume numbers or logical
1404  * eraseblock numbers. It returns zero in case of success and a negative error
1405  * code in case of failure.
1406  */
1407 int ubi_wl_flush(struct ubi_device *ubi, int vol_id, int lnum)
1408 {
1409 	int err = 0;
1410 	int found = 1;
1411 
1412 	/*
1413 	 * Erase while the pending works queue is not empty, but not more than
1414 	 * the number of currently pending works.
1415 	 */
1416 	dbg_wl("flush pending work for LEB %d:%d (%d pending works)",
1417 	       vol_id, lnum, ubi->works_count);
1418 
1419 	while (found) {
1420 		struct ubi_work *wrk, *tmp;
1421 		found = 0;
1422 
1423 		down_read(&ubi->work_sem);
1424 		spin_lock(&ubi->wl_lock);
1425 		list_for_each_entry_safe(wrk, tmp, &ubi->works, list) {
1426 			if ((vol_id == UBI_ALL || wrk->vol_id == vol_id) &&
1427 			    (lnum == UBI_ALL || wrk->lnum == lnum)) {
1428 				list_del(&wrk->list);
1429 				ubi->works_count -= 1;
1430 				ubi_assert(ubi->works_count >= 0);
1431 				spin_unlock(&ubi->wl_lock);
1432 
1433 				err = wrk->func(ubi, wrk, 0);
1434 				if (err) {
1435 					up_read(&ubi->work_sem);
1436 					return err;
1437 				}
1438 
1439 				spin_lock(&ubi->wl_lock);
1440 				found = 1;
1441 				break;
1442 			}
1443 		}
1444 		spin_unlock(&ubi->wl_lock);
1445 		up_read(&ubi->work_sem);
1446 	}
1447 
1448 	/*
1449 	 * Make sure all the works which have been done in parallel are
1450 	 * finished.
1451 	 */
1452 	down_write(&ubi->work_sem);
1453 	up_write(&ubi->work_sem);
1454 
1455 	return err;
1456 }
1457 
1458 static bool scrub_possible(struct ubi_device *ubi, struct ubi_wl_entry *e)
1459 {
1460 	if (in_wl_tree(e, &ubi->scrub))
1461 		return false;
1462 	else if (in_wl_tree(e, &ubi->erroneous))
1463 		return false;
1464 	else if (ubi->move_from == e)
1465 		return false;
1466 	else if (ubi->move_to == e)
1467 		return false;
1468 
1469 	return true;
1470 }
1471 
1472 /**
1473  * ubi_bitflip_check - Check an eraseblock for bitflips and scrub it if needed.
1474  * @ubi: UBI device description object
1475  * @pnum: the physical eraseblock to schedule
1476  * @force: dont't read the block, assume bitflips happened and take action.
1477  *
1478  * This function reads the given eraseblock and checks if bitflips occured.
1479  * In case of bitflips, the eraseblock is scheduled for scrubbing.
1480  * If scrubbing is forced with @force, the eraseblock is not read,
1481  * but scheduled for scrubbing right away.
1482  *
1483  * Returns:
1484  * %EINVAL, PEB is out of range
1485  * %ENOENT, PEB is no longer used by UBI
1486  * %EBUSY, PEB cannot be checked now or a check is currently running on it
1487  * %EAGAIN, bit flips happened but scrubbing is currently not possible
1488  * %EUCLEAN, bit flips happened and PEB is scheduled for scrubbing
1489  * %0, no bit flips detected
1490  */
1491 int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force)
1492 {
1493 	int err = 0;
1494 	struct ubi_wl_entry *e;
1495 
1496 	if (pnum < 0 || pnum >= ubi->peb_count) {
1497 		err = -EINVAL;
1498 		goto out;
1499 	}
1500 
1501 	/*
1502 	 * Pause all parallel work, otherwise it can happen that the
1503 	 * erase worker frees a wl entry under us.
1504 	 */
1505 	down_write(&ubi->work_sem);
1506 
1507 	/*
1508 	 * Make sure that the wl entry does not change state while
1509 	 * inspecting it.
1510 	 */
1511 	spin_lock(&ubi->wl_lock);
1512 	e = ubi->lookuptbl[pnum];
1513 	if (!e) {
1514 		spin_unlock(&ubi->wl_lock);
1515 		err = -ENOENT;
1516 		goto out_resume;
1517 	}
1518 
1519 	/*
1520 	 * Does it make sense to check this PEB?
1521 	 */
1522 	if (!scrub_possible(ubi, e)) {
1523 		spin_unlock(&ubi->wl_lock);
1524 		err = -EBUSY;
1525 		goto out_resume;
1526 	}
1527 	spin_unlock(&ubi->wl_lock);
1528 
1529 	if (!force) {
1530 		mutex_lock(&ubi->buf_mutex);
1531 		err = ubi_io_read(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
1532 		mutex_unlock(&ubi->buf_mutex);
1533 	}
1534 
1535 	if (force || err == UBI_IO_BITFLIPS) {
1536 		/*
1537 		 * Okay, bit flip happened, let's figure out what we can do.
1538 		 */
1539 		spin_lock(&ubi->wl_lock);
1540 
1541 		/*
1542 		 * Recheck. We released wl_lock, UBI might have killed the
1543 		 * wl entry under us.
1544 		 */
1545 		e = ubi->lookuptbl[pnum];
1546 		if (!e) {
1547 			spin_unlock(&ubi->wl_lock);
1548 			err = -ENOENT;
1549 			goto out_resume;
1550 		}
1551 
1552 		/*
1553 		 * Need to re-check state
1554 		 */
1555 		if (!scrub_possible(ubi, e)) {
1556 			spin_unlock(&ubi->wl_lock);
1557 			err = -EBUSY;
1558 			goto out_resume;
1559 		}
1560 
1561 		if (in_pq(ubi, e)) {
1562 			prot_queue_del(ubi, e->pnum);
1563 			wl_tree_add(e, &ubi->scrub);
1564 			spin_unlock(&ubi->wl_lock);
1565 
1566 			err = ensure_wear_leveling(ubi, 1);
1567 		} else if (in_wl_tree(e, &ubi->used)) {
1568 			rb_erase(&e->u.rb, &ubi->used);
1569 			wl_tree_add(e, &ubi->scrub);
1570 			spin_unlock(&ubi->wl_lock);
1571 
1572 			err = ensure_wear_leveling(ubi, 1);
1573 		} else if (in_wl_tree(e, &ubi->free)) {
1574 			rb_erase(&e->u.rb, &ubi->free);
1575 			ubi->free_count--;
1576 			spin_unlock(&ubi->wl_lock);
1577 
1578 			/*
1579 			 * This PEB is empty we can schedule it for
1580 			 * erasure right away. No wear leveling needed.
1581 			 */
1582 			err = schedule_erase(ubi, e, UBI_UNKNOWN, UBI_UNKNOWN,
1583 					     force ? 0 : 1, true);
1584 		} else {
1585 			spin_unlock(&ubi->wl_lock);
1586 			err = -EAGAIN;
1587 		}
1588 
1589 		if (!err && !force)
1590 			err = -EUCLEAN;
1591 	} else {
1592 		err = 0;
1593 	}
1594 
1595 out_resume:
1596 	up_write(&ubi->work_sem);
1597 out:
1598 
1599 	return err;
1600 }
1601 
1602 /**
1603  * tree_destroy - destroy an RB-tree.
1604  * @ubi: UBI device description object
1605  * @root: the root of the tree to destroy
1606  */
1607 static void tree_destroy(struct ubi_device *ubi, struct rb_root *root)
1608 {
1609 	struct rb_node *rb;
1610 	struct ubi_wl_entry *e;
1611 
1612 	rb = root->rb_node;
1613 	while (rb) {
1614 		if (rb->rb_left)
1615 			rb = rb->rb_left;
1616 		else if (rb->rb_right)
1617 			rb = rb->rb_right;
1618 		else {
1619 			e = rb_entry(rb, struct ubi_wl_entry, u.rb);
1620 
1621 			rb = rb_parent(rb);
1622 			if (rb) {
1623 				if (rb->rb_left == &e->u.rb)
1624 					rb->rb_left = NULL;
1625 				else
1626 					rb->rb_right = NULL;
1627 			}
1628 
1629 			wl_entry_destroy(ubi, e);
1630 		}
1631 	}
1632 }
1633 
1634 /**
1635  * ubi_thread - UBI background thread.
1636  * @u: the UBI device description object pointer
1637  */
1638 int ubi_thread(void *u)
1639 {
1640 	int failures = 0;
1641 	struct ubi_device *ubi = u;
1642 
1643 	ubi_msg(ubi, "background thread \"%s\" started, PID %d",
1644 		ubi->bgt_name, task_pid_nr(current));
1645 
1646 	set_freezable();
1647 	for (;;) {
1648 		int err;
1649 
1650 		if (kthread_should_stop())
1651 			break;
1652 
1653 		if (try_to_freeze())
1654 			continue;
1655 
1656 		spin_lock(&ubi->wl_lock);
1657 		if (list_empty(&ubi->works) || ubi->ro_mode ||
1658 		    !ubi->thread_enabled || ubi_dbg_is_bgt_disabled(ubi)) {
1659 			set_current_state(TASK_INTERRUPTIBLE);
1660 			spin_unlock(&ubi->wl_lock);
1661 
1662 			/*
1663 			 * Check kthread_should_stop() after we set the task
1664 			 * state to guarantee that we either see the stop bit
1665 			 * and exit or the task state is reset to runnable such
1666 			 * that it's not scheduled out indefinitely and detects
1667 			 * the stop bit at kthread_should_stop().
1668 			 */
1669 			if (kthread_should_stop()) {
1670 				set_current_state(TASK_RUNNING);
1671 				break;
1672 			}
1673 
1674 			schedule();
1675 			continue;
1676 		}
1677 		spin_unlock(&ubi->wl_lock);
1678 
1679 		err = do_work(ubi);
1680 		if (err) {
1681 			ubi_err(ubi, "%s: work failed with error code %d",
1682 				ubi->bgt_name, err);
1683 			if (failures++ > WL_MAX_FAILURES) {
1684 				/*
1685 				 * Too many failures, disable the thread and
1686 				 * switch to read-only mode.
1687 				 */
1688 				ubi_msg(ubi, "%s: %d consecutive failures",
1689 					ubi->bgt_name, WL_MAX_FAILURES);
1690 				ubi_ro_mode(ubi);
1691 				ubi->thread_enabled = 0;
1692 				continue;
1693 			}
1694 		} else
1695 			failures = 0;
1696 
1697 		cond_resched();
1698 	}
1699 
1700 	dbg_wl("background thread \"%s\" is killed", ubi->bgt_name);
1701 	ubi->thread_enabled = 0;
1702 	return 0;
1703 }
1704 
1705 /**
1706  * shutdown_work - shutdown all pending works.
1707  * @ubi: UBI device description object
1708  */
1709 static void shutdown_work(struct ubi_device *ubi)
1710 {
1711 	while (!list_empty(&ubi->works)) {
1712 		struct ubi_work *wrk;
1713 
1714 		wrk = list_entry(ubi->works.next, struct ubi_work, list);
1715 		list_del(&wrk->list);
1716 		wrk->func(ubi, wrk, 1);
1717 		ubi->works_count -= 1;
1718 		ubi_assert(ubi->works_count >= 0);
1719 	}
1720 }
1721 
1722 /**
1723  * erase_aeb - erase a PEB given in UBI attach info PEB
1724  * @ubi: UBI device description object
1725  * @aeb: UBI attach info PEB
1726  * @sync: If true, erase synchronously. Otherwise schedule for erasure
1727  */
1728 static int erase_aeb(struct ubi_device *ubi, struct ubi_ainf_peb *aeb, bool sync)
1729 {
1730 	struct ubi_wl_entry *e;
1731 	int err;
1732 
1733 	e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
1734 	if (!e)
1735 		return -ENOMEM;
1736 
1737 	e->pnum = aeb->pnum;
1738 	e->ec = aeb->ec;
1739 	ubi->lookuptbl[e->pnum] = e;
1740 
1741 	if (sync) {
1742 		err = sync_erase(ubi, e, false);
1743 		if (err)
1744 			goto out_free;
1745 
1746 		wl_tree_add(e, &ubi->free);
1747 		ubi->free_count++;
1748 	} else {
1749 		err = schedule_erase(ubi, e, aeb->vol_id, aeb->lnum, 0, false);
1750 		if (err)
1751 			goto out_free;
1752 	}
1753 
1754 	return 0;
1755 
1756 out_free:
1757 	wl_entry_destroy(ubi, e);
1758 
1759 	return err;
1760 }
1761 
1762 /**
1763  * ubi_wl_init - initialize the WL sub-system using attaching information.
1764  * @ubi: UBI device description object
1765  * @ai: attaching information
1766  *
1767  * This function returns zero in case of success, and a negative error code in
1768  * case of failure.
1769  */
1770 int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
1771 {
1772 	int err, i, reserved_pebs, found_pebs = 0;
1773 	struct rb_node *rb1, *rb2;
1774 	struct ubi_ainf_volume *av;
1775 	struct ubi_ainf_peb *aeb, *tmp;
1776 	struct ubi_wl_entry *e;
1777 
1778 	ubi->used = ubi->erroneous = ubi->free = ubi->scrub = RB_ROOT;
1779 	spin_lock_init(&ubi->wl_lock);
1780 	mutex_init(&ubi->move_mutex);
1781 	init_rwsem(&ubi->work_sem);
1782 	ubi->max_ec = ai->max_ec;
1783 	INIT_LIST_HEAD(&ubi->works);
1784 
1785 	sprintf(ubi->bgt_name, UBI_BGT_NAME_PATTERN, ubi->ubi_num);
1786 
1787 	err = -ENOMEM;
1788 	ubi->lookuptbl = kcalloc(ubi->peb_count, sizeof(void *), GFP_KERNEL);
1789 	if (!ubi->lookuptbl)
1790 		return err;
1791 
1792 	for (i = 0; i < UBI_PROT_QUEUE_LEN; i++)
1793 		INIT_LIST_HEAD(&ubi->pq[i]);
1794 	ubi->pq_head = 0;
1795 
1796 	ubi->free_count = 0;
1797 	list_for_each_entry_safe(aeb, tmp, &ai->erase, u.list) {
1798 		cond_resched();
1799 
1800 		err = erase_aeb(ubi, aeb, false);
1801 		if (err)
1802 			goto out_free;
1803 
1804 		found_pebs++;
1805 	}
1806 
1807 	list_for_each_entry(aeb, &ai->free, u.list) {
1808 		cond_resched();
1809 
1810 		e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
1811 		if (!e) {
1812 			err = -ENOMEM;
1813 			goto out_free;
1814 		}
1815 
1816 		e->pnum = aeb->pnum;
1817 		e->ec = aeb->ec;
1818 		ubi_assert(e->ec >= 0);
1819 
1820 		wl_tree_add(e, &ubi->free);
1821 		ubi->free_count++;
1822 
1823 		ubi->lookuptbl[e->pnum] = e;
1824 
1825 		found_pebs++;
1826 	}
1827 
1828 	ubi_rb_for_each_entry(rb1, av, &ai->volumes, rb) {
1829 		ubi_rb_for_each_entry(rb2, aeb, &av->root, u.rb) {
1830 			cond_resched();
1831 
1832 			e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
1833 			if (!e) {
1834 				err = -ENOMEM;
1835 				goto out_free;
1836 			}
1837 
1838 			e->pnum = aeb->pnum;
1839 			e->ec = aeb->ec;
1840 			ubi->lookuptbl[e->pnum] = e;
1841 
1842 			if (!aeb->scrub) {
1843 				dbg_wl("add PEB %d EC %d to the used tree",
1844 				       e->pnum, e->ec);
1845 				wl_tree_add(e, &ubi->used);
1846 			} else {
1847 				dbg_wl("add PEB %d EC %d to the scrub tree",
1848 				       e->pnum, e->ec);
1849 				wl_tree_add(e, &ubi->scrub);
1850 			}
1851 
1852 			found_pebs++;
1853 		}
1854 	}
1855 
1856 	list_for_each_entry(aeb, &ai->fastmap, u.list) {
1857 		cond_resched();
1858 
1859 		e = ubi_find_fm_block(ubi, aeb->pnum);
1860 
1861 		if (e) {
1862 			ubi_assert(!ubi->lookuptbl[e->pnum]);
1863 			ubi->lookuptbl[e->pnum] = e;
1864 		} else {
1865 			bool sync = false;
1866 
1867 			/*
1868 			 * Usually old Fastmap PEBs are scheduled for erasure
1869 			 * and we don't have to care about them but if we face
1870 			 * an power cut before scheduling them we need to
1871 			 * take care of them here.
1872 			 */
1873 			if (ubi->lookuptbl[aeb->pnum])
1874 				continue;
1875 
1876 			/*
1877 			 * The fastmap update code might not find a free PEB for
1878 			 * writing the fastmap anchor to and then reuses the
1879 			 * current fastmap anchor PEB. When this PEB gets erased
1880 			 * and a power cut happens before it is written again we
1881 			 * must make sure that the fastmap attach code doesn't
1882 			 * find any outdated fastmap anchors, hence we erase the
1883 			 * outdated fastmap anchor PEBs synchronously here.
1884 			 */
1885 			if (aeb->vol_id == UBI_FM_SB_VOLUME_ID)
1886 				sync = true;
1887 
1888 			err = erase_aeb(ubi, aeb, sync);
1889 			if (err)
1890 				goto out_free;
1891 		}
1892 
1893 		found_pebs++;
1894 	}
1895 
1896 	dbg_wl("found %i PEBs", found_pebs);
1897 
1898 	ubi_assert(ubi->good_peb_count == found_pebs);
1899 
1900 	reserved_pebs = WL_RESERVED_PEBS;
1901 	ubi_fastmap_init(ubi, &reserved_pebs);
1902 
1903 	if (ubi->avail_pebs < reserved_pebs) {
1904 		ubi_err(ubi, "no enough physical eraseblocks (%d, need %d)",
1905 			ubi->avail_pebs, reserved_pebs);
1906 		if (ubi->corr_peb_count)
1907 			ubi_err(ubi, "%d PEBs are corrupted and not used",
1908 				ubi->corr_peb_count);
1909 		err = -ENOSPC;
1910 		goto out_free;
1911 	}
1912 	ubi->avail_pebs -= reserved_pebs;
1913 	ubi->rsvd_pebs += reserved_pebs;
1914 
1915 	/* Schedule wear-leveling if needed */
1916 	err = ensure_wear_leveling(ubi, 0);
1917 	if (err)
1918 		goto out_free;
1919 
1920 #ifdef CONFIG_MTD_UBI_FASTMAP
1921 	if (!ubi->ro_mode && !ubi->fm_disabled)
1922 		ubi_ensure_anchor_pebs(ubi);
1923 #endif
1924 	return 0;
1925 
1926 out_free:
1927 	shutdown_work(ubi);
1928 	tree_destroy(ubi, &ubi->used);
1929 	tree_destroy(ubi, &ubi->free);
1930 	tree_destroy(ubi, &ubi->scrub);
1931 	kfree(ubi->lookuptbl);
1932 	return err;
1933 }
1934 
1935 /**
1936  * protection_queue_destroy - destroy the protection queue.
1937  * @ubi: UBI device description object
1938  */
1939 static void protection_queue_destroy(struct ubi_device *ubi)
1940 {
1941 	int i;
1942 	struct ubi_wl_entry *e, *tmp;
1943 
1944 	for (i = 0; i < UBI_PROT_QUEUE_LEN; ++i) {
1945 		list_for_each_entry_safe(e, tmp, &ubi->pq[i], u.list) {
1946 			list_del(&e->u.list);
1947 			wl_entry_destroy(ubi, e);
1948 		}
1949 	}
1950 }
1951 
1952 /**
1953  * ubi_wl_close - close the wear-leveling sub-system.
1954  * @ubi: UBI device description object
1955  */
1956 void ubi_wl_close(struct ubi_device *ubi)
1957 {
1958 	dbg_wl("close the WL sub-system");
1959 	ubi_fastmap_close(ubi);
1960 	shutdown_work(ubi);
1961 	protection_queue_destroy(ubi);
1962 	tree_destroy(ubi, &ubi->used);
1963 	tree_destroy(ubi, &ubi->erroneous);
1964 	tree_destroy(ubi, &ubi->free);
1965 	tree_destroy(ubi, &ubi->scrub);
1966 	kfree(ubi->lookuptbl);
1967 }
1968 
1969 /**
1970  * self_check_ec - make sure that the erase counter of a PEB is correct.
1971  * @ubi: UBI device description object
1972  * @pnum: the physical eraseblock number to check
1973  * @ec: the erase counter to check
1974  *
1975  * This function returns zero if the erase counter of physical eraseblock @pnum
1976  * is equivalent to @ec, and a negative error code if not or if an error
1977  * occurred.
1978  */
1979 static int self_check_ec(struct ubi_device *ubi, int pnum, int ec)
1980 {
1981 	int err;
1982 	long long read_ec;
1983 	struct ubi_ec_hdr *ec_hdr;
1984 
1985 	if (!ubi_dbg_chk_gen(ubi))
1986 		return 0;
1987 
1988 	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
1989 	if (!ec_hdr)
1990 		return -ENOMEM;
1991 
1992 	err = ubi_io_read_ec_hdr(ubi, pnum, ec_hdr, 0);
1993 	if (err && err != UBI_IO_BITFLIPS) {
1994 		/* The header does not have to exist */
1995 		err = 0;
1996 		goto out_free;
1997 	}
1998 
1999 	read_ec = be64_to_cpu(ec_hdr->ec);
2000 	if (ec != read_ec && read_ec - ec > 1) {
2001 		ubi_err(ubi, "self-check failed for PEB %d", pnum);
2002 		ubi_err(ubi, "read EC is %lld, should be %d", read_ec, ec);
2003 		dump_stack();
2004 		err = 1;
2005 	} else
2006 		err = 0;
2007 
2008 out_free:
2009 	kfree(ec_hdr);
2010 	return err;
2011 }
2012 
2013 /**
2014  * self_check_in_wl_tree - check that wear-leveling entry is in WL RB-tree.
2015  * @ubi: UBI device description object
2016  * @e: the wear-leveling entry to check
2017  * @root: the root of the tree
2018  *
2019  * This function returns zero if @e is in the @root RB-tree and %-EINVAL if it
2020  * is not.
2021  */
2022 static int self_check_in_wl_tree(const struct ubi_device *ubi,
2023 				 struct ubi_wl_entry *e, struct rb_root *root)
2024 {
2025 	if (!ubi_dbg_chk_gen(ubi))
2026 		return 0;
2027 
2028 	if (in_wl_tree(e, root))
2029 		return 0;
2030 
2031 	ubi_err(ubi, "self-check failed for PEB %d, EC %d, RB-tree %p ",
2032 		e->pnum, e->ec, root);
2033 	dump_stack();
2034 	return -EINVAL;
2035 }
2036 
2037 /**
2038  * self_check_in_pq - check if wear-leveling entry is in the protection
2039  *                        queue.
2040  * @ubi: UBI device description object
2041  * @e: the wear-leveling entry to check
2042  *
2043  * This function returns zero if @e is in @ubi->pq and %-EINVAL if it is not.
2044  */
2045 static int self_check_in_pq(const struct ubi_device *ubi,
2046 			    struct ubi_wl_entry *e)
2047 {
2048 	if (!ubi_dbg_chk_gen(ubi))
2049 		return 0;
2050 
2051 	if (in_pq(ubi, e))
2052 		return 0;
2053 
2054 	ubi_err(ubi, "self-check failed for PEB %d, EC %d, Protect queue",
2055 		e->pnum, e->ec);
2056 	dump_stack();
2057 	return -EINVAL;
2058 }
2059 #ifndef CONFIG_MTD_UBI_FASTMAP
2060 static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
2061 {
2062 	struct ubi_wl_entry *e;
2063 
2064 	e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
2065 	self_check_in_wl_tree(ubi, e, &ubi->free);
2066 	ubi->free_count--;
2067 	ubi_assert(ubi->free_count >= 0);
2068 	rb_erase(&e->u.rb, &ubi->free);
2069 
2070 	return e;
2071 }
2072 
2073 /**
2074  * produce_free_peb - produce a free physical eraseblock.
2075  * @ubi: UBI device description object
2076  *
2077  * This function tries to make a free PEB by means of synchronous execution of
2078  * pending works. This may be needed if, for example the background thread is
2079  * disabled. Returns zero in case of success and a negative error code in case
2080  * of failure.
2081  */
2082 static int produce_free_peb(struct ubi_device *ubi)
2083 {
2084 	int err;
2085 
2086 	while (!ubi->free.rb_node && ubi->works_count) {
2087 		spin_unlock(&ubi->wl_lock);
2088 
2089 		dbg_wl("do one work synchronously");
2090 		err = do_work(ubi);
2091 
2092 		spin_lock(&ubi->wl_lock);
2093 		if (err)
2094 			return err;
2095 	}
2096 
2097 	return 0;
2098 }
2099 
2100 /**
2101  * ubi_wl_get_peb - get a physical eraseblock.
2102  * @ubi: UBI device description object
2103  *
2104  * This function returns a physical eraseblock in case of success and a
2105  * negative error code in case of failure.
2106  * Returns with ubi->fm_eba_sem held in read mode!
2107  */
2108 int ubi_wl_get_peb(struct ubi_device *ubi)
2109 {
2110 	int err;
2111 	struct ubi_wl_entry *e;
2112 
2113 retry:
2114 	down_read(&ubi->fm_eba_sem);
2115 	spin_lock(&ubi->wl_lock);
2116 	if (!ubi->free.rb_node) {
2117 		if (ubi->works_count == 0) {
2118 			ubi_err(ubi, "no free eraseblocks");
2119 			ubi_assert(list_empty(&ubi->works));
2120 			spin_unlock(&ubi->wl_lock);
2121 			return -ENOSPC;
2122 		}
2123 
2124 		err = produce_free_peb(ubi);
2125 		if (err < 0) {
2126 			spin_unlock(&ubi->wl_lock);
2127 			return err;
2128 		}
2129 		spin_unlock(&ubi->wl_lock);
2130 		up_read(&ubi->fm_eba_sem);
2131 		goto retry;
2132 
2133 	}
2134 	e = wl_get_wle(ubi);
2135 	prot_queue_add(ubi, e);
2136 	spin_unlock(&ubi->wl_lock);
2137 
2138 	err = ubi_self_check_all_ff(ubi, e->pnum, ubi->vid_hdr_aloffset,
2139 				    ubi->peb_size - ubi->vid_hdr_aloffset);
2140 	if (err) {
2141 		ubi_err(ubi, "new PEB %d does not contain all 0xFF bytes", e->pnum);
2142 		return err;
2143 	}
2144 
2145 	return e->pnum;
2146 }
2147 #else
2148 #include "fastmap-wl.c"
2149 #endif
2150