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         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                       union map_info *map_context)
 276 {
 277         struct stripe_c *sc = ti->private;
 278         uint32_t stripe;
 279         unsigned target_request_nr;
 280
 281         if (bio->bi_rw & REQ_FLUSH) {
 282                 target_request_nr = dm_bio_get_target_request_nr(bio);
 283                 BUG_ON(target_request_nr >= sc->stripes);
 284                 bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
 285                 return DM_MAPIO_REMAPPED;
 286         }
 287         if (unlikely(bio->bi_rw & REQ_DISCARD)) {
 288                 target_request_nr = dm_bio_get_target_request_nr(bio);
 289                 BUG_ON(target_request_nr >= sc->stripes);
 290                 return stripe_map_discard(sc, bio, target_request_nr);
 291         }
 292
 293         stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
 294
 295         bio->bi_sector += sc->stripe[stripe].physical_start;
 296         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
 297
 298         return DM_MAPIO_REMAPPED;
 299 }
 300
 301 /*
 302  * Stripe status:
 303  *
 304  * INFO
 305  * #stripes [stripe_name <stripe_name>] [group word count]
 306  * [error count 'A|D' <error count 'A|D'>]
 307  *
 308  * TABLE
 309  * #stripes [stripe chunk size]
 310  * [stripe_name physical_start <stripe_name physical_start>]
 311  *
 312  */
 313
 314 static int stripe_status(struct dm_target *ti, status_type_t type,
 315                          unsigned status_flags, char *result, unsigned maxlen)
 316 {
 317         struct stripe_c *sc = (struct stripe_c *) ti->private;
 318         char buffer[sc->stripes + 1];
 319         unsigned int sz = 0;
 320         unsigned int i;
 321
 322         switch (type) {
 323         case STATUSTYPE_INFO:
 324                 DMEMIT("%d ", sc->stripes);
 325                 for (i = 0; i < sc->stripes; i++)  {
 326                         DMEMIT("%s ", sc->stripe[i].dev->name);
 327                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
 328                                 'D' : 'A';
 329                 }
 330                 buffer[i] = '\0';
 331                 DMEMIT("1 %s", buffer);
 332                 break;
 333
 334         case STATUSTYPE_TABLE:
 335                 DMEMIT("%d %llu", sc->stripes,
 336                         (unsigned long long)sc->chunk_size);
 337                 for (i = 0; i < sc->stripes; i++)
 338                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 339                             (unsigned long long)sc->stripe[i].physical_start);
 340                 break;
 341         }
 342         return 0;
 343 }
 344
 345 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 346                          int error, union map_info *map_context)
 347 {
 348         unsigned i;
 349         char major_minor[16];
 350         struct stripe_c *sc = ti->private;
 351
 352         if (!error)
 353                 return 0; /* I/O complete */
 354
 355         if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
 356                 return error;
 357
 358         if (error == -EOPNOTSUPP)
 359                 return error;
 360
 361         memset(major_minor, 0, sizeof(major_minor));
 362         sprintf(major_minor, "%d:%d",
 363                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
 364                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 365
 366         /*
 367          * Test to see which stripe drive triggered the event
 368          * and increment error count for all stripes on that device.
 369          * If the error count for a given device exceeds the threshold
 370          * value we will no longer trigger any further events.
 371          */
 372         for (i = 0; i < sc->stripes; i++)
 373                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 374                         atomic_inc(&(sc->stripe[i].error_count));
 375                         if (atomic_read(&(sc->stripe[i].error_count)) <
 376                             DM_IO_ERROR_THRESHOLD)
 377                                 schedule_work(&sc->trigger_event);
 378                 }
 379
 380         return error;
 381 }
 382
 383 static int stripe_iterate_devices(struct dm_target *ti,
 384                                   iterate_devices_callout_fn fn, void *data)
 385 {
 386         struct stripe_c *sc = ti->private;
 387         int ret = 0;
 388         unsigned i = 0;
 389
 390         do {
 391                 ret = fn(ti, sc->stripe[i].dev,
 392                          sc->stripe[i].physical_start,
 393                          sc->stripe_width, data);
 394         } while (!ret && ++i < sc->stripes);
 395
 396         return ret;
 397 }
 398
 399 static void stripe_io_hints(struct dm_target *ti,
 400                             struct queue_limits *limits)
 401 {
 402         struct stripe_c *sc = ti->private;
 403         unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;
 404
 405         blk_limits_io_min(limits, chunk_size);
 406         blk_limits_io_opt(limits, chunk_size * sc->stripes);
 407 }
 408
 409 static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 410                         struct bio_vec *biovec, int max_size)
 411 {
 412         struct stripe_c *sc = ti->private;
 413         sector_t bvm_sector = bvm->bi_sector;
 414         uint32_t stripe;
 415         struct request_queue *q;
 416
 417         stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
 418
 419         q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
 420         if (!q->merge_bvec_fn)
 421                 return max_size;
 422
 423         bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
 424         bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
 425
 426         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 427 }
 428
 429 static struct target_type stripe_target = {
 430         .name   = "striped",
 431         .version = {1, 5, 0},
 432         .module = THIS_MODULE,
 433         .ctr    = stripe_ctr,
 434         .dtr    = stripe_dtr,
 435         .map    = stripe_map,
 436         .end_io = stripe_end_io,
 437         .status = stripe_status,
 438         .iterate_devices = stripe_iterate_devices,
 439         .io_hints = stripe_io_hints,
 440         .merge  = stripe_merge,
 441 };
 442
 443 int __init dm_stripe_init(void)
 444 {
 445         int r;
 446
 447         r = dm_register_target(&stripe_target);
 448         if (r < 0) {
 449                 DMWARN("target registration failed");
 450                 return r;
 451         }
 452
 453         return r;
 454 }
 455
 456 void dm_stripe_exit(void)
 457 {
 458         dm_unregister_target(&stripe_target);
 459 }