Btrfs: Add support for multiple devices per filesystem

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 852 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
new file mode 100644
index 000000000000..90a8d45dc6d7
--- /dev/null
+++ b/fs/btrfs/volumes.c
@@ -0,0 +1,852 @@
+/*
+ * 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 "ctree.h"
+#include "extent_map.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "print-tree.h"
+#include "volumes.h"
+
+struct map_lookup {
+        struct btrfs_device *dev;
+        u64 physical;
+};
+
+/*
+ * 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 int find_free_dev_extent(struct btrfs_trans_handle *trans,
+                                struct btrfs_device *device,
+                                struct btrfs_path *path,
+                                u64 num_bytes, u64 *start)
+{
+        struct btrfs_key key;
+        struct btrfs_root *root = device->dev_root;
+        struct btrfs_dev_extent *dev_extent = NULL;
+        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;
+
+        start_found = 0;
+        path->reada = 2;
+
+        /* FIXME use last free of some kind */
+
+        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;
+        ret = btrfs_previous_item(root, path, 0, key.type);
+        if (ret < 0)
+                goto error;
+        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 (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
+         */
+        btrfs_release_path(root, path);
+        BUG_ON(*start < search_start);
+
+        if (*start + num_bytes >= search_end) {
+                ret = -ENOSPC;
+                goto error;
+        }
+        /* check for pending inserts here */
+        return 0;
+
+error:
+        btrfs_release_path(root, path);
+        return ret;
+}
+
+int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
+                           struct btrfs_device *device,
+                           u64 owner, u64 num_bytes, u64 *start)
+{
+        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;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        ret = find_free_dev_extent(trans, device, path, num_bytes, start);
+        if (ret)
+                goto err;
+
+        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_owner(leaf, extent, owner);
+        btrfs_set_dev_extent_length(leaf, extent, num_bytes);
+        btrfs_mark_buffer_dirty(leaf);
+err:
+        btrfs_free_path(path);
+        return ret;
+}
+
+static int find_next_chunk(struct btrfs_root *root, u64 *objectid)
+{
+        struct btrfs_path *path;
+        int ret;
+        struct btrfs_key key;
+        struct btrfs_key found_key;
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+
+        key.objectid = (u64)-1;
+        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) {
+                *objectid = 0;
+        } else {
+                btrfs_item_key_to_cpu(path->nodes[0], &found_key,
+                                      path->slots[0]);
+                *objectid = found_key.objectid + found_key.offset;
+        }
+        ret = 0;
+error:
+        btrfs_free_path(path);
+        return ret;
+}
+
+static struct btrfs_device *next_device(struct list_head *head,
+                                        struct list_head *last)
+{
+        struct list_head *next = last->next;
+        struct btrfs_device *dev;
+
+        if (list_empty(head))
+                return NULL;
+
+        if (next == head)
+                next = next->next;
+
+        dev = list_entry(next, struct btrfs_device, dev_list);
+        return dev;
+}
+
+static int find_next_devid(struct btrfs_root *root, struct btrfs_path *path,
+                           u64 *objectid)
+{
+        int ret;
+        struct btrfs_key key;
+        struct btrfs_key found_key;
+
+        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_release_path(root, 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;
+        u64 free_devid;
+
+        root = root->fs_info->chunk_root;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        ret = find_next_devid(root, path, &free_devid);
+        if (ret)
+                goto out;
+
+        key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+        key.type = BTRFS_DEV_ITEM_KEY;
+        key.offset = free_devid;
+
+        ret = btrfs_insert_empty_item(trans, root, path, &key,
+                                      sizeof(*dev_item) + device->name_len);
+        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_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_rdev(leaf, dev_item, device->rdev);
+        btrfs_set_device_partition(leaf, dev_item, device->partition);
+        btrfs_set_device_name_len(leaf, dev_item, device->name_len);
+        btrfs_set_device_total_bytes(leaf, dev_item, device->total_bytes);
+        btrfs_set_device_bytes_used(leaf, dev_item, device->bytes_used);
+
+        ptr = (unsigned long)btrfs_device_name(dev_item);
+        write_extent_buffer(leaf, device->name, ptr, device->name_len);
+
+        ptr = (unsigned long)btrfs_device_uuid(dev_item);
+        write_extent_buffer(leaf, device->uuid, ptr, BTRFS_DEV_UUID_SIZE);
+        btrfs_mark_buffer_dirty(leaf);
+        ret = 0;
+
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+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_rdev(leaf, dev_item, device->rdev);
+        btrfs_set_device_partition(leaf, dev_item, device->partition);
+        btrfs_set_device_total_bytes(leaf, dev_item, device->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;
+}
+
+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;
+}
+
+int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
+                      struct btrfs_root *extent_root, u64 *start,
+                      u64 *num_bytes, u32 type)
+{
+        u64 dev_offset;
+        struct btrfs_root *chunk_root = extent_root->fs_info->chunk_root;
+        struct btrfs_stripe *stripes;
+        struct btrfs_device *device = NULL;
+        struct btrfs_chunk *chunk;
+        struct list_head *dev_list = &extent_root->fs_info->devices;
+        struct list_head *last_dev = extent_root->fs_info->last_device;
+        struct extent_map_tree *em_tree;
+        struct map_lookup *map;
+        struct extent_map *em;
+        u64 physical;
+        u64 calc_size = 1024 * 1024 * 1024;
+        int num_stripes;
+        int ret;
+        int index = 0;
+        struct btrfs_key key;
+
+
+        ret = find_next_chunk(chunk_root, &key.objectid);
+        if (ret)
+                return ret;
+
+        num_stripes = 1;
+        chunk = kmalloc(btrfs_chunk_item_size(num_stripes), GFP_NOFS);
+        if (!chunk)
+                return -ENOMEM;
+
+        stripes = &chunk->stripe;
+
+        *num_bytes = calc_size;
+        while(index < num_stripes) {
+                device = next_device(dev_list, last_dev);
+                BUG_ON(!device);
+                last_dev = &device->dev_list;
+                extent_root->fs_info->last_device = last_dev;
+
+                ret = btrfs_alloc_dev_extent(trans, device,
+                                             key.objectid,
+                                             calc_size, &dev_offset);
+                BUG_ON(ret);
+
+                device->bytes_used += calc_size;
+                ret = btrfs_update_device(trans, device);
+                BUG_ON(ret);
+
+                btrfs_set_stack_stripe_devid(stripes + index, device->devid);
+                btrfs_set_stack_stripe_offset(stripes + index, dev_offset);
+                physical = dev_offset;
+                index++;
+        }
+
+        /* key.objectid was set above */
+        key.offset = *num_bytes;
+        key.type = BTRFS_CHUNK_ITEM_KEY;
+        btrfs_set_stack_chunk_owner(chunk, extent_root->root_key.objectid);
+        btrfs_set_stack_chunk_stripe_len(chunk, 64 * 1024);
+        btrfs_set_stack_chunk_type(chunk, type);
+        btrfs_set_stack_chunk_num_stripes(chunk, num_stripes);
+        btrfs_set_stack_chunk_io_align(chunk, extent_root->sectorsize);
+        btrfs_set_stack_chunk_io_width(chunk, extent_root->sectorsize);
+        btrfs_set_stack_chunk_sector_size(chunk, extent_root->sectorsize);
+
+        ret = btrfs_insert_item(trans, chunk_root, &key, chunk,
+                                btrfs_chunk_item_size(num_stripes));
+        BUG_ON(ret);
+        *start = key.objectid;
+
+        em = alloc_extent_map(GFP_NOFS);
+        if (!em)
+                return -ENOMEM;
+        map = kmalloc(sizeof(*map), GFP_NOFS);
+        if (!map) {
+                free_extent_map(em);
+                return -ENOMEM;
+        }
+
+        em->bdev = (struct block_device *)map;
+        em->start = key.objectid;
+        em->len = key.offset;
+        em->block_start = 0;
+
+        map->physical = physical;
+        map->dev = device;
+
+        if (!map->dev) {
+                kfree(map);
+                free_extent_map(em);
+                return -EIO;
+        }
+        kfree(chunk);
+
+        em_tree = &extent_root->fs_info->mapping_tree.map_tree;
+        spin_lock(&em_tree->lock);
+        ret = add_extent_mapping(em_tree, em);
+        BUG_ON(ret);
+        spin_unlock(&em_tree->lock);
+        free_extent_map(em);
+        return ret;
+}
+
+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_map_block(struct btrfs_mapping_tree *map_tree,
+                    u64 logical, u64 *phys, u64 *length,
+                    struct btrfs_device **dev)
+{
+        struct extent_map *em;
+        struct map_lookup *map;
+        struct extent_map_tree *em_tree = &map_tree->map_tree;
+        u64 offset;
+
+
+        spin_lock(&em_tree->lock);
+        em = lookup_extent_mapping(em_tree, logical, *length);
+        BUG_ON(!em);
+
+        BUG_ON(em->start > logical || em->start + em->len < logical);
+        map = (struct map_lookup *)em->bdev;
+        offset = logical - em->start;
+        *phys = map->physical + offset;
+        *length = em->len - offset;
+        *dev = map->dev;
+        free_extent_map(em);
+        spin_unlock(&em_tree->lock);
+        return 0;
+}
+
+int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio)
+{
+        struct btrfs_mapping_tree *map_tree;
+        struct btrfs_device *dev;
+        u64 logical = bio->bi_sector << 9;
+        u64 physical;
+        u64 length = 0;
+        u64 map_length;
+        struct bio_vec *bvec;
+        int i;
+        int ret;
+
+        bio_for_each_segment(bvec, bio, i) {
+                length += bvec->bv_len;
+        }
+        map_tree = &root->fs_info->mapping_tree;
+        map_length = length;
+        ret = btrfs_map_block(map_tree, logical, &physical, &map_length, &dev);
+        BUG_ON(map_length < length);
+        bio->bi_sector = physical >> 9;
+        bio->bi_bdev = dev->bdev;
+        submit_bio(rw, bio);
+        return 0;
+}
+
+struct btrfs_device *btrfs_find_device(struct btrfs_root *root, u64 devid)
+{
+        struct btrfs_device *dev;
+        struct list_head *cur = root->fs_info->devices.next;
+        struct list_head *head = &root->fs_info->devices;
+
+        while(cur != head) {
+                dev = list_entry(cur, struct btrfs_device, dev_list);
+                if (dev->devid == devid)
+                        return dev;
+                cur = cur->next;
+        }
+        return NULL;
+}
+
+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;
+        int ret;
+
+        logical = key->objectid;
+        length = key->offset;
+        spin_lock(&map_tree->map_tree.lock);
+        em = lookup_extent_mapping(&map_tree->map_tree, logical, 1);
+
+        /* already mapped? */
+        if (em && em->start <= logical && em->start + em->len > logical) {
+                free_extent_map(em);
+                spin_unlock(&map_tree->map_tree.lock);
+                return 0;
+        } else if (em) {
+                free_extent_map(em);
+        }
+        spin_unlock(&map_tree->map_tree.lock);
+
+        map = kzalloc(sizeof(*map), GFP_NOFS);
+        if (!map)
+                return -ENOMEM;
+
+        em = alloc_extent_map(GFP_NOFS);
+        if (!em)
+                return -ENOMEM;
+        map = kmalloc(sizeof(*map), 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;
+
+        map->physical = btrfs_stripe_offset_nr(leaf, chunk, 0);
+        devid = btrfs_stripe_devid_nr(leaf, chunk, 0);
+        map->dev = btrfs_find_device(root, devid);
+        if (!map->dev) {
+                kfree(map);
+                free_extent_map(em);
+                return -EIO;
+        }
+
+        spin_lock(&map_tree->map_tree.lock);
+        ret = add_extent_mapping(&map_tree->map_tree, em);
+        BUG_ON(ret);
+        spin_unlock(&map_tree->map_tree.lock);
+        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;
+        char *name;
+
+        device->devid = btrfs_device_id(leaf, dev_item);
+        device->total_bytes = btrfs_device_total_bytes(leaf, dev_item);
+        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);
+        device->rdev = btrfs_device_rdev(leaf, dev_item);
+        device->partition = btrfs_device_partition(leaf, dev_item);
+        device->name_len = btrfs_device_name_len(leaf, dev_item);
+
+        ptr = (unsigned long)btrfs_device_uuid(dev_item);
+        read_extent_buffer(leaf, device->uuid, ptr, BTRFS_DEV_UUID_SIZE);
+
+        name = kmalloc(device->name_len + 1, GFP_NOFS);
+        if (!name)
+                return -ENOMEM;
+        device->name = name;
+        ptr = (unsigned long)btrfs_device_name(dev_item);
+        read_extent_buffer(leaf, name, ptr, device->name_len);
+        name[device->name_len] = '\0';
+        return 0;
+}
+
+static int read_one_dev(struct btrfs_root *root, struct btrfs_key *key,
+                        struct extent_buffer *leaf,
+                        struct btrfs_dev_item *dev_item)
+{
+        struct btrfs_device *device;
+        u64 devid;
+        int ret;
+
+        devid = btrfs_device_id(leaf, dev_item);
+        if (btrfs_find_device(root, devid))
+                return 0;
+
+        device = kmalloc(sizeof(*device), GFP_NOFS);
+        if (!device)
+                return -ENOMEM;
+
+        fill_device_from_item(leaf, dev_item, device);
+        device->dev_root = root->fs_info->dev_root;
+        device->bdev = root->fs_info->sb->s_bdev;
+        list_add(&device->dev_list, &root->fs_info->devices);
+        memcpy(&device->dev_key, key, sizeof(*key));
+        ret = 0;
+#if 0
+        ret = btrfs_open_device(device);
+        if (ret) {
+                kfree(device);
+        }
+#endif
+        return ret;
+}
+
+int btrfs_read_sys_array(struct btrfs_root *root)
+{
+        struct btrfs_super_block *super_copy = &root->fs_info->super_copy;
+        struct extent_buffer *sb = root->fs_info->sb_buffer;
+        struct btrfs_disk_key *disk_key;
+        struct btrfs_dev_item *dev_item;
+        struct btrfs_chunk *chunk;
+        struct btrfs_key key;
+        u32 num_stripes;
+        u32 array_size;
+        u32 len = 0;
+        u8 *ptr;
+        unsigned long sb_ptr;
+        u32 cur;
+        int ret;
+        int dev_only = 1;
+
+        array_size = btrfs_super_sys_array_size(super_copy);
+
+        /*
+         * we do this loop twice, once for the device items and
+         * once for all of the chunks.  This way there are device
+         * structs filled in for every chunk
+         */
+again:
+        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.objectid == BTRFS_DEV_ITEMS_OBJECTID &&
+                    key.type == BTRFS_DEV_ITEM_KEY) {
+                        dev_item = (struct btrfs_dev_item *)sb_ptr;
+                        if (dev_only) {
+                                ret = read_one_dev(root, &key, sb, dev_item);
+                                BUG_ON(ret);
+                        }
+                        len = sizeof(*dev_item);
+                        len += btrfs_device_name_len(sb, dev_item);
+                } else if (key.type == BTRFS_CHUNK_ITEM_KEY) {
+
+                        chunk = (struct btrfs_chunk *)sb_ptr;
+                        if (!dev_only) {
+                                ret = read_one_chunk(root, &key, sb, chunk);
+                                BUG_ON(ret);
+                        }
+                        num_stripes = btrfs_chunk_num_stripes(sb, chunk);
+                        len = btrfs_chunk_item_size(num_stripes);
+                } else {
+                        BUG();
+                }
+                ptr += len;
+                sb_ptr += len;
+                cur += len;
+        }
+        if (dev_only == 1) {
+                dev_only = 0;
+                goto again;
+        }
+        return 0;
+}
+
+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, &found_key, leaf,
+                                                   dev_item);
+                                BUG_ON(ret);
+                        }
+                } 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);
+                }
+                path->slots[0]++;
+        }
+        if (key.objectid == BTRFS_DEV_ITEMS_OBJECTID) {
+                key.objectid = 0;
+                btrfs_release_path(root, path);
+                goto again;
+        }
+
+        btrfs_free_path(path);
+        ret = 0;
+error:
+        return ret;
+}
+