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