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