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1 /*
2  * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
3  *
4  * This file is released under the GPL.
5  */
6
7 #include <linux/device-mapper.h>
8
9 #include <linux/module.h>
10 #include <linux/init.h>
11 #include <linux/blkdev.h>
12 #include <linux/bio.h>
13 #include <linux/slab.h>
14 #include <linux/log2.h>
15
16 #define DM_MSG_PREFIX "striped"
17 #define DM_IO_ERROR_THRESHOLD 15
18
19 struct stripe {
20         struct dm_dev *dev;
21         sector_t physical_start;
22
23         atomic_t error_count;
24 };
25
26 struct stripe_c {
27         uint32_t stripes;
28         int stripes_shift;
29
30         /* The size of this target / num. stripes */
31         sector_t stripe_width;
32
33         uint32_t chunk_size;
34         int chunk_size_shift;
35
36         /* Needed for handling events */
37         struct dm_target *ti;
38
39         /* Work struct used for triggering events*/
40         struct work_struct trigger_event;
41
42         struct stripe stripe[0];
43 };
44
45 /*
46  * An event is triggered whenever a drive
47  * drops out of a stripe volume.
48  */
49 static void trigger_event(struct work_struct *work)
50 {
51         struct stripe_c *sc = container_of(work, struct stripe_c,
52                                            trigger_event);
53         dm_table_event(sc->ti->table);
54 }
55
56 static inline struct stripe_c *alloc_context(unsigned int stripes)
57 {
58         size_t len;
59
60         if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
61                              stripes))
62                 return NULL;
63
64         len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
65
66         return kmalloc(len, GFP_KERNEL);
67 }
68
69 /*
70  * Parse a single <dev> <sector> pair
71  */
72 static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
73                       unsigned int stripe, char **argv)
74 {
75         unsigned long long start;
76         char dummy;
77
78         if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
79                 return -EINVAL;
80
81         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
82                           &sc->stripe[stripe].dev))
83                 return -ENXIO;
84
85         sc->stripe[stripe].physical_start = start;
86
87         return 0;
88 }
89
90 /*
91  * Construct a striped mapping.
92  * <number of stripes> <chunk size> [<dev_path> <offset>]+
93  */
94 static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
95 {
96         struct stripe_c *sc;
97         sector_t width;
98         uint32_t stripes;
99         uint32_t chunk_size;
100         int r;
101         unsigned int i;
102
103         if (argc < 2) {
104                 ti->error = "Not enough arguments";
105                 return -EINVAL;
106         }
107
108         if (kstrtouint(argv[0], 10, &stripes) || !stripes) {
109                 ti->error = "Invalid stripe count";
110                 return -EINVAL;
111         }
112
113         if (kstrtouint(argv[1], 10, &chunk_size) || !chunk_size) {
114                 ti->error = "Invalid chunk_size";
115                 return -EINVAL;
116         }
117
118         width = ti->len;
119         if (sector_div(width, chunk_size)) {
120                 ti->error = "Target length not divisible by "
121                     "chunk size";
122                 return -EINVAL;
123         }
124
125         if (sector_div(width, stripes)) {
126                 ti->error = "Target length not divisible by "
127                     "number of stripes";
128                 return -EINVAL;
129         }
130
131         /*
132          * Do we have enough arguments for that many stripes ?
133          */
134         if (argc != (2 + 2 * stripes)) {
135                 ti->error = "Not enough destinations "
136                         "specified";
137                 return -EINVAL;
138         }
139
140         sc = alloc_context(stripes);
141         if (!sc) {
142                 ti->error = "Memory allocation for striped context "
143                     "failed";
144                 return -ENOMEM;
145         }
146
147         INIT_WORK(&sc->trigger_event, trigger_event);
148
149         /* Set pointer to dm target; used in trigger_event */
150         sc->ti = ti;
151         sc->stripes = stripes;
152         sc->stripe_width = width;
153
154         if (stripes & (stripes - 1))
155                 sc->stripes_shift = -1;
156         else
157                 sc->stripes_shift = __ffs(stripes);
158
159         r = dm_set_target_max_io_len(ti, chunk_size);
160         if (r)
161                 return r;
162
163         ti->num_flush_requests = stripes;
164         ti->num_discard_requests = stripes;
165
166         sc->chunk_size = chunk_size;
167         if (chunk_size & (chunk_size - 1))
168                 sc->chunk_size_shift = -1;
169         else
170                 sc->chunk_size_shift = __ffs(chunk_size);
171
172         /*
173          * Get the stripe destinations.
174          */
175         for (i = 0; i < stripes; i++) {
176                 argv += 2;
177
178                 r = get_stripe(ti, sc, i, argv);
179                 if (r < 0) {
180                         ti->error = "Couldn't parse stripe destination";
181                         while (i--)
182                                 dm_put_device(ti, sc->stripe[i].dev);
183                         kfree(sc);
184                         return r;
185                 }
186                 atomic_set(&(sc->stripe[i].error_count), 0);
187         }
188
189         ti->private = sc;
190
191         return 0;
192 }
193
194 static void stripe_dtr(struct dm_target *ti)
195 {
196         unsigned int i;
197         struct stripe_c *sc = (struct stripe_c *) ti->private;
198
199         for (i = 0; i < sc->stripes; i++)
200                 dm_put_device(ti, sc->stripe[i].dev);
201
202         flush_work(&sc->trigger_event);
203         kfree(sc);
204 }
205
206 static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
207                               uint32_t *stripe, sector_t *result)
208 {
209         sector_t chunk = dm_target_offset(sc->ti, sector);
210         sector_t chunk_offset;
211
212         if (sc->chunk_size_shift < 0)
213                 chunk_offset = sector_div(chunk, sc->chunk_size);
214         else {
215                 chunk_offset = chunk & (sc->chunk_size - 1);
216                 chunk >>= sc->chunk_size_shift;
217         }
218
219         if (sc->stripes_shift < 0)
220                 *stripe = sector_div(chunk, sc->stripes);
221         else {
222                 *stripe = chunk & (sc->stripes - 1);
223                 chunk >>= sc->stripes_shift;
224         }
225
226         if (sc->chunk_size_shift < 0)
227                 chunk *= sc->chunk_size;
228         else
229                 chunk <<= sc->chunk_size_shift;
230
231         *result = chunk + chunk_offset;
232 }
233
234 static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
235                                     uint32_t target_stripe, sector_t *result)
236 {
237         uint32_t stripe;
238
239         stripe_map_sector(sc, sector, &stripe, result);
240         if (stripe == target_stripe)
241                 return;
242
243         /* round down */
244         sector = *result;
245         if (sc->chunk_size_shift < 0)
246                 *result -= sector_div(sector, sc->chunk_size);
247         else
248                 *result = sector & ~(sector_t)(sc->chunk_size - 1);
249
250         if (target_stripe < stripe)
251                 *result += sc->chunk_size;              /* next chunk */
252 }
253
254 static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
255                               uint32_t target_stripe)
256 {
257         sector_t begin, end;
258
259         stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
260         stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
261                                 target_stripe, &end);
262         if (begin < end) {
263                 bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
264                 bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
265                 bio->bi_size = to_bytes(end - begin);
266                 return DM_MAPIO_REMAPPED;
267         } else {
268                 /* The range doesn't map to the target stripe */
269                 bio_endio(bio, 0);
270                 return DM_MAPIO_SUBMITTED;
271         }
272 }
273
274 static int stripe_map(struct dm_target *ti, struct bio *bio)
275 {
276         struct stripe_c *sc = ti->private;
277         uint32_t stripe;
278         unsigned target_request_nr;
279
280         if (bio->bi_rw & REQ_FLUSH) {
281                 target_request_nr = dm_bio_get_target_request_nr(bio);
282                 BUG_ON(target_request_nr >= sc->stripes);
283                 bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
284                 return DM_MAPIO_REMAPPED;
285         }
286         if (unlikely(bio->bi_rw & REQ_DISCARD)) {
287                 target_request_nr = dm_bio_get_target_request_nr(bio);
288                 BUG_ON(target_request_nr >= sc->stripes);
289                 return stripe_map_discard(sc, bio, target_request_nr);
290         }
291
292         stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
293
294         bio->bi_sector += sc->stripe[stripe].physical_start;
295         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
296
297         return DM_MAPIO_REMAPPED;
298 }
299
300 /*
301  * Stripe status:
302  *
303  * INFO
304  * #stripes [stripe_name <stripe_name>] [group word count]
305  * [error count 'A|D' <error count 'A|D'>]
306  *
307  * TABLE
308  * #stripes [stripe chunk size]
309  * [stripe_name physical_start <stripe_name physical_start>]
310  *
311  */
312
313 static int stripe_status(struct dm_target *ti, status_type_t type,
314                          unsigned status_flags, char *result, unsigned maxlen)
315 {
316         struct stripe_c *sc = (struct stripe_c *) ti->private;
317         char buffer[sc->stripes + 1];
318         unsigned int sz = 0;
319         unsigned int i;
320
321         switch (type) {
322         case STATUSTYPE_INFO:
323                 DMEMIT("%d ", sc->stripes);
324                 for (i = 0; i < sc->stripes; i++)  {
325                         DMEMIT("%s ", sc->stripe[i].dev->name);
326                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
327                                 'D' : 'A';
328                 }
329                 buffer[i] = '\0';
330                 DMEMIT("1 %s", buffer);
331                 break;
332
333         case STATUSTYPE_TABLE:
334                 DMEMIT("%d %llu", sc->stripes,
335                         (unsigned long long)sc->chunk_size);
336                 for (i = 0; i < sc->stripes; i++)
337                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
338                             (unsigned long long)sc->stripe[i].physical_start);
339                 break;
340         }
341         return 0;
342 }
343
344 static int stripe_end_io(struct dm_target *ti, struct bio *bio, int error)
345 {
346         unsigned i;
347         char major_minor[16];
348         struct stripe_c *sc = ti->private;
349
350         if (!error)
351                 return 0; /* I/O complete */
352
353         if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
354                 return error;
355
356         if (error == -EOPNOTSUPP)
357                 return error;
358
359         memset(major_minor, 0, sizeof(major_minor));
360         sprintf(major_minor, "%d:%d",
361                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
362                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
363
364         /*
365          * Test to see which stripe drive triggered the event
366          * and increment error count for all stripes on that device.
367          * If the error count for a given device exceeds the threshold
368          * value we will no longer trigger any further events.
369          */
370         for (i = 0; i < sc->stripes; i++)
371                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
372                         atomic_inc(&(sc->stripe[i].error_count));
373                         if (atomic_read(&(sc->stripe[i].error_count)) <
374                             DM_IO_ERROR_THRESHOLD)
375                                 schedule_work(&sc->trigger_event);
376                 }
377
378         return error;
379 }
380
381 static int stripe_iterate_devices(struct dm_target *ti,
382                                   iterate_devices_callout_fn fn, void *data)
383 {
384         struct stripe_c *sc = ti->private;
385         int ret = 0;
386         unsigned i = 0;
387
388         do {
389                 ret = fn(ti, sc->stripe[i].dev,
390                          sc->stripe[i].physical_start,
391                          sc->stripe_width, data);
392         } while (!ret && ++i < sc->stripes);
393
394         return ret;
395 }
396
397 static void stripe_io_hints(struct dm_target *ti,
398                             struct queue_limits *limits)
399 {
400         struct stripe_c *sc = ti->private;
401         unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;
402
403         blk_limits_io_min(limits, chunk_size);
404         blk_limits_io_opt(limits, chunk_size * sc->stripes);
405 }
406
407 static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
408                         struct bio_vec *biovec, int max_size)
409 {
410         struct stripe_c *sc = ti->private;
411         sector_t bvm_sector = bvm->bi_sector;
412         uint32_t stripe;
413         struct request_queue *q;
414
415         stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
416
417         q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
418         if (!q->merge_bvec_fn)
419                 return max_size;
420
421         bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
422         bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
423
424         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
425 }
426
427 static struct target_type stripe_target = {
428         .name   = "striped",
429         .version = {1, 5, 0},
430         .module = THIS_MODULE,
431         .ctr    = stripe_ctr,
432         .dtr    = stripe_dtr,
433         .map    = stripe_map,
434         .end_io = stripe_end_io,
435         .status = stripe_status,
436         .iterate_devices = stripe_iterate_devices,
437         .io_hints = stripe_io_hints,
438         .merge  = stripe_merge,
439 };
440
441 int __init dm_stripe_init(void)
442 {
443         int r;
444
445         r = dm_register_target(&stripe_target);
446         if (r < 0) {
447                 DMWARN("target registration failed");
448                 return r;
449         }
450
451         return r;
452 }
453
454 void dm_stripe_exit(void)
455 {
456         dm_unregister_target(&stripe_target);
457 }