source: mainline/uspace/lib/ext4/libext4_directory.c@ d510ac01

/*
 * 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_directory.c
 * @brief       Ext4 directory structure operations.
 */

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


/** Get i-node number from directory entry.
 *
 * @param de    directory entry
 * @return              i-node number
 */
uint32_t ext4_directory_entry_ll_get_inode(ext4_directory_entry_ll_t *de)
{
        return uint32_t_le2host(de->inode);
}

/** Set i-node number to directory entry.
 *
 * @param de    directory entry
 * @param inode i-node number
 */
void ext4_directory_entry_ll_set_inode(ext4_directory_entry_ll_t *de,
                uint32_t inode)
{
        de->inode = host2uint32_t_le(inode);
}

/** Get directory entry length.
 *
 * @param de    directory entry
 * @return              entry length
 */
uint16_t ext4_directory_entry_ll_get_entry_length(
                ext4_directory_entry_ll_t *de)
{
        return uint16_t_le2host(de->entry_length);
}

/** Set directory entry length.
 *
 * @param de            directory entry
 * @param length        entry length
 */

void ext4_directory_entry_ll_set_entry_length(ext4_directory_entry_ll_t *de,
                uint16_t length)
{
        de->entry_length = host2uint16_t_le(length);
}

/** Get directory entry name length.
 *
 * @param sb    superblock
 * @param de    directory entry
 * @return              entry name length
 */
uint16_t ext4_directory_entry_ll_get_name_length(
    ext4_superblock_t *sb, ext4_directory_entry_ll_t *de)
{
        if (ext4_superblock_get_rev_level(sb) == 0 &&
            ext4_superblock_get_minor_rev_level(sb) < 5) {

                return ((uint16_t)de->name_length_high) << 8 |
                            ((uint16_t)de->name_length);

        }
        return de->name_length;

}

/** Set directory entry name length.
 *
 * @param sb            superblock
 * @param de            directory entry
 * @param length        entry name length
 */
void ext4_directory_entry_ll_set_name_length(ext4_superblock_t *sb,
                ext4_directory_entry_ll_t *de, uint16_t length)
{
        de->name_length = (length << 8) >> 8;

        if (ext4_superblock_get_rev_level(sb) == 0 &&
                    ext4_superblock_get_minor_rev_level(sb) < 5) {

                de->name_length_high = length >> 8;
        }
}

/** Get i-node type of directory entry.
 *
 * @param sb    superblock
 * @param de    directory entry
 * @return              i-node type (file, dir, etc.)
 */
uint8_t ext4_directory_entry_ll_get_inode_type(
                ext4_superblock_t *sb, ext4_directory_entry_ll_t *de)
{
        if (ext4_superblock_get_rev_level(sb) > 0 ||
                    ext4_superblock_get_minor_rev_level(sb) >= 5) {

                        return de->inode_type;
        }

        return EXT4_DIRECTORY_FILETYPE_UNKNOWN;

}

/** Set i-node type of directory entry.
 *
 * @param sb    superblock
 * @param de    directory entry
 * @param type  i-node type (file, dir, etc.)
 */
void ext4_directory_entry_ll_set_inode_type(
                ext4_superblock_t *sb, ext4_directory_entry_ll_t *de, uint8_t type)
{
        if (ext4_superblock_get_rev_level(sb) > 0 ||
                        ext4_superblock_get_minor_rev_level(sb) >= 5) {

                de->inode_type = type;
        }

        /* else do nothing */

}

static int ext4_directory_iterator_seek(
                ext4_directory_iterator_t *, aoff64_t);
static int ext4_directory_iterator_set(
                ext4_directory_iterator_t *, uint32_t);


/** Initialize directory iterator.
 *
 * Set position to the first valid entry from the required position.
 *
 * @param it                    pointer to iterator to be initialized
 * @param inode_ref             directory i-node
 * @param pos                   position to start reading entries from
 * @return                              error code
 */
int ext4_directory_iterator_init(ext4_directory_iterator_t *it,
                ext4_inode_ref_t *inode_ref, aoff64_t pos)
{
        it->inode_ref = inode_ref;
        it->current = NULL;
        it->current_offset = 0;
        it->current_block = NULL;

        return ext4_directory_iterator_seek(it, pos);
}

/** Jump to the next valid entry
 *
 * @param it    initialized iterator
 * @return              error code
 */
int ext4_directory_iterator_next(ext4_directory_iterator_t *it)
{
        uint16_t skip;

        assert(it->current != NULL);

        skip = ext4_directory_entry_ll_get_entry_length(it->current);

        return ext4_directory_iterator_seek(it, it->current_offset + skip);
}

/** Seek to next valid directory entry.
 *
 * Here can be jumped to the next data block.
 *
 * @param it    initialized iterator
 * @param pos   position of the next entry
 * @return              error code
 */
int ext4_directory_iterator_seek(ext4_directory_iterator_t *it, aoff64_t pos)
{
        int rc;

        uint64_t size = ext4_inode_get_size(
                        it->inode_ref->fs->superblock, it->inode_ref->inode);

        /* The iterator is not valid until we seek to the desired position */
        it->current = NULL;

        /* Are we at the end? */
        if (pos >= size) {
                if (it->current_block) {
                        rc = block_put(it->current_block);
                        it->current_block = NULL;
                        if (rc != EOK) {
                                return rc;
                        }
                }

                it->current_offset = pos;
                return EOK;
        }

        /* Compute next block address */
        uint32_t block_size = ext4_superblock_get_block_size(
                        it->inode_ref->fs->superblock);
        aoff64_t current_block_idx = it->current_offset / block_size;
        aoff64_t next_block_idx = pos / block_size;

        /* If we don't have a block or are moving accross block boundary,
         * we need to get another block
         */
        if (it->current_block == NULL || current_block_idx != next_block_idx) {
                if (it->current_block) {
                        rc = block_put(it->current_block);
                        it->current_block = NULL;
                        if (rc != EOK) {
                                return rc;
                        }
                }

                uint32_t next_block_phys_idx;
                rc = ext4_filesystem_get_inode_data_block_index(it->inode_ref,
                                next_block_idx, &next_block_phys_idx);
                if (rc != EOK) {
                        return rc;
                }

                rc = block_get(&it->current_block, it->inode_ref->fs->device,
                                next_block_phys_idx, BLOCK_FLAGS_NONE);
                if (rc != EOK) {
                        it->current_block = NULL;
                        return rc;
                }
        }

        it->current_offset = pos;

        return ext4_directory_iterator_set(it, block_size);
}

/** Do some checks before returning iterator.
 *
 * @param it                    iterator to be checked
 * @param block_size    size of data block
 * @return                              error code
 */
static int ext4_directory_iterator_set(ext4_directory_iterator_t *it,
    uint32_t block_size)
{

        it->current = NULL;

        uint32_t offset_in_block = it->current_offset % block_size;

        /* Ensure proper alignment */
        if ((offset_in_block % 4) != 0) {
                return EIO;
        }

        /* Ensure that the core of the entry does not overflow the block */
        if (offset_in_block > block_size - 8) {
                return EIO;
        }

        ext4_directory_entry_ll_t *entry = it->current_block->data + offset_in_block;

        /* Ensure that the whole entry does not overflow the block */
        uint16_t length = ext4_directory_entry_ll_get_entry_length(entry);
        if (offset_in_block + length > block_size) {
                return EIO;
        }

        /* Ensure the name length is not too large */
        if (ext4_directory_entry_ll_get_name_length(it->inode_ref->fs->superblock,
            entry) > length-8) {
                return EIO;
        }

        /* Everything OK - "publish" the entry */
        it->current = entry;
        return EOK;
}


/** Uninitialize directory iterator.
 *
 * Release all allocated structures.
 *
 * @param it    iterator to be finished
 * @return              error code
 */
int ext4_directory_iterator_fini(ext4_directory_iterator_t *it)
{
        int rc;

        it->inode_ref = NULL;
        it->current = NULL;

        if (it->current_block) {
                rc = block_put(it->current_block);
                if (rc != EOK) {
                        return rc;
                }
        }

        return EOK;
}

/**     Write directory entry to concrete data block.
 *
 * @param sb            superblock
 * @param entry         pointer to entry to be written
 * @param entry_len     lenght of new entry
 * @param child         child i-node to be written to new entry
 * @param name          name of the new entry
 * @param name_len      length of entry name
 */
void ext4_directory_write_entry(ext4_superblock_t *sb,
                ext4_directory_entry_ll_t *entry, uint16_t entry_len,
                ext4_inode_ref_t *child, const char *name, size_t name_len)
{

        /* Check maximum entry length */
        uint32_t block_size = ext4_superblock_get_block_size(sb);
        assert(entry_len <= block_size);

        /* Set basic attributes */
        ext4_directory_entry_ll_set_inode(entry, child->index);
        ext4_directory_entry_ll_set_entry_length(entry, entry_len);
        ext4_directory_entry_ll_set_name_length(sb, entry, name_len);

        /* Write name */
        memcpy(entry->name, name, name_len);

        /* Set type of entry */
        if (ext4_inode_is_type(sb, child->inode, EXT4_INODE_MODE_DIRECTORY)) {
                ext4_directory_entry_ll_set_inode_type(
                                sb, entry, EXT4_DIRECTORY_FILETYPE_DIR);
        } else {
                ext4_directory_entry_ll_set_inode_type(
                                sb, entry, EXT4_DIRECTORY_FILETYPE_REG_FILE);
        }

}

/** Add new entry to the directory.
 *
 * @param parent        directory i-node
 * @param name          name of new entry
 * @param child         i-node to be referenced from new entry
 * @return                      error code
 */
int ext4_directory_add_entry(ext4_inode_ref_t * parent,
                const char *name, ext4_inode_ref_t *child)
{
        int rc;

        ext4_filesystem_t *fs = parent->fs;

        /* Index adding (if allowed) */
        if (ext4_superblock_has_feature_compatible(fs->superblock, EXT4_FEATURE_COMPAT_DIR_INDEX) &&
                        ext4_inode_has_flag(parent->inode, EXT4_INODE_FLAG_INDEX)) {

                rc = ext4_directory_dx_add_entry(parent, child, name);

                /* Check if index is not corrupted */
                if (rc != EXT4_ERR_BAD_DX_DIR) {

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

                        return EOK;
                }

                /* Needed to clear dir index flag if corrupted */
                ext4_inode_clear_flag(parent->inode, EXT4_INODE_FLAG_INDEX);
                parent->dirty = true;

                EXT4FS_DBG("index is corrupted - doing linear algorithm, index flag cleared");
        }

        /* Linear algorithm */

        uint32_t iblock = 0, fblock = 0;
        uint32_t block_size = ext4_superblock_get_block_size(fs->superblock);
        uint32_t inode_size = ext4_inode_get_size(fs->superblock, parent->inode);
        uint32_t total_blocks = inode_size / block_size;

        uint32_t name_len = strlen(name);

        /* Find block, where is space for new entry and try to add */
        bool success = false;
        for (iblock = 0; iblock < total_blocks; ++iblock) {

                rc = ext4_filesystem_get_inode_data_block_index(parent, iblock, &fblock);
                if (rc != EOK) {
                        return rc;
                }

                block_t *block;
                rc = block_get(&block, fs->device, fblock, BLOCK_FLAGS_NONE);
                if (rc != EOK) {
                        return rc;
                }

                /* If adding is successful, function can finish */
                rc = ext4_directory_try_insert_entry(fs->superblock, block, child, name, name_len);
                if (rc == EOK) {
                        success = true;
                }

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

                if (success) {
                        return EOK;
                }
        }

        /* No free block found - needed to allocate next data block */

        iblock = 0;
        fblock = 0;
        rc = ext4_filesystem_append_inode_block(parent, &fblock, &iblock);
        if (rc != EOK) {
                return rc;
        }

        /* Load new block */
        block_t *new_block;
        rc = block_get(&new_block, fs->device, fblock, BLOCK_FLAGS_NOREAD);
        if (rc != EOK) {
                return rc;
        }

        /* Fill block with zeroes */
        memset(new_block->data, 0, block_size);
        ext4_directory_entry_ll_t *block_entry = new_block->data;
        ext4_directory_write_entry(fs->superblock, block_entry, block_size, child, name, name_len);

        /* Save new block */
        new_block->dirty = true;
        rc = block_put(new_block);
        if (rc != EOK) {
                return rc;
        }

        return EOK;
}

/** Find directory entry with passed name.
 *
 * @param result        result structure to be returned if entry found
 * @param parent        directory i-node
 * @param name          name of entry to be found
 * @return                      error code
 */
int ext4_directory_find_entry(ext4_directory_search_result_t *result,
                ext4_inode_ref_t *parent, const char *name)
{
        int rc;
        uint32_t name_len = strlen(name);

        ext4_superblock_t *sb = parent->fs->superblock;

        /* Index search */
        if (ext4_superblock_has_feature_compatible(sb, EXT4_FEATURE_COMPAT_DIR_INDEX) &&
                        ext4_inode_has_flag(parent->inode, EXT4_INODE_FLAG_INDEX)) {

                rc = ext4_directory_dx_find_entry(result, parent, name_len, name);

                /* Check if index is not corrupted */
                if (rc != EXT4_ERR_BAD_DX_DIR) {

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

                /* Needed to clear dir index flag if corrupted */
                ext4_inode_clear_flag(parent->inode, EXT4_INODE_FLAG_INDEX);
                parent->dirty = true;

                EXT4FS_DBG("index is corrupted - doing linear search");
        }

        /* Linear algorithm */

        uint32_t iblock, fblock;
        uint32_t block_size = ext4_superblock_get_block_size(sb);
        uint32_t inode_size = ext4_inode_get_size(sb, parent->inode);
        uint32_t total_blocks = inode_size / block_size;

        /* Walk through all data blocks */
        for (iblock = 0; iblock < total_blocks; ++iblock) {

                /* Load block address */
                rc = ext4_filesystem_get_inode_data_block_index(parent, iblock, &fblock);
                if (rc != EOK) {
                        return rc;
                }

                /* Load data block */
                block_t *block;
                rc = block_get(&block, parent->fs->device, fblock, BLOCK_FLAGS_NONE);
                if (rc != EOK) {
                        return rc;
                }

                /* Try to find entry in block */
                ext4_directory_entry_ll_t *res_entry;
                rc = ext4_directory_find_in_block(block, sb, name_len, name, &res_entry);
                if (rc == EOK) {
                        result->block = block;
                        result->dentry = res_entry;
                        return EOK;
                }

                /* Entry not found - put block and continue to the next block */

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

        /* Entry was not found */

        result->block = NULL;
        result->dentry =  NULL;

        return ENOENT;
}


/** Remove directory entry.
 *
 * @param parent        directory i-node
 * @param name          name of the entry to be removed
 * @return                      error code
 */
int ext4_directory_remove_entry(ext4_inode_ref_t *parent, const char *name)
{
        int rc;

        /* Check if removing from directory */
        if (!ext4_inode_is_type(parent->fs->superblock, parent->inode,
            EXT4_INODE_MODE_DIRECTORY)) {
                return ENOTDIR;
        }

        /* Try to find entry */
        ext4_directory_search_result_t result;
        rc  = ext4_directory_find_entry(&result, parent, name);
        if (rc != EOK) {
                return rc;
        }

        /* Invalidate entry */
        ext4_directory_entry_ll_set_inode(result.dentry, 0);

        /* Store entry position in block */
        uint32_t pos = (void *)result.dentry - result.block->data;

        /* If entry is not the first in block, it must be merged
         * with previous entry
         */
        if (pos != 0) {

                uint32_t offset = 0;

                /* Start from the first entry in block */
                ext4_directory_entry_ll_t *tmp_dentry = result.block->data;
                uint16_t tmp_dentry_length =
                                ext4_directory_entry_ll_get_entry_length(tmp_dentry);

                /* Find direct predecessor of removed entry */
                while ((offset + tmp_dentry_length) < pos) {
                        offset += ext4_directory_entry_ll_get_entry_length(tmp_dentry);
                        tmp_dentry = result.block->data + offset;
                        tmp_dentry_length =
                                        ext4_directory_entry_ll_get_entry_length(tmp_dentry);
                }

                assert(tmp_dentry_length + offset == pos);

                /* Add to removed entry length to predecessor's length */
                uint16_t del_entry_length =
                                ext4_directory_entry_ll_get_entry_length(result.dentry);
                ext4_directory_entry_ll_set_entry_length(tmp_dentry,
                                tmp_dentry_length + del_entry_length);

        }

        result.block->dirty = true;

        return ext4_directory_destroy_result(&result);
}

/** Try to insert entry to concrete data block.
 *
 * @param sb                    superblock
 * @param target_block  block to try to insert entry to
 * @param child                 child i-node to be inserted by new entry
 * @param name                  name of the new entry
 * @param name_len              length of the new entry name
 * @return                              error code
 */
int ext4_directory_try_insert_entry(ext4_superblock_t *sb,
                block_t *target_block, ext4_inode_ref_t *child,
                const char *name, uint32_t name_len)
{
        /* Compute required length entry and align it to 4 bytes */
        uint32_t block_size = ext4_superblock_get_block_size(sb);
        uint16_t required_len = sizeof(ext4_fake_directory_entry_t) + name_len;
        if ((required_len % 4) != 0) {
                required_len += 4 - (required_len % 4);
        }

        /* Initialize pointers, stop means to upper bound */
        ext4_directory_entry_ll_t *dentry = target_block->data;
        ext4_directory_entry_ll_t *stop = target_block->data + block_size;

        /* Walk through the block and check for invalid entries
         * or entries with free space for new entry
         */
        while (dentry < stop) {

                uint32_t inode = ext4_directory_entry_ll_get_inode(dentry);
                uint16_t rec_len = ext4_directory_entry_ll_get_entry_length(dentry);

                /* If invalid and large enough entry, use it */
                if ((inode == 0) && (rec_len >= required_len)) {
                        ext4_directory_write_entry(sb, dentry, rec_len, child, name, name_len);
                        target_block->dirty = true;
                        return EOK;
                }

                /* Valid entry, try to split it */
                if (inode != 0) {
                        uint16_t used_name_len =
                                        ext4_directory_entry_ll_get_name_length(sb, dentry);

                        uint16_t used_space =
                                        sizeof(ext4_fake_directory_entry_t) + used_name_len;
                        if ((used_name_len % 4) != 0) {
                                used_space += 4 - (used_name_len % 4);
                        }
                        uint16_t free_space = rec_len - used_space;

                        /* There is free space for new entry */
                        if (free_space >= required_len) {

                                /* Cut tail of current entry */
                                ext4_directory_entry_ll_set_entry_length(dentry, used_space);
                                ext4_directory_entry_ll_t *new_entry =
                                                (void *)dentry + used_space;
                                ext4_directory_write_entry(sb, new_entry,
                                                free_space, child, name, name_len);

                                target_block->dirty = true;
                                return EOK;
                        }
                }

                /* Jump to the next entry */
                dentry = (void *)dentry + rec_len;
        }

        /* No free space found for new entry */

        return ENOSPC;
}

/** Try to find entry in block by name.
 *
 * @param block         block containing entries
 * @param sb            superblock
 * @param name_len      length of entry name
 * @param name          name of entry to be found
 * @param res_entry     output pointer to found entry, NULL if not found
 * @return                      error code
 */
int ext4_directory_find_in_block(block_t *block,
                ext4_superblock_t *sb, size_t name_len, const char *name,
                ext4_directory_entry_ll_t **res_entry)
{
        /* Start from the first entry in block */
        ext4_directory_entry_ll_t *dentry = (ext4_directory_entry_ll_t *)block->data;
        /*Set upper bound for cycling */
        uint8_t *addr_limit = block->data + ext4_superblock_get_block_size(sb);

        /* Walk through the block and check entries */
        while ((uint8_t *)dentry < addr_limit) {

                /* Termination condition */
                if ((uint8_t*) dentry + name_len > addr_limit) {
                        break;
                }

                /* Valid entry - check it */
                if (dentry->inode != 0) {

                        /* For more effectivity compare firstly only lengths */
                        if (name_len == ext4_directory_entry_ll_get_name_length(sb, dentry)) {
                                /* Compare names */
                                if (bcmp((uint8_t *)name, dentry->name, name_len) == 0) {
                                        *res_entry = dentry;
                                        return EOK;
                                }
                        }
                }

                uint16_t dentry_len = ext4_directory_entry_ll_get_entry_length(dentry);

                /* Corrupted entry */
                if (dentry_len == 0) {
                        return EINVAL;
                }

                /* Jump to next entry */
                dentry = (ext4_directory_entry_ll_t *)((uint8_t *)dentry + dentry_len);
        }

        /* Entry not found */
        return ENOENT;
}

/** Simple function to release allocated data from result.
 *
 * @param result        search result to destroy
 * @return                      error code
 */
int ext4_directory_destroy_result(ext4_directory_search_result_t *result)
{
        if (result->block) {
                return block_put(result->block);
        }

        return EOK;
}

/**
 * @}
 */