drivers/md/dm-stripe.c

   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
  35         /* Needed for handling events */
  36         struct dm_target *ti;
  37
  38         /* Work struct used for triggering events*/
  39         struct work_struct trigger_event;
  40
  41         struct stripe stripe[0];
  42 };
  43
  44 /*
  45  * An event is triggered whenever a drive
  46  * drops out of a stripe volume.
  47  */
  48 static void trigger_event(struct work_struct *work)
  49 {
  50         struct stripe_c *sc = container_of(work, struct stripe_c,
  51                                            trigger_event);
  52         dm_table_event(sc->ti->table);
  53 }
  54
  55 static inline struct stripe_c *alloc_context(unsigned int stripes)
  56 {
  57         size_t len;
  58
  59         if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
  60                              stripes))
  61                 return NULL;
  62
  63         len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
  64
  65         return kmalloc(len, GFP_KERNEL);
  66 }
  67
  68 /*
  69  * Parse a single <dev> <sector> pair
  70  */
  71 static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
  72                       unsigned int stripe, char **argv)
  73 {
  74         unsigned long long start;
  75         char dummy;
  76
  77         if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
  78                 return -EINVAL;
  79
  80         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
  81                           &sc->stripe[stripe].dev))
  82                 return -ENXIO;
  83
  84         sc->stripe[stripe].physical_start = start;
  85
  86         return 0;
  87 }
  88
  89 /*
  90  * Construct a striped mapping.
  91  * <number of stripes> <chunk size> [<dev_path> <offset>]+
  92  */
  93 static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  94 {
  95         struct stripe_c *sc;
  96         sector_t width;
  97         uint32_t stripes;
  98         uint32_t chunk_size;
  99         int r;
 100         unsigned int i;
 101
 102         if (argc < 2) {
 103                 ti->error = "Not enough arguments";
 104                 return -EINVAL;
 105         }
 106
 107         if (kstrtouint(argv[0], 10, &stripes) || !stripes) {
 108                 ti->error = "Invalid stripe count";
 109                 return -EINVAL;
 110         }
 111
 112         if (kstrtouint(argv[1], 10, &chunk_size) ||
 113             (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
 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
 168         /*
 169          * Get the stripe destinations.
 170          */
 171         for (i = 0; i < stripes; i++) {
 172                 argv += 2;
 173
 174                 r = get_stripe(ti, sc, i, argv);
 175                 if (r < 0) {
 176                         ti->error = "Couldn't parse stripe destination";
 177                         while (i--)
 178                                 dm_put_device(ti, sc->stripe[i].dev);
 179                         kfree(sc);
 180                         return r;
 181                 }
 182                 atomic_set(&(sc->stripe[i].error_count), 0);
 183         }
 184
 185         ti->private = sc;
 186
 187         return 0;
 188 }
 189
 190 static void stripe_dtr(struct dm_target *ti)
 191 {
 192         unsigned int i;
 193         struct stripe_c *sc = (struct stripe_c *) ti->private;
 194
 195         for (i = 0; i < sc->stripes; i++)
 196                 dm_put_device(ti, sc->stripe[i].dev);
 197
 198         flush_work_sync(&sc->trigger_event);
 199         kfree(sc);
 200 }
 201
 202 static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
 203                               uint32_t *stripe, sector_t *result)
 204 {
 205         sector_t chunk = dm_target_offset(sc->ti, sector);
 206         sector_t chunk_offset = sector_div(chunk, sc->chunk_size);
 207
 208         if (sc->stripes_shift < 0)
 209                 *stripe = sector_div(chunk, sc->stripes);
 210         else {
 211                 *stripe = chunk & (sc->stripes - 1);
 212                 chunk >>= sc->stripes_shift;
 213         }
 214
 215         *result = (chunk * sc->chunk_size) + chunk_offset;
 216 }
 217
 218 static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
 219                                     uint32_t target_stripe, sector_t *result)
 220 {
 221         uint32_t stripe;
 222
 223         stripe_map_sector(sc, sector, &stripe, result);
 224         if (stripe == target_stripe)
 225                 return;
 226
 227         /* round down */
 228         sector = *result;
 229         *result -= sector_div(sector, sc->chunk_size);
 230
 231         if (target_stripe < stripe)
 232                 *result += sc->chunk_size;              /* next chunk */
 233 }
 234
 235 static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
 236                               uint32_t target_stripe)
 237 {
 238         sector_t begin, end;
 239
 240         stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
 241         stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
 242                                 target_stripe, &end);
 243         if (begin < end) {
 244                 bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
 245                 bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
 246                 bio->bi_size = to_bytes(end - begin);
 247                 return DM_MAPIO_REMAPPED;
 248         } else {
 249                 /* The range doesn't map to the target stripe */
 250                 bio_endio(bio, 0);
 251                 return DM_MAPIO_SUBMITTED;
 252         }
 253 }
 254
 255 static int stripe_map(struct dm_target *ti, struct bio *bio,
 256                       union map_info *map_context)
 257 {
 258         struct stripe_c *sc = ti->private;
 259         uint32_t stripe;
 260         unsigned target_request_nr;
 261
 262         if (bio->bi_rw & REQ_FLUSH) {
 263                 target_request_nr = map_context->target_request_nr;
 264                 BUG_ON(target_request_nr >= sc->stripes);
 265                 bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
 266                 return DM_MAPIO_REMAPPED;
 267         }
 268         if (unlikely(bio->bi_rw & REQ_DISCARD)) {
 269                 target_request_nr = map_context->target_request_nr;
 270                 BUG_ON(target_request_nr >= sc->stripes);
 271                 return stripe_map_discard(sc, bio, target_request_nr);
 272         }
 273
 274         stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
 275
 276         bio->bi_sector += sc->stripe[stripe].physical_start;
 277         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
 278
 279         return DM_MAPIO_REMAPPED;
 280 }
 281
 282 /*
 283  * Stripe status:
 284  *
 285  * INFO
 286  * #stripes [stripe_name <stripe_name>] [group word count]
 287  * [error count 'A|D' <error count 'A|D'>]
 288  *
 289  * TABLE
 290  * #stripes [stripe chunk size]
 291  * [stripe_name physical_start <stripe_name physical_start>]
 292  *
 293  */
 294
 295 static int stripe_status(struct dm_target *ti,
 296                          status_type_t type, char *result, unsigned int maxlen)
 297 {
 298         struct stripe_c *sc = (struct stripe_c *) ti->private;
 299         char buffer[sc->stripes + 1];
 300         unsigned int sz = 0;
 301         unsigned int i;
 302
 303         switch (type) {
 304         case STATUSTYPE_INFO:
 305                 DMEMIT("%d ", sc->stripes);
 306                 for (i = 0; i < sc->stripes; i++)  {
 307                         DMEMIT("%s ", sc->stripe[i].dev->name);
 308                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
 309                                 'D' : 'A';
 310                 }
 311                 buffer[i] = '\0';
 312                 DMEMIT("1 %s", buffer);
 313                 break;
 314
 315         case STATUSTYPE_TABLE:
 316                 DMEMIT("%d %llu", sc->stripes,
 317                         (unsigned long long)sc->chunk_size);
 318                 for (i = 0; i < sc->stripes; i++)
 319                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 320                             (unsigned long long)sc->stripe[i].physical_start);
 321                 break;
 322         }
 323         return 0;
 324 }
 325
 326 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 327                          int error, union map_info *map_context)
 328 {
 329         unsigned i;
 330         char major_minor[16];
 331         struct stripe_c *sc = ti->private;
 332
 333         if (!error)
 334                 return 0; /* I/O complete */
 335
 336         if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
 337                 return error;
 338
 339         if (error == -EOPNOTSUPP)
 340                 return error;
 341
 342         memset(major_minor, 0, sizeof(major_minor));
 343         sprintf(major_minor, "%d:%d",
 344                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
 345                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 346
 347         /*
 348          * Test to see which stripe drive triggered the event
 349          * and increment error count for all stripes on that device.
 350          * If the error count for a given device exceeds the threshold
 351          * value we will no longer trigger any further events.
 352          */
 353         for (i = 0; i < sc->stripes; i++)
 354                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 355                         atomic_inc(&(sc->stripe[i].error_count));
 356                         if (atomic_read(&(sc->stripe[i].error_count)) <
 357                             DM_IO_ERROR_THRESHOLD)
 358                                 schedule_work(&sc->trigger_event);
 359                 }
 360
 361         return error;
 362 }
 363
 364 static int stripe_iterate_devices(struct dm_target *ti,
 365                                   iterate_devices_callout_fn fn, void *data)
 366 {
 367         struct stripe_c *sc = ti->private;
 368         int ret = 0;
 369         unsigned i = 0;
 370
 371         do {
 372                 ret = fn(ti, sc->stripe[i].dev,
 373                          sc->stripe[i].physical_start,
 374                          sc->stripe_width, data);
 375         } while (!ret && ++i < sc->stripes);
 376
 377         return ret;
 378 }
 379
 380 static void stripe_io_hints(struct dm_target *ti,
 381                             struct queue_limits *limits)
 382 {
 383         struct stripe_c *sc = ti->private;
 384         unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;
 385
 386         blk_limits_io_min(limits, chunk_size);
 387         blk_limits_io_opt(limits, chunk_size * sc->stripes);
 388 }
 389
 390 static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 391                         struct bio_vec *biovec, int max_size)
 392 {
 393         struct stripe_c *sc = ti->private;
 394         sector_t bvm_sector = bvm->bi_sector;
 395         uint32_t stripe;
 396         struct request_queue *q;
 397
 398         stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
 399
 400         q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
 401         if (!q->merge_bvec_fn)
 402                 return max_size;
 403
 404         bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
 405         bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
 406
 407         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 408 }
 409
 410 static struct target_type stripe_target = {
 411         .name   = "striped",
 412         .version = {1, 5, 0},
 413         .module = THIS_MODULE,
 414         .ctr    = stripe_ctr,
 415         .dtr    = stripe_dtr,
 416         .map    = stripe_map,
 417         .end_io = stripe_end_io,
 418         .status = stripe_status,
 419         .iterate_devices = stripe_iterate_devices,
 420         .io_hints = stripe_io_hints,
 421         .merge  = stripe_merge,
 422 };
 423
 424 int __init dm_stripe_init(void)
 425 {
 426         int r;
 427
 428         r = dm_register_target(&stripe_target);
 429         if (r < 0) {
 430                 DMWARN("target registration failed");
 431                 return r;
 432         }
 433
 434         return r;
 435 }
 436
 437 void dm_stripe_exit(void)
 438 {
 439         dm_unregister_target(&stripe_target);
 440 }