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raid0.c

/*
   raid0.c : Multiple Devices driver for Linux
             Copyright (C) 1994-96 Marc ZYNGIER
           <zyngier@ufr-info-p7.ibp.fr> or
           <maz@gloups.fdn.fr>
             Copyright (C) 1999, 2000 Ingo Molnar, Red Hat


   RAID-0 management functions.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
   
   You should have received a copy of the GNU General Public License
   (for example /usr/src/linux/COPYING); if not, write to the Free
   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  
*/

#include <linux/module.h>
#include <linux/raid/raid0.h>

#define MAJOR_NR MD_MAJOR
#define MD_DRIVER
#define MD_PERSONALITY

static void raid0_unplug(struct request_queue *q)
{
      mddev_t *mddev = q->queuedata;
      raid0_conf_t *conf = mddev_to_conf(mddev);
      mdk_rdev_t **devlist = conf->strip_zone[0].dev;
      int i;

      for (i=0; i<mddev->raid_disks; i++) {
            struct request_queue *r_queue = bdev_get_queue(devlist[i]->bdev);

            blk_unplug(r_queue);
      }
}

static int raid0_congested(void *data, int bits)
{
      mddev_t *mddev = data;
      raid0_conf_t *conf = mddev_to_conf(mddev);
      mdk_rdev_t **devlist = conf->strip_zone[0].dev;
      int i, ret = 0;

      for (i = 0; i < mddev->raid_disks && !ret ; i++) {
            struct request_queue *q = bdev_get_queue(devlist[i]->bdev);

            ret |= bdi_congested(&q->backing_dev_info, bits);
      }
      return ret;
}


static int create_strip_zones (mddev_t *mddev)
{
      int i, c, j;
      sector_t current_offset, curr_zone_offset;
      sector_t min_spacing;
      raid0_conf_t *conf = mddev_to_conf(mddev);
      mdk_rdev_t *smallest, *rdev1, *rdev2, *rdev;
      struct list_head *tmp1, *tmp2;
      struct strip_zone *zone;
      int cnt;
      char b[BDEVNAME_SIZE];
 
      /*
       * The number of 'same size groups'
       */
      conf->nr_strip_zones = 0;
 
      ITERATE_RDEV(mddev,rdev1,tmp1) {
            printk("raid0: looking at %s\n",
                  bdevname(rdev1->bdev,b));
            c = 0;
            ITERATE_RDEV(mddev,rdev2,tmp2) {
                  printk("raid0:   comparing %s(%llu)",
                         bdevname(rdev1->bdev,b),
                         (unsigned long long)rdev1->size);
                  printk(" with %s(%llu)\n",
                         bdevname(rdev2->bdev,b),
                         (unsigned long long)rdev2->size);
                  if (rdev2 == rdev1) {
                        printk("raid0:   END\n");
                        break;
                  }
                  if (rdev2->size == rdev1->size)
                  {
                        /*
                         * Not unique, don't count it as a new
                         * group
                         */
                        printk("raid0:   EQUAL\n");
                        c = 1;
                        break;
                  }
                  printk("raid0:   NOT EQUAL\n");
            }
            if (!c) {
                  printk("raid0:   ==> UNIQUE\n");
                  conf->nr_strip_zones++;
                  printk("raid0: %d zones\n", conf->nr_strip_zones);
            }
      }
      printk("raid0: FINAL %d zones\n", conf->nr_strip_zones);

      conf->strip_zone = kzalloc(sizeof(struct strip_zone)*
                        conf->nr_strip_zones, GFP_KERNEL);
      if (!conf->strip_zone)
            return 1;
      conf->devlist = kzalloc(sizeof(mdk_rdev_t*)*
                        conf->nr_strip_zones*mddev->raid_disks,
                        GFP_KERNEL);
      if (!conf->devlist)
            return 1;

      /* The first zone must contain all devices, so here we check that
       * there is a proper alignment of slots to devices and find them all
       */
      zone = &conf->strip_zone[0];
      cnt = 0;
      smallest = NULL;
      zone->dev = conf->devlist;
      ITERATE_RDEV(mddev, rdev1, tmp1) {
            int j = rdev1->raid_disk;

            if (j < 0 || j >= mddev->raid_disks) {
                  printk("raid0: bad disk number %d - aborting!\n", j);
                  goto abort;
            }
            if (zone->dev[j]) {
                  printk("raid0: multiple devices for %d - aborting!\n",
                        j);
                  goto abort;
            }
            zone->dev[j] = rdev1;

            blk_queue_stack_limits(mddev->queue,
                               rdev1->bdev->bd_disk->queue);
            /* as we don't honour merge_bvec_fn, we must never risk
             * violating it, so limit ->max_sector to one PAGE, as
             * a one page request is never in violation.
             */

            if (rdev1->bdev->bd_disk->queue->merge_bvec_fn &&
                mddev->queue->max_sectors > (PAGE_SIZE>>9))
                  blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

            if (!smallest || (rdev1->size <smallest->size))
                  smallest = rdev1;
            cnt++;
      }
      if (cnt != mddev->raid_disks) {
            printk("raid0: too few disks (%d of %d) - aborting!\n",
                  cnt, mddev->raid_disks);
            goto abort;
      }
      zone->nb_dev = cnt;
      zone->size = smallest->size * cnt;
      zone->zone_offset = 0;

      current_offset = smallest->size;
      curr_zone_offset = zone->size;

      /* now do the other zones */
      for (i = 1; i < conf->nr_strip_zones; i++)
      {
            zone = conf->strip_zone + i;
            zone->dev = conf->strip_zone[i-1].dev + mddev->raid_disks;

            printk("raid0: zone %d\n", i);
            zone->dev_offset = current_offset;
            smallest = NULL;
            c = 0;

            for (j=0; j<cnt; j++) {
                  char b[BDEVNAME_SIZE];
                  rdev = conf->strip_zone[0].dev[j];
                  printk("raid0: checking %s ...", bdevname(rdev->bdev,b));
                  if (rdev->size > current_offset)
                  {
                        printk(" contained as device %d\n", c);
                        zone->dev[c] = rdev;
                        c++;
                        if (!smallest || (rdev->size <smallest->size)) {
                              smallest = rdev;
                              printk("  (%llu) is smallest!.\n", 
                                    (unsigned long long)rdev->size);
                        }
                  } else
                        printk(" nope.\n");
            }

            zone->nb_dev = c;
            zone->size = (smallest->size - current_offset) * c;
            printk("raid0: zone->nb_dev: %d, size: %llu\n",
                  zone->nb_dev, (unsigned long long)zone->size);

            zone->zone_offset = curr_zone_offset;
            curr_zone_offset += zone->size;

            current_offset = smallest->size;
            printk("raid0: current zone offset: %llu\n",
                  (unsigned long long)current_offset);
      }

      /* Now find appropriate hash spacing.
       * We want a number which causes most hash entries to cover
       * at most two strips, but the hash table must be at most
       * 1 PAGE.  We choose the smallest strip, or contiguous collection
       * of strips, that has big enough size.  We never consider the last
       * strip though as it's size has no bearing on the efficacy of the hash
       * table.
       */
      conf->hash_spacing = curr_zone_offset;
      min_spacing = curr_zone_offset;
      sector_div(min_spacing, PAGE_SIZE/sizeof(struct strip_zone*));
      for (i=0; i < conf->nr_strip_zones-1; i++) {
            sector_t sz = 0;
            for (j=i; j<conf->nr_strip_zones-1 &&
                       sz < min_spacing ; j++)
                  sz += conf->strip_zone[j].size;
            if (sz >= min_spacing && sz < conf->hash_spacing)
                  conf->hash_spacing = sz;
      }

      mddev->queue->unplug_fn = raid0_unplug;

      mddev->queue->backing_dev_info.congested_fn = raid0_congested;
      mddev->queue->backing_dev_info.congested_data = mddev;

      printk("raid0: done.\n");
      return 0;
 abort:
      return 1;
}

/**
 *    raid0_mergeable_bvec -- tell bio layer if a two requests can be merged
 *    @q: request queue
 *    @bio: the buffer head that's been built up so far
 *    @biovec: the request that could be merged to it.
 *
 *    Return amount of bytes we can accept at this offset
 */
static int raid0_mergeable_bvec(struct request_queue *q, struct bio *bio, struct bio_vec *biovec)
{
      mddev_t *mddev = q->queuedata;
      sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
      int max;
      unsigned int chunk_sectors = mddev->chunk_size >> 9;
      unsigned int bio_sectors = bio->bi_size >> 9;

      max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
      if (max < 0) max = 0; /* bio_add cannot handle a negative return */
      if (max <= biovec->bv_len && bio_sectors == 0)
            return biovec->bv_len;
      else 
            return max;
}

static int raid0_run (mddev_t *mddev)
{
      unsigned  cur=0, i=0, nb_zone;
      s64 size;
      raid0_conf_t *conf;
      mdk_rdev_t *rdev;
      struct list_head *tmp;

      if (mddev->chunk_size == 0) {
            printk(KERN_ERR "md/raid0: non-zero chunk size required.\n");
            return -EINVAL;
      }
      printk(KERN_INFO "%s: setting max_sectors to %d, segment boundary to %d\n",
             mdname(mddev),
             mddev->chunk_size >> 9,
             (mddev->chunk_size>>1)-1);
      blk_queue_max_sectors(mddev->queue, mddev->chunk_size >> 9);
      blk_queue_segment_boundary(mddev->queue, (mddev->chunk_size>>1) - 1);

      conf = kmalloc(sizeof (raid0_conf_t), GFP_KERNEL);
      if (!conf)
            goto out;
      mddev->private = (void *)conf;
 
      conf->strip_zone = NULL;
      conf->devlist = NULL;
      if (create_strip_zones (mddev)) 
            goto out_free_conf;

      /* calculate array device size */
      mddev->array_size = 0;
      ITERATE_RDEV(mddev,rdev,tmp)
            mddev->array_size += rdev->size;

      printk("raid0 : md_size is %llu blocks.\n", 
            (unsigned long long)mddev->array_size);
      printk("raid0 : conf->hash_spacing is %llu blocks.\n",
            (unsigned long long)conf->hash_spacing);
      {
            sector_t s = mddev->array_size;
            sector_t space = conf->hash_spacing;
            int round;
            conf->preshift = 0;
            if (sizeof(sector_t) > sizeof(u32)) {
                  /*shift down space and s so that sector_div will work */
                  while (space > (sector_t) (~(u32)0)) {
                        s >>= 1;
                        space >>= 1;
                        s += 1; /* force round-up */
                        conf->preshift++;
                  }
            }
            round = sector_div(s, (u32)space) ? 1 : 0;
            nb_zone = s + round;
      }
      printk("raid0 : nb_zone is %d.\n", nb_zone);

      printk("raid0 : Allocating %Zd bytes for hash.\n",
                        nb_zone*sizeof(struct strip_zone*));
      conf->hash_table = kmalloc (sizeof (struct strip_zone *)*nb_zone, GFP_KERNEL);
      if (!conf->hash_table)
            goto out_free_conf;
      size = conf->strip_zone[cur].size;

      conf->hash_table[0] = conf->strip_zone + cur;
      for (i=1; i< nb_zone; i++) {
            while (size <= conf->hash_spacing) {
                  cur++;
                  size += conf->strip_zone[cur].size;
            }
            size -= conf->hash_spacing;
            conf->hash_table[i] = conf->strip_zone + cur;
      }
      if (conf->preshift) {
            conf->hash_spacing >>= conf->preshift;
            /* round hash_spacing up so when we divide by it, we
             * err on the side of too-low, which is safest
             */
            conf->hash_spacing++;
      }

      /* calculate the max read-ahead size.
       * For read-ahead of large files to be effective, we need to
       * readahead at least twice a whole stripe. i.e. number of devices
       * multiplied by chunk size times 2.
       * If an individual device has an ra_pages greater than the
       * chunk size, then we will not drive that device as hard as it
       * wants.  We consider this a configuration error: a larger
       * chunksize should be used in that case.
       */
      {
            int stripe = mddev->raid_disks * mddev->chunk_size / PAGE_SIZE;
            if (mddev->queue->backing_dev_info.ra_pages < 2* stripe)
                  mddev->queue->backing_dev_info.ra_pages = 2* stripe;
      }


      blk_queue_merge_bvec(mddev->queue, raid0_mergeable_bvec);
      return 0;

out_free_conf:
      kfree(conf->strip_zone);
      kfree(conf->devlist);
      kfree(conf);
      mddev->private = NULL;
out:
      return -ENOMEM;
}

static int raid0_stop (mddev_t *mddev)
{
      raid0_conf_t *conf = mddev_to_conf(mddev);

      blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
      kfree(conf->hash_table);
      conf->hash_table = NULL;
      kfree(conf->strip_zone);
      conf->strip_zone = NULL;
      kfree(conf);
      mddev->private = NULL;

      return 0;
}

static int raid0_make_request (struct request_queue *q, struct bio *bio)
{
      mddev_t *mddev = q->queuedata;
      unsigned int sect_in_chunk, chunksize_bits,  chunk_size, chunk_sects;
      raid0_conf_t *conf = mddev_to_conf(mddev);
      struct strip_zone *zone;
      mdk_rdev_t *tmp_dev;
      sector_t chunk;
      sector_t block, rsect;
      const int rw = bio_data_dir(bio);

      if (unlikely(bio_barrier(bio))) {
            bio_endio(bio, -EOPNOTSUPP);
            return 0;
      }

      disk_stat_inc(mddev->gendisk, ios[rw]);
      disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));

      chunk_size = mddev->chunk_size >> 10;
      chunk_sects = mddev->chunk_size >> 9;
      chunksize_bits = ffz(~chunk_size);
      block = bio->bi_sector >> 1;
      

      if (unlikely(chunk_sects < (bio->bi_sector & (chunk_sects - 1)) + (bio->bi_size >> 9))) {
            struct bio_pair *bp;
            /* Sanity check -- queue functions should prevent this happening */
            if (bio->bi_vcnt != 1 ||
                bio->bi_idx != 0)
                  goto bad_map;
            /* This is a one page bio that upper layers
             * refuse to split for us, so we need to split it.
             */
            bp = bio_split(bio, bio_split_pool, chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );
            if (raid0_make_request(q, &bp->bio1))
                  generic_make_request(&bp->bio1);
            if (raid0_make_request(q, &bp->bio2))
                  generic_make_request(&bp->bio2);

            bio_pair_release(bp);
            return 0;
      }
 

      {
            sector_t x = block >> conf->preshift;
            sector_div(x, (u32)conf->hash_spacing);
            zone = conf->hash_table[x];
      }
 
      while (block >= (zone->zone_offset + zone->size)) 
            zone++;
    
      sect_in_chunk = bio->bi_sector & ((chunk_size<<1) -1);


      {
            sector_t x =  (block - zone->zone_offset) >> chunksize_bits;

            sector_div(x, zone->nb_dev);
            chunk = x;

            x = block >> chunksize_bits;
            tmp_dev = zone->dev[sector_div(x, zone->nb_dev)];
      }
      rsect = (((chunk << chunksize_bits) + zone->dev_offset)<<1)
            + sect_in_chunk;
 
      bio->bi_bdev = tmp_dev->bdev;
      bio->bi_sector = rsect + tmp_dev->data_offset;

      /*
       * Let the main block layer submit the IO and resolve recursion:
       */
      return 1;

bad_map:
      printk("raid0_make_request bug: can't convert block across chunks"
            " or bigger than %dk %llu %d\n", chunk_size, 
            (unsigned long long)bio->bi_sector, bio->bi_size >> 10);

      bio_io_error(bio);
      return 0;
}

static void raid0_status (struct seq_file *seq, mddev_t *mddev)
{
#undef MD_DEBUG
#ifdef MD_DEBUG
      int j, k, h;
      char b[BDEVNAME_SIZE];
      raid0_conf_t *conf = mddev_to_conf(mddev);

      h = 0;
      for (j = 0; j < conf->nr_strip_zones; j++) {
            seq_printf(seq, "      z%d", j);
            if (conf->hash_table[h] == conf->strip_zone+j)
                  seq_printf(seq, "(h%d)", h++);
            seq_printf(seq, "=[");
            for (k = 0; k < conf->strip_zone[j].nb_dev; k++)
                  seq_printf(seq, "%s/", bdevname(
                        conf->strip_zone[j].dev[k]->bdev,b));

            seq_printf(seq, "] zo=%d do=%d s=%d\n",
                        conf->strip_zone[j].zone_offset,
                        conf->strip_zone[j].dev_offset,
                        conf->strip_zone[j].size);
      }
#endif
      seq_printf(seq, " %dk chunks", mddev->chunk_size/1024);
      return;
}

static struct mdk_personality raid0_personality=
{
      .name       = "raid0",
      .level            = 0,
      .owner            = THIS_MODULE,
      .make_request     = raid0_make_request,
      .run        = raid0_run,
      .stop       = raid0_stop,
      .status           = raid0_status,
};

static int __init raid0_init (void)
{
      return register_md_personality (&raid0_personality);
}

static void raid0_exit (void)
{
      unregister_md_personality (&raid0_personality);
}

module_init(raid0_init);
module_exit(raid0_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS("md-personality-2"); /* RAID0 */
MODULE_ALIAS("md-raid0");
MODULE_ALIAS("md-level-0");

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