source: mainline/uspace/lib/ext4/libext4_filesystem.c@ f2eece1

/*
 * 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        libext4_filesystem.c
 * @brief       More complex filesystem operations.
 */

#include <byteorder.h>
#include <errno.h>
#include <malloc.h>
#include "libext4.h"

/** Initialize filesystem and read all needed data.
 *
 * @param fs                            filesystem instance to be initialized
 * @param service_id            identifier if device with the filesystem
 * @return                                      error code
 */
int ext4_filesystem_init(ext4_filesystem_t *fs, service_id_t service_id)
{
        int rc;

        fs->device = service_id;

        // Initialize block library (4096 is size of communication channel)
        rc = block_init(EXCHANGE_SERIALIZE, fs->device, 4096);
        if (rc != EOK) {
                return rc;
        }

        // Read superblock from device to memory
        ext4_superblock_t *temp_superblock;
        rc = ext4_superblock_read_direct(fs->device, &temp_superblock);
        if (rc != EOK) {
                block_fini(fs->device);
                return rc;
        }

        // 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) {
                block_fini(fs->device);
                return ENOTSUP;
        }

        // Initialize block caching by libblock
        rc = block_cache_init(service_id, block_size, 0, CACHE_MODE_WT);
        if (rc != EOK) {
                block_fini(fs->device);
                return rc;
        }

        // 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 (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;

        return EOK;
}

/** Destroy filesystem instance (used by unmount operation).
 *
 * @param fs            filesystem to be destroyed
 * @param write_sb      flag if superblock should be written to device
 * @return                      error code
 */
int ext4_filesystem_fini(ext4_filesystem_t *fs, bool write_sb)
{
        int rc = EOK;

        // If needed, write the superblock to the device
        if (write_sb) {
                rc = ext4_superblock_write_direct(fs->device, fs->superblock);
        }

        // Release memory space for superblock
        free(fs->superblock);

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

        return rc;
}

/** Check sanity of the filesystem.
 *
 * Main is the check of the superblock structure.
 *
 * @param fs            filesystem to be checked
 * @return                      error code
 */
int ext4_filesystem_check_sanity(ext4_filesystem_t *fs)
{
        int rc;

        // Check superblock
        rc = ext4_superblock_check_sanity(fs->superblock);
        if (rc != EOK) {
                return rc;
        }

        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             flag if filesystem should be mounted only for reading
 * @return                              error code
 */
int 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;
}

/** 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
 */
int ext4_filesystem_get_block_group_ref(ext4_filesystem_t *fs, uint32_t bgid,
    ext4_block_group_ref_t **ref)
{
        int rc;

        // 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
        rc = block_get(&newref->block, fs->device, block_id, 0);
        if (rc != EOK) {
                free(newref);
                return rc;
        }

        // Inititialize in-memory representation
        newref->block_group = newref->block->data + offset;
        newref->fs = fs;
        newref->index = bgid;
        newref->dirty = false;

        *ref = newref;

        return EOK;
}

/** Compute checksum of block group descriptor.
 *
 * It uses crc functions from Linux kernel implementation.
 *
 * @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(~0, sb->uuid, sizeof(sb->uuid));

                // Include index of block group
                crc = crc16(crc, (uint8_t *)&le_group, sizeof(le_group));

                // Compute crc from the first part (stop before checksum field)
                crc = crc16(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(crc, ((uint8_t *)bg) + offset, ext4_superblock_get_desc_size(sb) - offset);
                }
        }

        return crc;

}

/** Put reference to block group.
 *
 * @oaram ref           pointer for reference to be put back
 * @return                      error code
 */
int ext4_filesystem_put_block_group_ref(ext4_block_group_ref_t *ref)
{
        int rc;

        // 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
        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
 */
int ext4_filesystem_get_inode_ref(ext4_filesystem_t *fs, uint32_t index,
    ext4_inode_ref_t **ref)
{
        int rc;

        // 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;
        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
 */
int ext4_filesystem_put_inode_ref(ext4_inode_ref_t *ref)
{
        int rc;

        // 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
        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
 */
int ext4_filesystem_alloc_inode(ext4_filesystem_t *fs,
                ext4_inode_ref_t **inode_ref, int flags)
{
        int rc;

        // 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;
        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;

        if (is_dir) {
                ext4_inode_set_mode(fs->superblock, inode, EXT4_INODE_MODE_DIRECTORY);
                ext4_inode_set_links_count(inode, 1); // '.' entry
        } else {
                ext4_inode_set_mode(fs->superblock, inode, EXT4_INODE_MODE_FILE);
                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
 */
int ext4_filesystem_free_inode(ext4_inode_ref_t *inode_ref)
{
        int rc;

        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) {
                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) {
                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;
                                }
                        }
                }

                block_put(block);
                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) {
                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;
                                                }
                                        }

                                }
                                block_put(subblock);

                        }

                        rc = ext4_balloc_free_block(inode_ref, ind_block);
                        if (rc != EOK) {
                                block_put(block);
                                return rc;
                        }


                }

                block_put(block);
                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 inode by allocator
        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);
        }
        if (rc != EOK) {
                return rc;
        }

        return EOK;
}

/** 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
 */
int ext4_filesystem_truncate_inode(
                ext4_inode_ref_t *inode_ref, aoff64_t new_size)
{
        int rc;

        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

                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) {
                        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
 */
int ext4_filesystem_get_inode_data_block_index(ext4_inode_ref_t *inode_ref,
                aoff64_t iblock, uint32_t *fblock)
{
        int rc;

        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)) {

                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
        int level = -1;
        for (int i = 1; i < 4; i++) {
                if (iblock < fs->inode_block_limits[i]) {
                        level = i;
                        break;
                }
        }

        if (level == -1) {
                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
                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 -= 1;

                // 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;
}

/** TODO comment
 *
 */
int ext4_filesystem_set_inode_data_block_index(ext4_inode_ref_t *inode_ref,
                aoff64_t iblock, uint32_t fblock)
{
        int rc;

        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 */
        int level = -1;
        for (int i = 1; i < 4; i++) {
                if (iblock < fs->inode_block_limits[i]) {
                        level = i;
                        break;
                }
        }

        if (level == -1) {
                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, *new_block;

        if (current_block == 0) {
                rc = ext4_balloc_alloc_block(inode_ref, &new_block_addr);
                if (rc != EOK) {
                        return rc;
                }

                ext4_inode_set_indirect_block(inode_ref->inode, level - 1, new_block_addr);

                inode_ref->dirty = true;

                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;
                }

                memset(new_block->data, 0, block_size);
                new_block->dirty = true;

                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) {

                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)) {
                        rc = ext4_balloc_alloc_block(inode_ref, &new_block_addr);
                        if (rc != EOK) {
                                block_put(block);
                                return rc;
                        }

                        rc = block_get(&new_block, fs->device, new_block_addr, BLOCK_FLAGS_NOREAD);
                        if (rc != EOK) {
                                block_put(block);
                                return rc;
                        }

                        memset(new_block->data, 0, block_size);
                        new_block->dirty = true;

                        rc = block_put(new_block);
                        if (rc != EOK) {
                                block_put(block);
                                return rc;
                        }

                        ((uint32_t*)block->data)[offset_in_block] = host2uint32_t_le(new_block_addr);
                        block->dirty = true;
                        current_block = new_block_addr;
                }

                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 -= 1;

                /* 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;
}

/** TODO comment
 *
 */
int ext4_filesystem_release_inode_block(
                ext4_inode_ref_t *inode_ref, uint32_t iblock)
{
        int rc;

        uint32_t fblock;

        ext4_filesystem_t *fs = inode_ref->fs;

        // EXTENTS are handled otherwise
        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 */
        int level = -1;
        for (int i = 1; i < 4; i++) {
                if (iblock < fs->inode_block_limits[i]) {
                        level = i;
                        break;
                }
        }

        if (level == -1) {
                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) {
                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 (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 -= 1;

                /* 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;
        }

        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
 */
int ext4_filesystem_append_inode_block(ext4_inode_ref_t *inode_ref,
                uint32_t *fblock, uint32_t *iblock)
{
        int rc;

        EXT4FS_DBG("");

        // 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);

        }

        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;
        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;
}

/** Add orphaned i-node to the orphans linked list.
 *
 * @param inode_ref             i-node to be added to orphans list
 * @return                              error code
 */
int ext4_filesystem_add_orphan(ext4_inode_ref_t *inode_ref)
{
        uint32_t next_orphan = ext4_superblock_get_last_orphan(
                        inode_ref->fs->superblock);

        // Deletion time is used for holding next item of the list
        ext4_inode_set_deletion_time(inode_ref->inode, next_orphan);

        // Head of the list is in the superblock
        ext4_superblock_set_last_orphan(
                        inode_ref->fs->superblock, inode_ref->index);
        inode_ref->dirty = true;

        return EOK;
}

/** Delete orphaned i-node from the orphans linked list.
 *
 * @param inode_ref             i-node to be deleted from the orphans list
 * @return                              error code
 */
int ext4_filesystem_delete_orphan(ext4_inode_ref_t *inode_ref)
{
        int rc;

        // Get head of the linked list
        uint32_t last_orphan = ext4_superblock_get_last_orphan(
                        inode_ref->fs->superblock);
        assert(last_orphan > 0);

        uint32_t next_orphan = ext4_inode_get_deletion_time(inode_ref->inode);

        // Check if the head is the target
        if (last_orphan == inode_ref->index) {
                ext4_superblock_set_last_orphan(inode_ref->fs->superblock, next_orphan);
                ext4_inode_set_deletion_time(inode_ref->inode, 0);
                inode_ref->dirty = true;
                return EOK;
        }

        ext4_inode_ref_t *current;
        rc = ext4_filesystem_get_inode_ref(inode_ref->fs, last_orphan, &current);
        if (rc != EOK) {
                return rc;
        }

        next_orphan = ext4_inode_get_deletion_time(current->inode);

        bool found = false;

        // Walk thourgh the linked list
        while (next_orphan != 0) {

                // Found?
                if (next_orphan == inode_ref->index) {
                        next_orphan = ext4_inode_get_deletion_time(inode_ref->inode);
                        ext4_inode_set_deletion_time(current->inode, next_orphan);
                        current->dirty = true;
                        found = true;
                        break;
                }

                ext4_filesystem_put_inode_ref(current);

                rc = ext4_filesystem_get_inode_ref(inode_ref->fs, next_orphan, &current);
                if (rc != EOK) {
                        return rc;
                }
                next_orphan = ext4_inode_get_deletion_time(current->inode);

        }

        if (found) {
                ext4_inode_set_deletion_time(inode_ref->inode, 0);
        }

        rc = ext4_filesystem_put_inode_ref(current);
        if (rc != EOK) {
                return rc;
        }

        if (!found) {
                return ENOENT;
        }

        return EOK;
}

/**
 * @}
 */