source: mainline/uspace/srv/fs/cdfs/cdfs_ops.c@ 0ca7286

/*
 * Copyright (c) 2011 Martin Decky
 * 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 fs
 * @{
 */

/**
 * @file cdfs_ops.c
 * @brief Implementation of VFS operations for the cdfs file system
 *        server.
 */

#include <bool.h>
#include <adt/hash_table.h>
#include <malloc.h>
#include <mem.h>
#include <loc.h>
#include <libfs.h>
#include <errno.h>
#include <libblock.h>
#include <str.h>
#include <byteorder.h>
#include <macros.h>
#include "cdfs.h"
#include "cdfs_endian.h"
#include "cdfs_ops.h"

/** Standard CD-ROM block size */
#define BLOCK_SIZE  2048

/** Implicit node cache size
 *
 * More nodes can be actually cached if the files remain
 * opended.
 *
 */
#define NODE_CACHE_SIZE  200

#define NODES_KEY_SRVC   0
#define NODES_KEY_INDEX  1

/** All root nodes have index 0 */
#define CDFS_SOME_ROOT  0

#define CDFS_NODE(node)  ((node) ? (cdfs_node_t *)(node)->data : NULL)
#define FS_NODE(node)    ((node) ? (node)->fs_node : NULL)

#define CDFS_STANDARD_IDENT  "CD001"

typedef enum {
        VOL_DESC_BOOT = 0,
        VOL_DESC_PRIMARY = 1,
        VOL_DESC_SUPPLEMENTARY = 2,
        VOL_DESC_VOL_PARTITION = 3,
        VOL_DESC_SET_TERMINATOR = 255
} vol_desc_type_t;

typedef struct {
        uint8_t system_ident[32];
        uint8_t ident[32];
} __attribute__((packed)) cdfs_vol_desc_boot_t;

typedef struct {
        uint8_t year[4];
        uint8_t mon[2];
        uint8_t day[2];
        
        uint8_t hour[2];
        uint8_t min[2];
        uint8_t sec[2];
        uint8_t msec[2];
        
        uint8_t offset;
} __attribute__((packed)) cdfs_datetime_t;

typedef struct {
        uint8_t year;  /**< Since 1900 */
        uint8_t mon;
        uint8_t day;
        
        uint8_t hour;
        uint8_t min;
        uint8_t sec;
        
        uint8_t offset;
} __attribute__((packed)) cdfs_timestamp_t;

typedef enum {
        DIR_FLAG_DIRECTORY = 2
} cdfs_dir_flag_t;

typedef struct {
        uint8_t length;
        uint8_t ea_length;
        
        uint32_t_lb lba;
        uint32_t_lb size;
        
        cdfs_timestamp_t timestamp;
        uint8_t flags;
        uint8_t unit_size;
        uint8_t gap_size;
        uint16_t_lb sequence_nr;
        
        uint8_t name_length;
        uint8_t name[];
} __attribute__((packed)) cdfs_dir_t;

typedef struct {
        uint8_t res0;
        
        uint8_t system_ident[32];
        uint8_t ident[32];
        
        uint64_t res1;
        uint32_t_lb lba_size;
        
        uint8_t res2[32];
        uint16_t_lb set_size;
        uint16_t_lb sequence_nr;
        
        uint16_t_lb block_size;
        uint32_t_lb path_table_size;
        
        uint32_t path_table_lsb;
        uint32_t opt_path_table_lsb;
        uint32_t path_table_msb;
        uint32_t opt_path_table_msb;
        
        cdfs_dir_t root_dir;
        uint8_t pad0;
        
        uint8_t set_ident[128];
        uint8_t publisher_ident[128];
        uint8_t preparer_ident[128];
        uint8_t app_ident[128];
        
        uint8_t copyright_file_ident[37];
        uint8_t abstract_file_ident[37];
        uint8_t biblio_file_ident[37];
        
        cdfs_datetime_t creation;
        cdfs_datetime_t modification;
        cdfs_datetime_t expiration;
        cdfs_datetime_t effective;
        
        uint8_t fs_version;
} __attribute__((packed)) cdfs_vol_desc_primary_t;

typedef struct {
        uint8_t type;
        uint8_t standard_ident[5];
        uint8_t version;
        union {
                cdfs_vol_desc_boot_t boot;
                cdfs_vol_desc_primary_t primary;
        } data;
} __attribute__((packed)) cdfs_vol_desc_t;

typedef enum {
        CDFS_NONE,
        CDFS_FILE,
        CDFS_DIRECTORY
} cdfs_dentry_type_t;

typedef struct {
        link_t link;       /**< Siblings list link */
        fs_index_t index;  /**< Node index */
        char *name;        /**< Dentry name */
} cdfs_dentry_t;

typedef uint32_t cdfs_lba_t;

typedef struct {
        fs_node_t *fs_node;       /**< FS node */
        fs_index_t index;         /**< Node index */
        service_id_t service_id;  /**< Service ID of block device */
        
        link_t nh_link;           /**< Nodes hash table link */
        cdfs_dentry_type_t type;  /**< Dentry type */
        
        unsigned int lnkcnt;      /**< Link count */
        uint32_t size;            /**< File size if type is CDFS_FILE */
        
        list_t cs_list;           /**< Child's siblings list */
        cdfs_lba_t lba;           /**< LBA of data on disk */
        bool processed;           /**< If all children have been read */
        unsigned int opened;      /**< Opened count */
} cdfs_node_t;

/** Shared index of nodes */
static fs_index_t cdfs_index = 1;

/** Number of currently cached nodes */
static size_t nodes_cached = 0;

/** Hash table of all cdfs nodes */
static hash_table_t nodes;

static size_t nodes_key_hash(unsigned long key[])
{
        return key[NODES_KEY_INDEX];
}

static size_t nodes_hash(const link_t *item)
{
        cdfs_node_t *node = hash_table_get_instance(item, cdfs_node_t, nh_link);
        
        unsigned long key[] = {
                [NODES_KEY_INDEX] = node->index
        };
        
        return nodes_key_hash(key);
}

static bool nodes_match(unsigned long key[], size_t keys, const link_t *item)
{
        cdfs_node_t *node = hash_table_get_instance(item, cdfs_node_t, nh_link);
        
        if (keys == 1) {
                return (node->service_id == key[NODES_KEY_SRVC]);
        } else {
                assert(keys == 2);
                return ((node->service_id == key[NODES_KEY_SRVC]) &&
                    (node->index == key[NODES_KEY_INDEX]));
        }
}

static bool nodes_equal(const link_t *item1, const link_t *item2)
{
        cdfs_node_t *node1 = hash_table_get_instance(item1, cdfs_node_t, nh_link);
        cdfs_node_t *node2 = hash_table_get_instance(item2, cdfs_node_t, nh_link);
        
        return node1->service_id == node2->service_id 
                && node1->index == node2->index;
}

static void nodes_remove_callback(link_t *item)
{
        cdfs_node_t *node = hash_table_get_instance(item, cdfs_node_t, nh_link);
        
        assert(node->type == CDFS_DIRECTORY);
        
        link_t *link;
        while ((link = list_first(&node->cs_list)) != NULL) {
                cdfs_dentry_t *dentry = list_get_instance(link, cdfs_dentry_t, link);
                list_remove(&dentry->link);
                free(dentry);
        }
        
        free(node->fs_node);
        free(node);
}

/** Nodes hash table operations */
static hash_table_ops_t nodes_ops = {
        .hash = nodes_hash,
        .key_hash = nodes_key_hash,
        .match = nodes_match,
        .equal = nodes_equal,
        .remove_callback = nodes_remove_callback
};

static int cdfs_node_get(fs_node_t **rfn, service_id_t service_id,
    fs_index_t index)
{
        unsigned long key[] = {
                [NODES_KEY_SRVC] = service_id,
                [NODES_KEY_INDEX] = index
        };
        
        link_t *link = hash_table_find(&nodes, key);
        if (link) {
                cdfs_node_t *node =
                    hash_table_get_instance(link, cdfs_node_t, nh_link);
                
                *rfn = FS_NODE(node);
        } else
                *rfn = NULL;
        
        return EOK;
}

static int cdfs_root_get(fs_node_t **rfn, service_id_t service_id)
{
        return cdfs_node_get(rfn, service_id, CDFS_SOME_ROOT);
}

static void cdfs_node_initialize(cdfs_node_t *node)
{
        node->fs_node = NULL;
        node->index = 0;
        node->service_id = 0;
        node->type = CDFS_NONE;
        node->lnkcnt = 0;
        node->size = 0;
        node->lba = 0;
        node->processed = false;
        node->opened = 0;
        
        link_initialize(&node->nh_link);
        list_initialize(&node->cs_list);
}

static int create_node(fs_node_t **rfn, service_id_t service_id, int lflag,
    fs_index_t index)
{
        assert((lflag & L_FILE) ^ (lflag & L_DIRECTORY));
        
        cdfs_node_t *node = malloc(sizeof(cdfs_node_t));
        if (!node)
                return ENOMEM;
        
        cdfs_node_initialize(node);
        
        node->fs_node = malloc(sizeof(fs_node_t));
        if (!node->fs_node) {
                free(node);
                return ENOMEM;
        }
        
        fs_node_initialize(node->fs_node);
        node->fs_node->data = node;
        
        fs_node_t *rootfn;
        int rc = cdfs_root_get(&rootfn, service_id);
        
        assert(rc == EOK);
        
        if (!rootfn)
                node->index = CDFS_SOME_ROOT;
        else
                node->index = index;
        
        node->service_id = service_id;
        
        if (lflag & L_DIRECTORY)
                node->type = CDFS_DIRECTORY;
        else
                node->type = CDFS_FILE;
        
        /* Insert the new node into the nodes hash table. */
        hash_table_insert(&nodes, &node->nh_link);
        
        *rfn = FS_NODE(node);
        nodes_cached++;
        
        return EOK;
}

static int link_node(fs_node_t *pfn, fs_node_t *fn, const char *name)
{
        cdfs_node_t *parent = CDFS_NODE(pfn);
        cdfs_node_t *node = CDFS_NODE(fn);
        
        assert(parent->type == CDFS_DIRECTORY);
        
        /* Check for duplicate entries */
        list_foreach(parent->cs_list, link) {
                cdfs_dentry_t *dentry =
                    list_get_instance(link, cdfs_dentry_t, link);
                
                if (str_cmp(dentry->name, name) == 0)
                        return EEXIST;
        }
        
        /* Allocate and initialize the dentry */
        cdfs_dentry_t *dentry = malloc(sizeof(cdfs_dentry_t));
        if (!dentry)
                return ENOMEM;
        
        /* Populate and link the new dentry */
        dentry->name = str_dup(name);
        if (dentry->name == NULL) {
                free(dentry);
                return ENOMEM;
        }
        
        link_initialize(&dentry->link);
        dentry->index = node->index;
        
        node->lnkcnt++;
        list_append(&dentry->link, &parent->cs_list);
        
        return EOK;
}

static bool cdfs_readdir(service_id_t service_id, fs_node_t *fs_node)
{
        cdfs_node_t *node = CDFS_NODE(fs_node);
        assert(node);
        
        if (node->processed)
                return true;
        
        uint32_t blocks = node->size / BLOCK_SIZE;
        if ((node->size % BLOCK_SIZE) != 0)
                blocks++;
        
        for (uint32_t i = 0; i < blocks; i++) {
                block_t *block;
                int rc = block_get(&block, service_id, node->lba + i, BLOCK_FLAGS_NONE);
                if (rc != EOK)
                        return false;
                
                cdfs_dir_t *dir = (cdfs_dir_t *) block->data;
                
                // FIXME: skip '.' and '..'
                
                for (size_t offset = 0;
                    (dir->length != 0) && (offset < BLOCK_SIZE);
                    offset += dir->length) {
                        dir = (cdfs_dir_t *) (block->data + offset);
                        
                        cdfs_dentry_type_t dentry_type;
                        if (dir->flags & DIR_FLAG_DIRECTORY)
                                dentry_type = CDFS_DIRECTORY;
                        else
                                dentry_type = CDFS_FILE;
                        
                        // FIXME: hack - indexing by dentry byte offset on disc
                        
                        fs_node_t *fn;
                        int rc = create_node(&fn, service_id, dentry_type,
                            (node->lba + i) * BLOCK_SIZE + offset);
                        if ((rc != EOK) || (fn == NULL))
                                return false;
                        
                        cdfs_node_t *cur = CDFS_NODE(fn);
                        cur->lba = uint32_lb(dir->lba);
                        cur->size = uint32_lb(dir->size);
                        
                        char *name = (char *) malloc(dir->name_length + 1);
                        if (name == NULL)
                                return false;
                        
                        memcpy(name, dir->name, dir->name_length);
                        name[dir->name_length] = 0;
                        
                        // FIXME: check return value
                        
                        link_node(fs_node, fn, name);
                        free(name);
                        
                        if (dentry_type == CDFS_FILE)
                                cur->processed = true;
                }
                
                block_put(block);
        }
        
        node->processed = true;
        return true;
}

static fs_node_t *get_uncached_node(service_id_t service_id, fs_index_t index)
{
        cdfs_lba_t lba = index / BLOCK_SIZE;
        size_t offset = index % BLOCK_SIZE;
        
        block_t *block;
        int rc = block_get(&block, service_id, lba, BLOCK_FLAGS_NONE);
        if (rc != EOK)
                return NULL;
        
        cdfs_dir_t *dir = (cdfs_dir_t *) (block->data + offset);
        
        cdfs_dentry_type_t dentry_type;
        if (dir->flags & DIR_FLAG_DIRECTORY)
                dentry_type = CDFS_DIRECTORY;
        else
                dentry_type = CDFS_FILE;
        
        fs_node_t *fn;
        rc = create_node(&fn, service_id, dentry_type, index);
        if ((rc != EOK) || (fn == NULL))
                return NULL;
        
        cdfs_node_t *node = CDFS_NODE(fn);
        node->lba = uint32_lb(dir->lba);
        node->size = uint32_lb(dir->size);
        node->lnkcnt = 1;
        
        if (dentry_type == CDFS_FILE)
                node->processed = true;
        
        block_put(block);
        return fn;
}

static fs_node_t *get_cached_node(service_id_t service_id, fs_index_t index)
{
        unsigned long key[] = {
                [NODES_KEY_SRVC] = service_id,
                [NODES_KEY_INDEX] = index
        };
        
        link_t *link = hash_table_find(&nodes, key);
        if (link) {
                cdfs_node_t *node =
                    hash_table_get_instance(link, cdfs_node_t, nh_link);
                return FS_NODE(node);
        }
        
        return get_uncached_node(service_id, index);
}

static int cdfs_match(fs_node_t **fn, fs_node_t *pfn, const char *component)
{
        cdfs_node_t *parent = CDFS_NODE(pfn);
        
        if (!parent->processed) {
                int rc = cdfs_readdir(parent->service_id, pfn);
                if (rc != EOK)
                        return rc;
        }
        
        list_foreach(parent->cs_list, link) {
                cdfs_dentry_t *dentry =
                    list_get_instance(link, cdfs_dentry_t, link);
                
                if (str_cmp(dentry->name, component) == 0) {
                        *fn = get_cached_node(parent->service_id, dentry->index);
                        return EOK;
                }
        }
        
        *fn = NULL;
        return EOK;
}

static int cdfs_node_open(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        
        if (!node->processed)
                cdfs_readdir(node->service_id, fn);
        
        node->opened++;
        return EOK;
}

static int cdfs_node_put(fs_node_t *fn)
{
        /* Nothing to do */
        return EOK;
}

static int cdfs_create_node(fs_node_t **fn, service_id_t service_id, int lflag)
{
        /* Read-only */
        return ENOTSUP;
}

static int cdfs_destroy_node(fs_node_t *fn)
{
        /* Read-only */
        return ENOTSUP;
}

static int cdfs_link_node(fs_node_t *pfn, fs_node_t *cfn, const char *name)
{
        /* Read-only */
        return ENOTSUP;
}

static int cdfs_unlink_node(fs_node_t *pfn, fs_node_t *cfn, const char *name)
{
        /* Read-only */
        return ENOTSUP;
}

static int cdfs_has_children(bool *has_children, fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        
        if ((node->type == CDFS_DIRECTORY) && (!node->processed))
                cdfs_readdir(node->service_id, fn);
        
        *has_children = !list_empty(&node->cs_list);
        return EOK;
}

static fs_index_t cdfs_index_get(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return node->index;
}

static aoff64_t cdfs_size_get(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return node->size;
}

static unsigned int cdfs_lnkcnt_get(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return node->lnkcnt;
}

static bool cdfs_is_directory(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return (node->type == CDFS_DIRECTORY);
}

static bool cdfs_is_file(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return (node->type == CDFS_FILE);
}

static service_id_t cdfs_service_get(fs_node_t *fn)
{
        return 0;
}

libfs_ops_t cdfs_libfs_ops = {
        .root_get = cdfs_root_get,
        .match = cdfs_match,
        .node_get = cdfs_node_get,
        .node_open = cdfs_node_open,
        .node_put = cdfs_node_put,
        .create = cdfs_create_node,
        .destroy = cdfs_destroy_node,
        .link = cdfs_link_node,
        .unlink = cdfs_unlink_node,
        .has_children = cdfs_has_children,
        .index_get = cdfs_index_get,
        .size_get = cdfs_size_get,
        .lnkcnt_get = cdfs_lnkcnt_get,
        .is_directory = cdfs_is_directory,
        .is_file = cdfs_is_file,
        .service_get = cdfs_service_get
};

static bool iso_readfs(service_id_t service_id, fs_node_t *rfn,
    cdfs_lba_t altroot)
{
        /* First 16 blocks of isofs are empty */
        block_t *block;
        int rc = block_get(&block, service_id, altroot + 16, BLOCK_FLAGS_NONE);
        if (rc != EOK)
                return false;
        
        cdfs_vol_desc_t *vol_desc = (cdfs_vol_desc_t *) block->data;
        
        /*
         * Test for primary volume descriptor
         * and standard compliance.
         */
        if ((vol_desc->type != VOL_DESC_PRIMARY) ||
            (bcmp(vol_desc->standard_ident, CDFS_STANDARD_IDENT, 5) != 0) ||
            (vol_desc->version != 1)) {
                block_put(block);
                return false;
        }
        
        uint16_t set_size = uint16_lb(vol_desc->data.primary.set_size);
        if (set_size > 1) {
                /*
                 * Technically, we don't support multi-disc sets.
                 * But one can encounter erroneously mastered
                 * images in the wild and it might actually work
                 * for the first disc in the set.
                 */
        }
        
        uint16_t sequence_nr = uint16_lb(vol_desc->data.primary.sequence_nr);
        if (sequence_nr != 1) {
                /*
                 * We only support the first disc
                 * in multi-disc sets.
                 */
                block_put(block);
                return false;
        }
        
        uint16_t block_size = uint16_lb(vol_desc->data.primary.block_size);
        if (block_size != BLOCK_SIZE) {
                block_put(block);
                return false;
        }
        
        // TODO: implement path table support
        
        cdfs_node_t *node = CDFS_NODE(rfn);
        node->lba = uint32_lb(vol_desc->data.primary.root_dir.lba);
        node->size = uint32_lb(vol_desc->data.primary.root_dir.size);
        
        if (!cdfs_readdir(service_id, rfn)) {
                block_put(block);
                return false;
        }
        
        block_put(block);
        return true;
}

/* Mount a session with session start offset
 *
 */
static bool cdfs_instance_init(service_id_t service_id, cdfs_lba_t altroot)
{
        /* Create root node */
        fs_node_t *rfn;
        int rc = create_node(&rfn, service_id, L_DIRECTORY, cdfs_index++);
        
        if ((rc != EOK) || (!rfn))
                return false;
        
        /* FS root is not linked */
        CDFS_NODE(rfn)->lnkcnt = 0;
        CDFS_NODE(rfn)->lba = 0;
        CDFS_NODE(rfn)->processed = false;
        
        /* Check if there is cdfs in given session */
        if (!iso_readfs(service_id, rfn, altroot)) {
                // XXX destroy node
                return false;
        }
        
        return true;
}

static int cdfs_mounted(service_id_t service_id, const char *opts,
    fs_index_t *index, aoff64_t *size, unsigned int *lnkcnt)
{
        /* Initialize the block layer */
        int rc = block_init(EXCHANGE_SERIALIZE, service_id, BLOCK_SIZE);
        if (rc != EOK)
                return rc;
        
        cdfs_lba_t altroot = 0;
        
        if (str_lcmp(opts, "altroot=", 8) == 0) {
                /* User-defined alternative root on a multi-session disk */
                if (str_uint32_t(opts + 8, NULL, 0, false, &altroot) != EOK)
                        altroot = 0;
        } else {
                /* Read TOC and find the last session */
                toc_block_t *toc = block_get_toc(service_id, 1);
                if ((toc != NULL) && (uint16_t_be2host(toc->size) == 10)) {
                        altroot = uint32_t_be2host(toc->first_lba);
                        free(toc);
                }
        }
        
        /* Initialize the block cache */
        rc = block_cache_init(service_id, BLOCK_SIZE, 0, CACHE_MODE_WT);
        if (rc != EOK) {
                block_fini(service_id);
                return rc;
        }
        
        /* Check if this device is not already mounted */
        fs_node_t *rootfn;
        rc = cdfs_root_get(&rootfn, service_id);
        if ((rc == EOK) && (rootfn)) {
                cdfs_node_put(rootfn);
                block_cache_fini(service_id);
                block_fini(service_id);
                
                return EEXIST;
        }
        
        /* Initialize cdfs instance */
        if (!cdfs_instance_init(service_id, altroot)) {
                block_cache_fini(service_id);
                block_fini(service_id);
                
                return ENOMEM;
        }
        
        rc = cdfs_root_get(&rootfn, service_id);
        assert(rc == EOK);
        
        cdfs_node_t *root = CDFS_NODE(rootfn);
        *index = root->index;
        *size = root->size;
        *lnkcnt = root->lnkcnt;
        
        return EOK;
}

static void cdfs_instance_done(service_id_t service_id)
{
        unsigned long key[] = {
                [NODES_KEY_SRVC] = service_id
        };
        
        hash_table_remove(&nodes, key, 1);
        block_cache_fini(service_id);
        block_fini(service_id);
}

static int cdfs_unmounted(service_id_t service_id)
{
        cdfs_instance_done(service_id);
        return EOK;
}

static int cdfs_read(service_id_t service_id, fs_index_t index, aoff64_t pos,
    size_t *rbytes)
{
        unsigned long key[] = {
                [NODES_KEY_SRVC] = service_id,
                [NODES_KEY_INDEX] = index
        };
        
        link_t *link = hash_table_find(&nodes, key);
        if (link == NULL)
                return ENOENT;
        
        cdfs_node_t *node =
            hash_table_get_instance(link, cdfs_node_t, nh_link);
        
        if (!node->processed) {
                int rc = cdfs_readdir(service_id, FS_NODE(node));
                if (rc != EOK)
                        return rc;
        }
        
        ipc_callid_t callid;
        size_t len;
        if (!async_data_read_receive(&callid, &len)) {
                async_answer_0(callid, EINVAL);
                return EINVAL;
        }
        
        if (node->type == CDFS_FILE) {
                if (pos >= node->size) {
                        *rbytes = 0;
                        async_data_read_finalize(callid, NULL, 0);
                } else {
                        cdfs_lba_t lba = pos / BLOCK_SIZE;
                        size_t offset = pos % BLOCK_SIZE;
                        
                        *rbytes = min(len, BLOCK_SIZE - offset);
                        *rbytes = min(*rbytes, node->size - pos);
                        
                        block_t *block;
                        int rc = block_get(&block, service_id, node->lba + lba,
                            BLOCK_FLAGS_NONE);
                        if (rc != EOK) {
                                async_answer_0(callid, rc);
                                return rc;
                        }
                        
                        async_data_read_finalize(callid, block->data + offset,
                            *rbytes);
                        rc = block_put(block);
                        if (rc != EOK)
                                return rc;
                }
        } else {
                link_t *link = list_nth(&node->cs_list, pos);
                if (link == NULL) {
                        async_answer_0(callid, ENOENT);
                        return ENOENT;
                }
                
                cdfs_dentry_t *dentry =
                    list_get_instance(link, cdfs_dentry_t, link);
                
                *rbytes = 1;
                async_data_read_finalize(callid, dentry->name,
                    str_size(dentry->name) + 1);
        }
        
        return EOK;
}

static int cdfs_write(service_id_t service_id, fs_index_t index, aoff64_t pos,
    size_t *wbytes, aoff64_t *nsize)
{
        /*
         * As cdfs is a read-only filesystem,
         * the operation is not supported.
         */
        
        return ENOTSUP;
}

static int cdfs_truncate(service_id_t service_id, fs_index_t index,
    aoff64_t size)
{
        /*
         * As cdfs is a read-only filesystem,
         * the operation is not supported.
         */
        
        return ENOTSUP;
}

static bool cache_remove_closed(link_t *item, void *arg)
{
        size_t *premove_cnt = (size_t*)arg;
        
        /* Some nodes were requested to be removed from the cache. */
        if (0 < *premove_cnt) {
                cdfs_node_t *node =     hash_table_get_instance(item, cdfs_node_t, nh_link);

                if (!node->opened) {
                        hash_table_remove_item(&nodes, item);
                        
                        --nodes_cached;
                        --*premove_cnt;
                }
        }
        
        /* Only continue if more nodes were requested to be removed. */
        return 0 < *premove_cnt;
}

static void cleanup_cache(service_id_t service_id)
{
        if (nodes_cached > NODE_CACHE_SIZE) {
                size_t remove_cnt = nodes_cached - NODE_CACHE_SIZE;
                
                if (0 < remove_cnt)
                        hash_table_apply(&nodes, cache_remove_closed, &remove_cnt);
        }
}

static int cdfs_close(service_id_t service_id, fs_index_t index)
{
        /* Root node is always in memory */
        if (index == 0)
                return EOK;
        
        unsigned long key[] = {
                [NODES_KEY_SRVC] = service_id,
                [NODES_KEY_INDEX] = index
        };
        
        link_t *link = hash_table_find(&nodes, key);
        if (link == 0)
                return ENOENT;
        
        cdfs_node_t *node =
            hash_table_get_instance(link, cdfs_node_t, nh_link);
        
        assert(node->opened > 0);
        
        node->opened--;
        cleanup_cache(service_id);
        
        return EOK;
}

static int cdfs_destroy(service_id_t service_id, fs_index_t index)
{
        /*
         * As cdfs is a read-only filesystem,
         * the operation is not supported.
         */
        
        return ENOTSUP;
}

static int cdfs_sync(service_id_t service_id, fs_index_t index)
{
        /*
         * As cdfs is a read-only filesystem,
         * the sync operation is a no-op.
         */
        
        return EOK;
}

vfs_out_ops_t cdfs_ops = {
        .mounted = cdfs_mounted,
        .unmounted = cdfs_unmounted,
        .read = cdfs_read,
        .write = cdfs_write,
        .truncate = cdfs_truncate,
        .close = cdfs_close,
        .destroy = cdfs_destroy,
        .sync = cdfs_sync
};

/** Initialize the cdfs server
 *
 */
bool cdfs_init(void)
{
        if (!hash_table_create(&nodes, 0, 2, &nodes_ops))
                return false;
        
        return true;
}

/**
 * @}
 */