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/blkdev.h>
  20 #include <linux/raid/md_u.h>
  21 #include <linux/seq_file.h>
  22 #include <linux/slab.h>
  23 #include "md.h"
  24 #include "linear.h"
  25
  26 /*
  27  * find which device holds a particular offset
  28  */
  29 static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
  30 {
  31         int lo, mid, hi;
  32         linear_conf_t *conf;
  33
  34         lo = 0;
  35         hi = mddev->raid_disks - 1;
  36         conf = rcu_dereference(mddev->private);
  37
  38         /*
  39          * Binary Search
  40          */
  41
  42         while (hi > lo) {
  43
  44                 mid = (hi + lo) / 2;
  45                 if (sector < conf->disks[mid].end_sector)
  46                         hi = mid;
  47                 else
  48                         lo = mid + 1;
  49         }
  50
  51         return conf->disks + lo;
  52 }
  53
  54 /**
  55  *      linear_mergeable_bvec -- tell bio layer if two requests can be merged
  56  *      @q: request queue
  57  *      @bvm: properties of new bio
  58  *      @biovec: the request that could be merged to it.
  59  *
  60  *      Return amount of bytes we can take at this offset
  61  */
  62 static int linear_mergeable_bvec(struct request_queue *q,
  63                                  struct bvec_merge_data *bvm,
  64                                  struct bio_vec *biovec)
  65 {
  66         mddev_t *mddev = q->queuedata;
  67         dev_info_t *dev0;
  68         unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
  69         sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
  70
  71         rcu_read_lock();
  72         dev0 = which_dev(mddev, sector);
  73         maxsectors = dev0->end_sector - sector;
  74         rcu_read_unlock();
  75
  76         if (maxsectors < bio_sectors)
  77                 maxsectors = 0;
  78         else
  79                 maxsectors -= bio_sectors;
  80
  81         if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
  82                 return biovec->bv_len;
  83         /* The bytes available at this offset could be really big,
  84          * so we cap at 2^31 to avoid overflow */
  85         if (maxsectors > (1 << (31-9)))
  86                 return 1<<31;
  87         return maxsectors << 9;
  88 }
  89
  90 static void linear_unplug(struct request_queue *q)
  91 {
  92         mddev_t *mddev = q->queuedata;
  93         linear_conf_t *conf;
  94         int i;
  95
  96         rcu_read_lock();
  97         conf = rcu_dereference(mddev->private);
  98
  99         for (i=0; i < mddev->raid_disks; i++) {
 100                 struct request_queue *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
 101                 blk_unplug(r_queue);
 102         }
 103         rcu_read_unlock();
 104 }
 105
 106 static int linear_congested(void *data, int bits)
 107 {
 108         mddev_t *mddev = data;
 109         linear_conf_t *conf;
 110         int i, ret = 0;
 111
 112         if (mddev_congested(mddev, bits))
 113                 return 1;
 114
 115         rcu_read_lock();
 116         conf = rcu_dereference(mddev->private);
 117
 118         for (i = 0; i < mddev->raid_disks && !ret ; i++) {
 119                 struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
 120                 ret |= bdi_congested(&q->backing_dev_info, bits);
 121         }
 122
 123         rcu_read_unlock();
 124         return ret;
 125 }
 126
 127 static sector_t linear_size(mddev_t *mddev, sector_t sectors, int raid_disks)
 128 {
 129         linear_conf_t *conf;
 130         sector_t array_sectors;
 131
 132         rcu_read_lock();
 133         conf = rcu_dereference(mddev->private);
 134         WARN_ONCE(sectors || raid_disks,
 135                   "%s does not support generic reshape\n", __func__);
 136         array_sectors = conf->array_sectors;
 137         rcu_read_unlock();
 138
 139         return array_sectors;
 140 }
 141
 142 static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
 143 {
 144         linear_conf_t *conf;
 145         mdk_rdev_t *rdev;
 146         int i, cnt;
 147
 148         conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(dev_info_t),
 149                         GFP_KERNEL);
 150         if (!conf)
 151                 return NULL;
 152
 153         cnt = 0;
 154         conf->array_sectors = 0;
 155
 156         list_for_each_entry(rdev, &mddev->disks, same_set) {
 157                 int j = rdev->raid_disk;
 158                 dev_info_t *disk = conf->disks + j;
 159                 sector_t sectors;
 160
 161                 if (j < 0 || j >= raid_disks || disk->rdev) {
 162                         printk(KERN_ERR "md/linear:%s: disk numbering problem. Aborting!\n",
 163                                mdname(mddev));
 164                         goto out;
 165                 }
 166
 167                 disk->rdev = rdev;
 168                 if (mddev->chunk_sectors) {
 169                         sectors = rdev->sectors;
 170                         sector_div(sectors, mddev->chunk_sectors);
 171                         rdev->sectors = sectors * mddev->chunk_sectors;
 172                 }
 173
 174                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 175                                   rdev->data_offset << 9);
 176                 /* as we don't honour merge_bvec_fn, we must never risk
 177                  * violating it, so limit max_segments to 1 lying within
 178                  * a single page.
 179                  */
 180                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
 181                         blk_queue_max_segments(mddev->queue, 1);
 182                         blk_queue_segment_boundary(mddev->queue,
 183                                                    PAGE_CACHE_SIZE - 1);
 184                 }
 185
 186                 conf->array_sectors += rdev->sectors;
 187                 cnt++;
 188
 189         }
 190         if (cnt != raid_disks) {
 191                 printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
 192                        mdname(mddev));
 193                 goto out;
 194         }
 195
 196         /*
 197          * Here we calculate the device offsets.
 198          */
 199         conf->disks[0].end_sector = conf->disks[0].rdev->sectors;
 200
 201         for (i = 1; i < raid_disks; i++)
 202                 conf->disks[i].end_sector =
 203                         conf->disks[i-1].end_sector +
 204                         conf->disks[i].rdev->sectors;
 205
 206         return conf;
 207
 208 out:
 209         kfree(conf);
 210         return NULL;
 211 }
 212
 213 static int linear_run (mddev_t *mddev)
 214 {
 215         linear_conf_t *conf;
 216
 217         if (md_check_no_bitmap(mddev))
 218                 return -EINVAL;
 219         mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 220         conf = linear_conf(mddev, mddev->raid_disks);
 221
 222         if (!conf)
 223                 return 1;
 224         mddev->private = conf;
 225         md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 226
 227         blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 228         mddev->queue->unplug_fn = linear_unplug;
 229         mddev->queue->backing_dev_info.congested_fn = linear_congested;
 230         mddev->queue->backing_dev_info.congested_data = mddev;
 231         md_integrity_register(mddev);
 232         return 0;
 233 }
 234
 235 static void free_conf(struct rcu_head *head)
 236 {
 237         linear_conf_t *conf = container_of(head, linear_conf_t, rcu);
 238         kfree(conf);
 239 }
 240
 241 static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
 242 {
 243         /* Adding a drive to a linear array allows the array to grow.
 244          * It is permitted if the new drive has a matching superblock
 245          * already on it, with raid_disk equal to raid_disks.
 246          * It is achieved by creating a new linear_private_data structure
 247          * and swapping it in in-place of the current one.
 248          * The current one is never freed until the array is stopped.
 249          * This avoids races.
 250          */
 251         linear_conf_t *newconf, *oldconf;
 252
 253         if (rdev->saved_raid_disk != mddev->raid_disks)
 254                 return -EINVAL;
 255
 256         rdev->raid_disk = rdev->saved_raid_disk;
 257
 258         newconf = linear_conf(mddev,mddev->raid_disks+1);
 259
 260         if (!newconf)
 261                 return -ENOMEM;
 262
 263         oldconf = rcu_dereference(mddev->private);
 264         mddev->raid_disks++;
 265         rcu_assign_pointer(mddev->private, newconf);
 266         md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 267         set_capacity(mddev->gendisk, mddev->array_sectors);
 268         revalidate_disk(mddev->gendisk);
 269         call_rcu(&oldconf->rcu, free_conf);
 270         return 0;
 271 }
 272
 273 static int linear_stop (mddev_t *mddev)
 274 {
 275         linear_conf_t *conf = mddev->private;
 276
 277         /*
 278          * We do not require rcu protection here since
 279          * we hold reconfig_mutex for both linear_add and
 280          * linear_stop, so they cannot race.
 281          * We should make sure any old 'conf's are properly
 282          * freed though.
 283          */
 284         rcu_barrier();
 285         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 286         kfree(conf);
 287         mddev->private = NULL;
 288
 289         return 0;
 290 }
 291
 292 static int linear_make_request (mddev_t *mddev, struct bio *bio)
 293 {
 294         dev_info_t *tmp_dev;
 295         sector_t start_sector;
 296
 297         if (unlikely(bio->bi_rw & REQ_FLUSH)) {
 298                 md_flush_request(mddev, bio);
 299                 return 0;
 300         }
 301
 302         rcu_read_lock();
 303         tmp_dev = which_dev(mddev, bio->bi_sector);
 304         start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
 305
 306
 307         if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
 308                      || (bio->bi_sector < start_sector))) {
 309                 char b[BDEVNAME_SIZE];
 310
 311                 printk(KERN_ERR
 312                        "md/linear:%s: make_request: Sector %llu out of bounds on "
 313                        "dev %s: %llu sectors, offset %llu\n",
 314                        mdname(mddev),
 315                        (unsigned long long)bio->bi_sector,
 316                        bdevname(tmp_dev->rdev->bdev, b),
 317                        (unsigned long long)tmp_dev->rdev->sectors,
 318                        (unsigned long long)start_sector);
 319                 rcu_read_unlock();
 320                 bio_io_error(bio);
 321                 return 0;
 322         }
 323         if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
 324                      tmp_dev->end_sector)) {
 325                 /* This bio crosses a device boundary, so we have to
 326                  * split it.
 327                  */
 328                 struct bio_pair *bp;
 329                 sector_t end_sector = tmp_dev->end_sector;
 330
 331                 rcu_read_unlock();
 332
 333                 bp = bio_split(bio, end_sector - bio->bi_sector);
 334
 335                 if (linear_make_request(mddev, &bp->bio1))
 336                         generic_make_request(&bp->bio1);
 337                 if (linear_make_request(mddev, &bp->bio2))
 338                         generic_make_request(&bp->bio2);
 339                 bio_pair_release(bp);
 340                 return 0;
 341         }
 342
 343         bio->bi_bdev = tmp_dev->rdev->bdev;
 344         bio->bi_sector = bio->bi_sector - start_sector
 345                 + tmp_dev->rdev->data_offset;
 346         rcu_read_unlock();
 347
 348         return 1;
 349 }
 350
 351 static void linear_status (struct seq_file *seq, mddev_t *mddev)
 352 {
 353
 354         seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
 355 }
 356
 357
 358 static struct mdk_personality linear_personality =
 359 {
 360         .name           = "linear",
 361         .level          = LEVEL_LINEAR,
 362         .owner          = THIS_MODULE,
 363         .make_request   = linear_make_request,
 364         .run            = linear_run,
 365         .stop           = linear_stop,
 366         .status         = linear_status,
 367         .hot_add_disk   = linear_add,
 368         .size           = linear_size,
 369 };
 370
 371 static int __init linear_init (void)
 372 {
 373         return register_md_personality (&linear_personality);
 374 }
 375
 376 static void linear_exit (void)
 377 {
 378         unregister_md_personality (&linear_personality);
 379 }
 380
 381
 382 module_init(linear_init);
 383 module_exit(linear_exit);
 384 MODULE_LICENSE("GPL");
 385 MODULE_DESCRIPTION("Linear device concatenation personality for MD");
 386 MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
 387 MODULE_ALIAS("md-linear");
 388 MODULE_ALIAS("md-level--1");