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
  79         if (sscanf(argv[1], "%llu", &start) != 1)
  80                 return -EINVAL;
  81
  82         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
  83                           &sc->stripe[stripe].dev))
  84                 return -ENXIO;
  85
  86         sc->stripe[stripe].physical_start = start;
  87
  88         return 0;
  89 }
  90
  91 /*
  92  * Construct a striped mapping.
  93  * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
  94  */
  95 static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  96 {
  97         struct stripe_c *sc;
  98         sector_t width;
  99         uint32_t stripes;
 100         uint32_t chunk_size;
 101         char *end;
 102         int r;
 103         unsigned int i;
 104
 105         if (argc < 2) {
 106                 ti->error = "Not enough arguments";
 107                 return -EINVAL;
 108         }
 109
 110         stripes = simple_strtoul(argv[0], &end, 10);
 111         if (!stripes || *end) {
 112                 ti->error = "Invalid stripe count";
 113                 return -EINVAL;
 114         }
 115
 116         chunk_size = simple_strtoul(argv[1], &end, 10);
 117         if (*end) {
 118                 ti->error = "Invalid chunk_size";
 119                 return -EINVAL;
 120         }
 121
 122         /*
 123          * chunk_size is a power of two
 124          */
 125         if (!is_power_of_2(chunk_size) ||
 126             (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
 127                 ti->error = "Invalid chunk size";
 128                 return -EINVAL;
 129         }
 130
 131         if (ti->len & (chunk_size - 1)) {
 132                 ti->error = "Target length not divisible by "
 133                     "chunk size";
 134                 return -EINVAL;
 135         }
 136
 137         width = ti->len;
 138         if (sector_div(width, stripes)) {
 139                 ti->error = "Target length not divisible by "
 140                     "number of stripes";
 141                 return -EINVAL;
 142         }
 143
 144         /*
 145          * Do we have enough arguments for that many stripes ?
 146          */
 147         if (argc != (2 + 2 * stripes)) {
 148                 ti->error = "Not enough destinations "
 149                         "specified";
 150                 return -EINVAL;
 151         }
 152
 153         sc = alloc_context(stripes);
 154         if (!sc) {
 155                 ti->error = "Memory allocation for striped context "
 156                     "failed";
 157                 return -ENOMEM;
 158         }
 159
 160         INIT_WORK(&sc->trigger_event, trigger_event);
 161
 162         /* Set pointer to dm target; used in trigger_event */
 163         sc->ti = ti;
 164         sc->stripes = stripes;
 165         sc->stripe_width = width;
 166
 167         if (stripes & (stripes - 1))
 168                 sc->stripes_shift = -1;
 169         else {
 170                 sc->stripes_shift = ffs(stripes) - 1;
 171                 sc->stripes_mask = ((sector_t) stripes) - 1;
 172         }
 173
 174         ti->split_io = chunk_size;
 175         ti->num_flush_requests = stripes;
 176         ti->num_discard_requests = stripes;
 177
 178         sc->chunk_shift = ffs(chunk_size) - 1;
 179         sc->chunk_mask = ((sector_t) chunk_size) - 1;
 180
 181         /*
 182          * Get the stripe destinations.
 183          */
 184         for (i = 0; i < stripes; i++) {
 185                 argv += 2;
 186
 187                 r = get_stripe(ti, sc, i, argv);
 188                 if (r < 0) {
 189                         ti->error = "Couldn't parse stripe destination";
 190                         while (i--)
 191                                 dm_put_device(ti, sc->stripe[i].dev);
 192                         kfree(sc);
 193                         return r;
 194                 }
 195                 atomic_set(&(sc->stripe[i].error_count), 0);
 196         }
 197
 198         ti->private = sc;
 199
 200         return 0;
 201 }
 202
 203 static void stripe_dtr(struct dm_target *ti)
 204 {
 205         unsigned int i;
 206         struct stripe_c *sc = (struct stripe_c *) ti->private;
 207
 208         for (i = 0; i < sc->stripes; i++)
 209                 dm_put_device(ti, sc->stripe[i].dev);
 210
 211         flush_work_sync(&sc->trigger_event);
 212         kfree(sc);
 213 }
 214
 215 static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
 216                               uint32_t *stripe, sector_t *result)
 217 {
 218         sector_t offset = dm_target_offset(sc->ti, sector);
 219         sector_t chunk = offset >> sc->chunk_shift;
 220
 221         if (sc->stripes_shift < 0)
 222                 *stripe = sector_div(chunk, sc->stripes);
 223         else {
 224                 *stripe = chunk & sc->stripes_mask;
 225                 chunk >>= sc->stripes_shift;
 226         }
 227
 228         *result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);
 229 }
 230
 231 static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
 232                                     uint32_t target_stripe, sector_t *result)
 233 {
 234         uint32_t stripe;
 235
 236         stripe_map_sector(sc, sector, &stripe, result);
 237         if (stripe == target_stripe)
 238                 return;
 239         *result &= ~sc->chunk_mask;                     /* round down */
 240         if (target_stripe < stripe)
 241                 *result += sc->chunk_mask + 1;          /* next chunk */
 242 }
 243
 244 static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
 245                               uint32_t target_stripe)
 246 {
 247         sector_t begin, end;
 248
 249         stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
 250         stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
 251                                 target_stripe, &end);
 252         if (begin < end) {
 253                 bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
 254                 bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
 255                 bio->bi_size = to_bytes(end - begin);
 256                 return DM_MAPIO_REMAPPED;
 257         } else {
 258                 /* The range doesn't map to the target stripe */
 259                 bio_endio(bio, 0);
 260                 return DM_MAPIO_SUBMITTED;
 261         }
 262 }
 263
 264 static int stripe_map(struct dm_target *ti, struct bio *bio,
 265                       union map_info *map_context)
 266 {
 267         struct stripe_c *sc = ti->private;
 268         uint32_t stripe;
 269         unsigned target_request_nr;
 270
 271         if (bio->bi_rw & REQ_FLUSH) {
 272                 target_request_nr = map_context->target_request_nr;
 273                 BUG_ON(target_request_nr >= sc->stripes);
 274                 bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
 275                 return DM_MAPIO_REMAPPED;
 276         }
 277         if (unlikely(bio->bi_rw & REQ_DISCARD)) {
 278                 target_request_nr = map_context->target_request_nr;
 279                 BUG_ON(target_request_nr >= sc->stripes);
 280                 return stripe_map_discard(sc, bio, target_request_nr);
 281         }
 282
 283         stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
 284
 285         bio->bi_sector += sc->stripe[stripe].physical_start;
 286         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
 287
 288         return DM_MAPIO_REMAPPED;
 289 }
 290
 291 /*
 292  * Stripe status:
 293  *
 294  * INFO
 295  * #stripes [stripe_name <stripe_name>] [group word count]
 296  * [error count 'A|D' <error count 'A|D'>]
 297  *
 298  * TABLE
 299  * #stripes [stripe chunk size]
 300  * [stripe_name physical_start <stripe_name physical_start>]
 301  *
 302  */
 303
 304 static int stripe_status(struct dm_target *ti,
 305                          status_type_t type, char *result, unsigned int maxlen)
 306 {
 307         struct stripe_c *sc = (struct stripe_c *) ti->private;
 308         char buffer[sc->stripes + 1];
 309         unsigned int sz = 0;
 310         unsigned int i;
 311
 312         switch (type) {
 313         case STATUSTYPE_INFO:
 314                 DMEMIT("%d ", sc->stripes);
 315                 for (i = 0; i < sc->stripes; i++)  {
 316                         DMEMIT("%s ", sc->stripe[i].dev->name);
 317                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
 318                                 'D' : 'A';
 319                 }
 320                 buffer[i] = '\0';
 321                 DMEMIT("1 %s", buffer);
 322                 break;
 323
 324         case STATUSTYPE_TABLE:
 325                 DMEMIT("%d %llu", sc->stripes,
 326                         (unsigned long long)sc->chunk_mask + 1);
 327                 for (i = 0; i < sc->stripes; i++)
 328                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 329                             (unsigned long long)sc->stripe[i].physical_start);
 330                 break;
 331         }
 332         return 0;
 333 }
 334
 335 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 336                          int error, union map_info *map_context)
 337 {
 338         unsigned i;
 339         char major_minor[16];
 340         struct stripe_c *sc = ti->private;
 341
 342         if (!error)
 343                 return 0; /* I/O complete */
 344
 345         if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
 346                 return error;
 347
 348         if (error == -EOPNOTSUPP)
 349                 return error;
 350
 351         memset(major_minor, 0, sizeof(major_minor));
 352         sprintf(major_minor, "%d:%d",
 353                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
 354                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 355
 356         /*
 357          * Test to see which stripe drive triggered the event
 358          * and increment error count for all stripes on that device.
 359          * If the error count for a given device exceeds the threshold
 360          * value we will no longer trigger any further events.
 361          */
 362         for (i = 0; i < sc->stripes; i++)
 363                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 364                         atomic_inc(&(sc->stripe[i].error_count));
 365                         if (atomic_read(&(sc->stripe[i].error_count)) <
 366                             DM_IO_ERROR_THRESHOLD)
 367                                 schedule_work(&sc->trigger_event);
 368                 }
 369
 370         return error;
 371 }
 372
 373 static int stripe_iterate_devices(struct dm_target *ti,
 374                                   iterate_devices_callout_fn fn, void *data)
 375 {
 376         struct stripe_c *sc = ti->private;
 377         int ret = 0;
 378         unsigned i = 0;
 379
 380         do {
 381                 ret = fn(ti, sc->stripe[i].dev,
 382                          sc->stripe[i].physical_start,
 383                          sc->stripe_width, data);
 384         } while (!ret && ++i < sc->stripes);
 385
 386         return ret;
 387 }
 388
 389 static void stripe_io_hints(struct dm_target *ti,
 390                             struct queue_limits *limits)
 391 {
 392         struct stripe_c *sc = ti->private;
 393         unsigned chunk_size = (sc->chunk_mask + 1) << 9;
 394
 395         blk_limits_io_min(limits, chunk_size);
 396         blk_limits_io_opt(limits, chunk_size * sc->stripes);
 397 }
 398
 399 static struct target_type stripe_target = {
 400         .name   = "striped",
 401         .version = {1, 3, 1},
 402         .module = THIS_MODULE,
 403         .ctr    = stripe_ctr,
 404         .dtr    = stripe_dtr,
 405         .map    = stripe_map,
 406         .end_io = stripe_end_io,
 407         .status = stripe_status,
 408         .iterate_devices = stripe_iterate_devices,
 409         .io_hints = stripe_io_hints,
 410 };
 411
 412 int __init dm_stripe_init(void)
 413 {
 414         int r;
 415
 416         r = dm_register_target(&stripe_target);
 417         if (r < 0) {
 418                 DMWARN("target registration failed");
 419                 return r;
 420         }
 421
 422         return r;
 423 }
 424
 425 void dm_stripe_exit(void)
 426 {
 427         dm_unregister_target(&stripe_target);
 428 }