/*
 * Copyright (c) 2018 Jiri Svoboda
 * 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/directory.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 *);
static errno_t ext4_filesystem_init_block_groups(ext4_filesystem_t *);
static errno_t ext4_filesystem_alloc_this_inode(ext4_filesystem_t *,
    uint32_t, ext4_inode_ref_t **, int);
static uint32_t ext4_filesystem_inodes_per_block(ext4_superblock_t *);

/** 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);
}

/** Create lost+found directory.
 *
 * @param fs Filesystem
 * @return EOK on success or error code
 */
static errno_t ext4_filesystem_create_lost_found(ext4_filesystem_t *fs,
    ext4_inode_ref_t *root_dir_ref)
{
	errno_t rc;
	ext4_inode_ref_t *inode_ref;

	rc = ext4_filesystem_alloc_inode(fs, &inode_ref, L_DIRECTORY);
	if (rc != EOK)
		goto error;

	rc = ext4_directory_add_entry(inode_ref, ".", inode_ref);
	if (rc != EOK)
		goto error;

	rc = ext4_directory_add_entry(inode_ref, "..", root_dir_ref);
	if (rc != EOK)
		goto error;

	rc = ext4_directory_add_entry(root_dir_ref, "lost+found", inode_ref);
	if (rc != EOK)
		goto error;

	inode_ref->dirty = true;

	uint16_t nlinks = ext4_inode_get_links_count(inode_ref->inode);
	ext4_inode_set_links_count(inode_ref->inode, nlinks + 1);

	rc = ext4_filesystem_put_inode_ref(inode_ref);
	if (rc != EOK)
		goto error;

error:
	return rc;
}

/** Create root directory.
 *
 * @param fs Filesystem
 * @return EOK on success or error code
 */
static errno_t ext4_filesystem_create_root_dir(ext4_filesystem_t *fs)
{
	errno_t rc;
	ext4_inode_ref_t *inode_ref;

	rc = ext4_filesystem_get_inode_ref(fs, EXT4_INODE_ROOT_INDEX,
	    &inode_ref);
	if (rc != EOK)
		goto error;

	inode_ref->dirty = true;

	rc = ext4_directory_add_entry(inode_ref, ".", inode_ref);
	if (rc != EOK)
		goto error;

	rc = ext4_directory_add_entry(inode_ref, "..", inode_ref);
	if (rc != EOK)
		goto error;

	uint16_t nlinks = ext4_inode_get_links_count(inode_ref->inode);
	ext4_inode_set_links_count(inode_ref->inode, nlinks + 1);

	rc = ext4_filesystem_create_lost_found(fs, inode_ref);
	if (rc != EOK)
		goto error;

	nlinks = ext4_inode_get_links_count(inode_ref->inode);
	ext4_inode_set_links_count(inode_ref->inode, nlinks + 1);

	rc = ext4_filesystem_put_inode_ref(inode_ref);
	if (rc != EOK)
		goto error;

error:
	return rc;
}

/** Create new filesystem.
 *
 * @param service_id Block device where to create new filesystem
 */
errno_t ext4_filesystem_create(service_id_t service_id)
{
	errno_t rc;
	ext4_superblock_t *superblock = NULL;
	ext4_filesystem_t *fs = NULL;
	size_t dev_bsize;
	aoff64_t dev_nblocks;
	ext4_inode_ref_t *inode_ref = NULL;
	bool block_inited = false;
	bool fs_inited = false;
	uint32_t idx;

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

	block_inited = true;

	/* Get device block size */
	rc = block_get_bsize(service_id, &dev_bsize);
	if (rc != EOK)
		goto err;

	/* Get device number of blocks */
	rc = block_get_nblocks(service_id, &dev_nblocks);
	if (rc != EOK)
		goto err;

	/* Create superblock */
	rc = ext4_superblock_create(dev_bsize, dev_nblocks, &superblock);
	if (rc != EOK)
		goto err;

	/* Write superblock to device */
	rc = ext4_superblock_write_direct(service_id, superblock);
	if (rc != EOK)
		goto err;

	block_fini(service_id);
	block_inited = false;
	ext4_superblock_release(superblock);
	superblock = NULL;

	fs = calloc(1, sizeof(ext4_filesystem_t));
	if (fs == NULL)
		goto err;

	/* Open file system */
	rc = ext4_filesystem_init(fs, service_id, CACHE_MODE_WT);
	if (rc != EOK)
		goto err;

	fs_inited = true;

	/* Init block groups */
	rc = ext4_filesystem_init_block_groups(fs);
	if (rc != EOK)
		goto err;

	/* Reserved i-nodes */
	for (idx = 1; idx < EXT4_REV0_FIRST_INO; idx++) {
		if (idx == EXT4_INODE_ROOT_INDEX) {
			rc = ext4_filesystem_alloc_this_inode(fs, idx,
			    &inode_ref, L_DIRECTORY);
			if (rc != EOK)
				goto error;

			rc = ext4_filesystem_put_inode_ref(inode_ref);
			if (rc != EOK)
				goto error;
		} else {
			/* Allocate inode by allocation algorithm */
			errno_t rc = ext4_ialloc_alloc_this_inode(fs, idx,
			    false);
			if (rc != EOK)
				return rc;

			rc = ext4_filesystem_get_inode_ref(fs, idx,
			    &inode_ref);
			if (rc != EOK)
				goto error;

			memset(inode_ref->inode, 0, ext4_superblock_get_inode_size(fs->superblock));
			inode_ref->dirty = true;

			rc = ext4_filesystem_put_inode_ref(inode_ref);
			if (rc != EOK)
				goto error;
		}
	}

	/* Create root directory */
	rc = ext4_filesystem_create_root_dir(fs);
	if (rc != EOK)
		goto err;

	/* Write superblock to device */
	rc = ext4_superblock_write_direct(service_id, fs->superblock);
	if (rc != EOK)
		goto err;

	ext4_filesystem_fini(fs);
	free(fs);
	return EOK;
err:
	if (fs_inited)
		ext4_filesystem_fini(fs);
	if (fs != NULL)
		free(fs);
	if (superblock != NULL)
		ext4_superblock_release(superblock);
	if (block_inited)
		block_fini(service_id);
	return rc;
error:
	return rc;
}

/** 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 group structures
 */
static errno_t ext4_filesystem_init_block_groups(ext4_filesystem_t *fs)
{
	errno_t rc;
	block_t *block;
	aoff64_t b;
	ext4_block_group_t *bg;
	ext4_superblock_t *sb = fs->superblock;
	ext4_block_group_ref_t *bg_ref;

	uint32_t block_group_count = ext4_superblock_get_block_group_count(sb);
	uint32_t block_size = ext4_superblock_get_block_size(sb);
	uint32_t desc_size = ext4_superblock_get_desc_size(fs->superblock);
	/* Number of descriptors per block */
	uint32_t descriptors_per_block =
	    ext4_superblock_get_block_size(fs->superblock) / desc_size;
	/* Block where block group descriptor (and first block group) starts */
	aoff64_t block_id =
	    ext4_superblock_get_first_data_block(fs->superblock) + 1;
	/* Number of blocks containing descriptor table */
	uint32_t dtable_blocks =
	    (block_group_count + descriptors_per_block - 1) /
	    descriptors_per_block;

	uint32_t bg_index;
	aoff64_t bg_block0;
	uint32_t dcnt;
	uint32_t i;
	uint32_t now;

	aoff64_t block_bitmap;
	aoff64_t inode_bitmap;
	aoff64_t inode_table;
	uint32_t free_blocks;
	uint32_t free_inodes;
	uint32_t used_dirs;
	uint32_t reserved;
	uint32_t inode_table_blocks;

	dcnt = block_group_count;

	/* Fill in block descriptors */
	b = block_id;
	bg_index = 0;
	bg_block0 = block_id;
	while (dcnt > 0) {
		rc = block_get(&block, fs->device, b, BLOCK_FLAGS_NOREAD);
		if (rc != EOK)
			return rc;

		if (dcnt > descriptors_per_block)
			now = descriptors_per_block;
		else
			now = dcnt;

		memset(block->data, 0, block_size);

		for (i = 0; i < now; i++) {
			bg = (ext4_block_group_t *) (block->data + i *
			    desc_size);

			block_bitmap = bg_block0 + dtable_blocks;
			inode_bitmap = block_bitmap + 1;
			inode_table = inode_bitmap + 1;

			free_blocks = ext4_superblock_get_blocks_in_group(sb,
			    bg_index);

			free_inodes =
			    ext4_filesystem_bg_get_itable_size(sb, bg_index) *
			    ext4_filesystem_inodes_per_block(sb);
			used_dirs = 0;

			ext4_block_group_set_block_bitmap(bg, sb, block_bitmap);
			ext4_block_group_set_inode_bitmap(bg, sb, inode_bitmap);
			ext4_block_group_set_inode_table_first_block(bg, sb,
			    inode_table);
			ext4_block_group_set_free_blocks_count(bg, sb,
			    free_blocks);
			ext4_block_group_set_free_inodes_count(bg, sb,
			    free_inodes);
			ext4_block_group_set_used_dirs_count(bg, sb,
			    used_dirs);

			/// XX Lazy
			ext4_block_group_set_flag(bg,
			    EXT4_BLOCK_GROUP_BLOCK_UNINIT);
			ext4_block_group_set_flag(bg,
			    EXT4_BLOCK_GROUP_INODE_UNINIT);

			bg_index++;
			bg_block0 += ext4_superblock_get_blocks_per_group(sb);
		}

		block->dirty = true;

		rc = block_put(block);
		if (rc != EOK)
			return rc;

		++b;
		dcnt -= now;
	}

	/* This initializes the bitmaps and inode table */
	for (bg_index = 0; bg_index < block_group_count; bg_index++) {
		rc = ext4_filesystem_get_block_group_ref(fs, bg_index, &bg_ref);
		if (rc != EOK)
			return rc;

		/*
		 * Adjust number of free blocks
		 */
		free_blocks = ext4_superblock_get_blocks_in_group(sb, bg_index);
		reserved = ext4_filesystem_bg_get_backup_blocks(bg_ref);
		inode_table_blocks = ext4_filesystem_bg_get_itable_size(sb,
		    bg_ref->index);
		/* One for block bitmap one for inode bitmap */
		free_blocks = free_blocks - reserved - 2 - inode_table_blocks;

		ext4_block_group_set_free_blocks_count(bg_ref->block_group,
		    sb, free_blocks);
		bg_ref->dirty = true;

		rc = ext4_filesystem_put_block_group_ref(bg_ref);
		if (rc != EOK)
			return rc;
	}

	return EOK;
}

/** 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);
	uint32_t blocks_group = ext4_superblock_get_blocks_per_group(sb);
	uint32_t bg_blocks = ext4_superblock_get_blocks_in_group(sb,
	    bg_ref->index);

	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->index);

	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));
		}
	}

	/* For last group need to mark blocks which are outside of the FS */
	for (uint32_t block = bg_blocks; block < blocks_group; block++) {
		ext4_bitmap_set_bit(bitmap, block);
	}

	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 block_size = ext4_superblock_get_block_size(sb);
	uint32_t inodes_per_block = ext4_filesystem_inodes_per_block(sb);

	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) {
				block_put(newref->block);
				free(newref);
				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_index Block group index
 *
 * @return         Size of the inode table in blocks.
 */
uint32_t ext4_filesystem_bg_get_itable_size(ext4_superblock_t *sb,
    uint32_t bg_index)
{
	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_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;
}

/** 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)
{
	return ext4_superblock_get_group_backup_blocks(bg->fs->superblock,
	    bg->index);
}

/** 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;
}

/** Initialize newly allocated i-node in the filesystem.
 *
 * @param fs        Filesystem to initialize i-node on
 * @param index     I-node index
 * @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
 *
 */
static errno_t ext4_filesystem_init_inode(ext4_filesystem_t *fs, uint32_t index,
    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;

	/* Load i-node from on-disk i-node table */
	errno_t 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;
}

/** 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;

	rc = ext4_filesystem_init_inode(fs, index, inode_ref, flags);
	if (rc != EOK) {
		ext4_ialloc_free_inode(fs, index, is_dir);
		return rc;
	}

	return EOK;
}

/** Allocate specific i-node in the filesystem.
 *
 * @param fs        Filesystem to allocated i-node on
 * @param index     Index of i-node to allocate
 * @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
 *
 */
static errno_t ext4_filesystem_alloc_this_inode(ext4_filesystem_t *fs,
    uint32_t index, 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 */
	errno_t rc = ext4_ialloc_alloc_this_inode(fs, index, is_dir);
	if (rc != EOK)
		return rc;

	rc = ext4_filesystem_init_inode(fs, index, inode_ref, flags);
	if (rc != EOK) {
		ext4_ialloc_free_inode(fs, index, is_dir);
		return rc;
	}

	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;
}

/** Get the number of inodes per block.
 *
 * @param sb Superblock
 * @return   Number of inodes per block
 */
static uint32_t ext4_filesystem_inodes_per_block(ext4_superblock_t *sb)
{
	uint32_t inode_size = ext4_superblock_get_inode_size(sb);
	uint32_t block_size = ext4_superblock_get_block_size(sb);

	return block_size / inode_size;
}

/**
 * @}
 */
