dm log: clean interface
[linux-2.6.git] / drivers / md / dm-log.c
1 /*
2  * Copyright (C) 2003 Sistina Software
3  * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
4  *
5  * This file is released under the LGPL.
6  */
7
8 #include <linux/init.h>
9 #include <linux/slab.h>
10 #include <linux/module.h>
11 #include <linux/vmalloc.h>
12
13 #include "dm-log.h"
14 #include "dm-io.h"
15 #include "dm.h"
16
17 #define DM_MSG_PREFIX "dirty region log"
18
19 static LIST_HEAD(_log_types);
20 static DEFINE_SPINLOCK(_lock);
21
22 int dm_dirty_log_type_register(struct dm_dirty_log_type *type)
23 {
24         spin_lock(&_lock);
25         type->use_count = 0;
26         list_add(&type->list, &_log_types);
27         spin_unlock(&_lock);
28
29         return 0;
30 }
31 EXPORT_SYMBOL(dm_dirty_log_type_register);
32
33 int dm_dirty_log_type_unregister(struct dm_dirty_log_type *type)
34 {
35         spin_lock(&_lock);
36
37         if (type->use_count)
38                 DMWARN("Attempt to unregister a log type that is still in use");
39         else
40                 list_del(&type->list);
41
42         spin_unlock(&_lock);
43
44         return 0;
45 }
46 EXPORT_SYMBOL(dm_dirty_log_type_unregister);
47
48 static struct dm_dirty_log_type *_get_type(const char *type_name)
49 {
50         struct dm_dirty_log_type *type;
51
52         spin_lock(&_lock);
53         list_for_each_entry (type, &_log_types, list)
54                 if (!strcmp(type_name, type->name)) {
55                         if (!type->use_count && !try_module_get(type->module)){
56                                 spin_unlock(&_lock);
57                                 return NULL;
58                         }
59                         type->use_count++;
60                         spin_unlock(&_lock);
61                         return type;
62                 }
63
64         spin_unlock(&_lock);
65         return NULL;
66 }
67
68 /*
69  * get_type
70  * @type_name
71  *
72  * Attempt to retrieve the dirty_log_type by name.  If not already
73  * available, attempt to load the appropriate module.
74  *
75  * Log modules are named "dm-log-" followed by the 'type_name'.
76  * Modules may contain multiple types.
77  * This function will first try the module "dm-log-<type_name>",
78  * then truncate 'type_name' on the last '-' and try again.
79  *
80  * For example, if type_name was "clustered-disk", it would search
81  * 'dm-log-clustered-disk' then 'dm-log-clustered'.
82  *
83  * Returns: dirty_log_type* on success, NULL on failure
84  */
85 static struct dm_dirty_log_type *get_type(const char *type_name)
86 {
87         char *p, *type_name_dup;
88         struct dm_dirty_log_type *type;
89
90         type = _get_type(type_name);
91         if (type)
92                 return type;
93
94         type_name_dup = kstrdup(type_name, GFP_KERNEL);
95         if (!type_name_dup) {
96                 DMWARN("No memory left to attempt log module load for \"%s\"",
97                        type_name);
98                 return NULL;
99         }
100
101         while (request_module("dm-log-%s", type_name_dup) ||
102                !(type = _get_type(type_name))) {
103                 p = strrchr(type_name_dup, '-');
104                 if (!p)
105                         break;
106                 p[0] = '\0';
107         }
108
109         if (!type)
110                 DMWARN("Module for logging type \"%s\" not found.", type_name);
111
112         kfree(type_name_dup);
113
114         return type;
115 }
116
117 static void put_type(struct dm_dirty_log_type *type)
118 {
119         spin_lock(&_lock);
120         if (!--type->use_count)
121                 module_put(type->module);
122         spin_unlock(&_lock);
123 }
124
125 struct dm_dirty_log *dm_dirty_log_create(const char *type_name,
126                                          struct dm_target *ti,
127                                          unsigned int argc, char **argv)
128 {
129         struct dm_dirty_log_type *type;
130         struct dm_dirty_log *log;
131
132         log = kmalloc(sizeof(*log), GFP_KERNEL);
133         if (!log)
134                 return NULL;
135
136         type = get_type(type_name);
137         if (!type) {
138                 kfree(log);
139                 return NULL;
140         }
141
142         log->type = type;
143         if (type->ctr(log, ti, argc, argv)) {
144                 kfree(log);
145                 put_type(type);
146                 return NULL;
147         }
148
149         return log;
150 }
151 EXPORT_SYMBOL(dm_dirty_log_create);
152
153 void dm_dirty_log_destroy(struct dm_dirty_log *log)
154 {
155         log->type->dtr(log);
156         put_type(log->type);
157         kfree(log);
158 }
159 EXPORT_SYMBOL(dm_dirty_log_destroy);
160
161 /*-----------------------------------------------------------------
162  * Persistent and core logs share a lot of their implementation.
163  * FIXME: need a reload method to be called from a resume
164  *---------------------------------------------------------------*/
165 /*
166  * Magic for persistent mirrors: "MiRr"
167  */
168 #define MIRROR_MAGIC 0x4D695272
169
170 /*
171  * The on-disk version of the metadata.
172  */
173 #define MIRROR_DISK_VERSION 2
174 #define LOG_OFFSET 2
175
176 struct log_header {
177         uint32_t magic;
178
179         /*
180          * Simple, incrementing version. no backward
181          * compatibility.
182          */
183         uint32_t version;
184         sector_t nr_regions;
185 };
186
187 struct log_c {
188         struct dm_target *ti;
189         int touched;
190         uint32_t region_size;
191         unsigned int region_count;
192         region_t sync_count;
193
194         unsigned bitset_uint32_count;
195         uint32_t *clean_bits;
196         uint32_t *sync_bits;
197         uint32_t *recovering_bits;      /* FIXME: this seems excessive */
198
199         int sync_search;
200
201         /* Resync flag */
202         enum sync {
203                 DEFAULTSYNC,    /* Synchronize if necessary */
204                 NOSYNC,         /* Devices known to be already in sync */
205                 FORCESYNC,      /* Force a sync to happen */
206         } sync;
207
208         struct dm_io_request io_req;
209
210         /*
211          * Disk log fields
212          */
213         int log_dev_failed;
214         struct dm_dev *log_dev;
215         struct log_header header;
216
217         struct dm_io_region header_location;
218         struct log_header *disk_header;
219 };
220
221 /*
222  * The touched member needs to be updated every time we access
223  * one of the bitsets.
224  */
225 static inline int log_test_bit(uint32_t *bs, unsigned bit)
226 {
227         return ext2_test_bit(bit, (unsigned long *) bs) ? 1 : 0;
228 }
229
230 static inline void log_set_bit(struct log_c *l,
231                                uint32_t *bs, unsigned bit)
232 {
233         ext2_set_bit(bit, (unsigned long *) bs);
234         l->touched = 1;
235 }
236
237 static inline void log_clear_bit(struct log_c *l,
238                                  uint32_t *bs, unsigned bit)
239 {
240         ext2_clear_bit(bit, (unsigned long *) bs);
241         l->touched = 1;
242 }
243
244 /*----------------------------------------------------------------
245  * Header IO
246  *--------------------------------------------------------------*/
247 static void header_to_disk(struct log_header *core, struct log_header *disk)
248 {
249         disk->magic = cpu_to_le32(core->magic);
250         disk->version = cpu_to_le32(core->version);
251         disk->nr_regions = cpu_to_le64(core->nr_regions);
252 }
253
254 static void header_from_disk(struct log_header *core, struct log_header *disk)
255 {
256         core->magic = le32_to_cpu(disk->magic);
257         core->version = le32_to_cpu(disk->version);
258         core->nr_regions = le64_to_cpu(disk->nr_regions);
259 }
260
261 static int rw_header(struct log_c *lc, int rw)
262 {
263         lc->io_req.bi_rw = rw;
264         lc->io_req.mem.ptr.vma = lc->disk_header;
265         lc->io_req.notify.fn = NULL;
266
267         return dm_io(&lc->io_req, 1, &lc->header_location, NULL);
268 }
269
270 static int read_header(struct log_c *log)
271 {
272         int r;
273
274         r = rw_header(log, READ);
275         if (r)
276                 return r;
277
278         header_from_disk(&log->header, log->disk_header);
279
280         /* New log required? */
281         if (log->sync != DEFAULTSYNC || log->header.magic != MIRROR_MAGIC) {
282                 log->header.magic = MIRROR_MAGIC;
283                 log->header.version = MIRROR_DISK_VERSION;
284                 log->header.nr_regions = 0;
285         }
286
287 #ifdef __LITTLE_ENDIAN
288         if (log->header.version == 1)
289                 log->header.version = 2;
290 #endif
291
292         if (log->header.version != MIRROR_DISK_VERSION) {
293                 DMWARN("incompatible disk log version");
294                 return -EINVAL;
295         }
296
297         return 0;
298 }
299
300 static inline int write_header(struct log_c *log)
301 {
302         header_to_disk(&log->header, log->disk_header);
303         return rw_header(log, WRITE);
304 }
305
306 /*----------------------------------------------------------------
307  * core log constructor/destructor
308  *
309  * argv contains region_size followed optionally by [no]sync
310  *--------------------------------------------------------------*/
311 #define BYTE_SHIFT 3
312 static int create_log_context(struct dm_dirty_log *log, struct dm_target *ti,
313                               unsigned int argc, char **argv,
314                               struct dm_dev *dev)
315 {
316         enum sync sync = DEFAULTSYNC;
317
318         struct log_c *lc;
319         uint32_t region_size;
320         unsigned int region_count;
321         size_t bitset_size, buf_size;
322         int r;
323
324         if (argc < 1 || argc > 2) {
325                 DMWARN("wrong number of arguments to dirty region log");
326                 return -EINVAL;
327         }
328
329         if (argc > 1) {
330                 if (!strcmp(argv[1], "sync"))
331                         sync = FORCESYNC;
332                 else if (!strcmp(argv[1], "nosync"))
333                         sync = NOSYNC;
334                 else {
335                         DMWARN("unrecognised sync argument to "
336                                "dirty region log: %s", argv[1]);
337                         return -EINVAL;
338                 }
339         }
340
341         if (sscanf(argv[0], "%u", &region_size) != 1) {
342                 DMWARN("invalid region size string");
343                 return -EINVAL;
344         }
345
346         region_count = dm_sector_div_up(ti->len, region_size);
347
348         lc = kmalloc(sizeof(*lc), GFP_KERNEL);
349         if (!lc) {
350                 DMWARN("couldn't allocate core log");
351                 return -ENOMEM;
352         }
353
354         lc->ti = ti;
355         lc->touched = 0;
356         lc->region_size = region_size;
357         lc->region_count = region_count;
358         lc->sync = sync;
359
360         /*
361          * Work out how many "unsigned long"s we need to hold the bitset.
362          */
363         bitset_size = dm_round_up(region_count,
364                                   sizeof(*lc->clean_bits) << BYTE_SHIFT);
365         bitset_size >>= BYTE_SHIFT;
366
367         lc->bitset_uint32_count = bitset_size / sizeof(*lc->clean_bits);
368
369         /*
370          * Disk log?
371          */
372         if (!dev) {
373                 lc->clean_bits = vmalloc(bitset_size);
374                 if (!lc->clean_bits) {
375                         DMWARN("couldn't allocate clean bitset");
376                         kfree(lc);
377                         return -ENOMEM;
378                 }
379                 lc->disk_header = NULL;
380         } else {
381                 lc->log_dev = dev;
382                 lc->log_dev_failed = 0;
383                 lc->header_location.bdev = lc->log_dev->bdev;
384                 lc->header_location.sector = 0;
385
386                 /*
387                  * Buffer holds both header and bitset.
388                  */
389                 buf_size = dm_round_up((LOG_OFFSET << SECTOR_SHIFT) +
390                                        bitset_size, ti->limits.hardsect_size);
391                 lc->header_location.count = buf_size >> SECTOR_SHIFT;
392                 lc->io_req.mem.type = DM_IO_VMA;
393                 lc->io_req.client = dm_io_client_create(dm_div_up(buf_size,
394                                                                    PAGE_SIZE));
395                 if (IS_ERR(lc->io_req.client)) {
396                         r = PTR_ERR(lc->io_req.client);
397                         DMWARN("couldn't allocate disk io client");
398                         kfree(lc);
399                         return -ENOMEM;
400                 }
401
402                 lc->disk_header = vmalloc(buf_size);
403                 if (!lc->disk_header) {
404                         DMWARN("couldn't allocate disk log buffer");
405                         kfree(lc);
406                         return -ENOMEM;
407                 }
408
409                 lc->clean_bits = (void *)lc->disk_header +
410                                  (LOG_OFFSET << SECTOR_SHIFT);
411         }
412
413         memset(lc->clean_bits, -1, bitset_size);
414
415         lc->sync_bits = vmalloc(bitset_size);
416         if (!lc->sync_bits) {
417                 DMWARN("couldn't allocate sync bitset");
418                 if (!dev)
419                         vfree(lc->clean_bits);
420                 vfree(lc->disk_header);
421                 kfree(lc);
422                 return -ENOMEM;
423         }
424         memset(lc->sync_bits, (sync == NOSYNC) ? -1 : 0, bitset_size);
425         lc->sync_count = (sync == NOSYNC) ? region_count : 0;
426
427         lc->recovering_bits = vmalloc(bitset_size);
428         if (!lc->recovering_bits) {
429                 DMWARN("couldn't allocate sync bitset");
430                 vfree(lc->sync_bits);
431                 if (!dev)
432                         vfree(lc->clean_bits);
433                 vfree(lc->disk_header);
434                 kfree(lc);
435                 return -ENOMEM;
436         }
437         memset(lc->recovering_bits, 0, bitset_size);
438         lc->sync_search = 0;
439         log->context = lc;
440
441         return 0;
442 }
443
444 static int core_ctr(struct dm_dirty_log *log, struct dm_target *ti,
445                     unsigned int argc, char **argv)
446 {
447         return create_log_context(log, ti, argc, argv, NULL);
448 }
449
450 static void destroy_log_context(struct log_c *lc)
451 {
452         vfree(lc->sync_bits);
453         vfree(lc->recovering_bits);
454         kfree(lc);
455 }
456
457 static void core_dtr(struct dm_dirty_log *log)
458 {
459         struct log_c *lc = (struct log_c *) log->context;
460
461         vfree(lc->clean_bits);
462         destroy_log_context(lc);
463 }
464
465 /*----------------------------------------------------------------
466  * disk log constructor/destructor
467  *
468  * argv contains log_device region_size followed optionally by [no]sync
469  *--------------------------------------------------------------*/
470 static int disk_ctr(struct dm_dirty_log *log, struct dm_target *ti,
471                     unsigned int argc, char **argv)
472 {
473         int r;
474         struct dm_dev *dev;
475
476         if (argc < 2 || argc > 3) {
477                 DMWARN("wrong number of arguments to disk dirty region log");
478                 return -EINVAL;
479         }
480
481         r = dm_get_device(ti, argv[0], 0, 0 /* FIXME */,
482                           FMODE_READ | FMODE_WRITE, &dev);
483         if (r)
484                 return r;
485
486         r = create_log_context(log, ti, argc - 1, argv + 1, dev);
487         if (r) {
488                 dm_put_device(ti, dev);
489                 return r;
490         }
491
492         return 0;
493 }
494
495 static void disk_dtr(struct dm_dirty_log *log)
496 {
497         struct log_c *lc = (struct log_c *) log->context;
498
499         dm_put_device(lc->ti, lc->log_dev);
500         vfree(lc->disk_header);
501         dm_io_client_destroy(lc->io_req.client);
502         destroy_log_context(lc);
503 }
504
505 static int count_bits32(uint32_t *addr, unsigned size)
506 {
507         int count = 0, i;
508
509         for (i = 0; i < size; i++) {
510                 count += hweight32(*(addr+i));
511         }
512         return count;
513 }
514
515 static void fail_log_device(struct log_c *lc)
516 {
517         if (lc->log_dev_failed)
518                 return;
519
520         lc->log_dev_failed = 1;
521         dm_table_event(lc->ti->table);
522 }
523
524 static int disk_resume(struct dm_dirty_log *log)
525 {
526         int r;
527         unsigned i;
528         struct log_c *lc = (struct log_c *) log->context;
529         size_t size = lc->bitset_uint32_count * sizeof(uint32_t);
530
531         /* read the disk header */
532         r = read_header(lc);
533         if (r) {
534                 DMWARN("%s: Failed to read header on dirty region log device",
535                        lc->log_dev->name);
536                 fail_log_device(lc);
537                 /*
538                  * If the log device cannot be read, we must assume
539                  * all regions are out-of-sync.  If we simply return
540                  * here, the state will be uninitialized and could
541                  * lead us to return 'in-sync' status for regions
542                  * that are actually 'out-of-sync'.
543                  */
544                 lc->header.nr_regions = 0;
545         }
546
547         /* set or clear any new bits -- device has grown */
548         if (lc->sync == NOSYNC)
549                 for (i = lc->header.nr_regions; i < lc->region_count; i++)
550                         /* FIXME: amazingly inefficient */
551                         log_set_bit(lc, lc->clean_bits, i);
552         else
553                 for (i = lc->header.nr_regions; i < lc->region_count; i++)
554                         /* FIXME: amazingly inefficient */
555                         log_clear_bit(lc, lc->clean_bits, i);
556
557         /* clear any old bits -- device has shrunk */
558         for (i = lc->region_count; i % (sizeof(*lc->clean_bits) << BYTE_SHIFT); i++)
559                 log_clear_bit(lc, lc->clean_bits, i);
560
561         /* copy clean across to sync */
562         memcpy(lc->sync_bits, lc->clean_bits, size);
563         lc->sync_count = count_bits32(lc->clean_bits, lc->bitset_uint32_count);
564         lc->sync_search = 0;
565
566         /* set the correct number of regions in the header */
567         lc->header.nr_regions = lc->region_count;
568
569         /* write the new header */
570         r = write_header(lc);
571         if (r) {
572                 DMWARN("%s: Failed to write header on dirty region log device",
573                        lc->log_dev->name);
574                 fail_log_device(lc);
575         }
576
577         return r;
578 }
579
580 static uint32_t core_get_region_size(struct dm_dirty_log *log)
581 {
582         struct log_c *lc = (struct log_c *) log->context;
583         return lc->region_size;
584 }
585
586 static int core_resume(struct dm_dirty_log *log)
587 {
588         struct log_c *lc = (struct log_c *) log->context;
589         lc->sync_search = 0;
590         return 0;
591 }
592
593 static int core_is_clean(struct dm_dirty_log *log, region_t region)
594 {
595         struct log_c *lc = (struct log_c *) log->context;
596         return log_test_bit(lc->clean_bits, region);
597 }
598
599 static int core_in_sync(struct dm_dirty_log *log, region_t region, int block)
600 {
601         struct log_c *lc = (struct log_c *) log->context;
602         return log_test_bit(lc->sync_bits, region);
603 }
604
605 static int core_flush(struct dm_dirty_log *log)
606 {
607         /* no op */
608         return 0;
609 }
610
611 static int disk_flush(struct dm_dirty_log *log)
612 {
613         int r;
614         struct log_c *lc = (struct log_c *) log->context;
615
616         /* only write if the log has changed */
617         if (!lc->touched)
618                 return 0;
619
620         r = write_header(lc);
621         if (r)
622                 fail_log_device(lc);
623         else
624                 lc->touched = 0;
625
626         return r;
627 }
628
629 static void core_mark_region(struct dm_dirty_log *log, region_t region)
630 {
631         struct log_c *lc = (struct log_c *) log->context;
632         log_clear_bit(lc, lc->clean_bits, region);
633 }
634
635 static void core_clear_region(struct dm_dirty_log *log, region_t region)
636 {
637         struct log_c *lc = (struct log_c *) log->context;
638         log_set_bit(lc, lc->clean_bits, region);
639 }
640
641 static int core_get_resync_work(struct dm_dirty_log *log, region_t *region)
642 {
643         struct log_c *lc = (struct log_c *) log->context;
644
645         if (lc->sync_search >= lc->region_count)
646                 return 0;
647
648         do {
649                 *region = ext2_find_next_zero_bit(
650                                              (unsigned long *) lc->sync_bits,
651                                              lc->region_count,
652                                              lc->sync_search);
653                 lc->sync_search = *region + 1;
654
655                 if (*region >= lc->region_count)
656                         return 0;
657
658         } while (log_test_bit(lc->recovering_bits, *region));
659
660         log_set_bit(lc, lc->recovering_bits, *region);
661         return 1;
662 }
663
664 static void core_set_region_sync(struct dm_dirty_log *log, region_t region,
665                                  int in_sync)
666 {
667         struct log_c *lc = (struct log_c *) log->context;
668
669         log_clear_bit(lc, lc->recovering_bits, region);
670         if (in_sync) {
671                 log_set_bit(lc, lc->sync_bits, region);
672                 lc->sync_count++;
673         } else if (log_test_bit(lc->sync_bits, region)) {
674                 lc->sync_count--;
675                 log_clear_bit(lc, lc->sync_bits, region);
676         }
677 }
678
679 static region_t core_get_sync_count(struct dm_dirty_log *log)
680 {
681         struct log_c *lc = (struct log_c *) log->context;
682
683         return lc->sync_count;
684 }
685
686 #define DMEMIT_SYNC \
687         if (lc->sync != DEFAULTSYNC) \
688                 DMEMIT("%ssync ", lc->sync == NOSYNC ? "no" : "")
689
690 static int core_status(struct dm_dirty_log *log, status_type_t status,
691                        char *result, unsigned int maxlen)
692 {
693         int sz = 0;
694         struct log_c *lc = log->context;
695
696         switch(status) {
697         case STATUSTYPE_INFO:
698                 DMEMIT("1 %s", log->type->name);
699                 break;
700
701         case STATUSTYPE_TABLE:
702                 DMEMIT("%s %u %u ", log->type->name,
703                        lc->sync == DEFAULTSYNC ? 1 : 2, lc->region_size);
704                 DMEMIT_SYNC;
705         }
706
707         return sz;
708 }
709
710 static int disk_status(struct dm_dirty_log *log, status_type_t status,
711                        char *result, unsigned int maxlen)
712 {
713         int sz = 0;
714         struct log_c *lc = log->context;
715
716         switch(status) {
717         case STATUSTYPE_INFO:
718                 DMEMIT("3 %s %s %c", log->type->name, lc->log_dev->name,
719                        lc->log_dev_failed ? 'D' : 'A');
720                 break;
721
722         case STATUSTYPE_TABLE:
723                 DMEMIT("%s %u %s %u ", log->type->name,
724                        lc->sync == DEFAULTSYNC ? 2 : 3, lc->log_dev->name,
725                        lc->region_size);
726                 DMEMIT_SYNC;
727         }
728
729         return sz;
730 }
731
732 static struct dm_dirty_log_type _core_type = {
733         .name = "core",
734         .module = THIS_MODULE,
735         .ctr = core_ctr,
736         .dtr = core_dtr,
737         .resume = core_resume,
738         .get_region_size = core_get_region_size,
739         .is_clean = core_is_clean,
740         .in_sync = core_in_sync,
741         .flush = core_flush,
742         .mark_region = core_mark_region,
743         .clear_region = core_clear_region,
744         .get_resync_work = core_get_resync_work,
745         .set_region_sync = core_set_region_sync,
746         .get_sync_count = core_get_sync_count,
747         .status = core_status,
748 };
749
750 static struct dm_dirty_log_type _disk_type = {
751         .name = "disk",
752         .module = THIS_MODULE,
753         .ctr = disk_ctr,
754         .dtr = disk_dtr,
755         .postsuspend = disk_flush,
756         .resume = disk_resume,
757         .get_region_size = core_get_region_size,
758         .is_clean = core_is_clean,
759         .in_sync = core_in_sync,
760         .flush = disk_flush,
761         .mark_region = core_mark_region,
762         .clear_region = core_clear_region,
763         .get_resync_work = core_get_resync_work,
764         .set_region_sync = core_set_region_sync,
765         .get_sync_count = core_get_sync_count,
766         .status = disk_status,
767 };
768
769 int __init dm_dirty_log_init(void)
770 {
771         int r;
772
773         r = dm_dirty_log_type_register(&_core_type);
774         if (r)
775                 DMWARN("couldn't register core log");
776
777         r = dm_dirty_log_type_register(&_disk_type);
778         if (r) {
779                 DMWARN("couldn't register disk type");
780                 dm_dirty_log_type_unregister(&_core_type);
781         }
782
783         return r;
784 }
785
786 void __exit dm_dirty_log_exit(void)
787 {
788         dm_dirty_log_type_unregister(&_disk_type);
789         dm_dirty_log_type_unregister(&_core_type);
790 }
791
792 module_init(dm_dirty_log_init);
793 module_exit(dm_dirty_log_exit);
794
795 MODULE_DESCRIPTION(DM_NAME " dirty region log");
796 MODULE_AUTHOR("Joe Thornber, Heinz Mauelshagen <dm-devel@redhat.com>");
797 MODULE_LICENSE("GPL");