btrfs-progs: test/fsck/021: Cleanup custom check by overriding check_image

[btrfs-progs-unstable/devel.git] / 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 <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <uuid/uuid.h>
#include <fcntl.h>
#include <unistd.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "print-tree.h"
#include "volumes.h"
#include "utils.h"
#include "kernel-lib/raid56.h"

struct stripe {
        struct btrfs_device *dev;
        u64 physical;
};

static inline int nr_parity_stripes(struct map_lookup *map)
{
        if (map->type & BTRFS_BLOCK_GROUP_RAID5)
                return 1;
        else if (map->type & BTRFS_BLOCK_GROUP_RAID6)
                return 2;
        else
                return 0;
}

static inline int nr_data_stripes(struct map_lookup *map)
{
        return map->num_stripes - nr_parity_stripes(map);
}

#define is_parity_stripe(x) ( ((x) == BTRFS_RAID5_P_STRIPE) || ((x) == BTRFS_RAID6_Q_STRIPE) )

static LIST_HEAD(fs_uuids);

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

        list_for_each(cur, head) {
                dev = list_entry(cur, struct btrfs_device, dev_list);
                if (dev->devid == devid &&
                    !memcmp(dev->uuid, uuid, BTRFS_UUID_SIZE)) {
                        return dev;
                }
        }
        return NULL;
}

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

        list_for_each(cur, &fs_uuids) {
                fs_devices = list_entry(cur, struct btrfs_fs_devices, list);
                if (memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE) == 0)
                        return fs_devices;
        }
        return NULL;
}

static 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);
                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;
                fs_devices->lowest_devid = (u64)-1;
                device = NULL;
        } else {
                device = __find_device(&fs_devices->devices, devid,
                                       disk_super->dev_item.uuid);
        }
        if (!device) {
                device = kzalloc(sizeof(*device), GFP_NOFS);
                if (!device) {
                        /* we can safely leave the fs_devices entry around */
                        return -ENOMEM;
                }
                device->fd = -1;
                device->devid = devid;
                device->generation = found_transid;
                memcpy(device->uuid, disk_super->dev_item.uuid,
                       BTRFS_UUID_SIZE);
                device->name = kstrdup(path, GFP_NOFS);
                if (!device->name) {
                        kfree(device);
                        return -ENOMEM;
                }
                device->label = kstrdup(disk_super->label, GFP_NOFS);
                if (!device->label) {
                        kfree(device->name);
                        kfree(device);
                        return -ENOMEM;
                }
                device->total_devs = btrfs_super_num_devices(disk_super);
                device->super_bytes_used = btrfs_super_bytes_used(disk_super);
                device->total_bytes =
                        btrfs_stack_device_total_bytes(&disk_super->dev_item);
                device->bytes_used =
                        btrfs_stack_device_bytes_used(&disk_super->dev_item);
                list_add(&device->dev_list, &fs_devices->devices);
                device->fs_devices = fs_devices;
        } else if (!device->name || strcmp(device->name, path)) {
                char *name;

                /*
                 * The existing device has newer generation, so this one could
                 * be a stale one, don't add it.
                 */
                if (found_transid < device->generation) {
                        warning(
        "adding device %s gen %llu but found an existing device %s gen %llu",
                                path, found_transid, device->name,
                                device->generation);
                        return -EEXIST;
                }

                name = strdup(path);
                if (!name)
                        return -ENOMEM;
                kfree(device->name);
                device->name = name;
        }


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

int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
{
        struct btrfs_fs_devices *seed_devices;
        struct btrfs_device *device;
        int ret = 0;

again:
        if (!fs_devices)
                return 0;
        while (!list_empty(&fs_devices->devices)) {
                device = list_entry(fs_devices->devices.next,
                                    struct btrfs_device, dev_list);
                if (device->fd != -1) {
                        if (fsync(device->fd) == -1) {
                                warning("fsync on device %llu failed: %s",
                                        device->devid, strerror(errno));
                                ret = -errno;
                        }
                        if (posix_fadvise(device->fd, 0, 0, POSIX_FADV_DONTNEED))
                                fprintf(stderr, "Warning, could not drop caches\n");
                        close(device->fd);
                        device->fd = -1;
                }
                device->writeable = 0;
                list_del(&device->dev_list);
                /* free the memory */
                free(device->name);
                free(device->label);
                free(device);
        }

        seed_devices = fs_devices->seed;
        fs_devices->seed = NULL;
        if (seed_devices) {
                struct btrfs_fs_devices *orig;

                orig = fs_devices;
                fs_devices = seed_devices;
                list_del(&orig->list);
                free(orig);
                goto again;
        } else {
                list_del(&fs_devices->list);
                free(fs_devices);
        }

        return ret;
}

void btrfs_close_all_devices(void)
{
        struct btrfs_fs_devices *fs_devices;

        while (!list_empty(&fs_uuids)) {
                fs_devices = list_entry(fs_uuids.next, struct btrfs_fs_devices,
                                        list);
                btrfs_close_devices(fs_devices);
        }
}

int btrfs_open_devices(struct btrfs_fs_devices *fs_devices, int flags)
{
        int fd;
        struct list_head *head = &fs_devices->devices;
        struct list_head *cur;
        struct btrfs_device *device;
        int ret;

        list_for_each(cur, head) {
                device = list_entry(cur, struct btrfs_device, dev_list);
                if (!device->name) {
                        printk("no name for device %llu, skip it now\n", device->devid);
                        continue;
                }

                fd = open(device->name, flags);
                if (fd < 0) {
                        ret = -errno;
                        error("cannot open device '%s': %s", device->name,
                                        strerror(errno));
                        goto fail;
                }

                if (posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED))
                        fprintf(stderr, "Warning, could not drop caches\n");

                if (device->devid == fs_devices->latest_devid)
                        fs_devices->latest_bdev = fd;
                if (device->devid == fs_devices->lowest_devid)
                        fs_devices->lowest_bdev = fd;
                device->fd = fd;
                if (flags & O_RDWR)
                        device->writeable = 1;
        }
        return 0;
fail:
        btrfs_close_devices(fs_devices);
        return ret;
}

int btrfs_scan_one_device(int fd, const char *path,
                          struct btrfs_fs_devices **fs_devices_ret,
                          u64 *total_devs, u64 super_offset, unsigned sbflags)
{
        struct btrfs_super_block *disk_super;
        char buf[BTRFS_SUPER_INFO_SIZE];
        int ret;
        u64 devid;

        disk_super = (struct btrfs_super_block *)buf;
        ret = btrfs_read_dev_super(fd, disk_super, super_offset, sbflags);
        if (ret < 0)
                return -EIO;
        devid = btrfs_stack_device_id(&disk_super->dev_item);
        if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_METADUMP)
                *total_devs = 1;
        else
                *total_devs = btrfs_super_num_devices(disk_super);

        ret = device_list_add(path, disk_super, devid, fs_devices_ret);

        return ret;
}

/*
 * find_free_dev_extent_start - find free space in the specified device
 * @device:       the device which we search the free space in
 * @num_bytes:    the size of the free space that we need
 * @search_start: the position from which to begin the search
 * @start:        store the start of the free space.
 * @len:          the size of the free space. that we find, or the size
 *                of the max free space if we don't find suitable free space
 *
 * 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
 *
 * @start is used to store the start of the free space if we find. But if we
 * don't find suitable free space, it will be used to store the start position
 * of the max free space.
 *
 * @len is used to store the size of the free space that we find.
 * But if we don't find suitable free space, it is used to store the size of
 * the max free space.
 */
static int find_free_dev_extent_start(struct btrfs_trans_handle *trans,
                               struct btrfs_device *device, u64 num_bytes,
                               u64 search_start, u64 *start, u64 *len)
{
        struct btrfs_key key;
        struct btrfs_root *root = device->dev_root;
        struct btrfs_dev_extent *dev_extent;
        struct btrfs_path *path;
        u64 hole_size;
        u64 max_hole_start;
        u64 max_hole_size;
        u64 extent_end;
        u64 search_end = device->total_bytes;
        int ret;
        int slot;
        struct extent_buffer *l;
        u64 min_search_start;

        /*
         * We don't want to overwrite the superblock on the drive nor any area
         * used by the boot loader (grub for example), so we make sure to start
         * at an offset of at least 1MB.
         */
        min_search_start = max(root->fs_info->alloc_start, (u64)SZ_1M);
        search_start = max(search_start, min_search_start);

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

        max_hole_start = search_start;
        max_hole_size = 0;

        if (search_start >= search_end) {
                ret = -ENOSPC;
                goto out;
        }

        path->reada = 2;

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

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        if (ret > 0) {
                ret = btrfs_previous_item(root, path, key.objectid, key.type);
                if (ret < 0)
                        goto out;
        }

        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 out;

                        break;
                }
                btrfs_item_key_to_cpu(l, &key, slot);

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

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

                if (key.type != BTRFS_DEV_EXTENT_KEY)
                        goto next;

                if (key.offset > search_start) {
                        hole_size = key.offset - search_start;

                        /*
                         * Have to check before we set max_hole_start, otherwise
                         * we could end up sending back this offset anyway.
                         */
                        if (hole_size > max_hole_size) {
                                max_hole_start = search_start;
                                max_hole_size = hole_size;
                        }

                        /*
                         * If this free space is greater than which we need,
                         * it must be the max free space that we have found
                         * until now, so max_hole_start must point to the start
                         * of this free space and the length of this free space
                         * is stored in max_hole_size. Thus, we return
                         * max_hole_start and max_hole_size and go back to the
                         * caller.
                         */
                        if (hole_size >= num_bytes) {
                                ret = 0;
                                goto out;
                        }
                }

                dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
                extent_end = key.offset + btrfs_dev_extent_length(l,
                                                                  dev_extent);
                if (extent_end > search_start)
                        search_start = extent_end;
next:
                path->slots[0]++;
                cond_resched();
        }

        /*
         * At this point, search_start should be the end of
         * allocated dev extents, and when shrinking the device,
         * search_end may be smaller than search_start.
         */
        if (search_end > search_start) {
                hole_size = search_end - search_start;

                if (hole_size > max_hole_size) {
                        max_hole_start = search_start;
                        max_hole_size = hole_size;
                }
        }

        /* See above. */
        if (max_hole_size < num_bytes)
                ret = -ENOSPC;
        else
                ret = 0;

out:
        btrfs_free_path(path);
        *start = max_hole_start;
        if (len)
                *len = max_hole_size;
        return ret;
}

int find_free_dev_extent(struct btrfs_trans_handle *trans,
                         struct btrfs_device *device, u64 num_bytes,
                         u64 *start)
{
        /* FIXME use last free of some kind */
        return find_free_dev_extent_start(trans, device,
                                          num_bytes, 0, start, NULL);
}

static int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
                                  struct btrfs_device *device,
                                  u64 chunk_tree, u64 chunk_objectid,
                                  u64 chunk_offset,
                                  u64 num_bytes, u64 *start, int convert)
{
        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;

        /*
         * For convert case, just skip search free dev_extent, as caller
         * is responsible to make sure it's free.
         */
        if (!convert) {
                ret = find_free_dev_extent(trans, device, 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_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);
err:
        btrfs_free_path(path);
        return ret;
}

static int find_next_chunk(struct btrfs_fs_info *fs_info, u64 *offset)
{
        struct btrfs_root *root = fs_info->chunk_root;
        struct btrfs_path *path;
        int ret;
        struct btrfs_key key;
        struct btrfs_chunk *chunk;
        struct btrfs_key found_key;

        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;

        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 != BTRFS_FIRST_CHUNK_TREE_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 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(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_fs_info *fs_info,
                     struct btrfs_device *device)
{
        int ret;
        struct btrfs_path *path;
        struct btrfs_dev_item *dev_item;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        struct btrfs_root *root = fs_info->chunk_root;
        unsigned long ptr;
        u64 free_devid = 0;

        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));
        if (ret)
                goto out;

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

        device->devid = free_devid;
        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, fs_info->fsid, ptr, BTRFS_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_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_fs_info *fs_info, struct btrfs_key *key,
                           struct btrfs_chunk *chunk, int item_size)
{
        struct btrfs_super_block *super_copy = 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 + sizeof(disk_key)
                        > 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 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 if (type & BTRFS_BLOCK_GROUP_RAID5)
                return calc_size * (num_stripes - 1);
        else if (type & BTRFS_BLOCK_GROUP_RAID6)
                return calc_size * (num_stripes - 2);
        else
                return calc_size * num_stripes;
}


static u32 find_raid56_stripe_len(u32 data_devices, u32 dev_stripe_target)
{
        /* TODO, add a way to store the preferred stripe size */
        return BTRFS_STRIPE_LEN;
}

/*
 * btrfs_device_avail_bytes - count bytes available for alloc_chunk
 *
 * It is not equal to "device->total_bytes - device->bytes_used".
 * We do not allocate any chunk in 1M at beginning of device, and not
 * allowed to allocate any chunk before alloc_start if it is specified.
 * So search holes from max(1M, alloc_start) to device->total_bytes.
 */
static int btrfs_device_avail_bytes(struct btrfs_trans_handle *trans,
                                    struct btrfs_device *device,
                                    u64 *avail_bytes)
{
        struct btrfs_path *path;
        struct btrfs_root *root = device->dev_root;
        struct btrfs_key key;
        struct btrfs_dev_extent *dev_extent = NULL;
        struct extent_buffer *l;
        u64 search_start = root->fs_info->alloc_start;
        u64 search_end = device->total_bytes;
        u64 extent_end = 0;
        u64 free_bytes = 0;
        int ret;
        int slot = 0;

        search_start = max(BTRFS_BLOCK_RESERVED_1M_FOR_SUPER, search_start);

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

        key.objectid = device->devid;
        key.offset = root->fs_info->alloc_start;
        key.type = BTRFS_DEV_EXTENT_KEY;

        path->reada = 2;
        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;

        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;
                        break;
                }
                btrfs_item_key_to_cpu(l, &key, slot);

                if (key.objectid < device->devid)
                        goto next;
                if (key.objectid > device->devid)
                        break;
                if (key.type != BTRFS_DEV_EXTENT_KEY)
                        goto next;
                if (key.offset > search_end)
                        break;
                if (key.offset > search_start)
                        free_bytes += key.offset - search_start;

                dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
                extent_end = key.offset + btrfs_dev_extent_length(l,
                                                                  dev_extent);
                if (extent_end > search_start)
                        search_start = extent_end;
                if (search_start > search_end)
                        break;
next:
                path->slots[0]++;
                cond_resched();
        }

        if (search_start < search_end)
                free_bytes += search_end - search_start;

        *avail_bytes = free_bytes;
        ret = 0;
error:
        btrfs_free_path(path);
        return ret;
}

#define BTRFS_MAX_DEVS(r) ((BTRFS_LEAF_DATA_SIZE(r)             \
                        - sizeof(struct btrfs_item)             \
                        - sizeof(struct btrfs_chunk))           \
                        / sizeof(struct btrfs_stripe) + 1)

#define BTRFS_MAX_DEVS_SYS_CHUNK ((BTRFS_SYSTEM_CHUNK_ARRAY_SIZE        \
                                - 2 * sizeof(struct btrfs_disk_key)     \
                                - 2 * sizeof(struct btrfs_chunk))       \
                                / sizeof(struct btrfs_stripe) + 1)

int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
                      struct btrfs_fs_info *info, u64 *start,
                      u64 *num_bytes, u64 type)
{
        u64 dev_offset;
        struct btrfs_root *extent_root = info->extent_root;
        struct btrfs_root *chunk_root = info->chunk_root;
        struct btrfs_stripe *stripes;
        struct btrfs_device *device = NULL;
        struct btrfs_chunk *chunk;
        struct list_head private_devs;
        struct list_head *dev_list = &info->fs_devices->devices;
        struct list_head *cur;
        struct map_lookup *map;
        int min_stripe_size = SZ_1M;
        u64 calc_size = SZ_8M;
        u64 min_free;
        u64 max_chunk_size = 4 * calc_size;
        u64 avail = 0;
        u64 max_avail = 0;
        u64 percent_max;
        int num_stripes = 1;
        int max_stripes = 0;
        int min_stripes = 1;
        int sub_stripes = 0;
        int looped = 0;
        int ret;
        int index;
        int stripe_len = BTRFS_STRIPE_LEN;
        struct btrfs_key key;
        u64 offset;

        if (list_empty(dev_list)) {
                return -ENOSPC;
        }

        if (type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
                if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
                        calc_size = SZ_8M;
                        max_chunk_size = calc_size * 2;
                        min_stripe_size = SZ_1M;
                        max_stripes = BTRFS_MAX_DEVS_SYS_CHUNK;
                } else if (type & BTRFS_BLOCK_GROUP_DATA) {
                        calc_size = SZ_1G;
                        max_chunk_size = 10 * calc_size;
                        min_stripe_size = SZ_64M;
                        max_stripes = BTRFS_MAX_DEVS(chunk_root);
                } else if (type & BTRFS_BLOCK_GROUP_METADATA) {
                        calc_size = SZ_1G;
                        max_chunk_size = 4 * calc_size;
                        min_stripe_size = SZ_32M;
                        max_stripes = BTRFS_MAX_DEVS(chunk_root);
                }
        }
        if (type & BTRFS_BLOCK_GROUP_RAID1) {
                num_stripes = min_t(u64, 2,
                                  btrfs_super_num_devices(info->super_copy));
                if (num_stripes < 2)
                        return -ENOSPC;
                min_stripes = 2;
        }
        if (type & BTRFS_BLOCK_GROUP_DUP) {
                num_stripes = 2;
                min_stripes = 2;
        }
        if (type & (BTRFS_BLOCK_GROUP_RAID0)) {
                num_stripes = btrfs_super_num_devices(info->super_copy);
                if (num_stripes > max_stripes)
                        num_stripes = max_stripes;
                min_stripes = 2;
        }
        if (type & (BTRFS_BLOCK_GROUP_RAID10)) {
                num_stripes = btrfs_super_num_devices(info->super_copy);
                if (num_stripes > max_stripes)
                        num_stripes = max_stripes;
                if (num_stripes < 4)
                        return -ENOSPC;
                num_stripes &= ~(u32)1;
                sub_stripes = 2;
                min_stripes = 4;
        }
        if (type & (BTRFS_BLOCK_GROUP_RAID5)) {
                num_stripes = btrfs_super_num_devices(info->super_copy);
                if (num_stripes > max_stripes)
                        num_stripes = max_stripes;
                if (num_stripes < 2)
                        return -ENOSPC;
                min_stripes = 2;
                stripe_len = find_raid56_stripe_len(num_stripes - 1,
                                    btrfs_super_stripesize(info->super_copy));
        }
        if (type & (BTRFS_BLOCK_GROUP_RAID6)) {
                num_stripes = btrfs_super_num_devices(info->super_copy);
                if (num_stripes > max_stripes)
                        num_stripes = max_stripes;
                if (num_stripes < 3)
                        return -ENOSPC;
                min_stripes = 3;
                stripe_len = find_raid56_stripe_len(num_stripes - 2,
                                    btrfs_super_stripesize(info->super_copy));
        }

        /* we don't want a chunk larger than 10% of the FS */
        percent_max = div_factor(btrfs_super_total_bytes(info->super_copy), 1);
        max_chunk_size = min(percent_max, max_chunk_size);

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

        calc_size /= stripe_len;
        calc_size *= stripe_len;
        INIT_LIST_HEAD(&private_devs);
        cur = dev_list->next;
        index = 0;

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

        /* build a private list of devices we will allocate from */
        while(index < num_stripes) {
                device = list_entry(cur, struct btrfs_device, dev_list);
                ret = btrfs_device_avail_bytes(trans, device, &avail);
                if (ret)
                        return ret;
                cur = cur->next;
                if (avail >= min_free) {
                        list_move_tail(&device->dev_list, &private_devs);
                        index++;
                        if (type & BTRFS_BLOCK_GROUP_DUP)
                                index++;
                } else if (avail > max_avail)
                        max_avail = avail;
                if (cur == dev_list)
                        break;
        }
        if (index < num_stripes) {
                list_splice(&private_devs, dev_list);
                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;
                }
                return -ENOSPC;
        }
        ret = find_next_chunk(info, &offset);
        if (ret)
                return ret;
        key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
        key.type = BTRFS_CHUNK_ITEM_KEY;
        key.offset = offset;

        chunk = kmalloc(btrfs_chunk_item_size(num_stripes), GFP_NOFS);
        if (!chunk)
                return -ENOMEM;

        map = kmalloc(btrfs_map_lookup_size(num_stripes), GFP_NOFS);
        if (!map) {
                kfree(chunk);
                return -ENOMEM;
        }

        stripes = &chunk->stripe;
        *num_bytes = chunk_bytes_by_type(type, calc_size,
                                         num_stripes, sub_stripes);
        index = 0;
        while(index < num_stripes) {
                struct btrfs_stripe *stripe;
                BUG_ON(list_empty(&private_devs));
                cur = private_devs.next;
                device = list_entry(cur, struct btrfs_device, dev_list);

                /* loop over this device again if we're doing a dup group */
                if (!(type & BTRFS_BLOCK_GROUP_DUP) ||
                    (index == num_stripes - 1))
                        list_move_tail(&device->dev_list, dev_list);

                ret = btrfs_alloc_dev_extent(trans, device,
                             info->chunk_root->root_key.objectid,
                             BTRFS_FIRST_CHUNK_TREE_OBJECTID, key.offset,
                             calc_size, &dev_offset, 0);
                if (ret < 0)
                        goto out_chunk_map;

                device->bytes_used += calc_size;
                ret = btrfs_update_device(trans, device);
                if (ret < 0)
                        goto out_chunk_map;

                map->stripes[index].dev = device;
                map->stripes[index].physical = dev_offset;
                stripe = stripes + index;
                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);
                index++;
        }
        BUG_ON(!list_empty(&private_devs));

        /* key was set above */
        btrfs_set_stack_chunk_length(chunk, *num_bytes);
        btrfs_set_stack_chunk_owner(chunk, extent_root->root_key.objectid);
        btrfs_set_stack_chunk_stripe_len(chunk, stripe_len);
        btrfs_set_stack_chunk_type(chunk, type);
        btrfs_set_stack_chunk_num_stripes(chunk, num_stripes);
        btrfs_set_stack_chunk_io_align(chunk, stripe_len);
        btrfs_set_stack_chunk_io_width(chunk, stripe_len);
        btrfs_set_stack_chunk_sector_size(chunk, info->sectorsize);
        btrfs_set_stack_chunk_sub_stripes(chunk, sub_stripes);
        map->sector_size = info->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;

        ret = btrfs_insert_item(trans, chunk_root, &key, chunk,
                                btrfs_chunk_item_size(num_stripes));
        BUG_ON(ret);
        *start = key.offset;;

        map->ce.start = key.offset;
        map->ce.size = *num_bytes;

        ret = insert_cache_extent(&info->mapping_tree.cache_tree, &map->ce);
        if (ret < 0)
                goto out_chunk_map;

        if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
                ret = btrfs_add_system_chunk(info, &key,
                                    chunk, btrfs_chunk_item_size(num_stripes));
                if (ret < 0)
                        goto out_chunk;
        }

        kfree(chunk);
        return ret;

out_chunk_map:
        kfree(map);
out_chunk:
        kfree(chunk);
        return ret;
}

/*
 * Alloc a DATA chunk with SINGLE profile.
 *
 * If 'convert' is set, it will alloc a chunk with 1:1 mapping
 * (btrfs logical bytenr == on-disk bytenr)
 * For that case, caller must make sure the chunk and dev_extent are not
 * occupied.
 */
int btrfs_alloc_data_chunk(struct btrfs_trans_handle *trans,
                           struct btrfs_fs_info *info, u64 *start,
                           u64 num_bytes, u64 type, int convert)
{
        u64 dev_offset;
        struct btrfs_root *extent_root = info->extent_root;
        struct btrfs_root *chunk_root = info->chunk_root;
        struct btrfs_stripe *stripes;
        struct btrfs_device *device = NULL;
        struct btrfs_chunk *chunk;
        struct list_head *dev_list = &info->fs_devices->devices;
        struct list_head *cur;
        struct map_lookup *map;
        u64 calc_size = SZ_8M;
        int num_stripes = 1;
        int sub_stripes = 0;
        int ret;
        int index;
        int stripe_len = BTRFS_STRIPE_LEN;
        struct btrfs_key key;

        key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
        key.type = BTRFS_CHUNK_ITEM_KEY;
        if (convert) {
                if (*start != round_down(*start, info->sectorsize)) {
                        error("DATA chunk start not sectorsize aligned: %llu",
                                        (unsigned long long)*start);
                        return -EINVAL;
                }
                key.offset = *start;
                dev_offset = *start;
        } else {
                u64 tmp;

                ret = find_next_chunk(info, &tmp);
                key.offset = tmp;
                if (ret)
                        return ret;
        }

        chunk = kmalloc(btrfs_chunk_item_size(num_stripes), GFP_NOFS);
        if (!chunk)
                return -ENOMEM;

        map = kmalloc(btrfs_map_lookup_size(num_stripes), GFP_NOFS);
        if (!map) {
                kfree(chunk);
                return -ENOMEM;
        }

        stripes = &chunk->stripe;
        calc_size = num_bytes;

        index = 0;
        cur = dev_list->next;
        device = list_entry(cur, struct btrfs_device, dev_list);

        while (index < num_stripes) {
                struct btrfs_stripe *stripe;

                ret = btrfs_alloc_dev_extent(trans, device,
                             info->chunk_root->root_key.objectid,
                             BTRFS_FIRST_CHUNK_TREE_OBJECTID, key.offset,
                             calc_size, &dev_offset, convert);
                BUG_ON(ret);

                device->bytes_used += calc_size;
                ret = btrfs_update_device(trans, device);
                BUG_ON(ret);

                map->stripes[index].dev = device;
                map->stripes[index].physical = dev_offset;
                stripe = stripes + index;
                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);
                index++;
        }

        /* key was set above */
        btrfs_set_stack_chunk_length(chunk, num_bytes);
        btrfs_set_stack_chunk_owner(chunk, extent_root->root_key.objectid);
        btrfs_set_stack_chunk_stripe_len(chunk, stripe_len);
        btrfs_set_stack_chunk_type(chunk, type);
        btrfs_set_stack_chunk_num_stripes(chunk, num_stripes);
        btrfs_set_stack_chunk_io_align(chunk, stripe_len);
        btrfs_set_stack_chunk_io_width(chunk, stripe_len);
        btrfs_set_stack_chunk_sector_size(chunk, info->sectorsize);
        btrfs_set_stack_chunk_sub_stripes(chunk, sub_stripes);
        map->sector_size = info->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;

        ret = btrfs_insert_item(trans, chunk_root, &key, chunk,
                                btrfs_chunk_item_size(num_stripes));
        BUG_ON(ret);
        if (!convert)
                *start = key.offset;

        map->ce.start = key.offset;
        map->ce.size = num_bytes;

        ret = insert_cache_extent(&info->mapping_tree.cache_tree, &map->ce);
        BUG_ON(ret);

        kfree(chunk);
        return ret;
}

int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len)
{
        struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
        struct cache_extent *ce;
        struct map_lookup *map;
        int ret;

        ce = search_cache_extent(&map_tree->cache_tree, logical);
        if (!ce) {
                fprintf(stderr, "No mapping for %llu-%llu\n",
                        (unsigned long long)logical,
                        (unsigned long long)logical+len);
                return 1;
        }
        if (ce->start > logical || ce->start + ce->size < logical) {
                fprintf(stderr, "Invalid mapping for %llu-%llu, got "
                        "%llu-%llu\n", (unsigned long long)logical,
                        (unsigned long long)logical+len,
                        (unsigned long long)ce->start,
                        (unsigned long long)ce->start + ce->size);
                return 1;
        }
        map = container_of(ce, struct map_lookup, ce);

        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 if (map->type & BTRFS_BLOCK_GROUP_RAID5)
                ret = 2;
        else if (map->type & BTRFS_BLOCK_GROUP_RAID6)
                ret = 3;
        else
                ret = 1;
        return ret;
}

int btrfs_next_bg(struct btrfs_fs_info *fs_info, u64 *logical,
                  u64 *size, u64 type)
{
        struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
        struct cache_extent *ce;
        struct map_lookup *map;
        u64 cur = *logical;

        ce = search_cache_extent(&map_tree->cache_tree, cur);

        while (ce) {
                /*
                 * only jump to next bg if our cur is not 0
                 * As the initial logical for btrfs_next_bg() is 0, and
                 * if we jump to next bg, we skipped a valid bg.
                 */
                if (cur) {
                        ce = next_cache_extent(ce);
                        if (!ce)
                                return -ENOENT;
                }

                cur = ce->start;
                map = container_of(ce, struct map_lookup, ce);
                if (map->type & type) {
                        *logical = ce->start;
                        *size = ce->size;
                        return 0;
                }
                if (!cur)
                        ce = next_cache_extent(ce);
        }

        return -ENOENT;
}

int btrfs_rmap_block(struct btrfs_fs_info *fs_info,
                     u64 chunk_start, u64 physical, u64 devid,
                     u64 **logical, int *naddrs, int *stripe_len)
{
        struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
        struct cache_extent *ce;
        struct map_lookup *map;
        u64 *buf;
        u64 bytenr;
        u64 length;
        u64 stripe_nr;
        u64 rmap_len;
        int i, j, nr = 0;

        ce = search_cache_extent(&map_tree->cache_tree, chunk_start);
        BUG_ON(!ce);
        map = container_of(ce, struct map_lookup, ce);

        length = ce->size;
        rmap_len = map->stripe_len;
        if (map->type & BTRFS_BLOCK_GROUP_RAID10)
                length = ce->size / (map->num_stripes / map->sub_stripes);
        else if (map->type & BTRFS_BLOCK_GROUP_RAID0)
                length = ce->size / map->num_stripes;
        else if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
                              BTRFS_BLOCK_GROUP_RAID6)) {
                length = ce->size / nr_data_stripes(map);
                rmap_len = map->stripe_len * nr_data_stripes(map);
        }

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

        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) /
                            map->stripe_len;

                if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
                        stripe_nr = (stripe_nr * map->num_stripes + i) /
                                    map->sub_stripes;
                } else if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
                        stripe_nr = stripe_nr * map->num_stripes + i;
                } /* else if RAID[56], multiply by nr_data_stripes().
                   * Alternatively, just use rmap_len below instead of
                   * map->stripe_len */

                bytenr = ce->start + stripe_nr * rmap_len;
                for (j = 0; j < nr; j++) {
                        if (buf[j] == bytenr)
                                break;
                }
                if (j == nr)
                        buf[nr++] = bytenr;
        }

        *logical = buf;
        *naddrs = nr;
        *stripe_len = rmap_len;

        return 0;
}

static inline int parity_smaller(u64 a, u64 b)
{
        return a > b;
}

/* Bubble-sort the stripe set to put the parity/syndrome stripes last */
static void sort_parity_stripes(struct btrfs_multi_bio *bbio, u64 *raid_map)
{
        struct btrfs_bio_stripe s;
        int i;
        u64 l;
        int again = 1;

        while (again) {
                again = 0;
                for (i = 0; i < bbio->num_stripes - 1; i++) {
                        if (parity_smaller(raid_map[i], raid_map[i+1])) {
                                s = bbio->stripes[i];
                                l = raid_map[i];
                                bbio->stripes[i] = bbio->stripes[i+1];
                                raid_map[i] = raid_map[i+1];
                                bbio->stripes[i+1] = s;
                                raid_map[i+1] = l;
                                again = 1;
                        }
                }
        }
}

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

int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
                      u64 logical, u64 *length, u64 *type,
                      struct btrfs_multi_bio **multi_ret, int mirror_num,
                      u64 **raid_map_ret)
{
        struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
        struct cache_extent *ce;
        struct map_lookup *map;
        u64 offset;
        u64 stripe_offset;
        u64 stripe_nr;
        u64 *raid_map = NULL;
        int stripes_allocated = 8;
        int stripes_required = 1;
        int stripe_index;
        int i;
        struct btrfs_multi_bio *multi = NULL;

        if (multi_ret && rw == READ) {
                stripes_allocated = 1;
        }
again:
        ce = search_cache_extent(&map_tree->cache_tree, logical);
        if (!ce) {
                kfree(multi);
                *length = (u64)-1;
                return -ENOENT;
        }
        if (ce->start > logical) {
                kfree(multi);
                *length = ce->start - logical;
                return -ENOENT;
        }

        if (multi_ret) {
                multi = kzalloc(btrfs_multi_bio_size(stripes_allocated),
                                GFP_NOFS);
                if (!multi)
                        return -ENOMEM;
        }
        map = container_of(ce, struct map_lookup, ce);
        offset = logical - ce->start;

        if (rw == WRITE) {
                if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
                                 BTRFS_BLOCK_GROUP_DUP)) {
                        stripes_required = map->num_stripes;
                } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
                        stripes_required = map->sub_stripes;
                }
        }
        if (map->type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6)
            && multi_ret && ((rw & WRITE) || mirror_num > 1) && raid_map_ret) {
                    /* RAID[56] write or recovery. Return all stripes */
                    stripes_required = map->num_stripes;

                    /* Only allocate the map if we've already got a large enough multi_ret */
                    if (stripes_allocated >= stripes_required) {
                            raid_map = kmalloc(sizeof(u64) * map->num_stripes, GFP_NOFS);
                            if (!raid_map) {
                                    kfree(multi);
                                    return -ENOMEM;
                            }
                    }
        }

        /* if our multi bio struct is too small, back off and try again */
        if (multi_ret && stripes_allocated < stripes_required) {
                stripes_allocated = stripes_required;
                kfree(multi);
                multi = NULL;
                goto again;
        }
        stripe_nr = offset;
        /*
         * stripe_nr counts the total number of stripes we have to stride
         * to get to this block
         */
        stripe_nr = 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_RAID5 | BTRFS_BLOCK_GROUP_RAID6 |
                         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, ce->size - offset,
                              map->stripe_len - stripe_offset);
        } else {
                *length = ce->size - offset;
        }

        if (!multi_ret)
                goto out;

        multi->num_stripes = 1;
        stripe_index = 0;
        if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
                if (rw == WRITE)
                        multi->num_stripes = map->num_stripes;
                else if (mirror_num)
                        stripe_index = mirror_num - 1;
                else
                        stripe_index = stripe_nr % map->num_stripes;
        } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
                int factor = map->num_stripes / map->sub_stripes;

                stripe_index = stripe_nr % factor;
                stripe_index *= map->sub_stripes;

                if (rw == WRITE)
                        multi->num_stripes = map->sub_stripes;
                else if (mirror_num)
                        stripe_index += mirror_num - 1;

                stripe_nr = stripe_nr / factor;
        } else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
                if (rw == WRITE)
                        multi->num_stripes = map->num_stripes;
                else if (mirror_num)
                        stripe_index = mirror_num - 1;
        } else if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
                                BTRFS_BLOCK_GROUP_RAID6)) {

                if (raid_map) {
                        int rot;
                        u64 tmp;
                        u64 raid56_full_stripe_start;
                        u64 full_stripe_len = nr_data_stripes(map) * map->stripe_len;

                        /*
                         * align the start of our data stripe in the logical
                         * address space
                         */
                        raid56_full_stripe_start = offset / full_stripe_len;
                        raid56_full_stripe_start *= full_stripe_len;

                        /* get the data stripe number */
                        stripe_nr = raid56_full_stripe_start / map->stripe_len;
                        stripe_nr = stripe_nr / nr_data_stripes(map);

                        /* Work out the disk rotation on this stripe-set */
                        rot = stripe_nr % map->num_stripes;

                        /* Fill in the logical address of each stripe */
                        tmp = stripe_nr * nr_data_stripes(map);

                        for (i = 0; i < nr_data_stripes(map); i++)
                                raid_map[(i+rot) % map->num_stripes] =
                                        ce->start + (tmp + i) * map->stripe_len;

                        raid_map[(i+rot) % map->num_stripes] = BTRFS_RAID5_P_STRIPE;
                        if (map->type & BTRFS_BLOCK_GROUP_RAID6)
                                raid_map[(i+rot+1) % map->num_stripes] = BTRFS_RAID6_Q_STRIPE;

                        *length = map->stripe_len;
                        stripe_index = 0;
                        stripe_offset = 0;
                        multi->num_stripes = map->num_stripes;
                } else {
                        stripe_index = stripe_nr % nr_data_stripes(map);
                        stripe_nr = stripe_nr / nr_data_stripes(map);

                        /*
                         * Mirror #0 or #1 means the original data block.
                         * Mirror #2 is RAID5 parity block.
                         * Mirror #3 is RAID6 Q block.
                         */
                        if (mirror_num > 1)
                                stripe_index = nr_data_stripes(map) + mirror_num - 2;

                        /* We distribute the parity blocks across stripes */
                        stripe_index = (stripe_nr + stripe_index) % map->num_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 = stripe_nr % map->num_stripes;
                stripe_nr = stripe_nr / map->num_stripes;
        }
        BUG_ON(stripe_index >= map->num_stripes);

        for (i = 0; i < multi->num_stripes; i++) {
                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++;
        }
        *multi_ret = multi;

        if (type)
                *type = map->type;

        if (raid_map) {
                sort_parity_stripes(multi, raid_map);
                *raid_map_ret = raid_map;
        }
out:
        return 0;
}

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

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

struct btrfs_device *
btrfs_find_device_by_devid(struct btrfs_fs_devices *fs_devices,
                           u64 devid, int instance)
{
        struct list_head *head = &fs_devices->devices;
        struct btrfs_device *dev;
        int num_found = 0;

        list_for_each_entry(dev, head, dev_list) {
                if (dev->devid == devid && num_found++ == instance)
                        return dev;
        }
        return NULL;
}

int btrfs_chunk_readonly(struct btrfs_fs_info *fs_info, u64 chunk_offset)
{
        struct cache_extent *ce;
        struct map_lookup *map;
        struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
        int readonly = 0;
        int i;

        /*
         * During chunk recovering, we may fail to find block group's
         * corresponding chunk, we will rebuild it later
         */
        ce = search_cache_extent(&map_tree->cache_tree, chunk_offset);
        if (!fs_info->is_chunk_recover)
                BUG_ON(!ce);
        else
                return 0;

        map = container_of(ce, struct map_lookup, ce);
        for (i = 0; i < map->num_stripes; i++) {
                if (!map->stripes[i].dev->writeable) {
                        readonly = 1;
                        break;
                }
        }

        return readonly;
}

static struct btrfs_device *fill_missing_device(u64 devid)
{
        struct btrfs_device *device;

        device = kzalloc(sizeof(*device), GFP_NOFS);
        device->devid = devid;
        device->fd = -1;
        return device;
}

/*
 * slot == -1: SYSTEM chunk
 * return -EIO on error, otherwise return 0
 */
int btrfs_check_chunk_valid(struct btrfs_fs_info *fs_info,
                            struct extent_buffer *leaf,
                            struct btrfs_chunk *chunk,
                            int slot, u64 logical)
{
        u64 length;
        u64 stripe_len;
        u16 num_stripes;
        u16 sub_stripes;
        u64 type;
        u32 chunk_ondisk_size;
        u32 sectorsize = fs_info->sectorsize;

        length = btrfs_chunk_length(leaf, chunk);
        stripe_len = btrfs_chunk_stripe_len(leaf, chunk);
        num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
        sub_stripes = btrfs_chunk_sub_stripes(leaf, chunk);
        type = btrfs_chunk_type(leaf, chunk);

        /*
         * These valid checks may be insufficient to cover every corner cases.
         */
        if (!IS_ALIGNED(logical, sectorsize)) {
                error("invalid chunk logical %llu",  logical);
                return -EIO;
        }
        if (btrfs_chunk_sector_size(leaf, chunk) != sectorsize) {
                error("invalid chunk sectorsize %llu", 
                      (unsigned long long)btrfs_chunk_sector_size(leaf, chunk));
                return -EIO;
        }
        if (!length || !IS_ALIGNED(length, sectorsize)) {
                error("invalid chunk length %llu",  length);
                return -EIO;
        }
        if (stripe_len != BTRFS_STRIPE_LEN) {
                error("invalid chunk stripe length: %llu", stripe_len);
                return -EIO;
        }
        /* Check on chunk item type */
        if (slot == -1 && (type & BTRFS_BLOCK_GROUP_SYSTEM) == 0) {
                error("invalid chunk type %llu", type);
                return -EIO;
        }
        if (type & ~(BTRFS_BLOCK_GROUP_TYPE_MASK |
                     BTRFS_BLOCK_GROUP_PROFILE_MASK)) {
                error("unrecognized chunk type: %llu",
                      ~(BTRFS_BLOCK_GROUP_TYPE_MASK |
                        BTRFS_BLOCK_GROUP_PROFILE_MASK) & type);
                return -EIO;
        }
        if (!(type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
                error("missing chunk type flag: %llu", type);
                return -EIO;
        }
        if (!(is_power_of_2(type & BTRFS_BLOCK_GROUP_PROFILE_MASK) ||
              (type & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0)) {
                error("conflicting chunk type detected: %llu", type);
                return -EIO;
        }
        if ((type & BTRFS_BLOCK_GROUP_PROFILE_MASK) &&
            !is_power_of_2(type & BTRFS_BLOCK_GROUP_PROFILE_MASK)) {
                error("conflicting chunk profile detected: %llu", type);
                return -EIO;
        }

        chunk_ondisk_size = btrfs_chunk_item_size(num_stripes);
        /*
         * Btrfs_chunk contains at least one stripe, and for sys_chunk
         * it can't exceed the system chunk array size
         * For normal chunk, it should match its chunk item size.
         */
        if (num_stripes < 1 ||
            (slot == -1 && chunk_ondisk_size > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE) ||
            (slot >= 0 && chunk_ondisk_size > btrfs_item_size_nr(leaf, slot))) {
                error("invalid num_stripes: %u", num_stripes);
                return -EIO;
        }
        /*
         * Device number check against profile
         */
        if ((type & BTRFS_BLOCK_GROUP_RAID10 && (sub_stripes != 2 ||
                  !IS_ALIGNED(num_stripes, sub_stripes))) ||
            (type & BTRFS_BLOCK_GROUP_RAID1 && num_stripes < 1) ||
            (type & BTRFS_BLOCK_GROUP_RAID5 && num_stripes < 2) ||
            (type & BTRFS_BLOCK_GROUP_RAID6 && num_stripes < 3) ||
            (type & BTRFS_BLOCK_GROUP_DUP && num_stripes > 2) ||
            ((type & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0 &&
             num_stripes != 1)) {
                error("Invalid num_stripes:sub_stripes %u:%u for profile %llu",
                      num_stripes, sub_stripes,
                      type & BTRFS_BLOCK_GROUP_PROFILE_MASK);
                return -EIO;
        }

        return 0;
}

/*
 * Slot is used to verify the chunk item is valid
 *
 * For sys chunk in superblock, pass -1 to indicate sys chunk.
 */
static int read_one_chunk(struct btrfs_fs_info *fs_info, struct btrfs_key *key,
                          struct extent_buffer *leaf,
                          struct btrfs_chunk *chunk, int slot)
{
        struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
        struct map_lookup *map;
        struct cache_extent *ce;
        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);
        num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
        /* Validation check */
        ret = btrfs_check_chunk_valid(fs_info, leaf, chunk, slot, logical);
        if (ret) {
                error("%s checksums match, but it has an invalid chunk, %s",
                      (slot == -1) ? "Superblock" : "Metadata",
                      (slot == -1) ? "try btrfsck --repair -s <superblock> ie, 0,1,2" : "");
                return ret;
        }

        ce = search_cache_extent(&map_tree->cache_tree, logical);

        /* already mapped? */
        if (ce && ce->start <= logical && ce->start + ce->size > logical) {
                return 0;
        }

        map = kmalloc(btrfs_map_lookup_size(num_stripes), GFP_NOFS);
        if (!map)
                return -ENOMEM;

        map->ce.start = logical;
        map->ce.size = length;
        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(fs_info, devid, uuid,
                                                        NULL);
                if (!map->stripes[i].dev) {
                        map->stripes[i].dev = fill_missing_device(devid);
                        printf("warning, device %llu is missing\n",
                               (unsigned long long)devid);
                        list_add(&map->stripes[i].dev->dev_list,
                                 &fs_info->fs_devices->devices);
                }

        }
        ret = insert_cache_extent(&map_tree->cache_tree, &map->ce);
        BUG_ON(ret);

        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->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);

        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_fs_info *fs_info, u8 *fsid)
{
        struct btrfs_fs_devices *fs_devices;
        int ret;

        fs_devices = 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) {
                /* missing all seed devices */
                fs_devices = kzalloc(sizeof(*fs_devices), GFP_NOFS);
                if (!fs_devices) {
                        ret = -ENOMEM;
                        goto out;
                }
                INIT_LIST_HEAD(&fs_devices->devices);
                list_add(&fs_devices->list, &fs_uuids);
                memcpy(fs_devices->fsid, fsid, BTRFS_FSID_SIZE);
        }

        ret = btrfs_open_devices(fs_devices, O_RDONLY);
        if (ret)
                goto out;

        fs_devices->seed = fs_info->fs_devices->seed;
        fs_info->fs_devices->seed = fs_devices;
out:
        return ret;
}

static int read_one_dev(struct btrfs_fs_info *fs_info,
                        struct extent_buffer *leaf,
                        struct btrfs_dev_item *dev_item)
{
        struct btrfs_device *device;
        u64 devid;
        int ret = 0;
        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, fs_info->fsid, BTRFS_UUID_SIZE)) {
                ret = open_seed_devices(fs_info, fs_uuid);
                if (ret)
                        return ret;
        }

        device = btrfs_find_device(fs_info, devid, dev_uuid, fs_uuid);
        if (!device) {
                device = kzalloc(sizeof(*device), GFP_NOFS);
                if (!device)
                        return -ENOMEM;
                device->fd = -1;
                list_add(&device->dev_list,
                         &fs_info->fs_devices->devices);
        }

        fill_device_from_item(leaf, dev_item, device);
        device->dev_root = fs_info->dev_root;
        return ret;
}

int btrfs_read_sys_array(struct btrfs_fs_info *fs_info)
{
        struct btrfs_super_block *super_copy = fs_info->super_copy;
        struct extent_buffer *sb;
        struct btrfs_disk_key *disk_key;
        struct btrfs_chunk *chunk;
        u8 *array_ptr;
        unsigned long sb_array_offset;
        int ret = 0;
        u32 num_stripes;
        u32 array_size;
        u32 len = 0;
        u32 cur_offset;
        struct btrfs_key key;

        if (fs_info->nodesize < BTRFS_SUPER_INFO_SIZE) {
                printf("ERROR: nodesize %u too small to read superblock\n",
                                fs_info->nodesize);
                return -EINVAL;
        }
        sb = btrfs_find_create_tree_block(fs_info, BTRFS_SUPER_INFO_OFFSET);
        if (!sb)
                return -ENOMEM;
        btrfs_set_buffer_uptodate(sb);
        write_extent_buffer(sb, super_copy, 0, sizeof(*super_copy));
        array_size = btrfs_super_sys_array_size(super_copy);

        array_ptr = super_copy->sys_chunk_array;
        sb_array_offset = offsetof(struct btrfs_super_block, sys_chunk_array);
        cur_offset = 0;

        while (cur_offset < array_size) {
                disk_key = (struct btrfs_disk_key *)array_ptr;
                len = sizeof(*disk_key);
                if (cur_offset + len > array_size)
                        goto out_short_read;

                btrfs_disk_key_to_cpu(&key, disk_key);

                array_ptr += len;
                sb_array_offset += len;
                cur_offset += len;

                if (key.type == BTRFS_CHUNK_ITEM_KEY) {
                        chunk = (struct btrfs_chunk *)sb_array_offset;
                        /*
                         * At least one btrfs_chunk with one stripe must be
                         * present, exact stripe count check comes afterwards
                         */
                        len = btrfs_chunk_item_size(1);
                        if (cur_offset + len > array_size)
                                goto out_short_read;

                        num_stripes = btrfs_chunk_num_stripes(sb, chunk);
                        if (!num_stripes) {
                                printk(
            "ERROR: invalid number of stripes %u in sys_array at offset %u\n",
                                        num_stripes, cur_offset);
                                ret = -EIO;
                                break;
                        }

                        len = btrfs_chunk_item_size(num_stripes);
                        if (cur_offset + len > array_size)
                                goto out_short_read;

                        ret = read_one_chunk(fs_info, &key, sb, chunk, -1);
                        if (ret)
                                break;
                } else {
                        printk(
                "ERROR: unexpected item type %u in sys_array at offset %u\n",
                                (u32)key.type, cur_offset);
                        ret = -EIO;
                        break;
                }
                array_ptr += len;
                sb_array_offset += len;
                cur_offset += len;
        }
        free_extent_buffer(sb);
        return ret;

out_short_read:
        printk("ERROR: sys_array too short to read %u bytes at offset %u\n",
                        len, cur_offset);
        free_extent_buffer(sb);
        return -EIO;
}

int btrfs_read_chunk_tree(struct btrfs_fs_info *fs_info)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_root *root = fs_info->chunk_root;
        int ret;
        int slot;

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

        /*
         * Read all device items, and then all the chunk items. All
         * device items are found before any chunk item (their object id
         * is smaller than the lowest possible object id for a chunk
         * item - BTRFS_FIRST_CHUNK_TREE_OBJECTID).
         */
        key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
        key.offset = 0;
        key.type = 0;
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto error;
        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 (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(fs_info, 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(fs_info, &found_key, leaf, chunk,
                                             slot);
                        BUG_ON(ret);
                }
                path->slots[0]++;
        }

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

struct list_head *btrfs_scanned_uuids(void)
{
        return &fs_uuids;
}

static int rmw_eb(struct btrfs_fs_info *info,
                  struct extent_buffer *eb, struct extent_buffer *orig_eb)
{
        int ret;
        unsigned long orig_off = 0;
        unsigned long dest_off = 0;
        unsigned long copy_len = eb->len;

        ret = read_whole_eb(info, eb, 0);
        if (ret)
                return ret;

        if (eb->start + eb->len <= orig_eb->start ||
            eb->start >= orig_eb->start + orig_eb->len)
                return 0;
        /*
         * | ----- orig_eb ------- |
         *         | ----- stripe -------  |
         *         | ----- orig_eb ------- |
         *              | ----- orig_eb ------- |
         */
        if (eb->start > orig_eb->start)
                orig_off = eb->start - orig_eb->start;
        if (orig_eb->start > eb->start)
                dest_off = orig_eb->start - eb->start;

        if (copy_len > orig_eb->len - orig_off)
                copy_len = orig_eb->len - orig_off;
        if (copy_len > eb->len - dest_off)
                copy_len = eb->len - dest_off;

        memcpy(eb->data + dest_off, orig_eb->data + orig_off, copy_len);
        return 0;
}

static int split_eb_for_raid56(struct btrfs_fs_info *info,
                               struct extent_buffer *orig_eb,
                               struct extent_buffer **ebs,
                               u64 stripe_len, u64 *raid_map,
                               int num_stripes)
{
        struct extent_buffer **tmp_ebs;
        u64 start = orig_eb->start;
        u64 this_eb_start;
        int i;
        int ret = 0;

        tmp_ebs = calloc(num_stripes, sizeof(*tmp_ebs));
        if (!tmp_ebs)
                return -ENOMEM;

        /* Alloc memory in a row for data stripes */
        for (i = 0; i < num_stripes; i++) {
                if (raid_map[i] >= BTRFS_RAID5_P_STRIPE)
                        break;

                tmp_ebs[i] = calloc(1, sizeof(**tmp_ebs) + stripe_len);
                if (!tmp_ebs[i]) {
                        ret = -ENOMEM;
                        goto clean_up;
                }
        }

        for (i = 0; i < num_stripes; i++) {
                struct extent_buffer *eb = tmp_ebs[i];

                if (raid_map[i] >= BTRFS_RAID5_P_STRIPE)
                        break;

                eb->start = raid_map[i];
                eb->len = stripe_len;
                eb->refs = 1;
                eb->flags = 0;
                eb->fd = -1;
                eb->dev_bytenr = (u64)-1;

                this_eb_start = raid_map[i];

                if (start > this_eb_start ||
                    start + orig_eb->len < this_eb_start + stripe_len) {
                        ret = rmw_eb(info, eb, orig_eb);
                        if (ret)
                                goto clean_up;
                } else {
                        memcpy(eb->data, orig_eb->data + eb->start - start,
                               stripe_len);
                }
                ebs[i] = eb;
        }
        free(tmp_ebs);
        return ret;
clean_up:
        for (i = 0; i < num_stripes; i++)
                free(tmp_ebs[i]);
        free(tmp_ebs);
        return ret;
}

int write_raid56_with_parity(struct btrfs_fs_info *info,
                             struct extent_buffer *eb,
                             struct btrfs_multi_bio *multi,
                             u64 stripe_len, u64 *raid_map)
{
        struct extent_buffer **ebs, *p_eb = NULL, *q_eb = NULL;
        int i;
        int ret;
        int alloc_size = eb->len;
        void **pointers;

        ebs = malloc(sizeof(*ebs) * multi->num_stripes);
        pointers = malloc(sizeof(*pointers) * multi->num_stripes);
        if (!ebs || !pointers) {
                free(ebs);
                free(pointers);
                return -ENOMEM;
        }

        if (stripe_len > alloc_size)
                alloc_size = stripe_len;

        ret = split_eb_for_raid56(info, eb, ebs, stripe_len, raid_map,
                                  multi->num_stripes);
        if (ret)
                goto out;

        for (i = 0; i < multi->num_stripes; i++) {
                struct extent_buffer *new_eb;
                if (raid_map[i] < BTRFS_RAID5_P_STRIPE) {
                        ebs[i]->dev_bytenr = multi->stripes[i].physical;
                        ebs[i]->fd = multi->stripes[i].dev->fd;
                        multi->stripes[i].dev->total_ios++;
                        if (ebs[i]->start != raid_map[i]) {
                                ret = -EINVAL;
                                goto out_free_split;
                        }
                        continue;
                }
                new_eb = malloc(sizeof(*eb) + alloc_size);
                if (!new_eb) {
                        ret = -ENOMEM;
                        goto out_free_split;
                }
                new_eb->dev_bytenr = multi->stripes[i].physical;
                new_eb->fd = multi->stripes[i].dev->fd;
                multi->stripes[i].dev->total_ios++;
                new_eb->len = stripe_len;

                if (raid_map[i] == BTRFS_RAID5_P_STRIPE)
                        p_eb = new_eb;
                else if (raid_map[i] == BTRFS_RAID6_Q_STRIPE)
                        q_eb = new_eb;
        }
        if (q_eb) {
                ebs[multi->num_stripes - 2] = p_eb;
                ebs[multi->num_stripes - 1] = q_eb;

                for (i = 0; i < multi->num_stripes; i++)
                        pointers[i] = ebs[i]->data;

                raid6_gen_syndrome(multi->num_stripes, stripe_len, pointers);
        } else {
                ebs[multi->num_stripes - 1] = p_eb;
                for (i = 0; i < multi->num_stripes; i++)
                        pointers[i] = ebs[i]->data;
                ret = raid5_gen_result(multi->num_stripes, stripe_len,
                                       multi->num_stripes - 1, pointers);
                if (ret < 0)
                        goto out_free_split;
        }

        for (i = 0; i < multi->num_stripes; i++) {
                ret = write_extent_to_disk(ebs[i]);
                if (ret < 0)
                        goto out_free_split;
        }

out_free_split:
        for (i = 0; i < multi->num_stripes; i++) {
                if (ebs[i] != eb)
                        free(ebs[i]);
        }
out:
        free(ebs);
        free(pointers);

        return ret;
}

/*
 * Get stripe length from chunk item and its stripe items
 *
 * Caller should only call this function after validating the chunk item
 * by using btrfs_check_chunk_valid().
 */
u64 btrfs_stripe_length(struct btrfs_fs_info *fs_info,
                        struct extent_buffer *leaf,
                        struct btrfs_chunk *chunk)
{
        u64 stripe_len;
        u64 chunk_len;
        u32 num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
        u64 profile = btrfs_chunk_type(leaf, chunk) &
                      BTRFS_BLOCK_GROUP_PROFILE_MASK;

        chunk_len = btrfs_chunk_length(leaf, chunk);

        switch (profile) {
        case 0: /* Single profile */
        case BTRFS_BLOCK_GROUP_RAID1:
        case BTRFS_BLOCK_GROUP_DUP:
                stripe_len = chunk_len;
                break;
        case BTRFS_BLOCK_GROUP_RAID0:
                stripe_len = chunk_len / num_stripes;
                break;
        case BTRFS_BLOCK_GROUP_RAID5:
                stripe_len = chunk_len / (num_stripes - 1);
                break;
        case BTRFS_BLOCK_GROUP_RAID6:
                stripe_len = chunk_len / (num_stripes - 2);
                break;
        case BTRFS_BLOCK_GROUP_RAID10:
                stripe_len = chunk_len / (num_stripes /
                                btrfs_chunk_sub_stripes(leaf, chunk));
                break;
        default:
                /* Invalid chunk profile found */
                BUG_ON(1);
        }
        return stripe_len;
}

/*
 * Return 0 if size of @device is already good
 * Return >0 if size of @device is not aligned but fixed without problems
 * Return <0 if something wrong happened when aligning the size of @device
 */
int btrfs_fix_device_size(struct btrfs_fs_info *fs_info,
                          struct btrfs_device *device)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_key key;
        struct btrfs_path path;
        struct btrfs_root *chunk_root = fs_info->chunk_root;
        struct btrfs_dev_item *di;
        u64 old_bytes = device->total_bytes;
        int ret;

        if (IS_ALIGNED(old_bytes, fs_info->sectorsize))
                return 0;

        /* Align the in-memory total_bytes first, and use it as correct size */
        device->total_bytes = round_down(device->total_bytes,
                                         fs_info->sectorsize);

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

        trans = btrfs_start_transaction(chunk_root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                error("error starting transaction: %d (%s)",
                      ret, strerror(-ret));
                return ret;
        }

        btrfs_init_path(&path);
        ret = btrfs_search_slot(trans, chunk_root, &key, &path, 0, 1);
        if (ret > 0) {
                error("failed to find DEV_ITEM for devid %llu", device->devid);
                ret = -ENOENT;
                goto err;
        }
        if (ret < 0) {
                error("failed to search chunk root: %d (%s)",
                        ret, strerror(-ret));
                goto err;
        }
        di = btrfs_item_ptr(path.nodes[0], path.slots[0], struct btrfs_dev_item);
        btrfs_set_device_total_bytes(path.nodes[0], di, device->total_bytes);
        btrfs_mark_buffer_dirty(path.nodes[0]);
        ret = btrfs_commit_transaction(trans, chunk_root);
        if (ret < 0) {
                error("failed to commit current transaction: %d (%s)",
                        ret, strerror(-ret));
                btrfs_release_path(&path);
                return ret;
        }
        btrfs_release_path(&path);
        printf("Fixed device size for devid %llu, old size: %llu new size: %llu\n",
                device->devid, old_bytes, device->total_bytes);
        return 1;

err:
        /* We haven't modified anything, it's OK to commit current trans */
        btrfs_commit_transaction(trans, chunk_root);
        btrfs_release_path(&path);
        return ret;
}

/*
 * Return 0 if super block total_bytes matches all devices' total_bytes
 * Return >0 if super block total_bytes mismatch but fixed without problem
 * Return <0 if we failed to fix super block total_bytes
 */
int btrfs_fix_super_size(struct btrfs_fs_info *fs_info)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_device *device;
        struct list_head *dev_list = &fs_info->fs_devices->devices;
        u64 total_bytes = 0;
        u64 old_bytes = btrfs_super_total_bytes(fs_info->super_copy);
        int ret;

        list_for_each_entry(device, dev_list, dev_list) {
                /*
                 * Caller should ensure this function is called after aligning
                 * all devices' total_bytes.
                 */
                if (!IS_ALIGNED(device->total_bytes, fs_info->sectorsize)) {
                        error("device %llu total_bytes %llu not aligned to %u",
                                device->devid, device->total_bytes,
                                fs_info->sectorsize);
                        return -EUCLEAN;
                }
                total_bytes += device->total_bytes;
        }

        if (total_bytes == old_bytes)
                return 0;

        btrfs_set_super_total_bytes(fs_info->super_copy, total_bytes);

        /* Commit transaction to update all super blocks */
        trans = btrfs_start_transaction(fs_info->tree_root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                error("error starting transaction:  %d (%s)",
                      ret, strerror(-ret));
                return ret;
        }
        ret = btrfs_commit_transaction(trans, fs_info->tree_root);
        if (ret < 0) {
                error("failed to commit current transaction: %d (%s)",
                        ret, strerror(-ret));
                return ret;
        }
        printf("Fixed super total bytes, old size: %llu new size: %llu\n",
                old_bytes, total_bytes);
        return 1;
}

/*
 * Return 0 if all devices and super block sizes are good
 * Return >0 if any device/super size problem was found, but fixed
 * Return <0 if something wrong happened during fixing
 */
int btrfs_fix_device_and_super_size(struct btrfs_fs_info *fs_info)
{
        struct btrfs_device *device;
        struct list_head *dev_list = &fs_info->fs_devices->devices;
        bool have_bad_value = false;
        int ret;

        /* Seed device is not supported yet */
        if (fs_info->fs_devices->seed) {
                error("fixing device size with seed device is not supported yet");
                return -EOPNOTSUPP;
        }

        /* All devices must be set up before repairing */
        if (list_empty(dev_list)) {
                error("no device found");
                return -ENODEV;
        }
        list_for_each_entry(device, dev_list, dev_list) {
                if (device->fd == -1 || !device->writeable) {
                        error("devid %llu is missing or not writeable",
                              device->devid);
                        error(
        "fixing device size needs all device(s) to be present and writeable");
                        return -ENODEV;
                }
        }

        /* Repair total_bytes of each device */
        list_for_each_entry(device, dev_list, dev_list) {
                ret = btrfs_fix_device_size(fs_info, device);
                if (ret < 0)
                        return ret;
                if (ret > 0)
                        have_bad_value = true;
        }

        /* Repair super total_byte */
        ret = btrfs_fix_super_size(fs_info);
        if (ret > 0)
                have_bad_value = true;
        if (have_bad_value) {
                printf(
        "Fixed unaligned/mismatched total_bytes for super block and device items\n");
                ret = 1;
        } else {
                printf("No device size related problem found\n");
                ret = 0;
        }
        return ret;
}