Subversion Repositories HelenOS

/*

 * Copyright (c) 2008 Jakub Jermar

 * 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    fat_ops.c

 * @brief   Implementation of VFS operations for the FAT file system server.

 */

#include "fat.h"

#include "fat_dentry.h"

#include "fat_fat.h"

#include "../../vfs/vfs.h"

#include <libfs.h>

#include <libblock.h>

#include <ipc/ipc.h>

#include <ipc/services.h>

#include <ipc/devmap.h>

#include <async.h>

#include <errno.h>

#include <string.h>

#include <byteorder.h>

#include <adt/hash_table.h>

#include <adt/list.h>

#include <assert.h>

#include <fibril_sync.h>

#include <sys/mman.h>

#include <align.h>

#define FAT_NODE(node)  ((node) ? (fat_node_t *) (node)->data : NULL)

#define FS_NODE(node)   ((node) ? (node)->bp : NULL)

/** 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_head);

static void fat_node_initialize(fat_node_t *node)

{

    fibril_mutex_initialize(&node->lock);

    node->bp = NULL;

    node->idx = NULL;

    node->type = 0;

    link_initialize(&node->ffn_link);

    node->size = 0;

    node->lnkcnt = 0;

    node->refcnt = 0;

    node->dirty = false;

}

static void fat_node_sync(fat_node_t *node)

{

    block_t *b;

    fat_bs_t *bs;

    fat_dentry_t *d;

    uint16_t bps;

    unsigned dps;

    assert(node->dirty);

    bs = block_bb_get(node->idx->dev_handle);

    bps = uint16_t_le2host(bs->bps);

    dps = bps / sizeof(fat_dentry_t);

    /* Read the block that contains the dentry of interest. */

    b = _fat_block_get(bs, node->idx->dev_handle, node->idx->pfc,

        (node->idx->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);

    d = ((fat_dentry_t *)b->data) + (node->idx->pdi % dps);

    d->firstc = host2uint16_t_le(node->firstc);

    if (node->type == FAT_FILE) {

        d->size = host2uint32_t_le(node->size);

    } else if (node->type == FAT_DIRECTORY) {

        d->attr = FAT_ATTR_SUBDIR;

    }

    /* TODO: update other fields? (e.g time fields) */

    b->dirty = true;        /* need to sync block */

    block_put(b);

}

static fat_node_t *fat_node_get_new(void)

{

    fs_node_t *fn;

    fat_node_t *nodep;

    fibril_mutex_lock(&ffn_mutex);

    if (!list_empty(&ffn_head)) {

        /* Try to use a cached free node structure. */

        fat_idx_t *idxp_tmp;

        nodep = list_get_instance(ffn_head.next, fat_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)

            fat_node_sync(nodep);

        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 NULL;

        nodep = (fat_node_t *)malloc(sizeof(fat_node_t));

        if (!nodep) {

            free(fn);

            return NULL;

        }

    }

    fat_node_initialize(nodep);

    fs_node_initialize(fn);

    fn->data = nodep;

    nodep->bp = fn;

    return nodep;

}

/** Internal version of fat_node_get().

 *

 * @param idxp      Locked index structure.

 */

static fat_node_t *fat_node_get_core(fat_idx_t *idxp)

{

    block_t *b;

    fat_bs_t *bs;

    fat_dentry_t *d;

    fat_node_t *nodep = NULL;

    unsigned bps;

    unsigned spc;

    unsigned dps;

    if (idxp->nodep) {

        /*

         * We are lucky.

         * The node is already instantiated in memory.

         */

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

        if (!idxp->nodep->refcnt++)

            list_remove(&idxp->nodep->ffn_link);

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

        return idxp->nodep;

    }

    /*

     * We must instantiate the node from the file system.

     */

    assert(idxp->pfc);

    nodep = fat_node_get_new();

    if (!nodep)

        return NULL;

    bs = block_bb_get(idxp->dev_handle);

    bps = uint16_t_le2host(bs->bps);

    spc = bs->spc;

    dps = bps / sizeof(fat_dentry_t);

    /* Read the block that contains the dentry of interest. */

    b = _fat_block_get(bs, idxp->dev_handle, idxp->pfc,

        (idxp->pdi * sizeof(fat_dentry_t)) / bps, BLOCK_FLAGS_NONE);

    assert(b);

    d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);

    if (d->attr & FAT_ATTR_SUBDIR) {

        /*

         * The only directory which does not have this bit set is the

         * root directory itself. The root directory node is handled

         * and initialized elsewhere.

         */

        nodep->type = FAT_DIRECTORY;

        /*

         * Unfortunately, the 'size' field of the FAT dentry is not

         * defined for the directory entry type. We must determine the

         * size of the directory by walking the FAT.

         */

        nodep->size = bps * spc * fat_clusters_get(bs, idxp->dev_handle,

            uint16_t_le2host(d->firstc));

    } else {

        nodep->type = FAT_FILE;

        nodep->size = uint32_t_le2host(d->size);

    }

    nodep->firstc = uint16_t_le2host(d->firstc);

    nodep->lnkcnt = 1;

    nodep->refcnt = 1;

    block_put(b);

    /* Link the idx structure with the node structure. */

    nodep->idx = idxp;

    idxp->nodep = nodep;

    return nodep;

}

/*

 * Forward declarations of FAT libfs operations.

 */

static fs_node_t *fat_node_get(dev_handle_t, fs_index_t);

static void fat_node_put(fs_node_t *);

static fs_node_t *fat_create_node(dev_handle_t, int);

static int fat_destroy_node(fs_node_t *);

static int fat_link(fs_node_t *, fs_node_t *, const char *);

static int fat_unlink(fs_node_t *, fs_node_t *, const char *);

static fs_node_t *fat_match(fs_node_t *, const char *);

static fs_index_t fat_index_get(fs_node_t *);

static size_t fat_size_get(fs_node_t *);

static unsigned fat_lnkcnt_get(fs_node_t *);

static bool fat_has_children(fs_node_t *);

static fs_node_t *fat_root_get(dev_handle_t);

static char fat_plb_get_char(unsigned);

static bool fat_is_directory(fs_node_t *);

static bool fat_is_file(fs_node_t *node);

/*

 * FAT libfs operations.

 */

/** Instantiate a FAT in-core node. */

fs_node_t *fat_node_get(dev_handle_t dev_handle, fs_index_t index)

{

    fat_node_t *nodep;

    fat_idx_t *idxp;

    idxp = fat_idx_get_by_index(dev_handle, index);

    if (!idxp)

        return NULL;

    /* idxp->lock held */

    nodep = fat_node_get_core(idxp);

    fibril_mutex_unlock(&idxp->lock);

    return FS_NODE(nodep);

}

void fat_node_put(fs_node_t *fn)

{

    fat_node_t *nodep = FAT_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_head);

            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);

    }

}

fs_node_t *fat_create_node(dev_handle_t dev_handle, int flags)

{

    fat_idx_t *idxp;

    fat_node_t *nodep;

    fat_bs_t *bs;

    fat_cluster_t mcl, lcl;

    uint16_t bps;

    int rc;

    bs = block_bb_get(dev_handle);

    bps = uint16_t_le2host(bs->bps);

    if (flags & L_DIRECTORY) {

        /* allocate a cluster */

        rc = fat_alloc_clusters(bs, dev_handle, 1, &mcl, &lcl);

        if (rc != EOK)

            return NULL;

    }

    nodep = fat_node_get_new();

    if (!nodep) {

        fat_free_clusters(bs, dev_handle, mcl);

        return NULL;

    }

    idxp = fat_idx_get_new(dev_handle);

    if (!idxp) {

        fat_free_clusters(bs, dev_handle, mcl);

        fat_node_put(FS_NODE(nodep));

        return NULL;

    }

    /* idxp->lock held */

    if (flags & L_DIRECTORY) {

        int i;

        block_t *b;

        /*

         * Populate the new cluster with unused dentries.

         */

        for (i = 0; i < bs->spc; i++) {

            b = _fat_block_get(bs, dev_handle, mcl, i,

                BLOCK_FLAGS_NOREAD);

            /* mark all dentries as never-used */

            memset(b->data, 0, bps);

            b->dirty = false;

            block_put(b);

        }

        nodep->type = FAT_DIRECTORY;

        nodep->firstc = mcl;

        nodep->size = bps * bs->spc;

    } else {

        nodep->type = FAT_FILE;

        nodep->firstc = FAT_CLST_RES0;

        nodep->size = 0;

    }

    nodep->lnkcnt = 0;  /* not linked anywhere */

    nodep->refcnt = 1;

    nodep->dirty = true;

    nodep->idx = idxp;

    idxp->nodep = nodep;

    fibril_mutex_unlock(&idxp->lock);

    return FS_NODE(nodep);

}

int fat_destroy_node(fs_node_t *fn)

{

    fat_node_t *nodep = FAT_NODE(fn);

    fat_bs_t *bs;

    /*

     * 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.

     */

    assert(fat_has_children(fn) == false);

    bs = block_bb_get(nodep->idx->dev_handle);

    if (nodep->firstc != FAT_CLST_RES0) {

        assert(nodep->size);

        /* Free all clusters allocated to the node. */

        fat_free_clusters(bs, nodep->idx->dev_handle, nodep->firstc);

    }

    fat_idx_destroy(nodep->idx);

    free(nodep->bp);

    free(nodep);

    return EOK;

}

int fat_link(fs_node_t *pfn, fs_node_t *cfn, const char *name)

{

    fat_node_t *parentp = FAT_NODE(pfn);

    fat_node_t *childp = FAT_NODE(cfn);

    fat_dentry_t *d;

    fat_bs_t *bs;

    block_t *b;

    unsigned i, j;

    uint16_t bps;

    unsigned dps;

    unsigned blocks;

    fat_cluster_t mcl, lcl;

    int rc;

    fibril_mutex_lock(&childp->lock);

    if (childp->lnkcnt == 1) {

        /*

         * On FAT, we don't support multiple hard links.

         */

        fibril_mutex_unlock(&childp->lock);

        return EMLINK;

    }

    assert(childp->lnkcnt == 0);

    fibril_mutex_unlock(&childp->lock);

    if (!fat_dentry_name_verify(name)) {

        /*

         * Attempt to create unsupported name.

         */

        return ENOTSUP;

    }

    /*

     * Get us an unused parent node's dentry or grow the parent and allocate

     * a new one.

     */

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

    bs = block_bb_get(parentp->idx->dev_handle);

    bps = uint16_t_le2host(bs->bps);

    dps = bps / sizeof(fat_dentry_t);

    blocks = parentp->size / bps;

    for (i = 0; i < blocks; i++) {

        b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NONE);

        for (j = 0; j < dps; j++) {

            d = ((fat_dentry_t *)b->data) + j;

            switch (fat_classify_dentry(d)) {

            case FAT_DENTRY_SKIP:

            case FAT_DENTRY_VALID:

                /* skipping used and meta entries */

                continue;

            case FAT_DENTRY_FREE:

            case FAT_DENTRY_LAST:

                /* found an empty slot */

                goto hit;

            }

        }

        block_put(b);

    }

    j = 0;

    /*

     * We need to grow the parent in order to create a new unused dentry.

     */

    if (parentp->idx->pfc == FAT_CLST_ROOT) {

        /* Can't grow the root directory. */

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

        return ENOSPC;

    }

    rc = fat_alloc_clusters(bs, parentp->idx->dev_handle, 1, &mcl, &lcl);

    if (rc != EOK) {

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

        return rc;

    }

    fat_append_clusters(bs, parentp, mcl);

    b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NOREAD);

    d = (fat_dentry_t *)b->data;

    /*

     * Clear all dentries in the block except for the first one (the first

     * dentry will be cleared in the next step).

     */

    memset(d + 1, 0, bps - sizeof(fat_dentry_t));

hit:

    /*

     * 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.

     */

    memset(d, 0, sizeof(fat_dentry_t));

    fat_dentry_name_set(d, name);

    b->dirty = true;        /* need to sync block */

    block_put(b);

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

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

    /*

     * If possible, create the Sub-directory Identifier Entry and the

     * Sub-directory Parent Pointer Entry (i.e. "." and ".."). These entries

     * are not mandatory according to Standard ECMA-107 and HelenOS VFS does

     * not use them anyway, so this is rather a sign of our good will.

     */

    b = fat_block_get(bs, childp, 0, BLOCK_FLAGS_NONE);

    d = (fat_dentry_t *)b->data;

    if (fat_classify_dentry(d) == FAT_DENTRY_LAST ||

        str_cmp(d->name, FAT_NAME_DOT) == 0) {

        memset(d, 0, sizeof(fat_dentry_t));

        str_cpy(d->name, 8, FAT_NAME_DOT);

        str_cpy(d->ext, 3, FAT_EXT_PAD);

        d->attr = FAT_ATTR_SUBDIR;

        d->firstc = host2uint16_t_le(childp->firstc);

        /* TODO: initialize also the date/time members. */

    }

    d++;

    if (fat_classify_dentry(d) == FAT_DENTRY_LAST ||

        str_cmp(d->name, FAT_NAME_DOT_DOT) == 0) {

        memset(d, 0, sizeof(fat_dentry_t));

        str_cpy(d->name, 8, FAT_NAME_DOT_DOT);

        str_cpy(d->ext, 3, FAT_EXT_PAD);

        d->attr = FAT_ATTR_SUBDIR;

        d->firstc = (parentp->firstc == FAT_CLST_ROOT) ?

            host2uint16_t_le(FAT_CLST_RES0) :

            host2uint16_t_le(parentp->firstc);

        /* TODO: initialize also the date/time members. */

    }

    b->dirty = true;        /* need to sync block */

    block_put(b);

    childp->idx->pfc = parentp->firstc;

    childp->idx->pdi = i * dps + j;

    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.

     */

    fat_idx_hashin(childp->idx);

    return EOK;

}

int fat_unlink(fs_node_t *pfn, fs_node_t *cfn, const char *nm)

{

    fat_node_t *parentp = FAT_NODE(pfn);

    fat_node_t *childp = FAT_NODE(cfn);

    fat_bs_t *bs;

    fat_dentry_t *d;

    uint16_t bps;

    block_t *b;

    if (!parentp)

        return EBUSY;

    if (fat_has_children(cfn))

        return ENOTEMPTY;

    fibril_mutex_lock(&parentp->lock);

    fibril_mutex_lock(&childp->lock);

    assert(childp->lnkcnt == 1);

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

    bs = block_bb_get(childp->idx->dev_handle);

    bps = uint16_t_le2host(bs->bps);

    b = _fat_block_get(bs, childp->idx->dev_handle, childp->idx->pfc,

        (childp->idx->pdi * sizeof(fat_dentry_t)) / bps,

        BLOCK_FLAGS_NONE);

    d = (fat_dentry_t *)b->data +

        (childp->idx->pdi % (bps / sizeof(fat_dentry_t)));

    /* mark the dentry as not-currently-used */

    d->name[0] = FAT_DENTRY_ERASED;

    b->dirty = true;        /* need to sync block */

    block_put(b);

    /* remove the index structure from the position hash */

    fat_idx_hashout(childp->idx);

    /* clear position information */

    childp->idx->pfc = FAT_CLST_RES0;

    childp->idx->pdi = 0;

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

    childp->lnkcnt = 0;

    childp->dirty = true;

    fibril_mutex_unlock(&childp->lock);

    fibril_mutex_unlock(&parentp->lock);

    return EOK;

}

fs_node_t *fat_match(fs_node_t *pfn, const char *component)

{

    fat_bs_t *bs;

    fat_node_t *parentp = FAT_NODE(pfn);

    char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];

    unsigned i, j;

    unsigned bps;       /* bytes per sector */

    unsigned dps;       /* dentries per sector */

    unsigned blocks;

    fat_dentry_t *d;

    block_t *b;

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

    bs = block_bb_get(parentp->idx->dev_handle);

    bps = uint16_t_le2host(bs->bps);

    dps = bps / sizeof(fat_dentry_t);

    blocks = parentp->size / bps;

    for (i = 0; i < blocks; i++) {

        b = fat_block_get(bs, parentp, i, BLOCK_FLAGS_NONE);

        for (j = 0; j < dps; j++) {

            d = ((fat_dentry_t *)b->data) + j;

            switch (fat_classify_dentry(d)) {

            case FAT_DENTRY_SKIP:

            case FAT_DENTRY_FREE:

                continue;

            case FAT_DENTRY_LAST:

                block_put(b);

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

                return NULL;

            default:

            case FAT_DENTRY_VALID:

                fat_dentry_name_get(d, name);

                break;

            }

            if (fat_dentry_namecmp(name, component) == 0) {

                /* hit */

                fat_node_t *nodep;

                /*

                 * Assume tree hierarchy for locking.  We

                 * already have the parent and now we are going

                 * to lock the child.  Never lock in the oposite

                 * order.

                 */

                fat_idx_t *idx = fat_idx_get_by_pos(

                    parentp->idx->dev_handle, parentp->firstc,

                    i * dps + j);

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

                if (!idx) {

                    /*

                     * Can happen if memory is low or if we

                     * run out of 32-bit indices.

                     */

                    block_put(b);

                    return NULL;

                }

                nodep = fat_node_get_core(idx);

                fibril_mutex_unlock(&idx->lock);

                block_put(b);

                return FS_NODE(nodep);

            }

        }

        block_put(b);

    }

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

    return NULL;

}

fs_index_t fat_index_get(fs_node_t *fn)

{

    return FAT_NODE(fn)->idx->index;

}

size_t fat_size_get(fs_node_t *fn)

{

    return FAT_NODE(fn)->size;

}

unsigned fat_lnkcnt_get(fs_node_t *fn)

{

    return FAT_NODE(fn)->lnkcnt;

}

bool fat_has_children(fs_node_t *fn)

{

    fat_bs_t *bs;

    fat_node_t *nodep = FAT_NODE(fn);

    unsigned bps;

    unsigned dps;

    unsigned blocks;

    block_t *b;

    unsigned i, j;

    if (nodep->type != FAT_DIRECTORY)

        return false;

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

    bs = block_bb_get(nodep->idx->dev_handle);

    bps = uint16_t_le2host(bs->bps);

    dps = bps / sizeof(fat_dentry_t);

    blocks = nodep->size / bps;

    for (i = 0; i < blocks; i++) {

        fat_dentry_t *d;

        b = fat_block_get(bs, nodep, i, BLOCK_FLAGS_NONE);

        for (j = 0; j < dps; j++) {

            d = ((fat_dentry_t *)b->data) + j;

            switch (fat_classify_dentry(d)) {

            case FAT_DENTRY_SKIP:

            case FAT_DENTRY_FREE:

                continue;

            case FAT_DENTRY_LAST:

                block_put(b);

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

                return false;

            default:

            case FAT_DENTRY_VALID:

                block_put(b);

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

                return true;

            }

            block_put(b);

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

            return true;

        }

        block_put(b);

    }

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

    return false;

}

fs_node_t *fat_root_get(dev_handle_t dev_handle)

{

    return fat_node_get(dev_handle, 0);

}

char fat_plb_get_char(unsigned pos)

{

    return fat_reg.plb_ro[pos % PLB_SIZE];

}

bool fat_is_directory(fs_node_t *fn)

{

    return FAT_NODE(fn)->type == FAT_DIRECTORY;

}

bool fat_is_file(fs_node_t *fn)

{

    return FAT_NODE(fn)->type == FAT_FILE;

}

/** libfs operations */

libfs_ops_t fat_libfs_ops = {

    .match = fat_match,

    .node_get = fat_node_get,

    .node_put = fat_node_put,

    .create = fat_create_node,

    .destroy = fat_destroy_node,

    .link = fat_link,

    .unlink = fat_unlink,

    .index_get = fat_index_get,

    .size_get = fat_size_get,

    .lnkcnt_get = fat_lnkcnt_get,