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 kstriped_ws;
  43
  44         struct stripe stripe[0];
  45 };
  46
  47 static struct workqueue_struct *kstriped;
  48
  49 /*
  50  * An event is triggered whenever a drive
  51  * drops out of a stripe volume.
  52  */
  53 static void trigger_event(struct work_struct *work)
  54 {
  55         struct stripe_c *sc = container_of(work, struct stripe_c, kstriped_ws);
  56
  57         dm_table_event(sc->ti->table);
  58
  59 }
  60
  61 static inline struct stripe_c *alloc_context(unsigned int stripes)
  62 {
  63         size_t len;
  64
  65         if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
  66                              stripes))
  67                 return NULL;
  68
  69         len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
  70
  71         return kmalloc(len, GFP_KERNEL);
  72 }
  73
  74 /*
  75  * Parse a single <dev> <sector> pair
  76  */
  77 static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
  78                       unsigned int stripe, char **argv)
  79 {
  80         unsigned long long start;
  81
  82         if (sscanf(argv[1], "%llu", &start) != 1)
  83                 return -EINVAL;
  84
  85         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
  86                           &sc->stripe[stripe].dev))
  87                 return -ENXIO;
  88
  89         sc->stripe[stripe].physical_start = start;
  90
  91         return 0;
  92 }
  93
  94 /*
  95  * Construct a striped mapping.
  96  * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
  97  */
  98 static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  99 {
 100         struct stripe_c *sc;
 101         sector_t width;
 102         uint32_t stripes;
 103         uint32_t chunk_size;
 104         char *end;
 105         int r;
 106         unsigned int i;
 107
 108         if (argc < 2) {
 109                 ti->error = "Not enough arguments";
 110                 return -EINVAL;
 111         }
 112
 113         stripes = simple_strtoul(argv[0], &end, 10);
 114         if (!stripes || *end) {
 115                 ti->error = "Invalid stripe count";
 116                 return -EINVAL;
 117         }
 118
 119         chunk_size = simple_strtoul(argv[1], &end, 10);
 120         if (*end) {
 121                 ti->error = "Invalid chunk_size";
 122                 return -EINVAL;
 123         }
 124
 125         /*
 126          * chunk_size is a power of two
 127          */
 128         if (!is_power_of_2(chunk_size) ||
 129             (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
 130                 ti->error = "Invalid chunk size";
 131                 return -EINVAL;
 132         }
 133
 134         if (ti->len & (chunk_size - 1)) {
 135                 ti->error = "Target length not divisible by "
 136                     "chunk size";
 137                 return -EINVAL;
 138         }
 139
 140         width = ti->len;
 141         if (sector_div(width, stripes)) {
 142                 ti->error = "Target length not divisible by "
 143                     "number of stripes";
 144                 return -EINVAL;
 145         }
 146
 147         /*
 148          * Do we have enough arguments for that many stripes ?
 149          */
 150         if (argc != (2 + 2 * stripes)) {
 151                 ti->error = "Not enough destinations "
 152                         "specified";
 153                 return -EINVAL;
 154         }
 155
 156         sc = alloc_context(stripes);
 157         if (!sc) {
 158                 ti->error = "Memory allocation for striped context "
 159                     "failed";
 160                 return -ENOMEM;
 161         }
 162
 163         INIT_WORK(&sc->kstriped_ws, trigger_event);
 164
 165         /* Set pointer to dm target; used in trigger_event */
 166         sc->ti = ti;
 167         sc->stripes = stripes;
 168         sc->stripe_width = width;
 169
 170         if (stripes & (stripes - 1))
 171                 sc->stripes_shift = -1;
 172         else {
 173                 sc->stripes_shift = ffs(stripes) - 1;
 174                 sc->stripes_mask = ((sector_t) stripes) - 1;
 175         }
 176
 177         ti->split_io = chunk_size;
 178         ti->num_flush_requests = stripes;
 179         ti->num_discard_requests = stripes;
 180
 181         sc->chunk_shift = ffs(chunk_size) - 1;
 182         sc->chunk_mask = ((sector_t) chunk_size) - 1;
 183
 184         /*
 185          * Get the stripe destinations.
 186          */
 187         for (i = 0; i < stripes; i++) {
 188                 argv += 2;
 189
 190                 r = get_stripe(ti, sc, i, argv);
 191                 if (r < 0) {
 192                         ti->error = "Couldn't parse stripe destination";
 193                         while (i--)
 194                                 dm_put_device(ti, sc->stripe[i].dev);
 195                         kfree(sc);
 196                         return r;
 197                 }
 198                 atomic_set(&(sc->stripe[i].error_count), 0);
 199         }
 200
 201         ti->private = sc;
 202
 203         return 0;
 204 }
 205
 206 static void stripe_dtr(struct dm_target *ti)
 207 {
 208         unsigned int i;
 209         struct stripe_c *sc = (struct stripe_c *) ti->private;
 210
 211         for (i = 0; i < sc->stripes; i++)
 212                 dm_put_device(ti, sc->stripe[i].dev);
 213
 214         flush_workqueue(kstriped);
 215         kfree(sc);
 216 }
 217
 218 static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
 219                               uint32_t *stripe, sector_t *result)
 220 {
 221         sector_t offset = dm_target_offset(sc->ti, sector);
 222         sector_t chunk = offset >> sc->chunk_shift;
 223
 224         if (sc->stripes_shift < 0)
 225                 *stripe = sector_div(chunk, sc->stripes);
 226         else {
 227                 *stripe = chunk & sc->stripes_mask;
 228                 chunk >>= sc->stripes_shift;
 229         }
 230
 231         *result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);
 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         *result &= ~sc->chunk_mask;                     /* round down */
 243         if (target_stripe < stripe)
 244                 *result += sc->chunk_mask + 1;          /* next chunk */
 245 }
 246
 247 static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
 248                               uint32_t target_stripe)
 249 {
 250         sector_t begin, end;
 251
 252         stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
 253         stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
 254                                 target_stripe, &end);
 255         if (begin < end) {
 256                 bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
 257                 bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
 258                 bio->bi_size = to_bytes(end - begin);
 259                 return DM_MAPIO_REMAPPED;
 260         } else {
 261                 /* The range doesn't map to the target stripe */
 262                 bio_endio(bio, 0);
 263                 return DM_MAPIO_SUBMITTED;
 264         }
 265 }
 266
 267 static int stripe_map(struct dm_target *ti, struct bio *bio,
 268                       union map_info *map_context)
 269 {
 270         struct stripe_c *sc = ti->private;
 271         uint32_t stripe;
 272         unsigned target_request_nr;
 273
 274         if (unlikely(bio_empty_barrier(bio))) {
 275                 target_request_nr = map_context->target_request_nr;
 276                 BUG_ON(target_request_nr >= sc->stripes);
 277                 bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
 278                 return DM_MAPIO_REMAPPED;
 279         }
 280         if (unlikely(bio->bi_rw & REQ_DISCARD)) {
 281                 target_request_nr = map_context->target_request_nr;
 282                 BUG_ON(target_request_nr >= sc->stripes);
 283                 return stripe_map_discard(sc, bio, target_request_nr);
 284         }
 285
 286         stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
 287
 288         bio->bi_sector += sc->stripe[stripe].physical_start;
 289         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
 290
 291         return DM_MAPIO_REMAPPED;
 292 }
 293
 294 /*
 295  * Stripe status:
 296  *
 297  * INFO
 298  * #stripes [stripe_name <stripe_name>] [group word count]
 299  * [error count 'A|D' <error count 'A|D'>]
 300  *
 301  * TABLE
 302  * #stripes [stripe chunk size]
 303  * [stripe_name physical_start <stripe_name physical_start>]
 304  *
 305  */
 306
 307 static int stripe_status(struct dm_target *ti,
 308                          status_type_t type, char *result, unsigned int maxlen)
 309 {
 310         struct stripe_c *sc = (struct stripe_c *) ti->private;
 311         char buffer[sc->stripes + 1];
 312         unsigned int sz = 0;
 313         unsigned int i;
 314
 315         switch (type) {
 316         case STATUSTYPE_INFO:
 317                 DMEMIT("%d ", sc->stripes);
 318                 for (i = 0; i < sc->stripes; i++)  {
 319                         DMEMIT("%s ", sc->stripe[i].dev->name);
 320                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
 321                                 'D' : 'A';
 322                 }
 323                 buffer[i] = '\0';
 324                 DMEMIT("1 %s", buffer);
 325                 break;
 326
 327         case STATUSTYPE_TABLE:
 328                 DMEMIT("%d %llu", sc->stripes,
 329                         (unsigned long long)sc->chunk_mask + 1);
 330                 for (i = 0; i < sc->stripes; i++)
 331                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 332                             (unsigned long long)sc->stripe[i].physical_start);
 333                 break;
 334         }
 335         return 0;
 336 }
 337
 338 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 339                          int error, union map_info *map_context)
 340 {
 341         unsigned i;
 342         char major_minor[16];
 343         struct stripe_c *sc = ti->private;
 344
 345         if (!error)
 346                 return 0; /* I/O complete */
 347
 348         if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
 349                 return error;
 350
 351         if (error == -EOPNOTSUPP)
 352                 return error;
 353
 354         memset(major_minor, 0, sizeof(major_minor));
 355         sprintf(major_minor, "%d:%d",
 356                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
 357                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 358
 359         /*
 360          * Test to see which stripe drive triggered the event
 361          * and increment error count for all stripes on that device.
 362          * If the error count for a given device exceeds the threshold
 363          * value we will no longer trigger any further events.
 364          */
 365         for (i = 0; i < sc->stripes; i++)
 366                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 367                         atomic_inc(&(sc->stripe[i].error_count));
 368                         if (atomic_read(&(sc->stripe[i].error_count)) <
 369                             DM_IO_ERROR_THRESHOLD)
 370                                 queue_work(kstriped, &sc->kstriped_ws);
 371                 }
 372
 373         return error;
 374 }
 375
 376 static int stripe_iterate_devices(struct dm_target *ti,
 377                                   iterate_devices_callout_fn fn, void *data)
 378 {
 379         struct stripe_c *sc = ti->private;
 380         int ret = 0;
 381         unsigned i = 0;
 382
 383         do {
 384                 ret = fn(ti, sc->stripe[i].dev,
 385                          sc->stripe[i].physical_start,
 386                          sc->stripe_width, data);
 387         } while (!ret && ++i < sc->stripes);
 388
 389         return ret;
 390 }
 391
 392 static void stripe_io_hints(struct dm_target *ti,
 393                             struct queue_limits *limits)
 394 {
 395         struct stripe_c *sc = ti->private;
 396         unsigned chunk_size = (sc->chunk_mask + 1) << 9;
 397
 398         blk_limits_io_min(limits, chunk_size);
 399         blk_limits_io_opt(limits, chunk_size * sc->stripes);
 400 }
 401
 402 static struct target_type stripe_target = {
 403         .name   = "striped",
 404         .version = {1, 3, 0},
 405         .module = THIS_MODULE,
 406         .ctr    = stripe_ctr,
 407         .dtr    = stripe_dtr,
 408         .map    = stripe_map,
 409         .end_io = stripe_end_io,
 410         .status = stripe_status,
 411         .iterate_devices = stripe_iterate_devices,
 412         .io_hints = stripe_io_hints,
 413 };
 414
 415 int __init dm_stripe_init(void)
 416 {
 417         int r;
 418
 419         r = dm_register_target(&stripe_target);
 420         if (r < 0) {
 421                 DMWARN("target registration failed");
 422                 return r;
 423         }
 424
 425         kstriped = create_singlethread_workqueue("kstriped");
 426         if (!kstriped) {
 427                 DMERR("failed to create workqueue kstriped");
 428                 dm_unregister_target(&stripe_target);
 429                 return -ENOMEM;
 430         }
 431
 432         return r;
 433 }
 434
 435 void dm_stripe_exit(void)
 436 {
 437         dm_unregister_target(&stripe_target);
 438         destroy_workqueue(kstriped);
 439
 440         return;
 441 }