source: mainline/uspace/srv/fs/minixfs/mfs_ops.c@ 5b38ecf0

/*
 * Copyright (c) 2011 Maurizio Lombardi
 * 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
 * @{
 */

#include <stdlib.h>
#include <fibril_synch.h>
#include <align.h>
#include <adt/hash_table.h>
#include "mfs.h"

#define OPEN_NODES_KEYS 2
#define OPEN_NODES_DEV_HANDLE_KEY 0
#define OPEN_NODES_INODE_KEY 1
#define OPEN_NODES_BUCKETS 256

static bool check_magic_number(uint16_t magic, bool *native,
                               mfs_version_t *version, bool *longfilenames);
static int mfs_node_core_get(fs_node_t **rfn, struct mfs_instance *inst,
                             fs_index_t index);

static int mfs_node_put(fs_node_t *fsnode);
static int mfs_node_open(fs_node_t *fsnode);
static fs_index_t mfs_index_get(fs_node_t *fsnode);
static unsigned mfs_lnkcnt_get(fs_node_t *fsnode);
static char mfs_plb_get_char(unsigned pos);
static bool mfs_is_directory(fs_node_t *fsnode);
static bool mfs_is_file(fs_node_t *fsnode);
static int mfs_has_children(bool *has_children, fs_node_t *fsnode);
static int mfs_root_get(fs_node_t **rfn, devmap_handle_t handle);
static devmap_handle_t mfs_device_get(fs_node_t *fsnode);
static aoff64_t mfs_size_get(fs_node_t *node);
static int mfs_match(fs_node_t **rfn, fs_node_t *pfn, const char *component);
static int mfs_create_node(fs_node_t **rfn, devmap_handle_t handle, int flags);
static int mfs_link(fs_node_t *pfn, fs_node_t *cfn, const char *name);
static int mfs_unlink(fs_node_t *, fs_node_t *, const char *name);
static int mfs_destroy_node(fs_node_t *fn);
static hash_index_t open_nodes_hash(unsigned long key[]);
static int open_nodes_compare(unsigned long key[], hash_count_t keys,
                link_t *item);
static void open_nodes_remove_cb(link_t *link);

static int mfs_node_get(fs_node_t **rfn, devmap_handle_t devmap_handle,
                        fs_index_t index);


static LIST_INITIALIZE(inst_list);
static FIBRIL_MUTEX_INITIALIZE(inst_list_mutex);
static hash_table_t open_nodes;
static FIBRIL_MUTEX_INITIALIZE(open_nodes_lock);

libfs_ops_t mfs_libfs_ops = {
        .size_get = mfs_size_get,
        .root_get = mfs_root_get,
        .device_get = mfs_device_get,
        .is_directory = mfs_is_directory,
        .is_file = mfs_is_file,
        .node_get = mfs_node_get,
        .node_put = mfs_node_put,
        .node_open = mfs_node_open,
        .index_get = mfs_index_get,
        .match = mfs_match,
        .create = mfs_create_node,
        .link = mfs_link,
        .unlink = mfs_unlink,
        .destroy = mfs_destroy_node,
        .plb_get_char = mfs_plb_get_char,
        .has_children = mfs_has_children,
        .lnkcnt_get = mfs_lnkcnt_get
};

/* Hash table interface for open nodes hash table */
static hash_index_t open_nodes_hash(unsigned long key[])
{
        /* TODO: This is very simple and probably can be improved */
        return key[OPEN_NODES_INODE_KEY] % OPEN_NODES_BUCKETS;
}

static int open_nodes_compare(unsigned long key[], hash_count_t keys,
                link_t *item)
{
        struct mfs_node *mnode = hash_table_get_instance(item, struct mfs_node, link);
        assert(keys > 0);
        if (mnode->instance->handle !=
            ((devmap_handle_t) key[OPEN_NODES_DEV_HANDLE_KEY])) {
                return false;
        }
        if (keys == 1) {
                return true;
        }
        assert(keys == 2);
        return (mnode->ino_i->index == key[OPEN_NODES_INODE_KEY]);
}

static void open_nodes_remove_cb(link_t *link)
{
        /* We don't use remove callback for this hash table */
}

static hash_table_operations_t open_nodes_ops = {
        .hash = open_nodes_hash,
        .compare = open_nodes_compare,
        .remove_callback = open_nodes_remove_cb,
};

int mfs_global_init(void)
{
        if (!hash_table_create(&open_nodes, OPEN_NODES_BUCKETS,
                        OPEN_NODES_KEYS, &open_nodes_ops)) {
                return ENOMEM;
        }
        return EOK;
}

void mfs_mounted(ipc_callid_t rid, ipc_call_t *request)
{
        devmap_handle_t devmap_handle = (devmap_handle_t) IPC_GET_ARG1(*request);
        enum cache_mode cmode;
        struct mfs_superblock *sb;
        struct mfs3_superblock *sb3;
        struct mfs_sb_info *sbi;
        struct mfs_instance *instance;
        bool native, longnames;
        mfs_version_t version;
        uint16_t magic;

        /* Accept the mount options */
        char *opts;
        int rc = async_data_write_accept((void **) &opts, true, 0, 0, 0, NULL);

        if (rc != EOK) {
                mfsdebug("Can't accept async data write\n");
                async_answer_0(rid, rc);
                return;
        }

        /* Check for option enabling write through. */
        if (str_cmp(opts, "wtcache") == 0)
                cmode = CACHE_MODE_WT;
        else
                cmode = CACHE_MODE_WB;

        free(opts);

        /* initialize libblock */
        rc = block_init(EXCHANGE_SERIALIZE, devmap_handle, 1024);
        if (rc != EOK) {
                mfsdebug("libblock initialization failed\n");
                async_answer_0(rid, rc);
                return;
        }

        /*Allocate space for generic MFS superblock*/
        sbi = malloc(sizeof(*sbi));

        if (!sbi) {
                async_answer_0(rid, ENOMEM);
                return;
        }

        /*Allocate space for filesystem instance*/
        instance = malloc(sizeof(*instance));

        if (!instance) {
                async_answer_0(rid, ENOMEM);
                return;
        }

        instance->open_nodes_cnt = 0;

        sb = malloc(MFS_SUPERBLOCK_SIZE);

        if (!sb) {
                async_answer_0(rid, ENOMEM);
                return;
        }

        /* Read the superblock */
        rc = block_read_direct(devmap_handle, MFS_SUPERBLOCK << 1, 1, sb);
        if (rc != EOK) {
                block_fini(devmap_handle);
                async_answer_0(rid, rc);
                return;
        }

        sb3 = (struct mfs3_superblock *) sb;

        if (check_magic_number(sb->s_magic, &native, &version, &longnames)) {
                /*This is a V1 or V2 Minix filesystem*/
                magic = sb->s_magic;
                goto recognized;
        }

        if (!check_magic_number(sb3->s_magic, &native, &version, &longnames)) {
                mfsdebug("magic number not recognized\n");
                block_fini(devmap_handle);
                async_answer_0(rid, ENOTSUP);
                return;
        }

        /*This is a V3 Minix filesystem*/

        magic = sb3->s_magic;

recognized:

        mfsdebug("magic number recognized = %04x\n", magic);

        /*Fill superblock info structure*/

        sbi->fs_version = version;
        sbi->long_names = longnames;
        sbi->native = native;
        sbi->magic = magic;
        sbi->isearch = 0;
        sbi->zsearch = 0;

        if (version == MFS_VERSION_V3) {
                sbi->ninodes = conv32(native, sb3->s_ninodes);
                sbi->ibmap_blocks = conv16(native, sb3->s_ibmap_blocks);
                sbi->zbmap_blocks = conv16(native, sb3->s_zbmap_blocks);
                sbi->firstdatazone = conv16(native, sb3->s_first_data_zone);
                sbi->log2_zone_size = conv16(native, sb3->s_log2_zone_size);
                sbi->max_file_size = conv32(native, sb3->s_max_file_size);
                sbi->nzones = conv32(native, sb3->s_nzones);
                sbi->block_size = conv16(native, sb3->s_block_size);
                sbi->ino_per_block = V3_INODES_PER_BLOCK(sbi->block_size);
                sbi->dirsize = MFS3_DIRSIZE;
                sbi->max_name_len = MFS3_MAX_NAME_LEN;
        } else {
                sbi->ninodes = conv16(native, sb->s_ninodes);
                sbi->ibmap_blocks = conv16(native, sb->s_ibmap_blocks);
                sbi->zbmap_blocks = conv16(native, sb->s_zbmap_blocks);
                sbi->firstdatazone = conv16(native, sb->s_first_data_zone);
                sbi->log2_zone_size = conv16(native, sb->s_log2_zone_size);
                sbi->max_file_size = conv32(native, sb->s_max_file_size);
                sbi->block_size = MFS_BLOCKSIZE;
                if (version == MFS_VERSION_V2) {
                        sbi->nzones = conv32(native, sb->s_nzones2);
                        sbi->ino_per_block = V2_INODES_PER_BLOCK;
                } else {
                        sbi->nzones = conv16(native, sb->s_nzones);
                        sbi->ino_per_block = V1_INODES_PER_BLOCK;
                }
                sbi->dirsize = longnames ? MFSL_DIRSIZE : MFS_DIRSIZE;
                sbi->max_name_len = longnames ? MFS_L_MAX_NAME_LEN :
                                    MFS_MAX_NAME_LEN;
        }
        sbi->itable_off = 2 + sbi->ibmap_blocks + sbi->zbmap_blocks;

        free(sb);

        rc = block_cache_init(devmap_handle, sbi->block_size, 0, cmode);

        if (rc != EOK) {
                block_fini(devmap_handle);
                async_answer_0(rid, EINVAL);
                mfsdebug("block cache initialization failed\n");
                return;
        }

        /*Initialize the instance structure and add it to the list*/
        link_initialize(&instance->link);
        instance->handle = devmap_handle;
        instance->sbi = sbi;

        fibril_mutex_lock(&inst_list_mutex);
        list_append(&instance->link, &inst_list);
        fibril_mutex_unlock(&inst_list_mutex);

        mfsdebug("mount successful\n");

        async_answer_0(rid, EOK);
}

void mfs_mount(ipc_callid_t rid, ipc_call_t *request)
{
        libfs_mount(&mfs_libfs_ops, mfs_reg.fs_handle, rid, request);
}

void mfs_unmount(ipc_callid_t rid, ipc_call_t *request)
{
        libfs_unmount(&mfs_libfs_ops, rid, request);
}

void mfs_unmounted(ipc_callid_t rid, ipc_call_t *request)
{
        devmap_handle_t devmap = (devmap_handle_t) IPC_GET_ARG1(*request);
        struct mfs_instance *inst;

        int r = mfs_instance_get(devmap, &inst);
        if (r != EOK) {
                async_answer_0(rid, r);
                return;
        }

        if (inst->open_nodes_cnt != 0) {
                async_answer_0(rid, EBUSY);
                return;
        }

        (void) block_cache_fini(devmap);
        block_fini(devmap);

        /* Remove the instance from the list */
        fibril_mutex_lock(&inst_list_mutex);
        list_remove(&inst->link);
        fibril_mutex_unlock(&inst_list_mutex);

        free(inst->sbi);
        free(inst);

        async_answer_0(rid, EOK);
}

devmap_handle_t mfs_device_get(fs_node_t *fsnode)
{
        struct mfs_node *node = fsnode->data;
        return node->instance->handle;
}

static int mfs_create_node(fs_node_t **rfn, devmap_handle_t handle, int flags)
{
        int r;
        struct mfs_instance *inst;
        struct mfs_node *mnode;
        fs_node_t *fsnode;
        uint32_t inum;

        mfsdebug("%s()\n", __FUNCTION__);

        r = mfs_instance_get(handle, &inst);
        on_error(r, return r);

        /*Alloc a new inode*/
        r = mfs_alloc_inode(inst, &inum);
        on_error(r, return r);

        struct mfs_ino_info *ino_i;

        ino_i = malloc(sizeof(*ino_i));
        if (!ino_i) {
                r = ENOMEM;
                goto out_err;
        }

        mnode = malloc(sizeof(*mnode));
        if (!mnode) {
                r = ENOMEM;
                goto out_err_1;
        }

        fsnode = malloc(sizeof(fs_node_t));
        if (!fsnode) {
                r = ENOMEM;
                goto out_err_2;
        }

        if (flags & L_DIRECTORY)
                ino_i->i_mode = S_IFDIR;
        else
                ino_i->i_mode = S_IFREG;

        ino_i->i_nlinks = 1;
        ino_i->i_uid = 0;
        ino_i->i_gid = 0;
        ino_i->i_size = 0;
        ino_i->i_atime = 0;
        ino_i->i_mtime = 0;
        ino_i->i_ctime = 0;

        memset(ino_i->i_dzone, 0, sizeof(uint32_t) * V2_NR_DIRECT_ZONES);
        memset(ino_i->i_izone, 0, sizeof(uint32_t) * V2_NR_INDIRECT_ZONES);

        mfsdebug("new node idx = %d\n", (int) inum);

        ino_i->index = inum;
        ino_i->dirty = true;
        mnode->ino_i = ino_i;
        mnode->instance = inst;
        mnode->refcnt = 1;

        link_initialize(&mnode->link);

        unsigned long key[] = {
                [OPEN_NODES_DEV_HANDLE_KEY] = inst->handle,
                [OPEN_NODES_INODE_KEY] = inum,
        };

        fibril_mutex_lock(&open_nodes_lock);
        hash_table_insert(&open_nodes, key, &mnode->link);
        fibril_mutex_unlock(&open_nodes_lock);
        inst->open_nodes_cnt++;

        mnode->ino_i->dirty = true;

        fs_node_initialize(fsnode);
        fsnode->data = mnode;
        mnode->fsnode = fsnode;
        *rfn = fsnode;

        return EOK;

out_err_2:
        free(mnode);
out_err_1:
        free(ino_i);
out_err:
        return r;
}

static int mfs_match(fs_node_t **rfn, fs_node_t *pfn, const char *component)
{
        struct mfs_node *mnode = pfn->data;
        struct mfs_ino_info *ino_i = mnode->ino_i;
        struct mfs_dentry_info d_info;
        int r;

        mfsdebug("%s()\n", __FUNCTION__);

        if (!S_ISDIR(ino_i->i_mode))
                return ENOTDIR;

        struct mfs_sb_info *sbi = mnode->instance->sbi;
        const size_t comp_size = str_size(component);

        unsigned i;
        for (i = 0; i < mnode->ino_i->i_size / sbi->dirsize; ++i) {
                r = read_dentry(mnode, &d_info, i);
                on_error(r, return r);

                if (!d_info.d_inum) {
                        /*This entry is not used*/
                        continue;
                }

                const size_t dentry_name_size = str_size(d_info.d_name);

                if (comp_size == dentry_name_size &&
                        !bcmp(component, d_info.d_name, dentry_name_size)) {
                        /*Hit!*/
                        mfs_node_core_get(rfn, mnode->instance,
                                          d_info.d_inum);
                        goto found;
                }
        }
        *rfn = NULL;
found:
        return EOK;
}

static aoff64_t mfs_size_get(fs_node_t *node)
{
        assert(node);

        const struct mfs_node *mnode = node->data;
        assert(mnode);
        assert(mnode->ino_i);

        return mnode->ino_i->i_size;
}

void mfs_stat(ipc_callid_t rid, ipc_call_t *request)
{
        libfs_stat(&mfs_libfs_ops, mfs_reg.fs_handle, rid, request);
}

static int mfs_node_get(fs_node_t **rfn, devmap_handle_t devmap_handle,
                        fs_index_t index)
{
        int rc;
        struct mfs_instance *instance;

        mfsdebug("%s()\n", __FUNCTION__);

        rc = mfs_instance_get(devmap_handle, &instance);
        on_error(rc, return rc);

        return mfs_node_core_get(rfn, instance, index);
}

static int mfs_node_put(fs_node_t *fsnode)
{
        int rc = EOK;
        struct mfs_node *mnode = fsnode->data;

        mfsdebug("%s()\n", __FUNCTION__);

        fibril_mutex_lock(&open_nodes_lock);

        assert(mnode->refcnt > 0);
        mnode->refcnt--;
        if (mnode->refcnt == 0) {
                unsigned long key[] = {
                        [OPEN_NODES_DEV_HANDLE_KEY] = mnode->instance->handle,
                        [OPEN_NODES_INODE_KEY] = mnode->ino_i->index
                };
                hash_table_remove(&open_nodes, key, OPEN_NODES_KEYS);
                assert(mnode->instance->open_nodes_cnt > 0);
                mnode->instance->open_nodes_cnt--;
                rc = put_inode(mnode);
                free(mnode->ino_i);
                free(mnode);
                free(fsnode);
        }

        fibril_mutex_unlock(&open_nodes_lock);
        return rc;
}

static int mfs_node_open(fs_node_t *fsnode)
{
        /*
         * Opening a file is stateless, nothing
         * to be done here.
         */
        return EOK;
}

static fs_index_t mfs_index_get(fs_node_t *fsnode)
{
        struct mfs_node *mnode = fsnode->data;

        assert(mnode->ino_i);
        return mnode->ino_i->index;
}

static unsigned mfs_lnkcnt_get(fs_node_t *fsnode)
{
        struct mfs_node *mnode = fsnode->data;

        mfsdebug("%s()\n", __FUNCTION__);

        assert(mnode);
        assert(mnode->ino_i);

        return mnode->ino_i->i_nlinks;
}

static int mfs_node_core_get(fs_node_t **rfn, struct mfs_instance *inst,
                             fs_index_t index)
{
        fs_node_t *node = NULL;
        struct mfs_node *mnode = NULL;
        int rc;

        mfsdebug("%s()\n", __FUNCTION__);

        fibril_mutex_lock(&open_nodes_lock);

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

        if (already_open) {
                mnode = hash_table_get_instance(already_open, struct mfs_node, link);
                *rfn = mnode->fsnode;
                mnode->refcnt++;

                fibril_mutex_unlock(&open_nodes_lock);
                return EOK;
        }

        node = malloc(sizeof(fs_node_t));
        if (!node) {
                rc = ENOMEM;
                goto out_err;
        }

        fs_node_initialize(node);

        mnode = malloc(sizeof(*mnode));
        if (!mnode) {
                rc = ENOMEM;
                goto out_err;
        }

        struct mfs_ino_info *ino_i;

        rc = get_inode(inst, &ino_i, index);
        on_error(rc, goto out_err);

        ino_i->index = index;
        mnode->ino_i = ino_i;
        mnode->refcnt = 1;
        link_initialize(&mnode->link);

        mnode->instance = inst;
        node->data = mnode;
        mnode->fsnode = node;
        *rfn = node;

        hash_table_insert(&open_nodes, key, &mnode->link);
        inst->open_nodes_cnt++;

        fibril_mutex_unlock(&open_nodes_lock);

        return EOK;

out_err:
        if (node)
                free(node);
        if (mnode)
                free(mnode);
        fibril_mutex_unlock(&open_nodes_lock);
        return rc;
}

static bool mfs_is_directory(fs_node_t *fsnode)
{
        const struct mfs_node *node = fsnode->data;
        return S_ISDIR(node->ino_i->i_mode);
}

static bool mfs_is_file(fs_node_t *fsnode)
{
        struct mfs_node *node = fsnode->data;
        return S_ISREG(node->ino_i->i_mode);
}

static int mfs_root_get(fs_node_t **rfn, devmap_handle_t handle)
{
        int rc = mfs_node_get(rfn, handle, MFS_ROOT_INO);
        return rc;
}

void mfs_lookup(ipc_callid_t rid, ipc_call_t *request)
{
        libfs_lookup(&mfs_libfs_ops, mfs_reg.fs_handle, rid, request);
}

static char mfs_plb_get_char(unsigned pos)
{
        return mfs_reg.plb_ro[pos % PLB_SIZE];
}

static int mfs_link(fs_node_t *pfn, fs_node_t *cfn, const char *name)
{
        struct mfs_node *parent = pfn->data;
        struct mfs_node *child = cfn->data;
        struct mfs_sb_info *sbi = parent->instance->sbi;

        mfsdebug("%s()\n", __FUNCTION__);

        if (str_size(name) > sbi->max_name_len)
                return ENAMETOOLONG;

        int r = insert_dentry(parent, name, child->ino_i->index);
        on_error(r, goto exit_error);

        if (S_ISDIR(child->ino_i->i_mode)) {
                r = insert_dentry(child, ".", child->ino_i->index);
                on_error(r, goto exit_error);
                child->ino_i->i_nlinks++;
                child->ino_i->dirty = true;
                r = insert_dentry(child, "..", parent->ino_i->index);
                on_error(r, goto exit_error);
                parent->ino_i->i_nlinks++;
                parent->ino_i->dirty = true;
        }

exit_error:
        return r;
}

static int
mfs_unlink(fs_node_t *pfn, fs_node_t *cfn, const char *name)
{
        struct mfs_node *parent = pfn->data;
        struct mfs_node *child = cfn->data;
        bool has_children;
        int r;

        mfsdebug("%s()\n", __FUNCTION__);

        if (!parent)
                return EBUSY;

        r = mfs_has_children(&has_children, cfn);
        on_error(r, return r);

        if (has_children)
                return ENOTEMPTY;

        r = remove_dentry(parent, name);
        on_error(r, return r);

        struct mfs_ino_info *chino = child->ino_i;

        assert(chino->i_nlinks >= 1);
        --chino->i_nlinks;

        if (chino->i_nlinks == 0 && S_ISDIR(chino->i_mode)) {
                parent->ino_i->i_nlinks--;
                parent->ino_i->dirty = true;
        }

        chino->dirty = true;

        return r;
}

static int mfs_has_children(bool *has_children, fs_node_t *fsnode)
{
        struct mfs_node *mnode = fsnode->data;
        struct mfs_sb_info *sbi = mnode->instance->sbi;
        int r;

        *has_children = false;

        if (!S_ISDIR(mnode->ino_i->i_mode))
                goto out;

        struct mfs_dentry_info d_info;

        /* The first two dentries are always . and .. */
        unsigned i;
        for (i = 2; i < mnode->ino_i->i_size / sbi->dirsize; ++i) {
                r = read_dentry(mnode, &d_info, i);
                on_error(r, return r);

                if (d_info.d_inum) {
                        /*A valid entry has been found*/
                        *has_children = true;
                        break;
                }
        }
out:

        return EOK;
}

void
mfs_read(ipc_callid_t rid, ipc_call_t *request)
{
        int rc;
        devmap_handle_t handle = (devmap_handle_t) IPC_GET_ARG1(*request);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*request);
        aoff64_t pos = (aoff64_t) MERGE_LOUP32(IPC_GET_ARG3(*request),
                                               IPC_GET_ARG4(*request));
        fs_node_t *fn;

        rc = mfs_node_get(&fn, handle, index);
        if (rc != EOK) {
                async_answer_0(rid, rc);
                return;
        }
        if (!fn) {
                async_answer_0(rid, ENOENT);
                return;
        }

        struct mfs_node *mnode;
        struct mfs_ino_info *ino_i;
        size_t len, bytes = 0;
        ipc_callid_t callid;

        mnode = fn->data;
        ino_i = mnode->ino_i;

        if (!async_data_read_receive(&callid, &len)) {
                rc = EINVAL;
                goto out_error;
        }

        if (S_ISDIR(ino_i->i_mode)) {
                aoff64_t spos = pos;
                struct mfs_dentry_info d_info;
                struct mfs_sb_info *sbi = mnode->instance->sbi;

                if (pos < 2) {
                        /*Skip the first two dentries ('.' and '..')*/
                        pos = 2;
                }

                for (; pos < mnode->ino_i->i_size / sbi->dirsize; ++pos) {
                        rc = read_dentry(mnode, &d_info, pos);
                        on_error(rc, goto out_error);

                        if (d_info.d_inum) {
                                /*Dentry found!*/
                                goto found;
                        }
                }

                rc = mfs_node_put(fn);
                async_answer_0(callid, rc != EOK ? rc : ENOENT);
                async_answer_1(rid, rc != EOK ? rc : ENOENT, 0);
                return;
found:
                async_data_read_finalize(callid, d_info.d_name,
                                         str_size(d_info.d_name) + 1);
                bytes = ((pos - spos) + 1);
        } else {
                struct mfs_sb_info *sbi = mnode->instance->sbi;

                if (pos >= (size_t) ino_i->i_size) {
                        /*Trying to read beyond the end of file*/
                        bytes = 0;
                        (void) async_data_read_finalize(callid, NULL, 0);
                        goto out_success;
                }

                bytes = min(len, sbi->block_size - pos % sbi->block_size);
                bytes = min(bytes, ino_i->i_size - pos);

                uint32_t zone;
                block_t *b;

                rc = read_map(&zone, mnode, pos);
                on_error(rc, goto out_error);

                if (zone == 0) {
                        /*sparse file*/
                        uint8_t *buf = malloc(sbi->block_size);
                        if (!buf) {
                                rc = ENOMEM;
                                goto out_error;
                        }
                        memset(buf, 0, sizeof(sbi->block_size));
                        async_data_read_finalize(callid,
                                                 buf + pos % sbi->block_size, bytes);
                        free(buf);
                        goto out_success;
                }

                rc = block_get(&b, handle, zone, BLOCK_FLAGS_NONE);
                on_error(rc, goto out_error);

                async_data_read_finalize(callid, b->data +
                                         pos % sbi->block_size, bytes);

                rc = block_put(b);
                if (rc != EOK) {
                        mfs_node_put(fn);
                        async_answer_0(rid, rc);
                        return;
                }
        }
out_success:
        rc = mfs_node_put(fn);
        async_answer_1(rid, rc, (sysarg_t)bytes);
        return;
out_error:
        ;
        int tmp = mfs_node_put(fn);
        async_answer_0(callid, tmp != EOK ? tmp : rc);
        async_answer_0(rid, tmp != EOK ? tmp : rc);
}

void
mfs_write(ipc_callid_t rid, ipc_call_t *request)
{
        devmap_handle_t handle = (devmap_handle_t) IPC_GET_ARG1(*request);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*request);
        aoff64_t pos = (aoff64_t) MERGE_LOUP32(IPC_GET_ARG3(*request),
                                               IPC_GET_ARG4(*request));

        fs_node_t *fn;
        int r;
        int flags = BLOCK_FLAGS_NONE;

        r = mfs_node_get(&fn, handle, index);
        if (r != EOK) {
                async_answer_0(rid, r);
                return;
        }

        if (!fn) {
                async_answer_0(rid, ENOENT);
                return;
        }

        ipc_callid_t callid;
        size_t len;

        if (!async_data_write_receive(&callid, &len)) {
                r = EINVAL;
                goto out_err;
        }

        struct mfs_node *mnode = fn->data;
        struct mfs_sb_info *sbi = mnode->instance->sbi;
        struct mfs_ino_info *ino_i = mnode->ino_i;
        const size_t bs = sbi->block_size;
        size_t bytes = min(len, bs - pos % bs);
        size_t boundary = ROUND_UP(ino_i->i_size, bs);
        uint32_t block;

        if (bytes == bs)
                flags = BLOCK_FLAGS_NOREAD;

        if (pos < boundary) {
                r = read_map(&block, mnode, pos);
                on_error(r, goto out_err);

                if (block == 0) {
                        /*Writing in a sparse block*/
                        r = mfs_alloc_zone(mnode->instance, &block);
                        on_error(r, goto out_err);
                        flags = BLOCK_FLAGS_NOREAD;
                }
        } else {
                uint32_t dummy;

                r = mfs_alloc_zone(mnode->instance, &block);
                on_error(r, goto out_err);

                r = write_map(mnode, pos, block, &dummy);
                on_error(r, goto out_err);
        }

        block_t *b;
        r = block_get(&b, handle, block, flags);
        on_error(r, goto out_err);

        async_data_write_finalize(callid, b->data + pos % bs, bytes);
        b->dirty = true;

        r = block_put(b);
        if (r != EOK) {
                mfs_node_put(fn);
                async_answer_0(rid, r);
                return;
        }

        ino_i->i_size = pos + bytes;
        ino_i->dirty = true;
        r = mfs_node_put(fn);
        async_answer_2(rid, r, bytes, pos + bytes);
        return;

out_err:
        mfs_node_put(fn);
        async_answer_0(callid, r);
        async_answer_0(rid, r);
}

void
mfs_destroy(ipc_callid_t rid, ipc_call_t *request)
{
        devmap_handle_t handle = (devmap_handle_t)IPC_GET_ARG1(*request);
        fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);
        fs_node_t *fn;
        int r;

        r = mfs_node_get(&fn, handle, index);
        if (r != EOK) {
                async_answer_0(rid, r);
                return;
        }
        if (!fn) {
                async_answer_0(rid, ENOENT);
                return;
        }

        /*Destroy the inode*/
        r = mfs_destroy_node(fn);
        async_answer_0(rid, r);
}

static int
mfs_destroy_node(fs_node_t *fn)
{
        struct mfs_node *mnode = fn->data;
        bool has_children;
        int r;

        mfsdebug("mfs_destroy_node %d\n", mnode->ino_i->index);

        r = mfs_has_children(&has_children, fn);
        on_error(r, return r);

        assert(!has_children);

        if (mnode->ino_i->i_nlinks > 0) {
                mfsdebug("nlinks = %d", mnode->ino_i->i_nlinks);
                r = EOK;
                goto out;
        }

        /*Free the entire inode content*/
        r = inode_shrink(mnode, mnode->ino_i->i_size);
        on_error(r, return r);
        r = mfs_free_inode(mnode->instance, mnode->ino_i->index);
        on_error(r, return r);

out:
        free(mnode->ino_i);
        free(mnode);
        free(fn);
        return r;
}

void
mfs_truncate(ipc_callid_t rid, ipc_call_t *request)
{
        devmap_handle_t handle = (devmap_handle_t) IPC_GET_ARG1(*request);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*request);
        aoff64_t size = (aoff64_t) MERGE_LOUP32(IPC_GET_ARG3(*request),
                                                IPC_GET_ARG4(*request));
        fs_node_t *fn;
        int r;

        r = mfs_node_get(&fn, handle, index);
        if (r != EOK) {
                async_answer_0(rid, r);
                return;
        }

        if (!fn) {
                async_answer_0(rid, r);
                return;
        }

        struct mfs_node *mnode = fn->data;
        struct mfs_ino_info *ino_i = mnode->ino_i;

        if (ino_i->i_size == size)
                r = EOK;
        else
                r = inode_shrink(mnode, ino_i->i_size - size);

        async_answer_0(rid, r);
        mfs_node_put(fn);
}

int mfs_instance_get(devmap_handle_t handle, struct mfs_instance **instance)
{
        link_t *link;
        struct mfs_instance *instance_ptr;

        fibril_mutex_lock(&inst_list_mutex);

        for (link = inst_list.next; link != &inst_list; link = link->next) {
                instance_ptr = list_get_instance(link, struct mfs_instance,
                                                 link);

                if (instance_ptr->handle == handle) {
                        *instance = instance_ptr;
                        fibril_mutex_unlock(&inst_list_mutex);
                        return EOK;
                }
        }

        mfsdebug("Instance not found\n");

        fibril_mutex_unlock(&inst_list_mutex);
        return EINVAL;
}

static bool check_magic_number(uint16_t magic, bool *native,
                               mfs_version_t *version, bool *longfilenames)
{
        bool rc = true;
        *longfilenames = false;

        if (magic == MFS_MAGIC_V1 || magic == MFS_MAGIC_V1R) {
                *native = magic == MFS_MAGIC_V1;
                *version = MFS_VERSION_V1;
        } else if (magic == MFS_MAGIC_V1L || magic == MFS_MAGIC_V1LR) {
                *native = magic == MFS_MAGIC_V1L;
                *version = MFS_VERSION_V1;
                *longfilenames = true;
        } else if (magic == MFS_MAGIC_V2 || magic == MFS_MAGIC_V2R) {
                *native = magic == MFS_MAGIC_V2;
                *version = MFS_VERSION_V2;
        } else if (magic == MFS_MAGIC_V2L || magic == MFS_MAGIC_V2LR) {
                *native = magic == MFS_MAGIC_V2L;
                *version = MFS_VERSION_V2;
                *longfilenames = true;
        } else if (magic == MFS_MAGIC_V3 || magic == MFS_MAGIC_V3R) {
                *native = magic == MFS_MAGIC_V3;
                *version = MFS_VERSION_V3;
        } else
                rc = false;

        return rc;
}

void
mfs_close(ipc_callid_t rid, ipc_call_t *request)
{
        async_answer_0(rid, EOK);
}

void
mfs_open_node(ipc_callid_t rid, ipc_call_t *request)
{
        libfs_open_node(&mfs_libfs_ops, mfs_reg.fs_handle, rid, request);
}

void
mfs_sync(ipc_callid_t rid, ipc_call_t *request)
{
        devmap_handle_t devmap = (devmap_handle_t) IPC_GET_ARG1(*request);
        fs_index_t index = (fs_index_t) IPC_GET_ARG2(*request);

        fs_node_t *fn;
        int rc = mfs_node_get(&fn, devmap, index);
        if (rc != EOK) {
                async_answer_0(rid, rc);
                return;
        }
        if (!fn) {
                async_answer_0(rid, ENOENT);
                return;
        }

        struct mfs_node *mnode = fn->data;
        mnode->ino_i->dirty = true;

        rc = mfs_node_put(fn);
        async_answer_0(rid, rc);
}

/**
 * @}
 */