HelenOS sources

root/uspace/srv/fs/exfat/exfat_ops.c

DEFINITIONS

1. exfat_node_initialize
2. exfat_node_sync
3. exfat_node_fini_by_service_id
4. exfat_node_get_new
5. exfat_node_get_new_by_pos
6. exfat_node_get_core
7. exfat_node_expand
8. exfat_node_shrink
9. exfat_root_get
10. exfat_bitmap_get
11. exfat_uctable_get
12. exfat_match
13. exfat_node_get
14. exfat_node_open
15. exfat_node_put
16. exfat_create_node
17. exfat_destroy_node
18. exfat_link
19. exfat_unlink
20. exfat_has_children
21. exfat_index_get
22. exfat_size_get
23. exfat_lnkcnt_get
24. exfat_is_directory
25. exfat_is_file
26. exfat_service_get
27. exfat_size_block
28. exfat_total_block_count
29. exfat_free_block_count
30. exfat_fs_open
31. exfat_fs_close
32. exfat_fsinfo
33. exfat_fsprobe
34. exfat_mounted
35. exfat_unmounted
36. exfat_read
37. exfat_close
38. exfat_sync
39. exfat_write
40. exfat_truncate
41. exfat_destroy

/*
 * Copyright (c) 2024 Jiri Svoboda
 * Copyright (c) 2008 Jakub Jermar
 * Copyright (c) 2011 Oleg Romanenko
 * 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 exfat
 * @{
 */

/**
 * @file        exfat_ops.c
 * @brief       Implementation of VFS operations for the exFAT file system
 *              server.
 */

#include "exfat.h"
#include "exfat_fat.h"
#include "exfat_dentry.h"
#include "exfat_directory.h"
#include "exfat_bitmap.h"
#include "../../vfs/vfs.h"
#include <libfs.h>
#include <block.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/hash.h>
#include <adt/list.h>
#include <assert.h>
#include <fibril_synch.h>
#include <align.h>
#include <stdio.h>
#include <stdlib.h>

/** Mutex protecting the list of cached free FAT nodes. */
static FIBRIL_MUTEX_INITIALIZE(ffn_mutex);

/** List of cached free FAT nodes. */
static LIST_INITIALIZE(ffn_list);

/*
 * Forward declarations of FAT libfs operations.
 */

static void exfat_fsinfo(exfat_bs_t *, service_id_t);
static errno_t exfat_root_get(fs_node_t **, service_id_t);
static errno_t exfat_match(fs_node_t **, fs_node_t *, const char *);
static errno_t exfat_node_get(fs_node_t **, service_id_t, fs_index_t);
static errno_t exfat_node_open(fs_node_t *);
/* static errno_t exfat_node_put(fs_node_t *); */
static errno_t exfat_create_node(fs_node_t **, service_id_t, int);
static errno_t exfat_destroy_node(fs_node_t *);
static errno_t exfat_link(fs_node_t *, fs_node_t *, const char *);
static errno_t exfat_unlink(fs_node_t *, fs_node_t *, const char *);
static errno_t exfat_has_children(bool *, fs_node_t *);
static fs_index_t exfat_index_get(fs_node_t *);
static aoff64_t exfat_size_get(fs_node_t *);
static unsigned exfat_lnkcnt_get(fs_node_t *);
static bool exfat_is_directory(fs_node_t *);
static bool exfat_is_file(fs_node_t *node);
static service_id_t exfat_service_get(fs_node_t *node);
static errno_t exfat_size_block(service_id_t, uint32_t *);
static errno_t exfat_total_block_count(service_id_t, uint64_t *);
static errno_t exfat_free_block_count(service_id_t, uint64_t *);

/*
 * Helper functions.
 */
static void exfat_node_initialize(exfat_node_t *node)
{
        fibril_mutex_initialize(&node->lock);
        node->bp = NULL;
        node->idx = NULL;
        node->type = EXFAT_UNKNOW;
        link_initialize(&node->ffn_link);
        node->size = 0;
        node->lnkcnt = 0;
        node->refcnt = 0;
        node->dirty = false;
        node->fragmented = false;
        node->lastc_cached_valid = false;
        node->lastc_cached_value = 0;
        node->currc_cached_valid = false;
        node->currc_cached_bn = 0;
        node->currc_cached_value = 0;
}

static errno_t exfat_node_sync(exfat_node_t *node)
{
        errno_t rc;
        exfat_directory_t di;
        exfat_file_dentry_t df;
        exfat_stream_dentry_t ds;

        if (!(node->type == EXFAT_DIRECTORY || node->type == EXFAT_FILE))
                return EOK;

        if (node->type == EXFAT_DIRECTORY)
                df.attr = EXFAT_ATTR_SUBDIR;
        else
                df.attr = 0;

        ds.firstc = node->firstc;
        if (node->size == 0 && node->firstc == 0) {
                ds.flags = 0;
        } else {
                ds.flags = 1;
                ds.flags |= (!node->fragmented << 1);
        }
        ds.valid_data_size = node->size;
        ds.data_size = node->size;

        exfat_directory_open_parent(&di, node->idx->service_id, node->idx->pfc,
            node->idx->parent_fragmented);
        rc = exfat_directory_seek(&di, node->idx->pdi);
        if (rc != EOK) {
                (void) exfat_directory_close(&di);
                return rc;
        }

        rc = exfat_directory_sync_file(&di, &df, &ds);
        if (rc != EOK) {
                (void) exfat_directory_close(&di);
                return rc;
        }
        return exfat_directory_close(&di);
}

static errno_t exfat_node_fini_by_service_id(service_id_t service_id)
{
        errno_t rc;

        /*
         * We are called from fat_unmounted() and assume that there are already
         * no nodes belonging to this instance with non-zero refcount. Therefore
         * it is sufficient to clean up only the FAT free node list.
         */

restart:
        fibril_mutex_lock(&ffn_mutex);
        list_foreach(ffn_list, ffn_link, exfat_node_t, nodep) {
                if (!fibril_mutex_trylock(&nodep->lock)) {
                        fibril_mutex_unlock(&ffn_mutex);
                        goto restart;
                }
                if (!fibril_mutex_trylock(&nodep->idx->lock)) {
                        fibril_mutex_unlock(&nodep->lock);
                        fibril_mutex_unlock(&ffn_mutex);
                        goto restart;
                }
                if (nodep->idx->service_id != service_id) {
                        fibril_mutex_unlock(&nodep->idx->lock);
                        fibril_mutex_unlock(&nodep->lock);
                        continue;
                }

                list_remove(&nodep->ffn_link);
                fibril_mutex_unlock(&ffn_mutex);

                /*
                 * We can unlock the node and its index structure because we are
                 * the last player on this playground and VFS is preventing new
                 * players from entering.
                 */
                fibril_mutex_unlock(&nodep->idx->lock);
                fibril_mutex_unlock(&nodep->lock);

                if (nodep->dirty) {
                        rc = exfat_node_sync(nodep);
                        if (rc != EOK)
                                return rc;
                }
                nodep->idx->nodep = NULL;
                free(nodep->bp);
                free(nodep);

                /* Need to restart because we changed the ffn_list. */
                goto restart;
        }
        fibril_mutex_unlock(&ffn_mutex);

        return EOK;
}

static errno_t exfat_node_get_new(exfat_node_t **nodepp)
{
        fs_node_t *fn;
        exfat_node_t *nodep;
        errno_t rc;

        fibril_mutex_lock(&ffn_mutex);
        if (!list_empty(&ffn_list)) {
                /* Try to use a cached free node structure. */
                exfat_idx_t *idxp_tmp;
                nodep = list_get_instance(list_first(&ffn_list), exfat_node_t,
                    ffn_link);
                if (!fibril_mutex_trylock(&nodep->lock))
                        goto skip_cache;
                idxp_tmp = nodep->idx;
                if (!fibril_mutex_trylock(&idxp_tmp->lock)) {
                        fibril_mutex_unlock(&nodep->lock);
                        goto skip_cache;
                }
                list_remove(&nodep->ffn_link);
                fibril_mutex_unlock(&ffn_mutex);
                if (nodep->dirty) {
                        rc = exfat_node_sync(nodep);
                        if (rc != EOK) {
                                idxp_tmp->nodep = NULL;
                                fibril_mutex_unlock(&nodep->lock);
                                fibril_mutex_unlock(&idxp_tmp->lock);
                                free(nodep->bp);
                                free(nodep);
                                return rc;
                        }
                }
                idxp_tmp->nodep = NULL;
                fibril_mutex_unlock(&nodep->lock);
                fibril_mutex_unlock(&idxp_tmp->lock);
                fn = FS_NODE(nodep);
        } else {
        skip_cache:
                /* Try to allocate a new node structure. */
                fibril_mutex_unlock(&ffn_mutex);
                fn = (fs_node_t *)malloc(sizeof(fs_node_t));
                if (!fn)
                        return ENOMEM;
                nodep = (exfat_node_t *)malloc(sizeof(exfat_node_t));
                if (!nodep) {
                        free(fn);
                        return ENOMEM;
                }
        }
        exfat_node_initialize(nodep);
        fs_node_initialize(fn);
        fn->data = nodep;
        nodep->bp = fn;

        *nodepp = nodep;
        return EOK;
}

static errno_t exfat_node_get_new_by_pos(exfat_node_t **nodepp,
    service_id_t service_id, exfat_cluster_t pfc, unsigned pdi)
{
        exfat_idx_t *idxp = exfat_idx_get_by_pos(service_id, pfc, pdi);
        if (!idxp)
                return ENOMEM;
        if (exfat_node_get_new(nodepp) != EOK)
                return ENOMEM;
        (*nodepp)->idx = idxp;
        idxp->nodep = *nodepp;
        return EOK;
}

/** Internal version of exfat_node_get().
 *
 * @param idxp          Locked index structure.
 */
static errno_t exfat_node_get_core(exfat_node_t **nodepp, exfat_idx_t *idxp)
{
        exfat_dentry_t *d;
        exfat_node_t *nodep = NULL;
        exfat_directory_t di;
        errno_t rc;

        if (idxp->nodep) {
                /*
                 * We are lucky.
                 * The node is already instantiated in memory.
                 */
                fibril_mutex_lock(&idxp->nodep->lock);
                if (!idxp->nodep->refcnt++) {
                        fibril_mutex_lock(&ffn_mutex);
                        list_remove(&idxp->nodep->ffn_link);
                        fibril_mutex_unlock(&ffn_mutex);
                }
                fibril_mutex_unlock(&idxp->nodep->lock);
                *nodepp = idxp->nodep;
                return EOK;
        }

        /*
         * We must instantiate the node from the file system.
         */

        assert(idxp->pfc);

        rc = exfat_node_get_new(&nodep);
        if (rc != EOK)
                return rc;

        exfat_directory_open_parent(&di, idxp->service_id, idxp->pfc,
            idxp->parent_fragmented);
        rc = exfat_directory_seek(&di, idxp->pdi);
        if (rc != EOK) {
                (void) exfat_directory_close(&di);
                (void) exfat_node_put(FS_NODE(nodep));
                return rc;
        }
        rc = exfat_directory_get(&di, &d);
        if (rc != EOK) {
                (void) exfat_directory_close(&di);
                (void) exfat_node_put(FS_NODE(nodep));
                return rc;
        }

        switch (exfat_classify_dentry(d)) {
        case EXFAT_DENTRY_FILE:
                nodep->type =
                    (uint16_t_le2host(d->file.attr) & EXFAT_ATTR_SUBDIR) ?
                    EXFAT_DIRECTORY : EXFAT_FILE;
                rc = exfat_directory_next(&di);
                if (rc != EOK) {
                        (void) exfat_directory_close(&di);
                        (void) exfat_node_put(FS_NODE(nodep));
                        return rc;
                }
                rc = exfat_directory_get(&di, &d);
                if (rc != EOK) {
                        (void) exfat_directory_close(&di);
                        (void) exfat_node_put(FS_NODE(nodep));
                        return rc;
                }
                nodep->firstc = uint32_t_le2host(d->stream.firstc);
                nodep->size = uint64_t_le2host(d->stream.data_size);
                nodep->fragmented = (d->stream.flags & 0x02) == 0;
                break;
        case EXFAT_DENTRY_BITMAP:
                nodep->type = EXFAT_BITMAP;
                nodep->firstc = uint32_t_le2host(d->bitmap.firstc);
                nodep->size = uint64_t_le2host(d->bitmap.size);
                nodep->fragmented = true;
                break;
        case EXFAT_DENTRY_UCTABLE:
                nodep->type = EXFAT_UCTABLE;
                nodep->firstc = uint32_t_le2host(d->uctable.firstc);
                nodep->size = uint64_t_le2host(d->uctable.size);
                nodep->fragmented = true;
                break;
        default:
        case EXFAT_DENTRY_SKIP:
        case EXFAT_DENTRY_LAST:
        case EXFAT_DENTRY_FREE:
        case EXFAT_DENTRY_VOLLABEL:
        case EXFAT_DENTRY_GUID:
        case EXFAT_DENTRY_STREAM:
        case EXFAT_DENTRY_NAME:
                (void) exfat_directory_close(&di);
                (void) exfat_node_put(FS_NODE(nodep));
                return ENOENT;
        }

        nodep->lnkcnt = 1;
        nodep->refcnt = 1;

        rc = exfat_directory_close(&di);
        if (rc != EOK) {
                (void) exfat_node_put(FS_NODE(nodep));
                return rc;
        }

        /* Link the idx structure with the node structure. */
        nodep->idx = idxp;
        idxp->nodep = nodep;

        *nodepp = nodep;
        return EOK;
}

errno_t exfat_node_expand(service_id_t service_id, exfat_node_t *nodep,
    exfat_cluster_t clusters)
{
        exfat_bs_t *bs;
        errno_t rc;
        bs = block_bb_get(service_id);

        if (!nodep->fragmented) {
                rc = exfat_bitmap_append_clusters(bs, nodep, clusters);
                if (rc != ENOSPC)
                        return rc;
                if (rc == ENOSPC) {
                        nodep->fragmented = true;
                        nodep->dirty = true;            /* need to sync node */
                        rc = exfat_bitmap_replicate_clusters(bs, nodep);
                        if (rc != EOK)
                                return rc;
                }
        }

        /* If we cant linear expand the node, we should use FAT instead */
        exfat_cluster_t mcl, lcl;

        /* create an independent chain of nclsts clusters in all FATs */
        rc = exfat_alloc_clusters(bs, service_id, clusters, &mcl, &lcl);
        if (rc != EOK)
                return rc;
        rc = exfat_zero_cluster(bs, service_id, mcl);
        if (rc != EOK) {
                (void) exfat_free_clusters(bs, service_id, mcl);
                return rc;
        }
        /*
         * Append the cluster chain starting in mcl to the end of the
         * node's cluster chain.
         */
        rc = exfat_append_clusters(bs, nodep, mcl, lcl);
        if (rc != EOK) {
                (void) exfat_free_clusters(bs, service_id, mcl);
                return rc;
        }

        return EOK;
}

static errno_t exfat_node_shrink(service_id_t service_id, exfat_node_t *nodep,
    aoff64_t size)
{
        exfat_bs_t *bs;
        errno_t rc;
        bs = block_bb_get(service_id);

        if (!nodep->fragmented) {
                exfat_cluster_t clsts, prev_clsts, new_clsts;
                prev_clsts = ROUND_UP(nodep->size, BPC(bs)) / BPC(bs);
                new_clsts =  ROUND_UP(size, BPC(bs)) / BPC(bs);

                assert(new_clsts < prev_clsts);

                clsts = prev_clsts - new_clsts;
                rc = exfat_bitmap_free_clusters(bs, nodep, clsts);
                if (rc != EOK)
                        return rc;
        } else {
                /*
                 * The node will be shrunk, clusters will be deallocated.
                 */
                if (size == 0) {
                        rc = exfat_chop_clusters(bs, nodep, 0);
                        if (rc != EOK)
                                return rc;
                } else {
                        exfat_cluster_t lastc;
                        rc = exfat_cluster_walk(bs, service_id, nodep->firstc,
                            &lastc, NULL, (size - 1) / BPC(bs));
                        if (rc != EOK)
                                return rc;
                        rc = exfat_chop_clusters(bs, nodep, lastc);
                        if (rc != EOK)
                                return rc;
                }
        }

        nodep->size = size;
        nodep->dirty = true;            /* need to sync node */
        return EOK;
}

/*
 * EXFAT libfs operations.
 */

errno_t exfat_root_get(fs_node_t **rfn, service_id_t service_id)
{
        return exfat_node_get(rfn, service_id, EXFAT_ROOT_IDX);
}

errno_t exfat_bitmap_get(fs_node_t **rfn, service_id_t service_id)
{
        return exfat_node_get(rfn, service_id, EXFAT_BITMAP_IDX);
}

errno_t exfat_uctable_get(fs_node_t **rfn, service_id_t service_id)
{
        return exfat_node_get(rfn, service_id, EXFAT_UCTABLE_IDX);
}

errno_t exfat_match(fs_node_t **rfn, fs_node_t *pfn, const char *component)
{
        exfat_node_t *parentp = EXFAT_NODE(pfn);
        char name[EXFAT_FILENAME_LEN + 1];
        exfat_file_dentry_t df;
        exfat_stream_dentry_t ds;
        service_id_t service_id;
        errno_t rc;

        fibril_mutex_lock(&parentp->idx->lock);
        service_id = parentp->idx->service_id;
        fibril_mutex_unlock(&parentp->idx->lock);

        exfat_directory_t di;
        rc = exfat_directory_open(parentp, &di);
        if (rc != EOK)
                return rc;

        while (exfat_directory_read_file(&di, name, EXFAT_FILENAME_LEN, &df,
            &ds) == EOK) {
                if (str_casecmp(name, component) == 0) {
                        /* hit */
                        exfat_node_t *nodep;
                        aoff64_t o = di.pos %
                            (BPS(di.bs) / sizeof(exfat_dentry_t));
                        exfat_idx_t *idx = exfat_idx_get_by_pos(service_id,
                            parentp->firstc, di.bnum * DPS(di.bs) + o);
                        if (!idx) {
                                /*
                                 * Can happen if memory is low or if we
                                 * run out of 32-bit indices.
                                 */
                                rc = exfat_directory_close(&di);
                                return (rc == EOK) ? ENOMEM : rc;
                        }
                        rc = exfat_node_get_core(&nodep, idx);
                        fibril_mutex_unlock(&idx->lock);
                        if (rc != EOK) {
                                (void) exfat_directory_close(&di);
                                return rc;
                        }
                        *rfn = FS_NODE(nodep);
                        rc = exfat_directory_close(&di);
                        if (rc != EOK)
                                (void) exfat_node_put(*rfn);
                        return rc;
                } else {
                        rc = exfat_directory_next(&di);
                        if (rc != EOK)
                                break;
                }
        }
        (void) exfat_directory_close(&di);
        *rfn = NULL;
        return EOK;
}

/** Instantiate a exFAT in-core node. */
errno_t exfat_node_get(fs_node_t **rfn, service_id_t service_id, fs_index_t index)
{
        exfat_node_t *nodep;
        exfat_idx_t *idxp;
        errno_t rc;

        idxp = exfat_idx_get_by_index(service_id, index);
        if (!idxp) {
                *rfn = NULL;
                return EOK;
        }
        /* idxp->lock held */
        rc = exfat_node_get_core(&nodep, idxp);
        fibril_mutex_unlock(&idxp->lock);
        if (rc == EOK)
                *rfn = FS_NODE(nodep);
        return rc;
}

errno_t exfat_node_open(fs_node_t *fn)
{
        /*
         * Opening a file is stateless, nothing
         * to be done here.
         */
        return EOK;
}

errno_t exfat_node_put(fs_node_t *fn)
{
        if (fn == NULL)
                return EOK;

        exfat_node_t *nodep = EXFAT_NODE(fn);
        bool destroy = false;

        fibril_mutex_lock(&nodep->lock);
        if (!--nodep->refcnt) {
                if (nodep->idx) {
                        fibril_mutex_lock(&ffn_mutex);
                        list_append(&nodep->ffn_link, &ffn_list);
                        fibril_mutex_unlock(&ffn_mutex);
                } else {
                        /*
                         * The node does not have any index structure associated
                         * with itself. This can only mean that we are releasing
                         * the node after a failed attempt to allocate the index
                         * structure for it.
                         */
                        destroy = true;
                }
        }
        fibril_mutex_unlock(&nodep->lock);
        if (destroy) {
                free(nodep->bp);
                free(nodep);
        }
        return EOK;
}

errno_t exfat_create_node(fs_node_t **rfn, service_id_t service_id, int flags)
{
        exfat_idx_t *idxp;
        exfat_node_t *nodep;
        exfat_bs_t *bs;
        errno_t rc;

        bs = block_bb_get(service_id);
        rc = exfat_node_get_new(&nodep);
        if (rc != EOK)
                return rc;

        rc = exfat_idx_get_new(&idxp, service_id);
        if (rc != EOK) {
                (void) exfat_node_put(FS_NODE(nodep));
                return rc;
        }

        nodep->firstc = 0;
        nodep->size = 0;
        nodep->fragmented = false;
        nodep->lnkcnt = 0;      /* not linked anywhere */
        nodep->refcnt = 1;
        nodep->dirty = true;

        nodep->idx = idxp;
        idxp->nodep = nodep;
        fibril_mutex_unlock(&idxp->lock);

        if (flags & L_DIRECTORY) {
                nodep->type = EXFAT_DIRECTORY;
                rc = exfat_node_expand(service_id, nodep, 1);
                if (rc != EOK) {
                        (void) exfat_node_put(FS_NODE(nodep));
                        return rc;
                }

                rc = exfat_zero_cluster(bs, service_id, nodep->firstc);
                if (rc != EOK) {
                        (void) exfat_node_put(FS_NODE(nodep));
                        return rc;
                }

                nodep->size = BPC(bs);
        } else {
                nodep->type = EXFAT_FILE;
        }

        *rfn = FS_NODE(nodep);
        return EOK;
}

errno_t exfat_destroy_node(fs_node_t *fn)
{
        exfat_node_t *nodep = EXFAT_NODE(fn);
        exfat_bs_t *bs;
        bool has_children;
        errno_t rc;

        /*
         * The node is not reachable from the file system. This means that the
         * link count should be zero and that the index structure cannot be
         * found in the position hash. Obviously, we don't need to lock the node
         * nor its index structure.
         */
        assert(nodep->lnkcnt == 0);

        /*
         * The node may not have any children.
         */
        rc = exfat_has_children(&has_children, fn);
        if (rc != EOK)
                return rc;
        assert(!has_children);

        bs = block_bb_get(nodep->idx->service_id);
        if (nodep->firstc != 0) {
                assert(nodep->size);
                /* Free all clusters allocated to the node. */
                if (nodep->fragmented)
                        rc = exfat_free_clusters(bs, nodep->idx->service_id,
                            nodep->firstc);
                else
                        rc = exfat_bitmap_free_clusters(bs, nodep,
                            ROUND_UP(nodep->size, BPC(bs)) / BPC(bs));
        }

        exfat_idx_destroy(nodep->idx);
        free(nodep->bp);
        free(nodep);
        return rc;
}

errno_t exfat_link(fs_node_t *pfn, fs_node_t *cfn, const char *name)
{
        exfat_node_t *parentp = EXFAT_NODE(pfn);
        exfat_node_t *childp = EXFAT_NODE(cfn);
        exfat_directory_t di;
        errno_t rc;

        fibril_mutex_lock(&childp->lock);
        if (childp->lnkcnt == 1) {
                /*
                 * We don't support multiple hard links.
                 */
                fibril_mutex_unlock(&childp->lock);
                return EMLINK;
        }
        assert(childp->lnkcnt == 0);
        fibril_mutex_unlock(&childp->lock);

        if (!exfat_valid_name(name))
                return ENOTSUP;

        fibril_mutex_lock(&parentp->idx->lock);
        rc = exfat_directory_open(parentp, &di);
        if (rc != EOK)
                return rc;
        /*
         * At this point we only establish the link between the parent and the
         * child.  The dentry, except of the name and the extension, will remain
         * uninitialized until the corresponding node is synced. Thus the valid
         * dentry data is kept in the child node structure.
         */
        rc = exfat_directory_write_file(&di, name);
        if (rc != EOK) {
                (void) exfat_directory_close(&di);
                fibril_mutex_unlock(&parentp->idx->lock);
                return rc;
        }
        rc = exfat_directory_close(&di);
        if (rc != EOK) {
                fibril_mutex_unlock(&parentp->idx->lock);
                return rc;
        }

        fibril_mutex_unlock(&parentp->idx->lock);
        fibril_mutex_lock(&childp->idx->lock);

        childp->idx->pfc = parentp->firstc;
        childp->idx->parent_fragmented = parentp->fragmented;
        childp->idx->pdi = di.pos;
        fibril_mutex_unlock(&childp->idx->lock);

        fibril_mutex_lock(&childp->lock);
        childp->lnkcnt = 1;
        childp->dirty = true;           /* need to sync node */
        fibril_mutex_unlock(&childp->lock);

        /*
         * Hash in the index structure into the position hash.
         */
        exfat_idx_hashin(childp->idx);

        return EOK;

}

errno_t exfat_unlink(fs_node_t *pfn, fs_node_t *cfn, const char *nm)
{
        exfat_node_t *parentp = EXFAT_NODE(pfn);
        exfat_node_t *childp = EXFAT_NODE(cfn);
        bool has_children;
        errno_t rc;

        if (!parentp)
                return EBUSY;

        rc = exfat_has_children(&has_children, cfn);
        if (rc != EOK)
                return rc;
        if (has_children)
                return ENOTEMPTY;

        fibril_mutex_lock(&parentp->lock);
        fibril_mutex_lock(&childp->lock);
        assert(childp->lnkcnt == 1);
        fibril_mutex_lock(&childp->idx->lock);

        exfat_directory_t di;
        rc = exfat_directory_open(parentp, &di);
        if (rc != EOK)
                goto error;
        rc = exfat_directory_erase_file(&di, childp->idx->pdi);
        if (rc != EOK)
                goto error;
        rc = exfat_directory_close(&di);
        if (rc != EOK)
                goto error;

        /* remove the index structure from the position hash */
        exfat_idx_hashout(childp->idx);
        /* clear position information */
        childp->idx->pfc = 0;
        childp->idx->pdi = 0;
        fibril_mutex_unlock(&childp->idx->lock);
        childp->lnkcnt = 0;
        childp->refcnt++;       /* keep the node in memory until destroyed */
        childp->dirty = true;
        fibril_mutex_unlock(&childp->lock);
        fibril_mutex_unlock(&parentp->lock);

        return EOK;

error:
        (void) exfat_directory_close(&di);
        fibril_mutex_unlock(&childp->idx->lock);
        fibril_mutex_unlock(&childp->lock);
        fibril_mutex_unlock(&parentp->lock);
        return rc;

}

errno_t exfat_has_children(bool *has_children, fs_node_t *fn)
{
        exfat_directory_t di;
        exfat_dentry_t *d;
        exfat_node_t *nodep = EXFAT_NODE(fn);
        errno_t rc;

        *has_children = false;

        if (nodep->type != EXFAT_DIRECTORY)
                return EOK;

        fibril_mutex_lock(&nodep->idx->lock);

        rc = exfat_directory_open(nodep, &di);
        if (rc != EOK) {
                fibril_mutex_unlock(&nodep->idx->lock);
                return rc;
        }

        do {
                rc = exfat_directory_get(&di, &d);
                if (rc != EOK) {
                        (void) exfat_directory_close(&di);
                        fibril_mutex_unlock(&nodep->idx->lock);
                        return rc;
                }
                switch (exfat_classify_dentry(d)) {
                case EXFAT_DENTRY_SKIP:
                case EXFAT_DENTRY_FREE:
                        continue;
                case EXFAT_DENTRY_LAST:
                        *has_children = false;
                        goto exit;
                default:
                        *has_children = true;
                        goto exit;
                }
        } while (exfat_directory_next(&di) == EOK);

exit:
        rc = exfat_directory_close(&di);
        fibril_mutex_unlock(&nodep->idx->lock);
        return rc;
}

fs_index_t exfat_index_get(fs_node_t *fn)
{
        return EXFAT_NODE(fn)->idx->index;
}

aoff64_t exfat_size_get(fs_node_t *fn)
{
        return EXFAT_NODE(fn)->size;
}

unsigned exfat_lnkcnt_get(fs_node_t *fn)
{
        return EXFAT_NODE(fn)->lnkcnt;
}

bool exfat_is_directory(fs_node_t *fn)
{
        return EXFAT_NODE(fn)->type == EXFAT_DIRECTORY;
}

bool exfat_is_file(fs_node_t *fn)
{
        return EXFAT_NODE(fn)->type == EXFAT_FILE;
}

service_id_t exfat_service_get(fs_node_t *node)
{
        return 0;
}

errno_t exfat_size_block(service_id_t service_id, uint32_t *size)
{
        exfat_bs_t *bs;
        bs = block_bb_get(service_id);
        *size = BPC(bs);

        return EOK;
}

errno_t exfat_total_block_count(service_id_t service_id, uint64_t *count)
{
        exfat_bs_t *bs;
        bs = block_bb_get(service_id);
        *count = DATA_CNT(bs);

        return EOK;
}

errno_t exfat_free_block_count(service_id_t service_id, uint64_t *count)
{
        fs_node_t *node = NULL;
        exfat_node_t *bmap_node;
        exfat_bs_t *bs;
        uint64_t free_block_count = 0;
        uint64_t block_count;
        unsigned sector;
        errno_t rc;

        rc = exfat_total_block_count(service_id, &block_count);
        if (rc != EOK)
                goto exit;

        bs = block_bb_get(service_id);
        rc = exfat_bitmap_get(&node, service_id);
        if (rc != EOK)
                goto exit;

        bmap_node = (exfat_node_t *) node->data;

        unsigned const bmap_sectors = ROUND_UP(bmap_node->size, BPS(bs)) /
            BPS(bs);

        for (sector = 0; sector < bmap_sectors; ++sector) {

                block_t *block;
                uint8_t *bitmap;
                unsigned bit;

                rc = exfat_block_get(&block, bs, bmap_node, sector,
                    BLOCK_FLAGS_NONE);
                if (rc != EOK) {
                        free_block_count = 0;
                        goto exit;
                }

                bitmap = (uint8_t *) block->data;

                for (bit = 0; bit < BPS(bs) * 8 && block_count > 0;
                    ++bit, --block_count) {
                        if (!(bitmap[bit / 8] & (1 << (bit % 8))))
                                ++free_block_count;
                }

                block_put(block);

                if (block_count == 0) {
                        /* Reached the end of the bitmap */
                        goto exit;
                }
        }

exit:
        exfat_node_put(node);
        *count = free_block_count;
        return rc;
}

/** libfs operations */
libfs_ops_t exfat_libfs_ops = {
        .root_get = exfat_root_get,
        .match = exfat_match,
        .node_get = exfat_node_get,
        .node_open = exfat_node_open,
        .node_put = exfat_node_put,
        .create = exfat_create_node,
        .destroy = exfat_destroy_node,
        .link = exfat_link,
        .unlink = exfat_unlink,
        .has_children = exfat_has_children,
        .index_get = exfat_index_get,
        .size_get = exfat_size_get,
        .lnkcnt_get = exfat_lnkcnt_get,
        .is_directory = exfat_is_directory,
        .is_file = exfat_is_file,
        .service_get = exfat_service_get,
        .size_block = exfat_size_block,
        .total_block_count = exfat_total_block_count,
        .free_block_count = exfat_free_block_count
};

static errno_t exfat_fs_open(service_id_t service_id, enum cache_mode cmode,
    fs_node_t **rrfn, exfat_idx_t **rridxp, vfs_fs_probe_info_t *info)
{
        errno_t rc;
        exfat_node_t *rootp = NULL, *bitmapp = NULL, *uctablep = NULL;
        exfat_bs_t *bs;

        /* initialize libblock */
        rc = block_init(service_id);
        if (rc != EOK)
                return rc;

        /* prepare the boot block */
        rc = block_bb_read(service_id, BS_BLOCK);
        if (rc != EOK) {
                block_fini(service_id);
                return rc;
        }

        /* get the buffer with the boot sector */
        bs = block_bb_get(service_id);

        /* Do some simple sanity checks on the file system. */
        rc = exfat_sanity_check(bs);
        if (rc != EOK) {
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                return rc;
        }

        /* Initialize the block cache */
        rc = block_cache_init(service_id, BPS(bs), 0 /* XXX */, cmode);
        if (rc != EOK) {
                block_fini(service_id);
                return rc;
        }

        rc = exfat_idx_init_by_service_id(service_id);
        if (rc != EOK) {
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                return rc;
        }

        /* Initialize the root node. */
        rc = exfat_node_get_new_by_pos(&rootp, service_id, EXFAT_ROOT_PAR,
            EXFAT_ROOT_POS);
        if (rc != EOK) {
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOMEM;
        }
        assert(rootp->idx->index == EXFAT_ROOT_IDX);

        rootp->type = EXFAT_DIRECTORY;
        rootp->firstc = ROOT_FC(bs);
        rootp->fragmented = true;
        rootp->refcnt = 1;
        rootp->lnkcnt = 0;      /* FS root is not linked */

        uint32_t clusters;
        rc = exfat_clusters_get(&clusters, bs, service_id, rootp->firstc);
        if (rc != EOK) {
                free(rootp);
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOTSUP;
        }
        rootp->size = BPS(bs) * SPC(bs) * clusters;
        fibril_mutex_unlock(&rootp->idx->lock);

        /* Open root directory and looking for Bitmap and UC-Table */
        exfat_directory_t di;
        exfat_dentry_t *de;
        rc = exfat_directory_open(rootp, &di);
        if (rc != EOK) {
                free(rootp);
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOTSUP;
        }

        /* Initialize the bitmap node. */
        rc = exfat_directory_find(&di, EXFAT_DENTRY_BITMAP, &de);
        if (rc != EOK) {
                free(rootp);
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOTSUP;
        }

        rc = exfat_node_get_new_by_pos(&bitmapp, service_id, rootp->firstc,
            di.pos);
        if (rc != EOK) {
                free(rootp);
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOMEM;
        }
        assert(bitmapp->idx->index == EXFAT_BITMAP_IDX);
        fibril_mutex_unlock(&bitmapp->idx->lock);

        bitmapp->type = EXFAT_BITMAP;
        bitmapp->firstc = uint32_t_le2host(de->bitmap.firstc);
        bitmapp->fragmented = true;
        bitmapp->idx->parent_fragmented = true;
        bitmapp->refcnt = 1;
        bitmapp->lnkcnt = 0;
        bitmapp->size = uint64_t_le2host(de->bitmap.size);

        /* Initialize the uctable node. */
        rc = exfat_directory_seek(&di, 0);
        if (rc != EOK) {
                free(rootp);
                free(bitmapp);
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOTSUP;
        }

        rc = exfat_directory_find(&di, EXFAT_DENTRY_UCTABLE, &de);
        if (rc != EOK) {
                free(rootp);
                free(bitmapp);
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOTSUP;
        }

        rc = exfat_node_get_new_by_pos(&uctablep, service_id, rootp->firstc,
            di.pos);
        if (rc != EOK) {
                free(rootp);
                free(bitmapp);
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOMEM;
        }
        assert(uctablep->idx->index == EXFAT_UCTABLE_IDX);
        fibril_mutex_unlock(&uctablep->idx->lock);

        uctablep->type = EXFAT_UCTABLE;
        uctablep->firstc = uint32_t_le2host(de->uctable.firstc);
        uctablep->fragmented = true;
        uctablep->idx->parent_fragmented = true;
        uctablep->refcnt = 1;
        uctablep->lnkcnt = 0;
        uctablep->size = uint64_t_le2host(de->uctable.size);

        if (info != NULL) {
                /* Read volume label. */
                rc = exfat_directory_read_vollabel(&di, info->label,
                    FS_LABEL_MAXLEN + 1);
                if (rc != EOK) {
                        free(rootp);
                        free(bitmapp);
                        free(uctablep);
                        (void) block_cache_fini(service_id);
                        block_fini(service_id);
                        exfat_idx_fini_by_service_id(service_id);
                        return ENOTSUP;
                }
        }

        rc = exfat_directory_close(&di);
        if (rc != EOK) {
                free(rootp);
                free(bitmapp);
                free(uctablep);
                (void) block_cache_fini(service_id);
                block_fini(service_id);
                exfat_idx_fini_by_service_id(service_id);
                return ENOMEM;
        }

        if (0)
                exfat_fsinfo(bs, service_id);

        *rrfn = FS_NODE(rootp);
        *rridxp = rootp->idx;

        if (info != NULL) {
#if 0
                str_cpy(info->label, FS_LABEL_MAXLEN + 1, label);
#endif
        }

        return EOK;
}

static void exfat_fs_close(service_id_t service_id, fs_node_t *rfn)
{
        /*
         * Put the root node and force it to the FAT free node list.
         */
        (void) exfat_node_put(rfn);
        (void) exfat_node_put(rfn);

        /*
         * Perform cleanup of the node structures, index structures and
         * associated data. Write back this file system's dirty blocks and
         * stop using libblock for this instance.
         */
        (void) exfat_node_fini_by_service_id(service_id);
        exfat_idx_fini_by_service_id(service_id);
        (void) block_cache_fini(service_id);
        block_fini(service_id);
}

/*
 * VFS_OUT operations.
 */

/* Print debug info */
static void exfat_fsinfo(exfat_bs_t *bs, service_id_t service_id)
{
        printf("exFAT file system mounted\n");
        printf("Version: %d.%d\n", bs->version.major, bs->version.minor);
        printf("Volume serial: %d\n", uint32_t_le2host(bs->volume_serial));
        printf("Volume first sector: %" PRId64 "\n", VOL_FS(bs));
        printf("Volume sectors: %" PRId64 "\n", VOL_CNT(bs));
        printf("FAT first sector: %d\n", FAT_FS(bs));
        printf("FAT sectors: %d\n", FAT_CNT(bs));
        printf("Data first sector: %d\n", DATA_FS(bs));
        printf("Data sectors: %d\n", DATA_CNT(bs));
        printf("Root dir first cluster: %d\n", ROOT_FC(bs));
        printf("Bytes per sector: %d\n", BPS(bs));
        printf("Sectors per cluster: %d\n", SPC(bs));
        printf("KBytes per cluster: %d\n", SPC(bs) * BPS(bs) / 1024);

        int i, rc;
        exfat_cluster_t clst;
        for (i = 0; i <= 7; i++) {
                rc = exfat_get_cluster(bs, service_id, i, &clst);
                if (rc != EOK)
                        return;
                printf("Clst %d: %x", i, clst);
                if (i >= 2) {
                        printf(", Bitmap: %d\n", exfat_bitmap_is_free(bs,
                            service_id, i) != EOK);
                } else {
                        printf("\n");
                }
        }
}

static errno_t exfat_fsprobe(service_id_t service_id, vfs_fs_probe_info_t *info)
{
        errno_t rc;
        exfat_idx_t *ridxp;
        fs_node_t *rfn;

        rc = exfat_fs_open(service_id, CACHE_MODE_WT, &rfn, &ridxp, info);
        if (rc != EOK)
                return rc;

        exfat_fs_close(service_id, rfn);
        return EOK;
}

static errno_t
exfat_mounted(service_id_t service_id, const char *opts, fs_index_t *index,
    aoff64_t *size)
{
        errno_t rc;
        enum cache_mode cmode;
        exfat_idx_t *ridxp;
        fs_node_t *rfn;

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

        rc = exfat_fs_open(service_id, cmode, &rfn, &ridxp, NULL);
        if (rc != EOK)
                return rc;

        *index = ridxp->index;
        *size = EXFAT_NODE(rfn)->size;

        return EOK;
}

static errno_t exfat_unmounted(service_id_t service_id)
{
        fs_node_t *rfn;
        errno_t rc;

        rc = exfat_root_get(&rfn, service_id);
        if (rc != EOK)
                return rc;

        exfat_fs_close(service_id, rfn);
        return EOK;
}

static errno_t
exfat_read(service_id_t service_id, fs_index_t index, aoff64_t pos,
    size_t *rbytes)
{
        fs_node_t *fn;
        exfat_node_t *nodep;
        exfat_bs_t *bs;
        size_t bytes = 0;
        block_t *b;
        errno_t rc;

        rc = exfat_node_get(&fn, service_id, index);
        if (rc != EOK)
                return rc;
        if (!fn)
                return ENOENT;
        nodep = EXFAT_NODE(fn);

        ipc_call_t call;
        size_t len;
        if (!async_data_read_receive(&call, &len)) {
                exfat_node_put(fn);
                async_answer_0(&call, EINVAL);
                return EINVAL;
        }

        bs = block_bb_get(service_id);

        if (nodep->type == EXFAT_FILE) {
                /*
                 * Our strategy for regular file reads is to read one block at
                 * most and make use of the possibility to return less data than
                 * requested. This keeps the code very simple.
                 */
                if (pos >= nodep->size) {
                        /* reading beyond the EOF */
                        bytes = 0;
                        (void) async_data_read_finalize(&call, NULL, 0);
                } else {
                        bytes = min(len, BPS(bs) - pos % BPS(bs));
                        bytes = min(bytes, nodep->size - pos);
                        rc = exfat_block_get(&b, bs, nodep, pos / BPS(bs),
                            BLOCK_FLAGS_NONE);
                        if (rc != EOK) {
                                exfat_node_put(fn);
                                async_answer_0(&call, rc);
                                return rc;
                        }
                        (void) async_data_read_finalize(&call,
                            b->data + pos % BPS(bs), bytes);
                        rc = block_put(b);
                        if (rc != EOK) {
                                exfat_node_put(fn);
                                return rc;
                        }
                }
        } else {
                if (nodep->type != EXFAT_DIRECTORY) {
                        async_answer_0(&call, ENOTSUP);
                        return ENOTSUP;
                }

                aoff64_t spos = pos;
                char name[EXFAT_FILENAME_LEN + 1];
                exfat_file_dentry_t df;
                exfat_stream_dentry_t ds;

                assert(nodep->size % BPS(bs) == 0);
                assert(BPS(bs) % sizeof(exfat_dentry_t) == 0);

                exfat_directory_t di;
                rc = exfat_directory_open(nodep, &di);
                if (rc != EOK)
                        goto err;

                rc = exfat_directory_seek(&di, pos);
                if (rc != EOK) {
                        (void) exfat_directory_close(&di);
                        goto err;
                }

                rc = exfat_directory_read_file(&di, name, EXFAT_FILENAME_LEN,
                    &df, &ds);
                if (rc == EOK)
                        goto hit;
                else if (rc == ENOENT)
                        goto miss;

                (void) exfat_directory_close(&di);

        err:
                (void) exfat_node_put(fn);
                async_answer_0(&call, rc);
                return rc;

        miss:
                rc = exfat_directory_close(&di);
                if (rc != EOK)
                        goto err;
                rc = exfat_node_put(fn);
                async_answer_0(&call, rc != EOK ? rc : ENOENT);
                *rbytes = 0;
                return rc != EOK ? rc : ENOENT;

        hit:
                pos = di.pos;
                rc = exfat_directory_close(&di);
                if (rc != EOK)
                        goto err;
                (void) async_data_read_finalize(&call, name,
                    str_size(name) + 1);
                bytes = (pos - spos) + 1;
        }

        rc = exfat_node_put(fn);
        *rbytes = bytes;
        return rc;
}

static errno_t exfat_close(service_id_t service_id, fs_index_t index)
{
        return EOK;
}

static errno_t exfat_sync(service_id_t service_id, fs_index_t index)
{
        fs_node_t *fn;
        errno_t rc = exfat_node_get(&fn, service_id, index);
        if (rc != EOK)
                return rc;
        if (!fn)
                return ENOENT;

        exfat_node_t *nodep = EXFAT_NODE(fn);

        nodep->dirty = true;
        rc = exfat_node_sync(nodep);

        exfat_node_put(fn);
        return rc;
}

static errno_t
exfat_write(service_id_t service_id, fs_index_t index, aoff64_t pos,
    size_t *wbytes, aoff64_t *nsize)
{
        fs_node_t *fn;
        exfat_node_t *nodep;
        exfat_bs_t *bs;
        size_t bytes;
        block_t *b;
        aoff64_t boundary;
        int flags = BLOCK_FLAGS_NONE;
        errno_t rc;

        rc = exfat_node_get(&fn, service_id, index);
        if (rc != EOK)
                return rc;
        if (!fn)
                return ENOENT;
        nodep = EXFAT_NODE(fn);

        ipc_call_t call;
        size_t len;
        if (!async_data_write_receive(&call, &len)) {
                (void) exfat_node_put(fn);
                async_answer_0(&call, EINVAL);
                return EINVAL;
        }

        bs = block_bb_get(service_id);

        /*
         * In all scenarios, we will attempt to write out only one block worth
         * of data at maximum. There might be some more efficient approaches,
         * but this one greatly simplifies fat_write(). Note that we can afford
         * to do this because the client must be ready to handle the return
         * value signalizing a smaller number of bytes written.
         */
        bytes = min(len, BPS(bs) - pos % BPS(bs));
        if (bytes == BPS(bs))
                flags |= BLOCK_FLAGS_NOREAD;

        boundary = ROUND_UP(nodep->size, BPC(bs));
        if (pos >= boundary) {
                unsigned nclsts;
                nclsts = (ROUND_UP(pos + bytes, BPC(bs)) - boundary) / BPC(bs);
                rc = exfat_node_expand(service_id, nodep, nclsts);
                if (rc != EOK) {
                        /* could not expand node */
                        (void) exfat_node_put(fn);
                        async_answer_0(&call, rc);
                        return rc;
                }
        }

        if (pos + bytes > nodep->size) {
                nodep->size = pos + bytes;
                nodep->dirty = true;    /* need to sync node */
        }

        /*
         * This is the easier case - we are either overwriting already
         * existing contents or writing behind the EOF, but still within
         * the limits of the last cluster. The node size may grow to the
         * next block size boundary.
         */
        rc = exfat_block_get(&b, bs, nodep, pos / BPS(bs), flags);
        if (rc != EOK) {
                (void) exfat_node_put(fn);
                async_answer_0(&call, rc);
                return rc;
        }

        (void) async_data_write_finalize(&call,
            b->data + pos % BPS(bs), bytes);
        b->dirty = true;                /* need to sync block */
        rc = block_put(b);
        if (rc != EOK) {
                (void) exfat_node_put(fn);
                return rc;
        }

        *wbytes = bytes;
        *nsize = nodep->size;
        rc = exfat_node_put(fn);
        return rc;
}

static errno_t
exfat_truncate(service_id_t service_id, fs_index_t index, aoff64_t size)
{
        fs_node_t *fn;
        exfat_node_t *nodep;
        exfat_bs_t *bs;
        errno_t rc;

        rc = exfat_node_get(&fn, service_id, index);
        if (rc != EOK)
                return rc;
        if (!fn)
                return ENOENT;
        nodep = EXFAT_NODE(fn);

        bs = block_bb_get(service_id);

        if (nodep->size == size) {
                rc = EOK;
        } else if (nodep->size < size) {
                /*
                 * The standard says we have the freedom to grow the node.
                 * For now, we simply return an error.
                 */
                rc = EINVAL;
        } else if (ROUND_UP(nodep->size, BPC(bs)) == ROUND_UP(size, BPC(bs))) {
                /*
                 * The node will be shrunk, but no clusters will be deallocated.
                 */
                nodep->size = size;
                nodep->dirty = true;            /* need to sync node */
                rc = EOK;
        } else {
                rc = exfat_node_shrink(service_id, nodep, size);
        }

        errno_t rc2 = exfat_node_put(fn);
        if (rc == EOK && rc2 != EOK)
                rc = rc2;

        return rc;
}

static errno_t exfat_destroy(service_id_t service_id, fs_index_t index)
{
        fs_node_t *fn;
        exfat_node_t *nodep;
        errno_t rc;

        rc = exfat_node_get(&fn, service_id, index);
        if (rc != EOK)
                return rc;
        if (!fn)
                return ENOENT;

        nodep = EXFAT_NODE(fn);
        /*
         * We should have exactly two references. One for the above
         * call to fat_node_get() and one from fat_unlink().
         */
        assert(nodep->refcnt == 2);

        rc = exfat_destroy_node(fn);
        return rc;
}

vfs_out_ops_t exfat_ops = {
        .fsprobe = exfat_fsprobe,
        .mounted = exfat_mounted,
        .unmounted = exfat_unmounted,
        .read = exfat_read,
        .write = exfat_write,
        .truncate = exfat_truncate,
        .close = exfat_close,
        .destroy = exfat_destroy,
        .sync = exfat_sync,
};

/**
 * @}
 */