source: mainline/uspace/lib/ext4/src/extent.c@ 38d150e

/*
 * 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  extent.c
 * @brief Ext4 extent structures operations.
 */

#include <byteorder.h>
#include <errno.h>
#include <mem.h>
#include <stdlib.h>
#include "ext4/balloc.h"
#include "ext4/extent.h"
#include "ext4/inode.h"
#include "ext4/superblock.h"

/** Get logical number of the block covered by extent.
 *
 * @param extent Extent to load number from
 *
 * @return Logical number of the first block covered by extent
 *
 */
uint32_t ext4_extent_get_first_block(ext4_extent_t *extent)
{
        return uint32_t_le2host(extent->first_block);
}

/** Set logical number of the first block covered by extent.
 *
 * @param extent Extent to set number to
 * @param iblock Logical number of the first block covered by extent
 *
 */
void ext4_extent_set_first_block(ext4_extent_t *extent, uint32_t iblock)
{
        extent->first_block = host2uint32_t_le(iblock);
}

/** Get number of blocks covered by extent.
 *
 * @param extent Extent to load count from
 *
 * @return Number of blocks covered by extent
 *
 */
uint16_t ext4_extent_get_block_count(ext4_extent_t *extent)
{
        return uint16_t_le2host(extent->block_count);
}

/** Set number of blocks covered by extent.
 *
 * @param extent Extent to load count from
 * @param count  Number of blocks covered by extent
 *
 */
void ext4_extent_set_block_count(ext4_extent_t *extent, uint16_t count)
{
        extent->block_count = host2uint16_t_le(count);
}

/** Get physical number of the first block covered by extent.
 *
 * @param extent Extent to load number
 *
 * @return Physical number of the first block covered by extent
 *
 */
uint64_t ext4_extent_get_start(ext4_extent_t *extent)
{
        return ((uint64_t)uint16_t_le2host(extent->start_hi)) << 32 |
            ((uint64_t)uint32_t_le2host(extent->start_lo));
}

/** Set physical number of the first block covered by extent.
 *
 * @param extent Extent to load number
 * @param fblock Physical number of the first block covered by extent
 *
 */
void ext4_extent_set_start(ext4_extent_t *extent, uint64_t fblock)
{
        extent->start_lo = host2uint32_t_le((fblock << 32) >> 32);
        extent->start_hi = host2uint16_t_le((uint16_t)(fblock >> 32));
}

/** Get logical number of the block covered by extent index.
 *
 * @param index Extent index to load number from
 *
 * @return Logical number of the first block covered by extent index
 *
 */
uint32_t ext4_extent_index_get_first_block(ext4_extent_index_t *index)
{
        return uint32_t_le2host(index->first_block);
}

/** Set logical number of the block covered by extent index.
 *
 * @param index  Extent index to set number to
 * @param iblock Logical number of the first block covered by extent index
 *
 */
void ext4_extent_index_set_first_block(ext4_extent_index_t *index,
    uint32_t iblock)
{
        index->first_block = host2uint32_t_le(iblock);
}

/** Get physical number of block where the child node is located.
 *
 * @param index Extent index to load number from
 *
 * @return Physical number of the block with child node
 *
 */
uint64_t ext4_extent_index_get_leaf(ext4_extent_index_t *index)
{
        return ((uint64_t) uint16_t_le2host(index->leaf_hi)) << 32 |
            ((uint64_t)uint32_t_le2host(index->leaf_lo));
}

/** Set physical number of block where the child node is located.
 *
 * @param index  Extent index to set number to
 * @param fblock Ohysical number of the block with child node
 *
 */
void ext4_extent_index_set_leaf(ext4_extent_index_t *index, uint64_t fblock)
{
        index->leaf_lo = host2uint32_t_le((fblock << 32) >> 32);
        index->leaf_hi = host2uint16_t_le((uint16_t) (fblock >> 32));
}

/** Get magic value from extent header.
 *
 * @param header Extent header to load value from
 *
 * @return Magic value of extent header
 *
 */
uint16_t ext4_extent_header_get_magic(ext4_extent_header_t *header)
{
        return uint16_t_le2host(header->magic);
}

/** Set magic value to extent header.
 *
 * @param header Extent header to set value to
 * @param magic  Magic value of extent header
 *
 */
void ext4_extent_header_set_magic(ext4_extent_header_t *header, uint16_t magic)
{
        header->magic = host2uint16_t_le(magic);
}

/** Get number of entries from extent header
 *
 * @param header Extent header to get value from
 *
 * @return Number of entries covered by extent header
 *
 */
uint16_t ext4_extent_header_get_entries_count(ext4_extent_header_t *header)
{
        return uint16_t_le2host(header->entries_count);
}

/** Set number of entries to extent header
 *
 * @param header Extent header to set value to
 * @param count  Number of entries covered by extent header
 *
 */
void ext4_extent_header_set_entries_count(ext4_extent_header_t *header,
    uint16_t count)
{
        header->entries_count = host2uint16_t_le(count);
}

/** Get maximum number of entries from extent header
 *
 * @param header Extent header to get value from
 *
 * @return Maximum number of entries covered by extent header
 *
 */
uint16_t ext4_extent_header_get_max_entries_count(ext4_extent_header_t *header)
{
        return uint16_t_le2host(header->max_entries_count);
}

/** Set maximum number of entries to extent header
 *
 * @param header    Extent header to set value to
 * @param max_count Maximum number of entries covered by extent header
 *
 */
void ext4_extent_header_set_max_entries_count(ext4_extent_header_t *header,
    uint16_t max_count)
{
        header->max_entries_count = host2uint16_t_le(max_count);
}

/** Get depth of extent subtree.
 *
 * @param header Extent header to get value from
 *
 * @return Depth of extent subtree
 *
 */
uint16_t ext4_extent_header_get_depth(ext4_extent_header_t *header)
{
        return uint16_t_le2host(header->depth);
}

/** Set depth of extent subtree.
 *
 * @param header Extent header to set value to
 * @param depth  Depth of extent subtree
 *
 */
void ext4_extent_header_set_depth(ext4_extent_header_t *header, uint16_t depth)
{
        header->depth = host2uint16_t_le(depth);
}

/** Get generation from extent header
 *
 * @param header Extent header to get value from
 *
 * @return Generation
 *
 */
uint32_t ext4_extent_header_get_generation(ext4_extent_header_t *header)
{
        return uint32_t_le2host(header->generation);
}

/** Set generation to extent header
 *
 * @param header     Extent header to set value to
 * @param generation Generation
 *
 */
void ext4_extent_header_set_generation(ext4_extent_header_t *header,
    uint32_t generation)
{
        header->generation = host2uint32_t_le(generation);
}

/** Binary search in extent index node.
 *
 * @param header Extent header of index node
 * @param index  Output value - found index will be set here
 * @param iblock Logical block number to find in index node
 *
 */
static void ext4_extent_binsearch_idx(ext4_extent_header_t *header,
    ext4_extent_index_t **index, uint32_t iblock)
{
        ext4_extent_index_t *r;
        ext4_extent_index_t *l;
        ext4_extent_index_t *m;
        
        uint16_t entries_count =
            ext4_extent_header_get_entries_count(header);
        
        /* Initialize bounds */
        l = EXT4_EXTENT_FIRST_INDEX(header) + 1;
        r = EXT4_EXTENT_FIRST_INDEX(header) + entries_count - 1;
        
        /* Do binary search */
        while (l <= r) {
                m = l + (r - l) / 2;
                uint32_t first_block = ext4_extent_index_get_first_block(m);
                
                if (iblock < first_block)
                        r = m - 1;
                else
                        l = m + 1;
        }
        
        /* Set output value */
        *index = l - 1;
}

/** Binary search in extent leaf node.
 *
 * @param header Extent header of leaf node
 * @param extent Output value - found extent will be set here,
 *               or NULL if node is empty
 * @param iblock Logical block number to find in leaf node
 *
 */
static void ext4_extent_binsearch(ext4_extent_header_t *header,
    ext4_extent_t **extent, uint32_t iblock)
{
        ext4_extent_t *r;
        ext4_extent_t *l;
        ext4_extent_t *m;
        
        uint16_t entries_count =
            ext4_extent_header_get_entries_count(header);
        
        if (entries_count == 0) {
                /* this leaf is empty */
                *extent = NULL;
                return;
        }
        
        /* Initialize bounds */
        l = EXT4_EXTENT_FIRST(header) + 1;
        r = EXT4_EXTENT_FIRST(header) + entries_count - 1;
        
        /* Do binary search */
        while (l <= r) {
                m = l + (r - l) / 2;
                uint32_t first_block = ext4_extent_get_first_block(m);
                
                if (iblock < first_block)
                        r = m - 1;
                else
                        l = m + 1;
        }
        
        /* Set output value */
        *extent = l - 1;
}

/** Find physical block in the extent tree by logical block number.
 *
 * There is no need to save path in the tree during this algorithm.
 *
 * @param inode_ref I-node to load block from
 * @param iblock    Logical block number to find
 * @param fblock    Output value for physical block number
 *
 * @return Error code
 *
 */
int ext4_extent_find_block(ext4_inode_ref_t *inode_ref, uint32_t iblock,
    uint32_t *fblock)
{
        int rc = EOK;
        /* Compute bound defined by i-node size */
        uint64_t inode_size =
            ext4_inode_get_size(inode_ref->fs->superblock, inode_ref->inode);
        
        uint32_t block_size =
            ext4_superblock_get_block_size(inode_ref->fs->superblock);
        
        uint32_t last_idx = (inode_size - 1) / block_size;
        
        /* Check if requested iblock is not over size of i-node */
        if (iblock > last_idx) {
                *fblock = 0;
                return EOK;
        }
        
        block_t *block = NULL;
        
        /* Walk through extent tree */
        ext4_extent_header_t *header =
            ext4_inode_get_extent_header(inode_ref->inode);
        
        while (ext4_extent_header_get_depth(header) != 0) {
                /* Search index in node */
                ext4_extent_index_t *index;
                ext4_extent_binsearch_idx(header, &index, iblock);
                
                /* Load child node and set values for the next iteration */
                uint64_t child = ext4_extent_index_get_leaf(index);
                
                if (block != NULL) {
                        rc = block_put(block);
                        if (rc != EOK)
                                return rc;
                }
                
                rc = block_get(&block, inode_ref->fs->device, child,
                    BLOCK_FLAGS_NONE);
                if (rc != EOK)
                        return rc;
                
                header = (ext4_extent_header_t *)block->data;
        }
        
        /* Search extent in the leaf block */
        ext4_extent_t* extent = NULL;
        ext4_extent_binsearch(header, &extent, iblock);
        
        /* Prevent empty leaf */
        if (extent == NULL) {
                *fblock = 0;
        } else {
                /* Compute requested physical block address */
                uint32_t phys_block;
                uint32_t first = ext4_extent_get_first_block(extent);
                phys_block = ext4_extent_get_start(extent) + iblock - first;
                
                *fblock = phys_block;
        }
        
        /* Cleanup */
        if (block != NULL)
                rc = block_put(block);
        
        return rc;
}

/** Find extent for specified iblock.
 *
 * This function is used for finding block in the extent tree with
 * saving the path through the tree for possible future modifications.
 *
 * @param inode_ref I-node to read extent tree from
 * @param iblock    Iblock to find extent for
 * @param ret_path  Output value for loaded path from extent tree
 *
 * @return Error code
 *
 */
static int ext4_extent_find_extent(ext4_inode_ref_t *inode_ref, uint32_t iblock,
    ext4_extent_path_t **ret_path)
{
        ext4_extent_header_t *eh =
            ext4_inode_get_extent_header(inode_ref->inode);
        
        uint16_t depth = ext4_extent_header_get_depth(eh);
        
        ext4_extent_path_t *tmp_path;
        
        /* Added 2 for possible tree growing */
        tmp_path = malloc(sizeof(ext4_extent_path_t) * (depth + 2));
        if (tmp_path == NULL)
                return ENOMEM;
        
        /* Initialize structure for algorithm start */
        tmp_path[0].block = inode_ref->block;
        tmp_path[0].header = eh;
        
        /* Walk through the extent tree */
        uint16_t pos = 0;
        int rc;
        while (ext4_extent_header_get_depth(eh) != 0) {
                /* Search index in index node by iblock */
                ext4_extent_binsearch_idx(tmp_path[pos].header,
                    &tmp_path[pos].index, iblock);
                
                tmp_path[pos].depth = depth;
                tmp_path[pos].extent = NULL;
                
                assert(tmp_path[pos].index != NULL);
                
                /* Load information for the next iteration */
                uint64_t fblock = ext4_extent_index_get_leaf(tmp_path[pos].index);
                
                block_t *block;
                rc = block_get(&block, inode_ref->fs->device, fblock,
                    BLOCK_FLAGS_NONE);
                if (rc != EOK)
                        goto cleanup;
                
                pos++;
                
                eh = (ext4_extent_header_t *)block->data;
                tmp_path[pos].block = block;
                tmp_path[pos].header = eh;
        }
        
        tmp_path[pos].depth = 0;
        tmp_path[pos].extent = NULL;
        tmp_path[pos].index = NULL;
        
        /* Find extent in the leaf node */
        ext4_extent_binsearch(tmp_path[pos].header, &tmp_path[pos].extent, iblock);
        *ret_path = tmp_path;
        
        return EOK;
        
cleanup:
        ;

        int rc2 = EOK;

        /*
         * Put loaded blocks
         * From 1: 0 is a block with inode data
         */
        for (uint16_t i = 1; i < tmp_path->depth; ++i) {
                if (tmp_path[i].block) {
                        rc2 = block_put(tmp_path[i].block);
                        if (rc == EOK && rc2 != EOK)
                                rc = rc2;
                }
        }
        
        /* Destroy temporary data structure */
        free(tmp_path);
        
        return rc;
}

/** Release extent and all data blocks covered by the extent.
 *
 * @param inode_ref I-node to release extent and block from
 * @param extent    Extent to release
 *
 * @return Error code
 *
 */
static int ext4_extent_release(ext4_inode_ref_t *inode_ref,
    ext4_extent_t *extent)
{
        /* Compute number of the first physical block to release */
        uint64_t start = ext4_extent_get_start(extent);
        uint16_t block_count = ext4_extent_get_block_count(extent);
        
        return ext4_balloc_free_blocks(inode_ref, start, block_count);
}

/** Recursively release the whole branch of the extent tree.
 *
 * For each entry of the node release the subbranch and finally release
 * the node. In the leaf node all extents will be released.
 *
 * @param inode_ref I-node where the branch is released
 * @param index     Index in the non-leaf node to be released
 *                  with the whole subtree
 *
 * @return Error code
 *
 */
static int ext4_extent_release_branch(ext4_inode_ref_t *inode_ref,
                ext4_extent_index_t *index)
{
        uint32_t fblock = ext4_extent_index_get_leaf(index);
        
        block_t* block;
        int rc = block_get(&block, inode_ref->fs->device, fblock, BLOCK_FLAGS_NONE);
        if (rc != EOK)
                return rc;
        
        ext4_extent_header_t *header = block->data;
        
        if (ext4_extent_header_get_depth(header)) {
                /* The node is non-leaf, do recursion */
                ext4_extent_index_t *idx = EXT4_EXTENT_FIRST_INDEX(header);
                
                /* Release all subbranches */
                for (uint32_t i = 0;
                    i < ext4_extent_header_get_entries_count(header);
                    ++i, ++idx) {
                        rc = ext4_extent_release_branch(inode_ref, idx);
                        if (rc != EOK)
                                return rc;
                }
        } else {
                /* Leaf node reached */
                ext4_extent_t *ext = EXT4_EXTENT_FIRST(header);
                
                /* Release all extents and stop recursion */
                for (uint32_t i = 0;
                    i < ext4_extent_header_get_entries_count(header);
                    ++i, ++ext) {
                        rc = ext4_extent_release(inode_ref, ext);
                        if (rc != EOK)
                                return rc;
                }
        }
        
        /* Release data block where the node was stored */
        
        rc = block_put(block);
        if (rc != EOK)
                return rc;
        
        return ext4_balloc_free_block(inode_ref, fblock);
}

/** Release all data blocks starting from specified logical block.
 *
 * @param inode_ref   I-node to release blocks from
 * @param iblock_from First logical block to release
 *
 */
int ext4_extent_release_blocks_from(ext4_inode_ref_t *inode_ref,
    uint32_t iblock_from)
{
        /* Find the first extent to modify */
        ext4_extent_path_t *path;
        int rc = ext4_extent_find_extent(inode_ref, iblock_from, &path);
        if (rc != EOK)
                return rc;
        
        /* Jump to last item of the path (extent) */
        ext4_extent_path_t *path_ptr = path;
        while (path_ptr->depth != 0)
                path_ptr++;
        
        assert(path_ptr->extent != NULL);
        
        /* First extent maybe released partially */
        uint32_t first_iblock =
            ext4_extent_get_first_block(path_ptr->extent);
        uint32_t first_fblock =
            ext4_extent_get_start(path_ptr->extent) + iblock_from - first_iblock;
        
        uint16_t block_count = ext4_extent_get_block_count(path_ptr->extent);
        
        uint16_t delete_count = block_count -
            (ext4_extent_get_start(path_ptr->extent) - first_fblock);
        
        /* Release all blocks */
        rc = ext4_balloc_free_blocks(inode_ref, first_fblock, delete_count);
        if (rc != EOK)
                goto cleanup;
        
        /* Correct counter */
        block_count -= delete_count;
        ext4_extent_set_block_count(path_ptr->extent, block_count);
        
        /* Initialize the following loop */
        uint16_t entries =
            ext4_extent_header_get_entries_count(path_ptr->header);
        ext4_extent_t *tmp_ext = path_ptr->extent + 1;
        ext4_extent_t *stop_ext = EXT4_EXTENT_FIRST(path_ptr->header) + entries;
        
        /* If first extent empty, release it */
        if (block_count == 0)
                entries--;
        
        /* Release all successors of the first extent in the same node */
        while (tmp_ext < stop_ext) {
                first_fblock = ext4_extent_get_start(tmp_ext);
                delete_count = ext4_extent_get_block_count(tmp_ext);
                
                rc = ext4_balloc_free_blocks(inode_ref, first_fblock, delete_count);
                if (rc != EOK)
                        goto cleanup;
                
                entries--;
                tmp_ext++;
        }
        
        ext4_extent_header_set_entries_count(path_ptr->header, entries);
        path_ptr->block->dirty = true;
        
        /* If leaf node is empty, parent entry must be modified */
        bool remove_parent_record = false;
        
        /* Don't release root block (including inode data) !!! */
        if ((path_ptr != path) && (entries == 0)) {
                rc = ext4_balloc_free_block(inode_ref, path_ptr->block->lba);
                if (rc != EOK)
                        goto cleanup;
                
                remove_parent_record = true;
        }
        
        /* Jump to the parent */
        --path_ptr;
        
        /* Release all successors in all tree levels */
        while (path_ptr >= path) {
                entries = ext4_extent_header_get_entries_count(path_ptr->header);
                ext4_extent_index_t *index = path_ptr->index + 1;
                ext4_extent_index_t *stop =
                    EXT4_EXTENT_FIRST_INDEX(path_ptr->header) + entries;
                
                /* Correct entries count because of changes in the previous iteration */
                if (remove_parent_record)
                        entries--;
                
                /* Iterate over all entries and release the whole subtrees */
                while (index < stop) {
                        rc = ext4_extent_release_branch(inode_ref, index);
                        if (rc != EOK)
                                goto cleanup;
                        
                        ++index;
                        --entries;
                }
                
                ext4_extent_header_set_entries_count(path_ptr->header, entries);
                path_ptr->block->dirty = true;
                
                /* Free the node if it is empty */
                if ((entries == 0) && (path_ptr != path)) {
                        rc = ext4_balloc_free_block(inode_ref, path_ptr->block->lba);
                        if (rc != EOK)
                                goto cleanup;
                        
                        /* Mark parent to be checked */
                        remove_parent_record = true;
                } else
                        remove_parent_record = false;
                
                --path_ptr;
        }
        
cleanup:
        ;

        int rc2 = EOK;

        /*
         * Put loaded blocks
         * starting from 1: 0 is a block with inode data
         */
        for (uint16_t i = 1; i <= path->depth; ++i) {
                if (path[i].block) {
                        rc2 = block_put(path[i].block);
                        if (rc == EOK && rc2 != EOK)
                                rc = rc2;
                }
        }
        
        /* Destroy temporary data structure */
        free(path);
        
        return rc;
}

/** Append new extent to the i-node and do some splitting if necessary.
 *
 * @param inode_ref      I-node to append extent to
 * @param path           Path in the extent tree for possible splitting
 * @param last_path_item Input/output parameter for pointer to the last
 *                       valid item in the extent tree path
 * @param iblock         Logical index of block to append extent for
 *
 * @return Error code
 *
 */
static int ext4_extent_append_extent(ext4_inode_ref_t *inode_ref,
    ext4_extent_path_t *path, uint32_t iblock)
{
        ext4_extent_path_t *path_ptr = path + path->depth;
        
        uint32_t block_size =
            ext4_superblock_get_block_size(inode_ref->fs->superblock);
        
        /* Start splitting */
        while (path_ptr > path) {
                uint16_t entries =
                    ext4_extent_header_get_entries_count(path_ptr->header);
                uint16_t limit =
                    ext4_extent_header_get_max_entries_count(path_ptr->header);
                
                if (entries == limit) {
                        /* Full node - allocate block for new one */
                        uint32_t fblock;
                        int rc = ext4_balloc_alloc_block(inode_ref, &fblock);
                        if (rc != EOK)
                                return rc;
                        
                        block_t *block;
                        rc = block_get(&block, inode_ref->fs->device, fblock,
                            BLOCK_FLAGS_NOREAD);
                        if (rc != EOK) {
                                ext4_balloc_free_block(inode_ref, fblock);
                                return rc;
                        }
                        
                        /* Put back not modified old block */
                        rc = block_put(path_ptr->block);
                        if (rc != EOK) {
                                ext4_balloc_free_block(inode_ref, fblock);
                                block_put(block);
                                return rc;
                        }
                        
                        /* Initialize newly allocated block and remember it */
                        memset(block->data, 0, block_size);
                        path_ptr->block = block;
                        
                        /* Update pointers in extent path structure */
                        path_ptr->header = block->data;
                        if (path_ptr->depth) {
                                path_ptr->index = EXT4_EXTENT_FIRST_INDEX(path_ptr->header);
                                ext4_extent_index_set_first_block(path_ptr->index, iblock);
                                ext4_extent_index_set_leaf(path_ptr->index, (path_ptr + 1)->block->lba);
                                limit = (block_size - sizeof(ext4_extent_header_t)) /
                                    sizeof(ext4_extent_index_t);
                        } else {
                                path_ptr->extent = EXT4_EXTENT_FIRST(path_ptr->header);
                                ext4_extent_set_first_block(path_ptr->extent, iblock);
                                limit = (block_size - sizeof(ext4_extent_header_t)) /
                                    sizeof(ext4_extent_t);
                        }
                        
                        /* Initialize on-disk structure (header) */
                        ext4_extent_header_set_entries_count(path_ptr->header, 1);
                        ext4_extent_header_set_max_entries_count(path_ptr->header, limit);
                        ext4_extent_header_set_magic(path_ptr->header, EXT4_EXTENT_MAGIC);
                        ext4_extent_header_set_depth(path_ptr->header, path_ptr->depth);
                        ext4_extent_header_set_generation(path_ptr->header, 0);
                        
                        path_ptr->block->dirty = true;
                        
                        /* Jump to the preceeding item */
                        path_ptr--;
                } else {
                        /* Node with free space */
                        if (path_ptr->depth) {
                                path_ptr->index = EXT4_EXTENT_FIRST_INDEX(path_ptr->header) + entries;
                                ext4_extent_index_set_first_block(path_ptr->index, iblock);
                                ext4_extent_index_set_leaf(path_ptr->index, (path_ptr + 1)->block->lba);
                        } else {
                                path_ptr->extent = EXT4_EXTENT_FIRST(path_ptr->header) + entries;
                                ext4_extent_set_first_block(path_ptr->extent, iblock);
                        }
                        
                        ext4_extent_header_set_entries_count(path_ptr->header, entries + 1);
                        path_ptr->block->dirty = true;
                        
                        /* No more splitting needed */
                        return EOK;
                }
        }
        
        assert(path_ptr == path);
        
        /* Should be the root split too? */
        
        uint16_t entries = ext4_extent_header_get_entries_count(path->header);
        uint16_t limit = ext4_extent_header_get_max_entries_count(path->header);
        
        if (entries == limit) {
                uint32_t new_fblock;
                int rc = ext4_balloc_alloc_block(inode_ref, &new_fblock);
                if (rc != EOK)
                        return rc;
                
                block_t *block;
                rc = block_get(&block, inode_ref->fs->device, new_fblock,
                    BLOCK_FLAGS_NOREAD);
                if (rc != EOK)
                        return rc;
                
                /* Initialize newly allocated block */
                memset(block->data, 0, block_size);
                
                /* Move data from root to the new block */
                memcpy(block->data, inode_ref->inode->blocks,
                    EXT4_INODE_BLOCKS * sizeof(uint32_t));
                
                /* Data block is initialized */
                
                block_t *root_block = path->block;
                uint16_t root_depth = path->depth;
                ext4_extent_header_t *root_header = path->header;
                
                /* Make space for tree growing */
                ext4_extent_path_t *new_root = path;
                ext4_extent_path_t *old_root = path + 1;
                
                size_t nbytes = sizeof(ext4_extent_path_t) * (path->depth + 1);
                memmove(old_root, new_root, nbytes);
                memset(new_root, 0, sizeof(ext4_extent_path_t));
                
                /* Update old root structure */
                old_root->block = block;
                old_root->header = (ext4_extent_header_t *)block->data;
                
                /* Add new entry and update limit for entries */
                if (old_root->depth) {
                        limit = (block_size - sizeof(ext4_extent_header_t)) /
                            sizeof(ext4_extent_index_t);
                        old_root->index = EXT4_EXTENT_FIRST_INDEX(old_root->header) + entries;
                        ext4_extent_index_set_first_block(old_root->index, iblock);
                        ext4_extent_index_set_leaf(old_root->index, (old_root + 1)->block->lba);
                        old_root->extent = NULL;
                } else {
                        limit = (block_size - sizeof(ext4_extent_header_t)) /
                            sizeof(ext4_extent_t);
                        old_root->extent = EXT4_EXTENT_FIRST(old_root->header) + entries;
                        ext4_extent_set_first_block(old_root->extent, iblock);
                        old_root->index = NULL;
                }
                
                ext4_extent_header_set_entries_count(old_root->header, entries + 1);
                ext4_extent_header_set_max_entries_count(old_root->header, limit);
                
                old_root->block->dirty = true;
                
                /* Re-initialize new root metadata */
                new_root->depth = root_depth + 1;
                new_root->block = root_block;
                new_root->header = root_header;
                new_root->extent = NULL;
                new_root->index = EXT4_EXTENT_FIRST_INDEX(new_root->header);
                
                ext4_extent_header_set_depth(new_root->header, new_root->depth);
                
                /* Create new entry in root */
                ext4_extent_header_set_entries_count(new_root->header, 1);
                ext4_extent_index_set_first_block(new_root->index, 0);
                ext4_extent_index_set_leaf(new_root->index, new_fblock);
                
                new_root->block->dirty = true;
        } else {
                if (path->depth) {
                        path->index = EXT4_EXTENT_FIRST_INDEX(path->header) + entries;
                        ext4_extent_index_set_first_block(path->index, iblock);
                        ext4_extent_index_set_leaf(path->index, (path + 1)->block->lba);
                } else {
                        path->extent = EXT4_EXTENT_FIRST(path->header) + entries;
                        ext4_extent_set_first_block(path->extent, iblock);
                }
                
                ext4_extent_header_set_entries_count(path->header, entries + 1);
                path->block->dirty = true;
        }
        
        return EOK;
}

/** Append data block to the i-node.
 *
 * This function allocates data block, tries to append it
 * to some existing extent or creates new extents.
 * It includes possible extent tree modifications (splitting).
 *<
 * @param inode_ref I-node to append block to
 * @param iblock    Output logical number of newly allocated block
 * @param fblock    Output physical block address of newly allocated block
 *
 * @return Error code
 *
 */
int ext4_extent_append_block(ext4_inode_ref_t *inode_ref, uint32_t *iblock,
    uint32_t *fblock, bool update_size)
{
        ext4_superblock_t *sb = inode_ref->fs->superblock;
        uint64_t inode_size = ext4_inode_get_size(sb, inode_ref->inode);
        uint32_t block_size = ext4_superblock_get_block_size(sb);
        
        /* Calculate number of new logical block */
        uint32_t new_block_idx = 0;
        if (inode_size > 0) {
                if ((inode_size % block_size) != 0)
                        inode_size += block_size - (inode_size % block_size);
                
                new_block_idx = inode_size / block_size;
        }
        
        /* Load the nearest leaf (with extent) */
        ext4_extent_path_t *path;
        int rc = ext4_extent_find_extent(inode_ref, new_block_idx, &path);
        if (rc != EOK)
                return rc;
        
        /* Jump to last item of the path (extent) */
        ext4_extent_path_t *path_ptr = path;
        while (path_ptr->depth != 0)
                path_ptr++;
        
        /* Add new extent to the node if not present */
        if (path_ptr->extent == NULL)
                goto append_extent;
        
        uint16_t block_count = ext4_extent_get_block_count(path_ptr->extent);
        uint16_t block_limit = (1 << 15);
        
        uint32_t phys_block = 0;
        if (block_count < block_limit) {
                /* There is space for new block in the extent */
                if (block_count == 0) {
                        /* Existing extent is empty */
                        rc = ext4_balloc_alloc_block(inode_ref, &phys_block);
                        if (rc != EOK)
                                goto finish;
                        
                        /* Initialize extent */
                        ext4_extent_set_first_block(path_ptr->extent, new_block_idx);
                        ext4_extent_set_start(path_ptr->extent, phys_block);
                        ext4_extent_set_block_count(path_ptr->extent, 1);
                        
                        /* Update i-node */
                        if (update_size) {
                                ext4_inode_set_size(inode_ref->inode, inode_size + block_size);
                                inode_ref->dirty = true;
                        }
                        
                        path_ptr->block->dirty = true;
                        
                        goto finish;
                } else {
                        /* Existing extent contains some blocks */
                        phys_block = ext4_extent_get_start(path_ptr->extent);
                        phys_block += ext4_extent_get_block_count(path_ptr->extent);
                        
                        /* Check if the following block is free for allocation */
                        bool free;
                        rc = ext4_balloc_try_alloc_block(inode_ref, phys_block, &free);
                        if (rc != EOK)
                                goto finish;
                        
                        if (!free) {
                                /* Target is not free, new block must be appended to new extent */
                                goto append_extent;
                        }
                        
                        /* Update extent */
                        ext4_extent_set_block_count(path_ptr->extent, block_count + 1);
                        
                        /* Update i-node */
                        if (update_size) {
                                ext4_inode_set_size(inode_ref->inode, inode_size + block_size);
                                inode_ref->dirty = true;
                        }
                        
                        path_ptr->block->dirty = true;
                        
                        goto finish;
                }
        }
        
        
append_extent:
        /* Append new extent to the tree */
        phys_block = 0;
        
        /* Allocate new data block */
        rc = ext4_balloc_alloc_block(inode_ref, &phys_block);
        if (rc != EOK)
                goto finish;
        
        /* Append extent for new block (includes tree splitting if needed) */
        rc = ext4_extent_append_extent(inode_ref, path, new_block_idx);
        if (rc != EOK) {
                ext4_balloc_free_block(inode_ref, phys_block);
                goto finish;
        }
        
        uint32_t tree_depth = ext4_extent_header_get_depth(path->header);
        path_ptr = path + tree_depth;
        
        /* Initialize newly created extent */
        ext4_extent_set_block_count(path_ptr->extent, 1);
        ext4_extent_set_first_block(path_ptr->extent, new_block_idx);
        ext4_extent_set_start(path_ptr->extent, phys_block);
        
        /* Update i-node */
        if (update_size) {
                ext4_inode_set_size(inode_ref->inode, inode_size + block_size);
                inode_ref->dirty = true;
        }
        
        path_ptr->block->dirty = true;
        
finish:
        ;

        int rc2 = EOK;

        /* Set return values */
        *iblock = new_block_idx;
        *fblock = phys_block;
        
        /*
         * Put loaded blocks
         * starting from 1: 0 is a block with inode data
         */
        for (uint16_t i = 1; i <= path->depth; ++i) {
                if (path[i].block) {
                        rc2 = block_put(path[i].block);
                        if (rc == EOK && rc2 != EOK)
                                rc = rc2;
                }
        }
        
        /* Destroy temporary data structure */
        free(path);
        
        return rc;
}

/**
 * @}
 */