xref: /linux/drivers/nvdimm/btt.c (revision d060296cc0300ae8ed08004ebd3994bf325fa257)
1 /*
2  * Block Translation Table
3  * Copyright (c) 2014-2015, Intel Corporation.
4  *
5  * This program is free software; you can redistribute it and/or modify it
6  * under the terms and conditions of the GNU General Public License,
7  * version 2, as published by the Free Software Foundation.
8  *
9  * This program is distributed in the hope it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
12  * more details.
13  */
14 #include <linux/highmem.h>
15 #include <linux/debugfs.h>
16 #include <linux/blkdev.h>
17 #include <linux/module.h>
18 #include <linux/device.h>
19 #include <linux/mutex.h>
20 #include <linux/hdreg.h>
21 #include <linux/genhd.h>
22 #include <linux/sizes.h>
23 #include <linux/ndctl.h>
24 #include <linux/fs.h>
25 #include <linux/nd.h>
26 #include "btt.h"
27 #include "nd.h"
28 
29 enum log_ent_request {
30 	LOG_NEW_ENT = 0,
31 	LOG_OLD_ENT
32 };
33 
34 static int arena_read_bytes(struct arena_info *arena, resource_size_t offset,
35 		void *buf, size_t n, unsigned long flags)
36 {
37 	struct nd_btt *nd_btt = arena->nd_btt;
38 	struct nd_namespace_common *ndns = nd_btt->ndns;
39 
40 	/* arena offsets may be shifted from the base of the device */
41 	offset += arena->nd_btt->initial_offset;
42 	return nvdimm_read_bytes(ndns, offset, buf, n, flags);
43 }
44 
45 static int arena_write_bytes(struct arena_info *arena, resource_size_t offset,
46 		void *buf, size_t n, unsigned long flags)
47 {
48 	struct nd_btt *nd_btt = arena->nd_btt;
49 	struct nd_namespace_common *ndns = nd_btt->ndns;
50 
51 	/* arena offsets may be shifted from the base of the device */
52 	offset += arena->nd_btt->initial_offset;
53 	return nvdimm_write_bytes(ndns, offset, buf, n, flags);
54 }
55 
56 static int btt_info_write(struct arena_info *arena, struct btt_sb *super)
57 {
58 	int ret;
59 
60 	/*
61 	 * infooff and info2off should always be at least 512B aligned.
62 	 * We rely on that to make sure rw_bytes does error clearing
63 	 * correctly, so make sure that is the case.
64 	 */
65 	WARN_ON_ONCE(!IS_ALIGNED(arena->infooff, 512));
66 	WARN_ON_ONCE(!IS_ALIGNED(arena->info2off, 512));
67 
68 	ret = arena_write_bytes(arena, arena->info2off, super,
69 			sizeof(struct btt_sb), 0);
70 	if (ret)
71 		return ret;
72 
73 	return arena_write_bytes(arena, arena->infooff, super,
74 			sizeof(struct btt_sb), 0);
75 }
76 
77 static int btt_info_read(struct arena_info *arena, struct btt_sb *super)
78 {
79 	WARN_ON(!super);
80 	return arena_read_bytes(arena, arena->infooff, super,
81 			sizeof(struct btt_sb), 0);
82 }
83 
84 /*
85  * 'raw' version of btt_map write
86  * Assumptions:
87  *   mapping is in little-endian
88  *   mapping contains 'E' and 'Z' flags as desired
89  */
90 static int __btt_map_write(struct arena_info *arena, u32 lba, __le32 mapping,
91 		unsigned long flags)
92 {
93 	u64 ns_off = arena->mapoff + (lba * MAP_ENT_SIZE);
94 
95 	WARN_ON(lba >= arena->external_nlba);
96 	return arena_write_bytes(arena, ns_off, &mapping, MAP_ENT_SIZE, flags);
97 }
98 
99 static int btt_map_write(struct arena_info *arena, u32 lba, u32 mapping,
100 			u32 z_flag, u32 e_flag, unsigned long rwb_flags)
101 {
102 	u32 ze;
103 	__le32 mapping_le;
104 
105 	/*
106 	 * This 'mapping' is supposed to be just the LBA mapping, without
107 	 * any flags set, so strip the flag bits.
108 	 */
109 	mapping &= MAP_LBA_MASK;
110 
111 	ze = (z_flag << 1) + e_flag;
112 	switch (ze) {
113 	case 0:
114 		/*
115 		 * We want to set neither of the Z or E flags, and
116 		 * in the actual layout, this means setting the bit
117 		 * positions of both to '1' to indicate a 'normal'
118 		 * map entry
119 		 */
120 		mapping |= MAP_ENT_NORMAL;
121 		break;
122 	case 1:
123 		mapping |= (1 << MAP_ERR_SHIFT);
124 		break;
125 	case 2:
126 		mapping |= (1 << MAP_TRIM_SHIFT);
127 		break;
128 	default:
129 		/*
130 		 * The case where Z and E are both sent in as '1' could be
131 		 * construed as a valid 'normal' case, but we decide not to,
132 		 * to avoid confusion
133 		 */
134 		WARN_ONCE(1, "Invalid use of Z and E flags\n");
135 		return -EIO;
136 	}
137 
138 	mapping_le = cpu_to_le32(mapping);
139 	return __btt_map_write(arena, lba, mapping_le, rwb_flags);
140 }
141 
142 static int btt_map_read(struct arena_info *arena, u32 lba, u32 *mapping,
143 			int *trim, int *error, unsigned long rwb_flags)
144 {
145 	int ret;
146 	__le32 in;
147 	u32 raw_mapping, postmap, ze, z_flag, e_flag;
148 	u64 ns_off = arena->mapoff + (lba * MAP_ENT_SIZE);
149 
150 	WARN_ON(lba >= arena->external_nlba);
151 
152 	ret = arena_read_bytes(arena, ns_off, &in, MAP_ENT_SIZE, rwb_flags);
153 	if (ret)
154 		return ret;
155 
156 	raw_mapping = le32_to_cpu(in);
157 
158 	z_flag = (raw_mapping & MAP_TRIM_MASK) >> MAP_TRIM_SHIFT;
159 	e_flag = (raw_mapping & MAP_ERR_MASK) >> MAP_ERR_SHIFT;
160 	ze = (z_flag << 1) + e_flag;
161 	postmap = raw_mapping & MAP_LBA_MASK;
162 
163 	/* Reuse the {z,e}_flag variables for *trim and *error */
164 	z_flag = 0;
165 	e_flag = 0;
166 
167 	switch (ze) {
168 	case 0:
169 		/* Initial state. Return postmap = premap */
170 		*mapping = lba;
171 		break;
172 	case 1:
173 		*mapping = postmap;
174 		e_flag = 1;
175 		break;
176 	case 2:
177 		*mapping = postmap;
178 		z_flag = 1;
179 		break;
180 	case 3:
181 		*mapping = postmap;
182 		break;
183 	default:
184 		return -EIO;
185 	}
186 
187 	if (trim)
188 		*trim = z_flag;
189 	if (error)
190 		*error = e_flag;
191 
192 	return ret;
193 }
194 
195 static int btt_log_read_pair(struct arena_info *arena, u32 lane,
196 			struct log_entry *ent)
197 {
198 	WARN_ON(!ent);
199 	return arena_read_bytes(arena,
200 			arena->logoff + (2 * lane * LOG_ENT_SIZE), ent,
201 			2 * LOG_ENT_SIZE, 0);
202 }
203 
204 static struct dentry *debugfs_root;
205 
206 static void arena_debugfs_init(struct arena_info *a, struct dentry *parent,
207 				int idx)
208 {
209 	char dirname[32];
210 	struct dentry *d;
211 
212 	/* If for some reason, parent bttN was not created, exit */
213 	if (!parent)
214 		return;
215 
216 	snprintf(dirname, 32, "arena%d", idx);
217 	d = debugfs_create_dir(dirname, parent);
218 	if (IS_ERR_OR_NULL(d))
219 		return;
220 	a->debugfs_dir = d;
221 
222 	debugfs_create_x64("size", S_IRUGO, d, &a->size);
223 	debugfs_create_x64("external_lba_start", S_IRUGO, d,
224 				&a->external_lba_start);
225 	debugfs_create_x32("internal_nlba", S_IRUGO, d, &a->internal_nlba);
226 	debugfs_create_u32("internal_lbasize", S_IRUGO, d,
227 				&a->internal_lbasize);
228 	debugfs_create_x32("external_nlba", S_IRUGO, d, &a->external_nlba);
229 	debugfs_create_u32("external_lbasize", S_IRUGO, d,
230 				&a->external_lbasize);
231 	debugfs_create_u32("nfree", S_IRUGO, d, &a->nfree);
232 	debugfs_create_u16("version_major", S_IRUGO, d, &a->version_major);
233 	debugfs_create_u16("version_minor", S_IRUGO, d, &a->version_minor);
234 	debugfs_create_x64("nextoff", S_IRUGO, d, &a->nextoff);
235 	debugfs_create_x64("infooff", S_IRUGO, d, &a->infooff);
236 	debugfs_create_x64("dataoff", S_IRUGO, d, &a->dataoff);
237 	debugfs_create_x64("mapoff", S_IRUGO, d, &a->mapoff);
238 	debugfs_create_x64("logoff", S_IRUGO, d, &a->logoff);
239 	debugfs_create_x64("info2off", S_IRUGO, d, &a->info2off);
240 	debugfs_create_x32("flags", S_IRUGO, d, &a->flags);
241 }
242 
243 static void btt_debugfs_init(struct btt *btt)
244 {
245 	int i = 0;
246 	struct arena_info *arena;
247 
248 	btt->debugfs_dir = debugfs_create_dir(dev_name(&btt->nd_btt->dev),
249 						debugfs_root);
250 	if (IS_ERR_OR_NULL(btt->debugfs_dir))
251 		return;
252 
253 	list_for_each_entry(arena, &btt->arena_list, list) {
254 		arena_debugfs_init(arena, btt->debugfs_dir, i);
255 		i++;
256 	}
257 }
258 
259 /*
260  * This function accepts two log entries, and uses the
261  * sequence number to find the 'older' entry.
262  * It also updates the sequence number in this old entry to
263  * make it the 'new' one if the mark_flag is set.
264  * Finally, it returns which of the entries was the older one.
265  *
266  * TODO The logic feels a bit kludge-y. make it better..
267  */
268 static int btt_log_get_old(struct log_entry *ent)
269 {
270 	int old;
271 
272 	/*
273 	 * the first ever time this is seen, the entry goes into [0]
274 	 * the next time, the following logic works out to put this
275 	 * (next) entry into [1]
276 	 */
277 	if (ent[0].seq == 0) {
278 		ent[0].seq = cpu_to_le32(1);
279 		return 0;
280 	}
281 
282 	if (ent[0].seq == ent[1].seq)
283 		return -EINVAL;
284 	if (le32_to_cpu(ent[0].seq) + le32_to_cpu(ent[1].seq) > 5)
285 		return -EINVAL;
286 
287 	if (le32_to_cpu(ent[0].seq) < le32_to_cpu(ent[1].seq)) {
288 		if (le32_to_cpu(ent[1].seq) - le32_to_cpu(ent[0].seq) == 1)
289 			old = 0;
290 		else
291 			old = 1;
292 	} else {
293 		if (le32_to_cpu(ent[0].seq) - le32_to_cpu(ent[1].seq) == 1)
294 			old = 1;
295 		else
296 			old = 0;
297 	}
298 
299 	return old;
300 }
301 
302 static struct device *to_dev(struct arena_info *arena)
303 {
304 	return &arena->nd_btt->dev;
305 }
306 
307 /*
308  * This function copies the desired (old/new) log entry into ent if
309  * it is not NULL. It returns the sub-slot number (0 or 1)
310  * where the desired log entry was found. Negative return values
311  * indicate errors.
312  */
313 static int btt_log_read(struct arena_info *arena, u32 lane,
314 			struct log_entry *ent, int old_flag)
315 {
316 	int ret;
317 	int old_ent, ret_ent;
318 	struct log_entry log[2];
319 
320 	ret = btt_log_read_pair(arena, lane, log);
321 	if (ret)
322 		return -EIO;
323 
324 	old_ent = btt_log_get_old(log);
325 	if (old_ent < 0 || old_ent > 1) {
326 		dev_err(to_dev(arena),
327 				"log corruption (%d): lane %d seq [%d, %d]\n",
328 			old_ent, lane, log[0].seq, log[1].seq);
329 		/* TODO set error state? */
330 		return -EIO;
331 	}
332 
333 	ret_ent = (old_flag ? old_ent : (1 - old_ent));
334 
335 	if (ent != NULL)
336 		memcpy(ent, &log[ret_ent], LOG_ENT_SIZE);
337 
338 	return ret_ent;
339 }
340 
341 /*
342  * This function commits a log entry to media
343  * It does _not_ prepare the freelist entry for the next write
344  * btt_flog_write is the wrapper for updating the freelist elements
345  */
346 static int __btt_log_write(struct arena_info *arena, u32 lane,
347 			u32 sub, struct log_entry *ent, unsigned long flags)
348 {
349 	int ret;
350 	/*
351 	 * Ignore the padding in log_entry for calculating log_half.
352 	 * The entry is 'committed' when we write the sequence number,
353 	 * and we want to ensure that that is the last thing written.
354 	 * We don't bother writing the padding as that would be extra
355 	 * media wear and write amplification
356 	 */
357 	unsigned int log_half = (LOG_ENT_SIZE - 2 * sizeof(u64)) / 2;
358 	u64 ns_off = arena->logoff + (((2 * lane) + sub) * LOG_ENT_SIZE);
359 	void *src = ent;
360 
361 	/* split the 16B write into atomic, durable halves */
362 	ret = arena_write_bytes(arena, ns_off, src, log_half, flags);
363 	if (ret)
364 		return ret;
365 
366 	ns_off += log_half;
367 	src += log_half;
368 	return arena_write_bytes(arena, ns_off, src, log_half, flags);
369 }
370 
371 static int btt_flog_write(struct arena_info *arena, u32 lane, u32 sub,
372 			struct log_entry *ent)
373 {
374 	int ret;
375 
376 	ret = __btt_log_write(arena, lane, sub, ent, NVDIMM_IO_ATOMIC);
377 	if (ret)
378 		return ret;
379 
380 	/* prepare the next free entry */
381 	arena->freelist[lane].sub = 1 - arena->freelist[lane].sub;
382 	if (++(arena->freelist[lane].seq) == 4)
383 		arena->freelist[lane].seq = 1;
384 	arena->freelist[lane].block = le32_to_cpu(ent->old_map);
385 
386 	return ret;
387 }
388 
389 /*
390  * This function initializes the BTT map to the initial state, which is
391  * all-zeroes, and indicates an identity mapping
392  */
393 static int btt_map_init(struct arena_info *arena)
394 {
395 	int ret = -EINVAL;
396 	void *zerobuf;
397 	size_t offset = 0;
398 	size_t chunk_size = SZ_2M;
399 	size_t mapsize = arena->logoff - arena->mapoff;
400 
401 	zerobuf = kzalloc(chunk_size, GFP_KERNEL);
402 	if (!zerobuf)
403 		return -ENOMEM;
404 
405 	/*
406 	 * mapoff should always be at least 512B  aligned. We rely on that to
407 	 * make sure rw_bytes does error clearing correctly, so make sure that
408 	 * is the case.
409 	 */
410 	WARN_ON_ONCE(!IS_ALIGNED(arena->mapoff, 512));
411 
412 	while (mapsize) {
413 		size_t size = min(mapsize, chunk_size);
414 
415 		WARN_ON_ONCE(size < 512);
416 		ret = arena_write_bytes(arena, arena->mapoff + offset, zerobuf,
417 				size, 0);
418 		if (ret)
419 			goto free;
420 
421 		offset += size;
422 		mapsize -= size;
423 		cond_resched();
424 	}
425 
426  free:
427 	kfree(zerobuf);
428 	return ret;
429 }
430 
431 /*
432  * This function initializes the BTT log with 'fake' entries pointing
433  * to the initial reserved set of blocks as being free
434  */
435 static int btt_log_init(struct arena_info *arena)
436 {
437 	size_t logsize = arena->info2off - arena->logoff;
438 	size_t chunk_size = SZ_4K, offset = 0;
439 	struct log_entry log;
440 	void *zerobuf;
441 	int ret;
442 	u32 i;
443 
444 	zerobuf = kzalloc(chunk_size, GFP_KERNEL);
445 	if (!zerobuf)
446 		return -ENOMEM;
447 	/*
448 	 * logoff should always be at least 512B  aligned. We rely on that to
449 	 * make sure rw_bytes does error clearing correctly, so make sure that
450 	 * is the case.
451 	 */
452 	WARN_ON_ONCE(!IS_ALIGNED(arena->logoff, 512));
453 
454 	while (logsize) {
455 		size_t size = min(logsize, chunk_size);
456 
457 		WARN_ON_ONCE(size < 512);
458 		ret = arena_write_bytes(arena, arena->logoff + offset, zerobuf,
459 				size, 0);
460 		if (ret)
461 			goto free;
462 
463 		offset += size;
464 		logsize -= size;
465 		cond_resched();
466 	}
467 
468 	for (i = 0; i < arena->nfree; i++) {
469 		log.lba = cpu_to_le32(i);
470 		log.old_map = cpu_to_le32(arena->external_nlba + i);
471 		log.new_map = cpu_to_le32(arena->external_nlba + i);
472 		log.seq = cpu_to_le32(LOG_SEQ_INIT);
473 		ret = __btt_log_write(arena, i, 0, &log, 0);
474 		if (ret)
475 			goto free;
476 	}
477 
478  free:
479 	kfree(zerobuf);
480 	return ret;
481 }
482 
483 static int btt_freelist_init(struct arena_info *arena)
484 {
485 	int old, new, ret;
486 	u32 i, map_entry;
487 	struct log_entry log_new, log_old;
488 
489 	arena->freelist = kcalloc(arena->nfree, sizeof(struct free_entry),
490 					GFP_KERNEL);
491 	if (!arena->freelist)
492 		return -ENOMEM;
493 
494 	for (i = 0; i < arena->nfree; i++) {
495 		old = btt_log_read(arena, i, &log_old, LOG_OLD_ENT);
496 		if (old < 0)
497 			return old;
498 
499 		new = btt_log_read(arena, i, &log_new, LOG_NEW_ENT);
500 		if (new < 0)
501 			return new;
502 
503 		/* sub points to the next one to be overwritten */
504 		arena->freelist[i].sub = 1 - new;
505 		arena->freelist[i].seq = nd_inc_seq(le32_to_cpu(log_new.seq));
506 		arena->freelist[i].block = le32_to_cpu(log_new.old_map);
507 
508 		/* This implies a newly created or untouched flog entry */
509 		if (log_new.old_map == log_new.new_map)
510 			continue;
511 
512 		/* Check if map recovery is needed */
513 		ret = btt_map_read(arena, le32_to_cpu(log_new.lba), &map_entry,
514 				NULL, NULL, 0);
515 		if (ret)
516 			return ret;
517 		if ((le32_to_cpu(log_new.new_map) != map_entry) &&
518 				(le32_to_cpu(log_new.old_map) == map_entry)) {
519 			/*
520 			 * Last transaction wrote the flog, but wasn't able
521 			 * to complete the map write. So fix up the map.
522 			 */
523 			ret = btt_map_write(arena, le32_to_cpu(log_new.lba),
524 					le32_to_cpu(log_new.new_map), 0, 0, 0);
525 			if (ret)
526 				return ret;
527 		}
528 
529 	}
530 
531 	return 0;
532 }
533 
534 static int btt_rtt_init(struct arena_info *arena)
535 {
536 	arena->rtt = kcalloc(arena->nfree, sizeof(u32), GFP_KERNEL);
537 	if (arena->rtt == NULL)
538 		return -ENOMEM;
539 
540 	return 0;
541 }
542 
543 static int btt_maplocks_init(struct arena_info *arena)
544 {
545 	u32 i;
546 
547 	arena->map_locks = kcalloc(arena->nfree, sizeof(struct aligned_lock),
548 				GFP_KERNEL);
549 	if (!arena->map_locks)
550 		return -ENOMEM;
551 
552 	for (i = 0; i < arena->nfree; i++)
553 		spin_lock_init(&arena->map_locks[i].lock);
554 
555 	return 0;
556 }
557 
558 static struct arena_info *alloc_arena(struct btt *btt, size_t size,
559 				size_t start, size_t arena_off)
560 {
561 	struct arena_info *arena;
562 	u64 logsize, mapsize, datasize;
563 	u64 available = size;
564 
565 	arena = kzalloc(sizeof(struct arena_info), GFP_KERNEL);
566 	if (!arena)
567 		return NULL;
568 	arena->nd_btt = btt->nd_btt;
569 
570 	if (!size)
571 		return arena;
572 
573 	arena->size = size;
574 	arena->external_lba_start = start;
575 	arena->external_lbasize = btt->lbasize;
576 	arena->internal_lbasize = roundup(arena->external_lbasize,
577 					INT_LBASIZE_ALIGNMENT);
578 	arena->nfree = BTT_DEFAULT_NFREE;
579 	arena->version_major = btt->nd_btt->version_major;
580 	arena->version_minor = btt->nd_btt->version_minor;
581 
582 	if (available % BTT_PG_SIZE)
583 		available -= (available % BTT_PG_SIZE);
584 
585 	/* Two pages are reserved for the super block and its copy */
586 	available -= 2 * BTT_PG_SIZE;
587 
588 	/* The log takes a fixed amount of space based on nfree */
589 	logsize = roundup(2 * arena->nfree * sizeof(struct log_entry),
590 				BTT_PG_SIZE);
591 	available -= logsize;
592 
593 	/* Calculate optimal split between map and data area */
594 	arena->internal_nlba = div_u64(available - BTT_PG_SIZE,
595 			arena->internal_lbasize + MAP_ENT_SIZE);
596 	arena->external_nlba = arena->internal_nlba - arena->nfree;
597 
598 	mapsize = roundup((arena->external_nlba * MAP_ENT_SIZE), BTT_PG_SIZE);
599 	datasize = available - mapsize;
600 
601 	/* 'Absolute' values, relative to start of storage space */
602 	arena->infooff = arena_off;
603 	arena->dataoff = arena->infooff + BTT_PG_SIZE;
604 	arena->mapoff = arena->dataoff + datasize;
605 	arena->logoff = arena->mapoff + mapsize;
606 	arena->info2off = arena->logoff + logsize;
607 	return arena;
608 }
609 
610 static void free_arenas(struct btt *btt)
611 {
612 	struct arena_info *arena, *next;
613 
614 	list_for_each_entry_safe(arena, next, &btt->arena_list, list) {
615 		list_del(&arena->list);
616 		kfree(arena->rtt);
617 		kfree(arena->map_locks);
618 		kfree(arena->freelist);
619 		debugfs_remove_recursive(arena->debugfs_dir);
620 		kfree(arena);
621 	}
622 }
623 
624 /*
625  * This function reads an existing valid btt superblock and
626  * populates the corresponding arena_info struct
627  */
628 static void parse_arena_meta(struct arena_info *arena, struct btt_sb *super,
629 				u64 arena_off)
630 {
631 	arena->internal_nlba = le32_to_cpu(super->internal_nlba);
632 	arena->internal_lbasize = le32_to_cpu(super->internal_lbasize);
633 	arena->external_nlba = le32_to_cpu(super->external_nlba);
634 	arena->external_lbasize = le32_to_cpu(super->external_lbasize);
635 	arena->nfree = le32_to_cpu(super->nfree);
636 	arena->version_major = le16_to_cpu(super->version_major);
637 	arena->version_minor = le16_to_cpu(super->version_minor);
638 
639 	arena->nextoff = (super->nextoff == 0) ? 0 : (arena_off +
640 			le64_to_cpu(super->nextoff));
641 	arena->infooff = arena_off;
642 	arena->dataoff = arena_off + le64_to_cpu(super->dataoff);
643 	arena->mapoff = arena_off + le64_to_cpu(super->mapoff);
644 	arena->logoff = arena_off + le64_to_cpu(super->logoff);
645 	arena->info2off = arena_off + le64_to_cpu(super->info2off);
646 
647 	arena->size = (le64_to_cpu(super->nextoff) > 0)
648 		? (le64_to_cpu(super->nextoff))
649 		: (arena->info2off - arena->infooff + BTT_PG_SIZE);
650 
651 	arena->flags = le32_to_cpu(super->flags);
652 }
653 
654 static int discover_arenas(struct btt *btt)
655 {
656 	int ret = 0;
657 	struct arena_info *arena;
658 	struct btt_sb *super;
659 	size_t remaining = btt->rawsize;
660 	u64 cur_nlba = 0;
661 	size_t cur_off = 0;
662 	int num_arenas = 0;
663 
664 	super = kzalloc(sizeof(*super), GFP_KERNEL);
665 	if (!super)
666 		return -ENOMEM;
667 
668 	while (remaining) {
669 		/* Alloc memory for arena */
670 		arena = alloc_arena(btt, 0, 0, 0);
671 		if (!arena) {
672 			ret = -ENOMEM;
673 			goto out_super;
674 		}
675 
676 		arena->infooff = cur_off;
677 		ret = btt_info_read(arena, super);
678 		if (ret)
679 			goto out;
680 
681 		if (!nd_btt_arena_is_valid(btt->nd_btt, super)) {
682 			if (remaining == btt->rawsize) {
683 				btt->init_state = INIT_NOTFOUND;
684 				dev_info(to_dev(arena), "No existing arenas\n");
685 				goto out;
686 			} else {
687 				dev_err(to_dev(arena),
688 						"Found corrupted metadata!\n");
689 				ret = -ENODEV;
690 				goto out;
691 			}
692 		}
693 
694 		arena->external_lba_start = cur_nlba;
695 		parse_arena_meta(arena, super, cur_off);
696 
697 		ret = btt_freelist_init(arena);
698 		if (ret)
699 			goto out;
700 
701 		ret = btt_rtt_init(arena);
702 		if (ret)
703 			goto out;
704 
705 		ret = btt_maplocks_init(arena);
706 		if (ret)
707 			goto out;
708 
709 		list_add_tail(&arena->list, &btt->arena_list);
710 
711 		remaining -= arena->size;
712 		cur_off += arena->size;
713 		cur_nlba += arena->external_nlba;
714 		num_arenas++;
715 
716 		if (arena->nextoff == 0)
717 			break;
718 	}
719 	btt->num_arenas = num_arenas;
720 	btt->nlba = cur_nlba;
721 	btt->init_state = INIT_READY;
722 
723 	kfree(super);
724 	return ret;
725 
726  out:
727 	kfree(arena);
728 	free_arenas(btt);
729  out_super:
730 	kfree(super);
731 	return ret;
732 }
733 
734 static int create_arenas(struct btt *btt)
735 {
736 	size_t remaining = btt->rawsize;
737 	size_t cur_off = 0;
738 
739 	while (remaining) {
740 		struct arena_info *arena;
741 		size_t arena_size = min_t(u64, ARENA_MAX_SIZE, remaining);
742 
743 		remaining -= arena_size;
744 		if (arena_size < ARENA_MIN_SIZE)
745 			break;
746 
747 		arena = alloc_arena(btt, arena_size, btt->nlba, cur_off);
748 		if (!arena) {
749 			free_arenas(btt);
750 			return -ENOMEM;
751 		}
752 		btt->nlba += arena->external_nlba;
753 		if (remaining >= ARENA_MIN_SIZE)
754 			arena->nextoff = arena->size;
755 		else
756 			arena->nextoff = 0;
757 		cur_off += arena_size;
758 		list_add_tail(&arena->list, &btt->arena_list);
759 	}
760 
761 	return 0;
762 }
763 
764 /*
765  * This function completes arena initialization by writing
766  * all the metadata.
767  * It is only called for an uninitialized arena when a write
768  * to that arena occurs for the first time.
769  */
770 static int btt_arena_write_layout(struct arena_info *arena)
771 {
772 	int ret;
773 	u64 sum;
774 	struct btt_sb *super;
775 	struct nd_btt *nd_btt = arena->nd_btt;
776 	const u8 *parent_uuid = nd_dev_to_uuid(&nd_btt->ndns->dev);
777 
778 	ret = btt_map_init(arena);
779 	if (ret)
780 		return ret;
781 
782 	ret = btt_log_init(arena);
783 	if (ret)
784 		return ret;
785 
786 	super = kzalloc(sizeof(struct btt_sb), GFP_NOIO);
787 	if (!super)
788 		return -ENOMEM;
789 
790 	strncpy(super->signature, BTT_SIG, BTT_SIG_LEN);
791 	memcpy(super->uuid, nd_btt->uuid, 16);
792 	memcpy(super->parent_uuid, parent_uuid, 16);
793 	super->flags = cpu_to_le32(arena->flags);
794 	super->version_major = cpu_to_le16(arena->version_major);
795 	super->version_minor = cpu_to_le16(arena->version_minor);
796 	super->external_lbasize = cpu_to_le32(arena->external_lbasize);
797 	super->external_nlba = cpu_to_le32(arena->external_nlba);
798 	super->internal_lbasize = cpu_to_le32(arena->internal_lbasize);
799 	super->internal_nlba = cpu_to_le32(arena->internal_nlba);
800 	super->nfree = cpu_to_le32(arena->nfree);
801 	super->infosize = cpu_to_le32(sizeof(struct btt_sb));
802 	super->nextoff = cpu_to_le64(arena->nextoff);
803 	/*
804 	 * Subtract arena->infooff (arena start) so numbers are relative
805 	 * to 'this' arena
806 	 */
807 	super->dataoff = cpu_to_le64(arena->dataoff - arena->infooff);
808 	super->mapoff = cpu_to_le64(arena->mapoff - arena->infooff);
809 	super->logoff = cpu_to_le64(arena->logoff - arena->infooff);
810 	super->info2off = cpu_to_le64(arena->info2off - arena->infooff);
811 
812 	super->flags = 0;
813 	sum = nd_sb_checksum((struct nd_gen_sb *) super);
814 	super->checksum = cpu_to_le64(sum);
815 
816 	ret = btt_info_write(arena, super);
817 
818 	kfree(super);
819 	return ret;
820 }
821 
822 /*
823  * This function completes the initialization for the BTT namespace
824  * such that it is ready to accept IOs
825  */
826 static int btt_meta_init(struct btt *btt)
827 {
828 	int ret = 0;
829 	struct arena_info *arena;
830 
831 	mutex_lock(&btt->init_lock);
832 	list_for_each_entry(arena, &btt->arena_list, list) {
833 		ret = btt_arena_write_layout(arena);
834 		if (ret)
835 			goto unlock;
836 
837 		ret = btt_freelist_init(arena);
838 		if (ret)
839 			goto unlock;
840 
841 		ret = btt_rtt_init(arena);
842 		if (ret)
843 			goto unlock;
844 
845 		ret = btt_maplocks_init(arena);
846 		if (ret)
847 			goto unlock;
848 	}
849 
850 	btt->init_state = INIT_READY;
851 
852  unlock:
853 	mutex_unlock(&btt->init_lock);
854 	return ret;
855 }
856 
857 static u32 btt_meta_size(struct btt *btt)
858 {
859 	return btt->lbasize - btt->sector_size;
860 }
861 
862 /*
863  * This function calculates the arena in which the given LBA lies
864  * by doing a linear walk. This is acceptable since we expect only
865  * a few arenas. If we have backing devices that get much larger,
866  * we can construct a balanced binary tree of arenas at init time
867  * so that this range search becomes faster.
868  */
869 static int lba_to_arena(struct btt *btt, sector_t sector, __u32 *premap,
870 				struct arena_info **arena)
871 {
872 	struct arena_info *arena_list;
873 	__u64 lba = div_u64(sector << SECTOR_SHIFT, btt->sector_size);
874 
875 	list_for_each_entry(arena_list, &btt->arena_list, list) {
876 		if (lba < arena_list->external_nlba) {
877 			*arena = arena_list;
878 			*premap = lba;
879 			return 0;
880 		}
881 		lba -= arena_list->external_nlba;
882 	}
883 
884 	return -EIO;
885 }
886 
887 /*
888  * The following (lock_map, unlock_map) are mostly just to improve
889  * readability, since they index into an array of locks
890  */
891 static void lock_map(struct arena_info *arena, u32 premap)
892 		__acquires(&arena->map_locks[idx].lock)
893 {
894 	u32 idx = (premap * MAP_ENT_SIZE / L1_CACHE_BYTES) % arena->nfree;
895 
896 	spin_lock(&arena->map_locks[idx].lock);
897 }
898 
899 static void unlock_map(struct arena_info *arena, u32 premap)
900 		__releases(&arena->map_locks[idx].lock)
901 {
902 	u32 idx = (premap * MAP_ENT_SIZE / L1_CACHE_BYTES) % arena->nfree;
903 
904 	spin_unlock(&arena->map_locks[idx].lock);
905 }
906 
907 static u64 to_namespace_offset(struct arena_info *arena, u64 lba)
908 {
909 	return arena->dataoff + ((u64)lba * arena->internal_lbasize);
910 }
911 
912 static int btt_data_read(struct arena_info *arena, struct page *page,
913 			unsigned int off, u32 lba, u32 len)
914 {
915 	int ret;
916 	u64 nsoff = to_namespace_offset(arena, lba);
917 	void *mem = kmap_atomic(page);
918 
919 	ret = arena_read_bytes(arena, nsoff, mem + off, len, NVDIMM_IO_ATOMIC);
920 	kunmap_atomic(mem);
921 
922 	return ret;
923 }
924 
925 static int btt_data_write(struct arena_info *arena, u32 lba,
926 			struct page *page, unsigned int off, u32 len)
927 {
928 	int ret;
929 	u64 nsoff = to_namespace_offset(arena, lba);
930 	void *mem = kmap_atomic(page);
931 
932 	ret = arena_write_bytes(arena, nsoff, mem + off, len, NVDIMM_IO_ATOMIC);
933 	kunmap_atomic(mem);
934 
935 	return ret;
936 }
937 
938 static void zero_fill_data(struct page *page, unsigned int off, u32 len)
939 {
940 	void *mem = kmap_atomic(page);
941 
942 	memset(mem + off, 0, len);
943 	kunmap_atomic(mem);
944 }
945 
946 #ifdef CONFIG_BLK_DEV_INTEGRITY
947 static int btt_rw_integrity(struct btt *btt, struct bio_integrity_payload *bip,
948 			struct arena_info *arena, u32 postmap, int rw)
949 {
950 	unsigned int len = btt_meta_size(btt);
951 	u64 meta_nsoff;
952 	int ret = 0;
953 
954 	if (bip == NULL)
955 		return 0;
956 
957 	meta_nsoff = to_namespace_offset(arena, postmap) + btt->sector_size;
958 
959 	while (len) {
960 		unsigned int cur_len;
961 		struct bio_vec bv;
962 		void *mem;
963 
964 		bv = bvec_iter_bvec(bip->bip_vec, bip->bip_iter);
965 		/*
966 		 * The 'bv' obtained from bvec_iter_bvec has its .bv_len and
967 		 * .bv_offset already adjusted for iter->bi_bvec_done, and we
968 		 * can use those directly
969 		 */
970 
971 		cur_len = min(len, bv.bv_len);
972 		mem = kmap_atomic(bv.bv_page);
973 		if (rw)
974 			ret = arena_write_bytes(arena, meta_nsoff,
975 					mem + bv.bv_offset, cur_len,
976 					NVDIMM_IO_ATOMIC);
977 		else
978 			ret = arena_read_bytes(arena, meta_nsoff,
979 					mem + bv.bv_offset, cur_len,
980 					NVDIMM_IO_ATOMIC);
981 
982 		kunmap_atomic(mem);
983 		if (ret)
984 			return ret;
985 
986 		len -= cur_len;
987 		meta_nsoff += cur_len;
988 		if (!bvec_iter_advance(bip->bip_vec, &bip->bip_iter, cur_len))
989 			return -EIO;
990 	}
991 
992 	return ret;
993 }
994 
995 #else /* CONFIG_BLK_DEV_INTEGRITY */
996 static int btt_rw_integrity(struct btt *btt, struct bio_integrity_payload *bip,
997 			struct arena_info *arena, u32 postmap, int rw)
998 {
999 	return 0;
1000 }
1001 #endif
1002 
1003 static int btt_read_pg(struct btt *btt, struct bio_integrity_payload *bip,
1004 			struct page *page, unsigned int off, sector_t sector,
1005 			unsigned int len)
1006 {
1007 	int ret = 0;
1008 	int t_flag, e_flag;
1009 	struct arena_info *arena = NULL;
1010 	u32 lane = 0, premap, postmap;
1011 
1012 	while (len) {
1013 		u32 cur_len;
1014 
1015 		lane = nd_region_acquire_lane(btt->nd_region);
1016 
1017 		ret = lba_to_arena(btt, sector, &premap, &arena);
1018 		if (ret)
1019 			goto out_lane;
1020 
1021 		cur_len = min(btt->sector_size, len);
1022 
1023 		ret = btt_map_read(arena, premap, &postmap, &t_flag, &e_flag,
1024 				NVDIMM_IO_ATOMIC);
1025 		if (ret)
1026 			goto out_lane;
1027 
1028 		/*
1029 		 * We loop to make sure that the post map LBA didn't change
1030 		 * from under us between writing the RTT and doing the actual
1031 		 * read.
1032 		 */
1033 		while (1) {
1034 			u32 new_map;
1035 
1036 			if (t_flag) {
1037 				zero_fill_data(page, off, cur_len);
1038 				goto out_lane;
1039 			}
1040 
1041 			if (e_flag) {
1042 				ret = -EIO;
1043 				goto out_lane;
1044 			}
1045 
1046 			arena->rtt[lane] = RTT_VALID | postmap;
1047 			/*
1048 			 * Barrier to make sure this write is not reordered
1049 			 * to do the verification map_read before the RTT store
1050 			 */
1051 			barrier();
1052 
1053 			ret = btt_map_read(arena, premap, &new_map, &t_flag,
1054 						&e_flag, NVDIMM_IO_ATOMIC);
1055 			if (ret)
1056 				goto out_rtt;
1057 
1058 			if (postmap == new_map)
1059 				break;
1060 
1061 			postmap = new_map;
1062 		}
1063 
1064 		ret = btt_data_read(arena, page, off, postmap, cur_len);
1065 		if (ret)
1066 			goto out_rtt;
1067 
1068 		if (bip) {
1069 			ret = btt_rw_integrity(btt, bip, arena, postmap, READ);
1070 			if (ret)
1071 				goto out_rtt;
1072 		}
1073 
1074 		arena->rtt[lane] = RTT_INVALID;
1075 		nd_region_release_lane(btt->nd_region, lane);
1076 
1077 		len -= cur_len;
1078 		off += cur_len;
1079 		sector += btt->sector_size >> SECTOR_SHIFT;
1080 	}
1081 
1082 	return 0;
1083 
1084  out_rtt:
1085 	arena->rtt[lane] = RTT_INVALID;
1086  out_lane:
1087 	nd_region_release_lane(btt->nd_region, lane);
1088 	return ret;
1089 }
1090 
1091 static int btt_write_pg(struct btt *btt, struct bio_integrity_payload *bip,
1092 			sector_t sector, struct page *page, unsigned int off,
1093 			unsigned int len)
1094 {
1095 	int ret = 0;
1096 	struct arena_info *arena = NULL;
1097 	u32 premap = 0, old_postmap, new_postmap, lane = 0, i;
1098 	struct log_entry log;
1099 	int sub;
1100 
1101 	while (len) {
1102 		u32 cur_len;
1103 
1104 		lane = nd_region_acquire_lane(btt->nd_region);
1105 
1106 		ret = lba_to_arena(btt, sector, &premap, &arena);
1107 		if (ret)
1108 			goto out_lane;
1109 		cur_len = min(btt->sector_size, len);
1110 
1111 		if ((arena->flags & IB_FLAG_ERROR_MASK) != 0) {
1112 			ret = -EIO;
1113 			goto out_lane;
1114 		}
1115 
1116 		new_postmap = arena->freelist[lane].block;
1117 
1118 		/* Wait if the new block is being read from */
1119 		for (i = 0; i < arena->nfree; i++)
1120 			while (arena->rtt[i] == (RTT_VALID | new_postmap))
1121 				cpu_relax();
1122 
1123 
1124 		if (new_postmap >= arena->internal_nlba) {
1125 			ret = -EIO;
1126 			goto out_lane;
1127 		}
1128 
1129 		ret = btt_data_write(arena, new_postmap, page, off, cur_len);
1130 		if (ret)
1131 			goto out_lane;
1132 
1133 		if (bip) {
1134 			ret = btt_rw_integrity(btt, bip, arena, new_postmap,
1135 						WRITE);
1136 			if (ret)
1137 				goto out_lane;
1138 		}
1139 
1140 		lock_map(arena, premap);
1141 		ret = btt_map_read(arena, premap, &old_postmap, NULL, NULL,
1142 				NVDIMM_IO_ATOMIC);
1143 		if (ret)
1144 			goto out_map;
1145 		if (old_postmap >= arena->internal_nlba) {
1146 			ret = -EIO;
1147 			goto out_map;
1148 		}
1149 
1150 		log.lba = cpu_to_le32(premap);
1151 		log.old_map = cpu_to_le32(old_postmap);
1152 		log.new_map = cpu_to_le32(new_postmap);
1153 		log.seq = cpu_to_le32(arena->freelist[lane].seq);
1154 		sub = arena->freelist[lane].sub;
1155 		ret = btt_flog_write(arena, lane, sub, &log);
1156 		if (ret)
1157 			goto out_map;
1158 
1159 		ret = btt_map_write(arena, premap, new_postmap, 0, 0, 0);
1160 		if (ret)
1161 			goto out_map;
1162 
1163 		unlock_map(arena, premap);
1164 		nd_region_release_lane(btt->nd_region, lane);
1165 
1166 		len -= cur_len;
1167 		off += cur_len;
1168 		sector += btt->sector_size >> SECTOR_SHIFT;
1169 	}
1170 
1171 	return 0;
1172 
1173  out_map:
1174 	unlock_map(arena, premap);
1175  out_lane:
1176 	nd_region_release_lane(btt->nd_region, lane);
1177 	return ret;
1178 }
1179 
1180 static int btt_do_bvec(struct btt *btt, struct bio_integrity_payload *bip,
1181 			struct page *page, unsigned int len, unsigned int off,
1182 			bool is_write, sector_t sector)
1183 {
1184 	int ret;
1185 
1186 	if (!is_write) {
1187 		ret = btt_read_pg(btt, bip, page, off, sector, len);
1188 		flush_dcache_page(page);
1189 	} else {
1190 		flush_dcache_page(page);
1191 		ret = btt_write_pg(btt, bip, sector, page, off, len);
1192 	}
1193 
1194 	return ret;
1195 }
1196 
1197 static blk_qc_t btt_make_request(struct request_queue *q, struct bio *bio)
1198 {
1199 	struct bio_integrity_payload *bip = bio_integrity(bio);
1200 	struct btt *btt = q->queuedata;
1201 	struct bvec_iter iter;
1202 	unsigned long start;
1203 	struct bio_vec bvec;
1204 	int err = 0;
1205 	bool do_acct;
1206 
1207 	if (!bio_integrity_prep(bio))
1208 		return BLK_QC_T_NONE;
1209 
1210 	do_acct = nd_iostat_start(bio, &start);
1211 	bio_for_each_segment(bvec, bio, iter) {
1212 		unsigned int len = bvec.bv_len;
1213 
1214 		BUG_ON(len > PAGE_SIZE);
1215 		/* Make sure len is in multiples of sector size. */
1216 		/* XXX is this right? */
1217 		BUG_ON(len < btt->sector_size);
1218 		BUG_ON(len % btt->sector_size);
1219 
1220 		err = btt_do_bvec(btt, bip, bvec.bv_page, len, bvec.bv_offset,
1221 				  op_is_write(bio_op(bio)), iter.bi_sector);
1222 		if (err) {
1223 			dev_err(&btt->nd_btt->dev,
1224 					"io error in %s sector %lld, len %d,\n",
1225 					(op_is_write(bio_op(bio))) ? "WRITE" :
1226 					"READ",
1227 					(unsigned long long) iter.bi_sector, len);
1228 			bio->bi_status = errno_to_blk_status(err);
1229 			break;
1230 		}
1231 	}
1232 	if (do_acct)
1233 		nd_iostat_end(bio, start);
1234 
1235 	bio_endio(bio);
1236 	return BLK_QC_T_NONE;
1237 }
1238 
1239 static int btt_rw_page(struct block_device *bdev, sector_t sector,
1240 		struct page *page, bool is_write)
1241 {
1242 	struct btt *btt = bdev->bd_disk->private_data;
1243 	int rc;
1244 
1245 	rc = btt_do_bvec(btt, NULL, page, PAGE_SIZE, 0, is_write, sector);
1246 	if (rc == 0)
1247 		page_endio(page, is_write, 0);
1248 
1249 	return rc;
1250 }
1251 
1252 
1253 static int btt_getgeo(struct block_device *bd, struct hd_geometry *geo)
1254 {
1255 	/* some standard values */
1256 	geo->heads = 1 << 6;
1257 	geo->sectors = 1 << 5;
1258 	geo->cylinders = get_capacity(bd->bd_disk) >> 11;
1259 	return 0;
1260 }
1261 
1262 static const struct block_device_operations btt_fops = {
1263 	.owner =		THIS_MODULE,
1264 	.rw_page =		btt_rw_page,
1265 	.getgeo =		btt_getgeo,
1266 	.revalidate_disk =	nvdimm_revalidate_disk,
1267 };
1268 
1269 static int btt_blk_init(struct btt *btt)
1270 {
1271 	struct nd_btt *nd_btt = btt->nd_btt;
1272 	struct nd_namespace_common *ndns = nd_btt->ndns;
1273 
1274 	/* create a new disk and request queue for btt */
1275 	btt->btt_queue = blk_alloc_queue(GFP_KERNEL);
1276 	if (!btt->btt_queue)
1277 		return -ENOMEM;
1278 
1279 	btt->btt_disk = alloc_disk(0);
1280 	if (!btt->btt_disk) {
1281 		blk_cleanup_queue(btt->btt_queue);
1282 		return -ENOMEM;
1283 	}
1284 
1285 	nvdimm_namespace_disk_name(ndns, btt->btt_disk->disk_name);
1286 	btt->btt_disk->first_minor = 0;
1287 	btt->btt_disk->fops = &btt_fops;
1288 	btt->btt_disk->private_data = btt;
1289 	btt->btt_disk->queue = btt->btt_queue;
1290 	btt->btt_disk->flags = GENHD_FL_EXT_DEVT;
1291 
1292 	blk_queue_make_request(btt->btt_queue, btt_make_request);
1293 	blk_queue_logical_block_size(btt->btt_queue, btt->sector_size);
1294 	blk_queue_max_hw_sectors(btt->btt_queue, UINT_MAX);
1295 	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, btt->btt_queue);
1296 	btt->btt_queue->queuedata = btt;
1297 
1298 	set_capacity(btt->btt_disk, 0);
1299 	device_add_disk(&btt->nd_btt->dev, btt->btt_disk);
1300 	if (btt_meta_size(btt)) {
1301 		int rc = nd_integrity_init(btt->btt_disk, btt_meta_size(btt));
1302 
1303 		if (rc) {
1304 			del_gendisk(btt->btt_disk);
1305 			put_disk(btt->btt_disk);
1306 			blk_cleanup_queue(btt->btt_queue);
1307 			return rc;
1308 		}
1309 	}
1310 	set_capacity(btt->btt_disk, btt->nlba * btt->sector_size >> 9);
1311 	btt->nd_btt->size = btt->nlba * (u64)btt->sector_size;
1312 	revalidate_disk(btt->btt_disk);
1313 
1314 	return 0;
1315 }
1316 
1317 static void btt_blk_cleanup(struct btt *btt)
1318 {
1319 	del_gendisk(btt->btt_disk);
1320 	put_disk(btt->btt_disk);
1321 	blk_cleanup_queue(btt->btt_queue);
1322 }
1323 
1324 /**
1325  * btt_init - initialize a block translation table for the given device
1326  * @nd_btt:	device with BTT geometry and backing device info
1327  * @rawsize:	raw size in bytes of the backing device
1328  * @lbasize:	lba size of the backing device
1329  * @uuid:	A uuid for the backing device - this is stored on media
1330  * @maxlane:	maximum number of parallel requests the device can handle
1331  *
1332  * Initialize a Block Translation Table on a backing device to provide
1333  * single sector power fail atomicity.
1334  *
1335  * Context:
1336  * Might sleep.
1337  *
1338  * Returns:
1339  * Pointer to a new struct btt on success, NULL on failure.
1340  */
1341 static struct btt *btt_init(struct nd_btt *nd_btt, unsigned long long rawsize,
1342 		u32 lbasize, u8 *uuid, struct nd_region *nd_region)
1343 {
1344 	int ret;
1345 	struct btt *btt;
1346 	struct device *dev = &nd_btt->dev;
1347 
1348 	btt = devm_kzalloc(dev, sizeof(struct btt), GFP_KERNEL);
1349 	if (!btt)
1350 		return NULL;
1351 
1352 	btt->nd_btt = nd_btt;
1353 	btt->rawsize = rawsize;
1354 	btt->lbasize = lbasize;
1355 	btt->sector_size = ((lbasize >= 4096) ? 4096 : 512);
1356 	INIT_LIST_HEAD(&btt->arena_list);
1357 	mutex_init(&btt->init_lock);
1358 	btt->nd_region = nd_region;
1359 
1360 	ret = discover_arenas(btt);
1361 	if (ret) {
1362 		dev_err(dev, "init: error in arena_discover: %d\n", ret);
1363 		return NULL;
1364 	}
1365 
1366 	if (btt->init_state != INIT_READY && nd_region->ro) {
1367 		dev_warn(dev, "%s is read-only, unable to init btt metadata\n",
1368 				dev_name(&nd_region->dev));
1369 		return NULL;
1370 	} else if (btt->init_state != INIT_READY) {
1371 		btt->num_arenas = (rawsize / ARENA_MAX_SIZE) +
1372 			((rawsize % ARENA_MAX_SIZE) ? 1 : 0);
1373 		dev_dbg(dev, "init: %d arenas for %llu rawsize\n",
1374 				btt->num_arenas, rawsize);
1375 
1376 		ret = create_arenas(btt);
1377 		if (ret) {
1378 			dev_info(dev, "init: create_arenas: %d\n", ret);
1379 			return NULL;
1380 		}
1381 
1382 		ret = btt_meta_init(btt);
1383 		if (ret) {
1384 			dev_err(dev, "init: error in meta_init: %d\n", ret);
1385 			return NULL;
1386 		}
1387 	}
1388 
1389 	ret = btt_blk_init(btt);
1390 	if (ret) {
1391 		dev_err(dev, "init: error in blk_init: %d\n", ret);
1392 		return NULL;
1393 	}
1394 
1395 	btt_debugfs_init(btt);
1396 
1397 	return btt;
1398 }
1399 
1400 /**
1401  * btt_fini - de-initialize a BTT
1402  * @btt:	the BTT handle that was generated by btt_init
1403  *
1404  * De-initialize a Block Translation Table on device removal
1405  *
1406  * Context:
1407  * Might sleep.
1408  */
1409 static void btt_fini(struct btt *btt)
1410 {
1411 	if (btt) {
1412 		btt_blk_cleanup(btt);
1413 		free_arenas(btt);
1414 		debugfs_remove_recursive(btt->debugfs_dir);
1415 	}
1416 }
1417 
1418 int nvdimm_namespace_attach_btt(struct nd_namespace_common *ndns)
1419 {
1420 	struct nd_btt *nd_btt = to_nd_btt(ndns->claim);
1421 	struct nd_region *nd_region;
1422 	struct btt_sb *btt_sb;
1423 	struct btt *btt;
1424 	size_t rawsize;
1425 
1426 	if (!nd_btt->uuid || !nd_btt->ndns || !nd_btt->lbasize) {
1427 		dev_dbg(&nd_btt->dev, "incomplete btt configuration\n");
1428 		return -ENODEV;
1429 	}
1430 
1431 	btt_sb = devm_kzalloc(&nd_btt->dev, sizeof(*btt_sb), GFP_KERNEL);
1432 
1433 	/*
1434 	 * If this returns < 0, that is ok as it just means there wasn't
1435 	 * an existing BTT, and we're creating a new one. We still need to
1436 	 * call this as we need the version dependent fields in nd_btt to be
1437 	 * set correctly based on the holder class
1438 	 */
1439 	nd_btt_version(nd_btt, ndns, btt_sb);
1440 
1441 	rawsize = nvdimm_namespace_capacity(ndns) - nd_btt->initial_offset;
1442 	if (rawsize < ARENA_MIN_SIZE) {
1443 		dev_dbg(&nd_btt->dev, "%s must be at least %ld bytes\n",
1444 				dev_name(&ndns->dev),
1445 				ARENA_MIN_SIZE + nd_btt->initial_offset);
1446 		return -ENXIO;
1447 	}
1448 	nd_region = to_nd_region(nd_btt->dev.parent);
1449 	btt = btt_init(nd_btt, rawsize, nd_btt->lbasize, nd_btt->uuid,
1450 			nd_region);
1451 	if (!btt)
1452 		return -ENOMEM;
1453 	nd_btt->btt = btt;
1454 
1455 	return 0;
1456 }
1457 EXPORT_SYMBOL(nvdimm_namespace_attach_btt);
1458 
1459 int nvdimm_namespace_detach_btt(struct nd_btt *nd_btt)
1460 {
1461 	struct btt *btt = nd_btt->btt;
1462 
1463 	btt_fini(btt);
1464 	nd_btt->btt = NULL;
1465 
1466 	return 0;
1467 }
1468 EXPORT_SYMBOL(nvdimm_namespace_detach_btt);
1469 
1470 static int __init nd_btt_init(void)
1471 {
1472 	int rc = 0;
1473 
1474 	debugfs_root = debugfs_create_dir("btt", NULL);
1475 	if (IS_ERR_OR_NULL(debugfs_root))
1476 		rc = -ENXIO;
1477 
1478 	return rc;
1479 }
1480 
1481 static void __exit nd_btt_exit(void)
1482 {
1483 	debugfs_remove_recursive(debugfs_root);
1484 }
1485 
1486 MODULE_ALIAS_ND_DEVICE(ND_DEVICE_BTT);
1487 MODULE_AUTHOR("Vishal Verma <vishal.l.verma@linux.intel.com>");
1488 MODULE_LICENSE("GPL v2");
1489 module_init(nd_btt_init);
1490 module_exit(nd_btt_exit);
1491