source: mainline/uspace/lib/ext4/src/filesystem.c@ 3061bc1

/*
 * Copyright (c) 2011 Martin Sucha
 * Copyright (c) 2012 Frantisek Princ
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup libext4
 * @{
 */
/**
 * @file  filesystem.c
 * @brief More complex filesystem operations.
 */

#include <byteorder.h>
#include <errno.h>
#include <mem.h>
#include <align.h>
#include <crypto.h>
#include <ipc/vfs.h>
#include <libfs.h>
#include <stdlib.h>
#include "ext4/balloc.h"
#include "ext4/bitmap.h"
#include "ext4/block_group.h"
#include "ext4/extent.h"
#include "ext4/filesystem.h"
#include "ext4/ialloc.h"
#include "ext4/inode.h"
#include "ext4/ops.h"
#include "ext4/superblock.h"

static errno_t ext4_filesystem_check_features(ext4_filesystem_t *, bool *);

/** Initialize filesystem for opening.
 *
 * But do not mark mounted just yet.
 *
 * @param fs         Filesystem instance to be initialized
 * @param service_id Block device to open
 * @param cmode      Cache mode
 *
 * @return Error code
 *
 */
static errno_t ext4_filesystem_init(ext4_filesystem_t *fs, service_id_t service_id,
    enum cache_mode cmode)
{
        errno_t rc;
        ext4_superblock_t *temp_superblock = NULL;

        fs->device = service_id;

        /* Initialize block library (4096 is size of communication channel) */
        rc = block_init(fs->device, 4096);
        if (rc != EOK)
                goto err;

        /* Read superblock from device to memory */
        rc = ext4_superblock_read_direct(fs->device, &temp_superblock);
        if (rc != EOK)
                goto err_1;

        /* Read block size from superblock and check */
        uint32_t block_size = ext4_superblock_get_block_size(temp_superblock);
        if (block_size > EXT4_MAX_BLOCK_SIZE) {
                rc = ENOTSUP;
                goto err_1;
        }

        /* Initialize block caching by libblock */
        rc = block_cache_init(service_id, block_size, 0, cmode);
        if (rc != EOK)
                goto err_1;

        /* Compute limits for indirect block levels */
        uint32_t block_ids_per_block = block_size / sizeof(uint32_t);
        fs->inode_block_limits[0] = EXT4_INODE_DIRECT_BLOCK_COUNT;
        fs->inode_blocks_per_level[0] = 1;
        for (unsigned int i = 1; i < 4; i++) {
                fs->inode_blocks_per_level[i] = fs->inode_blocks_per_level[i - 1] *
                    block_ids_per_block;
                fs->inode_block_limits[i] = fs->inode_block_limits[i - 1] +
                    fs->inode_blocks_per_level[i];
        }

        /* Return loaded superblock */
        fs->superblock = temp_superblock;

        uint16_t state = ext4_superblock_get_state(fs->superblock);

        if (((state & EXT4_SUPERBLOCK_STATE_VALID_FS) !=
            EXT4_SUPERBLOCK_STATE_VALID_FS) ||
            ((state & EXT4_SUPERBLOCK_STATE_ERROR_FS) ==
            EXT4_SUPERBLOCK_STATE_ERROR_FS)) {
                rc = ENOTSUP;
                goto err_2;
        }

        rc = ext4_superblock_check_sanity(fs->superblock);
        if (rc != EOK)
                goto err_2;

        /* Check flags */
        bool read_only;
        rc = ext4_filesystem_check_features(fs, &read_only);
        if (rc != EOK)
                goto err_2;

        return EOK;
err_2:
        block_cache_fini(fs->device);
err_1:
        block_fini(fs->device);
err:
        if (temp_superblock)
                ext4_superblock_release(temp_superblock);
        return rc;
}

/** Finalize filesystem.
 *
 * @param fs Filesystem to be finalized
 *
 */
static void ext4_filesystem_fini(ext4_filesystem_t *fs)
{
        /* Release memory space for superblock */
        free(fs->superblock);

        /* Finish work with block library */
        block_cache_fini(fs->device);
        block_fini(fs->device);
}

/** Probe filesystem.
 *
 * @param service_id Block device to probe
 *
 * @return EOK or an error code.
 *
 */
errno_t ext4_filesystem_probe(service_id_t service_id)
{
        ext4_filesystem_t *fs = NULL;
        errno_t rc;

        fs = calloc(1, sizeof(ext4_filesystem_t));
        if (fs == NULL)
                return ENOMEM;

        /* Initialize the file system for opening */
        rc = ext4_filesystem_init(fs, service_id, CACHE_MODE_WT);
        if (rc != EOK) {
                free(fs);
                return rc;
        }

        ext4_filesystem_fini(fs);
        return EOK;
}

/** Open filesystem and read all needed data.
 *
 * @param fs         Filesystem to be initialized
 * @param inst       Instance
 * @param service_id Identifier if device with the filesystem
 * @param cmode      Cache mode
 * @param size       Output value - size of root node
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_open(ext4_instance_t *inst, service_id_t service_id,
    enum cache_mode cmode, aoff64_t *size, ext4_filesystem_t **rfs)
{
        ext4_filesystem_t *fs = NULL;
        fs_node_t *root_node = NULL;
        errno_t rc;

        fs = calloc(1, sizeof(ext4_filesystem_t));
        if (fs == NULL) {
                rc = ENOMEM;
                goto error;
        }

        inst->filesystem = fs;

        /* Initialize the file system for opening */
        rc = ext4_filesystem_init(fs, service_id, cmode);
        if (rc != EOK)
                goto error;

        /* Read root node */
        rc = ext4_node_get_core(&root_node, inst, EXT4_INODE_ROOT_INDEX);
        if (rc != EOK)
                goto error;

        /* Mark system as mounted */
        ext4_superblock_set_state(fs->superblock, EXT4_SUPERBLOCK_STATE_ERROR_FS);
        rc = ext4_superblock_write_direct(fs->device, fs->superblock);
        if (rc != EOK)
                goto error;

        uint16_t mnt_count = ext4_superblock_get_mount_count(fs->superblock);
        ext4_superblock_set_mount_count(fs->superblock, mnt_count + 1);

        ext4_node_t *enode = EXT4_NODE(root_node);

        *size = ext4_inode_get_size(fs->superblock, enode->inode_ref->inode);

        ext4_node_put(root_node);
        *rfs = fs;
        return EOK;
error:
        if (root_node != NULL)
                ext4_node_put(root_node);

        if (fs != NULL) {
                ext4_filesystem_fini(fs);
                free(fs);
        }

        return rc;
}

/** Close filesystem.
 *
 * @param fs Filesystem to be destroyed
 *
 * @return EOK or an error code. On error the state of the file
 *         system is unchanged.
 *
 */
errno_t ext4_filesystem_close(ext4_filesystem_t *fs)
{
        /* Write the superblock to the device */
        ext4_superblock_set_state(fs->superblock, EXT4_SUPERBLOCK_STATE_VALID_FS);
        errno_t rc = ext4_superblock_write_direct(fs->device, fs->superblock);
        if (rc != EOK)
                return rc;

        ext4_filesystem_fini(fs);
        return EOK;
}

/** Check filesystem's features, if supported by this driver
 *
 * Function can return EOK and set read_only flag. It mean's that
 * there are some not-supported features, that can cause problems
 * during some write operations.
 *
 * @param fs        Filesystem to be checked
 * @param read_only Place to write flag saying whether filesystem
 *                  should be mounted only for reading
 *
 * @return Error code
 *
 */
static errno_t ext4_filesystem_check_features(ext4_filesystem_t *fs,
    bool *read_only)
{
        /* Feature flags are present only in higher revisions */
        if (ext4_superblock_get_rev_level(fs->superblock) == 0) {
                *read_only = false;
                return EOK;
        }
        
        /*
         * Check incompatible features - if filesystem has some,
         * volume can't be mounted
         */
        uint32_t incompatible_features;
        incompatible_features =
            ext4_superblock_get_features_incompatible(fs->superblock);
        incompatible_features &= ~EXT4_FEATURE_INCOMPAT_SUPP;
        if (incompatible_features > 0)
                return ENOTSUP;
        
        /*
         * Check read-only features, if filesystem has some,
         * volume can be mount only in read-only mode
         */
        uint32_t compatible_read_only;
        compatible_read_only =
            ext4_superblock_get_features_read_only(fs->superblock);
        compatible_read_only &= ~EXT4_FEATURE_RO_COMPAT_SUPP;
        if (compatible_read_only > 0) {
                *read_only = true;
                return EOK;
        }
        
        return EOK;
}


/** Convert block address to relative index in block group.
 *
 * @param sb         Superblock pointer
 * @param block_addr Block number to convert
 *
 * @return Relative number of block
 *
 */
uint32_t ext4_filesystem_blockaddr2_index_in_group(ext4_superblock_t *sb,
    uint32_t block_addr)
{
        uint32_t blocks_per_group = ext4_superblock_get_blocks_per_group(sb);
        uint32_t first_block = ext4_superblock_get_first_data_block(sb);
        
        /* First block == 0 or 1 */
        if (first_block == 0)
                return block_addr % blocks_per_group;
        else
                return (block_addr - 1) % blocks_per_group;
}


/** Convert relative block address in group to absolute address.
 *
 * @param sb Superblock pointer
 *
 * @return Absolute block address
 *
 */
uint32_t ext4_filesystem_index_in_group2blockaddr(ext4_superblock_t *sb,
    uint32_t index, uint32_t bgid)
{
        uint32_t blocks_per_group = ext4_superblock_get_blocks_per_group(sb);
        
        if (ext4_superblock_get_first_data_block(sb) == 0)
                return bgid * blocks_per_group + index;
        else
                return bgid * blocks_per_group + index + 1;
}

/** Convert the absolute block number to group number
 *
 * @param sb    Pointer to the superblock
 * @param b     Absolute block number
 *
 * @return      Group number
 */
uint32_t ext4_filesystem_blockaddr2group(ext4_superblock_t *sb, uint64_t b)
{
        uint32_t blocks_per_group = ext4_superblock_get_blocks_per_group(sb);
        uint32_t first_block = ext4_superblock_get_first_data_block(sb);

        return (b - first_block) / blocks_per_group;
}

/** Initialize block bitmap in block group.
 *
 * @param bg_ref Reference to block group
 *
 * @return Error code
 *
 */
static errno_t ext4_filesystem_init_block_bitmap(ext4_block_group_ref_t *bg_ref)
{
        uint64_t itb;
        uint32_t sz;
        uint32_t i;

        /* Load bitmap */
        ext4_superblock_t *sb = bg_ref->fs->superblock;
        uint64_t bitmap_block_addr = ext4_block_group_get_block_bitmap(
            bg_ref->block_group, bg_ref->fs->superblock);
        uint64_t bitmap_inode_addr = ext4_block_group_get_inode_bitmap(
            bg_ref->block_group, bg_ref->fs->superblock);
        
        block_t *bitmap_block;
        errno_t rc = block_get(&bitmap_block, bg_ref->fs->device,
            bitmap_block_addr, BLOCK_FLAGS_NOREAD);
        if (rc != EOK)
                return rc;
        
        uint8_t *bitmap = bitmap_block->data;
        
        /* Initialize all bitmap bits to zero */
        uint32_t block_size = ext4_superblock_get_block_size(sb);
        memset(bitmap, 0, block_size);
        
        /* Determine the number of reserved blocks in the group */
        uint32_t reserved_cnt = ext4_filesystem_bg_get_backup_blocks(bg_ref);

        /* Set bits from to first block to first data block - 1 to one (allocated) */
        for (uint32_t block = 0; block < reserved_cnt; ++block)
                ext4_bitmap_set_bit(bitmap, block);

        uint32_t bitmap_block_gid = ext4_filesystem_blockaddr2group(sb,
            bitmap_block_addr);
        if (bitmap_block_gid == bg_ref->index) {
                ext4_bitmap_set_bit(bitmap,
                    ext4_filesystem_blockaddr2_index_in_group(sb, bitmap_block_addr));
        }

        uint32_t bitmap_inode_gid = ext4_filesystem_blockaddr2group(sb,
            bitmap_inode_addr);
        if (bitmap_inode_gid == bg_ref->index) {
                ext4_bitmap_set_bit(bitmap,
                    ext4_filesystem_blockaddr2_index_in_group(sb, bitmap_inode_addr));
        }

        itb = ext4_block_group_get_inode_table_first_block(bg_ref->block_group,
            sb);
        sz = ext4_filesystem_bg_get_itable_size(sb, bg_ref);

        for (i = 0; i < sz; ++i, ++itb) {
                uint32_t gid = ext4_filesystem_blockaddr2group(sb, itb);
                if (gid == bg_ref->index) {
                        ext4_bitmap_set_bit(bitmap,
                            ext4_filesystem_blockaddr2_index_in_group(sb, itb));
                }
        }

        bitmap_block->dirty = true;
        
        /* Save bitmap */
        return block_put(bitmap_block);
}

/** Initialize i-node bitmap in block group.
 *
 * @param bg_ref Reference to block group
 *
 * @return Error code
 *
 */
static errno_t ext4_filesystem_init_inode_bitmap(ext4_block_group_ref_t *bg_ref)
{
        /* Load bitmap */
        uint32_t bitmap_block_addr = ext4_block_group_get_inode_bitmap(
            bg_ref->block_group, bg_ref->fs->superblock);
        block_t *bitmap_block;
        
        errno_t rc = block_get(&bitmap_block, bg_ref->fs->device,
            bitmap_block_addr, BLOCK_FLAGS_NOREAD);
        if (rc != EOK)
                return rc;
        
        uint8_t *bitmap = bitmap_block->data;
        
        /* Initialize all bitmap bits to zero */
        uint32_t block_size = ext4_superblock_get_block_size(bg_ref->fs->superblock);
        uint32_t inodes_per_group =
            ext4_superblock_get_inodes_per_group(bg_ref->fs->superblock);
        memset(bitmap, 0, (inodes_per_group + 7) / 8);
        
        uint32_t start_bit = inodes_per_group;
        uint32_t end_bit = block_size * 8;
        
        uint32_t i;
        for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)
                ext4_bitmap_set_bit(bitmap, i);
        
        if (i < end_bit)
                memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);
        
        bitmap_block->dirty = true;
        
        /* Save bitmap */
        return block_put(bitmap_block);
}

/** Initialize i-node table in block group.
 *
 * @param bg_ref Reference to block group
 *
 * @return Error code
 *
 */
static errno_t ext4_filesystem_init_inode_table(ext4_block_group_ref_t *bg_ref)
{
        ext4_superblock_t *sb = bg_ref->fs->superblock;
        
        uint32_t inode_size = ext4_superblock_get_inode_size(sb);
        uint32_t block_size = ext4_superblock_get_block_size(sb);
        uint32_t inodes_per_block = block_size / inode_size;
        
        uint32_t inodes_in_group =
            ext4_superblock_get_inodes_in_group(sb, bg_ref->index);
        
        uint32_t table_blocks = inodes_in_group / inodes_per_block;
        
        if (inodes_in_group % inodes_per_block)
                table_blocks++;
        
        /* Compute initialization bounds */
        uint32_t first_block = ext4_block_group_get_inode_table_first_block(
            bg_ref->block_group, sb);
        
        uint32_t last_block = first_block + table_blocks - 1;
        
        /* Initialization of all itable blocks */
        for (uint32_t fblock = first_block; fblock <= last_block; ++fblock) {
                block_t *block;
                errno_t rc = block_get(&block, bg_ref->fs->device, fblock,
                    BLOCK_FLAGS_NOREAD);
                if (rc != EOK)
                        return rc;
                
                memset(block->data, 0, block_size);
                block->dirty = true;
                
                rc = block_put(block);
                if (rc != EOK)
                        return rc;
        }
        
        return EOK;
}

/** Get reference to block group specified by index.
 *
 * @param fs   Filesystem to find block group on
 * @param bgid Index of block group to load
 * @param ref  Output pointer for reference
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_get_block_group_ref(ext4_filesystem_t *fs, uint32_t bgid,
    ext4_block_group_ref_t **ref)
{
        /* Allocate memory for new structure */
        ext4_block_group_ref_t *newref =
            malloc(sizeof(ext4_block_group_ref_t));
        if (newref == NULL)
                return ENOMEM;
        
        /* Compute number of descriptors, that fits in one data block */
        uint32_t descriptors_per_block =
            ext4_superblock_get_block_size(fs->superblock) /
            ext4_superblock_get_desc_size(fs->superblock);
        
        /* Block group descriptor table starts at the next block after superblock */
        aoff64_t block_id =
            ext4_superblock_get_first_data_block(fs->superblock) + 1;
        
        /* Find the block containing the descriptor we are looking for */
        block_id += bgid / descriptors_per_block;
        uint32_t offset = (bgid % descriptors_per_block) *
            ext4_superblock_get_desc_size(fs->superblock);
        
        /* Load block with descriptors */
        errno_t rc = block_get(&newref->block, fs->device, block_id, 0);
        if (rc != EOK) {
                free(newref);
                return rc;
        }
        
        /* Initialize in-memory representation */
        newref->block_group = newref->block->data + offset;
        newref->fs = fs;
        newref->index = bgid;
        newref->dirty = false;
        
        *ref = newref;
        
        if (ext4_block_group_has_flag(newref->block_group,
            EXT4_BLOCK_GROUP_BLOCK_UNINIT)) {
                rc = ext4_filesystem_init_block_bitmap(newref);
                if (rc != EOK) {
                        block_put(newref->block);
                        free(newref);
                        return rc;
                }
                
                ext4_block_group_clear_flag(newref->block_group,
                    EXT4_BLOCK_GROUP_BLOCK_UNINIT);
                
                newref->dirty = true;
        }
        
        if (ext4_block_group_has_flag(newref->block_group,
            EXT4_BLOCK_GROUP_INODE_UNINIT)) {
                rc = ext4_filesystem_init_inode_bitmap(newref);
                if (rc != EOK) {
                        block_put(newref->block);
                        free(newref);
                        return rc;
                }
                
                ext4_block_group_clear_flag(newref->block_group,
                    EXT4_BLOCK_GROUP_INODE_UNINIT);
                
                if (!ext4_block_group_has_flag(newref->block_group,
                    EXT4_BLOCK_GROUP_ITABLE_ZEROED)) {
                        rc = ext4_filesystem_init_inode_table(newref);
                        if (rc != EOK)
                                return rc;
                        
                        ext4_block_group_set_flag(newref->block_group,
                            EXT4_BLOCK_GROUP_ITABLE_ZEROED);
                }
                
                newref->dirty = true;
        }
        
        return EOK;
}

/** Compute checksum of block group descriptor.
 *
 * @param sb   Superblock
 * @param bgid Index of block group in the filesystem
 * @param bg   Block group to compute checksum for
 *
 * @return Checksum value
 *
 */
static uint16_t ext4_filesystem_bg_checksum(ext4_superblock_t *sb, uint32_t bgid,
    ext4_block_group_t *bg)
{
        /* If checksum not supported, 0 will be returned */
        uint16_t crc = 0;

        /* Compute the checksum only if the filesystem supports it */
        if (ext4_superblock_has_feature_read_only(sb,
            EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
                void *base = bg;
                void *checksum = &bg->checksum;
                
                uint32_t offset = (uint32_t) (checksum - base);
                
                /* Convert block group index to little endian */
                uint32_t le_group = host2uint32_t_le(bgid);
                
                /* Initialization */
                crc = crc16_ibm(~0, sb->uuid, sizeof(sb->uuid));
                
                /* Include index of block group */
                crc = crc16_ibm(crc, (uint8_t *) &le_group, sizeof(le_group));
                
                /* Compute crc from the first part (stop before checksum field) */
                crc = crc16_ibm(crc, (uint8_t *) bg, offset);
                
                /* Skip checksum */
                offset += sizeof(bg->checksum);
                
                /* Checksum of the rest of block group descriptor */
                if ((ext4_superblock_has_feature_incompatible(sb,
                    EXT4_FEATURE_INCOMPAT_64BIT)) &&
                    (offset < ext4_superblock_get_desc_size(sb)))
                        crc = crc16_ibm(crc, ((uint8_t *) bg) + offset,
                            ext4_superblock_get_desc_size(sb) - offset);
        }
        
        return crc;
}

/** Get the size of the block group's inode table
 *
 * @param sb     Pointer to the superblock
 * @param bg_ref Pointer to the block group reference
 *
 * @return       Size of the inode table in blocks.
 */
uint32_t ext4_filesystem_bg_get_itable_size(ext4_superblock_t *sb,
    ext4_block_group_ref_t *bg_ref)
{
        uint32_t itable_size;
        uint32_t block_group_count = ext4_superblock_get_block_group_count(sb);
        uint16_t inode_table_item_size = ext4_superblock_get_inode_size(sb);
        uint32_t inodes_per_group = ext4_superblock_get_inodes_per_group(sb);
        uint32_t block_size = ext4_superblock_get_block_size(sb);

        if (bg_ref->index < block_group_count - 1) {
                itable_size = inodes_per_group * inode_table_item_size;
        } else {
                /* Last block group could be smaller */
                uint32_t inodes_count_total = ext4_superblock_get_inodes_count(sb);
                itable_size =
                    (inodes_count_total - ((block_group_count - 1) * inodes_per_group)) *
                    inode_table_item_size;
        }

        return ROUND_UP(itable_size, block_size) / block_size;
}

/* Check if n is a power of p */
static bool is_power_of(uint32_t n, unsigned p)
{
        if (p == 1 && n != p)
                return false;

        while (n != p) {
                if (n < p)
                        return false;
                else if ((n % p) != 0)
                        return false;

                n /= p;
        }

        return true;
}

/** Get the number of blocks used by superblock + gdt + reserved gdt backups
 *
 * @param bg    Pointer to block group
 *
 * @return      Number of blocks
 */
uint32_t ext4_filesystem_bg_get_backup_blocks(ext4_block_group_ref_t *bg)
{
        uint32_t const idx = bg->index;
        uint32_t r = 0;
        bool has_backups = false;
        ext4_superblock_t *sb = bg->fs->superblock;

        /* First step: determine if the block group contains the backups */

        if (idx <= 1)
                has_backups = true;
        else {
                if (ext4_superblock_has_feature_compatible(sb,
                    EXT4_FEATURE_COMPAT_SPARSE_SUPER2)) {
                        uint32_t g1, g2;

                        ext4_superblock_get_backup_groups_sparse2(sb,
                            &g1, &g2);

                        if (idx == g1 || idx == g2)
                                has_backups = true;
                } else if (!ext4_superblock_has_feature_read_only(sb,
                    EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
                        /* Very old fs were all block groups have
                         * superblock and block descriptors backups.
                         */
                        has_backups = true;
                } else {
                        if ((idx & 1) && (is_power_of(idx, 3) ||
                            is_power_of(idx, 5) || is_power_of(idx, 7)))
                                has_backups = true;
                }
        }

        if (has_backups) {
                uint32_t bg_count;
                uint32_t bg_desc_sz;
                uint32_t gdt_table; /* Size of the GDT in blocks */
                uint32_t block_size = ext4_superblock_get_block_size(sb);

                /* Now we know that this block group has backups,
                 * we have to compute how many blocks are reserved
                 * for them
                 */

                if (idx == 0 && block_size == 1024) {
                        /* Special case for first group were the boot block
                         * resides
                         */
                        r++;
                }

                /* This accounts for the superblock */
                r++;

                /* Add the number of blocks used for the GDT */
                bg_count = ext4_superblock_get_block_group_count(sb);
                bg_desc_sz = ext4_superblock_get_desc_size(sb);
                gdt_table = ROUND_UP(bg_count * bg_desc_sz, block_size) /
                    block_size;

                r += gdt_table;

                /* And now the number of reserved GDT blocks */
                r += ext4_superblock_get_reserved_gdt_blocks(sb);
        }

        return r;
}

/** Put reference to block group.
 *
 * @param ref Pointer for reference to be put back
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_put_block_group_ref(ext4_block_group_ref_t *ref)
{
        /* Check if reference modified */
        if (ref->dirty) {
                /* Compute new checksum of block group */
                uint16_t checksum =
                    ext4_filesystem_bg_checksum(ref->fs->superblock, ref->index,
                    ref->block_group);
                ext4_block_group_set_checksum(ref->block_group, checksum);
                
                /* Mark block dirty for writing changes to physical device */
                ref->block->dirty = true;
        }
        
        /* Put back block, that contains block group descriptor */
        errno_t rc = block_put(ref->block);
        free(ref);
        
        return rc;
}

/** Get reference to i-node specified by index.
 *
 * @param fs    Filesystem to find i-node on
 * @param index Index of i-node to load
 * @oaram ref   Output pointer for reference
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_get_inode_ref(ext4_filesystem_t *fs, uint32_t index,
    ext4_inode_ref_t **ref)
{
        /* Allocate memory for new structure */
        ext4_inode_ref_t *newref =
            malloc(sizeof(ext4_inode_ref_t));
        if (newref == NULL)
                return ENOMEM;
        
        /* Compute number of i-nodes, that fits in one data block */
        uint32_t inodes_per_group =
            ext4_superblock_get_inodes_per_group(fs->superblock);
        
        /*
         * Inode numbers are 1-based, but it is simpler to work with 0-based
         * when computing indices
         */
        index -= 1;
        uint32_t block_group = index / inodes_per_group;
        uint32_t offset_in_group = index % inodes_per_group;
        
        /* Load block group, where i-node is located */
        ext4_block_group_ref_t *bg_ref;
        errno_t rc = ext4_filesystem_get_block_group_ref(fs, block_group, &bg_ref);
        if (rc != EOK) {
                free(newref);
                return rc;
        }
        
        /* Load block address, where i-node table is located */
        uint32_t inode_table_start =
            ext4_block_group_get_inode_table_first_block(bg_ref->block_group,
            fs->superblock);
        
        /* Put back block group reference (not needed more) */
        rc = ext4_filesystem_put_block_group_ref(bg_ref);
        if (rc != EOK) {
                free(newref);
                return rc;
        }
        
        /* Compute position of i-node in the block group */
        uint16_t inode_size = ext4_superblock_get_inode_size(fs->superblock);
        uint32_t block_size = ext4_superblock_get_block_size(fs->superblock);
        uint32_t byte_offset_in_group = offset_in_group * inode_size;
        
        /* Compute block address */
        aoff64_t block_id = inode_table_start + (byte_offset_in_group / block_size);
        rc = block_get(&newref->block, fs->device, block_id, 0);
        if (rc != EOK) {
                free(newref);
                return rc;
        }
        
        /* Compute position of i-node in the data block */
        uint32_t offset_in_block = byte_offset_in_group % block_size;
        newref->inode = newref->block->data + offset_in_block;
        
        /* We need to store the original value of index in the reference */
        newref->index = index + 1;
        newref->fs = fs;
        newref->dirty = false;
        
        *ref = newref;
        
        return EOK;
}

/** Put reference to i-node.
 *
 * @param ref Pointer for reference to be put back
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_put_inode_ref(ext4_inode_ref_t *ref)
{
        /* Check if reference modified */
        if (ref->dirty) {
                /* Mark block dirty for writing changes to physical device */
                ref->block->dirty = true;
        }
        
        /* Put back block, that contains i-node */
        errno_t rc = block_put(ref->block);
        free(ref);
        
        return rc;
}

/** Allocate new i-node in the filesystem.
 *
 * @param fs        Filesystem to allocated i-node on
 * @param inode_ref Output pointer to return reference to allocated i-node
 * @param flags     Flags to be set for newly created i-node
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_alloc_inode(ext4_filesystem_t *fs,
    ext4_inode_ref_t **inode_ref, int flags)
{
        /* Check if newly allocated i-node will be a directory */
        bool is_dir = false;
        if (flags & L_DIRECTORY)
                is_dir = true;
        
        /* Allocate inode by allocation algorithm */
        uint32_t index;
        errno_t rc = ext4_ialloc_alloc_inode(fs, &index, is_dir);
        if (rc != EOK)
                return rc;
        
        /* Load i-node from on-disk i-node table */
        rc = ext4_filesystem_get_inode_ref(fs, index, inode_ref);
        if (rc != EOK) {
                ext4_ialloc_free_inode(fs, index, is_dir);
                return rc;
        }
        
        /* Initialize i-node */
        ext4_inode_t *inode = (*inode_ref)->inode;
        
        uint16_t mode;
        if (is_dir) {
                /*
                 * Default directory permissions to be compatible with other systems
                 * 0777 (octal) == rwxrwxrwx
                 */
                
                mode = 0777;
                mode |= EXT4_INODE_MODE_DIRECTORY;
                ext4_inode_set_mode(fs->superblock, inode, mode);
                ext4_inode_set_links_count(inode, 1);  /* '.' entry */
        } else {
                /*
                 * Default file permissions to be compatible with other systems
                 * 0666 (octal) == rw-rw-rw-
                 */
                
                mode = 0666;
                mode |= EXT4_INODE_MODE_FILE;
                ext4_inode_set_mode(fs->superblock, inode, mode);
                ext4_inode_set_links_count(inode, 0);
        }
        
        ext4_inode_set_uid(inode, 0);
        ext4_inode_set_gid(inode, 0);
        ext4_inode_set_size(inode, 0);
        ext4_inode_set_access_time(inode, 0);
        ext4_inode_set_change_inode_time(inode, 0);
        ext4_inode_set_modification_time(inode, 0);
        ext4_inode_set_deletion_time(inode, 0);
        ext4_inode_set_blocks_count(fs->superblock, inode, 0);
        ext4_inode_set_flags(inode, 0);
        ext4_inode_set_generation(inode, 0);
        
        /* Reset blocks array */
        for (uint32_t i = 0; i < EXT4_INODE_BLOCKS; i++)
                inode->blocks[i] = 0;
        
        /* Initialize extents if needed */
        if (ext4_superblock_has_feature_incompatible(
            fs->superblock, EXT4_FEATURE_INCOMPAT_EXTENTS)) {
                ext4_inode_set_flag(inode, EXT4_INODE_FLAG_EXTENTS);
                
                /* Initialize extent root header */
                ext4_extent_header_t *header = ext4_inode_get_extent_header(inode);
                ext4_extent_header_set_depth(header, 0);
                ext4_extent_header_set_entries_count(header, 0);
                ext4_extent_header_set_generation(header, 0);
                ext4_extent_header_set_magic(header, EXT4_EXTENT_MAGIC);
                
                uint16_t max_entries = (EXT4_INODE_BLOCKS * sizeof(uint32_t) -
                    sizeof(ext4_extent_header_t)) / sizeof(ext4_extent_t);
                
                ext4_extent_header_set_max_entries_count(header, max_entries);
        }
        
        (*inode_ref)->dirty = true;
        
        return EOK;
}

/** Release i-node and mark it as free.
 *
 * @param inode_ref I-node to be released
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_free_inode(ext4_inode_ref_t *inode_ref)
{
        ext4_filesystem_t *fs = inode_ref->fs;
        
        /* For extents must be data block destroyed by other way */
        if ((ext4_superblock_has_feature_incompatible(fs->superblock,
            EXT4_FEATURE_INCOMPAT_EXTENTS)) &&
            (ext4_inode_has_flag(inode_ref->inode, EXT4_INODE_FLAG_EXTENTS))) {
                /* Data structures are released during truncate operation... */
                goto finish;
        }
        
        /* Release all indirect (no data) blocks */
        
        /* 1) Single indirect */
        uint32_t fblock = ext4_inode_get_indirect_block(inode_ref->inode, 0);
        if (fblock != 0) {
                errno_t rc = ext4_balloc_free_block(inode_ref, fblock);
                if (rc != EOK)
                        return rc;
                
                ext4_inode_set_indirect_block(inode_ref->inode, 0, 0);
        }
        
        block_t *block;
        uint32_t block_size = ext4_superblock_get_block_size(fs->superblock);
        uint32_t count = block_size / sizeof(uint32_t);
        
        /* 2) Double indirect */
        fblock = ext4_inode_get_indirect_block(inode_ref->inode, 1);
        if (fblock != 0) {
                errno_t rc = block_get(&block, fs->device, fblock, BLOCK_FLAGS_NONE);
                if (rc != EOK)
                        return rc;
                
                uint32_t ind_block;
                for (uint32_t offset = 0; offset < count; ++offset) {
                        ind_block = uint32_t_le2host(((uint32_t *) block->data)[offset]);
                        
                        if (ind_block != 0) {
                                rc = ext4_balloc_free_block(inode_ref, ind_block);
                                if (rc != EOK) {
                                        block_put(block);
                                        return rc;
                                }
                        }
                }
                
                rc = block_put(block);
                if (rc != EOK)
                        return rc;

                rc = ext4_balloc_free_block(inode_ref, fblock);
                if (rc != EOK)
                        return rc;
                
                ext4_inode_set_indirect_block(inode_ref->inode, 1, 0);
        }
        
        /* 3) Tripple indirect */
        block_t *subblock;
        fblock = ext4_inode_get_indirect_block(inode_ref->inode, 2);
        if (fblock != 0) {
                errno_t rc = block_get(&block, fs->device, fblock, BLOCK_FLAGS_NONE);
                if (rc != EOK)
                        return rc;
                
                uint32_t ind_block;
                for (uint32_t offset = 0; offset < count; ++offset) {
                        ind_block = uint32_t_le2host(((uint32_t *) block->data)[offset]);
                        
                        if (ind_block != 0) {
                                rc = block_get(&subblock, fs->device, ind_block,
                                    BLOCK_FLAGS_NONE);
                                if (rc != EOK) {
                                        block_put(block);
                                        return rc;
                                }
                                
                                uint32_t ind_subblock;
                                for (uint32_t suboffset = 0; suboffset < count;
                                    ++suboffset) {
                                        ind_subblock = uint32_t_le2host(((uint32_t *)
                                            subblock->data)[suboffset]);
                                        
                                        if (ind_subblock != 0) {
                                                rc = ext4_balloc_free_block(inode_ref, ind_subblock);
                                                if (rc != EOK) {
                                                        block_put(subblock);
                                                        block_put(block);
                                                        return rc;
                                                }
                                        }
                                }
                                
                                rc = block_put(subblock);
                                if (rc != EOK) {
                                        block_put(block);
                                        return rc;
                                }
                        }
                        
                        rc = ext4_balloc_free_block(inode_ref, ind_block);
                        if (rc != EOK) {
                                block_put(block);
                                return rc;
                        }
                }
                
                rc = block_put(block);
                if (rc != EOK)
                        return rc;

                rc = ext4_balloc_free_block(inode_ref, fblock);
                if (rc != EOK)
                        return rc;
                
                ext4_inode_set_indirect_block(inode_ref->inode, 2, 0);
        }
        
finish:
        /* Mark inode dirty for writing to the physical device */
        inode_ref->dirty = true;
        
        /* Free block with extended attributes if present */
        uint32_t xattr_block = ext4_inode_get_file_acl(
            inode_ref->inode, fs->superblock);
        if (xattr_block) {
                errno_t rc = ext4_balloc_free_block(inode_ref, xattr_block);
                if (rc != EOK)
                        return rc;
                
                ext4_inode_set_file_acl(inode_ref->inode, fs->superblock, 0);
        }
        
        /* Free inode by allocator */
        errno_t rc;
        if (ext4_inode_is_type(fs->superblock, inode_ref->inode,
            EXT4_INODE_MODE_DIRECTORY))
                rc = ext4_ialloc_free_inode(fs, inode_ref->index, true);
        else
                rc = ext4_ialloc_free_inode(fs, inode_ref->index, false);
        
        return rc;
}

/** Truncate i-node data blocks.
 *
 * @param inode_ref I-node to be truncated
 * @param new_size  New size of inode (must be < current size)
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_truncate_inode(ext4_inode_ref_t *inode_ref,
    aoff64_t new_size)
{
        ext4_superblock_t *sb = inode_ref->fs->superblock;
        
        /* Check flags, if i-node can be truncated */
        if (!ext4_inode_can_truncate(sb, inode_ref->inode))
                return EINVAL;
        
        /* If sizes are equal, nothing has to be done. */
        aoff64_t old_size = ext4_inode_get_size(sb, inode_ref->inode);
        if (old_size == new_size)
                return EOK;
        
        /* It's not suppported to make the larger file by truncate operation */
        if (old_size < new_size)
                return EINVAL;
        
        /* Compute how many blocks will be released */
        aoff64_t size_diff = old_size - new_size;
        uint32_t block_size  = ext4_superblock_get_block_size(sb);
        uint32_t diff_blocks_count = size_diff / block_size;
        if (size_diff % block_size != 0)
                diff_blocks_count++;
        
        uint32_t old_blocks_count = old_size / block_size;
        if (old_size % block_size != 0)
                old_blocks_count++;
        
        if ((ext4_superblock_has_feature_incompatible(inode_ref->fs->superblock,
            EXT4_FEATURE_INCOMPAT_EXTENTS)) &&
            (ext4_inode_has_flag(inode_ref->inode, EXT4_INODE_FLAG_EXTENTS))) {
                /* Extents require special operation */
                errno_t rc = ext4_extent_release_blocks_from(inode_ref,
                    old_blocks_count - diff_blocks_count);
                if (rc != EOK)
                        return rc;
        } else {
                /* Release data blocks from the end of file */
                
                /* Starting from 1 because of logical blocks are numbered from 0 */
                for (uint32_t i = 1; i <= diff_blocks_count; ++i) {
                        errno_t rc = ext4_filesystem_release_inode_block(inode_ref,
                            old_blocks_count - i);
                        if (rc != EOK)
                                return rc;
                }
        }
        
        /* Update i-node */
        ext4_inode_set_size(inode_ref->inode, new_size);
        inode_ref->dirty = true;
        
        return EOK;
}

/** Get physical block address by logical index of the block.
 *
 * @param inode_ref I-node to read block address from
 * @param iblock    Logical index of block
 * @param fblock    Output pointer for return physical block address
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_get_inode_data_block_index(ext4_inode_ref_t *inode_ref,
    aoff64_t iblock, uint32_t *fblock)
{
        ext4_filesystem_t *fs = inode_ref->fs;
        
        /* For empty file is situation simple */
        if (ext4_inode_get_size(fs->superblock, inode_ref->inode) == 0) {
                *fblock = 0;
                return EOK;
        }
        
        uint32_t current_block;
        
        /* Handle i-node using extents */
        if ((ext4_superblock_has_feature_incompatible(fs->superblock,
            EXT4_FEATURE_INCOMPAT_EXTENTS)) &&
            (ext4_inode_has_flag(inode_ref->inode, EXT4_INODE_FLAG_EXTENTS))) {
                errno_t rc = ext4_extent_find_block(inode_ref, iblock, &current_block);
                if (rc != EOK)
                        return rc;
                
                *fblock = current_block;
                return EOK;
        }
        
        ext4_inode_t *inode = inode_ref->inode;
        
        /* Direct block are read directly from array in i-node structure */
        if (iblock < EXT4_INODE_DIRECT_BLOCK_COUNT) {
                current_block = ext4_inode_get_direct_block(inode, (uint32_t) iblock);
                *fblock = current_block;
                return EOK;
        }
        
        /* Determine indirection level of the target block */
        unsigned int level = 0;
        for (unsigned int i = 1; i < 4; i++) {
                if (iblock < fs->inode_block_limits[i]) {
                        level = i;
                        break;
                }
        }
        
        if (level == 0)
                return EIO;
        
        /* Compute offsets for the topmost level */
        aoff64_t block_offset_in_level =
            iblock - fs->inode_block_limits[level - 1];
        current_block = ext4_inode_get_indirect_block(inode, level - 1);
        uint32_t offset_in_block =
            block_offset_in_level / fs->inode_blocks_per_level[level - 1];
        
        /* Sparse file */
        if (current_block == 0) {
                *fblock = 0;
                return EOK;
        }
        
        block_t *block;
        
        /*
         * Navigate through other levels, until we find the block number
         * or find null reference meaning we are dealing with sparse file
         */
        while (level > 0) {
                /* Load indirect block */
                errno_t rc = block_get(&block, fs->device, current_block, 0);
                if (rc != EOK)
                        return rc;
                
                /* Read block address from indirect block */
                current_block =
                    uint32_t_le2host(((uint32_t *) block->data)[offset_in_block]);
                
                /* Put back indirect block untouched */
                rc = block_put(block);
                if (rc != EOK)
                        return rc;
                
                /* Check for sparse file */
                if (current_block == 0) {
                        *fblock = 0;
                        return EOK;
                }
                
                /* Jump to the next level */
                level--;
                
                /* Termination condition - we have address of data block loaded */
                if (level == 0)
                        break;
                
                /* Visit the next level */
                block_offset_in_level %= fs->inode_blocks_per_level[level];
                offset_in_block =
                    block_offset_in_level / fs->inode_blocks_per_level[level - 1];
        }
        
        *fblock = current_block;
        
        return EOK;
}

/** Set physical block address for the block logical address into the i-node.
 *
 * @param inode_ref I-node to set block address to
 * @param iblock    Logical index of block
 * @param fblock    Physical block address
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_set_inode_data_block_index(ext4_inode_ref_t *inode_ref,
    aoff64_t iblock, uint32_t fblock)
{
        ext4_filesystem_t *fs = inode_ref->fs;
        
        /* Handle inode using extents */
        if ((ext4_superblock_has_feature_compatible(fs->superblock,
            EXT4_FEATURE_INCOMPAT_EXTENTS)) &&
            (ext4_inode_has_flag(inode_ref->inode, EXT4_INODE_FLAG_EXTENTS))) {
                /* Not reachable */
                return ENOTSUP;
        }
        
        /* Handle simple case when we are dealing with direct reference */
        if (iblock < EXT4_INODE_DIRECT_BLOCK_COUNT) {
                ext4_inode_set_direct_block(inode_ref->inode, (uint32_t) iblock, fblock);
                inode_ref->dirty = true;
                
                return EOK;
        }
        
        /* Determine the indirection level needed to get the desired block */
        unsigned int level = 0;
        for (unsigned int i = 1; i < 4; i++) {
                if (iblock < fs->inode_block_limits[i]) {
                        level = i;
                        break;
                }
        }
        
        if (level == 0)
                return EIO;
        
        uint32_t block_size = ext4_superblock_get_block_size(fs->superblock);
        
        /* Compute offsets for the topmost level */
        aoff64_t block_offset_in_level =
            iblock - fs->inode_block_limits[level - 1];
        uint32_t current_block =
            ext4_inode_get_indirect_block(inode_ref->inode, level - 1);
        uint32_t offset_in_block =
            block_offset_in_level / fs->inode_blocks_per_level[level - 1];
        
        uint32_t new_block_addr;
        block_t *block;
        block_t *new_block;
        
        /* Is needed to allocate indirect block on the i-node level */
        if (current_block == 0) {
                /* Allocate new indirect block */
                errno_t rc = ext4_balloc_alloc_block(inode_ref, &new_block_addr);
                if (rc != EOK)
                        return rc;
                
                /* Update i-node */
                ext4_inode_set_indirect_block(inode_ref->inode, level - 1,
                    new_block_addr);
                inode_ref->dirty = true;
                
                /* Load newly allocated block */
                rc = block_get(&new_block, fs->device, new_block_addr,
                    BLOCK_FLAGS_NOREAD);
                if (rc != EOK) {
                        ext4_balloc_free_block(inode_ref, new_block_addr);
                        return rc;
                }
                
                /* Initialize new block */
                memset(new_block->data, 0, block_size);
                new_block->dirty = true;
                
                /* Put back the allocated block */
                rc = block_put(new_block);
                if (rc != EOK)
                        return rc;
                
                current_block = new_block_addr;
        }
        
        /*
         * Navigate through other levels, until we find the block number
         * or find null reference meaning we are dealing with sparse file
         */
        while (level > 0) {
                errno_t rc = block_get(&block, fs->device, current_block, 0);
                if (rc != EOK)
                        return rc;
                
                current_block =
                    uint32_t_le2host(((uint32_t *) block->data)[offset_in_block]);
                
                if ((level > 1) && (current_block == 0)) {
                        /* Allocate new block */
                        rc = ext4_balloc_alloc_block(inode_ref, &new_block_addr);
                        if (rc != EOK) {
                                block_put(block);
                                return rc;
                        }
                        
                        /* Load newly allocated block */
                        rc = block_get(&new_block, fs->device, new_block_addr,
                            BLOCK_FLAGS_NOREAD);
                        if (rc != EOK) {
                                block_put(block);
                                return rc;
                        }
                        
                        /* Initialize allocated block */
                        memset(new_block->data, 0, block_size);
                        new_block->dirty = true;
                        
                        rc = block_put(new_block);
                        if (rc != EOK) {
                                block_put(block);
                                return rc;
                        }
                        
                        /* Write block address to the parent */
                        ((uint32_t *) block->data)[offset_in_block] =
                            host2uint32_t_le(new_block_addr);
                        block->dirty = true;
                        current_block = new_block_addr;
                }
                
                /* Will be finished, write the fblock address */
                if (level == 1) {
                        ((uint32_t *) block->data)[offset_in_block] =
                            host2uint32_t_le(fblock);
                        block->dirty = true;
                }
                
                rc = block_put(block);
                if (rc != EOK)
                        return rc;
                
                level--;
                
                /*
                 * If we are on the last level, break here as
                 * there is no next level to visit
                 */
                if (level == 0)
                        break;
                
                /* Visit the next level */
                block_offset_in_level %= fs->inode_blocks_per_level[level];
                offset_in_block =
                    block_offset_in_level / fs->inode_blocks_per_level[level - 1];
        }
        
        return EOK;
}

/** Release data block from i-node
 *
 * @param inode_ref I-node to release block from
 * @param iblock    Logical block to be released
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_release_inode_block(ext4_inode_ref_t *inode_ref,
    uint32_t iblock)
{
        uint32_t fblock;
        
        ext4_filesystem_t *fs = inode_ref->fs;
        
        /* Extents are handled otherwise = there is not support in this function */
        assert(!(ext4_superblock_has_feature_incompatible(fs->superblock,
            EXT4_FEATURE_INCOMPAT_EXTENTS) &&
            (ext4_inode_has_flag(inode_ref->inode, EXT4_INODE_FLAG_EXTENTS))));
        
        ext4_inode_t *inode = inode_ref->inode;
        
        /* Handle simple case when we are dealing with direct reference */
        if (iblock < EXT4_INODE_DIRECT_BLOCK_COUNT) {
                fblock = ext4_inode_get_direct_block(inode, iblock);
                
                /* Sparse file */
                if (fblock == 0)
                        return EOK;
                
                ext4_inode_set_direct_block(inode, iblock, 0);
                return ext4_balloc_free_block(inode_ref, fblock);
        }
        
        /* Determine the indirection level needed to get the desired block */
        unsigned int level = 0;
        for (unsigned int i = 1; i < 4; i++) {
                if (iblock < fs->inode_block_limits[i]) {
                        level = i;
                        break;
                }
        }
        
        if (level == 0)
                return EIO;
        
        /* Compute offsets for the topmost level */
        aoff64_t block_offset_in_level =
            iblock - fs->inode_block_limits[level - 1];
        uint32_t current_block =
            ext4_inode_get_indirect_block(inode, level - 1);
        uint32_t offset_in_block =
            block_offset_in_level / fs->inode_blocks_per_level[level - 1];
        
        /*
         * Navigate through other levels, until we find the block number
         * or find null reference meaning we are dealing with sparse file
         */
        block_t *block;
        while (level > 0) {
                
                /* Sparse check */
                if (current_block == 0)
                        return EOK;
                
                errno_t rc = block_get(&block, fs->device, current_block, 0);
                if (rc != EOK)
                        return rc;
                
                current_block =
                    uint32_t_le2host(((uint32_t *) block->data)[offset_in_block]);
                
                /* Set zero if physical data block address found */
                if (level == 1) {
                        ((uint32_t *) block->data)[offset_in_block] =
                            host2uint32_t_le(0);
                        block->dirty = true;
                }
                
                rc = block_put(block);
                if (rc != EOK)
                        return rc;
                
                level--;
                
                /*
                 * If we are on the last level, break here as
                 * there is no next level to visit
                 */
                if (level == 0)
                        break;
                
                /* Visit the next level */
                block_offset_in_level %= fs->inode_blocks_per_level[level];
                offset_in_block =
                    block_offset_in_level / fs->inode_blocks_per_level[level - 1];
        }
        
        fblock = current_block;
        if (fblock == 0)
                return EOK;
        
        /* Physical block is not referenced, it can be released */
        return ext4_balloc_free_block(inode_ref, fblock);
}

/** Append following logical block to the i-node.
 *
 * @param inode_ref I-node to append block to
 * @param fblock    Output physical block address of newly allocated block
 * @param iblock    Output logical number of newly allocated block
 *
 * @return Error code
 *
 */
errno_t ext4_filesystem_append_inode_block(ext4_inode_ref_t *inode_ref,
    uint32_t *fblock, uint32_t *iblock)
{
        /* Handle extents separately */
        if ((ext4_superblock_has_feature_incompatible(inode_ref->fs->superblock,
            EXT4_FEATURE_INCOMPAT_EXTENTS)) &&
            (ext4_inode_has_flag(inode_ref->inode, EXT4_INODE_FLAG_EXTENTS)))
                return ext4_extent_append_block(inode_ref, iblock, fblock, true);
        
        ext4_superblock_t *sb = inode_ref->fs->superblock;
        
        /* Compute next block index and allocate data block */
        uint64_t inode_size = ext4_inode_get_size(sb, inode_ref->inode);
        uint32_t block_size = ext4_superblock_get_block_size(sb);
        
        /* Align size i-node size */
        if ((inode_size % block_size) != 0)
                inode_size += block_size - (inode_size % block_size);
        
        /* Logical blocks are numbered from 0 */
        uint32_t new_block_idx = inode_size / block_size;
        
        /* Allocate new physical block */
        uint32_t phys_block;
        errno_t rc = ext4_balloc_alloc_block(inode_ref, &phys_block);
        if (rc != EOK)
                return rc;
        
        /* Add physical block address to the i-node */
        rc = ext4_filesystem_set_inode_data_block_index(inode_ref,
            new_block_idx, phys_block);
        if (rc != EOK) {
                ext4_balloc_free_block(inode_ref, phys_block);
                return rc;
        }
        
        /* Update i-node */
        ext4_inode_set_size(inode_ref->inode, inode_size + block_size);
        inode_ref->dirty = true;
        
        *fblock = phys_block;
        *iblock = new_block_idx;
        
        return EOK;
}

/**
 * @}
 */