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
  29         /* The size of this target / num. stripes */
  30         sector_t stripe_width;
  31
  32         /* stripe chunk size */
  33         uint32_t chunk_shift;
  34         sector_t chunk_mask;
  35
  36         /* Needed for handling events */
  37         struct dm_target *ti;
  38
  39         /* Work struct used for triggering events*/
  40         struct work_struct kstriped_ws;
  41
  42         struct stripe stripe[0];
  43 };
  44
  45 static struct workqueue_struct *kstriped;
  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, kstriped_ws);
  54
  55         dm_table_event(sc->ti->table);
  56
  57 }
  58
  59 static inline struct stripe_c *alloc_context(unsigned int stripes)
  60 {
  61         size_t len;
  62
  63         if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
  64                              stripes))
  65                 return NULL;
  66
  67         len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
  68
  69         return kmalloc(len, GFP_KERNEL);
  70 }
  71
  72 /*
  73  * Parse a single <dev> <sector> pair
  74  */
  75 static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
  76                       unsigned int stripe, char **argv)
  77 {
  78         unsigned long long start;
  79
  80         if (sscanf(argv[1], "%llu", &start) != 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->kstriped_ws, trigger_event);
 162
 163         /* Set pointer to dm target; used in trigger_event */
 164         sc->ti = ti;
 165
 166         sc->stripes = stripes;
 167         sc->stripe_width = width;
 168         ti->split_io = chunk_size;
 169         ti->num_flush_requests = stripes;
 170
 171         sc->chunk_mask = ((sector_t) chunk_size) - 1;
 172         for (sc->chunk_shift = 0; chunk_size; sc->chunk_shift++)
 173                 chunk_size >>= 1;
 174         sc->chunk_shift--;
 175
 176         /*
 177          * Get the stripe destinations.
 178          */
 179         for (i = 0; i < stripes; i++) {
 180                 argv += 2;
 181
 182                 r = get_stripe(ti, sc, i, argv);
 183                 if (r < 0) {
 184                         ti->error = "Couldn't parse stripe destination";
 185                         while (i--)
 186                                 dm_put_device(ti, sc->stripe[i].dev);
 187                         kfree(sc);
 188                         return r;
 189                 }
 190                 atomic_set(&(sc->stripe[i].error_count), 0);
 191         }
 192
 193         ti->private = sc;
 194
 195         return 0;
 196 }
 197
 198 static void stripe_dtr(struct dm_target *ti)
 199 {
 200         unsigned int i;
 201         struct stripe_c *sc = (struct stripe_c *) ti->private;
 202
 203         for (i = 0; i < sc->stripes; i++)
 204                 dm_put_device(ti, sc->stripe[i].dev);
 205
 206         flush_workqueue(kstriped);
 207         kfree(sc);
 208 }
 209
 210 static int stripe_map(struct dm_target *ti, struct bio *bio,
 211                       union map_info *map_context)
 212 {
 213         struct stripe_c *sc = (struct stripe_c *) ti->private;
 214         sector_t offset, chunk;
 215         uint32_t stripe;
 216
 217         if (unlikely(bio_empty_barrier(bio))) {
 218                 BUG_ON(map_context->flush_request >= sc->stripes);
 219                 bio->bi_bdev = sc->stripe[map_context->flush_request].dev->bdev;
 220                 return DM_MAPIO_REMAPPED;
 221         }
 222
 223         offset = bio->bi_sector - ti->begin;
 224         chunk = offset >> sc->chunk_shift;
 225         stripe = sector_div(chunk, sc->stripes);
 226
 227         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
 228         bio->bi_sector = sc->stripe[stripe].physical_start +
 229             (chunk << sc->chunk_shift) + (offset & sc->chunk_mask);
 230         return DM_MAPIO_REMAPPED;
 231 }
 232
 233 /*
 234  * Stripe status:
 235  *
 236  * INFO
 237  * #stripes [stripe_name <stripe_name>] [group word count]
 238  * [error count 'A|D' <error count 'A|D'>]
 239  *
 240  * TABLE
 241  * #stripes [stripe chunk size]
 242  * [stripe_name physical_start <stripe_name physical_start>]
 243  *
 244  */
 245
 246 static int stripe_status(struct dm_target *ti,
 247                          status_type_t type, char *result, unsigned int maxlen)
 248 {
 249         struct stripe_c *sc = (struct stripe_c *) ti->private;
 250         char buffer[sc->stripes + 1];
 251         unsigned int sz = 0;
 252         unsigned int i;
 253
 254         switch (type) {
 255         case STATUSTYPE_INFO:
 256                 DMEMIT("%d ", sc->stripes);
 257                 for (i = 0; i < sc->stripes; i++)  {
 258                         DMEMIT("%s ", sc->stripe[i].dev->name);
 259                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
 260                                 'D' : 'A';
 261                 }
 262                 buffer[i] = '\0';
 263                 DMEMIT("1 %s", buffer);
 264                 break;
 265
 266         case STATUSTYPE_TABLE:
 267                 DMEMIT("%d %llu", sc->stripes,
 268                         (unsigned long long)sc->chunk_mask + 1);
 269                 for (i = 0; i < sc->stripes; i++)
 270                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 271                             (unsigned long long)sc->stripe[i].physical_start);
 272                 break;
 273         }
 274         return 0;
 275 }
 276
 277 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 278                          int error, union map_info *map_context)
 279 {
 280         unsigned i;
 281         char major_minor[16];
 282         struct stripe_c *sc = ti->private;
 283
 284         if (!error)
 285                 return 0; /* I/O complete */
 286
 287         if ((error == -EWOULDBLOCK) && bio_rw_flagged(bio, BIO_RW_AHEAD))
 288                 return error;
 289
 290         if (error == -EOPNOTSUPP)
 291                 return error;
 292
 293         memset(major_minor, 0, sizeof(major_minor));
 294         sprintf(major_minor, "%d:%d",
 295                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
 296                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 297
 298         /*
 299          * Test to see which stripe drive triggered the event
 300          * and increment error count for all stripes on that device.
 301          * If the error count for a given device exceeds the threshold
 302          * value we will no longer trigger any further events.
 303          */
 304         for (i = 0; i < sc->stripes; i++)
 305                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 306                         atomic_inc(&(sc->stripe[i].error_count));
 307                         if (atomic_read(&(sc->stripe[i].error_count)) <
 308                             DM_IO_ERROR_THRESHOLD)
 309                                 queue_work(kstriped, &sc->kstriped_ws);
 310                 }
 311
 312         return error;
 313 }
 314
 315 static int stripe_iterate_devices(struct dm_target *ti,
 316                                   iterate_devices_callout_fn fn, void *data)
 317 {
 318         struct stripe_c *sc = ti->private;
 319         int ret = 0;
 320         unsigned i = 0;
 321
 322         do {
 323                 ret = fn(ti, sc->stripe[i].dev,
 324                          sc->stripe[i].physical_start,
 325                          sc->stripe_width, data);
 326         } while (!ret && ++i < sc->stripes);
 327
 328         return ret;
 329 }
 330
 331 static void stripe_io_hints(struct dm_target *ti,
 332                             struct queue_limits *limits)
 333 {
 334         struct stripe_c *sc = ti->private;
 335         unsigned chunk_size = (sc->chunk_mask + 1) << 9;
 336
 337         blk_limits_io_min(limits, chunk_size);
 338         blk_limits_io_opt(limits, chunk_size * sc->stripes);
 339 }
 340
 341 static struct target_type stripe_target = {
 342         .name   = "striped",
 343         .version = {1, 3, 0},
 344         .module = THIS_MODULE,
 345         .ctr    = stripe_ctr,
 346         .dtr    = stripe_dtr,
 347         .map    = stripe_map,
 348         .end_io = stripe_end_io,
 349         .status = stripe_status,
 350         .iterate_devices = stripe_iterate_devices,
 351         .io_hints = stripe_io_hints,
 352 };
 353
 354 int __init dm_stripe_init(void)
 355 {
 356         int r;
 357
 358         r = dm_register_target(&stripe_target);
 359         if (r < 0) {
 360                 DMWARN("target registration failed");
 361                 return r;
 362         }
 363
 364         kstriped = create_singlethread_workqueue("kstriped");
 365         if (!kstriped) {
 366                 DMERR("failed to create workqueue kstriped");
 367                 dm_unregister_target(&stripe_target);
 368                 return -ENOMEM;
 369         }
 370
 371         return r;
 372 }
 373
 374 void dm_stripe_exit(void)
 375 {
 376         dm_unregister_target(&stripe_target);
 377         destroy_workqueue(kstriped);
 378
 379         return;
 380 }