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) || !chunk_size) {
 113                 ti->error = "Invalid chunk_size";
 114                 return -EINVAL;
 115         }
 116
 117         width = ti->len;
 118         if (sector_div(width, chunk_size)) {
 119                 ti->error = "Target length not divisible by "
 120                     "chunk size";
 121                 return -EINVAL;
 122         }
 123
 124         if (sector_div(width, stripes)) {
 125                 ti->error = "Target length not divisible by "
 126                     "number of stripes";
 127                 return -EINVAL;
 128         }
 129
 130         /*
 131          * Do we have enough arguments for that many stripes ?
 132          */
 133         if (argc != (2 + 2 * stripes)) {
 134                 ti->error = "Not enough destinations "
 135                         "specified";
 136                 return -EINVAL;
 137         }
 138
 139         sc = alloc_context(stripes);
 140         if (!sc) {
 141                 ti->error = "Memory allocation for striped context "
 142                     "failed";
 143                 return -ENOMEM;
 144         }
 145
 146         INIT_WORK(&sc->trigger_event, trigger_event);
 147
 148         /* Set pointer to dm target; used in trigger_event */
 149         sc->ti = ti;
 150         sc->stripes = stripes;
 151         sc->stripe_width = width;
 152
 153         if (stripes & (stripes - 1))
 154                 sc->stripes_shift = -1;
 155         else
 156                 sc->stripes_shift = __ffs(stripes);
 157
 158         r = dm_set_target_max_io_len(ti, chunk_size);
 159         if (r)
 160                 return r;
 161
 162         ti->num_flush_requests = stripes;
 163         ti->num_discard_requests = stripes;
 164
 165         sc->chunk_size = chunk_size;
 166
 167         /*
 168          * Get the stripe destinations.
 169          */
 170         for (i = 0; i < stripes; i++) {
 171                 argv += 2;
 172
 173                 r = get_stripe(ti, sc, i, argv);
 174                 if (r < 0) {
 175                         ti->error = "Couldn't parse stripe destination";
 176                         while (i--)
 177                                 dm_put_device(ti, sc->stripe[i].dev);
 178                         kfree(sc);
 179                         return r;
 180                 }
 181                 atomic_set(&(sc->stripe[i].error_count), 0);
 182         }
 183
 184         ti->private = sc;
 185
 186         return 0;
 187 }
 188
 189 static void stripe_dtr(struct dm_target *ti)
 190 {
 191         unsigned int i;
 192         struct stripe_c *sc = (struct stripe_c *) ti->private;
 193
 194         for (i = 0; i < sc->stripes; i++)
 195                 dm_put_device(ti, sc->stripe[i].dev);
 196
 197         flush_work_sync(&sc->trigger_event);
 198         kfree(sc);
 199 }
 200
 201 static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
 202                               uint32_t *stripe, sector_t *result)
 203 {
 204         sector_t chunk = dm_target_offset(sc->ti, sector);
 205         sector_t chunk_offset = sector_div(chunk, sc->chunk_size);
 206
 207         if (sc->stripes_shift < 0)
 208                 *stripe = sector_div(chunk, sc->stripes);
 209         else {
 210                 *stripe = chunk & (sc->stripes - 1);
 211                 chunk >>= sc->stripes_shift;
 212         }
 213
 214         *result = (chunk * sc->chunk_size) + chunk_offset;
 215 }
 216
 217 static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
 218                                     uint32_t target_stripe, sector_t *result)
 219 {
 220         uint32_t stripe;
 221
 222         stripe_map_sector(sc, sector, &stripe, result);
 223         if (stripe == target_stripe)
 224                 return;
 225
 226         /* round down */
 227         sector = *result;
 228         *result -= sector_div(sector, sc->chunk_size);
 229
 230         if (target_stripe < stripe)
 231                 *result += sc->chunk_size;              /* next chunk */
 232 }
 233
 234 static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
 235                               uint32_t target_stripe)
 236 {
 237         sector_t begin, end;
 238
 239         stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
 240         stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
 241                                 target_stripe, &end);
 242         if (begin < end) {
 243                 bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
 244                 bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
 245                 bio->bi_size = to_bytes(end - begin);
 246                 return DM_MAPIO_REMAPPED;
 247         } else {
 248                 /* The range doesn't map to the target stripe */
 249                 bio_endio(bio, 0);
 250                 return DM_MAPIO_SUBMITTED;
 251         }
 252 }
 253
 254 static int stripe_map(struct dm_target *ti, struct bio *bio,
 255                       union map_info *map_context)
 256 {
 257         struct stripe_c *sc = ti->private;
 258         uint32_t stripe;
 259         unsigned target_request_nr;
 260
 261         if (bio->bi_rw & REQ_FLUSH) {
 262                 target_request_nr = map_context->target_request_nr;
 263                 BUG_ON(target_request_nr >= sc->stripes);
 264                 bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
 265                 return DM_MAPIO_REMAPPED;
 266         }
 267         if (unlikely(bio->bi_rw & REQ_DISCARD)) {
 268                 target_request_nr = map_context->target_request_nr;
 269                 BUG_ON(target_request_nr >= sc->stripes);
 270                 return stripe_map_discard(sc, bio, target_request_nr);
 271         }
 272
 273         stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
 274
 275         bio->bi_sector += sc->stripe[stripe].physical_start;
 276         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
 277
 278         return DM_MAPIO_REMAPPED;
 279 }
 280
 281 /*
 282  * Stripe status:
 283  *
 284  * INFO
 285  * #stripes [stripe_name <stripe_name>] [group word count]
 286  * [error count 'A|D' <error count 'A|D'>]
 287  *
 288  * TABLE
 289  * #stripes [stripe chunk size]
 290  * [stripe_name physical_start <stripe_name physical_start>]
 291  *
 292  */
 293
 294 static int stripe_status(struct dm_target *ti,
 295                          status_type_t type, char *result, unsigned int maxlen)
 296 {
 297         struct stripe_c *sc = (struct stripe_c *) ti->private;
 298         char buffer[sc->stripes + 1];
 299         unsigned int sz = 0;
 300         unsigned int i;
 301
 302         switch (type) {
 303         case STATUSTYPE_INFO:
 304                 DMEMIT("%d ", sc->stripes);
 305                 for (i = 0; i < sc->stripes; i++)  {
 306                         DMEMIT("%s ", sc->stripe[i].dev->name);
 307                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
 308                                 'D' : 'A';
 309                 }
 310                 buffer[i] = '\0';
 311                 DMEMIT("1 %s", buffer);
 312                 break;
 313
 314         case STATUSTYPE_TABLE:
 315                 DMEMIT("%d %llu", sc->stripes,
 316                         (unsigned long long)sc->chunk_size);
 317                 for (i = 0; i < sc->stripes; i++)
 318                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 319                             (unsigned long long)sc->stripe[i].physical_start);
 320                 break;
 321         }
 322         return 0;
 323 }
 324
 325 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 326                          int error, union map_info *map_context)
 327 {
 328         unsigned i;
 329         char major_minor[16];
 330         struct stripe_c *sc = ti->private;
 331
 332         if (!error)
 333                 return 0; /* I/O complete */
 334
 335         if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
 336                 return error;
 337
 338         if (error == -EOPNOTSUPP)
 339                 return error;
 340
 341         memset(major_minor, 0, sizeof(major_minor));
 342         sprintf(major_minor, "%d:%d",
 343                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
 344                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 345
 346         /*
 347          * Test to see which stripe drive triggered the event
 348          * and increment error count for all stripes on that device.
 349          * If the error count for a given device exceeds the threshold
 350          * value we will no longer trigger any further events.
 351          */
 352         for (i = 0; i < sc->stripes; i++)
 353                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 354                         atomic_inc(&(sc->stripe[i].error_count));
 355                         if (atomic_read(&(sc->stripe[i].error_count)) <
 356                             DM_IO_ERROR_THRESHOLD)
 357                                 schedule_work(&sc->trigger_event);
 358                 }
 359
 360         return error;
 361 }
 362
 363 static int stripe_iterate_devices(struct dm_target *ti,
 364                                   iterate_devices_callout_fn fn, void *data)
 365 {
 366         struct stripe_c *sc = ti->private;
 367         int ret = 0;
 368         unsigned i = 0;
 369
 370         do {
 371                 ret = fn(ti, sc->stripe[i].dev,
 372                          sc->stripe[i].physical_start,
 373                          sc->stripe_width, data);
 374         } while (!ret && ++i < sc->stripes);
 375
 376         return ret;
 377 }
 378
 379 static void stripe_io_hints(struct dm_target *ti,
 380                             struct queue_limits *limits)
 381 {
 382         struct stripe_c *sc = ti->private;
 383         unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;
 384
 385         blk_limits_io_min(limits, chunk_size);
 386         blk_limits_io_opt(limits, chunk_size * sc->stripes);
 387 }
 388
 389 static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 390                         struct bio_vec *biovec, int max_size)
 391 {
 392         struct stripe_c *sc = ti->private;
 393         sector_t bvm_sector = bvm->bi_sector;
 394         uint32_t stripe;
 395         struct request_queue *q;
 396
 397         stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
 398
 399         q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
 400         if (!q->merge_bvec_fn)
 401                 return max_size;
 402
 403         bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
 404         bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
 405
 406         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 407 }
 408
 409 static struct target_type stripe_target = {
 410         .name   = "striped",
 411         .version = {1, 5, 0},
 412         .module = THIS_MODULE,
 413         .ctr    = stripe_ctr,
 414         .dtr    = stripe_dtr,
 415         .map    = stripe_map,
 416         .end_io = stripe_end_io,
 417         .status = stripe_status,
 418         .iterate_devices = stripe_iterate_devices,
 419         .io_hints = stripe_io_hints,
 420         .merge  = stripe_merge,
 421 };
 422
 423 int __init dm_stripe_init(void)
 424 {
 425         int r;
 426
 427         r = dm_register_target(&stripe_target);
 428         if (r < 0) {
 429                 DMWARN("target registration failed");
 430                 return r;
 431         }
 432
 433         return r;
 434 }
 435
 436 void dm_stripe_exit(void)
 437 {
 438         dm_unregister_target(&stripe_target);
 439 }