source: mainline/uspace/srv/fs/ext2fs/ext2fs_ops.c@ 3bb732b

/*
 * Copyright (c) 2011 Martin Sucha
 * 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        ext2fs_ops.c
 * @brief       Implementation of VFS operations for the EXT2 file system server.
 */

#include "ext2fs.h"
#include "../../vfs/vfs.h"
#include <libfs.h>
#include <libblock.h>
#include <libext2.h>
#include <ipc/services.h>
#include <ipc/loc.h>
#include <macros.h>
#include <async.h>
#include <errno.h>
#include <str.h>
#include <byteorder.h>
#include <adt/hash_table.h>
#include <adt/list.h>
#include <assert.h>
#include <fibril_synch.h>
#include <sys/mman.h>
#include <align.h>
#include <adt/hash_table.h>
#include <sys/typefmt.h>
#include <malloc.h>
#include <stdio.h>
#include <inttypes.h>

#define EXT2FS_NODE(node)       ((node) ? (ext2fs_node_t *) (node)->data : NULL)
#define EXT2FS_DBG(format, ...) {if (false) printf("ext2fs: %s: " format "\n", __FUNCTION__, ##__VA_ARGS__);}
#define OPEN_NODES_KEYS 2
#define OPEN_NODES_DEV_HANDLE_KEY 0
#define OPEN_NODES_INODE_KEY 1

typedef struct ext2fs_instance {
        link_t link;
        service_id_t service_id;
        ext2_filesystem_t *filesystem;
        unsigned int open_nodes_count;
} ext2fs_instance_t;

typedef struct ext2fs_node {
        ext2fs_instance_t *instance;
        ext2_inode_ref_t *inode_ref;
        fs_node_t *fs_node;
        link_t link;
        unsigned int references;
} ext2fs_node_t;

/*
 * Forward declarations of auxiliary functions
 */
static int ext2fs_instance_get(service_id_t, ext2fs_instance_t **);
static int ext2fs_read_directory(ipc_callid_t, aoff64_t, size_t,
    ext2fs_instance_t *, ext2_inode_ref_t *, size_t *);
static int ext2fs_read_file(ipc_callid_t, aoff64_t, size_t, ext2fs_instance_t *,
    ext2_inode_ref_t *, size_t *);
static bool ext2fs_is_dots(const uint8_t *, size_t);
static int ext2fs_node_get_core(fs_node_t **, ext2fs_instance_t *, fs_index_t);
static int ext2fs_node_put_core(ext2fs_node_t *);

/*
 * Forward declarations of EXT2 libfs operations.
 */
static int ext2fs_root_get(fs_node_t **, service_id_t);
static int ext2fs_match(fs_node_t **, fs_node_t *, const char *);
static int ext2fs_node_get(fs_node_t **, service_id_t, fs_index_t);
static int ext2fs_node_open(fs_node_t *);
static int ext2fs_node_put(fs_node_t *);
static int ext2fs_create_node(fs_node_t **, service_id_t, int);
static int ext2fs_destroy_node(fs_node_t *);
static int ext2fs_link(fs_node_t *, fs_node_t *, const char *);
static int ext2fs_unlink(fs_node_t *, fs_node_t *, const char *);
static int ext2fs_has_children(bool *, fs_node_t *);
static fs_index_t ext2fs_index_get(fs_node_t *);
static aoff64_t ext2fs_size_get(fs_node_t *);
static unsigned ext2fs_lnkcnt_get(fs_node_t *);
static bool ext2fs_is_directory(fs_node_t *);
static bool ext2fs_is_file(fs_node_t *node);
static service_id_t ext2fs_service_get(fs_node_t *node);

/*
 * Static variables
 */
static LIST_INITIALIZE(instance_list);
static FIBRIL_MUTEX_INITIALIZE(instance_list_mutex);
static hash_table_t open_nodes;
static FIBRIL_MUTEX_INITIALIZE(open_nodes_lock);

/* Hash table interface for open nodes hash table */
static size_t open_nodes_key_hash(unsigned long key[])
{
        /* Hash construction recommended in Effective Java, 2nd Edition. */
        size_t hash = 17;
        hash = 31 * hash + key[OPEN_NODES_DEV_HANDLE_KEY];
        hash = 31 * hash + key[OPEN_NODES_INODE_KEY];
        return hash;
}

static size_t open_nodes_hash(const link_t *item)
{
        ext2fs_node_t *enode = hash_table_get_instance(item, ext2fs_node_t, link);

        assert(enode->instance);
        assert(enode->inode_ref);
        
        unsigned long key[] = {
                [OPEN_NODES_DEV_HANDLE_KEY] = enode->instance->service_id,
                [OPEN_NODES_INODE_KEY] = enode->inode_ref->index,
        };
        
        return open_nodes_key_hash(key);
}

static bool open_nodes_match(unsigned long key[], size_t keys, 
    const link_t *item)
{
        ext2fs_node_t *enode = hash_table_get_instance(item, ext2fs_node_t, link);
        assert(keys > 0);
        if (enode->instance->service_id !=
            ((service_id_t) key[OPEN_NODES_DEV_HANDLE_KEY])) {
                return false;
        }
        if (keys == 1) {
                return true;
        }
        assert(keys == 2);
        return (enode->inode_ref->index == key[OPEN_NODES_INODE_KEY]);
}

static hash_table_ops_t open_nodes_ops = {
        .hash = open_nodes_hash,
        .key_hash = open_nodes_key_hash,
        .match = open_nodes_match,
        .equal = 0,
        .remove_callback = 0,
};

/**
 * 
 */
int ext2fs_global_init(void)
{
        if (!hash_table_create(&open_nodes, 0, OPEN_NODES_KEYS, &open_nodes_ops)) {
                return ENOMEM;
        }
        return EOK;
}

int ext2fs_global_fini(void)
{
        hash_table_destroy(&open_nodes);
        return EOK;
}


/*
 * EXT2 libfs operations.
 */

/**
 * Find an instance of filesystem for the given service_id
 */
int ext2fs_instance_get(service_id_t service_id, ext2fs_instance_t **inst)
{
        EXT2FS_DBG("(%" PRIun ", -)", service_id);
        ext2fs_instance_t *tmp;
        
        fibril_mutex_lock(&instance_list_mutex);

        if (list_empty(&instance_list)) {
                EXT2FS_DBG("list empty");
                fibril_mutex_unlock(&instance_list_mutex);
                return EINVAL;
        }

        list_foreach(instance_list, link) {
                tmp = list_get_instance(link, ext2fs_instance_t, link);
                
                if (tmp->service_id == service_id) {
                        *inst = tmp;
                        fibril_mutex_unlock(&instance_list_mutex);
                        return EOK;
                }
        }
        
        EXT2FS_DBG("not found");
        
        fibril_mutex_unlock(&instance_list_mutex);
        return EINVAL;
}



int ext2fs_root_get(fs_node_t **rfn, service_id_t service_id)
{
        EXT2FS_DBG("(-, %" PRIun ")", service_id);
        return ext2fs_node_get(rfn, service_id, EXT2_INODE_ROOT_INDEX);
}

int ext2fs_match(fs_node_t **rfn, fs_node_t *pfn, const char *component)
{
        EXT2FS_DBG("(-,-,%s)", component);
        ext2fs_node_t *eparent = EXT2FS_NODE(pfn);
        ext2_filesystem_t *fs;
        ext2_directory_iterator_t it;
        int rc;
        size_t name_size;
        size_t component_size;
        bool found = false;
        uint32_t inode;
        
        fs = eparent->instance->filesystem;
        
        if (!ext2_inode_is_type(fs->superblock, eparent->inode_ref->inode,
            EXT2_INODE_MODE_DIRECTORY)) {
                return ENOTDIR;
        }
        
        rc = ext2_directory_iterator_init(&it, fs, eparent->inode_ref, 0);
        if (rc != EOK) {
                return rc;
        }

        /* Find length of component in bytes
         * TODO: check for library function call that does this
         */
        component_size = 0;
        while (*(component+component_size) != 0) {
                component_size++;
        }
        
        while (it.current != NULL) {
                inode = ext2_directory_entry_ll_get_inode(it.current);
                
                /* ignore empty directory entries */
                if (inode != 0) {
                        name_size = ext2_directory_entry_ll_get_name_length(fs->superblock,
                                it.current);

                        if (name_size == component_size && bcmp(component, &it.current->name,
                                    name_size) == 0) {
                                rc = ext2fs_node_get_core(rfn, eparent->instance,
                                        inode);
                                if (rc != EOK) {
                                        ext2_directory_iterator_fini(&it);
                                        return rc;
                                }
                                found = true;
                                break;
                        }
                }
                
                rc = ext2_directory_iterator_next(&it);
                if (rc != EOK) {
                        ext2_directory_iterator_fini(&it);
                        return rc;
                }
        }
        
        ext2_directory_iterator_fini(&it);
        
        if (!found) {
                return ENOENT;
        }
        
        return EOK;
}

/** Instantiate a EXT2 in-core node. */
int ext2fs_node_get(fs_node_t **rfn, service_id_t service_id, fs_index_t index)
{
        EXT2FS_DBG("(-,%" PRIun ",%u)", service_id, index);
        
        ext2fs_instance_t *inst = NULL;
        int rc;
        
        rc = ext2fs_instance_get(service_id, &inst);
        if (rc != EOK) {
                return rc;
        }
        
        return ext2fs_node_get_core(rfn, inst, index);
}

int ext2fs_node_get_core(fs_node_t **rfn, ext2fs_instance_t *inst,
                fs_index_t index)
{
        int rc;
        fs_node_t *node = NULL;
        ext2fs_node_t *enode = NULL;
        
        ext2_inode_ref_t *inode_ref = NULL;

        fibril_mutex_lock(&open_nodes_lock);
        
        /* Check if the node is not already open */
        unsigned long key[] = {
                [OPEN_NODES_DEV_HANDLE_KEY] = inst->service_id,
                [OPEN_NODES_INODE_KEY] = index,
        };
        link_t *already_open = hash_table_find(&open_nodes, key);

        if (already_open) {
                enode = hash_table_get_instance(already_open, ext2fs_node_t, link);
                *rfn = enode->fs_node;
                enode->references++;

                fibril_mutex_unlock(&open_nodes_lock);
                return EOK;
        }

        enode = malloc(sizeof(ext2fs_node_t));
        if (enode == NULL) {
                fibril_mutex_unlock(&open_nodes_lock);
                return ENOMEM;
        }

        node = malloc(sizeof(fs_node_t));
        if (node == NULL) {
                free(enode);
                fibril_mutex_unlock(&open_nodes_lock);
                return ENOMEM;
        }       
        fs_node_initialize(node);

        rc = ext2_filesystem_get_inode_ref(inst->filesystem, index, &inode_ref);
        if (rc != EOK) {
                free(enode);
                free(node);
                fibril_mutex_unlock(&open_nodes_lock);
                return rc;
        }
        
        enode->inode_ref = inode_ref;
        enode->instance = inst;
        enode->references = 1;
        enode->fs_node = node;
        link_initialize(&enode->link);
        
        node->data = enode;
        *rfn = node;
        
        hash_table_insert(&open_nodes, &enode->link);
        inst->open_nodes_count++;
        
        EXT2FS_DBG("inode: %u", inode_ref->index);
        
        EXT2FS_DBG("EOK");

        fibril_mutex_unlock(&open_nodes_lock);
        return EOK;
}

int ext2fs_node_open(fs_node_t *fn)
{
        EXT2FS_DBG("");
        /*
         * Opening a file is stateless, nothing
         * to be done here.
         */
        return EOK;
}

int ext2fs_node_put(fs_node_t *fn)
{
        EXT2FS_DBG("");
        int rc;
        ext2fs_node_t *enode = EXT2FS_NODE(fn);
        
        fibril_mutex_lock(&open_nodes_lock);

        assert(enode->references > 0);
        enode->references--;
        if (enode->references == 0) {
                rc = ext2fs_node_put_core(enode);
                if (rc != EOK) {
                        fibril_mutex_unlock(&open_nodes_lock);
                        return rc;
                }
        }

        fibril_mutex_unlock(&open_nodes_lock);
        
        return EOK;
}

int ext2fs_node_put_core(ext2fs_node_t *enode)
{
        int rc;

        unsigned long key[] = {
                [OPEN_NODES_DEV_HANDLE_KEY] = enode->instance->service_id,
                [OPEN_NODES_INODE_KEY] = enode->inode_ref->index,
        };
        hash_table_remove(&open_nodes, key, OPEN_NODES_KEYS);
        assert(enode->instance->open_nodes_count > 0);
        enode->instance->open_nodes_count--;

        rc = ext2_filesystem_put_inode_ref(enode->inode_ref);
        if (rc != EOK) {
                EXT2FS_DBG("ext2_filesystem_put_inode_ref failed");
                return rc;
        }

        free(enode->fs_node);
        free(enode);
        return EOK;
}

int ext2fs_create_node(fs_node_t **rfn, service_id_t service_id, int flags)
{
        EXT2FS_DBG("");
        // TODO
        return ENOTSUP;
}

int ext2fs_destroy_node(fs_node_t *fn)
{
        EXT2FS_DBG("");
        // TODO
        return ENOTSUP;
}

int ext2fs_link(fs_node_t *pfn, fs_node_t *cfn, const char *name)
{
        EXT2FS_DBG("");
        // TODO
        return ENOTSUP;
}

int ext2fs_unlink(fs_node_t *pfn, fs_node_t *cfn, const char *nm)
{
        EXT2FS_DBG("");
        // TODO
        return ENOTSUP;
}

int ext2fs_has_children(bool *has_children, fs_node_t *fn)
{
        EXT2FS_DBG("");
        ext2fs_node_t *enode = EXT2FS_NODE(fn);
        ext2_directory_iterator_t it;
        ext2_filesystem_t *fs;
        int rc;
        bool found = false;
        size_t name_size;

        fs = enode->instance->filesystem;

        if (!ext2_inode_is_type(fs->superblock, enode->inode_ref->inode,
            EXT2_INODE_MODE_DIRECTORY)) {
                *has_children = false;
                EXT2FS_DBG("EOK - false");
                return EOK;
        }
        
        rc = ext2_directory_iterator_init(&it, fs, enode->inode_ref, 0);
        if (rc != EOK) {
                EXT2FS_DBG("error %u", rc);
                return rc;
        }
        
        /* Find a non-empty directory entry */
        while (it.current != NULL) {
                if (it.current->inode != 0) {
                        name_size = ext2_directory_entry_ll_get_name_length(fs->superblock,
                                it.current);
                        if (!ext2fs_is_dots(&it.current->name, name_size)) {
                                found = true;
                                break;
                        }
                }
                
                rc = ext2_directory_iterator_next(&it);
                if (rc != EOK) {
                        ext2_directory_iterator_fini(&it);
                        EXT2FS_DBG("error %u", rc);
                        return rc;
                }
        }
        
        rc = ext2_directory_iterator_fini(&it);
        if (rc != EOK) {
                EXT2FS_DBG("error %u", rc);
                return rc;
        }

        *has_children = found;
        EXT2FS_DBG("EOK");
        
        return EOK;
}


fs_index_t ext2fs_index_get(fs_node_t *fn)
{
        ext2fs_node_t *enode = EXT2FS_NODE(fn);
        EXT2FS_DBG("%u", enode->inode_ref->index);
        return enode->inode_ref->index;
}

aoff64_t ext2fs_size_get(fs_node_t *fn)
{
        ext2fs_node_t *enode = EXT2FS_NODE(fn);
        aoff64_t size = ext2_inode_get_size(enode->instance->filesystem->superblock,
            enode->inode_ref->inode);
        EXT2FS_DBG("%" PRIu64, size);
        return size;
}

unsigned ext2fs_lnkcnt_get(fs_node_t *fn)
{
        ext2fs_node_t *enode = EXT2FS_NODE(fn);
        unsigned count = ext2_inode_get_usage_count(enode->inode_ref->inode);
        EXT2FS_DBG("%u", count);
        return count;
}

bool ext2fs_is_directory(fs_node_t *fn)
{
        ext2fs_node_t *enode = EXT2FS_NODE(fn);
        bool is_dir = ext2_inode_is_type(enode->instance->filesystem->superblock,
            enode->inode_ref->inode, EXT2_INODE_MODE_DIRECTORY);
        EXT2FS_DBG("%s", is_dir ? "true" : "false");
        EXT2FS_DBG("%u", enode->inode_ref->index);
        return is_dir;
}

bool ext2fs_is_file(fs_node_t *fn)
{
        ext2fs_node_t *enode = EXT2FS_NODE(fn);
        bool is_file = ext2_inode_is_type(enode->instance->filesystem->superblock,
            enode->inode_ref->inode, EXT2_INODE_MODE_FILE);
        EXT2FS_DBG("%s", is_file ? "true" : "false");
        return is_file;
}

service_id_t ext2fs_service_get(fs_node_t *fn)
{
        EXT2FS_DBG("");
        ext2fs_node_t *enode = EXT2FS_NODE(fn);
        return enode->instance->service_id;
}

/** libfs operations */
libfs_ops_t ext2fs_libfs_ops = {
        .root_get = ext2fs_root_get,
        .match = ext2fs_match,
        .node_get = ext2fs_node_get,
        .node_open = ext2fs_node_open,
        .node_put = ext2fs_node_put,
        .create = ext2fs_create_node,
        .destroy = ext2fs_destroy_node,
        .link = ext2fs_link,
        .unlink = ext2fs_unlink,
        .has_children = ext2fs_has_children,
        .index_get = ext2fs_index_get,
        .size_get = ext2fs_size_get,
        .lnkcnt_get = ext2fs_lnkcnt_get,
        .is_directory = ext2fs_is_directory,
        .is_file = ext2fs_is_file,
        .service_get = ext2fs_service_get
};

/*
 * VFS operations.
 */

static int ext2fs_mounted(service_id_t service_id, const char *opts,
   fs_index_t *index, aoff64_t *size, unsigned *lnkcnt)
{
        EXT2FS_DBG("");
        int rc;
        ext2_filesystem_t *fs;
        ext2fs_instance_t *inst;
        bool read_only;
        
        /* Allocate libext2 filesystem structure */
        fs = (ext2_filesystem_t *) malloc(sizeof(ext2_filesystem_t));
        if (fs == NULL)
                return ENOMEM;
        
        /* Allocate instance structure */
        inst = (ext2fs_instance_t *) malloc(sizeof(ext2fs_instance_t));
        if (inst == NULL) {
                free(fs);
                return ENOMEM;
        }
        
        /* Initialize the filesystem  */
        rc = ext2_filesystem_init(fs, service_id);
        if (rc != EOK) {
                free(fs);
                free(inst);
                return rc;
        }
        
        /* Do some sanity checking */
        rc = ext2_filesystem_check_sanity(fs);
        if (rc != EOK) {
                ext2_filesystem_fini(fs);
                free(fs);
                free(inst);
                return rc;
        }
        
        /* Check flags */
        rc = ext2_filesystem_check_flags(fs, &read_only);
        if (rc != EOK) {
                ext2_filesystem_fini(fs);
                free(fs);
                free(inst);
                return rc;
        }
        
        /* Initialize instance */
        link_initialize(&inst->link);
        inst->service_id = service_id;
        inst->filesystem = fs;
        inst->open_nodes_count = 0;
        
        /* Read root node */
        fs_node_t *root_node;
        rc = ext2fs_node_get_core(&root_node, inst, EXT2_INODE_ROOT_INDEX);
        if (rc != EOK) {
                ext2_filesystem_fini(fs);
                free(fs);
                free(inst);
                return rc;
        }
        ext2fs_node_t *enode = EXT2FS_NODE(root_node);
                
        /* Add instance to the list */
        fibril_mutex_lock(&instance_list_mutex);
        list_append(&inst->link, &instance_list);
        fibril_mutex_unlock(&instance_list_mutex);
        
        *index = EXT2_INODE_ROOT_INDEX;
        *size = 0;
        *lnkcnt = ext2_inode_get_usage_count(enode->inode_ref->inode);
        
        ext2fs_node_put(root_node);

        return EOK;
}

static int ext2fs_unmounted(service_id_t service_id)
{
        EXT2FS_DBG("");
        ext2fs_instance_t *inst;
        int rc;
        
        rc = ext2fs_instance_get(service_id, &inst);
        
        if (rc != EOK)
                return rc;
        
        fibril_mutex_lock(&open_nodes_lock);

        EXT2FS_DBG("open_nodes_count = %d", inst->open_nodes_count)
        if (inst->open_nodes_count != 0) {
                fibril_mutex_unlock(&open_nodes_lock);
                return EBUSY;
        }
        
        /* Remove the instance from the list */
        fibril_mutex_lock(&instance_list_mutex);
        list_remove(&inst->link);
        fibril_mutex_unlock(&instance_list_mutex);

        fibril_mutex_unlock(&open_nodes_lock);
        
        ext2_filesystem_fini(inst->filesystem);
        
        return EOK;
}

static int
ext2fs_read(service_id_t service_id, fs_index_t index, aoff64_t pos,
    size_t *rbytes)
{
        EXT2FS_DBG("");
        
        ext2fs_instance_t *inst;
        ext2_inode_ref_t *inode_ref;
        int rc;
        
        /*
         * Receive the read request.
         */
        ipc_callid_t callid;
        size_t size;
        if (!async_data_read_receive(&callid, &size)) {
                async_answer_0(callid, EINVAL);
                return EINVAL;
        }
        
        rc = ext2fs_instance_get(service_id, &inst);
        if (rc != EOK) {
                async_answer_0(callid, rc);
                return rc;
        }
        
        rc = ext2_filesystem_get_inode_ref(inst->filesystem, index, &inode_ref);
        if (rc != EOK) {
                async_answer_0(callid, rc);
                return rc;
        }
        
        if (ext2_inode_is_type(inst->filesystem->superblock, inode_ref->inode,
            EXT2_INODE_MODE_FILE)) {
                rc = ext2fs_read_file(callid, pos, size, inst, inode_ref,
                    rbytes);
        } else if (ext2_inode_is_type(inst->filesystem->superblock,
            inode_ref->inode, EXT2_INODE_MODE_DIRECTORY)) {
                rc = ext2fs_read_directory(callid, pos, size, inst, inode_ref,
                    rbytes);
        } else {
                /* Other inode types not supported */
                async_answer_0(callid, ENOTSUP);
                rc = ENOTSUP;
        }
        
        ext2_filesystem_put_inode_ref(inode_ref);
        
        return rc;
}

/**
 * Determine whether given directory entry name is . or ..
 */
bool ext2fs_is_dots(const uint8_t *name, size_t name_size) {
        if (name_size == 1 && name[0] == '.') {
                return true;
        }
        
        if (name_size == 2 && name[0] == '.' && name[1] == '.') {
                return true;
        }
        
        return false;
}

int ext2fs_read_directory(ipc_callid_t callid, aoff64_t pos, size_t size,
    ext2fs_instance_t *inst, ext2_inode_ref_t *inode_ref, size_t *rbytes)
{
        ext2_directory_iterator_t it;
        aoff64_t next;
        uint8_t *buf;
        size_t name_size;
        int rc;
        bool found = false;
        
        rc = ext2_directory_iterator_init(&it, inst->filesystem, inode_ref, pos);
        if (rc != EOK) {
                async_answer_0(callid, rc);
                return rc;
        }
        
        /* Find next interesting directory entry.
         * We want to skip . and .. entries
         * as these are not used in HelenOS
         */
        while (it.current != NULL) {
                if (it.current->inode == 0) {
                        goto skip;
                }
                
                name_size = ext2_directory_entry_ll_get_name_length(
                    inst->filesystem->superblock, it.current);
                
                /* skip . and .. */
                if (ext2fs_is_dots(&it.current->name, name_size)) {
                        goto skip;
                }
                
                /* The on-disk entry does not contain \0 at the end
                 * end of entry name, so we copy it to new buffer
                 * and add the \0 at the end
                 */
                buf = malloc(name_size+1);
                if (buf == NULL) {
                        ext2_directory_iterator_fini(&it);
                        async_answer_0(callid, ENOMEM);
                        return ENOMEM;
                }
                memcpy(buf, &it.current->name, name_size);
                *(buf + name_size) = 0;
                found = true;
                (void) async_data_read_finalize(callid, buf, name_size + 1);
                free(buf);
                break;
                
skip:
                rc = ext2_directory_iterator_next(&it);
                if (rc != EOK) {
                        ext2_directory_iterator_fini(&it);
                        async_answer_0(callid, rc);
                        return rc;
                }
        }
        
        if (found) {
                rc = ext2_directory_iterator_next(&it);
                if (rc != EOK)
                        return rc;
                next = it.current_offset;
        }
        
        rc = ext2_directory_iterator_fini(&it);
        if (rc != EOK)
                return rc;
        
        if (found) {
                *rbytes = next - pos;
                return EOK;
        } else {
                async_answer_0(callid, ENOENT);
                return ENOENT;
        }
}

int ext2fs_read_file(ipc_callid_t callid, aoff64_t pos, size_t size,
    ext2fs_instance_t *inst, ext2_inode_ref_t *inode_ref, size_t *rbytes)
{
        int rc;
        uint32_t block_size;
        aoff64_t file_block;
        uint64_t file_size;
        uint32_t fs_block;
        size_t offset_in_block;
        size_t bytes;
        block_t *block;
        uint8_t *buffer;
        
        file_size = ext2_inode_get_size(inst->filesystem->superblock,
                inode_ref->inode);
        
        if (pos >= file_size) {
                /* Read 0 bytes successfully */
                async_data_read_finalize(callid, NULL, 0);
                *rbytes = 0;
                return EOK;
        }
        
        /* For now, we only read data from one block at a time */
        block_size = ext2_superblock_get_block_size(inst->filesystem->superblock);
        file_block = pos / block_size;
        offset_in_block = pos % block_size;
        bytes = min(block_size - offset_in_block, size);
        
        /* Handle end of file */
        if (pos + bytes > file_size) {
                bytes = file_size - pos;
        }
        
        /* Get the real block number */
        rc = ext2_filesystem_get_inode_data_block_index(inst->filesystem,
                inode_ref->inode, file_block, &fs_block);
        if (rc != EOK) {
                async_answer_0(callid, rc);
                return rc;
        }
        
        /* Check for sparse file
         * If ext2_filesystem_get_inode_data_block_index returned
         * fs_block == 0, it means that the given block is not allocated for the 
         * file and we need to return a buffer of zeros
         */
        if (fs_block == 0) {
                buffer = malloc(bytes);
                if (buffer == NULL) {
                        async_answer_0(callid, ENOMEM);
                        return ENOMEM;
                }
                
                memset(buffer, 0, bytes);
                
                async_data_read_finalize(callid, buffer, bytes);
                *rbytes = bytes;
                
                free(buffer);
                
                return EOK;
        }
        
        /* Usual case - we need to read a block from device */
        rc = block_get(&block, inst->service_id, fs_block, BLOCK_FLAGS_NONE);
        if (rc != EOK) {
                async_answer_0(callid, rc);
                return rc;
        }
        
        assert(offset_in_block + bytes <= block_size);
        async_data_read_finalize(callid, block->data + offset_in_block, bytes);
        
        rc = block_put(block);
        if (rc != EOK)
                return rc;
        
        *rbytes = bytes;
        return EOK;
}

static int
ext2fs_write(service_id_t service_id, fs_index_t index, aoff64_t pos,
    size_t *wbytes, aoff64_t *nsize)
{
        EXT2FS_DBG("");
        return ENOTSUP;
}

static int
ext2fs_truncate(service_id_t service_id, fs_index_t index, aoff64_t size)
{
        EXT2FS_DBG("");
        return ENOTSUP;
}

static int ext2fs_close(service_id_t service_id, fs_index_t index)
{
        EXT2FS_DBG("");
        return EOK;
}

static int ext2fs_destroy(service_id_t service_id, fs_index_t index)
{
        EXT2FS_DBG("");
        return ENOTSUP;
}

static int ext2fs_sync(service_id_t service_id, fs_index_t index)
{
        EXT2FS_DBG("");
        return ENOTSUP;
}

vfs_out_ops_t ext2fs_ops = {
        .mounted = ext2fs_mounted,
        .unmounted = ext2fs_unmounted,
        .read = ext2fs_read,
        .write = ext2fs_write,
        .truncate = ext2fs_truncate,
        .close = ext2fs_close,
        .destroy = ext2fs_destroy,
        .sync = ext2fs_sync,
};

/**
 * @}
 */