source: mainline/uspace/lib/ext4/libext4_directory.c@ 2d53cfc

/*
 * 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 "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;
        
        /* Else do nothing */
}

/** 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)
{
        assert(it->current != NULL);
        
        uint16_t 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)
{
        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) {
                        int 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) {
                        int rc = block_put(it->current_block);
                        it->current_block = NULL;
                        
                        if (rc != EOK)
                                return rc;
                }
                
                uint32_t next_block_phys_idx;
                int 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)
{
        it->inode_ref = NULL;
        it->current = NULL;
        
        if (it->current_block)
                return block_put(it->current_block);
        
        return EOK;
}

/** Write directory entry to concrete data block.
 *
 * @param sb        Superblock
 * @param entry     Pointer to entry to be written
 * @param entry_len Length 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)
{
        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))) {
                int 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;
        }
        
        /* Linear algorithm */
        
        uint32_t iblock = 0;
        uint32_t 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 = str_size(name);
        
        /* Find block, where is space for new entry and try to add */
        bool success = false;
        for (iblock = 0; iblock < total_blocks; ++iblock) {
                int 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;
        int 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);
        
        return rc;
}

/** 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)
{
        uint32_t name_len = str_size(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))) {
                int 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;
        }
        
        /* Linear algorithm */
        
        uint32_t iblock;
        uint32_t 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 */
                int 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)
{
        /* 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;
        int 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 (ext4_directory_entry_ll_get_name_length(sb, dentry) ==
                            name_len) {
                                /* 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;
}

/**
 * @}
 */