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