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 struct dev_info *which_dev(struct mddev *mddev, sector_t sector)
  30 {
  31         int lo, mid, hi;
  32         struct linear_conf *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         struct mddev *mddev = q->queuedata;
  67         struct dev_info *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 int linear_congested(void *data, int bits)
  91 {
  92         struct mddev *mddev = data;
  93         struct linear_conf *conf;
  94         int i, ret = 0;
  95
  96         if (mddev_congested(mddev, bits))
  97                 return 1;
  98
  99         rcu_read_lock();
 100         conf = rcu_dereference(mddev->private);
 101
 102         for (i = 0; i < mddev->raid_disks && !ret ; i++) {
 103                 struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
 104                 ret |= bdi_congested(&q->backing_dev_info, bits);
 105         }
 106
 107         rcu_read_unlock();
 108         return ret;
 109 }
 110
 111 static sector_t linear_size(struct mddev *mddev, sector_t sectors, int raid_disks)
 112 {
 113         struct linear_conf *conf;
 114         sector_t array_sectors;
 115
 116         rcu_read_lock();
 117         conf = rcu_dereference(mddev->private);
 118         WARN_ONCE(sectors || raid_disks,
 119                   "%s does not support generic reshape\n", __func__);
 120         array_sectors = conf->array_sectors;
 121         rcu_read_unlock();
 122
 123         return array_sectors;
 124 }
 125
 126 static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
 127 {
 128         struct linear_conf *conf;
 129         struct md_rdev *rdev;
 130         int i, cnt;
 131
 132         conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(struct dev_info),
 133                         GFP_KERNEL);
 134         if (!conf)
 135                 return NULL;
 136
 137         cnt = 0;
 138         conf->array_sectors = 0;
 139
 140         list_for_each_entry(rdev, &mddev->disks, same_set) {
 141                 int j = rdev->raid_disk;
 142                 struct dev_info *disk = conf->disks + j;
 143                 sector_t sectors;
 144
 145                 if (j < 0 || j >= raid_disks || disk->rdev) {
 146                         printk(KERN_ERR "md/linear:%s: disk numbering problem. Aborting!\n",
 147                                mdname(mddev));
 148                         goto out;
 149                 }
 150
 151                 disk->rdev = rdev;
 152                 if (mddev->chunk_sectors) {
 153                         sectors = rdev->sectors;
 154                         sector_div(sectors, mddev->chunk_sectors);
 155                         rdev->sectors = sectors * mddev->chunk_sectors;
 156                 }
 157
 158                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 159                                   rdev->data_offset << 9);
 160                 /* as we don't honour merge_bvec_fn, we must never risk
 161                  * violating it, so limit max_segments to 1 lying within
 162                  * a single page.
 163                  */
 164                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
 165                         blk_queue_max_segments(mddev->queue, 1);
 166                         blk_queue_segment_boundary(mddev->queue,
 167                                                    PAGE_CACHE_SIZE - 1);
 168                 }
 169
 170                 conf->array_sectors += rdev->sectors;
 171                 cnt++;
 172
 173         }
 174         if (cnt != raid_disks) {
 175                 printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
 176                        mdname(mddev));
 177                 goto out;
 178         }
 179
 180         /*
 181          * Here we calculate the device offsets.
 182          */
 183         conf->disks[0].end_sector = conf->disks[0].rdev->sectors;
 184
 185         for (i = 1; i < raid_disks; i++)
 186                 conf->disks[i].end_sector =
 187                         conf->disks[i-1].end_sector +
 188                         conf->disks[i].rdev->sectors;
 189
 190         return conf;
 191
 192 out:
 193         kfree(conf);
 194         return NULL;
 195 }
 196
 197 static int linear_run (struct mddev *mddev)
 198 {
 199         struct linear_conf *conf;
 200
 201         if (md_check_no_bitmap(mddev))
 202                 return -EINVAL;
 203         conf = linear_conf(mddev, mddev->raid_disks);
 204
 205         if (!conf)
 206                 return 1;
 207         mddev->private = conf;
 208         md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 209
 210         blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 211         mddev->queue->backing_dev_info.congested_fn = linear_congested;
 212         mddev->queue->backing_dev_info.congested_data = mddev;
 213         return md_integrity_register(mddev);
 214 }
 215
 216 static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
 217 {
 218         /* Adding a drive to a linear array allows the array to grow.
 219          * It is permitted if the new drive has a matching superblock
 220          * already on it, with raid_disk equal to raid_disks.
 221          * It is achieved by creating a new linear_private_data structure
 222          * and swapping it in in-place of the current one.
 223          * The current one is never freed until the array is stopped.
 224          * This avoids races.
 225          */
 226         struct linear_conf *newconf, *oldconf;
 227
 228         if (rdev->saved_raid_disk != mddev->raid_disks)
 229                 return -EINVAL;
 230
 231         rdev->raid_disk = rdev->saved_raid_disk;
 232
 233         newconf = linear_conf(mddev,mddev->raid_disks+1);
 234
 235         if (!newconf)
 236                 return -ENOMEM;
 237
 238         oldconf = rcu_dereference(mddev->private);
 239         mddev->raid_disks++;
 240         rcu_assign_pointer(mddev->private, newconf);
 241         md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 242         set_capacity(mddev->gendisk, mddev->array_sectors);
 243         revalidate_disk(mddev->gendisk);
 244         kfree_rcu(oldconf, rcu);
 245         return 0;
 246 }
 247
 248 static int linear_stop (struct mddev *mddev)
 249 {
 250         struct linear_conf *conf = mddev->private;
 251
 252         /*
 253          * We do not require rcu protection here since
 254          * we hold reconfig_mutex for both linear_add and
 255          * linear_stop, so they cannot race.
 256          * We should make sure any old 'conf's are properly
 257          * freed though.
 258          */
 259         rcu_barrier();
 260         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 261         kfree(conf);
 262         mddev->private = NULL;
 263
 264         return 0;
 265 }
 266
 267 static int linear_make_request (struct mddev *mddev, struct bio *bio)
 268 {
 269         struct dev_info *tmp_dev;
 270         sector_t start_sector;
 271
 272         if (unlikely(bio->bi_rw & REQ_FLUSH)) {
 273                 md_flush_request(mddev, bio);
 274                 return 0;
 275         }
 276
 277         rcu_read_lock();
 278         tmp_dev = which_dev(mddev, bio->bi_sector);
 279         start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
 280
 281
 282         if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
 283                      || (bio->bi_sector < start_sector))) {
 284                 char b[BDEVNAME_SIZE];
 285
 286                 printk(KERN_ERR
 287                        "md/linear:%s: make_request: Sector %llu out of bounds on "
 288                        "dev %s: %llu sectors, offset %llu\n",
 289                        mdname(mddev),
 290                        (unsigned long long)bio->bi_sector,
 291                        bdevname(tmp_dev->rdev->bdev, b),
 292                        (unsigned long long)tmp_dev->rdev->sectors,
 293                        (unsigned long long)start_sector);
 294                 rcu_read_unlock();
 295                 bio_io_error(bio);
 296                 return 0;
 297         }
 298         if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
 299                      tmp_dev->end_sector)) {
 300                 /* This bio crosses a device boundary, so we have to
 301                  * split it.
 302                  */
 303                 struct bio_pair *bp;
 304                 sector_t end_sector = tmp_dev->end_sector;
 305
 306                 rcu_read_unlock();
 307
 308                 bp = bio_split(bio, end_sector - bio->bi_sector);
 309
 310                 if (linear_make_request(mddev, &bp->bio1))
 311                         generic_make_request(&bp->bio1);
 312                 if (linear_make_request(mddev, &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 - start_sector
 320                 + tmp_dev->rdev->data_offset;
 321         rcu_read_unlock();
 322
 323         return 1;
 324 }
 325
 326 static void linear_status (struct seq_file *seq, struct mddev *mddev)
 327 {
 328
 329         seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
 330 }
 331
 332
 333 static struct md_personality linear_personality =
 334 {
 335         .name           = "linear",
 336         .level          = LEVEL_LINEAR,
 337         .owner          = THIS_MODULE,
 338         .make_request   = linear_make_request,
 339         .run            = linear_run,
 340         .stop           = linear_stop,
 341         .status         = linear_status,
 342         .hot_add_disk   = linear_add,
 343         .size           = linear_size,
 344 };
 345
 346 static int __init linear_init (void)
 347 {
 348         return register_md_personality (&linear_personality);
 349 }
 350
 351 static void linear_exit (void)
 352 {
 353         unregister_md_personality (&linear_personality);
 354 }
 355
 356
 357 module_init(linear_init);
 358 module_exit(linear_exit);
 359 MODULE_LICENSE("GPL");
 360 MODULE_DESCRIPTION("Linear device concatenation personality for MD");
 361 MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
 362 MODULE_ALIAS("md-linear");
 363 MODULE_ALIAS("md-level--1");