drivers/md/linear.c

   1 /*
   2    linear.c : Multiple Devices driver for Linux
   3               Copyright (C) 1994-96 Marc ZYNGIER
   4               <zyngier@ufr-info-p7.ibp.fr> or
   5               <maz@gloups.fdn.fr>
   6
   7    Linear mode management functions.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2, or (at your option)
  12    any later version.
  13
  14    You should have received a copy of the GNU General Public License
  15    (for example /usr/src/linux/COPYING); if not, write to the Free
  16    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17 */
  18
  19 #include <linux/module.h>
  20
  21 #include <linux/raid/md.h>
  22 #include <linux/slab.h>
  23 #include <linux/raid/linear.h>
  24
  25 #define MAJOR_NR MD_MAJOR
  26 #define MD_DRIVER
  27 #define MD_PERSONALITY
  28
  29 /*
  30  * find which device holds a particular offset
  31  */
  32 static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
  33 {
  34         dev_info_t *hash;
  35         linear_conf_t *conf = mddev_to_conf(mddev);
  36         sector_t block = sector >> 1;
  37
  38         /*
  39          * sector_div(a,b) returns the remainer and sets a to a/b
  40          */
  41         block >>= conf->preshift;
  42         (void)sector_div(block, conf->hash_spacing);
  43         hash = conf->hash_table[block];
  44
  45         while ((sector>>1) >= (hash->size + hash->offset))
  46                 hash++;
  47         return hash;
  48 }
  49
  50 /**
  51  *      linear_mergeable_bvec -- tell bio layer if two requests can be merged
  52  *      @q: request queue
  53  *      @bvm: properties of new bio
  54  *      @biovec: the request that could be merged to it.
  55  *
  56  *      Return amount of bytes we can take at this offset
  57  */
  58 static int linear_mergeable_bvec(struct request_queue *q,
  59                                  struct bvec_merge_data *bvm,
  60                                  struct bio_vec *biovec)
  61 {
  62         mddev_t *mddev = q->queuedata;
  63         dev_info_t *dev0;
  64         unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
  65         sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
  66
  67         dev0 = which_dev(mddev, sector);
  68         maxsectors = (dev0->size << 1) - (sector - (dev0->offset<<1));
  69
  70         if (maxsectors < bio_sectors)
  71                 maxsectors = 0;
  72         else
  73                 maxsectors -= bio_sectors;
  74
  75         if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
  76                 return biovec->bv_len;
  77         /* The bytes available at this offset could be really big,
  78          * so we cap at 2^31 to avoid overflow */
  79         if (maxsectors > (1 << (31-9)))
  80                 return 1<<31;
  81         return maxsectors << 9;
  82 }
  83
  84 static void linear_unplug(struct request_queue *q)
  85 {
  86         mddev_t *mddev = q->queuedata;
  87         linear_conf_t *conf = mddev_to_conf(mddev);
  88         int i;
  89
  90         for (i=0; i < mddev->raid_disks; i++) {
  91                 struct request_queue *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
  92                 blk_unplug(r_queue);
  93         }
  94 }
  95
  96 static int linear_congested(void *data, int bits)
  97 {
  98         mddev_t *mddev = data;
  99         linear_conf_t *conf = mddev_to_conf(mddev);
 100         int i, ret = 0;
 101
 102         for (i = 0; i < mddev->raid_disks && !ret ; i++) {
 103                 struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
 104                 ret |= bdi_congested(&q->backing_dev_info, bits);
 105         }
 106         return ret;
 107 }
 108
 109 static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
 110 {
 111         linear_conf_t *conf;
 112         dev_info_t **table;
 113         mdk_rdev_t *rdev;
 114         int i, nb_zone, cnt;
 115         sector_t min_spacing;
 116         sector_t curr_offset;
 117         struct list_head *tmp;
 118
 119         conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(dev_info_t),
 120                         GFP_KERNEL);
 121         if (!conf)
 122                 return NULL;
 123
 124         cnt = 0;
 125         conf->array_sectors = 0;
 126
 127         rdev_for_each(rdev, tmp, mddev) {
 128                 int j = rdev->raid_disk;
 129                 dev_info_t *disk = conf->disks + j;
 130
 131                 if (j < 0 || j >= raid_disks || disk->rdev) {
 132                         printk("linear: disk numbering problem. Aborting!\n");
 133                         goto out;
 134                 }
 135
 136                 disk->rdev = rdev;
 137
 138                 blk_queue_stack_limits(mddev->queue,
 139                                        rdev->bdev->bd_disk->queue);
 140                 /* as we don't honour merge_bvec_fn, we must never risk
 141                  * violating it, so limit ->max_sector to one PAGE, as
 142                  * a one page request is never in violation.
 143                  */
 144                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 145                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 146                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 147
 148                 disk->size = rdev->size;
 149                 conf->array_sectors += rdev->size * 2;
 150
 151                 cnt++;
 152         }
 153         if (cnt != raid_disks) {
 154                 printk("linear: not enough drives present. Aborting!\n");
 155                 goto out;
 156         }
 157
 158         min_spacing = conf->array_sectors / 2;
 159         sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));
 160
 161         /* min_spacing is the minimum spacing that will fit the hash
 162          * table in one PAGE.  This may be much smaller than needed.
 163          * We find the smallest non-terminal set of consecutive devices
 164          * that is larger than min_spacing as use the size of that as
 165          * the actual spacing
 166          */
 167         conf->hash_spacing = conf->array_sectors / 2;
 168         for (i=0; i < cnt-1 ; i++) {
 169                 sector_t sz = 0;
 170                 int j;
 171                 for (j = i; j < cnt - 1 && sz < min_spacing; j++)
 172                         sz += conf->disks[j].size;
 173                 if (sz >= min_spacing && sz < conf->hash_spacing)
 174                         conf->hash_spacing = sz;
 175         }
 176
 177         /* hash_spacing may be too large for sector_div to work with,
 178          * so we might need to pre-shift
 179          */
 180         conf->preshift = 0;
 181         if (sizeof(sector_t) > sizeof(u32)) {
 182                 sector_t space = conf->hash_spacing;
 183                 while (space > (sector_t)(~(u32)0)) {
 184                         space >>= 1;
 185                         conf->preshift++;
 186                 }
 187         }
 188         /*
 189          * This code was restructured to work around a gcc-2.95.3 internal
 190          * compiler error.  Alter it with care.
 191          */
 192         {
 193                 sector_t sz;
 194                 unsigned round;
 195                 unsigned long base;
 196
 197                 sz = conf->array_sectors >> (conf->preshift + 1);
 198                 sz += 1; /* force round-up */
 199                 base = conf->hash_spacing >> conf->preshift;
 200                 round = sector_div(sz, base);
 201                 nb_zone = sz + (round ? 1 : 0);
 202         }
 203         BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));
 204
 205         conf->hash_table = kmalloc (sizeof (struct dev_info *) * nb_zone,
 206                                         GFP_KERNEL);
 207         if (!conf->hash_table)
 208                 goto out;
 209
 210         /*
 211          * Here we generate the linear hash table
 212          * First calculate the device offsets.
 213          */
 214         conf->disks[0].offset = 0;
 215         for (i = 1; i < raid_disks; i++)
 216                 conf->disks[i].offset =
 217                         conf->disks[i-1].offset +
 218                         conf->disks[i-1].size;
 219
 220         table = conf->hash_table;
 221         curr_offset = 0;
 222         i = 0;
 223         for (curr_offset = 0;
 224              curr_offset < conf->array_sectors / 2;
 225              curr_offset += conf->hash_spacing) {
 226
 227                 while (i < raid_disks-1 &&
 228                        curr_offset >= conf->disks[i+1].offset)
 229                         i++;
 230
 231                 *table ++ = conf->disks + i;
 232         }
 233
 234         if (conf->preshift) {
 235                 conf->hash_spacing >>= conf->preshift;
 236                 /* round hash_spacing up so that when we divide by it,
 237                  * we err on the side of "too-low", which is safest.
 238                  */
 239                 conf->hash_spacing++;
 240         }
 241
 242         BUG_ON(table - conf->hash_table > nb_zone);
 243
 244         return conf;
 245
 246 out:
 247         kfree(conf);
 248         return NULL;
 249 }
 250
 251 static int linear_run (mddev_t *mddev)
 252 {
 253         linear_conf_t *conf;
 254
 255         mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 256         conf = linear_conf(mddev, mddev->raid_disks);
 257
 258         if (!conf)
 259                 return 1;
 260         mddev->private = conf;
 261         mddev->array_sectors = conf->array_sectors;
 262
 263         blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 264         mddev->queue->unplug_fn = linear_unplug;
 265         mddev->queue->backing_dev_info.congested_fn = linear_congested;
 266         mddev->queue->backing_dev_info.congested_data = mddev;
 267         return 0;
 268 }
 269
 270 static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
 271 {
 272         /* Adding a drive to a linear array allows the array to grow.
 273          * It is permitted if the new drive has a matching superblock
 274          * already on it, with raid_disk equal to raid_disks.
 275          * It is achieved by creating a new linear_private_data structure
 276          * and swapping it in in-place of the current one.
 277          * The current one is never freed until the array is stopped.
 278          * This avoids races.
 279          */
 280         linear_conf_t *newconf;
 281
 282         if (rdev->saved_raid_disk != mddev->raid_disks)
 283                 return -EINVAL;
 284
 285         rdev->raid_disk = rdev->saved_raid_disk;
 286
 287         newconf = linear_conf(mddev,mddev->raid_disks+1);
 288
 289         if (!newconf)
 290                 return -ENOMEM;
 291
 292         newconf->prev = mddev_to_conf(mddev);
 293         mddev->private = newconf;
 294         mddev->raid_disks++;
 295         mddev->array_sectors = newconf->array_sectors;
 296         set_capacity(mddev->gendisk, mddev->array_sectors);
 297         return 0;
 298 }
 299
 300 static int linear_stop (mddev_t *mddev)
 301 {
 302         linear_conf_t *conf = mddev_to_conf(mddev);
 303
 304         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 305         do {
 306                 linear_conf_t *t = conf->prev;
 307                 kfree(conf->hash_table);
 308                 kfree(conf);
 309                 conf = t;
 310         } while (conf);
 311
 312         return 0;
 313 }
 314
 315 static int linear_make_request (struct request_queue *q, struct bio *bio)
 316 {
 317         const int rw = bio_data_dir(bio);
 318         mddev_t *mddev = q->queuedata;
 319         dev_info_t *tmp_dev;
 320         sector_t block;
 321
 322         if (unlikely(bio_barrier(bio))) {
 323                 bio_endio(bio, -EOPNOTSUPP);
 324                 return 0;
 325         }
 326
 327         disk_stat_inc(mddev->gendisk, ios[rw]);
 328         disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
 329
 330         tmp_dev = which_dev(mddev, bio->bi_sector);
 331         block = bio->bi_sector >> 1;
 332
 333         if (unlikely(block >= (tmp_dev->size + tmp_dev->offset)
 334                      || block < tmp_dev->offset)) {
 335                 char b[BDEVNAME_SIZE];
 336
 337                 printk("linear_make_request: Block %llu out of bounds on "
 338                         "dev %s size %llu offset %llu\n",
 339                         (unsigned long long)block,
 340                         bdevname(tmp_dev->rdev->bdev, b),
 341                         (unsigned long long)tmp_dev->size,
 342                         (unsigned long long)tmp_dev->offset);
 343                 bio_io_error(bio);
 344                 return 0;
 345         }
 346         if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
 347                      (tmp_dev->offset + tmp_dev->size)<<1)) {
 348                 /* This bio crosses a device boundary, so we have to
 349                  * split it.
 350                  */
 351                 struct bio_pair *bp;
 352                 bp = bio_split(bio, bio_split_pool,
 353                                ((tmp_dev->offset + tmp_dev->size)<<1) - bio->bi_sector);
 354                 if (linear_make_request(q, &bp->bio1))
 355                         generic_make_request(&bp->bio1);
 356                 if (linear_make_request(q, &bp->bio2))
 357                         generic_make_request(&bp->bio2);
 358                 bio_pair_release(bp);
 359                 return 0;
 360         }
 361
 362         bio->bi_bdev = tmp_dev->rdev->bdev;
 363         bio->bi_sector = bio->bi_sector - (tmp_dev->offset << 1) + tmp_dev->rdev->data_offset;
 364
 365         return 1;
 366 }
 367
 368 static void linear_status (struct seq_file *seq, mddev_t *mddev)
 369 {
 370
 371 #undef MD_DEBUG
 372 #ifdef MD_DEBUG
 373         int j;
 374         linear_conf_t *conf = mddev_to_conf(mddev);
 375         sector_t s = 0;
 376
 377         seq_printf(seq, "      ");
 378         for (j = 0; j < mddev->raid_disks; j++)
 379         {
 380                 char b[BDEVNAME_SIZE];
 381                 s += conf->smallest_size;
 382                 seq_printf(seq, "[%s",
 383                            bdevname(conf->hash_table[j][0].rdev->bdev,b));
 384
 385                 while (s > conf->hash_table[j][0].offset +
 386                            conf->hash_table[j][0].size)
 387                         seq_printf(seq, "/%s] ",
 388                                    bdevname(conf->hash_table[j][1].rdev->bdev,b));
 389                 else
 390                         seq_printf(seq, "] ");
 391         }
 392         seq_printf(seq, "\n");
 393 #endif
 394         seq_printf(seq, " %dk rounding", mddev->chunk_size/1024);
 395 }
 396
 397
 398 static struct mdk_personality linear_personality =
 399 {
 400         .name           = "linear",
 401         .level          = LEVEL_LINEAR,
 402         .owner          = THIS_MODULE,
 403         .make_request   = linear_make_request,
 404         .run            = linear_run,
 405         .stop           = linear_stop,
 406         .status         = linear_status,
 407         .hot_add_disk   = linear_add,
 408 };
 409
 410 static int __init linear_init (void)
 411 {
 412         return register_md_personality (&linear_personality);
 413 }
 414
 415 static void linear_exit (void)
 416 {
 417         unregister_md_personality (&linear_personality);
 418 }
 419
 420
 421 module_init(linear_init);
 422 module_exit(linear_exit);
 423 MODULE_LICENSE("GPL");
 424 MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
 425 MODULE_ALIAS("md-linear");
 426 MODULE_ALIAS("md-level--1");