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raid1.c

/*
 * raid1.c : Multiple Devices driver for Linux
 *
 * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
 *
 * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
 *
 * RAID-1 management functions.
 *
 * Better read-balancing code written by Mika Kuoppala <miku@iki.fi>, 2000
 *
 * Fixes to reconstruction by Jakob Ƙstergaard" <jakob@ostenfeld.dk>
 * Various fixes by Neil Brown <neilb@cse.unsw.edu.au>
 *
 * Changes by Peter T. Breuer <ptb@it.uc3m.es> 31/1/2003 to support
 * bitmapped intelligence in resync:
 *
 *      - bitmap marked during normal i/o
 *      - bitmap used to skip nondirty blocks during sync
 *
 * Additions to bitmap code, (C) 2003-2004 Paul Clements, SteelEye Technology:
 * - persistent bitmap code
 *
 * 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 "dm-bio-list.h"
#include <linux/raid/raid1.h>
#include <linux/raid/bitmap.h>

#define DEBUG 0
#if DEBUG
#define PRINTK(x...) printk(x)
#else
#define PRINTK(x...)
#endif

/*
 * Number of guaranteed r1bios in case of extreme VM load:
 */
#define     NR_RAID1_BIOS 256


static void unplug_slaves(mddev_t *mddev);

static void allow_barrier(conf_t *conf);
static void lower_barrier(conf_t *conf);

static void * r1bio_pool_alloc(gfp_t gfp_flags, void *data)
{
      struct pool_info *pi = data;
      r1bio_t *r1_bio;
      int size = offsetof(r1bio_t, bios[pi->raid_disks]);

      /* allocate a r1bio with room for raid_disks entries in the bios array */
      r1_bio = kzalloc(size, gfp_flags);
      if (!r1_bio)
            unplug_slaves(pi->mddev);

      return r1_bio;
}

static void r1bio_pool_free(void *r1_bio, void *data)
{
      kfree(r1_bio);
}

#define RESYNC_BLOCK_SIZE (64*1024)
//#define RESYNC_BLOCK_SIZE PAGE_SIZE
#define RESYNC_SECTORS (RESYNC_BLOCK_SIZE >> 9)
#define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
#define RESYNC_WINDOW (2048*1024)

static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data)
{
      struct pool_info *pi = data;
      struct page *page;
      r1bio_t *r1_bio;
      struct bio *bio;
      int i, j;

      r1_bio = r1bio_pool_alloc(gfp_flags, pi);
      if (!r1_bio) {
            unplug_slaves(pi->mddev);
            return NULL;
      }

      /*
       * Allocate bios : 1 for reading, n-1 for writing
       */
      for (j = pi->raid_disks ; j-- ; ) {
            bio = bio_alloc(gfp_flags, RESYNC_PAGES);
            if (!bio)
                  goto out_free_bio;
            r1_bio->bios[j] = bio;
      }
      /*
       * Allocate RESYNC_PAGES data pages and attach them to
       * the first bio.
       * If this is a user-requested check/repair, allocate
       * RESYNC_PAGES for each bio.
       */
      if (test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery))
            j = pi->raid_disks;
      else
            j = 1;
      while(j--) {
            bio = r1_bio->bios[j];
            for (i = 0; i < RESYNC_PAGES; i++) {
                  page = alloc_page(gfp_flags);
                  if (unlikely(!page))
                        goto out_free_pages;

                  bio->bi_io_vec[i].bv_page = page;
            }
      }
      /* If not user-requests, copy the page pointers to all bios */
      if (!test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery)) {
            for (i=0; i<RESYNC_PAGES ; i++)
                  for (j=1; j<pi->raid_disks; j++)
                        r1_bio->bios[j]->bi_io_vec[i].bv_page =
                              r1_bio->bios[0]->bi_io_vec[i].bv_page;
      }

      r1_bio->master_bio = NULL;

      return r1_bio;

out_free_pages:
      for (i=0; i < RESYNC_PAGES ; i++)
            for (j=0 ; j < pi->raid_disks; j++)
                  safe_put_page(r1_bio->bios[j]->bi_io_vec[i].bv_page);
      j = -1;
out_free_bio:
      while ( ++j < pi->raid_disks )
            bio_put(r1_bio->bios[j]);
      r1bio_pool_free(r1_bio, data);
      return NULL;
}

static void r1buf_pool_free(void *__r1_bio, void *data)
{
      struct pool_info *pi = data;
      int i,j;
      r1bio_t *r1bio = __r1_bio;

      for (i = 0; i < RESYNC_PAGES; i++)
            for (j = pi->raid_disks; j-- ;) {
                  if (j == 0 ||
                      r1bio->bios[j]->bi_io_vec[i].bv_page !=
                      r1bio->bios[0]->bi_io_vec[i].bv_page)
                        safe_put_page(r1bio->bios[j]->bi_io_vec[i].bv_page);
            }
      for (i=0 ; i < pi->raid_disks; i++)
            bio_put(r1bio->bios[i]);

      r1bio_pool_free(r1bio, data);
}

static void put_all_bios(conf_t *conf, r1bio_t *r1_bio)
{
      int i;

      for (i = 0; i < conf->raid_disks; i++) {
            struct bio **bio = r1_bio->bios + i;
            if (*bio && *bio != IO_BLOCKED)
                  bio_put(*bio);
            *bio = NULL;
      }
}

static void free_r1bio(r1bio_t *r1_bio)
{
      conf_t *conf = mddev_to_conf(r1_bio->mddev);

      /*
       * Wake up any possible resync thread that waits for the device
       * to go idle.
       */
      allow_barrier(conf);

      put_all_bios(conf, r1_bio);
      mempool_free(r1_bio, conf->r1bio_pool);
}

static void put_buf(r1bio_t *r1_bio)
{
      conf_t *conf = mddev_to_conf(r1_bio->mddev);
      int i;

      for (i=0; i<conf->raid_disks; i++) {
            struct bio *bio = r1_bio->bios[i];
            if (bio->bi_end_io)
                  rdev_dec_pending(conf->mirrors[i].rdev, r1_bio->mddev);
      }

      mempool_free(r1_bio, conf->r1buf_pool);

      lower_barrier(conf);
}

static void reschedule_retry(r1bio_t *r1_bio)
{
      unsigned long flags;
      mddev_t *mddev = r1_bio->mddev;
      conf_t *conf = mddev_to_conf(mddev);

      spin_lock_irqsave(&conf->device_lock, flags);
      list_add(&r1_bio->retry_list, &conf->retry_list);
      conf->nr_queued ++;
      spin_unlock_irqrestore(&conf->device_lock, flags);

      wake_up(&conf->wait_barrier);
      md_wakeup_thread(mddev->thread);
}

/*
 * raid_end_bio_io() is called when we have finished servicing a mirrored
 * operation and are ready to return a success/failure code to the buffer
 * cache layer.
 */
static void raid_end_bio_io(r1bio_t *r1_bio)
{
      struct bio *bio = r1_bio->master_bio;

      /* if nobody has done the final endio yet, do it now */
      if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
            PRINTK(KERN_DEBUG "raid1: sync end %s on sectors %llu-%llu\n",
                  (bio_data_dir(bio) == WRITE) ? "write" : "read",
                  (unsigned long long) bio->bi_sector,
                  (unsigned long long) bio->bi_sector +
                        (bio->bi_size >> 9) - 1);

            bio_endio(bio,
                  test_bit(R1BIO_Uptodate, &r1_bio->state) ? 0 : -EIO);
      }
      free_r1bio(r1_bio);
}

/*
 * Update disk head position estimator based on IRQ completion info.
 */
static inline void update_head_pos(int disk, r1bio_t *r1_bio)
{
      conf_t *conf = mddev_to_conf(r1_bio->mddev);

      conf->mirrors[disk].head_position =
            r1_bio->sector + (r1_bio->sectors);
}

static void raid1_end_read_request(struct bio *bio, int error)
{
      int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
      r1bio_t * r1_bio = (r1bio_t *)(bio->bi_private);
      int mirror;
      conf_t *conf = mddev_to_conf(r1_bio->mddev);

      mirror = r1_bio->read_disk;
      /*
       * this branch is our 'one mirror IO has finished' event handler:
       */
      update_head_pos(mirror, r1_bio);

      if (uptodate)
            set_bit(R1BIO_Uptodate, &r1_bio->state);
      else {
            /* If all other devices have failed, we want to return
             * the error upwards rather than fail the last device.
             * Here we redefine "uptodate" to mean "Don't want to retry"
             */
            unsigned long flags;
            spin_lock_irqsave(&conf->device_lock, flags);
            if (r1_bio->mddev->degraded == conf->raid_disks ||
                (r1_bio->mddev->degraded == conf->raid_disks-1 &&
                 !test_bit(Faulty, &conf->mirrors[mirror].rdev->flags)))
                  uptodate = 1;
            spin_unlock_irqrestore(&conf->device_lock, flags);
      }

      if (uptodate)
            raid_end_bio_io(r1_bio);
      else {
            /*
             * oops, read error:
             */
            char b[BDEVNAME_SIZE];
            if (printk_ratelimit())
                  printk(KERN_ERR "raid1: %s: rescheduling sector %llu\n",
                         bdevname(conf->mirrors[mirror].rdev->bdev,b), (unsigned long long)r1_bio->sector);
            reschedule_retry(r1_bio);
      }

      rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
}

static void raid1_end_write_request(struct bio *bio, int error)
{
      int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
      r1bio_t * r1_bio = (r1bio_t *)(bio->bi_private);
      int mirror, behind = test_bit(R1BIO_BehindIO, &r1_bio->state);
      conf_t *conf = mddev_to_conf(r1_bio->mddev);
      struct bio *to_put = NULL;


      for (mirror = 0; mirror < conf->raid_disks; mirror++)
            if (r1_bio->bios[mirror] == bio)
                  break;

      if (error == -EOPNOTSUPP && test_bit(R1BIO_Barrier, &r1_bio->state)) {
            set_bit(BarriersNotsupp, &conf->mirrors[mirror].rdev->flags);
            set_bit(R1BIO_BarrierRetry, &r1_bio->state);
            r1_bio->mddev->barriers_work = 0;
            /* Don't rdev_dec_pending in this branch - keep it for the retry */
      } else {
            /*
             * this branch is our 'one mirror IO has finished' event handler:
             */
            r1_bio->bios[mirror] = NULL;
            to_put = bio;
            if (!uptodate) {
                  md_error(r1_bio->mddev, conf->mirrors[mirror].rdev);
                  /* an I/O failed, we can't clear the bitmap */
                  set_bit(R1BIO_Degraded, &r1_bio->state);
            } else
                  /*
                   * Set R1BIO_Uptodate in our master bio, so that
                   * we will return a good error code for to the higher
                   * levels even if IO on some other mirrored buffer fails.
                   *
                   * The 'master' represents the composite IO operation to
                   * user-side. So if something waits for IO, then it will
                   * wait for the 'master' bio.
                   */
                  set_bit(R1BIO_Uptodate, &r1_bio->state);

            update_head_pos(mirror, r1_bio);

            if (behind) {
                  if (test_bit(WriteMostly, &conf->mirrors[mirror].rdev->flags))
                        atomic_dec(&r1_bio->behind_remaining);

                  /* In behind mode, we ACK the master bio once the I/O has safely
                   * reached all non-writemostly disks. Setting the Returned bit
                   * ensures that this gets done only once -- we don't ever want to
                   * return -EIO here, instead we'll wait */

                  if (atomic_read(&r1_bio->behind_remaining) >= (atomic_read(&r1_bio->remaining)-1) &&
                      test_bit(R1BIO_Uptodate, &r1_bio->state)) {
                        /* Maybe we can return now */
                        if (!test_and_set_bit(R1BIO_Returned, &r1_bio->state)) {
                              struct bio *mbio = r1_bio->master_bio;
                              PRINTK(KERN_DEBUG "raid1: behind end write sectors %llu-%llu\n",
                                     (unsigned long long) mbio->bi_sector,
                                     (unsigned long long) mbio->bi_sector +
                                     (mbio->bi_size >> 9) - 1);
                              bio_endio(mbio, 0);
                        }
                  }
            }
            rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
      }
      /*
       *
       * Let's see if all mirrored write operations have finished
       * already.
       */
      if (atomic_dec_and_test(&r1_bio->remaining)) {
            if (test_bit(R1BIO_BarrierRetry, &r1_bio->state))
                  reschedule_retry(r1_bio);
            else {
                  /* it really is the end of this request */
                  if (test_bit(R1BIO_BehindIO, &r1_bio->state)) {
                        /* free extra copy of the data pages */
                        int i = bio->bi_vcnt;
                        while (i--)
                              safe_put_page(bio->bi_io_vec[i].bv_page);
                  }
                  /* clear the bitmap if all writes complete successfully */
                  bitmap_endwrite(r1_bio->mddev->bitmap, r1_bio->sector,
                              r1_bio->sectors,
                              !test_bit(R1BIO_Degraded, &r1_bio->state),
                              behind);
                  md_write_end(r1_bio->mddev);
                  raid_end_bio_io(r1_bio);
            }
      }

      if (to_put)
            bio_put(to_put);
}


/*
 * This routine returns the disk from which the requested read should
 * be done. There is a per-array 'next expected sequential IO' sector
 * number - if this matches on the next IO then we use the last disk.
 * There is also a per-disk 'last know head position' sector that is
 * maintained from IRQ contexts, both the normal and the resync IO
 * completion handlers update this position correctly. If there is no
 * perfect sequential match then we pick the disk whose head is closest.
 *
 * If there are 2 mirrors in the same 2 devices, performance degrades
 * because position is mirror, not device based.
 *
 * The rdev for the device selected will have nr_pending incremented.
 */
static int read_balance(conf_t *conf, r1bio_t *r1_bio)
{
      const unsigned long this_sector = r1_bio->sector;
      int new_disk = conf->last_used, disk = new_disk;
      int wonly_disk = -1;
      const int sectors = r1_bio->sectors;
      sector_t new_distance, current_distance;
      mdk_rdev_t *rdev;

      rcu_read_lock();
      /*
       * Check if we can balance. We can balance on the whole
       * device if no resync is going on, or below the resync window.
       * We take the first readable disk when above the resync window.
       */
 retry:
      if (conf->mddev->recovery_cp < MaxSector &&
          (this_sector + sectors >= conf->next_resync)) {
            /* Choose the first operation device, for consistancy */
            new_disk = 0;

            for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
                 r1_bio->bios[new_disk] == IO_BLOCKED ||
                 !rdev || !test_bit(In_sync, &rdev->flags)
                       || test_bit(WriteMostly, &rdev->flags);
                 rdev = rcu_dereference(conf->mirrors[++new_disk].rdev)) {

                  if (rdev && test_bit(In_sync, &rdev->flags) &&
                        r1_bio->bios[new_disk] != IO_BLOCKED)
                        wonly_disk = new_disk;

                  if (new_disk == conf->raid_disks - 1) {
                        new_disk = wonly_disk;
                        break;
                  }
            }
            goto rb_out;
      }


      /* make sure the disk is operational */
      for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
           r1_bio->bios[new_disk] == IO_BLOCKED ||
           !rdev || !test_bit(In_sync, &rdev->flags) ||
                 test_bit(WriteMostly, &rdev->flags);
           rdev = rcu_dereference(conf->mirrors[new_disk].rdev)) {

            if (rdev && test_bit(In_sync, &rdev->flags) &&
                r1_bio->bios[new_disk] != IO_BLOCKED)
                  wonly_disk = new_disk;

            if (new_disk <= 0)
                  new_disk = conf->raid_disks;
            new_disk--;
            if (new_disk == disk) {
                  new_disk = wonly_disk;
                  break;
            }
      }

      if (new_disk < 0)
            goto rb_out;

      disk = new_disk;
      /* now disk == new_disk == starting point for search */

      /*
       * Don't change to another disk for sequential reads:
       */
      if (conf->next_seq_sect == this_sector)
            goto rb_out;
      if (this_sector == conf->mirrors[new_disk].head_position)
            goto rb_out;

      current_distance = abs(this_sector - conf->mirrors[disk].head_position);

      /* Find the disk whose head is closest */

      do {
            if (disk <= 0)
                  disk = conf->raid_disks;
            disk--;

            rdev = rcu_dereference(conf->mirrors[disk].rdev);

            if (!rdev || r1_bio->bios[disk] == IO_BLOCKED ||
                !test_bit(In_sync, &rdev->flags) ||
                test_bit(WriteMostly, &rdev->flags))
                  continue;

            if (!atomic_read(&rdev->nr_pending)) {
                  new_disk = disk;
                  break;
            }
            new_distance = abs(this_sector - conf->mirrors[disk].head_position);
            if (new_distance < current_distance) {
                  current_distance = new_distance;
                  new_disk = disk;
            }
      } while (disk != conf->last_used);

 rb_out:


      if (new_disk >= 0) {
            rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
            if (!rdev)
                  goto retry;
            atomic_inc(&rdev->nr_pending);
            if (!test_bit(In_sync, &rdev->flags)) {
                  /* cannot risk returning a device that failed
                   * before we inc'ed nr_pending
                   */
                  rdev_dec_pending(rdev, conf->mddev);
                  goto retry;
            }
            conf->next_seq_sect = this_sector + sectors;
            conf->last_used = new_disk;
      }
      rcu_read_unlock();

      return new_disk;
}

static void unplug_slaves(mddev_t *mddev)
{
      conf_t *conf = mddev_to_conf(mddev);
      int i;

      rcu_read_lock();
      for (i=0; i<mddev->raid_disks; i++) {
            mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
            if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
                  struct request_queue *r_queue = bdev_get_queue(rdev->bdev);

                  atomic_inc(&rdev->nr_pending);
                  rcu_read_unlock();

                  blk_unplug(r_queue);

                  rdev_dec_pending(rdev, mddev);
                  rcu_read_lock();
            }
      }
      rcu_read_unlock();
}

static void raid1_unplug(struct request_queue *q)
{
      mddev_t *mddev = q->queuedata;

      unplug_slaves(mddev);
      md_wakeup_thread(mddev->thread);
}

static int raid1_congested(void *data, int bits)
{
      mddev_t *mddev = data;
      conf_t *conf = mddev_to_conf(mddev);
      int i, ret = 0;

      rcu_read_lock();
      for (i = 0; i < mddev->raid_disks; i++) {
            mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
            if (rdev && !test_bit(Faulty, &rdev->flags)) {
                  struct request_queue *q = bdev_get_queue(rdev->bdev);

                  /* Note the '|| 1' - when read_balance prefers
                   * non-congested targets, it can be removed
                   */
                  if ((bits & (1<<BDI_write_congested)) || 1)
                        ret |= bdi_congested(&q->backing_dev_info, bits);
                  else
                        ret &= bdi_congested(&q->backing_dev_info, bits);
            }
      }
      rcu_read_unlock();
      return ret;
}


/* Barriers....
 * Sometimes we need to suspend IO while we do something else,
 * either some resync/recovery, or reconfigure the array.
 * To do this we raise a 'barrier'.
 * The 'barrier' is a counter that can be raised multiple times
 * to count how many activities are happening which preclude
 * normal IO.
 * We can only raise the barrier if there is no pending IO.
 * i.e. if nr_pending == 0.
 * We choose only to raise the barrier if no-one is waiting for the
 * barrier to go down.  This means that as soon as an IO request
 * is ready, no other operations which require a barrier will start
 * until the IO request has had a chance.
 *
 * So: regular IO calls 'wait_barrier'.  When that returns there
 *    is no backgroup IO happening,  It must arrange to call
 *    allow_barrier when it has finished its IO.
 * backgroup IO calls must call raise_barrier.  Once that returns
 *    there is no normal IO happeing.  It must arrange to call
 *    lower_barrier when the particular background IO completes.
 */
#define RESYNC_DEPTH 32

static void raise_barrier(conf_t *conf)
{
      spin_lock_irq(&conf->resync_lock);

      /* Wait until no block IO is waiting */
      wait_event_lock_irq(conf->wait_barrier, !conf->nr_waiting,
                      conf->resync_lock,
                      raid1_unplug(conf->mddev->queue));

      /* block any new IO from starting */
      conf->barrier++;

      /* No wait for all pending IO to complete */
      wait_event_lock_irq(conf->wait_barrier,
                      !conf->nr_pending && conf->barrier < RESYNC_DEPTH,
                      conf->resync_lock,
                      raid1_unplug(conf->mddev->queue));

      spin_unlock_irq(&conf->resync_lock);
}

static void lower_barrier(conf_t *conf)
{
      unsigned long flags;
      spin_lock_irqsave(&conf->resync_lock, flags);
      conf->barrier--;
      spin_unlock_irqrestore(&conf->resync_lock, flags);
      wake_up(&conf->wait_barrier);
}

static void wait_barrier(conf_t *conf)
{
      spin_lock_irq(&conf->resync_lock);
      if (conf->barrier) {
            conf->nr_waiting++;
            wait_event_lock_irq(conf->wait_barrier, !conf->barrier,
                            conf->resync_lock,
                            raid1_unplug(conf->mddev->queue));
            conf->nr_waiting--;
      }
      conf->nr_pending++;
      spin_unlock_irq(&conf->resync_lock);
}

static void allow_barrier(conf_t *conf)
{
      unsigned long flags;
      spin_lock_irqsave(&conf->resync_lock, flags);
      conf->nr_pending--;
      spin_unlock_irqrestore(&conf->resync_lock, flags);
      wake_up(&conf->wait_barrier);
}

static void freeze_array(conf_t *conf)
{
      /* stop syncio and normal IO and wait for everything to
       * go quite.
       * We increment barrier and nr_waiting, and then
       * wait until barrier+nr_pending match nr_queued+2
       */
      spin_lock_irq(&conf->resync_lock);
      conf->barrier++;
      conf->nr_waiting++;
      wait_event_lock_irq(conf->wait_barrier,
                      conf->barrier+conf->nr_pending == conf->nr_queued+2,
                      conf->resync_lock,
                      raid1_unplug(conf->mddev->queue));
      spin_unlock_irq(&conf->resync_lock);
}
static void unfreeze_array(conf_t *conf)
{
      /* reverse the effect of the freeze */
      spin_lock_irq(&conf->resync_lock);
      conf->barrier--;
      conf->nr_waiting--;
      wake_up(&conf->wait_barrier);
      spin_unlock_irq(&conf->resync_lock);
}


/* duplicate the data pages for behind I/O */
static struct page **alloc_behind_pages(struct bio *bio)
{
      int i;
      struct bio_vec *bvec;
      struct page **pages = kzalloc(bio->bi_vcnt * sizeof(struct page *),
                              GFP_NOIO);
      if (unlikely(!pages))
            goto do_sync_io;

      bio_for_each_segment(bvec, bio, i) {
            pages[i] = alloc_page(GFP_NOIO);
            if (unlikely(!pages[i]))
                  goto do_sync_io;
            memcpy(kmap(pages[i]) + bvec->bv_offset,
                  kmap(bvec->bv_page) + bvec->bv_offset, bvec->bv_len);
            kunmap(pages[i]);
            kunmap(bvec->bv_page);
      }

      return pages;

do_sync_io:
      if (pages)
            for (i = 0; i < bio->bi_vcnt && pages[i]; i++)
                  put_page(pages[i]);
      kfree(pages);
      PRINTK("%dB behind alloc failed, doing sync I/O\n", bio->bi_size);
      return NULL;
}

static int make_request(struct request_queue *q, struct bio * bio)
{
      mddev_t *mddev = q->queuedata;
      conf_t *conf = mddev_to_conf(mddev);
      mirror_info_t *mirror;
      r1bio_t *r1_bio;
      struct bio *read_bio;
      int i, targets = 0, disks;
      mdk_rdev_t *rdev;
      struct bitmap *bitmap = mddev->bitmap;
      unsigned long flags;
      struct bio_list bl;
      struct page **behind_pages = NULL;
      const int rw = bio_data_dir(bio);
      const int do_sync = bio_sync(bio);
      int do_barriers;

      /*
       * Register the new request and wait if the reconstruction
       * thread has put up a bar for new requests.
       * Continue immediately if no resync is active currently.
       * We test barriers_work *after* md_write_start as md_write_start
       * may cause the first superblock write, and that will check out
       * if barriers work.
       */

      md_write_start(mddev, bio); /* wait on superblock update early */

      if (unlikely(!mddev->barriers_work && bio_barrier(bio))) {
            if (rw == WRITE)
                  md_write_end(mddev);
            bio_endio(bio, -EOPNOTSUPP);
            return 0;
      }

      wait_barrier(conf);

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

      /*
       * make_request() can abort the operation when READA is being
       * used and no empty request is available.
       *
       */
      r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);

      r1_bio->master_bio = bio;
      r1_bio->sectors = bio->bi_size >> 9;
      r1_bio->state = 0;
      r1_bio->mddev = mddev;
      r1_bio->sector = bio->bi_sector;

      if (rw == READ) {
            /*
             * read balancing logic:
             */
            int rdisk = read_balance(conf, r1_bio);

            if (rdisk < 0) {
                  /* couldn't find anywhere to read from */
                  raid_end_bio_io(r1_bio);
                  return 0;
            }
            mirror = conf->mirrors + rdisk;

            r1_bio->read_disk = rdisk;

            read_bio = bio_clone(bio, GFP_NOIO);

            r1_bio->bios[rdisk] = read_bio;

            read_bio->bi_sector = r1_bio->sector + mirror->rdev->data_offset;
            read_bio->bi_bdev = mirror->rdev->bdev;
            read_bio->bi_end_io = raid1_end_read_request;
            read_bio->bi_rw = READ | do_sync;
            read_bio->bi_private = r1_bio;

            generic_make_request(read_bio);
            return 0;
      }

      /*
       * WRITE:
       */
      /* first select target devices under spinlock and
       * inc refcount on their rdev.  Record them by setting
       * bios[x] to bio
       */
      disks = conf->raid_disks;
#if 0
      { static int first=1;
      if (first) printk("First Write sector %llu disks %d\n",
                    (unsigned long long)r1_bio->sector, disks);
      first = 0;
      }
#endif
      rcu_read_lock();
      for (i = 0;  i < disks; i++) {
            if ((rdev=rcu_dereference(conf->mirrors[i].rdev)) != NULL &&
                !test_bit(Faulty, &rdev->flags)) {
                  atomic_inc(&rdev->nr_pending);
                  if (test_bit(Faulty, &rdev->flags)) {
                        rdev_dec_pending(rdev, mddev);
                        r1_bio->bios[i] = NULL;
                  } else
                        r1_bio->bios[i] = bio;
                  targets++;
            } else
                  r1_bio->bios[i] = NULL;
      }
      rcu_read_unlock();

      BUG_ON(targets == 0); /* we never fail the last device */

      if (targets < conf->raid_disks) {
            /* array is degraded, we will not clear the bitmap
             * on I/O completion (see raid1_end_write_request) */
            set_bit(R1BIO_Degraded, &r1_bio->state);
      }

      /* do behind I/O ? */
      if (bitmap &&
          atomic_read(&bitmap->behind_writes) < bitmap->max_write_behind &&
          (behind_pages = alloc_behind_pages(bio)) != NULL)
            set_bit(R1BIO_BehindIO, &r1_bio->state);

      atomic_set(&r1_bio->remaining, 0);
      atomic_set(&r1_bio->behind_remaining, 0);

      do_barriers = bio_barrier(bio);
      if (do_barriers)
            set_bit(R1BIO_Barrier, &r1_bio->state);

      bio_list_init(&bl);
      for (i = 0; i < disks; i++) {
            struct bio *mbio;
            if (!r1_bio->bios[i])
                  continue;

            mbio = bio_clone(bio, GFP_NOIO);
            r1_bio->bios[i] = mbio;

            mbio->bi_sector   = r1_bio->sector + conf->mirrors[i].rdev->data_offset;
            mbio->bi_bdev = conf->mirrors[i].rdev->bdev;
            mbio->bi_end_io   = raid1_end_write_request;
            mbio->bi_rw = WRITE | do_barriers | do_sync;
            mbio->bi_private = r1_bio;

            if (behind_pages) {
                  struct bio_vec *bvec;
                  int j;

                  /* Yes, I really want the '__' version so that
                   * we clear any unused pointer in the io_vec, rather
                   * than leave them unchanged.  This is important
                   * because when we come to free the pages, we won't
                   * know the originial bi_idx, so we just free
                   * them all
                   */
                  __bio_for_each_segment(bvec, mbio, j, 0)
                        bvec->bv_page = behind_pages[j];
                  if (test_bit(WriteMostly, &conf->mirrors[i].rdev->flags))
                        atomic_inc(&r1_bio->behind_remaining);
            }

            atomic_inc(&r1_bio->remaining);

            bio_list_add(&bl, mbio);
      }
      kfree(behind_pages); /* the behind pages are attached to the bios now */

      bitmap_startwrite(bitmap, bio->bi_sector, r1_bio->sectors,
                        test_bit(R1BIO_BehindIO, &r1_bio->state));
      spin_lock_irqsave(&conf->device_lock, flags);
      bio_list_merge(&conf->pending_bio_list, &bl);
      bio_list_init(&bl);

      blk_plug_device(mddev->queue);
      spin_unlock_irqrestore(&conf->device_lock, flags);

      if (do_sync)
            md_wakeup_thread(mddev->thread);
#if 0
      while ((bio = bio_list_pop(&bl)) != NULL)
            generic_make_request(bio);
#endif

      return 0;
}

static void status(struct seq_file *seq, mddev_t *mddev)
{
      conf_t *conf = mddev_to_conf(mddev);
      int i;

      seq_printf(seq, " [%d/%d] [", conf->raid_disks,
               conf->raid_disks - mddev->degraded);
      rcu_read_lock();
      for (i = 0; i < conf->raid_disks; i++) {
            mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
            seq_printf(seq, "%s",
                     rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
      }
      rcu_read_unlock();
      seq_printf(seq, "]");
}


static void error(mddev_t *mddev, mdk_rdev_t *rdev)
{
      char b[BDEVNAME_SIZE];
      conf_t *conf = mddev_to_conf(mddev);

      /*
       * If it is not operational, then we have already marked it as dead
       * else if it is the last working disks, ignore the error, let the
       * next level up know.
       * else mark the drive as failed
       */
      if (test_bit(In_sync, &rdev->flags)
          && (conf->raid_disks - mddev->degraded) == 1)
            /*
             * Don't fail the drive, act as though we were just a
             * normal single drive
             */
            return;
      if (test_and_clear_bit(In_sync, &rdev->flags)) {
            unsigned long flags;
            spin_lock_irqsave(&conf->device_lock, flags);
            mddev->degraded++;
            set_bit(Faulty, &rdev->flags);
            spin_unlock_irqrestore(&conf->device_lock, flags);
            /*
             * if recovery is running, make sure it aborts.
             */
            set_bit(MD_RECOVERY_ERR, &mddev->recovery);
      } else
            set_bit(Faulty, &rdev->flags);
      set_bit(MD_CHANGE_DEVS, &mddev->flags);
      printk(KERN_ALERT "raid1: Disk failure on %s, disabling device. \n"
            "     Operation continuing on %d devices\n",
            bdevname(rdev->bdev,b), conf->raid_disks - mddev->degraded);
}

static void print_conf(conf_t *conf)
{
      int i;

      printk("RAID1 conf printout:\n");
      if (!conf) {
            printk("(!conf)\n");
            return;
      }
      printk(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
            conf->raid_disks);

      rcu_read_lock();
      for (i = 0; i < conf->raid_disks; i++) {
            char b[BDEVNAME_SIZE];
            mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
            if (rdev)
                  printk(" disk %d, wo:%d, o:%d, dev:%s\n",
                         i, !test_bit(In_sync, &rdev->flags),
                         !test_bit(Faulty, &rdev->flags),
                         bdevname(rdev->bdev,b));
      }
      rcu_read_unlock();
}

static void close_sync(conf_t *conf)
{
      wait_barrier(conf);
      allow_barrier(conf);

      mempool_destroy(conf->r1buf_pool);
      conf->r1buf_pool = NULL;
}

static int raid1_spare_active(mddev_t *mddev)
{
      int i;
      conf_t *conf = mddev->private;

      /*
       * Find all failed disks within the RAID1 configuration 
       * and mark them readable.
       * Called under mddev lock, so rcu protection not needed.
       */
      for (i = 0; i < conf->raid_disks; i++) {
            mdk_rdev_t *rdev = conf->mirrors[i].rdev;
            if (rdev
                && !test_bit(Faulty, &rdev->flags)
                && !test_and_set_bit(In_sync, &rdev->flags)) {
                  unsigned long flags;
                  spin_lock_irqsave(&conf->device_lock, flags);
                  mddev->degraded--;
                  spin_unlock_irqrestore(&conf->device_lock, flags);
            }
      }

      print_conf(conf);
      return 0;
}


static int raid1_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
{
      conf_t *conf = mddev->private;
      int found = 0;
      int mirror = 0;
      mirror_info_t *p;

      for (mirror=0; mirror < mddev->raid_disks; mirror++)
            if ( !(p=conf->mirrors+mirror)->rdev) {

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

                  p->head_position = 0;
                  rdev->raid_disk = mirror;
                  found = 1;
                  /* As all devices are equivalent, we don't need a full recovery
                   * if this was recently any drive of the array
                   */
                  if (rdev->saved_raid_disk < 0)
                        conf->fullsync = 1;
                  rcu_assign_pointer(p->rdev, rdev);
                  break;
            }

      print_conf(conf);
      return found;
}

static int raid1_remove_disk(mddev_t *mddev, int number)
{
      conf_t *conf = mddev->private;
      int err = 0;
      mdk_rdev_t *rdev;
      mirror_info_t *p = conf->mirrors+ number;

      print_conf(conf);
      rdev = p->rdev;
      if (rdev) {
            if (test_bit(In_sync, &rdev->flags) ||
                atomic_read(&rdev->nr_pending)) {
                  err = -EBUSY;
                  goto abort;
            }
            p->rdev = NULL;
            synchronize_rcu();
            if (atomic_read(&rdev->nr_pending)) {
                  /* lost the race, try later */
                  err = -EBUSY;
                  p->rdev = rdev;
            }
      }
abort:

      print_conf(conf);
      return err;
}


static void end_sync_read(struct bio *bio, int error)
{
      r1bio_t * r1_bio = (r1bio_t *)(bio->bi_private);
      int i;

      for (i=r1_bio->mddev->raid_disks; i--; )
            if (r1_bio->bios[i] == bio)
                  break;
      BUG_ON(i < 0);
      update_head_pos(i, r1_bio);
      /*
       * we have read a block, now it needs to be re-written,
       * or re-read if the read failed.
       * We don't do much here, just schedule handling by raid1d
       */
      if (test_bit(BIO_UPTODATE, &bio->bi_flags))
            set_bit(R1BIO_Uptodate, &r1_bio->state);

      if (atomic_dec_and_test(&r1_bio->remaining))
            reschedule_retry(r1_bio);
}

static void end_sync_write(struct bio *bio, int error)
{
      int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
      r1bio_t * r1_bio = (r1bio_t *)(bio->bi_private);
      mddev_t *mddev = r1_bio->mddev;
      conf_t *conf = mddev_to_conf(mddev);
      int i;
      int mirror=0;

      for (i = 0; i < conf->raid_disks; i++)
            if (r1_bio->bios[i] == bio) {
                  mirror = i;
                  break;
            }
      if (!uptodate) {
            int sync_blocks = 0;
            sector_t s = r1_bio->sector;
            long sectors_to_go = r1_bio->sectors;
            /* make sure these bits doesn't get cleared. */
            do {
                  bitmap_end_sync(mddev->bitmap, s,
                              &sync_blocks, 1);
                  s += sync_blocks;
                  sectors_to_go -= sync_blocks;
            } while (sectors_to_go > 0);
            md_error(mddev, conf->mirrors[mirror].rdev);
      }

      update_head_pos(mirror, r1_bio);

      if (atomic_dec_and_test(&r1_bio->remaining)) {
            md_done_sync(mddev, r1_bio->sectors, uptodate);
            put_buf(r1_bio);
      }
}

static void sync_request_write(mddev_t *mddev, r1bio_t *r1_bio)
{
      conf_t *conf = mddev_to_conf(mddev);
      int i;
      int disks = conf->raid_disks;
      struct bio *bio, *wbio;

      bio = r1_bio->bios[r1_bio->read_disk];


      if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
            /* We have read all readable devices.  If we haven't
             * got the block, then there is no hope left.
             * If we have, then we want to do a comparison
             * and skip the write if everything is the same.
             * If any blocks failed to read, then we need to
             * attempt an over-write
             */
            int primary;
            if (!test_bit(R1BIO_Uptodate, &r1_bio->state)) {
                  for (i=0; i<mddev->raid_disks; i++)
                        if (r1_bio->bios[i]->bi_end_io == end_sync_read)
                              md_error(mddev, conf->mirrors[i].rdev);

                  md_done_sync(mddev, r1_bio->sectors, 1);
                  put_buf(r1_bio);
                  return;
            }
            for (primary=0; primary<mddev->raid_disks; primary++)
                  if (r1_bio->bios[primary]->bi_end_io == end_sync_read &&
                      test_bit(BIO_UPTODATE, &r1_bio->bios[primary]->bi_flags)) {
                        r1_bio->bios[primary]->bi_end_io = NULL;
                        rdev_dec_pending(conf->mirrors[primary].rdev, mddev);
                        break;
                  }
            r1_bio->read_disk = primary;
            for (i=0; i<mddev->raid_disks; i++)
                  if (r1_bio->bios[i]->bi_end_io == end_sync_read) {
                        int j;
                        int vcnt = r1_bio->sectors >> (PAGE_SHIFT- 9);
                        struct bio *pbio = r1_bio->bios[primary];
                        struct bio *sbio = r1_bio->bios[i];

                        if (test_bit(BIO_UPTODATE, &sbio->bi_flags)) {
                              for (j = vcnt; j-- ; ) {
                                    struct page *p, *s;
                                    p = pbio->bi_io_vec[j].bv_page;
                                    s = sbio->bi_io_vec[j].bv_page;
                                    if (memcmp(page_address(p),
                                             page_address(s),
                                             PAGE_SIZE))
                                          break;
                              }
                        } else
                              j = 0;
                        if (j >= 0)
                              mddev->resync_mismatches += r1_bio->sectors;
                        if (j < 0 || (test_bit(MD_RECOVERY_CHECK, &mddev->recovery)
                                    && test_bit(BIO_UPTODATE, &sbio->bi_flags))) {
                              sbio->bi_end_io = NULL;
                              rdev_dec_pending(conf->mirrors[i].rdev, mddev);
                        } else {
                              /* fixup the bio for reuse */
                              sbio->bi_vcnt = vcnt;
                              sbio->bi_size = r1_bio->sectors << 9;
                              sbio->bi_idx = 0;
                              sbio->bi_phys_segments = 0;
                              sbio->bi_hw_segments = 0;
                              sbio->bi_hw_front_size = 0;
                              sbio->bi_hw_back_size = 0;
                              sbio->bi_flags &= ~(BIO_POOL_MASK - 1);
                              sbio->bi_flags |= 1 << BIO_UPTODATE;
                              sbio->bi_next = NULL;
                              sbio->bi_sector = r1_bio->sector +
                                    conf->mirrors[i].rdev->data_offset;
                              sbio->bi_bdev = conf->mirrors[i].rdev->bdev;
                              for (j = 0; j < vcnt ; j++)
                                    memcpy(page_address(sbio->bi_io_vec[j].bv_page),
                                           page_address(pbio->bi_io_vec[j].bv_page),
                                           PAGE_SIZE);

                        }
                  }
      }
      if (!test_bit(R1BIO_Uptodate, &r1_bio->state)) {
            /* ouch - failed to read all of that.
             * Try some synchronous reads of other devices to get
             * good data, much like with normal read errors.  Only
             * read into the pages we already have so we don't
             * need to re-issue the read request.
             * We don't need to freeze the array, because being in an
             * active sync request, there is no normal IO, and
             * no overlapping syncs.
             */
            sector_t sect = r1_bio->sector;
            int sectors = r1_bio->sectors;
            int idx = 0;

            while(sectors) {
                  int s = sectors;
                  int d = r1_bio->read_disk;
                  int success = 0;
                  mdk_rdev_t *rdev;

                  if (s > (PAGE_SIZE>>9))
                        s = PAGE_SIZE >> 9;
                  do {
                        if (r1_bio->bios[d]->bi_end_io == end_sync_read) {
                              /* No rcu protection needed here devices
                               * can only be removed when no resync is
                               * active, and resync is currently active
                               */
                              rdev = conf->mirrors[d].rdev;
                              if (sync_page_io(rdev->bdev,
                                           sect + rdev->data_offset,
                                           s<<9,
                                           bio->bi_io_vec[idx].bv_page,
                                           READ)) {
                                    success = 1;
                                    break;
                              }
                        }
                        d++;
                        if (d == conf->raid_disks)
                              d = 0;
                  } while (!success && d != r1_bio->read_disk);

                  if (success) {
                        int start = d;
                        /* write it back and re-read */
                        set_bit(R1BIO_Uptodate, &r1_bio->state);
                        while (d != r1_bio->read_disk) {
                              if (d == 0)
                                    d = conf->raid_disks;
                              d--;
                              if (r1_bio->bios[d]->bi_end_io != end_sync_read)
                                    continue;
                              rdev = conf->mirrors[d].rdev;
                              atomic_add(s, &rdev->corrected_errors);
                              if (sync_page_io(rdev->bdev,
                                           sect + rdev->data_offset,
                                           s<<9,
                                           bio->bi_io_vec[idx].bv_page,
                                           WRITE) == 0)
                                    md_error(mddev, rdev);
                        }
                        d = start;
                        while (d != r1_bio->read_disk) {
                              if (d == 0)
                                    d = conf->raid_disks;
                              d--;
                              if (r1_bio->bios[d]->bi_end_io != end_sync_read)
                                    continue;
                              rdev = conf->mirrors[d].rdev;
                              if (sync_page_io(rdev->bdev,
                                           sect + rdev->data_offset,
                                           s<<9,
                                           bio->bi_io_vec[idx].bv_page,
                                           READ) == 0)
                                    md_error(mddev, rdev);
                        }
                  } else {
                        char b[BDEVNAME_SIZE];
                        /* Cannot read from anywhere, array is toast */
                        md_error(mddev, conf->mirrors[r1_bio->read_disk].rdev);
                        printk(KERN_ALERT "raid1: %s: unrecoverable I/O read error"
                               " for block %llu\n",
                               bdevname(bio->bi_bdev,b),
                               (unsigned long long)r1_bio->sector);
                        md_done_sync(mddev, r1_bio->sectors, 0);
                        put_buf(r1_bio);
                        return;
                  }
                  sectors -= s;
                  sect += s;
                  idx ++;
            }
      }

      /*
       * schedule writes
       */
      atomic_set(&r1_bio->remaining, 1);
      for (i = 0; i < disks ; i++) {
            wbio = r1_bio->bios[i];
            if (wbio->bi_end_io == NULL ||
                (wbio->bi_end_io == end_sync_read &&
                 (i == r1_bio->read_disk ||
                  !test_bit(MD_RECOVERY_SYNC, &mddev->recovery))))
                  continue;

            wbio->bi_rw = WRITE;
            wbio->bi_end_io = end_sync_write;
            atomic_inc(&r1_bio->remaining);
            md_sync_acct(conf->mirrors[i].rdev->bdev, wbio->bi_size >> 9);

            generic_make_request(wbio);
      }

      if (atomic_dec_and_test(&r1_bio->remaining)) {
            /* if we're here, all write(s) have completed, so clean up */
            md_done_sync(mddev, r1_bio->sectors, 1);
            put_buf(r1_bio);
      }
}

/*
 * This is a kernel thread which:
 *
 *    1.    Retries failed read operations on working mirrors.
 *    2.    Updates the raid superblock when problems encounter.
 *    3.    Performs writes following reads for array syncronising.
 */

static void fix_read_error(conf_t *conf, int read_disk,
                     sector_t sect, int sectors)
{
      mddev_t *mddev = conf->mddev;
      while(sectors) {
            int s = sectors;
            int d = read_disk;
            int success = 0;
            int start;
            mdk_rdev_t *rdev;

            if (s > (PAGE_SIZE>>9))
                  s = PAGE_SIZE >> 9;

            do {
                  /* Note: no rcu protection needed here
                   * as this is synchronous in the raid1d thread
                   * which is the thread that might remove
                   * a device.  If raid1d ever becomes multi-threaded....
                   */
                  rdev = conf->mirrors[d].rdev;
                  if (rdev &&
                      test_bit(In_sync, &rdev->flags) &&
                      sync_page_io(rdev->bdev,
                               sect + rdev->data_offset,
                               s<<9,
                               conf->tmppage, READ))
                        success = 1;
                  else {
                        d++;
                        if (d == conf->raid_disks)
                              d = 0;
                  }
            } while (!success && d != read_disk);

            if (!success) {
                  /* Cannot read from anywhere -- bye bye array */
                  md_error(mddev, conf->mirrors[read_disk].rdev);
                  break;
            }
            /* write it back and re-read */
            start = d;
            while (d != read_disk) {
                  if (d==0)
                        d = conf->raid_disks;
                  d--;
                  rdev = conf->mirrors[d].rdev;
                  if (rdev &&
                      test_bit(In_sync, &rdev->flags)) {
                        if (sync_page_io(rdev->bdev,
                                     sect + rdev->data_offset,
                                     s<<9, conf->tmppage, WRITE)
                            == 0)
                              /* Well, this device is dead */
                              md_error(mddev, rdev);
                  }
            }
            d = start;
            while (d != read_disk) {
                  char b[BDEVNAME_SIZE];
                  if (d==0)
                        d = conf->raid_disks;
                  d--;
                  rdev = conf->mirrors[d].rdev;
                  if (rdev &&
                      test_bit(In_sync, &rdev->flags)) {
                        if (sync_page_io(rdev->bdev,
                                     sect + rdev->data_offset,
                                     s<<9, conf->tmppage, READ)
                            == 0)
                              /* Well, this device is dead */
                              md_error(mddev, rdev);
                        else {
                              atomic_add(s, &rdev->corrected_errors);
                              printk(KERN_INFO
                                     "raid1:%s: read error corrected "
                                     "(%d sectors at %llu on %s)\n",
                                     mdname(mddev), s,
                                     (unsigned long long)(sect +
                                         rdev->data_offset),
                                     bdevname(rdev->bdev, b));
                        }
                  }
            }
            sectors -= s;
            sect += s;
      }
}

static void raid1d(mddev_t *mddev)
{
      r1bio_t *r1_bio;
      struct bio *bio;
      unsigned long flags;
      conf_t *conf = mddev_to_conf(mddev);
      struct list_head *head = &conf->retry_list;
      int unplug=0;
      mdk_rdev_t *rdev;

      md_check_recovery(mddev);
      
      for (;;) {
            char b[BDEVNAME_SIZE];
            spin_lock_irqsave(&conf->device_lock, flags);

            if (conf->pending_bio_list.head) {
                  bio = bio_list_get(&conf->pending_bio_list);
                  blk_remove_plug(mddev->queue);
                  spin_unlock_irqrestore(&conf->device_lock, flags);
                  /* flush any pending bitmap writes to disk before proceeding w/ I/O */
                  bitmap_unplug(mddev->bitmap);

                  while (bio) { /* submit pending writes */
                        struct bio *next = bio->bi_next;
                        bio->bi_next = NULL;
                        generic_make_request(bio);
                        bio = next;
                  }
                  unplug = 1;

                  continue;
            }

            if (list_empty(head))
                  break;
            r1_bio = list_entry(head->prev, r1bio_t, retry_list);
            list_del(head->prev);
            conf->nr_queued--;
            spin_unlock_irqrestore(&conf->device_lock, flags);

            mddev = r1_bio->mddev;
            conf = mddev_to_conf(mddev);
            if (test_bit(R1BIO_IsSync, &r1_bio->state)) {
                  sync_request_write(mddev, r1_bio);
                  unplug = 1;
            } else if (test_bit(R1BIO_BarrierRetry, &r1_bio->state)) {
                  /* some requests in the r1bio were BIO_RW_BARRIER
                   * requests which failed with -EOPNOTSUPP.  Hohumm..
                   * Better resubmit without the barrier.
                   * We know which devices to resubmit for, because
                   * all others have had their bios[] entry cleared.
                   * We already have a nr_pending reference on these rdevs.
                   */
                  int i;
                  const int do_sync = bio_sync(r1_bio->master_bio);
                  clear_bit(R1BIO_BarrierRetry, &r1_bio->state);
                  clear_bit(R1BIO_Barrier, &r1_bio->state);
                  for (i=0; i < conf->raid_disks; i++)
                        if (r1_bio->bios[i])
                              atomic_inc(&r1_bio->remaining);
                  for (i=0; i < conf->raid_disks; i++)
                        if (r1_bio->bios[i]) {
                              struct bio_vec *bvec;
                              int j;

                              bio = bio_clone(r1_bio->master_bio, GFP_NOIO);
                              /* copy pages from the failed bio, as
                               * this might be a write-behind device */
                              __bio_for_each_segment(bvec, bio, j, 0)
                                    bvec->bv_page = bio_iovec_idx(r1_bio->bios[i], j)->bv_page;
                              bio_put(r1_bio->bios[i]);
                              bio->bi_sector = r1_bio->sector +
                                    conf->mirrors[i].rdev->data_offset;
                              bio->bi_bdev = conf->mirrors[i].rdev->bdev;
                              bio->bi_end_io = raid1_end_write_request;
                              bio->bi_rw = WRITE | do_sync;
                              bio->bi_private = r1_bio;
                              r1_bio->bios[i] = bio;
                              generic_make_request(bio);
                        }
            } else {
                  int disk;

                  /* we got a read error. Maybe the drive is bad.  Maybe just
                   * the block and we can fix it.
                   * We freeze all other IO, and try reading the block from
                   * other devices.  When we find one, we re-write
                   * and check it that fixes the read error.
                   * This is all done synchronously while the array is
                   * frozen
                   */
                  if (mddev->ro == 0) {
                        freeze_array(conf);
                        fix_read_error(conf, r1_bio->read_disk,
                                     r1_bio->sector,
                                     r1_bio->sectors);
                        unfreeze_array(conf);
                  }

                  bio = r1_bio->bios[r1_bio->read_disk];
                  if ((disk=read_balance(conf, r1_bio)) == -1) {
                        printk(KERN_ALERT "raid1: %s: unrecoverable I/O"
                               " read error for block %llu\n",
                               bdevname(bio->bi_bdev,b),
                               (unsigned long long)r1_bio->sector);
                        raid_end_bio_io(r1_bio);
                  } else {
                        const int do_sync = bio_sync(r1_bio->master_bio);
                        r1_bio->bios[r1_bio->read_disk] =
                              mddev->ro ? IO_BLOCKED : NULL;
                        r1_bio->read_disk = disk;
                        bio_put(bio);
                        bio = bio_clone(r1_bio->master_bio, GFP_NOIO);
                        r1_bio->bios[r1_bio->read_disk] = bio;
                        rdev = conf->mirrors[disk].rdev;
                        if (printk_ratelimit())
                              printk(KERN_ERR "raid1: %s: redirecting sector %llu to"
                                     " another mirror\n",
                                     bdevname(rdev->bdev,b),
                                     (unsigned long long)r1_bio->sector);
                        bio->bi_sector = r1_bio->sector + rdev->data_offset;
                        bio->bi_bdev = rdev->bdev;
                        bio->bi_end_io = raid1_end_read_request;
                        bio->bi_rw = READ | do_sync;
                        bio->bi_private = r1_bio;
                        unplug = 1;
                        generic_make_request(bio);
                  }
            }
      }
      spin_unlock_irqrestore(&conf->device_lock, flags);
      if (unplug)
            unplug_slaves(mddev);
}


static int init_resync(conf_t *conf)
{
      int buffs;

      buffs = RESYNC_WINDOW / RESYNC_BLOCK_SIZE;
      BUG_ON(conf->r1buf_pool);
      conf->r1buf_pool = mempool_create(buffs, r1buf_pool_alloc, r1buf_pool_free,
                                conf->poolinfo);
      if (!conf->r1buf_pool)
            return -ENOMEM;
      conf->next_resync = 0;
      return 0;
}

/*
 * perform a "sync" on one "block"
 *
 * We need to make sure that no normal I/O request - particularly write
 * requests - conflict with active sync requests.
 *
 * This is achieved by tracking pending requests and a 'barrier' concept
 * that can be installed to exclude normal IO requests.
 */

static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster)
{
      conf_t *conf = mddev_to_conf(mddev);
      r1bio_t *r1_bio;
      struct bio *bio;
      sector_t max_sector, nr_sectors;
      int disk = -1;
      int i;
      int wonly = -1;
      int write_targets = 0, read_targets = 0;
      int sync_blocks;
      int still_degraded = 0;

      if (!conf->r1buf_pool)
      {
/*
            printk("sync start - bitmap %p\n", mddev->bitmap);
*/
            if (init_resync(conf))
                  return 0;
      }

      max_sector = mddev->size << 1;
      if (sector_nr >= max_sector) {
            /* If we aborted, we need to abort the
             * sync on the 'current' bitmap chunk (there will
             * only be one in raid1 resync.
             * We can find the current addess in mddev->curr_resync
             */
            if (mddev->curr_resync < max_sector) /* aborted */
                  bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
                                    &sync_blocks, 1);
            else /* completed sync */
                  conf->fullsync = 0;

            bitmap_close_sync(mddev->bitmap);
            close_sync(conf);
            return 0;
      }

      if (mddev->bitmap == NULL &&
          mddev->recovery_cp == MaxSector &&
          !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
          conf->fullsync == 0) {
            *skipped = 1;
            return max_sector - sector_nr;
      }
      /* before building a request, check if we can skip these blocks..
       * This call the bitmap_start_sync doesn't actually record anything
       */
      if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
          !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
            /* We can skip this block, and probably several more */
            *skipped = 1;
            return sync_blocks;
      }
      /*
       * If there is non-resync activity waiting for a turn,
       * and resync is going fast enough,
       * then let it though before starting on this new sync request.
       */
      if (!go_faster && conf->nr_waiting)
            msleep_interruptible(1000);

      raise_barrier(conf);

      conf->next_resync = sector_nr;

      r1_bio = mempool_alloc(conf->r1buf_pool, GFP_NOIO);
      rcu_read_lock();
      /*
       * If we get a correctably read error during resync or recovery,
       * we might want to read from a different device.  So we
       * flag all drives that could conceivably be read from for READ,
       * and any others (which will be non-In_sync devices) for WRITE.
       * If a read fails, we try reading from something else for which READ
       * is OK.
       */

      r1_bio->mddev = mddev;
      r1_bio->sector = sector_nr;
      r1_bio->state = 0;
      set_bit(R1BIO_IsSync, &r1_bio->state);

      for (i=0; i < conf->raid_disks; i++) {
            mdk_rdev_t *rdev;
            bio = r1_bio->bios[i];

            /* take from bio_init */
            bio->bi_next = NULL;
            bio->bi_flags |= 1 << BIO_UPTODATE;
            bio->bi_rw = READ;
            bio->bi_vcnt = 0;
            bio->bi_idx = 0;
            bio->bi_phys_segments = 0;
            bio->bi_hw_segments = 0;
            bio->bi_size = 0;
            bio->bi_end_io = NULL;
            bio->bi_private = NULL;

            rdev = rcu_dereference(conf->mirrors[i].rdev);
            if (rdev == NULL ||
                     test_bit(Faulty, &rdev->flags)) {
                  still_degraded = 1;
                  continue;
            } else if (!test_bit(In_sync, &rdev->flags)) {
                  bio->bi_rw = WRITE;
                  bio->bi_end_io = end_sync_write;
                  write_targets ++;
            } else {
                  /* may need to read from here */
                  bio->bi_rw = READ;
                  bio->bi_end_io = end_sync_read;
                  if (test_bit(WriteMostly, &rdev->flags)) {
                        if (wonly < 0)
                              wonly = i;
                  } else {
                        if (disk < 0)
                              disk = i;
                  }
                  read_targets++;
            }
            atomic_inc(&rdev->nr_pending);
            bio->bi_sector = sector_nr + rdev->data_offset;
            bio->bi_bdev = rdev->bdev;
            bio->bi_private = r1_bio;
      }
      rcu_read_unlock();
      if (disk < 0)
            disk = wonly;
      r1_bio->read_disk = disk;

      if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) && read_targets > 0)
            /* extra read targets are also write targets */
            write_targets += read_targets-1;

      if (write_targets == 0 || read_targets == 0) {
            /* There is nowhere to write, so all non-sync
             * drives must be failed - so we are finished
             */
            sector_t rv = max_sector - sector_nr;
            *skipped = 1;
            put_buf(r1_bio);
            return rv;
      }

      nr_sectors = 0;
      sync_blocks = 0;
      do {
            struct page *page;
            int len = PAGE_SIZE;
            if (sector_nr + (len>>9) > max_sector)
                  len = (max_sector - sector_nr) << 9;
            if (len == 0)
                  break;
            if (sync_blocks == 0) {
                  if (!bitmap_start_sync(mddev->bitmap, sector_nr,
                                     &sync_blocks, still_degraded) &&
                      !conf->fullsync &&
                      !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
                        break;
                  BUG_ON(sync_blocks < (PAGE_SIZE>>9));
                  if (len > (sync_blocks<<9))
                        len = sync_blocks<<9;
            }

            for (i=0 ; i < conf->raid_disks; i++) {
                  bio = r1_bio->bios[i];
                  if (bio->bi_end_io) {
                        page = bio->bi_io_vec[bio->bi_vcnt].bv_page;
                        if (bio_add_page(bio, page, len, 0) == 0) {
                              /* stop here */
                              bio->bi_io_vec[bio->bi_vcnt].bv_page = page;
                              while (i > 0) {
                                    i--;
                                    bio = r1_bio->bios[i];
                                    if (bio->bi_end_io==NULL)
                                          continue;
                                    /* remove last page from this bio */
                                    bio->bi_vcnt--;
                                    bio->bi_size -= len;
                                    bio->bi_flags &= ~(1<< BIO_SEG_VALID);
                              }
                              goto bio_full;
                        }
                  }
            }
            nr_sectors += len>>9;
            sector_nr += len>>9;
            sync_blocks -= (len>>9);
      } while (r1_bio->bios[disk]->bi_vcnt < RESYNC_PAGES);
 bio_full:
      r1_bio->sectors = nr_sectors;

      /* For a user-requested sync, we read all readable devices and do a
       * compare
       */
      if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
            atomic_set(&r1_bio->remaining, read_targets);
            for (i=0; i<conf->raid_disks; i++) {
                  bio = r1_bio->bios[i];
                  if (bio->bi_end_io == end_sync_read) {
                        md_sync_acct(bio->bi_bdev, nr_sectors);
                        generic_make_request(bio);
                  }
            }
      } else {
            atomic_set(&r1_bio->remaining, 1);
            bio = r1_bio->bios[r1_bio->read_disk];
            md_sync_acct(bio->bi_bdev, nr_sectors);
            generic_make_request(bio);

      }
      return nr_sectors;
}

static int run(mddev_t *mddev)
{
      conf_t *conf;
      int i, j, disk_idx;
      mirror_info_t *disk;
      mdk_rdev_t *rdev;
      struct list_head *tmp;

      if (mddev->level != 1) {
            printk("raid1: %s: raid level not set to mirroring (%d)\n",
                   mdname(mddev), mddev->level);
            goto out;
      }
      if (mddev->reshape_position != MaxSector) {
            printk("raid1: %s: reshape_position set but not supported\n",
                   mdname(mddev));
            goto out;
      }
      /*
       * copy the already verified devices into our private RAID1
       * bookkeeping area. [whatever we allocate in run(),
       * should be freed in stop()]
       */
      conf = kzalloc(sizeof(conf_t), GFP_KERNEL);
      mddev->private = conf;
      if (!conf)
            goto out_no_mem;

      conf->mirrors = kzalloc(sizeof(struct mirror_info)*mddev->raid_disks,
                         GFP_KERNEL);
      if (!conf->mirrors)
            goto out_no_mem;

      conf->tmppage = alloc_page(GFP_KERNEL);
      if (!conf->tmppage)
            goto out_no_mem;

      conf->poolinfo = kmalloc(sizeof(*conf->poolinfo), GFP_KERNEL);
      if (!conf->poolinfo)
            goto out_no_mem;
      conf->poolinfo->mddev = mddev;
      conf->poolinfo->raid_disks = mddev->raid_disks;
      conf->r1bio_pool = mempool_create(NR_RAID1_BIOS, r1bio_pool_alloc,
                                r1bio_pool_free,
                                conf->poolinfo);
      if (!conf->r1bio_pool)
            goto out_no_mem;

      ITERATE_RDEV(mddev, rdev, tmp) {
            disk_idx = rdev->raid_disk;
            if (disk_idx >= mddev->raid_disks
                || disk_idx < 0)
                  continue;
            disk = conf->mirrors + disk_idx;

            disk->rdev = rdev;

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

            disk->head_position = 0;
      }
      conf->raid_disks = mddev->raid_disks;
      conf->mddev = mddev;
      spin_lock_init(&conf->device_lock);
      INIT_LIST_HEAD(&conf->retry_list);

      spin_lock_init(&conf->resync_lock);
      init_waitqueue_head(&conf->wait_barrier);

      bio_list_init(&conf->pending_bio_list);
      bio_list_init(&conf->flushing_bio_list);


      mddev->degraded = 0;
      for (i = 0; i < conf->raid_disks; i++) {

            disk = conf->mirrors + i;

            if (!disk->rdev ||
                !test_bit(In_sync, &disk->rdev->flags)) {
                  disk->head_position = 0;
                  mddev->degraded++;
                  if (disk->rdev)
                        conf->fullsync = 1;
            }
      }
      if (mddev->degraded == conf->raid_disks) {
            printk(KERN_ERR "raid1: no operational mirrors for %s\n",
                  mdname(mddev));
            goto out_free_conf;
      }
      if (conf->raid_disks - mddev->degraded == 1)
            mddev->recovery_cp = MaxSector;

      /*
       * find the first working one and use it as a starting point
       * to read balancing.
       */
      for (j = 0; j < conf->raid_disks &&
                 (!conf->mirrors[j].rdev ||
                  !test_bit(In_sync, &conf->mirrors[j].rdev->flags)) ; j++)
            /* nothing */;
      conf->last_used = j;


      mddev->thread = md_register_thread(raid1d, mddev, "%s_raid1");
      if (!mddev->thread) {
            printk(KERN_ERR
                   "raid1: couldn't allocate thread for %s\n",
                   mdname(mddev));
            goto out_free_conf;
      }

      printk(KERN_INFO 
            "raid1: raid set %s active with %d out of %d mirrors\n",
            mdname(mddev), mddev->raid_disks - mddev->degraded, 
            mddev->raid_disks);
      /*
       * Ok, everything is just fine now
       */
      mddev->array_size = mddev->size;

      mddev->queue->unplug_fn = raid1_unplug;
      mddev->queue->backing_dev_info.congested_fn = raid1_congested;
      mddev->queue->backing_dev_info.congested_data = mddev;

      return 0;

out_no_mem:
      printk(KERN_ERR "raid1: couldn't allocate memory for %s\n",
             mdname(mddev));

out_free_conf:
      if (conf) {
            if (conf->r1bio_pool)
                  mempool_destroy(conf->r1bio_pool);
            kfree(conf->mirrors);
            safe_put_page(conf->tmppage);
            kfree(conf->poolinfo);
            kfree(conf);
            mddev->private = NULL;
      }
out:
      return -EIO;
}

static int stop(mddev_t *mddev)
{
      conf_t *conf = mddev_to_conf(mddev);
      struct bitmap *bitmap = mddev->bitmap;
      int behind_wait = 0;

      /* wait for behind writes to complete */
      while (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
            behind_wait++;
            printk(KERN_INFO "raid1: behind writes in progress on device %s, waiting to stop (%d)\n", mdname(mddev), behind_wait);
            set_current_state(TASK_UNINTERRUPTIBLE);
            schedule_timeout(HZ); /* wait a second */
            /* need to kick something here to make sure I/O goes? */
      }

      md_unregister_thread(mddev->thread);
      mddev->thread = NULL;
      blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
      if (conf->r1bio_pool)
            mempool_destroy(conf->r1bio_pool);
      kfree(conf->mirrors);
      kfree(conf->poolinfo);
      kfree(conf);
      mddev->private = NULL;
      return 0;
}

static int raid1_resize(mddev_t *mddev, sector_t sectors)
{
      /* no resync is happening, and there is enough space
       * on all devices, so we can resize.
       * We need to make sure resync covers any new space.
       * If the array is shrinking we should possibly wait until
       * any io in the removed space completes, but it hardly seems
       * worth it.
       */
      mddev->array_size = sectors>>1;
      set_capacity(mddev->gendisk, mddev->array_size << 1);
      mddev->changed = 1;
      if (mddev->array_size > mddev->size && mddev->recovery_cp == MaxSector) {
            mddev->recovery_cp = mddev->size << 1;
            set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
      }
      mddev->size = mddev->array_size;
      mddev->resync_max_sectors = sectors;
      return 0;
}

static int raid1_reshape(mddev_t *mddev)
{
      /* We need to:
       * 1/ resize the r1bio_pool
       * 2/ resize conf->mirrors
       *
       * We allocate a new r1bio_pool if we can.
       * Then raise a device barrier and wait until all IO stops.
       * Then resize conf->mirrors and swap in the new r1bio pool.
       *
       * At the same time, we "pack" the devices so that all the missing
       * devices have the higher raid_disk numbers.
       */
      mempool_t *newpool, *oldpool;
      struct pool_info *newpoolinfo;
      mirror_info_t *newmirrors;
      conf_t *conf = mddev_to_conf(mddev);
      int cnt, raid_disks;
      unsigned long flags;
      int d, d2;

      /* Cannot change chunk_size, layout, or level */
      if (mddev->chunk_size != mddev->new_chunk ||
          mddev->layout != mddev->new_layout ||
          mddev->level != mddev->new_level) {
            mddev->new_chunk = mddev->chunk_size;
            mddev->new_layout = mddev->layout;
            mddev->new_level = mddev->level;
            return -EINVAL;
      }

      md_allow_write(mddev);

      raid_disks = mddev->raid_disks + mddev->delta_disks;

      if (raid_disks < conf->raid_disks) {
            cnt=0;
            for (d= 0; d < conf->raid_disks; d++)
                  if (conf->mirrors[d].rdev)
                        cnt++;
            if (cnt > raid_disks)
                  return -EBUSY;
      }

      newpoolinfo = kmalloc(sizeof(*newpoolinfo), GFP_KERNEL);
      if (!newpoolinfo)
            return -ENOMEM;
      newpoolinfo->mddev = mddev;
      newpoolinfo->raid_disks = raid_disks;

      newpool = mempool_create(NR_RAID1_BIOS, r1bio_pool_alloc,
                         r1bio_pool_free, newpoolinfo);
      if (!newpool) {
            kfree(newpoolinfo);
            return -ENOMEM;
      }
      newmirrors = kzalloc(sizeof(struct mirror_info) * raid_disks, GFP_KERNEL);
      if (!newmirrors) {
            kfree(newpoolinfo);
            mempool_destroy(newpool);
            return -ENOMEM;
      }

      raise_barrier(conf);

      /* ok, everything is stopped */
      oldpool = conf->r1bio_pool;
      conf->r1bio_pool = newpool;

      for (d = d2 = 0; d < conf->raid_disks; d++) {
            mdk_rdev_t *rdev = conf->mirrors[d].rdev;
            if (rdev && rdev->raid_disk != d2) {
                  char nm[20];
                  sprintf(nm, "rd%d", rdev->raid_disk);
                  sysfs_remove_link(&mddev->kobj, nm);
                  rdev->raid_disk = d2;
                  sprintf(nm, "rd%d", rdev->raid_disk);
                  sysfs_remove_link(&mddev->kobj, nm);
                  if (sysfs_create_link(&mddev->kobj,
                                    &rdev->kobj, nm))
                        printk(KERN_WARNING
                               "md/raid1: cannot register "
                               "%s for %s\n",
                               nm, mdname(mddev));
            }
            if (rdev)
                  newmirrors[d2++].rdev = rdev;
      }
      kfree(conf->mirrors);
      conf->mirrors = newmirrors;
      kfree(conf->poolinfo);
      conf->poolinfo = newpoolinfo;

      spin_lock_irqsave(&conf->device_lock, flags);
      mddev->degraded += (raid_disks - conf->raid_disks);
      spin_unlock_irqrestore(&conf->device_lock, flags);
      conf->raid_disks = mddev->raid_disks = raid_disks;
      mddev->delta_disks = 0;

      conf->last_used = 0; /* just make sure it is in-range */
      lower_barrier(conf);

      set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
      md_wakeup_thread(mddev->thread);

      mempool_destroy(oldpool);
      return 0;
}

static void raid1_quiesce(mddev_t *mddev, int state)
{
      conf_t *conf = mddev_to_conf(mddev);

      switch(state) {
      case 1:
            raise_barrier(conf);
            break;
      case 0:
            lower_barrier(conf);
            break;
      }
}


static struct mdk_personality raid1_personality =
{
      .name       = "raid1",
      .level            = 1,
      .owner            = THIS_MODULE,
      .make_request     = make_request,
      .run        = run,
      .stop       = stop,
      .status           = status,
      .error_handler    = error,
      .hot_add_disk     = raid1_add_disk,
      .hot_remove_disk= raid1_remove_disk,
      .spare_active     = raid1_spare_active,
      .sync_request     = sync_request,
      .resize           = raid1_resize,
      .check_reshape    = raid1_reshape,
      .quiesce    = raid1_quiesce,
};

static int __init raid_init(void)
{
      return register_md_personality(&raid1_personality);
}

static void raid_exit(void)
{
      unregister_md_personality(&raid1_personality);
}

module_init(raid_init);
module_exit(raid_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS("md-personality-3"); /* RAID1 */
MODULE_ALIAS("md-raid1");
MODULE_ALIAS("md-level-1");

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