Print the root generation in btrfs-debug-tree

[btrfs-progs-unstable/devel.git] / utils.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.
 */

#define _XOPEN_SOURCE 600
#define __USE_XOPEN2K
#include <stdio.h>
#include <stdlib.h>
#ifndef __CHECKER__
#include <sys/ioctl.h>
#include <sys/mount.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#include <uuid/uuid.h>
#include <dirent.h>
#include <fcntl.h>
#include <unistd.h>
#include <mntent.h>
#include <linux/loop.h>
#include <linux/major.h>
#include <linux/kdev_t.h>
#include <limits.h>
#include "kerncompat.h"
#include "radix-tree.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "crc32c.h"
#include "utils.h"
#include "volumes.h"
#include "ioctl.h"

#ifdef __CHECKER__
#define BLKGETSIZE64 0
static inline int ioctl(int fd, int define, u64 *size) { return 0; }
#endif

#ifndef BLKDISCARD
#define BLKDISCARD      _IO(0x12,119)
#endif

static int
discard_blocks(int fd, u64 start, u64 len)
{
        u64 range[2] = { start, len };

        if (ioctl(fd, BLKDISCARD, &range) < 0)
                return errno;
        return 0;
}

static u64 reference_root_table[] = {
        [1] =   BTRFS_ROOT_TREE_OBJECTID,
        [2] =   BTRFS_EXTENT_TREE_OBJECTID,
        [3] =   BTRFS_CHUNK_TREE_OBJECTID,
        [4] =   BTRFS_DEV_TREE_OBJECTID,
        [5] =   BTRFS_FS_TREE_OBJECTID,
        [6] =   BTRFS_CSUM_TREE_OBJECTID,
};

int make_btrfs(int fd, const char *device, const char *label,
               u64 blocks[7], u64 num_bytes, u32 nodesize,
               u32 leafsize, u32 sectorsize, u32 stripesize)
{
        struct btrfs_super_block super;
        struct extent_buffer *buf;
        struct btrfs_root_item root_item;
        struct btrfs_disk_key disk_key;
        struct btrfs_extent_item *extent_item;
        struct btrfs_inode_item *inode_item;
        struct btrfs_chunk *chunk;
        struct btrfs_dev_item *dev_item;
        struct btrfs_dev_extent *dev_extent;
        u8 chunk_tree_uuid[BTRFS_UUID_SIZE];
        u8 *ptr;
        int i;
        int ret;
        u32 itemoff;
        u32 nritems = 0;
        u64 first_free;
        u64 ref_root;
        u32 array_size;
        u32 item_size;

        first_free = BTRFS_SUPER_INFO_OFFSET + sectorsize * 2 - 1;
        first_free &= ~((u64)sectorsize - 1);

        memset(&super, 0, sizeof(super));

        num_bytes = (num_bytes / sectorsize) * sectorsize;
        uuid_generate(super.fsid);
        uuid_generate(super.dev_item.uuid);
        uuid_generate(chunk_tree_uuid);

        btrfs_set_super_bytenr(&super, blocks[0]);
        btrfs_set_super_num_devices(&super, 1);
        strncpy((char *)&super.magic, BTRFS_MAGIC, sizeof(super.magic));
        btrfs_set_super_generation(&super, 1);
        btrfs_set_super_root(&super, blocks[1]);
        btrfs_set_super_chunk_root(&super, blocks[3]);
        btrfs_set_super_total_bytes(&super, num_bytes);
        btrfs_set_super_bytes_used(&super, 6 * leafsize);
        btrfs_set_super_sectorsize(&super, sectorsize);
        btrfs_set_super_leafsize(&super, leafsize);
        btrfs_set_super_nodesize(&super, nodesize);
        btrfs_set_super_stripesize(&super, stripesize);
        btrfs_set_super_csum_type(&super, BTRFS_CSUM_TYPE_CRC32);
        btrfs_set_super_chunk_root_generation(&super, 1);
        btrfs_set_super_cache_generation(&super, -1);
        if (label)
                strncpy(super.label, label, BTRFS_LABEL_SIZE - 1);

        buf = malloc(sizeof(*buf) + max(sectorsize, leafsize));

        /* create the tree of root objects */
        memset(buf->data, 0, leafsize);
        buf->len = leafsize;
        btrfs_set_header_bytenr(buf, blocks[1]);
        btrfs_set_header_nritems(buf, 4);
        btrfs_set_header_generation(buf, 1);
        btrfs_set_header_backref_rev(buf, BTRFS_MIXED_BACKREF_REV);
        btrfs_set_header_owner(buf, BTRFS_ROOT_TREE_OBJECTID);
        write_extent_buffer(buf, super.fsid, (unsigned long)
                            btrfs_header_fsid(buf), BTRFS_FSID_SIZE);

        write_extent_buffer(buf, chunk_tree_uuid, (unsigned long)
                            btrfs_header_chunk_tree_uuid(buf),
                            BTRFS_UUID_SIZE);

        /* create the items for the root tree */
        memset(&root_item, 0, sizeof(root_item));
        inode_item = &root_item.inode;
        btrfs_set_stack_inode_generation(inode_item, 1);
        btrfs_set_stack_inode_size(inode_item, 3);
        btrfs_set_stack_inode_nlink(inode_item, 1);
        btrfs_set_stack_inode_nbytes(inode_item, leafsize);
        btrfs_set_stack_inode_mode(inode_item, S_IFDIR | 0755);
        btrfs_set_root_refs(&root_item, 1);
        btrfs_set_root_used(&root_item, leafsize);
        btrfs_set_root_generation(&root_item, 1);

        memset(&disk_key, 0, sizeof(disk_key));
        btrfs_set_disk_key_type(&disk_key, BTRFS_ROOT_ITEM_KEY);
        btrfs_set_disk_key_offset(&disk_key, 0);
        nritems = 0;

        itemoff = __BTRFS_LEAF_DATA_SIZE(leafsize) - sizeof(root_item);
        btrfs_set_root_bytenr(&root_item, blocks[2]);
        btrfs_set_disk_key_objectid(&disk_key, BTRFS_EXTENT_TREE_OBJECTID);
        btrfs_set_item_key(buf, &disk_key, nritems);
        btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems), itemoff);
        btrfs_set_item_size(buf, btrfs_item_nr(buf, nritems),
                            sizeof(root_item));
        write_extent_buffer(buf, &root_item, btrfs_item_ptr_offset(buf,
                            nritems), sizeof(root_item));
        nritems++;

        itemoff = itemoff - sizeof(root_item);
        btrfs_set_root_bytenr(&root_item, blocks[4]);
        btrfs_set_disk_key_objectid(&disk_key, BTRFS_DEV_TREE_OBJECTID);
        btrfs_set_item_key(buf, &disk_key, nritems);
        btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems), itemoff);
        btrfs_set_item_size(buf, btrfs_item_nr(buf, nritems),
                            sizeof(root_item));
        write_extent_buffer(buf, &root_item,
                            btrfs_item_ptr_offset(buf, nritems),
                            sizeof(root_item));
        nritems++;

        itemoff = itemoff - sizeof(root_item);
        btrfs_set_root_bytenr(&root_item, blocks[5]);
        btrfs_set_disk_key_objectid(&disk_key, BTRFS_FS_TREE_OBJECTID);
        btrfs_set_item_key(buf, &disk_key, nritems);
        btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems), itemoff);
        btrfs_set_item_size(buf, btrfs_item_nr(buf, nritems),
                            sizeof(root_item));
        write_extent_buffer(buf, &root_item,
                            btrfs_item_ptr_offset(buf, nritems),
                            sizeof(root_item));
        nritems++;

        itemoff = itemoff - sizeof(root_item);
        btrfs_set_root_bytenr(&root_item, blocks[6]);
        btrfs_set_disk_key_objectid(&disk_key, BTRFS_CSUM_TREE_OBJECTID);
        btrfs_set_item_key(buf, &disk_key, nritems);
        btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems), itemoff);
        btrfs_set_item_size(buf, btrfs_item_nr(buf, nritems),
                            sizeof(root_item));
        write_extent_buffer(buf, &root_item,
                            btrfs_item_ptr_offset(buf, nritems),
                            sizeof(root_item));
        nritems++;


        csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
        ret = pwrite(fd, buf->data, leafsize, blocks[1]);
        BUG_ON(ret != leafsize);

        /* create the items for the extent tree */
        memset(buf->data+sizeof(struct btrfs_header), 0,
                leafsize-sizeof(struct btrfs_header));
        nritems = 0;
        itemoff = __BTRFS_LEAF_DATA_SIZE(leafsize);
        for (i = 1; i < 7; i++) {
                BUG_ON(blocks[i] < first_free);
                BUG_ON(blocks[i] < blocks[i - 1]);

                /* create extent item */
                itemoff -= sizeof(struct btrfs_extent_item) +
                           sizeof(struct btrfs_tree_block_info);
                btrfs_set_disk_key_objectid(&disk_key, blocks[i]);
                btrfs_set_disk_key_offset(&disk_key, leafsize);
                btrfs_set_disk_key_type(&disk_key, BTRFS_EXTENT_ITEM_KEY);
                btrfs_set_item_key(buf, &disk_key, nritems);
                btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems),
                                      itemoff);
                btrfs_set_item_size(buf, btrfs_item_nr(buf, nritems),
                                    sizeof(struct btrfs_extent_item) +
                                    sizeof(struct btrfs_tree_block_info));
                extent_item = btrfs_item_ptr(buf, nritems,
                                             struct btrfs_extent_item);
                btrfs_set_extent_refs(buf, extent_item, 1);
                btrfs_set_extent_generation(buf, extent_item, 1);
                btrfs_set_extent_flags(buf, extent_item,
                                       BTRFS_EXTENT_FLAG_TREE_BLOCK);
                nritems++;

                /* create extent ref */
                ref_root = reference_root_table[i];
                btrfs_set_disk_key_objectid(&disk_key, blocks[i]);
                btrfs_set_disk_key_offset(&disk_key, ref_root);
                btrfs_set_disk_key_type(&disk_key, BTRFS_TREE_BLOCK_REF_KEY);
                btrfs_set_item_key(buf, &disk_key, nritems);
                btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems),
                                      itemoff);
                btrfs_set_item_size(buf, btrfs_item_nr(buf, nritems), 0);
                nritems++;
        }
        btrfs_set_header_bytenr(buf, blocks[2]);
        btrfs_set_header_owner(buf, BTRFS_EXTENT_TREE_OBJECTID);
        btrfs_set_header_nritems(buf, nritems);
        csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
        ret = pwrite(fd, buf->data, leafsize, blocks[2]);
        BUG_ON(ret != leafsize);

        /* create the chunk tree */
        memset(buf->data+sizeof(struct btrfs_header), 0,
                leafsize-sizeof(struct btrfs_header));
        nritems = 0;
        item_size = sizeof(*dev_item);
        itemoff = __BTRFS_LEAF_DATA_SIZE(leafsize) - item_size;

        /* first device 1 (there is no device 0) */
        btrfs_set_disk_key_objectid(&disk_key, BTRFS_DEV_ITEMS_OBJECTID);
        btrfs_set_disk_key_offset(&disk_key, 1);
        btrfs_set_disk_key_type(&disk_key, BTRFS_DEV_ITEM_KEY);
        btrfs_set_item_key(buf, &disk_key, nritems);
        btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems), itemoff);
        btrfs_set_item_size(buf, btrfs_item_nr(buf, nritems), item_size);

        dev_item = btrfs_item_ptr(buf, nritems, struct btrfs_dev_item);
        btrfs_set_device_id(buf, dev_item, 1);
        btrfs_set_device_generation(buf, dev_item, 0);
        btrfs_set_device_total_bytes(buf, dev_item, num_bytes);
        btrfs_set_device_bytes_used(buf, dev_item,
                                    BTRFS_MKFS_SYSTEM_GROUP_SIZE);
        btrfs_set_device_io_align(buf, dev_item, sectorsize);
        btrfs_set_device_io_width(buf, dev_item, sectorsize);
        btrfs_set_device_sector_size(buf, dev_item, sectorsize);
        btrfs_set_device_type(buf, dev_item, 0);

        write_extent_buffer(buf, super.dev_item.uuid,
                            (unsigned long)btrfs_device_uuid(dev_item),
                            BTRFS_UUID_SIZE);
        write_extent_buffer(buf, super.fsid,
                            (unsigned long)btrfs_device_fsid(dev_item),
                            BTRFS_UUID_SIZE);
        read_extent_buffer(buf, &super.dev_item, (unsigned long)dev_item,
                           sizeof(*dev_item));

        nritems++;
        item_size = btrfs_chunk_item_size(1);
        itemoff = itemoff - item_size;

        /* then we have chunk 0 */
        btrfs_set_disk_key_objectid(&disk_key, BTRFS_FIRST_CHUNK_TREE_OBJECTID);
        btrfs_set_disk_key_offset(&disk_key, 0);
        btrfs_set_disk_key_type(&disk_key, BTRFS_CHUNK_ITEM_KEY);
        btrfs_set_item_key(buf, &disk_key, nritems);
        btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems), itemoff);
        btrfs_set_item_size(buf, btrfs_item_nr(buf,  nritems), item_size);

        chunk = btrfs_item_ptr(buf, nritems, struct btrfs_chunk);
        btrfs_set_chunk_length(buf, chunk, BTRFS_MKFS_SYSTEM_GROUP_SIZE);
        btrfs_set_chunk_owner(buf, chunk, BTRFS_EXTENT_TREE_OBJECTID);
        btrfs_set_chunk_stripe_len(buf, chunk, 64 * 1024);
        btrfs_set_chunk_type(buf, chunk, BTRFS_BLOCK_GROUP_SYSTEM);
        btrfs_set_chunk_io_align(buf, chunk, sectorsize);
        btrfs_set_chunk_io_width(buf, chunk, sectorsize);
        btrfs_set_chunk_sector_size(buf, chunk, sectorsize);
        btrfs_set_chunk_num_stripes(buf, chunk, 1);
        btrfs_set_stripe_devid_nr(buf, chunk, 0, 1);
        btrfs_set_stripe_offset_nr(buf, chunk, 0, 0);
        nritems++;

        write_extent_buffer(buf, super.dev_item.uuid,
                            (unsigned long)btrfs_stripe_dev_uuid(&chunk->stripe),
                            BTRFS_UUID_SIZE);

        /* copy the key for the chunk to the system array */
        ptr = super.sys_chunk_array;
        array_size = sizeof(disk_key);

        memcpy(ptr, &disk_key, sizeof(disk_key));
        ptr += sizeof(disk_key);

        /* copy the chunk to the system array */
        read_extent_buffer(buf, ptr, (unsigned long)chunk, item_size);
        array_size += item_size;
        ptr += item_size;
        btrfs_set_super_sys_array_size(&super, array_size);

        btrfs_set_header_bytenr(buf, blocks[3]);
        btrfs_set_header_owner(buf, BTRFS_CHUNK_TREE_OBJECTID);
        btrfs_set_header_nritems(buf, nritems);
        csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
        ret = pwrite(fd, buf->data, leafsize, blocks[3]);

        /* create the device tree */
        memset(buf->data+sizeof(struct btrfs_header), 0,
                leafsize-sizeof(struct btrfs_header));
        nritems = 0;
        itemoff = __BTRFS_LEAF_DATA_SIZE(leafsize) -
                sizeof(struct btrfs_dev_extent);

        btrfs_set_disk_key_objectid(&disk_key, 1);
        btrfs_set_disk_key_offset(&disk_key, 0);
        btrfs_set_disk_key_type(&disk_key, BTRFS_DEV_EXTENT_KEY);
        btrfs_set_item_key(buf, &disk_key, nritems);
        btrfs_set_item_offset(buf, btrfs_item_nr(buf, nritems), itemoff);
        btrfs_set_item_size(buf, btrfs_item_nr(buf,  nritems),
                            sizeof(struct btrfs_dev_extent));
        dev_extent = btrfs_item_ptr(buf, nritems, struct btrfs_dev_extent);
        btrfs_set_dev_extent_chunk_tree(buf, dev_extent,
                                        BTRFS_CHUNK_TREE_OBJECTID);
        btrfs_set_dev_extent_chunk_objectid(buf, dev_extent,
                                        BTRFS_FIRST_CHUNK_TREE_OBJECTID);
        btrfs_set_dev_extent_chunk_offset(buf, dev_extent, 0);

        write_extent_buffer(buf, chunk_tree_uuid,
                    (unsigned long)btrfs_dev_extent_chunk_tree_uuid(dev_extent),
                    BTRFS_UUID_SIZE);

        btrfs_set_dev_extent_length(buf, dev_extent,
                                    BTRFS_MKFS_SYSTEM_GROUP_SIZE);
        nritems++;

        btrfs_set_header_bytenr(buf, blocks[4]);
        btrfs_set_header_owner(buf, BTRFS_DEV_TREE_OBJECTID);
        btrfs_set_header_nritems(buf, nritems);
        csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
        ret = pwrite(fd, buf->data, leafsize, blocks[4]);

        /* create the FS root */
        memset(buf->data+sizeof(struct btrfs_header), 0,
                leafsize-sizeof(struct btrfs_header));
        btrfs_set_header_bytenr(buf, blocks[5]);
        btrfs_set_header_owner(buf, BTRFS_FS_TREE_OBJECTID);
        btrfs_set_header_nritems(buf, 0);
        csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
        ret = pwrite(fd, buf->data, leafsize, blocks[5]);
        BUG_ON(ret != leafsize);

        /* finally create the csum root */
        memset(buf->data+sizeof(struct btrfs_header), 0,
                leafsize-sizeof(struct btrfs_header));
        btrfs_set_header_bytenr(buf, blocks[6]);
        btrfs_set_header_owner(buf, BTRFS_CSUM_TREE_OBJECTID);
        btrfs_set_header_nritems(buf, 0);
        csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
        ret = pwrite(fd, buf->data, leafsize, blocks[6]);
        BUG_ON(ret != leafsize);

        /* and write out the super block */
        BUG_ON(sizeof(super) > sectorsize);
        memset(buf->data, 0, sectorsize);
        memcpy(buf->data, &super, sizeof(super));
        buf->len = sectorsize;
        csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
        ret = pwrite(fd, buf->data, sectorsize, blocks[0]);
        BUG_ON(ret != sectorsize);


        free(buf);
        return 0;
}

static u64 device_size(int fd, struct stat *st)
{
        u64 size;
        if (S_ISREG(st->st_mode)) {
                return st->st_size;
        }
        if (!S_ISBLK(st->st_mode)) {
                return 0;
        }
        if (ioctl(fd, BLKGETSIZE64, &size) >= 0) {
                return size;
        }
        return 0;
}

static int zero_blocks(int fd, off_t start, size_t len)
{
        char *buf = malloc(len);
        int ret = 0;
        ssize_t written;

        if (!buf)
                return -ENOMEM;
        memset(buf, 0, len);
        written = pwrite(fd, buf, len, start);
        if (written != len)
                ret = -EIO;
        free(buf);
        return ret;
}

static int zero_dev_start(int fd)
{
        off_t start = 0;
        size_t len = 2 * 1024 * 1024;

#ifdef __sparc__
        /* don't overwrite the disk labels on sparc */
        start = 1024;
        len -= 1024;
#endif
        return zero_blocks(fd, start, len);
}

static int zero_dev_end(int fd, u64 dev_size)
{
        size_t len = 2 * 1024 * 1024;
        off_t start = dev_size - len;

        return zero_blocks(fd, start, len);
}

int btrfs_add_to_fsid(struct btrfs_trans_handle *trans,
                      struct btrfs_root *root, int fd, char *path,
                      u64 block_count, u32 io_width, u32 io_align,
                      u32 sectorsize)
{
        struct btrfs_super_block *disk_super;
        struct btrfs_super_block *super = &root->fs_info->super_copy;
        struct btrfs_device *device;
        struct btrfs_dev_item *dev_item;
        char *buf;
        u64 total_bytes;
        u64 num_devs;
        int ret;

        device = kmalloc(sizeof(*device), GFP_NOFS);
        if (!device)
                return -ENOMEM;
        buf = kmalloc(sectorsize, GFP_NOFS);
        if (!buf) {
                kfree(device);
                return -ENOMEM;
        }
        BUG_ON(sizeof(*disk_super) > sectorsize);
        memset(buf, 0, sectorsize);

        disk_super = (struct btrfs_super_block *)buf;
        dev_item = &disk_super->dev_item;

        uuid_generate(device->uuid);
        device->devid = 0;
        device->type = 0;
        device->io_width = io_width;
        device->io_align = io_align;
        device->sector_size = sectorsize;
        device->fd = fd;
        device->writeable = 1;
        device->total_bytes = block_count;
        device->bytes_used = 0;
        device->total_ios = 0;
        device->dev_root = root->fs_info->dev_root;

        ret = btrfs_add_device(trans, root, device);
        BUG_ON(ret);

        total_bytes = btrfs_super_total_bytes(super) + block_count;
        btrfs_set_super_total_bytes(super, total_bytes);

        num_devs = btrfs_super_num_devices(super) + 1;
        btrfs_set_super_num_devices(super, num_devs);

        memcpy(disk_super, super, sizeof(*disk_super));

        printf("adding device %s id %llu\n", path,
               (unsigned long long)device->devid);

        btrfs_set_super_bytenr(disk_super, BTRFS_SUPER_INFO_OFFSET);
        btrfs_set_stack_device_id(dev_item, device->devid);
        btrfs_set_stack_device_type(dev_item, device->type);
        btrfs_set_stack_device_io_align(dev_item, device->io_align);
        btrfs_set_stack_device_io_width(dev_item, device->io_width);
        btrfs_set_stack_device_sector_size(dev_item, device->sector_size);
        btrfs_set_stack_device_total_bytes(dev_item, device->total_bytes);
        btrfs_set_stack_device_bytes_used(dev_item, device->bytes_used);
        memcpy(&dev_item->uuid, device->uuid, BTRFS_UUID_SIZE);

        ret = pwrite(fd, buf, sectorsize, BTRFS_SUPER_INFO_OFFSET);
        BUG_ON(ret != sectorsize);

        kfree(buf);
        list_add(&device->dev_list, &root->fs_info->fs_devices->devices);
        device->fs_devices = root->fs_info->fs_devices;
        return 0;
}

int btrfs_prepare_device(int fd, char *file, int zero_end, u64 *block_count_ret,
                         int *mixed)
{
        u64 block_count;
        u64 bytenr;
        struct stat st;
        int i, ret;

        ret = fstat(fd, &st);
        if (ret < 0) {
                fprintf(stderr, "unable to stat %s\n", file);
                exit(1);
        }

        block_count = device_size(fd, &st);
        if (block_count == 0) {
                fprintf(stderr, "unable to find %s size\n", file);
                exit(1);
        }
        zero_end = 1;

        if (block_count < 1024 * 1024 * 1024 && !(*mixed)) {
                printf("SMALL VOLUME: forcing mixed metadata/data groups\n");
                *mixed = 1;
        }

        /*
         * We intentionally ignore errors from the discard ioctl.  It is
         * not necessary for the mkfs functionality but just an optimization.
         */
        discard_blocks(fd, 0, block_count);

        ret = zero_dev_start(fd);
        if (ret) {
                fprintf(stderr, "failed to zero device start %d\n", ret);
                exit(1);
        }

        for (i = 0 ; i < BTRFS_SUPER_MIRROR_MAX; i++) {
                bytenr = btrfs_sb_offset(i);
                if (bytenr >= block_count)
                        break;
                zero_blocks(fd, bytenr, BTRFS_SUPER_INFO_SIZE);
        }

        if (zero_end) {
                ret = zero_dev_end(fd, block_count);
                if (ret) {
                        fprintf(stderr, "failed to zero device end %d\n", ret);
                        exit(1);
                }
        }
        *block_count_ret = block_count;
        return 0;
}

int btrfs_make_root_dir(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root, u64 objectid)
{
        int ret;
        struct btrfs_inode_item inode_item;
        time_t now = time(NULL);

        memset(&inode_item, 0, sizeof(inode_item));
        btrfs_set_stack_inode_generation(&inode_item, trans->transid);
        btrfs_set_stack_inode_size(&inode_item, 0);
        btrfs_set_stack_inode_nlink(&inode_item, 1);
        btrfs_set_stack_inode_nbytes(&inode_item, root->leafsize);
        btrfs_set_stack_inode_mode(&inode_item, S_IFDIR | 0555);
        btrfs_set_stack_timespec_sec(&inode_item.atime, now);
        btrfs_set_stack_timespec_nsec(&inode_item.atime, 0);
        btrfs_set_stack_timespec_sec(&inode_item.ctime, now);
        btrfs_set_stack_timespec_nsec(&inode_item.ctime, 0);
        btrfs_set_stack_timespec_sec(&inode_item.mtime, now);
        btrfs_set_stack_timespec_nsec(&inode_item.mtime, 0);
        btrfs_set_stack_timespec_sec(&inode_item.otime, 0);
        btrfs_set_stack_timespec_nsec(&inode_item.otime, 0);

        if (root->fs_info->tree_root == root)
                btrfs_set_super_root_dir(&root->fs_info->super_copy, objectid);

        ret = btrfs_insert_inode(trans, root, objectid, &inode_item);
        if (ret)
                goto error;

        ret = btrfs_insert_inode_ref(trans, root, "..", 2, objectid, objectid, 0);
        if (ret)
                goto error;

        btrfs_set_root_dirid(&root->root_item, objectid);
        ret = 0;
error:
        return ret;
}

/* checks if a device is a loop device */
int is_loop_device (const char* device) {
        struct stat statbuf;

        if(stat(device, &statbuf) < 0)
                return -errno;

        return (S_ISBLK(statbuf.st_mode) &&
                MAJOR(statbuf.st_rdev) == LOOP_MAJOR);
}


/* Takes a loop device path (e.g. /dev/loop0) and returns
 * the associated file (e.g. /images/my_btrfs.img) */
int resolve_loop_device(const char* loop_dev, char* loop_file, int max_len)
{
        int loop_fd;
        int ret_ioctl;
        struct loop_info loopinfo;

        if ((loop_fd = open(loop_dev, O_RDONLY)) < 0)
                return -errno;

        ret_ioctl = ioctl(loop_fd, LOOP_GET_STATUS, &loopinfo);
        close(loop_fd);

        if (ret_ioctl == 0)
                strncpy(loop_file, loopinfo.lo_name, max_len);
        else
                return -errno;

        return 0;
}

/* Checks whether a and b are identical or device
 * files associated with the same block device
 */
int is_same_blk_file(const char* a, const char* b)
{
        struct stat st_buf_a, st_buf_b;
        char real_a[PATH_MAX];
        char real_b[PATH_MAX];

        if(!realpath(a, real_a) ||
           !realpath(b, real_b))
        {
                return -errno;
        }

        /* Identical path? */
        if(strcmp(real_a, real_b) == 0)
                return 1;

        if(stat(a, &st_buf_a) < 0 ||
           stat(b, &st_buf_b) < 0)
        {
                return -errno;
        }

        /* Same blockdevice? */
        if(S_ISBLK(st_buf_a.st_mode) &&
           S_ISBLK(st_buf_b.st_mode) &&
           st_buf_a.st_rdev == st_buf_b.st_rdev)
        {
                return 1;
        }

        /* Hardlink? */
        if (st_buf_a.st_dev == st_buf_b.st_dev &&
            st_buf_a.st_ino == st_buf_b.st_ino)
        {
                return 1;
        }

        return 0;
}

/* checks if a and b are identical or device
 * files associated with the same block device or
 * if one file is a loop device that uses the other
 * file.
 */
int is_same_loop_file(const char* a, const char* b)
{
        char res_a[PATH_MAX];
        char res_b[PATH_MAX];
        const char* final_a;
        const char* final_b;
        int ret;

        /* Resolve a if it is a loop device */
        if((ret = is_loop_device(a)) < 0) {
           return ret;
        } else if(ret) {
                if((ret = resolve_loop_device(a, res_a, sizeof(res_a))) < 0)
                        return ret;

                final_a = res_a;
        } else {
                final_a = a;
        }

        /* Resolve b if it is a loop device */
        if((ret = is_loop_device(b)) < 0) {
           return ret;
        } else if(ret) {
                if((ret = resolve_loop_device(b, res_b, sizeof(res_b))) < 0)
                        return ret;

                final_b = res_b;
        } else {
                final_b = b;
        }

        return is_same_blk_file(final_a, final_b);
}

/* Checks if a file exists and is a block or regular file*/
int is_existing_blk_or_reg_file(const char* filename)
{
        struct stat st_buf;

        if(stat(filename, &st_buf) < 0) {
                if(errno == ENOENT)
                        return 0;
                else
                        return -errno;
        }

        return (S_ISBLK(st_buf.st_mode) || S_ISREG(st_buf.st_mode));
}

/* Checks if a file is used (directly or indirectly via a loop device)
 * by a device in fs_devices
 */
int blk_file_in_dev_list(struct btrfs_fs_devices* fs_devices, const char* file)
{
        int ret;
        struct list_head *head;
        struct list_head *cur;
        struct btrfs_device *device;

        head = &fs_devices->devices;
        list_for_each(cur, head) {
                device = list_entry(cur, struct btrfs_device, dev_list);

                if((ret = is_same_loop_file(device->name, file)))
                        return ret;
        }

        return 0;
}

/*
 * returns 1 if the device was mounted, < 0 on error or 0 if everything
 * is safe to continue.
 */
int check_mounted(const char* file)
{
        int fd;
        int ret;

        fd = open(file, O_RDONLY);
        if (fd < 0) {
                fprintf (stderr, "check_mounted(): Could not open %s\n", file);
                return -errno;
        }

        ret =  check_mounted_where(fd, file, NULL, 0, NULL);
        close(fd);

        return ret;
}

int check_mounted_where(int fd, const char *file, char *where, int size,
                        struct btrfs_fs_devices **fs_dev_ret)
{
        int ret;
        u64 total_devs = 1;
        int is_btrfs;
        struct btrfs_fs_devices *fs_devices_mnt = NULL;
        FILE *f;
        struct mntent *mnt;

        /* scan the initial device */
        ret = btrfs_scan_one_device(fd, file, &fs_devices_mnt,
                                    &total_devs, BTRFS_SUPER_INFO_OFFSET);
        is_btrfs = (ret >= 0);

        /* scan other devices */
        if (is_btrfs && total_devs > 1) {
                if((ret = btrfs_scan_for_fsid(fs_devices_mnt, total_devs, 1)))
                        return ret;
        }

        /* iterate over the list of currently mountes filesystems */
        if ((f = setmntent ("/proc/mounts", "r")) == NULL)
                return -errno;

        while ((mnt = getmntent (f)) != NULL) {
                if(is_btrfs) {
                        if(strcmp(mnt->mnt_type, "btrfs") != 0)
                                continue;

                        ret = blk_file_in_dev_list(fs_devices_mnt, mnt->mnt_fsname);
                } else {
                        /* ignore entries in the mount table that are not
                           associated with a file*/
                        if((ret = is_existing_blk_or_reg_file(mnt->mnt_fsname)) < 0)
                                goto out_mntloop_err;
                        else if(!ret)
                                continue;

                        ret = is_same_loop_file(file, mnt->mnt_fsname);
                }

                if(ret < 0)
                        goto out_mntloop_err;
                else if(ret)
                        break;
        }

        /* Did we find an entry in mnt table? */
        if (mnt && size && where)
                strncpy(where, mnt->mnt_dir, size);
        if (fs_dev_ret)
                *fs_dev_ret = fs_devices_mnt;

        ret = (mnt != NULL);

out_mntloop_err:
        endmntent (f);

        return ret;
}

/* Gets the mount point of btrfs filesystem that is using the specified device.
 * Returns 0 is everything is good, <0 if we have an error.
 * TODO: Fix this fucntion and check_mounted to work with multiple drive BTRFS
 * setups.
 */
int get_mountpt(char *dev, char *mntpt, size_t size)
{
       struct mntent *mnt;
       FILE *f;
       int ret = 0;

       f = setmntent("/proc/mounts", "r");
       if (f == NULL)
               return -errno;

       while ((mnt = getmntent(f)) != NULL )
       {
               if (strcmp(dev, mnt->mnt_fsname) == 0)
               {
                       strncpy(mntpt, mnt->mnt_dir, size);
                       break;
               }
       }

       if (mnt == NULL)
       {
               /* We didn't find an entry so lets report an error */
               ret = -1;
       }

       return ret;
}

struct pending_dir {
        struct list_head list;
        char name[256];
};

void btrfs_register_one_device(char *fname)
{
        struct btrfs_ioctl_vol_args args;
        int fd;
        int ret;
        int e;

        fd = open("/dev/btrfs-control", O_RDONLY);
        if (fd < 0) {
                fprintf(stderr, "failed to open /dev/btrfs-control "
                        "skipping device registration\n");
                return;
        }
        strncpy(args.name, fname, BTRFS_PATH_NAME_MAX);
        ret = ioctl(fd, BTRFS_IOC_SCAN_DEV, &args);
        e = errno;
        if(ret<0){
                fprintf(stderr, "ERROR: unable to scan the device '%s' - %s\n",
                        fname, strerror(e));
        }
        close(fd);
}

int btrfs_scan_one_dir(char *dirname, int run_ioctl)
{
        DIR *dirp = NULL;
        struct dirent *dirent;
        struct pending_dir *pending;
        struct stat st;
        int ret;
        int fd;
        int dirname_len;
        int pathlen;
        char *fullpath;
        struct list_head pending_list;
        struct btrfs_fs_devices *tmp_devices;
        u64 num_devices;

        INIT_LIST_HEAD(&pending_list);

        pending = malloc(sizeof(*pending));
        if (!pending)
                return -ENOMEM;
        strcpy(pending->name, dirname);

again:
        dirname_len = strlen(pending->name);
        pathlen = 1024;
        fullpath = malloc(pathlen);
        dirname = pending->name;

        if (!fullpath) {
                ret = -ENOMEM;
                goto fail;
        }
        dirp = opendir(dirname);
        if (!dirp) {
                fprintf(stderr, "Unable to open %s for scanning\n", dirname);
                return -ENOENT;
        }
        while(1) {
                dirent = readdir(dirp);
                if (!dirent)
                        break;
                if (dirent->d_name[0] == '.')
                        continue;
                if (dirname_len + strlen(dirent->d_name) + 2 > pathlen) {
                        ret = -EFAULT;
                        goto fail;
                }
                snprintf(fullpath, pathlen, "%s/%s", dirname, dirent->d_name);
                ret = lstat(fullpath, &st);
                if (ret < 0) {
                        fprintf(stderr, "failed to stat %s\n", fullpath);
                        continue;
                }
                if (S_ISLNK(st.st_mode))
                        continue;
                if (S_ISDIR(st.st_mode)) {
                        struct pending_dir *next = malloc(sizeof(*next));
                        if (!next) {
                                ret = -ENOMEM;
                                goto fail;
                        }
                        strcpy(next->name, fullpath);
                        list_add_tail(&next->list, &pending_list);
                }
                if (!S_ISBLK(st.st_mode)) {
                        continue;
                }
                fd = open(fullpath, O_RDONLY);
                if (fd < 0) {
                        fprintf(stderr, "failed to read %s: %s\n", fullpath,
                                        strerror(errno));
                        continue;
                }
                ret = btrfs_scan_one_device(fd, fullpath, &tmp_devices,
                                            &num_devices,
                                            BTRFS_SUPER_INFO_OFFSET);
                if (ret == 0 && run_ioctl > 0) {
                        btrfs_register_one_device(fullpath);
                }
                close(fd);
        }
        if (!list_empty(&pending_list)) {
                free(pending);
                pending = list_entry(pending_list.next, struct pending_dir,
                                     list);
                list_del(&pending->list);
                closedir(dirp);
                goto again;
        }
        ret = 0;
fail:
        free(pending);
        if (dirp)
                closedir(dirp);
        return ret;
}

int btrfs_scan_for_fsid(struct btrfs_fs_devices *fs_devices, u64 total_devs,
                        int run_ioctls)
{
        return btrfs_scan_one_dir("/dev", run_ioctls);
}

int btrfs_device_already_in_root(struct btrfs_root *root, int fd,
                                 int super_offset)
{
        struct btrfs_super_block *disk_super;
        char *buf;
        int ret = 0;

        buf = malloc(BTRFS_SUPER_INFO_SIZE);
        if (!buf) {
                ret = -ENOMEM;
                goto out;
        }
        ret = pread(fd, buf, BTRFS_SUPER_INFO_SIZE, super_offset);
        if (ret != BTRFS_SUPER_INFO_SIZE)
                goto brelse;

        ret = 0;
        disk_super = (struct btrfs_super_block *)buf;
        if (strncmp((char *)(&disk_super->magic), BTRFS_MAGIC,
            sizeof(disk_super->magic)))
                goto brelse;

        if (!memcmp(disk_super->fsid, root->fs_info->super_copy.fsid,
                    BTRFS_FSID_SIZE))
                ret = 1;
brelse:
        free(buf);
out:
        return ret;
}

static char *size_strs[] = { "", "KB", "MB", "GB", "TB",
                            "PB", "EB", "ZB", "YB"};
char *pretty_sizes(u64 size)
{
        int num_divs = 0;
        int pretty_len = 16;
        u64 last_size = size;
        u64 fract_size = size;
        float fraction;
        char *pretty;

        while(size > 0) {
                fract_size = last_size;
                last_size = size;
                size /= 1024;
                num_divs++;
        }
        if (num_divs == 0)
                num_divs = 1;
        if (num_divs > ARRAY_SIZE(size_strs))
                return NULL;

        fraction = (float)fract_size / 1024;
        pretty = malloc(pretty_len);
        snprintf(pretty, pretty_len, "%.2f%s", fraction, size_strs[num_divs-1]);
        return pretty;
}

/*
 * Checks to make sure that the label matches our requirements.
 * Returns:
       0    if everything is safe and usable
      -1    if the label is too long
      -2    if the label contains an invalid character
 */
int check_label(char *input)
{
       int i;
       int len = strlen(input);

       if (len > BTRFS_LABEL_SIZE) {
               return -1;
       }

       for (i = 0; i < len; i++) {
               if (input[i] == '/' || input[i] == '\\') {
                       return -2;
               }
       }

       return 0;
}

int btrfs_scan_block_devices(int run_ioctl)
{

        struct stat st;
        int ret;
        int fd;
        struct btrfs_fs_devices *tmp_devices;
        u64 num_devices;
        FILE *proc_partitions;
        int i;
        char buf[1024];
        char fullpath[110];

        proc_partitions = fopen("/proc/partitions","r");
        if (!proc_partitions) {
                fprintf(stderr, "Unable to open '/proc/partitions' for scanning\n");
                return -ENOENT;
        }
        /* skip the header */
        for(i=0; i < 2 ; i++)
                if(!fgets(buf, 1023, proc_partitions)){
                fprintf(stderr, "Unable to read '/proc/partitions' for scanning\n");
                fclose(proc_partitions);
                return -ENOENT;
        }

        strcpy(fullpath,"/dev/");
        while(fgets(buf, 1023, proc_partitions)) {

                i = sscanf(buf," %*d %*d %*d %99s", fullpath+5);
                ret = lstat(fullpath, &st);
                if (ret < 0) {
                        fprintf(stderr, "failed to stat %s\n", fullpath);
                        continue;
                }
                if (!S_ISBLK(st.st_mode)) {
                        continue;
                }

                fd = open(fullpath, O_RDONLY);
                if (fd < 0) {
                        fprintf(stderr, "failed to read %s\n", fullpath);
                        continue;
                }
                ret = btrfs_scan_one_device(fd, fullpath, &tmp_devices,
                                            &num_devices,
                                            BTRFS_SUPER_INFO_OFFSET);
                if (ret == 0 && run_ioctl > 0) {
                        btrfs_register_one_device(fullpath);
                }
                close(fd);
        }

        fclose(proc_partitions);
        return 0;
}