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volumes.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */
#include <linux/sched.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/blkdev.h>
#include <linux/random.h>
#include <linux/iocontext.h>
#include <asm/div64.h>
#include "compat.h"
#include "ctree.h"
#include "extent_map.h"
#include "disk-io.h"
#include "transaction.h"
#include "print-tree.h"
#include "volumes.h"
#include "async-thread.h"

00034 struct map_lookup {
      u64 type;
      int io_align;
      int io_width;
      int stripe_len;
      int sector_size;
      int num_stripes;
      int sub_stripes;
      struct btrfs_bio_stripe stripes[];
};

static int init_first_rw_device(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root,
                        struct btrfs_device *device);
static int btrfs_relocate_sys_chunks(struct btrfs_root *root);

#define map_lookup_size(n) (sizeof(struct map_lookup) + \
                      (sizeof(struct btrfs_bio_stripe) * (n)))

static DEFINE_MUTEX(uuid_mutex);
static LIST_HEAD(fs_uuids);

void btrfs_lock_volumes(void)
{
      mutex_lock(&uuid_mutex);
}

void btrfs_unlock_volumes(void)
{
      mutex_unlock(&uuid_mutex);
}

static void lock_chunks(struct btrfs_root *root)
{
      mutex_lock(&root->fs_info->chunk_mutex);
}

static void unlock_chunks(struct btrfs_root *root)
{
      mutex_unlock(&root->fs_info->chunk_mutex);
}

static void free_fs_devices(struct btrfs_fs_devices *fs_devices)
{
      struct btrfs_device *device;
      WARN_ON(fs_devices->opened);
      while (!list_empty(&fs_devices->devices)) {
            device = list_entry(fs_devices->devices.next,
                            struct btrfs_device, dev_list);
            list_del(&device->dev_list);
            kfree(device->name);
            kfree(device);
      }
      kfree(fs_devices);
}

int btrfs_cleanup_fs_uuids(void)
{
      struct btrfs_fs_devices *fs_devices;

      while (!list_empty(&fs_uuids)) {
            fs_devices = list_entry(fs_uuids.next,
                              struct btrfs_fs_devices, list);
            list_del(&fs_devices->list);
            free_fs_devices(fs_devices);
      }
      return 0;
}

static noinline struct btrfs_device *__find_device(struct list_head *head,
                                       u64 devid, u8 *uuid)
{
      struct btrfs_device *dev;

      list_for_each_entry(dev, head, dev_list) {
            if (dev->devid == devid &&
                (!uuid || !memcmp(dev->uuid, uuid, BTRFS_UUID_SIZE))) {
                  return dev;
            }
      }
      return NULL;
}

static noinline struct btrfs_fs_devices *find_fsid(u8 *fsid)
{
      struct btrfs_fs_devices *fs_devices;

      list_for_each_entry(fs_devices, &fs_uuids, list) {
            if (memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE) == 0)
                  return fs_devices;
      }
      return NULL;
}

static void requeue_list(struct btrfs_pending_bios *pending_bios,
                  struct bio *head, struct bio *tail)
{

      struct bio *old_head;

      old_head = pending_bios->head;
      pending_bios->head = head;
      if (pending_bios->tail)
            tail->bi_next = old_head;
      else
            pending_bios->tail = tail;
}

/*
 * we try to collect pending bios for a device so we don't get a large
 * number of procs sending bios down to the same device.  This greatly
 * improves the schedulers ability to collect and merge the bios.
 *
 * But, it also turns into a long list of bios to process and that is sure
 * to eventually make the worker thread block.  The solution here is to
 * make some progress and then put this work struct back at the end of
 * the list if the block device is congested.  This way, multiple devices
 * can make progress from a single worker thread.
 */
static noinline int run_scheduled_bios(struct btrfs_device *device)
{
      struct bio *pending;
      struct backing_dev_info *bdi;
      struct btrfs_fs_info *fs_info;
      struct btrfs_pending_bios *pending_bios;
      struct bio *tail;
      struct bio *cur;
      int again = 0;
      unsigned long num_run;
      unsigned long num_sync_run;
      unsigned long batch_run = 0;
      unsigned long limit;
      unsigned long last_waited = 0;
      int force_reg = 0;

      bdi = blk_get_backing_dev_info(device->bdev);
      fs_info = device->dev_root->fs_info;
      limit = btrfs_async_submit_limit(fs_info);
      limit = limit * 2 / 3;

      /* we want to make sure that every time we switch from the sync
       * list to the normal list, we unplug
       */
      num_sync_run = 0;

loop:
      spin_lock(&device->io_lock);

loop_lock:
      num_run = 0;

      /* take all the bios off the list at once and process them
       * later on (without the lock held).  But, remember the
       * tail and other pointers so the bios can be properly reinserted
       * into the list if we hit congestion
       */
      if (!force_reg && device->pending_sync_bios.head) {
            pending_bios = &device->pending_sync_bios;
            force_reg = 1;
      } else {
            pending_bios = &device->pending_bios;
            force_reg = 0;
      }

      pending = pending_bios->head;
      tail = pending_bios->tail;
      WARN_ON(pending && !tail);

      /*
       * if pending was null this time around, no bios need processing
       * at all and we can stop.  Otherwise it'll loop back up again
       * and do an additional check so no bios are missed.
       *
       * device->running_pending is used to synchronize with the
       * schedule_bio code.
       */
      if (device->pending_sync_bios.head == NULL &&
          device->pending_bios.head == NULL) {
            again = 0;
            device->running_pending = 0;
      } else {
            again = 1;
            device->running_pending = 1;
      }

      pending_bios->head = NULL;
      pending_bios->tail = NULL;

      spin_unlock(&device->io_lock);

      /*
       * if we're doing the regular priority list, make sure we unplug
       * for any high prio bios we've sent down
       */
      if (pending_bios == &device->pending_bios && num_sync_run > 0) {
            num_sync_run = 0;
            blk_run_backing_dev(bdi, NULL);
      }

      while (pending) {

            rmb();
            /* we want to work on both lists, but do more bios on the
             * sync list than the regular list
             */
            if ((num_run > 32 &&
                pending_bios != &device->pending_sync_bios &&
                device->pending_sync_bios.head) ||
               (num_run > 64 && pending_bios == &device->pending_sync_bios &&
                device->pending_bios.head)) {
                  spin_lock(&device->io_lock);
                  requeue_list(pending_bios, pending, tail);
                  goto loop_lock;
            }

            cur = pending;
            pending = pending->bi_next;
            cur->bi_next = NULL;
            atomic_dec(&fs_info->nr_async_bios);

            if (atomic_read(&fs_info->nr_async_bios) < limit &&
                waitqueue_active(&fs_info->async_submit_wait))
                  wake_up(&fs_info->async_submit_wait);

            BUG_ON(atomic_read(&cur->bi_cnt) == 0);
            submit_bio(cur->bi_rw, cur);
            num_run++;
            batch_run++;

            if (bio_sync(cur))
                  num_sync_run++;

            if (need_resched()) {
                  if (num_sync_run) {
                        blk_run_backing_dev(bdi, NULL);
                        num_sync_run = 0;
                  }
                  cond_resched();
            }

            /*
             * we made progress, there is more work to do and the bdi
             * is now congested.  Back off and let other work structs
             * run instead
             */
            if (pending && bdi_write_congested(bdi) && batch_run > 32 &&
                fs_info->fs_devices->open_devices > 1) {
                  struct io_context *ioc;

                  ioc = current->io_context;

                  /*
                   * the main goal here is that we don't want to
                   * block if we're going to be able to submit
                   * more requests without blocking.
                   *
                   * This code does two great things, it pokes into
                   * the elevator code from a filesystem _and_
                   * it makes assumptions about how batching works.
                   */
                  if (ioc && ioc->nr_batch_requests > 0 &&
                      time_before(jiffies, ioc->last_waited + HZ/50UL) &&
                      (last_waited == 0 ||
                       ioc->last_waited == last_waited)) {
                        /*
                         * we want to go through our batch of
                         * requests and stop.  So, we copy out
                         * the ioc->last_waited time and test
                         * against it before looping
                         */
                        last_waited = ioc->last_waited;
                        if (need_resched()) {
                              if (num_sync_run) {
                                    blk_run_backing_dev(bdi, NULL);
                                    num_sync_run = 0;
                              }
                              cond_resched();
                        }
                        continue;
                  }
                  spin_lock(&device->io_lock);
                  requeue_list(pending_bios, pending, tail);
                  device->running_pending = 1;

                  spin_unlock(&device->io_lock);
                  btrfs_requeue_work(&device->work);
                  goto done;
            }
      }

      if (num_sync_run) {
            num_sync_run = 0;
            blk_run_backing_dev(bdi, NULL);
      }

      cond_resched();
      if (again)
            goto loop;

      spin_lock(&device->io_lock);
      if (device->pending_bios.head || device->pending_sync_bios.head)
            goto loop_lock;
      spin_unlock(&device->io_lock);

      /*
       * IO has already been through a long path to get here.  Checksumming,
       * async helper threads, perhaps compression.  We've done a pretty
       * good job of collecting a batch of IO and should just unplug
       * the device right away.
       *
       * This will help anyone who is waiting on the IO, they might have
       * already unplugged, but managed to do so before the bio they
       * cared about found its way down here.
       */
      blk_run_backing_dev(bdi, NULL);
done:
      return 0;
}

static void pending_bios_fn(struct btrfs_work *work)
{
      struct btrfs_device *device;

      device = container_of(work, struct btrfs_device, work);
      run_scheduled_bios(device);
}

static noinline int device_list_add(const char *path,
                     struct btrfs_super_block *disk_super,
                     u64 devid, struct btrfs_fs_devices **fs_devices_ret)
{
      struct btrfs_device *device;
      struct btrfs_fs_devices *fs_devices;
      u64 found_transid = btrfs_super_generation(disk_super);

      fs_devices = find_fsid(disk_super->fsid);
      if (!fs_devices) {
            fs_devices = kzalloc(sizeof(*fs_devices), GFP_NOFS);
            if (!fs_devices)
                  return -ENOMEM;
            INIT_LIST_HEAD(&fs_devices->devices);
            INIT_LIST_HEAD(&fs_devices->alloc_list);
            list_add(&fs_devices->list, &fs_uuids);
            memcpy(fs_devices->fsid, disk_super->fsid, BTRFS_FSID_SIZE);
            fs_devices->latest_devid = devid;
            fs_devices->latest_trans = found_transid;
            mutex_init(&fs_devices->device_list_mutex);
            device = NULL;
      } else {
            device = __find_device(&fs_devices->devices, devid,
                               disk_super->dev_item.uuid);
      }
      if (!device) {
            if (fs_devices->opened)
                  return -EBUSY;

            device = kzalloc(sizeof(*device), GFP_NOFS);
            if (!device) {
                  /* we can safely leave the fs_devices entry around */
                  return -ENOMEM;
            }
            device->devid = devid;
            device->work.func = pending_bios_fn;
            memcpy(device->uuid, disk_super->dev_item.uuid,
                   BTRFS_UUID_SIZE);
            device->barriers = 1;
            spin_lock_init(&device->io_lock);
            device->name = kstrdup(path, GFP_NOFS);
            if (!device->name) {
                  kfree(device);
                  return -ENOMEM;
            }
            INIT_LIST_HEAD(&device->dev_alloc_list);

            mutex_lock(&fs_devices->device_list_mutex);
            list_add(&device->dev_list, &fs_devices->devices);
            mutex_unlock(&fs_devices->device_list_mutex);

            device->fs_devices = fs_devices;
            fs_devices->num_devices++;
      }

      if (found_transid > fs_devices->latest_trans) {
            fs_devices->latest_devid = devid;
            fs_devices->latest_trans = found_transid;
      }
      *fs_devices_ret = fs_devices;
      return 0;
}

static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
{
      struct btrfs_fs_devices *fs_devices;
      struct btrfs_device *device;
      struct btrfs_device *orig_dev;

      fs_devices = kzalloc(sizeof(*fs_devices), GFP_NOFS);
      if (!fs_devices)
            return ERR_PTR(-ENOMEM);

      INIT_LIST_HEAD(&fs_devices->devices);
      INIT_LIST_HEAD(&fs_devices->alloc_list);
      INIT_LIST_HEAD(&fs_devices->list);
      mutex_init(&fs_devices->device_list_mutex);
      fs_devices->latest_devid = orig->latest_devid;
      fs_devices->latest_trans = orig->latest_trans;
      memcpy(fs_devices->fsid, orig->fsid, sizeof(fs_devices->fsid));

      mutex_lock(&orig->device_list_mutex);
      list_for_each_entry(orig_dev, &orig->devices, dev_list) {
            device = kzalloc(sizeof(*device), GFP_NOFS);
            if (!device)
                  goto error;

            device->name = kstrdup(orig_dev->name, GFP_NOFS);
            if (!device->name)
                  goto error;

            device->devid = orig_dev->devid;
            device->work.func = pending_bios_fn;
            memcpy(device->uuid, orig_dev->uuid, sizeof(device->uuid));
            device->barriers = 1;
            spin_lock_init(&device->io_lock);
            INIT_LIST_HEAD(&device->dev_list);
            INIT_LIST_HEAD(&device->dev_alloc_list);

            list_add(&device->dev_list, &fs_devices->devices);
            device->fs_devices = fs_devices;
            fs_devices->num_devices++;
      }
      mutex_unlock(&orig->device_list_mutex);
      return fs_devices;
error:
      mutex_unlock(&orig->device_list_mutex);
      free_fs_devices(fs_devices);
      return ERR_PTR(-ENOMEM);
}

int btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices)
{
      struct btrfs_device *device, *next;

      mutex_lock(&uuid_mutex);
again:
      mutex_lock(&fs_devices->device_list_mutex);
      list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
            if (device->in_fs_metadata)
                  continue;

            if (device->bdev) {
                  close_bdev_exclusive(device->bdev, device->mode);
                  device->bdev = NULL;
                  fs_devices->open_devices--;
            }
            if (device->writeable) {
                  list_del_init(&device->dev_alloc_list);
                  device->writeable = 0;
                  fs_devices->rw_devices--;
            }
            list_del_init(&device->dev_list);
            fs_devices->num_devices--;
            kfree(device->name);
            kfree(device);
      }
      mutex_unlock(&fs_devices->device_list_mutex);

      if (fs_devices->seed) {
            fs_devices = fs_devices->seed;
            goto again;
      }

      mutex_unlock(&uuid_mutex);
      return 0;
}

static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
{
      struct btrfs_device *device;

      if (--fs_devices->opened > 0)
            return 0;

      list_for_each_entry(device, &fs_devices->devices, dev_list) {
            if (device->bdev) {
                  close_bdev_exclusive(device->bdev, device->mode);
                  fs_devices->open_devices--;
            }
            if (device->writeable) {
                  list_del_init(&device->dev_alloc_list);
                  fs_devices->rw_devices--;
            }

            device->bdev = NULL;
            device->writeable = 0;
            device->in_fs_metadata = 0;
      }
      WARN_ON(fs_devices->open_devices);
      WARN_ON(fs_devices->rw_devices);
      fs_devices->opened = 0;
      fs_devices->seeding = 0;

      return 0;
}

int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
{
      struct btrfs_fs_devices *seed_devices = NULL;
      int ret;

      mutex_lock(&uuid_mutex);
      ret = __btrfs_close_devices(fs_devices);
      if (!fs_devices->opened) {
            seed_devices = fs_devices->seed;
            fs_devices->seed = NULL;
      }
      mutex_unlock(&uuid_mutex);

      while (seed_devices) {
            fs_devices = seed_devices;
            seed_devices = fs_devices->seed;
            __btrfs_close_devices(fs_devices);
            free_fs_devices(fs_devices);
      }
      return ret;
}

static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
                        fmode_t flags, void *holder)
{
      struct block_device *bdev;
      struct list_head *head = &fs_devices->devices;
      struct btrfs_device *device;
      struct block_device *latest_bdev = NULL;
      struct buffer_head *bh;
      struct btrfs_super_block *disk_super;
      u64 latest_devid = 0;
      u64 latest_transid = 0;
      u64 devid;
      int seeding = 1;
      int ret = 0;

      list_for_each_entry(device, head, dev_list) {
            if (device->bdev)
                  continue;
            if (!device->name)
                  continue;

            bdev = open_bdev_exclusive(device->name, flags, holder);
            if (IS_ERR(bdev)) {
                  printk(KERN_INFO "open %s failed\n", device->name);
                  goto error;
            }
            set_blocksize(bdev, 4096);

            bh = btrfs_read_dev_super(bdev);
            if (!bh)
                  goto error_close;

            disk_super = (struct btrfs_super_block *)bh->b_data;
            devid = le64_to_cpu(disk_super->dev_item.devid);
            if (devid != device->devid)
                  goto error_brelse;

            if (memcmp(device->uuid, disk_super->dev_item.uuid,
                     BTRFS_UUID_SIZE))
                  goto error_brelse;

            device->generation = btrfs_super_generation(disk_super);
            if (!latest_transid || device->generation > latest_transid) {
                  latest_devid = devid;
                  latest_transid = device->generation;
                  latest_bdev = bdev;
            }

            if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING) {
                  device->writeable = 0;
            } else {
                  device->writeable = !bdev_read_only(bdev);
                  seeding = 0;
            }

            device->bdev = bdev;
            device->in_fs_metadata = 0;
            device->mode = flags;

            if (!blk_queue_nonrot(bdev_get_queue(bdev)))
                  fs_devices->rotating = 1;

            fs_devices->open_devices++;
            if (device->writeable) {
                  fs_devices->rw_devices++;
                  list_add(&device->dev_alloc_list,
                         &fs_devices->alloc_list);
            }
            continue;

error_brelse:
            brelse(bh);
error_close:
            close_bdev_exclusive(bdev, FMODE_READ);
error:
            continue;
      }
      if (fs_devices->open_devices == 0) {
            ret = -EIO;
            goto out;
      }
      fs_devices->seeding = seeding;
      fs_devices->opened = 1;
      fs_devices->latest_bdev = latest_bdev;
      fs_devices->latest_devid = latest_devid;
      fs_devices->latest_trans = latest_transid;
      fs_devices->total_rw_bytes = 0;
out:
      return ret;
}

int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
                   fmode_t flags, void *holder)
{
      int ret;

      mutex_lock(&uuid_mutex);
      if (fs_devices->opened) {
            fs_devices->opened++;
            ret = 0;
      } else {
            ret = __btrfs_open_devices(fs_devices, flags, holder);
      }
      mutex_unlock(&uuid_mutex);
      return ret;
}

int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
                    struct btrfs_fs_devices **fs_devices_ret)
{
      struct btrfs_super_block *disk_super;
      struct block_device *bdev;
      struct buffer_head *bh;
      int ret;
      u64 devid;
      u64 transid;

      mutex_lock(&uuid_mutex);

      bdev = open_bdev_exclusive(path, flags, holder);

      if (IS_ERR(bdev)) {
            ret = PTR_ERR(bdev);
            goto error;
      }

      ret = set_blocksize(bdev, 4096);
      if (ret)
            goto error_close;
      bh = btrfs_read_dev_super(bdev);
      if (!bh) {
            ret = -EIO;
            goto error_close;
      }
      disk_super = (struct btrfs_super_block *)bh->b_data;
      devid = le64_to_cpu(disk_super->dev_item.devid);
      transid = btrfs_super_generation(disk_super);
      if (disk_super->label[0])
            printk(KERN_INFO "device label %s ", disk_super->label);
      else {
            /* FIXME, make a readl uuid parser */
            printk(KERN_INFO "device fsid %llx-%llx ",
                   *(unsigned long long *)disk_super->fsid,
                   *(unsigned long long *)(disk_super->fsid + 8));
      }
      printk(KERN_CONT "devid %llu transid %llu %s\n",
             (unsigned long long)devid, (unsigned long long)transid, path);
      ret = device_list_add(path, disk_super, devid, fs_devices_ret);

      brelse(bh);
error_close:
      close_bdev_exclusive(bdev, flags);
error:
      mutex_unlock(&uuid_mutex);
      return ret;
}

/*
 * this uses a pretty simple search, the expectation is that it is
 * called very infrequently and that a given device has a small number
 * of extents
 */
static noinline int find_free_dev_extent(struct btrfs_trans_handle *trans,
                               struct btrfs_device *device,
                               u64 num_bytes, u64 *start,
                               u64 *max_avail)
{
      struct btrfs_key key;
      struct btrfs_root *root = device->dev_root;
      struct btrfs_dev_extent *dev_extent = NULL;
      struct btrfs_path *path;
      u64 hole_size = 0;
      u64 last_byte = 0;
      u64 search_start = 0;
      u64 search_end = device->total_bytes;
      int ret;
      int slot = 0;
      int start_found;
      struct extent_buffer *l;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;
      path->reada = 2;
      start_found = 0;

      /* FIXME use last free of some kind */

      /* we don't want to overwrite the superblock on the drive,
       * so we make sure to start at an offset of at least 1MB
       */
      search_start = max((u64)1024 * 1024, search_start);

      if (root->fs_info->alloc_start + num_bytes <= device->total_bytes)
            search_start = max(root->fs_info->alloc_start, search_start);

      key.objectid = device->devid;
      key.offset = search_start;
      key.type = BTRFS_DEV_EXTENT_KEY;
      ret = btrfs_search_slot(trans, root, &key, path, 0, 0);
      if (ret < 0)
            goto error;
      if (ret > 0) {
            ret = btrfs_previous_item(root, path, key.objectid, key.type);
            if (ret < 0)
                  goto error;
            if (ret > 0)
                  start_found = 1;
      }
      l = path->nodes[0];
      btrfs_item_key_to_cpu(l, &key, path->slots[0]);
      while (1) {
            l = path->nodes[0];
            slot = path->slots[0];
            if (slot >= btrfs_header_nritems(l)) {
                  ret = btrfs_next_leaf(root, path);
                  if (ret == 0)
                        continue;
                  if (ret < 0)
                        goto error;
no_more_items:
                  if (!start_found) {
                        if (search_start >= search_end) {
                              ret = -ENOSPC;
                              goto error;
                        }
                        *start = search_start;
                        start_found = 1;
                        goto check_pending;
                  }
                  *start = last_byte > search_start ?
                        last_byte : search_start;
                  if (search_end <= *start) {
                        ret = -ENOSPC;
                        goto error;
                  }
                  goto check_pending;
            }
            btrfs_item_key_to_cpu(l, &key, slot);

            if (key.objectid < device->devid)
                  goto next;

            if (key.objectid > device->devid)
                  goto no_more_items;

            if (key.offset >= search_start && key.offset > last_byte &&
                start_found) {
                  if (last_byte < search_start)
                        last_byte = search_start;
                  hole_size = key.offset - last_byte;

                  if (hole_size > *max_avail)
                        *max_avail = hole_size;

                  if (key.offset > last_byte &&
                      hole_size >= num_bytes) {
                        *start = last_byte;
                        goto check_pending;
                  }
            }
            if (btrfs_key_type(&key) != BTRFS_DEV_EXTENT_KEY)
                  goto next;

            start_found = 1;
            dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
            last_byte = key.offset + btrfs_dev_extent_length(l, dev_extent);
next:
            path->slots[0]++;
            cond_resched();
      }
check_pending:
      /* we have to make sure we didn't find an extent that has already
       * been allocated by the map tree or the original allocation
       */
      BUG_ON(*start < search_start);

      if (*start + num_bytes > search_end) {
            ret = -ENOSPC;
            goto error;
      }
      /* check for pending inserts here */
      ret = 0;

error:
      btrfs_free_path(path);
      return ret;
}

static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
                    struct btrfs_device *device,
                    u64 start)
{
      int ret;
      struct btrfs_path *path;
      struct btrfs_root *root = device->dev_root;
      struct btrfs_key key;
      struct btrfs_key found_key;
      struct extent_buffer *leaf = NULL;
      struct btrfs_dev_extent *extent = NULL;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      key.objectid = device->devid;
      key.offset = start;
      key.type = BTRFS_DEV_EXTENT_KEY;

      ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
      if (ret > 0) {
            ret = btrfs_previous_item(root, path, key.objectid,
                                BTRFS_DEV_EXTENT_KEY);
            BUG_ON(ret);
            leaf = path->nodes[0];
            btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
            extent = btrfs_item_ptr(leaf, path->slots[0],
                              struct btrfs_dev_extent);
            BUG_ON(found_key.offset > start || found_key.offset +
                   btrfs_dev_extent_length(leaf, extent) < start);
            ret = 0;
      } else if (ret == 0) {
            leaf = path->nodes[0];
            extent = btrfs_item_ptr(leaf, path->slots[0],
                              struct btrfs_dev_extent);
      }
      BUG_ON(ret);

      if (device->bytes_used > 0)
            device->bytes_used -= btrfs_dev_extent_length(leaf, extent);
      ret = btrfs_del_item(trans, root, path);
      BUG_ON(ret);

      btrfs_free_path(path);
      return ret;
}

int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
                     struct btrfs_device *device,
                     u64 chunk_tree, u64 chunk_objectid,
                     u64 chunk_offset, u64 start, u64 num_bytes)
{
      int ret;
      struct btrfs_path *path;
      struct btrfs_root *root = device->dev_root;
      struct btrfs_dev_extent *extent;
      struct extent_buffer *leaf;
      struct btrfs_key key;

      WARN_ON(!device->in_fs_metadata);
      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      key.objectid = device->devid;
      key.offset = start;
      key.type = BTRFS_DEV_EXTENT_KEY;
      ret = btrfs_insert_empty_item(trans, root, path, &key,
                              sizeof(*extent));
      BUG_ON(ret);

      leaf = path->nodes[0];
      extent = btrfs_item_ptr(leaf, path->slots[0],
                        struct btrfs_dev_extent);
      btrfs_set_dev_extent_chunk_tree(leaf, extent, chunk_tree);
      btrfs_set_dev_extent_chunk_objectid(leaf, extent, chunk_objectid);
      btrfs_set_dev_extent_chunk_offset(leaf, extent, chunk_offset);

      write_extent_buffer(leaf, root->fs_info->chunk_tree_uuid,
                (unsigned long)btrfs_dev_extent_chunk_tree_uuid(extent),
                BTRFS_UUID_SIZE);

      btrfs_set_dev_extent_length(leaf, extent, num_bytes);
      btrfs_mark_buffer_dirty(leaf);
      btrfs_free_path(path);
      return ret;
}

static noinline int find_next_chunk(struct btrfs_root *root,
                            u64 objectid, u64 *offset)
{
      struct btrfs_path *path;
      int ret;
      struct btrfs_key key;
      struct btrfs_chunk *chunk;
      struct btrfs_key found_key;

      path = btrfs_alloc_path();
      BUG_ON(!path);

      key.objectid = objectid;
      key.offset = (u64)-1;
      key.type = BTRFS_CHUNK_ITEM_KEY;

      ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
      if (ret < 0)
            goto error;

      BUG_ON(ret == 0);

      ret = btrfs_previous_item(root, path, 0, BTRFS_CHUNK_ITEM_KEY);
      if (ret) {
            *offset = 0;
      } else {
            btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                              path->slots[0]);
            if (found_key.objectid != objectid)
                  *offset = 0;
            else {
                  chunk = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                     struct btrfs_chunk);
                  *offset = found_key.offset +
                        btrfs_chunk_length(path->nodes[0], chunk);
            }
      }
      ret = 0;
error:
      btrfs_free_path(path);
      return ret;
}

static noinline int find_next_devid(struct btrfs_root *root, u64 *objectid)
{
      int ret;
      struct btrfs_key key;
      struct btrfs_key found_key;
      struct btrfs_path *path;

      root = root->fs_info->chunk_root;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
      key.type = BTRFS_DEV_ITEM_KEY;
      key.offset = (u64)-1;

      ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
      if (ret < 0)
            goto error;

      BUG_ON(ret == 0);

      ret = btrfs_previous_item(root, path, BTRFS_DEV_ITEMS_OBJECTID,
                          BTRFS_DEV_ITEM_KEY);
      if (ret) {
            *objectid = 1;
      } else {
            btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                              path->slots[0]);
            *objectid = found_key.offset + 1;
      }
      ret = 0;
error:
      btrfs_free_path(path);
      return ret;
}

/*
 * the device information is stored in the chunk root
 * the btrfs_device struct should be fully filled in
 */
int btrfs_add_device(struct btrfs_trans_handle *trans,
                 struct btrfs_root *root,
                 struct btrfs_device *device)
{
      int ret;
      struct btrfs_path *path;
      struct btrfs_dev_item *dev_item;
      struct extent_buffer *leaf;
      struct btrfs_key key;
      unsigned long ptr;

      root = root->fs_info->chunk_root;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
      key.type = BTRFS_DEV_ITEM_KEY;
      key.offset = device->devid;

      ret = btrfs_insert_empty_item(trans, root, path, &key,
                              sizeof(*dev_item));
      if (ret)
            goto out;

      leaf = path->nodes[0];
      dev_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_item);

      btrfs_set_device_id(leaf, dev_item, device->devid);
      btrfs_set_device_generation(leaf, dev_item, 0);
      btrfs_set_device_type(leaf, dev_item, device->type);
      btrfs_set_device_io_align(leaf, dev_item, device->io_align);
      btrfs_set_device_io_width(leaf, dev_item, device->io_width);
      btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
      btrfs_set_device_total_bytes(leaf, dev_item, device->total_bytes);
      btrfs_set_device_bytes_used(leaf, dev_item, device->bytes_used);
      btrfs_set_device_group(leaf, dev_item, 0);
      btrfs_set_device_seek_speed(leaf, dev_item, 0);
      btrfs_set_device_bandwidth(leaf, dev_item, 0);
      btrfs_set_device_start_offset(leaf, dev_item, 0);

      ptr = (unsigned long)btrfs_device_uuid(dev_item);
      write_extent_buffer(leaf, device->uuid, ptr, BTRFS_UUID_SIZE);
      ptr = (unsigned long)btrfs_device_fsid(dev_item);
      write_extent_buffer(leaf, root->fs_info->fsid, ptr, BTRFS_UUID_SIZE);
      btrfs_mark_buffer_dirty(leaf);

      ret = 0;
out:
      btrfs_free_path(path);
      return ret;
}

static int btrfs_rm_dev_item(struct btrfs_root *root,
                       struct btrfs_device *device)
{
      int ret;
      struct btrfs_path *path;
      struct btrfs_key key;
      struct btrfs_trans_handle *trans;

      root = root->fs_info->chunk_root;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      trans = btrfs_start_transaction(root, 1);
      key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
      key.type = BTRFS_DEV_ITEM_KEY;
      key.offset = device->devid;
      lock_chunks(root);

      ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
      if (ret < 0)
            goto out;

      if (ret > 0) {
            ret = -ENOENT;
            goto out;
      }

      ret = btrfs_del_item(trans, root, path);
      if (ret)
            goto out;
out:
      btrfs_free_path(path);
      unlock_chunks(root);
      btrfs_commit_transaction(trans, root);
      return ret;
}

int btrfs_rm_device(struct btrfs_root *root, char *device_path)
{
      struct btrfs_device *device;
      struct btrfs_device *next_device;
      struct block_device *bdev;
      struct buffer_head *bh = NULL;
      struct btrfs_super_block *disk_super;
      u64 all_avail;
      u64 devid;
      u64 num_devices;
      u8 *dev_uuid;
      int ret = 0;

      mutex_lock(&uuid_mutex);
      mutex_lock(&root->fs_info->volume_mutex);

      all_avail = root->fs_info->avail_data_alloc_bits |
            root->fs_info->avail_system_alloc_bits |
            root->fs_info->avail_metadata_alloc_bits;

      if ((all_avail & BTRFS_BLOCK_GROUP_RAID10) &&
          root->fs_info->fs_devices->rw_devices <= 4) {
            printk(KERN_ERR "btrfs: unable to go below four devices "
                   "on raid10\n");
            ret = -EINVAL;
            goto out;
      }

      if ((all_avail & BTRFS_BLOCK_GROUP_RAID1) &&
          root->fs_info->fs_devices->rw_devices <= 2) {
            printk(KERN_ERR "btrfs: unable to go below two "
                   "devices on raid1\n");
            ret = -EINVAL;
            goto out;
      }

      if (strcmp(device_path, "missing") == 0) {
            struct list_head *devices;
            struct btrfs_device *tmp;

            device = NULL;
            devices = &root->fs_info->fs_devices->devices;
            mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
            list_for_each_entry(tmp, devices, dev_list) {
                  if (tmp->in_fs_metadata && !tmp->bdev) {
                        device = tmp;
                        break;
                  }
            }
            mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
            bdev = NULL;
            bh = NULL;
            disk_super = NULL;
            if (!device) {
                  printk(KERN_ERR "btrfs: no missing devices found to "
                         "remove\n");
                  goto out;
            }
      } else {
            bdev = open_bdev_exclusive(device_path, FMODE_READ,
                              root->fs_info->bdev_holder);
            if (IS_ERR(bdev)) {
                  ret = PTR_ERR(bdev);
                  goto out;
            }

            set_blocksize(bdev, 4096);
            bh = btrfs_read_dev_super(bdev);
            if (!bh) {
                  ret = -EIO;
                  goto error_close;
            }
            disk_super = (struct btrfs_super_block *)bh->b_data;
            devid = le64_to_cpu(disk_super->dev_item.devid);
            dev_uuid = disk_super->dev_item.uuid;
            device = btrfs_find_device(root, devid, dev_uuid,
                                 disk_super->fsid);
            if (!device) {
                  ret = -ENOENT;
                  goto error_brelse;
            }
      }

      if (device->writeable && root->fs_info->fs_devices->rw_devices == 1) {
            printk(KERN_ERR "btrfs: unable to remove the only writeable "
                   "device\n");
            ret = -EINVAL;
            goto error_brelse;
      }

      if (device->writeable) {
            list_del_init(&device->dev_alloc_list);
            root->fs_info->fs_devices->rw_devices--;
      }

      ret = btrfs_shrink_device(device, 0);
      if (ret)
            goto error_brelse;

      ret = btrfs_rm_dev_item(root->fs_info->chunk_root, device);
      if (ret)
            goto error_brelse;

      device->in_fs_metadata = 0;

      /*
       * the device list mutex makes sure that we don't change
       * the device list while someone else is writing out all
       * the device supers.
       */
      mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
      list_del_init(&device->dev_list);
      mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);

      device->fs_devices->num_devices--;

      next_device = list_entry(root->fs_info->fs_devices->devices.next,
                         struct btrfs_device, dev_list);
      if (device->bdev == root->fs_info->sb->s_bdev)
            root->fs_info->sb->s_bdev = next_device->bdev;
      if (device->bdev == root->fs_info->fs_devices->latest_bdev)
            root->fs_info->fs_devices->latest_bdev = next_device->bdev;

      if (device->bdev) {
            close_bdev_exclusive(device->bdev, device->mode);
            device->bdev = NULL;
            device->fs_devices->open_devices--;
      }

      num_devices = btrfs_super_num_devices(&root->fs_info->super_copy) - 1;
      btrfs_set_super_num_devices(&root->fs_info->super_copy, num_devices);

      if (device->fs_devices->open_devices == 0) {
            struct btrfs_fs_devices *fs_devices;
            fs_devices = root->fs_info->fs_devices;
            while (fs_devices) {
                  if (fs_devices->seed == device->fs_devices)
                        break;
                  fs_devices = fs_devices->seed;
            }
            fs_devices->seed = device->fs_devices->seed;
            device->fs_devices->seed = NULL;
            __btrfs_close_devices(device->fs_devices);
            free_fs_devices(device->fs_devices);
      }

      /*
       * at this point, the device is zero sized.  We want to
       * remove it from the devices list and zero out the old super
       */
      if (device->writeable) {
            /* make sure this device isn't detected as part of
             * the FS anymore
             */
            memset(&disk_super->magic, 0, sizeof(disk_super->magic));
            set_buffer_dirty(bh);
            sync_dirty_buffer(bh);
      }

      kfree(device->name);
      kfree(device);
      ret = 0;

error_brelse:
      brelse(bh);
error_close:
      if (bdev)
            close_bdev_exclusive(bdev, FMODE_READ);
out:
      mutex_unlock(&root->fs_info->volume_mutex);
      mutex_unlock(&uuid_mutex);
      return ret;
}

/*
 * does all the dirty work required for changing file system's UUID.
 */
static int btrfs_prepare_sprout(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root)
{
      struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
      struct btrfs_fs_devices *old_devices;
      struct btrfs_fs_devices *seed_devices;
      struct btrfs_super_block *disk_super = &root->fs_info->super_copy;
      struct btrfs_device *device;
      u64 super_flags;

      BUG_ON(!mutex_is_locked(&uuid_mutex));
      if (!fs_devices->seeding)
            return -EINVAL;

      seed_devices = kzalloc(sizeof(*fs_devices), GFP_NOFS);
      if (!seed_devices)
            return -ENOMEM;

      old_devices = clone_fs_devices(fs_devices);
      if (IS_ERR(old_devices)) {
            kfree(seed_devices);
            return PTR_ERR(old_devices);
      }

      list_add(&old_devices->list, &fs_uuids);

      memcpy(seed_devices, fs_devices, sizeof(*seed_devices));
      seed_devices->opened = 1;
      INIT_LIST_HEAD(&seed_devices->devices);
      INIT_LIST_HEAD(&seed_devices->alloc_list);
      mutex_init(&seed_devices->device_list_mutex);
      list_splice_init(&fs_devices->devices, &seed_devices->devices);
      list_splice_init(&fs_devices->alloc_list, &seed_devices->alloc_list);
      list_for_each_entry(device, &seed_devices->devices, dev_list) {
            device->fs_devices = seed_devices;
      }

      fs_devices->seeding = 0;
      fs_devices->num_devices = 0;
      fs_devices->open_devices = 0;
      fs_devices->seed = seed_devices;

      generate_random_uuid(fs_devices->fsid);
      memcpy(root->fs_info->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
      memcpy(disk_super->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
      super_flags = btrfs_super_flags(disk_super) &
                  ~BTRFS_SUPER_FLAG_SEEDING;
      btrfs_set_super_flags(disk_super, super_flags);

      return 0;
}

/*
 * strore the expected generation for seed devices in device items.
 */
static int btrfs_finish_sprout(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root)
{
      struct btrfs_path *path;
      struct extent_buffer *leaf;
      struct btrfs_dev_item *dev_item;
      struct btrfs_device *device;
      struct btrfs_key key;
      u8 fs_uuid[BTRFS_UUID_SIZE];
      u8 dev_uuid[BTRFS_UUID_SIZE];
      u64 devid;
      int ret;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      root = root->fs_info->chunk_root;
      key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
      key.offset = 0;
      key.type = BTRFS_DEV_ITEM_KEY;

      while (1) {
            ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
            if (ret < 0)
                  goto error;

            leaf = path->nodes[0];
next_slot:
            if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                  ret = btrfs_next_leaf(root, path);
                  if (ret > 0)
                        break;
                  if (ret < 0)
                        goto error;
                  leaf = path->nodes[0];
                  btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                  btrfs_release_path(root, path);
                  continue;
            }

            btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
            if (key.objectid != BTRFS_DEV_ITEMS_OBJECTID ||
                key.type != BTRFS_DEV_ITEM_KEY)
                  break;

            dev_item = btrfs_item_ptr(leaf, path->slots[0],
                                struct btrfs_dev_item);
            devid = btrfs_device_id(leaf, dev_item);
            read_extent_buffer(leaf, dev_uuid,
                           (unsigned long)btrfs_device_uuid(dev_item),
                           BTRFS_UUID_SIZE);
            read_extent_buffer(leaf, fs_uuid,
                           (unsigned long)btrfs_device_fsid(dev_item),
                           BTRFS_UUID_SIZE);
            device = btrfs_find_device(root, devid, dev_uuid, fs_uuid);
            BUG_ON(!device);

            if (device->fs_devices->seeding) {
                  btrfs_set_device_generation(leaf, dev_item,
                                        device->generation);
                  btrfs_mark_buffer_dirty(leaf);
            }

            path->slots[0]++;
            goto next_slot;
      }
      ret = 0;
error:
      btrfs_free_path(path);
      return ret;
}

int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
{
      struct btrfs_trans_handle *trans;
      struct btrfs_device *device;
      struct block_device *bdev;
      struct list_head *devices;
      struct super_block *sb = root->fs_info->sb;
      u64 total_bytes;
      int seeding_dev = 0;
      int ret = 0;

      if ((sb->s_flags & MS_RDONLY) && !root->fs_info->fs_devices->seeding)
            return -EINVAL;

      bdev = open_bdev_exclusive(device_path, 0, root->fs_info->bdev_holder);
      if (!bdev)
            return -EIO;

      if (root->fs_info->fs_devices->seeding) {
            seeding_dev = 1;
            down_write(&sb->s_umount);
            mutex_lock(&uuid_mutex);
      }

      filemap_write_and_wait(bdev->bd_inode->i_mapping);
      mutex_lock(&root->fs_info->volume_mutex);

      devices = &root->fs_info->fs_devices->devices;
      /*
       * we have the volume lock, so we don't need the extra
       * device list mutex while reading the list here.
       */
      list_for_each_entry(device, devices, dev_list) {
            if (device->bdev == bdev) {
                  ret = -EEXIST;
                  goto error;
            }
      }

      device = kzalloc(sizeof(*device), GFP_NOFS);
      if (!device) {
            /* we can safely leave the fs_devices entry around */
            ret = -ENOMEM;
            goto error;
      }

      device->name = kstrdup(device_path, GFP_NOFS);
      if (!device->name) {
            kfree(device);
            ret = -ENOMEM;
            goto error;
      }

      ret = find_next_devid(root, &device->devid);
      if (ret) {
            kfree(device);
            goto error;
      }

      trans = btrfs_start_transaction(root, 1);
      lock_chunks(root);

      device->barriers = 1;
      device->writeable = 1;
      device->work.func = pending_bios_fn;
      generate_random_uuid(device->uuid);
      spin_lock_init(&device->io_lock);
      device->generation = trans->transid;
      device->io_width = root->sectorsize;
      device->io_align = root->sectorsize;
      device->sector_size = root->sectorsize;
      device->total_bytes = i_size_read(bdev->bd_inode);
      device->disk_total_bytes = device->total_bytes;
      device->dev_root = root->fs_info->dev_root;
      device->bdev = bdev;
      device->in_fs_metadata = 1;
      device->mode = 0;
      set_blocksize(device->bdev, 4096);

      if (seeding_dev) {
            sb->s_flags &= ~MS_RDONLY;
            ret = btrfs_prepare_sprout(trans, root);
            BUG_ON(ret);
      }

      device->fs_devices = root->fs_info->fs_devices;

      /*
       * we don't want write_supers to jump in here with our device
       * half setup
       */
      mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
      list_add(&device->dev_list, &root->fs_info->fs_devices->devices);
      list_add(&device->dev_alloc_list,
             &root->fs_info->fs_devices->alloc_list);
      root->fs_info->fs_devices->num_devices++;
      root->fs_info->fs_devices->open_devices++;
      root->fs_info->fs_devices->rw_devices++;
      root->fs_info->fs_devices->total_rw_bytes += device->total_bytes;

      if (!blk_queue_nonrot(bdev_get_queue(bdev)))
            root->fs_info->fs_devices->rotating = 1;

      total_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
      btrfs_set_super_total_bytes(&root->fs_info->super_copy,
                            total_bytes + device->total_bytes);

      total_bytes = btrfs_super_num_devices(&root->fs_info->super_copy);
      btrfs_set_super_num_devices(&root->fs_info->super_copy,
                            total_bytes + 1);
      mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);

      if (seeding_dev) {
            ret = init_first_rw_device(trans, root, device);
            BUG_ON(ret);
            ret = btrfs_finish_sprout(trans, root);
            BUG_ON(ret);
      } else {
            ret = btrfs_add_device(trans, root, device);
      }

      /*
       * we've got more storage, clear any full flags on the space
       * infos
       */
      btrfs_clear_space_info_full(root->fs_info);

      unlock_chunks(root);
      btrfs_commit_transaction(trans, root);

      if (seeding_dev) {
            mutex_unlock(&uuid_mutex);
            up_write(&sb->s_umount);

            ret = btrfs_relocate_sys_chunks(root);
            BUG_ON(ret);
      }
out:
      mutex_unlock(&root->fs_info->volume_mutex);
      return ret;
error:
      close_bdev_exclusive(bdev, 0);
      if (seeding_dev) {
            mutex_unlock(&uuid_mutex);
            up_write(&sb->s_umount);
      }
      goto out;
}

static noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
                              struct btrfs_device *device)
{
      int ret;
      struct btrfs_path *path;
      struct btrfs_root *root;
      struct btrfs_dev_item *dev_item;
      struct extent_buffer *leaf;
      struct btrfs_key key;

      root = device->dev_root->fs_info->chunk_root;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
      key.type = BTRFS_DEV_ITEM_KEY;
      key.offset = device->devid;

      ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
      if (ret < 0)
            goto out;

      if (ret > 0) {
            ret = -ENOENT;
            goto out;
      }

      leaf = path->nodes[0];
      dev_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_item);

      btrfs_set_device_id(leaf, dev_item, device->devid);
      btrfs_set_device_type(leaf, dev_item, device->type);
      btrfs_set_device_io_align(leaf, dev_item, device->io_align);
      btrfs_set_device_io_width(leaf, dev_item, device->io_width);
      btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
      btrfs_set_device_total_bytes(leaf, dev_item, device->disk_total_bytes);
      btrfs_set_device_bytes_used(leaf, dev_item, device->bytes_used);
      btrfs_mark_buffer_dirty(leaf);

out:
      btrfs_free_path(path);
      return ret;
}

static int __btrfs_grow_device(struct btrfs_trans_handle *trans,
                  struct btrfs_device *device, u64 new_size)
{
      struct btrfs_super_block *super_copy =
            &device->dev_root->fs_info->super_copy;
      u64 old_total = btrfs_super_total_bytes(super_copy);
      u64 diff = new_size - device->total_bytes;

      if (!device->writeable)
            return -EACCES;
      if (new_size <= device->total_bytes)
            return -EINVAL;

      btrfs_set_super_total_bytes(super_copy, old_total + diff);
      device->fs_devices->total_rw_bytes += diff;

      device->total_bytes = new_size;
      device->disk_total_bytes = new_size;
      btrfs_clear_space_info_full(device->dev_root->fs_info);

      return btrfs_update_device(trans, device);
}

int btrfs_grow_device(struct btrfs_trans_handle *trans,
                  struct btrfs_device *device, u64 new_size)
{
      int ret;
      lock_chunks(device->dev_root);
      ret = __btrfs_grow_device(trans, device, new_size);
      unlock_chunks(device->dev_root);
      return ret;
}

static int btrfs_free_chunk(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root,
                      u64 chunk_tree, u64 chunk_objectid,
                      u64 chunk_offset)
{
      int ret;
      struct btrfs_path *path;
      struct btrfs_key key;

      root = root->fs_info->chunk_root;
      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      key.objectid = chunk_objectid;
      key.offset = chunk_offset;
      key.type = BTRFS_CHUNK_ITEM_KEY;

      ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
      BUG_ON(ret);

      ret = btrfs_del_item(trans, root, path);
      BUG_ON(ret);

      btrfs_free_path(path);
      return 0;
}

static int btrfs_del_sys_chunk(struct btrfs_root *root, u64 chunk_objectid, u64
                  chunk_offset)
{
      struct btrfs_super_block *super_copy = &root->fs_info->super_copy;
      struct btrfs_disk_key *disk_key;
      struct btrfs_chunk *chunk;
      u8 *ptr;
      int ret = 0;
      u32 num_stripes;
      u32 array_size;
      u32 len = 0;
      u32 cur;
      struct btrfs_key key;

      array_size = btrfs_super_sys_array_size(super_copy);

      ptr = super_copy->sys_chunk_array;
      cur = 0;

      while (cur < array_size) {
            disk_key = (struct btrfs_disk_key *)ptr;
            btrfs_disk_key_to_cpu(&key, disk_key);

            len = sizeof(*disk_key);

            if (key.type == BTRFS_CHUNK_ITEM_KEY) {
                  chunk = (struct btrfs_chunk *)(ptr + len);
                  num_stripes = btrfs_stack_chunk_num_stripes(chunk);
                  len += btrfs_chunk_item_size(num_stripes);
            } else {
                  ret = -EIO;
                  break;
            }
            if (key.objectid == chunk_objectid &&
                key.offset == chunk_offset) {
                  memmove(ptr, ptr + len, array_size - (cur + len));
                  array_size -= len;
                  btrfs_set_super_sys_array_size(super_copy, array_size);
            } else {
                  ptr += len;
                  cur += len;
            }
      }
      return ret;
}

static int btrfs_relocate_chunk(struct btrfs_root *root,
                   u64 chunk_tree, u64 chunk_objectid,
                   u64 chunk_offset)
{
      struct extent_map_tree *em_tree;
      struct btrfs_root *extent_root;
      struct btrfs_trans_handle *trans;
      struct extent_map *em;
      struct map_lookup *map;
      int ret;
      int i;

      root = root->fs_info->chunk_root;
      extent_root = root->fs_info->extent_root;
      em_tree = &root->fs_info->mapping_tree.map_tree;

      /* step one, relocate all the extents inside this chunk */
      ret = btrfs_relocate_block_group(extent_root, chunk_offset);
      BUG_ON(ret);

      trans = btrfs_start_transaction(root, 1);
      BUG_ON(!trans);

      lock_chunks(root);

      /*
       * step two, delete the device extents and the
       * chunk tree entries
       */
      spin_lock(&em_tree->lock);
      em = lookup_extent_mapping(em_tree, chunk_offset, 1);
      spin_unlock(&em_tree->lock);

      BUG_ON(em->start > chunk_offset ||
             em->start + em->len < chunk_offset);
      map = (struct map_lookup *)em->bdev;

      for (i = 0; i < map->num_stripes; i++) {
            ret = btrfs_free_dev_extent(trans, map->stripes[i].dev,
                                  map->stripes[i].physical);
            BUG_ON(ret);

            if (map->stripes[i].dev) {
                  ret = btrfs_update_device(trans, map->stripes[i].dev);
                  BUG_ON(ret);
            }
      }
      ret = btrfs_free_chunk(trans, root, chunk_tree, chunk_objectid,
                         chunk_offset);

      BUG_ON(ret);

      if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
            ret = btrfs_del_sys_chunk(root, chunk_objectid, chunk_offset);
            BUG_ON(ret);
      }

      ret = btrfs_remove_block_group(trans, extent_root, chunk_offset);
      BUG_ON(ret);

      spin_lock(&em_tree->lock);
      remove_extent_mapping(em_tree, em);
      spin_unlock(&em_tree->lock);

      kfree(map);
      em->bdev = NULL;

      /* once for the tree */
      free_extent_map(em);
      /* once for us */
      free_extent_map(em);

      unlock_chunks(root);
      btrfs_end_transaction(trans, root);
      return 0;
}

static int btrfs_relocate_sys_chunks(struct btrfs_root *root)
{
      struct btrfs_root *chunk_root = root->fs_info->chunk_root;
      struct btrfs_path *path;
      struct extent_buffer *leaf;
      struct btrfs_chunk *chunk;
      struct btrfs_key key;
      struct btrfs_key found_key;
      u64 chunk_tree = chunk_root->root_key.objectid;
      u64 chunk_type;
      int ret;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
      key.offset = (u64)-1;
      key.type = BTRFS_CHUNK_ITEM_KEY;

      while (1) {
            ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
            if (ret < 0)
                  goto error;
            BUG_ON(ret == 0);

            ret = btrfs_previous_item(chunk_root, path, key.objectid,
                                key.type);
            if (ret < 0)
                  goto error;
            if (ret > 0)
                  break;

            leaf = path->nodes[0];
            btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

            chunk = btrfs_item_ptr(leaf, path->slots[0],
                               struct btrfs_chunk);
            chunk_type = btrfs_chunk_type(leaf, chunk);
            btrfs_release_path(chunk_root, path);

            if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM) {
                  ret = btrfs_relocate_chunk(chunk_root, chunk_tree,
                                       found_key.objectid,
                                       found_key.offset);
                  BUG_ON(ret);
            }

            if (found_key.offset == 0)
                  break;
            key.offset = found_key.offset - 1;
      }
      ret = 0;
error:
      btrfs_free_path(path);
      return ret;
}

static u64 div_factor(u64 num, int factor)
{
      if (factor == 10)
            return num;
      num *= factor;
      do_div(num, 10);
      return num;
}

int btrfs_balance(struct btrfs_root *dev_root)
{
      int ret;
      struct list_head *devices = &dev_root->fs_info->fs_devices->devices;
      struct btrfs_device *device;
      u64 old_size;
      u64 size_to_free;
      struct btrfs_path *path;
      struct btrfs_key key;
      struct btrfs_chunk *chunk;
      struct btrfs_root *chunk_root = dev_root->fs_info->chunk_root;
      struct btrfs_trans_handle *trans;
      struct btrfs_key found_key;

      if (dev_root->fs_info->sb->s_flags & MS_RDONLY)
            return -EROFS;

      mutex_lock(&dev_root->fs_info->volume_mutex);
      dev_root = dev_root->fs_info->dev_root;

      /* step one make some room on all the devices */
      list_for_each_entry(device, devices, dev_list) {
            old_size = device->total_bytes;
            size_to_free = div_factor(old_size, 1);
            size_to_free = min(size_to_free, (u64)1 * 1024 * 1024);
            if (!device->writeable ||
                device->total_bytes - device->bytes_used > size_to_free)
                  continue;

            ret = btrfs_shrink_device(device, old_size - size_to_free);
            BUG_ON(ret);

            trans = btrfs_start_transaction(dev_root, 1);
            BUG_ON(!trans);

            ret = btrfs_grow_device(trans, device, old_size);
            BUG_ON(ret);

            btrfs_end_transaction(trans, dev_root);
      }

      /* step two, relocate all the chunks */
      path = btrfs_alloc_path();
      BUG_ON(!path);

      key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
      key.offset = (u64)-1;
      key.type = BTRFS_CHUNK_ITEM_KEY;

      while (1) {
            ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
            if (ret < 0)
                  goto error;

            /*
             * this shouldn't happen, it means the last relocate
             * failed
             */
            if (ret == 0)
                  break;

            ret = btrfs_previous_item(chunk_root, path, 0,
                                BTRFS_CHUNK_ITEM_KEY);
            if (ret)
                  break;

            btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                              path->slots[0]);
            if (found_key.objectid != key.objectid)
                  break;

            chunk = btrfs_item_ptr(path->nodes[0],
                               path->slots[0],
                               struct btrfs_chunk);
            key.offset = found_key.offset;
            /* chunk zero is special */
            if (key.offset == 0)
                  break;

            btrfs_release_path(chunk_root, path);
            ret = btrfs_relocate_chunk(chunk_root,
                                 chunk_root->root_key.objectid,
                                 found_key.objectid,
                                 found_key.offset);
            BUG_ON(ret);
      }
      ret = 0;
error:
      btrfs_free_path(path);
      mutex_unlock(&dev_root->fs_info->volume_mutex);
      return ret;
}

/*
 * shrinking a device means finding all of the device extents past
 * the new size, and then following the back refs to the chunks.
 * The chunk relocation code actually frees the device extent
 */
int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
{
      struct btrfs_trans_handle *trans;
      struct btrfs_root *root = device->dev_root;
      struct btrfs_dev_extent *dev_extent = NULL;
      struct btrfs_path *path;
      u64 length;
      u64 chunk_tree;
      u64 chunk_objectid;
      u64 chunk_offset;
      int ret;
      int slot;
      struct extent_buffer *l;
      struct btrfs_key key;
      struct btrfs_super_block *super_copy = &root->fs_info->super_copy;
      u64 old_total = btrfs_super_total_bytes(super_copy);
      u64 diff = device->total_bytes - new_size;

      if (new_size >= device->total_bytes)
            return -EINVAL;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      trans = btrfs_start_transaction(root, 1);
      if (!trans) {
            ret = -ENOMEM;
            goto done;
      }

      path->reada = 2;

      lock_chunks(root);

      device->total_bytes = new_size;
      if (device->writeable)
            device->fs_devices->total_rw_bytes -= diff;
      unlock_chunks(root);
      btrfs_end_transaction(trans, root);

      key.objectid = device->devid;
      key.offset = (u64)-1;
      key.type = BTRFS_DEV_EXTENT_KEY;

      while (1) {
            ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
            if (ret < 0)
                  goto done;

            ret = btrfs_previous_item(root, path, 0, key.type);
            if (ret < 0)
                  goto done;
            if (ret) {
                  ret = 0;
                  break;
            }

            l = path->nodes[0];
            slot = path->slots[0];
            btrfs_item_key_to_cpu(l, &key, path->slots[0]);

            if (key.objectid != device->devid)
                  break;

            dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
            length = btrfs_dev_extent_length(l, dev_extent);

            if (key.offset + length <= new_size)
                  break;

            chunk_tree = btrfs_dev_extent_chunk_tree(l, dev_extent);
            chunk_objectid = btrfs_dev_extent_chunk_objectid(l, dev_extent);
            chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
            btrfs_release_path(root, path);

            ret = btrfs_relocate_chunk(root, chunk_tree, chunk_objectid,
                                 chunk_offset);
            if (ret)
                  goto done;
      }

      /* Shrinking succeeded, else we would be at "done". */
      trans = btrfs_start_transaction(root, 1);
      if (!trans) {
            ret = -ENOMEM;
            goto done;
      }
      lock_chunks(root);

      device->disk_total_bytes = new_size;
      /* Now btrfs_update_device() will change the on-disk size. */
      ret = btrfs_update_device(trans, device);
      if (ret) {
            unlock_chunks(root);
            btrfs_end_transaction(trans, root);
            goto done;
      }
      WARN_ON(diff > old_total);
      btrfs_set_super_total_bytes(super_copy, old_total - diff);
      unlock_chunks(root);
      btrfs_end_transaction(trans, root);
done:
      btrfs_free_path(path);
      return ret;
}

static int btrfs_add_system_chunk(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root,
                     struct btrfs_key *key,
                     struct btrfs_chunk *chunk, int item_size)
{
      struct btrfs_super_block *super_copy = &root->fs_info->super_copy;
      struct btrfs_disk_key disk_key;
      u32 array_size;
      u8 *ptr;

      array_size = btrfs_super_sys_array_size(super_copy);
      if (array_size + item_size > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE)
            return -EFBIG;

      ptr = super_copy->sys_chunk_array + array_size;
      btrfs_cpu_key_to_disk(&disk_key, key);
      memcpy(ptr, &disk_key, sizeof(disk_key));
      ptr += sizeof(disk_key);
      memcpy(ptr, chunk, item_size);
      item_size += sizeof(disk_key);
      btrfs_set_super_sys_array_size(super_copy, array_size + item_size);
      return 0;
}

static noinline u64 chunk_bytes_by_type(u64 type, u64 calc_size,
                              int num_stripes, int sub_stripes)
{
      if (type & (BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_DUP))
            return calc_size;
      else if (type & BTRFS_BLOCK_GROUP_RAID10)
            return calc_size * (num_stripes / sub_stripes);
      else
            return calc_size * num_stripes;
}

static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
                         struct btrfs_root *extent_root,
                         struct map_lookup **map_ret,
                         u64 *num_bytes, u64 *stripe_size,
                         u64 start, u64 type)
{
      struct btrfs_fs_info *info = extent_root->fs_info;
      struct btrfs_device *device = NULL;
      struct btrfs_fs_devices *fs_devices = info->fs_devices;
      struct list_head *cur;
      struct map_lookup *map = NULL;
      struct extent_map_tree *em_tree;
      struct extent_map *em;
      struct list_head private_devs;
      int min_stripe_size = 1 * 1024 * 1024;
      u64 calc_size = 1024 * 1024 * 1024;
      u64 max_chunk_size = calc_size;
      u64 min_free;
      u64 avail;
      u64 max_avail = 0;
      u64 dev_offset;
      int num_stripes = 1;
      int min_stripes = 1;
      int sub_stripes = 0;
      int looped = 0;
      int ret;
      int index;
      int stripe_len = 64 * 1024;

      if ((type & BTRFS_BLOCK_GROUP_RAID1) &&
          (type & BTRFS_BLOCK_GROUP_DUP)) {
            WARN_ON(1);
            type &= ~BTRFS_BLOCK_GROUP_DUP;
      }
      if (list_empty(&fs_devices->alloc_list))
            return -ENOSPC;

      if (type & (BTRFS_BLOCK_GROUP_RAID0)) {
            num_stripes = fs_devices->rw_devices;
            min_stripes = 2;
      }
      if (type & (BTRFS_BLOCK_GROUP_DUP)) {
            num_stripes = 2;
            min_stripes = 2;
      }
      if (type & (BTRFS_BLOCK_GROUP_RAID1)) {
            num_stripes = min_t(u64, 2, fs_devices->rw_devices);
            if (num_stripes < 2)
                  return -ENOSPC;
            min_stripes = 2;
      }
      if (type & (BTRFS_BLOCK_GROUP_RAID10)) {
            num_stripes = fs_devices->rw_devices;
            if (num_stripes < 4)
                  return -ENOSPC;
            num_stripes &= ~(u32)1;
            sub_stripes = 2;
            min_stripes = 4;
      }

      if (type & BTRFS_BLOCK_GROUP_DATA) {
            max_chunk_size = 10 * calc_size;
            min_stripe_size = 64 * 1024 * 1024;
      } else if (type & BTRFS_BLOCK_GROUP_METADATA) {
            max_chunk_size = 4 * calc_size;
            min_stripe_size = 32 * 1024 * 1024;
      } else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
            calc_size = 8 * 1024 * 1024;
            max_chunk_size = calc_size * 2;
            min_stripe_size = 1 * 1024 * 1024;
      }

      /* we don't want a chunk larger than 10% of writeable space */
      max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
                       max_chunk_size);

again:
      max_avail = 0;
      if (!map || map->num_stripes != num_stripes) {
            kfree(map);
            map = kmalloc(map_lookup_size(num_stripes), GFP_NOFS);
            if (!map)
                  return -ENOMEM;
            map->num_stripes = num_stripes;
      }

      if (calc_size * num_stripes > max_chunk_size) {
            calc_size = max_chunk_size;
            do_div(calc_size, num_stripes);
            do_div(calc_size, stripe_len);
            calc_size *= stripe_len;
      }
      /* we don't want tiny stripes */
      calc_size = max_t(u64, min_stripe_size, calc_size);

      do_div(calc_size, stripe_len);
      calc_size *= stripe_len;

      cur = fs_devices->alloc_list.next;
      index = 0;

      if (type & BTRFS_BLOCK_GROUP_DUP)
            min_free = calc_size * 2;
      else
            min_free = calc_size;

      /*
       * we add 1MB because we never use the first 1MB of the device, unless
       * we've looped, then we are likely allocating the maximum amount of
       * space left already
       */
      if (!looped)
            min_free += 1024 * 1024;

      INIT_LIST_HEAD(&private_devs);
      while (index < num_stripes) {
            device = list_entry(cur, struct btrfs_device, dev_alloc_list);
            BUG_ON(!device->writeable);
            if (device->total_bytes > device->bytes_used)
                  avail = device->total_bytes - device->bytes_used;
            else
                  avail = 0;
            cur = cur->next;

            if (device->in_fs_metadata && avail >= min_free) {
                  ret = find_free_dev_extent(trans, device,
                                       min_free, &dev_offset,
                                       &max_avail);
                  if (ret == 0) {
                        list_move_tail(&device->dev_alloc_list,
                                     &private_devs);
                        map->stripes[index].dev = device;
                        map->stripes[index].physical = dev_offset;
                        index++;
                        if (type & BTRFS_BLOCK_GROUP_DUP) {
                              map->stripes[index].dev = device;
                              map->stripes[index].physical =
                                    dev_offset + calc_size;
                              index++;
                        }
                  }
            } else if (device->in_fs_metadata && avail > max_avail)
                  max_avail = avail;
            if (cur == &fs_devices->alloc_list)
                  break;
      }
      list_splice(&private_devs, &fs_devices->alloc_list);
      if (index < num_stripes) {
            if (index >= min_stripes) {
                  num_stripes = index;
                  if (type & (BTRFS_BLOCK_GROUP_RAID10)) {
                        num_stripes /= sub_stripes;
                        num_stripes *= sub_stripes;
                  }
                  looped = 1;
                  goto again;
            }
            if (!looped && max_avail > 0) {
                  looped = 1;
                  calc_size = max_avail;
                  goto again;
            }
            kfree(map);
            return -ENOSPC;
      }
      map->sector_size = extent_root->sectorsize;
      map->stripe_len = stripe_len;
      map->io_align = stripe_len;
      map->io_width = stripe_len;
      map->type = type;
      map->num_stripes = num_stripes;
      map->sub_stripes = sub_stripes;

      *map_ret = map;
      *stripe_size = calc_size;
      *num_bytes = chunk_bytes_by_type(type, calc_size,
                               num_stripes, sub_stripes);

      em = alloc_extent_map(GFP_NOFS);
      if (!em) {
            kfree(map);
            return -ENOMEM;
      }
      em->bdev = (struct block_device *)map;
      em->start = start;
      em->len = *num_bytes;
      em->block_start = 0;
      em->block_len = em->len;

      em_tree = &extent_root->fs_info->mapping_tree.map_tree;
      spin_lock(&em_tree->lock);
      ret = add_extent_mapping(em_tree, em);
      spin_unlock(&em_tree->lock);
      BUG_ON(ret);
      free_extent_map(em);

      ret = btrfs_make_block_group(trans, extent_root, 0, type,
                             BTRFS_FIRST_CHUNK_TREE_OBJECTID,
                             start, *num_bytes);
      BUG_ON(ret);

      index = 0;
      while (index < map->num_stripes) {
            device = map->stripes[index].dev;
            dev_offset = map->stripes[index].physical;

            ret = btrfs_alloc_dev_extent(trans, device,
                        info->chunk_root->root_key.objectid,
                        BTRFS_FIRST_CHUNK_TREE_OBJECTID,
                        start, dev_offset, calc_size);
            BUG_ON(ret);
            index++;
      }

      return 0;
}

static int __finish_chunk_alloc(struct btrfs_trans_handle *trans,
                        struct btrfs_root *extent_root,
                        struct map_lookup *map, u64 chunk_offset,
                        u64 chunk_size, u64 stripe_size)
{
      u64 dev_offset;
      struct btrfs_key key;
      struct btrfs_root *chunk_root = extent_root->fs_info->chunk_root;
      struct btrfs_device *device;
      struct btrfs_chunk *chunk;
      struct btrfs_stripe *stripe;
      size_t item_size = btrfs_chunk_item_size(map->num_stripes);
      int index = 0;
      int ret;

      chunk = kzalloc(item_size, GFP_NOFS);
      if (!chunk)
            return -ENOMEM;

      index = 0;
      while (index < map->num_stripes) {
            device = map->stripes[index].dev;
            device->bytes_used += stripe_size;
            ret = btrfs_update_device(trans, device);
            BUG_ON(ret);
            index++;
      }

      index = 0;
      stripe = &chunk->stripe;
      while (index < map->num_stripes) {
            device = map->stripes[index].dev;
            dev_offset = map->stripes[index].physical;

            btrfs_set_stack_stripe_devid(stripe, device->devid);
            btrfs_set_stack_stripe_offset(stripe, dev_offset);
            memcpy(stripe->dev_uuid, device->uuid, BTRFS_UUID_SIZE);
            stripe++;
            index++;
      }

      btrfs_set_stack_chunk_length(chunk, chunk_size);
      btrfs_set_stack_chunk_owner(chunk, extent_root->root_key.objectid);
      btrfs_set_stack_chunk_stripe_len(chunk, map->stripe_len);
      btrfs_set_stack_chunk_type(chunk, map->type);
      btrfs_set_stack_chunk_num_stripes(chunk, map->num_stripes);
      btrfs_set_stack_chunk_io_align(chunk, map->stripe_len);
      btrfs_set_stack_chunk_io_width(chunk, map->stripe_len);
      btrfs_set_stack_chunk_sector_size(chunk, extent_root->sectorsize);
      btrfs_set_stack_chunk_sub_stripes(chunk, map->sub_stripes);

      key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
      key.type = BTRFS_CHUNK_ITEM_KEY;
      key.offset = chunk_offset;

      ret = btrfs_insert_item(trans, chunk_root, &key, chunk, item_size);
      BUG_ON(ret);

      if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
            ret = btrfs_add_system_chunk(trans, chunk_root, &key, chunk,
                                   item_size);
            BUG_ON(ret);
      }
      kfree(chunk);
      return 0;
}

/*
 * Chunk allocation falls into two parts. The first part does works
 * that make the new allocated chunk useable, but not do any operation
 * that modifies the chunk tree. The second part does the works that
 * require modifying the chunk tree. This division is important for the
 * bootstrap process of adding storage to a seed btrfs.
 */
int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
                  struct btrfs_root *extent_root, u64 type)
{
      u64 chunk_offset;
      u64 chunk_size;
      u64 stripe_size;
      struct map_lookup *map;
      struct btrfs_root *chunk_root = extent_root->fs_info->chunk_root;
      int ret;

      ret = find_next_chunk(chunk_root, BTRFS_FIRST_CHUNK_TREE_OBJECTID,
                        &chunk_offset);
      if (ret)
            return ret;

      ret = __btrfs_alloc_chunk(trans, extent_root, &map, &chunk_size,
                          &stripe_size, chunk_offset, type);
      if (ret)
            return ret;

      ret = __finish_chunk_alloc(trans, extent_root, map, chunk_offset,
                           chunk_size, stripe_size);
      BUG_ON(ret);
      return 0;
}

static noinline int init_first_rw_device(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct btrfs_device *device)
{
      u64 chunk_offset;
      u64 sys_chunk_offset;
      u64 chunk_size;
      u64 sys_chunk_size;
      u64 stripe_size;
      u64 sys_stripe_size;
      u64 alloc_profile;
      struct map_lookup *map;
      struct map_lookup *sys_map;
      struct btrfs_fs_info *fs_info = root->fs_info;
      struct btrfs_root *extent_root = fs_info->extent_root;
      int ret;

      ret = find_next_chunk(fs_info->chunk_root,
                        BTRFS_FIRST_CHUNK_TREE_OBJECTID, &chunk_offset);
      BUG_ON(ret);

      alloc_profile = BTRFS_BLOCK_GROUP_METADATA |
                  (fs_info->metadata_alloc_profile &
                   fs_info->avail_metadata_alloc_bits);
      alloc_profile = btrfs_reduce_alloc_profile(root, alloc_profile);

      ret = __btrfs_alloc_chunk(trans, extent_root, &map, &chunk_size,
                          &stripe_size, chunk_offset, alloc_profile);
      BUG_ON(ret);

      sys_chunk_offset = chunk_offset + chunk_size;

      alloc_profile = BTRFS_BLOCK_GROUP_SYSTEM |
                  (fs_info->system_alloc_profile &
                   fs_info->avail_system_alloc_bits);
      alloc_profile = btrfs_reduce_alloc_profile(root, alloc_profile);

      ret = __btrfs_alloc_chunk(trans, extent_root, &sys_map,
                          &sys_chunk_size, &sys_stripe_size,
                          sys_chunk_offset, alloc_profile);
      BUG_ON(ret);

      ret = btrfs_add_device(trans, fs_info->chunk_root, device);
      BUG_ON(ret);

      /*
       * Modifying chunk tree needs allocating new blocks from both
       * system block group and metadata block group. So we only can
       * do operations require modifying the chunk tree after both
       * block groups were created.
       */
      ret = __finish_chunk_alloc(trans, extent_root, map, chunk_offset,
                           chunk_size, stripe_size);
      BUG_ON(ret);

      ret = __finish_chunk_alloc(trans, extent_root, sys_map,
                           sys_chunk_offset, sys_chunk_size,
                           sys_stripe_size);
      BUG_ON(ret);
      return 0;
}

int btrfs_chunk_readonly(struct btrfs_root *root, u64 chunk_offset)
{
      struct extent_map *em;
      struct map_lookup *map;
      struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
      int readonly = 0;
      int i;

      spin_lock(&map_tree->map_tree.lock);
      em = lookup_extent_mapping(&map_tree->map_tree, chunk_offset, 1);
      spin_unlock(&map_tree->map_tree.lock);
      if (!em)
            return 1;

      map = (struct map_lookup *)em->bdev;
      for (i = 0; i < map->num_stripes; i++) {
            if (!map->stripes[i].dev->writeable) {
                  readonly = 1;
                  break;
            }
      }
      free_extent_map(em);
      return readonly;
}

void btrfs_mapping_init(struct btrfs_mapping_tree *tree)
{
      extent_map_tree_init(&tree->map_tree, GFP_NOFS);
}

void btrfs_mapping_tree_free(struct btrfs_mapping_tree *tree)
{
      struct extent_map *em;

      while (1) {
            spin_lock(&tree->map_tree.lock);
            em = lookup_extent_mapping(&tree->map_tree, 0, (u64)-1);
            if (em)
                  remove_extent_mapping(&tree->map_tree, em);
            spin_unlock(&tree->map_tree.lock);
            if (!em)
                  break;
            kfree(em->bdev);
            /* once for us */
            free_extent_map(em);
            /* once for the tree */
            free_extent_map(em);
      }
}

int btrfs_num_copies(struct btrfs_mapping_tree *map_tree, u64 logical, u64 len)
{
      struct extent_map *em;
      struct map_lookup *map;
      struct extent_map_tree *em_tree = &map_tree->map_tree;
      int ret;

      spin_lock(&em_tree->lock);
      em = lookup_extent_mapping(em_tree, logical, len);
      spin_unlock(&em_tree->lock);
      BUG_ON(!em);

      BUG_ON(em->start > logical || em->start + em->len < logical);
      map = (struct map_lookup *)em->bdev;
      if (map->type & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1))
            ret = map->num_stripes;
      else if (map->type & BTRFS_BLOCK_GROUP_RAID10)
            ret = map->sub_stripes;
      else
            ret = 1;
      free_extent_map(em);
      return ret;
}

static int find_live_mirror(struct map_lookup *map, int first, int num,
                      int optimal)
{
      int i;
      if (map->stripes[optimal].dev->bdev)
            return optimal;
      for (i = first; i < first + num; i++) {
            if (map->stripes[i].dev->bdev)
                  return i;
      }
      /* we couldn't find one that doesn't fail.  Just return something
       * and the io error handling code will clean up eventually
       */
      return optimal;
}

static int __btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
                       u64 logical, u64 *length,
                       struct btrfs_multi_bio **multi_ret,
                       int mirror_num, struct page *unplug_page)
{
      struct extent_map *em;
      struct map_lookup *map;
      struct extent_map_tree *em_tree = &map_tree->map_tree;
      u64 offset;
      u64 stripe_offset;
      u64 stripe_nr;
      int stripes_allocated = 8;
      int stripes_required = 1;
      int stripe_index;
      int i;
      int num_stripes;
      int max_errors = 0;
      struct btrfs_multi_bio *multi = NULL;

      if (multi_ret && !(rw & (1 << BIO_RW)))
            stripes_allocated = 1;
again:
      if (multi_ret) {
            multi = kzalloc(btrfs_multi_bio_size(stripes_allocated),
                        GFP_NOFS);
            if (!multi)
                  return -ENOMEM;

            atomic_set(&multi->error, 0);
      }

      spin_lock(&em_tree->lock);
      em = lookup_extent_mapping(em_tree, logical, *length);
      spin_unlock(&em_tree->lock);

      if (!em && unplug_page)
            return 0;

      if (!em) {
            printk(KERN_CRIT "unable to find logical %llu len %llu\n",
                   (unsigned long long)logical,
                   (unsigned long long)*length);
            BUG();
      }

      BUG_ON(em->start > logical || em->start + em->len < logical);
      map = (struct map_lookup *)em->bdev;
      offset = logical - em->start;

      if (mirror_num > map->num_stripes)
            mirror_num = 0;

      /* if our multi bio struct is too small, back off and try again */
      if (rw & (1 << BIO_RW)) {
            if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
                         BTRFS_BLOCK_GROUP_DUP)) {
                  stripes_required = map->num_stripes;
                  max_errors = 1;
            } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
                  stripes_required = map->sub_stripes;
                  max_errors = 1;
            }
      }
      if (multi_ret && (rw & (1 << BIO_RW)) &&
          stripes_allocated < stripes_required) {
            stripes_allocated = map->num_stripes;
            free_extent_map(em);
            kfree(multi);
            goto again;
      }
      stripe_nr = offset;
      /*
       * stripe_nr counts the total number of stripes we have to stride
       * to get to this block
       */
      do_div(stripe_nr, map->stripe_len);

      stripe_offset = stripe_nr * map->stripe_len;
      BUG_ON(offset < stripe_offset);

      /* stripe_offset is the offset of this block in its stripe*/
      stripe_offset = offset - stripe_offset;

      if (map->type & (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 |
                   BTRFS_BLOCK_GROUP_RAID10 |
                   BTRFS_BLOCK_GROUP_DUP)) {
            /* we limit the length of each bio to what fits in a stripe */
            *length = min_t(u64, em->len - offset,
                        map->stripe_len - stripe_offset);
      } else {
            *length = em->len - offset;
      }

      if (!multi_ret && !unplug_page)
            goto out;

      num_stripes = 1;
      stripe_index = 0;
      if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
            if (unplug_page || (rw & (1 << BIO_RW)))
                  num_stripes = map->num_stripes;
            else if (mirror_num)
                  stripe_index = mirror_num - 1;
            else {
                  stripe_index = find_live_mirror(map, 0,
                                  map->num_stripes,
                                  current->pid % map->num_stripes);
            }

      } else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
            if (rw & (1 << BIO_RW))
                  num_stripes = map->num_stripes;
            else if (mirror_num)
                  stripe_index = mirror_num - 1;

      } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
            int factor = map->num_stripes / map->sub_stripes;

            stripe_index = do_div(stripe_nr, factor);
            stripe_index *= map->sub_stripes;

            if (unplug_page || (rw & (1 << BIO_RW)))
                  num_stripes = map->sub_stripes;
            else if (mirror_num)
                  stripe_index += mirror_num - 1;
            else {
                  stripe_index = find_live_mirror(map, stripe_index,
                                    map->sub_stripes, stripe_index +
                                    current->pid % map->sub_stripes);
            }
      } else {
            /*
             * after this do_div call, stripe_nr is the number of stripes
             * on this device we have to walk to find the data, and
             * stripe_index is the number of our device in the stripe array
             */
            stripe_index = do_div(stripe_nr, map->num_stripes);
      }
      BUG_ON(stripe_index >= map->num_stripes);

      for (i = 0; i < num_stripes; i++) {
            if (unplug_page) {
                  struct btrfs_device *device;
                  struct backing_dev_info *bdi;

                  device = map->stripes[stripe_index].dev;
                  if (device->bdev) {
                        bdi = blk_get_backing_dev_info(device->bdev);
                        if (bdi->unplug_io_fn)
                              bdi->unplug_io_fn(bdi, unplug_page);
                  }
            } else {
                  multi->stripes[i].physical =
                        map->stripes[stripe_index].physical +
                        stripe_offset + stripe_nr * map->stripe_len;
                  multi->stripes[i].dev = map->stripes[stripe_index].dev;
            }
            stripe_index++;
      }
      if (multi_ret) {
            *multi_ret = multi;
            multi->num_stripes = num_stripes;
            multi->max_errors = max_errors;
      }
out:
      free_extent_map(em);
      return 0;
}

int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
                  u64 logical, u64 *length,
                  struct btrfs_multi_bio **multi_ret, int mirror_num)
{
      return __btrfs_map_block(map_tree, rw, logical, length, multi_ret,
                         mirror_num, NULL);
}

int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
                 u64 chunk_start, u64 physical, u64 devid,
                 u64 **logical, int *naddrs, int *stripe_len)
{
      struct extent_map_tree *em_tree = &map_tree->map_tree;
      struct extent_map *em;
      struct map_lookup *map;
      u64 *buf;
      u64 bytenr;
      u64 length;
      u64 stripe_nr;
      int i, j, nr = 0;

      spin_lock(&em_tree->lock);
      em = lookup_extent_mapping(em_tree, chunk_start, 1);
      spin_unlock(&em_tree->lock);

      BUG_ON(!em || em->start != chunk_start);
      map = (struct map_lookup *)em->bdev;

      length = em->len;
      if (map->type & BTRFS_BLOCK_GROUP_RAID10)
            do_div(length, map->num_stripes / map->sub_stripes);
      else if (map->type & BTRFS_BLOCK_GROUP_RAID0)
            do_div(length, map->num_stripes);

      buf = kzalloc(sizeof(u64) * map->num_stripes, GFP_NOFS);
      BUG_ON(!buf);

      for (i = 0; i < map->num_stripes; i++) {
            if (devid && map->stripes[i].dev->devid != devid)
                  continue;
            if (map->stripes[i].physical > physical ||
                map->stripes[i].physical + length <= physical)
                  continue;

            stripe_nr = physical - map->stripes[i].physical;
            do_div(stripe_nr, map->stripe_len);

            if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
                  stripe_nr = stripe_nr * map->num_stripes + i;
                  do_div(stripe_nr, map->sub_stripes);
            } else if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
                  stripe_nr = stripe_nr * map->num_stripes + i;
            }
            bytenr = chunk_start + stripe_nr * map->stripe_len;
            WARN_ON(nr >= map->num_stripes);
            for (j = 0; j < nr; j++) {
                  if (buf[j] == bytenr)
                        break;
            }
            if (j == nr) {
                  WARN_ON(nr >= map->num_stripes);
                  buf[nr++] = bytenr;
            }
      }

      *logical = buf;
      *naddrs = nr;
      *stripe_len = map->stripe_len;

      free_extent_map(em);
      return 0;
}

int btrfs_unplug_page(struct btrfs_mapping_tree *map_tree,
                  u64 logical, struct page *page)
{
      u64 length = PAGE_CACHE_SIZE;
      return __btrfs_map_block(map_tree, READ, logical, &length,
                         NULL, 0, page);
}

static void end_bio_multi_stripe(struct bio *bio, int err)
{
      struct btrfs_multi_bio *multi = bio->bi_private;
      int is_orig_bio = 0;

      if (err)
            atomic_inc(&multi->error);

      if (bio == multi->orig_bio)
            is_orig_bio = 1;

      if (atomic_dec_and_test(&multi->stripes_pending)) {
            if (!is_orig_bio) {
                  bio_put(bio);
                  bio = multi->orig_bio;
            }
            bio->bi_private = multi->private;
            bio->bi_end_io = multi->end_io;
            /* only send an error to the higher layers if it is
             * beyond the tolerance of the multi-bio
             */
            if (atomic_read(&multi->error) > multi->max_errors) {
                  err = -EIO;
            } else if (err) {
                  /*
                   * this bio is actually up to date, we didn't
                   * go over the max number of errors
                   */
                  set_bit(BIO_UPTODATE, &bio->bi_flags);
                  err = 0;
            }
            kfree(multi);

            bio_endio(bio, err);
      } else if (!is_orig_bio) {
            bio_put(bio);
      }
}

02865 struct async_sched {
      struct bio *bio;
      int rw;
      struct btrfs_fs_info *info;
      struct btrfs_work work;
};

/*
 * see run_scheduled_bios for a description of why bios are collected for
 * async submit.
 *
 * This will add one bio to the pending list for a device and make sure
 * the work struct is scheduled.
 */
static noinline int schedule_bio(struct btrfs_root *root,
                         struct btrfs_device *device,
                         int rw, struct bio *bio)
{
      int should_queue = 1;
      struct btrfs_pending_bios *pending_bios;

      /* don't bother with additional async steps for reads, right now */
      if (!(rw & (1 << BIO_RW))) {
            bio_get(bio);
            submit_bio(rw, bio);
            bio_put(bio);
            return 0;
      }

      /*
       * nr_async_bios allows us to reliably return congestion to the
       * higher layers.  Otherwise, the async bio makes it appear we have
       * made progress against dirty pages when we've really just put it
       * on a queue for later
       */
      atomic_inc(&root->fs_info->nr_async_bios);
      WARN_ON(bio->bi_next);
      bio->bi_next = NULL;
      bio->bi_rw |= rw;

      spin_lock(&device->io_lock);
      if (bio_sync(bio))
            pending_bios = &device->pending_sync_bios;
      else
            pending_bios = &device->pending_bios;

      if (pending_bios->tail)
            pending_bios->tail->bi_next = bio;

      pending_bios->tail = bio;
      if (!pending_bios->head)
            pending_bios->head = bio;
      if (device->running_pending)
            should_queue = 0;

      spin_unlock(&device->io_lock);

      if (should_queue)
            btrfs_queue_worker(&root->fs_info->submit_workers,
                           &device->work);
      return 0;
}

int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
              int mirror_num, int async_submit)
{
      struct btrfs_mapping_tree *map_tree;
      struct btrfs_device *dev;
      struct bio *first_bio = bio;
      u64 logical = (u64)bio->bi_sector << 9;
      u64 length = 0;
      u64 map_length;
      struct btrfs_multi_bio *multi = NULL;
      int ret;
      int dev_nr = 0;
      int total_devs = 1;

      length = bio->bi_size;
      map_tree = &root->fs_info->mapping_tree;
      map_length = length;

      ret = btrfs_map_block(map_tree, rw, logical, &map_length, &multi,
                        mirror_num);
      BUG_ON(ret);

      total_devs = multi->num_stripes;
      if (map_length < length) {
            printk(KERN_CRIT "mapping failed logical %llu bio len %llu "
                   "len %llu\n", (unsigned long long)logical,
                   (unsigned long long)length,
                   (unsigned long long)map_length);
            BUG();
      }
      multi->end_io = first_bio->bi_end_io;
      multi->private = first_bio->bi_private;
      multi->orig_bio = first_bio;
      atomic_set(&multi->stripes_pending, multi->num_stripes);

      while (dev_nr < total_devs) {
            if (total_devs > 1) {
                  if (dev_nr < total_devs - 1) {
                        bio = bio_clone(first_bio, GFP_NOFS);
                        BUG_ON(!bio);
                  } else {
                        bio = first_bio;
                  }
                  bio->bi_private = multi;
                  bio->bi_end_io = end_bio_multi_stripe;
            }
            bio->bi_sector = multi->stripes[dev_nr].physical >> 9;
            dev = multi->stripes[dev_nr].dev;
            BUG_ON(rw == WRITE && !dev->writeable);
            if (dev && dev->bdev) {
                  bio->bi_bdev = dev->bdev;
                  if (async_submit)
                        schedule_bio(root, dev, rw, bio);
                  else
                        submit_bio(rw, bio);
            } else {
                  bio->bi_bdev = root->fs_info->fs_devices->latest_bdev;
                  bio->bi_sector = logical >> 9;
                  bio_endio(bio, -EIO);
            }
            dev_nr++;
      }
      if (total_devs == 1)
            kfree(multi);
      return 0;
}

struct btrfs_device *btrfs_find_device(struct btrfs_root *root, u64 devid,
                               u8 *uuid, u8 *fsid)
{
      struct btrfs_device *device;
      struct btrfs_fs_devices *cur_devices;

      cur_devices = root->fs_info->fs_devices;
      while (cur_devices) {
            if (!fsid ||
                !memcmp(cur_devices->fsid, fsid, BTRFS_UUID_SIZE)) {
                  device = __find_device(&cur_devices->devices,
                                     devid, uuid);
                  if (device)
                        return device;
            }
            cur_devices = cur_devices->seed;
      }
      return NULL;
}

static struct btrfs_device *add_missing_dev(struct btrfs_root *root,
                                  u64 devid, u8 *dev_uuid)
{
      struct btrfs_device *device;
      struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;

      device = kzalloc(sizeof(*device), GFP_NOFS);
      if (!device)
            return NULL;
      list_add(&device->dev_list,
             &fs_devices->devices);
      device->barriers = 1;
      device->dev_root = root->fs_info->dev_root;
      device->devid = devid;
      device->work.func = pending_bios_fn;
      device->fs_devices = fs_devices;
      fs_devices->num_devices++;
      spin_lock_init(&device->io_lock);
      INIT_LIST_HEAD(&device->dev_alloc_list);
      memcpy(device->uuid, dev_uuid, BTRFS_UUID_SIZE);
      return device;
}

static int read_one_chunk(struct btrfs_root *root, struct btrfs_key *key,
                    struct extent_buffer *leaf,
                    struct btrfs_chunk *chunk)
{
      struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
      struct map_lookup *map;
      struct extent_map *em;
      u64 logical;
      u64 length;
      u64 devid;
      u8 uuid[BTRFS_UUID_SIZE];
      int num_stripes;
      int ret;
      int i;

      logical = key->offset;
      length = btrfs_chunk_length(leaf, chunk);

      spin_lock(&map_tree->map_tree.lock);
      em = lookup_extent_mapping(&map_tree->map_tree, logical, 1);
      spin_unlock(&map_tree->map_tree.lock);

      /* already mapped? */
      if (em && em->start <= logical && em->start + em->len > logical) {
            free_extent_map(em);
            return 0;
      } else if (em) {
            free_extent_map(em);
      }

      em = alloc_extent_map(GFP_NOFS);
      if (!em)
            return -ENOMEM;
      num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
      map = kmalloc(map_lookup_size(num_stripes), GFP_NOFS);
      if (!map) {
            free_extent_map(em);
            return -ENOMEM;
      }

      em->bdev = (struct block_device *)map;
      em->start = logical;
      em->len = length;
      em->block_start = 0;
      em->block_len = em->len;

      map->num_stripes = num_stripes;
      map->io_width = btrfs_chunk_io_width(leaf, chunk);
      map->io_align = btrfs_chunk_io_align(leaf, chunk);
      map->sector_size = btrfs_chunk_sector_size(leaf, chunk);
      map->stripe_len = btrfs_chunk_stripe_len(leaf, chunk);
      map->type = btrfs_chunk_type(leaf, chunk);
      map->sub_stripes = btrfs_chunk_sub_stripes(leaf, chunk);
      for (i = 0; i < num_stripes; i++) {
            map->stripes[i].physical =
                  btrfs_stripe_offset_nr(leaf, chunk, i);
            devid = btrfs_stripe_devid_nr(leaf, chunk, i);
            read_extent_buffer(leaf, uuid, (unsigned long)
                           btrfs_stripe_dev_uuid_nr(chunk, i),
                           BTRFS_UUID_SIZE);
            map->stripes[i].dev = btrfs_find_device(root, devid, uuid,
                                          NULL);
            if (!map->stripes[i].dev && !btrfs_test_opt(root, DEGRADED)) {
                  kfree(map);
                  free_extent_map(em);
                  return -EIO;
            }
            if (!map->stripes[i].dev) {
                  map->stripes[i].dev =
                        add_missing_dev(root, devid, uuid);
                  if (!map->stripes[i].dev) {
                        kfree(map);
                        free_extent_map(em);
                        return -EIO;
                  }
            }
            map->stripes[i].dev->in_fs_metadata = 1;
      }

      spin_lock(&map_tree->map_tree.lock);
      ret = add_extent_mapping(&map_tree->map_tree, em);
      spin_unlock(&map_tree->map_tree.lock);
      BUG_ON(ret);
      free_extent_map(em);

      return 0;
}

static int fill_device_from_item(struct extent_buffer *leaf,
                         struct btrfs_dev_item *dev_item,
                         struct btrfs_device *device)
{
      unsigned long ptr;

      device->devid = btrfs_device_id(leaf, dev_item);
      device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item);
      device->total_bytes = device->disk_total_bytes;
      device->bytes_used = btrfs_device_bytes_used(leaf, dev_item);
      device->type = btrfs_device_type(leaf, dev_item);
      device->io_align = btrfs_device_io_align(leaf, dev_item);
      device->io_width = btrfs_device_io_width(leaf, dev_item);
      device->sector_size = btrfs_device_sector_size(leaf, dev_item);

      ptr = (unsigned long)btrfs_device_uuid(dev_item);
      read_extent_buffer(leaf, device->uuid, ptr, BTRFS_UUID_SIZE);

      return 0;
}

static int open_seed_devices(struct btrfs_root *root, u8 *fsid)
{
      struct btrfs_fs_devices *fs_devices;
      int ret;

      mutex_lock(&uuid_mutex);

      fs_devices = root->fs_info->fs_devices->seed;
      while (fs_devices) {
            if (!memcmp(fs_devices->fsid, fsid, BTRFS_UUID_SIZE)) {
                  ret = 0;
                  goto out;
            }
            fs_devices = fs_devices->seed;
      }

      fs_devices = find_fsid(fsid);
      if (!fs_devices) {
            ret = -ENOENT;
            goto out;
      }

      fs_devices = clone_fs_devices(fs_devices);
      if (IS_ERR(fs_devices)) {
            ret = PTR_ERR(fs_devices);
            goto out;
      }

      ret = __btrfs_open_devices(fs_devices, FMODE_READ,
                           root->fs_info->bdev_holder);
      if (ret)
            goto out;

      if (!fs_devices->seeding) {
            __btrfs_close_devices(fs_devices);
            free_fs_devices(fs_devices);
            ret = -EINVAL;
            goto out;
      }

      fs_devices->seed = root->fs_info->fs_devices->seed;
      root->fs_info->fs_devices->seed = fs_devices;
out:
      mutex_unlock(&uuid_mutex);
      return ret;
}

static int read_one_dev(struct btrfs_root *root,
                  struct extent_buffer *leaf,
                  struct btrfs_dev_item *dev_item)
{
      struct btrfs_device *device;
      u64 devid;
      int ret;
      u8 fs_uuid[BTRFS_UUID_SIZE];
      u8 dev_uuid[BTRFS_UUID_SIZE];

      devid = btrfs_device_id(leaf, dev_item);
      read_extent_buffer(leaf, dev_uuid,
                     (unsigned long)btrfs_device_uuid(dev_item),
                     BTRFS_UUID_SIZE);
      read_extent_buffer(leaf, fs_uuid,
                     (unsigned long)btrfs_device_fsid(dev_item),
                     BTRFS_UUID_SIZE);

      if (memcmp(fs_uuid, root->fs_info->fsid, BTRFS_UUID_SIZE)) {
            ret = open_seed_devices(root, fs_uuid);
            if (ret && !btrfs_test_opt(root, DEGRADED))
                  return ret;
      }

      device = btrfs_find_device(root, devid, dev_uuid, fs_uuid);
      if (!device || !device->bdev) {
            if (!btrfs_test_opt(root, DEGRADED))
                  return -EIO;

            if (!device) {
                  printk(KERN_WARNING "warning devid %llu missing\n",
                         (unsigned long long)devid);
                  device = add_missing_dev(root, devid, dev_uuid);
                  if (!device)
                        return -ENOMEM;
            }
      }

      if (device->fs_devices != root->fs_info->fs_devices) {
            BUG_ON(device->writeable);
            if (device->generation !=
                btrfs_device_generation(leaf, dev_item))
                  return -EINVAL;
      }

      fill_device_from_item(leaf, dev_item, device);
      device->dev_root = root->fs_info->dev_root;
      device->in_fs_metadata = 1;
      if (device->writeable)
            device->fs_devices->total_rw_bytes += device->total_bytes;
      ret = 0;
      return ret;
}

int btrfs_read_super_device(struct btrfs_root *root, struct extent_buffer *buf)
{
      struct btrfs_dev_item *dev_item;

      dev_item = (struct btrfs_dev_item *)offsetof(struct btrfs_super_block,
                                         dev_item);
      return read_one_dev(root, buf, dev_item);
}

int btrfs_read_sys_array(struct btrfs_root *root)
{
      struct btrfs_super_block *super_copy = &root->fs_info->super_copy;
      struct extent_buffer *sb;
      struct btrfs_disk_key *disk_key;
      struct btrfs_chunk *chunk;
      u8 *ptr;
      unsigned long sb_ptr;
      int ret = 0;
      u32 num_stripes;
      u32 array_size;
      u32 len = 0;
      u32 cur;
      struct btrfs_key key;

      sb = btrfs_find_create_tree_block(root, BTRFS_SUPER_INFO_OFFSET,
                                BTRFS_SUPER_INFO_SIZE);
      if (!sb)
            return -ENOMEM;
      btrfs_set_buffer_uptodate(sb);
      btrfs_set_buffer_lockdep_class(sb, 0);

      write_extent_buffer(sb, super_copy, 0, BTRFS_SUPER_INFO_SIZE);
      array_size = btrfs_super_sys_array_size(super_copy);

      ptr = super_copy->sys_chunk_array;
      sb_ptr = offsetof(struct btrfs_super_block, sys_chunk_array);
      cur = 0;

      while (cur < array_size) {
            disk_key = (struct btrfs_disk_key *)ptr;
            btrfs_disk_key_to_cpu(&key, disk_key);

            len = sizeof(*disk_key); ptr += len;
            sb_ptr += len;
            cur += len;

            if (key.type == BTRFS_CHUNK_ITEM_KEY) {
                  chunk = (struct btrfs_chunk *)sb_ptr;
                  ret = read_one_chunk(root, &key, sb, chunk);
                  if (ret)
                        break;
                  num_stripes = btrfs_chunk_num_stripes(sb, chunk);
                  len = btrfs_chunk_item_size(num_stripes);
            } else {
                  ret = -EIO;
                  break;
            }
            ptr += len;
            sb_ptr += len;
            cur += len;
      }
      free_extent_buffer(sb);
      return ret;
}

int btrfs_read_chunk_tree(struct btrfs_root *root)
{
      struct btrfs_path *path;
      struct extent_buffer *leaf;
      struct btrfs_key key;
      struct btrfs_key found_key;
      int ret;
      int slot;

      root = root->fs_info->chunk_root;

      path = btrfs_alloc_path();
      if (!path)
            return -ENOMEM;

      /* first we search for all of the device items, and then we
       * read in all of the chunk items.  This way we can create chunk
       * mappings that reference all of the devices that are afound
       */
      key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
      key.offset = 0;
      key.type = 0;
again:
      ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
      while (1) {
            leaf = path->nodes[0];
            slot = path->slots[0];
            if (slot >= btrfs_header_nritems(leaf)) {
                  ret = btrfs_next_leaf(root, path);
                  if (ret == 0)
                        continue;
                  if (ret < 0)
                        goto error;
                  break;
            }
            btrfs_item_key_to_cpu(leaf, &found_key, slot);
            if (key.objectid == BTRFS_DEV_ITEMS_OBJECTID) {
                  if (found_key.objectid != BTRFS_DEV_ITEMS_OBJECTID)
                        break;
                  if (found_key.type == BTRFS_DEV_ITEM_KEY) {
                        struct btrfs_dev_item *dev_item;
                        dev_item = btrfs_item_ptr(leaf, slot,
                                      struct btrfs_dev_item);
                        ret = read_one_dev(root, leaf, dev_item);
                        if (ret)
                              goto error;
                  }
            } else if (found_key.type == BTRFS_CHUNK_ITEM_KEY) {
                  struct btrfs_chunk *chunk;
                  chunk = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
                  ret = read_one_chunk(root, &found_key, leaf, chunk);
                  if (ret)
                        goto error;
            }
            path->slots[0]++;
      }
      if (key.objectid == BTRFS_DEV_ITEMS_OBJECTID) {
            key.objectid = 0;
            btrfs_release_path(root, path);
            goto again;
      }
      ret = 0;
error:
      btrfs_free_path(path);
      return ret;
}

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