source: mainline/uspace/lib/ext4/libext4_filesystem.c@ 9b9d37bb

/*
 * Copyright (c) 2011 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       TODO
 */

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

/**
 * TODO doxy
 */
int ext4_filesystem_init(ext4_filesystem_t *fs, service_id_t service_id)
{

        int rc;
        ext4_superblock_t *temp_superblock;
        size_t block_size;

        fs->device = service_id;

        // TODO what does constant 2048 mean?
        rc = block_init(EXCHANGE_SERIALIZE, fs->device, 2048);
        if (rc != EOK) {
                return rc;
        }

        /* Read superblock from device */
        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 */
        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 */
        rc = block_cache_init(service_id, block_size, 0, CACHE_MODE_WT);
        if (rc != EOK) {
                block_fini(fs->device);
                return rc;
        }

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

        return EOK;
}

/**
 * TODO doxy
 */
void ext4_filesystem_fini(ext4_filesystem_t *fs)
{
        free(fs->superblock);
        block_fini(fs->device);
}

/**
 * TODO doxy
 */
int ext4_filesystem_check_sanity(ext4_filesystem_t *fs)
{
        int rc;

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

        return EOK;
}

/**
 * TODO doxy
 */
int ext4_filesystem_check_features(ext4_filesystem_t *fs, bool *o_read_only)
{
        /* Feature flags are present in rev 1 and later */
        if (ext4_superblock_get_rev_level(fs->superblock) == 0) {
                *o_read_only = false;
                return EOK;
        }

        uint32_t incompatible_features;
        incompatible_features = ext4_superblock_get_features_incompatible(fs->superblock);
        incompatible_features &= ~EXT4_FEATURE_INCOMPAT_SUPP;
        if (incompatible_features > 0) {
                *o_read_only = true;
                return ENOTSUP;
        }

        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) {
                *o_read_only = true;
        }

        return EOK;
}

/**
 * TODO doxy
 */
int ext4_filesystem_get_block_group_ref(ext4_filesystem_t *fs, uint32_t bgid,
    ext4_block_group_ref_t **ref)
{
        EXT4FS_DBG("");

        int rc;
        aoff64_t block_id;
        uint32_t descriptors_per_block;
        size_t offset;
        ext4_block_group_ref_t *newref;

        newref = malloc(sizeof(ext4_block_group_ref_t));
        if (newref == NULL) {
                return ENOMEM;
        }

        descriptors_per_block = ext4_superblock_get_block_size(fs->superblock)
            / EXT4_BLOCK_GROUP_DESCRIPTOR_SIZE;

        /* Block group descriptor table starts at the next block after superblock */
        block_id = ext4_superblock_get_first_data_block(fs->superblock) + 1;

        EXT4FS_DBG("block_size = \%d", ext4_superblock_get_block_size(fs->superblock));
        EXT4FS_DBG("descriptors_per_block = \%d", descriptors_per_block);
        EXT4FS_DBG("bgid = \%d", bgid);
        EXT4FS_DBG("first_data_block: \%d", (uint32_t)block_id);

        /* Find the block containing the descriptor we are looking for */
        block_id += bgid / descriptors_per_block;
        offset = (bgid % descriptors_per_block) * EXT4_BLOCK_GROUP_DESCRIPTOR_SIZE;

        EXT4FS_DBG("updated block_id: \%d", (uint32_t)block_id);

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

                EXT4FS_DBG("block_get error: \%d", rc);

                free(newref);
                return rc;
        }

        EXT4FS_DBG("block read");

        newref->block_group = newref->block->data + offset;

        *ref = newref;

        EXT4FS_DBG("finished");

        return EOK;
}

/**
 * TODO doxy
 */
int ext4_filesystem_get_inode_ref(ext4_filesystem_t *fs, uint32_t index,
    ext4_inode_ref_t **ref)
{
        EXT4FS_DBG("");

        int rc;
        aoff64_t block_id;
        uint32_t block_group;
        uint32_t offset_in_group;
        uint32_t byte_offset_in_group;
        size_t offset_in_block;
        uint32_t inodes_per_group;
        uint32_t inode_table_start;
        uint16_t inode_size;
        uint32_t block_size;
        ext4_block_group_ref_t *bg_ref;
        ext4_inode_ref_t *newref;

        newref = malloc(sizeof(ext4_inode_ref_t));
        if (newref == NULL) {
                return ENOMEM;
        }

        EXT4FS_DBG("allocated");

        inodes_per_group = ext4_superblock_get_inodes_per_group(fs->superblock);

        EXT4FS_DBG("inodes_per_group_loaded");

        /* inode numbers are 1-based, but it is simpler to work with 0-based
         * when computing indices
         */
        index -= 1;
        block_group = index / inodes_per_group;
        offset_in_group = index % inodes_per_group;

        EXT4FS_DBG("index: \%d", index);
        EXT4FS_DBG("inodes_per_group: \%d", inodes_per_group);
        EXT4FS_DBG("bg_id: \%d", block_group);

        rc = ext4_filesystem_get_block_group_ref(fs, block_group, &bg_ref);
        if (rc != EOK) {
                free(newref);
                return rc;
        }

        EXT4FS_DBG("block_group_ref loaded");

        inode_table_start = ext4_block_group_get_inode_table_first_block(
            bg_ref->block_group);

        EXT4FS_DBG("inode_table block loaded");

        inode_size = ext4_superblock_get_inode_size(fs->superblock);
        block_size = ext4_superblock_get_block_size(fs->superblock);

        byte_offset_in_group = offset_in_group * inode_size;

        block_id = inode_table_start + (byte_offset_in_group / block_size);
        offset_in_block = byte_offset_in_group % block_size;

        EXT4FS_DBG("superblock info loaded");

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

        EXT4FS_DBG("block got");

        newref->inode = newref->block->data + offset_in_block;
        /* we decremented index above, but need to store the original value
         * in the reference
         */
        newref->index = index+1;

        *ref = newref;

        EXT4FS_DBG("finished");

        return EOK;
}

int ext4_filesystem_put_inode_ref(ext4_inode_ref_t *ref)
{
        int rc;

        rc = block_put(ref->block);
        free(ref);

        return rc;
}

int ext4_filesystem_get_inode_data_block_index(ext4_filesystem_t *fs, ext4_inode_t* inode,
    aoff64_t iblock, uint32_t* fblock)
{
        int rc;
        aoff64_t limits[4];
        uint32_t block_ids_per_block;
        aoff64_t blocks_per_level[4];
        uint32_t offset_in_block;
        uint32_t current_block;
        aoff64_t block_offset_in_level;
        int i;
        int level;
        block_t *block;

        /* Handle simple case when we are dealing with direct reference */
        if (iblock < EXT4_INODE_DIRECT_BLOCKS) {
                current_block = ext4_inode_get_direct_block(inode, (uint32_t)iblock);
                *fblock = current_block;
                return EOK;
        }

        /* Compute limits for indirect block levels
         * TODO: compute this once when loading filesystem and store in ext2_filesystem_t
         */
        block_ids_per_block = ext4_superblock_get_block_size(fs->superblock) / sizeof(uint32_t);
        limits[0] = EXT4_INODE_DIRECT_BLOCKS;
        blocks_per_level[0] = 1;
        for (i = 1; i < 4; i++) {
                blocks_per_level[i]  = blocks_per_level[i-1] *
                    block_ids_per_block;
                limits[i] = limits[i-1] + blocks_per_level[i];
        }

        /* Determine the indirection level needed to get the desired block */
        level = -1;
        for (i = 1; i < 4; i++) {
                if (iblock < limits[i]) {
                        level = i;
                        break;
                }
        }

        if (level == -1) {
                return EIO;
        }

        /* Compute offsets for the topmost level */
        block_offset_in_level = iblock - limits[level-1];
        current_block = ext4_inode_get_indirect_block(inode, level-1);
        offset_in_block = block_offset_in_level / 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
         */
        while (level > 0) {
                rc = block_get(&block, fs->device, current_block, 0);
                if (rc != EOK) {
                        return rc;
                }

                assert(offset_in_block < block_ids_per_block);
                current_block = uint32_t_le2host(((uint32_t*)block->data)[offset_in_block]);

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

                if (current_block == 0) {
                        /* This is a sparse file */
                        *fblock = 0;
                        return EOK;
                }

                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 %= blocks_per_level[level];
                offset_in_block = block_offset_in_level / blocks_per_level[level-1];
        }

        *fblock = current_block;

        return EOK;
}

/**
 * @}
 */