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  *      @bio: the buffer head that's been built up so far
  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(request_queue_t *q, struct bio *bio, struct bio_vec *biovec)
  59 {
  60         mddev_t *mddev = q->queuedata;
  61         dev_info_t *dev0;
  62         unsigned long maxsectors, bio_sectors = bio->bi_size >> 9;
  63         sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
  64
  65         dev0 = which_dev(mddev, sector);
  66         maxsectors = (dev0->size << 1) - (sector - (dev0->offset<<1));
  67
  68         if (maxsectors < bio_sectors)
  69                 maxsectors = 0;
  70         else
  71                 maxsectors -= bio_sectors;
  72
  73         if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
  74                 return biovec->bv_len;
  75         /* The bytes available at this offset could be really big,
  76          * so we cap at 2^31 to avoid overflow */
  77         if (maxsectors > (1 << (31-9)))
  78                 return 1<<31;
  79         return maxsectors << 9;
  80 }
  81
  82 static void linear_unplug(request_queue_t *q)
  83 {
  84         mddev_t *mddev = q->queuedata;
  85         linear_conf_t *conf = mddev_to_conf(mddev);
  86         int i;
  87
  88         for (i=0; i < mddev->raid_disks; i++) {
  89                 request_queue_t *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
  90                 if (r_queue->unplug_fn)
  91                         r_queue->unplug_fn(r_queue);
  92         }
  93 }
  94
  95 static int linear_issue_flush(request_queue_t *q, struct gendisk *disk,
  96                               sector_t *error_sector)
  97 {
  98         mddev_t *mddev = q->queuedata;
  99         linear_conf_t *conf = mddev_to_conf(mddev);
 100         int i, ret = 0;
 101
 102         for (i=0; i < mddev->raid_disks && ret == 0; i++) {
 103                 struct block_device *bdev = conf->disks[i].rdev->bdev;
 104                 request_queue_t *r_queue = bdev_get_queue(bdev);
 105
 106                 if (!r_queue->issue_flush_fn)
 107                         ret = -EOPNOTSUPP;
 108                 else
 109                         ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk, error_sector);
 110         }
 111         return ret;
 112 }
 113
 114 static int linear_run (mddev_t *mddev)
 115 {
 116         linear_conf_t *conf;
 117         dev_info_t **table;
 118         mdk_rdev_t *rdev;
 119         int i, nb_zone, cnt;
 120         sector_t min_spacing;
 121         sector_t curr_offset;
 122         struct list_head *tmp;
 123
 124         conf = kmalloc (sizeof (*conf) + mddev->raid_disks*sizeof(dev_info_t),
 125                         GFP_KERNEL);
 126         if (!conf)
 127                 goto out;
 128         memset(conf, 0, sizeof(*conf) + mddev->raid_disks*sizeof(dev_info_t));
 129         mddev->private = conf;
 130
 131         cnt = 0;
 132         mddev->array_size = 0;
 133
 134         ITERATE_RDEV(mddev,rdev,tmp) {
 135                 int j = rdev->raid_disk;
 136                 dev_info_t *disk = conf->disks + j;
 137
 138                 if (j < 0 || j > mddev->raid_disks || disk->rdev) {
 139                         printk("linear: disk numbering problem. Aborting!\n");
 140                         goto out;
 141                 }
 142
 143                 disk->rdev = rdev;
 144
 145                 blk_queue_stack_limits(mddev->queue,
 146                                        rdev->bdev->bd_disk->queue);
 147                 /* as we don't honour merge_bvec_fn, we must never risk
 148                  * violating it, so limit ->max_sector to one PAGE, as
 149                  * a one page request is never in violation.
 150                  */
 151                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 152                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 153                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 154
 155                 disk->size = rdev->size;
 156                 mddev->array_size += rdev->size;
 157
 158                 cnt++;
 159         }
 160         if (cnt != mddev->raid_disks) {
 161                 printk("linear: not enough drives present. Aborting!\n");
 162                 goto out;
 163         }
 164
 165         min_spacing = mddev->array_size;
 166         sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));
 167
 168         /* min_spacing is the minimum spacing that will fit the hash
 169          * table in one PAGE.  This may be much smaller than needed.
 170          * We find the smallest non-terminal set of consecutive devices
 171          * that is larger than min_spacing as use the size of that as
 172          * the actual spacing
 173          */
 174         conf->hash_spacing = mddev->array_size;
 175         for (i=0; i < cnt-1 ; i++) {
 176                 sector_t sz = 0;
 177                 int j;
 178                 for (j=i; i<cnt-1 && sz < min_spacing ; j++)
 179                         sz += conf->disks[j].size;
 180                 if (sz >= min_spacing && sz < conf->hash_spacing)
 181                         conf->hash_spacing = sz;
 182         }
 183
 184         /* hash_spacing may be too large for sector_div to work with,
 185          * so we might need to pre-shift
 186          */
 187         conf->preshift = 0;
 188         if (sizeof(sector_t) > sizeof(u32)) {
 189                 sector_t space = conf->hash_spacing;
 190                 while (space > (sector_t)(~(u32)0)) {
 191                         space >>= 1;
 192                         conf->preshift++;
 193                 }
 194         }
 195         /*
 196          * This code was restructured to work around a gcc-2.95.3 internal
 197          * compiler error.  Alter it with care.
 198          */
 199         {
 200                 sector_t sz;
 201                 unsigned round;
 202                 unsigned long base;
 203
 204                 sz = mddev->array_size >> conf->preshift;
 205                 sz += 1; /* force round-up */
 206                 base = conf->hash_spacing >> conf->preshift;
 207                 round = sector_div(sz, base);
 208                 nb_zone = sz + (round ? 1 : 0);
 209         }
 210         BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));
 211
 212         conf->hash_table = kmalloc (sizeof (struct dev_info *) * nb_zone,
 213                                         GFP_KERNEL);
 214         if (!conf->hash_table)
 215                 goto out;
 216
 217         /*
 218          * Here we generate the linear hash table
 219          * First calculate the device offsets.
 220          */
 221         conf->disks[0].offset = 0;
 222         for (i=1; i<mddev->raid_disks; i++)
 223                 conf->disks[i].offset =
 224                         conf->disks[i-1].offset +
 225                         conf->disks[i-1].size;
 226
 227         table = conf->hash_table;
 228         curr_offset = 0;
 229         i = 0;
 230         for (curr_offset = 0;
 231              curr_offset < mddev->array_size;
 232              curr_offset += conf->hash_spacing) {
 233
 234                 while (i < mddev->raid_disks-1 &&
 235                        curr_offset >= conf->disks[i+1].offset)
 236                         i++;
 237
 238                 *table ++ = conf->disks + i;
 239         }
 240
 241         if (conf->preshift) {
 242                 conf->hash_spacing >>= conf->preshift;
 243                 /* round hash_spacing up so that when we divide by it,
 244                  * we err on the side of "too-low", which is safest.
 245                  */
 246                 conf->hash_spacing++;
 247         }
 248
 249         BUG_ON(table - conf->hash_table > nb_zone);
 250
 251         blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 252         mddev->queue->unplug_fn = linear_unplug;
 253         mddev->queue->issue_flush_fn = linear_issue_flush;
 254         return 0;
 255
 256 out:
 257         kfree(conf);
 258         return 1;
 259 }
 260
 261 static int linear_stop (mddev_t *mddev)
 262 {
 263         linear_conf_t *conf = mddev_to_conf(mddev);
 264
 265         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 266         kfree(conf->hash_table);
 267         kfree(conf);
 268
 269         return 0;
 270 }
 271
 272 static int linear_make_request (request_queue_t *q, struct bio *bio)
 273 {
 274         mddev_t *mddev = q->queuedata;
 275         dev_info_t *tmp_dev;
 276         sector_t block;
 277
 278         if (unlikely(bio_barrier(bio))) {
 279                 bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
 280                 return 0;
 281         }
 282
 283         if (bio_data_dir(bio)==WRITE) {
 284                 disk_stat_inc(mddev->gendisk, writes);
 285                 disk_stat_add(mddev->gendisk, write_sectors, bio_sectors(bio));
 286         } else {
 287                 disk_stat_inc(mddev->gendisk, reads);
 288                 disk_stat_add(mddev->gendisk, read_sectors, bio_sectors(bio));
 289         }
 290
 291         tmp_dev = which_dev(mddev, bio->bi_sector);
 292         block = bio->bi_sector >> 1;
 293
 294         if (unlikely(block >= (tmp_dev->size + tmp_dev->offset)
 295                      || block < tmp_dev->offset)) {
 296                 char b[BDEVNAME_SIZE];
 297
 298                 printk("linear_make_request: Block %llu out of bounds on "
 299                         "dev %s size %llu offset %llu\n",
 300                         (unsigned long long)block,
 301                         bdevname(tmp_dev->rdev->bdev, b),
 302                         (unsigned long long)tmp_dev->size,
 303                         (unsigned long long)tmp_dev->offset);
 304                 bio_io_error(bio, bio->bi_size);
 305                 return 0;
 306         }
 307         if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
 308                      (tmp_dev->offset + tmp_dev->size)<<1)) {
 309                 /* This bio crosses a device boundary, so we have to
 310                  * split it.
 311                  */
 312                 struct bio_pair *bp;
 313                 bp = bio_split(bio, bio_split_pool,
 314                                ((tmp_dev->offset + tmp_dev->size)<<1) - bio->bi_sector);
 315                 if (linear_make_request(q, &bp->bio1))
 316                         generic_make_request(&bp->bio1);
 317                 if (linear_make_request(q, &bp->bio2))
 318                         generic_make_request(&bp->bio2);
 319                 bio_pair_release(bp);
 320                 return 0;
 321         }
 322
 323         bio->bi_bdev = tmp_dev->rdev->bdev;
 324         bio->bi_sector = bio->bi_sector - (tmp_dev->offset << 1) + tmp_dev->rdev->data_offset;
 325
 326         return 1;
 327 }
 328
 329 static void linear_status (struct seq_file *seq, mddev_t *mddev)
 330 {
 331
 332 #undef MD_DEBUG
 333 #ifdef MD_DEBUG
 334         int j;
 335         linear_conf_t *conf = mddev_to_conf(mddev);
 336         sector_t s = 0;
 337
 338         seq_printf(seq, "      ");
 339         for (j = 0; j < mddev->raid_disks; j++)
 340         {
 341                 char b[BDEVNAME_SIZE];
 342                 s += conf->smallest_size;
 343                 seq_printf(seq, "[%s",
 344                            bdevname(conf->hash_table[j][0].rdev->bdev,b));
 345
 346                 while (s > conf->hash_table[j][0].offset +
 347                            conf->hash_table[j][0].size)
 348                         seq_printf(seq, "/%s] ",
 349                                    bdevname(conf->hash_table[j][1].rdev->bdev,b));
 350                 else
 351                         seq_printf(seq, "] ");
 352         }
 353         seq_printf(seq, "\n");
 354 #endif
 355         seq_printf(seq, " %dk rounding", mddev->chunk_size/1024);
 356 }
 357
 358
 359 static mdk_personality_t linear_personality=
 360 {
 361         .name           = "linear",
 362         .owner          = THIS_MODULE,
 363         .make_request   = linear_make_request,
 364         .run            = linear_run,
 365         .stop           = linear_stop,
 366         .status         = linear_status,
 367 };
 368
 369 static int __init linear_init (void)
 370 {
 371         return register_md_personality (LINEAR, &linear_personality);
 372 }
 373
 374 static void linear_exit (void)
 375 {
 376         unregister_md_personality (LINEAR);
 377 }
 378
 379
 380 module_init(linear_init);
 381 module_exit(linear_exit);
 382 MODULE_LICENSE("GPL");
 383 MODULE_ALIAS("md-personality-1"); /* LINEAR */