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 = kzalloc (sizeof (*conf) + mddev->raid_disks*sizeof(dev_info_t),
 125                         GFP_KERNEL);
 126         if (!conf)
 127                 goto out;
 128         mddev->private = conf;
 129
 130         cnt = 0;
 131         mddev->array_size = 0;
 132
 133         ITERATE_RDEV(mddev,rdev,tmp) {
 134                 int j = rdev->raid_disk;
 135                 dev_info_t *disk = conf->disks + j;
 136
 137                 if (j < 0 || j > mddev->raid_disks || disk->rdev) {
 138                         printk("linear: disk numbering problem. Aborting!\n");
 139                         goto out;
 140                 }
 141
 142                 disk->rdev = rdev;
 143
 144                 blk_queue_stack_limits(mddev->queue,
 145                                        rdev->bdev->bd_disk->queue);
 146                 /* as we don't honour merge_bvec_fn, we must never risk
 147                  * violating it, so limit ->max_sector to one PAGE, as
 148                  * a one page request is never in violation.
 149                  */
 150                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 151                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 152                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 153
 154                 disk->size = rdev->size;
 155                 mddev->array_size += rdev->size;
 156
 157                 cnt++;
 158         }
 159         if (cnt != mddev->raid_disks) {
 160                 printk("linear: not enough drives present. Aborting!\n");
 161                 goto out;
 162         }
 163
 164         min_spacing = mddev->array_size;
 165         sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));
 166
 167         /* min_spacing is the minimum spacing that will fit the hash
 168          * table in one PAGE.  This may be much smaller than needed.
 169          * We find the smallest non-terminal set of consecutive devices
 170          * that is larger than min_spacing as use the size of that as
 171          * the actual spacing
 172          */
 173         conf->hash_spacing = mddev->array_size;
 174         for (i=0; i < cnt-1 ; i++) {
 175                 sector_t sz = 0;
 176                 int j;
 177                 for (j=i; i<cnt-1 && sz < min_spacing ; j++)
 178                         sz += conf->disks[j].size;
 179                 if (sz >= min_spacing && sz < conf->hash_spacing)
 180                         conf->hash_spacing = sz;
 181         }
 182
 183         /* hash_spacing may be too large for sector_div to work with,
 184          * so we might need to pre-shift
 185          */
 186         conf->preshift = 0;
 187         if (sizeof(sector_t) > sizeof(u32)) {
 188                 sector_t space = conf->hash_spacing;
 189                 while (space > (sector_t)(~(u32)0)) {
 190                         space >>= 1;
 191                         conf->preshift++;
 192                 }
 193         }
 194         /*
 195          * This code was restructured to work around a gcc-2.95.3 internal
 196          * compiler error.  Alter it with care.
 197          */
 198         {
 199                 sector_t sz;
 200                 unsigned round;
 201                 unsigned long base;
 202
 203                 sz = mddev->array_size >> conf->preshift;
 204                 sz += 1; /* force round-up */
 205                 base = conf->hash_spacing >> conf->preshift;
 206                 round = sector_div(sz, base);
 207                 nb_zone = sz + (round ? 1 : 0);
 208         }
 209         BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));
 210
 211         conf->hash_table = kmalloc (sizeof (struct dev_info *) * nb_zone,
 212                                         GFP_KERNEL);
 213         if (!conf->hash_table)
 214                 goto out;
 215
 216         /*
 217          * Here we generate the linear hash table
 218          * First calculate the device offsets.
 219          */
 220         conf->disks[0].offset = 0;
 221         for (i=1; i<mddev->raid_disks; i++)
 222                 conf->disks[i].offset =
 223                         conf->disks[i-1].offset +
 224                         conf->disks[i-1].size;
 225
 226         table = conf->hash_table;
 227         curr_offset = 0;
 228         i = 0;
 229         for (curr_offset = 0;
 230              curr_offset < mddev->array_size;
 231              curr_offset += conf->hash_spacing) {
 232
 233                 while (i < mddev->raid_disks-1 &&
 234                        curr_offset >= conf->disks[i+1].offset)
 235                         i++;
 236
 237                 *table ++ = conf->disks + i;
 238         }
 239
 240         if (conf->preshift) {
 241                 conf->hash_spacing >>= conf->preshift;
 242                 /* round hash_spacing up so that when we divide by it,
 243                  * we err on the side of "too-low", which is safest.
 244                  */
 245                 conf->hash_spacing++;
 246         }
 247
 248         BUG_ON(table - conf->hash_table > nb_zone);
 249
 250         blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 251         mddev->queue->unplug_fn = linear_unplug;
 252         mddev->queue->issue_flush_fn = linear_issue_flush;
 253         return 0;
 254
 255 out:
 256         kfree(conf);
 257         return 1;
 258 }
 259
 260 static int linear_stop (mddev_t *mddev)
 261 {
 262         linear_conf_t *conf = mddev_to_conf(mddev);
 263
 264         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 265         kfree(conf->hash_table);
 266         kfree(conf);
 267
 268         return 0;
 269 }
 270
 271 static int linear_make_request (request_queue_t *q, struct bio *bio)
 272 {
 273         const int rw = bio_data_dir(bio);
 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         disk_stat_inc(mddev->gendisk, ios[rw]);
 284         disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
 285
 286         tmp_dev = which_dev(mddev, bio->bi_sector);
 287         block = bio->bi_sector >> 1;
 288
 289         if (unlikely(block >= (tmp_dev->size + tmp_dev->offset)
 290                      || block < tmp_dev->offset)) {
 291                 char b[BDEVNAME_SIZE];
 292
 293                 printk("linear_make_request: Block %llu out of bounds on "
 294                         "dev %s size %llu offset %llu\n",
 295                         (unsigned long long)block,
 296                         bdevname(tmp_dev->rdev->bdev, b),
 297                         (unsigned long long)tmp_dev->size,
 298                         (unsigned long long)tmp_dev->offset);
 299                 bio_io_error(bio, bio->bi_size);
 300                 return 0;
 301         }
 302         if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
 303                      (tmp_dev->offset + tmp_dev->size)<<1)) {
 304                 /* This bio crosses a device boundary, so we have to
 305                  * split it.
 306                  */
 307                 struct bio_pair *bp;
 308                 bp = bio_split(bio, bio_split_pool,
 309                                ((tmp_dev->offset + tmp_dev->size)<<1) - bio->bi_sector);
 310                 if (linear_make_request(q, &bp->bio1))
 311                         generic_make_request(&bp->bio1);
 312                 if (linear_make_request(q, &bp->bio2))
 313                         generic_make_request(&bp->bio2);
 314                 bio_pair_release(bp);
 315                 return 0;
 316         }
 317
 318         bio->bi_bdev = tmp_dev->rdev->bdev;
 319         bio->bi_sector = bio->bi_sector - (tmp_dev->offset << 1) + tmp_dev->rdev->data_offset;
 320
 321         return 1;
 322 }
 323
 324 static void linear_status (struct seq_file *seq, mddev_t *mddev)
 325 {
 326
 327 #undef MD_DEBUG
 328 #ifdef MD_DEBUG
 329         int j;
 330         linear_conf_t *conf = mddev_to_conf(mddev);
 331         sector_t s = 0;
 332
 333         seq_printf(seq, "      ");
 334         for (j = 0; j < mddev->raid_disks; j++)
 335         {
 336                 char b[BDEVNAME_SIZE];
 337                 s += conf->smallest_size;
 338                 seq_printf(seq, "[%s",
 339                            bdevname(conf->hash_table[j][0].rdev->bdev,b));
 340
 341                 while (s > conf->hash_table[j][0].offset +
 342                            conf->hash_table[j][0].size)
 343                         seq_printf(seq, "/%s] ",
 344                                    bdevname(conf->hash_table[j][1].rdev->bdev,b));
 345                 else
 346                         seq_printf(seq, "] ");
 347         }
 348         seq_printf(seq, "\n");
 349 #endif
 350         seq_printf(seq, " %dk rounding", mddev->chunk_size/1024);
 351 }
 352
 353
 354 static struct mdk_personality linear_personality =
 355 {
 356         .name           = "linear",
 357         .level          = LEVEL_LINEAR,
 358         .owner          = THIS_MODULE,
 359         .make_request   = linear_make_request,
 360         .run            = linear_run,
 361         .stop           = linear_stop,
 362         .status         = linear_status,
 363 };
 364
 365 static int __init linear_init (void)
 366 {
 367         return register_md_personality (&linear_personality);
 368 }
 369
 370 static void linear_exit (void)
 371 {
 372         unregister_md_personality (&linear_personality);
 373 }
 374
 375
 376 module_init(linear_init);
 377 module_exit(linear_exit);
 378 MODULE_LICENSE("GPL");
 379 MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
 380 MODULE_ALIAS("md-linear");
 381 MODULE_ALIAS("md-level--1");