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         conf = linear_conf(mddev, mddev->raid_disks);
 220
 221         if (!conf)
 222                 return 1;
 223         mddev->private = conf;
 224         md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 225
 226         blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 227         mddev->queue->unplug_fn = linear_unplug;
 228         mddev->queue->backing_dev_info.congested_fn = linear_congested;
 229         mddev->queue->backing_dev_info.congested_data = mddev;
 230         md_integrity_register(mddev);
 231         return 0;
 232 }
 233
 234 static void free_conf(struct rcu_head *head)
 235 {
 236         linear_conf_t *conf = container_of(head, linear_conf_t, rcu);
 237         kfree(conf);
 238 }
 239
 240 static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
 241 {
 242         /* Adding a drive to a linear array allows the array to grow.
 243          * It is permitted if the new drive has a matching superblock
 244          * already on it, with raid_disk equal to raid_disks.
 245          * It is achieved by creating a new linear_private_data structure
 246          * and swapping it in in-place of the current one.
 247          * The current one is never freed until the array is stopped.
 248          * This avoids races.
 249          */
 250         linear_conf_t *newconf, *oldconf;
 251
 252         if (rdev->saved_raid_disk != mddev->raid_disks)
 253                 return -EINVAL;
 254
 255         rdev->raid_disk = rdev->saved_raid_disk;
 256
 257         newconf = linear_conf(mddev,mddev->raid_disks+1);
 258
 259         if (!newconf)
 260                 return -ENOMEM;
 261
 262         oldconf = rcu_dereference(mddev->private);
 263         mddev->raid_disks++;
 264         rcu_assign_pointer(mddev->private, newconf);
 265         md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 266         set_capacity(mddev->gendisk, mddev->array_sectors);
 267         revalidate_disk(mddev->gendisk);
 268         call_rcu(&oldconf->rcu, free_conf);
 269         return 0;
 270 }
 271
 272 static int linear_stop (mddev_t *mddev)
 273 {
 274         linear_conf_t *conf = mddev->private;
 275
 276         /*
 277          * We do not require rcu protection here since
 278          * we hold reconfig_mutex for both linear_add and
 279          * linear_stop, so they cannot race.
 280          * We should make sure any old 'conf's are properly
 281          * freed though.
 282          */
 283         rcu_barrier();
 284         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 285         kfree(conf);
 286         mddev->private = NULL;
 287
 288         return 0;
 289 }
 290
 291 static int linear_make_request (mddev_t *mddev, struct bio *bio)
 292 {
 293         dev_info_t *tmp_dev;
 294         sector_t start_sector;
 295
 296         if (unlikely(bio->bi_rw & REQ_FLUSH)) {
 297                 md_flush_request(mddev, bio);
 298                 return 0;
 299         }
 300
 301         rcu_read_lock();
 302         tmp_dev = which_dev(mddev, bio->bi_sector);
 303         start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
 304
 305
 306         if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
 307                      || (bio->bi_sector < start_sector))) {
 308                 char b[BDEVNAME_SIZE];
 309
 310                 printk(KERN_ERR
 311                        "md/linear:%s: make_request: Sector %llu out of bounds on "
 312                        "dev %s: %llu sectors, offset %llu\n",
 313                        mdname(mddev),
 314                        (unsigned long long)bio->bi_sector,
 315                        bdevname(tmp_dev->rdev->bdev, b),
 316                        (unsigned long long)tmp_dev->rdev->sectors,
 317                        (unsigned long long)start_sector);
 318                 rcu_read_unlock();
 319                 bio_io_error(bio);
 320                 return 0;
 321         }
 322         if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
 323                      tmp_dev->end_sector)) {
 324                 /* This bio crosses a device boundary, so we have to
 325                  * split it.
 326                  */
 327                 struct bio_pair *bp;
 328                 sector_t end_sector = tmp_dev->end_sector;
 329
 330                 rcu_read_unlock();
 331
 332                 bp = bio_split(bio, end_sector - bio->bi_sector);
 333
 334                 if (linear_make_request(mddev, &bp->bio1))
 335                         generic_make_request(&bp->bio1);
 336                 if (linear_make_request(mddev, &bp->bio2))
 337                         generic_make_request(&bp->bio2);
 338                 bio_pair_release(bp);
 339                 return 0;
 340         }
 341
 342         bio->bi_bdev = tmp_dev->rdev->bdev;
 343         bio->bi_sector = bio->bi_sector - start_sector
 344                 + tmp_dev->rdev->data_offset;
 345         rcu_read_unlock();
 346
 347         return 1;
 348 }
 349
 350 static void linear_status (struct seq_file *seq, mddev_t *mddev)
 351 {
 352
 353         seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
 354 }
 355
 356
 357 static struct mdk_personality linear_personality =
 358 {
 359         .name           = "linear",
 360         .level          = LEVEL_LINEAR,
 361         .owner          = THIS_MODULE,
 362         .make_request   = linear_make_request,
 363         .run            = linear_run,
 364         .stop           = linear_stop,
 365         .status         = linear_status,
 366         .hot_add_disk   = linear_add,
 367         .size           = linear_size,
 368 };
 369
 370 static int __init linear_init (void)
 371 {
 372         return register_md_personality (&linear_personality);
 373 }
 374
 375 static void linear_exit (void)
 376 {
 377         unregister_md_personality (&linear_personality);
 378 }
 379
 380
 381 module_init(linear_init);
 382 module_exit(linear_exit);
 383 MODULE_LICENSE("GPL");
 384 MODULE_DESCRIPTION("Linear device concatenation personality for MD");
 385 MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
 386 MODULE_ALIAS("md-linear");
 387 MODULE_ALIAS("md-level--1");