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         (void)sector_div(block, conf->smallest->size);
  42         hash = conf->hash_table[block];
  43
  44         while ((sector>>1) >= (hash->size + hash->offset))
  45                 hash++;
  46         return hash;
  47 }
  48
  49 /**
  50  *      linear_mergeable_bvec -- tell bio layer if a two requests can be merged
  51  *      @q: request queue
  52  *      @bio: the buffer head that's been built up so far
  53  *      @biovec: the request that could be merged to it.
  54  *
  55  *      Return amount of bytes we can take at this offset
  56  */
  57 static int linear_mergeable_bvec(request_queue_t *q, struct bio *bio, struct bio_vec *biovec)
  58 {
  59         mddev_t *mddev = q->queuedata;
  60         dev_info_t *dev0;
  61         unsigned long maxsectors, bio_sectors = bio->bi_size >> 9;
  62         sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
  63
  64         dev0 = which_dev(mddev, sector);
  65         maxsectors = (dev0->size << 1) - (sector - (dev0->offset<<1));
  66
  67         if (maxsectors < bio_sectors)
  68                 maxsectors = 0;
  69         else
  70                 maxsectors -= bio_sectors;
  71
  72         if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
  73                 return biovec->bv_len;
  74         /* The bytes available at this offset could be really big,
  75          * so we cap at 2^31 to avoid overflow */
  76         if (maxsectors > (1 << (31-9)))
  77                 return 1<<31;
  78         return maxsectors << 9;
  79 }
  80
  81 static void linear_unplug(request_queue_t *q)
  82 {
  83         mddev_t *mddev = q->queuedata;
  84         linear_conf_t *conf = mddev_to_conf(mddev);
  85         int i;
  86
  87         for (i=0; i < mddev->raid_disks; i++) {
  88                 request_queue_t *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
  89                 if (r_queue->unplug_fn)
  90                         r_queue->unplug_fn(r_queue);
  91         }
  92 }
  93
  94 static int linear_issue_flush(request_queue_t *q, struct gendisk *disk,
  95                               sector_t *error_sector)
  96 {
  97         mddev_t *mddev = q->queuedata;
  98         linear_conf_t *conf = mddev_to_conf(mddev);
  99         int i, ret = 0;
 100
 101         for (i=0; i < mddev->raid_disks && ret == 0; i++) {
 102                 struct block_device *bdev = conf->disks[i].rdev->bdev;
 103                 request_queue_t *r_queue = bdev_get_queue(bdev);
 104
 105                 if (!r_queue->issue_flush_fn)
 106                         ret = -EOPNOTSUPP;
 107                 else
 108                         ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk, error_sector);
 109         }
 110         return ret;
 111 }
 112
 113 static int linear_run (mddev_t *mddev)
 114 {
 115         linear_conf_t *conf;
 116         dev_info_t **table;
 117         mdk_rdev_t *rdev;
 118         int i, nb_zone, cnt;
 119         sector_t start;
 120         sector_t curr_offset;
 121         struct list_head *tmp;
 122
 123         conf = kmalloc (sizeof (*conf) + mddev->raid_disks*sizeof(dev_info_t),
 124                         GFP_KERNEL);
 125         if (!conf)
 126                 goto out;
 127         memset(conf, 0, sizeof(*conf) + mddev->raid_disks*sizeof(dev_info_t));
 128         mddev->private = conf;
 129
 130         /*
 131          * Find the smallest device.
 132          */
 133
 134         conf->smallest = NULL;
 135         cnt = 0;
 136         mddev->array_size = 0;
 137
 138         ITERATE_RDEV(mddev,rdev,tmp) {
 139                 int j = rdev->raid_disk;
 140                 dev_info_t *disk = conf->disks + j;
 141
 142                 if (j < 0 || j > mddev->raid_disks || disk->rdev) {
 143                         printk("linear: disk numbering problem. Aborting!\n");
 144                         goto out;
 145                 }
 146
 147                 disk->rdev = rdev;
 148
 149                 blk_queue_stack_limits(mddev->queue,
 150                                        rdev->bdev->bd_disk->queue);
 151                 /* as we don't honour merge_bvec_fn, we must never risk
 152                  * violating it, so limit ->max_sector to one PAGE, as
 153                  * a one page request is never in violation.
 154                  */
 155                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 156                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 157                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 158
 159                 disk->size = rdev->size;
 160                 mddev->array_size += rdev->size;
 161
 162                 if (!conf->smallest || (disk->size < conf->smallest->size))
 163                         conf->smallest = disk;
 164                 cnt++;
 165         }
 166         if (cnt != mddev->raid_disks) {
 167                 printk("linear: not enough drives present. Aborting!\n");
 168                 goto out;
 169         }
 170
 171         /*
 172          * This code was restructured to work around a gcc-2.95.3 internal
 173          * compiler error.  Alter it with care.
 174          */
 175         {
 176                 sector_t sz;
 177                 unsigned round;
 178                 unsigned long base;
 179
 180                 sz = mddev->array_size;
 181                 base = conf->smallest->size;
 182                 round = sector_div(sz, base);
 183                 nb_zone = conf->nr_zones = sz + (round ? 1 : 0);
 184         }
 185
 186         conf->hash_table = kmalloc (sizeof (dev_info_t*) * nb_zone,
 187                                         GFP_KERNEL);
 188         if (!conf->hash_table)
 189                 goto out;
 190
 191         /*
 192          * Here we generate the linear hash table
 193          */
 194         table = conf->hash_table;
 195         start = 0;
 196         curr_offset = 0;
 197         for (i = 0; i < cnt; i++) {
 198                 dev_info_t *disk = conf->disks + i;
 199
 200                 disk->offset = curr_offset;
 201                 curr_offset += disk->size;
 202
 203                 /* 'curr_offset' is the end of this disk
 204                  * 'start' is the start of table
 205                  */
 206                 while (start < curr_offset) {
 207                         *table++ = disk;
 208                         start += conf->smallest->size;
 209                 }
 210         }
 211         if (table-conf->hash_table != nb_zone)
 212                 BUG();
 213
 214         blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 215         mddev->queue->unplug_fn = linear_unplug;
 216         mddev->queue->issue_flush_fn = linear_issue_flush;
 217         return 0;
 218
 219 out:
 220         kfree(conf);
 221         return 1;
 222 }
 223
 224 static int linear_stop (mddev_t *mddev)
 225 {
 226         linear_conf_t *conf = mddev_to_conf(mddev);
 227
 228         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 229         kfree(conf->hash_table);
 230         kfree(conf);
 231
 232         return 0;
 233 }
 234
 235 static int linear_make_request (request_queue_t *q, struct bio *bio)
 236 {
 237         mddev_t *mddev = q->queuedata;
 238         dev_info_t *tmp_dev;
 239         sector_t block;
 240
 241         if (bio_data_dir(bio)==WRITE) {
 242                 disk_stat_inc(mddev->gendisk, writes);
 243                 disk_stat_add(mddev->gendisk, write_sectors, bio_sectors(bio));
 244         } else {
 245                 disk_stat_inc(mddev->gendisk, reads);
 246                 disk_stat_add(mddev->gendisk, read_sectors, bio_sectors(bio));
 247         }
 248
 249         tmp_dev = which_dev(mddev, bio->bi_sector);
 250         block = bio->bi_sector >> 1;
 251
 252         if (unlikely(block >= (tmp_dev->size + tmp_dev->offset)
 253                      || block < tmp_dev->offset)) {
 254                 char b[BDEVNAME_SIZE];
 255
 256                 printk("linear_make_request: Block %llu out of bounds on "
 257                         "dev %s size %llu offset %llu\n",
 258                         (unsigned long long)block,
 259                         bdevname(tmp_dev->rdev->bdev, b),
 260                         (unsigned long long)tmp_dev->size,
 261                         (unsigned long long)tmp_dev->offset);
 262                 bio_io_error(bio, bio->bi_size);
 263                 return 0;
 264         }
 265         if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
 266                      (tmp_dev->offset + tmp_dev->size)<<1)) {
 267                 /* This bio crosses a device boundary, so we have to
 268                  * split it.
 269                  */
 270                 struct bio_pair *bp;
 271                 bp = bio_split(bio, bio_split_pool,
 272                                ((tmp_dev->offset + tmp_dev->size)<<1) - bio->bi_sector);
 273                 if (linear_make_request(q, &bp->bio1))
 274                         generic_make_request(&bp->bio1);
 275                 if (linear_make_request(q, &bp->bio2))
 276                         generic_make_request(&bp->bio2);
 277                 bio_pair_release(bp);
 278                 return 0;
 279         }
 280
 281         bio->bi_bdev = tmp_dev->rdev->bdev;
 282         bio->bi_sector = bio->bi_sector - (tmp_dev->offset << 1) + tmp_dev->rdev->data_offset;
 283
 284         return 1;
 285 }
 286
 287 static void linear_status (struct seq_file *seq, mddev_t *mddev)
 288 {
 289
 290 #undef MD_DEBUG
 291 #ifdef MD_DEBUG
 292         int j;
 293         linear_conf_t *conf = mddev_to_conf(mddev);
 294         sector_t s = 0;
 295
 296         seq_printf(seq, "      ");
 297         for (j = 0; j < conf->nr_zones; j++)
 298         {
 299                 char b[BDEVNAME_SIZE];
 300                 s += conf->smallest_size;
 301                 seq_printf(seq, "[%s",
 302                            bdevname(conf->hash_table[j][0].rdev->bdev,b));
 303
 304                 while (s > conf->hash_table[j][0].offset +
 305                            conf->hash_table[j][0].size)
 306                         seq_printf(seq, "/%s] ",
 307                                    bdevname(conf->hash_table[j][1].rdev->bdev,b));
 308                 else
 309                         seq_printf(seq, "] ");
 310         }
 311         seq_printf(seq, "\n");
 312 #endif
 313         seq_printf(seq, " %dk rounding", mddev->chunk_size/1024);
 314 }
 315
 316
 317 static mdk_personality_t linear_personality=
 318 {
 319         .name           = "linear",
 320         .owner          = THIS_MODULE,
 321         .make_request   = linear_make_request,
 322         .run            = linear_run,
 323         .stop           = linear_stop,
 324         .status         = linear_status,
 325 };
 326
 327 static int __init linear_init (void)
 328 {
 329         return register_md_personality (LINEAR, &linear_personality);
 330 }
 331
 332 static void linear_exit (void)
 333 {
 334         unregister_md_personality (LINEAR);
 335 }
 336
 337
 338 module_init(linear_init);
 339 module_exit(linear_exit);
 340 MODULE_LICENSE("GPL");
 341 MODULE_ALIAS("md-personality-1"); /* LINEAR */