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
 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
 215         sector_t offset = bio->bi_sector - ti->begin;
 216         sector_t chunk = offset >> sc->chunk_shift;
 217         uint32_t stripe = sector_div(chunk, sc->stripes);
 218
 219         bio->bi_bdev = sc->stripe[stripe].dev->bdev;
 220         bio->bi_sector = sc->stripe[stripe].physical_start +
 221             (chunk << sc->chunk_shift) + (offset & sc->chunk_mask);
 222         return DM_MAPIO_REMAPPED;
 223 }
 224
 225 /*
 226  * Stripe status:
 227  *
 228  * INFO
 229  * #stripes [stripe_name <stripe_name>] [group word count]
 230  * [error count 'A|D' <error count 'A|D'>]
 231  *
 232  * TABLE
 233  * #stripes [stripe chunk size]
 234  * [stripe_name physical_start <stripe_name physical_start>]
 235  *
 236  */
 237
 238 static int stripe_status(struct dm_target *ti,
 239                          status_type_t type, char *result, unsigned int maxlen)
 240 {
 241         struct stripe_c *sc = (struct stripe_c *) ti->private;
 242         char buffer[sc->stripes + 1];
 243         unsigned int sz = 0;
 244         unsigned int i;
 245
 246         switch (type) {
 247         case STATUSTYPE_INFO:
 248                 DMEMIT("%d ", sc->stripes);
 249                 for (i = 0; i < sc->stripes; i++)  {
 250                         DMEMIT("%s ", sc->stripe[i].dev->name);
 251                         buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
 252                                 'D' : 'A';
 253                 }
 254                 buffer[i] = '\0';
 255                 DMEMIT("1 %s", buffer);
 256                 break;
 257
 258         case STATUSTYPE_TABLE:
 259                 DMEMIT("%d %llu", sc->stripes,
 260                         (unsigned long long)sc->chunk_mask + 1);
 261                 for (i = 0; i < sc->stripes; i++)
 262                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 263                             (unsigned long long)sc->stripe[i].physical_start);
 264                 break;
 265         }
 266         return 0;
 267 }
 268
 269 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 270                          int error, union map_info *map_context)
 271 {
 272         unsigned i;
 273         char major_minor[16];
 274         struct stripe_c *sc = ti->private;
 275
 276         if (!error)
 277                 return 0; /* I/O complete */
 278
 279         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
 280                 return error;
 281
 282         if (error == -EOPNOTSUPP)
 283                 return error;
 284
 285         memset(major_minor, 0, sizeof(major_minor));
 286         sprintf(major_minor, "%d:%d",
 287                 MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
 288                 MINOR(disk_devt(bio->bi_bdev->bd_disk)));
 289
 290         /*
 291          * Test to see which stripe drive triggered the event
 292          * and increment error count for all stripes on that device.
 293          * If the error count for a given device exceeds the threshold
 294          * value we will no longer trigger any further events.
 295          */
 296         for (i = 0; i < sc->stripes; i++)
 297                 if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 298                         atomic_inc(&(sc->stripe[i].error_count));
 299                         if (atomic_read(&(sc->stripe[i].error_count)) <
 300                             DM_IO_ERROR_THRESHOLD)
 301                                 queue_work(kstriped, &sc->kstriped_ws);
 302                 }
 303
 304         return error;
 305 }
 306
 307 static struct target_type stripe_target = {
 308         .name   = "striped",
 309         .version = {1, 1, 0},
 310         .module = THIS_MODULE,
 311         .ctr    = stripe_ctr,
 312         .dtr    = stripe_dtr,
 313         .map    = stripe_map,
 314         .end_io = stripe_end_io,
 315         .status = stripe_status,
 316 };
 317
 318 int __init dm_stripe_init(void)
 319 {
 320         int r;
 321
 322         r = dm_register_target(&stripe_target);
 323         if (r < 0) {
 324                 DMWARN("target registration failed");
 325                 return r;
 326         }
 327
 328         kstriped = create_singlethread_workqueue("kstriped");
 329         if (!kstriped) {
 330                 DMERR("failed to create workqueue kstriped");
 331                 dm_unregister_target(&stripe_target);
 332                 return -ENOMEM;
 333         }
 334
 335         return r;
 336 }
 337
 338 void dm_stripe_exit(void)
 339 {
 340         dm_unregister_target(&stripe_target);
 341         destroy_workqueue(kstriped);
 342
 343         return;
 344 }