xref: /openbmc/linux/drivers/md/dm-log.c (revision f42b3800)
1 /*
2  * Copyright (C) 2003 Sistina Software
3  *
4  * This file is released under the LGPL.
5  */
6 
7 #include <linux/init.h>
8 #include <linux/slab.h>
9 #include <linux/module.h>
10 #include <linux/vmalloc.h>
11 
12 #include "dm-log.h"
13 #include "dm-io.h"
14 
15 #define DM_MSG_PREFIX "mirror log"
16 
17 static LIST_HEAD(_log_types);
18 static DEFINE_SPINLOCK(_lock);
19 
20 int dm_register_dirty_log_type(struct dirty_log_type *type)
21 {
22 	spin_lock(&_lock);
23 	type->use_count = 0;
24 	list_add(&type->list, &_log_types);
25 	spin_unlock(&_lock);
26 
27 	return 0;
28 }
29 
30 int dm_unregister_dirty_log_type(struct dirty_log_type *type)
31 {
32 	spin_lock(&_lock);
33 
34 	if (type->use_count)
35 		DMWARN("Attempt to unregister a log type that is still in use");
36 	else
37 		list_del(&type->list);
38 
39 	spin_unlock(&_lock);
40 
41 	return 0;
42 }
43 
44 static struct dirty_log_type *_get_type(const char *type_name)
45 {
46 	struct dirty_log_type *type;
47 
48 	spin_lock(&_lock);
49 	list_for_each_entry (type, &_log_types, list)
50 		if (!strcmp(type_name, type->name)) {
51 			if (!type->use_count && !try_module_get(type->module)){
52 				spin_unlock(&_lock);
53 				return NULL;
54 			}
55 			type->use_count++;
56 			spin_unlock(&_lock);
57 			return type;
58 		}
59 
60 	spin_unlock(&_lock);
61 	return NULL;
62 }
63 
64 /*
65  * get_type
66  * @type_name
67  *
68  * Attempt to retrieve the dirty_log_type by name.  If not already
69  * available, attempt to load the appropriate module.
70  *
71  * Log modules are named "dm-log-" followed by the 'type_name'.
72  * Modules may contain multiple types.
73  * This function will first try the module "dm-log-<type_name>",
74  * then truncate 'type_name' on the last '-' and try again.
75  *
76  * For example, if type_name was "clustered-disk", it would search
77  * 'dm-log-clustered-disk' then 'dm-log-clustered'.
78  *
79  * Returns: dirty_log_type* on success, NULL on failure
80  */
81 static struct dirty_log_type *get_type(const char *type_name)
82 {
83 	char *p, *type_name_dup;
84 	struct dirty_log_type *type;
85 
86 	type = _get_type(type_name);
87 	if (type)
88 		return type;
89 
90 	type_name_dup = kstrdup(type_name, GFP_KERNEL);
91 	if (!type_name_dup) {
92 		DMWARN("No memory left to attempt log module load for \"%s\"",
93 		       type_name);
94 		return NULL;
95 	}
96 
97 	while (request_module("dm-log-%s", type_name_dup) ||
98 	       !(type = _get_type(type_name))) {
99 		p = strrchr(type_name_dup, '-');
100 		if (!p)
101 			break;
102 		p[0] = '\0';
103 	}
104 
105 	if (!type)
106 		DMWARN("Module for logging type \"%s\" not found.", type_name);
107 
108 	kfree(type_name_dup);
109 
110 	return type;
111 }
112 
113 static void put_type(struct dirty_log_type *type)
114 {
115 	spin_lock(&_lock);
116 	if (!--type->use_count)
117 		module_put(type->module);
118 	spin_unlock(&_lock);
119 }
120 
121 struct dirty_log *dm_create_dirty_log(const char *type_name, struct dm_target *ti,
122 				      unsigned int argc, char **argv)
123 {
124 	struct dirty_log_type *type;
125 	struct dirty_log *log;
126 
127 	log = kmalloc(sizeof(*log), GFP_KERNEL);
128 	if (!log)
129 		return NULL;
130 
131 	type = get_type(type_name);
132 	if (!type) {
133 		kfree(log);
134 		return NULL;
135 	}
136 
137 	log->type = type;
138 	if (type->ctr(log, ti, argc, argv)) {
139 		kfree(log);
140 		put_type(type);
141 		return NULL;
142 	}
143 
144 	return log;
145 }
146 
147 void dm_destroy_dirty_log(struct dirty_log *log)
148 {
149 	log->type->dtr(log);
150 	put_type(log->type);
151 	kfree(log);
152 }
153 
154 /*-----------------------------------------------------------------
155  * Persistent and core logs share a lot of their implementation.
156  * FIXME: need a reload method to be called from a resume
157  *---------------------------------------------------------------*/
158 /*
159  * Magic for persistent mirrors: "MiRr"
160  */
161 #define MIRROR_MAGIC 0x4D695272
162 
163 /*
164  * The on-disk version of the metadata.
165  */
166 #define MIRROR_DISK_VERSION 2
167 #define LOG_OFFSET 2
168 
169 struct log_header {
170 	uint32_t magic;
171 
172 	/*
173 	 * Simple, incrementing version. no backward
174 	 * compatibility.
175 	 */
176 	uint32_t version;
177 	sector_t nr_regions;
178 };
179 
180 struct log_c {
181 	struct dm_target *ti;
182 	int touched;
183 	uint32_t region_size;
184 	unsigned int region_count;
185 	region_t sync_count;
186 
187 	unsigned bitset_uint32_count;
188 	uint32_t *clean_bits;
189 	uint32_t *sync_bits;
190 	uint32_t *recovering_bits;	/* FIXME: this seems excessive */
191 
192 	int sync_search;
193 
194 	/* Resync flag */
195 	enum sync {
196 		DEFAULTSYNC,	/* Synchronize if necessary */
197 		NOSYNC,		/* Devices known to be already in sync */
198 		FORCESYNC,	/* Force a sync to happen */
199 	} sync;
200 
201 	struct dm_io_request io_req;
202 
203 	/*
204 	 * Disk log fields
205 	 */
206 	int log_dev_failed;
207 	struct dm_dev *log_dev;
208 	struct log_header header;
209 
210 	struct io_region header_location;
211 	struct log_header *disk_header;
212 };
213 
214 /*
215  * The touched member needs to be updated every time we access
216  * one of the bitsets.
217  */
218 static  inline int log_test_bit(uint32_t *bs, unsigned bit)
219 {
220 	return ext2_test_bit(bit, (unsigned long *) bs) ? 1 : 0;
221 }
222 
223 static inline void log_set_bit(struct log_c *l,
224 			       uint32_t *bs, unsigned bit)
225 {
226 	ext2_set_bit(bit, (unsigned long *) bs);
227 	l->touched = 1;
228 }
229 
230 static inline void log_clear_bit(struct log_c *l,
231 				 uint32_t *bs, unsigned bit)
232 {
233 	ext2_clear_bit(bit, (unsigned long *) bs);
234 	l->touched = 1;
235 }
236 
237 /*----------------------------------------------------------------
238  * Header IO
239  *--------------------------------------------------------------*/
240 static void header_to_disk(struct log_header *core, struct log_header *disk)
241 {
242 	disk->magic = cpu_to_le32(core->magic);
243 	disk->version = cpu_to_le32(core->version);
244 	disk->nr_regions = cpu_to_le64(core->nr_regions);
245 }
246 
247 static void header_from_disk(struct log_header *core, struct log_header *disk)
248 {
249 	core->magic = le32_to_cpu(disk->magic);
250 	core->version = le32_to_cpu(disk->version);
251 	core->nr_regions = le64_to_cpu(disk->nr_regions);
252 }
253 
254 static int rw_header(struct log_c *lc, int rw)
255 {
256 	lc->io_req.bi_rw = rw;
257 	lc->io_req.mem.ptr.vma = lc->disk_header;
258 	lc->io_req.notify.fn = NULL;
259 
260 	return dm_io(&lc->io_req, 1, &lc->header_location, NULL);
261 }
262 
263 static int read_header(struct log_c *log)
264 {
265 	int r;
266 
267 	r = rw_header(log, READ);
268 	if (r)
269 		return r;
270 
271 	header_from_disk(&log->header, log->disk_header);
272 
273 	/* New log required? */
274 	if (log->sync != DEFAULTSYNC || log->header.magic != MIRROR_MAGIC) {
275 		log->header.magic = MIRROR_MAGIC;
276 		log->header.version = MIRROR_DISK_VERSION;
277 		log->header.nr_regions = 0;
278 	}
279 
280 #ifdef __LITTLE_ENDIAN
281 	if (log->header.version == 1)
282 		log->header.version = 2;
283 #endif
284 
285 	if (log->header.version != MIRROR_DISK_VERSION) {
286 		DMWARN("incompatible disk log version");
287 		return -EINVAL;
288 	}
289 
290 	return 0;
291 }
292 
293 static inline int write_header(struct log_c *log)
294 {
295 	header_to_disk(&log->header, log->disk_header);
296 	return rw_header(log, WRITE);
297 }
298 
299 /*----------------------------------------------------------------
300  * core log constructor/destructor
301  *
302  * argv contains region_size followed optionally by [no]sync
303  *--------------------------------------------------------------*/
304 #define BYTE_SHIFT 3
305 static int create_log_context(struct dirty_log *log, struct dm_target *ti,
306 			      unsigned int argc, char **argv,
307 			      struct dm_dev *dev)
308 {
309 	enum sync sync = DEFAULTSYNC;
310 
311 	struct log_c *lc;
312 	uint32_t region_size;
313 	unsigned int region_count;
314 	size_t bitset_size, buf_size;
315 	int r;
316 
317 	if (argc < 1 || argc > 2) {
318 		DMWARN("wrong number of arguments to mirror log");
319 		return -EINVAL;
320 	}
321 
322 	if (argc > 1) {
323 		if (!strcmp(argv[1], "sync"))
324 			sync = FORCESYNC;
325 		else if (!strcmp(argv[1], "nosync"))
326 			sync = NOSYNC;
327 		else {
328 			DMWARN("unrecognised sync argument to mirror log: %s",
329 			       argv[1]);
330 			return -EINVAL;
331 		}
332 	}
333 
334 	if (sscanf(argv[0], "%u", &region_size) != 1) {
335 		DMWARN("invalid region size string");
336 		return -EINVAL;
337 	}
338 
339 	region_count = dm_sector_div_up(ti->len, region_size);
340 
341 	lc = kmalloc(sizeof(*lc), GFP_KERNEL);
342 	if (!lc) {
343 		DMWARN("couldn't allocate core log");
344 		return -ENOMEM;
345 	}
346 
347 	lc->ti = ti;
348 	lc->touched = 0;
349 	lc->region_size = region_size;
350 	lc->region_count = region_count;
351 	lc->sync = sync;
352 
353 	/*
354 	 * Work out how many "unsigned long"s we need to hold the bitset.
355 	 */
356 	bitset_size = dm_round_up(region_count,
357 				  sizeof(*lc->clean_bits) << BYTE_SHIFT);
358 	bitset_size >>= BYTE_SHIFT;
359 
360 	lc->bitset_uint32_count = bitset_size / sizeof(*lc->clean_bits);
361 
362 	/*
363 	 * Disk log?
364 	 */
365 	if (!dev) {
366 		lc->clean_bits = vmalloc(bitset_size);
367 		if (!lc->clean_bits) {
368 			DMWARN("couldn't allocate clean bitset");
369 			kfree(lc);
370 			return -ENOMEM;
371 		}
372 		lc->disk_header = NULL;
373 	} else {
374 		lc->log_dev = dev;
375 		lc->log_dev_failed = 0;
376 		lc->header_location.bdev = lc->log_dev->bdev;
377 		lc->header_location.sector = 0;
378 
379 		/*
380 		 * Buffer holds both header and bitset.
381 		 */
382 		buf_size = dm_round_up((LOG_OFFSET << SECTOR_SHIFT) +
383 				       bitset_size, ti->limits.hardsect_size);
384 		lc->header_location.count = buf_size >> SECTOR_SHIFT;
385 		lc->io_req.mem.type = DM_IO_VMA;
386 		lc->io_req.client = dm_io_client_create(dm_div_up(buf_size,
387 								   PAGE_SIZE));
388 		if (IS_ERR(lc->io_req.client)) {
389 			r = PTR_ERR(lc->io_req.client);
390 			DMWARN("couldn't allocate disk io client");
391 			kfree(lc);
392 			return -ENOMEM;
393 		}
394 
395 		lc->disk_header = vmalloc(buf_size);
396 		if (!lc->disk_header) {
397 			DMWARN("couldn't allocate disk log buffer");
398 			kfree(lc);
399 			return -ENOMEM;
400 		}
401 
402 		lc->clean_bits = (void *)lc->disk_header +
403 				 (LOG_OFFSET << SECTOR_SHIFT);
404 	}
405 
406 	memset(lc->clean_bits, -1, bitset_size);
407 
408 	lc->sync_bits = vmalloc(bitset_size);
409 	if (!lc->sync_bits) {
410 		DMWARN("couldn't allocate sync bitset");
411 		if (!dev)
412 			vfree(lc->clean_bits);
413 		vfree(lc->disk_header);
414 		kfree(lc);
415 		return -ENOMEM;
416 	}
417 	memset(lc->sync_bits, (sync == NOSYNC) ? -1 : 0, bitset_size);
418 	lc->sync_count = (sync == NOSYNC) ? region_count : 0;
419 
420 	lc->recovering_bits = vmalloc(bitset_size);
421 	if (!lc->recovering_bits) {
422 		DMWARN("couldn't allocate sync bitset");
423 		vfree(lc->sync_bits);
424 		if (!dev)
425 			vfree(lc->clean_bits);
426 		vfree(lc->disk_header);
427 		kfree(lc);
428 		return -ENOMEM;
429 	}
430 	memset(lc->recovering_bits, 0, bitset_size);
431 	lc->sync_search = 0;
432 	log->context = lc;
433 
434 	return 0;
435 }
436 
437 static int core_ctr(struct dirty_log *log, struct dm_target *ti,
438 		    unsigned int argc, char **argv)
439 {
440 	return create_log_context(log, ti, argc, argv, NULL);
441 }
442 
443 static void destroy_log_context(struct log_c *lc)
444 {
445 	vfree(lc->sync_bits);
446 	vfree(lc->recovering_bits);
447 	kfree(lc);
448 }
449 
450 static void core_dtr(struct dirty_log *log)
451 {
452 	struct log_c *lc = (struct log_c *) log->context;
453 
454 	vfree(lc->clean_bits);
455 	destroy_log_context(lc);
456 }
457 
458 /*----------------------------------------------------------------
459  * disk log constructor/destructor
460  *
461  * argv contains log_device region_size followed optionally by [no]sync
462  *--------------------------------------------------------------*/
463 static int disk_ctr(struct dirty_log *log, struct dm_target *ti,
464 		    unsigned int argc, char **argv)
465 {
466 	int r;
467 	struct dm_dev *dev;
468 
469 	if (argc < 2 || argc > 3) {
470 		DMWARN("wrong number of arguments to disk mirror log");
471 		return -EINVAL;
472 	}
473 
474 	r = dm_get_device(ti, argv[0], 0, 0 /* FIXME */,
475 			  FMODE_READ | FMODE_WRITE, &dev);
476 	if (r)
477 		return r;
478 
479 	r = create_log_context(log, ti, argc - 1, argv + 1, dev);
480 	if (r) {
481 		dm_put_device(ti, dev);
482 		return r;
483 	}
484 
485 	return 0;
486 }
487 
488 static void disk_dtr(struct dirty_log *log)
489 {
490 	struct log_c *lc = (struct log_c *) log->context;
491 
492 	dm_put_device(lc->ti, lc->log_dev);
493 	vfree(lc->disk_header);
494 	dm_io_client_destroy(lc->io_req.client);
495 	destroy_log_context(lc);
496 }
497 
498 static int count_bits32(uint32_t *addr, unsigned size)
499 {
500 	int count = 0, i;
501 
502 	for (i = 0; i < size; i++) {
503 		count += hweight32(*(addr+i));
504 	}
505 	return count;
506 }
507 
508 static void fail_log_device(struct log_c *lc)
509 {
510 	if (lc->log_dev_failed)
511 		return;
512 
513 	lc->log_dev_failed = 1;
514 	dm_table_event(lc->ti->table);
515 }
516 
517 static int disk_resume(struct dirty_log *log)
518 {
519 	int r;
520 	unsigned i;
521 	struct log_c *lc = (struct log_c *) log->context;
522 	size_t size = lc->bitset_uint32_count * sizeof(uint32_t);
523 
524 	/* read the disk header */
525 	r = read_header(lc);
526 	if (r) {
527 		DMWARN("%s: Failed to read header on mirror log device",
528 		       lc->log_dev->name);
529 		fail_log_device(lc);
530 		/*
531 		 * If the log device cannot be read, we must assume
532 		 * all regions are out-of-sync.  If we simply return
533 		 * here, the state will be uninitialized and could
534 		 * lead us to return 'in-sync' status for regions
535 		 * that are actually 'out-of-sync'.
536 		 */
537 		lc->header.nr_regions = 0;
538 	}
539 
540 	/* set or clear any new bits -- device has grown */
541 	if (lc->sync == NOSYNC)
542 		for (i = lc->header.nr_regions; i < lc->region_count; i++)
543 			/* FIXME: amazingly inefficient */
544 			log_set_bit(lc, lc->clean_bits, i);
545 	else
546 		for (i = lc->header.nr_regions; i < lc->region_count; i++)
547 			/* FIXME: amazingly inefficient */
548 			log_clear_bit(lc, lc->clean_bits, i);
549 
550 	/* clear any old bits -- device has shrunk */
551 	for (i = lc->region_count; i % (sizeof(*lc->clean_bits) << BYTE_SHIFT); i++)
552 		log_clear_bit(lc, lc->clean_bits, i);
553 
554 	/* copy clean across to sync */
555 	memcpy(lc->sync_bits, lc->clean_bits, size);
556 	lc->sync_count = count_bits32(lc->clean_bits, lc->bitset_uint32_count);
557 	lc->sync_search = 0;
558 
559 	/* set the correct number of regions in the header */
560 	lc->header.nr_regions = lc->region_count;
561 
562 	/* write the new header */
563 	r = write_header(lc);
564 	if (r) {
565 		DMWARN("%s: Failed to write header on mirror log device",
566 		       lc->log_dev->name);
567 		fail_log_device(lc);
568 	}
569 
570 	return r;
571 }
572 
573 static uint32_t core_get_region_size(struct dirty_log *log)
574 {
575 	struct log_c *lc = (struct log_c *) log->context;
576 	return lc->region_size;
577 }
578 
579 static int core_resume(struct dirty_log *log)
580 {
581 	struct log_c *lc = (struct log_c *) log->context;
582 	lc->sync_search = 0;
583 	return 0;
584 }
585 
586 static int core_is_clean(struct dirty_log *log, region_t region)
587 {
588 	struct log_c *lc = (struct log_c *) log->context;
589 	return log_test_bit(lc->clean_bits, region);
590 }
591 
592 static int core_in_sync(struct dirty_log *log, region_t region, int block)
593 {
594 	struct log_c *lc = (struct log_c *) log->context;
595 	return log_test_bit(lc->sync_bits, region);
596 }
597 
598 static int core_flush(struct dirty_log *log)
599 {
600 	/* no op */
601 	return 0;
602 }
603 
604 static int disk_flush(struct dirty_log *log)
605 {
606 	int r;
607 	struct log_c *lc = (struct log_c *) log->context;
608 
609 	/* only write if the log has changed */
610 	if (!lc->touched)
611 		return 0;
612 
613 	r = write_header(lc);
614 	if (r)
615 		fail_log_device(lc);
616 	else
617 		lc->touched = 0;
618 
619 	return r;
620 }
621 
622 static void core_mark_region(struct dirty_log *log, region_t region)
623 {
624 	struct log_c *lc = (struct log_c *) log->context;
625 	log_clear_bit(lc, lc->clean_bits, region);
626 }
627 
628 static void core_clear_region(struct dirty_log *log, region_t region)
629 {
630 	struct log_c *lc = (struct log_c *) log->context;
631 	log_set_bit(lc, lc->clean_bits, region);
632 }
633 
634 static int core_get_resync_work(struct dirty_log *log, region_t *region)
635 {
636 	struct log_c *lc = (struct log_c *) log->context;
637 
638 	if (lc->sync_search >= lc->region_count)
639 		return 0;
640 
641 	do {
642 		*region = ext2_find_next_zero_bit(
643 					     (unsigned long *) lc->sync_bits,
644 					     lc->region_count,
645 					     lc->sync_search);
646 		lc->sync_search = *region + 1;
647 
648 		if (*region >= lc->region_count)
649 			return 0;
650 
651 	} while (log_test_bit(lc->recovering_bits, *region));
652 
653 	log_set_bit(lc, lc->recovering_bits, *region);
654 	return 1;
655 }
656 
657 static void core_set_region_sync(struct dirty_log *log, region_t region,
658 				 int in_sync)
659 {
660 	struct log_c *lc = (struct log_c *) log->context;
661 
662 	log_clear_bit(lc, lc->recovering_bits, region);
663 	if (in_sync) {
664 		log_set_bit(lc, lc->sync_bits, region);
665                 lc->sync_count++;
666         } else if (log_test_bit(lc->sync_bits, region)) {
667 		lc->sync_count--;
668 		log_clear_bit(lc, lc->sync_bits, region);
669 	}
670 }
671 
672 static region_t core_get_sync_count(struct dirty_log *log)
673 {
674         struct log_c *lc = (struct log_c *) log->context;
675 
676         return lc->sync_count;
677 }
678 
679 #define	DMEMIT_SYNC \
680 	if (lc->sync != DEFAULTSYNC) \
681 		DMEMIT("%ssync ", lc->sync == NOSYNC ? "no" : "")
682 
683 static int core_status(struct dirty_log *log, status_type_t status,
684 		       char *result, unsigned int maxlen)
685 {
686 	int sz = 0;
687 	struct log_c *lc = log->context;
688 
689 	switch(status) {
690 	case STATUSTYPE_INFO:
691 		DMEMIT("1 %s", log->type->name);
692 		break;
693 
694 	case STATUSTYPE_TABLE:
695 		DMEMIT("%s %u %u ", log->type->name,
696 		       lc->sync == DEFAULTSYNC ? 1 : 2, lc->region_size);
697 		DMEMIT_SYNC;
698 	}
699 
700 	return sz;
701 }
702 
703 static int disk_status(struct dirty_log *log, status_type_t status,
704 		       char *result, unsigned int maxlen)
705 {
706 	int sz = 0;
707 	struct log_c *lc = log->context;
708 
709 	switch(status) {
710 	case STATUSTYPE_INFO:
711 		DMEMIT("3 %s %s %c", log->type->name, lc->log_dev->name,
712 		       lc->log_dev_failed ? 'D' : 'A');
713 		break;
714 
715 	case STATUSTYPE_TABLE:
716 		DMEMIT("%s %u %s %u ", log->type->name,
717 		       lc->sync == DEFAULTSYNC ? 2 : 3, lc->log_dev->name,
718 		       lc->region_size);
719 		DMEMIT_SYNC;
720 	}
721 
722 	return sz;
723 }
724 
725 static struct dirty_log_type _core_type = {
726 	.name = "core",
727 	.module = THIS_MODULE,
728 	.ctr = core_ctr,
729 	.dtr = core_dtr,
730 	.resume = core_resume,
731 	.get_region_size = core_get_region_size,
732 	.is_clean = core_is_clean,
733 	.in_sync = core_in_sync,
734 	.flush = core_flush,
735 	.mark_region = core_mark_region,
736 	.clear_region = core_clear_region,
737 	.get_resync_work = core_get_resync_work,
738 	.set_region_sync = core_set_region_sync,
739 	.get_sync_count = core_get_sync_count,
740 	.status = core_status,
741 };
742 
743 static struct dirty_log_type _disk_type = {
744 	.name = "disk",
745 	.module = THIS_MODULE,
746 	.ctr = disk_ctr,
747 	.dtr = disk_dtr,
748 	.postsuspend = disk_flush,
749 	.resume = disk_resume,
750 	.get_region_size = core_get_region_size,
751 	.is_clean = core_is_clean,
752 	.in_sync = core_in_sync,
753 	.flush = disk_flush,
754 	.mark_region = core_mark_region,
755 	.clear_region = core_clear_region,
756 	.get_resync_work = core_get_resync_work,
757 	.set_region_sync = core_set_region_sync,
758 	.get_sync_count = core_get_sync_count,
759 	.status = disk_status,
760 };
761 
762 int __init dm_dirty_log_init(void)
763 {
764 	int r;
765 
766 	r = dm_register_dirty_log_type(&_core_type);
767 	if (r)
768 		DMWARN("couldn't register core log");
769 
770 	r = dm_register_dirty_log_type(&_disk_type);
771 	if (r) {
772 		DMWARN("couldn't register disk type");
773 		dm_unregister_dirty_log_type(&_core_type);
774 	}
775 
776 	return r;
777 }
778 
779 void dm_dirty_log_exit(void)
780 {
781 	dm_unregister_dirty_log_type(&_disk_type);
782 	dm_unregister_dirty_log_type(&_core_type);
783 }
784 
785 EXPORT_SYMBOL(dm_register_dirty_log_type);
786 EXPORT_SYMBOL(dm_unregister_dirty_log_type);
787 EXPORT_SYMBOL(dm_create_dirty_log);
788 EXPORT_SYMBOL(dm_destroy_dirty_log);
789