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         sector_t stripes_mask;
  30
  31         /* The size of this target / num. stripes */
  32         sector_t stripe_width;
  33
  34         /* stripe chunk size */
  35         uint32_t chunk_shift;
  36         sector_t chunk_mask;
  37
  38         /* Needed for handling events */
  39         struct dm_target *ti;
  40
  41         /* Work struct used for triggering events*/
  42         struct work_struct trigger_event;
  43
  44         struct stripe stripe[0];
  45 };
  46
  47 /*
  48  * An event is triggered whenever a drive
  49  * drops out of a stripe volume.
  50  */
  51 static void trigger_event(struct work_struct *work)
  52 {
  53         struct stripe_c *sc = container_of(work, struct stripe_c,
  54                                            trigger_event);
  55         dm_table_event(sc->ti->table);
  56 }
  57
  58 static inline struct stripe_c *alloc_context(unsigned int stripes)
  59 {
  60         size_t len;
  61
  62         if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
  63                              stripes))
  64                 return NULL;
  65
  66         len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
  67
  68         return kmalloc(len, GFP_KERNEL);
  69 }
  70
  71 /*
  72  * Parse a single <dev> <sector> pair
  73  */
  74 static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
  75                       unsigned int stripe, char **argv)
  76 {
  77         unsigned long long start;
  78         char dummy;
  79
  80         if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
  81                 return -EINVAL;
  82
  83         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
  84                           &sc->stripe[stripe].dev))
  85                 return -ENXIO;
  86
  87         sc->stripe[stripe].physical_start = start;
  88
  89         return 0;
  90 }
  91
  92 /*
  93  * Construct a striped mapping.
  94  * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
  95  */
  96 static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  97 {
  98         struct stripe_c *sc;
  99         sector_t width;
 100         uint32_t stripes;
 101         uint32_t chunk_size;
 102         char *end;
 103         int r;
 104         unsigned int i;
 105
 106         if (argc < 2) {
 107                 ti->error = "Not enough arguments";
 108                 return -EINVAL;
 109         }
 110
 111         stripes = simple_strtoul(argv[0], &end, 10);
 112         if (!stripes || *end) {
 113                 ti->error = "Invalid stripe count";
 114                 return -EINVAL;
 115         }
 116
 117         chunk_size = simple_strtoul(argv[1], &end, 10);
 118         if (*end) {
 119                 ti->error = "Invalid chunk_size";
 120                 return -EINVAL;
 121         }
 122
 123         /*
 124          * chunk_size is a power of two
 125          */
 126         if (!is_power_of_2(chunk_size) ||
 127             (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
 128                 ti->error = "Invalid chunk size";
 129                 return -EINVAL;
 130         }
 131
 132         if (ti->len & (chunk_size - 1)) {
 133                 ti->error = "Target length not divisible by "
 134                     "chunk size";
 135                 return -EINVAL;
 136         }
 137
 138         width = ti->len;
 139         if (sector_div(width, stripes)) {
 140                 ti->error = "Target length not divisible by "
 141                     "number of stripes";
 142                 return -EINVAL;
 143         }
 144
 145         /*
 146          * Do we have enough arguments for that many stripes ?
 147          */
 148         if (argc != (2 + 2 * stripes)) {
 149                 ti->error = "Not enough destinations "
 150                         "specified";
 151                 return -EINVAL;
 152         }
 153
 154         sc = alloc_context(stripes);
 155         if (!sc) {
 156                 ti->error = "Memory allocation for striped context "
 157                     "failed";
 158                 return -ENOMEM;
 159         }
 160
 161         INIT_WORK(&sc->trigger_event, trigger_event);
 162
 163         /* Set pointer to dm target; used in trigger_event */
 164         sc->ti = ti;
 165         sc->stripes = stripes;
 166         sc->stripe_width = width;
 167
 168         if (stripes & (stripes - 1))
 169                 sc->stripes_shift = -1;
 170         else {
 171                 sc->stripes_shift = ffs(stripes) - 1;
 172                 sc->stripes_mask = ((sector_t) stripes) - 1;
 173         }
 174
 175         ti->split_io = chunk_size;
 176         ti->num_flush_requests = stripes;
 177         ti->num_discard_requests = stripes;
 178
 179         sc->chunk_shift = ffs(chunk_size) - 1;
 180         sc->chunk_mask = ((sector_t) chunk_size) - 1;
 181
 182         /*
 183          * Get the stripe destinations.
 184          */
 185         for (i = 0; i < stripes; i++) {
 186                 argv += 2;
 187
 188                 r = get_stripe(ti, sc, i, argv);
 189                 if (r < 0) {
 190                         ti->error = "Couldn't parse stripe destination";
 191                         while (i--)
 192                                 dm_put_device(ti, sc->stripe[i].dev);
 193                         kfree(sc);
 194                         return r;
 195                 }
 196                 atomic_set(&(sc->stripe[i].error_count), 0);
 197         }
 198
 199         ti->private = sc;
 200
 201         return 0;
 202 }
 203
 204 static void stripe_dtr(struct dm_target *ti)
 205 {
 206         unsigned int i;
 207         struct stripe_c *sc = (struct stripe_c *) ti->private;
 208
 209         for (i = 0; i < sc->stripes; i++)
 210                 dm_put_device(ti, sc->stripe[i].dev);
 211
 212         flush_work_sync(&sc->trigger_event);
 213         kfree(sc);
 214 }
 215
 216 static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
 217                               uint32_t *stripe, sector_t *result)
 218 {
 219         sector_t offset = dm_target_offset(sc->ti, sector);
 220         sector_t chunk = offset >> sc->chunk_shift;
 221
 222         if (sc->stripes_shift < 0)
 223                 *stripe = sector_div(chunk, sc->stripes);
 224         else {
 225                 *stripe = chunk & sc->stripes_mask;
 226                 chunk >>= sc->stripes_shift;
 227         }
 228
 229         *result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);
 230 }
 231
 232 static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
 233                                     uint32_t target_stripe, sector_t *result)
 234 {
 235         uint32_t stripe;
 236
 237         stripe_map_sector(sc, sector, &stripe, result);
 238         if (stripe == target_stripe)
 239                 return;
 240         *result &= ~sc->chunk_mask;                     /* round down */
 241         if (target_stripe < stripe)
 242                 *result += sc->chunk_mask + 1;          /* next chunk */
 243 }
 244
 245 static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
 246                               uint32_t target_stripe)
 247 {
 248         sector_t begin, end;
 249
 250         stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
 251         stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
 252                                 target_stripe, &end);
 253         if (begin < end) {
 254                 bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
 255                 bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
 256                 bio->bi_size = to_bytes(end - begin);
 257                 return DM_MAPIO_REMAPPED;
 258         } else {
 259                 /* The range doesn't map to the target stripe */
 260                 bio_endio(bio, 0);
 261                 return DM_MAPIO_SUBMITTED;
 262         }
 263 }
 264
 265 static int stripe_map(struct dm_target *ti, struct bio *bio,
 266                       union map_info *map_context)
 267 {
 268         struct stripe_c *sc = ti->private;
 269         uint32_t stripe;
 270         unsigned target_request_nr;
 271
 272         if (bio->bi_rw & REQ_FLUSH) {
 273                 target_request_nr = map_context->target_request_nr;
 274                 BUG_ON(target_request_nr >= sc->stripes);
 275                 bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
 276                 return DM_MAPIO_REMAPPED;
 277         }
 278         if (unlikely(bio->bi_rw & REQ_DISCARD)) {
 279                 target_request_nr = map_context->target_request_nr;
 280                 BUG_ON(target_request_nr >= sc->stripes);
 281                 return stripe_map_discard(sc, bio, target_request_nr);
 282         }
 283
 284         stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
 285
 286         bio->bi_sector += sc->stripe[stripe].physical_start;
 287         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
 288
 289         return DM_MAPIO_REMAPPED;
 290 }
 291
 292 /*
 293  * Stripe status:
 294  *
 295  * INFO
 296  * #stripes [stripe_name <stripe_name>] [group word count]
 297  * [error count 'A|D' <error count 'A|D'>]
 298  *
 299  * TABLE
 300  * #stripes [stripe chunk size]
 301  * [stripe_name physical_start <stripe_name physical_start>]
 302  *
 303  */
 304
 305 static int stripe_status(struct dm_target *ti,
 306                          status_type_t type, char *result, unsigned int maxlen)
 307 {
 308         struct stripe_c *sc = (struct stripe_c *) ti->private;
 309         char buffer[sc->stripes + 1];
 310         unsigned int sz = 0;
 311         unsigned int i;
 312
 313         switch (type) {
 314         case STATUSTYPE_INFO:
 315                 DMEMIT("%d ", sc->stripes);
 316                 for (i = 0; i < sc->stripes; i++)  {
 317                         DMEMIT("%s ", sc->stripe[i].dev->name);
 318                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
 319                                 'D' : 'A';
 320                 }
 321                 buffer[i] = '\0';
 322                 DMEMIT("1 %s", buffer);
 323                 break;
 324
 325         case STATUSTYPE_TABLE:
 326                 DMEMIT("%d %llu", sc->stripes,
 327                         (unsigned long long)sc->chunk_mask + 1);
 328                 for (i = 0; i < sc->stripes; i++)
 329                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 330                             (unsigned long long)sc->stripe[i].physical_start);
 331                 break;
 332         }
 333         return 0;
 334 }
 335
 336 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 337                          int error, union map_info *map_context)
 338 {
 339         unsigned i;
 340         char major_minor[16];
 341         struct stripe_c *sc = ti->private;
 342
 343         if (!error)
 344                 return 0; /* I/O complete */
 345
 346         if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
 347                 return error;
 348
 349         if (error == -EOPNOTSUPP)
 350                 return error;
 351
 352         memset(major_minor, 0, sizeof(major_minor));
 353         sprintf(major_minor, "%d:%d",
 354                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
 355                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 356
 357         /*
 358          * Test to see which stripe drive triggered the event
 359          * and increment error count for all stripes on that device.
 360          * If the error count for a given device exceeds the threshold
 361          * value we will no longer trigger any further events.
 362          */
 363         for (i = 0; i < sc->stripes; i++)
 364                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 365                         atomic_inc(&(sc->stripe[i].error_count));
 366                         if (atomic_read(&(sc->stripe[i].error_count)) <
 367                             DM_IO_ERROR_THRESHOLD)
 368                                 schedule_work(&sc->trigger_event);
 369                 }
 370
 371         return error;
 372 }
 373
 374 static int stripe_iterate_devices(struct dm_target *ti,
 375                                   iterate_devices_callout_fn fn, void *data)
 376 {
 377         struct stripe_c *sc = ti->private;
 378         int ret = 0;
 379         unsigned i = 0;
 380
 381         do {
 382                 ret = fn(ti, sc->stripe[i].dev,
 383                          sc->stripe[i].physical_start,
 384                          sc->stripe_width, data);
 385         } while (!ret && ++i < sc->stripes);
 386
 387         return ret;
 388 }
 389
 390 static void stripe_io_hints(struct dm_target *ti,
 391                             struct queue_limits *limits)
 392 {
 393         struct stripe_c *sc = ti->private;
 394         unsigned chunk_size = (sc->chunk_mask + 1) << 9;
 395
 396         blk_limits_io_min(limits, chunk_size);
 397         blk_limits_io_opt(limits, chunk_size * sc->stripes);
 398 }
 399
 400 static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 401                         struct bio_vec *biovec, int max_size)
 402 {
 403         struct stripe_c *sc = ti->private;
 404         sector_t bvm_sector = bvm->bi_sector;
 405         uint32_t stripe;
 406         struct request_queue *q;
 407
 408         stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
 409
 410         q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
 411         if (!q->merge_bvec_fn)
 412                 return max_size;
 413
 414         bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
 415         bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
 416
 417         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 418 }
 419
 420 static struct target_type stripe_target = {
 421         .name   = "striped",
 422         .version = {1, 4, 0},
 423         .module = THIS_MODULE,
 424         .ctr    = stripe_ctr,
 425         .dtr    = stripe_dtr,
 426         .map    = stripe_map,
 427         .end_io = stripe_end_io,
 428         .status = stripe_status,
 429         .iterate_devices = stripe_iterate_devices,
 430         .io_hints = stripe_io_hints,
 431         .merge  = stripe_merge,
 432 };
 433
 434 int __init dm_stripe_init(void)
 435 {
 436         int r;
 437
 438         r = dm_register_target(&stripe_target);
 439         if (r < 0) {
 440                 DMWARN("target registration failed");
 441                 return r;
 442         }
 443
 444         return r;
 445 }
 446
 447 void dm_stripe_exit(void)
 448 {
 449         dm_unregister_target(&stripe_target);
 450 }